Control valve for prime mover speed control in hydraulic systems

A hydraulic valve assembly (10) comprising:

• a housing (11) forming a first flow path (21, 25) for communicating hydraulic fluid from a hydraulic pump (17) to an operational hydraulic cylinder (16);
• a spool (12) forming a spool bore (41) and an output signal port (60) from which a hydraulic pressure signal is transmitted to control the speed of a prime mover that drives the hydraulic pump (17), the spool (12) and the housing (11) forming a second flow path (20, 38, 55, 56) in communication with said output signal port (60);
• a reciprocating valve member (42) disposed in said spool bore (41), said reciprocating valve member (42) providing at least a portion (47) that is in fluid communication with said second flow path (20, 38, 55, 56);
• wherein said portion (47) of said reciprocating valve member (42) is responsive to the hydraulic pressure of said fluid received through said second flow path (20, 38, 55, 56) and the position of the spool (12) to generate a signal from said output signal port (60) to control the speed of said prime mover.

A method for controlling an operational hydraulic cylinder (16), while also controlling speed of a prime mover that controls a hydraulic pump (17) to control hydraulic supply pressure and flow, the hydraulic method comprising:

• receiving hydraulic fluid from the hydraulic pump (17) at a control valve (10) having a work port (14), a signal port (15) and a first valve member (12) which controls flow of hydraulic fluid to the work port (14);
• supplying hydraulic fluid to the operational hydraulic cylinder (16) from the work port (14) on the control valve (10) when the control valve (10) is in one of three positions;
• diverting a portion of the hydraulic fluid from the hydraulic pump (17) through a second valve member (42) within the first valve member to said signal port (15) on the control valve (10) when said control valve (10) is in said one of three positions to transmit a hydraulic signal to control the speed of the prime mover which is driving the hydraulic pump (17) to maintain supply pressure from said hydraulic pump;
• moving a single control member to place the control valve in said one of the three positions to supply hydraulic fluid to the operational hydraulic cylinder (16) from the work port (14);
• and
• generating said hydraulic signal from said signal port (15) to control the speed of the prime mover in response to the movement of said single control member to said one on the three positions.