Rotary electric field intensity measuring device

A rotary electric field intensity measuring device comprising a grounded housing, an amplifier mounted within said housing and electrically connected to an external recording device, an electric motor mounted within said housing and having an output shaft, said motor being adapted to be connected to an external power source, a rotary grounded shielding conical electrode means having a rotary shaft connected to said output shaft of the motor for rotation therewith and alternating voltage inducing means and a shielded stationary conical electrode means secured to said housing within said shielding rotary electrode means in spaced relationship to the latter and having alternating voltage inducing means in cooperation with said alternating voltage inducing means of the rotary electrode means.

BACKGROUND OF THE INVENTION 
This invention relates to an electric field intensity measuring device 
suitably employed in the open air under severe weather conditions and more 
particularly, to a rotary electric field intensity measuring device of the 
above type which includes a pair of electrode means having alternating 
voltage inducing means, respectively. 
An increasing number of open air leisure facilities such as golf courses 
for example, have been and being built even in regions where thunderbolts 
quite frequently stike and as a result, increasing attention has been paid 
to safety of players playing and employees working in such leisure 
facilities and regulations relating to personal safety in the open air 
leisure fecilities have become more and more severe. 
When it is forecasted that a thunderbolt seem to stike in a golf course, it 
is necessary to evacuate the players and employees rapidly out of the golf 
course to a safe location. In order to determine whether the players and 
emplyees should be evacuated out of the golf course or not, a number of 
thunder alarms have been developed and practically operated and as one 
most advanced or improved type thunder alarm, devices adapted to detect 
the electric field intensity on the surface of a selected ground and 
provide an alarming signal in response to the detection of a particular 
value of electric field intensity have been developed. Of the most 
advanced thunder alarming devices, the so-called rotary electric field 
intensity measuring devices have been most often accepted because of their 
simplicity in construction and high reliability in performance. 
When the rotary electric field intensity measuring device is operated in 
the open air rather than in a laboratory for the under forecast, in 
practice, it is particularly important to ensure that the device perform 
its function properly without being adversely affected even when exposed 
to wind and rain and provide a reliable and precise measuring result. 
However, the conventional rotary electric field intensity measuring device 
has the disadvantages that the insulation between the opposed charge 
induction faces and ground deteriorates when the device is operated in 
heavy rain and that the space defined between the charge induction faces 
is soon filled with rain water to thereby electrically connect the charge 
induction faces together throughout their area resulting in substantial 
reduction in induced voltage. In order to eliminate the disadvantages 
inherent in the conventional rotary electric field intensity measuring 
device, an insulator having a high resistance (silicone, for example) is 
usually employed between the charge induction faces and ground. Although 
the use of such a high resistance insulator may improve the insulation, 
electrostatic charge remains on the surface of the insulator for a long 
time after the deactuation of the device and will not disappear easily 
which may tend to cause error in measuring of electric field intensity by 
the device. Due to the disadvantages inherent in the conventional rotary 
electric field intensity measuring device referred to hereinabove, the 
timing of thunderbolt discharge will not always correspond to the electric 
field intensity measured by the measuring device. Thus, when the 
conventional rotary electric field intensity measuring device is operated 
as a thunder alarm for forecasting thunderbolt discharge, the device 
encounters difficulties in forecasting the timing of thunderbolt discharge 
with preciseness. 
SUMMARY OF THE INVENTION 
Therefore, one object of the present invention is to provide a rotary 
electric field intensity measuring device which can maintain its high 
insulation and is not adversely affected by electrostatic charge. 
According to the present invention, as distinguished from the conventional 
arrangement in which a stationary electrode is connected to a group of 
induction plates adhered to an insulator and they are connected together 
into a unitary structure by means of connector lines, a stationary 
electrode having alternating voltage inducing means in the form of 
openings is fixedly secured to the grounded housing of the measuring 
device by means of a shielded insulative support column which is also 
fixedly secured to the housing. In the arrangement of the electric field 
intensity measuring device of the invention when the device is operated in 
the rain, since the induction plates or stationary and rotary electrodes 
are adapted to be electrically connected together by rain water only 
infrequently and at only selected areas thereof, rather than the whole 
areas of the two electrodes being connected together with rain water, and 
since a high insulation is provided between the stationary electrode and 
ground, there is no possibility that the induced voltage will be 
materially reduced during rain. Although a further advantage may be 
obtained when silicone varnish or the like is applied on the insulation 
support column, the higher the resistance of the insulation column is, the 
longer time the electrostatic charge remains on the surface of the column 
after the deactuation of the device and therefore, it is necessary to 
dispose a grounded shielding plate in the form of a metal cylinder about 
the insulation column in a suitably spaced relationship to the column. The 
advantages of the shielding metal cylinder will be enumerated hereinbelow. 
1. The surface of the insulation support column is protected from being 
directly exposed to rain water. 
2. When the insulation support column is formed of a high resistance 
material (silicone, for example), although the insulation may be 
increased, but electrostatic charge will remain on the surface of the 
column for a prolonged time after the deactuation of the device resulting 
in error in measuring of electric field intensity. However, when the 
shielding metal cylinder is employed in conjunction with the insulation 
support column in the manner mentioned hereinabove, the electric field due 
to the electrostatic charge on the insulation support is confined within 
the space defined between the insulation support and metal cylinder to 
thereby eliminate the difficulties caused by the electrostatic charge.

PREFERRED EMBODIMENT OF THE INVENTION 
The present invention will be now described with reference to the 
accompanying drawing which shows one preferred embodiment of rotary 
electric field intensity measuring device of the invention for 
illustration purpose only, but not for limiting the scope of the same in 
any way. The rotary electric field intensity measuring device is generally 
shown by reference numeral 10 and generally includes a hollow cylindrical 
conductive housing 11 connected to ground 12 and having a motor 
compartment 13 defined in the center of the upper portion of the housing. 
An amplifier 14 is mounted on the bottom wall of the housing 11 and has an 
input side connected to one end of an induced charge take-out line 15 and 
an output side connected to an amplifier output take-out line 16 which 
leads to a suitable thunderbolt alarm (not shown) which is in turn 
connected to a suitable recording meter (not shown). A conventional 
suitable electric motor 17 is mounted within the motor compartment 13 of 
the housing 11 and has the output shaft 18. A hollow cylindrical 
insulative stationary electrode support column 19 extends vertically from 
the top wall of the housing 11 in the center thereof and has an outwardly 
and horizontally extending flange at the bottom end of the column which 
rides on the housing top wall. The flange has a plurality of holes 19' in 
a circumferentially spaced relationship. A metal sleeve 21 which has a 
diameter greater than that of the stationary electrode support column 19 
is disposed about the column in a peripherally spaced relationship to the 
latter to define an annular space therebetween through which the induced 
charge take-out line 15 extends. The sleeve 21 is also formed at the lower 
end with an outwardly and horizontally extending flange which rides on the 
flange of the support column 19. The sleeve 21 is also provided with a 
plurality of circumferentially spaced holes 21' in alignment with the 
corresponding holes 19' in the flange of the support column 19 and a 
plurality of drainage holes 21" at the bottom end of the body of the 
sleeve. A suitable conventional fastening means 20 extends through the 
aligned holes 19' and 21' in the flanges of the support column and sleeve 
and holes (not shown) in the top wall of the housing 11 so that both the 
support column and sleeve can be fixedly secured to the housing 11 and 
grounding the metal sleeve 21. The diameter of the upper portion of the 
hollow cylindrical stationary electrode support column 19 is reduced to 
provide a shoulder 20 for the purpose to be described hereinafter. A 
frusto-conical stationary electrode 22 is fixedly secured at the upper end 
to the shoulder 20 of the column 19 by means of suitable fastening means 
23. The other end of the induced charge take-out line 15 is connected to 
the stationary electrode means 22. The construction of the stationary 
electrode 22 will be in detail described hereinafter. A rotary shielding 
electrode supporting shaft 24 extends through the hollow interior of the 
column 19 with the lower end extending into the motor compartment 13 and 
connected to the output shaft 18 of the electric motor 17 by means of a 
flexible and insulative coupling 25. The rotary shaft 24 is journalled at 
suitable points along the length of the shaft in upper and lower bearings 
26, 26 which are in turn suitably supported in the support column 19. A 
slip ring 27 is integrally formed about the rotary shaft 24 in the portion 
of the shaft disposed within the motor compartment 13. A pair of brushes 
or spring ground contacts 28, 28 are provided with the outer ends secured 
to the housing top wall by means of suitable fastening means 28' and the 
inner or free ends in contact with the slip ring 27. A frusto-conical 
rotary shielding electrode 29 is fixedly secured at the top thereof to the 
upper end of the rotary shaft 24 for rotation with the shaft by suitable 
fastening means 29' a with a metal plate 29a interposed therebetween. 
Thus, it will be understood that the shielding rotary electrode 29 is 
connected to ground 12 through the rotary shaft 24, ground contacts 28 and 
housing 11. The rotary shielding electrode 29 has a shape substantially 
similar to that of the stationary electrode, but the dimensions of the 
rotary electrode are greater than those of the stationary electrode to 
thereby define an annular space having a frusto-conical cross-section 
between the two electrodes for the purpose to be described hereinafter. 
Reference numeral 30 denotes a shielded cord connected at one end to the 
electric motor 17 and adapted to be connected at the other end to a 
suitable external power source (not shown) which may be a domestic wall 
socket, for example. Reference numeral 31 denotes a detachable cover which 
covers the electrode assembly when the measuring device is not operated. 
The construction of the frusto-conical electrode 22 will be now in detail 
described referring to FIG. 2. The stationary electrode 22 is formed of a 
sheet metal and includes a plurality of longitudinally extending 
trapezoidal alternating voltage inducing openings 22' formed in a 
circumferentially spaced relationship and a plurality of smaller or 
auxiliary vertically spaced transverse anti-modulation or anti 
short-circuit openings 22" formed between adjacent longitudinal openings. 
The remaining solid area of the electrode 22 where no openings are 
provided forms the charge induction face of the associated electrode 22. 
Similarly, the rotary shielding electrode 29 (see FIG. 2) is formed of the 
same material as that of which the stationary electrode 22 is formed and 
includes a plurality of longitudinally extending trapezoidal alternating 
voltage inducing openings 29' formed in a circumferentially spaced 
relationship. As clearly shown in FIG. 2, since the area of each of the 
stationary and rotary electrodes where the openings are formed occupies a 
substantial portion of the whole area of the associated electrode and one 
electrode rotates relative to the other electrode when the measuring 
device is in operation, the possibility that water accumulates in the 
annular space between the electrodes can be effectively eliminated. 
Accumulation of water in the annular space may cause short-circuit and is 
helped to be drained out through the anti short-circuit openings 29". 
When it is desired to operate the electric field intensity measuring device 
in the open air in a thunder-storm, the line 30 is connected to an 
external power source (not shown) which may be a domestic wall socket, for 
example, the output take-out line 16 is connected to a thunder alarm and 
the cover 31 is removed from the housing 11. Then, charge is induced on 
the solid surface area of the stationary electrode means 22 and applied to 
the amplifier 14 through the line 15. The output appearing at the outlet 
side of the amplifier 14 is applied to the thunder alarm through the line 
16 and the thunder alarm then applies signals to a recorder (not shown) 
which is operatively connected to the thunder alarm. 
With the above construction and arrangement of the component parts of the 
electric field intensity measuring device of the invention, even when the 
measuring device is operated in the open air under severe conditions such 
as in heavy rain, for example, the sensibility of the measuring device 
will not be adversely affected to thereby assure precise measuring 
results. And the charge induction face of the stationary electrode will 
not be adversely affected by electrostatic charge which may otherwise 
remain for a long time and cause error in measuring. Thus, it will be 
noted that the present invention has provided a stable and practical 
electric field intensity measuring device which is suitably and reliably 
operated in the open air. 
Although the present invention has been described in its preferred form 
with a certain degree of particularity, it is understood that the present 
disclosure of the preferred form has been made only by way of example and 
that numerous changes in the details of construction and arrangement of 
parts may be resorted to without departing from the spirit and the scope 
of the invention as hereinafter claimed.