US2655128A

US2655128A - Electrostatic coating apparatus

Info

Publication number: US2655128A
Application number: US196374A
Authority: US
Inventors: Edwin M Ransburg
Original assignee: Ransburg Corp
Current assignee: Ransburg Corp
Priority date: 1946-03-16
Filing date: 1950-11-18
Publication date: 1953-10-13
Anticipated expiration: 1970-10-13

Description

Oct. 13, 1953 E. M. RANSBURG 2 ELECTROSTATICE COATING APPARATUS Original Filed March 16, 1946 INVENTOR.

EDWIN M. RANSBURG By 16%;, ga -w ATTORNEY atented Oct." 13, 1953 by mesne assignments, to Ransburg Electro- Coating Corp., Indianapolis, Ind., a corporation of Indiana Original application March 16, 1946, Serial No.

654,830. Divided and this application November 18, 1950, Serial No. 196,374

3 Claims. 118-51) This application is a division of my application Serial No. 654,830, filed March 16, 1946, which is now abandoned.

This invention relates to the coating of articles in an electrostatic field and more particularly to a means for supporting and maintaining the article as a terminal of the electrostatic field during the coating process.

In electrostatic coating apparatus in which the article to be coated is supported on a, grounded conveyor and is moved past a high potential electrode while liquid coating material is sprayed into the zone surrounding the article, it is desirable that a good electrical contact between the article and conveyor be maintained. As any given support for articles is repeatedly returned to the electrostatic coating field, it accumulates over a period of time a considerable coating of paint, which may prevent proper electrical contact of subsequent articles therewith. Also when the support passes through the coating zone without any item hung thereon, the contacting portion thereof may become coated. This prevents proper electrical contact between the article and conveyor which not only interferes with proper coating, but also may allow the article to accumulate a capacity charge which may raise the potential of the article high enough above ground potential to cause a spark to the grounded conveyor, and create a fire hazard.

An object of this invention is to provide electrostatic coating apparatus for applying a liquid coating material to articles in which the articles are always maintained as one terminal 01' an electrostatic field.

Another object of this invention is to provide a support for an article in an electrostatic apparatus which insuresthat there is at all times during the coating process a positive electrical connection between the article and a terminal of an electric circuit.

Another object or this invention is to provide a support for an article in an electrostatic coating zone, which has a portion shielded to prevent deposition-of coating material thereon.

Another object of the invention is to provide in an electrostatic coating apparatus a support for an article to be coated which resiliently maintains an electrical connection therewith.

Another object of the invention is to provide in an electrostatic coating apparatus a support for an article to be coated that is so shaped that the material accumulated on the contact portion thereof will be held to a minimum.

2 greater detail in connection with the accompanying drawings in which are illustrated a preferred embodiment of the invention by way of example, and in which:

Fig. 1 is an elevation of an electrostatic coating apparatus embodying an overhead conveyor,

Fig. 2 is an elevation of the hook support shown in Fig. l,

Fig. 3 is a cross sectional view taken on line III-III of Fig. 2;

Fig. 4 is a perspective view of a further modification illustrating a modified form of conveyor,

Fig. 5 is a perspective view of a detail of Fig. 4,

Fig. 6 illustrates a further modification in perspective, and

Fig. '7 is a perspective view of a detail of Figure 6.

Referring to Figure 1, a plurality of insulator posts I, suitably support electrode frames 2 and 3 in any suitable arrangement. Each electrode frame carries a plurality of fine wires, for example, as illustrated in Figure 4 of the application of Harold P. Ransburg, Serial No. 589,719 for Method for Coating Articles, filed April 23, 1945, now Patent No. 2,567,781, dated September 11, 1951. The frames are secured together by bottom electrode portion 6. The electrode wires are maintained by any suitable means, such as high voltage source 5, at a high electrical potential of the order of one hundred thousand volts and the conveyor chain is grounded as at 4.

I-beam Ill which provides a track for a trolley Ill and a bar 12 depending from the trolley is engaged by a conveyor chain l3 by which it is moved. An article support, indicated generally at I4 depends from chain l3 and is preferably in the form of a V-shaped metal hook having on the inner surface a sharp edge l8 (Fig. 2) which has a radius on the order of less than about 3 2 inch. The bail l9 secured to the article 2|, is inserted into the hook H and rests on sharp edge l8 at 22 and 23 (Figs. 2 and 3).

A spray nozzle 24 of any suitable type is sup ported to introduce into the electrostatic field between the article and electrodes, a stream of finely divided material, such as a settable finishing fluid, preferably accompanied by a carrierair stream, which is electrostatically deposited upon the surface of the article 2| and the bail I9. By reason of the sharp edges of the hook it engaging the bail at 22 and 23, a good electrical connection therewith to ground is established. The sharp edge l8 remainsrelatively tree or paint e present invention W111 be dumbed in 5 even when the hook is not loaded with an article,

- 3 due to the ionizing action 01' the sharp edge in the electrostatic field and the tendency oi the liquid coating material to draw away from the ed e. a

In the modification illustrated in Figures 4 and 5, the overhead conveyor illustrated in Figure 1 is replaced by the conveyor I8 having spindles II extending upwardly therefrom, each spindle carrying a pulley I2 which is rotated by a traveling belt 18 or the like. The spindle Ii at its upper end carries a member of any suitable shape, shown as a metal plate 14 having cut out portions 18 and I8 which are crimped outwardly to form spring fingers l1 and I8. .The object 11- lustrated to be coated is a Jar cap 8| having a threaded flange 82 and a cap liner 88 of insulation material which prevents the top of plate [4 from contacting the top of cap 8|. However. when the cap is placed over the plate H, the fingers I1 and I8 resiliently engage the threaded flange 82 on the interior and make electrical contact therewith. The resiliency of the fingers enables the cap to be easily removed from the support.

In the modification illustrated in Figures 6 and '7 the spindle H carries at its upper end a plate 88 having located about its edge a plurality oi positioning pins 81. At the center or the plate there is suitably secured, as by soldering thereto, a spiral spring 88, the end of which may be pointed as indicated at 88. The object illustrated is a cake cover 8| to be coated on the exterior surface and remain uncoated on the interior. The cake cover 8| is placed upon the plate 88 and is more or less centered by the pins 81 on the interior thereof, while the spring 88 makes electrical contact with the cake cover. The disc portion 88 closes up the interior of the cake cover and prevents the entrance of coating material thereto. The spring 88 ispointed at 88 to present to the field an ionizing point which produces a corona discharge when not covered by an article. In this manner the point 88 which is the contact portion of the support will remain substantially free of coating material and insure good electrical contact between the support and the article to be coated.

The invention may be embodied in various other forms without departing from the spirit or scope thereof.

I claim:

1. In apparatus including a voltage source for electrostatically coating an electrically conducting article by exposing it to a spray of charged particles in a coating zone, the combination of a .rigid support, a plurality oi article-engaging portions carried by said support, resilient means acting between two of said portions and urging them apart when both engage the article, said article-enga ing portions including one which is rigid and rigid with the support to locate the article relative to the support; one 01' the two portions between which said resilient means acts being electrically conductive and connected to said voltage source to maintain the article at an electrical potential substantially diilerent from that of the charged particles.

2. The invention set forth in claim 1 with the addition that said rigid portion is a member adapted for reception in a hollow article, the two first mentioned portions being the free ends of resilient fingers mounted on opposite sides or said rigid portion.

3. In apparatus including a voltage source for electrostatically coating an electrically conducting article by exposing it to a spray of charged particles in a coating zone, the combination of a rigid support having a rigid portion adapted to support an article from below, a resilient member carried by said support and having a, free end engageable with an article so supported and movable downwardly by the weight of the article, rigid abutment means on said support en-- gageable with the article to locate it relative to the support, said resilient means being electrically conductive and connected to said voltage source to maintain the article at an electrical potential substantially diiierent from that of the charged particles.

EDWIN M. RANSBURG.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 412,853 Keene Oct. 15, 1889 770,399 Strutz Sept. 20, 1904 2,247,963 Ransburg et a1 July 1, 1941 2,401,415 Duggan June 4, 1946 2,553,724 Ransburg May 22, 1951