US 2265475 A
Description (OCR text may contain errors)
Dec. 9, 1941. J. FODOR 2,265,475
ILLUMINATING SYSTEM Filed June 1, 1938 4 Sheets-Sheet l .Dec.9, 1941. J. FODOR 2,265,475'
ILLUMINATING SYSTEM Filed June' 1, 1938 4 Sheets-Sheet 2 Fig. 3.
Dec. 9, 1941. J. FoDoR ILLUMINATING SYSTEM Filed June 1, 1938 4 Sheets-Sheet s Fig. 5.
Fig. 40c 42 Fig. 7.
Dec. 9, 1941.
J. FODOR ILLUMINATING SYSTEM Filed June 1, 1938 4 Sh eetsSheet 4 ATTOR/VE'VJI Patented Dec. 9, 1941 IILUMINATING SYSTEM Joseph Fodor, London, England Application June 1, 1038, Serial In Great Britain June 3, 937
The present invention relates to a method of and apparatus for illumination in coal mines and other locations where explosive or ble gases or dust are present.
It is generally not permitted in such explosive atmospheres, such as at the coal face of a coal mine, to use an ordinary electric lamp to illuminate the coal face since if the bulb is broken the filament would immediately ignite the explosive gases present with disastrous results. It has been. proposed to enclose the lamps in thick glass casings and also wire gauze but these have also been rejected as being unsafe. As a result the present day miners use the wellknown miners lamp which gives only a 'very poor illumination.
According to the present invention the method of illumination in coal mines and other explosive atmospheres consists in energising a luminous electric discharge device solely by means of an electric field. The electric field is preferably produced by means of an oscillatory circuit enclosed in a flame-proof casing, and the luminous electric discharge device comprises a gas or vapour electric discharge device and preferably has no internal electrodes.
A feature of the invention consists in an illuminating system for use in mines and other explosive atmospheres comprising a gas or vapour discharge devicev without any internal electrodes or any external electrodes mounted thereon, andan electric field for energising said discharge device.
Another feature of the invention consists in an illuminating system for use in mines and other explosive atmospheres comprising a gas or vapour electric discharge device having no internal electrodes 'whatsoeverand having no external electrodes mounted on the discharge device which are connected to a source of electric current, and means for producing an electric field in the vicinity of said discharge device for energising it.
The discharge devices may be energised by the electric field created by electrical oscillations produced by a suitable generator which is preferably a high frequency generator, that is a generator producing a current having a frequency of above about 1,000 cycles per second. The discharge device may also be energised by an electric field created by means of electromagnetic waves.
The energy supplied to the discharge device may be such as to cause the gas or vapour to vice, a considerable proportion of the radiation is in the region of invisible light, the eiilciency of the illumination may be increased by the use of fluorescent material. Also, if fluorescent materialisusladitisnotnecessarytocausethe discharge deviceitself to glow but the whole discharge may produce invisible radiations.
Since even when the tube is glowing there is no actual flame in such devices, there is no danger of igniting the explosive gases if the discharge device should be accidentally broken.
If the electrical generator itself is located in the explosive atmosphere, it and other parts charged with electricity are enclosed in a flameproof casing or casings which, may even be hermetically sealed. The coupling between the generator and the discharge tube is effected electrostatically or inductively so that no charged conductors need be exposed to the atmosphere.
In the case where the generator is located at a point remote from the discharge device the means for distributingthe energy for operating the discharge device must be explosion-proof.
Various embodiments of the invention will now. be described with reference to the accompanying drawings, in which- Fig. 1 is a diagrammatic sectional view of a portable, self-contained, illuminating unit, emodving the invention;
P18. 2 is a atic elevational view showing a modified arrangement of illuminating unit;
Fig. 3 is a diagram illustrating a plurality of units of the type shown in Fig. 2, and also illustrating an electrical distribution system therefor, arranged in accordance with the invention;
Figs. 4 and 5 are sectional and side elevational views, respecievely, of a modified form of casing for the discharge device of an illuminating unit;
Fig. 6 is a view illustrating diagrammatically a discharge tube capacitatively coupled to a high frequency generator;
Fig. 7 is a diagram illustrating a high frequency distribution system comprising a plurality of conductors connected in parallel, for the sake of safety;
Figs. 8 and 9 are diagrams showing other ar- Y rangements of distribution systems in accordance with the invention; and
Fig. 10 is a diagram illustrating a method of energizing my improved discharge devices by means of electromagnetic waves.
In the embodiment of the invention illustrated in Figure l, a high frequency thermionic valve glow. Since, in. a gas or vapour discharge degenerator I, is sealed within a flame-proof casing 2 which is sufficiently strong to resist breakage and is closed by the cover 3 which may be sealed so that it cannot be opened without authority. The casing may accommodate the necessary batteries 4 and 5 for operating the generator. A discharge tube 8 without electrodes is positioned on the outside of the casing and glows when the generator is operating due to the electric field created by the generator. The discharge tube may be fixed n one or more faces of the casing in any suitable way but is preferably shaped with its ends 1 and 8- projecting inwards which can be inserted into sockets 9 and I0 formed in the casing. The inner surface of the discharge tube may be provided with a coating of fluorescent material.
The casing 2, 3 may be made of metal and the sockets 9 and [0 be made of insulating material with closed inner ends, and be surrounded inside the casing with metallic parts H, l2 which produce the electric field for energising the discharge tube. One, two or more sockets may be provided and the discharge tube is detachably connected to the generator box by inserting one or more ends or projections from the tube into the socket or sockets. A suitable reflector I3 is positioned behind the discharge tube. The discharge tube is covered by a protective covering ll of glass or other translucent material and also with a protective framework of metal l5, attached to an extension on the" front of the casing.
The generator I is constructed and operates as described in the specification of my British Patent No. 475,413, although it may be constructed in any other convenient way.
With the construction just described the discharge tube, the generator and its current sources are built into a self-contained unit. The apparatus may be providedwith a suitable handle I6 so that it can be used as a portable lamp.
Instead of making the generators as self-contained units they may be fed from a common source of electric supply. At the present day it is permitted to position the distribution board for the electric supply in a coal mine in the road leading to the coal face and about 100 yards therefrom, .and the illuminating units Just described may be connected by cables to such a distribution board. A switch may be provided on the generator casing provided that it is so constructed that air and explosive gases cannot leak inside the casing and thereby be ignited by the spark caused on breaking the circuit.
Alternatively, to overcome this difficulty the supply current may be connectedto the generator box by inductive coupling as shown in Fig. 2, the supply line 20 feeding current to a primary winding 2| arranged on a core 22 of iron or other magnetic material, preferably horse-shoe shaped.
A corresponding core 23, also preferably horseshoe shaped and having its poles spaced apart approximately the same distance as the first core, and carrying a secondary winding 24 which is connected to the generator 25, is also located in the generator box 2 so that by bringing the pole pieces of the two cores in close proximity there is a magnetic coupling between the primary and secondary windings whereby current is fed to the generator. The discharge device 6 may be extinguished byseparating the two cores and since no electrical circuit is broken, no spark occurs, and there is no risk of igniting the explosive gases.
The cores carrying the primary windings may be enclosed in a flame-proof casing 26 or sealed mechanically. couple the head boxes.
in boxes (hereinafter called coupling boxes) with the poles of the core at or adjacent to the surface thereof. The secondary core is enclosed in the generator box or alternatively may be enclosed in a separate secondary coupling box connected to the generator box by a cable. Suitable mechanical couplings, such as the hinge 21 and catch 28, may be provided between the coupling box and either the generator box or the secondary coupling box, as the case may be, in order to hold the two together with the core poles in close proximity to one another.
It will be understood, as shown in Fig. 3, that several coupling boxes 28, 26", etc., may be fed from the common supply or distribution line 20, and the generator boxes 2*, b", etc., carrying the discharge devices 6, 6', etc., may thus be arranged at, for example, every seven yards along the coal face. If desired, the voltage passing through the distribution line 20 may be very low, for example 1 volt, the primary windings in the coupling boxes being designed to step up or down the voltage to that required for operating the generator.
Similar coupling methods may be applied at the distribution box. For example, the main supply current to the mine, which is often in the neighbourhood of 6,000 volts, may terminate in one or more primary windings 29, 29'. connected in series or parallel and arranged on cores, preferably horse-shoe shaped, and all enclosed in a flame-proof casing or casings. This main distribution box is coupled to the distribution lines 20 through head boxes 30, 30 which are totally enclosed and comprise similar cores on which the secondary windings 3| connected with the dis-' tribution lines are wound. By mechanically securing the head boxes to the main distribution box (by mechanical coupling means shown diagrammatically at 32) the transmission of current may be effected through the distribution lines, and by suitably dimensioning the windings any desired voltage may be fed through the distribution lines.
It will be appreciated that the arrangement just described has advantages since as the coal face is advanced it is only necessary to shift forward the main distribution box and then again There is no necessity to break and remake many electrical connections with consequent danger which might arise through incorrect connections or insecurely closing the covers of the distribution boxes as at present employed. Moreover, if a loop of cable is left in'the distribution line, it is only necessary to shift the main distribution box, say once a month. Alternatively, the distribution system may be built up of link members of a suitable length of cable equipped with coupling boxes 33 as hereinbefore described at each end.
The method of making and breaking an electric circuit by the use of coupling boxes as hereinbefore mentioned may also be applied to control circuits for the motors of the coal cutting machines. Since the provision ofa main control switch on the machine itself has led .to disasters, the main control switch is at present located some considerable distance from the coal face and usually at the distribution box, and is controlled from the cutting machine by an auxiliary switch which through a remote control arrangement .mechanically operates the main.
switch. Such auxiliary switches, however, cause a spark on breaking the remote control circuit which is a source of danger, and according to the present invention the remote control circuit is actuated by coupling boxes of the type above described. For example, two such boxes may be fixed on the coal cutter, one containing a primary winding fed direct from the supply mains and the second containing a secondary winding connected to the relay operating e mains switch. By bringing the two boxes together the relay is energised and by separating them it is deenergised. The two boxes may, for example, be pivoted together and operated by a suitable lever.
It will be appreciated that various modiilcations may be made with such a distribution system. For example the coupling boxes for feeding the generators may be hinged together whereby not only the generator may be operated or stopped but also by adjusting the coupling to some intermediate value the intensity of the illuminating device may be adjusted to any desired value.
In the modified construction shown in Figs. 4
and 5, the casing 35 for supporting the discharge device is crescent-shaped in cross section, the outer surface 38 being part of the surface of a cylinder. The discharge device 6 is of elongated form and is arranged within the hollow part of the casing, the surface I! of which part may serve as a reflector. The ends of the tube may be bent round to engage in sockets 88 formed in the casing, to conductors 39 surrounding which the high frequency current is supplied as in the previous example.
Surrounding the casing is a cylindrical member 40 which may be rotated around the casing, and is divided longitudinally into two, three or more sections. One section may comprise a metal grid 40' oi wide mesh, another section a similar grid l0 of smaller mesh, and a third section |l a solid metal portion. By rotating the cylindrical member, the grids or solid portion may be moved in front of the lamp, and afford the necessary protection in ordinary use or during blasting. Additional protection may be provided for the lamp by means of a glass window H. The unit may be constructed as a portable lamp or provided with fixing brackets l2.
The discharge device used according to the present invention preferably has no internal electrodes whatsoever. If internal electrodes are provided, they become charged with electricity and thus particular expedients would have to be adopted to prevent these charged metallic parts from becoming dangerous in the event of a breakage of the tube. The tube is also preferably provided without any external electrodes mounted thereon, although since such external electrodes would not become charged with electricity unless directly connected to the high frequency generator, tubes employing such external electrodes may, if desired, be safely employed. An embodiment employing such a tube is diagrammatically illustrated in Fig. 6 wherein the high frequency generator is connected to con ductive members II and I! which are capacitively coupled to the external electrodes 43, 44 mounted on the discharge tube 6. Such an arrangement would not be dangerous since the external electrodes 43, 44 would not become charged with electricity. It is an important featme of this invention that all metallic parts which are charged with electricity and might become dangerous are entirely protected or enclmd in flame-proof casings, or in the case of a distribution system the distribution system itself is constructed in such a manner as to reduce the possibility of explosion due to sparking on short-circuiting or cutting of the cable.
Instead of arranging the generator in a box upon which the gas or vapour discharge device is mounted. the generator may be arranged at a point remote from the lighting device and the current fed thereto by a distribution system.
Such a distribution system, particularly in the case of a mine, must be explosion and sparkprooi'. Furthermore, the distribution system must be capable of being re-instalied every day in a fool-proof manner. Moreover, the energisation of the lamps by the distribution system must be such that the position of the lamps can be readily changed at short intervals of time.
For the distribution of high frequency current a conductor or conductor system may be employed which is earthed at one or more points.
For example, as shown in Fig. 7, the output circuit ll coupled to the high frequency generator may be earthed on one side and have its other side connected to. the conductor ll which is also earthed at its remote end 52, and may also be earthed at intermediate-points ll, 54, along its length. With such asystein the tension in the conductor is very small (of the order of a few millivolts) but the current therein is considerable. Danger would therefore arise if'the conductor were out due to, the spark produced and this danger may be avoided by connecting one or more further conductors, 56 in parallel or by making the conductor of very strong material, such as a steel cable. The parallel conductors may comprise the metal of the conveyor or coal cutting machine in the mine or any metal part at the coal face.
In order to operate the discharge devices from such a distribution system, the low tension in the conductor is transformed through a high frequency transformer, the primary of which consists of the distribution system itself and the secondary of which consists of an oscillatory circuit 51 coupled to the primary (the conductor) electro-magnetically, electro-statically or galvanically, whereby sufllcient tension is produced in the secondary winding to energise the electrodeless discharge device 6 which is placed in the field of the secondary circuit. The secondary circuit comprises an inductance 58 and capacity 59 (which may be the discharge tube itself), and since it is a source of danger it is enclosed within a flame-proof casing 60, preferably hermetically sealed in the same manner as explained above for the high frequency generator. The discharge device 6 is mounted on this casing in a manner similar to that described above. The box may be placed against the conductor and is preferably provided with a hook 6| for hooking it over the conductor at any desired point. A plate 52 or other conductor is preferably embedded in the material of the hook, which may conveniently be made of insulating material, and be connected to the oscillatory circuit. In this way the conductor in the hook is electrostatically coupled to the conductor of the distribution system and effects thereby the coupling between the distribution system and the oscillatory circuit. Since in this case the conductor Si is earthed, the conductor 62 may even be galvanically connected to the conductor ii.
The framework of the conveyor or coal cutter I secondary circuit need merely be coupled to or position.
The frequency of the auxiliary generator should be adjusted to be in tune with the fundamental frequency of the distribution system or a part thereof, or one of its harmonics, or vice versa.
In an alternative embodiment shown in Fig. 8, the distribution system may be fed with a low tension, whereby the necessity of earthing may be avoided. The coupling of the lighting devices and other arrangements may be effected as described above.
In another embodiment shown in Fig. 9, the distribution system is constituted by one or more oscillatory circuits I, II, which is/a're earthed at one or more points and sharply tuned to the generator frequency. Being earthed so that there is substantially no tension in the conductors of the oscillatory circuit, and being sharply tuned, should the wire be accidentally cut the system immediately falls out of tune so that the duration of the spark is very short and not sufficient to ignite the explosive gas. The discharge devices may be coupled to the distribution system as previously explained. In the event that the tension impressed upon the oscillatory circuit or circuits of the distribution system is in itself very low, the earthing of these circuits may be dispensed with.
The complete distribution system can be built up of a plurality of separate parts each having similar characteristics to those described in the various embodiments. In some cases the coal itself can be used as the conductor for the high frequency current.
The discharge devices which are used in the method according to this invention can also he energised in an electric field created by electromagnetic waves, generated at or near the coal face. As shown in Fig. 10, 10 indicates the generator of electromagnetic waves. In order to guide the electromagnetic waves in the desired direction, any conductor H, such as one or more wires, the framework of the conveyor or the coal high frequency device may comprise an antenna 13 which is connected to an oscillatory circuit 14 which latter constitutes the secondary of a transformer, the primary of which is the antenna itself. The receiver is tuned to the wavelength of the electromagnetic waves.
A combination distribution system for high frequency current and electromagnetic waves may be used for supplying the electric discharge device.
It will be understood that various modifications may be made without departing from the scope of this invention as defined by the appended claims."-
' 1. Illuminating system for use in mines and other explosive atmospheres comprising a high frequency generator, a distribution system for within the electric field created by said means.
2. System as claimed in claim 1, wherein said means for producing the electric field for ener:
gising the discharge device comprises an oscillatory circuit coupled to the distribution system and producingthe necessary tension for energising the discharge device, said oscillatory circuit being enclosed in a flame-proof casing.
3. A system as claimed in claim 1, wherein the coupling between the high frequency generator and the distribution system is such that the tension in the distribution system is very low. I
4. A system as claimed in claim 1, wherein the tension in the distribution system is made low by earthing the conductor system at one or more points;
5. System as claimed in claim 1, wherein the distribution system comprises two or more con- I ductors arranged inparallel for the purpose of avoiding the production of a spark should one of the cables become accidentally cut.
6. A system as claimed in claim 1, wherein the distribution system comprises an oscillatory circuit sharply tuned to the generator frequency so that in the event of cutting a conductor of the distribution system the system will immediately fall out of tune.