U.S. patent application number 10/584231 was filed with the patent office on 2007-09-20 for cavity former.
This patent application is currently assigned to The Australian Steel Company (Operations) Pty Ltd. Invention is credited to James Francis O'Grady.
Application Number | 20070214740 10/584231 |
Document ID | / |
Family ID | 34705568 |
Filed Date | 2007-09-20 |
United States Patent
Application |
20070214740 |
Kind Code |
A1 |
O'Grady; James Francis |
September 20, 2007 |
Cavity Former
Abstract
A cavity former for forming one or more cavities in a concrete
slab, includes a hollow body (20) about which, during use of the
former, poured concrete flows and subsequently cures to form a
concrete slab in which the hollow body defines a cavity. The hollow
body (20) has a first wall (27), a depending skirt wall (22) about
the periphery of the first wall, and structure (24) defining,
within the periphery, at least one depending hollow pillar
formation (25) for in situ bracing the first wall to an underlying
surface on which the skirt wall also rests.
Inventors: |
O'Grady; James Francis;
(Victoria, AU) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
The Australian Steel Company
(Operations) Pty Ltd
650 Lorimer Street
Port Melbourne, Victoria
AU
3207
|
Family ID: |
34705568 |
Appl. No.: |
10/584231 |
Filed: |
December 22, 2004 |
PCT Filed: |
December 22, 2004 |
PCT NO: |
PCT/AU04/01806 |
371 Date: |
March 27, 2007 |
Current U.S.
Class: |
52/577 |
Current CPC
Class: |
E04B 5/21 20130101; E04B
5/326 20130101; E04B 5/36 20130101; E04B 5/48 20130101; E04C 5/20
20130101 |
Class at
Publication: |
052/577 |
International
Class: |
E04C 5/00 20060101
E04C005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2003 |
AU |
2003907151 |
Claims
1. A cavity former for forming one or more cavities in a concrete
slab, including: a hollow body about which, during use of the
former, poured concrete flows and subsequently cures to form a
concrete slab in which the hollow body defines a cavity; wherein
said hollow body has a first wall, a depending skirt wall about the
periphery of the first wall, and structure defining, within said
periphery, at least one depending hollow pillar formation for in
situ bracing said first wall to an underlying surface on which said
skirt wall also rests.
2. A cavity former according to claim 1, wherein said structure
comprises a plurality of valleys in said first wall that define
said at least one hollow pillar formation at their
intersection.
3. A cavity former according to claim 1, wherein said structure
comprises a hollow tubular structure which constitutes said pillar
formation.
4. A cavity former according to claim 2 wherein said hollow tubular
structure has its interior open at said first wall.
5. A cavity former according to claim 1, wherein said hollow body
is configured to allow nesting of said cavity former with a second
similar cavity former, and thereby to allow stacking of a
multiplicity of said cavity formers.
6. A cavity former according to claim 5 wherein said skirt wall and
said structure defining the hollow pillar formation are tapered to
nest with the like features of a similar cavity former.
7. A cavity former according to claim 1, wherein said hollow body
further has a pair of intersecting upstanding ribs formed
integrally on the outer surface of said first wall for supporting
reinforcing mesh above said hollow body.
8. A cavity former according to claim 7 wherein said ribs are a
pair of crossed ribs.
9. A cavity former according to claim 1, wherein said skirt wall
includes at least one outstanding tab for interlocking with a skirt
wall of a similar cavity former so as to inhibit relative movement
of individual cavity formers during pouring of the wet
concrete.
10. A cavity former according to claim 1, wherein said hollow body
is a rectangular pod open on a lowermost side.
11. A cavity former according to claim 1, wherein said cavity
former has a plurality of hollow bodies or pods spaced apart by
integrally formed channels that receive elongated
slab-reinforcement.
12. A cavity former for forming one or more cavities in a concrete
slab, including: a hollow body about which, during use of the
former, poured concrete flows and subsequently cures to form a
concrete slab in which the hollow body defines a cavity; wherein
said hollow body has a first wall, and a depending skirt wall about
the periphery of the first wall, and is configured to allow nesting
of said cavity former with a second similar cavity former, and
thereby to allow stacking of a multiplicity of said cavity
formers.
13. A cavity former according to claim 12 wherein said skirt wall
and said structure defining the hollow pillar formation are tapered
to nest with the like features of a similar cavity former.
14. A cavity former for forming one or more cavities in a concrete
slab, including: a hollow body about which, during use of the
former, poured concrete flows and subsequently cures to form a
concrete slab in which the hollow body defines a cavity; wherein
said hollow body has a first wall, a depending skirt wall about the
periphery of the first wall, and a pair of intersecting upstanding
ribs formed integrally on the outer surface of said first wall for
supporting reinforcing mesh above said hollow body.
15. A cavity former according to claim 14 wherein said ribs are a
pair of crossed ribs.
16. A cavity former for forming one or more cavities in a concrete
slab, including: a hollow body about which, during use of the
former, poured concrete flows and subsequently cures to form a
concrete slab in which the hollow body defines a cavity; wherein
said skirt wall includes at least one outstanding upturned tab for
interlocking with a skirt wall of a similar cavity former so as to
inhibit relative movement of individual cavity formers during
pouring of the wet concrete.
17. A cavity former according to claim 16 wherein said interlocking
is such that the plural interlocked cavity formers provide a
moisture barrier between the concrete and an underlying ground
surface.
18. A cavity former according to claim 12, wherein said hollow body
is a rectangular pod open on a lowermost side.
19. A cavity former according to claim 12, wherein said cavity
former has a plurality of hollow bodies or pods spaced apart by
integrally formed channels that receive elongated
slab-reinforcement.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to the formation of
concrete slabs and foundations, and more particularly to structures
for forming cavities or voids in a slab or foundation.
BACKGROUND OF THE INVENTION
[0002] It is known to use cavity or void formers as space filling
elements in the preparation of a concrete slab or foundation, for
reducing the volume of concrete required to form the slab or
foundation. Such foundations are commonly known as waffle slab
foundations. While the reduction of concrete content in a slab as a
result of having multiple cavities on its underside serves in turn
to reduce the cost of the slab, it also advantageously allows the
slab to be built on unstable soil as expanding soils will flow into
the formed cavities. Such cavities also facilitate the placement of
electrical and plumbing conduits through the slab.
[0003] As the cavity formers must be sufficiently strong to
support, firstly, the weight of workers when the formers are in
place prior to a pour and, secondly, the load of wet concrete when
it is poured, the cavity formers are traditionally prefabricated
remote from the building site in standard sizes and then delivered
to the building site ready to be set in place prior to pouring of
the concrete. Known cavity formers include reinforced multiple
web-cardboard or fibreboard boxes and so called pods of foamed
polymeric material, such as polystyrene.
[0004] Cardboard or fibreboard formers must have sufficient
structural integrity to support a wet slab for a prescribed period,
eg 3 hours, after a concrete pour, before they weaken through
moisture absorption. Polystyrene pods overcome this limitation, but
have the disadvantage that, when larger pods are cut into smaller
shapes for filling cavities of irregular or smaller shape, large
quantities of fine polystyrene particles are often generated. Such
polystyrene particles present an environmental problem because they
are easily scattered by a breeze. Furthermore, polystyrene pods do
not disintegrate to more completely form the cavity or void and
this presents a disposal and environmental problem when the slab is
partially or wholly demolished or reshaped. For these reasons, the
use of polystyrene as a cavity former is being restricted in some
locations.
[0005] Typically, slab formation preparations involve leveling the
ground on which the slab is to be formed, erecting shutters to
define the perimeter of the slab, locating reinforcement for edge
beams of the building to be constructed, laying down building film,
i.e. plastics sheets, onto the leveled ground, and then arranging
multiple cavity formers in a spaced array on the building film. Bar
chairs are then located at spaced intervals in the spaces between
the cavity formers, and then reinforcement bars are placed on the
bar chairs to form a lattice of reinforcement bar surrounding the
cavity formers. Bar chairs are also located on the tops of the
cavity formers to support reinforcement mesh that is laid in a
blanket covering. After these preparations, the wet concrete is
poured about the cavity formers, and cures to form the concrete
slab or foundation. A process along these lines is described, for
example, in Australian patent 584769 to Koukourou & Partners
Pty Ltd.
[0006] The process of laying plastic sheets, arranging the cavity
formers and bar chairs, and then accurately locating the bar and
mesh reinforcement on the bar chairs is time consuming and
inconvenient.
[0007] Australian petty patents 727681 and 727665 disclose cavity
former modules fabricated in recycled plastic. The modules have
multiple box elements joined in an integral structure that also
defines channels between the box elements. Reinforcing bars are
supported in the channels on spaced integral bracket elements that
each have an upper edge shaped to center the bar, while reinforcing
mesh rests on upstanding ribs formed integrally on the top surfaces
of the box elements. Applicant has found that, while cavity former
modules of this kind alleviate the environmental concerns of
polystyrene pods and address the labor costs of foundation
preparation, the modules require a volume of plastic that adversely
affects their economics relative to cardboard and polystyrene. They
are also bulky to transport.
[0008] Reference herein to any specific prior document is not to be
taken as an admission or suggestion that the contents of the
document constitute common general knowledge.
[0009] It is an object of this invention to provide an improved
cavity former which embodies a satisfactory compromise between
various cost, handling and environmental considerations.
SUMMARY OF THE INVENTION
[0010] In a first aspect, the invention provides a cavity former
for forming one or more cavities in a concrete slab, including:
[0011] a hollow body about which, during use of the former, poured
concrete flows and subsequently cures to form a concrete slab in
which the hollow body defines a cavity; [0012] wherein said hollow
body has a first wall, a depending skirt wall about the periphery
of the first wall, and structure defining, within said periphery,
at least one depending hollow pillar formation for in situ bracing
said first wall to an underlying surface on which said skirt wall
also rests.
[0013] In one embodiment, said structure comprises a plurality of
valleys in said first wall that define said at least one hollow
pillar formation at their intersection. In another embodiment, said
structure comprises a hollow tubular structure which constitutes
said pillar formation and preferably has its interior open at said
first wall.
[0014] In a second aspect, the invention provides a cavity former
for forming one or more cavities in a concrete slab, including:
[0015] a hollow body about which, during use of the former, poured
concrete flows and subsequently cures to form a concrete slab in
which the hollow body defines a cavity; [0016] wherein said hollow
body has a first wall, and a depending skirt wall about the
periphery of the first wall, and is configured to allow nesting of
said cavity former with a second similar cavity former, and thereby
to allow stacking of a multiplicity of said cavity formers.
[0017] Preferably, a cavity former according to the second aspect
of the invention is also in accordance with the first aspect, said
skirt wall and said structure defining the hollow pillar formation
being tapered to nest with the like features of a similar cavity
former.
[0018] The invention further provides, in a third aspect, a cavity
former for forming one or more cavities in a concrete slab,
including: [0019] a hollow body about which, during use of the
former, poured concrete flows and subsequently cures to form a
concrete slab in which the hollow body defines a cavity; [0020]
wherein said hollow body has a first wall, a depending skirt wall
about he periphery of the first wall, and a pair of intersecting
upstanding ribs formed integrally on the outer surface of said
first wall for supporting reinforcing mesh above said hollow
body.
[0021] The ribs are preferably a pair of crossed ribs.
[0022] In a further, fourth, aspect of the invention, there is
provided a cavity former for forming one or more cavities in a
concrete slab, including: [0023] a hollow body about which, during
use of the former, poured concrete flows and subsequently cures to
form a concrete slab in which the hollow body defines a cavity;
[0024] wherein said skirt wall includes at least one outstanding,
preferably upstanding, tab for interlocking with a skirt wall of a
similar cavity former and thereby to inhibit relative movement of
individual cavity formers during pouring of the wet concrete.
[0025] In the fourth aspect, such interlocking is preferably such
that the plural interlocked cavity formers provide a moisture
barrier between the concrete and an underlying ground surface.
[0026] The hollow body may be a rectangular pod open on a lowermost
side. In an embodiment, the cavity former has a plurality of hollow
bodies or pods spaced apart by integrally formed channels that
receive elongated slab-reinforcement. The supports are preferably
arranged and spaced so that if the mesh reinforcement is randomly
dropped onto an array of cavity formers, the mesh reinforcement
will rest on the supports above the bodies. Seats may be integrally
formed in the channels to link adjacent pods and to support the
elongated slab reinforcement located in the channel. Preferably,
the seats automatically center the elongated slab-reinforcement
longitudinally within the respective channel.
[0027] The support for the slab reinforcement is preferably shaped
(eg. parabolic) to enable automatic centering of the
slab-reinforcement within the channels.
[0028] Preferably, the supports for the mesh, in a cavity former
including a plurality of bodies, are arranged and spaced to cover a
corresponding location on each body. The supports may be located on
the corresponding separable compartment of each body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The invention will now be further described, by way of
example only, with reference to the accompanying drawings, in
which:
[0030] FIG. 1 is a perspective view of a pair of coupled four-pod
cavity formers, embodying several aspects of the invention and
partially laid out with reinforcement bar and mesh in preparation
for wet concrete to be poured to form a concrete waffle slab
foundation with cavities defined by the pods of the cavity
formers;
[0031] FIG. 2 is a cross-section of one of the cavity formers shown
in FIG. 1 along the line 2-2, shown in a nesting configuration with
a similar cavity former shown in dashed lines;
[0032] FIG. 3 is a view similar to FIG. 2 but showing one of the
cavity formers in full lines, and the other in dashed lines;
[0033] FIG. 4 is a plan view of one of the cavity formers; and
[0034] FIGS. 5 and 6 illustrate (with only two pods shown) an
alternative structure for providing a pod with a central hollow
pillar, FIG. 6 being a cross-section on the line 6-6 in FIG. 5.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0035] FIG. 1 shows a pair of four-pod cavity formers 10 arranged
with reinforcing products, such as reinforcement mesh 12 and
reinforcement bar 14, supported by the cavity formers 10, in
preparation for pouring of wet concrete to form a slab foundation.
Each cavity former 10 includes four hollow bodies, ie. pods, 20,
arranged in a rectangular configuration and separated by channels
in the form of orthogonal intersecting trenches 40. It will be
appreciated that the wet concrete is poured about the cavity
formers such that the cured concrete slab has cavities or voids
defined by the respective pods 20.
[0036] The pods 20 and trenches 40 are integrally formed to space
the pods 20 apart such that reinforcement bar 14 is receivable
within the trenches 40 to reinforce the formed concrete slab. The
integrally formed cavity formers 10 comprising pods 20 and trenches
40 are moulded in any appropriate plastics or other suitable
material. A suitable material is a recycled polypropylene, virgin
or recycled. Other possible alternates include polyethylene,
cross-linked polyethylene and PET. The material is preferably
selected to provide an effective moisture barrier, as well as the
necessary structural properties.
[0037] Each pod 20 includes a first, planar top wall 27 and a
depending skirt wall 22 about the periphery of wall 27. Wall 27 is
normally horizontal in situ and has a top surface 28 on which is
provided an integrally formed support, in the form of a pair of
hollow outstanding ribs 30, for supporting reinforcement mesh 12
placed on the cavity former 10. Reinforcement mesh 12 supported on
the ribs 30 is held in a spaced relationship above the pod 20. The
ribs 30 intersect to define a cruciform shape such that the
reinforcement mesh 12 is supported above the pod 20 for any given
orientation of the mesh 12 relative to the pod 20, whereby
reinforcement mesh randomly dropped onto an array of the cavity
formers will rest on the supports above the bodies of the cavity
formers, without any need for separate bar chairs on the pods.
[0038] Peripheral skirt walls 22 taper downwardly and outwardly
relative to top surface 28 such that multiple cavity formers 10 may
nest, when stacked, to provide a reduced volume to facilitate
transport to a construction site. Nesting is further aided by the
ridges 30 being hollow in order to receive the ridges 30' of an
underlying nesting cavity former 10' (FIG. 2).
[0039] Intersecting minor channels, in the form of valleys 24, are
formed in each pod to provide separate hollow compartments 26 and
to define, within peripheral skirt wall 22 and at the centre of the
pod, a tapered hollow depending pillar formation 25 for in situ
bracing wall 27 to an underlying surface on which the skirt wall 22
also rests. Pillar formation 25 comprises the four intersecting
corners of the side walls of valleys 24, bounding a cavity 31 open
at 33 in top wall 27. This structure provides the pods with greater
strength for supporting the weight of workers prior to the wet
concrete being poured, the mesh when laid and the weight of wet
concrete once poured.
[0040] The compartments 26 are selectively separable from pods 20
at valleys 24 to customize the shape of the cavity former 10 as
required. The valleys 24 extend the height of the walls 22 to
ensure that the ability of the compartments 26, remaining after one
or more compartments 26 have been removed, to form cavities in the
poured concrete is not compromised. While the valleys 24 are
arranged in a cruciform shape, it will be appreciated that the
valleys 24 may be arranged in other configurations to provide
differently shaped separable compartments 26.
[0041] FIGS. 5 and 6, in which like features are indicated by like
primed reference numerals, illustrate an alternative structure for
defining hollow pillar formation 25' in each pod 20', ie. a hollow
tapered tubular structure with its interior cavity 31' open at 33'
in wall 27'.
[0042] The underside or interior of each pod 20 may typically
include integral fins 39 (FIGS. 2 and 3), corrugations or other
formations for increasing the strength and rigidity of the pod.
[0043] It will be appreciated that the presence of pillar formation
25, 25', and the provision of strengthening fins 39 and the like,
allows wall thickness, and thereby material usage per pod, to be
kept as small as possible.
[0044] The support ribs 30 are arranged and spaced to be located at
a corresponding compartment 26 on each pod 20. In FIGS. 1 and 4,
the supports are shown on corresponding separable compartments 26
of each pod 20.
[0045] An alternative embodiment of cavity former 10 comprises a
single pod 20 and integrated crossed ribs 30 as described above
with or without the valleys 24. This embodiment has the same
advantages as described above, i.e. enabling the reinforcement mesh
to be supported on the pod 20 in any orientation relative to the
cavity former 10 and avoiding the necessity for separate bar chairs
to support the mesh.
[0046] The pods 20 are linked by seats for supporting reinforcement
bar 14. The seats are integrally formed in the trenches 40. In one
embodiment (not illustrated), the seats are provided by the floor
of the trench 40 having a shape, eg. parabolic, that automatically
aligns and centers the reinforcement bar 14 longitudinally within
the trench 40. In the preferred embodiment, as illustrated,
however, the seats are provided in the form of saddles 42
integrally formed in the trenches 40 to link opposed pods 20 (FIGS.
2 and 4). The top edge 43 of each saddle 42, is formed with a
parabolic shape to enable automatic centering of a reinforcement
bar dropped into the trenches 40.
[0047] The saddles 42 respectively located in the perpendicularly
arranged trenches 40 are vertically offset to ensure that
reinforcement bar 14 in one trench 40 does not interfere with
reinforcement bar 14' located in a perpendicular trench 40 at the
point where the trenches 40 intersect.
[0048] While the upper edges of saddles 42 may have a parabolic
profile, it will be appreciated that any other shape suitable for
automatically centering reinforcement bar 14 in a trench 40 may
alternatively be adopted. For example, the saddles may have a
v-shaped profile spanning substantially the whole width of the
trenches 40.
[0049] A pair of upwardly turned tabs 50 are located on two
adjacent sides of the cavity former 10 to interlock adjacently
arranged cavity formers in situ (FIG. 3). By interlocking adjacent
cavity formers 10 together, individual cavity formers 10 are
prevented from relatively shifting during the pouring of the wet
concrete. Accordingly, the cavity formers of an array of
interlocked cavity formers 10 maintain their original positioning
during the concrete pour.
[0050] Rounded depressions 52 are formed in the upper sides of one
or more of the pods 20 to provide hook points for attachments to
lift the cavity former 10 or a plurality of nesting cavity formers
10 when they are upturned. Typically, nesting cavity formers 10 are
turned upside down for transport as the ribs 30 on the lowermost
cavity former 10 provide a clearance between the upper surface 28
of the pods 20 and the ground. This clearance enables suitable
lifting means, such as a fork lift, to slide underneath the nesting
cavity formers 12 and pick them up.
[0051] Slab formation preparations, using the cavity formers 10,
involve first delivering a required number of the cavity formers
10, in a nested stack, to the construction site. At the
construction site, the ground on which the slab is to be formed is
leveled and prepared, shutters are erected to define the perimeter
of the slab, and reinforcement elements are positioned for edge
beams of the building to be constructed. One or two workers then
place individual cavity formers 10 in an array on the leveled
ground such that they are interlocked by the upturned tabs 50.
Customized shaping of some cavity formers 10 may be necessary at
the margins of the slab site. The interlocked cavity formers 10
should provide blanket coverage over the leveled ground such that,
during pouring and curing, the ground is not exposed to the wet
concrete: the cavity formers are thereby able to take the place of
traditional ground sheeting both in its short term role in
containing moisture within the concrete gel matrix during curing of
the concrete, and in its longer term role as a vapor barrier
between the ground and the finished slab during the life of the
slab.
[0052] Once positioned, the trenches 40 of adjacent cavity formers
10 will be in alignment, thereby enabling reinforcement bar 14 to
be dropped directly into the trenches for automatic centering on
saddles 42. Accordingly, separate spacers are not required to
achieve the correct spacing between adjacent pods 20 and, moreover,
the use and positioning of bar chairs in the trenches 40 is not
required. Substantial time is thereby saved in preparing for the
wet concrete to be poured.
[0053] Reinforcement mesh 12 is then located on the cavity formers
10 for support by the ribs 30. As the cruciform arrangement of the
ribs 30 enables the reinforcement mesh 12 to be located on the
cavity formers in any orientation relative thereto, more time is
saved because neither bar chairs nor specific mesh orientations are
required.
[0054] Typically the cavity formers 10 are square and having side
lengths in the range of 800-1600 millimetres, but preferably
1000-1200 millimetres. They may be formed with a height in the
range of 150-400 millimetres, but specifically may be fabricated
with 175, 225, 300 or 375 millimetre heights for different slab
depths. The cavity formers 10 are composed of a suitable plastics
material to support the weight of wet concrete bearing down on the
cavity former during curing, or the weight of a person standing on
the cavity former. For example, the cavity formers are formed to
support a 150 kilogram point load. For the concrete curing process,
the cavity formers 10 are able to support about 280 kilograms per
square metre.
* * * * *