MXPA00012927A - Method and device for magnetic alignment of fibres - Google Patents

Abstract

Magnetisable fibres dispersed in a viscous body, particularly reinforcing metal fibres dispersed in a wet cementitious material, is carried out by providing a fibre aligning member (15) having a nonmagnetic wall (17) including a first wall portion (17A) and a second wall portion (17B), moving the aligning member (15) relative to the viscous body with the first wall portion (17A) leading and the second portion (17B) trailing it and with the first and second wall portions (17A, 17B) contacting the viscous body, and directing a magnetic field into the viscous body through the first wall portion (17A) to subject the fibres (F) to a moving magnetic field. A device for performing the method comprises:a fibre aligning member (15) having a nonmagnetic wall (17) including a first wall portion (17A) and a second wall portion (17B);and a magnet device (18) disposed adjacent the first wall portion (17A) for directing a magnetic field into the viscous body through the first wall portion (17A), and a manipulating device (14) for moving the fibre aligning member (15) relative to the viscous body with the first wall portion (17A) ahead of the second wall portion (17B) and with the first and second wall portions (17A, 17B) contacting the viscous body.

Description

METHOD AND DEVICE FOR ALIGNING FIBERS MAGNETICALLY The present invention relates to methods and devices for magnetically aligning scattered fibers in a viscous body. The invention has particular utility in its application in alignment (arrange in parallel) of metallic fibers, notably steel fibers, in freshly cast concrete and therefore wet as well as in other cementitious or pasty materials. For this reason, the invention will be described with this application taken as an illustrative example. It is known that to strengthen the concrete steel fibers are added to the viscous concrete, before it is strained. Usually, the fibers have a length of 2.5 to 8 cm and a diameter within the range of 0.5 to 1 mm, and in this way is relatively rigid. During the mixing of the fibers and the concrete, the fibers are dispersed in the concrete and are oriented in a random way in the three dimensions, in such a way that the cast and hardened concrete body is reinforced in all three dimensions. Ref No.: 125495 However, many, or even most concrete structures are only tensioned in one or two dimensions, so that reinforcement in one or two dimensions is adequate. This is also the case with the plates or plates of the concrete floor and the pavement of concrete roads, to mention just two examples. It is therefore desirable that in such concrete structures the fibers can be aligned in one or two dimensions, which correspond to the direction or directions of tension, in such a way that the fiber reinforcing material is used economically. It is also desirable that the fibers can be concentrated in the zone or zones of the concrete structure, where the demand for reinforcement is greater. According to a known method for aligning in one dimension, steel fibers in freshly cast concrete plates to a certain shape, a magnetic field is directed through the freshly cast, viscous concrete body found in the casting form, and it moves relative to a shape from one end or side thereof to the other, this in order to apply a temporary alignment force to the individual fibers to align them in the direction of relative movement. To facilitate the movement of alignment of the fibers under the action of the magnetic field, the concrete body is vibrated during the relative movement of the magnetic field and the concrete body. In the known method, the magnetic field is applied by means of a magnet device which is placed on the outside of the freshly cast concrete body and is on both sides and also in the form in which it has been cast. However, the alignment of the magnetic fibers in this way is, in many cases, impossible to implement, such is the case of cast concrete bodies in si t u. The? Jrandes concrete slabs or pavements cast on the ground, are two examples of concrete bodies in which the known method is difficult to apply. In the method and device according to the present invention as defined in the claims, the magnetic alignment of magnetizable fibers dispersed in a viscous body is performed by means of a fiber alignment member having a non-magnetic wall. A magnetic field is directed to the viscous body through a first portion of the non-magnetic wall, while the fiber alignment member moves relative to the viscous body with the non-magnetic wall in contact therewith, with a second portion of the non-magnetic portion that carries or brings with it the first portion. According to the above, the fibers are temporarily subjected to the magnetic field as the first portion moves past them. The fiber alignment member may be partially or completely immersed in the viscous body as it moves relative to the viscous body, with the first portion of the magnetic wall in front of the second portion and thus carried or pulled by the second. During relative movement, the fibers that are in the vicinity of the first portion of the non-magnetic wall are magnetically attracted to the first portion. However, it is prevented that these come into contact with the magnetic device through the non-magnetic wall, which forms a mesh or barrier that separates the magnet device from the viscous material in which the fibers are dispersed. Therefore, the fiber alignment member attracts the fibers and tends to pull them along, in the direction of their movement relative to the viscous body. Due to its viscosity, the material of the viscous body prevents the fibers from moving too fast towards the alignment member and adhere to it. Thus, the fiber alignment member will move relative to the fibers and subject them to the magnetic force only temporarily. Since the magnetic force has a component in the direction of relative movement of the fiber alignment member and the viscous body, it tends to align the fibers in the direction as they move past them. Preferably, the material from which the viscous body is formed is vibrated adjacent to the fiber alignment member, so as to facilitate the movement of alignment of the fibers. As a consequence, it is possible, by applying the principles of the invention, to align in a simple manner the fibers dispersed in a random manner in a cementitious, pasty or viscous material.; obtaining at the same time, a concentration of the fibers in a plane along which the fiber alignment member moves. This plane can be found in an area of the viscous body, which in the use of the hardened concrete body will have to absorb a heavy tensile stress. The present invention will be understood more fully from the following description with reference to the accompanying drawings, which show the application of the invention for the production of pavements or other cast concrete plates on a floor or ground. Figure 1 is the illustration of a general view, showing the successive steps for the production of a concrete pavement on a ground, one such step is the alignment of the reinforcing steel fibers according to the present invention; Figure 2 is a perspective view of a fiber alignment device used in the alignment step of the fibers of Figure 1; Figure 3 is a cross section of a section of the concrete pavement of Figure 1, in which the alignment of the fibers is carried out; Figures 4-6 are views in the form of diagrams, of three plates of different heights cast in the ground or floor, and are shown together with the fiber alignment devices according to the present invention; Figure 7 is a cross-sectional view showing a modification of the alignment device of Figure 6; Figure 8 is a cross-sectional view showing a modification of the alignment device of Figure 3.

As shown by way of example in Figure 1, the present invention is applied to the production of a pavement or concrete plates on the floor or a ground. The pavement is shown in different successive steps during its production, the first of the steps is shown on the left and the last of the steps is shown on the right. Further to the left, in A, the wet concrete is cast once the steel reinforcing fibers, or some other magnetizable material has been added to the concrete and these are dispersed evenly in the concrete with random orientation. Then, in B, the wet concrete is vibrated, and the reinforcing fibers are longitudinally aligned using a fiber alignment device 11, which represents the invention. The fiber alignment device 11 is supported by and slides on the rails 12, which are positioned along the longitudinal edges of the pavement. In C, the wet concrete with the already aligned fibers is treated by vacuum, and in D the pavement is smoothed. The fiber alignment device 11 comprises a main beam 13 which is horizontal and extends through the belt of the terrain to be paved and rests on the rails 12. This is manually moved and controlled by means of the bars. control 14 that has some handlebars. A horizontal and right fiber alignment member 15 having the shape of a beam or bar, is suspended from the main beam 13 by means of the supports 16 which are adjusted vertically to allow the positioning of the alignment member 15, a a selected height. The alignment member 15 extends through the entire space between the rails 12. An elongated housing or housing 17, which forms part of the alignment member 15, has a drop shape in cross section, so as to resemble a aerodynamic plane; the first or rounded guide flange of the housing is directed so that it is first or forward when the alignment device 11, with the alignment member 15, moves in the appropriate direction to the left in Figure 1, this during the alignment operation. This housing 17 is made of aluminum or some other suitable non-magnetic material. Along the inside of the housing 17 of the alignment member 15, a first or front wall portion 17A of the housing, and a magnet roller or cylinder 18 having a rotary stump arrangement extends along the length complete of the alignment member. The first portion 17A of the housing wall is arcuate in cross section, and the axis L of the magnet roller 18 coincides with the axis of the first wall portion 17A. Three permanent magnets 19, made of neodymium for example, are uniformly distributed around the magnet roller 18, each of said magnets extending approximately 1/6 of the circumference of the magnet roller. The external surfaces of the magnets 19 are placed on a circular surface concentric with and closely spaced from the first portion 17A of the wall of the housing 17. Accordingly, when the magnet roll 18 is caused to rotate as described below , the permanent magnets 19 will move close to the inner side of the first wall portion 17A. As indicated by the designations of south and north poles N and S and the magnetic field lines in figure 3, the magnets 19 are mounted on the magnet roller 18 in such a way that the field lines run in planes that are perpendicular to the axis L of the magnet roller 18. In the illustrated embodiment, the magnet roller 18 is rotated against clockwise, as seen in Figure 3, by a number of electric motors 20 spaced along the length of the alignment member 15. If desired or required, the direction of rotation of the magnet roll 18 can be reversible. To allow adjustment of the alignment member 15 to a desired angle of attraction, such that the second or driving portion 17B of the wall of the housing 17 is at a selected height, the alignment member is mounted to have a rotating movement about an axis that is parallel to, for example coinciding with, the axis L of the roller 18. Anchoring means, not shown, are provided to secure the alignment member in a selected angular position. During the operation of aligning the fibers, the fiber alignment device 11 rests on the rails 12 with the alignment member 15 positioned at a height, such that the lowermost segment of the first portion 17A, of the wall of housing 17, is relatively close to the lower side of the wet viscous concrete casting layer. In addition, the alignment member 15 adjusts angularly such that the second portion 17B, of the wall of the housing 17, is approximately at the same height as the lowermost segment of the first wall portion 17A. Once the alignment member 15 has been adjusted to the desired height and the desired angular position; the alignment device 11 moves slowly to the left as can be seen in figures 1-3, in such a way that the first portion 17A of the wall of the housing 17 is in front of and directed or carried by the second wall portion. 17B. The magnet roller 18 rotates continuously in the direction indicated by an arrow (counter-clockwise), and a vibrator V supported by the alignment device 11, operates to vibrate the concrete in the region of the concrete body in which operates the alignment member 15. As indicated by the arrows drawn in Figure 3, a portion of the concrete moves up and passes through the upper side of the alignment member 15, while the other portion moves down and passes through the lower side. During their movement along the inner side of the first wall or guide portion 17A, the permanent magnets 19 provided on the magneto roller, will direct their magnetic fields in the concrete in front, above and below the first wall portion. 17A. The magnetic fields, the field lines, which generally run in planes that, perpendicular to the axis L of rotation of the magnet roller 18, orbit in the counterclockwise direction together with the roller. During their orbital movement they apply to the reinforcing fibers F, supported by the magnetic fields, a magnetic attraction force which tends to attract the fibers towards the first wall or guide portion 17A of the housing 17, and they align the fibers as length of the planes of the field line. At the same time, the fibers placed above the level of the lowermost side of the alignment member 15 are pulled downward by the magnetic attraction and below the deflection of the concrete, and the fibers below that level are pulled upwards. Accordingly, the fibers F, or at least a good proportion of them, tend to move towards the underside of the alignment member 15 forming a horizontal layer of fibers aligned in the relative direction of movement of the concrete body and the alignment member. When a fiber F reaches a position at the level of the flat and intermediate wall portion 17C of the underside of the housing 17, the force of the magnetic field, and thus the magnetic attraction on the fiber, decreases abruptly because the magnet 19 , which is closest to the transition between the first wall portion 17A and the intermediate wall portion 17C, moves upward away from the fiber. According to the foregoing, the magnetic attraction on the fiber F will no longer be strong enough to pull the fiber together with the alignment member 15, so that the fiber will be left behind in the aligned position in the fiber layer. If a fiber concentrate F is desired in a layer in the upper region of the concrete body, the alignment member 15 adjusts angularly and, if necessary, moves its body vertically to a position in which the first and second portions 17A, 17B of the wall of the housing 17, are approximately in the same horizontal plane and at the desired height. In addition, the direction of rotation of the magnet roller 18 is reversed. Figures 4,5 and 6 diagrammatically show three different ways of practicing the present invention. The technique represented by figure 4 corresponds essentially to the technique shown in figures 1-3 described above. According to the above, the alignment of the fibers takes place once the concrete has been placed on the floor or ground. Figures 5 and 6 show some modalities in which the alignment of the fibers takes place during the placement of the concrete layer on the ground. More particularly, Figure 5 shows a device for placing the concrete and aligning the fibers that are intended to be carried by a laying vehicle along the surface on which the reinforced concrete body will be placed. In this device, the alignment of the fibers takes place in two steps. The wet concrete with the mixed fibers is fed into a steeply inclined container or compartment 21, in which two alignment members 22 similar to the alignment member 15 of Figures 1 to 3 are placed side by side. An alignment member Additional 22, similar to the alignment member 15, is placed in a placement nozzle 23. This nozzle forms a downward continuation of the container 21 and has a tube a straight discharge opening through which a layer of concrete of desired thickness is formed. discharge and placed on the ground or soil. The device shown in Figure 6 is primarily intended to be used to distribute narrow and relatively thin layers and is operated manually. This device includes a dispensing nozzle 24 which resembles the dispensing nozzle 23 of Figure 5, and a tubular arrow 25 in which wet concrete with the mixed fibers is fed from a concrete pump (not shown) through a hose. Within the dispensing nozzle 24, an alignment member 26 similar to the alignment member 15 of Figures 1 to 3 is placed. Figure 7 shows in greater detail the device of Figure 6. Figure 8 shows a modification of the member. of alignment 15 of figures 1 to 3. In this case, a second rotating magnet roller 27 is provided inside the rotating magnet roller 18 'which is placed in the rear region of the first or guide portion 17A of the wall of the housing 17. This is arranged to rotate at a speed that has a certain numerical ratio, 3: 1, of the speed at which the magnet roller 18 'rotates. The half of the magnet roller 27 is magnetized as indicated by the designations of pole N and S, while the other half is substantially unmagnetized. Each time one of the permanent magnets 19 of the magnet roller 18 enters the region in which it is placed on the magnet roller 27, the magnetic field of the magnet 19 will bring its magnetic lines closer through the magnet roller 27, in such a way that Only a small portion of the magnetic field is directed to the concrete body. Consequently, the attraction of the magnet roller 18 'is exerted on the reinforcing fibers in the concrete body, and thus the tendency of the alignment member 15 to pull the fibers lengthwise, is abruptly reduced when the fibers are found in the region below the magnet roll 27.

Various modifications of the presently preferred method and alignment device shown in the drawings are possible within the scope of the invention as defined in the claims. For example, the cross-section of the housing 17 of the alignment member 15 can be substantially symmetric with respect to a plane passing through the axis L of the magnet or magnet roller 18, and be substantially perpendicular to another plane passing through the axis L and the flange of the second portion 17B of the wall of the housing 17. With this symmetrical cross section, the alignment member consequently has a thin flange portion on opposite sides of the thicker section of the housing 17, where the magnet roller 18 is placed in such a way that it can move in opposite directions in the concrete, for example, through the width of a wide pavement belt, without a great resistance to movement being found. In this modification, it may be preferred to have two magnet rollers 18, which are associated with opposite sides of the housing 17, and rotate in opposite directions. Alternatively, a single magnet roller 18 can be provided by having a single magnet on the circumference and rotated alternately in opposite directions through an angle of no more than 180 degrees, and preferably approximately 270 degrees. The magnetic field will then be directed alternately in the concrete above the alignment member, and in the concrete below the alignment member. This reversed and intermittent mode of rotation ensures that the fibers are temporarily subjected to a magnetic pushing force, in the direction in which the alignment member 15 moves relative to the concrete. Although in the embodiment of the invention described and illustrated in the drawings, the fibers are aligned horizontally in the direction of relative movement and the concrete, it is possible to align the fibers in a horizontal direction, perpendicular to the direction of relative movement, if the magnets 19 in the magnet roller 18 are magnetized in such a way that their magnetic field lines run predominantly in planes extending along the length of the alignment member 15.

It should also be noted that the magnets or other means of producing the magnetic fields, or all such magnets or other means, do not necessarily need to move in relation to the alignment member. Fixed permanent magnets or other elements that produce magnetic fields in the alignment member can be incorporated in order to direct the constant or intermittent magnetic fields in the material containing the magnetizable fibers to align them. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (20)

1. A method for magnetically aligning scattered magnetizable fibers in a viscous body, characterized in that it comprises: providing a fiber alignment member, which has a non-magnetic wall, including a first wall portion and a second wall portion; moving the alignment member relative to the viscous body with the first wall portion of the non-magnetic wall guiding it and the second wall portion bringing it with or carrying it, and with the first and second wall portions having contact with the viscous body, and directing a magnetic field towards the viscous body through the first wall portion of the non-magnetic wall, this to subject the fibers in the viscous body to the movement of the magnetic field.

2. A method according to the claim 1, characterized in that the magnetic field is applied to the viscous body, predominantly through the first wall portion of the non-magnetic wall.

A method according to claim 1 or 2, characterized in that the magnetic field is applied to the viscous body substantially exclusively through the first wall portion of the non-magnetic wall.

4. A method according to one of claims 1 to 3, characterized in that the fiber alignment member moves substantially parallel to a surface of the viscous body.

5. A method according to one of claims 1 to 4, characterized in that the fiber alignment member is at least partially immersed in the viscous body.

6. A method according to one of claims 1 to 5, characterized in that the field lines of the magnetic field run predominantly, in planes that are substantially transverse to the non-magnetic wall, and substantially parallel to the direction of relative movement of the alignment member. of the fibers and the viscous body.

7. A method according to one of claims 1 to 5, characterized in that the field lines of the magnetic field run predominantly in planes containing a line parallel to the desired direction of alignment, and transverse to the direction of relative movement of the member. of alignment of the fibers and the viscous body.

8. A method according to one of claims 1 to 7, characterized in that the magnetic field is directed in the viscous body by means of a magnetic member, which is placed within the fiber alignment member, and can be angularly moved around an axis extending along the first wall portion of the non-magnetic wall.

9. A method according to one of claims 1 to 8, characterized in that the viscous body is a substantially horizontal plate.

10. A method according to one of claims 1 to 9, characterized in that the viscous body is a plate or layer of wet concrete.

11. A method according to one of claims 1 to 10, characterized in that the viscous body is vibrated during the movement of the fiber alignment member, in relation to the viscous body.

12. A device for magnetically aligning magnetizable fibers distributed in a viscous body, characterized in that it comprises: a fiber alignment member having - a non-magnetic wall that includes a first wall portion and a second wall portion, and - a magnet device positioned adjacent to the first wall portion of the non-magnetic wall to direct a magnetic field in the viscous body through the first wall portion of the non-magnetic wall, and - a handling device for moving the fiber alignment member, relative to the viscous body with the first wall portion of the non-magnetic wall, in front of the second portion , and with the first and second portions having contact with the viscous body.

13. A device according to claim 12, characterized in that the fiber alignment member comprises an elongated and recessed housing, which includes the non-magnetic wall and in which the magnet device is accommodated.

14. A device according to claim 13, characterized in that the magnet device is positioned near the non-magnetic wall adjacent to the first wall portion, and widely separated from the other parts of the non-magnetic wall.

15. A device according to claim 14, characterized in that the magnet device extends for substantially the entire length of the recessed housing.

16. A device according to one of claims 12 to 15, characterized in that the magnet device includes a cylindrical roller that is mounted inside the recessed housing, for an angular movement about an axis, which extends the length of the housing and which carries or brings with it at least one magnet on its circumferential surface.

17. A device according to claim 16, characterized in that it includes a motor for providing angular movement to the roller in the recessed housing.

18. A device according to claim 16 or 17, characterized in that the first portion of the non-magnetic wall is concentric with the roller.

19. A device according to claim 18, characterized in that the cross section of the recessed housing tapers from the first wall portion towards the second wall portion.

20. A device according to one of claims 12 to 19, characterized in that the fiber alignment member is placed in a nozzle having a discharge opening for a viscous compound, in which the magnetizable fibers are dispersed, the first portion Non-magnetic wall wall is directed away from the discharge opening. METHOD AND DEVICE FOR ALIGNING FIBERS MAGNETICALLY SUMMARY OF THE INVENTION The dispersion of magnetable fibers in a viscous body, particularly reinforced metal fibers dispersed in a wet cementitious material, is accomplished by providing a fiber alignment member (15) having a non-magnetic wall (17) including a first portion of wall (17A) and a second wall portion (17B), the alignment member (15) moving relative to the viscous body with the first wall portion (17A) of guidance, and the second portion (17B) bringing it with, and with the first and second wall portions (17A, 17B) in contact with the viscous body, and directing a magnetic field to the viscous body through the first wall portion (17A) to subject the fibers (F) to a moving magnetic field. A device for practicing the method comprises: a fiber alignment member (15) having a non-magnetic wall (17) including a first portion of. wall (17A) and a second wall portion (17B); a magnet or magnet device (18) positioned adjacent to the first wall portion (17A) to direct a magnetic field in the viscous body through the first wall portion (17A), and a handling device (14) to move the alignment member ( 15) of the fibers in relation to the viscous body with the first wall portion (17A) in front of the second wall portion (17B), and with the first and second wall portions (17A, 17B) in contact with the viscous body .