A device for dissipating electrostatic electricity from a person wearing a static protecting garment. The device comprises a means for continuously conducting electricity between the garment and the person; and means for continuously conducting electricity from the garment and person to ground. The invention is also directed to a method of preventing electrostatic damage to a device which is sensitive to electrostatic potentials, said device being handled by a person wearing a static protective garment. The method comprises simultaneously and continuously grounding the person and the garment.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to electrostatic protective devices, and 
in general to the protection of electrostatic sensitive equipment from 
static electricity built-up on clean room and other electrostatic 
protective garments. 
2. Description of the Prior Art 
The problem of preventing damage to electronic equipment is a serious one. 
Electrostatic potentials well below the level of human sensitivity (3.5 KV 
to 4 KV) can cause failure in bipolar and MOS devices, film resistors, 
silicon chips and many other electronic components, from early processing 
through assembly to an electronic system's end of life. These potentials 
can exist on solids or liquids that are electrically isolated from each 
other and from ground. The procedures and materials traditionally used for 
electrostatic devise (ESD) protection are in part designed to ensure that 
these electrostatic potentials are equalized. 
Protective containers such as IC rails, bags, and tote boxes--be they 
static dissipative (10.sup.6 -10.sup.13 ohms /sq) or conductive (less than 
10.sup.6 ohms /sq)-operate by allowing the transfer of static electricity 
across the material to ground. When transported in an ungrounded 
condition, however, these containers can still develop static potentials. 
Therefore, before the contents can be safely handled, either mechanically 
or by a human operator, the container and handler must be at the same 
potential. Electrostatic charges can be shared by direct connection or via 
an intervening material, such as a conductive tabletop. In a typical work 
station designed for ESD protection, the protective container is placed 
directly on the grounded work surface, while the operator is usually 
electrically connected to the work surface and to ground with a conductive 
wrist strap. 
Typically, in such surroundings static protective garments are also worn by 
the persons handling the electronic devices. These protective garments do 
not have what may be termed a zero static charge but rather produce or 
generate a minimum amount of static. The static protective characteristics 
of the fabric are generally achieved by the introduction of carbon yarn or 
other conductive yarn into the weave of the basic non-conductive fabric, 
and/or a topical anti-static finish applied to the garment during routine 
in-use laundry or dry cleaning processes. The basic non-conductive fabric 
is typically constructed of continuous filament non-conductive polyester. 
The routine application of a topical anti-stat, depending on its chemical 
formulation, can either increase the static dissipative properties of a 
material or minimize its triboelectric charge generating properties by 
inhibiting its ability to give up or accept electrons, or both. A 
preferred static protective fabric is one in which conductive fibers are 
interwoven into the polyester fibers in a grid design (approx. 1/2"). One 
such fabric is sold under the trademark ULTRA-CHIEF 10 by Worklon, a 
division of Superior Surgical Mfg. Co., Inc. 
Many of the static-protective devices known in the art dissipate an 
electrical charge generated by a person to a ground; see for example the 
following U.S. patents: 
U.S. Pat. No. 4,398,277 to Christiansen et al; 
U.S. Pat. No. 4,373,175 to Mykkanen; 
U.S. Pat. No. 3,857,397 to Brosseau; 
U.S. Pat. No. 3,596,134 to Burke; 
U.S. Pat. No. 3,084,700 to Fischer et al; and 
U.S. Pat. No. 1,940,491 to Freitag. 
Christiansen et al. describes a device which is strapped onto the users 
wrist to control the electrostatic charge accumulation on the body of a 
person. Typically, the wrist strap is a conductive polymer for conducting 
electrostatic charge via the individuals wrist to a ground cord secured to 
the wrist strap with an electrically conductive snap connection. The wrist 
strap can be closed by a Velcro, (trademark of Velcro U.S.A., Inc.) 
fastener to secure the wrist strap to the wrist of the individual wearer. 
The strap relies on the firm intimate contact of the conductive member to 
the body or person of the individual. 
Mykkanen describes a similar safety apparatus, e.g., wrist strap which is 
connected between a human and an electrically conductive terminal. 
Brosseau also describes an electrically conducive wrist strap worn on the 
wrist. 
Burke describes an apparatus to be worn by persons working in an 
electrostatic field for eliminating discomfort and ill effects of 
discharges of electrical energy through the person. The device comprises 
one or more bands in the form of garter or a belt, each having a flexible 
conductive element therein which conforms to the body shape and lies close 
to the skin. The garter belt is connected by leads to a conductor for 
contacting grounded structures. 
Fischer et al. relates to a grounded comb. 
Frietag relates to a device for grounding persons working near high-voltage 
electric power stations to prevent electrocution of or injury to a person. 
Thus, it can be seen that all of the aforedescribed devices are directed 
solely to discharging electrostatic charge from a person. 
SUMMARY AND OBJECTS OF THE INVENTION 
It is an object of this invention to provide a device which not only 
discharges static electricity from a person, but discharges static 
electricity generated by an electrostatic dissipating garment worn by such 
person. 
It is a further object of this invention to provide a device for 
simultaneously discharging static electricity from a garment worn by a 
person and from that person, said device being easy to put on and install. 
It is still a further object of this invention to provide a device which is 
simple in construction and inexpensive. 
It is an object of this invention to provide a device which prevents the 
accumulation of static electricity on an electrostatic dissipating 
garment. 
Another object of this invention to provide a device which prevents the 
accumulation of static electricity on the person or the electrostatic 
dissipating garment worn by such person without unduly incumbering the 
person with a multitude of grounding implements. 
It is another object of this invention to provide a device which prevents 
the accumulation of static electricity on the person or the electrostatic 
dissipating garment in an efficient manner with a minimum of interference 
to the person, and which includes provisions to minimize harm from 
accidental contact of the garment with high voltage sources. 
Yet another object of this invention to provide a device which contains 
components which are conductively connected, but which may be replaced if 
the individual components deteriorate in order to ensure adaquate 
performance, which is comfortable to wear, and which is durable in 
operation. 
Still another object of this invention to provide a device which provides a 
means for discharging static electricity generated by the clothing of a 
person wearing an electrostatic dissipating garment. 
A further object of this invention is to provide a device which provides a 
means to enable people to work in electrostatic free environments without 
having to remove or alter their clothing to reduce the interaction between 
themselves and their clothing. 
It is another object of this invention to provide a device which provides a 
means for dissipating electrostatic forces which are developed between a 
person and his normal clothing or the different layers of the person's 
normal clothing. 
All of the foregoing objects and others are achieved by a device for 
dissipating electrostatic electricity from a person wearing a static 
protective garment. The device comprises (a) a means for continuously 
conducting electricity between the garment and the person; and (b) a means 
for continuously conducting electricity from the garment or person to a 
ground. 
The invention is also directed to a method of preventing electrostatic 
damage to a device which is sensitive to electrostatic potentials, said 
device being handled by a person wearing a static protective garment. The 
method comprises simultaneously and continuously grounding the person and 
the garment.

DESCRIPTION OF THE INVENTION 
None of the known devices in the art relate to both simultaneously 
grounding a person and grounding the static protective garment worn by 
that person. In fact, there is no realization in the art that such is 
required. 
It has been found that although the carbon yarns in a static protective 
fabric are conductive, if the garment is not grounded and since the yarns 
in the fabric, e.g. polyester, are not conductive, whatever static is 
generated on these fibers is suspended thereon. Neither the charges on the 
carbon yarn nor the polyester fiber are dissipated until the person 
wearing the garment and the garment come in contact with a ground. Thus, 
while the presence of carbon or any other conductive fiber in the fabric 
assists in dissiptating the static charge, the polyester therein is not 
conductive at all and the static charge that is generated on these fibers 
(which are surrounded by conductive fibers) is suspended in that area. If 
the fabric has been treated with an anti-static topical finish, for 
example, during the final rinse cycle of the laundering process and the 
static is provided with paths to the nearest conductive yarn, i.e. it is 
dissipated throughout the garment. 
Applicant has discovered through tests that a deliberate continuous 
grounding of both the garment and person is highly desirable and necessary 
while working with highly sensitive equipment. For example, in one 
situation an individual donned an anti-static clean room type coverall 
made of 100% polyester fabric with carbon filament interwoven in a grid 
design. The fabric, sold in garments under the trademark ULTRA-CHIEF 10, 
by Worklon, was said to have an anti-static capability (surface 
resistivity of 1.times.10.sup.5 ohms/sq). The person then stepped onto a 
1" thick polystyrene insulation material and touched a 5,000 volt DC power 
supply. The 5/KV E-Field was immediately detected from the outside surface 
of the suit. When the suit and person were grounded this E-Field instantly 
disappeared and the individual lost the charge from his person. This test 
clearly demonstrates the importance of providing a deliberate continuous 
grounding system for both the garment and the wearer. 
The antistatic garment, in theory, acts as a basic Faraday cage. Such a 
cage effectively shields and protects items from electrical events which 
occur outside of the cage. To perform this function, it is not necessary 
that the cage be grounded. It is necessary, however, that all conductive 
material forming the cage be electrically connected to constitute a single 
conductor. The resistance of the conductive circuit through the cage must 
be sufficiently low so that any charge induced at one point on the cage 
will be conducted to the most distant locations on the cage more rapidly 
than the charge is induced. This generally accounts for the recommendation 
that static protective garments have a surface resistivity not exceeding 
1.times.10.sup.5 ohms/per sq. 
However, if a Faraday cage garment is not grounded within itself and 
contains charged items, the algebraic sum of all the contained charges is 
inductively coupled to the cage, and a corresponding E-field emanates from 
the entire outside of its surface. On the other hand, if the cage 
(garment) is grounded, the entire outer surface has a net charge of zero 
with respect to the ground and no field emanates from the garment. 
Thus, if one of the intended purposes of a clean room static protective 
garment is to protect external items from any charge existing inside the 
garment, it follows that the garment itself should be at ground potential. 
Thus the garment will form a protective Faraday cage which is capable of 
preventing the garments internal charges from being inductively coupled to 
items outside the garment. 
As previously indicated, it is quite commonplace for persons working on 
electrostatic sensitive devices to wear grounding straps around their 
wrists. These "wristlets" are generally made of a material which has a 
conductive fiber content, i.e. stainless steel or carbon. Typically, a 
contact is provided on the band to which is affixed a fastener. To this 
fastener, one end of a grounding cord is secured. A current limiting 
resistor, e.g. 1 megohm, is normally placed in series with the grounding 
wire at this point as a safety device to protect the user in the event he 
inadvertently contacts a fatal power supply voltage. On the other end of 
the cord is an alligator or bulldog clip which is affixed to a ground at 
the work station. The static protective garment, to applicant's knowledge, 
has never been affixed to this mechanism, firstly because there is no 
manner of accomplishing this and, foremost, there was never a recognition 
of a need for continuously grounding the garment. Applicant has discovered 
that there is a need for grounding such anti-static garment and has solved 
the problem of accomplishing such by grounding both the garment and the 
person utilizing a means for conducting electricity between the conducting 
fibers in the garment and the person, in conjunction with a means for 
transferring the electricity from the conducting fibers in the garment or 
person to the ground. 
Referring to the drawings, FIG. 1 describes one embodiment of the device 10 
of this invention. Wristlet 12 is wrapped securely around the wearers 
wrist 13 and may be similar to any of the aforedescribed wristlets which 
are well known in the art, except it is modified as described herein. The 
wristlet 12 has electrically conducting fibers which transfer electricity 
from the wrist 13 to the wristlet 12. At one end of the wristlet 12 is 
mounted a male snap connecting means 14. The snap 14 is mounted on the 
wristlet so as to conduct electricity from the conducting fibers in the 
wristlet 12 to the snap 14. Attached to the sleeve 22 of antistatic 
garment 20 is a female snap connecting means 16 which mates with and is 
electrically connected to snap 14. Snap means 16 is mounted on the sleeve 
22 so as to conduct electricity from the conducting fibers in sleeve 22. 
An additional male snap connecting means 18 is mounted to the garment 
sleeve 22 in the same manner as snap 16. A grounding cord 24 is provided 
with a snap means 26 thereon which mates with snap 18. Thus, the device 
enables the static electricity from the person and anti-static garment to 
be continuously at the same potential and grounded. 
FIGS. 2 and 3 show two other embodiments of this invention. 
In FIG. 2 two male snap connecting mean 28, 29 are provided on wristlet 12 
and a female snap connecting means 30 is provided on sleeve 22. Electrical 
connecting cord 32 is provided, one end of which has a female snap 
connecting means 34 and the other end of which has a male snap connecting 
means 36. The snap connecting means 34, 36 mate respectively with the snap 
connecting means 29 on the wristlet 12 and the snap connecting means 30 on 
the sleeve 22. A grounding cord 38 is provided with a snap means 40 which 
mates with snap 28 on wristlet 12. 
FIG. 3 shows another embodiment wherein a conductive eyelet 42 is provided 
at the end of sleeve 22. Attached to wristlet 12 is a male member 44 which 
matingly fits through eyelet 42 and is in electrical contact therewith. A 
grounding cord 46 is provided, one end of which has a female snap 48 
thereon which mates with male member 44 to provide an electrical 
connection therewith and maintain member 44 secure in eyelet 42. 
In connection with the embodiment shown in FIG. 3 it is also possible to 
use what is known as a "gypsy" stud and socket arrangement which reduces 
in half the number of components necessary for snap fastening. FIG. 4 
shows such an embodiment. In this embodiment a "gypsy" type stud and 
socket snap fastener 50 replaces the eyelet 42 construction used in FIG. 
3. Fastener 50 secures the grounding wire 70 and the wristband 60 to 
sleeve 52. A "gypsy" type stud and socket 50 are fastened to the sleeve 52 
of the garment 54. The "stud" side 56 engages and mates with a standard 
snap receptacle 58 disposed on the wristband 60. The other side 62, i.e. 
the "socket", of the "gypsy" type stud and socket 50 is disposed on the 
outer portion of the sleeve 52 adapted to mate with a male snap component 
64 of standard configuration which is attached to grounding wire 70. 
Preferably, as depicted in FIG. 4, the sleeve of the garment has four 
additional snaps used for size adjustment of the sleeve. As shown in FIG. 
4, there is one female snap 68 and three male stud portions 72. The female 
68 portion will be positioned near the top of the sleeve as worn by the 
user, i.e. on the top of the wrist, so that the sleeve 52 can be gathered 
up from around the bottom of the sleeve 52 so that the connection of the 
grounding cable 70 will be on the top of the wrist area of the user. This 
prevents cable 70 from interfering with the activities of the wearer of 
the garment. 
In all the embodiments depicted, provision may be made for attaching the 
wristlet to the sleeve of the garment on both sleeves to accommodate for 
right handed and left handed people. 
Optionally, but not shown, the end of the sleeves may have an elastic band 
therein to cause the sleeve end to act as a wristlet. The sleeve is then 
grounded by an appropriate wire connection. 
In each of the embodiments a current limiting resistor having a normal 
ohmic value of 1 megohm is incorporated into the grounding circuit. 
While the fastener for the various conductive means has been described here 
as snaps, it should be noted that any other convenient type of fasteners 
may also be used, where applicable. So for example, alligator clips or 
other types of fasteners are also capable of being used in various aspects 
of this invention. 
It should be pointed out that, typically, there is no continuous contact 
between the static protective garment and the skin of the wearer other 
than the conductive pathway produced by this invention. Typically, the 
static protective garment only comes in contact with the clothing worn by 
the user. However, because of the conductivity of the static protective 
garment, any electro-static charges which are developed due to the 
interaction of the clothing of the wearer between layers thereof and/or 
the skin of the wearer and the clothing are transferred to the static 
protective garment either by direct contact of the clothing to the garment 
or the deliberate contact between the skin of the wearer and the static 
protective garment by means of the grounded pathway created by this 
invention. 
From the foregoing embodiments it can be seen that the objects of this 
invention are achieved by providing a simple and inexpensive device and 
method for simultaneously and continuously grounding both the person and 
the anti-static garment being worn.