GB2195500A - Coaxial cable plug - Google Patents

Abstract

The present invention relates to an improvement in the construction of connector plugs for coaxial cables for car radio aerials, particularly suited for being connected to the coaxial cable by means of an automatic fitting. According to the invention, the connector plug is formed by a small insulating tube 10, which is essentially cylindrical and hollow inside, by a plug-in socket 14 which is inserted into the small tube and electrically connected to the central wire of the coaxial cable, and by an external thin metal sheet 30 surrounding the small tube and locking the cable and the braid in the terminal part. The external thin metal sheet is equipped with one or more fins 35, 36 obtained by cutting out the thin metal sheet itself and which are arranged in space in such a way that, when the connector plug is connected to the coaxial socket, the resultant of the elastic reaction forces is not zero and such that it produces a subsequent contact between the cylindrical part of the connector plug and the cavity of the socket. <IMAGE>

Description

SPECIFICATION Improvement in the construction of a plug for coaxial cables of autoradio antennas DESCRIPTION The invention concerns an improvement in the construction of plugs for coaxial cables of autoradio antennas, said plugs being particularly suited to be connected with the coaxial cable by means of an automatic assembly.

In the Italian Patent Application No.

85630/A/84 the same inventor has proposed the realization of a plug for coaxial cables for autoradio antennas suited to be automatically assembled. Said plug consists essentially of an insulating sleeve made of plastic material, having an external cylindrical shape presenting two different diameters and having an axial hole, which is also cylindrical with sections having different diameters. From one end of said hole a metal prong is introduced which blocks the central wire of the coaxial cable, while at the opposite end the braid, folded on itself and inserted for a certain length inside the sleeve, is blocked together with the cable by the winding of an external, shaped metal band. The metal band wound partly on the cable and partly on the sleeve of insulating material closes on three different diameters, since it is provided with appropriate slits.

Therefore, an area of said metal band blocks, as has been mentioned before, the coaxial cable on the antenna side, the central area is appropriately calibrated in order to receive the contact of the coaxial socket being connected with it, while the other part of the metal band is closed on the area where the sleeve receives the prong.

The simplicity of the components and the fact that no welding is necessary between the cable and the prong, makes such construction particularly advantageous in performing the assembly between the plug and the cable with automatic machines.

It has been observed that one of the limitations to the just described advantages consists in the difficulty of obtaining a perfect calibration of the central part of the prong in order to insure a good contact in the subsequent connection between the plug and the coaxial socket. In fact, when using automatic means, the calibration of the central body of the plug is obtained by closing the outside metal band on the plug using a press with a shaped male and female die. Sometimes the inconsistency of the characteristics of the materials, both as far as the metal band and the sleeve of plastic material are concerned, makes it possible to obtain, with the same die closing pressure, diameters exceeding the tolerance admissible in order to have a good contact with the plug.

The purpose of the present invention is that of overcoming the just mentioned inconveniences.

In particular the goal is to obtain that the plug, although it is assembled by means of automatic means, always insures a good contact with the coaxial socket.

Another goal is to obtain that the contacts between the plug and the socket are not influenced by the variations in the mechanical characteristics of elasticity of the materials.

Yet another goal is to obtain that the contact between the central body of the plug and the socket is insured both of the elastic fins obtained on the external metal band, and by a part of the cylindrical surface of said external metal band.

All the listed goals and others which will be better illustrated here-below are reached in the construction of a plug for coaxial cables including a sleeve of insulating material having an axial hole, a prong inserted in the hole of the sleeve and an external metal band enclosing the sleeve and clamped around the cable, characterized in that the external metal band of said plug presents on its cylindrical surface one or more elastic fins obtained from slits on the material effected on the metal band itself, the position of said fins on the surface being such, that the elastic reaction caused by the insertion of the plug into the socket creates a non-insignificant force resultant, such as to cause the center of gravity of the plug to be lowered, so as to insure further contact between the cylindrical area of the metal band of the plug being opposite to the fins and the cylindrical cavity of the socket. For instance, in the case that the metal band is provided with only two fins, in order to reach the goal it is sufficient that the plane containing the two main symmetry axes of the fins does not pass through the center of gravity axe of the plug.

An advantage being thus obtained, is that the contact between the plug and the socket is not only insured by the fins, but also by the part of the cylindrical surface of the plug which rests on the corresponding cavity of the socket, and since such part is long, it creates a contact which by itself equals the contact of an entire series of fins.

The increase in the contact surface is highly advantageous, since the contact resistance is thus lowered to the advantage of the signal received by the antenna.

These and other advantages and construction details will be better understood in the description of a preferred form of execution of the plug being the object of the present invention, which is given by way of example only, and is not meant to limit the scope of the present invention, and wherein: Figure 1 shows in perspective the three components of the plug; Figure 2 shows in perspective the assembled plug and coaxial cable; Figure 3 is a section which shows the con tacts between the plug and the coaxial socket; Figure 4 is a section showing the connections between the cable and the plug.

With reference to Figs. 1 and 4, the insulating sleeve, indicated as a whole with 10, presents an axial hole with sections having different diameters delimiting different cylindrical chambers. The cylindrical chamber having the largest diameter is indicated with 11 and it houses the coaxial cable 20 stripped of its insulation and the screening braid 22 folded backwards towards the cable. Chamber 12 adjacent to chamber 11 and having a smaller diameter than 11, houses insulating sleeve 21 of the coaxial cable covering central wire 23.

The chamber indicated with 13 and having the smallest diameter, has a section which repeats the shape of the terminal part of prong 14 which is inserted into said chamber.

The terminal part of coaxial cable 23 is also inserted into chamber 13, so that when prong 14 is inserted, wire 23 is comprised between the wall of chamber 13 and the prong, thus insuring the electric connection with the prong itself.

The external metal band indicated as a whole with 30 presents a longitudinal cut 31, it being obtained from a flat metal band which is subsequently cut and bent. Moreover, in said metal band two areas indicated with 32 and 33 are distinguished. The shorter area 32 is the part of the metal band which, after it has been compressed under a press, tightens around the bent braid 22 and the coaxial cable 20. The area indicated with 33 is the one which receives insulating sleeve 10 which is fixed to the metal band by means of the deformation obtained with the point of a working tool of the machine for the automatic assembly, said- deformation being made in correspondence with indentation 34.

In the same area 33 of the metal band two fins 35 and 36, bent at an angle and lifted from the cylindrical surface are obtained by cutting and bending the band itself, so that they react elastically when the plug is coupled with the socket.

With reference to Fig. 3, it can be observed that fins 35 and 36 have been obtained from metal band 30 in such a way that the plane passing through their symmetry axes does not contain the center of gravity axe of the plug.

Thus, when the plug is inserted into socket 40, the elastic reaction exerted on the fins by internal wall 40, causes the plug to be pushed into contact also with the inside wall of the socket in 41. Thus, with certainty at least three contact areas are created, two of which correspond to the fins and one (41) corresponds to the part of the cylindrical surface of metal band 30 being in contact with socket 40.

The contact between two cylindrical parts of the plug and of the socket can also be obtained with more than two fins, provided that the spatial arrangement of said fins is such as to cause a non-insignificant resultant of the elastic reaction forces which develop when inserting the plug into the socket.

Nothing changes if the fins, which are represented in the drawing with one of their ends detached from the metal band, are connected to the metal band by both of their ends, since, in order to obtain the just described multiple contact effect, the only condition necessary is the non-insignificant resultant of the elastic reaction of the fins, such condition being satisfied by the just mentioned spatial distribution.

The improvement being the object of the invention can also be applied with equal advantage to the coaxial plugs of the traditional type, that is td the plugs which have the central wire of the coaxial cable welded to the prong or fixed to it by means of a screw.

Claims (5)

1. A plug for a coaxial cable comprising a prong being electrically connected to the central wire of the coaxial cable, an insulating sleeve in which the prong is fixed and an external metal band enclosing the insulating sleeve and blocking the coaxial cable and being electrically connected to the braid (22) of said cable, characterized in that the external metal band (30) of said plug presents on its cylindrical surface one or more elastic fins (35, 36) being obtained by cutting the metal band itself, and being bent and lifted from the cylindrical surface of the metal band and being distributed on said surface in such a spatial arrangement that the elastic reaction force caused on the fins by the insertion of the plug into a coaxial socket (40) shows an non-insignificant resultant, such as to cause yet another contact (41) of the cylindrical part of the plug on the cavity of the socket.

2. A plug according to claim 1, characterized in that the connection between the central wire (23) of the coaxial cable and the prong (4) is made by contrast between the prong itself and the seat where the prong inserts itself, the wire (23) being comprised between the prong and the housing wall inside the insulating sleeve.

3. A plug for a coaxial cable according to the claims 1 or 2, characterized in that the fins being present on the metal band are two (35, 36) and are arranged spatially in such a way that the plane containing the symmetry axes of said fins does not contain the center of gravity axe of the plug.

4. A plug according to the claims 1 and 2, characterized in that the fastening between the external metal band (30) and the insulating sleeve (10) is obtained by means of a deformation caused by the pressure of a pointed tool in a weakened area (34) of the longitudinal cut (31) of the external metal band (30).

5. A plug according to the preceding claims and according to what has been described and illustrated in the enclosed figures of drawing.