In the fight against vehicle theft, a wide range of vehicle alarms and electronic immobilizers have been developed. However, by accessing the electronic control box of such systems which is typically located within the engine compartment, an experienced thief can usually bypass even the most sophisticated of such systems. To address this problem, secondary locking systems have been introduced in an attempt to prevent unauthorized access to the primary anti-theft systems. These locks are usually referred to in U. S.

English as"hood locks", and in U. K. English as"bonnet locks".

Hood locks are generally implemented as electromechanical locks which prevent operation of the cable release mechanism normally used to open the vehicle hood. Typically, an electromagnetic actuator (such as an electromagnet, solenoid or motor) displaces a bolt or other locking element to prevent movement of a block fixed to the cable.

Logically, a hood lock would be most effective if locked continuously whenever the primary anti-theft system is active. However, the commercially

available systems only lock the hood when an alarm has been triggered.

Continuous supply of electrical power to the electromagnetic actuator would otherwise drain the vehicle's battery unacceptably. Theoretically, the problem of battery drain could be solved by designing a bi-stable lock mechanism which only required electrical power when changing between the locked and unlocked states. However, such a design is unacceptable because it would be impossible to open the hood if an electrical fault developed while the hood was locked.

There is therefore a need for an electromechanical lock for a cable release mechanism which can be activated for extended periods without causing battery drain but which would allow the cable release mechanism to be operated in the case of an electrical fault.

SUMMARY OF THE INVENTION The present invention is a sensor actuated hood lock.

According to the teachings of the present invention there is provided, an electromechanical lock for selectively preventing movement of a cable sufficient to operate a cable release mechanism, the electromechanical lock being supplied from an external source of electrical power, the electromechanical lock comprising: (a) a lock mechanism including a moving element linked to the cable and a stop, the lock mechanism being constructed such that, when the cable is pulled, the stop and at least a part of the moving element undergo relative motion in a first direction from a locked configuration to an unlocked configuration followed by relative motion in a second direction

not parallel to the first direction, the lock mechanism further including an electromagnetic actuator configured so that, when the electromagnetic actuator is activated, the relative motion of the stop and the at least part of the moving element in the first direction is prevented; and (b) a sensor mounted so as to be activated by movement of the cable, the sensor being electrically associated with the electromagnetic actuator such that, when the cable is in its resting state, no power is supplied to the electromagnetic actuator and, when the cable begins to move, power is supplied to the electromagnetic actuator so as to prevent unlocking of the lock mechanism.

According to a further feature of the present invention, the stop is a fixed stop, the lock mechanism being configured such that, when the electromagnetic actuator is deactivated, pulling of the cable causes lateral displacement of at least part of the moving element such that the moving element bypasses the stop and, when the electromagnetic actuator is activated, the lateral displacement is inhibited such that a part of the moving element engages against part of the stop.

According to a further feature of the present invention, the lateral displacement of the at least part of the moving element corresponds to a rotational movement of the moving element.

According to a further feature of the present invention, the moving element has an elongated armature, the electromagnetic actuator being positioned to attract a distal portion of the elongated armature.

According to a further feature of the present invention, the lock mechanism is configured such that a given magnitude of force applied to the moving element by the electromagnetic actuator is sufficient to prevent the relative motion of the stop and the at least part of the moving element in the first direction independent of a magnitude of force applied to the cable.

There is also provided according to the teachings of the present invention, a method for selectively preventing movement of a cable sufficient to operate a cable release mechanism, the method comprising: (a) providing an electrically actuated lock mechanism linked to the cable in such a manner that, when the lock mechanism is deactivated, pulling of the cable actuates motion from a locked state to an unlocked state followed by a traveling motion and, when activated, a magnetic field is generated which prevents the motion to the unlocked state; (b) sensing movement of the cable indicative of an attempt to operate the cable release; (c) when the cable is in its resting state, deactivating the lock mechanism; and (d) when movement of the cable is sensed, activating the lock mechanism so as to prevent operation of the cable release mechanism.

According to a further feature of the present invention, the lock mechanism is implemented such that a given magnitude of the magnetic field is sufficient to prevent the motion to the unlocked state independent of a magnitude of force applied to the cable.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: FIG. 1 is a schematic representation of a sensor actuated electromechanical lock, constructed and operative according to the teachings of the present invention, and the corresponding electrical circuit; FIG. 2 is a schematic illustration of a first type of sensor responsive to application of tension to a cable for use in the electromechanical lock of Figure 1; FIG. 3 is a schematic illustration of a second type of sensor responsive to application of tension to a cable for use in the electromechanical lock of Figure 1; FIG. 4 is a schematic illustration of a third type of sensor responsive to application of tension to a cable for use in the electromechanical lock of Figure 1; FIG. 5 is an isometric view of a preferred implementation of a electromechanical lock, constructed and operative according to the teachings of the present invention, for preventing operation of a cable release mechanism; FIG. 6 is a side cross-sectional view through the electromechanical lock of Figure 5; FIG. 7 is a plan view of the electromechanical lock of Figure 5;

FIG. 8 is a schematic side view of a slide element of the electromechanical lock of Figure 5 illustrating the various forces exerted thereon; FIG. 9 is a partial side view of the lock mechanism of the electromechanical lock of Figure 5 as it appears when no additional tension is applied to the cable; FIGS. 10A and 10B are views similar to Figure 9 showing two stages of operation of the lock mechanism when the cable is pulled while the electromechanical lock is deactivated; FIG. 11 is a view similar to Figure 9 showing the effect of applying tension to the cable while the electromechanical lock is activated; and FIG. 12 shows a typical configuration for installation of the electromechanical lock of Figure 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is an electromechanical lock for a cable release mechanism, and a corresponding method of implementing such a lock.

The principles and operation of an electromechanical lock according to the present invention may be better understood with reference to the drawings and the accompanying description.

Before referring to the drawings directly, it will be helpful to point out that the features of the present invention may be subdivided into two groups. A first group of features, described with reference to Figures 1-4, relates to the

use of sensor actuation to overcome problems of power drain in the prior art hood lock structures. A particular problem encountered in implementing the sensor actuation is the speed of response of the locking mechanism. This problem is addressed by a second group of features, described with reference to Figures 5-12.

Referring now to the drawings, Figure 1 illustrates schematically the various components of a sensor actuated electromechanical lock, constructed and operative according to the teachings of the present invention. Generally speaking, the electromechanical lock features an electrically actuated lock mechanism, represented here by an electromagnetic actuator 10, which, when actuated, prevents operation of a cable release mechanism, represented here by cable 12. Electrically associated with electromagnetic actuator 10 is a sensor 14. Sensor 14 is configured to selectively enable supply of power, such as from a vehicle battery 16, to the lock mechanism when tension is applied to the cable.

When the electromechanical lock is activated by closing a primary activation switch 18, no current flows so long as no tension is applied to cable 12. When cable 12 is pulled, the initial application of tension triggers sensor 14 which in turn locks lock mechanism 10, thereby preventing operation of the cable release mechanism.

It will be readily apparent that the electromechanical lock described solves the aforementioned problems of power drainage. Since significant

current is only supplied to the lock mechanism while tension is applied to cable 12, the overall period of operation of the electromechanical lock is essentially unlimited. As a result, primary activation switch 18 may advantageously be associated with a primary anti-theft system so as to be activated whenever the primary system is activated.

It should be appreciated that the present invention is applicable to a wide range of mechanisms in which a cable, wire or rod is used to activate or release a remote mechanism. Similarly, the mechanism may appear in a wide range of applications including, but not limited to, vehicular applications. For convenience, all such mechanisms for all such applications will be referred to generically herein in the description and claims as"cable release mechanisms".

Turning now to the features of the electromechanical lock in more detail, the lock mechanism is preferably designed to lock only while power is supplied to electromagnetic actuator 10. This property is represented here schematically by a return spring 20. This ensures that the electromechanical lock returns to its unlocked state in the event of an electrical fault.

Sensor 14 is described as being actuated by"application of tension"to cable 12. Clearly, the cable has a certain inherent tension in its rest state. The "applied tension"to which the sensor is designed to respond corresponds to a certain level of tension in excess of the normal resting tension which indicates a possible attempt to operate the cable release. This function can be achieved either by a sensor structure which responds directly to a certain level of tension

in cable 12 or by a structure which responds to movement corresponding to such a level of tension.

An example of the former type of sensor is shown in Figure 2. In this case, sensor 14 features three posts between which passes cable 12. Since a slight bend is introduced to cable 12, increased tension in the cable causes outward force on the middle post, operating a microswitch.

An example of the latter type is shown in Figure 3. Here, a microswitch is directly linked to cable 12 such that a small axial movement of the cable operates the switch.

A preferred implementation of sensor 14 is illustrated in Figure 4.

Similar to the structure of Figure 3, this structure senses movement of the cable.

However, the positive displacement switch movement of the previous implementation is here replaced by a contact-breaking sensor, thereby ensuring that the sensor is triggered by even the smallest initial movement.

More specifically, Figure 4 shows a sensor 14 in which a small conductive cylinder 22 connected to cable 12 is biased by a spring 24 against a contact 26 which is mounted on an insulating block 28. Tension applied to cable 12 pulls cylinder 22 against spring 24, thereby breaking contact between cylinder 22 and contact 26. An electronic circuit (not shown) senses the breaking of the contact and responds by actuating the power supply to the lock mechanism.

It will be apparent that this sensor structure is advantageous since it inherently responds to even the smallest initial movement, thus ensuring that the lock mechanism is activated as early as possible during the attempted opening movement. The remaining features of this sensor configuration shown will be described in more detail below with reference to Figure 6.

In the examples of Figures 2 and 3, the connection of sensor 14 within the electrical circuit is most conveniently achieved by simple serial connection.

However, in the preferred implementation of Figure 4, a separate power supply circuit is actuated electronically by breaking of the sensor circuit.

As mentioned earlier, a particular problem in effective implementation of a sensor-actuated electromechanical lock is that the lock mechanism must respond sufficiently quickly to prevent operation of the cable release by even a rapid movement. A mechanism believed to be particularly advantageous in this respect will be described below with reference to Figures 5-12.

Turning now to Figures 5-12, a preferred implementation of an electromechanical lock, generally designated 30, constructed and operative according to the teachings of the present invention, will be described.

Figures 5-7 show the structure of electromechanical lock 30 which is connected to a cable 12.

Generally speaking, electromechanical lock 30 includes a fixed stop 32 and a moving element, referred to here as"slide"34, linked to cable 12. Slide 34 is pivotable between a closed orientation (Figure 9) in which a part of slide

34 is aligned to engage stop 32 to obstruct axial movement of the slide, and an open orientation (Figure 10A) in which axial movement of slide 34 is not obstructed by stop 32. The attachment of cable 12 to slide 34 is made at a connection 36 configured such that tension applied to cable 12 tends to induce pivoting of slide 34 from the closed orientation (Figure 9) to the open orientation (Figure 10A), also referred to as"unlocking"of the slide, followed by axial movement of the slide (Figure 10B). An electromagnetic actuator 38 is associated with slide 34 such that, when electromagnetic actuator 38 is activated, slide 34 is additionally biased to remain in the closed position such that tension applied to cable 12 brings slide 34 into engagement with stop 32 (Figure 11). In this state, substantial movement of cable 12 is prevented.

In this context, it should be noted that the term"axial"is used herein to refer to a direction parallel to the portion of cable 12 entering electromechanical lock 30. Similarly, the term"transverse"is used to refer to a direction perpendicular to this portion of the cable.

It should also be noted that the locked state of the electromechanical lock is described as preventing"substantial movement"of the release cable.

Some small movement of the release cable may result even in the locked state.

However, the magnitude of the movement is limited to the free play between the components as assembled and is significantly less than the length of movement required to operate the cable release.

Turning now to the features of electromechanical lock 30 in more detail, electromagnetic actuator 38 is here implemented as a simple electromagnet.

Alternative implementations may use other types of electromagnetic actuator including, but not limited to, a solenoid and various types of motor. It should be noted that the term"actuator"is used here in the sense that the electromagnetic actuator effects the change from the unlocked state to the locked state.

However, as will be clear from the described structure and functionality, the actuator does not need to generate any locking motion.

Slide 34 preferably has an elongated armature 40, the distal portion of which is formed with transverse projections 42. Projections 42 are configured to catch on the side walls which form stop 32 when slide 34 is in its closed orientation as described. In a preferred implementation, electromagnet 38 is positioned to attract the distal portion of elongated armature 40, thereby maximizing the turning moment exerted by the electromagnet. A spring 44 urges slide 34 axially against the direction in which cable 12 is drawn.

Figure 8 depicts the various forces acting upon slide 34. T represents the tension exerted by cable 12, S is the force exerted by spring 44, and M is the attractive force exerted by electromagnet 38. It should be noted that the evenly spread force of spring 44 is equivalent to a localized force S along the center line of the spring. If the connection 36 of cable 12 to slide 34 lies above the line of action of force S, application of force T in the absence of magnetic attraction M exerts a turning moment on the slide, thereby rotating slide 34 from its

closed resting orientation of Figure 9 to its open orientation of Figure 10A. In this position, further rotation of slide 34 is prevented by armature 40 hitting the inner surface of a housing 46 (see Figure 6). Further tension applied to cable 12 then results in linear displacement of the slide to a position as shown in Figure lOB.

When, on the other hand, electromagnet 38 is actuated to attract armature 40 with force M, the turning moment is canceled. It is important to appreciate that the canceling of the turning moment is independent of the magnitude of force T applied. To illustrate this point, consider the moments exerted around connection 36. Since force T acts through the connection, it exerts no moment thereabout. Thus, so long as the moment exerted by the electromagnet exceeds that exerted by the spring, no rotation of slide 34 will occur. As a result, a given magnitude of magnetic field and corresponding force M is sufficient to maintain the locked state independent of the magnitude of force T. Furthermore, the length of armature 40 over which force M acts is typically chosen to be at least about five times, and preferably at least about ten times, longer than the distance between the lines of action of forces S and T. As a result, a low power electromagnet will suffice to provide complete locking of the electromechanical lock.

As mentioned above, the structure of electromechanical lock 30 is particularly suited to use with the sensor activation described above. Since the locked state of the lock mechanism is mechanically identical to the normal

resting state of the mechanism,"locking"of the lock mechanism involves prevention of an unlocking motion rather than an active locking motion. All that is required to activate the lock from its resting state to its locked state is the supply of current to electromagnet 38 and the resulting magnetic field. As a result, the response time of the structure is extremely fast.

With particular reference to Figure 6, it should be noted that the sensor structure illustrated in Figure 4 has been incorporated to particular advantage.

By including the sensor within connection 36 and ensuring that spring 24 is weaker than spring 44, the structure dictates that the spring 24 must be compressed and the sensor circuit broken before additional tension in cable 12 is transmitted to slide 34. In addition, the circuit-breaking structure of the sensor ensures that the power supply to electromagnet 38 is already activated with the first infinitesimal movement of the cable. Only after cylinder 22 has moved sufficient distance to come into direct contact with slide 34 does the subsequent movement of the cable begin to exert a significant force T directly on the slide. By this time, however, the magnetic attraction M is already effective to prevent operation of the cable release.

Turning now to Figure 12, this shows the preferred configuration for attachment of electromechanical lock 30 to an existing cable release mechanism. In order to facilitate retro-fitting, cable 12 is preferably fixed by use of a connector 50 as a slightly angled branch from the primary release cable 52. The angle of the branching is chosen to be small so that cable 12 travels

approximately the same length of travel as cable 52. The position of electromechanical lock 30 is fixed against movement in the direction of cable 12 through a rigid sleeve 54 through which cable 12 passes. The use of sleeve 54 allows a non-linear path of cable 12 so that electromechanical lock 30 can be conveniently positioned.

It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the spirit and the scope of the present invention.