Patent GB-982856-A (GB)
Title: Improved gas bearing for strip material
IPC: G03B27/60
Filed: 1962-11-16
Abstract: 982,856. Bearings. INTERNATIONAL BUSINESS MACHINES CORPORATION. Nov. 16, 1962 [Dec. 14, 1961], No. 43374/62. Heading F2A. [Also in Division G2] A gas bearing for a sheet has a pair of gas-bearing elements having opposed parallel surfaces with a gap therebetween into which gas jets are directed from said surfaces. Means are operable, in response to a change in gas pressure due to the insertion of a sheet between the elements, to move one element towards the other element and reduce the gap. In the embodiment, a film-strip 10 is fed by a transport unit to a reading head 14, the gap of the latter being reduced to bring a transducer into focus with the film-strip. The transport unit comprises a left-hand portion 12-1 and a right-hand portion 12-2 and each portion consists of a pair of rails such as 12-1a, 12-1b Fig. 2, each rail having a channel 16 therein to receive the film-strip 10. Jets of air, introduced into the channels 16 by angled orifices 18, can drive the film-strip 10 in one direction, and angled orifices 20 are provided to drive the filmstrip in the opposite direction. The reading head 14, having elements 14-U, 14-L, is supplied with the film-strip 10 via the left-hand portion 12-1 of the transport unit and the film passes to the right-hand portion 12-2 until arrested by a stop 30 which positions a particular microphotograph image at the station 14. The element 14-L is automatically raised so that a lens 32, Fig. 3, is in focus with the image. The element 14-U is supported on an arm 48 by an L-shaped bracket 50 and has an annular chamber 62 which is supplied with air by a tube 66. Air flows from the chamber 62, via orifices 64 which pass through the surface 44 of the element 14-U, to atmosphere so as to exert pressure on the top side of the film strip 10. The lower element 14-L has chambers 72, 74 and is screw-threadedly attached to the lens 32 which is supported in the arm 48 by means of an air bearing; a ring 78 being force-fitted into a bore 80 in the arm 48 and air being supplied to the inner surface of the ring 78 through orifices 84 leading from a peripheral groove connected to a supply tube 82. Air is supplied to the chamber 72 by a tube 88 and is vented to atmosphere through orifices 86 at the surface 46 of the element 14-L so as to exert pressure on the bottom of the film-strip 10. Air is supplied to the chamber 74 by a tube 98 and is connected to atmosphere through the lower surface of the element 14-L by three equispaced holes 92. A piston 94 extends from each chamber 74 into a hole 92 and rests on a surface 96 of the arm 48, the piston being retained in the hole by a flange 112 and being prevented from rotating by a rubber element 114. Air in the chamber 74 forces the piston downwards to lift the element 14-L upwards. Some of the air supplied by the tubes 66 and 88 passes through an opening 70 in the element 14-U and through an opening 100 in the element 14-L which is connected to a chamber 104, the latter being formed between a lower surface 102 of the element and an upper surface 106 of the lens 32. Air is supplied to the chamber 104 by a pipe 108 which is connected by a pipe 110 to a cylinder 174 having a piston 176 thereon. An extension 178 of the piston 176 actuates a switch 138 so as to energize a coil 126. In operation, air is supplied to tubes 66, 88, 82 and 164; the switch 138 is open; the coil 126 is de-energized; and the element 14-L is in its down position. Air is supplied to the orifices 18 and the film-strip 10 is moved into position in the head 14. A low pressure already exists in the opening 100 and in the chamber 104. The entry of the film-strip into the gap causes a pressure build-up which is transmitted through the opening 100, the chamber 104, the pipe 108 and the tube 110, to the piston 174 so as to raise the piston 176 and close the switch 138. The coil 126, now energized, raises a plunger 124 to permit pressurized air, supplied by a pipe 160, to flow, through a valve 120 and a pipe 98, to the chamber 74. The piston 94 moves downwards, the element 14-L is raised, and the lens 32 is in focus. The removal of the film-strip from the station 14 by supplying air to the inclined orifices 20 in the transport unit, causes the opening 100 to be uncovered. This effects a reduction in pressure so that the piston 176 is returned, the switch 138 is opened, the coil 126 is de-energized; and the plunger 124 is returned by a spring 130 so as to cut-off the supply of air to the chamber 74. The latter is exhausted through the pipe 98, which leads to a passage 150 and an outlet 132 in the valve 120, and the element 14-L returns to its down position. Specification 982,855 is referred to.