Patent Publication Number: US-7900272-B1

Title: Static control garment

Description:
BACKGROUND 
     1. Field 
     This invention relates to static control garments. 
     2. Description of the Related Art 
     Static electricity represents a serious threat to electronic components, which may become damaged during the manufacturing process when the personnel handling these components are not effectively grounded. It is desirable to ground not only the bodies of the personnel working with these components, but their clothing as well, as charge can build up in either location. 
     The “bunny suit” is a popular garment used to ground personnel and their clothing. Typically, the bunny suit is made from a knit or woven fabric comprising an electrically conductive Faraday cage grid. The garment thereby effectively shields the personnel and his or her clothing from delicate electronic components. One or more close fitting connections may also be used to electrically couple the wearer&#39;s body to the bunny suit and/or to ground. For example, a wrist strap having an attached grounding cord may be incorporated into the bunny suit in order to couple the wearer&#39;s body to ground. 
     Unfortunately, the conventional bunny suit is not ideal. For example, in order to determine whether or not the bunny suit is effectively grounding its wearer, two connections should couple the wearer to a monitoring circuit. However, because the entire garment is made from electrically conductive material, a number of uncontrolled parallel electrical paths are formed between the wearer&#39;s body, street clothing and bunny suit, and the monitoring circuit. These parallel paths can make the monitoring circuit&#39;s output unreliable. 
     Moreover, the grounding of the bunny suit is typically only tested occasionally. The use of conventional monitoring circuits is inconvenient (often requiring the wearer to manually touch a ground, for example, to define a current loop), and they may be located far from where the wearer is working with the electronic components. 
     The prior art has not disclosed an effective way of monitoring the status of a wearer&#39;s connection to ground. The prior art has also not disclosed an effective way to ameliorate the problem of multiple, uncontrolled parallel electrical paths undermining the accuracy of ground monitoring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of a static control garment, a labcoat, according to one embodiment of the present invention. 
         FIG. 1A  shows an enlarged view of one cuff of the labcoat of  FIG. 1 . 
         FIG. 2  shows a perspective view of the labcoat of  FIG. 1  coupled to a monitoring device. 
         FIG. 3  shows a perspective view of a static control garment, a bunny suit, according to another embodiment of the present invention. 
         FIG. 3A  shows an enlarged cut-away of a seam of the bunny suit of  FIG. 3 . 
         FIG. 4  shows a perspective view of the bunny suit of  FIG. 3  including a coupled pair of booties. 
         FIG. 5  shows a perspective view of the bunny suit and the booties of  FIG. 4 , in an uncoupled configuration. 
         FIG. 6  illustrates the steps of one method of manufacturing a static control garment according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     Referring to  FIG. 1 , a static control garment configured to be worn by a user (not shown) is illustrated according to one embodiment of the present invention. As shown in  FIG. 1 , the garment comprises a labcoat  10 , although other configurations (such as that shown in  FIG. 3 ) may also be used. The labcoat  10  comprises first and second conductive portions  12   a ,  12   b , a first user interface  14   a  for electrically coupling the first conductive portion  12   a  to the user, a second user interface  14   b  for electrically coupling the second conductive portion  12   b  to the user, and an insulative portion  16  coupled to and separating the first and second conductive portions  12   a ,  12   b . In one embodiment, the first and second conductive portions  12   a ,  12   b  comprise substantially the same amount of conductive material. 
     As illustrated, the labcoat  10  may generally extend to around the mid-thigh of the user, and may be buttoned up the front using buttons made of an insulative material. However, this particular style of static control garment is shown solely for purposes of illustration, since the shape and style of the garment may be varied. 
     The first and second conductive portions  12   a ,  12   b  may be made from any relatively conductive fabric. In one embodiment, each of the conductive portions  12   a ,  12   b  comprises a knit or woven fabric including therein an electrically conductive and dissipative Faraday cage grid. For example, polyester carbon-infused nylon may be woven into a conductive grid pattern throughout each of the conductive portions. Thus, the nylon grid forms an electrically conductive carbon mesh that shields electrical components being worked on from the radiation of static electricity from a user&#39;s “street” clothing worn under the static control garment. In another embodiment, the fabric may comprise polyester, nylon, cotton or other synthetic or non-synthetic materials, or a blend of these fabrics. Running through these materials, conductive threads of copper, stainless-steel, carbon or silver-loaded filaments, or other metallic or non-metallic conductive elements may also comprise the conductive portions. 
     In some embodiments, the first and second conductive portions  12   a ,  12   b  may be made from different conductive materials having similar electrical properties, but in other embodiments, the same material is used to manufacture both portions. In one embodiment, the conductive material used to make these conductive portions  12   a ,  12   b  has a resistance of less than 10 9  ohms per square, but preferably not less than 10 3  ohms per square. 
     While the first and second conductive portions  12   a ,  12   b  are illustrated as each making up nearly all of one half of the labcoat  10 , it should be understood that the first and second conductive portions may, in other embodiments, comprise substantially less material. Thus, a significant percentage of the static control garment may comprise non-conductive material (e.g., the sleeves may not be conductive in one embodiment, or the legs of a bunny suit (as illustrated in  FIG. 3 ) may not be conductive in another embodiment). Preferably, however, the majority of each half of the labcoat does comprise conductive material, in order to effectively shield more of the user&#39;s body using the garment as a Faraday cage. 
     The first user interface  14   a  electrically couples the first conductive portion  12   a  to the user when the garment is worn. It may accomplish this electrical connection in any of a variety of ways. In one embodiment, as illustrated in  FIG. 1A  (which shows the cuff  19   a  inverted), the first user interface  14   a  comprises a metal plate  21   a  on the inside of a cuff  19   a  of the labcoat  10 . The cuff  19   a  may include elastic, stretchable material to compress the cuff  19   a  against a user&#39;s skin when worn. Thus, the metal plate  21   a  of the first user interface  14   a  is also pressed against the bare skin of the user&#39;s wrist, creating an electrical connection between the user and the first user interface  14   a . In one embodiment, multiple metal plates  21   a  are provided to form the first user interface  14   a , such that redundant electrical connections are made between the user and the static control garment. 
     In another embodiment, the elastic material comprising the cuff  19   a  may itself be electrically conductive and may thereby comprise the first user interface  14   a . In still another embodiment, the user may wear a separate wristband, and a first user interface  14   a  of the labcoat  10  may couple to this separate wristband (via snaps, wires, or other means) and be thereby electrically coupled indirectly to the user. Preferably, the user interface  14   a  couples to the user at the user&#39;s wrist because this is a portion of the user&#39;s body often left bare by street clothing. However, in other embodiments, the user interface  14   a  may couple to any body part to facilitate a relative secure electrical connection. 
     The first user interface  14   a  may be directly coupled to the first conductive portion  12   a , and may be understood to form a part of the first conductive portion  12   a . For example, the cuff  19   a  may comprise part of the first conductive portion  12   a , and the metal plate  21   a  comprising the first user interface  14   a  may be in direct electrical contact with the cuff  19   a . In another embodiment (shown in  FIG. 1 ), the first conductive portion  12   a  includes therein a ribbon of conductive material  15   a  that is not electrically isolated from the rest of the conductive portion  12   a . This ribbon of conductive material  15   a  may be sewn into a seam of the first conductive portion  12   a , as illustrated. The ribbon  15   a  may be formed from any of a variety of conductive materials, and in one embodiment comprises carbon-infused nylon. In other embodiments, carbon or copper-based conductive threads, ribbons or metal/metal-infused tapes may be used to form the ribbon  15   a . The first user interface  14   a  may electrically contact the ribbon  15   a , and may thereby electrically couple the user to the first conductive portion  12   a  through the ribbon. 
     In one embodiment, the second user interface  14   b  is configured identically to the first user interface  14   a , just on the other side of the garment. However, in other embodiments, of course, the two interfaces may be configured differently. 
     The insulative portion  16  is coupled to both the first and second conductive portions  12   a ,  12   b , and generally separates them. The insulative portion  16  may be coupled to the conductive portions  12   a ,  12   b  by a variety of methods used in the garment industry. For example, as illustrated in  FIG. 3A , the insulative portion  16  may be folded together with each conductive portion in a double felt configuration, and then joined by any of a number of stitches. Lock, common-tailor or other stitches, staples, glue, or other affixing means may also be used to couple the insulative portion  16  to the first and second conductive portions  12   a ,  12   b.    
     In one embodiment, the insulative portion  16  runs generally along a midline of the user&#39;s torso. However, in other embodiments, the insulative portion may be offset to one side of the user&#39;s torso or another according to the needs (aesthetic or technical) of a particular implementation. Indeed, while the insulative portion  16  is shown along a vertical midline, the insulative portion  16  may also run generally along a horizontal midline. In one embodiment, the insulative portion  16  may comprise a polyester material without conductive elements therethrough, so that the insulative portion and conductive portions have substantially similar wash-and-dry properties. However, other fabrics may also be used, including polyester, nylon, cotton or other synthetic or non-synthetic materials, or a blend of these fabrics. 
     The insulative portion  16  is located between the first and second conductive portions  12   a ,  12   b  as illustrated in  FIG. 1 . However, it need not completely isolate these conductive portions from each other. For example, in one embodiment, as illustrated, the first and second conductive portions  12   a ,  12   b  may come into momentary contact with each other if one conductive portion of the labcoat  10  rubs against the other conductive portion. As another example, when the labcoat  10  is worn, it may be buttoned up the front, and the first and second conductive portions  12   a ,  12   b  may be placed in relatively constant contact with each other. However, the first and second conductive portions  12   a ,  12   b  are preferably not sewn together or otherwise relatively permanently attached except through insulative material. In some embodiments, the labcoat may use insulated buttons, as shown in  FIG. 1 , or a zipper may be used that includes an insulative fabric to provide further isolation between the two sides of the garment (see  FIG. 3 ). Preferably, even if the first and second conductive portions  12   a ,  12   b  come into contact with each other, there is a much higher resistance to this contact than if they were a unitary piece. 
     In one embodiment, as set forth above, the first and second conductive portions  12   a ,  12   b  comprise substantially the same amount of conductive material. For example, the two portions may comprise the same amount of conductive material within manufacturing tolerances for manufacturing the garment. In another embodiment, the first and second conductive portions  12   a ,  12   b  comprise substantially the same amount of conductive material, such that the capacitance between each conductive portion of the garment and ground is approximately the same (within 10%). 
     In another embodiment, the amounts of material in the first and second conductive portions  12   a ,  12   b  do not differ by more than 30%. In another embodiment, the amounts of material in the first and second conductive portions  12   a ,  12   b  do not differ by more than 20%. In yet another embodiment, the amounts of material in the first and second conductive portions  12   a ,  12   b  do not differ by more than 10%. In yet another embodiment, the amounts of material in the first and second conductive portions  12   a ,  12   b  do not differ by more than 5%. It may be understood that different monitoring devices that may be used to ensure that the user and garment are effectively grounded may be more or less sensitive to differing amounts of material for the first and second conductive portions  12   a ,  12   b . Thus, in some environments, the amounts of material in the first and second conductive portions  12   a ,  12   b  should not differ by more than 5%, while in other environments, this requirement may be relaxed. 
     Referring to  FIG. 2 , the labcoat  10  may be further understood to include a torso portion  13 , and first and second arm portions  17   a ,  17   b . In one embodiment, the torso portion  13  of the labcoat  10  comprises first and second conductive portions  23   a ,  23   b , which are separated by the insulative portion  16 . As illustrated, the first and second conductive portions  23   a ,  23   b  that comprise the torso portion  13  form a part of the larger first and second conductive portions  12   a ,  12   b  (illustrated in  FIG. 1 ), which are discussed at length above. Thus, in one embodiment, the first and second conductive portions  12   a ,  12   b  comprise material from the respective arm portions  17   a ,  17   b , as well as the first and second conductive portions  23   a ,  23   b  of the torso portion  13 . 
     Of course, different configurations are possible. For example, the first and second arm portions  17   a ,  17   b  need not be made from conductive material. In one embodiment, the first and second arm portions  17   a ,  17   b  may comprise conductive fabric, but may each be electrically uncoupled from the torso portion  13 . 
     Referring further to  FIG. 2 , the labcoat  10  may further comprise first and second electrical interfaces  18   a ,  18   b  for electrically coupling to a monitoring device  20 . In one embodiment, as shown, leads  24   a ,  24   b  run from both electrical interfaces  18   a ,  18   b  to the monitoring device  20 . In other embodiments, only one of the electrical interfaces need be coupled to a monitoring device. These electrical interfaces  18   a ,  18   b  may be configured in a variety of ways. For example, the electrical interfaces  18   a ,  18   b  may comprise metallic snaps to which the monitoring device  20  can attach by leads  24   a ,  24   b  having mating connectors. In another embodiment, the electrical interfaces  18   a ,  18   b  comprise female receptacles for banana plugs coupled to the monitoring device  20 . Any other suitable electrical interfaces may be used to couple the labcoat  10  and monitoring device  20 . 
     A number of monitoring devices may be used with the labcoat  10  illustrated in  FIGS. 1 and 2 . In one embodiment, a monitoring device  20  may periodically send a current through a first lead, and receive a current through a second lead. The monitoring device  20  may thereby derive a resistance measurement of the circuit formed by the garment and user. If a large resistance is detected, an alarm may be triggered indicating that the user of the garment is not properly grounded. In another embodiment, a monitoring device, such as a Dual Wire Continuous Monitor, Part No. 19665, produced by Desco Industries, Inc., may be used. Other monitoring devices differently configured may also be used. 
     The monitoring device  20  may be coupled to the labcoat  10  while the user moves around performing job functions, or the monitoring device  20  may only be coupled to the labcoat  10  at particular ESD testing stations (not shown), so that grounding of the labcoat  10  is tested more intermittently. 
     As illustrated in  FIG. 2 , the first user interface  14   a  may be electrically coupled to the first electrical interface  18   a , and the second user interface  14   b  may be electrically coupled to the second electrical interface  18   b . Any electrical connection may be used. As illustrated, the first user interface  14   a  and first electrical interface  18   a  are coupled by the ribbon of conductive material  15   a . Similarly, the second user interface  14   b  and second electrical interface  18   b  are coupled by a ribbon of conductive material  15   b  extending through the labcoat  10 . In one embodiment, the two ribbons  15   a ,  15   b  are made from the same material. 
     As is also illustrated in  FIG. 2 , the second electrical interface  18   b  may be surrounded by the first conductive portion  12   a . In fact, as shown in the Figure, the second electrical interface  18   b  is embedded within the material that comprises the first conductive portion  12   a . However, in one embodiment, the second electrical interface  18   b  remains insulated from the first conductive portion  12   a . Thus, as shown, the ribbon  15   b  may pass through the second conductive portion  12   b  through a non-insulated seam, and, as it passes through the insulative portion  16  and into the first conductive portion  12   a , a strip of insulative material preferably surrounds and insulates the ribbon  15   b  from the first conductive portion  12   a  surrounding it. Other means of electrically isolating the ribbon  15   b  may be used in other embodiments. Similarly, the second electrical interface  18   b , although surrounded by the first conductive portion  12   a , is preferably electrically isolated from the first conductive portion  12   a  by insulative materials. 
     Preferably, the first and second electrical interfaces  18   a ,  18   b  are located adjacent one another and are surrounded by the first conductive portion  12   a . Such a configuration facilitates creating an electrical connection between the labcoat  10  and monitoring device  20 , as the user can quickly and easily attach and detach the leads from his waist. 
     Referring to  FIG. 3 , the static control garment may alternatively comprise a bunny suit  40 . Such a bunny suit  40  comprises arms  42   a ,  42   b , legs  44   a ,  44   b , and a torso portion  46 . In a preferred embodiment, the torso portion  46  further comprises first and second conductive torso portions  47   a ,  47   b  separated by an insulative portion  52 . 
     The bunny suit  40  may be further described as comprising first and second conductive portions  48   a ,  48   b  (which include the first and second conductive torso portions  47   a ,  47   b  of the torso portion  46  respectively), a first user interface  50   a  for electrically coupling the first conductive portion  48   a  to the user, a second user interface  50   b  for electrically coupling the second conductive portion  48   b  to the user, and an insulative portion  52  coupled to and separating the first and second conductive portions  48   a ,  48   b . In one embodiment, the first and second conductive portions  48   a ,  48   b  comprise substantially the same amount of conductive material. 
     The materials and structures comprising the bunny suit  40  may be generally the same as those discussed above used to construct different embodiments of the labcoat  10 . However, in a preferred embodiment, the legs  44   a ,  44   b  of the bunny suit  40  form part of the first and second conductive portions  48   a ,  48   b , respectively. Secondly, as illustrated, a zipper  60  may be used to close the bunny suit  40  when worn, in order to provide further insulation between the two conductive portions  48   a ,  48   b  of the bunny suit  40 . Thirdly, the ribbons of conductive material  54   a ,  54   b , coupling the user interfaces  50   a ,  50   b  to the electrical interfaces  56   a ,  56   b , respectively, may extend down the legs  44   a ,  44   b  of the bunny suit  40  in one embodiment. 
     Near the bottom of the bunny suit  40 , these ribbons of conductive material  54   a ,  54   b  may be electrically coupled to a pair of bootie interfaces  58   a ,  58   b . The bootie interfaces  58   a ,  58   b  may be configured in a variety of ways in order to support an electrical connection between the bunny suit  40  and a pair of booties  62   a ,  62   b  (such as those shown in  FIGS. 4 and 5 ). For example, in one embodiment, the bootie interfaces  58   a ,  58   b  comprise metallic snaps (which may be identical to the electrical interfaces  56   a ,  56   b ) to which the booties  62   a ,  62   b  can attach by mating connectors. 
     Referring to  FIGS. 4 and 5 , the first conductive portion  48   a  may comprise a first bootie  62   a , and the second conductive portion  48   b  may comprise a second bootie  62   b . These booties  62   a ,  62   b  preferably shield the user&#39;s feet, and ensure that excess charge does not build up and discharge via the user&#39;s shoes. In one embodiment, the fabric comprising the top portions of the booties  62   a ,  62   b  is the same material comprising the rest of the first and second conductive portions  48   a ,  48   b , and the booties  62   a ,  62   b  have rubber soles. Of course, other configurations for the booties are possible. 
     Referring to  FIG. 4 , the first and second booties  62   a ,  62   b  are illustrated as electrically coupled to the bunny suit  40 . In one embodiment, the ribbon of conductive material  54   a  is coupled through a bootie interface  58   a  of the bunny suit  40  to a corresponding ribbon of conductive material  64   a  running through the bootie  62   a . The other bootie  62   b  is configured similarly. Thus, the entire first conductive portion  48   a  may be understood to include the arm  42   a , one side of the torso portion  46 , the leg  44   a , and the bootie  62   a . In  FIG. 5 , the first and second booties  62   a ,  62   b  are illustrated in an uncoupled configuration, with the first and second bunny interfaces  66   a ,  66   b  visible. The first and second bunny interfaces  66   a ,  66   b  are preferably configured to correspond with and engage the first and second bootie interfaces  58   a ,  58   b  respectively to create an electrical connection. 
     Referring to  FIG. 6 , a flow chart illustrating the steps of a method of manufacturing a static control garment according to one embodiment of the invention is set forth. As illustrated, the method may comprise: providing first and second swaths of conductive material and a strip of insulative material (step  100 ); attaching the first conductive swath to the insulative strip (step  102 ); attaching the second conductive swath to the insulative strip (step  104 ); tailoring a static control garment from the first and second conductive swaths and the insulative strip, such that the static control garment comprises substantially the same amount of material from the first conductive swath and the second conductive swath (step  106 ); attaching a first user interface to the first conductive swath, the first user interface for electrically coupling to a user (step  108 ); and attaching a second user interface to the second conductive swath, the second user interface for electrically coupling to the user (step  110 ). 
     As shown at step  100 , first and second swaths of conductive material and a strip of insulative material are first provided. As discussed at length above, in one embodiment, the swaths of conductive material comprise polyester carbon-infused nylon, but may alternatively comprise any conductive fabric. The swaths of conductive material preferably include a continuous grid of conductive filaments. The strip of insulative material may also comprise any insulative fabric, and, in one preferred embodiment, comprises polyester. 
     The swaths of conductive material may be provided in many forms. In one embodiment, the fabric is sold in large rolls from which the swaths of conductive material may be cut. In one embodiment, the first and second swaths of conductive material comprise the same swath of conductive material until they are separated. The strip of insulative material may also be provided in many forms. It need not be uniform, and may vary greatly in dimension. In one embodiment, the strip of insulative material may be approximately 4 feet long and 1 inch wide. 
     At step  102 , the first conductive swath is attached to the insulative strip. The means of attaching these two materials are well-known to those of skill in the art. In one embodiment, they are sewn together as is shown in  FIG. 3A . 
     At step  104 , the second conductive swath is attached to the insulative strip. Preferably, the two materials are attached identically to the method used in step  102 , although variations are acceptable. The first and second conductive swaths are preferably attached to the same insulative strip, but are not attached directly to one another. In one embodiment, the first and second conductive swaths are attached to the insulative strip in order to insulate them from each other. 
     At step  106 , the static control garment is tailored from the first and second conductive swaths and the insulative strip. Suitable tailoring processes are well-known in the art. In one embodiment, the swaths and strip are first cut, and then stitched together in order to create a garment that is wearable. For example, the swaths and insulative strip may be tailored to create a bunny suit  40  (such as that shown in  FIG. 3 ) or a labcoat  10  (such as that shown in  FIG. 1 ). In certain embodiments, the tailoring yields at least a torso portion for surrounding the user&#39;s torso, and two arm portions for covering the user&#39;s arms. 
     During this tailoring step, the static control garment may be tailored to comprise substantially the same amount of material from the first conductive swath and the second conductive swath. Of course, the amount of material used from each swath will not be exactly the same due at least to manufacturing tolerances. The static control garment may be understood to be tailored from substantially the same amount of material from the first and second conductive swaths if it satisfies at least one of the criteria set forth above in great detail. In one embodiment, the tailoring is performed such that the insulative strip runs down a user&#39;s torso, and, in one embodiment, down a mid-line of a user&#39;s body, thereby roughly ensuring that the material from each conductive swath will be approximately the same. 
     At step  108 , a first user interface is attached to the first conductive swath, the first user interface for electrically coupling to the user. As discussed above, the first user interface may include a metal plate that may be pressed against a user&#39;s skin. In another embodiment, the second user interface may comprise a cuff, such as an elastic, stretchable cuff incorporated into the garment. 
     At step  110 , a second user interface is attached to the second conductive swath, the second user interface for electrically coupling to the user. Preferably, the second user interface is generally constructed and attached in a manner similar to the first user interface discussed above.