Concrete Dowel Placement Sleeves

The invention pertains generally to the art of concrete construction and more particularly to devices for facilitating placement of slip and/or non-slip dowel rods within adjacent concrete slabs.

In the art of concrete construction, it is commonplace to form "cold joints" between two or more poured concrete slabs. Such cold joints frequently become uneven or buckled due to normal thermal expansion and contraction of the concrete and/or compaction of the underlying soil caused by inadequate substrate preparation prior to pouring of the concrete. As a means of preventing buckling or angular displacement of such cold joints, it is common practice to insert smooth steel dowel rods generally known as "slip dowels" within the edge portions of adjoining concrete slabs in such a manner that the concrete slabs may slide freely along one or more of the slip dowels, thereby permitting linear expansion and contraction of the slabs while at the same time maintaining the slabs in a common plane and thus preventing undesirable buckling or unevenness of the cold joint.

In order to function effectively, slip dowels must be accurately positioned parallel within the adjoining concrete slabs. If the dowels are non-parallel positioned, such will prevent the desired slippage of the dowels and will defeat the purpose of the "slip dowel" application. Additionally, the individual dowels must be placed within one or both of the slabs in such a manner as to permit continual slippage or movement of the dowel within the cured concrete slab(s).

In the prior art, two methods of installing smooth "slip dowels" have become popular. According to the first method, a first concrete pour is made within a pre-existing form. After the first pour has cured, an edge of the form (usually wooden stud) is stripped away. A series of holes are then drilled parallel into the first pour along the exposed edge from which the form has been removed. The depth and diameter of the individual holes varies depending on the application and the relative size of the concrete slabs to be supported. As a general rule, however, such holes are at least 12" deep and typically have a diameter of approximately 5/8 of an inch.

After the parallel aligned series of holes has been drilled into the first pour, smooth dowel rods are advanced into each such hole such that one end of each dowel rod is positioned within the first pour and the remainder of each dowel rod extends into a neighboring area where a second slab of concrete is to be poured. Thereafter, concrete is poured into such neighboring area and is permitted to set with the parallel aligned dowels extending thereinto. After the second pour has set, the slip dowels will be held firmly within the second slab but will be permitted to slide longitudinally within the drilled holes of the first slab thereby accomodating longitudinal expansion and contraction of the two slabs while at the same time preventing buckling or angular movement therebetween.

Although the above described "drilling method" of placing slip dowels has become popular, it will be appreciated that such method is extremely labor intensive. In fact, it takes approximately ten minutes to drill a 5/8" diameter by 12" long hole into the first pour and the drilling equipment, bits, accessories, and associated set up time tends to be very expensive. Moreover, the laborers who drill the holes and place the slip dowels must be adequately trained to insure that the dowels are arranged perpendicular to the joint but parallel to one another so as to permit the desired slippage during subsequent use.

The second popular method of placing slip dowels involves the use of wax treated cardboard sleeves positioned over one end of each individual dowel. According to such method, a series of holes are drilled through one edge of a concrete form and smooth dowels are advanced through each such hole. Wax treated cardboard sleeves are placed over one end of each such dowel and the first pour is made within the form. After the first pour has set, the previously drilled form is stripped away leaving the individual dowels extending into a neighboring open space where the second pour is to be made. Subsequently, the second pour is made and permitted to cure. Thereafter, the slip dowels will be firmly held by the concrete of the second pour but will be permitted to longitudinally slide against the inner surfaces of the wax treated cardboard sleeves within the first pour. Thus, the waxed cardboard sleeves facilitate longitudinal slippage of the dowels, while at the same time holding the two concrete slabs in a common plane, and preventing undesirable buckling or angular movement thereof.

This second method, while presently popular, is nonetheless associated with numerous deficiencies. For example, after the first pour has been made, the free ends of the dowels are likely to project as much as 18" through the forms and into the open space allowed for the second pour. Because the drilled section of form must be advanced over these exposed sections of dowel to accomplish stripping or removal of the form, it is not infrequent for the exposed portions of the dowels to become bent and, thus, nonparallel. Also, the drilled section of form may become damaged or broken during the removal process, thereby precluding its reuse.

It is unfortunate that both of the above described popular methods of placing slip dowels often result in the dowels being finally positioned at various angles rather than in the desired parallel array. When such occurs, the necessary slippage of the dowels is impeded or prevented.

In other applications wherein longitudinal slippage of the dowels is not desired, it is common to employ non-slip dowels or rebar disposed through two or more adjacent concrete pours. Because it is sometimes desirable to insert such non-slip dowels or rebar into a prepoured and set concrete slab, it is further desirable to provide apparatus to facilitate insertion and or grouting in place of such rod, without the need for drilling or cutting of the existing concrete slab.

Accordingly, there remains a need in the art for methods and/or devices for facilitating the proper placement of slip dowels and non-slip dowels in various vertical and horizontal concrete applications.

In accordance with the present invention, there is provided a slip dowel placement sleeve comprising a generally cylindrical tube or sheath having a preferrably open proximal end, a closed distal end and a generally hollow interior compartment. A perpendicular flange extends at least partially about the proximal end of the sheath. The flange is adapted to be rapidly mounted to a conventional form by suitable fasteners such as nails or staples whereby multiple sleeves may be disposed in an array upon the form. Accordingly, the slip dowel placement sleeves, when attached to the form extend outwardly from one side of the form, extending parallel into an open area where a first concrete pour is to be made. Thereafter, the first pour is completed and allowed to set. After the pour has set, the form is separated from the slip dowel placement sleeves and is removed, leaving the sleeves in place within the first pour. Multiple slip dowels having outside diameters slightly less than the inner diameter of the placement sleeves are then inserted into each slip dowel placement sleeve and permitted to extend therefrom into a neighboring space where a second pour is to be made. Thereafter the second pour is made and allowed to set. As a result, the portion of each slip dowel which extends into the second pour will be held firmly within the concrete of the second pour while that portion of each slip dowel which resides within the slip dowel placement sleeves of the first pour will be permitted to slip longitudinally due to the loose fit of the slip dowel rod within the placement sleeve. Accordingly, the slip dowels will prevent the cold joint between the two pours from buckling or undergoing angular movement while, at the same time permitting, longitudinal expansion and contraction of the pours.

Further, in accordance with the invention, the slip dowel placement sleeve may be configured with a slight proximal to distal end taper so as to facilitate extraction of the placement sleeve from the first concrete slab upon stripping of the form, thereby leaving an open cylindrical void within the slab. The resultant cylindrical void will be specifically sized to permit insertion and slidable movement of the slip dowels without the need for time consuming and expensive drilling operations. Also, the extraction of the placement sleeves will permit them to be reused, thereby lowering cost.

Still further in accordance with the invention, the dowel rod placement sleeves of the present invention may be specifically configured to accomodate and hold non-slip dowel rod or rebar. The dowel rod placement tube employed in such non-slip dowel applications will generally comprise a corrugated "grout tube" for facilitating placement of the non-slip dowel or rebar. In such embodiment, the "grout tube" will be generally in the configuration of the above described slip dowel placement sleeve and will in addition be provided with a series of annular ridges forming indentations i.e. an irregular surface along the outer surface of the sleeve, and also forming annular indentations or intrusions into the inner cavity of the sleeve. As such, each grout tube will remain firmly implanted within a surrounding concrete pour. Thereafter, textured dowel rod or rebar may be inserted inside the inner cavity of the sleeve with grouting material or other adhesive material or filler filling the space to firmly bond the bar within the sleeve. As the grouting material, adhesive or filler sets, the rebar or textured dowel will be firmly held within the grout tube in a non-slipping manner.

These as well as other features of the present invention will become more apparent upon reference to the drawings wherein:

FIG. 1 is a perspective view of a preferred slip dowel placement sleeve of the present invention.

FIG. 2 is a perspective view of three separate preferred slip dowel placement sleeves of the present invention nailed to a section of wooden concrete form.

FIG. 3 is a cutaway view of a poured concrete slab abutted by a section of wooden concrete form and having a plurality of preferred slip dowel placement sleeves of the present invention extending thereinto.

FIG. 4 is a cutaway perspective view of a poured concrete slab having a plurality of slip dowel placement sleeves remaining therein following stripping away of a portion of the attendant concrete form.

FIG. 5 is a longitudinal sectional view of a cold joint formed between two poured concrete slabs with a slip dowel extending therethrough and positioned within a preferred slip dowel placement sleeve of the present invention.

FIG. 6 is an elevational view of a second preferred embodiment of the invention comprising an extractable slip dowel placement sleeve of tapered configuration.

FIG. 7 is a perspective view of a third preferred embodiment of the present invention comprising a corrugated "grout tube" for placement of non-slip dowel or rebar.

FIG. 8 is a longitudinal sectional view showing a cold joint between two poured concrete slabs, with a section of rebar extending therethrough and positioned within a corrugated "grout tube" of the present invention.

FIG. 9 is a partial perspective view of a preferred slip dowel placement sleeve of the present invention having a plurality of gussets extending between the proximal portion of the tubular sleeve and the perpendicularly attached rectangular flange to lend rigidity and support to the slip dowel placement sleeve during use.

The accompanying drawings are provided for purposes of illustrating presently preferred embodiments of the invention and are not intended to limit the scope of the invention in any way.

Referring now to the drawings, FIGS. 1 through 5 pertain to the basic slip dowel placement sleeve of the present invention, while FIGS. 6 through 9 pertain to additional embodiments wherein various additions, modifications, and/or alterations have been made to the basic sleeve shown in FIGS. 1-5 for the purposes of further facilitating its utility and/or permitting the use of non-slip dowel or rebar within a "grout tube" application.

As shown in FIG. 1, the basic slip dowel placement sleeve 10 of the invention comprises a generally cylindrical dowel receiving sheath 12 having a closed distal end 14, a preferrably open proximal end 16, and a hollow interior compartment formed therewithin. A generally rectangular flange 18 extends perpendicularly about the proximal end 16 of the sheath 12. A central aperture is formed in the flange 18 so as to permit passage of a dowel rod through the flange and into the open inner compartment of the sheath 12. Plural apertures 20, 22, 24, and 26 are formed near each corner of the flange 18 to permit nailing or stapling of the flange to the surface of a wooden concrete form or other surface. Preferrably, the sleeve 10 is integrally formed of a plastic material fabricated by conventional molding techniques.

The manner in which the basic slip dowel positioning sleeves 10 are employed is illustrated in FIGS. 2 through 5. As shown, a series of individual slip dowel placement sleeves 10A, 10B, 10C, and 10D are positioned and affixed in an array along the inner surface of a section of wooden concrete form 30 such that each individual sleeve 10A, 10B, 10C, 10D extends perpendicularly from the inner surface of the form 30 in substantially parallel disposition.

The attachment of the dowel rod placement apparatus, 10A, 10B, 10C, 10D to form 30 is made by passing staples or small head nails through the apertures 20, 22, 24, 26 of flanges 18A-D. Thereafter, the form 30 is held firmly in position by stakes 32, 34. A first concrete pour is made within the form 30 so as to form first concrete slab 36. After slab 36 has set, the form 30 is stripped away, separating the individual flanges, 18A-D and their associated nail or staple fasteners from the inner surface of the form 30. Such stripping away of the form 30 leaves the individual dowel rod positioning sleeves 10A-D in a parallel array within the slab 36 while the proximal flanges 18A-D thereof reside flush with the formed edge 38 of slab 36.

Sections of smooth dowel 40, 41, 42 are then inserted through apertures located in flanges 18A-D and advanced distally into the longitudinal inner cavities of the dowel receiving sheaths of sheeves 10A-D. The portion of the dowel rods 40, 41, 42 advanced into the sleeves 10A-D will remain slidably disposed therein while the remaining portion of dowel rods 40, 41, 42 extend outwardly into an adjacent space 46 wherein a second concrete pour is to be made.

Thereafter, concrete is poured into space 46 in a conventional manner and allowed to set, thereby forming a second concrete slab 48. A cold joint or seam 50 extends between the first slab 36 and the second slab 48. Through use of the dowel rod positioning sleeves 10A-D of the present invention, the dowel rods 40, 41, 42 remain parallel to one another and longitudinally slidable within the first slab 36 while being firmly cured in place within second slab 48. By such arrangement, the individual first 36 and second 48 slabs are permitted to undergo longitudinal expansion and contraction along the dowels 40, 41 and 42 while at the same time being prevented from buckling or undergoing vertical or angular displacement at the cold joint 50.

Many modifications, alterations and/or additions may be made to the basic slip dowel positioning apparatus 10. Several such modifications, alterations and additions are illustrated in FIGS. 6 through 9. Referring specifically to FIG. 6, the slip dowel positioning apparatus of the present invention may be configured so as to be "strippable" or extractable from the first concrete pour, thereby leaving an open cylindrical void within the first concrete slab, so as to permit insertion of the desired dowel rods without requiring continued presence of the dowel rod positioning apparatus.

The extractable or "strippable" positioning apparatus 100 of the invention differs from the basic positioning apparatus 10 in that the outer surface of the dowel receiving sheath 120 of the extractable apparatus 100 is distally tapered such that the distal end 140 thereof is smaller than the proximal end 160. The proximal flange 180 of the extractable apparatus 100 is structurally the same as that of the basic apparatus 10 described in FIG. 1. However, the provision of the tapered sheath 120 permits the extractable apparatus 100 to be pulled out of the first concrete slab automatically upon stripping of the form from the slab, thereby leaving an open cylindrical void within the slab. The extracted apparatus 100 may then be reused in subsequent concrete pours.

Another modified embodiment of the invention shown in FIG. 7 comprises a corrugated or ribbed non-slip dowel positioning apparatus or "grout tube" intended for use with textured dowel or rebar in applications where longitudinal slippage of the bar is not desired. Specifically, referring to FIG. 7 the corrugated or ribbed "grout tube" 200 comprises a corrugated sheath 220 having a closed distal end 240 and an open proximal end 260 with a flange 280 positioned on the proximal end 260 in a manner substantially identical to that of the basic apparatus 10. However, this "grout tube" embodiment 200 differs from the basic placement sleeve 10 in that the sheath 220 of the "grout tube" is provided with a multiplicity of annular ribs 282 upon the outer surface of the sheath 220 and further forming indentations within the inner cavity thereof. Such corrugated or ribbed construction firmly holds the "grout tube" in a set position within the center of a concrete slab 360. A section of rebar 400 is inserted into the inner cavity of the apparatus with a quantity of conventional grouting material 402 being applied so as to fill the space therewithin. As the grouting material 402 hardens it serves to hold the rebar 400 firmly in place within the "grout tube" 200. The remaining portion of the rebar 400 extends into an adjoining open area where it becomes set within a poured second slab 480 such that the rebar will be firmly held within first slab 360 by way of the grouting material 402 and grout tube while the opposite end of the rebar is firmly held within a second poured concrete slab. By such arrangement, the first and second concrete slabs 360 and 480 are prevented from moving longitudinally as well as angularly along cold joint 500.

A further modification of the basic device which is contemplated by the invention is the provision of fins or gussets 60 as shown in FIG. 9. Such fins or gussets are of generally triangular configuration and extend between the proximal end 16 of the tubular sheath 12 and the inner surface of flange 18 so as to impart additional strength and rigidity to the apparatus. Of course, various other types of fins, gussetts, supports, or braces may be employed and, such fins need not be limited to the triangular configurations shown in FIG. 9.

Although several possible additions, modifications and alterations of the basic invention have been described herein, it must be appreciated that many more additions, modifications and alterations will likely be apparent to those skilled in the art. Accordingly, it is intended that all such conceivable additions, alterations and modifications be included within the scope of the following claims and the equivalents thereof.