U.S. patent number RE35,214 [Application Number 08/385,038] was granted by the patent office on 1996-04-23 for grounded magnetic device for removing static charges.
This patent grant is currently assigned to M. Eileen McGarry. Invention is credited to Arnold A. Downs, Kevin M. McGarry.
United States Patent |
RE35,214 |
McGarry , et al. |
April 23, 1996 |
Grounded magnetic device for removing static charges
Abstract
A device for removing static charges from a moving paper web
includes two grounded and shielded permanent magnets with means to
support each magnet on opposite sides of the moving web with the
polarities of each magnet so oriented that the charge-neutral
center plane of the magnet is perpendicular to the path of the web.
The device removes static charges by exposing the paper web to a
grounded magnetic field first of one polarity and then to a
grounded magnetic field of the opposite polarity.
Inventors: |
McGarry; Kevin M. (Kirkwood,
MO), Downs; Arnold A. (Mt. Vernon, IL) |
Assignee: |
McGarry; M. Eileen (Los
Angeles, CA)
|
Family
ID: |
25237147 |
Appl.
No.: |
08/385,038 |
Filed: |
February 7, 1995 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
822853 |
Jan 21, 1992 |
05331503 |
Jul 19, 1994 |
|
|
Current U.S.
Class: |
361/214;
361/220 |
Current CPC
Class: |
H05F
3/02 (20130101); H05F 3/04 (20130101) |
Current International
Class: |
H05F
3/04 (20060101); H05F 3/02 (20060101); H05F
3/00 (20060101); H05F 003/00 () |
Field of
Search: |
;361/212,214,220,221,222 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaffin; Jeffrey A.
Attorney, Agent or Firm: Senniger, Powers, Leavitt &
Roedel
Claims
We claim:
1. Apparatus for removing static electrical charges on a moving web
passing therebetween, comprising in combination
a pair of elongated magnetic device of substantially equal length,
each of said pair of devices including
an elongated end-to-end assembly of substantially rectangular
permanently magnetic blocks of equal height and thickness,
assembled with magnetic poles of one polarity aligned along the
length of one side of said elongated assembly and magnetic poles of
the opposite polarity aligned along the length of the opposite side
of said elongated assembly;
said assembled blocks having two end surfaces and four side
surfaces, and a means to provide for grounding of each said
assembly,
said assembled blocks having magnetic shielding on two opposite
side surfaces and on one intermediate side surface, and being
exposed on the other intermediate side surface, together with
means to position the two said devices spaced narrowly apart in
parallel alignment with their like polarities opposite each other
so oriented as to provide a substantially common charge-neutral
plane perpendicular to the path of such web. .Iadd.
2. A process for removing a static electrical charge on a material
as the material moves in response to a material moving apparatus,
the process comprising the steps of:
positioning a magnet adjacent to the material moving apparatus;
wherein the magnet produces a magnetic filed having first and
second polarities;
grounding the magnet to provide a grounded magnetic field having
said first and second polarities; and
moving the material and the magnet relative to each other so that
the material passes through the first polarity of the grounded
magnetic field and thereafter passes through the second polarity of
the grounded magnetic field. .Iaddend. .Iadd.3. The process of
claim 2 wherein the positioning step further comprises the step of
positioning the magnet wherein the magnet produces a magnetic field
having a field strength of at least 390 mTesla. .Iaddend. .Iadd.4.
The process of claim 3 wherein the positioning step comprises the
step of positioning a permanent magnet adjacent to the material
moving apparatus; and wherein the grounding step comprises the step
of grounding said magnet. .Iaddend. .Iadd.5. The process of claim 4
wherein the moving step further comprises the step of moving the
material
along a path spaced from the magnet. .Iaddend. .Iadd.6. The process
of claim 5 further comprising the steps of:
positioning a second magnet adjacent to the first mentioned magnet;
wherein the second magnet produces a magnetic field having first
and second polarities corresponding to the first and second
polarities of the first mentioned magnet;
grounding the second magnet to provide a grounded magnetic field;
and
moving the material and both said magnets relative to each other so
that the material passes between said magnets. .Iaddend. .Iadd.7.
The process of claim 3 wherein the moving step further comprises
the step of moving the material along a path spaced from the
magnet. .Iaddend. .Iadd.8. The process of claim 2 wherein the
positioning step further comprises the step of positioning the
magnet wherein the magnet produces a magnetic field having a
nominal field strength of 390 mTesla. .Iaddend. .Iadd.9. The
process of claim 2 wherein the positioning step comprises the step
of positioning a permanent magnet adjacent to the material moving
apparatus; and wherein the grounding step comprises the step of
grounding said magnet. .Iaddend. .Iadd.10. The process of claim 2
wherein the positioning step comprises the step of positioning an
elongated permanent magnet adjacent to the material moving
apparatus; wherein said magnet has a
length greater than a width of the material. .Iaddend. .Iadd.11.
The process of claim 2 wherein the positioning step comprises the
step of positioning an elongated permanent magnet adjacent to the
material moving apparatus; wherein the length of said magnet is
about 2 inches longer than the width of the material. .Iaddend.
.Iadd.12. The process of claim 2 wherein the moving step further
comprises the step of moving the material along a path spaced from
the magnet. .Iaddend. .Iadd.13. The process of claim 2 wherein the
positioning step further comprises the step of positioning the
magnet wherein the magnet produces a magnetic field having a
charge-neutral plane and wherein the moving step further comprises
the step of moving the material along a path perpendicular to the
charge-neutral plane. .Iaddend. .Iadd.14. The process of claim 2
further comprising the steps of:
positioning a second magnet adjacent to the first mentioned magnet;
wherein the second magnet produces a magnetic field having first
and second polarities corresponding to the first and second
polarities of the first mentioned magnet;
grounding the second magnet to provide a grounded magnetic field;
and
moving the material and both said magnets relative to each other so
that
the material passes between said magnets. .Iaddend. .Iadd.15. A
process for removing a static electrical charge on a material as
the material moves in response to a material moving apparatus, the
process comprising the steps of:
positioning a magnet adjacent to the material moving apparatus;
wherein the magnet produces a magnetic field having a field
strength of at least about 390 mTesla; and
moving the material and the magnet relative to each other so that
the material passes through the magnetic field. .Iaddend. .Iadd.16.
The process of claim 15 wherein the positioning step comprises the
step of positioning a permanent magnet adjacent to the material
moving apparatus. .Iaddend. .Iadd.17. The process of claim 15
wherein the positioning step comprises the step of positioning an
elongated permanent magnet adjacent to the material moving
apparatus; wherein said magnet has a length greater than a width of
the material. .Iaddend. .Iadd.18. The process of claim 15 wherein
the moving step further comprises the step of moving the material
along a path spaced from the magnet. .Iaddend. .Iadd.19. The
process of claim 15 wherein the positioning step further comprises
the step of positioning the magnet wherein the magnet produces a
magnetic field having a charge-neutral plane and wherein the moving
step further comprises the step of moving the material along a path
perpendicular to the
charge-neutral plane. .Iaddend. .Iadd.20. The process of claim 15
further comprising the steps of:
positioning a second magnet adjacent to the first mentioned magnet;
wherein the second magnet produces a second magnetic field;
grounding the second magnet to provide a grounded magnetic field;
and
moving the material and both said magnets relative to each other so
that the material passes between said magnets. .Iaddend. .Iadd.21.
Charge removing apparatus for removing a static electrical charge
on a material as the material moves along a path in response to the
material moving apparatus, the charge removing apparatus
comprising:
a magnet positioned along the path of the material; wherein the
magnet produces a magnetic field having first and second
polarities; and
an electrical ground connected to the magnet to provide a grounded
magnetic field having said first and second polarities;
said magnet positioned to produce the magnetic field in the path of
the material such that, as the material moves relative to the
magnet in response to the material moving apparatus, the material
passes through the grounded magnetic field of the first polarity
and thereafter passes through the grounded magnetic field of the
second polarity. .Iaddend. .Iadd.22. The charge removing apparatus
of claim 21 wherein the magnet produces a magnetic field having a
field strength of at least 390 mTesla.
.Iaddend. .Iadd.23. The charge removing apparatus of claim 21
wherein the magnet comprises a permanent magnet positioned adjacent
to the material moving apparatus along the path of the material;
and wherein the electrical ground is connected to said magnet.
.Iaddend. .Iadd.24. The charge removing apparatus of claim 21
wherein the magnet comprises an elongated permanent magnet
positioned adjacent to the material moving apparatus along the path
of the material; and wherein said magnet has a length greater than
a width of the material. .Iaddend. .Iadd.25. The charge removing
apparatus of claim 21 wherein the position of the magnet is spaced
from the path of the material. .Iaddend. .Iadd.26. The charge
removing apparatus of claim 21 wherein the magnet produces a
magnetic field having a charge-neutral plane; and wherein the
magnet is positioned such that the charge-neutral plane is
perpendicular to the path of the material. .Iaddend. .Iadd.27. The
charge removing apparatus of claim 21 further comprising:
a second magnet positioned adjacent to the first mentioned
magnet;
wherein the second magnet produces a magnetic field having first
and second polarities corresponding to the first and second
polarities of the first mentioned magnet; and
an electrical ground connected to the second magnet to provide a
grounded magnetic field;
wherein the path of the material runs between said magnets.
.Iaddend.
.Iadd.8. Charge removing apparatus for removing a static electrical
charge on a material as the material moves along a path in response
to a material moving apparatus, the charge removing apparatus
comprising:
a magnet positioned along the path of the material;
wherein the magnet produces a magnetic field having a field
strength of at least about 390 mTesla;
said magnet positioned to induce the magnetic field in the path of
the material such that, as the material moves relative to the
magnet in response to the material moving apparatus, the material
passes through the magnetic field. .Iaddend. .Iadd.29. The charge
removing apparatus of claim 28 wherein the magnet comprises a
permanent magnet positioned along the path of the material.
.Iaddend. .Iadd.30. The charge removing apparatus of claim 28
wherein the magnet comprises an elongated permanent magnet
positioned along the path of the material; wherein said magnet has
a length greater than a width of the material. .Iaddend. .Iadd.31.
The charge removing apparatus of claim 28 wherein the position of
the magnet is spaced from the path of the material. .Iaddend.
.Iadd.32. The charge removing apparatus of claim 28 wherein the
magnetic field produced by the magnet has a charge-neutral plane;
and wherein the magnet is positioned such that the charge-neutral
plane is perpendicular to the path of the
material. .Iaddend. .Iadd.33. The charge removing apparatus of
claim 28 further comprising:
a second magnet positioned adjacent to the first mentioned magnet;
and
an electrical ground connected to the second magnet to provide a
grounded magnetic field;
wherein both said magnets are positioned with their respective
magnetic fields in the path of the material such that, as the
material moves relative to the magnets in response to the material
moving apparatus, the material passes through the magnetic fields.
.Iaddend. .Iadd.34. Charge removing apparatus for removing a static
electrical charge on a material as the material moves along a path,
the charge removing apparatus comprising:
a first magnet positioned along and spaced from the path of the
material;
a second magnet positioned adjacent to the first magnet; wherein
the magnetic poles of the first magnet are aligned with the
corresponding magnetic poles of the second magnet;
an electrical ground connected to the first and second magnets
wherein said magnets and ground provide a grounded magnetic field
having afield strength of at least about 390 mTesla; and
means for moving the material and said magnets relative to each
other so that the material passes between said magnets and through
the grounded
magnetic field. .Iaddend. .Iadd.35. Charge removing apparatus for
removing a static electrical charge on a web of paper as the paper
moves along a path through a printing press, the charge removing
apparatus comprising:
a magnet positioned along the path of the web;
wherein the magnet provides a magnetic field having a field
strength of at least about 390 mTesla; and
wherein said magnet is positioned with the magnetic field in the
path of the web such that, as the web moves along the path through
the printing press, the web passes through the magnetic field.
.Iaddend. .Iadd.36. Charge removing apparatus for removing a static
electrical charge on a paper comprising:
a paper moving apparatus;
a magnet positioned adjacent to the paper moving apparatus; and
an electrical ground connected to the magnet;
wherein the magnet and ground provide a grounded magnetic field
having a field strength of at least about 390 mTesla; and
wherein the paper moving apparatus moves the paper and the magnet
relative to each other so that the paper passes through the
grounded magnetic field. .Iaddend. .Iadd.37. Charge removing
apparatus for removing a static electrical charge on a material,
the charge removing apparatus comprising:
a magnet to produce a magnetic field having a field strength of at
least about 390 mTesla;
an electrical ground connected to the magnet to provide a grounded
magnetic field; and
means for moving the material and the magnet relative to each other
so that the material passes through the grounded magnetic field.
.Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for removing
static electricity by use of a grounded magnetic field.
2. Description of the Related Art
Static electricity as is generated by the passage of webs of
electrically non-conductive material over industrial equipment,
creates substantial problems in many industries, for example the
printing industry. Thus, charges caused by friction of paper
passing against the dissimilar material of a printing press,
conveyer or other machine may interfere with downline processes
such as folding or stacking.
Methods heretofore used in dealing with static electricity include
the use of powder sprays, silicon, etc. Such methods in reducing
friction may increase maintenance problems, as those due to spray
build-up, and may be unsuitable for use with many types of
materials.
"Static bars" have been designed to discharge a constant current
from a high voltage source to the paper to neutralize static
build-up. These have been generally ineffective because of the
continual variations in charge and in the location of the static
charge build-up.
SUMMARY OF THE INVENTION
In the preferred embodiment of the present invention a strong
grounded magnetic field is used to remove static charge build-up.
As utilized with paper webs, for example, a statically charged web
is passed between two elongated permanent magnet assemblies closely
spaced in parallel alignment, and positioned traverse to the
movement of the web. The magnetic assemblies are shielded along
three elongated sides of each magnet to increase the density of the
field emitted by the exposed side. Each magnet has it polarities
oriented so that the charge-neutral center plane is parallel to the
two opposite shielded sides. The result is that the opposite sides
of the passing web are first simultaneously exposed to one
polarity, and then to the opposite polarity.
While we are aware of no accepted theory regarding how magnetic
flux interacts with static charges, it is believed that flux of one
polarity attracts the static charges of opposite polarity and leads
them to ground.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of a magnetic device shielded on three
sides embodying the present invention. In this illustration, the
side shielding is broken away to show its assembly of several
magnetic blocks of equal size. The base extends beyond the magnet
assembly to allow clamping in position and for convenient
grounding. The polarities of the magnet assembly are marked by plus
and minus signs.
FIG. 2 is an end view of the FIG. 1 device. The dotted lines
illustrate the idealized shape of the magnetic field as shielded
and ideally emitted by the exposed surface of the device only. The
charge-neutral center plane where the oppositely charged flux
fields meet is also shown.
FIG. 3 is an isometric view of an alternative magnetic device in
which a single magnet of the desired length is used.
FIG. 4 is an isometric view illustrating movement of a web between
the grounded magnetic devices of either the FIG. 1 or FIG. 3 type
and supporting end brackets which maintain the parallel alignment
and spacing of the device and to which grounds are connected.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The magnetic device 10 shown in FIG. 1 utilizes a permanent magnet
16 constructed of several permanently magnetic blocks 17 of equal
size. Each block has its polarities oriented along its elongated
sides, their polarities being marked in FIG. 1. The blocks are
assembled end-to-end. This construction allows use of a plurality
of standard sized magnets 17 to construct a magnetic device 10 of
custom length. This type of assembly is especially advantageous
when the permanent magnet material is soft or brittle making
manufacture of a single magnet of sufficient length
impractical.
The permanent magnet 16 preferably made of the metal hereafter
described is shielded on three sides by a base plate 11 and two
side plates 12, 13 held to it along the side of opposite polarity
of magnet 16 by welds 14, 15. The shielding serves in effect to
shape and partially concentrate the magnetic field emitted; such a
shielded field is ideally illustrated in FIG. 2, with the field of
one polarity a and the field of opposite polarity b. The base
shielding plate 11 is preferably longer than the magnet 16, its
projecting ends haying bores 24, 25 to allow bolting of the
apparatus in place, and preferably both ends of the base plate are
connected to a relatively unimpeded electrical ground 22, 23. Side
shielding plates 12, 13 are of a height slightly greater than the
magnet 16, to protect the exposed surface 25 the magnet and to
improve the "focus" of its magnetic field a, b.
The preferred material presently available for the permanent magnet
16 is believed to be strontium ferrite oxide
(SrO.multidot.6Fe.sub.2 O.sub.3), a ceramic.
The shielding on the sides 12, 13 and base 11 of the magnet should,
at current state of the art, be at least 1/4 of an inch thick,
preferably 3/8ths of an inch thick. The side shields 12, 13
preferably extend 1/16" beyond the exposed surface face 25 of the
magnet. The presently preferred shield material is a steel alloy
containing 30% to 50% nickel, commercially available from Ford
Steel Co., St. Louis.
The magnetic device 10 shown in FIG. 3 use a single permanent
magnet 30 as an alternative to the FIG. 1 assembly 16.
For removing static electricity from both sides of a moving web c,
use of two magnetic devices 10 of the FIG. 1 or FIG. 3. 3 type
assembled together opposite each other as shown in FIG. 4 is
preferred. Each of the two magnetic devices 10 is constructed
preferably slightly longer than a width of a web c from which
static charges are to be removed. The web c passes between the two
narrowly spaced magnetic devices 10, they being supported and
secured by brackets 31, 32 in parallel alignment, with their
flux-emitting surfaces 25 facing each other, their like polarities
being opposite to each other, and their common charge-neutral
planes d perpendicular to the path of the moving web c. Each
bracket 31, 32 preferably has a slotted mounting hole 33 and an
arcuate slot 34 to facilitate relative spacing and alignment.
Preferably each end of both the magnetic devices has electrical
grounds 22, 23. The brackets 31, 32 are mounted so as to avoid
metal-to-metal conductive contact between the magnetic apparatus 10
and the printing press or other equipment which is generating the
static electricity on the moving web.
As used with a printing press, the two magnetic devices 10 are so
positioned by brackets 31, 32 that the paper passes between them
after exiting the printing press. The magnetic devices 10 are
preferably spaced as close as is practical, say within one inch of
each other, so that each side of the upper must pass within say 1/2
inch of an exposed surface 25 of the magnet.
The length of each magnetic device 10 is preferably slightly
greater than the width of the web c, way a minimum one inch overlap
on each end. The physical proportions of each device 10 must be
determined by the magnitude of the static electricity present on
the web c. We know of no mathematical equation to calculate the
field strength required.
Readings of static electricity may be taken by a standard static
charge meter such as Model ACL 400 sold under the trade name
"Static Location", commercially available from ACL, Inc. Elk Grove,
Ill., at several locations on the web c as it exits the printing
press. Variables will affect the amount of static electricity;
common variables include the speed of the press, the humidity in
the air, and the type of web material moving through the press.
A magnetic device 10 of strontium ferrite oxide made of available
standard size 1.times.2.times.6 inch blocks 17 having nominal
properties of residual induction 390 m Tesla, commercially
available from Crucible Magnetics Corp., Elizabethtown, Ky., as
Ferrimag R8A, when shielded as described herein will eliminate
static charges up to (+) or (-) 30,000 Volts. An apparatus 10
constructed of blocks 17 of magnets of greater mass, for example
2.times.2.times.6 inch, may be necessary to eliminate greater
quantities of static charge build-up.
Preferably each end of each magnetic device is connected to an
isolated ground 22, 23.
Paper webs passing through this magnetic apparatus have been found
to be substantially static free, eliminating a variety of common
problems encountered in downline processes such as stacking and
folding.
While grounding of the magnetic device at each end is generally
preferred, in certain instances, such as when an extremely long
magnetic device is constructed, additional intermediate grounds may
be desirable.
While this apparatus has proven effective for use with moving webs,
it may also be used with any material, regardless of shape, which
is relatively non-conductive and therefor likely to accumulate
static charges during manufacture or subsequent processing or use.
Likewise, this apparatus may also be used in cases where the magnet
moves relative to the materials, such as reciprocating movement by
the magnet.
Sinc288 e various modifications may be made in the apparatus and
use herein described without departing from the scope of the
invention, all matter contained in the foregoing description shall
be taken as illustrative rather than limiting.
* * * * *