GB2403766A - Automatic deadlatch - Google Patents

Abstract

An automatic deadlatch comprises a bolt 1 and associated biassing member 2 arranged such that, in use, the biassing member urges the bolt towards its extended position. A pivoted deadlocking member 4 is arranged, in use, to pivot (about A) between a deadlocked position where it is engaged with an opposing face on the bolt and a released position where it is not engaged with the bolt. A rotary cam 5 is arranged, in use, to alternate between permitting and preventing the engagement of the deadlocking member with the bolt. When the bolt is pushed from its extended position to its withdrawn position by a striker plate and the biassing member returns the bolt to its extended position within a keep, the movement of the bolt causes the rotary cam to permit engagement of the deadlocking member with the opposing face on the bolt to deadlock the bolt, and when the bolt is withdrawn to its withdrawn position and the biassing member returns the bolt to its extended position, the movement of the bolt causes the rotary cam to prevent engagement of the deadlocking member with the opposing face on the head of the bolt to release the bolt.

Description

À AUTOMATIC D"DLATCH The present invention relates to an automatic

deadlatch.

Latches are used in many areas to provide a mechanism for reliably keeping items such an doors and windows shut, whilst enabling them to easily be opened again when required with a handle or a key.

Latches which can be deadlocked to increase security, known as deadlatches, are also available. Conventional deadlatches have the disadvantage that a deadlocking mechanism which is separate from the latch mechanism is employed, with an external locking member required to activate the deadlock. This adds significantly to the number of parts needed in the latch, and therefore the cost. It also makes their installation more complicated and restricts the types of door to which they can be attached. Additionally, the security of the mechanism can be comprised due to external features which are prone to attack.

The present invention addresses some of the problems with conventional deadlatches and aims to provide automated deadlatching, without the need for an external member to activate the deadlock.

According to the present invention there is provided an automatic deadlateh comprising: a bolt and associated biassing member arranged such that, in use, the biassing member urges the bolt towards its extended position; a pivoted deadlocking member arranged, in use, to pivot between a deadlocked position where it is engaged with an opposing face on the bolt and a released position where it is not engaged with the bolt; and a rotary cam arranged, in use, to alternate between permitting and preventing the engagement of the deadlocking member with the bolt, wherein the bolt, deadlocking member and cam are arranged such that, in use, when the bolt is pushed from its extended position to its withdrawn position by a striker plate and the biassing member returns the bolt to 5. its extended position within a keep, the movement of the bolt causes the rotary cam to permit engagement of the deadlocking member with the opposing face on the bolt to deadlock the bolt, and when the bolt is withdrawn to its withdrawn position and the biassing member returns the bolt to its extended position, the movement of the bolt causes the rotary cam to prevent engagement of the deadlocking member with the opposing face on the head of the bolt to release the bolt.

According to the present invention there is also provided a method of deadlocking and releasing an automatic deadlatch comprising the steps of: pushing a bolt from its rest position to its withdrawn position by means of a striker plate, returning the bolt to its rest position within a keep 20. by means of a biassing member associated with the bolt, permitting engagement of the deadlocking member with an opposing face on the bolt to deadlock the bolt, by means of a rotary cam and the movement of the bolt during the pushing and returning steps, withdrawing the bolt to its withdrawn position, returning the bolt to its rest position by means of the biassing member, and preventing engagement of the deadlocking member with the opposing face on the head of the bolt to release the bolt, by means of the rotary cam and the movement of the bolt during the withdrawing and returning steps.

An example of the present invention will now be described with reference to the accompanying drawings, in which: 35. Figure 1 is a side view of an example automatic deadlatch, with the cover removed, in an open position; Figure 2 is a side view of an example automatic deadlatch, with the cover removed, in a deadlocked position Figure 3 is a cross sectional view of an example automatic deadlatch according to the invention in an open position; Figure 4 is an automatic deadlatch according to the present invention in a deadlocked position.

Figure 5 is an example rotary cam of an example automatic deadlatch according to the invention; Referring to Figure 1 and Figure 2, an example of an automatic deadlatch according to the invention has a bolt 1 and associated biassing member 2. In this example the biassing member 2 is a spring 2. A spring loaded indexing lever 3 is allowed to slide in the bolt 1. A hinged deadlock plate 4 which is pivoted about point A is provided which can engage with the bolt 1 to stop movement of the l bolt 1.

A rotary cam 5 controls movement of the deadlock plate 4 and is positioned near the bolt 1 and deadlock plate 4.

The cam 5 can connect with the indexing lever and with the deadlock plate 4, and is the means by which movement of the deadlock plate 4 is controlled.

Figure 5 shows an example design of a cam according to the present invention. The cam 5 shown in figure 5 has eight index sections 7 equally spaced around the periphery of the cam. Four equally spaced index sections 7 are partially filled in with the filled in portions 8 having one sloping face as shown in the figure. The cam 5 may alternatively be formed as a modified Belleville washer.

Referring again to figure 1, a cam plate spring 6 operates on the cam 5 to keep the cam 5 in position when the bolt 1 is returning to its fully extended position.

The housing 5 comprises modified conventional latch housing. A person can operate the latch with either a door handle or a key.

The operation of the latch will now be described, with reference to figures 1 to 4.

Starting from the position when a door containing a latch according the invention is open, the bolt 1 is in its extended position and the cam 5 is in a position where a partially filled index section 7 is in line with the deadlock plate 4. This depresses the deadlock plate 4 against the back of the casing so it is in its released position and cannot engage with the bolt 1. This is the open position in figure 4.

On shutting the door, the bolt 1 hits a striker plate on the doorframe, which pushes the bolt 1 into its withdrawn position. When the bolt moves towards its withdrawn position, the index lever 3, which is hooked into an index section 7 in the cam 5, also rotates into the next index section 7 along. This means that an open slit is now in line with the deadlock plate 4, so the deadlock plate 4 can pivot around, when allowed, into its deadlocked position and engage with the bolt 1, thus preventing the bolt 1 from moving.

When the bolt 1 moves back into its extended position within a keep in the door frame, on being urged by the spring 2, the index lever 3, being spring loaded, disengages the cam 5 (which then remains stationary) and returns with the bolt 1 to its extended position. This is the deadlocked position in figure 2 and figure 4.

On turning the door handle a follower 9 and actuator lever 10 rotate to retract a link plate 11, which in turn depresses the deadlock plate 4 against the back of the casing. The bolt 1 can then move into its withdrawn position. As it does so, the index lever 3 which is hooked into an index section 7, moves to the next index section 7 along. The bolt 1 moves back into its extended position.

This means that a partially filled in index section 7 is in line with the deadlock plate 4, which maintains the depression of the deadlock plate 4 against the back of the casing.

When the handle is released, the bolt 1 moves back into its extended position urged by the spring 2 and the spring loaded index lever 3 disengages the cam 5 (which then remains stationary) and returns with the bolt to its extended position (Figure 4).

On,turning the key to gain access, the link plate 11 similarly retracts to depress the deadlock plate 4 against the back of the casing. The bolt 1 can then move into its withdrawn position. As it does so, the index lever 3, which is hooked into an index section 7, moves to the next index section 7 along. The bolt 1 moves back into its extended position. This means that a partially filled in index section 7 is in line with the deadlock plate 4, which maintains the depression of the deadlock plate 4 against the back of the casing.

When the key is released, the bolt 1 moves back into its extended position urged by the spring 2 and the spring loaded index lever 3 disengages with the cam 5 (when the remains stationery) and returns with the bolt to its extended position (Figure 4).

Claims (6)

1. An automatic deadlatch comprising: a bolt and associated biassing member arranged such that, in use, the biassing member urges the bolt towards its extended position, a pivoted deadlocking member arranged, in use, to pivot between a deadlocked position where it is engaged with an opposing face on the bolt and a released position where it is not engaged with the bolt, and a rotary cam arranged, in use, to alternate between permitting and preventing the engagement of the deadlocking member with the bolt, wherein the bolt, deadlocking member and cam are arranged such that, in use, when the bolt is pushed from its extended position to its withdrawn position by a striker plate and the biassing member returns the bolt to its extended position within a keep, the movement of the bolt causes the rotary cam to permit engagement of the deadlocking member with the opposing face on the bolt to deadlock the bolt, and when the bolt is withdrawn to its withdrawn position and the biassing member returns the bolt to its extended position, the movement of the bolt causes the rotary cam to prevent engagement of the deadlocking member with the opposing face on the head of the bolt to release the bolt.

2. An automatic deadlatch according to claim 1, wherein the bolt and rotary cam are coupled together by means of an indexing lever.

3. An automatic deadlatch according to claim 1 or claim 2, wherein the rotary cam is a modified, multi-profile Belleville washer.

4. An automatic deadlatch according to any of claims 1 to 3, further comprising a lever connected to the bolt such that, in use, the bolt can be withdrawn to its withdrawn position by means of the lever.

5. An automatic deadlatch according to any of claims 1 to 3, further comprising a cam connected to the bolt such that, in use, the bolt.can be withdrawn to its withdrawn position by means of.the cam.

6. A method of deadlocking and releasing an automatic deadlatch comprising the steps of: pushing a bolt from its rest position to its withdrawn position by means of a striker plate, returning the bolt to its rest position within a keep by means of a biassing member associated with the bolt, permitting engagement of the deadlocking member with an opposing face on the bolt to deadlock the bolt, by means of a rotary cam and the movement of the bolt during the pushing and returning steps, withdrawing the bolt'to its withdrawn position, returning the bolt to its rest position by means of the biassing member, preventing engagement of the deadlocking member with the opposing face on the head of the bolt to release the bolt, by means of the rotary cam and the movement of the bolt during the withdrawing and returning steps.