Patent GB-1105519-A (GB)
Title: Device and method for effecting movement of the press-platens in a multi-platen hot press
IPC: B30B7/02
Filed: 1965-06-11
Abstract: 1,105,519. Multi-daylight presses; toggle presses. MOTALA VERKSTAD A.B. 11 June, 1965 [12 June, 19640, No.24865/65. Headings, B5A, B5P and BSN. [Also in Division D2] A multi-daylight press comprises a fixed, upper platen 1, a movable lower platen 2 connected to the upper platen by toggle linkages 9, 10 and a series of intermediate platens 3 operated by lifting rods it, each of which incorporates an hydraulically operated yieldable device. During the initial closure and opening stages of the press, in which the rods are subjected to high acceleration forces, the devices are not actuated so -that the rods remain effectively rigid and resistant to deformation. During the later stages of the closure, the devices are actuated and the rods become yieldable and can thus absorb any strain imposed upon them by uneven filling of the press from stage to stage. In the embodiment shown in Fig. 2, each yieldable device comprises a cylinder 13 which is pivoted at 23 to arm 9 of a toggle linkage and which contains an upper slidable piston 18 and a lower slidable piston 16, the piston-rod 17 of which is connected by a threaded collar 28 to a rod 11. During the initial stages of the press closure, fluid under high pressure is introduced into spaces 25 and 27 to press the pistons together, thus effectively rendering the rod rigid. During the final stages of the closure the pressures in 25 and 27 are lowered so that the rod may be extended or contracted if either an excessive or insufficient thickness of material is encountered in one stage. After closure of the press, the pressure in 25 is lowered to zero and the pressure in 27 adjusted so that the rods 17 and 11 exert an upward force on each platen equal to the weight of the platen. In this way the weight of the platens, which accumulated weight causes excessive pressure in the lower stories, is counteracted and even pressure maintained throughout the press. After pressing, the rods 11 are again rigidified by introducing high pressure fluid into spaces 31 surrounding a bushing 29, and the press opened. After opening, the pressure in 31 is reduced and the pressure in spaces 25 and 27 returned to their original values in preparation for another cycle. In a second embodiment (see Fig. 3, not shown), the upper piston 18 is omitted and the piston-rod 17 is connected by a pin-and-slot mechanism to the rod 11. During closure and opening the piston 18 is forced hard against the upper end wall of the cylinder 13, and during the pressing the fluid pressure below the piston is decreased to just counteract the weight of each associated platen. In a third embodiment (see Fig. 4, not shown), the rod 11 is slidable through a pressure fluid-operated clamping bushing pivoted to the arm 9. During the initial closure and opening of the press the bushing is forced tightly into engagement with the rod to render it effectively rigid and during the latter part of the closure, and the initial high pressure pressing phase, the bushing is relaxed to allow for change in effective length of the rods. The press is then slightly opened to allow the pressed, mats to cure, which curing is attended with a shrinking of the mats and movement of the bottom press platen. During the curing phase the bushings are again forced on to rods 11 so that the intermediate platens are rigidly interconnected with the bottom platen and move with it independently of their weights.