114 



HANDBOOK OF MECHANICAL DESIGN 



Tension spring 

 keeps bo/rin 

 engagement 



Fig. 205. 



Hand- operated / Projecfion Jnfegral 

 , cam ^ / niin cam engages ^ 



\ ; sloi- in bolf 



Boli 



Bolt 

 Bolt engaged 

 disengaged y ^qo 



Bolf 

 disengaged 



Bolt 

 engaged 



Pivof center 

 locafion 



Swinging loci; boll / Lug 



j^e lease / Cam 



"t^-" Lock boll 



ZA^Hand- 

 operoled 

 lever 



, Xy- Lock-boll' 

 Cenlering lugs-' plole 



Plan 

 Fig. 207. — By using a lock-bolt plate larger than the work, the indexing error is diminished. The swinging lock 

 bolt is released automatically by the spring plunger, which has a predetermined movement, when the hand-operated 

 lever is moved to the left, as shown by the arrow marked Release, and the cam contacts the rounded top surface of the 

 lock bolt. The ratchet is keyed with the lock-bolt plate to the spindle. As the lock bolt is released and the lever is 

 rotated 30 deg. counterclockwise, the pawl engages the ne.xt tooth in the ratchet wheel at X. The lever is then pulled 

 in the direction of the arrow marked Index, the cam moving the lock bolt downward into the next opening in the 

 lock-bolt plate. The plan view of the bolt shows the two centering lugs between which the lock bolt is additionally 

 supported. 



Spring-backed lock boll, 



L ock- boll plale 

 keyed lo spindle 



,-- Groove J 



---Xfe/K 



-Pin 

 -Prong 



^ Plale 



'Indexing 

 handle 



Locked 



Third prong 

 Prong 



Lock-boll operal- 

 ing plale freefo 

 rolale 



Pin 



^Groove F 

 'Lock boll 



Lock- boll plate ~ 



Fig. 208. Fig. 209. 



Fig. 208. — The handle is mounted on the plate and is independent of the lock-bolt plate. As the handle is pulled to 

 the left, the prong pushes against the pin driven into the spring-backed lock bolt, thereby disengaging the bolt. At 

 the same time, the second prong contacts the plate at Z. Both plates then move simultaneously, releasing the lock 

 bolt, which rides on the periphery of the lock-bolt plate, and the bolt falls into the next slot. The handle is then pushed 

 back again, clockwise, contacting the plate at R, upon which a third prong pushes against the pin-seating lock bolt 

 in a locked position. 



Fig. 209. — The plate is indexed through a half revolution in one direction and then back again in the opposite direc- 

 tion. The lock-bolt plate is keyed to the spindle. The lock-bolt operating plate is free to rotate on the spindle. When 

 the indexing handle is pushed counterclockwise, as shown at the right, groove F in the plate forces the lock bolt out of 

 engagement. The pin driven into the plate engages the slot in the plate, thereby lining up groove / with slot K. Upon 

 further movement in a counterclockwise direction, the roller on the bolt may slide into groove / and the bolt may enter 

 slot K. The dashed line in both views show the positions when indexing in the opposite directions. 



