Interlocking Precast Concrete Slabs

Abstract

Precast concrete slabs are joined together to form a walk or patio-like matrix by embedding a plurality of rods in each slab and providing cavities in the bottom faces of each slab. Each rod has a hooked end portion which projects beyond opposing end walls of the slab, the hooked end portions and the cavities being positioned such that the hooked end portions of one slab are receivable in the cavities of another slab, whereby the slabs may be interlocked end to end to form a strip of slabs. Similar cavities and rods having hooked ends may be positioned in each slab at right angles to the aforementioned rods and cavities to permit sidewise connection of the slabs along with the end-to-end connection.

Description

BACKGROUND OF THE INVENTION

This invention relates to precast concrete slabs, and more particularly to precast concrete slabs of the reinforced type for use in the construction of generally horizontal load-bearing surfaces, such as walks, roads, patios and the like.

It has long been recognized that precast concrete slabs must not only have inherent strength for good load bearing qualities and resistance to weathering and cracking, but also provision must be made for relative movement of the slabs and the expansion and contraction of individual slabs, due to various external or internal forces such as temperature differentials, weather conditions, natural expansion or contraction of the slab material, settling of the base or foundation material under the slabs, contours of the base or foundation, and characteristics of loads on the slabs, especially whether dead or alive.

For these and other reasons it has been the common practice to reinforce concrete slabs by embedding steel rods or the like in the slabs. Movement due to the foregoing forces often is accommodated simply by laying the slabs loosely adjacent one another to provide sufficient clearance to permit the movement, or by grouting the clearance between the slabs with a material which will readily expand or contract. Various attempts have also been made to reduce movement by connecting the slabs with mechanical devices, as by steel hooks and eyes, or the like, as in U.S. Pat. No. 2,780,150 -- Yeoman.

Despite the foregoing improvements, substantial problems still exist with respect to the stability of the slabs (when laid end to end or even when connected so as to prevent undue movement or shifting) relative to one another in one or more of the three principal planes and intermediate planes. The problem of movement or shifting becomes especially acute when settling of base or foundation material occurs under some of the slabs but not under adjacent slabs, or when it is not practical to prepare a perfectly level or solid base or foundation. Moreover, while it may be possible to mechanically connect slabs so rigidly as to avoid such undue relative movement, these efforts tend to be too complicated for efficient connection and laying of the slabs in many situations, such as the formation of walks and roads. Ease of placement and connection of concrete slabs is an extremely important consideration in the mass laying of roads, walks and the like.

OBJECTS AND SUMMARY

Accordingly, an object of the invention is to provide new and improved precast concrete slabs which can be connected to form a relatively stable, load bearing surface which at the same time permits the natural relative movement of such slabs due to various internal and external conditions.

Still another object is to provide new and improved precast concrete slabs reinforced in a manner which also provides for ease of connection and placement of the slabs in strips or in matrices.

These and other objects, features and advantages of the invention will be apparent from the specification which follows.

In summary outline, the precast concrete slabs of the invention satisfy the foregoing and other objects by the improvement of embedding in each slab a plurality of rods having hooked end portions projecting beyond opposing end walls of the slab, and by providing in each slab a plurality of cavities in the lower face of the slab corresponding in number to the hooked end portions, such that the hooked end portions of one slab are receivable in the cavities in another slab whereby the slabs are interlockable end to end to form a strip of slabs. Side-by-side connection of the strips of slabs to form a patio-like matrix is accomplished by providing similar hooked end portions and cavities at right angles to the first-mentioned hooked end portions and cavities.

The invention accordingly comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the article hereinafter described, and the scope of the invention will be indicated in the claims.

DETAILED DESCRIPTION

For a fuller understanding of the nature and objects of the invention, reference is had to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partially diagrammatic perspective view of several slabs of the invention connected end-to-end to form a strip of slabs;

FIG. 2 is a partially diagrammatic plan view of the bottom faces of the strip of slabs of FIG. 1;

FIG. 3 is a vertical section along the line 3--3 of FIG. 2;

FIG. 4 is the same view as FIG. 3 except for slight relative displacement of the slab sections shown;

FIG. 5 is a partially diagrammatic elevational view illustrating a method of laying a strip of slabs of the invention;

FIG. 6 is a bottom plan view of another embodiment of slab of the invention;

FIGS. 7 and 8 are fragmentary bottom plan views of still other embodiments of concrete slabs of the invention;

FIG. 9 is a vertical section along the line 9--9 of FIG. 8;

FIG. 10 is a vertical section similar to FIG. 9 showing a method of connection of two concrete slabs of the invention;

FIG. 11 is a partially diagrammatic bottom plan view of still another embodiment of concrete slabs of the invention joined together to form a strip of slabs;

FIG. 12 is a partially diagrammatic bottom plan view of a modification of the concrete slabs of FIG. 11 to illustrate how the slabs of FIG. 11 can be connected side by side as well as end to end;

FIG. 13 is a partially schematic top plan view of a plurality of the concrete slabs illustrated in FIG. 12 connected laterally and longitudinally to form a portion of a patio;

FIG. 14 is a partially diagrammatic vertical section along the line 14--14 of FIG. 13; and

FIG. 15 is a partially diagrammatic vertical section along the line 15--15 of FIG. 13.

With reference to FIGS. 1-4, one embodiment of precast concrete slab 20 of the invention, having a top face 21, a bottom face 22, end walls 23 and 24, and side walls 25 and 26, has embedded therein a plurality of reinforcing rods such as the four rods 27. As shown, the rods 27 have hooked end portions 28 projecting from the end walls of the concrete slab 20 so as to provide at least two such hooked end portions 28 projecting from end wall 23 and two such hooked end portions 28 projecting from end wall 24, in opposite directions. The pair of hooked end portions 28 projecting from end wall 23 is axially offset from the pair of hooked end portions 28 projecting from opposing end wall 24 so as to avoid interference with identical hooked portions extending from slabs placed adjacent one another to form a strip of slabs. Thus, in the arrangement of FIGS. 1-4, the rods 27 projecting from end wall 23 are positioned axially inside the rods 27 projecting from end wall 24, but other arrangements are useful as explained below.

Intermediate portions 29 of each of rods 27 are of a length sufficient to bridge a slight gap between adjacent slabs 20 and to support part of the weight of the adjacent slab, as explained below. Conventional reinforcing rods 31 may be embedded in the concrete slabs angularly to rods 27, if desired.

Corresponding in number to the rods 27 in each slab are cavities or recesses 32. The cavities or recesses 32 are dimensioned to receive in locking engagement the hooked end portions 28 of next-adjacent concrete slabs. With reference particularly to FIGS. 3 and 4, it will be noted that in this embodiment the intermediate rod portion 29 extends below each slab 20 and supports a portion of the bottom face 22 of the next adjacent slab. By reason of this support it will be evident that the next adjacent slab is stabilized with respect to relative vertical movement, while at the same time the engagement of the hooked end portion 28 in cavity 32 prevents undue movement in a horizontal (lateral and longitudinal) direction. Accordingly, upon connection of adjacent slabs in the manner illustrated, the slabs are held together so as to minimize relative movement, thereby stabilizing the connected slabs against undue movement. Since in this embodiment of the invention the intermediate rod portions 29 extend below the bottom faces 22 of the slabs, such slabs are more usually employed on a relatively soft foundation so that the intermediate rod portions 29 may sink into the foundation.

FIGS. 4 and 5 illustrate a method of connection and placement of slabs of the invention on a surface 33. One end wall of a slab 20 of the invention is inclined slightly upwardly from the surface 33, either by lifting or by placement thereunder of a block 34. While so oriented, the hooked end portions 28 of another slab are inserted under the raised end wall of the first slab, and the second slab is then lowered slowly into generally co-planar relative position such that the hooked end portions 28 slide into the cavities 32 of the other slab, the interengagement being effected by a scissor-like action of the slabs, with the edge of wall 23 (FIG. 4) resting on the rod 29 of the adjacent slab, as a pivot point. The opposing end wall of the second slab similarly then may be held in a slightly inclined position, again as by insertion of a block 34 thereunder, and the operation repeated. By this method, the rods 27 facilitate quick joinder of the slabs to form a stable strip, as in a roadway or walk.

FIGS. 6 and 7 show other arrangements of rods and cavities of concrete slabs of the invention. With reference to FIG. 6, there is embedded in a concrete slab 35 a pair of rods 36 wherein the ends of each rod form hooked end portions 37 and 38. Each rod 36 also includes intermediate portions 39 and 41 which project together with the hooked end portions from opposing end walls of the slab 35, providing the same functions as the rods 27 of FIGS. 1-5. As in the embodiment of FIGS. 1-5, the hooked end portions 37 are slightly offset with respect to the opposing hooked end portions 38 so that when the slabs are joined end to end, there will be no interference as between the rods 36. In the embodiment of FIG. 6, the hooked end portions are arranged such that hooked end portions 37 are axially outside of hooked end portions 38. The cavities 42 of this embodiment also are correspondingly offset slightly so as to mate with the corresponding hooked end portions of rods of another slab of this embodiment, in formation of a strip of such slabs, essentially as described with reference to FIGS. 1-5. One differencee, of course, from the embodiment of FIGS. 1-5 is that the concrete slab of FIG. 6 requires only two such rods 36, thus simplifying manufacture.

The offset feature of the rods 36 may be provided in many ways, one of which may be the angular or bent design of the rod 43 illustrated in FIG. 7.

For placement of slabs of the invention on a solid surface where it is desired to avoid clearance between the surface and the bottom face of the slabs, a slot 44 extending from each of the cavities 42 to an adjacent end wall of the slabs is provided, as illustrated in FIGS. 8-10. It will be noted that the slot 44 is positioned such that the intermediate portion 39 of the rod 36 of the next adjacent slab is received in the slot and such that the bottom surface of the portion 39 is co-planar with the bottom face of the slab. At the same time, the intermediate portion 39 retains its function of supporting the weight of the next adjacent slab so as to stabilize the next adjacent slab against undue vertical movement. Of course, in this embodiment, the rod 36 is embedded in the slab to a slightly greater depth than it is in the slabs 20 of FIGS. 1-5 in order to avoid projection of the intermediate portion 39 below the bottom face of the slab.

The inconvenience of carefully orienting each slab so that the appropriate end walls are made adjacent for engagement, as required in the embodiments of FIGS. 1-8, is avoided by a preferred arrangement of the rods 36 as illustrated in FIG. 11. In the embodiment of FIG. 11, it will be noted that the distance between the hooked end portions 37 is equal to the distance between the hooked end portions 38, although the pair of hooked end portions 37 is offset slightly from the pair of hooked end portions 38 so as to avoid interference between the hooked portions when the slabs are adjacent. By the equidistant positioning of the hooked end portions, each slab is interlockable from either end with either end of another slab, as illustrated in FIG. 11 with respect to the adjacent end walls A-B and adjacent end walls B--B.

The slabs can also be modified in another embodiment of the invention to permit side-by-side engagement as well as the end-to-end engagement depicted in FIGS. 1-5 and 11. With reference to FIGS. 12-15, it will be noted that at least one additional rod 47 is embedded in each concrete slab at generally right angles to the above-described rods 36, and also that each slab is provided with the same number of additional cavities 45 as additional rods 47, for mating with hooked end portions 48 of rods 47 of next adjacent slabs. The intermediate rod portions 49 may extend below each of the slabs, as illustrated in FIGS. 1-5, but preferably a slot 46 is provided from the cavity 45 to the next adjacent side wall of the slab so that the intermediate rod portion 49 of the next adjacent slab will be carried in the slot and spacing between the bottom face of the slabs and a foundation surface is avoided, analogous to the embodiments described with reference to FIGS. 8-10. The additional rods 47, of course, are positioned offset from cavities 42 and rods 36 so that interference between the rods and cavities is avoided upon joinder of slabs. Such orientations are shown in FIGS. 14 and 15.

FIG. 13 illustrates a method of laying the slabs of FIG. 12 to form a patio-like matrix. In constructing the matrix, it is convenient first to form a strip of the slabs I, II and III, as described above with reference to FIGS. 4 and 5. In the next step, since the additional rod 47 extends downwardly from slab I in the view of FIG. 13, and slab IV has a slot 46 running from the adjacent side wall to the cavity 45, the slab IV is simply placed adjacent slab I so that the rod 47 fits into the slot 46 and hooked end portion 48 fits into cavity 45. Each additional slab, such as slabs IV, V, VI and VII, may then be placed side-by-side with other slabs in the same manner. However, the end-to-end connection, as between slabs IV, V and VI is achieved as described with reference to the first strip of slabs I, II and III. If desired, upon completion of the matrix, the projecting hooked end portions 37 and 38 may be severed, especially in layouts where a border or curb co-planar with the upper face of the slabs is not used.

Many variations of the foregoing embodiments will be evident. For example, the dimensions of the cavities and hooked end portions may be such as to provide a tight engagement. Preferably, however, some clearance is desirable to accommodate slight relative movements as between adjacent slabs and to facilitate layout of the slabs. Also, while the number and arrangements of rods as shown in the drawings ordinarily will be sufficient, a greater number of rods and cavities other than those illustrated may be employed, especially when the dimensions of the slabs require greater reinforcement and stronger locking engagement. Still further, many variations are possible upon the slabs and rods themselves, such as different curvatures to accommodate placement of the slabs on inclined or curved foundations. Also, while the connecting rods in some instances need be the only reinforcing members embedded in the concrete, in some applications it may be desirable to enhance the reinforcement by embedding additional reinforcing rods in the slabs.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above article without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims

What is claimed is:

1. In a precast concrete slab for connection with other said slabs to form a generally horizontal, stable, load bearing surface, the improvement which comprises a plurality of rods firmly embedded in said slab and a plurality of cavities in the lower face of said slab and spaced from the adjacent edges thereof, said rods providing a plurality of first hooked end portions projecting beyond a first end wall of said slab adjacent the plane of said lower face and a plurality of second hooked end portions projecting beyond an opposing end wall of said slab also adjacent the plane of said lower face, said end walls corresponding to said adjacent edges, said hooked end portions being adapted to lie beneath a peripheral edge portion and to be received in said cavities of an adjacent slab having similar hooked end portions and cavities, said cavities and said hooked end portions of each slab corresponding in number, whereby a plurality of said slabs are interlockable end to end by a scissor action to form a strip of slabs.

2. A concrete slab as in claim 1 wherein said plurality of rods comprises first and second pairs of rods, the hooked end portions of said first pair projecting beyond an end wall of said slab opposite the end wall beyond which project the hooked end portions of said second pair.

3. A concrete slab as in claim 2 wherein the hooked end portions of said first pair of rods are spaced farther apart than the hooked end portions of said second pair of rods.

4. A concrete slab as in claim 2 wherein the hooked end portions of said first pair of rods are spaced apart substantially the same distance as the hooked end portions of said second pair of rods.

5. A concrete slab as in claim 1 wherein said plurality of rods comprises a pair of rods, each end of each rod defining a said hooked end portion and the end portions of each rod projecting beyond opposite end walls of said slab.

6. A concrete slab as in claim 5 wherein said rods are embedded generally parallel in said slab such that each rod passes between a pair of said cavities.

7. A concrete slab as in claim 6 wherein the hooked end portion of each rod is equidistant from the hooked end portion of the other rod which projects beyond the same end wall, whereby said slab is interlockable from either end with either end of another said slab.

8. A concrete slab as in claim 1 further including a slot corresponding to each cavity extending from each cavity to the adjacent end wall of said slab, and wherein said hooked end portions include projecting intermediate rod portions, said slots being positioned to receive said intermediate rod portions of others of said slabs whereby said intermediate rod portions, when said slabs are interlocked end to end, lie in a plane no lower than the lower faces of said slabs.

9. A concrete slab as in claim 1 further including an additional rod embedded in said slab, said slab having an additional cavity in the lower face thereof, said additional rod having a hooked end portion and an intermediate portion each projecting beyond a side wall at a generally right angle to said other hooked end portions, said cavity being positioned to receive said additional hooked end portion of an adjacent slab, whereby said slabs are interlockable side by side to form a matrix with others of said slabs which are interlocked end to end.

10. A concrete slab as in claim 9 further including a slot corresponding to each said additional cavity extending from each said additional cavity to an adjacent end wall of said slab, said slot being positioned to receive said projecting intermediate rod portion of another of said slabs whereby said intermediate rod portion, when said slabs are interlocked side by side to form said matrix, lies in a plane no lower than the lower faces of said slabs.

11. A precast slab for constructional use which comprises a slab body having substantially parallel first and second surfaces and end walls lying substantially normal to said surfaces, and at least one metal rod, said rod having an extended portion firmly embedded in said slab, an end portion bent to exit from the slab through said second surface, bent again to lie adjacent the plane of said second surface and to project beyond the adjacent end wall, the projecting end being further bent to lie substantially parallel to said end wall and having a length less than the thickness of the slab between the first and second surfaces, said second surface being provided with a recess spaced from said end wall and having a depth at least equal to the length of said last named rod bent end.

12. A precast slab according to claim 11 wherein the recess is spaced from the end wall by a distance equal to the length of the projecting rod from said end wall to said last named bent end.

13. A precast slab according to claim 11 which includes two rods as claimed lying substantially parallel and projecting beyond the same end of the slab and two recesses as claimed.

14. A precast slab according to claim 13 which includes another two rods as claimed lying substantially parallel and projecting beyond an opposite end wall and another two recesses spaced from said opposite end wall as claimed.