US3773880A - Slicing a column into slabs and reuniting the slabs in a tapered portion of the extrusion die - Google Patents

Abstract

Bolted to the auger barrel of a brick extruding machine is an internal tapering die base to which is clamped an internal tapering shaper cap whose cross section upstream of its mouth is provided with tensioned wires which slice the column longitudinally as it proceeds through said shaper cap. Downstream of the horizontal wires, the continued taper of the shaper cap forces into cohesion, by tremendous pressure, the adjacent longitudinal wire cut surfaces of the severally created adjacent slabs, sufficiently enough to permit each transversely cut section, of the resulting multi- sectioned extruded unit, to be safely man- or machine-handled and to be processed through its subsequent drying and firing cycles like normal full- size brick, units that can at any time after firing be tapped apart on the original wire cut lines to create brick slabs, each e.g., 3/8 " to 1" thick, which are especially economical and useful for facing the surfaces of industrialized mass-produced building panels of any practical size/

Description

Nov. 20, 1973 P. s. KELSEY SLICING A COLUMN INTO SLABS AND REUNITING THE SLABS IN A TAPERED PORTION OF THE EXTRUSION DIE 2 Sheets-Sheet 1 Filed May 10, 1972 Nov. 20, 1973 P. s. KELSEY 3,773,880

SLICING A COLUMN INTO SLABS ANI) RHUNI'IINL: 'lllll Jib/H3}; IN I\ TAPERED PORTION OF THE EXTRUSTON D1111 Filed May 10, 1972 2 Sheets-Sheet z United States Patent O US. Cl. 264-56 9 Claims ABSTRACT OF THE DISCLOSURE Bolted to the auger barrel of a brick extruding machine is an internal tapering die base to which is clamped an internal tapering shaper cap whose cross section up stream of its mouth is provided with tensioned wires which slice the column longitudinally as it proceeds through said shaper cap. Downstream of the horizontal wires, the continued taper of the shaper cap forces into cohesion, by tremendous pressure, the adjacent longitudinal wire cut surfaces of the severally created adjacent slabs, sufficiently enough to permit each transversely cut section, of the resulting multi-sectioned extruded unit, to be safely manor machine-handled and to be processed through its subsequent drying and firing cycles like normal full-size brick, units that can at any time after firing be tapped apart on the original wire cut lines to create brick slabs, each e.g., to 1'' thick, which are especially economical and useful for facing the surfaces of industrialized mass-produced building panels of any practical size.

This application is a continuation-in-part of application Ser. No. 18,173, filed Mar. 10, 1970, now abandoned.

BACKGROUND OF THE INVENTION In recent years, especially in the United States, brick has been losing ground as a construction material because of the high cost of bricklayer labor, the sensitivity of bricklaying scheduling to weather conditions, the difficulty of and need for handling individual bricks at a construction site, the relative slowness with which a bricked building can be closed-in so that building interior con struction can be begun.

On the other hand, brick is an elegant building material, since it requires so little maintenance over the building life and can constitute walls of indisputably handsome appearance, among other advantages.

So it is considered well worth an intensive effort to keep this elegant building material from suffering further deterioration of market penetration.

Most attempts at industrialized production of building panels including a fully or partly embedded/ exposed facing of coursed brick have employed standard-sized brick, e.g. 3 /2 to 3% inches thick by about 8 inches long. A very significant reason why such panels have not achieved significant market penetration is the predominating feeling among members of bricklayer unions that industrialized mass production of modular panels incorporating bricks can curtail the amount of labor cost for fabrication of brick faced buildings and thus diminish the employment and status of members of their unions. In fact, in certain instances, the right of craft union members to boycott construction sites utilizing prefabricated assemblies which could be fabricated on the job has been judicially upheld. The present invention seeks to avoid this problem by providing brick slabs so thin that they cannot normally be set by hand under field conditions since they are no more than about one inch thick and therefore can normally only be set in industrially prefabricated panels.

Brick are normally produced by extruding a column of green, plastic brick material, then severing it into individual green brick for drying and firing.

Accordingly, an obvious way to make brick slabs of one inch thickness and less, would be to stretch wires across the mouth of the die from which a brick column issues, thereby slicing individual brick up into three to seven brick slabs that thus could be held to any desired bed depth from /8 to l".

So-called brick slabs have been made for many, many years. Siding contractors for years covered old buildings with brick slabs that were held in place with steel clips that were nailed to existing outside walls and which governed the arrangement of the brick facings. Mortar was then tubed or tucked into the open joints. Of late years, there have been some sales of slabs to the do-it-yourself home owners. With some of the fine new adhesives on the market, it is not too difficult to glue on a very, very presentable brick facing that few would believe was only /2" thick.

To the best of the present inventors knowledge all slabs made to date have been made by slicing with so-called outside wires. The job done by wires so placed produces an acceptable final product, but it is difficult or impossible to knit the green slabs back into a single unit againone that can be handled with ease in the normal manner that regular full size brick are processed. The sliced-up brick slabs tend to fall apart, and each and every one of such brick slabs has to be handled very, very carefully. If an outside face (only one per slabbed brick), is to be used, then perhaps every other course of brick being set on the kiln cars for future drying and firing has to be reversed, so that every brick has its face in direct and full contact with the face of the brick it is setting on top of.

The latest and most modern brick plants which have mechanical setting machines could not cope with the separation problems experienced with outside wire brick column slicers.

The prior US. patents of others of which the inventor is aware include:

Converse et al., 551,306, wherein thin flat extrusions are provided with smooth, kerfed, future break points. The process disclosed is believed to be impractical for production of clay brick slabs.

Atkins, 276,326, prevents laminations in an extruded product by using a grating prior to the forming die.

Chambers, Jr., 275,467, discloses production of a uniform column and apparatus for cutting the column into uniform-sized pieces.

Hilgendorf, 1,783,287, divides the product of a single cavity die into two totally separate issues which will have like surface finish on all four sides. This is accomplished by first slicing the column, oiling the same, then separating the two halves with another slicer that continues to the face of the die.

Blom, 3,407,457, slices up a very fragile, non-plastic, uncured block and tries to transport the same to an autoclave without damage.

Ullrich, 2,103,802 is concerned with transforming a multi-covered extrusion into individual, hollow building brick through the use of cutting wires and piercing wedges which cut and fold end portions of hollow, rectangular extrusions into the equivalent of hollow brick.

Baer, 1,943,506 produces by extrusion plastic brick which have been presliced then pressed back together again suificiently tightly to permit their rough handling while still plastic, or when dried and/or burned without separating. Baers system involves oiling and an additional shaper cap as well as wires which appear to be ditficult to zlelplgce and which are located in a non-tapering area of Stuckey, 1,872,522 relates to the production of rocklike faces on concrete units.

Burch et al., 3,028,652 provides a system for slicing very tender and fragile material. No plastic mass is involved nor slicing of a continuously extruded plastic mass.

Jacobsson et al., 3,065,514 like Blom and Burch relates to a process for slicing preformed tender and fragile block.

Reed, 2,230,309 kerfs extrusions so, after firing, indi vidual blocks may be broken apart with smooth corners, but rough breaks.

SUMMARY OF THE INVENTION Bolted to the auger barrel of a brick extruding machine is an internal tapering die base to which is clamped an internal tapering shaper cap whose cross section upstream of its mouth is provided with tensioned wires which slice the column longitudinally as it proceeds through said shaper cap. Downstream of the horizontal wires, the continued taper of the shaper cap forces into cohesion, by tremendous pressure, the adjacent longitudinal wire cut surfaces of the severally created adjacent slabs, sufficiently enough to permit each transversely cut section, of the resulting multi-sectioned extruded unit, to be safely manor machine-handled and to be processed through its subsequent drying and firing cycles like normal full-size brick, units that can at any time after firing be tapped apart on the original wire cut lines to create brick slabs, each e.g., to 1" thick, which are especially economical and useful for facing the surfaces of industrialized mass-produced building panels of any practical size.

A particular means for tensioning and replacing the shaper cap wires is shown.

If the slicing wires are provided within the tapering shaper cap in accordance with the present invention, instead of outside the same, the slabs will be pressed back together tightly enough to give a homogeneous look and good physical handling ability to each multi-slab green brick, and yet leave a brick that can be easily tapped apart into its constituent slabs after burning.

In the preferred embodiment, the combination of a die base and shaper cap interior rather sharply tapers in all its length. It is this constant interior size reduction that helps compact the moistened clay into a slug that is very strong and smooth even though it is in a plastic state. The total pressure created from all exterior faces of the slug as it moves away from the slicing wires does the trick.

Not only will inside wires prove immensely helpful in making straight, thin facing slabs, but they can be just as beneficial in the manufacture of simple brick shapes which have all straight exterior lines.

All slabs and plain shapes have always commanded premium pricesfrom two to five times as much per ton as compared with regular brick. There can be produced when using the present invention just as many tons of slabs and plain shapes as of regular brick. Slabs and shapes can thus be very, very profitable items if, of course, any sizable sales can be generated.

The principles of the invention will be further hereinafter discussed with reference to the drawing wherein a preferred embodiment is shown. The specifics illustrated in the drawing are intended to exemplify, rather than limit, aspects of the invention as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal, vertical cross-sectional view through a brick forming die having its tapering shaper cap provided with inside wires in accordance with the present invention;

FIG. 2 is a front end view of the forming die of FIG. 1;

FIG. 3 is a bottom plan view of the forming die, illustrating the preferred means for holding the wires taut;

FIG. 4a is an elevat onal View of a reconstituted brick after firing; and

4 FIG. 4b is an elevational view of the brick of FIG. 4a after it has been tapped apart into individual slabs.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT A fragment of the auger barrel of a conventional brick extrusion machine is shown at 10 in FIG. 1. An example of such a machine is the No. 40, manufactured by J. C. Steele & Sons of Statesville, NC. The auger barrel 10 is provided with a port which communicates with a tapering die base 12 bolted to the auger barrel at 13. A die or shaper cap 14 is secured to the die base in order to determine the shape of the four outside surfaces of the brick column. The column issuing from the die is transversely severed into brick, i.e. along the vertical transverse plane containing the arrow 16, using a conventional cutter. An example of such a machine is the No. 18, manufactured by J. C. Steele & Sons of Statesville, NC.

A typical composition of as-extruded clay brick column 1s:

A typical composition of an as-extruded shale brick column is:

Constituent: Weight percent Water 13 Shale (dry basis) 87 The above are exemplary and subject to much variation as will be understood by those of ordinary skill in the art of brick manufacture.

In the example depicted, the cross-sectional internal dimensions of the shaper cap 14 are 8 /8 x 4% inches at the upstream end of the shaper and 8% x 3% inches at the downstream end of the shaper cap. In this same example, the longitudinal distance between the upstream and downstream ends of the shaper cap, measured along the longitudinal axis of the shaper cap is 4% inches.

At a location intermediate the ends thereof, for instance where its cross-sectional dimensions are 8% x 4 inches, the shaper cap is provided with a plurality of taut, parallel wires 19 extending between the short sides 20 of the interior of the shaper cap and parallel to the long sides 22 of the interior of the shaper cap.

The wires 19 extend through openings 24 provided in the short sides 20 of the shaper cap. Two, axially spaced lugs 26 are mounted on the exterior of each short side 20 of the shaper cap. Each lug has a like array of openings 28 therethrough for mounting nut 30 and bolt 32 assemblies 34 between axially aligned pairs of openings 28 of lugs 26 on the same short side 20 of shaper cap. Each bolt 32 is provided with at least one diametrical opening 36 for receiving an end portion of a wire 19. In this fashion, the central portions of the wires 19 are disposed within the central opening of the shaper cap and the end portions proceed out through the short side wall openings 24, through respective bolt openings 28 and wrap about respective bolts. Two nuts 30 tightened against opposite sides of one respective lug lock each nut and bolt assembly against undesired rotation and together with the similarly locked nut and bolt assembly at the opposite end of each wire, maintain the respective wires in taut condition. It should be apparent that this arrangement makes the individual wires 19 easy to keep tight and to replace when necessary. The wires 19 are preferably of 11 gauge steel. Each wire end is wrapped sufficiently about its respective bolt that it proceeds tangentially therefrom toward the shaper cap. This, together with predetermination of the spacing of the bolt holes arrays 28, ensures that the wire central portions within the shaper cap divide the central opening of the shaper cap into several substantially congruent rectangular areas,

as seen from and along the central longitudinal axis of the shaper cap.

In use, a brick extruding mixture, such as those set forth above by way of example, is extruded at an extruder barrel pressure of, e.g., 500 psi. at a rate of, 5g, 5 to 20 cubic feet per minute through the shaper cap where the brick column is sliced by the wires 19 into four slab columns. In passing through the remainder of the tapering shaper cap, the slab columns are reunited sufliciently to cause the composite issuing from the downstream end of the shaper cap to appear and be handleable as if it were a conventional, unsliced brick column. Upon issuing from the shaper cap, the column is cut by conventional means, as aforesaid, into composite brick of desired face height. These composite brick (i.e. each comprising four separate, reunited slabs) may be mechanically picked up and set in normal cubes on conventional kiln cars which may be pulled into a drier and kiln in the normal manner.

In a conventional drying and firing operation, to which the composite brick are subjected prior to being tapped apart into individual brick slabs, the composite green brick are typically subjected to the following conditions: 30 hrs. in a dryer reaching a temperature of about 300 F., and 42 hrs. in a kiln where the maximum temperature could vary between 1800 F. and 2400" F., depending on the raw materials.

Even after conventional drying and firing, the composite brick show no readily visible evidence of having been presliced and reunited, they look like conventional brick. However, upon being tapped, the composite brick B readily separates along the cutting planes of the wires 19, into four uniform faced brick slabs in the instance of the example, each measuring about 2% x 8 x M; inches.

It would be surprising if there is a single plant in the United States today that is producing building brick with the extrusion, drying firing systems and other equipment that were almost in universal use in 1930. In 1930 it was not too uncommon to have one production man on the payroll for each 800 brick produced daily. Today some plants have but one production employee for each 3,200 brick produced daily. Not only has labor productivity been increased up to 400%, but much of the real laborious work has been either eliminated or made much easier.

The extrusion and pugging machines in common use in 1930 required about one-and-a-half horse power per thousand brick produced per day. The brick as extruded were extremely soft by todays standards. They did not need to be very hard, and they were not. In those days freshly extruded brick were generally hacked onto socalled double decked dryer cars and the maximum height of the set on either deck was usually four coursesthe bottom courses of brick thus only had to be extruded stilf enough to support three other brick without being deformed (mashed down).

Todys extruders may be powered with as much as four horse power per thousand of daily production. The extruded brick have to be very stiif, because freshly extruded brick are generally set directly onto kiln cars and to a height of up to 21 courses, without materially deforming the bottom course units. The moisture content of freshly extruded brick has dropped from about 14-17 percent to about 12 percent or less.

Drying time has been cut from as long as four days to as little as 15 hours. Less initial moisture plus intense, high speed circulation of air at the right temperature and of the right humidity has made this up to 84% reduction in drying time possible.

In 1930 the tremendous benefits derived from deairing of building brick raw materials, prior to their extrusion, had just been discovered. However, general use of deairing was still years away. Deairing any clay at any moisture level greatly increases its green strength and its potential dry and burned strengths. Through deairing, green column strengths could be so drastically improved that extrusion moisture levels could almost be universally lowered. Many materials that, by themselves or in combination with others, were not sufiiciently plastic at any acceptable moisture level to permit undeaired extrusion became usable and desirable overnight through the use of deairing.

Today, deairing is substantially universally used in this country and substantially all brick extrusion machines now made in this country utilize the deairing process.

Changes in the processes for production of face brick in the U.S., have in turn greatly increased the problems encountered in preslicing and sufiiciently semi-rescaling a brick column, to permit its subsequent cutting, setting, drying, firing, cooling, packaging, shipping, unloading, storage and job placement as unseparated units, but at the same time, said units being readily and cleanly separable at their use site by either being gently tapped with a suitable hammer or with another like presliced and semi-presealed unit.

All basic building brick raw materials when ground and screened or similarly prepared, whether they are derived from surface clay, deep mined clay or bank shale or combinations of same, when moistened and worked, attain variable states of plasticity-the greater the moisture addition, within limits, and the more thorough the working," the more formable (extrudable) and stickier" each becomes. Evan in low mounds, a very selected few materials when horizontally wire cut into layers may immediately semi-reseal themselves, just through the downward pressure of their own weight, back into a seemingly unitary mass. Most all materials, however, at an equal moisture level and after equal working cannot even be semi-rescaled without pressures substantially greater than the force of gravity being exerted on same.

Todays nearly universal use of deairing extrusion machines and very high tunnel kiln car settings, have combined to eifect near common use of very hard, low moisture content green brick columns. Todays extrusions are so hard and strong that they can be walked on or even jumped on with scarcely any resulting marks or deformations. Twenty-one green brick can be piled on top of one another or cross set every other pair of courses to an equal height, without any noticeable deformation of even the bottom unit taking place. In 1930 it took years to train and assemble a screw of light enough fingered men to pick off and set green brick without marking same with finger pressures. When todays relatively dry, hard and low plasticity brick columns are presliced substantial pressures have to be exerted to effect satisfactory semi-reseals, just to permit the extrusion, cutting and setting operations to normally proceed.

In some instances, brick units that have ben conventionally sliced, then semi-rescaled sufiiciently to stay in one piece to permit placing on a kiln car, will separate during todays extremely fast drying cycles. Up to onehalf of a green bricks total eventual shrinkage may occur during drying, and it is not uncommon for this alone to amount to (on an 8" brick). When several days were utilized to remove the mechanical water (i.e., the water not chemically combined) from green brick, the removal proceeded at such as slow pace that the differential shrinkage within each unit was held to a minimum, the so-called interior slabs drying and shrinking very nearly at the same rate as the outside slabs (those with more exterior surface exposure). When brick are dried in 15 hours it is just about impossible with today's knowledge and equipment to prevent difierential shrinkage within individual pre-sliced and semi-rescaled units-the mainly exterior slabs shrinking long before the mainly interior slabs do, to set up terrific strains on the semi-reseal lines.

The very fast firing cycles presently used also present a like problem. Generally,.over half a bricks total shrinkage occurs during its firing%" not being too uncommon for an 8" brick. Here again, outside slabs get heated up considerably ahead of inside slabs in the same unit. Differential shrinkage can exert terrific pressures on the semi-reseal lines. Without sufiicient semi-resealing pressure, separations will occur, and separations at this stage can result in very, very costly kiln wrecks ((brick makers jargon for a toppled kiln car). One separated burned slab falling off the side of a car can start a pileup inside a kiln that can cost up to $65,000 in lost production alone. In prior years, with beehive stationary kiln operations, fall oifs of this type were inconsequential, the usual direct loss being at most the value of each fall olf slab.

Semi-rescaled units that have withstood internal and external strains through extrusion, cutting, hacking, drying and burning face yet another test of their semi-reseals. Current very fast cooling cycles, 2,000 F. down to 250 F. in as little as seven hours, for instance, create additional differential shrinkage strains, and I suspect, reseal failures. Here again, failures can produce fall offs, and fall offs, in turn, can cause very costly kiln wrecks.

Yet another straw exists to break our camels back. Cubing of burnt brick for fork lift handling, being practiced with increasing incidence, is very rough on individual brick units. Bottom brick adjacent to fork holes get rapped, poked and shoved. Air powered steel strapping tighteners and sealers exert point strains that can snap first quality unsliced brick. The careful manhandling and final nest of straw that use to feather-bed brick in transit are virtually no longer used.

Obviously, if one is going to make a success of manufacturing brick slab units, his method of producing semireseals has got to be positive, near foolproof and just as satisfactory to the buyer as it has been to make by the manufacturer. All former preslicing and semi-resealing systems that I know of cannot be used satisfactorily today. What one could get by with forty, thirty, twenty, or ten years ago under some or most circumstances will not work today. Every segment of brick manufacture has radically changed, and every such change has made semiresealing of presliced planes more and more difiicult. A new and diiferent method of obtaining satisfactory semiresealing was needed at the time my invention thereof was made.

I personally have tried to use spot oil lubrication on dry dies (dies that are normally not equipped with any means of lubrication) and have been my industry friends do the same. I have never seen spot oiling used successfully, that is without constant adjusting being required and frequent very out of balance extrusions being made, extrusions that had to be scrapped. Trying to balance a die by using a slicker" and spot lubrication is like locking the barn door after the horse has been stolen-it is too late. One may be able to make an improved appearing column, but the column Weaknesses remain.

Vast tonnages of clay, shale or mixtures thereof are being extruded today, and have been historically, without the use of any lubricant in any way. Sewer piper, flue lining, hollow tile, hot tops, drain tile, and the like, have historically been extruded through so-called dry dies, which are non-lubricated for very good reasons.

Lubricants are basically used to reduce the friction that is built up when plastic clays are forced at very high pressures against and along metallic enclosures such as the interior surfaces of die bases and shaper caps. The need to reduce this friction is dictated by the need to balance the flow of clay out of a die, a balanced flow being achieved when all cross-sectional areas of a clay column emerge from a shaper cap at the same speed and in a truly cohesive mass. In normal brick extrusion, without effective lubrication, the center of the column will run very fast, and when this happens, so-called laminations will develop. Lamination lines are the result of adjacent bodies of clay travelling at dilferent rates of speed, actually losing homogeneity, really becoming separate entities that are pressed tightly togetherso tightly that the extruded column appears to be homogeneous to the eye, can be cut into desired lengths with no problem and then be man-handled and stacked for drying. Ware cut from a seriously laminated column generally is unable to stand the strains and stresses encountered in drying and/or firing. One ends up with actual pieces, badly cracked units, deformed units (crooked-twisted), or units that cannot pass required strength tests; scrap, to be exact.

Generally speaking, exterior column lubrication, inside a die base and shaper cap, for example, is required when a sizable mass such as a brick body, solid or cored, is to be extruded. The exterior frictional drag, without lubrication being employed, simply becomes greater than the clay-to-clay bonding strength, and the center area breaks away and takes 01f on its own. The separation caused by different interior column speeds can actually result in multiple concentric rings (lamellae) of material, each of which are travelling at their own rate of speed and forming adjacent slicked surfaces in the process. It is these slicked surface parting lines that later give way when the body is subjected to rapid differential temperature changes.

To obtain the maximum benefit from any lubricating medium, it is necessary that effective lubrication start at the point where the clay mass being forced out of the augers starts to enter a reduced cross-sectional area. No application of lubrication at or near the tail end of the forming process can possibly mend previously formed lamination lines. The lubricated slicker of Baer 1,943,506 obviously could merely contain the sliced-up column long enough to have it extrude in a straight, horizontal line and achieve a very minimal amount of resealing through the build up of back pressure.

Now, when one extrudes relatively thin walled products, such as flue lining, sewer pipe and the like, the situation is entirely different. With such products the plastic material is forced between two closely spaced metal surfaces which results in a near equal frictional drag on both surfaces. This double, near equal drag, on relatively small cross-sections, rarely produces harmful laminations. The section is just too narrow and under too much equalized forward thrust to permit a relatively tiny center area to break loose and travel at a diflEerent speed from its adja cent sides. Dry dies have always had their application in such production and probably always will, so long as such products are manufactured.

To properly lubricate, with total coverage, the interior of a die base and its attached shaper cap, todays most popular lubrication system introduces its oil at the rear of the die base through a continuous encircling totally machined slit equivalent which employs an overhanging lip to provide clearance for oil introduction and to prevent plugging of the slit by clay. Oil is fed to this oiling ring by several spaced flexible hose lines in order to insure equal pressure at all points. These multiple lines all are generally fed from a common source and controlled by a single valve. Pressures of up to 300 psi. are employed. Pressures are varied slightly from day to day to suit different coring set ups, different textures, and the like. Once the lubricant is set for any specific set of conditions, it is not uncommon for a full days run to be made without further adjustments being called for, and near perfect protection is afforded against the formation of damaging laminations.

A propertly lubricated column, of course, requires less power expenditures than a non-lubricated column, but the power saving is incidental and not the primary reason for supplying lubrication. Baers rescaling was not and could not have been sufficient to work with todays low moisture content brick columns, very high green brick setting patterns, and fast drying, firing and cooling schedules, and that the differences between his method and mine, as disclosed, are material.

Recent tests A series of tests have been conducted under my direction and at my request at K.F. Brick Co. of South Windsor, Conn., utilizing tapered shaper caps constructed in accordance with the principles of the invention.

In a first test the die shaper cap used was configured as depicted in the figures of this application, except that four slicing Wires were installed with equal spacing across the shaper cap to produce five slabs. The so-called brick column started emerging in the normal manner, and individual brick cut from said column were quite normal, being in one piece and very difiicult to separate on the presliced lines. In a very short time, however, actual separations on one of the presliced lines was noticed, and the run 'was terminated forthwith.

Once the shaper cap assembly had been removed and cleaned out, the cause of the trouble was readily apparent. Someone had made a mistake in setting up the slicing assembly, by cutting the piano wire slicing wires too short-not long enough to permit the customary number of holding wraps around the exterior of the tightening posts. The lack of the normal number of wraps allowed a slippage to occur, resulting in a pronounced bowing of the piano wire slicing wires in the downstream direction of the clay column flow.

Each of the wires had slipped a different amount, but none of them had bowed as much as one-half its proper distance from the exit end of the shaper cap assembly, the wire with the greatest slippage just approaching the half-way mark. The location of the wire with the greatest slippage, as could be expected, matched up with the brick column separation that was discovered shortly after the run was started. Had the run been continued a 'bit longer, the other slicing wires would have no doubt shortly stretched enough to have caused column separations at their individual planes.

On this particular very short run of slabbed brick units at K.F., the units extruded and cut prior to the start of column separations were hacked onto kiln cars in the normal manner and subsequently dried and fired in the usual way. After firing it was found that many of the fired units had separations that did not exist when they were put on the kiln cars (individually by hand). Also, it was found that several units that had been fiat or edge set on the outsides or ends of the cars were actually missing one or more slabs, said slabs having obviously separated during the firing or cooling processes. All cars were visually inspected-both ends and both sidesafter going through the dryer and prior to going into the kiln and having fallen off in the kiln. Most fortunately, the slabs that did drop off just happened to fall and land so as not to jam a bottom course of brick and result ina kiln wreck; a forerunner, usually, of several toppled cars, as the spaced brick settings react very much like a row. of dominosa chain reaction that usually is not dissolved until the hydraulic car pusher pressure increase either sets off, an alarm or shuts down the pusher.

I have seen as many as fifteen adjacent cars of brick all toppled in one big mess up against the inside walls of a kiln, with portions of'tha't kiln at 2,000 F.

A kiln wreckis always a very expensive accident" and can be catastrophically so. They always completely shut down production, cause the lay off of as many as 90% of the plant labor "force, and on restartup, generally entail a considerable production of off-color ware. It can take as long 'as'three days to cool a kiln down sufficiently to allow workmen to enter it and clean out a wreck. Interior kiln damage caused by a bad wreck can take up two around-the-clock days to repair. Getting a kiln 'back up to temperature generally takes a minimum of four days. At the K.F. plant where the run of presliced brick was made, the kiln puts out 130,000 brick per daybrick that have a wholesale value of $50.00 per thousand. A serious kiln wreck can and has cost K.F. as much as $65,000.00 in lost production alone. Kiln wrecks are obviously a very serious matter. One cannot afford to take chances. Any presliced brick that K.F. or anyone else runs has to be near foolproof. One can rest assured, they will not permit the use of short wires at K.F. again.

The accident at K.F. certainly would seem to prove my contention that only a tapered die can semi-reseal a wire-cut plastic brick column sufficiently to permit modern handling, drying and firing of every brick cut from same. No company can aflford or would take chances of putting presliced semi-rescaled brick through a tunnel kiln if they were not positive that of the individual brick would remain in one place.

Specifically, this lapse in properly preparing a preslicing and semi-rescaling shaper cap for production proved:

(1) Even a tapered die section, located after the slicing wires, has to have a minimum length to eifect a satisfactory semi-reseal of wire cut column sections-a semi-reseal sufficiently good to permit 100% effectiveness through manual or mechanical setting operations, kiln car drying, tunnel kiln firing and cooling, hand or mechanical packaging, subsequent rail car or truck ship ment and the final receiving, storing, and in plant movement at the precast plant where the units will finally be tapped apart and the individual slabs used to face precast panels.

(2) Even a column of presliced brick units that have been semi-rescaled sufficiently to permit high speed cutting into brick units, very rough manual or mechanical setting on kiln cars and almost instantaneous stacking up to twenty-one courses high without deformation or separation may not be semi-rescaled good enough to stand today's very rapid drying, firing and cooling cycles which generate very fast and uneven expansion and contractionsthe expansions and contractions that split up such semi-rescaled brick slab units at K.F. Brick Co. and nearly caused a very serious kiln wreck.

(3) That 1930 semi-rescaling processes could hardly be expected to be satisfactory today; not one person I know of ever made use of a continuous tapered die section after slicing wires to semi-preseal a presliced unit, and I seriously doubt that an untapered die section could ever exert the pressure that a tapered section can and that even a substantial length of a tapered die section is needed, as a brief length of tapered section cannot reseal presliced brick sufficiently to even make a satisfactory brick column out of the certain deaired, very low moisture content raw material as used at K.F. Brick Co. at South Windsor Hill, Conn.

For a second test, four slicing wires were in place, giving various depth locations in the shaper cap, from a minimum of to a maximum of 3%.

First we ran a soft column above normal moisture content. The column ran and cut fine with no sign of any separations. This column was about equal in moisture content to what was commonly run in 1930. The cut brick were hackable about three courses high without serious deformation, but no higher. At this plant the normal set is 21 courses high. None of these unusable brick were saved for moisture content determination, drying or firing.

At the next stage of this test run, the moisture content of the clay and shale mix being extruded was cut back to what is presently normal. Immediately there was a complete separation of the column as it emerged from the mouth of the shaper cap at the presliced line from wire A which was only inside the shaper cap some 4". Furthermore, while the resea on the line out 1 1 by wire C (inside the shaper cap 1%") was good enough to prevent separation through issuance, cutting, transporting and setting, it was not good enough to allow it to go on a car into the dryer and kiln. Freshly cut brick could too easily be pulled apart on said line C.

The reseals experienced at lines E and G (back in the shaper cap 2 /2" and 3%", respectively) on this part of the test were normal, offering real resistance to forcible separation by hand.

I do not know any practical way to measure the tremendous resealing pressures that we obtain with interior preslicing in a tapered shaper cap section, but I am sure that they have to be many, many times that which could be attained with Baers system, which utilizes a straight sectioned containment after slicing. There was even a very noticeable difference in the texture of the four sets of facings produced with this setup, going from a comparatively coarse finish from wire A to a very fine finish from wire G. I feel sure we attained substantially more resealing pressure after wire A than Baer did with any of his wires. Certainly, all evidence available to me indicates this to be so.

During a third test, all eight wire stations were in use- A, B, C, D, E, F, G and H.

Again, on this test run, we started out with a relatively soft column but not nearly as soft as during our first run with this shaper cap or as soft as was run in most plants in 1930. We experienced some immediate minor reseal failures at line A, but some obviously were a result of the bit stiffer (dryer) clay mass being extruded than on previous test runs. The reseals on all the other lines appeared to 'be satisfactory. Forty-eight samples were boxed in (to prevent any possible fall off) on top of a kiln car set and on one which was run through the dryer in the regular manner. Three samples were also saved to be tested for water content.

Twenty-four samples were removed after the car came out of the dryer (before it was put in the kiln). Thirteen samples came out whole; 1 brick had a partial separation on line A; and had total separations on line A. The fidgeg moisture content on the three samples averaged We followed the same procedure with another test run using a presently normal moisture content mix. Again, we experienced separation problems with line A. Again, we put 48 good samples on top of a kiln car and sent them through the dryer, as well as saving three samples for moisture determinations. Nine of the 25 removed from this set came out whole, three were separated on line A and 13 had separated on line B. This shift in predominance of separations from line A to line B I believe to have been due to differential flow at that exact point. The preslicing at that weak" point just set it free. The fact that we had no trouble at the B point on previous normal consistency runs, when there was no wire there, and had never encountered any separation problems, at any point, in the bottom half of the brick column, which had been presliced by wires at E, F, G and H, all of which were better than half-way back in the shaper cap, I believe overwhelminingly substantiates this deduction. It is a well recognized fact, that with solid brick extrusions (not cored), the best lubrication systems and the most efficient de-airing, in combination, do not eliminate the extra center push that develops inside a die base and shaper cap. The natural stickiness of clay, and/or shale, with a good lubrication system and efiicient de-airing do not prevent harmful laminations from occurring. A preslicing wire at the right spot, and not far enough into the shaper cap to receive subsequent suflicient resealing pressure, leaves a slicked former separation that will give way when subjected to the strains set up by fast drying, burning and cooling. The drier the mix, the greater the problem of differential flow, and the more ditficult it is to reseal a presliced column. No separation problems were experienced at any process point through drying, at

any moisture level, at presliced lines C, D, E, F, G and H. This is evidence that not only is slicing in a tapered section needed, but that the slicing wires have to be well back in tapered section if sufiicient resealing pressures are to be appliedsufficient resealing pressures to insure positive protection from any separation at any point. The added moisture content on the three samples taken from this run average out at 12.51%

Ten of first brick made in this test, brick that averaged 13.8% added moisture, which came out of the dryer whole, were put on another kiln car and sent through the kiln. All of these brick survived the fast firing and fast cooling. While the slabs separated by wires A and B could generally be tapped free with no trouble, the slabs presliced by wires D, E, F, G and H could not be successfully tapped apart-they had been too effectively resealed-too much pressure had been applied on too soft, too plastic, too sticky and too wet a body. Had this body been as soft as most 1930 columns, it is very doubtful if even the B line could have been easily tapped apart.

The nine whole 12.51% brick that survived their trip through the dryer were put on a kiln car (the same one as the 13.8% brick) and sent through the kiln. Three of these suffered separations on A or B, or both, from fast firing or fast cooling or a combination of same. The balance were too tight on lines D, E, F, G and H-tOok too much tapping to separate and the losses were too high. I would like to point out that the just described so-called cold tests, as were these short test runs, will vary in results that one will get from real production runs. Cold tests in general use a very high percentage of re-run raw material, and the material extruded is relatively cool as are the extrusion machines augers, auger barrel die base and shaper cap. One can generally expect and get much more effective reseals with like slicing wire placement with cold runs than one can with hot production runs. In our normal production runs to date, we have had all slicing wires the same distance from the mouth of the shaper cap, in about 2%", which by itself makes for an extra squeeze. We have had only very minor problems in separating slabs for use and practically no separation problems during manufacture, packaging, etc.

Suitable die bases and shaper caps are available from J. C. Steele & Sons, Statesville, N.C. A suitable shaper cap is e.g. 4.25 inches long and has an internal taper of 2-4 degrees, more preferably 2.5-3.25 degrees. With cold runs, I have found that wires placed 0.75-0.1875 inch back in the shaper cap dependably give insufiicient resealing when stiff brick columns were extruded, e.g. of commercially significant moisture content. Likewise, I have found that wires placed more than 2 inches back produced over-resealed Ware in cold runs. However, in hot runs, i.e. sustained production, 1.75-2.00 inches appear to be an optimum set-back for the wires (measured from the small end of the shaper cap). Thus, for overall use and including a sufficient range to accommodate both hot and cold runs, and extrusions both somewhat wetter and somewhat drier than commercially optimum, a range of 1375-225 inches setback of the slicing wires from the small end of the shaper cap is suggested.

It should now be apparent that the improved method for making faced brick slabs as described hereinabove possesses each of the attributes set forth in the specification under the heading Summary of the Invention hereinbefore. Because the method for making faced brick slabs of the invention can be modified to some extent without departing from the principles of the invention as they have been outlined and explained in this specification, the present. invention should be understood as encompassing all such modifications as are within the spirit and scope of the following claims.

What is claimed is:

1. An improved method for making brick slabs comprising: extruding a column of green brick through a tapering die which has a taper in the range of 2-4 degrees; intermediate the tapering die between 1% and 2% inches from the smaller end thereof, continuously slicing the brick column into a plurality of slab columns; and utilizing the taper of the die downstream of performance of the slicing step to pressingly reunite said plurality of slab columns into an apparently unitary, composite brick column; cutting the apparently unitary, composite brick column into a plurality of apparently unitary, composite green brick of preselected face height; drying and firing said apparently unitary, composite green brick; and tapping the dried and fired apparently unitary, composite brick apart into a plurality of individual brick sla'bs along the line(s) of slicing of said column of green brick.

2. The improved method of claim 1 wherein said green brick column is more than three inches thick and wherein each brick slab is no more than one inch thick.

3. The improved method of claim 2 wherein said green brick column is essentially composed of clay and water.

4. The improved method of claim 2 wherein said green brick column is essentially composed of ground shale and water.

5. An improved method for making brick slabs comprising: extruding a column of green brick through a path of continuously decreasing cross-sectional area of 24 degrees taper; stationing at least one taut wire crosswise of the path of the column of green brick intermediate the extruding step within 1%-2% inches of the downstream end of said path and slicing said column with said at least one taut wire into a plurality of slab columns; downstream of the slicing step, squeezing the slab columns mutually toward one another into an apparently reunited column of green brick; cutting the apparently united column of green brick into a plurality of apparently unitary composite green brick of preselected face height; drying and firing said apparently unitary, composite green brick; and tapping the dried and fired apparently unitary, composite brick apart into a plurality of individual brick slabs along the line(s) of slicing of said column of green brick.

6. Apparatus for use with a brick column extrusion machine in the production of brick slabs comprising:

a tubular, tapering die of generally rectangular internal transverse cross-sectional shape;

at least one brick column slicer mounted on said die in such orientation as to divide the interior of said die into at least two laterally adjacent regions of generally rectangular transverse cross-sectional shape, said at least one brick column slicer being mounted axially intermediate the tapering die; whereby green brick being extruded in a column through said die is sliced by said at least one slicer into at least two laterally adjacent slab columns and pressed by the continuing taper of the die into an apparently reunited composite column of green brick; said die having a taper in the range of 24 degrees and said at least one slicer being set back 1%2% inches from the smaller end of the die.

7. The apparatus of claim 6 wherein the at least one brick column slicer comprises three, parallel, equally laterally spaced slicing wires and wherein said tubular, tapering dies is of such internal size and shape as to produce a composite column substantially equal in green brick length and green brick thickness to a conventional green brick column.

8. The apparatus of claim 7 further comprising means defining openings in said die for passing opposite end portions of said slicing wires to the exterior of said tapering die; and means mounted on the exterior of said die for tautening and securing the opposite end portions of said slicing wires.

9. The apparatus of claim 8 wherein said tautening and securing means comprise two pairs of axially spaced lugs mounted opposite one another on the exterior of said tapering die; means defining three pairs of axially aligned openings through each pair of axially spaced lugs; a nut and bolt assembly received through and mounted on each pair of axially aligned openings; the end portions of each slicing wire being secured to respective of said nut and bolt assemblies.

References Cited UNITED STATES PATENTS 287,699 10/1883 Meeker 264146 854,823 5/ 1907 lHedrich 26467 1,245,898 11/1917 Gates 425467 1,920,982 8/ 1933 Hedrich 2645 8 1,943,506 1/ 1934 B-aer 42597 2,209,643 7/ 1940 Chamblin 264152 FOREIGN PATENTS 269,761 4/ 1927 Great Britain.

JOHN H. MILLER, Primary Examiner US. Cl. X.R.

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