US2152392A - Abrasive article and method of manufacturing the same - Google Patents

Description

F. J. TONE March 28, 1939.

ABRAsIvE ARTICLE AND METHOD oF MANUFAcTURlNG THE SAME 2 sheets-sheet 1 Filed Jan. '26, 1937 INVENTOR. NK J. TON E F R A ATTORNEY.

March 28, 1939. F4 J. TONE ABRASIVE ARTICLE AND METHOD OF MANUFACTURING THE SAME Filed Jan. 26, 1937 2 Sheets-Sheet 2 INVENTOR. FQAN J, -roNa ATTORNEY.

Patented Mar. 28, 1939 UNITED STATES PATENT OFFICE ABRASIVE ARTICLE AND METHOD OF MANUFACTURING THE SAME Application January 26, 1937, Serial No. 122,446

5 Claims.

This invention relates to improved abrasive articles and to a method of manufacturing the saine. More particularly, the invention is directed to an improvement in' abrasive articles of the general character of abrasive discs and other flexible backed abrasive articles and to methods of making such articles.

This application is a continuation in part of my copending application Serial No. 756,994, filed December 11, 1934, which was a continuation in part of copending application Serial No. 628,221, led August 10, 1932.

While the invention is adapted to be used in various forms of flexible backed abrasives, it has been found to be of particular utility in the manufacture of abrasive discs of the type described and claimed in a patent to Herbert R. Stratford, No. 1,686,938. Discs of this type are employed in great numbers in the sanding of automobile bodies and consist essentially of a stiff, resilient backing coated on one surface with a layer of abrasive grains. They are commonly mounted on a flexible rotatable shaft which is provided with a supporting backing of the general character of a pad of felt which is somewhat smaller in diameter than the abrasive discs.

In the past discs of this type have been commonly made by the conventional methods of makling sandpaper. One of the most commonly used forms of discs contains a backing consisting of a layer of vulcanized ber and a layer of cloth adhesively attached to the iiber.` The abrasive grains are customarily applied to the cloth side of the combination. The discs are made by rst preparing the combination backing and then passing this backing through a conventional sandpaper making machine wherein it is coated With grains and a binder for attaching the grains to the cloth, treating to harden the binder and then cutting discs from the coated web. 'Ihe usual method of treating the coated fabric after it has been coated with thegrains and adhesive comprises feeding the web to a chamber where it is hung in festoons until the adhesive has set up. Discs cut from such material are therefore substantially flatv or plane. I have found that impr'oved discs may be made by employing a treatment which will give to the completed disc A a curvature in at least one direction.

It is accordingly an object of the invention to make improved abrasive discs having a stiff but resilient backing. Another object of the invention is to provide a method for making such discs. A still further object of the invention is to provide a method for treating abrasive coated webs.

Understanding of the invention will be facilitated by reference to the accompanying drawings wherein:

Figure 1 is a plan view of the disc made in accordance with the invention;

Figure 2 is a section along the lines II--II of Figure 1;

Figure 3 is a section along the lines III- III of Figure 1;

Figure 4 is a partial section of a disc mounted on a shaft;

Figure 5 is a diagrammatic representation of the method of making discs in accordance with the invention;

Figure 6 is a representation of one modification of apparatus used in carrying out a step of the invention.

Referring to the drawings, discs made in accordance with the invention comprise a backing consisting of a stiff, resilient material such as vulcanized iiber l, attached to a layer of cloth 2 to the outer surface of which abrasive grains 4 are attached by adhesive 3. As illustrated by Figures 1, 2 and 3, the discs are of such shape that a diameter along one particular direction as shown in Figures l and 2 is a substantially straight line while a section on a diameter substantially at right angles thereto is substantially the arc of a circle.

When discs of this type are mounted for use as illustrated in Figure 4, the abrasive disc 'l is v drawn against a yieldable supporting disc 8 which is in turn supported on a part of its surface by a suitable disc of stili material such as steel 9 by a screw I0, threaded into the rotatable shaft 6. The discs are of such dimensions that when they are flattened, as by pressure applied in the center, they are substantially circular in shape.

As stated, I have found that discs which are so curved are an improvement over discs which are normally plane or flat. I believe that the improvement results from the fact that the disc is caused to lie snugly against the supporting pad 8 which is not the case where the disc is normally plane as is the case with discs of the prior art. Since the discs normally have a curvature, it Will be seen that .when they are mounted as illustrated, in Figure 4, they are put under compression to some extent and therefore tend to remain in close contact with the backing pad 8.

I provide this curvature to the disc by winding the coated web into a roll prior to the treatment where the adhesive is nally set to its completely hardened condition. It is usually desirable to Wind the web into rolls of comparatively few number of turns so that the radius of curvature imparted to the web will not vary greatly from the inner layers of the roll to the outer layers, although I have found that the exact curvature imparted to the web is not critical.

Although the invention is especially adapted to the manufacture of abrasive discs I have also found it useful to apply the method herein described to the curing of abrasive products made on other kinds of backing, such as paper or cloth. The method has the advantage in the production of such articles that it permits the final treatment of the product in a minimum of space and is well adapted to production methods of manufacture. Furthermore, the slight curvature imparted to ordinary paper and cloth when it has been treated according to my process is frequently of advantage as in the manufacture of abrasive belts where it is desirable that the abrasive coated surface is slightly convex.

In curing abrasive coated paper-which is to be used for belts I have frequently found it to be desirable to wind the product into rolls under tension in order to minimize the amount which the belts will stretch in use. Where vsandpaper is curved by the usual method of festooning, there is a tendency for the paper backing to stretch when it is put under tension as in a belt. If the nal treatment of the coated product is made While the backing is under tension there is little tendency for abrasive belts made from such a product to stretch when in use.

yThe exact time in the process at which the abrasive coated web is Wound into a roll will depend to some extent on the character of the adhesive which is used to attach the grains to the backing as will the treatment which is subsequently given to the roll of the coated material. Where the adhesive is glue, the coated web is set up sufiiciently to harden the glue to the point where it will not be dislodged in the rolling process and so that the coated side of the web will not stick to the back of the layer which is adjacent to it when the web is wound into a roll. This hardening may be brought about by removal of much of the moisture from the glue. Where the adhesive is a resinous material such as a heat-hardenable condensation product, it is desirable to advance the resinous binder to the point where it is no longer liquid but is yet suiciently plastic so that the web will conform to the shape of the roll and assume a curvature as its normal condition. The binder may be hardened, or the web otherwise treated to prevent the coated side of the web from sticking to the back of the contiguous layer, by methods to be described hereinafter.

I Will now describe the method of making these improved articles, -including a description of the method usedin coating the web of backing ma` terial.

Referring to Figure 5 of the accompanying drawings the web material II which may be the combination of ber and cloth shown in Figures 2 and 3 or other suitable material such as paper or cloth, is supplied from a roll I2 and is carried over idler rolls I3 and I4 to an adhesive roll I5 which dips into a pan II for the purpose of applying a base coating of adhesive.l The adhesive roll I5 is provided with the usual press-ure roll I6 to regulate the thickness of the adhesive coating. The adhesive coated web is then passed under a grain hopper I8 which is provided with an adjustable gate I9 and cooperating feed roll 20 adapted to apply a regulated amount of grain onto the adhesive coated side of the web.

The abrasive .coated web is then passed to a position where a second or sizing coating of adhesive is applied over the layer of abrasive grain. I'he break 23 is indicated to show suil'i- Acient travel of the web to permit a partial set of the base adhesive coating so that the positions of the abrasive granules will not be appreciably disturbed by the application of the second or sizing coating of adhesive.

'I'he sizing coating of adhesive may be applied by any suitable apparatus. For convenience and illustration I have shown the conventional roll method of coating which is similar to that used in applying the base coating of adhesive although other methods of applying the sizing coating, as by means of spray nozzles, may be used. As illustrated in Figure 5, the coated, web is passed between the rolls 24 and 26 with the abrasive coated side in contact with the adhesive roll 24. This adhesive roll 24 dips into the adhesive container 25 and applies a i'llm of adhesive onto the abrasive coating. The roll 26 is provided to regulate the pressure on the back of the web and hence the thickness of the sizing coating so applied.

In making coated Webs wherein the adhesive is glue, the product from the sizing machine may be immediately wound into rolls as indicated by the reference character 28, when relatively fine abrasive grain is being applied. However, with coarse grits, it is sometimes desirable to allow a short time for the coating of glue to set before the coated material can be rolled. This is due to the fact that a thicker fllm of adhesive is applied in the case of the coarser grain. In practice therefore, I have found it convenient to pass the coated web from the sizing machine upwardly around suitable supporting rolls to a position immediately below the ceiling and along at this level for a distance of approximately 50 feet, then downwardly to a take-up drum where the coated fabric is wound into rolls as indicated by the reference character 30. By this method abrasive paper of any regular grain vsize can be manufactured without difficulties from sticking as would be experienced if the product were rolled before the adhesive had set to some extent. In Winding the coated material into rolls it is desirable, particularly where the adhesive contains water, to wind the coated fabric under tension so as to assist in removing any stretch which may develop.

While the method just described is satisfactory when the adhesive that is used partially sets by cooling or by evaporation of a volatile solvent, as typified by glue or a solution of an adhesive in alcohol, in adapting my process to the manu` One method which I- have found to be satisfactory for this purpose comprises subjecting the ,coated product to a comparatively high temy perature for a time suicient to harden, or at least reduce the tackiness of the outer surface of the adhesive, but insucient to damage the backing. s

An example of this method is as followf;A

A coated fabric was prepared wherein tlievadfv.z

hesive comprised an oil modified phenolic resin Vfree of adhesive.

of a slowly hardening type thinned with toluol to a viscosity suitable for attaching 36 grit abrasive grains. The abrasive coated fabric, suitably sized with some of the same resin further thinned with solvent, was then subjected to a temperature of 350 F. for 4 minutes by placing it in an oven maintained at that temperature. Upon removal from the oven it was found that the resin had hardened enough to permit rolling and yet the fabric had not been injured, so far as could be observed.

Another method which I have employed to permit rolling up the coated fabric for the purpose of curing the resin comprises the employment of a secondary coating which either is, or can be rendered, suiiiciently non-adhesive for the purpose as by passing through the air as is done with fabrics wherein the adhesive is glue. For example I have used, in conjunction with a heathardenable and normally liquid base adhesive coating, a secondary coating of a pulverized solid material. Alternatively an" air drying varnish, a fused thermoplastic resin of sufficiently high melting point, or a solution of a resin in a volatile solvent may be employed as the secondary coating and the coated fabric may be subjected to the atmosphere for a time sufficient to render the outer surface of the coated fabric suiiciently non-adhesive, festoonng being employed if desirable.

Another method of preventing the adhesive from sticking to the back of the fabric comprises interleaving a web of material to which the adhesive will not stick between adjacent layers of the coated fabric. Such a web may be, for eX- ample, a thin sheet of metal foil.

I may also prevent sticking by spraying on the sizing coat of adhesive. By this method the adhesive is atomized and forcibly projected so that the minute droplets are driven into the spaces between the individual abrasive grains leaving the tops of said grains uncoated and substantially Since the peaks of the grains are free of adhesive the abrasive granules themselves serve as a spacing material between the successive layers of the rolled product and eliminate any tendency of sticking. Using this method I have been able to roll the coated product immediatelyv after the sizing coating is sprayed on and place the rolled material' into an oven and complete the drying or curing of the adhesive material without the adjacent convolutions of the rolled product sticking together or the grain being displaced.

After winding the coated material into suitable rolls, I secure it to prevent slippage or unrolling and then remove the rolls and place them in suitable chambers to dry or cure. Since the backing of the coated material cannot contract during this step of the process, the product has little or no tendency to stretch in use. Furthermore I have sometimes found it desirable, particularly where the adhesive is glue, to roll the Web under tension whereby the stretch is reduced or substantially removed, the extent to which this is done be- /ing controlled by the application of a predetermined amount of tension to the web as it is wound into a roll.

The drying or curing is preferably carried out at slightly elevated temperatures which will depend upon the type of adhesive employed, being in the neighborhood between to 130 F. for

glue and to 200 F, or higher for resins of a heat-hardenable character.

Where the curing treatment comprises removing moisture or a solvent the drying may be facilitated by passing air through the roll between the layers of coated material. In this case it is desirable to separate the adjacent layers of abrasive coated materials to provide for passage of the air. This type of treatment may be conveniently carried out in an apparatus as illustrated in Fig. 6 where the roll of coated material is provided at each end with a suitable seal 33 and air is exhausted from one end 3| of the roll. A seepage of air, which may be humidied to any desired degree, may be allowed to enter from the opposite end 32 thereby employing a combination of vacuum and humidity drying. I have also dried the rolled material by merely passing air through the rolls without employing a vacuum although this method is somewhat slower than the process first mentioned. 'Ihis method of drying is also applicable to adhesives such as oil varnishes where a solvent must be removed and the setting of the bond requires an oxidation process such as is essential tothe drying of a drying oil such as linseed or tung oil.

Where the adhesive is of a character which requires only the application of heat to harden or cure it, the rolled products may be cured in an ordinary oven.

After the adhesive has been dried or cured to the desired degree the roll of material is removed from the drying chamber, unrolled, and cut` up into discs or sheets of sizes suitable for the trade.

My invention has a number of advantages which have been pointed out above. In addition it also has the advantage, when applied to products bonded with glue, that it practically eliminates the diilculties with what are known as glue edges. Abrasive paper bonded with glue and dried by the conventional method of suspending in festoons is subject to an over-drying of the glue near the edges of the web with the formation of these too thoroughly dried or glue edges which have to be removed. By completing the drying of glue bonded coated products in accordance with the method of my invention, the fomation vof glue edges is materially reduced -because the product is not exposed to the atmosphere to the degree that occurs when the webs are festooned. This elimination of glue edges is facilitated by using air humidied to correspond to the moisture content left in the glue in the finished product. The apparatus illustrated in Figure 6 is especially well adapted to such a method of humidication of the air used in the drying process.

My invention is adapted to the usual modifications in the manufacture of abrasive coated products and is not to be limited to the specific modifications and embodiments herein described but rather is to be considered as being of the scope of the appended claims.

I claim:

1. A relatively stiff but flexible abrasive disc for use in connection with a yieldable supporting pad against which the disc is held by attachment at the center only, said disc comprising a stiff, resilient backing having a thin layer of abrasive grains attached to a surface thereof and being 2. A relatively stiff` but exlble abrasive disc for use in connection with a yieldable supporting pad against which the disc is held by attachment at the center only, said disc comprising a stiff, resilient backing having a thin layer of abrasive grains attached to a surface thereof by a heathardened resinous binder, and being circular when pressed to form a plane surface but normally curved so that a particular diameter Will be a substantially straight line while a diameter intersecting the first-mentioned diameter at an angle of 90 degrees is substantially an arc of a circle, whereby the disc is suiciently compressed when mounted for use to cause it to lie snugly against the supporting pad.

3. In a method of making abrasive articles, the steps which comprise coating a backing with an adhesive and with a thin layer of abrasive grains, winding the coated article into a roll while the adhesive is still plastic, and hardening the adhesive while the article is in roll form whereby the nished article which is produced when the roll is unwound has a natural curvature yin one direction and is normally plane in a direction degrees thereto.

4. The method of manufacturing an abrasive coated fabric which comprises coating a fabric with adhesive material and abrasive grains, hardening the adhesive suiciently to prevent it from sticking to the back of the fabric and to prevent material movement of the grains when the article is Wound into a roll under tension but short of the point where-the `adhesive has taken a permanent set, Winding the thus formed article under tension into a roll, and completing the hardening of the adhesive whereby the finished article which is produced when the roll is un- Wound has a natural curvature in one direction and is normally plane in a direction 90 degrees thereto.

5. The method of making a flexible abrasive disc which is circular when pressed to form a plane surface but normally curved so that a particular diameter will be a substantially straight line While a diameter intersecting the first-mentioned diameter at an angle of 90 degrees is substantially an arc of a circle, which method comprises attaching abrasive grains to a web of backing material with a liquid adhesive, solidifying the adhesive to a plastic state, winding the coated web into a roll While the adhesive is sufciently rigid to prevent material movement of the grains but before it has taken a permanent set, hardening the adhesive, unwinding the coated web, and cutting discs from the web.

FRANK J. TONE.

DISCLAIMER 2,152,392-Fmn19 J. Tof/1,6,Niagara Fa11s,N. Y. ABRASIVE ARTICLE AND METHOD 0F MANUFACTURING THE SAME. Patent datedMarch28,1939. Disclaimer led June 12, 19111, by the assignee, The arbomndum Company. Hereby disclaims the subject matter of claims 1 and 2 of said Letters Patent.

[Oficial Gazette J @dy 1, 1.941.]

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