Liquid fuel injection pumping apparatus

Claim 1

A liquid fuel injection pumping apparatus comprising an injection pump for delivering fuel in timed relation to an associated engine said fuel injection pump comprising an inlet port, at least one outlet port and at least one working member adapted to move to draw fluid into and discharge fluid from a working chamber forward in part by said working member, a feed pump having an outlet for supplying fuel to the injection pump, valve means for controlling the output pressure of said feed pump so that it varies in accordance with the speed at which the apparatus is driven, a metering shuttle the excursion of which in a cylinder determines the maximum quantity of fuel which can be supplied to the injection pump, a further cylinder, a piston mounted in said further cylinder resilient means loading said piston to one end of said further cylinder, conduit means communicating said one end of the cylinder with the outlet of the feed pump, said piston acting as a stop to determine the extent of movement of the metering shuttle, a cam profile formed on said cam profile being shaped so that at one extreme position as determined by the resilient means, the metering shuttle is allowed to move to an extent such that an excess of fuel is supplied for starting purposes, the piston being subject at one end to fuel under pressure from the outlet of the feed pump so that as the speed at which the apparatus is driven increases, the piston will move against the action of the resilient means to reduce the excursion of the shuttle, an annular seal member positioned in said end of the further cylinder in which the piston is mounted, the seal member when the piston is at said one extreme position masking a portion of said one end of the pistion to prevent the fuel pressure acting thereon, and latch means for preventing said piston moving to said one extrEme position, said latch means being releasable to permit movement of the piston to said one extreme position in the absence of fuel pressure acting on said piston, the arrangement being such that when the piston is in said extreme position the fuel pressure must attain a higher value to effect initial movement of the piston away from the seal member.