AU660037B2 - Terminal cover - Google Patents

Description

Pi00/01I Roguladon 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT 660037 Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: STATE ENERGY COMMISSION OF WESTERN

AUSTRALIA

363 365 WELLINGTON STREET PERTH W.A. 6000 ALAN KINNEAR BARSDEN GRIFFITH HACK CO.

Patent Trade Mark Attorneys 256 Adelaide Terrace PERTH W.A. 6000 i:l:: Standard Complete Specification for the invention entitled: TERMINAL COVER Details of Associated Provisional Applications: PK7555 filed 1/8/91 by SECWA Details of Parent Application for Divisional Applications: The following is a full description of this invention, including the best method of performing it known to me:- 2 TERMINAL COVER The present invention relates to a terminal cover for covering an electrical terminal so that inadvertent contact with the terminal can be prevented, and relates particularly, though not exclusively, to a cover for a terminal of a low tension isolating switch.

The State Electricity Commission of Western Australia (SECWA) locates isolating switches on electricity supply poles wherever there may be a need to isolate a pole or electrical apparatus, such as a transformer mounted on the pole, from the electricity supply grid. Similar isolating switches are used by all electricity supply authorities and companies. Typically the isolating switch is an opening-closing point knife switch, in which the knife blade can be manually opened and closed with an appropriately insulated tool. In use, when. the switch is opened the switch remains "live" up to the end of the blade and therefore presents a hazard to SECWA employees working in close proximity to the blade.

Furthermore, it is possible, and in fact all too easy, for the blade to be accidently knocked so that the switch closes, exposing employees on the supposedly "dead" side of the switch to potentially serious injury or death through electrocution. It is not unusual for gear to be hauled up to employees on an electricity supply pole by rope. The gear may inadvertently strike the blade as it is being hauled up, causing the switch to close. Alternatively, a metal tool such as, for example, a spanner, may inadvertently touch the terminals of the isolating switch causing a closed circuit across the switch with similar potentially hazardous results.

The present invention was developed with a view to providing a terminal cover capable of inhibiting inadvertent contact with an electrical terminal, such as a terminal of an isolating switch.

3 According to the present invention there is provided a terminal cover for covering a protruding electrical terminal, the cover comprising: a skirt of electrically insulating material, for temporarily connecting the cover to the terminal and a handle to facilitate manual connection to, and removal from, the terminal whereby, in use, the skirt at least partially surrounds the terminal and can prevent inadvertent contact with the terminal being made while the cover is connected thereto.

Preferably the connecting means is made of the same electrically insulating material as the skirt and is adapted to temporarily adhere to the terminal by a friction fit.

Typically the connecting means comprises a structure adapted to wedge between opposing surfaces of the terminal. More typically the structure comprises a pair of wedge-shaped protrusions adapted to connect by a friction fit to the terminal between a corresponding pair of opposing surfaces of the terminal. Preferably the terminal cover is made of resilient plastics material, and said wedge-shaped protrusions are spaced apart to receive a part of said terminal therebetween.

In a preferred embodiment the skirt comprises first and second portions, a first substantially cylindrical portion and a second tapered portion which tapers towards an end of the cover at which said handle is provided. The cylindrical portion of the skirt preferably has a cut-away section designed to avoid fouling of the S 30 skirt with the terminal of an isolating switch.

In order uo facilitate a better understanding of the invention, a preferred embodiment of the terminal cover will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front elevation of an underslung isolating switch of the kind employed by SECWA; V O c S l 4 Figure 2 is a side elevation of the switch illustrated in Figure 1 in the direction of arrow Figure 3 is a front elevation of a preferred embodiment of the terminal cover for use in connection with the switch of Figures 1 and 2; Figure 4 is an end elevation in the direction of arrow "EB" of the terminal cover illustrated in Figure 3; and, Figure 5 is a side elevation of the terminal cover illustrated in Figures 3 and 4.

Figures 1 and 2 illustrate a low tension (400 amp, 600 volt) underslung isolating switch 10, of the kind employed by SECWA for isolating an electricity supply pole or other electricity supply apparatus, such as a transformer, from the electricity supply grid. The isolating switch 10 comprises a metal bracket 12 for bolting the switch to the underside of, for example, a cross beam on an electricity supply pole. A pair of ceramic insulators 14 insulate first and second electrical terminals 16 and 18 respectively from each other, and from the metal bracket 12 and, in turn, from the electricity supply pole (not shown) on which the switch is mounted. The electrical terminals 16 and 18 are spaced apart a prescribed distance, and the gap between them may be closed by a knife switch 20 which is pivotally connected to the second terminal 18. In Figure 1 the knife switch 20 is illustrated in the closed position, where it provides a close circuit between the electrical terminals 16 and 18. The knife switch is illustrated in broken outline moving towards an open position in which the first terminal 16 is isolated from the second terminal 18. Electricity supply cables are connected to the terminals 16 and 18 by means of lugs 22 and 24 respectively.

Knife switch 20 is provided with an aperture 26 therein at an end opposite to the end at which the knife switch is pivotally connected to terminal 18, to facilitate easy opening and closing of the isolating switch. In particular, an appropriately shaped tool (not shown) may be inserted through aperture 26 so that the switch may be manually opened by applying a downward force on the tool, or closed by applying 5 an upward force on the tool, causing the knife switch 20 to pivot to an open or closed position respectively. This enables the isolating switch to be opened or closed from the ground by using, for example, an extension pole with a hook mounted thereon.

As can be seen more clearly in Figure 2, the blade comprises a pair of parallel copper bars 28 which in the closed position are received in a friction fit between a corresponding pair of opposing surfaces 30 of the terminal 16.

Silver contacts are provided on the copper bars 28 and opposing surfaces 30 to provide a low impedance connection between the knife switch 29 and terminal 16 in the closed position.

Typically, the cable connected to the supply side of the electricity supply grid is connected to terminal 18, so that even when the isolating switch is open the switch remains "live" up to the end of the blade 20, and therefore presents a hazard as described in the introduction to the specification above. The preferred embodiment of the terminal cover according to the present invention was designed to cover terminal 16 to prevent inadvertent closing of the switch knife or closing of the gap between the terminals 16 and 18 by any other conductor such as, for example, a metal tool.

Figures 3, 4 and 5 illustrate the preferred embodiment of the terminal cover 40. Terminal cover comprises a skirt 42 of electrically insulating material and means 44 for temporarily connecting the cover 40 to a terminal.

Preferably, the cover 40 is moulded from plastics material, typically RIM polyurethane plastics material with the requisite electrical insulating properties. Any suitable electrically insulating material may be employed. As can be seen most clearly in Figure 3 connecting means 44 is made of the same electrically insulating material as the skirt 42, and comprises a pair of wedge-shaped protrusions 46 adapted to connect in a friction fit to terminal 16, between a corresponding pair of opposing surfaces 30 of the terminal. Terminal 16 illustrated in Figure 3 in broken outline corresponds to the first terminal 16 in Figures 1 and 2. Wedge-shaped protrusions 46 are spaced apart so that the recess therebetween is adapted to receive a 6 central bar 48 of the terminal 16, tightly wedged therein. Due to the resilience of the polyurethane material from which the terminal cover 40 is manufactured, the cover temporarily adheres to the terminal 16 by means of a wedging action produced by the protrusions 46.

The skirt 42 of the terminal cover 40 comprises a first substantially cylindrical portion 50 and a second tapered portion 52 which tapers towards an end of the cover 40 at which a handle 54 is provided. When the terminal cover 40 is connected to the terminal, the skirt 42 at least partially surrounds the terminal to prevent inadvertent contact with the terminal being made. In the illustrated embodiment the cylindrical portion 50 of the skirt is provided with a cut-away portion 56,, as can be seen most clearly in Figure 5, to avoid fouling of the skirt 42 with the terminal 16. In particular, cut-away portion 54 enables the skirt 42 to be received over the terminal 16 without interfering with the lug 22 of terminal 16, to which the electricity supply cable is connected. The cylindrical portion 50 of .the skirt 42 typically extends all the way up over the exterior of terminal 16, to a point just under the peripheral lip of the ceramic insulator 14 visible in Figures 1 and 2. The skirt 42 thus completely surrounds the terminal 16, apart from in the region of the cut-away portion 56. Handle 54 conveniently facilitates manual connection and disconnection of the cover 40 to the terminal 16. An aperture 58 provided in the cover 40 performs a similar function to the aperture 26 in the knife switch in that it enables the cover 40 to be removed by a person standing at ground level using a pole with a hook thereon.

Now that a preferred embodiment of the terminal cover has been described in detail, it will be apparent that the terminal cover provides a simple and effective means of ensuring the safety of personnel, by preventing inadvertent closing of the knife switch 26, or inadvertent contact between the terminal 16 and the knife switch blade 26 or terminal 18 of the isolating switch illustrated in Figures 1 and 2. The illustrated embodiment of the terminal cover is designed to connect to the stationary terminal 16 of the isolating switch.

7 However, the terminal cover may be readily modified to connect to the knife switch 26 of the isolating switch 10, by extending the length of the cylindrical portion 50 of the skirt 42. The terminal cover illustrated in the drawings is the preferred form, as it will readily connect to the stationary terminal of any isolating switch or similar electrical apparatus, whereas terminal covers for the knife switch 26 would need to come in varying sizes depending on the length of the blade In an alternative embodiment of the terminal cover the handle 54 is configured differently, having a grip portion extending substantially coaxially with the central longitudinal axis of the terminal cover. With this configuration the possibility of the terminal cover being accidently dislodged from the teriinal by an object striking the handle 54, is minimised. The reduced overall width dimension of this alternative terminal cover also makes it easier to pack away and store.

It will be apparent to those skilled in the appropriate arts that numerous other variations and modifications may be made to the illustrated terminal cover, without departing from the basic inventive concepts. For example, the shape and configuration of the skirt 42 may be significantly different from that illustrated, and need not have a cut-away portion 56. Furthermore, any suitable form of connecting means 44 can be employed to temporarily connect the terminal cover to the terminal. Obviously, modified forms of the terminal cover can be adapted to cover different types of electrical terminals, other than the terminals on an isolating switch. All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description and the appended claims.

Claims (9)

1. A terminal cover for covering a protruding electrical terminal, the cover comprising: a skirt of electrically insulating material, for temporarily connecting the cover to the terminal and a handle to facilitate manual connection to, and removal from, the terminal whereby, in use, the skirt at least partially surrounds the terminal and can prevent inadvertent contact with the terminal being made while the cover is connected thereto.

2. A terminal cover as claimed in claim i, wherein the connecting means is made of the same electrically insulating material as the skirt and is adapted to temporarily adhere to the terminal by a friction fit.

3. A terminal cover as claimed in claim 1 or claim 2, wherein said connecting means comprises a structure adapted to temporarily adhere to the terminal by a wedging action.

4. A terminal cover as claimed in claim 3, wherein said connecting means comprises a pair of wedge-shaped protrusions spaced apart so that a recess therebetween is adapted to receive a part of the terminal tightly wedged S.therein.

5. A terminal cover as claimed in claim 4, wherein 25 the pair of protrusions are made of resiliently deformable plastics material whereby, in use, said wedging action is produced therebetween.

6. A terminal cover as claimed in any one of the preceding claims, wherein the skirt comprises first and second portions, a first substantially cylindrical portion and a second tapered portion which tapers towards an end of 9

7. A terminal cover as claimed in claim 6, wherein the cylindrical portion of the skirt has a cut-away section designed to avoid fouling of the skirt with the terminal of an isolating switch.

8. A terminal cover substantially as herein described with reference to and as illustrated in any one or more of Figures 3 to 5 of the accompanying drawings. Dated this 27th day of February 1995 STATE ENERGY COMMISSION OF WESTERN AUSTRALIA By Its Patent Attorneys GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. ix'

9 ABSTRACT A terminal cover 40 for covering an electrical terminal so that inadvertent contact with the terminal can be prevented. The terminal cover 40 comprises a skirt 42 of electrically insulating material, for example, polyurethane plastics material. A connecting means 44 for temporarily connecting the cover 40 to a terminal is made of the same electrically insulating material as the skirt 42. The connecting means 44 comprises a pair of wedge-shaped protrusions 46 adapted to connect in a friction fit to a terminal 16. The wedge-shaped protrusions 46 are spaced apart so that the recess therebetween is able to receive a central bar 48 of the terminal 16, tightly wedged therein. The skirt 42 of the terminal cover 40 comprises a first substantially cylindrical portion 50 and a second tapered portion 52 which Si tapers towards an end of the cover 40 at which a handle 54 is provided. When the terminal cover is connected to the terminal, the skirt 42 at least partially surrounds the terminal to prevent inadvertent contact with the terminal being made. Drawing suggested to accompany abstract: Figure 3. C