Safes – bank protection – or a related device – Combined – With marking devices
Patent
1988-05-13
1989-08-01
Wilson, Neill R.
Safes, bank protection, or a related device
Combined
With marking devices
109 41, 109 42, 109 35, E05G 300, G08B 1322
Patent
active
048525022
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention refers to a safety box according to the generic clause of claim 1.
Such safety boxes, which are known e.g. from U.S. Pat. Nos. 3,559,593 and 3,851,602, have been used for transporting secret documents or money for a fairly long time. Such safety boxes have e.g. the form of a portfolio whose outward appearance corresponds to that of a conventional hard-shell case consisting of plastic material. The safety box wall, which is in most cases fabricated of metal or of plastic material, is normally provided with a large number of conductors extending in the wall of the safety box in a close-meshed pattern and connected to a detection circuit. If an unauthorized person tries to open the safety box by force by destructing the wall of the safety box, he will, in so doing, either break through one of the conductors or cause a short circuit between neighbouring conductors. This condition deviating from the normal condition can be detected by the detection circuit, which triggers an actuation signal. Said actuation signal is normally used for activating an alarm means on the one hand and, on the other hand, it is used for permanently destructing or for marking the documents or bank-notes contained in the safety box. In most cases, this is effected by igniting an explosive charge with the aid of said actuation signal, said explosive charge being used for ejecting from a reservoir an acid or a marking liquid and for spreading said acid or marking liquid over the documents and bank-notes, respectively. This means that, if someone tries to break open the safety box, the bank-notes or documents contained in said safety box will either be marked permanently by a colouring agent, or they will be fully dissolved by an acid, this being desirable in particular in the case of secret documents.
The major part of the known, commercially available safety boxes is provided with a wall of plastic material in which the conductor is embedded, said conductor being normally constructed as a conductor lattice. However, due to electrostatic charging of the box wall, undesirable activation of the circuit may occur in the case of such safety boxes so that unintentional marking or destruction of the bank-notes or documents transported may be effected also in cases in which the wall of the safety box has not been damaged. Moreover, it may happen that stray fields acting on the safety box from outside cause a voltage induction in the conductor located within the wall, and this, too, may result in faulty activation of the circuit.
Furthermore, there are safety boxes, which, for increasing the impact resistance of the safety box wall, are provided with a wall fabricated of metal. In the case of these safety boxes, the earth terminal of the safety circuit is connected to the metal box wall. Due to the complete shielding of the conductor, which responds to interruption and short-circuiting, respectively, in the case of a destruction of the wall, unintentional activation caused by external stray fields will not occur in the case of this type of boxes. It may, however, happen that, by applying voltages to the metal wall of the safety box, the detection circuit can be destructed or manipulated in such a way that a subsequently following destruction of the wall will not cause the circuit to produce an actuation signal. The safety boxes which are nowadays predominantly used have a non-shielded, insulated plastic wall.
In comparison with this prior art, the present invention is based on the task of further developing a safety box of the type mentioned at the beginning in such a way that the reliability with which the circuit detects a destruction of the safety box wall is further increased.
In the case of a safety box of the type mentioned at the beginning, this task is solved by the feature disclosed in the characterizing clause of claim 1.
In accordance with the invention, the safety box is provided with a shield means, said shield means being, however, galvanically separate from the circuit. Due to the fact that the c
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patent: 3825920 (1974-07-01), Nelson et al.
patent: 3851602 (1974-12-01), Lamping
patent: 4722435 (1988-02-01), Mareels et al.
Klingberg Sven
Persson Sixten
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