GB2213574A

GB2213574A - Improvements in or relating to furnaces

Info

Publication number: GB2213574A
Application number: GB8729063A
Authority: GB
Inventors: Alan Geoffrey Bramley
Original assignee: J Mcintyre
Current assignee: J Mcintyre
Priority date: 1987-12-12
Filing date: 1987-12-12
Publication date: 1989-08-16
Anticipated expiration: 2007-12-12
Also published as: GB2213574B; GB8729063D0

Abstract

A furnace door 54 is raised by a bar 62 and handle 64 windlass type winding mechanism, the top of the door being capable of being raised to above the height of the bar to open the furnace, and the bar being situated at a height whereby an operator can turn the handle whilst standing on the ground next to the furnace. <IMAGE>

Description

I.IPROVEXIEN'TS IN OR RELATING TO FURNACES The present invention relates to furnaces and more particularly to furnace door apparatus and lifting mechanisms therefor.

Furnaces and in particular furnaces designed for melting or burning scrap material require to have a relatively large and preferably unobstructed opening. The door therefore has to be reasonably large and is therefore very heavy. This is achieved in known furnace designs by having a door which is moulded on guide wheels within a frame and which is counterbalanced so that the weight of the door or at least a substantial proportion of the weight is taken by the counterweight. The door is normally lifted within the frame by wire ropes which pass over the upper end of the frame.

The disadvantages of this known arrangement are that firstly it is e'pensive to provide a counterweight for the door and secondly the frame required for the wire ropes has to be ver high because the counterweight, for safety reasons, is raised and lowered onto the top of the furnace.

It is an object of the present invention to provide a furnace with a door apparatus which includes a door slidably mounted in a frame the door being provided with attachment means to which respective first ends of lifting ropes are attached the other ends of the ropes being attached to a winding arrangement comprising a relatively small diameter bar the bar being rotatablv mounted substantially horizontally above the door and being provided with handle means for turning the bar to raise the door and ratchet means for latching the door in a desired position, in which the attachment means is situated at an intermediate position with respect to the door, and in which the bar is situated at a position ith respect to the upper edge of the door that on raising of the door the upper edge of the door can be raised to a position above the level of the horizontal bar.

In the present invention the term "rope" is intended to include wires, wire ropes and chains or similar and the term "bar" is intended to include tubes or similar torsional members.

Preferably two lifting ropes are provided for each door and these are preferably attached at a position approximately halfway along the length of the door and at a position adjacent the edges of the door. Thus if one rope snaps the other will prevent the door from dropping out of control.

Preferably the handle means is mounted at j height above the ground, when the furnace is standing on a level surface such that an operator can readily turn the handle.

The bar is preferably of circular cross-section and of a diameter such that the mechanical advantage provided by the length of the handle enables a single operator to lift the heavy furnace door.

The frame for the furnace door is preferably made from angle iron forming a V-shape and the edges of the furnace door are also preferably made from angle iron providing a V-shape which slides within the V-shape of the frame.

Preferably the frame for the furnace door is extended downwardly to form front legs for the furnace.

Embodiments of the present invention will now be described, by way of example with reference to the accompanying drawings, in which: Figure 1 shows a furnace according to the present invention in front elevation; Figure 2 shows the furnace of Figure 1 in side elevation; Figure 3 shows the furnace door in front elevation in greater detail illustrating the construction principle; Figure 4 shows the door of Figure 3 in side elevation; Figure 5 is a detail of the corner construction of the door of Figure 3; and Figure 6 is a diagrammatic plan view of the furnace of Figure 1.

With reference now to Figure 1 the furnace 10 comprises a main combustion chamber 12, a chimney 14 front and rear support legs 16, 18, 2O, 22. A blower 24 is shown for illustrative purposes only the detailed design of the main furnace combustion chamber not forming part of the inventive concept will not however be described in detail.

The construction of chamber 12 may be from sheet metal outer skin with a "fire brick" lining as illustrated by dotted lines 24, 26, 28 (Figure 2). The furnace floor 30 slopes in known manner away from the inlet entrance 32.

Entrance 32 in normal operation is closed by a door 40 which is rectangular in shape and which is able to slide up and down the legs 16, 15 which form the front support legs. Legs 16, 18 are made from angle iron as can be seen from Figure 6. The upper "edge" 42 of door 40 and the lower "edge" 44 are shown in dotted lines when the door is in its closed position and are shown in solid lines when the door is partially lifted. The top and bottom "edges" comprise two lines 42, 42' and 44, 44' because of the angle iron construction as shown in greater detail in Figures 3 to 5. The upper surface 48 of the furnace chamber 12 is shown as a further dotted line as it is obscured by the door in its partially raised position.

Two attachment points 50, 52 are provided on the front face D4 of the door. Dependent on the construction of the door these may be welded points if the outer skin of the door is metallic over a thermal inner or bolts if the door is of high thermal resistance material without a metallic outer skin.

To each point 50, 52 a respective chain 56, 58 is attached. Chains are preferred as these are readily available and are strong but wires or wire ropes could be used. For the purpose of the present invention all are encompassed by the term "rope" which will be used hereinafter.

Each rope 56, 58 iS attached at its other end to a winding arrangement 60 which comprises a bar or tube 62, which in a preferred embodiment is bent into a crank shape to form a handle 64. The bar 62 is rotatably mounted in bearings 66, 68 and secured in position by a washer and cotter pin arrangement 70.

At the handle 64 a ratchet arrangement is provided by a ratchet 72 which is welded (or otherwise secured) to bar 62 and a pawl 74 which is pivotted on a spigot 76 attached to upright 16. Thus the support for the winding arrangement 60 comprises the support legs 16, 18 which also provide the guide rails for the door 40.

To lift door 40 handle 64 is manually turned, the height H above a level floor being approximately 5 ft (1.1/2 Metres)thereby being at shoulder height and thus convenient for maximum effort by an operative. The diameter of bar 62 is relatively small being typically 1.1/2 inches (4 cm) and therefore there is a substantial mechanical advantage given by handle 64 the length L of which is typically 12 inches (30 cm) and this enables a single person to lift door 40 hich is of course extremely heavy because of its thermal (fire brick) lining and strong construction.The operative can rest at an time because ratchet mechanism 72, 74 will retain the door in a desired position. the door can be lowered bv releasing pawl 74 from engagement with ratchet 72 in known manner and because of the mechanical advantage the door can be lowered steadily.

The door in its fully raised position as shown by dotted lines i0' in Figure 2 protrudes well above the top of legs 16, 18 but because of its construction (as referred to in greater detail with reference to Figures 3 to 6) it is still firmly held without any possibility of jamming. It is noted that the upper edge 42' of the door 40' is approximately level with the top of chimney 14 and that no part of the furnace protrudes above this level.

Thus the furnace can be operated in restricted height buildings, and or moved through lo level doors or openings.

With reference now to Figures 3 to 5 the door 40 is constructed from four pieces of angle iron 41, 42, 43, 44 (typically 4 cm x 4 cm x 5 mm) of a desired length (typically approximately 1 metre) to give a desired size of door. The angle iron is welded together at the corners as shown in Figures 3 and 4 to give a "diamond" shape in side elevation and a front sheet of metal 54 is preferably welded to the front edges of the frame as shown in Figure 5. A suitable fire brick infill is provided as indicated by shaded area 54'.

With reference now to diagrammatic Figure 6, the door 40 is fitted in between legs 16, 18 which are also constructed from angle iron and set such that the apex of each angle iron guides the door 40 which, once slid in from the top cannot be removed (except by lifting it over the top of legs 16, 18) because of box plates 16', 18'.

Door 40 is thus constrained to move up and down between legs 16, 18 with no requirement for guide wheels and with virtually no risk of jamming because the whole of the length of each side 41, 43 serves as an elongate guide. The arrangement is therefore extremely simple but effective.

Claims

1. A furnace with a door apparatus which includes a door slidably mounted in a frame the door being provided with attachment means to which respective first ends of lifting ropes are attached the other ends of the ropes being attached to a winding arrangement comprising a relatively small diameter bar the bar being rotatably mounted substantially horizontally above the door and being provided with handle means for turning the bar to raise the door and ratchet means for latching the door in a desired position, in which the attachment means is situated at an intermediate position with respect to the door, and in which the bar is situated at a position with respect to the upper edge of the door that on raising of the door the upper edge of the door can be raised to a position above the level of the horizontal bar.

2. A furnace with a door apparatus as claimed in claim 1 in which two lifting ropes are provided for each door, these being attached at a position approximately halfway along the length of the door and at a position adjacent the edges of the door.

3. A furnace with a door apparatus as claimed in claim 1 or claim 2 in which the handle means is mounted at a height above the ground, when the furnace is standing on a level surface such that an operator can readily turn the handle.

4. A furnace with a door apparatus as claimed in any one of claims 1 to 3 in which the bar is of circular cross-section and of a diameter such that the mechanical advantage provided by the length of the handle enables a single operator to lift the heavy furnace door.

5. A furnace with a door apparatus as claimed in any one of claims 1 to 4 in which the frame for the furnace door is made from angle iron forming a V-shape and the edges of the furnace door are also made from angle iron providing a V-shape which slides within the V-shape of the frame.

6. A furnace with a door apparatus as claimed in claim 5 in which the frame for the furnace door is extended downwardly to form front legs for the furnace.

7. A furnace with a door apparatus substantially as described with reference to the accompanying drawings.