GB830478A - Improvements in or relating to self regulating reciprocating piston pumps - Google Patents

Abstract

830,478. Swash plate pumps. RECHERCHES ETUDES PRODUCTION R.E.P. March 15, 1957 [March 15, 1956; April 12, 1956], No. 8694/57. Class 102(1). In a swash plate pump in which pistons 11, Fig. 1, are reciprocated in cylinders 2 of a stationary cylinder block 1, liquid enters at 10 to a chamber 9 and passes to the cylinders through a semi-circular slot 33, Fig. 3, of a rotating plate 32 fixed to the drive shaft 13 of the pump and an axial passage 31 acting as an inlet orifice. The plate 32 is so arranged with respect to the swash plate that the slot 33 allows liquid to flow to each cylinder during the whole of its suction stroke. Liquid is delivered from each cylinder through a lateral passage to a chamber 35 containing a non-return valve and thence through passages 39 to a chamber 40 where it passes to the pump outlet 42. Arranged on the valve plate 32 on the opposite side to the slot 33 are a plurality of orifices 43 1 , 43z ... which are connected by passages 44 1 ... to orifices 45 1 , 45z ... of axial bore 46, the orifices 45 1 , 45 2 ... being arranged helically over the bore. In the bore 46 a slide 47-48 is urged to the right by a spring 51 against a differential piston which is normally held in the position shown by a tap 54 under the influence of spring 55 in which position the hollow portion 48 of the slide 47-48 covers the orifice 45 1 45 2 , ... One of the chambers 35 permits liquid at delivery pressure to pass through passage 57 to chamber 58a and acts on the differential piston 52. When the delivery pressure exceeds a predetermined value the piston 52 is urged to the right and allows the slide 47-48 to move to the right and uncover the first orifice 45 1 and at the beginning of the delivery stroke of each pump piston liquid is bypassed through orifice 31, orifice 43 1 passage 44 1 and orifice 45 1 to the bore 46 where it flows through passages 50 of the slide portion 48 to the inlet chamber 9. Should the delivery pressure still increase the slide 47-48 moves to the right due to further movement of piston 52 and opens orifice 45z and so on. In a modified form the orifices 43 1 , 43z ... pass right through the plate 32 and a segment in contact with the plate 32 and rotating with it is subjected to an angular displacement with respect to the plate in response to an excess delivery pressure and is provided with apertures which partial overlap the orifices 43 1 , 43 2 ... in turn the arrangement being such that as one orifice is partial overlapped by an aperture the previous orifices remain overlapped by their corresponding apertures. The number of orifices 43, is dependent upon the form of the inlet orifice 31 the condition being such that during the discharge stroke the inlet orifice 31 is always in communication with one of the orifices 43 1 , 43 2 ....