WO2001014178A1

WO2001014178A1 - An automatic gear locking device

Info

Publication number: WO2001014178A1
Application number: PCT/IB1999/001474
Authority: WO
Inventors: Manuel Da Costa Reis; Ettienne Cox
Original assignee: Manuel Da Costa Reis; Ettienne Cox
Priority date: 1999-08-25
Filing date: 1999-08-25
Publication date: 2001-03-01
Also published as: AU5297899A

Abstract

A security apparatus (90) is provided for selectively locking and unlocking a gear linkage via a locking shaft (37A). The unit includes a tamper-proof housing (92, 94, 96) through which the locking shaft (37A) slidably extends. The locking shaft is formed with a series of teeth (62A) which engage with a complemental series of teeth (64A) formed on a solenoid-operated latch (66A) located within the housing. Control circuitry (84) is also contained within the tamper-proof housing, and includes decoding circuitry for decoding incoming encoded signals from a remote transmitter, and an enabling circuit responsive to the decoded signals for energising the solenoid (100) to release the toothed latch (66A) from the toothed locking arm (37A). The latch is sprung biased into the locked position, and the solenoid is arranged to default to this position. The apparatus forms part of a gear locking device for automatically locking in any position the transmission train of a vehicle when it is left unattended.

Description

AN AUTOMATIC GEAR LOCKING DEVICE

BACKGROUND TO THE INVENTION

THIS invention relates to a security apparatus, and in particular, to an automatic gear locking device incorporating the security apparatus.

Most electro-mechanical access control and security devices which are operable via a coded signal are vulnerable, in that the signal path of the actuating signal for enabling the mechanical components is not always secure, and can normally be successfully interfered with or bypassed by skilled thieves.

Furthermore, numerous different types of gear locking devices exist for immobilising the gear lever or the gear lever linkage of a vehicle or a piece of machinery. Generally, these devices need to be manually activated by the driver or operator of the vehicle or machinery. Whilst relatively effective when they are locked, they are prone to human forgetfulness and laziness, which means that they are more often than not left in an unlocked position. SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a security apparatus for locking and unlocking a multi-positional mechanism, the apparatus comprising an actuating unit having a tamper-proof housing, a movable element arranged to be linked to the multi-positional mechanism, first mounting means for movably mounting the movable element relative to the tamper-proof housing, an electro-mechanical actuator located within the housing for locking and unlocking the movable element, and control circuitry located within the housing for controlling the operation of the electro-mechanical actuator, the control circuitry including decoding means for decoding incoming encoded signals, and the electro-mechanical actuator being responsive to decoded signals from the decoding means for unlocking the movable element and enabling the mechanism.

In a preferred form of the invention, the security apparatus includes tracking means for allowing the actuating unit and the movable element to track the movement of the multi-positional mechanism during operation thereof when in the unlocked position and to lock the mechanism via the movable element in at least one of the multiple positions of the mechanism when in the locked position.

Preferably, the tracking means comprises the first mounting means, and second mounting means for mounting the actuating unit pivotably or universally to a fixture, whereby the movable element has sufficient freedom of movement to track the movement of the multi-positional mechanism when in the unlocked condition.

Advantageously, the first mounting means comprises an aperture extending through the housing within which the movable element is slidably mountable, the movable element comprising a locking arm terminating in a connection for joining the locking arm to the mechanism.

Preferably, the locking arm includes a plurality of engaging formations along its length, and the electromechanical actuator includes a latch formed with at least one complemental engaging formation, first biasing means for biasing the engaging and complemental engaging formations into engagement with one another, and a solenoid assembly for disengaging the formations on being energised.

Conveniently, the solenoid assembly includes a plunger, and the latch is arranged to move in a transverse direction relative to the plunger, the latch being indirectly operable by the plunger via a rocker arm, and including antijamming means for preventing the engaging and complemental engaging formations from jamming in the engaged or locked position.

Typically, the plunger acts on the rocker arm via second biasing means, the second biasing means being arranged to override the first biasing means on disengagement of the engaging and complemental engaging formations so as to constitute the anti-jamming means.

Preferably, the plunger acts on the rocker arm via second biasing means, the second biasing means being arranged to override the first biasing means on disengagement of the engaging and complemental engaging formations so as to constitute the anti-jamming means, the locking arm being arranged to lock the gear change mechanism in any position.

The electro -mechanical actuator may be arranged to default to a locked position when unpowered.

Conveniently, the locking arm is arranged to be locked by the electromechanical actuator in response to the machinery or vehicle associated with the mechanical linkage being turned off for a predetermined time period.

In a preferred form of the invention, the solenoid assembly includes a single coil arranged to operate over a start cycle followed by a hold cycle, the control circuitry including a feedback voltage sensor arranged to maintain the coil voltage above a predetermined threshold during the hold cycle which is lower than the coil voltage during the start cycle.

Typically, the decoding means comprises a decoding sub-circuit including memory means for storing master and slave key codes, control software for controlling the memory means, decoder software for decoding the incoming encoded signals, and validation software for validating the enabling means on the basis of inputs from the decoder and control software.

Advantageously, the control circuitry comprises an enabling sub-circuit including control software responsive to the decoding means, and at least one external input for timing the period for which an off condition has existed, the control software being arranged to control the operation of switching means for operating the electromechanical actuator.

The invention extends to a security apparatus comprising a remote encoding transmitter including entry means for entering control signals, encoding means for encoding the control signals, and transmission means for transmitting the encoded control signals, and a receiver for receiving the encoded signals, for transmission on to the decoding means of the control circuitry.

Preferably, the remote encoding transmitter includes timing means for entering enabling control signals at predetermined or random intervals for receipt by the decoding means via the encoding means, the transmission means and the receiver, whereby the actuating unit is arranged to selectively disable or arm the device on non-receipt of an enabling control signal after a predetermined interval.

The invention extends to an automatic gear locking device for locking and unlocking a gear change mechanism, the device comprising an actuating unit having a tamper-proof housing, a movable element arranged to be linked to the gear change mechanism, first mounting means for movably mounting the movable element relative to the tamper-proof housing, an electro-mechanical actuator located within the housing for locking and unlocking the movable element, control circuitry located within the housing for controlling the operation of the electro-mechanical actuator, and tracking means for allowing the actuating unit and the movable element to track the movement of the mechanism during operation thereof when in the unlocked position and to lock the mechanism via the movable element in at least one of the multiple positions of the gear change mechanism when in the locked position.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a highly schematic block diagram of a security apparatus of the invention;

Figure 2 shows a flowchart diagram indicating one way in which a decoder forming part of the security apparatus is programmed;

Figure 3 shows a flowchart diagram of the normal operation of the decoder after programming has taken place;

Figure 4 shows a highly schematic view of a first embodiment of the security apparatus of the invention fitted to a vehicle;

Figure 5 shows a partly cut-away pictorial view of a first embodiment of an actuating unit of the invention;

Figure 6 shows an exploded pictorial view of the actuating unit of Figure

Figure 7 shows a partly cut away pictorial view of a second embodiment of an actuating unit of the invention;

Figure 8A shows a detailed cut-away view of the actuating unit of Figure 7;

Figure 8B shows a detailed cut-away view of the actuating unit of Figure 7 in an unlocked position;

Figure 9 shows a gear locking apparatus of the invention fitted so as to directly lock a gear box; Figure 10 shows the gear locking apparatus of the invention fitted so as to lock a gear lever;

Figure 11 shows a schematic perspective view of a gear locking apparatus of the invention fitted so as to lock a pair of gear linkages;

Figure 12 shows a functional block diagram of decoding and coil control circuitry forming part of the actuating unit;

Figure 13 shows a more detailed circuit diagram of the circuitry of Figure

12;

Figure 14 shows a flowchart diagram indicating the manner in which the actuating coil is controlled; and

Figure 15 shows a flowchart diagram indicating another way in which a decoder forming part of the security apparatus is programmed.

DESCRIPTION OF EMBODIMENTS

Referring first to Figure 1, a security apparatus 10 of the invention has as its three main components a remote encoding transmitter 12, a receiving unit 14 and an actuating unit 16. The encoding transmitter 12 is provided with first entry means in the form of a keypad or a series of buttons or switches 18 for sending control signals to activate an encoder 20. The output of the encoder is connected to a transmitter 22, or alternatively via protection circuitry 24 and a plurality of plug-in connectors 26 for connection with a corresponding plug-in socket 28 in the receiving unit 14. In the case of a wireless connection, the transmitter 22 communicates with a corresponding receiver 28A.

The receiving unit 14 is in turn hard-wired to the actuating unit 16 via protection circuitry 30 which leads to decoding and control circuitry 32 for decoding the encrypted or encoded signals. The decoding and control circuitry 32 controls the operation of one or more electrical switches 34, which in turn drive a solenoid- operated latch or other actuator 35 which is in turn linked to a gear box linkage element 36 via a locking shaft 37. The entire actuating unit is supported on a mounting bracket 38 via a swivel mounting which allows the unit to rotate in any required direction except along the axis of movement of the locking shaft.

In a preferred "master/slave" version of the invention, the inputs of the encoder are automatically activated by a means of second entry means in the form of one or more pre-set timers 39 so as to transmit encoded signals on a regular basis, as is shown at 39 A. This serves to inform the relevant decoder 32 of the encoder's presence and maintains primary control over the decoder. Additional encoded signals may be transmitted manually via the keypad 18 for controlling the actuating unit 16. The encoder is preferably programmed to transmit a different baud rates so as to further increase security. The receiving unit 14 includes protective circuitry for remote and local inputs 38 and 40 respectively, together with a status indicator in the form of a status LED 42.

In a particular embodiment, the encoder 20 and decoder 32 are implemented making use of the HCS200 Keelog® code-hopping encoder/decoder. The Keelog® encoders are programmed with a secret manufacturer's code and a unique serial number during the manufacturing process. These codes are used in an encryption algorithm to create a unique encryption key, which is also stored during the manufacturing process and cannot be interrogated by any practical means. The required codes are transmitted as an encrypted 66 bit code with 7 3x10 combinations, thereby defeating any code grabbing attempts by commercial scanners.

In the actuating unit 16, the decoder circuit 32 is based on a programmable micro-controller with firmware to decode the received signals and to control the required actuators 36 via the electrical switches 34. In the particular version, the Keelog® code-hopping software is used to decrypt the encrypted codes. All code-related programming, including the secret manufacturer's code and encryption algorithm, is entered and burnt in during the manufacturing process, and cannot be externally deciphered or accessed. The relevant decoder is programmed to receive memorised signals from one or more encoders 20 at regular intervals determined by the timer 39. In the absence of such signals, the decoder is programmed to control the actuator in a predetermined manner, such as by triggering an alarm or emergency procedure in the event of it losing contact with the encoder.

Referring now to Figure 2, it is first necessary to teach the decoder which codes are valid and to memorise a pre-set number of codes that are transmitted by valid encoders. The number of codes that can be memorised is limited according to the particular application so as to preserve system inaccessibility. If a master or slave code has not previously been entered, the decoder may also be preprogrammed to accept a special test encoder code that is only used for factory testing. This test code is not recognised as a master or slave code and is not stored as a valid code. During power up after installation, the decoder is programmed to accept the first encoder code as a master key that cannot be deleted or tampered with in any way. The key code is then used to programme the other encoder codes into the decoder.

By entering the master key and immediately retracting it, the decoder is set to "learn" mode. If the erasure of certain previous slave keys is required, the master key is left in the receiver for at least eight seconds. This process has been added so as to remove codes belonging to lost or stolen keys. The remaining slave keys can then be re-learned by the decoder, together with new keys.

Once the decoder has entered "learn" mode, the slave key is then entered and the serial number portion of the received code is checked with that in memory so as to ensure that the slave key has not been learned since the last erase operation. If this has not incurred, the encryption algorithm is used to combine the serial number of the particular slave key with the manufacturer's code stored in the decoder. The resulted encryption key is validated, and if acceptable, the decoder will wait for the next received code. At this stage the status LED will remain on.

The same slave key must then be re-entered so that synchronisation values can be checked and stored in memory. Once validated, the encryption code of the slave key, the serial number and the synchronisation value are all stored in memory, which is confirmed by flashing the status LED 42 for a few seconds. Once a preset number of keys have been entered, the decoder will not recognise more keys. Tf the same slave key is used in the memorising procedure, the LED will flash fast immediately to signal that this is the case.

Referring now to the flowchart of Figure 3, normal operation of the security apparatus is illustrated. The LED will flash slowly and wait for a valid code. Once the valid code has been received, the decoder will compare the key's serial number with those in memory. If the code is that of a master key, the decoder will enter the "learn" mode and operate in the manner previously described. If the key is a normal slave key, then the validation process of the type described above and illustrated in more detail in the flowchart of Figure 2 is carried out. At least one randomly generated bit in the transmitted code is arranged to set an internal flag which determines the baud rate. Only the particular decoder has then "learnt" and knows what baud rate to expect, as a result of which both the encrypted code and its baud rate need to be correct for a valid signal to exist. Once validation has occurred, the solenoid latch 35 is enabled or actuated via the electrical switches 34.

In Figure 4, the security device 10 is shown fitted to a vehicle. An ignition switch 50 and other optional switches such as a door switch 52 are hard wired to the actuating unit 16. The actuating unit 16 includes the locking shaft 37 which is connected directly to a gear actuating member 54 extending into a gearbox 56. The gear actuating member 54 is also acted on by a gear lever 58 via a gear linkage arm 59. The status of the ignition and door inputs is continuously monitored, and under normal operation, the status LED 42 will flash continuously, indicating that the system is armed.

Referring now to Figures 5 and 6, an actuating unit 16.3 of the type used to immobilise the gears or a gear train of a vehicle comprises a tubular hardened steel casing 44 and end plugs 46 and 48. The link 37 passes through an aperture 60 extending diametrically through the housing. The link 37 is provided with a series of teeth 62 which engage with a complemental array of teeth 64 carried on a latch 66. The latch 66 is contained within a latch housing 68. A compression spring 70 acts between an annular divider 72 and an overhanging surface 74 defining the rearmost portion of the head of the latch 66 so as to spring bias the teeth 64 of the latch into complemental engagement with the teeth 62 of the link 37. A round cylindrical tail portion 76 of the latch forms a solenoid assembly 78 in conjunction with a solenoid coil 80 which is wound onto a bobbin 82.

The decoder and control circuitry 84 is potted and is held in position by means of the top plug 48, with a central aperture 86 in the top plug providing access for non-secure wiring carrying encrypted codes from a receiver. The electrical switches and actuating wiring are located towards the innermost end of the potted circuitry 84, and wiring leads from the circuitry 84 via a wiring channel 88 formed in the latch housing 68 to the solenoid coil 80. It can clearly be seen how the wiring for energising the solenoid is inaccessible and secure within the housing 44.

Referring now to Figure 7, in which components similar to those described above are numbered with the same reference numerals postscripted by an "A", a preferred embodiment of the actuating unit 90 comprises a rectangular tubular case hardened steel housing 92 having steel end plates 94 and 96 blocking off opposite end openings in the housing 92. The locking shaft 37A passes through a passage 60A extending through the housing 92 and end plates 94 and 96. The locking shaft 37A is provided with a series of teeth 62A that engage with a complemental array of teeth 64A carried on a latch 66A. A spring 98 at the base of the latch 66 A serves to spring bias the teeth 64 A of the latch into engagement with the teeth 62 A of the locking shaft. A solenoid assembly 100 includes a bobbin 102 onto which start and hold coils 104 and 106 are wound. A solenoid plunger 108 extends through the centre of the bobbin, and is movable between an extended position indicated in Figure 8A and a retracted position indicated in Figure 8B. A rocker arm 110 is arranged to pivot about point 112, and includes a front pair of fingers, one of which is shown at 114, which engage a pair of recesses 116 formed in opposite faces of the latch. A rear pair of fingers 118 extend around a waisted portion 120 of the plunger, and abut against a shoulder 122 thereof. A coil spring 124 acts between a front disc-shaped portion 126 of the plunger and the rear fingers 118 of the rocker arm 110 so as to bias the fingers 1 18 against the shoulder 122. The rocker spring 124 is pre-compressed to exert a force slightly greater than that exerted by the latch spring 98 when the latch is in the retracted Figure 8B position.

Under normal operation, the solenoid is energised to retract the plunger from the Figure 8A position to the Figure 8B position. The greater compressive force of the spring 124 results in the rocker arm 110 pivoting about binge point 112, thereby retracting the latch 66A and disengaging the teeth 62A and 64A as the fingers or lugs 1 14 press downwards on the rear walls of the recess 116 against the weaker force of the latch spring 98.

In the event of a force being applied to the locking shaft 37A after the gear linkages have been locked by the actuator in the Figure 8A position, for example by forcible manipulation of the gear linkages, the teeth 62A of the locking shaft will be frictionally jammed against the teeth 64A of the latch, preventing the latch from retracting and the rocker arm 110 from rotating into the Figure 8B position. Under this jammed condition, the operation of the plunger 108 will now compress the hinge spring 124 which then will supply the required rotational force to the rocker arm 110 and apply the required retraction force to the latch 66A. Very slight manipulation of the gear linkages will then cause the latch to retract against the latch spring 98 due to the greater compressive force of the rocker spring 124.

In the case of a dual-stage solenoid, the start cycle energises the high power solenoid coil 104 to retract the spring-loaded latch 66A. The start cycle is relatively short in duration (typically one second), thereby preventing heat buildup in the start coil. During the subsequent hold cycle, the lower power solenoid coil 106 is energised, with the hold coil being activated at the same time as the start coil so as to hold the latch 66A retracted during normal operation. The start signal is arranged to feed power to both the start and hold coils in parallel, thereby ensuring a relatively strong start signal. For the hold signal, the start circuit is turned off and power is fed to both the start and hold coils in series, the power ensuring that the hold coil consumes relatively little power.

In an alternative embodiment, a single start and hold solenoid coil 104 is used which is controlled by means of a high frequency switching circuit. The start signal is a short duration full voltage signal (typically one second) which is powerful enough to energise the coil 104 and retract the plunger 108 even when the rocker arm 110 and latch 66A are jammed in the locked position, owing to the compressive assistance provided by the spring 124. The hold signal voltage is effectively created by switching the supply voltage to the coil 104 on and off at a high frequency (typically 1-lOOkHz) in order to reduce its average voltage to a pre-determined value of around 3 V. The coil voltage is effectively smoothed due to its own inductance and a parallel- connected capacitor.

The locking shafts 37 and 37A are long enough to allow freedom of movement in all the necessary directions corresponding to movement of the gear lever into any gear position, including neutral. In one embodiment of the invention, locking of the gearbox in a particular gear, such as reverse or park, may be achieved by only having teeth over a short section of the locking shaft 37A. The gear locking apparatus is then mounted in such a way that the teeth 62A of the locking shaft only engage the teeth 64A of the latch when the gear linkages are in the required gear. The entire actuating unit 90 is pivotably mounted to a part 126 of the chassis of a vehicle via a round cylindrical shaft 127 capped by a mushroom head fitting 128 which holds the unit in position.

The incoming wires to the decoding circuitry carry encrypted signals which cannot be intercepted or simulated, together with powering signals which, if removed, will result in the gear locking device defaulting to a locked position. The decoder incorporates a number of anti-tamper systems, including a sleep mode arranged to operate for a pre-set period of, say, 30 seconds, when the unit is initially switched on. The protection circuitry also includes full short and open circuit protection, together with high voltage protection on all wiring up to 80V DC or AC in a 12V DC installation.

In Figure 9, the actuating unit 16 is shown mounted to a vehicle chassis 130 on an L-shaped mounting arm 132 via a mounting bracket 134. Both the long and short legs of the L-shaped mounting arm 132 are round cylindrical, with the short leg being able to rotate and being held captive within the bracket 134 via an end leg and the long leg extending diametrically through the housing 44. Optionally, the arm may be T-shaped, with the arms of the T extending through a pair of mounting brackets for holding the arm captive. The housing 44 is rotatably mounted to the long leg of the mounting arm, and is held captive by means of a snap-off lock nut 136. An aperture 138 defined at the end of the locking arm accommodates the gear actuating member 54 together with the gear linkage arm 59, which is screwed in position by means of a snap-off lock nut 140. The mounting assembly allows the gear lever to be located in any gear prior to being automatically locked.

Referring now to Figure 10, the actuating unit 16 is shown mounted to the vehicle chassis using the same arrangement as that illustrated in Figure 9, save that the apertured end 142 of the locking arm extends around a lower portion of the gear lever 58 so as to lock the gear lever directly.

In Figure 1 1 , an alternative embodiment of a mounting arrangement is shown in which the actuating unit 90 is mounted to a pair of gear linkage arms 59A and 59B via mounting sleeves 144A and 144B. The mounting sleeve 144B is carried swivably on the square housing 92 of the gear locking device, and in the unlocked position, the locking shaft 37A is able to move freely, thereby allowing the gear linkages 59A and 59B to move relative to one another. When in the locked position, relative movement of the gear linkages 59A and 59B is prevented, thereby effectively disabling the entire gear train.

In all of the embodiments illustrated in Figures 4 to 11, the actuating unit is mounted in such a way that, when in the unlocked position, it allows the gear stick to operate the gearbox freely via the gear linkage to change gears. The actuating unit then operates automatically to lock the gear linkage in any position on the vehicle being left unattended. This avoids the need manually to fit a gearlock each time the vehicle is left, as well as the need manually to unlock the gearlock on re-entering the vehicle.

Referring now to Figures 12 and 13, a detailed circuit diagram of the decoding and coil controlled circuitry is shown. The coil control circuitry comprises a control TC 150 incorporating control software 152, a pulse width modulator 154, an ignition off timer 156 leading from ignition input signal protection circuitry 158 and control status outputs 160 leading to LED and other output driver circuitry 162. Key code decoder and validation circuitry is embodied in the aforementioned Keelog® IC 164, and includes decoder software 168 for receiving encoded signals from key code input protection circuitry 170 and a signal inverter 172. The key code signal is protected by the diode and resistor bridge constituting the input protection circuitry 170, and, by being inverted and regenerated through a transistor foπning part of the signal inverter circuitry 172, the decoding circuit input receives the key code in the correct form. The decoder software 168 communicates in turn with the validation software 174, which communicates with learn, erase and control software 176 linked to a "master and slave" key code memory module 178. A voltage supervisor circuit 179 supervises the input voltage level to the IC 164.

The key code signal is decoded according to the algorithm represented in flowchart form in Figure 15. If the signal is a valid key code type, the software checks if the learn mode was set by a master key. If so, then the new code is stored as a valid slave key unless previously entered and learn mode is reset. If no learn mode was previously set, then the software checks if a master key has been learned or stored. If so, then a check is run to see if this is the master code. The controller then sets the learn mode or erases all slave key memories in the event of the master code signal being maintained for a predetermined period of more than, say, 8 seconds. If the master code has not been stored, then the controller checks if the key is a valid slave key as stored in memory, and a valid key code signal is sent to the coil controller. This is the normal operating route when the automatic gear lock is disarmed.

If no master code has previously been stored, then a check is run to see if the code is a test key code. The test key code is different from the master and slave keys so that it can only be used for circuit testing during assembly. If so, then a valid slave key signal is sent to the coil controller to allow circuit testing. The test key code will be ignored in the event of a master key code having been saved.

Referring back to Figures 12 to 14, the coil controller IC 150 feeds a transistor- based FET driver circuit 180 for driving an FET switch 182 which in turn controls the operation of the solenoid coil 184. The FET power switch 182 supplies input power to the actuator coil via input power protection circuitry 186 and a voltage regulator 188. The coil voltage is smoothed using an RC smoothing circuit 190, and the smoothed signal is fed to a zener- and transistor- based voltage sensing circuit 192, which in turn provides feedback signals to the pulse width modulator 154 within the coil controller IC 150.

Referring now to Figure 14, in the event of a valid slave key code signal being received, the coil controller IC 150 immediately turns on the FET power switch 182 via the FET driver 180, thereby energising the solenoid coil 184 at full power for a relatively short duration of 0.5 to 1 second. This represents the start signal. In addition, the ignition off timer 156 is enabled, and the status outputs 160 are set to the disarmed condition, in which the LED and other output drivers are turned off. The hold signal is then generated by the pulse width modulator 154 where the on/off ratio can be adjusted. After completion of the start signal, and providing that the ignition is not timed out, the pulse width modulator 154 takes over control of the FET driver 180, with the on time being increased in the event of the voltage sensor signal from the voltage sensor 192 indicating that the coil voltage is below the reference voltage of 3 volts. In the event of the coil voltage being above 3 volts, the "on" time is correspondingly decreased. If the ignition is not switched on within a pre-set time of, say. 30 seconds after a valid key code signal has been received, or if the ignition is switched off at the same period of time, the controller 150 will disable the pulse width modulator 154 and switch off the FET driver circuit 180. Simultaneously, it will set the controller status outputs 160 to the armed condition.

The major advantage of the automatic gear locking device of the invention is that it is mounted between the vehicle and the gear linkage in such a way that it tracks the movement of the gear linkage and is able automatically to lock the gear lever in any desired position to prevent the vehicle from being driven. Additional security is provided by the combination of the tamper indicating housing and the encryption of the signal travelling into the housing via the wiring, with the decryption circuitry being inaccessible within the housing.

Claims

1 A security apparatus for locking and unlocking a multi-positional mechanism, the apparatus comprising an actuating unit having a tamper- proof housing, a movable element arranged to be linked to the multi- positional mechanism, first mounting means for movably mounting the movable element relative to the tamper-proof housing, an electromechanical actuator located within the housing for locking and unlocking the movable element, and control circuitry located within the housing for controlling the operation of the electro-mechanical actuator, the control circuitry including decoding means for decoding incoming encoded signals, and the electro-mechanical actuator being responsive to decoded signals from the decoding means for unlocking the movable element and enabling the mechanism.

2. A security apparatus according to claim 1 which includes tracking means for allowing the actuating unit and the movable element to track the movement of the multi-positional mechanism during operation thereof when in the unlocked position and to lock the mechanism via the movable element in at least one of the multiple positions of the mechanism when in the locked position.

3. A security apparatus according to claim 2 in which the tracking means comprises the first mounting means, and second mounting means for mounting the actuating unit pivotably or universally to a fixture, whereby the movable element has sufficient freedom of movement to track the movement of the multi-positional mechanism when in the unlocked condition.

4. A security apparatus according to any one of the preceding claims in which the first mounting means comprises an aperture extending through the housing within which the movable element is slidably mountable, the movable element comprising a locking arm terminating in a connection for joining the locking arm to the mechanism.

5. A security apparatus according to claim 4 in which the locking arm includes a plurality of engaging formations along its length, and the electromechanical actuator includes a latch formed with at least one complemental engaging formation, first biasing means for biasing the engaging and complemental engaging formations into engagement with one another, and a solenoid assembly for disengaging the formations on being energised.

6. A security apparatus according to claim 5 in which the solenoid assembly includes a plunger, and the latch is arranged to move in a transverse direction relative to the plunger, the latch being indirectly operable by the plunger via a rocker arm, and including anti-jamming means for preventing the engaging and complemental engaging formations from jamming in the engaged or locked position.

7. A security apparatus according to claim 6 in which the plunger acts on the rocker arm via second biasing means, the second biasing means being arranged to override the first biasing means on disengagement of the engaging and complemental engaging formations so as to constitute the anti-jamming means.

8. A security apparatus according to any one of the preceding claims in which the multi-positional mechanism is a gear change mechanism, and the movable element is mountable to a gear linkage extending from a gear change lever to a gearbox.

9. A security apparatus according to claim 8 in which the locking arm is arranged to lock the gear mechanism in any position.

10. A security apparatus according to any one of the preceding claims in which the electro-mechanical actuator is arranged to default to a locked position when unpowered.

1 1 . A security apparatus according to claim 10 in which the movable element is arranged to be locked by the electromechanical actuator in response to the machinery or vehicle associated with the multi- positional mechanism being turned off for a predetermined time period.

12. A security apparatus according to any one of claims 5 to 7 in which the solenoid assembly includes a single coil arranged to operate over a start cycle followed by a hold cycle, control circuitry including a feedback voltage sensor arranged to maintain the coil voltage above a predetermined threshold during the hold cycle which is lower than the coil voltage during the start cycle.

13. A security apparatus according to any one of the preceding claims in which the decoding means comprises a decoding sub-circuit including memory means for storing master and slave key codes, control software for controlling the memory means, decoder software for decoding the incoming encoded signals, and validation software for validating the enabling means on the basis of inputs from the decoder and control software.

14. A security apparatus according to any one of the preceding claims in which the control circuitry comprises an enabling sub-circuit including control software responsive to the decoding means, and at least one external input for timing the period for which an off condition has existed, the control software being arranged to control the operation of switching means for operating the electromechanical actuator.

15. A security apparatus according to any one of the preceding claims further comprising a remote encoding transmitter including entry means for entering control signals, encoding means for encoding the control signals, and transmission means for transmitting the encoded control signals, and a receiver for receiving the encoded signals, for transmission on to the decoding means of the control circuitry.

16. A security apparatus according to claim 15 in which the remote encoding transmitter includes timing means for entering enabling control signals at predetermined or random intervals for receipt by the decoding means via the encoding means, the transmission means and the receiver, whereby the actuating unit is arranged to selectively disable or arm the device on non-receipt of an enabling control signal after a predetermined interval. An automatic gear locking device for locking and unlocking a gear change mechanism, the device comprising an actuating unit having a tamper-proof housing, a movable element arranged to be linked to the gear change mechanism, first mounting means for movably mounting the movable element relative to the tamper-proof housing, an electro-mechanical actuator located within the housing for locking and unlocking the movable element, control circuitry located within the housing for controlling the operation of the electro-mechanical actuator, and tracking means for allowing the actuating unit and the movable element to track the movement of the mechanism during operation thereof when in the unlocked position and to lock the mechanism via the movable element in at least one of the multiple positions of the gear change mechanism when in the locked position.

An automatic gear locking device according to claim 17 in which the tracking means comprises the first mounting means, and second mounting means for mounting the actuating unit pivotably or universally to a fixture, whereby the movable element has sufficient freedom of movement to track the movement of the gear change mechanism when in the unlocked condition.

An automatic gear locking device according to either claim 17 or claim 18 in which the movable element is arranged to be locked by the electro-mechanical actuator in response to the machinery or vehicle associated with the gear change mechanism being turned off for a predetermined time period.