U.S. patent application number 11/705688 was filed with the patent office on 2007-06-28 for microdispensing pump.
This patent application is currently assigned to Ben Z. Cohen.. Invention is credited to Ben Z. Cohen, Nigel Kelly.
Application Number | 20070145078 11/705688 |
Document ID | / |
Family ID | 36045398 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070145078 |
Kind Code |
A1 |
Cohen; Ben Z. ; et
al. |
June 28, 2007 |
Microdispensing pump
Abstract
A pre-compression pump (10) dispenses microdoses of fluid (F).
The pump minimizes pulsing due to pressure fluctuations. The pump
is provided with the following to limit pulsing: a low force slow
return velocity return spring (46); enlarged fluid passage (58);
elastic bumper (74); and, a rachet tooth (76) bearing against the
stem (44). Further, a deflectable diaphragm (90), a splined (70)
stem (44), no dip tube, and an off-center, gravitational low-point
pump inlet (62) assist in printing the pump. The pump includes a
stem (44) with deflectable fingers (92) to ensure sufficient
momentum in pump operation. Detents (118) and grooves (120)
selectively lock a nozzle cap (14) in an inoperative position. To
ensure cleanliness, nozzle (60) cleaning is provided, wiping of the
nozzle to remove meniscus (M) therefrom, cuts (104) formed in a
shroud (98) assist in drawing excess fluid from the nozzle, and an
empty volume (108) for collecting fluid run-off from the nozzle. A
handle (H) is mounted to the pump providing a grip.
Inventors: |
Cohen; Ben Z.; (New York,
NY) ; Kelly; Nigel; (Rye, NY) |
Correspondence
Address: |
HOFFMANN & BARON, LLP
6900 JERICHO TURNPIKE
SYOSSET
NY
11791
US
|
Assignee: |
Ben Z. Cohen.
|
Family ID: |
36045398 |
Appl. No.: |
11/705688 |
Filed: |
February 13, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11296974 |
Dec 8, 2005 |
7207468 |
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11705688 |
Feb 13, 2007 |
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10069682 |
Aug 7, 2002 |
7014068 |
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PCT/US00/23206 |
Aug 23, 2000 |
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11296974 |
Dec 8, 2005 |
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60150405 |
Aug 23, 1999 |
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Current U.S.
Class: |
222/321.7 |
Current CPC
Class: |
B05B 11/3052 20130101;
B05B 11/305 20130101; B05B 15/52 20180201; B05B 11/3061 20130101;
B05B 11/0044 20180801; B05B 11/3018 20130101; B05B 11/3059
20130101; B05B 11/0032 20130101; B05B 11/0037 20130101 |
Class at
Publication: |
222/321.7 |
International
Class: |
B65D 88/54 20060101
B65D088/54 |
Claims
1. A pump for dispensing fluid, said pump comprising: a pump body
having a pump cylinder and a fluid reservoir for accommodating the
fluid, an inlet being formed in said pump cylinder in communication
with said pump reservoir; and a nozzle.
2. A pump as in claim 1, wherein said pump cylinder is disposed
within, and extends substantially coextensively with, said fluid
reservoir.
3. A pump as in claim 2, wherein said inlet is located in proximity
to a wall of said fluid reservoir.
4. A pump as in claim 1, wherein said inlet solely defines a
passage for said fluid between said fluid reservoir and said pump
cylinder.
5. A pump as in claim 4, wherein said inlet is coextensive with
said pump cylinder.
6. A pump as in claim 4, wherein said inlet protrudes slightly from
said pump cylinder.
7. A pump as in claim 1, wherein said pump cylinder has a tubular
body with a cylindrical wall, a generally open first end, and a
generally closed second end, said inlet being formed in said second
end, and wherein said second end having an inner surface facing
said first end, said inner surface being obliquely disposed
relative to said cylindrical wall.
8. A pump as in claim 7, said inlet being formed off-center in said
second end so as to be located further from said nozzle than the
center of said second end.
9. A pump as in claim 8, wherein said inlet is located
gravitationally below said center point.
10. A pump as in claim 1, wherein said pump cylinder has a tubular
body with a cylindrical wall, a generally open first end, and a
generally closed second end, said inlet being formed in said second
end, and wherein said inlet being formed off-center in said second
end so as to be located closer to certain portions of said
cylindrical wall than other portions of said cylindrical wall.
11.-17. (canceled)
18. A pump for dispensing fluid, said pump comprising: a pump body;
an elongated stem slidably disposed in said pump body; and, a seal
immovably mounted relative to said stem, wherein said stem being
slidably, and at least partially sealably, disposed in said seal;
wherein, said stem is formed with spaced-apart longitudinally
extending splines with recesses being defined between said splines,
said splines defining an outer diameter which sealingly engages
said seal.
19. A pump as in claim 18, wherein said recesses are relatively
shallow.
20. A pump as in claim 18, wherein said stem has a
constant-diameter portion extending from said splines.
21. A pump as in claim 18, wherein said stem has a conical portion
extending from said splines.
22. A pump for dispensing fluid, said pump comprising: a pump body;
a piston slidably disposed with said pump body; a stem slidably
disposed within said piston; and, a return spring disposed to urge
said stem towards said piston, wherein said stem separates from
said piston in dispensing the fluid.
23. A pump as in claim 22, wherein said return spring is formed
with a relatively weak spring force so that said stem is separated
relatively easily from said piston.
24. A pump as in claim 22, wherein said return spring is wound to
have a reduced return velocity.
25. A pump comprising: a nozzle; a pre-compression pump means for
pumping fluid; and, a passage communicating said pump means and
said nozzle, said passage having cross-sectionally enlarged
portions.
26. A pump as in claim 25, wherein said passage has at least one
bend, said bend being cross-sectionally enlarged compared to
portions of said passage adjacent to said bend.
27. A pump for dispensing fluid, said pump comprising: a pump body;
a nozzle; a stem slidably disposed in said pump body, said stem
slidable in directions generally to and away from said nozzle; and,
a bumper disposed between said stem and said nozzle.
28. A pump as in claim 27, wherein said bumper is mounted to said
stem.
29. A pump as in claim 28, wherein said bumper is an
elastically-deformable dome-shaped member mounted onto an end of
said stem.
30. A pump as in claim 28, wherein said bumper is an
elastically-deformable member at least partially extending from an
end of said stem.
31. A pump for dispensing fluid, said pump comprising: a pump body;
a piston slidably disposed in said pump body; a stem slidably
disposed in said piston; and, at least one ratchet tooth disposed
on said piston, said ratchet tooth bearing against said stem.
32. A pump as in claim 31, wherein said ratchet tooth is generally
plate-shaped.
33. A pump as in claim 31, wherein said ratchet tooth has a
generally triangular profile with an edge of said ratchet tooth
bearing against said stem.
34. A pump as in claim 31, wherein said ratchet tooth bears against
said stem continuously.
35. A pump for dispensing fluid, said pump comprising: a pump body;
a nozzle cap operatively mounted to said pump body, a nozzle being
disposed in said nozzle cap; and, a shroud rigidly fixed to said
pump body, said shroud having an opening formed therethrough for
registering with said nozzle during activation so as to allow an
amount of dispensed fluid to pass through said shroud from said
nozzle, wherein said nozzle moves relative to said shroud during
operation, and wherein a portion of said shroud being disposed in
proximity to said nozzle such that any meniscus of the fluid formed
on said nozzle after dispensing is at least partially wiped by said
opening with said nozzle moving relative thereto.
36. A pump as in claim 35, wherein portions of said shroud disposed
about said opening and facing said nozzle cap are roughened.
37. A pump for dispensing fluid, said pump comprising: a pump body;
a nozzle cap operatively mounted to said pump body, a nozzle being
disposed in said nozzle cap; and, a shroud rigidly fixed to said
pump body, said shroud having an opening formed therethrough for
registering with said nozzle during operation so as to allow an
amount of dispensed fluid to pass through said shroud from said
nozzle, wherein a plurality of cuts are formed in said shroud about
said opening, said cuts being spaced-apart so that a plurality of
lands are formed about said opening.
38. A pump as in claim 37, wherein said cuts radiate from said
opening.
39. A pump as in claim 38, wherein said cuts taper apart in
radiating from said opening.
40. A pump as in claim 37, wherein said lands are roughened.
41. A pump for dispensing fluid, said pump comprising: a pump body;
a nozzle cap operatively mounted to said pump body, a nozzle being
disposed in said nozzle cap; and, a shroud rigidly fixed to said
pump body, said shroud having an opening formed therethrough for
registering with said nozzle during operation so as to allow an
amount of dispensed fluid to pass through said shroud from said
nozzle, said shroud partially encompassing an empty void defined
externally of said nozzle cap and about said nozzle.
42. A pump as in claim 41, wherein said nozzle protrudes from said
nozzle cap so as to define a free end spaced from said nozzle
cap.
43. A pump as in claim 42, wherein said free end of said nozzle is
rounded.
44. A pump as in claim 43, wherein said free end is rounded with a
radius of 0.005 inches.
45. A pump as in claim 42, wherein said free end is roughened.
46. A pump for dispensing fluid, said pump comprising: a pump body;
a nozzle cap operatively mounted to said pump body, a nozzle being
disposed in said nozzle cap; and, a shroud rigidly fixed to said
pump body, said shroud having an opening formed therethrough for
registering with said nozzle during operation so as to allow an
amount of dispensed fluid to pass through said shroud from said
nozzle, wherein said nozzle cap is rotatable relative to said
shroud, at least one detent being formed on one of said shroud and
said nozzle cap, at least one groove being formed to receive in
seating engagement said detent, and wherein said groove is
positioned to receive said detent in seating engagement with said
nozzle being rotated away from said opening into a locked
position.
47. A pump as in claim 46, wherein at least two pairs of detents
and grooves are provided.
48. A pump as in claim 46, wherein said nozzle cap is formed with a
solid portion in registration with each of said detents in said
locked position, the registration of said detents and said solid
portions preventing activation of said nozzle cap.
49. A pump for dispensing fluid, said pump comprising: a pump body
having a wholly contained fluid reservoir; and, a tubular handle
extending from said pump body.
50. A pump as in claim 49, wherein said handle has a closed
end.
51. (canceled)
52. A pump for dispensing fluid, said pump comprising: a pump body;
a nozzle cap operatively mounted to said pump body, a nozzle being
disposed in said nozzle cap; and a shroud rigidly fixed to said
pump body, said shroud having an opening formed therethrough for
registering with said nozzle during operation so as to allow an
amount of dispensed fluid to pass through said shroud from said
nozzle, wherein said nozzle cap is rotatable relative. to said
shroud, wherein said nozzle cap being formed with at least one
radially extending sealing member, said shroud being formed with at
least one inwardly extending shroud sealing member, said sealing
members being located to overlap with said nozzle cap being rotated
to a pre-determined position relative to said shroud.
53. (canceled)
Description
[0001] This application claims priority of U.S. Provisional Patent
Application Ser. No. 60/150,405, filed Aug. 23, 1999.
[0002] This invention relates to pumps for dispensing fluids and
medications, and, more particularly, to microdispensing pumps.
[0003] In the prior art, positive displacement and pre-compression
pumps are known. In addition, U.S. Pat. No. 5,881,956, to the
inventors herein, discloses a positive displacement pump which is
capable of dispensing microdoses of fluid, as small as 5-10
microliters. U.S. Pat. No. 5,881,956 is incorporated by reference
herein. With such small dosing capability, the pumps of U.S. Pat.
No. 5,881,956 are advantageously usable to dispense opthalthmic
medication. Although some of the teachings of U.S. Pat. No.
5,881,956 can be applied to the pre-compression pump art, there are
significant differences between the pumps which prevent full
carry-over of the technology.
[0004] A pre-compression pump operates on the principle that the
pressure build-up within a pump cylinder propels a fluid out of the
pump. The ejection of the fluid drains the pump cylinder thereby
causing a pressure differential which results in additional fluid
being drawn into the pump cylinder. In contrast, a positive
displacement pump relies on one dose of fluid literally "pushing"
out, and thus causing ejection of, a preceding dose of fluid.
[0005] As can be appreciated, the consistent dispensing of
microdoses (5-10 microliters) of fluid presents a unique set of
problems. The problems of priming pumps with such small doses with
positive displacement pumps are addressed in U.S. Pat. No.
5,881,956. Because of the difference in operating principles
between positive displacement pumps and pre-compression pumps, the
disclosure of the aforementioned patent can not be fully applied to
pre-compression pumps to achieve microdosing of 5-10 microliters.
For example, it has been found that fluids generally pulse upon
dispensing from a pre-compression pump because of pressure
fluctuations, the pulsing action resulting in atomization of the
dispensed fluid. Particularly, pressure fluctuations are generated
during pump operation, where a pressure build-up within the
cylinder of the pump causes the stem of the pump to separate from
the piston, thereby allowing pressurized fluid to rush into, and
out of, the nozzle of the pump. However, upon initial separation of
the stem from the piston, the pressure within the cylinder quickly
decays, with the stem being urged back into sealing contact with
the piston by a return spring. The fluid is then quickly
re-pressurized in the cylinder, again causing separation of the
stem from the piston, thus, achieving further fluid delivery. This
repeated "opening" and "closing" of the pump cylinder occurs
rapidly with the dose being continuously and interruptedly
delivered. The internal pressure of the dose, however, fluctuates
as it is dispensed causing the dispensed fluid to pulse.
[0006] With typical uses of pre-compression pumps, pulsing does not
interfere with the required atomization of the dispensed liquid.
Typical doses are relatively large, and, thus, are substantially
insensitive to the pressure fluctuations; pre-compression pumps
generally dispense doses much larger than 10 microliters, with such
doses being on the order of at least 70 microliters. Where it is
desired to consistently dispense microdoses of fluid without
atomization, such as with ophthalmic medication, pressure
fluctuations have an adverse effect. Furthermore, medication is
ideally delivered in a stable, relatively laminar flow pattern,
with little pressure fluctuation throughout dosage delivery.
Atomization of the fluid is not desired.
[0007] Accordingly, it is an object of the subject application to
provide a pre-compression pump capable of consistently dispensing
repeated microdoses of fluid and medication without
atomization.
SUMMARY OF THE INVENTION
[0008] The aforementioned object is met by a pre-compression pump
having various inventive features. It should be noted that some of
the features can be carried over to other pump arts beyond the
field of pre-compression pumps, such as lift pumps.
[0009] In a first aspect of the invention, the pump includes
features to minimize the pulsing effect caused by pressure
fluctuations in a pre-compression pump, thereby avoiding
atomization in dispensing a fluid. Specifically, the pump is
provided with various elements which restrict the responsive
movement of the stem so that the stem does not quickly respond to
the pressure fluctuations in the pump cylinder. Accordingly, the
stem will respond relatively slowly to the decay of internal
pressure of the cylinder, thereby prolonging the uninterrupted
delivery of fluid without pulsing and allowing for a laminar
delivery. First, a return spring is provided to urge components
into a rest position which is formed with a low spring force and/or
is wound to have a slow return velocity (typical coil springs are
wound to have high return velocities). Accordingly, the spring will
react weakly/slowly to pressure decay within the pump cylinder with
the stem being urged into a closed position relatively slowly as
compared to the rate of pressure decay. Second, portions of the
fluid passage communicating the pump cylinder and the nozzle are
enlarged so as to reduce restriction to flow, thereby minimizing
throttling of the fluid, and to provide a damping effect on the
fluid. The reduction in throttling and the damping effect coact to
reduce pulsing in the fluid. Third, an elastically-deformable
bumper may be disposed on the end of the stem of the pump. The
bumper, which may be in the form of a deflectable dome or a solid
member, is disposed on an end of the stem so as to absorb, and
react to, pressure of the fluid, thereby minimizing the stem's
reaction to fluid pressure. Fourth, an internal seal may be formed
with a generally triangular cross-section to increase fluid drag on
the stem and further inhibit movement of the stem. Fifth, a ratchet
tooth may be disposed on the pump piston which bears against the
stem and inhibits movement of the stem, thereby also reducing the
stem's reaction to fluid pressure.
[0010] In addition, in a second aspect of the invention, priming of
the pump is a concern, since a relatively minor air pocket will
inhibit, or altogether prevent, the ability of the pump to dispense
microdoses. To aid in proper priming, a partially splined stem is
preferably used, wherein shallow recesses are formed between the
splines. The recesses are sufficiently shallow such that air
bubbles may pass between the splines via the recesses, but
un-pressurized fluid will not because of its viscosity. As such,
air bubbles may escape without hindering operation of the pump.
Also no dip tube is utilized, thereby eliminating the possibility
of an air pocket being trapped in the dip tube. During priming of a
pump with a dip tube, a sufficient amount of fluid must be drawn
from the dip tube to ensure no air pockets are therein. Air pockets
are compressible and inhibit, or defeat, continuous operation of a
pump. Without a dip tube, an inlet is formed in the pump cylinder
which is in direct communication with the fluid reservoir of the
pump. Preferably, the inlet is located off-center in the pump
cylinder and at a low point on a tapered surface. With the off-set
location and tapered surface, air bubbles will not become entrapped
at the bottom of the cylinder, and the air bubbles will have an
unobstructed path up along the outside of the pump cylinder to
escape the pump. In addition, a deflectable diaphragm may be
provided which is deflectable into the fluid reservoir to reduce
the volume thereof.
[0011] Furthermore, in a third aspect of the invention, the pump
includes a stem formed with deflectable fingers that yield under a
pre-determined amount of operational force thereby ensuring
sufficient momentum is provided in operating the pump. In this
manner, the pump can only be operated with sufficient force to
ensure full and proper fluid dispensing.
[0012] In a fourth aspect of the invention, cleanliness of the pump
is of concern. Cooperative detents and grooves are formed to
selectively lock the nozzle cap in an inoperative, locked position.
In a locked position, the nozzle of the pump is covered by a shroud
which prevents dirt and debris from collecting on the nozzle. The
nozzle cap and shroud are preferably formed with cooperating
members which overlap in a locked position to form a seal in
proximity to the nozzle to further inhibit the ingress of dirt and
debris between the shroud and nozzle cap. The pump also provides
for cleaning of the nozzle, with an opening in the shroud wiping
the nozzle to remove any meniscus therefrom after dispensing fluid.
Additionally, cuts are formed in the shroud facing the nozzle cap
which assist in drawing excess fluid from the nozzle, and an empty
void is located about the nozzle for collecting fluid run-off from
the nozzle.
[0013] In a fifth aspect of the invention, a handle is also mounted
to the pump to provide a comfortable grip for handling the
pump.
[0014] These and other features of the invention will be better
understood through a study of the following detailed description
and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an elevational view of a pump in accordance with
the subject invention;
[0016] FIG. 1A is a cross-sectional view taken along line 1A-1A of
FIG. 1;
[0017] FIG. 2 is an enlarged view of the nozzle of the pump;
[0018] FIG. 3 is an enlarged view of an alternative stem of the
pump;
[0019] FIG. 4 is an enlarged view of the stem;
[0020] FIG. 4A is a cross-sectional view taken along line
4A-4A;
[0021] FIG. 5 is an elevational view of the pump with a deflectable
diaphragm;
[0022] FIG. 6 is an enlarged view of the nozzle of the pump;
[0023] FIG. 7 is an elevational view of the portion of the shroud
about the dispensing opening in the shroud;
[0024] FIG. 8 is a top view showing the locking and operating
positions of the nozzle cap; and,
[0025] FIG. 9 is a plan view of the sealing members.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Referring to the FIGS., a pre-compression pump 10 is shown,
along with various features thereof. The pump 10 generally includes
a body 12, and a nozzle cap 14.
[0027] The body 12 is formed with a generally tubular outer wall 16
with a transverse web 18 which divides the body 12 into two
chambers, an upper chamber 20 and a lower chamber 22, and a web
opening 24 communicates the two chambers 20 and 22. The nozzle cap
14 is disposed in the upper chamber 20, whereas, the lower chamber
22 cooperates with a bottom wall 26 to define fluid reservoir 28.
The bottom wall 26 may be detachable from the outer wall 16 so as
to permit charging of fluid directly into the fluid reservoir
28.
[0028] A tubular cylinder 30 is mounted about the web opening 24
and extends into the fluid reservoir 28. As shown in FIG. 1, a
rubber washer 32 is disposed over, and presses against, the
cylinder 30. A holding member 34, disposed to engage and hold the
rubber washer 32, is preferably snap-fitted onto an annular ridge
36 protruding from the web 18. Also, vent holes 38 extend through
the web 18. It is preferred that the vent holes 38 be out of
contact with the rubber washer 32, so that air may be drawn through
the web 18 and into the fluid reservoir 28 during use.
[0029] A tubular piston 40 is disposed within the cylinder 30 and
extends therefrom through the rubber washer 32 and into the upper
chamber 20. The rubber washer 32 is generally circumferentially in
contact with, and forms a seal about, the piston 40. In addition,
the piston 40 has an outer surface 42 which is in contact with the
cylinder 30, due to an interference fit being defined therebetween.
It must be noted however that the interference fit may not be
excessive since the piston 40 must be slidable relative to the
cylinder 30. In addition the nozzle cap 14 is mounted onto the
piston 40 such that the two elements move together.
[0030] A cylindrical stem 44 is disposed within the cylinder 30 and
partially telescoped within the piston 40. The stem 44 is slidable
relative to both the cylinder 30 and the piston 40. Additionally,
the stem 44 is urged into contact with the piston 40 by a return
spring 46 disposed between the stem 44 and lower end 48 of the
cylinder 30. The interaction of top edge 50 of the stem 44 and lip
52 of the piston 40 limits the upward movement of the stem 44.
[0031] A fluid passage 54 is defined in the piston 40 about the
stem 44 and above the lip 52. The fluid passage 54 is in fluid
communication with passage 56 formed in the nozzle cap 14. The
passage 56 has a bend 58 which re-directs the passage 56 to nozzle
60.
[0032] In operation, fluid F is disposed within the fluid reservoir
28. With the pump 10 being fully primed, the fluid F is also
present within the cylinder 30. An inlet 62 is formed in the lower
end 48 which communicates cylinder chamber 64, encompassed by the
cylinder 30, and the fluid reservoir 28. An annular seal 66 is
mounted within the cylinder chamber 64 so as to form a seal about
the stem 44. Upon depressing the nozzle cap 14, the piston 40 is
translated downwardly, pressing against the top edge 50 of the stem
44 and against the spring force of the return spring 46. As the
piston 40 and the stem 44 move downwardly, the volume of the
cylinder chamber 64 above the annular seal 66 decreases, thereby
increasing the pressure of the fluid F trapped therein. The
pressure of the fluid F acts on all surfaces in contact with the
fluid F, including a tapered actuating surface 68. With further
downward movement, the pressure of the fluid F increases to the
point where the fluid F presses down on the actuating surface 68 so
as to separate the top edge 50 of the stem from the lip 52 of the
piston 40. The pressurized fluid F then escapes from the cylinder
chamber 64 through the fluid passage 54, into the passage 56, and
out of the nozzle 60. As the fluid F escapes, the internal pressure
of the cylinder chamber 64 decays. The phenomenon of pressure
fluctuations described above take effect with the fluid F being
dispensed from the nozzle 60. With the pressure within the cylinder
chamber 64 being sufficiently decayed the stem 44 is urged into
contact with the piston 40.
[0033] The stem 44 is formed with a plurality of longitudinally
extending splines 70 which separate recesses 72. When pressurizing
the cylinder chamber 64 during pumping, the splines 70 are located
below the seal 66 with the annular seal 66 generally sealing a full
circumference of the stem 44. In this manner, no fluid F by-passes
the seal 66. With the further decrease in pressure in the cylinder
chamber 64, a pressure differential is created across the annular
seal 66, the stem 44 is urged toward the piston 40, and the fluid F
is drawn into the cylinder chamber 66 through the recesses 72 under
the annular seal 66. Consequently, the pump 10 is re-charged, and
ready for re-use.
[0034] The description above generally describes the operation of
the pump 10. Below are various features which elaborate upon
different aspects of the invention.
[0035] Reduction of Fluid Pulsing
[0036] Various features are provided to minimize pressure
fluctuations, in repeated opening and closing of the pump 10 during
operation, to avoid repeated engagement and disengagement of the
top edge 50 of the stem 44 and the lip 52 of the piston 40.
Accordingly, non-atomized microdoses of fluid may be delivered.
First, the interference fit between the piston 40 and the cylinder
30 is reduced from that found in the prior art. Typically, the
interference fit is approximately 0.010 inches. With the subject
invention, the interference fit is approximately 0.005 inches.
Accordingly, the return spring 46 can be formed with a weaker
spring force than that in the prior art, since less resistance is
presented by the interference fit, and/or the return spring 46 can
be wound to have a slower return velocity than that found in the
prior art. In either regard, the weaker/slower response of the
return spring 46 will retard the spring's response to pressure
decay in the cylinder chamber 64. With the return spring 46
responding weakly/slowly, the stem 44 will not engage and disengage
the piston 40 as repeatedly in the prior art.
[0037] In addition, as shown in FIG. 2, a portion of the passage
56, preferably the bend 58, is enlarged relative to other portions
thereof. In this manner, the enlarged portions of the passage 56
reduce flow restriction, and, thus, reduce any potential throttling
of the fluid F above the stem 44. In addition, the increased area
serves as a pocket or cushion to smooth out pressure
fluctuations.
[0038] Separately, also as shown in FIG. 2, a bumper 74 may be
mounted to the top edge 50 of the stem 44. The bumper 74 is
elastically deformable to respond to pressure applied thereto by
the fluid F. The bumper 74 can be a hollow dome-shaped member which
protrudes from the stem 44, or, alternatively, can be a solid
pellet or ball which is partially inserted into the stem 44 and
extends therefrom. The bumper 74 will absorb some of the pressure
fluctuations in the fluid F and immunize the operation of the pump
10 thereagainst.
[0039] Referring again to FIG. 1, a ratchet tooth 76 may be formed
on the piston 40 to bear against the stem 44. The ratchet tooth 76
is plate shaped with a generally triangular profile. The bearing of
the ratchet tooth 76 against the stem 44 creates friction which
inhibits relative movement between the stem 44 and the piston 40.
Again, the inhibition of movement of the stem 44 serves to limit
the effect of pressure fluctuations. A plurality of ratchet teeth
76 may also be provided.
[0040] Furthermore, with reference to FIG. 3, the annular seal 66
may be formed with a generally right-triangular cross-section,
having a pointed edge 78 for engaging the stem 44. With this
structural arrangement, a generally planar lower surface 80 is
defined which is generally perpendicular to the axis of the stem
44. This perpendicular arrangement creates more fluid drag during
use against upward movement of the stem 44, thereby inhibiting the
movement of the stem 44 and further reducing the effects of
pressure fluctuations.
[0041] Typically in the pump art, a seal in a seal/shaft
arrangement is sized so that the seal diameter is a little smaller
than the shaft to ensure a good seal. Often, the seal is 0.010
inches smaller than a shaft diameter in seals typically used in
hand-held pre-compression pumps, such as the annular seal 66.
Referring to FIG. 4, a constant-diameter portion 82 is formed in
the stem 44 above the splines 70 which may be 0.010 inches larger
than the inner diameter of the annular seal 66. Alternatively, as
shown in FIG. 3, the constant-diameter portion may be substituted
for by conical portion 84. The conical portion 84 is preferably
made with an upper diameter 86 slightly greater, e.g. 0.002 inches,
than the inner diameter of the annular seal 66. Also, preferably a
lower diameter 87 is provided of 0.005 inches. The conical portion
84 provides a progressively looser fit in the seal 66 as it
progresses down through the seal 66 with the movement of the stem
44, thereby allowing the stem 44 to move downwards with less
resistance from the seal 66 throughout the dispensing stroke. This
reduction in resistance from the seal 66 reduces the creation of
pulses.
[0042] Priming
[0043] The elimination of air pockets and bubbles, especially upon
initial use of the pump 10 is critical to ensure proper priming is
achieved, especially where microdoses are concerned.
[0044] Most prior art pump dispensers house fluid to be dispensed
at the bottom of the dispenser; the dispenser then pulls, or lifts,
the fluid upwards via a dip tube which dips into the liquid. In
contrast, the pump 10 houses the fluid F around the cylinder 30 and
does not utilize a dip tube. Instead, the inlet 62 is in direct
communication with the fluid reservoir 28. As shown, the inlet 62
may be coextensive with the cylinder 30, or may be formed to extend
slightly therefrom. Costs are saved by removing the dip tube
component. Also, priming is enhanced, because the fluid F is
disposed at a higher elevation with respect to the cylinder 30 as
compared to the elevation of fluid in prior art pumps utilizing dip
tubes. With the subject invention, the fluid F at least partially
engulfs the stem 44 with the cylinder 30 substantially being
coextensive with the fluid reservoir 28 and the inlet 62 being
located in proximity to the bottom wall 26.
[0045] The recesses 72 allow air to leak freely out of the cylinder
chamber 64 during priming. The splines 70 are relatively shallow,
preferably 0.001 to 0.005 inches, which allows air to pass
downwards with the pump 10 not in use. The annular seal 66 is
disposed about the splines 70 with the pump 10 not in use. In
addition, because of the shallowness of the splines 70, fluids will
be generally too viscous to pass through the recesses 72, and,
thus, will remain above the seal 66 in an unactuated state. In
re-charging the cylinder chamber 64 after a dispensing operation,
the fluid F is urged through the recesses 72 under force of the
aforementioned pressure differential.
[0046] Additionally, as shown in FIG. 1, it is preferred that the
inlet 62 be located off-center in the lower end 48 of the cylinder
30. Preferably, the inlet 62 will be located off-center in a
direction away from the nozzle 60. Since the pump 10 will often be
inclined slightly towards the nozzle 60 in use, the off-center
location will encourage entrapped air to be expelled into the fluid
reservoir 28, where it can rise freely up to the vent holes 38.
[0047] Furthermore, the inside surface 88 of the lower end 48 is
preferably inclined, relative to the cylinder 30, so as to
encourage the fluid F to spread evenly across the inside surface 88
upon entry. This ensures that pockets of air do not become trapped
at this point.
[0048] As yet another additional feature, the pump 10 of the
subject application can be provided with a deflectable diaphragm 90
for accelerating the priming operation. Currently, prior art pumps
prime themselves prior to dosing liquid by stroking up and down
several times. Once fully flooded with liquid they then begin to
dose. The problem with very low dose pumps (any below 70
micro-liters) is that the number of strokes required to prime can
be high, simply because the internals of the pump are of relatively
high volume compared to the dose volume of the pump. Referring to
FIG. 5, the diaphragm 90 protrudes from the outer wall 16 prior to
initial use of the pump 10. Instead of priming the dispenser by
pressing the cap several times, the user presses the diaphragm 90,
which deflects inwards into the fluid reservoir 28 and remains in
that position. The indenting of the diaphragm 90 decreases the
volume of the fluid reservoir 28, thereby raising the pressure in
the fluid reservoir 28 which spontaneously drives the fluid F into
the cylinder 30. In order for the fluid F to be driven into the
cylinder 30, the stem/piston interaction of the top edge 50 and the
lip 52, when in a dry condition, and allowing air in the pump 10 to
pass therethrough. It should be noted that the rubber washer 32
should not leak at a lower pressure than the stem/piston
interaction because the deflection of the diaphragm 90 would result
in fluid leaking through the vent holes 38, without the pump 10
being actually primed.
[0049] Sufficient Operating Momentum
[0050] The basic operation described above is sufficient to
dispense fluid out of the pump 10. But, if the pump 10 is operated
very slowly, it is possible to dispense the fluid F so slowly that
it dribbles down the outside of the nozzle 60 instead of leaping
clear of the nozzle 60 as is desired for reliable operation. U.S.
Pat. No. 5,881,956 describes a latch mechanism which is utilized to
ensure a minimum amount of velocity is applied to actuate a pump.
The pump 10 is also provided with a mechanical latch in the form of
a plurality of fingers 92 which are cantilevered to, and extend
downwards from, the stem 44. The fingers 92 bear against and slide
freely against an upstanding pin 94 during downward movement of the
stem 44 and the piston 40. In an unactuated state of the pump 10,
it is preferred that the fingers 92 be located clear of and above
the pin 94.
[0051] The pin 94 has a tapered end 96, with increasing diameters
from smaller to larger. Preferably, the end 96 makes initial
contact with the fingers 92 just prior to the point at which the
upper end of the splines 70 on the stem 44 enter the seal 66 (which
is the point at which the pump is about to dispense fluid).
[0052] The point at which the fingers 92 engage the tapered end 96
may be slightly in advance of the point at which the splines 70
enter the seal 66. To further advance the stem 44 downwardly,
sufficient force must be applied to deflect the fingers 92 and
cause yielding thereof. The increased downward force required to
deflect the fingers 92 past the tapered end 96 provides sufficient
momentum needed to ensure a minimum velocity is provided to the
pump 10 to properly dispense a full dose of the fluid at an
acceptable velocity.
[0053] Cleanliness
[0054] With respect to another aspect of the invention, to achieve
reliable and safe dosing of fluid, the nozzle 60 and free space
around the nozzle cap 14 must remain clean and free from any
accumulation of excess fluid, or the dried remnants of fluid.
Cleanliness of the nozzle 60 may be managed in several ways.
[0055] The portion of the outer wall 16 disposed about the upper
chamber 20 defines a shroud 98 which shields the nozzle cap 14 and
the nozzle 60 from dirt and debris. A dispensing opening 100 is
defined in the shroud 98 which is located to register with the
nozzle 60 during dispensing, so that dispensed fluid may pass
through the shroud 98. When the pump 10 is not in use, and is in a
rest position, the nozzle 60 is positioned behind a portion of the
shroud 98. The nozzle 60 is disposed to be relatively close to a
snout 102 formed about the opening 100. The snout 102 is used to
aim the pump 10 when in use. The nozzle 60 is brought close enough
to the snout 102 so that any liquid meniscus M which might remain
on the nozzle 60 after dosing is wiped against the snout 102. As
shown in dashed lines in FIG. 6, the meniscus M overlaps with
portions of the snout 102. The wiping action has the tendency to
transfer some of the excess fluid onto, or adjacent to, the shroud
102, thus reducing the height of the meniscus M. It is preferred
that the liquid be transferred to the snout 102, rather than to
other portions of the pump 10.
[0056] When the pump 10 is not in use, the nozzle cap 14 is
rotated, preferably by about 40 degrees, into a locking position to
prevent inadvertent operation. During this locking operation, any
slight meniscus of liquid which might have gathered will not be
wiped around the inside of the shroud 102 which surrounds the cap
14 because of the prior wiping action against the inside of the
snout 102.
[0057] A further embellishment to encourage liquid to transfer from
the nozzle 60 to the snout 102 is provided by a series of angled
cuts 104 on the inside face 101 of the snout 102. These cuts 104
are angled such that tapered lands 106 are defined which
accommodate the excess liquid on the snout 102. The lands 106
diverge and becomes broader, and as the cap 14 is rotated to a lock
position, the nozzle 60 wipes past the broadening region of a land
106. The broadening land 106 tends to pull the liquid outwards to
its boundaries, defined by the cuts 104, which draw more liquid
away from the nozzle 60 as the cap 14 is rotated to the locked
position. Also, the cuts 104 act to break surface tension of the
meniscus M, as the meniscus M is passed thereover.
[0058] Given that the inside of the snout 102 wipes the meniscus M
on the nozzle 60, some of the excess liquid may partly transfer
onto the snout 102, but can also be pushed downwards from the mouth
of the nozzle 60 and roll over and down the outside of the
protruding nozzle. A void 108 is provided around the nozzle 60
where any excess liquid can be transferred. In this way, the excess
fluid can dry without interfering with the mouth of the nozzle
60.
[0059] To further encourage any meniscus M to roll over and onto
the outside conical section of the nozzle 60 and be deposited
within the void 108 defined about the nozzle 60, the front edge of
the nozzle is rounded with a full radius, of typically 0.005
inches. This small radius tends to reduce any meniscus formation by
encouraging the rolling over mechanism to occur.
[0060] As a further embellishment to all the features mentioned
above regarding meniscus elimination, all the surfaces which are
designed to receive excess liquid from the nozzle 60 can be
roughened during manufacture, on the basis that roughened surfaces
will more readily attract liquid.
[0061] As previously mentioned the cap 14 is rotated relative to
the body 12 of the pump 10 in order to lock it against unintended
operation. To facilitate rotation, grooves 110 are cut into the
outside of the cap 14 to provide a grip to provide for this
rotation. The pump 10 provides for the outer surfaces of these
grooves 110 to be roughened to improve the quality of the grip.
[0062] The rear part of the cap has flat faces 112 which can also
be used to rotate the cap 14 into and out of its locked position.
Pushing on one of the faces 112 will rotate the cap to lock, while
pushing on the other face 112 will rotate the cap to unlock.
[0063] A pair of slotted faces 114 cut into the outside diameter of
the cap 14 work in conjunction with a pair of protrusions 116 on
the inside diameter of the shroud 98 to define the position at
which the cap is permitted to descend and also the extremes of
rotational travel of the cap 14. A detent 118 is added to each of
the protrusions 116 within the shroud 98 which is formed to snap
into a groove 118 when the cap 14 is rotated into the lock
position. The detents 118 indicate that the lock position has been
achieved by holding the cap 14 in that position. Similar shaped
grooves 120 are formed to correspond to the operating position of
the cap 14, thus providing clear indications as to the locked and
operating positions.
[0064] Once the locked position is achieved it is desirable to
provide an intimate seal between the periphery of the cap 14
adjacent to the nozzle 60 and the inside of the shroud 98. This is
achieved by introducing three bands 122 of reduced diameter on the
inside of the shroud 98, preferably equi-spaced, and three bands
124 of increased diameter on the cap 14, also preferably
equi-spaced. One of the bands 124 on the cap 14 is preferably
centered upon the nozzle 60. The diameters of the inside bands on
the shroud 122 and outside bands 124 on the cap 14 are
approximately equal in diameter, to provide a seal when overlapped.
It is preferred that the overlapping occur when the pump 10 is
locked, with the bands of the cap 124 being in pressing engagement
with the bands of the shroud 122, preferably with transition fits.
When the pump 10 unlocked and the cap 14 is urged into an operating
position, the diameter bands on the shroud 122 and the cap 124 are
spaced apart to allow unrestricted downward operation of the cap
14.
[0065] Handle
[0066] Since the fluid reservoir 28 is generally coextensive with
the cylinder 30, the overall length of the pump 10 is relatively
short. Accordingly, a handle H is provided for convenient handling
and gripping. The handle H both provides an ergonomic grip for the
user and also serves to buffer the fluid reservoir 28. Preferably,
the pump 10 will be filled in an inverted position, and the handle
H will be snapped into place. The pump 10 will then be inverted to
the normal upright position for further manufacturing
operations.
[0067] The discussion set forth above is with respect to a
pre-compression pump. Those skilled in the art will understand that
the disclosure herein is exemplary and the inventive features may
be applied to other types of pumps.
[0068] The invention is not intended to be limited to the
embodiments discussed herein, but only limited by the scope of the
appended claims.
* * * * *