US2541912A - Method for conditioning rotatable grinding wheels - Google Patents

Description

Feb. 13, 1951 I w. w. BROUGHTON 2,541,912

METHOD FOR CONDITIONING ROTATABLE GRINDING WHEELS Filed June 18, 1947 FIGJ.

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U [mg n nnn 22 EIHIHIHIIEI [:HIHIJEI] nuu n nun IN VENTOR W. W. BROUGHTON A TTORNEY Patented Feb. 13, 1951 UNITED STATES TNT OFFICE METHOD FOR EONDITIONING ROTATABLE GRINDING W'HEELS York Application June 18, 1947, Serial No. 755,399

6 Claims.

This invention relates to a method of conditioning rotatable grinding wheels, more particularly diamond grinding wheels employed in -grind ing quartz crystals or the like.

Various methods and apparatus are employed in producing wafer-like'structures fro-m quartz crystals beginning with the mother stone and ending with the final wafer suitable for use in quartz crystal filters and other electrical units. The method of particular interest includes the use of a rotatable grinding wheel commercially known as a diamond grinding wheel, containing diamond particles embedded in a base of softer material, employed to grind quartz crystal members to given thicknesses. The crystals to be ground are cemented to one or more mounting plates di, posed upon a rotatable unit, such as a magnetic chuck, rotated about its axis relative to a rotatable grinding wheel. It has been necessary to recondition the rinding wheel after each grindin operation to sharpen the wheel by removing quantities of the base material and exposing diamond particles for the next grinding operation.

I Heretofore, the reconditioning or sharpening process was carried out by the aid of a carborundum stick held against the face of the grinding wheel while rotating, but positioned away from the chuck and mounting plates. The reconditioning operation was thus left to the discretion of the operation and when the crystals were ground 1 on a piecework basis, it was the tendency for the operator to apply the carborundum stick for a longer interval of time than was necessary to sharpen the grinding wheel, in an attempt to make the wheel extra sharp to shorten the time 3':

for grinding the crystals to their required thickness. As a result, the useful life of the grinding wheel was greatly shortened and its grinding action was made non-uniform by irregular sharpening of the wheel due to the application of the carborundum stick at certain portions of the grinding wheel for longer intervals of time than at other portions thereof.

The object of the present invention is to eliminate excess reconditioning wear of grinding wheels by the use of a methodwh-ich removes only the required quantity of base material and maintains the grinding wheel uniformly sharp.

With this and other objects in view the invention comprises the method of conditioning rotatable grinding wheels for grinding articles. The apparatus includes an abrasive member and a mounting element, for both the abrasive member and the article to be ground, mounted on a support and movable relative to "the grinding wheel.

2 The method includes the step of mounting an abrasive member on the support with the article to engage the grinding wheel during relative movement of the support and grinding wheel to condition the grinding wheel during grinding of the article.

In the present embodiment of the invention, carb'orundum wafers, greater in thickness than the initial thickness of the articles or quartz crystal members, are cemented on mounting plates with the articles at spaced positions whereby all surfaces of the grinding wheel will be engaged by the wafers durin grinding operation. The mounting plates are pie-shaped in general contour and are disposed upon a magnetic chuck Where they are held during rotation of the chuck about its axis. The axis of the chuck is offset from the axis of the grinding wheeland parallel therewith whereby the articles, together with the wafers are moved to be engaged by the grinding wheel. The grinding wheel has a given downward pressure to first engage the carborundum wafers and be reconditioned'thereby prior to the engagement of the grinding wheel with the articles, the carborundum wafers continuing to recondition the articles during the grinding operation reducing them to their given thickness.

Other objects and advantages will be apparent from the following detailed description when considered in conjunction with the accompanying drawing, wherein Fig. 1 is a fragmentary front elevational view of the grinding apparatus by the aid of which the method may be practiced;

Fig. 2 is a top plan view of the magnetic chuck with the mounting plates disposed thereon;

Fig. 3 is a fragmentary detailed view of a portion of the grinding wheel;

Fig. 4 is a perspective view of one of the conditioning wafers prior to mounting on the mountin'g plate;

Fig. 5 is a perspective view of one of the wafers at the completion of the grinding operation; and

Fig. 6 is a perspective view of a carborundum stick as employed in the former reconditioning method Referring now to the drawing, the apparatus includes a magnetic chuck Hi supported on avertical shaft H for rotation in agiven direction about the vertical axis of the shaft.

' Mounting plates l2 are pie-shaped in general contour whereby one, two, three or-four of them may be disposed upon the magnetic chuck for the grinding of articles M. In the present embodimerit-of the invention, the articles M are quartz crystal members which are to be reduced in thickness to a given dimension.

The grinding wheel mounted for rotation with its shaft l6, the axis of which is spaced from, but parallel with the shaft H, is employed to grind the articles to their given thickness. In the present embodiment of the invention, the grinding wheel is of the diamond type, including a multiplicity of diamond particles 18 embedded in a base or supporting material 19. During grinding operations upon quartz crystals or other similar materials, the diamond grinding wheel becomes dull and must be sharpened to increase its effectiveness by periodically removing portions of the base material to expose the diamond particles and to thus sharpen the grinding wheel. Heretofore the sharpening or conditioning operation has been accomplished by the aid of a carborundum stick 2e forced manually against the face of the grinding wheel.

This method had its unsatisfactory results, first in producing irregular sharpening of the wheel, and the rapid wearing away of the .wheel unnecessarily to greatly reduce its effective life.

The present apparatus includes wafers 22, formed of abrasive materials such as carborundum, mounted at spaced positions on the various supports [2 whereby all portions of the face of the grinding wheel will be engaged by the wafers prior to and during the grinding operation. It will be observed by viewing Fig. 1 that the conditioning wafers 22 are thicker than the initial thickness of the articles 14 whereby the face of the grinding wheel will be conditioned removing portions of the base material H] from the grinding wheel to expose diamond particles l8 and to thus sharpen the grinding wheel before it meets the articles I4 to begin the grinding operation thereof. Furthermore, the grinding operation is shortened by the constant conditioning of the'grinding wheel during the grinding operation. Although the wafers 22 are ground down to the initial thickness of the articles M in their initial conditioning step, they continue to condition the face of the grinding wheel as the articles are ground to their desired thickness.

In this manner, excess materials are not removed from the grinding wheel and the time previouslyrequired for conditioning the grinding wheel is greatly reduced. All that is required of the operator is the mounting of the wafers 22 at scattered positions on the mounting plates l2 among the articles I a which are to be ground. The wafers remaining upon the mounting plates at the completion of the grinding operation may be removed with the articles and when an additional supply of articles on mounting plates are disposed upon the chuck IE! with the desired number of wafers 22 selectively positioned on the supporting plates, no time is lost for conditioning the grinding wheel in that it is conditioned during its movement toward the articles.

Although specific improvements of the invention have been shown and described, it will be understood that they are but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as defined by the appended claims.

What is claimed is:

1. The method of conditioning rotatable grinding wheels for grinding articles disposed on a mounting element of a support therefor movable relative to the grinding wheel, the method comprising mounting an abrasive member on the mounting element with the article to engage the grinding wheel during relative movement of the support and grinding wheel to condition the grinding wheel during grinding of the article.

2. The method of conditioning rotatable diamond grinding wheels for grinding articles, such as quartz crystals, disposed on a mounting element of a support therefor movable relative to the grinding wheel, the method comprising mounting an abrasive member on the mounting element with the article to engage the grinding wheel during relative movement of the support and grinding wheel to condition the grinding wheel during grinding of the article.

3. The method of conditioning rotatable diamond grinding wheels for grinding articles, such as quartz crystals, disposedon a mounting element of a support therefor movable relative to the grinding wheel, the method comprising mounting an abrasive member thicker than the article on the mounting element with the article to engage the grinding wheel during relative movement of the support and grinding wheel to condition the grinding wheel prior to and during grinding of the article.

4. The method of conditioning rotatable grinding wheels, composed mainly of diamond particles in a molded bindin material, for grinding particles, such as quartz crystals, disposed on a mounting element of a support therefore movable relative to the grinding wheel, the method comprising mounting an abrasive member on the mounting element with the article to engage the grinding wheel during relative movement of the support and grinding wheel to remove portions of the binding material of the grinding wheel during grinding of the article to maintain the diamond particles exposed to the article.

5. The method of conditioning rotatable grinding wheels, composed mainly of diamond particles in a molded binding material, for grinding articles, such as quartz crystals, disposed on a mounting element of a support therefor movable relative to the grinding wheel, the method comprising mounting an abrasive member thicker than the article on the mounting element with the article to engage the grinding wheel during relative movement of the support and grinding wheel to remove portions of the binding material of the grindin wheel prior to its engagement with the article and during grinding of the article to maintain the diamond particles exposed to the article.

6. The method of conditioning a movable grinding element for grinding articles disposed on a mounting element of a support therefor movable relative to the grinding element, the method comprising mounting an abrasive member on the supporting element with the article to engage the grindin element during relative movement of the support and the grinding element to condition the grinding element during grinding of the article.

WILLIAM W. BROUGHTON.

REFERENCES orrsn The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Briney Mar. 28, 1944

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