Patent GB-845170-A (GB)
Title: Indexing mechanism
IPC: B23Q16/06
Filed: 1958-09-15
Abstract: 845,170. Machine-tool details; indexing. LITHIBAR CO. Sept. 15, 1958 [April 11, 1958], No. 29538/58. Class 83 (3). Indexing-mechanism for moving a table through an adjustable-angle comprises ratchet- and-pawl means, with a cam follower on the pawl engageable with a cam surface ,and limit means for restricting the radial distance the cam follower may travel along the cam surface, the limit means being adjustable so that the amount of angular movement which the table can make in response to a single cycle of actuation of the pawl can be varied as desired at different points around the circumference of the table. The indexible table 2, Fig. 1, is carried by a base 1 on bearings 17, 23, about an upstanding member 12. A ratchet wheel 4 is secured to the underside of the table, and a rim member 74 is also secured to the table, carrying a number of adjustable stop screws spaced around the rim according to the basic index positions required. A member 36 has a bearing around the pillar 12, and is frictionally braked by spring-pressed pins 37. This member carries an arm 34 having a pivot pin 62 for the pawl 6, Fig. 5. The pawl has ends 31, 32 to engage the teeth of the ratchet wheel, and one end 64 is extended beyond the pivot 62 and carries a pin 68 which engages upper and lower slotted members 111, 112, Fig. 2, of across-head 47, Fig. 7, secured to the end of a fluid-operated piston rod 46 forming part of a piston-and-cylinder device 3. A slidable control rod 52, having an adjustable stop collar 50 engageable by a pin 51 on the cross-head 47, is arranged on the base parallel to the piston rod 46. A cam member 58 on the end of the control rod engages a switch 59, Fig. 1, to stop the return movement of the piston and pawl, and to reverse the piston movement for an immediate new indexing operation, or after a dwell, during which some part of the machine, to which the table is applied, has operated. The arm 33, Fig. 5, of the pawl is arranged between a pair of arms 71, 72, Figs. 1, 2 and 5, which are also pivoted about the pin 62 and are joined together at the outer ends by cam follower piece 73. An extension 81 is also secured to this end of the arms in a substantially radially outward direction, and this has a right-angled upstanding end which engages the outer ends of the adjustable studs 76, Fig. 3, when these come into alignment. Operation.-Movement to the left, Figs. 1 and 2, of piston rod 46 moves the cross-head 47 and pin 68 secured to the pawl. The latter pivots clockwise about pin 62 to release it from the ratchet, and moves around in a generally clockwise direction until pin 51 moves the stop rod to opeiate switch 59. The collar 50 is previously set according to the amount of forward movement required, on rod 46 for the indexing movement. On reversal of the piston rod 46, the cross-head and pawl move in the opposite direction (anticlockwise) and the pawl moves in to engage the ratchet teeth. The table is then indexed in an anticlockwise direction, the movement continuing until the cam follower 73 strikes a pivoted cam block 91 carried on the base. The cam block is forced against the rim 74 of the table, and first acts as a brake to slow up the movement. The extension 81 is drawn in with the wedging movement between the follower 73 and cam surface 95 until finally its upstanding outer end contacts the appropriate stop or limit stud 76. The indexing movement is thus stopped at the point determined by the previous adjustment of the stud.