Fluid sprinkling – spraying – and diffusing – Electrostatic type
Reexamination Certificate
2000-01-07
2002-07-16
Doerrler, William (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Electrostatic type
C239S690100, C239S706000, C239S270000, C239S526000
Reexamination Certificate
active
06419171
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a static eliminator.
Static electricity is eliminated or removed as a harmful object in the industrial field where a semiconductor is handled or a surface treatment such as coating, plating, or evaporating is conducted. Conventional static electricity eliminating or removing instruments or tools, hereinafter referred to as static eliminator, will be explained below.
(1) Ionizer:
The ionizer ionizes an air and sprays out or issues out ions. The ionizer is attached to the machine to eliminate or remove static electricity from the work, or is held and moved by the operator to remove electricity from the work. In the former case, the work is put on the working table to which the ionizer is attached, and the ionizer is caused to issue ions toward the work and remove electricity from the work. In the latter case, the operator holds the ionizer so as to direct the ions from the ionizer toward the work and remove electricity from the work.
(2) Wrist Strap:
The wrist strap or conductive band is tied on the wrist of the operator to remove electricity from the human body. This is merely to remove electricity from the operator who sits at a working table on which the work is put, and electricity cannot be removed from the walking operator. Actually, the operator sometimes walks around without the wrist strap. Therefore, for the next operation, the operator would forget to tie the wrist strap on his wrist. Furthermore, the wrist straps are connected to the ground at the earth points by the electric wires. However, since the wires are connected to the wrist straps through many junctions, many accidents would be caused.
(3) Anti-static Electricity Clothes:
The operator wears clothes on which less static electricity is generated to prevent the generation of static electricity. The clothes can reduce the generation of static electricity, but cannot remove the generated electricity.
(4) Conductive Shoes:
The shoes which are used during the operation are made to be conductive, The shoes transfer the static electricity generated on the human body to the conductive floor. In this case, the conductive floor is required and the ordinary floor or non-conductive floor is not effective.
(
5
) Passive Electricity Removing Tool:
(a) Ring type
The ring type of the electricity removing tool is fit on the finger of the operator for use. The tool discharges the electric charges to escape the charges in the air when the charges are accumulated above a static potential, and then lowers the static potential. However, since the discharge of the electricity removing tool stops when the charges lowers below a certain static potential, the removing tool cannot remove a low static potential.
(b) Wrist watch type
The wrist watch type of the electricity removing tool is fit on the wrist of the operator for use. The tool discharges the electric charges to escape the charges in the air when the charges are accumulated above a static potential, and then lowers the static potential. However, since the discharge of the electricity removing tool stops when the charges lowers below a static potential, the removing tool cannot remove a relative low static potential.
Even when one of these electricity removing instruments or tools is used, electricity removement is rather difficult in the following cases. For example, when the operator walks around, the clothes causes the friction therebetween and then the electricity is generated to be accumulated on the human body. If the socks are made of conductive fibers, shoes are conductive, and the floor is conductive, the accumulated static electricity can escape from the human body. However, since in general the operator is not in a such environment, there are problems to be solved. For example, when the operator bearing charges touches the work, the work is electrically attacked and then broken. For another example, the dust on which the charge is accumulated is transferred to the work and then causes damage to the work. As mentioned above, conventionally, a perfect method of removing electricity from the walking operator was not present.
Furthermore, an air tool such as a cutter or buff is used when a big object such as a plastic ship body is machined, e.g. is cut or is ground. Since an air hose which connects an air source to the air tool is usually made of an insulator material where static electricity does not escape, the static electricity generated due to the friction during machining is accumulated on the human body through the air hose. As the static electricity or electric charge is accumulated up to a certain level, the discharge is abruptly caused toward the floor to give a big electric attack to the operator. In such a case, since the operator walks around, there is no perfect method of removing electricity.
A conventional ionizer includes an air-blow gun type of electricity. As shown in
FIG. 43
, The conventional air-blow gun type of static eliminator
600
is constructed so that an air blow bun is provided with an electric section, that is, a discharge electrode of ionizer. The air-blow gun comprises a cylindrical gun body
602
through which a compressed air is flowed, an air hose
604
through which the compressed air is supplied to the gun body
602
, and air nozzle
606
provided at the leading end of the gun body
602
.
The air blow gun is provided with a discharge electrode section
608
which comprises a cylindrical insulator
608
a
provided between the gun body
602
and the air nozzle
606
. and a discharge needle
608
b
disposed on the center of the cylindrical insulator
608
a
. The discharge needle
608
b
is applied with a high voltage from a high voltage generator
610
through a high voltage cable
612
.
Another conventional air-blow gun type of static eliminator is constructed so that a high voltage generator is disposed integrally with an gun body.
These conventional air-blow gun type of static eliminators are common in that a high voltage discharge electrode section is incorporated in the air-blow gun section or structure. For this reason, conventional air-blow gun type of static eliminator has a disadvantage described below.
(1) The air-blow gun uses a compressed air. The compressed air is carried up to the air-blow gun in which the air is expanded abruptly. Since the air is given adiabatic expansion and cooled, the generation of water droplets in the air-blow gun is inevitable. As shown in
FIG. 44
which is a cross-sectional view of the electric section, that is, discharge electrode section of the air-blow gun type of static eliminator, the air-blow gun is always attended with the generation of droplets. The electric is leaked from the discharge needle
608
b
of high voltage electrode or the high voltage cable
612
via the water droplets. That is, electric leakage is generated. As a result, the operator working while carrying the air-blow gun by hand would be in danger from an electric shock or electrification.
FIG. 45
is a view for a model of an electric circuit showing the status of the electric leakage. In
FIG. 45
, the high voltage V
0
made in the high voltage generating circuit
622
is led to the discharge needle through a current limiting resistor R. Assuming that voltage drop across the current limiting resistor R is V
D
, the discharge voltage is V
1
, the discharge current is I
1
, and the leak current is I
2
.
V
1
=V
0
−V
D
.
V
D
=(
I
1
+I
2
)
R
Now, assuming that the high voltage V
0
is 5 KV, the current limiting resistor is 100 M ohms, and the discharge current is 1 microampere, and there is no leakage, that is, I
2
is 0,
V
D
=(1*10
−6
)*(100*106
6
)=100 V.
and then the discharge needle voltage (V
0
−V
D
)=5 KV−100 V=4.9 KV.
On the other hand, assuming that there is a leakage and the leakage current is 50 microampere,
V
D
=(1*10
−6
+50*10
−6
)*(100*10
6
)=5,100 V,
and then the discharge needle voltage=5 KV−5.1 KV nearly equals 0 KV.
The voltage at the dischar
Chong Leighton K.
Doerrler William
Hwu Davis
Takayanagi Research Inc.
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