Spring actuated check valve

A check valve is for use in a fluid system. A valve body has an inlet end, a valve cavity, and an outlet end. A valve enables a valve assembly to control the flow of fluid therethrough. A plug of the valve assembly includes tapered and non-tapered sections, the tapered section having a cross section that increases in diameter in a direction that is downstream from the inlet end of the valve body. A sealing ring is mounted to reciprocate on the non-tapered section and an elastomeric actuation ring is mounted along the tapered section. The tapered section biases the actuation ring to a normal position, at which the actuation ring contacts and positions the sealing ring in contact with the valve body and the valve assembly to prevent fluid from flowing out the outlet end of the valve body.

BACKGROUND

Check valves are used in a variety of applications in fluid systems to allow for the unidirectional passage of upstream pressurized fluid, that is, pressurized fluid upstream of the outlet of a check valve, above a particular preselected threshold pressure level. Check valves of the expandable o-ring style type can include an elastomeric ring that can be mounted on a conical shaped tapered surface of a valve. The elastomeric ring usually has a memory shape and is mounted to constrict the tapered surface, causing the ring to be biased to a normal position on the tapered surface that has a smaller cross sectional diameter. When the elastomeric ring is in this normal position, the ring normally seals against the valve body to prevent the flow of fluid through the valve.

If fluid pressure downstream from the elastomeric ring is greater than fluid pressure upstream from the ring, the downstream pressure along with the bias of the elastomeric ring will cause the ring to return to the normal position, closing the valve. The check valve will also remain closed if upstream fluid pressure is greater than downstream pressure unless the upstream pressure exerts a total force against the elastomeric ring that is greater than a predetermined cracking force, opening the valve. The predetermined cracking pressure is typically dependent on the total biasing force of the ring's memory shape and the amount of surface area of the ring that is exposed to fluid pressure at a given time.

Expandable o-ring style check valves are desirable to use since they have an inherent advantage in that a check valve spring and sealing member are usually combined into a single elastomeric ring component. However, where a single elastomeric ring is used both as a valve spring and sealing member, a ring material must be selected that can allow the ring to perform adequately both in spring actuation and sealing capacities. It follows that the use of a single elastomeric ring may not allow for the use of ring shapes and materials optimal for both spring actuation and sealing.

SUMMARY

A check valve is for use in a fluid system such as an air compressor system, liquid pump or other fluid system that allows for the movement of fluid through the valve. A valve body has an inlet end through which a fluid, such as atmospheric air, enters the check valve, and an outlet end, through which fluid exits the check valve. A valve cavity within the valve body extends between about the inlet end and the outlet end of the valve. A valve assembly is located at a position relative to the valve cavity that enables the valve assembly to control the flow of fluid through the valve cavity.

A plug of the valve assembly includes both tapered and non-tapered sections, the tapered section having a cross section that increases in diameter in a direction that is downstream from the inlet end of the valve body. The valve assembly also includes a sealing ring that is mounted to reciprocate on the non-tapered section and an elastomeric actuation ring mounted along the tapered section. The tapered section biases the actuation ring to a normal position, at which the actuation ring contacts and positions the sealing ring in contact with the valve body and the valve assembly to prevent fluid from flowing downstream from the inlet end out the outlet end of the valve body.

The valve assembly allows fluid to flow downstream from the inlet and out the outlet end of the valve body when the fluid pump produces an amount of fluid pressure that is necessary to create a force against the sealing ring that is sufficient to cause the sealing ring to exert a force against the actuation ring and cause the sealing ring to be located at a position away from the valve body to create a preselected clearance between the valve body and sealing ring.

By including separate actuation and sealing rings, the invention allows each ring to have a shape or be constructed of a material that is better suited for performing the respective function of each ring. The combination of rings also allows the check valve to be better optimized to accommodate a particular liquid or gas, be better incorporated into in a particular system type, or be better adapted to a particular check valve application.

In some embodiments of the invention, the portion of the valve cavity, between about the inlet end of the valve body and the location where the sealing ring contacts the valve body, can have a minimum cross sectional area that allows the pressure of fluid flowing through the preselected clearance to be sufficient to continuously remove fluid from the valve cavity to prevent substantial accumulation of back pressure produced by the fluid pump upstream of the valve when the sealing ring is located at a position away from the valve body to create the preselected clearance between the valve body and sealing ring. Thus, in some embodiments, this ability to continuously remove fluid to prevent substantial accumulation of back pressure enables the accommodation of a process flow of fluid through the valve. The invention can also be incorporated in valves that are limited to accommodating non-process flows of fluid, such as leakage clearance flows and control flows, or applications where substantial accumulations of back pressure are acceptable or desirable.

Those skilled in the art will realize that this invention is capable of embodiments that are different from those shown and that details of the structure of the disclosed check valve can be changed in various manners without departing from the scope of this invention. Accordingly, the following drawings and descriptions are to be regarded as including such equivalent check valves as do not depart from the spirit and scope of the invention.

DETAILED DESCRIPTION

Referring to the drawings, similar reference numerals are used to designate the same or corresponding parts throughout the several embodiments and figures. Specific embodiment variations in corresponding parts are denoted with the addition of lower case letters and/or single or multiple prime indicators to reference numerals.

FIG. 1is an exploded perspective view of a check valve20aof the invention depicting an exterior view of a valve body22a. A valve assembly24aincludes an elastomeric sealing ring26a, actuation ring28a, and plug30a. The plug30aincludes a shaft32ahaving multiple flutes33apositioned to function as air passages when the plug30ais inserted into a valve cavity34aof the valve body22a. The valve body22aincludes upstream threads36alocated at an inlet end38aof the valve body22aand downstream threads40alocated at an outlet end42aof the valve body22a. The upstream and downstream threads36aand40aallow for attachment to other components of a fluid system along a path of flowing fluid. Engagement surfaces44aallow for installation of the valve body22ainto the fluid system using a wrench or other suitable installation tool.

As best understood with reference to the assembled side cross sectional view of the check valve20adepicted inFIGS. 2A and 2B, the valve cavity34aextends through the valve body22afrom the inlet end38ato the outlet end42aand is intended to allow air to pass in a direction46athat is downstream from the inlet end38a. A pressure chamber48ais the portion of the valve cavity34athat is located upstream from and adjacent the sealing ring26a.

The plug30aincludes a tapered section50aand a non-tapered section52a. The tapered section50ahas a cross section that increases in diameter in the direction46a, that is away from the face54aof the valve body22aand downstream from the inlet end38aof the valve body22a. The actuation ring28ais mounted around the plug30ato reciprocate on the tapered section50a. Due to an elastic spring force creating a memory shape, the internal diameter of the actuation ring28a, when assuming its memory shape, is slightly less than the smallest diameter of the tapered section50athat the actuation ring28asurrounds when positioned along the tapered section50a. As a result, the elastomeric seal74amaintains a sealing fit against the tapered section50ato prevent the passage of air therebetween. The memory shape of the actuation ring28aalso serves to bias the actuation ring28ato move along the tapered section50ato a normal position where the actuation ring28ais located at or toward the smallest diameter of the tapered section50a, as depicted inFIG. 2A.

The sealing ring26ais mounted around the plug30ato reciprocate on the non-tapered section52a. When the actuation ring28ais located at the normal position, the positioning of the actuation ring28aand its contact with the sealing ring26aalso causes the sealing ring26ato move along the non-tapered section52ato a normal position as depicted inFIG. 2A. When the sealing ring26aand actuation ring28aare in the normal positions, the sealing ring26acontacts the valve body22aat an inside chamfer56aof the valve cavity34a. The chamfer56ahas a cross section that increases in diameter in the direction46athat is downstream from the inlet end38aof the valve body22a. While the sealing ring26ais in the normal position, the curvature of the sealing ring26apartially fits into and seals with the chamfer56a, preventing the flow of air therebetween. Since the sealing ring26a, when in contact with the chamfer56a, seals against both the valve body22aand the actuation ring28a, the sealing ring26aprevents the passage of air through the outlet end42awhen in the normal position to close the check valve20a.

When the sealing ring26amoves along the non-tapered section52ain the downstream direction46a, the sealing ring26apushes against the actuation ring28ato move it in the downstream direction46aon the tapered section50a. The tapered section50aexpands the actuation ring28ain an outwardly radial direction from the tapered section50a, as shown inFIG. 2B. The memory shape of the actuation ring28aprovides a spring force that opposes this radial expansion, biasing the actuation and sealing rings28aand26ato the normal positions shown inFIG. 2A.

Consider the check valve20awhen used with an air compressor system in which a compressor pump (not shown inFIGS. 2A and 2B) forces air to enter the check valve20athrough the inlet end38a. Referring toFIG. 2A, as the compressor pump begins to pressurize the valve cavity34a, the amount of force exerted by the increased pressure against the sealing ring26ais directly related to the amount of surface area of the sealing ring26athat is exposed to the amount of pressure produced by the compressor pump and present in the valve cavity34a. A cracking pressure is the minimum level of air pressure that must be present in the valve cavity34ato create a cracking force against the sealing ring26a. Such force is required to initially move the sealing ring26aagainst the biasing force of the actuation ring28aand away from contact with the valve body22atoward a position that establishes a preselected clearance between the sealing ring74aand valve body22a.

The position of the sealing ring26aon the non-tapered section50aof the plug30aexposes the sealing ring26ato air pressure that is present throughout the valve cavity34a, including the flutes33aand pressure chamber48a. Thus, the actual amount of force that the sealing ring26ais subjected to is a result of the air pressure within the check valve20a. The sealing ring26ain turn exerts a force against the bias of the actuation ring28a. When a cracking force is exerted against the sealing ring26a, both the sealing ring26aand actuation ring28amove in the downstream direction46aagainst the bias of the actuation ring28ato create the preselected clearance between the sealing ring26aand valve body22a. Since the biasing force of the actuation ring28ais created by the memory shape of the actuation ring28aas it is stretched in a radial direction by the tapered section50a, the maintenance of the preselected clearance continues to depend on the actual force exerted by the air pressure against the sealing ring26aand actuation ring28a. This remains true even if the magnitude of the force is not directly and proportionately related to the magnitude of air pressure in the valve cavity34a.

ComparingFIGS. 2A and 2B, when the air pressure within the valve cavity34aof the closed check valve20areaches the cracking pressure to exert a cracking force against the sealing ring26a, the sealing ring26aloses contact with the chamfer56a. As the sealing ring26amoves away from contact with the chamfer56a, an increased amount of surface area of the sealing ring26abecomes exposed to upstream air pressure from the compressor pump. Some surface area of the actuation ring28aalso becomes initially exposed to upstream air pressure. Since the force exerted against the sealing ring26ais directly related to the amount of surface area that is exposed to air pressure moving downstream from the inlet end38a, the amount of force exerted against the sealing ring26awill increase in direct proportion to the increase in the amount of surface area that becomes exposed due to the lost contact between the sealing ring26aand chamfer56a. Therefore, once the sealing ring26amoves out of contact with the chamfer56a, the amount of force exerted against the sealing ring26awill increase by virtue of the increased amount of exposed surface area of the sealing ring26a, even if the amount of air pressure produced by the compressor pump does not itself increase further.

Once the contact between the sealing ring26aand chamfer56ais lost, the subsequent movement of air through the open valve20apast the sealing ring26awill also create a dynamic force, in addition to the force produced by the upstream air pressure itself, that will further increase the total amount of force that is exerted against the sealing ring26a. Since the lost contact between the sealing ring26aand chamfer56aalso results in the actuation ring28abecoming initially exposed to upstream air pressure, an additional amount of force, directly related to the amount of area of the actuation ring28aexposed to upstream air moving in the downstream direction46a, will be exerted against the actuation ring28aas well. This additional force against the actuation ring28ais added to the force exerted by the sealing ring26ato comprise the total force acting against the bias of the actuation ring28aafter it has moved on the tapered section50ain the downstream direction46a.

Due to the increased total forces that result from the lost contact between the chamfer56aand sealing ring26a, it may be possible to reduce the air pressure produced by the air compressor to a level that is below the cracking pressure, once the sealing ring26aand chamfer56aare out of contact, without causing the check valve20ato close. However, due to the spring force of the actuation ring28a, the total force actually exerted against the sealing ring26aand actuation ring28athat is necessary to keep the sealing ring26aout of contact with the chamfer56aand maintain a preselected clearance must be at least as great as the cracking force, which is the total force exerted against the sealing ring26aand actuation ring26aby the cracking pressure produced by the compressor pump when the sealing ring26ainitially moves out of contact with the chamfer56a. If at any time the total force exerted against the sealing ring26aand actuation ring28afalls below the cracking force, the spring force of the actuation ring28awill again cause the sealing ring26ato seal against the chamfer56aand close the check valve70a.

If the force exerted against the sealing and actuation rings26aand28acontinues to increase beyond the cracking force after the sealing ring26aand chamfer56alose contact, the sealing ring26awill continue to move along the non-tapered section52aand the actuation ring28awill continue to move along the tapered section until the check valve20ais opened fully and has reached a maximum preselected clearance or a “valve clearance”58abetween sealing ring28aand valve body22a, as depicted inFIG. 2B. The minimum amount of air pressure that the compressor pump must produce and maintain in the valve cavity34aof the check valve20ato create sufficient clearance force against the sealing and actuation rings26aand28aand maintain the check valve20ain the fully open position is the clearance pressure of the check valve20a. When the check valve20ais fully open, the increased total amount of clearance force exerted against the sealing ring24ais partly due to the increased amount of surface area of the sealing and actuation rings26aand28aexposed to air from the compressor and also partly due to the dynamic force of the air as it passes the sealing and actuation rings26aand28a.

When opened fully, the check valve20arestricts further movement of the sealing and actuation rings26aand28awith a restrictor60a, which impedes further radial stretching and movement of the actuation ring28ain the downstream direction46a. In this position, a valve clearance58aexists between the valve body22aand the sealing ring26a, which is the maximum preselected clearance that the check valve20aprovides for the passage of air from the valve cavity34aout the outlet end42aof the valve body22a.

Since the total amount of force exerted against the sealing and actuation rings26aand28aincreases due to increased exposed surface area of the sealing and actuation rings26aand28adue to the dynamic forces of moving air, for some embodiments of the invention, the amount of air pressure that must be maintained in the valve cavity34ato maintain the check valve20ain a fully open position and to maintain the valve clearance58abetween the valve body22aand the sealing ring26amay be an amount that is substantially less than the cracking pressure.

With the inclusion of separate actuation and sealing rings, the invention allows each ring to be constructed of a material that is better suited for performing the respective function of each ring. The combination of rings also allows the check valve to be better optimized to accommodate a particular liquid or gas, be better incorporated into in a particular system type, or be better adapted to a particular check valve application.

In one example, a suitable combination includes the use of a silicone elastomer actuation ring with a Teflon sealing ring for a check valve used in an air compressor system. Such combination is evaluated for the highly elastomeric, high-temperature resistance, viscosity-retaining, and hardening resistance properties of silicone, making silicone highly suited for use as an actuation ring. Other suitable actuation ring materials for air compressor systems include nitrile elastomers and viton elastomers. Nitrile and viton elastomers can also be appropriately implemented in actuation rings of check valves used in liquid systems such as those that accommodate oil and water.

However, in some check valve applications, such as those that accommodate liquid fluids such as oil or water, silicone is considered to be less effective as a sealing material due to its tendency to swell and its relatively low tear resistance. In comparison, Teflon, though lacking the highly elastic properties of silicone, exhibits resistance swelling, a low coefficient of friction, and effective sealing properties enabling the material to more effectively reciprocate along a non-tapered section of a plug of the invention and seal against a valve body of the invention. Although some properties of silicone can be improved with the addition of appropriate additives or when silicone is incorporated in certain gasket forms, Teflon is often considered superior as a sealing ring in such liquid-accommodating applications.

Other suitable sealing ring materials for both air compressor systems and liquid accommodating systems such as water and oil pump systems include hard viton elastomers, hard nitrate elastomers, and stainless steel. Brass is also considered suitable as a sealing ring material for some air compressor system applications.

Some types of materials, such as Aflas, include multiple material varieties that can be separately incorporated as either sealing rings, actuation rings, or both. However, such materials are often expensive and are therefore optimal only in highly specific applications.

Some embodiments of the invention can be sized with sufficient cross sectional clearances to prevent substantial accumulations of fluid backpressure upstream of the valve. This can be true regardless of whether the pumped fluid creating the backpressure is liquid or gas. For example, consider the check valve20aofFIGS. 2Aand B used with a fluid pump that is a compressor pump of an air compressor system. Referring toFIG. 2B, the portion of the valve cavity34a, that is between about the inlet end38aand about the location where the sealing ring26acontacts the valve body22aat the chamfer56a, is sized to have a cross sectional area that allows the pressure of air flowing through the valve clearance58ato be sufficient to continuously remove air from the valve cavity34aso as to prevent a substantial accumulation of back pressure produced by the air compressor upstream of the check valve20a, when repeated cycles of the compressor pump's compression cylinder repeatedly cause the sealing ring26aand actuation ring28ato be located at a position away from the valve body22ato create the preselected valve clearance58a. This holds true as the compressor pump maintains levels of air pressure in the valve cavity34aup to and including the clearance pressure, even if the clearance pressure is greater than the cracking pressure. Since inFIG. 2B, the location where the sealing ring28acontacts the body22ais the chamfer56aand since the pressure chamber48aof the valve cavity34ais directly adjacent the chamfer56a, the valve cavity34ais directly open to clearances between the valve body22aand sealing ring26avia the flutes33awhenever the valve20ais partially or fully open.

There will be a continuous flow of air from the valve cavity34athrough the clearance between the valve body22aand sealing ring26aso long as the total force exerted on the sealing ring26aand actuation ring28ais at least as great as the clearance force. This configuration removes the possibility that air pressure within the pressure chamber48amight “starve” or decrease at a rate that is greater than the pressure supplied by the valve cavity34a, so that air pressure from the valve cavity34amight decrease until it would become insufficient to maintain the preselected clearance58abetween the sealing ring26aand chamfer56aof the valve body22a. In accordance with one embodiment, the relationship between the size of the cross sectional area along the length of the valve cavity46aand the preselected valve clearance58ais determined empirically. However, check valves constructed as described above have operated satisfactorily with the cross sectional area of the valve cavity34aabout equal to or greater than that of the preselected clearance58a. When the size of the cross sectional area of the length of the valve cavity is sized appropriately, the pressure chamber48acan only starve if the compressor pump fails to maintain sufficient air pressure in the valve cavity34ato produce sufficient force to remove contact between the sealing ring26aand chamfer56a.

Referring toFIG. 2B, the valve clearance58ais sufficient for the pressure of air flowing there through to continuously remove air from the valve cavity34athrough the outlet end42aof the valve body22a. This continues to occur throughout the repeated cycles of the compression cylinder of the compressor pump. Since the valve cavity34ais directly open, via the flutes33aand pressure chamber48a, to the valve clearance58a, there is no substantial obstruction to prevent the continuous removal of air from the valve cavity34athrough the outlet end42aof the valve body22ato prevent substantial accumulation of back pressure in the valve cavity34aor upstream of the check valve20a.

As the compressor pump continues to pressurize the valve cavity34ato maintain an air pressure level that is sufficient to maintain a cracking force against the sealing and actuation rings26aand28a, the valve clearance58awill continue to exist between the sealing ring26aand valve body22a. If movement of the sealing ring26ain the downstream direction46ato locations along the non-tapered section52athat are away from the valve body22aresults in significant additional amounts of backpressure in the valve cavity34a, the resulting smaller clearance between the sealing ring26aand valve body22awill still allow the pressure of air flowing through the clearance between the sealing ring26aand valve body22ato remove sufficient amounts of air from the valve cavity34ato prevent substantial accumulation of back pressure. Referring toFIG. 2B, the pressure of air flowing through a valve clearance reduced in size from the preselected valve clearance58acontinues to be sufficient to continuously remove air from the valve cavity34ato prevent substantial accumulation of back pressure whenever the compressor pump produces a clearance pressure.

The ability of the check valve20ato operate without substantial accumulations of back pressure from the valve cavity34aenables the valve20ato be used to pass process flows of air from the inlet end38athrough the outlet end42bof the valve body22awithout creating substantial back pressure. Process flows of air generally involve the movement of substantial volumes of air such as those used to effect the operation of mechanical devices and fluid-driven processes. The ability of the check valve20ato admit large amounts of air through the preselected clearance58abetween the valve body22aand sealing ring26aenables the check valve20ato perform this function.

FIGS. 4-6depict an air compressor system62aincorporating check valves of the invention into various system components. The compressor system62aincludes an electric motor64configured to operate a piston66that is located within the compression cylinder68of a compressor pump70. A valve plate72positioned above the compression cylinder68includes an inlet check valve20a′ and an outlet check valve20a″ of the invention and forms the valve body of both valves. Air enters the compressor pump70through an inlet filter74and inlet port76to enter into and create upstream atmospheric air pressure in a cylinder inlet chamber78. When the piston66reciprocates within the compression cylinder68, the piston66makes repeated intake strokes (moving in a downward direction inFIGS. 4 and 6) and compression strokes (moving in an upward direction inFIGS. 4 and 6).

As best understood with reference toFIG. 6, during each intake stroke, the piston66creates a vacuum in the compression cylinder68. This causes a differential in air pressure between the cylinder inlet chamber78and compression cylinder68that is greater than the cracking pressure of the inlet check valve20a′. As a result, air from the cylinder inlet chamber78flows through the flutes33a′ and pressure chamber48a′ to push the sealing ring26a′ along the non-tapered section52a′ of the plug30a′ which in turn creates a preselected clearance by removing sealing contact between the sealing ring26a′ and valve plate72, allowing air to enter the compression cylinder68through the inlet check valve20a′. During each intake stroke, air cannot enter through the outlet check valve20a″ from a cylinder outlet chamber80since air pressure contained in the cylinder outlet chamber80and the spring force of the actuation ring28a″ force the sealing ring26a″ into sealing contact with the valve plate72, preventing the backflow of downstream air into the compression cylinder68.

During each compression stroke, the piston66compresses air previously drawn into the compression cylinder68during the preceding intake stroke. This causes a differential in air pressure between the compression cylinder68and cylinder outlet chamber80that is greater than the cracking pressure of the outlet check valve20a′. As a result, air from the compression cylinder68flows through the flutes33a″ and pressure chamber48a″ to force the sealing ring26a″ along the non-tapered section52a″ of the plug30a″ which in turn creates a preselected clearance by removing sealing contact between the sealing ring26a″ and valve plate72, allowing air to enter the cylinder outlet chamber80through the outlet check valve70a″. During each compression stroke, air cannot enter through the inlet check valve20a′ from the cylinder inlet chamber78since the compressed air of the compression cylinder68and the spring force of the actuation ring28a′ force the sealing ring26a′ into sealing contact with the valve plate72, preventing the flow of air into the compression cylinder68from the cylinder inlet chamber78.

Repeated compression strokes by the piston66will lead to pressurization of the air contained within the cylinder outlet chamber80and, via the outlet port82, the discharge tube84. Referring toFIG. 4, the discharge tube84leads to a reservoir check valve20a′″ of the invention which is connected to allow for the flow of compressed air into an air reservoir86. As best understood by comparingFIG. 4with the magnified view of the reservoir check valve20a′″ and an unloader valve88inFIG. 5, the discharge tube84connects to the inlet end38a′″ of the reservoir check valve20a′″ to allow compressed air from the compressor pump70to flow through the valve cavity34a′″ toward the outlet end42a′″. When air pressure in the valve cavity34a′″ exceeds the air pressure within the air reservoir86by a pressure differential that results in a force exceeding the cracking force of the check valve20a′″, the sealing ring26a′″ moves along the non-tapered section52a′″ of the plug30a′″ against the bias of the actuation ring28a′″ to remove the sealing ring26a′″ from sealing contact with the valve body22a′″ and creates a preselected clearance there between. This allows air to flow from the valve cavity34a′″ through the flutes33a′″ and pressure chamber48a′″ and past the sealing ring26a′″ into the air reservoir86.

Referring toFIG. 4, a pilot valve90is mounted on the air reservoir86and is responsive the level of air pressure that is present within the air reservoir86. A pilot valve tube92extends from the pilot valve90to the unloader valve88and allows the pilot valve90to transmit a pneumatic pressure signal to the unloader valve88which the unloader valve88receives from the pilot valve tube92through a signal chamber94.

Referring toFIGS. 4 and 5, consider a situation in which the compressor pump20continues to pressurize the air reservoir86until the air pressure within the reservoir86reaches a preselected maximum level. The pilot valve90, being responsive to the level of air pressure within the air reservoir86, detects that the level of air pressure present in the reservoir86is at the preselected maximum level and responds by transmitting a pneumatic signal through the pilot valve tube92. The pneumatic signal is received by the signal chamber94of the unloader valve88, resulting in an increase in the amount of pneumatic pressure present within the signal chamber94. The increased pressure in the signal chamber94results in pneumatic pressure being exerted through a signal aperture96to push against a sealing diaphragm98. The sealing diaphragm98in turn pushes against an actuating stem100connected to an unloader piston102located in an unloader chamber104.

The unloader valve88connects to the check valve20a′″ to link the unloader chamber104to the valve cavity34a′″ of the check valve20a′″. The unloader chamber104opens to the valve cavity34a′″ at a location that is upstream of the sealing ring26a′″, and extends to a vent106that is open to atmosphere. The unloader piston102is biased with an unloader spring108to a sealing position (shown inFIG. 5) that seals the unloader piston102against an unloader seat110, preventing the flow of air from the valve cavity34a′″ of the check valve20a′″ through the unloader chamber104and vent106to atmosphere.

When the sealing diaphragm98pushes against the actuating stem100, the stem100pushes the unloader piston102against the bias of the unloader spring108, removing the sealing contact of the unloader piston102against the unloader seat110. Therefore, in response to the maximum reservoir air pressure detected by the pilot valve90, the unseated unloader piston102allows air to flow from the valve cavity34a′″ of the check valve20a′″ through the unloader valve88to atmosphere. This also causes the pressure differential between the valve cavity34a′″and air reservoir86to drop to such an extent that air pressure in the valve cavity34a′″ can no longer exert a cracking force against the sealing ring26a′″ and actuation ring26a′″ and maintain the sealing ring26a′″ at a location along the non-tapered section52a′″ of the plug30a′″ that is away from the valve body22a′″, allowing the check valve20a′″ to close under the spring force of the actuation ring28a′″.

The unloader valve88continues to allow compressed air from the discharge tube84and valve cavity34a′″ to exit to atmosphere until the pilot valve90detects that the air pressure contained within the air reservoir86has fallen below a preselected minimum level. When such a fall in the level of reservoir air pressure occurs, the pilot valve90removes the pneumatic air signal from the pilot valve tube92, allowing the unloader piston102to move under the biasing force of the unloader spring108back into sealing contact with the unloader seat110and prevent the flow of air through the unloader valve88to atmosphere. This in turn allows air pressure in the valve cavity34a′″ of the check valve20a′″ to again rise to a cracking pressure to create a cracking force to move the sealing ring26a′″ from contact with the valve body22a′″ and allow for the further pressurization of the air reservoir86until the air pressure in the reservoir86again reaches the preselected maximum level. This configuration allows the compressor pump70to run continuously without exceeding the preselected maximum air pressure in the air reservoir86.

Although the invention has been shown and described with respect to an embodiment in which a sealing ring contacts a chamfer or flattened surface of the valve body, it will be appreciated that various types of sealing contact surfaces can be incorporated into a valve body within the scope of the invention, some of which are described below. By way of example,FIG. 3Ais a side cross sectional view of a check valve20bin which the valve body22bhas a face54bat the outlet end42bthat intersects the pressure chamber48bat an edge112b. The sealing ring26bis reciprocally mounted around the non-tapered section52band biased with the actuation ring28bto a normal position in which the sealing ring26bmakes sealing contact with the edge112bto prevent the flow of fluid from the pressure chamber48bthrough the outlet end42bof the valve body22b.

When the sealing ring26bis in this normal position, a portion of the curved outside surface of the sealing ring26bremains exposed to the pressure chamber48b. The edge112bforms a relatively small point for contact with the sealing ring26b, increasing the remaining curved outside surface area of the sealing ring26bthat remains exposed to the pressure chamber48b. By increasing the outside surface area of the sealing ring26bthat is exposed to the pressure chamber48b, the edge112bincreases the amount of sealing ring surface area that is exposed to fluid pressure present in the valve cavity34b, reducing the cracking pressure required to initially move the sealing ring26baway from the edge112bto create a preselected clearance there between and open the check valve20b. By forming a relatively small point of contact with the sealing ring26b, the edge112balso reduces the distance that the sealing ring26bmust move in the downstream direction46balong the tapered section50bto lose sealing contact with the edge112band allow for the flow of fluid between the pressure chamber48band outlet end42b, further reducing the cracking pressure of the check valve20b.

It will be further appreciated that some embodiments may allow variations in the configurations of the plug and pressure chamber.FIGS. 7A and 7Bdepict side cross sectional and front views of a check valve20chaving a plug30cthat is suspended in position at the outlet end42cof the valve body22cwith a restrictor disk60c. The plug30cis shaftless, with the valve assembly24cextending only slightly into the valve cavity34cat the outlet end42cof the check valve20c. This configuration eliminates the need for flutes for the passage of fluid in the valve cavity34cin the downstream direction46cfrom the inlet end38cto the pressure chamber48c. Fluid passages114allow fluid to pass through the valve assembly24cand out the outlet end42cwhen the sealing ring26cmoves in the downstream direction46caway from the valve body22cto create a preselected clearance and open the check valve20c. The edge112cof the pressure chamber48cis located upstream of the downstream terminus116cof the valve cavity34c.

In some contemplated embodiments of the invention, in which the elastomeric seal seals against an edge of the pressure chamber in the normal position, the edge may vary in construction, placement, and/or orientation with respect to the valve body or other check valve components.FIGS. 8A and 8Bdepict side cross sectional views of a check valve20din which the valve body22dincludes a washer insert118dthat is compression fit into the valve cavity34dat the outlet end42dto become part of the valve body22d. An exposed, downstream surface of the washer insert118dforms the face54dof the valve body22d. The washer insert118dalso forms part of the inside surface of the valve cavity34din the pressure chamber48d. Referring toFIG. 8B, when the check valve20dis fully open, the preselected valve clearance58dis determined by the clearance that exists between the sealing ring26d, as it is positioned against the restrictor60d, and the edge112dof the valve body22cthat is created by the washer insert118d. In addition to compression fitting, similar washer inserts can also be connected to the rest of the valve body with threads, adhesives, or other forms of attachment.

Such washer inserts can also be positioned within the valve cavity of a check valve to form a flange or similar structure that is part of the valve body extending inwardly into the valve cavity.FIGS. 9A and 9Bdepict side cross sectional views of such a check valve20ehaving a washer insert118ethat is compression fit to a position that is within the valve cavity34enear the outlet end42eto become part of the valve body22e. Due to this positioning of the washer insert118e, the face54eof the valve20eis formed by a downstream surface of the washer insert118eand is located in a position that is upstream of the downstream terminus116eof the valve cavity34e. The washer insert118ealso forms an inside surface120eof the valve cavity34ethat intersects the face54eto create an edge112eagainst which the sealing ring26ecan seal when in the normal position (as shown inFIG. 9A). The pressure chamber48eis located in a position that is immediately upstream of the washer insert118e.

Rather than including a separate washer insert or other assembly, the valve body can also include a flange extension or other inwardly extending formation that is formed directly from the valve body material itself.FIGS. 10A and 10Bdepict a check valve20fhaving a flange extension122that extends inwardly into the valve cavity34ffrom the valve body22f. The flange extension122is machined, cast, or otherwise formed from the material of the valve body22fand is located near the outlet end42f. Due to this positioning of the flange extension122, the face54fof the valve20fis formed by a downstream surface of the flange extension122and is located in a position that is upstream of the downstream terminus116fof the valve cavity34f. The flange extension122also forms an inside surface120of the valve cavity34fthat intersects the face54fto create an edge112fagainst which the sealing ring26fcan seal when in the normal position (as shown inFIG. 10A). The pressure chamber48fis located in a position that is immediately upstream of the flange extension126.

Some contemplated embodiments may also include tapered sections divided into segments having different incident angles. For example,FIGS. 11A-Cdepict a check valve outlet end42gin which the valve assembly24gis constructed around a plug36ghaving a tapered section50gdivided into a first tapered segment128gand an adjacent second tapered segment130g. The included angle of the second tapered segment130gis shallower than the included angle of the first tapered segment128g. However, the diameter of the second tapered segment130gis greater than the diameter of the first tapered segment128g. This difference between the included angles and diameters of the first and second tapered segments128gand130genables the valve assembly24gto allow for an increased fluid flow capacity during operation.

Consider the valve assembly24gprior to operation when the sealing ring26gand actuation ring28gare in the normal positions as depicted inFIG. 11A. The sealing ring26gremains in contact with the edge112gat the face54gto close the valve assembly24gand prevents fluid flow through the outlet end42g. At the normal position, the actuation ring28gcontacts the first tapered segment128gbut not the second tapered segment130gof the plug30g. The sealing and actuation rings26gand28gremain in their normal positions until a cracking pressure is introduced in the pressure chamber48g. To initially open the valve assembly24g, the cracking pressure must be sufficiently large to exert a sufficient amount of force against the sealing ring26g, acting on the limited surface areas of the sealing ring26gexposed to the pressure chamber48g, to move the sealing ring26gaway from the valve face54gand against the frictional forces encountered by the actuation ring28gagainst the steeper included angle of the first tapered segment128g. A sufficient amount of total force exerted against the sealing ring26gand actuation ring28gmust also continue to be present to move the actuation ring28gagainst the included angle of the first tapered segment128guntil the sealing and actuation rings26gand28gmove to the positions shown inFIG. 11B. However, since the diameter of the first tapered segment128gis less than the diameter of the second tapered segment130g, inward radial forces exerted by the actuation ring28gare relatively low. As the valve assembly24gopens, more surface area of the sealing ring26gbecomes exposed to the fluid pressure from the pressure chamber48g, increasing the total force exerted against the sealing ring26gand against the biasing force of the actuation ring28g.

Referring now toFIG. 11B, as the sealing ring26gcontinues to move along the non-tapered portion52gin the downstream direction46g, the actuation ring28gmoves to the second tapered segment130g. As the actuation ring28gmoves in the downstream direction46galong the second tapered segment130g, the increased diameter of the second tapered segment130gresults in increased inward radial forces being exerted by the actuation ring28gas it increasingly stretches. Frictional forces between the actuation ring28gand second tapered segment130galso increase as the actuation ring28gstretches further. Thus, as the diameter of the second tapered segment130gincreases, it becomes increasingly important to keep additional stretching of the sealing ring26gto a minimum.

The shallower included angle of the second tapered segment130gallows for a reduction in such stretching. As the actuation ring28gmoves along the second tapered segment130gto allow the sealing ring30gto move along the non-tapered section52gtoward the fully open preselected valve position depicted inFIG. 11C, the increased inward radial forces exerted by the actuation ring28gare less than they would be if the included angle of second tapered segment130gwere as steep as the first tapered segment128g. Thus, the overall amount of force required to move the actuation ring28gto points along the second tapered segment130gis reduced. For many operating conditions, and particularly those conditions in which there is sufficient pressure and force to move the actuation ring28gto the second tapered segment130g, this tends to allow for the displacement of the sealing ring26ga greater distance from the valve face54gfor a given pressure, allowing a larger volume of fluid to flow through the valve assembly24gat the given pressure.

It will be appreciated that any number of tapered sections or tapered segments can be included within the contemplated scope of the invention, and it is further contemplated that different tapered segments can share or have different included angles. For example,FIGS. 12A-Cdepict a check valve outlet end42hof the invention in which the valve assembly24hincludes a tapered section50hhaving a third tapered segment132hthat has an included angle that is shallower than the included angles of either the first tapered segment128hor second tapered segment130h. Due to the shallower included angle of the second tapered segment132h, after the actuation ring28hmoves along the first tapered segment128h, as depicted inFIG. 12A, less force is required to move the actuation ring28halong points of the second tapered segment130h, as depicted inFIG. 12B, than would be required if the second tapered segment132hhad the included angle of the first tapered segment128h. Due to the even shallower included angle of the third tapered segment132h, after the actuation ring28hmoves along the second tapered segment130h, less force is required to move the actuation ring28halong points of the third tapered segment132hthan would be required if the third tapered segment132hhad the included angles of either the first tapered segment128hor second tapered segment130h.

It will be further appreciated that tapered sections that are curved or that are otherwise shaped to have a non-constant incident angle can also be incorporated within the contemplated scope of the invention. For example,FIGS. 13A-Cdepict a check valve outlet end42iof the invention that includes a valve assembly24ihaving a curved tapered section50iwith a diameter that becomes increasingly wider but which has a curved slope that is increasingly shallow in downstream direction46i. The curved shape of the cross sectional slope of the tapered section50ican allow for increased flow capacity by the valve assembly24iunder some operating conditions.

Consider the valve assembly24iprior to operation when the sealing ring26iand actuation ring28iare in the normal positions as depicted inFIG. 13A. The sealing ring26iremains in contact with the edge112iat the face54ito close the valve assembly24iand to prevent fluid flow through the outlet end42i. At this position, the actuation ring28icontacts the curved tapered section50iat a position where the tapered section50ihas a relatively steep slope. The sealing and actuation rings26iand28iremain in the normal positions until a cracking pressure is introduced in the pressure chamber48i. To initially open the valve assembly24i, the cracking pressure must be sufficiently large to exert a sufficient amount of force against the sealing ring26i, acting on the limited surface areas of the sealing ring26iexposed to the pressure chamber48i, to move the sealing ring26iaway from the valve face54iand against the frictional forces of the actuation ring28iencountered as the sealing ring26imoves along the non-tapered section52iand the actuation ring28imoves along the tapered section50i. However, since the diameter of the tapered section50iis smaller near the non-tapered section52i, inward radial forces exerted by the actuation ring28iare relatively low. As the valve assembly24iopens, more surface area of the sealing ring26iand actuation ring28ibecomes exposed to the fluid pressure from the pressure chamber48i, increasing the total force exerted against the sealing ring26iand actuation ring28i.

Referring now toFIG. 13B, once the sealing ring26imoves away from the edge112i, the actuation ring28imoves along the tapered section50i, with the increased diameter of the tapered section50icausing the actuation ring28ito stretch, resulting in increased inward radial forces being exerted by the actuation ring28i. Frictional forces between the actuation ring28iand tapered section50ialso increase as the actuation ring28istretches further. Thus, as the actuation ring28imoves further along the tapered section50iand away from the valve face54i, it becomes increasingly important to keep additional stretching of the actuation ring28ito a minimum.

The curved cross sectional shape of the tapered section50i, in which the slope of the tapered section50ibecomes increasingly shallower in the downstream direction46i, allows for a reduction in such stretching. As the actuation ring28imoves along the tapered section50ito allow the valve assembly24ito assume the fully open preselected valve position depicted inFIG. 13C, the increased inward radial forces exerted by the actuation ring28iare less than they would be if the slope of the tapered section50iwas the same near the restrictor60ias it is near the non-tapered portion52i. Thus, the overall amount of force required to move the actuation ring28ito points along the tapered section50iis reduced. This tends to allow the sealing ring26ito be displaced a greater distance from the valve face54ifor a given pressure, allowing a larger volume of fluid to flow through the valve assembly24iat the given pressure.

Although the invention has been shown and described as having sealing and actuation rings that are cross sectional in shape, it will be appreciated that in some embodiments, other cross sectional shapes can be incorporated within the anticipated scope of the invention. For example,FIGS. 14A-Cdepict a check valve outlet end42jof the invention that includes a valve assembly24jhaving a sealing ring26jthat is rectangular in its cross sectional shape. As best understood with reference toFIG. 14A, the rectangular cross sectional shape of the sealing ring26jallows for increased surface contact between the sealing ring26jand the flat surface of the face54jwhen the valve assembly24jis closed and the sealing ring26jand actuation ring28jare in the normal positions. This can serve to enhance sealing of the valve assembly, depending on the selected material of the sealing ring26j, for some applications. It will be further appreciated that other cross sectional ring shapes are possible and that such variations in cross sectional ring shapes can also be made to actuation rings.

Although the invention has been shown and described as being incorporated into check valves of the invention having sufficient cross sectional clearances to allow for the evacuation of substantial accumulations of backpressure, it will be appreciated that the invention can also be incorporated into check valves where the cross sectional clearance of the valve is not sufficient to continuously remove fluid from the valve cavity so as to prevent a substantial accumulation of back pressure produced by the fluid compressor upstream of the check valve. Some embodiments may incorporate configurations in which such accumulations of gas or liquid fluid backpressure or valve starving is either intended or desired due to the specific application of the valve.

FIGS. 15A-Care cross sectional views of the outlet end42kof a check valve of the invention having a threaded shank member134kthat engages the inside threads136of the valve cavity34k. The shank member134kincludes a tapered section50kon which the sealing ring26kand actuation ring28kare reciprocally mounted. The sealing ring26kand actuation ring28kare biased to position the sealing ring26kagainst the face54kand prevent the flow of fluid through the outlet end42k, as shown inFIG. 15A.

As best understood by comparingFIG. 15Awith15B, the fitting between the shank member134kand inside threads136is sufficiently loose that a leakage clearance138exists between the mating threads of the shank member134kand inside threads136, permitting fluid140to flow through the leakage clearance138from upstream of the shank member134k, around an indentation fitting144of the non-tapered section52k, and toward the sealing ring26k. The leakage clearance138is small in comparison with the amount of fluid that would typically be fed by the compressor pump from upstream of the shank member134k.

As a result, the leakage clearance138does not generally allow for the passage of a sufficient amount of fluid from upstream of the shank member134kto prevent a substantial accumulation of upstream backpressure unless a check valve of an impractically large size is used. Under typical operating conditions, the compressor may therefore create a substantial backpressure in the valve cavity34kbefore a sufficient amount of flowing fluid140is capable of creating a cracking force to move the sealing and actuation rings26kand28kto the partially open positions depicted inFIG. 15B. Additional backpressure may be required to move the sealing and actuation rings26kand28kto the fully open positions to create a valve clearance58k, as depicted inFIG. 15C. However, such a configuration of the outlet end42kmay be used where the desired accommodated flow is less than a process flow, such as in smaller control flows of fluid for logic operations.

FIGS. 16A-16Cdepict cross sectional views of the outlet end42lof a check valve of the invention having a threaded shank member134lthat engages the inside threads136of the valve cavity34kto provide a leakage clearance138. As best understood by comparingFIGS. 16A and 16B, the threaded shank member134land non-tapered section52lof the plug30lare sized to create a shank clearance142with the valve cavity34lto allow flowing fluid140to pass toward the sealing ring26lwhile this allows fluid to pass from upstream of the threaded shank member134lto the sealing ring more easily than through an indentation fitting, the shank clearance142would not normally create a sufficient cross sectional area to allow a substantial evacuation of backpressure from the valve cavity34lduring normal operation of the compressor pump. Thus, it is would be highly likely for a substantial accumulation of backpressure to exist in the valve cavity34lby the time that flowing fluid140created sufficient force against the sealing ring26land actuation ring28lto create a valve clearance58lbetween the sealing ring26land face54l. Thus, such a configuration of the outlet end42lcan be similarly limited to the accommodation of flows less than a process flow of fluid, such as control flows of fluid for logic operations.

FIGS. 17Aand B depict a check valve20mof the invention having valve cavity34mopening to an fluid hole145that leads to a non-tapered section52mvia a slant passage150. The fluid hole145and slant passage150have cross sectional areas that are control clearances that are much smaller than the valve cavity34m. Due to the relatively small size of the control clearances, neither the fluid hole145nor slant passage150are capable of accommodating a process flow of fluid during normal operation. Thus, the valve20mcannot be used to continuously remove backpressure from the valve cavity34mduring normal operation of the compressor pump, but may be used for accommodating smaller fluid flows such as logic control flows.

As best understood with a comparison ofFIGS. 17Aand B, the slant passage150opens to only a single opening point152along the circumference of the non-tapered section52m. It is only generally at the opening point152that upstream fluid pressure contacts and exerts fluid pressure against the sealing ring26mand against the biasing force of the actuation ring28m. The position of the sealing ring26mmounted around the non-tapered section52mis generally represented with dotted lines26m′, and the position of the actuation ring28mmounted around the tapered section50mis generally represented with dotted lines28m′.

When sufficient pressure is present within the fluid hole145and slant passage150to exert a cracking force against the sealing ring26mand actuation ring28m, only the general area of the sealing ring26mnear the opening point152receives the force of the fluid pressure, resulting in a slightly crooked positioning of the sealing ring26mand actuation ring28m, as shown by dotted lines26m′ and28m′, on the non-tapered and tapered sections52mand50m. Thus, when sufficient fluid pressure is present in the fluid hole145and slant passage150to create a valve clearance58mnear the opening point152, there is normally insufficient fluid force to create such a clearance at other positions along the circumference of the non-tapered and tapered sections52mand50m, leaving a gap154between the actuation ring28mand restrictor60mat positions that are not in the general area of the opening point152even though the valve20mis fully open.

This invention has been described with reference to several preferred embodiments. Many modifications and alterations will occur to others upon reading and understanding the preceding specification. It is intended that the invention be construed as including all such alterations and modifications in so far as they come within the scope of the appended claims or the equivalents of these claims.