Patent GB-864908-A (GB)
Title: Comparator gage for checking article dimensions
IPC: G01B5/06
Filed: 1958-08-18
Abstract: 864,908. Linear-dimension gauging apparatus. SHEFFIELD CORPORATION. Aug. 18, 1958, No. 26479/58. Class 106 (2). A comparator comprises a work support 15 mounted on a base 14 for rocking movement about an axis 22, and manually actuated adjustment means 30, 31 for rocking the support 15 about the axis 22 to bodily position the work along the measuring axis which intersects the support at a point to one side of the axis 22. The workpiece is placed on a table 15 which can be pivoted about a horizontal axis by means of cams 30, 31 controlled by hand wheels 34, 36. Hand wheel 36 is used to give rough adjustments by means of the cam 31, whilst the cam 30 imparts a finer adjustment. The table 15 pivots on two hemispheres 22 and rests on a pin 27 through which the movement of a lever 26, spring-urged into contact with the cams 30, 31 is transmitted. The gauge head 18, shown in more detail in Fig. 4, is mounted for vertical sliding movement on a column 16. It consists of a gauging cartridge 90, the movable element 92 of which engages a cap 94 supported by the feeler 20, and an assembly 84 supported by spring strips 85, 86 for vertical movement, the assembly 84 carrying the feeler 20. The cartridge 90 is connected to an indicator 21, and the feeler 20 is urged into contact with the workpiece by a bent spring strip 107, the force applied by this strip being regulated by a cylinder 112 which is controlled by a knob 114 and carries projections 115 able to engage various portions of the strip. The head 18 can be raised or lowered by turning a screw thread 42 journalled in the top of the column 16 and can also be raised or lowered in steps (e.g. of one thousandth of an inch) by movement of a hand lever 52. This controls the movement of a shaft 50, journalled inside the column 16, which shaft carries, at its upper end, pawls 75, 76 engaging a ratchet wheel 79 fixed to the screw 42 inside the head 74 of the column 16. Thus repeated movement of the lever 52 from its central position to one side or the other raises or lowers the head 18 in steps. This is particularly useful if a series of objects, such as a set of slip gauges, whose nominal dimensions differ by known steps, are to be gauged. Means are described for adjusting the range of movement of the lever 52 and the movement of the pawls 75 can also be adjusted by use of screws 80. In use, a standard article is placed under the feeler 20 and the gauge head adjusted until the indicator 21 reads zero. The standard is then replaced by the object to be tested. If used in this way, gauging takes place as the feeler 20 moves upwards. In a modification (Fig. 6, not shown) an actuator, similar to a camera cable release, raises the assembly 84 for insertion of the workpiece and gauging takes place as the feeler moves downwards. In this embodiment, to ensure positive contact between the feeler assembly and the cartridge 90, the latter is used in an inverted position. In a further modification, the lever 26 is replaced by a bar clamped at one end and pivoted by means of a reduced portion. Adjustment is effected by moving the point at which it is clamped and by use of the cam 30, the cam 31 not being required.