Hydrostatic transmission

Claim 2

A hydrostatic transmission comprising a motor; a variable-delivery pump having a variable-delivery volume and being connected to said motor for driving said motor, said pump being operable in a range between two extreme values; at least one fixed-delivery pump having an invariable-delivery rate and being selectively connected to said motor in parallel with said variable-delivery pump; and a control means for adjusting the delivery rate of said variable-delivery pump and for selectively connecting and disconnecting said fixed delivery pump to said motor in response to said variable-delivery pump reaching one of said extreme values, said control means simultaneously causing a change-over of said variable-delivery pump from said one extreme value to the other extreme value upon said latter pump reaching said one extreme value.

Claim 3

A hydrostatic transmission as set forth in claim 1 wherein said control means includes an adjusting means for adjusting the delivery rate of said variable-delivery pump, and a changeover means connected in series with said adjusting means for moving said adjusting means from a first end position into a second end position to change over said variable-delivery pump from one extreme value to the other extreme value and for selectively connecting and disconnecting said fixed delivery pump to said motor in response to movement of said adjusting means from one of said end positions.

Claim 4

A hydrostatic transmission as set forth in claim 2 wherein said changeover means includes a changeover valve connected to said adjusting means and a control valve, said control valve being connected to said variable-delivery pump to respond to changes in the delivery rate of said variable delivery pump, said control valve being connected to said changeover valve to initiate operation of said valve in response to said variable-delivery pump reaching one of said extreme values to cause said valve to move said adjusting means from one end position to the other end position.

Claim 5

A hydrostatic transmission as set forth in claim 3 wherein said control valve is a rotary valve having a slotted link guide, and said adjusting means includes a projection projecting into said link guide to rotate said rotary valve in response to movements of said adjusting means between said end positions.

Claim 6

A hydrostatic transmission as set forth in claim 4 wherein said control valve further includes a disc-shaped cylinder chamber and a movable vane on said rotary valve sealingly mounted in said chamber to divide said chamber into two sections, said changeover valve being connected to said chamber on opposite sides of said vane to deliver pressurized medium from said changeover valve to a selective one of said sections of said chamber.

Claim 7

A hydrostatic transmission as set forth in claim 5 wherein said rotary valve includes a control duct for connecting and disconnecting said fixed-delivery pump to and from said motor.

Claim 8

A hydrostatic transmission as set forth in claim 2 which further comprises a blocking means for blocking said adjusting means upon movement of said adjusting means into each of said end positions.

Claim 9

A hydrostatic transmission as set forth in claim 2 which further includes a delivery line connected between each said pump and said motor for delivering pressurized medium to said motor, and wherein said control means further includes a control valve connected to at least one of said delivery line for controlling the supply of pressurized medium to said adjusting means, and a control lever connected to said control valve to actuate said valve.

Claim 10

A hydrostatic transmission as set forth in claim 8 wherein said control valve includes a self-holding means for retaining said valve in position during changeover of said variable-delivery pump until completion of changeovEr.

Claim 11

A hydrostatic transmission as set forth in claim 9 wherein said control means includes two of said control valves, said control lever being selectively connected to said control valves to operate one valve while the other valve remains inoperable.

Claim 12

A hydrostatic transmission comprising a motor having a delivery line; a variable-delivery pump having a variable-delivery volume and being connected to said motor for driving said motor, said pump being operable in a range between two extreme values; at least one fixed-delivery pump having an invariable-delivery rate and being selectively connected to said motor in parallel with said variable-delivery pump; an adjusting means for adjusting the delivery rate of said variable-delivery pump between said extreme values; a changeover valve connected to said adjusting means to reverse an adjustment of the delivery rate of said variable-delivery pump; a first control valve connected between said changeover valve and said delivery line of said motor to deliver a flow of pressurized medium to said changeover valve to activate said changeover valve; and a second control valve connected to said adjusting means between said fixed-delivery pump and said delivery line for connecting and disconnecting said fixed-delivery pump to and from said delivery line, said second control valve being connected to said first control valve to receive pressurized medium therefrom for activation of said second control valve to connect and disconnect said fixed-delivery pump to and from said delivery line in response to said adjusting means moving into one of two end positions, each end position corresponding to an extreme value of said variable-delivery pump.

Claim 13

A hydrostatic transmission comprising a motor having a delivery line; a variable-delivery pump having a variable-delivery volume and being connected to said motor for driving said motor, said pump being operable in a range between two extreme values; at least one fixed-delivery pump having an invariable-delivery rate and being selectively connected to said motor in parallel with said variable-delivery pump; an adjusting means for adjusting the delivery rate of said variable-delivery pump between said extreme values; a changeover valve connected to said adjusting means to reverse an adjustment of the delivery rate of said variable-delivery pump; a first control valve connected between said changeover valve and said delivery line of said motor to deliver a flow of pressurized medium to said changeover valve to activate said changeover valve; and a second control valve connected to said adjusting means between said fixed-delivery pump and said delivery line for connecting and disconnecting said fixed-delivery pump to and from said delivery line, said second control valve being connected to said first control valve to receive pressurized medium therefrom for activation of said second control valve to connect and disconnect said fixed-delivery pump to and from said delivery line in response to said adjusting means moving into one of two end positions, each end position corresponding to an extreme value of said variable-delivery pump.