US2417798A

US2417798A - Apparatus for coating articles

Info

Publication number: US2417798A
Application number: US492204A
Authority: US
Inventors: Harold P Ransburg; Richard E Helmuth
Original assignee: Harper J Ransburg Co Inc
Current assignee: Harper J Ransburg Co Inc
Priority date: 1943-06-25
Filing date: 1943-06-25
Publication date: 1947-03-18
Anticipated expiration: 1964-03-18
Also published as: BE462633A; GB604567A; FR919376A; NL66684C

Description

March 18, 1947. H. R. RANSBURG ET AL 3 APPARATUS FOR COATING ARTICLES Filed June 25, 1943 3 Sheets-Sheet; 1

I4 [Z l3 53 'WVE/VMQS 32 A942 40 QAPAA/SBURG March 18, 1947. H. P. RANSBURG ET AL 2,417,798

APPARATUS FOR COATING ARTICLES 3 Sheets-Sheet 2 & m vf/vroes HAROLD REA/VSBUEG 2/67/4490 E. HELI'H BY & 27 X fir OK/Vt'fi March 18, 1947. H. P. RANSBURG ET AL 2,417,793 I APPARATUS FOR COATING ARTICLES Filed June 25, 1943 s Sheets-Sheet s Patented Mar. 18, 1947 v APPARATUS FOR COATING ARTICLES Harold I. Ransburg and Richard E. Helmuth,

Indianapolis, Ind., assignors to Harper J. Ransburg, H. Gregg Ransburg, Harold P. litansburg, and Edwin M. Ransburg, co-partners doing business as Harper J. Ransburg Company Application June 25, 1943, Serial No. 492,204

18 Claims.

1 This invention relates generally to apparatus for coating articles with the aid of an electrostatic field as set forth in a general way in Letters Patent of Charles K. Gravley No. 2,359,476 granted October 5, 1944, entitled Electrostatic method and apparatus, and Letters Patent of Ransburg and Green No. 2,247,963 granted July 1, 1941, entitled Apparatus for spray coating articles."

This invention more particularly relates to improved coating apparatus and safety features incorporated therein.

It is the purpose of this invention to provide certain safety apparatus which will insure prevention of the gases being ignited, and thereby render entirely safe and practical the carrying out of the coating process or method as set forth in the above mentioned Letters Patent.

Another purpose of this invention is to obtain an improved coating on articles by properly com.. bining the forces of the electrostatic field and the force of gravity.

Another purpose of this invention is to minimize further'fiow of the coating material following the detearing action.

Still further purposes and advantages will become apparent both by direct recitation thereof and by implication from the context as the description proceeds.

' One featu e of the invention resides in the provision of. an electric circuit control by which the apparatuswill function only when there is sufliclent space or gap between the coated article and the electrode effective in conjunction therewith to provide the electrostatic field, to prevent any danger of such space or gap being so reduced as to be bridged by a spark. This is accomplished by providing a control-member, such as a switch actuating bar, contact wire or electriceye in a plan so spaced from the plane of the electrode as to insure that articles clearing it will pass the electrode in such spaced relation that a spark will not occur therebetween. If any article carried through the field is of such size or so supported as to otherwise pass close enough to the electrode to create a spark, it will first actuate a switch control which will stop the conveyor and shut off the power by reason of engagement with the switch bar, wire or affecting the circuit of the electric eye.

For the purposes hereinafter discussed. a blower is so mounted in respect to the electrode as to consiantly carry any volatile gases developed from coating of the articles passing thereby, away from the electrode. By means of the draft created by the blower, accumulation of volatile gases between the articles and the electrode will be dissipated and carried away so as to prevent an accumulation of an explosivemixture of solvent vapor, eliminating the possibility of ignition in case a spark should occur.

A further feature of the invention resides in the provision of an apertured electrode plate, such, for example, as may be formed of expanded metal. This arrangement is particularly advantageous when the electrode extends under the articles being processed whereby an induced air current may pass upwardly therethrough in the manner and for the purposes herein described. The advantage of the apertured electrode plate extending in a plane below the travel of the articles may well be appreciated when it is understood that the electrostatic forces may then be developed to be co-directional with the forces of gravity. This arrangement of the electrode plate below the articles results in the elimination of .flow lines, smoothing down the surface and facilitating the removal of gravity flowed tear drops.

A further advantage of the induced draft resides in its effect upon the coating material causing it to take a set simultaneously with the action of the electrostatic field in removing "tear drops," fatty edges and other gatherings of excess coating. This has the effect of preventing runs or additional accumulations thereafter.

Particularly in the case of hollow articles, we have found it is of advantage to remove the volatile gases entrapped therein. Otherwise the coating will remain fluid and not take its set during the processing. This difliculty is overcome by the induced draft directed into the interior of the article so as to dissipate the gases and permit timely setting of the coating.

The full nature of the invention will be understood from the accompanying drawings and the followin description and claims:

Fig. 1 is a diagrammatical illustration in perspective showing one method of coating the article before entering the electrostatic field. Fig. 2 is a diagrammatical illustration in perspective showing the articles entering and passing through the electrostatic field embodying the safety factors of this invention. Fig. 3 is a diagrammatical illustration in perspective showing the entrance gate with one type of circuit control mounted thereon. Fig. 4 is a schematic drawing showing the conveyor drive and control circuit. Fig. 5 is a modified form of that portion of the invention for directing air current past the coated articles.

For illustration, the invention is herein shown and described as applied to articles coated by dipping them in a bath of coating material such as lacquer. However, various other types of coating, such as paints, varnishes and similar finishes may be applied by dipping the article in a bath thereof or by spraying or the like. The invention is also described herein as applied to that type of apparatus wherein the articles are continuously conveyed through theelectrostatic field by a horizontally moving conveyor above the electrode, although the invention is similarly applicable to conveyors of the type wherein the article may be conveyed vertically through the electrostatic field with one or more electrodes spaced laterally therefrom.

As illustrated herein in Fig. 1, there is shown a clipping trough f containing a bath of coating in liquid form through which groups of articles I! are submerged and drawn. Said articles may comprise cylindrical shell casings to be lacquered, carried in groups or batteries suspended from a conveyor by hangers 2 through the medium of the hooks 3 engaging in the center percussion holes of the closed end of the casing, and wherein the open end of the casing is at the bottom. The hangers i2 are carried by a cross bar I4 having its ends supported by opposed conveyor chains l5 running in the channel iron tracks IS. The conveyor chains are driven in any suitable way. such as by the sprockets I! which in turn are driven through reduction gears i8 by an electric motor i9, whereby there would be a slow uniform movement of the articles through the bath, electrostatic field and drier.

As shown in Fig. 1, the conveyor tracks dip down so as to cause the oncoming articles to engage the forward end of the dipping trough and tilt downwardly into the bath so as to eliminate air pockets within the interior of the articles.

As shown in Fig. 2, the conveyor carries the articles from the dipping trough into and through the electrostatic field to effect removal of excess coating and tear drops. The passage of the articles through the electrostatic field is at such speed that they will remain in the field until the excess coating has been removed and that remaining on the articles has become sufficiently set to prevent further flow. Said field comprises essentially a high voltage electrode in the form of a wire mesh screen 20 which may besurrounded by a protective fencing 2|. The electrode is preferably of the width of the group of articles, and of a length predetermined by the time element above referred to. It receives a negative charge of high voltage through the power line 20a connected with one terminal of the power pack 22. The electrode is suspended by short insulators 23 from the channel iron tracks I6 at a predetermined distance below the lower end of the articles, such as will be efiective to create the desired field in connection therewith while sufficiently spaced to prevent a spark jumping the gap therebetween. The power pack 22 has its other terminal grounded as at 24, while the tracks I6 are similarly grounded. Thus, a circuit of high voltage created by the power pack is broken only by the gap between the articles l and the electrode 20, the articles receiving a positive charge in respect to the negative plate through the grounded track It, cross bar M, hangers l2 and hooks 3.

To prevent any possibility of an oversize article, hook or hanger causing an article so grounded to pass too closely to the electrode 20, there is provided a control member here shown as a trip bar 25, across the entrance gate 26 of the fence 2|. The trip bar extends across the gate in a plane sufiiciently spaced from the plane of the electrode to prevent any sparking between an article passing thereabove and the electrode. The trip bar is mounted to actuate a switch 21 contained in a switch box 28 which is in series with the master switch 29 in a control box 30. The switch 21 is normally closed, being opened only in event one of the articles strikes the trip bar 25. The switch then remains open until closed by removal of the oversize article. When opened, the circuit is broken through the power pack and the conveyor motor l9 so as to bring the operation to a stop until the condition is corrected. As shown in Fig. 4, the power pack 22 and motor I9 are connected in parallel and through the

switches

21, 29 with a source of power indicated at 3|. Similarly, the

switch

21 or 29 may be actuated by other known means for opening the. circuit through the power pack or motor as by a contact wire or electric eye." Also, in some instances if dripping from the articles interferes with the trip bar or the like by accumulation thereon, it may be positioned in advance of the dipping or coating operation instead of at the entrance to the electrostatic field.

Immediately below the articles H passing overthe electrode, as shown herein, there is positioned an apertured air duct 32 provided at one end thereof with a blower in the blower housing 33, driven by the motor 34 from a source of power indicated at 35. The apertures in the air duct are so arranged as to direct a forced draft of air upwardly with respect to the articles so as to dissipate any accumulation of explosive gases given off by the solvent of the coating material, whereby the electrostatic field will be kept clear of such gases.

In the modified form of Fig. 5, there is illustrated an arrangement whereby a natural draft is developed about the coated articles by passing them through a hood 40 open at the bottom and terminating at the top in a restricted passage or flue 4|. By reason of the restricted flue, in this case a single I-beam support it is provided by which the carrier 5 is conveyed and guided through the flue 4| by the rollers N1, the articles being suspended from the cross bar IN by hangers 2. A draft of air, indicated by arrows, may be drawn upwardly past the articles either by natural draft due to the flue 4| or by an exhaust fan connected at the outlet thereof, as-may be desired. Thus, any accumulation of volatile gases under and about the articles will be carried away so as not to present an explosive atmosphere between the articles and the electrode 20.

n the above described arrangements, an apparatus is provided in which the probability of sparking due to the high voltage of the electrodes is reduced to a minimum.

Another advantage is the elimination of gravity flowed tear drops, which permits of an improved finish on the coated article.

Still another advantage is the simplicity with which ignition hazards are reduced by the removal of solvent vapor accumulation from the electrostatic field.

The invention claimed is:

1. Apparatus for coating a series of articles with liquid coating material including an evaporating solvent capable of producing explosive gases, said apparatus comprising means for applying liquid coating to said articles, an electrode, means for establishing an electrostatic field between said articles and electrode, a conveyor for conveying said articles into said electrostatic -field past said electrode in predetermined spaced pl liquid coating to said articles, an electrode,

means for establishing an electrostatic field between said articles and electrode, a conveyor for conveying said articles into said electrostatic field past said electrode in predetermined spaced relation thereto, and means positioned at the entrance to said electrostatic field operable by one of said articles entering said field to render said apparatus inoperative where the path of travel of said article is such that upon entering said field it would so closely approach said electrode as to induce a spark therebetween.

3. Apparatus for coating a series of articles with liquid coating material including an evapof said articles entering said field to render said apparatus inoperative where the path of travel of said article is such that upon entering said field it would so closely approach said electrode as to induce a spark therebetween, and means for inducing a current of air directed past said electrode for dissipating and removing the accumulation of explosive gases.

4. Apparatus for coating a series of articles with liquid coating material including an evaporating solvent capable of producing explosive gases, said apparatus comprising means for applying liquid coating to said articles, an electrode, means for establishing an electrostatic field between said articles and electrode, a conveyor for conveying said articles into said electrostatic field past said electrode in predetermined spaced relation thereto, means positioned at the entrance to said electrostatic field operable by one of said articles ente said field to render said apparatus inoperative where the path of travel of said article is such that upon entering said field it would so closely approach said electrode as to induce a spark therebetween, an air duct positioned with respect to said electrode and articles to direct a current of air past said articles and away from said electrode to dissipate and remove any explosive gases accumulated therebetween, and a blower for forcing air through said duct.

5. Apparatus for coating a series of articles with a liquid coating material including an evaporating solvent capable of producing explosive gases. said apparatus comprising means for applying the liquid coating material to said articles, an elongated electrode, means for establishing an electrostatic field between said articles and electrode, a conveyor for continuously conveying said articles past said coating means into said electrostatic field and pastsaid electrode in spaced relation thereto, an electric motor for driving said conveyor, an electric circuit for controlling said motor and the means for establishing said field, and a member disposed at the entrance to said field operable by any one of said articles extending beyond a predetermined position with respect to said electrode for opening said "circuit and rendering the apparatus inoperative where said article would otherwise so closely approach said electrode as to permit of sparking therebetween.

6. Apparatus for coating a series of articles with a liquid coating material including an evaporatin'g solvent capable of producing explosive gases, said apparatus comprising means for applying the liquid coating material to said articles; an elongated electrode, means for establishing an electrostatic field between said articles and electrode, a conveyor for ccntinuously conveying said articles past said coating means into said electrostatic field and past said electrode in spaced relation thereto, an electric motor for driving said conveyor, an electric circuit for controlling said motor and the means for establishing said field, and a switch control member mounted at the entrance to said field in a plane of predetermined spaced relation to the plane of said electrode operable by any one of the articles extending beyond said plane to open said circuit and render the apparatus inoperative.

7. Apparatus for coating articles with a liquid coating material, said apparatus comprising means for dipping said articles in a bath of said coating material, means for conveying said dipped articles over a predetermined path with I said coating material in a liquid state, an openwork electrode plate extending in a plane below and spaced from the path of travel of said articles, and means for establishing an electrostatic field between said articles and electrode plate whereby the electrostatic forces of said fieldare substantially co-directional with the forces of gravity for effecting an even downward flow of said liquid coating material and the removal of excess material accumulating at the bottom of said articles.

8. Apparatus for coating articles with a liquid coating material embodying an evaporating solvent adapted to give off explosive gases, said apparatus comprising means for dipping said articles in a bath of said coating material, means for conveying said dipped articles over a predetermined horizontal path with said coa ing material in a liquid state, an o enwork electrode plate extending in a plane below and s aced from the path of travel of said articles. means for establishing an electrostatic field between said articles and electrode plate whereby the electrostatic forces of said field are substantially co-directional with the forces of gravitv for effecting an even downward fiow of said liouid coating material and the removal of excess material accumulating at the bottom of said articles, and means for inducing an u wardly directed current of air through said electrode about said articles while being conveyed through said field for removingof said'coating by force of gravity, an openwork electrode disposed below and in spaced relation to the path of travel of said articles over the plane or which they are adapted to pass during their travel through said space, and electrical means for providing an electrostatic force be-- tween said articles and electrode capable of establishing an electric force in addition to the force of gravity for drawing excess liquid coating material downwardly from said articles.

10. Apparatus'for coating articles comprising means for applying a liquid coating material to the surface thereof, means operable to convey said articles through space to permit drainage of said coating by force of gravity, a horizontally disposed openwork electrode mounted to extend below and in spaced relation to the path of travel of said articles, and electrical means 'for providing an electrostatic force between said articles and said electrode capable of establishing an electric force exerted in the same direction as the force of gravity and in addition thereto drawin excess liquid coating material downwardly from said articles.

11. Apparatus for coating articles comprising a tank containing a bath of coating material, a conveyor operable to submerge said articles in said bath and thereafter convey them beyond said tank, an openwork electrode spaced from said tank extending in a plane below and in spaced relation to the path of travel of said articles, and electrical means for providing an electrostatic force between said electrode and articles capable of drawing excess liquid coating material downwardly therefrom.

12. Apparatus for coating a series of articles with liquid coating material including an evaporating solventcapable of producing explosive gases, said apparatus comprising means for applying liquid coating to said articles, an electrode, means for establishing an electrostatic field between said articles and electrode, a convent adapted to give off explosive gases, comprising means for bathing said articles with said material, means for suspending said bathed'articles with said coating material in a liquid state, an openwork electrode plate extending in a plane below and spaced from said articles, means for establishing an electrostatic field between said articles and electrode plate, whereby the electros atic forces of said field cooperate with the forces of gravity for effecting an even flow of said liquid coating material over the surface of said articles, and means for inducing an upwardly directed cu rent of air past said electrode and about said articles while suspended in said field for removing and dissipating accumulated gases to permit timely setting of said coating material.

14. Apparatus for coating articles with a liquid coating material, said apparatus comprising means for bathing said articles with said coating material, means for suspending said articles while said coating material is in a liquid state, an electrode extending in a plane below and spaced from said articles, means for establishing an electrostatic field between said articles and electrode,

one or more insulators attached to said electrode,

and supporting means to which said insulators are in turn attached, the point of attachment of each insulator to said supporting means being located above the lower portion of said articles, whereby at least that portion of each insulator adjacent said supporting means will be out of the path and free of accumulation of such coating material as may be removed from said articles by the forces of said electrostatic field and gravity.

15. Apparatus for coating an article with a liquid coating material embodying a volatile solvent, said apparatus comprising means for applying an excess of the coating material to the article, an electrode, a conveyor for conveying said article through association with said applying means and then past and in spaced relation to said electrode while said coating is still in a liquid state, means for establishing an electrostatic field between the electrode and article as the latter moves past the electrode, and means for creating an air stream flowing through said field to remove volatilized solvent therefrom.

16. Apparatus for coating a series of articles with liquid coating material including a volatile solvent capable of producing explosive gases, said apparatus comprising means for applying liquid coating to said articles, an electrode, means for establishing an electrostatic field between said articles and electrode, a conveyor for conveying said articles into said electrostatic field past said electrode in predetermined spaced relation thereto, a power-source for said field-establishing means and conveyor, switch means associated with said power source, and a switch-operating means connected to said switch and disposed at the entrance to said field for actuation by one of said articles when it is positioned to extend beyond a predetermined position relative to said electrode for rendering the apparatus inoperative when said article upon entering said field would so closely approach said electrode as to induce a spark therebetween.

17. Apparatus for coating articles with a liquid coating material including an evaporating solvent adapted to give off explosive gases, said apparatus comprising means for dipping said article in a bath of said coating material, an electrode, means for establishing an electrostatic field between said article and electrode, said first mentioned means acting to convey said article into said electrostatic field past said electrode in predetermined spaced relation thereto, a powersource for said field-establishing means and said first mentioned means, switch means associated with said power source, and a switch-operating means connected to said switch and disposed at the entrance to said field for actuation b one of said articles when it is positioned to extend beyond a predetermined position relative to said electrode for rendering the apparatus inoperative when said article upon entering said field would so closely a proach said electrode as to induce a spark therebetween,

18. Apparatus for coating a series of articles with a liquid coating material including a volatile solvent capable of producing explosive gases. said apparatus comprising an e ongated electrode, means for establishing an electrostatic field between said article and electrode, a container for a supply of liquid coating material, a conveyor for carrying said articles through said supply of coating material into said electrostatic field and past said electrode in spaced relation thereto, an electric motor for driving said conveyor, an electric circuit including a switch for controlling said motor and the means for establishing said field, and a switch control member mounted at the entrance to said field in a plane of pedetermined spaced relation to the plane of said electrode 5 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Number Name Date Wintermute ..C Sept. 12, 1939 Meston etal. Sept. 26, 1939 FOREIGN PATENTS Country Date British Feb. 28, 1939