Patent Publication Number: US-6705875-B2

Title: Coaxial plug member

Description:
TECHNICAL FIELD 
     The invention relates to a coaxial plug member comprising a housing, an inner contact, an outer contact and an insulating piece which is arranged between the inner and outer contacts. 
     BACKGROUND OF THE INVENTION 
     In the event that such a plug member is plugged into a complementary plug member in order to establish a plug connection, there exists the danger that the two plug members are dislocated or turned in relation to a centered arrangement where the two middle axes of the plug members are coincident. In the case of such a misalignment, undesirably high loads are possibly exerted on the plug contacts. These loads are transferred, to some extent via the housing and to some extent in direct way, to the component to which the plug member is attached. If the contacts have been soldered with the components, in particular in SMT technology, there exists the danger that the loads acting on the soldering spot lead to a damaging of the soldering spots. 
     From WO 00/52788 there is known an adapter which serves for connecting two circuit boards, in particular in the field of RF engineering. A base member is mounted on one of the circuit boards, this base member being provided with a ball-shaped head. An insulating piece provided with an inner conductor and an outer conductor is pivotally attached to the ball-shaped member. The insulating piece can be plugged into a complementary base member which is mounted on the other circuit board. Due to the pivoting arrangement of the insulating piece, it is possible to compensate for a lateral offset between the two circuit boards. By plugging the insulating piece into the complementary base member at differing depths, deviations in the distance between the two circuit boards can be compensated for. The known adapter, however, does not concern a plug member, but a coaxial connection which serves for a permanent connection between two circuit boards in a stack of circuit boards. Moreover, the structural expenditure is comparably high, because with the articulated attachment of the insulating piece, making contact with the inner and outer conductors is very complicated. 
     BRIEF SUMMARY OF THE INVENTION 
     It is the object of the invention to further develop a coaxial plug member of the type initially mentioned to the extent that with low structural expenditure the contacts are subjected to lower loads, if it happens that the plug member is inserted into a complementary plug member with a misalignment being present. According to the invention, a coaxial plug member is provided which comprises a housing, an inner contact, an outer contact and an insulating piece which is arranged between the inner and outer contacts. The outer contact is pivotally attached to the housing, as a result of which also the insulating piece received in the outer contact and the inner contact received in the insulating piece are able to pivot as a unit. In this way there results a particularly simple construction, because solely one single component has to be pivotally attached to the housing, namely the outer contact. Nevertheless, on plugging in of the complementary plug connector, the contact unit consisting of the inner and outer contacts and of the insulating piece is able to automatically self-align corresponding to the misalignment of the two plug members, so that the middle axes of the contacts to be plugged into each other are coincident again. The contacts of the two plug members can then easily be pushed into each other, without excessive loads occurring. 
     According to the preferred embodiment it is provided for that the inner contact is provided with a ball-shaped head onto which a spring clip is slipped which can be connected with a circuit board by means of SMT technology. Using a ball-shaped head results in a connection between the inner contact and the spring clip in the nature of a ball joint, so that the contact unit is able to move relative to the spring clip without a movement being transferred to the spring clip. Thereby it is ensured that the SMT soldering spot, by means of which the spring clip can be connected with the circuit board, is not exposed to loads. The contribution of the ball joint-like connection between the inner contact and the spring clip, for pivotally arranging the contact unit, can be neglected. 
     Preferably it is provided for that the ball-shaped head is approximately coincident with the center of motion of the contact unit in the housing. Thereby it is ensured that no translatory motion occurs between spring clip and inner contact, if the unit of inner contact, outer contact and insulating piece is swiveled relative to the housing; there will merely occur a rotation by few degrees. 
     Advantageous designs of the invention will be apparent from the sub-claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows in a perspective view a coaxial plug member according to the invention; 
     FIG. 2 shows in a perspective, exploded view the coaxial plug member of FIG. 1; and 
     FIG. 3 shows in a sectional view the coaxial plug member of FIG. 1 together with a complementary plug member. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIGS. 1 and 2 there is shown a coaxial plug member which as the most important components has a housing  10  as well as two contact units  12 ,  14  that are attached to the housing  10 . Each contact unit is constituted by an outer contact  16 , an inner contact  18  and an insulating piece  20 . 
     The housing  10  consists of an electrically insulating material, for example plastics, and has two openings for receiving the contact units. Associated with the openings is one retention ring  11  each, the function of which will be explained below. 
     The outer contact  16  consists of an electrically conductive material and has at its end associated with the housing  10  a sleeve-shaped skirt  22  which is provided with two recesses  24 . The free end of the skirt  22  is provided with a surrounding projection which is interrupted by the two recesses  24 , so that the free end forms two latching hooks  25 . A shoulder  23  is provided at the transition of the skirt  22  to the body of the outer contact  16 . On the opposite end, the outer contact is provided with a plurality of elastic tongues  26 . 
     The insulating piece  20  consists of an electrically insulating material and is provided with two oppositely arranged protrusions  28 , the dimensions of which are chosen such that they are able to be slipped into the recesses  24  of the outer contact  16 . The inner contact  18  consists of an electrically conductive material and in this arrangement is configured as a sleeve, the one end of which is provided with a slot and the other end of which is provided with a ball-shaped head  30 . The inner contact  18  is further provided with a latching collar  32 . 
     Associated with the inner contact  18  is a spring clip  34  which is given a U-shape. The two oppositely arranged legs of the spring clip  34  are provided for elastically engaging the ball-shaped head  30  of the inner contact. The web connecting the two legs of the spring clip with each other is provided for to be connected with an electrically conductive surface area by means of SMT technology. 
     The coaxial plug member is assembled in the following way: First, the retention ring  11  is fixed in the housing  10 . The end face, lying within the housing, of the retention ring  11  then forms an undercut which could be manufactured only with great difficulty in the case of a one-piece design of the housing  10 . Next, the insulating piece  20  is pushed into the outer contact  16  such that the protrusions  28  engage in the recesses  24 . The outer contact  16  complete with the insulating piece  20  is then pushed into the retention ring  11 , with the latching hooks  25  snapping in place behind the end face of the retention ring  11 . The distance between the latching hooks  25  and the shoulder  23  of the outer contact  16  is larger than the length of the retention ring  11 , so that a defined play is present in axial direction. Furthermore, the inner diameter of the retention ring  11  is larger than the outer diameter of the skirt  22 , so that a defined play is present in radial direction, too. 
     The inner contact  18  is inserted in the insulating piece  20 , mounted in the housing  10 , from the other side than are the insulating piece and the outer contact  16 , as is shown in FIG.  2 . In so doing, the latching collar  32  of the inner contact  18  latches in place in the interior of the insulating piece  20 , so that the inner contact is firmly received. Finally, the spring clip  34  is slipped onto the ball-shaped head  30  of the inner contact  18 . With this, assembly of the coaxial plug member is completed. The important feature lies in that the pivoting arrangement of the contact unit on the housing is substantially established by the outer contact  16  only. The ability to pivot results from the radial and axial play between the retention ring  11  and the skirt  22  in the housing. 
     FIG. 3 shows the assembled coaxial plug member which in this arrangement is mounted in a receiving part  40 . There is further shown a complementary plug member  42  which is plugged into the assembled coaxial plug member. The complementary plug member has pin-shaped contacts  44  which are pushed into the inner contacts  18  of the coaxial plug member. It is clearly to be seen at the lower outer contact  16  of FIG. 3 how the latter is obliquely accommodated in the housing  10  and in the retention ring  11 : The distance between the left-hand end face of the retention ring  11  and the shoulder  23  is on the lower side much smaller than on the upper side, because the outer contact  16  together with the insulating piece  20  and the inner contact  18  is rotated relative to the housing  10  in anti-clockwise direction. Such pivoting motion of the contact unit occurs around a center of motion which is approximately coincident with the center of the ball-shaped head  30  of the inner contact  18 . This is why merely a rotational movement occurs between the spring clip  34  and the ball-shaped head  30  when the unit made up of outer contact  16 , inner contact  18  and insulating piece  20  adapts to an obliquely inserted complementary plug member. In spite of the frictional forces between the ball-shaped head  30  and the spring clip  34  and due to the large distance between the free front end of the contact units  12 ,  14  and the center of motion on the ball-shaped member  30 , this rotational movement can be achieved with low forces, as the forces acting have a large lever arm. These forces required are significantly smaller than those necessary for a translational movement between ball-shaped head and spring clip, because a translational movement does not benefit from a long lever arm.