Patent GB-1371841-A (GB)
Title: Reciprocating pump
IPC: F01L25/06
Filed: 1972-01-26
Abstract: 1371841 Reciprocating pumps; compressed gas motors PNEUMO DYNAMICS CORP 26 Jan 1972 3739/72 Headings F1A and F1M The pumping stroke of a reciprocating pump is derived from the movement of the piston of a gas motor included in the pump casing, the suction stroke being obtained from a return spring or the inlet pressure of the hydraulic fluid being pumped. In one embodiment, Fig. 2 gas from inlet 9 passes through a fixed porting tube 22 sealingly received in the hollow piston rod 14 of a reciprocable piston 13. The gas passes through ports 30, 31 into a valve bore 21 formed in the piston 13, which bore contains a movable valve plunger 20.. With plunger 20 in the position shown the gas then passes through ports 37 into the head end 18 of cylinder 12 to move to the right piston 13 and piston rod 14, the head of the latter, which is sealingly received in a pumping chamber 15 forming the pumping means. When the piston 13 and rod 14 have moved so far to the right that trigger port 34 is no longer in contact with gas from inlet 9 and port 30, firstly port 34 and later port 35 vent gas from the previously pressurized space at the right hand end of valve bore 21 through always open vent outlets 38, 10 so that valve plunger 20 moves to the right. This cuts communication between ports 31 and 37, and allows the cylinder head end 18 to vent via ports 37, duct 33 and outlet 10, so that under the action of spring 19 and/or the inlet hydraulic fluid pressure on rod 14 the rod and piston return to the left, until trigger port 35 communicates with gas from inlet 9 and port 30. The right hand end of valve bore 21 is then repressurized firstly via port 35 and then via trigger port 34, so that valve plunger 20 moves to the left to stop the venting of cylinder head end 18 and once more inter-connect ports 31 and 37 to move piston 13 and rod 14 back to the right. Preferably the trigger ports 34, 35, the spacing of which determines the stroke of the pump are spaced fractionally further apart than the valve plunger seals 41, 42 to prevent the valve plunger 20 locking and the pump stalling see Fig.6 (not shown). In a modification Fig.7 (not shown) the valve plunger may be reversed. In Fig. 8 (not shown) porting tube 22 is omitted, inlet and outlet ports (9', 10 ) communicating with annular grooves (43, 44) in the cylinder wall which register with piston ports during piston reciprocation. In another embodiment, Fig. 11 in which the piston 46 contains main and supplemental valve bores 50, 52 each containing a spring loaded valve plunger 48, 51 respectively, in the position shown gas from inlet 70 and pressure groove 71 passes through trigger port 61 and passage 65 to the head end 63 of the piston to move it and piston rod 69 to the right. Once the piston has moved so far to the right that trigger port 62 contacts vent groove 58, the spaces at the right hand ends of the valve bores 50, 52, which were both previously pressurized by gas from inlet 70 and port 62, since these spaces communicate via passage 53, are vented firstly via trigger port 62, groove 58 and vent port 56 and secondly, once valve plungers 48, 51 have moved to the right in their bores 50, 52 under the action of springs 47, 59 via passages 53, 54, 55 and 57, groove 58 and vent port 56. The movement of plunger 48 cuts off trigger port 61 from passage 65 and allows cylinder head end 63 to vent via passages 65 and 66 and vent port 56 so that the piston rod spring and/or the inlet hydraulic fluid pressure can move piston 46 and piston rod 69 back to the left until gas from inlet 70 firstly via pressure groove 71 and passages 57- 53 and later via trigger port 62, repressurizes the right hand ends of the valve bores 50 and 52. The plungers 48 and 51 are therefore moved once more to the left against springs 47 and 59 to again reverse the piston stroke and so complete the pumping cycle. To allow this spring 47 is weaker than spring 59.