GB1453918A - Vacuum holding device - Google Patents

Abstract

1453918 Vacuum work-holders T F HALE 5 March 1975 [29 March 1974] 9141/75 Heading B3D A vacuum werk-holder comprises a vacuum wall plate 86, Figs. 1 and 3, mounted on support means 86 and having a front surface against which workpieces are held, the cell plate housing a plurality of ares 76 about which are sealing means 78, conduit means 102 for connecting the areas to a vacuum source and including valve means each of which has a passageway having a valve seat 116 and a valve member 126 movable against the seat to close the passageway, and actuating means for determining when its associated cell area is completely covered by a workpiece and opening the cell area to the vacuum source, the actuating means including means 128 holding the valve member away from the seat and then disengaging the valve member for movement against the seat solely by the movement of air from the cell area when said area is not completely covered. The embodiment shown in Figs. 1 and 3 is arranged for operation in a vertical position (i.e. at 90 degrees to the position shown in Fig. 3) and for holding-a veneer flitch against the seal 78 on the front plate 90 of the work-holder, sharpened pins 94 engaging the workpiece to prevent sliding movement thereof. The front plate is secured to the support means 80 which is in the form of a plate also secured to a base-plate, a rubber sheet 96 being disposed between the plates 80, 82. Cavities 100 in the plate 80 are connected by passageways 102 to a vacuum source and register with cavities 98 in the baseplate 82 connected to a source of compressed air. A valve body 110 associated with each cavity 100 has a passageway 122 in communication with its respective cavity 100 and has opposed valve seats 116, 124 between which is a valve member 126 in the form of a rubber ball. Each valve means is associated with an actuator means comprising a plunger 128 formed by the shank of a screw clamped to the rubber sheet 96. A spring 138 urges the plunger away from the valve ball. When compressed air is supplied to cavities 98, the balls 126 are held by the plungers 128 against the valve seats 124 thus closing the passageways 122, the cavities 100 being evacuated by being connected to the vacuum source. The balls are held against the seats while the workpiece is placed against the work-holder. The compressed air is then disconnected from the cavities 98 so that the springs move the plungers 128 away from the balls. If the cell area is not completely covered by the workpiece, the flow of air from the area causes the ball to close the passageway 122 by engagement with the valve seat 116. If the area is completely covered, the flow of air from the cell area is not sufficient to move the ball against the seat 116 and the ball will drop downwardly to a position shown in Fig. 2 between the seats 116, 124. In another embodiment arranged for use in a horizontal position, the movement of the ball towards the valve seat when the cell area is completely covered is resisted by a calibrated spring.