230 



HANDBOOK OF MECHANICAL DESIGN 



TABLE FOR SEQUENCE 

 OF OPERATIONS 



I Press start button 



2 Pump motor starter closes 



3 Pressure switch closes 



4 Spindle motor starter closes 



5 Press feed start button 



6 Feed motor starter closes 



7 Stop button stops all motors 



8 Feed stop stops feed motor 



© 



® 



Sfop 

 buri-on 







@ 



Pressure 

 switch 



® 



Spindle 



moior 



starter 



® 



o 



® 



Feed 

 stop 



Feed 

 start 



Feed 

 motor 

 starter 



Feed 

 motor 



Fig. 462. — Electrical interlocking or sequencing of motors for large milling machine ensures that coolant pump 

 motor is running and pressure obtained before spindle motor starts and that spindle motor is running before feed motor 

 can be started. A master "stop" button dominates all controls. 



Limit switch 

 No. I - 



Limit switct? 

 No. 2 



Fig. 463. — Combination mechanical and electrical torque or load limiting device for control of motor-operated 

 valves, chucks, and clamps. When load becomes sufficiently high to stall wormwheel, the worm sliding on a splined 

 shaft moves axially, similarly to a screw threading through a nut. This movement compresses a calibrated torque 

 spring and opens a limit switch, thereby shutting oif the motor. 



