Distributor pump for injecting fuel into internal combustion engines

Claim 1

An injection pump comprising means for defining a pumping chamber within a housing, a piston mounted for rotary and reciprocal motion relative to said pumping chamber, feed duct means for feeding fuel into said pumping chamber, said feed duct means including first passage means in said housing and second passage means on said piston for delivering fuel to said pumping chamber upon fluid communication being established therebetween through the selective rotary and reciprocal motion of said piston, delivery duct means for delivering fuel from said pumping chamber, said delivery duct means including third passage means in said piston and fourth passage means in said housing for delivering fuel from said pumping chamber upon fluid communication being established therebetween through the selective rotary and reciprocal motion of said piston, said piston including a pair of axially spaced circumferential channels, fifth passage means for placing said third passage means in fluid communication with a first of said pair of circumferential channels, sixth passage means for placing a second of said pair of circumferential channels in fluid communication with said fourth passage means a circumferential wall portion disposed between said first and second circumferential channels, seventh passage means in said housing for placing said first passage means in selective fluid communication with said first and second circumferential channels through the selective rotary and reciprocal motion of said piston, said first circumferential channel and said seventh passage means being in fluid communication during at least a portion of the compression stroke of said piston, and said circumferential wall portion limiting the fluid communication between said first circumferential channel and said seventh passage means to only a fraction of the reciprocal stroke of said piston.