U.S. patent number 3,620,677 [Application Number 04/160,127] was granted by the patent office on 1971-11-16 for indicating device.
This patent grant is currently assigned to Miles Laboratories. Invention is credited to Ayers Morison.
United States Patent |
3,620,677 |
|
November 16, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
INDICATING DEVICE
Abstract
1. An indicating device comprising in combination a porous
capillary material characterized by connected voids of sufficiently
small size to induce the progressive absorption of a fluid, and an
impervious covering material enclosing at least the major portion
of the exterior surfaces of said capillary material and disposed in
intimate contact therewith defining an absorptive cavity of a
preselected volume, said device constructed to provide directional
guidance through said absorptive cavity of a fluid contacting an
exposed surface of said capillary material, indicating means on
said indicating device, said capillary material within said
absorptive cavity operable in conjunction with a fluid absorbed to
evidence in combination with said indicating means a characteristic
of the fluid absorbed therein.
Inventors: |
Ayers Morison (Gross Pointe,
MI) |
Assignee: |
Miles Laboratories (Inc.,
Elkhart)
|
Family
ID: |
26856620 |
Appl.
No.: |
04/160,127 |
Filed: |
December 18, 1961 |
Current U.S.
Class: |
422/423;
374/E3.004; 116/200; 116/207; 502/1; 96/153; 96/117.5 |
Current CPC
Class: |
B01D
15/08 (20130101); G01N 11/00 (20130101); G01N
31/22 (20130101); G01N 13/02 (20130101); G01N
33/04 (20130101); G01K 3/04 (20130101); G01N
30/92 (20130101); B01L 3/5023 (20130101); G01N
30/6065 (20130101); Y10T 137/5444 (20150401) |
Current International
Class: |
B01D
15/08 (20060101); G01N 13/00 (20060101); G01N
33/04 (20060101); G01N 11/00 (20060101); G01N
13/02 (20060101); G01N 31/22 (20060101); G01N
33/02 (20060101); G01K 3/00 (20060101); G01K
3/04 (20060101); G01N 30/92 (20060101); G01N
30/00 (20060101); G01N 30/60 (20060101); G01n
029/02 () |
Field of
Search: |
;73/53,29,358,335 ;58/1
;99/192TI ;116/114.19,114,114.20 ;158/96 ;67/53,70,71,69
;117/121.2,140R ;252/425.5 ;23/253TP,254 ;55/387 ;261/99,107 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Joseph Scovronek
Attorney, Agent or Firm: Harness, Dickey & Pierce
Claims
1. An indicating device comprising in combination a porous
capillary material characterized by connected voids of sufficiently
small size to induce the progressive absorption of a fluid, and an
impervious covering material enclosing at least the major portion
of the exterior surfaces of said capillary material and disposed in
intimate contact therewith defining an absorptive cavity of a
preselected volume, said device constructed to provide directional
guidance through said absorptive cavity of a fluid contacting an
exposed surface of said capillary material, indicating means on
indicating device, said capillary material within said absorptive
cavity operable in conjunction with a fluid absorbed to evidence in
combination with said indicating means a characteristic of the
2. An indicating device comprising in combination a porous
capillary material characterized by connected voids of sufficiently
small size to induce the progressive absorption of a fluid, and an
impervious covering material enclosing the exterior surfaces of
said capillary material and disposed in intimate contact therewith
defining an absorptive cavity of a preselected volume, closure
means on said indicating device including a portion of said
covering material adapted to be removed for exposing a selected
portion of said capillary material, said device constructed to
provide directional guidance through said absorptive cavity of a
fluid contacting the exposed portion of said capillary material,
indicating means on said indicating device, said capillary material
within said absorptive cavity operable in conjunction with a fluid
absorbed to evidence in combination with said indicating means a
characteristic of the
3. An indicating device comprising in combination a porous
capillary material characterized by connected voids of sufficiently
small size to induce the progressive absorption of a fluid, said
capillary material formed in a preselected configuration and of a
controlled porosity to provide for controlled changes in the
absorption characteristics thereof, and an impervious covering
material enclosing at least the major portion of the exterior
surfaces of said capillary material and disposed in intimate
contact therewith defining an absorptive cavity of a preselected
volume, said device constructed to provide directional guidance
through said absorptive cavity of a fluid contacting an exposed
surface of said capillary material, indicating means on said
indicating device, said capillary material within said absorptive
cavity operable in conjunction with a fluid absorbed to evidence in
combination with said indicating
4. An indicating device comprising in combination a porous
capillary material characterized by connected voids of sufficiently
small size to induce the progressive absorption of a fluid, and an
impervious covering material enclosing at least the major portion
of the exterior surfaces of said capillary material and disposed in
intimate contact therewith defining an absorptive cavity of a
preselected volume, said device constructed to provide directional
guidance through said absorptive cavity of a fluid contacting an
exposed surface of said capillary material, indicating means on
said indicating device, said capillary material within said
absorptive cavity operable in conjunction with a fluid absorbed to
evidence in combination with said indicating means a characteristic
of the fluid absorbed therein, said covering material formed with a
venting aperture therethrough disposed in communication with said
capillary material at a position located remote to said exposed
surface of said
5. A continuous strip of indicating material comprising in
combination an elongated porous capillary material characterized by
connected voids of sufficiently small size to induce the
progressive absorption of a fluid, and an elongated impervious
covering material enclosing the exterior surfaces of said capillary
material and disposed in intimate contact therewith, said strip
adapted to be cut at longitudinally spaced intervals forming a
plurality of indicating devices of a preselected length, each of
said indicating devices having the opposite ends of said capillary
material exposed and defining between said ends an absorptive
cavity of a preselected volume, indicating means on each of said
indicating devices, each of said indicating devices constructed to
provide directional guidance through said absorptive cavity of a
fluid contacting an exposed end of said capillary material, said
capillary material within said absorptive cavity operable in
conjunction with a fluid absorbed to evidence in combination with
said indicating means a characteristic of the
6. An indicating device as defined in claim 1 further characterized
as including a plurality of pieces of said capillary material each
having the major portion of the exterior surface thereof enclosed
within said covering material and separated from the next adjacent
one of said pieces
7. The indicating device as defined in claim 1 wherein said
capillary material is in the form of a substantially rectangular
planar strip of
8. The indicating device as defined in claim 1 wherein said
capillary material is of a controlled configuration comprising an
inlet section of a substantially constant cross section disposed in
absorptive contact with a second section of a cross section
different than that of said inlet
9. The indicating device as defined in claim 1 wherein said
capillary material is in the form of a circular disc of relative
constant thickness throughout and wherein the fluid to be absorbed
is adapted to be introduced through said impervious covering
material at substantially the
10. The indicating device as defined in claim 1 wherein said
capillary material is of a composite construction including a first
section of a controlled shape and porosity disposed in absorptive
contact with a second
11. An indicating device comprising in combination a porous
capillary material characterized by connected voids of sufficiently
small size to induce the progressive absorption of a fluid, and an
impervious covering material enclosing at least the major portion
of the exterior surfaces of said capillary material and disposed in
intimate contact therewith defining an absorptive cavity of a
preselected volume, said device constructed to provide directional
guidance through said absorptive cavity of a fluid contacting an
exposed surface of said capillary material, said capillary material
further characterized as incorporating an impregnant on the
internal surfaces thereof which is operative in response to and in
conjunction with the absorption of a fluid therethrough to provide
a visual indication of the depth of penetration of the fluid or of
a selected component thereof through said capillary material within
said
12. The indicating device as described in claim 11 wherein said
impregnant comprises an acid-base indicator which is operative to
change color to indicate the relative proportion of the penetration
of the acid-base
13. The indicating device as defined in claim 11 wherein said
impregnant comprises a reactive material which is operative to
react with the fluid or selected components thereof and an
indicator impregnated in said capillary material for visually
indicating the proportion of said reactive
14. An indicating device comprising in combination a porous
capillary material characterized by connected voids of sufficiently
small size to induce the progressive absorption of a fluid, and an
impervious covering material enclosing at least the major portion
of the exterior surfaces of said capillary material and disposed in
intimate contact therewith defining an absorptive cavity of a
preselected volume, said device constructed to provide directional
guidance through said absorptive cavity of a fluid contacting an
exposed surface of said capillary material, said capillary material
further characterized as possessing ion exchange characteristics on
the internal surfaces thereof for selectively adsorbing selected
ions in the fluid absorbed, and indicator means in said capillary
material for visually indicating the relative proportion of said
capillary material within said absorptive cavity which contains the
adsorbed
15. Analytical indicator characterized by prolonged shelf-life
comprising a substantially plane paper sheet having a wettable
surface impregnated with a reagent for producing a contrasting
color with respect to said paper sheet on spreading of a liquid
containing the substance of interest thereover as visual evidence
of the presence of said substance of interest in said liquid, said
indicator including superposed upper and lower layers of a
water-insoluble plastic material, with the paper sheet
therebetween, said upper and lower plastic layers overlying,
respectively, substantially the entire upper and lower surfaces of
the paper, said plastic layers extending beyond two opposite edge
portions of the test paper and being joined along the edges thereof
disposed outwardly of the strip forming a close-fitting closure
about the test paper, at least one end of the closure being open,
said test paper being united to at least one surface
16. Analytical indicator characterized by prolonged shelf-life
comprising a substantially plane paper sheet having a wettable
surface impregnated with a reagent for producing a contrasting
color with respect to said paper sheet on spreading of a liquid
containing the substance of interest thereover as visual evidence
of the presence of said substance of interest in said liquid, said
indicator including superposed upper and lower layers of a
water-insoluble plastic material, with the paper sheet
therebetween, said upper and lower plastic layers overlying,
respectively, substantially the entire upper and lower surfaces of
the paper and extending beyond two opposite edges of the test paper
and being joined along the edges thereof disposed outwardly of the
strip forming a close-fitting closure about the
17. Analytical indicator according to claim 16 wherein one of
said
18. An indicator including a series of interconnected analytical
test paper units characterized by prolonged shelf-life comprising a
plurality of substantially plane paper sheets having wettable
surfaces impregnated with a reagent for producing a contrasting
color with respect to said paper sheets on spreading of the liquid
containing the substance of interest thereover as visual evidence
of the presence of said substance of interest in said liquid, said
indicator including superposed upper and lower elongated layers of
water-insoluble plastic material, with the paper sheets disposed at
spaced intervals therebetween along the length of said layers, said
upper and lower plastic layers overlying, respectively,
substantially the entire upper and lower surfaces of the paper and
being joined along transverse portions thereof along the transverse
edge portions of each paper sheet, forming a close-fitting closure
about each sheet, at least one longitudinal edge portion of each
closure being open.
19. An indicator having prolonged shelf-life characteristics
comprising a substantially plane paper sheet having a wettable
surface impregnated with a reagent for producing a contrasting
color with respect to said paper sheet on spreading of the liquid
containing the subject of interest thereover as visual evidence of
the presence of said substance of interest in said liquid and at
least one paper sheet comprising a color comparison scale, said
indicator including superposed upper and lower elongated layers of
water-insoluble plastic material, with the paper sheets disposed at
spaced intervals therebetween along the length of said layers, said
upper and lower plastic layers overlying, respectively,
substantially the entire upper and lower surfaces of the paper and
being joined along transverse portions thereof along the transverse
edge portions of each paper sheet forming a close-fitting closure
about each sheet, at least one
20. An indicator for carrying out multiple determinations having
prolonged shelf-life characteristics comprising at least two
substantially plane paper sheets having wettable surfaces, each of
said paper sheets having been impregnated with a reagent for
producing a contrasting color respectively with respect to said
paper sheet on spreading of a liquid containing the subject of
interest thereover as visual evidence of the presence of said
substance of interest in said liquid, said indicator including
superposed upper and lower elongated layers of water insoluble
plastic material, with the paper sheets disposed at spaced
intervals therebetween along the length of said layers, said upper
and lower plastic layers overlying, respectively, substantially the
entire upper and lower surfaces of the paper and being joined along
transverse portions thereof along the transverse edge portions of
each paper sheet forming a close-fitting closure about each sheet,
at least one longitudinal edge
21. Analytical test tape of indefinite length characterized by
prolonged shelf-life comprising an indicator paper in strip form,
and upper and lower strips of hermetically sealing sheet material
disposed one above and one below the indicator paper strip covering
the same in close-fitting overlying relation, said layers extending
beyond the width of the indicator paper strip and being joined
together along longitudinal edge portions outwardly of the strip,
said layers being transversely disconnected at one end of the tape,
providing an opening for access to the indicator paper, at least
one of the said strips of sealing sheet material being transparent.
Description
The present invention broadly relates to indicating devices, and
more particularly to an improved indicating device which in various
shapes, combinations, and with various impregnants is adaptable to
enable visual or electrical indication of the measurement of a
variety of parameters such as time, temperature, temperature-time
relationships, physical relationships such as viscosity or surface
tension of liquids, and for chemical relationships such as
analytical determinations of concentrations or relative
concentrations of components in a solution, for analyzing and
separating components of a liquid emulsion or dispersion or other
fluids such as air, and the like.
In accordance with the present invention, an indication is obtained
which enables substantially accurate correlations to be made
between the rate and/or distance of travel of a fluid or a
component of the fluid along a sheathed wick in relationship to the
specific characteristics of the fluid or component and the
temperature and variations in the temperature of the environment in
which the indicating device is used. The present invention enables
a wick to be employed in combination with fluids of a controlled
composition and possessing selected physical properties as an
indicator device providing an accurate and inexpensive means for
furnishing information and data which heretofore could not be
accurately obtained or could be obtained only through relatively
elaborate, time-consuming and costly measuring techniques.
It is, accordingly, a primary object of the present invention to
provide an improved indicating device comprising a capillary
material enclosed within an impervious protective sheath or
covering material which is disposed in intimate contact with the
surfaces of the capillary material providing therewith a wick
having a controlled wicking action.
Still another object of the present invention is to provide an
improved indicating device which includes a capillary material
enclosed within an impervious protective sheath which substantially
completely eliminates the effect of gravity or motion upon the rate
of absorption of fluid therealong, which eliminates contamination
and evaporation of the fluid absorbed by the wick, which provides
for a uniform distribution of fluid therealong, which directs,
controls and limits the amount of fluid which is absorbed by the
wick with respect to the wick geometry, and which enables accurate
measurements and analyses to be made using a comparatively small
sample of fluid.
Still another object of the present invention is to provide an
improved indicating device of the indicated character wherein at
least a portion of the impervious sheath or covering material is
sufficiently transparent so as to enable visual inspection of the
position of the indicator substance or fluid in the wick in
relation to appropriate calibrations positioned on or adjacent to
the wick and oriented with respect to the absorptive direction of
the fluid.
A further object of the present invention is to provide an improved
indicating device including a sheathed wick wherein the capillary
material therein is of a preselected constant and/or variable shape
and porosity along its length to achieve a desired uniformity or
controlled variation in the wicking action thereof.
A still further object of the present invention is to provide an
elapsed time indicator incorporating therein a sheathed wick
calibrated to measure time and compensated to substantially
completely eliminate the effect of temperature variations over a
preselected range, the timing duration of which is established in
manufacture.
Yet still another object of the present invention is to provide a
combination temperature-elapsed time indicator device employing a
sheathed wick and which device is adapted to indicate the elapsed
time period since the article was subjected to a preselected
temperature.
Yet a still further object of the present invention is to provide a
shelf-life indicator device comprising a temperature-sensitive
timer whereby the rate of absorption of a liquid is effected by the
ambient temperature and is operable to correlate the elapsed time
and variations in temperature by employing selected liquids and a
controlled geometry and porosity of the sheathed capillary material
to accurately determine the shelf life, or freshness or suitability
for sale of perishable articles which are subject to spoilage or
deterioration on aging by an amount determined by their thermal
history and/or age such as frozen foods, meats, photographic films,
pharmaceuticals, and the like.
Another object of the present invention is to provide an indicator
device incorporating a sheathed wick and which device employs an
electrically conductive liquid which on attaining a predetermined
position along the wick is operative to complete an electric
circuit or to produce an electric signal as an indication of the
completion of a measured event.
Still another object of the present invention is to provide an
analytical indicator device employing a sheathed wick and which
device is suitable for the accurate analyses of the concentration
of a simple solution, the relative concentration of components in a
multiple solution, to measure the viscosity or surface tension of a
variety of liquids, and to perform analyses and separations on
liquid emulsions, colloids, and dispersions.
Yet still another object of the present invention is to provide an
indicator device employing a sheathed wick wherein the capillary
material is impregnated with a suitable indicator dye whereupon
absorption of a fluid to be tested effects a color change in the
indicator dye or a movement of the indicator dye, and the length of
the colored portion or spacing thereof from one end of the wick of
the indicator dye is indicative of the characteristics of the
solution or fluid such as the acidity thereof, for example.
Yet a still further object of the present invention is to provide a
sheathed wick indicator device the capillary material of which has
been rendered reactive with the fluid absorbed and/or impregnated
with an indicator which changes color to show the amount of
reactive capillary material which has reacted with the fluid.
Yet still another object of the present invention is to provide a
sheathed wick indicator device, the sensitivity of which can be
controlled and established in manufacture by controlling the amount
of a reactive impregnant, or controlling the condition, such as the
acidity or alkalinity, for example, of the capillary material.
Still another object of the present invention is to provide a
sheathed wick construction and an indicator device incorporating
said sheathed wick which is of simple design, of economical
manufacture, of extremely versatile use, and which, because of its
low cost, can either be discarded after use or can be readily filed
as a semipermanent record.
The foregoing and other objects and advantages of the present
invention are achieved by providing a material having capillary
qualities and enclosing the capillary material in an impervious
protective sheath which is disposed in intimate contact with the
exterior surfaces of the capillary material and thereafter
introducing a liquid of controlled physical characteristics
including viscosity, specific gravity, and surface tension at a
preselected point of the capillary material wherein the resultant
travel of the liquid along the wick is indicative of the elapsed
time/and or environment, or alternatively, introducing a fluid to
be analyzed at a point of the capillary material whereby the travel
of the fluid or an indicating agent is indicative of the
characteristics of the fluid or media in which the indicator device
is disposed. The fluid which is supplied to the capillary material
can be derived from a remote fluid supply such as a test solution
or from a liquid reservoir integrally contained in an indicator
device incorporating the capillary material which either on dipping
of the wick into the test solution or on the opening of a suitable
valve or the movement or rupture of a blocking member releases the
fluid into absorptive contact with the capillary material to
initiate the wicking action. It is also contemplated within the
scope of the present invention that the capillary material can be
impregnated with or modified by suitable additives which are
adapted to become dissolved in or modified chemically by the liquid
as it advances along the capillary material effecting either a
color change, a color migration, or a modification in the physical
properties of the liquid. The liquid can be controlled in
composition and physical behavior with respect to environment which
in correlation with a controlled geometrical configuration and
porosity of the capillary material produces the desired wicking
action along each incremental length of the capillary material
serving as an indicator of the particular parameter being
measured.
Other objects and advantages of the present invention will become
apparent from the following detailed description taken in
conjunction with the accompanying drawings, wherein:
FIG. 1 is a plan view of a sheathed wick incorporating a capillary
material of a preselected geometrical configuration laminated
between two transparent plastic films;
FIG. 2 is a transverse sectional view through the sheathed wick
shown in FIG. 1 and taken substantially along the line 2--2
thereof;
FIG. 3 is a plan view of an alternate satisfactory sheathed wick
wherein the capillary material projects from one end of the
sheath;
FIG. 4 is a plan view of an individually sheathed wick provided
with a venting aperture at the upper end thereof;
FIG. 5 is a plan view of an alternate satisfactory individually
sheathed wick employing a venting aperture disposed in
communication with the upper end portion of the wick and extending
between the plastic films to a point adjacent the opposite end
thereof;
FIG. 6 is a transverse sectional view of the sheathed wick shown in
FIG. 5 and taken substantially along the line 6--6 thereof;
FIG. 7 is a plan view of a continuous strip of a capillary material
sheathed within two plastic films which is adapted to be cut
transversely into a plurality of sheathed wicks of the desired
length;
FIG. 8 is a plan view of a sheathed wick having both ends thereof
exposed to the atmosphere such as obtained from cutting a length
from the continuous strip shown in FIG. 7;
FIG. 9 is a plan view of a continuous strip of a sheathed wick
incorporating therein a venting aperture extending parallel to the
capillary material;
FIG. 10 is a transverse sectional view of the strip shown in FIG. 9
and taken substantially along the line 10--10 thereof;
FIG. 11 is a plan view of a composite sheathed wick incorporating
two strips of capillary material disposed in overlying relation and
separated by an intervening impervious film;
FIG. 12 is a longitudinal sectional view through the composite
sheathed wick shown in FIG. 11 and taken substantially along the
line 12--12 thereof;
FIGS. 13-20 are plan views of alternate satisfactory geometrical
configurations and composite constructions of the capillary
material to obtain controlled variations in the absorption
characteristics thereof;
FIG. 21 is a plan view of a typical temperature-sensitive indicator
device employed for indicating freshness of perishable materials
and incorporating a sheathed wick and a liquid reservoir adjacent
to one end thereof;
FIG. 22 is a longitudinal sectional view of the structure shown in
FIG. 21 and taken substantially along the line 22--22 thereof;
FIG. 23 is a fragmentary plan view of a sheathed wick incorporating
a self-contained liquid reservoir which is connected by a conduit
which is selectively opened by unfolding the sheath along the
dotted fold line;
FIG. 24 is a fragmentary plan view of a sheathed wick incorporating
a self-contained liquid reservoir employing a closure member
between the reservoir and the end of the capillary material which
is adapted to be ruptured enabling initiation of the absorbing
action;
FIG. 25 is a fragmentary plan view of a sheathed wick incorporating
a self-contained liquid reservoir wherein a fusible material is
employed to prevent flow of the liquid to the wick until a
preselected temperature has been exceeded;
FIG. 26 is a fragmentary plan view of a sheathed wick incorporating
a self-contained liquid reservoir wherein a frangible plug is
employed for releasing the liquid to initiate the absorptive
action;
FIG. 27 is a fragmentary plan view of a sheathed wick incorporating
a self-contained liquid reservoir wherein a clip is provided for
preventing absorption of the liquid until removal thereof;
FIG. 28 is a transverse sectional view through the clip mechanism
and sheathed wick shown in FIG. 27 and taken along the line 28--28
thereof;
FIG. 29 is a fragmentary plan view of a sheathed wick incorporating
a self-contained liquid reservoir provided with a stopper valve
which, on actuation, releases the liquid to initiate the absorptive
action;
FIG. 30 is a longitudinal sectional view of the sheathed wick shown
in FIG. 29 and taken along the line 30--30 thereof;
FIG. 31 is a plan view of a sheathed wick incorporating a
self-contained liquid reservoir comprising a sheathed wick such as
derived from a continuous strip as shown in FIG. 7 which is closed
at the ends thereof by a cap and base containing an integral liquid
reservoir;
FIG. 32 is a longitudinal sectional view of the sheathed wick shown
in FIG. 31 and taken along the line 32--32 thereof;
FIG. 33 is a plan view of a sheathed wick incorporating
calibrations along the length of the wick and provided with a port
in the upper end thereof for drawing a predetermined volume of
fluid through the capillary material;
FIG. 34 is a longitudinal sectional view of the sheathed wick shown
in FIG. 33 and taken along the line 34--34 thereof;
FIG. 35 is a sectional view of the sheathed wick shown in FIGS. 33
and 34 having a syringe positioned in the port at the upper end
thereof for drawing a preselected volume of sample through the
capillary material;
FIG. 36 is a plan view of a typical time indicator device employing
a sheathed wick and a self-contained liquid reservoir;
FIG. 37 is a longitudinal sectional view of the indicator device
shown in FIG. 36 taken substantially along the line 37--37 thereof
and illustrating the plug in the closed position;
FIG. 38 is a longitudinal sectional view similar to that shown in
FIG. 37 with the plug moved to the open position releasing liquid
to become absorbed in the capillary material;
FIG. 39 is a plan view of an indicator device incorporating a
sheathed wick and an integral liquid reservoir therein;
FIG. 40 is a longitudinal sectional view through the indicator
device shown in FIG. 39 and taken substantially along the line
40--40 thereof;
FIG. 41 is a plan view of an indicator device incorporating a
self-contained liquid reservoir and a sheathed wick which is
operative on the completion of a measuring function to generate an
electric signal current;
FIG. 42 is a fragmentary longitudinal sectional view through the
battery portion of the indicator device shown in FIG. 41 and taken
along the line 42--42 thereof;
FIG. 43 is a plan view of an indicator device incorporating a
sheathed wick and a self-contained liquid reservoir which, on
completion of a measuring function, is adapted to close an
electrical circuit which in turn enables the energization of a
suitable control relay;
FIG. 44 is a transverse sectional view through the indicator device
shown in FIG. 43 and taken along the line 44--44 thereof;
FIG. 45 is a plan view of an alternate satisfactory indicator
device adapted to close an electrical circuit on the completion of
a measuring function from that shown in FIG. 43; and
FIG. 46 is a transverse sectional view through the indicator device
shown in FIG. 45 and taken along the line 46--46 thereof.
The capillary material employed in the sheathed wick construction
comprising the present invention can comprise any porous material
or media through which a fluid or solid can be absorbed, or caused
to be absorbed, imbibed, assimilated or passed through by either
solvation, diffusion, sublimation, or capillary action.
Principally, the wick material possesses capillary qualities
produced by a filamented capillaceous, porous, or interconnected
cellular structure characterized by connected voids of sufficiently
small size to induce the progressive taking up of a fluid by
absorption. Suitable capillary materials for construction of the
sheathed wick include finely particulated granular materials,
spongy or cellular materials and fibrous materials such as
cellulosic and synthetic fibrous networks such as cloth, paper, and
the like, having a large internal interconnected surface area with
respect to its volume. Of the foregoing materials, the capillary
material or wick is preferably comprised of a paper of controlled
physical and chemical properties either employing cellulosic,
synthetic or glass fibers which is of sufficient uniformity and
homogeneity with respect to porosity, density, and chemical
composition so that it can be commercially reproduced. The specific
density, hardness, surface characteristics, thickness, weight,
composition, filler content, and chemical nature, etc. can be
varied so as to achieve optimum absorptive action for each specific
measuring function.
The wick material can also be impregnated with suitable additives
or chemicals as will be subsequently described, which effect a
change in the rate of absorption of the absorbed fluids, or which
effects a change in the absorption characteristics of the absorbed
fluid, or which produce a color change on reaction with the
absorbed fluid to accentuate the distance of the penetration, which
react with one or more components of the absorbed fluid to provide
an indication of the amount and/or condition of the reacted or
unreacted portion of the fluid absorbed by the wick, or which
produce changes in the concentration of the dissolved impregnants
in the fluids,
It is also contemplated within the scope of the present invention
that the wick can be of a composite construction employing wicking
materials of dissimilar physical and chemical characteristics to
produce a controlled change in the manner and amount of absorption
of the fluid therethrough. Alternatively, the wick itself may
comprise one material which is geometrically shaped to produce
controlled changes in manner or amount of absorption or to produce
predictable changes in rate of the travel of the liquid absorbed
thereby.
The covering material employed for enclosing the capillary or wick
material within a protective sheath can comprise any suitable
material which is impervious to the fluid and which itself will not
substantially penetrate the pores of the wick material. The use of
a sheath around the wick material provides for the elimination of
evaporation of the absorbed liquids, the elimination of the
"surface effect" comprising a progressively decreasing thickness of
a layer of liquid along the outer surface of the wick as effected
by position of the wick which seriously affects the uniform wicking
action thereof, the elimination of uncontrolled capillary action
along the length of the wick, the elimination of uncontrolled
elongation of the wick as a result of the wetting and absorption of
liquid in the porous structure thereof, the elimination of low
structural strength and particularly the low wet strength of the
wick material, the elimination of contamination and staining of the
liquid in the wick material, and which strictly limits the amount
of material absorbed by the wick and directs and controls the
amount and direction of absorption in relation to wick geometry and
point of entrance of the fluid.
The particular material of which the covering material or
protective sheath is composed is not critical provided that it
itself is not porous and is substantially impervious to the fluid.
The rigidity and flexibility characteristics of the sheath material
is dependent on the specific characteristics desired of the
resultant sheathed wick as well as the particular type of wick
material employed. For example, when a granular type porous media
is employed as the wick material, it is preferred to employ a
substantially rigid protective sheath to maintain the uniformity of
distribution of the granules since any disturbance of the granular
media effects a substantial change in the capillary action and
absorption rate of the fluid. Since fibrous-type wicking materials
such as paper, for example, have a more permanent and elastic
physical structure, sheathing materials of a semirigid or flexible
nature can be satisfactorily employed for covering the exterior of
the wick material. For this purpose, any one of a number of plastic
film materials such as polyethylene, polypropylene, polyvinyl
polymers or copolymers such as polyvinyl chloride, polyvinyl
acetate, polyvinylidene chloride, polyethylene as well as composite
sheets such as polyethylene terephthalate (Mylar) and polyethylene,
for example, can be satisfactorily employed. Of the foregoing
materials, a composite sheet comprising a sheet of Mylar and
polyethylene constitutes the preferred material for sheathing the
wick.
A covering sheath of sufficient translucency or transparency is
employed to allow visual examination of the length of penetration
and progression of the fluid, fluid component, or indicator
condition through the wick material as is necessary in some
indicator devices. In indicator devices wherein an electrical
current or an electrical circuit is completed or a hidden
indication is desired on the completion of the measuring function,
opaque covering materials can be employed if desired, since visual
examination of the wick ordinarily is not necessary under such
circumstances.
The protective sheath is applied to the porous wick material in a
manner so that it is disposed in intimate contact with the side
surfaces thereof. The intimacy of contact between the sheath and
the side surfaces of the porous wick is critical since any
substantial space or gap left between the exterior surfaces of the
wick material and the overlying sheath material will itself serve
as a capillary causing a substantial deviation in the controlled
wicking characteristics of the sheathed wick.
A variety of coating techniques can be employed to sheath the wick
wherein the sheathing material is disposed in intimate contact with
the side surfaces of the wick material. When a thermoplastic film
material is employed such as cast transparent polyvinyl chloride
film, for example, for sheathing a fibrous wick material such as
cellulosic or acrylic fibrous paper, it is preferred to laminate
the wick material between a pair of plastic films under heat and
pressure effecting fusion and bonding of the films to each other
and to the surfaces of the wick material. The use of pressure
during the laminating operation is preferred since a large
proportion of the air entrapped within the porous structure of the
fibrous wick material can be expelled during the sheathing
operation.
Alternatively, the wick material can be coated either by dipping or
spraying the surfaces thereof with a high solids content
thermoplastic resin material which is controlled in viscosity and
composition so as not to incur appreciable penetration or blocking
of the interior porosity of the wick material. After dipping or
spraying the coated wick material can thereafter be dried to
evaporate all of the solvent therefrom leaving an impervious
residuary coating of the plastic material. Similarly, the exterior
surfaces of the wick material can be coated by conventional roller
coating techniques of the types well known in the art to effect a
uniform impervious film on the exterior surfaces thereof. Adhesive
materials applied to the inner faces of the covering material can
also be employed, such as pressure-sensitive adhesives of the types
well known in the art and including natural and synthetic rubbers,
for example, which effect tenacious bonding of the covered sheaths
to the surfaces of the wick and to each other forming a tenaciously
bonded and sealed sheath. In either event, the conditions of the
coating technique employed are controlled so as to produce a
sheathed wick having the desired pore size and resultant porosity
to produce the desired absorption of the selected fluid.
As an example of a liquid coating technique, a vinyl copolymer
resin commercially designated as Resyn 33-8012, available from the
National Starch & Chemical Corporation, was applied to the
surfaces of an acrylic plastic fibrous paper available from Hurlbut
Paper Company, designated as 922B, which had a thickness of about
0.010 inches. The plastic coating was applied by means of dipping,
and thereafter the coated paper was dried at room temperature until
substantially all of the water was removed leaving a residuary
impervious film over the entire surface thereof.
In the formation of indicator devices wherein the wick material is
mounted on a backing such as paperboard, for example, the surface
of the paperboard is provided with a coating of an impervious
material such as a synthetic plastic material, for example, and a
wick material and an overlying plastic film is thereafter applied
forming a laminated structure. Lamination under such conditions can
be varied so as to provide for the inclusion of integral reservoirs
for the liquid on the card-type indicator as will be subsequently
described in detail. Alternatively, indicator devices can be made
by the direct lamination of two plastic film materials wherein
calibration tables are applied to the plastic film, directly on the
wick, or on a separate chart appropriately positioned adjacent to
the porous wick material and laminated integrally between the
plastic sheets forming an accurate measuring indicating device.
Referring now in detail to the drawings, and as may be best seen in
FIGS. 1 through 10, a typical sheathed wick construction is
illustrated comprising a porous capillary or wick material 50
enclosed within an impervious protective sheath 52 which is
disposed in intimate contact with the exterior surfaces of the wick
material 50. A sheathed wick 54 is illustrated in FIGS. 1 and 2
wherein the wick material 50 is laminated within the protective
sheath 52 forming a sheathed wick wherein both ends of the wick
material are enclosed within the sheath. This construction prevents
any contamination or inadvertent absorption of a fluid by the wick
material prior to use. At such time that the sheathed wick 54 is to
be employed for a measuring function, the lower end thereof, as
well as the upper end, if desired, can be simply cut off by means
of scissors, for example, along a dotted cutoff line indicated at
56 rendering the sheathed wick operative on immersion or contact
with a fluid to be absorbed to directionally guide the absorbed
fluid longitudinally along the wick.
An alternate satisfactory construction of a sheathed wick 58 is
illustrated in FIG. 3 wherein the wick material 50 thereof projects
a distance beyond the lower open end of the protective sheath 52.
The sheathed wick 58 is also provided with suitable calibrations 60
extending therealong enabling a simple visual translation of the
length of penetration of a fluid, an indicator, or a component of
the fluid, along the wick material into the appropriate measuring
unit. Since the sheathed wicks of types shown in FIGS. 1-3 can be
made of any predetermined sensitivity, and accordingly can be
employed with a variety of different fluids, it is also
contemplated that the calibrations 60 can be positioned on the wick
material, on the sheath extending longitudinally of the wick
material, or on an independent scale laminated between the films
comprising the sheath, so as to subdivide the length of the wick
into 100 parts each representing 1 percent of the length of the
wick material. In this way, the depth of penetration of a liquid or
a component thereof or an indicator therein can be interpreted by a
suitable calibration chart graphically portraying the performance
of specific fluid in terms of the percentage indication on the wick
material.
The sheathed wick 54 as shown in FIGS. 1 and 2 and the sheathed
wick 58 as shown in FIG. 3, can be provided, if desired, with a
venting aperture 62 as shown in the sheathed wick 64 illustrated in
FIG. 4. The venting aperture 62 is disposed in communication with
the upper end of the wick material 50 and the surrounding
atmosphere enabling any entrapped air and/or vapors resulting from
the evaporation of the absorbed liquid to be vented to the
atmosphere. Another alternate satisfactory venting aperture 66 is
illustrated in the sheathed wick 68 shown in FIGS. 5 and 6. In this
case the venting aperture 66 extends longitudinally of the wick
material 50 having the upper end portion thereof as viewed in FIG.
5 disposed in communication with the upper end of the wick material
and the lower end thereof disposed in communication with the
atmosphere adjacent the exposed end of the wick material. The
diameter of the venting aperture 66 is such that it possesses a
relatively low capillary action and the immediate positive pressure
applied to any entrapped air or vapors forced upwards through the
wick material developed by the advancement of the liquid front
therethrough are vented out the lower end of the venting aperture
66 even though it may be immersed in a suitable test solution and
simultaneously prevents any inward flow of liquid into the venting
aperture 66.
The desirability of employing a vented or nonvented sheathed wick
construction depends on the specific use to which the sheathed wick
is to be employed, the particular method by which it has been
coated resulting in variations in the amount of air expelled from
the pores thereof, the volatility characteristics of the liquids to
be absorbed, and the specific properties and characteristics of the
wick material. In either event, the capillary or wicking action of
the sheathed wick will be constant for each specific type and
construction and can be accurately correlated with any particular
parameter to be measured to achieve accurate results.
The sheathed wick constructions shown in FIGS. 1 through 6 are
particularly applicable to a manufacturing process wherein
individual strips of the wick material 50 are sheathed within the
protected sheath 52. The sheathed wick comprising the present
invention can also be manufactured in the form of a continuous
strip such as a sheathed strip 70 shown in FIG. 7 incorporating a
strip of the wick material 50 laminated within the protected sheath
52. The sheathed strip 70 can thereafter be cut along the dotted
lines indicated at 72 spaced at any desired increment forming a
sheathed wick 74 as shown in FIG. 8 of any desired length and
having the upper and lower ends thereof exposed. Similarly, a
sheathed strip 76 as shown in FIG. 9 can be manufactured in any
desired lengths by employing a strip of the wick material 50
sheathed within a strip of protective sheathing 52 and formed so as
to incorporate a longitudinally extending aperture 78 therealong.
The sheathed strip 76 can be cut along the dotted cutoff line 80
indicated in FIG. 9 to any desired lengths and thereafter employed
for making vented wicks and indicator devices incorporating an
integral liquid reservoir as will be subsequently described in
detail. It will be understood that any desired number of wicks can
be sheathed simultaneously in spaced side by side relationship.
Still another alternate satisfactory wick construction is
illustrated in FIGS. 11 and 12 wherein a composite sheathed wick 82
is shown employing two strips of the wick material 50 which are
positioned in spaced overlying relationship and are separated by an
intervening plastic film 84 over which the protective sheath 52 is
disposed. The composite sheathed wick 82, by the use of two or more
wick materials 50 having different controlled absorption
characteristics, can be employed for simultaneously determining two
or more conditions of a test fluid being analyzed or provide means
for obtaining an accurate analysis of a particular characteristic
of a fluid having an unknown concentration or characteristic. For
example, one of the wick materials 50 of the composite sheathed
wick 82 can be impregnated with a suitable anionic exchange resin
and a suitable color indicator and the other wick material can be
impregnated with a suitable cationic exchange resin and a suitable
color indicator to accurately determine the alkalinity or acidity
of an unknown test solution.
The wick material 50 as employed in the sheathed wick constructions
shown in FIGS. 1 through 12, are of a rectangular configuration and
of a substantially uniform cross section. Controlled variations or
changes in the cross-sectional area, the porosity, and the specific
construction of the wick material can be made in accordance with
the wick material configurations shown in FIGS. 13 through 20. By
virtue of these configurations, variations can be obtained along
each incremental length or section of the wick material to achieve
controlled changes or predictable changes in the absorption
characteristics thereof.
A porous wick material 86 is shown in FIG. 13 comprising an
enlarged rectangular upper or tank portion 88 integrally connected
to a smaller rectangular feeder portion 90 connected substantially
to the lower center portion thereof. A configuration of the porous
wick material 86 as shown in FIG. 13 is adapted to be laminated
within a suitable protective sheath and is particularly suitable
for use in the analysis of fluids having a relatively low
concentration of the specific component to be measured enabling a
large volume to be absorbed in the tank portion 88 providing a
relatively accurate reading even for relatively small
concentrations. The configuration further provides a more
convenient and compact wick construction which is faster in filling
than a longer wick having a constant cross-sectional area
throughout its length and which is of equal total absorptive
volume.
Another alternate configuration of a wick material is illustrated
in FIG. 14 where a porous wick material 92 is illustrated having
divergent side edges forming therewith a wick material of
progressively increasing cross-sectional area in the direction of
the absorption of the fluid. The advantages provided by the porous
wick material 92 are similar to those obtained in the porous wick
material 86 shown in FIG. 13.
A porous wick material 94 is shown in FIG. 15 which is of a
symmetrically tapered configuration provided with arcuate curved
side edges formed in an exponential curve effecting a predictable
rate of change in the absorbing characteristics of the porous wick
material throughout its entire length. Still another porous wick
material 96 is illustrated in FIG. 16 which comprises an alternate
form of the porous wick material 86 shown in FIG. 13. The porous
wick material 96 as shown in FIG. 16 comprises an upper or tank
portion 98 which is of a porosity and has absorption
characteristics different than a feeder wick portion 100 positioned
in intimate contact therewith and adapted to transfer fluid
absorbed by the feeder wick to the tank portion 98. For absorption
of equivalent volumes the construction of the porous wick material
96 provides for quicker absorption in a relatively short length
since a more porous or thicker tank portion 98 is employed, to
provide a subsequent measuring indication upon the fluid absorbed
therein, to provide for a composite wick having different chemical
treatments applied to the tank portion and the feeder portion
enabling greater flexibility and versatility in the analysis and
measuring functions.
Another alternate satisfactory configuration of a porous wick
material is illustrated in FIG. 17 wherein a porous wick material
102 is illustrated comprising an enlarged feeder portion 104
connected to or disposed in intimate contact with a smaller
measuring portion 106. The lower feeder portion 104 can be of a
higher density than the measuring portion 106 so as to act as a
pressure buffer to absorb the impact of a pressurized fluid applied
to the lower open end thereof when enclosed in a protective sheath
thereby preventing any deviation from its normal absorptive
characteristics. Alternatively, the feeder portion 104 can simply
be employed as a reservoir for supplying a fluid to be tested to
the measuring portion 106. The feeder portion 104 can also serve as
a chemical filter to remove preselected components of a fluid to be
absorbed so as to render the subsequent measurement of the
transmitted fluid or component thereof to the measuring portion 106
of the wick more readily measurable. The feeder portion 104 can
also be employed as a physical filter to remove suspended solids in
the fluid to be analyzed or measured, which would otherwise
contaminate, plug, or affect the accuracy of the measuring
indication as indicated by the measuring portion 106 of the porous
wick material 102.
A porous wick material 108 is shown in FIG. 18 which is of a
uniform rectangular configuration but incorporates a section
bounded by the dotted lines 110 having absorbing characteristics
different from the balance of the wick material. For example, the
section bounded by the dotted lines 110 can be physically
compressed to increase the density thereof and thereby produce a
slower rate of absorption which can be employed to absorb the
pressure of the initial flow of a fluid applied to the open end of
the wick material so as to prevent a deviation from the normal
absorbing characteristics of the balance of the wick.
A porous wick material 112 is illustrated in FIG. 19 comprising a
circular configuration which is adapted to be enclosed within a
protective sheath, a portion of which is perforated to admit a
suitable fluid to be absorbed by the wick material. For example, an
opening can be provided in a protective sheath thereover at
substantially the center of the circular porous wick material 112
whereby absorption of the fluid would take place in a radial
direction outwardly toward the periphery thereof whereby the
indication provided would be in the form of one or more
substantially concentric rings.
The porous wick material 114 illustrated in FIG. 20 comprises a
sector of the porous wick material 112 shown in FIG. 19. The fluid
to be tested conventionally would be admitted to the pointed end of
the porous wick material 114 and be absorbed upwardly as viewed in
FIG. 20, producing an absorption effect similar to that obtained by
the porous wick material 92 shown in FIG. 14.
Sheathed wicks of the general type shown in FIGS. 1 through 12
employing a porous wick material having a rectangular configuration
or an irregular configuration such as shown in FIGS. 13 through 20
can be satisfactorily employed for the performance of a variety of
different analytical measurements. In accordance with the practice
of the present invention, analytical analyses performed by
employing a sheathed wick having a construction as hereinbefore
described, enables relatively unskilled persons to perform accurate
analytical analyses of a variety of different fluids which
heretofore could only be accomplished by employing relatively
complex laboratory analytical methods. The sheathed wick can be
employed to separate selected components of an absorbed fluid by
virtue of the surface condition of the porous wick material which
causes an adhesion of a thin molecular layer of the component as
the fluid is absorbed by the wick. Components of the fluid are
accordingly separated by the differences in their affinity for
adhesion to the surfaces effecting a progressive absorption of the
component as the fluid advances through the wick.
Alternatively, the porous wick material can be impregnated with
suitable reactive agents effecting a controlled preselected
reaction with one or more selected components of the fluid and
suitable indicators may be incorporated to visually indicate the
amount of the reactive impregnant which has reacted with a
component of the fluid or the proportion of unreacted impregnant
left when the liquid has attained the end of the wick material
giving thereby a direct quantitative indication of the amount of
the component present in the fluid.
The reactive impregnants may be immovably affixed to the surfaces
of the porous wick material whereupon reaction thereof with a
selected component or components in the absorbed fluid the reaction
product remains stationarily affixed relative to the position of
the reaction in the wick. Alternatively, the reactive impregnant
can be movably disposed within the porous wick material whereupon
reaction with one or more components of the absorbed fluid, the
reaction product travels with the fluid as it advances through the
wick.
An example of an immovably reactive impregnant is one which
comprises a portion of a porous wick material itself such as by
chemically modifying the characteristics of a cellulose base
capillaceous material rendering the surfaces thereof immovably
reactive with components of the fluid absorbed. This can be
achieved by incorporating suitable ion exchange resins on the
surfaces of the wick material or employing such ion exchange resins
substantially as a porous capillary material itself (such as ion
exchange paper) rendering the components reacted therewith immobile
as the fluid passes by. Suitable indicators incorporated within the
porous wick material of selected color characteristics can be
employed to visually indicate the reacted or unreacted portion of
the wick material which can suitably be translated to the amount of
the component or components in the absorbed fluid.
In the performance of analyses of the concentration of a solute
present in a solvent, for example, a sheathed wick of the general
type shown in FIGS. 1, 3 and 4, and 5, can be employed wherein an
exposed end of the wick material 50 is immersed in the test
solution and the solute and solvent is absorbed into the wick. The
ratio of distances of absorption of the solute and solvent is
proportional to the quantity or concentration of the solute present
in the solution. This ratio remains essentially constant
irrespective of the amount of fluid absorbed and, accordingly, the
length of the wick is immaterial with respect to the concentration
and is only useful in obtaining the desired accuracy of the reading
resulting therefrom. In instances where a high degree of accuracy
is required, a relatively long wick or a wick material having a
specific shape such as a circular shape, as shown in FIG. 19 can be
employed since a greater quantity of fluid is absorbed over a
greater area or a longer distance. To enable simple conversion into
conventional units, the wick material or the sheath adjacent to the
wick material can be suitably calibrated in the particular
measuring system desired so as to directly indicate the percent,
molarity, etc. of the solute present in the solvent and/or
solution.
The foregoing method is directly applicable for the analysis of the
concentration of solutions containing a colored solute therein. For
example, in the measurement of the concentration of a dye solution
such as malachite green dissolved in water, the height of rise of
the green dye in a calibrated sheathed wick can be converted into a
direct measurement of its concentration in the water solution.
When it is desired to measure the concentration of a solute in a
solution wherein the solute or combination of components comprising
the solute are colorless, it is preferred to treat the wick
material with an impregnant which is sensitive to the component or
the components of the solute being measured. As an example, in the
measurement of the concentration of colorless acidic or basic
solutions such as hydrochloric acid or sodium hydroxide, for
example, a suitable acid-base indicator such as methyl red,
phenolphthalein, or the like, is impregnated in the wick whereby
the ratio of the distance of penetration of the solute-solvent is
rendered visible by the change in color of the indicator.
In some cases it may be desirable to add two or more impregnants to
the porous wick material. As an example, in the measurement of the
concentration of a salt solution such as sodium chloride, for
example, the wick material can be impregnated with a reactant such
as silver nitrate in addition to an indicator such
dichlorofluorescein. As the test solution is absorbed into the
porous wick material, a chemical reaction takes place between the
sodium chloride and the impregnants which effects a change in the
color of the indicator to a height in the wick material
corresponding to the concentration of the salt in the solution
which can be appropriately calibrated in any one of a number of
conventional measuring systems.
Sheathed wicks employed for analytical purposes can also employ a
porous wick material wherein only a portion of the wick material,
namely, one end thereof, to which the initial test solution is to
be applied, is treated with a mobile impregnant or a group of
mobile impregnants which migrate through the pores of the wick
material in response to the advance of the fluid therethrough a
distance related to the specific characteristics of the fluid being
measured. For example, the concentration of a dilute hydrochloric
acid solution can be accurately measured by employing a wick
material comprising, for example, a Whatman No. 100 paper
impregnated at the inlet end thereof with an indicator dye such as
bromothymol blue. By immersing the sheathed wick such that the
treated end thereof is positioned in the acid solution, movement of
the indicator through the wick material is effected and the
distance of travel from the end of the wick can be directly
calibrated to indicate the specific acidity of the solution.
As hereinbefore mentioned, the porous wick material may also be
treated or impregnated with suitable reactive materials which are
selectively reactive with one or several components of the fluid
absorbed therethrough but which remain essentially fixed in
position along the path of travel of the fluid thereby causing the
component or the components reactive therewith to become
essentially fixed in position either on or in the vicinity of the
stationary fixed impregnant. Examples of such immobile or
stationary impregnants are ion exchange resins imbedded in a porous
capillaceous wick material such as Reeve Angel SB-2 anion exchange
paper and Reeve Angel SA-2 cation paper, or Whatman amino ethyl
cellulose anion exchange paper. In the Whatman anionic exchange
paper, the cellulose molecule itself is modified so as to act as an
ion exchanger. In accordance with this technique, the anions or
cations in the fluid absorbed in the wick are progressively removed
by the mechanism of ion exchange and the depth of penetration and
reaction of the anions at the time the fluid completes penetration
of the porous wick material or a preselected point thereon is
proportional to the concentration of the anions in the test
fluid.
As a specific example of the foregoing analytical sheathed wick
employing an anionic exchange wick material, a sheathed wick is
prepared employing a strip of Reeve Angel SB-2 anionic paper which
is preliminarily converted to the hydroxide from and suitably
sheathed within a protective sheath. The exposed end of the
sheathed wick can thereafter be immersed in a suitable acid
solution such as hydrochloric acid, for example, and the inclusion
of an acid indicator in the wick material effects a vivid visible
indication by a change in color of that portion of the wick which
has been saturated with or fully reacted with the ions of the test
solution. The saturated or fully reacted portion of the wick
contains unreacted anions therein supplied by the upwardly moving
test solution providing a color indication up to an interface
spaced from the forwardmost portion of the advancing liquid front
which is substantially neutral and devoid of indicating ions which
have previously been removed by the ion exchange resin. An accurate
indication of the concentration of the hydrochloric acid as
indicated by the ratio of the contrasting colored portions of the
wick is made at the time that the substantially neutral liquid
attains the end portion of the wick material or a preselected point
thereon.
The advantage of employing an ion exchange paper serves to decrease
the height of the rise of acid in the wick material in comparison
to a nonionic exchange wick material since the ion exchange resin
concentrates the acid into a smaller area and, accordingly, higher
concentration test solutions can be accurately analyzed with a
relatively smaller sized wick.
Sheathed wicks of the general type shown in FIGS. 1-12 can also be
satisfactorily employed for the analysis of components in gases.
For this purpose a sheathed wick 116 of the type shown in FIGS. 33
through 35 is employed which may comprise a porous wick material
118 such as a Whatman No. 100 filter paper, for example. In an
analysis for the determination of the total amount of water vapor
or moisture in air, for example, the porous wick material 118 of
the sheathed wick 116 can be impregnated with a hygroscopic
material such as lithium chloride or calcium chloride, for example,
containing a water sensitive indicator such as the Karl Fischer
Reagent.
The upper end of the sheathed wick 116 is provided with a suitable
port 120 in which the inlet end of a suitable syringe or pump 122
is inserted for drawing a preselected volume of air through the
wick material 118. As the air is drawn through the wick material,
the water vapor therein is continuously absorbed commencing at the
inlet end portion of the wick containing the hygroscopic material
and a color indication is provided. Since absorption occurs
commencing at the inlet end of the wick and moving upwardly as
saturation of the hygroscopic materially progressively occurs, the
progressive linear travel upwardly of the color indicator along the
length of the sheathed wick 116 can be directly correlated to the
amount of moisture in the air for a given volume of sample. For
this purpose, convenient calibrations 124 can be applied to the
wick material 118 or to the protective sheath 125 therearound which
can directly be interpreted in terms of weight percent, percent
humidity, etc. for a specified volume of sample.
Another specific analytical use of the sheathed wick relates to the
determination of the freshness of milk at the time of pickup from
dairy farmers. Because of the complex analytical procedures and
equipment heretofore required to effectively evaluate the freshness
of milk, each batch of milk has to be maintained in a segregated
condition during the pickup route until appropriate analyses can be
conducted in the dairy laboratory. Alternatively, the consolidation
of the individual milk batches during a pickup route has resulted
in the contamination of the entire tank wagon batch by dumping one
or more batches of sour or diluted milk therein because of lack of
analysis or impracticability of analysis of milk along the pickup
route. In the specific instance of evaluating the freshness of
milk, the status of bacteriological development in the milk is
reflected in the acidity of the milk wherein a progressive
deterioration of the milk results in a corresponding progressive
increase in the acidity thereof. In accordance with the present
invention, a sheathed wick can be employed of the general type
shown in FIGS. 1-12 wherein accurate analysis of each batch of milk
can be simply achieved by the truck driver assuring appropriate
freshness before the dumping thereof into the consolidated
batch.
As a typical example of a milk freshness indicator, a sheathed wick
of the type shown in FIG. 1 is prepared by enclosing a strip of a
capillaceous paper commercially designated as Grade SB-2 available
from the Reeve Angel Paper Company which is conveniently cut into
strips of 31/2inches in length by 1/8-inch wide. The paper is
preliminarily treated with a 10 percent solution of sodium
hydroxide in order to convert the paper additives such as an
Amberlite resin into the hydroxide form which are thereafter washed
out with clean, clear water and allowed to dry. The dry treated
paper is thereafter impregnated with a 1 percent solution of methyl
red indicator in an alcohol solvent and allowed to dry. The strip
of paper is then laminated between two sheet of 8 mil polyvinyl
chloride plastic film forming an integrally united impervious
protective sheath therearound.
On testing of a batch of milk, the protective sheath is cut off
along the dotted line 56 of the sheathed wick 54 illustrated in
FIG. 1, leaving a net length of 3 inches and is immersed in the
milk. The height of travel of the pink area of the wick material
when the closed end of the wick was reached by the solvent
indicates the proportion of acid, and accordingly the freshness of
the milk. Calibration of the specific wick material with acidic
solutions of known and progressively increasing acidity enables
calibration of the wick wherein the distance that the edge of the
colored area is spaced from the end of the wick can readily be
translated in terms of the freshness or bacteriological growth
content of the milk providing a quick, simple and accurate analysis
thereof.
The foregoing technique can be employed for analyzing any
particular liquid by preparing a series of test solutions of
varying concentration or acidity, for example, and then
establishing the relationship of height of travel of the colored
area with respect to the end of the wick for each of the different
solutions. The porous wick material can be made of alternate
satisfactory shapes such as a circular shape as shown in FIG. 19 or
a composite shape as shown in FIG. 17 wherein the feeder portion
104 serves as a physical filter to remove suspended materials from
the liquid preventing a plugging of the measuring portion 106
thereof. A series of sheathed wicks can thereafter be calibrated in
accordance with the relationship established and imprinted in a
manner similar to the calibrations 60 on the sheathed wick 58 shown
in FIG. 3 and can be employed thereafter for accurately analyzing
the concentration or acidity, as the case may be, of a series of
liquids.
The sheathed wick comprising the present invention can also be
provided with an integral reservoir for supplying a fluid to the
porous wick material. A construction of this type is particularly
adaptable for indicator devices which are applicable for the
measurement of such parameters as time, time-temperature
relationships and the like, wherein the fluid supplied to the
porous wick material possesses controlled physical characteristics.
An indicator device 126 is shown in FIGS. 21 and 22 comprising a
porous wick material 50 enclosed within a protective sheath 52
formed at the lower end thereof with a liquid reservoir 128 adapted
to contain a suitable liquid for absorption by the wick material.
The liquid reservoir 128 is disposed in direct communication with
the end of the wick material adjacent thereto whereby the
absorption of the liquid into the wick, commences as soon as the
liquid is introduced in the reservoir or when it attains a liquid
state and can be absorbed. To delay initiation of the wicking
action, the liquid can be introduced in the form of a frozen pellet
for example which, on subsequent melting thereof immediately
initiates absorption and a suitable measuring function of the
device. It will be understood that a gelatin capsule or other
suitable means can be employed to introduce the liquid.
The particular construction of the indicator device 126 shown in
FIGS. 21 and 22 is particularly applicable to freshness indicators
of the type adapted to measure the wholesomeness or freshness of
perishable articles which are applied to the article at the time of
packaging. The wicking action of the wick material 50 and the
specific physical properties of the liquid contained in the
reservoir 128 and variation of these properties with respect to
temperature, must be carefully tailored to the specific
deterioration curves or aging characteristics of a particular
material to which the indicator device is to be applied. By
controlling the characteristics of the wick material and the
liquid, the ideal time temperature sensitivity of the indicator
device can be achieved whereby the freshness or shelf life of any
product which is dependent on the time and the thermal environment
to which it is subjected, can be accurately measured.
A simple application of this principle employing a remote source of
supply of the liquid is that of employing the wick to evaluate the
degradation of frozen foods caused by periodic intervals of thawing
followed by the freezing. By embedding the open end of a sheathed
wick in a frozen food package, the melted water or other liquids
formed the instant thawing occurs causes initiation or resumption
of the upward rise of the liquid in the wick material at a rate
proportional to the temperature of the liquid and which advance
will subsequently cease when the package is refrozen. Accordingly,
an accumulation of thawed periods will be permanently recorded on
the indicator device reflecting the freshness of the package at the
time of use.
The freshness indicator shown in FIGS. 21 and 22 employs a liquid
having selected physical properties in the reservoir 128. A typical
use of such a device is for the determination of the rate of
deterioration of fresh beef, for example, wherein the bacteria
causing the degradation multiply according to the temperature at
which the meat is maintained and the duration of time at that
temperature. It is now known that there is a direct correlation
between the bacteria population and the suitability of beef for
consumption. Accordingly, a freshness indicator can be devised by
matching the time temperature bacteria growth curve of beef or any
other food product with a selected combination of a wick material
and liquid so that when the liquid attains the upper end of the
wick or a preselected point thereon, the maximum tolerated spoilage
has occurred.
In the specific example of a freshness indicator for beef, having
an estimated maximum bacteria content tolerable of about one
million organisms per square centimeter, a wick material was
prepared comprising a Wattman No. 50 filter paper which was cut in
rectangular strips 11/2-inches long and 1/8 -inch wide and
impregnated with a 0.5 percent solution of potassium thiocyanate,
dried, and sheathed within a polyvinyl chloride film having a
thickness of 8 mils by employing a dielectric heated laminating
technique and utilizing a pressure of 60 p.s.i. As hereinafter
explained in detail, the appropriate liquid required to achieve the
desired rate of movement through the wick is derived from
establishing the constant K for the wick material under the
specific laminating or sheathing conditions and establishing a
curve relating to the maximum height of absorption desired versus
the time of absorption in hours. Thereafter the ratio of surface
tension to viscosity is established for each particular temperature
and a liquid is formulated corresponding to these characteristics.
In accordance with this procedure, a suitable liquid for
determining the freshness or decay rate of fresh beef comprises a
blend containing 50 percent by volume glycerine, 40 percent ferric
chloride, and 10 percent water.
Having produced a liquid whose advance through a wick follows the
general bacteria growth curve which applies to the spoilage of food
products, it is possible by changing a constant such as wick
composition, density and/or impregnation, size of pores, and wick
geometry to match the bacteria growth curve of many food products.
The liquid may also be adjusted in physical characteristics but
does not necessarily have to exactly match the bacteria growth
curve characteristics. A liquid which approximates these
characteristics can be also satisfactorily employed and provide a
measure of safety.
A time-temperature-sensitive indicator is also applicable as a
dosage indicator to antimicrobiological drugs which decrease in
efficiency and frequently are affected adversely by their age and
storage temperature. Similarly, the aging characteristics of other
materials and products not related to bacteria growth such as
photographic film, for example, can also be matched by selecting
the appropriate wick material and liquid combination.
An alternate satisfactory indicator device 130 is illustrated in
FIG. 23 wherein a liquid reservoir 132 formed in the protective
sheath 52 is connected to one end of the porous wick 50 by means of
a conduit 134 which is adapted to be closed when the indicator
device is folded along the dotted line indicated at 136. By virtue
of this construction, the unfolding of the indicator device serves
to open the conduit 134 enabling the liquid in the liquid reservoir
132 to become absorbed in the wick material 50 initiating the
measuring function at the desired time.
An alternate satisfactory valve means for an indicator device 138
is illustrated in FIG. 24 wherein a conduit 140 connecting a liquid
reservoir 142 formed in the protective sheath is provided with a
partially sealed section indicated at 144 preventing entry of
liquid to the absorptive end of the wick material 50. The indicator
device 138 is activated by pressing the liquid reservoir effecting
a rupture of the sealed section 144 whereby the liquid contained
therein contacts the adjacent end of the wick and is progressively
absorbed upwardly through the wick material.
Still another alternate satisfactory valving means is illustrated
in an indicator device 146 shown in FIG. 25 employing a fusible
plug indicated at 148 positioned in a conduit 150 connecting a
liquid reservoir 152 with one end of the porous wick material 50.
The fusible plug 148 can comprise any suitable material such as a
wax or a blend of waxes which are selected to melt or fuse when a
preselected temperature is attained. On fusion of the fusible plug
148 the liquid contained in the reservoir 152 flows upwardly
through the conduit 150 and is progressively absorbed in the wick
material 50.
As noted in FIG. 25, the conduit 150 is provided with a side branch
indicated at 154 which may be vented if desired and which
preferably is of a progressively decreasing diameter and of a
smaller capillary size than the conduit 150 so as to preferentially
attract the molten fusible plug and cause it to become deposited
therein, thereby avoiding contamination and restriction of the
porous wick material 50. The construction of the indicator device
146 shown in FIG. 25 is particularly suitable for use as an elapsed
time-indicator which is adapted to measure the elapsed time since a
preselected temperature has been exceeded.
Still another suitable valving means is shown in an indicator
device 156 illustrated in FIG. 26 employing a frangible plug 158
disposed in a conduit 160 connecting a liquid reservoir 162 to one
end of the porous wick material 50. The frangible plug 158 may
comprise any suitable fragile material which on the application of
pressure thereto disintegrates so as to enable the liquid from the
reservoir to pass upwardly through the conduit 160 and become
progressively absorbed in the wick material. The lower portion of
the wick material 50 may comprise a section adapted to function as
a physical filter for removing the fragments of the disintegrated
frangible plug to avoid contamination and plugging of the wick
material.
Another indicator device 164 is illustrated in FIGS. 27 and 28
wherein a conduit 166 connecting a liquid reservoir 168 to the wick
material 50 is closed by a resilient biased clip 170 removably
positioned thereon serving as a valve for restricting the flow of
liquid from the reservoir to the wick material. On removal of the
clip 170 the liquid is permitted to flow upwardly and become
absorbed in the wick material initiating the measuring function. It
will be appreciated that the protective sheath 52 of the indicator
device 164 must be of a flexible nature to enable compression
thereof by the clip 170 effecting substantially complete sealing of
the conduit 166.
Still another alternate satisfactory valving mechanism for
selectively releasing liquid to initiate absorption in the wick
material is illustrated by an indicator device 172 shown in FIGS.
29 and 30. The indicator device 172 as shown incorporates a liquid
reservoir 174 which is connected by means of a conduit 176 to one
end of the porous wick material 50. A removable plug 178 is
removably positioned in the conduit 176 and effects substantially
complete sealing of the conduit. At such time that it is desired to
initiate a particular measuring function, the removable plug 178 is
withdrawn by means of a pull string 180 enabling the liquid in the
reservoir 174 to travel upwardly and become progressively absorbed
in the wick material 50.
Another satisfactory construction of an indicator device 182 is
illustrated in FIGS. 31 and 32 which comprises a composite
construction in comparison to the integral construction of the
indicator devices shown in FIGS. 21 through 30. The indicator
device 182 is adapted to be constructed from a continuous sheathed
strip such as the sheathed strip 76 illustrated in FIGS. 9 and 10
to one end of which a cap 184 is heat sealed or otherwise
adhesively fastened. The cap 184 is formed of a flexible material
similar to the plastic film of which the sheath 52 enclosing the
porous wick material 50 is comprised as hereinbefore set forth. The
cap 184, in the specific construction shown, is formed with a
suitable cavity indicated at 186 which forms a communicating
conduit between the upper end portion of the wick material 50 and
the venting aperture 78 extending longitudinally of the wick
material. With only the cap 184 secured thereon, the resultant
composite wick resembles and functions the same as the integral
sheathed wick 68 shown in FIG. 5.
A base 188 can be similarly affixed to the other end of the
sheathed wick and securely sealed or adhesively fastened thereto
which is provided with a liquid reservoir 190 adapted to be
disposed in communication with one end of the porous wick material
50 and the venting aperture 78 through a suitable connecting
conduit 192. The conduit 192 can be provided with suitable valve
means of the general type illustrated in FIGS. 21 through 30 for
selectively introducing the liquid contained in the liquid
reservoir 192 one end of the porous wick material to initiate a
measuring function. The indicator device 182 further illustrates a
method of venting the wick whereby the opposite end of the wick is
vented to the liquid reservoir so as to provide for equalization of
pressure of any vapors or any entrapped air in the wick material
during the absorption of the liquid therethrough.
It will be apparent from the foregoing that suitable indicator
devices can be constructed to measure a particular parameter by
controlling the uniformity or variation in the wicking action or
rate of travel of the liquid along the porous wick material as a
result of variations in the geometry of the wick as well as in the
variation of its porosity along sections thereof to achieve the
desired results. The selection of the particular wick material and
liquid to accomplish a particular measuring operation is
facilitated by employing the following mathematical
relationship:
h.sup.2 /t= s/nK Wherein: h = the distance or height of the liquid
in the wick t = the time s = the surface tension of the liquid n =
the absolute viscosity of liquid absorbed, and K = a constant
dependent on the chemistry and structure of the porous wick
material
In accordance with the foregoing relationship, a wick having known
characteristics and a selected liquid whose physical
characteristics are known, can be employed and correlated together
enabling accurate calibration of an indicator device to measure
parameters such as time, temperature, time-temperature
relationships, viscosity, surface tension, as well as for various
qualitative and quantitative analyses, as the case may be.
Any one of a number of suitable fluids can be employed to achieve
the desired absorption by the wick material to provide measurement
of a specific parameter. Fluids which can be satisfactorily
employed include those which have a viscosity which permits
absorption by the wick. Heating can reduce liquid viscosity and
permit absorption at a higher rate if the temperature does not
exceed the thermal tolerance of the wick and sheath which in the
case of some materials and some wicks, for instance, glass fiber
paper can exceed 500.degree. F. The liquids can comprise relatively
pure compounds or solutions of dissolved salts or liquids therein.
Knowledge of the particular constant K of the wick material in
combination with the viscosity and surface tension of the liquid as
well as variations in the change of the viscosity and surface
tension of the liquid with respect to temperatures enables the
height and time relationship to be readily calculated in accordance
with the foregoing mathematical relationship. In indicator devices
wherein a timing function is to be measured it is desirable to
employ a liquid which does not materially change with respect to
its surface tension and viscosity with changes in temperature.
Since most liquids and even silicone liquids change quite markedly
in their physical properties with changes in temperature, suitable
additives in the liquid or impregnated in the wick material can be
employed which maintain substantially constant viscosity and
surface tension or maintain the ratio between these two physical
properties substantially constant in spite of large fluctuations in
temperature. By virtue of this technique, the accuracy of the
timing device will be maintained over a thermal environment of a
preselected range contemplated.
The effect of vapor pressure of the liquid can readily be
controlled by selecting one which has a relatively low vapor
pressure in the range of temperatures to be encountered and/or
venting the wick to the reservoir or atmosphere. Similarly the
density of the liquid does not usually constitute a critical factor
since density variations are relatively negligible over the
temperature ranges contemplated, such as, for example, from about
-20.degree. F. to about 120.degree. F.
Of the foregoing materials, the one of the viscosity of the liquid
with respect to the temperature is most critical. One method of
insuring a constant viscosity of a liquid over a given temperature
range is to maintain a maximum concentration of certain dissolvable
materials in the liquid. For example, certain salts such as
inorganic salts like lithium chloride or ammonium nitrate, for
example, when dissolved in a liquid such as water, for example, at
maximum concentration, impart a substantially constant viscosity to
the liquid over a wide temperature range. By maintaining maximum
concentration of salts, for example, in the liquid throughout a
wick length, a controlled rate of absorption can be achieved over a
wide temperature range. This can readily be achieved by
impregnating the wick material with a sufficient quantity of the
dissolvable material to maintain a maximum concentration in the
liquid as the liquid proceeds through the wick material and during
which time variations in temperature may occur. The liquid itself,
preferably would also contain a maximum dissolved concentration of
the same material to reduce any time lag resulting from the time
required to dissolve the material and to assure constant viscosity
during each incremental advancement through the wick.
As a typical example it has been found that lithium chloride in
water as the liquid solvent in combination with a sheathed porous
wick containing lithium chloride can be constructed to
substantially eliminate the temperature effect on viscosity and
maintain a predictable travel of the liquid along the wick over the
temperature range of 32.degree. F. to 140.degree. F. for a period
of 5 days.
It has also been found that a combination of several materials,
including soluble and insoluble materials, or a combination of
soluble materials that produce insoluble materials, can be
constructed in a sheathed porous wick to maintain a predictable
travel of the liquid along the wick over a useful temperature
range. For example, it has been found that the combination of
potassium bromide and potassium nitrate in water as the liquid
solvent in combination with a sheathed porous wick can be
constructed to maintain a predictable travel of the liquid along
the wick over the temperature of 32.degree. F. to 70.degree. F. for
a period of 24 hours. It has been found that the more complex
combination of calcium chloride, ammonium chloride, zinc sulfate,
and potassium nitrate (which includes the formation of insoluble
calcium sulfate) increased the predictable travel of the liquid
along the wick to a period of 160 hours over the same temperature
range of 32.degree. F. to 70.degree. F.
Preparation of a sheathed wick having a dissolvable substance such
as a salt, for example, impregnated in the porous wick material
thereof can be simply accomplished by applying a solution
containing the salt or salts, for example, to be impregnated, and
thereafter drying the impregnated wick material until substantially
all of the solvent is removed. It is usually preferred to build up
the required amount of salt, for example, in the wick by passing
the wick through a series of relatively dilute solutions of the
salt, for example, followed by an intervening drying step until the
desired residuary salt concentration, for example, is obtained.
In order to improve the readability of an indicator device
employing a sheathed wick, the porous wick material can be
preliminarily impregnated with suitable color reagents or materials
which on contact with the absorbed liquid form color bodies
enabling simple visual determination of the length of penetration
of the liquid therealong. An example of such a coloring system
comprises a porous wick impregnated with potassium thiocyanate and
a liquid supplied either from an independent or integrally
connected reservoir comprising a water solution containing
dissolved ferric chloride. As the liquid is absorbed by the wick,
the ferric ion reacts with the thiocyanate to form a deep
red-colored compound comprising a complex ion. The distinctive red
color travels with the interface giving a pronounced visual
indication of the rate of travel and amount of penetration of the
liquid. Another suitable coloring impregnant would be a
conventional soluble dye which dissolves in the liquid as it
advances through the wick. Suitable dyes of this type include
Patent blue VS technical, Water violet 4BN technical, Medium green
N technical, and the like. The dissolving of the Patent blue dye in
water, for example, produces a bright blue distinctive color which
generally concentrates at the interface or advancing portion of a
liquid producing a bright blue distinctive mark. Alternate suitable
indicator dyes can be employed which are invisible in ordinary
light but which provide a distinctive color indication when
subjected to ultraviolet light, for example, providing thereby a
hidden, selectively readable indication.
The sheathed wick construction hereinbefore described having a
preselected porosity and geometrical configuration, employed in
combination with a liquid of known physical characteristics and
modified if desired by incorporating suitable color indicators or
impregnants in the porous wick material and dissolved in the liquid
to achieve satisfactory indication and viscosity control can be
employed for a large variety of different indicator devices several
of which are herein specifically described in detail. One useful
application of the sheathed wick construction is illustrated by an
elapsed time indicator device indicated at 194 in FIGS. 36 through
38 and comprising a capillary material 196 laminated between a pair
of plastic films 198 which is formed so as to provide a capsule or
reservoir 200 in which a suitable liquid is contained. The
reservoir 200 is connected to the feed-end portion of the wick
material 196 by means of a small conduit or tube 202 which may be
provided with suitable valve means on the opening of which the
timing sequence commences. In the specific elapsed time indicator
194 shown in FIGS. 36-38, the tube 202 is provided with a removable
plug generally indicated at 204 at the outlet of the reservoir 200
which on withdrawal from a closed position shown in FIG. 37 to an
open position shown in FIG. 38 releases the liquid and initiates
the timing action.
The wick material 196 is suitably calibrated in appropriate time
units such as hours, for example, to indicate the elapsed time
period since the initiation of the timing cycle. Suitable coloring
agents and other impregnants such as the salts hereinbefore
described, can be incorporated in the wick material 196 as well as
dissolved in the liquid to maintain a substantially constant
viscosity-surface tension relationship over the temperature range
to be encountered.
Another satisfactory indicator device is illustrated in FIGS. 39
and 40 incorporating therein the principles of the present
invention. The indicator device 206 comprises a wick material 208
having the lower end portion thereof connected by means of a tube
210 to a liquid reservoir 212 formed in an overlying plastic sheet
213 tenaciously adhered to a paperboard backing sheet 214 which is
provided with an impervious coating on the surface thereof on which
the wick material 208 is positioned. The indicator device 206 is
provided with valve means comprising a removable plug 216 of the
same type employed in the time indicator device 194 shown in FIGS.
36-38 which on movement to an open position initiates the
temperature-time-measuring function.
Still another typical indicator device generally indicated at 218
in FIGS. 41 and 42 is shown which is operative to generate an
electrical signal when the timing function has been completed. The
indicator device 218 comprises a sheathed wick material 220, the
lower end of which is connected by means of a tube 222 to a
reservoir 224 containing an electrolyte. The upper end of the
sheathed wick material 220 terminates in a multiple plate battery
226 as best seen in FIG. 42 comprising alternate sheets of copper
and zinc, for example, indicated at 228, which are separated by
sheets of the porous wick material 230 connected to the principal
wick material 220. Conductors 232 are connected to the battery 226
and in turn are connected to a suitable control relay to be
energized thereby. Initiation of the timing function, for example,
is accomplished by withdrawing a movable stopper 234 to the open
position or other suitable valve means effecting a flow of the
electrolyte from the reservoir 224 to the inlet end of the sheathed
wick material 220. When the electrolyte advances to a position
wherein it is absorbed in the sheet of the porous wick material 230
disposed between the metal sheets 228, the circuit of the battery
is completed effecting generation of current which passes through
conductors 232 to a sensing device connected thereto. Arrangements
of this general type have enabled the generation of a signal
current at 2.5 volts at the completion of the timing function which
can be varied depending on the specific construction of the battery
226.
A similar electrical indicator device generally indicated at 236 is
illustrated in FIGS. 43 and 44. The indicator device 236 comprises
a sheathed wick material 238 connected at its lower end by a tube
240 to a reservoir 242 containing a suitable electrolyte or other
electrically conductive liquid. A pair of electrodes 244a, 244b are
disposed in spaced relationship and extend longitudinally along
each side of the sheathed wick material 238 as shown in FIG. 43.
The electrode 244a is disposed in fixed relationship relative to
the wick material 238 whereas the electrode 244b is longitudinally
movable adjustably presetting the indicator device to produce a
signal after a preselected expired time interval after the timing
function has been initiated. The electrodes 244a, 244b are
connected to a suitable current source and to a suitable control
relay which when the electrolyte advances to a position adjacent to
the downwardly extending end of the electrode 244b, completes the
circuit and the control relay is energized and is effective to
perform the desired control.
Another alternate satisfactory indicator device similar to the
indicator device 236 shown in FIGS. 43 and 44 is illustrated in
FIGS. 45 and 46 which is operative to complete an electrical
circuit on the completion of a predetermined time interval. The
indicator device 246 as shown in FIGS. 45 and 46 comprises a
sheathed wick material 248 incorporating an electrode 250 which
extends longitudinally along one side of the sheathed wick material
248. The upper end of the electrode 250 is connected by a suitable
conductor to control relay and a current source which in turn is
connected to an alligator-type clip 252. The clip 252 is provided
with piercing jaws and is selectively positionable at any
preselected position along the length of the sheathed wick material
248. The piercing jaws of the clip 252 are resiliently biased so
that when installed at a preselected position is operative to
puncture the sheathing material enclosing the wick material 248 and
become disposed in conductive contact with the wick material.
Initiation of the timing function is achieved by withdrawing a
movable plug 254 releasing an electrolyte or other suitable
conductive liquid in a reservoir 256 which is progressively
absorbed by the wick material. When the electrolyte attains a
position adjacent to the clip 252, a circuit is completed between
the clip 252 and the electrode 250 effecting energization of the
control relay which in turn is effective to perform the desired
control function.
While it will be apparent that the preferred embodiments herein
illustrated are well calculated to fulfill the objects above
stated, it will be appreciated that the invention is susceptible to
modification, variation and change without departing from the
proper scope or fair meaning of the subjoined claims.
* * * * *