U.S. patent application number 13/923049 was filed with the patent office on 2013-10-24 for valve design.
The applicant listed for this patent is Isentropic Limited. Invention is credited to Jonathan Sebastian Howes, James Macnaghten.
Application Number | 20130276917 13/923049 |
Document ID | / |
Family ID | 40527515 |
Filed Date | 2013-10-24 |
United States Patent
Application |
20130276917 |
Kind Code |
A1 |
Howes; Jonathan Sebastian ;
et al. |
October 24, 2013 |
Valve Design
Abstract
A valve includes a first pan defining a first array of apertures
(20') and a second part (50) defining a second array of apertures
(60'), the first pan (10') being moveable relative to the second
part (50) between a first configuration in which passage of a fluid
through the valve is substantially prevented and a second
configuration in which passage of fluid is allowed. In one
embodiment, the first pan (10') includes a flexible plate-like
member configured to engage a sealing face of the second part (50)
when in the second configuration and lock in the second
configuration in response to a pressure differential across the
valve. The plate-like member is sufficiently flexible to conform to
a profile of the sealing face in response to a pressure
differential across the valve.
Inventors: |
Howes; Jonathan Sebastian;
(Hampshire, GB) ; Macnaghten; James; (Hampshire,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Isentropic Limited |
Hampshire |
|
GB |
|
|
Family ID: |
40527515 |
Appl. No.: |
13/923049 |
Filed: |
June 20, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12747467 |
Aug 20, 2010 |
8496026 |
|
|
PCT/GB2008/004087 |
Dec 11, 2008 |
|
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13923049 |
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Current U.S.
Class: |
137/511 |
Current CPC
Class: |
Y10T 137/7837 20150401;
F16K 15/14 20130101; Y10T 137/86759 20150401; F16K 3/0254 20130101;
F16K 3/188 20130101; Y10T 137/86734 20150401; F16K 3/029
20130101 |
Class at
Publication: |
137/511 |
International
Class: |
F16K 15/14 20060101
F16K015/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 2007 |
GB |
0724158.1 |
Feb 29, 2008 |
GB |
0803794.7 |
Feb 29, 2008 |
GB |
0803795.4 |
Jul 24, 2008 |
GB |
0813571.7 |
Claims
1. A valve comprising a first part defining a first array of
apertures and a second part defining a second array of apertures,
the first part being moveable laterally relative to the second part
between a closed configuration in which the first and second arrays
of apertures are not registered and passage of a fluid through the
valve is substantially prevented and an open configuration in which
the first and second arrays of apertures are registered and passage
of fluid is allowed; wherein the first part comprises a flexible
plate-like member configured to engage a sealing face of the second
part when in the closed configuration and lock in the closed
configuration against lateral movement in response to a pressure
differential across the valve.
2. A valve according to claim 1, wherein the first and second parts
are configured to lock in the closed configuration against lateral
movement in the presence of a pressure differential across the
valve by means of limiting friction between the first and second
parts.
3. A valve according to claim 1, wherein the plate-like member is
sufficiently flexible to conform to a profile of the sealing face
in response to a pressure differential across the valve.
4. A valve according to claim 1, wherein the flexible plate-like
member is constrained to move in the plane of the member by a
retaining plate
5. A valve according to claim 4, wherein the first part is
constrained to move substantially parallel to a surface defined by
the sealing face of the second part.
6. A valve according to claim 5, wherein the first part is
supported by the sealing face of the second part during movement
between the closed and open configurations.
7. A valve according to claim 1, further comprising an opening
mechanism for moving the first part from the closed configuration
to the open configuration and a closing mechanism for moving the
first part from the open configuration to the closed
configuration.
8. A valve according to claim 1, wherein the first part further
comprises a strengthening member.
9. A valve according to claim 8, wherein the strengthening member
comprises an elongate part extending from substantially one lateral
side of the first part to a second lateral side of the first part,
opposed to the first part.
10. A valve according to claim 7, wherein the first part further
comprises a strengthening member and wherein at least one of the
opening mechanism and the closing mechanism engage the
strengthening member when moving the first part relative to the
second part.
11. A valve according to claim 1, wherein the first part comprises
a pair of moveable plates, each plate of the pair comprising a
sub-set of the first array of apertures.
12. A valve according to claim 11, wherein each plate of the pair
is configured to seal a different group of apertures in the second
array of apertures.
13. A valve according to claim 11, wherein each plate of the pair
is configured to seal a different section of the same group of
apertures in the second array of apertures.
14. A valve according to claim 11, wherein the pair of moveable
plates move in opposite directions to one another as the first part
moves between the closed and open configurations.
15. A valve comprising a first part defining a first array of
apertures and a second part defining a second array of apertures,
the first part being moveable laterally relative to the second part
between a closed configuration in which the first and second arrays
of apertures are not registered and passage of a fluid through the
valve is substantially prevented and an open configuration in which
the first and second arrays of apertures are registered and passage
of fluid is allowed; wherein the first part comprises a flexible
plate-like member configured to engage a sealing face of the second
part when in the closed configuration and lock in the closed
configuration against lateral movement in response to a pressure
differential across the valve; and wherein the plate-like member is
sufficiently flexible to conform to a profile of the sealing face
in response to a pressure differential across the valve.
16. A valve according to claim 15, wherein the flexible plate-like
member is constrained to move in the plane of the member by a
retaining plate.
17. An expander or compressor including a valve comprising a first
part defining a first array of apertures and a second part defining
a second array of apertures, the first part being moveable
laterally relative to the second part between a closed
configuration in which the first and second arrays of apertures are
not registered and passage of a fluid through the valve is
substantially prevented and an open configuration in which the
first and second arrays of apertures are registered and passage of
fluid is allowed; wherein the first part comprises a flexible
plate-like member configured to engage a sealing face of the second
part when in the closed configuration and lock in the closed
configuration against lateral movement due to a pressure
differential across the valve.
18. An expander according to claim 17, wherein the expander
comprises an expansion chamber and the pressure differential across
the valve is between a space inside the expansion chamber and a
space outside the expansion chamber.
19. A compressor according to claim 17, wherein the compressor
comprises a compression chamber and the pressure differential
across the valve is between a space inside the compression chamber
and a space outside the compression chamber.
Description
RELATED APPLICATION DATA
[0001] This application is a continuation of U.S. application Ser.
No. 12/747,467, which was a U.S. national phase application based
on international application no. PCT/GB2008/004087, which was filed
on Dec. 11, 2008, which, in turn, claimed priority to British
national patent application no. 0724158.1, which was filed on Dec.
11, 2007, British national patent application no. 0803795.4, which
was filed on Feb. 29, 2008, British national patent application no.
0803794.7, which was filed on Feb. 29, 2008, and British national
patent application no. 0813571.7, which was filed on Jul. 24, 2008.
Priority benefit of these earlier filed applications is hereby
claimed.
DESCRIPTION
[0002] The present invention relates generally to valves for
controlling flow of gases and/or liquids between two discrete
spaces. In particular, the present invention relates to valves for
use in applications in which the pressure in each of the discrete
spaces can vary such that at some stage there is no pressure
difference between the spaces and at other stages there is a
pressure difference. One application of such valves is in the
compression and/or expansion of gases. However, the valve of the
present invention may be suitable for use in any application that
needs a high efficiency, large valve area, fast valve response and
low pressure losses. This covers, but is not limited to, engines,
vacuum pumps, compressors, expanders, other pumps, ducts and
pipeflow situations.
[0003] Current compression machinery valves are normally of the
non-return type. This means that they can be reed valves, plate
valves, ball valves, poppet valves or other similar devices. For
example, in normal operation in a reciprocating air compressor
comprising a piston configured to move in a cylinder space, the
piston would move from top dead centre (TDC) towards bottom dead
centre (BDC) leading to a drop in the pressure within the cylinder
space. When the pressure has dropped sufficiently to overcome a
spring holding one or more inlet valves closed, the one or more
inlet valves would open and a charge of air is drawn into the
cylinder space. As the piston approaches BDC the airflow will slow
and the pressure difference will decrease allowing the one or more
inlet valves to shut. The piston will now move back towards TDC
compressing the fresh charge of air in the cylinder space. When the
air pressure in the cylinder space is sufficiently high to overcome
a spring holding one or more exhaust valves closed, the one or more
exhaust valves will open allowing the charge of compressed air to
pass into a pressurised space. As the piston approaches TDC this
pressure difference and flow decrease allow the one or more exhaust
valves to close.
[0004] In the case of the simple valve described above, there are a
number of problems associated with the operation of the valve which
limit its effectiveness. Firstly, there needs to be a force acting
to close the valve and this means that there must be a certain
amount of pressure difference applied to overcome this force and
open the valve. This inevitably means there will be some pressure
losses through the valve and that there must be a delay in opening
the valve while the pressure difference increases. There is a
further issue with this type of valve, which is that it can stop
operating correctly if certain resonant frequencies are reached,
possibly leading to the occurrence of valve flutter. A stiff valve
and strong spring may be deployed to limit such undesirable
behaviour, but the stronger the closing spring the greater the
forces required to open the valve, which leads to unnecessary work
and low efficiency.
[0005] If a machine is required to run at high speeds the valves
must open and close more quickly than would be required at lower
speeds leading to higher impact loads when the valves close. The
normal solution is to limit the lift of the valve so that it has
minimal distance to travel. While such an approach may reduce the
impact loads experienced at high speed operation, it also
undesirably reduces the effective valve area.
[0006] In general, expansion Valves are much more complicated than
compression valves as they need to be held open against a flow that
is normally moving in a direction that induces closure forces on
the valve. This means that expansion valves must be actively
controlled. This active control is normally carried out with a cam
and poppet valve arrangement, in which the valve opens and closes
at a preset point in each cycle regardless of the pressure
difference between the two discrete spaces separated by the valve.
This method of operation of expansion valves leads to significant
losses as it is extremely difficult to configure such a valve to
open at or near pressure equalisation (i.e. when the pressure
difference across the valve is substantially zero).
[0007] The expansion valves described above normally require a
strong supporting structure to allow the valves to open against a
pressure differential. This means that such expansion valves are
usually large and heavy components that must be rigid enough not to
lock shut when there is a pressure difference between the two
discrete spaces. Such valves are normally inefficient as they
suffer significant pressure losses when they open without pressure
equalisation.
[0008] Sealing can become an issue when a stiff valve is seated
against a stiff valve face since any contamination by particles can
lead to the valves not sealing and leakages occurring through the
valves when closed. Obtaining good sealing between a valve and
valve face can require precision grinding and/or running the valve
in for a prolonged period.
[0009] The above prior art valves also normally include a guard to
limit the lift of the valve and incorporate the closure spring. In
the example of a piston compressor inlet valve, such a guard forms
an integral space beyond the range of the piston stroke for fluid
to pass into and this space is referred to as deadspace or
clearance.
[0010] In addition to the problems discussed above, the
conventional valve designs all suffer from significantly limited
valve area. In a normal compression piston/cylinder arrangement
where the inlet and outlet valves are both set within a head of the
cylinder, a valve area of 5% or 6% of the piston area is not
uncommon. This limited valve area has a second problem in that
fluid flows through the valve area are often at very high rates if
the compressor is running at a reasonable speed and the pressure
losses through these valves may become significant. A doubling of
valve area will lower the flow velocity through the valve by a
factor of 2 and drop the pressure losses by a factor of
approximately 4.
[0011] To increase the valve area it is common practice in
compressor design to space multiple valves around the cylinder.
This has the effect of increasing the valve area, but also has the
effect of increasing the amount of deadspace or clearance as the
piston rings must be kept below the level of the inlet/outlet
ports.
[0012] The deadspace in the valves, their connection to the main
cylinder and the space around the piston at TDC all combine to give
a total clearance volume. Clearance is normally defined as a ratio
of the clearance volume to the maximum volume (swept
volume+clearance volume):
Clearance = Clearance Volume ( % ) Swept Volume + Clearance Volume
##EQU00001##
and for a piston compressor is normally in the 5%-15% range. The
clearance has a very strong impact on volumetric efficiency, which
is defined as:
Volumetric Efficiency = Gas actually ingested per stroke ( % )
Swept Volume ##EQU00002##
Neglecting Pressure Losses this approximates to:
Volumetric Efficiency = Total Volume - Volume at Suction Valve
Opening ( % ) Swept Volume ##EQU00003##
Where Total Volume=Swept Volume+Clearance Volume
[0013] For most normal piston compressors the volumetric efficiency
is in the region of 70%-80%, but this will vary depending upon a
number of factors, such as the pressure ratio of the
compressor.
[0014] Accordingly, there is a desire to provide an improved valve
which overcomes, or at least alleviates some of the problems
associated with the prior art. In particular, there is a desire to
provide an improved valve that offers fast opening and closing
times, low inertia, high volumetric efficiency, low pressure
losses, pressure activated opening and good sealing when compared
to current valves.
[0015] In accordance with the present invention there is provided a
valve comprising a first part defining a first aperture and a
second part defining a second aperture, the first part being
moveable relative to the second part between a closed configuration
in which passage of a fluid through the valve is substantially
prevented and an open configuration in which passage of fluid is
allowed.
[0016] The first and second parts may configured to lock in the
closed configuration in response to a pressure differential across
the valve. In addition, the first part may be configured to be
sealed against the second part by a pressure differential across
the valve when the first and second parts are locked in the closed
configuration. In this way, a valve may be provided in which a
pressure differential across the valve provides the sealing force
and which remains locked in a sealed configuration whilst any
significant pressure differential exists across the valve. The
valve will automatically release from the locked, sealed
configuration when the pressure differential across the valve drops
to substantially zero. Wear is kept to a minimum as the valve only
moves when it is unloaded or lightly loaded and there is no or very
little pressure difference between the two spaces. This means the
valve may be unlubricated if required.
[0017] In one embodiment the first part may comprise a flexible
plate-like member configured to engage a sealing face of the second
part when in the closed configuration and lock in the closed
configuration in response to a pressure differential across the
valve. The plate-like member may be sufficiently flexible to
conform to a profile of the sealing face in response to a pressure
differential across the valve in order to seal the valve. In this
way, a valve is provided in which a lightweight valve member may be
locked in place by even a small pressure difference and may be used
to provide fast valve movements for a small energy input.
[0018] The conformability of the flexible plate-like member may
further allow the plate-like member to provide a good seal against
the sealing face of the second part even when there is some
contamination between the first and second parts.
[0019] The first part may be moveable laterally relative to the
second part (e.g. in the plane of the second part) such that in the
closed configuration the first and second apertures are not
registered and in the open configuration the first and second
apertures are registered. In this way the first part is held out of
the flow path of the gas when the first and second parts are in the
open configuration and thus any tendency to flutter is avoided and
the air has an unrestricted path through the valve. The first part
may be configured to move parallel to the surface of the sealing
face. The surface of the sealing face may be a plane, a single
curvature surface (e.g. cylindrical surface), or a surface of
rotation.
[0020] The first part may be configured to move linearly relative
to the second part (i.e. to form a linear slide valve) or may be
configured to rotate relative to the second part (i.e. to form a
rotary slide valve). The first part may be supported by the sealing
face of the second part during movement between the open and closed
configurations. Advantageously, the sliding motion of the first
part relative to the second part will tend to act as a
self-cleaning mechanism.
[0021] In one embodiment, the first part may be constrained to move
substantially parallel to the surface of the sealing face of the
second part. For example, in the case of a first part comprising a
flexible plate-like member, the flexible plate-like member may be
constrained to move in the plane of the member (i.e. its stiffest
axis). The flexible plate-like member may be constrained to move
along the surface of the sealing face by a retaining plate.
[0022] The retaining plate may comprise a foraminous screen
configured to substantially cover the flexible plate-like member.
In addition to constraining movement, the retaining plate may
additionally serve to protect the flexible plate-like member. The
retaining plate may be configured allow the flexible plate-like
member to move freely along the plane of the member whilst
substantially resisting movement normal to the plane of the member.
In this way, the retaining plate may reduce buckling or rippling of
the flexible plate-like member. The retaining plate may comprise a
substantially planar body. In this way, the retaining plate may be
configured to provide minimal deadspace when positioned in a
compression or expansion chamber. In one embodiment, the retaining
plate may comprise a relatively thin material (for example laser
cut, water cut or photo etched) that is shaped to provide minimum
deadspace while not impacting on the flow through the valve. For
example, the retaining plate may comprise one of a series of wires
in tension, a series of studs with caps, a thin cut metal sheet or
metallic webbing.
[0023] Since the retaining plate does not need to be moveable, the
retaining plate may be constructed using material selected for
their strength or thermal properties regardless of weight. For
example, the retaining plate may comprise stainless steel with a
thermally beneficial coating (e.g. thermally insulating
coating).
[0024] It is preferable that the retaining plate does not obstruct
the fluid flow through the first and second apertures and, where
near-isentropic behaviour is important that it creates minimal
additional turbulence. If a suitable material or surface coating is
selected then the retaining plate may have low emissivity and/or
low thermal conductivity, which may also contribute to improved
near-isentropic behaviour. The retaining plate may also protect the
valve plate from debris that might otherwise strike the first
part.
[0025] The first and second parts may be configured to lock in the
closed configuration in the presence of a pressure differential
across the valve by means of limiting friction between the first
and second parts. For example, the friction between the flexible
plate-like member when conformed to the profile of the sealing face
of the second part and the sealing face may be sufficient to
substantially prevent lateral movement of the flexible plate-like
member relative to the sealing face. In situations where it is not
possible to rely on limiting friction, locking means may still be
provided by the pressure differential to maintain the first and
second parts in the closed configuration. The locking means may
comprise a positive pressure actuated locking mechanism (e.g. a
latch mechanism) or a static pressure actuated geometric constraint
(e.g. retraining protuberance or stud) for providing additional
resistance against lateral movement between the first and second
parts.
[0026] The valve may comprise opening means for moving the first
part from the closed configuration to the open position and closing
means for moving the first part from the open position to the
closed configuration. The opening means and closing means may be
two discrete mechanisms or may comprise a single mechanism (e.g.
single pneumatic actuator).
[0027] In one embodiment the opening means may comprise opening
biasing means configured to apply a biasing action when the first
part is in the closed configuration and the valve further comprises
trigger means for selectively engaging the closing means when the
first part is in the open configuration. In this way, the opening
device will act to apply a biasing force to the valve while
pressure is still locking the valve in place, whereby the valve
will open at or near pressure equalisation as the biasing force
overcomes the locking force (e.g. frictional force) produced by the
pressure differential.
[0028] The closing means may comprise closure force producer means
configured to overcome the opening biasing means. Operation of the
trigger means may be independent of the pressure across the valve.
In one embodiment, the closure force producer means comprises a
pre-loaded force producer, such that the closure event is fast
relative to the time taken to pre-load the force producer. In
another embodiment, one of the first and second parts may comprise
locating slots to receive one or more closure pins to locate and
additionally reset the closing means. Similarly, one of the first
part and the second part may comprise one or more locating holes to
allow one or more opening pins to locate.
[0029] The closure location may be controlled by one or more
accurately located pins in combination with the closure force
producer, with the flexible plate-like member being held in tension
therebetween. In another embodiment, the lateral position of the
first part relative to the second part when in the opening
configuration may be controlled by one or more accurate location
pins in combination with the opening biasing means, with the plate
being held in tension therebetween.
[0030] The valve may further comprising reset means for selectively
disengaging the closing means when the first part is locked in the
closed configuration by the pressure differential. The closure of
the valve may be actuated mechanically at selectable varying points
in the cycle.
[0031] The opening means may comprise opening housing means,
opening pin means and opening spring means. The closing means may
comprise closing housing means, closing pin means, trigger means
and closing spring means. The closing spring means may be stronger
than the opening spring means. In the case that the opening means
and closing means are provided by a single mechanism, the opening
pin means and the closing pin means may comprise a single pin.
[0032] The first part may be configured to move from the open
configuration to the closed configuration when the trigger means is
activated and the closing spring means moves (via the closing pin
means) the first part to the closed configuration. As the first
part moves towards the closed configuration, the opening pin means
and opening spring means may be configured to move at the same time
since the closing spring means is stronger than the opening spring
means.
[0033] The closing means may be configured to be mechanically reset
and the trigger means locked into place before the opening means is
engaged. The opening means may be configured to bias the first part
in the open configuration via the opening spring means and the
opening pin means. In this way, when the pressure either side of
the valve plate is equal or near equal the first part will move
automatically from the closed configuration to the open
configuration.
[0034] The first part may comprise a strengthening member for
providing localised stiffness. In the case of a flexible plate-like
member, the strengthening member may help to avoid large stresses
in the flexible plate material whilst maintaining the ability of
the flexible plate-like member to conform to the profile of the
sealing face and without significantly increasing the weight of the
first part. The strengthening may comprise an elongate part
extending from substantially one lateral side of the first part to
a second lateral side of the first part, opposed to the first part
or as required by the stress field in the first part. The
stiffening member may be a separate member or it may be an integral
part of the same structure.
[0035] At least one of the opening means and the closing means may
engage the strengthening member when moving the first part relative
to the second part. The opening means and/or closing means may
engage the strengthening member at a location on or ahead of the
centre of gravity of the first part. This configuration is
particular advantageous in the case of a flexible plate-like
member. If the flexible plate-like member is pushed from a point
located behind the centre of gravity, then precise guides may be
necessary to keep the flexible plate-like member in line.
[0036] In one embodiment, the first and second parts comprise
interengageable parts for controlling relative movement (e.g.
oscillating movement) between the first and second parts. In one
embodiment the interengageable parts comprise a guide pin and a
corresponding slot for receiving the guide pin. In this way,
relative movement between the first and second parts may be
restricted to move in path defined by the slot thereby controlling
both the direction and distance of relative movement between the
first and second parts.
[0037] In one embodiment movement of the first part relative to the
second part is constrained by two or more accurately located and
sized location pins such that the first part can only move
backwards and forwards relative to the second part in a single
straight line or single arc and movement in any other direction is
minimised. Advantageously, the use of such an arrangement allows
the movement between the first and second parts to be accurately
controlled without having to provide a precise actuating mechanism.
In one embodiment, one of the first and second parts may further
comprise a stop pin for abutting a guide pin on the other part when
the first and second parts have attained the open or closed
configuration. In one embodiment the stop pin and the location pin
serve the same function by providing both accurate guidance and an
accurate stop position.
[0038] In one embodiment, the first part comprises a first array of
apertures and the second part comprise a second array of apertures.
The first part is moveable laterally relative to the second part
such that in the first configuration the first and second arrays of
apertures are not registered and in the second configuration the
first and second arrays of apertures are registered.
[0039] Each aperture of the first and second array of apertures may
have a relatively small cross-sectional area compared with the area
of the first and second parts respectively. In this way, only a
small relative movement between the first and second parts is
necessary to move the parts between the open and closed
configurations. Furthermore, the use of arrays of relatively small
apertures allows first and second parts having non-uniform shapes
to be produced without the loss of valve area. This also means that
parts of the valve can be interrupted by other structure (such as
supporting struts) with minimal impact on valve area. Lightweight
structures can also be fitted within reciprocating pieces, such as
the piston head.
[0040] In the case of a first part comprising a flexible plate-like
member, the aperture size may be configured such that the flexible
plate-like member can bridge corresponding apertures in the second
part without significant sagging. Furthermore, the aperture size
may be configured to ensure that the flexible plate-like member
does not catch a lip of the corresponding apertures in the second
part as the first part moves into the closed configuration.
[0041] In one embodiment, the total open aperture area (i.e. the
total open aperture area when the first and second parts are in the
open configuration) is over 20% of the total valve area. In another
embodiment, the total open aperture area is over 30% of the total
valve area. In yet another embodiment, the total open aperture area
is over 40% of the total valve area. In yet another embodiment, the
total open aperture area is over 50% of the total valve area.
[0042] In one embodiment, the aperture density (i.e. the number of
apertures per unit area of valve surface) is greater than 1000 per
m.sup.2. In another embodiment, the aperture density is greater
than 2000 per m.sup.2. In another embodiment, the aperture density
is greater than 4000 per m.sup.2. In yet another embodiment, the
aperture density is greater than 8000 per m.sup.2. In yet a further
embodiment, the aperture density is greater than 12000 per m.sup.2.
In a yet a further embodiment, the aperture density is greater than
16000 per m.sup.2.
[0043] In one embodiment, the average aperture area is less than 1%
of the total valve area. In another embodiment, the average
aperture area is less than 2% of the total valve area. In a further
embodiment, the average aperture area is less than 3% of the total
valve area. In yet a further embodiment, the average aperture area
is less than 4% of the total valve area. In a yet further
embodiment, the average aperture area is less than 5% of the total
valve area.
[0044] In one embodiment, the sealing area around the apertures is
less than 40% of the total valve area. In another embodiment, the
sealing area around the apertures is less than 30% of the total
valve area. In a further embodiment, the sealing area around the
apertures is less than 20% of the total valve area. In yet a
further embodiment, the sealing area around the apertures is less
than 10% of the total valve area.
[0045] In one embodiment the valve has a mass of less than kg per
m.sup.2. In another embodiment, the valve has a mass of less than
15 kg per m.sup.2. In yet another embodiment, the valve has a mass
of less than 10 kg per m.sup.2. In yet a further embodiment, the
valve has a mass of less than 5 kg per m.sup.2. In a yet further
embodiment, the valve has a mass of less than 2 kg per m.sup.2.
[0046] The first and second array of apertures may be evenly (e.g.
homogenously) distributed across the first and second parts.
Advantageously, such a homogenous distribution of apertures has
been identified to reduce unwanted turbulence when near-isentropic
compression or expansion processes are required.
[0047] The first part may comprise of one or more valve plates,
which can be configured in one layer or in multiple layers.
[0048] In one embodiment the first part comprises a pair of
moveable plates (e.g. linearly moveable or rotatably moveable),
each plate of the pair comprising a sub-set of the first array of
apertures. The pair of moveable plates may be configured to move in
opposite directions to one another as the first part moves between
the first and second configurations. In one embodiment, each plate
of the pair is configured to seal a different group of apertures in
the second array of apertures. In another embodiment, each plate of
the pair is configured to seal a different section of the same
group of apertures in the second array of apertures. In this way,
the valve may be configured to either reduce the closure time or
increase the valve area beyond that achievable with one or more
valve plates sliding in a single layer.
[0049] In the case that the first part is configured to move
linearly relative to the second part, the first part may in one
embodiment comprise two further pairs of moveable plates, each pair
being associated with a different axis (e.g. different coplanar
axis), with each pair of moveable plates being configured to move
in opposite directions along its respective axis. In another
embodiment, the first part may comprise three further pairs of
moveable plates, each pair being associated with a different axis
(e.g. different coplanar axis), with each pair of moveable plates
being configured to move in opposite directions along its
respective axis. Each axis associated with a pair of moveable
plates may be equally spaced from an adjacent axis.
[0050] In one embodiment, the profile of the sealing face of the
second part is configured permit smooth movement of the first part
relative thereto. For example, the or each aperture in the sealing
face may comprise a peripheral edge region having a radius
configured to ensure good sealing whilst enabling the first part to
slide thereover. In this way, the risk of the first part `picking`
the edge as it slides over the second part may be reduced. Such
picking may be a particular problem where the first part comprises
the flexible plate-like member since the plate may be flexible
enough to sag slightly as it crosses the open aperture. For example
with an aperture size of 4 mm by 4 mm, a 0.5 mm mylar valve and a
sealing edge of 1 mm around the aperture, a radius of between 0.05
mm and 0.1 mm could be used on the aperture in the second part.
[0051] The valve material does not need to be particularly strong
as it is supported by the sealing face, this means it can be
lighter, have lower inertia and hence, can move faster for less
energy. The valve sealing area may not be particularly large in
relation to the valve area. The smaller the sealing area the higher
the precision that is required to control the valve plate position
in order to avoid leakage. Generally with one valve plate a
theoretical maximum of just under 50% of the total area can be
achieved and with two plates this figure can be increased to just
under 66.7%. Other useful linear combinations are made up from 6
and 8 valve plates with theoretical maximums of just under 86% and
89% respectively. One further advantage of multiple valve plates
with large total aperture areas is that each plate can be very
light and can therefore be faster acting.
[0052] The valve material can be made from a variety of materials,
some examples are plastics (e.g. Mylar, Peek), composites (e.g.
Carbon, Glass, Aramid Epoxy), metals (e.g. stainless steel) and
ceramics (e.g. thin silicon Carbide Carbon sheets). The
temperatures and pressures involved will have a significant impact
on the actual material selected to ensure that it does not
adversely deform under use. In certain applications it can be
useful to use materials that suffer from creep and plastic
deformation as they have other beneficial properties. In these case
the creep and plastic deformation can be overcome by bonding a
stronger material to provide localised strength, such as stainless
steel on Mylar. The valve material (including the flexible
plate-like member) may be laser cut, water cut, photo etched, cut
or formed by other means.
[0053] Embodiments of the present invention will now be described
by way of example with reference to the accompanying drawings in
which:
[0054] FIG. 1a shows a schematic illustration of a double acting
piston comprising a valve according to a first embodiment of the
present invention;
[0055] FIG. 1b is a schematic illustration of a section "A" of a
valve plate means of the piston of FIG. 1a;
[0056] FIGS. 2a and 2b are schematic illustrations of a valve plate
means in combination with sealing face plate means with the valve
plate means in the open and closed positions respectively;
[0057] FIG. 3 is a schematic illustration of the sealing face means
of FIGS. 2a and 2b without the valve plate means;
[0058] FIGS. 4a and 4b are schematic illustrations of an opening
means of the piston of FIG. 1a;
[0059] FIGS. 5a and 5b are schematic illustrations of a closing
means of the piston of FIG. 1a;
[0060] FIG. 6 is a schematic view of valve plate means of a valve
in accordance with another embodiment of the present invention;
[0061] FIG. 7 is a schematic view of sealing face plate means for
use with the valve plate means of FIG. 6;
[0062] FIG. 8 is a schematic view of a valve comprising the valve
plate means and sealing face plate means illustrated in FIGS. 6 and
7 in an open position;
[0063] FIG. 9 is a schematic cross-sectional view of the valve of
FIG. 8 in the open position;
[0064] FIG. 10 is a schematic view of the valve of FIG. 8 in a
closed position;
[0065] FIG. 11 is a schematic cross-sectional view of the valve of
FIG. 8 in the closed position;
[0066] FIGS. 12a, 12b, 12c, 12d, 12e and 12f are schematic plan
views showing different multiple linear and rotary valve
configurations in a valve in accordance with embodiments of the
present invention;
[0067] FIGS. 13a, 13b, 13c, 13d, 13e and 13f show schematic
cross-sectional views of passageway configurations in accordance
with embodiments of the invention where 13e and 13f show the
preferred implementation; and
[0068] FIG. 14 is a schematic view of a first retaining plate;
[0069] FIG. 15 shows a geometric restraint in the form of a
restraining stud that can be used when limiting friction is not
sufficient to lock the valve plate in place under the force of a
pressure differential; and
[0070] FIG. 16 is a schematic detailed view of a valve plate means
with integral stiffening member.
DETAILED DESCRIPTION OF FIGURES
FIGS. 1a and 1b
[0071] FIG. 1a shows a schematic illustration of a double acting
piston 1 comprising a valve 5 including: piston face means 2
including multiple sealing ports 60; retaining plate means 3; valve
plate means 10; opening means 100; and closing means 200.
[0072] As shown in FIG. 1b, valve plate means 10 comprises:
multiple valve plate ports 20; multiple attachment point means 30;
and locating pins means 40. In use, valve plate means 10 is
moveable relative to piston face means 2 between a closed position
for substantially preventing fluid flow through the valve 5 and an
open position for allowing passage of fluid through the valve. In
the closed position, sealing ports 60 and valve plate ports 20 are
wholly unregistered and the valve plate means is sealed against the
piston face means 2. In the open position, sealing ports 60 and
valve plate ports 20 are registered to form a multiple passageways
through the valve.
FIG. 2a
[0073] FIG. 2a shows valve plate means 10' according to a second
embodiment of the invention in combination with sealing face means
50. Valve plate means 10' comprises strengthening strip means 70
and multiple valve plate ports 20'; sealing face plate means 50
comprises multiple sealing face ports 60'; and locating pins means
40'. As shown in FIG. 2a, the valve plate means 10' is in the open
position with the valve plate ports 20' wholly aligned with the
sealing face ports 60' on the sealing face means 50.
FIG. 2b
[0074] FIG. 2b shows valve plate means 10' in the closed position
with the valve plate ports 20' wholly offset with the sealing face
ports 60' on the sealing face means 50.
FIG. 3
[0075] FIG. 3 shows sealing face means 50 comprising multiple
sealing face ports 60' and location pins 40'.
FIGS. 4a and 4b
[0076] FIGS. 4a and 4b shows opening means 100 comprising opening
spring means 101, opening pin means 102 and opening housing means
103.
[0077] When the opening spring pin means 102 is moved in the
direction that compresses the opening spring means 101 the opening
spring means 101 provides a biasing force that can be used to move
valve plate means 10 via the opening pin means 102 from the closed
position to the open position when the pressure differential across
the valve 5 is at or near pressure equalisation.
FIGS. 5a and 5b
[0078] FIGS. 5a and 5b shows a closing means 200 comprising closing
spring means 201, closing housing means 203, trigger means 204 and
closing shaft means 207 comprising closing pin means 202, trigger
slot means 205 and reset roller 206.
[0079] When the reset roller means 206 runs along a reset cam means
(not shown) it pushes the closing shaft means into the closure
housing means 203 such that the closure spring means 201 is
compressed and the trigger means 204 drops into the trigger slot
means 205. The reset roller means 206 moves past the reset cam
means (not shown) and the closure spring means 201 pushes the
closing shaft means 207 via the trigger slot means 205 against the
trigger means 204. In this position opening means 100 can move
valve plate means 10 from the closed position to the open position
at or near pressure equalisation.
[0080] When the trigger means 204 contacts a trigger stop means
(not shown) it lifts the trigger means 204 out of the trigger slot
means 205 and the closing spring means 201 moves the closing pin
means 202 via the closing shaft means 207 such that valve plate
means 10 coupled to the closing pin means 202 will move from the
open position to the closed position.
[0081] The closing spring means 201 is stronger than the opening
spring means 101 such that the movement of the valve plate means 10
may also `reload` the opening spring means 101 by compressing
it.
FIGS. 6 to 10
[0082] FIGS. 6 to 10 show valve means 300 according to another
embodiment of the invention, valve means 300 comprising first valve
plate means 302, second valve plate means 301, and valve sealing
face means 303. In use, second valve plate means 301 is located
between first valve plate means 302 and valve sealing face means
303.
[0083] FIGS. 8 and 9 show valve means 300 in the open position. In
order to close the valve it is necessary to move valve plate means
302 a distance x to the left and valve plate means 301 a distance y
to the right. In the open position there is no pressure
differential across the valve plate means 301 and 302 and they can
therefore slide easily over each other and the valve sealing face
means 303.
[0084] FIGS. 10 and 11 show valve means 300 in the closed position.
In use there will be a pressure differential across the valve means
300 such that valve plates 302 is forced on to valve plate means
301 which in turn is forced on to valve sealing face means 303.
This force will vary with the pressure and will only drop close to
zero at or near pressure equalisation across the valve means
300.
[0085] In this closed position the valve sealing port means are
covered by solid section means 307 of the valve plate means 302 and
the valve sealing port means 306 are covered by the solid section
means 308 of the valve plate means 301.
FIG. 12a
[0086] FIG. 12a shows the basic movement action of a single acting
valve means 400 where a valve cover means can move in a linear
direction as indicated to cover a valve port means 402. The
theoretical maximum valve area with this configuration is just less
than 50%.
FIG. 12b
[0087] FIG. 12b shows the basic movement action of a double acting
valve means 410 where a valve cover means can move in a linear
direction as indicated to cover a valve port means 413 and another
valve cover means 412 moves in the opposite direction to cover
valve port means 414. The theoretical maximum valve area with this
configuration is just less than 66.6%.
FIG. 12c
[0088] FIG. 12 c shows the basic movement action of a six way
linear valve means 420, where valve cover means 421,422,423,424,425
and 426 move in the indicated directions to cover ports
427,428,429,430,431 and 432. The theoretical maximum valve area
with this configuration is just less than 86%.
FIG. 12d
[0089] FIG. 12d shows the basic movement action of an eight way
linear valve means 440, where valve cover means 441, 442, 443, 444,
445, 446, 447, 448, 449 and 450 move in the indicated directions to
cover ports 451, 452, 453, 454, 455, 456, 457, 458, 459 and 460.
The theoretical maximum valve area with this configuration is just
less than 89%.
FIG. 12e
[0090] FIG. 12e shows the basic movement action of a single acting
rotary valve means 470 where a valve cover means 471 can move in a
rotational direction indicated by the arrow to cover a valve port
means 472. The theoretical maximum valve area with this
configuration is just less than 50%.
FIG. 12f
[0091] FIG. 12f shows the basic movement action of a double acting
rotary valve means 480 where a valve cover means 481 can move in a
rotational direction indicated by the arrow to cover a valve port
means 483 and another valve cover means 482 moves in the opposite
rotational direction to cover valve port means 484. The theoretical
maximum valve area with this configuration is just less than
66.6%.
FIGS. 13a and 13b
[0092] FIGS. 13a and 13b shows a valve sealing face port means 600
and a port edge means 603. A valve plate means has corner means 602
that may catch on port edge means during operation as both corners
have 90 degree corners with no rounding. This is potentially
problematic and should be avoided if possible.
FIGS. 13c and 13d
[0093] FIGS. 13c and 13d shows a valve sealing face port means 610
and a port edge means 613. A valve plate means has corner means 612
that will not catch on port edge means 613 as this has been over
rounded. This is not preferable as the rounding covers the whole of
the sealing area and the valve plate means 611 is unlikely to seal
properly.
FIG. 13e
[0094] FIGS. 13e and 13f shows a valve sealing face port means 620
and a port edge means 623. A valve plate means has corner means 622
that will not catch on port edge means 623 as this has been
slightly rounded. In this case where the rounding covers, for
example, 5-10% of the sealing area then the valve plate means 621
will still seal. This is likely to be least problematic, however
the final degree of rounding is determined by port size, valve
plate thickness and valve plate material properties.
FIG. 14
[0095] FIG. 14 shows a retaining plate means 501 comprising
aperture means 502 that allow free flow of fluid through the ports
and cover means 503 that constrain the one or more valve plates
(not shown). The retaining plate means 301 has a shallow profile
that helps to minimise deadspace.
FIG. 15
[0096] FIG. 15 shows a geometric constraint in the form of a
restraining stud 700 for restraining movement of valve plate means
710 relative to valve sealing face 720. In FIG. 15, F.sub.N is the
normal force on the valve, the product of a local effective area
and the pressure differential (F), .theta. is the angle of the
restraining stud at the valve seating surface, F.sub.o is the force
to be overcome by the applied opening force (=F tan .theta.), and D
is the direction of the applied opening force.
[0097] Screen valves of the type used in the piston of FIG. 1a rely
on pressure differentials across the valve to lock the valve closed
such that an opening force may be applied ahead of the opening
resulting in a rapid opening when the pressure differential
approaches zero. Two forms of restraint against opening are
available: limiting friction and geometric constraint.
Limiting Friction
[0098] The use of limiting friction is appropriate to a
non-lubricated valve. Limiting friction provides absolute restraint
against motion if the normal force on the valve (generally close to
the product of the pressure and the available opening area of the
valve) multiplied by the limiting friction coefficient is greater
than the imposed opening force applied to slide the valve in its
own plane. As an example:
Porosity of valve=30% Maximum pressure differential for
opening=0.01 bar (1000 N/m.sup.2) Limiting friction
coefficient=0.35 Total valve opening area; Diameter of valve=0.3
m
Opening area of valve = .pi. .times. 0.3 2 .times. 0.28 4 = 0.0198
m 2 ##EQU00004##
Force to open valve at 0.01 bar pressure differential
= 0.0198 .times. 1000 .times. 0.35 = 6.93 N ##EQU00005##
Since a valve of this type may, typically, be required to work at a
10 bar differential in an engine application this represents
operation triggered by cycle gas pressure at 0.1% of cycle peak
pressure.
Geometric Constraint
[0099] If the valve is to work in a lubricated environment limiting
friction may not be available to lock the valve in place as the
lubricant will provide a viscous restraint and so the valve may
drift open due to the applied opening force.
[0100] In this case a restraining stud 700, or group of studs, is
provided and the gradient of the stud 700 at the point of contact
with the valve plate provides a lateral component of resistance to
opening when a pressure differential exists.
[0101] Due to valve plate flexibility, the entire valve area may
not be effective in providing normal force to resist climbing over
the restraining stud and so an "effective area" is now multiplied
by the sealing pressure on the plate. When multiplied by the
tangent of the stud angle the necessary opening force is found.
Steeper stud angles will correspond to greater opening forces and
hence to lower pressure differentials at opening. This method of
valve locking can work in the absence of useful friction.
FIG. 16
[0102] FIG. 16 shows a valve plate means 10'' comprising multiple
valve plate ports 20' and an integral stiffening member 70'defined
by a thicker and hence stiffer localised section of the valve plate
means 10''.
* * * * *