Electronic key reader

Description of the invention

The invention relates to an electronic key reader.

In controlled access, each authorized user has an identification card provided with an electronic device which, when powered from an external source, sends an encoded signal allowing, for example, the door to be opened upon recognition by a reader.

The reader transmits the energy needed to operate the identification card by self-inductive coupling, which means that both the reader and the card contain a coil antenna.

The reader is located outside the locked room and therefore measures are necessary to prevent its destruction by unauthorized persons. In general, the reader is closed in a very resistant, metal casing permanently attached to the external wall of the room. There is a slot in the outer wall of this housing that allows the antenna's transmitting beam to be emitted to the outside. In some cases, the reader itself is attached and its front wall is covered with a metal plate.

Experience has shown that for the card to work effectively it needs to be relatively close to the reader. This is due to the fact that the housing or the metal pollen acts like a winding through which the flux emitted by the antenna passes, which absorbs some of the energy emitted by the antenna and converts it into heat.

The present invention addressing the above drawback is characterized in that the housing has a slot extending from one edge of the housing to, essentially towards, the center of its front wall.

The subject of the invention is shown in an embodiment in the drawing, in which fig. 1 shows a perspective view of a known housing, fig. 2 shows a front view of the casing according to the invention, fig. 3 shows a top view of the casing shown in fig. 2, fig. 4 shows, analogous to Fig. 2, another embodiment of the invention.

As can be seen in Fig. 1, the reader is enclosed in a metal casing 1, behind the front wall 2, which has a common antenna, shown schematically as a frame 3.

There are openings 4 in the wall 2 to extract the streams emitted by the frame 3. Experience has shown that only a small part of the energy emitted by the frame 3 was received by the user card, with the result that it had to be relatively close to the reader.

This phenomenon is explained by the fact that the housing behaves like an induction winding and absorbs part of the flux emitted by the antenna.

The invention which remedies the above disadvantage is characterized in that the housing has a slot 5 extending from the edge 2a of wall 2 to the center of the wall, this slot extending over the side wall 6 of the housing so as to open onto surface 6a. .

In the event that the housing is limited to the metal plate covering the reader that is embedded, the above-described slot opens at either edge of the plate.

Experience has shown that the absorption effect of the metal casing was significantly reduced by the mere presence of the slot 5 in Fig. 2, which made it possible to recognize the user despite being at a much greater distance from the reader than with known readers.

Of course, nothing prevents the reader from having holes similar to the holes 4 on the front wall of the reader.

The effect of the invention can be enhanced by using several slots, such as the slots 7 of Fig. 4.

Preferably, the end 5a of the slit 5 extends beyond the centerline AB connecting the centers of the edges adjacent to the edge onto which said slit opens.