U.S. patent number 3,906,513 [Application Number 05/263,699] was granted by the patent office on 1975-09-16 for low-pressure inking system.
This patent grant is currently assigned to Beckman Instruments, Inc.. Invention is credited to Raymond M. Pawlak, Robert N. Quoss, Abe Siegelman.
United States Patent |
3,906,513 |
Siegelman , et al. |
September 16, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Low-pressure inking system
Abstract
A low-pressure inking system for oscillographic pen recorders is
disclosed in which the pen is biased against the recording medium
(paper) at low pressure so that special pen motors are unnecessary.
The system includes a low-viscosity aqueous ink containing a glycol
ether, a coloring agent and a soluble resin such as
polyvinylpyrrolidone or polyethylene oxide. Low stylus tip pressure
may be used so that the pen motor driving torque required to obtain
good writing without hysteresis is substantially less than with
conventional pressurized ink writing systems and retrofitting of
conventional capillary recorders is made possible.
Inventors: |
Siegelman; Abe (Morton Grove,
IL), Quoss; Robert N. (Clarendon Hills, IL), Pawlak;
Raymond M. (Addison, IL) |
Assignee: |
Beckman Instruments, Inc.
(Fullerton, CA)
|
Family
ID: |
26728493 |
Appl.
No.: |
05/263,699 |
Filed: |
June 16, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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50652 |
Jun 29, 1970 |
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Current U.S.
Class: |
346/140.1;
524/376; 106/31.58 |
Current CPC
Class: |
C09D
11/16 (20130101) |
Current International
Class: |
C09D
11/16 (20060101); G01D 015/16 () |
Field of
Search: |
;106/22,23 ;346/140 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hayes; Lorenzo B.
Attorney, Agent or Firm: Mason, Kolehmainen, Rathburn &
Wyss
Parent Case Text
This application is a continuation of applicants' copending
application Ser. No. 50,652, filed June 29, 1970, now abandoned.
Claims
We claim:
1. A low-pressure hydrostatic writing system which comprises a
record medium with an effectively absorbent surface, a pen having a
tubular tip section biased against the surface of said record
medium forming a closure therewith during writing operations, an
ink having a viscosity in the range of about 1-30 cps within said
pen, said ink comprising 20% to 35% by weight ethylene glycol
monomethyl ether, a water-soluble coloring agent and a
water-soluble resin selected from the group consisting of
polyvinylpyrrolidone and polyethylene oxide, the amount of
polyvinylpyrrolidone being 0.1% to 5% by weight and the amount of
polyethylene oxide being 0.01% to 0.3% by weight, a hydrostatic
head for applying a pressure of less than about 2 psig. to said ink
during a writing operation sufficient to force said ink through the
tip of said pen and against the surface of said record medium to
cause said ink to be absorbed in the surface of said record medium,
and means biasing said tubular pen against said record medium with
a force of about 1-3 grams.
2. A low-pressure hydrostatic writing system which comprises a
record medium with an effectively absorbent surface, a pen having a
tubular tip section biased against the surface of said record
medium forming a closure therewith during writing operations, an
ink having a viscosity in the range of about 1-30 cps within said
pen, said ink comprising a major proportion of water containing 10%
to 40% by weight of a water-soluble ether of ethylene or diethylene
glycol of the formula R--(OCH.sub.2 CH.sub.2).sub.n --OH wherein R
is hydrocarbon radical containing one to six carbon atoms and n is
an integer from one to two, inclusive, a water-soluble coloring
agent and a water-soluble resin selected from the group consisting
of polyvinylpyrrolidone and polyethylene oxide, the amount of
polyvinylpyrrolidone being 0.1% to 5% by weight and the amount of
polyethylene oxide being 0.01% to 0.3% by weight, a hydrostatic
head for applying a pressure of less than about 2 psig. to said ink
during a writing operation sufficient to force said ink through the
tip of said pen and against the surface of said record medium to
cause said ink to be absorbed in the surface of said record medium,
and means biasing said tubular pen against said record medium with
a force of about 1-3 grams.
Description
GENERAL DESCRIPTION OF INVENTION
This invention relates to an improved ink and hydrostatic inking
system useful in oscillographic pen recorders and the like. In
particular, it relates to a low-pressure hydrostatic inking system
including a low-viscosity ink under a low hydrostatic head.
In the past the usual pen recorder of the oscillographic type used
a liquid ink to write on a moving paper chart. This system had many
advantages over electric writing and photographic systems in that
it was relatively inexpensive and was instantaneous. However, it
for years has suffered from many disadvantages. These disadvantages
were sufficiently great that for many applications electric writing
is used in spite of the high cost of the record medium;
photographic devices are employed even though the film is expensive
and has to be developed over a period of time; special ultraviolet
recorders are used; and chemical recorders are used with heat; and
straight heat recorders are used.
The chief disadvantages of the inking system as it was heretofore
known have been due to the liquid ink which was used. This liquid
ink had to dry quickly after it was applied to the moving record
medium because otherwise it would smear as the paper was rolled up
and the operator would often touch the wet ink causing loss of
accuracy of the record, unsightly records, etc. The quick drying
quality which was so highly desirable when the ink was applied to
the chart paper was a tremendous disadvantage when the pen recorder
was not used for a while, as it caused clogging of the small hole
in the tip of the pen and consequently the pen often would not
write when the instrument was first started. Systems were employed
to force the ink out of the pen tip to clear the passageway so that
the capillary forces involved in the pen and in the tube connecting
the liquid ink supply to the pen would thereafter supply adequate
ink for writing on the moving paper.
Another disadvantage inherent in the liquid ink system is that the
rapidly oscillating pen tip would often throw drops of ink around
the room.
A further disadvantage of prior systems is that certain of them
(e.g., Brown Re. 25,692, Dec. 1, 1964) have required high-viscosity
ink which had to be forced through the equipment under relatively
high pressure. Such systems necessarily included pumps or
pressurized gases which forced the ink through ducts to tubular
pens. Generally the tubular pens were arranged so that the pen tips
were held against record paper or similar material with substantial
biasing force, and the ink under relatively high pressure was
extruded against the record paper and sheared off as the pen tip
moved relative to the latter. These systems have required special
high-powered pen motors to move the pens which are biased against
the record media.
The system of the present invention is an inking mechanism, having
all the advantages of the previous liquid ink systems in that it is
relatively inexpensive and is instantaneous, and in addition the
new system obviates the disadvantages inherent in such liquid ink
systems.
An object of the present invention is to provide a low-pressure
hydrostatic inking system which does not require high viscosity
ink, high pressure ink-supplying equipment, high biasing force on
the pen tip or a special pen motor to activate the biased pen.
A further object of the invention is to provide low viscosity inks
for use in such low-pressure hydrostatic inking systems.
Another object is to provide a low-viscosity ink which has adequate
capillary strength suitable for use in low-pressure inking systems,
which is rapidly absorbed by most types of paper, and which does
not smear or "feather" on the paper.
Still another object is to provide a low-viscosity ink which is
stable on storage at high and low pressures, does not bleed from
pen tips, even when left in contact with paper for extended
times.
A still further object is to provide a low-viscosity ink which does
not splatter when the pen is moving rapidly or erratically.
These and other objects are apparent from and are achieved in
accordance with the following disclosure, taken in connection with
the attached drawing in which the single FIGURE illustrates a
typical low-pressure inking system arrangement of the present
invention.
Referring now to the drawing, the low-pressure, low viscosity
inking system of the present invention is herein illustrated as
comprising a pen motor, indicated generally at 10, which is
arranged to be energized by any suitable electrical signal and
provides rotation of the output shaft 12 thereof in proportion to
the amplitude of said electrical input signal. A pen arm 14 is
pivotally mounted on a carriage 16 secured to the upper end of the
shaft 12 and is provided with a right angle pen tip portion 18
which is biased against the chart paper 20 by means of the spring
clip member 22. Upon rotation of the shaft 12 the pen tip 18 is
moved transversely of the paper 20 and ink stored in the chamber 24
is drawn out of this chamber through the tubing 26 and pen conduit
28 so that a fine, brilliant line is made on the paper 20
corresponding to the electrical input signal. Preferably, the
tubing 26 is of polyethylene or butyl rubber and the conduit 28 is
of stainless steel or inconel to avoid undesired interaction with
and possible clogging of the ink described in detail hereinafter.
The vertical position of the chamber 24 may be adjusted by means of
a clamp member 30 to provide any desired gravimetric head but it is
pointed out that the ink described hereinafter will function
satisfactorily even under negative pressure, i.e., when the level
of ink in the chamber 24 is below the pen tip 18.
In the illustrated embodiment the chart paper 20 is of the Z-fold
type, a pack 32 of this type of paper being stored below the
writing table 34 and being pulled tautly over the surface of this
table by any suitable drive means. It is pointed out, however, that
the chart paper may be of the roll type without folds. Also, in
accordance with an important feature of the invention, the ink
described hereinafter may be used with chart paper 20 of either the
coated or uncoated type. When used with low-cost, uncoated paper
the ink does not splatter and yet provides a high contract,
brilliant record trace which is comparable to that obtained with
coated paper except for the high gloss of the paper itself. The
inking system of the present invention is also particularly suited
for use with coated paper of the Z-fold type because the low stylus
pressure requirements of the pen tip 18 and the particular
characteristics of the ink described hereinafter accomodate the
fold portions of this type of paper and the loose paper fibers
which are usually present therein without clogging of the pen tip
or interfering with the free flow of ink therefrom. A jewel pen tip
18 having a rounded bottom edge is preferably employed with this
type of paper to let the pen slide over the paper folds easily.
Furthermore, the fact that the spring clip 22 need exert only a
slight baising force on the pen tip 18 means that the torque
requirements imposed on the pen motor 10 are relatively small, as
compared to high-presssure, high-viscosity inking systems such as
shown in Brown U.S. Pat. No. Re. 25,692, and hence conventional
capillary ink systems with non-servo type galvanometers may be
adapted to use coated, high gloss paper without requiring a change
in the pen motor or driver electronics associated therewith.
In accordance with the present invention it has been discovered
that low viscosity (i.e., 1-30 cps.) inks containing a major
proportion of water and minor proportion of an alkylene glycol
ether and a water-soluble resin are particularly desirable in
low-pressure inking systems. Such inks do not spatter during
operation of the equipment and effectively dry very rapidly, thus
avoiding feathering and smearing, and can be used on coated
recording paper, such as Kromekote paper, Trycite paper and similar
high gloss paper, uncoated papers such as sulfite and sulfate
papers, tissue paper, newsprint, tracing vellum, and films of
polyamide. Moreover, such low viscosity inks can be fed to the pen
tip under ordinary gravity pressure (0-8 inches), thus avoiding
pumps and other pressurizing equipment called for by prior inking
systems, and they can even be used at zero or negative pressure at
lower writing rates by reason of their capillary strength. As a
consequence, low stylus pressure (1-3 grams) is suitable to produce
sharp recordings and high torque pen servomotors and position
transducers are unnecessary.
The preferred viscosity of the ink is 5-10 cps. at 20.degree.C.
This ink can be supplied to the pen tip under pressures of less
than 1/4 psig. Pressures up to 2 psig. are satisfactory for all of
the inks described herein.
The low viscosity ink contains a major proportion of water, and a
water soluble dye is used in the ink of a type which will not
greatly increase viscosity. The other essential components are a
glycol ether which generally constitutes from about 10% to 40% of
the weight of the ink, and a water-soluble resin such as
polyvinyl-pyrrolidone or polyethylene oxide.
The glycol ether is an alkyl ether of ethylene or diethylene
glycol, such as diethylene glycol mono-n-butyl ether, diethylene
glycol monomethyl ether and diethylene glycol monoethyl ether,
ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,
ethylene glycol mono-n-butyl ether and ethylene glycol monophenyl
ether.
The ink contains sufficient water-soluble dye to produce a colored
marking on paper or similar sheet material. Many such dyes are well
known and can be selected on the basis of desired color, stability
and compatibility with the other ink components.
A small percentage of a water-soluble resin such as
polyvinylpyrrolidone (PVP) is used to prevent splattering at high
speed pen travel. PVP is usually present in an amount from about
0.1% to 5% of the weight of the ink. It prevents breaking of the
capillary in the pen tip, reduces friction in the pen and tubing,
keeps the ink cohesive, aids in holding the dye in solution, and
prevents bleeding of the ink from the pen tip when the system is
not in use. Polyethylene oxide serves the same purposes and can be
substituted in smaller amounts for PVP. Usually the amount of
polyethylene oxide is from about 0.01% to 0.3% of the weight of the
ink. The preferred molecular weight range of this material is from
about 500,000 to 5,000,000; with higher molecular weights less of
the polyethylene oxide is required.
The aqueous, low viscosity ink is preferably neutral or slightly
alkaline. Sometimes the dye and other components produce an
alkaline solution, but in other situations it is often desirable to
adjust the pH of the ink to 7 or slightly higher (e.g. 7.5 to 8) by
adding traces of an organic amine such as ethanolamine. Other
nonvolatile, water-soluble amines can be used, such as
diethanolamine, propanolamine and the like. However, slightly
acidic inks with pH's between 6.5 and 7 are operative. Some inks
which are slightly acidic (e.g., pH 6) are suitable but usually
slightly alkaline inks are preferred.
It has been found in some cases that the addition of a small amount
of phenol or similar agent reduces or prevents the growth of
bacteria, mold and other microorganisms in the ink. These materials
need be present only in low effective amounts (e.g. 0.01 to 0.5%).
Usually they are not required because the glycol ether suppresses
the growth of bacteria and mold.
The following examples illustrate formulations of suitable inks for
the inking system of this application.
EXAMPLE 1
A low viscosity ink is produced from the following materials:
200 g. deionized water
100 g. diethylene glycol monobutyl ether
5 g. polyvinylpyrrolidone K-90 (PVP)
0.5 g. phenol
10 g. methyl violet dye (6B concentrate)
Sufficient ethanolamine to bring the pH to about 7.5.
The PVP is dissolved in the water with mixing, followed by the
glycol ether and phenol. Mixing is continued and the dye is sifted
into the vortex and completely dissolved. Then, ethanolamine (about
5 drops) is added dropwise with mixing until the pH is on the basic
side (7.5 to 8).
The viscosity of the ink so produced is in the range from 10 to 15
cps. The ink is filled and stored in bottles.
This ink and the other aqueous glycol ether inks described herein
are compatible with glycol-based inks such as the steam setting
inks widely used in printing lines on oscillograph recording sheets
and they form continuous lines over such inks.
EXAMPLE 2
Other suitable inks are produced by the procedure of Example 1 with
the following formulations:
A.
100 g. deionized water
50 g. diethylene glycol monobutyl ether
2.5 g. polyvinylpyrrolidone K-90
8 g. acid red 6BC dye
Viscosity, 16.2 cps.; pH, 9.7.
B.
100 g. distilled water
50 g. diethylene glycol monobutyl ether
2.5 g. PVP K-90
8 g. acid bright blue 2M dye
5 drops ethanolamine
Viscosity, 15 cps.; pH, 8.5.
C.
250 ml. distilled water
25 ml. diethylene glycol monobutyl ether
5 g. PVP K-90
0.5 g. phenol
10 g. methylviolet (6B) dye
11 drops ethanolamine
Viscosity, 15 cps., pH, 7.1.
D.
200 ml. deionized water
100 ml. diethylene glycol monobutyl ether
5 g. PVP K-90
0.5 g. phenol
10 g. methyl violet (6B) dye
13 drops ethanolamine
Viscosity, 16.8 cps.; pH, 6.85
E.
100 g. water
50 g. diethylene glycol monobutyl ether
2.5 g. PVP K-90
5 g. acid green (4L extra concentrated) dye
2 drops ethanolamine
Viscosity, 14.3 cps.; pH, 9.3
F.
100 g. water
50 g. diethylene glycol monobutyl ether
2.5 g. PVP K-90
8 g. acid green (4 LEX) dye
Viscosity, 15 cps.; pH, 6.1
EXAMPLE 3
A low-viscosity ink suitable for both sulfite and Kromecote papers
was made of the following materials:
150 g. water (deionized)
50 g. ethylene glycol monomethyl ether
6 g. Pontacyl violet S4B
0.125 g. polyethylene oxide WSR-301 (approx. mol. wt.
4,000,000)
The polyethylene oxide was dissolved in the water, followed by the
glycol ether and the dye. An intense violet ink, pH 8, viscosity 7
cps., was produced.
EXAMPLE 4
A green ink was produced by the procedure of Example 3 from the
following:
150 g. water
50 g. ethylene glycol monomethyl ether
6 g. Keco acid green 4LEX
0.125 g. polyethylene oxide WSR-301
It had pH 6.4 and viscosity 7 cps.
EXAMPLE 5
A red ink was produced by the procedure of Example 3 from the
following:
450 g. water
150 g. ethylene glycol monomethyl ether
18 g. Pontacyl carmine 2G
0.375 g. polyethylene oxide WSR-301
It had pH 9.7 and viscosity 6 cps.
EXAMPLE 6
A violet ink was produced from the following materials:
450 g. water
150 g. ethylene glycol monomethyl ether
0.375 g. polyethylene oxide WSR-301
12 g. Crystal violet 6B conc.
It was adjusted to pH 7.9 with two drops of ethanolamine; viscosity
6.5 cps.
EXAMPLE 7
The following formula produces a suitable red ink:
150 g. water
50 g. ethylene glycol monomethyl ether
6 g. Keco acid red 6BC
0.125 g. polyethylene oxide WDR-250 (approx. mol. wt. 600,000)
It had pH 9.7 and viscosity 7 cps.
The inks described in Examples 1 and 2 are particularly suited for
use on coated paper. The slightly lower viscosity inks described in
Examples 3 to 7, inclusive, write well on both coated and uncoated
paper, and other materials, without splattering or bleeding and
also exhibit slightly better non-clogging characteristics than the
inks of Examples 1 and 2.
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