US2207621A - Centrifugal chuck - Google Patents

Description

July 9, 1940- c. E. HlTE CENTRIFUGAL CHUCK Filed Sept. 22, 1938 5 Sheets-Sheet 1 5km f Jul 9, 1940.

C. E. HITE CENTRIFUGAL CHUCK Filed Sept. 22, 1938 52 j'fl 5 Sheets-Sheet 2 July 9, 1940.

v 2 A I l 2 mate; 5am

5 Sheets-Sheet 5 Jk eniar I Patented July 9,1940

UNITED 'STATES CENTRJFUGAL CHUCK Charles E. Hite, Philadelphia, Pa., assignor to Lewis J. Musser, Newtown, Pa.

Application September 22, 1938, Serial No. 231,174

18 Claims.

The present invention relates to chucks for V holding wheels and disks and that more usually are intended for holding grinding wheels and disks when operating upon the wheels and disks in manufacture and subsequently when using them selectively for grinding or facing operations.

The terms wheel and grinding wheel as used herein are intended to apply broadly not only to disk grinding wheels, cup and cone grinding wheels, and facing and sanding plates but also to any similar device adapted to be held by the mechanism of the present invention.

A purpose of the invention is to grip a grinding wheel centrifugally when rotation starts, re-

leasing the grip automatically by the cessation of the rotation or optionally maintaining the grip until manually released and on release retracting the gripping jaws preferably automatically and preferably to a definite and desirably adjustable stop, and preferably with a very small range of jaw movements to permit an easy and rapid change of wheel.

A further purpose is to coordinate the movements of centrifugally operated chuck jaws,

automatically centering a wheel as it is centrifugally gripped by the jaws.

A further purpose is to adapt holding jaws having a small range of radial movement to use with wheels over a relatively wide range of sizes.

Further purposes will appear in the specification and in the claims.

I have elected to illustrate a number only out of the many forms of my invention, selecting forms however that are practical and efficient in operation and which well illustrate the principles involved.

Figures 1 and 2, in top plan and elevation respectively, are intended to illustrate conventionally chuck mechanism in accord with the present invention, showing a wheel held by any desired number (three in the figures) of chuck jaws of any suitable form and gripping the wheel by the centrifugal action of any. suitable mechanism within the body of the chuck.

Figure 3 is a bottom plan of one form of the chuck of Figures 1 and 2,.

Figures 4, 4a, 4b, 4c, 4d, 4e, 4i and 49 are sectional elevations illustrating successively different jaw operating mechanismsQFigure 4 corresponding to a section upon the line 4-4 of Figure 3 and some of the other figures being in accord with appropriately indicated section lines on other figures, as indicated by the section lines thereof.

Figure 5 is a fragmentary section of Figure 4a, taken upon the line 55 thereof.

Figure 6 is a fragmentary bottom plan of Figure 4b, with part of the bottom plate broken away.

Figures 7 and 8 are-fragments, bottom plan and left elevation respectively, of Figure 40.

Figures 9 and 10 are sectional fragments of Figures 4d and ie-upon the lines 99 and Iii-i0 thereof in the directions of the arrows. 1

Figures 11 and 12 are sectional fragments upon the lines ll-li and l2-l2 of Figures 4 and 49 respectively, in the directions of the arrows.

Like numerals refer to like parts in all figures.

Describing in illustration and not in limitation 1. and referring to the drawings:

In Figures 1 and 2, a wheel I5 is held by the jaws l6 of a chuck l'l upon a spindle l8 of any suitable machine beyond the spindle. This machine may be, for example, one for facing and trimming unfinished wheels, or it may be a grinding machine for using different wheels selectively for grinding, or it may be any mechanism forsuitably rotating the spindle.

An operator using my chuck on a machine for facing and trimming unfinished wheels normally operates upon wheels of different standard commercial sizes, first upon a succession of wheels of one size, then upon a succession of wheels of another size, and so on with wheels of other 30 sizes, changing the wheel each time rotation ceases and at intervals changing the setting of the chuck to accommodate a different size (diameter) of wheel.

With my chuck on a grinding machine, an op- 35 erator with some classes of work may not change the wheel over many periods of rotation and in other classes of work selects his wheel to suit the work, often using one wheel for initial rough grinding and changing to one or more other wheels before final grinding, with all of the wheels probably more usually being of the same commercial size but sometimes of diiferent. sizes, particularly if the spindle i8 is to operate selectively at different speeds or if the chuck is to be used selectively on different spindles of different speeds.

When' the chuck is rotating centrifugal action of mechanism within the chuck causes that mechanism to press the jaws radially inward upon the wheel, gripping the wheel by the centrifugal action of the mechanism within the chuck.

When the rotation of 'the chuck stops the centrifugal action also stops and I intend the 55 grip of the jaws upon the wheel then selectively automatically to release or, under the action of jaw-holding mechanism, to maintain until the operator releases the jaw-holding mechanism.

When the operation is to be with a succession of wheels, as one wheel I5 during each period of rotation and a different wheel l5 during the next period of rotation, I intend the jaws to release and open automatically as the rotation stops, and the degree of opening preferably then to be merely that permitting an easy and rapid change of wheels, and I show in Figure 1 what is intended for a conventional showing of any suitable means for thus limiting the degree of opening of the jaws.

As illustrated in Figure 1, one of the jaws l6 presents the head end of an adjustable screw l8 toward an inwardly directed wall surface 28 of the body portion of the chuck, whereby the jaw opening is limited to the small adjustable distance between the body surface 28 and the head of the screw l9. The means for adjustably limiting the opening of the jaws l6 desirably may be associated with the centrifugal mechanism within the chuck body, which mechanism preferably is associated also with equalizer mechanism coordinating the jaws to move alike, all as described later.

Each time rotation starts after changing one wheel for another the somewhat retracted jaws l6 move inward coordinately upon the inserted wheel l5, centering it and grippinug it.

When an operation is to be repeated over and over with the same wheel usually I prefer to maintain the jaws in their wheel gripping positions after rotation ceases until or unless they are released by the operator releasing jaw-holding mechanism and I show in Figure 1 what is intended for a conventional showing of any suitable means to this end.

As shown in Figure 1, a toggle lever 2| pivots at 22 to the face of the chuck and is pulled by a tension spring 23 toward a position for its continuing jaw-holding engagement with one of the jaws l6 and in which position it will permit the jaw to move inward but not outward.

A screw 24 in the face of the chuck has its head cut away on one side at 25 and is positioned to hold the toggle lever 2| away from the jaw when the screw is turned to present the round of its head to the toggle lever, as in Figure 1, and to permit the toggle lever to engage and holdthe jaw when the screw is turned to present the flat 25 of its head toward the toggle lever.

When an operation is to be repeated over and over with the same wheel the screw 24 is turned ninety degrees from its position in Figure 1 so that its fiat 25 is toward the toggle lever 2|, after which the jaws do not open when rotation ceases until the screw is turned to hold the toggle away from the jaw by presenting the round of its head to the toggle. Desirably a resilience, as indicated at 26, may be inserted between the jaw and wheel to insure resilience of gripping during the non-rotation periods.

I intend the chuck to be adapted to hold wheels of different commercial sizes while the jaws may have ranges of movement relatively small, and to this end, in Figures 1 and 2, I show the jaws with steps 21, 28 and 29 with corresponding base portions 30 and 3| of radial extension to suit different commercial sizes of wheel, the wheels of sizes larger than that suiting them to be held by bottom step surfaces 21 of the jaws being intended to rest upon the appropriate raised base Whenever my chuck is intended to be used exclusively with wheels to be mounted on a centering pin the means, later described, for equalizing the jaw movements optionally may be omitted:

Different forms of suitable operating mecha nism within the body of the chuck are illustrated in Figures 3 to 12.

In Figures 3 and 4, the jaws l6 adapted to slide in radial slots 50 through the top of the hollow body are positioned along these slots by bell crank'rockers 5|.

The bell crank rockers 5| are pivoted to the body at 52 near the body periphery and have their arms 54 and 55 dimensioned and located arcuately to move their ends in directions generally radial of the chuck, one am moving inward as the other moves outward. The arm 54 is operatively connected to the jaw l6 by a suitable slot and pin connection-at 56; and the arm 55 is enlarged at its outer end at 51 to provide an operating weight heavy enough to overbalance centrifugally the reversely acting centrifugal forces of the jaw l8 and of the arm 54 and to transmit. the desired inward force upon the jaw l6.

The mechanisms operating the different jaws being alike a description of one applies to all.

The jaw mechanisms are coordinated to move together, each bell crank 5| having its arm 54 in link connection with an equalizer ring 58. The ring 58 turns on a hub portion 59 of the body above a retaining ring 60 fastened to the hub. The links 6| pivotally connected at 62 and 63 respectively to the equalizer ring 58 and the arm 54 of each bell-crank are alike and located and dimensioned to permit movement of any bell crank only with an equal movement of each of the other bell cranks.

As shown, the system is resiliently retracted by springs 64 compressed between downward projections 65 of the weights 5! and the outer shell 66 of the body, with oppositely directed spring-retaining lugs 61 and 68 at the spring ends.

While a spring 64 is shown for each of the bell cranks, optionally the resilience may be applied at any suitable part or parts of the system, as to one only of the bell cranks or to the equalizer ring, the spring retraction being in direction to move the system counter to the centrifugal force of the weight, i. e., to move the jaws outward when rotation ceases. Y

' In the structure of Figures 4a and '5 the jaw I6 .is provided with a succession of transverse slots 69 to receive the upper end of the pivot. pin 56' selectively, and the pin 56 is adapted to be pulled down beyond the bottom of the jaw to permit shifting of the jaw with respect to the jaw-operating pin 56' and to receive the pin 56 in any one of its slots 69.

The pin 56" is spring-pressed upwardly by a spring 10 surrounding a downwardly extending stem ll of thestem and compressed between a on the side thereof to provide coordinated movehead or flange portion 12 of the pivot and the upper surface of a bottom plate I3 radially slotted at 14 to pass the stem II.

The jaw I8 slides in a radial inverted T slot I5 and has lateral runners I6 fitting corresponding runway portions 11 of the slot. The jaw is shown for the major portion of its length at the top even with .the face of the chuck and toward its inner end is provided with an upward extension I8 across its full width and presenting a suitably dimensioned adapter to the wheel l5.

There is shown a pin connection at I9 between the adapter 38 and the upward extension 18 of .the jaw. The bell crank arm 54 is shown with a hub 88 extending upwardly into and at the sides loosely fitting a lower extension 8| of the T slot I5. The hub 88 provides an increased length of bearing for the pin 58'. The radial slot ,14 in the bottom plate is of length adequate for the range of radial movement of the jaw and stem. The equalizer mechanism 58, SI, 54' and the mechanism for outwardly retracting the jaws when rotation ceases may be as described for Figures 3 and 4.

When an operator desires to set the chuck of Figures 4a; and 5 for use with a difierent size of wheelhe pulls down the pivot pin 56 against the upward retraction of the spring I8 and slides the jaw I 6' outward or inward to the desired setting, setting the other jaws in the same way.

In the structure of Figures 41) and 6 the jaw I6 is generally similar to the jaw I6 of Figures 4a. and 5 except that it has been shown somewhat longer adapting it to an additional setting with respect to a jaw operating pin 58 and with its upward recesses 89 selectively presented to the operating pin suitably circular recesses fitting the circular operating pin, the pin 58 of Figures 41) and 6 being limited to straight line movements while the corresponding movements of the pin 56' of Figures 4a and 5 are arcuate.

Also, in the structure of Figures 4b and 6 the jaw has been reversed end for end from the position of the jaw I6 in Figure 4a, to hold a very large wheel I5 in Figure 41) while a very small one is held in Figure 4a. The adapter 38 has been put upon the reverse side of the transverse upward extension 18' of the jaw from that in Figure 4a The opposite vertical faces of the upward extensions I8 and I8 of the jaw are suitably alike in that they are alternatively presented toward a wheel and. these extensions are centrally bored at 82 for the pin I9 fastened in the adapter 36' or 36 the adapter registering its pin I9 in the bore 82 on either side of the upward extension In Figures 4b and 6 the operating pin 56 of the jaw is carried by a member guided to radial straight line movement as distinguished from a substantially radial arcuate movement.

As illustrated, there are three jaws to the chuck, moved by means of pins 56 carried in hubs 83 that are integrally connected by difierent rack plates to weight members 51'.

Each jaw operating member thus includes a pin 58 and an integral member loosely mounting the pin and comprising a hub 83, a weight 51 diametrally opposite the hub and a rack plate 84, 85 or 86 connecting the weight and hub.

The rack plate is centrally slotted at 81 to surround a gear 88 mounted upon the hub 59' of the chuck. Each of the plates 84, 85 and 88 has rack teeth 89 on one side only of the slot, the teeth 89 meshing with the pinion gear 88 and ment of the jaws and jaw operation mechanisms.

'The jaw operating mechanism of the different jaws, as illustrated, is intended to differ merely in the location of the plates 84, 85 or 88 with respect to the hub and weight members 83 and 51' at their diametrally opposite ends. The plates 84, 85 and 86 are located successively one above and against the other.

Each weight 51' is provided with an upward lug 98 within a guideway radial slot 9| of the chuck body and at the opposite end of the diameter the hub 83 slides in a guideway slot 92.

The upward recesses 69' in the jaw are suitably circular to fit the end of the pin 58 while in the structure of Figure 4a the corresponding recesses 69 are transverse slots to accommodate the arcuate movement of the pin 56.

The pinion 88 is provided with a flange 93 laterally underlapping the plate 86 at opposite sides of the slot 81, thereby retaining the plates from downward movement. The pinion 88 itself is spring-pressed upwardly by a compression and torsion spring 94 having its opposite ends 95 and 96 extending respectively upward into the pinion 88 and inwardly into the hub 59 of the chuck,

'- the direction of torsion of the spring 94 being such as to retract the weight members 51 radially inwardly and thereby the jaws on-the opposite side of the chuck outwardly.

The retraction of the weight members and thereby of the jaws is adjustably limited by upwardly extending pins 91 in a bottom. plate 98 of the chuck. The bottom plate 98 is provided with a central hub 99 about the hub 59' of the chuck, to which it is angularly adjustably fastened by a screw I88 threading into the hub 59' through a'peripheral slot 18! in the hub 99, as indicated in Figure 8 for the structure of Figure 40.

The weight 51' is provided with a diagonal cam step I82 to engage the pin 91 at different inward positions of the weight according to the angular setting of the plate 98.

The pin 58 is illustrated as maintained in its operating position by a flat spring I 83 carried by each of the plates 84, 85 and 86, with suitable minor modification of the mounting of the spring I83 to best adapt it to maintain the pin in its operating position and in view of the somewhat different locations of the intermediate plate portion 84 or 85.

As shown, the end of the spring I83 underlaps a shoulder I84 of the pin 56 A downwardly extending stem 'II' from. the pin 56 is to be like that of Figures 4b and 6 except with respect to mechanism for coordinating the movements of the centrifugal mechanism and thereby of the jaws, and for resiliently retracting the mechanism and with a minor difference in the means for adjustably limiting the retraction.

The pinion 88 of Figure 4b and the rack teeth upon the plate portions 84, 85' and 86' of the integral members 83, 51 have been dispensed with. The plates 84', 85' and 86, one above another as in Figure 4b, have their central slots 81' more narrow than the slots 81 in Figure 4b in that these slots are now of width merely to pass the hub 58, while in Figure 4b the correspending slots must pass the pinion 88 mounted outside the hub 58'.

Each weight 51 is provided with a cam slot I81 which receives the upwardly projecting end of a pin I88 rigidly mounted in a retraction plate I88, the lower end of the pin I88 extending downwardly to adjustably limit the retraction by engaging a cam edge I I8 of a stop plate III that is angularly adjustable with respect to the hub 58 of the chuck.

A torsion spring II2 has its ends I I3 and H4 extending into the hub 58" and the retraction plate I88 respectively, the torsion of the plate being in direction to pull the weights 61 radially inwardly by means of the upper end of the pins I88 in the cam slots I81 of the respective weights,

thereby retracting the jaws outwardly.

The screw I88 has a taper body at I I5 adapted to clamp against the sloping edges II6 of a slot IIlI in the hub 88 of the stop plate, thereby permitting peripheral adjustment of the plate upon loosening this screw, shifting the plate to the desired position and then retightening the screw. A collar I I1 fastened to the hub 59 ooop-. eratively with the torsion plate I88 and the stop plate III at the set screw I88 may conveniently carry the weight of the operating mechanism.

The weight centrifugally moving outward to press the jaw inward may be either on the same side or the opposite side of the chuck from that of the jaw. Thus, in Figures 4b and 40 it is located diametrically opposite the jaw. In Figures 4d and 9 the weight is located below the jaw with a pinion II8 between the jaw and weight meshing with downwardly presented rack teeth on the bot- 40 tom of the jaw and with upwardly presented rack teeth on the weight.

As illustrated, the jaws I6 of which one only is shown, are intended to be connected by coordinating links 6I to an equalizer ring- 58 generally similar to the corresponding structure of Figures 3 and 4, except that the links IiI pivotaliy connect directly to the jaws instead of to rocker members moving the jaws.

The pinion I I8 turns upon a pin II8 supported between downwardly extending lugs I28-and I2I from the body portion of the chck. The lugs I28 and I2I are formed at their lower edges to guide the weight I 22 which is slidably supported and additionally guided by a rod I23. .The weight I22 is resiliently retracted by a tension spring I24 stretched between the weight and hub 58 of the chuck and presents rack teeth I25 to the bottom of the gear H8, and the jaw I6 is provided withed to be of pressed metal and the radial rods I23,

fastened as described, stiffen and strengthen the shell as well as supporting the weights I22. The shell I28 is extended up in one piece to form a shield at I'3I over the jaws and near the wheel. The shell I28 fits over and around a ring I32 shrunk upon the main body portion I33 of the chuck. v

In the structure of Figures 4e and 10 each jaw I6 slidably mounted in a radial guideway I34 01' the body is provided with a downwardly extending lug I35 having a through pin I36. The extending ends of the through pin are operatively engaged by the opposite arms of forks I31 and I38 which extend upwardly from and as shown are integral with a weight I38 pivoted upon a pin I48. The pin I48 is carried by lugs MI and I42 that extend down from the body portion of the chuck.

The jaws are coordinated in their movements exactly as described for the structure of Figure 4d. The outer shell I28, suitably of pressed metal, is extended inward at the top at I3I' to provide the shield and the outer ring I32 of the body has been extended up to the top of the jaws.

With rotation of the chuck, the weights I38 move centrifugally outward with a corrsponding inward movement of the jaws upon the intermediate wheel, and with cessation of rotation the weights I38 swing back beneath their pivots I48 with a corresponding automatic opening of the jaws.

In the structure of Figures 4i and 11 the jaws I6 operate under the action of a differential gear on each weight, each difierential gear having a middle section I43 of relatively large diameter meshing with downwardly directed rack teeth I44 of the jaw and outer or end sections I45 and I46 of relatively small diameter meshing with downwardly directed racks I41 and I48 from the chuck body to opposite sides ofthe middle section of the difierential gear, the gear being carried by the weight I48, turning upon its end sections I46 and I46 in suitable upwardly directed groove bearings I58 presented by the weight. Movement of the weight in either direction can only take place with the jaw moving in reverse direction to accommodate the connections to the differential gear.

The weights I48 are provided at the bottom with cam grooves I81 which receive pins I88 from a retraction plate I88 as already described for the structure of Figure 4c, the outward retraction or opening of the jaws being adjustably limited by cam surfaces I I8 on an adjustable stop plate II I, as in the structure of Figure 4c.

When it is desired to shift the jaws for use with a wheel of different size, the screw I88 is loosened and the stop plate III turned to bring the upward recess I5I from the slot I8I' in regispositioned, the stop plate is pushed up and then turned peripherally to adjustably limit the openin of the jaws. v

In the structure of Figures 4g and 12, the jaws I6 are provided with any desired number of between the arms I54 and I55 fulcru'ms' the weight between vertical surfaces I58 and I58'presented. by lugs I68 and I6-I extending downwardly from the face portion I62 of the body of the chuck.

The body of the chuck is radially tee-slotted at I64 to provide a suitable guideway forthe jaws and vertically slotted to upwardly pass the arms I54 and I55 and the pin I53 of the weight member I56 and to permit adequate arcuate movement of the weight member I56 about the axis of the fulcrum pin I51,

The weight I56 is provided with a cam slot I01 as already described for the structure of Figure 40, a retraction plate H19 presenting the upper end of a pin I08 into the cam slot I01 and presenting the lower end of the pin across the cam surface III] of an adjustable stop plate II I all as described with the structure of Figure 40.

When it is desired to set the jaw to hold a wheel of different size, the weight member I56 is lifted at the top bodily far enough for the pin I53 to clear the walls of the groove bearings I52, after which the jaw may be slid to any desired position and the weight member permitted to go down to present the jaw-operating pin I53 into the selected groove.

The weight of the members I56 may be carried upon the retraction plate N19 or, usually less desirably, upon the jaws I6 at the pin I53. The bottom of the weight I56 is shown curved at I65 to maintain the jaw-operating pin I53 at a small substantially constant distance from the bottom of its groove bearing I52, thereby supporting the weight upon the plate I09 rather than upon the jaw.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a chuck for holding a grinding wheel a chuck body, jaws and mechanism within the body centrifugally moving outward with rotation of the chuck and connections between the mechanism and jaws adapting the mechanism to move the jaws inward in centrifugally moving outward, the body comprising a generally circular working top, a downward central hub and a down-,

ward peripheral shell, with the hub adapted to mount the chuck upon the top of an operating spindle, the working top having radial throughslots and the slot walls mounting and guiding the jaws and the said mechanism and connections being located within the annular hollow between the hub and shell.

2. In a chuck for holding a grinding wheel a chuck body, jaws movable radially of the chuck axis for holding a wheel, centrifugal means within the chuck body adapting the jaws automatically to grip the wheel when rotation of the chuck starts and means for preventing automatic grip release movement of the jaws upon cessation of rotation, the body comprisinga generally circular working top, a downward central hub and a downward peripheral shell, with the hub adapted to mount the chuck upon the top of an operating spindle, with the jaws mounted and guided in through slots of the working top and the said centrifugal means being located within the annular hollow between the hub and shell.

3. In a chuck for holding a grinding wheel a chuck body, jaws movable radially of the chuck axis for holding a wheel, centrifugal means within the chuck body adapting the jaws automatically to grip the wheel when rotation of the chuck starts and means for adjustably limiting tral hub and a downward peripheral shell, with the hub adapted to mount the chuck upon the top of an operating spindle, with the jaws mounted and guided in through-slots of the working top and the said centrifugal means being located within the annular hollow between the hub and shell.

4. In a chuck for holding a grinding wheel a chuck body, jaws movable radially of the chuck axis for holding a wheel, centrifugal means within the chuck body adapting the jaws automatically to grip the wheel when rotation of the chuck starts and means coordinating the jaw movements, limiting the movement of each jaw to an equal movement of each of the other jaws, the

body comprising a generally circular Working top, a downward central hub and a downward peripheral shell, with the hub adapted to mount the chuck upon the top of an operating spindle, with the jaws mounted and guided in throughslots of the working top and the said centrifugal means being located within the annular hollow between the hub and shell.

5. The structure of claim 1 and in which the said mechanism includes bell crank rockers, one

for each jaw of the chuck, each rocker having a pivot support within the body of the chuck near the chuck periphery and arms located and dimensioned to move in directions generally radial with respect to the chuck axis, one arm moving outwardly as the other arm moves inwardly, one arm having a weight to centrifugally control the gripping of the jaw, and the other arm having an operating connection with the jaw.

6. In a chuck for holding a grinding wheel, a chuck body, jaws and mechanism within the body centrifugally moving outward with rotation of the chuck and connections between the mechanism and jaws adapting the mechanism to move the jaws inward in centrifugally moving outward and in which the said mechanism includes bell crank rockers, one for each jaw of the chuck, each rocker having a pivot support within the body of the chuck near the chuck periphery and arms located and dimensioned to move in directions generally radial with respect to the chuck axis, one arm having a weight to centrifugally control the gripping of the jaw, and the other arm having an operating connection with the jaw, and including an equalizer ring adapted to turn about the axis of the chuck and connections betwen the ring and said mechanism limiting the movement of each jaw to equal movement of each of the other jaws;

7. In a chuck for holding a grinding wheel, a chuck body, jaws and mechanism within the body centrifugally moving outward with rotation of the chuck and connections between the mechanism and jaws adapting the mechanism to move the jawsinward in centrifugally moving outward in which each jaw presents downwardly directed rack teeth, in which the body presents along side of and somewhat downwardly of the rack teeth other rack teeth, in which a differential pinion has a portion of relatively large diameter meshing with the teeth presented by the jaw and in which a radially movable weight upwardly supports the differential pinion to mesh simultaneously with the rack of the jaw and the rack of the body.

8. In a chuck for holding a grinding wheel, 7

a chuck body, jaws and mechanism within the body centrifugally moving outward with rotation of the chuck and connections between the mechanism and jaws adapting the mechanism to move the jaws inward in centrifugally moving outward in which each jaw presents downwardly directed rack teeth, in which the body presents along side of and somewhat downwardly of the rack teeth other rack teeth, in which a difleren- 10 tial pinion has a portion of relatively large diameter meshing with the teeth presented by the jaw and in which a radially movable weight upwardly supports the differential pinion to mesh simultaneously with the rack of the jaw and the rack of the body and including an equalizer plate angularly movable about the hub of the chuck and pin and cam slot connection between the plate'and each weight whereby each weight can move radially of the chuck only with equal radial movement of each of the other weights.

9. In a chuck for holding a grinding wheel, a chuck body, jaws and mechanism within the body centrifugally moving outward with rotation of the chuck and connections between the mechanism and jaws adapting the mechanism to move the jaws inward in centrifugally moving outward in which each jaw presents downwardly directed rack teeth, in which the body presents along side of and somewhat downwardly of the rack teeth other rack teeth, in which a dinerential pinion has a portion of relatively large diameter meshing with the teeth presented by the jaw and in which a radially movable weight upwardly supports the differential pinion to mesh simultaneously with the rack of the jaw and with the rack of the body, including an equalizer plate angularly movable about the hub of the chuck and pin and slot connection between the late and each weight whereby. each weight can move radially of the chuck only with equal radial movement of each of the other weights and including a torsion spring between the chuck hub and equalizer plate and with an angularly adjustable stop plate upwardly supporting the equalizer plate and having a cam connection with the equalizer plate adjustably limiting the retraction thereof.

10. In a chuck for holding a grinding wheel, a chuck body, jaws and mechanism within the body centrifugally moving outward with rotation of the chuck and connections between the mechanism and jaws adapting the mechanism to move the jaws inward in centrifugally moving outward in which each jaw presents a plurality of radially spaced upwardly directed pin bearings, in which a weight has an upwardly directed arm and a horizontal jaw-operating pin adapted to engage the groove bearings selectively, and a fulcrum pin parallel to and lower than the operating pin, and the body of the chuck presenting abutments to opposite sides of the fulcrum pin.

11. In a chuck for holding a grinding wheel, a chuck body, jaws and mechanism within the body centrifugally moving outward with rotation of the chuck and connections between the mechanism and jaws adapting the mechanism to move the jaws inward in centrifugally moving outward in which each jaw presents a plurality of radially spaced upwardly directed pin hearings, in which a weight has an upwardly directed arm and a horizontal jaw-operating pin adapted to engage the groove bearings selectively, and a fulcrum pin parallel to and lower than the operating pin, and the body of the chuck presenting abutments to opposite sides of the fulcrum pin, and in which an equalizer plate having pin and cam slot connection with the respective weights and angularly movable about the chuck is mounted beneath the weights to coordinate the movements thereof.

12. In a chuck or holding a grinding wheel, a chuck body, jaws and mechanism within the body centrifugally moving outward with rotation of the chuck and connections between the mechanism and jaws adapting the mechanism to move the jaws inward in centrifugally moving outward in which each jaw presents a plurality of radially spaced upwardly directed pin bearings, in which a weight has an upwardly directed arm and a horizontal jaw-operating pin adapted to engage the groove bearings selectively, and a fulcrum pin parallel to and lower than the operating pin, and the body of the chuck presenting abutments to opposite sides of the fulcrum pin, and in which an equalizer plate having pin and slot connection 1 with the respective weights and angularly movable about the chuck is mounted beneath the weights to coordinate the movements thereof and the structure including a torsion spring between the equalizer plate and the body of the chuck, and a stop plate adapted to adjustably limit the retraction of the equalizer plate has an angularly adjustable mount below the equalizer plate.

13. The structure of claim 4 and means for spring-retracting the said coordinating means.

14. The structure of claim 4, means for springretracting the said coordinating means and an adjustable stop adjustably limiting the spring retraction thereby adjustably limiting the opening of the jaws.

15. The structure of claim 4 and in which the said coordinating means comprises a ring surrounding the hub and operatively connected to centrifugal mechanisms operating the individual Jaws.

16. The structure of claim 4 and means for preventing automatic grip-release movement of one of the jaws at cessation of rotation.

1'7. The structure of claim 4 and a spring-toggle lock adapted to prevent jaw retraction at cessation of rotation.

18. The structure of claim 1 and in which the said mechanismand connections include firstclass levers, one for each jaw, each lever having an intermediate pivot connection with the body,

one arm operatively connected to one of the jaws and the other arm weighted to move outward centrifugally with rotation of the chuck.

CHARLES E. mm.

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