GB2313148A - Locks - Google Patents

Abstract

A key-operated lock, especially a slam lock, has a bolt plate (16) which is withdrawn by operation of the levers of the lock via an interposed slide plate (24). In the locked condition, a solenoid operated stop block (44) engages a notch (48) in the slide plate, so preventing the bolt (14) from being withdrawn. The solenoid (40) is energised only when an authorised access code is supplied. The key may be arranged to trigger a time delay via a microswitch (68) before the solenoid (40) is energised.

Description

LOCKS This invention relates to key-operated locks suitable for use as door locks, especially where enhanced security is required, the lock being of a lever type having a sliding plate that actuates the bolt of the lock. The invention is especially, though without limitation, applicable to slam locks.

A conventional type of security door lock in common use has a set of levers, typically five or more, which, when displaced by the correct key, enable a sliding plate to be drawn back; the sliding movement of this plate withdraws the bolt, so that if there is no other lock on the door not yet unlocked, the door can then be opened.

Numerous ways of increasing the resistance of such locks to unauthorised tampering are known. For example, in some cases hardened steel rollers are fitted within the bolt, to increase the difficulty of sawing through the bolt. Such locks are however not fully proof against being picked, or operated by means of a skeleton key. Furthermore, this expedient is not available in a slam lock.

In general, if a way can be found to displace the levers correctly without using the authorised key, then the lock can be opened.

An object of the invention is to overcome this disadvantage, and to improve the security of a conventional key-operated lever lock, especially a slam lock.

According to the invention in a first aspect, a keyoperated lever lock for a door, having a sliding plate for actuating the bolt of the lock, also has an electrically-releasable stop element cooperating with the sliding plate to prevent retraction of the bolt.

In the case where the bolt is carried by a sliding bolt plate actuated by a slide plate, the stop element is preferably arranged to cooperate with the slide plate.

The stop element may be mounted for reciprocating or swinging movement into and out of engagement with the said sliding plate. In the former case, the lock preferably contains a solenoid carrying the stop element, while in the case of a pivoted or swinging stop element, the lock preferably contains an electromagnet for moving the stop element.

The lock may also have an interruptor, such as a microswitch, which is preferably actuated directly by the key, so as to operate a time delay device for delaying release of the stop element from the sliding plate.

According to the invention in a second aspect, a security system comprises a door provided with a lock according to the first aspect of the invention, and a control system including an electronic access control unit and input means for supplying coded enabling signals to the access control unit, an output of the latter being connected electrically to electrical actuating means in the lock, whereby the stop element is released from the sliding plate only after a said enabling signal has been received.

Some preferred embodiments of the invention will now be described, by way of example only and with reference to the accompanying simplified drawings, in which: Figure 1 is a front view of a slam lock according to the invention in a first embodiment, with its cover plate removed, the lock being shown in its locked condition; Figure 2 is a view in cross section taken on the line II-II in Figure 1, with some parts omitted for simplicity, and some shown only partly; Figure 3 is a partial view corresponding to Figure 1 but with the levers omitted, the lock being shown unlocked and in its released condition, i.e. with the bolt withdrawn; Figure 4 shows a modified embodiment of certain components of the lock; Figure 5 is a view as seen from the right hand side of Figure 4; and Figure 6 is a schematic circuit diagram of one electrical control system for a lock according to the invention.

Reference is first made to Figures 1 to 3, in which the slam lock has a rectangular case 10 closed by a cover plate 12 (Figure 2), in which a keyhole, not shown, is formed. A bolt 14, sliding in a rectangular hole 11 in one end wall of the case, is carried by a bolt plate 16 which slides against the base 18 of the case, in which a hole 34 is aligned with the keyhole for engaging the nose of the key. The bolt plate has a window 20 engaged by a first lug 22 of a slide plate 24 having a camming surface 25 for engagement by the key (not shown), so as to move the plate 24, and therefore the bolt 14, to its withdrawn position shown in full lines in Figure 3.

The plates 16 and 24 are able to slide horizontally with respect to a post or pillar 26 fixed to the base 18, these plates being formed with slots 27 for this purpose. A return spring 29 engages the back of the bolt 14 for returning the latter to its extended (locking) position shown in Figure 1.

The slide plate 24 has an outwardly projecting second lug 28 engaged in the cam slots 30 of a set of levers 32, which are pivoted freely on the post 26. The levers 32 are shown partly cut away in Figure 2. In this example there are five levers, displaced by the key when the latter is inserted through the keyhole 34 and turned. There may of course be any desired number of levers. Each lever has the usual return spring 36 in the form of a leaf spring engaging a fixed boss 38 in the case 10. Displacement of the levers 32 by the correct key enables the slide plate 24 to be moved to the left (Figure 3), so withdrawing the bolt 14.

The door to which the lock is fitted can then be opened, and the bolt 14 is returned to its extended position (Figure 1) by the spring 29. The bolt has the usual camming surface whereby, when the door is closed, the bolt engages the striker plate on the doorpost, which pushes it back into the retracted position (seen in full lines in Figure 3) until the door is fully home, so that the spring 29 can again push the bolt 14 to its Figure 1 position. Since the bolt is now concealed within the structure around the door, it can only be withdrawn by operation of the correct key to unlock the lock.

Thus far, the construction and operation of the lock are well known.

A solenoid 40 is fixed to the case 10 within the latter, and incorporates a plunger 42 carrying a stop block 44. The plunger 42 carries a light coil spring 46, to bias the block 44 to its extended position, shown in Figures 1 and 2, when the solenoid is deenergised.

With the bolt 14 in its extended position (Figure 1), the stop block 44 cooperates with the slide plate 24 by engaging in a notch 48 formed in the rear end of the slide plate, thus preventing any rearward movement of the latter. Thus, any unauthorised attempt to displace the levers 32 or slide plate 24, whether using the correct key or otherwise, cannot cause the slide plate 24 to move, and cannot therefore retract the bolt 14.

To enable unlocking to take place, the solenoid 40 is energised, so raising the stop block 44 clear of the lock mechanism, as shown in Figure 3. The key can now be used in the normal way to actuate the levers 32 so that it can be rotated to engage the camming surface 25 and so draw the slide plate 24 back to the position shown in full lines in Figure 3, thus causing the bolt 14 to be retracted. Figure 3 shows a circle of revolution 70 of the key: the radius of this circle is the radius of the key with respect to its axis of rotation.

Once the lock has been unlocked, the solenoid can be de-energised. As the bolt 14 and slide plate 24 are urged to the right by the spring 29, the spring 46 returns the stop block 44 to its inhibiting position shown in Figure 1.

It should be noted from Figure 2 the rear side of the stop block has a rebate 49 to give clearance for movement of the bolt plate 16 when the block 44 is in its lower position.

Figures 4 and 5 show a modified slide plate 50 having a modified form of the lug 22 that engages the bolt plate, and with stiffening ribs 52 formed adjacent to the notch 48. It will of course be realised that in a lock according to the invention the slide plate, and other components, may be of any appropriate design, and not necessarily those shown in the drawings.

In Figure 4, in place of the solenoid 40 there is a fixed electromagnet 54. The reciprocating stop block 44 is replaced by a stop finger 56, carried by a pivot 58 in a fixed location in the casing for swinging movement between the engaged position shown in full lines, in which it engages in the notch 48 to prevent movement of the slide plate 50 to the left in the Figure, and the raised position shown in phantom lines, in which the slide plate is free to move. The finger 56 is in this raised position when the electromagnet 54 is energised, and it is biased towards its lower position, in which it engages the notch 48 when the magnet is de-energised, by a return spring (not shown), such as a torsion spring around the pivot 58.

The electrical actuating means for releasing the stop element 44 or 56, i.e. the solenoid 40 or electromagnet 54, may be energised from any suitable source and according to any desired procedure. Figure 6 illustrates diagrammatically elements of a security system comprising a door 60 having a lock (which may be a lock according to the invention), and a control system. In this control system a keypad 62, mounted on the outside of the door, is connected, via a set of signal wires 64 passing through the door, to an electronic access control unit 65. The latter is fitted to the inside of the door or in another suitably concealed position, together with a power source 66.

The power source may for example consist of a rechargeable battery connected to the mains through a charger, not shown. Coded enabling signals, keyed in on the keypad 62, are received by the unit 65, and the solenoid 40 or electromagnet 54 is connected across output terminals of the unit 65. The latter energises the element 40 or 54 in response to the correct enabling signals.

This action may if desired, however, be subject to a predetermined time delay after the enabling code has been keyed in. In that case, the unit 65 incorporates a suitable time delay circuit, in the form of a pulse counter which is started when an interruptor 68 is closed.

In addition, the system may include a suitable time clock 78, such that the enabling signal will only be transmitted within a time period preset on the time clock.

The interruptor 68 may for example be a microswitch fitted inside the lock case 10. Figures 1 and 3 show such a microswitch 68 which is operated by the key in such a way that the key deflects the actuating lever 72 of the switch so as to close the latter. A leaf 74, such as a brass shim, may be interposed over the lever 72 so as to prevent damage to the lever by the key.

The lock may for example be fitted to a door of a room, or a door of a safe. It may have additional locking devices, and these may include one or more electrically-operated locks or security bolts. These may be arranged to be released by keying in the access code on the keypad 62: by way of example, Figure 6 shows diagrammatically two electric security bolts 76, connected in parallel with the element 40 or 54 to the output of the access control unit 65.

It will be appreciated that modification of a conventional security lock, especially a slam lock, for operation in accordance with the invention, is relatively simple and involves only the fitting of the stop element and its associated electrical release device (such as 44 or 56, and 40, 54 respectively); and minor modification of the slide plate to ensure proper engagement with the stop element.

The sliding member engaged by this stop element may be the bolt plate where the lock is one that does not have a slide plate interposed between the bolt plate and the levers. The bolt plate is then engaged directly by the key.

Claims (12)

1. A key-operated lever lock for a door, having a sliding plate for actuating the bolt of the lock, and an electrically-releasable stop element cooperating with the sliding plate to prevent retraction of the bolt.

2. A lock according to Claim 1, wherein the bolt is carried by a sliding bolt plate actuated by a slide plate, the stop element cooperating with the slide plate.

3. A lock according to Claim 1 or Claim 2, wherein the stop element is mounted for reciprocation into and out of engagement with the said sliding plate.

4. A lock according to Claim 3, having a solenoid carrying the stop element.

5. A lock according to Claim 1 or Claim 2, wherein the stop element is pivoted for swinging movement into and out of engagement with the said sliding plate.

6. A lock according to Claim 5, having an electromagnet for moving the stop element.

7. A lock according to any one of the preceding Claims, having an interruptor arranged to be actuated as the lock is unlocked, for operating a time delay device for delaying release of the stop element from the sliding plate.

8. A lock according to Claim 7, wherein the interruptor is operable directly by the key.

9. A key-operated lock for a door, substantially as described in the foregoing description with reference to Figures 1 to 3 of the accompanying drawings.

10. A lock according to Claim 9 when modified substantially as described in the foregoing description with reference to Figures 4 and 5 of the accompanying drawings.

11. A security system comprising a door having a lock according to any one of the preceding Claims, and a control system including an electronic access control unit and input means for supplying coded enabling signals to the access control unit, an output of the latter being connected electrically to electrical actuating means in the lock, whereby the stop element is released from the sliding plate only after a said enabling signal has been received.

12. A system according to Claim 11, in which the lock is a lock according to Claim 7 and wherein the access control unit includes a time delay device, the said interruptor being connected to an input of the access control unit.