GB631983A - Improvements in or relating to presses for moulding plastic material - Google Patents

Abstract

631,983. Presses for moulding rubber. FIRESTONE TIRE & RUBBER CO. July 2, 1947, No. 17442. Convention date, Jan. 1, 1943. [Class 87 (ii)] In a press for moulding articles from plastic material the upper and lower platens 22, 18 of a moulding unit are hinged together with lost motion on a pin 33 so as to open and close by swinging movement when the lower platen is moved from and towards the upper platen, a pin 21 of fixed position constituting a support for the upper platen and a hydraulic ram 13, pivotally connected at 17 to the lower platen, constituting the sole support therefore and a means for raising and lowering it. The upper and lower platens carry steam heated platens 25, 24 and mould sections 27, 26 respectively. Mounted on the hinge pin 33 is an arm 36 which extends between the mould sections 26, 27 which are recessed to receive it, and projects to form a hand grip 37, and which carries a pair of mandrels projecting on opposite sides of it, which are received in corresponding moulding cavities. A finger 42 projects backwards from the arm 36 at such an angle that, when the platens are fully separated, it engages the rear faces of the mould section 27 and platen 25 and supports the arm 36, with its mandrels, in a horizontal position. Fig. 1 shows a dual press, employing two moulding units disposed back to back and operated by a single ram, the press comprising parallel vertical plates 11 with slots 15 in which slide blocks 14 attached to the ram and with bosses 20 holding the pivot pins 21. The two moulding units are of identical construction. When the upper and lower platens are separated and the arm 36 is horizontal the material to be moulded is placed in the cavities in the mould section 26 and on the mandrels. The arm 37 is placed in engagement with the mould section 27 and retained by a latch 41. The ram 13 is then raised and the press closed. After moulding, the ram 13 is lowered and, because of the lost motion in the hinge, the mould sections initially remain parallel as they separate and, because the arm 36 is held in engagement with the mould section 27, the work is stripped from the mould section 26. As the platens further separate the pin 33 moves in its slots with the result that the rear portion of the arm 36 leaves the mould section 27 and strips the work therefrom. The latch 41 is then released and the arm 36 lowered till it is horizontal, when the work may be removed from the mandrels. The Specification describes in outline an arrangement for raising the ram under low hydraulic pressure to close the platens and applying high pressure during the moulding process.