Patent GB-722305-A (GB)
Title: Tire curing press
IPC: B29D30/06
Filed: 1952-12-08
Abstract: 722,305. Moulding tyres. NATIONAL RUBBER MACHINERY CO. Dec. 8, 1952 [Dec. 13, 1951], No. 31110/52, Class 87 (2). A tyre curing press comprises a pair of complementary mould sections between which an uncured tyre carcass is adapted to be positioned and means for relatively moving the mould sections to mating engagement whereat they define a tyre-shaped cavity, a radially expansible diaphragm movable from a position removed from the space between the mould sections to a position extending between them and disposed within the tyre carcass to deform the latter to tyre shape during relative movement of the mould sections to mating engagement, and means for turning the diaphragm inside out for withdrawing it from between the mould sections and out of the shaped carcass. The fixed bottom 'mould section 4 carries a toe ring 6 on the inner periphery of the bottom half cavity 5, which toe ring forms the support for the lower beaded edge of an uncured tyre carcass of " pulley band " shape. Bolted to the base of the machine is a tubular member 30 from which a cylinder 32 extends downwards into a wall. A piston 33 is reciprocable in the cylinder 31 and into the top end of its piston rod 34 is screwed a post 36. Up and down movement is imparted to the press head 12 by crank wheels 9, driven through gearing by an electric motor, and connecting rods comprising dual members 10. There is a crank and connecting rod on each side of the machine, but only one is shown in Fig. 1. The assembly 17 which incorporates the top mould section 19 is threaded into the movable press head 12, the thread giving stroke adjustment. The top mould section 19 carries a toe ring 21 on the inner periphery of the top half cavity 20, forming the support for the upper beaded edge of an uncured tyre carcass. The toe ring 21 is also secured to a bell-shaped stripping member 25 on the end of a piston rod 24 with its piston 23 reciprocable in a cylinder 26 formed in the assembly 17. A tubular diaphragm 41 with beaded top and bottom edges is initially housed in the tubular member 30, Fig. 3. The top edge of the diaphragm is clamped between rings 47, 48, the ring 47 carrying a screwed tubular extension 50 on which a nut 49 is threaded and effects preliminary clamping. Screws threaded through the nut 49 bear on the ring 48 and effect final clamping. The bottom edge of the diaphragm is clamped between rings 38, 39 by bolts. The ring 39 is held on the post 36 between a collar 43 thereon and a split collar 44 clamped on the threaded upper end of the post. The ring 38 is tapered to fit in a recess in the stripping member 25 when the press closes. With the press open and the moving parts in the positions shown in Fig. 1 an uncured tyre carcass is inserted and supported on the toe ring 6, which has previously been treated with an anti-sticking compound.'The sequence of operations is then as follows, automatic electric timing means being used where required in known manner: (i) Fluid, e.g. compressed air, is admitted under the piston 33 to lift the diaphragm out of the member 30 into the uncured tyre T, Fig. 5. (ii) Motion is imparted to the cranks 9 to lower the press head 12, the stripping member 25 engaging the ring 38 and the toe ring 21 engaging the upper beaded edge of the uncured tyre. (iii) As the press head continues to descend superheated water under pressude is admitted to the inside of the diaphragm 41 which is caused to bulge the tyre carcass outwards, Fig. 6. (iv) When the press has closed, Fig. 7, the tyre carcass is held against the surface of the mould cavities 5, 20 (which have tread-forming configurations) by the pressure exerted by the diaphragm 41 while curing is effected. (v) The press head 12 is raised again, set pressure being maintained under the piston 33 and pressure being maintained in the diaphragm so that the edges of the cured tyre move apart again, resulting in stripping the tyre from the mould surfaces. As the press head continues to rise the lower edge of the tyre clips away from the toe ring 6 because of its anti-sticking coating (vi) Air pressure is released from below the piston 33 and admitted above it, causing the diaphragm 41 to be stripped from the tyre and turned inside out to re-enter the housing 30, Fig. 9. (vii) Compressed air is admitted above the piston 23 and the stripping member 25 moves downwards to free the tyre from the toe ring 21, a conveyer or platform being introduced between the mould sections to catch the tyre. The operation may be modified by lowering the press head slightly, so causing the uncured tyre to bulge outwards, before admitting pressure below the piston 33. The piston is then raised, while superheated water is admitted to the inside of the diaphragm which is progressively laid against the inside of the tyre carcass, the operation then continuing as before. Also, if desired, the cured tyre may remain in the bottom mould section upon opening the press. The relative positions of the toe ring 6 and the diaphragm clamping ring 48 may be adjusted to accommodate mould sections 4 of different thicknesses by rotating the clamping assembly relatively to a threaded member 53, with which a threaded sleeve 52 extending from the ring 48 engages. The member 53 is slidable in a housing surrounding the member 30, but keyed against rotation. To provide access to the wrenchengaging recess in the ring 48 for the above adjustment, compressed air is admitted through a port 56, so raising the clamping assembly, with the sleeve 53, locking pins 54 also rising clear of notches in lugs spaced round the member 30. When the assembly drops back again after the adjustment, on release of the air pressure, the ring 48 becomes locked in the its new position. The means clamping the bottom edge of the diaphragm may be adjusted for height by screwing the post 36 in or out of the piston rod 34 and tightening the collar 44 against turning. Heating means are incorporated in the top and bottom mould sections, which respectively carry heat shields 22, 7 which form a closed chamber, when the press is closed, to reduce heat losses. Instead of the diaphragm being moved by a piston and cylinder device a member may be projected downwards from the press head to grip it and pull it upwards. Linkage or the equivalent may be associated with the diaphragm head rather than the piston and cylinder assembly, and lazy-tongs may be used to reduce the depth of or to eliminate the necessity for, a well beneath the machine.