Patent GB-499405-A (GB)
Title: Improvements in torsional vibration dampers
IPC: F16F15/173
Filed: 1937-06-22
Abstract: 499,405. Torsional vibration-dampers; flywheels. THEGE, E. O. P. June 22, 1937, No. 17332. Convention date, June 25, 1936. [Class 108 (iii)] [Also in Group XXVI] In a torsional vibration-damper comprising one or more inertia masses movable relatively to a vibrating member between stops formed by enclosed liquid cushions and having means for trapping the liquid cushions in terminal positions of the mass or masses, the movement of the mass or masses is regulated by adjusting the position of the trapping means or is varied by imparting a continuous movement to the trapping means, the spaces enclosing the liquid being entirely filled with liquid in all the different positions of the trapping means. In a modified form of the invention, the trapping means is constituted bv the inertia mass or masses which form angularly-adjustable or rotatable control pistons. The torsional vibration-damper shown in Figs. 1, 2 comprises a pair of cylinders 2 fixed to the shaft 1 the oscillations of which are to be damped, each cylinder containing an inertia mass in the form of a double-ended piston 4 adapted on reciprocation to force liquid through passages 8, 10, 9 from one end of the cylinder to the other until one end of the piston overlaps the corresponding end of the passage 8 or 9. In order to vary the free travel of the piston and consequently the rate of damping, a portion of each end of the piston is formed oblique to the longitudinal axis of the piston, and the piston is adapted to be rotated by external means comprising an operating lever 21, Fig. 2, a sleeve 16 slidable axially on the shaft, and a toothed segment 17 engaging a toothed portion 5 of the piston. Flow of oil from the damper back to the supply pipe 15 is prevented by a non-return valve 13. Figs. 3 4 show a second construction in which the inertia mass 27 is mounted on the shaft 25 and has projections 32 each engaging between pistons 28 29 which have ends shaped similarly and which function similarly to the piston 4, Fig. 1. In this case however each pair of pistons is adapted to be rotated automatically by means of toothed portions 30, 31 on the pistons co-operating with gear wheels 41, 42 fixed to the shaft. In a modification Figs. 5, 6, the rate of damping is varied by means of auxiliary pistons 68 each having obliquely formed ends adapted to co-operate with the open ends 60, 61 of passages 58, 59 leading from the piston pressure chambers and each being rotatable by means of racks 69 engaging therewith and movable axially of the shaft by rods 71, 72 and a sleeve 73. In another form of the invention, Fig. 7, the inertia mass 83, shaped as shown, co-operates with vane-like members 81 fixed to the shaft and when moved relatively to the vanes forces liquid through a passage 91 or 92 into one end of one of a pair of cylinders each containing an auxiliary doubleended piston 89 which is moved by the pressure of the liquid to restrict or close the exit passage 92 or 91 in the opposite end of the cylinder. The piston 89 is automatically rotatable by means of gearing and has its ends shaped to vary the rate of damping. In a modification only one auxiliary piston is provided and is adapted to be rotated from the shaft by wormgearing and an adjustable friction or other clutch. Fig. 11 shows another construction in which movement of the inertia, piston-like mass 123 forces liquid through a channel 124 or 125 and an inlet passage 126 or 127, the flow through the outlet passage 127 or 126 being controlled by one of the shaped ends of an auxiliary control piston 132 rotation of which is effected by means of a gear 136 rotatable on axial movement of the helically-threaded portion 138 of a double-ended piston 137. The channels 124, 125 also communicate with the chambers at each end of the piston 137 which is spring-pressed towards one end of the casing, the ends 128, 129 of the channels always being uncovered. Thus, for example, on movement of the mass 123 to the right in Fig. 11, liquid is forced through passage 125, past valve 131, and through passage 129 and presses piston 137 to the left thus rotating piston 132 to uncover the passages 126, 127, thus increasing the free movement of the mass. The auxiliary mass and each control piston may be spring-pressed to normal central position. Various forms of shaped piston-ends adapted to co-operate with the liquid inlet and outlet orifices are shown. The variation may also be effected by manual speed regulation of a motor or by a speed governor. The free travel of the mass may also be increased when a critical speed is reached by means of a control rod co-operating with curved guides, and it is stated that the free travel may also be varied by pneumatic, hydraulic, electric, or other servomotors or by the pressure of exhaust gasses &c. Specification 447,188 is referred to. The Specification as open to inspection under Sect. 91 comprises also constructions in which the control pistons are formed as true cylinders and the orifices in the working cylinders are shaped to vary the rate of damping. This subject-matter does not appear in the Specification as accepted.