US 2409953 A
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Description (OCR text may contain errors)
Oct. 22, 1946. R. PASH MATERIAL TREATNG APPARATUS Filed oct. 15, 1943 i Q\` I N i 'ri-fr? I TI l l :A I l IIN 2 Sheets-Sheet l INI/ EN TOR R. P SH A fron/v51 R, PASH MATERIAL TREATING APPARATUS Filed Oct. 13, 1945 2 Sheets-Sheet 2 Fl C. 2
mwulm' ATTORNEY Patented Oct 22, 1946 MATERIAL TREATIN G APPARATUS -I Robert Pash, Roselle, N, IJ.. assignor to Western Electric Company, Incorporated, `New York, N. Y., a corporation of New York Application October 13, 1943, Serial No. 506,052
3 Claims. (Cl. 51-133) This invention relates to material treating apparatus, and more particularly to apparatus for lapping a plane face on an article. i Of recentyears and especially in connection with a Variety of electrical products used by the armed services, many applications have been developed of small slabs, slices or wafers of crystalline quartz, in which certain electrical characteristics depend upon and are controllable as to value by the dimensions ofthe crystal slice. This is usually Va thin wafer with accurately parallel broad face and of rectangular peripheral contour. In some applications of such rectangular wafers of crystalline quartz, hereinafter termed simply crystals, it may be necessary to diminish the thickness of a crystal minutely and evenly to adjust an electrical characteristic of the crystal to a precisely predetermined value, While maintaining the flatness and parallelism of the broad faces of the crystal accurately true. I
An object of the present invention is to provide an apparatus for lapping an` existing flat surface of, an tarticle to remove material therefrom evenly and thus maintain both the flatness of the lapped` surface and its orientation on'the article.
With the above and other objects in view, the invention may be` embodied in an apparatus for precision lappingand having a lapping disk and means to press anarticle to be lapped against the disk, a low speed shaftl to. both support and drive the disk injrotation, a high speed shaft side by side with andparallelto thelow speed s haft to support and drive the varticle pressing means in rotary motion eccentric to the rotation of the disk, meansjto drive the high speed shaft, and speed reduction gearing driven by the high speed shaft to drive the low speed shaft.`
Other objects and features will appear from the following detailed description of one embodiment thereof, taken in connection with the appended drawings,'in` which the same reference numerals are applied to identical partsin the several figures, `and in which Fig. 1 is a view in plan-and partly in horizontal 4section and` with parts broken away of an apparatus constructed in accordance with the invention;
Fig. 2.i s a view on the line 2-2 of Fig. 1; Fig. 3 is a ViewV on the line 3-3 of Hg. 2; and
` Fig. 4l is a broken View on the line 4-4 of Fig. 1. The-apparatus herein disclosed as an illustrativeembodiment of the invention, comprises a rotatable circular` lap It) and an article driving pin II, .drivable to revolve in a relatively small circle about an axis parallel to the pin and to Y 2 the axis of the lap, the revolution axis of the pin being offset from the rotation axis of the lap. One end of the pin is enterable into and removable from a corresponding central cavity I2 in a crystal holder I4, being shiftable axially o'f itself for this purpose. The crystal holder I4 is a simple disk of metal or other suitable 'material `whose outer face is sufficiently plane so that if this face be moistened slightly, a crystal a may be wrung to the surface and will adhere there-x to sufficiently tightly for the operation hereinafter described to be carried out. The lap I!) is a circular disk of metal or other suitable material whosebroad faces are accurately planeand are formed with a system of grooves I5 therein. The pin II is mounted in the transverse cap I6 of a cylindrical sleeve I'I telescopically slidingly supported on a helical spring IB and a flange I9 formed on` a' hollow stub shaft 20. An inner hollow shaft 2| is mounted in the shaft 20 Concentrically within the spring I8 `and sleeve I1 and has at its outer end a guide aperture in `which the inner Vportion of the pin Il is slidably guided. The stub shaft 2l)` is mounted excentrically in a collar 22 which in turn is excentrically mounted on the end of a Work drive shaft 24. The lap I0 is mounted transversely and detachably on a lap drive shaft 25 to be rotated thereby.
The shafts 24 and 25 are mounted parallel to `each other and suitably spaced apart in journals in the Walls of a housing 26. A transverse shaft 21 is also journalled in the housing at right angles to and suitably spaced from theshafts 24 and 25. A right hand Yworm 28 on the shaft 24 engages a corresponding gear 29 on the shaft 21; and a left hand Worm 30 on the shaft 21 engages a corresponding gear 3| on the shaft 25. Thus When the hand Wheel 32 on the shaft 24 is rotated in the sense indicated bythe arrow by means of the handle 33, the shaft 24 is rotated in the sense of the arrow thereon at relatively high speed while the shaft 25 is rotated in the opposite sense at relatively low speed.
The shafts 2l! and 25 are preferably horizontal so that the main plane of the lap I0 is vertical. A vertical, open topped tank 34 is provided to contain a mixture of an abrasive powder and a liquid vehicle, e. g. carborundum powder in water, and is so proportioned and filled that the lower portion of the lap runs well down in the abrasive mixture.
. In operation, the sleeve I'I and therewith the pin II may be retracted manually, against the tension 0f the spring It, to allow a crystal holder I4 having a crystal 9 wrung thereto to be placed on the end of the pin II, as shown in Fig. Ll. The sleeve and pin are allowed to move then into the position of Figs. 1 and 2, where the crystal 9 is pressed against the lap I by the spring I8. The handle 33 is then revolved manually in either direction, but preferably clockwise as seen from the right of Fig. 1 and as shown by the arrows on the wheel 32 and shaft 24. The rotatinglshaft 24 then causes the offset shaft 2d and therewith the pin II, crystal holder I4 and crystal 9 to re.- volve in the same sense at a radius equal to the offset of the shaft 20, about the axis of the shaft 24, and at the rotary speed of the handle 33.Y
Simultaneously, the reduction gearing 28, 29, 30', 3l drives `the shaft 25 at a relatively much ,slower speed, e. g. one twenty-fifth of the speed of the d shaft 24.
By this acti-on the crystal 9 is revolved VVin its own plane in a circle whose radius is the offset of the shaft 20 from the shaft 24 andclockwise as seen in Fig. 3, about a stationary axisperpendicular to the lapping surfaces of the'lap Il) and midway between the outer and inner peripheries of the'annular, effective, lapping surface. The lapping surface rotates slowly against the thus revolving crystal, counterclockwise in Fig. 3. If the lapping surface were stationary, every point of the crystal would tend to describe a circleon the .lapping surface. Since the lapping surface rotates as described, the point of the crystal surface being lapped, which is in the axis of the pin I l, traces on the lapping surface the hypocycloidally helical path shown in Fig. 3. Were the revolution of the crystal irrotational, i. e. did the crystal not rotate about its own axis (also the axis of the pin I I) as well as revolve about the axis of the shaft 24, every point ofthe crystal surface being lapped would trace a similar hypocycloidal helix on'the lap. However, the pin I I turns clockwise once onits own axis for each revolution about the axis of 24; and, although the engagement of the pin II inthe cavity I2 of the holder I4 is preferably a loose one, the frictional drag of the pin on the holder tends to cause the holderV and crystal to rotate slowly clockwise. Furthermore, when the holder and crystal are in the extreme rightward position shown in Fig. 3, the crystal hangs the lap considerably, as shown, on the right or outer side. There is therefore, at this time, a greater frictional drag between the crystal and lap to the left of the downwardly moving pin II; and hence the crystal tends to turnv clockwise on the pin at this time. When the pin and crystal have completed a half revolution about the shaft 24 to the position shown in dotted lines in Fig. 1, the crystal overhangs the inner or. left edge of the lapping surface, the frictional drag is greater on the right of the pin than on the left; and, since the pin is then moving up, the crystal again tends to turn clockwise on the pin. Hence, generally speaking, while the point of the crystal face being lapped directly in the axis of the pin will describe on the lap substantially the hypocycloidal helix shown, other points of the lapped surface will tend to move on the lap in paths of the same general form but slightly more closely coiled. In any event it is found that the lapping effect'due to the relative motions described is such that the flatnesses of both the lapping surface and the lapped surface tend to be maintained with generally effective uniformity,
' the interfrictional pattern of these surfaces indicated by the path shown in Fig. 3, being such is moving down on the lap surface, and also overthat wear is substantially uniform over the entire lapping surface as well as over the lapped surface.
The lap in moving as described through the abrasive material in the tank, `picks up the abrasive on its surface as well as in the grooves I5 and thus brings continually a fresh supply of abrasive to the lapping location. With the relative motion as shown, the distance abrasive has to be carried from the bath to the crystal is short, hence the preference above notedfor r0- tation of the handle 33 in the direction indicated.
Since the lapping pressure is constant when theapparatusis inv use, the amount of material removed from a crystal by a given number of revolutions of the .handle 33 or of the lap I0 is constant; and the turns required to remove a given thickness from a crystal are easily predeterminable. This is not practically possible with the prior art method of rubbing a crystal by hand on a stationary lap, nor is the accurate maintenance of ilatness of the lapped surface.
What is claimed is: Y
1. Apparatus for precision lapping of a p lane surface on an article and comprising a low speed shaft, a lapping disk rigidly secured on the' shaft to rotate therewith and having a plane annular lapping surface both perpendicular and concentric to the axis of the shaft, a high speed shaft side by side with and parallel to the'low speed shaft, and spaced laterally therefrom a distance between axes equal to the radius of themiddle of the annular lapping surface, means to drive the high speed shaft in rotation, an intermediate shaft transverse to and spaced from both said shafts, a worm on the high vspeed shaft,'a
gear on the intermediate shaft engaged by the Y- worm, a second wormv on the intermediate shaft, a second gear on the-low speed shaft'engaged by the worm on the intermediate shaft, an article driving pin mounted on the high speed shaft parallel to the axis of said shaft and offset therefrom, and reciprocable parallel thereto, yielding means interposed between the pin andthe high speed shaft to press the pin resilientlytoward the lapping surface, and an articleholdillgmember detachably mounted on the pin to hold an article to be resiliently pressed by the p in against the lapping surface while theV article is being revolved by the pin about the axis of thehigh speed shaft.
2. Apparatus for precision lapping of a plane surface on an article and comprising a low speed shaft, a lapping disk rigidly secured on the shaft to rotate therewith and having a plane annular lapping surface both perpendicular and concentric to the axis of the shaft, a high speed shaft side by lside with and parallel to the low speed shaft, and spaced laterally therefrom a distance between axes equal to the radius of the middle of the annular lapping surface, means to drive the high speed shaft in rotation, an intermediate shaft transverse to and spaced from both said shafts, a, worm on the high speed shaft, a gear on the intermediate shaft engaged by the worm, a second worm on the intermediate shaft, opposite in sense of pitch from the rst named gear, a second gear on the 10W speed shaftengaged by the worm on the intermediate shaft, an article driving pin mounted on the high speed shaft parallel to the axis of said shaft and offset therefrom, and reciprocable parallel thereto, yielding means interposed between the pin and the high speed shaft to press the pin resiliently toward the lapping surface, and an article Vto be resili- 5 Y ently pressed by the pin against the lapping surface While the article is being revolved by the pin about the axis of the high speed shaft.
3. In an apparatus for precision lapping and having a lapping disk and means to p-ress an article to be lapped against the disk, a low speed shaft to 100th support and drive the disk in rotation, a high speed shaft side by side with and parallel to the low speed shaft t0 support and drive the article pressing means in rotary motion 10 eccentric to the rotation of the disk, an intermediate shaft transverse to and spaced from both said shafts, a Worm on the high speed shaft, a gear on the intermediate shaft engaged by the Worm, a second Worm on the intermediate shaft, a second gear on the 10W speed shaft engaged by the Worm on the. intermediate shaft, and means to drive the high speed shaft.