HF coaxial cable with angular plug connection, and a method for producing same

Abstract

The invention is characterized in that a HF coaxial cable is designed as a conventional corrugated sheath cable comprising a cable outer conductor, in the form of a metal corrugated tube, having a line impedance Z.sub.k and a minimum bending radius r.sub.k,min specified by the manufacturer as a characteristic feature of the coaxial cable; in corrugated sheath cable, directly or indirectly following the straight plug connector, is bent to have a bending radius r.sub.α, where 0.2 r.sub.k,min≦r.sub.α≦0.9 r.sub.k,min, which alters the line impedance Z.sub.k by a maximum of 1 ohm. The bend with the bending radius r.sub.α is produced by cold forming corrugated sheath cable with the introduction of bending forces and tensile forces directed along said corrugated sheath cable.

Claims

1. A method for producing a high-frequency (HF) coaxial corrugated cable including a plug connector located at at least one of two ends, a cable inner conductor, a dielectric layer surrounding and contacting the cable inner conductor and tubular metallic corrugated outer conductor surrounding and contacting the dielectric layer comprising: providing a HF corrugated coaxial cable including a tubular metallic corrugated outer conductor which centrally surrounds a cable inner conductor and a dielectric layer, the HF corrugated coaxial cable having characteristic features including line impedance Z.sub.k, and a minimum bending radius r.sub.k,min specified by a manufacturer; trimming an end of the HF corrugated coaxial cable to provide access to the cable inner conductor, the dielectric layer surrounding and contacting the inner cable conductor and the metallic outer conductor surrounding and contacting the dielectric layer; connecting the plug connector to the trimmed cable end to join the cable inner conductor with an inner conductor of the plug connector and the cable metallic corrugated outer conductor with an outer metallic conductor of the plug connector; and cold forming a region of the HF corrugated coaxial cable attached to the plug connector or spaced from the plug connector by applying a bending force directed transversely to a longitudinal part of the HF corrugated coaxial cable and a tensile force directed longitudinally to the HF coaxial cable to form a permanent curved bend subtending an angle between 85° and 95° in the corrugated coaxial cable with a radius length r.sub.α extending from a center point to a curved bend of the HF corrugated coaxial cable which alters the line impedance Z.sub.k r.sub.k,min a maximum of less than 1 ohm when 0.2 r.sub.k,min≦r.sub.α≦0.9 r.sub.k,min.

2. The method according to claim 1, comprising: coating at least the bend of the HF corrugated cable with a plastic or an adhesive.

3. The method according to claim 1, comprising: forming the HF corrugated coaxial cable to join the angular plug connector to the cable end while the cable is releasably attached to a retainer, which is guided pivotably relatively to a bending guide to form a bend; and wherein the retainer includes the angular plug connector joined to the HF corrugated cable which is pivoted relative to the bending guide, the HF corrugated coaxial cable is attached to or spaced from the plug connector and contacts the bending guide while an orthogonal bending force is applied to the bending guide and an axial force is applied to the HF coaxial corrugated cable longitudinally at a region spaced apart from the plug connection and the axial force creates tensile stress within the HF corrugated coaxial cable during the pivoting of the retainer.

4. The method according to claim 2, comprising: forming the HF corrugated coaxial cable to join the angular plug connector to the cable end while the cable is releasably attached to a retainer, which is guided pivotably relatively to a bending guide to form a bend; and wherein the retainer includes the angular plug connector joined to the HF corrugated cable which is pivoted relative to the bending guide, the HF corrugated coaxial cable is attached to or spaced from the plug connector and contacts the bending guide while an orthogonal bending force is applied to the bending guide and an axial force is applied to the HF coaxial corrugated cable longitudinally at a region spaced apart from the plug connection and the axial force creates tensile stress within the HF corrugated coaxial cable during the pivoting of the retainer.

5. The method according to claim 3, comprising: applying the orthogonal force to the HF coaxial corrugated cable during pivoting of the retainer relative to the bending guide.

6. The method according to claim 4, comprising: applying the orthogonal force to the HF coaxial corrugated cable during pivoting of the retainer relative to the bending guide.

7. The method according to claim 5, comprising: applying the orthogonal force by guiding a rolling or sliding body relative to the bending guide which contacts the HF corrugated coaxial cable.

8. The method according to claim 3, comprising: contacting the HF corrugated coaxial cable with the rolling or the sliding body with at least an eighth of a circumferential edge thereof.

9. The method according to claim 4, comprising: contacting the HF corrugated coaxial cable with the rolling or the sliding body with at least an eighth of a circumferential edge thereof.

10. The method according to claim 1, comprising: cold forming the HF corrugated coaxial cable which joins the straight plug connector to the cable end while the cable end is fixed to a stationary retainer.

11. The method according to claim 2, comprising: cold forming the HF corrugated coaxial cable which joins the straight plug connector to the cable end while the cable end is fixed to a stationary retainer.

12. The method according to claim 1, comprising: applying the bending force and the tensile stress during cold forming without altering an electrical diameter of the bend to vary more than 10% from an electrical diameter of a straight region of the HF corrugated coaxial cable.

13. The method according to claim 1, comprising: bending the HF corrugated coaxial cable permanently to have a bending radius r.sub.α, where 0.4 r.sub.k,min≦r.sub.α≦0.6 r.sub.k,min, while the HF corrugated coaxial cable is attached to or is spaced from the plug connector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described by way of example in the following without limitation of the general inventive idea on the basis of exemplary embodiments with reference to the drawings. In the figures:

(2) FIG. 1 shows a longitudinal section through an HF coaxial cable with an angular plug connection constructed according to the invention;

(3) FIG. 2 shows a longitudinal section through a bent corrugated sheath cable for illustration of the electrical diameter;

(4) FIG. 3 shows a longitudinal section through a straight plug connector attached on the cable end of a corrugated sheath cable;

(5) FIGS. 4a-c show a sequential image illustration for cold forming according to the invention of the corrugated sheath cable with straight plug connector;

(6) FIG. 5 shows an alternative bending device for a corrugated sheath cable for producing the smallest bending radii; and

(7) FIG. 6 shows a graph for comparing the standing wave ratio between a straight connection, a bent embodiment according to the invention and a conventional angular plug connection with mountable plug connection.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) FIG. 1 shows a longitudinal sectional illustration for an HF coaxial cable with an angular plug connection constructed according to the invention. The HF coaxial cable used according to the invention constitutes a conventional corrugated sheath cable 1, which has a cable outer surrounding metallic conductor 2, which is corrugated in a spirally undulated manner. An inner cable conductor 4, which is guided centrally to the cable outer conductor 2 is surrounded by and contacts a cable dielectric 3. The cable outer conductor 2 is typically encapsulated by a plastic envelope 5.

(9) The cable end of the corrugated sheath cable 1 of FIG. 1 has a protruding end 41 of the cable inner conductor 4 opposite a trimmed cable dielectric 3 and a cable outer conductor 2. The end 41 of the cable inner conductor 4 leads into a receptacle opening inside an inner conductor 42 provided on the plug side which is gripped in a component 7 to provide electrical insulation with respect to a plug-side outer conductor 6. The end of the cable outer conductor 2 is surrounded on the outside by an accommodating sleeve 61 of the plug outer conductor 6, and is securely joined to the same, preferably by means of a solder connection 62. A union nut 8 is additionally attached externally on the plug outer conductor 6 such that it can move longitudinally and cannot be lost. The plug connector S, which is securely connected to the corrugated sheath cable 1 at the end in FIG. 1, constitutes a straight plug connector that is known per se. It is possible to use customary joining techniques that are simple to master for the attachment thereof on the prefabricated cable end of the corrugated sheath cable 1. In addition, an envelope 10 is provided around the bent region of the corrugated sheath cable 1, which is not covered with the cable covering 5. The envelope can preferably be produced by a thermoplastic forming process and in addition to it providing a mechanical support function, the thermoplastic also ensures a sealing and protecting function with respect to external influences.

(10) The novelty of the angular plug connection illustrated in FIG. 1 on the one hand lies in the use of the corrugated sheath cable 1, on the assembled cable end to which a straight a conventional plug connector S is attached with the corrugated sheath cable 1 having a bend, having a uniform bending radius r.sub.α. The bending radius according to the invention is chosen to be significantly smaller than a minimum bending radius r.sub.k,min specified as a minimum by the manufacturer of the corrugated sheath cable 1. Only by significantly undershooting the minimum bending radius r.sub.k,min permitted by the manufacturer can an angular plug connection be achieved, with the overall height h corresponding to or undercutting the dimensions of known angular plug connections being reduced relative to a height that would be achieved if r.sub.α was equal to r.sub.k,min.

(11) The actually achievable bending radius r.sub.α is dimensioned on a circumferential contour facing the inward bend along the cable outer conductor 2, which comes into contact with a correspondingly fitted bending tool, as is also described below. Additional application-specific properties can be realized with the envelope.

(12) The bending of the corrugated sheath cable 1 takes place in a cold forming process, which is performed with sufficient care to not impair the electrically effective diameter d.sub.e. The electrically effective diameter d.sub.e for a corrugated sheath cable 1, which has a decisive influence on the HF signal transmission along the corrugated sheath cable 1, is composed of half of the sum of the maximum and minimum diameter of the corrugated sheath cable 1 resulting from the corrugated cable outer conductor structure thereof.

(13) The dielectric diameter d.sub.e is illustrated with two dashed lines l.sub.1 and l.sub.2 in FIG. 2 which is a longitudinal section of a bent corrugated sheath cable 1. The cable 1 is connected at one end to a straight plug connector S, which is explained in more detail in conjunction with FIG. 1. Both dashed lines l.sub.1 and l.sub.2 run centrally through the corrugated cross-sectional contour of the cable outer conductor 2. In order to retain the required unchanged HF transmission qualities along the corrugated sheath cable 1 in spite of significant undershooting of the minimum bending radius r.sub.k,min defined by the manufacturer, it is necessary to carry out the bending along the corrugated sheath cable 1 with unchanged dielectric diameter d.sub.e. The electrically effective diameters d.sub.e at the representatively indicated cable points A, B, C, D are ideally identical. A tolerable deviation of the actual cable diameter at the points C, B compared to a non-bent cable region, for example A, D may be 10% at most.

(14) To produce the angular plug connection according to the invention, a straight end of a corrugated sheath cable 1 is prepared and provided by trimming the outer cable sheath 5 as far as the cable sheath end 51 of the cable outer conductor 2 and of the cable dielectric 3, as it were, with respect to the cable inner conductor 4 (cf. FIG. 3). It may only be mentioned for the sake of completeness that the cable sheath 5 is only shortened as far as the cable sheath end 52 if no subsequent bending of the cable sheath 1 takes place.

(15) Subsequently, a conventional straight plug connector S can be joined to the assembled cable end. The plug inner conductor 42 may be securely connected, for example by soldered or crimped, to the exposed cable inner conductor 4. Subsequently, the plug outer conductor 6 is pushed on or alternatively screwed on and soldered, clamped, welded or otherwise securely connected to the cable outer conductor 2. In this case, the straight plug connector S can be completed in advance, for example using a union nut 8, an insulating component 7 or, if necessary, using a seal 9. Alternatively, the straight plug connector S can be a plug, as a coupler or in a hybrid manner.

(16) The cold-forming procedure takes place in the next step, which is explained with reference to the FIGS. 4a to c on the basis of a first exemplary embodiment. A retainer 12 is illustrated in FIG. 4a, which has a receptacle opening 13, which is adapted in an oppositely contoured manner to a supporting section of the plug connection S, so that the straight plug connector S is releasably fixed in a secure manner relatively to the retainer 12, which is attached in a stationary manner. A bending guide 14 adjoins the retainer 12 on one side along the corrugated sheath cable 1. The bending contour of the bending guide 14 corresponds to a predetermined bending radius r.sub.α. The corrugated sheath cable 1 is connected to a clamping and tensioning device 15 at a distance from the retaining means 12. The clamping and tensioning device creates both a tensile force Fz orientated longitudinally along the cable longitudinal extent L and a bending force F.sub.r directed transversely to the cable longitudinal extent L onto the corrugated sheath cable 1, as is illustrated in FIG. 4b. Here, the clamping/tensioning element 15 including corrugated sheath cable 1 is guided around the bending guide 14 in a force-loaded manner, so that the region of the corrugated sheath cable 1 divested of the cable sheath 5 clings to the surface of the bending guide 14 in the manner illustrated in FIG. 4b.

(17) The bending process is ended as soon as the clamping/tensioning element 15 has cold formed the corrugated sheath cable 1 by 90°, as is illustrated in FIG. 4c.

(18) The bending guide 14 advantageously has a concavely constructed contact surface. In use the bending guide 14 comes into contact with at least one eighth and preferably up to a half of the circumferential edge of the corrugated cable outer conductor of the corrugated sheath cable 1. The concave construction of the bending guide 14 supports the shape retention of the cross-sectional geometry of the corrugated sheath cable 1 and, connected therewith, the constant electrically effective diameter d.sub.e during the cold forming process.

(19) The adaptation of the forces F.sub.z and F.sub.r acting on the corrugated sheath cable 1 during the cold forming process is of central importance. In particular, during the choice of the tensile force F.sub.z acting along the corrugated sheath cable 1, it is necessary to note that the inner surfaces 16 and 17 of two corrugated guides (cf. FIG. 2), which directly face the bending guide 14, are spaced apart from one another by a corresponding stretching action and not pressed together by the bending process. On the other hand, the tensile force F.sub.z must not lead to tears or other material degradations forming on the side of the cable outer conductor 2 facing away from the bending guide 14. Thus, the force contribution of the bending process and acting on the corrugated sheath cable, which is composed of the sum of tensile force F.sub.z and bending force F.sub.r, is chosen individually in each case as a function of size and material type and also of the material composition of the corrugated sheath cable. The forming on the one hand constitutes a plastic forming, providing the desired, bent spatial form of the corrugated sheath which is retained without further force contribution, and on the other hand does not lead to any of the previously described material degradations.

(20) FIG. 5 shows an alternative bending tool with a stationarily attached bending guide 11, to which a retaining means 18 is pivotably attached, into which the straight plug connector S can be inserted in a fixed manner such that it cannot be released. A rolling or sliding body 19 is provided together with the retainer 18 attached such that it can pivot about the bending guide 11 to which the rolling or sliding body is attached radially spaced apart from the circumferential edge of the bending guide 11. During the pivoting process, the rolling or sliding body 19 exerts a contact force onto the corrugated sheath cable 1, which is directed orthogonally onto the bending guide 11 which causes the corrugated sheath cable 1 to be cold formed on the basis of the bending contour of the bending guide 11. Along the corrugated sheath cable 1, the corrugated sheath cable 1 is pressed against a likewise stationarily attached guide unit 20 with a retaining force F.sub.R. As a result, the corrugated sheath cable 1 experiences a tensile stress orientated along the corrugated sheath cable, which together with the bending force leads to the cold forming according to the invention. In this case also, it is necessary to choose the retaining force F.sub.R, by means of which the tensile and bending forces explained in connection with the FIGS. 4a to 4c are predetermined, in such a manner that a forming, which is plastic and maintains the corrugated outer contour of the corrugated sheath cable, is achieved, with there being no considerable deformation or material degradations, which influence the HF transmission properties of the bent corrugated sheath cable, occur.

(21) In FIG. 6 a graph is shown for comparing the standing wave ratio between a straight (Function 1), a corrugated sheath cable bent according to the invention with angular plug connector (Function 2), and a conventionally bent angular plug connection with mountable plug connector (Function 3). The standing wave ratio is a measure for the standing wave, which arises along a waveguide due to reflection. In the case of a standing wave ratio close to the value 1, virtually the entire HF power fed in is transmitted through the transmission line into a load. This is the desired state if the line is used for energy transmission. With increasing values of the standing wave ratio, the reflected portion increases and thus the loss increases. In the illustrated graph, the so-called electrical voltage standing wave ratio (VSWR) is shown along the ordinate as a function of the frequency f of 0 to 6000 MHz, which is entered along the abscissa.

(22) Starting from a straight, unbent corrugated sheath cable, to which a straight connector is attached to feed in a HF signal, VSWR values from close to 1 up to 1.04 maximum are shown. Using a corrugated sheath cable bent according to the invention, VSWR values in the range of 1 and maximum of 1.08 in the specified frequency range of 0 to 6000 MHz can be achieved. By contrast, in the case of a corrugated sheath cable conventionally assembled with an angular plug, a clear increase of the VSWR value is shown at frequencies from approximately 4500 MHz.

(23) In addition, the simple structure of the angular plug connector formed according to the invention opens up, in view of a reduced number of parts, a significant reduction of intermodulation risks that occur definitely in conventionally formed angular plug connectors already due to their complex and multi-component structure.

REFERENCE LIST

(24) 1 Corrugated sheath cable 2 Cable outer conductor 3 Cable dielectric 4 Cable inner conductor 41 End of the cable inner conductor 42 Plug inner conductor 5 Cable sheath 51 Cable sheath end for angular plug connection 52 Cable sheath end for straight plug connection 6 Plug external conductor 61 Accommodating sleeve 62 Solder connection 7 Insulating support 8 Union nut 9 Seal 10 Covering 11 Bending guide 12 Retaining means 13 Recess 14 Bending guide 15 Clamping/tensioning element 16 Internal surface of a cable outer conductor corrugated guide 17 Internal surface of a cable outer conductor corrugated guide 18 Retaining means 19 Rolling or sliding body 20 Guide unit S Plug connector h Overall height F.sub.z Tensile force F.sub.r Bending force F.sub.R Retaining force