GB2149073A - Kilns and ware decks - Google Patents

Abstract

A kiln with steel framework (11) and thermal insulation (12) has a floor area smaller than associated ware decks (19). The kiln is raised by a hydraulic ram (21) so the kiln's bottom edges clear the decks and then when the kiln is over a deck the kiln is lowered onto the ware deck. The kiln can be movable over stationary ware decks or the ware decks can be movable under a stationary kiln. Ware on the decks enter the kiln through a door so the amount of lift required is small. High temperature seals (22) are provided on the bottom edges of the kiln to engage the ware decks. <IMAGE>

Description

SPECIFICATION Kilns and ware decks FIELD OF THE INVENTION The present invention relates to kilns and ware decks for use in firing bricks and ceramics.

BACKGROUND OF THE INVENTION Top hat kilns are known and these are lowered over stacks of pottery and other ware.

The use of such kilns tends to be restricted to certain processes in view of safety requirements. Therefore most industrial kilns are permanent installations into which ware stacked on ware decks is moved by means of doors.

The mobile ware decks have to be sealed into the kilns usually by means of labyrinth seals between the decks and the decks and the walls. A labyrinth seal by its very nature leaves a clearance between the members being sealed and this is usually between 2 and 3 millimetres. Multiplying this clearance by the perimeter of the kiln gives an area of 500 square centrimetres for the passage of leakage. In view of this relatively large area kilns are usually limited to an operating pressure of less than + millimetre water guage; this limits the escape of hot gases escaping from, and cold air entering, the kiln. Any entry of cold air leads to uncontrolled atmosphere and temperature distribution within the kiln.

SUMMARY OF THE INVENTION One aspect of the present invention provides a kiln comprising walls and at least one door for receiving ware decks, which kiln is provided with means for causing sufficient relative vertical movement of the kiln relative to the ware decks to create and remove a vertical clearance between an upper surface of the work decks and bottom edges of the kiln walls.

The means does not lift the kiln the inside height of the kiln but merely a few centimetres. Since kilns, nowadays, are of light weight construction, not much power is needed.

Another aspect of the present invention provides a kiln and ware decks for use with the kiln, the kiln having walls and a door, wherein the width of the decks is greater than the inside width of the kiln, wherein the kiln has associated with it means for raising the kiln relative to the ware decks to enable the kiln to move horizontally relative to the ware decks so that edges of the ware decks can be moved below bottom edges of the kiln walls and the kiln then lowered to rest on the deck edges, and wherein a high temperature seal is provided between the deck edges and the said bottom edges.

The invention can be applied to arrangements wherein the ware decks are fixed being in the form of thermally insulating plinths with the kiln being movable over the decks to arrangements wherein the kiln is vertically immovable but the ware decks are lifted by the vertical motion causing means with the ware decks being in a fixed location or movable into the kiln, and to arrangements wherein the kiln is fixed in location with the ware decks being movable into the kiln and with the kiln being raised and lowered onto the decks.

In this description, walls where the context permits includes a fixed back to the kiln and, of course there is a roof to the kiln and heating appliances. The back is integral with the other walls and seals on an edge of the deck in the same way, the back and the roof form an integral whole with the side walls and are sealed together in the conventional way.

The ware enters the kiln through the door with only the edges of the deck going beneath the kiln walls. If, as is usual, the kiln receives a plurality of decks these are sealed together to form effectively a single deck. The deck is pushed against the back of the kiln and forms a seal therewith. The trailing end of the deck is preferably flush with the ends of the walls forming a door frame. The door is either of the up-and-over type similar to a garage door or moves vertically in a straight lift similar to a guillotine-door but has associated means for pushing the door against the frame in a final closing movement of the door to make a seal.

A convenient form of seal is formed by a stack of edge-bonded refractory fibre sheets, such as Safil (RTM). Such seals can be provided with stops to limit the amount of compression and these stops can be adjustable.

A kiln embodying the invention can be operated at pressures many times those permitted by labyrinth seals (a figure of 100 times is thought possible) and virtually have no problem due to cold air ingress. Running at a higher pressure improves heat transfer to the wares and improves the temperature distribution within the kiln. A further advantage is that the atmosphere can be controlled more easily to give an oxidising or carburising atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic side view of a kiln embodying the invention, Figure 2 is a detail view of a seal used in the embodiment of Fig. 1, Figure 3 is a schematic side view of another kiln embodying the invention, Figure 4 is a schematic side view of a further kiln embodying the invention, and Figure 5 is a detail view of a leading or trailing edge of a ware deck.

BEST MODES OF PERFORMING THE INVEN TION The embodiments of the invention now to be described are given by way of example.

Kilns are of a steel framework 11 lined internally with thermal insulation 12 forming the back 14, sides 1 5 and top or roof 1 6 of a rectangular box-type structure. Ware is introduced into the kiln through a door 1 7 loaded on ware decks 1 8. Traditionally the edges of the ware decks formed a T-join with the wall of the kiln with the ware deck forming the upright of the T but with the present invention the bottom edges of the walls abut the racks.

A first embodiment of the present invention is illustrated in Figs. 1 and 2. In this embodiment, there is a line of fixed plinths 1 9 which act as the ware decks. These plinths are of thermally insulating material such as aerated thermal-resistant concrete possibly with a higher grade material protective top. Running along each side of the plinths there is a rail 1 3 an which runs wheels 20 mounting the steel framework 11 of the kiln. In this embodiment each end of the kiln has to have a door 1 7 or the kiln must be movable along the line and then transversely. These wheels are held down during rolling motion each by means of a hydraulic ram 21.The plinths are wider than the inside dimension of the kiln and with the wheels held down the bottom edges 22 of the kiln's side walls pass over the side edges 23 of the plinths but when the rams are released the bottom edges will sink down into engagement with the side edges.

The bottom edges are formed with two confronting flanges 29 on which are threaded stacks of edge bonded sheets of a refractory fibrous material 24 having a degree of edgewise resilient yield and a high hydraulic impedance forming a compressible high-temperature seal; the amount of compression of this seal can be limited by a screw 25 which can be adjusted to cope with any set occurring after some use and wear. Preferably the seal is provided behind, and protected by, the primary high-temperature insulation 26 of the kiln. Conveniently each plinth would have associated with it, a stop (not shown) to locate the kiln with its ends flush with the ends of the plinth.The doors 17, if head room permits, are of the guillotine-type or otherwise of the up-and-over type but have a finel closing movement giving a sealing pressure on seals similar to those described of stacks of edge bonded refractory fibre sheets between the doors and the ends of the kiln and the plinth.

Such a final closing movement can be achieved either by having the door slidable in a generally vertical frame 27 which can be pivoted slightly about an axis 28 above the kiln and forcibly driven about that axis by means (not shown) to provide that closing motion or by using quick acting fasteners (not shown) to clamp the door shut manually.

The embodiment of Fig. 3 is very similar except that the ware decks 30 are provided on wheeled cars 31 and the kiln is fixed both in position and height with a hydraulic platform 32 being used to jack up the cars so that the bottom edges of the walls sealing engage the edges of the decks.

The embodiment of Fig. 4 is again similar and differs from the embodiment of Fig. 3 in that the kiln is fixed in position as before but is raised by jacks 33 to allow the cars to be wheeled underneath and is then lowered to make the seal. In this version, it is highly desirable that the kiln cannot be lowered so the bottom edges of the kiln rest on the floor; if they did people might get their feet trapped under the kiln.

It is of course feasible for the seals to be carried by the ware decks rather than the walls and this might be advantageous if the seals have to be replaced. However this would entail providing a seal on each ware deck rather than only one on the kiln and, whilst more difficult of access, a seal on the kiln works out more economical in the long run.

It will be apparent that in the embodiments of Figs. 3 and 4 that only a single door 1 7 is needed and that a permanent back 1 4 can be used. Generally in these kilns a plurality of ware cars are fired at the same time and these cars are sealed together at deck level by means of labyrinth seals. To take advantage of the present invention, it is desired to seal the cars together by high-temperature compressible seals as inbetween the walls and the deck.

In Fig. 5 a car 40 with a deck 41 carries a seal 42 of edge-bonded refractory fibre on the leading edge which abuts the trailing edge of the preceding car at deck level or with the back of the kiln.

Claims (11)

1. A kiln comprising walls and at least one door for receiving ware on decks, which kiln is provided with means for causing sufficient vertical movement to create and remove a vertical clearance between an upper surface of the ware deck and bottom edges of the walls.

2. A kiln and ware decks for use with the kiln, the kiln having walls and a door, wherein the width of the decks is greater than the inside width of the kiln, wherein the kiln has associated with it means for raising the kiln relative to the ware decks so that the edges of the ware decks can be disposed below bottom edges of the kiln's walls and the kiln then lowered to rest on the deck edges, and wherein a high temperature seal is provided between the deck edges and the said bottom edges.

3. A kiln and ware decks according to claim 2 wherein the high temperature seal has associated with it means for limiting the pressure on the seal.

4. A kiln and decks according to claim 3 wherein the limiting means is adjustable to cope with any set assumed by the seal.

5. A kiln and ware decks according to claim 2, 3 or 4 wherein the seal is of edge bonded refractory fibre sheets.

6. A kiln and decks according to any one of claims 2 to 5 having a single door and a back permanently attached to the side walls wherein the back wall is arranged to sit on an edge of the deck and be sealed thereto by the high temperature seal.

7. A kiln and decks according to any one of claims 2 to 5 having a door both at the front of the kiln and at the back.

8. A kiln and ware decks according to any one of claims 2 to 7 wherein the inside length of the kiln is such that the kiln receives a train of decks, the decks having means for sealing abutting ends together.

9. A kiln and decks according to anyone of claims 2 to 8 wherein the or each door in its closed position abuts the adjacent end of the kiln and the adjacent end of a or the ware deck.

10. A kiln and decks according to claim 9 wherein the or each door has a closing motion such as the door is pushed hard against the adjacent end of the kiln and the adjacent deck end.

11. A kiln and decks substantially as herein described with reference to the accompanying drawings.