U.S. patent application number 11/167713 was filed with the patent office on 2005-12-29 for foam encased pump.
Invention is credited to Leonhard, Todd W..
Application Number | 20050287007 11/167713 |
Document ID | / |
Family ID | 35505948 |
Filed Date | 2005-12-29 |
United States Patent
Application |
20050287007 |
Kind Code |
A1 |
Leonhard, Todd W. |
December 29, 2005 |
Foam encased pump
Abstract
A compact pump has a uni-body, or alternately a two-part,
housing of self-skinning foam construction for superior noise and
vibration reduction, such as needed for medical nebulizer
applications. The uni-body foam housing is formed by molding the
housing around a pump assembly having special features designed to
shield and space apart moving or sensitive internal components of
the pump assembly from the foam during the insert molding process.
The alternate two-part foam housing is assembled using a union ring
having multiple barbed pins that fit into openings in mating faces
of the two housing sections.
Inventors: |
Leonhard, Todd W.;
(Sheboygan, WI) |
Correspondence
Address: |
QUARLES & BRADY LLP
411 E. WISCONSIN AVENUE
SUITE 2040
MILWAUKEE
WI
53202-4497
US
|
Family ID: |
35505948 |
Appl. No.: |
11/167713 |
Filed: |
June 27, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60583424 |
Jun 28, 2004 |
|
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Current U.S.
Class: |
417/11 |
Current CPC
Class: |
F04B 53/003
20130101 |
Class at
Publication: |
417/011 |
International
Class: |
F04B 031/00 |
Claims
What is claimed is:
1. A pump having a cylinder and piston disposed along a piston
axis, the piston being driven to reciprocate within the cylinder
along the piston axis and pass air through a valve head having an
intake port and an exhaust port in communication with the cylinder
and respective inlet and outlet ports of a housing being of molded
foam construction and forming an internal cavity containing the
cylinder and piston.
2. The pump of claim 1, wherein the foam is self-skinning.
3. The pump of claim 1, wherein the housing is of uni-body
construction.
4. The pump of claim 3, wherein the housing defines a handle.
5. The pump of claim 1, wherein the housing includes first and
second housing sections.
6. The pump of claim 1, wherein the first and second housing
sections have peripheral faces and are coupled together by a double
sided union ring mated to the peripheral faces.
7. The pump of claim 6, wherein the union ring is plastic.
8. The pump of claim 6, wherein union ring is mated to the
peripheral faces by pin and slot connections.
9. The pump of claim 8, wherein the union ring has a first set of
pins extending from one side and a second set of pins extending in
an opposite direction from the first set from an opposite side such
that the first set of pins is disposed in an associated plurality
of openings in the peripheral face of the first housing section and
the second set of pins is disposed in an associated plurality of
openings in the peripheral face of the second housing section.
10. The pump of claim 9, wherein the first and second set of pins
have tapered locking barbs.
11. The pump of claim 6, wherein the union ring in part defines the
inlet of the housing.
12. The pump of claim 6, wherein the peripheral faces of the first
and second housing sections define a handle opening and wherein the
union ring defines a handle opening aligned with the handle
openings of the first and second housing sections.
13. The pump of claim 1, wherein the housing includes a plurality
of vent passages venting the internal cavity to ambient.
14. The pump of claim 1, wherein the piston is driven by an
armature of an electromagnet mounted within the housing by one or
more springs.
15. The pump of claim 14, wherein the electromagnet is contained
within an electromagnet housing inside of the internal cavity of
the housing.
16. The pump of claim 15, wherein the electromagnet housing
includes an opening in communication with a vent in the
housing.
17. The pump of claim 15, wherein the electromagnet housing has an
open end that is closed by an end cap which defines an air volume
in which a reciprocating component can move along the piston
axis.
18. The pump of claim 17, wherein the end cap is dome-shaped and
has an opening in communication with a vent in the housing.
19. The pump of claim 1, wherein the valve head includes a valve
plate with an annular wall defining an air volume in which the
cylinder is disposed.
20. The pump of claim 1, wherein the annular wall has an opening in
communication with a vent in the housing.
21. A method of making a pump having a pump assembly including a
cylinder and piston arrangement and a valve head having an intake
port and an exhaust port in communication with the cylinder, the
method comprising the steps of: pre-assembling the pump assembly;
inserting the pump assembly into a mold die; and molding a foam
housing around the pump assembly.
22. The method of claim 21, further including the step of allowing
the foam cure and form a skin.
23. The method of claim 21, further including the step of forming
inlet and outlet passages in the housing in communication with the
respective intake and exhaust ports of the valve head.
24. The method of claim 21, further including the step of forming
one or more vents in the housing.
25. The method of claim 21, further including the step of forming a
handle unitary with the housing.
26. The method of claim 21, further including the step of coupling
a power switch and lead to the electromagnet wire coil.
27. The method of claim 21, wherein an electromagnet is contained
within an electromagnet housing inside of the internal cavity of
the housing.
28. The method of claim 27, wherein the electromagnet housing
includes an opening in communication with a vent in the
housing.
29. The method of claim 28, wherein the electromagnet housing has
an open end that is closed by an end cap which defines an air
volume in which a reciprocating component can move along the piston
axis.
30. The method of claim 29, wherein the end cap is dome-shaped and
has an opening in communication with a vent in the housing.
31. The method of claim 21, wherein the valve head includes a valve
plate with an annular wall defining an air volume in which the
cylinder is disposed.
32. The method of claim 31, wherein the annular wall has an opening
in communication with a vent in the housing.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit to U.S. Provisional Patent
Application No. 60/583,424, filed on Jun. 28, 2004.
STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to pumps and compressors and
in particular to pumps and compressors with low noise
characteristics, especially suited for use in medical nebulizer
applications.
[0004] Nebulizers are commonly used to deliver medication to
persons with respiratory ailments. For example, bronchodialators,
which are used to open airway passages, are commonly administered
with nebulizers. A nebulizer changes liquid medication into a fine,
atomized mist or vapor. The medicinal vapor is inhaled through a
mouthpiece or mask and the atomized medication is able to penetrate
deeply into one's airways because of its fine particle size. The
liquid medicine is atomized by mixing it with compressed air or
oxygen.
[0005] Typical nebulizers include a small compressor with a piston
that reciprocates rapidly within a cylinder to pressurize the air.
U.S. Pat. No. 6,135,144, assigned to the assignee of the present
invention and hereby incorporated by reference as though fully set
forth herein, discloses a compressor with a wobble piston. The
piston is connected by a connecting rod to an eccentric mounted to
a rotating shaft so that its head pivots as it slides within the
cylinder. The pressurized air is forced out of the cylinder through
a valve head and exhaust chamber to a hose leading to a mixing
chamber. Internal conduit is usually necessary to direct the
pressurized air leaving the valve head to the outlet port of the
housing. After leaving the compressor, the pressurized air passes
over an orifice leading from the liquid medicine to aspirate and
atomize the medicine, which is then ordinarily mixed with ambient
air, oxygen or oxygen enriched air for inhalation.
[0006] Persons with significant respiratory problems often require
multiple nebulizer treatments every day, each taking several
minutes to administer. It is also not uncommon for such persons to
receive nebulizer treatments in hospitals, at work or other public
places. It is thus important for the nebulizer compressors to
operate discreetly. Quiet operation of the compressor can be
obtained by insulating the housing, however, this adds bulk and can
cause cooling problems. Mufflers can be added at the compressor
exhaust, however, this adds hardware and cost.
[0007] Conventional metal housings are prone to vibrate in response
to the reciprocating components during operation of the pump at an
audible frequency that may be too loud for suitable for hospital
and home use. To avoid this, various vibration damping spring
arrangements have been devised. For example, spring arrangements
can be provided to isolate the moving components from the housing
to dampen vibration and noise. However, this adds parts and
complicates assembly, thereby increasing unit costs.
SUMMARY OF THE INVENTION
[0008] The present invention provides a pump, particularly designed
for use with a medical nebulizer having improved noise, vibration
and manufacturing characteristics.
[0009] Specifically, the present invention provides a piston pump
having a cylinder and piston disposed along a piston axis and a
valve head having an intake port and an exhaust port in
communication with the cylinder and respective inlet and outlet
ports of a housing. The housing, forming an internal chamber
containing the cylinder, piston and valve head, is of molded foam
construction. In an especially preferred form, the foam is
self-skinning so that the foam has a smooth, generally non-porous
outer surface.
[0010] In one preferred form, the housing is of uni-body
construction. The pump is formed by inserting a pre-assembled pump
assembly, including the cylinder and piston arrangement and valve
head into a mold die and then molding a uni-body foam housing
around this assembly. The pump assembly has special components
designed to encapsulate and protect internal components during the
insert molding process and provide the internal air space necessary
for the drive components to reciprocate after the housing is
formed. Preferably, the foam is allowed to cure and develop on its
own a skin layer. Inlet and outlet passages are also molded into
the housing in communication with the respective intake and exhaust
ports of the valve head as are vent passages and a unitary carrying
handle. Assembly is completed by attaching a power switch and lead
to the actuator, which may be an electromagnet wire coil moving an
armature linearly or a motor rotatably driving the piston to
reciprocate.
[0011] Another preferred form of the pump has a split housing with
two similar housing sections that are coupled together by a double
sided plastic union ring mated to peripheral faces of the two
housing sections by a pin and slot connection. Preferably, the
union ring has two sets of tapered barbed pins extending from
opposite sides that fit into two sets of openings in the peripheral
faces of the two housing sections. The union ring in part defines
the inlet of the housing as well as a handle opening aligned with
handle openings defined by the housing sections.
[0012] The present invention thus provides a compact piston pump
having a foam housing providing very low operating vibration and
noise such that it is particularly suitable for use in a medical
nebulizer device. The pump can have a uni-body construction in
which the pump components are pre-assembled and insert molded with
the foam forming the housing. Or, the pump can have a split housing
in which the parts are assembled with a special ring providing a
simple pin and socket connection. Further, the reciprocating drive
components of the pump assembly can be suspended in the housing by
individual springs or spring stacks to further isolate the housing
from vibration caused by the reciprocating elements of the
assembly, and thereby reduce noise. The integral air inlet and
outlet ports simplify assembly and cost by eliminating the need for
separate air lines or tubing.
[0013] These and other advantages of the invention will be apparent
from the detailed description and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view of a pump having a foam housing
according to the present invention;
[0015] FIG. 2 is side plan view thereof;
[0016] FIG. 3 is an end plan view thereof;
[0017] FIG. 4 is an opposite end plan view thereof;
[0018] FIG. 5 is a perspective view thereof with the housing shown
exploded;
[0019] FIG. 6 is another perspective view thereof with the housing
shown exploded;
[0020] FIG. 7 is a fully exploded perspective view thereof;
[0021] FIG. 8 is a side cross-sectional view taken along line 8-8
of FIG. 4;
[0022] FIG. 9 is a top cross-sectional view taken along line 9-9 of
FIG. 2;
[0023] FIG. 10 is another top cross-sectional view taken along line
10-10 of FIG. 2;
[0024] FIG. 11 is an end cross-sectional view taken along line
11-11 of FIG. 8;
[0025] FIG. 12 is perspective view of alternate embodiment of the
pump according to the present invention having a one-piece or
uni-body foam housing;
[0026] FIG. 13 is a side plan view thereof;
[0027] FIG. 14 is a perspective view thereof with the pump assembly
shown exploded from the uni-body housing;
[0028] FIG. 15 is a fully exploded perspective view thereof;
[0029] FIG. 16 is a side cross-sectional view taken along line
16-16 of FIG. 19;
[0030] FIG. 17 is a bottom cross-sectional view taken along line
17-17 of FIG. 16;
[0031] FIG. 18 is an end view cross-sectional view taken along line
18-18 of FIG. 13; and
[0032] FIG. 19 is another end cross-sectional view taken along line
19-19 of FIG. 13.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] The present invention provides a pump with a foam housing
construction providing quiet operation such that the pump is
suitably used in a medical nebulizer application. The foam housing
gives the pump improved noise and vibration dampening
characteristics in a compact, preferably hand-held, package. These
characteristics of the foam housing reduce dependency on other
vibration dampening components, such as suspension spring
assemblies disposed between the reciprocating components and the
housing or isolation springs supporting the fixed components in the
housing.
[0034] The pump of the present invention will be described herein
in two different embodiments. A first embodiment, shown in FIGS.
1-11, has a two-piece foam housing in which the two parts are
joined by union ring with multiple pin elements that engage the
housing parts. A second embodiment, shown in FIGS. 12-19, has a
uni-body foam housing formed around the components of the pump
assembly, preferably by an insert molding process. The pump is
shown and described herein as an axial (or linear) piston pump.
However, other types of pump arrangements are included within the
scope of the invention, including rotary driven piston pumps such
as wobble type piston pumps.
[0035] Referring to FIGS. 1-7, the pump 10 has a compact, generally
oblong foam housing 12. The foam can be any moldable or
thermoformable foam material, however, the foam is preferably an
expanded polyurethane self-skinning foam in which a smooth "skin"
forms at the exterior surface of the pump housing 12 as the foam
cures so that it is generally non-porous. The foam material is
lightweight but strong so as to resist damage or cracking.
Importantly, the foam has very good sound insulating and vibration
dampening properties.
[0036] The foam housing 12 has two shell parts 14 and 16. The
shells 14 and 16 are generally the same, each has a peripheral wall
18 with openings 20 spaced there along. Each has two feet 22 and
forms a handle opening 24 and vent passages 26. When joined, the
shells 14 and 16 define a handle 28 at the top of the housing 12
adjacent the opening 24 and also define an inner cavity 30, an
intake passageway 32 and an opening 34 for a power switch 35. Shell
14 is formed with a side opening 36 for an exhaust nipple 38, as
discussed below.
[0037] The housing shells 14 and 16 are joined by a union ring 40
having a wall 42 disposed between the peripheral walls 18 with a
number of barbed pin elements 44 projected toward opposite sides
thereof to fit into the openings 20 in the shells 14 and 16,
thereby providing a mechanical, pin and socket connection of the
two shells 14 and 16. The pins 44 can be formed as a unitary part
of the union ring 40 or than can be separate components that fit
into associated openings of the union ring 40. A flange 46 extends
around the wall 42 to overlap the edges of the shells 14 and 16.
The union ring 40 is also formed with an interior wall 48 defining
a handle opening 50 aligned with the handle openings 24 in the
shells 14 and 16 as well as a port 52 disposed in the intake
passageway 32 and an opening 54 disposed in the switch opening 34.
The union ring 40 is preferably made of a suitable moldable
plastic, such as nylon, ABS, or polystyrene, having sufficient
resiliency so that the wall 42 and flange 46 seal against the
shells 14 and 16 and form an air tight connection.
[0038] Referring now to FIGS. 5, 6 and 8, a pump assembly 56 is
contained within the inner cavity 30 of the housing 12. The pump
assembly 56 generally includes an electromagnet 58, a piston 60, a
cylinder 62 and a valve head 64, all aligned concentrically about a
piston axis 66.
[0039] Working from left to right in FIG. 8 and right to left in
FIGS. 7, 9 and 10, a tail piece 68 having an enlarged trailing end
mounts to an axially extending hub 70 of an armature 72. The
armature 72 has a series of axial bores 74 (see FIG. 11)
therethrough spaced about the axis 66. The armature 72 slides in
and out of an annular cavity 76 of a stator 78 which holds a bobbin
80 about which is wound a wire coil 82, thereby comprising the
electromagnet 58 when energized by an input current. A diode 83
(shown in FIG. 9) is electrically coupled to the coil 82 to rectify
the alternating current input signal so that it drives the armature
72 in only one direction, preferably toward the stator 78.
[0040] The armature hub 70 has a bore receiving a narrowed threaded
end of a connecting rod 84 to which the tail piece 68 threads to
clamp the armature 72 between the tail piece 68 and the connecting
rod 84. Clamped between the armature hub 70 and the tail piece 68
is a center portion of one or more leaf springs 86 having their
outer peripheries held fixed with respect to the housing 12 by
being clamped between a retainer ring 88 and a spacer 90. The
connecting rod 84 extends along the piston axis 66 through the
center of the armature 72 and the stator 78 to another narrowed
threaded end that threads into a bore in a stem of the piston 60,
which has an enlarged head 92 to which a piston seal or cup 94 is
clamped by a cup retainer 96. The piston cup 94 creates a sliding
seal against the inner diameter of the cylinder 62 which is mounted
between the valve head 64 and another spacer 98. The spacer 98 is
fixedly mounted in the housing 12 to clamp the outer periphery of
another one or more leaf springs 100 between it and another
retainer ring 102, which is notched to abut and capture the outer
edge of the stator 78. The center of the spring(s) 100 are clamped
between the connecting rod 84 and the piston stem. The cup retainer
96 is secured by a screw threaded into the connecting rod 84
through the bore of the piston stem. The leaf springs 86 and 100
preferably are configured with a pair of concentric circular rings
joined by three spokes. The outer ring preferably includes hair pin
elements disposed between the spokes.
[0041] The valve head 64 is clamped against one open end of the
cylinder 62. The valve head 64 includes a valve plate 103, a
chamber housing 104 and a cover 106. The valve plate 103 includes
intake 108 and exhaust 110 ports over which are mounted flapper
valves (not shown) to control flow through the ports. The intake
flapper valve is mounted to the valve plate 103 at the interior of
the cylinder 62 and the exhaust flapper valve is mounted at the
opposite side of the valve plate 102. The chamber housing 104 is
clamped between the valve plate 103 and the cover 106, with a seal
107 therebetween, to define intake 112 and exhaust 114 chambers
isolated from each other by a partition wall 116. The exhaust
chamber 114 is communication with the exhaust nipple 38 through an
opening in the side of the chamber housing 104. The intake chamber
112 is in communication with an intake port 118 in the cover 106
and the intake passageway 32 in the housing 12 leading to ambient
via port 52. Suitable o-rings or other gaskets, like seal 107, can
be disposed between the components of the valve head 64 and/or
between the ends of the cylinder 62 and the mating components as
necessary to ensure an air tight seal.
[0042] During operation, energizing the coil 82 creates a magnetic
flux that drives the armature 72 toward the stator 78, which in
turn drives the piston 60 to reciprocate within the cylinder 62. In
one preferred version of the pump 10, the piston stroke length is
approximately 9 mm (4.5 mm in each direction) and is positioned
approximately 1 mm from the top of the cylinder 62 when at top dead
center (furthest right in FIG. 9). The piston 60 and the armature
72 reciprocate (along with the tail piece 68 and the connecting rod
84) against the internal spring forces of the springs 86 and 100
arising from the centers of the springs reciprocating with the
piston 60 and armature 72.
[0043] The reciprocating piston 60 and armature 72 causes the
assembly inside the housing 12 to vibrate. The associated noise and
movement is dampened by the spring 86 and 100. The number and size
of leaf springs is primarily a function of the mass of the piston
and the power input frequency. The springs are selected so that in
combination (between the two sets) they result in a resonant
frequency of the piston and springs (i.e., the spring-mass system)
approximately equal to the input frequency, that is 50 or 60 Hertz.
For example, in one preferred embodiment there is one spring (or
possibly two) at this location and a stack of two springs (or
possibly three) at the piston in a 115 v/60 Hz application. A stack
of two springs are preferably at each location for a 230 v/50 Hz
application. Operating at the resonant frequency improves
efficiency and reduces vibration, and thereby reduces noise.
[0044] FIGS. 12-19 show an alternate embodiment of the pump in
which the foam housing has a uni-body construction. Components of
this embodiment that are similar to the above-described embodiment
are referred to with similar reference numerals albeit with the
suffix "A".
[0045] Referring to FIGS. 12-14, the pump 10A has a compact,
generally oblong foam housing 12A. Like in the preceding
embodiment, the foam is preferably an expanded polyurethane
self-skinning foam in which a smooth, non-porous "skin" forms at
the exterior surface. Here, the housing 12A has a uni-body
construction such that the components of the pump assembly need to
be pre-assembled and inserted into the mold before the housing 12A
is formed. The housing 12A is formed with a handle 28A at the top
and four feet 22A at the bottom. Vent passages 26A are also formed
into the side of the housing 12A as are intake passageway 32A, an
opening 34A for an on/off switch 35A and an opening 36A for an
exhaust nipple 38A. The vent passages 26A, intake passageway 32A,
switch opening 34A and exhaust opening 38A can be formed during the
molding process or by a machining operation thereafter.
[0046] Referring now to FIGS. 14 and 15, a pump assembly 56A is
contained within the inside of the housing 12A and generally
includes an electromagnet 58A, a piston 60A, a cylinder 62A and a
valve head 64A, all aligned concentrically about a piston axis
66A.
[0047] With reference to FIGS. 15-19 and working from left to right
in FIG. 15 and right to left in FIGS. 16 and 17, the pump assembly
56A includes a dome-shaped end cap 202 defining an interior space
for movement of the piston 60A and an armature 72A. The end cap 202
has openings in communication with associated vent openings 26A
allowing ambient conditions to exist therein and prevent back
pressure piston. This piece is necessary here because of the
uni-body construction of this embodiment and the fact that the pump
assembly 56A is inserted molded within the housing 12A, without it
the foam would adhere to, or at least form tightly around, the pump
assembly 56A so as to prevent reciprocation of the otherwise
movable components. The end cap 202 has a section defining an open
cavity 203 for the power switch 35A. The end cap 202 has an annular
flange at its periphery that is notched to receive the periphery of
an annular spacer 90A between which is clamped one or more leaf
springs 86A (one shown). The spacer 90A abuts the periphery of a
stator 78A, which defines a cavity 76A (see FIG. 16) in which is
disposed a bobbin 80A about which is wound a wire coil 82A, thereby
providing the electromagnet 58A when energized by an input current.
As before, a diode 83A, shown in FIG. 17, is electrically coupled
to the coil 82A to rectify the alternating current input signal so
that it drives the armature 72A in only one direction, preferably
toward the stator 78A. Also as before, the armature 72A has a
series of axial bores 74A therethrough and slides in and out of
part of the annular cavity 76A of the stator 78A.
[0048] The armature 72A has a central hub 70A with a bore through
which extends a bolt 204 passing through a connecting rod 84A and
threading into the stem of the piston 60A. Clamped between the
armature hub 70A and a head of the bolt 204 is a center portion of
the one or more leaf springs 86A (one shown in FIG. 15), configured
as described above, which have their outer peripheries held fixed
with respect to the housing 12A. The connecting rod 84A extends
along the piston axis 66A through the center of the stator 78A and
abuts the stem of the piston 60A, which as before has an enlarged
head 92A to which a piston seal or cup 94A is clamped by a cup
retainer 96A. Clamped between the piston 60A and the connecting rod
84A are the center portions of one or more leaf springs 100A (two
shown in FIG. 15), which have their outer peripheries clamped
between a retainer ring 102A and an annular electromagnet cup or
housing 206, which surrounds the stator 78A and armature 72A and
has a recess at one end in which one end of the cylinder 62A is
disposed. The other end of the cylinder 62A fits into a groove in a
valve plate 103A, which in this case takes a cup shape having an
annular wall 208 spaced from and surrounding the cylinder 62A and
abutting the electromagnet cup 206.
[0049] The valve plate 103A and the electromagnet cup 206 have the
cup-like configuration to enclose the components therein to shield
and space them from the foam during the molding of the housing, as
is the purpose of the end cap 202. Both the valve plate 103A and
the electromagnet cup 206 also have openings that are communication
with the housing vents 26A to allow cooling air flow therethrough
as well as to allow these non-compression or vacuum areas of the
pump assembly to operate at ambient pressure.
[0050] The valve head 64A includes the valve plate 103A, a chamber
housing 104A and a cover 106A. The valve plate 103A includes intake
108A and exhaust 110A ports over which are mounted flapper valves
(not shown) to control flow through the ports. The intake flapper
valve is mounted to the valve plate 103A at the interior of the
cylinder 62A and the exhaust flapper valve is mounted at the
opposite side of the valve plate 103A. The chamber housing 104A is
clamped between the valve plate 103a and the cover 106A to define
intake 112A and exhaust 114A chambers isolated from each other by a
partition wall 116A. The exhaust chamber 114A is communication with
the exhaust nipple 38A through an opening in the side of the
chamber section 104A. The intake chamber 112A is in communication
with an intake port 118A in the cover 106A and the intake
passageway 32A in the housing 12A leading to ambient air. Like
above suitable o-rings or other gaskets can be disposed between the
components of the valve head 64A and/or between the ends of the
cylinder 62A and the mating components as necessary to ensure an
air tight seal.
[0051] As mentioned, given the uni-body construction of this
embodiment of the pump, a special insert molded assembly method is
utilized. In particular, the aforementioned components of the pump
assembly 56A are pre-assembled and inserted into a mold die. The
foam resin is then, preferably injected, into the die to form the
housing 12A around the pump assembly 56A. A non-porous skin forms
at the exterior of the foam as it cools, preferably while the
housing 12A is still inside the mold. As mentioned, preferably the
vent and intake and exhaust openings are formed by the molding
process to be in communication with the respective intake and
exhaust ports of the valve head 64A. Similarly, the vent passages
and handle are also preferably so formed. The power on/off switch
35A, with leads (not shown) connecting it to the electromagnet wire
coil, is mounted to the housing 12A at the switch opening 200. The
switch opening 200 is located to allow access to the coil 82A for
coupling the electrical leads thereto.
[0052] The present invention thus provides a compact axial piston
pump having a foam housing providing very low operating vibration
and noise such that is particularly suitable for use in a medical
nebulizer device. The pump can have a uni-body construction in
which the pump components are pre-assembled inserted molded with
the foam forming the housing. Or, the pump can have a split housing
in which the parts are assembled with a special ring providing a
simple pin and socket connection. Further, the drive assembly can
be suspended in the housing by spring stacks to further isolate the
housing from vibration caused by the reciprocating elements of the
assembly, and thereby reduce noise. The integral air inlet and
outlet ports simplifies assembly and cost by eliminating the need
for separate air lines or tubing.
[0053] Illustrative embodiments of the present invention have been
described above in detail. However, the invention should not be
limited to the described embodiments. For example, it is within the
scope of the invention to substitute other spring members for the
leaf springs described above, such as compression springs or other
energy absorbing members made of suitably resilient materials, such
as rubber or foam. To ascertain the full scope of the invention,
the following claims should be referenced.
* * * * *