Patent GB-1048648-A (GB)
Title: Improvements in and relating to pressure compensating devices
Inventor: ADAMS CECIL EDWIN
IPC: F15B11/05
Filed: 1963-08-23
Abstract: 1, 048, 648. Fluid pressure servomotor systems. BRAKESHOE INTERNATIONAL S.A. Aug. 23, 1963, No. 33522/63. Heading G3P. A pressure compensating device 11, Fig. 1 adapted to control the output of a variable capacity pump 12 connected to the inlet 19 of the device, comprises a sequence valve 21 the outlet of which is connected through a passage 22 and a check valve 27 to the inlet of a relief valve 31 further connected to the change volume mechanism 13 of the pump through two parallel fluid passages 36, 37 containing oppositely acting check valves 39, 42, the arrangement being such that the relief valve 31 opens when the sequence valve 21 is closed, to allow pressure supplied to the change volume mechanism 13 to be relieved. The compensating device Figs. 2-4 (not shown) has an inlet port 71 connected to the pump delivery line 19. If the pressure in the port 71 exceeds a predetermined valve the compensator is operative to supply fluid under pressure through an outlet 196 (Fig. 4) connected to the change volume mechanism of the pump to thereby decrease the pump output. In operation fluid is communicated through a restrictor 73 and bores 76, 87, 96, 100, 101, 109, 308 to the underside of an electrically loaded poppet member 106 arranged to open when the pressure exceeds a predetermined valve. Opening of the poppet 106 allows fluid to drain through bores 112, 102, 132, 133, 134, a groove 123 and a tank port 62, thereby reducing the pressure in a chamber 98 above a poppet 87 which constitutes the movable element of the sequence valve 21. The poppet 87 therefore opens due to the pressure in the inlet port 71 and fluid passes to an outlet groove 84 (Fig. 3) which communicates via a bore 92 with a restrictor 33, a bleed valve 26 and the check valve 27. The check valve 27 biased by a spring 173 is opened and fluid passes to a chamber 193 and flows therefrom through a bore 68 (Fig. 4) and an adjustable flow restricting valve 38. Fluid passing the restricting valve 38 opens the check valve 39 allowing fluid to pass to the outlet 196 to thereby decrease the output of the pump. If a build up of pressure occurs in the bore 68 due to the restricting valve 38, an adjustable pilot relief valve 231 opens due to the pressure supplied through the the restrictor 33 acting on a push-off piston 255. Opening of the valve 231 allows a small flow of fluid to drain through a bore 258 in the push-off piston 255, a chamber 235 and bores 234, 136 to the groove 123 connected to the tank port 62. The main relief valve 31 (Fig. 3) comprises a poppet 126 subjected on its lower side to pressure in the chamber 193 and on its upper side to a spring 128 and to pressure from bore 92 communicated through the push off piston 255 and a restrictor 239. The collapse of pressure on the upper side of the poppet 126 due to the opening of the pilot valve 231 allows fluid in chamber 193 to open the poppet 126 and drain through tank port 62. If the pressure at the inlet 71 starts to drop the electrically loaded poppet 106 closes, thereby closing the poppet 87, which causes the pressure in the bore 92 and hence the pressure closing the relief valve poppet 126; to drain through the adjustable opening 144 of bleed valve 26. The relief valve 126 therefore opens and fluid supplied to the change volume mechanism outlet 196 returns through a bore 194 (Fig. 4) the adjustable opening 178 of a restricting valve 41, the check valve 42 (Fig. 3), the chamber 193, the poppet relief valve 126 to the tank port 62. In Fig.5 (not shown) the electrically loaded poppet 106 of the embodiment described is replaced by an adjustable spring loaded pilot sequence valve, similar in construction and operation to the pilot relief valve 231.