WO1993023839A1

WO1993023839A1 - A display device

Info

Publication number: WO1993023839A1
Application number: PCT/IE1993/000026
Authority: WO
Inventors: Gerard Patrick Kennedy; John Patrick Martin Donnelly
Original assignee: Gerard Patrick Kennedy; John Patrick Martin Donnelly
Priority date: 1992-05-13
Filing date: 1993-05-13
Publication date: 1993-11-25
Also published as: AU4270893A

Abstract

A display device (1) for displaying a no smoking symbol (3) comprises a plug member (25) for releasably engaging a cigarette lighter socket of a motor vehicle. The no smoking symbol (3) is screen printed onto a display panel (29) which is retained in engagement with the plug member (25) by a lens (30) secured to the plug member (25). A bulb (41) in a hollow interior region (38) of the plug member (25) illuminates the display panel (29), and in turn the no smoking symbol (3). Electrical power is delivered to the bulb (41) through a compression spring contact (69) and side retaining members (53), which act as electrical contacts for engaging corresponding electrical contacts in the socket of the cigarette lighter.

Description

"A display device"

The present invention relates to a display device for displaying ^ a character, the display device being of the type comprising a

» display means for displaying the character and a plug means for 5 engaging an electrically powered cigarette socket, the plug means being connected to the display means.

Due to the decline in the smoking habit in recent years, particularly in the more developed countries, in many cases, it is desirable to politely advise the public that they are

10 requested not to smoke in certain areas. This is particularly so in the case of motor vehicles, such as, for example, cars and the like. A typical method for advising people not to smoke in a motor vehicle is to provide a sign which carries a no smoking symbol. Such signs typically are in the form of a self-adhesive

15 label which may be stuck to the dash board or other suitable location in the motor vehicle. Such signs, in general, suffer from a number of disadvantages, firstly in general, they tend to be rather unsightly. Secondly, they are virtually impossible to remove without, for example, leaving a residue of adhesive which

20 in many cases, may be impossible to remove from the surface to which the sign had been affixed. In other cases, the removal of such signs may cause damage to the paint work or surface onto which they had been affixed. This presents a particular problem where it is desired to remove such signs in the event of the

25 motor vehicle being sold. A further disadvantage of such signs is that they are impossible to see in the dark.

Indeed, there are many other requirements a display device for displaying other characters besides no smoking symbols which may or may not impart a message, either by way of symbols or by way 30 of written words.

It is known to provide illuminated signs for use with motor vehicles, for example, British Patent Application No. GB- 2,228,130A discloses illuminated signs which may be secured to the front and rear windscreen of a motor vehicle to impart a message to passing motorists. The signs are powered through a plug which is engageable in an electrically powered cigarette lighter socket of the motor vehicle which is connected by a pair of flexible leads to the signs. Such signs, however, require to be secured to the windscreen of a motor vehicle, and in general, would require an adhesive which in general, would suffer from similar disadvantages to those discussed with regards to self- adhesive label type signs.

It is an object of the invention to provide a display device which overcomes at least some of the disadvantages of known display devices.

The present invention overcomes at least some of the advantages of known display devices by virtue of the fact that the invention provides a display device for displaying a character of the type comprising a display means for displaying the character, and a plug means for engaging an electrically powered cigarette lighter socket_f the plug means being connected to the display means, wherein the plug means extends from the display means and supports the display means when the plug means is engaged in the cigarette lighter socket.

The advantages of the invention are many. A particularly important advantage of the invention is that by virtue of the fact that the plug means supports the display means when the plug means is engaged in the cigarette lighter socket the display means is supported and is readily visible. Thus, the need for other means of securing the display means is avoided. Accordingly, where the display device is inserted into the cigarette lighter socket of a motor vehicle, the display means is supported by the plug means, and is readily easily visible within the motor vehicle. Another advantage of the invention is that by virtue of the fact that the plug means is engageable with the cigarette lighter socket, the cigarette lighter socket is rendered safe by use of the display device. In other words, there is no danger of children or others inserting objects into the cigarette lighter socket when the cigarette lighter has been removed for, for example, safety reasons. In many cases, car owners deem it expedient to remove the cigarette lighter from the cigarette lighter socket to avoid children playing with the cigarette lighter with the consequent danger of setting fire to the vehicle. Additionally, the display device avoids an unsightly hole being left in the dash board console of a motor vehicle when a cigarette lighter has been removed for safety reasons.

Preferably, the plug means is rigidly connected to the display means. The advantage of rigidly connecting the display means to the plug means is that a device of relatively simple construction is provided, and in particular, the display means is provided so that the character displayed by the display means, is readily easily visible.

In one embodiment of the invention a character is carried on the display means. In another embodiment of the invention the character is for imparting a message. In a further embodiment of the invention the character is a symbol, and in a still further embodiment of the invention the character is a no smoking symbol. The advantage of providing the character as a no smoking symbol enables one to advise the public in a relatively clear and unambiguous way, and at the same time, in a polite fashion that smoking is not permitted. Indeed, the display device permits any character or symbol which would impart a message to be displayed clearly and unambiguously. A particularly important advantage of providing a no smoking symbol, or indeed, a no smoking message on the display device is that the no smoking symbol on the message is provided exactly where a person intending to smoke would reach for a cigarette lighter, and accordingly, on seeing the no smoking message or^'symbol on the display device, the individual will immediately be appraised of the fact in a polite fashion that smoking is not permitted.

In one embodiment of the invention a plurality of characters provided by letters are carried on the display means, the letters forming a word or group of words to impart the message.

In one embodiment of the invention the plug means comprises a plug member having an outer surface which defines a hollow interior socket region of the cigarette lighter socket. The advantage of this feature of the invention is that the display readily easily is insertable into the cigarette lighter socket.

In another embodiment of the invention the plug member comprises an elongated cylindrical body member. This feature of the invention provides a relatively simple, straightforward and robust construction of the device.

Advantageously, the display means defines a front face from which the character is viewed and a rear face, the plug means extending substantially perpendicularly from the rear face of the display means, and preferably, the plug means extends substantially centrally from the rear face of the display means. This feature of the invention provides a display device in which the display panel is readily easily visible.

In another embodiment of the invention a lens is provided extending over the display means. This is a convenient construction of the device.

In a further embodiment of the invention the display means comprises a display panel. The advantage of this feature of the invention is that the character can readily easily be provided on the display panel.

In a further embodiment of the invention the area of the display panel is greater than the transverse cross-sectional area of the plug means. Preferably, the area of the display panel is in the range of 1 to 3 times the transverse cross-sectional area of the plug means. Advantageously, the area of the display panel is in the range of 2 to 2.5 times the transverse cross-sectional area of the plug means. Preferably, the area of the display panel is approximately 2.25 times the transverse cross-sectional area of the plug means. By providing the area of the display panel within the above ranges relative to the plug means, a relatively neat and convenient display device is provided.

Advantageously, the display panel is circular.

In one embodiment of the invention a retention means is provided on the plug means for releasably retaining the plug means in the cigarette lighter socket. Preferably, the retention means comprises a resilient member extending radially from the plug means. The advantage of providing a tension means is that the display device is securely releaseably retained in the cigarette lighter socket.

In another-embodiment of the invention a light source receiving means is provided for receiving an electrically powered light source means for illuminating the display means.

Provision of a light source receiving means in the device enables a light source to be provided for illuminating the display means, and in turn, the character so that the character displayed can readily easily be seen in the dark.

In one embodiment of the invention the plug means defines a hollow interior region, and the light source receiving means is mounted in the hollow interior region for directing light through the display means for illuminating the character. The advantage of this feature of the invention is that it provides a relatively convenient construction of device, and furthermore, allows the display means to be illuminated by passing light through the display means.

Preferably, the plug means carries first and second mutually insulated electrically conductive contact means for electrically engaging corresponding contact means in the cigarette lighter socket, the light source receiving means being electrically connected to the respective first and second contact means for providing electrical power to the light source means.

In another embodiment of the invention one of the first and second contact means is provided on a side of the plug means and the other of the first and second contact means is provided at an end of the plug means remote from the display means.

In a further embodiment of the invention the first contact means is a resilient member which acts as the retaining means for retaining the plug means in the cigarette lighter socket.

In a still further embodiment of the invention the second contact means extends in a general axial direction from the transverse end of the plug means. Advantageously, the second contact means comprises an electrically conductive compression spring.

In one embodiment of the invention switch means for isolating the light source receiving means from one of the first and second contact means is electrically connected between the light source receiving means and the said one of the first and second contact means. Advantageously, the switch means is responsive to the voltage being applied across the first and second contact means being below a predetermined value for isolating the light source receiving means from the said contact means.

The provision of the switch means is particularly advantageous when the predetermined value of voltage is set at a level which ensures that the bulb will remain isolated from the cigarette lighter socket when the vehicle is not in use, in other words, when the battery is not being charged. This thus avoids any danger of inadvertent discharge of the vehicle battery.

Advantageously, the switch means comprises a transistor. Preferably, the transistor is connected in series with the light source receiving means and the said one of the first and second contact means so that current flows through the collector/emitter of the transistor through the light source receiving means, the base of the transistor being biased to the other of the first and second contact means. Advantageously, the base of the transistor is connected to the said one of the first and second contact means through a zener diode. In one embodiment of the invention the light source receiving means comprises a bulb socket. Preferably, an electrically powered light source means is engaged in the light source receiving means. Advantageously, the electrically powered light source means comprises an electric light bulb.

Alternatively, the bulb is a low power requirement bulb. In one embodiment of the invention a reflecting means is provided in the hollow interior region for reflecting light from the light source means through the display means.

In a further embodiment of the invention the plug means releasably engages the cigarette lighter socket.

Additionally the invention provides a cigarette lighter socket defining a hollow interior socket region, and a display device according to the invention engaged in the hollow interior socket region. Preferably, the display device is releasably engaged in the hollow interior socket region.

The invention will be more clearly understood from the following description of a preferred embodiment thereof which is given by way of example only with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of a display device according to the invention,

Fig. 2 is a perspective view of the display device of Fig. 1 from another direction,

Fig. 3 is a longitudinal cross-sectional view of the display device of Fig. 1,

Fig. 4 is a longitudinal cross-sectional view of the display device of Fig. 1 in use,

Fig. 5 is a perspective view of portion of the display device of Fig. 1,

Fig. 6 is a front elevational view of another portion of the display device of Fig. 1,

Fig. 7 is a front elevational view of an alternative portion to the portion of Fig. 6 of the display device of Fig. 1 which may be used in place of the portion of Fig. 6, and

Fig. 8 is a circuit diagram of the display device of Fig. 1.

Referring to the drawings there is illustrated a display device according to the invention indicated generally by the reference numeral 1 for releasably engaging an electrically powered cigarette lighter socket 2 in a motor vehicle (not shown) for displaying a character, in this embodiment of the invention a no smoking symbol 3. Before describing the display device 1 the cigarette lighter socket 2 will first be described. The cigarette lighter socket 2 comprises a hollow cylindrical housing 4 of plastics material open at one end 5 and closed at the other by an end cap 6 also of plastics material which with the housing 4 defines a hollow interior socket region 7 for normally receiving an electrically powered heater element type cigarette lighter (not shown). The socket 2 is normally mounted on the dash board console of the motor vehicle. A portion 8 of the dash board console is illustrated. An inner cylinder 10 of electrically conductive material, typically, brass is mounted within the socket region 7, and extends around the interior of the housing 4 and forms a side electrical contact 11 for delivering electrical power to one terminal of the heater element of the cigarette lighter (not shown). A central electrical contact 12 of electrically conductive material, namely, brass is located centrally on the end cap 6 for delivering power to the other terminal of the heater element of the cigarette lighter. Terminals 13 and 14 extending from the side contact 11 and the central contact 12, respectively, through the housing 4 and end cap 6 receive wires for connection to the vehicle battery (not shown). A resilient bracket 15 of spring steel material mounted on the end cap 6 releasably engages a plug portion of the cigarette lighter (not shown) for releasably retaining a cigarette lighter in the socket region 7. The construction of such cigarette lighter sockets will be well known to those skilled in the art, and it is not intended to describe the socket 2 in further detail.

The display device 1 comprises a plug means, namely, a plug member 25 having an outer surface 24 which substantially defines the hollow interior socket region 7 of the cigarette lighter socket 2 for releasably engaging the socket region 7. A display means for displaying the no smoking symbol 3 comprises a circular display panel 29 of translucent plastics material having a front face 27 from which the no smoking symbol 3 is viewed and a rear face 28. The no smoking symbol 3 is screen printed onto the front face 27 and is viewed through a circular lens 30 of transparent plastics material secured to the plug member 25. The lens 30 as will be described below secures the display panel 29 to the plug member 25 so that the plug member 25 extends substantially centrally and perpendicularly from the rear face 28 of the display panel 29.

The plug member 25 comprises a hollow cylindrical body member 26 one end 32 of which is open and the other end 34 is closed by an end cap 36. Both the body member 26 and the end cap 36 are of an electrically insulating plastics material. The body member 26 and the end cap 36 define a hollow interior region 38 within which is mounted an electrical light source receiving means, namely, a bulb socket 40 for receiving an electrical light source means, namely, a screw type electrical bulb 41 for illuminating and directing light through the display panel 29 and the lens 30. The bulb socket 40 is carried on a printed circuit board 42 which is mounted in the hollow interior region 38 adjacent the end cap 36. A circuit 44 described below with reference to Fig. 8 is formed on the printed circuit board 42 and delivers electrical power to an electrically conductive central contact 46 in the socket 40 and to an electrically conductive side wall 47 of the socket 40 which acts as a side contact for the bulb 41. The construction of such bulb sockets 40 will be well known to those skilled in the art.

Retaining means comprising a pair of retaining members 53 of resilient tin plated spring steel strip material extend radially on opposite sides of the body member 26 for releasably engaging the side contact 11 in the socket region 7 of the cigarette lighter socket 2, and for retaining the plug member 25 in the socket 2. The retaining members 53 are electrically conductive and are anchored to, and electrically connected to the printed circuit board 42, and act as first contact means for delivering power to the circuit 44 of the printed circuit board 42 from the side contact 11 of the socket 2. An arcuate portion 55 of each retaining member 53 extends through a corresponding slot 56 in the body member 26, and a free end 57 of each retaining member 53 engages the outer surface 24 of the body member 26. A mounting flange 59 extends radially outwardly and circumferentially around the body member 26, and restricts longitudinal movement of the free ends 57 of the retaining members 53 in a direction towards the flanges 59, thereby inducing a radially outwardly directed biasing force in the retaining members 53 so that the retaining members 53 tightly engage the side contact 11 for releasably securing the plug 25 in the socket region 2 and for providing good electrical contact between the retaining members 33 and the side contacts 11.

Second contact means comprising a compression spring contact 69 of electrically conductive resilient tin plated spring steel wire is mounted in a recess 70 in the end cap 36 and is electrically connected to the circuit 44 of the printed circuit board 42. The spring contact 69 extends axially outwardly from the end cap 36 for engaging the central contact 12 in the socket region 7 of the cigarette lighter socket 2 for delivering power to the circuit 44. The provision of the spring contact 69 enables the device 1 to be used in cigarette lighter sockets of different depth of socket region 7 with the mounting flange 59 substantially abutting the dash board console 8.

A circular lip 71 of plastics material extends axially from and around the mounting flange 59 to define a retaining surface 72 for engaging and retaining a corresponding lip 73 extending around the lens 30 for securing the lens 30 to the plug 25. The display panel 29 is held captive between the lens 30 and the lip 71. The display panel 29 being of translucent material allows light from the bulb 41 to pass therethrough for illuminating the no smoking symbol 3.

In this embodiment of the invention the body member 26 is formed in two parts of injection moulded plastics material joined at 74. An end portion 75 adjacent the end 36 is of reduced cross- sectional area for releasably engaging the resilient bracket 15 which further act to securely releasably retain the display device 1 in the socket 2, in cases where the depth of the socket region 7 and the length of the plug member 25 are substantially similar.

Referring now to Fig. 8 the circuit 44 on the printed circuit board 42 will now be described. Terminals 80 and 81 of the circuit 44 are connected to the spring 69 and the retaining members 53, respectively. Terminals 83 and 84 of the printed circuit board 42 are connected to the central contact 46 and the side wall 47, respectively, of the bulb socket 40. Switch means comprising a PNP bipolar transistor Tl which is connected between the terminals 80 and 83 isolates the terminal 83 from the terminal 80, in other words, isolates the bulb socket 40 from the compression spring 69, and retains the bulb socket 40 isolated from the spring 69 until the voltage applied across the terminals 80 and 81 exceeds a predetermined voltage, in this case, 12.7 volts. In this embodiment of the invention the predetermined voltage of 12.7 volts ensures that the bulb 41 will not be switched on unless the battery of the motor vehicle is being charged. Thus, any danger of the batter being discharged by the display device 1 when the motor vehicle is not in use is avoided. The transistor Tl is connected between the terminals 80 and 83 so that current flows through the emitter collector circuit of the transistor Tl. A 12 volt zener diode ZD1 connected in series with a resistor Rl biases the base of the transistor Tl to the terminal 81 to prevent the transistor Tl conducting through its collector emitter circuit when the voltage is below 12.7 volts. The resistance of the resistor Rl may be of any value from 200 ohms to 2,000 ohms depending on the gain of the transistor Tl. Needless to say, the components of the circuit 44 may be chosen to isolate the bulb socket 40 from the spring 69 at a different voltage depending on the operating voltage of the motor vehicle.

In this embodiment of the invention the bulb 41 may be a 12 to a 30 volt bulb drawing approximately 40 milliamps and delivering approximately 0.5 watts at 12 volts. Referring now to Fig. 6 there is illustrated a display panel 86 which may be used in the display device 1 in place of the display panel 29. The display panel 86 is identical to the display panel 29 with the exception that the character displayed on the display panel 86 instead of being a symbol, comprises the words NO SMOKING PLEASE to impart a similar message to people in the motor vehicle as that imparted by the no smoking symbol, in other words, smoking is not permitted in the vehicle.

While the display device has been described as comprising a light source receiving socket of a particular construction, any other light source receiving sockets may be used. Indeed, in certain cases, it is envisaged that the display device may be provided without such a light source receiving socket, and in which case, a light source means may not be provided, and thus, the display panel would not be illuminated. It is also envisaged that the light source means may be mounted directly onto the printed circuit board. Needless to say, it will be appreciated that while the display device has been described as comprising a switch means for isolating the bulb socket from the central spring contact in the end cap of the plug member, the switch means may be omitted, and in other cases, switch means of other construction and/or circuitry may be provided. It is also envisaged that where the switch means is omitted, a low power output bulb may if desired be used to minimize discharge and run down of a battery when a vehicle is not in use.

It will of course be appreciated that where the display device is provided without a light source means, the electrical contacts may be omitted, and the retaining means where provided may be of a plastics material or any other suitable or desired material. Needless to say, other suitable retaining means may be provided and in certain cases, it is envisaged that the retaining means may be omitted. While the display means has been described as comprising a display panel and a lens, any other suitable arrangement or construction of display means may be provided. It will also of course be appreciated that while the display panel and lens have been described as being circular, they may be of any other desired shape, and it will be appreciated that in all cases it is not essential that the plug member should extend perpendicularly from the display panel. Needless to say, while the character carried by the display panel has been described as being a no smoking symbol or a no smoking sign, any other character or characters may be provided on the display panel.

While the display device has been described as being of plastics material, the display device may be of any other suitable or desired material. It will also be appreciated that the plug means may be of other shape and construction besides being provided by a cylindrical body member.

It is also envisaged that reflective means, for example, a reflector may be provided in the hollow interior region 38 of the plug member 25 behind the bulb for reflecting light through the panel member 29. Alternatively, the interior of the plug 29 may be coated with a reflective paint or the like if desired.

Needless to say, it will be appreciated that the retaining member and spring contact may be of any other suitable or desired materials, and it will of course be appreciated that while it is preferable it is not essential that the second contact means at the end of the plug member should be provided by a spring. The second contact means may be provided by a rigid contact member secured to the end of the plug means.

Claims

1. A display device for displaying a character (3), the device (1) being of the type comprising a display means (29) for displaying the character (3), and a plug means (25) for engaging an electrically powered cigarette lighter socket (2), the plug means (25) being connected to the display means (29), characterised in that the plug means (25) extends from the display means (29) and supports the display means (29) when the plug means (25) is engaged in the cigarette lighter socket (2).

2. A display device as claimed in Claim 1 characterised in that the plug means (25) is rigidly connected to the display means (29).

3. A display device as claimed in Claim 1 or 2 characterised in that a character (3) is carried on the display means (29).

4. A display device as claimed in Claim 3 characterised in that the character (3) is for imparting a message.

5. A display device as claimed in Claim 3 or 4 characterised in that the character (3) is a symbol.

6. A display device as claimed in Claim 5 characterised in that the character (3) is a no smoking symbol.

7. A display device as claimed in any of Claims 3 to 6 characterised in that a plurality of characters (3) provided by letters are carried on the display means (29), the letters forming a word or group of words to impart the message.

8. A display device as claimed in any preceding claim characterised in that the plug means (25) comprises a plug member (25) having an outer surface (24) which defines a hollow interior socket region (7) of the cigarette lighter socket (2).

9. A display device as claimed in Claims 8 characterised in that the plug member (25) comprises an elongated cylindrical body member (26).

10. A display device as claimed in any preceding claim characterised in that the display means (29) defines a front face (27) from which the character (3) is viewed and a rear face (28), the plug means (25) extending substantially perpendicularly from the rear face (28) of the display means (29).

11. A display device as claimed in Claim 10 characterised in that the plug means (25) extend substantially centrally from the rear face (28) of the display means (29).

12. A display device as claimed in any preceding claim characterised in that a lens (30) is provided extending over the display means (29).

13. A display device as claimed in any preceding claim characterised in that the display means (29) comprises a display panel (29).

14. A display device as claimed in Claim 13 characterised in that the area of the display panel (29) is greater than the transverse cross-sectional area of the plug means (25).

15. A display device as claimed in Claim 14 characterised in that the area of the display panel (29) is in the range of 1 to 3 times the transverse cross-sectional area of the plug means (25).

16. A display device as claimed in Claim 15 characterised in that the area of the display panel (29) is in the range of 2.0 to 2.5 times the transverse cross-sectional area of the plug means (25).

17. A display device as claimed in Claim 16 characterised in that the area of the display panel (29) is approximately 2.25 times the transverse cross-sectional area of the plug means (25).

18. A display device as claimed in any of Claims 13 to 17 characterised in that the display panel (29) is circular.

19. A display device as claimed in any preceding claim characterised in that a retention means (53) is provided on the plug means (25) for releasably retaining the plug means (25) in the cigarette lighter socket (2).

20. A display device as claimed in Claim 19 characterised in that the retention means (53) comprises a resilient member (53) extending radially from the plug means (25).

21. A display device as claimed in any preceding claim characterised in that a light source receiving means (40) is provided for receiving an electrically powered light source means (41) for illuminating the display means (29).

22. A display device as claimed in Claim 21 characterised in that the plug means (25) defines a hollow interior region (38), and the light source receiving means (40) is mounted in the hollow interior region (38) for directing light through the display means (29) for illuminating the character (3).

23. A display device as claimed in Claim 21 or 22 characterised in that the plug means (25) carries first and second mutually insulated electrically conductive contact means (53,69) for electrically engaging corresponding contact means (11,12) in the cigarette lighter socket (2), the light source receiving means (40) being electrically connected to the respective first and second contact means (53,69) for providing electrical power to the light source means (40).

24. A display device as claimed in Claim 23 characterised in that one of the first and second contact means (53,69) is provided on a side of the plug means (25) and the other of the first and second contact means (53,69) is provided at an end of the plug means (25) remote from the display means (29).

25. A display device as claimed in Claim 23 or 24 characterised in that the first contact means (53) is a resilient member (53) which acts as the retaining means (53) for retaining the plug means (25) in the cigarette lighter socket (2).

26. A display device as claimed in any of Claims 23 to 25 characterised in that the second contact means (69) extends in a general axial direction from the transverse end of the plug means (25).

27. A display device as claimed in any of Claims 23 to 26 characterised in that the second contact means (69) comprises an electrically conductive compression spring (69).

28. A display device as claimed in any of Claims 23 to 27 characterised in that switch means (Tl) for isolating the light source receiving means (40) from one of the first and second contact means (53,69) is electrically connected between the light source receiving means (40) and the said one of the first and second contact means (53,69).

29. A display device as.claimed in Claim 28 characterised in that the switch means (Tl) is responsive to the voltage being applied across the first and second contact means (53,69) being below a predetermined value for isolating the light source receiving means (40) from the said contact means (53,69).

30. A display device as claimed in Claim 28 or 29 characterised in that the switch means (Tl) comprises a transistor (Tl).

31. A display device as claimed in Claim 30 characterised in that the transistor (Tl) is connected in series with the light source receiving means (40) and the said one of the first and second contact means (53,69) so that current flows through the collector/emitter of the transistor (Tl) through the light source receiving means (40), the base of the transistor (Tl) being biased to the other of the first and second contact means (53,69).

32. A display device as claimed in Claim 30 or 31 characterised in that the base of the transistor (Tl) is connected to the said one of the first and second contact means (53,69) through a zener diode (ZD1).

33. A display device as claimed in any of Claims 21 to 32 characterised in that the light source receiving means (40) comprises a bulb socket (40).

34. A display device as claimed in any of Claims 21 to 33 characterised in that an electrically powered light source means (41) is engaged in the light source receiving means (40).

35. A display device as claimed in Claim 34 characterised in that the electrically powered light source means (41) comprises an electric light bulb (41).

36. A display device as claimed in Claim 35 characterised in that the bulb (41) is a low power requirement bulb.

37. A display device as claimed in any of Claims 22 to 36 characterised in that a reflecting means is provided in the hollow interior region (38) for reflecting light from the light source means (41) through the display means (29).

38. A display device as claimed in any preceding claim characterised in that the plug means (25) releasably engages the cigarette lighter socket (2).

39. A cigarette lighter socket defining a hollow interior socket region (7), and a display device (1) according to any preceding claim engaged in the hollow interior socket region (7).

40. A cigarette lighter socket as claimed in Claim 39 characterised in that the display device (1) is releasably engaged in the hollow interior socket region (7).