Patent GB-514512-A (GB)
Title: Linear indexing mechanism
IPC: B23Q16/02
Filed: 1938-04-05
Abstract: 514,512. Linear indexing mechanism for grinding-machines. COVENTRY GAUGE &. TOOL CO., Ltd., HARLEY, S. J., and OLAH, G. April 5, 1938, No. 10361. [Class 60] [Also in Groups XXII and XX] A linear indexing mechanism comprises a main indexing element, such as a drum 1, having a series of steps, an auxiliary indexing element, such as a lead screw 3, the said indexing elements coacting with corresponding abutments and means being provided to engage the auxiliary element with and disengage the main element from its respective abutment before indexing and to re-engage the main element with its abutment after the indexing movement. The position of the work table 2 to be indexed is determined by the drum 1, having steps 1a, and engaging a roller 12 on a variable ratio main lever 4 pivoted at 10 to the frame. The upper arm of the lever engages at 9 with a main contact roller 8 on the work table. The lever may be disengaged from the table and from the drum, and the table moved by auxiliary mechanism prior to reengagement of the main contact elements 8, 12 with lever 4. The auxiliary mechanism includes a lever 5 pivoted to the frame and engaging at its upper end with a roller 13 on the work table and at the lower end with a roll 17 carried by a nut 18 on a lead screw 3 or a cam connected to the drum by gearing. The main and auxiliary levers are connected by a link 56. The rollers 8, 15 are carried on slides 19, 20 which are simultaneously adjusted by screws 21, 22 driven by gearing from a shaft associated with setting scales to determine the lever arm ratio and hence the table travel corresponding to a step on the drum. The slides 19, 20 are locked by a screw operated taper gib 29. To give initial adjustment of the table 2 a member 33 carrying the slides 19, 20 is mounted on a screw-actuated slide 34. The drum is held in its set positions by an index locking finger 37 engaging a gear 38 on the drum spindle, and controlled by a cam 41 operated by a rack 42 actuated by a hydraulic cylinder 43. An auxiliary index finger 46 is carried by a member 45 which may be operated by a rack 48 and cylinder 49. During the forward stroke of the first rack the cam engages the auxiliary finger and disengages the main finger. The drum is then free to be indexed by the forward movement off the second rack acting through the engaged auxiliary finger, the amount of the movement depending on the stroke of this second rack. During the return stroke of the first rack the main index finger is re-engaged and the auxiliary one disengaged. Finally the second rack performs an idle return movement. To disengage the main contacting elements from the drum to permit indexing the cam 41 carries planetary gears 53 associated with the sun wheel 38 and with a second loose sun wheel 54 which drives a pinion 55 on the lead screw. During the forward stroke of cam 41 the nut on the lead screw is thus moved to operate the auxiliary lever and move the work table out of contact with the main lever. The link 56 operates to swing the main lever and disengage its lower end from the drum, the table position being then determined by the auxiliary lever. During the forward stroke of the second rack 48 the gear 38 transmits motion through the planetary gear to the lead screw so that the table is moved by the auxiliary contacts to an extent corresponding to the number of indexing steps. During the return of cam 41 the auxiliary contacts are cleared and the main contacts re-engaged. To compensate for errors in the mechanism an eccentric roll 6 operates against the plane rear surface of drum 1 and is actuated by adjusting screws 7, one for each step of the drum. The eccentric roll is actuated by a rod 57, one end of which carries a contact member 60 bearing on an adjusting screw and the other end is connected to a lever on the eccentric roll, which is thus adjusted to a setting which corresponds to the setting of the adjustment screw. The cam 41 engages a roll 58 to withdraw the contact member from the screw 7 when the drum is to be revolved. A weight (not shown) attached to the table co-operates with springs 65 in maintaining contact between the drum and the roll 6. Means are provided to disengage the drum and the roll 6 before rotating the drum. Specification 513,688 is referred to.