Patent GB-1111599-A (GB)
Title: Improvements in vacuum holders
IPC: G03B27/60
Filed: 1966-01-10
Abstract: 1,111,599. Suction heads. D. F. MUIR. 10 Jan., 1966, No. 1037/66. Heading B8H. [Also in Divisions B6 and G2] Fig. 1 shows a vacuum holder comprising a series of concentric chambers 22, 24, 26, the innermost chamber 26 communicating via a conduit 32 with a vacuum pump 30. Communication between chambers 26 and 24, and 24 and 22, is controlled by respective spring-loaded valves 34, 36. When the pressures in two adjacent chambers are equal, the spring- loading holds the valve closed. When the pressure difference between them becomes sufficiently high, the valve opens, to place the two chambers in communication. The holder itself is a perforated board 14, forming a wall common to all the chambers. If the object being held is smaller than the area of chamber 26, only that chamber is connected to the vacuum pump, the pressure difference between chambers 26 and 24 never being great enough to operate valve 34. If the object overlaps chamber 24, the pressure difference becomes sufficiently great to operate the valve, so that chamber 24 becomes connected to the vacuum pump. Similarly, with chamber 26. Fig. 2 shows the construction of a valve in detail. It comprises two valve follower cylinders 56, the one on the right being shown in exploded view. Within each cylinder 56 slides a piston 54, mounted on a stem bolt 40. This is bolted to the valving member 28, and normally, under the action of spring 50, holds member 38 against the valve body 44, so as to close by sealing the orifices 46 which place chambers 22 and 24 in communication. Cylinders 56 are closed at the rear by a plate 60, which has a pair of bores 64. These open to the rearward side of pistons 54, and also, via bores 66 in the back member 12 to the ambient atmosphere or pressure. Ports 68 forwardly of the pistons open into chamber 22. Thus when in the shut position, cylinder 50 communicates with the atmosphere on one side of the piston, and with the interior of the chamber on the other side. The piston is therefore subjected to atmospheric pressure on one side and to the chamber pressure on the other. As the pressure in chamber 24 is decreased, the pressure differential between chamber 24 and 22 becomes great enough to operate the valve, so placing the chambers in communication, the pump now acting directly on chamber 22 also. When the pressure differential between chamber 22 and atmosphere becomes large enough, the ambient pressure acts, through bores 66 and 64, against the pistons 54 to hold the valves open independently of the pressure difference between the chambers 24 and 22. This relieves the pump 30 from providing the force required to hold the valve open, so allowing it to undertake the load of opening the next valve as required. Figs. (not shown) 3, 4, 5, 6 show modified forms of valve construction. Fig. 7 (not shown) is a further modification, showing the invention as applied to the conveying of continuous sheet material (590) of varying widths, by a perforated cylinder (588). The cylinder has a central chamber (526), to which vacuum is applied, and outer chambers (522). Interconnecting valves (536) act in the same manner as is described above.