GB2146312A

GB2146312A - Apparatus for distributing short stiff loose metal fibres over a surface

Info

Publication number: GB2146312A
Application number: GB08323882A
Authority: GB
Inventors: Stig Hasselqvist
Original assignee: EKEBRO AB
Current assignee: EKEBRO AB
Priority date: 1983-09-06
Filing date: 1983-09-06
Publication date: 1985-04-17
Also published as: GB8323882D0

Abstract

Apparatus is provided for distributing short stiff loose metal fibres over a surface (9) as a fibrous layer or mat, with the fibres generally in alignment lengthwise, comprising, in combination: (1) a fibre reservoir (1) having walls defining an outlet (16) at a lower end thereof, the reservoir having a lead in chute (2) which is vibrated by vibrator (17), the fibres being fed downward into the lower end of the reservoir by a spiked wheel 30; (2) an oscillating feed roller (3) disposed at the lower end of the fibre reservoir and having a plurality of outwardly-extending projections (4) reaching towards the outlet walls, the feed roller blocking the lower end outlet to free passage by loose fibres, and the projections extending into the fibre supply in the reservoir, so that upon oscillation of the feed roller the projections pluck fibres from the supply, and deliver them via a partitioned chute (6) to the surface. <IMAGE>

Description

SPECIFICATION Apparatus for distributing short stiff loose metal fibers over a surface For many industrial applications, such as the manufacture of fiber-reenforced sheets and fiber-reenforced pavements for streets, roads and highways, as well as poured concrete Structures, such as bridges, tunnels and buildings, fibrous layers or mats of short stiff metal fibers such as steel, iron, aluminium, tantalum or bronze are required. In many cases, to meet required stress strain limits, it is desirable that the fibers be more or less oriented substantially in parallel planes and even, on occasion, in alignment lengthwise. When the fibers are short and stiff, however, such distribution from a mass in which the fibers are oriented heterogeneously, extending in all directions, is not easy to accomplish.

One way is to cause the fibers to pass through tubes which are smaller in diameter than the fibers are long, but this method is not really practical to produce wide mats, because a multiplicity of tubes is required, and the tubes must be arranged in parallel, with the fibers fed into the tubes lengthwise.

Another method is to lay down the fibers on a surface, and then try to orient the fibers by raking the mat, but the longer the fibers, the more difficult this is, and the greater the tendency to disrupt the uniformity of the spread of the mat across the surface.

In accordance with the present invention, apparatus is provided for distributing short stiff loose metal fibers over a surface as a fibrous layer or mat, comprising, in combination: (1) a fiber reservoir having walls defining an outlet at a lower end, retaining and gravity feeding from the lower end outlet a supply of short stiff loose metal fibers, the reservoir being inclined at an appropriate angle to the horizontal that the fibers move freely downwardly; without pressing and packing the fiber masses in the outlet area.

(2) an oscillating feed roller disposed at the lower end of the fiber reservoir, and having a plurality of outwardly-extending projections reaching towards the outlet walls, the feed roller blocking the lower end outlet to free passage by loose fibers, and the projections extending into the fiber supply in the reservoir, so that upon rotation of the feed roller, the projections pluck and fling fibers from the supply to the wall where the fibers are disaggregated and slide along the wall down to the surface, for laydown thereon as as a fibrous layer or mat.

To assist in lengthwise orientation of the fibers, the fibers can be delivered by the feed roller to a chute inclined at a sufficient angle to the horizontal to cause the fibers to move freely downwardly along the chute surface and having a plurality of upwardly extending generally parallel longitudinal ribs at a spacing between the ribs that is less than the length of the fibers. The fibers, already partially oriented by the feed roller, thus become oriented more or less completely lengthwise in the same plane as they pass downwardly along the chute, the ribs completing the bridging of the fibers into this alignment. In order to prevent binding of the fibers along the walls of the ribs, the distance between the ribs should be less than the fiber length.

To assist in causing the fibers to move downwardly along the chute, the chute can be vibrated, and so also can the fiber reservoir.

By the aid of vibration, the angle of the chute can be brought closer to the horizontal. The vibrations also aid in bringing the fibers into alignment lengthwise.

Preferred embodiments of the apparatus of the invention are illustrated in the drawings, in which: Figure 1 is a schematic representation of an apparatus of the invention provided with vibrating chutes before and after the feed reservoir, which in this case is a vertical hopper.

Figure 2 is a perspective view from above the top of the outlet portion of the fiber reservoir or hopper, showing the feed roller; Figure 3 shows an apparatus of the invention arranged to feed a fibrous layer or mat between superimposed layers of plastic matrix material which merge to form a fiber-reenforced plastic sheet; and Figure 4 illustrates a system in which the apparatus of the invention is arranged to feed a fibrous layer or mat as reinforcement between the plastic layers of fluid concrete which merge to become a fiber-reenforced concrete pavement.

The apparatus shown in Fig. 1 has a vertical hopper 1 with inwardly-sloping walls, and an outlet 8 at the lower end. A feed chute 2 is arranged to deliver a supply of loose short stiff metal fibers, such as steel fibers, into the hopper. This chute is arranged to be vibrated by the vibrator mechanism 17, which is of conventional design and forms no part of the invention.

Extending across the outlet of the hopper 1 but within the hopper is a rotatable feed roller 3, provided with a plurality of outwardlyextending pegs 4.

Rotatably arranged at the top of hopper is spiked wheel 30, shown with four rows of spikes, controlling the feed of fibers 5 from the chute 2 into the hopper.

Positioned below the outlet 8 of the hopper 1 is an inclined chute 6. The chute surface is provided with a plurality of longitudinal paral lel ribs 7, at a spacing less than the length of the fibers 5, but greater than one-half of the length of the fibers 5. These ribs extend longitudinally all the way to the bottom end of the chute, and complete the orienting of the fibers lengthwise as they pass along the chute. The chute is suspended on the support rods 11, at an angle such that the fibers move freely down the chute as they are delivered thereto by the pegged roller 3, so that the chute delivers a uniform mass of aligned fibers to the conveyor belt 9 as a fiber mat 10, with the fibers in longitudinal alignment on the belt.

In operation, the spiked wheel 30 is rotated by electric motors and the pegged roller 3 is rotated by a pneumatic cylinder and a crank.

Governing the speed of the cylinder is a valve with adjustable choking outlets. The fibers are placed on the chute 2 as a heterogeneous mass, with no particular orientation of the fibers. The pegged roller 3 plucks fibers from the mass, extends into the mass of fibers in the hopper 1 and delivers the fibers, already in some degree of longitudinal alignment due to the plucking, to the vertical chute 6, where their lengthwise alignment is completed with the aid of ribs 7. The fibers then pass in a relatively uniform distribution across the surface of the belt 9, the width of the mat being determined by the width of the chute 6, thereby forming the mat 10 with the fibers in lengthwise alignment.

Figure 3 shows a system for manufacturing fiber-reenforced sheet material. In this case, a fibrous mat prepared and delivered by an apparatus of the invention is sandwiched between separately delivered matrix layers of the material delivered from two spreading devices 17a, 17b, as a semi-solid. As the layers merge with the fibrous mat, a fiber reenforced sheet 28 is formed upon the surface of the continuous conveyor belt 1 8.

The matrix feeder 1 7a feeds a layer 25 of semi-solid flowable matrix material onto the surface of the conveyor belt 1 8. This layer then passes beneath the apparatus 21 of the invention, which is of the type shown in detail in Figs 1 and 2. This delivers a mat 23 of fibers oriented lengthwise upon the matrix layers 25. A second semi-solid flowable matrix layer 26 is then delivered on top of the mat 23 of fibers by the matrix spreading device 17b, the matrix layer being spread uniformly over the fibrous mat by the roller 22. The two layer 25, 26 flow together around and through the mat 23, resulting in a fiberreenforced sheet 28.

The material of which the matrix is formed itself forms no part of the invention, and can be thermoplastic, in which event the fiberreenforced sheet is simply hardened or allowed to cool to harden, following completion of the sheet. Alternatively, the matrix can be of partially polymerized thermosetting material, which is heat-cured to a thermoset condition following the feed roller 22, or a cementitious material.

Shown as a part of the apparatus of the invention is the table 20, where the loose fibers are fed into the chute 2.

The highway pavement system shown in Fig. 4 is mounted on one or more vehicles that are moved along the pavement site or highway, and includes two concrete hoppers 35, 36 with an intermediate apparatus 50 according to the invention feeding a mat 33 of fibrous material between separately-applied layers 31, 32 of semi-solid flowable concrete, which as the concrete flows together around and through the mat 33 to form a single mass becomes the central reinforcement layer of the final concrete pavement.

The concrete pavement is laid down upon a suitable substrate 29 of conventional type, such as aggregate, i.e. sand or gravel. The concrete hopper 35 lays down a layer 31 of semi-solid flowable concrete as it is moved to the right, along the base layer. There then follows the apparatus 50 of the invention, which corresponds, for example, to that shown in Fig. 1. This lays down the fibrous layer 33, which is in turn covered by another concrete layer 32 delivered from the hopper 36. A vibrator 38b consolidates the combined layers into one or many layer 39, which is then allowed to cure in the usual way. The final concrete layer 39 can include a proportion of loose fibers 40, as shown, which are added to the concrete in hoppers 35, 36. but these are not necessary, and can be omitted.

The complete system, composed of the two concrete hoppers 35, 36 and the fibrous layer feeder 50 of the invention, is best mounted together on a single platform or vehicle, and spreads a concrete layer of the desired width upon the base material. The device 50 of the invention can be arranged to distribute a fibrous layer less wide than the concrete layers, and moved back and forth between the limits of the concrete layers, as the concrete hoppers are moved forward.

The fibers processed by the apparatus of the invention are short enough to be nonballing; their aspect ratio A. R. is below about 100. The aspect ratio is defined as the ratio L/D where L is the length and D the diameter of the fiber. Exemplary stiff fibers that can be processed include iron, steel, aluminium, bronze, brass, tantalum, molybdenum, titanium, and nickel, and alloys of any one or more of the above with other metals and carbon, such as Monel, stainless steel, and Hastalloy.

Claims

1. An apparatus movable relatively to an underlaying surface for distributing short, stiff loose metal fibers over the surface as a fibrous layer or mat, comprising, in combination: (1) a fiber reservoir having walls defining an outlet at a lower end retaining and gravity feeding from the lower end outlet a supply of short stiff loose metal fibers, the reservoir being so inclined at an appropriate angle to the horizontal that the fibers move freely downwardly without pressing and packing fiber masses in the outlet area; and (2) an oscillating feed roller disposed at the lower end of the fiber reservoir and having a plurality of outwardly-extending projections reaching towards the outlet walls, the feed roller blocking the lower end outlet to free passage by loose fibers, and the projections extending into the fiber supply into the reservoir, so that upon oscillation with a possible unsymmetric speed of the feed roller the projections pluck fibers from the supply and fling them by centrifugal acceleration to the opposite wall, where bundles of fibers are disaggregated and the fibers slide down along the walls for laydown as a fibrous layer or mat.

2. An apparatus according to claim 1, comprising a pneumatic cylinder connected to the oscillating feed roller by means of a crank and a valve with throttle means for governing the oscillating speed of the feed roller.

3. An apparatus according to claim 2, wherein the throttle means imparts to the feed roller a speed which is higher when the feed roller is moving towards the wall than when it is moving towards the fiber reservoir.

4. An apparatus according to any one of the foregoing claims comprising an inclined chute disposed with one end beneath the lower end outlet of the fiber reservoir, in which the chute has a fiber-receiving surface comprising a plurality of parallel longitudinal ribs, orientating the fibers for laydown as a fibrous layer or mat at its other end, and with adjustable distance between this end and the surface, carrying the fibrous layer or mat.

5. An apparatus for distributing short stiff loose metal fibers, constructed and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.