Concrete dowel placement sleeves

Abstract: Slip and non-slip dowel placement sleeves (10,100) are disclosed. The slip dowel placement sleeve (10) generally comprises a tubular dowel receiving sheath (12) having a closed distal end (14) and an open proximal end (16). A connecting means of perpendicular flange (18) is formed around the proximal opening (16) of the sheath to facilitate attachment of the sheath to a concrete form (30). Smooth sections of dowel rod (42) may then be advanced through holes drilled in the concrete form (30) and into the interior compartment of the sheath (12). Concrete (36) is poured within the form (30) and the dowel rod (42) remains slidably disposed within the interior of the sheath (12). Variations of the basic slip dowel placement sleeve (10) of the invention includes a tapered "extractable" sleeve (100) and a Corrugated "grout tube (200)" for placement of non-slip dowel or rebar (400).

Description: 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 0.305 m (12") deep and typically have a diameter of approximately 1.54cm (5/8"). 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 1.54 cm (5/8") diameter by 0.305 m (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 10.46 m (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. Concrete dowel placement apparatus has been proposed in EP-A-0 328 484 comprising a tubular dowel receiving sheath having an outer surface and a hollow interior compartment extending axially therein attached to a flat surface of a concrete form, said sheath having an open proximal end and an integrally formed closed distal end, and a flange at said open proximal end for mounting the apparatus to said concrete form, said flange being formed completely about and extending perpendicularly from said open proximal end and having a peripheral edge, an inner surface which is directed toward the closed distal end of the sheath, and an outer surface having a generally planar configuration for placement into abutting contact with the flat surface of the concrete form to prevent seepage of concrete into said interior compartment of said sheath. Whilst such an arrangement overcomes many of the deficiencies discussed above, there remains a need to provide reliable apparatus which is particularly strong and unlikely to become mis-shapen. In accordance with the present invention, there is provided concrete dowel placement apparatus generally of the type disclosed in EP-A-0 328 484, characterised in that said sheath is of generally rounded cylindrical configuration with a substantially constant wall thickness, and in that at least one strength imparting gusset is provided having a first side extending along the inner surface of the flange and terminating inwardly of the peripheral edge, a second side extending along a proximal portion of the outer surface of said sheath, and a third side extending between the first and second sides, said third side having a length substantially exceeding the length of the first side. Preferably, the flange at the open proximal end has a generally rectangular configuration and may be provided with apertures for receiving fasteners to facilitate attachment to a concrete form. These as well as other features of the present invention will become more apparent upon reference to the drawings wherein: Figure 1 is a perspective view of a dowel placement apparatus in the form of a sleeve, in accordance with the present invention. Figure 2 is a perspective view of three such sleeves nailed to a section of wooden concrete form. Figure 3 is a cutaway view of a poured concrete slab abutted by a section of wooden concrete form and having a plurality of such sleeves extending thereinto. Figure 4 is a cutaway perspective view of a poured concrete slab having a plurality of such sleeves remaining therein following stripping away of a portion of the attendant concrete form, and Figure 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 such sleeve. The accompanying drawings are provided for purposes of illustrating a presently preferred embodiment of the invention and are not intended to limit the scope of the invention in any way. Referring now to the drawings, as shown in Figure 1, the slip dowel placement sleeve 10 comprises a generally rounded cylindrical dowel receiving sheath 12 of substantially constant wall thickness having a closed distal end 14 which is integrally formed, an 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. Referring also to Figure 5, the sleeve 10 is provided with gussets 60. These 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. Preferably, 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 Figures 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 18 A - 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, 18 A - 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 position sleeves 10A - D in a parallel array within the slab 36 while the proximal flanges 18 A - 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 18 A - D and advanced distally into the longitudinal inner cavities of the dowel receiving sheaths of sleeves 10 A - D. The portion of the dowel rods 40, 41, 42 advanced into the sleeves 10 A - 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 10 A - 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. It will be appreciated that modifications and alterations of the basic invention described above are possible within the scope of the following claims.

Claims: A concrete dowel placement apparatus of the type comprising a tubular dowel receiving sheath (12) having an outer surface and a hollow interior compartment extending axially therein attached to a flat surface of a concrete form (30), said sheath (12) having an open proximal end (16) and an integrally formed closed distal end (14), and a flange (18) at said open proximal end for mounting the apparatus to said concrete form, said flange (18) being formed completely about and extending perpendicularly from said open proximal end (16) and having a peripheral edge, an inner surface which is directed toward the closed distal end (14) of the sheath (12), and an outer surface having a generally planar configuration for placement into abutting contact with the flat surface of the concrete form (30) to prevent seepage of concrete into said interior compartment of said sheath (12); characterised in that said sheath (12) is of generally rounded cylindrical configuration with a substantially constant wall thickness, and in that at least one strength imparting gusset (60) is provided having a first side extending along the inner surface of the flange (18) and terminating inwardly of the peripheral edge, a second side extending along a proximal portion of the outer surface of said sheath (12), and a third side extending between the first and second sides, said third side having a length substantially exceeding the length of the first side. A concrete dowel placement apparatus according to Claim 1, characterised in that said flange (18) has a generally rectangular configuration/ A concrete dowel placement apparatus according to Claim 1 or 2, characterised in that a plurality of apertures (20, 22, 24, 26) are formed in said flange (18), said apertures being sized, configured and positioned to permit the passage of fasteners therethrough in such a manner as to facilitate the attachment of said flange (18) to said flat surface of said concrete form (30) such that the outer surface of the flange (18) is held in abutting contact with the flat surface of the form (30). A concrete dowel placement apparatus according to any one of Claims 1 to 3, characterised in that said interior compartment of said dowel receiving sheath (12) is sized and configured to permit a dowel rod (40) to be slidably inserted therein and to allow said dowel rod (40) to remain longitudinally slidable therewithin so long as said dowel rod (40) resides within said interior compartment. A concrete dowel placement apparatus according to any one of Claims 1 to 4, characterised in that said apparatus is formed of molded plastic.

Inventors: SHAW LEE A, SHAW LEROY E, SHAW RONALD D, SHAW, LEE A., SHAW, LEROY E., SHAW, RONALD D.
Applicants: SHAW LEE A, SHAW LEROY E, SHAW RONALD D, SHAW, LEE A., SHAW, LEROY E., SHAW, RONALD D.
Application year: 1990
Main classification: E01C11
IPC codes: F16B13, E01C11, E04B1