GB2129866A - Key operated lock - Google Patents

Abstract

A key-operated lock has tumblers (26-28) biased into a position to prevent movement of a bolt (15) by a single spring element (22), the provision of a single spring element (22) facilitates assembly of the lock and enables the use of a spring of substantial strength, all of the force of which can be utilised to return a tumbler movement of which is more difficult than the other tumblers from a bolt movement permitting to a bolt movement preventing position. <IMAGE>

Description

SPECIFICATION Key-operated locks The present invention relates to key-operated locks of the kind comprising a plurality of tumblers adapted to be moved by a key to permit of movement of a bolt between a locking position and an unlocked position, the tumblers having an at rest position in which they prevent movement of the bolt.

Locks as described above are usually provided with a plurality of springs to apply a resilient force to each of the tumblers in order to bias them into their "at rest"position in which movement of the bolt is prevented, such movement usually being prevented through inter-engagement of the tumblers with a part carried by, or associated with, the bolt.

It is known for each tumbler to be resiliently biased into an "at rest" position, the biasing means usually comprising a spring, such as a wire spring, having one end engaged with a slot or other recess formed in the tumbler, the other end of the spring bearing against a surface so that on assembly of the lock, the spring is in a bent condition to provide said biasing force.

Such an arrangement of a lock and the form of biasing the tumblers can lead to problems.

Since each tumbler has its own spring and it is usual to provide several tumblers in a lock, the assembly of such a lock, due to the insertion of the springs and subsequent assembly of the tumblers, is time consuming and hence increases the cost of manufacture of such a lock.

Furthermore, since there may be many springs in a single lock, and, it will be appreciated that the resilient biasing force they provide must be overcome by turning the key, the force of each individual spring must be fairly small in order that the key can be turned manually without a very large force having to be exerted by the person turning the key.

Since the resilient biasing force of each spring is therefore relatively small, if foreign matter enters the lock, or the tumblers become rusty, the resilient biasing force may be insufficient to return the tumblers to the position in which they prevent movement of the bolt, thus leading to premature failure of the lock.

It is an object of the present invention to provide a lock that overcomes or reduces the problems mentioned above.

According to one aspect of the present invention, we provide a lock comprising a plurality of tumblers adapted to be moved by a key to permit of movement of a bolt between a locked position and an unlocked position, said tumblers being biased into a position to prevent movement of said bolt by a single spring element adapted to act on said tumblers.

Preferably the dimensions and/or configuration of said tumblers, said spring element and said key are such that said spring element acts on said tumblers substantially continuously throughout their movement between a bolt movement preventing position and a bolt movement permitting position.

Preferably said spring element may comprise a single leaf spring having end portions, one of the end portions of the leaf spring being adapted to bear on the tumblers, the other end portion being adapted to bear on another part of the lock.

Conveniently the leaf spring has a width sufficient to enable the spring to bear on the tumblers, thereby obviating the need for any special bearing arrangement.

Preferably said spring element may comprise a single piece of spring wire and conveniently may have a loop formed between its end portions for locating the spring element, one of the end portions of the spring element being adapted to bear on the tumblers, the other end portion being adapted to bear on another part of the lock.

Conveniently the end portion of the spring wire which bears on the tumblers may be bent to provide an end portion capable of engaging all of the tumblers.

A lock incorporating such spring means is easier and faster to assemble thereby decreasing the production time and hence reducing the manufacturing costs. The cost of a single spring element may also be significantly less than the cost of a plurality of individual spring elements.

Furthermore, since when operating the lock the key only has to overcome the force of a'single spring, theforce applied by the single spring may be greater than the force applied by each individual spring element provided in known locks, enabling the spring element in the lock of the present invention to be of a larger physical size and hence more robust, which assists in decreasing the likelihood of failure if movement of one of the tumblers back to its "at rest" position is hindered since in such case all the force of the stronger spring will be applied to the errant tumbler until it takes up its normal position.

An embodiment of the present invention will now be described in more detail, with reference to the accompanying drawings, wherein: FIGURE 1 is a perspective view of one embodiment of lock of the present invention; FIGURE 2 is a section through the tumblers of the lock shown in Figure 1 with a key inserted; FIGURE 3 is a perspective view of a lock having an alternative form of spring.

Referring first to Figure 1, the lock comprises a casing generally indicated at 10, which casing 10 will have a cover plate (not shown) for enclosing the lock mechanism within the casing, which cover plate is secured in position by a fastener threadedly engaged with a thread formed on an upstanding spigot 11.

A spring loaded catch element 12 is operable by a handle (not shown) passing through an aperture 13 and which has a cam arrangement acting on forked member 14.

A bolt 1 5 is mounted for sliding movement relative to the back face 1 6 of the casing 10 and has an unlocked position, as shown in Figure 1, in which it does not project beyond the face 1 7 of the plate 18, and a locked position in which it projects outwardiy from the face 1 7.

The bolt 15 is moved manually by operation of a key, part of which is shown at 20 in Figure 2, movement of the bolt 1 5 is being prevented by a plurality of tumblers generally indicated at 21 which are biased into an "at rest" position as shown in Figure 1 by a leaf spring element 22.

Movement of the bolt 1 5 from either its locking position or its unlocked position is not possible.

Such movement of the bolt 1 5 is prevented by inter-engagement between a projecting element or elements on the bolt such as the tongue 23 extending from the bolt slide plate 24 and projections on each tumbler such as the projection 25 formed on tumbler 26.

Each of the tumblers 26,27 and 28 is formed with a projection, to interfere with tongue 23 and so prevent movement of bolt 1 5.

In order to cause movement of the bolt 15, the tumblers 26 to 28 first have to be displaced. The tumblers are mounted for pivotal movement on a pin 28 and on insertion of key 20 and rotation thereof are engaged by the key and are pivoted in a clockwise direction about the pin 28.

The dimension of the tumblers 26 to 28, at least in the region contacted ty the key 20, and the arrangement and width of leaf spring 22 and key 20 ensure that the end portion 30 of leaf spring 22 contacts all the tumblers 26 to 28 during their movement between bolt movement preventing and permitting positions.

Since movement of the key 20 necessarily has to overcome the force of the spring 22 in order to reiease the bolt and then move the bolt, the smallest force applied to the tumblers is that provided by the spring 22, such force being necessary to return the tumblers to their "at rest" position.

If for any reason one of the tumblers has its return movement towards its "at rest" position interfered with, for example by a foreign body entering the lock, or the presence of rust on the tumblers or a part with which they are in contact, then all of the force of the spring 22 would be applied to that tumbler, assuming the others are free to move, until it took up its normal position when the end portion 30 of spring the 22 would abut all three tumblers 26 to 28.

The provision of a single leaf spring 22 formed with one end region 30 extending over the tumblers 26 to 28, and with its other end region 31 bearing against the lock casing enables speedy and simple assembly of the lock, the leaf spring element 22 has a centre portion 32 which conveniently bears against the spigot 11, to both locate and prestress the leaf spring 22.

Referring now to Figure 3 which illustrates a lock similar to the lock shown in Figure 1, the difference is that the leaf spring 22 has been replaced by a wire spring 35 having one end region 36 bearing against the lock casing, the other end 37 being bent to extend over the tumblers 26 to 28, the spring wire element 35 being formed with a central loop portion 38 so that the spring 35 may conveniently be located around spigot 11.

It will be appreciated that whereas only three tumblers have been shown, the lock may have any number of tumblers and the spring element 22 may be of any desired configuration and could, for example, comprise a coil spring acting directly or through follower means on the tumblers.

The features disclosed in the foregoing description, in the following claims and/or in the accompanying drawings may, both separately and in any combination thereof, be material for realising the invention in diverse forms thereof.

Claims (12)

1. A lock comprising a plurality of tumblers adapted to be moved by a key to permit of movement of a bolt between a locked position and an unlocked position, said tumblers being biased into a position to prevent movement of said bolt, by a single spring element adapted to act on said tumblers.

2. A lock according to Claim 1 wherein the dimensions and/or configuration of said tumblers, said spring element and said key are such that said spring element acts on said tumblers substantially continuously throughout their movement between a bolt movement preventing position and a bolt movement permitting position.

3. A lock according to Claim 1 or Claim 2 wherein said spring element comprises a leaf spring, one end of which is located relative to the casing of the lock, said leaf spring having a portion which bears on said tumblers.

4. A lock according to Claim 3 wherein the portion of said leaf spring which bears on said tumblers comprises an end portion.

5. A lock according to Claim 1 or Claim 2 wherein said spring element comprises a single piece of spring wire having a portion located relative to a casing of the lock and a portion which bears on said tumblers.

6. A lock according to Claim 5 wherein said spring wire has a loop formed between its ends for locating the spring element relative to said casing, said spring wire having two based end portions, one end portion bearing on said tumblers and the other end portion bearing on the lock casing.

7. A lock according to Claim 5 or Claim 6 wherein the portion of said spring wire which bears on the tumblers comprises an end portion, which end portion is bent relative to the part of the spring wire from which it extends so as to provide an end portion capable of engaging all of the tumblers.

8. A lock according to any one of the preceding claims wherein said tumblers are mounted such that, in use of the lock said tumblers are biased into their bolt movement preventing position by said spring element and by the force of gravity.

9. A lock according to Claim 1 or Claim 2 wherein said single spring element comprises a coil spring.

10. A lock substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

11. A lock substantially as hereinbefore described with reference to and as illustrated in Figure 3 of the accompanying drawings.

12. Any novel feature or novel combination of features disclosed herein and/or shown in the accompanying drawings.