US2129661A - Composite abrasive sheet - Google Patents

Description

Sept. 13, 1938. A. l.. BALL l COMPOSITE AERASIVE SHEET Filed Jan. l5, 1936 f INVENTOR. ALBERT L.. BALL. @mM/VWM.

ATTORNEY.

Patented Sept. 13, 1938 COMPOSITE ABRASIVE SHEET Albert L. Ball, Lewiston Heights, Lewiston, N. Y.,

assignor, by mesne assignments, to The Carhorundum Company, Niagara Falls, N. Y., a corporation ol' Delaware `Application January 13, '1936, Serial No. 58,865

4 Claims.

This invention relates to the manufacture ofabrasive coated material and particularly to a simplified method of forming such material, and to an improved composite backing for sheet abra- 5 sive articles.

The conventional method of manufacturing a composite sheet or web abrasive material usually consists of adhesively securing asheet of paper or the like to a cloth sheet in a face-to-face rela- 10 tion by means of glue, which is spread on the adjacent face surfaces to bind the cloth and the paper together. The abrasive granules are generally aiiixed to the outer surface of the paper or the cloth by an additional coating of adhesive l5 or glue. It will be appreciated that the operations necessary to manufacture abrasive material in such a manner result in an expensive finished article. That is to say, an operation is necessary to combine the paper and the cloth into a composite sheet or web, such as gluing the surfaces thereof, and an additional gluing operation is required'to coat the composite material so that 'the abrasive granules may be attached to a surface thereof. l

It is therefore an object of the present invention to eliminate one or more of the customary operations in the manufacture of abrasive coated material by uniting the paper and the cloth without the use of an adhesive and, at the same time, 30 provide an improved composite backing support for the abrasive sheet or article.I

In many abrading operations, -and particularly Where an abrasive disk is used in connection with a power driven flexible supporting pad, it is desirable and in many cases ynecessary to provide the abrasive granules with a relatively rigid backing to prevent buckling of the'abrasive sheet or disk. The abrasive disk is usually driven by means of a clamp member provided for securing the disk 40 to the supporting pad near the center thereof and it is necessary to provide a relativelystiif disk in order that' the driving force applied near the center will be properly transmitted to the periphery of the disk. Such an abratlve article is usually formed by adhesively securing the granules to afabric or cloth sheet and also gluing the abrasive coated cloth to a relatively stiifsheet. of backing material.` A backing kmaterial of this nature has been developed in the past by treating i0 paper or pulp fibers with zinc chloride to form what has been known as vulcanized ber `or` a hydrolyzed cellulose. `The hydrated material thus formed and employed as a backing fora granular foundation has the characteristic of being 5 flexible enough to follow the contour of an abrafabric to form a composite web, including apparasive supporting pad over the irregular work surface, but is at the same time relatively stiff so that when the same is used as a backing for the abrasive foundation a desirable abrasive structure is provided. An abrasive disk, for instance, 5 formed from such material will therefore be rigid enough to be operated in connection with a flexible power driven supporting pad Without buckling. `An unfortunate characteristic of the hydrated material of vulcanized fiber is that the l0 yieldable characteristic thereof is substantially lost in a relatively short space of time. The tend# ency of the hydrolyzed cellulose or vulcanized fiber to become Vbrittle probably results from the inability of known processes to remove all of the l5 zinc chloride during the washing operations. The zinc chloridev process is involved and the numerous operations necessary to properly treat, roll and wash the pulp fibers into a dense mass is expensive and uneconomical. It will be apprecl- 20 -ated that the abrasive coated article provided with such a backing renders the composite granular support stiff but that certain limitations in the commercial application thereof prevent its complete utilization as a universal abrasive article. That is to say, the hydrolyzed cellulose or vulcanized fiber must be used within a compartively short period of time to prevent its deterioration as a result of becoming brittle. y

It il. therefore a further object of my invention to provide a relatively tough abrasive coated material with a comparatively stiff backing which will not become brittle asa result of age and which maintains a yieldable characteristic for an indeflniteperlod.

In the accompanying drawing Figure 1 is a diagrammatic view of the composite web-forming apparatus, illustrating a method of uniting pulp fibers with an open woven 40 tus for stiffening and granular coating the composite web;

Figure 2 is an enlarged sectional view of the interlock between the pulp fibers and the fabric before consolidation thereof;

Figure 3 is an enlarged sectional view of the composite sheet material after the same has been compressed, -dried and impregnated; and

Figure 4 is an enlarged sectional view of the finished granularly coated material.

`Referring to the drawing, therel is represented in Figure 1 apparatus for carrying out the present invention, or a method of making the improved abrasive coated material in a simplified manner. A web II of loose or open Woven textile fabric, such as knitted cotton or cheesecloth, is fed into a paper-making machine or onto a moving Fourdrinier wire I2 from a supply roll or reel I3. In the diagrammatically illustrated papermaking apparatus the Fourdrinier wire is supported in a horizontal manner and moved by a rotated pulley- I4 and a rotatable cylinder or roll I6.' Immediately after the fabric web II passes the roll I6 a layer or pulp fibers is deposited thereon from a reservoir I1 which is adapted to' receive a supply of an aqueous suspension of pulp. A nozzle I8 or any other suitable distributing means is provided to spread a layer of pulp fibers in suspension evenly over the fabric web II. A valve or gate I9 is arranged in the nozzle I8 to regulate the flow of pulp suspension to the web and the thickness of the pulp layer may to some extent be controlled thereby. It will be appreelated that the thickness of the pulp layer may be varied in any or all of numerous ways, for example by changing the speed of the moving Fourdrinier wire I2 and by controlling the` flow of the pulp solution. As the web II is moved by the Fourdrinier wire I2, the liquid from the pulp suspension is drained through the open woven fabric and a portion of the pulp fibers is moved and intermingled with the fabric web and engages the woven strands of the textile web to provide an interlock between the fabric web and the adjacent pulp fibers. A plurality of suction boxes 2I and 22 may also beprovidedalong the underside of the Fourdrinier wire I2 to remove the liquid of the pulp suspensiondownwardly and to further carry the pulp fibers into the porous weave of the fabric web II. The fabric web carrying the layer of pulp is moved along by the are deposited on the fabric.

`spect to the Fourdrinier endless foraminous conveyer I2 so that by the time the same is immediately above the cylinder I4 substantially all pf the liquid has departed from the pulp fibers leaving a moist uncompressed layer thereof along the upper face of the fabric web with the contacting portion of the felted pulp fiber intermingled and interlocked with the woven fabric II. l

The penetration of the pulp bers into the weave of the open woven fabric will to some extent depend upon the force by which the bers It is important that sufficient penetration occur during the pulp layer formation period when the fibers are wet and in order that the fibers may be caused to properly intermingle with the strands of the lfabric the yheight ofthe aqueous suspension of pulp may be maintained constantly at a high level in the reservoir I1 to increase the pressure at the nozzle I8. The reservoir may also be raised with rewire I2 by any well known means such as by a rope and pulley arrangement 20 whereby the pulp ber will be brought into contact with the open woven fabric with greater force by reason of the increased velocity ofthe pulp solution falling a greater distance.

An enlarged section of the pulp ber in the uncompressed state as carried by the fabric web in leaving the cylinder Il, is shown in Figure 2. The longitudinally extending strands 23 of:k the web are woven or knit with the transverse strands 24 to forma loose or open woven material in the nature of cheesecloth. The pulp fibers 2S greatly enlarged are shown above the woven fabinterlock the pulp layer and the fabric web intoxl a composite sheet.

fibers and carriedto After the fabric web II leaves the Fourdrinier wire or endless conveyer I2 the pulp layer carried thereby is compressed with the fabric and dried by the heated rolls or cylinders 21 and 28, which tend to further interlock the pulp fibers and the fabric.

The compressed composite web is then fed into a series of rolls indicated in general as 3D for the purpose of applying a filler or stiffener to the pulp layer. The pulp layer as hereinafter described becomes the backing for the abrasive granules attached to the fabric side of the ,composite web and it is necessary to provide the backing or the pulp with a relatively stiff characteristic. That is to say, the pulp must be formed into a relatively rigid state but which is, at the same time, yieldable enough to permit the abrasive web or sheet to be used in abrading operations over irregular surfaces. One method that may be employed in stiffening the pulp is byapplying a suitable compound to the pulp bers and this may be accomplished by spreading a liquid compound over the surface of the pulp by means of a roller 32 which carries a fiuid layer of such a compound from' the surface of a roll 33. The roll or cylinder 33 is coated with a supply of compound from the reservoir 34. A valve 36 is provided in the supply? line to control the amount of compound that maybe applied to the roll and hence to the pulp. Any number of stiifening compounds may be used to stiffen the pulp, such as glue, sodium silicate, resin or latex, and applied thereto after the pulp has been felted lon the fabric web. One compound that will provide the pulp with the characteristic of stiffness is an polyvinyl acetate acetal type which may be rendered solvent by acetone andapplied to the pulp by means of the rolls 32 and 33. A resin of this type is thermoplastic and the impregnated pulp may then be further compressed by a series of pressure rolls indicated generally at 31 to form a relatively stiff backing for the fabric web II. The amount of resin supplied to the pulp fibers may be controlled by the valve 36 and also by the speed of a traveling web II. It will be appreciated that the unit volume of the resin as compared to the unit volume ofthe pulp fibers and the pressure to which the impregnated pulp is subjected will govern the density of a backing and, accordingly, the rigidity thereof. It may be desirable in forming abrasive material for use in some abrading operations to supply only a surface coating to the pulp and thus combine the pulp fibers along the upper surface of the com- Alvar resin of the the flow of liquid resin to the impregnating rolls 36, or by increasing the speed of the moving composite web through the rolls 3| and 32.

The stiffening compound may .be applied to the pulp fibers by adding the same to the pulp solution contained in the reservoir I1. A resin may be applied to the pulp fibers in this manner by adding a dispersion of phenolic resin to the aqueous pulp solution contained in the reservoir I1. In this case the resin is mixedwith the pulp the pulp layer during the paper-making operation. This type of resin or binder is heat-hardenable and the pulp layer may be cured by any well known method of (l applying heat to the composite web. One method of stiffening the pulp fibers treated with phenolic resin may be accomplished by compressing the the glue coating applied thereto.

, sembled in a simplified manner.

is coated with an adhesive such as glue by meansv of a plurality of rolls 4I and 42, which are so arranged that the roll 4l carries a coating of glue from the receptacle 43 to the outer surface of the fabric. Abrasive granules are then deposited on the adhesively coated fabric in any well known manner, such as' spreading the grain over the surface from a hopper 38 and a roll 39. The abrasive coated composite web may then be moved to suitable racks to properly cure the granul securing glue.

An abrasive web, such as is shown in Figure 4, is therefore provided by the present method of preparing the composite web and coating the same. with the abrasive grain. The enlarged grains 46, shown in Figure 4, are secured to the fabric face of the composite web by means of a glue coating 41 which is applied thereto by means of the roller 4I. A tough foundation is thus provided for the abrasive grain by the textile fabric web Il, which is relatively tough in the initial state and becomes more kso by the addition of A relatively stiff backing is also provided for the fabric foundation by the pulp layer 48 which has been treated by a compound to bind the pulp bers into a comparatively dense mass. The method of manufacturing the present abrasive coated material contemplates treatment of the elements of the composite web from the raw state `with the vdefinite objective of forming a relatively stiff"l abrasive article, and it is to be appreciated that the elements of an abrasive article' formed in accordance -with' the present invention are as- That is to say, the paper and the cloth elements lare combined without the use `of an adhesive and a separate mechanical process but are interlocked to each other by forming the paper on the c th. The pulp or paperbacking has been sti ened in a simple inexpensive manner to produce an efficient abrasive sheet which will not become brltl tle over an indefinite period of time.

I claim: A

1. A composite abrasive article comprising a web of relatively loose Woven textile fabric having a coating of pulp from suspension deposited on and intermingled with one'surfacevthereof, l

a fillerv for said pulp adapted to stiffen said coating, a layer of abrasive' granules arranged along the opposite surface of said: fabric and affixed thereto by means of an adhesive carried by said 2. A composite abrasive article comprising a web of relatively loose woven textile fabric having a coating of pulp from suspension depositedv thereon, and a portion thereof intermingled with one face of'. said fabric, a resinous compound for said pulp adapted to stien said coating, a layer of abrasive grains arranged along the oppo# sitel face of said fabric and attached thereto by v an adhesive material. f

3. A composite abrasive `article comprising a Vweb of relatively loose Woven textile fabric having a layer lof relatively stiff pulp arranged along one face-of said fabric and interlocked therewith by having a portion of pulp fibers intermingled with and engaging the texture of said fabric, abrasivev granules arranged along the opposite face of said fabric and glued thereto to provide a tough foun dation for said granules.

4. A composite abrasive article comprising a. web of relatively loose woven textile fabric having a sheet layer of' relatively stiff pulp arrangedv along and laterally intermingled with one'face' of said fabric to bind the fabric and the pulp together, abrasive granules `arranged along the opposite face of said Afabric and adhesively se-Y cured thereto providing a tough foundation for said granules and a relatively stiff backing for said foundation.

ALBERT L. BALL.

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