U.S. patent number 3,693,310 [Application Number 05/087,924] was granted by the patent office on 1972-09-26 for support for elongated reinforcing members in concrete structures.
This patent grant is currently assigned to Pre-Stress Concrete, Inc.. Invention is credited to Thomas E. Middleton.
United States Patent |
3,693,310 |
Middleton |
September 26, 1972 |
SUPPORT FOR ELONGATED REINFORCING MEMBERS IN CONCRETE
STRUCTURES
Abstract
A support for reinforcing members used in fabricating concrete
structures including a base and an upright portion which is formed
to receive and support two intersecting reinforcing members in a
concrete structure at the point where the members intersect. The
support holds the reinforcing members during the pouring of
concrete to maintain the reinforcing members at a predetermined
position with reference to the ground or the outer surface of the
concrete structure.
Inventors: |
Middleton; Thomas E. (Houston,
TX) |
Assignee: |
Pre-Stress Concrete, Inc.
(Houston, TX)
|
Family
ID: |
22208082 |
Appl.
No.: |
05/087,924 |
Filed: |
November 9, 1970 |
Current U.S.
Class: |
52/685;
52/689 |
Current CPC
Class: |
E04C
5/168 (20130101) |
Current International
Class: |
E04C
5/16 (20060101); E04c 005/16 () |
Field of
Search: |
;52/684,685,686,689 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,484,976 |
|
Feb 1969 |
|
DT |
|
1,029,643 |
|
May 1966 |
|
GB |
|
1,142,886 |
|
Feb 1969 |
|
GB |
|
211,591 |
|
Aug 1966 |
|
SW |
|
Primary Examiner: Sutherland; Henry C.
Claims
What is claimed is:
1. A slab chair integrally formed of a plastic material for
supporting elongated reinforcing members at a desired position in a
concrete structure comprising
a circular planar base,
a tubular support member extending centrally from said base for
supporting two intersecting elongated reinforcing members a
predetermined distance from said base, said tubular support member
having openings therethrough permitting concrete to enter the
interior thereof,
four equidistantly spaced radially disposed arms projecting from
said base along the length of said hollow support member and
extending above the top of said support member for receiving and
providing lateral support for said two intersecting elongated
reinforcing members, said extending arms having inwardly projecting
portions at the tips thereof for retaining said elongated members
between said arms, the spacing between the top surface of said
support member and the inwardly projecting portions at the tips of
said extending arms being substantially equal to the sum of the
diameters of said two elongated reinforcing members, the spacing
between the inwardly projecting portions of adjacent arms being
less than the diameter of said elongated reinforcing members, said
arms being capable of flexing to receive said reinforcing members
therebetween.
2. A slab chair as described in claim 1, wherein said base,
extending arms and hollow support member are integrally formed of
synthetic resinous material.
Description
BACKGROUND OF THE INVENTION
In using concrete as a building material, it is often necessary to
reinforce the concrete by using reinforcing bars, wire, mesh,
cable, or strand, or by pre-stressing the concrete structures. A
concrete structure is ordinarily pre-stressed by using
pretensioning or post-tensioning techniques. In pretensioning,
steel bars, wires or cables are stretched between the end points of
a concrete form and tension is applied thereto. Then concrete is
poured into the forms and allowed to set to form a concrete
structure. When the concrete sets, the tension on the cables is
relieved thereby inducing compressive stresses in the concrete to
pre-stress the concrete structure.
In post-tensioning, the cables are similarly positioned, but have
little or no tensile forces applied thereto until after the
concrete is poured and sets. Then, the cables are tensioned using
hydraulic jacks or the like. The ends of the tensioned cables are
then anchored to the concrete structure to pre-stress the
structure. To prevent the cable from bonding to the concrete, so
that there can be relative movement therebetween to accomplish the
pre-stressing, a sheathed cable is used.
In using any technique of pre-stressing, however, it is desirable
that the bars or cables be positioned within the concrete structure
near the center thereof to provide uniform strength thereto.
Consequently, it is necessary to support the cables and hold them
in the desired position during the pouring of the concrete,
otherwise the cables will sag or otherwise be improperly
positioned, thereby weakening the structure.
Heretofore, support members which are capable of holding only a
single strand or cable have been used to support the cable at
various positions within the form. When using such support members,
it has been necessary to tie the cables together with wire at the
points where the cables intersect one another in order to keep all
of the reinforcing cable in substantially the same plane. Unless
the reinforcing cables are tied at the intersecting points, they
tend to snake either before or during the pouring of the concrete
structure, resulting in an improperly reinforced structure. It can
be appreciated that a considerable amount of time and effort is
utilized in the positioning of the support members and in the
individual wire tying together of every intersecting point of each
cable.
The subject device not only eliminates the wire material necessary
for tying intersecting cables together, but also reduces
considerably the labor time required in fabricating a reinforced
concrete structure.
SUMMARY OF THE INVENTION
The subject support member or slab chair is capable of holding two
intersecting cables at the point where they intersect and
supporting them relative to the ground or to the bottom of a wood
form so that the desired spacing between the ground and the plane
in which the strands lie is maintained. The subject device includes
a base portion having a supporting portion which extends
substantially perpendicularly from the base portion. Slots or
spaces are formed in or near the top of the supporting portion for
receiving and holding two cables at the intersection thereof. Since
the two cables are securely held together at the intersecting
point, there is no need to tie wire the cables together. Holes are
generally provided in the upright support portion to permit
concrete to enter and thus solidly hold the slab chair in the
concrete structure. Use of the slab chairs at the intersecting
points of the cables adequately supports the cables during the
pouring of the concrete.
While the slab chair is described herein for use primarily in
horizontal slabs or applications, it is also applicable for use in
vertical concrete structures such as retaining walls. In these
applications, the slab chairs could, for example, be nailed to a
wood form in order to hold vertically positioned reinforcing
members in the proper position spaced from the walls of the
form.
The subject device eliminates the need for any wire tying at the
intersections of reinforcing members, and reduces the amount of
materials and labor required in fabricating a concrete structure.
Other advantages of the present invention will be apparent from the
following detailed description when considered in conjunction with
the following detailed drawings. It is apparent that many
alternative embodiments may be fabricated for supporting two
intersecting cables at a predetermined distance from the ground in
accordance with the principles of this invention. It is to be
noted, however, that the drawings illustrate only typical
embodiments of the invention and are therefore not to be considered
limiting of its scope, for the invention may admit to other equally
effective embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial perspective view of a typical concrete form
having reinforcing members which are supported by slab chairs
embodying the principles of this invention.
FIG. 2 is a perspective view of a slab chair embodying the
principles of this invention.
FIG. 3 is a perspective view of the slab chair shown in FIG. 2
supporting two intersecting reinforcing members.
FIG. 4 is a top view of the slab chair shown in FIG. 3 further
illustrating the manner in which the intersecting reinforcing
members are held.
FIG. 5 is a cross-sectional view of the slab chair taken along line
5--5 from FIG. 2.
FIG. 6 is an alternative embodiment of the present invention
including a substantially U-shaped member for supporting the
intersecting reinforcing members.
FIG. 7 is another alternative embodiment of the present invention
illustrating a slab chair having a substantially square or
rectangular cross-section.
FIG. 8 is still another alternative embodiment of the present
invention illustrating a slab chair having a substantially circular
cross-section.
DESCRIPTION OF THE INVENTION
Referring to FIG. 1, there is shown a portion of a typical assembly
from which a concrete slab can be fabricated. The assembly includes
a concrete form illustrated by boards 11 and 12 which are usually
adequately supported in a vertical position by braces and stakes
which are not shown. Immediately above the ground a moisture
barrier 13, commonly a sheet of plastic such as polyethylene, is
placed to prevent moisture from seeping into the concrete structure
from the ground. A plurality of reinforcing members 14 and 15 which
can be reinforcing bar, cables, strand, wires, or the like, are
positioned in intersecting relationship at equal points along the
boards 11 and 12. Supporting the reinforcing members are a
plurality of slab chairs 16 which are positioned at each
intersection of the reinforcing members 14 and 15 to receive and
support the members at the intersections thereof.
As shown in FIGS. 2 through 6, the slab chair 16 generally includes
a rounded base 17. While bases of any shape may be utilized, it is
desirable that the base not have any sharp corners so as to
preclude piercing of the plastic sheet 13 which acts as a moisture
barrier. The slab chair 16 includes a tubular portion 18 which
extends upwardly from the base 17. While the tubular portion is
shown as having a circular cross-section, it may be formed to have
a square or other shaped cross-section as well. The tubular portion
18 is desirably hollow so as to permit concrete to flow through the
open end 19 and also through holes 21 which are provided in the
sides of the tubular portion 18. Thus, when concrete is poured,
there will be no voids in the concrete structure which may tend to
weaken the structure, and also the slab chair 16 will be securely
held in the concrete structure after the concrete sets. Four
vertical arms 23, 24, 25, and 26 are provided for holding the
intersecting cables 14 and 15 as shown in FIG. 3. Typically, the
cables 14 and 15 are assembled with all of the first group of
parallel cables, such as 14, being installed first, and then all of
the second group of parallel cables, such as 15, being installed
afterwards and being positioned substantially perpendicular to and
on top of the first group of cables 14. Thus, the first group of
cables 14 will lie in a slightly lower plane than the second group
of cables 15. Nevertheless, both planes desirably will be near the
middle of the concrete structure.
The upper part of each of the arms 23, 24, 25, and 26 have inwardly
projecting portions 31, 32, 33, and 34, respectively. The space
between adjacent inwardly projection portions, such as 31 and 32,
is less than the diameter of a cable 14 or 15. Likewise, the same
is true of the spacing between the other adjacent inwardly
projecting portions. The space provided between the inwardly
projecting portions, such as 31, and the top 30 of the tubular
portion 18 is approximately equal to the sum of the diameters of
the cables 14 and 15. In other words, the space between the
projection 31 and the top of the tubular portion 18 is sufficient
to accommodate and hold the two intersecting cables.
To install the slab chair 16, one of the cables 14 is first pressed
into the openings between opposing pairs of arms, such as the arms
25 and 26 on one side, and arms 23 and 24 on the other side as
shown in FIG. 3. As the cable 14 is pressed downwardly, the
opposing arms 25 and 26 are urged apart from on another and the
arms 23 and 24 are likewise urged apart to permit the cable 14 to
move down between the arms and rest on the top 30 of the tubular
portion 18. The intersecting cable 15 is then similarly positioned
between arms 23 and 26 on one side and arms 24 and 25 on the other
side and is pressed downwardly to force the arms apart until cable
15 is resting on top of cable 14. The arms spring back after the
cable 15 is in its proper position on top of cable 14 and the
projections 31, 32, 33, and 34 extend partially over the cable 15
and serve to hold both the cables 14 and 15 secure and properly
spaced from the ground. The distance that the projections 31, 32,
33, and 34 extend over the cables 14 and 15 can most easily be seen
in FIG. 4. The arms 23, 24, 25, and 26 are advantageously made
relatively thin so that they are easily flexed when the cables are
installed therein. It has been found advantageous to have the slab
chair 16 integrally molded in one piece out of a plastic such as
polypropylene. However, numerous other materials can be used as
well as plastic, and likewise, the device can be built in separate
pieces and, for example, welded or glued together if so
desired.
FIG. 5 is a cross-section of the slab chair 16 more clearly
illustrating the tubular portion 18, which may be tapered as shown,
the base 17, and arms 23, 24, and 25. Base 17 has a central
aperture 20 which further facilitates the securing of the slab
chair 16 in the concrete structure by permitting the concrete to
flow thereinto. The other openings 21 in the tubular portion 18
serves a similar purpose, as stated previously.
Referring now to FIG. 6, there is shown an alternative embodiment
of a slab chair which is generally designated as 41 and has a
U-shaped cross-section. A base 42 supports the U-shaped structure
which consists of a central wall 43 and two opposite side walls 44
and 45. A vertical slot 49 is formed in the central wall 43 to
receive and support the lower cable 14. An elongated horizontal
slot 47 is formed in side wall 44 and a similar slot 48 is formed
in side wall 45 for receiving and supporting the upper cable 15.
The dimensions of the side walls 44 and 45 are such that the slots
47 and 48 are positioned substantially near the top of the side
walls so that the upper portions of the side walls are formed into
relatively thin tabs 50 and 60. These tabs 50 and 60 may be bent
downwardly as shown by the dotted lines around cable 15 to securely
grip the cable if desired. The lower cable 14 is supported by the
bottom of slot 49 and is prevented from inadvertently coming out of
the slot 49 by the upper cable 15 which lies on top of it. If
desired, the sharpened corners where the side walls 44 and 45 meet
the base 42 may be rounded off to prevent accidental piercing of
the moisture barrier 13. While the slab chair 41 preferably leads
itself to being made out of metal, it may, of course, be made out
of plastic or other materials if so desired. The tabs 50 and 60 may
then not be bendable, but they can be sufficiently resilient to
hold the cables securely within the slots.
Referring now to FIG. 7, there is shown another embodiment of a
slab chair generally designated as 51 which has either a square or
a rectangular cross-section. The slab chair 51 includes a base 52
and four vertical side walls 53, 54, 55, and 56. The opposing side
walls 54 and 56 each have deep slots 61 and 62 formed therein for
receiving the lower cable 14 and supporting it. The other side
walls 53 and 55 have shallower slots 63 and 64 formed therein for
receiving and supporting the upper cable 15. The slab chair 51 may
have holes formed in the lower portions of the side walls if
desired, to permit concrete to easily flow thereinto. However, in
view of the large open top area, this is not deemed necessary.
Referring to FIG. 8, there is shown still another embodiment of a
slab chair generally designated as 71, having a substantially
circular cross-section. The slab chair 71 includes a base 72 having
a cylindrical vertical portion 73 mounted thereto. Deep slots 76
and 77 are formed vertically in the cylindrical portion 73 to
receive the lower cable 14. Shallower slots 78 and 79 are formed
equidistantly from the slots 76 and 77 to receive the upper cable
15. The width of the slots 76, 77, 78, and 79 are desirably made
slightly smaller than the diamerter of the cables 14 and 15 so that
the cables are tightly gripped when inserted into the slots.
Openings 81 are provided near the bottom of the tubular portion 73
to permit concrete to enter through the sides as well as the top to
fill the void inside the slab chair 71 as previously described.
In use, after the moisture barrier 13 is put in place and the
reinforcing members 14 and 15 are laid out, a worker will take a
quantity of slab chairs such as 16 and go to each cable
intersection attaching the intersecting cables 14 and 15 to the
slab chair 16 by pressing each between the upstanding arms or into
the appropriate slots as previously described. The subject slab
chairs support the cables 14 and 15 the desired distance above the
ground and securely hold them in place while concrete is poured and
while the concrete sets. Slab chairs of different heights may, of
course, be used for different applications. The use of the subject
slab chairs eliminates the necessity of wiring the intersecting
cables together and saves both time and materials in the
fabrication of a concrete structure. The holes provided in the
lower portion of the slab chair 16 permits concrete to fill in the
voids and thus solidly hold the chair in the concrete
structure.
It is to be understood that the above described embodiments are
merely illustrative of an application of the principles of this
invention, and that numerous other arrangements and modifications
may be made within the spirit and scope of the invention.
* * * * *