Patent Publication Number: US-2012038125-A1

Title: Monocoque rollerski

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application which claims benefit under 35 USC 371 to co-pending International Application PCT/EP2009/062218, filed Sep. 21, 2009, and which claims priority under the Paris Convention to Italian application serial no. TV2008A000121, filed on Sep. 23, 2008, the entire contents of each of which are incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a roller ski having improved performance. 
     Roller skis are widely known in the state of the art. 
     A traditional roller ski structure comprises a supporting frame including a beam having ends provided with wheel mounts for operatively connecting to one or more wheels. 
     Different constructional technologies are currently adopted for providing the supporting frame. 
     According to a first known solution, the frame comprises a metal bar that is machined at the two ends to allow wheel mounting. Wheel mounts are also made of a metal material. 
     This solution has the advantage of a reduced weight but it provides poor shock absorption on rough ground and poor reaction to forces imparted by the user during the sports activity. 
     According to another known solution, the frame includes a beam composed of honeycomb wood panels. At the beam ends two metal blocks are fixed, suitably machined to allow wheel mounting. 
     This arrangement provides excellent absorption on rough ground and good reaction to forces from the user but it is characterised by high weight and loss of flexibility through use. 
     According to a further known solution, the frame includes a beam composed of two parallel metal side struts, which act also as wheel mount, said parallel struts being joined by moulded plastic material. 
     This solution is characterised by average weight, good absorption on rough ground and poor reaction to forces exerted by the user. The practice has shown that losses of flexibility may arise through use. 
     In general, such a constructional solution is also characterised by a relatively short lifespan of the equipment due to different flexibility of the materials used. 
     According to a further solution, composite materials are used to bind the two parallel metal side struts forming the frame beam. 
     This kind of structure is characterised by a low weight but it has many disadvantages, such as poor shock absorption, poor reaction to forces exerted by the user, loss of flexibility through use and reduced lifespan. 
     According to yet a further solution, the frame includes a beam made of composite fibre materials and metal wheel mounts. 
     This frame structure provides good absorption on rough ground and good reaction to mechanical stresses. Main disadvantages are a high weight and reduced lifespan of the equipment due to different flexibility of the materials used. 
     SUMMARY 
     The present disclosure overcomes the drawbacks of the state of the art by providing a roller ski structure according to one or more embodiments. 
     In a further aspect, the present disclosure provides also a process for manufacturing a roller ski structure according to another embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will be now described in details with reference to the attached figures, in which: 
         FIG. 1  shows a lateral view of a preferred embodiment of the roller ski structure, according to an embodiment; and 
         FIG. 2  shows a lower view of the roller ski structure of  FIG. 1 ; and 
         FIG. 3  shows a lateral view of the supporting frame in the roller ski structure of  FIG. 1 ; and 
         FIG. 4  shows a sectional view A-A′ of the supporting frame of  FIG. 3 ; and 
         FIG. 5  shows a portion of the supporting frame of  FIG. 3 ; and 
         FIG. 6A-6B  show the roller ski structure of  FIG. 1  in two different operative positions; and 
         FIG. 7A-7B  show perspective views of inserts for mounting wheels used in the roller ski structure of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the cited figures, the present disclosure relates to a roller ski structure  1 , which comprises a supporting frame  10  that is operatively connected to at least a rear wheel  11  and a front wheel  12 . 
     The supporting frame  10  has a monocoque structure that comprises at least a beam member, preferably a single beam member  100 . 
     The beam member  100  comprises an outer rigid shell  101 , which comprises a first non-metal material, preferably carbon or a composite material, such a carbon fibre composite material or a glass-fibre composite material. Plastic materials may be preferably avoided for the outer shell  101 . 
     The beam member  100  comprises also an inner core  102 , which comprises a second non-metal filling material, which can be wood or PVC (Polyvinyl Chloride) or a thermoplastic material or polystyrene. 
     The beam member  100  comprises a substantially quadrangular cross-section, having the lower and upper faces  100 B and  100 A and the side faces  100 C. 
     As it is possible to appreciate from  FIG. 2 , the cross section of the beam member  100  is slightly larger at a central region  106  thereof, so as to provide a larger support for the user&#39;s foot. 
     The side faces  100 C of the beam member  100  are thus preferably arranged in parallel and outwardly curved. 
     Preferably, the beam member  100  comprises a reinforcing rib  105 . 
     Such a reinforcing rib extends along the length of the beam at the lower face  100 B, from which it downwardly projects at least partially. 
     The reinforcing rib  105  has a thickness that preferably varies along the length of the beam member  100 , said thickness being lower at the end regions  103  and  104  and higher at the central region  106  of the beam member  100 . 
     Advantageously, at the end regions  103  and  104  the thickness of the reinforcing rib  105  is substantially equal to zero, while at the central region  106  it is about 6 mm. 
     The reinforced rib  105  is thus preferably shaped as a reversed arch, having a couple of narrower ends  105 A and  105 B, which drown in the main body of the beam member  100 , and a wider curved central portion  105 C, protruding down of the lower face  100 B of the beam member  100 . 
     The reinforcing beam is thus designed so that the central portion  105 C of the reinforcing rib  105  is positioned lower than the centre of mass, the remaining upper portion of the beam member  100  being positioned higher than the centre of mass. 
     When the beam member is subjected to pressure, the upper portion is elongated while the rib central portion  105 C is subjected to traction. 
     The beam member  100  can thus easily bend for a certain interval (around 4 mm), after which the bending of the beam member  100  is progressively blocked even if pressure increases. 
     The end regions  103  and  104  of the beam member  100  are advantageously structured, so as to act as wheel mounts and fenders for the wheels  11  and  12  of the roller ski structure. 
     Preferably, each of the end regions  103  and  104  is shaped as an overturned-U, so as to form the fenders  113  and  114  and the wheel mounts  111  and  112 . 
     Preferably, each of the wheel mounts  111  and  112  comprises a couple of substantially vertical slots  108 , each of which housing an end of the pins  11 A or  12 A of the corresponding wheels  11  or  12 . 
     A perforated metal insert  107  can be arranged in each of the slots  108  and kept in position therein thanks to a further perforated metal insert  110 . 
     Each metal insert  107  has a through hole  109  that is eccentrically placed and that is aimed at accommodating an end of the wheel pins  11 A or  12 A. 
     Each metal insert  107  can thus be arranged in the corresponding vertical slot  108 , according to a first position  107 A ( FIG. 6A ), corresponding to an upper position for the wheel axis (W), or a second position  107 B ( FIG. 6B ), corresponding to a lower position for the wheel axis (W). 
     The axes (W) of the wheels  11  and  12  can thus be lowered or raised according to the needs, each of the different operative positions of the metal inserts  107  corresponding to a different position of the centre of mass of the roller ski  1 . 
     The supporting frame  10  is preferably manufactured according to a process which comprises the following steps of: 
     providing one or more layers of said first non-metal material; 
     providing a solid frame core element, which comprises said second non-metal material; 
     coating said solid core with said layers of first material; 
     placing the assembly so obtained in a mould; 
     heating the mould so as to cure said layers of first material and forming at least a beam member having an outer rigid shell surrounding said solid core. 
     In other words, a manufacturing process for the supporting frame  10  preferably consists in creating a substantially quadrangular-shaped tube, including a solid core made of said second non-metal material, on which various layers of said first non-metal material are superimposed. At the two ends of the tube, the carbon-based material canvases have no core and therefore have the form of a single layer. The first material layers are then cured in a mould placed in a press or autoclave. 
     The monocoque structure so obtained can then be subsequently machined to create the slots  108  for constraining the wheels. 
     The roller ski, according to the present disclosure, differs from conventional products due to its extreme lightness and elasticity. 
     It absorbs the ground roughness, offering greater comfort and excellent response to the forces imparted by the user during thrust. As the elasticity of the non-metal materials of the beam member is known, the thrust exerted by the user is in fact returned almost completely while in known roller skis the majority of the thrust is absorbed by the metal parts that are present thereof