GB2290107A - Door securing device - Google Patents

Abstract

A securing device for doors, particularly doors of a railway carriage, has a latching arrangement including a latch bolt 43 and a corresponding receptor into which the bolt is to be urged, the latch bolt being designed for use in a secondary locking system. In order to allow the latch to open even when a passenger is leaning against it, the latch bolt has an oblique end surface so that it can be pushed out of the receptor by a force applied in a direction transverse to the urging direction. To make the latch nevertheless secure when the train is moving the latching arrangement further includes a deadlocking means provided by bellcrank 49 and a recess 40 operable on the bolt 43 so as to prevent the bolt being pushed out when the deadlock has been actuated. The device preferably includes a mechanical sensor (55), (Fig 6B) to indicate whether the door is closed. The deadlocking means in (Fig 2a) includes a pair of pivoted levers. <IMAGE>

Description

Door Securing Device for Secondary Locking System The invention relates to a door securing device with particular application to securing the doors of passenger trains.

One of the main safety problems on passenger trains is the danger to passengers when the doors are opened prematurely as the train enters a station or indeed should a door open while the train is in motion.

On some more recently constructed trains, these problems are overcome with the installation of pneumatically operated doors. The driver of such a train is able to check that the doors are closed before leaving a station because sensors in each doorway indicate the open or closed status of the doors.

Furthermore, it is only possible for a passenger to open a door when the train is stationary owing to a disabling means acting on the door mechanism while the train is in motion. Unfortunately older rolling-stock is not provided with such safety features.

Older trains are provided with conventional hinged doors having a straightforward mechanised latch operated manually by the passenger. Such a door is shut by slamming the door and opened by manually withdrawing the latch against a spring. The safety problems with such a system are numerous. In particular, the station staff have to rely on a visual check of the doors to ensure that they are secure and, with passengers able to climb aboard even as the train is leaving, this check is often not sufficient. In any case it does nothing to solve the problem of passengers opening the door while the train is in motion and once a door is just slightly ajar there is a high likelihood of the door being pulled open by aerodynamic effects.

Replacing existing doors would be very expensive and it is therefore desirable to find a way of preserving the existing doors while overcoming the problems of (a) ensuring the doors are closed before setting the train in motion and (b) improving the safety of the doors while the train is in motion. In general terms therefore a secondary locking system is required, in particular one which can be fitted to existing doors.

Such a system has been described before in UK patent application no. 9401335.6. This discloses a door securing system including a primary latch of conventional design and a second bolt system operated remotely by for example the driver of a train.

Essentially the driver causes a second bolt mounted in the door frame to be shot home or withdrawn depending on the situation, and a sensor system is included to allow the driver to detect whether the doors were safely secured or not.

A problem with this locking system is the difficulty in releasing the second latching arrangement, i.e. withdrawing the bolt, when a side load was applied, the typical instance of this being when a passenger had operated the first latch bolt and was pushing the door outwardly while waiting for the second bolt to be released. The side load effectively prevented the second bolt from being withdrawn. This problem could in theory be overcome by increasing the size of the components so as to overcome a reasonable side load. However, apart from the expense this solution is disadvantageous where space considerations are of importance.

It is an aim of the present invention to provide a door securing system having a latch arrangement which may be operated against a side load. In particular this latch arrangement is suitable for use as a remotely controlled second latch arrangement in addition to a conventional locally operated latch as already indicated above.

According to one aspect of the present invention there is provided a securing device for doors having a latching arrangement including a latch bolt and a corresponding receptor into which the bolt is to be urged, wherein the latch bolt has a cam means such as an oblique end surface so that it can be pushed out of the receptor by a force applied in a direction transverse to the urging direction, and the latching arrangement further includes a deadlocking means operable on the bolt so as to prevent the bolt being pushed out when the deadlock is actuated.

By giving the bolt of the security device an oblique camming surface on the opening side, in addition to the usual oblique face which allows a door to be pushed shut, the bolt can act as a spring latch which can be released by pushing on the door because the slanting face rides up on the edge of the receptor.

A door using the securing device can thus be held shut by the deadlock but once the deadlock is released the latch presents no obstacle to the door being opened.

In its application to railway rolling stock, it is envisaged that this latching arrangement is provided as a secondary latching arrangement in a locking system having a conventional manual first latching arrangement to be operated by a passenger. However, in its application for example to door securing systems in buildings, the function of the latch bolt is to operate as a simple ball catch, but one which is securable or releasable by means of a possibly remotely operated dead-locking system. This is thought to be particularly suitable for use in fire doors. It may be unnecessary in such applications for a manual main latching arrangement to be present.

The deadlocking means can simply be an elbow-lever arrangement which has a top-dead-centre position into which it can be urged by an actuator, the lever in this position preventing the bolt from retracting into the housing. The lever can be constructed so that it is urged out of the top-dead-centre position by a restoring means such as a torsion spring so that when the actuator is released, the bolt is able to be retracted reliably into the housing; a second pneumatic activator could also be used as a restoring means.

In an alternative version a lever arrangement can be used in which a single lever pivots about a point in the housing and has a part which abuts against the latch bolt. In one pivot position the lever is deadlocked by virtue of the pivot point and the abutment being parallel to the line of action for retracting the bolt, while when the lever is pivoted out of this position, for instance by an actuator or return spring, the bolt can be retracted.

For automatic systems a sensor is preferably associated with the bolt. In railway doors this sensor would give a signal indicating whether the door was shut. In a particularly advantageous manner the sensor can be designed to act as an additional means of releasing the deadlock of the bolt itself as it moves from the "open" indication to the 11closed" indication.

This ensures that slam-shutting of a railway carriage door is still possible after the deadlock actuator is activated if this occurs while the door is open. Such a sensor could itself have a latch-like construction.

The invention in another aspect relates to methods for adapting existing door latches by the addition of the above described latch mechanism as a second latch mechanism, as described, to the frame of the door and a corresponding receptor arrangement on the door.

The invention might be constructed in a number of ways but one specific embodiment will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a schematic view of a locking system suitable for securing a train door which is mounted in a door frame, the corresponding components being mounted in the door; Figures 2(a) and (b) are cross-sectional views of the door-mounted components and show the dead-locking arrangement in unlocked and locked configurations respectively; Figure 3 is a cross-sectional view of the doormounted locking arrangement showing sensor means and lock-out arrangement; Figure 4 is a cross-sectional view of the locking arrangement including the microswitch; Figure 5 is a vertical cross-section of the apparatus at the level of the second bolt;; Figures 6A-D show a second embodiment of the invention schematically in various configurations; and Figure 7 gives a more detailed view of the embodiment of Figure 6.

As shown in Figure 1, the door-securing apparatus essentially comprises two integrated latching arrangements, the components of which are mounted partly in the door and partly in the door frame. The major parts of the first latch are mounted in the door, while the major parts of the secondary latch are in the frame. The door-mounted part, shown generally at 2, contains the first bolt 6 of the first latching arrangement, which is the conventional manual latch.

The first bolt 6 is mounted in a slidable manner and is spring-loaded so that the chamfered lip of the first bolt 6 extends in the resting state outside the door 8.

Pressure on the chamfered edge 6A of the lip causes the bolt 6 to be pushed into its housing. The chamfered edge 6A is on the closing side of the bolt so that the door may be closed and secured easily. The bolt 6 can also be withdrawn into its housing by manipulation of a handle (not shown). Thus far this arrangement is entirely conventional.

Also present on this door-mounted part is an extension of the housing 2, preferably integral, including a recess 1 forming part of a striker plate for the second bolt 3 of the second latching arrangement (to be described), which is the secondary or safety locking system operated by the train crew.

The frame-mounted part, shown generally at 4, houses the bulk of the second latching arrangement and is positioned attached to the door frame so that the receptor 7 in the frame-mounted housing 4 is adapted to receive the lip of the first bolt 6 and correspondingly the receptor in the door-mounted arrangement is adapted to receive the second bolt 3. Both the first 6 and second 3 bolts are spring-loaded so as to extend outwardly from their housings in the normal, resting state. For the door to be opened, both the first and second latching arrangements must be withdrawn against their spring-loading.

Figures 2(a) and 2(b) show in detail the framemounted components of the securing apparatus in the unlocked and locked configurations respectively. Both latches are spring-loaded to extend outwardly from their respective housings so as to be able to interact with their corresponding receptors when the door is closed. In operation in the unlocked configuration of the securing device, a passenger may operate the first locking arrangement by using a handle to withdraw the first bolt 6 from engagement in the receptor 7 in the door frame, and in normal use weight would be applied to the door 8 in order to open it. When the door 8 is pushed resistance will be met since the second bolt 3 is extended into its receptor 1. There is no handle with which to operate this second bolt.

In order to facilitate the withdrawal of the second bolt 3, a cam in the form of an angled face 21A is provided on the interior of the receptor 1 (see Figure 5) which abuts against a corresponding angled face 22A provided on the inner side of the second bolt 3. A side force provided by the weight applied by a passenger so as to open the door 8 causes the two faces to interact and the second bolt 3 is pushed back into the housing 4 against a spring resistance provided by spring 13 and the door can be opened.

Another version of this invention, the spring 13 may be omitted altogether. The secondary bolt 3 may be actuated by the deadlocking means (to be described) so that when the secondary locking is de-energised there is no spring loading forcing the secondary bolt 3 into the receptor 1 and so no additional weight need be applied to the door 8 to open it after the first bolt 6 has been disengaged.

The door-securing arrangement must be such that, once opened, the door may be slammed shut. As in conventional slam-type doors, the first bolt 6 of the present example has a chamfered edge 6A arranged so that when the door is closed it contacts a striker plate and causes the bolt 6 to be pushed back into its housing. In other words, the handle need not be used to withdraw the first bolt 6 on closing the door. Once closed, the first bolt 6 is then able to spring into the corresponding receptor 7 in the door frame.

It must also be possible in the unlocked configuration for the spring-loading of the second bolt 3 to be overcome for slamming the door shut. The above conventional arrangement and the following second bolt design are shown clearly in Figure 5. Here, since the second bolt 3 is also spring-loaded by the return spring 13 so as to extend outwardly from its housing, on closing the door will come up against this second bolt 3. To enable the door 8 to close effectively, the second bolt 3 must be caused to be withdrawn. In this arrangement therefore, a second angled face 22B is provided, this time on the outside edge of the second bolt 3, and a corresponding angled face 21B is also provided on the housing of the door-mounted part of the lock so that the two faces meet when the door is nearly closed.The side force acting between the two faces causes the bolt 3 to be pushed back into its housing until the door is closed sufficiently to allow the second bolt 3 to spring into its receptor 1. Both bolts 3, 6 are therefore resiliently withdrawn by interaction of the angled faces on the bolts and housings respectively allowing the door to close reliably.

In the unlocked state therefore, both bolts act as conventional door bolts, the first bolt 6 having to be actively withdrawn to open the door and the second bolt 3 acting in much the same way as the "ball catch" often seen fitted to domestic cupboards. Indeed the first bolt 6 may be totally conventional meaning that existing bolts may be retained on existing doors as the first latching arrangement, and a second latching arrangement may be added.

To fulfil its function as a remotely operated lockable second latching arrangement, the second latching arrangement is provided with a further mechanical system which acts to lock the door shut to prevent local opening of the door once the locking action has been taken. In this arrangement the first bolt 6 is not affected by this mechanical system and its handle may be operated, withdrawing the first bolt 6 though with no effect on opening the door since it is held shut by the now secured second bolt 3. The mechanical "dead-locking" system effectively prevents the second bolt 3 from operating like a simple "ball catch" and is illustrated in its unlocked and locked configurations in Figs. 2(a) and (b) respectively.

The immobilising of the second bolt 3 - "deadlocking" - is achieved in this example by a system of levers. In a preferred configuration of the invention, an essentially V-shaped lever arrangement is used. One arm or lever 9 is pivoted at one end on a fixed part of the housing 4, and another arm or lever 10 is connected at one end to the end of the lever 9 not connected to the housing 4 and at its other end to an extension 31 of the second bolt 3. A spring 11 is arranged to act between the lever 9 and the housing 4 so as to tend to maintain the "V-shaped" configuration of the levers 9 and 10 when in their resting position as shown in Fig.

2(a). In this embodiment a torsion spring has been employed but alternatives such as tension springs may also be used. A slotted hole 12 is provided in the extension 31 of the second bolt 3 in which the end of lever 10 remote from lever 9 is connected. The slotted hole 12 allows some freedom of movement of the lever 10 so that the V-shaped configuration may be adopted.

With the levers arranged thus, it is apparent that in the unlocked configuration it is possible to push open the door, which in turn pushes back the second bolt 3 against its return spring 13, the angle between levers 9 and 10 possibly becoming more acute depending on the geometry or the length of the slot 12. In the nondead-locked situation therefore the lever system is able to move to follow the movement of the second bolt 3.

To provide the "dead-locking" effect, an actuator 14 is provided such that it bears against either one of the two levers 9 or 10, somewhere in the area of the pivoted joint or actually at the pivoted joint. When operated, the actuator 14 overcomes the action of the spring 11 causing the "V-shaped" configuration and forces the levers into a straight line (Fig. 2(b)) against a stop 10A (which may alternatively be part of the bolt 3 or sensor 15) where they are held in position by the action of the actuator 14. Subsequent force applied against the head of the second bolt 3 will have little effect since the force will be applied in the direction of the straight line configuration of the levers. It is envisaged that the force applied by the actuator 14 to maintain this dead-locking effect need not be large and depends largely on the strength of spring 11.Indeed although in the diagrams, the deadlocking position is shown with the levers in a topdead-centre position, it is envisaged that the relative strength of the actuator and the spring will be such that for deadlocking to occur, the levers need only be in a near top-dead-centre position. Preferably this would be just short of top-dead-centre position.

When the actuator 14 is released, the spring 11 is able to return the levers 9 and 10 to their "V-shaped" position, the second bolt 3 reverts to its "ball catch" operation and may be pushed back to release the door for example by pushing against the door as described above and causing the tapered edges to push against one another as described above. It is envisaged that the mechanical advantage of the lever system is such that a modest spring is adequate as the spring 11 to release the levers from the "straight line locked" position to "unlocked" even if considerable end load is applied to the second bolt 3.

The actuator 14 is preferably an air cylinder. In this embodiment of the invention, a solenoid valve is mounted directly on the cylinder. Operation of the appropriate control circuit for example by the driver of a train operates the solenoid valve which admits or exhausts air from the cylinder and provides an almost instantaneous action. Alternatively a solenoid could be employed as an actuator 14 but for reasons given below, an air cylinder is preferred.

The invention described thus far achieves the basic object in that it provides a secondary locking system which works even when a side load is applied to the bolt. However, for the secondary locking system to be practical, further refinements are necessary. So far, if one or more of the doors are not closed when the secondary system is actuated, the second bolts will become dead-locked and prevent the doors from closing.

The system would have to be disabled centrally to allow the doors to be closed. To prevent this, a visual check could of course be made to establish that the doors are shut before activation of the second bolts.

However, it is desirable that the doors can be instructed to lock when some or all doors are open without the need subsequently to disable the system.

It is also desirable and important from a safety point of view that some means of indicating that all doors are both properly closed and locked is provided.

As shown in Fig. 3 an arrangement is provided to meet these objectives. In the housing 4 is fitted a mechanical sensor 15 which comprises a main arm arranged adjacent the second bolt 3 and an extension 16 extending downwardly from the sensor arm. The sensor 15 is spring-loaded so as to project (35) outside the housing 4 alongside the second bolt 3 by means of a spring 17 which acts between the housing 4 and the arm along its the sensor axis. In the present arrangement the projecting part 35 of the sensor arm extends outwardly to much the same extent as the second bolt 3.

In operation, the sensor 15 is depressed against its spring resistance when the door is successfully closed.

In other words, since it is arranged adjacent and in the vertical plane of the second bolt 3, as the second bolt 3 is depressed as it passes over the edge of the door, so is the sensor 15. However, since there is no receptor in the door leaf for receiving the end 35 of the sensor arm, it remains depressed even as the second bolt 3 is able to spring into receptor 1. With appropriate indicating means the sensor 15 is therefore able to provide a means of indicating that the door 8 is closed (see later).

The extension 16 is provided on the sensor arm for interacting with the lever system. Its purpose is to allow the doors to close even if the dead-locking command has already been given, the dead-locking only taking effect when the door is subsequently closed and without the need to withdraw then re-issue the deadlocking command, as explained below.

In the Figure the plane in which the extension 16 lies is shown above that of the lever system, but it could be below it instead, or even in the same plane.

The deadlocking system must be effective in a number of situations. In the situation where the door is properly closed and the command to dead-lock the second bolt 3 is given, the following configuration exists. The second bolt 3 is extended so as to mate with its receptorin the door 8. The sensor arm 15 is pushed back into the housing 4 since its end 35 abuts against the edge of the door 8 or housing 2 (it has no receptor). In this situation, the extension 16 (being part of the sensor 15) is pushed back in the direction of arrow X towards the rear of the housing and in no way interacts with the lever system comprising lever arms 9 and 10. The dead-locking achieved by actuation of the actuator 14 and the straightening of lever arms 9 and 10 is brought into effect and the door remains dead-locked until the actuator is withdrawn.

In the situation where the door is open (as shown in Figure 3), the second bolt 3 is extended so as to project from the housing 4 as is the projecting part 35 of the sensor 15. In this case the extension 16 of the sensor is positioned so as to interact with the lever system, for example with the pin 36 linking the lever arms 9 and 10. When the actuator 14 tries to push the arms 9 and 10 into their straight line configuration, it is prevented by the extension 16 abutting against the pin 36 and the second bolt 3 is not dead-locked.

If a passenger then tries to shut the door 8, the second bolt 3 is pushed back into the housing 4 in the normal way although possibly with some added resistance caused by the pressure of the actuator 14 on the lever system. Once the door is closed, the second bolt 3 springs into its receptor 1, but the sensor 15 is pushed back into its housing 4, removing the obstruction caused by extension 16 and allowing the lever system to achieve its dead-locking configuration.

The door 8 cannot then be opened again without centrally or otherwise disabling (for example by operating an emergency access device) the dead-locking system.

In the third possible situation where the projection 35 is maliciously depressed while the door is open, in other words so that the extension 16 is not in a position to prevent dead-locking, and the command to lock the door is given, the dead-locking has to be overcome since this would otherwise prevent the door from closing. For this purpose the extension 16 is provided with an angled face 16A. When the sensor 15 has been held depressed while the door is open, the sensor must be released before the door closes, since otherwise fingers would be trapped. No matter how momentarily the sensor is then released, the spring 17 acts on the sensor 15 so as to push it out of the housing and, at the same time, the angled face 16A of the extension 16 is pushed against the pin 36 linking the levers 9 and 10.The camming effect of this force moves the levers into their "V-shape" configuration thereby releasing the deadlocking against the force of the actuator 14. Clearly the relative forces of the spring 17 and spring 11 and the actuator 14 must be balanced accordingly. Also, since the sensor 15 is working against the actuator 14, it is desirable that an air cylinder actuator is employed, as its actuating force is linear throughout its stroke. On closing of the door, the second bolt 3 can now be depressed before shooting into the receptor 1. It will be appreciated that if the second bolt 3 remained in the dead-locked configuration before the door was closed, then it would not be possible to close the door until the actuator 14 was released.

In a practical system it would be desirable in a train for the driver to be aware of the locked or unlocked status of the doors. For this purpose a microswitch 18 is fitted to the housing 4 in such a way that it is operated when the levers 9 and 10 are in a straight line and the second bolt 3 is dead-locked (Fig. 4). It will be appreciated that because of the sensor arrangement 15 described above in normal operation the second bolt 3 can only be dead-locked when the door is closed (or the sensor 15 is held in).

The microswitch is able to indicate this condition, and signals taken from all the doors on the train can be communicated to the driver to inform him in combination with the usual visual check that all doors are correctly closed and locked.

Furthermore, signals may be taken from the microswitch 18 to indicate to both passengers and railway staff (by electrical lamps or other devices not here described) the status of each individual lock or group of locks on a train.

In certain systems the wiring of the remote latching and monitoring circuitry might be such that if all the doors are not secured properly, the vehicle is unable to move. To avoid problems where components such as the microswitch 18 fail, thereby preventing movement of the train although all the doors are secured correctly, a bypass arrangement is included (Figure 3). In this embodiment this comprises a "lock out device 19. The lock-out device 19 is movable between two positions and is retained in these positions by means of a spring 39. The lockout device acts so that the second bolt 3 may be deadlocked by manual or other mechanical means, bypassing for example an air-cylinder failure. A further microswitch 20 is included which bypasses a spurious signal sent from the microswitch 18.In such a way a correct signal for the lock status indicators may be achieved and the train allowed to proceed. It is envisaged that this bypass arrangement may be operated from either inside or outside the vehicle and might require the application of a particular tool or key to prevent misuse.

Although the door securing means has been described where the status of the doors is detected by a combination of a visual check and the microswitch 18 detection, it is apparent that other sensors may also be included. For example a sensor may be positioned in the receptor 7 to detect the presence of the primary bolt 6.

It is desirable that such a door securing means may be provided with a means of releasing the second bolts centrally in an emergency. It is also desirable to provide local emergency releases. Such releases are not here described in detail, but may be simple valves or switches configured to interrupt the air or electrical power supply to the designated locks.

In another embodiment of this invention (shown in Figures 6 and 7), the secondary bolt 43 and sensor 55 are arranged so that they retract into the housing 44 when the lock is not energised. This avoids the possibility of passengers catching clothing or luggage on the protruding bolt or sensor when entering or leaving the train.

Figure 6 shows the secondary lock in four simplified views; in Figures 6A and 6C the secondary lock is deadlocked, the view Figure 6A being shown with the sensor removed for clarity. Figure 6B shows the secondary lock energised with the door open; and Figure 6D shows the secondary lock in the de-energised condition. Figure 7 shows a more representative view of the actual construction.

In this version of the invention, two actuators 41 and 42 are employed, one of which (41) operates analogously to the actuator 14 of Figure 2 to deadlock the secondary bolt 43, while the other (42) takes the place of the return spring 17 fitted to the lock sensor 15. For reasons given previously, air cylinders are the preferred method of actuation. It is possible to arrange the pneumatic cylinders in such a way that the two operating pistons are mounted in a common, monobloc cylinder body 46; this allows the use of a common air supply as shown in Figure 6.

In contrast to the previous embodiment a spring 56 is provided to withdraw the secondary bolt when it is not engaged; this ensures that in the rest state nothing protrudes from the door frame to catch on passengers' clothing or luggage. A projection 47 on the sensor 55 engages with a rearward face 48 on the secondary bolt so that the return spring 56 is enabled to withdraw both the secondary bolt and the sensor into the lock body 50 when the lock is de-energised. The same abutment allows the locking actuator 42 to urge both the sensor 55 and the bolt 43 out of their housing.

An alternative means of providing the deadlock is shown whereby in place of the V-linkage described before a bellcrank 49 is employed in combination with certain inclined faces on the bolt 43 and sensor 55.

The bellcrank is sprung (spring not shown) so as to adopt the non-deadlocking position shown in Figure 6D until acted upon by the actuator 41. A cam 51 (Figure 7) is fitted to the bellcrank so as to operate a microswitch 52 to indicate correct locking.

A shaped cutout 40 is provided in the secondary bolt 43. This prevents the secondary bolt from being deadlocked unless the bellcrank is in the locked position, so as to enable the door to be slammed shut, as will be described below.

When the secondary lock is energised with the door closed, starting therefore from the configuration shown in Figure 6D, the piston 42 pushes the secondary bolt 43 and the lock sensor 55 out until the bolt sensor encounters the body of the primary lock 2. Meanwhile the piston 41 pushes on the lower arm 44 of the bellcrank, causing the pin 45 to impinge with a cam action on the right-hand (door-side) slope of the shaped cutout 40. This action pushes the secondary bolt 43 into the locked position in a manner corresponding to the "straight line position" of the Vlinkage described earlier. The position is locked by virtue of the steep slope of the recess 40 in its base region, in which the pin 45 rests on a level with the axis of the bellcrank 49, i.e. forming a line parallel to the direction of movement of the bolt.

An angled face 66 (corresponding to the face 16A in the previous embodiment of the invention) is provided on the sensor 55 to defeat malicious depression of the sensor when the door is opened and subsequently enable the door to be slammed shut as described before.

If the system is activated with the door open, as in Fig. 6B, the actuator 42 forces both the bolt 43 and the sensor 55 out of the housing. The actuator 41, which can be of a different size to the other activator, as necessary, is unable to rotate the crank 49 clockwise since the leverage on the sloping face 66 is less than the net urging force of the second actuator 42. However, when the sensor 55 is retracted by slamming the door the pin 45 can ride down the slope 66 to the deadlocking position of Fig. 6B. If the sensor is held in while the door is open the bellcrank 49 will move into the deadlocking position, but as soon as the sensor is released the slope 66 will cam the crank up again, releasing the deadlocking and allowing the door to shut.

When the secondary lock is released, as in Fig.

6D, the spring 56 urges both bolt 43 and sensor 55 back into their housing, and the right-hand slope of the cutout 40 rotates the crank 49 into its rest position.

Although the invention has been described with particular application to trains, it is apparent that there is scope for the invention to be used in other environments, for example in buildings where a central locking system might be advantageous in conjunction with individual door locks and/or door catches. In particular it is envisaged that the arrangement might be used to great effect for centrally securing doors (e.g. fire doors) of buildings. For this purpose a manually operated first bolt may not be necessary provided there existed a door catch (such as the ball catch) to hold the door closed such that in the unlocked state gentle pressure on the door would be sufficient to open it. Further, the invention has been described with reference to a secondary latch mounted on the door frame. It is however possible in principle to mount the secondary lock on the door leaf, even though this would not normally be practicable owing to the difficulty of making electrical, pneumatic, mechanical or other connections for signal or power supply across the door hinge. Nevertheless the invention is to be construed to cover such a possibility.

Claims (13)

1. A securing device for doors having a latching arrangement including a latch bolt (3;43) and a corresponding receptor into which the bolt is to be urged, wherein the latch bolt has a cam means to enable the latch to be pushed out of the receptor by a force applied in a direction transverse to the urging direction, and the latching arrangement further includes a deadlocking means (9,10;49) operable on the bolt so as to prevent the bolt being pushed out when the deadlock is actuated.

2. A securing device according to claim 1 and having an actuator urging the deadlocking means into its deadlocking configuration.

3. A securing device according to claim 2, in which the deadlocking means is a jointed lever arrangement (9,10) which has a top-dead-centre position into which it can be urged by the actuator, the lever in this position preventing the bolt from retracting.

4. A securing device according to claim 3, in which the lever arrangement is constructed so that it is urged out of the top-dead-centre position by a restoring means such as a torsion spring so that when the actuator is released, the bolt is able to be retracted reliably into the housing.

5. A securing device according to claim 2, in which the deadlocking means includes a lever (49) biased by a restoring means towards the release position and urged by the actuator towards the deadlocking position.

6. A securing device according to claim 5, in which the bolt (43) is associated with a camming face which urges the lever out of deadlocking when the bolt is urged into its open position.

7. A securing device according to any preceding claim, and further including a sensor (15; 55) which detects whether the door is closed.

8. A securing device according to claim 7, in which the sensor includes means for preventing the deadlock from operating if the sensor detects that the door is not closed.

9. A securing device according to claim 5 or 6 and 7 or 8, and including a further actuator (42) for urging the sensor into the position in which it indicates that the door is open.

10. A security arrangement including one or more doors each fitted with a securing device according to any preceding claim.

11. A security arrangement according to claims 10 and 2 and further including a control means for the or each actuator.

12. A train including a security arrangement according to claim 11, each door further having a main latching arrangement operable by the passengers.

13. A securing device substantially as described herein with reference to either of the embodiments shown in the accompanying drawings.