Tubular ceramic contact for filter connector

Abstract: Filter connector comprising a contact (1) provided with its own filter (6) such that the filter is held around an intermediate portion (5) of the contact by means of a spring (14) compressed between a sleeve (13) resting against an end (17) of the filter and an adapter element (15) mounted at a rear end (4) of the contact. The filter is also held around this intermediate portion by a shoulder (8) of the contact. The adapter element is used to receive a cable. The filter mounted around this contact may be a capacitive filter or else a Pi (π) filter.

Description: An object of the present invention is a tubular ceramic contact for filter connectors. It can be applied more particularly in the field of connectors, whether male or female, having one or more contacts such that each of the contacts has its own electrical filter. Connectors of this kind are preferably used in electronic instruments sensitive to undesired signals such as parasitic RF signals. The advantage of the invention is that it proposes a connector in which the filters of the contacts can be easily withdrawn and replaced. In the prior art, there are known contacts provided with filters and mounted in connectors. A contact provided with a filter has an elongated conductive part having a coupling extremity at a first end and a reception extremity at the second end. The coupling extremity is generally opposite the reception extremity. The reception extremity can receive, for example, a wire or a cable strand. On an intermediate part, between the first end and the second end, the filter contact has a filter mounted around the contact. The filter is brittle, and the filter contact thus obtained is brittle. In a preferred example, the contacts are generally mounted permanently in a connector to ensure that there are no stresses on each of the different portions of the filter contact. A connector of this kind poses a problem, especially when one of the contacts has to be replaced, for example when one of its ends is defective or when one of the filters is damaged. Indeed, the replacement of a filter contact inside a connector of this kind is a lengthy business inasmuch as it is difficult to handle small-sized elements, especially when they are brittle. Furthermore, the total replacement of such connectors is costly, given the intrinsic cost of each of the filter contacts. In the prior art, there also exist connectors for which the mounting and dismantling and, if necessary, the replacement is simplified by the designing of a three-part contact. Such a contact comprises especially a detachable, front coupling part, a rear reception part which is also detachable, and a central stem provided with a filter, the central stem alone being anchored in the casing of the connector. Since the two parts, namely the front and rear parts, are detachable, it is easy to replace them. For example, the rear reception part is connected with the central stem by means of a union nut. Furthermore, the coupling front part may be mounted by means of keying means and elastic bolts. These means may be positioned on the outer rim of a casing containing the filtered central stem. However, the filtered central stem is preferably mounted in such a way that it is held at a front end of the casing, on the front part side, and similarly at a rear end of this central stem, on the rear part side. The filtered central stem is held, for example, by a wall of the casing. This wall is preferably obtained by moulding an epoxy resin around the filter contact. A mounting of this kind is clearly irreversible. A device of this kind is described especially in the document FR-A-2 464 581. The advantage of the device is that the contacts compatible with the filter contact portion are individually detachable and replaceable. Should one of these reception and/or coupling parts be faulty, it can easily be changed. However, this type of connector poses a problem since it is still impossible to access the filtered central stem to make a replacement if necessary. Indeed, the filtered central stem may be damaged during the connection and disconnection with the non-filtered front and rear parts, because of mishandling or deteriorating connections. In this case, it is always necessary to make a total replacement of the portion of the connector comprising especially the filtered central stem. Now this portion of the connector is the most expensive part. It is an object of the invention to resolve the problem by proposing a filter connector comprising a filter contact, such that the filter of this contact is easily detachable. In the solution of the invention, the filter is mounted so as to be sliding on the contact. Furthermore, this filter is held on the contact by means of a spring to that is compressed between a retention bushing, mounted so as to be supported on the filter, and an adapter element. This adapter element is held by mechanical means on a rear end of the contact. This adapter means is preferably used as the reception extremity of a cable. This spring, along with the retention bushing and the adapter element, are mounted so as to be sliding around the contact. Thus, the simple withdrawal of the adapter element mounted at the end of the contact releases the spring and thus eliminates the compression force applied to the retention bushing of the filter. Since the filter is itself in a sliding position, it can be easily dismounted from the contact. Indeed, the filter is itself held around the contact between a ring of this contact and the retention bushing. The invention is defined by the features according to claim 1. The invention will be understood more clearly from the following description and the appended figures. These figures are given purely by way of an indication and in no way restrict the scope of the invention. Of these figures: Figure 1 a shows a sectional view of a filter contact according to a first embodiment of the invention; Figure 1 b is a schematic diagram representing an electrical equivalent of the filter contact shown in figure 1a; Figure 2a shows a sectional view of a filter contact according to a second embodiment of the invention; Figure 2b is a schematic diagram representing an electrical equivalent of the filter contact shown in figure 1a. Figure 1a shows a filter contact 1 according to the invention. The contact 1 is designed to be mounted in a casing of a connector. The contact 1 has a shape such that it is preferably elongated along an axis of orientation 2. The contact 1 has a general cylindrical shape along this axis 2. The contact 1 has chiefly a front end 3, a rear end 4 and an intermediate portion 5 around which a filter 6 is mounted. The intermediate portion 5 also has a cylindrical shape. The front end 3 corresponds to a male pin but it can also correspond to a female receptacle. The front end 3 corresponds to a coupling zone designed to be coupled with a complementary contact positioned for example in a complementary connector of the filter connector. Indeed, it is possible to define a coupling length 7 of the front part 3 such that this length 7 is demarcated between a terminal end of the front end 3 and a shoulder 8 of the intermediate portion 5. Furthermore, the front end 3 has a constriction 9 before this shoulder 8. For example, this constriction 9 improves the retaining of the contact 1 in an insulator of the connector designed to receive the contact 1. But above all, and in general, this constriction 9 attenuates the mechanical stresses on the filter during the connection/disconnection of the connector. In one variant, the front end 3 may have, at the constriction 9, a threaded part that gets engaged in a complementary nut presented in a rear part 10 of the shoulder 8. In this case, the front end 3, which is the coupling zone, may be mounted and dismounted from the filtered intermediate portion 5. In another variant, the contact 1 is obtained by moulding and is formed in one piece. In a preferred example, the terminal end of the front end 3 is gold-plated so as to improve the electrical performances and the quality of the connection made at this coupling zone. The intermediate portion 5 has a diameter of the order of the diameter of the constriction 9. It therefore has a diameter smaller than the diameter of the shoulder 8. Since the intermediate portion 5 is preferably cylindrical, the filter 6 for its part is then also cylindrical and corresponds to a sleeve. The rear end 4 is given a profile such that it is an exact prolongation of the intermediate portion 5 so as to enable a sliding from this rear end 4 towards the intermediate portion 5. It therefore has a same diameter and a same cylindrical shape as this portion 5. Hence, since the filtering sleeve 6 acts as a filter, it is preferably inserted from the rear end 4. The filtering sleeve 6 can slide along the rear end 4 until it comes around the intermediate portion 5. An inner diameter of the filtering sleeve 6 is that it is slightly greater than the outer diameter of the intermediate portion 5. Thus, the filter 6 is not directly in contact with the intermediate portion 5. Indeed, the filtering sleeve 6 is in contact solely with the shoulder 8. This shoulder 8 itself is in direct contact with the intermediate portion 5. The shoulder 8 in particular has a rim 11 on which a border 12 of the filter 6 is supported. In one example, the filtering sleeve 6 is made of ceramic. It is then perfectly symmetrical and has a total homogeneity of structure. In another example, the filtering sleeve 6 may be obtained by a winding, on several layers, of a double foil comprising a first insulating foil 11 and a second conductive foil, the second conductive foil alone being connected with the contact 1 and the first insulating foil being connected to a ground. To be held in position strictly at the intermediate zone 5, the filtering sleeve 6 is held by means of a second insulating sleeve 13. This insulating sleeve 13 works together with a spring 14. The spring 14 is compressed between an adapter element 15 and the insulating sleeve 13. The adapter element 15 is mounted at the level of the real end 4. Similarly, the second insulating sleeve 13 is inserted around the intermediate part 5 by sliding from the rear end 4. The insulating sleeve 13 has a length such that it enables the walls of this insulating sleeve 13 to be positioned between the intermediate contact portion 5 and the filter 6. This ensures the perfect alignment and centring of the intermediate portion 5 in the middle of the filtering sleeve 6. This insulating sleeve 13 has a flange 16 through it is possible to present a retention means at the second border 17 of the filter 6. This second border 17 is opposite the border 12. Furthermore, this flange 16 offers a support surface 18 on which the spring 14 can rest. The spring 14 is furthermore held at an edge 19 of the adapter element 15. The spring 14 is compressed so as to retain the filtering sleeve 6 between the shoulder 8 and the flange 16. This edge 19 is preferably presented at a hole opening out into a cavity 20 of the adapter element 15, the cavity 20 receiving the rear end 4. The adapter element 15 may for example be a shaft mounted on the rear end 4. For example, this shaft 15 is crimped or soldered to this rear end 4. Should the shaft 15 be simply crimped to the rear end 4, then it is possible to dismantle this adapter element. The adapter element 15 has a second shaft 21 with a second end opposite the shaft compatible with the rear end 4, for example to receive a cable. Thus, the contact 1 sets up a connection between a cable inserted at the rear end into the shaft 21 and a contact of a complementary connector of the front end 3. From the electrical viewpoint, as shown in the schematic diagram of figure 1b, the contact 1 described here above is an electrical assembly provided with a capacitor filter. Indeed, the current passing through the path 22 is filtered by a capacitor 23 parallel-mounted on this path 22. A plate of this capacitor 23 is connected to a ground 24. In a second embodiment shown in figure 2a, the contact 1 has a Pi (π) filter. In a preferred example, the contact 1 comprises ferrites 25. The ferrites 25 preferably have a tubular shape and are mounted around the contact 1 at the intermediate portion 5 in such a way that they are positioned between this intermediate portion 5 and the filter 6. The insulating sleeve 13 then has a different shape. In this case, the insulating sleeve 13 is conductive. In particular, in this example, the insulating sleeve 13 no longer has long walls along the intermediate portion 5 so as to centre the contact 1 in the middle of the filter 6. In this example, the insulating sleeve 13 has a narrowed portion 26 behind the flange 16. This narrowed portion 26 has a small length and extends slightly along the intermediate portion 5 between the contact 1 and the filter 6. In fact, the centring of the intermediate portion 5 in the middle of the filter 6 is guaranteed by means of the ferrites 25. Furthermore, this insulating sleeve 13, on the other side of the flange 26, may have a narrowed and split part 27 that sets up the electrical continuity and lies partly along the rear end 4 of the contact 1. Thus, the holding of the insulating sleeve 13 along the axis 2 does not damage the structure of the contact 1. Indeed, given the length of the contact 1, the insulating sleeve 13 thus permits a slight mobility of the contact 1 within the filter 6. With respect to the mode of retention of the filter 6 at the intermediate portion 5, the insulating sleeve 13 also cooperates with the spring 14 and the adapter element 15 mounted around the rear end 4 of the contact 1. This shaft is similarly crimped or else soldered. For example, a ferrite tube 25 has a length such that it is totally masked by the filter 6. Furthermore, the length of the narrowed portion 26 is designed in such a way that the ferrite 25 is positioned so as to be centred with respect to the filter 6, along the axis 2. Thus, the structure of the filter proposed in figure 2a is perfectly symmetrical. The schematic diagram of the filter proposed by this configuration is shown in figure 2b. It also comprises the path 22 connected to the first capacitor 23, a plate of this capacitor 23 being connected to the ground 24, and series-connected with a coil 28 corresponding to the ferrite 25. This: coil is parallel-connected with a second node 29 with a second capacitor 30. The ferrite 25 therefore plays the role of the coil 28. The coil 28 is series-connected with the path 22 conveying the current received by the contact 1. It has an electromagnetic shielding role. The structure thus described truly corresponds to a Pi (π) filter. Inasmuch as the filter 6 is perfectly homogeneous and as the ferrite 25 is also constituted by a homogeneous tube and positioned so as to be centred with respect to the filter 6, the capacitors 26 and 30 each correspond to two half-capacitors of equal value. The Pi (π) filter is a quadrupole filter, namely an inductive-effect filter. Its main purpose is high-frequency filtering and it additionally provides a shielding against disturbances conducted by the contact 1. A Pi (π) filter is useful especially when the disturbances generated in the coupling zone are great. Furthermore it has the effect of counterbalancing the inductive effect of the spring 14.

Claims: An electrical filter connector comprising an elongated contact (1) with an electrical filter mounted slidably on said contact between a shoulder (8) on said contact and an adapter element (15) mounted at a rear end (4) of the contact, whereby a sleeve (13) also mounted slidably on said contact between the filter (6) and the adapter element (15) is held against the filter by means of a spring (14) compressed between a supporting surface (18) of the sleeve (13) and said adapter element (15). Connector according to claim 1, whereby the filter is a tubular sleeve, preferably made of ceramic, sliding and mounted from the rear end around the contact. Connector according to one of the claims 1 to 2, whereby the filter is obtained by the winding of a double foil comprising a first insulating foil and a second conductive foil, this second foil being connected alone with the contact, the first foil being connected to a ground (24). Connector according to one of the claims 1 to 3, whereby the filter is a capacitive filter. Connector according to one of the claims 1 to 3, whereby the filter is a Pi (π) filter. Connector according to claim 5 whereby it comprises a ferrite, this ferrite (25) preferably forming a tube mounted around the contact between the contact and the filter. Connector according to one of the claims 1 to 6, whereby the adapter element is a shaft soldered to the rear end (4) of the contact. Connector according to one of the claims 1 to 7, whereby the adapter element is a shaft crimped on the rear end (4) of the contact. Connector according to one of the claims 1 to 8, whereby the sleeve (13) and the adapter element (15) respectively comprise a shoulder (18, 19) on which the spring takes support.

Inventors: GUEDEAU PHILIPPE, PICARD JEAN-PIERRE, GUEDEAU, PHILIPPE, PICARD, JEAN-PIERRE
Applicants: FRAMATOME CONNECTORS INT, FCI
Application year: 2001
Main classification: H01R13
IPC codes: H01R13