US2646654A - Device for dressing coated abrasive belts - Google Patents

Description

y 1953 R. E. BRINK 7 2,646,654

DEVICE FOR DRESSING COATED ABRASIVE BELTS Filed March 1'7, 1950 2 Sheets-Sheet l July 28, 1953 R. E. BRINK 2,646,654

DEVICE FOR DRESSING COATED ABRASIVE BELTS Filed March 17, 1950 2 Sheets-Sheet 2 Patented July 28, 1953 UNITED STATES PATENT OFFICE 2,646,654 DEvICEFoRnaEssmG COATED ABBASIVE BELTS V I, Richard E. Brink, St. Paul, Minn., assignor to Minnesota Mining & ManufacturingCompany, Sit-Paul, Minm, a corporation of Delaware Application 17, 1950, Serial No. 150,306

. .7 Claims (c1. 51f-1a5.)i'

This invention relates to'the art of'machine sanding with coated abrasives and provides a roller device for rehabilitating coated abra'sive belts which have become dulled from use on a workpiece. k

Two principal reasons for dulling'of an abrasive belt after it has been used for a period oftime on a workpiece are glazing and filling. Glazing is the wearing down or breaking off ofthe tips of the abrasive grains which project farthest from the surface of the sheet, so that these blunt surfaces may be observed as a series of discrete reflective points when the abrasive sheet-is held at the proper angle'ina beam of light. In a belt in' this condition, only the worn down, blunt segmentsof abrasive grains contact the workpiece. Such grains no longer have effective abrading action of their own, but prevent contact between the'workpieceand other sharp, usable abrading grains which may lie beneath them.

Filling of an abrasive belt commonly occurs after the belt hasbeen used for a period of time in sanding a relatively soft material such as wood, aluminum or plastic. In such'an operation, a quantity of abraded material gradually accumulates on the abrasive surface of the belt. This material fills the surface of the belt, i. e., clogs the open spaces between abrasive grains, eventually covering the grains entirelyon certain portions of the surface. Areas so "fil1ed no longer have eifectiveness for abrading for the reason that the cutting tips of the abrasive particles are surrounded by foreign matter.

The device of my invention provides a roller having a plurality of protuberances around its periphery for pressing against the back side of a coated abrasive belt in filled or glazed condition to correct such conditions and to extend the effective working life of the'belt. Use of my pressing roller on 'a glazed belt .dislodges the blunt segments of abrasive grains from the binder so that a further quantity of'abrading mineral is exposed. Use of my device on a filled belt dislodges the accumulated surface covering material to again expose the abrading surface of the belt.

The invention is exemplified by devices described hereinafter and illustrated in the accompanying drawings in which:

Figure 1 is an end elevational view of one form of studded roller, with a portion shown in section.

Figure 2 is a side elevational view of the roller illustrated in Figure 1, with a quarter section thereof shown in cross-section, along the line 2-2 in Figure 1.

' Figure 3 is an end elevational view of another form of roller.

Figure 4 is a plan view of an expanded portion of the periphery of the roller..

'Figure5 is-aside elevationalviewof a-frag- I ment of abrasive belt in contact with an individual I stud.

'Figure 6 is a diagrammatic side elevational view of a sanding device using the studded roller.

usedfuifl l Figure-H is a diagrammatic side elevation .of a portion of anothersanding device, in which the studded roller is =us'ed in conjunction with .a back-up roller for the'belt wherein the studded roller and -the-ba'ck-up" roller. are directly ;opp sed .l. n... u

' Figure-8 is a-diagrammatic side elevationalyiew ofa portion of an abrading device. similar .to Figure 8 in-which :the'- studded roller and the back-up roller are not-directly. opposed.

Figure 9 isa side elevation-of a portion of another abrading machine in which. the studded rolleris used incombination with. an ordinary idle roller V. 5.; w a b Ref erring-in-detail to the drawings. .(in the. several views of whichlike reference characters denote. similar parts), in Figures 1,. 2 and 3 the reference char'ac ter -3' indicates a. .cy1indrical roller. In vieweof the fact :that the.roller.3 .is preferably rotated merelybythe .drag or pull of the abrasive web, it .is desirable. that .it be made oflightweig'htmaterial to reduce the amount of inertia which it .presentsto the travelling-abrasiveweb. .have found thatirollers formed of aluminum' combine the desirable light= ness of'weightwi'th .thelquality, of. standing up under-a long periodxof. hard usage. In order to reduceifurtherLthe Weight. ofthe roller, the central portion :of each side face. thereof maybe cast. hollow to a. depth of about one-third of the roller width. For instahcerin thealuminum roller illustrated in the accompanying drawings, thearea'generally'indicated by the numeral 4 has been cast hollow. ltishouldbe understood that this construction is. perferred. merely for the purpose-.of-reducing.the load on the ,motor orthe like whichdrivesthe-abrasive belt, and that; in those-instances-wherezsuch objective is not of importance, the side recessions are not necessary. It shouldalsobe understood that my roller can be madelof. wood,-:steel,r.orany other serviceable material, and. that,.if desired, .it can have a-peripheral coveringuofaleathenahard..rubber ,or. the use. In fact, such' -a peripheral covering. is .advantageous whenrcertain types. of :studs are .used (as hereinafter-:described') since such-studs can then be afiixe'd more easily to the roller periphery. The center of :the .roller'iisr provided with a passage-5 for sreception .of :lthe: shaft upon which the rolle'ris rotatably mounted. i. 'AroundJth'e periphery" of the-' -roller are a plurality of protuberances Bisom'etimes for convenienceihe're inafterreferred to as studs) which maybe-of any suitable material hard enough lto with'stand as a replacement for the idler roller normally deformation and friction wear by pressure exerted thereon by the abrasive belt. For the purpose of illustration, the protuberances shown in Figures 1 and 2 comprise the heads of a plurality of allen screws which have been sunk in the pea riphery of the roller.

I prefer that the studs on the roller be "flattopped; that is, that a relatively sharp angle be formed by the juncture of the sides and top of the studs so that it will be necessary to exert less pressure to achieve the desired'result. However, in some instances it may be desirable toavoid a sharp angle and use a stud having a spheroidal shape, as for instance, when the backing material for the belt is of a nature that it is easily torn or scuffed.

The distance which the heads of the allen screws or other protuberances should project, will depend, in part, upon the weight or thickness of theabrasive belt being dressed. In the coarser grits of coated abrasives a heavier backing material is commonly used, and, because the abrasive grains which are to be adhered to said backing are larger, a thicker coating of adhesive is required. The composite abrasive web in the coarser grits is therefore stiffer than such a web in a finer grit. In such case, it is desirable that the protuberances on roller 3 extend further radially from the periphery of the roller than they do when the roller is used on a web coated with a finer abrasive grit, so that the localized pressure exerted by them on the back of the web will be transmitted through the backing material and be sufiicient to dislodge the blunt abrasive grains from the adhesive binder or the surface covering material from the sheet. I have found, in dressing a medium-grit coated abrasive belt (e. g. grit 50) with a studded roller having fiat-topped studsthat a stud projection of. about gives good results, whereas in dressing a web of finer grit (e. g. grit 100), studs that project about as" perform very satisfactorily. When a coarse grit web is being treated, the studs may project as much as 5. A stud projection of more than is generally too great, in that it may cause an excessive amount of usable mineral, as well as the blunt segments of abrasive grains, to be lost from the belt. Where allen screws are used to form the pressing protuberances, they can be raised or lowered, by the insertion, or removal, of washers, for instance, so that the same roller will be suitable for belts of all grits.

In the accompanying drawings the fiat-topped studs 6 are shown as having a circular perimeter. They have been thus illustrated for convenience only and studs having a perimeter other than circular in outline may equally well be used, subject of course to the requirement that they be of a shape which will not tear the backing of the abrasive web.

Figure 3 illustrates another manner of affixing studs to the peripheral surface of a roller 3, generally similar to the roller illustrated in Figures 1 and 2. In this instance, studs 6 are securely affixed to a strong flexible sheet material I which is wrapped around and secured to the outer circumference of the roller by adhesive 8.

The sheet material 1 must be sufficiently flexible to conform snugly to the circumference of the roller, and must be reasonably abrasionresistant to withstand the wear imposed upon it by the abrasive web, particularly at the points between studs. 1 havefound that woven fabric material of about the weight and flexibility used as backing for ordinary surgical tape provides or the like are also suitable.

excellent results. It conforms well to the periphery of the roller and the studs can be securely affixed to it. I have also successfully used a square woven fabric material having a thread count of as x 48 (weighing 1 pound per 5 yards of material 36" wide), and an abrasion-resistant vinyl plastic sheeting.

The studs 6 illustrated in Figure 3 may be made of any hard substance which can conveniently be affixed to the sheet so as not to be dislodged during use. I have used shirt buttons, cylinders of vulcanized fiber and female snap fasteners, among other things, all with successful results. Studs made of heat-hardened resin, hard rubber The studs may be secured to the covering sheet I by stitching, stapling or the like or by any tenacious adhesive of. which polyvinyl acetate emulsion may be given as an example. Hide glue may also be used to attach the studs, particularly in the case where the stud is made of fibrous material such as the cylinders of vulcanized fiber which I have used with success. I have found it somewhat more advantageous to secure the studs to the wraparound sheet by means of an adhesive rather than by stitching or stapling, for the reason that when the former method is used, the edge portions of the studs are less likely to lift from the sheet and snag the abrasive web.

The studs on this form of roller may be of any convenient, relatively small width, and should conformto the curvature of the roller. Thus a female snap fastener, which is about in width, would not be suitable for use on a roller having a diameter of 5" or less although it would work nicely :on a 10-inch roller, for instance. I have found that a stud having a diameter of about works particularly well on a roller 6" in diameter.

The distance which the studs should project beyond the periphery is again dependent upon the weight or stiffness of the abrasive web being treated. I have found, however, that a fiattopped stud which projects more than is likely to cause excessive loss of mineral, whereas a stud projecting ,4 of an inch or less produces negligible results unless a particularly lightweight'web is being treated.

As shown in Figure 3, the covering sheet I may be secured to the roller 3 by any adhesive 8 sufficiently strong to hold it in place against the drag of the web. For convenience, however, it is advantageous to use an adhesive of the pressuresensitive type which will adhere to the back side of the material when it is stripped ofi the roller. The roller will then be clean and ready for the immediate replacement of a fresh studded sheet.

The studs 6 should be distributed sufliciently far apart from each other around the periphery of the roller so that the abrasive web coming in contact with them will not span or bridge the space between adjacent studs. When a belt is being treated with a studded roller 6" in diameter or less, I have found that the studs should be at least 1 apart. If placed closer than this, adjacent studs tend to support the belt uniformly away from the periphery of the roller rather than individually pressing into the back side thereof. In other words, the pressing action by one stud is reduced by too close proximity of adjacent studs. In the case where a roller of larger diameter is being used, the studs should be placed farther apart to avoid bridging or spanning. For example, to obtain the most'satisfactory results with a studded roller having a diameter of 12" the studsshould be spaced at-least 2';' apart. The studs should be located sufficiently close to each other so that all portions of the abrasive belt will receive dressing treatment as the belt travels about in the sanding machine.

- Referring now particularly to Figure 4, the studs 6 are shown distributed irregularly over the surface of the roller in such manner that they are not in either longitudinal or horizontal alignment. Such irregular distribution is advantageous to avoid the possibility that longitudinal or horizontal strips of the web would receive particular dressing action by reason of the studs being arranged in rows. It is to be understood of course that the particular irregular arrangement shown is merely illustrative, and that neither this arrangement, nor any other particular arrangement of studs is necessary for the successful operation of my roller. A uniform pattern of studs is shown-in Figures 1 and 2 primarily for convenience of illustration. However, as above indicated, an irregular distribution such as is shown in Figure 4, is preferred. i

The action of an individual stud 6 upon a fragment of an abrasive web 9 is illustrated 'in Figure 5.

v A modified form of one type of abrasive belt sanding machine, very commonly used, is shown in Figure 6. It comprises an endless abrasive belt [8 mounted upon a contact roller II and upon a back-stand idler roller I2 which in this case is my studded roller. (The back stand may be of any conventional type and accordingly is not shown.)

The contact roller H is preferably of the resilient type, for example, as shown in Herchenrider Patents Nos. 2,477,602; 2,162,279; or 2,145,418. The rollers II and [2 are supported respectively upon a drive shaft l3 and upon an idle shaft M. The workpiece to be abraded is brought into contact with the periphery of the contactroll at about the point 15 shown thereon. There may be, and frequently is, a stationary platform adjacent the contact roll at this location, upon which the workpiece may be rested.

Figure 6 illustrates the use of my studded roller as a replacement for the ordinary idle roller which is customarily used in belt sanding machines of this kind. In this manner of using the studded roller, it may be advantageous to space the studs somewhat farther apart than they are spaced when the studded roller is used as an auxiliary to an ordinary idle roller (as illustrated in Figures 8 and 9) for the reason that, in Figure 6, the studded roller is continuously in contact with the belt and excessive loss of abrasiveparticles may result if the dressing action is too severe. Back-stand grinders are customarily provided with means for reducing the pressure exert'ed'on the belt by the studded roller so that the dressing action by the studs will be minimized, if desired.

Figs. '7 and 8 show the use of my studded roller as an auxiliary to an ordinary idle roller. In Figure 7, an endless abrasive belt l6 passes round a contact roll and idle roll (not shown), in a manner similar to that shown in Figure 6. Rotatably positioned above and below a span of the abrasive belt between the contact roller and the idle roller by means of idle shafts 16a and I6, are'my studded roller [2 and a back-up or supporting roller H, The back-up roller I! may be covered with a layer of resilient material 18, such as rubber, against which the abrasive web may be pressed by the studs on my roller. The

studded roller 12 maybe moved upwardly,"-"by raising lever [9 .around pivot point 20, "-tci bear against the moving abrasive belt 10 and bring it into peripheral contact with back-up roller Ll'li the axes of said rollers then being in verticalv alignment. In that position, both'rollers'will be rotated by the traveling abrasive belt sandwiched between them. The lever 19 is provided with a pin 2| carried in 'slot 22 of bracket 23. By means. of the arrangement shown in Figure 7, the dressing treatment given to the belt can be regulated by the upward pressure exerted on lever [9 by the operator. Furthermore, the treatment can be limited to such times when it is needed; that is, a fresh belt can be used until it becomes glazed or filled, and'then treated with the studded roller to resharpen it. As it again becomes dull, the process can be repeated, etc. Figure 7 is merely illustrative of one of the many ways in which my studded roller and a back-up roller maybe arranged so that they are normally out of contact but capable of being brought int'o'contact when it is desired to dressthe belt; and any one of many other well-known mechanical devicesmay be substituted for the lever I 9.

I Figure 8 illustrates apparatus similar to "that shown in Figure '7. The studded roller l2 and idle roller i? are mounted on shafts lfib'andlfic, respectively, the ends of which are rotatably jornalled in lever 24. Upon raising'the lower end of lever 24, the peripheries of rollers 12 and IT are brought into contact' with opposite surfaces of the moving abrasive belt l 0. As shown in Fig ure 8, the lower end of lever bears against a" stop member 25 when the studded roller l2'isin its disengaged position. This arrangement provides for a milder dressing treatment of the belt than does the arrangement shown in Figure '3, when an equal amount of force is exerted on the lever in each case. 7

In Figure 9 an endless abrasive belt 26'passe's around a contact wheel'2'l, an'o'rdinary idle r011 er 2% and my studded roller I2. The contact roll is mounted upon driving shaft 29. [Rollers i 2 and 28 are rotatably mounted, with peripheral portions opposed and spaced apart, uponjcor'i' necting member 30 by means of shafts 3l and 35a. At the longitudinal center of connecting member 30, equidistant betweenthe axes of roll.- ers l2 and 28, is pivot shaft: 32- about which member 30 and rollers I2 and zii may be ro tated. I N f As the assemblage comprising; rollers fl and 28 and connecting member 30"is rotated in a clockwise direction around pivot shaft 32, studded roller I2 is advanced into more severe contact with belt 26.. At thesame time, pressure contact between idle roller 28.and thebeltis lessened. Similarly, counter-clockwise rotation will provide for greater pressure contact by idle roller 28 and less contact by studdedroller l2. Member 3%} is provided with threaded passage 33 for reception of screw member 34 which may be tightened to bear on shaft 32 to hold member 30 in fixed position. Y

By means of the arrangement shown in Figure 9. any degree of contact between the studded" roller and' the beltmay be obtained. Theiendless belt 2:; 111 be under suffilcient tension,":i r respective of the positioniof rolls J2 and 28 around pivot shaft 32. The belt slack necess ry to a l w adv ncemen r g J spr -y vided by't'hesimultaneous withdrawal of roller 28, and vice versa.

What I claim is;

1. In a backstand grinder comprising a driven contact roller, an idle roller and an abrasive coated belt trained thereon, means for rehabilitating said belt when it has become dulled from use on a workpiece comprising a rotatably mounted pressing roller disposed at a span of the belt between said contact roller and said idle roller, said pressing roller facing the uncoated surface of the belt and extending axially parallel to and transversely of the surface of the belt; a rotatably mounted resilient supporting roller disposed at the same span of the belt as said pressing roller; said supporting roller disposed facing the coated surface of the belt and extending axially parallel to and transversely thereof, and means for bringing said rollers into peripheral engagement with the belt; said pressing roller having unyielding peripheral protuberances circumferentially distributed to press independently against the belt to dislodge dulled abrasive grains and accumulated abraded material from the abrasive surface of the belt, said protuberances being spaced so as to provide that substantially all portions of the back surface of the belt will be subjected to pressing action as the belt travels about in the sanding machine.

2. In an abrasive-belt sanding machine, in-. cluding a contact roller against which a work piece is pressed, and a driven abrasive belt trained over said contact roller; and idle roller adapted to be brought into and out of peripheral engagement with the back side of said belt, the periphery of said idle roller being provided with a plurality of fixed, unyielding studs each having a width of from 2 to /2, said studs being spaced apart a distance at least equal to four times the width of a stud, and being distributed about the circum ere c f; the. i le roller n s h m er that a direct line about the circumference of said idle roller through any point on the width thereof willpass through at least one stud,

3 In an abrasive-belt sanding machine comprising a contact roller and a driven abrasive belt trained thereover, an idle roller in peripheral engagement with the back side said belt, the periphery of said idle roller being provided with a plurality of fixed, non-yielding studs each having a width of from to V2", said studs being spaced apart a distance at least equal to four times the width of a stud, and being distributed about the circumference of said idle roller in such arrangement that substantially all portions of the back side of said belt will be contacted by one or more studs in not less than twenty circuits of said driven belt in said sanding machine.

' 4. In an abrading machine including an end-. less driven coated abrasive belt and contact roller adjacent the back side of said belt to maintain said belt in abrading contact with a work piece pressed against said belt, an accessory for rehabilitating said coated abrasive belt when it has become dulled from use on said work piece, said accessory comprising an idle roller provided with a plurality of fixed, non-yielding studs each having a width of from to /g", said studs being spaced apart a distance at least equal to four times the width of a stud, and being distributed about the circumference of said idle roller in such arrangement that substantially all portions of the back side of said belt will be eontacted by one or more studs as said belt.

travels about. in said abrading machine.

5. An abrasive-belt sanding machine comprising in combination a resilient driven roller against which the work piece to be abraded is placed, a peripherally studded idle roller, a peripherally smooth idle roller, a rotatably mounted arm, means for holding said arm in fixed position, and an abrasive belt trained over said rollers; said idle rollers being rotatably mounted on opposite end portions of said arm equidistant from the axis of rotation of said arm, said idle rollers being adapted to be brought into and out of peripheral engagement with the back side of said abrasive belt; said studded idle roller being provided with a plurality of fixed, non-yielding studs each having a width of from 6?" to /2, said studs being spaced apart a distance at least equal to four times the width of a stud, and being distributed about the circumference of said studded idle roller in such arrangement that a direct line about the circumference of the studded idle roller through any point on the width thereof will pass through at least one stud.

6. In an abrading machine including a driven coated abrasive belt and a member adjacent the back side of said belt to maintain said belt in abrading contact with a work piece pressed thereagainst; a device for rehabilitating said coated abrasive belt when it has become dulled from use on said work piece; said device comprising a roller in peripheral engagement with the back side of said belt, said roller having unyielding protubcrances fixedly mounted upon its periphery, each of said protuberances having a width of from of an inch to inch and a height of not more than twice its width, said protuberances occupying not more than 15 per cent of the area of the periphery of said roller, and bedistributed about the circumference of said roller in such arrangement that a direct line about the circumference of said roller through any point on the Width thereof will pass through at least one protuberance.

'7. As a new article of manufacture, a device for rehabilitating a coated abrasive belt which has become dulled from use in an abrasive-belt sanding machine, said device comprising a roller having unyielding protuberances fixedly mounted upon its periphery, each of said protuberances having a width of from a; of an inch to onehalf inch, said protuberances occupying not more than 15% of the area of the periphery of said roller, and being distributed about the circumference of said roller in such arrangement that a direct line about the circumference of said roller through any point on the Width thereof will pass through at least one protuberance.

RICHARD E. BRINK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,034,959 Bertram Aug. 6, 1912 1,036,783 Bein Aug. 27, 1912 1,042,354 Kroeze Oct. 22, 1912 1,179,999 Blevney Apr. 18, 1916 1,701,814 Maddox Feb. 12, 1929 2,162,279 Herchenrider June 13, 1939 FOREIGN PATENTS Number Country Date 658,868 France June 21, 1929

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