GB665740A - Improvements in or relating to piston and cylinder assemblies - Google Patents

Abstract

665,740. Pistons. OLAER MARINE. Dec. 30, 1947 [Sept. 28, 1946], No. 34805/47. Class 122(i). [Also in Groups XXVIII and XXIX] In a piston and cylinder assembly the piston is formed with an extended portion operating in the same cylinder and having a diameter slightly less than that of the piston so as to have a loose fit in the cylinder and the extended portion is formed with an annular groove adjacent the working face of the piston and communicating with the cylinder at that side of the piston remote from the extended portion whereby any fluid leaking around the extended portion into the annular groove is prevented from leaking between the piston and the inner cylinder wall when the piston is at rest. High hydraulic or pneumatic pressures may be employed. Fig. 2 shows a fluid pressure jack in which a reduced portion 3 is separated from a main portion 21, of a piston 1, by a groove 5. The groove is connected with the exhaust side of the piston by diametrically opposite channels 4, one only of which is shown. It is stated that the arrangement prevents the piston sticking to the cylinder wall due to destruction of an oil film between the piston and cylinder by radial forces occurring with operation at high pressure. Fig. 7 shows a control valve having pistons 12 with reduced portions 3 and' grooves 5 the grooves being connected to an axial passage 14 by radial passages 13. The valve is connected to exhaust at 16. Fig. 5 (not shown) comprises an arrangement in which, a piston, similar to that of Fig. 2, is used as a balancing piston for a manually operated spring loaded ball valve. The pistons can be of circular, ellipitical, rectangular, hexagonal or other cross-section.