Locking Apparatus

The present invention relates to locking apparatus, particularly, but not exclusively to locking apparatus for use on a mechanical combination door lock thereby restricting entry to a secure area.

It is desirable in many applications to allow building entry doors, windows, cupboards etc. to be opened only by those who have been authorised to do so. One way of achieving this is to use a locking mechanism which requires a predetermined code to be entered before it can be unlocked. Mechanical combination door locks are widely used for this purpose. Such locks typically have a series of alphanumeric buttons (often 4, 6 or 8) and a knob or handle which can be grasped by the user. In operation, the code is dialled into the mechanism by the authorised user, the knob or handle is turned and the mechanism unlocks. However, such combination locks are often limited by the number of permutations available for a given number of buttons since they typically allow the integers of the predetermined code to be entered randomly in order to gain access, rather than requiring them to be entered in sequence. For example, if the entry code is 1 , 2, 3, 4, a person entering the code 4, 2, 3 1 would be able to gain access. Another disadvantage of known combination locks is that they typically require the keypad to be removed from the door followed by the removal of some internal components before the code can be changed.

According to the present invention, there is provided locking apparatus for a lock having an actuating handle and an associated bolt opening mechanism, the locking apparatus comprising:- a lock release arm;

engagement means in communication with the lock release arm for selectively engaging the actuating handle with the bolt opening mechanism ; a code entry mechanism which selectively allows the lock release arm to cause engagement between the actuating handle and the bolt opening mechanism when a correct code is entered, the code entry mechanism comprising; a rotatable shaft; an obstruction portion provided on the rotatable shaft for selective engagement with a portion of the lock release arm; at least a clutch mechanism provided on the rotatable shaft, the clutch mechanism comprising a drive component rotatable relative to the rotatable shaft, a driven component substantially fixed relative to the rotatable shaft and an actuation portion communicable with an associated entry button such that actuation of the associated entry button selectively results in rotation of the clutch mechanism drive component thereby selectively resulting in rotation of the clutch mechanism driven component and hence the rotatable shaft and disengagement of the obstruction portion and the lock release arm to cause actuation of the lock release arm thereby allowing the engagement means to engage the actuation handle with the bolt opening mechanism.

Preferably, the clutch mechanism comprises a slot and pin arrangement. Preferably, the slot extends around at least a portion of the drive member and the drive pin is provided on the driven member.

Typically, the rotatable shaft has a plurality of clutch mechanisms provided therealong. The rotatable shaft may typically be provided with a number

of grooves therealong which are meshed with corresponding teeth provided on the drive member of the clutch mechanism drive component.

Preferably, the orientation of the slot and pins are staggered around the circumference of the rotatable shaft such that the rotatable shaft will only incrementally rotate when an actuation button is pressed in sequence.

The lock release arm may comprise a main spar provided with teeth corresponding to obstruction members provided on each clutch mechanism. Alternatively, the lock release arm may comprise a plate having prongs for alignment with the corresponding obstruction portion provided on the rotatable shaft. The lock release arm may have a window to communicable with the engagement means. Preferably, the lock release arm is spring loaded such that it will communicate with the engagement means when the obstruction portion of the lock release arm and the rotatable shaft align with one another. The apparatus may also be provided with resilient button holding means which deactivate an actuation button once it has been pressed.

The engagement means preferably comprises a cammed member in communication with a barrel of the actuation handle and a spring loaded engagement pin in communication with a spindle of the bolt opening mechanism. The cammed member has an inner cam profile provided with an engagement notch capable of receiving the spring loaded engagement pin such that when the lock release arm is in the obstructed configuration it holds the engagement pin out of the engagement notch and when the release arm is released it allows the engagement pin to spring into the engagement notch such that rotation of the actuation arm results in rotation of the bolt opening mechanism spindle.

The barrel may also be provided with a shaft resetting cam which resets the rotatable shaft to its initial configuration upon actuation of the handle. The barrel may also be provided with a release arm resetting cam which resets the lock release arm to its initial configuration upon actuation of the handle.

Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which :-

Fig. 1 is a schematic perspective view showing a first embodiment of the locking apparatus according to the present invention. The view only shows a single clutch mechanism although it will be appreciated that several clutch mechanisms may be provided along the shaft for association with each code entry button;

Fig. 2 is a schematic perspective view of a reset cam and a re-lock cam of the apparatus of Fig. 1 ;

Fig. 3 is a perspective view of a housing box in which the apparatus of Fig. 1 may be mounted;

Fig. 4 is a more detailed perspective view of the clutch mechanism in an engaged configuration; Fig. 5 is a perspective view of the clutch mechanism of Fig. 4 where the clutch is in a pre-engagement position;

Fig. 6 is a perspective view of the clutch mechanism of Fig. 5 where the clutch is in a post-engagement position;

Fig. 7 is a perspective view of locking apparatus according to a second embodiment of the apparatus, as it would be installed on a door;

Fig. 8 is a rear view of the apparatus of Fig. 7 where the internal mechanism can be seen;

Fig. 9 is a partially disassembled upper view of the apparatus of Fig. 7;

Fig. 10 is a partially disassembled lower view of the apparatus of Fig. 7;

Fig. 11 is a partially disassembled view of the apparatus showing an actuation handle installed thereon; Fig. 12 is a close up view of engagement means at the end of the chamber of the invention;

Fig. 13 is an underside view of the arrangement of Fig. 12;

Fig. 14 is a further view of the arrangement of Fig. 14 showing the end of the column detail; Fig. 15 is a perspective side view of the engagement means;

Fig. 16 is a perspective view looking into the engagement means showing engagement between the lock release arm, engagement pin and an internal cammed engagement surface;

Fig. 17 is a perspective view of a clutch mechanism according to the second embodiment of the present invention;

Fig. 18 is a perspective view of one end of the coding mechanism;

Fig. 19 is an isolated side view of the column of the code entry mechanism;

Fig. 20 is a perspective, partially exploded view of the clutch mechanism of Fig. 17;

Fig. 21 is a further perspective side view of the code entry mechanism mounted in a housing according to the second embodiment of the invention;

Fig. 22 is a perspective view of the end of the column engaged with the engagement means;

Fig. 23 is a side view of the apparatus of Fig. 22;

Fig. 24 is a plan view of the coding mechanism mounting in the housing of the apparatus

Fig. 25 is a rear view if the lever plate resetting mechanism of the invention;

Fig. 26 is a detail perspective view of the engagement means, lock release arm and code entry mechanism of the invention;

Fig. 27 is amore detailed illustration of the column of Fig. 19; and Fig. 28 is a detailed view of the underside of a bolt opening mechanism spindle and engagement pin.

With reference to Figs 1 to 6, in a first embodiment of the apparatus, the three main assemblies making up the locking apparatus include a code entry mechanism 20, an engagement assembly 30 and a housing 40.

The code entry mechanism 20 is mounted on a rotatable shaft 22 and comprises an end nut 24, clutch mechanism 26 and a release clutch 28. A lock release arm 32 is also provided. The rotatable shaft 22 has a threaded portion at one end to accept the end nut 24 which ensures that the components remain in position along the rotatable shaft 22. The other end of the rotatable shaft 22 has another end nut where the cylindrical nut is formed into a rectangular protrusion 34. The rotatable shaft 22 has a number of longitudinal grooves provided along its length. In the embodiment shown there are four grooves provided; each circumferentially spaced around the rotatable shaft 22 at 90 degree intervals.

Each clutch mechanism 26 comprises a drive member in the form of a lever plate 27 and a driven member in the form of a latch plate 29. The inner surface of the drive member (lever plate 27) is freely rotatable around the outer surface of the driven member (latch plate 29). The lever plate 27 comprises a disc having a button connection arm 38 protruding from one edge of the disc, an obstruction member 42 protruding from the other edge of the disc and a drive transfer slot 44 through a portion of the disc surface. Another drive transfer slot 44 may be provided on the

opposite side of the disc. As best seen in Figs. 4 to 6, the driven latch plate 27 has a cylindrical section 46 of uniform diameter, and an enlarged diameter section which may be provided by a washer 50. The washer is fixed around the uniform diameter section 46 by gear teeth 52 on its inner circumference. The washer 50 separates the latch and lever plates by a small distance longitudinally along the rotatable shaft 22. A drive transfer pin 54 projects from the face of the washer 50 in order to correspond with the drive transfer slot 44 of the lever plate 27. With this arrangement it can be seen that (if the drive transfer slot 44 and drive transfer pin 54 were not present) rotation of the lever plate 27 would not cause any rotation of the latch plate 29 nor the shaft 22.

The button connection arm 38 of the lever plate 27 has a hole which accepts an end of a coiled spring (not shown). This assists with resetting the apparatus after actuation.

Each clutch mechanism 26 and associated component mounted on the rotatable shaft 22 are held in position along the shaft by the nut 24. Typically the nut will be expanded, to avoid self-unscrewing during the lifetime of the locking apparatus.

The locking apparatus is also provided with a release clutch 28 at the lower end of the rotatable shaft 22. The release clutch 28 is similar in construction to each clutch mechanism 26 although it does not provide the same clutch action since no drive transfer pin or slot are provided between the drive and driven member. The release clutch 28 is also provided with a slot 58 in its outer circumference. The slot is positioned at a location on the release clutch 28 outer edge which allows it to be aligned with a corresponding protrusion 59 of the lock release arm 32 when the correct code has been entered into the code entry mechanism 20. In all

other configurations the outer edge of the release clutch 28 obstructs movement of the protrusion 59 and, hence the lock release arm, 32 past the release clutch 28.

Although illustrated schematically in Fig. 1 , in use, the lock release arm 32 is attached to a side plate of the lock housing 40 in such a way that it may slide parallel with the rotatable shaft 22 longitudinal axis. In order to ensure the lock release arm 32 is held in compression within the housing 40 when the apparatus is installed, and to ensure the locking apparatus returns to a standby configuration after activation of the lock, a spring (not shown) is provided between the lock release arm 32 and the side plate of the housing 40. The lock release arm 32 has a main spar 60 extending parallel with and spaced apart from the rotatable shaft 22. Projecting from the spar 60 are teeth 62 which coincide with the clutch mechanisms 26 of the code entry mechanism 20. The arm 32 has a bridging member 64 in the form of a rectangular extension at its lower end. The bridging member 64 interacts with the unlocking assembly 30 in order to control whether opening of the lock is possible, as will be described subsequently.

With reference to Fig. 2, the opening assembly comprises a lock re-arm cam 66, rest cam 68 and engagement pin 70. The rest cam 68 is a hollow cylindrical member which is provided with a flatted portion 72 having side wings 74 which project outwardly from the flattened portion 72 in a gradual radius which curves in the opposite direction to that of the cylindrical member. The flattened portion 72 and wings 74 provide a support for the nose of the rectangular protrusion 34 of Fig. 1. On one side, the rest cam 68 is in communication with the lock re-arm cam 66 by way of the engagement pin 70. The engagement pin 70 is situated between both the rest cam 66 and the re-arm cam 68 and selectively engages with a seating area 76 provided on the inner circumference of the rest cam 68 cylindrical

member. On the other side, the rest cam 68 is linked to the housing 40 of the apparatus in order to allow actuation by a handle 5. The engagement pin 70 is held in tension by a coiled spring provided in its interior.

The housing 40 has a U-shaped bracket member comprising a back plate 80, with two parallel side plates 82 projecting from either side thereof. A rectangular facing plate 84 is provided on the front of the U-shaped bracket member and is slightly oversized in order to overlap the edges of the U-shaped bracket member. A cap plate 86 is provided at the top of the U-shaped bracket.

In the embodiment shown, the left hand side of the facing plate 84 is provided with a series of six slots though which code entry buttons 88 project. Holes 90 are provided adjacent each button which allow a coiled spring to connect each button connection arm 38 to the facing plate. A central window 92 is provided in the facing plate to allow easy access to the locking mechanism.

The left hand side plate 82 has rectangular slots 94 which coincide with the button attachment arms 38 of the lever plate 27. Each button 88 is formed of a rectangular rod having a slot at the bottom to allow straightforward attachment to the button attachment arm 38 of the lever plate 27. The slots 94 in the side plate 82 help to hold the lever plates 27 of the code entry mechanism 20 in position along the shaft 22.

When the apparatus is assembled, the rotatable shaft 22 and its associated components, lock release arm 32 and unlocking assembly 30 are connected to one another within the housing 40. In this regard, the code entry mechanism 20 and lock release arm 32 are mounted within the main chamber of the housing 40 and the unlocking assembly 30 is

mounted in the holes 81 of the facing plate 84 and the back plate 80. When mounted in this way, the bridging member 64 sits within the hollow cylindrical portion of the rest cam 68 and is in contact with the engagement pin 70.

The location of the obstruction members 42 on each lever plate 27 is arranged such that when the apparatus is in a locking configuration, each obstruction member 42 will reside in between the gap between each of the corresponding teeth 62 of the lock release arm 32. This, in combination with the action of the release clutch 28, prevents the lock release arm 32 from sliding down the length of the rotatable shaft 22 and hence maintains the apparatus in the locked configuration.

In use, when a user wishes to operate the lock, he presses the first button required by the unlocking code. The action of pushing the button 88 causes the lever plate 27 to rotate around the shaft 22 but does not itself cause rotation of the shaft 22. This rotation of the lever plate 27 causes the obstruction member 42 to move out of the gap between the teeth 62 (if it is a correctly coded button) and hence frees up that portion of the lock release arm 32 to vertical movement down the housing 40 (although no such movement can occur yet because each of the other obstruction members 42 remain in position between the teeth 62). As the lever plate 27 is being rotated, the inner edge of the drive transfer slot 44 abuts against the drive transfer pin 54 of the driven latch plate 29 and causes the latch plate 29 to rotate by an equal amount. Since the latch plate 29 has teeth 45 which mesh with the grooved slots of the rotatable shaft 22, the shaft 22 rotates by the same amount as the latch plate 29. This rotation of the shaft 22 causes the orientation of each of the other clutch mechanisms 26 along the shaft 22 to be altered. The skilled reader will therefore realise that such rotation of the shaft 22 results in the code

requiring to be entered in the correct sequence. Subsequent pressing of the code entry buttons 88 in the correct sequence therefore moves each of the obstruction members 42 out of the gaps between the teeth 62 and out of an obstructing position. Simultaneously, the release clutch 28 is rotated by each stepwise rotation of the shaft 22 until the slot 58 in its outer circumference is aligned with the corresponding protrusion 59 in the lock release arm 32. At this point, movement of the lock release arm 32 is no longer restricted by the lever plates 27 or the release clutch 28 and it can therefore slide downwardly within the housing 40. This action causes the bridging portion to move the engagement pin 70 into its seated position in the seating area 76. This engages the rest cam 68 and the lock re-arm cam 68 together. Now, when the user turns the handle 5, both the rest cam 68 and the lock re-arm cam 66 will rotate therewith and the locking apparatus will unlock, as required.

The action of rotating the rest cam 68 and re-arm cam 66 in order to open the mechanism, will simultaneously rotate the whole shaft 22 to its original position. The curved wings 74 will, as they are turned, also cause the whole shaft 22 to move vertically upward (by way of the nose of rectangular member 34 which is resting thereon) thereby resetting all of the latch plates 27 to their original position. At the same time, rotation of the lock re-arm cam will move the lock release arm 32 vertically upward, thereby resetting the buttons 88, disengaging the rest cam 68 and lock rearm cam 66 and resetting the lock opening arm 32 to a position where it is once again obstructed by the release clutch 28. In this regard, in the situation where the rest cam 68 and re-arm cam 66 are not engaged by the pin 70 (i.e. where the correct code has not been entered in sequence), rotation of the handle 5 by the user will simply freely rotate the rest cam 68 thereby instantly resetting the lock code entry mechanism without opening of the lock.

The apparatus will not allow the mechanism to be unlocked when the code is entered in any sequence other than the correct sequence as will now be described.

Referring to Figs. 4, 5 and 6, when a button 88 is pressed in the correct sequence, the shaft is rotated (roughly 9 or 10 degrees in the embodiment shown) due to the interaction between the lever plate 27 and the latch plate 29 by way of the drive transfer slot 44 and pin 46. Subsequent clutch mechanisms provided further down the shaft 22 may not initially be in an engaging position, but instead may be in a disengaged position depicted in Fig. 5. In this position, the pin 54 of the latch plate does not reside within the drive transfer slot 44 of the lever plate 27 but instead rides on the rear face of the lever plate 27. In this position, if the button associated with the disengaged clutch mechanism is pressed (out of sequence) there is no driving communication between the lever plate 27 and the latch plate 29 present. Therefore, rotation of the lever plate 27 will not rotate the shaft 22. This leaves each subsequent clutch mechanism 26 out of alignment and hence results in pressing of subsequent buttons 88 ineffective in opening the lock.

Furthermore, referring to Fig. 6, if a button 88 has already been pressed (out of sequence) any further driving communication between the lever plate 27 and the latch plate 29 is removed. This is because, the drive pin 54 will already have been moved by the inner end of the drive transfer slot 44 of the lever plate 27 and, since the distance by which the lever plate 27 may be rotated is limited, further rotation of the lever plate 27 will be ineffective. Once actuated, the only way of resetting the apparatus is to press a reset button which returns each of the clutch mechanisms 26 to their initial standby position.

It will therefore be appreciated by the skilled reader that the code must be entered sequentially in order to unlock the apparatus. In this regard, the mechanism can be thought of as having a memory in that when a button 88 is pressed, its state (whether it has been pressed or not) is memorised. This allows each button 88 to be pressed only once for each code entry sequence.

A further advantage of the present invention is that it offers an arrangement which allows the entry code to be changed relatively easily. In this regard, a hinged facia may be provided over the housing 40. In normal use this facia will remain in a closed position in which the internal mechanism of the housing 40 are covered. The facia can be secured in this closed position by a number of screws, for example, which are accessible only from the secure side of the structure on which the locking apparatus is mounted (e.g. the inside of a secure door). When it is necessary to change the entry code, an operator simply unfastens the screws from the inside of the door, flips up the facia and then changes the orientation of each clutch mechanism 26 relative to the shaft 22 as desired. The facia may then be flipped back into position over the housing 40 and the screws re-fastened from the inside of the door.

With reference to Figs. 7 to 28 a second embodiment of the invention will now be described. In order to minimise repetition, similar features of the second embodiment have been numbered with a common two-digit reference numeral and have been differentiated by a third digit placed before the two common digits. Such features are structured similarly, operate similarly, and/or have similar functions unless otherwise indicated.

In the second embodiment of the apparatus, the three main assemblies forming the locking apparatus include a code entry mechanism 120, engagement means 100 and a housing frame 140.

As seen in Figs. 8, 10 and 19, the code entry mechanism 120 is mounted on a rotatable shaft 122 and comprises an end nut 124, a series of clutch mechanisms 126 and a release clutch 128 at the end of the shaft opposite the nut 124. A lock release arm 132 (Fig. 26) having a pair of prongs 106 and a window portion 108 is also provided. The rotatable shaft 122 has a threaded portion at one end to accept the end nut 124, which ensures that the components remain in position along the rotatable shaft 122. The other end of the rotatable shaft 122 is formed into a "cone" shape C. The cone shape has a hole 119 for receiving a guide pin (not shown). This end of the rotatable shaft 122 is attached to the housing of the locking apparatus by a bracket 121 which has a tapered guide surface 123. Connecting rods 139 associate each button 188 with a corresponding button connection arm 138 of each clutch mechanism 126.

Each clutch mechanism 126 comprises a drive member in the form of a lever plate 127, a driven member in the form of a releasing plate 110 and a shaft gear 111 for mounting the clutch mechanism to the rotatable shaft 122.

The lever plate 127 comprises a disc shaped member having a button connection arm 138 protruding from one edge, a button holding protrusion 102 protruding from the diametrically opposed edge and a drive transfer slot 144 through a portion of the disc surface. A drive transfer recess 104 is also provided on the edge of the plate 127 opposite the drive transfer slot 144. The button holding portions 102 of the lever plates 127 mate with leafed springs 103 fixed to the housing frame 140. The action of these

springs 103 deactivates a button once it has been pressed. Therefore, if a button is pressed out of sequence the shaft 122 will not advance toward the opening angular position but the lever plate 127 will have been locked in an inactive position.

The releasing plate 110 comprises a disc shaped member having a collar 117 on its outer circumference. The collar 117 has an alignment slot 115 therein and a drive transfer pin 154 projecting from a front face of the collar 117. The drive transfer pin 154 corresponds with the drive transfer recess 104 of the lever plate 127. Another drive transfer pin 155 is also provided on the opposed side of the lever plate 127.

The shaft gear 111 has an outer diameter corresponding to the inner diameter of the lever plate 127 and the release plate 110. The mating outer surface of the shaft gear 111 and inner surface of the lever plate 127 are relatively smooth to allow the lever plate 127 to freely rotate around the shaft gear 111 without causing the shaft gear 111 to turn, whereas the mating outer surface of the shaft gear 111 and inner surface of the releasing plate 110 engage with one another such that the shaft gear will rotate when the release plate 110 rotates. The inner surface of the shaft gear 111 is provided with a flattened engagement wall 113 which mates with a corresponding flattened portion (not shown) on the rotatable shaft 122 such that rotation of the shaft gear 111 causes rotation of the rotatable shaft 122 and vice versa.

A washer (not shown) is provided between the lever plate 127 and the releasing plate 110 to avoid binding.

A release clutch 128 is also provided at the top of the rotatable shaft 122 to provide a reference point which determines the rotational position of the

shaft 122 that will unlock the locking apparatus. The release clutch 128 is similar in construction to each clutch mechanism 126 although it does not have a lever plate thereon. A slot is positioned at a location on the release clutch 128 outer edge which allows it to be aligned with a corresponding protrusion on the prongs 106 of the lock release arm 132 when the correct code has been entered into the code entry mechanism 120. In all other rotational configurations the release clutch 128 obstructs movement of the lock release arm 132 there past and hence maintains the locking apparatus in the locked configuration.

In use, the lock release arm 132 is attached to a side plate of the lock housing 140 in such a way that it may slide parallel with the rotatable shaft 122 longitudinal axis. In order to ensure the lock release arm 132 is held in a locking position when the code has not been entered correctly, and to ensure the locking apparatus returns to its initial locking configuration after activation of the lock, a spring (not shown) is provided between the lock release arm 132 and the side plate of the housing 140. The prongs 106 of the lock release arm 132 extend beneath the rotatable shaft 122 and extend under the fixing bracket 121. The arm 132 then bends upwardly to form an engagement window 108. The engagement window 108 interacts with the engagement means 100 in order to selectively open the lock, as will be described subsequently.

Referring to Figs. 12, 13 and 16, engagement means 100 comprises a barrel having a handle holder 112, a release arm reset member 114, a column reset member 116 and a pin engagement member 118. As shown in Fig. 28, a spring loaded engagement pin 120 which connects to a spindle 125 of the bolt opening mechanism is also provided.

Handle holder 112 connects to the actuation lever 5 of the lock to allow the user to rotate the barrel and hence the bolt opening mechanism after entering the correct entry code, in sequence.

As seen in Fig. 25, the release arm reset member 114 has a cammed outer surface which, when rotated with the handle holder 112, causes a correspondingly shaped head of plate 114A to move down the length of the apparatus thereby disengaging the button holding portions 102 from the leaf springs 103 and returning the lever plates 127 to their initial position.

The column reset member 116 has a cammed outer surface which, when rotated with the handle holder 112, pushes against the cone C of the rotatable shaft 122 thereby moving it downward along the longitudinal axis of the apparatus. This downward movement causes the guide pin (not shown) in the hole 119 to abut against the tapered guide surface 123 of bracket 121 thereby causing the rotatable shaft 122 to rotate back to its initial rotational configuration.

Referring to Fig. 16, pin engagement member 118 has an inner cam profile 118A provided with an engagement notch 118B capable of receiving the spring loaded engagement pin 120 of spindle 125. When the lock release arm 132 has not been activated (i.e. when the apparatus is locked) the edge of window 108 holds the engagement pin 120 out of the notch 118B and, when the release arm is released, it allows the engagement pin 120 to spring into the engagement notch 118B such that rotation of the barrel via the actuation handle 5 results in rotation of the bolt opening mechanism spindle 125 and hence opening of the lock.

When the apparatus is assembled, the code entry mechanism 120, lock release arm 132 and engagement means 100 are connected to one another within the housing 140. In this regard, the code entry mechanism 120 and lock release arm 132 are mounted longitudinally within the main chamber of the housing 140 and the engagement means 100 is mounted vertically in line with the window 108 of the lock release means 132, as seen in Fig. 10.

In use, when a user wishes to operate the lock, he presses the first button 188 required by the unlocking code. The action of pushing the button 188 and hence its associated connecting rod 139 causes its associated lever plate 127 to rotate around the shaft gear 111 but does not cause rotation of the shaft gear 111. This rotation of the lever plate 127 causes the inner edge of the drive transfer recess 104 to abut against the drive transfer pin 154 of the release plate 110 and the other drive transfer pin 155 to abut against the inner edge of the drive transfer slot 144. This results in release plate 110 rotating incrementally. Since the release plate 110 is rotationally fixed to the shaft gear 111 , the shaft gear 111 incrementally rotates by the same amount as the release plate 110. The reader will therefore realise that this results in rotation of the shaft 122 by an equal incremental amount. Subsequent pressing of the code entry buttons 188 in the correct sequence therefore rotates the shaft 122 by further incremental amounts. This causes the release clutch 128 at the upper end of the rotatable shaft 122 to rotate angularly by the sum of the incremental rotations. The release clutch 128 is now in the correct angular position to allow the spring loaded lock release arm 132 to slide upwardly within the housing 140. This action causes window 108 to allow the engagement pin 120 to engage with the notch 118B. Now, when the user turns the actuation handle 5 the bolt opening mechanism will open the lock. At the same time the action of turning the handle 5 will cause the

release arm reset member 114 and column reset member 116 to also turn. The cammed surfaces on the column reset member 114 pushes against the top of the cone C on the rotatable shaft 122 thereby causing it to rotate (due to the previously described interaction between its guide pin and the tapered guide surface 123 of bracket 121) thereby returning the rotatable shaft 122 to its initial angular position. The cammed outer surface of the release arm reset member 114 will also rotate, thereby disengaging the button holding portions 102 from the leaf springs which causes the lever plates 127 to return to their initial starting position.

The apparatus does not allow unlocking when the code is entered in any sequence other than the correct sequence, as will now be described.

When a button is pressed in the correct sequence, the shaft 122 is rotated (roughly 9 or 10 degrees in the embodiment shown) due to the interaction between its associated lever plate 127 and release plate 110 by way of the drive transfer recess 104, drive transfer slot 144 and pins 154, 155. The alignment of subsequent clutch mechanisms 126 associated with other buttons, along the shaft 122 are therefore dependent upon the previous button press(es). In other words, the pin 154 of the release plate 110 will not initially abut against the end of the drive transfer recess 104 of the lever plate 127 but instead will be part of the way along the recess 104 or indeed be at the opposite end of the recess 104. The same goes for the other drive transfer pin 155 and the drive transfer slot 144. In this position, if the button 188 associated with the disengaged clutch mechanism 126 is pressed (out of sequence) there is no driving communication between the lever plate 127 and the release plate 110. Therefore, the shaft 122 will not rotate by the required angle. This leaves each subsequent clutch mechanism 126 out of rotational alignment and hence means that

pressing subsequent buttons out of sequence is ineffective in opening the lock.

In this situation, since the engagement pin 120 remains held out of the engagement notch 118B by the lock release arm 132, rotation of the handle 5 by the user simply freely rotates the inner cammed surface 118A of engagement member 118 around the stationary engagement pin 120 without opening the lock.

Modifications and improvement may be made to the foregoing, without departing from the scope of the invention, for example:-

Although the embodiments described have a series of six buttons on one side of the facing plate 84, minimal modification would be required in order to allow a far greater number of buttons 88 to be provided on either or both sides of the facing plate 84. This may be desirable in order to increase the number of permutations to the code available or to simply have the buttons on one side of the apparatus rather than the other depending upon the layout of the door or other structure on which the apparatus is installed.