Abstract:
An electrostatic grounding hand covering in the form of a glove, made from a relatively nonconductive material such as acrylonitrile-butadiene copolymer, or other polymer or polymer blend, and having an electrically conductive tape on inner and outer surfaces of the glove. The electrically conductive tape runs from the outside surface to the inner and provides a path for an electrostatic charge to pass between an object in contact with the electrically conductive tape and the hand and finally to ground.

Description:
FIELD OF THE INVENTION 
     This invention relates to a hand covering for controlling electrostatic discharges, specifically by grounding an operator in an electrostatic environment. 
     BACKGROUND OF THE INVENTION 
     Naphtha and methyl ethyl ketone are organic solvents used in automotive painting. To prevent operators from coming into skin contact with these solvents, it is necessary for them to wear some form of chemically resistant hand covering. Traditionally, such hand covering has been gloves made from acrylonitrile-butadiene co-polymers, commonly called nitrile rubber. Nitrile rubber provides good resistance to chemicals used in automotive paint lines. The gloves are generally seamless to prevent any solvent from seeping in. However, cut and sewn polyvinyl chloride gloves are sometimes used when contact with organic solvents is minimal. 
     In electrostatic painting, the object to be painted is negatively charged while the paint and paint spray dispenser are positively charged. The paint droplets are attracted to the negatively charged object just as the north pole of a magnet is attracted to the south pole of another magnet. This gives even coverage of paint and minimizes waste. 
     However, if the operator is wearing a glove made of a material which is relatively nonconductive, such as nitrile rubber, it prevents the operator from being adequately grounded and some paint may fly back toward the operator. To prevent this, it is necessary to ground the operator, preferably without sacrificing the operator&#39;s protection from the paint solvents. 
     Various grounding devices have been proposed for a variety of reasons. For example, U.S. Pat. No. 3,596,134 teaches the protection of persons from electrical discharge in electrostatic fields by means of foot sandals, belt, and gloves all interconnected by conductive leads. This ensemble is used to disperse electrical charges concentrated in particular parts of the person&#39;s body. The construction of such a glove includes an outer surface of leather with a conductive lining on the inside so that the accumulated charge in the hand area is removed through the inner conductive lining, through the lead to ground. In this configuration, the charge has to pass through the insulative material, such as leather, to the inner lining which presents a substantially high resistive path. 
     U.S. Pat. No. 5,704,066 teaches the grounding of persons handling spark plug wires by means of a metal mesh glove attached to the metal frame work of the automobile by a conductive wire and alligator clip. Although this structure eliminates the danger of electric shock, it does not fulfill the need for improved protection against skin absorption and skin contact with toxic chemicals or solvents. Also, it is cumbersome to operate and is not cost effective for electrostatic painting. 
     U.S. Pat. No. 5,855,301 teaches electrostatic grounding for manually operated fluid dispensers, in which an operator is grounded by means of a conductive glove. The glove is made from a synthetic rubber such as Nitrilite from Ansell-Edmont Industrial Inc. of Coshocton, Ohio and which has a resistance of 10 8  to 10 11  ohms. Although this glove is used in conjunction with a wrist band, this combination by no means provides an easy path for the electric charge, and is cumbersome in operation. 
     Accordingly, it is an object of this invention to provide a cost-effective solution to controlling electrostatic discharge by providing a conductive path away from a charged object to ground. 
     It is also an object of the invention to provide a structure with a protective material to mitigate skin contact with toxic chemicals, including aqueous solutions and organic solvents, wherein such a material has a low permeation rate with a high fluid breakthrough time. 
     SUMMARY OF THE INVENTION 
     A hand covering in the form of a glove is provided for protecting an operator from solvents used in automotive painting while grounding the operator. This is accomplished by applying conductive tape to a finished glove. The tape is secured to the outer surface of the glove, positioned on the palm side of the glove and extends down the cuff or gauntlet, around to the inside of the glove, back up the cuff or gauntlet to the inside palm of the glove. This allows an electrical charge to be transferred from the paint spray dispenser to the palm of the glove and then to the operator, thereby grounding the operator. 
     The tape can be applied using a solvent resistant adhesive such as the acrylic adhesive on Scotch™ Electrical Tape 1194. It should be noted that the adhesive can be non-conductive. A variety of gloves can be used, provided that the outer surface is solvent resistant and the tape can be firmly attached. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects and advantages will become apparent upon reading the following detailed description in conjunction with the drawings, in which: 
     FIG. 1 is a front view of a glove, showing positioning of a first electrically conductive tape portion, shown in solid outline, on the palm side of the glove, and also a second electrically conductive tape portion on the inside of the glove, shown in ghost outline; 
     FIG. 2 is a side view of the glove of FIG. 1; 
     FIG. 3 is a cross-section of the glove of FIG. 1 drawn on line  3 — 3  of FIG. 1; 
     FIG. 4 is a back view of a glove according to a second embodiment, opposite the palm side, showing the fabric parts that are sewn together; and 
     FIG. 5 is a front view of FIG. 4, showing positioning of a first electrically conductive tape portion, shown in solid outline, on the palm side of the glove, and also a second electrically conductive tape portion on the inside of the glove, shown in ghost outline. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In a preferred embodiment shown in FIGS. 1 to  3 , a hand covering in the form of a glove for controlling electrostatic discharges is designated generally by reference numeral  20 . The glove  20  is made from an insulative material to form a protective housing  21  which includes an outer surface and an inner surface and defines a cavity  22  for receiving a hand. An electrically conductive tape  23  secured on an inner surface of the glove  20  and extending longitudinally to an outer surface of the glove provides an electrical path for electrostatic charge to flow from an operator wearing the glove to ground. 
     In an electrostatic environment, such as automotive painting, an object is painted by positively charged paint spray emanating from a paint spray dispenser. The object to be painted is negatively charged and the paint is positively charged by ionization, so that the negatively charged object attracts the paint. Typically, the operator is in contact with the positively charged paint spray dispenser, so that the positive charge is transferred to the operator. This results in the negatively charged paint flying back to the operator. The electrically conductive tape  23  is composed of a first electrically conductive portion  24  and a second electrically conductive portion  26 . The first electrically conductive portion  24  is secured on the outer surface of the housing  21 , while the second electrically conductive portion  26  (drawn in ghost outline) is secured on the inner surface of the housing  21 . 
     The first electrically conductive portion  24  extends from the base of a finger portion  30  of the glove  20  to a cuff  32 . The first electrically conductive portion  24  is dimensioned to cover a part of a palm portion  28  of the glove  20 , while providing adequate contact with the paint spray dispenser. As mentioned above, the second conductive portion  26  of the tape  23  is secured to the inner surface of the glove  20 , and has similar dimensions to the first electrically conductive portion  24  and is electrically coupled thereto. This can be done in several ways. In the preferred embodiment, the first and second conductive portions  24  and  26  form one integral strip which extends from the outer surface of the glove  20  to the inner surface of the glove  20 . Thus, the second conductive portion  26  is in contact with the operator&#39;s skin on the palm portion  28  of the glove  20 , while the first electrically conductive portion  24  is in contact with a paint spray dispenser. 
     Since the glove material, such as nitrile-butadiene is largely non-conductive, the flow of charge across its surface is limited. However, given the low electrical resistance of the first conductive portion  24 , the charge is adapted to flow away easily from the outer surface of the glove  20 . The conductive portions  24  and  26  are made from copper or other suitable conductor of low resistivity. Preferably, it is the commercially available Scotch™ Tape 1194 from 3M, Minnesota. This electrically conductive tape  23  is solvent resistant and is coated on one side with pressure sensitive adhesive so that it can be easily bonded to the outer and inner surfaces of the glove  20 . Given the electrical coupling between the conductive portions  24  and  26 , the adhesive does not need to be conductive. 
     Thus, in operation, any positive charge on the glove  20  is conducted away from the outer surface of the glove  20  by the first conductive portion  24 , through the second electrically conductive portion  26  to the palm side  28  of the operator&#39;s hand and, through the operator&#39;s body to ground. To complete this circuit, the operator should preferably be wearing non-rubber soled footwear or relatively conductive footwear. In such a situation, the operator is at ground potential and at a potential lower than the paint spray dispenser. The glove housing  21  will be manufactured by conventional means, preferably by dipping a mold shaped in the form of a hand on which a release wax and release agent is applied into nitrile-butadiene or a suitable solvent resistant material, while maintaining uniform thickness. The nitrile-butadiene is then allowed to “set” and is ultimately peeled from the mold. The glove  20  thus forms a housing  21  defining a cavity  22  for receiving a hand. The second conductive portion  26  is secured to the surface of the glove  20  by suitable adhesive. The glove  20  is then turned inside out for securement of the first conductive portion  24  preferably on the palm side  28  of the glove  20 . 
     Referring to FIGS. 1,  2  and  3 , it can be seen that the conductive portions  24  and  26  can be of any length provided there is sufficient contact between the paint spray dispenser and the palm side  28  of the glove  20 . The portions  24 ,  26  are positioned back to back and preferably on the palm side of the glove  20 . This configuration is ideal because the pressure resulting from the operator grasping the paint spray dispenser decreases the respective interface resistance between the first electrically conductive portion  24  and the paint spray dispenser interface and the second conductive portion  26  and operator&#39;s palm interface. This conversely increases the conductive surface at both interfaces which facilitates in the dissipation of charge away from the operator. 
     In another embodiment shown in FIGS. 4 and 5, a glove  40  has a configuration that includes a finger portion  42 , a palm portion  44  and a wrist portion  46 . The finger portion  42  and palm portion  44  are made from a plurality of finger sheaths  48 ,  50 ,  52 ,  54  and  56  stitched together in the form of a hand and attached to the wrist portion  46  at a seam  70  which encircles the wrist. Preferably the glove  40  is based on a stitched fabric design and is made from a non-conductive material such as fabric material, polyvinyl chloride, or polyurethane. The glove  40  is fabricated by cutting the individual sheaths  48 ,  50 ,  52 ,  54 ,  56  and wrist portion  46  with a die, and sewing the individual sheaths  48 ,  50 ,  52 ,  54 ,  56  and wrist portion  46  together to form a housing  58 . A cavity  60  for receiving a hand is thus defined by the housing  58 , such that the finished glove  40  has an outer surface and an inner surface. 
     As in the preferred embodiment of FIGS. 1 to  3 , an electrically conductive tape  62  composed of a first electrically conductive tape portion  64  and a second electrically conductive tape portion  66  is applied to the outer and inner surfaces of the glove, respectively. Preferably, the first and second electrical conductive portions  64 ,  66  are secured to the outer and inner surfaces by adhesive. The electrically conductive portions  64  and  66  are integrally formed and are joined to the glove  40  through the seam  70  before stitching the palm portion  44  at the seam  70  to the wrist portion  46 . Referring to FIG. 5, the conductive portions  64 ,  66  are positioned centrally on the palm portion  44  of the glove  40  and extend from the finger portion  42  to the base of the palm portion. This positioning provides a fairly large contact area with an object, such as a paint spray dispenser, to effectively dissipate the electrostatic charges. 
     For added comfort and perspiration absorption, the inner surface is preferably lined with a cloth material to interface with the operator&#39;s skin such as Goretex™ which conveniently is also lint free. This embodiment is suitable for operation in an environment where the probability of a solvent permeating the glove  40  is reduced. 
     In use, the gloves described above control the electrostatic charge present on the operator by providing a conductive path for the electrostatic charge through the first conductive and the second conductive portions of the electrically conductive tape. Also, the gloves provide a protective barrier to toxic chemicals, including aqueous solutions and organic solvents by being relatively non-permeable to such fluids. 
     While only certain preferred embodiments of this invention have been described, it will be understood by those skilled in the art that many variations of this invention may be made without departing from the scope of the appended claims. In particular, the electrically conductive tape may be integrally moulded during fabrication of the glove so as to be integrated into the housing without requiring any adhesive to secure the tape to the inner and outer surfaces of the glove. It will also be appreciated that the hand covering can take the form of a mitten.