GB2463991A - Striker plate for use in a door latch with angled tongue - Google Patents

Abstract

A striker plate 2 for a door latch includes flat plate (7, Fig. 2) and a bolt ramp 3. The bolt ramp extends rearward from the flat plate, an angle of between 65-75° (degrees) is formed between ramp and the plate. The ramp may reduce the risk of jamming of a bolt in the striker should the door be placed under load during attempted withdrawal of the bolt. The bolt 11 preferably has a contact face 15 angled at 9-11° to the direction of movement thereof.

Description

Striker Plate This invention relates to a striker plate for a door jamb, and particularly to a striker plate adapted to improve the ease of retraction of a bolt under load.

A door is usually held closed by the positioning of a bolt in the bolt aperture of a striker plate attached to an upright door jamb. The bolt aperture is typically rectangular and upright and has a vertical height and horizontal width when in place on a door jamb.

When a door is opened normally, a handle or door knob is used to retract the bolt from the striker plate, allowing the door to move freely in a pre-determined direction. However, if a door is placed under a load at the same time as the handle or knob is being turned, the bolt can be forced against the edge of the bolt aperture and become substantially immovable, thus preventing the door from opening.

This potential failing is of especial concern in the case of emergency exit doors. Such doors may be required to open in the event of evacuation of a building, often a commercial building with many people inside. In such a situation people are inclined to panic, which can lead to people pressing hard against an emergency door in an attempt to open it, not realising that this could have the unwanted effect of jamming the bolt against withdrawal. The only way to then open the door is to relieve the pressure on it and allow the bolt to move freely; however, this is difficult to achieve if a crowd of anxious people are trying to leave a building as quickly as possible.

Legislation may require a door bolt to release from a striker plate when a significant load, e.g. I 000N, is applied to the door face.

What is required is a means of ensuring that a bolt can be withdrawn smoothly and without excessive force, whether the door is under a face load or not. The solution should be applicable to emergency door release mechanisms, and to standard key or handle operated door bolts.

According to the invention there is provided a striker plate for a door jamb and comprising a flat plate having a front side, a rear side, and a bolt aperture, a bolt ramp comprising an angled projection extending from the bolt aperture on the rear side, the angle between the bolt ramp and the plane of the plate being between 65° and 75°, and the bolt ramp facing said aperture. The angled bolt ramp ensures that a relatively low force generated by a release load on the door handle or, in the case of many emergency doors, crash bar, enables the bolt to withdraw, and does in fact encourage withdrawal of the bolt as side load is applied to the bolt.

The invention differs from the prior art in that the bolt engages a surface (the bolt ramp) which is at an angle to the direction of bolt movement, and facilitates such movement in the release direction by generating a force in the withdrawal direction as a result of an orthogonal load. However the bolt ramp should not be at so great an angle that a door will open merely under excessive load applied to the face thereof.

A particular advantage of the invention is that there is no additional cost compared to that of an existing striker plate. Conventionally a bolt aperture is punched or sheared out; instead of being bent back orthogonally to provide a bolt engaging surface which is parallel to the direction of bolt movement, a sheared lip is bent back at the required angle of less than 90°.

The leading lip at the edge of the striker plate is bent into position as a manufacturing step, so no extra manufacturing stage is required to bend the bolt ramp into place. Cost will in fact be saved as less waste material is created due to the bolt ramp being formed from the shearing required to form the bolt aperture.

In a preferred embodiment, the striker plate is formed from a single sheet of material, ideally steel of a thickness suitable for the required stiffness of the plate and bolt ramp. Preferably, the striker plate is of uniform thickness. Stainless steel of 2mm thickness is preferred.

In a preferred embodiment the angle of the bolt ramp is between 68° and 72°, most preferably between 69° and 71°. In another preferred embodiment, the angle is 70°.

Preferably, the bolt ramp comprises a planar rectangle, formed from the entire cut out area of the bolt aperture, and symmetrically positioned with respect to said aperture. The area of the bolt ramp may alternatively be smaller than the bolt aperture, either in the length direction or the width direction, or both directions.

In a second embodiment a striker plate has two bolt apertures, one or both of which have a bolt ramp, allowing the striker plate to be used for a door with two or more bolts, such as a latch bolt and an emergency dead bolt.

In use the striker plate is positioned so that the bolt ramp is on the load receiving side of the bolt. This leads to the side load forces in the bolt being partially resolved in the direction of retraction of the bolt.

In a most preferred embodiment the face of the bolt which contacts the bolt ramp is at an angle to the direction of bolt movement, typically in the range 91l0, most preferably 100.

Such an angle, in conjunction with an angled bolt ramp has been found to give superior withdrawal operation under substantial loads upon the door face, but without the risk that the bolt will be forced in the withdrawal direction merely as a result of such face loads.

According to a second aspect of the invention there is provided the aforesaid striker plate having a bolt ramp at an angle of 65-75° and a bolt having a bolt face for contact with said ramp and at 91l0 to the direction of movement of the bolt. The bolt is typically part of a latch or lock assembly.

Other features of the invention will be apparent from the following description of a preferred embodiment shown by way of example only in the accompanying drawings: Fig. 1: a perspective view of the striker plate attached to a door jamb, Fig. 2: a front elevation of the striker plate, Fig. 3: a side elevation of the striker plate, Fig. 4: an end elevation of the striker plate showing a corresponding bolt.

With reference to Fig. 1, a striker plate 2 consists of a single piece of material, typically stainless steel, shaped so that when fitted to a door jamb 8 it holds in place the extended bolt of the latch of a closed door. The main portion 7 of the striker plate 2 is attached to a door jamb 8 by screws in two holes 5 (usually countersunk) so that it lies flat against it. The striker plate could also be rebated, for example in a wooden jamb. The door closes, usually against an abutment (not shown), in the direction of arrow D. A bolt ramp 3 extending at an angle from the edge of a bolt aperture 6 into a recess 9 in the jamb 8, is positioned in order to facilitate the retraction of the bolt when the door is under pressure. The distance A between the edge of bolt ramp 3 and the opposing edge of aperture 6 in the plane of the striker plate, shown in Fig. 4, is equal to or more than the corresponding width of the bolt, allowing it to extend freely when the door is not under pressure.

The height of the bolt ramp 3 is equal to or less than the height of the bolt aperture 6, the height of the aperture being vertical and the width horizontal across the door jamb 8 when the striker plate is fitted to a normal door. Preferably the bolt ramp 3 will be longer than the bolt so that no damage due to friction at the edge can be caused. A skilled man will select the width of the bolt ramp and the width of the aperture 6 from which it will be formed. The acute angle B, shown in Fig. 4, at which the bolt ramp 3 extends is about 70° in order for the bolt to be effectively retracted when under pressure.

One side of the main portion 7 of the striker plate is extended at an angle C, also shown in Fig. 4, creating an angled lip 4. The striker plate 2 is positioned so that this lip 4 is on the side of the jamb 8 where the door closes and thus facilitates the closing of the door. The angle C is typically between 20° and 40° in order for the door to be closed with ease. While this lip is useful for guiding spring-loaded latch bolts, it is not needed for a dead bolt.

The striker plate is typically formed from a single piece of stainless steel sheet of 2mm; other materials and dimensions may be chosen by the skilled man according to the stiffness and durability required. Typically manufacture would consist of punching a striker plate blank from a sheet of material, shearing a tongue and bending the tongue to form the bolt ramp 3.

The lip 4 may be formed at the same time.

A typical latch bolt 11 for use with the invention is illustrated in Fig. 4, and has a reverse face 12 at an angle of about 45° to the direction of movement 13 of the door. The bolt is sprung out of the case in a conventional door latch bolt. The reverse face 12 meets the lip 4 upon closing movement, and the bolt is forced back against the spring as the door closes in the direction 14, before springing back into the bolt aperture 6.

The front face 15 of the bolt is at an angle of about 100 to the direction of movement 14, and has been found to give a desirable low release load when under load in the opening direction of the door. The front and back faces of the bolt converge towards the free end of the bolt, as shown.

The engaged position of the bolt is illustrated in dotted outline in Fig. 4.

The preferred embodiment is described with reference to an upright door jamb. However, it 1 5 will be appreciated that the striker plate can be mounted in a horizontal plane and is not limited to vertical use. The striker plate can be used wherever assistance is required for opening. For example, although the invention is specifically created for a dead bolt, it can be used to reduce the force needed to overcome a spring latch bolt. In this example it would be a cheaper and easier alternative to change the striker plate than the spring of the bolt assembly.

In a second embodiment (not shown) the striker plate 2 has provision for two or more bolts, one above the other, and can be used where a door has more than one fastening, for example a panic latch and a dead bolt. In this case, although the panic latch does not require it, both bolt apertures preferably have a bolt ramp, so that the striker plate can be fixed to the door jamb either way up, and thus be used for a door opening in either direction.

Claims (18)

1. Claims 1. A striker plate for a door jamb and comprising a flat plate having a front side, a rear side, and a bolt aperture, a bolt ramp comprising an angled projection extending from the bolt aperture on the rear side, the angle between the bolt ramp and the plane of the plate being between 65° and 75°, and the bolt ramp facing said aperture.
2. 2. A striker plate according to Claim I wherein the bolt ramp is a planar projection.
3. 3. A striker plate according to Claim 2 wherein the bolt ramp is substantially rectangular.
4. 4. A striker plate according to Claim 3 wherein the width of the bolt ramp is substantially equal to or less than the width of the bolt aperture.
5. 5. A striker plate according to Claim 4 wherein the height of the bolt ramp is substantially equal to the length of the bolt aperture.
6. 6. A striker plate according to Claim 4 wherein the height of the bolt ramp is less than the length of the bolt aperture.
7. 7. A striker plate according to Claim 6 wherein the bolt ramp is symmetrically positioned within the bolt aperture.
8. 8. A striker plate according to any preceding claim wherein the striker plate has constant thickness.
9. 9. A striker plate according to any preceding claim wherein the device is formed from a single sheet of material.
10. 10. A striker plate according to any preceding claim having two apertures in series, one of which having a bolt ramp.
11. 11. A striker plate according to any preceding claim having two apertures in series, each of which having a respective bolt ramp.
12. 12. In combination a striker plate according to any of claims i-li and a bolt adapted to orthogonally enter said bolt aperture in use.
13. 13. The combination of claim 12 wherein said bolt comprises a planar face for contact with said bolt ramp, said face being at 9-11° to the direction of movement of said bolt in use.
14. 14. The combination of claim 12 or claim 13 wherein said bolt comprises part of a latch or lock assembly.
15. 15. A method of forming a striker plate according to any of claims 1-1 1 and comprising the steps of cutting a flat blank from a sheet of material, shearing from said blank a C-shaped aperture and bending said bolt ramp from this aperture to the said aiigle.
16. 16. A striker plate as described herein with reference to the accompanying drawings.
17. 17. A combination of striker plate and bolt substantially as described herein with reference to the accompanying drawings.
18. 18. A method of forming a striker plate as substantially described herein with reference to the accompanying drawings.