US2629990A - Resilient coupling for abrasive wheels - Google Patents

Description

March 3, 1953 B. TOCCl-GUILBERT RESILIENT COUPLING FOR ABRASIVE WHEELS Filed Sept. 30, 1949 mms/vro/z sen/v: 70:61- 60148597 Patented Mar. 3, 1953 RESILIENT COUPLING FOR ABRASIVE WHEELS Berne Tocci-Guilbert, San Francisco, Calif., assignor, by mcsne assignments, to Berne Tocci- Guilbert, San Francisco, and Henry Gifford Hardy, Berkeley, Calif., jointly, as trustees Application September 30, 1949, Serial No. 118,820

2 Claims.

1 This invention relates to constrictive means for modifying and limiting the vibratory oscillating torque of resilient couplings, particularly those of the type disclosed in the copending application bearing Serial No. 55,620, filed October 20, 19 58, entitled Resilient Couplings.

Among the objects of the invention is the control of, and extending the usefulness of, means for introducing an oscillating or gyrating torque between the motor shaft and the abrasive assembly, to eliminate concentric and other scoring effects common in the use of flexible abrasive discs, cup wire brushes, fiat emory wheels and the like.

A particular object is the control of the degree of oscillation in the coupling to render it adaptable to a wide range of applications in the abrasive art, from coarse planal grinding of flat surfaces, to the grinding and polishing of curved surfaces such as the fenders of automobile bodies and the like.

Another object is the introduction of a structure and mode of operation adapted to overcome the tendency of revolving grinding wheels and. discs, to jump laterally out of control when the revolving grinder is applied to a stationary surface, especially a flat surface. Such loss of control of the grinding assembly often results in injury to the surface being ground and to the operator.

Couplings having a rubber-like cushion interposed between the driving and driven elements, containing a suflicient mass of cushion to be efficient in relatively light abrasive operations, get out of control at grinding speeds when coarser grits are used, and especially when heavier, rigid r; nding wheels are substituted for the flexible abrasive discs.

The present invention results in the reduction of still and experience required by the operator, to safely practice the art of manually applying a portable grinder to the surfaces to be reduced by abrasion when relatively heavy stones or cup wire brushes are used.

Broadly stated, the present invention comprises an external band encircling the oscillating cushion of a resilient couplingfor reducing the range of oscillation of said cushion, while at the same time increasing the modulus. The use of the present invention permits employment of an oscillator designed to operate at speeds up to 5000 R. P. M. with one pound of weight maximum, to carry loads up to live and six times greater than the maximum, all with perfect safety. The

increase in modulus produces a much higher rate of gyrations than originally intended for the oscillator with the lighter maximum load, again all with perfect safety to the operator and the work. This becomes especially important where the tool has a pneumatic motor with variable speeds up to greatly in excess of 5000 R. P. M., such as are used on fine surfaces or very soft surfaces such as marble, cork, linoleum, etc.

Other objects and advantages will appear as the description proceeds. In the specification and the accompanying drawings the invention is disclosed in its preferred form. But, it is to be understood that it is not limited to this form because it may be embodied. in modifications within the spirit of the invention as defined in the claims following the description.

In the drawings:

Figur l is a vertical section showing a resilient coupling having this invention applied thereto as an accessory.

Figure 2 is perspective of the constrictive cup for encircling the coupling cushion, looking into its completely open end.

Figure 3 is a view similar to Figure l, with a solid grinding wheel substituted for the flexible grinding disc.

'In detail, the structure shown in Figure 1 comprises the motor II, having the reduction gear case l2, with the threaded hub I3 of the driving gear projecting therefrom and functioning as the driving shaft of the coupling. The continuation of the motor unit not shown, normally terminates in a longitudinal handle, from which the service cable extends to the source of power. The motor housing has the side handle I2 for two-handed control of the motor unit.

The structure of the resilient coupling comprises the substantially flat driving head. I5 having an internally threaded hub I4 and a concentric peripheral flange I6, undercut as at IT. The hub I4 has an annular flange I8 projecting radially therefrom.

The driven head I9, in opposed relation to the driving head I5, has the similar peripheral flange 20, undercut at 2I and integral with the internally threaded hub 22 that is axially aligned with the driving hub I4. The face 23 of the head I0 is preferably countersunk with the taper extending inwardly toward the hub 22. This hub also has the annular flange 24 projecting radially therefrom.

The space between the heads 15 and I9 is filled with a rubber-like, resilient material 25 vulcanized therein and adhering to all contacting surfaces, or is otherwise secured therein in any suitable manner. The bonding of the resilient material to the heads, hubs, and flanges forms a unitary structure capable of transmitting torque. The resilient material 25 is keyed to the driving head l5 by its mass within the radial flange I8 and the undercut peripheral flange it, and to the driven head [9 by the mass between the radial flange 24 and the undercut peripheral flange 20. The resilient body 25 includes a continuous web 25' which passes between the flanges l8 and 24 and provides an extended area against which the flanges may work. The resilient material which separates the driving and driven heads extends flush with the perimeters of the inturned flanges it and 20 to form an integral flexible coupling to the drive shaft it against the shoulder of which the hub M abuts. The torque of the drive shaft i3 is transmitted to the driven head [9 by the resilient cushion 25. It will be observed that the resilient cushion 25 is in shear normally with the respect to the driving head I5 and the driven head iii.

The flexible plate, or back pad, 26 has the depressed center portion 21 fitting snugly within the dished surface 23. This plate, or back pad 26, is composed of any suitable material such as a plastic sheet, fibre, rubber, non-fatiguing metal or the like and serves as a backing plate for the abrasive disc 28.

The abrasive disc 28 is free of grit centrally so that it may be depressed to conform to the countersunk or dished surface 23 of the driven plate I9. The abrasive disc 28 and backing plate 26 are held in working position by the head 29 of the nut 36, threaded into the driven hub 22. Tightening the nut 30 causes the plate 25 and disc 28 to conform to the dished surface 23, These discs are usually composed of plastic or fibrous sheet material coated on one or both sides with a plastic binder into which a granular abrasive is embedded the cutting qualities of which range from coarse to the finer grades for polishing.

The particular machine shown in the drawing, equipped with the oscillator, is manipulated by grasping the two handles on the housing of the motor unit with both hands and applying the whole exposed face of the disc 23 to the surface to be worked, rather than leading peripheral edge only, with manually applied pressure. To prevent burning the surface the disc 28 is constantly moved over the surface. The greater the pressure applied to the disc 23 the greater the deviating eccentricity resulting in the oscillating orbit, making it practically imr ossible to form concentric score lines in the surface be ing worked. The oscillating effect is caused by the distortion of the resilient cushion 25, by the driving torque and the constant lateral movement of the disc 28 across the frictionally resistant surface being abraded and produces a highly desirable free floating action or lap grind.

Since the cushion 25 of the oscillator is designed primarily to function properly with comparatively light loads of back pads 26 and abrasives 28, the operation with heavier loads or higher speeds will result in exaggerated oscillation beyond the point of usefulness. Accordingly, the mass of cushion 25 must be restrained. For most uses the restraint of the member 32 is sufflcient to restrict oscillatory movement to useful limits. Likewise, the member 32 adds a safety feature at higher loads and speeds by intercepting the shear plane of the cushion 25. As illustrated in Figure 3, the gyro-oscillation of age to bearings and gears.

4 the cushion 25 should be restricted to prevent the increased momentum of the greater weight load getting out of easy manual control by the operator.

The present resilient coupling may be adapted to a wide range of functioning, from the coarse heavy wheel 31 grinding to fine adbrasive or polishing attachments such as the disc 28, by the use of the accessory shown in Figure 2. This consists of the cushion constricting cup having the cylindrical band 32, integral with the end 33, having the axial hole 34, encircling the drive shaft l3, and counterbored to fit the hub of the head 15. The band 32 encircles the exposed periphery of the cushion 25 in frictional contact therewith and has the internally beveled edge extending forward to a point spaced from the margin of the flange 20 0f the driven head. This band prevents and restricts excessive lateral distortion of the cushion 25 under heavy loads and the variable R. P. M. of the driven head under variable working loads, as well as increasing the modulus. These cups may be provided with different longitudinal width of bands 32 and may be applied to the coupling in accordance with the load to be applied to the driven head l9, if desired, to secure diifering effects and results.

The auxiliary stud 3i) replaces nut 38 and is provided for mounting the hollow grinding wheel at onto the driven head 29. It consists of the threaded end 38, which may be screwed into the internal thread in this head, up to the tapered flange 455, which is adapted to fit flush in the dished head. The threaded stud end 39 extends through the wheel 3! locking the same against the flat face of flange either by threads in wheel bushing or by the hexagonal nut it, in the usual manner. The driving torque screws tighten these various threaded elements.

This solid wheel 3i is particularly adaptable to the surfacing of stone, terrazo, marble and similar building walls, floors, steel decks and the like, where a flat plane without score lines is essential. Because of its shock absorbing and gyro-oscillating qualities a sufficient mass of resilient cushion 25, is essential to prevent concentric scoring of the surface being worked, the constricting cup band 32 is superior to a mere reduction in the quantity mass of the cushion 25 in that it becomes variable and requires a cliiferent size for each different use. If needed, the width of the band 32 relative to the exposed periphery of the cushion 25 may be chosen in, accordance with the gyro-oscillating qualities desired.

The dynamic balance of the present resilient coupling with its restricted oscillation and increased modulus is such that the face of the abrasive disc 28, or the face of the wheel 3!, may be operated fiat on the surface being worked without causing concentric score lines or the machine deviating from its working location without manual control, other than to balance the overhanging weight of the motor relative to the plane of the worked surface. This greatly reduces the skill and labor required when the backing 25 is flexed or the wheel 3i applied to the surface off its axial center. No axial distortion of the drive shaft results with consequent dam- This is due largely to the distribution of the mass of the cushion between the driving and driven heads l5 and iii.

The correction of axial distortion is not interfered with. i

I claim:

1. An oscillating resilient coupling comprising a driving head and a driven head arranged in coaxial spaced relation, a central hub on each said head, said hubs extending inwardly toward each other, a radial flange on the inner end of each said hub, said flanges being arranged in 1 parallel to each other in spaced relation and perpendicular to the axis of the coupling, a body of rubber-like material including a web thereof passing between said flanges, disposed between and bonded to said heads and flanges to form a unitaryjstructure capable of transmitting torque, means for attaching the driving head to the spindle shaft of a driving element, means for attaching a driven element to said driven head and a cup member surrounding one of said heads and extending axially to partially surround said body leaving a portion of the periphery exposed.

2. An oscillating resilient coupling comprising a driving head and a driven head arranged in coaxialspaced relation, a central hub on each said head, said hubs extending inwardly toward each other, a flange 0n the inner end of each said hub, said flanges being arranged opposed to each other in spaced relation, a body of resilient material including a web passing between said flanges, disposed between and bonded to said heads and flanges to form a unitary structure capable of transmitting torque, means for attaching the driving head to the spindle shaft of a driving element, means for attaching a driven element to said driven head, and a cup member surrounding one of said heads and extending axially to partially surround said body leaving a portion of the periphery thereof exposed.

BERNE TOCCI-GUILBERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,261,683 Behn Apr. 2, 1918 2,170,627 Berryman Aug. 22, 1939 2,174,010 Patterson Sept. 26, 1939 2,394,882 Weynand Oct. 25, 1949 2,486,078 Tocci-Guilbert Oct. 25, 1949 FOREIGN PATENTS Number Country Date 307,542 Great Britain Mar. 11, 1929

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