US3890504A

US3890504A - Adjustable corona discharge electrode

Info

Publication number: US3890504A
Application number: US451570A
Authority: US
Inventors: Pyam Pendleton; Myron R Waldman
Original assignee: WALCO SYSTEMS Inc
Current assignee: WALCO SYSTEMS Inc
Priority date: 1973-02-27
Filing date: 1974-03-15
Publication date: 1975-06-17
Anticipated expiration: 1992-06-17

Abstract

An electrode assembly utilized in the electrical surface treatment of a material having a conductive belt of varying width. The belt is capable of being rotated to a predetermined position in accordance with the width of the material treated. In operation a corona discharge takes place only along that portion of the belt adjacent the material being treated.

Description

United States Patent Pendleton et al.

ADJUSTABLE CORONA DISCHARGE ELECTRODE Inventors: Pyam Pendleton; Myron R.

Waldman, both of Warwick, RI.

Walco Systems, Inc., Providence,

Filed: Mar. 15, 1974 Appl. No.: 451,570

Related US. Application Data Continuation of Ser. No. 336,203, Feb. 27, 1973, abandoned.

Assignee:

U.S. Cl. 250/325; 250/324; 317/262 A Int. Cl G03g 15/00 Field of Search 250/324, 325; 317/262 A References Cited UNITED STATES PATENTS 5/1965 Brandt et al. 250/324 VOLTAGE SOURCE June 17, 1975 3,291,711 12/1966 Moyer 204/165 3,334,227 8/1967 Cipriani 250/324 3,348,022 11/1967 Schirmer..... 3,397,136 8/1968 Balogh 3,409,537 11/1968 Cannon 3,419,489 12/1968 Delaney 3,578,970 5/1971 Michand 250/325 Primary Examiner-James W, Lawrence Assistant ExaminerB. C. Anderson Attorney, Agent, or FirmR0bert T. Dunn 5 7] ABSTRACT An electrode assembly utilized in the electrical surface treatment of a material having a conductive belt of varying width. The belt is capable of being rotated to a predetermined position in accordance with the width of the material treated. In operation a corona discharge takes place only along that portion of the belt adjacent the material being treated.

9 Claims, 5 Drawing Figures PATENTEDJUN 17 I975 3; Y

VOLTAGE SOURCE VOLTAGE SOURCE VOLTAGE SOURCE ADJUSTABLE CORONA DISCHARGE ELECTRODE This is a continuation of application Ser. No. 336,203 filed Feb. 27, 1973, now abandoned.

This invention relates generally to the electrical surface treatment of materials by Corona Effect, and, more particularly, to an adjustable electrode for use therewith.

It is common knowledge that some materials such as polyolefins, ie., polyethylene, polypropylene, etc., do not have the chemical structure to readily accept adhesives and inks including the newer types of tulol inks used in high speed presses. Furthermore, difficulties have been encountered in bonding processes such as extrusion coating and laminating processes. It has therefore been necessary to first pre-treat such materials. There are various methods by which this can be done, all of which alter the surface of the material processed to make it more receptive to inks, adhesives,

coating materials or the like. The most common of suchmethods is the Corona Effect method.

In the corona treating of plastic film and other web materials, two electrodes are utilized and so positioned that the plasma formed therebetween passes through the material being treated. Usually one electrode is in the form of a grounded metal roll covered with any suitable dielectric material and the other electrode is in the form of a metal bar spaced axially over the roll or first electrode. The material being treated is passed be tween the two electrodes making intimate contact with the roll. There is usually an air gap of approximately one-eighth inch between the surface of the material on the dielectric coated roll and the metal bar electrode.

One of the major problems with the equipment utilized in a Corona Effect method as set forth hereinabove is that materials of varying widths can not be properly treated. It is desireable that during the treatment of the material, the active width of the metal bar electrode conforms to the width of the material being treated. Such an arrangement avoids discharge from the electrode passing outside the material and causing damage to the electrode, and further avoids the discharge from missing the edge portions of the materials. In addition, it is sometimes necessary to treat only a certain segment of the material, and such treatment is virtually impossible with the electrodes heretofore in use.

In the past, complex systems such as shown in U.S. Pat. No. 3,334,227 have been utilized in adjusting the length of the active electrode. However, as is quite evident, such an arrangement is highly complex in construction and still fails when it becomes necessary to selectively treat portions of the material. It has become essential in the field to develop an adjustable electrode which is not only inexpensive to construct, but also highly reliable in operation as well as being capable of selectively treating portions of the material.

The instant invention sets forth an adjustable electrode assembly for a Corona Discharge method which overcomes all the problems set forth hereinabove. In this invention the metal bar electrode of the past is replaced with the adjustable electrode assembly of this invention which may take on any of a variety of configurations all within the scope of the invention.

The arrangement of an embodiment of the present invention utilizes a belt of wire mesh or sheet material cut on a bias. The shape of the belt when laid flat may resemble, for example, a truncated triangle. This belt is fixedly secured to the surface of a non-conductive roller. The roller with the belt thereon replaces the conventional metal bar electrode, with the material to be treated passing between the electrode of this invention and a roll as heretofore in existence. Depending upon the width of the material to be treated, the roller containing the belt electrode of this invention can be rotated until the proper width of the belt is juxtaposed the material passing therebeneath. The Corona Discharge effect now properly takes place.

When a greater adjustability is required with the electrode assembly of this invention, the belt electrode may be enlarged and placed over two parallel spaced rollers or one roller and a stationary bearing member. The width of the belt adjacent the material to be treated changes as the roller or rollers are rotated. The belt surface over the length of one of the rollers acts as the electrode (metal bar) if the roller or bearing surface guiding it is of a dielectric material.

If it becomes further necessary to treat only a preselected portion of a material, the interior configuration of the belt may be selected accordingly so that the electrode is of any desired configuration.

It is therefore an object of this invention to provide -a Corona Discharge electrode which is capable of being readily adjusted;

It is another object of this invention to provide a Corona Discharge electrode which takes on a preselected configuration;

It is a further object of this invention to provide a C0- rona Discharge electrode assembly which is economical to produce, highly reliable in operation and which utilizes conventional, currently available components that lend themselves to standard mass producing manufacturing techniques.

For a better understanding of the present invention together with other and further objects thereof, reference is made to the following description taken in conjunction with the accompanying drawings and its scope will be pointed out in the appended claims.

FIG. 1 represents a pictorial view of one embodiment of the adjustable Corona Discharge electrode assembly of this invention;

FIG. 2 represents a front view of another embodiment of the adjustable Corona Discharge electrode assembly of this invention;

FIG. 3 represents a front view of a further embodiment of the adjustable Corona Discharge electrode assembly of this invention;

FIG. 4 represents a plan view of a modified belt utilized with the adjustable Corona Discharge electrode assembly of this invention; and

FIG. 5 represents matching shapes of the conductive belt and workpiece for an embodiment where the belt and workpiece move together.

Reference is now made to FIG. 1 of the drawing which illustrates a preferred embodiment of the adjustable electrode assembly 10 of the instant invention.

The apparatus for producing a Corona Effect for the treatment of the workpiece 12 which may be a web of suitable material, is made up of any suitable propelling means 14 which is usually in the form of a grounded metal roll 16 covered by any suitable dielectric material 18. The adjustable electrode assembly 10 of this invention comprises a belt electrode 20 in the shape of a truncated triangle when laid flat or of any other configuration of varying width. In addition, belt is made of any suitable conductive material such as a flexible sheet of metal foil or wire mesh. In position, belt 20 fixedly encompasses roller 22 which is made of any suitable non-conductive material as shown in FIG. 1.

Any conventional electrical source 21 is connected to belt 20 by brush 22 or the like to provide sufficient electrical energy to produce a corona discharge between electrode or belt 20 and grounded roll 14. This discharge is limited to the width W of belt 20 which varies as roller 22 is rotated. Any suitable driving means such as a manual hand crank 24 (FIG. 1), stepper motor 26 (FIG. 2) or pneumatic motor 28 (FIG. 3) may be operably connected to roller 22 to provide movement thereof. When the appropriate width W of belt 20 is directly adjacent a web of material of width w any satisfactory locking mechanism such as pin 30 in conjunction with apertures 32 may be utilized to fixedly secure belt 20 in position. The plasma formed between belt electrode 20 and grounded roll 14 is thereby limited by the length W of belt 20. Furthermore, the effective size of electrode 20 may be altered even with the Corona Effect apparatus in operation.

If it is found that belt 20 shown in FIG. 1 is of insufficient size to produce the desireable width W for the electrode, the instant invention may take the form shown in FIGS. 2 and 3 of the drawing. In the embodiment shown in FIG. 2 adjustable electrode assembly 11 incorporates a belt 40 therein made of the same material and configuration as belt 20 shown in FIG. 1, but larger in size. Belt 40 is therefore secured around a pair of

rollers

42 and 44, respectively, as shown in FIG. 2 or a roller 42 and suitable stationary bearing 46 as shown in FIG. 3. Although roller 42 and bearing 46 are interchangeable, it is essential in the embodiments shown in FIGS. 2 and 3 that the roller 44 or bearing 46 adjacent web 12 and roll 14 be ofa non-conductive material. Upper roller 42 may either be made ofa conductive material as shown in FIG. 2 or of a non-conductive material utilized with a suitable electrical connector such as brush 48 as shown in FIG. 3.

In FIG. 2 a conventional stepper motor 26 drives any suitable arrangement such as belt and pulleys 50 in order to rotate belt electrode 40. FIG. 3 illustrates a conventional pneumatic motor 28 directly driving roller 42. It should be noted that all driving means 24, 26 and 28 are interchangeable with one another as well as capable of being substituted for by other conventional driving means. In these embodiments, however, it is es- "sential that some stop means be utilized to fixedly secure belt electrode 20 or 40 in a desired position. Furthermore, in the embodiment shown in FIG. 3, it should be noted that roller 42 can be replaced with bearing 46 as long as the member adjacent roller 41 is a nonconductive material.

FIG. 4 illustrates a belt 60 similar to belts 20 and 40 which is made of any suitable conductive material. Belt 60 can be mounted on any of the apparatus shown in FIGS. 1 to 3 and is utilized when only preselected portions of a material are to be treated-For example, if it is desirable to treat only the perimeter of a web, a cutout portion 62 of any desired shape is formed within belt 60. This cut-out 62 may be of the design shown in FIG. 4 but may be of any other configuration required in a specific treating operation.

The use of embodiments of the present invention shown in FIGS. 1 to 4 and described above provides for positioning the conductive belt electrode to place a portion thereof at the width W of the belt on stationary position with respect to the grounded metal roll elec-' may be moved in synchronism with the workpiece during the treatment, in such a manner that the portion of the belt positioned opposite the grounded roll electrode is the same width as the portion of the workpiece therebetween. This use is illustrated in FIG. 5 which shows a representative shape of belt 63 and workpiece 64 having the same shape. The motor drive 65 drives the

rollers

42 and 44 in synchronism with the movement of the workpiece 64 moved between

rollers

44 and 14 in the direction of arrow 66.

Although this invention has been described with reference to various embodiments, it will be understood to those skilled in the art that this invention is also capable of a variety of alternate embodiments within the spirit and scope of the appended claims.

What is claimed is:

1. An electrode assembly for use in the electrical surface treatment of a material comprising,

a first elongated electrode having a longitudinal dimension,

a second electrode provided by an electrically conductive surface, said surface being of varying width from one end to the other of the length thereof,

means having a longitudinal dimension for positioning a portion of said second electrode surface spanning a selected width thereof in juxtaposition to a longitudinal surface of said first electrode,

said longitudinal dimension of said first electrode and said longitudinal dimension of said positioning means being in substantially parallel spaced relationship to one another to provide juxtaposed surfaces of said first and second electrodes of length equal to said selected width of said second electrode surface,

means for actuating said positioning means to move said second electrode surface relative to said first electrode from one position to another position in the direction of the length thereof, perpendicular to the longitudinal dimension of said first electrode, to change said portion of the second electrode surface juxtaposed to said longitudinal surface of said first electrode, and

means for applying a voltage across said electrodes,

whereby upon passing a material to be treated between said juxtaposed first and second electrode surfaces in a direction perpendicular to said selected width while an electrical voltage is applied between said electrodes, a corona discharge takes place between said second electrode and said material.

2. An electrode assembly as in claim 1 wherein,

means are provided for fixing the position of the second electrode surface relative to the first electrode before commencing the treatment. I

3. An electrode assembly as in claim 1 wherein,

said second electrode surface has the shape of a truncated triangle.

.4. An electrode assembly in claim 1 wherein,

said second electrode surface is in the form of a belt. 5. An electrode assembly as in claim 4 wherein, said positioning means includes a non-conductive rotatable member upon which the belt is mounted. 6. An electrode assembly as in claim 4 wherein, said positioning means includes two elongated parallel, spaced members upon which the belt is mounted, one of said members positioning said selected portion of the second electrode surface in the central portion thereof.

Claims

1. An electrode assembly for use in the electrical surface treatment of a material comprising, a first elongated electrode having a longitudinal dimension, a second electrode provided by an electrically conductive surface, said surface being of varying width from one end to the other of the length thereof, means having a longitudinal dimension for positioning a portion of said second electrode surface spanning a selected width thereof in juxtaposition to a longitudinal surface of said first electrode, said longitudinal dimension of said first electrode and said longitudinal dimension of said positioning means being in substantially parallel spaced relationship to one another to provide juxtaposed surfaces of said first and second electrodes of length equal to said selected width of said second electrode surface, means for actuating said positioning means to move said second electrode surface relative to said first electrode from one position to another position in the direction of the length thereof, perpendicular to the longitudinal dimension of said first electrode, to change said portion of the second electrode surface juxtaposed to said longitudinal surface of said first electrode, and means for applying a voltage across said electrodes, whereby upon passing a material to be treated between said juxtaposed first and second electrode surfaces in a direction perpendicular to said selected width while an electrical voltage is applied between said electrodes, a corona discharge takes place between said second electrode and said material.

2. An electrode assembly as in claim 1 wherein, means are provided for fixing the position of the second electrode surface relative to the first electrode before commencing the treatment.

3. An electrode assembly as in claim 1 wherein, said second electrode surface has the shape of a truncated triangle.

4. An electrode assembly as in claim 1 wherein, said second electrode surface is in the form of a belt.

5. An electrode assembly as in claim 4 wherein, said positioning means includes a non-conductive rotatable member upon which the belt is mounted.

6. An electrode assembly as in claim 4 wherein, said positioning means includes two elongated parallel, spaced members upon which the belt is mounted, one of said members positioning said selected portion of the second electrode surface in juxtaposition to the first electrode surface.

7. An electrode assembly as in claim 6 wherein, said positioning means is actuated by rotating one of said members on its longitudinal axis.

8. An electrode assembly as in claim 6 wherein, one of said members holds said width portion of said second electrode surface juxtaposed said first electrode longitudinal surface and is non-conductive.

9. An electrode assembly as in claim 4 wherein, the belt has a cut-out of preselected configuration in the central portion thereof.