US2194253A

US2194253A - Coating apparatus

Info

Publication number: US2194253A
Application number: US639837A
Authority: US
Inventors: Raymond C Benner; Romie L Melton; Henry P Kirchner
Original assignee: Carborundum Co
Current assignee: Unifrax 1 LLC
Priority date: 1932-10-27
Filing date: 1932-10-27
Publication date: 1940-03-19
Anticipated expiration: 1957-03-19

Description

Mam]! 4 R. c. BENNER ET AL 4,253

- COATING APPARATUS I I Filed 001:. 27, 1932 2 Sheets-Sheet 1 INVENTORS RAYMOND c. BENNER Rome L.MELTON y HENRY P. KlRGHNER A TTORNEY March 19, 1940." R. BENNER H M 2,194,253

COATING APPARATUS Filed Oct. 27, 1932 -2 Sheets-Sheet 2 INVENTORS RAYMOND 0. Banana Rome L. MELTON y HENRY P. K\RGHNER A TTORNE-Y Patented Mar. 19, 1940 UNITED STATE cosmic mans-ms Raymond G. Bonner, llomie L. Melton, and Henry P. Kirchner, Niagara Falls, N. Y., asaignorl, by memo assignments, to The Oarborundnm Com pany, Niagara Falls, N. Y a corporation of Delaware Application October 27,

' io Clam This invention relates to improved apparatus for the manufacture of granular coated webs of such materials as paper, cloth, or the like and has for an object the provision of improved machin- 5 cry for securing a superior product, greater eiiiciency, and/or lower cost of production,

articles. x More specifically, this invention relates to apparatus by the use of which granular materials can be projected upwardly and-at an oblique angle to an adhesive coated side of a web. 7

It has been found heretofore that superior granular coated webs forsuch'uses as abrading can be made by arranging those particles that have a generally elongated shape in such'a way that these longer particles project from the web with their longer dimensions normal to the surface-of the web. Maximum benefit from parti-. cles arranged in this manner results only when at least a substantial proportion of the particles in a inasspf abrasive grains are of the elongated type, since these particles that are more or less of the same dimension in all directions can, not

of. coated be oriented with a longer dimension in any' par- '25 tlcular direction. v

r We have found that a faster cutting abrasive coated web can be made by projecting the particles upwardly and at an oblique angle with respect to the surface of the coated web because these angularly projected particles embed themselves in the adhesive coating of the web at'an oblique angle with respect to the surface of the web regardless of whether they are of an elongated shape or not. Those particles that are of elongated shape impinge upon the adhesive coating in an endwise manner and therefore become oriented with their longer dimension projecting at an oblique angle from the surface of the web.

Those particles that are. of general irregular 40 shape, of which there usually is a substantial procoating at an oblique angle insteadof at a right I angle as is the case when apparatus heretofore known has ben used. The general result of this upward and at the same time angular, projection of the patricles to the adhesive coated web is a faster cutting abrasive article because substantially all of the particles are arranged on the web like the teeth of a saw and moreover, this result is accomplished without the necessity of preselecting grains of generally elongated shape.

An abrasive cloth or paper of this character if used, for example, as a sanding belt can bedriven 5 in the direction of inclinationof the particles so to the adhesive side of the web P; means D for 19:2, Serial No. siassr as to secure a very rapid cutting or abrading action. It driven in the opposite direction, the action is more of a polishing or finishing action; Thus, a single belt can be employed for both rapid abrading and finishing.

Whi le the degree of inclination can be varied as desired, we have found that inclination of the grains at about 15 to to the plane of the backing gives the best results for rapid cutting.

A- better understanding of our inven ion can be obtained by reference-to the accompanying drawings in which:

Figure 1 is a diagrammatic elevation of apparatus embodying our invention;

Figure .2 isa diagrammatic elevation showing a modification of the grain depositing means;

Figure-3 is-an enlargedview of the electrode assembly shown in Figure ,1;

Figure 4 is a view partly insection of a modificfation -oi' -the lower electrodes; and

Figured shows a sectional view through the plane V-V ofFlg'ur'e 4. r

The apparatus shown in Figure 1 illustrates our invention in connection with apparatus for the manufacture of, abrasive 'coated,webs, and includes a means A for holding and dispensing a roll 2 of the web P of paper, cloth or the like, I means B for applying adhesive to one face of the web P; means C for applying granular material 30 causing a preliminary set of the adhesive, and

. means E for drawing the web through the coating apparatus and into the drying chamber.

The means A ior holding and dispensing the web P comprises, as shown in the drawings, a 35 'framei that supports the roll 2 of web v1?; an id- 'ler roll {forguiding the web; printing rolls 4 and 5 for marking the web with any desired legend or identification; and an idler roll 1 for guiding the web. I

' The adhesive applying means B comprises, as shown inthe drawings,idlerrolls 8 and 9 for guiding the web; a roll H positioned to dip into a pan I! of adhesivena roll, I! for maintaining contact between the web P and the roll II; a drum l5 and an adhesive distributing brush it positioned above the said drum is; and an idler roll H! for guiding the web as it is brought from the distribupper portion of the feed belt being positioned between

electrodes

23 and 24 and nearer to the electrodes 24. The feed belt, with its supporting

rollers

42, 42a, 43 and 43a, and the

electrodes

23 and 24 are all positioned on a carriage 50 which is rotatable about the point 40 for cooperation with the

adjustable electrodes

23 and 24 in producing different angles of projection with respect to the web. If desired, the feed belt 4| can have a somewhat corrugated surface for preventing relative movement of the granular material with respect to the belt.

A better understanding of the construction of a suitable electrode can be had by reference to Figure 3, which shows in detail one modification of electrode structure suitable for use in our apparatus. The electrodes 23, as shown in Figure 3, are formed of pieces of wood 60 and BI between which is placed a metal conducting plate 62. We have found it advantageous to use a distributing plate 62 in order to cause the charging current to divide and spread substantially evenly over the wooden electrode and also to reduce the unit density of leakage current upwardly through the wood to its top surface. We prefer to enclose the metal plate rather than have it attached to the bottom of the electrode in order that leakage in other directions than that toward the upper surface of the electrode may be reduced, A good insulating material, such as glass, can be used instead of wood for the lower piece 60 of the electrode 23.

As shown in Figure 3, the electrodes are supported on frame members 63 which are hung from a support 33 by means of hanger bars 66 of highly insulating material such as hard rubber. The upper electrodes 24, which can be of any good conducting material, are attached to the bar '27. The bar is hung from the support 28 by means of the

screws

29 and 33 which are threaded into adjusting

nuts

33 and 32, respectively.

The support 28 is slidably mounted on the frame member 33 and is adjustable along a plane parallel to the lower electrode 23. Such adjustment is provided by means of a handwheel 66 and screw threaded shaft 61, journaled on the frame 33 and engaging a threaded projecting portion 68 of the support 23. The lower electrodes 23 are interconnected by means of the conductors 26 while the upper electrodes 2 are interconnected by means of the bus bar 27.

Figures 4 and illustrate a modified form of electrode suitable for use as a lower electrode in our apparatus. As illustrated in the drawings, it comprises a cylinder ii of poorly conducting material, end pieces 72 of highly insulating material and a conductor 73 running through the end pieces and through the cylinder.

On the carriage 50 also are mounted

rolls

24, 22 and 49, which rolls are adjustable as a unit. for positioning the web between the feed belt 4i and the upper electrodes 2%, and a source 48 I of air of low velocity and relatively large volume A source of eleotromotive force, not shown specifically in the drawings, but indicated by the positive and the negative symbols, also is included in the means C for applying granular material to the web P. The source of electromotive force, which is capable of producing an effective potential difference of about 30,000 volts and more, can be one that produces a continuous unidirectional current, or a pulsating current such as intermittent unidirectional current, or a current such as is commonly called alternating current. The duration of each pulsation, when pulsating current is produced by the source of electromotive force, should be such that the particles will become charged and projected from the feed belt. We have found that apparatus built in accordance with our invention operates more effectively when the lower electrodes are connected to the negative terminal of the source of the electromotive force and the upper electrode is connected to the positive terminal. This positive terminal is also grounded as a precautionary measure. The polarity of the

electrodes

23 and 24 can be reversed, however, if it is so desired.

The means C for applying'granular material to the web P comprises also a variable speed driving means 44 and 45 for moving the feed belt 46 around'the

pulleys

42, 42a, 43 and 53a, and a hopper 47 for catching the excess grain discharged by the feed belt 4|.

The means D for causing the adhesive to acquire a preliminary set comprises, as shown in the drawings, an idler roll 49 and a fan blower 48 for supplying a large volume of air at a low velocity to the adhesive and granular coated side of the web P.

The means E for drawing the Web P from the coating apparatus into the drying chamber comprises, as shown in the drawings, one or more suction drums 5i and 52; an idler roll 53; a rack 55 for supporting the web P, and an endless conveyor 54 for transporting loops of the web P to the rack The projecting means shown in Figures 1, 2 and 3 of the drawings comprises a plurality of electrodes interconnected to form an upper electrode surface and another plurality of electrodes interconected to form a lower electrode surface. We have found it desirable in apparatus for the purpose disclosed in this application to make both the upper and lower electrode surfaces of a number of smaller units rather than as a large unit in each case, because it is desired to set up an electrostatic field that passes through the feed belt and the Web P at an oblique angle. Two large area electrodes when placed close together will set up a field between them that is normal to their surfaces, even though one of the electrodes is not positioned squarely above the other, and since there is not sufiicient space between the upper and lower electrodes to permit of an appre- 'ciable angular relationship between the web and the field, it is impossible to produce orientation at any angle appreciably different than 90. By making the upper and lower electrodes of separate small units and positioning these small units in each group at a distance greater than the distance between the interacting units of the upper and lower electrodes, an electrostatic field can be set up that will intersect the web P at an oblique angle. The upper and lower electrode surfaces are each made of separate units for the additional reason that it becomes possible thereby to increase or decrease the breadth of the field by adding or taking away units as the case may be.

We have found that the upper electrode units aromas can be made of any good conducting material such as metal, but that the lower electrode units serve in a particular manner and preferably aremade of a material that will hold back the flow of current that ordinarily would take place when a large potential difference is applied to the ordinary electrodes and yet will permit some current to flow to the upper surface of the lower elec' trodes.

The material of which these lower electrodes is made is of considerable importance in the successful operation of machines built in accordance with our invention. It appears that a poor conductor of electricity is required for these electrodes because some leakage is required in order to provide sufiicient current to charge the particles that are brought into the electrostatic field by the feed belt 4|. substantially prevent passage of the current at the potentials we prefer to use are not satisfactory because they prevent the projection of the particles from the feed belt to theadhesivqcoated web. Metal or other good conducting materials permit substantially free and unrestricted passage of the current when the applied electromotive force is sufficient to produce ionization of the air between the electrodes, and cause spark-over or arcing. Such arcing or sparkover is detrimental to the manufacture of satisfactory abrasive coated webs since each sparkover or are not only causes a bare streak ,to occur been given as illustrations of good conductors.

.lar particles to the degree necessary for their projection by the electromotive force applied to the electrodes. 1

Other woods than pine and other materials than wood can be used for the lower electrodes. Laminated materials in which one or more of the laminae are of the type of the material referred to above as good insulators are 'not satisfactory, but composite materials, such as cotton fabrics bonded with resinous materials, such as Bakelite or Redmanol, are suitable for the lower electrodes of our apparatus. It is preferred. however, that when materials of this general character are used, the fibers be so positioned that they lie in such a direction that when the material is formed into an electrode, they will carry the current lengthwise toward the active surface of the electrode.

Our copending application, Serial No. 647,244, filed December 14, 1932, discloses and claims electrodes of poorly conducting material and their use in other types of apparatus than that em- Materials that insulate and 24 and thelower electrodes 23.

The metals have the frame I and the web is threaded over the roll I and between the printing rolls 4 and 5 and thence in contact with the idler rolls l,- 8 and 9 to the pressure roll l3 and the adhesive roll II. The adhesive roll dips into liquid adhesive contained in the adhesive tank i2 and, on the upward movement of travel of the roll I I, a layer of adhesive isapplied to the web. I

The adhesive coated web P passes between the brush drum i5 and a vibrating brush it which evenly distributes the adhesive and smoothsout any ridges. The web is then guided by the idler rolls l8, l9 and adjustable roll 21 into an elecbetween the electrodes 23 sition of which is such that it is parallel to the web P in the space between the upper electrodes The variable speed driving mechanism 44 moves the feed belt 4| through the space between the electrodes in the same direction that the web P is moved.

In the modification shown in Figure 1, different degrees of angularity of the particles with respect to the web are produced by rotating the carriage 50 about its axis to such a position that the web makes the same angle with the vertical as the angle at which it is desired to have the particles take with respect to the web. The upper group of electrodes is then shifted parallel to the web until they are so positioned that a substantially vertical field will be established between the upper and lower electrodes when the electromotive force'is applied. Different degrees of angularity are secured wit the modification shown in Figure 2 by the simple expedient of shifting the upper group of electrodes horizontally to the right or left, as the case may be, and adjusting the guide roll 49 up or down, as required to position the web at the same angle with the vertical as it is desired to have the particles take with respect to the web.

The granular material, as it moves intoand through the field, becomes electrically charged and leaves the beltto move upwardly toward the adhesive coated web as aspray or rain of particles spacedv apart from one another. The upwardly moving particles strike the adhesive coated web and become attached thereto.

The forces produced by the electric field turn those particles that are of elongated shape so that their major axes are parallel to the lines of force of the field. These oriented, elongated par- 1 Observation of the space between the upper and lower electrodes, when the machine is in operation, shows a distinct bluish color and freedom from localized arcing or spark-over. The bluish coloration indicates that a corona field exists between the upper and lower electrodes. The grain particles on the belt may receive their negative electrostatic charges by conduction through the fibers of the belt, byinduction, or by the corona discharge from the bottom .electrode through the belt, and possibly by a combination of these. Whatever is the mechanism of the transmission of electrostatic charges to the grains, the fact remains that the granular particles receive suflicient electrostaticv charge to cause them to be forcibly driven upwardly through the'strong electrostatic field from the feed belt against the under side of the adhesive coated web. As pointed out above, the elongated particles not only are projected upwardly but are oriented and projected.

In operating our apparatus, we prefer to space the

electrodes

23 and 24 about one inch apart and to apply a potential difierence of between 30.000 and 100 ""3 volts. The potential difi'erence applied to the electrodes is adjusted to such value that the abrasive particles on the feed belt 4| become charged and are propelled toward the upper plate 24 and strike the adhesive coating on the web P with suflicient force to partially embed themselves and adhere thereto. We have found, other factors remaining constant, that the electromotive force required to electrostatically propel the charged granules into engagement with the adhesively coated web varies in proportion to the size or mass of the granules; that is, a higher electromotive force is required for large grainthan for a smaller size. For grits of from 50 to 200 mesh and finer, we have found that potential differences of from 30,000 to 50,000 volts are suitable. Coarser grits require higher voltagcs and in the case of grits as large as 16 mesh, an electromotive force of about 90,000 volts may be required to orient and propel the granular material from the feed belt to the adhesive coated web. Thus, by means of the variable voltage apparatus, the potential difierence applied to the electrodes can be adjusted to such a value that grain of a certain specific size will be electrically deposited on the adhesive coating, whereas any grain of a larger size, which might be present on the feed belt, will remain and be carried into the bin 41.

We have found that inasmuch as the grain is raised from the feed belt by electrostatic forces and that the quantity of grain that is raised is controllable by adjustment of the potential difference supplied to the electrodes, an excess of grain on the feed belt is desirable for the production of a uniform coating on the web. If it is found that the density of the coating being applied to the web is lighter than desired, an increase in the potential difference applied to the electrodes will cause more grain to rise and become embedded in the adhesive coating of the web. Conversely, if a heavier coating than is desired is being deposited on the adhesive coated web, a decrease in the potential difference applied will operate to make the coating less dense. After being coated with granular material, the web is then moved through a zone in which the adhesive is given a preliminary set in order to fix the particles in the positions they took when they were deposited upon the adhesive coated web. The position of the granular coated web while it is moving through'this zone is such that the justment to meet different conditions.

grains hang substantially vertically like tiny pendulums. Those grains that have been oriented in the desired positions remain so oriented because of gravitational attraction, and those grains that impinged upon the adhesive coating at any other angle than the desired angle'are pulled into the desired positions by the action of gravity. Thus, gravity is utilized not only to preserve a particular orientation but to produce the desired orientation.

Apparatus constructed in accordance with our invention has the advantage that it is simple to construct, easy to operate, and flexible as to ad- There are no complicated mechanical movements nor delicate parts to get out of order. when once adjusted to produce the desired type of coating it operates with no more attention than is required in the ordinary type of coating machine and when adjustments are necessary, they can be made very simply by changing the applied potential difference or by changes in the relative positions of the various parts of the apparatus.

Raising or lowering of the frame 50, which carries with it the grain depositing apparatus, and a slight shift in the relative positions of the upper and lower electrodes, is all that is necessary to produce webs in which the grains are positioned at different angles. When the frame 50 is more nearly horizontal than vertical, the

electrodes

23 and 24 being positioned to produce a substantially vertical field, the particles are deposited upon the adhesive coated web at an angle very much smaller than the angle at which they are deposited when the frame is in a position less nearly horizontal. The ease with which this change from a small angle to a relatively large angle, or vice versa, can be made is of great advantage.

The control of the density of the coating on the web by the change in field intensity or by the use of a different number of lower electrodes, either large or small, also is of considerable advantage because it permits close adherence to standards of quality as to weight of grain per unit of surface and also because it makes it possible to eliminate coarse grits that might get into the grain mixture.

Another simple adjustment that can be made with apparatus made in accordance with our invention is the alteration of the density of the granular coating by moving the web closer to the feed belt. The grains are projected upwardly as a rain or spray, not as a body, and not all of the particles raised by the electrostatic forces are projected the same distance. By moving the web closer to the feed belt, those particles which would otherwise fallback to the feed belt are caught by the adhesive coating and held.

Apparatus constructed in accordance with our invention has the advantage that gravitational attraction serves to assist in the orientation of the particles on the web and to preserve the desired orientation once it has been secured. The position of the web while the adhesive is yieldable is such that the particles tend to turn into vertical positions if they are not already arranged in that direction, and since the web is at the preferred angle with respect to the vertical the particles therefore assume the preferred angularity. This advantageous use of gravitational force has not been found in any of the machines heretofore known for applying granular materials to webs.

Other advantages will be apparent from the foregoing disclosure to those skilled in the art and while specific embodiments have been used to illustrate our invention, it is to be understood that the invention is not limited to those embodiments but is defined by the appended claims.

We claim:

1. Apparatus for the manufacture of granular coated webs comprising means for supporting an adhesive coated 'web with an adhesive side downward, a plurality of interconnected electrodes spaced apart from each other and positioned, above said web, a plurality of interconnected, electrodes spaced apart from each other and positioned below said web, the interacting electrodes on either side of the webbeing QJMBS so positioned that a line drawn through the longitudinal axes of any pair of interacting electrodes will intersect the plane of the web at an oblique angle, and means located above said lower electrodes and below said webifor supporting granular material.

2. Apparatus for the manufacture of granular coated webs comprising means for movably sup- 7 porting an adhesive coated web with an adhesive 10 side downward, a plurality of interconnected electrodes spaced apart from each other and posi- .tioned above said web, a plurality of interconnected electrodes spaced apart from each other and positioned below said web, the interacting electrodes on either side ofthe web being so positioned that a line drawn through the longitudinal axes of any pair of interacting electrodes will intersect the planaof the web at an oblique angle,

and movable means located above said lower so electrodes and below said web for supporting granular material. I I

3. Apparatus for the manufacture of granular coated webs comprising means for supporting an adhesive coated web with the adhesive-side down- 26' ward, a plurality of interconnected electrodes spaced apart from each other and positioned above said web, a plurality'of interconnected electrodes spaced apart from each other and positioned below said web, the interacting elecgo trodes on either side of the web being so positioned that a line drawn through the longitudinal axes of any pair of interacting electrodes will intersect the plane of the web at an oblique angle, means located above said lower electrodes and 35 below saidweb for supporting granular material, and means for applying a potential difierence to the upper and lower electrodes, said apparatus being adapted to electrostatically project granular material against the downwardly facing adhesive surface of said web.

4. Apparatus for the manufacture of granular coated webs comprising means for movably supporting an adhesive coated web with the adhesive side downward, a plurality of interconnected elecll trodes spaced apart from each other and positioned above said web, a plurality of interconnected electrodes spaced apart from each other and positioned below said web, "the interacting electrodes on either side of the web being so 66 positioned that a line drawn through the longitudinal axes of any pair of interacting electrodes will intersect the plane of the web at an oblique angle, movable means located above' said lower electrodes and below said web for supporting as granular material, and means for applying a potential diilerence to the upper and lower electrodes, said apparatus being adapted to electrostatically project granular material against the downwardly facing adhesive surface of said web. 5. Apparatus for the manufacture of granular coated webs comprising means for movably supporting an adhesive coated web with an adhesive coated side downward, a plurality of intercom nected electrodes of good conducting material 65 spaced apart from each other and positioned above said web, a plurality of interconnected electrodes of poorly conducting material spaced apart from each other and positioned below said web, the interacting electrodes on either side of '70 the web being so positioned that a line drawn through the longitudinal axes of any pair of interacting electrodes will intersect the plane of the web at an oblique angle, movable means located above said lower electrodes and below said u web for supporting granular material, and means for applying a potential diflerence to-said upper and said lower electrodes. said apparatus being adapted to electrostatically project granular material against the downwardly facing adhesive surface of the web. 6. An apparatus for the manufacture of granular coated webs comprising a plurality of electrodes of good conducting material spaced apart from each other and positioned above a plurality of electrodesof a materialhaving suflicient conductivity to permit a leakage curent to flow therethrough, but of sufllcient resistance to prevent spark-over or arcing to the upper electrodes, means for applying a potential difference to the said upper and lower electrodes, means for supporting an adhesive coated web between said electrodes and with an adhesive coated surface downward, the interacting electrodes on either side of the web being so positioned that a line drawn through the longitudinal axes of any pair of interacting electrodes will intersect the plane of the web at an oblique angle, movable means v located above said lower electrodes and below said web for supporting granular material, and means for applying a potential difference to said upper and said lower electrodes, said apparatus being adapted to electrostatically project granular material against the downwardly facing adhesive surface of the web. A

7. Apparatus for the manufacture of granular coated webs comprising electrostatic means for projecting the granular material vertically upward, means for movably supporting an adhesive coated web at an oblique angle with respect to .the vertical and with an adhesive coated side downward to receive the upwardly projected granular material, and means for causing the adhesive to acquire a preliminary set located adjacent to said electrostatic projecting means and in a position subsequent thereto with respect to the directionof movement of said web.

8. Apparatus for the manufacture of granular coated webs comprising the electrostatic means for projecting granular material upwardly at an oblique angle with respect to the vertical, means for movably supporting an adhesive coated web in a horizontal position with an adhesive coated surface facing downward to receive the upwardly projected granular material, and means for causing the adhesive to acquire a preliminary set without disturbing the positions of the deposited granules, said means being located adjacent to said electrostatic projecting means and in a an adhesive coated surface downward, said electrostatic projecting means and said web supporting means being positioned with respect to each other to cause the projected granular material to be deposited on the web at an oblique angle with respect to the surface of said web, means for supplying granular particles between said web and the said lower electrodes and means for causing the adhesive to acquire a preliminary set located adjacent to said electrostatic means for projectoblique angle, comprising electrostatic means for projecting the granular material upward, means for movably supporting an adhesive coated web at an oblique angle with respect to the upward projection of said granules and with an adhesive side downward to receive the upwardly projected granular material.

RAYMOND C. BENNER. ROMIE L. MELTON. HENRY P. KIRCHNER.