Patent GB-617801-A (GB)
Title: Improvements in or relating to presses, particularly for vulcanizing
IPC: B29D30/06
Filed: 1946-09-26
Abstract: 617,801. Vulcanizing tyres. McNEIL MACHINE & ENGINEERING CO. Sept. 26, 1946, No. 28781. Convention date, April 11. [Class 87 (ii)] A tyre-vulcanizing press with a two-sectioned mould which is opened by moving one section away from the other has a safety device to prevent the tyre bursting if the internal pressure accidentally remains in it when the mould is opened, based on the principle that lost motion introduced between the mechanism for opening the mould and the movable mould section will be taken up when the mechanism starts to open the mould if there is no residual internal pressure, and comprising : a feeler having spring action when moved in one direction but operable when moved in the other direction to open a switch and so arrest the movement of the mechanism, a striker which will make contact with the feeler if the lost motion is not taken up, and adjustable mountings for the feeler and striker, said feeler and striker being located near the connection between the opening mechanism and the movable mould section. In a preferred form a control switch box 30 is attached to a fixture on the movable mould section and an operating plate 35 is secured by clamping bolts 38 to the toggle arm of the operating mechanism which is pivoted at one end to a shaft 21 on the movable mould section, the pivotal connection having clearance between the shaft and the bearing 18. The striker 34 is press fitted into the operating plate 35 and therefore follows the movement of the toggle arm, and has a knife edge at its forward lower edge. The feeler 45 is a plunger with its upper end cut away to present a knife-edge opposed to that on the striker, and is slidable in the vertical arm of an angular lever arm 48 and urged upward by a spring 52, the lever arm 48 being press fitted on a shaft 60, in the base of the housing 30, on which is mounted an arm 65 restrained by a spring 70. If there is no residual pressure in the tyre when the press starts to open the tip of the striker 34 follows the chain-dotted line S in Fig. 3 as the toggle breaks and then rises by the amount P as the lost motion is taken up (i.e., as the clearance between the shaft 21 and the bearing 18 is transferred from below the shaft to above it) and continues above the edge of the plunger 45 without touching it. The effect of residual pressure in the tyre is to keep the bearing 18 in contact with the bottom of the shaft 21, so that the rise P cannot take place and the striker meets the feeler (see Fig.7), which is rocked and causes the arm 65 to operate a pushbutton switch 80 and stop the opening mechanism. To adjust the feeler so that it will protrude sufficiently into the path of the striker a set screw 55 is provided which bears against a shoulder 54 cut in the side of the plunger 45. A means for setting the device so that the striker 34 approaches as closely as possible to the plunger 45 before the rise occurs is given by a flat 74 on a rotatable stop pin 72. Adjustment is made to this setting by turning the pin 72 so that the lever arm 48 may be brought to meet the flat 74 by depressing the arm C and then loosening the clamping bolts 38 and moving the plate 35, as permitted by arcuate slots 40, till the striker and feeler touch, the bolts 38 being then tightened and the pin 72 turned so that the setting is imposed. The pin 72 is prevented from turning when set by a small pin 75 lying in a groove in its head, against which it is held by the pressure of a spring below the flange of the head. In another form the feeler 158 is a spring metal strip clamped at its bottom edge to the base of the control switch box 130 and with its upper end reduced to a knife edge which lies in the path of the striker when there is residual pressure in the tyre as the mould is opened and is then moved to actuate a switch and stop the opening mechanism. Rebound of the spring feeler is guarded against by a pivoted counterbalance with an arm that rests against the feeler by gravity. Adjustment is by slots in the base of the control switch box through which the holding-down bolts pass. Specification 543,489 is referred to.