Hydraulic motor

A hydraulic motor having an axle with an internal bore, said motor operated by a pressure medium carried in supply and return lines respectively for connection to a reservoir and power supply separate from the motor, said motor comprising first and second sets of cylinders with included pistons radially surrounding the motor axis, the diameter of the cylinders of said first set being smaller than the diameters of said second set;

• means internally of the motor and axially movable therein for directing the pressure medium into any one of (a) the two sets of cylinders in combination creating a first motor speed range, (b) the larger diameter cylinder set only creating a second motor speed range, and (c) the smaller diameter cylinder set only creating a third motor speed range, said axially movable pressure medium directing means including a first hollow valve spindle disposed inside the bore of said axle and movable between first and second axially spaced apart positions, the outer wall of first spindle having therein a first opening located to connect the interior space of said spindle with the pressure medium supply line in both positions of said spindle, a second opening located and dimensioned to connect the interior space of said first spindle with the pressure supply conduits of the larger cylinder set when said spindle is in its first position, the connection being broken when said spindle is in its second position, the third opening located to connect the interior space of said first spindle with the pressure supply conduits of the smaller cylinder set when said spindle is in its second position, a fourth opening located to connect the interior space of said first spindle with the pressure supply conduits of the smaller cylinder when said spindle is in its first position, an axial recess located to connect the return conduits of both cylinder sets within the pressure medium return line, and a separate radial groove and axial passageway located to connect the return conduits of the larger cylinder set to the reservoir when said first spindle is in its second position;
• a second hollow valve spindle having a portion disposed inside said first spindle and a second portion adjacent the end of said first spindle within the axial bore, said second spindle being movable between first and second axially spaced apart positions, the portion of said second spindle disposed inside said first spindle being of a length that permits the connection between the interior space of first spindle to the pressure supply conduits of the smaller cylinder set through the opening of said first spindle when said second spindle is in its first position relative to said first spindle and which in the second position of said second spindle relative to said first spindle blocks this connection, the outer wall of the portion of said second spindle disposed within said first spindle and the inner surface of the cylindrical wall of said first spindle having axial grooves formed therein that communicate with one another and connect the fourth opening with the reservoir when said spindle is in its second position relative to first spindle;
• a piston axially adjacent and in contact with said first valve spindle to move said first valve spindle when pressure is supplied to said piston;
• means for controlling the movement of said axially movable means to select the speed range desired;
• and
• supply conduits and return conduits for said pressure medium interconnecting the cylinders of said first set with said axially movable pressure medium directing means, the cylinders of said second set with said axially movable pressure medium directing means, and said control means with said axially movable pressure medium directing means.