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Патент USA US3048727

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Aug. 7, 1962
R. w. CLOUD
3,048,720
CHARGING SYSTEM FOR ELECTROSTATIC GENERATORS
Filed Sept. 15, 1958
United states Patent 0 "1”lee
1
3,048,720
Patented Aug. 7, 1962
2
U.S. Patent No. 2,697,793, an inducing plate is provided
3,048,720
CHARGING SYSTEM FOR ELECTROSTATIC
GENERATORS
Robert W. Cloud, Lexington, Mass, assignor to High
Voltage Engineering Corporation, Burlington, Mass.,
a corporation of Massachusetts
Filed Sept. 15, 1958, Ser. No. 761,255
3 Claims. (Cl. 310-5)
This invention relates to electrostatic belt-type genera
near the pulley so that the electric ?eld is created ‘from
the pulley to the plate. Electric charge is then transferred
‘between the pulley and the conductive parts of the belt
which come in contact with the pulley. In accordance
with the present invention, two inducing plates 5, 6 are
provided so as to ?ank the belt 1 and a contacting leaf 7
is provided so that the conductive portions 8 of the belt 1
are connected to a ?xed potential as they travel between
the inducer plates 5, 6. The inducing plates 5, 6 are con
tors and in particular to a novel method of and apparatus
for the transfer of electric charge between the charge car
nected together by a lead 9 so as to be at a common po
method of charge transfer and induction-conduction charg
ing methods. The present invention is concerned with
the latter of the two methods. Various proposals have
been made for induction-conduction charging methods. 20
of the belt as well as the rate of charging are limited by
tential ‘which differs from that of the leaf 7. As a result,
rier and the controlled potential portions of the apparatus;
there are two electric ?elds, one on each side of the belt 1.
namely, the high voltage terminal and ground.
By using two ?elds in this manner, it is possible to put as
In general, charging mechanisms for electrostatic belt 15 much charge on the belt as the belt is capable of carrying
type generators are of two types: the corona discharge
to the terminal, since both the charge-carrying capabilities
In one, as disclosed in U.S. Patent No. 2,697,793 to Trump
and Cloud, the belt itself consists of a semi-conductive
the breakdown gradient in the insulating gas. Hence by
using two ?elds in accordance with the invention, the
charging capabilities are doubled over that obtainable with
a single ?eld as applied at the pulley. The potential dif
ference between the contact and the inducing plates may
be created in any conventional manner, and in FIG. 1,
material and is charged by induction-conduction methods.
In another type, suggested by Raymond G. Herb at the
the leaf 7 is shown as being grounded, while the inducing
University of Wisconsin, the necessary conducting zones 25 plates 5, 6 are maintained at a positive potential by a
may be introduced into the belt very simply by using
voltage source 10. As a result, negative charge is de
staples.
posited on the belt 1.
Induction-conduction charging has de?nite advantages
In addition to moving the charge transfer location from
over corona charging. With induction-conduction charg
the pulley and using two ?elds rather than one, my in
ing, there is no ionization of the insulating gas by the 30 vention also comprehends imbedding the charge-carrying
corona discharge wtih resultant production of corrosive
Wires or other conductors in the middle of the belt. In
lay-products. In corona charging the production of these
the case of induction-conduction charging at the pulley,
this is impossible since the conducting portions must come
by-products is undesirable in any event, and even prevents
use of certain gases which would be good insulators such
in contact with the pulley. The conductive material in
as sulphur hexa?uoride. In the present state of the art, 35 the middle of the belt may be wire or conducting rubber
and may conveniently be positioned by sandwiching the
semiconductors have not been developed to a su?icient
degree to permit use of the device disclosed in the afore
wire or conducting rubber between two pieces of belt
vulcanized together. In the embodiment shown in FIG. 2,
mentioned U.S. Patent No. 2,697,793. The use of staples
in the belt has been used successfully, but the current is
the wires 8 stick out at one end of the belt 1 but not at
less than that obtainable by corona methods. In accord
the other, and electrical contact is made with the leaf 7
ance with the invention, it is possible to get charging cur
via these projecting ends 11. In FIG. 2, the extent of
projection is somewhat exaggerated for clarity; the wires
rents comparable to those available by corona, and various
other advantages are attendant upon the present invention,
as will appear from the following description.
The invention may best be understood from the fol
lowing detailed description thereof having reference to
the accompanying drawing in which:
FIG. 1 is a diagrammatic view of an electrostatic belt
type generator embodying the present invention;
8 need only project just beyond the surface of the belt 1.
One of the main advantages of imbedding the conductors
in the solid dielectric of which the belt is made is the
resultant higher breakdown gradients which permit more
charge to be carried by the belt.
Referring now to FIG. 3, the belt 1 therein shown is
constructed in the same manner as the belt 1 shown in
'FIG. 2 is a detail in perspective showing the charging
mechanism of the device shown in FIG. 1;
FIG. 2, except that the leaf contact 7 of FIG. 2 is shown
in FIG. 3 as being replaced by a pulley 12 in order to re
FIG. 3 is a front elevation showing an alternative
duce friction.
charging mechanism constructed in accordance with the
In the embodiment shown in FIGS. 4 and 5 both ends
of
the wires 8 are buried in the dielectric of the belt 1 in
invention;
55
FIG. 4 is a front elevation showing an alternative meth
order to prevent corona which might otherwise result from
od of charging in accordance with the invention; and
the relatively sharp ends of the wire 8. Contact is made
FIG. 5 is a side elevation of the apparatus shown in
FIG. 4.
Referring to the drawing and ?rst to FIGS. 1 and 2
at the center of the belt 1 between an exposed area as
shown at 13 and a pulley 14 or a leaf as hereinbefore
described. In order to prevent any mechanical pressure
on the belt 1, a pair of pulleys 14, 15 may be provided as
shown in FIG. 5 in order to compensate for lateral me
not be described herein in any detail. Suffice it to say
chanical forces.
that electric charge is carried by an insulating belt 1 sup
In prior art devices wherein induction-conduction
porting between two pulleys 2., 3 from the grounded end 65 charging is done at the pulley, the current in a conventional
generator having a belt ?ve inches in width was limited to
of the apparatus to a hollow electrode 4 which constitutes
thereof, the operation of the electrostatic belt-type gen
erator therein shown is in general well known and need
200 microamperes. Using two inducing ?elds in accord
ance with the invention described herein, but without im
bedding the conductors in the belt, current available was
United States Patent No. 1,991,236 to Van de Graff and
No. 2,252,668 to Trump and at vol. XI, page 1 of “Re 70 increased to 350 microamperes. With proper design of
the belt in accordance with the invention currents of 500
ports on Progress in Physics” (1948). ‘In accordance with
a high voltage terminal. Details of operation of electro
static belt-type generators may be found, for example, in
conventional induction-conduction charging as shown in
microamperes may be obtained on a ?ve-inch belt.
3,048,720
4
The charge may be removed in the high voltage termi
nal 4 by merely contacting the exposed portions of the
ducing a net charge on said conductive zones at the
comprising a pair of inducing plates ?anking said belt and
by said hollow electrode, said charging means comprising
a contact maintained at a ?xed potential with respect to
a pair of inducing plates ?anking said belt and a contact
maintained at a ?xed potential with respect to said in
grounded end of said electrostatic generator, and means
conductors 8 in the belt 1, as by a simple brush 15. If
within said hollow electrode for transferring said charges
it is desired to charge the down run of the belt, the charge
from each conductive zone to said hollow electrode when
transfer mechanism within the high voltage terminal may C1 such conductive zone is electrically completely enclosed
be identical to that described herein with appropriate re
by said hollow electrode, said charging means comprising
versal of polarity.
a pair of inducing plates ?anking said belt and a contact
Having thus described the principles of the invention
maintained at a ?xed potential with respect to said in
together with several illustrative embodiments thereof, it
ducing plates and adapted to make temporary electrical
is to be understood that although speci?c terms are em
contact with said conducting zones at their exposed posi
ployed, they are used in a generic and descriptive sense
tions during travel of said conducting zones between said
inducing plates.
and not for purposes of limitation, the scope of the in
vention being set forth in the following claims.
3. An electrostatic generator comprising in combina
I claim:
tion a hollow electrode and an insulating traveling belt
1. An electrostatic generator comprising in combina 15 having conductive zones of which the dimensions are short
tion a hollow electrode and an insulating traveling belt
in the direction of travel of said belt but extending sub
having conductive zones of which the dimensions are short
stantially the width of the belt transverse thereto insulated
in the direction of travel of said belt but extending sub
from one another along the length of said belt and im
stantially the width of the belt transverse thereto insulated
bedded therein, said belt being longitudinally divided so
from one another along the length of said belt, charging 20 that only a small portion of each zone between the lateral
means for producing a net charge on said conductive zones
extremities thereof is exposed, charging means for pro
at the grounded end of said electrostatic generator, and
ducing a net charge on said conductive zones at the
means within said hollow electrode for transferring said
grounded end of said electrostatic generator, and means
charges from each conductive zone to said hollow elec
within said hollow electrode for transferring said charges
trode when such conductive zone is electrically completely
from each conductive zone to said hollow electrode when
enclosed by said hollow electrode, said charging means
such conductive zone is electrically completely enclosed
said inducing plates and adapted to make temporary elec
trical contact with said conducting zones at their exposed
positions during travel of said conducting zones between
said inducing plates.
2. An electrostatic generator comprising in combina
tion a hollow electrode and an insulating traveling belt
having conductive zones of which the dimensions are short 35
in the direction of travel of said belt but extending sub
stantially the width of the belt transverse thereto insulated
from one another along the length of said belt and imbed
ded therein so that only a small portion thereof extends
beyond the surface of said belt, charging means for pro 4 O
ducing plates and adapted to make temporary electrical
contact with said conducting zones at their exposed posi
tions during travel of said conducting zones between said
inducing plates.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,610,994
2,644,903
2,697,793
Bosch et al. __________ __ Sept. 16, 1952
Lehrer _______________ __ July 7, 1953
Trump et al. _________ __ Dec. 21, 1954
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