"A system for connecting electrical cables to electrical apparatus, in particular, to the starter motor of a motor vehicle"

Abstract: A connection system (1) for connecting a battery output cable (2) and an electromagnet excitation cable (3) to a conductor terminal (6) of a motor vehicle starter motor, in which respective cable terminals (13, 16) of the said cables (2, 3) are locked together on the conductor terminal (6), isolated from each other; the terminal (6) includes a threaded shaft (7) constituting a first contact (4) for a first cable terminal (13), and an annular track (9) disposed concentric about the shaft (7) to form a second contact (5) for a second cable terminal (16); the track (9) is isolated from the threaded shaft (7) by an isolating ring (20) mounted thereon, and the second cable terminal (16) is locked against the track (9) by means of a protective element (26) of the first cable terminal (13) which is, in turn, locked to the shaft (7) together with the first cable terminal (13), by a nut (34). The protection element (26) may also include a guide element (33) for the battery cable (2), capable of cooperating with an end portion of this latter to form a predetermined angle thereof with respect to the conductor terminal (6).

Description: The present invention concerns a system for connecting electrical cables to electrical apparatus, particularly for connecting a battery cable and an electromagnet excitation cable to the starter motor of a motor vehicle. It is known to realise the wiring for the starter motor of a motor vehicle by fixing the output cable of a battery to a first terminal of the starter motor itself, and fixing the cable terminal of the electromagnet excitation cable to a separate second terminal isolated from the first. Two separate terminals are thus required for the above-indicated cables, each of which must be connected to the associated terminal by means of a suitable lock assembly. Connection systems of this type have severaldisadvantages due mainly to the fact that the wiring of the starter motor leads to two separate connection points: these systems are thus difficult to assemble, requiring a relatively high number of manual operations, and they are also relatively costly in that they involve many components; furthermore, the presence of two separate connection terminals can give rise to a notable space problem. A more effective arrangement is disclosed in EP-A-0506624, which from the other hand presents a main drawback in that neither cable terminals nor associated contacts are electrically isolated from each other. The object of the present invention is to provide a system for the connection of electrical cables to a terminal of electrical apparatus free from the disadvantages described and, in particular, which is inexpensive, of reduced size and easy to assemble. This object is achieved by the invention in that it concerns a system for connecting electrical cables to electrical apparatus, in particular, to the starter motor of a motor vehicle, as claimed in claim 1. The said lock means include a protective element for the said first cable terminal, formed from an insulating material, the said second cable terminal being locked to the said second contact by the said first cable terminal by means of the interposition of the said protective element. According to a preferred embodiment, the said first contact is constituted by a threaded shaft which projects from a casing of the said apparatus; the said second contact being constituted by a conductive track located on a surface of the said casing, surrounding the said threaded shaft. In this way, many components forming part of the lock assembly of the electromagnet excitation cable terminal are eliminated in comparison with the known connection systems, as they are incorporated into the single battery cable unit, with a consequent constructional simplification of the system itself and, therefore, a reduction in cost. Furthermore, the connection system according to the present invention enables simpler and faster mounting operations, contributing to a further reduction in overall production costs. A preferred embodiment of the invention will now be described, purely by way of non-limitative example and with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a system for connecting an electrical cable to a terminal of electrical apparatus formed according to the invention; and Figure 2 is a sectional view of the system of Figure 1, assembled. With reference to Figures 1 and 2, the reference numeral 1 generally indicates a system for connecting two electrical cables 2, 3 to associated contacts 4,5 of electrical apparatus, which contacts are separate and electrically isolated from each other: in this particular non-limitative example, the electrical apparatus is a motor vehicle starter motor, known and not shown for simplicity, the cable 3 is an excitation cable of the starter motor electromagnet, connected to the contact 5 which constitutes the output of the winding of the electromagnet, and the electrical cable 2 is the output cable of the motor vehicle battery and is connected to the contact 4, constituted by a conductor terminal 6 of the starter motor itself. In the non-limitative embodiment illustrated, the conductor terminal 6 is constituted by a threaded shaft 7 made from a conductive material, which projects from a casing 8 of the starter motor; the second contact 5 is, on the other hand, constituted by a conductive track 9 located on a surface 10 of the casing 8 surrounding the threaded shaft 7: as illustrated in Figure 1, the conductive track 8 is annular and concentric about the threaded shaft 7, but could clearly be of different shape. The battery output cable 2 is provided at one of its ends 12, intended for the electrical connection with the contact 4, with a cable terminal connector 13 shaped like a lug 14, of substantially known type, and fixed firmly to the end 12 of the cable itself. The lug 14 of the cable terminal 3 has an internal diameter substantially equal to that of the threaded shaft 7 such that it can be inserted therein with little radial play. Similarly, a second cable terminal connector 16, also shaped as a lug 17 and of known type, is fixed firmly to an end 18 of the excitation cable 3 intended for connection to the contact 5. The lug 17 of this second cable terminal 16 has an internal diameter greater than that of the lug 14 of the cable terminal 13, and is such that once the lug 17 has been fitted with some play around the shaft 7, it lies over the conductive track 9 disposed on the surface 10 of the casing 8. The conductive track 9 is isolated from the threaded shaft 7 by means of a ring 20 formed from an insulating material, for example, a polymeric material, mounted about the shaft 7 and held to the surface 10 of the casing 8 by a washer 21 and a first nut 22 which screws onto the threaded shaft 7. The external diameter of the isolating ring 20 is substantially equal to the internal diameter of the lug 17 of the cable terminal 16, so that it remains radially interposed between the lug 17 and the threaded shaft 7. The washer 21 and the nut 22 also have substantially the same external diameter as the isolating ring 20. The connection system 1 further includes locking means 25 for locking the cable terminals 13, 16 to the associated contacts 4,5. In this example, the locking means 25 include a protective element 26 for the cable terminal 13, made from an insulating material, for example, a polymeric material, which also functions, in fact, to protect the cable terminal 13 and the conductive terminal 6, which have no insulation, from accidentally coming into contact with other metal parts. The protective element 26 is formed from a substantially cylindrical portion 27 longitudinally split by a lateral through-hole 28, and having two substantially flat, parallel walls 29, 30 which extend radially from respective edges of this aperture. The cylindrical portion 27 of the protection element 26 has a base plate 31 provided with a circular through-hole 32 capable of being engaged by the threaded shaft 7 and of surrounding the isolating ring 20, the washer 21 and the bolt 22 once these have been fitted onto the shaft itself such as to abut, together with the base plate 31, against the track 9 and the associated cable terminal 16 possibly coupled thereto. The cylindrical portion 27 of the protective element 26 thus surrounds the conductor terminal 6, while the parallel walls 29, 30 constitute a guide element 33 for the cable 3. The locking means 15 of the connection system 1 further includes a second nut 34 which is also being capable of being screwed to the threaded shaft 7, and which has an external diameter greater than that of the first nut 22. During assembly, after having positioned the terminal 4 by locking the isolating ring 20 against the surface 10 of the casing 8 by means of the first nut 22 and the associated washer 21, the cable terminal 16 of the excitation cable 3 is fitted around the threaded shaft 7 by means of the lug 17; the protective element 26 is then fitted such that the hole 32 formed in the base plate 31 engages the isolating ring 20 and the base plate 31 abuts against the lug 17 of the cable terminal 16. The cable terminal 13 of the cable 3 is then fitted onto the threaded shaft 7 such that the lug 14 abuts against the base plate 31 of the protective element 26 and against the first nut 22. Finally, the second nut 34 is screwed onto the threaded shaft 7 thus locking the entire connection system 1 into the correct use position. Locking the nut 34 simultaneously locks both the cable terminals 13 and 16 and the casing 26 to the conductor terminal 6. The cable terminal 16 thus remains locked to the associated contact 5 (constituted by the conductive track 9) by the cable terminal 13, with the protective element 26 interposed; in turn, the cable terminal 13 is locked by the nut 34. The electrical connection of the cable terminal 16 to the starter motor is ensured by the conductive track 9 against which the cable terminal is held by the locking means 25 and, in particular, by the protective element 26 and the nut 34; however, the electrical connection of the cable terminal 13 is ensured by the threaded shaft 7 and the nuts 22, 34: in fact, the cable terminal 13, as described above, is locked between the two nuts 22, 34 which are screwed onto the threaded shaft 7 and thus maintain the electrical connection between this latter and the cable terminal 13. The cable terminals 13, 16 are, in turn, electrically isolated from each other by the protective element 26. According to the preferred embodiment illustrated in Figures 1 and 2, in order to impose an angular orientation on the battery output cable 2 that is predetermined with respect to the conductor terminal 6, the protective element 26, including the guide element 33 defined by the walls 29, 30, is also provided with a stop tooth 35: the stop tooth 35 projects radially from an outer lateral surface of the cylindrical portion 27 of the protective element 26, and is capable of engaging a corresponding check element 36 on the casing 8, in this particular example constituted by a seat formed on the surface 10. When, in use, the stop tooth 35 engages the seat 36, the guide element 33 means that the cable 2 remains firmly orientated in the desired direction. It is clear that many variations may be introduced into the connection system 1 described above: for example, the casing 26 could be provided with an upper closure cap, fixed or removable, or the guide element 33, instead of being integrated into the protective element 26, could be formed as a separate piece. The connection system according to the invention gives rise to significantly reduced production costs: in fact, the sequential assembly of the two cable terminals 13, 16 of the battery output cable 2 and the electromagnet excitation cable 3 is effected simply and rapidly, reducing assembly times and costs. In addition, in comparison with the currently available systems, the system according to the invention requires fewer components and is therefore less costly. Finally, it is clear that modifications and variations may be introduced into the connection system described above without by this departing from the ambit of protection as defined in the claims.

Claims: A system (1) for connecting electrical cables to electrical apparatus, in particular to the starter motor of a motor vehicle, including a conductor terminal (6) of the said apparatus, a first cable terminal (13) of a first electrical cable (2) connected to a first contact (4) of the said conductor terminal (6), and a second cable terminal (16) of a second electrical cable (3) connected to a second contact (5) of the said apparatus; the said second contact (5) being disposed close to the said first contact (4); the said connection system (1) further including locking means (25) capable of locking together the said first and second cable terminals (13, 16) to the said conductor terminal (6) against the associated contacts (4, 5); being characterised by first isolating means (20) between the said first contact (4) and the said second contact (5) to electrically isolate said contacts (4, 5) from each other; and second isolating means (26) between the said first cable terminal (13) and the said second cable terminal (16) to electrically isolate said cable terminals (13, 16) from each other. A connection system according to Claim 1, characterised in that the said locking means (25) include a protective element (26) of the said first cable terminal (13), formed from an insulating material and constituting the said second isolating means; the said second cable terminal (16) being locked to the said second contact (5) by the said first cable terminal (13) with the said protective element (26) interposed between the said first cable terminal (13) and the said second cable terminal (16). A connection system according to Claim 1 or Claim 2, characterised in that the said first contact (4) is constituted by a threaded shaft (7) which projects from a casing (8) of the said apparatus; the said second contact (5) being constituted by a conductive track (9) disposed on a surface (10) of the said casing (8) surrounding the said threaded shaft (7). A connection system according to Claim 3, characterised in that the said conductive track (9) is shaped as a concentric ring about the said shaft (7) and is connected to an installation outlet of the said apparatus. A connection system according to Claim 3 or Claim 4, characterised in that the said first and second cable terminals (13, 16) are shaped to form respective lugs (14, 17) and are fixed firmly to respective ends (12, 18) of the said first and second electrical cables (2, 3) intended for electrical connection with the said first and second contacts (4, 5); the said lug (14) of the first cable terminal (13) having an internal diameter substantially equal to that of the said threaded shaft (7) so that it can be inserted onto this latter with little play; the said lug (17) of the second cable terminal (16) having an internal diameter greater than that of the lug (14) of the said first cable terminal (13) such as to superimpose the said conductive track (9), at least partly, once the said second cable terminal (16) has been fitted about the said threaded shaft (7). A connection system according to Claim 5, characterised in that the said protective element (26) includes a substantially cylindrical portion (27) longitudinally spaced from a lateral through-hole (28), the said cylindrical portion (27) having a base plate (31) provided with a through-hole (32) capable of being engaged with play by the said threaded shaft (7), the said base plate (31) being axially interposed between the said first and second cable terminals (13, 16) and capable of electrically isolating them. A connection system according to Claim 5 or Claim 6, characterised in that the said lock means (25) include first (22) and second (34) nuts capable of being screwed onto the said threaded shaft (7), the said lug (14) of the first cable terminal (13) being locked between the said nuts (22, 34) so as to be in electrical contact with the said threaded shaft (7).

Inventors: PALAZZOLO FABIO, SPINA DONATO, PALAZZOLO, FABIO, SPINA, DONATO
Applicants: FIAT AUTO SPA, FIAT AUTO S.P.A.
Application year: 1998
Main classification: H01R9
IPC codes: H02K5, H01R9, H01R4