GB2268224A - Letterplates - Google Patents

Abstract

A letterplate comprising an assembly (10) which includes a mounting plate (11) and closure flap (12), and preferably a sleeve (13) to extend within a slot in a door or the like, is provided with intumescent material (31,32,33) so as to seal the slot and provide effective fire resistance when subjected to a high temperature. Preferably, the letter plate further comprises an inner assembly which includes a sleeve telescopically engageable with the sleeve (13) of the mounting plate assembly (10) and having one or more of a brush-like sealing device, a further pivoted flap and a hood, the sleeve being provided externally with further intumescent material. <IMAGE>

Description

Title: "Letterplates" Descrxption of the invention This invention relates to letterplates, that is to say fittings for mounting on doors, walls, partitions or other panel-like members to facilitate the passage of items of mail and the like through a slot formed in such member for this purpose, and to close the slot against the ingress of rain and draughts.

Conventionally, a letterplate comprises an assembly of a mounting plate for attachment to one face of a door (normally the outer face) or other member in register with a slot, the mounting plate defining a frame which extends around the mouth of the slot, and a pivoted flap carried by the mounting plate so as to extend across the slot and close same except when displaced temporarily.

Additionally, such a letterplate may optionally comprise an inner assembly for attachment to the opposite (normally inner) face of the door or the like in register with the slot, said inner assembly including one or more of a brush-like sealing device to extend across the slot, a further pivoted flap to extend across the slot, and a hood to partially enclose the slot and direct any incoming material downwardly, for example into an associated collection basket also mounted on the door below the slot.

However, such conventional letterplates afford a potential hazard with regard to fire risk. Whilst conventional letterplates offer generally adequate resistance to rain and wind, they afford little or no resistance to fire or hot gases resulting from a fire, so that if installed on a fire resistant member the fire resistance of the member is greatly diminished.

The object of the present invention is therefore to provide an improved letterplate having fire and smoke resistant capability to match that of a fire resistant member on which it is used.

In accordance with the invention we provide a letterplate comprising an assembly including a mounting plate for attachment to one face of a door or other panel-like member in register with a slot formed in said member, the mounting plate defining a frame which extends around the mouth of the slot, and a pivoted flap carried by the mounting plate so as to extend across the slot and close same except when displaced temporarily, wherein the mounting plate assembly has associated therewith a body of intumescent material which is so arranged as, when subject to a high temperature, to expand and effectively fill and seal the slot to provide effective fire resistance.

The intumescent material is preferably located within the slot when the mounting plate assembly is installed, and preferably the mounting plate assembly is formed or provided with a sleeve which projects from the mounting plate into the slot forming a lining within the slot, the intumescent material being carried by said sleeve.

The intumescent material may extend around the entire periphery of such sleeve at least internally thereof and preferably also externally.

Where an inner assembly as described above is provided, said sleeve may alternatively be formed or provided on said inner assembly instead of on said mounting plate assembly, but preferably the inner assembly, where provided, is formed or provided with a second sleeve so dimensioned as to be telescopfcally engageable with the sleeve associated with the mounting plate assembly.

Additional intumescent material may then be provided around said second sleeve, externally and/or internally thereof around all or part of its periphery.

The intumescent material is preferably such as to begin to expand at a temperature of approximately 1200C and become fully expanded at a temperature not greater than approximately 3000C. The intumescent material may comprise graphite and vermiculite, preferably preformed into strips, blocks, or appropriately shaped sections.

According to the invention we also provide a fire-retardant fitting for sealing a letter slot formed in a door or other similar panel-like member, the fitting comprising a mounting member defining an opening to register with said slot and intumescent material so disposed on one side of said mounting member as to enter said slot without closing said opening and so dimensioned as to expand when subject to a high temperature to the extent required to seal the slot and provide effective fire resistance The invention further resides in a door or other panel-like member of fire resistant or fire retardant material having a slot formed therein to facilitate the passage of items of mail and the like, wherein such a letterplate is provided in association with the slot.

The invention will now be described by way of example with reference to one specific embodiment of letterplate as illustrated in the accompanying drawings, wherein: FIGURE 1 shows a rear view of a mounting plate and closure flap assembly forming an outer assembly; FIGURE 2 shows a side view of the outer assembly together with an inner assembly for use therewith; and FIGURE 3 shows a section through the complete letterplate comprising inner and outer assemblies as fitted to a door or other member.

As illustrated diagrammatically, the letterplate comprises an outer assembly 10 including a generally flat mounting plate 11 which defines a rectangular mouth 11a in which a flap 12 is pivotally supported for outward movement. The mounting plate 11 carries a rearwardly projecting rectangular section sleeve 13 formed from opposed C-shaped end pieces 14 and top and bottom pieces 15,16. The mounting plate 11 also carries rearwardly projecting bolts 17 for attachment to an inner assembly 20.

The inner assembly 20 includes an optional hood member 21 with a pivotally mounted inner flap 22, and a sleeve 23 which extends forwardly from the hood member. The sleeve 23 comprises opposite C-section end pieces 24 and top and bottom pieces 25,26. Within the sleeve 23 adjacent to the hood member 21 a pair of opposed brush assemblies 28 are provided in known manner to form a draught/smoke seal at the inner end of the slot defined by the sleeve.

In use, the mounting plate assembly 10 is arranged on the outer face of a door (D) or other similar member with the sleeve 13 extending into a rectangular slot formed in the door member. The inner assembly 20 is arranged at the inner face of the door member with the sleeve 23 overlapping the sleeve 13 in a telescopic relationship. The bolts 17 pass through suitable apertures (not shown) in the inner assembly 20 and the two assemblies are secured together by means of nuts threaded onto the bolts, thereby clamping the entire letterplate in place.

In accordance with the invention, the sleeve 13 of the mounting plate assembly 10 is lined with intumescent material. In the illustrated embodiment, such material comprises a top block 31 which is secured beneath the top piece 15 of the sleeve, side blocks 32 which are secured within the C-shaped end pieces 14, and also envelop the bolts 17, and a thin strip 33 is carried by the bottom piece 16 of the sleeve 13.

Whilst the mounting plate 11, flap 12 and hood member 21 may generally be made from any suitable metal or possibly plastics materials or combinations thereof, the sleeves 13 and 23 should preferably be made of steel or similar heat resistant material.

The sleeve 23 of the inner assembly 20 may also carry intumescent material. As illustrated this comprises a strip 36 of the intumescent material on the upper side of the top piece 25, respective strips 37 on the outside faces of the end pieces 24 and a further strip 38 at the underside of the bottom piece 26. If desired, additional strips may be provided within the sleeve 23 or on the outside of the sleeve 13.

In use, in the event of a fire raising the temperature in the vicinity of the letterplate to a value in access of about 1200C, the intumescent material expands so as effectively to close off the sleeve 13 entirely and to seal the slot in the door.

Whilst in the embodiment as described the intumescent material comprises a number of separate pieces, it will be appreciated that the block-like bodies 31 and 32 may be formed as single components of such material. Also, whilst differing thicknesses of intumescent material are provided at different sides of the sleeve 13, the material may be of equal thickness throughout. Alternatively the material may be provided only at top and bottom of the slot or it may all be carried by, for example, the top piece 15 of the sleeve 13.

It will be appreciated that the inner flap 22 and/or brush assemblies 28 may be omitted if required, but where the hood member 21 is provided it is preferred in accordance with a further feature of the invention also to provide a bag of fire resistant material, for example of the kind used for fire blankets, attached to the outlet of the hood so as to receive and secure any incendiary matter which may deliberately be passed through the letterplate. However, the inner assembly may omit the hood member and instead comprise a simple mounting plate carrying the inner flap 22 and/or brush assemblies 28.

Whilst the sleeves 13 and 23 are preferably dimensioned so as to overlap in telescopic manner, it would be possible for them not to overlap but be of relatively reduced front-to-rear width, preferably each carrying intumescent material.

Further, it would be possible for either one or other of the sleeves to be omitted, the remaining sleeve carrying all the required intumescent material.

Indeed, the sleeves could be omitted entirely, the intumescent material then being carried by the mounting plate assembly and/or inner assembly as appropriate.

In some cases the inner assembly 20 may be omitted, and in which case the bolts 17 of the mounting plate assembly 10 could be positioned externally of the sleeve 13 (where provided) so as to pass through the door externally of the slot for fixing purposes, preferably within sleeves of intumescent material.

Claims (14)

ClAIMS:-

1. A letter plate comprising an assembly including a mounting plate for attachment to one face of a door or other panel-like member in register with a slot formed in said member, the mounting plate defining a frame which extends around the mouth of the slot, and a pivoted flap carried by the mounting plate so as to extend across the slot and close same except when displaced temporarily, wherein the mounting plate assembly has associated therewith a body of intumescent material which is so arranged as, when subject to a high temperature, to expand and effectively fill and seal the slot to provide effective fire resistance.

2. A letterplate according to Claim 1 wherein the mounting plate assembly further includes a sleeve which projects from the mounting plate and into the slot when in use, forming a lining within the slot, the intumescent material being carried by said sleeve.

3. A letterplate according to Claim 1 further comprising an inner assembly for attachment to the opposite face of the panel-like member in register with the slot and including one or more of a brush-like draught/smoke sealing device to extend across the slot, a further pivoted flap to extend across the slot, and a hood to partially enclose the slot and direct any incoming material downwardly.

4. A letterplate according to Claim 3 wherein the inner assembly further comprises a sleeve which projects into the slot, when in use, forming a lining within slot, the intumescent material being carried by said sleeve.

5. A letterplate according to Claim 4 wherein the inner assembly sleeve carries intumescent material.

6. A letterplate according to Claim 2 or Claim 5 wherein the intumescent material extends around the entire periphery of the sleeve.

7. A letterplate according to Claim 2 in combination with Claim 5 wherein the sleeves of the mounting plate assembly of the inner assembly are so dimensioned as to be telescopically engageable within the slot when in use.

8. A letterplate according to anyone of the preceding claims wherein the intumescent material is such as to begin to expand at a temperature of approximately 1200C and become fully expanded at a temperature not greater than approximately 3000C.

9. A letterplate according to anyone of the preceding claims wherein the intumescent material comprises graphite and vermiculite.

10. A letterplate according to Claim 3 further comprising a bag of fire resistant material secured to said inner assembly in such a manner as to receive material from the slot.

11. A fire-retarding fitting for sealing a letter slot formed in a door or other similar panel-like member, the fitting comprising a mounting member defining an opening to register with said slot and intumescent material so disposed on one side of said mounting member as to enter said slot without closing said opening and so dimensioned as to expand when subject to a high temperature to the extent required to seal the slot and provide effective fire resistance.

12. A panel-like member of fire resistant or fire retardant material having a slot formed therein to facilitate the passage of items of mail or the like, wherein a letterplate or fitting according to anyone of the preceding claims is provided in association with said slot.

13. A letterplate substantially as hereinbefore described with reference to and as shown in Figures 1 to 3 of the accompanying drawings.

14. A panel-like assembly formed with a slot and having assembled therewith a letterplate according to Claim 13.