Note: Descriptions are shown in the official language in which they were submitted.
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Titel: Friction lock
- This invention relates to a friction lock comprising a
needle having a shank and a head, and a lock body capable of
receiving the shank of the needle, said lock body including a
tapered chamber containing a plurality of clamping elements
which, in operation, in a locking position, grip the needle
shank and with a special unlocking tool can be moved to a
position in which they release the needle.
Such friction locks are often used for securing anti-
shop-lifting tags to articles of merchandise, in particular
clothing. A friction lock may be a separate element which is
used to secure a loose detection plate or a label to a piece
of clothing, but may also be an integral part of such a tag.
This latter is mostly the case if the tags take the form of
electronic detection plates, often referred to as wafers,
which by means of an electromagnetic interrogation field can
be detected in a detection zone.
A certain part of the clothing is clamped between the
lock body and a relatively broad needle head. The needle is
inserted through the fabric of the piece of clothing into the
lock body. The wafer is safeguarded from fraudulent removal by
the lock. Owing to the frictional and clamping forces between
the needle shank and the clamping elements, the needle cannot
be drawn out of the lock body. When the price is being paid,
the wafer is removed from the piece of clothing or other
article by a shop assistant. The removal of the wafer is
effected at the cash desk by means of a special tool, such as
an ~electro) magnet which pulls the clamping elements free
from the needle. If a client omits to have the wafer removed
and enters the detection zone provided at the shop entrances
and exits, an alarm signal is generated by a
transmitter/receiver upon detection.
Friction locks of the above kind are known in various
embodiments. US patent 4,286,256, US patent 3,855,280 and US
patent 4,523,356 disclose friction locks having ball-shaped
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clamping elements disposed in a conical space. Furthermore,
British patent 1,570,508 discloses a friction lock with a
cylindrical clamping element.
One disadvantage of the known friction locks is that
these are sometimes difficult to unlock. The clamping means
may be wedged between the shank of the needle and the wall of
the tapered chamber with such a large force that attempts at
pulling them into a wider portion of the tapered chamber by
means of the special unlocking tool, which is mostly an
electromagnet, fail.
This problem can be overcome by driving the needle just
slightly further into the lock body beyond its original locked
position during the unlocking operation. The needle shank then
pushes the clamping elements already in the di^ection of the
wider portion of the tapered chamber, so that the clamping
force is diminished. This, however, is only possible if the
material of the article being safeguarded and clamped between
the needle head and the lock body can be compressed further to
a sufficient extent. If, however, a thin summer dress, for
20 example, is safeguarded by the wafer, the release of the ,
needle is apt to present problems. The fabric has too little
resiliency to permit the needle to be driven further into the
wafer lock. Not any material of the goods being safeguarded
has sufficient resiliency for the needle to be released in a
reliable manner. Another disadvantage is that the part of the
- needle head which contacts the material may cause damage toclothing when it is attempted to move the needle further into
the wafer lock.
It is an object of the invention to overcome the
disadvantages outlined above.
To this effect, according to the invention, a friction
lock of the kind described is characterized by resiliently
compressible means for permitting the needle, in the position
in which it is locked, to be pushed slightly further into said
lock body with resilient deformation of said resiliently
compressible means.
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Some embodiments of the invention will now be described
in more detail, by way of example, with reference to the
accompanying drawings. In said drawings,
Fig. 1 is a diagrammatic part-sectional elevation of one
embodiment of a friction lock according to this invention;
Fig. 2 shows, in side-elevational view, an example of a
needle for a friction lock according to the invention;
Fig. 3 shows the needle of Fig. 2 in bottom view;
Fig. 4 shows a cross-sectional view of a different
example of a needle for a friction lock according to the
invention;
Fig. 5 shows the needle of Fig. 4 in bottom view; and
Fig. 6 shows still another example of a needle for a
friction lock according to this invention.
Fig. 1 shows an example of a friction lock according to
the present invention, suitable for use as a lock for a wafer.
The lock has a needle with a head 1 and a shank 2. Shank 2
extends, in the operative condition, through the material of
an article 9, such as a piece of clothing, to be safeguarded,
and into the body 4 of the wafer lock.The wafer, which may
contain a conventional electrical circuit, is shown
diagrammatically at 10, and in this example can be regarded as
forming part of the lock body. Provided within body 4, in this
example, are a plurality of balls 5, disposed in a conical
member 6. The balls are pushed into the conical me~ber by a
pad 7 and a helical spring 8, and this into the direction of
the tapered end thereof. Shank 2 of the needle can be driven
through a bore 11 in the wafer and a corresponding bore 12 in
the tapered end of the conical member between the balls. The
shank of t~he needle is then clamped in known manner and cannot
be removed unless, and until, the balls are moved to the wider
end of the conical body. For this purpose use can be made, as
is also well-known, of an electromagnet which can pull the
balls against the action of spring 8 to the wider part of the
conical member.
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The conical member is preferably formed so that the ballc
make linear contact with the inner wall of the conical member.
Such a construction is described in applicants' US patent
4,280,256.
The contact between the clamping elements, formed as
balls, and the conical member, and the shank of the needle is
maintained as pad 7 drives the balls through a collar 13 into
the direction of the tapered end of the conical me~ber.
In order to provide for a reliable release of the needle,
independently of the nature of the material of the article 9
being safeguarded, in the example shown, the head 1 of the
needle is provided along its circumference with a plurality of -
supports 3, three in this example, through which the head -
bears on the material of article 9. Head 1 of he needle is in
this example dome-shaped, but may have any other form, for
example, disk-shaped.
The effect of supports 3 is that when a pushing force P
is exerted on the head of the needle into the direction of
shank 2, the needle head can be resiliently deformed, and the
shank pushed slightly further into the lock. During this
movement, the balls roIl somewhat into the direction of the
wider portion of the conical member, so that the clamping
forces acting between the balls and the conical member and the
shank of the needle are reduced.
Accordingly, if the balls are at the same time pulled
into the direction of the wider part of the conical member by
a special unlocking tool, such as an (electro) magnet, less
force is required to overcome the clamping forces.
If a wafer has to be removed from a given thin material
having insufficient resiliency, it will be possible, by
pressing on the rounded supports 3, via needle head 1, to
cause needle head 1 to be deformed, so as to provide the
necessary resiliency to enable the needle to move further into
the wafer lock.
3S Fig. 2, in side elevational view, and Fig. 3 in bottom
view, once more illustrate -the needle 2 of Fig. 1 with a
needle head 1 according to the invention, provided in this
case with three segments in the form of supports 3. The dome-
shaped needle head is in this example further provided with
interior strengthening ribs 14.
Figs. 4 and 5 show a needle with a needle head 15 which
has a stepped configuration. The stepped configuration of the
needle head provides a certain degree of resiliency. In this
embodiment, too, the needle head can be resiliently compressed
in such a manner that the needle can be moved sufficiently far
into the wafer lock. The stepped needle head is preferably
covered with a smooth cap 16.
Fig. 6 shows an example of a needle with a disk-shaped
needle head, which is provided at the bottom with a plurality
of supports 18 arranged along the circumferent al edge
thereof. Supports 18 make it possible for the central part of
the needle head with the shank to be depressed somewhat,
whereby the shank is driven more deeply into the lock body.
It is observed that, after reading the above, various
modification will readily occur to those skilled in the art.
Thus the needle head is mostly made of synthetic plastics and
the shank of steel, but alternatively the needle head may be
made of metal.Also, the invention may be applied to friction
locks with differently shaped clamping elements. Furthermore,
it is possible for the lock body or the wafer to be made
resiliently deformable in the area 17 (Fig.1) in juxtaposition
- to the needle head, whether or not in combination with a
resiliently deformable needle head. These and similar
modifications are considered to fall within the scope of the
present invention.
