GB2282636A - Magnetically operated latch - Google Patents

Abstract

A locking or security device comprises a casing having a recess for accommodating a first magnet (3) and a slot in which a lever (5) is pivotally mounted. The lever has a second magnet (4) at one end which can be received in the recess accommodating the first magnet (3) and a hook-like projection or catch (6) at its other end which projects from the casing. The magnets (3 and 4) normally attract one another whereby the lever is caused to pivot to move the catch into engagement with co-operating means and thus to serve as a lock. The catch can be disengaged to release the lock by moving a third magnet (9) fig 4 (not shown) adjacent to the first magnet (3) which causes the first and second magnets (3 and 4) to repel one another which is effective to cause the lever (5) to pivot and thereby move the catch (6) out of engagement. <IMAGE>

Description

Title: IMPROVEMENTS IN SECURITY DEVICES This invention relates to security devices and is particularly concerned with lockable seals.

One application to which the present invention has utility is in the field of c.-rgo containers. When a cargo container is to be transported from one country to another, it is usual to apply a locking device to the container in order to prevent unauthorised access to the container and thereby pilfering of the cargo. The locking device also serves to indicate to customs officials that the appropriate duty has been paid.

A major problem with existing locking devices is that they can be broken into and it is not immediately apparent that they have been tampered with. This results not only in loss of cargo from the containers but. if the lock is replaced after the cargo has been removed, it is some time before the theft of the cargo is discovered thereby making detection of the crime and recovery of the stolen cargo well nigh impossible.

The present invention aims to provide a locking device which is virtually tamper proof but which, if it is tampered with or broken into, will give an immediate indication that the device is no longer secure.

According to the invention, there is provided a locking device which comprises a casing, magnetic means at least partially movably mounted in the casing, catch means arranged to be actuated by said magnetic means and a further magnet designed to co-operate with said magnetic means to cause the latter to move the catch means from an engaging position to a dis-engaging position.

Preferably, the magnetic means comprise a first magnet which is fixedly mounted in the casing and a second magnet which is movably mounted in the casing and to which the catch means are operatively attached.

The catch means desirably takes the form of a lever which is secured at one end to the second magnet and of which its other end projects from a wall of the casing.

The casing is desirably made in two portions, secured together, after assembly of the magnets and catch means, for example by welding, such as ultrasonic welding. According to one embodiment, the first magnet is fixedly mounted in a first portion and the second magnet and catch means is located in a slot in the second portion of the casing.

In another embodiment, one of the portions of the casing is provided with a recess and a slot, the first magnet being secured in the recess and a slot, the first magnet being secured in the recess and the catch means being located in the slot.

The said further magnet is desirably mounted in a further casing which is adapted to fit at least partially over the first-mentioned casing. With this arrangement, correct alignment of the magnets in order to release the catch means is assured.

The invention will now be further described, by way of example, with reference to the drawings, in which: Fig. 1 is a perspective view of a first portion of a casing of one embodiment of a locking or security device according to the invention; Fig. 2 is a perspective view of a second portion of a casing which is intended to co-operate with the first portion of the casing shown in Fig. 1; Fig. 3 is a perspective view of a catch means and second magnet which are adapted to be fitted in the casing portion shown in Fig. 2; Fig. 4 is a perspective view of a further casing which is adapted to fit over one end of the casing formed by the casing portions shown in Figs. 1 and 2; Fig. 5 is a diagram explaining the operation of the magnetic means in one example of a device according to the invention.

Fig. 6 is a perspective view of the underneath of a first portion of a casing of a second embodiment of a locking or security device according to the invention; Fig. 7 is a perspective view of a second portion of a casing which is intended to co-operate with the first portion of the casing shown in Fig. 6; Fig. 8 is a perspective view of a catch means and second magnet which are adapted to be fitted in the casing portion shown in Fig. 7; Fig. 9 is a perspective view of a further casing which is adapted to fit over one end of the casing formed by the casing portions shown in Figs. 6 and 7; and Fig. 10 is a diagram explaining the operation of the magnetic means of the embodiment shown in Figs. 6 to 9.

In the drawings, like parts are denoted by like reference numerals.

Reference will first be made to Figs. 1 to 4 of the drawings in which the locking or security device according to the invention comprises a first casing portion 1 which consists of a substantially planar rectangular body provided with a circular closed bore 12 in one face 11. A first magnet 3 is located in this bore and is preferably secured therein, for example, by means of a suitable adhesive. A second casing portion 2 also consists of a substantially rectangular body but in this case one face 21 is provided with an elongate slot 23 which extends from a circular closed hore 22.The bores 12 and 22 are so located in the respective faces 11 and 21 of the casing portions 1 and 2 that they are located opposite one another when the casing portions are brought together with the faces 11 and 21 in contact with each other and the side walls of the casing portions substantially co-terminous with each other.

The end of the casing portion 2 remote from the bore 22 is of reduced height to form a shoulder 24 from which two projections 25 extend. The slot 23 extends into the reduced height region of the casing portion 2.

A second magnet 4 is mounted on one end of a pawl or lever 5 the other end of which carries a hook-like projection 6. The lever 5 is further provided, intermediate its ends, with a pivot pin 7 which extends through the lever. As indicated by the arrow leading from Fig. 3 to Fig. 2, the lever 5 is receivable in the slot 23 and the magnet 4 is receivable in the bore 22. The pivot pin 7 is located in lateral extensions 27 of the slot 23. NVhen the lever 5 is located in the slot 23, the hook-like projection 6 projects from the surface of the casing portion 2 which is opposite to and remote from the surface 21.

Once the magnets 3 and 4 and the lever 5 have been assembled in their respective casing portions 1 and 2, the two casing portions are joined together by their faces 11 and 21 by a suitable adhesive or by ultrasonic welding. The locking or security device is then ready for use. The magnets 3 and 4 are so arranged that they act to attract each other so that the hook-like projection 6 is urged in a direction away from the surface opposite to the surface 21 of the casing portion 2. The device can therefore be fitted over suitable co- operating means on a cargo container for example so that the projection 6 will engage in a suitable co-operating slot and the device will be firmly secured.Since no key is provided, the device cannot be removed by unauthorised personnel without smashing the device which will thus give an immediate indication that the device is no longer secure and that the cargo of the container may have been pilfered or tampered with.

It is, however, necessary for authorised personnel to be able to remove the security device and for this purpose a third magnet 9 is provided which is mounted in a second casing 8. The second casing 8 is adapted to fit over the end of the casing assembled from the casing portions 1 and 2 at which the magnets 3 and 4 are located and the location of the magnet 9 and its magnetic signature is such that the magnet 9 is effective to cause the lever 5 to move to disengage the hook-like projection 6 so that the device can be removed from the container or other object.

The embodiment shown in Figs. 6 to 9 of the drawings differs from the previously described embodiment in that the first casing portion 31 consists of a substantially rectangular body provided with a pair of slots 32 in one face 33. A second casing portion 34 is similar to the casing portion 2 of the previous embodiment but in this case the first magnet 3 is located at the base of the circular closed bore 22. The projections 25 are replaced by projections 35 which project above the face 21 of the casing portion 34. The projections 35 are shaped to co-operate with and to engage in the slots 32 in the casing portion 31 when the two portions of the casing are fitted together.

A pawl or lever 36 is similar to the pawl or lever 5 with a magnet 4 at one end but in this case a hook-like projection 37 projects from the opposite side of the pawl or lever 36 as compared to the projection 6 on the pawl or lever 5. The pawl or lever 36 is receivable in the slot 23 in the casing portion 34 with the magnet 4 being receivable in the bore 22.

As with the previously-described embodiment, once the magnets 3 and 4 and the lever 36 have been assembled in the respective casing portions 31 and 34, the two casing portions are joined together by their faces 33 and 21 by a suitable adhesive or by ultrasonic welding. As before, the locking or security device is then ready for use. The magnets are so arranged that they act to attract each other so that the hook-like projection 37 is urged in a direction away from and projects from the outer surface of the casing portion 31 so that it can engage in a suitable cooperating slot to secure the device as with the previously-described embodiment.

In the case of this embodiment, a second casing 38 provided with a third magnet 9 is adapted to fit over the end of the casing assembled from the casing portions 31 and 34 to cause the magnets 3 and 4 to move the lever 36 to disengage the hook-like projection 37 in a similar manner to that previously described.

To assist in understanding the magnetic principles of the devices according to the invention, reference will now be made to Figs. 5 and 10 of the drawings. In the absence of the magnet 9, the magnets 3 and 4 act to attract each other. Since the magnet 3 is fixed, the magnet 4 is therefore attracted towards the magnet 3, the lever 5 or 36 pivots and the projection 6 or 37 is urged to move in the direction of the arrows respectively shown in Figs. 5 and 10. This represents the normal engaged or latched condition of the devices.

The magnets 3 and 4 preferably take the form of discs each having a diameter of 9mm and a thickness of 3mm. If the magnet 3 is represented by "B" and the magnet 4 is represented by "A", the force between the magnets "A" and "B" can be calculated as follows: Force = Bg2 x A/2,ao where po = 4ir x 10 A = CSA If the third magnet 9 is now introduced in repulsion to magnet 3, the flux density of magnet 3 will be reduced from +ve to slightly -ve thus changing the polarity of magnet 3. The magnet 3 is then in repulsion with the magnet 4 and therefore repels magnet 4 which has the effect of increasing the distance between the magnets. The lever 5 is therefore caused to move the projection 6 out of the latching or engaging position.The security device can therefore now be released by removing the casing from the means co-operating with the projection 6 or 37.

On removal of the magnet 9, the magnet 3 returns to its original polarity and value of flux density owing to its intrinsic coercive force. The magnets 3 and 4 now again attract each other so that the security device can again be latched.

According to a preferred embodiment of the invention, each of the magnets 3 and 4 consists of the following: Size:- 9.00mm O x 3.00 (A) Axially Magnetised.

Material:- Neodymium, Iron, Boron. (NdFeB) Material Grade:- N-30H.

Residual Induction:- Br 1120 - 1200 mTesla 11.2 - 12.0 KGauss.

Coercive Force:- BHc 667 - 876 KA/m 8.5- 11 KOe.

Intrinsic Coercive Force:- Ilic 1353 - 1592 KA/m 17.0 - 20.0 KOe.

Maximum Energy Product:- BH(max) 223 - 255 KJ/m3 28 - 32 MGOe.

Average Temperature Coefficient:- % I "C -12.

Maximum Operating Temperature:- 120 C.

The magnet 9 desirably consists of the following: Size:- 22. lmm O x 10.00 (A) Axially Magnetised.

Material:- Neodymium, Iron, Boron (NdFeB).

Material Grade:- Crumax. 355.

Residual Induction:- BR 1230 mTesla 12.3 KGauss Coercive Force:- BHc 890 KA/m.

11.3 KOe.

Intrinsic Coercive Force:- IHc > 1100 KA/m.

14.0 KOe.

Maximum Energy Products:- BH(max) 278 KJ/m3 35 MGOe.

Average Temperature Coefficient:- % / "C -0.1.

Maximum Operating Temperature:- 1500C.

The casing portions 1 and 2 or 21 and 34 as well as the casings 8 or 38 may be made of any suitable non-magnetic material although a plastics material is preferred. Alternatively the casing portions may be made of die-cast aluminium or an alloy thereof. In the case of being made of a plastics material, the two casing portions are desirably joined together by ultrasonic welding. Preferably, the casing has the dimensions 120mm long x 65mm wide x 25 to 30mm thick but the invention is not restricted to these dimensions.

Although intended for use as a seal or lock on cargo containers, the security device according to the invention is not restricted to this use. The device is substantially silent in operation and intrinsically safe and can be used for example in situations where there is a potential fire hazard such as oil rigs for example.

The casing may be given any desired colour during manufacture.

By utilising magnetic force, it is not necessary to have conventional keys since the magnets can be given a unique signature so that the magnet 4 in each casing can only be repelled by the magnet 3 if the correct magnet 9 is applied. The device according to the invention also dispenses with the need for springs for operating the catch or projection 6 or 37 and is thus maintenance free.

The invention is not restricted to the above-described embodiments but variations and modifications may be made without departing from the scope of the invention.

For example, by suitable reconfiguration of the lever 5 and catch 6 or lever 36 and cattn 37, the magnets 3 and 4 may be arranged to attract each other in the normal engaged position of the catch and to repel each other in the presence of the magnet 9 in order to release the catch. Further, the device according to the invention is not restricted to use with cargo containers but is capable of many other applications and uses requiring the use of a security device.

Claims (15)

1. A locking device which comprises a casing, magnetic means at least partially movably mounted in the casing, catch means arranged to be actuated by said magnetic means and a further magnet designed to co-operate with said magnetic means to cause the latter to move the catch means from an engaging position to a dis-engaging position.

2. A locking device according to claim 1, wherein the magnetic means comprise a first magnet which is fixedly mounted in the casing and a second magnet which is movably mounted in the casing and to which the catch means are operatively attached.

3. A locking device according to claim 2, wherein the catch takes the form of a lever which is pivotally mounted in the casing.

4. A locking device according to claim 3, wherein one end of the lever is secured to the second magnet and wherein the other end of the lever projects from a wall of the casing.

5. A locking device according to any one of claims 2 to 4, wherein the casing is made in two portions, said portions being secured together after assembly of the magnets and catch means.

6. A locking device according to claim 5, wherein the casing portions are secured together by welding.

7. A locking device according to claim 6, wherein the welding is ultrasonic welding.

8. A locking device according to any one of claims 5 to 7, wherein the first magnet is fixedly mounted in a first portion of the casing and the catch means is located in a slot in the second portion.

9. A locking device according to any one of claims 5 to 7, wherein one of the portions of the casing is provided with a recess and a slot, the first magnet being secured in the recess and the catch means being located in the slot.

10. A locking device according to any one of claims 2 to 9, wherein the magnets take the form of discs.

11. A locking device according to any preceding claim, wherein the said further magnet is mounted in a further casing which is adapted to fit at least partially over the first-mentioned casing.

12. A locking device according to any preceding claim, wherein the or each casing is made of a non-magnetic material.

13. A locking device according to claim 12, wherein the or each casing is made of a plastics material.

14. A locking device substantially as described herein with reference to Figs.

1-5 of the drawings.

15. A locking device substantially as described herein with reference to Figs.

6-10 of the drawings.