Patent GB-724228-A (GB)
Title: Improvements in or relating to pneumatic gauges
Inventor: BOOSEY FREDERICK ROBERT
IPC: G01B13/08
Filed: 1953-06-30
Abstract: 724,228. Linear-dimension gauges. SIGMA INSTRUMENT CO., Ltd. June 30, 1953 [July 1, 1952], No. 16577/52. Class 106 (2). [Also in Group XXIX] A measuring head for a pneumatic gauge comprises a measuring anvil connected to a needle valve so that measuring movement of the anvil causes movement of the valve whose needle part is located in a jet and is shaped so that when the anvil is moved the escape area between the needle part and the jet varies directly with the movement of the anvil. In the embodiment described a measuring head for a pneumatic gauge comprises a floating member 56, hinged to a base member 54 by blade springs 55, and a lever 60, with sapphire platens 69, 70, supported by a shaft 59 carried by ball-races 58 between the cheeks 57 of a U-shaped bracket 57A secured to the member 54 by a screw 61 and pins 62. Clockwise movement of the lever 60 is limited by a block 87A extending from the member 54 and the floating member 56 is urged downwards by a spring 66 attached to an arm 67 thereof and to an anchorage 64 carried by a transverse bar 63 connecting the cheeks 57. Downward movement of the floating member 56 is adjustably limited by a screw 6 with locknut 7. The lower end of the member 56 has a block 68 for removable engagement with an anvil 3 co-operating with a stationary anvil for gauging linear-dimensions. A knife element 72 carried by a spring strip 73 clamped to the floating member 56 has a knife edge 71 bearing on the platen 69 contact being maintained during upward gauging movement of the anvil 3 by a spring 82 pressing down on a needle valve 78 whose lower end 77 bears on the platen 70. The needle part 86 of the valve 78 is of paraboloid form and co-operates with a circular jet 85 fed with air under pressure from the pneumatic gauge system of Specification 724,205, the air eventually escaping to atmosphere through a grill 98. The transmission ratio between the lever system 60 may be adjusted by turning a screw 74 to vary the point of contact between the knife edge 71 and platen 69 between the limits 1: 1 and 2: 1. The jet 85 is disposed in a body member 79 in which the valve 78 moves and the member 79 may be adjusted vertically a few thousandths of an inch by a screw 81 in a tapped hole bearing on the upper part of the bracket 57A. The base member 54 is clamped to a base-plate 50, used for securing the gauging-head to a machine, e.g. to a rail thereof, the stationary anvil being carried by another such rail, clamping being by means of machine screws 53 passing through slots 52 in recesses 51. Adjustment of the base 54 with respect to the plate 50 may be effected by turning the head 88 of a hollow rod 87 fitting in the base 54 with an eccentric part 89, a turning fit in the plate 50. After adjustment the parts are locked by tightening a head 91 to draw a shaft 90 down on to the plate 50 through a nut 93. Owing to the paraboloid form of the needle valve 78 movements of the gauging anvil 3 are linearly related to the movement of the indicator in the vertical tube of the pneumatic gauge and if several dimensions are to be gauged, the several tubes may be placed side-byside with two horizontal lines to indicate the tolerances, compensating for any differences in the tolerances allowed by suitably choosing the size of the paraboloid needle in each gauging- head and/or by adjusting the transmission ratios of the lever systems 60.