Machine for producing metal fiber and relative production method

FIELD OF THE INVENTION

The present invention concerns a machine, and the relative method, for producing metal fiber to be used as a reinforcement element in concrete casts in the production of reinforced concrete works, particularly floors or coverings.

BACKGROUND OF THE INVENTION

Metal fiber is known, used as a reinforcement element in reinforced concrete structures such as floors, coverings, slabs, concrete beds or suchlike. The metal fiber consists of small shaped pieces of metal wire, usually with a hook shape at the ends, for example of a length from 20 mm to 70 mm and with a diameter of from about 0.6 mm to 1.0 mm, which are mixed with the concrete and which replace the metal mesh normally used.

An example of such metal fiber is shown in fig. 1 of EP-A-0.475.917.

These pieces of metal wire normally have the shape of a broken line, in order to guarantee a better adherence with the concrete and hence to confer greater resistance and rigidity, particularly with reference to compression, to the structure to be made.

Metal fiber is normally produced by means of machines comprising a drawing and shaping assembly and a cutting assembly.

The drawing and shaping assembly consists of one or more pairs of counter-rotating toothed wheels or rollers, or differently shaped, which draw and simultaneously shape a plurality of metal wires disposed one adjacent to the other.

The cutting assembly is located downstream of the drawing and shaping assembly and performs the cutting to size simultaneously of all the wires being worked.

A machine is also known, from the US patent US-A-3,199,175, usable for the zig-zag shaping of metal wires, which comprises two shaped tracks, counter-rotating and opposite each other, on which triangular shaping tools are mounted with reciprocally facing tops. The tools of one track are mounted off-set by half a pitch with respect to the tools of the other track, so that by gripping the metal wires between them they determine the formation of the zig-zag conformation.

The machine described in US-A-3,199,175 is effective only when it is making a shape on the wires, for example to make a toothing, a zig-zag or suchlike, which is repeated constantly for the whole length of each single piece of metal wire and is without rectilinear segments of a certain entity between one shaped part and the other.

However, if the shape provides, for example, a rectilinear segment with a hook shape only at the ends, a machine like the one described in US-A-3,199,175 cannot be used, since it cannot prevent slipping and a differentiated feed of the wires being worked, with a consequent out-of-phase cut, which is performed at points that are too far forward or too far back with respect to what is required.

The resulting pieces, after cutting, thus lack the hook-shape at the ends, or these shapes are inadequately defined, so that the pieces are unusable with consequent high levels of discards.

Apart from that, a machine like the one described in US-A-3,199,175 needs specific guide grooves, made on the shaping tools, in order to guide the metal wire or wires to be shaped, which imposes a close correlation between the shaping of the tools and the number and shape of the wires that can be worked simultaneously.

This determines a lack of flexibility and productivity of the machine due to the specific use thereof, both with regard to the diameter of the wires to be shaped and also with regard to the number of wires that can be shaped simultaneously, requiring the complete replacement of the shaping tools every time the parameters of the wires to be shaped change.

One purpose of the present invention is to achieve a machine, and the relative production method, which allow to produce metal fiber having substantially any shape, in particular shapes with rectilinear segments of a certain entity, without causing slipping and misalignment of the metal wires being worked and hence guaranteeing that a final product of high quality and accuracy is obtained.

Another purpose of the present invention is to achieve a machine for producing metal fiber which is simple, reliable and versatile, and which allows to modify the shape to be made with rapid and easy equipping operations.

The Applicant has devised and embodied the present invention to overcome the shortcomings of the state of the art, in order to achieve the above purposes and to obtain other advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized essentially in the main claims, while the dependent claims describe other innovative characteristics of the invention.

The machine according to the invention comprises, like traditional machines for producing metal fiber, a drawing and shaping assembly, able to feed and simultaneously shape a plurality of metal wires, and a cutting assembly, located downstream of the drawing and shaping assembly, able to perform the cutting to size of said metal wires.

According to a characteristic feature of the present invention, the drawing and shaping assembly comprises at least a pair of counter-rotating track means which include, or support, shaping means able to impart the shape to the metal wires and then to remain gripping said metal wires at least for the terminal part of their feed towards the cutting assembly.

In a first embodiment, the track means are reciprocally convergent towards the terminal part of the feed of the wires. In this case, the first segment of the track means determines only the feed of the metal wires, while the second segment, facing towards the cutting means, determines the progressive shaping until the final shape of the metal fiber is achieved.

Alternatively, the track means are substantially parallel to each other.

According to the invention, the shaping means comprises a plurality of tools or blocks, attached to the relative tracks one adjacent to the other, so as to determine not only the feed but also, at least for the terminal portion of the gripping segment, the shaping of the metal wires to be shaped. The tools or blocks of one track are reciprocally facing the blocks of the other track, and have a reciprocally mating shaping, for example, one with a male part and the other with a female part which, interacting with each other in the gripping segment, impart the desired shaping to the metal wires.

Since every metal wire is gripped, particularly in the terminal segment of its feed between the tracks, and is shaped by the specific shaping tools, slipping or differentiated feed of the metal wires are prevented.

In this way, all the metal wires being worked arrive in correspondence with the cutting assembly disposed substantially co-planar and aligned with respect to each other, which allows to cut the shaped metal wires at exactly the required point, and to obtain pieces of metal fiber having the predetermined shape, which are all identical and therefore suitable for the use for which they are intended.

If it becomes necessary to effect shapings on series of wires with different structural and shaping parameters, it is enough to dis-assemble the blocks from the relative links, keeping the other components of the drawing and shaping assembly unchanged.

If the shaped pieces of the metal fiber have a substantially rectilinear central segment and two bent ends, two adjacent blocks of two respective track means act with the respective shaped parts on a segment of metal wire which, when cut, will form two different pieces of metal fiber.

The shaped part of the block can have, in a first embodiment, exactly the form of the shape to be imparted on the metal wire. According to a variant, the shaping of the block does not correspond exactly with the form of the shape to be made, but this shaping is obtained as a combination of the form of the shaping of the blocks and the movement of reciprocal approach of the tracks in the gripping segment. The shaping imparted to the metal wires is normally a loop or bend, which corresponds to two contiguous ends of two different pieces of metal fiber.

With the invention, particularly in the case of convergent tracks and/or progressive shaping performed especially in the final segment of feed, the metal wires are shaped and deformed without being subjected to the permanent compression of their section, so that excessive and unforeseen variations in the length of the wire do not occur, guaranteeing precision in the cutting position of the individual fibers.

Moreover, the cutting assembly is driven, in coordination with the feed of the metal wires, so as to cut them always at the middle point of the loop or bend, so that the shaped pieces obtained are always exactly identical.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of some preferential forms of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

• fig. 1 shows a side view of the machine for producing metal fiber according to the invention;
• fig. 2 shows the section from A to A of the machine in fig. 1;
• fig. 3 shows a detail of a first form of embodiment of the machine in fig. 1;
• fig. 4 shows a detail of fig. 3;
• fig. 5 shows a detail of a second form of embodiment of the machine in fig. 1;
• fig. 6 shows a detail of fig. 5;
• fig. 7 shows the metal fiber obtained by means of the machine in fig. 1.

DETAILED DESCRIPTION OF SOME PREFERENTIAL FORMS OF EMBODIMENT OF THE INVENTION

With reference to the attached drawings, the number 10 denotes generally a machine for producing metal fiber 11 according to the invention.

The metal fiber 11 consists of small pieces 12 of metal wire 18, each of which in this case has a rectilinear central segment 12a and two ends 12b bent at an obtuse angle (fig. 7).

This conformation, already known in itself, defines end-hooks which, during the solidification of the concrete, function as gripping elements in order to guarantee an optimum effect of resistance to compression.

The machine 10 (figs. 1 and 2) comprises a frame 13 on which are mounted a drawing and shaping assembly 14, able to act simultaneously on a plurality of metal wires 18, advantageously up to twenty five and more, and a cutting assembly 15 able to cut to size the metal wires 18 so as to obtain the pieces 12.

The functioning of the drawing and shaping assembly 14 and the cutting assembly 15 is coordinated by a command and control unit 16, for example of the PLC type, provided with a control panel 17 of the pivoting type.

The drawing and shaping assembly 14 comprises, in this case, two pairs of tracks 20, each one comprising an upper track 21 and a lower track 22.

Upstream of each pair of tracks 20 there is also a guide profile 19 through which a plurality of metal wires 18, fed by respective reels 33, which are preferentially kept substantially stationary, are conveyed, parallel and aligned with each other, to said pair of tracks 20, on a horizontal plane "X" disposed in an intermediate position between the upper track 21 and the lower track 22.

The guide profile 19, in a known manner, has a plurality of guide channels (not shown), one for every metal wire 18 to be fed to the drawing and shaping assembly 14.

Each track 21, 22 consists of two end toothed wheels 23 on which an articulated belt 24 is mounted, so as to define a closed ring. The articulated belt 24 consists of a plurality of links 25 able to engage on the toothed wheels 23.

Relative blocks 27a, 27b are mounted on the links 25, and are described in greater detail hereafter.

In this case, between the two toothed wheels 23 there is a tensioning member 26, able to keep the belt 24 adequately tensed.

The lower tracks 22 are made to rotate, with a feed towards the cutting assembly 15, by a motor 30 associated with a first return wheel 31 connected to one of the toothed wheels 23; the upper tracks 21 instead are made to rotate in the opposite direction to the lower tracks 22, so that they too advance in the direction of the cutting assembly 15, by a second return wheel 32 which takes motion from the lower tracks 22 themselves.

In the embodiment shown in figs. 3 and 4, the upper tracks 21 and the lower tracks 22 are disposed reciprocally convergent with respect to the plane X, towards the terminal part of the feed of the metal wires 18, that is, towards the cutting unit 15, so that the shaping of the latter is effected mainly in proximity with the cutting unit 15.

To be more exact, at inlet of the tracks 21 and 22 on the side of the guide profile 19, the blocks 27a and 27b do not substantially grip on the metal wires 18, until they exert maximum shaping pressure in correspondence with the terminal segment, facing towards the cutting unit 15, of the feed of the wires 18 between the tracks 21 and 22.

On the outer surface the blocks 27a, 27b have a part, in this case at their front end, conformed so as to define the bend of the ends 12b of the pieces 12 of the metal fiber 11 to be produced.

To be more exact, on each link 25 of the upper track 21 a first block 27a is mounted, the front end part of which has a ridge 29, with a substantially rectangular section, having a profile with a shape and size coordinated with the development of two contiguous and specular segments which will form, after cutting, the end 12b of two different pieces 12.

Each link 25 of the lower track 22, instead, is associated with a second block 27b the front end part of which has a hollow 28 with a conformation complementary to that of the ridge 29 of the first block 27a. To be more exact, the hollow 28 has a slightly bigger size than the ridge 29, so that the deformation of the metal wires 18 occurs with the ridge 29 entering progressively into the hollow 28, going to generate the trapezoid shaping of the metal wires 18.

The convergent disposition of each pair 20 of tracks 21, 22 is such that every first block 27a, when it is in the lower segment of the upper track 21, is facing, at least in the terminal part of the feed of the metal wires 18, at a distance substantially equivalent to the diameter of the metal wire 18, a corresponding second block 27b which at that moment is in the upper segment of the lower track 22.

In this way, as will be described in greater detail hereafter, the two moving tracks 21, 22 draw with an initial segment thereof, almost by skimming, the metal wires 18 along the plane X and progressively press thereon orthogonally to said plane, until they determine the deformation of the metal wires 18 and define the shaping thereof. The progressively effected shaping allows to make loops 38 with a constant interaxis on a plurality of metal wires 18 at the same time, without deformation and compression, also maintaining a constant grip on each metal wire 18 from which various pieces 12 will be obtained.

The blocks 27a and 27b are very close together longitudinally, along the relative tracks 21, 22, so that reciprocal displacements are prevented, which would cause modifications to the conformation of the shaping imparted to the metal wires 18.

In an advantageous embodiment, the blocks 27a and 27b can move in a direction orthogonal to the plane of feed X of the metal wires 18, which facilitates the progressive deformation by pressure-bending of the metal wires 18 themselves.

In the preferential form of embodiment shown in figs. 5 and 6, the upper tracks 21 and the lower tracks 22 are disposed substantially parallel to each other and the metal wires 18 are subjected to a deformation pressure from an initial part to the terminal part of the feed of the metal wires 18.

In this embodiment, on each link 25, a relative block 127a, 127b is removably mounted, having on the outer surface a central part with a substantially trapezoid conformation mating with the bend of the ends 12b of the pieces 12 of the metal fiber 11 to be produced.

To be more exact, on each link 25 of the upper track 21 a first block 127a is mounted, the central outer part of which has a hollow 128, with a substantially trapezoid section, having a profile with a shape equivalent to the development of two contiguous and specular segments which will form, after cutting, the end 12b of two different pieces 12; each link 25 of the lower track 22, instead, is associated with a second block 127b the central outer part of which has a ridge 129 with a conformation complementary to that of the hollow 128 of the first block 127a.

The disposition of each pair 20 of tracks 21, 22 is such that every first block 127a, when it is in the lower segment of the upper track 21, is facing, at a distance substantially equivalent to the diameter of the metal wire 18, a corresponding second block 127b which at that moment is in the upper segment of the lower track 22.

As in the embodiment described above, the two moving tracks 21, 22 draw and at the same time shape, achieving loops 38 with a constant interaxis, a plurality of metal wires 18 at the same time, maintaining a constant grip along a segment of each metal wire 18 from which various pieces 12 will be obtained.

The cutting assembly 15 is located at outlet from the drawing and shaping assembly 14 and comprises two rotating shears 35, each of which is located at outlet from a respective pair of tracks 20, driven simultaneously by a motor 36.

Each rotating shears 35 cooperates with an abutment plane 39 so as to cut to size the shaped metal wires 18 exiting from the relative pair of tracks 20.

To be more exact, the drive of the rotating shears 35, coordinated by the command and control unit 16 according to the speed of feed of the metal wires 18, causes the latter to be cut exactly at the intermediate point of each loop 38 performed by the pair of tracks 20, so that the pieces 12 thus obtained all have the bends of the ends 12b identical to each other.

Below the cutting assembly 15 there is a box-like profile 34, by means of which the pieces 12 cut by the rotating shears 35 are conveyed to a discharge device, for example a conveyor belt or suchlike.

The machine 10, which allows the simultaneous working of two bundles of metal wires 18, one for each pair of tracks 20, functions as follows.

The metal wires 18 of each bundle, after a possible previous straightening treatment, are made to transit resting on a support 37 and then made to pass through the guide profile 19, which provides to complete the straightening thereof and to dispose them adjacent to each other on the plane "X".

In this condition, the metal wires 18 are fed to the relative pair of tracks 20 which provide to draw them, deforming them, in the direction of the cutting assembly 15.

To be more exact, as they advance, the tracks 21, 22, at least in the terminal part of their feed, compress the wires 18, thus achieving, with a constant interaxis, the shaped loops 38 on the wires 18.

Particularly in the embodiment shown in figs. 5 and 6, the front and rear portions of the blocks 127a, 127b do not come into contact with the metal wires 18, so that the latter, in their segments corresponding to said portions, keep their rectilinear conformation.

After the relative loop 38 has been made, the blocks 27a, 27b and 127a, 127b maintain their grip on the metal wires 18 until they are next to the cutting assembly 15, preventing slipping and/or misalignment of the metal wires 18; the latter therefore arrive in correspondence with the cutting assembly 15 all with the relative loops 38 transversely aligned with respect to each other.

The rotating shears 35 then cut to size the metal wires 18 exactly at the median point of said loops 38, allowing to obtain all identical pieces 12 which, falling inside the box-like profile 34, are conveyed to the discharge device.

Should it be necessary to modify the geometry of the pieces 12, while keeping the length unchanged, it is enough to remove the blocks 27a, 27b and 127a, 127b and replace them with other blocks able to shape the metal wires 18 differently, without needing to completely dismantle the tracks 21, 22. To facilitate the removal of the blocks 27a, 27b and 127a, 127b the latter are advantageously associated with the relative links 25 by means of quick attachment elements.

It is clear, however, that modifications and/or additions of parts or steps may be made to the machine 10, and the relative production method as described heretofore, without departing from the scope of the present invention.

For example, the machine 10 may have a single pair, or more than two pairs, of tracks 20.

Or it may have a cutting assembly 15 with other devices rather than rotating shears 35.

It is also clear that, although the present invention has been described with reference to specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of machine, and/or perfect analogous methods, for producing metal fiber, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.