US2820333A - Contact wheel with grooves and slits - Google Patents

Description

Jan. 21, 1958 w. J; cosMos CONTACT WHEEL-WITH GROOVES AND- SLITS Filed July 25, 1955 William; J 605m as f' D. Pra yer tat United CONTACT WHEEL WITH GROOVES AND SLITS William J. Cosmos, Mundelein, Ill.

Application July 25, 1955, Serial No. 524,033

3 Claims. (Cl. 51-141) This invention relates to contact wheels for driving and cushioning abrasive belts. It provides a wheel of this kind with a highly etficient combination of operating characteristics, by a novel combination of grooves and slits on the working surface of the wheel.

I The wheels in question generally have a rim of rubber- 3 meat like material which is subjected to centrifugal forces when successive ridges and grooves of the contact Wheel rim,

moving the belt over the workpiece, resiliently flex the belt; as a result, the products of abrasion are readily removed, instead of clogging or glazing the abrasive belt. Ordinary files are either single-cut or cross-cut; and likewise the serrations of contact wheels have been made either in single directions or in cross-serrated manner. Cross-serration was expected to add to the filing action of the abrasive belt and also to make the rim of the contact wheel more flexible and thereby to adapt it better to curved workpiece surfaces. However, the cross-serrating of contact wheels gave rise to serious dilficulties. "It produced markings or even scratches, extending through the workpiece area that was ground off or polished. In accordance with my copending application Serial No. 429,811 such marking and scratching was overcome by staggering the various serrations so that the intersections of all cross-serrations and main serrations travel in separate "paths. However a new difiiculty resulted. Along both edges of the cross-serrated contact wheel,

with staggered serrations, the material of the oblique "cross serrations and the like. This will avoid the marks and scratches extending through the polished area and the transverse chatter'marks which I have mentioned; however another difiiculty is then encountered since sharp and abrupt outer edges of the ground or polished surface are formed, which are just as objectionable as the markings extending through the ground or polishedsurface.

Y Ihave now discovered a form of working surface of a contact'wheel which'has the adaptability and smoothness ofacr'oss-serrated surface-fully avoiding the ditliculties 2,820,333 I'; Patented -.lan-.= 2l',y195

of the single-serrated wheel, while having none of the drawbacks of the aforementioned cross-serrated wheels. Particularly the new contact wheel, used with'any suitable abrasive belts, avoids the edge-grinding difilculty as well as the marking and scratching problems. At the same time the new working surface can be produced very cheaply; in fact more cheaply than the cross serrations of the prior art. To provide a contact wheel with a working surface of such improved character is a primary object of this-invention.

A specific object is that the contact wheel should be adaptable to variously curved workpiece surfaces. Another specific object is that the contact wheel should provide uni-form action: it should avoid sharp transitions from ground to unground area, longitudinal markings and scratches through the ground area and transverse chatter marks and the like in the ground area. Another object is to allow efficient edgegrinding as well as' grinding on the peripheral area of the belt and wheel. Another object is that a wide and practically-universal range; of rough, intermediate and fine abrasive belts should bekepta'vailable, so-that one and the same contact wheel,-with the different belts, canbe used for stock removal, polishing andfinishing of :a given workpiece. Still another object of course is that the contact wheel should bewell ventilated, well balanced, readily interchangeable and otherwise efilcient and economical inaccordance with modern requirements. Heretofore it was impossible to achieve all of these specific objects byone and the'sarne contact wheel. Particularlyit was impossible to make the wheel adaptable and uniform in action and at the same time to allow efficient edge grinding.

, By means of the new invention all of the enumerated objects have been achieved, by providing a contact wheel with a working surface which has deep and wide, grooves in oblique planes across the wheel and equally deep but extremely narrowslits in planes parallel to the sides of the wheel. The oblique ridges of the working surface are thus divided into individualislands the sides of which are in contact with one another. These islands yield to pressure somewhat in the manner of the keys of the different keyboards of an organ, except for particular features of their attachment, as a result of which all scratching and marking is avoided as well as with the staggered cross serrations of said earlier application, while -edge-grinding is performed more efiiciently. The advantageis obtained at no extra expense; actually the newv wheel is cheaper than that of said earlier application.

The details will be understood from the following dc"- scription fo a preferred embodiment of this invention.

In the drawing:

Figure 1 is a side elevation of said preferred embodiment.

Figure 2 is a front elevation of the same with a portion of the abrasive belt cut away.

Figure 3 is an enlarged detail from the lower left hand portionof Figure 2.

Figures 4 and 5 are sections taken along lines 4-4 and 5-5 in Figure 3 respectively. I

Figure 6 is a more enlarged detail from Figure 3 with additional belt portions removed.

Figure 7 is a detail similar to that of Figure 6 illustrating one step in the manufacture of the new contact wheel.

The main part of the new contact wheel is a rim R suitably bonded to a hub H. The hub is shown as being mounted on a shaft S by the usual nut and thread engagement N. An abrasive belt X is driven by the rim R in a direction Y over the surface of a workpiece P, while the workpiece is manually or automatically pressed against a portion of the belt in contact with the wheel.

in the peripheral surface of the rim R, principal s erra tions or grooves 10 are formed. These grooves have substantial depth as compared with the thickness of the abrasive belt; likewise they have substantial width, sometimes even greater than said depth. Thus substantially spaced, successive rows of particles of the abrasive coating of the belt are brought into working contact with the material to be ground off, while intermediate abrasive particles, with their supporting belt portions, are flexed away from the workpiece surface, at any one moment of the grinding operation. The grooves 19 extend obliquely across the rim, at an angle to the axis of the wheel, from one side 13 to the other side 14 of the rim. The surface of the rim is thus divided into spaced oblique ridges 11.

The ridges 11 are subdivided into individual islands 12, by similarly deep but very narrow slits 15; and these narrow slits according to the present invention lie in planes parallel with one another and with the sides 13, 14- of the wheel. 'Desirably the slitshave the form of knife cuts, as distinguished from saw cuts or the like, so that adjacent side surfaces of islands 12 are normally in surface contact with one another, not spaced from one another. Thus the different islands of each ridge 11 resemble the keys of a keyboard; however they are resiliently hinged'to an oblique base.

In Figure 3, consecutive ridges 11- have been identified by letters A, B, C, etc. and different rows of islands 12', extending parallel to the sides 13', 14 have been identified by numbers I; II, III, etc. Accordinglyindividual islands can and will be identified bysuch combinations of symbols as A I, B H, etc. Each of them can flex freely and individually in the direction parallel with the sides 13, 1'4 and slits 15. On the other hand the mutually contacting islands encounter some little resistance when flexing in directions across these sides and slits. However even the latter flexingis possible to some extent; con siderably more so than in the case of undivided, singlecut ridges. This applies mainly adjacent the sides 13, 14, where greater or smaller groups of the individual islands can fiex rather freely both in and across the direction of rotation.

In view of previous experience with cross-serrated contact wheels and with the contact wheels having staggered cross-serrations I had hesitated for some time before I tried the method of slitting in the direction of rotation and without staggering of slits. such slitting I found the grinding and polishing results, obtained with standard abrasive belts, most satisfactory and rewarding. On further investigation I found that intersections between main grooves and slits can be allowed to travel in uniformplanes andmarking or scratching of workpiece surfaces can still be avoided, so long as the forms and dimensions of such intersections are such that no spots of highly concentrated abrasive impact stress reach the same point of the workpiece surface in close succession. This condition is fulfilled in the present working surface, as well as in a single-serrated rim. However the present surface also provides the adaptability and smoothness of a cross-serrated contact wheel, which a. single-serrated contact wheel does not.

Little needs to be said about the manufacture of the new contact Wheel andthe details of its design. When the wide grooves have been formed either by molding or cutting, in known manner, the narrow slits 15 can be made in the manner illustrated in Figure 7. Knives IK, IIK, III-K, etc. are rigidly mounted by suitable means, not shown, with their cutting edgesv pointing in directions opposite the rotating direction Y; the first knife IK being suitably spaced from the left hand edge 14 and the other knives being uniformly spacedapart. One revolution of'th'e wheel is then performed at any suitable speed while the knives are in such position relative to the rim as to sink a knife cut of the desired depth, indicated in Figure 4 'at K Norim material is removed in-eidentto this-cutting; the material ,of the ridges. 11. is; only split: and allowed to form islands with mutually contacting side surfaces, as mentioned.

However when I tried Thus the slitting in directions parallel with the rotation of the wheel is an operation of the utmost simplicity and economy, which can be performed on single-serrated wheels of various designs, previously made or specially made hereunder. The operation can be performed by skilled or semi-skilled or even unskilled labor, on various simple lathes or other machines and without any great difficulty or loss of time for set-up or control, or loss due to rejects. Likewise it is considerably cheaper than the molding of special cross-serrations; this will be understood mainly when it is remembered that great varieties of contact wheel rims and corresponding molds are required in any event because of differences in radius, width, depth of serration, form of serration and other characteristics of the wheels.

The ridges and islands 1t 12 may have front surfaces l6-referring to the surfaces first reaching the workpiece upon rotation in the direction Ywhich surfaces may be sloping or inclined in various suitable degrees, as well known to the art. The back surfaces 17 of the ridges and islands are shown as oppositely inclined. In any case all of the islands 12 advantageously have broad and solid bases, firmly anchoring them to the hub H. This applies to the islands 12 across the entire working surface of the wheel, including notably the islands adjacent the sides 13, 14. They are all constructed in identical manner and have identical base area, inherent strength and resistance to wear and tear. Said wear and tear takes place mainly at the corner line 18 between the front surface 16 and the peripheral or working surface 19 of each island 12. The latter surface is dressed to a, predetermined, usually cylindrical and uniform shape for the entire contact wheel, such dressing being performed when the wheel rotates at the design velocity for which it is to be balanced dynamically and at which it is to be used in operation. If necessary the present contact wheel can be redressed after it has been subject to some appreciable wear and tear. No repeated serrating, grooving or slitting is required at such time. Also no special difficulty is encountered by the islands adjacent the sides 13, 14, upon such redressing.

It may be noted on close observation of a wheel made according to Figure 7 that the slits 15 made by any one of the knives IK, etc., while all lying substantially in a single plane, are slightly offset at the corner line 20 between the working surface 19 and the back surface 17. The reason is that the knives, held in the position described above, cut first into bottom portions of the front surface 16 (see knife III-K) then progressively into the front surface 16 and across the front edge 18 (see knife II-K); then through the working. surface 19 (see knife IK). As this latter cutting is completed, the corner line 20 reaches successive positions 20a, 20b 20f. Incident to this progress, as shown mainly at 2.01, the ridge material between the surfaces 19 and 17 is dis.- torted to some extent, causing the small offsets 21. With given rim materials and other characteristics these offsets can be made somewhat greater or smaller, depending largely upon the velocity of wheel rotation during the slitting process; they tend to be more pronouncedif the slitting is performed at slow rotating speed.

When such offsetting is slight-such as an offset of A inch while using a spacing of about inch between slits, substantially as illustrated-the effect of the offset 21 upon the operation of the contact wheel and belt is often negligible. When the offsetting is made more pro nounced the offsetting may have a more pronounced effect; and I find such eflect quite desirable. The effect is that flexing of the islands in the direction, of. rotation is dampened to a substantial extent- In a piano keyboard a similar effect would be obtainedv by jamming paper or cardboard between the keys. The. extentto which the individual islands can be flexed either in: or across the direction of rotation remains the same. as before but the momentary flexing resultingfrom a single dynamic impact is reduced and its extent is made more nearly the same, regardless of direction of original impact.

The operation of the wheel is easy to understand from the foregoing description, in the light of the prior art. The wheel H, R is rotated by the shaft S at a velocity for which the wheel has been dynamically balanced so as to avoid undesirable vibration in spite of the centrifugal expansion of the rim R and islands 12, required for the driving of the belt X against the braking action of the workpiece P. This workpiece is held against the moving belt supported by the rim; and the workpiece surface to be ground or polished is practically embedded in the belt and rim. It displaces various islands 12 in different manners, as shown in Figure 3 for the edge grinding of a more or less circular workpiece convex to the abrasive belt. The approximate outline of the embedded area is shown by the broken line Q, which is part of an irregular ellipse; the irregularity being due to the sequence of ridges and grooves 11, 10.

Before the different islands 12 are flexed by the pressure of the workpiece P they are substantially in the position shown in Figure 4. Here the corner between the. front and working surfaces 16, 19 is more or less acute or right-angled. Under the flexing action, as shown in Figure 5, the same corner is compressed into a more obtuse form while the entire island is flexed backwards. The backward flexing and mainly the compression of the corner 18 constitutes the most severe strain imposed on the contact wheel in normal operation. It leads to a gradual aging of the rubber-like material adjacent the cornerjltt, which as mentioned may require resurfacing after a certain period of use.

As shown in Figure 3, by arrows Z, the flexing of the islands 12, under the various portions of the curved workpiece surface, takes place in different directions and to different extents because of the deeper or less deep embedding of different points and the different orientation of the workpiece surface at the various points. The radii Z may be considered as vectors, showing both directions and magnitudes of typical pressures at various points. It will thus be seen that for instance the island AI may tend to flex slightly in a direction parallel with the rotation Y; when arriving in position B--I the same island will be flexed more thoroughly and with a leftward component. Other islands, as shown at BIV, CIV, etc. may he flexed with rightward components in various stages of the process. These variations of rightward, leftward and straight backward flexing directions are imparted to some extent to the different portions of the belt X, mainly those overlying adjacent grooves 10. These belt portions as shown at X-1 in Figure 5, may have some flexing and fullness because of the backward flexing of the-adjacent islands 12, thereby allowing motion of belt portions both in and across the direction of rotation Y. The ultimate result is, a relative motion between belt portions and workpiece surfaces in wavy or spiraling lines rather than straight lines; a form of grinding which is known to be most desirable and most conducive to smooth abrasion and polishing without markings and irregularities.

The extent to which a wavy or spiraling trend enters the grinding motion depends very largely upon the form and also the exact positions of the workpiece P. Even minor vibrations of the hands or devices holding this workpiece against the abrasive belt and contact wheel are reflected by rather substantial variations of the individual vectors Z of flexing of the individual islands 12.

As a result of these conditions, the intersections or corners 22, between the main grooves and the slits 15, will change their position to some little extent, relative to one another, as the grinding operation proceeds. For instance Figure 3 shows an outermost corner 22 of island B-I substantially displaced backwards and also outwards due to the considerable magnitude and pronounced lateral component of the pertinent vector Z.

arran e Air" adjacent island B -H has'the' corresponding-"corner slightly in front of the immediately adjacent part of the edge 18 of island 8-4 and in some cases, asfor instance in island CIV, said corner 22' may also -'be displaced leftward to some little extent as shown in Figure 6.

Because of the narrowness of the slits 15 and in some cases because of the effect of offsets 21 the flexing as mentioned is dampened and restricted, as 'a result of which the relative separations between directly adjoining island portions never becomes very great; the condition of Figure 6 being more or less an extreme. Both of the islands shown in that figure may be considered as being flexed backwards to some certain extent, together, the island at left however being flexed backward to a some; what greater extent and also being flexed laterally to some little extent, relative to the island 'at right. This latter, relative flexing at any given instant, between directly adjoining islands, is further reduced by the inherent damping action of the overlying abrasive belt X, a small portion of which is shown in Figure 6 and which acts more or less as a tie between the adjacent portions of working surfaces 19.

Because of the smallness of relative flexing motions, regardless of magnitude of joint flexing motions, the actual dimension of the exposed corner 22, in frontof the adjacent edge l8 in Figure 6', is kept, veryysmall in accordance herewith. As a result, even if a number of consecutive corners 22 reach one and the same point of the workpiece surface in succession, the impacts of abrasive particles occurring at such point will. not e concentrated very much, in comparison with the impacts performed by abrasive particles overlying the other portions in the area of the edge 18. Considering further the effect of such impacts upon small or large areas rather than points on the workpiece it will be seen that practically all of the abrasive particles, overlying corners 22 and overlying other parts of the edges 18, travel over the workpiece in similar more or less wavy lines crossing one another at innumerable points. A very even, smooth and uniform grinding and polishing action is thus obtained over the entire area. Also no sharp marking is occasioned adjacent the edges of the ground-off area, that is, at the right hand end of the area within the line Q in Figure 3. In said region the ground-off area produced in any one position of the workpiece merges very gradually into the unground area surrounding it, so that the complete surface can be ground and polished, without strip or edge effects, in a minimum of time.

Even at the left hand edge 14 of the wheel in Figure 3, where the abrasive belt seemingly ends abruptly and the convex workpiece surface is deeply embedded in the belt and rim, the formation of a sharp and undesirable mark or borderline of the ground and polished area is effectively avoided according to this invention. The wavy or spiraling action of the belt, caused by lateral flexing of the islands, is at a maximum in this region because of the end of lateral mutual support between the islands 12. Thus the belt, in operation, not only moves rapidly over the workpiece in direction Y but also oscillates between positions 22 and 22a, thereby making it rather easy to finish the complete grinding or polishing of the workpiece, without undesirable overlaps, marks or other irregularities between individual ground-off areas. Likewise, as mentioned, no chatter marks or the like are occasioned, all of the islands 12 at the sides 13, 14 being uniformly protected from wear and tear.

Innumerable variations of course are possible as to the shape of the workpiece, the details of the wheel and even the details of the main grooves and serrations in the rim of the wheel.

I claim:

1. In a contact wheel for driving and cushioning an abrasive belt, an elastic tire having a generally cylindrical peripheral surface extending between parallel side planes,

asa aas" said surface comprising a system of islands separated relative to each other by two intersecting series of deep parallel separations; one of said series comprising parallel grooves. extending obliquely and continuously between said side planes to fully separate the islands from one another in a peripheral direction; and the other of said series comprising. parallel slits extending continuously between. said side planes and lying in planes parallel with one another and with said side planes said slits constituting-lines of contiguous material separation between adjacent islands, the opposed edge surfaces defined between adjacent islands by said slits being normally in displaceable surface contact with one another; whereby each island can flex freely and individually in a peripheral direction and groups of adjacent islands can flex relatively freely botlr in and across said peripheral direction.

2'. In. a contact wheel. for driving and cushioning an abrasive belt, an elastic ti -re having agenerally cylindrical peripheral surface extending. between parallel side planes, said. surface: comprising a system of islands separated relative to each other by two intersecting series of deep parallel. separations; one of said series comprising parallel grooves extending obliquely and continuously between said. side planes to fully separate the islands from one another in a peripheral direction, said grooves being of substantial peripheral width and radial depth, whereby said tire. surface is adapted to allow considerable flexing of an abrasive belt therein; and the other of said series comprising. parallel slits extending continuously between said side planes and lying in planes parallel with one another and said side planes said slits constituting lines of contiguous material separation between adjacent islands, the opposed edge surfaces defined between adjacent islands by said slits being normally in displaceable surface contact. with one another; whereby each island. can flex freely and individually in a peripheral direction and groups, of adjacent islands can fiex relatively freely both in and. acrosssaid peripheral direction.

3. In a contact wheel for driving and cushioning an abrasive belt, an elastic tire havinga generally cylindrical peripheral surface extending between parallel side planes, said surface comprising a system of islands separated relative to each other by two intersecting series of deep parallel separations; one of said series comprising parallel grooves extending obliquely and continuously between said side planes to fully separate the islands from one another in a peripheral direction, said grooves being of substantial peripheral width and radial depth, whereby said tire surface is adapted to allow considerable flexing of an abrasive belt therein, each island having a front and a back surface defined by the adjacent grooves, said front surfaces of the islands defining relatively sharp corners with the adjacent peripheral surfaces thereof; and the other of said series comprising parallel slits extending continuously between said side planes and lying in planes parallel with one another and with said side planes said slits constituting lines of contiguous material separation between adjacent islands, the opposed edge surfaces defined between adjacent islands by said slits being normally in displaceable surface contact with one another; whereby each island can flex freely and individually in a pcripheral direction and groups of adjacent islands can flex relatively freely both in and across said peripheral direction.

References Cited in the file of this patent UNITED STATES PATENTS

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