Patent GB-824945-A (GB)
Title: Improvements in or relating to high pressure hydraulic pumps or motors
Inventor: BOWERS ERIC HIDER
IPC: F16J15/34
Filed: 1956-05-10
Abstract: 824,945. Stuffing-box substitutes. DOWTY HYDRAULIC UNITS Ltd., and THOMA, O. May 1, 1957 [May 10, 1956; Sept. 18, 1956], Nos. 14616/56 and 28524/56. Class 122 (5). [Also in Groups XXVIII and XXIX] An annular seal 37, Fig. 5, of metal or other hard material for sealing the balancing cylinder 33, Fig. 1, of a pump or motor of the revolving- cylinder swash-plate type in which the cylinder block 1 rotates on a valve plate 22, is forced by hydraulic pressure in the balancing cylinder 33 against an abutment face 38 secured by a rod 34 to the valve plate 22. Pressure acts against the abutment 38 over a small area 42 of the seal 37 to provide a substantially liquid-tight seal whilst permitting relative rotation between the seal and the abutment face 38 on an enlargement 35 of the rod 34, forming with the seal 37 the balancing means; this is located in a coaxial extension of the balancing cylinder 33 of enlarged bore 36. The seal 37 has a wall portion 39 which is a close fit in the cylinder 33 and a reinforcing ring 41 which carries the seating 42, the inner edge of which is of a slightly smaller diameter than that of the cylinder 33 whilst the outer edge extends into the enlarged bore 36. The ring 41 has a recess 43 to reduce the area of the sealing surface 42. The dotted lines on Fig. 5 show the differences in the diameters of the differential pressure areas required to urge the member 37 into sealing engagement with the face 38 with a minimal resistance to rotation. Pressure is admitted to the balancing cylinder through non-return valves located in passages communicating through a filter with the central bore 54 of the rod 34 and with the inlet and outlet ports 23, 24 of the pump. The filter, of the permanent-magnet bar-type, is located at the entrance to the bore 54. The space within the enlarged bore 36 is connected to the lowpressure side by a small clearance around the balancing means 35 so that a pressure gradient exists across the seating 42. The high pressure acting radially on the walls 39 of the seal 37 expands it into liquid-tight engagement with the cylinder 33 thereby exerting a frictional grip on the cylinder wall so that the seal will rotate with the block 1 and the seat 42 will rotate on the face 38. The first Provisional Specification describes also a sealing member generally applicable for use between two relatively rotating members where the seal is held in sealing rotating relationship with at least one of the members by hydraulic pressure, but is hydraulically balanced to obviate heavy pressure against the relatively rotating member. The seating member may have a series of radial grooves leading to a circular channel in the face in contact with the balancing means 35; these sealing faces may alternatively be conical or cylindrical, and the portion of the seal which is intended to grip the rotating member may be peripherally grooved internally or externally to increase its resilience and one or both sealing portions may be spring-loaded. The second Provisional Specification describes also a felt and magnetic filter which is inserted in the highpressure line or lines leading to the balancing cylinder to prevent ferrous or other particles from reaching the sealing faces.