Improvements in self-regulating piston pumps and in particular fuel injection pumps
848,188. Fuel injection pumps. BESSIERE, P. E. Jan. 20, 1959 [Jan. 28, 1958], No. 2133/59. Class 102(1). A fuel injection pump comprises a piston 1, Fig. 1, which divides a cylinder 2 into a pumping chamber 2a and a regulation chamber 2b interconnected by a conduit 14. The piston is mechanically actuated on the pump delivery stroke by any suitable means such as a cam 7 and is acted upon by resilient means such as a spring 6. In operation on the delivery stroke of the piston fuel is delivered from the pumping chamber 2a past non-return valve 5 and fuel flows from the supply past valve 16 to chamber 2b, a non-return valve 23 prevents back flow from the chamber 2b and the delivery is ended by the opening of by-pass conduit 22 by groove 20. On the return stroke fuel is transferred from chamber 2b to 2a through conduit 14 provided with a throttle 3, adjustable by hand or automatically, which brakes the flow of fuel. When the speed of the engine increases above a predetermined value the cam moves a slider 11 to commence the delivery stroke before the piston 1 reaches its lowermost position thus reducing the effective delivery stroke of the piston. Fig. 3 shows an alternative control in which the throttle is replaced by a slide valve 25 actuated mechanically to close the conduit 14 during the delivery stroke of the pump. The valve is urged into an open position by a spring 26 and is attached to a piston member 32 which opens a conduit 31 when the valve is closed and allows liquid to flow into the cylinder 30. During the return stroke of the slider 11 the liquid in cylinder 30 escapes past a throttle valve 27 which delays the opening of the conduit 14 by the valve 25 and thus delays the transfer of fuel from chamber 2b to chamber 2a, thus above a predetermined engine speed the effective stroke of the piston 1 is reduced as above. An extension 17 may be fitted to the upper side of the piston of the same diameter as the slider 9 thus equalising the volume change in the chambers 2a, 2b.