U.S. patent application number 10/703645 was filed with the patent office on 2005-05-12 for releasable coupling device for use with reinforcing tendons and method of using the same.
Invention is credited to Giesel, Ronald D., Lampe, Bryan J..
Application Number | 20050097843 10/703645 |
Document ID | / |
Family ID | 34551933 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050097843 |
Kind Code |
A1 |
Giesel, Ronald D. ; et
al. |
May 12, 2005 |
Releasable coupling device for use with reinforcing tendons and
method of using the same
Abstract
A coupling device for attaching a protruding tendon disposed in
a concrete structure to an extension strand comprises a barrel
having a first end and a second end, a first conical bore disposed
adjacent the first end having a first pair of wedges and sized to
receive and grip the protruding tendon, a second conical bore
disposed adjacent the second end and having a second pair of wedges
and sized to receive and grip the extension strand, and a release
bushing adapted for placement adjacent the first end of the barrel
and having an aperture sized to receive the protruding tendon. The
release bushing includes a contact surface positioned to contact
the first pair of wedges and arranged to shift the first pair of
wedges to a disengaged position in response to shifting the first
end of the barrel toward the release bushing.
Inventors: |
Giesel, Ronald D.; (Rowland
Heights, CA) ; Lampe, Bryan J.; (Irvine, CA) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP
6300 SEARS TOWER
233 S. WACKER DRIVE
CHICAGO
IL
60606
US
|
Family ID: |
34551933 |
Appl. No.: |
10/703645 |
Filed: |
November 7, 2003 |
Current U.S.
Class: |
52/223.1 |
Current CPC
Class: |
E04C 5/122 20130101;
E04C 5/08 20130101; E04C 5/165 20130101 |
Class at
Publication: |
052/223.1 |
International
Class: |
E04C 005/08 |
Claims
What is claimed:
1. A coupling device for attaching a protruding tendon disposed in
a concrete structure to an extension strand, the coupling device
comprising: a barrel having a first end and a second end; a first
conical bore disposed adjacent the first end having a first pair of
wedges, the first conical bore sized to receive the protruding
tendon such that the protruding tendon is grippable by the first
pair of wedges when the first pair of edges are shifted to an
engaged position; a second conical bore disposed adjacent the
second end and having a second pair of wedges, the second conical
bore sized to receive the extension strand such that the extension
strand is grippable by the second pair of wedges when the second
pair of wedges are shifted to an engaged position; and a release
bushing, the release bushing adapted for placement adjacent the
first end of the barrel and having an aperture sized to receive the
protruding tendon, the release bushing including a contact surface
positioned to contact the first pair of wedges, the contact surface
of the release bushing arranged to shift the first pair of wedges
to a disengaged position in response to shifting the first end of
the barrel toward the release bushing.
2. The coupling device of claim 1, wherein the barrel is separable
into a first part and a second part, and wherein the second part
includes an internal spring positioned to bias the second pair of
wedges in an outward direction.
3. The coupling device of claim 2, wherein each of the first part
and the second part includes a threaded internal bore, and
including a threaded barrel for joining the first part to the
second part.
4. The coupling device of claim 3, wherein the internal spring
engages the threaded barrel and the second pair of wedges.
5. The coupling device of claim 1, wherein the second pair of
wedges are spring biased in an outward direction, and further
wherein the second pair of wedges are arranged to shift in an
inward direction in response to insertion of the extension strand
in the second conical bore.
6. The coupling device of claim 1, wherein the first conical bore
and the first pair of wedges are sized to expose a tip of the first
pair of wedges.
7. The coupling device of claim 1, wherein the first conical bore
and the first pair of wedges are sized to permit a tip of the first
pair of wedges to extend out of the first conical bore when the
first pair of wedges are in an engaged position.
8. The coupling device of claim 7, wherein the release bushing
includes an outer sidewall surrounding the contact surface, the
contact surface depressed relative to the outer sidewall.
9. The coupling device of claim 8, wherein the outer sidewall
includes an edge sized to engage a corresponding edge on the first
end of the barrel when the release bushing is brought into contact
with the barrel.
10. A coupling device for operatively connecting a protruding
tendon disposed in a concrete structure to an extension strand, the
coupling device comprising: a main body having a first end and a
second end; a first bore disposed adjacent the first end and
arranged to receive the protruding tendon; a first pair of wedges
disposed within the main body adjacent the first end, the first
pair of wedges shiftable between a disengaged position in which the
protruding tendon is moveable within the first bore and an engaged
position in which the protruding tendon is secured within the first
bore; a second bore disposed adjacent the second end and arranged
to receive the extension strand; a second pair of wedges disposed
within the main body adjacent the second end, the second pair of
wedges shiftable between a disengaged position in which the
extension strand is moveable within the second bore and an engaged
position in which the extension strand is secured within the second
bore; and a release bushing, the release bushing adapted for
placement adjacent the first end of the main body and having an
aperture sized to receive the protruding tendon, the release
bushing positioned to contact the first pair of wedges, the release
bushing arranged to shift the first pair of wedges to the
disengaged position in response to shifting the main body toward
the release bushing.
11. The coupling device of claim 10, wherein the first bore is
aligned with the second bore.
12. The coupling device of claim 10, wherein the second pair of
wedges are biased toward the engaged position, the second pair of
wedges arranged to shift toward the disengaged position in response
to inserting the extension strand into the second bore.
13. The coupling device of claim 12, wherein the main body is
separable into a first part and a second part, and wherein the
second part including the second bore, the second part further
including an internal spring positioned to bias the second pair of
wedges toward the engaged position, the spring bearing against a
plug threaded into the first bore and the second bore.
14. The coupling device of claim 10, wherein the first pair of
wedges include a tip, the first bore and the first pair of wedges
sized to expose the tip when the first pair of wedges are in the
engaged position.
15. The coupling device of claim 10, wherein the first bore and the
first pair of wedges are sized to position the first pair of wedges
for contact with the release bushing when the first pair of wedges
are in the engaged position.
16. The coupling device of claim 15, wherein the first bore is
conical, the first pair of wedges sized to protrude from the first
bore when the first pair of wedges are in the engaged position, and
wherein the release bushing includes an outer sidewall surrounding
a depressed contact surface.
17. The coupling device of claim 16, wherein the outer sidewall
defines a contact surface positioned to engage a first end of the
body when the release bushing is brought into contact with the
body.
18. A coupling device for operatively connecting a protruding
tendon disposed in a concrete structure to an extension strand, the
coupling device comprising: a main body having a first end and a
second end; first and second oppositely facing conical bores, the
first bore arranged to receive the protruding tendon; a first pair
of wedges disposed within the first bore and shiftable between a
disengaged position in which the protruding tendon is axially
moveable within the first bore and an engaged position in which the
protruding tendon is secured within the first bore; a second pair
of wedges disposed within the second bore and shiftable between a
disengaged position in which the second pair of wedges are
positioned to permit an extension strand to move axially within the
second bore and an engaged position in which the second pair of
wedges are positioned to grip an extension strand disposed within
the second bore; and a release bushing, the release bushing adapted
for placement adjacent the first bore and having an aperture sized
to receive the protruding tendon, the release bushing including a
first surface positioned to contact the first pair of wedges when
the release bushing and the main body are brought toward each other
to thereby shift the first pair of wedges to the disengaged
position.
19. The coupling device of claim 18, wherein the first bore is
axially aligned with the second bore, and including a spring
disposed adjacent the second pair of wedges and arranged to bias
the second pair of wedges toward the engaged position, the spring
arranged to permit the second pair of wedges to shift toward the
disengaged position in response to insertion of the extension
strand into the second bore.
20. The coupling device of claim 19, wherein the main body includes
a first part and a second part joined by a threaded plug, the
spring positioned to bear against the threaded plug.
21. The coupling device of claim 20, wherein the first pair of
wedges include a tip sized to protrude from the first bore when the
first pair of wedges are in the engaged position, and wherein the
first surface of the release bushing is defined by a depressed
central portion surrounding the aperture.
22. The coupling device of claim 21, wherein the release bushing
includes an outer sidewall surrounding the depressed central
portion.
23. A method of releasing the tension on a tendon protruding from a
concrete structure comprising the steps of: providing a chair sized
to fit over a wedge plate; positioning the chair over the wedge
plate; providing a coupling device having first and second pairs of
oppositely facing wedges; providing a release bushing over the
protruding tendon and positioned to engage the first pair of
wedges; securing the first pair of wedges to the protruding tendon;
positioned an extension strand in the second pair of wedges; using
a tensioning ram to grasp the extension strand and to apply a
greater tension to the tendon to thereby displace the tendon away
from a first position in a first direction; removing an original
pair of wedges from adjacent the displaced tendon; using the
tensioning ram to displace the tendon in a second direction
opposite the first direction to a second position; and displacing
the tendon in the second direction a distance sufficient to cause
the release bushing to shift the first pair of wedges out of
engagement with the protruding tendon.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to reinforced
concrete structures having reinforcing strands or tendons and, more
specifically, to a coupling device for grasping a tendon protruding
from a concrete structure.
BACKGROUND OF THE INVENTION
[0002] In many reinforced concrete structures one or more of the
reinforcing strands or tendons may protrude from the structure.
Typically, the protruding tendon is maintained at a desired tension
by a pair of conical wedges that engage a conical bore in a wedge
plate that bears against the concrete structure. For a variety of
reasons, it may become necessary at some point to lessen the
tension on the reinforcing tendon or to release the tendon
entirely.
[0003] Unfortunately, in many applications, only a short piece of
the tendon protrudes past the wedge plate. In such circumstances,
there may not be enough of the tendon protruding beyond the wedge
plate to permit the tendon to be suitably grasped by a tensioning
ram. One approach for releasing the tension on such tendons is to
cut away the original retaining wedges and/or a portion of the
tendon, which permits the tension on the tendon to be released
entirely. However, in some situations the tendon may be surrounded
by grease, which may present a fire hazard when using a cutting
torch. In still other situations, the use of cutting torches or
other flames may not be advisable in any event due to other
environmental concerns. Therefore, some provision for providing a
coupling device for grasping and releasing the protruding strand
and/or for permitting attachment to an extension strand may be
desirable.
SUMMARY OF THE INVENTION
[0004] In one aspect of the invention, a coupling device for
attaching a protruding tendon disposed in a concrete structure to
an extension strand comprises a barrel having a first end and a
second end, a first conical bore disposed adjacent the first end
having a first pair of wedges, the first conical bore sized to
receive the protruding tendon such that the protruding tendon is
grippable by the first pair of wedges when the first pair of edges
are shifted to an engaged position, a second conical bore disposed
adjacent the second end and having a second pair of wedges, the
second conical bore sized to receive the extension strand such that
the extension strand is grippable by the second pair of wedges when
the second pair of wedges are shifted to an engaged position, and a
release bushing adapted for placement adjacent the first end of the
barrel and having an aperture sized to receive the protruding
tendon. The release bushing includes a contact surface positioned
to contact the first pair of wedges and arranged to shift the first
pair of wedges to a disengaged position in response to shifting the
first end of the barrel toward the release bushing.
[0005] In further accordance with the disclosed example, the barrel
may be separable into a first part and a second part, and the
second part may include an internal spring positioned to bias the
second pair of wedges in an outward direction. Each of the first
part and the second parts may include a threaded internal bore, and
a threaded barrel or plug may be used to join the first part to the
second part. The internal spring may engage the threaded plug and
the second pair of wedges. Preferably, the second pair of wedges
are biased in an outward direction and are arranged to shift in an
inward direction in response to insertion of the extension strand
in the second conical bore.
[0006] The first conical bore and the first pair of wedges
preferably are sized to expose a tip of the first pair of wedges.
The first conical bore and the first pair of wedges may be sized to
permit a tip of the first pair of wedges to extend out of the first
conical bore when the first pair of wedges are in an engaged
position. The release bushing may include an outer sidewall
surrounding the contact surface, and the contact surface may be
depressed relative to the outer sidewall. The outer sidewall
includes an edge sized to engage a corresponding edge on the first
end of the barrel when the release bushing is brought into contact
with the barrel.
[0007] In accordance with another aspect of the invention, a
coupling device for operatively connecting a protruding tendon
disposed in a concrete structure to an extension strand includes a
main body having a first end and a second end, a first bore
disposed adjacent the first end and arranged to receive the
protruding tendon, a first pair of wedges disposed within the main
body adjacent the first end and shiftable between a disengaged
position in which the protruding tendon is moveable within the
first bore and an engaged position in which the protruding tendon
is secured within the first bore, a second bore disposed adjacent
the second end and arranged to receive the extension strand, a
second pair of wedges disposed within the main body adjacent the
second end and shiftable between a disengaged position in which the
extension strand is moveable within the second bore and an engaged
position in which the extension strand is secured within the second
bore, and a release bushing. The release bushing may be adapted for
placement adjacent the first end of the main body and preferably
includes an aperture sized to receive the protruding tendon. The
release bushing is positioned to contact the first pair of wedges
and is arranged to shift the first pair of wedges to the disengaged
position in response to shifting the main body toward the release
bushing.
[0008] In accordance with a further aspect of the invention, a
coupling device for operatively connecting a protruding tendon
disposed in a concrete structure to an extension strand comprises a
main body having a first end and a second end, first and second
oppositely facing conical bores, the first bore arranged to receive
the protruding tendon, a first pair of wedges disposed within the
first bore and shiftable between a disengaged position in which the
protruding tendon is axially moveable within the first bore and an
engaged position in which the protruding tendon is secured within
the first bore, a second pair of wedges disposed within the second
bore and shiftable between a disengaged position in which the
second pair of wedges are positioned to permit an extension strand
to move axially within the second bore and an engaged position in
which the second pair of wedges are positioned to grip an extension
strand disposed within the second bore, and a release bushing. The
release bushing is adapted for placement adjacent the first bore
and includes an aperture sized to receive the protruding tendon,
with the release bushing further including a first surface
positioned to contact the first pair of wedges when the release
bushing and the main body are brought toward each other to thereby
shift the first pair of wedges to the disengaged position.
[0009] In a still further aspect of the invention, a method of
changing the tension on a tendon protruding from a concrete
structure comprises the steps of providing a chair sized to fit
over a wedge plate, positioning the chair over the wedge plate,
providing a coupling device having first and second pairs of
oppositely facing wedges, securing the first pair of wedges to the
protruding tendon, positioned an extension strand in the second
pair of wedges, using a tensioning ram to grasp the extension
strand and to apply a greater tension to the tendon to thereby
displace the tendon away from a first position in a first
direction, removing an original pair of wedges from adjacent the
displaced tendon, and using the tensioning ram to displace the
tendon in a second direction opposite the first direction to a
second position.
[0010] In further accordance with a preferred form of the
invention, the method may include the step of inserting a new pair
of wedges adjacent the tendon when the tendon is adjacent the
second position to maintain the tendon in the second position. The
method also may include the step of placing a release bushing over
the tendon prior to securing the first pair of wedges to the
tendon, and may further include the step of displacing the tendon
in the second direction until the release bushing forces the first
pair of wedges to a disengaged position in which the tendon is
released from the first pair of wedges.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective of a coupling device assembled in
accordance with the teachings of the present invention;
[0012] FIG. 2 is an exploded view in perspective of the coupling
device illustrated in FIG. 1;
[0013] FIG. 3 is a cross-sectional view of the coupling device and
illustrating a reinforcing tendon and an extension strand both
gripped by the coupling device;
[0014] FIG. 4 is a cross-sectional view similar to FIG. 3 and
illustrating the reinforcing tendon in a de-stressed state having
been released by the coupling device;
[0015] FIG. 5 is a fragmentary cross-sectional view illustrating an
alternate embodiment of the coupling device and showing the
reinforcing tendon and the extension strand both gripped by the
coupling device;
[0016] FIG. 6 is a cross-sectional view similar to FIG. 5 and
illustrating the reinforcing tendon in a de-stressed state having
been released by the coupling device;
[0017] FIG. 7 is a fragmentary cross-sectional view of a concrete
reinforced structure having a tendon protruding from a wedge plate
and showing a de-tensioning chair in place over the wedge
plate;
[0018] FIG. 8 is a fragmentary cross sectional view similar to FIG.
7 and illustrating one end of the coupling device attached to the
protruding portion of the tendon and illustrating an extension
strand protruding from another end of the coupling device;
[0019] FIG. 9 is a cross-sectional view similar to FIG. 8 and
showing the tendon displace to the right of the Figure by the
tensioning ram thereby permitting the original wedges to be removed
from the wedge plate;
[0020] FIG. 10 is a cross-sectional view similar to FIG. 9 and
illustrating the existing strand being displaced to the left of the
Figure by the tensioning ram; and
[0021] FIG. 11 is a cross-sectional view similar to FIG. 10 and
illustrating the release bushing in contact with the wedge plate
and shifting the internal wedges to a release position thereby
releasing all tension on the tendon.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The examples described herein are not intended to be
exhaustive or to limit the scope of the invention to the precise
form or forms disclosed. Rather, the following exemplary
embodiments have been chosen and described in order to best explain
the principles of the invention and to enable others skilled in the
art to follow the teachings thereof.
[0023] Referring now to FIGS. 1-4 of the drawings, a coupling
device assembled in accordance with the teachings of a first
disclosed example of the present invention is shown and is
generally referred to the reference numeral 20. As shown in FIGS. 7
through 11, the coupling device 20 is generally intended for use
with a tendon 22 that protrudes from a concrete structure 24. As is
generally known, the tendon 22 includes an original pair of wedges
26a and 26b, which are disposed in a generally conical bore 28 of a
wedge plate 30. The tendon 22 includes an end 22a. Also, it will be
appreciated that the concrete structure 24 may include a number of
protruding tendons 22.
[0024] The coupling device 20 includes a barrel 32 having a first
end 34 and a second end 36. A first conical bore 38 is formed in
the barrel 32 generally adjacent to the first end 34, and a second
conical bore 40 is formed in the barrel 32 generally adjacent to
the second end 36. As will be discussed in greater detail below,
the first conical bore 38 is size to receive at least a portion of
the protruding tendon 22. A first pair of wedges 42 are disposed in
the first conical bore 38, with the first pair of wedges 42 being
arranged to grip the tendon 22 when the tendon 22 is disposed
within the first conical bore 38. A second pair of wedges 44 are
disposed within the second conical bore 40, with the second pair of
wedges 44 being arranged to grip an extension strand 46 as will be
explained in greater detail below. The construction of the first
and second pairs of wedges 42 and 44 may be conventional and would
be known to those of ordinary skill in the art.
[0025] As shown in FIGS. 1 and 4, a release bushing 48 may be
provided. The release bushing 48 preferably includes an aperture 50
which is sized to fit over the tendon 22. In the disclosed example,
the aperture 50 comprises a generally round hole through the
release bushing 48. Alternatively, the aperture 50 may comprise a
slot in the release bushing 48. The release bushing 48 includes a
first end 52 which is generally sized and positioned to make
contact with a surface, such as a surface 52 on the wedge plate 30.
The release bushing 48 also includes a second end 56. The release
bushing 48 also includes a contact surface 58. In the disclosed
example, the contact surface 58 is defined by a depressed center 60
formed in the release bushing 48. The depressed center 60 may
generally surround the aperture 50. Alternatively, and as discussed
in greater detail below and as is shown in FIGS. 5 and 6, the
contact surface 58 may be formed by the second end 56. In the
disclosed example of FIGS. 1 through 4, the release bushing 48
includes a raised sidewall or skirt 62, with the skirt 62 generally
surrounding the aperture 50. The skirt 62 includes an edge 64.
[0026] As shown in FIG. 2, the coupling device 20 may be separable
into a first half 66 and a second half 68. Referring to FIGS. 2-4,
the first-half 66 may be positioned generally toward the concrete
structure 24, while the second-half 68 may be positioned generally
away from the concrete structure 24. Also, it will be appreciated
that the first conical bore 38 is formed in the first half 66,
while the second conical bore 40 is formed in the second half 68.
The first half 66 preferably includes a threaded portion 70, while
the second half 68 preferably includes a threaded portion 72. A
threaded barrel or plug 74 may be provided in order to permit the
first half 66 to be joined to the second half 68.
[0027] It will be appreciated that, in the disclosed example, the
first conical bore 38 and the second conical bore 40 are axially
aligned with each other. Also, the first threaded portion 70 and
the second threaded portion 72 of the first and second halves 66
and 68, respectively, are generally axially aligned with each
other. A spring 76 may be provided, with the spring 76 bearing
against the plug 74 and the second pair of wedges 44. Accordingly,
the second pair of wedges 44 will be biased outwardly and away from
the structure 24 when viewing FIGS. 3 & 4. As an alternative,
the first half 66 and the second half to 68 may be joined together
using any other suitable method of connection. As a still further
alternative, the first half 66 and the second half 68 may be
integrally formed into a single main body. Also, the spring 76 may
bear against some other ledge or abutment (not shown) as may
suitably be provided by those of skill in the art.
[0028] The first pair of wedges 42 are shiftable between a
retracted or disengaged position and an extended or engaged
position. When the first pair of wedges 42 are disposed in the
disengaged position, it will be appreciated that the wedges 42 have
generally been shifted into or toward a widened portion 38a of the
first conical bore 38. On the other hand, when the first pair of
wedges 42 are disposed in the engaged position, it will be
appreciated that the first pair of wedges 42 have generally been
shifted into or toward a narrowed portion 38b of the first conical
bore 38.
[0029] Similarly, when the second pair of wedges 44 are disposed in
the disengaged position, it will be appreciated that the second
pair of wedges 44 have generally been shifted into or toward a
widened portion 40a of the second conical bore 40. On the other
hand, when the second pair of wedges 44 are disposed in the engaged
position, it will be appreciated that the second pair of wedges 44
have generally been shifted into or toward a narrowed portion 40b
of the second conical bore 40.
[0030] As would be known to those of skill in the art, when either
the first pair of wedges 42 or the second pair of wedges 44 are
disposed toward their respective engaged positions, the wedges will
grasp or otherwise secure a cable, tendon, or strand disposed in
the appropriate conical bore. Accordingly, it will be appreciated
that, when the tendon 22 is disposed in the first conical bore 38
and the first pair of wedges and 42 are in the disengaged position
disposed toward the widened the portion 38b , that the tendon and
22 may be shifted axially within the first conical bore 38.
However, when tension is applied to the tendon 22 (i.e., either the
tendon 22 is pulled in one direction or the coupling device 20 is
pulled in the opposite direction), the tendon 22 will, due to
frictional forces, be gripped by the first pair of wedges 42 as the
first pair of wedges 42 are shifted toward the narrowed portion 38b
of the bore 38. Thus, the first pair of wedges 42 will apply a
progressively greater gripping force to the tendon 22.
[0031] Similarly, when the extension strand 46 is disposed in the
second conical bore 40 and the second pair of wedges 44 are in the
disengaged position disposed toward the widened portion 40a, the
extension strand 46 may be shifted axially within the second
conical bore 40. However, when tension is applied to the extension
strand 46, the extension strand 46 will, due to the frictional
forces, be gripped by the second pair of wedges 44 as the second
pair of wedges 44 are shifted toward the narrowed portion 40b of
the second conical bore 40. Thus, the second pair of wedges 44 will
apply a progressively greater gripping force to the extension
strand 46.
[0032] Referring now to FIG. 3, it will be appreciated that the
extension strand 46 may be inserted into the coupling device 20
when the coupling device 20 is fully assembled with the first and
second halves 66 and 68 joined together by the plug 74. The second
pair of wedges 44 are, by virtue of the spring 76, normally
disposed in the engaged position in which the second pair of wedges
44 are biased outwardly and toward the right of the Figure toward
the engaged position under the force of the spring 76. Upon
inserting an end 46 of the extension strand 46 into the second
conical bore 40, the insertion force of the extension strand 46
will shift the second pair of wedges 44 toward the widened portion
40b of the bore 40, until the second pair of wedges have spread
apart enough such that the and 46a of the extension strand 46 will
fit between the second pair of wedges 44. At this point, tension
applied to the extension strand 46 will, due to frictional forces,
cause the second pair of wedges 44 to apply a progressively greater
gripping force to the extension strand 46 in a known manner.
[0033] Referring now to FIGS. 3, 4 and 8, it will be appreciated
that, in the disclosed example, the first pair of wedges 42 and/or
the first conical bore 38 may be sized and/or shaped using known
principles such that an end or tip 80 of the first pair of wedges
42 will be exposed or otherwise protrude from the narrowed portion
38b of the first conical bore 38.
[0034] As an alternative, and referring to FIGS. 5 and 6, the first
end 34 of the coupling device 20 may include a countersunk bore 82
that connects with the first conical bore 38. Should the coupling
device 20 be structured as shown in FIGS. 5 and 6, then a modified
release bushing 49 may be constructed as is shown in FIGS. 5 and 6.
Using the modified form of the release bushing 49, it will be
appreciated that the release bushing 49 and/or the countersunk bore
82 are sized such that the release bushing 49 will fit into the
countersunk bore 82 so as to come into contact with the exposed tip
80 of the first pair of wedges 42 as will be discussed in greater
detail below. In the construction of FIGS. 5 and 6, a first end 84
of the bushing 49 is generally flat and generally similar to the
first end 52 of the release bushing 48, while a second end 86 of
the bushing 89 is generally flat and forms a contact surface 88.
The contact surface 88 will form the surface that makes contact
with the tip 80 of the first pair of wedges 42 as will be discussed
in greater detail below.
[0035] Referring now to FIGS. 7 through 11, a chair 90 is
preferably provided. The chair 90 facilitates the use of a
conventional tensioning ram 92 (shown schematically in FIGS. 8
through 11). The details of a suitable chair 90 and the operation
of the tensioning ram 92 is known to those of skill in the art. As
would be known, the chair 90 is sized to fit over the wedge plate
30 so as to bear against a surface 24a of the concrete structure
24. Preferably, the chair 90 includes a surface 91 and one or more
legs 94 which are sized and positioned to make contact with the
surface 24a of the concrete structure 24, with the legs 94
preferably sized to defined a working area 96.
[0036] In operation, the coupling device 20 assembled in accordance
with the teachings of either disclosed embodiment of the present
invention may be used in at least two exemplary operational modes.
For example, in certain circumstances a user (not shown) may desire
to lessen the tensile force on one or more all of the tendons 22.
In such a situation, the coupling device 20 disassembled in
accordance with the foregoing discussion with the first and second
sets of wedges 40, 42 disposed in their respective conical boars
38, 40. The coupling device 20 is positioned over the protruding
tendon 22 and attached to and end 22a of the tendon 22 in a known
manner. This step may require that the coupling device 20 be
separated into its first and second halves 66, 68, which is
accomplished by unthreading at least the first half 66 from the
plug 74. The first pair of wedges 42 also are inserted into the
first conical bore 38 in a known manner, and the coupling device 20
may be fully re-assembled.
[0037] By applying a pulling force to the coupling device 20, the
first pair of wedges 42 will suitably grip the tendon 22. The end
46a of the extension strand 46 is inserted into the second conical
bore as discussed above, such that the second pair of wedges 44
will be positioned to apply a gripping force to the extension
strand 46. The user then attaches the conventional tensioning ram
92 to the extension strand 46 and prepares to apply a pulling or
tensile force to the extension strand 46 in a known manner. The
step may require the tensioning ram 92 to bear against the concrete
structure 24 and/or the chair 90.
[0038] Upon applying a pulling or tensile force to the extension
strand 46, the coupling device 20 transfers the force from the
extension strand 46 to the tendon 22. In the process, as the
extension strand 46 and the coupling device 20 are suitably
displaced to the right when viewing the FIGS., the tendon 22 is
also suitably displaced in the same direction. When this
displacement occurs, the user may remove the original pair of
wedges 26.
[0039] At this point, the tensioning ram 92 may be tensioned in a
controlled manner as would be known, thereby permitting the
coupling device 20 to be displaced back toward the concrete
structure 24 and past the original position of the coupling device
20. As the coupling device 20 passes its original position and is
now disposed closer toward the concrete structure 24, it will be
appreciated that the tension on the tendon and 22 is now reduced
relative to the original tension. When a desired position and/or
tension is achieved, a user may simply insert a replacement pair of
wedges 100 into the conical bore 28 in the wedge plate 30. The
tendon 22 is now suitably de-tensioned.
[0040] In a preferred mode of operation of the present invention,
the coupling device 20 may be used to completely release the tendon
22 as is shown in FIGS. 7 through 11. The coupling device 20 is
secured to the protruding tendon 22 in the manner outlined above,
and the tensioning ram 92 is secured to the extension strand 46 in
the manner outlined above. Preferably, the release bushing 48 is
first positioned over the protruding tendon 22. Alternatively,
should the bushing 48 be provided with a slot as opposed to a round
aperture 50, then the release bushing 48 may be suitably positioned
adjacent to the tendon 22 later in the process. Using the
tensioning ram 92, again the extension strand 46 and the coupling
device 20 are suitably displaced away from the concrete structure
24 until the user can remove the original pair of wedges 26. At
this point, the tensioning ram 92 is suitably de-tensioned,
allowing the coupling device to be displaced back toward the
concrete structure 24.
[0041] When the coupling and device 20 is shifted far enough back
toward the concrete structure 24, the exposed tip 80 of the first
pair of wedges 42 will make contact with the contact surface 58 on
the release bushing 48. When this contact is made, no further
movement of the wedges toward the concrete structure 24 is
possible. However, due to continued the de-tensioning, the coupling
device 20 will continue moving toward the concrete structure 24.
This relative movement between the coupling device and the
now-stationary first pair of wedges 42 causes the first pair of
wedges 42 to shift gradually into the widened portion 38a of the
first conical bore 38, which eventually causes the first pair of
wedges 42 release their frictional grip on the tendon 22. At this
point, the tendon 22 is completely released and may slide or
otherwise displace completely into the concrete structure 24.
[0042] In accordance with the disclosed example, the coupling
device 20 of the present invention may permit the tension on the
tendon 22 to be released entirely without having to resort to the
use of cutting devices, torches, or other methods of release
involving flames and/or heat. Thus, in those circumstances or
environments where the use of torches, etc., is not advisable, the
coupling device 20 of the present invention offers, in accordance
with the disclosed example, certain advantages that are not
achievable using standard prior art coupling devices.
[0043] Numerous additional modifications and alternative
embodiments of the invention will be apparent to those skilled in
the art in view of the foregoing description. This description is
to be construed as illustrative only, and is for the purpose of
teaching those skilled in the art the best mode of carrying out the
invention. The details of the structure and method may be varied
substantially without departing from the spirit of the invention,
and the exclusive use of all modifications which come within the
scope of the appended claims is reserved.
* * * * *