DRUM GP-PADDED 1212794 - Caterpillar

When the engine rotates shaft F (13), drum assembly (16) and valve plate (22) which are spline coupled, also rotate. Piston shoe assembly (139), which is inserted into 9 piston holes around the circumference of drum assembly (16), is pressed against creep plate (8) on hanger (7) by shoe retainer (140).Consequently, when drum assembly (16) rotates, the piston shoe assembly also rotates, and piston reciprocating motion changes the cylinder volume (volume of piston holes), causing hydraulic oil to be sucked in or delivered. (2) Control section operation Pump delivery flow is varied by varying the inclination of hanger (7). This pump has an auto-pressure mechanical servo in which the pump delivery pressure itself is used to change the inclination of hanger (7). Control types of this pump are cross-sensing full horsepower control, negative flow control and high-pressure cut-off control.1. Principle of operation of auto-pressure mechanical servo This mechanical servo uses the delivery pressure to adjust the inclination of hanger (7) to correspond to the position of spool (141). When hanger (7) is in a state of equilibrium, the position of spool (141) relative to sleeve (142) is zero and all throttles A1 through A4 are closed. Now, when the pressure rise spool (141) moves to the left, throttles A1 and A4 open, and A2 and A3 remain closed. Therefore, a delivery pressure is transmitted to chamber Vb, and Va is open to the pump casing. For this reason, hanger (7) rotates in the direction of decreasing inclination angle. Dual lever (35) follows the movement of hanger (7), and sleeve (142) in turn follows the movement of the dual lever, so as the angle of hanger (7) decreases moving sleeve (142) to the left and the openings of throttles A1 and A4 become narrower. When throttles A1 and A4 are closed all the way, hanger (7) stops. Next, when spool (141) moves to the right, throttles A2 and A3 open, while throttles A1 and A4 remain closed. A delivery pressure is transmitted to chamber Va, and chamber Vb is open to the pump casing. For this reason hanger (7) rotates in the direction of increasing inclination angle. As explained above, as the angle of inclination of hanger (7) increases, sleeve (142) moves to the right and the openings of throttles A2 and A3 become narrower. When throttoles A2 and A3 are closed all the way, hanger (7) stops.2. Cross-sensing full horsepower control In previous models of pumps with fixed horsepower control the maximum allowable input horsepower to the pump was half of the engine horsepower, but in this method when the output of one of the pumps is small, the engine capacity cannot be used effectively. Therefore, if the input horsepower to the other pump can be increased within the allowable engine horsepower, it follows that the engine horsepower can be fully utilized. Thus, this pump has cross-sensing horsepower control in which changes in the output of one pump are used to vary the pressure - flowrate characteristics