Patent ID: 7127890

Claim:
A hydrostatic transmission comprising: a hydraulic pump having a pump rotary axis; a hydraulic motor having a motor rotary axis; and a center section including a pump mounting surface onto which said hydraulic pump is mounted so that said pump rotary axis is disposed perpendicularly to said pump mounting surface, wherein said pump mounting surface is disposed in parallel to said motor rotary axis, a motor mounting surface onto which said hydraulic motor is mounted so that said motor rotary axis is disposed perpendicularly to said motor mounting surface, wherein said motor mounting surface is disposed perpendicularly to said pump mounting surface and in parallel to said pump rotary axis, first and second kidney ports whose openings are extended on said pump mounting surface in a direction substantially perpendicular to said motor rotary axis, third and fourth kidney ports whose openings are extended on said motor mounting surface in a direction substantially parallel to said pump rotary axis, first and second parallel oil passages extended below said pump mounting surface in a direction perpendicular to said pump rotary axis and said motor rotary axis so as to overlap said first kidney port when viewed in plan, wherein said first and second oil passages are connected at one ends thereof to said respective third and fourth kidney ports, and wherein said first oil passage is connected at the other end thereof to said first kidney port, and a third oil passage extended below said pump mounting surface in a direction perpendicular to said pump rotary axis and said first and second oil passages and parallel to said motor rotary axis, wherein said third oil passage connects the other end of said second oil passage to said second kidney port.