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Title:
APPARATUS FOR CONNECTING AN ELECTRIC CABLE TO A CABLE LUG
Document Type and Number:
WIPO Patent Application WO/2008/104980
Kind Code:
A3
Abstract:
An apparatus for connecting an electric cable to a cable lug is described. The lug has a palm portion, and a barrel portion integrated with the palm portion for receiving wires of the cable. The apparatus comprises one or more inductor coils. Each coil comprises a pair of connector terminals separated by a slot; and an aperture having dimension sufficient for placing the barrel portion therein. The apparatus also comprises an electric discharge unit coupled to the pair of connector terminals for providing a rapid intense current discharge through the inductor coil. The aperture of the coil has a shape that conforms to the shape of a cross-section of the lug along its length.

Inventors:
GAFRI OREN (IL)
LIVSHIZ YURI (IL)
Application Number:
PCT/IL2008/000253
Publication Date:
October 16, 2008
Filing Date:
February 28, 2008
Export Citation:
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Assignee:
PULSAR WELDING LTD (IL)
GAFRI OREN (IL)
LIVSHIZ YURI (IL)
International Classes:
H01R43/048; B21D26/14; B23K20/06
Domestic Patent References:
WO1997022426A21997-06-26
Foreign References:
US20020003159A12002-01-10
DE19728231A11998-02-12
US3832509A1974-08-27
GB1484560A1977-09-01
Attorney, Agent or Firm:
REINHOLD COHN AND PARTNERS (Tel-Aviv, IL)
Download PDF:
Claims:

CLAIMS:

1. An apparatus for connecting an electric cable to a cable lug (11, 43, 53, 63) having a palm portion (14, 431, 531), and a barrel portion (16, 432, 532) integrated with the palm portion for receiving wires of the cable, the apparatus comprising: at least one inductor coil (41, 51, 61, 72, 84, 91, 101) comprising: a pair of connector terminals (411a, 411b; and 58a, 58b) separated by a slot (412, 55, 68); and an aperture (42, 52, 62) having dimension sufficient for placing the barrel portion therein; and an electric discharge unit (24, 71) coupled to said pair of connector terminals for providing a rapid intense current discharge through the inductor coil; the apparatus characterized in that said aperture (42, 52, 62) has a shape that conforms to the shape of a cross-section of the lug (11, 43, 53, 63) along its length.

2. The apparatus of claim 1, wherein said palm portion (431) is in the form of a planar plate which projects from the barrel portion (432) tangentially to the barrel portion (432); and wherein the aperture (42) has a substantially triangular shape having an apex (421) at the slot (412) and a base (422) opposite to the slot (412).

3. The apparatus of claim 2, wherein the barrel portion faces the apex (421) during current discharge through the inductor coil.

4. The apparatus of claim 1, wherein said palm portion (531) is in the form of a planar plate which axially projects from the barrel portion (532); and wherein the aperture (52) has a substantially circular shape in which a first groove (54) and a second groove (56) are arranged along an axis (57) that passes through a slot (55) separating connector terminals (58a, 58b).

5. The apparatus of claim 1, wherein said palm portion is in the form of a planar plate which axially projects from the barrel portion; and wherein the inductor coil (61) includes a first groove (64) and a second groove (65) in the inductor coil (61) which are arranged along an axis (66) that is perpendicular to an axis (67) passing through a slot (68).

6. The apparatus of claim 1, wherein said inductor coil is equipped with a field- shaper (92) mounted within the aperture.

7. The apparatus of claim 6, wherein an inner surface of the field shaper (92) conforms to the shape of a cross-section of the lug along its length.

8. The apparatus of claim 6, wherein a gap (94) between an inner wall of the inductor coil (91) and an outer wall of the field shaper (92) is in the range of about 1.5mm to about 3.5mm.

9. The apparatus of claim 1, wherein the inductor coil (41, 51, 61, 72, 84, 91, 101) is further equipped with ribs (102) configured for air cooling.

Description:

Apparatus for connecting an electric cable to a cable lug

FIELD OF THE INVENTION

This invention relates to electrical cable lugs and apparatuses adapted to crimp the lugs around one or more wires of an electric cable.

BACKGROUND OF THE INVENTION Cable lugs are usually mounted on the ends of a cable for making electrical connection between conducting wires of the cable and other electrical equipment. Fig. 1 shows a cable lug 11 joined with bared conducting wires 12 of an end 13 of a cable (not shown). Cable lug 11 comprises a palm portion 14 for connecting the lug 11 to the electrical equipment (not shown), usually by means of a bolt (not shown) passing through an opening 15, and a barrel (or sleeve) portion 16 with a lumen 17. The barrel portion 16 is integral with the palm portion 14 and usually extends therefrom, for receiving the bared wires 12 within the lumen 17. The conductor wires 12 can have a circular, polynomial, D-shaped or other shaped cross-section.

Usually, the conductor wires 12 are retained in the lug barrel portion 16 by crimping. The crimping can for example, be carried out by a compression crimp (or swage) tool. The die of a swage tool compresses the barrel of the lug to form a good mechanical and electrical connection to the bare cable wires.

Moreover, magnetic pulse forming devices can be used for joining a cable to a lug. Reference is now made to Fig. 2 showing, in a semi-schematical manner, a known magnetic pulse device suitable for joining cable wires 21 to a barrel portion 22 of the lug 23. The device, generally designated by a reference numeral 20 comprises an electric discharge unit 24 including a bank of capacitors (not shown) which can provide a rapid intense current discharge, electric leads 25a and 25b for the transfer of the current and a inductor coil 26. The electric leads 25a and 25b are electrically linked to the coil 26 by means of connector terminals 27a and 27b separated by a slot 28.

Typically, the inductor coil 26 protrudes from a surface, e.g. a working table, represented here by a dotted-lined surface S 3 with the rest of the device constituents being hidden behind the surface. The inductor coil 26 has an aperture 29 into which the barrel portion 22 is inserted. The internal walls of the inductor coil 26 and the slot 28 are typically lined by insulating lining material 30.

In operation, the magnetic pulse device 20 stores energy within the bank of capacitors and releases the energy in electric discharge through the inductor coil 26 that creates a magnetic force strong enough to collapse the components positioned within the inductor coil 26. In this regard, the barrel 16 and the cable wires 21 are pre- assembled and positioned within the center of the coil's aperture 29. The energy released through the inductor coil 25 generates a magnetic field strong enough to collapse the barrel 22 inwardly into engagement with the wires 21.

Figs. 3a and 3b show schematically cross-sections of a barrel portion 31 of a lug before and after compression. If the energy stored in the bank of capacitors is sufficient, the inward collapsing velocity will be sufficient to compress round wires 33 such that their circular cross-section will change their shape, for example to become substantially hexagonal, thereby to fill up voids 34 between the round wires 33. In a typical cable, wires fill up about 40% - 60% of its internal space, owing to voids. After full compression, where the wires' cross-sections become hexagonal, the wires come to fill essentially 90% - 100% of the internal space of the cable. This means that the cable after full compression constricts its original diameter.

Known magnetic pulse devices typically employ inductor coils having generally circular apertures (e.g., the aperture 29 in Fig. 2) operative to surround the portions of the conductive work pieces to be formed or swaged, hi order to concentrate the energy, the space between the work piece and the inner surface of the coil should be as small as possible. Many electromagnetic forming operations make use of solenoid inductor coils in conjunction with electromagnetic field shapers designed to concentrate the electromagnetic field pressure in the working area. When using such an inductor coil with certain types or shapes of work pieces, a problem frequently arises in the ability of the work pieces to be inserted within the coil aperture defining the forming area or in withdrawal of the connected work pieces from the coil aperture. This is a particular problem when the work piece or assembly being formed has an enlarged or irregular configuration or has flanged ends which make it difficult, if not impossible, to insert or

pass the work piece through a circular coil aperture by axial movement of the work piece. For example, in the case when a cross-section dimension L of the palm portion 14 of the lug (11 in Fig. 1 or 23 in Fig. 2) is greater than the outer diameter D of its barrel portion (16 in Fig. 1 or 22 in Fig. 2), a conventional circular inductor coil must be used with the diameter of the circular coil aperture greater than D and L. Otherwise, if the coil's diameter is less than L, it will not be possible to withdraw the cable from the coil's aperture after mounting lugs at each end of the cable.

SUMMARY OF THE INVENTION The present invention partially eliminates disadvantages of the prior art conventional circular inductor coil and provides a novel magnetic pulse forming apparatus for joining a lug to an electric cable. The lug has a palm portion, and a barrel portion integrated with the palm portion for receiving wires of the cable.

According to one embodiment of the invention, the apparatus comprises one or more inductor coils. Each coil comprises a pair of connector terminals separated by a slot; and an aperture having dimension sufficient for placing the barrel portion therein. The apparatus also comprises an electric discharge unit coupled to the pair of connector terminals for providing a rapid intense current discharge through the inductor coil. The aperture of the coil has a shape that conforms to the shape of a cross-section of the lug along its length.

According to one embodiment of the invention, the palm portion is in the form of a planar plate which projects from the barrel portion tangentially to the barrel portion. In this case, the aperture has a substantially triangular shape having an apex at the slot, and a base opposite to the slot. The barrel portion faces the apex during current discharge through the inductor coil.

According to another embodiment of the invention, the said palm portion is in the form of a planar plate which axially projects from the barrel portion. In this case, in accordance with one example, the aperture has a substantially circular shape in which a first groove and a second groove are arranged along an axis that passes through a slot separating connector terminals. In accordance with another example, the inductor coil includes a first groove and a second groove in the inductor coil which are arranged along an axis that is perpendicular to an axis passing through the slot.

According to a further embodiment of the invention, the inductor coil is equipped with a field-shaper mounted within the aperture. An inner surface of the field shaper conforms to the shape of a cross-section of the lug along its length. A gap between an inner wall of the inductor coil and an outer wall of the field shaper is in the range of about 1.5mm to 3.5mm.

According to a further embodiment of the invention, the inductor coil is further equipped with ribs configured for air cooling.

There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows hereinafter may be better understood. Additional details and advantages of the invention will be set forth in the detailed description, and in part will be appreciated from the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, preferred embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a perspective view of an assembly consisting of a cable and a cable lug after insertion of the end of the cable into the lumen of the cable lug; Fig. 2 shows in a semi-schematical manner a conventional magnetic pulse device suitable for joining a cable to the cable lug;

Figs. 3a and 3b show schematically cross-sections of a barrel portion of the lug shown in Fig. 1 before and after compression.

Fig. 4 shows a schematic plane view of an inductor coil, according to one embodiment of the invention;

Fig. 5 shows a schematic plane view of an inductor coil, according to another embodiment of the invention;

Fig. 6 shows a schematic plane view of an inductor coil, according to another embodiment of the invention; Fig. 7 shows a schematic view of the apparatus employing the inductor coil shown in Fig. 4, Fig. 5, Fig. 6, Figs. 9A and 9B, or Fig. 10, according to one embodiment of the invention;

Fig. 8 shows a schematic view of the apparatus employing the inductor coil shown in Fig. 4, Fig. 5, Fig. 6, Figs. 9A and 9B, or Fig. 10, according to another embodiment of the invention;

Figs. 9A and 9B show schematic plane and cross-sectional views of an inductor coil, according to still another embodiment of the invention;

Fig. 10 shows perspective views of inductor coils, according to yet a further embodiment of the invention;

Figs. HA and HB show fabrication of a lug, according to one embodiment of the present invention; Figs. 12 A, 12B and 12C show fabrication of a lug, according to another embodiment of the present invention;

Figs. 13A, 13B and 13C show fabrication of a lug, according to yet another embodiment of the present invention;

Figs. 14A, 14B and 14C show fabrication of a lug, according to yet another embodiment of the present invention; and

Fig. 15 shows a schematic view of the apparatus employing the inductor coils shown in Fig. 4, Fig. 5, Fig. 6, Figs. 9A and 9B or Fig. 10, according to a further embodiment of the invention; and

Fig. 16 shows a schematic plane of the inductor coil according to yet another embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The principles and operation of a method and an apparatus according to the present invention may be better understood with reference to the drawings and the accompanying description, it being understood that these drawings are given for illustrative purposes only and are not meant to be limiting. The same reference numerals will be utilized for identifying those components which are common in the vessel and the working coil shown in the drawings throughout the present description of the invention. Dimensions of inductor coils, lugs and their portions may be exaggerated for clarity. Referring to Fig. 4 a schematic plane view of an inductor coil 41 is illustrated, according to one embodiment of the invention. According to this embodiment, the inductor coil 41 is in the form of the Greek symbol omega (ω). The inductor coil 41

includes one or more turns of conducting material extending from connector terminals 411a and 411b, and defining an aperture 42 of the coil. The connector terminals 411a and 411b are separated by a slot 412. When desired, the internal walls of the inductor coil 41 and the slot 412 can be lined by insulating lining material (not shown). According to the present invention, the shape of the aperture 42 conforms to the shape of a cross-section of a lug 43 along its length. The lug 43 includes a palm portion and a barrel portion integrated with the palm portion. Cross-sectional areas of the palm portion and the barrel portion are designated by reference numerals 431 and 432, correspondingly. Generally, the shape of a palm portion and a barrel portion depends on application and can have any desired form. A cross-section dimension L of the palm portion 431 can be greater or less than a diameter D of the barrel portion 432.

For example, the palm portion 431 can be in the form of a planar plate which projects from the barrel portion 432 tangentially to a cylindrical surface (not shown) of the barrel portion 432. In this case, as shown in Fig. 4, the aperture 42 has a substantially triangular shape having an apex 421 at the slot 412 and a base 422 opposite to the slot 412. When the lug 43 is inserted in the aperture 42, the palm portion of the lug fits the base 421 and passes through the aperture further, whereas the barrel portion faces the apex 421 and should remain in the aperture 42 during the current discharge for joining the lug with cable wires (not shown). It should be understood that when the dimension of the lap portion is greater than the diameter of the barrel portion, the inductor coil with the aperture described above has advantages over a circular aperture having the dimension sufficient for passing the lap portion therethrough. In particular, the inductor coil of the present invention has a smaller aperture area and thereby higher concentration of magnetic field, than the corresponding conventional circular inductor coil, which has the aperture diameter sufficient for passing the lap portion therethrough. Another advantage is a possibility to make more uniform application of the magnetic field to the barrel portion of the lug, when compared to a circular aperture with a slot. Indeed, the concentration of the magnetic field near the slot 412 is less than the field concentration not close to the slot. Thus, preferably, the barrel portion should be more close to the inner wall of the inductor coil near the apex 421 than to the base 422, thereby compensating for the drop of magnetic field concentration near the slot 412. When desired, the internal walls of the

0253

- 7 - inductor coil and the slot of this embodiment as well as of further embodiments described hereinbelow can be lined by insulating lining material (not shown).

Fig. 5 shows a schematic plane view of an inductor coil 51, according to another embodiment of the invention. According to this embodiment, the shape of an aperture 52 of the coil 51 is conformed to the shape of a cross-section of a lug 53 having a planar palm portion 531 axially projected from a barrel portion 532. The width of the palm portion 531 is greater than the diameter of the barrel portion 532. According to this embodiment, the aperture 52 has a substantially circular shape in which a first groove 54 and a second groove 56 are arranged along an axis 57 that passes through a slot 55 separating connector terminals 58a and 58b. hi particular, the first groove 54 in the coil 51 is arranged near the slot 55 and the second groove 56 in the coil is arranged at the place diametrically opposite to the slot 55. The aperture 52 is fitted to the barrel dimension. Moreover, the size of the grooves 54 and 56 is sufficient for accommodation of the lug's palm portion 531. Fig. 6 shows a schematic plane view of an inductor coil 61, according to still another embodiment of the invention. The inductor coil 61 differs from the inductor coil 51 shown in Fig. 5 by the fact that a substantially circular aperture 62 of the inductor coil 61 includes a first groove 64 and a second groove 65 in the coil 61 which are arranged along an axis 66 that is perpendicular to an axis 67 passing through a slot 68. The shape of the aperture 62 of the coil 61 is conformed to the shape of a cross-section of the lug 63 having a planar palm portion axially projected from a barrel portion.

Referring to Figs. 7 and 8, a schematic representations of two embodiments of an apparatus of the present invention is illustrated. The embodiment shown in Fig. 7 and generally designated by a reference numeral 70 comprises an electric discharge unit 71 and an inductor coil 72. The electric discharge unit 71 includes an electric discharge circuitry 74 having a discharge capacitor or bank of capacitors 75 and a pulse control module 76. In the embodiment of Fig. 7, the forming coil 72 is in direct electric contact with the discharge circuitry 74.

The embodiment shown in Fig. 8, generally designated by a reference numeral 80, comprises an electric discharge unit 81, an inductor coil assembly 82 comprising a primary coil 83 and a secondary coil 84. The secondary coil 84 operates as an inductor coil. The primary coil 83 and the secondary coil 84 are in an inductance relationship with one another, i.e., they form two coils of a transformer. The primary coil 83 is in

direct electric contact with an electric discharge circuitry 85 of electric discharge unit 81 similarly as in the embodiment of Fig. 7. The electric discharge circuitry 85 comprises a capacitor or bank of capacitors 86 and a pulse control module 87.

The apparatuses shown in Figs. 7 and 8 are generally known per se. The novelty in accordance with the invention resides in the nature of the inductor coils, which are exemplified in the embodiments described above with reference to Figs. 4, 5 and 6.

Referring to Figs. 9A and 9B together, a front view and a cross-sectional longitudinal view of an inductor coil 91 are illustrated, according to a further embodiment of the invention. According to this embodiment, the magnetic forces are created by an inductor coil equipped with a field-shaper 92.

For example, the field shaper 92 can have a cylindrical outer surface with diameter slightly less than the inner diameter of the inductor coil 91. For example, a gap 94 between an inner wall of the inductor coil 91 and an outer wall of the field shaper 92 can be in the range of about 2mm to about 3 mm. The inner surface of the field shaper 92 has such a shape so that the aperture defined by the inner surface would conform to the shape of a cross-section of a lug along its length. As shown in Figs. 9A the inner surface of the field shaper 92 is configured to accommodate the lug (43 in Fig. 4). Likewise, the inner surface of the field shapers can also be configured to accommodate the lug<53 in Fig. 5), the lug (63 in Fig. 6). When desired, the inductor coil 91 can include canals 93 for passage of a cooling liquid, such as water, transformer oil, etc. The canals 93 can be covered by covers 94.

Generally, any conductive material can be suitable for the field shaper 92. Examples of such materials include, but are not limited to Cu-Be alloys. Fig. 10 shows a perspective view of an inductor coil 101, according to yet another embodiment of the invention. The inductor coil 101 can be any inductor coil shown in Figs. 4, 5, 6 or 9A and 9B, further equipped with ribs 102 configured for air cooling.

Referring to Figs. HA and HB together, fabrication of a lug 111 is shown according to one embodiment of the present invention. As shown in Fig. HA, the lug 111 is formed from a suitable tubular element 112, one end of which is squeezed to form a palm portion 113. The remaining part of the tubular element 112 forms a barrel

L2008/000253

- 9 - section 114. When desired, an opening 115 in the palm portion can further be drilled or punched out.

Figs. 12A, 12B and 12C show main steps of fabrication of a lug 121, according to another embodiment of the present invention. In this case, the lug 121 is fabricated from a flat metal sheet 122, which is bent or rolled upwardly and around into a tubular element 123. Sides 124a and 124b of the sheet 122 are welded, brazed, soldered or otherwise secured together along a joint line 125. Further, one end of the tubular element 123 is squeezed to form a palm portion 126. The remaining part of the tubular element 123 forms a barrel section 127. When desired, an opening 115 in the palm portion can be drilled or punched out.

Figs. 13A, 13B and 13C show fabrication of a lug 131, according to yet another embodiment of the present invention. According to this embodiment, a blank 132 is cut, as indicated by broken lines 133, from a metal sheet 134. The two strip-like arms 135a and 135b are then bent or rolled upwardly and around into a tubular portion 136. Sides 137a and 137b of the arms 135a and 135b are welded, brazed, soldered or otherwise secured together along a joint line 138.

Figs. 14A, 14B and 14C show fabrication of a lug 141, according to yet another embodiment of the present invention. According to this embodiment, the lug 141 is fabricated by a forging process. Referring to Fig. 14A, a cylindrical rod 142 is hammered or pressed into a die 143 having a desired shape of the lug. Referring to Fig. 14B, when the material of the rod fills the space of the die (not shown), a lumen 144 is formed in a barrel portion 145 of the lug 141. Examples of the methods of forming the lumen 144 include, but are not limited to punching, drilling, etc. Referring to Fig. 14C, the lug 141 is removed from the die (143 in Fig. 14A), and an opening 146 in the palm portion 147 of the lug is drilled or punched out.

Examples of materials suitable for the lugs fabricated as shown above include, but are not limited to, Al, Cu, steel and their alloys. When required to protect from aggressive environment, the lugs can be coated with a protective layer (not shown).

According to one embodiment of the present invention, the method of connecting an electric cable to a cable lug begins with pre-assembling. For this purpose, bared wires of electric cable, after stripping off the insulation, are placed into a lumen of the cable lug. Then, the pre-assembled structure is inserted into an aperture of an inductor coil of an apparatus of the present invention described above. Preferably, at

000253

- 10 - least 60% of .the longitudinal dimension of the working zone of the inductor coil should be occupied by the length of the lug's barrel portion. Further, the inductor coil is energized to generate a magnetic force sufficient for collapsing the barrel portion of the lug inwardly into engagement with the wires. The magnitude of the force should be sufficient for compressing the wires so that they come to fill essentially 80% - 100% of the original internal space of the cable. Preferably, but not mandatory, the force should be sufficient not only for crimping the barrel of the lug, but also for causing the molecules of the lug to penetrate into the metal of the neighboring wires, thereby producing a full metallurgical joint between the wires and the lug in the cold stage. As such, those skilled in the art to which the present invention pertains, can appreciate that while the present invention has been described in terms of preferred embodiments, the concept upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, systems and processes for carrying out the several purposes of the present invention. It is apparent that although the examples of the lugs having a circular cross- section of the barrel portion were shown in the present description, the method and apparatus of the present invention can be applied, mutatis mutandis, for the connecting of an electric cable to a lug having the barrel portion of an arbitrary cross-sectional shape. It should be understood that connecting an electric cable 154 to electric lugs 155 and 156 can be performed either individually for each cable end or simultaneously for the two cable ends. Fig. 15 shows a magnetic pulse apparatus 150 suitable for the latter case. The apparatus 150 includes two inductor coils 151 and 152 energized simultaneously from an electric discharge unit 153. The inductor coil 151 and 152 can be any inductor coils shown in Figs. 4, 5, 6, 9A and 9B or 10.

Although an example of the forming inductor coil in the form of the Greek symbol omega (ω) was shown in Figs. 4, 5, 6, 9A and 9B, and 10, generally, the inductor coil can be formed in any desired shape, for example, as symbols "U", "O", etc. An example of the inductor coil according to another embodiment of the invention is shown in Fig. 16. According to this embodiment, connector terminals 461 and 462 are parallel to axis O, and are separated by a slot 163.

Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

- li lt is important, therefore, that the scope of the invention is not construed as being limited by the illustrative embodiments set forth herein. Other variations are possible within the scope of the present invention as defined in the appended claims. Other combinations and sub-combinations of features, functions, elements and/or properties may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such amended or new claims, whether they are directed to different combinations or directed to the same combinations, whether different, broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of the present description.