Patent GB-584487-A (GB)
Title: Improvements in or relating to presses, for example, for moulding and vulcanizing tyres
IPC: B29D30/06
Filed: 1943-08-04
Abstract: 584,487. Vulcanizing presses for tyres &c. STEVENS, A. H. (McNeil Machine and Engineering Co.). Aug. 4, 1943, No. 12588. [Class 87 (ii)] If, when the press begins to open, there is still a dangerous residual pressure in the air bag, the said pressure raises the movable half of the press away from its seating on its support (this raising movement being permitted by a slight play, e.g., 1/32nd of an inch, between the movable half and its support) and this raising movement allows an open electric switch to stop the motor which is raising the movable half. The invention is described with reference to a press comprising, Fig. 1, a stationary lower half 2 and a movable upper half 3 mounted on a crosshead 24 carried by a link 30 pivoted at 31 in side links 32. The press is opened and closed by an electric motor 38 via shaft 37, gear 35 and link 33. During the opening movement of the press the link-pin 34 travels from A to B, and during the closing movement (still travelling clockwise) from B to A. Three switches 1, 2, 3 (Fig. 10) are mounted in a housing 50 surrounding the gear shaft 36 and are controlled by a cam on the shaft, and a fourth switch 4 (the "safety" switch) is mounted on a nut 28 secured to the upper end of one of two bolts 20 which are secured to the upper mould half, the weight of which is, during the opening and closing movements, supported by the nuts 28, there being some play at x, Fig. 4. When the press is closed, however (and this is the condition shown in Figs. 1, 4 and 10), the weight of the upper mould half is not supported by the nuts, there being some play at x<1>, between the nut 28 and its washer 29. The switch 4 is, as shown, open, but is closed when the weight of the upper mould half is taken by the nuts, by abutment of a set screw 64 on the washer 29 with the switch operating pin 4a. Fig. 10 shows a circuit diagram for the motor 38, starting and stopping of which is controlled by a main switch 46 operated by a magnet 47. Operation:- When the curing period has elapsed, the timer motor M moves switch 41 to the left. the magnet 47 being thereby energized through "hold-in" switch 2, and the press starts to open. ("Limit" switch 1 immediately drops off the cam to the dotted line position. When the press has opened a little way, hold-in switch 2 also drops off the cam, whereupon if there is no residual pressure in the airbag 5, the weight of the upper mould section is taken by the nuts 28, the switch 4 being thus closed (raised) and an alternative hold-in circuit is formed for magnet 47 through (lowered) switch 2 and (raised) switch 4. If, however, there is enough residual pressure in the airbag 5 to raise the upper mould half, i.e., to keep the weight thereof off the nuts, the switch 4 is not closed (raised), there is no holdin circuit for magnet 47, the switch 46 opens, and the motor stops. If there is a little residual pressure in the airbag, but not enough to raise the upper mould half, the press opens. During curing a green light 71 shows. When the switch 4 is down, a red light 70 shows. The invention may be applied to a press in which the upper half is stationary and the lower half movable, or to a press in which both halves are movable. Specification 543,489 is referred to.