Patent ID: 8112991

Claim:
A hydrostatic transmission comprising: a hydraulic pump; a hydraulic motor; and a center section shaped to include: a pump mounting surface, onto which the hydraulic pump is mounted; a motor mounting surface, onto which the hydraulic motor is mounted, wherein the motor mounting surface is extended perpendicular to the pump mounting surface so that an imaginary extension surface from the motor mounting surface intersects the pump mounting surface; first and second kidney ports opened at the pump mounting surface, wherein the first and second kidney ports are aligned opposite to each other and perpendicular to an extension direction of the imaginary extension surface so as to have the imaginary extension surface therebetween; third and fourth kidney ports opened at the motor mounting surface, wherein the third and fourth kidney ports are aligned opposite to each other along the extension direction of the imaginary extension surface, and wherein the third kidney port is closer to the pump mounting surface than the fourth kidney port; a first fluid passage interposed between the first and third kidney ports, wherein the first fluid passage has a first end joined to the first kidney port, and has a second end joined to the third kidney port, and wherein the entire first fluid passage between the first and second ends, when viewed to face the motor mounting surface, is straight and parallel to the pump mounting surface; and a second fluid passage interposed between the second and fourth kidney ports, wherein the second fluid passage has a third end joined to the second kidney port, and has a fourth end joined to the fourth kidney port, wherein the second fluid passage includes a straight portion extended parallel to the pump mounting surface and the motor mounting surface, and wherein a portion of the first fluid passage ranged along the motor mounting surface to the second end, when viewed to face the motor mounting surface, entirely overlaps the straight portion of the second fluid passage.