Multi-path static control garment and wrist strap combination

A static electricity control combination including an electrically conductive smock and a dual-contact wrist strap. It further comprises an elongate insulated flexible conductor that is sewn along one sleeve and along the body of the smock. A first grounding path extends from the wrist strap to the insulated flexible conductor and thus to a first contact on the body and to ground. A second grounding path extends from the wrist strap to the sleeve and body to a second contact on the body and to ground.

BACKGROUND OF THE INVENTION 
In the copending U.S. patent application 191,625, there is shown and 
described a garment having cuffs and having separate grounding paths. 
There is no wrist strap. 
There are, in the field of static control garments, applications that 
require a wrist strap to be worn; for example, where a wrist strap is 
designated by the customer as the body contacting mechanism for a 
dual-path ground. Some companies require that the contact with the wrist 
strap be metal to the body. An example of the latter wrist strap is in the 
nature of a "Speidel" watchband. There are also fabric-type wrist straps 
that have two metal plates as conductive body-contact elements. 
The stated metal-to-the-body requirement would be a difficult requirement 
to comply with in a garment, especially one made of a soft textile 
(fabric) material. The metal would have to be permanently attached to the 
fabric, and this means that the metal would be laundered under the same 
washing conditions required for laundering of the garment. The result 
could be a problem relative to metal deterioration caused by such factors 
as corrosion, or coating of the metal with an insulator. Build-up of 
insulator could be caused on the metal by soaps and washing chemicals. 
Until now, a wrist strap having two isolated body contact points, and 
directly contacted to a dual-wire cord leading directly to the ground, has 
been the only way to satisfy the metal-to-the-body requirement in a 
redundant dual-path monitoring system. But direct connection from wrist 
strap to ground has at least one disadvantage, and at least one 
nonadvantage. The disadvantage is that the wrist is tethered-which can be 
an annoying and efficiency-reducing thing. The nonadvantage is that there 
is no "Faraday cage" (Faraday cage-like) action such as is described 
below. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a multiple-path Faraday 
cage garment that, at its body portion, is connected by separate paths to 
ground and that, at its sleeve hem portion, is connected by separate paths 
through a wrist strap into contact with the wearer's wrist. 
Another object of the present invention is to provide a wrist strap-type 
double grounding system in which there is combination flexible cloth 
insulation and a conductive ribbon within the garment. 
Another object of the present invention is to provide a wrist strap-type 
double grounding system in which the double connection from the wrist 
strap to the sleeve hem interferes only minimally, if at all, with 
movements of the hand of the operator. 
In carrying out principles of the present invention in accordance with the 
preferred embodiment thereof, a multipath static control garment comprises 
an electrically conductive body section and first and second electrically 
conductive sleeve sections. First and second electrically conductive body 
contact means connected to one of the sleeve sections are adapted to 
contact an arm of the wearer of the garment, such body contact means being 
in a wrist strap. The first body contact means is connected through the 
garment to a first grounding terminal on the garment body section. The 
second body contact means is connected through an independent grounding 
path to a second grounding terminal on the body section. Such second 
terminal is insulated from the garment. 
Thus, the garment-wrist strap combination comprises two separate, 
independent and mutually isolated grounding paths to first and second 
mutually insulated grounding terminals on the body section, and including 
a wrist strap connected to the garment, thereby achieving an improved 
redundant grounding of the wearer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Said U.S. patent application Ser. No. 08/191,625, for MULTI-PATH STATIC 
CONTROL GARMENT, filed Feb. 4, 1994, Inventor Kay L. Adams, is hereby 
incorporated by reference herein. 
The garment illustrated in FIG. 1 of the present patent application is in 
the form of a smock or a shop jacket of generally knee or mid-thigh 
length, having a metal snap front that can be opened and closed. This 
particular style of garment is shown solely for purposes of illustration, 
since the shape and style of the garment can vary without departing from 
principles of the present invention. 
The garment includes a body section 10, and sleeve sections 12, 14 that 
terminate in hems 16, 18, respectively. All of the garment is made of a 
knit (or woven) fabric or cloth having knit therein an electrically 
conductive Faraday cage grid. In a presently preferred example, the 
garment is knit of 89% polyester having 11% of carbon-suffused 
monofilament nylon knitted into a conductive grid pattern therein. Such 
grid is formed of a monofilament nylon that is suffused with carbon to 
provide electrically conductive carbon fibers throughout the entire body 
section and sleeve sections of the garment. The knit carbon suffused grid 
has squares of approximately 1/8 to 1/4 inch size. The grid defines a 
Faraday cage shield to shield the components being worked on from any 
radiation of static electricity off the wearer's regular clothing, since 
the illustrated garment is generally worn over the wearer's regular 
clothing. 
The words "hem" and "hems" as used in this application denote any type of 
outer end of either sleeve, except only cuffs that engage the skin and are 
electrically conductive as set forth in the above-cited copending patent 
application. In the preferred form, the cloth is reverse-bent and sewn 
into a conventional hem (FIG. 2), but there are other types of sleeve ends 
that could be used. These include sleeve ends having multiple stitching 
with or without reinforcement (reinforcing layers). The Dual Grounding 
Path Includinq Wrist Strap and Garment 
Various types of dual-path wrist straps may be used, for example, as shown 
and described in U.S. Pat. No. 4,639,825 which is incorporated by 
reference herein. 
The wrist strap shown in FIG. 2 and FIG. 6 hereof, and numbered 21, has two 
stretchable (for example, knit) cloth sections 22, 23. Each such section 
22, 23 is electrically conductive on its inside surface, so as to provide 
contact with the wrist of the wearer, but is insulating on its outer 
surface. Sections 22, 23 do not electrically connect to each other; 
instead, each extends between a contact element 24 and a length-adjustment 
mechanism or buckle 26. The contact element and the buckle are each formed 
of insulating synthetic resin so as to electrically isolate sections 22, 
23 from each other. 
As shown by FIG. 6, contact element 24 has metal plates 25a, 25b on the 
inner side thereof--for direct contact with the skin of the wearer's 
wrist. Plate 25a connects electrically to strap section 23. Plate 25b 
connects electrically to strap section 22. The plates are insulated from 
each other. 
A metal stud 27 (FIG. 2), part of a snap connector, is provided on contact 
element 24 and electrically connected to plate 25b and to cloth section 
22. A second metal stud or snap connector 28 on element 24 is electrically 
connected to plate 25a and to cloth section 23. 
A metal stud 30, part of a snap connector, is mounted on hem 18 of sleeve 
14, at the upper side of such sleeve (FIG. 2). Stated otherwise, connector 
30 is mounted on hem 18 at a region generally opposite the underside of 
sleeve 14, such underside having a longitudinal seam 31 sewn therein as 
shown in FIG. 4. 
Another stud, part of a metal snap connector, and numbered 32, is mounted 
on the body 10 of the garment, as best shown in FIG. 3. The preferred 
location is the upper-outer corner of the pocket 33 of a garment. 
Preferably, the pocket 33 is the lower-left pocket of the garment. 
An insulated flexible wire 35, having a female portion of the metal snap 
connector at each end (FIG. 2), is snap-connected between stud 28 on wrist 
strap 21 and stud 30 on hem 18. A second insulated flexible wire, numbered 
36 (FIG. 1), is snap-connected between stud 32 and ground. Stated more 
definitely, wire 36 forms part of a dual grounding cord 37 (FIG. 1) that 
extends from the body of the garment to circuit elements 38 and thence to 
ground 39. Ground 39 may be (for example) an electrically conductive clamp 
that is secured to a metal pipe (or other grounding element) in the 
structure. Circuit elements 38 are indicated by a box, reference being 
made to the above-cited U.S. Pat. No. 4,639,825. 
There is, accordingly, a first grounding path that extends from wrist strap 
section 23 and metal plate 25a through connector (stud) 28 and wire 35 to 
connector 30, and thence through the sleeve 14 to the body 10 of the 
garment, and thence through various paths in such body 10 to connector 32 
and wire 36 to circuit elements 38 and ground 39. In addition, static 
electricity passes directly from the regular clothing of the wearer of the 
smock to the Faraday cage contained within the smock or shop coat, and 
thence through wire 36 to ground. 
There is contact to the wrist of the wearer at the inner portion of cloth 
section 23, and metal-to-skin contact to the wrist of the wearer through 
metal contact element 25a. 
Proceeding next to a description of the second of the dual grounding paths, 
this includes the section 22 of wrist strap 21, and the metal plate 25b on 
the underside of contact element 24, both of which connect electrically to 
a metal stud (part of a snap connector) 27 on the contact element 24. 
Connector 27 connects through a second insulated flexible wire, numbered 
41, which wire connects electrically to a stud (part of a snap connector) 
54 mounted on hem 18 of sleeve 14 but not electrically connected to such 
hem (or to any part of the sleeve). (It is to be understood that the 
insulated flexible wires 35, 41 may be secured to each other 
longitudinally into a single cord having two mutually-insulated sections.) 
There will next be described the portion of the second grounding path that 
is in the garment, and that provides comfortable and minimally-annoying 
locations for connection to wrist strap 21 and to the dual grounding cord 
37. 
A long, flexible, electrically conductive ribbon 42 is provided, and at all 
portions thereof is enclosed in an insulating sheath 43 (FIGS. 2 and 3). 
The construction is such that opposite sides of sheath 43 sandwich the 
conductive ribbon 42 between them. The sheath is secured, namely, sewn, to 
the garment by nonconductive thread. 
Insulating sheath 43 is a cloth--for example, a cloth binding 
material--made of nonconductive cotton or the like. The conductive ribbon 
42 and its sheath 43 combine to form an elongate, washable, flexible, 
sewable insulated electrical conductor, which is numbered 44. 
One end of such conductor 44 is sewn to the exterior of hem 18 on sleeve 
14, by nonconductive thread, such end being numbered 47. End 47 is on the 
upper portion of sleeve 14, generally opposite the seam of such sleeve 
14--which seam is along the underside of the sleeve. End 47 is spaced a 
short distance from the above-indicated metal stud (snap connector) 30. 
From end 47, conductor 44 is sewn around the exterior of hem 18 at the 
forward side thereof (when the sleeve 14 projects as shown in FIG. 1), 
being parallel to the extreme outer edge of hem 18. 
At a region adjacent the bottom seam 31 of sleeve 14, the flexible 
electrical conductor 44 is bent underneath itself, outwardly, in a 
hospital corner (the angled edge of which is numbered 48 in FIG. 2). It is 
then bent upwardly around the extreme outer edge of hem 18, as shown at 
49, so as to be inside sleeve 14 and adjacent the bottom seam 31 (FIG. 4) 
of such sleeve. 
The hospital corner is sewn, and the flexible electrical conductor 44 is 
sewn along bottom seam 31 (always by nonconductive thread), reference 
being made to FIG. 4. 
The flexible conductor 44 then bends downwardly around the armpit region 
(through the armhole) of the garment, and down the side seam 51 of body 
10. (It is emphasized that (FIGS. 1 and 3) the body 10 has vertical side 
seams 51 that extend directly downwardly from the armpit regions of the 
garment and that meet the bottom seams 31 of the sleeves). Such side seams 
are sewn. 
The flexible electrical conductor 44 is sewn along the side seam 51 of body 
10, until an elevation generally the same as the left pocket 33 (upper 
region thereof) is reached. 
A hospital corner is then made on the inside of the garment (FIG. 3), 
having an angled corner as indicated at 52. The flexible conductor 44 is 
extended out through the side seam 51 of body 10 (FIG. 3) so as to be on 
the exterior of the garment. The hospital corner is sewn and the remainder 
of the flexible conductor 44 is then sewn horizontally along the exterior 
of body 10 to the vicinity of the outer side of pocket 33 as shown in FIG. 
3. 
Referring again to FIG. 3, a stud (part of a metal snap connector) 53 is 
connected to the flexible conductor 44 at a region near the 
above-mentioned stud (metal snap connector) 32. The distance between 
connectors 53 and 32 is preferably in the range 13/4 inches and 2.0 
inches. At the opposite end of the flexible connector 44, another stud 
(part of a metal snap connector) 54 is mounted (FIG. 2). Relative to each 
of the connectors 53, 54, and referring to FIG. 5, there is electrical 
connection only to the conductive ribbon 42, not to the body 10 of the 
garment. Thus, as shown in FIG. 5, a portion of the connector 53 extends 
through the outer side of sheath 43 at an opening therein, and extends 
through conductive ribbon 42, having a flange 56 at its inner end that 
bears against the inner surface of conductive ribbon 42, as illustrated. 
Stud (connector) 54 (FIG. 2) is mounted and connected and constructed 
identically to stud 53 (FIG. 5). Thus, FIG. 5 is equally applicable to 
connectors 53 and 54. 
To complete the second grounding path, the second insulated flexible wire 
41 (FIG. 1) is snap-connected to connector 54, while an insulated flexible 
wire 57, that forms the second portion of the dual grounding cord 37, is 
snap-connected to snap connector 53. 
Operation 
The described combination garment and wrist strap achieve, in a practical 
and effective way, the known advantages of dual-path grounding of workers 
in electronics plants (for example), and achieve the metal-to-skin contact 
desired by a number of manufacturers. Such metal-skin contact is between 
plates 25a and 25b (FIG. 5) and the wrist of the wearer. 
Furthermore, the connections between wrist strap 21 and the hem 18 of 
sleeve 14 are at such locations (connectors 30 and 54) as to provide 
minimal effect (if any) on the operations of the worker wearing the 
garment. The connectors 30, 54 are at the top of the sleeve where they are 
not likely to rub on any supporting surface or any work. Very importantly, 
the elongate, flexible, washable electrical conductor 44 provides no 
interference whatever with the operator or worker, either at its exterior 
portions (at the sleeve end and near pocket 33) or its interior portions 
(adjacent the seam 31, FIG. 4, on the underside of sleeve 14) or adjacent 
the side seam 51 (FIG. 3) of body 10. 
After the ground cord 37 and the flexible conductors 35, 41 are 
disconnected from the garment, the garment is easily washable many times 
over without causing any deterioration of the contact between the worker 
(especially at metal plates 25a, 25b) and ground. 
There is further achieved the important advantage of having one of the 
paths be throughout .large portions of the garment, with the described 
Faraday cage effect, and the other path be isolated or dedicated and 
insulated from the electrically conductive body and left sleeve of the 
garment. 
In an alternative embodiment, the wires 35, 41 are not employed. Instead, 
studs 30, 54 (FIG. 2) are mounted on the inside of the hem 18 and are 
directed inwardly. Furthermore, studs 27, 28 on the wrist strap 21 are 
both replaced by female connector portions adapted to receive studs 30, 
54. The wrist strap 21 is caused to be near or within hem 18, and 
connector elements 27, 54 and 28, 30 are directly mated with each other. 
The insulated flexible conductor 44, at its region that is sewn around hem 
18 on the outside of the sleeve end, is preferably instead sewn around the 
inside of the sleeve end; there is then no portion 49 that bends around 
the sleeve end. Stud 30 is connected directly to the sleeve, while stud 54 
is mounted as shown in FIG. 5--insulated from the sleeve and connected to 
the conductive ribbon. At least in the embodiment described in this 
paragraph, the female elements replacing 27, 28 are not located as shown 
in FIG. 1, but instead are both located in a single plane perpendicular to 
the axis of the wrist band 21 (as shown in schematic FIG. 1). 
The foregoing detailed description is to be clearly understood as given by 
way of illustration and example only, the spirit and scope of this 
invention being limited solely by the appended claims.