US2753577A

US2753577A - Roller coater

Info

Publication number: US2753577A
Application number: US325173A
Authority: US
Inventors: Jr William C Van Clief
Original assignee: Pittsburgh Plate Glass Co
Current assignee: PPG Industries Inc
Priority date: 1952-12-10
Filing date: 1952-12-10
Publication date: 1956-07-10
Anticipated expiration: 1973-07-10

Description

y 1956 w. c. VAN CLIEF, JR 2,753,577

ROLLER COATER Filed Dec. 10, 1952 5 Sheets-Sheet 1 INVENTOR. WILLIAM C VAN CL/EF JK QWiEJmM July 10, 1956 w. c. VAN CLJEF, JR

ROLLER COATER 5 Sheets-Sheet 2 Filed Dec. 10, 1952 7 7 FIG-3 6a C Q 10 a m m M r m V N c 1 B a B m M mm a m ATTUZ/VEY y 1956 w. c. VAN CLIEF, JR 2,753,577

ROLLER COATER Filed Dec. 10, 1952 5 Sheets-Sheet 3 INVENTOR. WILLIAM C. VII/V CZIEF J? United States Patent RULLER COATER William C. Van Chief, .lr., Baltimore, Md., assignor to Pittsburgh Plate Glass Company, Allegheny County, Pa., a corporation of Pennsylvania Application December It), 1952, Serial No. 325,173

1 Claim. (Cl. 15-1325) This invention relates to a process of and an apparatus for applying coatings to various surfaces. More particularly, the invention relates to a process of and an apparatus for applying to such surfaces, coating materials which comprise water emulsions of various organic vehicles.

One object of the invention is to provide a process of and apparatus for applying water emulsion materials from a roller reservoir by the use of which an exceptionally smooth surface which is relatively free of bubbles, pits and like imperfections is obtained.

A second object of the invention is to provide a process of and apparatus for applying water emulsion coating compositions in which the entrapment of lint in the surface film is avoided.

A third object of the invention is to provide a roller covering for roller reservoir applicators which is not subject to substantial shrinkage and which will withstand repeated washings without noticeable change.

A fourth object of the invention is to provide a roller cover for roller reservoir applicators which can readily be washed free of residual coating material.

A fifth object of the invention is to provide a covering material for roller reservoir applicators which has an exceptionally high cushioning capacity and which, therefore, will more readily accommodate itself to irregularities in the surfaces undergoing coating than do conventional covering materials.

A sixth object of the invention is to provide a porous, permeable, sponge-like roller covering from which the coating material is easily expelled upon the application of roller pressures against a surface.

A seventh object of the invention is to provide a roller covering material which is resistant to the various solvents commonly encountered in home painting materials.

These and other objects of the invention will be apparent from consideration of the following description and the accompanying drawings wherein:

Figure l is a side elevational view of a convenient embodiment of coating apparatus to which the porous roller coating medium of this invention may be applied.

Figure 2 is an end view of the coating apparatus shown in Figure 1;

Figure 3 is a sectional view taken upon the line 33 of Figure 2;

Figure 4 is an enlarged fragmentary sectional view showing the structural details of the end of the rotary reservoir coating roller;

Figure 5 is an enlarged fragmentary rear elevational view of the coating roller supporting member;

Figure 6 is an enlarged fragmentary front elevational view of the members shown in Figure 5;

Figure 7 is a view partially in section and partially in elevation of a modified form of roller reservoir coating apparatus to which the principles of the invention may be applied;

Figure 8 is a view upon the line 8-8 in Figure 7;

Figure 9 is a fragmentary sectional view of a portion of the roller covering shown in Figure 7.

A convenient method of applying paints and similar coating media to surfaces such as walls, involves the application of a supply of the coating material to the surface of a solid roller member and then transferring the material to the surface to be coated by rolling contact. In the use of such rollers only a small amount of material can be applied to the surface of the roller at any one time and therefore frequent and repeated recharging of the roller is required. In order to obviate this difficulty, it has also been proposed to provide hollow rollers of foraminous structure constituting a roller reservoir and being adapted to be charged with the coating material which is to be applied. These rollers are covered with a permeable material such as carpeting through which the coating medium can permeate to replenish the surface film upon the roller as it is used up. Such rollers are susceptible of being charged with a substantial amount of the coating medium and therefore require only occa sional recharging. However, these embodiments of apparatus are characterized by many disadvantages. For example, the fabric coverings often tend to shed lint which becomes embedded in the paint film applied. Also, the fabrics often tend to shrink when employed in application of water emulsion coating compositions and they further tend to lose resilience as well as the capacity for maintaining an adequate flow of paint to the zone of application. A further disadvantage of the conventional coating materials resides in a tendency to retain substantial amounts of the coating material, even after persistent washing operations, thus making thorough cleaning a difficult operation.

It has also been suggested to form coverings for rotary reservoir type roller paint applicators of sponge rubber or rubber substitutes such as may be derived from polymerization of conjugately unsaturated compounds and monomers such as styrene. These coverings do not behave well with aqueous emulsion vehicles such as now enjoy a large and increasing degree of popularity.

The conventional covering materials for the rollers are often characterized by a relatively low degree of cushioning action and therefore they are not well adapted to effect uniform contact when applied to surfaces having irregularities.

The present invention is based upon the discovery that a hydrophilic, porous or cellular, permeable polyvinyl alcohol sponge constitutes an exceptionally satisfactory medium for covering the surfaces of roller coaters of the rotary reservoir type and by use of this medium as a roller covering, in the application of emulsion vehicles to surfaces, the difficulties attending the use of conventional reservoir type roller coverings are eliminated or reduced to the minimum.

In the practice of the invention, any suitable conventional cellulated polyvinyl alcohol sheet in which there is a reasonable degree of intercommunication between the cells may be employed as a covering medium for the roller reservoir. Cellulated polyvinyl alcohols of sponge like structure in which there is intercommunication with the cells so that the material will readily permit the permeation of water emulsion coating compositions are available as commercial materials. The foaming or cellulation of various emulsion compositions including polyvinyl alcohol is a well-recognized art not constituting a part of the present invention. Any of the conventional techniques may be employed in the cellulation of polyvinyl alcohol for roller coverings. For example, they may be cellulated by mixing a liquid polyvinyl alcohol with a gassing agent such as particles of frozen carbon dioxide or ammonium carbonate or any other gas forming material which readily evolves bubbles of gas when slightly heated and which can be uniformly distributed in the polyvinyl alcohol. it is to be understood that the polyvinyl alcohol in the cellulation stage should be reasonably fluid. This state may be attained by use of solvents that can be subsequently exaporated, or a gassing agent may be added to the plastic and the latter then fused. Heat present in the fused material will result in the liberation of gas bubbles, thereby causing the material to become foamed or cellulated often to a highly permeable spongelike state. When the material is cooled, a permanent cellular structure is provided. If there is insuflicient communication between cells to provide a material with adequate permeability to permit passage of aqueous emulsion coating materials, in accordance with the provisions of the present invention, the cellulated polyvinyl alcohol may be subjected to suitable techniques in order to increase the degree of permeability. For example, it may be subjected to a needling operation in which the cell walls are punctured by repeated applications of a needle. This is repeated until adequate permeability is attained.

Some cellulated or foamed polyvinyl alcohol materials apparently have adequate intercommunication between contiguous cells without subjection to a needling or other operation.

An appropriate cellulated or foamed polyvinyl alcohol material suitable for use as the roller covering in the practice of the present invention is sold by Ivano, Inc. of Chicago, Illinois. The product is designated by the trade name Ivalon. This material can be obtained in the form of a sheet for suitable application to any coater comprising a foraminous roller reservoir.

The principal advantage of vinyl resin sponge-like materials as a covering for the cylindrical container is that such a material deposits water-base emulsion paints without the formation of bubbles in the surface of the coating. Such bubbles are frequently formed with coating rollers covered with fleece and pile fabrics or cellulose derivative sponge materials. The bubbles burst when formed and produce craters and bumps in the finished coating. The polyvinyl alcohol resin sponges produce coatings which are either free from bubbles or the bubbles formed therein are very minute. In the latter event, the coating levels when these small bubbles burst. The polyvinyl alcohol resin sponges have the advantage of being resistant to solvents present in paints and they do not shrink or lose their resilience, even after repeated washings. Such roller coverings are easily cleaned and are free from lint at all times. These sponge coverings are soft and possess a cushioning quality which readily absorbs the irregularities of the surface to which the paint is applied, with the result that smooth, even coatings are formed.

The polyvinyl alcohol sponges may be applied to various embodiments of rolling reservoir applicators. One such structure is disclosed in my copending applicatiom Serial No. 305,963 filed August 23, 1952. The structural details of this apparatus are disclosed in Figures 1 to 6 of the drawings of this application, in which the coating apparatus shown comprises, in general, the supporting member 1 and a rotary reservoir or roller 2 mounted thereon. cylindrical can-like container 3 having a wall which is pervious by reason of a plurality of perforations 4 formed therein. One end of the container 3 has an annular rim 5 providing an opening for filling the container 3 with paint or other coating material. A snap-v on cover 6, having a cylindrical rim portion 6a engaging. rim 5, is provided for this end of the container 3 as a The coating roller 2 comprises a closure for the filling opening. The cover 6 is provided with a lever 7, having a shank portion 7a extending through rim 6a and engaging rim 5, to facilitate removing the cover from the container. The opposite end of the cylindrical container 3 is provided with an end closure member 8 having an axially outwardly extending peripheral flange 9. The end of the container 3 adjacent the flange 9 is bent thereover as shown at 10. The flange 9 and the portions of the end of the container 3 bent thereover, may be crimped together to form a bead 11. This bead is bent inwardly toward the center of the end closure 8 so that it overlies the end closure and provides an annular recess 12.

The outer wall of the cylindrical container 3 is covered with a sheet of a porous polyvinyl alcohol resinous material 13, which may be retained by cement, by frictional engagement, or by any other appropriate means. The resinous material is highly porous and sponge-like in character. The body of the resinous material contains many minute passageways which extend between the faces of the sheet and are interconnected. As previously indicated, this highly porous structure is produced by expanding gases present in the body of the resin during the polymerization thereof. The aqueous emulsion material will permeate unidirectionally from the source of supply in container 3 completely through the covering layer from back to front.

The supporting frame member 1 for the coating roller 2 comprises a die-cast metal arm having a roller supporting'portion 14 which is positioned adjacent the end closure 8 of the container 3 and a handle supporting portion 15 which extends over the surface of the coating roller and is spaced therefrom. The portion 15 is bent rearwardly to provide a shank upon which a hand grip 16 is mounted. A supporting foot member 17 is formed in the roller supporting portion 14 of the metal arm adjacent the point where the portion 14 is joined to the handle supporting portion 15. The support 17 has'a flat surface 17a at the lowermost edge thereof. The support 17 extends a substantial distance beyond each side of the roller supporting portion 14 to provide a stable support for the coating apparatus.

The roller supporting portion 14 of the supporting frame member 1 has a bushing 18 formed therein adjacent the end thereof. A stub-shaft 19 is rotatably mounted in this bushing and is provided at one end thereof with a washer 20 which is secured to the shaft by a snap-ring 21. The opposite end of the stub-shaft 19 is provided with a washer 22, and on the outermost end thereof is mounted a substantially Y-shaped spider member 23. The

legs

23a, 23b and 230 of the spider member extend radially with respect to the axis of rotation of the stub-shaft 19. The

legs

23a and 23b of the spider are the same in length and each terminate in outwardly olfset portions. A lever 24, or other retractable means, is pivotally mounted on the outer face of the spider leg 230, which is shorter in length, than

legs

23a and 23b. The lever 24 terminates in a cam portion 24a at the end thereof adjacent the outer end of the leg 23b. An operating arm 24b is formed in the other end of the lever 24, which arm extends inwardly toward the bushing 18 of the roller supporting portion 14. The face of'the lever 14 adjacent the spider member 24 is provided with latch member 240 which is adapted to engage a recess 2'3dformed in the. opposed face of the spider member 23.

The rotary reservoir or roller 2 is secured to the supporting member 1 by inserting the terminal offset portions of the

legs

23a and 23b of the spider member in the annular recess 12 at the end of the coating roller. The lever 24 is then rotated until the terminal cam portion 24a thereof is engaged in the annular recess, 12 of the coating roller and the latch 24c is engaged in the recess 23a. The coating roller 2 is thus rotatably seur d o he PPQ t ns mb 1 an h xes of tation of the roller and the stub-shaft 19 are in alignment.

smea /"r The coating roller 2 may be detached by unlatching and rotating the lever 24. In using this coating apparatus, it may be positioned to rest upon one end of the stubshaft 19 and the supporting foot 17. The closure 6 may be removed to fill the cylindrical container 3 with paint or other coating material and then replaced. The coating apparatus may thereupon be used in the customary manner to apply a coating to a surface. The coating roller 2 may be removed from the supporting member 1 in the manner described above by retracting the latch 24 when the coating operation is completed and the roller may then be discarded. It is also possible, if de sired, to remove the coating roller and store it for a period of time ranging from several days to several weeks, after which it may again be mounted on the supporting member 1 and the use thereof resumed. In this coating apparatus it is feasible to replace one coating roller with another in the supporting member 1 and, in this manner, the operator may employ the apparatus using a plurality of coating rollers 2, separately, each containing coating compositions of different types or colors. It will be apparent from the above description, that the coating roller, per se, employed in this coating apparatus is very simply and inexpensively constructed. Because of the low cost of these coating rollers they may be discarded after use as are paint cans and other containers for coating materials.

While it is true that the foregoing apparatus possesses many important advantages, it will be apparent that in the practice of this invention it may be replaced by other coaters comprising a foraminous roller-type reservoir and a coating of cellulated or sponge-like polyvinyl alcohol adapted to transmit by permeation, an aqueous emulsion, or suspension of coating material from the inner to the outer surface. A simplified embodiment of apparatus suitable for use in the practice of the invention is illustrated in Figures 7, 8 and 9. This apparatus includes a handle structure indicated broadly at 30 and including a grip portion 31, a laterally angularly offset neck portion 32, and a portion 33 at the extremity of the neck and being disposed approximately parallel to the grip portion 31. Portion 33 is also provided with a spindle portion 34 disposed at right angles to portion 33, and con stituting a shaft for a roller 36.

The roller includes an inner can or shell 37, preferably of sheet metal and being perforated at frequent intervals as indicated at 38 to permit the exudation of an aqueous suspension of an appropriate coating material. The shell or can 37, as will be observed in Figure 1, is provided with end members 39 constituting closures designed to retain a supply of coating material in the latter. The end members are provided with embossments as indicated at 41 centrally or axially disposed with respect to the outer shell or support 37, and the embossments and the end members are bored, rotatably to receive the spindle portion 34. For purposes of retaining the support or shell upon the spindle portion, the latter is threaded as indicated at 43 and a retaining nut 44 is threaded thereupon. Aqueous emulsion material to be applied as a coating by means of the roller may be in-- troduced into the latter through an appropriate opening formed in the end member 39 and being closed by a screw-threaded plug 46 which can be removed in order to permit the filling of the reservoir and can then be re inserted to retain the material except as it is transmitted outwardly to the surface of the covering member of the roller.

The foraminous shell 37 is provided with a coating layer of polyvinyl alcohol sponge 47 having intercommunicating cells. The intercommunicating cells of this sponge readily transmit aqueous emulsion coating vehicles from the interior of the shell to the exterior surface of the coating or covering 47 where it is transferred to the surface of a wall, or a similar surface to be coated, the transfer being effected by rolling contact between the surface and the roller so that there is little or no sliding of the roller surface upon the surface to be coated.

Particular emphasis has been placed upon the use of a sponge of cellulated polyvinyl alcohol as the coating medium for the reservoir type roller herein disclosed. However, although they do not possess all of the virtues of the polyvinyl alcohol sponge, in an emergency, other hydrophilic plastics may sometimes be substituted for the more desirable material, for example, a sponge formed from a soluble cellulose compound prepared by conventional regeneration technhiques may be employed These sponges of regenerated cellulose are less desirable than the polyvinyl alcohol since they often tend to form bub bles of relatively large size in the film as it is applied. These bubbles may burst, and because of their size they do not adequately level out. Therefore, pits may be formed in the surface of the film.

The cellulated, or sponge-like coverings of polyvinyl alcohol herein disclosed are particularly designed for the application of aqueous emulsion coating compositions. Many non-aqueous materials, such as conventional oil paints, are not suitable for use in the process of the present invention. However, in an emergency the polyvinyl alcohol sponges may be preliminarily wet with water and used for a time in the application of the conventional oil base coating materials.

Reservoir applicators such as herein disclosed when equipped with coverings of polyvinyl alcohol sponge may be employed in combination with any of the more usual aqueous emulsion coating materials. For example, an appropriate aqueous emulsion may be formed by the use of casein, methyl cellulose or other emulsifying agent for oil modified alkyd resins. Conventional aqueous emulsions such as natural or synthetic rubber latex coating materials are also suitable for use in the practice of the invention.

One convenient type of emulsion comprises an oil modified alkyd resin which has been cooked with a polyethylene glycol preferably of rather high molecular weight such as one having a molecular weight above about 300 and preferably below about 2500 or 3000. One such polyethylene glycol suitable for use in the preparation of emulsifiable oil base alkyds is disclosed as having a molecular weight of about 1500. These polyethylene glycols are sold by the Carbide and Carbon Chemicals Corporation. They are designed by the trade name Carbowax. The art of preparing emulsifiable oil modified alkyds by cooking a polyethylene glycol into the alkyd is disclosed and claimed in patent application Serial No. 158,611, filed April 27, 1950 by Rudolph P. Arndt. This application was allowed as of July 18, 1952. The disclosure of the application is incorporated herein as representing an appropriate method of preparing emulsifiable coating compositions which may be applied to a surface by the apparatus and method herein disclosed. It will be apparent that any other aqueous emulsion coating composition may likewise be employed in the practice of the invention.

Obviously, any of the aqueous coating materials useful in the practice of this invention may and usually does include a pigment or filler such as titanium dioxide, calcium carbonate, lithopone or the like.

The embodiments of the invention herein disclosed are given by way of illustration. It will be apparent to those skilled in the art that numerous modifications may be made therein without departure from the spirit of the invention or the scope of the appended claim.

1 claim:

In a coating apparatus comprising a hollow perforated cylindrical roller adapted to contain a liquid coating material, the improvement comprising a permeable covering upon said roller, consisting of a layer of a sponge of a hydrophilic polyvinyl alcohol, said covering being adapted when rolled over a surface to be coated and with a charge of an aqueous emulsion coating material. in the roller,

7 8 of distributing said emulsion upon the surface as a highly 2,491,709 Briggs et a1 Dec. 20, 1949 uniform film which is substantially free of pits. 2,525,965 Smith Oct. 17, 1950 2 ,591,530 Findley et al Apr. 1, 1952 References Cited in the file of this patent OTHER REFERENCES UNITED STATES PATENTS Canadian Paint & Varnish Magazine, vol. 24, No. 5, 2,007,588 Wescott July 9, 1935 260/29], May 1950, Latex Emulsion Paints by Burr et al.

2,312,853 Toland et al Mar. 2, 1943 (pp 22 24 2 50 51 and 3 2,378,900 Adams June 26, 1945