US2244734A - Precision spindle for grinding wheels and the like - Google Patents

Description

ROLLIWMSEVERANCE June 10, 1941.

R. M. SEVERANC'E PRECISION SPINDLE FOR GRINDiNG WHEELS AND THE LI Filed March 15, 1939 A BN m N\ S] m mm H l1 4. w .QQQENQQ n m 5, x. ax. w 59 Q w MN AWN INVENTOR ATTORNEY.

Patented June 10, 1941 PRECISICN SPINDLE FOR GRINDING WHEELS AND THE LIKE l tollin Severance, Saginaw, Mich.

Application March 15, 1939, Serial No. 261,900

' 1 Claim.

This invention relates to grinding machines and pertains more particularly to a precision spindle mounting device for grinding wheels used in certain classes of work that require extreme wheel accuracy for the rapid removal of metal from a work piece and for giving maximum durability to the grinding wheel.

Correct appreciation of the novelty and advantages in use of my present improvement requires a brief explanation of well-known characteristics which attend the use of grinding wheels in devices of the character to which this invention is especially adaptable.

In the mass production of milling cutters, drills, reamers and the like the work piece is held'by means of automatic profiling appliances, but such equipment is very expensive and is economical only when used in mass production of identical parts.

There is an extensive field wherein relatively small numbers of special shaped tools are required that can not be made economically on machines equipped with automatic work holding and guiding devices.

Special shaped tools in small lots must be made on less expensive machines, the work being guided and directed by the operators hands as in diamond cutting, and gauged by his eyesight with the aid of a magnifying glass. My present improvement is especially adapted to do that class of work. At first small diameter grinding Wheels are used. They were made very hard, and proved unsatisfactory principally because their rate of removal of metal from the WOIk piece was too slow. It was found by experiment and research that for best cutting results the particles of abrasive should Wear away from the Wheel continually during the work so as to keep presenting a fresh grinding surface. Softer wheels were tried and gave somewhat better rates of metal removal, but soft wheels had the serious disadvantage that they would get slightly out of true and as soon as they commenced to wabble, run unevenly, or waver even slightly in their plane of rotation excessive wear would occur on the wheel itself. This was probably because even the minutest fraction of an inch of wabble or wavering results in bringing the grinding face of the tool into contact with the work piece at intervals during the rotation of the wheel, instead of being in contact all the time, and the result of that action was of course to wear the surface of the wheel out of true and aggravate the depreciation of the wheel. From the standpoint of toolproduction this was a serious defeet because it was necessary to stop production and dress the wheel as soon as even a slight erratic wheel action occurred. Thus, along with the advantage of using a soft wheel there developed a disadvantage of not having a wheel mounting that would show a sufficiently high degree of sustained accuracy and durability.

My improvement provides such a mounting in a highly satisfactory manner and the device herein described and claimed accomplishes the objects of the invention which are, to provide a mounting for a grinding wheel that will keep the axis of the wheel in a fixed line while running and will prevent any movement of the wheel or its spindle in a direction lengthwise of the axis; to provide such a bearing arrangement for the wheel spindle that will in addition permit the bearing nearest the wheel to be adjusted to take up wear on the peripheral rubbing surfaces of the bearing, and to provide means for holding the wheel against endwise movement, both adjustments being attained by merely turning the appropriate screw threaded members on the housing of the spindle and without dismantling the wheel supporting structure.

Another object is to provide a simplified device for effecting the adjustments above mentioned by means of spindle bearings only.

With the foregoing and certain other objects in view which will appear later in the specification, my invention comprises the devices described and claimed and the equivalents thereof.

In the drawing,

Fig. 1 is a cross-sectional side view of a grinding wheel and spindle mounted on a housing embodying my improvement;

Fig. 2 is a perspective View of the rear bear- Fig. 3 is a sectional view of the rear cap; and

Fig. 4 is a sectional View of the front cap.

Referring now to Fig. l, the grinding Wheel I is located between a pair of center flanges 2, 3 on the threaded end 4 of the spindle and is secured by means of a nut 5 in the usual way. On the spindle is a tapered journal 6, its larger end being nearest the wheel. Between journal 6 and wheel I and integral with the spindle is an outwardly projecting circular flange or collar 1.

The tapered journal 6, the collar 1, the grinding wheel I, the respective bearings in which journal 6 and collar 1 run and the means for adjusting these bearings in their co-operative relationship, constitutes an important feature of my improvement, as will be explained in detail later.

At the end of the spindle remote from the wheel I, being the left-hand end in Fig. 1, is a journal 8 cylindrical in form, running in a rear bearing 9, which bearing is longitudinally split so as to be adjustable for taking up wear of the cylindrical running faces.

Gbserving now the mounting of tapered journal 6, Fig. 1, it is seen that the journal rotates in a correspondingly tapered bushing H) of anti friction metal secured by a press fit in the counterbore H of a tubular housing I2.

But the rear bearing 9 for journal 3 is bored cylindrically and as shown in Fig. 2, the outer tapered surface of the bearing 9 is fluted peripherally by grooves 13 that extend longitudinally. The grooves impart a degree of peripheral yield to the bearing for adjusting its tightness on the journal 9. A longitudinal split 54 is provided for the same purpose.

The rear bushing 9 has endwise adjustment in a tapered fitting [5 which is mounted by a press fit in a counterbore 46 at the rear end of housing 52. Thus the spindle is rotatably mounted in the housing so that its tapered journal 6 rotates in bushing H].

To maintain the necessary accuracy of fit between journal in and its bushing HI, I have provided a simplified and dependable means for adjusting those parts relatively to each other and for keeping them in proper running relation.

To hold the tapered journal 6 against movement lengthwise I provide collar 1 integral with the spindle between journal 6 and Wheel II, and also provide adjustable means for permitting the collar to rotate freely while preventing dust and grit from entering the journal bearing.

A sleeve I l, threaded internally and externally, is adjustably screwed on the reduced threaded end of housing E2, the forward or right-hand end of the sleeve I"! carrying a flange IQ of antifriction metal, against which the rear face of the collar 7 runs.

On the external thread 29 of the sleeve H a cap, shown in detail in Fig. 4, is screwed. This cap has an inwardly directed end flange 2i faced inside with an annular anti-friction washer 22 which engages the forward face of collar i. Screw threads 23 provide for adjustably placing the washer 22 against the forward face of the flange 1 so that the flange will be prevented from moving in the direction of the length of the spindle.

A ring 24 is threaded on the reduced end of the housing l2 and serves as a lock-nut to keep the sleeve l1 and its associated parts locked in their lengthwise adjusted position.

Tapered journal 6 is accurately formed, highly polished and preferably chromium plated. It fits as exactly into the tapered bushing Iii as is commercially possible, the closeness of the fit being re'gulatable by shifting the spindle very slightly in the direction of its length. The bearing surfaces are lubricated by a suitable oiler shown in Fig. 1, V

The endwise positioning of the tapered journal 6 is attained by shifting the fore-and-aift position of the spindle by means of its integral collar '1. This is done by first loosening the looking ring 24, rotating sleeve I! in the proper direction so that the flange [9 of sleeve II will clear the collar 1 and permit it to be moved corres'pondingly, thereby giving the desired closeness of a running fit between the journal 6 and bushing ID. The collar 1 then can be held against the flange l9 in its proper running position by rotating the cap on its screw 23.

Thus fore and aft positioning of the spindle as a whole relatively to the housing I2 is adjusted by means of the sleeve l1, and the spindle is held in such position by the locking ring 24, the flange I9, and the flange 2| of the cap. Merely turning the ring 24 and the sleeve I! adjusts the tightness of the running fit at journal 6 without disturbing the endwise thrust adjustment of collar I; or such thrust adjustment can be altered by turning the cap without disturbing the adjustment of the running fit.

Cylindrical journal 8 at the rear end of the spindle is, of itself, always free to move lengthwise, hence when the tapered journal 6 is being adjusted in the manner above described it will have no effect upon the adjustment of the rear spindle bearing 8.

To keep the journal 8 centered, that is, coaxial with the spindle, and to prevent all sidewise play the flexible rear bushing 9, detailed in Fig, 2, surrounds the journal 8. Bushing 9, which is tapered exteriorly is received in the internally tapered fitting 15. It can be adjusted lengthwise of the fitting and lengthwise of the journal 8 by means of the rear cap 25 which is threaded at 26 onto the tapered fitting l5. When the cap is turned in the tightening direction on the fitting I5 it takes against the end of member 9 and forces it toward the right, Fig. 1, causing member 9 to contract and tighten around the journal 8.

The large rearward end of member 9 is externally threaded at 2'! to receive a pull ring (not shown) whereby member 9 can be withdrawn from the tapered fitting l5 for inspection.

A groove 28 or internal channel is provided in the end washer 22 to, form an oil seal that preients dust from entering the bearing surfaces of collar 1 and journal 6.

By the means above described the grinding wheel is is kept in its true rotating plane 29 and is prevented from shifting in that plane; that is to say, the cutting rim 3!! of the wheel must run in a perfectly true plane of revolution. over, there can not be any radial or tangential jump or vibration at the periphery of the grinding zone which is at 30.

As has been stated, effective cutting action by the grinding wheel is dependent upon wearing away of the wheel itself, for if the wheel is not constantly wearing away and thereby renewing the surface of its grinding zone its efficiency as a production unit is impaired. In order that the abrading surface of a grinding wheel may function in this essential respect the wheel must be relatively soft, as distinguished from what is known as a hard grinding wheel. But obviously, softness of the wheel accompanied by any vibration or jump in the motion of the wheel will result in wavy or irregular places being formed on the operating zone of the abrading surface, necessitating constant correction by trueing up the wheel, which in turn cuts down the daily output capacity of the operator.

From the foregoing description of the structure and mode of operation of my improved precision spindle mounting it will be apparent that real and important difficulties have been entirely overcome and, for the first time in this art as far as I am aware, a thoroughly dependable, accurate, durable mounting has been provided for a precision grinding tool that can be easily adjusted and under all normal conditions of use will lviorekeep the grinding wheel so exactly in condition of proper running stability that soft grinding wheels can be employed and will yield greater production, give better work, and will effect important savings in the costs for upkeep and replacement of grinding wheels. A noteworthy result is that a soft wheel, when used on this improved spindle, will outwear and out-produce a so-called hard grinding wheel of the same size and design.

Another advantage is that larger diameter grinding wheels can be used than was possible without the wheel stability provided by my improvement. Consequently work can be done faster on account of the higher rim speed, and more difi'erent kinds of work can be done, for example, accurate surfacing of flats, cylindrical or conical bosses, as well as the shaping of the teeth of cutting tools such as described in the foregoing specification.

claim and desire to secure by Letters Patent is:

In a precision grinding tool including a spindle having a grinding wheel on one end and a tapered journal and cylindrical journal, said spindle being rotatable in a tubular housing with bearings for said journals; having in combination, a fixed collar projecting peripherally from the spindle and situated beyond and spaced from the end of the housing and intermediate the said tapered bearing and the grinding wheel, a sleeve threaded adjustably on the end portion of the housing and having an inwardly projecting flange arranged to take against the rear face of said collar, a screw cap adjustably threaded on said adjustable sleeve and having an inwardly directed flange taking against the forward face of said collar; said cap and sleeve constituting means for adjusting the running fit of the collar between the said flanges and for keeping the collar and spindle from moving lengthwise; and

go also constituting means for adjusting the running Having thus described my invention, what I fit of said tapered spindle in its bearing.

ROLLIN M. SEVERANCE.

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