Patent GB-1082563-A (GB)
Title: Improvements in or relating to lapping machines and methods of lapping
IPC: B24B37/34
Filed: 1965-03-09
Abstract: 1,082,563. Lapping. SPEEDFAM CORPORATION. March 9, 1965 [April 28, 1964], No. 9976/65. Heading B3D. A lapping machine comprises a framework, a lapping disc rotatably mounted on the framework, means for moving an entire retaining member having a plurality of workpieces confined therein on to the lapping disc where the one sides of the workpieces may be lapped, and means, independent of the last named means, for moving the entire retaining member and workpieces therein off the lapping disc after the one sides of the workpieces have been lapped. A method of lapping a plurality of workpieces in a lapping machine having a lapping disc comprises the steps of: (a) moving a plurality of confined workpieces as a group on to the lapping disc beneath a pressure plate arranged within a truing ring and spaced together with the truing ring above the lapping disc, (b) lowering the truing ring and pressure plate respectively into engagement with the lapping disc and workpieces, (c) rotating the lapping disc to lap the sides of the workpieces in contact with the lapping disc, (d) raising the truing ring and pressure plate from the lapping disc and workpieces, and (e) moving the plurality of confined workpieces as a group off the lapping disc. The cycle for lapping both sides of a batch of workpieces is as follows. An annular retaining member 36 is placed on a lateral extension 46 of the staging table 42 and loaded with unlapped workpieces 34. Pneumatic piston and cylinder devices 22 are actuated to raise pressure plates (28) from the lapping disc 14; each pressure plate engages lugs (32) on a truing ring 30 within which the pressure plate fits with slight clearance so that the truing rings are also raised from the lapping disc. A pneumatic piston and cylinder device 56 is actuated causing an arm 54 to pivot to push the retaining member 36 with contained workpieces on to the lapping disc 14 beneath the pressure plate (28) at a first lapping station. The arm 54 is pivoted back to its initial position and the pressure plate (28) and truing ring 30 lowered into engagement respectively with the workpieces and the lapping disc, so that the workpieces are lapped flat on one side by the rotating lapping disc. To accommodate unevenness in the surfaces of unlapped workpieces a pad (250) of felt or the like is interposed between the pressure plate (28) and the workpieces. At the completion of this first lapping operation the pressure plates (28) and truing rings 30 are raised. A pneumatic piston and cylinder device 154 is actuated causing a latch mechanism 162 to move forwardly; latch members (172) rise over the edge of the retaining member 36 and drop into engagement with the inner surface thereof. The latch mechanism 162 is then moved rearwardly so pulling the retaining member 36 with contained workpieces off the lapping disc 14, across the staging table 42 and on to a platen 86 of inverting means, the latch members (172) being disengaged from the retaining member 36 by camming surfaces (178) when the latch mechanism 162 reaches its initial position. The inverting means 80 comprises platens 84, 86 pivotally mounted at facing edges about a shaft (100). The platen 84 is pivoted by a pneumatic piston and cylinder device 132 through a rack (120) and pinion (114); the platen 86 is pivoted by a pneumatic piston and cylinder device 142 through a rack (122) and pinion (118). To effect inversion of the workpieces which have been lapped on one side the platen 84 is pivoted through 180 degrees towards the platen 86 whereby the retaining member 36 with contained workpieces is confined between the platens 84, 86. The platens are pivoted conjointly through 180 degrees, returning the platen 84 to its initial position. The platen 86 is pivoted back to its initial position. A pneumatic piston and cylinder device 184 is actuated causing a pusher member 192 to move forwardly, pushing the inverted retaining member 36 with contained workpieces off the platen 84, across the staging table 42 and on to the lapping disc beneath a pressure-plate (28) at a second lapping station. The pusher member 192 is returned to its initial position and the pressure plates (28) and truing rings 30 are lowered so that the workpieces are lapped flat on the other side. The pressure applied to the workpieces at the second lapping station may be different from that applied at the first lapping station, e.g. it may be higher. At the completion of the second lapping operation, the pressure-plates (28) and truing rings 30 are raised. A pneumatic piston and cylinder device 218 is actuated causing an arm 214 to pivot until latch means 234 carried thereby engages the retaining member 36. The arm 214 is returned so moving the retaining member 36 with contained workpieces off the lapping disc, across the staging table 42 and on to a conveyer belt 204, the latch means 234 being disengaged from the retaining member 30 by a carrying surface (248) when the arm 214 reaches its initial position. When the machine is fully operative there are retaining members 36 with contained workpieces at the first and second lapping stations; while lapping proceeds, a retaining member 36 with contained workpieces is inverted by the means 80 on to the platen 84 and a retaining member 36 at station 46 is loaded with workpieces. When lapping is complete, the pressure plates (28) and truing rings 30 are raised; a retaining member 36 with contained workpieces is unloaded from the first lapping station to the platen 86 and a retaining member 36 with contained workpieces is unloaded from the second lapping station to the conveyer 204. Subsequently a retaining member 36 with contained workpieces is loaded from station 46 to the first lapping station and a retaining member 36 with contained workpieces is loaded from the platen 84 to the second lapping station. The mechanism may be duplicated at the other side of the machine. The pneumatic devices are supplied from a pump through a control system incorporating air regulators. An electric circuit including limit switches controls the sequence of operation of the devices. An hydraulic system may partly or wholly replace the pneumatic system.