US3138901A - Sphere grinder - Google Patents

Description

June 30. 1964 E. F. HEINTZELMAN ETAL 3,138,901

SPHERE GRINDER Filed Aug. 14, 1962 INVENTOR5. ERNEST F. HEINTZELMAN JOHN G. STEWART CLIFFORD G. REED BY W ATTY.

United States Patent() v 3,138,901 SPHERE GRHQDER Ernest F. Heintzelman, Hyattsville, John G. Stewart, Beltsville, and Ciiiiord G. Reed, Poolesville, Md, assignors to the United States of America as represented by the Secretary of the Navy I Filed Aug. 14, 1962, Ser. No. 217,731 11 Claims. (Cl. 51-129) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used' by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to apparatus for grinding and polishing spheres and more particularly to semi-automatic apparatus for grinding and polishing, for example, yttrium-iron garnets and other ceramic type spheres.

In the field of sphere grinding and polishing, it has been the general practice to employ a donut mill in which the sphere is tumbled against an abrasive media; hollow pipe apparatus in which the sphere is mounted between two hollow pipes, one of which is rotating and with abrasive in the hollow pipes; flat plate apparatus in which the garnet is rolled between flat plates in an abrading medium; and a hand polishing technique using appropriate abrasives. Although such devices and techniques have served the purpose, they have not proved entirely satisfactory. For example, the donut mill and two-pipe apparatus both require a long polishing time and constant manipulation and artistry on the part of the operator of the apparatus; the flat plate apparatus has been prone to produce flats on the spheres; and the hand polishing technique is extremely slow in attaining a sphere which is quite smooth, but in many cases lacking in spheroidicity.

The general purpose of this invention is to provide a sphere grinding apparatus which embraces all the advantages of similarly employed prior art devices and possesses none of the aforedescribed disadvantages. To attain this, the present invention contemplates a unique sphere grinding and polishing apparatus whereby spheres are produced with a highly polished surface and a 'very close spheroidicity tolerance in a short period of time.

It is therefor an object of this invention to provide new and improved apparatus of the character described.

7 Another object is to provide a sphere grinding and polishing apparatus which is semi-automatic, requires no critical adjustments, and does not require constant manipulation and artistry on thepart of an operator.

A further object of the invention is the provision of grinding and polishing apparatus which is compact, simple in construction, inexpensive to manufacture, and having parts which are easily replaceable.

Still another object is to provide apparatus for etficiently grinding and polishing spheres of various materials and sizes in a short period of time.

Yet another object of the present invention is the provision of sphere grinding and polishing apparatus for producing spheres having a highly polished surface and a very close spheroidicity tolerance.

A still further object is to provide a sphere grinding apparatus wherein the grinding pressure can be easily and accurately controlled and abrasives can be readily changed.

Other objects and various further features of novelty and invention will be apparent to those skilled in the art from a reading of the following specification and claims in conjunction with the accompanying drawing, which 3,l38,%1 l atented June 30, 1964 shows, for illustrative purposes only, one form of the invention and in which:

FIG. 1 is an elevational view, partly in section, of one form of the invention; and

FIG. 2 is a sectional view taken along line 2-2 in FIG. 1.

In the illustrated example of the invention, and referring first to FIG. 1, the reference numeral 11 designates a chuck of the jewelers lathe type which may be rotatably mounted in any suitable manner on any type of suitable support means, for example, a supporting frame or table for the entire grinding apparatus or a separate supporting frame, for the chuck itself. The chuck 11 may be rotated by any suitable type of variable drive means such as a variable speed motor which may be coupled to the chuck in any known manner. The chuck 11 is provided with a central bore 12 therein, and the lower cylindrical end 13 of an anvil member 14' is mounted within the bore 12. The mounting of the lower end 13 of the anvil member 14 in the bore 12 is such that the anvil member will rotate with the chuck, but still be removable from the chuck bore when a change of .the anvil member is desired. A laterally extending flange i5 is formed on the anvil member 14 and rests on the fiat end face 16 of the chuck 11 to limit the amount of extension of the anvil member into the chuck bore 12 to only the lower end portion 13. The anvil member is provided with an upper cylindrical end portion 17 having a fiat end surface 18 upon which the workpiece 19 to be ground and polished and the appropriate abrasive are placed.

A cylindrical sleeve member 21 is located above and in vertical alignment with the anvil member 14. A bore 22 is formed in the lower end of the sleeve member 21 to slidably and rotatably receive a part of the upper end 17 of the anvil member 14. The bore 22 terminates in a fiat surface 20 which is parallel to the flat end surface 13 on the anvil upper end 17. The tubular pore tion 23 of the sleeve member 21 surrounding the bore 22 serves to retain the abrasive and the workpiece 19. between the fiat surfaces 18 and 20. A spherical recess 24 is provided in the upper end of the sleeve member 21 to removably receive a spherical weight 25 therein for the purpose of providing a controlled grinding pres sure on the workpiece 19.

Referring now to FIGS. 1 and 2, the sleeve member 21 is prevented from rotating and maintained in vertical alignment with the anvil member 14 by a support arm 26 having a U-shaped portion 27 at one end thereof into which the sleeve member is received. A U-shaped clamp 28 contacts the sleeve member to prevent rotary movement thereof and is connected to the U-shaped portion 27 on the arm 26 by a pivotal connection 29 and a wing nut connection 30. The support arm 26 is provided with a laterally extending dovetail portion 31 at the other end thereof which is slidably mounted in a vertical dovetail groove 32 in a supporting member 33 that is rigidly attached by any suitable means to a fixture 34 which may be part of a supporting frame, work table or any other suitable supporting means for the entire grinding apparatus or for the supporting member 33 only. The dovetm'l portion Sland therefore the sup port arm 26 are supported within the dove-tail groove 32 by a spring 35 mounted in the groove 32, thereby providing a flexible suspension in a vertical direction for the support arm 26 and the sleeve member 21.

The size of and the material used for the anvil member 14 and the sleeve member 21 will be dependent upon the workpiece material and size. Also, the type and schedule of abrasives used, the size of the weight 25, and the rotatronal speed range of the chuck 11 will vary with the sphere material and the final size, polish, smoothness and accuracy of the finished sphere that is desired. Normally, the workpiece will be a rough sphere of a desired diameter that has been produced from an irregular piece in suitable grinding apparatus such as a donut mill. It is noted, however, that it is possible for the workpiece to be a jagged or irregular spherical piece and still result in a near perfect sphere with excellent smoothness through the use of the present apparatus.

As an example, when the workpiece is a single crystal yttrium-iron garnet and a finished sphere of a diameter ranging from to 100 thousandths of an inch is desired, the diameter of the sleeve member 21 will be approximately 0.312 inch with a bore 22 of approximately 0.140 inch and the diameter of the upper end 17 of the anvil member 14 will be approximately 0.135 inch. Under these conditions, a 1 to 8 gram Weight 25 is placed on the sleeve member 21 and a chuck rotational speed range of approximately 1,500 to 2,500 revolutions per minute is used. For optimum spheroidicity, a 2 gram weight and a chuck rotational speed of 2,000 revolutions per minute have been found to yield the best results. When using a yttrium-iron garnet for the workpiece, a linen base phendic sleeve member and anvil member have been found to yield the best results, and an accurate and highly polished sphere can be produced in approximately 6 hours in accordance with the following schedule:

Abrasive: Grinding time micron (diamond compound) hrs 3 6 micron (diamond compound) hr 1 3 micron (diamond compound) hr /2 1 micron (diamond compound) hr /2 /2 micron (diamond compound) min 15 micron (diamond compound) min 15 Fine Abrasive Linde A min 15 Fine Abrasive Linde B min 15 This schedule and therefore the total grinding and polishing time can be varied in accordance with the size and material of the sphere to be ground, the accuracy of the results desired, and other pertinent factors.

With the present invention, a highly polished sphere accurate to :0.001 inch can be produced, as evidenced by Shadowgraph tests. To insure such accurate results, since the abrasive becomes embedded in the sleeve and anvil members, these members should be changed when there is a change of abrasive, and the workpiece should be cleaned between the abrasive stages. Since the sleeve and anvil members are removably mounted in a simple manner in the support arm 26 and the chuck 11, respectively, it is a simple operation to replace these members when there is a change of abrasive and to thoroughly clean the workpiece between the abrasive stages. With the present invention, therefore, the workpiece is ground and polished between flat abrasive-loaded surfaces which have the ability to hold the abrasive, become wear resistant, and remain flat, which aids the final attainment of spheroidicity. Except for the changing of abrasive and the anvil and sleeve members, and the cleaning of the workpiece, the present apparatus is fully automatic and requires no constant manipulation or artistry on the part of the operator. Variations in the anvil and sleeve materials can be used to give varying surfaces on different materials used for the workpiece. For example, Teflon, steel, lucite and copper anvil and sleeve members have been successfully used to grind and polish spheres of such materials as nylon, aluminum and Teflon. It is noted that various other materials could be used for the anvil and sleeve members as well as the workpiece, depending on the results desired.

Various modifications could be made in the construction of the present invention without departing from the scope thereof; for example, the weights used need not be spherical but could be of any desired shape to seat in a correspondingly-shaped recess in the sleeve member; the sleeve member could be supported in vertical alignment with the anvil member and prevented from rotating by any suitable type of clamping means and any suitable type of support arm; the support arm could be flexibly suspended in a vertical plane by any suitable means; and the anvil member could be removably supported in alignment with the sleeve member by any suitable rotatable means.

While the invention has been described in detail for the illustrated form, it will be understood that many other modifications may be made within the scope of the invention as defined in the appended claims.

What is claimed is:

1. Apparatus for grinding and polishing minute spheres comprising rotatable support means having at the upper end thereof a flat surface upon which the sphere to be polished and an abrasive are placed, and nonrotatable means for retaining the sphere on said flat surface having a fiat face near the bottom thereof disposed vertically above said fiat surface and resting on the sphere.

2. Apparatus for grinding and polishing minute spheres comprising rotatable support means having at the upper end thereof a flat surface upon which the sphere to be polished and an abrasive are placed, means for retaining the sphere on said fiat surface having a flat face near the bottom end thereof disposed vertically above said flat surface and resting on the sphere, and means connected to said retaining means for preventing the rotation thereof and for flexibly supporting said retaining means in a vertical direction.

3. Apparatus for grinding and polishing minute spheres comprising rotatable support means having at the upper end thereof a fiat surface upon which the sphere to be polished and an abrasive are placed, nonrotatable means for retaining the sphere on said flat surface having a flat face near the bottom end thereof disposed vertically above said flat surface and resting on the sphere, and means mounted on said retaining means for applying a controlled grinding pressure to the sphere.

4. Apparatus for grinding and polishing minute spheres comprising rotatable support means having at the upper end thereof a flat surface upon which the sphere to be polished and an abrasive are placed, means for retaining the sphere on said flat surface having a flat face near the bottom end thereof disposed vertically above said fiat surface and resting on the sphere, means connected to said retaining means for preventing the rotation thereof and for flexibly supporting said retaining means in a vertical direction, and means mounted on said retaining means for applying a controlled grinding pressure to the sphere.

5. The apparatus of claim 4 wherein said support means includes a rotatable chuck having an anvil member mounted thereon to rotate therewith, said anvil member having said flat surface thereon.

6. The apparatus of claim 5 wherein said retaining means comprises a sleeve member having at the lower end thereof a bore therein which terminates at said flat face, said flat surface and a portion of said anvil mem ber being located within said bore, whereby the sphere will be retained on said fiat surface within said bore.

7. The apparatus of claim 6 wherein said means for preventing rotation of and flexibly supporting said retain ing means includes a support arm having clamping means thereon for receiving said sleeve member and preventing rotational movement thereof, and spring means for flexibly supporting said support arm in a vertical direction.

8. The apparatus of claim 7 wherein said sleeve mem' ber is provided with a recess at the upper end thereof, and said means for applying a grinding pressure comprises a weight which is seated in said recess.

9. Apparatus for grinding and polishing spheres to a high degree of smoothness and accuracy comprising a rotatable variable speed chuck, an anvil member having the lower end thereof removably mounted on said chuck to rotate therewith and having a flat surface at the upper end thereof upon which an abrasive and the sphere to be ground and polished are placed, a sleeve member in vertical alignment with said anvil member and having at the lower end thereof a bore terminating in a flat face within said anvil member, said flat face being dis posed vertically above said fiat surface and resting on the sphere, said fiat surface and a portion of the upper end of said anvil member being located within said bore to retain the abrasive and the sphere on said flat surface, means connected to said sleeve member for preventing the rotation thereof and for flexibly supporting said sleeve member in a vertical direction, and means mounted on said sleeve member for applying a controlled grinding pressure to the sphere.

10. The apparatus of claim 9 wherein said means for preventing rotation of and flexibly supporting said sleeve member includes a support arm having clamping means thereon for receiving said sleeve member and preventing rotational movement thereof, and spring means for flexibly supporting said support arm in a vertical direction.

11. The apparatus of claim 9 wherein said sleeve member is provided with a recess at the upper end thereof, and said means for applying grinding pressure comprises a weight which is removably seated in said recess.

References Cited in the file of this patent UNITED STATES PATENTS 363,994 Draper May 31, 1887 422,966 Ormsby Mar. 11, 1890 976,875 Hayden Nov. 29, 1910 1,020,803 Crecelius Mar. 19, 1912 2,075,216 Mancuso Mar. 30, 1937 2,703,470 Porter et a1. Mar. 8, 1955 2,912,799 Boettcher Nov. 17, 1959

Claims (1)

1. APPARATUS FOR GRINDING AND POLISHING MINUTE SPHERES COMPRISING ROTATABLE SUPPORT MEANS HAVING AT THE UPPER END THEREOF A FLAT SURFACE UPON WHICH THE SPHERE TO BE POLISHED AND AN ABRASIVE ARE PLACED, AND NONROTATABLE MEANS FOR RETAINING THE SPHERE ON SAID FLAT SURFACE HAVING A FLAT FACE NEAR THE BOTTOM THEREOF DISPOSED VERTICALLY ABOVE SAID FLAT SURFACE AND RESTING ON THE SPHERE.

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