Kiln casing

Abstract: A casing (10) for a kiln includes at least one casing unit comprising: vertical and horizontal frame members (11-18) assembled according to the shape of a framework of the kiln; outer plates (21,22,26,27) secured to at least one of the vertical and horizontal frame members to cover spaces encircled by said vertical and horizontal frame members; guide fittings (40) provided at spacings (t) between outer plates adjacent in a longitudinal direction of the kiln for slidably supporting the ends of said outer plates; and securing means such as bolts or welds for securing said outer plates to said vertical frame member or horizontal frame member so that adjacent outer plates can expand into the spaces (t) between them in a longitudinal direction of the kiln.

Description: The present invention relates to a casing used for industrial kilns, and more particularly to an improved casing for tunnel-shaped kilns. A conventional roller hearth kiln known as an industrial kiln has a kiln made of refractory bricks in the form of a tunnel, which is housed or stored in a casing made of heat resisting steel. The casings are connected in the longitudinal direction of the kiln to form a tunnel-shaped kiln usually several tens of meters in total length. FIGURES 9(a), 9(b) and 9(c) in the accompanying drawings show a conventional casing unit. A casing unit 1 comprises horizontal frame members 2 provided in a longitudinal direction of the kiln, horizontal frame members 3 provided on the bottom of the kiln in an axial direction of rollers (not shown) and vertical frame members 4 standing vertically at both ends of the horizontal frame members 3. Bottom plates 7 and side plates 5 are fixed to inner sides of frame members 2, 3 and 4 at their outer peripheries by spot welding. Supporting fittings 6 are provided between upper vertical frame members 4 and lower vertical frame members 4. Rollers indicated by dotted line 8 in FIGURE 9(c), are inserted in a width direction of the kiln. A plurality of rollers 8 are arranged in a parallel relationship with each other in a longitudinal series along the kiln. However, a problem with such a conventional casing for kilns is that the total length of the kiln increases during firing operations. The side plates 5 and the bottom plates 7 adjacent in a longitudinal direction of the kiln and welded to each other expand themselves according to the high temperature, which causes accumulation in total length. As a result, the total length of the casing increases so that the distance between the kiln and the peripheral devices provided in front of and in the rear of the kiln is changed, causing problems. In addition, when the side plates 5 and the bottom plates 7 do not perform thermal expansion uniformly, the adjacent side plates 5 and the bottom plates 7 themselves compress and interfere with each other, resulting in deformation of the casing and dislocation of the kiln center, which often leads to misalignment of the kiln itself particularly when the temperature of the kiln is elevated or lowered. Distortion also occurs in the pipings or ducts around the kiln. It may be noted that US-A-4764108 describes a kiln in which there is an outer and an inner shell. The outer shall is rigidly fixed to a foundation, but the inner shell may slide relative to the foundation. This design is intended to simplify construction, as the oven may be built out of several modules. FR-A-2268236 describes a kiln housing for a roller-type kiln, in which top and bottom longitudinal frame members do not get as hot as the middle frame members. To account for uneven expansion, the middle frame members are made non-contiguous, and rigidly fixed only at one end. Outer steel plates extend continuously from the top to the bottom frame members, and are fixed at both longitudinal ends. This document therefore discusses a way of taking into account non-uniformity in expansion of the frame between the middle section and the top and bottom. This document forms the basis of the pre-characterising part of claim 1. It is therefore desirable to provide an improved kiln casing preventing the increase in total length of the casing caused by the heat conducted from inside of the kiln, or at least preventing excessive increase in total length of the kiln. Consequently, it may be possible to provide an improved kiln casing preventing occurrence of the malfunction of the kiln and the peripheral devices around the kiln. The present invention provides a casing for a kiln including at least one casing unit comprising upright and horizontal frame members rigidly assembled together according to the shape of the kiln, and outer plates secured to the frame members to cover spaces defined by the frame members, wherein the outer plates are fixed to the frame member by securing means over only a short longitudinal extent of the plates, whereby the remaining major longitudinal proportion of the plates can expand thermally with longitudinal movement relative to the longitudinal frame members; and in that guide fittings are provided at or near spacings between longitudinally adjacent said outer plates to support the plate ends slidably and allow the longitudinal plate spacing to vary under such expansion. The outer plates may comprise side plates disposed on the side wall of the casing unit. The outer plates may comprise bottom plates disposed on the bottom wall of the casing unit. The securing means may include welding. The securing means may include a bolt. The securing means of the outer plates may be located at, near or around the centres of the outer plates, in a longitudinal direction of the kiln, preferably at or adjacent side edges thereof. For example, the securing means of the outer plates may be located on two or three positions in the vicinity of the center of the both opposite ends of the outer plates in the longitudinal direction of the kiln. A plurality of the casing units may be linked with each other in the longitudinal direction to form an elongate casing e.g. for a tunnel kiln. In such an arrangement, the outer plates are supported slidably relative to the upright or horizontal frame members. The ends of the outer plates can be supported by guide fittings slidably in a longitudinal direction of the kiln, so that their ends are slidable in the guides in the longitudinal direction. The outer plates adjacent in the longitudinal direction expand freely in a longitudinal direction of the kiln in a spacing formed between the adjacent outer plates so that the adjacent outer plates will not interfere with each other. Accordingly, when the outer plates expand thermally, the casing does not expand remarkably in total length. In particular this is achieved by fixing the outer plates longitudinally relative to the frame members at only a short longitudinal region thereof so that a major proportion of the plate length can expand longitudinally relative to the frame members. By way of example, the drawings show an embodiment. FIGURE 1 is a partial elevational view showing the inner side of a casing for a kiln in accordance with the present invention. FIGURE 2 is a partial elevational view showing the outer side of the casing. FIGURE 3 is a front view of the casing. FIGURE 4 is a plan view of the casing. FIGURE 5 is a perspective view showing horizontal and vertical frame members. FIGURE 6 is a plan view showing the mounting conditions of a guide fittings. FIGURE 7 is a sectional view taken along a line VII - VII in FIGURE 6. FIGURE 8 is an enlarged view of portion VIII in FIGURE 3. FIGURE 9(a) is a plan view of a casing unit in accordance with the prior art. FIGURE 9(b) is an elevational view of the casing units shown in FIGURE 9(a). FIGURE 9(c) is a front view of the casing units of FIGURE 9(a). DETAILED DESCRIPTION OF THE EMBODIMENT In FIGURE 1 through 8, a casing for a kiln constructed according to the present invention is shown. The casing for a kiln is used for a roller hearth kiln. The roller hearth kiln utilises casing units linked with each other in a longitudinal direction of the kiln, and is of the order of several tens of meters in total length. A casing unit 10 comprises vertical and horizontal frame members as shown in FIGURE 5. Referring to the frame members, a horizontal top frame member 11, a horizontal upper frame member 12, a horizontal lower frame member 13, and a horizontal bottom frame member 14 are provided in a longitudinal direction of the kiln. A horizontal bottom intermediate frame member 15 is provided between the horizontal bottom frame members 14, which are provided at the opposite ends of the casing unit 10. A horizontal bottom link frame member 16 connecting the horizontal bottom frame members 14 with each other at the opposite ends is provided at the bottom of the casing unit 10 in a width direction of the kiln. The vertical frame members comprise a vertical upper frame member 17 and a vertical lower frame member 18. The horizontal top frame member 11 is linked with the horizontal upper frame member 12 by the vertical upper frame member 17. The horizontal lower frame member 13 is linked with the horizontal bottom frame member 14 by the vertical lower frame member 18. A jack bolt 28 is mounted to the lower end of the vertical lower frame member 18. A supporting means 24 is mounted between the vertical upper frame member 17 and the vertical lower frame member 18. Now an outer plate will be described. As shown in FIGURES 1 and 2, upper side plates 21 are welded to the horizontal top frame member 11 and the horizontal upper frame member 12 respectively at short upper and lower intermediate portions B₁ and B₂ thereof, in longitudinal register, to locate them in rectangular spaces defined by the horizontal top frame member 11, the horizontal upper frame member 12 and the vertical upper frame member 17. Lower side plates 22 are welded to the horizontal upper frame members 13 and the horizontal bottom frame members 14 respectively at the upper and lower intermediate portions C₁ and C₂, so that they are located within rectangular spaces encircled by the horizontal lower frame member 13, the horizontal bottom frame member 14 and the vertical lower frame member 18. As shown in FIGURES 1 and 6, guide fittings 40 are provided in spacings t₁ formed between adjacent upper side plates 21. As shown in FIGURE 7, each of the guide fittings 40 comprises a bolt 42 which extends through the vertical upper frame member 17 provided on outside of the kiln with respect to the upper side plate 21, a pressing plate 43 located in the inside of the kiln and a nut 44 threadingly engaged with the bolt 42. The guide fitting 40 are secured to the upper side plates 21 by fastening the bolt 42 and nut 44. The end 21 b of the upper side plates 21 are slidable in right and left directions as viewed in FIGURE 7. The upper side plate 21 has a bent portion 21 a which is horizontally bent at the top thereof as shown in FIGURE 8. The bent portion 21 a is slidable along the horizontal upper frame member 11. This enables the bent portion 21a to freely expand or contract relative to the horizontal top frame member 11 in a longitudinal direction of the kiln when the upper side plate 21 is thermally expanded. As shown in FIGURES 3 and 4, ceiling members 20 are rested on the bent portions 21 a of the upper side plates 21. The bottom plates 26 and 27 used as outer plates are located in a space encircled by the horizontal bottom frame member 14, the horizontal bottom intermediate frame member 15 and the horizontal bottom linking member 16. The bottom plates 29 and 27 are welded to the horizontal bottom intermediate frame members 15 at the positions shown by A . The bottom plates 26 and 26, bottom plates 27 and 27 are adjacent to with each other in a longitudinal direction of the kiln, and spaced at a spacing t₃ between the each of them, wherein the bottom plates 26 and 27 expand or contract freely. A kiln body is disposed within the described casing unit 10. The plates 21,22,26,27 are disposed at the inside of the frame members. In the casing unit 10 subjected to heat from the kiln, the upper and lower side plates 21 and 22 extend in a longitudinal direction of the kiln while the side plates 21 and 22 are secured to the frame members 11, 12, 13 and 14 at the described welded points. At this time, the end portion of the upper side plate will not interfere with the end portion of the lower side plate since the spacings t₁ and t₂ absorb the expansion of the side plates . At the same time the adjacent bottom plates 27 and 27, 26 and 26 will not interfere with each other since the spacing t₃ absorbs the expansion of the adjacent bottom plates. Accordingly, the total length of the casing unit 10 will not increase remarkably and the total length of the casing will not increase remarkably either, since such casing units are linked with each other in a longitudinal direction of a kiln and form the casing for the kiln. As a result, the casing prevents the kiln from interfering with peripheral equipment and piping, which are provided in front of or at the rear of the kiln. In the above mentioned embodiment, means for securing the frame members 11 through 16 to the upper side plate 21 and lower side plates 22 or the bottom plates 26 and 27 functioning as outer plates is welding. However, it will be recognized that there are other equivalent means of securing in the present construction such as bolts or other fastening means. It is desirable to fix the outer plates in opposite positions in the vicinity of the center thereof. It would be possible to fix the side plates at one point located upper and center thereof and to secure the lower end of the side plates by the guide fittings. It would be also possible to fix the side plates at a plural number of positions for sound securing, for example, a several positions in the vicinity of the center of the side plates. Similarly the guide fittings may take a number of possible forms provided that they serve their function, as described above, of helping to retain the outer plates in position on the frame members while allowing them a degree of at least longitudinal movement relative to the frame member at the guide fitting location. As will be apparent from the foregoing, the present invention provides an improved casing for kiln, wherein the ends of the outer plates in the longitudinal direction of the kiln are free from the vertical frame members or horizontal frame members. Therefore, the outer plates adjacent with each other in the longitudinal direction will freely expand or contract without interfering with each other according to thermal expansion or contraction. As a result, such advantages are achieved that the casing will not expand remarkably in total length and will not interfere with peripheral equipment and ducts around the kiln, and hence will ensure the safety of the kiln.

Claims: A casing for a kiln including at least one casing unit comprising upright and horizontal frame members (11-18) rigidly assembled together according to the shape of the kiln, and outer plates (21,22,26,27) secured to the frame members to cover spaces defined by the frame members, characterised in that the outer plates are fixed to the frame member by securing means (A,B,C) over only a short longitudinal extent of the plates, whereby the remaining major longitudinal proportion of the plates (21,22,26,27) can expand thermally with longitudinal movement relative to the longitudinal frame members (11-14); and in that guide fittings (40) are provided at or near spacings (t) between longitudinally adjacent said outer plates to support the plate ends slidably and allow the longitudinal plate spacing (t) to vary under such expansion. A casing for a kiln according to claim 1 wherein the securing means for a said outer plate is located in the vicinity of the longitudinal center thereof. A casing for a kiln according to claim 1 or claim 2 wherein the securing means for a said outer plate is located at two or three positions in the vicinity of the longitudinal center thereof. A casing for a kiln according to any one of the preceding claims wherein said securing means fix the outer plates longitudinally relative to the frame members at a locality (A,B,C) on one or both longitudinally-extending edges thereof. A casing for a kiln according to any one of the preceding claims wherein said outer plates comprise side plates (21,22) disposed at the side wall of the casing unit. A casing for a kiln according to any one of the preceding claims wherein said outer plates comprise bottom plates (26,27) disposed at the bottom wall of the casing unit. A casing for a kiln according to any one of the preceding claims wherein said securing means includes welding. A casing for a kiln according to any one of the preceding claims wherein said securing means includes a bolt. A casing for a kiln as defined in any one of the preceding claims wherein said casing includes a plurality of the casing units linked with each other in the longitudinal direction of the kiln.

Inventors: YAMAGUCHI MINORU, YAMAGUCHI, MINORU
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1991
Main classification: F27B9
IPC codes: F27B9, F27D1