Electrical connectors – Metallic connector or contact having movable or resilient... – Duplicate receiving means having independently operated...
Patent
1997-10-03
2000-03-28
Abrams, Neil
Electrical connectors
Metallic connector or contact having movable or resilient...
Duplicate receiving means having independently operated...
411 5, 411309, 439814, H01R 1109
Patent
active
060424303
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to improvements in fasteners, in particular to improvements in shearable fasteners. Such fasteners are particularly suitable for securing electrical conductors to electrical connectors.
Electrical connectors are widely used for the jointing of two or more electrical cables or conductors. One form of such connector comprises a body with blind bores into which the ends of the conductors are inserted. Each conductor is fixed in place by threaded fasteners which are engaged with threaded bores in the wall of the blind bore and which hold the conductor against the opposite internal face of the bore. Commonly, Such fasteners have shearable heads which break off at a certain predetermined applied torque. This prevents excessive and possibly damaging, force being applied to the conductor and also results in the assembled joint having a reasonably smooth profile.
Known systems of the type described above suffer from the disadvantage, however that because the conductors joined together using the connector may take various different sizes it is necessary for the shearable fasteners to be produced in a corresponding range of lengths in order to ensure that the assembled joint has the desired smooth profile. This means that a fitter must carry a suitable supply of all different sizes and can result in mistakes being made and inappropriate fasteners being used.
British Patent Application No GB 2281599 describes a threaded fastener which, when applied using a special tool, is arranged to shear at an axial position along its length corresponding to the surface of an electrical connector with which it is engaged. However, such a fastener can only be used in conjunction with such a special tool.
There has now been devised an improved fastener, of particular use in securing an electrical conductor to an electrical connector, which overcomes or substantially mitigates the above mentioned disadvantage.
SUMMARY OF THE INVENTION
According, to the invention, there is provided a shearable fastener having a threaded shank adapted for engagement with a threaded bore and a head portion formed for engagement with a drive tool, the shank being formed with a series of axially separated weakenings defining a series of shear planes, wherein the weakenings are formed such that the applied torque necessary to cause the shank to shear increases progressively from the shear plane furthest from the head portion to the shear plane nearest the head portion.
The fastener according to the invention is advantageous primarily in that as the fastener is engaged with the threaded bore the shear planes enter the threaded bore in succession. As the thread on either side of each shear plane on the shank engages with the threaded bore, that shear plane becomes supported and this increases the torque required to shear the fastener at that point. When rotation of the fastener is prevented, the fastener will shear at either the shear plane immediately external to the threaded bore or at a partially supported shear plane within but immediately adjacent to the external end of the threaded bore, depending on which requires the lower shear torque. In either case, the fastener will shear substantially flush with the external end of the threaded bore with a minimal length of shank standing proud of the threaded bore. Thus, the same fastener can be used for securing conductors of differing diameter. No special tools are required to ensure that the shank of the fastener shears at the desired shear plane. The drive tool may, for example, be a conventional spanner or socket wrench, since the drive tool plays no part in determining the plane in which the shank of the fastener shears.
According to a further aspect of the invention, there is provided an electrical connector comprising first and second connector parts between which an electrical conductor may be received, and a threaded fastener engageable with a threaded bore in the first connector part such that the fastener may engage the conductor, either directly
REFERENCES:
patent: 2842180 (1958-07-01), Brown et al.
patent: 3865007 (1975-02-01), Starback
patent: 3876279 (1975-04-01), Underwood
patent: 4199216 (1980-04-01), Gryctko
Abrams Neil
B & H (Nottingham) Limited
Patel T. C.
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