CA1057032A - Method and apparatus for manufacturing a series of elongate prestressed concrete construction elements - Google Patents

Abstract

METHOD AND APPARATUS FOR MANUFACTURING A SERIES OF
ELONGATE PRESTRESSED CONCRETE CONSTRUCTION ELEMENTS
Abstract of the Disclosure Method and apparatus for manufacturing a series of elongate prestressed concrete construction elements are disclosed.
Prestressed reinforcements are positioned above and along an elongate moulding area provided with heating means. The reinforcements are then tensioned. A portion of each element is moulded by pouring concrete into a moulding assembly positioned about the reinforcement, the moulding assembly being moveable along the moulding area and having a front wall and a retractable rear wall arranged across the moulding area and a series of mutually parallel formers extending along the moulding between the front and the rear walls to form a series of moulds. The poured concrete is then vibrated and the rear wall of the moulding means is retracted. The moulding assembly is moved along the moulding area to leave behind moulded portions of the elements. Successive portions of each element are moulded in the same manner until a desired length of element has been obtained. The elements are then heated to harden the concrete, and the tension in the reinforcements is released.

Description

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The present in~ention relates to a method and apparatus for manufacturing reinforced concrete elements, namely elongated construction elements, such as beams, girders, joists, lintels, posts, piles or the like, of prestressed concrete.
:- Generally speaking, an aim of the invention is to provide a method by which concrete elements, in particular elongated construction elements such as beams or joists of prestressed concrete, can be manufactured under optimum industrial conditions.
According to one aspect of this invention there is provided a method of manufacturing a series of elongate ¦ concrete construction elements by manufacturing successive : portions of said elements comprising: i- molding a portion of each element by pouring concrete into a molding unit comprising, located on a molding area, a front wall and a t retractable rear wall arranged across the molding area and ;. a series of mutually parallel formers extending along the ,. .
~:~ molding area and constituting lateral walls between the front . 20 and the rear walls to form a series of molds, said walls being .. adapted to move on the molding area; ii- vibrating the poured concrete; iii- after the concrete has sufficiently hardened, .. retracting the rear wall of the molding unit; iv- displacing ~ with a translatory movement the lateral walls along the molding .1 area to leave behind molded portions of the elements while maintaining stationary the front wall; v- displacing with a ~` translatory movement the front wall along the molding area up to the successive portion; vi- molding a successive portion ~:. of each element by pouring concrete into the space provided .,~` 30 between the front wall, the lateral walls, the front ends of ;
the already cast portions and tne molding area; vii- vibrating ; 2 ~
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. : , the poured concrete; ~iii- molding successive portions of each element in the same manner until a desired length of element has been obtained; and ix- eventually heating the elements to harden the concrete.
According to another aspect of this invention there ie provided apparatus for manufacturing a series of elongate prestressed concrete construction elements comprising: i) a manufacturing bed designed to absorb the compressive forces developed during the manufacture of the elements, ii) an elongate molding area above the bed; iii) means for heating the molding area; iv) a series of molds comprising a plurality ~ of lateral walls fixed on a first movable assembly mounted for :" , translatory movement along the bed, said assembly having at its rear end - relative to the direction of displacement along the bed during manufacture - a retractable flap adapted r~' to form the rear wall of the molds, and front walls constituted by the ends of arms of a second movable assembly, said arms being located between the lateral walls; v) means with - vibrating members for feeding and distributing concrete into the series of molds; vi) means for displacing the movable assemblies independently from each other in a direction parallel .....
to the lateral walls, so that the second movable assembly remains stationary during the forward displacement of the ~- first movable assembly, the retractable flap having been raised before this forward displacement and so that after , displacement of the first movable assembly, said second `` movable assembly can be displaced forwardly.
Preferably, the apparatus comprises means for ".
automatically vibrating additional reinforcements, sometimes known as stirrups or binders, crosswise into the freshly poured concrete in the moulds.
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Preferably, means are also provided which, after ?~`
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pouring the concrete, cover the entire area on which partially hardened concrete elements are still supported with a large size thermal insulating tarpaulin which is automatically rolled and unrolled by means of a carriage displaceable along rails.
The invention will be fully understood by the : description of embodiments thereof which follows, by way of example, with reference to the accompanying drawings, in which:
Figures la, lb and lc are plan views in schematic 10 forms of apparatus according to the invention in the various t positions of the casting procedure;
Figure 2 is a perspective view in simplified form : of a portion of apparatus according to one embodiment of . this invention;
Figure 3 is a partial longitudinal section of the body of a bed of the plant according to the invention;
Figure 4 is a view similar to that of Figure 2, but for another alternative embodiment;
Figure S (located with Figures 8 and 9) is a longi-20 tudinal sectional view of an end of the bed;
;; Figure 6 is a partlal top view of the manufacturing bed for still another embodiment;
,5, .. Figure 7 is a sectional view on line 7-7 in Figure 6;
Figure 8 is a sectional view on line 8-8 in Figure 6;
;. Figure 9 is a partial longitudinal sectional view of ~: an end of the bed of an alternative embodiment;
Figure 10 is a bottom view of a moulding area for _another alternative embodiment;
: Figure 11 is a sectional view on line 11-11 in Figure 10, but on an enlarged scale;
Figure 12 is a sectional view on line 12-12 in Figure ~` 10, but on an enlarged scale;

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:: Figure 13 is a schematic view of the heating circuit for the bed; :~
Figure 14 is a view similar to that of Figure 13, : but for an alternative embodiment;
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Figure 15 is a schematic view in section of seal means for a heating pipe;
, Figure 16 is a schematic view illustrating heating . means for the bed according to another embodiment;
Figure 17 is a sectional view along line 17-17 of . 10 Figure 16, but on an enlarged scale;
~, Figure 18 is a schematic view in section of still another heating system;
-~ Figure 19 is an elevational view of an embodiment of l means for tensioning prestressing reinforcements;
;~. Figure 20 is a view similar to that of Figure 19, ~';. but for another embodiment;
Figure 21 is an elevation view of a part of the means . shown in Figure 20 viewed in the direction of arrow F in Figure 20;
Figure 22 is a plan view of a part of the moulding ; unit of a plant according to the invention;
Figure 23 is a sectional view taken along line 23-23 in Figure 22;
Figure 24 (located after Figure 26) is a sectional ~! view of a component part of the moulding unit;
i., Figure 25 (located after Figure 26) is a perspective ~ view of the part of the moulding unit illustrated in Figures ~, 22 and 23;
.; Figures 26a and 26b are sectional views of mold .i ~
'i 30 elements;
i Figure 27 is a view of a winch device for a plant;

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Figure 28 shows brake means for a movable assembly of the molding unit;
Figure 29 is a detail view of a part of the moulding unit;
Figure 30 is a top view of a part of the moulding unit;
Figure 31 is an elevation view of part of the moulding , unit;
Figure 32 is a side view of part of the moulding unit;
Figure 33 is a view similar to that of Figure 32, but for an alternative embodiment;
Figure 34a is a schematic view of another embodiment of the drive means for the moulding unit;
. Figure 34b is a view in section taken on line 6-6 in Figure 34a;
Figure 34c is a sectional view taken on line c-c in 'Figure 34a;
'Figure 35 is an elevation view of a bucket for pouring the concrete;
Figure 36 is a sectional view taken on line 36-36 in , . ~
.,20 Figure 35;

Figure 37 is a top view of the bucket shown in ,Figure 35;

Figures 38 and 39 are schematic views similar to that of Figure 36 for illustrating the operation of the bucket for .. ,, pouring concrete;

Figure 40 is an elevation view of a device for positioning transverse reinforcements;

_ Figure 41 is a side view of the device for positioning . transverse reinforcements;
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Figure 42 is a schematic view of apparatus for positioning the thermal insulating tarpaulin;

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Figure 43 is a plan view of the overall plant with its superstructure; and Figure 44 is a sectional view taken on the line 44-44 in Figure 43, but on an enlarged scale.
In the preferred embodiments of the invention as described below, elongated prestressed concrete elements are formed by casting first portions of the elements in a plurality of molds, displacing the molds along the already cast portions up to a second molding position where second portions of the elements are cast and, if necessary, with-drawn in a similar manner so that subsequent portions can be cast until elements of the desired length are obtained.
This principle is illustrated schematically in Figures la to lc of the drawings. The lateral walls of tne - molds are constituted by elements 126 fixed on a movable assembly. A retractable flap 160 on the movable assembly forms a rear wall for the molds with respect to the displace-ment direction of the movable assembly. The front walls of the mold are formed by blocks 175 located between the lateral ~ ., i' 20 walls of the molds and fixed on a second movable assembly ,........................................................................... .
(Fig. la).
When first portions of the elements have been cast in the molds defined by the lateral walls 126, front walls 175 and rear wall 160, the rear wall is raised. The first movable assembly is then displaced forwardly while the front ; walls 175 fixed on the second movable assembly are maintained stationary (Fig. 16). In this manner, the first cast portions ~of elements are rigidly maintained in position during their withdrawal so that the elements 126 do not damage the already cast portions.

When the first movable assembly has reached its ~ - 7 -.:.' .:. .
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second molding position, the walls 175 of the second mo~able assembly are displaced forwardly so that second portions of the elements can be cast (Fig. lc).
Successive portions of each element are thus molded until a desired element has been obtained.
Suitable apparatus of this type is shown in Fig.

2 where like reference numerals indicate corresponding parts.
The apparatus and method are described in more detail below with reference to Figs. 3 to 44.
Each of the elements of the preferred apparatus is described below under the appropriate headlng.
A. The Bed of the plant The bed of the plant comprises two sunken masses or piers at the ends of the concrete bed. Depending on the nature ; of the soil, the piers are simple massive bodies or are com-posed of a block and anchoring means with, if necessary, tie rods for interconnecting the masses. A ribbed slab or beam extends between the two masses which support the moulding area and absorb the compres~ive forces developed by the tension ~; 20 in the prestressing reinforcements of the elements being manufactured.
When the ground on which the plant is to be located ; is of good quality, one end mass or pier comprising a wall 1 ~ ~Figure 3) of reinforced concrete comprising at the upper end , ...................................................................... .
of its outer surface an embedded metal section 2 bearing the ; means for tensioning the prestressing reinforcements, described ; in detail hereinbelow, which are received in a pit 20 delimited by a wall 21 and a bottom wall 23 with cavities 24 . .
and 24a for receiving a metal part of the means for tensioning and releasing the tension in the reinforcements transmitting the reaction forces Q developed by the tension in the prestressed :., :
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~ 3 .: ~., . , , .. . -1~5703Z ' reinforcements of the elements to be manufactured.
Perpendicular to the wall 1, the bed comprises a concrete slab 5 having an end portion 5a, which is thicker than its central portion 5b, for distributing the compressive forces, the end portion 5a being connected to the central ~,, .
portion 5b by a zone 5d which is poured and matted after the portions 5a and 5b of the slab have shrunk.
The slab 5 is separated, as shown at 5c, from the -- end mass forming the pit so that any eventual sinking of the pier or end mass under the effect of the alternating ~' forces does not cause the sinking of the wall 1.
The lower surface of the upper part of the slab 5 is provided with thermal insulation 8, the length of which . .
s may be in the range of sixty meters and the width from two to three meters, and a recessed portion 4 adapted to receive heating means for the flat work or moulding area comprising ,. .
metal plates 3 forming the bottom of the moulds into which the concrete is poured.
In a further embodiment (Figure 4), particularly ~ 20 useful when the heating for the work area is effected with ; expanded steam, two HN type sections 11 and lla act as guiding means for fixing the movable assemblies against movement on the rails, the recessed portion 12 having inclined surfaces ,; 12a necessary for draining off the condensate.
:; If necessary, the end masses of the manufacturing bed forming the pit for receiving the means for tensioning and ~. .
releasing the tension in the prestressing reinforcements are ';.'`
~ interconnected by prestressing cables 26 (Figure 5) or by the : :.
concrete reinforcements passing through a box girder 16.
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Irrespective of the construction of the bed, it is ` poured in several steps in order to avoid cracks caused by ,~ _ g_ ~i ~

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1~57032 the shrinking of the concrete, sealing zones-are provided, e.g. ~one 5d, being matted when the major part of the shrinking has occured.
We are also-concerned with adapting the bed for the manufacture of construction elements of different lengths, `~
using a bed as shown in Figures 6-8, i.e. in which the slab 5 is replaced by a massive girder 27 of reinforced concrete prestressed by reinforcements or cables 27b, the upper surface 27a of which being adapted to receive the moulding or work area, and the girder is broken up at one or more suitable points along its length with wells 28 and 28a extending over the entire height thereof (Figure 8). The wells 28 are of substantially square cross-section and their transverse faces in the longitudinal direction of the bed have upper and lower metal fixtures 29 and 29a respectively for supporting the means for tensioning and releasing the tension in the reinforcements.
In a plant with such a bed, the wells 28 are closed with metal covers 30 when the entire height of the wells are to be used, and means for tensioning and releasing the tension in the reinforcements are installed at each end of the bed.
, Alternatively, however, the means for tensioning and "' releasing the tension in the prestressing reinforcements of the elements being manufactured may be provided at only one end of the bed, if the other is as shown in Figure 9, i.e. a pier 31 integral with the slab 5 without a seal therebetween, along which a plate 32 with rectangular anchoring cutouts for the ends of the prestressing reinforcements, the plate being anchored in the concrete of the pier or mass 31 by steel reinforcements such as shown at 33.
B. The Moulding or Work Area ` The moulding area is fixed on the bed and comprises ., . r,- . .

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',' 105703z very thick metal plates 3, for example ten or more milli-meters thick, of large dimensions, for example 2 x 6 m, provided advantageously with stiffening means.
; In an embodiment which employs a heating system in which steam is expanded in a vapour chamber 43 (Figures 10-12), the moulding area is supported on the bed by short metal pillars 42 embedded in the bed, the height of the pillars -- being adjustable by screwing. I-beams 36, 36a bear against the pillars welded to the underface of the metal plates 3 which are also supported on the I-beams 11 fixed to the bed.
The chamber 43 which is supplied by tubes 44 carrying steam for heating is delimited at its upper end by the juxtaposed metal plates 3 joined together by the flat bars 39a, welded at 39b to one of the plates and fixed to the adjacent plate by screws 40 with countersunk heads and by the split pins 45 absorbing the shearing force due to expansion which could not be taken by the screws 40. As in the first embodiment of the ; moulding or work area, two lateral screws 41 and 41a secure ,~ one of the metal plates to the bed, preferably over a third ;~ 20 of the length thereof.
C. Heating System for the Moulding or Work area In an embodiment utilising hot water flow through pipes 37 (Fig. 13) a water chest 46 with partitions 47 is .......
, located at one end of the bed fixed, relative thereto, under the moulding area. A hot water feed conduit 48 and an outlet ; conduit 49 extend into the water chest, the water circulation ....
being at a high flow rate with a low temperature gradient _between its intake and delivery conduits.

~; When the width of the bed is relatively large (Fig. 14), the water chest 50 provided at one end of the bed is divided .,.
~ with partitions 51 and 52 into two compartments 53 and 54 , .. . .

1~57032 which are connected to a forked conduit 55 for feeding the hot water and a compartment 56 which is connected to a delivery conduit 57. A blow-off device 58 for blowing out air pockets may be provided in either embodiment.
- To compensate for the expansion of the pipes 37, sliding seal means are provided (Figure 15) comprising, on each pipe 37, an end flange 60 bolted to a sleeve 61 by another flange 62 and, on the water chest, a short length 63 of pipe connected to a nipple 64 of the water chest by flanges 65, 65a; the free end of the length 63 of pipe carries a seal 66, for example of neoprene, clamped between a flange 67 and a flange 68; the sleeve 61 is machined on its outer surface and slides inside the seal 66.
When, as shown in Figure 12, the metal plates 3 forming the moulding or work area are heated with expanded steam, the steam injection tubes 44 (Figures 16 and 17) are provided with calibrated orifices 70 capped with deflectors 71 adapted to ensure an excellent distribution of the heating fluid which is supplied at the mid-point along the length of the bed from an equilibrium header 72 connected by a conduit 73 to a boiler :~ and by conduits 74 to flexible loops to a blow-off device 80 . with an automatic bleeder 81. One or more temperature probes 76 located in the chamber 43 control a valve 77 with a by-pass 78 for manual control by appropriate means.
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Besides the two embodiments of heating systems de-scribed above, by means of the circulation of hot water through a group of pipes or by means of expanded steam, other means for :, heating the moulding or work area may be provided.

In the embodiment of Figure 18 which employs Joule effect heating, the resistance heaters 85 are distributed at appropriate intervals under the plates 3 and coated with a "" :
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special product held by galvanized shells. The plates 3 are supported on the short pillars, such as 42, and a perfectly flat bed of dry sand 86 which is provided in the recess in the upper surface of the bed, a fluid-tight layer 87 being provided along the surfaces of the recess beneath the bed of sand.
D. Means for Tensioning and Releasing the Tension in Reinforcement members In a pit 20 at at least one end of the bed, means 88 for tensioning and releasing the tension in the prestressing 10 reinforcement of the elements being manufactured are housed < (Figure l9). The ends of the reinforcements which are not secured to the means 88 are fixed to a stationary anchorage, such as shown in Figure 9, or fixed to means similar to means , 88 and located at the other end of the bed or in one of the pits, such as 28 or 28a, provided along the length of the bed between the ends thereof.
; The means for tensioning and releasing the tension in the relnforcement members comprises two parallel arms pivotably mounted about a horizontal pivot at their lower ends , 20 under the action of hydraulic jacks. In case of leaking in the hydraulic control circuit of the jacks, safety means are provided for preventing displacement of the arms during the operating phase. Means are associated with the arms for hooking and holding the ends of the prestressing reinforcements ; against movement.
In a first embodiment (Figure 19), the jacks 19 for actuating the arms 93 are single-action jacks pivoted at 91a _on the arms, the piston rods 91c of which are pivoted at 91b on the metal frame 92 bearing against the wall 1 of the bed, 30 the frame is also used for positioning the means 88 owing to ; the cross members 92a and 92b pivotally connected at 92c.

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''' llQ~7032 The end of the cross member 92b opposite the pivot point bears on the wall 21 of the pit 20 by a pressure screw 92d.
The arms 93 which are substantially vertical in the tensioning position of the reinforcements A are adapted to pivot in the direction of the arrow F about the pivot pins ;
89 carried at the ends of the cross members 92a received in the cavity 24 in the bottom of the pit 20 in which a part 90 for positioning means 88 for tensioning and releasing the - tension in the prestressing reinforcements is located.
For securing to means 88 the ends of the prestressing reinforcement members, or reinforcements, of the concrete elements to be manufactured, provision is made for connecting ; to the arms 93 horizontal plates 94 separating by spacing members 95 and a shim 97, the lower end of the shim resting on a block 98 on which a rod 96 is fixed parallel to the arms.
~; Pairs of adjacent horizontal plates form between one another spaces through which pass the prestressing reinforcements A
which are adapted to be tensioned by means of a jack and then " anchored by means of any appropriate device, for example, jaws MO.
In an embodiment shown in Figures 20 and 21, the jacks 111 are double-action jacks and the arms 93 of the preceding embodiment are replaced by a portal frame 113 whose `;~ legs are connected by a cross beam 113a with a superposed plate 113b forming rectangular notches 113c (Figure 21) for receiving the prestressing reinforcements.
As in the embodiment of Figure 19, a part 110 of the means for tensioning and releasing the tension in the re-inforcements is received in a cavity 24 at the bottom 23 of ~` 30 the pit 20, the double-action jacks 111 bearing against the bed through a massive horizontal girder 112 on which guide , ' 7: ~ - 14 -. ''~'`
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-` -l~)S7032 `--pulleys 116 for the prestressing r~inforcements are fixed.
The girder 112 is supported on masonry or concrete supports 112a, each jack 111 being pivotally mounted at llla on the portal frame 113 and at lllb on the girder 112 which bears against the wall 1 through bearing rollers 114 and 115.
The safety device associated with the means for tensioning and releasing the tension in the prestressing reinforcements comprises arms 117 with square threads pivotally mounted at 117a on the legs of the portal frame 113 and with guide members 118. The arms 117 co-operate with the nuts 118' which are fixed to the actuating flanges 119 - of a swinging pawl ll9a for controlling the supply of current to the motor of the hydraulic pump. After tensioning the prestressing reinforcements of the construction elements to be manufactured, the nuts 118' are tightened by hand on bearing parts 120 pivoted at 120a on the girder 112, and during the relieving of the pressure in the jacks 111, if the nuts 118' are not previously loosened, the swinging of the pawl ll9a stops the supply of current to the hydraulic pump thereby preventing displacement in case of leaking in the hydraulic circuit during this phase of operation.
E. Moulding Unit The moulding unit comprises a group of moulds and means for supplying and distributing the concrete in the moulds.
El. The Group of Moulds The bottom of the moulds is formed by the moulding _area comprising metal plates 3, a first movable assembly 125 (Figures 22 and 23) carries suitable formers 126 for con-stituting the lateral walls of the moulds and a secondmovable assembly with fingers or projections housed between .
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two adjacent former elements, the ends of the second movable assembly carry blocks (Figures 24 and 25) of section com-plementary to the elements to be manufactured on the bed, these blocks form the forward transverse walls of the moulds into which the concrete is poured.
The elements 126 constituting the lateral walls of the mould are fixed at their forward ends to a cross member 127 on the movable assembly 125 and at their rear ends to the cross member 128 on the same movable assembly as shown in Figure 1.

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` In a first embodiment (Figure 26a) which is advantageous because it prevents the transmission of the vibrations for setting the concrete on the moulding area, bracing members 131a are welded to the metal casing 130 and pass through openings 131b in the central web. The interior of the casing 130 is filled with plastic foam material 133, for example high-der,ity polyurethane foam, which ensures the desired rigidity of the assembly as well as the joining of the central web 131 to the casing 130. The portion of the central web 131 inside the casing is less than the height of the casing.
In a particularly advantageous embodiment tFigure 26b), the central web is provided at its lower end rubbing against the moulding or work area of metal plates 3 with a wear-resistant pad 135 adapted to be removably secured to the web ` by screws (not shown).
The movable assembly 125 with front wheels 136 and rear wheels 137 is adapted to be displaced on the rails on ~`; the bed by means of a winch 140 (Figure 27) having a cable 141 secured to the forward cross member 127 or by means of a motor with reducticn gear mechanism; hydraulic braking ., .:
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: , , means 142 ~Figure 28) with linings 143 and 144 mounted on the levers 145 and 146 which are pivotally mounted on the piston-and-cylinder unit 147 is provided for fixing the movable assembly against movement on the bed during the pouring of concrete.
For manufacturing prestressed concrete elements of the same type but with different heights, the wheels 136 and 137 of the movable assembly 125 include height adjusting means (Figure 29) in which the axle 150 for the wheels 136 and 137 has an eccentric bearing relative to its end journals `. 152 and 153. The position of the axle 150 is adjusted by means of a wheel 154 fixed for rotation with the shaft 151 ,: with peripheral teeth 155, a rib carried by a frame 157 of assembly 125 as well as a blocking key 158 are adapted to . pass between adjacent teeth 155.
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.: The rear wall of the moulds for pouring concrete relative to the direction of displacement of the movable assembly 125 during the manufacture of the elements comprises a retractable flap or partition 160 for the movable assembly 125 in the immediate vicinity of the rear cross member 128 ; (Figures 1, and 30-33) in its lowered position as shown in solid lines in Figures 32 and 33 (indicated by arrows having broken lines in Fig. 1) during the pouring of concrete and in raised position as shown in phantom lines in Figures 32 and 33 (solid lines in Fig. 1) during the removal from the moulds, i.e. during the movement in the direction of the arrow _ (Figure 22) of the movable assembly 125. A stiffening plate :: 161 is welded to the rear face of the retractable flap or partition 160 which also has at its lower end vertical slots of different heights 162 and 163 (Figure 31) adapted to ~ receive for positioning the prestressing reinforcements A
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which extend from one end of the bed to the other. To complete the positioning of the reinforcements, the retractable flap 160 also comprises flat bar projections 164 mounted on the vertical spindles 165, the number of which corresponds to the number of elements to be manufactured simultaneously along the width of the bed and which may pivot when the cranks 166 connected to each other by a coupling bar 167 are moved perpendicular to the longitudinal axis of the bed.
During the pouring of concrete, the projections 164 are perpendicular to the prestressing cables A of the elements to be manufactured which are thus held captive between the projections and the slots 162, 163 in the retractable flap .j, .
while prior to the withdrawal of the moulded elements, the actuation of the bar 167 causes the spindles to rotate for bringing the projections 164 parallel to the prestressing cables, whereas the actuation of a spindle 169 fixed to a gear wheel controls the raising movement of a gear rack 171 fixed to the retractable flap 160 in slides 172.
As shown, the front ends of the moulds are formed by blocks 175 (Figures 1 and 25) having sections complementary to those of the elements to be manufactured which are fixed by the fingers or projections on a second movable assembly to ; which the cable 141a of the winch 140 is clamped; alternatively the second movable assembly is provided with a motor with a reduction gear mechanism. The blocks 175 comprise a metal web 176, steel wear resistant sleeves 177 passing through the metal web 176 for receiving prestressing cables A and a friction pad 178 at the lower end of the block 175 for contact with ; the metal plates of the moulding or work area. The web 176 and the sleeves 177 are preferably embedded in a suitable ` material 179, for example plastics material, an attachment :. ~
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~OS703Z --member 180 for the projections or fingers of the second movable assembly projects through the plastics material which may be commercially available under the trade mark "Rilsan".
Reference will now be made to Figures 35-39 which ,~ illustrate the construction and the operation of the means for feeding and distributing concrete in the moulds.
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E2. Means for Feeding and Distributing : Concrete in the moulds This principally comprises automated bucket 181 ~, 10 displaceable along a track 182 straddling the bed and driven v by a motor with reduction gear mechanism 183 supplied withcurrent through one or more electric cables 184 wound on a drum 185. The drive means is preferably two speed, the higher speed, for example in the range of 30 m/minute, is used for the displacement of the bucket between the pouring location and the concrete hopper while the lower speed, for example in the range of 4 m/minute, is used for distributing the concrete in the moulds of the bank.
. At the lower end of the bucket a pivoted drop gate 20 186 is provided enabling adjustable opening of the bucket by ........... means of a hydraulic or pneumatic jack 187 fixed to the outer :. wall 188 of the bucket carrying on its opposite wall 189 . external vibrators 190 intended to regulate and facilitate the descent of the concrete contained in the bucket. A hand , . . .
i pump accumulator 191 provides the control fluid source for ~ .
`.~ the jack ].87, adjustment being effected by a lever 192.
.'~ In addition, vibrating means for the poured concrete are fixed to the frame 193 of the bucket 181 and comprise :.,.;: vibrating shoes 195 of steel, the number of which being .~J 30 equal to that of the elements being poured along the width ?
of the bank, connected to each other, for example in groups ~ -- 1 9 --~05703Z

of four or six, by a bearing bar 196 supporting a vibration generator 197, the operating frequency of which being in the ~ range of 3000 Hz. A hood 198 protects the vibration generator 197 from straying concrete and a swinging chute 199 orientates the stream of concrete from the bucket 181 forwards or rearwards relative to the direction of forward displacement shown by the arrow d.
F. Drive Means for the Moulding Unit For the displacement of the two movable assemblies a winch device 140 is provided (Fiyure 27) with two drums 200 and 201 having a slow operating speed and high starting ~- torque. The cable 141 is wound on the drum 200 and is adapted to effect the forward movement of the movable assembly 125 whereas the drum 201 with the same operating torque but having a different rotational velocity than that of the drum 200 winds the cable 141a connected to the second movable assembly, the ends of the projections or fingers of which carry the blocks 175, the electrobrake 207 for the motor with a reduction gear mechanism of the winch device 140 maintaining . 20 the cables 141 and 141a at constant tension when the winch device is not operating. In a plant for the manufacture of ...
beams or girders of prestressed concrete by means of a plurality of beds arranged in parallel, the device 140 is preferably mounted on a track 202 perpendicular to the lontitudinal axis of the bed so that a single winch device is sufficient for controlling the moulding units on a plurality of beds, a suitable work schedule being determined ~j:
for each bed.
In order to ensure the balancing of the pulling force . . .
of the cables 141 and 141a, provision is made, parallel to the rails of the track 202, for a forward abutment rail 203 ,: .
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with which a section 204 fixed to the frame of the winch device 140 is adapted to co-operate and an anti-swing device 205 adapted to co-operate with a member 206 also fixed to the frame of the winch device.
In another embodiment of the drive means for the moulding unit (Figures 34a, 34b, 34c), the blocks 175 are integral with a portal frame 301 comprising a beam 300 extending along the entire width of the bed and lateral legs 302 in which braking means 303 for fixing the portal frame in variable positions along the length of the bed is provided. The portal frame 301 may be displaced in the direction of the arrow d which is the direction of the forward movement of the unit during manufacture of concrete elements EL, by a winch 304 fixed on the forward cross member 127 of the first movable assembly 125, the cable 305 being attached to the , beam 300. A cable 306 of a winch 307 is also attached to this beam 300. The winch 307 is fixed to the rear cross member 128 of the movable assembly 125, the rear cross member 128 being adjacent to the retractable flap 160.
Alternatively, the displacement of the portal frame 301 may be effected by rack-and-pinion means, chain means, jacks, friction rollers or the like.
G. Means for Positioning Transverse Reinforcements Beams or girders of prestressed concrete comprising longitudinal reinforcements must frequently be equipped with transverse reinforcements, known as binders or stirrups, which for elements of small dimensions may be formed as corrugated ~bars with two or three corrugations. For the positioning of the transverse reinforcements in the freshly poured concrete of the elements, there is provided (Figures 40 and 41) a device which is a box-like drum 215 in the illustrated ':
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~05703Z
embodiment, mounted for displacement on a track 211 outside the bed and comprising a portal frame 212 mounted for rotation on its vertical legs 213 and 214 perpendicular to said legs and for translation parallel to said legs. Cor-rugated transverse reinforcements at are arranged along the sides of the box and held thereon by quick opening clamping means. The number of corrugated transverse reinforcements at corresponds to the number of elements to be manufactured across the width of the bed. ~
For putting a series of binders or stirrups at in place in the freshly poured concrete, a hydraulic or pneumatic device for the portal frame 212 controls the rapid descent of the box-like drum 215 and the embedding of the transverse reinforcements by vibration after opening the clamping device.
For the positioning of a second series of transverse reinforce-ments, the box-like drum 215 rises, turns through 90 after the portal frame 212 is displaced by movement along the track 211 and a procedure similar to that which has just been described is started again.
H. Device for Heat Treatment of Moulded Elements In order to speed up the setting of the concrete of the moulded elements, it is proposed to bake them. With this - aim in mind, all the elements on the bed are covered with a tarpaulin 220 (Figure 42) of large dimensions, for example

3 x 60 m, adapted to be automatically rclled and unrolled by a carriage 221 displaceable along the rails 222. In the illustrated embodiment, the rolling and unrolling of the tarpaulin is controlled by a motor 223 housed in the drum ~i 224 on to which the tarpaulin is rolled.
In a non-illustrated embodiment, a hand wheel is used for rolling and unrolling the tarpaulin.
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~057032 The operation of the plant is described hereinbelow with reference to Figures 43 and 44 which is a plant for manufacturing beams and girders of prestressed concrete utilising the method according to the invention complete ; with superstructure.
In such a plant, two beds 250 and 251, identical to the one described hereinabove, are arranged in parallel in a building structure of the type having an umbrella-type roof 252 with curved plates of the Wonder Building (trade mark) 10 type as shown at the left in Figure 44, or light portal structural work 253 as shown to the right in the same figure.
A propped portal frame 254 mounted on a track 255 at a distance of about one metre from the ground S is used for handling while a concrete conveyor 256 is used for supplying concrete to the bucket 181 displaceable along the track 182 of the bed 250, a service track 257 is arranged adjacent to t , the track 182 for supplying raw materials to the beds 250 ; and 251 as well as removing manufactured elements and the like. The track 257 extends beyond the beds 250 and 251 at ; 20 the extreme right of Figure 54 to a storage area for manufactured elements and to the other end of the bed to the top storage areas 260 and 261 for the moulding equipment not in service and then to an area 262 for the washing of this equipment.
In the vicinity of the areas 260 and 261 and per-; pendicular to the beds 250 and 251, the track 202 along which : the winch 140 adapted to be associated with each of the ,, ,:
_moulding units operating on the beds 250 and 251 is displaceable.

For the manufacture of beams, girders or the like of .j~` 30 prestressed concrete in the plant, the prestressing cables for `` the series of elements to be manufactured are prepared by ~, .

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cutting a plurality of lengths of cable, and shaping the ends of the lengths as a rivot or head adapting them to be secured between the rectangular teeth 113a on the head for tensioning and releasing the tension in the reinforcements. The reinforce-ments which may be 60 to 100 m long are rolled in a coil which is transported, for example, by the portal frame 254 onto the bed 250. There, the ends of the cables without rivots or heads are passed through the sleeves 177 in the blocks and then are secured to one end of the bed, for example, the right-hand side in Figure 43 on a traction head or a fixed anchorage of the type illustrated in Figure 9.
. A head or comb for distributing the cables along the ;, width of the bed is associated with the movable assembly carrying the blocks 175, the displacement of the movable assembly in the direction d (Figure 43) ensures the positioning ~,~ of the cables along the bed.
, ~ The free ends of the cables are then secured to the :.
; traction head and all the cables are then simultaneously tensioned.
, ~' 20 The manufacturing area comprising metal plates 3 is i,,!,~. ~
heated.
The movable assembly 125 is, for example, at the right end of the bed and secured against movement by the braking device 142. The second movable assembly with blocks 175 is near the forward end of the movable assembly 125. The ;~ retractable flap 160 is in its lowered position thus delimiting r''l with the blocks 175, the manufacturing area and the form elements 126, the moulds into which the bucket 181 (previously charged with concrete supplied by the concrete conveyor 256) ~` 30 pours the concrete for moulding the elements.
During a first phase of the pouring of the concrete, ~` .
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: ~ ' the swingin~ chute 199 is in the position shown in Figure 38 and the concrete delivered by the bucket is immediately vibrated by the vibrating shoes 195. The bucket is displaced slowly in the direction of the arrow _, and when a certain length of the moulds are filled, the swinging chute 199 is swung to the position shown in Figure 39. The bucket 181 is then returned to its initial position by displacement in the direction of the arrow _' and then is displaced once again in the direction of the arrow d up to the forward end of the movable assembly 125 thereby moulding the first portions of the elements into which transverse binders at are introduced by means of the device 210.
~ When the bucket reaches the vicinity of the forward ; end of the movable assembly 125 which is fixed against movement, the braking device 142 is released; the hand wheel is manoeuvred and the retractable flap 160 is raised while simultaneously the actuation of the bars effect the rotation of the spindles 165 which brings the fingers or projections 164 parallel to the prestressing reinforcements. In the case of a plant in which the drive means for the moulding unit comprises a winch device 140, this winch device 140, which was rolled along the track 202 opposite the bed then in operation, is driven by means of the drum 200, displacing the movable assembly 125 in the direction of the arrow _, the second movable assembly with blocks 175 remaining fixed against movement.
The withdrawal of the first portions of the moulded elements is thus ensured after the second movable assembly _with blocks 175 is also displaced forwardly by the operation of the drum 201 of the winch device 140, further portions of elements are moulded according to the procedure which has just been described.

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~L05703Z
In a plant in which the drive means for the moulding unit is as shown in Figures 34a, 34b, 34c, the withdrawal of the first portions of the moulded elements is effected by the winch 307, the braking device 142 being released while the braking device 303 of the portal frame 301 is applied.
When the movable assembly 125 has been displaced the requisite distance, the braking device 142 is applied, the braking device 303 released and by the operation of the winch 304 and the portal frame 301, to which the blocks are fixed for move-ment, is displaced in the direction of the arrow _, and so on.
The recharging of the bucket 181 with concrete ispreferably effectuated during periods for removing the moulded elements from their moulds by high speed displacement and charging by the concrete conveyor 256, and then high speed return along the axis of the bed which the concrete which has just been charged is to be poured.
, After pouring the total concrete necessary for the . moulding of the elements, the thermal insulating tarpaulin ,~ 220 is brought over the bed on which the elements are ;~, supported, the enclosure formed by the bed and the tarpaulin is heated according to a predetermined adjustable cycle.
; When the concrete has sufficiently hardened, the means for tensioning and releasing the tension in the pre-stressing reinforcements are rendered operative and after rolling away the tarpaulin 200 by means of the motor 223, the ~, manufactured elements are removed from the bed by conventional means with which the plant is equipped.

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Claims (29)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1.- A method of manufacturing a series of elongate concrete construction elements by manufacturing successive portions of said elements comprising :
i- molding a portion of each element by pouring concrete into a molding unit comprising, located on a molding area, a front wall and a retractable rear wall arranged across the molding area and a series of mutually parallel formers extending along the molding area and constituting lateral walls between the front and the rear walls to form a series of molds, said walls being adapted to move on the molding area;
ii- vibrating the poured concrete;
iii- after the concrete has sufficiently hardened, retracting the rear wall of the molding unit;
iv- displacing with a translatory movement the lateral walls along the molding area to leave behind molded portions of the elements while maintaining stationary the front wall;
v- displacing with a translatory movement the front wall along the molding area up to the successive portion;
vi- molding a successive portion of each element by pouring concrete into the space provided between the front wall, the lateral walls, the front ends of the already cast portions and the molding area;
vii- vibrating the poured concrete;
viii- molding successive portions of each element in the same manner until a desired length of element has been obtained;
and ix- eventually heating the elements to harden the concrete.

2.- A method according to claim 1, wherein before the pouring of concrete, prestressing reinforcements are positioned above the molding area and then tensioned, the tension in the reinforcements being released after step ix-.

3.- A method according to claim 2, wherein additional reinforcements are inserted crosswise in each molded element by vibration before the concrete has hardened.

4.- Apparatus for manufacturing a series of elongate prestressed concrete construction elements comprising :
i) a manufacturing bed designed to absorb the compressive forces developed during the manufacture of the elements;
ii) an elongate molding area above the bed;
iii) means for heating the molding area;
iv) a series of molds comprising a plurality of lateral walls fixed on a first movable assembly mounted for translatory movement along the bed, said assembly having at its rear end -relative to the direction of displacement along the bed during manufacture- a retractable flap adapted to form the rear wall of the molds, and front walls constituted by the ends of arms of a second movable assembly, said arms being located between the lateral walls;
v) means with vibrating members for feeding and distributing concrete into the series of molds;
vi) means for displacing the movable assemblies independently from each other in a direction parallel to the lateral walls, so that the second movable assembly remains stationary during the forward displacement of the first movable assembly, the retractable flap having been raised before this forward displacement and so that after displacement of the first movable assembly, said second movable assembly can be displaced forwardly.

5.- Apparatus as claimed in claim 4, further comprisi means for positioning reinforcements along the area and a series of reinforcement tensioning devices including hydraulic jacks and safety means to prevent release of reinforcement tension in the event of hydraulic failure.

6.- Apparatus as claimed in claim 5 and including means moveable along the molding area to vibrate additional reinforcements crosswise into each molded element.

7.- Apparatus according to claim 4 and further comprising means for covering the entire area on which the molded, partially hardened concrete elements are supported, the covering means including a thermal insulating tarpaulin and a carriage for effecting the automated rolling and unrolling of the tarpaulin.

8.- Apparatus according to claim 5, wherein each tensioning device comprises a traction head pivotally mounted at its lower end on the bed, the traction head having rectangular teeth and cut-outs for positioning and removably securing the ends of the prestressing reinforcements thereon.

9.- Apparatus according to claim 4, wherein the moving means for displacing the two moveable assemblies comprises a double-drum winch device.

10.- Apparatus according to claim 4, wherein the moving means for displacing the two moveable assemblies comprises two winch devices respectively at the front and rear ends of the first assembly, cables for the winch device being attached to the second assembly which is provided with braking means.

11.- Apparatus according to claim 5, wherein said safety means for the hydraulic jacks comprises screw-and-nut means for actuating cut-off switches for electric current supplying hydraulic pump motors operatively connected to the jacks.

12.- Apparatus according to claim 4, wherein said first moveable assembly has means for adjusting the height above the molding area of the walls of the mold carried by the moveable assembly.

13.- Apparatus according to claim 12, wherein the mc able assembly has wheels and the means for adjusting the height of the walls of the molds comprises eccentric members on axles for the moveable assembly's wheels.

14.- Apparatus according to claim 5, wherein the tensioning devices for prestressing the reinforcements are driven by double-action hydraulic jacks, the piston rods of the jacks being pivotably mounted on the legs of a pivoting portal frame, the jacks being secured to a beam which bears against the bed and guide means for the prestressing reinforcements being carried at the upper end of the beam.

15.- Apparatus according to claim 4, wherein the bed comprises a beam or a slab extending along its entire length, piers or end masses distinct from the beam or slab being located at the ends thereof.

16.- Apparatus according to claim 15, wherein the piers are interconnected by tie rods.

17.- Apparatus according to claim 15, wherein the beam or slab constitutes the major portion of the bed and is broken up into sections by pits or wells forming the positions for housing the tensioning devices so that the effective operating length of the bed can be changed.

18.- Apparatus according to claim 4, wherein the molding area is constituted by metal plates joined together with screws having countersunk heads and with pins for absorbing the shearing stress caused by expansion of the plates.

19.- Apparatus according to claim 4, wherein the means for heating the molding area comprises a group of pipes for circula-ting hot water and water chests at the ends of the bed connected to the pipes by means of sliding expansion seal means.

20.- Apparatus according to claim 4, wherein the means for heating the molding area comprises resistance heaters arranged under the metal plates of the molding area, the metal plates being supported on a bed of dry sand.

21.- Apparatus according to claim 4, wherein the pa llel formers constituting the lateral walls of the molds comprise metal casings filled with plastics foam material.

22.- Apparatus according to claim 21, wherein walls of the metal casings are interconnected with tie rods passing through openings in a central stiffening web, the height of the web inside its casing being less than the total height of the casing.

23.- Apparatus according to claim 21, wherein the metal casing comprises two shells welded together on a central, stiffening web, the lower end of the web extending beyond the casing to co-operate with the molding area and being provided with a removable wear-resistant pad.

24.- Apparatus according to claim 4, wherein the ends of arms of the second moveable assembly which form the forward walls of the molds carry blocks having sections complementary to those of the elements being manufactured with wear-resistant sleeves passing longitudinally therethrough for receiving the prestressing reinforcements for the elements being manufactured.

25.- Apparatus according to claim 4, wherein the retractable rear wall is mounted for translatory movement perpendicular to the direction of movement of the first moveable assembly.

26.- Apparatus according to claim 4, wherein the means for feeding and distributing the concrete comprises a bucket, means for displacing the bucket at two different speeds along the bed, and vibrating shoes fixed thereto connected to vibration generators.

27.- Apparatus according to claim 26, wherein the bucket for supplying and distributing the concrete has at its lower end a swinging chute for orienting the stream of concrete discharged from the bucket.

28.- Apparatus according to claim 6, wherein the means for vibrating in crosswise reinforcements comprises, on a portal frame displaceable along the bed, a drum-like device mounted for rotation perpendicular to the legs of the portal fram nd mounted for translation parallel to the legs of the portal frame and means for applying vibrations for introducing the reinforce-ments into newly poured concrete.

29.- Apparatus according to any one of claims 4, 5 or 6, comprising a plurality of beds and apparatus therefore, a winch device, for pulling on the moveable assemblies, mounted on a track across the length of the beds, handling means, and means for supplying concrete to the bucket provided for each of the beds.