Patent GB-1200284-A (GB)
Title: Improvements in or relating to lapping machines
IPC: B24B53/017
Filed: 1968-08-16
Abstract: 1,200,284. Lapping. SPEEDFAM CORP. 16 Aug., 1968 [14 Sept., 1967], No. 39389/68. Heading B3D. A lapping machine comprises: (i) framework; (ii) a lapping disc rotatably mounted about a vertical axis on the framework; (iii) a contour control member having a lower horizontal surface engageable with the lapping disc; (iv) a vertical floating spindle; (v) means mounting said spindle on the framework above said contour control member; (vi) coupling means connecting the lower end of said spindle to said contour control member; and (vii) adjustment means for selectively engaging and raising said spindle whereby to withdraw said contour control member from engagement with the lapping disc. A lapping machine comprises framework, including a lower housing section 12, an upright rear-end housing section 14 and an upper overhanging housing section 16 having a lower horizontal wall 18. The section 12 provides support for an annular lapping disc 20, driven by an electric motor 24 through a reducer 26, and for a staging table 22 surrounding the disc. Mounted in the section 16 are four pneumatic assemblies 28, two on one side of the machine and two on the other side, each assembly including a cylinder 30 and a piston-rod 32, secured to a pressure plate 34 fitting with slight clearance within truing and retaining rings 36 resting on the disc. The rings 36 slightly overlap the inner and outer peripheries of the annular lapping surface of the disc. Workpieces are confined within the rings 36 and below the plates 34 therein. A mixture of oil carrier and abrasive particles is fed to the disc through spouts 38. To supplement the normal dressing action of the rings 36, there is provided independent contour control apparatus 40. This comprises a tubular easing 42 extending through and secured to the wall 18, and having threaded in its lower end an axially adjusted sleeve 44. A floating spindle 46 extending through the casing 42 and sleeve 44 has a radial shoulder 48. A ball-bearing assembly 50 secured to the upper part of the spindle 46 is axially movable within the casing 42. A ball-bearing assembly 52 secured in the sleeve 44 is axially movable along the lower part of the spindle 46. A contour control member 54, connected by coupling means 56 to the spindle 46, has in its lower face a central recess 58 and a concentric recess 60 in which is secured, e.g. by epoxy cement, a wear ring 62, e.g. of boron carbide. The coupling means 56 comprises a ball 66 located in a conical seat 64 in the member 54 and engaged by a flexible metal diaphragm 68 secured to the member 54; a collar 70 is secured to the central portion of the diaphragm and to the spindle 46. The member 54 is positioned circumferentially intermediate of two rings 36 and slightly overlapping the outer periphery of the lapping disc 20. The spindle 46 is driven by a belt 82 passing round a crown pulley 80 on the shaft of an electric motor 72. When corrective treatment of the lapping surface is necessary, the sleeve 44 is threaded axially downwardly permitting the lower surface of the member 54 to engage the lapping surface; the bearing assembly 52 is withdrawn from engagement with the shoulder 48, whereby the full weight of the spindle 46 bears downwardly on the member 54, giving the desired contact pressure, e.g. up to 10 pounds per sq. in. The motor 72 is energized. Corrective treatment is carried out at intervals and for varying periods as necessary. Reference has been directed by the Comptroller to Specification 1,067,807.