GB1588615A - Electrical spark gap device - Google Patents

Description

(54) ELECTRICAL SPARK GAP DEVICE (71) We, WELWYN ELECTRIC LIMITED, of Bedlington, Northumberland NE22 7AA, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an electrical spark gap device for use in the protection of electrical apparatus and/or circuits.

In apparatus involving high voltages, and particularly in television receivers, it is often required to provide means for preventing excessively high voltages from occurring at certain points of circuits incorporated therein. A simple means already proposed for achieving this is the incorporation of a spark gap in a circuit. Such a spark gap basically comprises a pair of electrodes separated by an air gap and arranged such that if a voltage in excess of a particular value occurs in the circuit, breakdown occurs across the gap and a spark of discharge occurs between the electrodes. In this way the excessively high voltage may be conducted to some safe point, such as earth. The voltage at which break-down across the gap occurs is determined by the dimensions of the gap.

It is an object of the present invention to provide an improved spark gap device of this nature.

The present invention provides an electrical spark gap device for electrically connecting to conductors in an electrical circuit or apparatus and comprising a pair of electrodes each formed of a single wire bent to form a curved portion and having a terminal portion adapted to be connected to a said conductor, said electrodes being supported in a housing of electrically insulating material such that said curved portions curve towards one another and are separated by a predetermined gap and said terminal portions extend in substantially parallel spaced relationship from said housing, said housing having been formed from at least two sections sealed together around said electrodes, said electrodes being located in recesses provided in said sections, said housing having a hollow interior where the portions of said electrodes curve towards one another.

Preferably said terminal portions of said electrodes extend from said housing where said two sections are sealed together.

Preferably said housing is formed having inner surfaces at least partially of substantially corrugated form to provide maximum effective tracking distance between said electrodes.

Preferably said housing is formed of an organic plastics material.

Preferably said sections of said housing have been sealed together by an ultrasonic welding technique.

The housing may be provided with one or more protruding portions extending in the direction of said terminal portions of the electrodes and shaped whereby said device may be connected by said terminal portions to a circuit board with said protruding portion or portions contacting a surface of said board to provide a stand-off for the device.

The invention is now described by way of example with reference to the accompanying drawings in which Figure 1 shows a perspective view of an embodiment of a spark gap device of the invention in partly exploded form and Figure 2 shows a perspective view of the embodiment of Figure 1 fully assembled.

Referring to Figure 1, an electrical spark gap device is constructed as follows. Two sections 1 A and 1 B of a housing are moulded from a thermoplastic organic plastics material, e.g.

glass filled nylon. The two sections are formed so as to be substantially identical to one another and are each provided with a hollow interior having surfaces 2, 3 and 4 of corrugated form (only the interior of section 1 A being visible in the drawings). Recesses 5, 6,7 and 8 are also formed in both sections of the housing and into these recesses in section 1 A are located two electrodes, generally designated 9 and 10, each formed of a single wire bent to provide contoured portions 11 and 12 in the form of curves and arranged so that the portions 11 and 12 curve towards one another. The curved portions are dimensioned so that a gap G exists between them, the dimension of G being selected according to the voltage at which the device is required to operate.Terminal portions 13 and 14 are provided on the electrodes and extend from the section 1 A of the housing.

These terminal portions are arranged to be connected to electrical conductors in a circuit or apparatus which the spark gap device is required to protect. The two sections 1A and 1 B 6f the housing are sealed together to produce the resulting spark gap device of Figure 2, the contoured portions 11 and 12 of the electrodes 9 and 10 being enveloped within the housing and the terminal portions 13 and 14 extending from the housing in substantially parallel spaced relationship. An adhesive may be used to secure the two sections 1A and 1B together. Alternatively and preferably the two sections are sealed together by an ultrasonic welding technique, a suitable technique being described in U.K. Patent No. 1498439.When ultrasonic welding is employed, the two sections of the housing are preferably provided with raised ultrasonic energyconcentrating portions 15 and 16 to assist the welding process, the use of such raised portions being described in U.K. Patent No. 1498439. Protrusions 17 and 18 are provided on sections 1A and 1B of the housing so that when the resulting device is desired to be connected to conductors on a printed circuit board the protruding portions 17 and 18 contact the surface of the circuit board, thereby providing a predetermined stand-off for the body of the device from the circuit board.

When a voltage in excess of a predetermined level occurs in a circuit or apparatus to which the spark gap of the invention is connected, break-down occurs across the gap G and the excess voltage is thereby conducted away to some safe point. The corrugations 2, 3 and 4 inside the housing maximise the effective tracking distance between the electrodes and ensure optimum efficiency of operation of the device.

Since the contoured portions 11 and 12 of the electrodes are completely enveloped within the housing, they are unaffected by dust etc., which may be present in the surrounding atmosphere and carried into the apparatus.

Although it is considered to be generally self-evident from a study of Figure 1, for the sake of complete clarification and explanation, it is to be understood that in this specification the expression 'sealed together around said electrodes' covers the cases where the sections of the housing in being sealed together are also either sealed or not sealed onto the emerging terminal sections of the electrodes thereby resulting in a housing which is either hermetically sealed or non-hermetically sealed as required.

Some degree of non-hermeticity is often desirable to maintain the atmosphere within the housing substantially at the pressure of the surrounding atmosphere, but such that significant ingress of dust etc. into the housing is inhibited.

WHAT WE CLAIM IS: 1. An electrical spark gap device for electrically connecting to conductors in an electrical circuit or apparatus and comprising a pair of electrodes each formed of a single wire bent to form a curved portion and having a terminal portion adapted to be connected to a said conductor, said electrodes being supported in a housing of electrically insulating material such that said curved portions curve towards one another and are separated by a predetermined gap and said terminal portions extend in substantially parallel spaced relationship from said housing, said housing having been formed from at least two sections sealed together around said electrodes, said electrodes being located in recesses provided in said sections, said housing having a hollow interior where the portions of said electrodes curve towards one another.

2. A device according to Claim 1 in which said electrodes extend from said housing where said two sections are sealed together.

3. A device according to Claim 1 or 2 in which said electrodes are in the form of wires.

4. A device according to any one of the preceding claims in which said housing is formed having inner surfaces at least partially of substantially corrugated form to provide maximum effective tracking between said electrodes.

5. A device according to any one of the preceding claims in which said housing is formed of an organic plastics material.

6. A device according to any one of the preceding claims in which said sections of said housing have been sealed together by an ultrasonic welding technique.

7. A device according to any one of the preceding Claims in which said housing is provided with one or more protruding portions extending in the direction of said terminal portions of said electrodes and shaped whereby said device may be connected by said terminal portions to a circuit board with said protruding portion or portions contacting a surface of said board to provide a stand-off for the device.

8. An electrical spark gap device constructed and arranged substantially as herein described and shown in Figures 1 and 2 of the accompanying drawings.

WELWYN ELECTRIC LIMITED

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. and extend from the section 1 A of the housing. These terminal portions are arranged to be connected to electrical conductors in a circuit or apparatus which the spark gap device is required to protect. The two sections 1A and 1 B 6f the housing are sealed together to produce the resulting spark gap device of Figure 2, the contoured portions 11 and 12 of the electrodes 9 and 10 being enveloped within the housing and the terminal portions 13 and 14 extending from the housing in substantially parallel spaced relationship. An adhesive may be used to secure the two sections 1A and 1B together. Alternatively and preferably the two sections are sealed together by an ultrasonic welding technique, a suitable technique being described in U.K. Patent No. 1498439.When ultrasonic welding is employed, the two sections of the housing are preferably provided with raised ultrasonic energyconcentrating portions 15 and 16 to assist the welding process, the use of such raised portions being described in U.K. Patent No. 1498439. Protrusions 17 and 18 are provided on sections 1A and 1B of the housing so that when the resulting device is desired to be connected to conductors on a printed circuit board the protruding portions 17 and 18 contact the surface of the circuit board, thereby providing a predetermined stand-off for the body of the device from the circuit board. When a voltage in excess of a predetermined level occurs in a circuit or apparatus to which the spark gap of the invention is connected, break-down occurs across the gap G and the excess voltage is thereby conducted away to some safe point. The corrugations 2, 3 and 4 inside the housing maximise the effective tracking distance between the electrodes and ensure optimum efficiency of operation of the device. Since the contoured portions 11 and 12 of the electrodes are completely enveloped within the housing, they are unaffected by dust etc., which may be present in the surrounding atmosphere and carried into the apparatus. Although it is considered to be generally self-evident from a study of Figure 1, for the sake of complete clarification and explanation, it is to be understood that in this specification the expression 'sealed together around said electrodes' covers the cases where the sections of the housing in being sealed together are also either sealed or not sealed onto the emerging terminal sections of the electrodes thereby resulting in a housing which is either hermetically sealed or non-hermetically sealed as required. Some degree of non-hermeticity is often desirable to maintain the atmosphere within the housing substantially at the pressure of the surrounding atmosphere, but such that significant ingress of dust etc. into the housing is inhibited. WHAT WE CLAIM IS:

1. An electrical spark gap device for electrically connecting to conductors in an electrical circuit or apparatus and comprising a pair of electrodes each formed of a single wire bent to form a curved portion and having a terminal portion adapted to be connected to a said conductor, said electrodes being supported in a housing of electrically insulating material such that said curved portions curve towards one another and are separated by a predetermined gap and said terminal portions extend in substantially parallel spaced relationship from said housing, said housing having been formed from at least two sections sealed together around said electrodes, said electrodes being located in recesses provided in said sections, said housing having a hollow interior where the portions of said electrodes curve towards one another.

2. A device according to Claim 1 in which said electrodes extend from said housing where said two sections are sealed together.

3. A device according to Claim 1 or 2 in which said electrodes are in the form of wires.

4. A device according to any one of the preceding claims in which said housing is formed having inner surfaces at least partially of substantially corrugated form to provide maximum effective tracking between said electrodes.

5. A device according to any one of the preceding claims in which said housing is formed of an organic plastics material.

6. A device according to any one of the preceding claims in which said sections of said housing have been sealed together by an ultrasonic welding technique.

7. A device according to any one of the preceding Claims in which said housing is provided with one or more protruding portions extending in the direction of said terminal portions of said electrodes and shaped whereby said device may be connected by said terminal portions to a circuit board with said protruding portion or portions contacting a surface of said board to provide a stand-off for the device.

8. An electrical spark gap device constructed and arranged substantially as herein described and shown in Figures 1 and 2 of the accompanying drawings.

WELWYN ELECTRIC LIMITED