US 1945681 A
Description (OCR text may contain errors)
1934. A. H. FARRENS 1,945,681
TRUSS TILE Filed July 9, 1931 2 Sheets-Sheet l 3 mw wroz A.]i] 'arrens A. H. FARRENS Feb. 6, 1934.
TRUSS TILE Filed July 9, 1931 2 Sheets-Sheet 2 3140mm A .HFar-rens Patented Feb. 6, 1934 .TRUSS TILE Albert II. Farrens, Lincoln, Nebr. Application July 9, 1931. Serial No. 549,715
My invention relates to building tile and more particularly to the burnt clay type of tile, the primary object of the invention being the provision of a clay block having lighter weight and greater load bearing strength than any of the tile heretofore known.
Another object of the invention is the provision of a tile having a form which will stand up under rough handling in the green state.
Another object of the invention is the provision of a tile having a plurality of substantially cylindrical cells surrounded by continuous rectangular walls which are tangential to the walls of the cylindrical cells and integral therewith.
Another object of the invention is the provision of a. tile designed with reference to the lines of cleavage of the material from which the tile is made.
Another object of the invention is the provi-' sion of a tile made by forcing clay through a die, the die being so designed that the interior friction of the clay in passing through the die substantially counterbalances the exterior friction.
Another object of the invention is the provision of a tile having an exterior design so that the tile may be laid in the wall in any one of three positions and so that the mortar joint may be provided either with or without a dead air space.
Still another object of the invention is the pro sion of an end surface for the tile such as to provide ample keys for the mortar of the joints.
Having in view these objects and others which will be pointed out in the following description, I will now refer to the drawings, in which I Figure 1 is a view in perspective of the truss tile.
Figure 2 is an end view of the tile showing particularly the appproximate positions of the lines of cleavage of the tile. The view might also be taken to represent a face view of the die used in forming the block.
Figure 3 is a diagrammatic view of a portion of the end of the tile showing particularly the truss formation of the tile upon which its load bearing function depends.
The form of the block is shown in Figure 1. This block is rectangular in form and it is providedwith two large cells 10, the exterior walls of the block being rectangular and tangential and integral with the walls surrounding the cells 10. Other but smaller cells 11 are provided at each of the corners of the block. Along the median line between the two cells 10 are wedge-shaped cells 12 each having two walls which are substantially parallel to the webs between the side walls of the block and the cells 10 are relatively wide and they areeach provided with one or more small cells 13 in elliptical form.
Exteriorly the block is provided on each of two opposite sides with a pair of semi-cylindrical channels 14. The space between the channels 14 is grooved or corrugated at 15, and similar grooves or corrugations 16 are provided in the spaces to the outer sides of the channels 14. In my drawings I have shown one wall as left smooth at 17 while the opposite wall is provided with means for keying a plaster coat. If desired, both opposite walls may be made smooth or with keyways for the plaster. As shown in my drawings the plaster key is in the form of two corrugated or grooved surfaces 18 with a smooth surface 19 between the corrugated surfaces 18. It is obvious, however, that the plaster keys may be in any desired form and that the smooth walls may be omitted entirely if so desired.
I shall now discuss the tile of this form with reference to its manufacture. Nearly all tiles at the present time are made by machinery which includes dies for giving the tiles the desired cross sectional form. The thoroughly puddled clay is forced under powerful pressure through the die after which it is cut into the desired lengths. The pressure is applied by means of an auger which gives the clay not only a forward movement but also a movement in a curvilinear direction about the axis of the auger. The clay then leaves the die in the form of an endless column having .a longitudinal grain due to theforward impulse imparted, by the auger and having also avery decided curvilinear grain. T e grain in the clay is roughly in spiral form but closelyapproaching the circular form. It is a well known fact that this grain is present not only in the green blocks but that it remains during burning and as long as the block retains its form. The grain inthe block both in the green and in the burnt stages determines the lines of cleavage of the block. The block in effect has a laminated structure.
The grain is further affected by various other factors. The clay in the auger is under powerful pressure and this pressure is greatest at the periphery and least at the axis of the auger. This results in pronounced laminations at the outer edges of the block and with practically no grain whatever as the center of the block is approached; Then too, the auger has its forward end at some distance in the rear of the die. As clay leaves the auger and a slight distance forward of the walls or the cells 10. The 5 i to better resist compression die, the clay has a void in the space previously occupied by the shaft of the auger. Due to internal pressure of the clay, this void becomes filled with clay resulting both in a slight change of direction of the weak grain and also in a slight decrease in density of the clay at the center of the block. The die is positioned in the machine with its center point in alignment with the projected axis of the auger so that the finished block as it leaves the auger will be symmetrical as regards the grain of the clay.
The machine manufacture of clay blocks involves still another problem. The clay has a more or less colloidal structure and when itis forced under powerful pressure through a die, the friction on the exterior surface of theblock will be so great as to cause a slightly more rapid movement of the clay at the interior of the block. When the column is then cut into blocks, the clay has a tendency to resume its normal form and in doing so the end portions will tend' to recede so that the ends of the block are apt to become concave. To avoid this it is necessary that the die be so formed as to provide cells in the blocks, the purpose being to introduce sufficient friction on the interior of the block to balance the friction on the outer surface of the block. While the cells have their primary function when the block is in use in the wall of a building, it is exceedingly important that they be so designed as to introduce the proper amount of friction when the clay is passing through the die. Since the density of the clay at the center of the column is less than that at the outside of the column it is necessary that the outlines of the cells be slightly greater than the exterior outline of the block.
The greatest resistance against distortion in any material is in the direction of its grain. Referring now to Figure'Z of my drawings, the circular lines represent approximately the directions of the grain in the block. In the wall the block is subjected to forces producing compression in the block. These forces are transmitted through the block in the various webs surrounding the channels. The outer web 20 with the cells is so designed that the lines of cleavage are broken as little as possible by the cells and so that these lines of cleavage will be in the approximate position of the lines of force when the block is under compression. I The direction of these lines of force is determined to some extent by the truss formation of the block which will be discussed later. At any rate it will be seen that the compression is transmitted through the strongest parts of the block and in the direction best able to resist such forces. Under actual compression tests it has been found that the present block will withstand greater pressures than other blocks which have been tested and that the present block will collapse entirely while the prior blocks show ruptures along the lines of cleavage at a much lower pressure. The position of the cells with reference to the lines of cleavage not only enables the block after it has been placed in a wall but this structure has important advantages in nearly every step in its manufacture and use. The endless column leaving the die is carried forwardly on a belt conveyor where it is first cut into blocks of the desired length. The blocks are transported from the conveyor to carts usually in the hands of the workmen. The green blocks are handled rather roughly as they are subjected to frequent impacts in their travel from the belt conveyor to the cart. Breakage is frequent in the case of prior blocks because the position of the cells is usually such as to shorten the lines of cleavage. The next step in the manufacture of the blocks is the drying which is then followed by the burning. The drying is performed as evenly as possible since unequal drying results in strains and stresses which crack the block usually along the lines of cleavage. Here again the function of the long lines of cleavage in the webs will be apparent. The greater length of these lines of cleavage will resist the tendency toward separation due to uneven drying. The same is true when the blocks are in the kiln. Any
slight fluctuations in the heat to which the blocks are subjected are liable to cause unequal expansion and contraction but these forces also are resisted by the laminated structure of my block in which the lines of cleavage are relatively long.
The truss formation of the block can best be explained with reference to Figure 3. If the block were out along the vertical axes of the two cells 10, the block would then be in the form of three pieces as shown in Figure 3. The middle of the three pieces is clearly in the form of an I-beam while the two end pieces are channel beams. The complete block thus embodies a middle I-beam with two end channel beams all of integral structure. The advantage of this construction in its load bearing properties will be readily apparent to all those skilled in the art.
From the foregoing description it will be apparent that the above described block has nu-. merous advantages over the prior blocks. The breakage in handling and drying is reduced to a minimum because of the design whereby the cells are arranged with reference to the lines of cleavage of the block. With the prior tiles the breakage in'handling and drying usually runs from 5% to 25%. Under the same conditions of handling and drying the breakage of blocks of the above described type will average from 1% to 3% thus effecting a great reduction in the breakage of the tiles. This holds true in the subsequent handling operations of the tile which must first be introduced into the kiln for burning, then. removed from the kiln to a place of storage and then handled repeatedly during transportation before it reaches the ultimate user. When ready to be placed in the wall it is again subjected to more or less rough handling. At all places where the tile is handled, the breakage is less than that of the prior tiles.
After the tile is in the wall whatever breakage there is, is due to its structural strength or weakness rather than to handling. It is at this place where the truss formation of my block proves the usefulness of that formation. The load carried by the block may crush the block completely but it will not rupture the block as in thecase of the prior blocks. My block has, however, been subjected to crushing tests and it has been found to greatly exceed in strength all requirements for blocks of this character.
The block also is provided with numerous cells of greater volume than those heretofore manufactured. This also is important at every step of the manufacture and use of the block. During every step of handling the block is lighter in weight than the prior blocks thus enabling the workmen to handle a larger number of the blocks to thus reduce the labor cost of handling. This reduction in weight is also of material benefit in the transportation of the tile since the freight tariffs are based on weight. The finished tile receives its final handling when it is placed by the mason in the wall. When it is in the wall the large number and volume of the cells makes the block more elTective as an insulator against heat and against moisture. The dead air spaces prevent the transfer of heat through the Wall in both winter and summer and they thus make the building structure warmer in winter and cooler in summer than the prior structures. The moisture also is more readily trapped in the larger voids of my building tile so that practically no moisture whatever can pass through the wall to dampen the interior of the structure. The mouths of the relatively large number of cells also provide ample keys for the mortar joints.
The exterior surface of my block has also been carefully designed for the convenience of the mason and of the architect. The block may be made in any suitable dimensions and in any suitable size but the block as shown may be placed in a wall in any of three positions. When the weight of the wall above is great the block should be laid in the position shown in Figure 2. The smooth face 1'7 may be provided as an exterior face if it is desired to have a smooth unplastered face for the wall. The horizontal mortar joints may be applied either to the entire upper surface of the block or to the surfaces 16 only. If applied to the surfaces 16 and compression of the mortar will force some of the mortar into the channels 14 to prevent the slippage of one block on the other, the blocks being in effect keyed to each other. The middle portion 15 of the block will then provide a dead air space to prevent the creeping of moisture through the mortar joint. If the mortar is placed over the entire upper surface of the block, the mortar will then be keyed not only in the two channels 14 but also in the corrugated surfaces 15 and 16. The ends of the block are buttered with mortar which keys readily into the numerous cells 10, 11, 12, and 13. If the block is to be placed in a vertical position in Figure l, the same advantages will outside, or one of the other walls may be positioned on the outside if it is desired to give the exterior of the wall a plaster coat. In any case the blocks may be secured together by means of mortar joints which readily become keyed to the blocks.
Having thus described my invention in such full, clear, and exact terms that its construction and operation will be readily understood by others skilled in the art to which it pertains, what I claim as new and desire to secure by Letters Patent of the United States is:
A building block comprising a body portion having a pair of spaced apart cells and an intermediate web having a height substantially equal to half the thickness of the block, each end of said web terminating in a T-head, each T-head having a relatively small air opening thereby providing a pair of short, thick arcuate bracing arms, the outer ends of which merge into the respective ends of the T-head and the outer surface of the block and the inner ends of which merge into the web, said body portion also having at each outer portion a Web having a height substantially equal to that of the first mentioned web and terminating at each end in an angle head which extends inwardly toward the T-head, each angle head having a relatively small air opening to provide a short, thick arcuate bracing arm, the outer end of which merges into the angle head and outer surface of the block and the inner end of which merges into the second mentioned web.
ALBERT H. FARRENS.