The present invention is generically directed on a level detection system whereat the level of a product within a container is monitored. This may be e.g. the level of oil in an oil tank, may be the level of a substance in a production plant, e.g. the level of a coolant and/or lubricant in a respective reservoir of a machine. Such level detection systems operate on the basis of sending very high frequency (VHF) electromagnetic waves towards the surface of the product, the level of which having to be monitored in the container and to measure time lag with which such electromagnetic waves are received at a distinct locus in the container after having been reflected by the surface of the product.

Thereby, in one approach, the level detection may be performed in a non-contact technique in which the electromagnetic waves are emitted towards the level surface of the substance along the gaseous atmosphere upon such level surface, are reflected at that surface, retransmitted through the gaseous atmosphere towards and onto the receiver. In another approach which is known from the so-called "Time Domain Reflectometry" (TDR) the antenna arrangement of the level detection system is immersed into the substance and level detection occurs on the basis of reflected electromagnetic waves as a function of the locus of the addressed level surface along such antenna arrangement and due to a step-like change of electric characteristics at such level surface and along the antenna arrangement.

In spite of the fact that the present invention is primarily directed on the second approach - TDR -, problems and respectively the solution of such problems according to the present invention are also valid for the first mentioned, i.e. the non-contact approach.

The addressed monitoring or detection techniques use electromagnetic waves in the GHz frequency range. E.g. the TDR systems emit pulses of very high frequency (GHz) electromagnetic waves at a pulse rate in the MHz range. Time lag between emitted and received pulses is evaluated as an indicative entity for the distance between product surface on one hand, emitter and receiver on the other hand. Thereby, the receiver and the emitter are customarily operated via the same VHF antenna arrangement and time delay between emitted and received pulses is evaluated in a unitary generator and evaluation unit. Whenever such a system is applied to a container which contains a product the level of which having to be monitored, it is mandatory to feed a VHF signal through the wall of the addressed container. Customarily, an opening is provided in the wall of the container and the VHF signal is bidirectionally transmitted therethrough via a feedthrough device. The overall level detection system may be subdivided in an electronic generator and evaluation unit located outside the container, a feedthrough device to be mounted to the opening of the container and, within the container, an antenna arrangement. Such a feedthrough device named just "feedthrough" additionally seals off at the opening of the container the inside atmosphere of the container from the outside atmosphere of the container, customarily ambient. The feedthrough has to be able to withstand demanding pressure and thermal loading from inside of the container and has to be chemically resistant against products inside the container.

The feedthrough has further to provide mechanical stability to the antenna arrangement. The antenna arrangement extending into the container can have considerable weight depending on its length and construction. When being immersed into a liquid product, turbulences of such liquid e.g. during filling of the container, can cause movement of the antenna arrangement and thus substantial lateral forces which have to be absorbed by the feedthrough. On the other hand bulky solid products can generate very high tensile forces on the antenna arrangement, which have also to be absorbed by the feedthrough. Customarily such a feedthrough comprises an outer tubular mount part with an outer surface having a mount section - e.g. a thread or a flange - to be mounted to the addressed wall opening.

It is electrically conceived in coaxial construction, whereby an electrical insulation has to be established between an inner conductor and an outer conductor providing for a predetermined line impedance of e.g. 50 Ω.

The bidirectional VHF signal transmission should be possible through the feedthrough with smallest possible distortion over the exploited bandwidth to guarantee highest possible monitoring sensitivity.

According to the US 6 642 807 a coaxial feedthrough of the addressed type comprises along the inner and outer conductors two or more insulating cylinders which are designed specifically to withstand high temperatures, to perform sealing action and to provide for temperature resistance. Considered along the inner conductor the insulating cylinders provide for different dielectric constants and for step-like changes of diameter. This establishes for significant disturbances of the VHF signals transmitted through the feedthrough and over the exploited bandwidth especially for pulsed operation as in TDR.

A further coaxial feedthrough of the addressed type is known from the DE 100 45 235. It has a highly complex construction leading to highly complex changes of the impedance along the feedthrough and thereby to hardly controllable disturbances of the VHF signal. Several sealing members are provided leading to locally varying dielectric constant.

Further attention is drawn upon the DE 100 19 129.

The DE 10 2005 042 646 teaches a coaxial feedthrough as addressed above which provides for a multitude of step-like geometric variations of the inner conductor and of the insulator, which negatively affects VHF signal propagation. The same is valid for the feedthroughs as taught by the DE 10 2004 060 119, the DE 100 58 026 and the DE 100 27 228.

It is an object of the present invention to provide a coaxial feedthrough of a very high frequency level sensing system to be mounted in a wall opening of a container, the level of a product contained in the container having to be monitored, which system remedies at least some of the drawbacks of the addressed prior art devices. This is achieved by the coaxial feedthrough according to the present invention which comprises a central axis and an outer tubular mount part with an outer surface having a mount section to be mounted to the opening of the wall and which has an inner surface. The feedthrough further comprises an inner conductor mounted along the addressed axis in the tubular mount part and having an outer surface. There is further provided a dielectric, tubular insulator with an outer surface and with an inner surface which is provided between the inner surface of the mount part and the outer surface of the inner conductor.

The outer tubular mount part is the outer conductor of the coaxial feedthrough. The outer surface of the dielectric, tubular insulator snugly resides on the inner surface of the tubular mount part on one hand and, on the other hand, the inner surface of the dielectric, tubular insulator snugly resides on the outer surface of the inner conductor.

The outer surface of the inner conductor which resides on the inner surface of the dielectric tubular insulator is a smooth surface. The outer surface of the dielectric tubular insulator which resides on the inner surface of the mount part is smooth as well. At least one of the outer surface of the inner conductor which resides on the inner surface of the dielectric, tubular insulator and of the outer surface of the dielectric tubular insulator which resides on the inner surface of the tubular mount part has a section with a diameter which steadily converts towards the center axis, considered in the direction from the end of the coaxial feedthrough to be exposed to the inside of the container towards the end of the feedthrough to be exposed to the exterior of the container.

Definitions :

When we speak of a "central axis" of the coaxial feedthrough, we understand a geometric axis along which the inner conductor is arranged. Such central axis needs therefore not to be straight, but might be bent for some applications .

When we speak of the respective surfaces between the dielectric, tubular insulator and the outer tubular mount part on one hand, and the inner conductor on the other hand being "smooth", we understand that no intrusions or extrusions are encountered along such surfaces which are tailored to provide for disturbances or distortions of the transmitted VHF signals within the bandwidth to be exploited above a predetermined amount. Such intrusions or extrusions may be provided only of an extent to neglectably establish VHF-signal disturbances or distortions.

We further understand under the diameter "steadily" converting, that the diameter continuously diminishes or diminishes in a multitude of steps, maintaining the converting surface to be "smooth".

We further understand under a "tubular" part a part which has a pass-through opening. Such part needs not be "cylindrically tubular", in spite of the fact, that latter is one preferred realization form of such "tubular" part.

The feedthrough according to the present invention is thus substantially conceived from three parts, namely the inner conductor, the dielectric, tubular insulator and the tubular mount part which is simultaneously the outer conductor. Thereby, due to the addressed steady diameter conversion towards the central axis and considered in direction from that end of the feedthrough to be exposed to the inner of the container towards that end of the feedthrough to be exposed to the exterior of the container, pressure loading the feedthrough by pressure within the container is transmitted from the dielectric tubular insulator evenly to the tubular mount part. Thereby, sealing action of the dielectric, tubular insulator to the tubular mount part is increased.

Further, due to the fact that the dielectric, tubular insulator as well as the inner conductor and the outer tubular mount part mutually reside upon each others along smooth surfaces, there occurs no step-like change of impedance considered along the inner conductor and thus substantially no signal distortion of the VHS signal transmitted through the addressed feedthrough.

In one further embodiment of the feedthrough according to the invention, which may be combined with any of the addressed embodiments, the outer surface of the dielectric tubular insulator, which resides on the inner surface of the mount part consists, considered from that end of the feedthrough exposed to the inner of the container towards the other end, of a first substantially cylindrical section and of a second section with the addressed steady diameter conversion towards the central axis.

In one embodiment of the feedthrough according to the invention, which may be combined with any embodiment, the inner conductor has a section with a diameter steadily converting towards the central axis, considered in direction from that end of the feedthrough to be exposed to the inner of the container towards that end of the feedthrough to be exposed to the exterior of the container.

In one embodiment of the feedthrough according to the invention, which may be combined with any of the addressed embodiments, the feedthrough comprises an integral standard coaxial connector which is electrically connected to the inner connector and to the mount part, said standard coaxial connector being provided at that end of the feedthrough which is to be exposed to the exterior of the container.

In one embodiment of the feedthrough according to the invention, which may be combined with any of the addressed embodiments, the dielectric tubular insulator is of at least one of the following materials: a plastic material, a ceramic material, a resin material, a glass material, thereby in a good embodiment of PEEK (polyetherkethone) plastic material.

Thereby the dielectric, tubular insulator is preferably of just one of the addressed materials. In one embodiment of the feedthrough according to the invention, which may be combined with any of the addressed embodiments, the dielectric tubular insulator is mounted between the inner conductor and the outer tubular mount part by at least one of a force fit mount and of a form fit mount. Thereby, the dielectric, tubular insulator may be manufactured directly within the interspace between the inner conductor and the outer tubular mount. Preferably, no additional mount parts are used for the mount of the dielectric, tubular insulator respectively to the inner conductor and the outer tubular mount part. In one embodiment of the feedthrough according to the invention, which may be combined with any of the addressed embodiments, the dielectric tubular insulator is overmolded over the inner conductor and is press-fitted to the inner surface of the outer tubular mount part. Thereby, a highly sealed mutual connection of the dielectric, tubular insulator to the inner conductor and to the outer tubular mount part is established. Press-fitting of the outer tubular mount part may thereby be established by exploiting heating by the overmolding process or by additionally heating up the outer tubular mount part so as to expand and then to shrink upon the dielectric, tubular insulator after cooling down.

In one embodiment of the feedthrough according to the invention, which may be combined with any of the addressed embodiments with the exception of that embodiment which uses overmold, the dielectric, tubular insulator is applied between the inner conductor and the outer tubular mount part by injection molding. Thereby too, the inner surface of the tubular mount part and/or the outer surface of the inner conductor may be provided with small intrusions or extrusions, thereby not impeding smoothness of such surfaces, but nevertheless providing for form fit mount.

Within the frame of tailoring the inner surface of the outer tubular mount part, the outer surface of the dielectric, tubular insulator on one hand and of the outer surface of the inner conductor and the inner surface of the dielectric, tubular insulator as has been defined above, it is further also possible to provide at least along sections of the addressed surfaces threaded surfaces as e.g. with a fine-pitch thread. Thereby, the dielectric, tubular insulator may be prefabricated and mounted to the tubular mount part and/or to the inner conductor by the addressed threaded surface sections. Respective fine circular grooves may also be provided at the addressed surfaces for improving fixation and sealing of the tubular insulator when the insulator is manufactured directly within the interspace between inner conductor and outer mount part as by injection molding or by overmolding. In one embodiment of the feedthrough according to the invention, which may be combined with anyone of the addressed embodiments, the end of the dielectric tubular insulator adjacent to that end of the feedthrough to be exposed to the interior of the container, is freely exposed.

It is to be noted that the end of the feedthrough to be exposed to the exterior of the container is in fact established by the direction of diameter conversion of the dielectric, tubular insulator. In one embodiment of the feedthrough according to the invention, which may be combined with any of the addressed embodiments, such feedthrough comprises a releasable mount arrangement for a generator and evaluation unit at that end to be exposed to the exterior of the container and/or a releasable mount for an antenna arrangement at that end to be exposed to the inside of the container.

Thereby and especially with an eye on the releasable mount for the antenna arrangement and with an eye on flexibly applying different VHF level sensing system antennas, such an embodiment may especially be easily realized in combination with the embodiment, whereat the respective end of the dielectric tubular insulator is freely exposed.

By the addressed releasable mounts it becomes possible to flexibly apply to the feedthrough, once mounted to the wall of a container, different selectable generator and evaluation units as well as different antenna arrangements. This may be highly advantageous especially to establish which antenna technology or which evaluation technology fits best to a specific application.

The present invention is further directed to a level- sensing system with a coaxial feedthrough according to the feedthrough of the invention or one of its embodiments.

The invention is further directed to a container with such a system.

Still further, the present invention is directed on a method for manufacturing a coaxial feedthrough according to the feedthrough of the invention and its embodiments, which method comprises fixating the dielectric, tubular insulator between the tubular mount part and the inner conductor by establishing a force fit mount and/or a form fit mount between the inner conductor, said dielectric, tubular insulator and said tubular mount part. Thereby, in one embodiment of the addressed manufacturing method, the dielectric, tubular insulator is formed by overmolding the inner conductor by a plastic material.

In a further embodiment of the addressed manufacturing method the dielectric tubular insulator is provided of a sinter ceramic material or of a glass.

Still in a further embodiment of the addressed manufacturing method providing the dielectric tubular insulator is performed by injection molding be it of a plastic material or of a glass. Further, the present invention is directed on a high- frequency level sensing system which comprises a feedthrough device, a generator and evaluation unit and an antenna arrangement. The generator and evaluation unit is mounted to the feedthrough by means of a first releasable mechanical and electrical connector and/or the antenna arrangement is mounted to the feedthrough by means of a second releasable mechanical and electrical connector. Thereby, such a system is highly flexible in that without removing the feedthrough from the opening in the wall of a container a respectively suited generator and evaluation unit as well as an antenna arrangement may be applied. Thus, the antenna arrangement may be exchanged without removing the feedthrough from the container wall to optimally suit to a specific application and e.g. the generator and evaluation unit may be adapted to the respectively provided antenna arrangement by easily exchanging such unit as well.

The invention shall now further be exemplified with the help of figures.

The figures show:

Fig. 1 by means of a schematic cross-sectional representation, a first embodiment of a feedthrough according to the present invention as a part of a level-sensing system according to the invention and mounted to the wall of a container so as to establish for a container with a level- sensing system according to the invention;

Fig. 2 in a schematic representation in analogy to that of fig. 1, an embodiment of the feedthrough according to the invention as realized today, thereby showing additional features which may also be combined selectively with the embodiment as of fig. 1, and Fig. 3 schematically and in a partial sectional representation, a feedthrough according to the present invention with a further embodiment of realizing a releasable link between the feedthrough and a coaxial connection of an antenna arrangement.

In fig. 1 there is schematically shown, most generically, the principle of the present invention by means of a cross- sectional representation of a feedthrough according to the invention in a first embodiment. A container is established by container wall 3 defining the interior I and the exterior E of the container. In the container wall 3 there is provided an opening 5 e.g. with a mountin flange 7. A VHF level detection system 9 is applied to the container as e.g. and especially a level detection system operated by Time Domain Reflectometry (TDR) . Such system 9 consists principally of a signal generator and evaluation unit 11, the feedthrough device 13 and an antenna arrangement 14. The generator and evaluation unit 11 is operationally connected electrically for bidirectional VHS signal transmission to the coaxial feedthrough device 13, latter to the antenna arrangement 14. The feedthrough device 13, named just "feedthrough" in the following, comprises an outer generically tubular mount part 15 coaxial to an axis 17. An inner conductor 19' is provided along axis 17. Between the outer tubular mount part 15 and the inner conductor 19 there is provided a dielectric, substantially tubular insulator 21. The dielectric, tubular insulator 21 has an outer surface 23 and an inner surface 25. The outer surface 23 of dielectric, tubular insulator 21 snugly resides on an inner surface 27 of the tubular mount part 15. The inner surface 25 of the dielectric, tubular insulator 21 snugly resides on an outer surface 29 of the inner conductor 19. Thereby, we understand under "snugly" that the addressed surfaces reside upon each other without air entrapment.

Further, all the surfaces which snugly reside upon each others, i.e. 23/27 as well as 25/29 are smooth surfaces. The outer tubular mount part 15 which is of a metal material acts as the outer conductor of the coaxial feedthrough 13 and comprises along its outer surface 31 a mount arrangement for mount to the rim of opening 5 as e.g. a thread-mount (not shown) .

As may be seen in fig. 1 the dielectric, tubular insulator 21 has a diameter Φ ₂ i which diminishes i.e. converts steadily in the direction form that end of the feedthrough exposed to the interior I of the container towards that end of the feedthrough exposed to the exterior E of the container. The steady decrease of the addressed diameter Φ ₂₁ according to the embodiment of fig. 1 is established all along the length extent of the dielectric, tubular insulator 21, but may in some good embodiments as will be explained later be present only along that part of the addressed insulator 21 which is adjacent to the end of the feedthrough exposed to the exterior E.

Due to the respective surfaces 23/27 and 25/29 which snugly reside upon each other, a highly effective large surface seal is established between exterior E and interior I of the container along the feedthrough. Thereby, pressure loading of that end of the dielectric, tubular insulator 21 which is exposed to the interior I of the container strengthens the addressed seal along the surfaces 23 and 27. The steadily tapered shape of the dielectric tubular insulator 21 establishes an optimal VHS signal bidirectional transmission through the feedthrough e.g. with a line impedance of 50 Ω. The dielectric, tubular insulator 21 is thereby made of a plastic material and/or of a ceramic material and/or of glass. Two or more than two of the addressed materials may be used for the addressed insulator 21 if there is need, but it is highly preferred to make the addressed insulator 21 homogeneously of one of the addressed materials to avoid any abrupt change of dielectric constant along the addressed insulator. In today's preferred embodiment the dielectric, tubular insulator 21 is of PEEK. With the help of fig. 2 additional features which may be incorporated also in an embodiment according to fig. 1 shall be exemplified. Fig. 2 shows schematically and in cross- sectional representation in analogy to fig. 1 a feedthrough according to the present invention and as an embodiment as realized today. As may be seen from fig. 2, the dielectric, tubular isolator 21' consists of a cylindrical bottom section C and a top-section T along which the diameter Φ ₂ i' steadily tapers, i.e. converts, towards the axis 17. Additionally, the inner conductor 19' tapers as well at its end adjacent to the end of the feedthrough exposed to the exterior E of the container along section T. Thereby, such tapering, i.e. converting of the diameter Φ ₁₉ ' of the inner conductor 19' results in the fact that any pressure which is exerted upon the antenna arrangement and which is transmitted to the inner conductor 19' is transmitted upon the inner surface of the dielectric, tubular insulator 21' and to the inner surface of the tubular outer mount part 15' , along large areas which increases mutual seal of the inner conductor 19' with respect to the dielectric, tubular insulator 21' . At that end of the feedthrough which is on one hand exposed to the exterior of the container E and towards which the respective diameter Φ ₂ i' and Φ _i9 ' gently diminish, there is integrated a standard coaxial connector 39, in a today's preferred mode, a SMB-type connector. This allows flexible electrical and mechanical connection of a generator and evaluation unit 11 as of fig. 1. Clearly, such standard coaxial connector may also be provided at the embodiment according to fig. 1.

Further, the outer tubular mount part 15' has, adjacent to the end of the feedthrough exposed to the exterior E of the container, a mount 40 as e.g. a thread, by which the generator and evaluation unit 11 according to fig. 1 may be additionally mechanically secured to the feedthrough. Thereby, the releasable mount 40 and the releasable standard coaxial connector 39 allow for a flexible exchange of the generator and evaluation unit 11 and thereby adapting the level detection system to prevailing requirements without dismounting the feedthrough from the container wall 3 of fig. 1.

With an eye on fig. 2 a subsequent section of the outer tubular mount part shown at 42 is tailored to be gripped by a mounting tool and is e.g. shaped with a nut profile.

A subsequent section of the tubular outer mount part 15', 44, is tailored to be mounted in the opening of the container and is provided e.g. with a respective thread. As may be seen from fig. 2 on one hand the inner conductor 19' projects at that end of the feedthrough which is to be exposed to the interior I of the container and further the bottom face 21 _O of the dielectric, tubular insulator 21' is freely exposed as a plane surface towards the addressed end. This facilitates the realization of the present invention according to a second aspect. According to this second aspect not only the generator and evaluation unit 11 according to fig. 1 may be easily replaced due to the standard coaxial connector 39 as well as mechanical simply releasable mount at 40, but additionally or alternatively an antenna arrangement as shown in fig. 1 at 14 may replaceably and easily be attached to the feedthrough. Conceiving under this second aspect the feedthrough as was just addressed with respect to the inner conductor 19' and the plane surface 21 _O of an insulator 21' allows to establish an electrical high-quality connection between the outer conductor of the feedthrough realized at the feedthrough according to the present invention by the outer tubular mount 15, 15' , the intermediate insulator, realized in the feedthrough according to the present invention by dielectric, tubular insulator 21, 21' and the inner conductor, realized at the feedthrough according to the present invention by inner conductor 19, 19' to respective parts of the antenna arrangement 14. This is, as an example, schematically shown in fig. 2 by an inner conductor 19' _a , further by an intermediate insulator 21 _a and an outer conductor 15' _a of an antenna arrangement connector, wherein the index "a" stands for "antenna". The overall arrangement of the antenna connector 45 is biased towards the feedthrough, e.g. with the help of a mount 47 at the outer surface of the tubular outer mount part 15' , and a respective mount 47 _a at the antenna connector 45. As exemplified in fig. 2 the mounts 47 and 47a are realized by an outer thread. The antenna connector 45 is biased towards the feedthrough by means of an inside threaded lock nut 49. Clearly, the metallic as well as the dielectric contacts between the respective parts of the feedthrough and of the antenna connector 45 are conceivable in a multitude of different techniques as known from coaxial interconnections.

In fig. 3 there is still schematically shown a part of a further good embodiment of the feedthrough according to the present invention by which the second aspect of the invention is realized. The representation of fig. 3 is a cross- sectional representation of that part of the feedthrough which provides for flexible interchangeable link to an antenna arrangement in a further variant with respect to that one which was explained in context with fig. 2. The outer tubular mount 15' ' of the feedthrough comprises at its end which is directed towards the interior I of the container a thread 50. A lock nut 52 with an inner thread according to thread 50 is releasably screwed upon the outer tubular mount 15''. A ferrule 54 is thereby biased towards and onto the outer conductor 15 _a ' of the coaxial connector of the antenna arrangement. Thus, by screwing the lock nut 52 onto the outer tubular mount 15' ' of the feedthrough the outer conductor 19 _a ' of the antenna arrangement is tightly fixed and electrically connected to the outer tubular mount part 15' ' via the addressed ferrule 54. For a rod antenna arrangement as customarily applied in systems operating in TDR mode the insulator 21 _a is realized by a void interspace between the outer conductor 15 _a ^r and the inner conductor 19 _a ^r of the coaxial connection of the antenna arrangement. This dielectric interspace 21 _a becomes in operation at least to a part filled with the product contained in the tank, the level of which having to be sensed by the system. Thereby, the inner conductor 19 _a ' of the coaxial connector of the antenna arrangement is e.g. tightly connected to the inner conductor 19' of the feedthrough by a screw coupling as schematically shown at 56 in fig. 3. With an eye on fig. 1 it is perfectly clear that in the embodiment of that figure the dielectric isolator 21 _a ' may also be realized by a void interspace and the two inner conductors 19' and 19 _a ' may then be interconnected by a screw coupling as exemplified in fig. 3 at 56.

Still with an eye on the embodiment of fig. 3 it may be seen that the lock nut 52 has threaded sections 58 by which the feedthrough is mounted to the opening in the wall of the Container in analogy to threaded section 44 of fig. 2.

With an eye on fig. 2 it should be noted that the diameter of the section with thread 44 may be and is normally made larger than the diameter of the lock nut 49 to allow premount of a rod-type antenna arrangement before mounting the assembled feedthrough and rod-type antenna on the container. Nevertheless, once mounted, the antenna arrangement may be replaced without removing the feedthrough from the container.

It should be noted that the addressed concept of providing the antenna arrangement to be easily and releasably exchangeable at the feedthrough is considered per se as an invention. This independent therefrom, whether the feedthrough per se is conceived according to the present invention or not. Turning back to the feedthrough according to the present invention:

The dielectric, tubular insulator 21, 21' is today preferably- made of PEEK. The feedthrough is thereby manufactured using a plastic material for the dielectric, tubular insulator 21, 21' which material is overmolded over the inner conductor 19, 19' up to complete filling of the interspace between the inner surface 27 (see fig. 1) of the outer tubular mount part 15, 15' and the outer surface 29 (see fig. 1) of the inner conductor. Thereby, in a good embodiment there is established press- fitting of the dielectric, tubular insulator 21, 21' to the outer tubular mount part 15, 15' e.g. by exploiting heating up of the addressed metallic member 15, 15' which shrinks after cooling down upon the material of the dielectric, tubular insulator 21, 21' . Additionally, there might be provided along the inner surface 27 of the outer tubular mount part 15, 15' gripping projections and/or intrusions which additionally provide for a form fitting fixation of the addressed insulator 21, 21' to the mount part 15, 15' . Such manufacturing process is today established making use of PEEK material .

Alternatively, the dielectric, tubular insulator 21, 21' may be manufactured by plastic material injection molding into the interspace between inner conductor 19, 19' and inner surface 27 of the outer tubular mount part 15, 15' , whereby a highly rigid connection on one hand to the outer surface 29 of the inner conductor 19, 19' , on the other hand to the inner surface 27 of the outer tubular mount part 15, 15' is established primarily by force-fitting and is, if necessary, improved by form-fitting as providing by respective intrusions and/or extrusions at the addressed outer surfaces 29 and/or 27. Very similarly to plastic material injection molding for manufacturing the dielectric, tubular insulator 21, 21' , a glass material may be injected to establish the addressed insulator of a glass material. In a further variant the addressed dielectric, tubular insulator 21, 21' may be prefabricated e.g. of a sinter ceramic material. As a prefabricated part such part is introduced into the interspace between the outer tubular mount part 15, 15' and the inner conductor 19, 19' . By heating up the outer tubular mount part 15, 15' and cooling down the inner conductor 19, 19' , then introducing the prefabricated insulator 21, 21' into the addressed interspace, cooling down of the outer tubular mount part 15, 15' and warming up of the inner conductor 19, 19' will lead to press-fitting of the addressed prefabricated insulator 21, 21' respectively on the inner conductor 19, 19' and the outer tubular mount part 15, 15' . Thereby, additionally, intrusions and/or extrusions may be provided at the respective surfaces 29 and 27 cooperating with respective intrusions and/or extrusions at the respective surfaces of the prefabricated insulator to strengthen mechanical fixation and seal action. Clearly, the dielectric, tubular insulator 21, 21' may also be prefabricated in another than a sinter ceramic material, even in plastic material.

Further, the mount of the dielectric tubular insulator of the feedthrough according to the present invention may additionally or alternatively to the measures as described be established as shown in fig. 1 in dash line at 60 by means of a shoulder rim 60 of the outer tubular mount part which is mechanically pressed upon the surface of the dielectric insulator, as shown schematically at F in fig. 1.