GB874521A - Improvements in reciprocating action liquid pumps and in particular in fuel injection pumps - Google Patents

Abstract

874,521. Fuel injection pumps. BESSIERE, P. E. Dec. 5, 1957 [Dec. 6, 1956], No. 37911/57. Class 102(1). A reciprocating pump in particular for injecting fuel into internal combustion engines comprises a main pump cylinder 1 and piston 2 and an auxiliary cylinder 7, fixed relatively to cylinder 1, containing an auxiliary piston 8 which divides the cylinder 7 into two chambers 7a, 7b the chamber 7a communicating with the main cylinder 1 by conduit 5 having a non- return valve 6, and the chamber 7b communicating with the delivery conduit 12. The cylinder 7 is provided with a by-pass conduit 23 for the chamber 7a, a by-pass conduit 27 and longitudinal groove 28 co-operating with a conduit 26 in the piston 8 for the chamber 7b, and a conduit 14 connecting the chambers 7a, 7b for certain positions of the piston 8, these three conduits being so arranged that the piston 8 opens the two by-pass conduits at the same time as it closes the connection between conduit 14 and chamber 7b, as indicated by the three equal dimensions a. The conduit 14 contains a spring loaded valve 15 and may have a throttle 29. In operation (assuming that the throttle 29 is not provided) on the delivery stroke of the main piston 2 liquid first acts on the valve 15 to close the conduit 14 and then causes upward movement of the piston 8 against an adjustable spring 9 delivering liquid in chamber 7b through delivery conduit 12 until the by-pass conduits 23 and 27 are opened and port 14a is closed. Liquid in chamber 7b is then by passed through conduit 27 and liquid in chamber 7a flows through throttled conduit 23. On the return stroke of main piston 2, piston 8 returns under the action of spring 9 and continues to cause flow from chamber 7a through conduit 23 whilst creating a partial vacuum in chamber 7b until the by-pass conduits 23 and 27 are closed and port 14a of coundit 14 is opened. The piston 8 then returns suddenly (in the absence of throttle 29) to its lower position transfering the liquid from chamber 7a to 7b via conduit 14, valve 15 being open. Some of this liquid is taken up in filling the partial vacuum in chamber 7b and since the volume transferred is constant, the amount delivered from chamber 7b or the subsequent stroke of piston 8 depends upon the height to which the piston 8 has moved on its previous stroke. This distance varies with the speed of the main piston 2. If the speed of the main piston 2 is such that piston 8 does not move a sufficient distance to close the by-pass conduit 23 on its downward stroke before the main piston 2 starts its next delivery stroke, no liquid will be transferred to chamber 7b and consequently no delivery to outlet 12 will occur. If the conduit 14 contains the throttle 29 the piston 8 will not move down suddenly after closing by-pass 23 and when the speed of the main piston 2 reaches a predetermined value a liquid abstract will be provided for the piston 8, as described in Specification 861,754, which further controls the delivery in accordance with the speed of the piston 2. In a modification the by-pass conduit 23 may lead to two throttled conduits controlled by a spring loaded valve moved by the pressure of liquid delivered by piston 2 so that one throttled passage by-pass the liquid on the upward stroke of piston 8 and the other on the downward stroke of this piston. Alternatively the valve may act against a spring loaded member so that the valve first opens the bypass conduit at the commencement of the delivery stroke of piston 2 and with increased pressure starts to close this conduit thus providing an adjustable throttle. A second conduit normally closed by a needle valve may be provided connecting conduit 14, downstream of throttle 29, to chamber 7b above the port 14a, this needle valve being opened to provide extra fuel on starting the engine.