The present invention relates to a lock w ich is operated by a magnetic key and to a key for operating such a lock. One such lock is described in EP0024242.

Briefly, in such locks a slide member carries a plurality of tumblers in the form of small cylindrical magnets (magnet pins) which are slidably received in bores in the slide member so as to slide transversely of the direction of movement of the member. In the locked position, the pins are attracted towards a magnetic plate so that they extend part way_out of the bores and through apertures in a non-magnetic lock plate which is fixed in position and located between the slide member and magnetic plate. Hence the pins lock the slide member in position relative to the non-magnetic lock plate. To unlock the lock, a magnetic key is slid between the magnetic plate and slide member, and repels the pins so that they are pushed out of the apertures in the lock plate. The slide member is then free to slide relative to the lock plate. The key engages a flange on the slide member so that further movement of the , key moves the slide to allow operation of the lock.

The code of the lock is governed by the number,

position and polarity of the magnet pins relative to the lock plate. EP0024242 describes a system in which the code of the lock can be changed without dismantling the lock. A rotatable wheel mounted in the slide member carries a magnet pin allowing the pin to be moved between four positions which correspond to four respective apertures in the lock plate. To move the pin, a code changing key is inserted to repel the pins from the lock plate and then move the slide member to a position where the wheel can be rotated by a tool inserted through the outside housing of the lock.

It has been found that if the pin is not moved precisely into one of its four positions it may, when an attempt is made subsequently to operate the lock, be caught in another aperture provided in the lock plate as the slide moves relative to the plate. This can cause further rotation of the wheel but generally results in a spurious code for the lock and a special procedure is sometimes required to repel the pin from the aperture in the lock plate so that the proper code can be set. The system of EP0024242 works well in practice but is time consuming as it requires a special manual operation to change the lock code.

Many hotels now have lock systems in which the lock code is changed automatically for each guest. This is presently done only with electronic locks: by recoding them directly from a central computer at the hotel desk; or by giving the hotel guest a key which carries a different code to that used by the previous guest. In the latter system, the lock runs independently of the central computer and contains a battery powered microprocessor which is programmed to detect the key code. If the code falls in the appropriate position in a list of codes carried in the lock memory the lock will be operated by the key. This system minimises difficulties caused by power failures but requires that a computer at the hotel desk be kept in synchronism with the code changes of all the independent locks at all times so that the hotel management knows which key to issue to a subsequent guest. Errors occur frequently in this system particularly due to electronic malfunctions, which requires resetting of locks that get out of sequence.

The present invention aims to provide a magnetic key operated lock having a facility for automatically and mechanically changing the lock code without the need for a central computer with on line door locks, or independent locks with electronics or batteries,

thus providing the benefits of the electronic systems at a low cost.

A first aspect of the invention provides a magnetic key operated lock comprising

a slide member movable from a locked position to an unlocking position with a key having a magnetic code encoded in it,

a plurality of magnet pins slidable transversely of the slide member from a first position locking the slide member in said locked position to a second position unlocking said slide member on operation of the lock by a said key, the position and polarity of some or all of the magnet pins forming a code for the lock,

a plurality of said magnet pins being mounted in a plurality of rotatable carriers in said lock for moving said pins from a first location to a second location to change the code of the lock from a first code to a second code ,

said carriers being rotated through a

predetermined angle on insertion into said lock of a code changing key having a code changing code encoded in it,

wherein at least two of said carriers are caused automatically to rotate through different predetermined angles on insertion of said code changing key, whereby a said carrier is rotated through more than one complete rotation before a code of the lock is repeated.

Other aspects of the invention are set forth in the accompanying independent claims.

Other preferred features and advantages of the invention will be apparent from the following description and the accompanying claims.

The invention will be further described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a plan view of a magnetic key operated lock and a key;

Figure 2 is a side view of the lock and key of Fi gure 1 ;

Figure 3 is a cross-section view of the lock and key of Figure 1 on enlarged scale along the line 111-111 of Figure 6;

Figure 4 shows a detail view of the lock with part, thereof cut away to show a slide member of the lock;

Figure 5 is a cross-section along the line V-V of Figure 4;

Figure 6 is a detail view corresponding to Figure 4 but with wheels of the lock rotated from a firstposi tion (Figure 4) to a second position;

Figure 7 is a cross-section along the line VII-VII of Figure 6;

Figure 8 shows schematically the 12 different lock codes of the lock of Figures 1 to 7;

Figures 9 shows a plan of a lock plate for the lock of Figures 1 to 8;

Figure 10 to 14 are schematic illustrations of other embodiments of the invention.

Figure 15 is a plan view of a slide member of a lock forming a particularly preferred embodiment of . the nvention;

Figure 16 is a plan view of a lock plate of the embodiment of Figure 15;

Figure 17 is a detail of a plan view of the lock plate and slide member of Figures 15 and 16, the lock plate laying over the slide member (cf. Figure 3);

Figure 18a _^ to 181_ illustrate the operation of the lock of Figure 15 and;

Figure 19 illustrates lock codes and the corresponding key codes for the lock of Figure 15.

Referring to Figures 1 and 2 a lock in accordance with the invention comprises an elongate lock case 1 which supports a rotatable knob 2. The knob is arranged to be coupled to a spindle 3 when the lock is in the unlocking position so that rotation .of the knob 2 will turn the spindle to retract a latch or bolt (not shown). When the lock is in the locked position the knob 2 is freely rotatable on .the case 1 so that the lock cannot be forced. To unlock the

lock a magnetic key 5 is inserted in a slot 4 in the case 1. This operation will be described in more detail hereinafter. The key 5 comprises a sheet of magnetic material sandwiched between steel plates. The sheet is magnetised with a plurality of discrete north and south poles on one face which form a code matching the code of the lock, as described for example in U.S.4077242.

Referring to Figure 3, the case 1 houses an inner case 7 which carries the lock mechanism. The inner case 7 is fixed in position in the case 1.

A slide member 6 is mounted in the inner case 7 and is slidable by the key 5 in the direction of arrow A. The slide member 6 has a plurality of blind bores 14 which are distributed across the plane of the slide member. Tumblers of the lock are formed by magnet pins 15 (small cylindrical permanent magnets) which are accommodated in some or all of the bores 14. Overlaying the open ends of the bores is a lock plate 12 which is fixed in position in the inner case 7 and has apertures 13 which, in the locked position of the slide 6, are aligned with the open ends of the bores 14. A first guide plate 9 of non-magnetic material , such as brass, overlays the fixed plate 12 and, also, is fixed in position with

- 9 - the plate 12. A second, thicker, guide plate 8 bears on the first guide plate 9 and is biassed against the first plate b.y a leaf spring 10 supported on a wall 11 of the inner case 7. The second guide plate is of magnetizable material such as ferromagnetic steel .

In the locking position, seen in Figure 3, the magnet pins 15 are attracted to the second guide plate 8 so that the ends of the pins project into the apertures 13 and abut the first guide plate 9. Hence the slide 6 cannot be slid relative t© the lock plate 12. To unlock the lock, a key 5 is slid between the first and second guide plates, 9, 8, the guide plate 8 moving back against the force of the spring 10. The key 5 has a plurality of magnetic poles imprinted on its operating side 5a, these poles are positioned so that when the key is; fully inserted, its tip 5' abutting a toe 23 on the slide member 6, the poles are arranged opposite the magnet pins 15 and are of the same polarity as the adjacent ends of the pins 15. Hence the pins are pushed out of the apertures 13 by magnetic repulsion and sit on the bottom of the blind bores 14. The slide member 6 is thus unlocked and can be slid by pushing further on the key 5 in the direction of arrow A. A wedge shaped heel 19 on the slide member 6 has, a cam

surface 20 which depresses a fork 21 which in turn moves a coupling sleeve 22 in the direction of arrow X to connect the knob 2 with the spindle 3 so that the bolt or latch etc. can be opened by rotating the spindle 3. Such an arrangement is described in more detail in EP0241323.

As the key 5 is inserted it rides over two cams 41 which causes the slide member to be held in place when it reaches the unlocking position. This allows the user to release the key and turn the knob 2, and hence open the lock with one hand. When the key 5 is removed, the slide member stays in the unlocking position until the key 5 is withdrawn past the cams 41 , (see for example EP0241323).

As the key 5 is fully withdrawn the slide member 6 is pulled to its locked position by a coil spring 16 attached between the heel 19 and a stop 17 on the inner casing 7 (the spring having been tensioned during the forward stroke of the slide member), the magnet pins entering the apertures 13 when the slide member returns to its locked position.

Also seen in Figure 3 is a movable magnet pin 28b which forms a particular feature of the invention. The magnet pin 28b is received in a through bore 40

in a carrier in the form of a wheel 24b which is rotatably mounted in a bore 32 in the si ide' πrember 6. Four such wheels, 24a, 24b, 24c, 24d of equal size, each carrying a respective magnet pϊn 28a, 28b, 28c, 28d, and a fifth wheel 25 of larger size carrying a magnet pin 26 are provided in respective bores 32 in the slide member 6. The wheels are cog like and intermesh so that rotation of one wheel causes all five wheels to move. The larger wheel' 25 has 1-1/2 times the number of teeth of the smaller wheels 24a, 24b, 24c, 24d. The teeth of the wheels sit on ledges on the inner surface of the bores 32.

In operation of the lock, at any one time one of the magnet pins 24a, 24b, 24c, 24d forms" a code-chang ng pin which is utilised to change the code of the lock, whilst the other pins 24b, 24c, 24d and 26 are locking pins, that is they form part of the lock code and project into respective apertures 13' in the lock plate 12 and must be repelled therefrom by the key 5 to unlock the lock.

Looking at figure 4, the magnet pin 28a s the code-changing pin. This pin 28a is utilised to rotate the wheel 24a and hence wheels 24b, '24c, 24d and 25 by 90 degrees so that all four pins 24-a , 24b, 24c, 24d are moved through 90 degrees and pin 24 is

moved through 60 degrees only due to the greater number of teeth on wheel 25. At this point (Figures 3 and 6) magnet pin 28a becomes a locking pin, magnet pin 28b is a code-changing pin and magnet pins 28c and 28d are locking pins. The disposition of the locking pins has thus been changed and so the code of the lock is changed.

The code-changing operation of the lock will now be described in more detail.

Let Figure 4 show the lock with a first code and hence openable by a first key carrying the first code. The code-changing magnet pin 28a projects into an elongate slot 35a in the lock plate 12. When the first key 5(1) is inserted it repels locking magnet pins 15 and magnet pins 28b, 28c, 28d and 26 from their respective apertures in the lock plate 12. The key 5(1) does not repel code changing pin 28a which thus still projects into the elongate slot 35a. This pin is held in the slot by its attraction towards the guide plate 9, or a magnetic spot may be provided on the key to attract the pin more positively into the slot. The pin 28a slides in the slot 35a as the slide member 6 slides and hence the first key can operate the lock, the locations of the magnet pins 28a, 28b, 28c, 28d and

26 remaining constant as the lock is operated. Engagement of the pin 28a in the elongate slot 35 serves to prevent unwanted rotation of the wheels 24a, 24b, 24c, 24d and 25.

To change the lock code to a second code a second key 5(2) is inserted. This key has encoded on it the first code, the second code and a lock changing code. The first and second codes both include parts corresponding to the pins 15, that is to repel them. The first code repels pins 28b, 28c, 28d and 26 in the Figure 4 position, and the second code repels pins 28a, 28c, 28d and 26 in the Figure 6 position. The first lock changing code is a magnetic spot which, in the Figure 4 position, repels the pin 28a.

As stated previously, pin 28a (and pins 28b, 28c and 28d) are located in bores 40 which are open at both ends. When the second key 5(2) is inserted it repels the pin 28 out the "back" of the respective bore 40 against a back wall 18 of inner casing- 7. Accordingly as the second key is inserted it repels all the locking pins to unlock the slide member 6 using the first code, and it repels the pin 28a. The slide member 6 is free to move as the key 5.(2) is pushed in further. As the slide member moves

(in the direction of arrow A in Figures 4 and 6) the pin 28a engages an edge 44a of a tang 43 which is pressed from the back wall 18 of the inner casing 7. Thus, further movement of the slide member 6 causes the wheel 24a to be rotated, the pin 28a being allowed to move sideways across the abutting edge 44a of the tang 43a. When the slide member 6 is at the limit of its travel , the pin 28a has been moved through 90 degrees, as have the other pins 28b, 28c, 28d to the Figure 6 position. Whilst the pin 26 in the larger wheel 25 is moved through 60 degrees only because of the ratio in the wheel diameters. Also, of course, coupling member 22 is moved to allow the latch or bolt to be retracted, and the slide member 6 is held in the unlocking position due to the action of cams 41.

As the key 5(2) is withdrawn, the pins 28a, 28b, 28c, 28d are all attracted towards the magnetic plate 8. As the slide moves back to its locked position the second code changing pin 28b engages in a respective elongate aperture 35b in the fixed plate 12,the first code changing pin 28a is attracted into a respective locking aperture 13' and the pins 28c, 28d, 26 engage in respective (new) locking apertures 13' , as seen in Figures 3 and 6.

At this time the lock can be opened again by a key bearing the second code, and, in particular, by the key 5(2) which carries the second code. Key 5(2) does not repel pin 28b in the Figure 6 position and key 5(1 ) will not open the lock because its code does not correspond to the position of pins 28c, 28d, and 26.

Preferably key 5(2) has a magnetic spot to attract pin 28b to ensure that it locates securely in the elongate aperture 35b during movement of the slide 6.

To change the lock code from the second code to a third code, a third key 5(3) is used. Key 5(3") has the second lock code (to release the slide member 6), a lock changing code (to repel pin 28b) and the third lock code to allow it to open the lock after the code has been changed. As key 5(3) is inserted it releases the slide member 6, and repeVs pin 28b to engage the respective edge 44b of a tang 43b to cause wheel 24b (and wheels 24a, 24c, 24d and 25) to rotate as the slide member 6 is moved. The wheels thus adopt a new position where pins 28a, 28b, 28d and 26 form part of the third lock code and pin 28c is the new code changing pin. Thus keys 5(1 ) and 5(2) are eliminated.

A fourth key 5(4) changes the code from the third code to a fourth code by means of code changing pin 28c and a fifth key 5(5) changes the code from the fourth code to a fifth code by means of the code changing pin 28d. This eliminates keys 5(3) and 5(4). At this time it can be seen that the wheels 24a, b, c and d have turned a full circle, but that wheel 26 has turned only 240 degrees. Thus pin 28a once again is a code changing pin, but key 5(1 ) will not unlock the lock again because the locking pin in wheel 26 is in another position.

Accordingly a further 8 code changes can be made before all the magnet pins 28a, 28b, 28c, 28d and 26 are returned to their original (Figure 4) position, i.e. three revolutions of the wheels 28 and two revolutions of the wheel 25. Figure 8 shows the full twelve positions of the magnet pins. Hence the codes can be cycled through continuously but only in the prescribed sequence.

By forming the abutments or edges 44 from tangs 43, the tangs provide a ramp in the return direction of the slide member 6. Hence if a pin retracts from its. elongate aperture during the return of the slide member and protrudes out the rear of the bore 40 it will simply ride up over the ramp, which will bring

- 17 - it back towards the attracting plate 8.

The wheel 24a is arranged to rotate in the opposite direction to the other wheels 24b, 24c, 24d, and in particular to wheel 24b, so that slot 35a which is associated with the abutment 43a can be placed to one side where it will not overlap the path of a magnet pin in the wheel 24b, since otherwise the wheels might inadvertently lock in an incorrect position due to a pin entering an incorrect elongate aperture. Similar considerations apply to the location of the locking apertures 13, 13'.

It will be appreciated that the abutments 44 are positioned to one side of the respective wheel axis, relative to the direction of movement of the slide, to ensure rotation of the wheel as the respective pin engages the abutment.

An abutment may be formed on a slant to provide a slight sideways impetus if the abutment is close to the line of movement of the wheel axis.

If desired, other users can be issued with keys corresponding only to the codes 1 to 12 which do not repel the respective code changing pins.

Management can have special keys which only change the code but need not subsequently open the lock and so need comprise only say, the first code and the code-changing code. Another use of this feature is in facilities requiring a key which is usable once only. The user may be issued a key, having the initial unlocking code and the code changing code, but not having the subsequent unlocking code. Hence, for example, when a key with code 1 is inserted it opens the lock and simultaneously changes the code to code 2, which cannot subsequently be unlocked by that key.

Various modifications may be made to the described embodiment. For example, the number of wheels may be changed and a wheel may carry more than one magnet pin. The ratio between the wheel sizes may be varied to obtain a different number of codes in a complete cycle of codes. Care must be taken however, because some arrangements may result in a key which can unlock more than one code in a complete cycle.

To increase the number of stationary locking pins, such a pin may be provided on the axis of rotation of a wheel , for example, the wheel 26 in the embodiment shown.

Figure 9 shows a plan of a lock plate for the embodiment of Figures 1 to 8.

In addition to the automatic code changing facility, the slide member 6 may include a manually rotatable wheel carrying a magnet pin, as described in EP0024242. If a maids key is lost, then a common code of the locks operated by that key can be changed by manually rotating the wheel.

It is possible to provide a variety of keys suitable for hotel use with the system of Figures 1 to 8. In particular a master or maids key, which will open the lock in any code but not change the code, and a recycle key to reset the lock to a particular code.

A maids key will have a code which will repel all the pins 15 and the pins 28, 26 at any of their 1 ocking positions but will attract the pins 28a, 28b, 28c, 28d at their code changing positions and so not cause any code change.

A recycle key will have a code which will attract pin 26 at one position and repel it at all others, and repel the pins 28a, 28b, 28c, 28d at their locking positions and their code changing

positions. Repeated insertion of the key will cycle the lock through the codes until the key attracts the pin 26 when it will stop the cycle. Management will then know that the lock has been reset to one of two codes.

It is possible to arrange for a single wheel to provide a code changing function more than once per rotation. Such a wheel may comprise only code changing pins and be used to drive a wheel or wheels which carry locking pins.

By using wheels of different sizes, the number of rotations of the code changing wheel before a code is repeated can be made e ry large. The main limitation on such systems is the need to provide an adequate number of stationary pins to allow basic codes specific to users, that is buildings, and to floors of buildings, e.g. in hotels, without unduly increasing the lock size and the key size. Also it is necessary to ensure that as the slide moves, the path of a pin crosses only one locking aperture in the lock plate, i.e. the aperture specific to that pin. If the path of a pin crosses another, incorrect, aperture the pin may be attracted into that aperture when the key is removed, which may result in the slide being held in the unlocked

po s i t i o n .

Particularly favourable combinations can be achieved by providing pins of opposing polarity in the wheels, although this can prevent master keying of the system with a single master key.

Further embodiments illustrating the above variations will now be described schematically. It will be appreciated that in all cases the basic code changing operation, by repelling (or attracting) a code changing pin, is the same and that other, stationary, locking pins are present.

Figure 10a shows a system using two wheels 51 , 52 of equal size for producing a lock with four different codes. One of the wheels 51 , is used to d ive the other wheel 52. Wheel 51 carries 4 magnets 53 whose polarity alternates north and south around the wheel . Wheel 52 carries two magnets 54 of opposite polarity. A code changing edge 55 is located behind wheel 51 adjacent one of the bores in the wheel 51 and an elongate slot 57 is positioned in the lock plate (not shown) in front of the wheels 51 , 52. The magnets 53 are used only for code changing, whilst the magnets 54 are used only for locking. Four apertures are provided in the lock plate above

the stationary positions of the magnets 54 in the wheel 52.

To effect a code change, a key is inserted which releases the slide member, i.e repels the magnets 15, 54. Movement of the slide in the direction of arrow A will cause the magnet 53a to engage the edge 55 and so rotate the wheel 51 anti-clockwise through 90 degrees as the wheels are moved with the slide. This brings magnet 53b to a position where it will engage in the elongate aperture 57 when the slide member returns and wheel 52 is also rotated through 90 degrees, to give a second locking code, Figure 10b. The key can include the second locking code, i.e. spots corresponding to the new position of the magnets in wheel 52 and so will unlock the lock. However, the code changing code which repelled magnet 53a will now attract magnet 53b, which is of opposite polarity, into the elongate aperture 57 and so the lock code will not change again.

To change the code to the third code a key having the second lock code, i.e. repelling, inter alia, the pins 54 in the Figure 10b position, and a code changing code, i.e. repelling the pin 53b is inserted in the lock. The key will also have a code to repel the pins 54 in the Figure 10c position,

which shows the third code.

Figure lOd shows the fourth lock code.

This embodiment illustrates a modification to the elongate slot. The slot is curved at its bottom end, in the direction of travel of the slide member, so that a magnet pin will come into the area _^ of the slot even if the pin does not move fully through 90 degrees. This may occur, for example, if the slide member is not pushed down fully when opening the lock. If the pin enters the slot at the elbow 58 it will be guided round to its upper position as 'the slide is moved back. Preferably the magnet is a relatively tight fit in the upper end of the slot to ensure proper alignment of all the locking magnet pins with the lock plate apertures. By using the slot to complete the rotation of wheels in this way a greater degree of rotation can be obtained for a small travel of the slide member.

Figure 11 shows an embodiment in which two code changing positions are provided for a wheel . A wheel 60 carries three magnets 61 spaced at 120 degrees and is stepped through six positions. The magnets are of different polarities (e.g. 1 north and 2 south) and engage in locking apertures in the

lock plate when not at a code changing position. Code changing edges 62 are provided behind the wheel 60 at two adjacent stopping positions for the magnets, both positions being to the same side of a line through the centre of the wheel 60 in the direction of movement. Referring to Figure 11a, magnet 61a is at the code changing position and located in the top of the slot 63a in the lock plate. When the code is to be changed to the Figure lib position, a code changing key repels the magnet 61a and magnets 61b and 61c. Magnet 61a engages the rear edge 62a as the slide is moved in the direction of arrow A. This rotates the wheel through 60 degrees (the amount of rotation is limited by the extent of movement of the slide) so that the magnet 61a will enter the aperture 62b when the slide returns to the locked position. The same code changing key repels magnets 61b, 61c in their new positions but attracts magnet 61a in the Figure lib position so that it will open the lock in the new code but will not change the lock code when used agai n.

The next code changing key (2) must repel the magnet 61a in the Figure lib position, and also repel the magnets 61b and 61c in this position. The code is then changed to the Figure lie position where the

magnet 61b becomes a code change magnet using edge 62a. The key (2) will then repel magnets 61a and 61c in the Figure lie position and attract magnet 61b to operate the lock but not change the code agai n .

The six codes can be cycled through .as shown in Figures 11a to llf, and the next change will return to the starting code 11a.

To provide a more complex coding the wheel 60 may drive a second wheel 70 which comprises only a locking magnet or magnets, as seen in Figure 12. This wheel 70 is preferably of different size, having say 2/3 the number of teeth so that it steps through 90 degrees. Thus three rotations of the wheel 70 may be required for a complete cycle through 12 different lock codes. At least two magnets are preferred over 1 to prevent wheel 70 rotating in the event that the slide member is moved by a key which does not repel the (single) magnet in wheel 70 but does repel the pins in wheel 60.

A drawback of the system of Figures 11 and 12 is that a single full cycle master key cannot be provided because all locking positions at one time or another during the full cycle contain both north and south polarities and

a single location on a key can only be one polarity.

Figure 13 shows another 12 code lock, utilising 3 wheels 81 , 82, 83. Wheels 81 and 83 each carry two pins 84, 85 and have one code changing position as illustrated by the elongate apertures 86, 87 and abutments 89. The third wheel 82 has 1-1/2 times as many teeth as wheels 81 , 83 and so moves through 60 degrees for each 90 degree rotation of the wheels 81 , 82. The wheel 82 preferably carries 1 pin, two diametrically opposed pins of opposite polarity, or three pins spaced by 120 degrees with one pin of different polarity to the other pins. The number of pins and their polarities determining the number of code changes. The code changing positions 89 on the wheels 81 , 83 are brought into operation alternately. If for example, at least one of the small wheels 81 , 82 carries magnets of opposite polarity and wheel 82 carries a single pin or two diametrically opposed pins of opposite polarity, the small wheel must complete 3 revolutions, i.e. 12 code changes, to return to the position shown in Figure 13.

Figure 14 shows another embodiment of the invention which comprises a single wheel 90 having six positions through which it rotates. The wheel carries three magnets 91a, 91b, 91c. The wheel has two associated

- 27 - abutments 96, 97 for rotating the wheel 90 by means of a magnet pin located at either of two positions No.4 and 5. A particular feature of this embodiment is that one of the abutments is provided on the lock plate, and the other is provided on the back wall 18 of the inner ^' carrier 7.

Referring to Figure 14a, positions 1 , 2 and 3 are used as locking positions, that is a magnetic pin in any one of these positions is a locking magnet pin. A magnet pin in one of the positions 4 and 5 is used to rotate the wheel , and hence change the lock code, specifically the location of a pin in the 1 , 2, 3 positions.

A first L-shaped aperture 94 is cut into the lock plate, which is in front of the wheel as viewed in the drawing and a second reversed L-shaped recess 95 is formed in the wall 18.

To change the lock code from the Figure 1 position, a magnet pin 91a is attracted by an area of a code changing key (1 ) so that it projects into the lower arm 94a of the aperture 94 in the lock plate. The other magnet pins 91b, 91c (and 15) are repelled to release the slide member 6. Movement of the slide member in the direction of arrow A causes the pin 91a to abut the abutment 96 (the bottom edge of the arm 94a) and so the

wheel is caused to rotate, the pin 91a moving along the arm until it is at the lower end of the vertical arm

94b. As the slide member 6 is released and returns the pin 91a slides up in the slot 94b (Figure 14b). The wheel has thus rotated 60 degrees, bringing pin 91c into position No. 4. Pin 91b thus forms the only locking pin for the wheel .

To change the code again a key (2) is inserted to repel pins 91b and 15 to release the slide member, to repel pin 91a to allow rotation of the wheel 90, and to repel pin 91c into the lower arm 95b of the slot 95. This time, the pin 91c will abut abutment 97 formed by the bottom edge of the rear slot 95b and so cause the wheel 90 to turn as the slide moves. Pin 91c moves into the No. 5 position and pins 91a and 91b form locking pins, as shown at Figure 14c.

To continue to open the lock, but not change the code, the key (2) must repel the pin 91c so that it slides in the rear slot 95a during movement of the slide member, and also repel pins 91a, 91b at their new positions.

The polarities of the magnetic spots of keys which will change the lock code, and continue to open the lock but not change its code, are shown to the right hand side of Figure 14.

- 29 -

Rotation of the wheel 90 thus provides 6 different lock codes. There is some cross-keying in that key (4) will open the lock in code 14f.

To provide a very large number of lock codes, a plurality of wheels 90 could be provided, the wheels being rotated independentl of one another, to give 6x6 codes (2 wheels), 6x6x6 (3 wheels) or even more. Use . of this system can eliminate cross-keying by having the key change a second wheel at that code.

A single master key or recycle key is not possible with this sytem.

In the particularly preferred embodiment of Figures 15 to 18 the abutments, for engagement by the code changing pins, are all formed in the lock plate. This can be particularly advantageous where the rear of the slide member serves another purpose, such as in U.S. 4133194 and it would be less convenient to have pins at a number of positions moving out the rear of the slide member.

The basic structure of the lock is as described for the embodiment of Figure 1.

Figure 15 shows a non-magnetic plastics slide member 100 which has a plurality of fixed-position blind bores 102 for receiving magnet pins 123a. A manually rotatable wheel 103 is provided in the slide member 102 and has a blind bore 102" carrying a magnet pin 123"a. Wheel 103 operates in the manner described in EP 24242.

Two toothed non-magnetic plastics wheels 104, 106 are housed in blind recesses in the slide member 100. The wheels 104, 106 are each provided with two diametrically opposed blind bores 108, 110, 112, 114, and are meshed so that one pair of bores is ninety degrees out of phase with the other. Hence the bores 108, 110 in wheel 104 are aligned with the apices of teeth 116, whilst bores 110, 114 in wheel 106. are aligned with the troughs between the teeth 116. Each wheel 104, 106 has a through bore 109, 111 which receives a stub axle 113, 115 which is integral with the body of the slide member 100, the wheels 104, 106 rotating about the axles 113, 115.

Figure 16 shows a lock plate 118, and Figure 17 shows a detail of the lock plate with the slide member 100 below it. With the slide member 100 in the locked position, code-changing magnet pins 108a, 110a, 112a, 114a • carried by the wheels 104, 106 are attracted to

the steel shield plate 8 (Figure, 3) and so . project through the slots 120, 122 and 126. Other, fixed-position, magnet pins 123a project through respective apertures 123.

The lock plate 118 has symmetrically arranged slots 120, 122 which function as the abutments for engagement by code-changing pins. For convenience the bottom end (as pictured in the drawing) of each slot is formed as a locking aperture 123' for receiving a locking pin 123'a in a corresponding bore 102' in the slide member 100. A horizontal elongate aperture 126 serves as a locking aperture "for an appropriately positioned magnet pin carried by the wheels 104, 106.

Figures 17 and 18a show the position with the slide member 100 in the locked position and wheels 04, 106 in the position of Figure 15. Each bore 108, 110, 112, 114 carries a respective magnet pin 108a, 110a, 112a, 114a. In this position, the pin 110a projects into the aperture 126 in the lock plate, locking the slide member 100 relative to the lock plate 118. The pin 108a is also attracted into an ear 128 in the slot 120. The pin 108a abuts against a bottom edge 130 of the ear 128 in the event that the slide, member 100 is urged downwards (Figure 18b). This serves to

balance the forces on the wheel 104, preventing it from tending to rotate whilst the pin 110a is in the slot 126.

The pins in bores 110, 112 of wheel 106 serve no locking function in the position shown, but are attracted into the slot 122, and so serve to prevent rotation of the two meshed wheels 104, 106.

To change the code of the lock, a code change key (1 ) which repels the pins 110a, 112a and 114 and attracts the pin 108a is inserted in the lock. Once pins 110a, 112a, 114a are repelled the wheels 104, 106 are free to rotate. As with previous examples, the key (1) must also repel all the stationary locking magnet pins, including pin 123"a in wheel 103. As the slide member 100 is moved downwards by the key, arrow A, relative to the lock plate 118, the wheel 104 is caused to rotate due to pin 108a abutting abutment 130 (Figure 18b). Pin 108a slides along the abutment 130, (Figures 18b to 18d) as the wheel 104 is caused to rotate clockwise, until the pin 108a is almost in the 12 o'clock position (Figure 18e, 18f), when it rides over a lip 132 and enters a vertical channel 134, as the slide member 100 has neared the bottom of its travel. As seen in Figures 18e to 18g magnet 110a on clearing knee 134a of the slot 134 is

attracted by a magnetic spot on the key 1 (see Figure 19) and as the slide member continues to move downward the pin slides along the edge 134b of the slot 134 to aid in guiding the wheel to full 90 degree rotation. At this position (Figure 18g), pins 108a and 110a are aligned with the vertical length 134 of the slot 130, pin 114a has been rotated around with wheel 106 (which has been rotated due 'to its geared connection to wheel 104) until it is aligned ^' with but below an ear 136 of slot 122 and pin 114a is aligned with but below the locking aperture 126. The bottom edge region 134c of slot 134 is arcuate and forms a seat for pin 110a to properly position the wheels 104, 106 when the slide member reaches the end of its travel . Slot 122 has a similar arcuate edge region 140C.

As the slide member 100 is released to return to its locked position, the key (1 ) being withdrawn, the pins 108a, 110a are attracted into vertical portion 134 of slot 120, pin 114a will enter ear 136 and pin 112a enters locking aperture 126 (Figures 18h and 18j), due to the attraction of the steel shield plate 8 (see Fi gure 1 ) .

At the upper end of the travel of the slide member, (Figure 18j) pin 108a is guided into the apex of the

slot 120 to ensure that the wheel 104 remains with its two pins vertically aligned, the apex pressing on the pin 108a at this point.

The slots 120 and 122 are shaped to ensure a code change even if the slide member is not pushed down the full distance. As described previously, when the slide member 100 is depressed by the key, the magnet pin that was immediately previously positioned in ^' locking aperture 126 is rotated downwards and before the core is fully depressed the pin enters a knee portion 134a, 140a of elongate slot portion 134, 140 (Figure 18e) and is attracted to a magnetic spot on the key 1. If the slide member is not depressed further but instead is allowed to return upwards to the locked position, the pin is urged by the cam action of the edge 134d, 140d of the slot above the knee 134a, 140a, to complete the rotation of the wheels through 90 degrees (Figures 18k, 181 , 18j).

If key 1 is to continue to unlock the lock, but not change the code again, it will have four additional magnetic spots to repel pins 114a and 112a in their new position and attract pins 108a, 110a in their new position. (If the key is not intended not to open the lock, once it has been set to the new code, then the four additional magnetic spots are arranged to

attract all the pins 108a, 110a, 112a, 114a in their new pos i ti ons ) .

When the code of the lock is to be changed a second time, the second code change key (2) will have magnetic spots to repel pins 108a, 110a and pin 112a, as well as all other locking magnet pins 123a, and 123'a. Pin 114a is attracted so as to stay in the ear 136. As the slide member 100 moves downwards relative to the locking plate 116, the pin 114a abuts edge 138 of ear 136 and so causes the wheel 106 to rotate in the anti-clockwise direction. Pin 114a slides across the edge 138 until it is in the vertical channel 140 of slot 122. At this time pin 114a is aligned with the vertical channel 140, pin 110a is aligned with but below ear 130, and pin 108a is aligned with but below locking aperture 126. As the key is withdrawn and the slide member 100 returns to its locked position, pin 108a enters aperture 126 and pin 112a enters ear 130. If the key is to continue to open the lock (but not change the code), it will have magnetic spots to repel pins 108a, 110a in their (new) positions and attract pins 112a, ll4a.

If each wheel has magnet pins of the same polarity, e.g. both pins in wheel 104 have exposed north poles and both pins in wheel 106 have exposed south (or

north) poles, the lock will be back at the position of Figure 18a. Thus only two codes are available and will alternate.

To have a four code cycle sequence for the lock, the pairs of pins in each wheel must be of opposite pol ari t .

Figure 19 shows schematically the position of the pins and the respective coding for keys with a four code system, using opposite polarity magnet pins in each wheel. Key codes are shown for keys which will change the code (once) and continue to unlock the lock, and the reset and maids keys are also shown. As shown, the poles of the magnet pins 108a, 110a, 112a, 114a are as viewed from the lock plate, and the poles on the key are the pattern on the "underside" surface of the key which faces the pins, when viewed from "above".

The slide member 100 shown has also a separate disc 103 of the type described in EP 24242 containing one locking magnet pin 123'a which is manually movable by rotation of the disc 103 from outside the lock to any of four positions as described in EP 24242. After an automatic code sequence of four codes, manually rotating the disc 103 to another position

will change the overall code of the lock and so another cycle of automatic code changes giving four more codes are possible, the lock having overall , a different set of codes to the previous sequence, In this manner a total cycle of 16 codes is possible, a manual change being made after each four automatic changes. The full cycle of 16 codes can be repeated, by rotating the disc pin to original starting position, or changing the position or polarity of any other fixed magnet 123a in the slide member can provide a further series of 16 codes.

With each sequence of four codes, two keys coded as "re-cycle keys" each changing the code once for each of two insertions can cycle the lock through the four codes: the first key will cycle from code 1 to 2, and then from 2 to 3 but it will not operate the lock again in code 3. The second key will cycle from code 3 to 4 and from code 4 to 1 but it will not operate the lock again in code 1. Thus only two recycle keys are necessary to reset the lock to any of the four codes. If these same keys master the four positions of the disc 103 they can be used to set the lock to any of the 16 possible codes, the position of pin 123"a being determined by the manual rotation of disc 103.

This embodiment can also have a single-use key in which the key has a code to open the lock once, changing the code, and will not operate the new code. In this way a system in which keys open the lock only once can be provided. Two master keys which operate codes 1 and 2 and 3 and 4, but will not change the code, can also be provided. If they master the four positions of disc 103 they become grant masters for the system. A single master key is not possible as each location is occupied variously by a north or a south pole of a pin, and of course it is not possible to have different polarity spots at the same position on a key.

A system which is particularly useful for hotels makes use of an eight cycle sequence, i.e. two cycles of four automatically changed codes Nos.1-4 and Nos.5-8 by using two positions of the wheel 103, say the first position for codes Nos.1-4 and the third position for Nos.5-8. The second and fourth positions of wheel 103 would be used in the event that maid master keys, which open the lock in all eight codes of the sequence are lost: the wheel 103 being rotated to the second position to lock out the lost maids keys but allowing continuing use of guest codes Nos.1-4, and rotated to the fourth position to allow continued use of guest codes Nos.5-8. The

guest keys Nos.1-4 are coded to repel the pin 123"a in wheel 103 when it is in the first and second poitions, and keys Nos.5-8 are coded to repel the pin when in the third and fourth positions. Hence it is not necessary to issue new guest keys when the maids keys are replaced, two sets of maids keys being possible with this system. When both sets of maids keys are lost, the system can be recoded by changing the position or polarity of one of the fixed position magnet pins.

It will be appreciated that a lock may incorporate two (or more) independently operable automatic code changing mechanisms. Thus if each system provided a cycle of 4 codes, a total of 16 automatically changeable codes could be achieved. The lock may incorporate two (or more) different embodiments of code changing mechanisms or two similar embodiments. A lock using the embodiments of Figures 4 and 13, for example, could have 120 different codes which can be cycled through automatically. The code changing keys would, preferably, operate only one of the code changing mechanisms at a time.

It will be apprec ated that the code-changing mechanism need not be positioned in the upper part of the slide member, but may be positioned near the toe

23 .

Various modifications may be made to the described embodiments and it is desired to include all such modifications as fall within the scope of the accompanying claims.