Eaton Corporation

Mark D Schuster

Marvin L Bernstrom

Michael W Barto

John B Heckel

A two-speed gerotor motor ( ) including motor valve means ( ) to communicate fluid to and from expanding ( E) and contracting ( ) fluid volume chambers. The motor includes a shift valve spool ( ) to cause the motor to operate either in the normal, low-speed, high-torque (LSHT) mode (FIG. ) or in a high-speed, low-torque (HSLT) mode (FIG. ). When the motor operates in HSLT mode, certain of the volume chambers comprise recirculating volume chambers ( R). The motor ( ) defines a supplemental fluid passage ( ) through which fluid is communicated from a system charge pump ( ) to each of the recirculating volume chambers ( R). A control valve ( ) is operable, in a shift mode (S) to permit fluid communication from the charge pump ( ) to the supplemental fluid passage ( ), thus preventing cavitation during shifting of the motor ( ), especially when shifting from the HSLT mode to the LSHT mode.

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Wahpeton, ND, United States of America

Mark D Schuster