Power control device for two or more hydraulic pumps

Claim 2

A power control apparatus for two or more adjustable hydraulic pumps, driven by a common driving means and each having its own power regulator, including a power control device for each pump for continuously adjusting the regulator to maintain a desired power value of the associated pump, and a pressure responsive device in fluid communication with and responsive to the delivery pressure of the companion pump and arranged to adjust the power of its own associated pump according to the said delivery pressure of the companion pump, and wherein the power control device of each pump comprises a pilot valve acted on by a spring, the force of which depends on the delivery flow adjustment of its associated pump, said pilot valve having a piston surface in fluid communication with and acted on by a control pressure depending upon the delivery pressure of its associated pump, the power control device of each pump also comprises two restricted orifices connected in series and in fluid communication with the output of its associated pump, and wherein said control pressure is derived from a point between the two restricted orifices connected in series whilst the pressure responsive device comprises a throttle valve adjustable in accordance with the delivery pressure of the companion pump and connected in parallel with one of the restricted orifices.

Claim 3

A power control apparatus for two or more adjustable hydraulic pumps, driven by a common driving means and each having its own power regulator, including a power control device for each pump for continuously adjusting the regulator to maintain a desired power value of the associated pump, and a pressure responsive device in fluid communication with and responsive to the delivery pressure of the companion pump and arranged to adjust the power of its own associated pump according to the said delivery pressure of the companion pump, a device limiting the maximum delivery pressure of each pump, and wherein the power control device for each pump also has a delivery flow responsive device responsive to the delivery flow of the companion pump and arranged to adjust the power or its own pump according to the said delivery flow, and wherein the power control device of each pump comprises a pilot valve acted on by a spring, the force of which depends on the delivery flow adjustment of its associated pump, said pilot valve having a piston surface in fluid communication with and acted on by a control pressure depending upon the delivery pressure of its associated pump, the power control device of each pump also comprises two restricted orifices connected in series and in fluid communication with the output of its associated pump, and wherein said control pressure is derived from a point between the two restricted orifices connected in series whilst the pressure responsive device comprises a throttle valve adjustable in aCcordance with the delivery pressure of the companion pump and connected in parallel with one of the restricted orifices and wherein the delivery flow measuring device comprises a throttle valve adjustable in accordance with the delivery flow of the companion pump and also connected in parallel with the restricted orifice and the pressure responsive throttle valve.

Claim 4

A power control apparatus for two or more adjustable hydraulic pumps, driven by a common driving means and each having its own power regulator, including a power control device for each pump for continuously adjusting the regulator to maintain a desired power value of the associated pump, and a pressure responsive device in fluid communication with and responsive to the delivery pressure of the companion pump and arranged to adjust the power of its own associated pump according to the said delivery pressure of the companion pump, a device limiting the maximum delivery pressure of each pump, and wherein the power control device for each pump also has a delivery flow responsive device responsive to the delivery flow of the companion pump and arranged to adjust the power or its own pump according to the said delivery flow, and wherein the power control device of each pump comprises a pilot valve acted on by a spring, the force of which depends on the delivery flow adjustment of its associated pump, said pilot valve having a piston surface in fluid communication with and acted on by a control pressure depending upon the delivery pressure of its associated pump, the power control device of each pump also comprises two restricted orifices connected in series and in fluid communication with the output of its associated pump, and wherein said control pressure is derived from a point between the two restricted orifices connected in series whilst the pressure responsive device comprises a throttle valve adjustable in aCcordance with the delivery pressure of the companion pump and connected in parallel with one of the restricted orifices and wherein the delivery flow measuring device comprises a throttle valve adjustable in accordance with the delivery flow of the companion pump and also connected in parallel with the restricted orifice and the pressure responsive throttle valve.

Claim 5

Control apparatus according to claim 1, in which an adjustable throttle valve constitutes said one of the restricted orifices.

Claim 6

Control apparatus as claimed in claim 2, in which the pressure-responsive throttle valve closes as the delivery pressure of the companion pump increases, and the flow-responsive throttle valve opens as the flow of the companion pump decreases, and the arrangement is such that in the regulation range of the power control device the two throttle valves are closed, or offer a maximum restriction.