Description of the Prior Art.

Most mobile telephones from leading manufacturers have by now become so small that a flip has become essen- tial for the mount of a microphone element. The reason is that it is desired to place said microphone in a most possible close proximity to the user's mouth, to thereby achieve the best possible fidelity of the voice transmit- ted.

The situation regarding antennas can be formulated in equivalent terms. Antennas for specific applications always has to have a specific length to operate as desired. There- fore, if it is desired to arrange an antenna of extendible kind at a mobile telephone of the size in question, there are in essence two choices. Either use is made of a tele- scopic antenna having a desired length when extended, however, having obvious drawbacks, or use is made of an extendible antenna with a fixed length in itself. In the latter case the housing of the telephone limits the possible length of such an antenna, which therefore might have to be length reduced into an antenna of so called quarter-wave type. Such a reduction however necessitates the use an earth plane inside the telephone, which of course is not desired. The alternative to such a reduced

wavelength antenna is to let the antenna deviate inside the housing, thereby making it possible for the housing to accommodate an antenna of greater (half-wave) length than otherwise would be possible.

The achievement of such a bend however puts a great strain on choice of material. Inter alia the antenna material has to be both electrically conductive and bendable without during many extensions and retractions become plastically deformed or prematurely fatigued. Also the friction during extenuation and retraction has to be as low as possible. In this context also an effect that has been named"stick-slip", should be avoided or at least be kept to a minimum. Stick-slip is the effect arising when an object for instance lying on a surface is forced to move.

Due to the coefficient of friction p and the normal force N from the surface, it should suffice to exert a force amounting to N on the object in a direction to slide it in the same direction. This is however not the case since it is necessary to make a greater effort to start the movement, which will occur suddenly. A sticky impression is experienced while at the same time the sudden movement sometimes becomes almost violent. The same effect can be experienced with solutions further described below.

According to JP 8293713 a durable design for suppressing the deterioration of the necessary sliding force in combination with sliding antennas bent to a certain extent is shown. Nothing is however shown regarding means for in combination achieving a material repeatably bendable to a relatively large extent, which at the same time provides low friction properties and a good signal reception.

Another Japanese publication, JP 8335813, shows an another possible solution to improve the antenna efficiency and to secure a smooth draw-out/housing operation of the antenna. Here a tube for accommodation the antenna in its

retracted position is on its inner surface coated with a substance that minimises the friction between the surfaces, so that extension and retraction of the antenna can be made smoothly.

None of these references however show a solution to the problem encountered here, since these solutions mainly deal with smaller deviations in antenna channels in telephone housings, being dependent on constructional or design limitations of the telephone housing.

Summary of the invention It is therefore an object of the present invention to provide a mobile telephone apparatus with improved means for housing a slidable antenna inside the housing thereof, which antenna due to its length in an extended condition in relation to the size of the housing of the telephone, has to be bent to a great extent inside the housing when retracted.

A secondary object of the present invention is to provide a solution which in essence facilitates the choice of construction materials for such an antenna and its tube for guidance of the antenna into the housing of the mobile telephone.

According to the invention the antenna and/or its tubular configuration/-s have parts springing up from a core thereof, for achieving a reduced contact surface between the antenna and said configuration/-s.

According to another aspect of the invention said tubular configuration is a rigid tube. A rigid tube instead of sections of tubular configuration continuously control the sliding movement and give a more reliable, rigid, feeling of good performance.

In a further aspect of the invention said up- springing parts are formed like ridges, which in essence means that the contact surfaces can be designed as either sliding line contacts or dot contacts.

According to yet a further aspect of the invention said up-springing parts can be either uniformly or non uniformly distributed. By non-uniformly distributing said parts it is possible to elaborate with the location of the contact surfaces to thereby arrange them so as to achieve the smallest possible resistance during extension and retraction of the antenna.

Brief Description of the Drawings Below the invention will be described in more detail with reference to the enclosed drawings, in which: FIG 1 schematically in an exploded perspective view shows an embodiment of an arrangement at a mobile telephone according to the invention; FIG 2a shows a cross section from II-II of an antenna and its tube in a first embodiment of the invention; FIG 2b shows a cross section like the one according to Fig 2a in a first alternative embodiment of the invention; FIG 2c like above shows a cross section like figs 2a and 2b in a second alternative embodiment of the invention.

FIG 3 schematically shows a view from III-III in Fig. lof a coned entrance to a tubular configuration for housing the extendible/retractable antenna in the housing.

Detailed Description of the Invention FIG 1 in an exploded view shows parts like a lower housing 1, an upper housing 2 as well as an antenna 3 and a flip 4 of a cellular mobile telephone, for illustrating the mechanisms behind the solution of the present invention.

The lower housing 1 encompass a tube (not shown) for guiding the antenna 3 and its details (not shown) along a selected path 6 during its extension and retraction. It should in this context be noted that any equivalent to a tube, for instance accommodating ears, a driving slot, a follower or the like may, if appropriate, be used instead of said tube.

The selected path 6 for the retraction/extension of said antenna 3 is shown as a dash-dot line within the lower housing 1 according to FIG 1. The problem encountered in connection with the extension and retraction of the antenna, without a solution according to the invention is readily understood if FIG 1 is more closely studied. A radius R like the one shown, would most certainly from the first time used give rise to a heavy stick-slip effect between the tube and the material of the antenna. It should for the sake of completeness be mentioned that FIG 1 also show parts of the cellular mobile telephone necessary, however, not in this context. These parts are, a power supply connection 7 between a battery (not shown) and a PCB (printed circuit board; not shown), a power and external antenna connection 8, screws 9 for connecting the lower and upper housings to each other and snap fasteners 10 for the same purpose.

FIGS 2A-C all show a cross sections taken along II- II in FIG 1 in the vicinity of the orifice of the antenna tube 5. The co-operating surfaces 11,12, i. e. the sliding surface 11 of the antenna 3 (shown in black) and the sliding surface 12 of the antenna tube, has according the three different embodiments of the invention shown in FIGS 2A-C, alternatingly been provided as either one plain surface and one surface showing parts 14 springing up from a core 15 of either the antenna or the tube or both. In the latter case the up-springing parts must on at least the one part be ridges. If the up-springing parts 14 on both parts are ridges, the ridges on each part must be differently directed so as not to fall into a pure surface contact, which was the situation started from according to the prior art. By providing both the tube and the antenna with such up-springing parts 14, the contact between the parts in question is reduced into several, during the extension and retraction of the antenna, sliding dot-shaped or linear

contact surfaces 11,12 which dependent upon a pitch between each up-springing part 14 gives a variable number of contacts, according to requirement.

Finally FIG 3 shows a cutaway part of an entrance portion 16 to the antenna tube in section along III-III in FIG 1. By providing such an entrance portion 16 to the tube, the risk for functional disruption regarding of the retractability of the antenna is eliminated. This means that the antenna will always be able to be retracted and that consequently the risk for functional disruption due to problems regarding retraction never will occur unless it is neglected to retract the antenna after use, which of course may cause deterioration thereof.