GB861754A - Improvements in reciprocating liquid pumps, and in particular in fuel injection pumps - Google Patents

Abstract

861,754. Fuel injection pumps. BESSIERE, P. E. July 18, 1957 [Aug. 14, 1956 ; Nov. 7, 1956 ; Jan. 10, 1957], No. 22748/57. Class 102(1). A fuel injection pump comprises a piston member 5, Fig. 1, loaded by a spring 6 which divides a cylinder 7 into two chambers 7a, 7b whose ends are interconnected by a conduit 9 provided with an adjustable throttle 8, a conduit 15 leads from the chamber 7b to the engine cylinders. A reciprocating piston 2 on its discharge stroke first delivers fuel through conduits 10 and 13 to move a slide valve 12 to close the conduit 9 and fuel is then delivered past non-return valve 11 to the chamber 7a thus moving the piston 5 against the spring 6 until the piston opens a by-pass conduit 17. This movement of the piston 5 delivers the fuel in chamber 7b to the engine cylinders through conduit 15. On the downward stroke of piston 2 the slide valve 12 immediately opens the conduit 9 and the fuel in chamber 7a is transferred to the chamber 7b by the downward movement of the piston 5. As the speed of the engine and hence the speed of reciprocation of piston 2 increases a speed is reached at which, due to the throttle 8, the piston 5 does not complete its downward stroke before the piston 2 starts its upward stroke, thus a " liquid abutment " is formed in the chamber 7a reducing the length of subsequent strokes of the piston 5 and hence the quantity of fuel delivered to the engine cylinders. The adjustment of the throttle 8 to determine the maximum speed of the engine may be controlled by any suitable means, and the throttle may be made from suitable materials to provide an automatic adjustment with changes in temperature of the fuel. To provide for additional fuel to be delivered at low engine speeds a second conduit similar to conduit 9 may be provided opening into the chamber 7a at a point between the bottom of the chamber and the dry-pass 17 as in Fig. 3 (not shown). Alternatively the spring 6 may be replaced by two springs one continually acting on the piston 5 while the other only acts during the first part of the downward stroke of this piston. The slide valve 12 may be actuated to close the conduit 9 either by a second piston moving in synchronism with the piston 2 or by a pressure supply controlled by grooves on the piston 2 acting as valves for this supply. In the embodiment shown in Fig. 6, the piston 2 delivers the fuel directly to the outlet 15 via conduit 27 containing a throttle 28 at the same time fuel is delivered through conduit 31a to move the piston 5a and delivery of fuel from the pump is terminated when the piston 5a opens a by-pass conduit 29. On the suction stroke of the piston 2 fuel below the piston 5a flows back to the cylinder 1 through the throttled conduit 31b, a non-return valve 33 in conduit 27 prevents any flow through this conduit during the suction stroke of the piston 2. The throttle passage 31b acts in the same manner as the conduit 9 above to reduce the downward stroke of the piston 5a above a certain speed by the provision of the " liquid abutment " thus reducing the quantity of fuel delivered by the pump due to the earlier opening of the by-pass 29 by the piston 5a. To provide excess fuel at low speeds a second throttle conduit may lead from between the valve 33 and throttle 28 to cylinder 30 above the piston 5a when in its rest position and a throttle conduit may extend from the cylinder 30 to the cylinder 1 from below the by-pass 29 as in Fig. 7 (not shown). In a further modification the throttled passage 31b may lead direct to the outside instead of the cylinder 1 this conduit being controlled by a slide valve similar to the valve 12 in Fig. 1. Specification 861,753 is referred to.