US3436120A

US3436120A - Blast furnace teardown apparatus

Info

Publication number: US3436120A
Application number: US389432A
Authority: US
Inventors: John Armstrong
Original assignee: J J GRADY CO Inc
Current assignee: J J GRADY CO Inc
Priority date: 1964-08-13
Filing date: 1964-08-13
Publication date: 1969-04-01
Anticipated expiration: 1986-04-01

Description

April 1969 J. ARMSTRONG 3,436,120

BLAST FURNACE TEARDOWN APPARATUS Filed Aug. 15, 1964 Sheet INVENTOR. JOHN ARMSTRONG ATTORNEY A ril 1, 1969 J. ARMSTRONG 3,435,120

sus'r wanes 'rmanown APPARATUS Filed Aug. 15, 1964 Sheet 2 of 5 FIG.4

INVENTOR JOHN ARMSTRONG ATTORNEY April 1969 J. ARMSTRONG 3,436,120

BLAST warmer: TEARDOWN APPARATUS Filed Aug. 15, 1964 Sheet 3 of 5 FIGS INVENTOR, JOHN ARMSTRONG ATTORNEY April 1969 J. ARMSTRONG 3,436,120

BLAST FURNACE TEARDOWN APPARATUS Filed Aug. 1:, 1964 Sheet 4 of 5 Q 1 LL m INVENTOR w JOHN ARMSTRONG BY gal- M;

O ATTORNEY A ril 1, 1969 J. ARMSTRONG BLAST FURNACE TEARDOWN APPARATUS Filed Aug. 13, 1964 Sheet J IN VENTOR. JOHN ARMSTRONG FIG. I3 BY ymfi A TTOR NE Y 3,436,120 BLAST FURNACE TEARDOWN APPARATUS John Armstrong, Michigan City, Ind., assignor to J. J.

Grady (10., Inc., Pitttsburgh, Pa., a corporation of Indiana Filed Aug. 13, 1964, Ser. No. 389,432

Int. Cl. E211) 35/02 U.S. Cl. 29970 6 Claims The present invention relates to new improved means for removing brick or masonry linings etc. from circular structures such as iron-making blast furnaces and the like.

A typical modern iron-making blast furnace comprises an outer steel shell lined on the inside with refractory brick having embedded therein water cooled coils etc. The operation of the blast furnace causes such linings to become worn, cracked or badly broken; and, periodically, it is necessary to tear down the furnace lining so that the furnace may be rebuilt with a new lining, cooling coils etc.

The usual procedure for tearing down and removing the lining is to lower into the blast furnace from the top a scaffold bearing a number of men (e.g. -20) using air hammers, pickaxes and rakes etc. for manually tearing down the lining from the shell and to remove debris from the scaffold. From time to time, the scaffold is lowered so that the men may progressively tear down successively lower sections of the blast furnace lining until the furnace teardown is completed. Also, since the lower portion of a blast furnace stack is larger than the upper portion, it is necessary to enlarge the scaffold as it is lowered in the stack, to enable the men to manually break up the furnace lining with air hammers and like manual tools. According to present practice, the scaffold platform is enlarged as it is progressively lowered in the blast furnace by adding radial stringers and boards. Of course, this holds up the furnace teardown work, besides requiring mid-air assembly which is undesirable from the safety viewpoint. In addition, the extended wooden stringers are subject to breakage; and enlargement of the platform increases the likelihood of the scaffold tipping due to movement of men, equipment and loading of debris disposed at an increased distance from the platforms center of gravity.

The job of blast furnace teardown is a quite formidable one, and such manual procedures for teardown require the use of many laborers over a considerable period of time; eg according to present practice prevailing in the U.S. steel industry, it requires about 15-20 men working as above described about 72 hours continuous work to tear down a blast furnace. This is not only a slow and expensive procedure in terms of man hours consumed, but it results in substantial additional expense due to delay in rebuilding the furnace so that it may be returned to production. Further, undue delay may adversely affect the efiiciency of the entire steel making plant which is dependent on the blast furnace for the pig iron used in making steel.

The problems and shortcomings of the above-discussed manual furnace teardown system have been recognized for some time, as exemplified by U.S. patent to Putnam No. 2,710,418 proposing a power scaffold for blast furnace teardown to eliminate manual procedures.

Accordingly, it is a primary object of the present invention to provide a new improved power-operated blast furnace teardown system and apparatus for quickly and efficiently removing the linings from blast furnaces, overcoming the shortcomings and disadvantages of prior methods and apparatuses heretofore available and used.

It is an object of the present invention to provide a new improved blast furnace teardown apparatus comprisatet ing a novel combination of a conventional mass-produced digging machine with a novel turntable scaffold arrangement. It is a related object to provide such a new improved power-operated blast furnace teardown device incorporating a platform which may be lowered by a crane into the top of a blast furnace and thereafter progressively lowered to desired positions for progressive teardown of the furnace lining. It is another related object to provide such a new improved power teardown apparatus in which the center of gravity of the digging machine is substantially at the center of the platform, for increased stability and to avoid dangerous tipping of the platform which might cause men or equipment to fall from it.

It is still another related object to provide a new improved power-operated apparatus for tearing down a blast furnace lining in which the load is primarily vertically imposed on the scaffold supporting cablesfor increased stability. It is yet another related object to provide a new improved method and apparatus for tearing down a blast furnace lining which makes it possible to conduct the actual breaking up of the furnace lining at a level approximately at or below the level of the platform, to prevent debris from striking men on the platform helping the digging machine operator.

It is another object to provide a new improved poweroperated blast furnace teardown apparatus including a scaffold having a centrally mounted digging machine with an extensible boom, whereby it is unnecessary to enlarge the platform as it is lowered into the enlarged lower sections of the blast furnace thereby avoiding the delay and disadvantages of present teardown practices requiring such platform enlargement. It is another object of the present invention to provide a new improved poweroperated blast furnace teardown apparatus which is adapt ed for use in oversized blast furnaces.

It is still another object of the present invention to provide a novel scaffold suspension incorporating a novel cross head, platform, and cable arrangement whereby the boom of a digging machine on the platform may swing in a circle without interference from the supporting cables, for efficient teardown operations. It is another related object to provide an improved power teardown device incorporating a scaffold turntable with means for locking in desired position a conventional digging machine having 200 swing and permitting ready reorientation of the digging machine for tearing down the entire circular periphery of the furnace.

It is still another object of the present invention to provide a novel improved scaffold platform having removable side portions making it possible to use the same platform for blast furnaces of different sizes, and particularly permits insertion of the platform and related equipment through a smaller blast furnace throat.

It is a further object of the present invention to provide a novel improved power-operated blast furnace teardown system and apparatus which enables four men to tear down a typical blast furnace in about 36 hours, with an approximate 35% reduction in cost compared to prevailing manual practices in the U.S. steel industry.

It is another object to provide such a power teardown system using a minimum of special machinery, and making it possible to quickly obtain mass-produced spare parts at low cost (in addition to minimizing cost of designing and producing equipment).

The above and other objects and advantages of the present invention will be apparent from the following description thereof with reference to the accompanying drawings and claims.

In the drawings (wherein like parts are identified by like numerals):

FIG. 1 is an idealized diagrammatic cross section of an iron-making blast furnace, showing in side elevation Patented Apr. l, 196%? a blast furnace teardown device according to the present invention (in upper position in solid line, and in lower position in dotted line);

FIG. 2 is an enlarged side elevation of part of the scaffold or platform suspension arrangement of the present invention shown in FIG. 1;

'FIG. 2A is a top plan view of a portion of the platform suspension means shown in FIG. 2 (looking down along line 2A--2A in FIG. 2)

FIG. 3 is a top plan view of the upper cross head used in the platform suspension of this invention (looking along line 3-3 in FIGS. 1 and 3);

FIG. 4 is a side elevation of the upper cross head shown in FIG. 3;

FIG. 5 is a top plan view of the platform which supports the digging machine and workmen according to the present invention (looking down along line 55 in FIG. 2), with portions of the platform surface omitted in the left half of FIG. 5 for greater clarity;

FIG. 6 is a side elevation of the platform shown in FIG. 5 (looking along line 66 in FIG. 5);

FIG. 7 is a vertical sectional view looking along line 77 in FIG. 5;

FIG. 8 is a partial vertical sectional view looking along line 88 in FIG. 5;

FIG. 9 is a partial vertical sectional view looking along line 99 in FIG. 5;

FIG. 10 is a side elevation view showing the device for locking the digging machine mount bearing to locate the digging machine in desired position;

FIG. 11 is a partial horizontal sectional View taken along line 11--11 in FIG. 10;

FIG. 12 is a side elevation and partial sectional view illustrating use of the power-operated apparatus of this invention for tearing down the lining in the upper narrower throat portion of a blast furnace;

FIG. 13 is a side elevation and partial sectional view similar to FIG. 12 illustrating use of the power-operated apparatus of this invention for tearing down the lining in the lower wider portion of a blast furnace, with a modification of the mount for the air hammer on the boom of the digging machine.

Referring to the drawings, particularly FIG. 1, the new improved blast furnace teardown apparatus according to the present invention is indicated generally at 20 and is shown in connection with a more or less conventional blast furnace 22 having an outer steel shell 24 lined with fire brick lining 26. While the bustle pipe 28, mantle 30, columns 32 and tuyere 34 are shown, the other conventional parts of the furnace 22 have been omitted for the purpose of clarity.

The improved teardown apparatus 20 of this invention comprises a scaffold platform 36 having a digging machine 38 rotatably mounted thereon. The platform 36 and the digging machine 38 are suspended by means of cables 40 from a crosshead 42. The crosshead and thus the platform and digging machine are raised and lowered within the furnace by the suspension means shown generally at 44.

More specifically, the suspension means 44 includes a cable or wire rope 46 which is attached at one end to a suitable hoist or the like (not shown) and extends around the pulley or pulleys 48, with its other end attached to a grab ring 50. The pulleys 48 are mounted in a bracket 52 attached to the blast furnace building superstructure 54. Four chains 46, which are of equal length, have opposite ends secured to the grab ring 50 and crosshead 42.

As shown especially in FIGS. 1, 3 and 4, the lower end of each of the chains 56 is fastened to one of four brackets 58 which are welded to upper flanges 60 of the steel I-beams '62 and 64, adjacent the ends thereof.

Beams

62 and 64 form the primary members of the crosshead 42 and are spliced and welded together at their midpoints,

with the intersection 66 of these beams being reenforced by plates 68. For added stability and strength, four I-

beams

72, 74, 76, and 78 are welded t9 beams 62 and 64 4 at suitable points, as illustrated. A bracket 70 may be provided for the attachment of a safety cable, not shown.

As shown particularly in FIGS. 2 and 4, beams 62 and 64 have a portion of their lower flanges 80 cut away adjacent each end, and reenforcing plates 82 are welded to each side of the web 84 above the cut-away portion, with a hole 86 being drilled through the plates 82 and web 84 for attaching the upper ends of the cables 40. Cables 40 extend between

beams

62 and 64 and the platform 36 to support the latter.

Alternatively, it is possible to cut away the upper flanges 60 adjacent each end of

beams

62 and 64, drill a second hole through the plates 82 and web 84, and attach the lower ends of the chains 56 thereto instead of to the brackets 58.

The lower ends of the cables 40 are attached to the ends of steel I-bearns 88 and 90 which are spliced and welded together at their midpoints and comprise primary members of the platform 36. Plates 92 reen-force the intersection 94 of

beams

88 and 90. At each end of the

beams

88 and 90, the upper and

lower flanges

96 and 98 are cut away, and a plate 100 is welded to each side of the web 102, with a pair of horizontally spaced

holes

104 and 106 being drilled through plates 100 and web 102. The lower ends of the cables 40 are secured to the inside hole 106, with the length of all the cables 40 being equal between the points of attachment on the crosshead and on the platform. By reason of this suspension arrangement of crosshead 42, platform 36, and cables 40, the platform 36 will always remain parallel to the crosshead 42 and will not tip or tilt even when the weight thereon due to equipment, men and/or debris is unevenly distributed or suddenly shifted. The stability of the platform 36 is further enhanced by the fact that the intersection 66 of the

beams

62 and 64, the intersection 94 of the

beams

88 and 90 and the vertical axis of the grab ring 50 all lie substantially on a common vertical line.

Referring now to FIGS. 2 and 2A, one end of a relatively short wire rope or cable 108, called a igtail, is secured to the outside hole 104 drilled in the ends of platform beams 88 and 90. The other ends of these four pigtails are clamped to each of four wire ropes or cables 110 by a plurality of conventional commercially available clamps 112, which are positioned above the platform 36 so that a workman standing thereon can loosen or tighten the clamps without difficulty.

The four steel cables 110 are attached at their upper ends by cable anchor means 114 to a top ring 116 mounted on the throat of blast furnace 22. These anchor means 114 are spaced at 90 intervals about the upper flange 118 of top ring 116 and comprise two C-shaped

members

120 and 122 which engage the outside edge of top ring flange 118.

Members

120 and 122 are bolted to

plates

124 and 126 which sit on the upper surface of the flange 118. The inner ends of the plates form a yoke 128 for receiving the upper end of the cable 110 as it passes around the upper, inside edge of the flange 118. A conventional wire rope or cable socket 130 for receiving and anchoring the upper end of the cable 110 is held between the upper ends of the

plates

124 and 126 by the pin or bolt 132.

The cables 110 extend from the anchor means 114 to the bottom of the furnace. The lower ends of the cables may hang loosely, but preferably are extended through holes in the furnace wall, such as through the tuyere 34, and are secured to a furnace column 32. Securing the lower ends of the cable 110 to the furnace superstructure minimizes swinging of the platform 36 within the furnace. Alternatively, wooden outriggers (not shown) can also be utilized to prevent the platform from swinging excessively. The pigtails 108 support the platform 36 and digging machine 38 within the furnace 22 at various vertical positions for teardown operations.

As stated above, the pair of spliced steel I-

beams

88 and 90 are the primary supporting members of the platform 36. Four relatively short steel I-

beams

138, 140, 142

and 144 are welded between and interconnect the

beams

88 and 90, forming an inner square as shown particularly in FIGURE 5. Four additional steel I-

beams

146', 148, 150 and 152 are also welded between and interconnect the

beams

88 and 90 forming an outer concentric square, as shown in FIG. 5. For added strength, four L-shaped reinforcing

members

154, 156, 158 and 160 are fastened between the midpoints of beams 138-144 and beams 146-152 respectively, as shown in FIG. 5.

The area between the inner square formed by beams 138-144 and the outer square formed by beams 146- 152 is covered by thick, wooden planking, shown generally at 162. This planking is fastened to the main platform cross/beams 88 and 90 and the described

platform members

138, 140, 142, 144, 146, 148, 150, 152 and 160 by a plurality of bolts and nuts, the heads of bolts 161 being countersunk in the planking 162 to provide a smooth upper platform surface. As shown in FIG. 9, a piece of Wood or metal 164 is placed between the upper surface of the members 154-160 and the planking to compensate for the thickness of the I-beam flanges.

As shown in FIG. 5, the above desiribed generally square base portion of the platform may be enlarged by attaching

supplementary sections

166, 168, 170 and 172 to its sides, whereby the platform 36 assumes a generally circular shape having a diameter equal to the length of the

main beams

88 or 90.

The primary supporting members for each of sections 166-172 are three like

triangular braces

174, 176 and 178. These triangular braces are mounted between the upper and lower flanges of the beams 14 6-152; and, as shown in FIGS. 6 and 7, they are attached thereto by long bolts 180 which pass through aligned holes drilled in the upper and lower flanges of beams 146-152 and in the upper and

lower extensions

179 and 181 forming part of the braces. The braces can be pivoted about the bolts 180 whereby they either project from the sides of the beams 146-152, as in FIG. 5, or are swung so that they lie adjacent the web 182 of the I-beams 14 6-152. The braces are placed in this latter position when not in use. But, if it is desired to enlarge the surface of the platform 36, the braces are swung out to the positions shown in FIG. 5, and heavy wooden planking 184, similar to 162, is laid over the braces and fastened to the braces, preferably by countersunk bolts. Pieces of wood or metal 186 are placed between planking 184 and braces 174-178 to compensate for the thickness of the I-beam flanges.

Thus, when the supplementary sections 166-172 are used, the upper surface platform 36 is covered by relatively smooth, uninterrupted planking except for a small area at each end of the

main members

88 and 90 and the center square bounded by the four I-beams 138-144, over which the digging machine 38 is mounted, as now discussed.

As shown in FIG. 5, four mounting

plates

188, 190, 192 and 194 are fastened to the platform 36 at the junc tures of

beams

88 and 90 with beams 138-144. A bottom plate 196 is also fastened to the platform 36 by a plurality of bolts, and overlies the mounting plates 188-194 and the central area bounded by the four beams 138-144. In practice, the same bolts secure both the mounting plate and the bottom plate to the plaform 36, alhough, of course, this is not necessary.

Referring especially to FIGURE 10, there is mounted on the bottom plate 196 a lower portion 198 of the housing of -a heavy weight thrust bearing 200 which is of conventional commercially available design. The upper portion 202 of this bearing housing is attached to the bottom of the digging machine 38. The outer ring 205 of the bearing 200 is provided with a gear 206, and the ring 205 is secured to the plate 198 and thus the platform 36. This gear 206 which is part of the commercial bearing 200 is utilized to prevent the digging machine 38 from rotating relative to the platform 36 when the lock- 6 ing mechanism 208 is engaged. This mechanism 208, shown in FIGS. 10 and 11, comprises a handle 210 which can be actuated by the operator of the machine and which is attached to a vertical shaft 212 extend-ing downwardly through a guide 214 to the horizontal plane of the gear 206. The lower end of the shaft 212 is connected to a crank 216, which through link 218, is connected to a lock 220 supported and guided by a lock guide 222 and slide bearing 224. The mechanism 208 is arranged so that movement of the handle 210 in one direction causes the lock 220 to advance towards the gear 206 and intermesh with the teeth thereof, thus preventing the machine 38 from rotating relative to platform 36. Movement of the handle 210 in the opposite direction causes the lock 220 to move away from the gear 206 and allows the machine 38 to rotate freely with respect to platform 36.

The digging machine 38 is mounted on the platform 36 such that the centers of gravity of the machine and the platfrom lie on a common vertical line. The machine 38 is basically a conventional hydraulic excavator unit comprising motor 226, pump (not shown), operators controls 228, boom 230, stick 232, and tool 234, etc. The Hopto Model 220TM excavator manufactured and sold by Warner & Swasey of Cleveland, Ohio, and similar excavators made by International Harvester Company and others may be used for digging machine 38, with minor modifications of the commercial model. For example, due to space limitations and environment, the conventional gasoline or diesel engine is replaced by a compact 220 or 440 volt electric motor, and the engine mounting portion shortened to permit rotation on a smaller diameter platform.

Assuming use of a Hopto Model 220TM, the machine 38 has a hydraulically actuated boom 230, stick 232, and tool mount 240. The boom 230 can be swung through a working arc of about 200 degrees, independent of any movement of the machine itself; and the tool 234 pivoted about the end of the stick 232 through an angle of about 165 degrees. The boom, stick and tool can be brought in close to the center of the platform so that the boom can be swung through an arc of more than degrees without hitting the

cables

40, 108, or 110.

The tool 234, includes a standard commercial air hammer 236, for example, the Ingersoll Rand Buster Model X-72, with a moil 238, attached thereto. The length of the moil may be between 1-6 feet, and preferably is 2 feet.

The air hammer 236 and moil 238 are mounted along the base of a triangular bracket 240 of U-shaped crosssection, which may be attached to the end of the stick 232 in either of two positions. As shown in FIG. 12, the bracket 240 is attached apex up to the hydraulic motor means 242 at the angle opposite the base which is pivotedly attached at one end to the end of the stick itself. When mounted in this manner, the moil 238 is generally directed or pointed upward. As shown in FIG. 13, the bracket 240 can also be attached apex down to the stick at the angle opposite the base, which is secured at one end to the motor means 242. When attached in this manner, the moil 238 is generally directed or :pointed downward. The orientation of bracket 240 on the stick 232 can be easily changed While the machine is in the furnace to modify the Working angle of air hammer moil 238.

Since the total reach of the boom and stick of the Hopto Model ZOOTM is approximately 19 feet plus the length of the moil, it is apparent that the machine 38 is capable of tearing down the lining in all but the largest blast furnaces. However, if the radius of the furnace is larger than the combined reach of the boom, stick and moil, the platform 36 can be shifted off-center and held there by guy lines or suitable Outriggers (not shown) extending from platform 36. The suspension system 44 is such that even in this off-center position, the platform remains parallel to the ground, and operation is stable.

The extensible boom permits the machine 36 to be mounted in the center of the platform throughout the entire teardown operation and thus the vertical loading always remains substantially the same. Furthermore, there is no need to modify or enlarge the platform 36 as the teardown operation progresses down the ever-increasing diameter furnace 22, as heretofore required.

Operation After the furnace, whose lining is to be torn down and replaced, has cooled sufficiently the anchor means 114 and the cables 110 are installed in the furnace. If the throat of a furnace is large enough, the crosshead 42, platform 36, and digging machine 38 are lowered as a unit directly into the furnace to the proper level and the pigtails 108 attached to the cables 11%. However, if the throat is narrow, the digging machine 38 and the peripheral platform sections 166-172 are removed so that platform 36 may itself be lowered sideways into the furnace, and then leveled so that the pigtails 108 can be attached to the cables 110. Once the platform is in the furnace the crosshead 42 is suspended over the platform and the cables 40 are connected between the platform and crosshead. Next the machine 38 and also platform sections 166472 are remounted on the platform 36.

The platform is supported by the pigtail 108 and the cables 110, and bears the load imposed when the air hammer moil 238 is applied to the furnace lining 26 to break it away from shell 24, as shown in. FIG. 12 or in FIG. 13. In general practice, the lining is torn down proceeding from the top of the furnace to the bottom and the platform is usually suspended at, or slightly above, the level of the remaining lining to prevent pieces of brick etc. from striking the workmen on the platform. The digging machine 36 and air hammer 236 are operated in conventional manner as will be apparent to those in the art in light of the disclosure herein. The moil 238 is operated in downward direction to the extent feasible, to load cables 110 vertically.

When it is desired to lower or raise the platform 36 and machine 38 within the furnace 22, as when all the lining 26 has been removed at a given level, the clamps 112 are loosened and the platform is accordingly raised or lowered by the hoist 46 through the suspension system 44. The clamps 112 are then retightened, at the new vertical level and the machine can again begin tearing down the lining. When it is desired to rotate the machine, as for example to teat-down the opposite side of the furnace, the moil 238 is securely embedded in the brick lining 2-6, with the boom and stick extending between two cables. The lock mechanism 208 is released, and the actuating means for boom 230 is operated, thereby causing the machine 38 to rotate up to 200 relative to platform 36 since the tool and boom are fixed. Thereafter, the gear 206 is again locked again-st rotation of machine 38, and the boom, stick and moil are retracted within the cables 40 and 110 (see dotted line in FIGURE 12), and the boom is swung past the cables to relocate the moil for continued teardown operation. If further rotation of the machine is desired, this procedure is repeated.

A further advantage of the above-described crosshead 42, cables 40 and platform 36 arrangement is that the boom, etc. of the machine 36 can be swung through a full 90 degree are before it contacts one of the cables, and the machine 36 can be rotated through 360 degrees relative to the platform.

While the apparatus of this invention can, of course, be constructed in various sizes, in the preferred embodiment, the beams 83 and 90 of the platform and the

beams

62 and 64 of the crosshead are 15 feet in length and the other parts of the apparatus are scaled accordingly.

It is apparent from the foregoing that the new improved blast furnace teardown apparatus of this invention provides quicker and more efficient removal of the linings of blast furnaces than was possible with apparatus and methods heretofore used; that the apparatus of this invention is safer than prior systems; that this system requires significantly fewer men and total man-hours to do a superior job; that the new system of this invention is flexible and adaptable to different size blast furnaces; and that the present invention achieves various objectives, advantages and improved results as set forth earlier in this application.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. An improved apparatus for tea-ring down the lining in the shell of a blast furnace comprising: a platform; means for raising and lowering said platform within a furnace; means for stabilizing the platform at a desired location; and power operated teardown means rotatably mounted on said platform and capable of tearing down the lining of said furnace throughout its circumference, said second recited means including a plurality of elongated cables secured to an upper portion of the furnace and extending towards the bottom thereof, with means attached to said platform for connecting the platform with said elongated cables.

2. An apparatus as defined in claim 1 wherein the lower ends of said elongated cables pass through apertures in the furnace walls and are secured externally of the furnace shell.

3. In combination, an apparatus for tearing down the lining in a blast furnace comprising: a platform adapted to pass through the throat of said furnace; cable means secured to an upper portion of the furnace and extending toward the bottom of the furnace; means for connecting said platform to said cable means whereby said platform may be supported at desired vertical position within said furnace; hoist means for raising and lowering said platform in said furnace including a crosshead positioned above and connected with said platform by a plurality of cables of substantially equal length; and a power operated digging machine mounted on the top surface of said platform, said platform having substantially a square shape and including two main beams spliced together, with two sets of shorter beams interconnecting said main beams, one set being near said intersection of said main beams and the other set being adjacent the ends of said main beams, supporting braces interconnecting the beams of said one set with the beams of said other set, and planking secured to said beams for covering the area between the said two sets of beams.

4. The combination recited in claim 3 in which brackets are pivotably attached to the outer.sides of said other set of beams and can be covered with planking so as to extend the platform with a substantially circular shape having a diameter equal to the length of said main beams.

5. An improved teardown apparatus for tearinig down the lining in a blast furnace comprising: a platform including a main frame; means coupled to said platform for supporting it within a blast furnace; bearing means on the top surface of said main frame; a digging machine having an extensible boom mounted on said bearing means above said main frame, the machine being rotatable with respect to the platform; and locking means for preventing rotational movement of said machine relative to said platform; supporting means for raising and lowering said platform from within said furnace including a cable extending from without said furnace and connected to a crosshead, said crosshead including frame members having portions thereof connected to parts of the platform by cables so that said platform is maintained substantially parallel to said crosshead; a plurality of elongated cables secured to upper portions of said furnace with their lower ends extending adjacent the bottom of said furnace, and means for connecting said cable means to said platform to support the platform.

6. An improved teardown apparatus for tearing down the lining in a blast furnace comprising: a platform including a main frame; means coupled to said platform for supporting it within a blast furnace; bearing means on the top surface of said main frame; a digging machine having an extensible boom mounted on said bearing means above said main frame, the machine being rotatable with respect to the platform; locking means for preventing rotational movement of said machine relative to said platform, said platform including main supporting beams, supporting members interconnecting said beams, means covering said beams and members so that said platform has an unobstructed upper surface, braces pivotaibly and. removably attached to the outer edges of said platform and 10 adapted to project therefrom, and additional means for covering said braces for providing an extension of said platform surface.

References Cited UNITED STATES PATENTS 3,346,300 10/1967 Grant 29970 3,302,976 2/1967 Grant 29970 748,962 1/1904 Lewis 182142 X 1,067,375 7/1913 Proctor 299-70 X 2,346,033 4/ 1944 Jordon 18212'8 2,710,418 6/ 1955 Putnam. 2,983,496 5/1961 Grant 29970 X 3,090,983 5/1963 Modrak et al. 299-70 X ERNEST R. PURSER, Primary Examiner.

US. Cl. X.R. 17343; 182128 3 5 33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3 L120 Dated April 1 1969 Inventor(s) John Armstrong It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I" Column 3, line 12 should read along line 3-3 in FIGS.

1 and 2); Column 5, line 63, "alhough" should be altho SIGNED Arw SEALED DEC 2 19% Axum Flewhe" WILLIAM E. SOHUYL'SR, JR. Attestmg Offic sioner of Patents

Claims

1. AN IMPROVED APPARATUS FOR TERARING DOWN THE LINING IN THE SHELL OF A BLAST FURNACE COMPRISING: A PLATFORM; MEANS FOR RAISING AND LOWERING SAID PLATFORM WITHIN A FURNACE MEANS FOR STABILIZING THE PLATFORM AT A DESIRED LOCATION; AND POWER OPERATED TEARDOWN MEANS ROTATABLY MOUNTED ON SAID PLATFORM AND CAPABLE OF TEARING DOWN THE LINING OF SAID FURNACE THROUGHOUT ITS CIRCUMFERENCE, SAID SECOND RECITED MEANS INCLUDING A PLURALITY OF ELONGATED CABLES SECURED TO AN UPPER PORTION OF THE FURNACE AND EXTENDING TOWARDS THE BOTTOM THEREOF, WITH MEANS ATTACHED TO SAID PLATFORM FOR CONNECTING THE PLATFORM WITH SAID ELONGATED CABLES.