U.S. patent number RE30,826 [Application Number 06/045,826] was granted by the patent office on 1981-12-15 for instrument for air ionization.
Invention is credited to Cecil A. Laws.
United States Patent |
RE30,826 |
Laws |
December 15, 1981 |
Instrument for air ionization
Abstract
An air ionizer is provided of the type in which a corona
discharge is produced at the point of a sharp `needle` by
connecting it to a source of high potential. One or more needles,
mounted in an insulator, point in a direction opposite to the
eventual flow of air ions. At ions emitted from the point of the
needle are reflected by a reflector. The reflector may comprise a
sheet of insulating material or an electrically conductive
material, e.g. a metal, mounted on insulators. The reflector may be
provided with perforations for the passage of air therethrough such
that the ionizer may, with advantage, be placed in a moving air
stream. The insulator on which the needle(s) is or are mounted may
comprise a polythene cable or a printed circuit board.
Inventors: |
Laws; Cecil A. (Oxted, Surrey,
GB2) |
Family
ID: |
26239392 |
Appl.
No.: |
06/045,826 |
Filed: |
June 5, 1979 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
875232 |
Feb 6, 1978 |
04139879 |
Feb 13, 1979 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Feb 5, 1977 [GB] |
|
|
4824/77 |
Feb 17, 1977 [GB] |
|
|
6602/77 |
|
Current U.S.
Class: |
361/230;
361/231 |
Current CPC
Class: |
H01T
23/00 (20130101) |
Current International
Class: |
H01T
23/00 (20060101); H01T 019/00 () |
Field of
Search: |
;361/212,213,214,220,225,229,230,231 ;250/324-326 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
910948 |
|
Nov 1962 |
|
GB |
|
911787 |
|
Nov 1962 |
|
GB |
|
1195331 |
|
Jun 1970 |
|
GB |
|
Primary Examiner: Moose, Jr.; Harry E.
Attorney, Agent or Firm: Tilton, Fallon, Lungmus &
Chestnut
Claims
I claim:
1. An instrument for air ionization comprising a needle mounted in
an insulator .Iadd.and having a pointed end, .Iaddend.and an air
ion reflector, the needle, in operation of the instrument, being
connected to a source of high potential, and .Iadd.the needle point
.Iaddend.being directed towards said air ion reflector, in a
direction opposite to that in which the eventual flow of air ions
is required.
2. An instrument according to claim 1, wherein said air ion
reflector comprises a sheet of insulating material.
3. An instrument according to claim 1, wherein said air ion
reflector comprises an electrically conductive material, mounted on
insulating means.
4. An instrument according to claim 3, wherein said electrically
conductive material is a metal.
5. An instrument according to claim 1, wherein said air ion
reflector has perforations for the passage of air therethrough.
6. An instrument according to claim 1, wherein at least one
conductive plate is placed in proximity to the point of said
needle.
7. An instrument according to claim 6, wherein a bias circuit is
connected between said at least one conductive plate and earth.
8. An instrument according to claim 6, further comprising an
indicator for indicating the efficiency of operation in use of the
said instrument, wherein said at least one conductive plate is
connected to said indicator.
9. An instrument according to claim 1, wherein said insulator
comprises a polythene cable.
10. An instrument according to claim 1, wherein said insulator
comprises a printed circuit board.
Description
This invention relates to air ionizers of the type in which a
corona discharge is produced at the point of a sharp `needle` by
connecting it to a source of high potential, typically 3000 to 6000
volts. The corona gives rise to a stream of electrically charged
air molecules, or ions, the sign of which corresponds to the sign
of the potential applied to the `needle.` The ions are propelled
into the surrounding air by the well known `electric wind`
effect.
It is usual in such ionizers for the `needle` to be mounted so that
the stream of ionized air leaving its point flows directly into the
adjacent air-space for breathing. The needle is therefore pointing
towards the patient or other recipient and, unless protected, can
be dangerous mechanically, as a sharp point, and in some cases
electrically, because of its high potential. It is of course usual
to incorporate a current limiting device in the electrical supply
to the needle, but sensitive people can sometimes find electrical
contact with the needle disturbing. Since anything in the nature of
a protective grill placed over the needle will completely stop the
flow of ions, it is usual in such instruments for the needle(s) to
remain largely unprotected.
The object of the present invention is to provide full protection
for the `needle,` or `needles,` whilst still retaining an unimpeded
flow of air ions.
According to the present invention, in a first aspect thereof, an
instrument for air ionization comprises a needle mounted in an
insulator, the needle, in operation of the instrument, being
connected to a source of high potential, and being directed towards
an air ion reflector, in a direction opposite to that in which the
eventual flow of air ions is required.
The air ion reflector may comprise a sheet of insulating material.
Alternatively the air ion reflector may be made of an electrically
conductive material, preferably a metal, and mounted on insulating
means.
Desirably the air ion reflector has perforations to permit the
passage of air therethrough.
An instrument embodying the invention, and modifications thereof,
will now be described, by way of example only, with reference to
the accompanying diagrammatic drawings, in which:
FIG. 1 is a side view of the said instrument;
FIG. 2 is a perspective view of a first said modification;
FIG. 3 shows a bias circuit for use with the said instrument;
FIGS. 4 to 6 illustrate a second said modification;
FIG. 7 shows an indicator for use with the said instrument;
FIGS. 8 to 11 illustrate a third said modification; and
FIGS. 12 and 13 show respectively sectional and perspective views
of a fourth said modification.
Referring first to FIG. 1. A `needle` 1, mounted in an insulator 2,
and connected to a suitable source of high potential E, is directed
towards an air ion reflector in the form of a plate 3 in a
direction opposite to that in which the eventual flow of air ions
is required. The point of the needle is therefore directed away
from the user so that the risk of injury by accidental contact
direct from the front is removed. Air ions emitted at the needle
tip impinge on the plate 3 and a surface charge of static
electricity, having the same sign as that of the ions, is
established. A state of equilibrium is quickly reached in which
only a small number of ions, sufficient to compensate for any
leakage from the surface, continue to reach plate 3, the vast
majority being deflected back in the opposite direction by virtue
of the repulsion effect of the electrostatic field created by the
charged surface. The plate 3 therefore acts as an electrostatic
reflector or `mirror,` enabling the air ions to be deflected in a
direction substantially opposite to that in which the needle is
pointing. The plate 3 may comprise a sheet of insulating material,
or alternatively it may comprise a conductive material, such as a
metal, mounted on suitable insulating means (not shown).
In practice, the electrostatic charge laid down on plate 3 and on
insulator 2, being of the same sign and of comparable potential to
that of needle 1, operate to reduce the field strength at the
needle tip to below that at which the corona discharge can be
maintained. With a needle in free space the necessary field exists
by virtue of the difference in potential between the needle and its
surroundings, or `earth`. The necessary field is therefore restored
by introducing one or more conductive plates 5 (FIG. 2) in suitable
proximity to the needle tip, plates 5 being held at earth or other
suitable potential. One consequence of this is that an ion current
Ip flows from the needle tip to plates 5. Under some conditions
current Ip can reach a magnitude such that unacceptable amounts of
ozone are produced. As a further feature of this invention, current
Ip is controlled at an acceptable value by applying a suitable bias
potential V, of the same sign as potential E to plates 5. This bias
potential can be derived from an external source, or developed
automatically from a self regulating bias circuit consisting of a
very high value resistor R connected between plates 5 and earth
(FIG. 3). This function is best performed by making use of the
reverse voltage characteristics of a small silicon high voltage
rectifier which meets the necessary requirements of very small
leakage current and high operating voltage. In addition, the onset
of the avalanche condition serves to limit the maximum potential
which can be acquired by plates 5 under fault conditions. The
potential developed across resistor, or rectifier R, finds an
equilibrium point when it reaches a value at which the ion current
drawn is just sufficient to maintain it. This follows from the fact
that the ion current Ip, falls off as the plate bias potential V
rises. The circuit therefore provides an automatic control of plate
bias and therefore of ozone level, the operating point being
determined by the choice of the resistor or rectifier R.
FIGS. 4 to 6 illustrate one practical modification of the
invention. The insulator 2, in FIG. 2, is replaced by a length of
polythene insulated cable 2A, the needle, or needles 1, being
pushed through the insulation so as to contact the central wire 6,
as shown in FIG. 4. Plates 5 can, for example, take the form of
foil or other conductive wrappings round the polythene insulation.
This assembly may then be mounted in a simple plastics extrusion 7
(FIG. 5) which may then be mounted over plate 3 (FIG. 6) on members
or pillars 10. Connection to the needles, via conductor 6 in cable
2A, is effected via one mounting screw 9, and that to the plates 5,
via the other mounting screw 9. By keeping the spacing between
extrusion 7 and insulator panel 3 small, the needles 1, are fully
protected.
The underside of plate 3 may be used for mounting the electrical
components of the high potential supply circuit providing the probe
potentials E and, where required, bias potential V. When necessary
this can take the form of a printed circuit board. The complete
assembly may then be mounted in a box, or as required.
The small current Ip collected by the plates 5, or their
equivalents on an alternative printed circuit assembly, can be used
to operate an indicator consisting of a small neon lamp N and
capacitor C (FIG. 7) and preferably a ballast resistor R. In
operation, the current Ip serves to charge the capacitor C to a
potential sufficient to trigger the neon lamp N, whereupon the
capacitor is discharged through the neon lamp, which then ceases to
conduct. The capacitor C then charges again and the cycle is
repeated. The rate at which the neon lamp flashes is a measure of
current Ip, and therefore of the efficiency of the circuit
operation.
A further practical modification of the invention is illustrated in
FIGS. 8 to 11 where a printed circuit board is used instead of the
polythene cable referred to in FIG. 4.
In this modification, a printed circuit board of known type 12,
having conductive foil on both surfaces is etched on one surface
(FIG. 9) to produce the required number of plates 5, all
interconnected and being suitably spaced to allow needles 1 to be
mounted in holes drilled in the insulating board between them. On
the other side of the board (FIG. 10) the conductive foil is etched
away so as to leave a thin conductive strip 13 having pads 14 to
which the undersides of the needle are soldered, and pad 15 for
connection to the supply. The needle points therefore project
upwards between the plates 5, as in side elevation FIG. 8. The
complete strip may be mounted in a suitable moulded housing 16, as
shown in FIG. 11 and again mounted, for example, in the manner
shown in FIG. 6. The surface of the plate 3, may in either case be
flat as illustrated or alternatively it can be curved in a convex
or concave manner to give a preferred distribution of the reflected
ions.
FIGS. 12 and 13 provide for applications in which it is required to
mount the ionizer instrument in a moving air stream for the purpose
of ionizing the air flowing past it. For example, it may be
required to ionize the air emerging from a ventilation or heating
duct into a living room, office or other space.
In such a case, the plate 3 may present an obstruction to the
moving air, thus preventing it from passing effectively through the
ionization area between the said plate and the needle assembly. In
the present invention this limitation is overcome by constructing
the plate 3 from a suitable material having perforations through
which the moving air can pass. These can take any suitable form,
such as closely spaced holes or slots, or the material can take the
form or wire or metal mesh mounted on suitable insulators.
A needle assembly, making use of a printed circuit board 12 (FIG.
12), is mounted in a suitably moulded housing 16. Such an assembly
may have any required number of needles 1, consistent with the
total length of the assembly. As shown in FIG. 13, the assembly is
then mounted on two members 10, secured to a rectangular frame, 17,
in such a way that the needles are facing towards the frame. In the
illustration a wire mesh, constituting the plate 3 is mounted in
frame, 17, the frame itself or suitable inserts, serving to
insulate the mesh electrically. The complete assembly is then
mounted over a ventilating or heating duct, terminating in a
conventional grill fitting 18. Air emerging from the grill
therefore passes through the mesh 3, and thus through the ionizing
area, as indicated by the arrows 19.
The design of the ionizer and reflector assembly can, of course, be
adapted to conform to any size or shape of duct or grill, and more
than one housing 16 containing ionizing means may be employed.
Again, the ionizer/reflector assembly may be designed to fit in
front of a fan, or blower unit instead of a duct, or it may be
mounted over a heater, radiator, or similar device producing a
moving current of air. The unit may be designed to fit over a
window vent through which air is drawn by an extractor fan mounted
elsewhere.
* * * * *