US3733173A

US3733173A - Tower furnace collecting mechanism

Info

Publication number: US3733173A
Application number: US00210706A
Authority: US
Inventors: M Csapo; N Waldman; W Micho
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1971-12-22
Filing date: 1971-12-22
Publication date: 1973-05-15
Anticipated expiration: 1990-05-15
Also published as: NL7217344A; CA978353A; AU4947972A; GB1397287A; AU470745B2; DE2262466A1; FR2165476A5; JPS4870718A; BE792769A; IT969216B

Abstract

There is disclosed an endless conveyor belt for moving hot material from under a tower furnace, with the drive from the belt having provisions to compensate for changes in the length and the width of the belt due to expansion and contraction.

Description

i in

1% States atent 1 [H1 3,733,173 sapo et ai. [4 1 May 15, 1973 [54] TOWER FURNACE COLLECTING [56] References Cited MECHANISM UNITED STATES PATENTS [75] Inventors: Michael Csapo, Wyncote, Pa.;

Nathan w m Midkmd, Mich; 2,271,845 2/1942 Parsons ..65/21X William E. Micho, Ironton, Ohio 7 1 6/1957 Wilbur-m- 2,994,518 8/1961 Crans 1 Assignees: The Dow Chemical pa y, 3,056,184 10/1962 Blaha Midland, Mich.; Selas Corporation 3,627,285 12/1971 Siemssen ..263/21B of America, Dresher, Pa. Primary ExaminerJohn J. Camby 7 [22] Flled Dec 19 l Attorney-E. Wellford Mason [21] App]. No.: 210,706

[57] ABSTRACT CL 5/21, 432 There is disclosed an endless conveyor belt for moving 432/ 13, 32/ 146, 432/245 hot material from under a tower furnace, with the (2L.7 u- ..F27b drive from thc having provisions to compensate [58] Field of Search ..263/8, 21 123/2271; f changes in length and the width f the belt due to expansion and contraction.

7 Claims, 4 Drawing Figures s a m in W FI G.2

PATENTED W B 3,733,173

SHEET 2 BF 3 PATENTEDMAY 15 1975 3,733,173

SHEET 3 OF 3 TOWER FURNACE COLLECTING NIECHANISM The present invention relates to the manufacture of ceramic foam, and more particularly to the drive mechanism for a collecting belt upon which the foam forming material is collected.

BACKGROUND In the manufacture of ceramic foam small particles of clay or a similar bloatable material are dropped through the bloating zone of a tower furnace. As the particles fall they are bloated into individual, hollow spheres that are collected as an agglomerated mass at the bottom of the furnace. This mass is moved from under the furnace at a rate dependent upon the thickness of the slab it is desired to produce. For example, see Blaha U.S. Pat. No. 3,056,184 and Hess U.S. Pat. No. 3,240,850.

The intense heat of the particles, particularly at the location immediately beneath the furnace where they are collected, has caused difficulty with the collection apparatus. Primarily, the trouble has been due to warping and short service life of the collecting belt or conveyor.

Various dual drive mechanisms have been suggested for controlling the stresses placed in a conveyor belt. For example, U.S. Pat. Nos. 2,393,563 and 2,229,973 teach such mechanisms.

It is an object of the invention to provide collecting apparatus for use with a tower furnace that will operate indefinitely in the heat to which it is subjected.

It is a further object of the invention to provide a novel drive means for a collecting belt that is designed to operate under high temperature.

SUMMARY There is provided a mesh belt made of a high temperature alloy that is guided around a pair of drive sprockets. One of these sprockets is driven by a variable speed drive to move the agglomerated material from beneath the furnace to an annealing oven. The other sprocket is powered by a constant torque hydraulic drive to keep the belt under tension and to compensate for any variations in length or width of the belt due to the thermal conditions to which it is subjected. There is also provided a device for depositing a parting agent and insulating material on the belt as it is moving under the furnace into collecting position. i

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred emobdiment of the invention. In the drawings:

F IG. 1 is a longitudinal section of the apparatus taken on line ll of FIG. 2

FIG. 2 is a transverse section with the left-hand portion being taken on line 2a2a and the right-hand portion being taken on line 2b2b of FIG. 1.

FIG. 3 is a top view of the tail shaft drive mechanism, and

FIG. 4 is a side view of said mechanism.

The apparatus of the invention includes an endless conveyor 1 that moves around a head roller assembly 2 and a tail roller assembly 3, details of which will be described later. The upper course of the belt or conveyor moves under a preheating zone 4, a collecting zone 5, and a solidifying zone 6 which is adjacent to and opens into an annealing zone 7.

Conveyor 1 comprises a wire mesh belt 8 formed of a suitable alloy which will withstand the temperatures to which it is subjected. The edges of the belt are attached to roller chains 11 that are used to guide and move the belt through its path. The rollers of the roller chains on their upper course ride along guide rails 13 to hold them level in the desired plane of travel while the lower course of the belt is supported by the roller chains as they move along lower rails 14.

Adjacent to the left end of the upper course of the conveyor belt, a parting agent is placed on this belt. To this end there is provided a supply bin 15, the lower end of which is formed as a rectangular spout 16 of a length equal to the width of the belt. The parting agent, which is granular in form and has good insulating characteristics, flows through the spout 16 onto the belt as the latter is moving to the right. There is provided a plow 17 which smooths the upper surface of the parting agent. This plow can be adjusted vertically in order to determine the thickness of the layer of parting agent laid on the belt. As the upper course of the belt moves to the right it will move underneath a refractory structure 18 that forms the area of the preheating zone. A plurality of burners 19 are located in the side walls and roof of this structure in order to heat the upper surface of the parting agent to a temperature approaching the temperature of the material that will be collected in the adjacent collecting zone. Because of the insulating value of the parting agent, the belt itself remains relatively cool.

Collecting zone 5 is immediately below the open bottom of a tower furnace 21 of the type described in the abovementioned Blaha U.S. Pat. No. 3,056,184. As the belt with its layer of parting agent moves through the collecting zone, material falling through the furnace is collected on the parting agent. This is shown as a slab 22 of gradually increasing thickness as the belt moves to the right. The thickness of the slab that is collected will depend jointly upon the speed of the belt and the volume of material which is being dropped through the furnace. By the time the belt has reached the right edge of the collection zone, the slab is of the proper thickness. The slab on the belt then moves into a solidifying zone 6 in which the collected material forming the slab cools sufficiently so that is is selfsupporting and rigid. This zone is formed by refractory structure 23 which is built around the conveying belt. This zone may also have its temperature regulated by means of burners 19 as was the case in the preheating zone.

It will be seen, particularly in the left side of FIG. 2, that the lower edge of the side wall of structure 23 is provided with a pair of downwardly directed blades 26 which extend into the edge of the layer of parting agent. These form a sand seal" to prevent infiltration of cooling air at the edges of the belt. A similar construction is used on the other side of structure 23 and on the sides of the structure 18 forming the preheating zone and the structure beneath the furnace forming the collection zone. Thus, the entire area, from the point of deposit of the parting agent on the belt to and including annealing zone 7, forms a closed chamber with the belt acting as a moving floor.

Slab 22 travels on rollers 25 through an annealing zone 7 of the required length. Since the belt does not extend into the annealing zone, the structure forming this zone entirely surrounds the conveyor rolls 25 so that the slab continues to move through a closed chamber. Suitable seals are built around the ends of roll assembly 2 in order to prevent infiltration of cooling air between the solidifying and annealing zones. Thus, the slab is kept in a controlled environment from the time it is formed.

As belt 8 passes around head roller assembly 2 the parting agent will fall into a transversly extending collecting trough 27 from which it is removed by a conveyor chain 28 that passes over

sprockets

29 and 31 at opposite sides of the apparatus. It is noted that the sprocket 31 is driven by a suitable motor 32. The conveyor chains 28 are connected by pusher rods 33 that move through trough 27 to carry the parting agent and small pieces of slab that were cut from the edges to a bin 34 for disposal.

The head roll assembly 2 comprises a shaft 35 which extends across the apparatus and is joumaled in bearings 36 that are mounted on the frame. This shaft has mounted on it a cylinder 37 which supports belt 8. Shaft 35 has on it, between the bearings and the ends of cylinder 37, sprockets 39 for roller chains 11 to which the belt is attached. Shaft 35 has on its outer end a drive sprocket 41 that is driven in a conventional manner by a variable drive speed motor 42. This motor, by rotating shaft 35 and the parts attached thereto, pulls the upper course of the conveyor belt to the right in FIG. 1 at a constant preset speed. The head drive shaft is locked into the bearing 36 on the side driven by the motor 42. In like manner the drive sprocket 41 and sprocket 39 on the drive side are keyed and locked to shaft 35. To provide for axial expansion of the shaft 35 the sprocket 39 on the non-drive side is keyed but not locked to shaft 35 (i.e., it floats). Also the shaft 35 floats in bearing 36 on the non-drive end of the shaft.

The tail roll assembly 3 is of the same construction as head roll assembly 2. This roll is provided with a shaft 43 and has provided on its sprockets 44 for the roller chains 1 l of the conveyor. In order to provide for expansion of the belt in both length and width, the bearings for shaft 43 are movable. For this purpose one end of the shaft is joumaled in a bearing 45 that is slideable in a guide 46 in the direction of movement of the belt. The other end of the shaft 43 is mounted in a bearing 47 that is also slideable in the direction of the movement of the belt in a guide 48. The guide 48 is mounted on a plate 49 that has joumaled at its ends and parallel thereto a shaft 51 provided with a roller 52 at each end. One end of the plate is provided with a third roller 53. One roller 52 and roller 53 move along a track 55 while the other roller moves along a track 54. Thus, the second mentioned end of shaft 43 is mounted in a bearing that can also move in and out as the belt and its carrying roller expand in an axial direction. Shaft 43 is biased to the left in FIG. 1 in order to take up slack in the belt as it changes in length by means of a pair of chains 56 which are attached at one end to the

bearings

45 and 47 respectively and which pass over sprockets 57 with counterweights 58 fastened to the other ends. Sprockets 57 are keyed to shaft to provide for weight transfer from one side of the belt to the other in the event of uneven expansion in chain 11.

The collecting belt and its load are heavy enough so that a drive is used at both ends. The drive for the head end, driven by motor 42, pulls the upper course of the belt, the parting agent, and the slab to the right away from the furnace. The lower course of the belt is driven by a hydraulic drive which is designed so that it, in effect, drives each end of the shaft separately. This type of drive supplies a constant pull to both chains attached to the lower course of the belt regardless of the position of the shaft, and whether or not it expands axially. This drive is powered by a motor 61 which is connected to the input shaft of a constant torque type hydraulic drive and gear box unit 62. The output shaft of drive 62 is provided with a sprocket 64 that, through a chain 65, drives a second sprocket 66 on a shaft 67 extending across the width of the apparatus. Shaft 67 has on it two

sprockets

68 and 69, each of which serves to drive one end of shaft 43. The drives between shaft 67 and each end of shaft 43 are identical and similar parts will be given similar reference numerals. Sprocket 68 drives a countershaft 71 by means of a chain 72 and a sprocket 73. A second sprocket 74 on counter shaft 71 serves, through a chain 75, to drive a sprocket 76 on the outboard end of shaft 43. The lower run of chain is kept under a constant tension by means of an idler sprocket 77 that is mounted to rotate on the upper end of a vertical shaft 78. This shaft is biased downwardly with a constant force by means of a compression spring 79. The upper run of chain 75 passes over a guide sprocket 80 and has any slack in it taken up by a second idler 81 mounted on the end of an arm 82 which is pivoted at its other end to move around a fixed point 83 on the frame of the apparatus.

In operation of the system, the drive motor 61 for the tail assembly is started first to apply constant torque to the lower course of the belt without driving the upper course of the belt. The head drive motor 42 is then started and adjusted to the desired speed. Sprockets 39 on shaft 35 pull the upper course of the belt and keep it taut. As the belt starts to move, parting agent is placed on it in a layer of a thickness determined by the position of the blade 17. The surface of the parting agent is heated as it passes through chamber 4 to a temperature substantially equal to that of the bloated particles falling onto it as it moves below the furnace 21. The slab 22 builds up to the desired thickness and is cooled sufficiently in zone 6 to be self-supporting by the time it has reached head roller assembly 2. Here the slab passes on rollers 25 through an annealing zone while the parting agent falls into trough 27. This material is moved by pusher rods 33 to a collection zone where it is disposed of or treated for reuse.

The tail shaft 43 upon which sprockets 44 are mounted is driven by the hydraulic drive mechanism 62. This drive, as explained above, is applied equally and separately to both ends of shaft 43. Thus, as the belt changes in length and width, due to expansion and contraction, weights 58 will take up the increase in length. Drive chains 75 are acted on by spring-biased sprockets 77 so that the chains are under constant tension and will serve to transmit the same torque to the sprockets 76 on the ends of shaft 43 even if one edge of the belt should expand more than the others. Thus, the upper course of belt 5 is driven by head shaft 35 at a fixed speed by its drive motor 42. The lower course of belt 5 is driven at a speed depending upon the speed of the upper course and is maintained at a constant tension which takes into account the changing length of the belt. Driving the endless belt from both ends of its path of travel reduces the tension under which the belt must be placed and insures that there will be no tendency for the drive to bind.

The parting agent is placed on the upper surface of belt in a thick enough layer so that the insulating effect of the agent prevents the belt from being overheated.

The area above the belt surrounding the slab is actually a closed chamber with the belt forming the floor and whose temperature can be accurately controlled. Since the space between and below the courses of belt is open to the air, and may be force cooled, if desired, the various metal parts are kept well below the temperature they are designed to withstand with a consequent increase in their useful life.

While in accordance with the provisions of the Statutes we have illustrated and described the best form of embodiment of our invention now known to us, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit and scope of the invention set forth in the appended claims, and that in some cases certain features of our invention may be used to advantage without a corresponding use of other features.

What is claimed is:

1. In combination with a tower furnace having an opening in the bottom thereof, collecting mechanism to collect material dropped through said opening comprising an endless belt having an upper and a lower course moving horizontally beneath and to both sides of said furnace, a pair of drive rolls around which said belt is guided, first drive means connected to drive one of said drive rolls to move the upper course of the belt at a fixed speed to move material from under said furnace, a sprocket attached to each end of the other drive roll, a second drive means operative to exert a constant torque, and means to connect said second drive means individually to said sprockets to exert a constant torque to the lower course of said belt in a direction opposite to the direction of movement of the upper course.

2. The combination of claim 1 including means to mount said other drive roll for movement in the direction of movement of said belt to compensate for changes in length thereof, and means to bias said mounting means to take up any slack in said belt.

3. The combination of claim 1 including structure cooperating with said belt at each side of said furnace forming a chamber over said belt, means to deposit a layer of insulating material on said belt in advance of said structure, and means to heat said structure on both sides of said furnace.

4. The combination of claim 3 including a trough extending across said structure beneath said belt at said one side of said furnace into which the insulating material will fall as said belt moves around its roller, and means to remove the insulating material from said trough.

5. The combination of claim 1 including a shaft upon which said other drive roll is mounted, a sprocket on each end of said shaft, said second drive means including a chain individually to rotate each sprocket, and means to maintain the driving portion of each chain under a constant tension.

6. In combination, a first and a second spaced and substantially parallel rolls, means to mount said first roll for rotation around its axis, means to drive said first roll at a selected constant speed, means to mount said second roll for rotation around its axis, an endless belt extending around said rolls with its upper course moving through a plane at a given level, means to deposit a layer of material on said belt to be moved through said plane, structure including a top and downwardly extending sides over the upper course of said belt to form a chamber with the belt the floor thereof, the sides of said structure including a portion extending into the layer of material on said belt to seal the space between said sides and said belt, means to adjust the mounting means for said second roller toward and from said first roller, and constant torque drive means for said second roller.

7. The combination of claim 6 including burners in said structure to heat said chamber.