Lamp socket adapter with safety circuit

The present invention rebates to an adapter with a first lamp socket adapted to permit connection of a iamp intended for a first voltage and a first current to a second lamp socket belonging to a device intended for a second voltage and a second current, where the first voltage and the first current are lower than the second voitage and the second current.

A safety circuit associated with the adapter comprises a breaking component connected in series to the first lamp socket and adapted to be able to maintain a closed initial state or assume an opened breaking state depending upon which current passes through the breaking component. The breaking component is adapted to maintain the closed initial state rf an apparatus to which the adapter is connected supplies the first current, and to assume the open state if an apparatus to which the adapter is connected supplies the second current.

In lighting in connection with filming or photography, different light sources are employed. These may be in the form of both floodlight and flashlight, In iighting systems for these areas of application, there are standardised components which may be combined in different ways to achieve the desired effects. Fundamental components are lamps with reflectors of different types, as well as power units for supplying energy to these lamps. Lamps with reflectors are often mounted on different devices which, on the one hand, permit an adjustment of the position of the lamps and the reflectors and which also constitute conductors for voltage and current from the power unit to the lamp,

Traditionally, these systems were based on voltage levels which coincided with the mains voitage employed, for instance 230 V. However, in recent years portable battery-powered systems have become increasingly common which are often built around battery-based power assembiies which supply a much lower voltage, for example 12 V.

This implies that there are two different systems with different voltage ievels, In order to be able to employ as much material as possible in both systems, a 12 V system is thus often adapted so that devices from a 230 V system are also

suited for mechanical and electric connection to a 12 V system. For a 12 V lamp to be able to be connected to a device which is originally rated for a 230 V system, an adapter is required which permits the connection of a 12 V lamp to a iamp holder or iamp socket for a 230 V lamp. Such adapters are previously known in the art and make it simple to use the same devices for both 12 V systems and 230 V systems.

Problems may occur if the lamp which is connected to the device is not intended for the power unit employed. This is not a major problem if a 230 V lamp is used in a 12 V system, since such a mistake merely entails that the lamp does not light or that it does not deliver sufficient light, which will then immediately be discovered and can be remedied. However, the problem is more serious if a 12 V lamp is connected to a 230 V system since this not only results in a lamp being destroyed, but may aiso result in a exptosion-like effect when the lamp is destroyed, which in turn could result in personal injury, in order to reduce this risk, it is previously known in the art to iπciude in an adapter a safety circuit with a breaking component, such as a fuse, so that lhe fuse will break the current to the lamp if a device with a connected 12 V lamp were erroneously to be connected to a unit supplying 230 V.

In certain contexts, such as in flashlights, it is a technical probiem to be able, in those cases when a 12 V lamp is connected via an adapter to a device and a power unit supplying 230 V ₁ to break the incoming current to the lamp sufficiently quickly in order to have time to save the lamp before it is destroyed.

A breaking component, which is often a fuse, has a certain inertia, and this is required in order that the supply to the lamp will not be disconnected unnecessarily because the fuse is so sensitive that it disconnects on the wrong occasions. Simultaneously, the fuse must be sufficiently rapid to be able to break the current in time in, for example, flashlight photography and a supply voltage of 230 V to a 12 V lamp.

With the object of resolving one or more of the above-outlined problems, and taking as the point of departure the state of the art as disclosed above, the present invention discloses that the safety circuit belonging to the adapter encompasses a short-circuiting component connected in parallel with the first lamp socket and adapted to be abie to maintain an open initial state or a closed, short circuiting state depending upon which voltage is connected across the short- circuiting component. The present invention further discloses that the short- circuiting component is adapted to maintain the open initial state if a device to which the adapter is connected supplies the first voltage, and to assume the closed short circuiting state if a device to which the adapter is connected supplies the second voltage. Such a short-circuiting component which is connected in parallel across the first lamp socket short circuits the lamp socket and diverts the current away from the sensitive lamp, at the same time as the short circuiting entails a current surge with the result that the breaking component breaks the current even if this takes place with a certain time lag because of its inherent

While the adapter according to the present invention is adapted to protect a lamp from the second voltage or the second current, it may be so that the sensitivity of the lamp results in the lamp being destroyed by currents which are iower than the second current. Consequently, the present invention discloses that the breaking component may be adapted to assume the open state if a device to which the adapter is connected supplies a current which is harmful to a lamp connected to said adapter and that the short-circuiting component is adapted to assume the closed state if a device to which the adapter is connected supplies a voltage which is harmful to a lamp connected to the adapter.

Simple components which may constitute a part of an adapter according to the invention are a fuse which may constitute the breaking component and a spark gap which may constitute the short-circuiting component. Normal voltage ievels for mains driven and battery driven systems, respectively, are 230 and 12 V, respectively and the present invention discloses that an adapter according to the present invention may be adapted so that the first voitage consists of a battery voltage, for example 12 V, and so that the second voltage consists of a mains voltage, for example 230 V.

The present invention further discloses that the first lamp socket is adapted for photo lamps or flashlights driven by a battery voltage, and that the adapter is adapted to a connection to a device with a second lamp socket adapted to photography lamps or flashlights powered by a mains voltage unit.

Those advantages which may principally be associated with an adapter according to the present invention are that existing devices adapted for 230 V systems may also be employed in systems for battery power with lower voltage and with the aid of an adapter for the employed lamps without lhe risk of destroying a lamp intended for taw voitage if the device is erroneously connected in a system for high voltage.

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An adapter displaying the properties associated with the present invention will now be described in greater detail hereinbelow for purposes of exemplificalion, with reference to the accompanying Drawings, in which:

Fig. 1 illustrates schematically and in highly simplified form an adapter

Fig. 2 schematically illustrates a simplified circuit solution for a safety circuit

With reference to Fig. I ₁ an adapter according to the present invention is thus shown, the adapter 1 having a first iamp socket 11 adapted to permit connection of a lamp 2 intended for a first voltage U1 and first current 11 , to a second lamp socket 31 associated with a device 3 intended for a second voltage U2 and a second current I2. The first voltage U1 and the first current 11 are lower than the second voltage U2 and the second current I2. The adapter 1 does not constitute a voltage adapter, but simply a mechanical adapter which makes for a mechanical and electrical connection of a iamp 2 which in size does not fit in the second lamp socket 31. Thus, the device 3 may, as a result of the adapter, also be employed in systems using the lower voitage V1 and with lamps 2 adapted to this lower voltage.

A safety circuit 12 associated with the adapter 1 , also illustrated in Fig. 2,

11 and adapted to be able to maintain a closed initial state or assume an open breaking state depending upon which current I passes through the breaking component 12a. The breaking component 12a is adapted to maintain its closed initial state if a device 3 to which the adapter 1 is connected supplies the first current 11 , but it is adapted to assume its open state If a device 3 to which the adapter 1 is connected suppiies the second current I2.

The present invention further discloses that the safety circuit 12 iπciudes a short-circuiting component 12b connected in parallel to the first lamp socket 11 , and adapted to be able to maintain an open initial state or a closed short circuiting state depending upon which voltage U is connected across the short-circuiting component 12b. This short-circuiting component 12b is adapted to maintain its open initial state if a device 3 to which the adapter 1 is connected supplies the first voltage U1 , but to assume its dosed state if a device 3 Io which the adapter 1 is connected supplies the second voltage U2.

The present invention further discloses that the breaking component 12a may be adapted to assume its open breaking state if a device 3 to which the adapter 1 is connected supplies a current I which is harmful to a lamp 2 connected to the adapter, and that the short-circuiting component 12b may be adapted to assume its closed short circuiting state if a device 3 to which the adapter 1 is connected supplies a voltage U which is harmful to a lamp 2 connected to the

One embodiment of the present invention discloses that the breaking component 12a consists of a fuse, and that the short-circuiting component 12b consists of a spark gap.

Further, mains powered voltage units often supply a voitage level corresponding to the mains voltage, for instance 230 V ₅ while battery driven voltage units supply a normal battery voltage, for instance 12 V ₁ with the result that the first voltage may consist of a battery voltage, for instance 12V ₃ and the second voltage may consist of a mains voltage, for instance 230 V.

The present invention is suitable in lighting systems for film and photography where devices 3 for iighting are occasionally driven by mains powered voltage units and occasionally by battery driven voltage units. Thus, the

first lamp socket 11 may be adapted to photography lamps or flashlights drivers by a battery voltage, where the adapter is adapted to a connection to a device 3 with a second lamp socket 31 adapted for photography lamps or flashlights driven by a

Naturally, the present invention is not restricted to the embodiments disclosed above by way of example, but may undergo modifications without departing from the scope of the inventive concept as this is illustrated in the Clair