Patent ID: 7275474

Claim:
An improved optical position sensing device for a variable displacement type hydraulic pump/motor assembly including one of an angularly movable yoke and an angularly movable swashplate, an optical/electronic sensor unit capable of reading indicia markings, for sensing the movement of at least one of said yoke, said swashplate and means for moving said swashplate, relative to a reference location in a stationary housing of said pump/motor assembly, said one of said yoke, said swashplate and said means for moving said swashplate, being provided with a plurality of absolute scale indicia markings, wherein said improvement comprises: a. said absolute scale indicia markings being in the form of a bar-type pattern and being located on a surface of one of said angularly movable yoke, said swashplate and said means for moving said swashplate; and b. said optical/electronic sensor unit being fixedly located on said stationary housing and including an optical read head sealingly extending into the interior of said housing and being located at a predetermined, spaced distance from said indicia markings for sensing said indicia markings and producing an optical signal.