Method For Making A Neutralizing Device

Abstract

A method for manufacturing a brush like device for neutralizing static electrical charges from resilient, supple conductive filaments of minute diameter. The method includes positioning two support rods in spaced parallel relationship, winding the filaments spirally about the pair of rods with successive windings being in side by side relationship, attaching the contacting section of the filaments to the rods, and severing the filaments extending between the two rods to produce two devices.

Description

BACKGROUND OF INVENTION

This invention relates to a method for manufacturing brush like devices from extremely soft and flexible fibers, and in one aspect relates to a method for manufacturing a device for neutralizing static electrical charges on a surface which comprises a multiplicity of supple, resilient, conductive filaments of minute diameter attached to a supporting means. The filaments used in the neutralizing device have at least one of their ends extending from the supporting means in a generally uniform direction. The device may be electrically attached to a unit at ground potential and be positioned with the distal ends of the filament in contact with or spaced from the path of a possibly charged surface so that the device may serve as a contact or induction neutralizer for reduction of static electrical charges on the surface.

Manufacture of this device presents a problem due to the extremely fine and supple nature of the filaments. Normal manufacturing techniques for attaching material such as hair, bristles or wires to a backing are not suitable, as they require more rigidity in the material to be attached than is possessed by the filaments utilized in the present invention. Also, their conductivity makes the use of some flocking techniques impractical.

The present method of manufacture affords the production of one embodiment of a device for neutralizing static electricity using the afore-mentioned filaments.

The manufacturing method for neutralizing devices of the present invention includes positioning two rods in parallel opposed spaced relationship on a frame, winding a strand comprised of conductive filaments about the two rods so that successive points of contact between the rods and the strand are generally uniform axially of the rods, attaching the sections of the strands in contact with the rods to the surface of the rods by suitable securing means, preferably an adhesive potting material, and severing the strand at points between the two rods. By severing the strand at each half way point in a winding midway between the axis of each rod, two similar neutralizing devices are produced.

DESCRIPTION OF THE DRAWING

The invention will be further described with reference to the accompanying drawings wherein like numbers refer to like parts in the several views and wherein:

FIG. 1 is a perspective view of a neutralizing device manufactured according to the present invention;

FIG. 2 is a schematic perspective view illustrating a device for performing a step in the manufacture of neutralizing devices according to the present invention; and

FIG. 3 is a schematic perspective view showing two steps of the method of manufacture of the present invention.

Referring now to FIG. 1 there is shown a neutralizing device 10 which was manufactured according to the method of the present invention. The supporting means of the device 10 is a rod 11 which may be conductive and over which are draped a multiplicity of lengths of a conductive filament 12. The filaments 12 are retained in position on the rod 11 by a potting compound 14 and are partially covered by a U-shaped conductive exterior shield 15.

The conductive filaments 12 utilized in the device 10 are a conductive fiber material produced by a process of thermochemically converting regenerated-cellulose fiber starting material to corresponding black insulative organic fiber material and then carbonizing the latter to provide corresponding conductive fiber material as disclosed in U.S. Pat. Nos. 3,235,323 and 3,484,183, incorporated herein by reference. While a variety of different conductive filaments may be produced according to the process disclosed in these referenced patents and while any of these various filaments may be suitable for use in the static eliminating device 10, one filament which has been utilized and which provides good results is commercially sold by Minnesota Mining and Manufacturing Company, Saint Paul, Minnesota under the trade name "Pluton" and designation --H -25 Roving. This filament is supplied in a non-twisted strand 17 of about 720 individual filaments 12, each filament 12 being only about 0.00034 inches in diameter. The strand 17 has a denier of 625 and a breaking strength of over 3 pounds. "Pluton" H-25 Roving has a carbon content of 98.3 percent and the strands 17 have an electrical resistance of 22 ohms per inch of length.

The device 10 has from about four to 20 lengths of the "Pluton" strands 17 evenly distributed along each inch of the length of the rod 11 in side by side relationship. Thus, the device 10 provides from about 5,760 to 28,800 free ends of filaments 12 per inch of length of the rod 11 which ends will make intimate contact with and conduct static electrical charges away from a contacted surface when the 10 is used as a contact neutralizer or which will provide sharp points to induce flow of static electrical charges when the device 10 is spaced from a surface and used as an induction neutralizer.

The metal shield 15 provides a conductive connection between the filaments 12, protects the filaments 12, and provides a directing means to position the extending ends of the filaments 12 in a row. The shield 15 also includes a pair of pierced tabs 18 at its ends to provide means for mounting and grounding the device 10. A pair of edges 16 on the shield are rounded by rolling the edge of the sheet metal back upon itself to prevent cutting of the filaments 12 when they are deflected against one of the edges 16.

An example of a suitable bonding material or potting compound 14 to secure the filaments to the rods is identified as RTV Silicone room temperature curing material.

Referring now to FIG. 2 there is schematically illustrated a device for simultaneously manufacturing two or more of the devices 10 according to the method of the present invention. Means are provided for supporting two rods 11 in parallel opposed spaced relationship on a rotatable frame 20, with the rods 11 being parallel to and equal distant from the axis of rotation of the frame 20. The frame 20 comprises two circular end plates 22 and 23 each of which is attached to a coaxially positioned stub shaft 24, (only one of which is shown) journaled on means not shown. The end plates 22 and 23 are both attached to a thin rectangular spacing bar 26 which has its cross sections centered upon the common axis of the end pieces 22, 23 and the shafts 24. The rods 11 are positioned on the frame 20 and the ends of the rods 11 are received in spring clip devices 25 secured to the end plates at diameteric positions aligned with the spacing bar 26.

The rotating frame 20 is driven about the axis of the stub shafts through a pulley 27 formed on the end piece 22 via a V-belt 28 driven by a pulley connected to gear reduced motor 30 through shaft 32.

A spool 33 wound with a strand 17 of the filaments 12 is provided with an appropriate support means and friction means (not shown) for providing a desired tension in the strand 17 as it is wound upon and along the rods 11.

Means are provided to guide the continuous strand 17 as it is wound about the two rods 11 so that successive points of contact between the strand 17 and each rod 11 are spaced uniformly axially along the length of the rods 11. The guide means illustrated is a reciprocating level wind apparatus 37 similar to that commonly used in casting reels, which is driven from the motor 30 through a pulley and V-belt drive including a pulley 36. The level wind apparatus comprises a driving screw 38 to which the pulley 36 is attached which drives a follower assembly 40 including an eye 42 for guiding the strand 17. A pair of fixed guide bars 44 between which assembly 40 slides is also provided. The drive for the level wind apparatus 37 and for the rotating frame 20 are designed to produce a predetermined uniform advance of the eye 40 for each revolution of the frame 20 so that the contact point between each rod 11 and the strand 34 will uniformly vary axially of the rods 10 to produce a predetermined density of filaments 12 per inch of rod 11 length.

To wind the strand 17 about a pair of rods 11 which have been positioned in the clips 25 on the end pieces 22 and 23, the motor 30 is operated to place the follower assembly 40 at one end of the driving screw 38. The strand 17 from the spool 33 is threaded through the eye 42 and attached as by tying to a rod 11. The motor 30 is then started to wind the strand 17 about the rods 11. When the follower assembly has traveled the entire length of the driving screw 38 the motor 30 is shut off and the strand 34 is severed.

The strands are then secured to the rods 11 as is shown in FIG. 3, potting compound is spread over the sections of the strand 17 in contact with the rods 11 by suitable means, e.g. a manually operated squeeze bottle 50, after which a shield 15 is placed over each rod 11. The shield 15 is generally U-shaped in section and is placed over the rod with the legs or flanges extending in the direction of the fibers. Alternatively, the potting compound may be placed in the channel of the shield 15 and the shield 15 placed over the rod, forcing the potting compound around the rod 11 and the sections of the strand 17 contracting the rod 11 as the bight of the U-shaped shield is pressed into contact with the filaments.

After the potting compound has sufficiently dried to retain the shields 15 and filaments 12 in place, the strand 17 is severed at points between the rods 11 on each side of bar 26. Preferably the strand 17 is severed at each point midpoint between the rods in two separate operations by a suitable instrument such as a knife 52. The knife 52 may be guided by a straight edge 54 on an L-shaped guide plate 56 which is manually placed over the strand 17 wound about the two rods 11 to gauge the midpoint of each winding of the strand 17 extending between the rods 11. The inside surface of the short leg of the L-shaped guide plate 56 is positioned in contact with the section of the filaments 12 which extend over one of the rods 11 and the guide plate 56 is then used to press the filaments 12 into contact with the bar 26 to prevent distorting them as they are cut by the knife 52. Two static eliminating devices 10 may then be removed from the apparatus by removing the ends of the rods 11 from the spring clip devices 25.

Claims

Having thus described the method of the present invention, what is claimed is:

1. A method of manufacturing brush-like neutralizing devices for reduction of static electrical charges on a surface which comprises the steps of: positioning two stiff support rods on a frame in a parallel opposed spaced relationship; winding a strand comprised of supple electrically conductive carbonaceous filaments about the two rods so that the lengths of the strand contacting each rod are uniformly spaced axially along the rods; securing the strand to the rods by applying an adhesive potting compound to the lengths of the strand contacting the rods, and for each rod pressing a stiff conductive U-shaped shield over and into contact with the lengths of the strand contacting the rod and the uncured potting compound with the legs of the shield extending in the direction of the lengths of the strand extending between the rods; severing the strand at positions between the two rods to form free ends of the filaments and two brush-like neutralizing devices; and removing the neutralizing devices from the frame.

2. A method of manufacturing brush-like neutralizing devices according to claim 1 wherein said step of winding comprises: guiding the strand onto the rods; rotating the frame about an axis parallel to and centered between the rods to wind the strand about the two rods; and moving the guide point at a predetermined rate axially of the rods.

3. A method of manufacturing brush-like neutralizing devices according to claim 1 wherein the frame includes a bar parallel to and centered between the rods and having opposed planar faces positioned to be parallel to the lengths of the wound strand extending between the rods, and said step of severing comprises; pressing the wound strand into contact with the adjacent planar surface of the bar along a line equal distant from the axis with the straight edge of a guide plate; and cutting against the planar surface along the straight edge with the blade of a knife to sever the strand.

4. A method of manufacturing brush-like devices comprising strands of supple fibers which comprises the steps of: positioning two stiff support rods on a frame in a parallel opposed spaced relationship; winding a strand of supple fibers about the two rods so that the lengths of the strand contacting each rod are uniformly spaced axially along the rods; securing the strand to the rods by applying an adhesive potting compound to the lengths of the strand contacting the rods, and for each rod pressing a stiff U-shaped shield over the lengths of the strand contacting the rod and the uncured potting compound with the legs of the shield extending in the direction of the lengths of the strand extending between the rods; severing the strand at positions between the two rods to form free ends of the filaments and two brush-like devices; and removing the devices from the frame.

5. A method of manufacturing brush-like devices according to claim 4 wherein said step of winding comprises: guiding the strand onto the rods; rotating the frame about an axis parallel to and centered between the rods to wind the strand about the two rods; and moving the guide point at a predetermined rate axially of the rods.

6. A method of manufacturing brush-like devices according to claim 4 wherein said step of severing comprises severing the length of the strand extending between the rods equidistant from the axes of the rods.