GB805377A - Improvements in or relating to pneumatic brakes - Google Patents

Abstract

805,377. Fluid friction brakes. BOBST & FILS S.A., J. June 22, 1956 [June 22, 1955], No. 19496/56. Class 103 (1). In a pneumatic braking device for a rotatable element, the latter is coupled by a connecting rod to a piston capable of producing compression of a gaseous mass in a cylinder; the cylinder head being provided with an opening leading to atmosphere controlled by a movable element contained therein and drawn by the escaping gaseous medium against a resilient resistance and which by its displacement progressively throttles the opening leading to atmosphere. In the embodiment illustrated in Fig. 1, a penumatic braking device as disclosed in Specification 555,311 is shown wherein an intermittently rotatable element 1 carrying a crank 7 and connecting rod 8, is arranged to turn in a counter-wise direction while a toothed quadrant 2, engaging therewith and pivoted about pivot 3, oscillates in the direction 6 under the action of a rod connected at 4. During each leftwards stroke of the quadrant 2, the rotatable element remains stationary; the pinion 1 meshing with the quadrant is arranged to transmit rotatory motion to the pinion 1 through the medium of dog-clutch means (not shown) of the character disclosed in Specification 556,971, [Group XVI], a cylinder 10 is pivotally connected at 11 to a crank 12 and is provided with an adjustable port 13 permanently open to atmosphere. In the position shown the cylinder is freely open to atmosphere through passages 14 and 15 in the cylinder 10 and pivot 11 respectively. In the first part of the movement of the rotatable element from the position shown in Fig. 1 in the direction of the arrow 5 the piston 9 moves downwards and the cylinder 10 is moved upwards but there is no braking action since the passages 14 and 15 are still in register; however, when position d is reached and passed, the cylinder 10 continues its upward movement at a progressively increasing speed and the crank 7 again commences its downward movement and the cylinder makes the last stage of its upward movement until position a is reached and the cylinder 10 and crank 12 are in their uppermost positions and the passages 14 and 15 are out of register and compression of the gaseous mass in the cylinder is such as to prevent further movement of the rotatable crank 1. In the specific constructional example of the present invention illustrated in Fig. 2, the orifice 13 disclosed above is replaced by a movable sleeve 17 provided with an orifice 16 mounted in the end of the cylinders 10; the sleeve 17 being held in position by a spring 19; the tension of which may be adjusted by a nut 20 screwed on an abutment screw 21 which in turn limits the axial displacement of the sleeve 17 to the desired maximum stroke. Lateral openings 23 are provided in the cylinder 10 to constitute supplementary air escapement means which can be closed by means of screw in order to modify at will the speed at which compressed gaseous mass will escape from the cylinder 10 upon a downward stroke of piston 9.