WO2025010249A2 - Axial piston pump with integrated axial piston energy recovery device - Google Patents

Abstract

An axial piston pump having an energy recovery system.

Description

AXIAL PISTON PUMP WITH INTEGRATED AXIAL PISTON ENERGY RECOVERY DEVICE

RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Application No. 63/524,722 filed under 35 U.S.C. § 111(b) on July 3, 2023, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] Numerous industrial fluid-based processes involve a process stream that needs to be pressurized to a high level required to achieve a transformation of the process stream in a beneficial manner. The stream entering the process is called the input stream. The output of the process may be a single output stream or multiple output streams with one or more of the output streams retaining a substantial fraction of the input pressure. High-pressure output streams hold the possibility of recovering hydraulic energy to reduce net energy consumption.

[0003] Figure 1-A depicts a reverse osmosis desalination system. The input stream, seawater in this example, enters through pipe 1 and is pressurized by high-pressure pump 2 to about 55 to 65 bars before admitted into reverse osmosis (RO) membranes 3. RO membranes 3 selectively block dissolved substances from crossing the semi-permeable membrane of the RO element and thus a portion of the input stream is purified and exits through pipe 4 at low pressure. Anywhere from 35-50 percent of the input stream is purified and 50-65 percent of the input stream exits membrane 3 as an output brine stream at a pressure slightly less than input stream in pipe 1 through pipe 5 and control valve 6 to drain 7. This output brine stream offers the potential for recovering hydraulic energy. Figure 1-B shows an energy recovery device 8 that transfers energy from output stream in pipe 5 to input stream in pipe 1. Note that input stream has a flow substantially higher than output stream. [0004] Figure 1-C depicts a liquid-based absorption process used to purify gases such as natural gas. Raw gas enters contractor 52 by pipe 1. Liquid absorbent is sprayed from nozzles 53 at the top of contractor to absorb CO₂ from the gas flowing upwards to exit through pipe 54 as purified gas. The absorbent, now laden with contaminants, collects at the bottom and exits through pipe 58 through control valve 57 regulated by liquid level monitor 56. The output stream of absorbent enters stripper 59 which removes contaminants from the liquid absorbent with contaminates exiting through pipe 60 and then is admitted through pipe 61to pump 55 that repressurizes the absorbent to the pressure in contractor 52 thus completing the purification cycle. Typical contractor pressure is 60 bar and stripper pressure well below 10 bar thus there is significant hydraulic energy available for recovery. Figure 1-D shows an energy recovery device 8 that transfers hydraulic energy from the output stream flowing through pipe 58 to the input stream flowing through pipe 61. Note that the input and output streams have similar flow rates.

[0005] The process above has an input stream flowrate approximately equal to the output stream flowrate. Also, the output stream is laden with gaseous components that will come out of solution when the pressure is reduced hence the volume of the output stream can exceed the input stream as well as contain additional energy available from the expansion of the gaseous component.

[0006] The invention described herein can accommodate the above operating scenarios.

[0007] Many types of hydraulic energy recovery devices have been developed. The most numerous use a turbine to recover hydraulic energy. The mechanical energy generated by the turbine can be used to help drive the pressurization pump or be used for another application. Turbine-based energy recovery is most feasible for high flow rates (above 100 m³/hr.) which is favorable to high efficiency. Lower flows have a negative effect on efficiency thereby reducing the economic justification for using such equipment. Positive displacement energy recovery devices can have high efficiency at low flow rates but are generally expensive thereby reducing the economic justification. [0008] The present invention is an improvement in process hydraulic energy recovery by combining the pressurization pump and the depressurization energy recovery device into a single unit using positive displacement. Combining the high-pressure pump and energy recovery device into one unit reduces the cost and complexity of the system resulting in a greater economic justification to apply energy recovery to various processes. The additional flexibility of handling input and output streams of differing flow rates with gaseous components increases the range of application and energy recovery potential. DESCRIPTION OF THE PRIOR ART

[0009] Figures 2 and 3 show a typical axial piston pump relevant to the present invention. Casing 75 and end caps 72 and 21 are attached by bolts 74-A and 74-B and bolts 22-A and 22-B respectively. Shaft 24 with keyway 25 passes through end cap 21 with seal 31 preventing leakage. The inboard end of shaft 24 is attached to barrel 12 by keyway 26 and key 27 thus rotates as a unit.

[0010] Swash plate 20 is attached to end cap 21 by bolts 23-A and 23-B. Swash plate 20 is cylindrical and is cut or disposed at an angle with respect to end cap 21 at about 15 to 25 degrees. Barrel 12 (bold outline for clarity) contains a plurality of axially disposed cylinders 11 circumferentially arranged around the centerline of barrel 12 as more clearly illustrated in Figure 3. The number of cylinders typically are 5, 7 or 9 with the higher number providing smoother fluid flow while the lower number reduces costs of manufacture. Port plate 77 is held to end cap 72 by bolts 74A and 74B.

[0011] Piston 10 in each cylinder 11 is connected to connecting rod 38 and the connecting rod is attached to spherical ball 32. Ball 32 fits into socket 13 with the amount of engagement sufficient to trap ball 32. Socket 13 and ball 32 are free to pivot with respect to each other. Socket 13 is attached to slipper 14. Slipper 14 is free to slide across the swash plate in a circular path defined by the location of cylinders 11 in barrel 12. Lubrication channel 18 connects pumping chamber 19 with bearing pocket 17 in slipper 14. Fluid pressure in chamber 19 is communicated to bearing pocket 17 to provide hydrostatic lift to create running clearance 15 that reduces friction and wear between slipper 14 and swash plate 20 during operation.

[0012] In operation, shaft 24 and barrel 12 are rotated by a motor as is well known in the art. As barrel 12 rotates, slippers 14, connecting rod 38 and piston 10 are caused to make a reciprocating motion as slipper 14 follows the angled swash plate 20. The reciprocating motion is timed such that when piston 10 is moving away from port plate 77, cylinder 10 is in communication with the suction inlet 1 and suction arcuate shaped area 36 of port plate 77 illustrated in Figure 3. Input stream fluid is drawn into cylinder 11 through inlet connection 1. At a point in the rotation of barrel 12, the reciprocating motion slows, then stops and then begins to reverse direction towards port plate 77. During the transition between the suction stroke and the discharge stroke, cylinder 11 is covered by the close running seal area 35 and 37 of the port plate 77, best illustrated in Figure 3. It is critical that the width of lands 35 and 37 between ports 34 and 36 be wider than the diameter of cylinder 11, otherwise leakage between ports 34 and 36 can occur. This close running clearance minimizes leakage from high-pressure port 34 to the low-pressure port 36. Further rotation of barrel 12 causes piston 10 to move towards port plate 77. Cylinder 11 is now in communication with the arcuate shaped high-pressure port 34 of port plate 77 which in turn is in communication with output port 2. The decreasing volume of cylinder 11 caused by advancing piston 10 as it moves towards port plate 77 causes pressure in cylinder 11 to raise to the pressure existing in discharge outlet 2 and downstream piping. The preceding description is typical of axial piston pumps.

[0013] Pressure between port plate 77 and barrel 12 will be high in the discharge arc (pumping section) thereby tending to force the barrel away from the port plate. This force can be counteracted by necking down the opening in cylinder 11 as indicated by shoulder 28. Fluid pressure will act on the shoulder 28 area pushing the barrel towards port plate 77. By using a correct area of shoulder 28, the pressure force from port plate 77 can be largely balanced with a slight net force desired to maintain a nearly rubbing clearance to reduce leakage from the high-pressure zone to the low-pressure zone.

[0014] Bearing 8 maintains radial position of barrel 12. A small clearance 9 allows lubricating and cooling flow.

[0015] Leakage from barrel 12, pistons 10 and bearing pocket 17 is drained through drain port 30.

[0016] Other prior art is shown in Figure 4 depicting an axial piston pump with hydraulic energy recovery functionality. The pump section 80 is similar to the pump of Fig 2. The key feature here is a second port plate 68 located at the opposite end of barrel 12. High-pressure brine output stream, such as the output stream that exits a RO membrane 3 through pipe 5 as shown in Figures lA and B, enters through inlet port 69, flows through port plate 68, and into energy recovery cylinder 81. Fluid pressure acting on the bottom 76 of piston produces a force that lessens the amount of energy required to achieve discharge pressure and lessens the load on swash plate 73. The force reduction equals the cross-sectional area of piston 66 minus the cross-sectional area of connecting rod 67 times the pressure of the output stream. This force acting on the bottom 76 of piston 66 times the piston stroke is equal to the amount of energy recovered by that cylinder less frictional loses.

[0017] During the suction stroke the fluid that acts upon the top of piston 65 in the pump cylinder 11 moves the piston towards the swash plate 73. The fluid in the energy recovery cylinder moves through port plate 68 and is discharged through flow channel 70.

[0018] Connecting rod 67 reduces the displacement volume swept by reciprocating motion of pistons 65 and 66 thus the output stream flow needs to be less than the input stream flow. In the case of reverse osmosis systems, the output brine stream is typically 50% to 65% the volume of the input of the process flow thus the rod cross-sectional area should be similarly sized in relation to the input and output flow volumes.

[0019] Apparent problems with prior art depicted in Figure 4 includes clearance between barrel 12 and port plates 77 and 68. There is no possibility to ensure simultaneous close or lightly rubbing clearance for both clearances. Attempts to manufacture the components to achieve clearances measured to microns, even, if possible, would not be able to accommodate dimensional changes caused by wear, thermal growth or dimensional changes from pressurization.

[0020] Also note that the diameter of barrel 12 is significantly increased to accommodate flow channels 69 and 70 resulting in increased costs and greater leakage around the barrel.

SUMMARY OF THE INVENTION

[0021] An axial piston pump having an energy recovery system.

DETAILED DESCRIPTION OF THE DRAWINGS

[0022] Figure 1A is a side elevational view of a reverse osmosis desalination system.

[0023] Figure IB is a side elevational view of a reverse osmosis desalination system with an energy recovery device.

[0024] Figure 1C is a side elevational view of a liquid-based absorption process.

[0025] Figure ID is a side elevational view of a liquid-based absorption process with an energy recovery device.

[0026] Figure 2 is a cross sectional side view of an axial piston pump.

[0027] Figure 3 is a cross sectional view taken along line cutting plane line A-A in Figure 2

[0028] Figure 4 is a cross sectional side elevational view of an axial piston pump with prior art energy recovery. [0029] Figure 5 is a cross sectional side elevational view of an axial piston pump with an energy recovery device of the present invention.

[0030] Figure 6 is a cross sectional view taken along cutting plane line B-B in Figure 5.

[0031] Figure 7 is a cross sectional side elevational view of another embodiment of axial piston pump with an energy recovery device of the present invention.

[0032] Figure 8 is a cross sectional view taken along cutting plane line C-C in Figure 7

[0033] Figure 9 is a side elevational view of another feature of the invention.

[0034] Figure 10 is a side elevational view of another feature of the invention.

[0035] Figure 11 is a cross sectional view taken along line A-A in figure 1.

[0036] Figure 12 is a cross sectional view taken along line B-B in figure 1.

[0037] Figure 13 is a cross sectional view taken along line C-C in figure 1.

[0038] Figure 14 is a side elevational view of another feature of the invention.

DESCRIPTION OF THE INVENTION

[0039] Figures 5 and 6 depict one embodiment of the invention combining an axial pump with energy recovery functionality. Much of the pump portion is similar to construction and operation described above as prior art so that description will not be repeated here. However, similar components will be referenced in the following description. The invention will be described as the axial piston high- pressure pump 2 that supplies the feed under pressure to a reverse osmosis membrane 3 as described in Figures 1A and IB. The energy recovery portion of the pump will utilize the high-pressure brine outflow from the membrane that flows through pipe 5.

[0040] Many processes, such as RO desalination, involve input and output streams that contain particulate matter. Filter 16 at the top face of piston 10 in Figure 5 prevents particulate matter from passing through lubrication channel 18 and entering bearing pocket 17 that would otherwise damage slipper 14 and swash plate 20.

[0041] Energy Recovery Section 39 has a low-pressure outlet 43 and high-pressure inlet 44. The high-pressure outlet is disposed for receiving the brine output stream in pipe 5 from an RO membrane as shown in Figures 1A and IB. Outlet 43 and inlet 44 are in fluid communications with circumferential channels 46 and 45, respectively, and better shown in Figure 6.

[0042] Figures 5 and 6 show that energy recovery cylinders 79 opens into high- and low-pressure channels 45 and 46. Connecting rods 38 passes through the high- and low-pressure channels and through seals 40. Lands 48 and 49 are in close contact with the cylindrical sides of barrel 12 and this close contact minimizes leakage between the high- and low-pressure chambers 45 and 46. The circumferential width of each land is greater than energy recovery cylinder port 41 thus minimizes leakage from the high-pressure channel 45 to low-pressure channel 46. Flow arrows indicate the general direction to and from the cylinders.

[0043] During operation, the input stream of fluid that is to be pumped enters through inlet pipe 61 and is discharged at high pressure through outlet 62 in response to rotation of barrel 12 with reciprocating pistons 10 in cylinders 11 that are caused to reciprocate by swash plate 20 to provide pressurization as described in greater detail previously.

[0044] High-pressure brine output stream, as from an RO membrane as previously discussed, enters port 44 and into circumferential channel 45. Pistons 10 is moving upward towards port plate 77 thereby allowing high-pressure fluid to enter energy recovery cylinder 79 through energy recovery cylinder port 41 and act upon the area 42 of the piston 10 that is adjacent the connecting rod 38 as shown in Figure 5. The force acting on piston 10 is equal to piston area 42 multiplied by fluid pressure. This force reduces the net force required to drive piston 10 towards port plate 77. Therefore, the torque exerted by shaft 24 to generate rotation of barrel 12 relative to the swash plate 20 and to cause pistons 10 to be reciprocated is reduced thereby reducing the motor energy consumption.

[0045] As a given piston 10 moves toward port plate 77 , to top dead center of its stroke, barrel 12 rotation moves energy recovery port 41 across land 48 that minimizes leakage from high-pressure channel 45 to low-pressure channel 46. Note that piston axial velocity is essentially zero at top dead center and at bottom dead center. Energy recovery cylinder 79 and piston 10, due to the rotation of barrel 12, then enter channel 46 and moves downward expelling fluid from energy recovery cylinder 79 through energy recovery port 41 into channel 46 and through outlet 43.

[0046] The displacement of the piston stroke in the energy recovery section 39 is equal to the area of cylinder 11 times stroke length of the piston 10. However, the force acting on area 42, of the connecting rod 38, reduces piston area and thus reduces displacement. For example, a connecting rod with a diameter of 50% of the piston diameter means that the displacement on the energy recovery side of the piston is about 70% of the pumping side of the piston. For certain processes such as reverse osmosis, the brine output stream is approximately 50% of the input stream thus permitting a connecting rod diameter that is feasible. If the output stream is equal to the input stream, then the connection rod diameter would need to be zero which is, of course, not feasible.

[0047] Figure 7 illustrates another feature of the invention that allows output flows to be equal to or larger than the input stream and allows a sufficiently large connector rod to reliably carry the mechanical load. This operating scenario would be for a typical gas processing, refinery, ammonia, and petrochemical production process in which the output stream is equal to or larger than the input stream. Piston 10 has an additional piston section 50 with a diameter greater than piston 10. Cylinder 11 has a greater diameter to accommodate piston section 50. The diameter of piston section 50 is sized to increase displacement sufficiently to handle the output stream taking into account the required diameter of connecting rod 38 to handle mechanical loads.

[0048] Operation is identical to the pump previously described in Figures 5 and 6. However, cylinder volume 83, defined by first piston section face 82 and second cylinder section face 89 formed in the cylinder 11, changes due to reciprocating motion of piston 50. Therefore, cylinder volume 80 must be vented to allow inflow and outflow of fluid. One method for venting is to include channel 84 that connects the top of volume 80 to drive end volume 85. Another method is with vent port 86 that connects volume 87 between barrel 12 and casing 75 to line 88 that extends from volume 87 to drive-end volume 85. This allows piston leakage to be vented to volume 85 and drain port 30.

[0049] Another feature is to accommodate output streams that include gaseous components including gas that is in solution that would be released when the fluid is depressurized. In such cases, provision should be made to allow the liquid/gas stream to undergo expansion to capture additional energy.

[0050] Figure 8 illustrates the necessary modification to achieve an expansion of fluids within cylinder 79, as shown in figure 5. Lands 48 and 49 provide sealing between high-pressure channel 45 and low-pressure channel 46. To accommodate expansion of the output stream in cylinder 79, the circumferential length of land 48 is extended in the direction opposite of barrel 12 rotation indicated by arrow 90. Thus, fluid entry into energy recovery cylinder 79 is terminated before the full stroke has been completed. Dissolved gas containing fluid volume within cylinder 79 is free to expand once the cylinder is sealed off from high pressure channel 45 until cylinder 79 reaches low-pressure channel 46. The diameter of piston 50 would be made to take into account the reduced amount of time the piston is in communication with high pressure channel 45 so as to receive the correct amount of output fluid. For instance, if the circumferential length land 48 is increased by 15% for gas expansion purposes than the amount of time cylinder 79 is in communication with high pressure channel 45 is reduced by a similar amount of 15%. This reduced amount of communication time can be compensated for by increasing the diameter of cylinder 79. The amount of energy available to be recovered is a function of the output streams volume and pressure. Output stream energy losses are associated with frictional losses through piping, fittings, and valves.

[0051] Close running clearances are required to minimize leakage with means illustrated in Figures 7 and 8. Ceramic rings 91 and 92 are affixed to casing 75 above and below circumferential channels 45 and 46. Oppositely disposed are ceramic ring 93 with a radial clearance of 0.025 mm or less with ceramic rings 91 and 92 attached to barrel 12. Barrel 12 is clad in ceramic in the area that has close rotational clearance with lands 48 and 49. Lands 48 and 49 have ceramic faces 96 and 97 that are in close clearance with barrel 12. The face of barrel 12 opposite port plate 77 can be ceramic clad. Also, the port plate can be made of ceramic material. Ceramic is a preferred material, however, other non-galling and dimensionally stable materials in various combinations may also be used.

[0052] Another operating scenario for an axial piston pump 104, the details of which have been previously described, as shown in Figure 9, is solely energized by a high-pressure fluid stream thus dispensing with a motor or other driver as may be required in a hazardous area such as the presence of flammable gases. In this embodiment, input fluid is admitted through inlet connection 106 and discharged through outlet connection 107. High-pressure pump 101 is driven by an electric motor 102 or another prime mover. The high-pressure fluid from discharge connection 103 is in communication with the high- pressure inlet 44 of the axial piston pump 104. The cylinder/piston diameter of the energy recovery section 39 is determined by the flow rate and discharge pressure of the motor driven pump 101 and the desired flow rate and pressure differential of the pump end outlet 62 of the present invention 104. For example, the discharge pressure of pump end outlet 62 could be twice the pressure of the inlet pressure of energy recovery section 39, thus the working diameter of the energy recovery piston would be about 1.41 times greater than the pump piston area plus the area taken up by the connecting rod as illustrated in figure 5. The embodiment shown in figure 9 has a closed hydraulic loop arrangement utilizing connecting pipe 105 in which the low-pressure output stream exits through outlet connection 43 of energy recovery section 39 is recirculated back to the inlet connection 100 of the motor driven pump 101. This arrangement would preserve the purity and other physical and chemical characteristics of the recirculating flow as well as the process fluid pumped by axial piston pump 104.

[0053] Referring to figure 10, the axial piston pump/energy recovery device (APP/ERD) system 200 has end cap 201 attached to casing 204 by bolt 202 with O-ring 203 providing sealing. Fluid inlet port 205 admits fluid to casing 204 and fluid outlet port 220 discharges fluid from casing 204. Barrel 211 is driven by rotation of shaft 210 that is fixed to barrel 211 by key 209. Pump cylinders 227 are evenly arrayed in barrel 213. Each cylinder contains a piston 216 which includes lubrication channel 215 and a fluid filter 217. ERD inlet 9 and ERD outlet 8 and piston seal 12 were previously described. Casing 204 includes bearing pocket 222 adjacent to barrel 211. Flow passage 221 leads from pump discharge 220 to bearing pocket 222 with the passage including a grooved channel in the face of casing 20 4. A needle valve 224 can be adjusted to control flow resistance through channel 221. Bearing 213 has pocket 218 on the discharge side and pocket 207 on the inlet side disposed 180 degrees apart.

[0054] Referring to figure 11, Bearing 213 surrounds the cylindrical portion of barrel 211 with a close clearance 206 with respect to barrel 211. The bearing area of hydrostatic bearing pocket 222 is biased toward the high-pressure side of barrel 211 to accommodate greater thrust generated by the high cylinder pressures in that area.

[0055] Referring to figurel2, the number of pistons in a barrel typically are 5, 7 or 9. Circumferential passage 230A connects the pump cylinders with outlet port 220. Circumferential passage 230B connects the pump cylinders 227 with inlet port 205. Bearing section 228 and 229 of bearing 213 connect the bearing across the passages and serve as a close running pressure seal between the inlet port 205 and the outlet port 220.

[0056] Referring to figure 13 the second circumferential bearing pocket 207 will have a greater circumferential length than first circumferential bearing pocket 218. Groove 214, in the inner diameter of bearing 213 connects the first and second circumferential bearing pockets 207 and 218. Groove 214 passes high pressure pumpage from the first circumferential bearing pocket 218 to the second circumferential bearing pocket 207.

[0057] During operation, piston 216 in barrel 211 has a reciprocating motion imparted by swash plate 226 due to rotation of barrel 211 and which produces a suction effect during motion toward swash plate and pressure rise effect as described previously. The high pressures on the pump outlet 220 and ERD inlet 209 combine to generate a strong force that pushes barrel 211 perpendicular to the axis of rotation in the direction of pump inlet 205. To counteract this force, second circumferential bearing pocket 207 is provided with high pressure fluid via groove 214 from the first circumferential pocket 218. The high pressure in the second circumferential pocket207 acts as a hydrostatic bearing and prevents rubbing contact between barrel 211 and bearing 213.

[0058] Pressure in region 219 located in the ERD area of barrel 211 and high pressure during the pump strokes of piston 227 generates a force toward end cap 203. This force is counteracted by high pressure fluid in bearing pocket 222 provided by channel 221 connected to pump outlet 220. Needle valve 224 can be adjusted as needed to ensure that there is sufficient pressure to prevent rubbing contact between barrel 211 and bearing 213 without allowing excessive flow that can reduce efficiency or create an unstable position in barrel 211. [0059] As shown in figure 14 the axial piston pump previously described could be modified to funebon as a bent axis axial piston pump. In this arrangement, the pump 316 has a drive shaft 118 with keyway 333. Bearings 327 and 329 accommodate radial and axial forces on drive shaft 118. Seal 325 prevents leakage in bearing cavity 337. Drive shaft 118 is attached to drive plate 315 and are disposed at an angle relabve to pump shaft 317. Pump shaft 317 is driven by gear 319 attached to pump shaft 317 that engages gear 321 attached to drive plate 315. Piston 216 in cylinder 130 in barrel 128 is attached to piston rod 219 that is attached to ball 305 enclosed by socket 307. Note that piston 216 and piston rod 219 moves in a reciprocating linear motion in cylinder 130. Socket 307 is attached to rod 309 that is attached to ball 311 enclosed by socket 313 attached to drive plate 315. Rotation of drive plate 315 causes barrel 128 and cylinders 130 with pistons 216 and piston rods 219 to move in a circular motion. However, due to the angular misalignment of drive plate 315 with respect to pump shaft 317 and attached barrel 128, socket 313, ball 311 and shaft 309 move in an oval relative to the motion of piston rod 219. Hence the moveable joint formed by ball 305 and socket 307 allow a changing angle during rotation. Note that the present invention requires that piston rod 219 remain centered with cylinder 130 to allow seal 211 around piston rod 219 to properly function. The extra ball 305 and socket 307 joint is necessary to accommodate the requirement of seal 211. The pump barrel 128 has several cylinders 130, usually 5, 7, or 9. The barrel and pistons are disposed at an angle, typically between 20 to 40 degrees, to the drive plate. The rotating barrel, drive plate, pistons, inlet and discharge connections are similar in design and operation as the swash plate variants of the invention as previously described.

[0060] Figures 15 and 16 show another feature of the invention that is similar to the variable diameter pistons previously described in figure 7. The function and configuration of the pistons 10 is the same as described with respect to figures 7 and 8 and for the sake of brevity will not be repeated as these details are covered with the description for figures 7 and 8. The pump of figures 15 and 16 also utilize the configuration of figures 10 and 11 where the fluid inlet port 205 and fluid outlet port 220 are in casing 204. The details of this arrangement are shown in detail in figures 10 and 11 and for the sake of brevity will not be repeated as reference can be made to the disclosure for these prior figures.

[0061] The description as detailed in the above disclosure and drawings is intended to represent the features of the invention. It should be understood that the invention is to cover all modifications, equivalents, and alternatives within the scope of the following claims.

Claims

1. An axial piston pump comprising: a casing having an inlet port and an outlet port; a rotatable barrel having a plurality of cylinders positioned in the housing, the cylinders being disposed to be in communication with the inlet port and the outlet port as the barrel is rotated; a piston moveably positioned in each of the plurality of cylinders, the pistons having a first end and a second end, the first end of the pistons being in communication with inlet port and the outlet port as the barrel is rotated; a plurality of connecting rods having a first end and a second end, the first end of the connecting rods being connected to one of each of the plurality of pistons, the second end of the connecting rods operatively engaging an angled plate; a drive means operatively connected to the barrel to cause the barrel to rotate, rotation of the barrel causing the pistons to be moved in the plurality of cylinders as the second end of the connecting rod is moved along the angled plate; a high-pressure inlet formed in the casing, the high-pressure inlet being in communication with the plurality of cylinders when the cylinders are in communication with the outlet port in the casing, the high-pressure inlet being disposed to be in alignment with the connecting rod and the second end of the piston in the plurality of cylinders; and a low-pressure outlet formed in the casing, the low-pressure outlet being in communication with the plurality of cylinders when the cylinders are in communication with the inlet port in the casing, the low-pressure inlet being disposed to be in alignment with the connecting rod and the second end of the piston in the plurality of cylinders.

2. The pump of claim 1 wherein the pistons have a first section that is adjacent the inlet port and a second section that is adjacent the connecting rod for the piston.

3. The pump of claim 2 wherein the second section has a diameter that is larger than the diameter of the first section.

4. The pump of claim 1 wherein a ceramic seal is positioned in the casing above and below the high-pressure inlet and the low-pressure outlet.

5. The pump of claim 3 wherein a drain port is disposed in the cylinder adjacent the first section of the piston, the drain port being in communication with an area of the casing adjacent the connecting rod.

6. The pump of claim 5 wherein a channel extends from the drain port to the area in the casing adjacent the connecting rod.

7. The pump of claim 1 wherein a lubrication channel extends through the pistons and connecting rods, the end of the lubrication channel and the second end of the connecting rod that is spaced apart from the piston being in communication with the angled plate.

8. The pump of claim 7 wherein a filter is positioned in the lubrication channel.

9. The pump of claim 1 wherein the drive means is a motor.

10. The pump of claim 1 wherein the drive means is a source of fluid under pressure that is operatively connected to the high-pressure inlet.

11. The pump of claim 10 wherein the source of the fluid under pressure is a high-pressure pump.

12. The pump of claim 11 wherein the low-pressure outlet is operatively connected to a fluid inlet for high-pressure pump.

13. The pump of claim 1 wherein the high-pressure inlet port and the low-pressure outlet port extend through the rotatable barrel.

14. The pump of claim 13 wherein the high-pressure inlet and the low-pressure outlet are disposed to be substantially perpendicular to the connecting rods.

15. The pump of claim 1 wherein the inlet port and the outlet port pass through the barrel and are in communication with the first end of the pistons.

16. The pump of claim 15 wherein the inlet port and the outlet port are disposed substantially perpendicular to the connecting rods.

17. The pump of claim 16 wherein the barrel has a first end that is disposed adjacent a top of the casing.

18. The pump of claim 17 wherein a bearing pocket is disposed in the casing adjacent the first end of the barrel, a passageway connects the outlet port with the bearing pocket wherein the bearing pocket forms a hydrostatic bearing between the casing and the first end of the barrel.

19. The pump of claim 18 wherein a needle valve is positioned in the passageway that connects the bearing pocket with the outlet port, the needle valve controlling the flow of fluid from the outlet port to the bearing pocket.

20. The pump of claim 15 wherein a circumferential passageway has a first area that connects the cylinders with the outlet port and a second area that connects the cylinders with the inlet port.

21. The pump of claim 20 wherein a first bearing section and a second bearing section are positioned in the circumferential passageway to define the first and second areas.

22. The pump of claim 15 wherein a first circumferential bearing pocket and a second circumferential bearing pocket is disposed between the barrel and the casing., the first circumferential bearing being in communication with the high-pressure inlet, a groove connecting the first circumferential bearing pocket with the second circumferential bearing pocket.

23. The pump of claim 22 wherein the second circumferential bearing pocket has a larger circumferential length than the first circumferential bearing pocket.

24. The pump of claim 9 wherein the angled plate is connected to the motor.

25. The pump of claim 24 wherein the motor has a shaft, the shaft being disposed at an angle to the connecting rods of the pistons.

26. An Axial piston pump comprising: a casing having an inlet port and an outlet port; a rotatable barrel having a plurality of cylinders positioned in the housing, the cylinders being disposed to be in communication with the inlet port and the outlet port as the barrel is rotated, the inlet and outlet ports extending through the rotatable barrel; a piston moveably positioned in each of the plurality of cylinders, the pistons having a first end and a second end, the first end being in communication with the inlet port and the outlet port as the barrel is rotated; a plurality of connecting rods having a first end and a second end, the first end being connected to one of the each of the plurality of pistons, the second end operatively engaging an angled plate, the inlet port and the outlet port being disposed substantially perpendicular to the connecting rods; a drive means operatively connected to the barrel to cause the barrel to rotate, rotation of the barrel causing the pistons to be moved in the plurality of cylinders as the second of the connecting rods are caused to move by the angled plate.

27. The pump of claim 26 wherein a lubrication channel extends through the pistons and connecting rods, the end of the lubrication channel and the second end of the connecting rod being in communication with the angled plate.

28. The pump of claim 27 wherein a filter is positioned in the lubrication channel.

29. The pump of claim 26 wherein the drive means is a motor30.

30. The pump of claim 29 wherein the motor has a shaft, the angled plate being mounted on the shaft, the shaft being disposed at an angle to the connecting rods.