Patent GB-901875-A (GB)
Title: An improved lapping machine
IPC: B24B37/08
Filed: 1959-12-22
Abstract: 901,875. Lapping. BOVENSIEPEN, H. F., [trading as WOLTERS, P., [Firm of]]. Dec.22, 1959 [Dec. 22, 1958 (2); March 2, 1959], No. 43593/59. Class 60  A lapping machine in which the workpiece loading is equal to the sum of a positive or negative piston force and of the weight of the parts liftable and lowerable relatively to the lap wheel, or in the case of two-wheel lapping machines relatively to the lower lap wheel, is characterized in that cylinder producing the piston force is provided with a control device by means of which the piston force can be adjusted in accordance with a predetermined loading. A lower lap wheel 3, Fig. 1, has a vertical shaft mounted in a bearing 1 in the machine frame 2 and driven by a belt 5. The upper lap wheel 10 has a vertical shaft 9 mounted by bearings 14 in a sleeve 15, the upper end of the shaft 9 being in splined engagement with a pulley 12 driven by a belt 13 and mounted by bearing 19 in the head 8 of a part 6 pivoted at 7 to the frame 2 so that the wheel 10 can be swung into a projection of the trough 41 of the machine. The sleeve 15, which is restrained from rotation, is formed with a double-acting piston 25 movable in a cylinder 28, pressure liquid being supplied by a pump 31 and controlled by a valve assembly 29 comprising electromagneticallyoperated valves 63, 64, Fig. 5. The hydraulic circuit includes a valve 34 for adjusting the predetermined position force of the piston 25, a valve 35 for adjusting the predetermined negative piston force, and a valve 36 for adjusting the predetermined preliminary load piston force. A member 43, Fig. 3, secured to a ring 23 on the sleeve 15, has a cylindrical lower portion and a wedge face 44 extending upwardly from a recess 45. The wedge face 44 co-operates with the feeler 52 of a switch 42 carried by an adjustable bracket 50 pivotally mounted on the detachable front plate 33. Mounted on the front plate 33 are a pressuregauge 37 and a specified-value scale pair 38, Fig. 9, forming functionally one combination. The side pair comprises a segment 78 removably secured to the front plate 33 and a rotary knob 81. A segment 78 bearing the indication " 700 x 180 " is used for a cast-iron upper lapwheel having an external diameter of 700 mm. and a ring width of 180 mm.; the segment has an adjustment mark 83 and a scale " 0 to 80 " relating to lap wheel thickness which is 80 mm. when the lap wheel is new. The rotary knob 81 has a scale 80 with a positive range " 0 to + 11 " and a negative range " 0 to - 8." The pressure gauge 37 reacts from 0 to 11. Modifications are described in which the pressure gauge and the scale part are combined. The optimum loading of each individual workpiece. 11 is multiplied by the number of workpieces in the batch to be lapped simultaneously. If, for example, the desired loading is 275 kg., the knob 81 is rotated to bring the value 2.75 on the scale 80 in register with the mark 83. The thickness of the upper lap wheel is measured. If, for example, it is 40 mm., the reading on the scale 80 opposite the reading 40 on the scale "0-80" is taken, viz. +0.5, and the valve 34 is adjusted until the pressure gauge indicates 50 kg. If, however, the upper lap wheel thickness is 80 mm., the reading on the scale 80 opposite the reading 80 on the scale " 0-80 " is taken, viz. - 0.25, and the valve 35 is adjusted until the pressure gauge indicates 25 kg. In a complete working cycle, the upper lap wheel 10 is raised and the workpieces are inserted. The upper lap wheel 10 is moved down at high speed until, shortly before the lap wheel contacts the workpieces, the wedge face 44 actuates the switch 42. The lap wheel then contacts the workpieces without shock and exerts a preliminary loading, determined by the setting of the valve 36, insufficient to cause cracks or fractures in the workpiece or elastic deformation thereof. After an interval, during which the material above the line 101, Fig. 13, and below the lines 102, 102 has been removed, a time relay operates and full locking is applied, as determined by the setting of valve 34 or valve 35, until lapping is completed.