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Патент USA US3050288

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Aug. 21, 1962
|_. F. TUMEY
3,050,283
APPARATUS FOR DEPRESSING CABLES
Filed Jan. 26, 1960
4 Sheets-Shéet 1
TIE-p1
so
82
\
INVENTOR
LAWRENCE F. TUMEY
BY MM "é: /W4
ATTORNEY
Aug. 21, 1962
L. F. TUMEY
3,050,283
APPARATUS FOR DEPRESSING CABLES
Filed Jan. 26, 1960
4 Sheets-Sheet 2
OP
OF
mm
80/
QM.)
.VN.
Q3
(X)
LAWRENCE F. TUMEY
i‘ BY
ATTORNEY
Aug. 21, 1962
L. F. TUMEY
3,050,283
APPARATUS FOR DEPRESSING CABLES
Filed Jan. 26, 1960
4 Sheets-Sheet 5
F'I3_E7
I08
IO
INVENTOR
LAWRENCE F. TUMEY
ATTORNEY
Aug. 21, 1962
L. F. TUMEY
3,050,283
APPARATUS FOR DEPRESSING CABLES
Filed Jan. 26, 1960
4 Sheets-Sheet 4
F:L
_
_
_
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_
_
_
_
_
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INVENTOR
LAWRENCE F. ‘rune!
BY £75144”
.
ATTORNEY‘
Patented Aug. 21, 1962
1
3,050,283
APPARATUS FOR DEPRESSING CABLES
Lawrence F. Tumcy, Lakeland, Fla” assignor to FIVIC
Corporation, a corporation of Delaware
Filed Jan. 26, 1960, Ser. No. 4,785
9 Claims. (Cl. 254-61)
2.
cessive steps involved in depressing a plurality of pre
stressing cables within the mold cavity.
FIGURE 9 is a partial side elevation of a modi?ed
form of the cable depressing apparatus.
FIGURE 10 is a partial end elevation of the cable
depressing apparatus illustrated in FIG. 9.
A portion of a form or mold 12 for a prestressed
This invention pertains to apparatus for molding con
double-T concrete beam is illustrated in FIG. 1. The
crete structural members and more particularly relates
form 12 comprises an elongate sheet member 14 (FIGS.
10
to apparatus for depressing the cables used in prestressed
1 and 2) which is bent longitudinally to provide two
concrete beams.
molding cavities 15 and 16 and to provide flat surfaces
Concrete is strong in compression but Weak in tension,
17, 18 and 19 for molding the undensurface of the slab
consequently, concrete products such as slabs and beams
of the double-T beam. The elongate sheet member 14
which carry vertical loads must be reinforced in the areas
is supported above a concrete casting bed 22 on a suitable
where the most tensile stress occurs. One type of rein 15 number of longitudinally spaced, transversely extending
forcement frequently employed is steel cables. By ten
welded frames, one of which is indicated at 24.
sioning the cables and locating them in the lower regions
High tensile strength steel cables 30 (FIG. 1)
of the form, a beam having precompressed lower ?bers
stressing the concrete beam are strung horizontally
is provided. The amount of compressive stress imposed
tween the ends of the form in the region adjacent the
by the cables is designed to be equal to the tensile stress 20 of the two stem molding cavities 15 and 16. In
for
be
top
the
imposed on the beam by the design load. The stresses
particular instance illustrated, six such cables are super
counteract each other and therefore, the concrete in a
posed with respect to each other and comprise the group
beam supporting the design load will be substantially
of cables in each of the stem molding cavities. It is to be
unstressed.
noted, however, that each group may consist of other
25
When the cables imposing compressive prestress are
numbers of cables, or in certain cases, a single cable
located in the lower portion of a beam throughout the
full length of the beam the ?nished beam arches upward
assuming a “camber” and is horizontal only when sub
jected to the design load. Beams having cambers often
impose difficult construction problems when they are used
in buildings and the like. It has been found that by an
choring the prestressing cables at a relatively high location
may be employed in each mold cavity. Furthermore,
more than one group of superposed cables could be
placed in each mold cavity if it is desired.
One or more cable depressing devices 40 (FIG. 1)
transversely bridge the form 12. Each device 40 engages
the group of cables in each stem molding cavity 15 and
16 and applies downward pressure to these groups of
at the ends of a beam and depressing the cables at mid
superposed cables to bend the cables so that their center
span, the camber of the beam is reduced or completely
regions are depressed to lower positions in their respective
eliminated while the advantages of prestressing are re 35 cavities while the cable ends remain ?xed in their original
tained.
high positions.
An object of the invention is to provide an improved
The portion of the elongate sheet member 14 ‘which de
cable depressing device for use with forming apparatus
?nes the stem molding cavity 15 is illustrated in FIGS. 5,
for prestressed concrete structural members.
6, 7, and 8. These four ?gures illustrate four successive
Another object of the invention is to provide a cable 40 steps involved in the depression of the several super
depressing device which has unusually high load capa
posed cables in a stem molding cavity.
cities.
The several stressing cables 30 in the superposed group
Another object of the invention is to provide a cable
are in planar alignment and are strung in the longitudinal
depressing device which can be used in the production of
45 mid-plane of the stern molding cavity of the apparatus 12
beams of large dimensions.
(FIG. 1) and with the upper part of the cavity. A cable
Another object of the invention is to provide a cable
engaging clip 50 of inverted U-shaped form is next placed
depressing device which is adjustable longitudinally along
over the six cables 30 (FIG. 5). The upper portion of
the beam forming apparatus.
the
clip 50 is then engaged by the notched lower end 52
These and other objects and advantages of the inven
of
a
downwardly tapered depressing rod 54 (FIGS. 4 and
50
tion will be apparent from the following description taken
5) whose upper end is attached to the cable depressing
in conjunction with the accompanying drawings, in which:
apparatus 40 (FIG. 1). When thus assembled a clip 50
FIGURE 1 is a perspective of the cable depressing ap
constitutes a detachable lower end for the respective rod.
paratus of the invention, illustrating a portion of the
When actuated by the cable depressing apparatus 40
mold for forming a prestressed concrete beam.
the depressing rod 54 and the attached clip 50 are moved
FIGURE 2 is a side elevation of the cable depressing 55
downward in the stem forming cavity 15 of the form
apparatus of the present invention, illustrating the appa
12 to the ?nal position shown in FIGURE 6. The six
ratus after cable depression has occurred.
cables are held in their superposed relationship by the
FIGURE 3 is an end elevation of the cable depressing
apparatus shown in FIG. 2.
FIGURE 4 is an isometric on an enlarged scale of a
clip ‘which is used in depressing several superposed cables.
FIGURES 5, 6, 7, and 8 are fragmentary transverse
sections through a typical mold cavity for a stem portion
of a prestressed concrete beam, illustrating several suc
clip 50 as they are depressed and continue to be so held
while the concrete ‘is being poured and while it hardens.
Concrete 56 is next poured into the stem molding cavity
15 (FIG. 7) and when the concrete has hardened suffi
ciently, the tapered rod 54- is vertically withdrawn. The
notched lower end 52 of the tapered rod 54 readily re—
3
leases the clip 50 and is easily withdrawn upward by
the cable depressing apparatus 40. The clip 50 and the
several superposed cables 30 remain in ‘the depressed
cavity. Consequently, the rods 54 and 55 are materially
shorter than the cable depressing rods in common use,
location in the stem portion of the concrete beam and
heavy loads without buckling.
and they are thus adapted to handle correspondingly
the tapered hole 58 remaining after the withdrawal of
the tapered depressing rod 54 may be ?lled with concrete
’
A bearing plate 120 (FIGS. 1-3) is welded to the top
With this procedure, cables are depressed at
surfaces of the channel members 100 and 102 at each
end of the cross bridge 75. A hydraulic jack 122 is
midspan to be positioned in the lower regions of the
placed on each bearing plate 120. The head 126 (FIG.
mortar.
3) of the piston of each jack 122 bears against the as
sociated brace member 86. The two hydraulic jacks
ef?ciency in resisting vertically imposed loads.
122 are extended concurrently by manual operation of
Each of the frames 24 which support the sheet mem
their handles 124 to force the cross bridge 75, the at
tached cable depressing rods 54 and 55 and the stressing
ber 14 has a pair of short projecting members 60 (FIGS.
cables 30 downward to their lower positions in the form
1 and 2) welded thereto which members are connected
by bolts 62 to the horizontal concrete casting bed 22. 15 (FIGS. 2 and 6-8).
The form 12 is leveled by adjusting nuts 66 on the bolts
If a cable 30 breaks during ‘its depression, there is
62.
little danger that workmen will be hit by the end of
stems of the double-T beam so that the lower ?bers of
the beam thus cast are precornpress'ed to increase its
‘the broken cable flying through the
because the end
will usually ?y upward and the jack operating workmen
Each cable depressing apparatus 40 (FIGS. 1-3) in
cludes ‘two upright guide assemblies 70 and 72 placed
on opposite sides of the form 12, and includes a cross 20 are, of course, positioned not above the forming appa
ratus but beside it and out of the danger zone.
bridge 75. The upright guide assembly 70 is made from
a pair of channel members 76 and 77 and the upright
The reaction force resulting from the depression of
guide assembly 72 is made ‘from a pair of channel mem
the cables 30 acts on the cross bridge 75 considerably
closer to the ends thereof where the jacks 122 are placed
bers 78 and 79 (FIGS. 1—3). The channel members
of each upright guide ‘are welded to a respective foot 25 than in- commcnly known cable depressing devices. With
ing plate 80 (FIGS. 1-3) secured by bolts 82 to the
casting bed 22.
this construction, therefore, the amount of bending stress
that must be resisted by the cross bridge 75 is reduced.
The upper ends of the channel members of each up
Therefore the cross bridge 75 can be constructed from
right guide assembly 70 and 72 (FIG. 1) carries a ver
comparatively light channel members, which, of course,
Ptically movable brace member 86 (FIG. 1). Each brace 30 reduces the cost of the apparatus. The relatively small
member 86 comprises a short channel member 88 whose
amount of bending stress on the cross bridge 75 allows
ends are welded to side plates 89 and 90. The side
the present apparatus to be used with apparatus which
plates lie outside the ?ange ‘faces of the channel mem
forms very large dimensioned beams.
bers of the associated upright guide assembly, so that
It will be appreciated, therefore, that the cable de
the brace member 86 is guided for vertical movement 35 pressing device 40 of the present invention makes it
between the vertical channels.
feasible to produce prestressed concrete beams consider
ably wider and deeper than heretofore.
Each brace member ‘86 is adapted to be connected to
the associated upright guide assembly 70 or 72 in either
The cross bridge 7 5 may be locked in the extreme lower
of two distinct locations, vertically spaced pairs of holes
96 and 98 being provided in each guide assembly for
that purpose. A bolt ‘94 passing through the ?anges of
position or cable-depressing position (FIGS. 2 and 6)
40 or in any intermediate position between the positions illus—
trated in FIGURES 5 and 6, respectively, by threaded
the channel member 88 of the brace member 86 is adapt
ed to connect the brace member to the associated upright
hold-down devices 140 (FIGS. 1 and 3) one of which is
connected to each end of the cross bridge 75. Each hold
guide assembly by passing through either the upper pair
down device 140 comprises an elongate bolt 142 con
of holes 96 or the lower pair of holes 98. The height 45 nected to a plate 144 (FIGS. 2 and 3) welded to the
of a brace member ‘86 with respect to the associated
under surface of the cross bridge channel members 100
guide assembly can be changed by removing the bolt
94, sliding the brace member into alignment with the
and 102 adjacent the associated end thereof. Each bolt
142 is threaded throughout its entire length and extends
other pair of holes 96 or 98, as the case might be, and
then replacing the bolt.
through a hole in an abutment member 146 (FIGS. 1
50 and 3) welded between the channel members of the as
The ends of the cross bridge 75 (FIGS. 1-3) are
guided for vertical movement within the upright guide
assemblies 70 and 72. The previously described cable
sociated upright guide assemblies 70, 72.
A nut 148
on each bolt 142 may be adjusted to retain the bolt 142
and the corresponding end of the cross bridge 75 in any
depressed position. The two abutment members 146
depressing rod 54 and an identical cable depressing rod
55 are connected to the cross bridge 75 at points directly 55 are located to also act as stop members, limiting the
downward travel of the cross bridge 75.
above the centers of the stern molding cavities 15 and
16, respectively, of the form 12 (FIG. 2). The cross
bridge 75 is made from two spaced-apart channel mem
bers 100 ‘and 102 (FIGS. 1 and 3). Pairs of bearing
plates 104 and 106 (FIGS. 1 and 2) are welded to the
upper and lower ?ange surfaces of the spaced-apart chan
nel members 100 and 102 and the bearing plates 104
1If the two hydraulic jacks 122 used with the cable
depressing apparatus 40 cannot be extended su?‘iciently
to depress the cables 30 to the desired location, when
the braces 86 are fastened to the upright guide assemblies
70 and '72 at the level of the upper holes 96, the cables
'30 can be locked in place by the hold-down devices 140
and 106 are drilled to accommodate the upper ends of
while the braces 86 are lowered to be connected at the
holes 98. With this construction complete cable de
upper ends of the cable depressing rods 54 and 55 (FIGS. 65 pression can be achieved with relatively inexpensive hy
draulic jacks 122 having stroke lengths that are insu?'i
1, 2, '6 and 7) are threaded and are disposed in the space
cient to fully depress the cables when the cross brace
between the webs of the cross bridge channel members
members 86 are connected at holes 96. When complete
100 and 102. The threaded end of each rod 54, 55
cable depression is achieved the nuts 148 of the cable
carries two ‘adjusting nuts 108 above and below the as
sociated bearing plates 104 or 106, as the case might 70 hold-down devices 140 are tightened against the respec
be, which permit the tapered rods 54 and 55 to be ver
tive abutment members 146 and both hydraulic jacks 122
the cable-depressing rods 54 and 55, respectively. The
'tically adjusted relatively to the cross bridge 75. It will
be noted that the parts of the cable-depressing rods 54
and 55 that project downward from the cross bridge sub
stantially correspond in length to the depth of the mold 75
can be removed, with the result that jacks are not re
quired to maintain the cables depressed while the concrete
in the form 12 is hardening. A hook 150 (FIGS. 1 and 2)
is centrally connected to the upper surface of the cross
3,050,283
5
6
bridge 75 and is provided for lifting the cross bridge and
the attached cable depressing rods 54 and 55 when the
of the spanning means for guiding the same in vertical
movement, hydraulically actuated means engageable with
each end of the spanning means and with the associated
guide means and operable to depress said spanning means
concrete has hardened.
It is sometimes desirable to have the cross bridge
and the upright guide assemblies movable longitudinally
and the engaged cable with respect to the form, and
along the concrete forming apparatus 12, so that when
the length of a beam is changed the depressing apparatus
means located at each end of the spanning means for
locking it and the engaged cable in a selected depressed
can be located at midspan of the beam to be cast.
position.
To
4. Apparatus for depressing a stressing cable in a mold
device possible, a modi?ed form 160 (FIGS. 9 and 10) 10 ing form comprising a vertically movable beam spanning
the concrete molding form, a cable engaging member
of an upright guide assembly is provided for use at each
carried by the beam, guide means adjacent each end of
end of the disclosed cross bridge 75. The modi?ed up
the beam, hydraulically actuated means adapted to be
right guide assembly 160 includes two vertical channel
interposed between each end of the beam and the re
members 162 and 164. The lower portion of each of
the channel members 162 and 164 is welded to a guide 15 spective guide means, said hydraulically actuated means
being operable to depress said beam and the engaged
block 166 and a guiding angle member 168. The guide
cable with respect to the form, means for adjusting the
block 166 and the guiding angle member 168 are spaced
position of the cable engaging member with respect to
apart su?iciently to accommodate a guide rail 170 there
between. The upper surface 172 of the guide block 166
the beam, and means located at each end of the beam for
contacts and can he slid along the lower surface 174 20 locking it and the engaged cable in selected position.
of the guide rail 170. A pair of locking bolts 178 en
5. In apparatus for manufacturing prestressed concrete
gage nuts 180 which are welded to the guiding angle
beams including an elongate form for molding a beam,
member 168. The bolts 178 are tightened through the
and a plurality of concrete stressing members in planar
nuts 180 against the upper surface 175 of the guide
alignment within said elongate form, the combination of
rail 170 and lock the upright guide assembly 160 in 25 a movable stressing member depressing device spanning
the selected longitudinal location along the guide rail 170.
said form, means for guiding the depressing device in
Each upright guide assembly 160 includes one of the
movement toward and away from said elongate form,
previously described hold-down devices 140. The guide
means engaging said depressing device for forcing said
assemblies 160 receive the cross bridge 75 and operate
device toward the form, a clip embracing said stressing
in the manner described in connection with the cable 30 members for maintaining said alignment thereof, and a
depressing device 40 (FIGS. 1-3).
rod secured to the depressing device and engaging the
The guide rail 170 is illustrated as being cast as an
clip to depress the stressing members in the form upon
integral part of the edge of forming apparatus 190. This
operation of said forcing means, said rod being releasable
form 190 is made from concrete and includes a metal
from the clip to leave the clip in embracing relation with
forming sheet 191. A guide rail 170 extends for a
the stressing members upon movement of the depressing
considerable distance along each side of the apparatus
device away from the form.
190, and it will be apparent that the guide rails 170
6. In apparatus for manufacturing prestressed concrete
could be made as a part of a separate framework which
beams including an elongate form for molding a beam,
would be placed along each side of the form 12 (FIGS. 1
and a plurality of concrete stressing members in planar
and 2), for example, and bolted down to the casting
alignment within said elongate form, the combination of
bed 22.
a movable stressing member depressing device spanning
It will be understood that modi?cations and varia
said form, means for guiding the depressing device in
tions of the invention disclosed herein may be resorted
movement toward and away from said elongate form,
to without departing from the scope of the invention as
means for guiding the depressing device in movement
de?ned by the claims.
45 substantially parallel to said elongate form, means engag
The invention having thus been described, that which
ing said depressing device for forcing said device toward
is claimed as new and which is desired to be protected
the form, a clip embracing said stressing members for
by Letters Patent is:
maintaining their alignment, and a rod engaged with the
1. Apparatus for depressing stressing cables in a pre
clip and connected to the depressing device to depress
stressed concrete molding form comprising a vertically 50 the stressing members in the form upon operation of said
movable bridge spanning the concrete molding form,
forcing means, said rod being releasable from the clip to
guide means adjacent each end of the bridge adapted to
leave the clip in embracing engagement with the stressing
guide the bridge during vertical movement thereof, a - members upon movement of the depressing device away
cable engaging rod extending downward from the bridge,
from the form.
hydraulic means connected between said guide means and 55
7. Apparatus for depressing cables in a concrete mold
said bridge for forcing the cables downward in the form,
ing form comprising a vertically movable bridge spanning
and means connected to the bridge for locking the bridge
the molding form, guide means adjacent each end of the
and depressed cables in a selected vertical position.
bridge, each of said guide means being mounted for move
2. Apparatus for depressing stressing cables in a pre
ment along said form and adapted to guide the bridge dur
stressed concrete molding form comprising a vertically 60 ing its vertical movement, a cable engaging rod extend
movable bridge spanning the concrete molding form, guide
ing downward from the bridge, hydraulic means con
means adjacent each end of the bridge adapted to guide
nected between each guide means and said bridge for
the bridge during vertical movement thereof, a cable
forcing the cables downward in the form, and means con
engaging rod extending from the bridge into the form,
nected to the bridge for locking the bridge and depressed
means connected between the rod and the bridge for ad
cables in a selected position.
justing the extension of the rod ‘with respect to the
18. In apparatus for manufacturing prestressed concrete
bridge, hydraulic means connected between said guide
beams including an elongate form for molding a beam,
means and said bridge for ?exing the cables within the
the combination of a guide rail mounted adjacent each
form, and means connected to the bridge for locking
side of the form and‘ extending parallel thereto, a cable
the bridge in a selected position and the cables in the
depressing device spanning said form, guide means for
corresponding ?exed position.
said depressing device mounted on each of said rails for
3. Apparatus for depressing a stressing cable in a pre
longitudinal movement along said form, said guide means
engaging said cable depressing device for guiding said de
stressed concrete molding form comprising vertically mov
vice in a plane perpendicular to the form, and adjustable
able means spanning the concrete molding form, cable
engaging means carried thereby, means adjacent each end 75 means adapted to be connected to said guide means for
make this longitudinal adjustment of the cable depressing
3,050,283
8
engaging the cable depressing device and moving it in
‘said plane.
9. In apparatus for manufacturing prestressed concrete
beams including 'an elongate form for molding a beam,
the combination of a guide ‘rail mounted on each side of
the form and extendingparallel thereto, a cable depressing
device spanning said form, guide means for said depress
ing device mounted on each of said rails for longitudinal
movement along ‘said form, each of "said guide means
engaging'a respective end 'of said cable depressing device 10
for guiding said device in a plane intersected by the form,
adjustable means adapted to be connected to said guide
‘means for engaging the cable depressing device and mov
ing it in 'said plane, and means connected between the
cable depressing device and the guide means for retain
ing the device in selected position of adjustment on said
guide means.
vReferences Cited in the ?le of this patent
UNITED STATES PATENTS
455,687
McCarthy _____-_ _______ __ July 7, 1891
:l44,l93
220,179
Great Britain _________ __ June 10, 1920
Australia ____________ __ May 22, 1958
FOREIGN PATENTS
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