GB1346452A - Double acting servomotor - Google Patents

Abstract

1346452 Pistons P BLOK and T J VIERSMA 19 April 1971 [5 Feb 1970] 21393/71 Heading F2T [Also in Division G3] A fluid pressure servomotor system comprises a control valve 28 and a piston 2, the annular clearance 19, 20 between the piston and cylinder being tapered outwardly towards the piston-rods and at their inner end communicating with a groove 21, bore 22, a line 23 to a reservoir 14; and the end sleeves being tapered to provide clearances 10, 15 also communicating with the reservoir. Pressure fluid is continuously passed through the clearances forming a high pressure region at the wider clearance and a lower pressure at the narrower so that fluid pressure exerts a centering action and eliminates coulomb friction. The control valve 28 controls working fluid to the chambers 24, 25 via bores 26, 27 respectively and throttled passages 34, 35 provide fluid to the chambers 24, 25 when the piston is held stationary to compensate fluid leakage to the reservoir. In an alternative embodiment (Fig. 2, not shown) two pistons (41, 42) define working chambers (46, 45) respectively, the fluid leakage to the reservoir taking place through clearances (49, 48) of a member (47) rigid with the cylinder, and also past the pistons (41, 42) and through passages (55). Fluid loss is compensated by passing fluid through passages (62 and 63). Fig. 4 shows a piston having the shape of the clearances reversed to that of Fig. 1 with high pressure fluid being applied at 29 to a groove 38. A similar modification can be made to the embodiment of Fig. 2 (Fig. 3, not shown).