摘要 |
An indexing, or positioning, device for a table guided for movement on a base. The positioning device comprises a pair of indexing discs connected via a totalizing transmission with the table to be positioned. Each indexing disc is driven through a differential transmission from a pair of motors, each of which has a brake to lock the motor when it is deenergized. Presettable counters control the motors and a pulse generating device associated with each disc feeds countdown pulses to the counters to stop the disc when a position thereof corresponding to the preset value in the counter is reached. Lost motion in the drive from the positioning device to the table is compensated for by a tensioning drive connected to the table and biasing the table in feed direction during indexing thereof and in the opposite direction at the end of a feed movement thereof. |