GB2032096A - Method of producing an imitation log and imitation log produced by the method - Google Patents

Abstract

An imitation log 30 suitable for use in an open-grate-type gas fire, is made by firstly stiffening a tubular element of compressed ceramic bulk fibres with a stiffening agent such as starch and baking a first time to harden the agent. This renders the previously-soft and pliable element workable, to enable it to be shaped at its ends, as at 17, 18 and 19 to resemble a natural sawn or chopped log. The open ends are then filled with a ceramic fibre/cement mixture, as at 23 and the resultant assembly is then coated with a body stain to resemble bark and is baked a second time to render this stain permanent. Finally, the ceramic fibre/cement mixture fillings 23 are painted with a yellow or ochre glaze to resemble inner wood and the assembly is subjected to a third baking to set this glaze. The resultant log is light and can readily be brought to red heat in an open-grate- type gas fire, so that it is not just decorative but serves as a radiant component. <IMAGE>

Description

SPECIFICATION Method of producing an imitation log and imitation log produced by the method This invention concerns a method of producing an imitation log and a log produced by the method. The invention is more particularly concerned with imitation logs of the kind used for open-grate-type gas fires.

Hitherto it has been usual for such imitation logs to be made of heat-resistant concrete. In use, the logs are positioned in an appropriate array on a bed of sand in an open-type grate embodying one or more gas jets. Gas issuing from the jets is ignited and produces flames at least parts of which are visible above the logs.

The flames do, in fact, increase the temperature of the logs, but in practice the logs rarely acquire a sufficient temperature to constitute effective heatradiating components. Accordingly, they essentially provide only a decorative effect, the mass of the logs tending to absorb heat rather than to give it out.

An object of the present invention is to provide a method of producing an imitation log which results in a log construction which is light, which absorbs very little heat, and which can readily be raised to red heat, at least in regions thereof, so that it constitutes an effective radiant element, so that its use in an open-grate-type gas fire as aforesaid enables the fire to be used properly to emit heat as compared with the decorative function previously achieved.

With this object in view, the present invention provides a method of producing an imitation log for suitable use in an open-grate-type gas fire which comprises impregnating a tubular element of compressed ceramic bulk fibres with a heathardenable stiffening agent, subjecting the impregnated tubular element to a first baking to harden the stiffening agent and thereby to stiffen the tubular element, shaping and/or severing the ends of the stiffened tubular element to resemble natural sawn or chopped log ends, blanking off the tubes openings at the shaped and/or severed ends of the element with respective fillings of ceramic fibre/cement mixture, applying an outer coating of a first heat-curable ceramic colouring medium to resemble wood bark, and subjecting the element to a second baking to cure the colouring medium, colouring the fillings blanking off the ends of the element with a second heat-curable or setting ceramic colouring medium, so as to resemble inner wood, and subjecting the element to a third baking to cure the second colouring medium.

The invention log so produced is very light in weight and can be raised to red heat very easily and with a low expenditure of time and/or energy, so that in use it both glows visually and radiates heat. Accordingly, its use in an open-grate-type gas fire serves to transform the gas fire from its former decorative function to a significantly moreuseful heat-radiating function.

If desired, the tubular element may be additionally shaped, prior to the application of the outer coating of the first heat-curable ceramic colouring medium, by the application thereto of one or more tubular parts resembling projecting branches or stumps, the open ends of each of these parts then being filled also with respective fillings of the ceramic fibre cement mixture, and the fillings also being coloured with the second colouring medium.

The stiffening agent conveniently consists of a potato starch dispersion in water, and the impregnation thereof into the tubular element may conveniently be effected by dipping. The first baking of the impregnated element is then preferably effected by heating in a dry oven at a temperature such as to dry out the dispersion, for example in the range of 200 to 2500F (approximately 90 to 1 200C for a period, for instance of the order of 8 hours).

The first heat-curable ceramic colouring medium may conveniently comprise a so-called body stain or engobe suitable for ceramic materials, again conveniently applied by dipping, the second baking being effected in a similar temperature range as above mentioned for an appropriate shorter period, for instance of the order of 4 hours.

The invention will be described further, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a perspective view illustrating a tubular element of compressed ceramic bulk fibres suitable for use in the process of the present invention; Figs. 2 to 8 are schematic views which serve diagrammatically to illustrate successive steps in a preferred process according to the invention; Fig. 9 is a perspective view illustrating the imitation log produced by the method exemplified by Figs. 2 to 8, from one end; Fig. 10 is a view similar to Fig. 9 but taken from the other end of the imitation log; and Fig. 11 is a diagrammatic perspective view illustrating the use of a plurality of the imitation logs aforesaid in an open-grate-type gas fire.

Referring firstly to Fig. 1 of the drawings, in a preferred way of carrying into effect the method of the invention, which is for producing an imitation log for use in an open-grate-type gas fire (as will be described later), one starts off with a tubular element 10 made of compressed ceramic bulk fibres. Such elements are already commercially available, as prefabricated lagging elements for pipework, being marketed, for example, by the Carborundum Company Limited under the designation "VF Tubes." In their marketed form, these tubular element are relatively soft and pliable so that they can be shaped to follow bands and/or convolutions of pipes onto which they have been flitted.

As is illustrated diagrammatically in Fig. 2 of the drawings, as a first step in the preferred process, the tubular element 10 is impregnated with a stiffening agent which is hardenable by the application of heat, by dipping said element 10 into a bath 11 of the agent, contained in an appropriate receptacle which is illustrated, for example, as an open-topped tank 12. The bath 11 is preferably a solution of potato starch, but other heat-hardenable stiffening agents, such as rice starch or a heat curable resin may be employed.

The impregnated tubular element, now indicated by the reference numeral 1 3 in Fig. 3, is next introduced into an oven, illustrated diagrammatically at 14 in Fig. 4, wherein it is baked at an elevated temperature induced by a heating element which is indicated generally by the numeral 1 5. This heating element is shown as being an electric heating element, but other forms of heating, for instance micro-wave heating, may be employed. This baking is effected at a temperature in the range 200 to 250"F (approximately 90 to 1200 C) for a period of 8 hours and serves to harden the stiffening agent, without causing any carbonisation thereof, so that the element 13, when removed from the oven 14 is relatively stiff and can be worked by cutting (and even machining if desired).

The next step in the preferred process is to shape the ends of the stiffened tubular element, indicated by the numeral 16 in Fig. 4 so as to resemble the ends of a sawn or chopped log. In the illustrated case, this is achieved by sawing at one end to provide a single oblique end face 1 7 and at the other end to provide two intersecting oblique faces 18 and 19.

At this stage, as illustrated diagrammatically in Fig. 5, short side branches or stumps, of which two are indicated respectively at 20 and 21, are fitted to the tubular element 1 6. These branches or stumps 20, 21 are each in the form of a short length of stiffened tubular material prepared in exactly the same way as the tubular element 16, but using, as starting material, a compressed ceramic bulk fibre tube of a smaller diameter than that of the element 16, and they may be fitted initially by insertion into respective holes (of which only hole 22 for the branch or stump 20 can be seen in Fig. 5) in the tubular element 1 6.

Next, as has been illustrated in Fig. 6, the cut ends 17 and 18, 19 of the tubular element 16 are blanked off by means of respective fillings of a ceramic fibre/cement mixture, such as that marketed commercially by the Carborundum Company Limited aforesaid, under the designation "H-mouldable." One such filling can be seen at 23, in the end 17, in Fig. 6. Where the log being prepared has side branches or stumps, such as those indicated at 20, 21, the transitions between such branches or stumps are now cemented around as at 24 and the ends of the branches or stumps are filled as at 25.

This having been compieted, the assembly so far achieved, indicated generally by the reference numeral 26 is dipped in a brown body stain or "engobe" of a kind generally suitable for ceramic materials, indicated generally at 27 in Fig. 7 and shown schematically as being contained in a receptacle 28, although application of stain can be effected in any suitable manner. Stains of this sort can be obtained commerciaiiy, for example, from Messrs. C.E. Ramsden 8 Company Limited, of Stoke-on-Trent, Staffordshire.

The stain or engobe having been applied, the coated assembly, now indicated by the reference numeral 29 in Fig. 8 is returned to the oven 14 and is baked a second time at the same temperature as before but for a shorter period, for instance of the order of 4 hours, so as to cure the stain and render it permanent on the exterior of the assembly.

Final finishing of the imitation log is effected by painting the fillings 23, 25 in the ends of the assembly and of the side branches or stumps so as to resemble interior wood, using a yellow or ochre prefired glaze, which material is also commercially available, for example, from the same source as the body stain or engobe discussed above. This glaze is thereupon hardened and rendered permanent by baking once again, at the same temperature as before, but this time for about only three hours.

Figs. 9 and 10 illustrate the finished imitation log, now indicated by the numeral 30, viewed in perspective and respectively from opposite ends.

It is relatively light in weight, being considerably lighter than the equivalent-sized priorconventional concrete logs, yet has a very striking resemblance to a natural log.

Fig. 11 shows a number of the logs 30 arranged as an array on a bed of sand (not visible) in an open-grate-type fireplace 31 which is equipped with gas jets (not visible) enabling flames 32 to be formed as illustrated. These flames, the logs and the fireplace do not serve only a decorative purpose, as is generally the case with the prior known proposals in which the majority of the heat given out by the flames is absorbed by the logs and not radiated by the latter. On the contrary, they readily achieve red heat, even if only in local areas upon which the flames play directly, and as a result they constitute effective radiant elements serving to transmit heat usefully into the room in which the firepiace is installed.

The invention is not confined to the precise details of the foregoing example, and variations may be made thereto. Naturally, the size, shape, dimensions and proportions of the log may be selected as desired and it is essential for side branches or stumps to be provided thereon, although of course these add to the verisimilitude of the product. The various steps, as explained, have been illustrated schematically or diagrammatically in the drawings and it is to be understood that the dipping, cutting and baking steps may be effected otherwise than as shown, for instance as automatic or automated steps in a continuous process. Colouring materials other than the described body stain, engobe and glaze can be used, as desired.

Claims (12)

1. A method of producing an imitation log suitable for use in an open-grate-type gas fire, which comprises impregnating a tubular element of compressed ceramic bulk fibres with a heat hardenable stiffening agent, subjecting the impregnated tubular element to a first baking to harden the stiffening agent and thereby to stiffen the tubular element, shaping and/or severing the ends of the stiffened tubular element to resemble natural sawn or chopped log ends, blanking off the tube openings at the shaped and/or severed ends of the element with respective fillings of ceramic fibre/cement mixture, applying an outer coating of a first heat curable ceramic colouring medium to resemble wood bark, and subjecting the element to a seeoridbaking to cure the colouring medium, colouring the fillings blanking off the ends of the element with a second heat-curable or setting ceramic colouring medium, so as to resemble inner wood, and subjecting the element to a third baking to cure the second colouring medium.

2. A method as claimed in claim 1 wherein the tubular element is additionally shaped, prior to the application of the outer coating of the first heatcurable ceramic colouring medium, by the application thereto of one or more tubular parts resembling projecting branches or stumps, the open ends of each of these parts then being filled also with respective fillings of the ceramic fibre/cement mixture, and the fillings also being coloured with the second colouring medium.

3. A method as claimed in claim 1 or 2 wherein the stiffening agent consists of a potato starch dispersion in water.

4. A method as claimed in claim 1, 2 or 3 wherein the impregnation with the stiffening agent is effected by dipping.

5. A method as claimed in claim 3 or in claims 3 and 4 wherein the first baking of the impregnated element is effected by heating in a dry oven.

6. A method as claimed in claim 5 wherein the first baking is effected at a temperature in the range of 90 to 1 200C for a period of about 8 hours.

7. A method as claimed in any preceding claim wherein the first heat curable ceramic colouring medium comprises a body stain or engobe.

8. A method as claimed in claim 7 wherein the body stain or engobe is applied by dipping.

9. A method as claimed in claim 7 or 8 wherein the second baking is effected at a temperature in the range of 90 to 1 200C for a shorter period than the first baking.

10. A method as claimed in claim 9 wherein the second baking is effected for about 4 hours.

11. A method of producing an imitation log substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

12. An imitation log made by the method of any of the preceding claims.