DISCONNECTION DETECTION APPARATUS FOR LAMPS

Abstract: PCT No. PCT/JP88/00307 Sec. 371 Date Nov. 24, 1989 Sec. 102(e) Date Nov. 24, 1989 PCT Filed Mar. 25, 1988 PCT Pub. No. WO89/09533 PCT Pub. Date Oct. 5, 1989.A detecting device can centrally monitor and detect a lamp failure of one or more lamps connected in series such as guide lamps in the runway of an airfield. A core (12) is disposed on a power line (P1) of each lamp (L1-Ln). The power line (P1) is wound on the core (12) as a first winding (N1). A second winding (N2) for extracting the power of the power line (P1) is wound on the core (12). An oscillator (13) is provided which uses the output voltage of the second winding (N2) as the power supply to generate a frequency corresponding to each lamp (L1-Ln). The output signal from this oscillator (13) is fed back to the power line (P1) through a third winding (N3). Accordingly, a signal consisting of a frequency which represents each lamp flows through the lamp circuit and any failed lamp or lamps can be detected by checking this feedback signal.

Description: This invention relates to a device for detecting the failure or disconnection of any of a plurality of electric lamps connected in series and has particular reference to such a device which is suitably used for detecting the failure of any of a large number of taxiway or guide lamps illuminating the runway of an airfield. There are known certain devices designed to detect the failure of any one of guide lamps simply by the occurrence of a breakage of the circuit to which such numerous lamps are connected in series. Such known devices, described for example in "Illuminating Equipment for Safe Aviation" published 1984 by New Tokyo International Airport Corporation, have a drawback in that failure of one lamp results in extinction of all of the remaining lamps. DE-0-36 35 682 describes a lamp failure detecting device for use with each of a plurality of serially connected lamps, each device comprising: a means connected in series to the corresponding lamp for detecting a respective lamp current; a signal generator operable by an output voltage of said detecting means; and a means connected in series to the corresponding lamp for feeding an output signal from said signal generator back to a lamp power line. Improvements have been made in which a switch is provided, as illustrated in FIG. 6 of the accompanying drawings, to give a short circuit to the terminals of each of serially connected lamps so that failure of any one lamp does not affect all the other lamps. However, this circuit device has the disadvantage that it is difficult to know which of so many remotely located lamps has failed and therefore to monitor all the lamps centrally from one place. With the foregoing difficulties of the prior art in view, the present invention seeks to provide a device for detecting lamp failure which is capable of preforming accurate detection and remote central monitoring of a large number of electric lamps. The above stated object of the invention is achieved by the provision of a lamp failure detecting device which essentially comprises a transformer means disposed on a lamp power line and having a core, a first winding wound on said core and connected in series to the corresponding lamp and a second winding wound on said lamp power line through said core; and an oscillator operating on the output voltage of said second winding and generating a predetermined frequency, for supplying an output signal having the predetermined frequency from said oscillator onto said lamp power line characterised in that the oscillator supplies an output signal to the lamp power line via a third winding wound on said core. Thus, in the event of failure of any one lamp, this can be confirmed by detecting the absence of such feedback signal in that particular lamp circuit. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagram illustrating a lamp failure detecting device according to one embodiment of the invention; FIG. 2 is a schematic circuit diagram showing a plurality of lamps connected in series; FIG. 3 schematically illustrates the terminals being short-circuited upon failure of a lamp filament; FIG. 4 is a schematic circuit diagram illustrating a lamp failure detecting device according to another embodiment of the invention; FIG. 5 shows a modified circuit in part of FIG. 4; and FIG. 6 is a schematic circuit diagram showing a typical prior art lamp circuit. Referring now to the drawings and FIGS. 1 and 2 in particular, there is shown a lamp failure detecting device according to one embodiment of the invention for detecting the failure of any of a number of lamps L₁ - L n connected in series (FIG. 2) which are powered by a supply source E having a commercial frequency. FIG. 1 is a circuit diagram on enlarged scale of a lamp L₁ having a filament 10. A short-circuitng circuit 11 is provided for giving a short circuit between the opposite terminals of the lamp filament 10. The circuit 11 is conventional, including a switch SW₁ which operates to close the circuit 11 in the event of lamp failure. The circuit 11 is connected to a power line P₁ at points A and B. A core 12 is provided on the power line P₁ between one terminal of the lamp filament 10 and the connection point A. The core 12 has wound thereon a first winding N₁, which is an extension of the power line P₁, a second winding N₂ for extracting power from the first winding N₁ via core 12 and a third winding N₃ for transferring a signal S₁ to the first winding N₁ to provide the lamp L₁ with a signal of a predetermined frequency f₁. The second winding N₂ functions as a means of detecting a current flow through the power line P₁ to turn on the lamp L₁. A signal generator 13 is connected to the output terminal of the second winding N₂ and designed as an oscillator to be excited by the output voltage of the second winding N₂ to generate a specific frequency f₁. The output of the signal generator 13 is connected to the third winding N₃ to feed back its output signal as a current through the core 12 to the power line P₁ so that the lamp L₁ is normally (i.e. when turned on) supplied with a signal of frequency f₁. Designated at L p is an inductance adapted to prohibit entry of the feedback signal from the third winding N₃ into the signal generator 13 and allow passage of the frequency components of the lamp power current alone in the circuit. The detecting device for the lamp L₁ is used commonly, as shown in FIG. 2, for each of the remaining lamps L₁ - L n with their respective predetermined frequencies f₂ - f n supplied in superimposed relation. There are provided filters F₁ - F n in the lamp power circuit assigned to corresponding lamps L₁ - L n and adapted to extract their respective feedback signals; namely, feedback frequencies. Central monitoring of the lamp operation is effected by the circuit arrangement above described in which failure of the filament 10 in the lamp L₁ causes the switch SW₁ to close to permit current flow through the circuit 11, whereupon the current to the lamp L₁ and hence the signal f₁ from the signal generator 13 are discontinued and the frequency component f₁ in the lamp circuit can no longer be detected by the filter F₁ thereby ascertaining the occurrence of failure of the lamp L₁. The same applies to each of the remaining lamps. Alternatively, lamp monitoring can also be effected with the core 12 provided on the short-circuiting line P₂, in which case the feedback signal does not flow through the lamp circuit as long as the lamp is on, but in the event of failure begins to flow with a frequency corresponding to that particular lamp which has failed and will be received by the corresponding one of the filters (F₁ - F n ) thereby detecting the occurrence of failure of which particular one of the serially connected lamps. Another embodiment of the invention is illustrated in FIGS. 3 and 4, in which the filament 10 is broken but with the current continued to flow through the power line P₁ and the signal generator 13 produces a feedback signal of frequency f₁. The circuit arrangement shown in FIG. 4 incorporates a photodiode PHD adjacent to the lamp. In the event of failure of the lamp L₁, no current flows through the photodiode PHD with no output at an AND-circuit 14 and hence no feedback signal received at the filter F₁, indicating that the lamp L₁ has failed. Alternatively, when the core 12 is provided on the short-circuiting line P₂, the circuit may be a negative input AND-circuit so that the output of the photodiode PHD becomes a negative input, as shown in FIG. 5. First of all, the detecting device embodying the present invention is provided in each of the numerous serially connected lamp circuits so that the lamp operation can be remotely controlled and failure of any of the many lamps can be readily detected. The inventive device may be most suitably used to control the operation of for example guide lamps illuminating the runway of an airfield so as to contribute to safety in the take-off and landing of air planes. Secondly, since according to the invention the power for the signal generators and the signals indicative of the lamp operation are likewise received by the current transformers, there is only remote possibility for the signal generators (and their associated power circuits) to sustain damage on account of surge which may occur in the lamp power line P₁. In reality, power E shown in FIG. 2 is remotely supplied and the power line for lamps L₁ - L n extend over a long distance. Therefore, surge is liable to occur by thunders. However, according to the first embodiment of the invention hereinabove advanced, the power consumed by the core 12 is far less compared to that consumed by the filament 10, so that the effect of surge on the power line P₁ is negligible. Furthermore, since power E in FIG. 2 is generated as a current which is supplied to the filaments for lamps L₁ - L n via transformers, these transformers in the event of lamp failure become unloaded and saturated, leading to the occurrence of spike-like surge voltage. However, the effect of this surge is only appreciable because the power consumption on the core 12 is considerably small as compared to the lamp filaments for the reasons above noted.

Claims: A lamp failure detecting device for use with each of a plurality of serially connected lamps, each device comprising: a transformer means disposed on a lamp power line (P₁) and having a core (12), a first winding (N₁) wound on said core (12) and connected in series to the corresponding lamp (L₁ - L n ) and a second winding (N₂) wound on said lamp power line (P₁) through said core (12); and an oscillator (13) operating on the output voltage of said second winding (N₂) and generating a predetermined frequency (f₁ - f n ), for supplying an output signal having the predetermined frequency (f₁ - f n ) from said oscillator (13) onto said lamp power line (P₁) characterised in that the oscillator (13) supplies an output signal to the lamp power line (P₁) via a third winding (N₃) wound on said core (12). A lamp failure detecting device according to Claim 1 which further includes a photodiode (PHD) located adjacent to each of the plurality of serially connected lamps (L₁ - L n ) and a respective AND circuit (14) for producing an output signal of a respective predetermined frequency (f₁ - f n ) on an AND condition of the output of said photodiode (PHD) and the output signal of said oscillator (13).

Inventors: FUTSUHARA K YONO FACTORY OF TH, KATO M YONO FACTORY OF THE NIP, FUTSUHARA, K. YONO FACTORY OF THE NIPPON, KATO, M. YONO FACTORY OF THE NIPPON
Applicants: NIPPON SIGNAL CO LTD, THE NIPPON SIGNAL CO. LTD.
Application year: 1988
Main classification: H05B37
IPC codes: H05B37, G01F23, G01R31