GB2377557A

GB2377557A - Strap clamp for earthing connection to pipe

Info

Publication number: GB2377557A
Application number: GB0117211A
Authority: GB
Inventors: John Graeme Hinley
Original assignee: NIGLON Ltd
Current assignee: NIGLON Ltd
Priority date: 2001-07-14
Filing date: 2001-07-14
Publication date: 2003-01-15
Anticipated expiration: 2021-07-14
Also published as: GB0117211D0; GB2377557B

Abstract

An electrical connector 10 for connecting an earth wire to a pipe 12 comprising a clamp body 14 and a flexible strap 52. The clamp body 14 has a channel shaped section with leg portions 18. A clamping screw 24 engages the strap 52 when inserted through slots 20 in the leg portions 18. Each leg portion 18 has reinforcing rib formations 30, and a chamfer 34 on the inner edge.

Description

ELECTRICAL CONNECTORS The present invention relates to electrical connectors for establishing an earth connection to water, gas or similar pipes, as part of the electrical wiring installations in buildings.

As disclosed in UK patent GB 2,245, 772, the disclosure of which is incorporated herein by reference thereto, electical connectors of this type conventionally comprise a clamp body, a flexible strap for holding the clamp body to the pipe, a pipe contact element carried by the clamp body and a clamping screw engaging the clamp body, the clamping screw being arranged to tighten the strap around the pipe, to grip the strap against the pipe contact element and to drive the pipe contact element into firm engagement with the pipe. The contact element also preferably has an earth wire connection.

It has been proposed to replace the clamp body and pipe contact element of the above described electrical connector with a one-piece element.

However, electrical connectors of this type must comply with British Standard BS951: 1999, which requires the connector to exhibit a minimum non-slipping torque, when secured to a standard mandrel and the clamping screw is tightened to a torque specified by the Standard.

The one-piece clamps proposed to-date have difficulty in complying with this Standard.

According to one aspect of the present invention, an electrical connector comprises a clamp body and a flexible strap, the clamp body being of channel section having a base portion with leg portions extending from longitudinal edges of the base portion substantially parallel to one another and perpendicular, to one side of the base portion; the leg portions having aligned slots for the strap, the slots extending parallel to and adjacent the

base portion, a clamping screw being provided in a screw threaded aperture in the base portion for engagement of the strap when inserted through the slots in the leg portions ; each leg portion having reinforcing rib formations, one on either side of the slot therein, the rib formations extending from the free edge of the leg portion to the base portion and a chamfer being provided on the inner edge of the free longitudinal edge of each of the leg portions.

With the electrical connector described above, the clamp body is mounted on a pipe with the free longitudinal edges of the leg portions running parallel to the pipe, so that the chamfers on the free edges engage the pipe. The flexible strap is located through the slots in the leg formations, around the pipe and back through the slots. The flexible strap is pulled as tight as possible by hand and is then further tightened by means of the clamping screw, which will firstly clamp one length of strap against the other, as they pass between the leg portions of the clamp body and will then deform the lengths of strap to tighten the strap about the pipe.

Engagement of the pipe by the chamfered edges of the leg portions will thereby provide sufficient frictional engagement to meet the British Standard BS951: 1999. The rib formations of the leg portions prevent the leg portions from splaying outwardly as the strap is tightened.

According to a preferred embodiment of the invention, the rib formations in the leg portions extend outwardly and the portions of the leg portions adjacent to the free edges and between the rib formations are indented, the chamfers being provided on the inner edges of these indented portions. In this manner, the inclination at which the chamfers engage the pipe is reduced, thereby reducing the loads tending to cause the leg portions to splay outwardly.

According to a further preferred embodiment, a terminal for an earth wire

is provided on the clamp body.

An embodiment of the invention is now described, by way of example only, with reference to the accompanying drawings, in which :- Figure 1 shows a side elevation of an electrical connector in accordance with the present invention; Figure 2 shows a plan view from below of the clamp body of the connector shown in Fig. 1; Figure 3 is a section along the line III-III of the clamp body of the connector illustrated in Fig. 1; and Figure 4 shows a part sectional end elevation of the electrical connector illustrated in Fig. 1, secured to a pipe.

As illustrated in Figs. 1 to 3, an electrical connector 10 for connecting an earth wire to a metal pipe 12, comprises a clamp body 14 of channel section having a base portion 16 with leg portions 18 extending to one side of the base portion 16, perpendicularly thereof from longitudinal edges of the base portion 16. The leg portions have aligned slots 20 which extend substantially parallel to and adjacent the base portion 16. A threaded aperture 22 is provided in the base portion for engagement of a correspondingly threaded clamping screw 24. A lock nut 26 is provided on the clamping screw 24.

Each of the leg portions 18 has a pair of reinforcing ribs 30 extending from the base portion 16 to the free longitudinal edges thereof, one reinforcing rib 30 on either side of the slot 20. The reinforcing ribs 30 extend outwardly of the leg portions 18. A portion 32 of each leg portion

18 extending between the reinforcing ribs 30 and adjacent the free edges of the leg portions 18 are indented, a chamfer 34 being provided on the inner edge of the free edge defined by this indented portion 32 of the leg portion 18.

A terminal formation 40 is provided on a longitudinal extension 42 of the base portion 16. The longitudinal edges of the extension 42 are bent perpendicularly to the extension 42 to the opposite side of the base portion 16 from the leg portions 18, to form wings 44. A threaded aperture 46 is provided in the extension 42 for engagement of a terminal screw 48, by which an earth wire may be secured to the connector 10.

The wings 44 prevent undesired spread of the earth wire and, with a washer formation 50 on the terminal screw 48, act to trap the earth wire when the terminal screw 48 is tightened.

As illustrated in Fig. 4, the body portion of the connector 10 is located on a length of pipe 12, so that the leg portions 18 engage the pipe 12 longitudinally. A thin stainless steel strap 52 is located through the aligned slots 20 in the clamp body 14, the end 54 of the strap 52 being bent over to prevent the strap 52 from being pulled through the slots 20.

The free end 56 of the strap 52 is then pulled around the tube 12 and back through the slots 20, the strap 52 is then tightened by hand, so that the chamfers 34 engage the surface of the tube 12. The clamping screw 24 may then be tightened so that the lengths of the strap 52 extending between the leg portions 18 are clamped together and are deformed to tighten the strap 52 about the tube 12.

Finally, locking nut 26 may be tightened against the base portion 16 to lock the clamping screw 24.

The earth wire may then be secured to the connector by means of

terminal screw 48, as described above.

The electrical connector described with reference to Figs. 1 to 4 is designed to comply with British Standard BS951: 1999, while accommodating a range of pipe sizes. Typically, to cover a range of pipe sizes from 12mm to 35mm, the overall outside dimensions of the clamp body 14, excluding the terminal extension 42, would be of the order of 25mm long by 15 mm wide by 15mm high. The outside width across the indented portions of the leg portions 18 being about 12mm with a material thickness of 1.5mm, giving an inside dimension of about 9mm.

Typically, the chamfer 34 is from 150 to 200, preferably 180.

Claims

1. An electrical connector comprising a clamp body and a flexible strap, the clamp body being of channel section having a base portion with leg portions extending from longitudinal edges of the base portion substantially parallel to one another and perpendicular, to one side of the base portion; the leg portions having aligned slots for the strap, the slots extending parallel to and adjacent the base portion, a clamping screw being provided in a screw threaded aperture in the base portion for engagement of the strap when inserted through the slots in the leg portions; each leg portion having reinforcing rib formations, one on either side of the slot therein, the rib formations extending from the free edge of the leg portion to the base portion and a chamfer being provided on the inner edge of the free longitudinal edge of each of the leg portions.

2. An electrical connector according to claim 1 in which the reinforcing rib formations extend outwardly of the leg portions of the clamp body.

3. An electrical connector according to claim 2 in which portions of the leg portions extending between the rib formations and adjacent the free edges of the leg portions, are indented.

4. An electrical connector according to claim 3 in which the chamfers are provided on the inner edges of the indented portions.

5. An electrical connector according to any one of the preceding claims in which a terminal formation is provided on a longitudinal extension of the base portion of the clamp body.

6. An electrical connector according to claim 5 in which the terminal

formation defines a pair of parallel wings with a terminal screw located therebetween and adapted to clamp a wire between the head of the terminal screw and the wings.

7. An electrical connector according to any one of the preceding claims in which the chamfer on the inner edge of the free longitudinal edges of the leg portions are at an angle of between 1 50 and 200.

8. An electrical connector substantially as described herein with reference to and as shown in Figs. 1 to 4 of the accompanying drawings.