Patent Publication Number: US-11639592-B2

Title: Spacer structure for a saw disc assembly and a saw disc assembly

Description:
BACKGROUND 
     The present invention relates to a spacer structure for a saw disc assembly of a sawing machine, comprising a hub device having a central axis and being adapted to be coaxially arranged between a pair of saw discs. It also relates to a spacer structure for a saw disc assembly of a sawing machine, comprising at least one elongated spacer means adapted to be arranged between a pair of axially peripheral saw discs in a substantially radial manner in relation to a central portion of said pair of peripheral saw discs. It furthermore relates to a spacer structure for a saw disc assembly of a sawing machine, comprising a hub device having a central axis and being adapted to be coaxially arranged between a pair of axially peripheral saw discs. 
     It also relates to a saw disc assembly comprising a pair of axially peripheral saw discs having a common rotational axis and a central portion coaxial to said rotational axis, and furthermore provided with such a spacer structure. 
     It furthermore relates to a sawing machine comprising a saw disc assembly. 
     Such spacer structure, such a saw disc assembly and such a sawing machine is known from WO 2012/102659, respectively. When manufacturing such a spacer structure, the material waste will be large due to the fact that the elongated spacer means and the huh device are cut out in one single piece. 
     OBJECT OF THE INVENTION 
     An object of the invention is to improve the design of the spacer structure, in order to simplify its manufacture. 
     SUMMARY OF THE INVENTION 
     This object has been solved by a spacer structure of the initially defined kind, wherein said huh device is configured and adapted to be detachably or non-detachably arranged at a proximal portion of an elongated spacer means. 
     The object has also been solved by a spacer structure of the initially defined kind, wherein a proximal portion of said elongated spacer means is constituted and adapted to be detachably or non-detachably arranged at a hub device, a distal portion of said elongated spacer means being configured and adapted to be detachably or non-detachably arranged between said pair of saw discs. The object has furthermore been solved by a spacer structure of the initially defined kind, wherein said hub device is configured and adapted to detachably or non-detachably receive a proximal portion of an elongated spacer means in a substantially radial manner in relation to the central axis of said hub device, said elongated spacer means being adapted to be arranged between said pair of saw discs, a distal portion of said elongated spacer means being constituted and adapted to detachably or non-detachably connect to said pair of peripheral saw discs. 
     Hereby is achieved a less complicated manufacturing or repair process, since in case a small part of the spacer structure has been damaged, it will not be necessary to remove and exchange only a part of the spacer structure, instead of the whole spacer structure. 
     Furthermore, during manufacture at least the elongated spacer means can be produced with less material waste, since they can be cut out more or less parallel to one another. Furthermore, cleaning of the cut out parts can be performed more easily. 
     It has also been solved by a saw disc assembly of the initially defined kind comprising the spacer structure of the invention. 
     Preferably, the central portion of said pair of peripheral saw discs and the huh device of said spacer structure, respectively, is provided with first fastening means for allowing said hub device to be connected between said pair of peripheral saw discs. 
     Hereby, heavy lifting of the spacer structure is avoided during its assembly. Furthermore, the spacer structure is glued onto the saw disc, and this operation is made easier by using a set of parts of a hub device and a plurality of elongated spacer means. 
     Yet furthermore, it has been solved by a sawing machine of the initially defined kind, comprising the saw disc assembly comprising the spacer structure of the invention. 
     Suitably, said hub device is substantially planar and is provided with first connection means and said elongated spacer means is substantially planar and is provided with second connection means, said first and second connection means being configured and adapted in such a way that they are corresponding connection means, said planar hub device and said planar elongated spacer means wall having substantially the same thickness parallel to said central axis, said hub device having at least one opening for receiving a fastening element for connection of said hub device to said central portion of said pair of peripheral saw discs, a distal portion of said spacer means having at least one bore for receiving a fastening element for connection to said pair of peripheral saw discs. 
     Preferably, said first connection means comprises a female member, the circumferential wall of said hub device defining an opening into a circumferential portion of said huh device and a retention portion extending from said opening and substantially in the circumferential direction of said hub device, said opening and said retention portion forming said female member. Furthermore, said second connection means comprises a male member, said male member including a protrusion in the proximal portion of said elongated spacer means. 
     Alternatively, said first connection means comprises a male member, said male member including a protrusion extending substantially radially at the circumference of said hub device. Furthermore, said second connection means comprises a female member, the proximal portion of said elongated spacer means defining an opening into the elongated spacer means, and a retention portion extending from said opening and in a transversal direction of said elongated spacer means, said opening and said retention portion forming said female member. 
     Hereby is achieved two alternative secure connections of the hub device and each elongated spacer means. 
     Suitably, the shape and dimensions of said male member correspond to those of the female member, the corresponding dimensions having predetermined dimensions. 
     Alternatively, said first connection means comprises a first bevelled surface of said hub and a said second connection means comprises a second bevelled surface of said elongated spacer means, said first and second bevelled surfaces being adapted for welding or soldering. 
     Hereby is achieved a third alternative secure connection of the hub device and the elongated spacer means. 
     Preferably, said elongated spacer means is made of metal, such as steel or aluminium. It may alternatively be made of a polymer material. Use of aluminium or a polymer material reduces the weight and cost of the product. 
     Suitably, at least the distal portion of said elongated spacer means is made of a material harder than that of the elongated spacer means. Alternatively, the distal portion of said elongated spacer means is a separate part, said separate part being made of a material harder than that of the elongated spacer means. 
     Hereby, the spacer means will add to the efficiency cutting operation, and will also not be subjected to wear quicker than that of the working portion of the saw disc. 
     Preferably, said distal portion is made of a powder metal material. Alternatively, said distal portion is made of a high speed steel having a hardness of at least 60 HRC. 
     Suitably, said distal portion is provided with a coating containing a nitride, such as TiCN, TiN, TiAlN, TiAlCN or CrN, applied by physical vapour deposition. 
     Preferably, the first fastening means of the saw disc assembly further comprises a plurality of first through holes in the central portion of said peripheral saw discs, and a plurality of first bores in said hub device, said first through holes of said pair of peripheral saw discs, and said first bores of said hub device being aligned with one another, and furthermore being parallel to said rotational axis when mounted. Suitably, a peripheral portion of said pair of peripheral saw discs and the distal portion of said elongated spacer means of said spacer structure is provided with second fastening means for allowing said elongated spacer means to be connected between said pair of peripheral saw discs. 
     Hereby is achieved a simplified assembly. 
     Preferably, said second fastening means comprises at least one second through hole in the radially peripheral portion of said pair of axially peripheral saw discs, and at least one second bore in the distal portion of said elongated spacer means, said second through hole of said pair of peripheral saw discs and said second bore of said spacer means being aligned with one another, and furthermore being parallel to said rotational axis when mounted. 
     Suitably, said peripheral saw discs are provided with at least one fluid inlet for allowing a fluid, such as air and/or water to enter the space between the peripheral saw discs not being occupied by the spacer structure. 
     Hereby, efficient cooling of the saw disc is achieved. Furthermore, dirt, i.e. sand, earth, concrete or asphalt between the saw blades is allowed to be flushed away during the cutting operation. 
     Preferably, an intermediate saw disc is arranged between said pair of peripheral saw discs, said spacer structure being arranged between a first of said peripheral saw discs and said intermediate saw disc, and optionally a second spacer structure being arranged between a second of said peripheral saw discs and said intermediate saw disc. 
     Alternatively, a pair of intermediate saw disc are arranged between said pair of peripheral saw discs, said spacer structure being arranged between the pair of intermediate saw disc, and optionally a second spacer structure being arranged between a first of said peripheral saw discs and a first of said intermediate saw disc, and optionally a third spacer structure being arranged between a second of said peripheral saw discs and a second of said intermediate saw disc. Preferably, at least one of the peripheral saw discs is an annular saw disc. Both peripheral saw discs may be annular saw discs. 
     Alternatively, a plurality of intermediate saw disc are arranged between said pair of peripheral saw discs, said spacer structure being arranged between at least two adjacent saw discs, and optionally at least one further spacer structure being arranged between one or more further adjacent saw discs. Preferably, at least one of the peripheral saw discs is an annular saw disc. Both peripheral saw discs may be annular saw discs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the invention will be described while referring to the accompanying drawings, in which 
         FIG.  1   a    is a rear perspective view of a laying machine with a sawing machine having a saw disc device; 
         FIG.  1   b    is a front perspective view of the laying machine shown in  FIG.  1   ; 
         FIG.  2    is an exploded view of the saw disc device shown in  FIGS.  1   a  and  1   b   , including a saw disc assembly provided with spacer structures. 
         FIG.  3    is a zoomed in part of a cross-section of a peripheral portion of the saw disc assembly shown in  FIG.  2   ; 
         FIGS.  4   a - 4   d    are side views of a spacer structure of the kind shown in  FIGS.  2  and  3   ; 
         FIG.  5    is a side view of an alternative spacer structure; 
         FIG.  6    is a side view of a part of an alternative spacer structure; 
         FIG.  7    is a side view of a part of an alternative spacer structure; 
         FIG.  8    is a side view of a part of an alternative spacer structure; 
         FIGS.  9   a - 9   b    are side views of an alternative spacer structure; 
         FIGS.  10   a - 10   b    are side views of an alternative spacer structure; 
         FIG.  11    is a side view of an alternative spacer structure; and 
         FIG.  12    is a side view of an alternative spacer structure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS.  1   a - 1   b    show a laying machine  1  including a sawing machine  4  including a saw disc device  2  for making a trench  5  in the ground and a consolidation and laying means  3  for clearing and safeguarding the trench  5  from collapsing while laying at least one flexible casing or tube, cable or wire into the trench  5 . The at least one flexible casing or tube, cable or wire can be rolled off from a not shown reel mounted on the machine  1 . A disc guard  18  covers the portion of the saw disc device  2  that is above ground level. 
     The machine  1  shown in  FIGS.  1   a - 1   b    has two front wheels  7  and a rear wheel  8 . A motor  6 , preferably a diesel engine, provides power to propel the machine  1 . The motor  6  is also responsible for rotating the saw disc device  2 , preferably through a belt transmission (not shown). 
     The saw disc device  2 , the disc guard  18 , and the consolidation and laying means  3  are mounted at a first side of the machine  1 , here shown as the right hand side of the machine  1 . This enables the operator to place the trench  5  close to side structures such as walls. The saw disc device  2  and the consolidation and laying means  3  can be moved from the first side of the machine to the opposite second side (i.e. the left hand side). When changing sides, the disc guard  18  is replaced by a corresponding disc guard having a mirrored configuration. 
     As shown in  FIGS.  1   a - 1   b   , a seat  9  and feet support  10  are provided in the rear of the machine  1  straight behind the saw disc device  2  so that a seated driver can drive the machine  1  while closely monitoring and controlling the trench making, consolidation and laying operation. In the shown embodiment the seat  9  and the feet support  10  protrudes somewhat more to the right than the saw disc device  2  with the disc guard  18  and the consolidation and laying means  3 , which will somewhat limit how close the machine  1  can make a trench  5  along a wall. However, it would of course be possible to have a driver seat  9  which does not protrude farther than the saw disc device  2  with the disc guard  18  and the consolidation and laying means  3 . Such an embodiment may however reduce a seated operator&#39;s ability to visually monitor the trench making operation. The clearance Δh between the ground and the feet support  10  is suitably around 20-30 cm. This enables the machine  1  to go very close to lower side structures such as a pavement along a road. The laying machine  1  may also be arranged to be arranged to be controlled wireless so that the operator can choose between seated operation and remote controlled operation. 
     The saw disc device  2  is preferably driven by the same motor  6  that propels the machine  1  (the motor can e.g. be the same as used in the road saw model Husqvarna RS 8500 D or the floor saw model FS 9900 D). However, it would of course be possible to use separate motors for the saw disc device  2  and the propulsion of the machine  1 , as well as other motors types than those exemplified. 
     The motor  6  drives a shaft  17  that connects to the centre of the saw disc device  2 . The shaft  17  with the saw disc device  2  can be moved upwards and downwards to adjust the cutting depth of the trench  5 . The raising and lowering of the shaft  17  with the saw disc device  2  is preferably powered by the hydraulic system (not shown) that is powered by the motor  6 . In its most upward position the saw disc device  2  is above ground level, i.e. it is in a transport position, and in its most downward position the shaft  17  holding the saw disc device  2  is moved to a position close to the ground, e.g. only a few centimetres from ground level. The maximum trench depth can therefore be made almost as deep as the radius of the saw disc device  2 . Depending on how the machine  1  is configured, different blade diameters can be used; preferably the blade diameters are between 500-1200 mm. In one embodiment the saw disc device  2  can be lowered or raised to any position between these extremes, i.e. the trench depth can thereby be varied. In another embodiment the machine  1  has one or several fixed operating depths. 
     The working portion, i.e. the active portion at the periphery of the saw disc device  2 , is between 5-50 mm thick, preferably 5-30 mm, more preferably 10-25 mm, most preferably 15-25 mm. Thereby a thin trench can be cut, which requires less work to make than a thicker one. The saw disc device  2  is preferably of a kind used for floor saws and road saws including a saw disc assembly  200  of two or more saw discs  201  (see  FIG.  2   ). The saw disc assembly  200  may comprise a steel plate that preferably has diamond-impregnated segments at the periphery (working portion) of the blade. Steel plates having diamond-impregnated segments at the periphery are for instance sold by Husqvarna AB. Alternatively, the periphery of the saw disc may comprise metal powder or a coating containing a nitride, such as TiCN, TiN, TiAlN, TiAlCN or CrN. 
     As can be seen in  FIGS.  1   a - 1   b   , the disc guard  18  includes a hinged lid  18   a  that can be opened to access the saw disc device  2 . When closed the disc guard  18  has a width slightly larger than the width of the saw disc device  2 . In the preferred embodiments the saw disc device  2  is arranged to rotate in an upcut direction, i.e. a rotational direction where the lowest portion of the saw disc device  2  moves in the forward driving direction of the machine  1 . Therefore, dust and any debris from the trench making, consolidation and laying operation will mainly exit the trench  5  in front of the saw disc device  2 . To collect this dust and debris dust duct  19  is provided in the front section of the disc guard  18 . The dust duct  19  has an dust inlet  22  arranged close to the ground in front of the saw disc device  2  for receiving dust from the upcut rotation of the saw disc device  2 , and a disc guard dust outlet  21  located above the disc guard dust inlet  22 . An upper wall of the disc guard dust duct  19  is partly defined by a flexible sealing member  20  sealing towards the saw disc device  2  and preventing dust from entering the upper volume of the disc guard  18 . The sealing member  20  could e.g. be two rubber strips or two brushes. 
     A not shown dust collector can be connected to the disc guard dust outlet  21 , to receive dust and debris from the trench making operation. The dust collector may include suction means or other active means for conveying dust to a receiving compartment of the dust collector, for instance a screw conveyor. 
     The consolidation and laying means  3  shown in  FIGS.  1   a - 1   b    is manually put into the trench  5  and secured at the operating depth. When making a trench  5 , the laying machine  1  first makes au initial trench  5  with the saw disc device  2 . In this initial step the consolidation and laying means  3  is detached from the machine  1 . When the initial trench  5  has been made the saw disc device  2  is raised, and the consolidation and laying means  3  is inserted into the trench  5 , preferably already supporting the at least one flexible casing or tube, wire or cable. Alternatively the at least one flexible casing or tube, wire or cable can be provided to the consolidation and laying means  3  while in the trench  5 . Thereafter the consolidation and laying means  3  is secured to the laying machine  1  and the saw disc device  2  is lowered to the operating depth. 
     Furthermore, when arranged behind saw disc device  2 , i.e. during the trench making, consolidation and laying operation, the lowest portion of the consolidation and laying means  3 , i.e. its bottom  13 , is arranged to be located above the lowest portion of the saw disc device  2 , preferably between 10-100 mm above, more preferably 10-60 mm, most preferably 20-50 mm. Preferably the bottom  13  is not levelled but continuously or sequentially increasing the clearance to the bottom of trench  5  when moving from the front of the consolidation and laying means  3  to the rear of it. 
     The side walls  12  of the consolidation and laying means  3  prevents the trench walls from partly or completely collapsing before the at least one flexible casing or tube, cable or wire is fed into the trench  5 . The consolidation and laying means  3  further has one or more feeding ducts  14  that each has a inlet at an upper portion  15  of the consolidation and laying means  3  for receiving the flexible casing, cable or wire and an outlet at a rear end  16  of the consolidation and laying means  3  for feeding the cable or wire to the trench  5 . Each feeding duct  14  can be arranged to guide one or more flexible casings or tubes, wires, or cables, preferably one flexible casing or tube. Thus the at least one feeding duct  14  can be one, e.g. feeding a larger flexible casing with room for multiple cables, or several tubes, wires or cables on top of each other. Preferably the feeding duct  14  is at least two, preferably at least four. The consolidation and laying means  3  is preferably made open or openable at the upper portion of and towards the rear end  16  of the consolidation and laying means  3 , so that the at least one flexible casing or tube, wire, or cable can be fed by pushing it down into the consolidation and laying means  3 , i.e. this could be done while it is already in the trench  5 . Another alternative is to push the at least one flexible casing or tube, wire, or cable through the inlet of the feeding duct  14  to the outlet of the feeding duct  14 . A further option would be to have one of the side walls  12  of the consolidation and laying means  3  detachable, i.e. detaching it and putting the at least one flexible casing or tube, wire, or cable into the desired feeding duct  14 . 
     The consolidation and laying means  3  may have the same thickness or is no more than 1 mm thinner than the saw disc device  2 . The advantage with this embodiment is that both the saw disc device  2  and the consolidation and laying means  3  can be made as thin as possible, i.e. as thin as the size of the flexible casing or tube, cable or wire allows. 
     Alternatively, the consolidation and laying means  3  is made thinner than the saw disc device  2 , preferably at least 1 mm thinner, more preferably at least 2 mm thinner, most preferably at least 5 mm thinner, even more preferred 10 mm thinner. One advantage of having the consolidation and laying means  3  thinner than the saw disc device  2 , is that if the trench  5  is not to be cut in a straight line but rather allowing for a curvature, the lesser thickness of the consolidation and laying means  3  reduces the risk for it to get stuck in the trench  5 , i.e. the more thinner the consolidation and laying means  3  is in relation to the saw disc device  2 , the steeper curves can be done when making the trench  5 . 
     The wire laying machine  1  could further include, a temperature sensor (not shown) for sensing the temperature of the saw disc device  2 , a coolant and/or consolidation liquid supply means (not shown) for supplying liquid to the saw disc device  2 , and means for regulating the amount of supplied liquid (not shown) to the saw disc device  2  based on inputs from the temperature sensor. The coolant and/or consolidation liquid for either cooling the saw disc device  2 , or consolidating the trench  5  by wetting it thereby reducing risk of partly or entirely collapsing trench walls, or a combination of cooling the saw disc device  2  and consolidating the trench  5 . 
     Regarding the rotational direction of the disc, even though it is preferred to have upcut direction, the opposite would also be feasible. Of course then the dust inlet  22  and dust outlet  21  are suitably arranged at the rear end of the saw disc device  2 . When laying fibre optic cables it is common to put out hollow tubes or flexible casings where the fibre optic cables are blown out using air pressure through already installed tubes and/or casings, i.e. after that the tubes and/or flexible casings have been put down in trenches and been covered. The laying machine  1  may also include as UPS receiver which saves positional data which can be used in combination with digital maps to document the excavated trenches. 
     Furthermore the laying machine  1  may also include means for monitoring the cutting depth and to save this information in combination with the positional data. Also information about how many and which kind of flexible casings, tubes, cables or wires that have been laid down in the trenches. 
     Thereby a full documentation can be provided about where the trenches have been excavated, how deep they are, and what kind and how many cables, wires etc. that has been laid down in the trenches. 
       FIG.  2    shows a saw disc device  2  in the form of a saw disc assembly  200 , according to one embodiment, that is suitable for cutting a trench  5  with the laying machine  1 . The saw disc assembly  200  includes an inner first saw disc  201  and intermediate second saw disc  202  and an outer third saw disc  203 . 
     Each saw disc  201 ;  202 ;  203  has a working portion  201   a ;  202   a ;  203   a  at the periphery of the saw disc and a central portion  201   c ;  202   c ;  203   c  around the centre of the saw disc constituting an axis A-A of the saw disc assembly, and furthermore a saw disc support structure  201   b ;  202   b ;  203   b  extending between the working portion  201   a ;  202   a ;  203   a  and the central portion  201   c ;  202   c ;  203   c.    
     The saw discs are preferably made of metal, such as steel or aluminium or alloys thereof, but may be made of a polymer material. Alternatively, they may fully or partly be made of a speed steel having a HRC of more than 60 HRC, or a powder metal. Disregarding the base metal used, the periphery of the discs may have diamond-impregnated segments at the periphery or be provided with a coating containing a nitride, such as TiCN, TiN, TiAlN, TiAlCN or CrN. 
     The total thickness of the saw disc assembly  200  at is periphery is preferably 15-30 mm, more preferably 15-25 mm. The diameters of the first and third saw discs are preferably in the range 500-1200 mm. The intermediate second saw disc  202  can be of equal diameter or have up to 100 mm smaller diameter. The thickness of the saw discs is preferably in the range of 2-10 mm, more preferably 3-5 mm. The thickness of the segments is preferably in the range of 3-12 mm, more preferably 3.5-6 mm. The thickness of the segments of the intermediate second saw disc  202  may be thinner than those of the outer saw discs, e.g. 0.2-1 mm thinner. 
     A first spacer structure  204  is arranged between the inner first saw disc  201  and the intermediate second saw disc  202 , and a corresponding second spacer structure  205  is arranged between the intermediate second saw disc  202  and the outer third saw disc  203 . The spacer structures  204 ,  205  are of flat, substantially annular shape, including star shapes. 
     As can be seen in  FIG.  2   , the saw disc assembly  200  is clamped together at the central portion  201   c ;  202   c ;  203   c  of the saw discs  201 ,  202 ,  203  between an inner member  210  and an outer member  211 , a plurality of not shown securing bolts extending through first through holes  206  in the saw discs  201 ,  202 ,  203  and in corresponding first bores  225  in the spacer structures  204 ,  205 . 
     As can be seen in  FIGS.  2  and  3   , the saw disc assembly  200  is also secured by a plurality of bolts  213  in second through holes  207  in the periphery of the saw discs  201 ,  202 ,  203  and in corresponding second bores  238  in the spacer structures  204 ,  205 . A fluid inlet  208  is provided at a plurality of positions in the saw discs  201 ,  202 ,  203  to allow introduction of a fluid. This will be further discussed in connection with  FIG.  4   d    below. 
     In  FIGS.  4   a - 4   c    are shown the first spacer structure  204  provided with a hub device  220  provided with the first bores  225  and twelve elongated spacer means  230  provided with the second bores  238 . 
     The huh device  220  is furthermore provided with alternative first bores  225 ′ for adapting to alternative connection standards of sawing machines. 
     The elongated spacer means  230  is furthermore provided with a pair of peripheral guide holes  226  and a central guide hole  227 . 
     The hub device  220  has a substantially circular shape and is provided with twelve circumferentially arranged radially extending openings  221 , and a retention portion  222  extending from said radially extending opening  221  and substantially in the circumferential direction of said hub device  220 , said radially extending opening  221  and said retention portion  222  constituting a female member  223 . 
     In the huh device, a central opening  224  is arranged, adapted to receive said central bolt  215  (see  FIG.  2   ), also constituting a central axis A-A for the saw disc assembly  200 . 
     The elongated spacer means  230  provided at its proximal portion  231  with an axially extending stem  232 , and at the end of the axially extending stem a protrusion  233  extending in the transverse direction of said elongated spacer means  230 . The width of the axially extending stem  232  and the protrusion  233  are made with slightly smaller dimensions than that of the radially extending openings  221  and the retention portions  222 , i.e. the female member  223  of the hub device  220 , the axially extending stem  232  and the protrusion  233  together constituting a male member  234 . 
     At the distal portion  235  of the elongated spacer means  230 , a radially extending portion  236  is provided, having a clockwise extending portion  237   a  and in a counter-clockwise extending portion  237   b . Substantially centrally in the radially extending portion  236  of the distal portion  235 , a second bore  238  is provided for receiving said bolt  213  (see  FIG.  3   ). 
     It should be noted that at the proximal portion  231  of the elongated spacer means  230  has an end surface  239 , and that the axially extending stem  232  extends from the end surface  239 . According to this embodiment, the end surface  239  has the shape of an arc of a circle corresponding to and conforming to the substantially circular shape of the hub device  220 . 
     In  FIG.  4   d    is shown the first spacer structure  204  (or the second spacer structure  205 ), i.e. the hub device  220  and the twelve elongated spacer means  230  mounted onto the inner first saw disc  201 . Of course, it could as well be the intermediate second saw disc  202  or the outer third saw disc  203 . 
     When mounting the spacer structure onto the saw disc, the huh device is first glued onto and secured against the saw disc  201  by not shown bolts in the first bores  225  or in the alternative first bores  225 ′. 
     The peripheral guide holes  226  and a central guide hole  227  may be utilised when attaching a to facilitate gluing of the elongated spacer means  230  onto the saw disc, i.e. while positioning the male member  234  in the female member  222  and aligning the second bore  238  of the elongated spacer means with the second through hole  207  of the saw disc. They may also be utilised when performing e.g. physical vapour deposition or laser welding or laser sintering to achieve a hard surface at the distal portion  235  of the elongated spacer means  230 . 
     As mentioned above, the saw discs  201 ,  202 ,  203  are provided with fluid inlets  208 . The fluid may be a gas (such as air) or a liquid (such as water), or a combination, such as a mixture of water and air. 
     More particular, the fluid inlets  208  are provided in the saw discs  201 ,  202 ,  203  at a position radially outside the hub device  220  and in a circumferential direction between the elongated spacer means  230  to allow introduction of a fluid into the spaces between the elongated spacer means  230  inside the saw disc assembly  200 . The fluid is introduced inside the disc guard  18  (see  FIGS.  1   a - 1   b   ) by suitable means, such as a gas hose or a liquid hose either on one side of the saw disc assembly  200  or on both sides thereof. Preferably, the hose is provided with a not shown nozzle directed towards and at a distance from the first and/or third saw discs  201 ,  203 . The fluid is thus sprayed towards the first and/or third saw discs  201 ,  203 . The fluid is introduced through the fluid inlets  208  and will enter into the spaces between the saw discs  201 ,  202 ,  203  and move substantially radially between the elongated spacer means  230  and towards the periphery of the saw discs  201 ,  202 ,  203 . 
       FIG.  5    shows an alternative embodiment, according to which the elongated spacer means is divided into a radially extending part closest to the huh device  220 , and a peripheral, separate part  240  including the clock-wise and counter-clockwise extending portions  237   a ,  237   b  of the distal portion  235 . The separate part  240  are attached to the radially extending part  236  via distal female and male members  241 ,  242 , in a manner corresponding to that of the female and male members  223 ,  234  of the hub device  220  and the proximal end of the elongated spacer means  230 . Hereby, it is possible to choose different materials of the radially extending portion  236  and the separate part  240 . 
       FIG.  6    shows an alternative shape of the elongated spacer means  230 . Apart from a male member  234  at its proximal portion, the opposite, distal portion  235  has a cut-out  243  extending toward the proximal and for reducing weight of the spacer structure. 
       FIG.  7    shows the elongated spacer means  230  in the form of a circle sector  244 . Such a shape adds to the stability of the spacer structure. 
       FIG.  8    shows the elongated spacer means  230  having at its distal portion a counter-clockwise extending portion  237   b . This shape allows for production with less material spillage than what is the case regarding the embodiment shown in  FIG.  6   . 
       FIGS.  9   a - 9   b    show a variant, according to which the hub device  220  includes twelve male members  234  in the radial circumference thereof. The male member  234  has radially extending stem  232  and a protrusion  233  extending in the circumferential direction of the hub device  220 . 
     The proximal portion  231  of said elongated spacer means  230  defines an opening  221  from the end surface  239  and into the elongated spacer means, and a retention portion  222  extending from said opening  221  and in a transversal direction of said elongated spacer means  230 . 
     Thus, according to this variant, the hub device  220  is provided with a male member  234  about its substantially circumference, while the elongated spacer means  230  is at its proximal portion  231  provided with a corresponding female member  223 . 
     Also in this case, the proximal portion  231  of the elongated spacer means  230  has the shape of an arc of a circle (at  239 ) corresponding and conforming to the substantially circular shape of the huh device  220 . 
     Of course, also in this case, the clock-wise and counter-clockwise extending portions  237   a ,  237   b  of the distal portion  235  of the elongated spacer means  230  may be provided on a separate part  240 , as shown in  FIG.  5   . And of course, the female opening may instead be arranged on the separate part  240  and the male part on the radially extending portion  236 . 
       FIGS.  10   a - 10   b    illustrates an alternative embodiment, according to which the female member  223  of the hub device has a dovetail shape and the male member  234  has a corresponding dovetail shape. 
     Furthermore, the hub-device is a dodecagon (a 12-sided regular polygon) for receiving twelve elongated spacer means  230 , the proximal and of which having a substantially flat end surface  239  corresponding and conforming to the flat surfaces  245  of the dodecagonal hub device  220 . 
     Of course, also in this case, the clock-wise and counter-clockwise extending portions  237   a ,  237   b  of the distal portion  235  of the elongated spacer means  230  may be provided on a separate part  240 , as shown in  FIG.  5   . And of course, the female opening may instead be arranged on the separate part  240  and the male part on the radially extending portion  236 . 
     Of course, the female member  223  may instead be arranged on the elongated spacer member  230  and the male member  234  on the huh device  220 , in a manner corresponding to that of  FIGS.  9   a - 9   b   , however with flat end surface  239  of the elongated spacer means  230  and flat surfaces  245  of the hub device  220 . 
     As can be seen in  FIG.  11   , a substantially circular shaped hub device  220  may be provided with elongated spacer means  230  being interconnected by male and female members  223 ,  234  having a dovetail shape, arranged on the elongated member and the hub device, or vice versa 
     Consequently, the proximal portion  231  of the elongated spacer means  230 , i.e. the end surface  239  has the shape of an arc of a circle corresponding to and conforming to the substantially circular shape of the hub device  220   
     In order to allow connection of the elongated spacer means  230  to the hub device  220  by welding or soldering, a hub-device having a dodecagon shape with  12  first bevelled surfaces  250   a  is shown in  FIG.  12   . Also the proximal portion  231  of each elongated spacer means  230  (only one shown in  FIG.  12   ) is provided with a second bevelled surface  250   b . Depending on what kind of welding or soldering method is used, the first and second bevelled surfaces  250   a ,  250   b  may be made as male and female members or only as two male members (i.e. two correspondingly bevelled surfaces  250   a ,  250   b  pointing towards one another). 
     Of course, also in this case, the clock-wise and counter-clockwise extending portions  237   a ,  237   b  of the distal portion  235  of the elongated spacer means  230  may be provided on a separate part  240 , as shown in  FIG.  5   . And of course, the female opening may instead be arranged on the separate part  240  and the male part on the radially extending portion  236 . 
     When the saw disc assembly  200  is rotating, the spacer structure  204 ,  205  provides suction from the centre towards the periphery of the saw disc assembly, i.e. it operates similar to a centrifugal fan with radial fan saw discs. Therefore air and water will be transported from the centre and out at the periphery, efficiently cooling the saw discs. Of course instead the arrangement could be for transporting only air or only fluid or different combinations as further described below. 
     The fluid flow during operation is preferably in the range of 1-10 litre/minute. 
     Even though the number of saw discs  201 - 203  have been described as three, it would be possible to use only two saw discs and with one spacer structure in between. 
     Furthermore it could be possible to use even more saw discs, adding one spacer structure for each added saw disc. 
     Whereas the invention has been shown and described in connection with the preferred embodiments thereof it will be understood that many modifications, substitutions, and additions may be made which are within the intended broad scope of the following claims. From the foregoing, it can be seen that the present invention accomplishes at least one of the stated objectives. 
     For instance, the different embodiments of saw disc assemblies described in the present application could be used in other machines than the one described in the present application using circular cutting saw discs. For instance, the saw disc assemblies could be used in road saws and in hand held power cutters. Of course, in hand held power cutters, the saw disc diameter and other size factors can be smaller than the ranges mentioned above. 
     Furthermore, in the embodiments shown above, the number of elongated spacer means  230  is twelve. It should however be noted that any number of elongated spacer means could be used, as long as it does not affect the balance of the rotating saw disc assembly  200 . Thus, even as few as two diametrically arranged elongated spacer means could be used. Of course, more than twelve elongated spacer means could also be used. Depending on the number of elongated spacer means used, the huh device  220  may have to be adapted to the number of elongated spacer means. Consequently, in case three of five elongated spacer means are to be attached to the hub device, the female members or male members of the hub device will have to be distributed differently on the circumference of the hub device. 
     LIST OF REFERENCE SIGNS 
     
         
         Axis A-A 
         Clearance Δh 
         Laying machine  1   
         Saw disc device  2   
         Consolidation and laying means  3   
         Sawing machine  4   
         Trench  5   
         Motor  6   
         Front wheel  7   
         Rear wheel  8   
         Seat  9   
         Feet support  10   
         Side wall  12   
         Bottom  13   
         Feeding duct  14   
         Upper portion  15   
         Rear end  16   
         Shaft  17   
         Disc guard  18   
         Hinged lid  18   a    
         Dust duct  19   
         Sealing member  20   
         Dust outlet  21   
         Dust inlet  22   
         Saw disc assembly  200   
         Inner first saw disc  201   
         Intermediate second saw disc  202   
         Outer third saw disc  203   
         Working portion  201   a ;  202   a ;  203   a    
         Saw disc support structure  201   b ;  202   b ;  203   b    
         Central portion  201   c ;  202   c ;  203   c    
         First spacer structure  204   
         Second spacer structure  205   
         First through hole  206   
         Second through hole  207   
         Fluid inlet  208   
         Inner member  210   
         Outer member  211   
         Bolt  213   
         Central bolt  215   
         Hub device  220   
         Radially extending opening  221   
         Retention portion  222   
         Female member  223   
         Central opening  224   
         First bore  225   
         Male retention portion  229   
         Elongated spacer means  230   
         Proximal portion  231   
         Stem  232   
         Protrusion  233   
         Male member  234   
         Distal portion  235   
         Radially extending portion  236   
         Clockwise extending portion  237   a    
         Counter-clockwise extending portion  237   b    
         Second bore  238   
         End surface  239   
         Separate part  240   
         Distal female member  241   
         Distal male member  242   
         Cut-out  243   
         Circle sector  244   
         Flat surface  245   
         First bevelled surface  250   a    
         Second bevelled surface  250   b