Arrangement for generating ions

An apparatus is disclosed for generating ions into the atmosphere in which ion generation from a high voltage wire electrode is enhanced and accelerated by a high voltage reflective screen and a partially conductive auxiliary electrode which collects a charge. The auxiliary electrode defines an opening through which the ions pass and are accelerated. The apparatus is contained in an insulating housing.

The invention relates to an arrangement for generating ions, especially for 
ionisation of air. The arrangement has an electrically conducting wire 
connected to a high voltage source and a reflector screen arranged at a 
distance from the wire. This screen is at a high electric potential and 
the screen partly encloses the wire. The screen is held in an insulating 
housing with an opening allowing passage of ions. The high electric 
potential on the reflector screen has the same polarity as the wire 
potential. 
Arrangements of this kind have the disadvantage that the repulsing effect 
of the wire on the electrons or ions decreases rapidly with increasing 
distance. Hence also the velocity of the emitted ions is rapidly reduced 
together with increasing distance from the wire. A low velocity, however, 
considerably promotes the deposition of ions on dust particles whence the 
movement of the ions will stop completely. Hence it becomes impossible to 
enrich a room to some extent uniformly with ions. 
It is, in principle, also possible to provide additional electrodes which 
have a repulsing effect on the electrons or ions in order to achieve a 
higher repulsion effect at a greater distance from the wire. However, in 
doing this the voltage applied to the additional electrodes is very 
critical. If, for example, too low a voltage is applied to the additional 
diode then its effect is also very low so that the problems described 
above will still exist and no significant improvement of the distribution 
of ions in the room is achieved. However, a higher voltage applied to the 
additional electrode causes a sensible reduction of the electric field on 
the wire. Hence, however, the emission of ions or electrodes is markedly 
retarded and emission will completely stop at excessively high voltage on 
the additional electrode. With an additional electrode which is connected 
to a fixed potential it is possible to achieve the required effect of 
increase of velocity of ions at a greater distance from the wire; in any 
case there exists the danger that under certain circumstances the emission 
of electrons or ions will completely stop and the additional electrode 
becomes ultimately ineffective because any such ions whose velocity could 
be increased no longer exist. This undesirable side effect could only be 
avoided by a relatively expensive monitoring and control arrangement which 
monitors the emission of electrons or ions and if the emission falls below 
a certain value then it initiates suitable correction measures, for 
example a decrease of the potential applied to the additional electrode. 
The objective of the invention is to propose an arrangement mentioned above 
which on the one hand ensures a sufficiently high velocity of the emitted 
electrons or ions at a greater distance from the wire used as an 
ionisation source in order to prevent deposition of ions on dust particles 
to a greater extent and which, on the other hand, has a very simple design 
and which operates without expensive regulating and monitoring 
arrangements. 
According to the invention this is achieved by providing an auxiliary 
electrode which projects at least along one part of the circumference of 
the passage opening of the housing and which is placed on the housing with 
insulation. 
The auxiliary electrode is charged by the emission of electrons or ions due 
to the wire under high voltage. The increasing potential of the auxiliary 
electrode causes focussing, increasing in intensity, of the emerging 
electron or ion flux so that fewer and fewer electrons reach the auxiliary 
electrode and the increase of the auxiliary electrode potential is 
retarded and finally it comes to a stop. At the same time, together with 
increasing potential of the auxiliary electrode, the forces, caused by the 
electrode, which exert repulsing effect on the electrons or ions, 
increase. 
Suppression of electron or ion emission of the kind possible with an 
auxiliary electrode at a fixed potential cannot, however, occur or will 
occur only for a short time because the auxiliary electrode,s due to 
finite insulation resistance of the insulating materials, is constantly 
discharged and the potential of the auxiliary electrode when emission of 
electrons is suppressed is constantly reduced which causes renewed 
emission of electrons from the wire. 
The design, according to the invention, of an arrangement for generating 
ions hence ensures an automatic regulation of the potential applied to the 
auxiliary electrode. 
Experiments have shown that the form and spacing of the auxiliary electrode 
and the insulating material specified between the electrode and the 
housing can be varied without disturbing the self stabilising effect of 
the arrangement according to the invention. Especially favourable emission 
conditions are obtained if the auxiliary electrode is designed as a plate 
with a perforation. 
The auxiliary electrode is usefully made from metal and it can be provided 
with thin insulating coats, for example electrolytically applied oxide 
layers, lacquer coatings or plastics material coatings which ensures scope 
for influencing the charging and discharging rate of the auxiliary 
electrode. 
In some cases it is also advantageous if the auxiliary electrode is made 
from an insulating material whose surface conductivity is higher than that 
of the housing. 
By suitable selection of the materials used, and also if necessary by 
suitable selection of surface treatment of the housing and auxiliary 
electrode, it is possible to adjust the required charging and discharging 
rate of the electrode which is important especially in arrangements for 
low frequency pulsating emission of electrons.

The electrically conducting wire is designated by 1, and to this wire, as 
well as to the reflector screen 2 partly enclosing the wire 1, can be 
applied a high voltage adjusted by means of the control system 5 in which 
the potentials applied to the wire or reflector screen 2 have different 
values but the same polarity. 
The wire 1, reflector screen 2 and control system 5 are arranged in a 
housing 6 made from insulating material which is fastened by brackets 7 
for example on a wall. The opening 8 of the housing 6 facilitates the exit 
of emitted electron or ion flux. 
On the outside of the housing 6 an auxiliary electrode 3 is mounted on a 
stand 4 of insulating material. This electrode extends along the 
circumference of the opening 8 of the housing 6 and is designed as a plate 
10 provided with a perforation 9.