PUMP HAVING MULTI-STAGE GAS COMPRESSION

BACKGROUND

This disclosure relates to pumping systems. More specifically, this disclosure relates to pumping systems for compressed gasses. Such pumping systems can text missing or illegible when filed

Gas pumps are used across a variety of applications, such as those used to extract gas from matter (e.g., vapor), develop a vacuum, and/or generate compressed gas. The pump includes a moving member, such as a piston, that pumps the gas for the desired application. The pump is controlled to achieve the desired pressure and flow rate for the process gas pumped by the pump. The environments that gas pumps are used in can be crowded where space is at a premium. Increasing the flow rate requires an increase in the size of the piston and/or the stroke length of the piston, which can be impractical in crowded operating environments. Piston compressors also require moving mechanical seals to maintain pressurization.

SUMMARY

According to an aspect of the disclosure, a pump configured to serially compress a gas includes a first compression stage having a first diaphragm, a first stage inlet, and a first stage outlet, the first diaphragm configured to reciprocate on a pump axis to alter a volume of a first compression chamber of the first compression stage; a second compression stage having a second diaphragm a second stage inlet and a second stage outlet, the second diaphragm configured to reciprocate on the pump axis to alter a volume of a second compression chamber of the second compression stage; a drive disposed at least partially between the first fluid displacement member and the second fluid displacement member, the drive operably connected to the first fluid displacement member and the second fluid displacement member to displace the first fluid displacement member through a first suction stroke and to displace the second fluid displacement member through a second suction stroke. The first compression stage is fluidly connected to the second compression stage such that gas compressed in the first compression chamber in the first compression stage is routed to the second compression chamber.

According to an additional or alternative aspect of the disclosure, a method of compressing a gas includes reciprocating a first diaphragm along a pump axis and a second diaphragm along the pump axis with a drive disposed at least partially directly between the first diaphragm and the second diaphragm; compressing the gas in a first compression chamber to a first pressure with the first diaphragm; expelling the compressed gas from the first compression chamber through a first outlet of the first compression chamber; routing the compressed gas from the first compression chamber into a second compression chamber; compressing the compressed gas to a second pressure greater than the first pressure in the second compression chamber with a second diaphragm configured to reciprocate on the pump axis; and expelling the compressed gas from the second compression chamber. A pumping stroke of the first diaphragm both compresses the gas within the first compression chamber and moves previously compressed gas into the second compression chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a pump system.

FIG. 2A is an isometric view of a pump.

FIG. 2B is an end view of the pump.

FIG. 2C is a cross-sectional view taken along line C-C in FIG. 2A

FIG. 2D is a cross-sectional view taken along line D-D in FIG. 2A.

FIG. 3A is a schematic block diagram of a pump in a serial flow mode.

FIG. 3B is a schematic block diagram of a pump in a parallel flow mode.

FIG. 4 is a graph showing standing pressure over time for a pump in a parallel flow mode and in a serial flow mode.

FIG. 5 is a graph showing flow rate for an output pressure for a pump in a parallel flow mode and in a serial flow mode.

DETAILED DESCRIPTION

FIG. 1 is a schematic block diagram of pump 10. Pump 10 includes compression stages 12a, 12b; check valves 14a-14d, drive 16, inlet conduit 18, and outlet conduit 20. Compression stages 12a, 12b respectively include fluid displacement members 22a, 22b and compression chambers 24a, 24b.

Pump 10 is configured to pump process gas, as indicated by flow arrows FA. For example, pump 10 can be used to extract gas from matter (e.g., vapor), develop a vacuum, and/or generate compressed gas, among other applications. In one example, pump 10 can be used in a system used to extract oils from organic matter. In some examples of such a system, cooled petroleum products, such as butane and propane, are used to strip oils from the organic matter. The resulting combination is heated and pump 10 can be used to extract the petroleum gasses for recirculation, condensation, and reuse in the extraction system. It is understood, however, that pump 10 can be used in any desired gas handling system.

Drive 16 is operably connected to components of pump 10 to cause pumping by pump 10. Drive 16 can be and/or include a motor, such as an electric motor among other options. The motor can be an electric rotary type motor, such as an alternating current (AC) induction motor or a direct current (DC) brushed or brushless motor, among other options. Drive 16 provides an output to mechanically drive fluid displacement members 22a, 22b through a suction stroke and, in some examples, through both suction and pumping strokes.

Pump 10 is configured to pump gas from inlet conduit 18 to outlet conduit 20. More specifically, compression stages 12a, 12b pump the gas from the inlet conduit 18 to the outlet conduit 20. Fluid displacement members 22a, 22b are disposed on opposite axial sides of drive 16 along pump axis PA. Fluid displacement members 22a, 22b at least partially define compression chambers 24a, 24b, respectively. Fluid displacement members 22a, 22b reciprocate within compression chambers 24a, 24b to pump the gas from the inlet conduit 18 to the outlet conduit 20. Fluid displacement members 22a, 22b reciprocate to alter the volumes of compression chambers 24a, 24b, respectively, to pump the gas. Fluid displacement members 22a, 22b can be of any configuration suitable for pumping gasses. For example, fluid displacement members 22a, 22b can be diaphragms or pistons, among other options. Whether fluid displacement members 22a, 22b are diaphragms, pistons, or of another configuration, the fluid displacement members 22a, 22b can have a circular cross-section orthogonal to their respective reciprocation axes and, in some examples, can be coaxial with respect to each other on pump axis PA.

Fluid displacement members 22a, 22b each linearly reciprocate through respective pump cycles, with each pump cycle including a pumping stroke and a suction stroke. In a pumping stroke, fluid displacement member 22a, 22b moves to decrease the available volume within the respective compression chamber 24a, 24b to compress gas within the compression chamber 24a, 24b as well as expel gas downstream from the compression chamber 24a, 24b. In a suction stroke, fluid displacement member 22a, 22b moves away from the respective compression chamber 24a, 24b to increase the available volume within the compression chamber 24a, 24b to pull more gas into the compression chamber 24a, 24b from upstream.

Fluid displacement members 22a, 22b can be fixed relative to each other or movable relative to each other during operation. As discussed in more detail below, fluid displacement members 22a, 22b can be moved by the drive 16 through respective suction strokes but decoupled from drive 16, and thus from the other fluid displacement member 22a, 22b, during respective pumping strokes. In some examples, fluid displacement members 22a, 22b are fixed relative each other such that fluid displacement member 22a is always 180-degrees out of phase with fluid displacement member 22b. For example, the first fluid displacement member 22a travels through its pumping stroke while the second fluid displacement member 22b travels through it suction stroke, and each changes over to the other phase at the same time. In some other embodiments, the fluid displacement members 22a, 22b can be offset in phase to some degree other than 180-degrees.

Fluid displacement members 22a, 22b are configured to draw gas into compression chambers 24a, 24b through inlets 26a, 26b and to output gas from compression chambers 24a, 24b through outlets 28a, 28b. Intermediate conduit 30 extends between and fluidly connects compression chamber 24a and compression chamber 24b. Intermediate conduit 30 defines a flowpath for serial flow through compression chambers 24a, 24b. Intermediate conduit 30 can be formed by a tube external to a body of pump 10, can be formed internally through a body of pump 10, or can be formed partially internal to the body of pump 10 and partially external to the body of pump 10.

Check valves 14a-14d regulate the flow of incoming and outgoing gas from the first and second compression chambers 24a, 24b. Check valve 14a is associated with inlet 26a and is configured to allow gas to flow into compression chamber 24a and to prevent retrograde flow out of compression chamber 24a. Check valve 14b is associated with outlet 28a and is configured to allow gas to flow downstream out of compression chamber 24b and to prevent retrograde flow to compression chamber 24a. Check valve 14c is associated with inlet 26b and is configured to allow gas to flow into compression chamber 24b and to prevent retrograde flow from compression chamber 24b. Check valve 14d is associated with outlet 28b and is configured to allow gas to flow downstream out of compression chamber 24b and to prevent retrograde flow to compression chamber 24b.

While check valve 14b and check valve 14c are described as separate components, it is understood that check valve 14b and check valve 14c can be integrated into a single flow regulating assembly. For example, pump 10 may include only three check valves, with a first check valve associated with inlet 26a, a second check valve associated with outlet 28b, and a third check valve intermediate the first and second compression stages 12a, 12b. The check valves 14a-14d can be flapper type, ball and seat, or other type of check valve. Further, some of the check valves 14a-14d can be a first type and other ones of the check valves 14a-14d can be one or more other types.

During operation, pump 10 serially compresses gas, which pumped gas can be referred to as a process gas. The gas flows serially through pump 10 between inlet conduit 18 and outlet conduit 20. Gas flows from inlet conduit 18 to compression chamber 24a, from compression chamber 24a to compression chamber 24b through intermediate conduit 30, and from compression chamber 24b to outlet conduit 20 in the serial flow mode.

Drive 16 is operated to cause reciprocation of fluid displacement members 22a, 22b through respective pump cycles. Fluid displacement member 22a draws gas into compression chamber 24a from inlet conduit 18 through inlet 26a during the suction stroke. Fluid displacement member 22a moves through the suction stroke to increase the volume of compression chamber 24a, thereby drawing gas into compression chamber 24a. The gas is pulled through first check valve 14a and into first compression chamber 24a by fluid displacement member 22a. Inlet 26a can also be referred to as a pump inlet because inlet 26a is the location that the process gas enters pump 10.

Drive 16 causes fluid displacement member 22a to changeover into a pumping stroke to compress the gas within compression chamber 24a. Fluid displacement member 22a moves through the pumping stroke to decrease the volume of compression chamber 24a, thereby increasing the pressure of the gas within compression chamber 24a. Fluid displacement member 22a moving through the pressure stroke can cause first check valve 14a to close. The pressure within first compression chamber 24a becomes equal to or greater than the gas pressure downstream of compression chamber 24a, such as within intermediate conduit 30 and/or within compression stage 12b. The pressure differential across check valve 14b allows fluid displacement member 22a to force the compressed gas out of compression chamber 24a through outlet 28a, past second check valve 14b, and into intermediate conduit 30. Fluid displacement member 22a changes stroke directions and repeats another pump cycle including a suction stroke and a pumping stroke.

Fluid displacement member 22b draws gas into compression chamber 24b from intermediate conduit 30 through inlet 26b during the suction stroke. Fluid displacement member 22b moves through the suction stroke to increase the volume of compression chamber 24b, thereby drawing gas into compression chamber 24b. The gas is pulled through first check valve 14b and into first compression chamber 24b by fluid displacement member 22b. It is understood that the gas can one or both of be pushed into compression chamber 24b by upstream pressure (e.g., due to movement of fluid displacement member 22a during a pumping stroke) and be pulled into compression chamber 24b by lower downstream pressure (e.g., due to movement of fluid displacement member 22b during the suction stroke).

Drive 16 causes fluid displacement member 22b to changeover into a pumping stroke to compress the gas within compression chamber 24b. Fluid displacement member 22b moves through the pumping stroke to decrease the volume of compression chamber 24b. In some examples, fluid displacement member 22b further increases the pressure of the gas within compression chamber 24b. The pressure within the second compression chamber 24b becomes equal to or greater than the gas pressure downstream of compression chamber 24b, such as within outlet conduit 20. The pressure differential across check valve 14d allows fluid displacement member 22b to force the compressed gas out of compression chamber 24b through outlet 28b, past fourth check valve 14b, and into outlet conduit 20. Outlet 28b can also be referred to as a pump outlet because outlet 28b is a location that the pumped gas exits pump 10. Fluid displacement member 22b then changes stroke directions and repeats another pump cycle including a suction stroke and a pumping stroke.

The gas flows serially through multiple compression stages to provide a higher pressure output from pump 10 than can be provided by a single compression stage. In particular, the embodiment of pump 10 shown includes two compression stage 12a, 12b, though it is understood that other numbers of compression stages are possible. The incoming gas is compressed in each of compression stages 12a, 12b serially such that the gas is compressed in the first stage 12a and then transported to the second stage 12b in which it is further compressed to an even greater degree (i.e. higher pressure), and then output from the pump 10. The gas is initially received at a base pressure. The base pressure can be ambient pressure, atmospheric pressure, uncompressed, compressed, or in another state. In some examples, inlet conduit 18 may be removed such that the pump inlet (e.g., inlet 26a) draws gas from the atmosphere surrounding pump 10. The gas experiences a first compression within compression stage 12a. Compression stage 12a outputs the gas at a first pressure, the first pressure greater than the base pressure. The gas flows to compression stage 12b and is acted upon by second fluid displacement member 22b. Compression stage 12b outputs the gas at a second pressure. The second pressure is greater than the base pressure and can be, in some examples, greater than the first pressure. During operation, the minimum second pressure actually being output by compression stage 12b is at least equal to the maximum first pressure actually being output by compression stage 12b.

In some examples, each of compression chamber 24a, intermediate conduit 30, and compression chamber 24b are at ambient pressure at the beginning of operation. Pump 10 can build standing pressure internally prior to outputting gas through outlet 28b. The standing pressure builds to a desired output pressure such that the second pressure output from pump 10 is at a desired pressure for operation. For example, the output of pump 10 can be put in a deadhead condition in which the pump outlet (e.g., outlet 28b) empties into a sealed reservoir or dead-end path. For example, outlet conduit 20 can dispense to or be a pressurized location, such as a holding tank. In other examples, outlet conduit 20 can be or include a valve that can be placed in a closed state, among other deadheading options. In examples where pump 10 is used for recovery and recirculation, such as in extraction systems for oils from organic compounds, the downstream location can be a pressurized recovery tank. The pressure in the tank can determine the operating pressure for pump 10. With the operating pressure level set, such as by the deadhead condition, fluid displacement members 22a, 22b reciprocate to move gas from the pump inlet 26a to the pump outlet 28b. Pump 10 ramps the standing pressure to be equal to or exceed the downstream system pressure.

In some examples, second compression stage outlet check valve 14d can be configured to have a crack pressure threshold such that, over multiple cycles of fluid displacement member 22b pressurized gas is progressively amassed in the second compression chamber 24b and then only passed through outlet check valve 14d and into outlet conduit 20 after the standing pressure of this supply of pressurized gas representing multiple pump cycles within compression chamber 24b overcomes the resistance of the second compression stage outlet check valve 14d. For example, a spring can bias the valve member of the check valve 14d into a closed state. The resistance of the spring is set to control the crack pressure at which check valve 14d actuates from the closed state to the open state. The standing pressure overcoming the resistance allows at least part of this mass of gas (which may represent more than a single cycle of the second compression stage 12b) to move through outlet 28b and downstream from pump 10.

During pressure ramping, fluid displacement member 22a compresses the gas to a first pressure that is output through outlet 28a. The pressurized gas having the first pressure flows through intermediate conduit 30 and to compression chamber 24b. Fluid displacement member 22b further compresses the already pressurized gas. The resistance at check valve 14d (e.g., due to pressure downstream of check valve 14d or a bias in check valve 14d) maintains check valve 14d in a closed state such that the gas pressure within compression chamber 24b increases from the first pressure to a second pressure. Pressure builds at the pump outlet 28b and in second compression chamber 24b such that there is continuously pressurized gas within the second compression chamber 24b before, during, and after each pump cycle. The standing pressure builds within the intermediate conduit 30 downstream of second check valve 14b such that there is continuously pressurized gas within the intermediate conduit 30 before, during, and after each pump cycle. The pressure continues to build in second compression chamber 24b until the second pressure reaches or exceeds the downstream (e.g., operating) pressure. The pressure differential across check valve 14d with second pressure reaching or exceeding the downstream pressure causes check valve 14d to shift to the open state to output the pressurized gas. The standing pressure in the second compression chamber 24b and the intermediate conduit 30 can, in some examples, be exhausted once the pump outlet 28 is allowed to vent to atmosphere, such as after operation.

In some examples, second compression stage inlet check valve 14c, or another check valve located between the compression stages 12a, 12b (e.g., check valve 14b) can be configured to have a crack pressure threshold such that, over multiple cycles of the fluid displacement member 22a pressurized gas is progressively amassed in the intermediate conduit 30 and then only passed into the second compression chamber 24b after the pressure of this reserve of pressurized gas representing multiple pump cycles within the intermediate conduit 30 overcomes the resistance of the second compression stage inlet check valve 14c. For example, the one or more intermediate check valves between compression stages 12a, 12b can have a spring biasing the valve member of the check valve into a closed state, with the spring resistance controlling the crack pressure. The pressurized gas overcoming the resistance allows at least part of this mass of gas (which may represent more than a single cycle of the first stage of compression) to move into the second compression chamber 24b.

The gas is initially compressed by first compression stage 12a and subsequently compressed by second compression stage 12b. Second compression stage 12b receives pre-pressurized gas and further compresses the gas to increase the pressure. In some examples, first compression stage 12a is configured to compress incoming gas to about 0.83 megapascal (MPa) (about 120 pounds per square inch (psi)) and second compression stage 12b is configured to further increase the pressure to about 1.03-1.17 MPa (about 150-170 psi).

In some examples, pump 10 is operated serially but with the second stage 12b acting as a pass-through stage. In such an operating mode, the second stage 12b may pump the gas without further pressurizing the gas. The second pressure can thus be substantively the same as the first pressure. Without the downstream resistance (e.g., either the deadhead condition or the crack pressure of the check valve) being greater than the first pressure, second compression stage 12b outputs flow during each pump cycle. As such, second compression stage 12b may only pass along the same volume that was compressed in the first compression stage 12a without further compressing the gas from the first compression stage 12a.

Compression stage 12a can both output gas from compression chamber 24a and pump gas into compression chamber 24b during a pumping stroke of fluid displacement member 22a. In some examples, the gas pumped into compression chamber 24b by compression stage 12a during a respective pumping stroke can be different from the gas expelled from compression stage 12a during that respective pumping stroke.

The displacement of a first one of fluid displacement members 22a, 22b can be greater than the displacement of a second one of fluid displacement members 22a, 22b. For example, the first fluid displacement member 22a, 22b can have a greater gas-contacting cross sectional area than the second fluid displacement member 22a, 22b such that the first fluid displacement member 22a, 22b displaces a greater volume per pumping stroke than the second fluid displacement member 22a, 22b. The first fluid displacement member 22a, 22b can displace the larger volume despite the same distance of travel for each pumping stroke of the fluid displacement members 22a, 22b.

Fluid displacement members 22a, 22b can be decoupled during at least a portion of the respective pump cycles. In some examples, one of the fluid displacement members 22a, 22b has a greater length of travel along axis PA than the other one of the fluid displacement members 22a, 22b. The fluid displacement member 22a, 22b with the greater length of travel can displace the larger volume of gas despite the other fluid displacement member 22a, 22b having the same or a greater gas-contacting cross-sectional area as compared to the greater length-of-travel fluid displacement member 22a, 22b.

The first fluid displacement member 22a, 22b can have a greater length of travel by being configured to travel a greater maximum distance through a pumping stroke or by moving more quickly through the pumping stroke. For example, each of fluid displacement members 22a, 22b can have a dedicated pressure source to displace that fluid displacement member 22a, 22b through its respective pumping stroke. The pressures can be set to different levels (e.g., a lower relative pressure for fluid displacement member 22a and a higher relative pressure for fluid displacement member 22b) to cause different displacement parameters for the fluid displacement members 22a, 22b.

Pump 10 provides significant advantages. Pump 10 is configured to compress gas to a first pressure level and can be operated to output the gas at that first pressure level or at a higher, second pressure level. Pump 10 thereby facilitates a range of output pressures for the pumped gas. Pump 10 is configured to compress gasses to pressures greater than those facilitated by a typical double diaphragm pump operating in parallel. The higher pressures can facilitate more efficient process gas recovery and recirculation. Fluid displacement members 22a, 22b being coaxial on pump axis PA reduces off balance loads on drive, increasing efficiency and preventing undesired wear on components of pump 10. Check valves 14a-14d regulate flow through pump 10 to facilitate building the standing pressure, facilitating pump 10 outputting gas at a second pressure greater than the first pressure output by compression stage 12a.

FIG. 2A is an isometric view of pump 10. FIG. 2B is an end view of pump 10. FIG. 2C is a cross-sectional view taken along line C-C in FIG. 2A. FIG. 2D is a cross-sectional view taken along line D-D in FIG. 2A. FIGS. 2A-2D will be discussed together. Compression stages 12a, 12b; check valves 14a, 14b; drive 16; fluid displacement members 22a, 22b; inlets 26a, 26b; outlets 28a, 28b; intermediate conduit 30; housing 34, and covers 36a, 36b of pump 10 are shown. Fluid displacement members 22a, 22b are shown as diaphragms that include rigid portions 38 and membranes 40. Each rigid portion 38 is formed by plates 42. Motor 44, crank 46, and connectors 48a, 48b of drive 16 are shown.

Housing 34 supports other components of pump 10. Housing 34 can be a single cast and machined part or can be composed of multiple parts. Housing 34 can be formed from metal, among other material options. Housing 34 can be cylindrical and include a generally hollow interior. Other components of pump 10 can be disposed within the hollow interior of housing 34. In some examples, housing 34 at least partially defines a charge chamber 50. The charge chamber 50 is further defined by fluid displacement members 22a, 22b. The charge chamber 50 can be filled with a pressurized fluid during operation of pump 10. The pressurized fluid in the charge chamber 50 can, in some examples, be configured to displace each fluid displacement member 22a, 22b through at least a portion of the respective pump cycle, as discussed in more detail below. As such, a charge pressure within the charge chamber 50 can be used to set the desired output pressure of pump 10.

Pump 10 includes compression stages 12a, 12b that are configured to serially compress gas. Compression stages 12a, 12b respectively include compression chambers 24a, 24b and fluid displacement members 22a, 22b. Fluid displacement members 22a, 22b reciprocate on axis PA to compress gas and pump the gas through compression chambers 24a, 24b. Fluid displacement members 22a, 22b vary the sizes of compression chambers 24a, 24b, respectively, as fluid displacement members 22a, 22b reciprocate such that the available volume in the compression chambers 24a, 24b increases and decreases as fluid displacement members 22a, 22b reciprocate. Compression chambers 24a, 24b are respectively at least partially defined by fluid displacement members 22a, 22b and by covers 36a, 36b.

Covers 36a, 36b are disposed at opposite axial ends of housing 34. Covers 36a, 36b are fixed to housing 34. Covers 36a, 36b and housing 34 can together be considered to form a body 32 of pump 10. Covers 36a, 36b are mounted to housing 34 to form pump body 32. Each cover 36a, 36b can be formed from a single piece or multiple pieces. Covers 36a, 36b can be formed from a resilient material capable of interfacing with various gasses. For example, covers 36a, 36b can be formed from metal, among other options. In the example shown, covers 36a, 36b have generally circular cross sections taken orthogonal to pump axis PA to fit on the annular ends of the cylindrical housing 34. Covers 36a, 36b can annularly seal with housing 34. Covers 36a, 36b at least partially define compression chambers 24a, 24b, respectively. Cover 36a can be identical to cover 36b. As such, a single configuration of a cover can be utilized to form both of the upstream compression chamber 24a and the downstream compression chamber 24b. The common configuration of covers 36a, 36b reduces part count, simplifies manufacturing, simplifies assembly, and simplifies maintenance. The common configuration of covers 36a, 36b thus provides time, material, cost, and storage space savings.

Inlets 26a, 26b provide flowpaths into compression chambers 24a, 24b, respectively. Outlets 28a, 28b provide flowpaths out of compression chambers 24a, 24b, respectively. Inlet 26a, which forms the pump inlet in the example shown, is formed in cover 36a. Outlet 28a is formed in cover 36a. Inlet 26b is formed in cover 36b. Outlet 28b, which formed the pump outlet in the example shown, is formed in cover 36b. In the example shown, inlets 26a, 26b and outlets 28a, 28b define flowpaths having multiple portions. Inlets 26a, 26b and outlets 28a, 28b are formed through axially inner portions 52 of covers 36a, 36b and through axially outer portions 54 of covers 36a, 36b. Each inlet 26a, 26b thereby includes a downstream flowpath through the inner portion 52 and an upstream flowpath through the outer portion 54. Each outlet 28a, 28b includes an upstream flowpath through the inner portion 52 and a downstream flowpath through the outer portion 54. The inner portions 52 of covers 36a, 36b interface with housing 34. The inner portions 52 can thus be referred to as housing portions. The inner portions 52 of covers 36a, 36b interface with membranes 40 to form a static seal with membranes 40 to prevent gas from leading out of compression chambers 24a, 24b. The outer portions 54 of covers 36a, 36b interface with and are connected to the inner portions 52 of covers 36a, 36b. Fittings 58 are connected to the outer portions 54 of covers 36a, 36b at inlets 26a, 26b and outlets 28a, 28b. The outer portions 54 of covers 36a, 36b can thus be referred to as fitting portions.

Inlets 26a, 26b are radially offset from pump axis PA while outlets 28a, 28b are disposed on axis PA such that axis PA passes through at least a portion of outlets 28a, 28b. It is understood, however, that one, some, or all of inlets 26a, 26b and outlets 28a, 28b can be disposed at different locations in other embodiments.

One or both of outlets 28a, 28b can be formed as one or more bores through which pump axis PA extends. In some examples, one or both of outlets 28a, 28b can be disposed coaxially with pump axis PA. Outlets 28a, 28b can have one or more portions that define circular cross-sectional areas for the flowpaths defined by outlets 28a, 28b when taken orthogonal to pump axis PA. Outlets 28a, 28b being disposed on pump axis PA facilitates efficient pumping and improved pressure and flow control. Outlets 28a, 28b being aligned on pump axis PA positions outlets 28a, 28b furthest from fluid displacement members 22a, 22b along axis PA. Outlets 28a, 28b facilitate a maximum volume of gas to be evacuated from compression chambers 24a, 24b by the diaphragms during the respective pumping strokes of fluid displacement members 22a, 22b.

In the example shown, the bores of outlets 28a, 28b through inner portions 52 include converging walls such that outlets 28a, 28b narrow axially outward through the inner portions 52. The bores of outlets 28a, 28b through inner portions 52 provide a recess that can receive the heads of fasteners 58 during reciprocation of fluid displacement members 22a, 22b. Outlets 28a, 28b thereby allows for a longer stoke length, providing in a greater compression ratio in each compression chamber 24a, 24b.

Intermediate conduit 30 extends between outlet 28a and inlet 26b to fluidly connect compression chambers 24a, 24b. Intermediate conduit 30 is connected to fittings 58 at both covers 36a, 36b. Intermediate conduit 30 transfers compressed gas between covers 36a, 36b. In the example shown, intermediate conduit 30 is a pipe or tube disposed external to the main housing 34 and that fluidly connects the outlet 28a of the first compression stage 12a to the inlet 26b of the second compression stage 12b. The tube forming intermediate conduit 30 is canted relative to pump axis PA. For example, a line CL extending between the first end of the tube at outlet 28a and the second end of the tube at inlet 26b is transverse relative to pump axis PA. The line CL is still be considered to be transverse to pump axis PA even in cases where the line CL does not directly intersect with pump axis PA.

The entirety of the output of the first compression stage 12a is routed into the inlet 26b of the second compression stage 12b through intermediate conduit 30 such that all of the gas output from the first compression stage 12a goes to the second compression stage 12b. All of the gas input into the second compression stage 12b comes from the first compression stage 12a. The second compression stage 12b further compresses the gas to higher pressure than was output by the first compression stage 12a.

Check valves 14a-14d are one-way valves that regulate gas flow through pump 10. Check valve 14a is associated with inlet 26a, check valve 14b is associated with outlet 28a, check valve 14c is associated with inlet 26b, and check valve 14d is associated with outlet 28b. In the example shown, check valves 14a-14d are formed as flapper valves. The valve members, such as the flappers of the flapper valves, of the check valves 14a-14d can be metal, such as stainless steel, among other options. In the example shown, the valve members of the outlet check valves 14b, 14d are disposed between the inner portions 52 and outer portions 54 of covers 36a, 36b. The bores of outlets 28a, 28b through outer portions 54 converge axially away from drive 16 to provide space for the valve members of check valves 14b, 14d to shift between open and closed. In the example shown, the valve members of the inlet check valves 14a, 14c are disposed on the inner portions 52.

Fluid displacement members 22a, 22b pump the gas through compression chambers 24a, 24b. In the example shown, fluid displacement members 22a, 22b are diaphragms. Diaphragms are at least partially formed from flexible material, such as rubber or other type of polymer. Diaphragms are flexible discs whose center can move relative to its circular peripheral edge. In the example shown, the centers of the diaphragms are formed by rigid portions 38. The outer radial side and the inner radial side, which may be a point on pump axis PA, of each rigid portion 38 remain fixed relative to each other along axis during reciprocation of fluid displacement members 22a, 22b. In the example shown, plates 42 form the rigid portion 38 of the diaphragms. An axially outer one of plates 42 is exposed to the gas in the respective compression chambers 24a, 24b. It is understood, however, that rigid portions 38 can be formed in any desired manner, such as by a plate or other component embedded within a flexible member, such as a membrane 40. In such an example, membrane 40 can form the only portion of diaphragm contacting the gas.

A circular peripheral edge of each diaphragm is held in place while the center of the diaphragm is moved through pumping and suction strokes. For example, the circular peripheral edge can be pinched between the housing 34 and respective cover 36a, 36b. A portion of the diaphragm can thus be secured between one of the covers 36a, 36b and the housing 34. The center the diaphragm can be moved in a reciprocating manner by drive 16, as further discussed herein. A gas-tight seal is formed between the fluid displacement members 22a, 22b and pump body 32 to fluidly isolate compression chambers 24a, 24b from charge chamber 50. In the example show, the peripheral edge of the membrane 40 is clamped between a cover 36a, 36b and housing 34 to form a static seal. The static seal remains stationary relative to pump axis PA during reciprocation of the fluid displacement member 22a, 22b.

In the example shown, membranes 40 form the flexible portions of fluid displacement members 22a, 22b. The flexible portions extend radially between the rigid portion 38 and the static seal between fluid displacement members 22a, 22b and pump body 32. Membranes 40 are flexible such that the radially outer side of membrane 40 at the static interface and the radially inner side of membrane 40 at rigid portion 38 can move relative to each other along axis PA during reciprocation of the fluid displacement members 22a, 22b.

Plates 42 are disposed on opposite axial sides of the membrane 40. A portion of membrane 40 is sandwiched between an axially inner one of plates 42 and an axially outer one of plates 42. Plates 42 support the membrane 40. The axially outer plate 42 at least partially defines a respective compression chamber 24a, 24b and acts on the gas during pumping. A radial gap is formed between the radially outer edge rigid portion 38 the radially inner wall of the cover 36a, 36b defining compression chamber 24a, 24b. The radial gap is an annular gap. In the example shown, the radial gap extends annularly around the axially outer one of plates 42. The charge pressure of the pressurized fluid in charge chamber 50 acts on membrane 40 to push membrane 40 axially away from drive 16. The pressurized fluid can cause membrane 40 to project axially though the annular gap between plate 42 and cover 36a, 36b. Membranes 40 can balloon into the annular gap. Membrane 40 extending into the annular gap reduces the available volume of compression chambers 24a, 24b when fluid displacement members 22a, 22b are at the ends of the pressure strokes, thereby increasing the compression ratios of compression stages 12a, 12b. The increased compression ratio facilitates more efficient pressurization and pumping by pump 10 and facilitates increased output pressures from each compression stage 12a, 12b.

While the first and second fluid displacement members 22a, 22b are shown and discussed as diaphragms, the first and second fluid displacement members 22a, 22b can instead be pistons. Such pistons can be reciprocated back and forth by drive 16 along the axis PA, though pumping and suction strokes. In some examples, fluid displacement members 22a, 22b are similarly configured. For example, the diaphragms or pistons can have the same diameter for each fluid displacement member 22a, 22b. It is understood, however, that not all examples are so limited.

Drive 16 is disposed at least partially within housing 34. Drive 16 is operatively connected to fluid displacement members 22a, 22b to cause reciprocation of fluid displacement members 22a, 22b. At least a portion of drive 16 can be disposed directly between fluid displacement members 22a, 22b. Drive 16 includes motor 44. Motor 44 can be an electric rotary type motor, such as an AC induction or DC brushless, among other options. Motor 44 is, in some examples, at least partially disposed within housing 34. In some examples, motor 44 can be fully disposed within housing 34. In some examples, motor 44 can be disposed at least partially directly between fluid displacement members 22a, 22b. In the example shown, motor 44 projects vertically below housing 34 to minimize a footprint of pump 10. Motor 44 is operatively connected to crank 46 to operate crank 46.

Crank 46 includes an eccentric or cam that moves connectors 48a, 48b. In the example shown, crank 46 is disposed directly between fluid displacement members 22a, 22b. Connectors 48a, 48b are attached to crank 46 to be reciprocated along pump axis PA. The asymmetry of the rotating portion of the crank 46 can cause first connector 48a to move the first fluid displacement member 22a through a suction stroke while the second connector 48b moves the second fluid displacement member 22b through a pumping stroke. The movement can then be reversed as the crank 46 moves to another phase of its rotation to cause the first connector 48a to move the first fluid displacement member 22a through the pumping stroke while the second connector 48b moves the second fluid displacement member 22b through a suction stroke. In the example shown, connectors 48a, 48b are attached to fluid displacement members 22a, 22b by fasteners 58. In the example shown, crank 46 interfaces with shuttle 60 to cause reciprocation of shuttle 60 along pump axis PA. Connectors 48a, 48b interface with shuttle 60 to cause reciprocation of connectors 48a, 48b.

In the example shown, connectors 48a, 48b only pull fluid displacement members 22a, 22b through suction strokes. Connectors 48a, 48b do not force fluid displacement members 22a, 22b through pumping strokes. Connectors 48a, 48b can also be referred to as pulls. Connectors 48a, 48b are movable relative to shuttle 60 and within the connector receiving chambers formed in shuttle 60. Connectors 48a, 48b can decouple fluid displacement members 22a, 22b from crank 46 to facilitate relative axial movement therebetween. In the example show, connectors 48a, 48b are configured to decouple fluid displacement members 22a, 22b during respective pumping strokes.

In the example shown, the pressurized fluid within charge chamber 50 acts on the inner axial sides of fluid displacement members 22a, 22b (e.g., both on the axially inner plate 42 and inner face of membrane 40) to exert a driving force on fluid displacement members 22a, 22b. The driving force pushes fluid displacement members 22a, 22b to drive fluid displacement members 22a, 22b axially outward through respective pumping strokes. An advantage of such a system is that the pumping pressure is generally managed by the charge pressure inside the housing and the output pressure of the gas (e.g., the second pressure) is not susceptible to the pressures spikes of (sometimes inflexible) mechanical system.

In a deadhead condition, fluid displacement members 22a, 22b can stop moving but shuttle 60 can continue to reciprocate relative to connectors 48a, 48b and fluid displacement members 22a, 22b, reducing the load and wear on drive 16 that can be caused by starts and stops. In some examples, the downstream fluid displacement member 22b can be in a deadhead condition due to standing pressure built in second compression chamber 24b while the upstream fluid displacement member 22a continues to reciprocate to build pressure in intermediate conduit 30 and, in some examples, compression chamber 24a. As such, the upstream one of fluid displacement members 22a can complete one or more pump strokes, suction strokes, and/or pump cycles while the downstream fluid displacement member 22b remains stationary.

In some examples, the reciprocation of the fluid displacement members 22a, 22b is entirely managed by pressurized fluid within the main housing 34 such that the fluid displacement members 22a, 22b are not mechanically driven through either pumping or suction stroke. For example, working fluid can be flowed to and vented from various chambers within housing 34 to cause reciprocation of fluid displacement members 22a, 22b.

In some examples, connectors 48a, 48b are axially fixed relative to both fluid displacement members 22a, 22b. Fluid displacement members 22a, 22b are thereby coupled for simultaneous movement along axis PA. For example, fluid displacement members 22a, 22b can be coupled to be 180-degrees out of phase relative to each other, such that one fluid displacement member 22a, 22b is at the end of a suction stroke while the other fluid displacement member 22a, 22b is at the end of a pumping stroke. The pumping cycles of the fluid displacement members 22a, 22b can be out of phase such that the first diaphragm and the second diaphragm are not concurrently in either one of the pumping stroke and the suction stroke. The pumping cycles of fluid displacement member 22a can be out of phase with respect to the pumping cycles of the fluid displacement member 22b such that one of the fluid displacement members 22a, 22b is performing a pumping stroke while the other fluid displacement member 22a, 22b is performing a suction stroke.

Drive 16 causes reciprocation of fluid displacement members 22a, 22b to cause pumping by pump 10. Drive pulls fluid displacement member 22a in first axial direction AD1 and through a suction stroke to increase the volume of compression chamber 24a. Fluid displacement member 22a draws gas into compression chamber 24a through check valve 14a. Simultaneously, the pressurized fluid in charge chamber 50 pushes fluid displacement member 22b through a pumping stroke to decrease the volume of compression chamber 24b. If compression chamber 24b is charged to a standing pressure sufficient to open check valve 14d, then second compression stage 12b discharges pressurized gas downstream. If the standing pressure in compression chamber 24b does not reach a level sufficient to overcome the resistance at check valve 14d, then fluid displacement member 22b compresses the gas to increase the pressure in compression chamber 24b.

Drive 16 then causes fluid displacement member 22a to changeover to a pumping stroke, which closes the first compression stage inlet check valve 14a as the movement of the first fluid displacement member 22a decreases the volume of compression chamber 24a and further increases the gas pressure of the pressurized gas within first compression chamber 24a. The pressurized fluid in charge chamber 50 can drive fluid displacement member 22a through the pumping stroke. Drive 16 also causes the first fluid displacement member 22b to changeover to the suction stroke as the second compression stage outlet check valve 14d closes and the second compression stage inlet check valve 14c opens to allow the entry of more gas into the second compression chamber 24. The pump cycles of fluid displacement members 22a, 22b repeat as long as pump 10 is operated to pump and compress gas. In some examples, fluid displacement member 22a moving through the pumping stroke both outputs gas from outlet 28a and drives gas into compression chamber 24b through inlet 26b. In some examples, at least a portion of the gas driven into compression chamber 24b is different from the gas output by fluid displacement member 22a during that pumping stroke (e.g., the gas had been output by a previous pumping stroke).

In some examples, first compression stage 12a and second compression stage 12b are similarly configured to serially compress the gas. For example, each compression stage 12a, 12b can have the same or similar compression ratios. The compression ratios control the pressure that can be generated. Compression stage 12b receives the gas at an elevated pressure (e.g., that output by first compression stage 12a) relative to the gas received by compression stage 12a and can further pressurize the gas to output the gas at a second pressure level higher than the first pressure level output by compression stage 12a. The similar compression ratios provide uniform loading on components of pump 10 and drive 16, reducing wear and maintenance costs. The similar compression ratios facilitate increased output pressure with a smaller footprint of pump 10. It is understood, however, that not all examples are so limited.

In some examples, compression stage 12a is configured to displace a larger volume of gas per pump stroke than compression stage 12b. For example, fluid displacement members 22a, 22b can be of differing configurations (e.g., different diameters). Fluid displacement member 22a can have a greater gas-contacting cross-sectional area (e.g., represented by an area exposed to a respective compression chamber 24a, 24b) than fluid displacement member 22b. Compression stage 12a can thereby displace a greater volume of gas per pump stroke than compression stage 12b despite the same travel distance for each pumping stroke. In additional or alternative examples, compression chamber 24a can have a larger maximum volume than compression chamber 24b. For example, fluid displacement members 22a, 22b can have similar sizes but different displacement lengths.

As shown, a single drive mechanism (e.g., drive 16) operates two compressors in series. For example, a single motor 44 operates two compressors (e.g., displaces first and second fluid displacement members 22a, 22b) in series. These compressors are supported by a common housing 34. In another aspect, a single crank (or other type of eccentric) operates first and second fluid displacement members 22a, 22b to compress gas in series. In various embodiments, at least part of the drive 16 is located directly between the first and second fluid displacement members 22a, 22b. In some embodiments, the entire drive 16 is located directly between the first and second fluid displacement members 22a, 22b. As another aspect, a single crank (or other type of eccentric) is located at least partially between first and second fluid displacement members 22a, 22b to compress gas in series. In some embodiments, the single crank (or other type of eccentric) is located entirely directly between first and second fluid displacement members 22a, 22b to compress gas in series.

It is understood that the flow rate of the pump 10 when pumping in the serial compression mode is decreased as compared to conventional double diaphragm pumps because all of the compressed gas flows serially through each compression chamber 24a, 24b in stages instead of being used to pump in parallel. While flow rate is decreased relative to a conventional double diaphragm pump with parallel pumping chambers, output pressure is increased. In addition, pump 10 outputs gas at flowrates greater than those capable of being produced by comparably sized piston pumps, which are typically single displacement.

Pump 10 provides significant advantages. Compression stages 12a, 12b can be commonly configured and serially compress the gas. The common configurations of fluid displacement members 22a, 22b and/or covers 36a, 36b reduces part count and facilitates efficient maintenance and assembly. Pump 10 thereby reduces downtime and increases productivity. Pump 10 can pump at higher pressures as compared to standard double diaphragm pumps. Pump 10 can also pump at higher flow rates as compared to piston gas compressors. Fluid displacement members 22a, 22b are disposed coaxially on pump axis PA, balancing the load on drive 16 and fluid displacement members 22a, 22b. The pressurized fluid in charge chamber 50 causes membrane 40 to extend axially outward, away from charge chamber 50 and into a respective compression chamber 24a, 24b in the annular gap between plate 42 and the inner wall of a respective cover 36a, 36b. The bulging of membrane 40 reduces the minimum volume of compression chambers 24a, 24b with fluid displacement members 22a, 22b at the end of a pumping stroke, providing an improved compression ratio and evacuation from compression chamber 24a, 24b. Diaphragms form static seals that have reduced wear as compared to moving, dynamic seals. Pump 10 thereby reduces downtime and maintenance costs.

FIG. 3A is a schematic diagram of pump 10 in a serial pumping mode. FIG. 3B is a schematic diagram of pump 10 in a parallel pumping mode. FIGS. 3A and 3B will be discussed together. Pump 10 includes compression stages 12a, 12b, check valves 14a-14d, inlet conduit 18, outlet conduit 20, and switching valve 62. Compression stages 12a, 12b respectively includes fluid displacement members 22a, 22b and compression chambers 24a, 24b. Switching valve 62 includes flow director 64 and actuator 66.

Pump 10 is configured to pump in a serial flow mode and a parallel flow mode. In the serial flow mode, the process gas flows serially from the inlet conduit 18 to compression stage 12a, from compression stage 12a to compression stage 12b, and from compression stage 12b to outlet conduit 20. No process gas flows through compression stage 12b without first passing through and being pressurized by compression stage 12a with pump 10 in the serial flow mode. In the parallel flow mode, compression stages 12a, 12b are fluidly isolated from each other. The process gas flows from inlet conduit 18 to one of compression stages 12a, 12b and from the compression stages 12a, 12b directly to outlet conduit 20. No process gas passes from one compression stage 12a, 12b to the other compression stage 12a, 12b in the parallel flow mode.

Pump 10 is shown as including switching valve 62 to actuate pump 10 between the serial and parallel flow modes. Switching valve 62 is configured to direct flows of the process fluid based on whether switching valve 62 is in a first state associated with the serial flow mode (shown in FIG. 3A) or if switching valve 62 is in a second state associated with the parallel flow mode (shown in FIG. 3B). Flow director 64 is disposed within a body of switching valve 62 and is movable between a first position (shown in FIG. 3A) associated with the serial flow mode and a second position (shown in FIG. 3B) associated with the parallel flow mode. Actuator 66 is operatively connected to flow director 64 to move the flow director 64 between the first and second positions. For example, actuator 66 can be a toggle, knob, switch, button, slider, or of any other form suitable for causing a change in the position of flow director 64. Actuator 66 can be mechanically, electrically, magnetically and/or otherwise connected to flow director 64 to shift flow director 64.

With pump 10 in the serial flow mode, flow director 64 is in the first position and inlet conduit 18 is directly fluidly connected to inlet 26a of compression stage 12a and fluidly isolated from inlet 26b of compression stage 12b. The full volume of gas entering pump 10 from inlet conduit 18 flows to compression chamber 24a through inlet 26a and check valve 14a. Fluid displacement member 22a is driven through a pumping stroke to pressurize the gas and drive the gas downstream out of compression chamber 24a through outlet 28a and check valve 14b. Compression stage 12a outputs the gas at a first pressure.

The output from compression stage 12a flows to switching valve 62. Switching valve 62 fluidly isolates the output from compression stage 12a from both inlet conduit 18 and outlet conduit 20. Switching valve 62 directly fluidly connects the output from compression stage 12a to compression stage 12b. The gas flows to compression chamber 24b through inlet 26b and check valve 14c. The gas received by compression stage 12b is at the first pressure, which is elevated as compared to the gas pressure input to compression stage 12a. Fluid displacement member 22b is driven through a pumping stroke to drive the gas downstream out of compression chamber 24b through outlet 28b and check valve 14d. The gas is output to outlet conduit 20 by compression stage 12b. Compression stage 12b outputs the gas at a second pressure that can be elevated relative to the first pressure.

Pump 10 can be placed in the parallel flow mode to provide a greater flow rate of the gas as compared to the serial flow mode. Actuator 66 is actuated to cause flow director 64 to move from the first position shown in FIG. 3A to the second position shown in FIG. 3B. With flow director 64 in the second position, inlet conduit 18 is fluidly connected to both inlet 26a and inlet 26b, outlet 28a is fluidly isolated from inlet 26b, and outlet 28a is fluidly connected to outlet conduit 20. The gas flow from inlet conduit 18 flows to both inlet 26a of compression stage 12a and inlet 26b of compression stage 12b. The gas flows to compression chamber 24a though inlet 26a and check valve 14a and to compression chamber 24b through inlet 26b and check valve 14c.

Fluid displacement member 22a is driven through a pumping stroke to drive the gas downstream out of compression chamber 24a through outlet 28a and check valve 14b. Flow director 64 fluidly isolates the output from compression stage 12a from the inlet 26b of compression stage 12b and fluidly connects the output from compression stage 12a with outlet conduit 20. As such, compression stage 12a directly provides pressurized gas to outlet conduit 20 with pump 10 in the parallel flow mode.

Simultaneously to or out of phase with fluid displacement member 22a, fluid displacement member 22b is driven through a pumping stroke to drive the gas downstream out of compression chamber 24b through outlet 28b and check valve 14d. The output from compression stage 12b is provided to outlet conduit 20 with pump 10 in both the serial flow mode and the parallel flow mode.

Pump 10 provides significant advantages. Pump 10 can be actuated between the serial flow mode, providing higher pressure relative to the parallel flow mode, and the parallel flow mode, providing higher flow relative to the serial flow mode. Pump 10 thereby facilitates both high flow and high pressure applications, reducing costs and increasing operational efficiency. Switching valve 62 provides a simple, efficient manner of actuating pump 10 between the serial flow and parallel flow modes.

FIG. 4 is a graph showing a standing pressure built downstream of pump 10 over time for pump 10 operating in the parallel flow mode and the serial flow mode. The graph of FIG. 4 shows pump 10 operating with a charge pressure of about 1.03 MPa (about 150 psi) in charge chamber 50. The lower horizontal axis represents time and the left vertical axis represents pressure downstream of pump 10 (e.g., downstream of outlet 28b). In the example shown, parallel flow line PF1 represents the output from pump 10 operating in the parallel flow mode, while serial flow line SF1 represents the output from pump 10 operating in the serial flow mode. The example shows pressure build in a downstream tank having a capacity of 7-gallons. It is understood that similar pressure vs. time profiles for line PF and line SF are applicable for downstream locations having different capacities, with reduced time to reach pressure in larger volume tanks and increased time to build pressure in larger volume tanks.

As shown, pump 10 can initially build pressure more quickly when operating in the parallel flow mode. However, the pressure output by pump 10 operating in the serial flow mode overtakes and exceeds the pressure output during the parallel flow mode prior to the parallel flow mode reaching a maximum pressure output. Pump 10 continues to build pressure generally linearly during the serial flow mode as the pressure output during the parallel flow mode levels off.

The compression ratios of compression stages 12a, 12b limit the maximum pressure that can be output by any one of compression stages 12a, 12b. Pre-pressurizing the gas in compression stage 12a facilitates a further increase in pressure even with the same or similar compression ratio. The serial flow line SF1 shows that pump 10 can output pressure up to about the charge pressure in charge chamber 50, whereas the parallel flow line PF1 shows that the maximum pressure output by pump 10 in the parallel flow mode is a fraction of the charge pressure. The serial flow mode of pump 10 thereby provides greater pressure control as the actual maximum output pressure corresponds to the charge pressure. The user can thus set the charge pressure in charge chamber 50 to control the output pressure as the maximum pressure output by pump 10 during the serial flow mode directly corresponds with the charge pressure.

FIG. 5 is a graph showing gas pressure verses flow rate output from pump 10 operating in the parallel flow mode and the serial flow mode. The graph of FIG. 5 shows pump 10 operating with a charge pressure of about 1.03 MPa (about 150 psi) in charge chamber 50. The lower horizontal axis pressure downstream of pump 10 (e.g., downstream of outlet 28b) and the vertical axis represents flow rate in cubic feet per minute (CFM). In the example shown, parallel flow line PF2 represents the output from pump 10 operating in the parallel flow mode, while serial flow line SF2 represents the output from pump 10 operating in the serial flow mode.

As shown, pump 10 can output a greater flow rate while operating in the parallel flow mode as compared to the serial flow mode at relatively lower pressures. However, pump 10 can begin to produce a higher flow rate in the serial flow mode as compared to the parallel flow mode prior to the pressure output during the parallel flow mode reaching a maximum pressure. In some examples, pump 10 can have a variation from a maximum flow at minimum pressure and a maximum flow at maximum pressure of less than about 50%. In some examples, the variation is less than about 35%. As shown by serial flow line SF2, pump 10 in the example shown has a variation in flow rate of less than about 40% between the maximum flow rate (about 2CFM in the example shown) at the minimum pressure output (about 34.5 kilopascal (KPa) (about 5 psi) in the example shown) and the maximum flow rate (about 1.25CFM in the example shown) at the maximum pressure output (about 1.03 MPa (about 150 psi) in the example shown). In some examples, pump 10 can have a variation in flow rate in a middle third of the pressure range of less than about 10% from the flow rate at the low end of the middle third of the pressure range (at about 0.35 MPa (about 50 psi) in the example shown) to flow rate at the high end of the middle third of the pressure range (at about 0.69 MPa (about 100 psi) in the example shown). In some examples, pump 10 can have a variation in flow rate in a middle two-thirds of the pressure range of less than about 25% from the flow rate at the low end of the middle two-thirds of the pressure range (at about 0.17 MPa (about 25 psi) in the example shown) to flow rate at the high end of the middle two-thirds of the pressure range (at about 0.86 MPa (about 125 psi) in the example shown). In some examples, pump 10 can have a variation in flow in a middle 50% of the pressure range of less than about 20% from the flow rate at the low end of the middle 50% of the pressure range (at about 0.26 MPa (about 37.5 psi) in the example shown) to flow rate at the high end of the middle 50% of the pressure range (at about 0.78 MPa (about 112.5 psi) in the example shown). In some examples, pump 10 can have a variation in flow rate in an upper half of the pressure range of less than about 20% from the flow rate at the low end of the upper half of the pressure range (at about 0.52 MPa (about 75 psi) in the example shown) to flow rate at the high end of the upper half of the pressure range (at about 1.03 MPa (about 150 psi) in the example shown). In some examples, pump 10 can have a variation in flow rate of in an upper half of the pressure range of less than about 20% from the flow rate at the low end of the upper half of the pressure range (at about 0.52 MPa (about 75 psi) in the example shown) to flow rate at the high end of the upper half of the pressure range (at about 1.03 MPa (about 150 psi) in the example shown). Pump 10 provides a relatively consistent flow rate across a variety of output pressures. The steady flow across a wide pressure range provides consistency between applications and facilitates efficient gas recovery.

While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

PUMP HAVING MULTI-STAGE GAS COMPRESSION

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