Patent GB-1380759-A (GB)
Title: Grinding machine
IPC: B24B5/06
Filed: 1972-12-08
Abstract: 1380759 Grinding, trueing grinding wheels TOYODA KOKI KK 8 Dec 1972 [10 Feb 1972] 56850/72 Heading B3D  A grinding machine comprises first means for supporting a grinding device 3, second means for supporting a dressing tool 13, and control means operable at a predetermined stage of a grinding operation involving the first means to temporarily halt the operation and, during the temporary halt, to cause relative movement of the first and second means so as to enable a dressing operation controlled by the control means independently of the preceding grinding to be effected. As applied to an internal grinding machine, the device 3 consists of a wheel mounted in a head 2 and driven by a motor 5, the head being transversely adjustable by a screw 39 on a table 4 reciprocatable by a piston 16 in a cylinder 15, dogs D1...D6 being mounted on the table and associated with a control circuit. The screw 39 is rotatable by a pawl-and-ratchet mechanism 43, 44 driven by a pinion 42 engaged by a rack 45 on the rod 41 of a piston 38 in a cylinder 37. A workpiece W is held in a chuck 11 of a head 8 and rotated by a belt drive 12. The head is transversely adjustable by rotation of a screw 53 connected by gears 50, 52 with a pinion 49 engaging a rack 48 on a piston 47 slidable in a cylinder 46. The dressing tool 13 is carried by an arm 14 movable downwardly from an inoperative position to an operative position by a pinion 69 engaged by a rack on the rod 68 of a piston 67 in a cylinder 66, the operative position being determined by a stop 71. The supply of fluid to the cylinder 15 for reciprocating the bath 4 is controlled by a valve V4 which is actuated by a switch lever 18 movable by the dogs D5, D6, but dog D5 can be lifted to an inoperative position by a plate 21 movable by a rod 23 when the table is to be moved back to an original position, as shown, and during a dressing operation. The switch lever can be clamped in position to prevent advance of the table by a pawl 28 which engages a pin 27 on the lever and is connected to a piston 24 in a cylinder 22. In operation, the wheel head 2 and work head 8 are in their original positions, the switch lever 18 is held in its left-hand position by the clamping cylinder 22 and the plate 23 holds the dog D5 in its upper inoperative position. Upon actuation of a button, a valve V1 supplies oil to cylinder 22 to release the switch lever 18. Valve V3 is switched so that a lever 20 is moved to rock switch lever 18 to its other position switching valve V4 and thus supplying fluid to cylinder 15 to effect a rapid advance of the table 4, the fluid also passing through valve V2 so that the rod 23 lowers plate 21 and hence the dog D5. As the table advances the dog D2 acts on the rod 29 of a valve V7 to effect a slow feed as the grinding wheel enters the workpiece W. At the end of the advance, dog D6 actuates switch lever 18 and valve V4 to reverse the fluid supply to cylinder 15 until the lowered dog D5 engages the switch lever 18 and valve V4 is again operated to reverse the flow to the cylinder 15, the reciprocation of the table continuing under the control of the dogs D5, D6. At the same time as the table reciprocation is initiated, a valve V11 is actuated so that fluid is supplied to cylinder 46 which, through the rack-andpinion 48, 49 and gears 50, 51, 52, effects the advance of the workhead 8 at a rough grinding speed. When the rough grinding is completed, the workpiece is in the full line position, shown in Fig. 2, and a dog D8 operates a switch L55 and fluid is supplied to a cylinder 56 to move its piston 57 to the left and pass fluid to the cylinder 46 to move the piston 47, and hence the workhead 8, back through a predetermined distance. Simultaneously, valve V10 is actuated so that piston 38 is advanced in cylinder 37 to cause the grinding wheel to be advanced to the phantom position 3a, valve V2 is actuated so that the rod 23 and plate 21 lift dog D5 to its inoperative position, and cylinder 66 is supplied with fluid to move the dressing tool to its operative position. As the table 4 is retracted, the speed of the table when the grinding wheel has reached the position 3b is reduced to a dressing feed velocity for passing the wheel past the dressing tool. The movement of the table continues past the position normally limited by the dog D5 up to a position determined by a dog D4 whereupon valve V3 is actuated to move the switch lever 18 and valve V4 to reverse the movement of the table 4 so that the grinding wheel is again dressed by the tool 13. The dog D1 actuates valve V7 to effect the grinding feed velocity, and the piston 67 retracts the dressing tool. When the grinding wheel enters the workpiece and is reciprocating under the control of the dogs D5, D6, fluid is again supplied to cylinder 46 to advance the workpiece a distance determined by the amount of fluid to be returned to cylinder 56 and thereafter at a fine feed determined by a throttle valve until a dog D9 initiates a timer for a "spark out" finish grinding.