GB533709A - Improvements in liquid pumps - Google Patents

Abstract

533,709. Fuel-injection pumps. DAIMLERBENZ AKT.-GES. Aug. 14, 1939, Nos. 23398 and 23399. Convention dates, Aug. 13, 1938 and June 10, 1939. [Class 102 (i)] In a pump comprising a main piston 2, and an accumulator piston 3, the pistons are formed with machined end surfaces 12, 13 which come into intimate contact at the end of the delivery stroke and thereby expel all air or vapour, accumulation thereof in the system being thereby prevented. Preferably the piston 2 is actuated by a cam 4 and spring 5, and the piston 3 is actuated during the delivery stroke by weak and strong springs 6, 9. The piston 3 is formed with a collar 7 which abuts on the spring 6 and an adjustable stop-nut 8, and the spring 9 abuts on a collar 10 which rests on the cylinder 1. Fuel enters the space 14 through a passage 15, and when the piston 2 rises, the piston 3 is raised in opposition to the spring 6 and then in opposition to both springs 6, 9. The piston 3 then delivers fuel through a passage 16, delivery ceasing when the end surfaces 12, 13 of the pistons come into intimate contact. The double spring 6, 9 may be replaced by an equivalent spring, for instance, a spring of inverted conical shape. When a feed-pump is employed, the inletpassage 15 is provided with a non-return valve and is formed with a wide mouth, the pistons being arranged to separate opposite the mouth at the beginning of the suction-stroke. The arrangement prevents formation of vapour in the inlet passage, particularly when very light fuels are employed. The non-return valve may be omitted. The Specification, as open to inspection under Sect. 91, comprises also-means for placing the space between the pistons in communication with a relief-passage for the purposes of suddenly terminating delivery. This subject-matter does not appear in the Specification as accepted but now forms the subject-matter of Specification 537,772.