GB2429032A

GB2429032A - Electromagnetic lock actuator and mechanism

Info

Publication number: GB2429032A
Application number: GB0515932A
Authority: GB
Inventors: Anthony Brotherton Ratcliffe
Original assignee: Paxton Access Ltd
Current assignee: Paxton Access Ltd
Priority date: 2005-08-02
Filing date: 2005-08-02
Publication date: 2007-02-14
Anticipated expiration: 2025-08-02
Also published as: GB2429032B; GB0515932D0

Abstract

An electromagnetic lock actuator having stable locking and unlocking states is disclosed. The lock actuator comprises a moveable member moveable between a first position and a second position and an electromagnet adapted, when powered, to move the moveable member between the first and second positions, the direction of movement being dependent on the polarity of the electromagnet. A permanent magnet is adapted to retain the moveable member in its current one of the first and second positions when the electromagnet is unpowered. Lock mechanisms using the lock actuator are also described. Additionally, a lock having a proximity reader and user-operable activation means for controlling supply of power to the proximity reader is disclosed. Finally, a battery-powered electromagnetic lock having a proximity reader and a locking mechanism plus a device for determining the level of charge disclosed.

Description

Lock mechanism The present invention relates to an electromagnetic lock

actuator and to an electromagnetically activated lock using such an actuator.

Electromagnetically activated locks often require a constant supply of power to retain the lock in either or both of its locked and unlocked states.

Due to the high power consumption, locks of this kind are often unsuitable for battery operation and generally require connection to a mains power supply.

Where batteries are used to power such locks, battery life tends to be short, and batteries need be replaced frequently. The short battery life can also result in reduced reliability and security.

This problem is exacerbated where an electronic access system is used to control the lock, for example using a proximity reader in combination with RFID-based access cards. Proximity readers consume power when active, making their use in battery-powered locks difficult.

The present invention seeks to alleviate some of these problems.

Accordingly, in a first aspect of the invention, there is provided an electromagnetic lock actuator comprising: a moveable member moveable between a first position and a second position; an electromagnet adapted, when powered, to move the moveable member between the first and second positions, the direction of movement being dependent on the polarity of the electromagnet; and a permanent magnet adapted to retain the moveable member in its current one of the first and second positions when the electromagnet is unpowered.

No power is thus required to retain the lock actuator in either of its states (corresponding to locked and unlocked states of an associated lock mechanism). Furthermore, only a relatively short activation impulse is required to move the moveable member from the first to the second or from the second to the first position, thus switching the associated lock mechanism between locked and unlocked states. The resulting low power consumption can make the actuator more suitable for low-power locks (especially battery-powered locks). Because of the relatively small mechanical resistance involved in switching the mechanism between positions, a relatively weak activation current can be sufficient to operate the actuator, and mechanical wear can also be reduced, leading to improved reliability.

The moveable member may comprise the permanent magnet, and a fixed part may be provided which includes the electromagnet. Alternatively, the permanent magnet could be provided in a fixed part, and the moveable member may include the electromagnet.

Preferably, the electromagnet comprises: first and second outer portions spaced from each other and magnetisable to form part of a first pole of the electromagnet, and an inner portion between and spaced apart from the outer portions and magnetisable to form part of a second pole of the electromagnet; and the moveable member comprises the permanent magnet and has a magnetic north pole portion extending into the space between the inner portion and one of the outer portions of the electromagnet, and a magnetic south pole portion extending into the space between the inner portion and the other of the outer portions of the electromagnet; the moveable member being moveable in response to magnetisation of the electromagnet to an appropriate polarity between the first position, in which the north pole portion is adjacent one of the outer portions of the electromagnet and the south pole portion is adjacent the inner portion of the electromagnet, and the second position, in which the north pole portion is adjacent the inner portion of the electromagnet and the south pole portion is adjacent the other outer portion of the electromagnet.

In this way, a relatively compact actuator can be provided. The lock actuator preferably comprises a magnetisable core, the inner portion extending from one end of the core, and the outer portions being connected to the other end of the core by a magnetic conductor. For ease of manufacture and reduced cost, at least one, and preferably several or all, of the inner portion and outer portions may be integrally formed with the core.

The electromagnet typically comprises a coil, the moveable member preferably being moveable from the first to the second position or from the second to the first position depending on the direction of current flowing in the coil. In this way, locking and unlocking of a locking mechanism associated with the lock actuator can be achieved simply by way of an appropriately directed current pulse, simplifying control and operation of the actuator.

Preferably, the inner and outer portions are spaced from each other in a direction substantially perpendicular to the axis of the coil, and, correspondingly, the moveable member is preferably arranged to move along an axis substantially perpendicular to the axis of the coil. This provides for a more compact design of the actuator.

The lock actuator preferably comprises a single coil winding, the electromagnet including the coil winding, and preferably comprises a sing'e permanent magnet. This can make the actuator cheaper and easier to manufacture.

In a further aspect, the invention provides an electromagnetic lock mechanism comprising an electromagnetic lock actuator as described herein, the moveable member of the lock actuator serving to switch the lock mechanism between locked and unlocked states.

The electromagnetic lock mechanism may, for example, comprise a blade having an aperture through which a locking pin having a retaining formation can pass, the apertured blade being adapted to selectively engage and disengage from the retaining formation on the locking pin in response to movement of the moveable member. In this way, a simple lock mechanism having relatively few moving parts can be provided. The lock mechanism preferably comprises said locking pin.

Alternatively or in addition, the electromagnetic lock mechanism may comprise a pivotable locking arm pivotable in response to movement of the moveable member between a first position allowing free movement of a locking member and a second position where the locking arm obstructs movement of the locking member. The locking member preferably comprises a retaining formation, the pivotable locking arm being arranged to engage the retaining formation in the second position. The locking member may, for example, be a locking pin, or may be a shaft having a cam portion, in which case the pivotable locking arm is preferably adapted, in the second position, to engage a step in the cam portion to prevent rotation of the shaft. Preferably, the electromagnetic lock mechanism further comprises biasing means associated with the pivotable locking arm, the moveable member being arranged, in response to a locking impulse supplied to the lock actuator, to act on the biasing means so as to bias the pivotable locking arm to the second position in which it obstructs movement of the locking member. Thus, locking of the mechanism can be successful even if the locking impulse is supplied at a time where the mechanism is not in a lockable state (for example, because the locking member is not in a position where it can engage the pivotable locking arm).

The electromagnetic lock mechanism may be incorporated into a variety of different types of lock such as a cabinet lock or door lock. For example, the electromagnetic lock mechanism may comprise or be associated with a rotary handle (such as a door handle), and adapted, in a locked configuration, to inhibit rotation of the handle.

The invention also provides a bi-.stable electromagnetic lock mechanism comprising: an actuating member moveable between a locking position in which the lock mechanism is in a locked configuration and a non- locking position in which the lock mechanism is in an unlocked configuration; an electromagnet adapted, when powered, to move the actuating member between the locking and non-locking positions, the direction of movement being dependent on the polarity of the electromagnet; and a permanent magnet adapted to retain the actuating member in its current one of the locking and non-locking positions when the electromagnet is unpowered.

In a further aspect of the invention, there is provided a bi-stable electromagnetic lock actuator for an electromagnetic locking mechanism, adapted, in an unpowered state, to remain at separate times stably in a locked configuration and an unlocked configuration, the lock actuator comprising an electromagnet and being switchable between the locked and unlocked configurations by way of a current impulse supplied to the electromagnet having a duration of not more than 200ms, preferably not more than lOOms.

By requiring only a relatively short actuating pulse, power consumption can be reduced, and a more responsive locking mechanism can be provided.

In a further aspect of the invention, there is provided a bi-stable electromagnetic lock actuator for an electromagnetic locking mechanism, adapted, in an unpowered state, to remain at separate times stably in a locked configuration and an unlocked configuration, the lock actuator comprising an electromagnet and being switchable between the locked and unlocked configurations by way of a current impulse supplied to the electromagnet, the energy required to switch between the locked and unlocked configurations being no more than 2OmJ, and preferably not more than lOmJ.

In a further aspect of the invention, there is provided an electromagnetic lock actuator comprising an electromagnet having an actuating coil, and a moveable actuating member having a permanent magnet, the moveable actuating member being adapted to move in response to changes in the magnetic field generated by the electromagnet, the movement directions of the moveable actuating member being perpendicular to the axis of the actuating coil. In this way, a more compact actuator can be provided.

The invention further provides a lock comprising an electromagnetic lock actuator or an electromagnetic lock mechanism as described herein.

In a yet further aspect of the invention, there is provided a lock comprising: a proximity reader for detecting an access device; a locking mechanism switchable from a locked to an unlocked state when a valid access device is detected by the proximity reader; and user-operable activation means for controlling supply of power to the proximity reader.

By providing user-operable activation means for controlling supply of power to the proximity reader, the proximity reader can be powered only when actually needed (typically when an access card is being presented), which can significantly reduce the lock's power consumption.

The term proximity reader' preferably encompasses any device for detecting access devices held by users for the purpose of identification and authentication. Typically (but not exclusively), communication between the proximity reader and the access devices is contactless. The proximity reader may, for example, be an RFID reader, and the access devices may be cards incorporating RFID tags (such cards often resemble credit cards in shape and size and may carry identifying information such as a photograph or name).

The activation means preferably comprises a mechanical switch, but may alternatively or additionally comprise non-mechanical activation means such as an energising circuit. Preferably, the activation means comprises a push button adapted to enable power supply to the proximity reader when depressed. The push button is preferably further adapted to return to a raised position in which power supply to the proximity reader is interrupted when released. In this way, power is supplied to the proximity reader for a limited time. For convenience, the user may, for example, operate the push button using the access device itself. At least part of the proximity reader may be integrated into the push button, preferably an antenna part. In this way, the lock can be more reliable and easier to use.

The power is preferably supplied to the proximity reader by one or more batteries. By providing a battery-operated lock, installation is not dependent on a mains power supply, which can reduce the cost of installation and allow the lock to be used where no mains power supply is available.

In a further aspect of the invention, there is provided a battery-powered electromagnetic lock comprising: a proximity reader for detecting an access device; a locking mechanism adapted to switch from a locked to an unlocked state when a valid access device is detected by the proximity reader; and means for determining the level of charge remaining in a battery or batteries powering the lock and delaying the switching of the locking mechanism to the unlocked state by a delay period if the measured charge level is below a threshold level.

In this way, users can be effectively warned when batteries are nearing depletion. Due to the delay before unlocking, the lock becomes less responsive, which can be an intuitive way of signalling that the batteries need to be replaced. To further enhance this effect, the lock may be adapted to increase the delay period as the charge level approaches zero.

In a further aspect, the invention provides a battery-powered electromagnetic lock comprising: a proximity reader for detecting an access device; a locking mechanism adapted to switch from a locked to an unlocked state when a valid access device is detected by the proximity reader; and means for determining the level of charge remaining in a battery or batteries powering the lock and, if the measured charge level is below a threshold level, switching the locking mechanism to a predetermined one of the locked and unlocked states and deactivating the lock so as to remain in that state until the battery or batteries are replaced or recharged.

In this way, it can be ensured that the lock fails in a safe state when the batteries become depleted. Whether the safe state is the locked or unlocked state will depend on the circumstances and in particular on the relative importance of security and accessibility or safety. For example, where accessibility is more important than security, the predetermined state may be the unlocked state. To ensure safe failure, the threshold level is preferably selected in accordance with the minimum charge level required for switching the locking mechanism to the predetermined state.

The lock preferably comprises a lock actuator or lock mechanism as described herein.

The invention extends to methods and/or apparatus substantially as herein described with reference to the accompanying drawings.

Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa.

Preferred features of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which:Figure IA is a perspective view of an electromagnetic lock actuator; Figure lB is a cross-sectional view of the lock actuator of Figure 1A; Figures 2A and 2B show a lock mechanism incorporating the lock actuator of Figure 1; Figures 3A and 3B show an alternative lock mechanism incorporating the lock actuator of Figure 1; Figures 4A and 4B show a door lock incorporating the lock actuator of Figure 1; and Figure 5 is a schematic diagram of a door lock using a manually activated proximity reader in combination with an RFID-based access card.

Embodiments of the present invention use a bi-stable electromagnetic lock actuator having two unpowered stable states corresponding to locked and unlocked states of the lock. The lock actuator comprises an actuating coil and a moveable actuating member including a permanent magnet. The moveable actuating member moves between two stable positions corresponding to the stable states. The moveable actuating member is held in either of its two positions by the permanent magnet, and is moved between those positions by a transient current in the coil. Movement of the actuating member is perpendicular to the axis of the coil. In this way, a compact lock actuator and lock mechanism can be provided. The moveable actuating member can be coupled, for example, to a latch or other locking means in a lock mechanism.

An electromagnetic lock actuator according to an embodiment of the invention is shown in Figures 1A and lB.

The lock actuator 10 comprises an electromagnet 12 and a slider 14 moveable in response to a magnetic field produced by the electromagnet.

The electromagnet comprises a coil 22 and a steel core 20 mounted between support plates 15. A portion of the core 20 extends through an aperture in the lower support plate 15 and forms a first pole 18 of the electromagnet. An outer steel conductor plate 24 is connected to the core 20 at the end opposite pole 18, extends parallel to the core and coil and ends in a U-shaped portion 16 having two arms extending from the conductor plate 24 to either side of pole 18. The arms of the U-shaped portion 16 form the second pole of the electromagnet and are spaced apart from the first pole 18.

The slider 14 comprises a permanent magnet 30 with two steel blades 32, 34 extending from respective poles into the spaces between the first pole 18 of the electromagnet 12 and respective arms of the U-shaped portion 16 forming the second pole of the electromagnet. Thus, in the example shown, blade 32 of slider 14 forms part of the north pole of the permanent magnet 30, and blade 34 forms part of its south pole.

The slider is moveable between a first position (Figure 1B), in which blade 32 (north pole) is in contact with one of the arms of U-shaped portion 16, and blade 34 (south pole) is in contact with pole 18, and a second position (Figure IA) in which the blade 32 (north pole) is in contact with pole 18, and blade 34 (south pole) is in contact with the other arm of the U- shaped portion 16.

While no current is flowing in coil 22, the slider 14 is held in either the first or second position by the permanent magnet 30. The slider can be moved between positions by passing a current through the coil. The direction of movement of the slider is determined by the direction of the current flow in the coil (which determines the polarity of the electromagnet).

In the example of Figure IB, the slider is in its first position. A short current pulse is supplied to the electromagnet, with the U-shaped portion 16 forming the north pole of the electromagnet, and portion 18 forming the south pole. These poles are in contact with corresponding poles of the permanent magnet, resulting in a repelling force which causes the slider to move to its second position. The duration of the impulse is selected to be sufficient to enable movement of the slider from one position to the other.

Thus, a relatively short current impulse (typically no more than a second and preferably no more than half a second) causes the slider to move between its stable first and second positions. In preferred embodiments, a pulse of not more than lOOms is required to move the slider, ensuring that a small amount of energy is required to effect the change of state, and making the lock actuator suitable for use in battery-powered locks. Embodiments may be provided which have even shorter actuation times, for example operating with pulse durations of no more than 5Oms or even 2Oms or less. The maximum energy required for a single actuation (i.e. a single movement of the slider) is preferably no more than 6OmJ, and more preferably no more than 4OmJ. In certain preferred embodiments the required activation energy is no more than 2OmJ.

A further advantage of the lock actuator is that it can be relatively cheap and easy to manufacture.

As mentioned above, the slider 14 is connected to a locking component, such as a latch, of the lock mechanism to effect locking and unlocking of the lock mechanism.

Figures 2A and 2B illustrate the use of the above-described electromagnetic lock actuator in a cabinet lock 100.

Here, the slider 14 of the lock actuator 10 moves an apertured blade 102 which engages a latch pin 104 passing through the aperture. In the locked position (Figure 2B), the blade captures the latch pin. Movement of the slider 14 and blade 102 releases the latch pin (Figure 2A).

Figures 3A and 3B illustrate an alternative cabinet lock incorporating the electromagnetic lock actuator.

In this example, cabinet lock 200 comprises a bolt 210 moveable between a retracted and an extended position (Figures 3A and 3B respectively). In the extended position the bolt can engage a corresponding lock part in, for example, a cabinet door. The bolt is moved by rotation of a shaft 204, operated, for example, by way of a rotary knob or handle (not shown). Shaft 204 comprises a cam portion 206 having a step 208.

Slider 14 of lock actuator 10 is connected to a pivoting locking arm 202.

Movement of the slider 14 pivots the arm between a first position allowing free movement of the shaft 204 and cam portion 206 (Figure 3A) and a second position in which the arm 202 can engage step 208 of cam portion 206 (Figure 3B). When engaged, rotation of the shaft and hence retraction of bolt 210 is prevented.

Figures 4A and 4B illustrate the use of the electromagnetic lock actuator in a door lock.

The door is operated by way of a handle (not shown) connected to a rotary portion 310. The rotary portion comprises an outer portion 308 having an aperture or recess 312 for receiving a locking pin 304. The locking pin may be biased downward by its own weight only or may additionally be spring- biased. The locking pin has a tapered tip to allow it to move freely up out of recess 312 when in an unlocked state, thus allowing free rotation of the rotary portion 310.

The slider 14 of lock actuator 10 is coupled to a pivoting locking arm 302. In the unlocked position (Figure 4A), the pivoting arm allows free movement of the locking pin 304. When the slider 14 is moved to pivot the locking arm 302 outwards, the arm engages a step in locking pin 304 to prevent upward movement of the locking pin and hence rotation of the rotary portion 310 (Figure 4B).

The locking mechanism described may not lock successfully if the locking impulse occurs at a time where the locking pin is in the raised position (shown in Figure 4A), thus preventing locking arm 302 from pivoting into the locking position. To prevent this, biasing means associated with the locking arm 302 may be provided, and the slider 14 may be adapted to act on the biasing means to bias the locking arm 302 to the locking position (for example by compression of a spring). As soon as the locking pin is lowered, the bias then causes the locking arm 302 to pivot into the locking position and engage the step in the locking pin. In this way, it can be ensured that a single locking impulse supplied to the electromagnetic lock actuator results in successful locking of the lock mechanism, even if the mechanism is not in a lockable state at the time of the impulse. A similar arrangement may be incorporated into the other lock mechanisms described above (for example, biasing means may be associated with locking arm 202 of Figure 3A).

Locks such as the door lock described above may be used in conjunction with suitable electronic access systems, for example using keypads, magnetic or swipe cards, contactless access cards or keys (e.g RFID or infrared) and the like. Multiple locks may also be remotely controlled by a central access control system.

An example of a door lock using an RFID-based access system will now be described with reference to Figure 5. The door lock may use an electromagnetic lock actuator and/or lock mechanism as described above or may use other actuating and locking mechanisms.

Typically, proximity readers continuously emit a signal so that transponders (such as RFID tags) incorporated into access cards are activated instantly on entering the vicinity of the reader. This leads to high power consumption. In the present example, therefore, mechanical activation means, for example in the form of a switch or push button, are provided on the housing of the lock to manually power the proximity reader. Thus, the proximity reader is activated only in response to a button or switch being pressed by the user seeking to unlock the door.

- 12 - Alternatively, some other activation means could be used instead of the mechanical activation means, and some other detection means may be used instead of the proximity reader. An important aspect of the described system is that detection means with relatively high power consumption is combined with activation means having relatively low (or no) power consumption for (temporarily) activating the detection means. In this way, the lock's battery life can be prolonged considerably (when compared to a system in which the detection means is permanently active). For example, the activation means may comprise a low-power energising circuit. A purely mechanical activation means such as a switch has the further advantage that no power at all is consumed during the inactive state.

In the specific example illustrated in Figure 5, a door lock 400 comprises a power supply in the form of a battery 402 connected to an access control device 410 via a user-operable switch 404, preferably in the form of a push button. The access control device 410 comprises a proximity reader 412 for detecting and reading information from an access card 420 incorporating an RFID tag 422. The proximity reader typically comprises an antenna 436 packaged with a transceiver 434 and decoder 432.

The door is initially in the locked state. A user seeking to unlock the door presses the button or switch 404 to activate the proximity reader 412, and then holds the access card 420 against or near the lock's proximity reader 412. The proximity reader 412 detects the RFID tag 422 in the access card 420 and obtains identification details from the RFID tag, which are transmitted to a controller 414 (for example, in the form of a microprocessor). The controller checks access privileges associated with the access card 420, and, if access is to be granted, controls a lock actuating mechanism 416 (such as an electromagnetic lock actuator as described above) to unlock the door.

Optionally, the controller could be configured to communicate with a remote access control system to check the identification details received from the RFID tag and to determine whether access is to be granted.

By using a switch or button to manually activate the proximity reader, power consumption can be reduced significantly since the proximity reader does not continuously emit a signal. The switch or button preferably controls power supply to both the proximity reader 412 and the controller 414. Where the lock uses an electromagnetic lock actuator as described above, the controller controls the flow and direction of current in the coil 22 of the electromagnet 12 to move the slider 14 as required to lock or unlock the door.

Preferably, for ease of operation, the button and proximity reader are arranged so that a user can unlock the door in a single action by using the access card itself to depress the button, which then powers the proximity reader and controller to detect the access card and unlock the door. The button and the access card (or other access device) are shaped so that this is an ergonomic action. The button is released by removing the access card, at which point power supply to the proximity reader and controller is interrupted.

Thus power is supplied to the proximity reader and controller for only as long as is necessary to unlock the door. The proximity reader is preferably located near or behind the button. Part or all of the proximity reader may also be incorporated into the button itself. For example, an antenna or magnetic coil of the proximity reader (e.g. the antenna 436) could be incorporated into the button.

The reduced power consumption provided by use of the bi-stable electromagnetic lock actuator and the manually activated proximity reader/ control circuit allows the lock to be battery-powered. Thus, the inconvenience and cost of connecting the door lock to a mains power supply can be avoided.

Preferred embodiments are able to achieve a battery life of around 200,000 operations using three AAA cells, corresponding to a battery life of approximately three to five years.

Battery operated access systems generally suffer from the disadvantage that replacement (or recharging) of batteries is often left too late batteries are often not changed until after the old ones have run out. In preferred embodiments, the controller 414 delays operation of the lock actuator as the battery nears depletion. To achieve this, the controller obtains a measurement of the remaining charge level of the battery or batteries, and compares this to a predetermined threshold. If the charge level falls below the threshold, then the controller waits for a predetermined time period after presentation of a valid access card before unlocking the lock. The controller - 14 - may also increase the delay period as the battery charge level approaches zero. The lock thus reacts more and more slowly to the presentation of an access card, and the delay provides an intuitive signal to the user that the batteries are nearing depletion.

Preferably, to provide a safe failure mode, when the controller detects that the battery charge level has fallen below a further threshold representing the minimum charge level required to successfully lock or unlock the door, the controller can set the lock position to open' before shutting down for the last time before battery replacement. Thus the lock can be reactivated simply by replacing the batteries without the need for complicated override procedures or damage to the lock. Alternatively, where security is of greater importance, the fail-safe mode may involve setting the lock to the locked' position before shutting down. The failsafe mode may be selectable.

With the use of low power radio networking technology, the system can is be further adapted to provide remote control and programming (typically of multiple locks) from a central control system as well as central data logging to provide audit trails of events, whilst still keeping power consumption relatively low.

Claims

I An electromagnetic lock actuator comprising: a moveable member moveable between a first position and a second position; an electromagnet adapted, when powered, to move the moveable member between the first and second positions, the direction of movement being dependent on the polarity of the electromagnet; and a permanent magnet adapted to retain the moveable member in its current one of the first and second positions when the electromagnet is unpowered.
2. A lock actuator according to Claim 1, wherein the moveable member includes the permanent magnet.
3. A lock actuator according to Claim 1 or 2, wherein the electromagnet comprises: first and second outer portions spaced from each other and magnetisable to form part of a first pole of the electromagnet, and an inner portion between and spaced apart from the outer portions and magnetisable to form part of a second pole of the electromagnet; and wherein the moveable member comprises the permanent magnet and has a magnetic north pole portion extending into the space between the inner portion and one of the outer portions of the electromagnet, and a magnetic south pole portion extending into the space between the inner portion and the other of the outer portions of the electromagnet; the moveable member being moveable in response to magnetisation of the electromagnet to an appropriate polarity between the first position, in which the north pole portion is adjacent one of the outer portions of the electromagnet and the south pole portion is adjacent the inner portion of the electromagnet, and the second position, in which the north pole portion is adjacent the inner portion of the electromagnet and the south pole portion is adjacent the other outer portion of the electromagnet.
4. A lock actuator according to Claim 3, comprising a magnetisable core, the inner portion extending from one end of the core, and the outer portions being connected to the other end of the core by a magnetic conductor.
5. A lock actuator according to Claim 4, wherein at least one of the inner portion and outer portions is integrally formed with the core.
6. A lock actuator according to Claim 4 or 5, wherein the inner and outer portions are formed integrally with the core.
7. A lock actuator according to any of the preceding claims, wherein the electromagnet comprises a coil, the moveable member being moveable from the first to the second position or from the second to the first position depending on the direction of current flowing in the coil.
8. A lock actuator according to Claim 7 when dependent on Claim 3, wherein the inner and outer portions are spaced from each other in a direction substantially perpendicular to the axis of the coil.
9. A lock actuator according to Claim 7 or 8, wherein the moveable member is arranged to move along an axis substantially perpendicular to the axis of the coil.
10. A lock actuator according to any of the preceding claims, comprising a single coil winding, the electromagnet comprising the coil winding.
11. A lock actuator according to any of the preceding claims, comprising a single permanent magnet. - 17-
12. An electromagnetic lock mechanism comprising an electromagnetic lock actuator as claimed in any preceding claim, the moveable member serving to switch the lock mechanism between locked and unlocked states.
13. An electromagnetic lock mechanism according to Claim 12, comprising a blade having an aperture through which a locking pin having a retaining formation can pass, the apertured blade being adapted to selectively engage and disengage from the retaining formation on the locking pin in response to movement of the moveable member.
14. An electromagnetic lock mechanism according to Claim 13, further comprising said locking pin.
15. An electromagnetic lock mechanism according to Claim 12, comprising a pivotable locking arm pivotable in response to movement of the moveable member between a first position allowing free movement of a locking member and a second position where the locking arm obstructs movement of the locking member.
16. An electromagnetic lock mechanism according to Claim 15, wherein the locking member comprises a retaining formation, the pivotable locking arm being arranged to engage the retaining formation in the second position.
17. An electromagnetic lock mechanism according to Claim 15 or 16, wherein the locking member is a locking pin.
18. An electromagnetic lock mechanism according to Claim 15 or 16, wherein the locking member is a shaft having a cam portion, the pivotable locking arm being adapted, in the second position, to engage a step in the cam portion to prevent rotation of the shaft.
19. An electromagnetic lock mechanism according to any of Claims to 18, further comprising biasing means associated with the pivotable locking arm, the moveable member being arranged, in response to a locking impulse supplied to the lock actuator, to act on the biasing means so as to bias the pivotable locking arm to the second position in which it obstructs movement of the locking member.
20. An electromagnetic lock mechanism according to any of claims 12 to 19, further comprising a rotary handle, and adapted, in a locked configuration, to inhibit rotation of the handle.
21. A bi-stable electromagnetic lock mechanism comprising: an actuating member moveable between a locking position in which the lock mechanism is in a locked configuration and a non-locking position in which the lock mechanism is in an unlocked configuration; an electromagnet adapted, when powered, to move the actuating member between the locking and non-locking positions, the direction of movement being dependent on the polarity of the electromagnet; and a permanent magnet adapted to retain the actuating member in its current one of the locking and non-locking positions when the electromagnet is unpowered.
22. A bi-stable electromagnetic lock actuator for an electromagnetic locking mechanism, adapted, in an unpowered state, to remain at separate times stably in a locked configuration and an unlocked configuration, the lock actuator comprising an electromagnet and being switchable between the locked and unlocked configurations by way of a current impulse supplied to the electromagnet having a duration of not more than lOOms.
23. An electromagnetic lock actuator comprising an electromagnet having an actuating coil, and a moveable actuating member having a permanent magnet, the moveable actuating member being adapted to move in response to changes in the magnetic field generated by the electromagnet, - 19 - the movement directions of the moveable actuating member being perpendicular to the axis of the actuating coil.
24. A lock comprising an electromagnetic lock actuator or an electromagnetic lock mechanism according to any preceding claim.
25. A lock comprising: a proximity reader for detecting an access device; a locking mechanism switchable from a locked to an unlocked state when a valid access device is detected by the proximity reader; and useroperable activation means for controlling supply of power to the proximity reader.
26. A lock according to Claim 25, wherein the activation means comprises a mechanical switch.
27. A lock according to Claim 25 or 26, wherein the activation means comprises a push button adapted to enable power supply to the proximity reader when depressed.
28. A lock according to Claim 27, wherein the push button is further adapted to return to a raised position in which power supply to the proximity reader is interrupted when released.
29. A lock according to Claim 27 or 28, wherein at least part of the proximity reader is integrated into the push button, preferably an antenna part.
30. A lock according to any of claims 25 to 29, wherein the power is supplied to the proximity reader by one or more batteries.
31. A battery-powered electromagnetic lock comprising: a proximity reader for detecting an access device; a locking mechanism adapted to switch from a locked to an unlocked state when a valid access device is detected by the proximity reader; and means for determining the level of charge remaining in a battery or batteries powering the lock and delaying the switching of the locking mechanism to the unlocked state by a delay period if the measured charge level is below a threshold level.
32. A battery-powered electromagnetic lock according to claim 31, adapted to increase the delay period as the charge level approaches zero.
33. A battery-powered electromagnetic lock comprising: a proximity reader for detecting an access device; a locking mechanism adapted to switch from a locked to an unlocked state when a valid access device is detected by the proximity reader; and means for determining the level of charge remaining in a battery or batteries powering the lock and, if the measured charge level is below a threshold level, switching the locking mechanism to a predetermined one of the locked and unlocked states and deactivating the lock so as to remain in that state until the battery or batteries are replaced or recharged.
34. A battery-powered electromagnetic lock according to Claim 33, wherein the threshold level is selected in accordance with the minimum charge level required for switching the locking mechanism to the predetermined state.
35. A battery-powered electromagnetic lock according to Claim 33 or 34, wherein the predetermined state is the unlocked state.
36. A lock according to any of claims 25 to 35, comprising a lock actuator according to any of Claims 1 to 11 22 and 23 or a lock mechanism according to any of Claims 12 to 21.
37. An electromagnetic lock actuator substantially as herein described with reference to and/or as illustrated in any of the accompanying drawings.
38. A lock substantially as described herein with reference to and/or as illustrated in any of the accompanying drawings.