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(11) | EP 0 009 060 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Eccentric bore electrical terminal |
| (57) A female part (8) of the terminal has a wire receiving first bore (22) with an eccentric
counterbore (24) in which is a plug (40) having a wire receiving second bore (42)
aligned with the first bore (22) and being eccentric with respect to the axis of the
plug (40). The plug (40) is rotatable in the counterbore (24), to an extent limited
by stop surfaces (36 and 52), so that a wire when received in the bores (22 and 42)
is constricted. A body (38) projects from the counterbore (24). In order to simplify the manufacture of the terminal and to adapt it for use with aluminium wire, the plug (40) is rigidly connected to the body (38), the stop surfaces (36 and 52) being external surfaces of the female part (8) and the body (38) and being so relatively positioned that during the relative rotation, substantial torsional shearing forces are applied to the wire. |
[0001] This invention relates to the art of making line connections and in particular to an eccentric bore electrical terminal for this purpose.
[0002] There is described in United States Patent Specification No. 2,264,754 an eccentric bore electrical terminal comprising a female part having a first bore communicating with a counterbore which is laterally offset therefrom, a plug received in the counterbore and having an eccentric second bore there through coaxial with the first bore, means retaining the plug in the counterbore whilst permitting relative rotation between the female part and the plug to constrict an electrical conductor when such is received in the bores, a body projecting from the female part and being rotatable relative thereto, the body being connected to the plug, and stop surfaces effective to limit the relative rotation between the plug and the female part to a predetermined angle.
[0003] In this known terminal, the plug is eccentrically received in the body so as to be drivable in rotation by the body, relative to the female part, the plug being movably mounted in the female part in such a way that its main component of movement relative to the female part is transverse to the axis of the first bore, the angle of relative rotation between the plug and the female part being limited only to a few degrees by the stop surfaces which are provided within the counterbore. The construction of the known terminal is such that the angle of relative rotation cannot be increased significantly even by modifying the arrangement of the stop surfaces.
[0004] The problem of which the invention is intended to solve is that of producing an electrical terminal of the eccentric bore type which is not only more economical to manufacture than the known terminal but which is capable of making effective and permanent electrical connection with an aluminium electrical conductor, especially a multi-stranded aluminium wire.
[0005] The invention proceeds from the realisation that the plug and the body should constitute a single unit, the stop surfaces being provided exteriorly thereof, and the permitted angle of rotation between the plug and the body being substantial e.g. 180° so that a cold welded joint is achieved between the conductor and the terminal.
[0006] According to the invention therefore an eccentric bore electrical terminal as defined in the second paragraph of this specification is characterised in that the plug is rigidly connected to the body and the stop surfaces are constituted by co-operating external surfaces of the female part and of the body, the predetermined angle being such that cold flow is produced between the conductor and the bore walls by substantial torsional shearing forces at the transition zone between the first bore and the counterbore to produce a cold welded joint between the conductor and the terminal, where the cross-sectional area of the conductor approximates to that of the bores.
[0007] It has been found that these substantial torsional shearing forces cause, where the conductor is a multi-stranded aluminium wire, the alumina coatings of the strands to become separated from the underlying metal and cold flow to be produced amongst the strands so that they are welded into a substantially homogeneous electrically conductive mass. The minimal rotational component of movement of the plug achievable in a known terminal could produce no such effect.
[0008] Since the terminal of the present invention comprises only two relatively simple male and female parts and since the stop surfaces are formed externally of these parts, the terminal can be manufactured very economically, e.g. by die casting. The fact that the plug and the female part have been relatively rotated to the full permitted extent can easily be ascertained by visual inspection, since the stop surfaces are external.
[0010] Some patent specifications which are illustrative of the state of the art at this time are United States Patent Specifications Numbers 1,141,882, 1,872,048, 1,989,861, 2,074,393, 2,121,984, 2,336,175, 2,920, 305, 3,125,397, 3,235,944, 3,280,856, 3,329,928, 3,765,420, 3,931,726 and 4,029,383; and United Kingdom Patent Specification No. 28,156/1913.
[0011] For a better understanding of the invention reference will now be made by way of example to the accompanying drawings, in which:-
Figure 1 is a perspective view of the bared end portion of an electrical cable having a multi-stranded electrically conductive core;
Figure 2 is a perspective view of a two-part eccentric bore electrical terminal in accordance with a first embodiment of the invention, secured to the bared end portion of the cable core;
Figure 3 is a diagrammatic, exploded perspective view of the terminal with parts not shown;
Figure 4 is an enlarged axial-sectional view of the terminal showing the parts of the terminal in assembled relationship prior to the terminal being secured to the bared end portion of the cable core;
Figure 5 is an end view taken in the direction of the arrows of V - V of Figure 4;
Figure 6 is a view taken on the lines VI - VI of Figure 7;
Figure 7 is a similar view to that of Figure 4 but showing the positions of the parts after the terminal has been secured to the bared end portion of the core;
Figure 8 is a perspective view of a two-part eccentric bore electrical terminal in accordance with a second embodiment of the invention, secured to the bared end portion of the cable core;
Figure 9 is an exploded perspective view of the terminal of Figure 8;
Figure 10 is an axial-sectional view of the terminal of Figures 8 and 9 showing the parts thereof in assembled relationship prior to the terminal being secured to the bared end portion of the cable core;
Figure 11 is an end view of Figure 10;
Figure 12 is a view taken on the lines XII - XII of Figure 13;
Figure 13 is a view similar to that of Figure 10 but showing the positions of the parts after the terminal has been secured to the bared end portion of the core;
Figure 14 is a perspective view of one part of the terminal of Figures 7 to 13; and
Figure 15 is a perspective view of the other part of the terminal of Figures 7 to 13, displaced through 180° with respect to the position in which such part is shown in Figure 9.
[0012] The first embodiment will now be described with reference to Figures 1 to 7. The terminal which is generally referenced 2, is intended to be secured to the bared end portion of the electrically conductive core 4 of a cable 6 which may be for example a heavy gauge cable of aluminium or copper, for example of AWG (American) Wire Gauge) 6 through AWG 10, having a multi-stranded core as shown, the strands thereof being referenced 58.
[0013] The terminal 2 comprises a female part 8 and a male part lO, which parts may conveniently be produced by die casting. The parts 8 and 10 are preferably made of aluminium alloy where the core 4 is of aluminium. The female part 8 has a body 12 having oppositely facing sides 14 and 16. A ring tongue 18 extending from the side 16 has a hole 20 for receiving a fastener (not shown) for attaching the terminal 2 to an electrical bus-bar (not shown), or other support.
[0014] A bore 22 for receiving the core end portion extends into the body 12 from the side 16 thereof, the diameter of the bore 22 being substantially equal to, and slightly greater than, the diameter of the core 4. A plug receptacle in the form of a counterbore 24 having a base 28 extends inwardly from the side 14 and communicates with the inner end of the bore 22 intermediate the sides 14 and 16 of the body 12. The axis of the counterbore 24 is offset downwardly (as seen in Figures 4 and 5) from that of the bore 22. A radius 26 is provided about the intersection of the bore 22 and the counterbore 24 in order to prevent shearing of the core 4, when the terminal is being secured thereto as will be described below. The mouth of the counterbore 24 is advantageously flared as shown at 30 to facilitate assembly of the parts 8 and 10 as will also be described below. A lip 34 extending from the side 14 of the body 12, in the opposite direction to the tongue 18 and across full width of the side 14 has a central arcuate recess 36 in its inner face 70.
[0015] The male part 10 has a polygonal body 38 from one side 39 of which extends a circular cross-section cylindrical plug 40. A bore 42 extending from the opposite side 41 of the body 38 and through the full length of the plug 40, is of a diameter which is substantially the same as that of the bore 22, the axis of the bore 42 being offset upwardly (as seen in Figure 4) from that of the plug 40. The leading end i.e. the free end, of the plug 40 has a bevelled outer edge 44 to facilitate assembly of the parts 8 and 10, and an internal radius 43 in order to avoid shearing of the core 4, when the terminal is being secured thereto as will be explained below. A fillet 46 is provided between the plug 40 and the body 38 in order to avoid such stress concentration occuring in the core 4 as would produce voids therein as the terminal 2 is secured thereto.
[0016] The body 38 is shaped, as seen in cross-section, as a regular polygon having sides 50, 52, 54, 56, 58 and 60, the centre 66 of such polygon being located to the left (as seen in Figure 5) of the axis 64 of the plug 40. As shown in Figure 5, the axis 62 of the core 42 is in vertical alignment with the axis 64 and lies above the centre 66 when the parts 8 and 10 are relatively angularly positioned as shown in Figure 5.
[0017] The parts 8 and 10 are secured in assembled relationship by means of a split ring 68 engaged in a circumferential recess 48 in plug 40, which ring 68 snaps into a circumferential recess 32 in the counterbore 24 when the parts 8 and 10 have been assembled as shown in Figure 4. The radius 43, the bevelled edge 44 and the split ring 68 are not shown in Figure 3.
[0018] In their assembled position the parts 8 and 10 are so oriented that the side 58 of the body 38 is adjacent to the face 70 of the lip 34 as shown in Figure 5. It will be apparent from Figure 5 that the parts 8 and 10 are so dimensioned that the apex 57 defined by the sides 56 and 58 is slightly to the right hand (as seen in Figure 5) side of the recess 36 in the face 70. The parts 8 and 10 are supplied to the user in the assembled condition shown in Figures 4 and 5 so that the male part 10 can be rotated through an angle of substantially 180° until the parts 8 and 10 are relatively positioned as shown in Figure 6.
[0019] In use of the terminal, the end portion of the multi-stranded cable 6 is stripped of its insulation and the bared end portion of the core 4 is inserted through the aligned bores 42 and 22 from the side 41 of the body 38. The male part 10 is then rotated relative to the female part 8 by means of wrenches or spanners, for example, through an angle of 180° until the side 52 lies against the surface 70 (Figures 6 and 7). The parts 8 and lO cannot then further be relatively rotated in the same sense because the apex 51 defined by the sides 52 and 50 is located at a substantial distance to the right (as seen in Figure 6) of the recess 36, such rotation being prevented by the abutment of the side 52 and the face 70.
[0020] During relative rotation of the parts 8 and 10, the passageway initially defined by the aligned bores 22 and 42 is greatly constricted in the vicinity of the base 28 of the counterbore 24 so that the core 4 is drastically constricted and is thus deformed and compressed in this transition zone between the bores 22 and 42, cold flow being produced between the core 4 and the walls of the bores 22 and 42. As a result of this, a high pressure cold welded electrical connection is provided between the terminal 2 and the core 4.
[0021] The radii 26 and 43 provide smooth transition surfaces for the core 4 in the transition zone so that the strands of the core 4 are not sheared, even if the core 4 comprises very fine aluminium wire strands.
[0022] During the rotation of male part 10 relative to female part 8, the walls of both the bores 22 and 42 exert both transverse, and rotational or torsional, shearing forces on the strands 58 of the core 4. Both of these shearing modes cause the strands 58 to move relative to one another. Initially, the shearing forces cause the strands 58 to compact, but plastic deformation of the strands 58 and cold flow amongst the strands 58 shortly follows. The rotational shearing force and the relative movement of the strands 58 under the forces exerted by the constricting walls of the bores 22 and 42 have a scraping or abrasive action on the strands 58 which is transmitted through most of the strands 58, so that where these strands are of aluminium, the brittle alumina coating (which is an insulator) thereon is separated from the underlying metal. As the constriction of the core 4 continues, a cold welded joint is formed between metal surfaces of adjacent strands as well as between the outer strands 58 and the walls of the bores 22 and 42, the strands being welded into a substantially homogeneous electrically conductive mass. The electrical contact formed by the said cold flow under the rotational shearing forces is far better than that which would be formed by the action of transverse shearing forces alone.
[0023] Another significant advantage of the terminal described above is that it is comprised only of two parts, if the split ring 68 (which is a standard item) be excluded. The terminal can readily be secured to the core 4 by the use e.g. of open wrenches by an unskilled technician at a work site. Further, the electrical connection between the terminal 2 and the core 4 can be visually inspected, so that it is apparent to the eye whether or not the terminal 2 has been properly secured to the core 4.
[0024] The terminal may, for example, otherwise be constructed as a splicing device for connecting the ends of two cable cores, or as a commoning block for connecting two or more cable cores at a common position.
[0025] The second embodiment of the invention will now be described with reference to Figures 8 to 15.
[0026] The terminal, which is generally referenced 102 comprises a female part 104 and a male part 106, which also can economically be manufactured by die-casting and are preferably made from an aluminium alloy where the terminal is to be secured to a multi-stranded aluminium cable core. Although the terminal may be made for use with cable cores of other electrically conductive materials, for example copper, the terminal is specifically adapted for use with stranded aluminium cored cable, especially heavy gauge aluminium cable, for example of A.W.G. 2 or 1.
[0027] The female part lO4 comprises a generally rectangular body 112 having formed integrally therewith a ring tongue 108 having a fastener-receiving hole 110. The body 112 has two opposite chamfered edges 113 and 113'. A bore 116 extending from a rear face 114 of the body 112 communicates with a counterbore 118 extending inwardly from the opposite face 117 (Figure 14) of the body 112, the axis of the bore 116 being offset from that of the counterbore 118, as best seen in Figure 10. The transition between the bore 116 and the counterbore 118 is defined by a radiused edge 119 extending completely around the bore 116. A rib 124 extends about the interior periphery of the counterbore 118 through 180°. A transverse passage 122 extends from the lower (as seen in Figures 10 and 13) external face 123 of the part 104 into the counterbore 118 to define one lateral face of which is provided by the base 101 of the counterbore 118. The passage 122 may be formed during die-casting of the part 104. The inner face 115 of a lip 126 extending from the right hand (as seen in Figures 9, 10, 13 and 14) lower part of the face 117 is radially outwardly offset from the circumferential edge of counterbore 118. A boss 121 in the wall 120 of the counterbore 118 remote from the lip 126, and which was formed after assembly together of the parts 104 and l06 extends into a groove 125 in the latter, loosely to retain the parts l04 and l06 together as initially assembled.
[0028] The male part 106 consists of a plug 128 formed integrally with a polygonal, substantially rectangular body 130 having opposite chamfered edges 132 and 132'. The portion of the body 130 adjacent to its rear, or right hand (as seen in Figures 10 and 13) face 131 has a cross-section which coincides with that of the body 112. The body 130 is formed, immediately adjacent to the plug 128, with an arcuate surface 138 extending through an arc of 180°, and being bounded by flat faces 140 and 142. The surface 138 is tangential to two adjacent peripheral flats 134 and 136 of the body 130. Between the groove 125 and the surface 138 there is formed on the plug 128, a circular cylindrical surface of a right circular cylindrical portion 146 of the plug 128. The axially outer surface of a semi-circular rib 150 extending about the free end portion of the plug 128 coincides with the free end face 152 of the plug 128, the groove 125 being defined by the axially inner surface of the rib 150 and the axially outer surface of the portion 146. A bore 154 extending entirely through the plug 128 and the body 130 is of a diameter which is substantially equal to that of the bore 116, the axis of bore 154 being offset from that of the plug 128. The bore 154 has an internal radius 103 at its end adjacent the bore 116.
[0029] In the initially pre-assembled condition of the parts l04 and 106, as shown in Figures 10 and 11, with the plug 128 received in the counterbore 118, and the bores 116 and 154 in alignment, the common axis 164 (Figures 10 and 11) of the portion 146 and of the counterbore 118 is offset from the common axis 162 of the bores 116 and 154. The face 152 is immediately adjacent to the transition zone between the bore 116 and the counterbore 118 and the rib 150 is aligned with the passage 22. Relative rotation between the parts l04 and l06 can only occur about the axis 164.
[0030] In use of the terminal, the bared end of the core 4 of the cable 6 is inserted into the aligned bores 116 and 154 from the base 131 and part 106 is rotated relative to the part l04 in the direction of the arrow A in Figure 12 (i.e. in a clockwise, as seen in Figures 11 and 12 sense) about the axis 164, so that the rib 150 is received in the passage 122 thereby to prevent relative axial movement between the parts 104 and 106. Axial forces tending to separate the parts 104 and 106 during their mutual rotation are resisted by the interengagement of the ribs 150 and 124. The arcuate surface 138 is immediately adjacent to the face 115 of the lip 126 of female part 104, so that the part 106 can rotate (through an arc of 180°) until the flat 134 of the male part 106 abuts the face 115 so that the part 106 can be rotated no further in the same sense. It will be apparent from Figure 13 that the core 4 is subjected to both transverse and rotational shearing forces as in the case of the first embodiment, a cold welded joint being produced between the core and the terminal by cold flow between the core and the bore walls. The chamfered edge 113 of the part 104 is now aligned with the chamfered edge 132 of the part 106, the chamfered edge 113' of the part 104 being in alignment with the chamfered edge 132' of the part 106, thereby indicating that the core 4 has been correctly terminated i.e. that the parts 104 and 106 have been relatively rotated through the required 180°, so that the bores 116 and 154 are offset to their maximum extent.
1. An eccentric bore electrical terminal (2 or 102) comprising a female part (8 or
104) having a first bore (22 or 116) communicating with a counterbore (24 or 118)
which is laterally offset therefrom, a plug (40 or 128) received in the counterbore
(24 or 118) and having an eccentric second bore (42 or 154) there through coaxial
with the first bore (22 or 116), means (32, 48, 68; or 121 125) retaining the plug
(40 or 128) in the counterbore (24 or 118) whilst permitting relative rotation between
the female part (8 or 104) and the plug (40 or 128) to constrict an electrical conductor
(4) when such is received in the bores (22 or 116; or 42, 154), a body (38 or 130)
projecting from the female part (8 or 104) and being rotatable relative thereto, the
body (38 or 130) being connected to the plug (40 or 128), and stop surfaces (52, 70
or 115, 134) effective to limit the relative rotation between the plug (40 or 128)
and the female part (8 or 104) to a predetermined angle; characterised in that the
plug (40 or 128) is rigidly connected to the body (28 or 130) and the stop surfaces
are constituted by co-operating external surfaces (52 and 70 or 115 and 134) of the
female part (8 or 104) and of the body (38 or 130), the predetermined angle (180°)
being such that cold flow is produced between the conductor (4) and the bore walls
by substantial torsional shearing forces at the transition zone between the first
bore (22 or 106) and the counterbore (24 or 118) to produce a cold welded joint between
the conductor (4) and the terminal (2 or 102), where the cross-sectional area of the
conductor (4) approximates to that of the bores (22 or 116; and 42 or 154).
2. A terminal according to Claim 1, characterised in that the adjacent edges of the
first and second bores (22 and 42; or 116 and 154) are formed with radii (26 and 43;
or l03 and 119).
3. A terminal according to Claim 1 or 2, characterised in that one of the stop surfaces
is provided on a lip (34 or 126) projecting from the female part (8 or 104) beside
the body (38 or 130), the other stop surface being provided by a side (58 or 136)
of the body (38 or 130).
4. A terminal according to Claim 3, characterised in that the body (38) is shaped,
as seen in cross-section, as a regular polygon (50, 52, 54, 58 and 60), the plug (40)
extending from the body (38) at a position offset from the centre of the polygon,
the lip (34) having a concave recess (36) facing the body (38) and receiving apices
of the polygon during the relative rotation between the plug (40) and the female parts
(8).
5. A terminal according to any one of the preceding claims, characterised in that
the retaining means comprises aligned peripheral recesses (32 and 48) in the counterbore
(24) and on the plug (40) and a split retaining ring (48) received in the recesses.
6. A terminal according to Claim 1, 2 or 3, characterised in that a rib (150) extends
about a part of the periphery of the plug (128), the counterbore (24) being formed
with an integral recess (122) which receives the peripheral rib (150) during the relative
rotation between the plug (128) and the female part (104) to restrain relative axial
movement there between.
7. A terminal according to Claim 6, characterised in that the rib (150) is received
between a shoulder (124) extending inwardly of the counterbore (118) and the base
(101) of the counterbore (118).
8. A terminal according to Claim 6 or 7, characterised in that an internal boss (121)
in the counterbore (118) projects there into on the side of the rib (150) remote from
the base (101) of the counterbore (118) to restrain withdrawal of the plug (128) from
the counterbore (118).
9. A terminal according to any one of Claims 1 to 3, or 6 to 8, characterised in that
the stop surfaces comprise a first flat surface (126) on the female part (104) and
a second flat surface (134) on the body (130), the second flat surface (134) being
adjacent to one end of an arcuate surface (138) extending peripherally of the body
(130), and being tangential to such arcuate surface (138).
lO. A terminal according to any one of the preceding claims, the conductor being received
in the bores and being a multi-stranded aluminium conductor, characterised in that
the predetermined angle (180°) is such that cold flow is provided amongst the strands
(58) of the conductor (4) so that they are welded into a substantially homogeneous
electrically conductive mass.