GB2031331A - Method and apparatus for producing reinforced concrete panels - Google Patents

Abstract

Apparatus and a method is disclosed for producing reinforced concrete panels having a number of vertical spaced-apart through-bores. The method comprises the steps of arranging a set of cores 18 corresponding to the through-bores in a compartmented concrete slab mold 5, positioning the iron reinforcement, and casting a fluid concrete mortar which is vibrated, and vertically removing the cores simultaneously after the concrete mortar has partially set. <IMAGE>

Description

SPECIFICATION Method for producing reinforced concrete panels and apparatus for performing such method This invention relates to a method for the production of reinforced concrete panels for the.

building industry, which have vertical, spaced apart through-bores having parallel axes, and to an apparatus for performing said method.

In the building industry the use is ever and ever becoming widespread of prefabricated reinforcedconcrete panels or wall slabs having a height equal to the height of a building floor, these panels having through-bores along their entire height which are parallel and spaced apart. These through-bores, in addition to reducing the own weight of each panel considerably, with conspicuous advantages to the end of the manipulation and shipping, serve, in part, as moulding spaces for casting concrete in situ or for receiving pipes and the like.

There is an interest in increasing to the utmost the cross-sectional areas of the through-bores or void spaces while minimizing the concrete thickness to a value which is the acceptable minimum for making possible a convenient handling of the panels.

The production of panels of the kind referred to above, which have a monolithic structure, involves a number of problems in view of the requirement of forming in the concrete casting a considerable number of bores or void spaces through the entire height, which necessitate the presence in the mold of an equal number of cores, so that the area of contact between the concrete and the surfaces of the mould and the cores becomes very wide: unmoulding the cast panels becomes thus a problem and a hazardous operation since there is the danger of collapsing the panel as the cores are withdrawn therefrom.

The problem becomes still more intricate in that reasons of economy and quick processing require that the cores may be slipped all at a time from casting in which they were inserted. On bearing in mind that the panels can be 3 metres tall and over and up to 6 metres long, with upto 30 throughbores in the sense of the height, it becomes easy to appreciate the difficulties to be overcome whenever it is desired to produce such a panel of reinforced concrete.

Attempts have been made to carry out the casting in horizontally laid down molds, but such a procedure has not given satisfactory results, also because this method makes it possible to have only one of the two principal surfaces of the panel in a smooth condition. In addition, such a procedure requires very intricate apparatus which are bulky and expensive and does not allow safely to carry out the unmoulding without hazard of damaging the piece. Lastly, this method permits to produce only those panels which have throughbores of a round cross-sectional outline.

An object of the present invention is thus that of providing a simple and reliable method, by which it becomes possible to produce monolithic reinforced concrete panels, said panels having a plurality of parallel vertical bores and having also the minimum concrete cross-sectional area which is required for permitting their handling.

In order that such an object may be achieved, it has been envisaged to produce such panels by vertical casting but it has been ascertained that this is possible only if certain conditions, which are critical to the end result aimed at, must be abode by.

In the first place the composition of the concrete compounds to be used for vertical casting has proven to be a decisive factor. More particularly, it has been ascertained that the compounds to be used for producing such bored panels by vertical casting are to fulfil at the same time the requirement of a high fluidity and that of a high resistance to compression. These requirements are self-contradictory and conflict with the advisability of using lightweight fillers if it is desired to minimize the panel own weight.

Another critical factor is the setting time of the concrete mortar: on the one hand, this time must be such as to permit the completion of the casting within the requested time without having the setting started, and, on the other hand, it must permit that the resistance necessary for the article to be unmold and handle it may be reached within a reasonably short delay.

The most critical time at which the cores inserted in the casting must be withdrawn by pulling them upwards is bound to the setting time of the mortar, and the procedure of such core withdrawal is likewise critical.

The method according to the invention for the production of reinforced concrete panels having vertical spaced apart through-bores comprise the steps of arranging in a vertical mold parallel and spaced apart cores each having a transversal cross-section either rectangular or square corresponding to the cross-section of the relative through-bore to be provided through the panel, arranging an iron reinforcement in the spaces between the mold wails and the core spaces, casting from above a fluid mortar of concrete in said first named space, causing the ramming of the mortar by vibration, vertically withdrawing the cores after a first setting time and unmolding the panel after a further setting time of the concrete mortar.

More particularly, such method is characterized in that a concrete mortar is employed which, at the cone test, shows a lowering of the cone of about 20 cm, and which has after 1 6-18 hours as from casting, and after 28 days as from casting has a resistance to compression of about 40 kg/cm2, and of at least 250 kg/cm2, respectively, and which after a setting time of from 2 hour to 4 hours from the completion of casting the cores are withdrawn. The cores have a cross-sectional outline which is slightly tapering towards the end away of the pulling end, the pulling taking place by simultaneously drawing up vertically the cores at a maximum speed, at least as the pulling beings, of 25 cm/minute, while the unmolding of the panel is carried out subsequently within 1 6 to 18 hours as from the completion of casting.

In order that the requirements of a high fluidity and a high resistance indicated above may be simultaneously fulfilled, the concrete mortar can be properly prepared by the use of conventional fiuidizers which permit to reduce the watercement ratio while affording the requested fluidity for the mortar.

In addition, the concrete mortar has, advantageously, a content of conventional accelerators which are capable of starting the setting not immediately but rather after the time required for completing casting and also adapted to have the mortar reaching the necessary resistance (about 40 kg/cm2) for unmolding and handling within 1 6-18 hours as from the completion of casting.

The appropriate selection of the fillers in the mortar permits that the specific gravity of the panel may be varied, while still fulfilling the fluidity and resistance requirements aforementioned.

By way of example, the following reports two composition of concrete mortars which have given very good results in their use as provided according to the method of the present invention.

COMPOUND 1 light mortar, spec.gr. y = 1,600 kg/m3 based on expanded clay: Cement type 425 450 kg/m3 Sand O to 3 mm grit 380 kg/m3 Expanded clay 1-3 mm grit 220 kg/m3 Expanded clay 3-8 mm grit 350 kg/m3 Water 250 litres/m3 Accelerator and fluidizer variable proportions relative to the weight of cement.

COMPOUND 2 Light mortar having density of y = 2000 kg/m3 based on loose filler of volcanic origin of the type of lava splinters: cement type 425. 425 kg/m3 Sand 0--3 mm 700 kg/m3 Lava splinters (lapilli) 700 kg/m3 Water 220 kg/m3 Accelerator and fluidizer variable proportions relative to the weight of cement.

The selection of the instant of time at which the simultaneous removal of the casting cores and the procedure of unslipping take a considerable importance in the method according to the invention.

As a matter of fact, while a premature withdrawal may cause, due to the adhesive tension between the cores being moved and the concrete surface, the collapse of the article, on the other hand, if the withdrawal is delayed too much, there is the hazard of having the cores permanently embedded in the casting so that it becomes impossible to pull them out.

The withdrawal speed is likewise important as it must not exceed the maximum indicated value, at least during the initial pulling until the cores have been unstuck from the walls of the bores formed by the cores in the casting. It should be observed that the cores are formed, advantageously, by sheet-metal tubes having a square or rectangular outline in cross-section, which are slightly tapered towards their end away of the end at which they are grasped for being pulled up.

For a height of about 3 metres of each tube, the difference in length between a side of the largest section and a side of the smaller one is for example 1 cm.

Advantageously enough, the cores are sprayed with a mould release oil which facilitates the release of concrete.

All the cores for the same panel are ganged together by a connection strut, so that their insertion in the mold, and their removal, take place concurrently.

For an appropriate production of bored panels with the method of the invention, there is used a suitable apparatus which is composed by a vertical assembly comprising a plurality of compartments which can be matched side by side in any desired number, each compartment having associated therewith integral set of parallel cores arranged at modular spacings and slightly tapered in a direction opposite to that of pulling out, the bottom walls of said compartments being formed by level-adjustable metal sheets which are foraminous, such perforations being intended to receive in a sealtight manner the bottom ends of the cores, on the tops of the sidewalls of the assembly vibrators being applied, means being provided in correspondence with the assembly headers for effecting vertical displacements, said means being capable of acting on the coreganging struts.

An exemplary embodiment of the apparatus according to the invention will now be described in more detail with reference to the accompanying drawings which are a diagrammatical showing of the vertical assembly.

In the drawings: FIGURE 1 is a cross-sectional view taken along the line I-I of FIGURE 2.

FIGURE 2 is a lengthwise cross-sectional view taken along the line Il-Il of FIGURE 1, and FIGURE 3 is a horizontal cross-sectional view taken along the line Ill-Ill of FIGURE 2.

The apparatus illustrated in the drawings comprises a supporting structure 1 with runway 2 for an overhead traveling crane 3, equipped with a pulley 4 with a lifting hook.

The overhead crane with its lifting hook is intended, as disclosed in detail hereinafter, to shift and to insert in a mold the tubular cores intended for forming the vertical through-bores in the casting.

The mold is a vertical assembly, generally indicated at 5 and comprises a plurality of compartments which can be matched side by side.

There are provided a longitudinal fixed closure wall 6, a longitudinal movable closing wall 7 and movable longitudinal partition walls 8. Wail 6 is solid with a fixed structure 9 and wall 7 is integral with a movable structure 10 carried by carriages 11 sliding over sliding guideways 12. The partition walls 8, in their turn, are movable by the agency of carriages 13 which are slidable on the guideways 12 aforesaid so as to vary the lengths of the compartments.

The latter carriages 1 3 carry also supporting channel irons 14 for adjustable spacers 1 5, on which foraminous sheet metal bottom plates 1 6 rest: these are the level-adjustable bottom wall of each compartment of the assembly.

Laterally, the compartments are closed by sidewalls 17 which can be removed and latched by the agency of conventional mechanisms, not shown.

The longitudinals 6, 7 and 8 can be latched to one another and relative to the fixed structure 9 by other conventional mechanisms, not shown.

In each compartment of the assembly, a set of tubular cores 18 is intended to be inserted, each set being comprised of a number of cores which corresponds to the number of perforations of the bottom walls 16 and the cores of every set are borne by a top strut 1 9. It is thus possible to transfer by the overhead crane 3 and its lifting hook a set of tubular cores 1 8 over a compartment of the assembly to insert the cores in said compartment.

As can be seen in FIGURES 1 and 2, the bottom ends of the tubular cores 18 are tapered and thus can be inserted to provide a tight seal into the holes of the bottom elements 16. Thus, a correct centering is obtained for the core set in the compartment of the assembly.

It is to be noted moreover. that each tubular core 1 8 has a cross-sectional outline, for example square as shown in the drawing, or rectangular, which slightly tapers evenly from the top end to the bottom end.

The struts 19 carrying the core set 18 have such a length that their ends jut laterally from the sidewalls 17 when the cores are inserted in the assembly compartments.

This circumstance enables beams 20 arranged in correspondence with the assembly headers and liftable by appropriate mechanisms, such as hydraulic jacks 21, to lift all the struts 19 carrying the cores 1 8 simultaneously in order to withdraw the cores from the concrete casting.

It should be noted, lastly, that the assembly is equipped with vibrators 22 applied, for example, on the top section on the sidewalls of the assembly, to ram the cast concrete.

Each compartment of the assembly can be transversally partitioned into a number of chambers by means of special separators having a cross-section slightly wider than the cross-section of the cores. By so doing, it is possible to obtain more than one panel in the same compartment.

These separators (not shown) are arranged in the desired position in the compartment to receive one of the cores of the set which is inserted in the compartment concerned.

It is noted, moreover, that the sidewalls 1 7 are ,hollowed out at the top (FIGURE 1) to receive the ends of the connection struts 1 9 which carry the cores 1 8. By so doing an upper gutter is provided on the panel, so as to permit to cast a reinforced kerb in position.

In the vertical assembly described above, the cores are inserted from above into the several compartments and, once the casting has been completed and the appropriate time of partial set has elapsed, the cores are unslipped upwards.

Anyone skilled in the art will readily appreciate that such an arrangement can also be inverted in the sense of placing at the top the vertical assembly and inserting the cores from below. In this case, unslipping takes place downward and can be obtained by free fall. This embodiment of the apparatus can further reduce the hazard of damage to the panel during unslipping of the cores all at a time and permits to obtain panels having even smoother external walls.

In the latter case, it is apparent that the cores must be tapered upward while the connection struts of the several core rows will be placed below and will be connected all together by a monolithic structure, so that also in the course of insertion of the cores in the assembly compartments all the cores are moved simultaneously by appropriate lifting mechanisms.

The top connection struts of the first embodiment of the apparatus will be separated in this second case from the core and will be intended exclusively for providing the top gutters in the panels. These top struts will thus be inserted discretely in the specially provided seats of the compartment sidewalls.

it should be observed, lastly, that these top struts may have appropriate centering hollows for the individual cores, which, to this purpose, may be terminated at the top with a point having an appropriate conical outline.

The foregoing disclosure makes conspicuous the numerous technical advantages achieved with the method and the apparatus according to the present invention, these advantages essentially consisting in the fact that it has been made possible, for the first time, to produce rationally and with the safety which is essential for a mass production on an industrial scale, large panels having a considerable number of perforations and the wall thickness of which is minimized to ensure their integrity during handling.

While preferred embodiments of the invention have been shown and described, be it understood that modifications and changes can be introduced therein without thereby departing from the scope of this invention.

Claims (12)

1. A method for the production of reinforced concrete panels for the building industry, having vertical spaced apart through-bores, characterized in that it comprises the steps of arranging in a vertical mold parallel spaced-apart cores having each a cross-sectional outline which is either square or rectangular corresponding to the cross- section of the relative through-bore to be formed in the panel, placing in the spaces between the mold walls and the cores an iron reinforcement, casting from above a fluid concrete mortar in said spaces, causing the ramming of the mortar by vibration, withdrawing vertically the cores from the casting after a first setting time and unmolding the panel after a further setting time of the concrete mortar.

2. Method according to Claim I,characterized 1, characterized in that a concrete mortar is employed, which at the cone test has a cone lowering about 20 cm and which at 16-18 hours and at 28 days as from casting has a resistance to compression of about 40 kg/cm2, and of a least 250 kg/cm2, respectively.

3. Method according to Claim 2, characterized in that a concrete mortar is used which contains fluidizers and/or accelerators.

4. Method according to Claim 1, characterized in that the vertical simultaneous withdrawal of the cores having a tapered cross-section towards the end opposite to the withdrawal end is carried out after a setting time of from T hour to 4 hours from the completion of the casting art a maximum withdrawal speed, at least in the initial section, of 25 cm/min, and in that the unmolding of the panel is carried out within 1 6-1 8 hours as from the completion of casting.

5. An apparatus for performing the method according to the preceding Claims, characterized in that it is composed by a vertical assembly comprising a plurality of compartments laid side by side and capable of being united in a variable number, each compartment being associated to a monolithic set of parallel cores arranged at modular distances from each other and tapered slightly in a direction opposite to the direction of withdrawal of the cores, the bottom walls of said compartments being formed by level adjustable formaminous metal sheets, in the perforations of which are intended to enter in a sealtight manner the lower ends of the cores, on the top portion of the assembly sidewalls there being applied vibrators and in correspondence with the assembly headers there being provided means for verticaily displacing which are adapted to act upon core-connecting struts.

6. Apparatus according to Claim 5, characterized in that the assembly is composed by longitudinal closing walls, one at least of which is movable and by longitudinal walls also movable, and also by removable sidewalls, latching means being provided for latching together the several walls.

7. Apparatus according to Claim 6, characterized in that the sidewalls have at their tops seatings adapted to receive overhead beams.

8. Apparatus according to Claim 5, characterized in that the vertical assembly is located in a lower position and that rows of parallel cores connected together by upper connection beams can be inserted from above into the assembly compartments.

9. Apparatus according to Claim 5, characterized in that the vertical assembly is situated at a top position and that rows of parallel cores connected together by lower connection struts can be inserted from below into the assembly compartments, the connection struts of the cores of the several rows being connected together also by transversally arranged structures.

10. A method for the preparation of reinforced concrete panels, substantially as hereinbefore described with reference to the accompanying drawings.

11. Apparatus for the production of reinforced concrete panels, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

12. Any novel feature or combination of features disclosed herein.