US3816817A

US3816817A - Electrical connectors

Info

Publication number: US3816817A
Application number: US00315431A
Authority: US
Inventors: E Ball; J Mcconnell
Original assignee: Pirelli General Cable Works
Current assignee: Prysmian Cables and Systems Ltd
Priority date: 1972-12-15
Filing date: 1972-12-15
Publication date: 1974-06-11
Anticipated expiration: 1991-06-11

Abstract

An electrical connector for joining a branch conductor to an insulated mains conductor comprising a conductive collar for clamping about the mains conductor, means for connecting the branch conductor with the collar, and a screw engaged in the collar for screwing inwardly to penetrate the insulation on the mains conductor and make electrical contact with the core of the mains conductor. In one form of the invention one or more glass beads are formed on the inner surface of the collar opposite the screw so as to penetrate the insulation and abut the core when the screw is tightened against the core.

Description

United States Patent [191 Ball et al.

[ ELECTRICAL CONNECTORS [75] Inventors: Edmund Hugh Ball, Southampton;

James McConnell, Otterboume,

both of England [73] Assignees Pirelli General Cable Works Limited [22] Filed: Dec. 15, 1972 [21] Appl. No.: 315,431

[52] US. Cl. 339/97 P, 339/242, 339/272 R a [51] Int. Cl HOlr 7/04 [58] Field of Search .41339/95, 97-99,

[56] References Cited I UNITED STATES PATENTS 2,196,383 4/l940 Buchanan 339/272 UC 3,689,867 9/1972 Jenner 339/97 R FOREIGN PATENTS OR APPLICATIONS 298,542 ll/l965 Netherlands .t 339/97 R June 11, 1974 6,715,581 5/1968 Netherlands. 339/272 A 1,090,286 10/1960 Germany 339/97 R 1.277.977 9/1968 Germany 339/97 PrimaryExaminer-Joseph H. McGlynn Attorney, Agent, or Firm-Brisebois & Kruger [5 7] ABSTRACT An electrical connector for joining a branch conductor to an insulated mains conductor comprising a conductive collar for clamping about the mains conductor, means for connecting the branch conductor with the collar, and a screw engaged in the collar for screwing inwardly to penetrate the insulation on the mains conductor and make electrical contact with the core of the mains conductor. In one form of the invention one or more glass beads are formed on the inner surface of the collar opposite the screw so as to penetrate the insulation and abut the-core when the screw is tightened against the core.

7 Claims, 4 Drawing Figures memenmn 1914- 3 816 817 sum 20$ 2 BACKGROUND OF THEINVENTION This invention relates to electrical connectors.

More particularly, the invention is concerned with electrical connectors for making a mechanically strong electrical connection to a conductor, for example an insulated conductor of a power supply cable.

The need for an electrical connection between a main conductor and a branch or service conductor frequently arises when a house service joint is made to a main power cable to supply power to a house service cable; each conductor of the main cable, which is usually an underground cable of the kind having insulated solid aluminium conductors, has to be connected to an individual service cable conductor. For this purpose several types of clamp connector are currently available which are designed to be mechanically clamped to the main cable conductor to effect the desired electrical connection thereto.

Most of the existing clamp type connectors suffer from the following practical disadvantages:

i.. the connectors'exert little or no spring action on the clamped conductor, so that creep relaxation of the clamp on the conductor, particularly where this is of aluminium, can lead to slackening of the clamp;

ii. the main conductor insulation has to be removed to fit the clamp;

iii. because the insulation has to be removed, and because service joints are invariably made with the main conductor live, safety regulations usually require that two men are employed on such operations, in case of accident;

iv. the effectiveness of the electrical connection and its tightness is determined by the tightening of the clamp, and a torque spanner is necessary to ensure accurately repeatable sound connections.

An object of this invention is to facilitate the making of electrical connections, avoiding the abovementioned disadvantages.

SUMMARY OF THE INVENTION 1 The invention provides an electrical connector comprising:

a. an electrically conductive collar for embracing an c. an inwardly extending threaded bore formed in wardly to make contact with the conductor, further tightening shears off the outer end of the screw so that the outer end can then be withdrawn by the spanner or key.

Preferably the conductive collar comprises a metal block and a spring strip adapted to pass around the insulated conductor and resiliently engagable with the block to clamp the latter against the insulated conductor.

DESCRIPTION OF THE DRAWINGS Embodiments of the invention are illustrated by way of examples in the accompanying drawings, in which:

FIG. 1 is a diagrammatic cross-section of an electrical connector in accordance with the invention;

FIG. 2 is a diagrammatic cross-section of the connector of FIG. 1 when connected to a cable conductor;

FIG. 3 is a diagrammatic cross-section of a second connector in accordance with the invention, and

FIG. 4 is a diagrammatic cross-section of a third connector in accordance with the invention.

DESCRIPTION THE PREFERRED EMBODIMENTS effecting the joint. The connector 1 has an aluminium block 4 having a shallow V-shaped notch, with an apex angle of 120 for a 3-core cable (or alternatively for a 4-core cable), the two faces 5, 6 of which are arranged to engage the part-cylindrical outer surface of the conductor insulation 3 symmetrically on opposite sides of the apex.

A screw-threaded bore 7 extends throughthe block 4 at the apex of the notch in the latter, and is adapted to receive an aluminium screw 8 having a pointed or specially shaped sharp inner end 9. The outer end of the screw 8 is formed with an integral head 10 adapted to be engaged by an insulated box spanner (not shown). Alternatively, the screw 8 may be formed with a socket or slot at its outer end for engagement by an insulated key or screwdriver.

The connector 1 further, includes a steel spring clamping strip 11 which passes around the insulated conductor 2. The ends of the strip 11 are bent inwardly towards each other and are seated on

respective shoulders

12, 13 formed on the outer surface of the block 4 opposite the

notch faces

5, 6 so as to urge the

faces

5, 6 into clamping engagement with the conductor, the strip 11 itself being bent into a triangular shape to engage the flat faces of the insulation 3 of the sectorshaped conductor.

The connector block 4 is further provided with two through

bores

14, 15, perpendicular to the bore 7, pro- Y vided with perpendicular screw-threaded bores fitted with

pinching screws

17, 18 to form respective tunnel terminals for connection to respective service cable conductors (not shown).

To effect a service joint while the main cable is live, the connector 1, with service cable conductor(s) already connected in the tunnel terminals, is first placed in position around the insulated conductor 2, as shown in FIG. 1, without removing any of the conductor insulation 3, and is firmly clamped in position by the spring strip 11. The screw 8 is inserted in the bore 7 of the block 4 and an insulated box spanner placed on the head of the screw. The entire connector 1 is then enclosed in an insulating sheet 16 (FIG. 2) fastened with a suitable adhesive or fastener to form an enclosure with the box spanner protruding from the enclosure.

The screw 8 is now advanced by means of the insulated box spanner so that its pointed end 9 penetrates the insulation 3, making electrical contact with the live conductor 2. The screw 8 is further tightened to cause the head 10 to shear off at the outer face of the aluminium block 4, as shown in FIG. 2, the sheared-off head 10 being withdrawn with the box spanner. The opening in the insulating enclosure through which the spanner was withdrawn is finally closed to complete the connection.

Referring to FIG. 3 of the drawings, the connector shown therein is similar to that shown in FIGS. 1 and 2 and like parts between the Figures are denoted by like reference numerals. In the connector shown in FIG. 3, the service cable conductors, indicated at 20, 21 seat in

channels

22, 23 in the connector block 4, and pinching screws l7, 18 are threaded through bores in clamping strip 11 to bear in clamping manner on

conductors

20, 21. This provides a means of varying the spring pressure on the power supply cable core 2.

The connector shown in FIG. 4 is similar to that shown in FIG. 3. On its internal surface in contact with the conductor insulation 3, the strip 11 is provided with at least one projection of hard insulation in the form of two glass beads 24 arranged symmetrically on opposite sides of the axis of symmetry of the strip 11 and adhered to the latter. The beads 24 bite into the insulation 3 when the strip 11 is clamped in position, and have sufficient height to penetrate the insulation 3 and bear directly against the underlying conductor 2 when the clamping strip 11 is tightened.

The glass beads 24 are provided since, under load conditions, the cable conductor 2 can become hot, and this can lead to softening of the plastics insulation 3. In the absence of the projecting beads 24 of hard insulation in these circumstances, the insulation 3 would tend to flow from the regions where it is compressed, leading to a possible slackening of the connector 1. The presence of the beads 24 helps to ensure that the connector 1 remains firmly clamped regardless of softening of the insulation 3, since the conductor 2 is engaged directly by the screw 8 and the beads 24.

It will be appreciated that in the embodiments described, the resilience provided by the spring strip 11 minimizes the effect of any creep relaxation which might occur once the connector has been clamped to the mains conductor and which might otherwise lead to substantial slackening of the clamping force with consequential deterioration in the electrical contact with the mains conductor. Moreover, the connector may be fitted safely to a mains conductor without first removing the insulation from the conductor and whilst the conductor is live. Furthermore, the described embodiments enable repeatable sound connections to be made without use of a torque wrench being required.

What is claimed is: 1. An electrical connector comprising: a. an electrically conductive collar for embracing an insulated main conductor and comprising i. a block of conductive material, ii. a threaded bore formed through said block and extending inwardly of said collar,

iii. first and second shoulders formed on said block,

and

iv. a curved spring strip formed with inwardly bent ends engaged with said shoulders, whereby to receive a main conductor between said block and said strip;

b. a screw threadedly engaged in said inwardly extending bore and sharpened at its inner end so as to penetrate the insulation on a main conductor embraced by said collar when screwed inwardly against the mains conductor and makes electrical connection with the core of the conductor; and

c. branch connection means comprising i. at least one tunnel terminal comprising a channel formed in said block to receive a branch conductor and,

ii. a clamping screw threadedly engaged with said strip for screwing inwardly against said branch conductor.

2. An electrical connector as claimed in claim 1 wherein a V-shaped channel having an apex and inclined side face is formed in the surface of saidblock facing said strip with said bore extending through said block in said apex and said channel extending in an axial direction relative to said collar.

3. An electrical connector comprising:

a. an electrically conductive collar for embracing an insulated main conductor, said collar including a curved spring strip;

b. branch connection means associated with said collar for connecting at least one branch conductor thereto;

c. an inwardly extending threaded bore formed in said collar,

d. a screw threadedly engaged in said inwardly extending bore and sharpened at its inner end so as to penetrate the insulation on a main conductor embraced by said collar when screwed inwardly against that conductor and make electrical connection with the core of that conductor;

e. an inner surface on said collar for engaging a surface of a main conductor embraced by said collar; and

f. at least one projection of insulating material formedon said inner surface generally opposite said bore for penetrating the insulation and engaging the core of a main conductor embraced by said collar.

4. An electrical connector as claimed in claim 3, wherein said collar comprises a block of conductive material with said bore formed therein and having first and second shoulders and wherein said curved spring strip is formed with inwardly bent ends engaged with said shoulders, whereby to receive a main conductor between said block and said strip, and wherein each said projection of insulating material is a glass bead secured to said inner surface of said collar.

5. An electrical connector as claimed in claim' 4 wherein said branch connection means comprises at least one tunnel terminal formed in said block.

6. An electrical connector as claimed in claim 5, wherein each said tunnel terminal comprises a channel formed in said block to receive a branch conductor and a clamping screw threadedly engaged with said strip for screwing inwardly against the branch conductor.

7. In an electrical and mechanical connection between a main conductor comprising a conductive core and insulating material surrounding said conductive core and a branch conductor;

a. An electrically conductive collar embracing said main conductor and including a curved spring strip;

b. branch connection means mechanically and electrically connecting said branch conductor with said collar;

c. an inwardly extending threaded bore formed in tion to abut the surface of said core.

Claims

1. An electrical connector comprising: a. an electrically conductive collar for embracing an insulated main conductor and comprising i. a block of conductive material, ii. a threaded bore formed through said block and extending inwardly of said collar, iii. first and second shoulders formed on said block, and iv. a curved spring strip formed with inwardly bent ends engaged with said shoulders, whereby to receive a main conductor between said block and said strip; b. a screw threadedly engaged in said inwardly extending bore and sharpened at its inner end so as to penetrate the insulation on a main conductor embraced by said collar when screwed inwardly against the mains conductor and makes electrical connection with the core of the conductor; and c. branch connection means comprising i. at least one tunnel terminal comprising a channel formed in said block to receive a branch conductor and, ii. a clamping screw threadedly engaged with said strip for screwing inwardly against said branch conductor.

2. An electrical connector as claimed in claim 1 wherein a V-shaped channel having an apex and inclined side face is formed in the surface of said block facing said strip with said bore extending through said block in said apex and said channel extending in an axial direction relative to said collar.

3. An electrical connector comprising: a. an electrically conductive collar for embracing an insulated main conductor, said collar including a curved spring strip; b. branch coNnection means associated with said collar for connecting at least one branch conductor thereto; c. an inwardly extending threaded bore formed in said collar, d. a screw threadedly engaged in said inwardly extending bore and sharpened at its inner end so as to penetrate the insulation on a main conductor embraced by said collar when screwed inwardly against that conductor and make electrical connection with the core of that conductor; e. an inner surface on said collar for engaging a surface of a main conductor embraced by said collar; and f. at least one projection of insulating material formed on said inner surface generally opposite said bore for penetrating the insulation and engaging the core of a main conductor embraced by said collar.

5. An electrical connector as claimed in claim 4 wherein said branch connection means comprises at least one tunnel terminal formed in said block.

7. In an electrical and mechanical connection between a main conductor comprising a conductive core and insulating material surrounding said conductive core and a branch conductor; a. An electrically conductive collar embracing said main conductor and including a curved spring strip; b. branch connection means mechanically and electrically connecting said branch conductor with said collar; c. an inwardly extending threaded bore formed in said collar; d. a screw threadedly engaged in said bore with its inner end penetrating said insulation and making electrical contact with said core; and e. at least one projection of insulating material formed on said collar and penetrating said insulation to abut the surface of said core.