US3542577A - Methods for severing a protective coating on coated members - Google Patents

Description

NOW. 24 AL 3,542,577

METHODS FOR SEVERING A PROTECTIVE COATING 0N COATED MEMBERS Filed D80. 18, 1967 Rene J: A/

INVEN'I'OR.

JCT/Cg.

United States Patent Int. Cl. B44d 1/094 US. Cl. 1174 Claims ABSTRACT OF THE DISCLOSURE The particular embodiments described herein as illustrative of the present invention relate to the selective severing of protective coatings on members that have been coated. More particularly, the present invention as disclosed herein is directed to methods for severing a protective coating that has been applied continuously over interfitted members by one of the several fusion-coating techniques using pulverulent particles of a fusible thermoplastic or thermosetting coating material. After the members have been coated and the coating has at least firmed, a severing member movably disposed therebetween is moved in such a manner as to leave a well-defined termination of the coating on each coated member, with these terminations in some instances preferably being raised in relation to the adjacent portions of the coating to provide a mating sealing surface for similar terminations extending from the other or another coated member when the two members are ultimately connected.

It is, of course, quite common to coat metal articles by heating the article to an elevated temperature and, by one of the powder-coating techniques, applying a suitable pulverulent coating composition to those surfaces of the article that are to be coated. As the coating particles approach or contact these heat-releasing surfaces, the particles absorb heat from the article and are melted to form a continuous fused coating on the substrate surfaces. Where necessary, the coated articles are again heated to complete the fusion process and leave an effective protective coating on the substrate surfaces. There are, of course, many well-known techniques for applying such powdered coatings and subsequently conditioning the fused particles to obtain a desired coating; and those skilled in the art are fully cognizant of the various ramifications involved to achieve a desired result.

It is, of course, recognized that a mask must be used to prevent such powdered coatings from being accepted by those portions of an article which are heated but which are not to be coated. Where, however, an article to be coated is comprised of two or more interfitted elements, it is often much simpler to coat the article with its various elements fitted together to prevent the coating from contacting the interfitting surfaces raher than masking the critical surfaces and coating the elements separately. This poses somewhat of a problem since the coating will cover both elements and make it necessary, therefore, to carefully cut the coating along the junction of the interfitted coated elements with one another. It will be appreciated that this usually requires a tedious manual operation that generally leaves an irregular edge at the termination of the coating on each element. A similar problem will also exist where a number of articles to be coated are temporarily connected so that they may be coated in a single operation. Thus, irrespective of the application technique used or the particular fusion-coating composition involved, no suitable procedure has yet been devised for severing such fused coatings to leave a smooth and uniform edge after the elements have been separated.

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Accordingly, it is an object of the present invention to provide new and improved methods for severing a continuous powder-coating over separable elements in such a manner that a smooth and uniform termination will be formed along the severed edges of the coating.

This and other objects of the present invention are attained by interposing a severing member of a heatconductive material and having a minimum mass between adjacent elements to be coated, with the severing member being adapted for movement relative to the elements. Thus, after the elements have been coated and the coating has at least firmed, by moving the severing member, the band of coating joining the elements to one another will be severed to leave smooth and uniformly terminated edges on the finished coating.

The novel features of the present invention are set forth with particularity in the appended claims. The operation, together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings, in which:

FIG. 1 depicts one embodiment of apparatus arranged in accordance with the principles of the present invention for severing a coating on an article having complementally fitting elements;

FIGS. 2 and 3 show alternate embodiments of severing apparatus for use in the practice of the present invention to sever a coating on an article such as shown in FIG. 1; and

FIG. 4 shows still another embodiment of severing apparatus incorporating the principles of the present invention.

Turning now to FIG. 1, a severing device 10 arranged in accordance with the principles of the present invention is shown mounted on a typical electrical junction box 11 that has been powder-coated, as at 12. It will be appreciated, of course, that the severing device 10 was positioned before the closure 13 and body 14 of the junction box 11 were connected. Once the severing device 10 and junction box 11 were coupled, they were heated in some convenient manner to a selected temperature above the sintering or melting temperature of Whatever thermoplastic or thermosetting pulverulent composition is to be applied to achieve the coating 12. The range of preheating temperatures practical for the methods of this invention has a lower limit set by the melting or sintering point of the coating material adequate to cause adherence to the substrate surfaces, and an upper limit determined by the melting, softening, or deterioration temperature of the article being coated as well as by the transient decomposition temperature of the pulverulent coating substance.

It will also be appreciated that the external surfaces of the junction box 11 that were to be coated were previously prepared as required to obtain adherence thereto of the coating 12 developed as the pulverulent coating particles are coalesced by the heat given up by the heatreleasing surfaces of the closure 13 and body 14. Inasmuch as the particular techniques required to obtain a satisfactory coating 12 and its adequate bonding are well understood by those skilled in the art of powder-coatings and powder-coating techniques and these details are only incidental to an understanding of the present invention, it is believed sufficient to say only that the coating 12 is a powder-coating that has been applied to the properly prepared surfaces by any one of the typical powder-coating techniques.

The open ends of the coupling bosses 15 on the junction box 11 must, of course, be covered to prevent entrance of the pulverulent coating composition into the interior of the box during the coating operation. Since it has been customary in some instances to coat tubular members, such as a pipe or a conduit, that are to be connected to a junction box, as at 11, the plugs 16 used to close the bosses 15 are arranged to provide somewhat of a seal between such coated tubular members and the junction box. To obtain such a seal, it has been found desirable to form an outwardly-projecting pliable sleeve, as at 17, around each of the sockets on the bosses 15, with these sleeves being adapted to snugly receive a coated tubular member (not shown) when it is connected to the junction box 11. The pliable sleeves 17 extending from the bosses 15 will be respectively formed to have an internal diameter that is only slightly larger than the anticipated external diameter of the coated tubular member (not shown) that is to be ultimately received by the socket.

In one typical manner of forming such pliable sleeves 17, the end plugs 16 are respectively provided with a cylindrical extension 18 of suitable dimensions and the outer exposed surfaces of these extensions are previously prepared (as by either coating them with a non-sticking compound ordepending upon the powder composition usedby not priming their exposed surfaces) so that the powder-coating will not adhere to the extensions when they and the junction box 11 are powder-coated. Thus, when the junction box 11 and the various temporary members connected thereto are preheated and the pulverulent coating powders brought into contact therewith, the coating 12 will extend without interruption over the temporary members as well. It will be appreciated, therefore, that the coating 12 will be bonded to the junction box 11 but that the extended sleeve portions 17 thereof over the cylindrical extensions 18 will not be adhered to the extensions so that pliable sleeves will be formed after their ends are cut and the extensions are removed. This technique is familiar to those skilled in the powder-coating art and further elaboration is believed unnecessary.

The severing device shown in FIG. 1 serves two functions. In addition to its severing function, the severing device 10 is arranged to form a depending pliable skirt, as at 19, of the coating 12 around the lip of the closure 13 when the coating is ultimately severed. To accomplish this, the severing device 10 includes an annular body 20 of a heat-conductive material that is formed to fit loosely around the depending threaded extension 21 of the closure 13. The outer diameter of the annular body 20 is sized to form the internal diameter of the pliable skirt 19 to subsequently fit snugly over that portion (as at 22) of the coating 12 around the circuilar access opening 23 of the body 14 when the junction box 11 is coated and assembled. The thickness of the annular body 20 will, of course, determine the height of the pliable skirt 19. It will, therefore, be appreciated that the external surface of the annular body 20 is previously treated in a similar or the same manner as the cylindrical extensions 18 so that although the skirt 19 will be formed over the annular body during the coating process, the skirt will not be adhered thereto.

Accordingly, once the exposed surfaces of the severing device 10 and end plugs 16 are properly prepared to not adhere to a powder-coating deposited thereon, the plugs are inserted into their respective sockets on the bosses 15 and the severing device 10 is mounted on the threaded extension 21 of the closure 13. The closure 13 is then loosely connected to the body 14 as shown in FIG. 1 with the annular body being free to rotate in relation to the junction box 11. The assembled members 10, 11 and 16 are then heated to an elevated temperature in a typical manner.

By using one of the typical powder-coating techniques, a selected pulverulent coating composition having a fusion or sintering temperature less than the elevated temperature of the assembled members 10, 11 and 16 is then contacted with the assembled members for a suflicient time to form the coating 12 on the box 11 of a desired thickness. Once the assembled members 10, 11 and 16 are removed from contact with the pulverulent coating composition, it will be appreciated that the coating 12 will be extended continuously over all exposed surfaces of the assembled members. The coating 12 will, of course, not be bonded to the exterior surfaces of either the cylindrical extensions 18 or the annular body 20.

Then, while the coating 12 is preferably still relatively soft, a lateral cutting member 24 extending outwardly from the annular body 20 is rotated for at least a full circle about the threaded cover extension 21. In this manner, the coating 12 is parted or severed along a plane transcending the pliable skirt 19 and the adjacent portion 22 of the coating around the access opening 23. The coating 12 is, of course, treated furtherif required-in the usual manner to achieve the desired final condition of the coating. Then, once the coating 12 has become at least firmed sufficiently to allow handling, the closure 13 is removed to withdraw the severing device 10. The coating 12 is also cut around the distal ends of the end plugs 16 and the plugs removed from the bosses 15. Thus, as already pointed out, the closure 13 will be coated with its portion of the coating 12 bonded thereto and defining the pliable skirt 19. Similarly. the body 14 will be coated with the other portion of the coating 12 bonded thereto and defining the pliable sleeves 17.

The lateral cutting member 24 of the severing device 10 is appropriately sized to be capable of cutting through the warm coating 12 but to not be coated during the coating process. In one manner of accomplishing this, the cutting member 24 is formed as a relatively-thin pin with either a fiat, ovaloid, or cylindrical transverse crosssection and lying generally in the plane of rotation of the severing device 10. Thus, as the severing device 10 is rotated in relation to the junction box 11, the relatively-thin leading edge of the lateral pin 24 will easily cut through the warm coating 12. Moreover, by arranging the pin 24 to have a minimal mass with respect to the annular body 20, it has been found that the pin 24 itself will quickly cool below the sintering temperature once the assembled members 10, 1 1 and 16 are removed from the source of heat and before any large proportion of the coating composition is applied thereto so that little or no coating will be coalesced on the body of the pin itself. The annular body 20 and the other members 11 and 16, of course, have such a relatively larger mass that they will retain sufiicient heat to remain at a temperature adequately above the sintering temperature to coalesce the pulverulent particles contacting these members.

Accordingly, it will be appreciated that the severing device 10 needs only to have a lateral projection, as at 24, with a relatively-thin leading edge and of a minimal heat-absorption mass. In this manner, the heat-retention capacity of the lateral projection 24 is held to a minimum and the time typically spent in transferring the assembled members 10, 11 and 16 from their heating source (not shown) to the coating-application apparatus (not shown) will usually be adequate for the projection to cool to a reduced temperature that is not suificient to coalesce the powdered coating composition being employed. Then, while the coating 12 is still soft, the movement of the severing device 10 around the access opening 23 will readily divide the coating 12 and leave the portions 19 and 22 thereof with smooth and uniform terminations opposing one another.

Turning now to FIG. 2, an alternate embodiment is shown of a severing device 10' that is also suited for applications such as already described with respect to FIG. 1. As seen in FIG. 2, the annular body 20' is provided with a flat, outwardly-projecting, annular disc 24 that is journalled thereto in a convenient manner so as to be free to rotate with respect thereto. The disc 24' has such a reduced mass in relation to the annular body 20' that the disc will quickly cool in the same manner as the lateral pin 24 so that little or no coating will be formed thereon. The opposed edges of the coating portions (corresponding to the coating portions 19 and 22 in FIG. 1) will terminate on opposite faces of the disc 24' and (by virtue of the proximity of the adjacent heatreleasing surfaces of the body 20 and member being coated), in some instances, be bonded thereto. Rotation of the disc 24 about the closure member will, however, clearly sever any bonded edge.

Although it may be preferred to coat a multi-element article as a unit in the manner described with respect to FIG. 1, there may be situations where it is desired to coat the various elements separately. Accordingly, in another manner of practicing the present invention, a masking device 100 is shown in FIG. 3 releasably mounted between two opposed bodies 101 and 102 of typical electrical conduit junction boxes. Although the bodies 101 and 102 could just as well be elongated or generally rectangular in cross-section the bodies are illustrated as being similar to or identical to the body 14 previously described. Since it is not necessary to'form an outstanding skirt on the bodies 101 and 102, the cutting device 100 is simply a thin, fiat sheet of a heat-conductive material, such as a metal, a ceramic, or other glass-like materials, with a central opening 103 therein. End plugs 104 and 105 arranged in the same manner as the end plugs 16 are disposed in the open sockets of the bosses 106 and 107 of the bodies 102 and 101 respectively.

Although satisfactory means can, of course, be provided exteriorally of the bodies 101 and 102 for clamping them on opposite sides of the severing device 100, the opposite ends of relatively- stiff rods 108 and 109 are arranged to be inserted into sockets 110 and 111 in the end plugs 104 and 105 and span the length of the bodies. A spring 112 is passed through the opening 103 in the plate 100 and its opposite ends are respectively connected to the rods 108 and 109*. Once the bodies 101 and 102 are clamped together on opposite sides of the plate 100, the assembly is heated and then powder-coated in the same manner as already described.

It will be appreciated that since at least the protruding portions of the plate 100 are of a relatively minimal mass, these protruding portions will quickly cool so that by the time the coating composition is contacted therewith, little or no coating will be formed thereon. Thus, once a fused coating 113 and 114 is respectively formed on the bodies 101 and 102 and the assembly is removed from further contact with the pulverulent coating particles, the plate 100 needs only to be moved relative to the bodies to sever the edges of the coatings. It will be appreciated that this relative movement can be either a rotative movement or a sliding movement. Similarly, if desired, the bodies 101 and 102 can also be moved in relation to the stationary plate 100 to accomplish the desired severing of the coatings 113 and 114 from the plate. In any event, the coatings 113 and 114 will be terminated with uniform and smooth edges.

It will be noted from FIG. 3 that the terminal edges of the coatings 113 and 114 are respectively protruding outwardly, as at 115 and 116, in the immediate proximity of the plate 100. These protrusions 115 and 116 are possibly formed by a slight release of heat from the portions of the plate 100 in contact with the bodies 101 and 102. In any event and irrespective of either the coating composition used or the type of edge termination provided for the coating on the closures (not shown) subsequently mounted on the bodies 101 and 102, these peripheral protrusions or beads 1'15 and 116 will be of benefit.

Assuming that a coated closure as at 13 in FIG. 1 and having a pliable skirt, as at 19, therearound is subsequently fitted onto the body 101, the distension of the pliable skirt as it slips over the bead 115 will provide a better seal therebetween. A better seal will also be provided by the bead 115 even where the coating on the closure member (not shown) is terminated substantially flush with the edges of the closure. For example, where the coating on the closure member is also terminated in a peripheral bead similar to the bead 115, the two beads will be abutted against one another when the closure is placed on the body 101. This arrangement will, of course, be usually found where the plastic coatings are not pliable and cannot, therefore, be formed into pliable skirts.

The preceding descriptions have not disclosed how the present invention can be employed to clearly sever the free ends of the pliant sleeves as at 17 in FIG. 1. Accordingly, as seen in FIG. 4, severing means 200 arranged in accordance with the present invention are shown for smoothly terminating the free ends of pliant sleeves 201 and 202 formed around and extended from bosses 203 and 204 on typical conduit fittings 205 and 206.

In general, the severing means 200 are comprised of oppositely directed end plugs 207 and 208 that are similar to those already disclosed. In this manner, the end plugs 207 and 208 can be used to hold the fittings 205 and 206 together during the coating process and form the pliant sleeves 201 and 202. The end plugs 207 and 208 are either made as an integral body or of releasably joined members. In either case, however, an annular disc 209 of a relatively-thin heat-conductive material is rotatably mounted around the mid-portion of the joined plugs 207 and 208. Thus, as will now be realized from the foregoing descriptions, rotation of the flat disc 209 in relation to the end plugs 207 and 208 will cleanly terminate the free ends of the pliant sleeves 201 and 202. It will be realized. that the desired severing action is obtained by achieving relative rotation of the disc 209 with respect to the pliant sleeves 201 and 202. Thus, a similar result will be ac complished by fixing the disc 209 to the end plugs 207 and 208. With this arrangement, rotation of one or both bodies 205 and 206 relative to the end plugs 207 and 208 will cause the pliant sleeves 201 and 202 to be rotated in relation to the disc 209 since the sleeves are not bonded to the end plugs.

Accordingly, it will be appreciated that the various exemplary embodiments of the present invention described above will now permit a powdered coating to be quickly severed along a well-defined plane so that all exposed edges of the coating will be uniform and smooth. In each instance, a thin or small member of a relatively minimal mass is arranged to project outwardly beyond the surface to be coated. Thus, since the heat-retention capability of the projecting member is substantially negligible, the projecting member will quickly cool although the articles adjacent thereto that are to be coated will not. This will prevent pulverulent coating particles from coalescing on the projecting member as a fused coating is being formed on the adjacent heat-releasing surfaces. Thus, once the coating process is discontinued, by moving the projecting member in relation to the now-coated heat-releasing surfaces, these coatings will be quickly and reliably severed along a predetermined plane to leave well-defined, uniform and smooth terminating edges thereon.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A method for powder-coating selected first and sec ond surfaces of heat-conductive materials and comprising the steps of: interposing between said selected surfaces a member of a heat-conductive material and having a portion of a reduced mass protruding outwardly from said selected surfaces; heating said interposed member and said selected surfaces to an elevated temperature greater than the sintering temperature of a selected pulverulent coating composition; before said selected surfaces have cooled below said sintering temperature, applying a pulverulent coating composition having a sintering temperature lower than said elevated temperature to said selected surfaces and at least the adjacent surfaces of said protruding reduced-mass portion of said interposed member to form a continuous fused coating thereon; and, after said fused coating has at least firmed, moving said interposed member in relation to said selected surfaces to sever said fused coating and form a smooth termination along the resulting severed edges thereof.

2. The method of claim 1 wherein said protruding portion of said interposed member has a thin edge extending away from said selected surfaces along a plane transcending said selected surfaces.

3. The method of claim 2 wherein said protruding portion of said interposed member is a lateral projection thereof extending away from only a portion of said selected surfaces and adapted for movement along said plane for severing said coating between the remaining portions of said selected surfaces.

4. The method of claim 2 wherein said protruding portion of said interposed member is a lateral projection thereof extending away from all of said selected surfaces and adapted for movement along said plane for severing said coating between said protruding portion and said selected surfaces.

5. The method of claim 1 wherein said selected surfaces define an enclosure having an opening therein and said interposed member is disposed across said opening and adapted for transverse movement in a plane transcending said selected surfaces.

6. The method of claim 1 wherein said selected surfaces are cylindrical and said interposed member is a thin plate adapted for rotational movement in relation to said selected surfaces and having a peripheral edge spatially disposed from and circumscribing said selected surfaces.

7. The method of claim 1 wherein said selected surfaces are cylindrical and said protruding portion of said interposed member is a lateral projection thereof extending away from a portion of said selected surfaces and rotatable about the axis of revolution thereof for severing said coating between the remaining portions of said selected surfaces.

8. A method for powder-coating a selected surface of a member of a heat-conductive material and comprising: mounting a plate of a reduced mass and of a heat-conductive material transversely across one end of said selected surface with a portion of said plate protruding outwardly from said surface; heating said member and said plate to an elevated temperature greater than the sintering temperature of a selected pulverulent coating composition; before said member has cooled below said sintering temperature, contacting said selected coating composition with said selected surface and at least the adjacent surface of said plate to' form a continuous fused coating thereon; and, after said fused coating has at least firmed, moving said plate and said member in relation to one another to sever that portion of said fused coating over the junction of said contacted surfaces and form a smooth termination along the resulting severed edge thereof.

9. A method for powder-coating a selected surface of a member of a heat-conductive material and having coupling means thereon, and comprising: connecting to said coupling means a cylindrical member of a heat-conductive material and having an annular disc of a heat-conductive material and a reduced mass mounted thereon; heating said members to an elevated temperature greater than the sintering temperature of a selected pulverulent coating composition; before said members have cooled below said sintering temperature, contacting said selected coating composition with said selected surface and at least the adjacent surface of said disc to form a fused coating of said coating composition over said contacted surfaces; and, after said fused coating has at least firmed, relatively rotating said disc in relation to one of said members to sever that portion of said coating over the junction of said contacted surfaces and form a smooth termination along the resulting severed edge of said coating.

10. The method of claim 9 further including the step of preparing the exterior surface of said cylindrical member to not adhere to said fused coating so that, after said cylindrical member has been removed, said fused coating will define a tubular extension projecting away from said selected member and around said coupling means.

References Cited UNITED STATES PATENTS 3,136,650 6/1964 Avila 11721 3,185,131 5/1965 Manning 118421 3,226,245 12/1965 Dettling et al. 1l738 WILLIAM D. MARTIN, Primary Examiner R. M. SPEER, Assistant Examiner US. Cl. X.R.

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