GB2060763A - Lever locks - Google Patents

Abstract

A lock (10) employing sliding (as shown) or pivoting lever tumblers is provided with means to prevent double rotation of the key (11) consisting of a rotor (21) surrounding the key and rotating with it, and a leaf spring (27) tangential to the rotor (21) and engaging against a radial abutment face (26) when an attempt is made to rotate the key further after locking. The leaf spring (27) is held away from the rotor (21) until the first, locking rotation of the key takes place, by a portion of the bolt lath. <IMAGE>

Description

SPECIFICATION Lever locks Description of invention This invention relates to lever locks.

A lever lock has a plurality of pivoted or slidably mounted levers or detainers which are adapted to be engaged and lifted by rotation of a compatible key. The levers or detainers have aperture means through which, when the levers or detainers are correctly lifted by the key, a projection on a bolt lath can be passed, the bolt lath being moved under the control of the key from an unlocked condition to a locked condition. A lever lock as described above will hereinafter be referred to as being "of the type specified".

The invention particularly relates to lever locks of the type specified which are made to standards such that they can be regarded as security locks complying with British Standard No. 3621.

In such a security lock, it is customary to provide a rotor, sometimes known as a "curtain" which has a restricted opening for entry of the key, which cannot therefore be inserted into the lock if the rotor is not correctly aligned with the key-hole.

A detent is provided to prevent the rotor from rotating except when it is being turned by the key so as to ensure that the rotor is in a correct position for reinserting the key after it has. been removed from the lock.

It is a necessry feature of a security lock that it cannot be "pushed back" to allow a condition in which the key has been turned but the bolt has not been shot to the "locked" condition. This could happen if the key did not positively control the sliding movement of the bolt lath and some obstruction was placed in the way of the bolt either accidentally or deliberately.

Furthermore, once the bolt has been shot to the "locked" condition, it is a requirement that a second rotation of the key in the same direction, with consequent lifting of the levers, cannot take place. If a second rotation could take place, this could release the force which positively holds the bolt in the locked condition.

It has previously been proposed to prevent double rotation of the key by various means but none of these has been entirely satisfactory, particularly in relation to locks of a relatively small size.

For example, it has been proposed to alter slightly the "timing" of the lifting of the levers relative to the rotation of the key by providing slightly distorted cam surfaces on the levers to be engaged by the key bit. The levers therefore lift with a slight intermediate dipping movement so that the bolt lath can pass through in forward movement on the first rotation of the key but so that the levers are obstructed and cannot lift fully on a second movement. This alteration of the timing is difficult to achieve and it is thought possible that extra wear on the lever cam surfaces may reduce the life of the lock and that any failure of the lock as a result could occur when the bolt is partly or wholly engaged.

Another proposal has been to utilise a stop on the rear of the bolt lath. As the bolt is shot, by the first turn of the key, this stop moves with the bolt lath into a position where it obstructs the further rotation ot the key, preventing a second turn. This arrangement is effective but requires the bolt lath to be relatively long and in turn this means that the lock must be relatively large.

It is an object of the present invention to provide a lever lock of the type specified in which a second rotation of the key is prevented by a new or improved means.

According to the invention there is provided a lever lock of the type specified including a member rotating in unison with the key and having a recess means, and a stop means co-operable with the recess means to arrest rotation of the member, the stop means being resiliently mounted and being held out of the path of movement of the recess means by the bolt lath only when the bolt lath is in the fully withdrawn "unlocked" condition.

The member rotating in unison with the key may comprise a rotor or curtain having a restricted opening for entry of the key.

The stop means may comprise a leaf spring disposed generally tangentially of the rotor. The recess means may comprise a notch having an abutment face disposed generally radially of the rotor.

The abutment face may be disposed adjacent or may form part of a rotor detent notch cooperable with a detent spring provided adjacent the leaf spring and capable of acting as a detent to hold the rotor in a condition in which the key can be inserted and removed through the restricted opening of the rotor. Thus, the detent spring will be provided in such a position that it operates when the key-hole and the restricted opening in the rotor are aligned. The adjacent abutment face of the notch will then be engaged by the resiliently mounted stop means if an attempt is made to rotate the key further than this position when the bolt has been shot to the locked condition. It will be appreciated that, while the bolt is in the fully withdrawn "unlocked" condition, the stop means is held out of the path of the recess means and hence cannot arrest its motion.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings in which: FIGURES 1 and 2 are sequence drawings of the lock mechanism in the fully unlocked and partly locked conditions; FIGURE 3 is a detail view of part of the lock when the key has been rotated through a full 3600 rotation; FIGURE 4 is a detail similar to Figure 3 but showing the condition of the lock when the key is rotated slightly beyond the 3600 rotation shown in Figure 3.

Referring to Figures 1 and 2 of the drawings, a lever lock is generally indicated at 10 and includes a key-hole in which a key 11 can be seen, a plurality of levers or detainers 12, movable by rotation of the key 11 and a bolt 13 which can be caused to slide in response to movement of the key 11 between an "unlocked" condition shown in Figure 1 and a fully locked condition in which the bolt 1 3 projects into a corresponding socket (not shown). The lock 10 will normally be mounted in or on a door and the socket will normally be found in the jamb of the door.

The levers or detainers 12 are, in the example shown, mounted for sliding movement on a pair of pegs 14. In an alternative form, they could be mounted for pivotal movement about a single peg but the principle of operation is the same whether levers or detainers are used. Each lever has a pair of large apertures 1 5 joined by a narrow passageway 1 6, the position of the passageways 16 varying from one lever to the next. The key 11 is so shaped that, as it rotates, it engages cam edges 17 of the respective levers and each is lifted by an amount depending on the shape of the key.

Only when the correct key is used will all of the levers be lifted by the correct amount so that the passageways 1 6 are all aligned. Simultaneously, rotation of the key drives a bolt lath 1 8 which is formed integrally or is secured to the bolt 13. The bolt lath 1 8 is slid longitudinally, having a cam surface co-operable with the key 1 The timing of the lock is such that, as the key rotates, the bolt lath is slid to a position where a projection 1 9 carried on the bolt lath passes through the aligned passageways 1 6 of the levers.The levers are biased downwardly by individual leaf springs 20 so that they remain positively controlled by the key as it rotates against the cam edges 1 7 and the bolt lath is also positively controlled by the key during its sliding movement.

By comparison of Figures 1 and 2 of the drawings, it will be seen that the projection 19 has moved from one of the large apertures 15 of the levers to pass through the passageways 1 6 of the levers and it will also be seen that some of the levers have been raised by a greater extent than others according to the shape of the key.

Referring to Figure 3 of the drawings, this is a detail view showing the condition of part of the lock 10 when the key has been rotated through 3600 from the initial position and the bolt has been shot fully home to the "locked" condition.

It will be seen that the key is inserted through a rotor 21, sometimes known as a "curtain" which affords extra security to the lock. The rotor 21 takes the form of a disc having a slot 22 which provides a restricted opening through which the key can be inserted and also comprises an axially slotted cylindrical tubular part 23 which receives the stem of the key. The presence of the rotor permits the key to be inserted only when the lock is either fully locked or fully unlocked because the slot 22 must be aligned with the key-hole. To ensure that no movement of the rotor takes place when the key is not present in the lock, a detent is provided by means of a V-shaped spring 24 engaging within a detent notch 25 which is also a V-shape.The spring 24 can be forced out of position simply by rotation of the key but the position of the detent can be "felt" by the user and the detent is sufficient to hold the rotor in position once the key has been removed from the lock.

Alongside the detent notch 25, there is provided a generally radially disposed abutment edge 26 which is co-operable with a leaf spring 27 to prevent the key from being rotated more than once in the locking direction. It will be seen that the leaf spring 27 is mounted by means of a rivet or the like in the casing of the lock and is directed tangentially of the rotor 21 directly towards the abutment face 26. When the lock is in the unlocked condition shown in Figure 1 of the drawings, the rear of the bolt lath engages the leaf spring 27 and holds it out of the path of rotation of the rotor until the bolt lath moves through the condition shown in Figure 2 of the drawings, whereupon the leaf spring 27 is released by the bolt lath.Continued rotation of the key through the full 3600 takes place without hindrance but, once the key has reached the condition shown in Figure 3, the detent provided by the spring 24 and notch 25 has to be overcome and then the leaf spring 27 engages the abutment face and arrests the rotation of the rotor 21. Since the key cannot move without the rotor, this effectively prevents the key from moving any further and completely eliminates the possibility of the levers being raised for a second time by a second rotation of the key.

The resilience of the leaf spring tends to force it in a direction towards the levers and any force exerted on the key in an attempt to force it past the condition shown in Figure 4 of the drawings, that is its limit condition, only results in the leaf spring being more firmly trapped between the abutment face 26 and the side faces 28 of the levers. The side faces 28 are cut away or tapered as shown so as to make the locking action very positive.

Thus, it will be seen that a second rotation of the key is prevented by means which occupy very little space within the lock, namely, the small leaf spring 27 located alongside the levers. This is the only additional part which needs to be used in the lock since the rotor is already present for other reasons. The only further modification which is required is the provision of the generally radial abutment face 26.

Claims (6)

1. A lever lock of the type specified including a member rotating in unison with the key and having a recess means, and a stop means cooperable with the recess means to arrest rotation of the member, the stop means being resiliently mounted and being held out of the path of movement of the recess means by the bolt lath only when the bolt lath is in the fully withdrawn "unlocked" condition.

2. A lever lock according to Claim 1 wherein the member rotating in unison with the key comprises a rotor or curtain having a restricted opening for entry of the key.

3. A lever lock according to Claim 2 wherein the stop means comprise a leaf spring disposed generally tangentially of the rotor.

4. A lever lock according to Claim 2 or Claim 3 wherein the recess means comprise a notch having an abutment face disposed generally radially of the rotor.

5. A lever lock according to Claim 4 wherein the abutment face is disposed adjacent or forms part of a rotor detent notch co-operable with a detent spring provided adjacent the leaf spring and capable of acting as a detent to hold the rotor in a condition in which the key can be inserted and removed through the restricted opening of the rotor.

6. A lever lock of the type specified, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.