CA1157541A - Heat-recoverable connector for electrical connections - Google Patents
Heat-recoverable connector for electrical connectionsInfo
- Publication number
- CA1157541A CA1157541A CA000273739A CA273739A CA1157541A CA 1157541 A CA1157541 A CA 1157541A CA 000273739 A CA000273739 A CA 000273739A CA 273739 A CA273739 A CA 273739A CA 1157541 A CA1157541 A CA 1157541A
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- Canada
- Prior art keywords
- conductor
- band
- connector
- heat
- recoverable
- Prior art date
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Abstract
ABSTRACT
Barth connections are made to substrates such as the sheath of an electrical cable by using a heat- recoverable connector which is positioned wholly or partially around the substrate and which is subsequently recovered into gripping engagement therewith The connector preferably consists of a band made from a memory metal and is preferably provided with means for independently receiving one or more other substrate prior to recovery. The heat-recoverable member is preferably of discontinuous cross-section, e.g. comprises a band with a gap in its circumference, in order to obtain substantial dimensional recovery. The invention is especially applicable to the formation of connections between substrates in side-by-side relationship.
Barth connections are made to substrates such as the sheath of an electrical cable by using a heat- recoverable connector which is positioned wholly or partially around the substrate and which is subsequently recovered into gripping engagement therewith The connector preferably consists of a band made from a memory metal and is preferably provided with means for independently receiving one or more other substrate prior to recovery. The heat-recoverable member is preferably of discontinuous cross-section, e.g. comprises a band with a gap in its circumference, in order to obtain substantial dimensional recovery. The invention is especially applicable to the formation of connections between substrates in side-by-side relationship.
Description
p 1 1$7S~
BACKGROUND OF THE INVENTION
This invention relates to connectors, and more particularly to connectors for making an electrical connection between two or more substrates.
The usual method for attaching an earth lead to a solid outer conductive sheath o~ an electrical cable is by soldering, However, although a good electrical connection can be obtained by this method, it is both operator dependent and time consuming, and the resultant connection is not mechanically strong. Furthermore, it is not easy to form soldered connections to aluminium sheathed cables, and difficulties have also been experienced in soldering an earth lead to the copper sheath of a mineral insulated cable, of the type found for example in fire protection systems, since the copper sheath is frequently covered with a tightl~y adhering coating of oxide, which necessitates vigorous abrasion of the surface to expose the metal, with the consequent risk o~ damage to the copper sheath.
In certain types of electrical apparatus there is a need to connect an earth lead to an edge of a metal surface, and it is known to use a clamp connector pro-vided with a screw for this purpose. However with such edge connectors it is rrequently difficult to obtain a connection having a good long term electrical performance.
.
.
1 157~1 There is thus a need for a method of connection which may provide a good mechanical and electrical connection between a variety of substrates and for a connector which is simple to install and reliable in service.
- 2a -l 1575~1 SU~RY OF THE INVE~ION
According to the present invention, the connection is made by the use of a connector comprising a heat recoverable member which is recovered into gripping engagement with at least one of the substrates.
In one aspect of the present invention, therefore, there is provided a method of making an earth connection to a substrate in which there is used a connector comprising a heat recoverable member which is fitted wholly or partly around the substrate and is recovered into gripping engage-ment therewith.
The present invention provides a method of electrically connecting a first conductor to a second conductor, which comprises (a) placing at least partly around said first conductor a dimensionally heat recoverable memory metal con-nector having a discontinuous cross-section, having means integral therewith for facilitating attachment ....
of said second conductor and having parts capable of independently receiving the conductors in side-by-side relationship, (b) positioning ~ithin and attaching to the connector said second conductor in side-by-side relationship with said first conductor,and (c) heating said connector to cause it to recover into electrical connection with said first conductor.
Step (b) may be carried out before, during or after step (c~. Advantageously, the connector comprises means _ 3 _ , .
} 1~75~1 for independently receiving a plurality of conductors prior to recovery.
The present invention also provides a method of electrically connecting a first conductor to a second conductor, which comprises (a) placing at least partly around said fi.rst conductor a first band of a dimensionally heat recoverable memory metal connector having in cross-section the form of a broken figure of eight providing first and second discontinuous bands in side-by-side relationship, (b) attaching to the connector said second conductor,and (c) heating said connector to cause it to recover into gripping engagement with said first conductor, step (b) being carried out before, during or after step (c).
Advantageously, the second conductor is positioned at least partly within the second band, and steps (b) and (c) are carried out simultaneously.
The present invention further provides a method of electrically connecting a first conductor to a second conductor, which comprises (a) placing at least partly around said first conductor a connector band of dimensionally heat recoverable memory metal, the band being provided with at least one peripheral slot for receiving a second conductor, the band and the slot being so shaped that upon recovery the first and second conduc~ors are each 1 ~57Sdl independently gripped by cont~action o~ the band and the slot, (b) placing said second conductor within said slot, and (c) heating the connector to cause recovery into gripping engagement with said first co~ductor by contraction of the band and with said second conductor by con-traction of the slot.
Advantageously, the band is formed with a channel shaped deformation extending across the width of the band in an axial direction, there being situated within the channel an upstanding bridge portion bounded on each side by slots cut in the channel, the slots being adapted to receive the second conductor therethroughO
The present invention still further provides a method of making an earth connection to a conductor in which there is used a connector comprising a dimensionally heat recoverabLe memory metal band which has a discontinuous cross-section and which is fitted wholly or partly around the conductor and a second conductor and is recovered into gripping engagement with the conductors and ~orces them together to make the earth connection The invention also provides connectors suitable for use in these methods~ Accordingly, there is provided a connector comprising a dimensionally heat recoverable memory metal member which has a discontinuous cross-section and which is constructed so as to fit wholly or partly around, and be recovered into gripping engagement with,a ~irst conductor and which is provided with means integral - 4a .
1 ~575~1 therewith for independently receiving, and facilitating the mechanical attachment of, a second conductor positioned within the heat recoverable member in side-by-side relationship to the first, and wherein the connection between the members is made on recovery of the member.
Advantageously, the heat recoverable member has the form, in cross-section, of a broken figure of eight, hereby providing two discontinuous bands in side-by-side relationship, The invention further provides a connector comprising a dimensionally heat recoverable memory metal band which has a discontinuous cross-section and which is constructed so as to fit wholly or partly around, and be recovered into gripping engagement with, a first conductor, the band bei-ng provided with at least one peripheral slot adapted to receive a second conductor, the second conductor being of smaller diameter than the first conductor, and the band and the slot being so shaped that upon recovery the-first and second conductors are each independently gripped by contraction of the band and the slot respectively, Advantageously, the band is formed with a channel shaped deformation extending across the width of the band in an axial direction, there being situated within the channel an upstanding bridge portion bounded on each side by slots cut in the channel, the slots being adapted to receive the second conductor therethrough.
The invention still further provides a connector comprising a dimensionally heat recoverable memory metal - 4b ~
~, ~.
~Y
l 1575~1 band which has a discontinuous cross-section and which is constructed so as to fit wholly or partly around, and be recovered into gripping engagement with, a first conductor and which is provided with a recess in one or both of its jaws for independently receiving, and facilitating the mechanical attachment of, a second conductor In an especially preferred embodiment of a conductor according to the invention the heat recoverable member is of discontinuous cross-section and is arranged to recover in a bending mode. For example, where the connector com-prises a heat recoverable band, the band is preferably discontinuous, being provided with a gap in its circum-ference. The width of the gap is preferably small relatlve to the diameter of the band. A discontinuous band has the ~1575~
particular advantage that it can be given a bending deformation which combines tensional and compressive stresses with the result that higher effective degrees of dimensional recovery can be attained than with a continuous band. The extra recovery is especially advantageous insofar as it makes dimensional tolerance requirements much less critical.
This extra dimensional recovery is especially advantageous when the heat-recoverable member is made from a memory metal (as described below) because such metals e~hibit a relatively low degree of recoverable strain. Fu~thermore, these metals are usually resilient in their recovered state and the presence of a dis-continuity similarly increases the degree of resiliently recoverable deformation which can be imparted to them in _ the recovered state. Thus members exhibiting such a discontinuity are more able to accommodate dimensional changes which may occur in the substrate after installa-tion (for example during heat aging).
The provision ofa discontinuity also greatly facilitates the application of the connector to sub-strates such as edges. A further advantage, where the connector is used to form a connection to a cable sheath, is that on recovery the edges of the discontinuity in the band are forced into a firmer gripping relationship with the sheath, and if the sheath material is sufficiently malleable a small portion thereof may even be extruded ~ 15~5~ 1 into the discontinuity thus providing an additional protection against circumferential movement of the connector relative to the sheath.
In some applications, it ma~ be advantageous to form the connection to one of the substrates, for example an earth lead, by, for example, crimping or soldering, and the connectors may be provided with means, such as for example a flange or lug, or a solder pot, for this purpose. In another embodiment, the connector may be provided with an upstanding threaded portion and a complementary nut for attach-ment of the earth lead.
In general, however, it will be preferred that the recovery of the heat-recoverable member acts as the sole agent for forming the connection, In a preferred embodiment according to the invention, the connector comprises a heat-recoverable - band adapted to fit around a first substrate, the band being provided with at least one peripheral slot adapted to receive a second substrate, the second substrate being of smaller diameter than the first substrate, and the band and the slot being so shaped that upon recovery the first and second substrates are each independently gripped by contraction of the band and the slot respectively. It is a particular feature of certain embodiments of the present invention that the band can grip the first substrate by radial contraction 1 1575~ ~
and the second substrate by contraction of the peri-pheral slot, in a single heat recovery operation. The band may, for example, be formed with a channel-shaped deformation, preferably extending across the width of the band in an axial direction, there being situated within the channel an upstanding bridge portion kounded on each side by slots cut in the channel, the slots being adapted to receive the second substrate there-through.
Pxeferably the heat-recoverable member is formed from a memory metal. Amongst suitable memory metals for use ln the present invention there may be mentioned various alloys of titanium and nickel which are des-cribed, for example in UnS. Patents Nos. 3,174,851, 3,351,463, 3,753,700, 3,759,552, British Patents - Nos. 1,327,441 and 1,337,442 and NASA Publication SP 110, "55-Nitinol - The Alloy with a Memory, etc"
(U.S. Government Printing Office, Washington, D.C.
1972). The property of heat-recoverability has not, h~wever, been solely confined to such titanium-nickel alloys Thus, for example, various beta-brass alloys have been demonstrated to exhibit this property in e.g. N Nakanishi et al, Scripta Metallurqica 5, 433-440 (Per~ammon Press 1971) and such materials may be doped to lower their transition temperatures to cryogenic regimes by known techniques. Similarly, 304 stainless steels have been shown to enjoy such 5 ~ ~
characteristics, E, Enami Q al, id at pp~ 663-68.
In general these metals have a transition tempera-ture within the range of from -196C to +135C, especially from -196C to -70C (this being the lowest tempeature they are liable to encounter during everyday use), and thus may be broug~t into their martensitic state by immersion in liquid nitrogen, However, more recently, it has been found possible to "precondition"
memory metals so as transiently to raise their trans-ition temperature. This enables the articles made fromsuch alloys to be kept at room temperature prior to use, when they can be recovered by heating. Such pre conditioning methods, which eliminate the need for liquid nitrogen during storage and transportation, are described, for example, in German Patent Applications oS 26 03 878 and OS 26 03 911 published 18th August, 1976.
~ he preferred memory metal for use in the present invention is heat-recoverable brass since this has excellent electrical properties and permits soldered connections to be madeO
As previously mentioned, the present invention is particularly adapted to the connection of earth leads to the conductin~ sheaths of electric cables.
In a particularly preferred embodiment according to this aspect of the invention the connector is positioned within a heat-recoverable plastic sleeve 1 15~5~
so that on recovery the sleeve provides an environ-mental seal for the connection made by the article.
In terminations and splices for mineral insulated cables the heat-recoverable sleeve is preferably provided with a fusible insert as described in British Patent No. 1,098,304. Such an arrangernent provides a single heat recoverable part which in one operation is capable of providing an earth connection and a seal for the mineral insulated cable termina-tion or splice. Preferably, the temperature at whichthe connector recovers is lower than the temperature of recovery of the heat-recoverable sleeve and the temperature of fusion of the ~usible insert.
However another application for the connectors of the present invention is in the earthing of leads _ to edges of electrical apparatus. In such an edge connector, one part is adapted to receive and grip the edge upon recovery and another part is adapted to receive the earth lead. For example, such a connector may comprise a discontinuous band having a recess in one or both of its jaws. The discontinuous band is posi tioned about the edge and the earth lead is positioned in a recess. Upon recovery, the jaws move together to grip the edge and thereby force the earth lead into connection with it. Alternatively, the earth lead may, in some cases, be simply positioned within the discontinuous band next to the edge.
_ g _ ~ 1575~
In another embodiment of a connector designed to make an earth connection, the heat-recoverable member has the form, in cross section, of a broken figure of eight thereby effectively providing two discontinuous bands in side-by-side relationship. Then, for example, the edge may be placed within one band and the earth lead within the other.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a first connector according to the invention, Figure 2 shows the connector of Figure 1 heat-recovered in position about the solid outer sheath of a mineral insulated cable, Figure 3 shows a cross section through lines 1-1 15 of Figure 2, - .
Figure 4 illustrates a second connector according to the invention, Figure 5 shows a third connector according to the invention heat-recovered in position about the solid outer sheath of a cable and protected by a heat-recovered moulded sleeve, Figure 6 shows a fourth connector according to the invention heat-recovered in position about the solid outer sheath of a cable, Figure 7 illustrates a previously proposed edge connector' 1 ~7~1 Figure 8 illustrates one form of edge connector-in accordance with the present invention, Figure 9 illustrates a second form of edge connector in accordance with the present invention' 5Figure 10 represents a third form of edge connector in accordance with the present invention' Figure 11 represents yet another form of edge con-nector in accordance with the present invention;
Figure 12 illustrates a connector for joining cables in accordance with the present invention, Figure 13 illustrates the use of a connector in accordance with the present invention for joining a power cable to its branch cables.
DETAILED DESCRIPTION OF THE DRAWINGS
--~
- Referring to Figure 1 there is shown a connector comprising a discontinuous band 1, formed from a memory metal, having a gap 2 and a channel portion indicated generally by reference numeral 3. The channel portion 20 -3 comprises a channel 4 having a raised bridge portion 5 defined by slots 6 cut into the channel 4.
Figure 2 shows the connector of Figure 1 recovered about the solid outer sheath 7 of a cable 8 and connect-ing an earth lead 9 thereto. The earth lead 9 is stripped to expose the centre conductor 10 which is inserted into the channel 4 through slots 6 and under the bridge portion 5, The band 1 is positioned about I 11 575~ 1 the outer sheath 7 and heated to cause it to recover towards its original configuration. On recovery the band 1 tightens radially about the outer sheath 7, and the raised bridge portion 5 and the channel 4 tend to flatten so as to grip the conductor 10 in the slots 6.
Figure 3 shows a cross section through lines 1-1 of Figure 2. The conductor 10 of the earth lead 9 is clamped against the outer sheath 7 of the cable 8 by the bridge portion 5.
Figure 4 shows a second form of connector accord-ing to the present invention comprising a discontinuous memory meta~ band 11 having a single circumferential slot 12 therein. The material of the band in the area of the slot 12 has been formed to provide a channel 13 extending from the slot to the edge of the band 11 and a raised portion 14 extending from the slot 12 to the opposite edge of the band 11.
The connector of Figure 5, shown recovered about - the sheath of a cable, comprises a discontinuous band 15 of memory metal having a gap 16 therein. The con-ductor of an earth lead 17 has been soldered at 18 to the band 15 and a heat-recoverable plastic moulded part 19 has been heat-recovered about the connector to provide an environmental protectionO
The connector of Figure 6 has also been recovered about the sheath of a cable. The connector, indicated generally by reference numeral 20 comprises a band 21 1 ~5~S~l of memory metal having a raised lug 22 to which has been soldered an earth lead 23. Clearly the lug may have a configuration other than that shown, for example it may comprise a d~formable portion which may be crimped about the conductor of the earth lead, or may have a screw threaded portion and a mating nut, In Figure 7 there is illustrated an edge connector representative of those at present used in the art. As can he seen, the edge connector comprises a generally U-shaped member 31 adapted to receive the edge concerned between the arms of the U, and which may also be pro-vided with a groove or recess 32 adapted to receive an earth lead which is to be connected to the edge. When the two components are in position the connection is made by tightening screw 33 until the head 34 breaks off.
_ In Figure 8 there is shown an edge connector in accordance with the present invention. This comprises a band 35 which is split longitudinally so as to form two jaw portions 36 and 37, the jaw 37 having a recess 38 adapted to receive an earth lead. (If desired the edge 36 may also be provided with such a recess in order to accommodate 2 second earth lead.) In use the band 35 is deformed by bending it so as to open the jaws 36 and 37 and, upon subsequent recovery these jaws move together in the direction shown by the arraws so as to grip edge 39 and form a secure connection to the earth lead.
1 ~575~ 1 In Figure 9 there is shown a second edge connector in accordance with the present invention, the cross section of which is generally of the form of a figure of eight, each o~ the rings of the eight being longitudinally split so as to provide increased dimensional recovery.
In use an edge 40 may be positioned within one ring 41 and an earth lead or second edge may be positioned within the other ring 42. Upon recovery in the direction shown by the arrows the two components are securely gripped so as to form the desired connection. The connector may, of course, equally well be used to conne~ttwo cables or two sheets or material.
In Figure 10 a simple form of connector comprising a discontinuous memory metal band 43 is used to form a connection between an earth lead 44 and an edge member 45 in accordance with the method of the present invention. Upon recovery the jaws of the band 43 move together in the direction shown by the arrows so as securely to grip the earth lead 44 to the edge member 45.
The connector shown in Figure 11 operates in a similar fashion in that the jaws of heat-recoverable band 46 move together as indicated by the arrows to grip edge member 47. However, in this case the earth lead 48 is attached to the band 46 by soldering within the channel 49 which is provided for this purpose, Figure 12 shows haw a connector in accordance with the present invention may be used to join cables. The 1 1575~1 connector comprises a heat-recoverable member 50 provided with grooves 51 and 52 adapted to receive cables 53 and 54, respectively. Upon recovery the member 50 moves in the direction indicated by the arrows so as to form a secure connection between the cables.
Finally, in Figure 13 there is shown a somewhat similar connector designed to join a power cable 55 to two branch cables 56 and 57. In this case the connector 58 is provided with gripping arms 59 and 60 for connection with the power cable 55 and is also provided with grooves 61 and 62 adapted to receive the branch cables 56 and 57, respectively. Upon recovery the connector-58 moves in the direction shown by the arrows so as to form the connection.
- The present invention has been specifically described with references to the embodiments shown in the accompanying drawings, but it will be appreciated that, in its broadest sense, this invention contemplates the use of heat-recoverable metal members, especially discontinuous bands, for making connections and par-ticularly electrical connections, for example the connection of earth leads to cable sheaths, edges, etc. and that, within this context, many other variations and modifications of connector are possible.
BACKGROUND OF THE INVENTION
This invention relates to connectors, and more particularly to connectors for making an electrical connection between two or more substrates.
The usual method for attaching an earth lead to a solid outer conductive sheath o~ an electrical cable is by soldering, However, although a good electrical connection can be obtained by this method, it is both operator dependent and time consuming, and the resultant connection is not mechanically strong. Furthermore, it is not easy to form soldered connections to aluminium sheathed cables, and difficulties have also been experienced in soldering an earth lead to the copper sheath of a mineral insulated cable, of the type found for example in fire protection systems, since the copper sheath is frequently covered with a tightl~y adhering coating of oxide, which necessitates vigorous abrasion of the surface to expose the metal, with the consequent risk o~ damage to the copper sheath.
In certain types of electrical apparatus there is a need to connect an earth lead to an edge of a metal surface, and it is known to use a clamp connector pro-vided with a screw for this purpose. However with such edge connectors it is rrequently difficult to obtain a connection having a good long term electrical performance.
.
.
1 157~1 There is thus a need for a method of connection which may provide a good mechanical and electrical connection between a variety of substrates and for a connector which is simple to install and reliable in service.
- 2a -l 1575~1 SU~RY OF THE INVE~ION
According to the present invention, the connection is made by the use of a connector comprising a heat recoverable member which is recovered into gripping engagement with at least one of the substrates.
In one aspect of the present invention, therefore, there is provided a method of making an earth connection to a substrate in which there is used a connector comprising a heat recoverable member which is fitted wholly or partly around the substrate and is recovered into gripping engage-ment therewith.
The present invention provides a method of electrically connecting a first conductor to a second conductor, which comprises (a) placing at least partly around said first conductor a dimensionally heat recoverable memory metal con-nector having a discontinuous cross-section, having means integral therewith for facilitating attachment ....
of said second conductor and having parts capable of independently receiving the conductors in side-by-side relationship, (b) positioning ~ithin and attaching to the connector said second conductor in side-by-side relationship with said first conductor,and (c) heating said connector to cause it to recover into electrical connection with said first conductor.
Step (b) may be carried out before, during or after step (c~. Advantageously, the connector comprises means _ 3 _ , .
} 1~75~1 for independently receiving a plurality of conductors prior to recovery.
The present invention also provides a method of electrically connecting a first conductor to a second conductor, which comprises (a) placing at least partly around said fi.rst conductor a first band of a dimensionally heat recoverable memory metal connector having in cross-section the form of a broken figure of eight providing first and second discontinuous bands in side-by-side relationship, (b) attaching to the connector said second conductor,and (c) heating said connector to cause it to recover into gripping engagement with said first conductor, step (b) being carried out before, during or after step (c).
Advantageously, the second conductor is positioned at least partly within the second band, and steps (b) and (c) are carried out simultaneously.
The present invention further provides a method of electrically connecting a first conductor to a second conductor, which comprises (a) placing at least partly around said first conductor a connector band of dimensionally heat recoverable memory metal, the band being provided with at least one peripheral slot for receiving a second conductor, the band and the slot being so shaped that upon recovery the first and second conduc~ors are each 1 ~57Sdl independently gripped by cont~action o~ the band and the slot, (b) placing said second conductor within said slot, and (c) heating the connector to cause recovery into gripping engagement with said first co~ductor by contraction of the band and with said second conductor by con-traction of the slot.
Advantageously, the band is formed with a channel shaped deformation extending across the width of the band in an axial direction, there being situated within the channel an upstanding bridge portion bounded on each side by slots cut in the channel, the slots being adapted to receive the second conductor therethroughO
The present invention still further provides a method of making an earth connection to a conductor in which there is used a connector comprising a dimensionally heat recoverabLe memory metal band which has a discontinuous cross-section and which is fitted wholly or partly around the conductor and a second conductor and is recovered into gripping engagement with the conductors and ~orces them together to make the earth connection The invention also provides connectors suitable for use in these methods~ Accordingly, there is provided a connector comprising a dimensionally heat recoverable memory metal member which has a discontinuous cross-section and which is constructed so as to fit wholly or partly around, and be recovered into gripping engagement with,a ~irst conductor and which is provided with means integral - 4a .
1 ~575~1 therewith for independently receiving, and facilitating the mechanical attachment of, a second conductor positioned within the heat recoverable member in side-by-side relationship to the first, and wherein the connection between the members is made on recovery of the member.
Advantageously, the heat recoverable member has the form, in cross-section, of a broken figure of eight, hereby providing two discontinuous bands in side-by-side relationship, The invention further provides a connector comprising a dimensionally heat recoverable memory metal band which has a discontinuous cross-section and which is constructed so as to fit wholly or partly around, and be recovered into gripping engagement with, a first conductor, the band bei-ng provided with at least one peripheral slot adapted to receive a second conductor, the second conductor being of smaller diameter than the first conductor, and the band and the slot being so shaped that upon recovery the-first and second conductors are each independently gripped by contraction of the band and the slot respectively, Advantageously, the band is formed with a channel shaped deformation extending across the width of the band in an axial direction, there being situated within the channel an upstanding bridge portion bounded on each side by slots cut in the channel, the slots being adapted to receive the second conductor therethrough.
The invention still further provides a connector comprising a dimensionally heat recoverable memory metal - 4b ~
~, ~.
~Y
l 1575~1 band which has a discontinuous cross-section and which is constructed so as to fit wholly or partly around, and be recovered into gripping engagement with, a first conductor and which is provided with a recess in one or both of its jaws for independently receiving, and facilitating the mechanical attachment of, a second conductor In an especially preferred embodiment of a conductor according to the invention the heat recoverable member is of discontinuous cross-section and is arranged to recover in a bending mode. For example, where the connector com-prises a heat recoverable band, the band is preferably discontinuous, being provided with a gap in its circum-ference. The width of the gap is preferably small relatlve to the diameter of the band. A discontinuous band has the ~1575~
particular advantage that it can be given a bending deformation which combines tensional and compressive stresses with the result that higher effective degrees of dimensional recovery can be attained than with a continuous band. The extra recovery is especially advantageous insofar as it makes dimensional tolerance requirements much less critical.
This extra dimensional recovery is especially advantageous when the heat-recoverable member is made from a memory metal (as described below) because such metals e~hibit a relatively low degree of recoverable strain. Fu~thermore, these metals are usually resilient in their recovered state and the presence of a dis-continuity similarly increases the degree of resiliently recoverable deformation which can be imparted to them in _ the recovered state. Thus members exhibiting such a discontinuity are more able to accommodate dimensional changes which may occur in the substrate after installa-tion (for example during heat aging).
The provision ofa discontinuity also greatly facilitates the application of the connector to sub-strates such as edges. A further advantage, where the connector is used to form a connection to a cable sheath, is that on recovery the edges of the discontinuity in the band are forced into a firmer gripping relationship with the sheath, and if the sheath material is sufficiently malleable a small portion thereof may even be extruded ~ 15~5~ 1 into the discontinuity thus providing an additional protection against circumferential movement of the connector relative to the sheath.
In some applications, it ma~ be advantageous to form the connection to one of the substrates, for example an earth lead, by, for example, crimping or soldering, and the connectors may be provided with means, such as for example a flange or lug, or a solder pot, for this purpose. In another embodiment, the connector may be provided with an upstanding threaded portion and a complementary nut for attach-ment of the earth lead.
In general, however, it will be preferred that the recovery of the heat-recoverable member acts as the sole agent for forming the connection, In a preferred embodiment according to the invention, the connector comprises a heat-recoverable - band adapted to fit around a first substrate, the band being provided with at least one peripheral slot adapted to receive a second substrate, the second substrate being of smaller diameter than the first substrate, and the band and the slot being so shaped that upon recovery the first and second substrates are each independently gripped by contraction of the band and the slot respectively. It is a particular feature of certain embodiments of the present invention that the band can grip the first substrate by radial contraction 1 1575~ ~
and the second substrate by contraction of the peri-pheral slot, in a single heat recovery operation. The band may, for example, be formed with a channel-shaped deformation, preferably extending across the width of the band in an axial direction, there being situated within the channel an upstanding bridge portion kounded on each side by slots cut in the channel, the slots being adapted to receive the second substrate there-through.
Pxeferably the heat-recoverable member is formed from a memory metal. Amongst suitable memory metals for use ln the present invention there may be mentioned various alloys of titanium and nickel which are des-cribed, for example in UnS. Patents Nos. 3,174,851, 3,351,463, 3,753,700, 3,759,552, British Patents - Nos. 1,327,441 and 1,337,442 and NASA Publication SP 110, "55-Nitinol - The Alloy with a Memory, etc"
(U.S. Government Printing Office, Washington, D.C.
1972). The property of heat-recoverability has not, h~wever, been solely confined to such titanium-nickel alloys Thus, for example, various beta-brass alloys have been demonstrated to exhibit this property in e.g. N Nakanishi et al, Scripta Metallurqica 5, 433-440 (Per~ammon Press 1971) and such materials may be doped to lower their transition temperatures to cryogenic regimes by known techniques. Similarly, 304 stainless steels have been shown to enjoy such 5 ~ ~
characteristics, E, Enami Q al, id at pp~ 663-68.
In general these metals have a transition tempera-ture within the range of from -196C to +135C, especially from -196C to -70C (this being the lowest tempeature they are liable to encounter during everyday use), and thus may be broug~t into their martensitic state by immersion in liquid nitrogen, However, more recently, it has been found possible to "precondition"
memory metals so as transiently to raise their trans-ition temperature. This enables the articles made fromsuch alloys to be kept at room temperature prior to use, when they can be recovered by heating. Such pre conditioning methods, which eliminate the need for liquid nitrogen during storage and transportation, are described, for example, in German Patent Applications oS 26 03 878 and OS 26 03 911 published 18th August, 1976.
~ he preferred memory metal for use in the present invention is heat-recoverable brass since this has excellent electrical properties and permits soldered connections to be madeO
As previously mentioned, the present invention is particularly adapted to the connection of earth leads to the conductin~ sheaths of electric cables.
In a particularly preferred embodiment according to this aspect of the invention the connector is positioned within a heat-recoverable plastic sleeve 1 15~5~
so that on recovery the sleeve provides an environ-mental seal for the connection made by the article.
In terminations and splices for mineral insulated cables the heat-recoverable sleeve is preferably provided with a fusible insert as described in British Patent No. 1,098,304. Such an arrangernent provides a single heat recoverable part which in one operation is capable of providing an earth connection and a seal for the mineral insulated cable termina-tion or splice. Preferably, the temperature at whichthe connector recovers is lower than the temperature of recovery of the heat-recoverable sleeve and the temperature of fusion of the ~usible insert.
However another application for the connectors of the present invention is in the earthing of leads _ to edges of electrical apparatus. In such an edge connector, one part is adapted to receive and grip the edge upon recovery and another part is adapted to receive the earth lead. For example, such a connector may comprise a discontinuous band having a recess in one or both of its jaws. The discontinuous band is posi tioned about the edge and the earth lead is positioned in a recess. Upon recovery, the jaws move together to grip the edge and thereby force the earth lead into connection with it. Alternatively, the earth lead may, in some cases, be simply positioned within the discontinuous band next to the edge.
_ g _ ~ 1575~
In another embodiment of a connector designed to make an earth connection, the heat-recoverable member has the form, in cross section, of a broken figure of eight thereby effectively providing two discontinuous bands in side-by-side relationship. Then, for example, the edge may be placed within one band and the earth lead within the other.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a first connector according to the invention, Figure 2 shows the connector of Figure 1 heat-recovered in position about the solid outer sheath of a mineral insulated cable, Figure 3 shows a cross section through lines 1-1 15 of Figure 2, - .
Figure 4 illustrates a second connector according to the invention, Figure 5 shows a third connector according to the invention heat-recovered in position about the solid outer sheath of a cable and protected by a heat-recovered moulded sleeve, Figure 6 shows a fourth connector according to the invention heat-recovered in position about the solid outer sheath of a cable, Figure 7 illustrates a previously proposed edge connector' 1 ~7~1 Figure 8 illustrates one form of edge connector-in accordance with the present invention, Figure 9 illustrates a second form of edge connector in accordance with the present invention' 5Figure 10 represents a third form of edge connector in accordance with the present invention' Figure 11 represents yet another form of edge con-nector in accordance with the present invention;
Figure 12 illustrates a connector for joining cables in accordance with the present invention, Figure 13 illustrates the use of a connector in accordance with the present invention for joining a power cable to its branch cables.
DETAILED DESCRIPTION OF THE DRAWINGS
--~
- Referring to Figure 1 there is shown a connector comprising a discontinuous band 1, formed from a memory metal, having a gap 2 and a channel portion indicated generally by reference numeral 3. The channel portion 20 -3 comprises a channel 4 having a raised bridge portion 5 defined by slots 6 cut into the channel 4.
Figure 2 shows the connector of Figure 1 recovered about the solid outer sheath 7 of a cable 8 and connect-ing an earth lead 9 thereto. The earth lead 9 is stripped to expose the centre conductor 10 which is inserted into the channel 4 through slots 6 and under the bridge portion 5, The band 1 is positioned about I 11 575~ 1 the outer sheath 7 and heated to cause it to recover towards its original configuration. On recovery the band 1 tightens radially about the outer sheath 7, and the raised bridge portion 5 and the channel 4 tend to flatten so as to grip the conductor 10 in the slots 6.
Figure 3 shows a cross section through lines 1-1 of Figure 2. The conductor 10 of the earth lead 9 is clamped against the outer sheath 7 of the cable 8 by the bridge portion 5.
Figure 4 shows a second form of connector accord-ing to the present invention comprising a discontinuous memory meta~ band 11 having a single circumferential slot 12 therein. The material of the band in the area of the slot 12 has been formed to provide a channel 13 extending from the slot to the edge of the band 11 and a raised portion 14 extending from the slot 12 to the opposite edge of the band 11.
The connector of Figure 5, shown recovered about - the sheath of a cable, comprises a discontinuous band 15 of memory metal having a gap 16 therein. The con-ductor of an earth lead 17 has been soldered at 18 to the band 15 and a heat-recoverable plastic moulded part 19 has been heat-recovered about the connector to provide an environmental protectionO
The connector of Figure 6 has also been recovered about the sheath of a cable. The connector, indicated generally by reference numeral 20 comprises a band 21 1 ~5~S~l of memory metal having a raised lug 22 to which has been soldered an earth lead 23. Clearly the lug may have a configuration other than that shown, for example it may comprise a d~formable portion which may be crimped about the conductor of the earth lead, or may have a screw threaded portion and a mating nut, In Figure 7 there is illustrated an edge connector representative of those at present used in the art. As can he seen, the edge connector comprises a generally U-shaped member 31 adapted to receive the edge concerned between the arms of the U, and which may also be pro-vided with a groove or recess 32 adapted to receive an earth lead which is to be connected to the edge. When the two components are in position the connection is made by tightening screw 33 until the head 34 breaks off.
_ In Figure 8 there is shown an edge connector in accordance with the present invention. This comprises a band 35 which is split longitudinally so as to form two jaw portions 36 and 37, the jaw 37 having a recess 38 adapted to receive an earth lead. (If desired the edge 36 may also be provided with such a recess in order to accommodate 2 second earth lead.) In use the band 35 is deformed by bending it so as to open the jaws 36 and 37 and, upon subsequent recovery these jaws move together in the direction shown by the arraws so as to grip edge 39 and form a secure connection to the earth lead.
1 ~575~ 1 In Figure 9 there is shown a second edge connector in accordance with the present invention, the cross section of which is generally of the form of a figure of eight, each o~ the rings of the eight being longitudinally split so as to provide increased dimensional recovery.
In use an edge 40 may be positioned within one ring 41 and an earth lead or second edge may be positioned within the other ring 42. Upon recovery in the direction shown by the arrows the two components are securely gripped so as to form the desired connection. The connector may, of course, equally well be used to conne~ttwo cables or two sheets or material.
In Figure 10 a simple form of connector comprising a discontinuous memory metal band 43 is used to form a connection between an earth lead 44 and an edge member 45 in accordance with the method of the present invention. Upon recovery the jaws of the band 43 move together in the direction shown by the arrows so as securely to grip the earth lead 44 to the edge member 45.
The connector shown in Figure 11 operates in a similar fashion in that the jaws of heat-recoverable band 46 move together as indicated by the arrows to grip edge member 47. However, in this case the earth lead 48 is attached to the band 46 by soldering within the channel 49 which is provided for this purpose, Figure 12 shows haw a connector in accordance with the present invention may be used to join cables. The 1 1575~1 connector comprises a heat-recoverable member 50 provided with grooves 51 and 52 adapted to receive cables 53 and 54, respectively. Upon recovery the member 50 moves in the direction indicated by the arrows so as to form a secure connection between the cables.
Finally, in Figure 13 there is shown a somewhat similar connector designed to join a power cable 55 to two branch cables 56 and 57. In this case the connector 58 is provided with gripping arms 59 and 60 for connection with the power cable 55 and is also provided with grooves 61 and 62 adapted to receive the branch cables 56 and 57, respectively. Upon recovery the connector-58 moves in the direction shown by the arrows so as to form the connection.
- The present invention has been specifically described with references to the embodiments shown in the accompanying drawings, but it will be appreciated that, in its broadest sense, this invention contemplates the use of heat-recoverable metal members, especially discontinuous bands, for making connections and par-ticularly electrical connections, for example the connection of earth leads to cable sheaths, edges, etc. and that, within this context, many other variations and modifications of connector are possible.
Claims (12)
1. A method of electrically connecting a first conductor to a second conductor, which comprises (a) placing at least partly around said first conductor a dimensionally heat-recoverable memory metal con-nector having a discontinuous cross-section, having means integral therewith for facilitating attachment of said second conductor and having parts capable of independently receiving the conductors in side-by-side relationship, (b) positioning within and attaching to the connector said second conductor in side-by-side relationship with said first conductor, and (c) heating said connector to cause it to recover into electrical connection with said first conductor.
2. A method as claimed in claim 1, wherein the connector comprises means for independently receiving a plurality of conductors prior to recovery,
3. A method of electrically connecting a first conductor to a second conductor, which comprises (a) placing at least partly around said first conductor a first band of a dimensionally heat-recoverable memory metal connector having in cross-section the form of a broken figure of eight providing first and second discontinuous bands in side-by-side relationship, (b) attaching to the connector said second conductor and (c) heating said connector to cause it to recover into gripping engagement with said first conductor, step (b) being carried out before, during,or after step (c).
4. A method as claimed in claim 3, wherein the second conductor is positioned at least partly within the second band, and steps (b) and (c) are carried out simultaneously.
5. A method of electrically connecting a first conductor to a second conductor, which comprises (a) placing at least partly around said first conductor a connector band of dimensionally heat-recoverable memory metal, the band being provided with at least one peripheral slot for receiving a second conductor, the band and the slot being so shaped that upon recovery the first and second conductors are each independently gripped by contraction of the band and the slot, (b) placing said second conductor within said slot, and (c) heating the connector to cause recovery into gripping engagement with said first conductor by contraction of the band and with said second conductor by con-traction of the slot.
6. A method according to claim 5, in which the band is formed with a channel shaped deformation extending across the width of the band in an axial direction, there being situated within the channel an upstanding bridge portion bounded on each side by slots cut in the channel, the slots being adapted to receive the second conductor therethrough.
7. A method of making an earth connection to a conductor in which there is used a connector comprising a dimensionally heat-recoverable memory metal band which has a discontinuous cross-section and which is fitted wholly or partly around the conductor and a second con-ductor and is recovered into gripping engagement with the conductors and forces them together to make the earth connection.
8. A connector comprising a dimensionally heat-recoverable memory metal member which has a discontinuous cross-section and which is constructed so as to fit wholly or partly around, and be recovered into gripping engage-ment with, a first conductor and which is provided with means integral therewith for independently receiving, and facilitating the mechanical attachment of, a second con-ductor positioned within the heat-recoverable member in side-by-side relationship to the first, and wherein the connection between the members is made on recovery of the member.
9. A connector according to claim 8, in which the heat-recoverable member has the form, in cross-section, of a broken figure of eight, thereby providing two discontinuous bands in side-by-side relationship.
10. A connector comprising a dimensionally heat-recoverable memory metal band which has a discontinuous cross-section and which is constructed so as to fit wholly or partly around, and be recovered into gripping engage-ment with, a first conductor, the band being provided with at least one peripheral slot adapted to receive a second conductor, the second conductor being of smaller diameter than the first conductor, and the band and the slot being so shaped that upon recovery the first and second con-ductors are each independently gripped by contraction of the band and the slot respectively.
11. A connector according to claim 10, in which the band is formed with a channel shaped deformation extending across the width of the band in an axial direction, there being situated within the channel an upstanding bridge portion bounded on each side by slots cut in the channel, the slots being adapted to receive the second conductor therethrough.
12. A connector comprising a dimensionally heat-recoverable memory metal band which has a discontinuous cross-section and which is constructed so as to fit wholly or partly around and be recovered into gripping engagement with a first conductor and which is provided with a recess in one or both of its jaws for independently receiving, and facilitating the mechanical attachment of, a second conductor.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB10117/76 | 1976-03-12 | ||
| GB4202576 | 1976-10-08 | ||
| GB42025/76 | 1976-10-08 | ||
| GB1011776A GB1579734A (en) | 1977-03-11 | 1977-03-11 | Methods of making electrical connections and connectors for use therein |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1157541A true CA1157541A (en) | 1983-11-22 |
Family
ID=26247296
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000273739A Expired CA1157541A (en) | 1976-03-12 | 1977-03-11 | Heat-recoverable connector for electrical connections |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1157541A (en) |
-
1977
- 1977-03-11 CA CA000273739A patent/CA1157541A/en not_active Expired
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |