GB289453A - - Google Patents

Abstract

289,453. Paetow, P. April 29, 1927, [ Convention date]. Grant of Patent refused. Jacks. -Fluid pressure jacks having' two or more telescopic pistons are provided with means for automatically preventing injury to the jack through continued pumping when the jack has reached its maximum extension. When the outer piston 8 and inner piston 13 are fully extended, the packing leather 17 of the inner piston uncovers one or more apertures 18 in the outer piston. The apertures are connected by grooves 19 in the piston wall, channels 24 in the head, an annular space 26 and channels 27 in the casing 2, to the pump chamber 1, so that if pumping is continued the pressure fluid returns to the pump chamber. A release valve may be provided at the head of the inner piston and is opened when the piston reaches its maximum extension to allow the pressure fluid to escape. Or the release valve may be fitted in the head of the outer piston and have an upwardly extended rod passing through the inner piston and provided with a head adapted to be lifted by the inner piston at the top of its stroke, so opening the valve. The Specification as open to inspection under Sect. 91 (3) (a), comprises also safety means such as an automatic stop valve for the pressure pipe line or a stop device for the pump. This subjectmatter does not appear in the Specification as accepted.