US2544806A - Electrostatic coating apparatus - Google Patents

Description

March 13, 1951 E. M. RANSBURG 2,544,806

ELECTROSTATIC COATINGAPPARATUS Filed Nov. 19, 1945 INVENTOR. -H.V. EDWIN M. RANSBURG 3 To ELECTRODE BY Patented Mar. 13, 1951 ELECTROSTATIC COATING APPARATUS Edwin M. Ransburg, Indianapolis, Ind., assignor, by direct and mesne assignments, to Ransburg Electro-Coating Corp, Indianapolis, Ind., a corporation of Indiana Application November 19, 1945, Serial No. 629,608

This invention relates to the treatment of articles in an electrostatic field and relates, in particular, to an improved apparatus for preventing hazardous conditions in the treating zone.

In the treatment of articles in an electrostatic field the voltage used and spacing of electrodes to articles is such as to avoid development of a spark between the electrodes and the articles being treated. A reduction of the spacing used for effective treating or the articles may result in a spark, and breakdown of the electrostatic field in the vicinity of the spark that would interfere with proper treatment of the article, and might also ignite any inflammable vapors in the vicinity. This might occur, for example, if an object which is being treated or an extraneous object falls on to the electrode and reduces the distance between the electrode and the objects being treated to that at which a spark would occur, or creates a physical obstruction to the passage of objects to be treated through the treating zone.

An object of this invention is to provide an apparatus for electrostatically treating articles on a conveyor which is constructed to stop operation of the conveyor, with or without deenergizing the electrostatic field when an abnormal condition occurs in the treating zone.

Another object of this invention is to provide an apparatus for electrostatically treating articles in which a warning signal is actuated when an abnormal condition occurs in the treating zone.

Another object of this invention is to provide an apparatus for electrostatically treating arti-- cles in which the occurrence of an abnormal condition in the treating zone deenergizes an electrical circuit.

A further object of this invention is to provide an apparatus for electrostatically coating or detearing objects which embodies a mass actuated switch to stop the conveyor carrying the articles to be treated, deenergize the electrodes and actuate a signal when an object falls on the electrode, or may accomplish any one or all of the above functions.

The invention will be described in greater detail in connection with the accompanying drawings in which is illustrated preferred embodiments of the invention by way of example, and

wherein:

Figure 1 is a perspective view of an electrostatic coating apparatus embodying my invention,

Figure 2 is a cross sectional view of a detail, .1 Figure 3 is a wiring diagram of the electric cir- 9 Claims. (Cl. 91-18) 2 cuit for the embodiment illustrated in Figure 1, and

Figure 4 is a perspective view of a modification embodying m invention.

Referring to Figure 1 there is schematically shown a conveyor in of any suitable construction on which the articles l l to be treated, shown here as cylindrical containers, are supported by suitable hangers l2. Any suitable atomizing means !3, shown here schematically, may be employed such as, for example, a type employing converging air and liquid streams, and such atomizing means is arranged in a suitable position adjacent the articles to direct a stream of finely divided coating material toward the articles. An electrode frame l4, shown in the preferred embodiment as comprised of the rectangular panels [5, l6, and IT made of metal bars welded into a channel shape, is sufiiciently rigid to support a plurality of spaced wires I8, Which are preferably stretched taut on the frame. The electrode frame 14 is supported by four insulator rods I9 suitably secured thereto. The upper ends of rods l9 are. associated with suitably supported switch mechanisms 20 to be later described.

7 In the modification shown in Figure 1 the taut wires it constitute ionizing electrodes and are maintained at a suitable potential difference with respect, to the articles to be treated. However, the electrodes may assume any form which produces. an ionizing discharge at the potential employed. The conveyor I0 is preferably suitably grounded but, if desired, it may be suitably insulated from ground and connected to the terminal of the electric supply of opposite polarity to the electrodes. The apparatus may be surrounded by a suitable booth (not shown) The articles I l to be coated are carried through the coating zone on the conveyor Ill, and atomizing means 13 directs a stream of finely divided material into the electrostatic zone to deposit the In normal op-' coating material on the articles. erating arrangement the articles are spaced at a distance from the electrodes farther than that at which a spark will occur, but if this distance is accidentally reduced so that a spark occurs,

the spark will cause a breakdown of the elec- Referring to Figure 2, a cylindrical member 2| has a threaded extension 22 passing through a hole 23in a fixed member 24 which may be apart of a spray booth or other supporting structure. -A nut 25 threaded on the end of the ex- The means for eliminating the assasoe tension 22 clamps cylindrical member 2i and plate 29 to the top of the spray booth. Switch housing 29 is secured above the nut at the top of the spray booth by screws 28 passing through spacer 29 and screwed into the switch housing, and. lead wires 34 and 35 connect the switch con tacts to the terminals of an electric power supply. Push rod 39 passes through the extension 22 into engagement with a spring pressed plunger 39 to actuate the switch contacts. The switch 29 is of a known construction in which a small movement of the switch contacts, on the order of a thousandth of an inch, opens or closes an electrical circuit, and the details of construction therefore need not be described.

Push rod 39 passes through a gland 40 which is threaded into a screw threaded aperture M on the inside of the cylindrical member 26, and a compression spring 42 abuts at one end against the upper fiat surface of gland 40 and at the other end against the lower fiat surface of a flange 43 on push rod 39 to urge the rod upwardly against plunger 39 and hold the switch contacts in engagement. The sensitivity of the apparatus may be adjusted by turning gland 49. When the bias of spring 42 is increased, a greater pull is necessary to pull rod 38 to open the contacts in switch housing 29, and when the bias of spring 42 is decreased a lesser pull is necessary to pull down rod 38 to open the switch contacts. end of rod 38 is suitably secured to insulator posts l9, as by a screw threaded connection (not shown), and if desired, a skirt 45 may be provided on the gland 49 surrounding the insulator post l9 to prevent deposition of material on the rod 38.

Referring now to the wiring diagram in Figure 3 there is shown diagrammatically a pair of power supply lines 5| and 52 to which is connected lead wire 34 to a switch mechanism 20. There are four switch mechanisms 20 arranged in series so that the opening of any one of them will deenergize a common electrical circuit, and the action of only one switch mechanism need be described in detail. Lead wire 35 connects a switch 20 with one terminal of a relay having a solenoid 54, the other terminal of the solenoid being connected by wire 55 to a switch contact 51. A contact member 58 on the rod 59 of the core 69 bridges contacts 51 and GI, the latter contact being connected by a wire 62 and normally closed manual switch 63 to the supply line 52. Switch 63 is provided to enable the operator to manually cut off the high voltage supply if desired. When switches 20 are closed the current through 5016-. noid 54 attracts the core 69 to the left to hold switch member 58 against contacts 51 and 6!, against the bias of a spring 65. A pair of switch members 61, 61 on rod 59 is held in contact with the terminals 68, BB, and 69, 69' in the supply line H of the high voltage pack l2. A starting push button switch 15 is provided which is connected by wires 16 and 55 to the terminal of solenoid 54. If desired, the conveyor motor 18 may be connected by wires 80 and 8| into the supply lines ll of the high voltage power pack to be responsive to switch members 61, 61, or if desired a separate switch may be employed for this purpose. Also, if desired, an alarm actuating switch member 89 may be provided, which upon movement to the right bridges contacts 9! and 92 connected by wires 93 and 94 tov the power supply, and containing a suitable alarm signalling device 95.

The operation of the apparatus decribed is as The lower 4 follows: When an object falls on the yieldingly supported electrode frame, its weight will exert a downward pull on one of the insulator posts l9 which is transmitted to rod 38 against the bias of spring 42, and rod 38 is thus drawn away from plunger 39 to allow switch 20 to open. This opens the holding circuit of the solenoid 54 which is thus deenergized and allows spring 65 to open switch contacts 61 and 61 which opens the supply line H to the power pack 12 to cut off the voltage supply to the electrode l4. At the same time the power circuit 1 I, 80, and 8| of the conveyor motor is opened to stop operation of the conveyor. Movement of rod 59 to the right also closes switch contacts 89, 9|, and 92 to actuate the alarm device 95. The potential of the electrode having been reduced to a safe value, the operator can remove the object from the electrode, which allows the rod 38 to move into contact with plunger 39 to close the switch 20. To resume operation push button 15 is depressed to close the actuating circuit of solenoid 54 through wires 16, 55, 35, switches 20 and wire 34, to pull core 60 to the left thus closing switch contacts 58, 61, and 61, open the alarm circuit and to restore the electrode power supply circuit and conveyor to normal operation condition.

If it is desired to only partially deenergize the electrode the relay may be provided with a sec-- ond set of contacts engageable by switch members 61, 61' whichthrows a high resistance into the supply circuit for the high voltage pack 12 to reduce the electrode potential to a safe value. The relay illustrated herein is one example of various mechanical or electronic control devices which may be employed to partially or completely deenergize the electrodes or the conveyor motor, or to actuate an alarm circuit. It is to be understood that reduction of the potential of the electrode to a value such that sparking will not occur, or which will enable the operator to remove the body causing actuation of the alarm without danger, is contemplated within the meaning of the term deenergizing.

In the modification illustrated in Figure 4, a detearing apparatus comprises an expanded metal plate 96 constituting an electrode which is maintained at a suitable potential difference with respect to the articles H to be deteared. If desired, an imperforate plate may be used for this purpose. A body falling upon the electrodeor excessive accumulation of paint or the like thereon will open a switch 29' to cut off the high voltage supply to the electrode, as described in connection with the wiring diagram in Figure 3.

It is apparent that the alarm device 95 and its circuit may be omitted if desired, also, if desired, wires 89v and Bi may be directly connected to the power supply lines 5! and 52. Variou other modifications may be made inthe structure and arrangements shown withoutv departing from the invention.

I claim:

1. Apparatus for electrostatically treating an article comprising a support for the article, an electrode movably mounted in spaced relation to the article, means for creating an electrostatic.

field between the article and the electrode, and means operatively associated with said fieldcreating means and being responsive to a predetermined movement of said electrode for deenergizing said field.

2. Apparatus for electrostatically coating an article comprising a support for an article, an electrode, yielding means for supporting said electrode in spaced relation to the article, means for creating an electrostatic field between said electrode and the article, means for introducing finely divided coating material to the electrostatic field, and an electric switch mechanism operatively associated with said field-creating means and said yielding support means and being responsive to a predetermined yielding 01 said support means for de-energizing said field.

3. Apparatus for electrostatically detearing an article comprising mean for applying an excess of liquid coating material to the article, a support for the article coated with excess material, an electrode yieldingly supported in spaced relation to the article, means for creating an electrostatic field between the article and said electrode of sufficient strength to remove excess liquid coating material from the article, and means operatively associated with said fieldcreating means and being responsive to a predetermined yielding of said electrode for de-energizing the electrostatic field.

4. Apparatus for electrostatically treating an article comprising a support for an article, an electrode spaced from the article, a yielding support for said electrode, a high voltage source for creating an electrostatical field between the article and said electrode, an alarm mechanism, and means operatively associated with said high voltage source and said alarm mechanism and being responsive to a predetermined yielding of said support for de-energizing said field and actuating said alarm mechanism.

5. Apparatus for electrostatically treating an article comprising a conveyor to carry the artrode spaced from said conveyor, the improveport and responsive to a predetermined move ment of said electrode for stopping said conveyor.

7. An apparatus for electrostatically treating an article comprising a conveyor for moving the article, an electrode yie-ldably supported in spaced relation to the article, mean for creating an electrostatic field between the article and said electrode, and means operatively associated with said conveyor, said field-creating means and said electrode and being responsive to a predetermined yielding of said electrode for ole-energizing said field and stopping said conveyor.

8. In apparatus for electrostatically treating an article including a conveyor for moving the article over a predetermined path and an electrode spaced from said conveyor, the improvement which comprises movable support for said electrode, an alarm mechanism and means operatively associated with said conveyor, said movable electrode support and said alarm mechanism and being responsive to a predetermined movement of said electrode for stopping said conveyor and actuating said alarm mechanism.

9. In apparatus for electrostatically treating an article includin an electrode spaced from the article and means including an electric circuit for establishing an electrostatic field between the article and said electrode, the improvement which comprises a support for yieldably support ing said electrode, a normally closed switch in said circuit operable to render said field-establishing means inoperative, and means responsive to a predetermined movement of said electrode for opening said switch.

EDWIN M. RANSBURG.

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

UNITED STATES PATENTS Number Name Date 148,459 Homan Mar. 10, 1874 2,247,963 Ransburg et al. July 1, 1941 2,359,476 Gravley Oct. 3, 1944 2,417,798 Ransburg et a1. Mar. 18, 1947

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