Patent GB-1179783-A (GB)
Title: Improvements in or relating to Double Disc Grinders and the Control thereof
IPC: B24B37/04
Filed: 1967-02-21
Abstract: 1,179,783. Grinding. LANDIS TOOL CO. 21 Feb., 1967 [24 Feb., 1966]. No. 8152/67. Heading B3D. A double disc grinder for grinding relatively thin workpieces comprises: (i) oppositely disposed abrasive discs movable axially toward and from one another, (ii) guide members for guiding workpieces between said discs, (iii) an incremental positioning means for each disc, and (iv) a single sensing means adapted to be actuated when one of the discs reaches a predetermined position relative to the guide members as a result of advancement by the respective incremental means, such actuation of the sensing means causing simultaneous retraction of said one disc by a predetermined amount and advancement of the other disc by the same amount in order to restore the discs to a substantially central relationship with the guide members. A machine for grinding the opposite faces of very thin workpieces W, e.g. piston rings, has abrasive discs 11, 12 rotated by electric motors 13, 14. The discs are adjustable towards and away from one another through adjusting mechanisms 15, 17 driven by electric stepping motors 16, 18. Horizontally spaced side guides 22 direct the workpieces to move between the discs; vertically spaced guide bars 20, 21 are provided between the discs. A gauge 24 includes a housing 30 to which is secured a resilient diaphragm 31. L-Shaped arms 34, 35 are clamped to opposite sides of the diaphragm so as to pivot about a vertical axis. The free end of the arm 35 has a clamp 41 in which is replaceably mounted a very thin gauge arm 25 which projects in between the discs 11, 12 within the plane of the guide bars 20, 21 and carries a sensing disc 26, of a carbide or other wear-resistant material, opposed to the face of the disc 11 and projecting beyond the guide bars 20, 21. The free end of the arm 34 is opposed to a nozzle 44 mounted in the housing 30, its spacing from the nozzle being determined by an adjusting screw 45. The nozzle 44 is connected to a source of pressure air by a line 27 containing a pressure regulator 28 and a pressure-sensitive switch 29. Air leaves the housing 30 through discharge 48. The housing 30 is mounted in a fixed position. After the workpieces W pass between the discs 11, 12 the thickness is measured and as it approaches the limit of the oversize tolerance a signal is given. Operation.-When the thickness measuring means gives a signal, a switch 50 is closed manually or automatically, resulting in energizing of the motor 18 whereby the disc 12 is advanced one increment; closure of the switch also energizes a counting relay 4CTR and advances it one step. Incremental advance of the disc 12 upon each closure of the switch 50 is repeated until the relay 4CTR counts out, opening contact 4CTR1 and closing contact 4CTR2. Thereafter, closure of the switch 50 results in energizing of the motor 16 whereby the disc 11 is advanced one increment. Incremental advance of the disc 11 upon each closure of the switch 50 is repeated until the disc 11 contacts the sensing disc 26 of the gauge 24 resulting in closure of the pressure-sensitive switch 29. This results in (i) resetting of the counting relay 4CTR, (ii) reverse energizing of the motor 16 to retract the disc 11 a predetermined number of increments towards alignment with the side guides 22 and away from the sensing disc 26, and (iii) energizing of the motor 18 to advance the disc 12 by the same number of increments.