US2592184A - Furnace roof or arch - Google Patents

Description

April s, 1952 J, E, PLUCK 2,592,184

FURNACE Roo?l 0R ARCH Filed April 23, 1948 2 SHEETS-SHEET l fo/1w .FDA/HRD PL ack HUMA/f,

Attorney -April 8, 1952 J. E. PLUCK FURNACE ROOF 0R ARCH Filed April 25, 194e 2 SHEETS-SHEET 2 Q5 Q a N "0 O h n Q .Q x, I

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f i l :i 0 l/ l 'Ak il v 2 il N f N O /Il /nventor .7o/,w EDA/,ofen PL UCK Patented Apr. 8, 1952 FURNACE ROOF OR ARCH John Edward Pluck, Rotherham, England Application April 23, 1948, Serial No. 22,781 In Great Britain April 29, 1947 8 Claims.

This invention relates to the roofs or arches of industrial furnaces for use at high temperatures, which are built up `of bricks of refractory material, particularly to the roofs or arches of tilting furnaces of this type. The normal roof` material for such furnaces is silica, which possesses the property of almost completing its thermal expansion below 600 C., with the result that the temperature fluctuations encountered in normal working cause substantially no alteration in the shape or condition of the roof. In the construction of open hearth basic steel furnaces the use in place of silica of basic refractory materials, such as chrome magnesite, is very desirable on metallurgical grounds. Owing to the substantially linear thermal expansion of these basic refractories, the temperature fluctuations encountered in practice cause not only expansion and contraction of the roof but also substantial increase and decrease of its radius of curvature. Various proposals have already been made for supporting roofs of basic refractory material in such a way as to accommodate the movement produced by temperature variations.

In the specification of the prior United States Patent 2,444,365 of the inventor herein, there is described a construction for a stationary furnace in which the roof buttresses are attached to the lower ends of a pair of pivoted levers whose upper ends are coupled together through a reversing lever and a tie rod, so that the buttresses move equally and oppositely. The upper end of the lever carrying the rear buttress is connected to the short arm of a bell crank lever which is pivoted to a fixed point and has a weight bar hung from its longer arm. The 4arrangement is such that the leverage of the weight varies with the position of the roof, so that the varying roof thrust is balanced (with a margin of safety) at all temperatures in the working range.

According to the present invention a construction which is in general similar to that described in the above mentioned patent specification is modified for use in tilting furnaces. The invention comprises a tilting furnace having a roof of basic refractory material, in which the roof buttresses are attached to the lower ends of a pair of pivoted levers whose upper ends are coupled together in such a way that the buttresses move equally and oppositely and are also couj pled to a lever arm from which there is suspended a weight for balancing the roof thrust, the weight lever arm being inclined to the horizontal when the furnace is upright, so that when the furnace is tilted the weight lever arm will move towards the horizontal and the leverage of the weight will automatically be increased to balance the increased load in the roof.

Other and further objects, features and advantages of the invention will be pointed out hereinafter and set forth in the appended claims forming part of the application.

In the accompanying drawing a now preferred embodiment of the invention is shown by way of illustration and not by way of limitation.

In the drawing:

Fig. 1 is a vertical section through a furnace according to the invention in its upright position, and

Fig. 2 is a section similar to Fig. l showing a furnace in its tilted position.

The furnace proper comprises a bath receiving lined receptacle I6 with a tap spout I'I and a roof or arch 4. The receptacle is cradled in a furnace support structure generally designated by I8. The structure is carried on arcuate base members I, which are supported on rollers 2, so that the furnace can be tilted (clockwise in the drawing) by means of an hydraulic jack 3 operatively coupled with support structure I8 and a base I9. Fig. 2 shows clearly the positions of the various parts in the tilted position of the furnace. The ends of the furnace roof 4, are engaged by buttresses 5, attached to the lower ends of a pair of pivoted levers 6, whose pivot points are so chosen as to allow for both theexpansion and contraction and the change in shape of the roof caused by temperature changes. The upper ends of levers 6 are coupled together through a reversing lever 1 and a tie rod 8 and the upper end of the lever 6 carrying the rear buttress is connected to the shorter arm of a bell crank lever 9 pivoted by means of a pivot I3 to the top of support structure I8. From the longer arm of this lever there is suspended a bar 2U carrying weights I0 which are adjusted to balance the roof thrust with a suitable margin of safety, some of the weights being removed as the roof thins with use. The tie rod 8 is also connected through bell crank leversY and links to rolled steel joists II which bear on the upper surface of the roof and prevent it from collapsing outwards.

The arm of bell crank lever 9 from which the weights bar 20 is suspended is inclined upwardly and rearwardly when the furnace is in the upright position illustrated, so that when the furnace is tilted towards the tap hole side as can best be seen on Fig. 2, the distance between the line of action of the weight and the fulcrum point of the lever is automatically increased to a balance the increased load in the roof. In the particular design of furnace illustrated, in which the included angle of the roof (in the hot condition shown in Fig. 1 in full lines) is approximately 60 and the tilting angle is approximately 30, the load increase on tilting was found to be about 15%. The increased pressure on the buttresses necessary to balance this increased load could thus be obtained by inclining the weight lever arm upwardly at an angle of approximately 30 to the horizontal.

With such an arrangement, if the weight bar were suspended from a fixed point on the lever arm, a movement of the roof towards its cold position (shown in Fig. 1 in dotted lines) would result in an increase in the pressure applied to the buttresses, instead of the decrease in pressure required to balance the roof load. Accordingly, the effective length or the arm of crank lever 9 from which the weight I0 is suspended is made'- variable'corresponding to the roof movements due to temperature changes. For this purpose the aforesaid lever arm is provided with an elongated slot ld, and a cam plate l2 having an appropriate elongated slot l5 is xedly secured to support structure in a position parallel tothe plane of movement of lever The weight bar 20 is suspended by means of a pin 2l which is passed through both said slots. As will be evident, a variation of the angular position of the lever relative to structure le due to temperature caused roof movements will result in a displacement of the pin within the slots and hence in a corresponding change in the effective length of thelong; arm of lever e. Fig. l shows in full lines the weight suspension for a hot roof and the dotted lines the weight suspension for `a cold roof. It will further be evident that by suitable shaping and positioning of slots le and l5, the position of the suspension pin and hence of the weight can be automatically so adjusted that the weightv always produces the neces-- sary balancing pressure on; the buttresses.

In the construction illustrated, the levers 5 supporting the buttresses and the bell crank'lever e and reversing lever 'i connected to their upper ends are pivotally supported upon the bach and front wall stays, that is to fixed parts of the furnace. Alternatively, however, the pivots of these levers may be suspended for vertical sliding movement as described in the above mentioned patent specification. Y

What is claimed is:

l. An industrial furnace tiltable from an upright position into an inclined position having a bath receiving receptacle and a roof of basic refractory material engaged at its ends by buttresses attached tothe lower ends jof apair of pivotal levers coupled together attheir upper ends by linkage means causing the buttresses to move equally and oppositely in response to movements of the roof due to temperature changes, in combination `with support Ameans providing for tilting the furnacek with the receptacle and the roof from an upright position into an inclined position relative to' thesupport means, level means secured-to the linkage jmeans and to the furnace for angularv movement together with the latter, said lever meansbeing positioned upwardly inclined to the `horizontal when the furnace is in its uprightposition, and a counterweight suspended from saidv lever means for balancing the roof-thrust on the buttresses, tilting of the furnace moving the lever means toward the horld zontal, thereby increasing the leverage of said counterweight.

2. An industrial furnace as described in claim l, in combination with weight suspension means displaceable along the lever axis of said lever means, and adjustment means lixedly secured to the furnace and engaging said suspension means for varying the position thereof relative to the lever axis in response to a change in the position of the lever means caused by roof movements due to temperature changes, thereby varying the weight leverage in accordance with the roof movements and automatically balancing the variations of the roof pressure upon the buttresses as caused by said roof movements due to temperature changes.

3.. An industrial furnace as described in claim 2, wherein said adjustment means comprise a cam member iixedly mounted on the furnace for a tilting movement in unison with a tilting movement of the furnace and engaging said suspension means for displacing the same incorrespondence with the aforesaid roof movements due to temperature changes.

v4:. An industrial furnace as described in claim 3, wherein said lever means comprise aleverv arm having an axial elongated slot, and wherein said cam member comprises a cam plate mounted substantially parallel to the plane of said lever arm and including an elongated slot positioned at an angle to the lever slot, and wherein said suspen-l sion means comprise a Ipin elementvsupporting the counterweight and engagingsaid/slots, the relative angular position of the slots controlling the position of the pin elementin the lever vslot and, hence, the leverage of said counterweight; 1^"

5. An industrial furnace of thevtype comprising a bath receiving receptacle, `a furnace support structure, a roof arch associated therewith, supporting levers at opposite ends of said arch, buttresses for said arch received 4by one end of each of said levers, pivot means intermediate the ends of said levers for pivoting the same to the furnace support structure, suspension means connected to said levers for supporting the same and the arch from said furnace support structure, and connecting means lconnecting the ends of said supporting levers opposite the arch receiving ends for accommodating inward and outward movements of said arch ends withrespect to each other due to expansion and contraction'of the arch, in combination with supportmeans providing for tilting the'furnace support structure with the receptacle and the roof from an upright position relative to the support means into an inclined position, lever means pivoted to the furnace support structure and coupled to said con# necting means, the angular position of said lever means relative to the furnace being controlled by movements of the connecting means as caused by expansions and contractions of the roof arch, and relative to the horizontal by the position of tilt of the furnace support structure, the said lever means being in an upwardly inclinedv position when the furnace support structure is in its upright position, and a counterweight suspended from said lever means for balancing the roof thrust on the buttresses, tilting of thefurnace support structure moving the lever means toward the horizontal, thereby increasing the leverage of the counterweight when the furnace support structure is tilted from its upright position into an inclined position. l

6. An industrial furnace Ias defined in claim 5, wherein said lever means comprise a bell crank,

one arm of said bell crank being pivoted to said connecting means and the other arm supporting said counterweight.

'7. An industrial furnace as dened in claim 5, in combination with compensating means compensating for variations in thrust upon said buttresses as caused by expansions and contractions of the roof arch, the said compensating means comprising suspension means for said counterweight and a member xedly secured to the furnace support structure for tilting in unison therewith, said lever means and said xed member each having bearings slidably engaged by said suspension means for supporting the latter, the position of the suspension means within and relative to the bearings determining the effective length of the lever means, and hence, the leverage of the counterweight, the said position of the suspension means being controlled by the angular position of the lever means relative to the furnace support structure, and, hence relative to the said fixed member.

8. An industrial furnace as defined in claim '7, wherein said lever means comprise a lever arm having an axially elongated slot, and wherein said fixed member comprises a cam member mounted substantially parallel to the plane of 6 said lever arm and including an elongated slot positioned at an angle to the slot in the lever arm, and wherein said suspension means com- Y prise a pin element supporting the counterweight and engaging said slots. the relative angular position of the slots being controlled by the angular position of the lever means relative to the furnace support structure and, hence, relative to the cam member and controlling the position of the pin element in the lever slot, thereby also controlling the leverage of said counterweight.

JOHN EDWARD PLUCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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