US2255294A - Coating apparatus - Google Patents

Description

p 1941- R. L. MELTON EI'AL 2,25 ,294

COATING APPARATUS Filed July 23, 1934 INVENTORS ROMIE L. MELTON RAYMOND a BENNER; BY HENRY P. KlRC-HNER ATTORNEY.

consists of a mixture of elongated and blocky Patented Sept. 9. 1941 imrrlao STATES.

PATENT OFFICE COATING APPARATUS Delaware Application July 23, 1934, Serial No. 736,540

1 Claim.

This invention relates to the manufacture of abrasive coated webs of such material as paper, cloth and the like. The invention relates more particularly to apparatus for the manufacture of abrasive coated webs of the so-called oriented 5 type in which the elongated abrasive particles are oriented at an angle, preferably approximately at right angles, to the surface of the web.

This application is a continuation in part of our co-pending application, Serial No. 647,241, filed December 14, 1932, and issued December 27, 1938, as U. S. Patent No. 2,141,658.

Abrasive particles commonly used in the manufacture of abrasive coated webs are of irregu lar shape and have some surfaces or edges that are sharper than others and more suitable for abrading operations when these sharper surfaces, edges or points, are positioned to engage the material being abraded.

The type of abrasive material that is particularly adaptable for use in this invention may be described as elongated, by which is meant either a splintery, needle-like type, one of whose dimensions is substantially greater than the others, or a platey type having two dimensions greater than another. Another general type of grain, which can be described as blocky, has no dimension appreciably greater than other dimensions, but is rather, as the name-implies, more regular in shape and has no axis susceptible to orientation. Such grain, of course, can not be oriented advantageously,

Abrasive granular material as received usually grains, the proportions of which will vary depending upon the composition of the grain and also on the kind of apparatus usedv in reducing the crude material to smaller sizes. While our apparatus will orient the elongated particles that occur in the usual granular material, and will position the blocky type in somewhat the same way. we usually find'it desirable to separate the two types, selecting grains containing at least a major proportion of the elongated type. Such a separation may be carried out by any suitable means, as'for example, a"winnowing process by means of an air separator.

In the usual process by which abrasive coated materials have been made for many years, the abrasive particles were dropped onto a web of paper or cloth, as the case-might be, upon which there was a surface coating of a suitable adhesive. The operation of coating the web with granular abrasive material was carried out with hesive coated surface of the web. Due to the action of gravity the elongated particles of abrasive grain for the most part were turned over and laid substantially flat against the surface, and were, therefore, in a position which afiorded a minimum cutting or abrading action when the abrasive paper or cloth was used.

We have found that a superior product can be made by depositing the grains upon the adhesive coated web in a manner difierent from that used heretofore, In practicing our invention, we support the adhesive coated web in an inverted position or, in other words, with the adhesive coated side downward and then project the grains upward to this adhesive coated surface. We have found that by coating the web in this manner, the granules can be made to strike the adhesive coated web endwise instead of fiatwise and that the inverted position of the adhesive coated web, because of the effect of gravity upon the particles, will maintain the endwise attachment of the particles and also will tend to cause all particles to assume the same general relationship with respect to the-surface of the web. In this manner.

it is possible to so position the grains on the adhesive coated web that the major axes of a substantial proportion of the granules are normal that the particles are directed at an oblique angle toward the web, a substantial proportion of the grains become oriented at an oblique angle with respect to the web. Whether the particles are normal with respect to the web or at an oblique angle with respect to the web or some are normal and others oblique, the result is an abrasive coated web that is sharper than that previously made in the usual manner by gravity depositionof the grains upon an upwardly facing v adhesive coated surface.

The character of the abrasive coated surface obtained by our apparatus can be best described in a brief way by calling it a serrated surface and this term shall be understood to mean, wherever it is used in this specification, a surface in which the granular particles are so positioned that a substantial proportion of them project from the surface of the web in an upstanding position instead of lying flat upon the web. As a matter of convenience in expressing the different degrees of sharpness of the abrasive coating, we make use of the term index of serration, and wish to have it understood that wherever that term is used in this specification it means the percentage relationship of the number of projecting grains to the total number of grains, as determined by microscopic count.

We have found that the index of serration of abrasive coated webs made by our method is greater than 50 per cent and frequently is between 60 per cent and 90 per cent, whereas the index of serration of the abrasive coated webs' made in the usual way is less than 40 per cent.

A better understanding of the nature of a serrated surface and its contrast with the abrasive coated surfaces made in the usual way, as well as methods and apparatus for the production of such serrated surfaces, can be secured by reference to the accompanying drawing in which:

Figure 1 illustrates a side elevation of the abrasive coated webs made in the usual way by applying the abrasive grain by gravity;

Figure 2 shows a serrated surface in which in Figure 2. The grains, as shown in Figure. 1,

lie flat on the web and are almost completely embedded in the adhesive and thus cannot cut as rapidly or as efliciently as those positioned with their major axes extending from the web in an upstanding position and which are not embedded in the adhesive, as illustrated by the angularly positioned grains in Figure 2.

The diagrammatic or schematic drawing, Figure 3, illustrates one form of apparatus embodying our invention. The web material I which may be, for example, paper or cloth, is supplied from a roll II and is carried over idler rolls l2, l3 and H to a glue roll l6 which dips into a glue pan l1 for the purpose of applying the base glue coating indicated at 2 in Fig. l. The glue roll I6 is provided with the usual pressure roll IS. The adhesive coated web I is then passed over idler rolls l9 and 20, which contact with its uncoated face, to apparatus generally indi-' cated by reference character A for applying the oriented abrasive coating. The coated web I is carried in a horizontal position with its adhesive coated surface facing downwardly over a device which projects the abrasive grain upward arrows. Abrasive grain is fed in regulated amount to the belt from the grain hopper 24 which is provided with an adjustable feed gate The grain is 25 and cooperating feed roll 26. carried along by the belt over the beaters 22 which consist of rotary shafts having extending flns21 which. contact with the bottom of the belt. The beaters are rotatable at speeds as desired and so positioned with respect to the upper surface of the belt that they deliver quick, sharp blows to the under side of the belt, when they are rotated. The striking of these beaters against the under side of the belt causes the granules carried by the belt to be projected upwardly, and because of their high initial velocity and upward projection through space, a substantial proportion of the grains become oriented with their major axes parallel to their lines of flight. Therelative positions of the adhesive coated web and the grain carrying belt 2| are such that the upwardly projected granules strike the adhesive surface endwise and adhere to that surface in the same positions as they strike. Thus, if the web is held in a horizontal position and the granules are projected vertically upward, a substantial proportion of granules become positioned on the adhesive coated web in such manner that their major axes are normal to the surface of the web. If, on the other hand, theweb is not positioned horizontally, or if the grains are not projected vertically upward, the result is oblique positioning of the grains with respect to the web. The coated side of the web being downward, gravity tends to bring all of the particles into the same relationship with respect to the web.

in such a manner that the grain is oriented and strikes the adhesive coated surface in an upstanding position. The device illustrated is of the belt and heater type and consists of a feed belt 2! and a number of co-acting beaters 22 mounted on the vertically adjustable supporting member 40. The feed belt 2| is driven by any suitable means and travels continuously over driving'rolls 23 in the direction indicated by the A supplemental supporting roller 28 is provided for limiting the vibrating portion of the belt to that underneath the web. Any excess grain which does not adhere to the adhesive coated surface of the web is discharged into a box 29 for reuse.

The break 30 is indicated in the web to show a number of feet of travel, say twenty to thirty feet, of. the web in a horizontal direction after the abrasive particles are applied to its under side. Additional provision for causing the base coat of adhesive to acquire at least a preliminary set after the granules-have been deposited on the web is made by incorporating a blower 3| capable of delivering a large volume of air at a low velocityto the adhesive and granular coated web. This blower is located between the projecting means and the idler roll 32 in order that the direction taken by the coated web does not change until the adhesive has acquired sufficient firmness to prevent the granules from being positioned in any other manner 'than that desired.

From the vertically adjustable supporting roll 32, the coated web is fed by the suction drum 3! and roll 34 to a suitable drying chamber. This drying chamber comprises a rack 31 for supporting the web I, and an endless conveyor 25 for transporting loops of the web to the rack 31. While the abrasive coated web is on the drying rack the base coat of adhesive is preferably thoroughly set so as to give as much support as possible for the upstanding abrasive grain during the subsequent steps of manufacture.

We have found that the abrasive grains are generally projected from the conveyor in a more or less haphazard manner. The elongated grains however, which are so oriented that their longer axes are parallel to the direction of flight or become so oriented immediately upon being pro- J'ected, meet with less air resistance and consequently are projected a greater distance with a given impetus than the unoriented grains. This causes a winnowing efiect or separation of the oriented particles from the unoriented and means are provided in our apparatus whereby the spacing between the grain projecting means and the adhesively coated web may be varied sufliciently to produce an abrasive coated web of maximum sharpness. This spacing is such that fora particular grain size and velocity of projection only the oriented grains will travel across the intervening space and be deposited onto the adhesively coated surface of the web. The unoriented grains encountering greater air resistance travel-only part way to the web and fall back onto the conveyor to be again projected.

Further control of the orientation produced is provided by means whereby the force of the impact blow against the underside of the grain feed or conveyor may be varied.

In the manufacture of abrasive coated materials, it is necessary to maintain a substantially constant relationship between the thickness of.

the adhesive coating that is applied to the backing andgthe size of the abrasive granules- In order to accomplish this purpose, it is customary to use adhesives of difierent viscosity for different grit sizes.

We have found that the abrasive particles penetrate the surface of the adhesive layer less readily when the viscosity of said adhesive is increased and, in order to produce an abrasive coating of predetermined or standard weight, we have found it necessary to increase the velocity ol the projected granules proportionately to the decrease in viscosity of the adhesive.

In order to control and regulate the weight of the applied abrasive coatings, regardless of the viscosity of the adhesive or the size of the granules, we have provided in our apparatus means for varying the initial velocity of the projected particles. Referring again to Figure 3, the .velocity at which the abrasive granules are projected from the conveyor belt 2| I may be controlled and adjusted to any desired degree by changes in the amplitude of the oscillations of the conveyor belt. Such adjustment may be efl'ected bymeans of the adjustable member 40, supporting the rotatable beaters, whereby the fins or projecting portion 21 of the heaters 22 can be made to strike the conveyor belt toa greater or less degree during each half revolution.

It will be seen from the foregoing disclosure our apparatus produces a superior granular coated web. By projecting the grains upwardly to a web with its adhesive coated face positioned downward to catch the upwardly projected grains, a surface results that is sharper. The grains are so positioned on the web that they are better adapted to penetrate the material being abraded and to do this with an expenditure of less work than has been required with the usual abrasive paper or cloth. I

We have found from actual tests that a ser-'- rated surface produced in accordance with our invention sometimes lasts twice as long, and usu- V ally from 50 per cent to 100 per cent longer in actual operation, than the ordinary coatedwebs, and that the abrading or cutting rate is from two to three times as fast as that obtained with the usual abrasive coated webs.

While we have described our invention with specific illustrations, it is not intended that these illustrations shall define the scope of our invention. Various modifications may be made by those skilled in the art without departing from the spirit or scope of our invention as defined in the appended claim.

We claim: Apparatus for the manufacture of abrasive coated webs comprising means for supporting an adhesive coated web with. an adhesive surface downward, a feed belt for conveying, abrasive particles into a position beneath said web, means for striking said feed belt with sufli'cient force to drive the abrasive particles upwardly and into engagement with the adhesive coated surface of said web and means for varying the amplitude of vibration of said belt.

7 ROMJE L. MELTON.

RAYMOND C. BENNER. HENRY P. KIRCHNER.

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