GB1331931A - Method of and apparatus for checking the form of a concave surface - Google Patents

Abstract

1331931 Testing surface shape JOSEPH LUCAS (INDUSTRIES) Ltd 13 Oct 1970 [22 July 1969] 36802/69 Heading G1M An apparatus for testing the shape of a concave surface comprises a ball ended member 20, a mounting 35 for holding a test piece, a device 23 sensitive to linear displacement extending within the member so as to be engageable in use with a point on the concave surface, means for rotating the mounting about an axis thereof and means for rotating this axis about an axis of the said ball. As described a piston slipper under test is placed in cup 35 of plunger assembly 32. Spring 36 urges the piston slipper into making contact with ball 21 and into contact with the end of plunger 23 of a probe 75 sensitive to axial displacement of the plunger. The output of probe 75 is displayed on a recorder 76. Switch 62 is closed, then switch 61 is pressed to operate the motor to rotate shaft 39 and thus via gear train 40, 29, 30, 31, 34 to rotate the slipper to a desired position, when switch 61 is released. Plunger 52 is pushed in against spring 54 and turned so that peg 55 engages a step in recess 56 to retain the plunger. This action causes the plunger to move member 49 transversely to the axis of sleeve 24, and shaft 39, engaging wedgeshaped member 48, moving it axially of shafts 24, 39 and sliding clutch member 43 on splines 44 against the force of spring 45 into contact with a second clutch member 42. Sleeve 24 and shaft 39 then rotate together and the slipper rotates about the axis of spindle 33 and the axis of sleeve 24 and 39. After a predetermined degree of rotation of shaft 24, the end of a recess 47 in collar 46 engages the peg 55 to disengage it from the step in recess 56, when the plunger moves outwardly under the influence of spring 54 and switches off via switch 77 the motor and via switch 59 the recorder 76. If the surface of the slipper corresponds exactly to the wating end of ball 21 the trace on recorder 76 will be a straight line. For other forms of mating surface, the trace will be characteristic of the surface, to be compared against a reference standard.