Patent Publication Number: US-2021170292-A1

Title: Tire insert for a tire of a model vehicle

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     Priority is claimed to German Patent Application No. DE 20 2019 105 920.6, filed Oct. 24, 2019. The entire disclosure of said application is incorporated by reference herein. 
     FIELD 
     The present invention relates to a tire insert for a tire of a model vehicle, the tire insert being a closed-cell foam with an outer surface, an inner surface, and two perforated disk surfaces. The present invention also relates to a tire of a model vehicle, and to a model vehicle. 
     BACKGROUND 
     When tires are used in model construction, a certain deformation of the tires while driving is desirable to protect the vehicle against the unevenness of the ground. The deformation of the tires is called “cushioning” or “flexing”. 
     When driving across off-road terrain, a high degree of flexing and thus strong cushioning is desirable. The flexing is at the same time the largest component of the rolling resistance which, however, increases the energy consumption of the vehicle. A low degree of flexing is therefore desirable when driving over even ground, particularly the road. Tire pressure is used to vary the degree of flexing in the case of tires with air chambers. 
     Lightweight model vehicles, particularly vehicles under 3 kg, do not have air chambers in their tires. Hollow tires without a carcass, which have pressure equalization between the interior and the exterior, are instead used. The interior can additionally be filled with a foam insert. The cushioning function is taken over by the thin outer walls. 
     Such hollow tires allow only a limited degree of cushioning, however, and require several manufacturing steps. For heavy model vehicles, particularly those above 3 kg, tires made from an elastic solid material or with a pressurized chamber are hence used. Tires made of a solid material only flex to a very limited degree and, in particular on bends, provide only little line contact and low roadholding. In contrast thereto, tires with air chambers are susceptible to damage, particularly punctures, and require even greater manufacturing effort. 
     SUMMARY 
     An aspect of the present invention is to improve upon the prior art. 
     In an embodiment, the present invention provides a tire insert for a tire of a model vehicle. The tire insert is made of a closed-cell foam and includes an outer surface, an inner surface, two perforated disk surfaces, and at least one cushioning cavity comprising at least one opening. The two perforated disk surfaces are each configured to connect the outer surface with the inner surface. The at least one opening is arranged on one or on each of the two perforated disk surfaces so that the tire insert has at least one of a defined flexibility and an increased flexibility. The inner surface is substantially parallel to the outer surface so that the tire insert has a form of a hollow cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
         FIG. 1  shows a schematic perspective view of a ring-shaped rubber wheel rim with an outer surface, an inner surface, a chamfer, and a top side surface into which cushioning holes are introduced; 
         FIG. 2  shows a schematic side view of a first alternative rubber wheel rim with the outer rim and the cushioning holes; 
         FIG. 3  shows a schematic perspective view of a second, alternative rubber rim with an outer surface, an inner surface, rim grooves, and a top side surface, which has large alternative cushioning holes and smaller alternative cushioning holes, each arranged on concentric circles; and 
         FIG. 4  shows the second alternative rubber rim in a side view. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention provides a tire insert for a tire of a model vehicle, the tire insert being a closed-cell foam with an outer surface, an inner surface, and two perforated disk surfaces, the perforated disk surfaces each connecting the outer surface and the inner surface, and the inner surface being essentially parallel to the outer surface so that the tire insert has the form of a hollow cylinder, the tire insert having a cushioning cavity with one opening or with several openings, the opening or the openings being arranged on one of the two or on both perforated disk surfaces so that the tire insert has a defined and/or greater flexibility. 
     A tire insert made of solid material, which exhibits greater flexibility, can therefore be provided in a single processing step. By introducing a cushioning cavity into a tire insert made of solid material, the flexibility of the tire insert is increased, and cushioning and damping are achieved, for example, when the vehicle is in operation. The tire insert can be suitable for mating the tire to the wheel rim. The outer surface is in contact with the tire and the inner surface with the rim. 
     A key aspect of the present invention is particular that a defined and/or increased flexibility of a tire insert made of solid material is provided by introducing a cushioning cavity, since the flexibility of a foam can be increased via cavities. A desired flexibility can thus be achieved by specifically selecting the size and arrangement of the cavity. 
     The cushioning cavity can here be arranged so that an increased and/or defined flexibility at right angles to the axle of the vehicle results. The outer surface and the inner surface can have an essentially equidistant separation from each other so that a central axis of the outer surface runs parallel to an axle of the model vehicle which is inserted into the inner surface. The perforated disk surfaces can be arranged orthogonal to the outer surface and orthogonal to the inner surface, resulting in the form of a hollow cylinder. 
     The following terms are here explained: 
     A “tire insert” is in particular a disk-shaped object with a circular contour, which can be bearing mounted so as to allow rotation about or with a vehicle axle, and which maintains the shape of the tire while the vehicle is rolling. 
     “Model vehicle” means, for example, a miniature representation of a vehicle. A “vehicle” here means a device for moving people or goods. A model vehicle can in particular be a land vehicle, such as a car or a train, an aircraft, or an amphibious vehicle. 
     “Foam” here, for example, means a structure with gas-filled cavities and a surrounding matrix of a flexible material. The flexible material can in particular be a synthetic material. A “closed-cell foam” means a foam where almost all the gas-filled spaces are completely surrounded by the matrix and are not interconnected. Polyurethane, polyethylene, expanded rubber, or also sponge rubber (EPDM) can be used as the synthetic material for the foam. 
     “Outer surface” can mean a surface of a cylinder or hollow cylinder which has a curved surface and a circular contour. The outer surface can be bounded by an edge, where the edge can, for example, be formed by the outer surface and the perforated disk surface. 
     The “perforated disk surface” can, for example, be an essentially round surface whose external diameter corresponds to a circumference of the outer surface. The perforated disk surface can in this case be arranged orthogonally to the outer surface. The perforated disk surface can, however, also be arranged at an oblique angle to the outer surface. The perforated disk surface can have a cavity in its center, the surface of the cavity being formed by the inner surface. The outer surface is connected on two sides and has a perforated disk surface on each of its other sides. 
     “Cushioning cavity” can mean an indentation in the perforated disk surface. 
     “Opening” means an imaginary surface which is defined by the edge of the cushioning cavity in the perforated disk surface. 
     The cushioning cavity is thus in particular a cavity in the closed-cell foam, the cushioning cavity being in contact with at least one perforated disk surface. The cushioning cavity can alternatively be in contact with only the inner surface, or can be a through-opening so that it is either in contact with both perforated disk surfaces or with one perforated disk surface and the inner surface. This in particular allows the flexibility to be set to a defined value. 
     The flexibility of the tire insert can be increased by enlarging the cushioning cavity and can thus be set to a specific value by the cushioning cavity having a specific size. 
     In a further embodiment, the tire insert has several cushioning cavities. 
     By introducing further cushioning cavities, the flexibility can be further increased and the flexibility of the tire insert can be set to specific values at various positions. The tire insert can also have increased flexibility over its whole surface via a suitable distribution of several cushioning cavities. 
     To provide a uniform effect on the flexibility of the tire insert, the cushioning cavity has or the cushioning cavities have an essentially round, oval or polygonal cross-sectional shape. 
     “Cross-sectional area shape” can mean a surface which is defined by a wall surface of the cushioning cavity and which is aligned orthogonally to a central axis. The cross-sectional area shape can thus run parallel to the opening. 
     The symmetry of the tire insert can be increased by the cushioning cavity having a uniform cross-sectional area shape, the cross-sectional area shape being round, oval or polygonal. This results in the tire insert having uniform flexibility, for example, and thus more uniform behavior on the road. 
     In a further embodiment, the cushioning cavities can, for example, be distributed along a circular curve on the perforated disk surface. 
     “Circular curve” can mean a circular arrangement. The central axes of the cushioning cavities can thus be arranged on an imaginary circle on the perforated disk surface. The circular curve can, for example, here run concentrically to a circumference of the outer surface. 
     Distributing the cushioning cavities on a circular curve results in a further increase in the symmetry and thus more uniform road behavior of a model vehicle which uses the tire insert mentioned. Cushioning cavities are arranged on several concentric circular curves in order to increase the number of cushioning cavities on the perforated disk surface in a symmetric manner. Arranging the cushioning cavities on several concentric circles makes it possible to increase the percentage of the perforated disk surface which is covered by an opening without reducing the symmetry of the arrangement. The flexibility of the tire insert can thus be increased further. 
     In a further embodiment, the opening or the openings can, for example, cover 2% to 50% of the perforated disk surface or the perforated disk surfaces. 
     By having a degree of cover of between 2% and 50%, a flexibility is achieved which contributes to cushioning the model vehicle. 
     To achieve a balanced ratio between acceleration and maximum speed, the (exterior) outer surface in particular has a circumference of between 1.2 cm and 150 cm. 
     Greater acceleration can be achieved with small tires, whereas a higher final speed can be achieved with large tires. An outer surface with a circumference of between 1.2 cm and 150 cm results in an optimized ratio of acceleration and maximum speed for sizes which are usual for model vehicles. 
     In a further embodiment, the tire insert can, for example, have no air-filled chambers or have one air-filled chamber or several air-filled chambers. 
     Not using air-filled chambers makes it easier to manufacture the tire insert and the tire insert has greater resistance against punctures. Using air-filled chambers or one air-filled chamber can, however, improve the cushioning behavior. 
     A “chamber” here means a gas-filled cavity which has no gas-exchanging connection to other cavities and takes up at least 3% of the volume of the tire insert. 
     To avoid overlaps between the cushioning cavities, central axes of the cavities run parallel to a central axis of the tire insert so that the central axes of the cushioning cavities run parallel to each other. A high percentage of the perforated disk surfaces can thus be covered with openings without overlaps being created between the cushioning cavities. The design and the manufacture of the tire insert are furthermore facilitated by the parallel arrangement. 
     The central axes of the cushioning cavities run at an oblique angle to a central axis of the tire insert in order to increase the proportion of the volume of the cushioning cavities with respect to the total volume of the tire insert. 
     In a further embodiment, the central axes of the cushioning cavities can, for example, run parallel to each other. 
     A parallel orientation of the axes with respect to each other further increases the possible proportion of the cushioning cavities with respect to the total volume. The increased volume of the cushioning cavities furthermore saves on material. 
     The central axes of the cushioning cavities run at an oblique angle to each other to make the tire insert twist resistant. 
     The cushioning cavities running at an oblique angle to each other results in a structure which is less regular. This results in a smaller point of action for a force which could lead to a twisting of the tire insert or to damage. The robustness of the tire insert is therefore enhanced. 
     In a further aspect, the present invention provides a tire of a model vehicle which contains a tire insert as described above. 
     This results in the above-mentioned advantages when the tire insert is combined with the tire of a model vehicle. 
     In a further aspect, the present invention provides a model vehicle which has an tire described above. 
     The combination of tire insert, tire, and model vehicle creates a cushioning and flexing effect so that shocks caused by the road are not transmitted to the bodywork to the same extent as when the model vehicle drives across an uneven surface. 
     The present invention is explained in greater detail below under reference to an example embodiment as shown in the drawings. 
     A foam rim  101  is manufactured from closed-cell foam (polyurethane) in the shape of a ring by foam-filling a mold. The foam rim  101  has an outer surface  107 , an inner surface  111 , a bottom side surface  115 , and a top side surface  109 . Cushioning holes  103 , which have the form of blind holes, are introduced into the top side surface  109 . The edge between the top side surface  109  and the inner surface  111  has the form of a chamfer  113 . 
     The use of the first alternative rubber rim is hereinafter described: 
     An axle of a model car has a size corresponding to the inner surface  111  of the foam rim  101 . The axle furthermore has a protrusion corresponding to the chamfer  113  of the rubber rim. A rubber tire is mounted on the outer surface  107  of the foam rim  101 , and the rubber rim with rubber tire is mounted on the axle so that the inner surface  111  and the chamfer  113  are in contact with the axle of the car and the outer surface  107  is in contact with the tire. The top side surface  109  with the cushioning holes  103  faces towards the model car, the bottom side surface  115  faces outwards. 
     When driving on an uneven road, the foam rim  101  can be compressed more easily in the area with the cushioning holes  103  than in an area without cushioning holes  103 . The forces acting on the tires are thus partially cushioned by the foam rim  101  so that the body of the model vehicle retains its relatively stable support. 
     When driving round a left-hand bend, the left side of the wheels on the left are subjected to greater stress. Since the cushioning holes  103  are blind holes, a marked cushioning effect exists only on the side of the top side surface  109 . In the area of the bottom side surface  115  which faces away from the vehicle and is thus located on the left for a tire on the left-hand side, the cushioning effect is smaller or non-existent since the cushioning holes  103  do not extend into this area. The increased load exerted when driving through a left-hand bend hence does not compress the part of the rubber rim on which the load is mainly exerted, or compresses it only to a small extent. An unfavorable tilting of the vehicle can thus be prevented. 
     An alternative second foam rim  201  made of closed-cell foam (polyethylene) in a ring shape has an outer surface  207 , an inner surface  211 , a bottom side surface  215 , and a top side surface  209 . Large cushioning holes  203  are arranged on the top side surface  209  on an outer circular curve, and small cushioning holes  205  are arranged on an inner, concentric, circular curve. The large cushioning holes  203  have the form of blind holes and only extend to the middle between the top side surface  209  and the bottom side surface  215 . In a further alternative, these blind holes in contrast extend almost all the way through, and the bottom of the blind hole is only approximately 3 mm away from perforation. The smaller, alternative cushioning holes  205  in contrast have the form of through holes and extend from the top side surface  209  to the bottom side surface  215 . 
     The use of a second foam rim  201  is hereinafter described: 
     The rim grooves  213  of the wide, second foam rim  201  engage with the rim when the second foam rim  201  is mounted and thus reduce the risk of the rim rotating on the axle. 
     When the model car is driven across uneven ground, the small cushioning holes  205  create a cushioning effect across the complete width of the second foam rim  201  with respect to small bumps. The large cushioning holes  203  provide a cushioning effect in the inner part of the rim with respect to large bumps. 
     The present invention is not limited to embodiments described herein; reference should be had to the appended claims. 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               101  (First) Foam rim 
               103  Cushioning hole 
               107  Outer surface 
               109  Top side surface 
               111  Inner surface 
               113  Chamfer 
               115  Bottom side surface 
               201  (Second) Foam rim 
               203  Large cushioning hole 
               205  Small cushioning hole 
               207  Outer surface 
               209  Top side surface 
               211  Inner surface 
               213  Rim groove 
               215  Bottom side surface