Fuel injection pumping apparatus

Claim 1

A fuel injection pumping apparatus for supplying fuel to an internal combustion engine, comprising a rotary distributor member (10) housed in a body part (11) and adapted to be driven in timed relationship with an associated engine, a pair of plungers (20, 21, 47, 48) slidable in the bore, cam means (19) for imparting inward movement to the plungers, passage means (24, 25, 27) for feeding fuel displaced by the plungers during inward movement thereof to outlet ports (26) in turn and for supplying fuel from a source (30) of fuel under pressure to effect outward movement to the plungers, and valve means defined by said plungers, characterised in that one of said plungers (20, 47) defines a plunger bore (31, 49) in which is slidable a piston (33, 51) integral with the other plunger (21, 48), the inner ends of the plungers and the annular space defined about the piston (33, 51) and bounded by the bore (22) in the distributor member, defining a pumping chamber (23) from which fuel is displaced to an outlet (26) during inward movement of the plungers, port means (34, 50) formed in the wall of the plunger bore, through which fuel can escape from said pumping chamber (23), and a reduced portion on said piston (33, 51) adjacent the plunger, said reduced portion defining with the wall of the plunger bore (31, 49) a flow path (36) from said pumping chamber (23) and which is opened to said port means (34, 50) at a predetermined relative position during the inward movement of the plungers.

Claim 6

An apparatus according to any of Claims 1 to 3 characterised in that said passage (35) communicates with a spring-loaded relief valve (60) which is responsive to a predetermined pressure in said passage (35) to spill fuel therefrom to a low pressure return line (62).