U.S. patent application number 12/190274 was filed with the patent office on 2009-02-26 for pump diaphragm.
Invention is credited to Joseph Anthony Griffiths.
Application Number | 20090053081 12/190274 |
Document ID | / |
Family ID | 38566738 |
Filed Date | 2009-02-26 |
United States Patent
Application |
20090053081 |
Kind Code |
A1 |
Griffiths; Joseph Anthony |
February 26, 2009 |
PUMP DIAPHRAGM
Abstract
A diaphragm for use in a fluid pump comprising a disc of
resilient material having a substantially dished shape. The
curvature of the disc is formed from a plurality of steps.
Inventors: |
Griffiths; Joseph Anthony;
(Aldershot, GB) |
Correspondence
Address: |
CARTER, DELUCA, FARRELL & SCHMIDT, LLP
445 BROAD HOLLOW ROAD, SUITE 420
MELVILLE
NY
11747
US
|
Family ID: |
38566738 |
Appl. No.: |
12/190274 |
Filed: |
August 12, 2008 |
Current U.S.
Class: |
417/413.1 |
Current CPC
Class: |
F05C 2225/04 20130101;
F04B 43/0054 20130101 |
Class at
Publication: |
417/413.1 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 21, 2007 |
GB |
0716294.4 |
Claims
1. A diaphragm for use in a fluid pump comprising a disc of
resilient material having a substantially dished shape, the
curvature of the disc being formed from a plurality of steps.
2. A diaphragm according to claim 1 wherein the plurality of steps
are formed from a series of flat annular rings of increasing
diameter axially displaced from one another and joined at their
adjacent edges by shoulder portions extending in an axial
direction.
3. A diaphragm according to claim 1 having a substantially
inelastic chemically resistant coating on at least one side
thereof.
4. A diaphragm according to claim 3 wherein the chemically
resistant coating is formed on a concave side of the diaphragm when
in its natural un-deflected state.
5. A diaphragm according to claim 3 wherein the chemically
resilient material is PTFE.
6. A diaphragm according to claim 1 wherein the resilient material
is an elastomeric material.
7. A diaphragm according to claim 2 having a substantially
inelastic chemically resistant coating on at least one side
thereof.
8. A diaphragm according to claim 4 wherein the chemically
resilient material is PTFE.
9. A diaphragm according to claim 2 wherein the resilient material
is an elastomeric material.
10. A diaphragm according to claim 1 wherein the disk is one of
circular and oval in shape.
11. A diaphragm for use in a fluid pump system, the diaphragm
comprising: a plurality of annular rings, wherein each ring defines
an inner annular edge and an outer annular edge, wherein the inner
annular edge and the outer annular edge of adjacent rings are
substantially axially aligned with one another; and an annular
shoulder portion interconnecting adjacent annular rings to one
another such that each annular ring is axially spaced from an
adjacent annular ring, wherein at least the annular rings are
elastomeric.
12. A method of manufacturing a diaphragm comprising the steps of:
collecting a plurality of flat annular rings of increasing
diameter; axially displacing each ring from one another; joining
the rings at their adjacent edges by shoulder portions in an axial
direction; and coating a substantially inelastic chemically
resilient material on at least one side thereof.
13. The method of claim 12 wherein the resilient material is formed
on the concave side of the diaphragm.
14. The method of claim 12 wherein the resilient material is formed
on the convex side of the diaphragm.
15. The method of claim 12 wherein the resilient material is formed
on both sides of the diaphragm.
16. The method of claim 12 wherein the resilient material is an
elastomeric material.
17. The method of claim 12 wherein the resilient material is
PTFE.
18. The method of claim 12 wherein the resilient material is
rubber.
19. The method of claim 12 wherein the resilient material is a
low-temperature resistant rubber material.
20. The method of claim 12 wherein the resilient material is
nitrile.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of and priority
to Great Britain (GB) Application Serial No. 0716294.4, filed on
Aug. 21, 2007, the entire content of which is incorporated herein
by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a diaphragm for use in a
fluid pump, and more particularly, to a diaphragm configured to be
coated with a protective layer such that the protective layer would
avoid fracturing in use.
[0004] 2. Background of Related Art
[0005] Diaphragm-type fluid pumps and, in particular liquid pumps,
have a flexible pumping diaphragm which is driven to effect the
pumping action of the pump. In such pumps, the diaphragm comprises
a flexible circular or oval disc which has its outer peripheral
edge clamped and sealed within the body of the pump. The diaphragm
may have a central aperture which is secured to a moveable actuator
such as a piston, which reciprocates back and forth causing the
diaphragm to flex between a concave and a convex configuration. In
an alternative pump configuration, however, the diaphragm does not
have a central aperture and forms a partition with a driving fluid
chamber in which the hydraulic pressure of the driving fluid is
repeatedly alternated between high and low pressures, thereby
causing the diaphragm to flex between a concave and a convex
configuration. In both pump types, the repeated flexing of the pump
diaphragm causes fluid displacement in a pumping chamber which
results in the pumping action.
[0006] When such pumps are used to pump inert or un-reactive
fluids, such as water, the diaphragm can be constructed from plain
rubber material, since there is no problem with the fluid reacting
with or corroding the diaphragm material. However, if the pump is
intended for use with fluids having a more chemically reactive
nature, an elastomeric diaphragm, such a natural rubber, alone is
unsuitable as it is rapidly corroded, leading quickly to pump
failure.
[0007] In order to solve this problem, it is desirable to provide
the elastomeric diaphragm with a protective coating to prevent the
pump fluid from reacting with or corroding the elastomer. However,
the materials which would be most desirable to use for such a
protective layer due to their excellent chemical resistance
properties, such at PTFE, have plastic material properties, meaning
they are unable to stretch and recover their original shape.
However, when conventional pump diaphragms are in use, the repeated
flexing between convex and concave positions causes the rubber of
the diaphragm to repeatedly stretch and deform. Therefore, if a
conventional diaphragm is coated with a protective layer, such as
PTFE, it results in the protective coating cracking and splitting
when the pump is in use, since the protective layer cannot cope
with the repeated elastic deformation which the diaphragm
experiences.
[0008] It is therefore an object of the present invention to
provide a pump diaphragm that substantially alleviates or overcome
the problems mentioned above.
SUMMARY
[0009] Accordingly, the present invention provides a diaphragm for
use in a fluid pump comprising a disc of resilient material having
a substantially dished shape, the curvature of the disc being
formed from a plurality of steps.
[0010] Preferably, the diaphragm is circular, but may also be
oval.
[0011] The plurality of steps are preferably formed from a series
of flat annular rings of increasing diameter axially displaced from
one another and joined at their adjacent edges by shoulder portions
extending in an axial direction.
[0012] In a preferred embodiment, the diaphragm has a substantially
inelastic chemically resistant coating on at least one side
thereof. The chemically resistant coating may be formed on the
concave side of the diaphragm or may be formed on the convex side,
or may be formed on both/all sides of the diaphragm.
[0013] Preferably, the chemically resilient material is PTFE.
[0014] The resilient material may be rubber. However, if the
diaphragm is for use in a hydraulic pressure type pump in which the
diaphragm deflection is achieved by alternating hydraulic pressure
of a driving fluid, then the resilient material will need to be
compatible with the hydraulic media (e.g. oil). In such cases, the
resilient material may be nitrile or a low-temperature resistant
rubber material.
DETAILED DESCRIPTION OF THE DRAWINGS
[0015] Embodiments of the present invention will now be described,
by way of example only, with reference to the accompanying
drawings, in which:
[0016] FIG. 1 shows a schematic view of a prior art diaphragm
pump;
[0017] FIG. 2 shows a series of cross-sectional views of a prior
art pump diaphragm as used in the pump of FIG. 1;
[0018] FIG. 3 shows a perspective view of a pump diaphragm
according to the present invention in its un-deflected natural
state;
[0019] FIG. 4 shows a cross-sectional view along the line X-X shown
in FIG. 3; and
[0020] FIG. 5 shows a cross-sectional view of the diaphragm of FIG.
4 in a deflected position.
DETAILED DESCRIPTION OF EMBODIMENTS
[0021] An example of a known diaphragm pump 10 is shown
schematically in FIG. 1 and comprises a chamber 11, through which
fluid being pumped flows, having an inlet 12 and an outlet 13. The
inlet 12 includes a one-way valve 14 which allows fluid to flow
into the chamber 11 though the inlet 12 but not out of the chamber
11 therethrough, and the outlet 13 includes a one-way valve 15
which allows fluid to flow out of the chamber 11 through the outlet
13 but not into the chamber 11 therethrough. A flexible diaphragm
16 is mounted in the wall of the chamber 11 separating the chamber
11 from a cavity 17. The diaphragm 16 is connected at its centre to
a piston 18 of a pump driver 19. The piston 18 is driven backwards
and forward in the direction shown by arrow `A` to cause the
diaphragm 16 to deform between position I in FIG. 1 where it
extends into the cavity 17, and position II in FIG. 1, where it
extends into the chamber 11. As discussed above, the prior art pump
described here is of the type where the diaphragm deflection is
actuated by a piston. However, alternative embodiments of prior art
pumps use a driving fluid on the side of the diaphragm remote from
the fluid being pumped, where the driving fluid pressure is
alternated, which causes the diaphragm to flex. In such
embodiments, the diaphragm clearly does not have the central
aperture.
[0022] The fluid to be transported is caused to flow through the
diaphragm pump chamber 11 by repeated reciprocation of the piston
18 between positions I and II. When the diaphragm 16 extends to
position I, the volume of the chamber 11 is increased and the fluid
pressure therein is reduced. This causes the fluid outside the
chamber 11, which is unable to pass into the chamber 11 through the
outlet one-way valve 15, to be drawn into the chamber 11 through
the inlet 12 through the inlet one-way valve 14. Then, when the
diaphragm 16 extends to position II, the volume of the chamber 11
is reduced and the fluid pressure therein is increased. Therefore,
the fluid in the chamber 11, unable to pass through the inlet
one-way valve 14, is forced out of the outlet 13 through the outlet
one-way valve 15. As this cycle is repeated, the resulting repeated
fluid displacement causes the fluid to be pumped through the
diaphragm pump 10 from the inlet 12, through the chamber 11 and out
of the outlet 13.
[0023] It will be appreciated that if the fluid being pumped is
reactive or corrosive, then the diaphragm 16 will need to be
provided with a protective layer interposed between the fluid and
the rubber material of the body of the diaphragm 16, to prevent the
diaphragm 16 from being corroded and causing the pump 10 to fail.
It is important then, that this protective layer remains intact at
all times to protect the rubber diaphragm 16 underneath. In the
prior art pump shown, the diaphragm 16 deflects between positions I
and II, and in doing so, the surface is stretched and compressed.
This can be seen more clearly from FIG. 2 which shows the prior art
diaphragm 16 in more detail in three positions, namely positions I
and II at the most concave and convex positions in its range of
motion, and also at a third position III, which is intermediate
positions I and II where the diaphragm is deflected into a flat
shape. The side of the diaphragm exposed to the fluid being pumped
is on the concave side in FIG. 1. A reference distance between two
radially-spaced points a,b on the concave side of the diaphragm in
position I is shown as d1. As the diaphragm is forced to deflect to
position III, the deformation of the diaphragm causes the distance
between the same two reference points a,b to reduce to d2, as the
surface of the diaphragm compresses. Then, as the diaphragm
deflects further to position II, the distance between the same two
reference points increases to d3 as the surface of the diaphragm
stretches again. In this range of movement, the relationship
between the distances is as follows:
d3>d1>d2
[0024] Therefore, if a protective layer is bonded to the diaphragm
which has plastic properties, such as PTFE, the layer cannot cope
with the repeated elastic stretching and compressing deformation
that the diaphragm undergoes, and so the layer cracks. In use,
these cracks would expose the rubber material of the diaphragm to
the corrosive fluid being pumped, and so would cause the diaphragm
to corrode and the pump to fail.
[0025] FIGS. 3-5 show a diaphragm 100 of the present invention for
use in a pump such as that shown in FIG. 1, that does not suffer
the drawbacks described above of known prior art pump
diaphragms.
[0026] It can be seen that the diaphragm 100 is generally
dish-shaped, as are known pump diaphragms, but its dish-shape is
formed by a series of tiers or stepped layers 101 in the diaphragm
material which are each displaced from one another in an axial
direction of the central axis Y-Y of the diaphragm 100. Each layer
101 is formed as a flat annular ring, the rings increasing in
diameter to form the tiers or steps, the inner peripheral edge 101a
and the outer peripheral edge 101b of each ring being connected to
the outer/inner peripheral edge 101b, 101a respectively of the
adjacent ring 101 by shoulder portions 102 which extend in an axial
direction.
[0027] The embodiment of the invention is shown having a chemically
protective layer 103 of PTFE coated on the concave side of the
diaphragm, seen more clearly in FIGS. 3-4. However, the pump could
be configured such that the diaphragm is secured the other way
round in the pump, in which case, the chemically protective layer
would be coated on the convex side of the diaphragm, so that it is
on the side in contact with the fluid being pumped.
[0028] The diaphragm 100 includes a central aperture 104 for a
piston of a driver of a fluid pump to be secured thereto in a known
manner, as schematically illustrated with the prior art device in
FIG. 1.
[0029] As explained above in reference to FIGS. 1 and 2 of a prior
art fluid pump and diaphragm, the diaphragm 100 of the present
invention is repeatedly moved from its natural shape, shown in FIG.
4 to a deflected position, as shown in FIG. 5. In this repeated
movement, the annular rings 101 do not stretch. Instead, they flex
such that much of the deflection of the diaphragm 100 is effected
at the annular rings 101. In addition, in the deformation of the
diaphragm 100, the wall or shoulder portions 102 do not themselves
bend or flex at all, but remain un-deformed. Therefore, the whole
diaphragm 100 is able to repeatedly deflect between concave and
convex positions without any part of its surface stretching to any
significant degree. Therefore, the coating of PTFE 104 on the
concave side (or convex side, in reversed diaphragm embodiments of
the pump) of the diaphragm 100 in its natural position is not put
under any strain to stretch during the repeated deflections and so
the PTFE coating is not at any risk of cracking or fracturing in
operation of a fluid pump having such a diaphragm 100 of the
present invention.
[0030] The above embodiment is described having a protective
coating of PTFE applied thereto. However, the scope of the
invention is not limited to the diaphragm having a protective
coating and includes an uncoated diaphragm of the configuration to
accept such a coating without fracturing in use, as defined in
claim 1. In addition, other protective coatings may be used in
conjunction with the diaphragm of the present invention aside from
PTFE.
[0031] Although a coating is shown on the concave side of the
diaphragm, it may also be provided on both sides thereof to
entirely coat the diaphragm, or may be provided on the opposite
side thereof.
[0032] Although the embodiment of the diaphragm shown is circular,
it may also be an oval disc shape within the scope of the
claims.
[0033] The embodiment shown and described is for use in a fluid
pump where the diaphragm flexing is actuated by a driving piston.
However, the invention is not limited to such a diaphragm, and also
covers diaphragms for use in hydraulically actuated fluid pumps, as
described above. In such embodiments, the diaphragm would not have
a central aperture 104.
[0034] Although the embodiment shown and described is configured
with the diaphragm positioned with the concave side proximate the
fluid being pumped, the invention is not limited to this
configuration, and the diaphragm may be suitable for use with the
convex side proximate the fluid being pumped, in which case, the
protective coating would be provided at least on the convex side of
the diaphragm.
* * * * *