GB2166795A - Latch bolt - Google Patents

Abstract

In a latching mechanism for a hinged door the latch bolt 14 which extends the full length of the door edge is pivoted about an axis 15 parallel to the closing edge of the door 2 and is biassed to move to a position in which it engages an abutment 16 on a door frame when the door is shut. Means to pivot the latching member about the said axis into a disengaged position when the door is to be opened comprise a conventional handle 1. The door is preferably a fire door comprising a pair of heat resisting barrier sheets slidably secured to a framework. <IMAGE>

Description

SPECIFICATION Latching mechanisms for hinged doors This invention relates to latching mechanisms for hinged doors.

Hinged doors are normally provided with latches which act at one position only at their closing edges to engage the door when closed with its doorframe, and comprise means to disengage the latch when the door is to be opened. The opposite edge of the door is adapted to swing from the opposite side of the doorframe.

More secure doors, especially fire doors, may be latched at three points, one of which is normally a mid point on the closing edge of the door and the others are either at the top and bottom of the closing edge or are at the top and bottom edges of the door near to the closing edge. Such doors if constructed of fire resistant materials, are useful as fire doors as the use of three latching points tends to restrain them from bowing when exposed to fire on one side.

The use of three latching points however complicates construction not only because of the latches themselves but because for convenience in opening the door means are needed for disengaging all of the latches by a single action of the operator, which is normally turning a handle which operates all of the latches by means of mechanical linkages.

This invention comprises a latching mechanism for a hinged door assembly which comprises a latching member adapted to flex about an axis parallel to the closing edge of a door and biassed to move to a position in which it engages the closing edge of the door along substantially the whole of its length with a doorframe when the door is shut and means to flex the latching member about the said axis into a disengaged position when the door is to be opened.

The latching member may be a hinged leaf which in this case flexes by movement of the hinge.

Suitably the latching member is secured to the closing edge of the door and engages the door with the frame by flexing so as to engage in a recess in the frame as the door is closed. It may be biassed to move into the engagement position by springs or other mechanisms or may itself be made of resilient material, for example spring steel, and mounted so as to move when undeformed into the engagement position. Suitably the latching member is higned to the closing edge of the door and is engaged and disengaged by a conventional latch of the type in which a tongue is biassed to protrude into engagement with a recess in a doorframe, by connecting the latching member with the tongue.

Suitably the latching member is shaped as a radial arm extending from the axis of flexion which is bent at its outer end to form an approximate arc of a circle centred on the said axis. This arrangement facilitates smooth functioning of the mechanism. Suitably, a recess is provided in the frame into which the end of the arc can engage when the latch is subject to pressure as this reinforces the strength of the latch.

The invention also comprises hinged doors which comprise a latching mechanism according to the invention and hinged door assemblies which comprise such doors installed in suitable doorframes.

The doors suitably comprise two heat resistant barrier sheets for example of steel on a framework. By "barrier sheets" is meant sheets which obstruct a doorway when the door is closed. Preferably they are constructed to slide on the framework when subjected to heat to take up expansion and thereby to reduce distortion of the door; suitably the doorframe is adapted to hold an expanded edge at the swinging edge of the door and thereby to reinforce the integrity of the door when it is subjected to heat.

One form of the invention will now be describe with reference to the accompanying drawings which represent a horizontal cross section of a closed firedoor and doorframe at a position above a handle (1) for opening the door.

A door (2) comprising two facing skins of steel (3) and (4) held by steel U sections (5) and (6) closing the hinged and closing edges of the door respectively which are held by a framework (not shown) within the skins (3) and (4). Both edges of the skins are folded back over the arms of U sections (5) and (6) to give a sliding fit.

At the swinging edge of the door, hinge (7) which extends along substantially the whole of the edge is secured by welding or rivets to steel doorframe (8) by one leaf of which the extremity is turned back to form an abutment (9).

At the closing edge of the door a conventional latch (10) operated by handle (1) is secured to U section (6) through which its tongue (11) protrudes. Tongue (11) is secured by a flexible coupling (12) to block (13) which is screwed to leaf (14) of hinge (15), which extends along substantially all of the closing side of the door. Leaf (14) is shaped at its extremity as an arc centred on the hinge pivot, and is shown in the latched position abutting lip (16) of doorframe (17). Springs (not shown) are provided above and below latch (10) urging the leaf (14) into the latching position, thus reinforcing urging by latch (10).

The door may be released by turning handle (1) which operates latch (10) to withdraw tongue (1) thus withdrawing leaf (14) into a disengaged position in which it clears lip (16) and thus permits the door to be swung open on hinge (7).

If the door is subjected to fire, buckling is reduced by the ability of the skins (3) and (4) to expand on the frame and skin (2) tends to expand into the space between abutment (9) and the doorframe, thus holding the hinged edge of the door which is also held by hinge (7); in both cases substantially the whole length of the hinged edge of the door is so held. Leaf (14) also holds the closing edge of the door throughout substantially its whole length.

If desired supports may be provided under the free end of the arc of leaf (14) such that, in the event of pressure being exerted on the arc sufficient to cause distortion, both sides of the arc are supported.

Claims (11)

1. A latching mechanism for a hinged door assembly which comprises a latching member adapted to flex about an axis parallei to the closing edge of a door and biassed to move to a position in which it engages the closing of the door along substantially the whole of its length with a doorframe when the door is shut and means to flex the latching member about the said axis into a disengaged position when the door is to be opened.

2. A mechanism as claimed in claim 1 in which the latching member is a substantially rigid leaf of a hinge of which the pivot is along the said axis, the latching member flexing about the said axis by means of movement about the pivot.

3. A mechanism as claimed in claim 1 or 2 in which the latching member is secured to the closing edge of a door and engages the door with a doorframe by flexing so as to engage in a recess in the frame as the door is closed.

4. A mechanism as claimed in claim 3 in which the latching member is moved into engagement or disengagement by means of a latch of the type in which a tongue is biassed to protrude to engage a door with a doorframe and is provided with means to retract the tongue, the tongue of the said latch being adapted to operate the said latching member.

5. A mechanism as claimed in any preceding claim in which the latching member is shaped as a radial arm extending from the axis of flexion which is bent at its outer end to form approximately an arc of a circle centred on the said axis.

6. A hinged door which comprises a latching mechanism as claimed in any preceding claim.

7. A door as claimed in claim 6 which comprises two heat resisting barrier sheets on a framework on which they are adapted to slide when subject to heat to take up expansion and thus to reduce distortion of the door.

8. An assembly of a door as claimed in claim 7 and a doorframe which is adapted to hold an expanded edge and thereby to reinforce the integrity of the door when it is subjected to heat.

9. A latching member substantially as described with reference to the drawing.

10. A door substantially as described with reference to the drawing.

11. An assembly of a door in a doorframe substantially as described with reference to the drawing.