U.S. patent number 3,640,434 [Application Number 05/037,809] was granted by the patent office on 1972-02-08 for variable capacity fluid-dispensing device.
This patent grant is currently assigned to Sherwood Medical Industries Inc.. Invention is credited to Clarence L. Walker.
United States Patent |
3,640,434 |
Walker |
February 8, 1972 |
VARIABLE CAPACITY FLUID-DISPENSING DEVICE
Abstract
A pipette or other device for measuring and dispensing liquids
which includes an aligned series of decreasing diameter, stepped
cylinder chambers, e.g., three, contained in a barrel with the
three chambers serviced by a common stepped piston for emptying and
filling a receiver or reservoir carried by the device in
communication with the chambers. A chamber at one end of the array
is maintained in unobstructed flow communication with the receiver
or reservoir which may or may not be a removable tip or nozzle on
the device. A vented passageway communicates with vent ports from
each chamber. A valving member is provided in the passage for
selectively venting one or more of the chambers or connecting them
in flow communication with the receiver or reservoir. In a specific
form, the passageway can be formed between the barrel and a sleeve
or collar surrounding the barrel which is rotationally slidable on
the barrel. The valving member can be in the form of an elliptical
ring on the inner surface of the sleeve or collar in sealing
sliding engagement with the barrel outer surface, the ports of two
of the other chambers falling between the longitudinal extents of
the elliptical ring; and the center of the elliptical ring being
located between the two ports. Rotation of the sleeve to a position
placing the ring between the port vents one port while placing the
other in flow communication with the nozzle, and rotation of the
sleeve 90.degree. one way or the other vents both ports or places
both in flow communication with the nozzle to increase or decrease
the liquid handling capacity of the device depending on the
direction of rotation.
Inventors: |
Walker; Clarence L. (Webster
Groves, MO) |
Assignee: |
Sherwood Medical Industries
Inc. (St. Louis, MO)
|
Family
ID: |
21896464 |
Appl.
No.: |
05/037,809 |
Filed: |
May 15, 1970 |
Current U.S.
Class: |
222/144.5;
73/864.17; 73/864.18 |
Current CPC
Class: |
G01F
11/06 (20130101) |
Current International
Class: |
G01F
11/06 (20060101); G01F 11/02 (20060101); B67d
005/02 () |
Field of
Search: |
;222/309,386,387,388,336,137,386.5,206,134,135,136,145,144.5
;128/218P,234,235,DIG.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reeves; Robert B.
Assistant Examiner: Bartuska; Francis J.
Claims
I claim:
1. A variable capacity measuring and dispensing device for a
liquid, comprising a body having a plurality of separate fluid
holding chambers each having a port therein, reservoir means
carried by said device and in communication with said chambers in
said body for receiving and holding a measured volume of said
liquid, a connecting passage having a vented end and connecting
said ports in generally linear flow communication between the
vented end and the reservoir means, means for selectively
delivering fluid into and from each chamber, and operable means for
selecting one or more chambers to be filled with said fluid and for
selectively blocking the flow of said fluid to the nonselected
chambers and for venting the nonselected chambers whereby only
selected chambers are filled with said fluid which draws an equal
measured volume of liquid into the reservoir means by operation of
the delivering means, said operable means for blocking said fluid
flow including a movable sealing member mounted for movement from a
position sealing the vented end from all ports whereby all chambers
are filled with said fluid which draws a measured volume of liquid
into the reservoir means by said delivering means, to positions
intermediate adjacent ports in said connecting passage whereby
nonselected chambers are vented through said vented end and only
selected chamber ports receive said fluid through said passage
which draws an equal volume of said liquid into said reservoir
means.
2. The device of claim 1, wherein said operable means includes
means retaining said blocking means against movement to a position
between the reservoir means and one of the chamber ports
communicating with said passageway.
3. A variable capacity measuring and dispensing device for a
liquid, comprising a stepped barrel having a plurality of separate
fluid-holding cylinders approximately of equal length and formed as
a linear array in order of decreasing diameter and volume in said
barrel, means for selectively delivering fluid into and from each
cylinder, including displacement means mounted for concurrent
movement within said cylinders, said displacement means being in
the form of a common stepped piston movable between a retracted
position and a discharge position and having a discharge or
displacement element properly sized for each cylinder with the
discharge element for each cylinder positioned in the next larger
cylinder while the piston is in a retracted position and including
a port for each cylinder extending through the sidewall of the
barrel, reservoir means carried by said device and in communication
with said cylinders in said barrel, said reservoir means receiving
and holding a measured volume of said liquid, and operable means
including means for selecting one or more cylinders to be filled
with said fluid and for selectively blocking the flow of said fluid
to the nonselected cylinders and for venting the nonselected
cylinders whereby only selected cylinders are filled with said
fluid which draws an equal measured volume of liquid into said
reservoir means by operation of the delivering means, and said
operable means includes means for selectively connecting each of a
plurality of said ports to said reservoir means or venting to
atmosphere for varying the number of cylinders filled with fluid as
said reservoir means is filled with an equal volume of liquid
thereby varying the capacity of the device.
4. The device of claim 3, wherein said operable means comprises
means mounted on the outer surface of the barrel for movement
between a plurality of selectable positions, each representing a
different volume or capacity for the device and including sealing
means on the inner surface of said mounted means for sealing a
different number of said ports upon movement to each selected
position.
5. The device of claim 4, where said mounted means comprises a
collar surrounding the barrel over said ports.
6. The device of claim 5, wherein said collar is mounted for rotary
sliding movement of the outer surface of said barrel.
7. The device of claim 6, wherein the sealing means comprises an
elliptical sealing ring secured to the inside of said collar in
slidable sealing contact with the outer surface of said barrel and
wherein two of said ports for two adjacent chambers are spaced from
each other along the length of said barrel, the upper and lower
expanse of said ring along the length of the barrel being above and
below said two ports and the center of the extent of said ring
along the length of the barrel being between said two ports,
whereby rotation of the sleeve to position the center of the ring
between the two ports communicates the upper port with the upper
portion of the passageway between the collar and barrel and
communicates the lower port with the lower portion of the
passageway between the collar and barrel while rotation from said
center position 90.degree. in one direction communicates both ports
with the lower portion of the passageway and rotation of the sleeve
90.degree. from the center position in the other direction
communicates both ports with the upper portion of the
passageway.
8. The device of claim 7, wherein at least one of the plurality of
chambers has its port disposed below the lowermost extend of the
ring and said reservoir means is in direct flow communication with
said lower chamber.
9. The device of claim 7, wherein said reservoir means is a nozzle
on said sleeve in flow communication with the passageway between
the collar and barrel above the uppermost expanse of said sealing
means, and said plurality of chambers includes a chamber having its
port communicating with the passageway above the uppermost extent
of said sealing ring and of larger volume than the next lower
chamber, and means sealing the end of the passageway beyond the
nozzle and chamber outlet.
10. A variably capacity pipette for measuring and dispensing a
liquid comprising a body having a plurality of fluid chambers
therein, a movable plunger having a plurality of fluid displacement
means respectively disposed for fluid displacement movement in said
chambers, a reservoir for holding and dispensing said liquid,
passage means for establishing fluid communication between said
reservoir and said chambers, and selectively operable sealing means
in said passage means, said sealing means being movable to a first
position wherein one of said chambers is in fluid communication
with said reservoir and a second position wherein plural chambers
are in fluid communication with said reservoir thereby to
selectively vary the effective number of said chambers in fluid
communication with said reservoir to vary the volume of liquid
drawn into and dispensed from said reservoir.
11. The pipette according to claim 10, wherein said plurality of
chambers are disposed in a linear array and said displacement means
are disposed in a linear array.
12. The pipette according to claim 11, wherein said displacement
means are rigidly connected together.
13. The pipette according to claim 11, wherein said plurality of
displacement means are of different fluid displacement sizes.
14. The pipette according to claim 11, wherein said displacement
means comprises interconnected coaxial piston means of different
diameters, and said fluid is air.
15. The pipette according to claim 14, wherein at least one of said
piston means is movable in more than one of said chambers and all
of said piston means are concurrently movable.
16. The pipette according to claim 15, wherein each of said
chambers comprises a cylindrical bore having a stationary sealing
ring for each of said pistons means.
17. The pipette according to claim 10, wherein said plunger is
movable a predetermined distance to effect the drawing in of a
predetermined volume of liquid into said reservoir when said
sealing means is in said first position, and said plunger is
movable said same predetermined distance when said sealing means is
in said second position to effect the drawing in of a volume of
liquid into said reservoir which is different than said
predetermined volume, said fluid chambers are substantially
coaxial, and said plurality of fluid displacement means are
substantially coaxial.
18. The pipette according to claim 17, wherein said passage means
has an end vented to atmosphere, said sealing means when in said
first position venting to atmosphere and sealing from fluid
communication with said reservoir all of said chambers except said
one chamber, said sealing means when in said second position
sealing said plural chambers from atmosphere.
19. The pipette according to claim 18, wherein said chambers
comprise a plurality of cylinders in a linear array, and said
plurality of displacement means comprise a plurality of pistons of
different sizes rigidly connected together in a linear array.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to variable capacity liquid measuring and
dispensing devices and more particularly to a new and improved
variable capacity pipette.
2. Description of the Prior Art
One type of prior variable capacity pipette utilizes an adjustable
stroke, single piston to attain different capacities. However, when
such a device is provided for measuring and dispensing three
different volumes it can require a stroke change of up to 4 to 1 or
5 to 1 and a hand operating device of such a stroke change can be
quite uncomfortable to the operator. Variable stops are often
employed in such devices but suffer from increased inaccuracy on
use.
SUMMARY OF THE INVENTION
The present invention provides a variable capacity liquid measuring
and dispensing device which utilizes the same liquid delivery
actuator, e.g., a common plunger, for each capacity handled. The
device of the present invention has a common receiver or reservoir
for receiving a plurality of different volumes loaded by operation
of separate chambers with a separate port for each chamber which
can be selectively communicated with the common receiver or
reservoir for selective delivery of different volumes of liquid
into the receiver or reservoir each time the actuator is
operated.
While illustrative embodiments of the invention are shown in the
drawings and will be described in detail herein, the invention is
susceptible of embodiment in many different forms, but it is to be
understood that the present disclosure is used as an
exemplification of the principles of the invention and is not
intended to limit the invention to the embodiments illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary perspective view of the device of this
invention shown in use for drawing liquid from a container into the
receiver or reservoir of the device;
FIGS. 2 and 3 are enlarged fragmentary longitudinal sections
through the upper portion of the device of FIG. 1 showing the
device with its plunger in retracted and depressed positions
respectively;
FIGS. 4 and 5 are enlarged longitudinal sections through the lower
portions of the device as seen in FIGS. 2 and 3 respectively;
and
FIG. 6 is a fragmentary section through another device of this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a pipette 10 as an embodiment of the present invention
with a receiver or reservoir which may be either a fixed tip or
nozzle, or as shown is a removable tip or nozzle 12 having its
outlet end immersed in liquid 16 in a container 14, for drawing
measured amounts of liquid into the tip or nozzle of the
pipette.
As better seen in FIGS. 2 through 5, the pipette is of the type
having a barrel 20 with a bore in which a reciprocal plunger 22 is
slideably mounted. A knob 24 is provided at the upper end of the
plunger for operating the plunger. The upper end of barrel 20 is
closed by a retaining cap 26 through which the plunger 22 slidably
projects. A return compression coil spring 28 surrounding the
plunger 22 is supported by a spring support shoulder 32 within
barrel 20 and extends upwardly and biases against a shoulder
surface 30 defined by an outwardly projecting flange on plunger 22.
A special arrangement is provided whereby the cap 26 can be turned
relative to the barrel 20 so as to lengthen or shorten the stroke
of the plunger for varying the initial volume of material drawn
into the nozzle or tip.
An enlargement 34 is provided on plunger 22 for centering plunger
22 within the bore of the barrel 20 during its reciprocal stroke
travel below shoulder 32. Enlargement 34 also functions as an
element of a stroke-modifying system so that an extra length of
thrust stroke can be given to plunger 22 during discharge of the
device, compared with the stroke given to evacuate the device
preparatory to filling. Accordingly, considering FIGS. 2 and 4 with
the plunger in its retracted position, a compression spring 36, of
greater strength than return compression spring 28, is provided
around plunger 22 and is supported in a cup fitting 38 through the
bottom of which plunger 22 slideably extends. Spring 36 is capped
in a cap fitting 40 which is slideably received on plunger 22 and
is axially slidable within the barrel 20.
The top of cap fitting 40 is spaced below enlargement 34, with the
plunger in retracted position, a distance equal to the evacuation
stroke for readying the device for drawing up liquid. Accordingly,
to evacuate the device and prepare for drawing up liquid the knob
24 is urged downward until enlargement 34 seats against the upper
surface of cap fitting 40 and the increased resistance of spring 36
is encountered by the user. The end of the tip or nozzle 12 seated
on the end of the device is then placed beneath the level of the
liquid and the pressure on knob 24 is released to permit spring 28
to return plunger 22 to the position shown in FIGS. 2 and 4. The
nozzle or tip of the device is now filled with liquid. To discharge
the liquid, the plunger 22 is again depressed and when the
resistance of spring 36 is felt the plunger is depressed even
further until the rim of cap fitting 40 engages the rim of cup
fitting 38, spring 36 being compressed therebetween as shown in
FIG. 5, thereby adding to the discharge stroke to assure complete
discharge of all liquid in the nozzle or tip of the device. On
release of pressure on knob 24, both springs 28 and 36 return to
their normal or rest positions as in FIGS. 2 and 4 with the plunger
22 retracted.
As best seen in FIGS. 4 and 5 the liquid drawing system for the
device includes a plurality of three axially aligned cylindrical
chambers 42, 44 and 46 of equal length and of decreasing diameter
in linear order from top to bottom. The top of each chamber is
sealed by a sealing ring or O-ring 48, 50 or 52 of proper size
sealing against the outer surface of the portion of plunger 22 to
be used to displace the predetermined volume of air or fluid from
the respective chamber. Each of chambers 42, 44 and 46 is provided
with a laterally extending port 54, 56 and 58 through the sidewall
of barrel 20 and in flow communication with an annular passage 60
defined between a reduced portion 62 in the outer surface of barrel
20 and a collar 64 slidably fitted in the reduced portion 62. The
bottom end of passage 60 is sealed with a sealing O-ring 66 beyond
the lowermost port 58 and the upper end of passage 60 is vented to
atmosphere at 67.
An elliptical groove 68 receives and retains an elliptical sealing
ring 70 at the inner surface of collar 64 with sealing ring 70
sealing against the outer surface of barrel 20 in reduced portion
62. Because of its elliptical shape the ring 70 extends in groove
68 along the length of reduced portion 62 from a position above
port 54 on the right in FIGS. 4 and 5 to a position below port 56
on the left, shown (full lines) as position A in FIGS. 4 and 5.
With the sealing ring 70 in position A, both the ports 54 and 56
are vented to the atmosphere by passageway 60 and 67 thereby
venting both of chambers 42 and 44 to the atmosphere.
Turning collar 64 in an amount of 90.degree. in one direction will
cause the elliptical sealing ring to move to a position B (in
phantom in FIGS. 4 and 5) lying between ports 54 and 56 so that
only port 54 is vented at 67 to atmosphere while port 56
communicates with the passageway 60 below the sealing ring 70 and
is in air or fluid flow communication with port 58. Turning collar
64 in the same direction another 90.degree. will move ring 70 to
position C (again in phantom in FIGS. 4 and 5) blocking the
passageway 60 above port 54 so that both ports 54 and 56 are in air
or fluid flow communication with port 58 and both are sealed
against venting at 67. The plunger 22 is stepped at shoulders 72
and 74 to provide reduced diameter piston portions 22a and 22b for
operation in the decreased diameter chambers 44 and 46
respectively. Although the plunger 22 is continually sealed between
chambers 42, 44 and 46 by O-rings 48, 50 and 52, the outer surface
of the plunger does not seal against the interior of the cylinder
walls of the chambers 42, 44 and 46 during operation but rather
rides closely spaced from the walls during both upward and downward
movement.
During drawing of liquid into the receiver or reservoir which is
shown as the nozzle or tip 12 of the device with the elliptical
sealing ring 70 in position A (which is the minimum volume setting)
as the plunger is retracted to fill the nozzle or tip with liquid,
liquid is drawn up into the nozzle or tip in an amount equal to the
maximum displacement of plunger 22 in chamber 46 during the
downward or thrust stroke when the device is evacuated in
preparation for filling. During the discharge stroke the nozzle or
tip 12 is emptied. To increase the volume of the device the collar
64 is rotated 90.degree. to place the sealing ring 70 in position
B. Now when the plunger 22 is retracted during the filling
operation, suction for drawing liquid into the nozzle or tip is
also provided from passageway 60 and port 56 so that air or fluid
flows from chamber 46 through port 58, passageway 60, and port 56
to fill the space between the inner walls of chamber 44 and the
outer surface of piston portion 22b providing a volume of liquid in
the nozzle or tip equal to the sum of the displacements of plunger
22 in chambers 44 and 46 created during the filling stroke of
plunger 22. During a discharge stroke the flow of liquid from the
nozzle or tip is reversed and the new total volume is
discharged.
In order to further increase the capacity of the device for drawing
a still further increased total volume of liquid into the receiver
or reservoir 12, the collar 64 is rotated another 90.degree. to
place sealing ring 70 in position C. It will be seen that now
during a filling stroke air or fluid is drawn from passageway 60
through both of ports 54 and 56 to fill the annular portions within
chambers 42 and 44 surrounding plunger 22 while chamber 46 is also
being filled, thereby giving a total volume of liquid drawn into
the receiver or reservoir by the device equivalent to the sum of
the displacements created by the plunger 22 in chambers 42, 44 and
46 during the filling stroke. It will also be seen that at all
times while either or both of ports 54 and 56 are not being used
for liquid filling and liquid discharge purposes they are vented to
atmosphere by the upper portion of passageway 60, above the
position of ring 70, at 67 so that suction and compression forces
are not built up within the vented portions of the device during
its operation.
Fig. 1 shows collar 64 in a first position (position A) indicated
by the numeral 1 for handling a predetermined amount of liquid and
shows a second position (position B) indicated by the numeral 2 to
which the volume indicator on collar 64 can be turned for changing
the capacity of the device.
Turning now to FIG. 6, there is illustrated a modification of the
device. This modification handles its smallest selectable volume as
a difference in displacements between piston portions rather than
directly from the displacement of the smallest piston portion. In
this device the end of chamber 46a has been sealed as at 80 and the
receiver or reservoir 12a is connected with an offset discharge
portion 15 which is mounted on and forms a part of the rotatable
collar 64a and has a passage 17 which communicates directly with
the annular passage 60a. The annular passage 60a beyond the passage
17 of discharge portion 15 is sealed with an O-ring 66a, and port
54a from chamber 42a is provided adjacent discharge portion 15 and
between O-ring 66a and the elliptical sealing ring 70. A vent 67a
from passageway 60a is provided beyond sealing ring 70, this time
at the bottom end of collar 64a. In this embodiment the elliptical
sealing ring 70 is used to switch either or both of ports 56a and
58a from communication with either vent 67a or discharge portion 15
for changing the capacity of the device.
It will readily be seen that with ring 70 in position A in FIG. 6,
all chambers will be filled during operation of plunger 22 and the
device will draw the maximum amount of liquid into the nozzle or
tip 12a during its intake and discharge cycles, i.e., an amount
equal to the sum of the displacements of the plunger 22 in all
three chambers during the evacuation thrust stroke in preparation
for filling, less the displacement after filling. With ring 70
moved to position B, port 58a and chamber 46a are vented and during
the intake stroke a volume of air or fluid will be introduced into
both of chambers 42a and 44a around plunger 22 so that the volume
of liquid taken into the nozzle or tip 12a is approximately equal
to the sum of the displacements of plunger 22 in chambers 42a and
44a during the evacuation stroke in preparation for filling, less
the displacement of plunger 22 in these two chambers after filling.
If the device is operated with ring 70 shifted to position C, then
both of chambers 44a and 46a are vented to atmosphere and only the
annular space around plunger 22 in chamber 42a is filled with an
amount of air or fluid (which corresponds to the amount of liquid
drawn into the nozzle) equal to the displacement of plunger 22 in
chamber 42a created during the filling stroke of plunger 22.
Although the above specifically described embodiments use equal
length cylinders or chambers of varying diameters which are
selectively connected in flow communication with the nozzle or
vented to atmosphere, it is apparent that a variety of different
sizes and shapes of cylinders can be used. Additionally, although
each embodiment uses a linear array of three coaxial cylinders with
the sealing ring operating on the vents of two of the cylinders, it
will be apparent that a larger number of cylinders or chambers can
be provided in any one array and can be serviced by the same
movable collar. For example, either of the devices illustrated
above can be merely extended with additional chambers of decreasing
diameter and additional lengths of appropriately stepped piston.
The collar is correspondingly lengthened and one or more additional
elliptical sealing rings are provided on the inside of the collar
to operate in the same general manner with the outlet ports from
the additional chambers as the collar is rotated. Such additional
outlet ports may advantageously be in linear alignment with the
other ports or may be spaced circumferentially therefrom.
Also, in the illustrated devices the ports in each pair operated by
the elliptical ring are spaced lengthwise from each other. However,
the ring can also operate to open and close circumferentially
spaced ports as the ring is rotated, as will be evident to those
skilled in the art. Additionally, the sealing ring need not be
elliptical but can be circular or any other shape and can be
mounted in a collar which is axially slidable on the barrel rather
than rotatable thereon for selection of the variable
capacities.
* * * * *