Connector for coaxial cables

Abstract: A connector for coaxial cables is described having low parasitic inductance and capacitance which permits the typical impedance value of the coaxial cable to which it is connected to be maintained unaltered, and also creates good screening thanks to a special stop dowel which is electrically earthed to the equipment in which the connection between the printed circuit of the user equipment and the lead of the coaxial cable is obtained by means of a pin held in position between insulated elements and thus having no contact with the external metal parts of the connector.

Description: This invention relates to a connector which can be used on any type of electronic and/or electrical equipment which requires connection to a coaxial cable in order to function, with particular reference to the construction of distribution systems of radio and television signals. Its special characteristic is that it permits secure circuit connection without changing the typical impedance value of the coaxial cable. It is known that various types of metal terminals are used to connect coaxial cables to electronic outlet boards, particularly in the connections of radio and television sockets. The disadvantage of these metal terminals is that they alter the typical impedance value of the coaxial cables because of the effect of the parasitic inductance present in the socket itself. In the case of high frequencies, the final result is that the signal received is altered or at least subharmonic disturbance is introduced. The documents WO-A-8701520 and DE-U-8710240 relate to two similar devices, in which the connection between the live head of the coaxial cable and the socket terminal is effected with a complex mechanical system, where the screening is obtained by means of a screening cover which is an element of the contact system for the coaxial lead. The document DE-C-739043 filed in the year 1937 when television was unknown relates to a socket for simple electrical cables. Document CH-A-238042, also filed when television in Europe was still inexistant (1943), relates to a device to be used for simple electric cables. The present invention attempts to eliminate the unwanted problems deriving from the negative effects of the parasitic inductance present in the socket, providing a connector for coaxial cables having the features recited in the characterizing part of Claim 1. Additional advantageous features are indicated in the dependent Claims 2 to 4. This invention eliminates all this since the cable and the electronic circuit are only connected electrically, all parasitic inductances being isolated and cut out, at the same time obtaining a good level of screening thanks to the special stop dowel which is electrically earthed to the mass of the equipment. In effect, the invention comprises a connector which houses an insulated contact pin onto which is screwed a stop dowel with an insulated washer which screws down the head of the live lead of the coaxial cable. This connector is also extremely practical since the cable does not have to be inserted into a gauged aperture but into the special housing in the flat, lightly knurled head of the contact pin and it is then screwed down by means of the insulated stop dowel. The above-mentioned characteristics permit a connection to be obtained and this permits the whole equipment to function over a range of frequencies up to 2 GHz, maintaining relatively limited dimensions so as to permit easy use of the devices (TV sockets, various distributors) in the special flush-mounted wall boxes. These and the other characteristics will be explained more clearly in the course of the following detailed description provided purely as an indicative and non-limiting example of the scope of this invention, and supported by the various illustrations in the drawings attached herewith, in which: Figure 1 shows a very enlarged front view of the pin-holder collet and the stop dowel dissasociated from the insulating element which exerts the connecting pressure on the conductor; Figure 2 shows an exploded cross section of the various components of the connector in question; Figure 3 shows a general view of the connector, demonstrating how the coaxial conductor is screwed down by the insulated stop dowel; Figure 4 shows a full view of a radio and TV socket provided with the connector in question; Figure 5 shows a full view of a radio and TV socket provided with the connector in question, showing the connected coaxial cables; and Figure 6 shows a cross section of the metal box structure which contains the connectors according to this invention. Referring now to the attached drawings, the connector 1 in question comprises a metal box structure 2, forming part of the body 3 of the socket 4, in which two cylindrical threaded seats 5 have been hollowed out, provided with apertures 6 at the front and having a profile 7 at the back which permits the insertion of the insulated element 8, into which the connecting pin 9 is inserted. The aforesaid element 8 is inserted up to the underlying counterboring 11, and only the terminal 12 of the pin 9 pierces through the lower part of the counterboring 11 and is then soldered to the circuit plate 13 of the socket 4. A stop dowel 14 consisting of an external threaded hollow body 15 into which a flexible metal element 17 and the insulated presser 16 are inserted, is screwed into the aforesaid cylindrical threaded seats 5. The said stop dowel 14 has an internal circumferential rib 18 in order to reduce the attrition between the internal seat 19 and the presser 16 which is subject to axial play during screwing down. At this point the socket 4 is already set up for the coaxial connection. After the cable 20 has been appropriately stripped, the live lead 21 is inserted into the connector terminals in correspondance to the flat knurled head 22 of the connecting pin 9 and the dowel 14 is screwed down completely thus ensuring the electrical connection with the circuit board 13 which is underneath. The head 22 of the pin 9 is knurled to improve the hold of the internal conductor. Subsequently the braiding 23 of the two coaxial cables is earthed by a traditional fixing plate 24 provided with a threaded locking element 25 located in a central position. It must be noted that the external body of the connector can be of a different external shape and the internal sizes can be different in order to adopt to the various types of sockets and the various types of utilisations foreseen. This detailed description demonstrates that this connector is practical to use and produces a considerable reduction in disturbance induced by parasitic inductance, as has already been said. Finally, it must be emphasised that the present embodiment does not limit the scope of this invention but, on the contrary, numerous modifications, additions, variations or replacements of elements can be made to this invention without affecting its principle or its objects as defined in the claims attached hereto.

Claims: Connector (1) for ensuring electrical connection between the outlet boards of electronic or electric equipment and the lead end (21) of a coaxial cable (20), comprising a metal box structure (2) which is part of the body (3) of a wall socket (4), characterized in that the metal box structure (2) is provided with two cylindrical seats (5) having an upper and lower part, an insulated element (8) being inserted in the lower part of each of said seats (5), each of said insulated element (8) receiving a central conductive connecting pin (9) provided with a flat head (22) on which the live end (21) of the coaxial cable (20) is placed and is held with the required locking pressure by an insulated presser (16) arranged in the internal seat (19) of a stop dowel (14) screwed down in the upper threaded part of the internal seats (5) of the box structure (2). Connector according to Claim 1, characterized in that the flat head (22) of the connecting pin (9) is knurled to ensure optimum electrical connection between said pin (9) and the live end (21) of the coaxial cable (20) and minimize interference produced by parasitic inductance. Connector according to Claim 1, characterized in that an elastic flexible washer (17) is arranged in the internal seat (19) of the stop dowel (14) above the insulated presser (16) to ensure electric connection between the live end (21) of the coaxial cable (20) and said pin (9) even if the stop dowel (14) is not fully screwed down. Connector according to Claim 1, characterized in that the insulated presser (16) is held in position on the live end (21) of the coaxial cable (20) being received in a contoured upper hollow seat of the insulated element (8), said seat having also a front aperture, the shape of the seat and its front aperture matching a complementary profile (7) and aperture (6) of the cylindrical seats (5) of the box structure (2) of the socket (4).

Inventors: SCIARMA SAURO, VALERI SANDRINO, SCIARMA, SAURO, VALERI, SANDRINO
Applicants: HELMAN ELETTRONICA SPA, HELMAN ELETTRONICA S.P.A.
Application year: 1989
Main classification: H01R17
IPC codes: H01R13