GB2358240A - Beacon lamp with plural flashing rates - Google Patents

Abstract

A beacon lamp including a housing 14,22 within which a printed circuit board associated with alight source (19, fig 3) is received, a disruptable link on the circuit board which when made results in flashing of light source at first predetermined rate and when broken results in flashing of light source at second predetermined rate. Means for disrupting link are accessible at exterior of housing and may comprise severable electrical loop or mechanical, unplugging means. The light source may be a xenon tube. The electrical control circuitry are shown in Figures 3 and 4.

Description

2358240 BEACON LAMPS This invention relates to beacon lamps for use as

warning lamps on vehicles, or road barriers and the like, the lamp being of the kind in which an electrically powered light source is caused to flash.

It is known to produce an electrically powered beacon lamp in which the energisation and control circuit of the light source is carried primarily on a printed circuit board received within a housing of the beacon lamp, the printed circuit board including a manually operable switch for controlling whether the light source, which may be, for example, a xenon tube, is operated at a first flash rate, or a second different flash rate. The known arrangement is disadvantageous in that it requires the flash rate to be set when the beacon lamp is being manufactured, or alternatively it requires a vendor, or a user to substantially disassemble the beacon lamp in order to gain access to the switch on the printed circuit board to alter the flash rate. It is an object of the present invention to provide a beacon lamp in which this disadvantage is obviated. The invention also resides in the energisation and control system of the beacon lamp.

In accordance with the present invention, there is provided a beacon lamp including a housing within which a circuit board associated with the light source of the beacon lamp is received, a disruptable link on the printed circuit board which when made results in flashing of the light source of the beacon lamp at a first rate and which when broken results in flashing of the light source at a second, different rate, and, means accessible at the exterior of the housing for breaking said link whereby the link can be broken without gaining access to the interior of the housing of the circuit board.

Conveniently said means for breaking said link comprises an elongate loop of electrically conductive lead forming part of said link and extending from said circuit board through an aperture in said housing so as to be accessible at the exterior of the housing, whereby the loop can be severed at the exterior of the housing to break said link.

Alternatively said means for breaking said link comprises an elongate member mechanically coupled at one end to said link on the circuit board, and extending from the circuit board through an aperture in the wall of said housing to be accessible at the exterior of the housing, whereby said member can be pulled, or otherwise moved manually, at the exterior of the housing, to unplug, or otherwise break the link on the circuit board within the housing.

Preferably said housing is within an outer enclosure in use, and desirably access to said means for disrupting said link is obtained by removal of part of said enclosure.

One example of the present invention is illustrated in the accompanying drawings wherein:Figures 1 and 2 are diagrammatic cross-sectional views in perpendicular planes respectively of a beacon lamp; Figure 3 is a block diagram illustrating the energisation and control circuits of the beacon lamp of Figures 1 and 2, and, Figure 4 is a detailed circuit diagram, identifying individual components of the circuit illustrated in block form in Figure 3.

Referring first to Figures 1 and 2 of the accompanying drawings, there is shown a beacon lamp intended to be mounted on the roof of a road vehicle. It is to be recognised however that with suitable modifications to the base of the beacon lamp, the beacon lamp could be used in other environments.

The beacon lamp includes a molded synthetic resin base 11 of circular cross-section, the base being generally hollow and having a frustoconical outer wall 12. The lower edge 13 of the base 11 is intended to seat against the roof panel of a vehicle, and be secured thereto in any convenient manner such, for example, as the use of a magnetic fixing device or screws. Within the base 11 and formed integrally therewith is a cylindrical receptacle 14 coaxial with the base 11. The receptacle 14 has a base wall 15 spaced upwardly (in use) above the lower edge 13 of the base 11 and a cylindrical wall 16 extending upwardly at right angles to the base 15. The cylindrical wall 16 protrudes beyond the upper edge of the frusto-conical wall 12 of the base 11 and an external peripheral shoulder 17 is defined at the upper edge of the wall 12 where the cylindrical wall 16 of the receptacle 14 protrudes therefrom. An outer, transparent or translucent, molded synthetic resin dome 18 is positioned with its open end presented to the shoulder 17, and a screw, or bayonettype coupling secures the dome 18, at its lower edge, to the base 11 in the region of the upstanding part of the wall 16. A gasket 19 is interposed between the lower edge of the dome 18 and the shoulder 17 to provide a seal against ingress of dirt and moisture into the lamp. It is intended that the lower edge 13 of the base 11 shall be in sealing engagement with the roof panel of the vehicle, a gasket or the like being interposed between the edge 13 and the roof panel. Thus when the beacon lamp is mounted on the vehicle roof panel and the dome 18 is attached to the base 11 the interior of the base 11 and dome 18 is a sealed environment.

The receptacle 14 is formed internally with a plurality of integral formations for receiving and supporting components of a drive and control circuit for the light source of the beacon lamp. The light source, in this particular example, is a xenon tube 19 secured to, and protruding from, one end of a rectangular printed circuit board 21. The printed circuit board 21 is disposed with its plane parallel to and containing, the longitudinal axis of the beacon lamp.

A cylindrical, fresnel lens unit 22 is secured to the base 11 and protrudes above the open end of the receptacle 14 into the volume of the dome 18. The unit 22 is molded in a transparent or translucent synthetic resin material, and may, if desired, be coloured in known manner. The unit 22 includes a cylindrical sleeve 23 coaxial with the base 11 and having the lens formation on its outer cylindrical surface. The sleeve 23 is partially obstructed at its lower end by a pair of diametrically opposed, inwardly projecting, integral flanges 24, and the sleeve 23 is extended downwardly beyond the plane of the flanges 24 to define a frusto- conical shroud 25 extending downwardly into the open end of the receptacle 14. The unit 22 is seated on the base 11 through the intermediary on one or more spacers 26 extending downwardly from the flanges 24 and abutting the upper ends of corresponding pillars 27 integral with and protruding upwardly from the base wall 15 of the receptacle 14. The unit 22 can be secured to the base 11 by screws or rivets extending through the flanges 24 and spacers 26, or by heat sealing, adhesives or the like.

The unit 22 and the receptacle 14 together define a housing receiving the majority of the control and drive circuitry of the light source 19. The housing is not a closed housing as the sleeve 23 is open at its end remote from the receptacle 14 and there is an annular gap between the periphery of the shroud 25 and the periphery of the wall 16 but nevertheless the components 14, 23, 25 define. a housing containing and protecting the circuit components associated with the light source 19. The printed circuit board 21 is received primarily within the receptacle 14 and shroud 25 but protrudes upwardly between the flanges 24 so that the tube 19 is positioned centrally of the sleeve 23. Power leads 28 extend from the circuit board 21 through an aperture in the base wall 15 of the receptacle 14 for connection to the electrical circuit of the vehicle.

The energisation and control circuit of the tube 19 is so designed that it can be powered from either a 12 volt or a 24 volt supply by way of the leads 28J. and furthermore is arranged to cause periodic energisation of the tube 19 so that the light source flashes at one of two predetermined flash rates. The presence, or absence of a particular electrical link on the circuit board 21 determines whether the tube 19 is caused to flash at the first or the second flash rate. In the example illustrated in the accompanying drawings, the link is defined by an elongate loop of insulated wire 29 which extends from the circuit board 21 within the housing defined by the sleeve 23, shroud 25 and receptacle 14 and protrudes at 31 (Figure 1) through the annular gap between the shroud 25 and the wall 16, so as to be accessible at the exterior of the housing adjacent the point at which the dome 18 attaches to the base 11.

In the situation where the link is intact then when the lamp is energised the tube 19 will flash at a first predetermined rate. Should it be required that the lamp operates at the second predetermined flash rate then it is necessary only for the vendor, or the user, to remove the dome 18 from the base 11 to gain access to the protruding portions 31 of the loop, and to severe the loop so breaking the link. Thereafter the tube 19 will be operated at the second predetermined flash rate. It will be recognised that removal and replacement of the dome 18, to gain access to the portion 31 of the lead 29 is an extremely simple exercise. It does not involve any further dismantling of the lamp, and in particular it does not involve any disturbance of the lens unit 22 or the circuit board 21.

In a modification the link of the printed circuit board 21 is a component which can easily be detached, at least at one end, from the printed circuit board to break the link. The link may for example be a small wire bridge one end of which is received in a plug and socket connection on the board. In order to allow for disruption of the link without disassembling the housing defined by the sleeve 23, shroud 25 and receptacle 14, an elongate flexible plastic strap is physically attached to the link at one end, and protrudes from the circuit board 21 through the annular gap between the shroud 25 and the wall 16 of the receptacle 14 again to be accessible at the exterior of the housing. In order to break the link, to alter the flash rate the dome 18 is removed and the operator grasps the protruding end of the strap and pulls it to disrupt the link on the printed circuit board 21 thus altering the flash rate. It can be arranged that during this operation the strap becomes detached after the 1 i nk has been cl isru pted so that the user can remove the strap by way of the aperture between the shroud 25 and the cylindrical wall 16. Moreover the wire bridge could be in the form of a jumper push fitted onto parallel pins protruding from the board 21, the strap or other electrically insulating pulling device being accessible at the exterior of the housing by extending through the aperture defined by the open end of the sleeve if desired. Such an arrangement would be advantageous if the jumper is located on the board 21 adjacent the tube 19 and the use of avpull-off' connection would be preferable to cutting a wire in high voltage applications where the risk of electrical shock to an operator is of greater concern.

It will be recognised that in a modification the lead 29, or the strap or the like, can extend through an aperture in the base wall 15 of the receptacle 14 so as to be accessible at the undersurface of the base 11. If such an arrangement is chosen, it will be recognised that the link must be disrupted prior to fitting the lamp to its supporting structure if removal of the lamp from its supporting structure in order to change the flash rate is to be avoided.

Figures 3 and 4 illustrate the preferred drive and control circuit for the xenon tube 19.

The circuit arrangement is best understood by reference to Figure 3 which breaks down the circuit into a series of inter-related functional modules. It must be understood however that the functional modules do not necessarily correspond to physical modules identifiable on the circuit board itself. Figure 4 shows the discrete components which are interconnected to produce the modules of Figure 3. The arrangement of discrete components, and the selection of their values, is well within the ability of a skilled man in the art once the functional interrelationship of the modules of Figure 3 has been appreciated. In order to relate Figure 3 more easily to Figure 4 each of the modules drawn in Figure 3 contains within its boundary the identification of the principle components seen in Figure 4.

A high voltage module 31 including an electrolytic capacitor CS provides the high voltage supply for energising the xenon tube 19. Discharge of the capacitor CS through the xenon tube 19 to cause the tube to flash is controlled by a trigger module 32. The high voltage module 31 receives power by way of a step-up transformer TR1 the primary winding of which is coupled to the DC supply and is switched at a high rate by a transistor switch module 33. In known manner, the rapid switching of the primary circuit of TR1 generates high voltage in the.secondary winding of TR1 which is used to charge capacitor CS. A switch mode controller 34 controls the switching rate of the transistor switch module 33 and includes a high voltage monitor which ensures that the switch mode controller ceases operation when capacitor CS is charged to a predetermined voltage, for example 300 volts. Since the lamp is intended to be able to operate from either a 12 volt, or a 24 volt D.C. supply a voltage clamp 35 is provided to protect the transistor switch module 33. Similarly a protection module 36 monitors the supply voltage to the primary winding of transformer TR1 and protects the primary winding against voltage spikes.

-g- An oscillator 37 provides a repeating sequence of square wave pulses to the trigger module 32. These pulses are conveniently at 0.5 second intervals and upon receipt of each pulse the trigger module 32 triggers the tube 19 so that the capacitor CS discharges through the tube producing a flash of light. The interval between adjacent pulses from the oscillator 37 is more than adequate to permit the capacitor CS to be fully recharged between pulses. A high voltage inhibition module 38 associated with the switch mode controller 34 is responsive to the pulses supplied from the oscillator 37 to the trigger module 32 and suspends operation of the switch mode controller, and therefore the transistor switch 33 to prevent charging of the capacitor CS for a brief period following each triggering pulse to ensure that the xenon tube is fully extinguished after each flash.

It will be recalled that the high voltage monitor associated with the switch mode controller limits the charging voltage of the capacitor C5 to a predetermined voltage, conveniently 300 volts. In order to provide a second predetermined flash rate, greater than the flash rate determined solely by the output pulses from the oscillator 37, there is provided a voltage detector module 39 having the disruptabie link associated therewith. Figure 3 shows the link lead 29, 31 associated with the module 39. The arrangement is such that when the link is complete then the detector 39 is disabled and plays no part in the control of the discharge of the xenon tube 19. However, breaking the link, for example by cutting the lead 29, enables the voltage detector 39. When enabled the detector 39 monitors the charging of the capacitor CS, and when a predetermined voltage is reached, which is less than the voltage set by the high voltage monitor but greater than the voltage needed to ensure satisfactory discharge of the tube 19, the detector 39 causes operation of a pulse generator 41 which supplies a square wave pulse to the trigger module 32. The square wave pulse from the generator 41 is the same as the pulses supplied to the trigger module 32 from the oscillator 37 and thus, because the capacitor C5 has charged to a high enough voltage, causes the tube 19 to discharge producing a flash.

Conveniently the voltage detector 39 is set to detect when the capacitor C5 charges to 200 volts. It will be recalled that there is more than adequate time between adjacent pulses generated by the oscillator 37, for the capacitor C5 to charge to its full voltage. Clearly therefore the capacitor C5 will charge to 200 volts at a time intermediate two adjacent pulses from the oscillator 37 and thus after a first pulse from the oscillator 37 fires the tube 19, the next triggering pulse for the trigger module 32 to fire the tube 19 will be a pulse generated by the pulse generator 41.

Subject to the operation of the high voltage inhibitor 38, immediately after the tube 19 has fired the capacitor C5 will begin to charge again. In order to ensure that the next triggering pulse supplied to the trigger module 32 comes from the oscillator, and not from the pulse generator 41 the voltage detector 39 is arranged to be bistable. Having once detected the voltage at the capacitor C5 reaching 200 volts and thus caused the pulse generator 41 to generate a triggering pulse the detector 39 becomes inoperative until reset by an appropriate signal. The circuit is arranged such that the reset signal for the detector 39 is the next triggering pulse generated by the oscillator and thus immediately following a triggering pulse generated by the osci I lator the detector 39 is reset so that the next time the voltage at the capacitor C5 reaches 200 volts an intermediate triggering pulse will be generated by the pulse generator 41.

11- The sequence of operation will be therefore that assuming the detector 39 is enabled by breaking of the link then the first pulse generated by the oscillator will ensure that the detector 39 is operative and will also fire the tube 19 by way of the trigger module 32. Thereafter the capacitor CS will commence recharging and when it reaches 200 volts the detector 39 will cause the pulse generator 41 to supply a triggering pulse to fire the tube 19 again. Thereafter, the capacitor CS will again commence charging but charging to 200 volts will not now trigger another pulse from the pulse generator 41 since the previous operation of the detector 39 left the detector 39 in an inoperative condition. By the time that the next pulse is generated by the oscillator 37 the capacitor CS will have charged fully and in addition to firing the tube 19 the next pulse from the oscillator 37 will reset the detector 39 so that subsequently, the next time the capacitor CS charges to 200 volts, the tube will be fired by a pulse from the pulse generator 41. Thereafter the cycle repeats.

The component layout as illustrated in Figure 4 mirrors the module diagram of Figure 3, and represents a convenient component layout for achieving the functions of the modules of Figure 3. The component identifications on Figure 4 are repeated within the modules of Figure 3 so that it can be seen that for example the pulse generator 41 of Figure 3 includes the components C14; Q1; D7; and R22 seen in Figure 4.

CIMMS:- 1 A beacon lamp including a housing within which a circuit board associated with the light source of the beacon lamp is received, a disruptable link on the printed circuit board which when made results in flashing of the light source of the beacon lamp at a first rate and which when broken results in flashing of the light source at a second, different rate, and, means accessible at the exterior of the housing for breaking said link whereby the link can be broken without gaining access to the interior of the housing of the circuit board.

2. A beacon lamp as claimed in claim 1 wherein said meansfor breaking said link comprises an elongate loop of electrically conductive lead forming part of said link and extending from said circuit board through an aperture in said housing so as to be accessible at the exterior of the housing, whereby the loop can be severed at the exterior of the housing to break said link.

3. A beacon lamp as claimed in claim 1 wherein said means for breaking said link comprises an elongate member mechanically coupled at one end to said link on the circuit board, and extending from the circuit board through an aperture in the wall of said housing to be accessible at the exterior of the housing, whereby said member can be pulled, or otherwise moved manually, at the exterior of the housing, to unplug, or otherwise break the link on the circuit board within the housing.

4. A beacon lamp as claimed in any one of the preceding claims wherein said housing is within an outer enclosure in use.

5. A beacon lamp as claimed in claim 4 wherein part of said enclosure is removable to obtain access to said means for disrupting said link.