GB681005A - Hydraulic driving means for racks - Google Patents

Abstract

681,005. Ratchet gearing. HUMPHREYS & GLASGOW, Ltd., and HOBBS, A. F. May 18, 1950 [June 23, 1949; July 14, 1949], Nos. 16752/49 and 18642/49. Class 80 (iii). [Also in Group XXIX] A toothed member 15, Fig. 1, driving a rack 16 is reciprocated by two coaxial hydraulic main rams having cylinders 13, 12 and the driving member 15 is urged by hydraulic means e.g., auxiliary rams 22, 21 into and out of engagement with the rack 16 when the main rams are substantially stationary. The member 15 is slidably mounted in a housing 14 integral with the main ram plungers, and is displaced radially to and from the rack 16 at the beginning and end of the working stroke of the main rams by an eccentric 17 rotatable in an arm 35 pivoted to the member and actuated by the rams 22, 21 through a lever 23 and coupled shafts 19, 18. In operation liquid under high pressure is first supplied through a conventional hydraulic reversing valve (not shown) to the ram 22 to effect engagement of the members 15, 16 whereupon a bell crank ]ever 24 opens a valve 25 to supply high pressure liquid to the main ram cylinder 13 to effect the working stroke; the cylinder 12 being exhausted through a poppet valve 26 into a header or tank forming a low pressure reservoir. The return stroke is effected on operation of the reversing valve to exhaust cylinders 13, 22 and valve 25 to drain, and high pressure is supplied to cylinder 21 to disengage the members 15, 16 whereupon the lever 24 opens the valve 26 to supply low pressure liquid to the cylinder 12. In a modification the driving ram cylinder 13 is of smaller diameter than the return ram cylinder 12, and on the return stroke the cylinder 12 instead of being supplied with low pressure is put into communication with the cylinder 13 by an auxiliary valve actuated by the shaft 19. In a further modification fluid is supplied through a main reversing valve 36, Fig. 12, to the cylinders 12, 13 and through ducts 37, 38 to the auxiliary rams simultaneously. Ports 20a, 20b throttled by plungers 19a, 19b restrict the initial movement of the main rams at the start of the working and return strokes until the auxiliary rams have effected engagement and disengagement of the driving member. In a further modification wherein fluid is supplied to the main auxiliary ram cylinders simultaneously, a separate throttling unit actuated by the driving member restricts fluid flow to and from one cylinder only at the end of each stroke.