US3090169A - Lapping machine fixture - Google Patents

Description

y 1963 s. A. BOETTCHER 3,090,169

LAPPING MACHINE FIXTURE Filed May 11, 1961 28heets-Sheet 1 INVENTOR. fiiyhenflzfioeiidzer J2 May 21, 1963 s. A. BOETTCHER 3,

LAPPING MACHINE FIXTURE Filed May 11, 1961 2 W fiV/VW/ T f 45 4446 w 24 INVENTOR.

JivizenQBoeZZc/zex Sheets-Eben 2 This invention relates to lapping machines and provides a fixture for lapping thin planar parts to an accuracy of one ten-thousandth of an inch or less.

The fixture intervenes between the weight or pressure plate and the work pieces on the lapping surface within the truing retainer ring the basic idea being to allow lapping of the work pieces to finish thickness, and then automatically discontinuing the lapping by removal of the down pressure, without stopping the machine.

The invention is illustrated in the accompanying drawings, in which:

FIGURE 1 is a cross-sectional view of the machine in general, taken approximately on its vertical center line;

FIGURE 2 is a horizontal cross-sectional View, taken on the plane of the line 22 of FIGURE 1, looking downwardly, and on a larger scale, portions being broken away;

FIGURE 3 is a vertical cross-sectional view, taken on the planes of the dot-and-dash line 33 of FIGURE 2, looking in the direction of the arrows; and

FIGURES 4 and 5 are two corresponding sectional views of a portion of FIGURE 3, on a still larger scale, showing respectively, the positions of the fixture before and after the lapping operation, the vertical dimension of the work piece being exaggerated for clarity.

Referring firstly to FIGURE 1:

The machine has a substantially cylindrical pedestal 11 supported by a base ring 12. The pedestal has an access door 13. A cylindrical collar 14 is disposed within the upper end of pedestal 11, the same being mounted 'by means of an inclined wall 15 forming a drip pan for receiving abrasive and carrier mixture used in the lapping operation above.

Mounted within the pedestal is a main drive motor 16 operatively connected by means of sheave Wheels 17 and 18 and a V-belt 19 with shaft 20 of a conventional gear reducer unit 21, the output shaft 22 of which carries a hub member 23, upon which the horizontal circular plate or disk 24, which provides the lapping surface 25, is mounted for rotation. This disk has a central well-bore 26, leaving an annular lapping area, and a plurality of radial slots 27 to lead the used abrasive and carrier mixture to the drip pan 15.

Surrounding the lapping disk is a staging table 28 from which work pieces can be moved onto the lapping surface and to which they can be returned when the lapping operation is completed.

Vertical channel columns 29, 29 are mounted in upright position at diametrically opposite sides of the pedestal housing 11, joined at the top by bridge member 30, which is provided with two intermediary transverse arms 31, 31, having vertical bores for receiving vertically adjustable spindles 32, two of which are shown. Each spindle has a knurled upper end 33 for manual grasping, and is held by a set screw 34. The lower end of each spindle is journaled in the center of a circular weight or pressure plate 35 and thus defines the axis of rotation of such plate.

Each weight or pressure plate 35 fits, with slight clearance, within a truing-retainer ring 36 which rests on the lapping surface 25 of the plate or disk 24, and the weight or pressure plate rests upon the fixture to be described, which, in turn, rests upon the work pieces on the lapping surface. The rings 36 function continuously to dress the lapping wheel for maintenance of its planar condition.

atent ce 3,090,169 Patented May 21, 1963 In the lower portion of the pedestal housing 11 there is provided a tank 37 for the abrasive and carrier mixture, having a filling tube 37 and, within it, means 38, powered by motor 39, for agitating the said mixture and for circulating it, by means of tubing 40 and 41, passing through one of the channel columns 29, to the level of the bleedotf spout 42, disposed in overlapping relation to the plate or disk 24, for drop-by-drop feed of the mixture to the lapping surface 25.

The fixture of the present invention, indicated as a whole in FIGURE 1 by the reference numeral 43, is there shown in elevation, disposed within the truing-retainer ring 36 between the weight plate 35 and the lapping disk 24 as above stated.

Reference is now made to FIGURES 2, 3, 4 and 5, illustrating the fixture in detail and on larger scales.

It comprises three elements, i.e. circular back plate 44, stop ring 45, and circular reference plate 46, together with retaining screw 47 and three set screws 48.

The back plate 44 has a peripheral shoulder 49, which engages the top of the stop ring 45, tightly fitted to the reduced periphery of the plate, as shown. The reference plate 46 fits within the stop ring 45 with slight clearance. The work pieces, indicated at w, circular disks for instance lie on the lapping surface 25, within the stop ring 45, and the under surface of the reference plate engages the work pieces, the heavy black lines above and below them indicating the films of lapping medium, i.e. the abrasive and carrier mixture above mentioned. The lower film of lapping medium of course extends under the stop ring and the truing retainer ring 36.

The stop ring 45 must not lap, and, accordingly, I make it of ceramic material and select an aluminum oxide or garnet abrasive for the lapping medium.

The height of the reference plate, relative to the bottom of the stop ring determines the ultimate vertical dimension of the work pieces and is adjustable by means of the set screws 48, held as adjusted by tightening the retaining screw 47.

Work pieces which have been lapped on the one side in the usual manner, are inverted and so placed on the lapping surface 25 within the inner area of the stop ring, and then the fixture 43 is placed upon them, followed by the Weight or pressure plate 35, a felt pad 51} between them, if desired. A convenient method of loading the machine with thin work pieces, is as follows: After the fixture has been adjusted for the desired spacing of the under side of the reference plate 46 and the bottom of the stop ring 45, it may be inverted, a small amount of lapping medium spread on its exposed surface, and then laying the work pieces thereon, with light hand pressure, causing them to adhere; the fixture is then righted and placed on the lapping surface within the truing-retaining ring, followed by the weight or pressure plate 35, a felt pad 50 intervening, if desired.

FIGURE 4 shows the parts at the start of the operation, and FIGURE 5 shows them at the pre-determined completion of the operation. In these figures the vertical dimension of the work piece has been exaggerated for purposes of clarity.

The fixture provides means for determining in advance the vertical dimension of the work pieces with the utmost accuracy, and when the selected dimension has been attained the lapping ceases automatically, and continued operation of the machine is without effect.

I claim:

1. In a lapping machine fixture for predetermining the extent of lapping work pieces positioned on a rotating lapping disc within a truing and retaining ring thereon, a plate for resting on said work pieces, a second plate parallel thereto and adjustably distanced therefrom, and means carried by said second plate for engaging the lapping disk to arrest the downward movement of said plates.

2. In a lapping machine fixture for predetermining the extent'of lapping work pieces positioned on a rotating lapping disc within a truing and retaining ring thereon, a plate for resting on said Work pieces, a second plate parallel thereto and adjustably distance-d therefrom, and a ring carried by said second plate surrounding said firstnamed plate for engaging the lapping disk to arrest the downward movement of said plates.

3. In a lapping machine fixture for predetermining the extent of lapping work pieces positioned on a rotating lapping disc within a truing and retaining ring thereon, a plate for resting on said work pieces, a second plate parallel thereto, set screws in one of said plates for engaging the other plate to adjust the distance between them, means for securing said plates together in adjusted position, and a ring carried by said second plate for engaging the lapping disk to arrest the downward movement of said plates.

4. In a lapping machine fixed for predetermining the extent of lapping work pieces positioned on a rotating lapping disc within a timing and retaining ring thereon, a plate for resting on said work pieces, a second plate parallel thereto and adjustably distanced therefrom, and a ceramic ring carried by said second plate surrounding said first-named plate for engaging the lapping disk to arrest the downward movement of said plates.

5. In a lapping machine fixture for predetermining the extent of lapping work pieces positioned on a rotating lapping disc within a truing. and retaining ring thereon, a first horizontal plate for resting on said work pieces, a second horizontal plate parallel thereto and adjustably distanced thereabove, said second plate having an annular reduced periphery defining a peripheral shoulder, an annular ring at its upper end forcibly fitted to said redumd periphery and seated against said shoulder in said second plate, said ring having an inner diameter substantially conforming to the outer diameter of said first plate, and said ring extending axially downwardly beyond the plane of the lower face of said first plate for engaging the lapping disc to arrest the downward movement of said plates.

6. The combination of claim 5 characterized by the provision of set screws in one of said plates for engaging the other plate to adjust the distance between them, and

means for securing said plates together in adjusted 1 position.

References Cited in the file of this patent UNlTE-D STATES PATENTS 2,565,590 Bullard Aug. 28, 1951 2,722,089 Boettcher Nov. 1, 1955 2,842,906 Carter et al. July 15, 1958 2,967,380 =Damgaard Ian. 10, 1961 2,971,298 Garthwaite et al. Feb. 14, 1961 2,979,868 Emeis Apr. 18, .1961 2,983,086 La Chapelle May 9, 1961

Claims (1)

1. IN A LAPPING MACHINE FIXTURE FOR PREDETERMINING THE EXTENT OF LAPPING WORK PIECES POSITIONED ON A ROTATING LAPPING DISC WITHIN A TRUING AND RETAINING RING THEREON, A PLATE FOR RESTING ON SAID WORK PIECES, A SECOND PLATE PARALLEL THERETO AND ADJUSTABLY DISTANCED THEREFROM, AND MEANS CARRIED BY SAID SECOND PLATE FOR ENGAGING THE LAPPING DISK TO ARREST THE DOWNWARD MOVEMENT OF SAID PLATES.

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