GB2081531A

GB2081531A - Hand lamp

Info

Publication number: GB2081531A
Application number: GB8120661A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1980-07-26
Filing date: 1981-07-03
Publication date: 1982-02-17

Abstract

A hand lamp includes light sources 12, 13 which can be connected to a sealed storage accumulator 10 through switches 14, 15 and a pair of normally closed relay contacts 16. Normally open relay contacts 22 are provided to connect the accumulator to a charging circuit which includes a regulator 21 and terminals 17, 18. The terminals 17, 18 can be connected to an external DC source of supply and a relay winding 19 is connected across the terminals so that when the terminals are connected to the source the relay coil is energised, the light sources 12, 13 are disconnected from the accumulator and the latter is connected to the charging circuit. The circuit shown in Fig. 2 indicates the state of charge of the accumulator by illuminating LED's 29, 30, 31 at certain accumulator voltage levels. <IMAGE>

Description

SPECIFICATION Hand lamps This invention reiates to hand lamps of the kind comprising a storage accumulator, a switch and a light source connected in a series circuit across the accumulator and terminals for connection to external means whereby the accumulator can be charged from an external source of supply.

Such hand lamps are known in which the storage accumulator is of the lead acid type employing liquid electrolyte. Such lamps have a high weight and the accumulator needs to be designed so that the electrolyte cannot spill whilst at the same time provision must be made for the escape of gas during the charging process.

Sealed lead acid accumulators are known and providing a limit is set on the light output the weight of the lamp can be kept to a reasonable value. Charging of a sealed accumulator must be carried out with great care in order to prevent damage and in order to provide a satisfactory shelf life between charges it is essential that the drain on the accumulator when the light source is out of use is kept as low as possible.

The object of the present invention is to provide a hand lamp of the kind specified in a simple and convenient form.

According to the invention a hand lamp of the kind specified comprises a first normally closed pair of relay contacts connected in said series circuit, a second normally open pair of relay contacts connected in a charging circuit including the accumulator and said terminals, a relay winding which is energised when said terminals are connected to an external source of supply and regulating means in said charging circuit.

An example of an hand lamp in accordance with the invention will now be described with reference to the accompanying circuit diagrams in which: Figure 1 is a circuit of the hand lamp; and Figure 2 is a circuit of a state of charge indicator for the accumulator.

Referring firstly to Fig. 1, there is provided a sealed lead acid storage accumulator 10 the positive terminal of which is connected to a positive supply rail 11. The lamp includes a pair of light sources 12, 1 3 each having a terminal connected to the supply rail 11 and having their other terminals connected by way of switches 14, 1 5 respectively to the negative terminal of the accumulator 10 by way of a normally closed pair of relay contacts 1 6.

Clearly when either of the switches 14, 1 5 is closed the respective light source will be illuminated and current will be drawn from the accumulator 10 providing relay contacts 1 6 are closed.

A charging circuit is provided which is connected to terminals 17, 1 8 for connection to external charging means not shown. Terminal 1 8 is connected to the positive supply rail 11 and when the charging circuit is in use, is connected to the positive terminal of a d.c.

supply. Terminal 1 7 in use is connected to the negative terminal of the d.c. supply and is also connected to one end of a relay winding 19, the other end of which is connected by way of a resistor 20, to the supply rail 11.

The terminal 1 7 is also connected to the input terminal of a regulator 21 which conveniently is an integrated circuit regulator having the type number LM 1 20. The output terminal of the regulator 21 is connected through a diode 38, to one contact of a pair of normally open contacts 22 the other contact of which is connected to the negative terminal of the accumulator 1 0. The regulator includes a control terminal which is connected by way of a variable resistor 23 to the supply rail 11 and also to the output terminal of the regulator by way of a resistor 24. A capacitor 25 is connected between the input terminal of the regulator and the supply rail 11 and a smoothing circuit comprising a capacitor 26 and a resistor 27, is connected between the output terminal of the regulator 21 and the supply rail 11.

In operation, when the charging circuit is connected to an external source of supply, the relay winding 1 9 is energised and the pairs of contacts 16, 22 assume their opposite state so that the accumulator is disconnected from the light sources and connected to the charging circuit. The charging current is of course controlled by the regulator 21 and the value of the charging current can be pre-set by adjustment of the variable resistor 23. The capacitor 25 and the smoothing circuit act to minimise voltage transients such as may occur when the external source of supply is removed and the flux in the relay winding 1 9 collapses.

The diode 38 is provided to ensure that when the terminals 1 7 and 1 8 are disconnected from the external supply, the relay winding cannot remain energised by current flowing from the accumulator through the closed contacts 22 and the regulator 21.

With the arrangement so far described the light sources cannot be used whilst the accumulator is being charged however, by connecting the by-pass diode 28 between the terminal 1 7 and the contacts of the switches 14 and 1 5 which are normally connected to the accumulator, the light sources can be used whilst the accumulator is being charged, the current for the light sources in this mode of operation being from the source of supply.

This may be for example the storage accumulator of a vehicle. Using the integrated circuit regulator ensures that the charging current to the accumulator 10 can be kept substantially constant which would not be the case if a simple diode were used.

In order to provide an indication of the state of charge of the accumulator, the circuit shown in Fig. 2 is connected across the terminals of the accumulator. This circuit comprises three light emitting diodes 29, 30, 31.

Diode 29 is connected in a series circuit including resistor 32 and zener diode 33 whilst diode 30 is connected in a series circuit including resistor 34 and zener diode 35.

Diode 31 is connected in a series circuit including zener diode 36 and resistor 37 one end of this circuit being connected to the junction of the resistor 34 and diode 30. In operation, it is arranged that the light emitting diode 31 is illuminated at approximately 10.5 volts, the diode 30 at approximately 11.5 volts and the diode 29 at approximately 13.9 volts. When all three diodes are illuminated then the battery can be regarded as being fully charged and when all the diodes are extinguished the battery can be regarded as being completely discharged although it is anticipated that charging should be effected when only the diode 31 remains illuminated.

Claims

1. A hand lamp comprising a storage accumulator, a switch and a light source connected in a series circuit across said accumulator, terminals for connection to external means whereby the accumulator can be charged from an external source of supply, a first normally closed pair of relay contacts connected in said series circuit, a second normally open pair of relay contacts connected in a charging circuit including the accumulator and said terminals, a relay winding which is energised when said terminals are connected to an external source of supply and regulating means in said charging circuit.

2. A hand lamp according to Claim 1 in which said relay winding is connected across said terminals.

3. A hand lamp according to Claim 2, including a blocking diode operable to prevent flow of current from the accumulator to the relay winding whilst said second pair of relay contacts are closed.

4. A hand lamp according to Claims 1, 2 or 3, including a by-pass diode operable to permit current flow to said light source from said terminals when said terminals are connected to the external source of supply.

5. A hand lamp according to Claim 1 in which said regulating means comprises an integrated circuit regulator.

6. A hand lamp according to any one of the preceding Claims, in which said accumulator is of the sealed lead acid type.

7. A hand lamp according to any one of the preceding claims including means for providing an indication of the state of charge of the accumulator.

8. A hand lamp comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying circuit diagrams.