Improvements in pneumatic fluid pressure motors particularly suitable for wind-screen wipers

摘要

620,474. Engine valve gear. FABRICA ITALIANA MAGNETI MARELLI. March 17, 1942, Nos. 3540 and 3541. Convention dates, March 18, 1941, and June 4, 1941. [Class 122(ii)] In a pneumatic fluid pressure motor comprising a pair of connect e d differential pistons 5, 6 having packing rings 8, 9 and in which fluid is supplied to the working face of the small diameter piston 5 continuously but to the piston 6 only during its working stroke, admission of fluid to and its exhaust from the large diameter piston cylinder 3 is controlled by a pair of valves 16, 17 seated in the pistons and actuated at the ends of the working strokes by their abutment against the cylinder ends. In operation compressed air entering the cylinder 2 by a conduit 4 forces the pistons 5, 6 forward with the valve 16 seated but the valve 17 unseated so as to allow exhaust from the cylinder 3 to traverse chambers 21, 27, an orifice 28, a space 9, and an orifice 30 to atmosphere. On the valve 17 closing and the valve 16 opening at the end of the forward stroke, compressed air is admitted to the cylinder 3 through a chamber 20, an annular space 15 and a conduit 31. A shaft 13 of a driven member e.g., a windscreen wiper, is geared to the connecting rod 7 by a rack 11 and a toothed sector 12. In a modification air is exhausted from the space 29 along a helical groove cut in the surface of the shaft 13, and the pistons are guided by means of pivoted rollers.