Abstract:
A torsion system ( 20 ) comprising a housing ( 24 ) adapted to be secured to a structural portion of a vehicle. A shaft ( 23 ) has a core portion ( 32 ) accommodated in the housing ( 24 ) and defines concavities ( 34 ) in the core portion ( 32 ). The shaft ( 23 ) has a connector end ( 30 ) connected to a crank arm. The connector end ( 30 ) protrudes out of the housing ( 24 ). Elastomeric members ( 25,25′ ) are received in the concavities ( 34 ) of the shaft ( 23 ). The elastomeric members ( 25,25 ) each have a geometry so as to at least partially fill the concavities ( 34 ) and contact an inner surface of the housing ( 24 ), whereby a rotation of the crank arm results in a deformation of the elastomeric members ( 25,25′ ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This patent application claims priority on Canadian Patent Application No. 2,526,736, filed on Nov. 20, 2005. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to torsion axles and suspensions as used in vehicles such as trailers and, more particularly, to a configuration of torsion system as used in torsion axles and torsion suspensions. 
         [0004]    2. Background Art 
         [0005]    Torsion axles represent a cost-effective way to provide some independent suspension to the wheels of vehicles. Because they are cost-effective, torsion axles and torsion suspensions are commonly used with low-priced vehicles, such as hitched trailers. 
         [0006]    Referring to  FIG. 1 , a torsion axle in accordance with the prior art is generally shown at  10 . The torsion axle  10  has a hub  11  upon which a wheel (not shown) is mounted. The hub  11  is supported by a free end of a crank arm  12 . The other end of the crank arm  12  is connected to a torsion system that has a housing  13  of rectangular section, a shaft  14  in the housing  13 , and elastomeric members  15  compressed within the housing  13 . The shaft  14  has a selected section so as to exert pressure against the elastomeric members  15  when rotating within the housing  13 . It is therefore the elastomeric members  15  that provide the shock absorption. 
         [0007]    Referring to  FIG. 2 , a torsion suspension of the prior art is generally shown at  16 , and is generally similar to the torsion axle  10 , whereby like elements bear like reference numerals. The torsion suspension  16  has a pair of crank arms  12 , and the output ends  17  can be used as hubs. The crank arms  12  are optionally independent from one another, in which case each crank arm  12  has its own shaft within the housing  13 . 
         [0008]    The torsion axles and suspensions of the prior art are currently manufactured by insertion of elongated members  15  of elastomeric material between the shaft  14  and the interior of the housing  13  ( FIG. 1 ). As non-negligible pressures are involved in fitting the shaft  14  and the elongated members  15  in the housing  13  under compression, equipment such as hydraulic presses and freezers is required, therefore resulting in an increase in price of the torsion axle/suspension. Under these circumstances, it is difficult to repair a torsion system if the elastomeric material is damaged or worn. Also, torsion axles/suspensions often have to be delivered from the manufacturer completely assembled. 
       SUMMARY OF INVENTION 
       [0009]    It is therefore an aim of the present invention to provide a torsion system for torsion axles and torsion suspensions that addresses issues associated with the prior art. 
         [0010]    Therefore, in accordance with the present invention, there is provided a torsion system comprising: a housing adapted to be secured to a structural portion of a vehicle; a shaft having a core portion accommodated in the housing and defining at least one concavity in the core portion, the shaft having a connector end connected to a crank arm, the connector end protruding out of the housing; and an elastomeric member received in the concavity of the shaft, the elastomeric member having a geometry so as to at least partially fill the concavity and contact an inner surface of the housing; whereby a rotation of the crank arm results in a deformation of the elastomeric member. 
         [0011]    Further in accordance with the present invention, there is provided a method for inserting elastomeric members in a torsion system, comprising the steps of: positioning at least one unused elastomeric member on a shaft of a torsion system; manually inserting the shaft and the at least one unused elastomeric member in a housing of the torsion system; and locking support blocks to maintain the shaft and elastomeric member captive in the housing of the torsion system. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]    A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which: 
           [0013]      FIG. 1  is a perspective view of a torsion axle constructed in accordance with the prior art; 
           [0014]      FIG. 2  is a perspective view of a torsion suspension in accordance with the prior art; 
           [0015]      FIG. 3  is a perspective view, fragmented, of a torsion system constructed in accordance with an embodiment of the present invention; 
           [0016]      FIG. 4  is a perspective view of a shaft of the torsion system of  FIG. 3 ; 
           [0017]      FIG. 5  is a cross-section view of a core portion of the shaft of  FIG. 4 ; 
           [0018]      FIG. 6  is a perspective view of a first embodiment of an elastomeric member used in the torsion system of  FIG. 3 ; 
           [0019]      FIG. 7  is a perspective view of a support block of the torsion system of  FIG. 3 ; and 
           [0020]      FIG. 8  is a perspective view of a second embodiment of an elastomeric member used in the torsion system of  FIG. 3 . 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0021]    Referring to the drawings, and more particularly to  FIG. 3 , a torsion system in accordance with an embodiment is generally shown at  20 . 
         [0022]    The torsion system  20  is shown having a crank arm  21 . In the illustrated embodiment, the crank arm  21  is made of a tube of rectangular section, but may be a solid piece, a single machined or cast piece, etc. The crank arm  21  has a connector hole  22  at a free end so as to support a hub, or any other rod-like member compatible with the torsion system  20 . Alternatively, the crank arm  21  may incorporate a shaft, hub, or fastener at its free end. 
         [0023]    A shaft  23  is connected at the opposed end of the crank arm  21 . The shaft  23  is enclosed in housing  24 . Elastomeric members  25  are positioned between the shaft  23  and the interior of the housing  24 . Support blocks  26  are provided at opposed ends of the shaft  23 . Some of the support blocks  26  are used in combination with fasteners, such as bolt  28  and nut  29  passing through the housing  24  at holes  27  to maintain the shaft  23  captive within the housing  24 . As other alternatives, a screw (not shown) can be bolted directly into the support block  26 , with or without tapping in the holes  27  of the housing  24  or in the support blocks  26 . Moreover, the support blocks can be end caps positioned at opposed ends of the housing or the like. 
         [0024]    The housing  24  is the interface of the torsion system  20  with the structure of the vehicle. Although not shown, it is considered to provide the housing  24  with connection flanges on its outer surface, such that the torsion system  20  may be connected to the structure of the vehicle using bolts or like fasteners. Moreover, the housing  24  is illustrated as having a square cross-section, but other cross-sectional shapes are considered. 
         [0025]    Referring to  FIG. 4 , the shaft  23  is shown individually. The shaft  23  has a connector end  30 , by which it is connected to the crank arm  21 . Supported surfaces  31  are separated by a core portion  32 . A flange  33  is provided at the end of the shaft  23  away from the connector end  30 . In an embodiment, the crank arm  21  and the shaft  23  form an integral piece. 
         [0026]    The core portion  32  is the portion of the shaft  23  that will be interfaced with the elastomeric members  25  ( FIG. 3 ). In the embodiment of  FIGS. 4 and 5 , the core portion  32  is a circular rod in which concavities  34  have been defined. The concavities  34  are receptacles in which a portion of the elastomeric members  25  are received. 
         [0027]    Referring to  FIG. 5 , the core portion  32  is shown having four of the concavities  34 , such that the core portion  32  defines a cross-shaped section. Although the illustrated embodiment of the core portion  32  is shown with four concavities  34 , it is considered to provide any suitable number of concavities, starting with a single concavity. The number of elastomeric members  25  used will have a direct effect on the shock absorption level of the torsion system  20 . 
         [0028]    Referring concurrently to  FIGS. 3 and 6 , one of the elastomeric members  25  is shown. The geometry of the elastomeric member  25  is defined so that the elastomeric member  25  matches the shape of one of the concavities  34 . Moreover, when accommodated in the concavity  34 , the elastomeric member  25  has two of its walls coplanar with the inner walls of the housing  24 . 
         [0029]    Accordingly, as shown in  FIG. 3 , a rotation of the shaft  23  about its longitudinal axis is opposed by the elastomeric member  25 . The elastomeric members  25  must be deformed for the shaft  23  to rotate about its longitudinal axis. Therefore, the durometer hardness of the elastomer used is selected as a function of the shock absorption level that is desired from the torsion system  20 . For an increasing load rating for the torsion system  20 , the hardness of the elastomer increases. The elastomeric material used is any suitable elastomer, such as a polymer, a rubber or the like. In one embodiment, the elastomer is urethane at a durometer hardness of 70, but a wide range of hardnesses are considered. It is considered to increase the length and/or diameter of the torsion system  20 , so as to increase the load capacity of the torsion system. 
         [0030]    In an embodiment, the elastomeric members  25  are extruded. The cross-shaped section of the core portion  32  as embodied in  FIG. 3  is advantageous in that all elastomeric members  25  have the same cross-section. Therefore, all elastomeric members  25  may be extruded from a single extrusion. 
         [0031]    It is pointed out that the configuration of the shaft  23 /elastomeric members  25  enables the torsion system  20  to be mounted without the shaft  23  being pre-stressed. Therefore, as opposed to the prior-art torsion axles and torsion suspensions, neither hydraulic presses nor freezing equipment are required to assemble the torsion system  20  of  FIG. 3 . 
         [0032]    One contemplated solution to maintain the shaft  23  aligned within the housing  24  is the support blocks  26 . Referring to  FIG. 7 , the support blocks  26  are used in pairs to define a circular opening by the alignment of semi-cylindrical cavities  40 . Two pairs of the support blocks  26  are used to each accommodate one of the supported surfaces  31  of the shaft  23 . In  FIG. 7 , a throughbore  41  is provided in the support block  26 . The throughbore  41  is used with a fastener (e.g., bolt) or a rod, to maintain the support block in position within the housing  24 . The flange  33  at the end of the shaft  23  ( FIG. 1 ) ensures that the shaft  23  remains in alignment within the housing  24 . Although only the distal pair of support blocks  26  are provided with throughbores  41 , it is considered to also lock the proximal pair of support blocks  26  with fasteners/rods. 
         [0033]    Referring to  FIG. 8 , an alternative embodiment of the elastomeric member is illustrated at  25 ′. The elastomeric member  25 ′ has a throat portion  50  between opposed ends  51  of operative cross-section. Accordingly, to reduce the resistance of the elastomeric member against the rotation of the shaft  23 , the length of the throat portion  50  is increased, as it is the ends  51  that provide the resistance. The elastomeric member may be carved into the shape illustrated by  25 ′ starting from the shape illustrated by  25  by the end user. 
         [0034]    As the torsion system  20  is readily assembled without presses and such equipment, it is considered to sell the torsion system  20  separate from the elastomeric members  25 . Therefore, elastomeric members  25  can be selected as a function of the shock absorption level desired. Moreover, elastomeric members  25  can be replaced when worn out, by simply removing the shaft  23  from the housing  24 . As such, the torsion system can be sold in a kit, with additional or replacement elastomeric members  25  being available to the customer such that the shock absorption level of the torsion system  20  may be changed. 
         [0035]    The elastomeric members  25 / 25 ′ are inserted in the torsion system  20  by positioning the elastomeric member  25 / 25 ′ on the shaft  23 . Whether or not the support blocks  26  are positioned on the shaft  23 , the latter is manually inserted with the elastomeric member  25 / 25 ′ in the housing  24 . The support blocks  26  are locked to maintain the shaft  23  and elastomeric member  25 / 25 ′ captive in the housing  24  of the torsion system  20 . The steps are reversed to remove the shaft  23  from the housing  24 , for instance to replace the elastomeric members  25 / 25 ′. 
         [0036]    It is within the ambit of the present invention to cover any obvious modifications of the embodiments described herein, provided such modifications fall within the scope of the appended claims.