[0001] The invention relates to an antenna foot of the kind disclosed in the preamble to
claim 1.
[0002] This type of antenna foot is used to a great extent for movable antennae in connection
with radio and/or radio telephone antennae for cars. With the known types, the side
facing the car roof is covered with a cap of plastic or rubber, thus preventing the
roof of the car from being scratched or damaged in any way when the antenna is mounted,
taken off or moved. It is necessary for the protective cap to be relatively thin
on the side facing the car, hereby excluding the formation of too great a gap between
the magnet poles and the metal roof of the car, which would otherwise reduce the magnetic
forces which secure the foot of the antenna to the car roof.
[0003] In practice, the known types of protective caps have proved to be easily damaged,
in that the downwards-facing edge of the antenna foot's dish-shaped metal holder
penetrates the cap, thus giving rise to the possibility of direct contact with and
consequent damage to the car roof, especially if the antenna is moved or removed without
due care, e.g. by pulling on the antenna cable.
[0004] The object of the invention is to provide an antenna foot of this kind which is arranged
in such a manner that damage to the roof of the car is excluded, regardless of the
way in which the antenna with the antenna foot is removed or mounted on the car roof.
[0005] This object is achieved by configuring the antenna foot according to the invention
as disclosed and characterized in claim 1. The permanently secured protective element
ensures that the downwards-facing edge of the antenna foot's dish-shaped holder can
never come into contact with the roof of the car, and at the same time determines
the distance of the antenna foot's magnet poles from the metal roof. The protective
element is configured as an annular, flexible or yielding item of half-hard material
which is incapable of scratching or damaging the car roof. The distance between the
metal parts of the antenna foot and the car roof is thus not established by these
parts being separated by a thin membrane of rubber or plastic. Moreover, the permanent
securing prevents any ingress of water in between the protective element and the
holder.
[0006] The permanent securing ensures that the antenna foot is always provided with the
protective element, and one avoids the frequent situation with the known constructions,
i.e. the protective cap gets lost and, for reasons of lack of time, it is necessary
to use the antenna foot without the protective element and with consequent damage
to the roof of the car.
[0007] When the antenna foot according to the invention is configured as disclosed and characterized
in claim 2, maximum security is achieved against damage to the car roof in connection
with the use of the antenna foot.
[0008] The antenna foot according to the invention is preferably configured as disclosed
and characterized in claim 3, whereby increased securing possibilities for the protective
element are achieved, hereby enabling it to surround and adhere to the full extent
of the edge of the dish-shaped holder.
[0009] If the antenna foot according to the invention is configured as disclosed and characterized
in claim 4, a number of advantages are achieved from the view of production technique,
in that the manufacture of the antenna foot can be simplified, and one and the same
material is used for both the assembly operation and the formation of the protective
element, and these operations can therefore be effected simultaneously. It is a considerable
technical simplification and a cost-reducing advantage to be able to assemble and
join all of the parts together in one operation, e.g. in an injection moulding operation.
[0010] Other embodiments of the invention, particularly with regard to the configuration
and securing of the protective element, are disclosed and characterized in claims
5-7. The embodiment desired for use can, for example, depend on the type of production
equipment at disposal, and also on the technology over which one has most control.
For example, with the embodiment disclosed and characterized in claim 6, the antenna
foot can be provided with a surface of non-magnetic material over the dish-shaped
holder, and with the embodiment disclosed and characterized in claim 7, one completely
avoids having to undertake an external surface treatment of the dish-shaped holder,
which is covered and protected by the protective element. A completely finished product
is obtained via one injection moulding process. More over, the holder can be manufactured
with less precision, in that the moulding equalizes production tolerances and conceals
marks and irregularities which arise in the production of the dish-shaped holder.
[0011] A preferred practical embodiment of the invention is disclosed and characterized
in claim 8. The annular slots with binding materal ensure that the magnetic circuit
becomes completely as desired, i.e. with the main part of the field opposite the underside
of the antenna foot so that strong magnetic fields are established through the metal
roof of the car. The same securing element secures both the magnet yoke and the antenna
itself, which simplifies both the construction and the assembly hereof.
[0012] The invention also relates to a method for the manufacture of the antenna foot according
to the invention. The method is preferably as disclosed and characterized in claim
9, i.e. all of the individual parts of the antenna foot are disposed and positioned
in an injection mould arranged for this purpose, after which the moulding is effected
so that at one and the same time the moulding is carried out of the protective element
and a casting of the magnet item during the centering and formation of distance slots.
[0013] After the preliminary work on the antenna foot according to the invention has been
completed, the magnet item is magentized. This is preferably a ring magnet which is
magnetized so that the one pole faces towards that side of the dish-shaped holder
which is in direct contact with the ring magnet, and the other magnet pole faces away
from the underside, i.e. down towards the car roof.
[0014] The underside of the antenna foot according to the invention can be finished in the
final working as disclosed and characterized in claim 10. The coating can be an application
of lacquer, paint or other coating, or be a foil, for example a self-adhesive foil,
which is applied so that the product is given an area printed with information for
the user, advertisement etc.
[0015] The invention will now be described in more detail with reference to the drawing,
in that
fig. 1 shows an antenna foot according to the invention according to a first embodiment,
fig. 2 shows the same antenna as in fig. 1 but seen partly in section,
fig. 3 shows an antenna foot according to a second embodiment, and
fig. 4 is a sketch of the moulding tools for use in the manufacture of the antenna
foot according to figs. 1 and 2, and for use in the manufacture of a third embodiment.
[0016] In figs. 1 and 2 is seen a preferred embodiment of the antenna foot according to
the invention. The antenna foot consists of a dish-shaped holder 1 formed in 1-3mm
thick iron plate with a central threaded hole through which a screw 2 secures an antenna
3 on the top of the holder. In the normal position of use, the dish-shaped holder
1 is thus open down towards that surface, e.g. a car roof, on which the antenna is
to be placed. The screw 2 also secures and centres a central soft-iron yoke 5. Around
the yoke 5 there is disposed a ring magnet 4, separated by a concentric mass 12,
and thus an annular slot exists between the yoke 5 and the magnet 4. Around the magnet
4 there is also an annular slot filled out with a binding material 11 which, as shown
in fig. 2, extends over into an annular outer profile 6 via an area 10 running under
the lower edge 7 of the dish-shaped holder 1, and thus the whole of the annular edge
on the holder 1 is covered. In order to increase the stiffness of the annular profile
6 and to increase the adherence to the holder 1, its outer edge can be configured
with an annular groove 9 or a similar arrangement, e.g. a series of annularly-extending
holes, which will increase the adherence.
[0017] The underside of the antenna foot is covered with a foil 8, e.g. a self-adhesive
foil. In fig. 2 it will be seen that the lower edge 7 of the holder 1 will normally
be slightly raised in relation to the lower edge of the ring magnet 4 and the foil
8, and that the lower edge of the annular profile 6 is slightly lower than the underside
of the foil 8.
[0018] The moulding or binding material, which comprises the protective element 6 with underpart
10 and the annular distance slots 11 and 12, is configured, for example, of thermoplastic
rubber, artificial rubber or synthetic resin, for example Perstorp Dryflex type DF,
DFG or mixtures hereof; Akzo - Armitel injection moulding plastic; Polyurethane -
the elastomer Elastogran or similiar materials.
[0019] In fig. 3 is seen a second embodiment of the invention, where a further cap 13,
e.g. of metal, is used instead of a groove 9 to secure the annular protective element
6, which can be in one with the annular moulding material between the magnet 4 and
the holder 1, but which as shown can also be configured as an independent, encircling
profile ring secured to the outer side of the holder 1 and reinforced and secured
by the outer cap 13. The protective element 6 is thus an independent, encircling profile
ring which is mounted and secured after the rest of the antenna foot has been produced
in the normal manner by casting of the magnet item. In this embodiment, the profile
ring 6 can be produced of the same material as the binding material 11 or of another
material with other characteristics.
[0020] It is also possible to configure the encircling protective element in such a manner
that it surrounds the whole of the outer side of the holder 1, whereby a large contact
surface is achieved and herewith a particularly strong adherence to the outer side
of the holder 1, see right-hand half of fig. 4. This embodiment is described in more
detail later in connection with the method for the manufacture of the antenna foot.
[0021] It will also probably be sufficient to have an encircling protective element 6,
e.g. as shown in fig. 2, and also without the element extending in under the lower
edge 7 of the holder 1, in which case an extremely careful securing is required around
the whole of the edge, and in such a way that it is ensured that the edge 7 is held
at the desired distance from the car roof.
[0022] The left-hand side of fig. 4 shows a sketch of a tool for use in the assembly of
an antenna foot according to the invention and of the kind which is shown in figs.
1 and 2 of the drawing, and in the right-hand side is seen a sketch of a tool for
use in the assembly of an embodiment where the moulded material completely surrounds
the outer side of the antenna foot. Firstly, the bolt 2 is screwed through the yoke
5 firmly into the threaded hole in the holder 1, thus securing the yoke firmly in
place centrally in the holder. A ring magnet 4 is then mounted as shown, positioned
with an annular distance slot in towards the yoke, and similarly so that an annular
distance slot arises between the magnet and the edge of the holder. The parts are
now placed in the mould part 14 as shown, and the mould parts 15 and 16 are closed
against the part 14, whereby the ring magnet 4 is secured in place. A normal injection
moulding can now be carried out with a suitable binding material through an inlet
hole 17 in the mould part 16. In one operation there is hereby moulded both the encircling
protective element around the edge of the holder 1, and the annular distance slots
are formed around the magnet 4, which is hereby secured in the dish-shaped holder.
[0023] With the tool in the right-hand half, the outer side of the holder 1 is also covered
with a layer of moulding material 18, for example 1.5 mm thick, ex cept for the area
blocked by the ring mandrel 19 where the antenna is subsequently mounted. As shown,
it is possible to provide blow holes 20 in the holder 1, so that the moulding material
fills out the mould cavities more quickly and effectively. With this construction,
it is possible for the annular groove 9 in the holder 1 to be dispensed with.
[0024] The underside of the antenna foot can hereafter be finished if necessary, and covered
with a coating 8 which, for example, is a self-adhesive foil, and the magnet item
4 is excited.
[0025] It will be obvious to those familiar with the art that the mould can be arranged
otherwise than shown in fig. 4. Normally, the mould will be arranged for the moulding
of several units simultaneously, possibly in different sizes so that optimum use
is gained from the injection moulding machine.
1. Antenna foot for movable antenna comprising a dish-shaped holder (1) of magnetizable
material and with securing element (2) for an antenna (3) on the top side, a permanent
magnet (4) secured in the dish-shaped holder and a magnet yoke (5), and where the
underside of the antenna foot is provided with a protective element, characterized in that the protective element comprises at least one encircling item (6) of yielding
material permanently secured to the dish-shaped holder (1), and configured in such
a manner that it extends out over the lower edge (7) of the holder.
2. Antenna foot according to claim 1, characterized in that the item (6) of yielding material is configured with such a cross-sectional
profile (6,10) that it covers the annular lower edge (7) of the dish-shaped holder
and is permanently secured hereto.
3. Antenna foot according to claim 1 or 2, characterized in that the item (6) is configured in one with the means (11) which is used to position
and secure the permanent magnet (4), which is an annular magnet.
4. Antenna foot according to claim 3, characterized in that the item (6) and the means (11) are of the same material, preferably a thermoplastic
rubber or resin.
5. Antenna foot according to claim 1 or 2, char acterized in that the item (6) is an independent, encircling profile ring which is permanently
secured to the holder (1), e.g. by gluing or hot welding.
6. Antenna foot according to claim 1 or 2, characterized in that the item (6) is an independent, encircling profile ring (fig. 3) which is
secured by a further dish-shaped holder (13) which wholly or partly surrounds the
first-mentioned dish-shaped holder (1).
7. Antenna foot according to claim 1 or 2, characterized in that the item (6) is configured in such a manner that wholly or partly it surrounds
and covers the whole of the upwardly-turning outer side of the dish-shaped holder
(1).
8. Antenna foot according to claim 1, characterized in that the magnet is a ring magnet (4), and in that centrally herein there is disposed
a magnet yoke (5) which, together with the holder (1), comprises the magnetic circuit,
and that between the parts there are annular slots filled out with binding material
(11,12), and in that the yoke (5) has a central hole for a securing element (2) for
an antenna (3), said securing element also securing and positioning the yoke (5).
9. Method for the manufacture of an antenna foot according to claims 1-4 or 8, characterized in that the dish-shaped holder (1), a magnet item (4) and the magnet yoke (5) with
securing element (2) are placed and positioned in a mould (14), after which the mould
is closed with the mould parts (15,16) arranged so that the parts are cast in by injection
moulding at the same time that the encircling item (6) is formed.
10. Method according to claim 9, characterized in that the underside of the antenna foot within the encircling item (6) is cleaned
and possibly turned, after which the area is covered with a thin foil or coating
and the magnet item is excited.