Patent GB-950598-A (GB)
Title: Improvements in and relating to reciprocating pumps
IPC: F02M41/12
Filed: 1960-04-01
Abstract: 950,598. Reciprocating pumps. P. E. BESSIERE. April 1, 1960 [Dec. 1, 1959], No. 11631/60. Heading F1A. In a reciprocating pump and in particular a fuel injection pump, the pump output is automatically regulated by a slide valve 12 controlling a discharge conduit from the pump chamber 2 comprising ducts 14a, 14b. The valve 12, during the discharge stroke of the pump plunger 3, is urged upwardly against the action of a spring.26 by pressure liquid supplied by an auxiliary pump having a piston 15 constituted by an enlargement of the plunger 3 and during the suction stroke of the pump moves downwardly at a retarded rate, a throttled passage 22, 20 connecting the space below the valve 12 to the auxiliary pump chamber 16. The throttle comprises a manually adjustable member 24 having a control edge 23 and the adjustment of the throttle determines the speed at which the valve 12 will return to its lowermost position against a stop 27 and hence engine speed. As the engine speed increases the return position of the valve 12 will get farther and farther away from the stop 27 so that on subsequent discharge strokes of the pump the distance the valve has to travel before the duct 14a, 14b is opened becomes less and less so controlling the time during which delivery takes place. To obtain over-delivery of the pump at low engine speeds a recess or flat 29 is formed on the piston 15 and this together with an annular recess 30 in the auxiliary pump chamber 16 allows communication between an inlet port 19 and the pump chamber 16 for a longer period of time and until the inlet port 19 is closed upward movement of the valve 12 is delayed and hence delivery cut-off. As engine speed increases the recess or flat 29 becomes less effective so that at high speeds over-delivery practically disappears. Also to effect over-delivery at low engine speeds a groove 35 cut at the bottom of the valve 12 co-operates with a duct 32 controlled by an extension 33 of the throttle member 24. The valve 12 may be rotated to bring the groove 35 opposite the duct 32 and the member 24 screwed inwardly to reduce the throttle opening at 23 and at the same time open the duct 32 to discharge. Pressure beneath the valve 12, as before, takes longer to build up, thus delaying upward movement of the valve 12 and delivery cut-off. As engine speed increases the groove 35 becomes less and less effective and over-delivery practically disappears. As shown, the pump controls the supply of fuel to a number of cylinders, the pump plunger being rotatable as well as reciprocable by means not shown. During pump suction, fuel from an inlet 4 passes through a groove 11, one for each cylinder, an annular groove 10 and passages 9, 8 to the pump chamber 2 and during pump discharge, fuel is delivered through a valved outlet 5, one for each cylinder. A groove 37, and an inclined face 36 may be formed on the valve 12 and on rotation of the valve, the groove 37 may be brought into register with the duct 14b so that the pump chamber 2 is constantly open to discharge whence the engine is under "no load" condition. Also, the inclined face 36 may be adjusted with respect to the duct 14b so that it is opened earlier than would otherwise be the case on the upward stroke of the valve. When the groove 35 is aligned with the duct 32 the duct 14b is located immediately above a point about half way up the inclined face 36 for low engine speeds during starting.