Patent GB-684551-A (GB)
Title: Improvements in hydraulic pumps or motors
IPC: F04B53/14
Filed: 1945-10-30
Abstract: 684,551. Revolving-cylinder pumps. VON ROLL' SCHEN EISENWERKE AKT.-GES., L. Oct. 30, 1945 [Oct. 30, 1944], No. 28732/45. Class 102 (i) [Also in Group XXIX] A rotable cylinder block is movable over a non-rotary control surface provided with an inlet port and an outlet port and at least one additional port is provided in the control surface which connects the several cylinders successively during their transfer from the inlet port to the outlet port with a space in which a predetermined pressure is maintained by means of a pump or acts through a very light valve which operates instantaneously each time the additional port is connected to a cylinder to connect the latter with the next following port in the control surface. Fig. 1 shows the face of a valve block of a revolving cylinder swashplate type hydraulic pump of the kind in which the end of a cylinder barrel containing cylinders parallel to the axis of rotation of the barrel co-operates with the valve block to control the flow of liquid into and out of the cylinders. The valve comprises a pressure port 10 and a suction port 11. Between these ports are either provided ports 13 and 18 or ports 19. Fig. 2 shows the port 13 connected with the pressure port 10 by way of a passage containing a non-return valve 14. The opening 18 co-operates with a valve which allows the oil from the inlet side to flow into the cylinder as soon as the pressure is substantially reduced in the cylinder. If the alternative openings 19 are used these are connected to pumps. For example an opening 19 can be fed from a charging or feed pump which is used in some cases to place the inlet pipe under excess pressure. In a modification designed to permit reversal of the direction of rotation the ports 13 are arranged to be equidistant from the adjacent end of the pressure and suction ports and as shown in Fig. 6 a ball valve is provided so that the rear side of the non-return valve is connected to whichever port 10 or 11 is under pressure. In another modification the ports 13 instead of being connected to either the pressure or suction ports could be connected each to a separate pump or to sources of liquid under pressure. A single pump could be used, its suction side being connected to one port and its pressure side to the other. Fig. 9 shows a pump 33 which in the case of a seven cylinder pump is driven by a transmission gear of 7:1 ratio from the pump main shaft. The crank is adjusted so that it leaves the dead centre position when one of the pump cylinders has reached a position corresponding to the dead centre position of its piston which is the case when it is located at the middle of the surface between the adjacent ends of the inlet and outlet ports. The crank 34 of the pump 33 could be adjustable or the adjustment of the pump relative to its driving shaft could be effected by longitudinal movements of a pinion 35 with inclined teeth. Alternatively the crank could be replaced by driving gear employing several aligned cams any of which could be selected by sliding movement. Use of driving arrangements of known hydraulic pumps with axially or radially arranged cylinder is referred to. There could be two pumps similar to 33 or one double acting pump in the case of a pump with an even number of cylinders. The pump 33 must be fed with liquid. As a rule a connection to a pressure feed pipe through a non-return valve is advisable. The separate pump could be an adjustable piston pump. Additional liquid may be supplied to or withdrawn from the cylinders directly. The invention is stated to be applicable to radial cylinder machines. A pump comprising a cam actuated plunger may be mounted in the valve block. Also it is possible to use a pump which alternately serves one or other opening 13. This arrangement can be used where there is an uneven number of cylinders. It is possible to increase the spacing between the ports in control surface and obtain the desired quietness of running. The Specification as open to inspection under Sect. 91, contains further details. For example it refers to use of a throttle valve in cases where oil is fed under pressure to the control surface. The throttle valve may be arranged so that it is opened only during the time when its effect is necessary and is closed during the remainder of the time by the rotating cylinder barrel. The additional ports and valve instead of being provided in the port block can be located in the cylinder barrel. It is stated that the source of pressure may be a pressure accumulator. This subjectmatter does not appear in the Specification as accepted.