GB2313496A

GB2313496A - Fused isolation device

Info

Publication number: GB2313496A
Application number: GB9709886A
Authority: GB
Inventors: David Hutchins; John Robert Leslie; William Alexander Morton
Original assignee: British Nuclear Fuels PLC
Current assignee: Sellafield Ltd
Priority date: 1996-05-25
Filing date: 1997-05-16
Publication date: 1997-11-26
Anticipated expiration: 2017-05-16
Also published as: GB2313496B; GB9611029D0; GB9709886D0

Abstract

An isolation device, for use with an electrical component provided with a removable fuse in a fuse holder (neither shown), comprises a shield 20 which prevents access to a recess vacated by the fuse and is located by two members 21, 22. A bar 32 on the member 22 passes through holes in the shield 20 and member 21 (Figures 3 to 5) and receives a lock 34 to secure the members and the shield 20. The shield has a dependant shank (27 Figure 4) with a screw threaded part (29) which is received in the threaded recess 18 vacated by the fuse. Cables 3, 4 in the component are secured to terminals 10, 13 by screws 12, 15. The device may be mounted on a rail (2 Figure 1).

Description

An Electrical Isolation Device The present invention relates to an isolation device for use with an electrical terminal component. In particular, the invention relates to an isolation device for use with an electrical terminal component of the type incorporating a fuse element normally establishing an electrical connection between two contacts of the terminal component.

In the maintenance or inspection of electrical equipment it is often required for safety reasons to isolate the equipment requiring attention from the source of electrical supply. This can be achieved by removing a fuse element from a terminal component arranged in the circuit serving the equipment. To prevent inadvertent insertion of a fuse element it is known to place an adhesive label bearing an isolation warning over the recess normally accommodating the fuse element. A disadvantage of this arrangement is that the adhesive label can become detached, or it can be removed easily, thus rendering the isolation potentially useless.

It is an object of this invention to provide an isolation device which overcomes or at least minimises the aforementioned disadvantages.

According to the invention there is provided an isolation device for use with an electrical component of the type having a removable fuse element normally establishing a connection between electrical contacts on said electrical component, said isolation device comprising a shielding member adapted to prevent access to a recess vacated by said fuse element upon removal thereof, locating means arranged on said electrical component so as to locate the shielding member, and locking means arranged to secure said locating means to said shielding member.

The locking means preferably comprises a padlock having a pivoted hook portion arranged to pass through said locating means.

Preferably, the locating means comprising first and second members, one of said first and second members having a bar portion which cooperates with a positioning means on said shielding member.

The positioning means on the shielding member preferably comprises a hole through which the bar portion extends.

The bar portion may also extend through a passage provided in the other of said first and second members.

The shielding member may extend into the recess vacated by the fuse element.

The shielding member may comprise a screw-threaded region which is received by a correspondingly screwthreaded portion provided in the recess.

Advantageously, the bar portion extends substantially perpendicularly with respect to an axis along which the shielding member extends into the recess, each of said first and second members having a limb portion extending substantially parallel to and spaced from said axis, each of said limb portions being located close to or so as to engage respective surfaces on said terminal component.

Preferably the locking means is attached to said bar portion.

The isolation device may be so dimensioned that a device can be fitted to each of two adjacent electrical components when said components are arranged in end-to-end relationship.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a front elevation of a plurality of electrical terminal components, one of which is equipped with an isolation device according to the invention; Figure 2 is a part cross-sectional end elevation of the electrical terminal component equipped with the isolation device shown in Figure 1, and Figures 3, 4 and 5 show various components of the isolation device shown in Figures 1 and 2.

Referring to Figures 1 and 2, a plurality of electrical terminal components 1 are removably mounted in end-to-end contacting relationship on a mounting rail 2.

Each terminal component 1, which is moulded from a flameresistant plastics material, provides a fused junction between two electrical cables 3, 4 forming part of an electrical circuit. The terminal component 1 has a lower projection 5 which is formed so as to enable the component to be snapped on to the mounting rail 2. Cable access openings 6, 7 are provided, respectively, in parallel front and rear surfaces 8, 9 of the terminal component.

The cable 3 extends through the opening 6 into a clamp 10 where the cable is held firmly against a contact strip 11 by means of a screw 12. Similarly, the cable 4 extends through the opening 7 into a clamp 13 so as to be held firmly against a contact strip 14 by means of a screw 15.

The ends of the contact strips 11, 14 remote from the respective clamps 10, 13 are formed so as to provide a gap which is normally bridged by a fuse element (not shown).

The fuse element is mounted in a fuse holder (not shown) which is housed in a recess 16 provided in an upper surface 17 extending substantially perpendicular to the front and rear surfaces 8, 9. A screw-threaded region 18 is provided in the recess 16 to receive a correspondingly screw-threaded region on the fuse holder. As is well known, the fuse element includes a piece of fusible metal which melts and interrupts the electrical current when an excess current flows. Thus, the electrical equipment served by the circuit is protected against the effects of excess currents.

In the event that the equipment served by the electrical circuit requires attention, for example, for maintenance purposes, it is usual for safety reasons to isolate the equipment by removing the fuse holder and fuse element from the terminal component. To achieve secure isolation upon removal of the fuse element, the terminal component is fitted with a lockable isolation device 19.

The isolation device comprises a shielding insert member 20 which occupies the recess vacated by the fuse holder and the fuse element and is held in position by first and second locating members 21, 22. As seen in Figure 3, the first locating member 21 is generally L-shaped and comprises a shorter limb 23 extending perpendicularly with respect to a longer limb 24. Each of the shorter and longer limbs 23, 24 is of rectangular cross-section.

Extending through the longer limb 24 is a cylindrical passage 25. The insert member 20 is made from a nonconducting material, for example, a plastics material and comprises a head 26 of cuboid form and a shank 27. A cylindrical positioning hole 28, having substantially the same diameter as the passage 25, extends through the head 26. The shank 27 comprises a series of cylindrical regions, the diameters of which reduce progressively in a direction away from the head. Included in the shank 27 is a screw-threaded region 29 which can be screwed into the correspondingly threaded region 18 in the terminal component 1. The screw-threaded region 29 may be formed from stainless steel material. Figure 5 shows the second locating member 22 which comprises a limb 30 extending perpendicularly with respect to a limb 31. Each of the limbs 30, 31 are of rectangular cross-section. A cylindrical extension bar 32 projects from the limb 31 and has a diameter such that it can pass through the hole 28 in the insert member 20 and through the passage 25 in the first locating member 21. Towards the end of the bar 32 a hole 33 is drilled to receive a locking means, which, as seen in Figures 1 and 2, comprises a padlock 34 of a conventional type.

In use, when it is required to isolate the equipment, the fuse holder is removed from the associated terminal component 1. The insert member 20 is then screwed into the recess 16 vacated by the fuse holder so as to prevent access to the recess. The bar 32 of the second locating member 22 is then inserted through the hole 28 to position the insert member and through the passage 25 in the first locating member 21. Securement of the front and second locating members 21, 22 to the insert member 20 is achieved by passing the pivoted hook of the padlock 34 through the hole 31 in the second locating member 22.

After locking the padlock 34, the key is removed to deter unauthorised access to the terminal component 1. The arrangement is such that the limbs 23, 30 of the respective locating members 21, 22 extend parallel to an axis along which the insert member 20 extends and are close to or clamped against the front and rear surfaces 8,9 of the terminal component 1. The location of the limbs 23, 30 close to or against the surfaces 8, 9 prevents rotation of the isolation device 19 about the axis of the shielding member 20 so that the shielding member 20 cannot be unscrewed from the recess 16.

Futhermore, it is not possible to gain access to the terminal screws 12, 15 by twisting the isolation device sideways.

As will be seen from Figure 1, the isolation device 19 has a narrower width than that of the terminal component 1. It is therefore possible to fit isolation devices to adjacent terminal components. The isolation device is of simple and robust construction and can be fitted quickly to a terminal component.

Claims

1. An isolation device for use with an electrical component of the type having a removable fuse element normally establishing a connection between electrical contacts on said electrical component, said isolation device comprising a shielding member adapted to prevent access to a recess vacated by said fuse element upon removal thereof, locating means adapted to engage said electrical component so as to locate the shielding member, and locking means arranged to secure said locating means to said shielding member.

2. An isolation device according to Claim 1, wherein the locking means comprises a padlock having a pivoted hook portion arranged to pass through said locating means.

3. An isolation device according to Claim 1, wherein the locating means comprises first and second members, one of said first and second members having a bar portion which cooperates with a positioning means on said shielding member.

4. An isolation device according to Claim 3, wherein the positioning means on the shielding member comprises a hole through which the bar portion extends.

5. An isolation device according to Claim 3 or 4, wherein the bar portion extends through a passage provided in the other of said first and second members.

6. An isolation device according to any one of the preceding Claims, wherein the shielding member extends into the recess vacated by the fuse element.

7. An isolation device according to Claim 6, wherein the shielding member comprises a screw-threaded region which is received by a correspondingly screw-threaded portion provided in the recess.

8. An isolation device according to any one of Claim 3, 4 or 5, wherein the bar portion extends substantially perpendicularly with respect to an axis along which the shielding member extends into the recess, each of said first and second members having a limb portion extending substantially parallel to and spaced from said axis, each of said limb portions being located close to or so as to engage respective surfaces on said terminal component.

9. An isolation device according to any one of Claims 3 to 7, wherein the locking means is attached to said bar portion.

10. An isolation device according to any one of the preceding Claims, wherein the device is so dimensioned that a device can be fitted to each of two adjacent electrical components when said components are arranged in end-to-end relationship.

11. An isolation device substantially as hereinbefore described with reference to the accompanying drawings.