Plug connector and method for connecting same

A flexible coaxial cable has a special plug connector with a tensile strength comparable to that of the cable at the connecting point to the cable. This plug connector (14) consists of a nipple (1) which is threaded with a plug sleeve (3). Between these two plug elements is arranged a contact ring (2) which is soldered to the covering (23). This contact ring (2) includes a bore (13), through which the soldering can be optically controlled and the vapors can be vented during soldering. The end surfaces of the contact ring (2) and the cable dielectric (21) are face-turned. Accordingly, the cable lengths can also be precisely determined. The exposed inner conductor (20) is soldered to a plug pin (4). The plug dielectric (5), plug pin (4) and the plug housing (3) itself are held in rigid positions in the plug housing (3) by means of a bore (10) filled with epoxy resin (9) and by a constriction (11) in the plug pin (4). This plug connector (14) also permits a precise control of impedance adaptation during and after soldering.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an improved plug connector for flexible 
coaxial cables and to a method for connecting same. 
2. Prior Art 
In the magazine Mikrowellen Magazin Nr. 3, 1977, the company Gore & Co. 
GmbH, D8011 Putzbrunn bei Muenchen, compares a flexible coaxial cable with 
a semirigid cable. The design of such a flexible coaxial cable includes an 
inner conductor made of 19-stranded silvered copper. The stranding results 
in the required flexibility and prevents the inner conductor from 
wandering within the dielectric layer during bending. A 
polyetetrafluorethylene is suggested as the dielectric, which substance 
has been stretched and therefore, as a matrix-like structure, it has a 
high proportional component of air. To achieve the necessary concentric 
structure, the dielectric material is coiled here about the inner 
conductor. 
As is known, the covering reduces emissions or radiation to a minimum. With 
flexible coaxial cables the electrical values must be assured, even during 
bending. In the described coaxial cable this is achieved in that a 
silvered copper foil was overlappingly coiled onto the dielectric layer 
and this first covering is surrounded with a second covering of woven 
silvered copper wire. Finally, the thus-constructed cable is provided with 
a plastic exterior cover. 
In a second publication in the same magazine, Mikrowellen Magazin Nr. 4, 
1980, it is mentioned that a new cable construction will require new plug 
connectors. Such a new plug is not described in either of the publications 
with any specificity beyond simple suggestions. 
There is a need in the art for a plug connector which fulfills the peculiar 
requirements of flexible microwave coaxial cables. 
SUMMARY OF THE INVENTION 
According to the invention this is achieved by a plug connector having the 
characteristics in the characterizing portion of independent claim 1. A 
method for connecting the plug connector is described in claim 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The coaxial cable 15 according to FIG. 2 consists, as viewed from the 
inside out, of an inner conductor 20, a layer 21 of a dielectric material 
concentrically surrounding this inner conductor, such as 
polytetrafluorethylene, a first covering 22 of silvered copper strip 
overlappingly coiled onto the layer 21, a second covering 23 of woven 
copper wire and an exterior cover 24, for example, of 
polytetrafluorethylene. 
The coaxial plug connector 14 consists of the following details: a nipple 1 
with an exterior threading 1a lying closely against the exterior cover 24, 
a contact ring 2 having a radial bore 13 which can be made as a 
penetrating bore, a plug housing 3 with an interior threading 3a 
complementary to the exterior threading 1a and with a sleeve 3b on the end 
lying opposite the interior threading 3a, a plug dielectric 5 located in a 
sleeve 3b, and a connecting sleeve 8. A plug pin 4 having a constricted 
section 11 includes an axial hollow chamber 12 at the inner end of the 
plug for the inner conductor 20 of the coaxial cable 15. The sleeve 3b and 
the plug dielectric 5 are also diametrically bored through. This bore 10, 
when constructed, is aligned with the constricted section 11 of the plug 
pin 4. This bore 10 is filled with cast epoxy resin, so that a radial 
centering support 9 is formed. 
A circlip or snap ring 6 is inserted in an annular groove 6a in the outer 
wall of the sleeve 3b, which circlip 6 engages in an annular groove 8a in 
the inner wall of the connecting sleeve 8 and thereby holds the connecting 
sleeve 8 in a condition in which it can rotate freely with at most a 
limited amount of axial play. Finally, an additional seal 7 of an elastic 
material, such as rubber, is placed on a shoulder 3c on the outside of the 
sleeve 3b. 
In the constructed condition according to FIG. 2 the inner conductor 20 of 
the coaxial cable 15 is soldered in the hollow chamber 12 of the plug pin 
4. The contact ring 2 lies on the second covering 23 and is also soldered 
thereto. The bores 13 serve on the one hand to provide optical control for 
proper soldering, i.e., whether the soldering material has flowed 
correctly, and on the other hand steam and the gas of the flux material 
can escape through these bores 13, so that the soldering material also has 
enough space to spread out. 
To connect the plug connector 14 to a coaxial cable 15, the coaxial cable 
15 is first cut to the precise length. The cut surface 24(a ) must be 
smooth. Then the outer cover 24 is cut all the way around at three 
locations 31, 32, and 33. There are thus produced an end cover section 36, 
a center cover section 35 and an inner cover section 34 (FIG. 3). The 
center cover section 35 is then removed (FIG. 4) and the exposed weaving 
of the second covering 23 is tinned. A soft solder, which melts at 
180.degree. C. is used for this purpose, so that a tinned section 37 is 
produced. The end cover section 36 is then removed, a shrink tube (not 
shown) is pushed over the thus-prepared cable 15. From the plug connector 
14 the nipple 1 is then pushed onto the exterior cover 24 (FIG. 5). The 
contact ring 2 is then pushed onto the tinned section 37, before the inner 
cover section 34 is then removed and the contact ring 2 can be pushed down 
to the exterior cover 24. In this manner the construction according to 
FIG. 6 is attained. In this phase of construction the contact ring 2 is 
soldered to the covering 23. Here, too, a solder is used having a melting 
point of 180.degree. C. The cable 15 is then cut about 1.8 mm above the 
contact ring 2 (FIG. 7), and the cut surface is then face-turned, and 
simultaneously the contact ring 2 is shortened by 0.1-0.2 mm. By this 
procedure the inner conductor 20 is exposed (FIG. 8) and the cable length 
can also be determined in this manner. In the known plug connectors this 
was not possible in such a simple manner. According to FIG. 9 the plug pin 
4 is then soldered to the inner conductor 20. This can take place 
advantageously by means of resistance soldering. 
The cable is then introduced into the plug housing 3, which is then 
threaded onto the nipple 1 (FIG. 10). In this condition the cable and its 
connecting points with the plug connector can then be examined. If a 
shrink tube was pushed onto the cable in the phase according to FIG. 5, it 
can now be correctly positioned before it is shrunk with hot air at about 
150.degree. C. 
Finally, the bore 10 must be filled with epoxy resin and the resin must be 
permitted to cure before the circlip 6 can be put in place and the seal 7 
and connecting sleeve 8 can finally be installed. 
The plug connector described here can also be used for a bent connection, 
such as that described in DE-A No. 29 90 577. The cable cover of the 
finished cable manufactured by the method steps according to FIGS. 3 
through 10 is cut at two spaced points. The space between the cuts should 
at least approximately encompass the bend. Then the cable is bent with the 
smallest possible bending radius, the cable cover is removed and at least 
the outer covering is tinned. This tinning is also advantageously 
performed with soldering tin that melts at 180.degree. C. The 
thus-produced curve can finally be covered by means of a shrink tube 
section. Accordingly, in a simple and inexpensive manner, an angle 
connection can be formed in which the cable lengths can be compensated and 
in which the electrical relationships remain uniform and controllable up 
to the plug transition in the connector element.