Patent GB-926751-A (GB)
Title: Improvements in or relating to lapping machines
Inventor: BOETTCHER STEPHEN ARTHUR
IPC: B24B37/10
Filed: 1959-09-04
Abstract: 926,751. Lapping. ABRADING SYSTEMS CO. Sept. 4, 1959, No. 30312/59. Class 60. In a lapping machine comprising a disc arranged for rotation about a vertical axis and having a horizontal planer lapping surface and a retainer ring arranged to rest on the lapping surface for retaining workpieces, a planar staging table provided adjacent the lapping surface is movable to a predetermined position slightly above the lapping surface to facilitate sliding of the retaining ring and workpieces from the staging table to the lapping surface and to a further predetermined position slightly below the lapping surface to facilitate sliding of the retaining ring and workpieces from the lapping surface to the staging table. A lapping machine comprises a base ring 12 and a cylindrical pedestal 11 connected by support lugs 13 to which they are both welded. The pedestal has a hinged access door 14. A collar 17 disposed within the upper end of the pedestal is mounted slightly off-centre with respect to the axis of the pedestal by an inclined elliptically-shaped drip pan 18 welded to the collar 17 and to the pedestal 11. The pan catches the lapping medium which passes through a spout 20 to a removable tank within the pedestal. A rotatable lapping wheel 40 comprises a circular wear-resisting metallic alloy disc with a central well-bore 41 providing an annular lapping area having radial slots 42 cut downwardly to the depth of the well-bore. The wheel 40 is secured, as by screws 39, to a hub 38 rigidly fixed, e.g. keyed, to the output shaft of a gear reducer unit 35 mounted within the collar 17. The input shaft of the unit 35 is driven, through a V-belt 29, by a motor 32 mounted on a plate 25 carried by an axle 26 mounted in brackets 27 secured to the pedestal. The plate 25 carries an adjustable bolt 28 engaging the pedestal, whereby the belt 29 can be tensioned. Surrounding the lapping wheel 40 is a ring 43 on which is mounted a table 44 having notches 45, 45 for loosely fitting about vertical channel columns 46, 46 secured to the pedestal and serving to guide the table 44 for vertical movement. Arcuate cam blocks 52, secured by bolts 53 to the underside of the table 44, are engaged by the upper ends of adjustable studs 50 carried by a ring 51 resting upon the upper end of the pedestal 11. The ring 51 has a handle 55 by which the operator may move it angularly, resulting in vertical adjustment of the table 44, the angular movement being limited by engagement of the studs 50 with the bolts 53. A bridge member 60 secured, e.g. welded, to the upper ends of the upright columns 46, 46 has transverse arms 61, 61 having at their outer ends vertical bores in which spindles 62 are held by set-screws 64. The lower end of each spindle takes into a ball bearing 67 in the centre of a circular weight plate 68 engaging the tops of workpieces 71 and fitting with slight clearance within a truing-retaining ring 70. Near the lower end each spindle 62 has a radial arm 65 at the outer end of which is mounted a roller 66 or a friction block e.g. of wood contacting the plate 68. Lapping medium is contained in a cylindrical tank 74 within the pedestal 11. The tank has a filling spout 75 and a top closure plate 76 on which is mounted a motor 77 driving an impeller shaft 80. At the lower end of the shaft 80 is mounted a centrifugal impeller 81, with vanes 86, disposed beneath a baffle plate 82 carried by rods 83 depending from the plate 76. Radial baffles 84 project upwardly from plate 82. The impeller constantly circulates the lapping medium within the tank 74 and centrifugally impacts it against a partial scroll member 85 having a curvilinear outer wall 87, a bottom wall 88 of flaring formation and an end wall 89 having a pocket 90 for trapping medium centrifugally thrown against the wall 87. An opening 91 at the apex of the pocket 90 communicates with a discharge pipe 92. The central opening 93 in the baffle plate 82 is enlarged to effect circulation so that the medium is agitated whereby the abrasive particles are kept in adequately uniform suspension in the carrier. The discharge pipe 92 contains a filter 92a and is connected to the part 96 of a manifold 94 secured in one of the channel columns 46. Port 95 is connected to a return line 102 leading back to the tank 74 and containing a valve 103. A tube 105 having an orifice 106 at its inner end bleeds off some of the lapping medium passing through the manifold 94 and delivers it, drop by drop, on to the lapping surface of the wheel 40. A timing switch 110 mounted on the bridge member 60 automatically stops the drive motor 32 and pump motor 77 after expiry of a predetermined lapping period.