U.S. patent application number 11/150403 was filed with the patent office on 2006-06-15 for system and method for concrete slab connection.
Invention is credited to Donald S. Nadler.
Application Number | 20060127179 11/150403 |
Document ID | / |
Family ID | 36584080 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060127179 |
Kind Code |
A1 |
Nadler; Donald S. |
June 15, 2006 |
System and method for concrete slab connection
Abstract
Systems and methods of transferring loads between adjacent
cast-in-place slabs, such as concrete slabs, and for accurately
positioning dowels between adjacent sections of slabs are provided.
A generally planar plate-type dowel is used which may be positioned
within a cutaway in a preexisting slab of concrete. The dowel is
shaped to generally conform to the shape of the cutaway, which is
made by a saw blade. Once the dowel is positioned within the
preexisting slab, a new slab is poured adjacent the preexisting
slab. Rubber seals are included on the edges of the dowels to
provide spacing or a gap between the dowel and the preexisting slab
to allow for lateral independent movement of the adjacent slabs,
and to prevent concrete from the newly poured second slab from
entering into the gap. A saw unit for making a generally planar cut
horizontally into an edge of a hardened concrete slab is also
provided.
Inventors: |
Nadler; Donald S.; (Blue
Springs, MO) |
Correspondence
Address: |
SONNENSCHEIN NATH & ROSENTHAL LLP
P.O. BOX 061080
WACKER DRIVE STATION, SEARS TOWER
CHICAGO
IL
60606-1080
US
|
Family ID: |
36584080 |
Appl. No.: |
11/150403 |
Filed: |
June 10, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60578512 |
Jun 10, 2004 |
|
|
|
Current U.S.
Class: |
404/47 ;
404/74 |
Current CPC
Class: |
E01C 11/14 20130101;
B28D 1/02 20130101; B28D 1/045 20130101; E01C 23/04 20130101; E04C
5/12 20130101 |
Class at
Publication: |
404/047 ;
404/074 |
International
Class: |
E01C 11/02 20060101
E01C011/02 |
Claims
1. A method of connecting adjacent slabs, said method comprising
the steps of: cutting into an edge of a first existing slab to form
a cutaway; positioning a generally planar dowel into the cutaway
such that a portion of the dowel extends from the edge of the first
slab; and pouring a second slab adjacent the first slab surrounding
the portion of the dowel extending from the first slab.
2. The method as claimed in claim 1 wherein an end of the dowel
generally conforms to an inner surface of the cutaway.
3. The method as claimed in claim 1 wherein said cutting step is
accomplished with a saw blade.
4. A dowel for connecting adjacent slabs comprising, a generally
planar plate.
5. The dowel as claimed in claim 4 further comprising a seal
protruding from said plate.
6. The dowel as claimed in claim 5 wherein said seal comprises a
rubber material.
7. The dowel as claimed in claim 4 wherein said plate is shaped to
conform generally to the shape of a cutaway in which the dowel is
positioned.
8. A saw unit for use in a system of connecting slabs, said saw
unit comprising: a saw blade; a positioning mechanism for aligning
said saw blade along an edge of a slab; and an engaging mechanism
for driving said saw blade into the edge of the slab.
9. The saw unit as claimed in claim 8 wherein said positioning
mechanism comprises a vertical positioning mechanism for adjusting
a height of said saw blade.
10. The saw unit as claimed in claim 8 wherein said positioning
mechanism comprises an edge guide sensor.
11. The saw unit as claimed in claim 8 wherein said engaging
mechanism comprises an engagement cylinder associated with said saw
blade.
Description
[0001] This application claims priority pursuant to 35 U.S.C.
119(e) to co-pending U.S. Provisional Patent Application Serial No.
60/578,512, filed Jun. 10, 2004, the entire disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present inventions relate generally to systems and
methods for pavement reinforcement. More particularly, the present
inventions are concerned with systems and methods of transferring
loads between adjacent cast-in-place slabs, such as concrete slabs,
and for accurately positioning dowels between adjacent sections of
slabs.
BACKGROUND OF THE INVENTION
[0003] In the construction of concrete floors or surfaces (i.e.
sidewalks, driveways, roads, etc.), it has long been the practice
to make the surface from a series of individual blocks or slabs.
Adjacent slabs meet each other at joints which are typically spaced
so that each slab has enough strength to overcome internal stresses
that would otherwise cause random stress relief cracks.
[0004] One problem that can arise when slabs are poured in separate
subsections is that the junctions or joints between adjacent
sections are subject to damage from downward forces exerted against
the slab. To reduce the effects of such forces, it is common
practice to embed dowels into the slab. The dowels bridge across
the joint between adjacent subsections of the slab and extend a
short distance into each subsection. The dowels are placed at
regular intervals along the joint, and act to equalize and transfer
loads that are exerted against the joint. Various systems have been
developed utilizing dowels of a variety of shapes and sizes,
including generally planar plate-type dowels, as well as dowels
having square, circular or other shaped cross-sections.
[0005] If the dowels are not installed correctly, problems can
arise. Specifically, if the dowels are not parallel to the slab
surface and perpendicular to the joint between the slab sections,
unwanted stresses can be created in the slab, which can lead to
cracking of the slab. A number of systems and methods have been
developed to better ensure proper alignment of the dowels. In some
systems dowels, or sheaths for supporting the dowels, are attached
to forms prior to pouring of a concrete slab. For example, in U.S.
Pat. No. 6,354,760, the disclosure of which is incorporated herein
by reference in its entirety, a generally planar plate-type dowel
is shown which is supported by a sheath that is embedded within one
of two adjacent concrete slabs. The sheath is nailed to an inner
surface of a wood form as a first slab is poured. Once the slab has
properly hardened, the form is removed and the sheath remains. The
dowel is then positioned in the sheath such that half of the dowel
protrudes beyond the edge of the slab into a location that will be
occupied by the adjacent slab. The adjacent slab is poured and the
protruding portion of the dowel is surrounded by the concrete of
the second slab.
[0006] The generally planar plate-type dowels discussed above
provide several advantages over square and round tubular dowels
such as increased relative movement between slabs in a direction
parallel to the longitudinal axis of the joint; and reduced
loadings per square inch close to the joint, while transferring
loads between adjacent cast-in-place slabs. Nevertheless, current
systems and methods utilizing planar plate-type dowels require that
the dowel be installed in new concrete as it is poured.
Alternatively, systems and methods have been developed in which a
hole is drilled into pre-existing hardened concrete for insertion
of a tubular dowel, allowing tubular dowels to be utilized in
section repair or other retrofitting applications in which the
concrete has been poured and set/hardened prior to placement of
dowel (or sheath) within the slab. Notwithstanding, the noted
disadvantages of tubular dowels versus planer dowels, drilling in
existing concrete is extremely time consuming and creates
considerable dust which is undesirable for interior retrofit
applications. Therefore, it would be beneficial to provide a system
and method for utilizing planar dowels in connection with existing
or retrofit concrete applications, and which is easier and less
dusty than existing retrofit systems utilizing tubular dowels.
[0007] A disadvantage of prior art systems and methods of utilizing
planar dowels in new concrete pours in which a sheath is embedded
in a slab, is that only wooden forms can be used for forming the
slab. This is because the sheath must be nailed to the form before
the concrete is poured. Nevertheless, many contractors prefer to
utilize reusable metal forms as opposed to wooden forms. Therefore,
it would be beneficial to provide a system and method for utilizing
planar dowels in slabs that are made with metal forms.
[0008] Utilization of the generally planar sheaths of the prior art
for positioning dowels within a slab require vibration of the wet
concrete to allow the concrete to consolidate around the sheath.
When the adjacent slab is poured, the wet concrete for that slab
must also be vibrated to allow the concrete to consolidate around
the protruding portion of the dowel. Vibration of the wet concrete
requires additional labor and special tools that are not necessary
in applications in which generally narrow tubular dowels are
utilized. Therefore it would be beneficial to provide a system and
method for utilizing planar dowels in slabs that reduces the labor
required during pouring.
[0009] Another disadvantage of prior art systems for locating
planar dowels in a slab is that attachment of the sheath to the
form requires extremely careful positioning of the sheath with
respect to the top edge of the form as well as extremely careful
leveling of the form at the location in which the slab edge is to
be made. Even slight misalignment of either the sheath or of the
form board will result in misalignment of the dowel with the slab
and can result in undesired stresses in the slab. Misalignment or
dislocation of the sheaths can result after the sheath has been
mounted to the form either as the form is being positioned or after
the form is in position by workers accidentally stepping on the
sheaths or bumping against the sheaths. Misalignment of the form
board can also result from workers accidentally kicking the form
board, or misalignment can be the result of a warped form board.
Therefore, it would be beneficial to provide a system and method
for ensuring proper alignment of planar dowels in slabs.
SUMMARY OF THE INVENTION
[0010] An object of the instant invention is to provide a system
and method for doweling in existing concrete that is faster and
cleaner than drilling. Another object of the instant invention is
to provide a system and method for positioning planar dowels into
existing concrete. Yet another object of the instant invention is
to provide a system and method for utilizing planar dowels with
metal forms in new concrete applications. Still another object of
the instant invention is to provide a system and method for
properly aligning planar dowels in a slab. Another object of the
instant invention is to provide a system and method for utilizing
planar dowels in a slab that minimizes the amount of labor required
during new concrete pours.
[0011] The objects of the instant invention are accomplished
through the use of a generally planer plate-type dowel and a
machine, such as a saw, for making a generally planar cut
horizontally into an edge of a hardened concrete slab. One end of
the dowel is shaped to generally conform to the shape of the cut
made by the saw. The size of the dowel is slightly smaller than the
size of the cut to allow slight movement generally parallel to the
edge of the slab in which the cut is located.
[0012] In operation, a first slab of concrete is either a
pre-existing slab that is being repaired, or a relatively new slab
that has been allowed to set or harden. In the context of a repair
application, a generally straight edge to the existing concrete may
be made by cutting away a section of the existing slab. In the
context of a relatively new slab, a straight edge will be made by a
form board that is removed after the concrete has hardened. Once
the concrete is hardened and/or a straight edge is obtained, a saw
is used to plunge-cut into the edge of the slab at a depth midway
between the top surface and the base of the slab. The dowel is then
inserted into the cut and the adjacent slab such that half of the
dowel is located within the cut in the existing slab and half is
protruding from the slab into a location in which an adjacent slab
of concrete is to be poured. The adjacent slab is then poured and
vibration of the wet concrete of the adjacent slab is used to
consolidate the concrete around the protruding portion of the
dowel.
[0013] Although vibration of the concrete is necessary for the
adjacent slab, roughly half the amount of vibration-related labor
is utilized in connection with the system and method of the instant
invention as is required by systems of the prior art. This is
because vibration labor is only utilized on the adjacent slab, as
opposed to both slabs as is necessary in the prior art systems.
Cutting into an existing, hardened, slab and placement of a dowel
in the cut-away, eliminates the need for vibration in the first
slab.
[0014] In a preferred embodiment of the instant invention the saw
is self-guided by a control unit that moves across the top of the
slab following the slab edge. The saw can be adjusted to provide a
series of spaced-apart cuts along the edge of the slab. In another
preferred embodiment, the saw will include a mist system to
eliminate dust created as the concrete is cut. Such a system is
ideal for interior use of the inventive system.
[0015] In a preferred embodiment of the instant invention rubber
gaskets, or seal spacers, are connected to the dowel to aid in
alignment of the dowel in the cutaway in the slab and to prevent
concrete slurry from migrating into the cutaway area in which the
dowel is located as the adjacent slab is poured.
[0016] The dowel plates utilized in the instant invention can be
made in a variety of shapes and sizes depending upon the desired
application and the shape of the cut into which the dowel is to be
located. The shape can include two generally symmetrical ends, one
of which is positioned in the cut-away of the existing slab and the
other protruding from the slab to extend into the adjacent slab
when it is poured. Alternatively, the shape can be asymmetrical. If
an asymmetrical dowel plate is utilized, one end will have a shape
generally conforming to the shape of the cut that is made in the
existing slab. The shape of the other end will have little
significance as the wet concrete will consolidate around the
protruding end by vibration of the concrete. The dowel plates
utilized in the instant invention can also be utilized in
connection with a mounting sheath similar to that used by systems
of the prior art, allowing a single dowel to be used both for new
construction and retrofit applications.
[0017] The system and method of the instant invention provides a
means for positioning planar dowels into a retrofit application
that is much faster and cleaner than the systems of the prior art.
Sawing into a slab of concrete is much faster than drilling. In
addition, the use of a wet saw device greatly reduces the amount of
dust created during installation. In addition, the system of the
instant invention allows the use of any type of forms, whether
wood, metal or otherwise, as there is no need to nail sheaths to
the forms prior to pouring of the slab. Furthermore, the instant
invention eliminates the possibility of misalignment of dowels
caused by improper form alignment or by accidental dislocation of
dowel mounting sheaths as the slab is poured. This is accomplished
by cutting into the slab after the slab has hardened. The angle and
position of the cut is gauged by the actual surface of the slab,
providing ideal alignment of the dowel with respect to the slab
surface.
[0018] The foregoing and other objects are intended to be
illustrative of the invention and are not meant in a limiting
sense. Many possible embodiments of the invention may be made and
will be readily evident upon a study of the following specification
and accompanying drawings comprising a part thereof. Various
features and subcombinations of invention may be employed without
reference to other features and subcombinations. Other objects and
advantages of this invention will become apparent from the
following description taken in connection with the accompanying
drawings, wherein is set forth by way of illustration and example,
an embodiment of this invention and various features thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Preferred embodiments of the invention, illustrative of the
best mode in which the applicant has contemplated applying the
principles, are set forth in the following description and are
shown in the drawings and are particularly and distinctly pointed
out and set forth in the appended claims.
[0020] FIG. 1 is an elevation view of a plunge-cut saw unit of the
instant invention.
[0021] FIG. 2 is a top view of the saw unit shown in FIG. 1.
[0022] FIG. 3 is a top section view of a planar dowel plate located
within a cutaway in an existing concrete slab through the system
and method of the instant invention.
[0023] FIG. 4 is a side section view of the planar dowel located
within a cutaway in an existing concrete slab shown in FIG. 3.
[0024] FIG. 5 is a top plan view of a plastic sheath (receiver) for
locating a dowel plate of the inventive system into a newly poured
slab of concrete as the slab is poured.
[0025] FIG. 6 is top section view of an alternative embodiment of a
dowel plate of the system of the instant invention.
[0026] FIG. 7 is a top section view of another alternative
embodiment of a dowel plate of the system of the instant
invention.
[0027] FIG. 8 shows a detailed view of a ring saw of the instant
invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0028] As required, a detailed embodiment of the present inventions
is disclosed herein; however, it is to be understood that the
disclosed embodiment is merely exemplary of the principles of the
invention, which may be embodied in various forms. Therefore,
specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a basis for the claims
and as a representative basis for teaching one skilled in the art
to variously employ the present invention in virtually any
appropriately detailed structure.
[0029] Referring to FIGS. 1 and 2, a plunge-cut saw unit (10) of
the instant invention is shown. As shown in FIG. 1, saw unit 10
travels over the top of preexisting concrete slab 100 on wheels 20
following edge 110 of slab 100. The height of cutting blade 18 is
adjustable to control the vertical depth at which the cut is made
into slab 100 by raising and lowering mechanism (not shown) which
raises and lowers drive unit 14 along with saw blade 18 relative to
support arm 15. Alternatively, the height of saw blade 18 may be
adjustable by extending and retracting blade drive shaft 22 from
blade drive unit 14. Depth stop sensor 19 is included to prevent
the vertical depth of the cut from being made too close to the
bottom of slab 100. As shown in FIG. 1, depth stop sensor 19 is a
member extending downward from drive unit 14. Depth stop sensor 19
will bottom out on the ground if drive unit 14 is positioned too
close to the ground, providing a minimum height for the plunge cut
by saw blade 18.
[0030] Saw blade 18 is plunged horizontally into edge 110 of slab
100 through the extension of engagement cylinder 16 and is
retracted from slab 100 by springs (not shown) which are positioned
to provide a retracting force on saw blade 18 when engagement
cylinder 16 is in the extended position. In a preferred embodiment
engagement cylinder 16 comprises a hydraulic piston, however it
will be appreciated that alternative engagement mechanisms may be
utilized. When pressure is applied to the hydraulic piston,
engagement cylinder 16, which is connected to the end of support
arm 15, is extended to push drive unit 14 (as well as saw blade 18)
inward on support arm 15 towards power unit 12. When pressure is
released from the hydraulic piston, the force of the springs will
pull drive unit 16 outwards towards the end of support arm 15 away
from power unit 12. Drive unit 14 moves horizontally along support
arm 15 by riding along slide rails 13.
[0031] Power unit 12 includes a drive mechanism or motor to propel
saw unit 10 on wheels 20. Power unit 12 also includes control
circuitry for saw unit 10 including controls for saw drive unit 14,
saw blade 18, engagement cylinder 16, retracting cylinder 17, and
any other desired components of saw unit 10. Retracting cylinder 17
connects power unit 12 to support arm 15, such that upon retraction
of retracting cylinder 17 support arm 15 is pivotally raised upward
to raise saw blade 18 away from the surface of slab 100 for
transportation of saw unit 10. Upon extension of retracting
cylinder 17 support arm 15 is pivotally lowered toward the surface
of slab 100 into the generally parallel orientation shown in FIG.
1.
[0032] As is shown in FIG. 2, saw unit 10 includes edge guide
sensors 11 extending from support arm 15. Edge guide sensors 11 are
designed to maintain contact with edge 110 of slab 100 when saw
unit 10 is properly following edge 110. Edge sensors 11 allow saw
unit 10 to be programmed to follow edge 110 and create plunge cut
at preset intervals along edge 110 so that dowels 30 of the instant
invention can be positioned in slab 100.
[0033] Referring to FIG. 8, a detailed view of an embodiment of a
motor assembly for saw blade 18 is shown. The motor assembly
includes saw motor 24 which drives drive motor 26 which in turn
rotates saw blade 18. In an embodiment of the instant invention
shown in FIGS. 1 and 2, saw motor 24 is located in drive unit 14,
and drive shaft 22 functions as the drive motor.
[0034] Referring to FIGS. 3 and 4, one embodiment of an inventive
dowel plate (30) as it is used in accordance with the system and
method of the instant invention is shown. FIGS. 3 and 4 show an
embodiment in which dowel 30 is positioned in a preexisting,
hardened slab of concrete, 100, and then a new slab of concrete,
200, is poured adjacent to the existing slab. Cutaway 120 is made
in edge 110 of slab 100. Cutaway 120 can be made using saw unit 10
described above, or otherwise made with alternative saw units, such
as ring saws of the prior art. Steel dowel 30 shown in FIG. 3 has
semi-circular edge which is shaped to conform generally to the
shape of cutaway 120. Dowel 30 includes a pair of slots, 32, for
receiving and holding rubber centering seals 35 which protrude from
dowel 30. Seals 35 function to center dowel 30 within cutaway 120
such that gap 130 is provided between the outer surface of cutaway
120 and edge 31 of dowel 30. Gap 130 allows for lateral independent
movement of the two concrete slabs that are being joined together
via dowel 30 (including preexisting slab 100, and future slab 200
located directly adjacent slab 100). Once dowel 30 is properly
positioned in preexisting slab 100, new slab 200 of concrete is
poured and the concrete is subjected to vibration to allow the
concrete to consolidate around to portion of dowel 30 located in
new slab 200. Seals 35 will prevent concrete from new slab 200 from
flowing into gap 130.
[0035] Referring to FIG. 5, an embodiment of a sheath/receiver
(150) similar to that used by systems of the prior art (such as in
U.S. Pat. No. 6,354,760) is shown. Sheath 150 is made of a plastic,
or other suitable material and includes inner void 151 for
receiving dowel 30. In one embodiment, spacers 152 project from the
inner surface of void 151 to create gap 130 between dowel 30 and
the slab in which sheath 150 is located. Spacers 152 can be molded
into sheath 150, or alternatively can be separate components
attached to, or otherwise associated with, sheath 150. Sheath 150
also includes pre-mounted nails 170 which are driven into slab form
boards 160 to mount sheath 150 in position prior to pouring of the
slab. Once sheath 150 is mounted to form 160 for the slab, the slab
is poured. Tape 154 covers the opening of void 151 so that concrete
will not flow into void 151 when the slab is poured. The wet
concrete is vibrated to allow the concrete to consolidate around
sheath 150. Once the concrete has sufficiently hardened, form
boards 160 are removed and dowel 30 is inserted into void 151 of
receiver/sheath 150, such that half of dowel 30 is located within
void 151 (which is surrounded by concrete) and half of dowel 30
extends outward from sheath 150 (not surrounded by concrete). A new
slab of concrete is then poured adjacent to the first slab such
that the new concrete surrounds the exposed portion of dowel 30
protruding from sheath 150. Spacers 152, which are compressed
against dowel 30, will prevent concrete from the second slab from
entering void 151. The wet concrete is then vibrated to allow the
concrete to consolidate around dowel 30.
[0036] FIG. 6 shows an alternative embodiment of dowel 30 having an
elongated shape. As is shown in FIG. 6, the elongated shape of
dowel 30 allows deeper penetration into slabs 100 and 200 than the
embodiment shown in FIGS. 3-5. FIG. 6 shows a situation in which
dowel 30 is placed into a preexisting slab of concrete (slab 100);
however, dowel 30 of FIG. 6 may also be used in connection with a
sheath/receiver in the manner discussed above. When the elongated
dowel 30 of FIG. 6 is used in a preexisting slab, a deeper cutaway
(120) is necessary than with the generally elliptical dowel of
FIGS. 3-5, resulting in generally straight edges 125 of cutaway
120. As is shown in FIG. 6, dowel 30 includes rubber spacers 36
located toward the end of dowel 30 between edge 120 of preexisting
slab 100, in addition to centering seals 35. Spacers 36 provide
additional support for the elongated dowel of FIG. 6; nevertheless,
it will be appreciated that spacers 36 could be used with other
dowel shapes, including those shown in FIGS. 3-5.
[0037] FIG. 7 shows another alternative embodiment of dowel 30
having a generally rectangular elongated shape. Dowel 30 of FIG. 7
can include a generally straight or flat end (39), or alternatively
may include a slightly curved end to conform to the shape of the
inner surface of cutaway 120 of edge 110 of preexisting slab 100.
The end of dowel 30 opposite of end 39 can have a generally
straight or flat shape since it will be located in the newly poured
slab (200).
[0038] In the foregoing description, certain terms have been used
for brevity, clearness and understanding; but no unnecessary
limitations are to be implied therefrom beyond the requirements of
the prior art, because such terms are used for descriptive purposes
and are intended to be broadly construed. Moreover, the description
and illustration of the inventions is by way of example, and the
scope of the inventions is not limited to the exact details shown
or described.
[0039] Although the foregoing detailed description of the present
invention has been described by reference to an exemplary
embodiment, and the best mode contemplated for carrying out the
present invention has been shown and described, it will be
understood that certain changes, modification or variations may be
made in embodying the above invention, and in the construction
thereof, other than those specifically set forth herein, may be
achieved by those skilled in the art without departing from the
spirit and scope of the invention, and that such changes,
modification or variations are to be considered as being within the
overall scope of the present invention. Therefore, it is
contemplated to cover the present invention and any and all
changes, modifications, variations, or equivalents that fall with
in the true spirit and scope of the underlying principles disclosed
and claimed herein. Consequently, the scope of the present
invention is intended to be limited only by the attached claims,
all matter contained in the above description and shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
[0040] Having now described the features, discoveries and
principles of the invention, the manner in which the invention is
constructed and used, the characteristics of the construction, and
advantageous, new and useful results obtained; the new and useful
structures, devices, elements, arrangements, parts and
combinations, are set forth in the appended claims.
[0041] 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.
* * * * *