GB2297385A - Fuse Tester - Google Patents

Description

Fuse Tester This invention relates to a fuse tester.

1 3 amp. Fused plugs are used to connect a variety of electrical appliances to 240 volt electrical supplies in the United Kingdom.

Every functional plug contains a replaceable cylindrical fuse of common pattern, construction and size conforming to British Standard 1 362.

In general these fuses are manufactured either as 3 amp, or 1 3 amp. Fuses although a relativeiy small number are produced as 1 amp and 5 amp. The fuse rating is clearly displayed on an external surface. 3 amp fuses are recommended for appliances rated below 750 watt and 1 3 amp fuses for the majority of other products for domestic use.

When an electrical appliance unexpectantly stops working it becomes extremeiy important to know if the fuse is continuing to protect the user of the appliance from harm. This can be determined by removing the fuse from the plug and examining its electrical conductivity to determine whether or not the fuse is interrupting the flow of electricity. This is not an easy task for the average householder who is unlikely to possess an electrical test meter normally used by engineers and technicians.

According to the present invention there is a fuse testing device comprising a bulb, bulb holder, battery, fuse, spring, insulating sleeves and plunger. These components are all arranged co-axially within a demountable case.

The plunger, which is spring loaded, is conveniently used as a momentary push button switch attempting to establish electrical continuity within the device.

Prior to use the fuse testing device can be checked to establish that it is working satisfactorily. The fuse already within the device is used to establish continuity which is indicated by lamp illumination. Any component found to be faulty ie.

bulb, battery or fuse may be conveniently replaced before using the device to test a suspect fuse.

When it has been determined that the fuse tester is working correctly the two parts of the outer case are parted, the 'sound' fuse of known integrity is removed and the fuse to be tested inserted in its place. The outer case is re-assembled, the plunger is pressed and the electrical continuity of the inserted fuse is revealed.

If the bulb lights, the fuse being tested is sound and assuming the 1 3 amp plug connections and the electrical supply are satisfactory, the appliance in question must be faulty.

If the bulb fails to light, the fuse being tested has failed. A new, third fuse intended for replacement can be tested prior to insertion in the 1 3 amp plug. In some circumstances the appliance fitted with a tested fuse will still cease to work.

The fuse may then be retested. This will establish that the fuse has failed in situ and served its intended purpose in preventing further damage to the equipment, or its potential user.

A specific embodiment of the invention will be described by way of example with reference to the accompanying Figure 1.

Figure 1 shows a sectional view through the fuse tester. For descriptive purposes only it is convenient to regard all the components as being circular in section.

The outer case comprises two parts case (1) and case (2). In the assembled condition these are screwed together and are normally only separated to facilitate the removal and replacement of bulb (3) bulb holder (4) battery (5) or fuse (6).

The fuse (6) lies within an open-ended sleeve (7) which is an electrical insulator and is rigidly retained in a pre-determined fixed position within case (2).

Another sleeve (8) also an electrical insulator lies behind sleeve (7) inside case (2) the outside diameter of sleeve (8) is a loose sliding fit within the inside diameter of case (2). A plunger (9) lies permanently within holes in sleeve (8) and the end wall of case (2). The plunger is a loose sliding fit within both holes and is free to rotate.

Movement of the plunger along the longitudinal axis X - X is restricted by a fixed collar (11) and a double conical helical spring which exerts a holding force reacted through its contact with sleeve (8) and collar (11).

Fastening case (1) and case (2) together causes all the items within the case assembly to lie on a common longitudinal axis X - X. Sleeve (7) maintains its predetermined position at some distance from Datum Y. The fuse (6) is subjected to a longitudinal force transmitted by sleeve (8) from the spring (10). This holds fuse (6) against battery (5) which contacts bulb (3). The bulb holder (4) moves forward to nest against the inside of case (1). In the simplest arrangement illustrated in figure 1 case (1) and case (2) are electrical conductors. In other arrangements the fitting together of cases (1) and (2) by a screw, push fit or other mechanical means could create a similar conductive path involving additionai components.It can be observed that a certain accumulation of dimensional tolerances along the longitudinal axis X - X is catered for by the provision of lateral movement of sleeve (8) controlled by spring (10) the spring is metallic and a good electrical conductor. On initial assembly it is wound into the case (2) under compression so that the largest diameter coils of spring (10) maintain contact and common conductivity with the inner surface of case (2). One end of spring (10) is free to move along the plunger (9) and bears against sleeve (8). The other end of spring (10) is also free to move along the plunger (9) and bears against collar (11).

Referring to figure 1 when cases (1) and (2) are fully screwed together the spring (10) causes the bulb (3) bulb holder (4) battery (5) and fuse (6) to move to the left end of case (1). Within case (2) the sleeve (8) is moved as far to the left, by spring (10), as is necessary to hold components (1) (3) (4) (5) and (6) in electrical contact. The spring (10) also forces collar (11) to make contact with the right inside end of case (2). In this arrangement pluriger (9) is visible and accessible, protruding from the right hand outer end of case (2). The opposite end of plunger (9) is permanently restrained radially through a loose sliding fit within sleeve (8).

The inner end of plunger (9) lies within sleeve (8) and does not normally make contact with fuse (6). Plunger (9) is capable of longitudinal movement along the X - X axis but is restrained by a force exerted by spring (10) on a collar (11) which is rigidly attached to the plunger (9).

To check the electrical conductivity of a fuse (6) the external portion of the plunger (9) is pressed with thumb or finger. This causes the internal end of the plunger to contact the fuse. A continuous path of electrical conductors is made through the bulb (3) battery (5) fuse (6) plunger (9) collar (11) spring (10) body (2) body (1) bulb holder (4) returning to bulb (3). This permits the bulb to light if the components, including the fuse, are conducting electricity satisfactorily.

Once the plunger (9), which is acting as a momentary push switch, is released the electrical contact between fuse (6) and plunger (9) is lost and can only be re established by operating the plunger (9) at the discretion of the user.

The device described can be used to test continuity in any circular fuse of the type previously described irrespective of ampere rating.

Claims (7)

1) A fuse testing device comprising a housing adapted to incorporate in a longitudinal sequence a bulb, a battery, a test location to receive a fuse for testing, and drive means for urging a fuse from an electrically isolated position in the test location to a test position whereby the fuse is incorporated in an electrical loop also including the bulb and battery and a conducting path preferably defined by the housing so that in the event the fuse is in a conducting condition the loop is closed to enable the battery to provide a voltage drop across the bulb; and resilient biassing means acting to enable a fuse located in the test location to remain in the electrically isolated postition.

2) A fuse testing device as claimed in Claim 1 wherein the housing is in two demountable parts and access to the test location is provided by separating the two parts of the housing.

3) A fuse testing device as claimed in Claim 1 wherein the housing serves lo define an aperture providing access to the test location.

4) A fuse testing device as claimed in any preceding claim wherein the drive means comprises a plunger and the biassing means a spring.

5) A fuse testing device as claimed which conveniently retains a tested fuse available for immediate use.

6) A fuse testing device as claimed which can be used as a torch.

7) A fuse testing device as herein before described with reference to, and as illustrated in, the sole figure of the accompanying drawing.