US2526780A - Apparatus for coating articles - Google Patents

Description

Oct. 24, 1950 STQDDARD 2,526,780

APPARATUS FOR COATING ARTICLES Filed Oct. 22. 1945 /4 /4 r- Fl ,2 E}

k w H a 4 3/ I e 1. i m 'mA. 5 HAROLD K J TODD/1RD Patented Oct. 24, 1950 APPARATUS FOR COATING ARTICLES Harold K. Stoddard, Indianapolis, Ind., assignor, by mesne assignments, to Ransburg Electro- Coating Corp., of Indiana Indianapolis, Ind., a corporation Application October 22, 1945, Serial No. 623,783

1 This invention relates to improvements on the detearing apparatus and process set forth in United States Letters Patent No. 2,359,476, to Gravley.

In the process of the Gravley patent the articles to be coated are first treated, as by dipping, with an excess of coatin material and are then brought into spaced relation with a detearing electrode between which and the articles there is maintained an electrostatic field.

The article and electrode are arranged so that the electrostatic field, over those portions of the article-surface to which excess coating material tends to flow under the influence of gravity, is sufiiciently strong to cause material accumulating there to be repelled from the article. Certain types of articles, however, possess pockets or recesses or other characteristics of formation which interrupt the flow of coating material to the point from which detearing takes place; and in many instances the coating material may collect in places on the article-surface where it is protected from the detearing effect of the field. In the case of such articles, it is diflicult to obtain satisfactory detearing by prior methods.

It is the object of my invention to improve the detearing of articles having pockets, recesses, or other features of surface formation which tend to trap excess coating material and prevent it from reaching a point on the article from which it otherwise could be readily deteared by the action of an electrostatic field.

In carrying out my invention in its preferred form an article coated with an excess of coating material is brought into association with a detearing electrode which is provided with one or more auxiliaryv portions, pointed or sharply curved, which are disposed opposite to and preferably directed toward the points at which the coating material tends to be trapped. In quantity production, the articles are supported from a conveyor which moves them continuously through association with the article-coating means and past the detearin electrode, and the auxiliary-electrode portions either possess considerable longitudinal extent or are arranged in longitudinally extending series.

The accompanying drawing illustrates my invention: Fig. l is a side elevation, somewhat diagrammatic in character, illustrating one form of my improved detearing apparatus; Fig. 2 is an end elevation of thedetearing apparatus; Fig. 3 is an isometric view on an enlarged scale illustrating one form of article for the detearing of which my invention is suited; and Fig. 4 is an 9 Claims. (Cl. 91- 18) isometric view illustrating a modified form of electrode.

In the apparatus illustrated in Fig, 1, an overhead conveyor |0 supports a series of racks II from each of which a group of articles l2 to be deteared are suspended. Beneath the path of travel of the articles l2 there is provided a detearin electrode l3 mounted through insulators I4 and connected to one terminal of a high-voltage source [5 the other terminal of which is grounded as indicated at Hi. The conveyor II] is grounded, as indicated at H, and the racks II are of metal or other electrical conducting material so that as the articles I2 move over the electrode l3 an electrostatic field will exist between them and the electrode.

The apparatus as so far described operates satisfactorily to detear articles over which the excess coating material previously applied can flow freely downwardly to the lowermost points of the articles where it will be deteared by the action of the electrostatic field. However, if the article is so shaped that some of the excess coating mate'- rial is trapped above the lower-most points of the article, detearing may not be complete.

The article l2 illustrated in Fig. 3 will exemplify the type of article diflicult to detear satisfactorily by any prior detearing method of which I am aware. That article is a clip formed of a strip of sheet-metal, provided at one end with a hole 20, and bent at the other end into the form of a hook.v When such an article is coated with an excess of coating material and supported in the vertical position illustrated, the excess coating material tends to flow downwardly over the surface of the article to the lowermost point thereof. However, some of such coating material will tend to collect within the bend 2| of the clip; and, if the throat 22 of the clip is narrow enough, excess coating material may bridge it and not flow downwardly below it. Coating material collecting within the bend of the hook 2| or within the throat 22 will not be deteared.

I have found that the detearing of coating material collectin in such places as the bend 2i and throat 22 of the article [2 can be satisfactorily effected if the detearing electrode I3 is provided with a sharply pointed or sharply curved auxiliary portion located opposite the points at which coating material tends to collect. In the apparatus shown in Figs. 1 and 2 such auxiliary portions are provided by rods 25 which extend upwardly from the electrode l3 and have pointed ends 26 bent inwardly of the electrode toward the articles I2 passing in association with it. As will be clear from Fig. 2. the points 28 of the rods 28 are located opposite the bent or hook-like portion of the clips l2 suspended from the rack ll. Since the articles move continuously over the electrode It in the preferred form 01' the invention, it is desirable to provide along the path of article travel a series of the rods 25 each provided with an inwardly directed pointed end 26. 'The trapped coating material is repelled from the article as a result of the presence of the points 26 and leaves the article in the form of fine droplets which, under the combined infiuence of gravity and the field, follow a generally outward and downward course.

In the modified electrode shown in Fig. 4, the auxiliary electrode portions are in the form of longitudinally extending wires 30 of small diameter supported from the body of the electrode,

"by rods 3|, opposite those portions of the articles where coating material tends to collect. The sharply curved surfaces of the fine wires 30 perform substantially the same function as do the points 26 of the electrode shown in Figs. 1 and 2.

It is to be understood that my invention is not limited to the detearing of the particular form of article illustrated in Fig. 3, as there are an unlimited number of articles which present detearing problems similar to those presented by the article l2 by reason of the tendency of coating material to collect in excess quantity within the bend 2| and throat 22. For example, articles which it is desired to coat by the dip-and-detear process may possess one or more holes across the outer end of which a film or web of coating material tends to form. By providing the detearing electrode with one or more auxiliary portions such as a series of the points 26 or a fine wire 30 located opposite such a hole, the web or film of coating material will be ruptured.

I claim as my invention:

1. In apparatus for electrostatically detearing excess liquid coating material from an article having a surface feature which traps some of such excess coating material, an electrode, a support for supporting in spaced relation to said electrode the article to be deteared, and means including a high-voltage source for creating an electrostatic field between the article an'd electrode, said electrode embodying an extended body portion dis-' posed beneath an article on said support and an auxiliary portion having above said body portion a surface of small area located opposite and pre-. sented toward the coating-material trapping.

feature of the article.

2. In apparatus for electrostatical y detearing,

excess coating material, an electrode, a conveyor n determined path spaced from the electrode, and means including a high-voltage source' for creating an electrostatic field betweenL-the electrode and the article moving past it, said electrode embodying an extended body portion disposed beneath the path of article travel and auxiliary portions having above said body portion a series of small-area surfaces located opposite and presented toward the path of travel of the coating material trapping feature of the article.

3. In apparatus for electrostatically detearing excess liquid coating material from an article having a surface feature which traps some of such excess coating material, an electrode, a conveyor for moving the article to be deteared over a predetermined path spaced from the electrode,

and means including a high-voltage source for creating an electrostatic field between the electrode and the article moving past it, said electrode embodying an extended body portion disposed beneath the path of article travel and above said body portion a longitudinally extending wire located opposite the path of travel of the coating material trapping feature of the article.

4. A detearing electrode, comprising a laterally and longitudinally extended electrical conducting body portion, an electrical conducting auxiliary portion located near one side of said body portion, said auxiliary portion having an inwardly presented surface of small area spaced from said body portion in a direction normal thereto, and an insulating support for electrically insulating said body and auxiliary portions, said insulating support permitting the charging of said body and auxiliary portions to a high voltage.

5. A detearing electrode, comprising a laterally and longitudinally extended body portion, a wire extending generally parallel to said body portion near one side thereof and spaced from said body portion in a direction normal thereto, and an insulating support for electrically insulating said body portion and wire.

6. In apparatus for electrostatically detearing excess liquid coating material from an article having a surface feature for trapping some of such excess coating material, means for supporting the article to be deteared, an electrode positioned in spaced relation from the article, said electrode comp-rising an extended body portion located beneath the supported article and a pointed portion located above said body portion, at one side of the supported article, and opposite the coating-material trapping feature of the article, and means including a high voltage source for creating an electrostatic field betwee the article and said electrode.

7. In apparatus for electrostatically detearing excess liquid coating material from an article having a surface feature for trapping some of such excess coating material, a conveyor for moving the article to be deteared over a predetermined path, an electrode spaced from .the path of article travel, said electrode comprising an extended body portion located beneath the path of article travel and a pointed portion located above said body portion, and opposite the path followed by the coating-material trapping feature at one side of the path of article travel, and means including a high voltage source for creating an electrostatic field between said electrode and the article on said conveyor, while said electrode and article are in field-creating relationship.

8. In apparatus for electrostatically detearing excess liquid coating material from an article having a surface feature for trapping some of such excess coating material; means for supporting the article to be deteared; an electrode positioned in spaced relation adjacent the article. said electrode comprising an extended body portion and an auxiliary portion having a small area surface located near one side of said body portion and extending forwardly thereof toward and generally opposite the coating-material trapping feature of the article; and means including a high voltage source for creating an electrostatic field between said electrode and the article.

9. A detearing electrode comprising a laterally and longitudinally extended electrical conducting body portion, an electrical conducting auxiliary portion projecting generally normal to and at one side of said body portion and terminating in an inturned end, and an insulating support for electrically insulating said body and auxiliaryportions, said insulating support permitting the charging of said body and auxiliary portions to a, high voltage.

HAROLD K. STODDARD.

REFERENCES CITED The following references are of record in the m file of this patent:

UNITED STATES PATENTS Name Date Anderson Nov. 29, 1904 Number Number Number Name Date Johnston Nov. 14, 1924 Smyser Jan. 13, 1931 Meston Oct. 26, 1937 Meston Mar. 28, 1939 Hill Oct, 8, 1940 Ransburg et a1 July 1, 1941 Smyser June 30, 1942 Gravley Oct. 3, 1944 Fruth Sept. 11, 1945 FOREIGN PATENTS Country Date Great Britain July 27, 1894

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