Terminal for a conductor

Abstract: A single conductor (10) in a multi-conductor cable is terminated to a terminating part (7,8) on a contact pin or contact socket in a plug or a socket contact, possibly on a circuit board or a contact piece, by inserting a stripped, metallic centre conductor (9) longitudinally between at least one pair of gripping claws (12) of an electrically conductive material. The gripping claws (12) are specially shaped so that an inner, substantially forward facing and sharp edge portion (13a) touches the surface (11) of the metallic conductor along a substantially helical curve having a large pitch angle. Thereby, if an attempt is made to pull the conductor (10) in a rearward direction, the sharp edge portion (13a) will carve lockingly into the surface (11) of the metallic conductor and cause locking of the conductor (10).

Description: The present invention concerns the problem of terminating an electrical conductor to a contact pin or a contact socket in a plug or a socket contact without using a terminating tool. In particular, the invention relates to a contact pin and a contact socket having a terminating part of a special type for tool-free terminating thereto of a solid conductor in a cable. An electrical contact assembly usually consists of a plug or male contact having a number of contact pins mounted in a contact housing, and a socket contact or female contact having a corresponding number of contact sockets mounted in a contact housing. In some cases the contact assembly may comprise hermaphroditic contacts, with a mixture of contact pins and contact sockets in each respective one of two contact pieces that are in principle of the same type. In such cable contacts of plug, socket contact and hermaphroditic contact type, the electric cable conductors are terminated permanently to the respective contact pins and contact sockets using various terminating methods (see FR2454191). Examples of such methods are terminating the cable conductors on knife contacts, or by fixing contact pins/sockets to the conductors by crimping. These methods require special tools. terminating by means of a screw connection or by soldering. These methods do not require special tools, but are usually relatively time-consuming. The present invention offers an alternative method for permanent terminating of a conductor, preferably in a low current cable, to a contact pin or a contact socket, without use of any terminating tool. The invention may form part of contact solutions for cables having one or several conductors with solid , i.e. not a multi-strand, metallic conductor core. The invention is suitable for transmission of electrical signals having frequencies from 0 (DC) to beyond 1 GHz. Terminating by means of the contact pin/contact socket in accordance with the invention will only require preparation amounting to stripping the insulation from a forward piece of the insulated conductor (normally several such insulated conductors are included in a cable). Further, the invention is intended for once-for-all terminating, when the conductors have been attached, they are not intended to be released again from the pin/socket terminal. Thus, the invention provides a quick and simple manner for terminating conductors in contact housings, with no other special tool than a stripping tool. Hence, in a first aspect of the invention there is provided a contact pin for use in a plug or a socket contact, possibly together with further contact pins, said contact pin having a forward engagement pin part to be entered in a contact socket in a socket contact or a plug, and a rear terminating pin part for tool-free terminating thereto of a conductor in a cable, said conductor comprising an insulation sheath and a central metallic conductor which is solid and has a substantially circular cylindrical surface. The contact pin in accordance with the invention is characterized in that the terminating pin part comprises at least one pair of gripping claws made of an electrically conductive material to provide a good electrical connection with the metallic conductor by springy and tight envelopment when it is inserted in a forward direction between the gripping claws, and that each claw in a pair has an inner, substantially forward-facing and sharp edge shaped in such a manner that when the metallic conductor has been inserted, a portion of the sharp edge touches the surface of the metallic conductor along a substantially helix-shaped curve having a large pitch angle, so that said forward-facing edge portions will carve into the surface of the metallic conductor and lock the metallic conductor if an attempt is made to pull the conductor in a rearward direction with a reasonable pulling force. In a second aspect of the invention there is provided a contact socket for use in a socket contact or a plug, possibly together with further contact sockets, said contact socket having a forward engagement socket part to envelop tightly a contact pin in a plug or a socket contact, and a rear terminating socket part for tool-free terminating thereto of a conductor in a cable, said conductor comprising an insulation sheath and a central metallic conductor which is solid and has a substantially circular cylindrical surface. The contact socket in accordance with the invention is characterized in that the terminating socket part comprises at least one pair of gripping claws made of an electrically conductive material to provide a good electrical connection with the metallic conductor by springy and tight envelopment when it is inserted in a forward direction between the gripping claws, and that each claw in a pair has an inner, substantially forward-facing and sharp edge shaped in such a manner that when the metallic conductor has been inserted, a portion of the sharp edge touches the surface of the metallic conductor along a substantially helix-shaped curve having a large pitch angle, so that said forward-facing edge portions will cut into the surface of the metallic conductor and lock the metallic conductor if an attempt is made to pull the conductor in a rearward direction with a reasonable pulling force. In both of the above stated aspects of the invention, the terminating part may comprise a successive row of pairs of gripping claws having a gradually narrower passage for the metallic conductor, for reception and terminating of metallic conductors having various diameters. In the case with a row of pairs of gripping claws, the first pair of gripping claws in the row to be entered by a stripped conductor to be terminated, may preferably be provided with an outward opening, funnel-like conductor insertion part at the insertion end to simplify insertion of the tip of the metallic conductor. In a preferred embodiment of the invention, the terminating part, possibly the complete contact pin respectively contact socket, is formed from a flat metal piece by stamping and bending. In the preferred embodiment of the invention, each gripping claw extends, from a base part that is substantially longitudinal in relation to the metallic conductor, cylindrically curving and transverse relative to the base part, via a narrow neck section to a top part which has is largest dimension in the longitudinal direction when the metallic conductor is held, said top part having an end edge which then faces and is substantially parallel to a corresponding end edge of the other gripping claw in the pair, but where the top part end edge forms an oblique angle with the longitudinal direction of the metallic conductor prior to insertion thereof, and each gripping claw has the above mentioned sharp edge in a forward region from the neck section and in on the top part. In a third aspect of the invention there is provided a contact assembly that comprises a plug and a socket contact, preferably for use with a low current cable, wherein the plug and the socket contact comprise contact pins and contact sockets intended for mutual engagement, and wherein the contact pins and contact sockets are such as stated in the first two aspects of the invention. In a fourth aspect of the invention there is provided a cable terminating part for use on a circuit board or a contact piece, for tool-free terminating thereto of a conductor in a cable, said conductor comprising an insulation sheath and a central metallic conductor which is solid and has a substantially circular cylindrical surface, the terminating part being adapted to receive the metallic conductor by a forward insertion movement in a longitudinal direction therefor. The terminating part is characterized in that it comprises at least one pair of gripping claws made of an electrically conductive material to provide a good electrical connection with the metallic conductor by springy and tight envelopment when it is inserted in a forward direction between the gripping claws, and that each claw in a pair has an inner, substantially forward-facing and sharp edge shaped in such a manner that when the metallic conductor has been inserted, a portion of the sharp edge touches the surface of the metallic conductor along a substantially helix-shaped curve having a large pitch angle, so that said forward-facing edge portions will cut into the surface of the metallic conductor and lock the metallic conductor if an attempt is made to pull the conductor in a rearward direction with a reasonable pulling force. In the following, the invention shall be described in closer detail while referring to preferred embodiments that appear from the appended drawings, wherein fig. 1 shows schematically and in a general form a simple contact assembly including a plug with contact pins as well as a corresponding socket contact with contact sockets, figs. 2a and 2b show a preferred embodiment of the invention, i.e. a contact pin and a contact socket respectively, with a terminating part of a special type, figs. 2c and 2d show the same as figs. 2a and 2b, however with conductors inserted in the terminating parts, fig. 3 shows the preferred embodiment of the actual terminating part, in a top view, side view and a cross section view, respectively, and fig. 4 shows the same as fig. 3, however with a conductor inserted and attached in the terminating part. Fig. 1 shows a general design of a simple contact assembly comprising a male contact or plug 1 having four contact pins 3, arranged to provide connection with a female contact or socket contact 2 which comprises four contact sockets 4. Assembled cables enter the plug and the socket contact, and branch into four insulated conductors 10 each containing a metallic conductor 9. Every metallic conductor 9 is in some way or other attached, i.e. terminated, to the rear end 7 respectively 8 of contact pin 3 respectively contact socket 4. The manner of terminating does not appear from this figure, which merely shows in a general manner a rather common contact assembly, where, as it appears, the forward part 5 of the contact pins are intended to engage the forward part 6 of the contact sockets. The contact assembly shown here is merely an example, the number of pins and sockets may of course be quite different, and it is also possible with hermaphroditic contact assemblies where each contact piece 1,2 comprises pins 3 as well as sockets 4. The manner of attaching the metallic conductor 9 to the rear end 7 respectively 8 of pin 3/socket 4, can in general be one of the manners mentioned above, but in the present invention there is stated a special and novel method of terminating the metallic conductor 9 to the rear end 7 respectively 8. When the invention is discussed in the following, the rear end of pin respectively socket 4 will be named terminating part 7 respectively 8. A preferred embodiment of the invention appears from figs. 2a and 2b, i.e. the same type of terminating part 7,8 is here shown at the rear end of a contact pin 3 respectively a contact socket 4. In the following the terminating parts 7 and 8 are treated in the same manner, i.e. it is sufficient to discuss one terminating part, but from practical reasons, reference numerals will be found in the figures distributed equally between figs. 2a and 2b. In the embodiment shown here, an elongate terminating part having a base part 15 comprises three erect structures 12 in the form a gripping claws adapted to enclose a circular cylindrical conductor to be inserted from the rear and in a direction forward toward the engagement pin part 5 respectively the engagement socket part 6. The terminating part may comprise only one such gripping claw 12, or possibly two, three or more gripping claws 12. If there is only one gripping claw 12, the terminating part will be suitable for one special conductor diameter, but to be able to receive and retain fixedly conductors having diameters within a specified diameter range, a number of such gripping claws may be arranged in a row, where the rearmost gripping claw is adapted to the larger diameter in the specified range, and the forwardmost gripping claw is adapted to the smaller diameter in this range, while intermediate gripping claws are adapted to successively decreasing diameters from the rear and forward. When a conductor is inserted, it will pass easily through the larger gripping claws, while it will be held in the adapted gripping claw 12. In figs. 2c and 2d is shown, in a corresponding manner as in figs. 2a and 2b, the same contact pin and contact socket, however in a situation where the metallic conductor 9 has been entered through the rear gripping claw 12 to be retained in the intermediate gripping claw. This means that the forwardmost gripping claw is still not under any tension, the intermediate gripping claw is tautened such as intended in order to retain the circular cylindrical conductor, while the rearward gripping claw has been pivoted somewhat from its start position, but not to a sufficient degree to retain the metallic conductor 9. The gripping claws 12 are shaped in a special manner and are arranged in pairs. They operate in accordance with a springy and locking principle, which is most easily explained in connection with figs. 3 and 4. It is therefore referred to those figures in the following, however figs. 2a-d will also exhibit some of the geometry that is important for the invention. Fig. 3 shows a terminating part having three pairs of gripping claws 12, in a condition without any conductor inserted. The terminating part is shown on top in a top view, in the middle in a side view, and lowermost appears a cross section as seen in a position A-A such as indicated in the side view. In principle, the size or the inner diameter e of the three claw pairs decreases successively from the right toward the left. The gripping claws curve upwards from a base part 15 extending all the way along the terminating part, and each gripping claw has a narrow neck section 16 before expanding again upward to a top part 17 that in a relaxed condition has an upper end edge 18 which in the side view is slanted forward and downward. The same edge 18 also exhibits a small oblique angle d in relation to the main direction of the base part 15, in a view from above. However, a central and crucial feature appears from the side view in fig. 3, namely the curved edge part 13 on the forward underside of each gripping claw, at a position where the gripping claw expands from the narrow neck section 16 to the top part 17. The portion 13, or more specifically a certain intermediate portion 13a, exhibits a shape that is specially adapted for helical engagement against a conductor of appropriate size that has been inserted in the claw and has caused the claw to pivot up to a position such as shown in fig. 4, the intermediate claw. In fig. 4 it will appear that the metallic conductor 9 that has been inserted, and that has a diameter which the intermediate claw 12 has been adapted to, has levelled the top section 17 of the intermediate claw in such a manner that the edges 18 of the intermediate claw lie parallel to the longitudinal direction of the base part, which corresponds to the longitudinal direction of the conductor, and also in such a manner that the top part, as seen in a side view, encloses the surface 11 of the conductor tightly. In this situation the portion 13a, or more specifically the inner edge of portion 13a, engages the surface 11 along a helical line with high pitch, i.e. a low pitch angle. The central feature of the inner edge portion 13a on the top part 17, which also just like the rest of the intermediate claw pair 12 encloses the conductor in a springy and tight manner, gives the following special effect: If an attempt is now made to pull the insulated conductor 10 rearwardly, the inner edge of the portion 13a will bite and lock itself into the surface 11 of the metallic conductor. This inner edge is made particularly sharp in order to provide a scoring/carving effect when such a whitdrawal of the metallic conductor 9 is attempt. The consequence is then that top part 17 tends to pivot forwardly, which provides a further scoring and locking effect. The total effect will be that the metallic conductor 9 is locked in its position, and the terminating is secured. Thus, the crucial feature is the geometrical shape of portion 13a, in connection with a sharp inner edge in this portion. Hence, when terminating is to be effected, the metallic conductor 9 is pushed forward between the pairs of gripping claws 12. The gripping claws make electrical contact in a springy stress situation, part by having the forward end of the gripping claws 12 pressed upwards and outwards, part by having the distance between gripping claws strained to become a little larger. This appears clearly from figs. 2c and 2d. At the same time the gripping claws 12 will, for a moderate pulling force, lock the metallic conductor 9 if it is pulled rearwardly, since the gripping claws will carve into the conductor surface 11 with portion 13a such as explained above. Normally the conductor material will be a soft metal, pure copper or tin coated/silver coated copper with a high electrical conductivity. By arranging several pairs of gripping claws 12 in a successive row, such as appearing from the embodiment example shown, where grip height and gap between the gripping claws are diminished gradually or step-wise from one pair to the next, a terminating part 7,8 will be able to terminate metallic solid conductors 9 having various diameters. For example, commonly used conductor diameters in a low current cable between 0,5 and 0,64 mm may be terminated on the same contact pin or socket. The terminating part constituting the essential feature of the invention, must be made from a springy material having good conduction characteristics, e.g. phosphor bronze or beryllium copper. The terminating part with the gripping claws can advantageously be shaped in a combined stamping and bending tool from a flat metal piece. A typical material thickness may be 0,16 mm. Important design parameters will be material thickness of the metal piece (see fig. 3, a) width of neck section 16 length of top part 17 for each pair of gripping claws 12 (see fig. 3, c) twist angle d for top part 17 smallest enclosing diameter (see fig. 3, e), and the profile shape 13 of the forward part of each gripping claw 12. These parameters shall be mutually tuned so that the spring load allows entry of the metallic conductor 9 by means of moderate hand force. At the same time the twist angle d for the top part 17 in question, the smallest claw enclosure diameter e and the profile 13 on the forward part of each gripping claw shall be tuned in such a manner that the gripping claws 12 enclose the metallic conductor 9 as tight as possible, provide a pressure force on surface 11 that is distributed as uniformly as possible, and in particular a resistance that is as large as possible, by means of biting/carving, if an attempt is made to pull the metallic conductor 9 rearwardly, such as mentioned above. It is favourable if the outermost claw pair 12 is provided with an outwardly tapered, funnel-shaped conductor entry part 14 in order to simplify insertion of the tip of the metallic conductor 9. Such a part 14 is shown in the drawings, and constitutes in the section at the bottom of fig. 3 the top "ears" pointing outward. It is to be noted at the same time that in the same section also appear, as inward pointing edges in the upper part of the circle, the forward tips of gripping claws 12 to the extreme right in the side view above. In the section drawing B-B in fig. 4, the entry portion 14 appears just scarcely as small ears pointing outward, because the right claw pair in this situation, with a metallic conductor 9 that has been inserted, lays partly pivoted toward a horizontal position. In this last section view the inner space is filled by the metallic conductor 9. Finally it shall be mentioned that a terminating part of the type shown in connection with pins respectively sockets for use in plugs and socket contact, advantageously can be used as pure terminating parts e.g. soldered to a printed circuit board, either standing perpendicularly to the circuit board or edge mounted according to conventional technique. Besides, the terminating part in accordance with the invention may also be conceived mounted to contact parts in general contact pieces, i.e. other types of contact parts than pins and sockets as mentioned above.

Claims: A contact pin for use in a plug (1) or in a socket, possibly together with further contact pins, said contact pin (3) having a forward engagement pin part (5) to be inserted in a contact socket (4) of a socket (2) or a plug, and a rear terminating pin part (7) for tool-free terminating thereto of a conductor (10) in a cable, said conductor (10) comprising an insulation sheath and a central, metallic conductor (9) that is solid and has a substantially circular cylindrical surface (11), characterized in that said terminating pin part (7) comprises at least one pair of gripping claws (12) of an electrically conductive material to provide a good electrical contact with the metallic conductor (9) through springy and tight enclosure when the metallic conductor (9) is inserted in a forward direction between said gripping claws (12), and that each claw (12) in a pair has an inner and substantially forward facing sharp edge (13) formed so that when the metallic conductor (9) has been inserted, a portion (13a) of said sharp edge (13) touches the surface (11) of the metallic conductor along a substantially helical curve having a large pitch angle, so that said forward facing edge portions (13a) will carve into the surface (11) of the metallic conductor to lock said metallic conductor (9) if an attempt is made to pull said metallic conductor (9) rearwardly using a moderate pulling force. A contact socket for use in a socket (2) or in a plug, possibly together with further contact sockets, said contact socket (4) having a forward engagement socket part (6) to envelop tightly a contact pin (3) of a plug (1) or a socket, and a rear terminating socket part (8) for tool-free terminating thereto of a conductor (10) in a cable, said conductor (10) comprising an insulation sheath and a central, metallic conductor (9) that is solid and has a substantially circular cylindrical surface (11), characterized in that said terminating socket part (8) comprises at least one pair of gripping claws (12) of an electrically conductive material to provide a good electrical contact with the metallic conductor (9) through springy and tight enclosure when the metallic conductor (9) is inserted in a forward direction between said gripping claws (12), and that each claw (12) in a pair has an inner and substantially forward facing sharp edge (13) formed so that when the metallic conductor (9) has been inserted, a portion (13a) of said sharp edge (13) touches the surface (11) of the metallic conductor along a substantially helical curve having a large pitch angle, so that said forward facing edge portions (13a) will carve into the surface (11) of the metallic conductor to lock said metallic conductor (9) if an attempt is made to pull said metallic conductor (9) rearwardly using a moderate pulling force. The contact pin respectively socket of claim 1 or claim 2, characterized in that said terminating part comprises a successive row of pairs of gripping claws (12) having gradually narrower passage for said metallic conductor (9), for reception and terminating of metallic conductors having various diameters. The contact pin respectively socket of claim 3, characterized in that the first pair of gripping claws (12) in the row to be entered by a metallic conductor (9) that is to be terminated, is equipped with an outward tapered, funnel-shaped conductor entry part (14) on the entry side in order to simplify insertion of the tip of said metallic conductor (9). The contact pin respectively socket of one of the previous claims, characterized in that said terminating part (7,8), possibly the whole contact pin respectively socket, is shaped from a flat metal piece by stamping and bending. The contact pin respectively socket of one of the previous claims, characterized in that every gripping claw (12) extends, from a base part (15) that is substantially longitudinal relative to the metallic conductor (9), cylindrically curving and transverse in relation to the base part (15), via a narrow neck section (16) to a top part (17) which has its largest dimension (c) in the longitudinal direction when the metallic conductor (9) is retained, said top part (17) having an end edge (18) which then faces and is substantially parallel to a corresponding end edge (18) of the other gripping claw (12) of the pair, however where the end edge (18) of said top part forms an oblique angle (d) to the longitudinal direction of the metallic conductor (9) prior to insertion thereof, and that each gripping claw (12) has said sharp edge (13) in a forward region from the neck section (16) and on to the top part (17). A contact assembly comprising a plug and a socket, preferably for use with a low current cable, said plug (1) and said socket (2) comprising contact pins (3) and contact sockets (4) that can engage each other mutually, characterized in that the contact pins (3) and contact sockets (4) are as indicated in claims 1 and 2, possibly also as indicated in claims 3-6. A cable terminating part for use on a circuit board or a contact piece, for tool-free terminating thereto of a conductor (10) in a cable, said conductor (10) comprising an insulation sheath and a central, metallic conductor (9) that is solid and has a substantially circular cylindrical surface (11), characterized in that said terminating part (7) comprises at least one pair of gripping claws (12) of an electrically conductive material to provide a good electrical contact with the metallic conductor (9) through springy and tight enclosure when the metallic conductor (9) is inserted in a forward direction between said gripping claws (12), and that each claw (12) in a pair has an inner and substantially forward facing sharp edge (13) formed so that when the metallic conductor (9) has been inserted, a portion (13a) of said sharp edge (13) touches the surface (11) of the metallic conductor along a substantially helical curve having a large pitch angle, so that said forward facing edge portions (13a) will carve into the surface (11) of the metallic conductor to lock said metallic conductor (9) if an attempt is made to pull said metallic conductor (9) rearwardly using a moderate pulling force.

Inventors: NAELAND GEIR, NAELAND, GEIR
Applicants: TELESAFE AS
Application year: 1999
Main classification: H01R4
IPC codes: H01R4