US2308512A - Grinding machine - Google Patents

Description

Jan. 19, 1943. 1 P. R. HOFFMAN 2,308,512

GRINDING MACHINE Filed Dec. 6, 1941 2 Sheets-Sheet l [34 a V I /a /6 ll 20 e0 6 60 Jan. 19, 1943. P. R. HOFFMAN f3 2,308,512

GRINDING uAcIiIm-f Filed Dec. 6, 1941 isheets-sheet 2 Philip R. Hoffmdnz method and means.

7 other objects of the vention is disclin Patented Jan. 19, 1943 Philip B. Hoflman, Car, Pa Grover C. Hunt, Carlisle, Pa

' Application December 0, 1941, Serial No. 421,999

This invention relates to grinding machines of the type generally known as lapping machines and, more specifically, relates to lapping machines which are particularly intended for the grinding of polygonal, relatively thin devices or articles such as piezo-electric crystals.

It has heretofore been proposed, and is now known, to provide a lapping machine in which externally geared, disc-like work holders aredisposed between two superposed abrasive discs and are geared to an inner rotating pinion which is located centrally of the discs and to a ring gear which surrounds and is concentric with the pinion, either the pinion or the ring gear being rotated to cause the work holders to describe a planetary movement about the centers of the discs and, simultaneously, to rotate about their respective axes. The articles carried by the work holders are thus caused to move in either an epicycloidal or hypocycloidai path across the faces of the discs.

It is an object of the invention to provide a in a lapping machine of the type in which the work holders move in a planetary path and simultaneously rotate about their respective centers, to cause the articles being ground to follow a non-cycloidal path in which they will be swept circumferentially of the discs throughout their movement, thereby providing an improved grinding action. It is also an object of the invention to provide a machine which is particularly useful and advantageous in the diilicult and exacting work of grinding piezo-electric crystals.

Means for effecting these objects, as well as invention, will be made apparent by the following description and the annexed drawings, it being understood that the description and drawings are only illustrative of the invention, for the limits of which reference must be had to the appended claims.

Referring to the drawings, in which the same reference numerals and letters refer to like parts,

Pig. 1 is a vertical sectional view of a machine according to my invention, taken on line ii of Fig. 2 is a plan view of the machine of 1, taken on line 2-2 of 1, and 1 Fig. 3 is a schematic view of one of the discs. showing the typical path of an article being ground when my invention is employed. a thefeaturesofmyin- A machine the Thus, as shown in Fig. 1, the machine comprises a base or pulley and belt arrangement 22.

standard 2 which supports a lower abrasive disc 4 adapted to be receivedwithin which is fixed against movement, as by rigid at tachment to the base. The lower disc is provided with a preferably circular central opening within which is disposed a pinion gear 6 which may be driven by any suitable" means such as the pulley and belt 8. The gear dextends substantially above the upper surface of the lower disc. Surrounding the disc 4 is a ring gear i0 which is provided with internal and external teeth I2, II respectively, it being noted that the pinion gear 8 and ring gear Iii are concentric. The ring gear I0 is mounted for rotation and is supported by bearings l6 which engage the lower surface of an annular flange or cover 18 which is connected to the upper surface of the ring gear. A driving gear 20 engages the external gear teeth ring gear l0 and, in order to rotate the ring gear, may be driven by suitable means such as the An upper abrasive disc 80, which is substantially identical with the iowerdisc is attached to a cover 32 and is the ring gear, whereby the abrasive faces of the two discs are opposed and will be in engagement with each other unless the crystals or the work holding means which are described hereinafter are interposed between them. The cover 82 is provided with openings within which a fixed pin, such as N, may be received in order to prevent rotary or other movement of the upper disc. The cover may also be provided with handles 38 whereby it and the attached upper disc may be lifted. The upper disc and the cover therefor provided with a central opening the upper portion of the pinion gear 6. Between the two so each of which is provided with gear teeth on its external periphery and is of such size that the those on the pinion. gear I and the internal teeth l2 of the ring gear. Openings 8: are provided in each work holder, within which the crystals are received and held during movement of the work holders.

In accordance with my invention, the pinion By reason of the rotation of both gears in'the. same direction and at different speeds the work holders will move in such a way that a crystal M of the discs are provided circular work holders over the faces of the discs, by reason of the fact that the slower rotation of the ring gear in the "produced by rotation of the pinion gear and the rin gear at the specific speeds mentioned hereinbei'ore. By reason of this movement the grinding action on the crystals is improved and the wear on the abrasive surfaces is made more uniform.

It will be seen, by reference path followed by a crystal when ground in a machine constructed and operated in accordance with this invention iollows long, sweeping, overlapping lines having large circumferential components. The radial travel from the outermost periphery to the innermost periphery, as between points a and b in the direction of the arrow, requires a travel of almost one-half of the circumference of the discs. Thes: lines of travel, overlapping as shown in Fig. 3 cause the entire faces tom.s,tnsttne of the discs to be traversed by the crystals being ground, thus causing completely even wear of the surfaces of the discs, whereby the character of the grinding is improved and the life of the discs prolonged.

While I have described my invention with refer-' ence to the grinding of crystals, it will be understood that the invention is of general application and is not limited to the grinding of any particular materials or devices. It will also be understood that while I have described my invention with reference to a machine having flxed,-

horizontal, vertically-spaced abrasives, it may without departing in any way from the invention be applied to other types and constructions ofgrinding machines.

Although only one form of the invention is illusthis application, it will.

trated and described in be understood by those skilled in the art that modifications and improvements 'may be made without departing in any way from the spirit or scope of the invention. for the limits of which reference must be had to the appended claims.

Iclaim:

1. A lapping machine comprising a pair of opposed abrasive discs, a pinion gear at the center of said discs, 9. ring gear concentric with said pinion gear and surrounding said discs, a plurality of externally geared work holders between said discs and arranged in a series about the pinion gear and being geared to said pinion and ring gear, and means for rotating both said pinion gear and ring gear.

2. A lapping machine comprising a pair of opposed abrasive discs, a pinion gear at the center of said discs, a ring gear concentric with said pinion gear and surrounding said discs. a pinrality of externally geared work holders between said discs and arranged in a series about the pinion gear and being geared to said pinion gear and ring gear, means for rotating the pinion gear.

and means for rotating the ring gear at a speed in R. P. M. less than that or the pinion gear.

3. A lapping machine comprising a pair of opposed abrasive discs, a pinion gear at the center of said discs, an internal ring gear concentric with said pinion gear and surrounding said discs, a plurality of externally geared work holders between said discs and arranged in a series about the.pinion gear and being geared to said pinion gear and ring gear, and means for rotating both the pinion gear and the ring gear at diiierent speeds in R. P. M. v

4. In the grinding or articles by machines of the type comprising two opposed abrasive discs, a pinion gear disposed at the center of the discs, a ring gear disposed concentrically or the pinion gear and surroundingthe discs, and a work holder disposed between the discs and having external gear teeth meshing with those of the pinion gear and the ring gear, the method of causing articles held by the work holder to move over the discs which consists in rotating the pinion gear and rotating the ring gear at a speed in R. P. M. which is less than that or the pinion gear.

PHILIP R. mm.

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