Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHOD FOR
LIFTING TILT-UP WALL CONSTRUCTION
Cross-reference to ~elated Applica~ions
This applica~ion is a division of Application No.
613,973, filed September 28, 1989.
Backqround of the Invention
The field of this invention is apparatus and
methods for hoisting and positioning prefabricated
tilt-up concrete slabs. More specifically, the
invention relates to improvements in anchor
assem~lies, void formers and clutch assemblies of such
apparatus.
Prefabricated concrete walls or panels are common
components of building constructions. Such panels are
generally cast in a horizontal position where they are
allowed to set. The hoisting and positioning of the
finished panel presents problems in that the panels are
very heavy and difficult to handle without cracking or
breaking. Preliminary attempts to solve this problem
can be found in United States Patent No. 3,883,170, to
Fricker et al., disclosing the use of an anchor
imbedded in a concrete slab as a point of attachment
and lifting in combination with a hoisting shackle, and
in United States Patent Nos. 4,367,892 and 4,437,642,
to Holt, disclosing the use of a t-shaped anchor also
for use with a hoisting shackle.
SummarY of the Invention -
The present invention provides many advantages
over the previous hoisting systems described above.
First, it employs an anchor in the form of a lifting
clevis and which is supported by anchor bases. Such
anchors have greater strength in that they are less
prone to bend or shear during the lifting process and
are also less expensive to manufacture since less
costly materials and production processes may be
employed. Such anchors are also advantageous in that
they provide two points of attachment for anchor
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supports, as well as additional stee~ reinforcement in
the panel, thereby permitting stress to be ~istributed
more broadly in the panel.
The invention also provides a void former which is
asymmetric in configuration for producing a uniquely
shaped recess that allows access to the clevis of the
anchor in but one way. The void former comprises a
body and plug configured to ensure that the clevis is
fully and completely exposed once the slab is set.
The clutch assembly is proportioned for
complimentable and snug receipt within the recess
produced by the void former, and is provided with
hoisting means. The clutch assembly engages the anchor
by means of a linear engaging pin. Once coupled, the
clutch assembly is capable of little if any movement
about the clevis. Such a configuration minimizes the
chances that the anchor or panel will become damaged
during hoisting. Furthermore, the clutch assembly of
the present invention provides an easy, reliable and
safe means for engaging the anchor when the slab is
horizontal and for disengaging when the slab is
vertically placed, particularly where the anchors
become located high up on the slab after placement.
A principal object of this invention is to provide
an improved anchor which has a better shock-load
resistance and is less likely to fail when stressed,
which gives extra embedment strength and which is
easier and less costly to fabricate.
Another object of this invention is to provide an
improved void former for use with the improved anchor.
A further object of this invention is to provide
an improved clutch which mates more securely with an
anchor imbedded in a concrete slab, which is easier to
engage with and places less stress on an anchor, and
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which provides a more reliable, less stressful range of
motion relative to the concrete panel.
Brief Description of the Drawings
FIG. 1 is an exploded view in perspective showing
the anchor assembly and void former of the invention.
FIG. 2 is a view in perspective showing the
clutch assembly of the invention
FIG. 3 is a view in perspective showing the
clutch assembly engaged with the anchor embedded in a
concrete panel.
FIG. 4 is a cross-sectional elevational view
showing the anchor assembly and void former in place
within a concrete panel.
FIG. 5 is a top plan view of the void former in
open condition.
FIG. 6 is a view in cross-section of the void
former in closed condition, taken on the plane
designated by line 6 - 6 in FIG. 5, coupled to the
anchor.
FIG. 7 is a view in cross-section of the clutch,
taken on the plane designated by line 7 - 7 in FIG. 2.
FIG. 8 is a view in cross-section of the clutch,
taken on the plane designated by line 8 - 8 in FIG. 7.
DESCRIPTION OF TH~ PREFERRED EMBODIMENT
With reference to the drawings, a tilt-up concrete
slab 1 which is generally cast at the job site in
horizontal, ground supported form, not shown, is cast
around an anchor assembly 10 and a void former 30.
The anchor assembly 10 comprises a wire anchor 12
and two anchor supports 14. The wire anchor 12 is
formed from a quandrangularly configured wire segment
(not shown) by bending the segment substantially in
half to form two legs 16 joined at an apex or clevis
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18. The legs 16 diverge from the clevis 18 at an angle
of 34-36. Each leg 16 of the wire anchor 12 is
further bent to form a distal tip 20. The distal tips
20 diverge out of a plane defined by the clevis 18 and
legs 16 at an angle of 88-92. The material of the
wire anchor is metallic, preferably steel.
The wire anchor 12 is supported and positioned
within the concrete slab 1 by anchor supports 14.
Each anchor support 14 comprises a platform 22
supported by foot elements 24. The upper surface of
the platform is provided with an apertured box 26
complemental in shape to and capable of snug receipt
over a distal tip 20 of the wire anchor 12. The
anchor support 14 can be made of any durable material,
such as polymer plastic.
The void former 30, shown in Figs. 1, 4, 5 and 6,
is comprised of a body 32, a plug 34 and a lid 36.
The body 32 is asymmetrically configured and is
defined exteriorly by a flat side wall 38, a partially
flat, partially curved side wall 40, a flattened end
wall 42, a curved end wall 44, and a transversely
curved underside wall 46.
The body 32 is provided on its underside with a
socket 48 for complimentable receipt of the clevis 18
of the wire anchor 12 and the plug 34. The socket 48
is defined by an interior sloping wall 50, interior
side walls S2, an interior receiving wall 54, and
interior coupling walls 56. The interior receiving
wall S4 is provided with pegs or dowels 58 for mating
with and holding the plug 34 in place.
The plug 34 is configured for snug receipt within
the socket 48 in which the clevis 18 of the wire
anchor 12 is already in place and is provided with peg
sockets 60 for receipt of the pegs 58 of the interior
receiving wall 54 of t~e socket 48. The plug 34 is
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dimensioned so that when the plug 34 is in place
within the body 32 of the void former 30, the exterior
surface of the plug 34 is flush with the exterior
surface of the body 32.
The lid 36 comprises peripherally distributed,
downwardly projected camming lugs 62 and a plurality of
upwardly projecting locator rods 64. The camming lugs
62 are adapted to snap into and interengage with an
equal number of lug sockets 66 which are peripherally
distributed along the upper edge of the body 32.
Emplacement of the wire anchor 12 within the
concrete slab 1 takes place as follows. The wire
anchor 12 is connected to the anchor supports 14 by
sliding each of the distal tips 20 of the wire anchor
12 into the apertured box 26 of the anchor support 14.
The void former 30 is then assembled about the clevis
18 of the wire anchor 12. First, the body 32 of the
void former 30 is placed over the clevis 18 such that
the clevis 18 is snugly received with the socket 48.
The plug 34 is then inserted beneath the body 32/wire
anchor 12 combination and snapped securely in place by
engaging the peg sockets 60 with pegs 58, thereby
enclosing the clevis 12 of the wire anchor. The lid 36
is snapped into position on the top of the body 32 by
lockingly engaging the camming lugs 62 with the lug
sockets 66. The combination of anchor assembly 10 and
void former 30 is then positioned as desired on the
wall form. The slab is then poured and cured.
In Fig. 4, the protruding rods 64 show the
location of the wire anchor 12 with the slab 1. The
thin layer of cement above the void former is then
chipped away and the lid 36 popped off. The body 32 of
the void former 30 can then be pulled out by gripping
and pulling on internal ribs 57 with pliers. ~emoval
of the ~ody 32 creates a recess 2 to the rear of the
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plug 34. The plug 34 is then gripped by pliers, pulled
from under the wire anchor 12 into the recess 2 and
then removed.
The clutch assem~ly 70 comprises a housing 72; a
housing cover 74 which is attached to the housing 72 by
screw 76; a linear engaging pin 78 slidably mounted
within a passage 79 in the housing; and a lever 80
which is comprised of an arm member 82, a shaft member
84 and a handle member 86. The lever 80 is pivotally
engaged with pin 78 by means of a stud 88 which is
carried by the engaging pin 78 and extends through a
slot 90 in the arm member of the lever 80.
The housing 72 of the clutch assembly 70 is
configured for complimentable receipt with the recess 2
left by the void former 30 and further comprises an
engagement socket 92 for receipt over the clevis 18 of
the wire anchor 12. ~igs. 7 and 8 illustrate the
engagement pin 78 in retracted relation relative to the
engagement socket.
The clutch assembly 70 is also provided with
hoisting means as shown in FIGS. 2, 3 and 8. The
hoisting means comprises: a bail 100; an external
collar 102 fastened to the bail 100 by dowel pins 104;
an internal collar (not shown) on the housing 72
rotatably received in the external collar 102, and a
bolt 106 and plate washer 108 which fasten the
external collar to the housing 72 for rotation about
the internal collar.
Coupling with and hoisting of the concrete slab by
the clutch assembly 70 takes place as follows. The
housing 72 of the clutch assembly 70 is guided into the
recess ~eft by t~he void former 30 and over the clevis
18 of the imbedded wire anchor 12 with the engaging
pin 78 in the retracted position. Once the housing 72
is snugly in place, the clevis 18 is engaged by moving
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the lever 80 to slide the engaging pin 78 in place.
Having securely coupled the clutch assembly 70 to the
concrete slab 1, a hoisting cable or rope (not shown)
can be attached to the bail 100 with lifting force then
applied to position the c~ncrete slab in a desired
position. Since the ho~sing 72 is complimentably
nested within the recess left by the void former 30,
shearing force on the wire anchor 12 is reduced as is
the threat of damage to the slab 1 resulting frDm
uncontrolled movement of the clutch assembly 70 in
relation to the wire anchor 12. Once the slab 1 is in
place, the lever 80 is returned to its original
position, thereby sliding the engaging pin 78 into its
retracted position and releasing t~e clutch assembly 70
from the wire anchor 12 and the slab 1.
From the above description, it is apparent that a
novel and advantageous apparatus and method for
tilting up concrete slabs or panels is describPd.
Although the disclosure above is illustrative ~f
certain exemplary embodiments of the present invention,
one skilled in the art will understand that other
embodiments are possible which fall within the spirit
or the essential characteristics of the invention, the
scope of which is set forth in the following claims.
