PUMP

Abstract

A pump includes a drive assembly having a drive shaft rotatable about a drive axis, and an eccentric coupled to the drive shaft for rotation therewith. The eccentric includes a shaft portion defining an eccentric axis that is offset from the drive axis. The shaft portion includes a shaft end defining a first alignment feature. A piston is rotatably coupled to the shaft portion and defines a second alignment feature. A cylinder reciprocatingly receives the piston. Positioning the first alignment feature in a predetermined orientation with respect to the second alignment feature locates the piston in one of a top-dead-center position and a bottom-dead-center position with respect to the cylinder.

Description

BACKGROUND

The present invention relates to pumps, particularly to oil free piston pumps and more particularly to an oil free piston pump suitable for use in medical applications.

Pumps are used for a variety of applications and in a variety of environments. One type of pump is a dual piston pump having a centrally-located electric motor that drives more or less identical piston/cylinder assemblies mounted on each side of the motor. To provide a consistent output and to balance the pump, the pistons of each piston/cylinder assembly are preferably out of phase with one another such that when one piston is in a top-dead-center position, the other piston is in a bottom-dead-center position.

Like most industrial products, it is desirable to provide a pump that is easy to assemble, low cost, durable, and that includes a minimal number of parts.

SUMMARY

In one embodiment a pump includes a drive assembly including a drive shaft rotatable about a drive axis. An eccentric is coupled to the drive shaft for rotation therewith. The eccentric includes a shaft portion defining an eccentric axis. The eccentric axis is offset from the drive axis. The shaft portion includes a shaft end defining a first alignment feature. A piston is rotatably coupled to the shaft portion. The piston defines a second alignment feature. A cylinder reciprocatingly receives the piston. Positioning the first alignment feature in a predetermined orientation with respect to the second alignment feature locates the piston in one of a top-dead-center position and a bottom-dead-center position with respect to the cylinder.

The pump can be configured such that first alignment feature includes at least one of a projection extending from the shaft end and a recess formed in the shaft end. The second alignment feature can include two alignment features and a plane extending through the two alignment features of the second alignment feature. The first alignment feature can include at least one side, and the predetermined orientation can include wherein the plane is substantially parallel with the at least one side. The predetermined orientation can also include wherein the plane extends through the first alignment feature. The first alignment feature can include at least one side, and the predetermined orientation can include wherein the plane is oriented at a predetermined angle with respect to the side.

The second alignment feature can include at least one of an opening and a projection. The first alignment feature can be a projection extending from the shaft end and including two parallel sides, and the second alignment feature can be a pair of diametrically opposed openings formed in an end face of the piston and a plane extending through the diametrically opposed openings. The pump can be configured such that when the plane is substantially parallel to the two parallel sides, the piston is in one of the top-dead-center position and the bottom-dead center position with respect to the cylinder. The projection can be substantially rectangular and the openings can be substantially circular.

The drive shaft can include a first end to which the eccentric is coupled, and a second end opposite the first end. The pump can also include a second eccentric coupled to the second end for rotation therewith. The second eccentric can include a second shaft portion defining a second eccentric axis. The second eccentric axis can be offset from the drive axis, and the second shaft portion can include a second shaft end defining a third alignment feature. The pump can also include a second piston rotatably coupled to the second shaft portion, where the second piston defines a fourth alignment feature. A second cylinder can reciprocatingly receive the second piston, such that positioning the third alignment feature in the predetermined orientation with respect to the fourth alignment feature locates the second piston in one of a top-dead-center position and a bottom-dead-center position with respect to the second cylinder. When the piston is in the top-dead-center position with respect to the cylinder, the second piston can be in the bottom-dead-center position with respect to the second cylinder.

The first alignment feature can be non-circular. For example, the first alignment feature can have a shape including one of a cross, oval, rectangle, polygon, triangle, teardrop, and star. The first alignment feature can also be circular and offset from the eccentric axis.

In other embodiments, a dual piston pump includes a first piston, a second piston, a drive shaft having opposite ends, a first eccentric on one end of the drive shaft, and a second eccentric on an opposite end of the drive shaft. The first eccentric includes a shaft portion having a first alignment feature. The first piston has a second alignment feature. The second eccentric includes a shaft portion having a third alignment feature, and the second piston has a fourth alignment feature. A method for orienting the first piston and the second piston in the dual piston pump includes mounting the first piston on the shaft portion of the first eccentric, rotating the first eccentric to position the first alignment feature in a first predetermined orientation with respect to the second alignment feature, thereby locating the first piston in one of a top-dead-center position and a bottom-dead-center position, mounting the second piston on the shaft portion of the second eccentric, rotating the second eccentric to position the third alignment feature in a second predetermined orientation with respect to the fourth alignment feature, thereby locating the second piston in the other of the top-dead-center position and the bottom-dead-center position, securing the first eccentric to the one end of the drive shaft to prevent relative rotation between the first eccentric and the drive shaft, and securing the second eccentric to the opposite end of the drive shaft to prevent relative rotation between the second eccentric and the drive shaft.

Rotating the first eccentric to position the first alignment feature in the first predetermined orientation can include engaging a first alignment tool with the first alignment feature and the second alignment feature. The first alignment tool can include a first mating feature for mating with the first alignment feature, and a second mating feature for mating with the second alignment feature, and engaging the first alignment tool can include mating the first mating feature with the first alignment feature and mating the second mating feature with the second alignment feature. Rotating the second eccentric to position the third alignment feature in the second predetermined orientation can include engaging a second alignment tool with the third alignment feature and the fourth alignment feature. The second alignment feature can include two alignment features and a plane extending through the two alignment features of the second alignment feature, and rotating the first eccentric to position the first alignment feature in the predetermined orientation with respect to the second alignment feature can include positioning the first alignment feature such that the plane extends through the first alignment feature. The first alignment feature can include at least one side, and the second alignment feature can include two alignment features and a plane extending through the two alignment features of the second alignment feature, and rotating the first eccentric to position the first alignment feature in the predetermined orientation with respect to the second alignment feature can include orienting the side to be substantially parallel to the plane. Rotating the first eccentric to position the first alignment feature in the predetermined orientation with respect to the second alignment feature can also include orienting the side at a predetermined angle with respect to the plane.

In still other embodiments, a pump includes a motor including a motor housing having a first end and a second end, a first crankcase coupled to the first end, a second crankcase coupled to the second end, a first cylinder coupled to the first crankcase, a second cylinder coupled to the second crankcase, a first valve body coupled to the first cylinder, and a second valve body formed separately from the first valve body and coupled to the second cylinder. A first valve cover is coupled to the first valve body, and a second valve cover is formed separately from the first valve cover and is coupled to the second valve body. A connecting tube is formed separately from the first valve cover and the second valve cover and provides fluid communication between the first valve cover and the second valve cover.

The motor can include a motor housing, a stator within the motor housing, and a rotor rotatably received within the stator. The rotor can include a drive shaft having a first end extending into the first crankcase and a second end extending into the second crankcase, and the drive shaft can define a drive axis. The can also include a first eccentric coupled to the first end and a second eccentric coupled to the second end, and each eccentric can include a shaft portion defining an eccentric axis offset from the drive axis, and a counterweight portion positioned opposite the shaft portion with respect to the drive axis. The shaft portion of each eccentric can include a first alignment feature. A first piston can be received by the first cylinder and rotatably coupled to the shaft portion of the first eccentric, and a second piston can be received by the second cylinder and rotatably coupled to the shaft portion of the second eccentric. Each of the first piston and the second piston can include a second alignment feature. When the first alignment feature of the first eccentric is in a predetermined orientation with respect to the second alignment feature of the first piston, the first piston can be in one of a top-dead-center position and a bottom-dead-center position, and the second piston can be in the other of the top-dead-center position and the bottom-dead-center position. When the first alignment feature of the first eccentric is in the predetermined orientation with respect to the second alignment feature of the first piston, the first alignment feature of the second eccentric can be in substantially the same predetermined orientation with respect to the second alignment feature of the second piston.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a pump embodying the invention.

FIG. 2 is a front view of the pump of FIG. 1.

FIG. 3 is a back view of the pump of FIG. 1.

FIG. 4 is a left side view of the pump of FIG. 1.

FIG. 5 is a right side view of the pump of FIG. 1.

FIG. 6 is a top view of the pump of FIG. 1.

FIG. 7 is a bottom view of the pump of FIG. 1.

FIG. 8 is an exploded perspective view of the pump of FIG. 1.

FIG. 9. is a section view, shown in perspective, taken along line 4-4 of FIG. 1.

FIG. 10 is an enlarged view showing a portion of the section view of FIG. 4.

FIG. 11 is an elevational section view also taken along line 4-4 of FIG. 1.

FIG. 12 is an enlargement of a portion of the section view of FIG. 11 showing an end cap sealing arrangement for the pump of FIG. 1.

FIG. 13 is partially exploded perspective view of the pump of FIG. 1.

FIG. 14 is a partially exploded perspective view of the pump of FIG. 1.

FIG. 15 is an exploded perspective view of a valve assembly for the pump of FIG. 1.

FIG. 16 is an alternate exploded perspective view of the valve assembly of FIG. 15.

FIG. 17 is an enlargement of a portion of the section view of FIG. 11 showing a valve body sealing arrangement for the valve assembly of FIG. 15.

FIG. 18 is a perspective view of a piston assembly and piston alignment tool for the pump of FIG. 1.

FIG. 19 is an alternate perspective view of the piston assembly and piston alignment tool of FIG. 18.

FIG. 20 is a plan view of the piston alignment tool of FIG. 18.

FIG. 21 is a section view taken along line 21-21 of FIG. 20.

FIG. 22 is a perspective view of an alternative embodiment of the piston assembly and piston alignment tool for the pump of FIG. 1.

FIG. 23 is an alternate perspective view of the piston assembly and piston alignment tool of FIG. 22

FIG. 24 is a section view of a vent plug for the pump of FIG. 1.

It is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or illustrated, in the drawings. The present invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

DETAILED DESCRIPTION

FIGS. 1-7 illustrate a dual piston pump 10 embodying the invention. The pump 10 includes a motor assembly 14, a first piston-cylinder assembly 18a positioned on one end of the motor assembly 14, and a second piston-cylinder assembly 18b positioned on an opposite end of the motor assembly 14. For ease of manufacturing and commonality of parts, in the illustrated construction, the components of the first piston-cylinder assembly 18a are substantially the same as the components of the second piston-cylinder assembly 18b, and will therefore be identified by like reference numbers. Where appropriate, differences between the first and second piston-cylinder assemblies 18a, 18b will be specifically identified.

The motor assembly 14 includes a generally cylindrical motor housing 22. Each piston-cylinder assembly 18a, 18b includes a crankcase 26 coupled to the motor housing 22, a cylinder 30 coupled to the crankcase, a valve body 34 coupled to the cylinder 30, and a valve cover 38 coupled to the valve body 34 and securing the valve body 34 and the cylinder 30 to the crankcase 26. The valve bodies 34 and valve covers 38 of each cylinder assembly 18a, 18b are formed separately from one another. While the illustrated motor assembly 14 is an electric motor, the pump could also be powered hydraulically, if desired.

Each crankcase 26 includes a plurality of outwardly extending ears 42, with the ears 42 of one crankcase 26 each defining a through bore 46, and the ears 42 of the other crankcase 26 each defining a threaded hole 50. A plurality of elongated fasteners 54 extend between the crankcases 26 and clamp the crankcases 26 against the ends of the motor housing 22. More specifically, each fastener 54 extends through the through bore 46 of one of the crankcases 26, extends along the outside of the motor housing 22, and is threaded into the threaded hole 50 of the other crankcase 26. In alternative embodiments, both crankcases 26 may include through bores 46 and the fasteners 54 can be secured with nuts. In still other embodiments, the crankcases can be snap fit onto the motor housing 22 or can be secured to the motor housing 22 using clamps, twist-lock arrangements, or substantially any other suitable means of connection.

Each crankcase 26 defines a plurality of vent openings 58 adjacent the motor housing 22 to provide ventilation for the motor assembly 14. Each crankcase 26 also defines at least one (e.g., two, as illustrated) crankcase port 62 for intake or exhausting of the working fluid of the pump 10. The crankcases 26 also include generally cylindrical cylinder supports 66 that open into the crankcase 26 for supporting the cylinders 30. Each cylinder support 66 includes a pair of diametrically opposed bosses 70 that define threaded bores 74 (see also FIG. 13). Fasteners 78 extend through each valve cover 38 and valve body 34 and along the sides of each cylinder 30, to couple the respective valve cover 38, valve body 34, and cylinder 30 to the crankcase 26. The fasteners 78 are threaded into the treaded bores 74 of the cylinder support bosses 70.

Referring also to FIGS. 8-11, the motor assembly 14 includes a stator 82 fixedly mounted within the motor housing 22, and a rotor 86 rotatably received within the stator 82. The rotor 82 includes a drive shaft having a first end 90 extending into one of the crankcases 26 and a second end 94 extending into the other of the crankcases 26. The drive shaft rotates about a drive axis 98 and is mounted in bearings 102 supported by the crankcases 26.

Each of the first end 90 and the second end 94 of the drive shaft has coupled thereto an eccentric 106. Each eccentric 106 includes a bore 110 that receives the first end 90 or the second end 94. Each eccentric 106 also includes a counterweight portion 114 positioned on one side of the drive axis 98, and a shaft portion 118 positioned on an opposite side of the drive axis 98. In this regard, the counterweight portion 114 and the shaft portion 118 are diametrically opposed to one another with respect to the drive axis 98. The shaft portion 118 defines an eccentric axis 122 that is substantially parallel to and offset from the drive axis 98. The shaft portion 118 also includes an alignment projection 124 that extends axially from the distal end of the shaft portion 118. In the illustrated embodiment, the alignment projection 124 is generally in the form of a rectangle, but other shapes are also possible. The alignment projection 124 aids in proper assembly of the pump 10, as discussed further below.

When the drive shaft rotates, the counterweight portion 114 and the shaft portion 118 of each eccentric 106 revolve around the drive axis 98. As shown in FIG. 11 and discussed further below, the eccentrics 106 are coupled to the respective first and second ends 90, 94 so that when the counterweight portion 114 of one eccentric 106 is above the drive axis 98, the counterweight portion 114 of the other eccentric 106 is below the drive axis 98.

Referring also to FIG. 12, each crankcase 26 includes an end opening 126 that affords access to the interior of the crankcase 26 for assembly and maintenance. During use, the end opening 126 of each crankcase is covered by a crankcase cover 130. The crankcase cover 130 includes an inner, generally cylindrical wall 134 that fits within the end opening 126, and an outer, generally annular wall 138 that abuts an end surface 142 of the crankcase 26. The annular wall 138 includes a circumferential groove 146 that receives a resilient O-ring 150. In the illustrated embodiment, screws 154 are used to secure the crankcase cover 130 to the crankcase 26. More specifically, the screws 154 extend through tabs 158 on the crankcase cover 130 and screw into threaded bores 162 (FIG. 8) provided on the crankcase 26. In this way, when the screws 154 are tightened the crankcase cover 130 is drawn axially toward the crankcase such that the O-ring 150 is compressed between the end surface 142 of the crankcase 26 and the circumferential groove 146. Other embodiments of the pump 10 can replace or supplement the screws 154 with various types of clamping mechanisms, over-center mechanisms, ratchet mechanism, snap-fit configurations, and the like to provide an axial clamping force that draws the crankcase cover 130 snugly against the end surface 142. By axially compressing the O-ring 150, the resulting seal is less susceptible to leakage due to components expanding and contracting as the pump 10 changes temperatures during operating cycles. This is particularly true where the crankcase 26 and crankcase cover 130 are formed of materials having different thermal expansion properties. For example, in one embodiment the crankcase 26 is formed of metal and the crankcase cover 130 is formed from plastic.

Referring also to FIGS. 13-14, a piston 166 is rotatably coupled to the shaft portion 118 of each eccentric 106. Each piston 166 includes a first, disk-like sealing portion 170 that is received by the cylinder 30, an elongated connecting portion 174 extending from the first portion 170, and a generally annular second portion 178 that is coupled to the shaft portion 118. A bearing 182 is pressed into the second portion 178 and pressed over the shaft portion 118 to rotatably couple the piston 166 to the eccentric 106.

The second portion 178 of the piston 166 includes a generally annular end face 186 that faces toward the end opening 126 when the pistons 166 are installed in their respective crankcases 26. The end face 186 defines a pair of alignment apertures in the form of diametrically opposed bores 190. The bores 190 are oriented along a plane P (FIG. 14) that is substantially perpendicular to the longitudinal extent of the elongated connecting portion 174. The bores 190 can be blind bores or can be through bores.

As best shown in FIG. 10, the first portion 170 of the piston 166 includes a top surface 192, a bottom surface 193 opposite the top surface 192, and an outer perimeter defining a shoulder 194 for receiving a sealing member. The sealing member includes a resilient portion 198 having a generally L-shaped cross-section and engaging an inner wall 202 of the cylinder 30, and a substantially rigid ring-like portion 206 that secures the resilient portion 198 against the shoulder 194 of the piston 166. When the piston 166 is installed in the cylinder 30 and the valve body 34 is installed on the cylinder 30, the piston 166 and the valve body 34 cooperate to define a chamber 208 having a volume that changes as the piston 166 moves up and down in the cylinder 30. The first portion 170 also defines a valve opening 210 that extends through the first portion 170 between the top and bottom surfaces 192, 193, and that is located between the center of the first portion 170 (e.g., approximately where the elongated connecting portion 174 connects to the first portion 170) and the shoulder 194.

A first reed valve 214 includes a fixed portion 216 coupled to the center of the first portion 170 by a screw 218, and a moveable portion 222 that overlies the valve opening 210. The first reed valve 214 is flexible such that when the pressure on the bottom surface 193 of the piston 166 is greater than the pressure on the top surface 192 of the piston 166, as occurs, for example, when the piston 166 moves downwardly in the cylinder 30, the first reed valve 214 flexes upwardly such that the moveable portion 222 moves away from the valve opening 210 and the working fluid of the pump is allowed to flow through the valve opening 210. In contrast, when the pressure on the top surface 192 of the piston 166 is greater than the pressure on the bottom surface 193 of the piston 166, as occurs, for example, when the piston 166 moves upwardly in the cylinder 30, the moveable portion 222 is urged against the valve opening 210 and thus prevents the flow of working fluid through the valve opening 210. A small groove 224 is formed in the top surface 192 and extends below the reed valve 214 where the moveable portion 222 meets the fixed portion 216 to relieve bending stresses on the reed valve 214. Although reed valve 214 is shown as controlling the flow of working fluid past the first portion 170 of the piston 166, those skilled in the art will readily appreciate that other valve types can also be used.

FIGS. 15-17 show details of the valve body 34 and valve cover 38. As noted above, the valve body 34 and valve cover 38 are coupled to the cylinder 30 and crankcase 26 by the fasteners 78. More specifically, the valve body 34 includes a pair of diametrically opposed ears 226, and each ear 226 defines a through hole 230 that receives one of the fasteners 78. The valve cover 38 also includes a pair of diametrically opposed ears 234 that also define through holes 238 for receiving the fasteners 78. The fasteners 78 both align the valve body 34 and the valve cover 38 with one another and with the cylinder 30 and secure the valve body 34, the valve cover 38, and the cylinder 30 to the crankcase 26.

The valve body 34 includes an upper flange portion 242 having an outer diameter similar to that of the cylinder 30. A reduced-diameter insert portion 246 extends axially from the flange portion 242 and has an outer diameter sized to snugly fit within the cylinder 30. As best shown in FIG. 17, the insert portion 246 defines a radially-outwardly facing circumferential groove 250 that receives a first sealing O-ring 254. The flange portion 242 defines an axially-facing circumferential groove 258 that receives a second sealing O-ring 262. When the insert portion 246 is inserted into the cylinder 30, the first O-ring 254 is compressed between the groove 250 and the inner wall 202 of the cylinder 30 to provide an air-tight seal between the valve body 34 and the cylinder 30. Similarly, when the valve cover 38 is tightened against the valve body 34, the second O-ring 262 is compressed between the groove 258 and a bottom surface 266 of the valve body 34 (see also FIG. 16) to provide an air-tight seal between the valve body 34 and the valve cover 38.

As best shown in FIGS. 10, 15, and 16, the valve body 34 defines a centrally-located valve opening 270 extending through the valve body 34 from a first side 274 of the valve body 34 that faces the piston 166 to a second side 278 of the valve body 34 that faces the valve cover 38. A second reed valve 282 is coupled to the second side 278 of the valve body 34 and includes a fixed portion 286 coupled to the second side 278 by a screw 290, and a moveable portion 294 that overlies the valve opening 270. The second reed valve 282 is flexible such that when the pressure on the first side 274 of the valve body 34 is greater than the pressure on the second side 278 of the valve body 34, as occurs, for example, when the piston 166 moves upwardly in the cylinder 30, the second reed valve 282 flexes upwardly such that the moveable portion 294 moves away from the valve opening 270 and the working fluid of the pump is allowed to flow through the valve opening 270. In contrast, when the pressure on the second side 278 of the valve body 34 is greater than the pressure on the first side 274 of the valve body 34, as occurs, for example, when the piston 166 moves downwardly in the cylinder 30, the moveable portion 294 is urged against the valve opening 270 and thus prevents the flow of working fluid through the valve opening 270. Although reed valve 282 is shown as controlling the flow of working fluid past the valve body 34, those skilled in the art will readily appreciate that other valve types can also be used.

The valve cover 38 cooperates with the valve body 34 to define a chamber 298. In the illustrated embodiment, the chamber 298 is a pressure chamber that is pressurized during operation of the pump 10 as discussed further below. The valve cover 38 includes a substantially cylindrical outer wall 302 and a flange portion 306 extending radially outwardly from a bottom end of the outer wall 302. The flange portion 306 defines the bottom surface 266 of the valve body that cooperates with the O-ring 262 to provide the seal between the valve cover 38 and the valve body 34. The valve cover 38 also includes a top wall 307 having a plurality of elongated ribs 308 that function as heat sinks to help regulate the temperature of the valve cover 38.

The valve cover 38 also includes a conduit portion 310 that extends across the middle of the valve cover 38, is oriented substantially transversely to the diametrically opposed ears 234, and that substantially bisects the top wall 307. The conduit portion 310 includes an outlet port 314 on one end and a connection port 318 on the other end. Both the outlet port 314 and the connection port 318 are in communication with the chamber 298. The connection port 318 is configured to receive one end of a connection tube 322 that extends between the two valve covers 38. The connection tube 322 includes circumferential grooves 326 at each end, which grooves 326 each receive an O-ring 330 to provide an air tight seal between the valve covers 38 and the connection tube 322. The connection tube 322 affords fluid communication between the chambers 298 of each piston/cylinder assembly 18a, 18b.

In the illustrated embodiment, the outlet port 314 of one of the valve covers 38 is tapped so that a threaded pressure release valve 334 can be inserted therein. The other outlet port 314 is illustrated as having a smooth inner surface for receiving a connector or coupler for attachment to other equipment, but could also be threaded depending upon the specific application.

FIGS. 19-22 illustrate the piston 166 and the eccentric 106 along with an alignment tool 338 that is used during assembly or installation of the eccentric 106 and piston 166 to the drive shaft. As mentioned above, the end of the shaft portion 118 includes an alignment projection 124 that extends outwardly from the shaft portion 118. Also, bores 190 are formed in the annular end face 186 of the piston 166. In the illustrated construction, the alignment projection 124 is substantially rectangular and includes a pair of substantially parallel sides 342. The alignment tool 338 is substantially disk shaped and defines a first mating feature in the form of a substantially rectangular slot or alignment recess 346 that receives the alignment projection 124, and second mating feature in the form of a pair of substantially circular alignment projections or pins 350 that extend into and are received by the bores 190 in the piston 166. As best shown in FIGS. 18 and 20, the alignment recess 346 and pins 350 are substantially co-planar. As such, when the alignment tool 338 is engaged with the assembled piston 166 and eccentric 106, the alignment tool 338 aligns the parallel sides 342 of the alignment projection 124 with the bores 190 such that the plane P extending through the bores 190 is substantially parallel with the sides 342. When the eccentric 106 and piston 166 are located in this predetermined orientation, the piston will be in either a top-dead-center position or a bottom-dead center position. As shown in FIGS. 18 and 19, the eccentric 106 includes a set screw 354 that extends into the bore 110 so that when the set screw 354 is loosened the eccentric 106 can be rotated with respect to the first or second end 90, 94 of the drive shaft and when the set screw 354 is tightened the eccentric 106 is fixed for rotation with the first or second end 90, 94 of the drive shaft. As understood by those skilled in the art, the top-dead-center position and the bottom-dead-center positions are the two positions in which the longitudinal extent of the piston 166 is aligned with a plane defined by the drive axis 98 and the eccentric axis 122. During operation of the pump, the top-dead-center position and the bottom-dead-center position represent the moment in time when the piston 166 reverses its direction of movement in the cylinder.

During installation of the pistons 166 for manufacturing or repair of the pump 10, two alignment tools 338 are used to position one of the pistons 166 in the top-dead-center position and the other of the pistons 166 in the bottom-dead-center position. For example, as shown in FIG. 11, the piston 166 on the right in the piston/cylinder assembly 18a is in the bottom-dead-center position and the piston 166 on the left in the piston/cylinder assembly 18b is in the top-dead-center position. Although the steps can be performed in various sequences, in one exemplary method of assembly, a first piston 166 and its bearing 182 are installed onto the shaft portion 118 of a first eccentric 106, and a second piston 166 and its bearing 182 are installed onto the shaft portion 118 of a second eccentric. A first alignment tool 338 is then engaged with the first eccentric 106 and the first piston 166 to hold the first piston 166 in one of the top-dead-center position or the bottom-dead-center position. A second alignment tool 338 is then engaged with the second eccentric 106 and the second piston 166 to hold the second piston 166 in the other of the top-dead-center position and the bottom-dead-center position.

Each eccentric 106, piston 166, and alignment tool 338 combination can then be inserted into the crankcase 24 through the opening defined by a respective one of the cylinder supports 66. During this process the alignment tools 338 maintain the pistons 166 in the top-dead-center or bottom-dead-center orientation with respect to the eccentrics 106. The bore 110 of each eccentric 106 is positioned over the respective first or second end 90, 94 of the drive shaft and the respective set screws 354 are tightened so that each eccentric 106 is coupled for rotation with the drive shaft about the drive axis 98. As shown in FIG. 3, the crankcase ports 62 are positioned to afford access to the set screws 354 for tightening and loosening with an appropriate tool. Once the set screws 354 have been tightened, the alignment tools 338 can be disengaged from the eccentric 106 and the piston 166 and extracted from the crankcase 26 through the end openings 126.

In some situations, such as for adjustment when the eccentrics 106 are already positioned on the ends 90, 94 of the drive shaft, the set screws 354 can be kept loose or loosened and the alignment tools 338 can be inserted into the crankcase through the end openings 126. The eccentrics 106 can then be rotated with respect to the drive shaft and the alignment tools 338 engaged with the respective eccentric 106 and piston 166 to orient one of the pistons in the top-dead-center position and the other piston 166 in the bottom-dead-center position. Then, while the alignment tools 338 maintain the proper orientation of the pistons 166, the set screws 354 can be tightened such that the eccentrics 106 are coupled for rotation with the drive shaft.

It should be appreciated that the present invention is not necessarily limited to the specific configuration and relative placement of the alignment projection 124 and the bores 190 illustrated in the drawings. For example, instead of the alignment projection 124 the alignment feature of the eccentric 106 could be defined by a recess formed in the shaft portion 118, in which case the alignment tool 338 would include a suitable projection. The configuration of the bores 190 and the pins 350 could similarly be reversed such that the piston 166 includes a pair of pins or other protrusions and the alignment tool 338 includes a pair of bores or openings. Moreover, the piston 166 could include only one projection, only one recess, or even one projection and one recess. The specific shapes of the alignment features can also vary. For example, if the alignment feature on the shaft portion 118 is substantially centered on the eccentric axis 122, the alignment feature could be substantially any non-circular or polygon shape, such as a square, star, cross, oval, pentagon, triangle, teardrop, or star, without limitation. The alignment feature on the shaft portion 118 could also be offset with respect to the eccentric axis 122, in which case a circular or non-circular shape would be suitable and capable of orienting the eccentric 106 and the piston 166 relative to one another. The bores 190 and pins 350 could similarly be formed of any variety of shapes, provided that the combination chosen is sufficient to locate the pistons 166 in one of the top-dead-center and bottom-dead-center locations.

By way of example only, FIGS. 22 and 23 illustrate an alternative embodiment in which the second alignment features or bores 190 have been positioned differently on the piston 166. In FIGS. 22 and 23, the bores 190 are again located on the end face 186 of the piston 190, but it should be appreciated that the bores 190 or any other alignment features could also be located on the connecting portion 174. As before, a plane P extends through the bores 190 and provides a reference for determining the predetermined orientation of the bores 190 relative to the first alignment feature or projection 124 of the eccentric 106. In the example of FIGS. 22 and 23, the predetermined orientation for locating the piston 190 in either the top-dead-center or bottom-dead-center location involves locating projection 124 at a predetermined angle with respect to the plane P. More specifically, at least one of the sides 342 of the projection 124 is oriented at a predetermined angle with respect to the plane P. As best shown in FIG. 22, the alignment tool 338 is also configured differently in a manner corresponding to the different configuration of the bores 190. More specifically, the pins or projections 350 on the alignment tool 338 are reoriented such that when the pins 350 are inserted into the bores 190 and recess 346 receives the projection 124, the piston 166 is properly located in either the top-dead-center or the bottom-dead-center location.

FIG. 24 illustrates a port insert in the form of a plug 358 that can be used for obstructing any of the crankcase ports 62, outlet ports 314, or connection ports 318 to configure the pump in a particular way. In FIG. 22 the plug 358 is shown obstructing one of the crankcase ports 62. The plug 358 is generally cylindrical and includes a body 362 having a reduced-diameter inner end 366 that is received within the port 62 and an enlarged-diameter outer end 370 that abuts a shoulder 374 defined by the crankcase port 62. The inner end defines an inner circumferential groove 378 that receives a single sealing O-ring 382. When the plug 358 is inserted into the port 62, the O-ring is compressed between the circumferential groove 378 and the port 62 to provide the seal. An outer circumferential groove 386 is formed between the inner end 366 and the outer end 370 and partially defines a substantially annular and inwardly-facing engagement surface 390 that abuts the shoulder 374. Although the illustrated port insert is the plug 358, similarly configured port inserts can also be provided for coupling external fluid lines to the pump 10. By way of example only, a wide variety of port inserts having, among other things, threaded extension, barbed connection, 90-degree or −45 degree elbows, and the like can be provided for connecting the pump 10 to external equipment.

With reference primarily to FIGS. 9-11, in operation, the illustrated pump 10 is configured to draw working fluid into the crankcases 26 by way of the crankcase ports 62 and compress the working fluid in the chambers 208, thereby forcing working fluid into the chambers 298 and providing a high-pressure output of working fluid at the outlet port 314. Referring to the piston/cylinder assembly 18b, and starting with the piston 166 in the top-dead-center position (as illustrated), when the motor assembly 14 operates and rotates the stator 86, the first end 90 of the drive shaft rotates the eccentric 106 about the drive axis 98. As the eccentric 106 rotates about the drive axis 98, the piston 166 begins moving downwardly within the cylinder 30. As the piston 166 moves downwardly the volume of the chamber 208 begins to increase, creating a net negative pressure within the chamber 208.

At the second reed valve 282, the negative pressure within the chamber 208 draws the flexible portion 294 tightly against the second side 278 of the valve body 34, thereby blocking flow through the valve opening 270. Substantially simultaneously, the negative pressure within the chamber 208 opens the first reed valve 214 by bending the flexible portion 222 of the first reed valve 214 away from the top surface 192 of the sealing portion 170 of the piston 166, thereby allowing working fluid to flow into the chamber 208 by way of the valve opening 210. Flow of working fluid through the valve opening 210 and into the chamber 208 generally continues until the piston 166 reaches the bottom-dead-center position, at which point the piston 166 reverses direction and begins moving upwardly in the cylinder 30.

As the piston 166 rises in the cylinder, the pressure in the chamber 208 begins to increase. As a result, the flexible portion 222 of the first reed valve 214 is pressed against the top surface 192 of the piston, thus closing the first reed valve 214 and preventing fluid flow through the valve opening 210. Substantially simultaneously, the increasing pressure in the chamber 208 bends the flexible portion 294 of the second reed valve 282 away from the second side 278 of the valve body 34, thus opening the second reed valve 282 and allowing pressurized working fluid to flow into the chamber 298 through the valve opening 270. Eventually the piston 166 reaches top-dead-center again and the cycle repeats. While this is going on, the same cycle occurs with the piston 166 of the piston/cylinder assembly 18a, however when the piston 166 of the piston/cylinder assembly 18b is moving upwardly in the cylinder 30, the piston 166 of the piston/cylinder assembly 18a is moving downwardly in the cylinder 30.

As previously mentioned, the pistons 166 of the piston/cylinder assemblies 18a, 18b are arranged such that when one is in the top-dead-center position the other is in the bottom-dead-center position. As a result, except for the very brief moments when both pistons 166 are at either top-dead-center or bottom-dead-center and are thus stationary in their respective cylinders 30, there is always one cylinder forcing working fluid into the chamber 298 to maintain a more consistent pressure output.

In the illustrated embodiment, the pressurized working fluid is discharged by way of the outlet port 314 in the piston/cylinder assembly 18a. The pressure release valve 334 in the outlet port 314 of the piston/cylinder assembly 18b prevents excessive pressure from building up within the chambers 298. The connecting tube 322 allows pressurized working fluid to flow from the chamber 298 of the piston/cylinder assembly 18b to the chamber 298 of the piston/cylinder assembly 18a.

Various features of the invention are set forth in the following claims.

Claims

1. A pump comprising:

a drive assembly including a drive shaft rotatable about a drive axis;

an eccentric coupled to the drive shaft for rotation therewith, the eccentric including a shaft portion defining an eccentric axis, the eccentric axis offset from the drive axis, the shaft portion including a shaft end defining a first alignment feature;

a piston rotatably coupled to the shaft portion, the piston defining a second alignment feature; and

a cylinder reciprocatingly receiving the piston, wherein positioning the first alignment feature in a predetermined orientation with respect to the second alignment feature locates the piston in one of a top-dead-center position and a bottom-dead-center position with respect to the cylinder.

2. The pump of claim 1, wherein the first alignment feature includes at least one of a projection extending from the shaft end and a recess formed in the shaft end.

3. The pump of claim 1, wherein the second alignment feature includes two alignment features and a plane extending through the two alignment features of the second alignment feature.

4. The pump of claim 3, wherein the first alignment feature includes at least one side, and wherein the predetermined orientation includes wherein the plane is substantially parallel with the at least one side.

5. The pump of claim 3, wherein the predetermined orientation includes wherein the plane extends through the first alignment feature.

6. The pump of claim 3, wherein the first alignment feature includes at least one side, and wherein the predetermined orientation includes wherein the plane is oriented at a predetermined angle with respect to the side.

7. The pump of claim 1, wherein the second alignment feature includes at least one of an opening and a projection.

8. The pump of claim 1, wherein the first alignment feature is a projection extending from the shaft end and including two parallel sides, wherein the second alignment feature is a pair of diametrically opposed openings formed in an end face of the piston and a plane extending through the diametrically opposed openings, and wherein when the plane is substantially parallel to the two parallel sides, the piston is in one of the top-dead-center position and the bottom-dead center position with respect to the cylinder.

9. The pump of claim 8, wherein the projection is substantially rectangular and wherein the openings are substantially circular.

10. The pump of claim 1, wherein the drive shaft includes a first end to which the eccentric is coupled, and a second end opposite the first end, the pump further comprising:

a second eccentric coupled to the second end for rotation therewith, the second eccentric including a second shaft portion defining a second eccentric axis, the second eccentric axis offset from the drive axis, the second shaft portion including a second shaft end defining a third alignment feature;

a second piston rotatably coupled to the second shaft portion, the second piston defining a fourth alignment feature; and

a second cylinder reciprocatingly receiving the second piston, wherein positioning the third alignment feature in the predetermined orientation with respect to the fourth alignment feature locates the second piston in one of a top-dead-center position and a bottom-dead-center position with respect to the second cylinder.

11. The pump of claim 10, wherein when the piston is in the top-dead-center position with respect to the cylinder, the second piston is in the bottom-dead-center position with respect to the second cylinder.

12. The pump of claim 1, wherein the first alignment feature is non-circular.

13. The pump of claim 12, wherein the first alignment feature has a shape including one of a cross, oval, rectangle, polygon, triangle, teardrop, and star.

14. The pump of claim 1, wherein the first alignment feature is circular and is offset from the eccentric axis.

15. A method for orienting a first piston and a second piston in a dual piston pump, the pump including a drive shaft having opposite ends, a first eccentric on one end of the drive shaft, and a second eccentric on an opposite end of the drive shaft, the first eccentric including a shaft portion having a first alignment feature, the first piston having a second alignment feature, the second eccentric including a shaft portion having a third alignment feature, and the second piston having a fourth alignment feature, the method comprising:

mounting the first piston on the shaft portion of the first eccentric;

rotating the first eccentric to position the first alignment feature in a first predetermined orientation with respect to the second alignment feature, thereby locating the first piston in one of a top-dead-center position and a bottom-dead-center position;

mounting the second piston on the shaft portion of the second eccentric;

rotating the second eccentric to position the third alignment feature in a second predetermined orientation with respect to the fourth alignment feature, thereby locating the second piston in the other of the top-dead-center position and the bottom-dead-center position;

securing the first eccentric to the one end of the drive shaft to prevent relative rotation between the first eccentric and the drive shaft; and

securing the second eccentric to the opposite end of the drive shaft to prevent relative rotation between the second eccentric and the drive shaft.

16. The method of claim 15, wherein rotating the first eccentric to position the first alignment feature in the first predetermined orientation includes engaging a first alignment tool with the first alignment feature and the second alignment feature.

17. The method of claim 16, wherein the first alignment tool includes a first mating feature for mating with the first alignment feature, and a second mating feature for mating with the second alignment feature, and wherein engaging the first alignment tool includes mating the first mating feature with the first alignment feature and mating the second mating feature with the second alignment feature.

18. The method of claim 16, wherein rotating the second eccentric to position the third alignment feature in the second predetermined orientation includes engaging a second alignment tool with the third alignment feature and the fourth alignment feature.

19. The method of claim 15, wherein the second alignment feature includes two alignment features and a plane extending through the two alignment features of the second alignment feature, and wherein rotating the first eccentric to position the first alignment feature in the predetermined orientation with respect to the second alignment feature includes positioning the first alignment feature such that the plane extends through the first alignment feature.

20. The method of claim 15, wherein the first alignment feature includes at least one side, wherein the second alignment feature includes two alignment features and a plane extending through the two alignment features of the second alignment feature, and wherein rotating the first eccentric to position the first alignment feature in the predetermined orientation with respect to the second alignment feature includes orienting the side to be substantially parallel to the plane.

21. The method of claim 15, wherein the first alignment feature includes at least one side, wherein the second alignment feature includes two alignment features and a plane extending through the two alignment features of the second alignment feature, and wherein rotating the first eccentric to position the first alignment feature in the predetermined orientation with respect to the second alignment feature includes orienting the side at a predetermined angle with respect to the plane.

22. A pump comprising:

a motor including a motor housing having a first end and a second end;

a first crankcase coupled to the first end;

a second crankcase coupled to the second end;

a first cylinder coupled to the first crankcase;

a second cylinder coupled to the second crankcase;

a first valve body coupled to the first cylinder;

a second valve body formed separately from the first valve body and coupled to the second cylinder;

a first valve cover coupled to the first valve body;

a second valve cover formed separately from the first valve cover and coupled to the second valve body; and

a connecting tube formed separately from the first valve cover and the second valve cover and providing fluid communication between the first valve cover and the second valve cover.

23. The pump of claim 22, wherein the motor includes a motor housing, a stator within the motor housing, and a rotor rotatably received within the stator, the rotor including a drive shaft having a first end extending into the first crankcase and a second end extending into the second crankcase, the drive shaft defining a drive axis.

24. The pump of claim 22, further comprising a first eccentric coupled to the first end and a second eccentric coupled to the second end, each eccentric including a shaft portion defining an eccentric axis offset from the drive axis, and a counterweight portion positioned opposite the shaft portion with respect to the drive axis.

25. The pump of claim 24, wherein the shaft portion of each eccentric includes a first alignment feature.

26. The pump of claim 25, further comprising a first piston received by the first cylinder and rotatably coupled to the shaft portion of the first eccentric, and a second piston received by the second cylinder and rotatably coupled to the shaft portion of the second eccentric, each of the first piston and the second piston including a second alignment feature.

27. The pump of claim 26, wherein when the first alignment feature of the first eccentric is in a predetermined orientation with respect to the second alignment feature of the first piston, the first piston is in one of a top-dead-center position and a bottom-dead-center position, and the second piston is in the other of the top-dead-center position and the bottom-dead-center position.

28. The pump of claim 27, wherein when the first alignment feature of the first eccentric is in the predetermined orientation with respect to the second alignment feature of the first piston, the first alignment feature of the second eccentric is in substantially the same predetermined orientation with respect to the second alignment feature of the second piston.