CA2818509A1

CA2818509A1 - Piston machine apparatus, and method of varying a volume of a chamber of the apparatus

Info

Publication number: CA2818509A1
Application number: CA2818509A
Authority: CA
Inventors: Alexander Korolev
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-06-14
Filing date: 2013-06-14
Publication date: 2014-12-14
Also published as: CA2913374A1; US20160123148A1; WO2014197971A1

Abstract

A method of varying a volume of a chamber defined by a first rotor, a second rotor, and a piston in a housing of a piston machine apparatus involves: causing the first rotor to rotate around a first axis of rotation; causing the second rotor to rotate around a second axis of rotation different from the first axis of rotation; and causing the piston to slide, in response to rotation of the second rotor around the second axis of rotation, along a first linear path relative to a first coupling portion of the first rotor coupled to the piston. Causing the second rotor to rotate around the second axis of rotation involves causing a second coupling portion of the second rotor coupled to the piston to revolve around the second axis of rotation in a path around the first coupling portion. Piston machine apparatuses and uses thereof are also disclosed.

Description

PISTON MACHINE APPARATUS, AND
METHOD OF VARYING A VOLUME OF A CHAMBER OF THE APPARATUS
FIELD
This disclosure relates generally to a piston machine apparatus, and to a method of varying a volume of a chamber of the apparatus.
RELATED ART
One known machine includes a disc mounted on a main shaft of the machine, an eccentrically mounted drum, and a curved flap hinged to the disc and to the drum. An entry port is almost tangential to a circumference of the drum, and fluid from the entry port can impinge on, and press, the flap to cause rotation of the disc and of the drum, and thus of the main shaft. As the disc and the drum rotate, the flap moves towards a recess defined by the drum, and then to a position in front of the entry port, whereby a cycle of operations is repeated. As such, the machine can function as a turbine, a pump, or the like. However, because the flap is hinged to the disc and to the drum and pivots relative to the drum towards and away from the recess defined by the drum, the drum rotates at uneven angular speed, rotating relatively fast as the flap moves towards the recess defined by the drum and relatively slowly as the flap moves away from the recess defined by the drum. Such repeated increase and decrease in angular speed of the drum can disadvantageously cause instability and wear in such a machine.
SUMMARY
According to one illustrative embodiment, there is provided a method of varying a volume of a chamber defined by a first rotor, a second rotor, and a piston in a housing of a piston machine apparatus. The method involves: causing the first rotor to rotate around a first axis of rotation; causing the second rotor to rotate around a second axis of rotation different from the first axis of rotation; and causing the piston to slide, in

- 2 -response to rotation of the second rotor around the second axis of rotation, along a first linear path relative to a first coupling portion of the first rotor coupled to the piston. Causing the second rotor to rotate around the second axis of rotation involves causing a second coupling portion of the second rotor coupled to the piston to revolve around the second axis of rotation in a path around the first coupling portion.
Causing the piston to slide along the first linear path may involve maintaining a relative orientation of the piston relative to the first rotor.
The first linear path may extend generally parallel to a plane of rotation of the first rotor and at an acute angle to a radius perpendicular to the first axis of rotation.
The method may further involve causing the piston to slide along a second linear path relative to the second coupling portion in response to rotation of the first rotor around the first axis of rotation and in response to rotation of the second rotor around the second axis of rotation.
The second linear path may extend generally parallel to a plane of rotation of the second rotor and generally perpendicular to a radius perpendicular to the second axis of rotation.
Causing the piston to slide along the first linear path may involve varying a separation distance between the second path and the first axis of rotation.
Varying the volume of the chamber may involve expanding the chamber when the chamber is in fluid communication with a fluid inlet defined by the housing of the piston machine.
Expanding the chamber may involve revolving the second coupling portion away from the inlet along the path around the first coupling portion.
The method may further involve controlling fluid flow through the fluid inlet in response to rotation of the first rotor around the first axis of rotation.

- 3 -The method may further involve controlling fluid flow through the fluid inlet in response to rotation of the second rotor around the second axis of rotation.
Varying the volume of the chamber may involve contracting the chamber when the chamber is in fluid communication with a fluid outlet defined by the housing of the piston machine.
Contracting the chamber may involve revolving the second coupling portion towards the outlet along the path around the first coupling portion.
The method may further involve controlling fluid flow through the fluid outlet in response to rotation of the first rotor around the first axis of rotation.
The method may further involve controlling fluid flow through the fluid outlet in response to rotation of the second rotor around the second axis of rotation.
According to another illustrative embodiment, there is provided a piston machine apparatus. The apparatus includes: a housing defining a fluid inlet and a fluid outlet; a piston in the housing; a first rotor including a first coupling portion coupled to the piston, the first rotor rotatable in the housing around a first axis of rotation; and a second rotor including a second coupling portion coupled to the piston, the second rotor rotatable in the housing around a second axis of rotation different from the first axis of rotation. The second coupling portion has a position that revolves around the second axis of rotation in a path around the first coupling portion in response to rotation of the second rotor around the second axis of rotation. The piston is slidable along a first linear path relative to the first coupling portion in response to rotation of the second rotor around the second axis of rotation. The first rotor, the second rotor, and the piston are positionable to define a first chamber, in fluid communication with the fluid inlet, that expands in volume in response to revolving the second coupling portion in the path around the first coupling portion and away from the fluid inlet. The first rotor, the second rotor, and the piston are also positionable to define a second chamber, different from the first chamber and in fluid communication with the fluid

- 4 -outlet, that contracts in volume in response to revolving the second coupling portion in the path around the first coupling portion and towards the fluid outlet.
The piston and the first coupling portion may maintain a relative orientation of the piston relative to the first rotor when the piston slides along the first linear path relative to the first coupling portion in response to rotation of the second rotor around the second axis of rotation.
The first linear path may extend generally parallel to a plane of rotation of the first rotor and at an acute angle to a radius perpendicular to the first axis of rotation.
The piston may be slidable along a second linear path relative to the second coupling portion in response to rotation of the first rotor around the first axis of rotation and in response to rotation of the second rotor around the second axis of rotation.
The second linear path may extend generally parallel to a plane of rotation of the second rotor and generally perpendicular to a radius perpendicular to the second axis of rotation.
Rotation of the first rotor around the first axis of rotation and rotation of the second rotor around the second axis of rotation may vary a separation distance between the second linear path and the first axis of rotation, and may cause the piston to slide along the first linear path.
The piston may include first and second opposite and non-parallel side edges.
The piston may be coupled to the first coupling portion such that the first side edge is slidable along the first linear path, and the piston may be coupled to the second coupling portion such that the second side edge is slidable along the second linear path.
The housing may define a generally annular inner surface.

- 5 -The first rotor may include a curved outer surface positioned to slide, in response to rotation of the first rotor around the first axis of rotation, along a first portion of the generally annular inner surface of the housing between the fluid inlet and the fluid outlet.
The second rotor may include a curved outer surface proximate the second coupling portion and positioned to slide, in response to rotation of the second rotor around the second axis of rotation, along a second portion of the generally annular inner surface of the housing.
The first rotor may define a recess sized to receive at least a portion of the piston.
The first rotor may define a recess having a position that controls fluid flow through the fluid inlet in response to rotation of the first rotor around the first axis of rotation.
The first rotor may define a recess having a position that controls fluid flow through the fluid outlet in response to rotation of the first rotor around the first axis of rotation.
The second rotor may define a recess having a position that controls fluid flow through the fluid inlet in response to rotation of the second rotor around the second axis of rotation.
=
The second rotor may define a recess having a position that controls fluid flow through the fluid outlet in response to rotation of the second rotor around the second axis of rotation.
According to another illustrative embodiment, there is provided use of the apparatus to pump a fluid.
Other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of illustrative embodiments in conjunction with the accompanying figures.

- 6 -BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an exploded perspective view of a piston machine apparatus according to an illustrative embodiment;
Figure 2 is a perspective view of a first end body of the apparatus of Figure 1;
Figure 3 is a perspective view of a first rotor of the apparatus of Figure 1;
Figure 4 is a plan view of the first rotor of the apparatus of Figure 1;
Figure 5 is a perspective view of an intermediate body of the apparatus of Figure 1;
Figure 6 is a first perspective view of a piston of the apparatus of Figure 1;
Figure 7 is a second perspective view of the piston of Figure 6;
Figure 8 is a plan view of a second rotor of the apparatus of Figure 1;
Figure 9 is a perspective view of the second rotor of the apparatus of Figure 1;
Figure 10 is an assembled perspective view of the apparatus of Figure 1;
Figure 11 is a cross-sectional view of the apparatus of Figure 1, taken along the lines XI-XI in Figures 10 and 12;
Figure 12 is a cross-sectional view of the apparatus of Figure 1, taken along the line XII-XII in Figure 10;
Figure 13 is a cross-sectional view of the apparatus of Figure 1, showing rotation of the first and second rotors relative to the positions shown in Figure 12;
Figure 14 is a cross-sectional view of the apparatus of Figure 1, showing further rotation of the first and second rotors relative to the positions shown in Figure 12;

- 7 -Figure 15 is a cross-sectional view of the apparatus of Figure 1, showing further rotation of the first and second rotors relative to the positions shown in Figure 12;
Figure 16 is an exploded perspective view of a piston machine apparatus according to another illustrative embodiment;
Figure 17 is a first perspective view of a piston of the apparatus of Figure 16;
Figure 18 is a second perspective view of the piston of Figure 17;
Figure 19 is a cross-sectional view of a first rotor of the apparatus of Figure 16, taken along the line XIX-XIX in Figure 16;
Figure 20 is a cross-sectional view of a second rotor of the apparatus of Figure 16, taken along the line XX-XX in Figure 16;
Figure 21 is an exploded perspective view of a piston machine apparatus according to another illustrative embodiment;
Figure 22 is a perspective view of a piston and of a first rotor of the apparatus of Figure 21;
Figure 23 is a perspective view of the piston and of a second rotor of the apparatus of Figure 21;
Figure 24 is a first exploded perspective view of a piston machine apparatus according to another illustrative embodiment;
Figure 25 is a second exploded perspective view of the apparatus of Figure 24;
Figure 26 is a first exploded perspective view of a piston machine apparatus according to another illustrative embodiment;

- 8 -Figure 27 is a second exploded perspective view of the apparatus of Figure 26;
Figure 28 is an exploded perspective view of a piston machine apparatus according to another illustrative embodiment;
Figure 29 is an assembled perspective view of the apparatus of Figure 28;
Figure 30 is a cross-sectional view of the apparatus of Figure 28, taken along the line XXX-XXX in Figure 28;
Figure 31 is an exploded perspective view of a piston machine apparatus according to another illustrative embodiment;
Figure 32 is an assembled perspective view of the apparatus of Figure 31;
Figure 33 is a cross-sectional view of the apparatus of Figure 31, taken along the line XXXIII-XXXIII in Figure 31;
Figure 34 is an exploded perspective view of a piston machine apparatus according to another illustrative embodiment;
Figure 35 is an assembled perspective view of the apparatus of Figure 34; and Figure 36 is a cross-sectional view of the apparatus of Figure 34, taken along the line XXXVI-XXXVI in Figure 34.
DETAILED DESCRIPTION
Referring to Figure 1, a piston machine apparatus according to an illustrative embodiment is shown generally at 100 and includes a first end body 102, a first rotor 104, an intermediate body 106, a piston 108, a second rotor 110, and a second end body 112.

- 9 -Referring to Figures 1 and 2, the first end body 102 is generally cylindrical and has an outer side shown generally at 114 and an inner side shown generally at 116 and opposite the outer side 114. In this context, "generally cylindrical" refers to a body that includes some surfaces of a cylinder but that may vary from a perfect cylinder as described below or for other reasons that permit functions substantially similar to those described below. More generally, "generally" herein contemplates variations that may or may not be described herein and that permit functions substantially similar to those described herein. On the outer side 114, the first end body 102 has a generally circular outer surface 118, and on the inner side 116, the first end body 102 has a generally circular inner surface 120. Through-openings shown generally at 122 and 124 extend between the surface 118 and the surface 120 of the first end body 102. Further, the surface 120 defines a generally cylindrical recess shown generally at 126 and defined by a generally circular recessed surface 128 and a generally annular surface 130 surrounding and extending away from the surface 128. The surface 128 is recessed by an axial height 132 of the surface 130. As shown in Figure 2, a portion of the through-opening 122 extends through the surface 128, and the through-opening 122 extends across the surface 130. Otherwise, the through-opening 124, the surface 128, and the surface 130 are generally rotationally symmetric around an axis 134 of the first end body 102, and more particularly, the through-opening 124 extends by a radius 136 from the axis 134, the surface 128 extends by a radius from the axis 134, and the surface 130 is spaced apart from the axis 134 by the radius 138.
Referring to Figures 1, 3, and 4, the first rotor 104 is generally cylindrical and has an outer side shown generally at 140 and an inner side shown generally at 142 and opposite the outer side 140. On the outer side 140, the first rotor 104 has a generally circular outer surface 144, and the first rotor 104 defines a generally cylindrical projection 146 projecting away from the surface 144. The surface 144 extends by a radius 148 from an axis 150 of the first rotor 104, and the projection 146 extends by a radius 152 from the axis 150. On the inner side 142, the first rotor 104 has a raised

- 10 -surface 154 and a recessed surface 156. The surface 154 and the surface 156 are generally parallel to and spaced apart from the surface 144, and a curved outer surface 157 extends around the first rotor 104 between the surface 144 and the surfaces 154 and 156. Further, the surface 154 is spaced apart from the surface 144 by an axial thickness 158, and the surface 156 is spaced apart from the surface 144 by an axial thickness 160. Accordingly, the surface 154 is spaced apart from the surface 156 by an axial thickness 162, which is a difference between the thickness 158 and the thickness 160. On the inner side 142, the first rotor 104 also has axial surfaces 164, 166, 168, and 170 extending generally parallel to the axis 150 and generally perpendicular to the surfaces 154 and 156. The surface 156 and the surfaces 164, 166, 168, and 170 define a recess shown generally at 172 in the first rotor 104. Further, in the recess 172, the first rotor 104 defines a groove shown generally at 174 in the surface 156. The groove 174 extends generally parallel to the surface 170 and at an acute angle 176 to the radius 148.
Referring back to Figures 1 and 2, the radius 136 is approximately equal to the radius 152, the radius 138 is approximately equal to the radius 148, and the height 132 is approximately equal to the thickness 160. In this context, "approximately equal" refers either to precisely equal or to sufficiently equal to permit functions substantially similar to those described below. More generally, "approximately" herein contemplates variations that permit functions substantially similar to those described herein.
Accordingly, a disc portion 178 of the first rotor 104, namely the portion of the first rotor 104 that extends by the thickness 160 from the surface 144, may be received in the recess 126. When the disc portion 178 is received in the recess 126, the surface 144 contacts the surface 128, the axes 134 and 150 are generally collinear, a portion of the surface 157 contacts the surface 130, the projection 146 is received in the through-opening 124 and is accessible from the outer side 114 of the first end body 102, and the surfaces 120 and 156 (shown in Figures 3 and 4) are generally coplanar.

- 11 -Referring to Figures 1 and 5, the intermediate body 106 is generally annular and has a first side shown generally at 180 and a second side shown generally at 182 and opposite the first side 180. The intermediate body 106 also has a first generally annular surface 184 on the first side 180, a second generally annular surface 186 on the second side 182, and a generally annular inner surface 188 extending between the surfaces 184 and 186. The surface 188 defines a first recess shown generally at 190 and extending between the surfaces 184 and 186, and a second recess shown generally at 192 and extending between the surfaces 184 and 186. In various embodiments, the surface 120 (shown in Figure 2) may be attached to the surface 184 by one or more fasteners (such as bolts, screws, or rivets, for example), by complementary threads (not shown) on the surfaces 120 and 184, by welding, by soldering, or by adhesive, for example, and the first recess 190 is positioned to be in fluid communication with the through-opening 122 when the surface 120 is attached to the surface 184.
The first and second recesses 190 and 192 divide the surface 188 into a first curved portion 194 and a second curved portion 196. The first curved portion 194 extends along an arc of a circle 198 extending by a radius 200 around an axis 202, and the second curved portion 196 extends along an arc of a circle 204 extending by a radius 206 around an axis 208. The radius 200 is smaller than the radius 206, and the axis 202 is generally parallel to but spaced apart (or different) from the axis 208. Further, the axis 202 extends between the axis 208 and the first curved portion 194.
Consequently, the first recess 190 is not opposite the second recess 192, and an arc length 210 of the first curved portion 194 is less than an arc length 212 of the second curved portion 196. Further, the radius 200 is approximately equal to the radius 148, so when a portion of the surface 157 is positioned against the first curved portion 194, the axes 150 and 202 are generally collinear, the portion of the surface 157 closely contacts at least portion of the first curved portion 194, and portions of the surface 157 slide along the first curved portion 194 along the arc length 210 in response to rotation of the first rotor 104 around the axis 150.

- 12 -Referring to Figures 6 and 7, the piston 108 has a first generally planar surface 214 and a second generally planar surface 216 opposite and generally parallel to the first surface 214. The piston 108 also has side surfaces 218, 220, 222, 224, and 226 extending between the first and second surfaces 214 and 216. The piston 108 defines a first elongate projection 228 extending away from the first surface 214 and along the surface 218, and a second elongate projection 230 extending away from the second surface 216 and along the surface 224. The surfaces 218 and 224 extend non-parallel to each other, so the first and second projections 228 and 230 also extend along directions non-parallel to each other. Other than the first and second projections 228 and 230, the piston 108 has an axial thickness 232 that is approximately equal to the thickness 162 shown in Figures 1 and 3, and the surfaces 218, 220, and 222 are sized to abut the surfaces 166, 168, and 170 (shown in Figures 3 and 4) respectively when a portion of the piston 108 including the surfaces 218, 220, and 222 is received in the recess 172 (shown in Figures 1, 3, and 4). The recess 172 is thus sized to receive such a portion of the piston 108.
Referring to Figures 1, 3, 4, and 6, the first projection 228 is sized to be received in the groove 174 (shown in Figures 3 and 4) so that when the first projection 228 is received in the groove 174, the piston 108 can slide relative to the first rotor 104 in a first linear path defined by the groove 174, namely in a direction generally parallel to the surface 170 and generally parallel to a plane of rotation of the first rotor 104.
Accordingly, the piston 108 may be coupled to the first rotor 104 at the groove 174, so the portion of the first rotor 104 defining the groove 174 is a first coupling portion of the first rotor 104 and the piston 108 can slide along the first linear path relative to the first coupling portion.
Further, the first projection 228 is longer than a width of the groove 174, so when the first projection 228 is positioned in the groove 174, the first projection 228 and the groove 174 cooperate to prevent rotation of the piston 108 relative to the first rotor 104. In other words, the first projection 228 and the groove 174 permit the piston 108 to slide relative to the first rotor 104 and maintain a relative orientation of the piston

- 13 -108 relative to the first rotor 104 by maintaining the surface 218 generally parallel to the surface 170. Herein, expressions such as "prevent rotation" and "maintain a relative orientation" may refer to maintaining a precise relative orientation, or to permitting some changes to the relative orientation (for example, due to differences between a thickness of the first projection 228 and a width of the groove 174, or to curves in the groove 174) while maintaining functions substantially similar to those described herein. Further, the groove 174 and the first projection 228 are positioned such that when the first projection 228 is received in the groove 174, the surface 218 is held against the surface 170.
Referring to Figures 1, 8, and 9, the second rotor 110 includes a generally cylindrical portion 234 having an axial thickness 235 and extending by a radius 236 from an axis 238, except for a recess shown generally at 239 at a periphery of the generally cylindrical portion 234. The second rotor 110 has a first side shown generally at 240 and a second side shown generally at 242 and opposite the first side 240, and the second rotor 110 defines a projection 244 on the first side 240 projecting away from the generally cylindrical portion 234. The projection 244 also has a curved outer surface 246 facing away from the axis 238 and extending away from the generally cylindrical portion 234 at a radius 248 from the axis 238. The radius 248 is less than the radius 236. The projection 244 has a generally planar axial surface 250 facing towards the axis 238 and extending away from the generally cylindrical portion generally perpendicular to the radius 248. Further, on the first side 240, the second rotor 110 defines a groove shown generally at 252, which extends generally parallel to the surface 250 and generally perpendicular to the radius 248. On the second side 242, the second rotor 110 defines a generally cylindrical projection 254 projecting away from the generally cylindrical portion 234 and extending by a radius 256 from the axis 238.
Referring to Figures 1 and 7 to 9, the second projection 230 is sized to be received in the groove 252 so that the piston 108 can slide relative to the second rotor 110 along a second linear path defined by the groove 252, namely in a direction generally

- 14 -parallel to the surface 250 (and thus generally perpendicular to a radius of the second rotor 110) and generally parallel to a plane of rotation of the second rotor 110 when the second projection 230 is received in the groove 252. Further, the second projection 230 is longer than a width of the groove 252, so when the second projection 230 is positioned in the groove 252, the second projection 230 and the groove 252 cooperate to prevent rotation of the piston 108 relative to the second rotor 110. In other words, the second projection 230 and the groove 252 permit the piston 108 to slide relative to the second rotor 110 and maintain a relative orientation of the piston 108 relative to the second rotor 110 by maintaining the surface 224 generally parallel to the surface 250. Further, the groove 252 and the second projection 230 are positioned such that when the second projection 230 is received in the groove 252, the surface 224 is held against the surface 250. Accordingly, the piston 108 may be coupled to the second rotor 110 at the groove 252, so the portion of the second rotor 110 defining the groove 252 is a second coupling portion of the second rotor proximate the surface 246, the piston 108 can slide along the second linear path relative to the second coupling portion, and the second coupling portion of the second rotor 110 revolves around the axis 238 and in a path around the first coupling portion (namely, the portion of the first rotor 104 defining the groove 174 shown in Figures 3 and 4) when the second rotor 110 revolves around the axis 238.
Referring to Figures 1, 5, and 8, the radius 248 is approximately equal to the radius 206, so when the surface 246 is positioned against the second curved portion 196, the axes 238 and 208 are generally collinear and the surface 246 closely contacts a portion of the second curved portion 196 and slides along the second curved portion 196 substantially along the arc length 212 in response to rotation of the second rotor 110 around the axis 238.
Referring back to Figure 1, the second end body 112 includes a generally cylindrical end wall 258 and a generally annular wall 260 that define a generally cylindrical recess shown generally at 262. The recess 262 has an axial height 264 and extends by a radius 266 from an axis 268 of the second end body 112. The wall 260 also

- 15 -defines through-openings shown generally at 270 and 272 and extending into the recess 262. The through-opening 270 is near the wall 260, and the through-opening 272 extends by a radius 274 from the axis 268. In various embodiments, the wall 260 may be attached to the surface 186 by one or more fasteners (such as bolts, screws, or rivets, for example), by complementary threads (not shown) on the wall 260 and on the surface 186, by welding, by soldering, or by adhesive, for example, and the through-opening 270 is axially aligned with the second recess 192 when the wall 260 is attached to the surface 186.
The radius 266 is approximately equal to the radius 236 and the radius 274 is approximately equal to the radius 256 (shown in Figure 9), so the generally cylindrical portion 234 may be received in the recess 262 and positioned against the wall with the projection 254 received in the through-opening 272. When the generally cylindrical portion 234 is positioned against the wall 258, the axes 238 and 268 are generally collinear, and the generally cylindrical portion 234 covers the through-opening 270 except when the generally cylindrical portion 234 is rotationally positioned such that the recess 239 is positioned over the through-opening 270.
Therefore, when the wall 260 is attached to the surface 186 with the generally cylindrical portion 234 positioned against the wall 258, the through-opening 270 is positioned to be in fluid communication with the second recess 192 when the generally cylindrical portion 234 is rotationally positioned such that the recess 239 is positioned over the through-opening 270. In other words, the generally cylindrical portion 234 can control fluid flow through the through-opening 270 in response to rotation of the generally cylindrical portion 234 around the axis 238.
Referring to Figures 1 to 12, the apparatus 100 may be assembled by positioning the disc portion 178 in the recess 126 with the projection 146 received in the through-opening 124, by attaching the surface 120 to the surface 184 with the first recess 190 in fluid communication with the through-opening 122, by positioning the first surface 214 against the surface 156 with the first projection 228 positioned in the groove 174, by positioning the generally cylindrical portion 234 against the surface 154 with the

- 16 -projection 244 positioned against the surface 120 and with the second projection 230 positioned in the groove 252, and by attaching the wall 260 to the surface 186 with the generally cylindrical portion 234 positioned against the wall 258, with the projection 254 received in the through-opening 272, and with the through-opening 270 positioned to be in fluid communication with the second recess 192 when the generally cylindrical portion 234 is rotationally positioned such that the recess 239 is positioned over the through-opening 270. When the apparatus 100 is assembled as shown in Figures 10 to 12, the first end body 102, the intermediate body 106, and the second end body 112 collectively form a housing of the apparatus 100 and the first rotor 104, the piston 108, and the second rotor 110 are in the housing. When the apparatus 100 is assembled as shown, the axes 150 and 202 are generally collinear and the axes 238 and 208 are generally collinear, and because the axes 202 and are different as indicated above, the axes 150 and 238 are also different.
Referring to Figure 12, when the apparatus 100 is assembled as shown, the first rotor 104 can rotate around the axis 150 (which is generally collinear with the axes 134 and 202) and the second rotor 110 can rotate around the axis 238 (which is generally collinear with the axes 208 and 268). Further, as indicated above, when the apparatus 100 is assembled as shown, the first projection 228 (shown in Figures 1 and 6) and the groove 174 (shown in Figures 3 and 4) permit the piston 108 to slide relative to the first rotor 104 and maintain a relative orientation of the piston 108 relative to the first rotor 104 by maintaining the surface 218 generally parallel to the surface 170, and the second projection 230 (shown in Figures 1 and 7) and the groove 252 (shown in Figures 1, 8, and 12) permit the piston 108 to slide relative to the second rotor 110 and maintain a relative orientation of the piston 108 relative to the second rotor 110 by maintaining the surface 224 generally parallel to the surface 250. Accordingly, rotation of the first rotor 104 around the axis 150 causes rotation of the second rotor 110 around the axis 238 because when the first rotor 104 is rotated around the axis 150, the first rotor 104 exerts a force on the piston 108 to maintain the relative orientation of the piston 108 relative to the first rotor 104, and the piston

-17-108 exerts a force on the second rotor 110 to maintain the relative orientation of the piston 108 relative to the second rotor 110. Conversely, rotation of the second rotor 110 around the axis 238 causes rotation of the first rotor 104 around the axis 150.
As indicated above with reference to Figures 1 and 5, the axis 202 extends between the axis 208 and the first curved portion 194, and because the axis 202 is generally collinear with the axis 150 and the axis 208 is generally collinear with the axis 238 when the apparatus 100 is assembled as shown, the axis 150 extends between the axis 238 and the first curved portion 194. Accordingly, and still referring to Figure 12, a separation distance 276 between the surface 250 and the axis 150 varies in response to rotation of the first rotor 104 around the axis 150 and in response to rotation of the second rotor 110 around the axis 238. More particularly, the separation distance 276 is relatively small when the projection 244 is proximate the first curved portion 194 as shown in Figure 13, the separation distance 276 is relatively large when the projection 244 is opposite the first curved portion 194 as shown in Figure 15, and the separation distance 276 is relatively intermediate when the projection 244 is between positions that are proximate and opposite the first curved portion 194 as shown in Figures 12 and 14.
Because the piston 108 is coupled to the second rotor 110 at the groove 252, which extends generally parallel to the surface 250, because rotation of the second rotor 110 around the axis 238 varies the separation distance 276 between the surface (and thus the surface 224 held against the surface 250) and the axis 150, and because the first rotor 104 rotates around the axis 150, rotation of the second rotor 110 around the axis 238 causes the piston 108 to slide along the first linear path defined by the groove 174 (shown in Figures 3 and 4), namely in the direction generally parallel to the surface 170 and generally parallel to a plane of rotation of the first rotor 104, relative to the first rotor 104. Also, because the surface 170 extends at the acute angle 176 to the radius 148 (also shown in Figures 3 and 4), when the piston 108 slides along the first linear path defined by the groove 174 in response to rotation of the first rotor 104 around the axis 150 and in response to rotation of the

- 18 -second rotor 110 around the axis 238, the piston 108 also slides along the second linear path defined by the groove 252, namely in the direction generally parallel to the surface 250 (and thus generally perpendicular to a radius of the second rotor 110) and generally parallel to a plane of rotation of the second rotor 110.
As indicated above with reference to Figures 1, 3, 4, 6, and 7, the surfaces 218, 220, and 222 are sized to abut the surfaces 166, 168, and 170 respectively when a portion of the piston 108 including the surfaces 218, 220, and 222 is received in the recess 172, and the groove 174 and the surface 170 extend at the acute angle 176 to the radius 148. Also, as indicated above with reference to Figures 1 and 7 to 9, the first projection 228 and the groove 174 permit the piston 108 to slide relative to the first rotor 104 while maintaining the surface 218 generally parallel to the surface 170, and the groove 174 and the first projection 228 hold the surface 218 against the surface 170. Therefore, when the separation distance 276 is relatively small as shown in Figure 13, the surfaces 218, 220, and 222 abut the surfaces 166, 168, and 170 respectively, and as the separation distance 276 increases, the surface 220 becomes spaced apart from the surface 168 and the surface 222 becomes spaced apart from the surface 170.
Figure 14 illustrates the apparatus 100 after the projection 244 rotates around the axis 238 and in the direction of the arrow 278 past the first recess 190. In the position shown in Figure 14, the projection 244 is between positions that are proximate and opposite the first curved portion 194, so the separation distance 276 is relatively intermediate, the surface 220 is spaced apart from the surface 168, and the surface 222 is spaced apart from the surface 166. As indicated above, when the apparatus 100 is assembled as shown, a portion of the surface 157 closely contacts at least a portion of the first curved portion 194, the surface 218 is held against the surface 170, the surface 224 is held against the surface 250, and the surface 246 closely contacts a portion of the second curved portion 196. The first rotor 104, the piston 108, and the projection 244 therefore collectively define a fluid barrier extending from the portion of

- 19 -the surface 188 that closely contacts the portion of the surface 157 to the portion of the surface 188 that closely contacts the surface 246.
As such, when the projection 244 is in the position shown in Figure 14, the first rotor 104, the piston 108, the second rotor 110, and the housing (including the surface 188 of the intermediate body 106) define a chamber shown generally at 280 and in fluid communication with the first recess 190, and thus in fluid communication with the through-opening 122 (shown in Figures 1 and 2) as indicated above. More particularly, in various positions, one or more of the surface 120 (shown in Figure 2), the surface 156 (shown in Figures 3 and 4), the surfaces 164, 166, 168, and 170, the surface 188 (shown in Figures 1 and 5), the surfaces 220 and 222, the surface 250, and the generally cylindrical portion 234 define the chamber 280. Because the surfaces 220 and 222 define the chamber 280, and because the surfaces 220 and 222 are on a trailing side (namely, a side opposite the direction of the arrow 278) of the piston 108, the chamber 280 may be referred to as a "trailing-side"
chamber.
Figure 15 illustrates the apparatus 100 after the projection 244 further rotates around the axis 238 and in the direction of the arrow 278. In general, such rotation varies the portion of the surface 188 that closely contacts the surface 246, and therefore varies the aforementioned fluid barrier defined by the first rotor 104, the piston 108, and the projection 244. Accordingly, such rotation also generally varies volumes of fluid chambers defined by the first rotor 104, the piston 108, the second rotor 110, and the housing. In the position shown in Figure 15, the piston 108 is farther from the first recess 190 and from the axis 150, and as such, rotation of the first rotor 104 around the axis 150 and rotation of the second rotor 110 around the axis 238 cause a volume of the chamber 280 to increase. In other words, expanding the volume of the chamber 280 involves revolving the second coupling portion (the portion defining the groove 252) of the second rotor 110 around the axis 238 in the direction of the arrow 278 and in the aforementioned path around the first coupling portion (namely, the portion of the first rotor 104 defining the groove 174 shown in Figures 3 and 4) away from the first recess 190 in fluid communication with the chamber 280.

- 20 -Referring back to Figure 14, after the projection 244 rotates around the axis 238 and in the direction of the arrow 278 past the first recess 190, the first rotor 104, the piston 108, the second rotor 110, and the housing (including the surface 120 shown in Figure 2 of the first end body 102 and the surface 188 of the intermediate body 106) define a chamber shown generally at 282 in fluid communication with the second recess 192. More particularly, in various positions, one or more of the surface 120 (shown in Figure 2), the surface 157, the surface 170, the surface 188, the surfaces 218 and 226, the surface 250, and the generally cylindrical portion 234 define the chamber 282. Because the surfaces 218 and 226 define the chamber 282, and because the surfaces 218 and 226 are on a leading side (namely, a side in direction of the arrow 278) of the piston 108, the chamber 282 may be referred to as a "leading-side" chamber. The chamber 282 is on an opposite side from the chamber 280 of the aforementioned fluid barrier defined by the first rotor 104, the piston 108, and the projection 244. More generally, the aforementioned fluid barrier fluidly isolates the chamber 280 from the chamber 282, and the chamber 282 is different from the chamber 280.
As indicated above, Figure 15 illustrates the apparatus 100 after the projection 244 further rotates around the axis 238 and in the direction of the arrow 278. In the position shown in Figure 15, the piston 108 is closer to the second recess 192, and as such, rotation of the first rotor 104 around the axis 150 and rotation of the second rotor 110 around the axis 238 cause a volume of the chamber 282 to decrease.
In other words, contracting the volume of the chamber 282 involves revolving the second coupling portion (the portion defining the groove 252) of the second rotor 110 around the axis 238 in the direction of the arrow 278 and in the aforementioned path around the first coupling portion (namely, the portion of the first rotor 104 defining the groove 174 shown in Figures 3 and 4) towards the second recess 192 in fluid communication with the chamber 282.
In summary, a volume of the chamber 280 or a volume of the chamber 282 may be varied by causing the first rotor 104 to rotate around the axis 150, by causing the

- 21 -second rotor 110 to rotate around the axis 238 and thereby causing the second coupling portion (the portion defining the groove 252) of the second rotor 110 coupled to the piston 108 to revolve around the axis 238, which is different from the axis 150, in a path around the first coupling portion (namely, the portion of the first rotor 104 defining the groove 174 shown in Figures 3 and 4), and by causing the piston 108 to slide along a first linear path defined by the groove 174, namely in a direction generally parallel to the surface 170, relative to the first rotor 104 in response to rotation of the second rotor 110 around the axis 238.
Referring back to Figure 12, the projection 244 is shown further rotated around the axis 238 and in the direction of the arrow 278 until the projection 244 almost reaches the second recess 192 (shown in Figures 1, 5, and 13 to 15). At that time, the chamber 280 is relatively large, the chamber 282 is relatively small, and the recess 239 is positioned over the through-opening 270, so the second recess 192, and thus the chamber 282, are in fluid communication with the through-opening 270.
In operation, referring to Figures 12 to 15, the through-opening 122 (shown in Figure 1) may be coupled to a fluid source (not shown), and a torque may be applied to one or both of the projections 146 (shown in Figure 1) and 254 (shown in Figure 9) to cause the first rotor 104 to rotate repeatedly around the axis 150 in the direction of the arrow 278 and to cause the second rotor 110 to rotate repeatedly around the axis 238 in the direction of the arrow 278. In various embodiments such as those described herein, torques may be applied by one or more of different types of motors, turbines, or other torque sources (not shown) as may be appropriate. As indicated above, such rotation causes a volume of the chamber 280 (which is in fluid communication with the through-opening 122) to increase as the projection 244 moves in the direction of the arrow 278 from the position shown in Figure 14 to the position shown in Figure 12. Therefore, applying a torque in the direction of the arrow 278 to one or both of the projections 146 and 254 may cause a fluid (not shown) from the fluid source coupled to the through-opening 122 to be drawn into the chamber 280. The through-opening 122 may thus function as a fluid inlet.

- 22 -As the projection 244 moves in the direction of the arrow 278 past the second recess 192 into the position shown in Figure 13, the fluid drawn into the chamber 280 is in the chamber 282, namely the "leading-side" chamber in fluid communication with the second recess 192. As indicated above, rotation of the first rotor 104 around the axis 150 in the direction of the arrow 278 and rotation of the second rotor 110 around the axis 238 in the direction of the arrow 278 cause a volume of the chamber 282 to decrease. Therefore, applying a torque in the direction of the arrow 278 to one or both of the projections 146 and 254 may cause fluid that was drawn into the chamber to be pressurized when in fluid communication with the second recess 192. As indicated above, when the apparatus 100 is assembled as shown, the through-opening 270 (shown in Figure 1) is in fluid communication with the second recess 192 when the recess 239 (shown in Figures 1, 8, and 9) is positioned over the through-opening 270, and as indicated above, the recess 239 is positioned over the through-opening 270 when the projection 244 almost reaches the second recess 192 as shown in Figure 12. Also as indicated above, when the projection 244 almost reaches the second recess 192 as shown in Figure 12, the chamber 282 is relatively small, so the fluid in the chamber 282 is pressurized. As such, in response to rotation of the first rotor 104 around the axis 150 in the direction of the arrow 278, and in response to rotation of the second rotor 110 around the axis 238 in the direction of the arrow 278, pressurized fluid from the chamber 282 is communicated through the through-opening 270. The through-opening 270 may thus function as a fluid outlet.
Still referring to Figures 12 to 15, at least a portion of the surface 157 closely contacts at least portion of the first curved portion 194, thereby maintaining the aforementioned fluid barrier defined by the first rotor 104, the piston 108, and the projection 244, except when the projection 244 passes past the first curved portion 194 as shown in Figure 13. However, in such positions, the fluid outlet of the apparatus 100 is closed because the recess 239 is not positioned over the through-opening 270.
Therefore, in such positions, the generally cylindrical portion 234 may prevent fluid leakage from the fluid outlet of the apparatus 100 to the fluid inlet of the apparatus 100.
Figure 13

- 23 -also illustrates that the surfaces 164, 166, and 170 are positioned such that the surface 167 is separated from the first curved portion 194 for a sufficient range of rotational positions of the first rotor 104 around the axis 150 to allow the projection 244 to pass past the first curved portion 194 as shown in Figure 13.
Otherwise, because the first curved portion 194 extends between the first and second recesses 190 and 192, when a portion of the surface 157 closely contacts at least portion of the first curved portion 194, the fluid barrier defined by the first rotor 104, the piston 108, and the projection 244 fluidly separates the first and second recesses 190 and 192, and thus fluidly separates the fluid inlet of the apparatus 100 from the fluid outlet of the apparatus 100.
In general, the apparatus 100 may function as a fluid pump because applying a torque in the direction of the arrow 278 to one or both of the projections 146 and 254 may cause the apparatus 100 to cycle through positions shown in Figures 12 to and may cause a fluid from a fluid source coupled to the through-opening 122 (or fluid inlet) to be pressurized and communicated through the through-opening 270 (or fluid outlet). Further, because the first projection 228 (shown in Figures 1 and 6) and the groove 174 (shown in Figures 3 and 4) maintain a relative orientation of the piston 108 relative to the first rotor 104, and because the second projection 230 (shown in Figures 1 and 7) and the groove 252 maintain a relative orientation of the piston 108 relative to the second rotor 110, the first rotor 104 rotates at a relatively more consistent angular speed when compared to other piston machines, which may avoid some disadvantages of inconsistent angular speed in such other piston machines.
Although not shown, one or more valves may be positioned in fluid communication with one or both of the fluid inlet and the fluid outlet.
Alternative embodiments may differ from the apparatus 100 in various ways. For example, referring to Figure 16, a piston machine apparatus according to another illustrative embodiment is shown generally at 284 and includes a first end body 286, a first rotor 288, a piston 290, a second rotor 292, and a second end body 294.
The first end body 286 is substantially the same as the first end body 102 (shown in Figures 1

-24 -and 2) integrally formed with the intermediate body 106 (shown in Figures 1 and 5), and more generally, in the various embodiments described herein, the first end bodies or the second end bodies may be integrally formed (by molding, casting, or machining, for example) with the intermediate bodies. Further, the second end body 294 is substantially the same as the second end body 112 (shown in Figure 1).
Referring to Figures 16 to 18, the piston 290 is substantially the same as the piston 108 (shown in Figures 1, 6, 7, and 12 to 15) and has side surfaces 296, 298, 300, 302, and 304 that are substantially the same as the side surfaces 218, 220, 222, 224, and 226 respectively, except that the piston 290 defines an elongate dovetail projection 306 extending along the surface 296, and an elongate dovetail projection 308 extending along the surface 302.
Referring to Figures 16 and 19, the first rotor 288 is substantially the same as the first rotor 104 (shown in Figures 1, 3, 4, and 12 to 15) and has an axial surface 310 that is substantially the same as the axial surface 170, except that the first rotor 288 defines an elongate dovetail recess shown generally at 312 and extending along the surface 310. The recess 312 is sized to receive the projection 306 such that when the projection 306 is received in the recess 312, the projection 306 can slide along the recess 312 with the surface 296 held against the surface 310. Accordingly, when the projection 306 is received in the recess 312, the projection 306 and the recess 312 cooperate to prevent rotation of the piston 290 relative to the first rotor 288. In other words, the projection 306 and the recess 312 permit the piston 290 to slide relative to the first rotor 288 and maintain a relative orientation of the piston 290 relative to the first rotor 288 by maintaining the surface 296 generally parallel to the surface 310.
Referring to Figures 16 and 20, the second rotor 292 is substantially the same as the second rotor 110 (shown in Figures 1, 8, 9, and 12 to 15) and has a generally planar axial surface 314 that is substantially the same as the generally planar axial surface 250, except that the second rotor 292 defines an elongate dovetail recess shown generally at 316 and extending along the surface 314. The recess 316 is sized to

- 25 -receive the projection 308 such that when the projection 308 is received in the recess 316, the projection 308 can slide along the recess 316 with the surface 302 held against the surface 314. Accordingly, the piston 290 may be coupled to the second rotor 292 at the recess 316, so the portion of the second rotor 292 defining the recess 316 is a coupling portion of the second rotor 292. Further, when the projection 308 is received in the recess 316, the projection 308 and the recess 316 cooperate to prevent rotation of the piston 290 relative to the second rotor 292. In other words, the projection 308 and the recess 316 permit the piston 290 to slide relative to the second rotor 292 and maintain a relative orientation of the piston 290 relative to the second rotor 292 by maintaining the surface 302 generally parallel to the surface 314.
Therefore, the apparatus 284 may function as a fluid pump in substantially the same way as the apparatus 100.
As another example, referring to Figure 21, a piston machine apparatus according to another illustrative embodiment is shown generally at 318 and includes a first end body 320, a first rotor 322, a piston 324, a second rotor 326, and a second end body 328. The first end body 320 is substantially the same as the first end body (shown in Figure 16), and the second end body 328 is substantially the same as the second end body 294 (also shown in Figure 16).
Referring to Figures 21 to 23, the piston 324 is substantially the same as the piston 108 (shown in Figures 1, 6, 7, and 12 to 15) and has side surfaces 330, 332, 334, 336, and 338 that are substantially the same as the side surfaces 218, 220, 222, 224, and 226 respectively, except that the piston 324 does not define any projections and instead defines a cavity shown generally at 340 and open to an opening in the surface 334.
Referring to Figures 21 and 22, the first rotor 322 is substantially the same as the first rotor 104 (shown in Figures 1, 3, 4, and 12 to 15) with axial surfaces 342 and 344 that are substantially the same as the axial surfaces 166 and 170 respectively and with a disc portion 346 that is substantially the same as the disc portion 178, except that the

- 26 -first rotor 322 defines a projection 348 projecting from the surface 344 and spaced apart from the disc portion 346. The projection 348 has an end surface 350 facing the surface 342 and generally parallel to and spaced apart from the surface 342, and the cavity 340 is sized to receive the projection 348 with the surface 350 received in the cavity 340 and holding the surface 330 against the surface 342 while permitting the piston 324 to slide along the surface 342 in a direction generally parallel to the surface 342. Accordingly, when the projection 348 is received in the cavity 340, the projection 348 and the cavity 340 cooperate to prevent rotation of the piston relative to the first rotor 322. In other words, the projection 348 and the cavity 340 permit the piston 324 to slide relative to the first rotor 322 and maintain a relative orientation of the piston 324 relative to the first rotor 322 by maintaining the surface 330 generally parallel to the surface 342.
Referring to Figures 21 and 23, the second rotor 326 is substantially the same as the second rotor 110 (shown in Figures 1, 8, 9, and 12 to 15) with a generally planar axial surface 352 that is substantially the same as the generally planar axial surface 250 and with a generally cylindrical portion 354 that is substantially the same as the generally cylindrical portion 234, except that the second rotor 326 defines a projection 356 spaced apart from the generally cylindrical portion 354. The projection 356 has a surface 358 facing the surface 352 and generally parallel to and spaced apart from the surface 352, and the cavity 340 is sized to receive the projection 348 with the surface 358 received in the cavity 340 and holding the surface 336 against the surface 352 while permitting the piston 324 to slide along the surface 352 in a direction generally parallel to the surface 352. Accordingly, the piston 324 may be coupled to the second rotor 326 at the projection 356, so the projection 356 is a coupling portion of the second rotor 326. Further, when the projection 356 is received in the cavity 340, the projection 356 and the cavity 340 cooperate to prevent rotation of the piston 324 relative to the second rotor 326. In other words, the projection 356 and the cavity 340 permit the piston 324 to slide relative to the second rotor 326 and maintain a relative orientation of the piston 324 relative to the second rotor 326 by

- 27 -maintaining the surface 336 generally parallel to the surface 362. Therefore, the apparatus 318 may function as a fluid pump in substantially the same way as the apparatus 100 or the apparatus 284.
As another example, referring to Figures 24 and 25, a piston machine apparatus according to another illustrative embodiment is shown generally at 360 and includes a first rotor 362, a piston 364, and a second rotor 366. The apparatus 360 also includes end bodies (not shown) such as those described above. The piston 364 defines generally cylindrical recesses shown generally at 368 and 370. Further, the first rotor 362 defines a generally cylindrical projection 372 sized to be received in the recess 368, and the second rotor 366 defines a generally cylindrical projection 374 sized to be received in the recess 370. Accordingly, the piston 364 may be coupled to the second rotor 366 at the projection 374, so the projection 374 is a coupling portion of the second rotor 366. When the projection 372 is received in the recess 368, the projection 372 and the recess 368 cooperate to prevent rotation of the piston relative to the first rotor 362 and thus permit the piston 364 to slide relative to the first rotor 362 and maintain a relative orientation of the piston 364 relative to the first rotor 362. Further, when the projection 374 is received in the recess 370, the projection 374 and the recess 370 cooperate to prevent rotation of the piston 364 relative to the second rotor 366 and thus permit the piston 364 to slide relative to the second rotor 366 and maintain a relative orientation of the piston 364 relative to the second rotor 366. Otherwise, the apparatus 360 may function as a fluid pump in substantially the same way as the apparatus 100, the apparatus 284, or the apparatus 318.
As another example, referring to Figures 26 and 27, a piston machine apparatus according to another illustrative embodiment is shown generally at 376 and includes a first rotor 378, a piston 380, and a second rotor 382. The apparatus 376 also includes end bodies (not shown) such as those described above. The piston 380 defines elongate recesses shown generally at 384 and 386. Further, the first rotor 378 defines an elongate projection 388 sized to be received in the recess 384, and the second rotor 382 defines an elongate projection 390 sized to be received in the recess 386.

- 28 -Accordingly, the piston 380 may be coupled to the second rotor 382 at the projection 390, so the projection 390 is a coupling portion of the second rotor 382. When the projection 388 is received in the recess 384, the projection 388 and the recess 384 cooperate to prevent rotation of the piston 380 relative to the first rotor 378 and thus permit the piston 380 to slide relative to the first rotor 378 and maintain a relative orientation of the piston 380 relative to the first rotor 378. Further, when the projection 390 is received in the recess 386, the projection 390 and the recess 386 cooperate to prevent rotation of the piston 380 relative to the second rotor 382 and thus permit the piston 380 to slide relative to the second rotor 382 and maintain a relative orientation of the piston 380 relative to the second rotor 382. Otherwise, the apparatus 376 may function as a fluid pump in substantially the same way as the apparatus 100, the apparatus 284, the apparatus 318, or the apparatus 360.
Although the aforementioned illustrative embodiments include particular structures for coupling a piston to a first rotor and to a second rotor to allow the piston to slide relative to the first rotor and relative to the second rotor in response to rotation of the first rotor around a first axis of rotation and in response to rotation of the second rotor around a second axis of rotation, alternative embodiments may include various different structures, including combinations and variations of the aforementioned structures, and including structures that differ from the aforementioned structures.
As an example of another illustrative embodiment, referring to Figures 28 to 30, a piston machine apparatus is shown generally at 392 and includes a first end body 394, a first rotor 396, a piston 398, a second rotor 400, and a second end body 402.
Like the first end body 286 (shown in Figure 16), the first end body 394 is similar to the first end body 102 (shown in Figures 1 and 2) integrally formed with the intermediate body 106 (shown in Figures 1 and 5). As shown in Figure 30, the first end body 394 has a generally annular inner surface 404 that is substantially the same as the generally annular inner surface 188 (shown in Figures 1 and 5). More particularly, the generally annular inner surface 404 defines a first recess shown generally at 406 and that is positioned in substantially the same location in the

- 29 -apparatus 392 as the first recess 190 (also shown in Figures 1 and 5) in the apparatus 100, and the generally annular inner surface 404 defines a second recess shown generally at 408 and that is positioned in substantially the same location in the apparatus 392 as the second recess 192 (also shown in Figures 1 and 5) in the apparatus 100. However, unlike the first end body 102, which (as indicated above) defines the through-opening 122 positioned to be in fluid communication with the first recess 190 and thus functioning as a fluid inlet, the first end body 394 defines a through-opening shown generally at 410 and positioned to be in fluid communication with the second recess 408, and the through-opening 410 is thus positioned to function as a fluid outlet.
The first rotor 396, the piston 398, and the second rotor 400 are substantially the same as the first rotor 322, the piston 324, and the second rotor 326 (shown in Figures 21 to 23) respectively, except that the second rotor 400 defines a recess shown generally at 412 and that is positioned differently from the recess 239 (shown in Figures 1, 8, 9, and 12) as shown in Figures 28 and 30.
The second end body 402 is substantially the same as the second end body 112 (shown in Figure 1), which (as indicated above) defines the through-opening positioned to be in fluid communication with the second recess 192 and thus functioning as a fluid outlet, except that the second end body 402 defines a through-opening shown generally at 414 and positioned to be in fluid communication with the first recess 406, and the through-opening 414 is thus positioned to function as a fluid inlet. However, as described above with respect to the recess 239, the second rotor 400 covers the through-opening 414 except when the second rotor 400 is rotationally positioned such that the recess 412 is positioned over the through-opening 414.
Therefore, the through-opening 414 is positioned to be in fluid communication with the first recess 406 when the second rotor 400 is rotationally positioned such that the recess 412 is positioned over the through-opening 414. In other words, the second rotor 400 can control fluid flow through the through-opening 414 in response to rotation of the second rotor 400.

- 30 -In summary, the apparatus 392 is similar to the apparatus 100, but the fluid inlet and the fluid outlet of the apparatus 392 are on opposite sides when compared to the apparatus 100, and the recess 412 is positioned differently from the recess 239. As such, the second rotor 400 controls fluid flow through the fluid inlet of the apparatus 392 instead of the fluid outlet as in the apparatus 100.
As another example, referring to Figures 31 to 33, a piston machine apparatus according to another illustrative embodiment is shown generally at 416 and includes a first end body 418, a first rotor 420, a piston 422, a second rotor 424, and a second end body 426. The apparatus 416 is similar to the apparatus 392 shown in Figures 28 to 30, except that the first end body 418 defines a through-opening shown generally at 428 and positioned to function as a fluid inlet, and a through-opening shown generally at 430 and positioned to function as a fluid outlet. Also, the first rotor 420 defines a peripheral recess shown generally at 432.
As shown in Figure 33, the first end body 418 has a generally annular inner surface 434 that is substantially the same as the generally annular inner surface 188 (shown in Figures 1 and 5). More particularly, the surface 434 includes a first curved portion 436 similar to the first curved portion 194 (also shown in Figures 1 and 5), and a second curved portion 438 similar to the second curved portion 196 (also shown in Figures 1 and 5). The first curved portion 436 extends along an arc of a peripheral outer surface 440 of the first rotor 420, and the second curved portion 438 extends along an arc of a peripheral outer surface 442 of the second rotor 424. The first curved portion 436 thus curves along a smaller radius of curvature than the second curved portion 438. The through-opening 428 extends between the first curved portion 436 and the second curved portion 438, and is thus in fluid communication with a chamber defined by the apparatus 416 except when the second rotor 424 covers the through-opening 428. However, the through-opening 430 is spaced apart from the surface 434 but proximate the first curved portion 436, and is thus covered by the first rotor 420 except when the except when the first rotor 420 is rotationally positioned such that the recess 432 is positioned over the through-opening 430.

- 31 -Therefore, the first rotor 420 can control fluid flow through the through-opening 430 (and thus through the fluid outlet of the apparatus 416) in response to rotation of the first rotor 420.
As another example, referring to Figures 34 to 36, a piston machine apparatus according to another illustrative embodiment is shown generally at 444 and includes a first end body 446, a first rotor 448, a piston 450, a second rotor 452, and a second end body 454. The apparatus 444 is similar to the apparatus 416 shown in Figures 31 to 33, and the first end body 446 defines a through-opening shown generally at and positioned to function as a fluid inlet, and a through-opening shown generally at 458 and positioned to function as a fluid outlet. Also, the first rotor 448 defines a peripheral recess shown generally at 460 that is positioned differently from the recess 420 (shown in Figures 31 and 33) as shown in Figures 34 and 36. As in the apparatus 416, the first end body 446 has a generally annular inner surface 462 that includes a first curved portion 464 and a second curved portion 466, the first curved portion 464 curving along a smaller radius of curvature than the second curved portion 466.
However, unlike the apparatus 416, the through-opening 458 (which is positioned to function as a fluid outlet) extends between the first curved portion 464 and the second curved portion 466, and is thus in fluid communication with a chamber defined by the apparatus 444 except when the second rotor 452 covers the through-opening 458, and the through-opening 456 (which is positioned to function as a fluid inlet) is spaced apart from the surface 462 but proximate the first curved portion 464, and is thus covered by the first rotor 448 except when the except when the first rotor 448 is rotationally positioned such that the recess 460 is positioned over the through-opening 456. Therefore, the first rotor 448 can control fluid flow through the through-opening 456 (and thus through the fluid inlet of the apparatus 444) in response to rotation of the first rotor 448.
In summary, in apparatuses such as those described above, the first rotor or the second rotor can control fluid flow through the fluid inlet or through the fluid outlet.

- 32 -Structures such as those described above may be combined with other structures such as those described above or other structures. For example, in some embodiments, one rotor may control fluid flow through a fluid inlet as described above and another rotor may control fluid flow through a fluid outlet as described above.
Controlling such fluid flow may, in some embodiments, facilitate use of such an apparatus as a fluid pumps by, for example, controlling pressure at the fluid inlet or at the fluid outlet of the apparatus.
Further, in apparatuses such as those described above, the piston can be coupled to the first rotor and to the second rotor in various ways that maintain the piston in a relative orientation relative to the first coupling portion, and in a relative orientation relative to the first rotor, so the first rotor rotates at relatively consistent angular speeds when compared to other piston machines. Therefore, apparatuses such as those described above may avoid some disadvantages of inconsistent angular speed in such other piston machines.
Still further, apparatuses such as those described above may be operated without seals because the various components may be machined or otherwise manufactured to tolerances that permit the apparatuses to function without requiring seals that may degrade or fail over time.
In various embodiments, the components of apparatuses such as those described above may have varying dimensions and configurations, and may be formed by one or more of molding, casting, machining, or other methods from one or more of various different materials such as metal or plastic materials as may be appropriate for particular temperatures, pressures, fluids, or other considerations in particualr applications.
Although specific embodiments have been described and illustrated, such embodiments should be considered illustrative only and not as limiting the invention as construed according to the accompanying claims.

Claims

- 33 -

1. A method of varying a volume of a chamber defined by a first rotor, a second rotor, and a piston in a housing of a piston machine apparatus, the method comprising:
causing the first rotor to rotate around a first axis of rotation;
causing the second rotor to rotate around a second axis of rotation different from the first axis of rotation; and causing the piston to slide, in response to rotation of the second rotor around the second axis of rotation, along a first linear path relative to a first coupling portion of the first rotor coupled to the piston;
wherein causing the second rotor to rotate around the second axis of rotation comprises causing a second coupling portion of the second rotor coupled to the piston to revolve around the second axis of rotation in a path around the first coupling portion.

2. The method of claim 1 wherein causing the piston to slide along the first linear path comprises maintaining a relative orientation of the piston relative to the first rotor.

3. The method of claim 1 or 2 wherein the first linear path extends generally parallel to a plane of rotation of the first rotor and at an acute angle to a radius perpendicular to the first axis of rotation.

4. The method of claim 1, 2, or 3 further comprising causing the piston to slide along a second linear path relative to the second coupling portion in response to rotation of the first rotor around the first axis of rotation and in response to rotation of the second rotor around the second axis of rotation.

5. The method of claim 4 wherein the second linear path extends generally parallel to a plane of rotation of the second rotor and generally perpendicular to a radius perpendicular to the second axis of rotation.

6. The method of claim 5 wherein causing the piston to slide along the first linear path comprises varying a separation distance between the second path and the first axis of rotation.

7. The method of any one of claims 1 to 6 wherein varying the volume of the chamber comprises expanding the chamber when the chamber is in fluid communication with a fluid inlet defined by the housing of the piston machine.

8. The method of claim 7 wherein expanding the chamber comprises revolving the second coupling portion away from the inlet along the path around the first coupling portion.

9. The method of claim 7 or 8 further comprising controlling fluid flow through the fluid inlet in response to rotation of the first rotor around the first axis of rotation.

10. The method of claim 7 or 8 further comprising controlling fluid flow through the fluid inlet in response to rotation of the second rotor around the second axis of rotation.

11. The method of any one of claims 1 to 6 wherein varying the volume of the chamber comprises contracting the chamber when the chamber is in fluid communication with a fluid outlet defined by the housing of the piston machine.

12. The method of claim 11 wherein contracting the chamber comprises revolving the second coupling portion towards the outlet along the path around the first coupling portion.

13. The method of claim 11 or 12 further comprising controlling fluid flow through the fluid outlet in response to rotation of the first rotor around the first axis of rotation.

14. The method of claim 11 or 12 further comprising controlling fluid flow through the fluid outlet in response to rotation of the second rotor around the second axis of rotation.

15. A piston machine apparatus comprising:
a housing defining a fluid inlet and a fluid outlet;
a piston in the housing;
a first rotor comprising a first coupling portion coupled to the piston, the first rotor rotatable in the housing around a first axis of rotation; and a second rotor comprising a second coupling portion coupled to the piston, the second rotor rotatable in the housing around a second axis of rotation different from the first axis of rotation;
wherein the second coupling portion has a position that revolves around the second axis of rotation in a path around the first coupling portion in response to rotation of the second rotor around the second axis of rotation;
wherein the piston is slidable along a first linear path relative to the first coupling portion in response to rotation of the second rotor around the second axis of rotation;
wherein the first rotor, the second rotor, and the piston are positionable to define a first chamber, in fluid communication with the fluid inlet, that expands in volume in response to revolving the second coupling portion in the path around the first coupling portion and away from the fluid inlet; and wherein the first rotor, the second rotor, and the piston are positionable to define a second chamber, different from the first chamber and in fluid communication with the fluid outlet, that contracts in volume in response to revolving the second coupling portion in the path around the first coupling portion and towards the fluid outlet.

16. The apparatus of claim 15 wherein the piston and the first coupling portion maintain a relative orientation of the piston relative to the first rotor when the piston slides along the first linear path relative to the first coupling portion in response to rotation of the second rotor around the second axis of rotation.

17. The apparatus of claim 15 or 16 wherein the first linear path extends generally parallel to a plane of rotation of the first rotor and at an acute angle to a radius perpendicular to the first axis of rotation.

18. The apparatus of claim 15, 16, or 17 wherein the piston is slidable along a second linear path relative to the second coupling portion in response to rotation of the first rotor around the first axis of rotation and in response to rotation of the second rotor around the second axis of rotation.

19. The apparatus of claim 18 wherein the second linear path extends generally parallel to a plane of rotation of the second rotor and generally perpendicular to a radius perpendicular to the second axis of rotation.

20. The apparatus of claim 19 wherein rotation of the first rotor around the first axis of rotation and rotation of the second rotor around the second axis of rotation vary a separation distance between the second linear path and the first axis of rotation and cause the piston to slide along the first linear path.

21. The apparatus of claim 18, 19, or 20 wherein the piston comprises first and second opposite and non-parallel side edges, the piston coupled to the first coupling portion such that the first side edge is slidable along the first linear path, and the piston coupled to the second coupling portion such that the second side edge is slidable along the second linear path.

22. The apparatus of any one of claims 15 to 21 wherein the housing defines a generally annular inner surface.

23. The apparatus of claim 22 wherein the first rotor comprises a curved outer surface positioned to slide, in response to rotation of the first rotor around the first axis of rotation, along a first portion of the generally annular inner surface of the housing between the fluid inlet and the fluid outlet.

24. The apparatus of claim 22 or 23 wherein the second rotor comprises a curved outer surface proximate the second coupling portion and positioned to slide, in response to rotation of the second rotor around the second axis of rotation, along a second portion of the generally annular inner surface of the housing.

25. The apparatus of any one of claims 15 to 24 wherein the first rotor defines a recess sized to receive at least a portion of the piston.

26. The apparatus of any one of claims 15 to 25 wherein the first rotor defines a recess having a position that controls fluid flow through the fluid inlet in response to rotation of the first rotor around the first axis of rotation.

27. The apparatus of any one of claims 15 to 25 wherein the first rotor defines a recess having a position that controls fluid flow through the fluid outlet in response to rotation of the first rotor around the first axis of rotation.

28. The apparatus of any one of claims 15 to 25 and 27 wherein the second rotor defines a recess having a position that controls fluid flow through the fluid inlet in response to rotation of the second rotor around the second axis of rotation.

29. The apparatus of any one of claims 15 to 26 wherein the second rotor defines a recess having a position that controls fluid flow through the fluid outlet in response to rotation of the second rotor around the second axis of rotation.

30. Use of the apparatus of any one of claims 15 to 29 to pump a fluid.