US3110987A

US3110987A - Sphere lapping apparatus

Info

Publication number: US3110987A
Application number: US130537A
Authority: US
Inventors: Harold E G Arneson
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-08-10
Filing date: 1961-08-10
Publication date: 1963-11-19
Anticipated expiration: 1980-11-19

Description

Nov. 19, 1963 H. E. G. ARNESON SPHERE LAPPING APPARATUS 4 Sheets-Sheet 1 Filed Aug. 10, 1961 INVENTOR. #42010 I. 6'. HIM E504! Nov. 19, 1963 H. E. G. ARNESQN SPHERE LAPPING APPARATUS 4 Sheets-Sheet 2 Filed Aug. 10, 1961 INVENTOR. M42040 6 flRA/Esa Nov. 19, 1963 H. E. G. ARNESON 3,110,987

SPHERE LAPPING APPARATUS Filed Aug. 10, 1961 4 Sheets-Sheet 3 I N VEN TOR. #42040 if 6 flRn/Esa/v BY JQM 4 TTORIVEVS Nov. 19, 1963 H. E. 5. ARNESON 3,110,987

SPHERE LAPPING APPARATUS Filed Aug. 10. 1961 4 Sheets-Sheet 4 FIE. '7

INVENTOR. #4200 E 6. 192M550 WM M 3,110,987 SPHERE LAPPING APPARATUS Harold E. G. Arneson, Professional Instruments Co., 6824 W. Lake St, Minneapolis, Minn. Filed Aug. 10, 1961, Ser. No. 130,537 12 Claims. (Cl. 51-417) This invention relates to an improvement in grinding and polishing apparatus, and particularly in such apparatus as is used in connection with the grinding and polishing of spherical bodies and which is more specifically referred to as lapping apparatus.

In a lapping apparatus it is desirable to have perfect random movement of the work piece and this is developed as a result of the relative friction of the laps or lap heads. However in presently designed lapping apparatus there is present the element of the pressure of gravity in addition to the pressure of the lap heads. The pressure of gravity prevents a uniformity of 'lappin g pressure over the surface of the work piece. As a result of the lack of uniformity in lapping pressure there develops a systematic motion which tends to prevent perfect random motion on the part of the work piece and to directly affect the degree of sphericity resulting from the lapping.

It is desirable therefore to construct and arrange the lapping apparatus to offset or negative the tendency for gravity pressure to develop or be present. It is desirable to support the lapping members or lapping assembly so that the lap heads will be unaifected by gravity in their lapping operation whereby there will be an even distribution of lapping pressure over the surface of the work piece. Uniformity of lapping pressure is a major factor in producing or causing the perfect random movement of the work piece and eliminates the tendency for systematic or arbitrary motion on the part of the work piece.

It is an object of this invention to provide an apparatus constructed and arranged for substantially perfect free random movement of the work piece.

It is another object of this invention to provide a support for the work piece with relation to the lapping members for free random movement of the work piece.

It is a further object of this invention to provide an even distribution of lapping pressure over the surface of the work piece to avoid the presence and effect of the pressure points of lapping as commonly developed or generated by the pressure of gravity.

It is an object of this invent-ion to provide a plurality of lapping members constructed and arranged to have selfaligning axes.

It is also an object of this invention to provide lap members respectively being constructed and arranged to exercise variable thrust force and variable rotating action in connection with a stationary or rotatable supporting member for the work piece and further to provide for a cyclical variation of said thrust force and rotative action.

These and other objects and advantages of the invention will be fully set forth in the following description made in connection with the accompanying drawings in which like reference characters refer to similar parts throughout the several views and in which:

FIG. 1 is a view in front elevation with some portions being broken away;

FIG. 2 is a top plan view of applicants apparatus;

FIG. 3 is a view in end elevation with some portions being broken away;

FIG. 4 is a fragmentary view of a detail of applicants apparatus in perspective on an enlarged scale;

FIG. 5 is a fragmentary view in vertical section taken on line 5-5 of FIG. 1 as indicated by the arrows, and shown on an enlarged scale;

FIG. 6 is a view similar to FIG. 5 showing a modification thereof; and

' te States atent O "ice FIG. 7 is a fragmentary view of a modification of a portion of applicants device in vertical section on an enlarged scale.

Referring to the drawings, applicants lapping apparatus 10 in the embodiment of the invention here disclosed comprises a principal supporting member 1-1 here shown in the form of an upstanding shaft anchored in a supporting base 12 of suitable construction and here indicated diagrammatically only.

Carried by said shaft 11 is a plate member or tray 14 shown to be substantially rectangular in plan and having a somewhat rearwardly centrally located aperture 15 having an integral depending hub portion 16 forming a split clamp secured to said shaft by clamp bolts 181.

Upstanding substantially forwardly transversely of said plate member 14 and adjacent either end thereof are spaced plate brackets 2.0 and 21 having right-angled lower end portions secured to said plate member by bolts 22. Secured to the upper forward side portions of said

members

21 and 22 by bolts 24 is an elongated horizontally disposed supporting frame member 25 substantially rectangular in cross section.

With particular reference to FIG. 5, a work piece supporting structure 29 is indicated comprising a bearing block .33 secured to said supporting member 25 by bolts 2'7 and being positioned substantially centrally longitudinally thereof. Said bearing block has a bore 31 vertically therethrough with an annular groove 32 of some width centrally of the bore of said block. A transverse passage 33 connects said groove to the atmosphere and connected to said passage in a suitable manner is a conduit 34 which will communicate with a suitable supply of fluid under pressure. Recessed at either end of said block 39 are annular bushings 37. lournaled in said block is a shaft 39 extending outwardly at either end thereof and is here shown having a collar 40 thereabout secured thereto by a set screw 41 and bearing on the upper surface of said block acting as a thrust bearing or retaining ring. Disposed about said shaft adjacent either end of said groove 32 are sealing rings 42 indicated as being O-rings. As indicated, the upper portion of said shaft is shown having a bore 43 therethrough with radial passages 44 at the lower end of said bore within the area of said groove 32. Secured to the lower end of said shaft by a set screw 4-6 is a pulley 48.

Carried on the upper end of said shaft 35 and secured thereto by a set screw 56 is a supporting head 38 cylindrical in form having a relief area 51 at its lower side and extending upwardly thereof is an upstanding cup portion 38a of reduced diameter having its annular upper end portion 38b arcuate in transverse section and of suitable dimension to adequately support said spherical work piece 53. Said cup portion has a relief portion 38c centrally thereof in communication with said bore 53.

A drip tray 55 having a retaining wall thereabout is here shown provided with a central aperture 55a and is disposed over said block 30 having frictional supporting engagement therewith by means of an annular resilient collar or gasket 56 lining said aperture.

With reference to FIG. 3, the rearward portion of said plate member 14 is shown here having an upwardly extended angled shelf portion 64 made integral therewith in a suitable manner. Carried on said member 14 is a motor 66 secured by bolts 67. Said motor is equipped with a drive shaft 68 having secured thereto a pulley 69 having a belt 74) pass thereover and over said pulley 43. Said motor is provided with a variable speed control mechanism operated by the lever 72. Mounted on the upper shelf portion is a small timing motor 74 of a common design having an upstanding drive shaft 75 having a crank 76 secured thereto and also connected to said lever 72 by a wire link 78. Hence said motor 74- operates to vary the speed of the motor 66 by reciprocating the variable speed control lever 72 and is adapted to do so cyclically.

In cooperative association with the supporting member 29 are lapping assemblies fill and 863. The structure of each including associated elements is the same. Hence only one lapping assembly will be described and corresponding parts of the other will be indicated by like nu merals with primes added. a I

Vertically supported by said member 25 is a lap supporting bracket 81 secured thereto by an angled plate 82 with bolts 33 extending through one face portion of said plate and longitudinal slots in said frame for longitudinal adjustment with a bolt 84 extending through the other face portion of said plate and a vertical slot 81a of said bracket. Said bracket is substantially rectangular in cross section and is disposed in a plane at right angles to the plane of said supporting member 25. Said bracket has a spaced pair of upwardly extending armstiilb secured by bolts 81c forming a bifurcated upper end port-ion 81d having pivoted therein by means of bolts '85 a gimbal 86 of a common design.

The center or vertical plate 86a. of said gimbal has an aperture 88b therein through which is disposed one end of an elongated sleeve 38 secured therein by set screws 96 as indicated in FIG. 4, with said screws also serving to provide a vertical axis for the pivotal movement of said plate 86a. Said sleeve is shown having bushings 92 at either end thereof and slidably disposed therethrough is a spindle 94 extending outwardly'at either end of said sleeve and in the present embodiment is shown being tubular in form having a passage 94a therethrough.

Secured to the upper or outer end of said spindle 94 by a set screw 97 is a collar 1 6 having integral therewith oppositely extending pins 98 from the periphery thereof. Pressed onto the lower or inner end portion of said spindle is a collar 1%. Extending outwardly of said collar and forwardly of said spindle are a plurality of projecting fingers 101 having respectively disposed therethrough cocked set screws 103 which are inclined downwardly and inwardly in the direction of said collar 100, as indicated in FIGS. and 7. Constructed and arranged to be adjustably positioned between said set screws and in engagement with said collar 1% is a cylindrical lap tool or lap head 105 of a common design having a semi-spherical recess therein for lapping or polishing engagement with the work piece. Said lap head is here shown having spaced from its forward end an annular angular notch 105a having an inclined wall or land in a plane substantially at right angles to the plane of the axis of said set screws 163. Said lap head is formed having a central aperture or bore 105b, as

indicated in FIG. 7.

Upstanding from said sleeve 88 forward of said gimbal 86 is a plate member 110 having an integral hub or collar portion extending forwardly thereof with said collar and plate portions being apertured to slip over said sleeve and be secured thereon by a set screw 111. An L frame-like balancing member 112 is secured by bolts 113 at the free end of its shorter leg to the upper end of said plate 11% and extends rearwardly and downwardly therefrom. At the lower free end of said member 112 are outwardly extending pins 112a adapted to retain weights 115. Said member 112 will be weighted to balance the lapping assembly 80 to locate the center of gravity with reference to the point of said gimbal 86 whereby there will be no pressure'of gravity of consequence affecting the operation of the lap head 105. V

Mounted on the forward side of said plate member 110 is a small motor 117 which will be connected to a suitable source of power and which will rotate an eccentric crank 121) mounted thereon. An elongated U bracket 122 is mounted on said sleeve 88 forwardly of said motor 117 having upstanding legs apertured to have a rod 124 slidably disposed therethrough with said rod having a yielding upstanding pin 125 with a coil spring 126 about said rod extending between said pin and the rearward upstanding leg 122a of said bracket whereby said rod is normally urged forwardly into contact with said cylindrical plate member 1% to move the spindle 94 and lap head 1&5 forwardly into engagement with the work piece 53. An arm 128 connects the upper end portion of said pin 125 and said crank 1-20 to control and vary the axim thrust exerted.

Spaced rearwardly of said bracket 81 is an elongated upstanding vertically angled plate bracket 13% having an open-ended vertical slot 136:: at its lower end portion through which is disposed a bolt 132 adjustably securing said bracket to said member 25.

Carried at the upper end portion of said bracket 130 in a suitable manner as by being welded thereto is a housing 132 here shown as a sleeve bearing having a shaft 135 journaled therein and extending outwardly at either end thereof and having a passage 1% therethrough. Said shaft will be substantially in axial alignment with said spindle 9 -5. Carried at the upper extended portion of said shaft 135 is a pulley 140 secured thereto by a set screw 141.

Secured to the other end of said shaft 135 isa collar 149 secured as by being pressed onto said shaft. Disposed about said collar 149 is a collar 159 secured by a set screw'151 and having extending forwardly thereof a pair of diametrally spaced pins 152 integral with said collar and constructed and arranged to engage the pins 93 to form a pin or fork type coupling.

With reference to FIG. 3 particularly, secured to said shaft 11 extending rearwardly thereof and being spaced above said tray or plate member 14 is a tray or shelf memher 160 indicated here as being apertured to be disposed over said shaft 11 and having a depending hub portion 161 forming a split clamp which is tightened by bolts 163. Said tray 16!) has an upwardly extending angled portion 165 similar to the supporting portion 64. A variable speed motor of a common design which will be connected to a suitable source of power is secured onto said tray 160 as by bolts 171, and is equipped with a variable speed lever 173. Secured onto said shelf 165 is a small timing motor 177 similar to motor 74 having a drive shaft 173 carrying a crank 179 connected to said lever 173 by a crank arm or connecting link 180. Secured to the drive shaft 172 of said motor 170 is a pulley 182 and passing thereover and over said pulley 149 is an endless belt 185.

Said tray 160 extends to either side of said shaft 11 to carry motor 179 in operative alignment with the lap assembly 8t} and a second identical motor 17b in a corresponding operative association with the lap assembly 8t).

Carried upwardly of said shaft 11' is a tray having integral therewith a split clamp 191 secured to said shaft. Supported on said tray is a vessel 193 to carry a supply of suitable lapping compound which in the embodiment here shown will be gravity fed by a depending tube 195 whereby said compound as indicated in FIG. 1 will drip onto the work piece.

In operation, the work piece which in the embodiment of the invention here disclosed is a spherical or ball-like member 53 supported in the cup-like supporting member 38. The lapping assemblies 3% and 8% respectively will be positioned to have the lap heads 1&5 and 105' engaging the work piece at either side thereof. The lapping assemblies will be-counter-balanced by the

members

112 and 112 respectively so that the centers of specific gravity with reference to the gimbals as and 86 so far as the lap headslhj and 165 are concerned, will be at such points that no weight or pressure of any consequence caused by gravity will affect the lapping of the work piece. This represents a substantial improvement over the regular practice in lapping wherein the upper portion of the lap head on the upper portion of the work piece will exert greater pressure upon the work piece than will the lower portion thereof. Moreover the gimbals in providing a relatively uninhibited universal pivotal support for the lap heads permit the lap heads to freely align themselves with the surface areas they are respectively lapping. Thus the counter-balancing and universal pivotal support present here permit a uniformity of lap pressure on the work piece and this in addition to the varied axial thrust present contributes to a more perfect random movement on the part of the work piece. The applicants structure serves to avoid a systematic action of lapping which is a common occurrence in ordinary practice and which serves to affect the work piece to prevent it from exercising perfect random movement.

Thus the lapping of the work piece 53 will be substantially free from any effect of the pressure of gravity. The only substantial pressure upon the work piece will be the axial thrust exerted by the

spindles

94 and 94. The thrust exerted by said spindles will vary as a result of the action of the motors 116 and 117 in governing the pressure of the

springs

126 and 126 on the shafts 12.4 and 124' in respectively causing said shafts to increase and decrease the axial thrust of the

spindles

94 and 94 cyclically in the embodiment of the invention here presented. Said spindles will be respectively rotated through associated elements by means of the motors 170 and 17 respectively driving the pulleys 140 and 14h. Said pulleys may be and normally will be respectively rotated at different rates of speed and in the same or opposite directions as may be desired. Preferably they will be rotated in opposite directions. As a result of the action of the timing motors 177 and 177', there will be a cyclical variance in the rate of speed at which said pulleys are respectively driven, and thus there will be a cyclical variance of the angular velocities of the lap heads. This will be controlled as may be desired. The shaft 39 will be rotated through associated elements by the motor 66 and the ro tation of this shaft may be cyclically varied by means of the timing motor 74. The shaft 39 may be used as stationary support as may be desired in the lapping operation.

As illustrated in FIG. 5, the supporting cup-shaped portion 38a forms a hydrodynamic bearing with fluid being introduced through the supply line 34 and the passage 43 into the relief portion 380 of said portion 38a and onto the land or edge portions 381) on which the work piece is supported. A relatively wide groove 32 in the bearing block 39 provides a chamber for the fluid and from this point it passes through the passage in the shaft 39 upwardly to the supporting portion 38a. The portion 38a will be of a size to suitably support the work piece.

It is noted that a pin type of coupling is used to transmit the driving force from the pulleys 140 and 140' respectively to the

spindles

94 and 94 respectively so that no adverse torque is developed to affect the axial alignment of the

spindles

94 and 94 nor to affect their delicate balance as previously indicated. The spindles 94 and W will be aligned with respect to one another so that an extension of their axes will intersect at a point representing the center of the work piece.

Lapping compound is indicated as being gravity fed onto the work piece by means of the supply line 195, as indicated in FIG. 1.

Applicants device has been unusually efficient and effective in lapping spheres to a degree of perfection in sphericity which has heretofore seemed impossible as a practical thing. It provides an unusual degree of freedom of random movement of the workpiece and the uniformity of lapping pressure not only contributes to the unusual degree of random movement present, but also directly contributes to the perfect sphericity obtained.

With reference to FIG. 5, it is noted that the lap head N is adjustably held by the spaced cocked set screws 103 which allow for a very nice adjustment of said lapping head in setting up the apparatus for a lapping operation.

With reference to FIG. 6, a work piece supporting structure 280 is shown which is a modification of the supporting structure 29. The supporting structure 2% is 6 secured to the member 25 by bolts 27 and supports the tray 55 in like manner, as in connection with the supporting member 29.

The structure 200 is disclosed as being stationary and comprising a block or housing 201 having a central vertical passage 202 therein connected at its lower end by a suitable fitting 203 to a supply line 264 communicating with a suitable supply of fluid under pressure.

The upper portion of said block 261 has a vertical bore 205 therein into which is pressed the lower end portion of an upstanding shaft 207 having a passage 2% therethrough in communication with the passage 2%. Carried on said shaft is a supporting head 21% having a central bore 217 extending upwardly therein into which is received the upper portion of said shaft 2&7. Said member 210 has a substantially cylindrical base portion having a relief portion 211 at the under side thereof and having upstanding therefrom a saddle-shaped supporting portion 212 arcuate in longitudinal vertical section with its curvature being such as to nicely embrace the segment portion of the work piece disposed therein. Said member 2-16 is removiab ly held in position by a set screw 213.

The modified supporting member above described provides a stationary support for the work piece. It is noted that the supporting portion 212 in being saddle-shaped provides support for a larger segment of the work piece than does the supporting portion 335:, as indicated in FIG. 5. This is particularly adapted to be used as a hydrostatic bearing with fluid under suitable pressure being introduced through the passages 232 and 2% to provide a fluid support for the work piece. In all respects the operation will be as above described.

Detail structure of the lapping assemblies 34B and till is indicated in the sectional view shown in FIG. 7. However in addition in FIG. 7 are shown two elements not indicated in the assemblies as shown in FIG. 1 and which provide an alternate operation in feeding lapping compound to the work piece and this is in substitution for the receptacle 193 and its feed line 195.

A supply line 145 is shown connected to the extended end of the bored shaft outwardly of the pulley by a rotary seal 146. The supply line will be connected to a suitable source of lapping compound.

The passage 136 in the shaft 135 is of a smaller diameter than the passage in the spindle 94. A tube 155 will have one end pressed into said passage 136 and have its other end extend freely into the passage of said spindle to provide a line of communication from said supply line through the passage 94a of said spindle.

Thus with this arrangement lapping compound may be fed onto the work piece through either

spindle

94 or 94 or through both as may be desired.

Thus it is seen that I have provided a relatively simply constructed lapping apparatus which provides an unusual degree of uniformity in lapping a work piece. This apparatus has proved to be unusually successful in operation.

It will of course be understood that various changes may be made in the form, details, arrangement and pro portions of the parts, without departing from the scope of applicants invention which, generally stated, consists in a device capable of carrying out the objects above set forth, in the parts and combinations of parts disclosed and defined in the appended claims.

What is claimed is:

1. A lapping apparatus for lapping a spherical body having in combination, a plurality of laps, balanced means respectively supporting said laps for universal pivotal movement, and fiuid means vertically supporting said spherical body in lapping engagement with said laps.

2. A lapping apparatus for lapping a spherical body having in combination, a plurality of laps, means respectively supporting said laps for axial and rota-tive movement, means automatically cyclically varying said axial movement of said laps and means supporting said spherical body in lapping engagement with said laps.

'7 3. A lapping apparatus for lapping a spherical body having in combination, a plurality of laps, balanced means respectively supporting said laps for uninhibited universal alignment'with the surface of said spherical body, and iluid means vertically supporting said spherical body in lapping operation.

4. A lapping apparatus for lapping a spherical body having in combination, a plurality of laps, said laps respectively comprising spindles, slee es respectively having said spindles disposed therethrough for free axial and rotative movement, means universally pivotally supporting said spindles, means counter-balancing said spindles fixing their respective centers of gravity at their pivotal supporting points for uniform pressure of said laps about the full area of their engagement with said spherical body,

and means vertically supporting said spherical body in lapping engagement With said laps.

5. A lapping apparatus for lapping a spherical body having in combination, a supporting structure, a pair of lap assemblies having adjacent end portions, means in connection with said supporting structure universally pivotally supporting said lap assemblies in opposed relation,

an upstanding member comprising a fiuid cushion sup-' heads, and means rotating said lap heads.

6. The structure set forth in claim 5, and means rotating said supporting member of said spherical body and means automatically cyclically varying the rate of said rotation.

7. A lapping apparatus for lapping a spherical body having in combination, a supporting structure, a lap assembly comprising a lap head, rneans mounting said lap assembly on said supporting structure for universal pivotal movement, means pivotally counterbalancing said lap assembly with respect to the point of said mounting means to negative the eilect of gravity at the point of said lap head in operating position.

8. The structure set forth in claim 7, said lap head having axial movement, and means for automatically cyolically varying the axial thrust of said lap head relative to said spherical body.

9.' A lapping apparatus for lapping a work piece having a spherical surface having in combination, a. plurality of laps, balanced means respectively supporting said laps for axial and rotative movement, and means respectively supporting said last mentioned means for free universal alignment of said laps to said spherical surface.

10. The structure set forth in claim 9, means automatically cyclically varying said axial and rotative movement.

11. The structure set forth in claim 9, said last mentioned means being remote from said laps.

12. The structure set forth in claim 9, and means comprising a iluid cushion supporting said Work piece in lap ping engagement with said laps.

References Cited in the file of this patent UNITED STATES PATENTS' 1,806,918 Riggs May 26, 1931 1,950,785 Capps Mar. 13, 1934 2,405,344 Cloutier Aug. 6, 1946 2,479,898 Beaude-tte Aug. 23, 1949 2,787,093 S-undberg Apr. 2, 1957 2,892,326 Porter June 30, 1959 3,024,578 Mushkin Mar, 13, 1962

Claims

1. A LAPPING APPARATUS FOR LAPPING A SPHERICAL BODY HAVING IN COMBINATION, A PLURALITY OF LAPS, BALANCED MEANS RESPECTIVELY SUPPORTING SAID LAPS FOR UNIVERSAL PIVOTAL MOVEMENT, AND FLUID MEANS VERTICALLY SUPPORTING SAID SPHERICAL BODY IN LAPPING ENGAGEMENT WITH SAID LAPS.