Electronic Antitheft Device Using An Electronic Safety Lock

Abstract

An antitheft device operated by a key containing electronic contacts insertable into a lock comprising electronic circuitry, the contacts being uniquely arranged to actuate the electronic circuitry. The keyhole has two positions such that insertion of the key into the first position actuates the circuitry into a pre-alarm state wherein any unauthorized tampering with the system will sound an alarm. Insertion of the key into the second position deactivates the electronic circuitry.

Description

The present invention relates to an electronic device designed to be used as an antitheft device for motor vehicles and/or as a safety lock for doors, safes, drawers and other similar applications.

The main feature of the device according to the invention resides in that the device comprises an electronic circuit formed by two interlocking main parts. The first is fixed and is mounted on the motor vehicle or along a moving door or wall whose opening is to be controlled. The other part is removable and forms the key or guide element which is coupled to the first part and capable to activate it thereby allowing the opening and/or the closing of the member or members to be controlled. It also cuts off or closes the alarm electric circuit connected to said controlled members.

Another feature of the invention is that the fixed part of the device comprises:

AN ANALYZER CIRCUIT WHICH IN TURN IS FORMED BY THREE LOGICAL CIRCUITS;

AN INTERMEDIATE LOGICAL CIRCUIT WHICH MAY BE ACTIVATED BY THE OUTPUT SIGNALS FROM THE ANALYZER CIRCUIT;

A FINAL CIRCUIT CONNECTED TO THE PRECEDING CIRCUITS AND PROVIDED WITH SUITABLE MEANS TO EFFECT THE ACTIVATION OR THE DEACTIVATION OF THE ALARM MEANS, AND THE ELECTRICAL OR ELECTROMECHANICAL MEANS CONTROLLING THE OPERATIVE MEMBERS;

A LOCK OR SEAT FOR A KEY, PROVIDED WITH INTERNAL ELECTRICAL CONTACTS AND DESIGNED TO RECEIVE A KEY WHICH CARRIES A PORTABLE AND REMOVABLE CIRCUIT STAGE.

The invention has a further feature in that when the device is set for operation, it locks the motor vehicle ignition, as well as the doors and hood and also controls an audible and/or visual alarm conveniently located. The alarm is triggered by any unauthorized starting, any attempt to introduce a false key into the lock or unauthorized entry of hood, trunk compartment or other parts controlled by the automatic electrical switches.

Another feature of the invention relates to the structure of the removable stage or circuit section, operating as a key, whose dimensions are substantially corresponding to those of a normal key and which is provided with a plurality of small electrical circuits providing a pre-established short circuit combinations, chosen from a very wide range of possibilities, each and only one of said combinations being capable to cooperate with a corresponding electrical lock provided with electrical contact terminals arranged in the fixed circuit section.

Further features of the invention will become apparent from the following description taken in conjunction with the annexed drawings which are presented only by way of a demonstrative and not limiting example, wherein:

FIG. 1 is a side view of a preferred embodiment of the removable circuit section, having the shape of a flat or laminate key;

FIG. 2 is a view of a lock keyhole for the key of FIG. 1, partially broken along a diametral plane parallel to the entrance slit for the key;

FIG. 3 shows a detail of the key, separated from the same;

FIG. 4 is the preferred arrangement of the electronic diagram for a device whose operation is controlled by the key of FIG. 1 cooperating with the lock keyhole of FIG. 2.

The key shown in the embodiment of FIG. 1 comprises a support 20, made of an electrically insulating material having a suitable mechanical strength and suitable shaped. On one of the plane faces of its flat tang 22 are arranged electrical contacts, whose number may be any pre-determined number but not less than two, indicated by 32, 33 . . . 38 which, by means of small conductor bridges, indicated by dark shaded areas may or may not be short-circuited by an analogous contact 31. A further contact element 39, electrically insulated from the others, is also provided.

It is easily understood that the combinations which may be obtained with such a type of key depend on the number of contacts 32 . . . 38 and their short-circuit arrangement.

The total number of combinations which may be obtained with a key of said type results from different short-circuit arrangements of the contacts, which may easily be formed by starting from a printed circuit. The total sum number is obtained by raising the number 2 to the power n (excluding the contacts 31 and 39) and substracting 2, that is: 2.sup.n - 2 which is equal to the number of different combinations on the keys. Further, by varying, with respect to the others, the position of the contact indicated by 31, the combinations obtainable are multiplied by the number of different positions said contact 31 may assume. Thus, the number of different combinations and therefore the number of different keys obtainable is very great.

The slit keyhole of the lock, FIG. 2, is provided with a set of electrical terminals 1, 2, 3 . . . 10 insulated from each other and provided with internal metal lamellar projections 1a, 2a . . . 10a protruding within the cavity 41, and capable to accommodate the tang 22 of key 20. The projections 1a, 2a . . . 10a form a number of electrical contacts, which by sliding, are able to cooperate with contacts 31, 32 . . . 39 carried by tang 22. The tang 22 of key 20 is provided at its fore end with a notch 40, while the bottom of the keyhole 41 is provided with a resilient lamellar member 42 which presents a moderate resistance to the insertion of the key to the full length. As a result, when the key is inserted in the cavity 41, the tang 22 may assume two positions:

the first, an incomplete insertion, with its end 39a stopped on top of the spring 42;

the second, a complete insertion, with its end 39a resting against the bottom 9b of the keyhole, after having overcome the resistance of spring 42.

The key 20 is therefore inserted and/or extracted with respect to cavity 41 of the lock without any rotational movement of the key. The key is so called only for its shape but, in reality, it forms a removable section with a unique combination of the device electrical circuit. Also, the slit keyhole 41, designed to receive the tang 20, is not a true lock but has the function to transmit, through its electrical terminals to the analyzer circuit, the combination of contacts on tang 22.

The device analyzer circuit, FIG. 4, has the terminal F electrically grounded and terminal H connected to the electrical power source, for example, the positive pole of an on board battery whose other pole is also grounded. It further comprises three logical circuits providing outputs of the 0/1 type, which for example are voltage levels of about +0.5 volt / +12 Volt.

The terminals indicated by: 1, 2, 3 . . . 10 are electrically connected to the terminals of the keyhole, FIG. 2, respectively indicated by the same reference number.

The terminal G is connected to the motor ignition coil.

Terminals I are connected to one or more audible warning devices.

Terminal L is connected to the pushbutton switches which close the alarm circuit when one of the doors or the motor hood cover or the trunk are being opened.

E indicates an additional input terminal of the alarm circuit, which may be connected for example to other protective devices.

D1, D2, D3 . . . D12 indicate the diodes used in the circuitry of the device.

Ri, R2, R3 indicate bias resistances.

RL1 indicates a relay operating the closing or opening of the alarm circuit.

RL2 indicates a relay operating the closing or opening of the electrical feeding of the device.

As already stated, the analyzer circuit is formed by three logical circuits, FIG. 4, using three transistors: Tr1, Tr2, Tr3 whose outputs correspond to the leads respectively indicated by A, B, C.

The first logical circuit employing Tr1 responds to any short to ground of one or more input terminals 2 . . . 8 and changes the value of its output at A, from "0" to "1" (from zero to one). Thus, by the insertion of tang 22 of key 20 into the slit keyhole 41, any contact carried by the same is connected to the input terminal of circuit Tr1 which provides the indication of "key presence" signal.

The second logical circuit Tr2 is designed to check that all the contacts 6, 7, 8, "none excluded", are being short-circuit to ground.

The third logical circuit Tr3 is designed to check that "not any" of the contacts being excluded from the key combination, that is, in this example contacts 2, 3, 4, 5 are short-circuited to ground.

In case of the correct combination, that is, when the corresponding key 20, 22 is introduced in the slit 41 (FIG. 2), there will be at outputs A = Tr1; B = Tr2; C = Tr3, values according to the following code:

A = 1 - presence of signal

B = 1 - presence of signal

C = 0 - absence of signal.

This code passes to the analyzer circuit formed by transistors:

Tr4, Tr5, Tr6, connected as follows:

The output of A excites the base of Tr4 which has its collector load, the alarm relay RL1.

Under these conditions, if the key inserted in 41 is the correct one, the output at B will be of the "1" type and therefore Tr5 will be excited. However, since the collector of Tr5 is connected to the output terminal A, the output signal is reduced to "0" (zero). As a result, RL1 is not excited, and it does not close the alarm circuit.

The output of C being a signal "0" (zero) under normal conditions, it does not affect the operation of Tr4 and Tr5. However, if the circuit combination caused by the key 20, 22 is wrong, there may be a presence of signal "1" at C whereby Tr6 is excited since its collector is connected to the output terminal B it will reduce to "0" the signal. Under these conditions, Tr5 does not prevent the output A to excite RL1 which closes the alarm circuit.

Similarly, if the contacts 6, 7, 8 are not all short-circuited, Tr5 will not prevent the excitation of RL1 and therefore the alarm circuit will be closed.

The voltage at collector Tr4 is brought to the base of transistor Tr7 which acts as an inverter for the self-holding of the alarm relay RL1. In effect, when the alarm is excited, even from an instantaneous voltage from Tr4, Tr7 brings back to the base of Tr4 a second permanent signal of the "1" type. Thus, the alarm relay RL1 is always predisposed for the electrical feeding and furthermore, when it is excited it may be released only by the introduction within 41 of the key carrying the correct circuit combination.

Output B, through the capacitor M and the pair of directional diodes D10, D11, is utilized to change the state of the flip-flop formed by transistors Tr8 and Tr9 which operates the connection and/or the disconnection of the device. The output B provides in any case, a signal the effect of which is opposed to that of the A output signal, and is therefore suitable for the purpose.

In effect, the device must be connected or disconnected without the excitation of the alarm relay RL1.

It is further essential that the flip-flop circuit changes its state only with stepped signals which change from "0" to "1" which allows the connection of the device when the key is fully inserted. The disconnection is effected in a partial insertion position of the key. When the key, after having connected the device is extracted, as the key leaves the sliding contact 1, a voltage step is generated which goes from "1" to "0" and which therefore, is ineffective to change the state of the flip-flop.

When the key is introduced while the device is already connected, the device is firstly disconnected (the signal at B had previously gone from "0" to "1" to connect and subsequently changes from "1" to "0" due to the disconnection of the feeding effected by RL2). Then as the key shorts the contacts 9 and 10, the voltage at B returns from "0" to "1" and the flip-flop changes again its state exciting RL2 and feeding permanently the device.

The circuit Tr8, Tr9 forming the flip-flop is suitably calculated so that it presents a condition wherein RL2, which is the relay which actuates the switch 47, is released. Said switch 47 connected in parallel with contacts 9 and 10, when open and RL2 is released it disconnects the electrical feeding to the whole device and prevents its being set even if only the electrical contacts 9 and 10 are short-circuited. From the foregoing stated it appears clearly that only with the introduction of the correct key 20, 22 within the slit 41 may the antitheft device according to the invention be controlled for either its connection and its disconnection.

With reference to FIGS. 2 and 4, by completely inserting key 20, 22 within the slit 41 and then extracting the key the electrical contacts are closed along dot-and-dash lines 43, 44, 45 whereby the relay RL2 closes, the feeding the circuit for the whole device. In this condition, the antitheft device of the invention is in the pre-alarm condition. If then a false key is introduced in the slit 41, or one or more of the switches connected to the electric line L are being closed, the switch controlled by the relay RL1 closes and the alarm means connected to lines I are activated.

From the preceding statements it is clear that the key 20, 22 must not and cannot rotate within the slit 41. Hence, the manoeuvres to connect and disconnect the antitheft device are almost identical. In order to differentiate said manoeuvres, the key has been provided with the terminal notch 40. When the key is partially inserted in the slit 41, the end 39a of the tang 22 meets with the arcuated spring 42. If the manoeuvre stops at this point, and the key is extracted, the short-circuiting between contacts 9 and 10 is avoided, and the relay RL2 is released and the switch 47 is opened. Under these conditions, the feeding for the whole device is lacking.

If, on the contrary, the key is completely inserted, the relay RL2 closes the switch 47 and when the key is then extracted, the device remains in the pre-alarm state.

To further clarify the foregoing statements and supposing that it is not known if the antitheft device is connected or not.

If the device has to be connected:

The key must be completely inserted and then extracted. If the device was already connected, when the end 39a of the key reaches in the first position of physical stop against the spring 42, the device will be disconnected. By surpassing the resilient stop of spring 42 and noting the slight snap of the spring into the notch 41, thereby completely inserting the key, the device is again connected.

If the device has to be disconnected:

If the device was previously connected, the manoeuver is evident, that is, the key must be partially inserted until it encounters the resilient stop 42 and then removed. If the device was previously disconnected, the same procedure occurs but no changes result. In any doubtful case, it will be sufficient to suppose that the device is in the condition opposed to the desired condition.

From the described operation of the device is it evident that only the particular key, provided with the unique pre-arranged circuit combination is capable to control the anti-theft device, while the use of any other type of key or tool does not allow the disconnection of the device. Furthermore, as long as any unauthorized key includes the contact 31 in the same position of the correct key, it causes the immediate actuation of the alarm circuit.

By increasing, therefore, the combinations of the different keys it will be useful to locate said contact 31 always in the same position. Any attempt to disconnect the antitheft device with any unauthorized conductor element will cause the actuation of the alarm circuit when any of the contacts of the keyhole 41 will be short-circuited with said contact 31, excluding the contacts 9 and 10. Even the cutting of the conductors connecting the lock to the analyzer circuit would not remove the antitheft device, but on the contrary there will be the possibility of accidental short-circuit with consequent actuation of the alarm circuit.

Signal of the "1" type may be, evidently, driven through directional diodes to the output terminal A. These alarm signals may be generated by suitable trap-pushbuttons or any other suitable device, in order to prevent thereby any possible tampering of the analyzer circuit.

As already stated, the example described hreinbefore referred to motor vehicles, as a particular use for the antitheft device, this is not at all limiting, as it is evident that the same device may be advantageously employed, with the suitable variants, (operating voltage, polarity, etc.) for other purposes and wherever any need of security locks particularly for safes.

To this end it is also possible to make the identification of the valid combination unfeasible by analyzing it by means of an apparatus known as an "electronic picklock." It is possible to separate the contacts, FIG. 4, connected to diode D4 by means of directional diodes connected as the D1, D2, D3 and to add bias resistances R1. In this way all the contacts of the combination connected to the keyhole 41 are made electrically equal preventing thereby their identification.

FIG. 3 represents a mask 46 which may be applied, by embedding it, longitudinally onto the central part of the tang 22 in order to mask the circuitry section, that is the arrangement of the small bridges between opposed contacts. Said mask 46 is embedded and fits onto the printed circuit provided on the tang 22. Even if the mask is removed, it causes the removal of the circuitry section on which it is applied, thereby preventing whoever might be in temporary possession of a key, from constructing a duplicate of the key. The only duplicate may be made by the original manufacturer through the identification number of each key.

While the key or removable circuit section of the device according to the invention does not require any angular movement to pilot the device, the same key may also be used as a start key for the motor of the motor vehicle. To this end it is sufficient to provide the motor vehicle with a suitable key-controlled switch wherein the same key controlling the antitheft device may by an additional movement of inserting or angular turning within the keyhole also start the engine.

As already mentioned in the foregoing description, by the use of a suitable relay RL2, that is provided with the required technical characteristics and a sufficient number of contacts, the device of the invention may control the opening and closing of lock latches operating with electric pulses. It is evident that the locks controlled by means of this device, easily contructed, become inviolable and result in an efficient alarm device.

Another advantage, deriving from the use of the device according to the invention, resides further in that a single key or removable circuit section, may control electrical locks and alarm systems which are identical and situated in different places. For example, for the same person, on the automobile, on the house door, the office door, the safe and/or writing desk, etc. reducing thereby to only one, the number of keys a person normally needs.

It is obvious that the device of the present invention is in no way limited to the example described and illustrated and that, without departing from the scope of the invention, it may be varied and improved according to the practical use requirements. It may be necessary, for example, to substitute the relays with static devices, particularly if the device is used in explosive atmospheres. These devices can operate with transistors or controlled diodes. The circuit may be further simplified by replacing the flip-flop with a stepping relay, even if this substitution would increase the dimensions and the cost of the device.

Claims

We claim:

1. An electronic antitheft device for preventing the unauthorized opening of a closeable member by the activation of an alarm and adapted to be energized from a power supply, said device comprising: a fixed circuit section contained within a lock mounted on said closeable member, and further comprising a keyhole, a plurality of electrical terminals placed along said keyhole, additional electrical terminals arranged on said keyhole and blocking means within said keyhole establishing a first and second positions along said keyhole; a movable circuit section contained on a key-shaped member capable of insertion within said keyhole and further comprising guide means for guiding the inserted key with relation to said blocking means into said first and said second positions, a plurality of electrical contacts arranged along the tongue portion of the key and designed to interconnect predetermined ones of said plurality of terminals when said key is in both said first and second positions, and additional electrical contacts arranged on the said tongue portion and designed to interconnect said additional terminals when said key is in said second position; and electronic circuit means further comprising code checking means which when energized by said power supply recognizes the presence of a member in said keyhole such that in response to the presence of a key containing said predetermined interconnections produces a switch signal and in response to any other member activates the alarm, and switch means having a first state for energizing said code checking means from the power supply and a second state for de-energizing said code checking means from the power supply, said switch means alternately changing state in response to successive switch signals; and wherein said additional contacts when interconnecting said additional terminals energize said code checking means from said power supply independently of said switch means, whereby when said key is inserted into said second position said device is placed in a pre-alarm condition and said closeable member is locked, and when said key is placed into said first position said device is disconnected and said closeable member is opened.

2. An electronic antitheft device, as in claim 1, wherein said switch means includes a flip-flop circuit triggered by said switch signal and relay switch means controlled by the state of said flip-flop and coupled between the power supply and said code checking means.

3. An electronic antitheft device, as in claim 1, wherein said code checking means includes relay switch means connected to the alarm.

4. An electronic antitheft device as in claim 1, wherein said key shaped member is of electrically insulating material and contains thereon said plurality of contacts, some of which are short-circuited to each other according to a pre-established combination.

5. An electronic antitheft device as in claim 4, wherein said key shaped member has a flat tang portion insertable into said keyhole.

6. An electronic antitheft device as in claim 5, wherein said tang portion is masked and coated to make said plurality of contacts undetectable.

7. An electronic antitheft device as in claim 4, wherein said plurality of contacts are formed as a printed circuit and whose numbers and locations are randomly selected wherein the total number of possible unique keys are equal to 2.sup.n - 2 where n is the number of unique combinations resulting from the different positions assumed by the contacts on one key.

8. An electronic antitheft device as in claim 4, wherein said key contains five short-circuited contacts and a plurality of electrically insulated contacts.

9. An electronic antitheft device as in claim 1, wherein said key has only longitudinal motion with respect to said keyhole.

10. An electronic antitheft device as in claim 1, wherein said key undergoes longitudinal motion and angular motion with respect to said keyhole.

11. An electronic antitheft device as in claim 10, and further comprising an independent means wherein said angular motion of the key activates said independent means.

12. An electronic antitheft device as in claim 9 and further comprising an independent means wherein after complete insertion of said key in said keyhole a further longitudinal push upon said key temporarily activates said independent means.