AIR BAG FOR PUSHING DOWN STONE SLABS DESCRIPTION

Field of the invention

The present invention relates to stone mining and, more in detail, the invention relates to the detachement of stone slabs, for example marble, granite, from a wall of a quarry.

The invention relates, in particular, to a reinforcement system for an air bag for widening the cut slits and for pushing down stone slabs.

Description of the prior art

In stone quarries, stone slabs are cut from rocky walls and eventually pushed down starting from a vertical orientation to a horizontal one by means of various devices including inflatable plane air bag. These air bags, which are initially flat since air-free, are inserted from the top of the slab into a cut slit created by quarry cutting systems.

The air bags are then inflated to a certain pressure so that a progressive increase in volume and their higher position relative to the basis of the slab produces an enlargement of the slit and/or a tilt of the slab which gradually detaches from the wall of the mountain by rotating down to a horizontal position. An example of such air bags is described in ITPI20080090 and ITPI200901 12.

The main disadvantage of the above-mentioned inflatable devices are frequent perforations, which predominantly occur at the corner zones of the plane air bags. Normally, the air bags are obtained by coupling two planar layers made of fibre-reinforced plastic used for example for inflatable boats and therefore with high resistance. Despite this, after short periods of use, perforations still occur close to the corner zones because they are caused by high stresses due to both the "spreading" effect of the pressurized air in the corner zones and the exposure to friction between the edges and the sharp rock.

Moreover, air bags with circular symmetry are known specifically designed for breaking rocks in stone quarries, as described for example in WO9203635. Such devices, once put into cylindrical holes cut in the rock, are gradually inflated so that their progressive increase in volume produces a distributed load on the cylindrical wall up to cracking the stone around it.

However, these air bags are not suitable to be put into a plane cut slit for pushing down stone slabs.

Summary of the invention

It is therefore a feature of the present invention to provide an air bag for pushing down stone slabs that has not the above-mentioned disadvantages of perforations.

It is another feature of the present invention to provide an air bag for pushing down stone slabs that can be put into narrow plane cut slits.

It is still a feature of the present invention to provide an air bag for pushing down stone slabs that do not decrease its inflating capacity and the capacity of pushing down cut slits with respect to the prior art air bags.

It is a further feature of the present invention to provide an air bag for pushing down stone slabs that have a low production cost.

These and other objects are achieved by an air bag for pushing down stone slabs, comprising at least two overlapped flexible plane layers welded to each other, the air bag configured to be put into a plane cut slit between a quarry wall and a cut stone slab and to be inflated in such a way to push down the stone slab, the flexible plane layers forming a corner zone.

At least one couple of stiff block elements is arranged at the corner zone, external to the plane layers, and arranged to press firmly the layers against each other at the corner zone.

With respect to the prior art, as described in ITPI20080090 and ITPI200901 12, the force exerted by the block elements against the flexible plane layers of the air bag causes a remarkably increase in the widening resistance at the corner zone.

A further advantage provided by such a block elements is to protect the corner zone from collisions and rubbings.

Moreover, the block elements do not cause a substantially increase of the air bag thickness, allowing the air bag to be positioned into thin slits between the quarry wall and the slab wall.

Considering the prior art device described in WO9203635, an inflatable cylindrical element is configured to be put into cylindrical holes cut in the rock for breaking it by increasing cy!indrica!!y lis volume. Conversely, in the present invention, two flexible plane layers allow the air bag, when deflated, to be put into a plane cut slit and to be inflated in such a way to cause the whole layers to bear a uniform distributed load. This effect is not achievable by the cylindrical device described in WO9203635, because the radial expansion of the cylindrical device within a plane cut slit would cause a stress concentration only along the narrow regions around a generatrix of the cylindrical element in contact with the wall of the slit. Therefore, the air bag described in WO9203635 is designed only to uniformly act on the cylindrical wall of a hole and due to its reduced load it is not suitable for overturning stone slabs.

In a possible exemplary embodiment, the stiff block elements comprise a couple of plates configured to press between each other the two overlapped flexible plane layers, and a tightening element wich is arranged to tighten the plates to each other, in order to press with a predetermined force the layers between the plates.

Advantageously, the tightening element is a screw comprising a screw threaded stem and a head, and a first plate of the plates has a hole with a housing for the head, and a second plate of the plates has a screw threaded hole for engaging with the screw threaded stem.

The presence of the screw allows to apply high tightening force between the plates, with minimal amount of space and reducing costs.

In a possible exemplary embodiment, the second plate has a sleeve- shaped protrusion oriented in use towards the first plate, and the screw threaded hole extends within the sleeve-shaped protrusion.

This way, the sleeve-shaped protrusion exteds the grip length of the thread in an inner zone comprised between the two layers, without casing the air bag thickness to increase.

In a possible exemplary embodiment, the plates have triangular shape, arranged to fit the triangular shape at a right angle of the corner zone of an air bag of square or rectangular shape.

In another exemplary embodiment, the plates have substantially rectangular shape, in order to cross at an angle the corner zone of the air bag.

In another exemplary embodiment, the plates are formed as several couples of plates, which can be fixed in couples to block the layers. In an exemplary embodiment of the invention, wherein the plane layers are pre-apertured in the corner zone to allow an insertion movement of the tightening element. This avoid the screw to lacerate the air bag.

In another exemplary embodiment of the invention, the plane layers are pre-apertured in the corner zone to allow an insertion of the sleeve-shaped protrusion. This allows a simple and accurate assembly.

In an exemplary embodiment of the invention, at least one of the plates presents a recess for housing a head of the tightening element, in particular a frustum conical headed screw. This embodiment reduces the overall thickness of the plates in order to allow the air bags to be put into cut slits of a few centimeters.

Brief description of the drawings

Further characteristic and/or advantages of the present invention will be made clearer with the following description of an exemplary embodiment thereof, exemplifying but not limitative, with reference to the attached drawings in which:

- Fig. 1 shows a perspective view of the operation of overturning stone slabs by means of inflatable air bags;

- Fig. 2 shows a perspective view of an air bag for pushing down stone slabs, according to the invention, comprising a corner zone; - Fig. 3 diagrammatically shows a perspective view of a corner zone of an air bag for pushing down stone slabs, according to the invention;

- Fig. 4 diagrammatically shows a perspective view of a couple of block elements, according to the invention;

- Fig. 5 diagrammatically shows a top plan view of the corner zone of an air bag for pushing down stone slabs, according to the invention;

- Fig. 6 diagrammatically shows a cross section of the corner zone of an air bag for pushing down stone slabs, according to the invention, comprising two flexible plane layers overlapped to each other and a couple of block elements;

- Fig. 7 shows a cross sectional view of a first block element, according to the invention;

- Fig. 8 shows a cross sectional view of a second block element, according to the invention; - Fig. 9 diagrammatically shows a perspective view of an exemplary embodiment of the corner zone, according to the invention, of an air bag for pushing down stone slabs;

- Fig. 10 diagrammatically shows a perspective view of a further exemplary embodiment of the corner zone, according to the invention, of an air bag for pushing down stone slabs.

Detailed description of some exemplary embodiments

Fig. 1 diagrammatically shows the extraction 100 of stone blocks of prior art. Generally, a compressor 120 pumps air into plane air bags 1 10 which are put into a cutting slit 150 of a slab 130 of a mountain wall 150 created by quarry cutting systems. Plane air bags 1 10 are put into cutting slit 150 from the top of slab 130.

This way, when air bags 1 10 are inflated, their progressive increase in volume and their higher position relative to the basis of slab 130 produces an enlargement of the slit and/or a tilt of slab 130 which gradually detaches from the wall of the mountain. In some cases, as described in ITPI20080090 and ITPI200901 12, to cause the detachement of stone slab additional air bags are added into enlarged cutting slit 150.

Fig. 2 shows a plane air bag 1 10 comprising a corner zone 200. Air bag 1 10 comprises two flexible plane layers 1 1 1 , 1 12 overlapped and welded to each other. According to the invention, figure 2 shows four reinforced corner zones. Alternatively, it is possible to reinforce one, two or three corner zones.

In particular, air bag 1 10 shown in figure 2 is arranged to be placed into a cutting slit 150 (Fig. 1 ) of a stone slab 130 and to be inflated in such a way as to overturn stone slab 130 form quarry wall 140. Each reinforced corner zone 200, including block elements 210, 220, is configured to have an overall thickness less than the overall thickness of the cutting slit in which air bag 1 10 will be placed.

As shown in Figs. 2 and 3, one couple of stiff block elements 210, 220 external to plane layers 1 1 1 , 1 12 provide a reinforced system configured for tightening corner zone 200.

In particular, stiff block elements 210 and 220 are a couple of plates configured to sandwich between each other the two overlapped flexible plane layers 1 1 1 , 1 12. Stiff block elements 210 and 220 are pressed against layers 1 1 1 , 1 12 by means of a tightening element 230 which is arranged to block plates 210 and 220 to each other with a predetermined force. In particular, tightening element 230 is a screw comprising a screw threaded stem and a head, for example with a slot head or a phillips head or an exagon head for a screw driver or a hex key. Alternatively, the tightening element can be a nail or a pin connected by means of riveting or gluing. Both plates 210 and 220 can have a planar surface. A first plate 210 has a hole 21 1 with a housing for the head of screw 230, and a second plate 220 has a screw threaded hole 221 for engaging with the screw threaded stem in order to provide a desired tightening force.

Moreover, layers 1 1 1 , 1 12 can be pre-apertured in corner zone 200 to allow the passage of screw 230.

In a possible exemplary embodiment, for example as shown in Figs. 4-8 a first plate 210 has a hole 21 1 with a housing for a countersunk screw 230, and a second plate 220 has a screw threaded hole 221 with a sleeve-shaped protrusion 222 for engaging with the screw threaded stem.

In particular, the sleeve-shaped protrusion is configured to be oriented in use towards first plate 210, and screw threaded hole 221 extends within the sleeve-shaped protrusion.

The two layers 1 1 1 and 1 12 can be pre-apertured in the corresponding corner zone 200 in order to allow introduction of tightening element 230 and sleeve-shaped protrusion 222.

In the exemplary embodiments of Figs. 3-8 plates 210 and 220 can have triangular shape, arranged to fit the triangular shape at a right angle of the corner zone 200 of air air bag 1 10 of square or rectangular shape.

As shown on Fig. 6, plane layer 1 12 can be pre-apertured in the corner zone 200 to allow the passage of sleeve-shaped protrusion 222.

In another exemplary embodiment of Fig. 9, plates 210 and 220 (the latter not visible) can have substantially rectangular shape, in order to cross at an angle the corner zone 200 of the air bag. In this case, plates 210 and 220 can have several tightening elements 230, in particular screws that can screwed at a same side or at opposite side.

In another exemplary embodiment shown in Fig. 10, plates 210 are formed as several couples of plates, which can be fixed two-by-two to block layers 1 1 1 , 1 12. The foregoing description of some exemplary specific embodiments will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt in various applications the specific exemplary embodiments without further research and without parting from the invention, and, accordingly, it is meant that such adaptations and modifications will have to be considered as equivalent to the specific embodiments. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation.