Gear checking machine having a frictionally driven support table and position encoder

Abstract

A gear checking machine for measuring the involute profile and the helical lead of a gear having a support table which is coupled to a base disc that is driven by a friction drive mechanism is disclosed. The friction drive is achieved by means of a small drive wheel which drives the large base disc which has its shaft coupled to the rotatable support table. An encoder having a small drive wheel which is frictionally driven by the large base disc is employed whereby the encoder supplies electrical output signals representative of the degree of rotation of the support table and the gear. Involute and lead checking probes are mounted so they may move in the horizontal and vertical directions, respectively, relative to the gear being checked.

The invention is claimed as follows: 
     
       1. A gear checking machine comprising a frame, indicating means, a table rotatably mounted in said frame for supporting a gear to be checked, sensing means mounted adjacent said gear for supplying a signal to said indicating means which is indicative of the surface variations of said gear, a first shaft, a relatively large diameter circular disc coupled to said table by said first shaft and supported; below said table by said first shaft, first and second small circular wheels each having a diameter substantially smaller than the diameter of said large disc, said first small wheel having its periphery in engagement with the periphery of said large disc, .Iadd.a second shaft coupled to said first small wheel, said second small wheel having its periphery in engagement with the periphery of said large disc, .Iaddend.disc drive means coupled to said second shaft for simultaneously revolving said first and second small wheels, said table and said large disc, sensing drive means for driving said sensing means in synchronism with said table and said disc, a third shaft coupled to said second small wheel and encoder means coupled to said third shaft for supplying output signals which are a function of the rotation of said table. 
     
     
       2. A gear checking machine as claimed in claim 1 wherein said first and second small wheels are of approximately the same diameter. 
     
     
       3. A gear checking machine as claimed in claim 1 wherein said drive means comprises a gear reduction means coupled to said second shaft. 
     
     
       4. A gear checking machine as claimed in claim .[.2.]. .Iadd.3 .Iaddend.wherein said drive means comprises a stepping motor having an output shaft which is coupled to said gear reduction means. 
     
     
       5. A gear checking machine as claimed in claim 4 wherein said first and second small wheels are of approximately the same diameter.