GB1572092A - Lock for operation by magnetic key - Google Patents

Description

(54) LOCK FOR OPERATION BY MAGNETIC KEY (71) We, LOWE & FLETCHER LIMITED, a British Company of Fryers Road, Leamore, Walsall, West Midlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a lock of the kind suitable for operation by rotation of a key applied to the lock, there being assoc sated with the key a magnetic field.

According to the invention, there is provided a lock of the kind referred to which comprises first and second members mounted for relative movement along an axis of the lock, an elongated channel defined by the first and second members collectively and a magnetic element movable along the channel between a locking position in which it restrains relative axial movement of the first and second members and a releasing position in which limited relative axial movement of said members is permitted, the lock being adapted to receive a key whereby the magnetic element can be moved into its releasing position by magnetic interaction between said element and the key and the lock comprising a cam mechanism operable by rotation of the key to cause relative axial movement of the first and second members.

By a 'magnetic element' we mean an element which is subjected to a substantial force when placed in a magnetic field. The magnetic element may comprise a permanent magnet or be formed of a ferro-magnetic material which is not permanently magnetised.

Preferably, the first member is adapted to receive the key, is rotatable about the axis when the key is applied but is constrained by means other than the magnetic element against axial displacement and the second member is axially displaceable relative to the key receiving member by the cam mechanism when the key is applied to the key receiving member and is turned about the axis. With this arrangement, any axially directed force which may be applied by a user to the key receiving membr is not resisted by or transmitted to the second member by the magnetic elements and jamming of the magnetic elements by the application of such force can be avoided.

The invention will now be described by way of example with reference to the accompanying drawing wherein: Figure 1 shows a lock and a key for operation thereof, the lock being shown in longitudinal cross section and the key being present in a key-receiving member of the lock; Figure 2 shows a cross section on the line II-II of Figure 1, and Figure 3 shows a fragmentary cross section on the line III-III of Figure 1.

The lock shown in Figure 1 comprises a body 10 which, when the lock is in use, is normally disposed in a housing of a device to be controlled by the lock. From one end of the body, called herein the inner end, there projects a driving member 11 which, when the correct key 12 is applied to the lock, can be rotated about a longitudinal axis 13 of the lock to release or operate the associated device.

As shown in Figure 1, a driven member 14 of the device may be received on the driving member 11, keyed thereto and retained thereon by a circlip 15.

The associated device may be a bolt or latch for a door or drawer, in which case the driven member 14 may be in the form of a crank for moving the bolt or latch. Alternatively, the lock could be incorporated in a vehicle antitheft device, in which case the driven member 14 may be a cam arranged for moving a bolt of the device in a substantially known manner.

The driven member 11 is integral with or rigidly secured to a key-receiving member of the lock which is in the form of a barrel 16.

The barrel is rotatable about the axis 13 dur in operation of the lock and is constrained at al times against axial movement relative to the body 10. An outer end face of the barrel is presented towards and engageable with a radially projecting flange 17 on the body 10, which flange defines an opening 18 in the body for receiving the key 12. An axially inwardly facing shoulder on the barrel abuts a ring 19 which is in sliding contact with an annular closure member 20. The closure member is secured in the inner end of the body 10 by a screw thread and prevents axially inward movement of the ring 19. The ring is keyed to the barrel. It will be seen that the driving member 11 projects through the central opening of the closure member 20 and is freely rotatable therein.

Also disposed within the body 10, there is an obstructing member 21 for obstructing rotation of the barrel 16 when the proper key is absent therefrom. The obstructing member is in the form of a sleeve and, for convenience of manufacture and assembly, is formed in three parts 22, 23 and 24, each of which is a sleeve. The sleeve 22 forms the axially inner end of the obstructing member, the sleeve 24 forms the axially outer end of the obstructing member. The middle sleeve 23 has a smaller diameter portion which is received within a larger diameter portion of the sleeve 22 and a larger diameter portion within which a smaller diameter portion of the sleeve 24 is received. The barrel 16 is formed at one side with a longitudinally extending spline 25 which is received in aligned, axially extending grooves formed in the radially inwardly presented faces of the sleeves 22, 23 and 24.This spline therefore constrains the obstructing member to rotate with the barrel but permits axial movement of the obstructing member relative to the barrel.

From the axially outwardly presented face of the sleeve 24 there projects a cam formation 26. When the key is absent from the lock and the obstructing member is in the outer position shown in Figure 1, this cam formation is received in a corresponding recess 27 formed in a rearwardly presented internal face of the body 10. Whilst the cam formation is situated in this recess, rotation of the sleeve 24 and therefore of the other sleeves and of the barrel 16 is prevented. The obstructing member 21 is urged in the outward axial direction by a spring 28 so that the cam formation 26 remains in the recess 27 whenever the rotational position of the sleeve 24 is such that the formation 26 is in alignment with the recess 27.The shape of the cam formation 26 is such that it can be driven out of the recess 27 by rotation of the sleeve 24, provided that axial movement of the sleeve 24 relative to the body 10 and therefore relative to the barrel 16 is permitted.

In the absence of the proper key, each one of the sleeves 22, 23 and 24 is constrained against axial movement relative to the barrel 16 by respective magnetic locking elements 29, 30 and 31. Other parts of the lock are formed of non-magnetic materials. Accordingly, the elements 29, 30 and 31 can be controlled by a suitably magnetised key. When the proper key is inserted into a keyway of the barrel 16, the elements 29, 30 and 31 are moved into releasing positions such that the sleeves 22, 23 and 24 are freed for axial movement relative to the barrel.

In the radially outwardly presented face of the barrel 16, there are formed three circumferentially extending grooves 32, which are spaced apart along the axis 13. These grooves do not extend completely around the axis 13 but subtend an angle of approximately 300 thereat. Each of the grooves 32 lies radially inwardly of a corresponding one of the sleeves 22, 23 and 24. Each sleeve is formed in its radially inner face with an arcuate recess 33, the position of which along the axis 13 is the same as that of the corresponding groove 32 when the parts are in the position shown in Figures 1 and 2. The axial extent of each recess 33 is the same as that of each groove 32.

Each recess 33, together with a part of its corresponding groove 32, forms a channel in which a corresponding one of the locking elements 29, 30 and 32 is received. The locking elements are adapted to roll along their respective channels and are preferably in the form of cylindrical rollers. The axial extent of each locking element is only slightly less than that of the corresponding groove 32, so that the locking elements can move freely along their respective channels but are constrained against axial movement relative to the barrel 16.

The recess 33 of each of the sleeves 22, 23 and 24 is bounded at its axially outermost side by a wall 34 in which there is formed at least one notch 35. The notch is of sufficient size to accommodate that part of the transverse cross-section of the associated locking element which projects from the groove 32.

Accordingly, if each locking element is aligned axially with the notch 35 of its corresponding sleeve, the sleeve can move axially relative to the barrel in the inward direction so that the locking element enters the notch.

If one locking element is not completely aligned with its notch, axial movement of the associated sleeve and therefore of the obstructing member as a whole relative to the barrel is prevented.

The locking elements 29, 30 and 31 preferably present for engagement with abutment surfaces on the walls 34 of the associated sleeves 22,23 and 24 and for engagement with abutment surfaces on the walls of the grooves 32 flat end faces.

With this arrangement, even a small degree of overlap between the end face of the locking element and the wall of the associated sleeve will prevent axial movement of the obstructing member. Furthermore, the locking elements will not readily deform the associated sleeves even under high axial pressures.

When the key is absent from the lock, each of the locking elements 29, 30 and 31 will occupy a locking position which will normally be the lowest position that locking element can reach by movement along its channel. In its locking position, each locking element is engaged between a respective abutment surface of the barrel 16 and an abutment surface of an associated one of the sleeves 22, 23 and 24 in such a manner as to prevent axial movement of the sleeve from the position shown in Figure 1. When the key is withdrawn, the locking elements are moved to their locking positions by gravity.

The key 12 is adapted to so control the locking elements 29, 30 and 31 that, when the key is applied to the lock, each of these elements is moved from its locking position into and is held in its releasing position, in which the locking element is aligned with the corresponding notch 35. The key has three magnetised regions, each comprising a permanently magnetised element, 36,37 and 38 of approximately annular form. The magnetised elements (magnets) are carried on a stem 39 of the key which extends through the central openings. Each magnet has a pair of pole faces, these being presented in opposite directions along the key so that its unlike poles are spaced apart longitudinally of the key and of the axis 13.

Adjacent to each pole face there is a magnetic conductor 40, the conductors also being of approximately annular form and carried on the stem 39.

It is the respective forms of the conductors 40 which determines the positions to which the locking elements 29,30 and 31 are moved by the key. In the particular example illustrated in Figure 1, there is one conductor 40 for each pole face of each magnet and adjacent conductors associated with different magnets are spaced apart by shield elements 41. These shield elements have a low magnetic permeability and shield the conductors associated with one magnet from the field associated with an adjacent magnet.

When the key is fully inserted into the barrel 16, the two conductors 40 associated with the magnet 36 are substantially in alignment with oPposite end portions of the locking element 29. The conductors associated with the magnets 37 and 38 have a similar relationship to the locking elements 30 and 31 respectively.

The shape of the magnetic conductors 40 is such, relative to the paths along which the locking elements 29, 30 and 31 move between their locking and releasing positions that the distance between each locking element and the associated conductors varies as the locking element moves along its channel and is a minimum at the releasing position. In the particular example shown, each locking element is free to move along a path which forms an arc of a circle centered on the axis 13.

As viewed in a direction along the key, the conductors 40 have non-circular profiles as shown in Figure 2. Two diametrically opposite parts of the periphery of each conductor are situated further from the axis 13 than are all other parts of the periphery.

One or other of these diametrically opposite parts corresponds to the releasing position of the associated locking element. This enables the locking elements to be set in their releasing positions when the key is inserted into the barrel in either one of two alternative angular positions which differ by 180C about the axis 13.

The cross section of the stem 39 is noncircular and the central opening of each conductor 40 has a corresponding shape, so that the conductors cannot turn relative to the stem. For convenience of illustration, the particular example illustrated in the drawing is such that the locking elements 29,30 and 31 are in axial alignment with one another when in their releasing positions. Accordingly, all of the magnetic conductors 40 are identical.

Different samples of the lock would be produced with different releasing positions of the locking elements, the shape of the sleeves 22, 23 and 24 and of the conductors 40 being modified accordingly.

As shown in Figure 2, in the particular example illustrated in Figures 1, 2 and 3, the notch 35 of each of the sleeves 22, 23 and 24 is situated half way along the recess 33. In different samples of the lock, the notch may be situated away from the middle of the recess 33 so that locks having the recess 33 similarly positioned cannot be operated by the same key, the key being required to correspond to the positions of the notches 35. A number of locking elements greater than three may be provided in the lock, the number of sleeves in the obstructing member being increased accordingly.

If required, each of the sleeves 22, 23 and 24 may be formed with more than one notch 35. This would enable the lock to be operated by at least two different keys, , one of which could be a master key for operating a suite of locks.

To enable torque to be transmitted from the key 12 to the barrel 16, the key is provided with a pair of radial projections 42 which project from a part of the key lying between the stem 39 and a handle portion of the key (not shown). When the key is inserted into the lock, these projections pass through diametri cally opposite notches in the flange 17 and engage in recesses 44 in the barrel 16. These recesses are open at their axially outer ends, but are closed at their axially inner ends so that it is possible to apply an axially inwardly directed force to the barrel by means of the key.

When the key is inserted into the lock, each of the locking elements 29, 30 and 31 is moved to its releasing position. This frees the obstructing member 21 for axial movement relative to the barrel 16. The key can then be rotated to rotate the barrel and obstructing member about the axis 13. During an initial part of such rotation, the cam formation 26 drives the obstructing member 21 axially inwardly until the cam formation is com letely withdrawn from the recess 27.

Further rotation can then take place without any axial movement occurring. Until the key is returned to the initial position by reverse rotation, the key is retained in the lock as the projections 42 are situated axially inwardly of the flange 17 and would engage this flange if an attempt is made to withdraw the key.

If, whilst the key is absent from the lock, an attempt is made to turn the barrel 16 by means of some other instrument inserted into the lock, the application of torque to the barrel will, through the action of the cam formation 26, result in the application to the obstructing member 21 of an axially inwardly directed force. This will establish pressure contact between, on the one hand the locking elements 29, 30 and 31 and, on the other hand, the walls 34 of the corresponding sleeves 22, 23 and 24 and the barrel 16.

Such contact pressure will establish sufficient friction to prevent subsequent movement of the locking elements to their releasing positions until the application of torque to the barrel is discontinued.

When torque is applied to the barrel 16 by means other than the correct key, the locking elements 29, 30 and 31 are not required to withstand the entire force applied to the barrel. Friction between the cam projection 26 and the body 10 is such that, when axial movement of the obstructing member 21 is prevented, the major part of any torque applied to the barrel is resisted by co-operation between the cam projection and the body. The cam projection can be made sufficiently large to ensure that unauthorised rotation of the barrel 16 is prevented and the sleeve 24, including the cam projection, can be formed of a strong material, for example steel.

In the particular example of lock illustrated in the drawing, the locking elements 29, 30 and 31 are formed of a magnetic material but are not permanently magnetised. These elements are therefore urged to the positions along their respective paths of movement at which density of the magnetic flux established by the key is greatest, irrespective of the polarity of each magnetised region of the key. If required, each locking element could be permanently magnetised, in which case only a key having an appropriate polarity of each magnetised region would be capable of operating the lock. It is intended that the key should be assembled with the magnets 36, 37 and 38 in an unmagnetised condition and that the key should then be treated to permanently magnetise these magnets with the required polarities. The magnets 36, 37 and 38 may be formed of a sintered ferrite.The magnetic conductors 40 are formed of a magnetic steel, preferably one having high carbon content.

A plurality of different locks may be arranged so that they can be operated by a single key. Such key would have one or more magnetic conductors of such a form that there are a plurality of positions around the axis of the key and at the same distance from that axis at which the strength of the magnetic field is greater than at other positions. The locks would be arranged to provide different paths of movement for their locking elements, each path corresponding to a respective one of the maximum field strength positions of the key.

This specification is divided from that accompanying application No. 10416/76 (SerialNo. 1572091).

WHAT WE CLAIM IS: 1. A lock suitable for operation by rotation of a key applied to the lock, there being associated with the key a magnetic field, the lock comprising first and second members mounted for relative movement along an axis of the lock, an elongated channel defined by the first and second members collectively, and a magnetic element movable along the channel between a locking position in which it restrains relative axial movement of the first and second members and a releasing position in which limited relative axial movement of said members is permitted, the lock being adapted to receive a key whereby the magnetic element can be moved into its releasing position by magnetic interaction between said element and the key and the lock comprising a cam mechanism operable by rotation of the key to cause relative axial movement of the first and second members.

2. A lock according to claim 1 comprising a plurality of magnetic elements and wherein there are defined by the first and second members collectively a number of channels, each containing one of the magnetic elements, and the channels are spaced apart along the axis of the lock.

3. A lock according to claim 2 wherein the first member has, for each channel, a respective abutment surface which faces in a first direction along the axis and defines a first boundary of the channel, the second member has, for each channel, a respective abutment

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. cally opposite notches in the flange 17 and engage in recesses 44 in the barrel 16. These recesses are open at their axially outer ends, but are closed at their axially inner ends so that it is possible to apply an axially inwardly directed force to the barrel by means of the key. When the key is inserted into the lock, each of the locking elements 29, 30 and 31 is moved to its releasing position. This frees the obstructing member 21 for axial movement relative to the barrel 16. The key can then be rotated to rotate the barrel and obstructing member about the axis 13. During an initial part of such rotation, the cam formation 26 drives the obstructing member 21 axially inwardly until the cam formation is com letely withdrawn from the recess 27. Further rotation can then take place without any axial movement occurring. Until the key is returned to the initial position by reverse rotation, the key is retained in the lock as the projections 42 are situated axially inwardly of the flange 17 and would engage this flange if an attempt is made to withdraw the key. If, whilst the key is absent from the lock, an attempt is made to turn the barrel 16 by means of some other instrument inserted into the lock, the application of torque to the barrel will, through the action of the cam formation 26, result in the application to the obstructing member 21 of an axially inwardly directed force. This will establish pressure contact between, on the one hand the locking elements 29, 30 and 31 and, on the other hand, the walls 34 of the corresponding sleeves 22, 23 and 24 and the barrel 16. Such contact pressure will establish sufficient friction to prevent subsequent movement of the locking elements to their releasing positions until the application of torque to the barrel is discontinued. When torque is applied to the barrel 16 by means other than the correct key, the locking elements 29, 30 and 31 are not required to withstand the entire force applied to the barrel. Friction between the cam projection 26 and the body 10 is such that, when axial movement of the obstructing member 21 is prevented, the major part of any torque applied to the barrel is resisted by co-operation between the cam projection and the body. The cam projection can be made sufficiently large to ensure that unauthorised rotation of the barrel 16 is prevented and the sleeve 24, including the cam projection, can be formed of a strong material, for example steel. In the particular example of lock illustrated in the drawing, the locking elements 29, 30 and 31 are formed of a magnetic material but are not permanently magnetised. These elements are therefore urged to the positions along their respective paths of movement at which density of the magnetic flux established by the key is greatest, irrespective of the polarity of each magnetised region of the key. If required, each locking element could be permanently magnetised, in which case only a key having an appropriate polarity of each magnetised region would be capable of operating the lock. It is intended that the key should be assembled with the magnets 36, 37 and 38 in an unmagnetised condition and that the key should then be treated to permanently magnetise these magnets with the required polarities. The magnets 36, 37 and 38 may be formed of a sintered ferrite.The magnetic conductors 40 are formed of a magnetic steel, preferably one having high carbon content. A plurality of different locks may be arranged so that they can be operated by a single key. Such key would have one or more magnetic conductors of such a form that there are a plurality of positions around the axis of the key and at the same distance from that axis at which the strength of the magnetic field is greater than at other positions. The locks would be arranged to provide different paths of movement for their locking elements, each path corresponding to a respective one of the maximum field strength positions of the key. This specification is divided from that accompanying application No. 10416/76 (SerialNo. 1572091). WHAT WE CLAIM IS:

1. A lock suitable for operation by rotation of a key applied to the lock, there being associated with the key a magnetic field, the lock comprising first and second members mounted for relative movement along an axis of the lock, an elongated channel defined by the first and second members collectively, and a magnetic element movable along the channel between a locking position in which it restrains relative axial movement of the first and second members and a releasing position in which limited relative axial movement of said members is permitted, the lock being adapted to receive a key whereby the magnetic element can be moved into its releasing position by magnetic interaction between said element and the key and the lock comprising a cam mechanism operable by rotation of the key to cause relative axial movement of the first and second members.

2. A lock according to claim 1 comprising a plurality of magnetic elements and wherein there are defined by the first and second members collectively a number of channels, each containing one of the magnetic elements, and the channels are spaced apart along the axis of the lock.

3. A lock according to claim 2 wherein the first member has, for each channel, a respective abutment surface which faces in a first direction along the axis and defines a first boundary of the channel, the second member has, for each channel, a respective abutment

surface which faces in a second direction along the axis and defines a second boundary of the channel, each magnetic element, when in its locking position, is engageable between said abutment surfaces of its channel to restrain relative axial movement of the members and the second member defines in each of its abutment surfaces an opening for receiving the associated magnetic element when in the releasing position, whereby limited axial movement of the first and second members is permitted by entry of the magnetic element into said opening.

4. A lock according to any preceding claim wherein the first member is adapted to receive the key but is constrained by means other than the magnetic element against axial displacement and the second member is axially displaceable relative to the key receiving member by the cam mechanism when the key is applied to the key receiving member and is turned about the axis.

5. A lock according to claim 4 wherein the key receiving member is rotatable about the axis with the key when the key is applied to the member.

6. A lock according to claim 4 wherein the second member is constrained to rotate about the axis with the key receiving member and the cam mechanism acts between the second member and the body of the lock.

7. A lock according to any preceding claim wherein the second member is urged by a resilient element in an axial direction opposite to that in which it is moved by the cam mechanism.

8. A lock according to any preceding claim wherein the second member is in the form of a sleeve and the first member is disposed within the sleeve.