WO2008130310A1

WO2008130310A1 - Mortar spraying device and method

Info

Publication number: WO2008130310A1
Application number: PCT/SE2008/050404
Authority: WO
Inventors: Bo Nitz; Libor Kubina
Original assignee: Maxit Group Ab
Priority date: 2007-04-24
Filing date: 2008-04-09
Publication date: 2008-10-30
Also published as: EP2142308A4; EP2142308A1; SE0700975L; SE531084C2

Abstract

The present invention relates to a mortar spraying device for spraying a fibre reinforced mortar material onto a surface, comprising a spraying nozzle (10) with a central tube (11 ) for transporting a fibre flow (A) of cut fibres to a downstream end of the spraying nozzle (10), and an outer tube (12) enclosing at least a portion of the central tube (11 ) and forming a passage between the tubes (11, 12) for transporting a mortar flow (B) to the downstream end of the spraying nozzle (10). The spraying nozzle (10) comprises a fibre flow directing means (26) to direct the fibre flow (A) radially into the mortar flow (B) when exiting the spraying nozzle (10). The invention also relates to a mortar spraying method.

Description

MORTAR SPRAYING DEVICE AND METHOD

FIELD OF THE INVENTION

The present invention relates to a mortar spraying device and method.

More specifically the present invention relates to a mortar spraying device and method for spraying a fibre reinforced mortar material onto a surface. Such devices of this type comprise a spraying nozzle, such as a hand- operable spraying nozzle, for spraying mortar materials, such as primers, reinforcing layers, renders, plasters, etc. on a surface to build up one or more layers of such materials on said surface. For example, such devices are used to provide a rendering or a plastering on a surface, such as exterior or interior walls of houses and other buildings.

PRIOR ART

A plurality of devices and methods for spraying mortar are disclosed in the prior art. One such device is disclosed in GB1516401. This document discloses a spraying apparatus for producing fibre reinforced construction materials, comprising a central tube, forming a conduit for a stream of airborne fibres, and a coaxial tube of greater diameter surrounding said central tube, forming a conduit for mortar. At the downstream end a member having an inwardly inclining annular passageway or bores for pressurized air is arranged to split up the mortar material into particles or drops and force the mortar material into the stream of fibres just before leaving the device.

Another prior art device and method of this type is disclosed in US4263346. This document discloses a method and device for spraying mortar materials and disintegrated fibres by means of pressure air, comprising a spraying nozzle with a central tube, forming a central passage for fibres, and an outer tube, forming a passage for mortar, concentrically surrounding said central tube. The mouths of the tubes, respectively, are so designed that the mortar outside the spraying nozzle forms an outer casing around a core of fibres in an essential part of the distance to the surface to be sprayed. One problem with such prior art devices and methods for spraying mortar is that they are ineffective and costly to use.

One drawback with such prior art devices and methods is a substantial loss of fibres when spraying, resulting in a more expensive surface coating. Another problem with such prior art devices and methods is that they can result in a surface coating having an unfavourable strength, wherein the surface coating easily can crack.

Another drawback with such prior art devices and methods is that they are adapted to mortars of a specific consistence and are not suitable for spraying ordinary mortar or different types of mortar materials.

Another drawback with such prior art devices is that they are cumbersome and difficult to use.

BRIEF DESCRIPTION OF THE INVENTION

One object of the present invention is to overcome the above- mentioned problems and drawbacks. The present invention provides an efficient and user-friendly mortar spraying device and method for spraying a fibre reinforced mortar material onto a surface, wherein a strong mortar layer, such as a rendering, is obtained without substantial loss of fibres. The present invention prevents rebounding of fibres from inter alia the surface to be coated and provides a more uniform distribution of fibres in the mortar by disrupting the flow path of the fibres and directing the fibres radially into the surrounding mortar beam, wherein the fibres are wetted by the mortar, also when spraying an ordinary mortar mix for rendering.

Hence, the present invention relates to a mortar spraying device for spraying a fibre reinforced mortar material onto a surface, comprising a spraying nozzle with a central tube for transporting a fibre flow of cut fibres to a downstream end of the spraying nozzle, and an outer tube enclosing at least a portion of the central tube and forming a passage between the tubes for transporting a mortar flow to the downstream end of the spraying nozzle, characterised in that the spraying nozzle comprises a fibre flow directing means for directing the fibre flow radially into the mortar flow when exiting the spraying nozzle. The fibre flow directing means redirect the fibre flow so that the fibres are wetted by the enclosing mortar flow, wherein the fibres are caught by the mortar flow and follows the mortar flow onto the surface to be sprayed. This results in a reduced bouncing of fibres against the surface to be sprayed and a more efficient spraying of fibre reinforced mortar. Further, this results in a stronger rendering or similar as the use of the fibres is more efficient and as the fibre distribution more easily can be controlled.

The fibre flow directing means is arranged to provide turbulence and disrupt the substantially linear flow of cut fibres and redirect or guide the fibre flow into the mortar flow. The fibre flow directing means can be arranged inside the central tube just before the downstream end thereof. Alternatively, the fibre flow directing means can be substantially aligned with the mouth of the central tube. Alternatively, the fibre flow directing means can be arranged just outside the central tube, for example by means of a support or similar. The fibre flow directing means can comprise at least one curved blade for directing the fibre flow into the mortar flow, and suitably the fibre flow directing means comprises at least two or more curved blades for directing the fibre flow into the mortar flow. For example, a first blade is curved in one direc- tion and a second blade is curved in the opposite direction, wherein the fibre flow is distributed more evenly into the mortar flow. Then, for example, a first portion of the fibre flow is directed into a first half of the mortar flow, such as the left or lower part, wherein a second portion of the fibre flow is directed into a second half of the mortar flow, such as the right or upper half. The blades can be substantially triangular having an apex pointing upstream and a side arranged at the downstream end of the central tube, so that the fibre flow smoothly can follow and be guided by the blades. Alternatively, the device comprises a plurality of fibre flow directing means, such as curved blades or similar, distributed around the envelope surface of the central tube. Alternatively, the fibre flow directing means comprises at least one helical blade, suitably at least two helical blades, which can extend substantially diagonally in relation to each other to obtain a more uniform distribution of fibres. The central tube can be connected to a cutter for cutting thread fed to the cutter from a thread storing device or a fibre storing device, such as a bobbin with a winded thread or uncut fibre or similar. Alternatively, the central tube can be connected to a supply of cut fibres. The cutter and the thread or fibre storing device can be arranged remote from the spraying nozzle, wherein the spraying nozzle can be of light weight and easy to handle. Simultaneously, the fibre or thread storing device and optionally the cutter can be positioned in a remote box for protecting the thread and the cutter from moisture as moisture can result in that the thread is sticking and getting jammed. The cutter can be connected to the central tube through a fibre feeding hose for feeding cut fibre from the cutter to the central tube. For example, the fibre feeding hose extends from the cutter arranged inside said box and the central tube of the spraying nozzle. Alternatively, the cutter is arranged on the spraying nozzle, so that the cutter is carried along with the spraying nozzle, wherein thread for example is fed from the thread storing device through the hose to the cutter.

The outer tube can comprise a plurality of venturi bores distributed around the outer tube and connected to an air stream forming device to provide the mortar flow. Hence, the spraying nozzle can be driven by means of a compressor or similar to provide the mortar flow. The venturi bores are for example evenly distributed around the outer tube to obtain a smooth and evenly distributed mortar flow.

The spraying nozzle can be hand-operable, so that one person easily can operate the spraying nozzle. The cutter comprises a housing having a thread inlet for a thread or uncut fibre to be cut into fibres, a cutting wheel and a counter wheel inside said housing for cutting said fibre, and an air inlet for an air stream providing an accelerated flow of cut fibres. The cutting wheel can be arranged as a driving wheel rotating the counter wheel, so that fibre is clamped and pulled in between the wheels to be cut by the action of cutting knives or edges on the cutting wheel. Also the cutter can be driven by means of an air stream forming device, such as a compressor, wherein the driving cutter wheel is rotated by means of a pneumatic engine. Also, the air stream introduced through the air inlet can be obtained from a compressor or similar.

The housing of the cutter can be formed to obtain a smooth air flow from the rear or upstream portion of the cutter, around the periphery of the housing interior and towards the outlet to provide a smooth non-jamming fibre flow. The housing can be formed with a rounded rear portion which terminates in a funnel towards the outlet. The air inlet is provided in the rounded rear portion. An air guide can be positioned in front of the air inlet on the inside of the housing for guiding the air stream around the wheels arranged therein and guiding the air stream along the interior surface of the housing. For example, the air guide is formed for dividing the air stream into an upper air stream above the cutting wheel and the counter wheel and a lower air stream below the cutting wheel and the counter wheel, which upper and lower air streams are brought together again at the downstream end of the cutter towards the outlet. The air stream prevents the cut fibres from entering undesired portions of the cutter and guides the cut fibres towards the outlet, wherein the air stream and the cut fibres form the accelerated fibre flow which is fed to the central tube of the spraying nozzle.

The cutter and/or the spraying nozzle can be connected to the fibre feeding hose through a swivel, wherein the hose can be rotated without affecting the spraying nozzle and the spray direction for the operator. The spraying nozzle can also be connected with a mortar hose through a swivel to facilitate use of the device. In addition the cutter can be formed with a plurality of inlets for different types of fibres, polymer or similar additives to be cut and included in the rendering.

The exterior of the central tube or a portion thereof can be provided with a replaceable protective coating to prevent wearing of the central tube due to the mortar flow. Otherwise the mortar transported in the annular space between the tubes wears out the central tube, wherein the central tube must be replaced frequently. For example, the protective coating is formed as a hose of a rubber material, such as polyurethane rubber, which is inexpensive and easily replaced. The present invention also relates to a mortar spraying method for spraying a fibre reinforced mortar material onto a surface by means of a spraying nozzle, comprising the steps of feeding a flow of cut fibres to a central tube of said spraying nozzle, and feeding a mortar flow through an outer tube enclosing at least a portion of the central tube and forming a mortar flow in a passage between the tubes, characterised by the step of directing the fibre flow radially into the mortar flow when exiting the spraying nozzle. The fibre flow is directed radially outwards providing a conical beam of cut fibres outside the central tube. The method can further comprise the steps of directing the fibre flow inside the central tube at the downstream end thereof, wetting at least a substantial amount of the cut fibres with mortar in front of the central tube or the spraying nozzle but before reaching the surface to be coated by the fibre reinforced mortar, introducing an air stream to the outer tube through a plurality of venturi bores in said outer tube and thereby providing the mortar flow, and/or feeding cut fibres to the spraying nozzle from a remote fibre storing device. The method can also comprise the steps of feeding the thread or uncut fibre to a cutter, cutting the thread or fibre by means of a cutting wheel and a counter wheel of said cutter, introducing an air stream to said cutter, dividing said air stream into a first air stream and a second air stream and guiding the air streams around the cutting wheel and the counter wheel, and thereby providing the fibre flow of cut fibres.

Consequently, the present invention is favourable for providing a surface with a rendering, and different material layers can be applied onto the surface with the device and method according to the invention. For example the surface can initially be coated with a primer, with or without cut fibres or other additives, wherein the fibre feeding and cutting function of the device can be turned on and off and primer can be supplied to the outer tube. Then a reinforcing mortar layer having cut fibres can be applied, wherein the rein- forcing mortar layer can be coated with a final rendering and paint or similar. Further characteristics and advantages of the present invention will become apparent from the description of the embodiments below, the appended drawings and the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail by means of embodiment examples and with reference to the enclosed drawings, on which:

Fig. 1 is a schematic section view of a mortar spraying device according to one embodiment of the invention,

Fig. 2 is a schematic section view of a mortar spraying device according to another embodiment of the invention,

Fig. 3 is a schematic section view of the downstream portion of the spraying nozzle, showing a fibre flow directing means according to one embodiment of the present invention,

Fig. 4 is a schematic perspective view of the downstream portion of the spraying nozzle according to Fig. 3,

Fig. 5 is a schematic section view of the downstream portion of the spraying nozzle, showing a fibre flow directing means according to another embodi- ment of the present invention,

Fig. 6 is a schematic section view of the downstream portion of the spraying nozzle, showing a fibre flow directing means according to yet another embodiment of the present invention,

Fig. 7 is a schematic view of a spraying nozzle connected to a remote thread storing device and a mortar supply, Fig. 8 is a schematic section view of a spraying nozzle comprising a cutter, and

Fig. 9 is a schematic section view of a cutter according to one embodiment of the invention.

THE INVENTION

Fig. 1 illustrates one embodiment of a mortar spraying device accord- ing to the invention. The mortar spraying device comprises a spraying nozzle 10 for spraying mortar materials and fibre reinforced mortar materials onto a surface, such as a wall, and build up one or more mortar layers, such as a rendering, plastering or similar surface coating, on said surface. For example, the mortar spraying device is arranged to enable spraying of different types of mortars, such as primers, reinforcing layers, final renders and similar, wherein the mortar spraying device can be used to build up a complete rendering having a plurality of layers. The spraying nozzle 10 according to the illustrated embodiments is hand-operable, wherein a single operator can grip, carry and control the spraying nozzle by hand. The spraying nozzle 10 comprises a central tube 11 forming a conduit for fibres, and an outer tube 12 forming a conduit for mortar or similar. The tubes 11 , 12 are, for example, made of steel. The central tube 11 is for example cylindrical having a substantially circular circumference externally as well as internally, wherein the outer tube 12 is arranged with a substantially circular cylindrical interior. Of course, other shapes can be used, such as tubes having a polygonal cross section.

The central tube 11 is arranged for transporting cut fibres to a downstream end of the spraying nozzle by means of a first air stream forming an accelerated fibre flow of the cut fibres. The air stream is, for example, pro- vided by means of a compressed air aggregate, such as a compressor or similar. For example, the central tube 11 is arranged with a diameter of about 2-50 mm, suitably 5-25 mm and for example 6-10 mm or about 8 mm to reduce the consumption of air. The central tube 11 is connected to a supply of cut fibres or a cutter for cutting thread fed to the cutter from a thread storing device, so that cut fibres are introduced to the central tube 11. The cutter and the thread storing device are described in more detail below. The fibre is, for example, transported from the thread storing device or the cutter through a first hose 13 or similar. The first hose 13 is, for example, connected to the central tube 11 through a swivel 14, wherein the first hose 13 can be rotated without effecting the spray direction for the operator.

According to the illustrated embodiments, the central tube 11 extends upstream and projects out from the outer tube 12 and is followed by a curved portion 15 which terminates in a straight portion 16. Hence, cut fibres are introduced into the central tube 11 through the straight portion 16 and the curved portion 15, wherein the fibre flow follows a smooth predetermined path as the central tube 11 is rigid so that the fibres are prevented from getting stuck. The outer tube 12 encloses at least a portion of the central tube 11 and is arranged with a greater diameter than the central tube 11 , forming an annular passage between the tubes 11 , 12 for transporting mortar to the downstream end of the spraying nozzle 10. The outer tube 12, or at least a portion thereof, is coaxial to the central tube 11. The outer tube 12 is arranged for transporting mortar materials from a mortar supply to the downstream end of the spraying nozzle 10 by means of a second air stream forming an accelerated mortar flow. For example, the outer tube 12 or a portion thereof is replaceable, so that the diameter thereof is variable in accordance with the diameter of the central tube and the application. According to the embodiment of Fig. 1 the outer tube 12 is provided with a coupling 17 connected to a compressed air aggregate through an air conduit 18 to introduce an air stream into the outer tube 12. The coupling 17 is preferably arranged for enclosing a portion of the outer tube 12, forming a space 19 around said portion of the outer tube. Hence, compressed air can be produced by the compressed air aggregate, conducted through the air conduit 18 to the space 19 formed by the coupling 17, and introduced to the outer tube 12 through venturi bores 20 connecting the space 19 and the inte- rior of the outer tube 12. The venturi bores 20 extend from the interior of the outer tube 12 to the exterior thereof and into the space 19, wherein compressed air can be introduced to the outer tube 12 through the venturi bores 20 to obtain the accelerated mortar flow. The coupling 17 is, for example, connected to the outer tube 12 in a conventional manner. The compressed air fed to the outer tube 12 is adjustable by means of a control.

The outer tube 12 extends along at least a portion of the central tube

11 as described above. The outer tube 12 is connected to a second hose 21 for supply of mortar. The second hose 21 is connected to the mortar supply and the mortar is, for example, fed through the second hose 21 to the outer tube 12 of the spraying nozzle 10 by means of a pump or similar. According to the illustrated embodiment the second hose 21 is connected to the outer tube 12 through a swivel 22, wherein the second hose 21 can be rotated without effecting the spray direction for the operator. The mortar spraying device is suitably provided with a control for controlling the mortar flow.

According to the illustrated embodiment, the outer tube 12 comprises or is provided with or is formed with a grip portion 23, such as a pistol-grip, for the operator. The grip portion 23 is connected to the second hose 21 , for example through the swivel 22, wherein mortar is introduced through the grip portion 23. A rear portion 24 of the outer tube 12 is arranged for sealing against the central tube 11 where the central tube 11 enters the outer tube12.

The central tube 11 is for example displaceable along the outer tube 12, wherein the central tube 11 can be inserted through a rear opening in the outer tube 12 and positioned according to the application. The central tube 11 can extend to a position just inside the downstream end of the outer tube

12 as shown in the drawings. Alternatively, the central tube 11 can extend to the downstream end of the outer tube 12, wherein the downstream ends of the tubes 11 , 12 are aligned. Alternatively, the central tube 11 can extend somewhat beyond the downstream end of the outer tube 12. The position of the downstream end of the central tube 11 is adjustable to enable setting of the beam of fibres in relation to the beam of mortar. The central tube 11 is, for example, fastened to the rear portion 24 of the outer tube 12 by means of a screw 25 extending through an aperture in the outer tube 12.

The spraying nozzle 10 is arranged for transporting mortar through the outer tube 12 and cut fibres through the central tube 11 simultaneously, wherein the mortar and the cut fibres are blown out from the downstream end of the spraying nozzle simultaneously and wherein the mortar flow forms an enclosing casing around the fibre flow.

The downstream end of the spraying nozzle 10 is provided with a fibre flow directing means 26 to redirect the fibre flow and guide it radially into the mortar flow when the mortar exits the spraying nozzle 10. The fibre flow is directed into the mortar flow by means of the fibre flow directing means 26, wherein the fibres are wetted by the mortar before reaching the surface to be coated, without substantially disturbing the mortar flow. Preferably the cut fibres are wetted by the mortar just in front of the spraying nozzle 10. The flow directing means 26 will be described in more detail below.

Fig. 2 illustrates another embodiment of a mortar spraying device according to the invention. According to the embodiment of Fig. 2 the outer tube 12 is formed by the grip portion 23, the rear portion 24 and a venturi portion 27 connected to a mouth portion 28 through an intermediate portion 29. The venturi portion 27 is connected to the coupling 17, wherein the air stream produced by the compressed air aggregate can be introduced into the outer tube 12 through the air conduit 18, the space 19 formed by the coupling 17, and the venturi bores 20 in the venturi portion 27. The venturi portion 27, the intermediate portion 29 and the mouth portion 28 are, for example, threaded for detachable connection to each other and to the remaining part of the outer tube 12.

The venturi bores 20 are inclined towards the downstream end to direct the air stream and accelerate the mortar flow towards said downstream end, wherein the mortar flow is guided by the fibre flow directing means 26. For example the venturi portion 27 of the outer tube 12 is provided with ten venturi bores, uniformly distributed around it to provide a uniform beam of mortar. For example, the venturi portion 27 is provided with at least six ven- turi bores, suitably at least ten and preferably at least twelve venturi bores to obtain a favourable mortar spray beam being evenly distributed to enclose the fibre flow or fibre beam and also to obtain a homogenous mortar flow or mortar spray beam. Fig. 3 and Fig. 4 schematically illustrate the downstream portion of the spraying nozzle 10 and the fibre flow direction means 26 according to one embodiment of the invention. The fibre flow from the upstream end is substantially linear or straight. The fibre flow directing means 26 is arranged in the central tube 11 to direct the flow of cut fibres into the mortar flow when leaving the central tube 11 or the spraying nozzle 10. Hence, the fibre flow directing means 26 is arranged to redirect the fibre flow from an axial direction along the central tube 11 to an inclined radial direction to guide the fibre flow into the mortar flow. The fibre flow is illustrated by means of the arrows A and the mortar flow is illustrated by means of the arrows B in Fig. 3. Hence, the fibre flow direction means 26 forms a turbulence chamber or a whirl chamber at the downstream end to disturb the substantially linear fibre flow inside the central tube 11 and direct it in a radial direction when leaving the central tube 11. As is evident from the context the fibre flow is not directed to a completely and exclusively radial direction but is redirected from a substan- tially linear and axial direction to an inclined non-axial and outward direction towards the mortar flow substantially enclosing the fibre flow, wherein fibres are blown out in a conical or frusto-conical beam having the smaller diameter upstream. Hence, the direction of the fibre flow is changed from a substantially linear flow along the central tube 11 to a more turbulent flow resulting in a redirected fibre flow and a conical beam of cut fibres when exiting the downstream end of the central tube 11 , wherein the beam of cut fibres is wetted by the mortar flow outside or just in front of the spraying nozzle 10 or the central tube 11.

The fibre flow directing means 26 is fastened inside the central tube 11 just before the downstream end thereof. Alternatively, the fibre flow directing means 26 is arranged just outside the central tube 11 by means of a support or similar. According to the embodiment of Fig. 3 and Fig. 4 the fibre flow directing means 26 is formed by or comprises at least one curved blade for directing the fibre flow A into the mortar flow B. For example, the fibre flow directing means 26 comprises a first blade 26a curved in one direction and a second blade 26b curved in the opposite direction. For example, the first blade 26a is curved somewhat to the left or somewhat downwards to guide a portion of the fibre flow A in the same direction into the mortar flow B. Then the second blade 26b is curved somewhat to the left or somewhat upwards to guide the remaining portion of the fibre flow somewhat to the left or somewhat upwards into the mortar flow B. Alternatively, the fibre flow directing means 26 comprises a plurality of blades, such as three or more blades, ar- ranged in the central tube 11. For example, the fibre flow directing means 26 comprises 2-12 blades, suitably 4-10 and for example 6 blades distributed around the envelope surface of the central tube 11. The blades 26a, 26b are substantially triangular having an apex pointing upstream and a side arranged at the downstream end of the central tube 11. Hence, the upstream portion of the blades 26a, 26b are narrower than the downstream end thereof. Further, the blades 26a, 26b are fastened to the interior surface of the central tube 11.

Fig. 5 schematically illustrates the fibre flow direction means 26 according to one alternative embodiment of the invention. The fibre flow direct- ing means 26 according to the embodiment of Fig. 5 comprises or is formed as a triangular or conical unit 26c having a narrower upstream end and a wider downstream end to force the fibre flow A out in a radial direction and into the mortar flow B.

Fig. 6 schematically illustrates the fibre flow direction means 26 ac- cording to yet another alternative embodiment of the invention. The fibre flow directing means 26 according to the embodiment of Fig. 6 is formed by at least one helical plate 26d or blade or turned sheet or similar. Such a helical plate 26d is, for example, turned approximately half a turn. The helical plate 26d is inclined or arranged at an angle in relation to the central tube 11 and the substantially linear fibre flow A therein. According to one embodiment of the invention, the helical plate 26d extends diagonally inside a portion of the central tube 11 , for example from one wall portion to an opposite wall portion of the central tube 11. Hence, the helical plate 26d is arranged with a first end directed towards the downstream end of the central tube 11 and a second end directed towards the upstream end thereof. According to one embodiment of the invention a first and a second helical plate are arranged in a crosswise position in the central tube 11. Fig. 7 is a schematic view of a spraying device according to one embodiment of the present invention, wherein the spraying device comprises a spraying nozzle 10 connected to a remote thread storing device 30 and a mortar supply 31. The spraying nozzle 10 is for example connected to the thread storing device 30 by means of the first hose 13 and to the mortar sup- ply 31 by means of the second hose 21. The thread storing device 30 is for example formed as a box 32 or similar having a lid 33, wherein the box 32 is substantially moisture resistant so that the content in the box 32 can be kept substantially dry to avoid the fibre from clogging or sticking. The box 32 is arranged to contain a conventional thread bobbin 34 or fibre bobbin of winded uncut fibre. According to the embodiment of Fig. 7 the box 32 is arranged also to contain the cutter 35 for cutting the thread into fibres. Further, the box 32 comprises a compressed air aggregate to provide the flow of cut fibres to the spraying nozzle 10 through the first hose 13. Hence, the box 32 containing the fibre bobbin 34 and the cutter 35 is arranged remote to the spraying nozzle 10, wherein the fibre bobbin 34 and the cutter 35 is protected from moisture and wherein the spraying nozzle 10 can be handled easily.

The mortar supply 31 is also arranged remote to the spraying nozzle 10. The mortar supply 31 is, for example, arranged as a mortar container for premixed mortar or as a mortar mixer for mixing a dry mortar mix with water or a solution to form mortar. Further the mortar supply comprises or is connected to a pump for pumping the fresh mortar to the spraying nozzle 10.

Alternatively, the cutter 35 is arranged on the spraying nozzle 10, which is illustrated with reference to Fig. 8. According to the embodiment of Fig. 8 the cutter 35 is connected to the upstream portion of the central tube 11 , which then may be terminated just beyond the rear portion 24 of the outer tube 11. Then the spraying nozzle 10 comprises or carries the cutter 35. Fig. 9 is a schematic section view of a cutter 35 according to one embodiment of the invention. The cutter 35 is arranged to cut a thread or uncut fibre into pieces, e.g. to cut a continuous thread or fibre into smaller pieces of fibre. The cutter 35 comprises a housing 36, at least one thread inlet 37 for the thread, an outlet 38 for cut fibres, a cutting wheel 39 for cutting the thread into fibres and a counter wheel 40 for bearing against the cutting wheel 39 and for pressing the thread towards the cutting wheel 39. For example, the cutter 35 is driven by compressed air or similar in a conventional manner and thus comprises or is connected to an air engine. Further, the thread inlet 37 is for example connected to a thread storing device as described above through a hose or similar.

The cutter wheel 39 is for example a driving wheel rotating the counter wheel 40. For example, the counter wheel 40 is a rubber wheel comprising a rubber coating to increase the friction and facilitate the driving action. The counter wheel 40 is for example adjustable, so that the distance to and pressing action against the cutter wheel can be adapted in accordance with the application. Further, the cutter 35 according to the embodiment of Fig. 9 comprises a pressing wheel 41 for guiding the thread around the counter wheel 40 towards the cutting wheel 39. For example, the pressing wheel 41 is biased towards the counter wheel 40 by means of an o-ring or similar conventional means.

The cutting wheel 39 comprises at least one and preferably a plurality of cutting knifes or edges 42, wherein fibre is cut or broken off when clamped between the rotating counter wheel 40 and the rotating cutting wheel 39. For example, the cutting edges 42 are straight and extend along the exterior of the cutting wheel 39. Alternatively the cutting edge 42 is diagonal, inclined or helical.

Hence, the thread is introduced into the cutter 35 through the inlet 37, which is illustrated by means of the arrow C. Then the thread or uncut fibre is clamped between the pressing wheel 41 and the counter wheel 40, wherein the thread is pulled into the cutter 13 by the wheels 40, 41 when these are rotated. Also the thread is guided towards the cutting wheel 39 for cutting the thread into fibres having suitable length. Cut fibre is then fed to the outlet 38 in a fibre flow in the direction illustrated by means of the arrow D.

The cutter 35 comprises an air inlet 43 for introducing an air stream into the cutter 35 to provide the fibre flow D of cut fibres inside the cutter 35 and for transporting the cut fibre out through the outlet 38 and to the spraying nozzle through a hose or directly. The air inlet 43 is arranged in the rear portion or upstream portion of the cutter 35, wherein the outlet 38 is arranged in a front portion or a downstream portion thereof. Air, such as compressed air, is introduced into the cutter 35 in a direction illustrated by means of the arrow E, for example through a conventional conduit connected to a compressed air aggregate such as a compressor, which are not illustrated in Fig. 9.

Just inside the housing 36 of the cutter 35 and in front of the air inlet 43 is an air guide 44 arranged to guide the introduced air around the wheels 39-41 , or around the cutting wheel 39, the counter wheel 40 and the pressing wheel 41. Hence, the air guide 44 is arranged a distance from the interior end of the air inlet 43 and substantially between the air inlet 43 and the wheels 39-41 arranged inside the housing 36 to force the air around them and substantially guide the air to follow the interior surface of the housing 36. The air guide 44 is positioned in front of the air inlet 43 for dividing the air stream into a first air stream, which is illustrated by means of the arrow F, on one side of the cutting wheel 39 and the counter wheel 40 and a second air stream, which is illustrated by means of the arrow G, on the opposite side of the cutting wheel 39 and the counter wheel 40. For example the first air stream F is an upper air stream, wherein the second air stream G is a lower air stream. The housing 36 is formed with a rounded shape at its rear or upstream portion to smoothly guide the air along the inner surface of the housing 36 wall. The rounded shape of the housing 36 is then terminated in a funnel towards the downstream end and the outlet 38, so that the fibre flow D formed by cut fibres and the air stream smoothly can exit the cutter 35 without get- ting stuck to avoid jamming.

According to one embodiment of the invention a surface, such as a wall, is provided with mortar, such as a rendering or a plastering, in a plurality of layers. For example, the surface is provided with three layers of mortar, i.e. a first mortar layer with or without any reinforcing fibres, a fibre reinforced second mortar layer, and a third mortar layer without any fibres. The first mortar layer is sprayed by means of a spraying nozzle as described above, wherein the fibre flow has been turned off. The first mortar layer is for example a mortar primer or similar. Then, the fibre flow is activated, for example by means of a conventional control such as a lever or a button, wherein the fibre reinforced second layer is provided by spraying both mortar and fibre with the spraying nozzle. Then, the fibre flow is again turned off or deactivated, wherein the third mortar layer is provided by means of spraying with the spraying nozzle. The third mortar layer is for example a final coating or rendering. The mortar supply is for example adjustable, wherein the mortar mix, flow rate, type and composition are adjustable in accordance with the application.

Claims

1. A mortar spraying device for spraying a fibre reinforced mortar material onto a surface, comprising a spraying nozzle (10) with a central tube (11) for transporting a fibre flow (A) of cut fibres to a downstream end of the spraying nozzle (10), and an outer tube (12) enclosing at least a portion of the central tube (11 ) and forming a passage between the tubes (11, 12) for transporting a mortar flow (B) to the downstream end of the spraying nozzle (10), characterised in that the spraying nozzle (10) comprises a fibre flow directing means (26) to direct the fibre flow (A) radially into the mortar flow (B) when exiting the spraying nozzle (10).

2. A mortar spraying device according to claim 1, characterised in that the fibre flow directing means (26) is arranged inside the central tube (11 ) at the downstream end thereof.

3. A mortar spraying device according to claim 1 or2, characterised in that the fibre flow directing means (26) comprises at least one curved blade for directing the fibre flow (A) into the mortar flow (B).

4. A mortar spraying device according to claim 3, characterised in that the fibre flow directing means (26) comprises a first blade (26a) curved in one direction and a second blade (26b) curved in the opposite direction.

5. A mortar spraying device according to claim 4, characterised in that the first blade (26a) is arranged to redirect fibres flowing in one portion of the central tube (11) and the second blade (26b) is arranged to redirect fibres flowing in another portion of the central tube(11).

6. A mortar spraying device according to claim 5, characterised in that the blades (26a, 26b) are substantially triangular having an apex pointing upstream and a side arranged at the downstream end of the central tube (11).

7. A mortar spraying device according to any of claims 1-5, characterised in that the fibre flow directing means (26) comprises at least one helical blade.

8. A mortar spraying device according to any of the preceding claims, characterised in that the central tube (11 ) is connected to a cutter (35) for cutting thread fed to the cutter (35) from a thread storing device (30).

9. A mortar spraying device according to claim 8, characterised in that the cutter (35) and the thread storing device (30) is arranged remote from the spraying nozzle (10).

10. A mortar spraying device according to claim 9, characterised in that the cutter (35) is connected to the central tube (11) through a fibre feed- ing hose (13) for feeding cut fibre from the cutter (35) to the central tube (11 ).

11. A mortar spraying device according to claim 10, characterised in that the cutter (35) and the thread storing device (30) is arranged in a box (32) protecting the thread from moisture.

12. A mortar spraying device according to claim 8, characterised in that the cutter (35) is arranged on the spraying nozzle (10).

13. A mortar spraying device according to claim 12, characterised in that the cutter (35) is connected to the thread storing device (30) through a thread feeding hose (13) for feeding the thread.

14. A mortar spraying device according to any of the preceding claims, characterised in that the outer tube (12) comprises a plurality of ven- turi bores (20) distributed around the outer tube (12) and connected to an air stream forming device to provide the mortar flow (B).

15. A mortar spraying device according to any of the preceding claims, characterised in that the spraying nozzle (10) is hand-operable.

16. A mortar spraying device according to any of the preceding claims, characterised in that the cutter (35) comprises a housing (36) having a thread inlet (37), a cutting wheel (39) and a counter wheel (40) inside said housing (36) for cutting said fibre, and an air inlet (43) for an air stream providing an accelerated flow of cut fibres.

17. A mortar spraying device according to claim 16, characterised in that an air guide (44) is positioned in front of the air inlet (43) for dividing the air stream into a first air stream (F) on one side of the cutting wheel (39) and the counter wheel (40) and a second air stream (G) on the opposite side of the cutting wheel (39) and the counter wheel (40).

18. A mortar spraying device according to claim 17, characterised in that the housing (36) is provided with a rounded shape terminating in a downstream funnel to guide the first and second air streams (F, G) around the cutting wheel (39) and the counter wheel (40) and towards the funnel and an outlet (38).

19. A mortar spraying method for spraying a fibre reinforced mortar material onto a surface by means of a spraying nozzle (10), comprising the steps of feeding a flow (A) of cut fibres to a central tube (11 ) of said spraying nozzle (10), and feeding a mortar flow (B) through an outer tube (12) enclosing at least a portion of the central tube (11) and forming a passage between the tubes (11, 12) for the mortar flow (B), characterised by the step of directing the fibre flow (A) radially into the mortar flow (B) when exiting the spraying nozzle (10).

20. A mortar spraying method according to claim 19, characterised by the step of directing the fibre flow (A) inside the central tube (11 ) at the downstream end thereof.

21. A mortar spraying method according to claim 19 or 20, characterised by the step of wetting at least a substantial amount of the cut fibres with mortar in front of the spraying nozzle (10) but before reaching the surface to be coated by the fibre reinforced mortar.

22. A mortar spraying method according to any of claims 19-21, characterised by the step of introducing an air stream to the outer tube (12) through a plurality of venturi bores (20) in said outer tube (12) and thereby providing the mortar flow (B).

23. A mortar spraying method according to any of claims 19-22, characterised by the step of feeding cut fibres to the spraying nozzle (10) from a remote thread storing device (30).

24. A mortar spraying method according to any of claims 19-23, characterised by the steps of feeding thread to a cutter (35), cutting the thread into fibres by means of a cutting wheel (39) and a counter wheel (40) of said cutter (35), introducing an air stream (E) to said cutter (35), dividing said air stream into a first air stream (F) and a second air stream (G) and guiding the air streams (F, G) around the cutting wheel (39) and the counter wheel (40), and thereby providing the fibre flow (D, A).