Device for the lighting and instantaneous hot-relighting of lamps, particularly of the discharge type

Abstract: A device for the lighting and instantaneous hot-relighting of lamps of the discharge type, including: a transformer (3) having a first winding (11) and a second winding (6); a discharge lamp (2), in which a first electrode (5) is connected to the second winding; one or more capacitive means (13, 12), which are series-connected to the first winding (11); and trigger means (14) adapted to trigger, by means of pulses, discharge control means (19) that are connected thereto; the discharge control means (19) produce the discharge of the one or more capacitive means (13, 12) on the first winding (11), which induces on the second winding (6) a high voltage for the hot-lighting of the discharge lamp (2).

Description: The present invention relates to a device for the lighting and instantaneous hot-relighting of lamps, particularly of the discharge type. It is known that a discharge lamp using mercury vapors, sodium, or mixtures with metallic halides must reach a certain pressure, after lighting, before it can deliver maximum brightness, and this occurs over a certain time interval (approximately three minutes). If mains power is interrupted, the lamp switches off and cannot be switched on again immediately when power is restored; it takes approximately ten minutes for the lamp to cool and then reach the operating pressure to obtain maximum brightness. This is a serious drawback if discharge lamps are used in public places such as sports facilities, airports, and the like, where a delay in relighting can entail dangers. Furthermore, in some cases the use of lamps is time-controlled by means of tokens, and therefore there is the drawback that after a first automatic switching-off the subsequent user must wait approximately ten minutes to relight the lamp. The solutions adopted so far to avoid this delay for the relighting of a discharge lamp have entailed the drawbacks of being bulky and most of all considerably expensive, much more than the discharge lamp itself, thus preventing their use. Cold-lighting a discharge lamp in fact requires approximately 4 kV, which are provided by means of a conventional commercial starter, whereas hot-lighting requires a much higher voltage obtainable exclusively with large and expensive devices. From US-B-31 486 it is known a starting device for a gas discharge lamp having a ballast and means for applying to the lamp a transient voltage pulse which initially changes in amplitude in a polarity direction relatively in opposition to the polarity of the main voltage simultaneously supplied to the electrodes of the lamp. These means include circuitry to cause said pulse to thereafter change in amplitude in a polarity direction in aid of the polarity of the main voltage simultaneously supplied to the electrodes of the lamp. However, this device is both complicated and costly, in addition to be bulky. EP-0 505 947 discloses a high-voltage transformer having a low-voltage and a high-voltage windings wound on a main iron core. The transformer is housed in a casing and the free space within such casing is filled with an insulating compound. EP-0 405 715 discloses a lamp starting circuit having a transformer acting both as pulse transformer and as a ballast and having discharge control means and associated triggering means. A principal aim of the present invention is therefore to provide a device for the lighting and instantaneous hot-relighting of lamps, particularly of the discharge type. Within the scope of this aim, an object of the present invention is to provide a device for the lighting and relighting of lamps that allows to hot-relight a lamp with the maximum possible brightness. Another object of the present invention is to provide a device for the lighting and instantaneous hot-relighting of lamps having limited dimensions. Another object of the present invention is to provide a device for the lighting and instantaneous hot-relighting of lamps having a low cost. Another object of the present invention is to provide a discharge lamp that is modified to adapt to hot-lighting requirements so as to be compatible with the device of figure 1. Another object of the present invention is to provide a lamp holder adapted for socket lamps in accordance with the device according to the invention. Another object of the present invention is to provide a device for the lighting and hot-relighting of lamps that is highly reliable, and relatively easy to manufacture at competitive costs. This aim, these objects, and others which will become apparent hereinafter are achieved by a system, as defined in claim 1. Further characteristics and advantages of the invention will become apparent from the following detailed description of a preferred but not exclusive embodiment of the device according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a circuit diagram of the device for lighting and instantly hot-relighting a discharge lamp which is part of the system according to the invention; figure 2 is a view of a lamp of the discharge type, modified for use with the device of figure 1; figure 3a is a perspective view of a bobbin on which windings are formed for use in the device of figure 1; figure 3b is a side view of the bobbin shown in figure 3a; figure 3c is a perspective view of the insertion of the bobbin of figure 3a in an appropriate container; figure 4 is a view of a lamp of the discharge type, modified for use with the device of figure 1; figure 5 is a sectional view of a lamp holder for socket lamps, modified for use with the device of figure 1; and figure 6 is a view of the insertion of a socket lamp in the lamp holder shown in figure 5. With reference to figure 1, the system according to the invention, comprises a lamp 2 of the discharge type connected between a first transformer 3 and a second transformer 4. The first discharge electrode 5 of the lamp 2 (hot-side electrode) is connected to a winding 6 (second winding) of the first transformer 3, and the second discharge electrode 7 of the lamp 2 (cold-side electrode) is connected to a first winding 8 of the second transformer 4. The second winding 6 of the first transformer 3 and the first winding 8 of the second transformer 4 are connected respectively to a first terminal 9 and to a second terminal 10, to which the alternating supply voltage is applied. First and second capacitive means, advantageously constituted by two capacitors 12 and 13, are series-connected to the terminals of the first winding 11 of the first transformer 3. The first capacitor 12 is series-connected to trigger means 14, whereas the second capacitor 13 is connected to the supply terminal 10. The trigger means 14 are appropriately constituted by a diac 15, a variable resistor 16, a resistor 17, and a capacitor 18, and are connected to discharge control means comprising a triac 19 interposed between the power supply terminal 10 and the power supply terminal 9. Inductive means 20, conveniently constituted by a coil, limiter means 21, connected in series to the coil 20 and advantageously constituted by a limiting resistor, and adjustment means 22, conveniently comprising a manual-reset thermostat, are interposed between the triac 19 and the power supply terminal 9. The thermostat 22 is in turn connected to switching means 23 comprising a relay, the normally-closed contacts whereof (as shown in figure 1) allow to supply power to the trigger means 14. The second winding 24 of the second transformer 4 is connected to delay means adapted to delay the opening switching of the relay 23. Said delay means advantageously comprise a diode 25 that is parallel-connected to a high-capacity electrolytic capacitor 26. The second winding 6 of the first transformer 3 has a greater number of turns than the first winding 11 of the same transformer, whereas the first winding 8 of the second transformer 4 has a smaller number of turns than the second winding 24 of the same transformer. Figure 2 is a view of the discharge lamp 2 with the respective discharge electrodes 5 and 7 and a wire 27 (also shown in figure 1) that is located outside the lamp 2 and is adapted to facilitate the starting of the lamp 2. Figure 3a is a view of a bobbin 28 with a plurality of sections, on which the windings 6 and 11 of the first transformer 3 are formed. Figure 3b is a side view of the bobbin 28 of figure 3a, whereas figure 3c is a view of the insertion of the bobbin 28 in a container 29 for forming the first transformer 3. The container 29 is conveniently made of plastics and is filled with quick-curing resins. Figure 4 is a view of a discharge lamp 2 of the type with a standard threaded socket, modified by adding a ring 30 of highly insulating material to adapt it for use of the circuit shown in figure 1. Figure 4 shows an interspace, designated by the reference numeral 31, that is filled with heat-resistant plastics and from which the wires directed to the socket protrude. Figure 5 is instead a view of a lamp holder 32 for discharge lamps of the threaded socket type (shown in figure 4). The reference numeral 33 designates the contact of the threaded ring (cold-side contact, corresponding to 7 in figure 1), and the reference numeral 34 designates the central contact of the lamp 2 (hot side, corresponding to 5 in figure 1). The reference numeral 35 designates an elastic heat-resistant insulating compound, for example a silicone compound, that covers the bottom of the lamp holder 32, forming a recess 36 (see figure 6) that provides the seat for the socket 37 of the lamp 2. In this case, the insulating ring 30 is eliminated, since it is replaced with the insulating compound 35. With reference to the above figures, the operation of the device according to the invention is as follows. The alternating supply voltage is applied to the terminals 9 and 10 of the circuit shown in figure 1. The first winding 6 of the first transformer 3 acts as a ballast, with the purpose of limiting the current of the lamp 2 with its discharge electrodes 5 and 7. The wire 27 located outside the lamp 2 has the purpose of facilitating the lighting of said lamp. The trigger means 14 trigger the triac 19 by means of pulses; in this manner, every time the triac 19 is triggered, the capacitors 12 and 13 discharge onto the first winding 11 of the first transformer 3; said capacitors are kept constantly charged by the limiting resistor 21. The capacitor 12 has the purpose of considerably increasing the discharge on the winding 11. The voltage of the capacitors 12 and 13, discharged by pulses by means of the triac 19 on the winding 11, induces a very high voltage in the second winding 6 (the number of turns whereof is greater than that of the winding 11). Normally, approximately 4 kV, obtained with a conventional commercial starter, are required to cold-light a discharge lamp. In the circuit according to the invention, by virtue of the (high-voltage) ballast-transformer 3 composed of the windings 6 and 11, a voltage of approximately 30 kV is obtained that allows hot-lighting under pressure of the lamp 2, avoiding forced pauses. The coil 20 has the purpose of protecting the triac 19, whereas the reference numeral 16 designates a variable resistor that allows to give the trigger pulse to the lamp 2 in the correct point of the alternating sinusoid of the lamp power supply. The lamp lights more easily if the trigger pulse precedes the positive and negative cusps of the sine curve, since the triac 19 acts on each period of the sine curve. Said resistor 16 is adjusted according to the type of lamp 2 in order to achieve the best possible hot-lighting. Since the trigger voltage at the lamp 2 is required only for a few moments, a second transformer 4 is arranged in series to the lamp 2 in order to automatically interrupt the trigger voltage (which is very high, approximately 30 kV) as soon as the lamp has lighted. When the lamp 2 has been started, alternating current flows in the winding 8 and induces on the winding 24 a voltage adapted to drive the relay 23. The diode 25 and the high-capacity electrolytic capacitor 26 have the purpose of delaying the attraction of the relay 23, which supplies, by means of its normally-closed contacts (as shown in figure 1), the trigger circuit formed by the trigger means 14 and by the triac 19. This delay allows to give a certain duration to the trigger pulses and ensures the lighting of the lamp 2. The manual-reset thermostat 22 has a safety function, since it interrupts the trigger circuit when the lamp 2 does not work due to aging or to possible malfunction thereof. Therefore, the trigger pulses occur until the limiting resistor 21, by overheating, trips the thermostat 22 that is series-connected thereto. After replacing the malfunctioning lamp 2, the thermostat 22 is reset manually to restore the trigger circuit. Figure 2 illustrates the modification of the lamp 2 for adaptation to hot-relighting requirements. This modification consists in adding the wire 27 to improve lighting of the lamp 2. This solution is used for high-power lamps in which the distance between the discharge electrodes 5 and 7 is considerable. If low-power lamps (normally up to 400 W) are used, the wire 27 is not necessary, since the distance between the discharge electrodes 5 and 7 is much smaller and the high lighting voltage is sufficient. The transformer 3 of figure 1 is formed by means of the bobbin 28, on which the windings 6 and 11 are formed; said bobbin is inserted in the container 29 made of plastics. The container is then filled with quick-curing resins that allow to obtain a single high-insulation block that is insensitive to humidity. Ordinary commercially available discharge lamps, of the type with a standard threaded socket, are designed to operate at medium voltage and are therefore not adapted when the voltages involved are very high, as occurs with the device according to the invention. These sockets are not adapted because they discharge between the two electrodes of the lamp. In order to eliminate this drawback, the ring 30 is added; said ring is made for example of ceramic material or of another material providing high electrical and thermal insulation. Said ring 30 considerably increases insulation, allowing high-voltage starting of the lamp 2. Furthermore, the interspace 31 of the lamp 2 where the wires leading to the socket protrude is filled with heat-resistant plastic material, for example resins, silicone products, and the like. Therefore, with these solutions, a conventional lamp, adapted exclusively for lighting pulses of a few kV, is converted into a lamp adapted for hot-lighting, where it is necessary to apply a very high lighting voltage. Figure 5 shows a lamp holder 32 for lamps of the above described socket type. In this case, the lamp holder is modified by adding an elastic heat-resistant insulating compound 35 that covers the bottom of the lamp holder. In this manner, by screwing the lamp 2 in the lamp holder 32, the elastic insulating compound 35 increases the insulation, since between the electrodes 33 and 34, which correspond respectively to the electrodes 7 and 5 of figure 1, there is an insulation of approximately 20 kV-mm, which corresponds to the value of the insulating compound 35, instead of air (which provides an insulation of 1 kV-mm). In this case, the ring 30 shown in figure 4 is replaced with said insulating compound 35. In practice it has been observed that the device according to the invention fully achieves the intended aim, since it allows to light and instantaneously hot-relight a lamp of the discharge type, avoiding the delays arising from the need to wait for said lamp to cool before subsequent re-lighting. Furthermore, the device according to the invention is compact and very convenient. For example, in applications using high-pressure sodium lamps, which are normally easier to hot-light, a self-starting element (so-called SIDAC, or in-gas dischargers) is used instead of the triac 19 and of the corresponding trigger means 14 in order to simplify the circuit according to the invention. Furthermore, instead of the thermostat 22 it is possible to use an element in which resistance increases as the temperature rises (known as PTC element), performing the same function. After a short period of continuous operation of the starting circuit, caused by anomalies in the discharge lamp 2, this element considerably increases its ohmic value and accordingly considerably limits the voltage at the diac 15, which no longer supplies trigger pulses to the triac 19. Finally, all the details may be replaced with other technically equivalent elements. In practice, the materials employed, so long as they are compatible with the specific use, as well as the dimensions, may be any according to the requirements and the state of the art. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims: A system comprising a device for lighting and instantly hot-relighting a discharge lamp, a discharge lamp (2) having a socket and a lamp holder (32), wherein the device for lighting and instantly hot-relighting the discharge lamp comprises: a first transformer (3) having a first and a second winding (11, 6) respectively supplied by first and second supply terminals (9, 10), said second winding (6) being connected to a first electrode (5) of said discharge lamp (2); capacitive means (12, 13), which is series-connected to the first winding (11) of the first transformer (3); trigger means (14) connected to said first winding (11) and supplied by said first and second supply terminals (9, 10); discharge control means (19), connected to said trigger means (14); said first and second windings (11, 6) of said first transformer (3) being provided on a bobbin (28) with a plurality of adjoining sections inserted in a container (29) filled with insulating material; said discharge control means (19) producing the discharge of said capacitive means (12, 13) on said first winding (11) of the first transformer (3), said first winding (11) inducing, on said second winding (6), a high voltage for the hot-relighting of said discharge lamp (2), said first transformer (3) acting both as a ballast for limiting the current of the lamp (2) and as a high-voltage pulse generator to hot-relight said discharge lamp, the number of turns of said second winding (6) of the first transformer being greater than the number of turns of the first winding (11) thereof; and wherein said discharge lamp has a threaded-type socket with an interspace (31) filled with heat-resistant material and is inserted in a lamp holder (32), either the socket being provided with a ring (30) of insulating material or the bottom of the lamp holder being covered with an insulating material forming a seat for the insertion of said lamp. The system according to claim 1, characterized in that a second transformer (4) having a first and second windings (8, 24) is series-connected to a second electrode (5) of said discharge lamp (2), said second transformer (4) acting as a current sensor. The system according to claim 1, characterized in that said trigger means (14) comprise a variable resistor (16), a capacitor (18), and a resistor (17) to which a diac (15) is series-connected. The system according to claim 1, characterized in that said discharge control means are (19) connected between one terminal of the first winding (11) of the first transformer (3) and the first supply terminal (9) and comprise a triac. The system according to claim 4, further comprising a coil (20) series-connected to said triac. The system according to claim 1, characterized in that said trigger means (14) and said discharge control means (19) comprise a self-starting element. The system according to claim 1, characterized in that said capacitive means (12, 13) comprise a first capacitor (12) that is connected to one terminal of said first winding (11) of the first transformer (3) and a second capacitor (13) that is connected between the other terminal of said first winding (11) and said first supply terminal (9). The system according to claim 1, characterized in that the number of turns of said first winding (11) of said first transformer (3) is smaller than the number of turns of said second winding (6) of the first transformer (3). The system according to claim 1, characterized in that said first winding (8) of said second transformer (4) has one terminal connected to the second electrode (5) of said discharge lamp (2) and one terminal connected to said first supply terminal (9). The system according to claim 1, further comprising switching means (23) adapted to connect and interrupt the supply of power to said trigger means (14). The system according to claim 10, characterized in that said switching means (23) comprise a relay the terminals whereof are respectively connected to said second supply terminal (10) and to said trigger means (14). The system according to claim 11, further comprising delay means (25, 26) connected to the terminals of said second winding (24) of the second transformer (4), said delay means (25, 26) being adapted to delay the opening switching of said relay. The system according to claim 12, characterized in that said delay means (25, 26) comprise a diode (25) and a capacitor (26) that are parallel-connected to each other. The system according to claim 11, further comprising adjustment means (22) connected between one terminal of said relay and said trigger means (14). The system according to claim 14, characterized in that said adjustment means (22) comprise a thermostat (22), a limiting resistor being (21) series connected to said thermostat (22). The system according to claim 14, characterized in that said adjustment means (22) comprise a resistor the value whereof increases with temperature.

Inventors: ZANARDO GIUSEPPE, ZANARDO GIUSEPPE                                  ARDO GIUSEPPE & C., ZANARDO Giuseppe and ZANARDO Luciano trading under the trading style PHOTO ELECTRONICS S.n.c. di Zanardo Giuseppe &amp; C.
Applicants: ZANARDO GIUSEPPE AND ZANARDO L, ZANARDO GIUSEPPE AND ZANARDO LUCIANO TRADING UNDER THE TRADING STYLE PHOTO ELECTRONICS S.N.C. DI ZANARDO GIUSEPPE & C.
Application year: 1995
Main classification: H05B41
IPC codes: H05B41