Patent GB-598987-A (GB)
Title: Precision antivibration device and methods and machines for assembling same
IPC: B25B27/28
Filed: 1945-07-24
Abstract: 598,987. Testing resilient mountings &c. THIRY, L. F. July 24, 1945, No. 18945. [Class 106 (ii)] [Also in Group XXXII] A method of making a vibration mounting of the kind comprising a pair of rigid members 11, 15, Fig. 1, secured to and separated by a rubber element 10, with a predetermined deflection characteristic, includes the step of displacing a bumper 14 in a permanent manner relatively to the rigid member 11, with which it is associated, in a direction parallel to the direction of deflection of the mounting, into a relationship with the rubber element which gives the predetermined characteristic. In the apparatus shown in Fig. 14, the mounting is supported by its outer rigid member on a lever arm 122 having a fulcrum 121. The inner rigid member 11 is clamped between a lower supporting element 126 adjustable by a lever 129 and a head 157 of a plunger 156, the clamping pressure being applied by a hydraulic piston 171 actuated by control of a valve 182. The bumper ring 154 is carried by a pressing ring 152 secured to the hollow piston-rod 147 of a hydraulic cylinder 144, the pressure of fluid supplied to which is controlled by a valve 183. The arm 122 is loaded by weights 124 and its deflection is measured by a pointer 136 and scale 138. A hand lever 140 in its vertical setting positions a stop 142 to hold the arm 122 against the force of the weights 124. A finger 203 rigid with the lever 140 actuates operating levers 192, 187 of the valves 182, 183 in sequence while also removing the stop 142 from the lever arm 122 so that the plunger head 157 is first lowered to clamp the member 11 and the bumper ring 154 is then pressed on the member 11. Deflection of the mounting against the action of the weight 124 is recorded by the pointer 136 and diminishes as the bumper ring is pressed further on. When the rated deflection is indicated against an index 139, the lever 140 is then swung back to relieve pressure on the bumper ring and release the head 157 from the member 11. The valve 183 may be replaced by a valve operated by an electric solenoid energized on the closing of contacts associated with the pointer 136 and index 139 to enable pressure on the bumper to be automatically released at the correct instant. In a similar construction (Fig. 4, not shown), the hydraulic cylinder 144 is replaced by a manually-operated screw pressure head. In the constructions shown in Figs. 16 and 20, the outer member 12 of the mounting is carried by a ring 255 pivotally mounted on a lever arm 248 which is fulcrumed to the machine frame at 249 and the opposite end of which is supported by a spring 261 which is calibrated, or the loading of which is adjustable by a screw 258, in relation to the rated load of the mounting 10, 11, 12. A screw adjusted plunger 266 co-operates with the plunger of a micro-switch 270 so that an electrical circuit is energized when the arm 248 receives a downward deflection just equal to the deflection of the spring 261 corresponding to the rated load transmitted from the mounting by the arm 248. The bumper ring 296 is pressed on by the plunger 283 of a hydraulic cylinder 276. In operation, an arbor 246 of calibrated length is placed below the member 11 to limit deflection of the latter to that corresponding to the rated load. The bumper ring is pressed on by the plunger 285 and this causes a progressively increasing load to be applied to the spring 261 so that at the correct setting of the bumper ring 296, the circuit of the switch 70 is connected to operate a relay and an associated hydraulic valve, Fig. 22 (not shown), thereby releasing pressure to the cylinder 276. A hand-operated electric switch is provided in conjunction with a further relay and associated valve to apply pressure to the cylinder 276 at the commencement of the operation. Pressure to the cylinder 276 may alternatively be cut off by manual control when an indicator lamp is lighted by operation of the micro-switch 270. In a modified construction, Fig. 16, the arm 248 is limited in upward movement by a stop so that it is not moved by load applied by the mounting until the rated load is reached. The construction shown in Fig. 25 is used in conjunction with a mounting in which the bumper ring is formed by the flanges 376, 377 of the outer rigid members 372, 373 of the mounting. The rated load is applied by the weights 402 acting on a lever arm 399 fulcrumed in ball bearings at 400, and a plunger 391. The corresponding deflection of the mounting is measured by a dial indicator 410, the plunger 411 of which bears on the arm 399. The bumper flange 377 is pressed into the rubber element 375 by pressure of the rubber against a supporting ring 388, from a head 387, under action of a rack bar 383 and operating lever 384 until the correct deflection is indicated on the indicator 410, during each reading of which pressure on the lever 384 must be released. A lever 406 operates a stop 404 to bear the weight 402 when the machine is not in operation. In a simpler form of apparatus, not shown, the desired characteristic is judged by the deflection of a dial indicator gauge, the plunger of which is deflected by a lever in contact with the free surface of the rubber element which progressively distorts as the bumper ring is driven on the inner rigid member. The bumper ring may alternatively be spaced from the rubber element, the correct spacing being estimated by the insertion of feeler gauges between the edge of the ring and the free surface of the rubber.