In electrical circuit arrangements it is known to provide several terminal components in side-by-side relationship on a mounting rail. An input cable from an electrical source and an outlet cable serving circuit equipment are connected to contacts on each terminal component. Each terminal component is provided with a contact member, for example, a fuse or switch element, which normally establishes a connection between the contacts. The contact member can be withdrawn or removed so as to isolate the equipment served by the terminal component from the source of electrical supply. With the contact member in a withdrawn position, maintenance and/or inspection of the electrically isolated equipment can be carried out in safety. Inadvertent or accidental replacement of the contact member would endanger the maintenance personnel.

An isolation member is therefore attached to the terminal member so as to engage and maintain the contact member in its withdrawn position. For safety reasons, it is important that unauthorised removal of the isolation members from the terminal component is deterred.

It is an object of this invention to provide a locking assembly which prevents or deters unauthorised or inadvertent removal of an isolation member from its associated terminal component.

According to the invention there is provided a locking assembly for securing a plurality of electrical isolation members, each isolation member being connected to an electrical terminal component so as to isolate equipment served thereby from an electrical source of supply, the locking assembly comprising a support member, securing means adapted to secure a rod to said support member, the rod extending from the support member and passing through said isolation members, and a lockable device arranged on the support member so as to prevent removal of said securing means.

Preferably, the electrical terminal components are attached to and arranged along a mounting rail, the locking assembly including fastening means for fixing the support member to the mounting rail.

In a preferred embodiment the rod is secured in a hole provided in the support member, the hole being in alignment with apertures provided in the isolation members whereby to provide an axial passage for receiving the rod.

The securing means may comprise a screw which is located in a first channel communicating with the hole in which the rod is secured.

Preferably, the fastening means comprises a further screw which is located in a further channel communicating with the hole in which the rod is secured.

The lockable device preferably is adapted to prevent access to the securing means.

In a preferred embodiment, the lockable device comprises a padlock, a portion of which obstructs an entrance to said first channel whereby to prevent access to the securing means.

Preferably, each terminal component comprises a contact member which is movable from an operative position, in which the contact member establishes an electrical connection between electrical contacts on the component to an inoperative position, in which the contact member breaks the electrical connection, the isolation member being adapted to maintain the contact member in the inoperative position whereby to isolate the equipment served by the terminal component.

The locking assembly may comprise a first support member fixed to the mounting rail at one end of the terminal components and a second support member fixed to the mounting rail at the other end of the terminal components, the rod extending between and supported by each support member so as to pass through the isolation members, the lockable device being provided on at least one of the support members so as to prevent removal of the securing means.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic front elevation of a locking assembly for securing a plurality of electrical isolation members according to a preferred embodiment of the invention, Figure 2 is a sectional elevation on the line II-II shown in Figure 1 at an enlarged scale, Figure 3 is a side elevation of a support member forming part of the locking assembly shown in Figure 1 at an enlarged scale, and Figure 4 is a sectional elevation on the line IV-IV shown in Figure 1 at an enlarged scale.

Figures 1 and 2 illustrate an electrical terminal arrangement which forms part of an electrical circuit. The terminal arrangement comprises a plurality of terminal components 1 which are releasably attached, in side-by-side relationship, to and along a mounting rail 2. In a front surface of each terminal component 1 an inlet opening 3 is provided for an electrical input cable 4. The input cable 4 is connected to a first contact 5 within the terminal component 1. In a rear surface of the terminal component 1 an outlet opening (not shown) is provided for an outlet cable 6 which is connected to a second contact 7 within the component.

Each terminal component 1 includes a movable contact member 8, in the form of a switch component, pivotably mounted on a pivot pin 9.

When the contact member 8 is in an operative position, two contact leaves 10 establish a connection between the first and second contacts 5,7 and thereby between the inlet and outlet cables 4,6. It will be apparent that the terminal component 1 may be of a different type. For example, the contact member could incorporate a fuse element which, in the operative position of the contact member, bridges the gap between the two contacts 5,7.

To break the electrical connection between the contacts 5,7, the contact member 8 is pivoted about the pin 9 to an inoperative position, as shown in Figure 2. Thus, the equipment served by the terminal arrangement is isolated from the electrical source, enabling inspection and/or maintenance of the equipment to be carried out safely.

To maintain the contact member 8 in the inoperative position, an isolation member 11 is mounted on the upper surface of the terminal component 1.

The isolation member 11 may of the types disclosed in the Applicant's co-pendina application number GB 9809029.3.

Formed as a single moulding of plastics material, the isolation member 11 has a peripheral rim extending laterally on either side of a central web 13. Two portions of the rim 12 form a base 14,15 which is provided with two locating dowels 16 for insertion in holes provided in the terminal component 1. A recess 17 formed in the base 14,15 receives the contact member 8 when in its inoperative position. Return of the contact member 8 to its operative position is prevented by the sides of the recess 17. Extending from the base 14 is a catch 18 which clips to the terminal component 1 so as to inhibit removal of the isolation member 11. An aperture in the form of a slot 19 is provided in the central web 13 for the purpose described below.

For safety reasons, it is important to ensure that the isolation members 11 cannot be removed from the terminal components 1. Otherwise, it would be possible to return the contact members 8 to their operative positions thereby risking injury to the personnel carrying out maintenance on the equipment served by the electrical circuit.

For this purpose, the isolation members 11 are secured by a locking assembly 20. The locking assembly 20 comprises an end stop, in the form of a support member 21, positioned on the mounting rail 2 at either end of the terminal components 1.

As seen in Figures 3 and 4, each support member 21, which is a single moulding of plastics material, generally comprises a peripheral rim 22 extending laterally on either side of a central web 23. Indents 24,25 at a lower end of the support member 21 enable the member to be clipped on to the mounting rail 2, in a manner similar to the attachment of the terminal components 1 to the rail. An extension 26 at the upper end of the support member 21 has a central slot 27 bridged by a bar 28.

A circular channel 29 extends through the support member 21 from an upper surface 30 to the base region of the member. In a reduced diameter portion at the lower end of the channel 29 is a grub screw 31 which is tightened against the mounting rail 2 so as to secure the support member thereto. The grub screw 31 may be of the self-tapping type.

Extending transversely through the channel 29, towards the upper end thereof, is a hole 32. When the support member 21 is fitted to the mounting rail 2, the hole 32 is in alignment with the slots 19 in the isolation members 11. The holes 32 and the slots 19 form an axial passage, so enabling a rod 33 to be inserted through the two support members 21 and the isolation members 11.

A channel 34 extends from the hole 32 and has an inlet end which opens into the slot 27. The rod 33 is secured in the support member 21 by a further grub screw 35 inserted into the channel 34 and tightened against the rod. The grub screw 35 may be of the self-tapping type.

A padlock 36 is secured to the support member 21 by placing a pivotable hook 37 around the bar 28. Using a key, in the usual manner, the hook 37 is locked into the padlock body 38.

In this position the body 38 conveniently rests on the upper surface 30.

The padlock hook 37 obscures the inlet to the channel 34 so that it is not possible to insert a tool to untighten the grub screw 35. Therefore, unless the padlock 36 is removed it is not possible to withdraw the rod 33 from the locking assembly 20. Consequently, the isolation members 11 cannot be removed from the terminal components 1, ensuring that the contact members are retained in their inoperative positions. The key for the padlocks 36 can be stored at a secure location so that it is available to unauthorised persons only, whereby unauthorised access to the isolation members 11 is prevented.

It will be apparent that it may not be necessary to isolate all of the terminal components 1. In some circumstances only those components associated with equipment requiring attention need to be isolated.