GB622319A - Apparatus for measuring backlash in gears - Google Patents

Abstract

622,319. Testing toothed gears. FELLOWS GEAR SHAPER CO. Feb. 19, 1947, No. 4890. Convention date, April 4, 1946. [Class 106 (ii)] Apparatus for measuring the backlash of toothed gears by measuring the changes in distance between the centres of pairs of fully meshed gears comprises means for modifying the indications of these changes to take into account the various pressure angles of the teeth of different gears. As shown, a base 1 supports a removable fixture carrying a stud 3 in which the gear W to be tested is mounted, and a carriage 8 adjustable along the base has a stud 7 on which is pivoted a holder 4 having a stud 5 on which a master gear 6 is mounted. A modified fixture can be used when internal gears are to be tested. A bracket 9 in the free end of the holder 4 supports in bearings a conversion shaft 12 having a cam face 13 thereon which is engaged by one end 28 of a bell-crank lever 27. This lever is pivotally supported by a bracket 26 secured to the casing of a sensitive dial gauge 18, and the other end 29 of the lever engages the plunger 21 of the gauge. The shaft 12 can be turned by an indicator knob 14 which co-operates with a scale 16 marked to correspond with the pressure angles of the gears to be tested. The gauge 18 is carried by the carriage 8, and is of the type in which the dial face can be rotated relatively to the pointer 19 and having two further pointers 24, 25 to indicate tolerance limits. A screw 31 and spring means 30 on the holder 4 ensure that the gears are in full mesh. In operation, a second master gear having the same dimensions as the gear W to be tested is mounted in the stud 3, the carriage 8 advanced to mesh the gears, the conversion shaft 12 set according to the pressure angle of the gear to be tested and so change the position of the cam face 13, and the dial face of the gauge 18 adjusted so that the pointer 19 indicates the known backlash of the master gear on stud 3. The gear W to be tested is then substituted for the master gear in the stud 3, the gears rotated, and the movements of the pointer 19 noted. Since the stud 5 is mid-way between the axes of pivot 7 and shaft 12 and the cam face 13 is set according to the pressure angle of the test gear, a direct reading of backlash is given by the pointer 19. By suitably setting the cam face, the apparatus can be used to read directly the change in centre distance between a master gear and a test gear. In a modification, the pivoted master gear holder 4 is connected to an arm by a spring and a distance piece, this arm being pivotally-connected at its other end by a leaf spring mounting to a block on the movable carriage 8. The dial gauge 18 in this case is adjustably-mounted in a slot in the carriage so that its plunger can engage the arm at different distances from the pivot of the latter and so compensate for the different pressure angles of the test gears.