GB2146110A

GB2146110A - Fireplace unit

Info

Publication number: GB2146110A
Application number: GB08323990A
Authority: GB
Inventors: Raby Nicholas Jonathan Muers; Charles James Simpson
Original assignee: JETMASTER FIRES Ltd
Current assignee: JETMASTER FIRES Ltd
Priority date: 1983-09-07
Filing date: 1983-09-07
Publication date: 1985-04-11
Also published as: GB2146110B; GB8323990D0

Abstract

A fireplace unit has a firebox (10), a flue (17), a firehousing (11) with an air jacket between the firehousing and the firebox, an air inlet vent (26) and an outlet duct (25) for heated air. Air is drawn into the jacket by convection to be heated by the fire, and a baffle arrangement (16, 30, 28) within the jacket ensures that the air lingers over the hottest part of the fire. <IMAGE>

Description

SPECIFICATION Fireplace unit This invention relates to fireplace units.

Our earlier patent application No. 7912712 shows a typical fireplace unit that is similar to the kind to which the present invention re lates. In this basis unit the flue comprises a pair of outlets which are provided on either side of the unit. In between the flue outlets there is a duct through which heated air is expelled, by convection, into the surrounding atmosphere. It will be observed that in this basic unit, air drawn into the chamber behind the firebox is able to circulate and pass straight out of the duct. On account of this relativey easy passage behind the firebox, the air does not remain long in contact with the hot walls of the firebox and consequently, the temperature of the convected air is not raised by as much as it would be if the air spent longer in contact with the firebox.

According to the invention there is provided a fireplace unit of the kind comprising a firebox which is open at a front side, a flue outlet, a fire housing which together with the firebox defines therebetween a chamber in the form of an air jacket, vent means below the firebox through which air can be drawn from the surrounding atmosphere, and duct means above the firebox through which heated air can be expelled into the surrounding atmopshere, the air jacket extending between the vent means and the duct means whereby, by convection, air is drawn into the air jacket from the vent means, is heated by the walls of the firebox and is expelled from the duct means, there being means for extending the length of the time within which air remaining within the air jacket is in contact with the firebox.

The means for extending the length of time within which air is in contact with the firebox may include additionally providing the air jacket with passageways extending on either side of the firebox.

By way of example, an embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a front view of a fireplace unit according to the invention.

Figure 2 is a sectional side view through the unit of Fig. 1, and Figure 3 is a part sectional plan view of the unit of Figs. 1 and 2.

A fireplace unit comprises a firebox 10 and a fire housing 11. The firebox 10 is open at the front and has a backplate 1 2 from which side plates 1 3 and 1 4 and bottom plate 1 5 extend forwardly to a frame 24. An upper portion 1 6 of the backplate 1 2 is inclined towards the open side of the firebox 10. A flue 1 7 is positioned above and rearwardly of the upper inclined portion 1 6 of the backplate 12, and a hingedly mounted damper flap 1 8 is provided in the flue for controlling the rate of combustion of the fire.A baffle plate 1 9 positioned above and forwardly of the upper inclined portion 1 6 of the backplate 1 2 acts to deflect the combustion gases from the firebox 10 up the flue 17. The baffle plate 19 also defines a forwardly-opening duct 25, as will be described in more detail later.

The fire housing 11 is likewise open a the front and has a back panel 20 from which side panels 21 and 22 and bottom panel 23 extend forwardly to the frame 24. The respective panels of the fire housing 11 are spaced from the corresponding plates of the firebox 10 so that passageways are defined below, behind and to both sides of the firebox 10 forming a kind of air jacket around the firebox. Air in this air jacket is heated through the walls of the firebox 10 and, as the heated air rises, it is channelled into the duct 25, though which it is expelled into the surrounding atmosphere. At the same time, fresh air from the surrounding atmosphere is drawn into the passageway beneath the firebox 10 through a vent 26.

The air flow patterns in the air jacket around the firebox 10 are as follows: air travelling up the passageways on either side of the firebox 10 enters the duct 25 from either side thereof and is then expelled forwardly from the front opening of the duct. Air travelling up the passageway to the rear of the firebox 10 also enters the duct 25 from either side thereof, but having first been deflected laterally by a roof portion 30 of the backplate 1 2. The roof portion 30 is an extension of the upper inclined portion 1 6 of thk backplate 1 2 and it forms part of the flue outlet 1 7 for the firebox 10.

The upper inclined portion 1 6 and roof portion 30 of the backplate 1 2 provides the air jacket with an enlarged cross-section in the region generally indicated by 27. This region 27 is over the hottest part of the fire. The enlarged cross-section acts to encourage the entrapment of a pocket of air in the region 27. Thus, as the flow of air is retarded in this region 27, this enables the maximum transfer of heat to occur. As a further aid to preventing air from escaping too rapidly from the region 27, a deflector 28 is mounted on the roof portion 30 of the backplate 1 2.

Also, a number of radiating fins 29 are mounted on the back of the firebox 10 to improve the heat exchange to the air in this region. In this case there are three fins 29, and these are in the form of angle irons which are welded along their apices to the backplate 12, but any other suitable number or form of fins may of course be used.

The above embodiment has the advantage that air is prevented from passing too quickly through the air jacket, meaning an extension of the time within which theair remaining in the air jacket is in contact with the firebox, thus the air is heated to a higher temperature.

This is an advantage over the arrangement of, for example, the fireplace unit of our earlier application No. 7912712 in which convected air could pass without difficulty straight out of a central duct. It will be appreciated that other means of extending the length of time within which air is in contact with the firebox could be employed, for example, by arranging that the air takes a tortuous route round deflectors or baffles.

Claims

1. A fireplace unit of the kind comprising a firebox which is open at a front side, a flue outlet, a fire housing which together with the firebox defines therebetween a chamber in the form of an air jacket, vent means below the firebox through which air can be drawn from the surrounding atmosphere, and duct means above the firebox through which heated air can be expelled into the surrounding atmosphere, the air jacket extending between the vent means and the duct means whereby, by convection, air is drawn into the air jacket from the vent means, is heated by the walls of the firebox and is expelled from the duct means, there being means for extending the length of time within which air remaining within the air jacket is in contact with the firebox.

2. A fireplace unit as claimed in claim 1 wherein said means for extending the length of time includes additionally providing the air jacket with passageways extending on either side of the firebox.

a region of enlarged cross-section to encourage the entrapment of a pocket of air.

4. A fireplace unit as claimed in claim 1, claim 2 or claim 3 wherein the duct means is in a position offset from the flue outlet whereby air is prevented from passing directly out of the duct means by the flue outlet.

5. A fireplace unit as claimed in claim 4 wherein the flue outlet is central and the duct means is positioned either side of the flue outlet.

6. A fireplace unit as claimed in any preceding claim wherein said means for extending the length of time includes the provision of one or more deflectors or baffles within the air jacket.

7. A fireplace unit as claimed in any preceding claim comprising radiating fins on the air jacket side of the firebox to aid the transfer of heat to the air in the air jacket.

8. A fireplace unit substantially as hereinbefore described with refrence to and as shown in the accompanying drawings.