WO1999027218A1

WO1999027218A1 - Sensor actuated hood lock and method for implementing such a lock

Info

Publication number: WO1999027218A1
Application number: PCT/IL1998/000554
Authority: WO
Inventors: Chaim Brody
Original assignee: Brody Engineering Ltd.
Priority date: 1997-11-25
Filing date: 1998-11-13
Publication date: 1999-06-03
Also published as: ZA9810572B; IL122301A0; AU1171899A

Abstract

An electromechanical lock (30) for preventing operation of a cable release mechanism (12) features a lock mechanism including an electromagnet (38). The lock mechanism is configured so as to prevent operation of the cable release when the electromagnet (38) is activated. The electromechanical lock (30) also includes a microswitch (14) mounted so as to be activated by application of tension to the operator cable (12). The microswitch (14) is electrically connected to the electromagnet (38) such that, when the operator cable (12) is free from excess tension, the microswitch (14) interrupts supply of power to the electromagnet (38) and, when tension is applied to the operator cable (12), the microswitch (14) connects the supply of power to the electromagnet (38) so as to prevent significant movement of the release cable (12). Preferably, the lock mechanism includes a selectively lockable slide (34) constructed so that pulling of the operator cable (12) causes sequentially unlocking of the slide (34) followed by an axial sliding motion of the slide (34). In this case, the electromagnet (38) is configured so that actuation of the electromagnet prevents unlocking of the slide (34).

Description

Sensor Actuated Hood Lock and Method for Implementing Such a Lock

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to vehicle security and, in particular, it

concerns a device with low power consumption for preventing unauthorized

access to a vehicle engine compartment.

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

l;

FIG. 4 is a schematic illustration of a third type of sensor responsive to

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 J:he 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 O 99/27218

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 10 A) 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

10B.

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.

Claims

WHAT IS CLAIMED IS:

1. 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, said lock mechanism being constructed such that,

when the cable is pulled, said stop and at least a part of said

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 said first

direction, said lock mechanism further including an

electromagnetic actuator configured so that, when said

electromagnetic actuator is activated, said relative motion of said

stop and said at least part of said moving element in said first

direction is prevented; and

(b) a sensor mounted so as to be activated by movement of the cable,

said sensor being electrically associated with said electromagnetic

actuator such that, when the cable is in its resting state, no power

is supplied to said electromagnetic actuator and, when the cable

begins to move, power is supplied to said electromagnetic

actuator so as to prevent unlocking of said lock mechanism.

2. The electromechanical lock of claim 1, wherein said stop is a

fixed stop, said lock mechanism being configured such that, when said

electromagnetic actuator is deactivated, pulling of the cable causes lateral

displacement of at least part of said moving element such that said moving

element bypasses said stop and, when said electromagnetic actuator is

activated, said lateral displacement is inhibited such that a part of said moving

element engages against part of said stop.

3. The electromechanical lock of claim 2, wherein said lateral

displacement of said at least part of said moving element corresponds to a

rotational movement of said moving element.

4. The electromechanical lock of claim 3, wherein said moving

element has an elongated armature, said electromagnetic actuator being

positioned to attract a distal portion of said elongated armature.

5. The electromechanical lock of claim 1, wherein said lock

mechanism is configured such that a given magnitude of force applied to said

moving element by said electromagnetic actuator is sufficient to prevent said

relative motion of said stop and said at least part of said moving element in said

first direction independent of a magnitude of force applied to the cable.

6. 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 said 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 said

motion to said 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 said lock

mechanism; and

(d) when movement of the cable is sensed, activating said lock

mechanism so as to prevent operation of the cable release

mechanism.

7. The method of claim 6, wherein said lock mechanism is

implemented such that a given magnitude of said magnetic field is sufficient to

prevent said motion to said unlocked state independent of a magnitude of force

applied to the cable.