Abstract:
A jack, defining a portable accessory for replacing a motor vehicle wheel, is adapted to be placed on the ground and has a scissors-like pantograph provided with a first and a second arm hinged to each other; the first and second arms have respective lower end portions, which can be moved close or away by actuating a screw/nut-screw device; the second arm is shorter than said first arm and is provided with an upper end portion hinged to an intermediate portion of the first arm; the jack further has a supporting member, which is supported only by an upper end of the first arm and can rotate about an axis.

Description:
[0001]    The present invention relates to a jack defining a portable accessory for replacing a motor vehicle wheel. 
       BACKGROUND OF THE INVENTION 
       [0002]    Some vehicles are provided with a spare wheel and a kit of accessories that can be used directly by the driver, without mechanical workshop assistance, in order to mount the spare wheel in place of a worn or damaged wheel. Among said accessories a jack is comprised. The jack has to placed underneath predetermined points of the vehicle chassis and is manually operated for lifting a part of the chassis and the wheel that must be replaced. 
         [0003]    Jacks are known having a lower base adapted to be placed on the ground, a top bracket adapted to support the chassis, and a pantograph defined by four arms arranged so as to form a diamond-like shape. The pantograph has a lower vertex arranged at the base, an upper vertex arranged at the bracket, and two side vertices coupled to one another by way of a screw/nut-screw device. By operating such a device, the two side vertices of the pantograph can be moved close or away, so as to raise or lower the bracket with respect to the base. 
         [0004]    A solution of this type, though widely used, has a high overall dimension in the vertical direction, when the bracket is fully lowered, therefore cannot be used in sport type motor vehicles. In fact, in said type of vehicles, the chassis is lowered and/or is provided with aerodynamic side appendixes colloquially called “mini-skirts”, therefore the distance of the chassis from the ground available for the insertion of the jack is extremely limited. 
         [0005]    The German utility model DE20313940U1, corresponding to the preamble of claim  1 , shows a lifting device having a scissors-like pantograph, therefore more compact than the known solutions described above, but not enough to be suitable for use as a portable accessory for sport type motor vehicles. 
       SUMMARY OF THE INVENTION 
       [0006]    A purpose of the present invention is to provide a jack defining a portable accessory for replacing a motor vehicle wheel, which allows to fulfill in a simple and economic way the requirements set out above and, preferably, is relatively simple to implement, is relatively lightweight, and has relatively few components. 
         [0007]    According to the present invention, a jack defining a portable accessory for replacing a motor vehicle wheel, as defined by claim  1  is provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting embodiment, wherein: 
           [0009]      FIG. 1  shows, in perspective, a preferred embodiment of the jack defining a portable accessory for replacing a motor vehicle wheel, according to the present invention; and 
           [0010]      FIG. 2  shows, in enlarged scale, the jack of  FIG. 1  in an extended configuration in order to lift a part of the vehicle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    In  FIG. 1 , number  1  denotes a jack, which defines a portable accessory for replacing a wheel  2  of a motor vehicle  3  (partially illustrated). In other words, the jack  1  constitutes part of a kit of accessories for the mounting of a spare wheel, not shown, and finds advantageous application in sport type motor vehicles  3 , i.e. vehicles having a chassis  4  which is lowered and/or is provided with aerodynamic side appendixes  5  colloquially known as “mini-skirts”. 
         [0012]    With reference to  FIG. 2 , the jack  1  comprises a base  6 , which is elongated along a horizontal direction  7  and comprises a horizontal wall  8  adapted to be placed on the ground. In particular, in use, the wall  8  is oriented in a direction transverse to the travelling direction of the vehicle  3  ( FIG. 1 ). Preferably, the base  6  is defined by a channel having a U-shaped cross section, comprising two vertical flanges  9 , which protrude upwards starting from the longitudinal side edges of the wall  8 . 
         [0013]    The jack  1  comprises, moreover, a scissor-like pantograph  10 , formed by two arms  11 , 12  hinged to each other about a horizontal axis  13 , orthogonal to the direction  7 . The arms  11 , 12  comprise respective lower end portions  14 , 15 , which are coupled to the base  6  in a rotating mode about respective axes  16 , 17  parallel to the axis  13 . One of the two axes  16 , 17  is fixed with respect to the base  6 . The other of the two axes  16 ,  17  can move along the direction  7  with respect to the base  6 , as the corresponding portion  14 , 15  is coupled in a sliding manner to a horizontal guide  20  carried by the base  6 . 
         [0014]    In particular, it is the portion  14  of the arm  11  to be coupled to the guide  20 . In greater details, the guide  20  is defined by two grooves or slots  21 , which are made into the flanges  9  in positions facing one another and are engaged in a sliding manner by the axial ends of a hinge pin  22  that extends along the axis  16 . 
         [0015]    According to an aspect of the present invention, the arm  11  is longer than the arm  12  and terminates at the top with a portion  26 , which supports a plate or bracket  27 , adapted to be placed underneath the chassis  4  and supported at predetermined points provided for lifting. In particular, the plate  27  is supported by a single axis  29 , defining an abutting axis about which the plate  27  can rotate with respect to the portion  26 . Preferably, the axis  29  is parallel to the axis  13 . In other words, while resting on the chassis  4 , during the lifting, the plate  27  automatically adjusts its angle as a function of the resting conditions, while the angle of the arm  11  varies. 
         [0016]    Preferably, the jack  1  further comprises an elastic element  30 , for example a helical spring, which connects the plate  27  to the portion  26  so as to maintain the plate  27  at an angular reference position, parallel to the arm  11 , when the plate  27  is lowered and/or is not resting on the chassis  4  ( FIG. 1 ). 
         [0017]    The plate  27  is supported solely by the arm  11 , i.e. disengaged from the arm  12 , as the latter terminates at the top with a portion  31  which is hinged to an intermediate portion of the arm  11  about the axis  13 . 
         [0018]    Preferably, the intermediate portions of the arms  11  and  12  have U-shaped cross sections, i.e. are each formed, by an intermediate wall and by two side flanges, which protrude vertically from the side edges of the corresponding intermediate wall. In the arm  11 , the side flanges are denoted by the reference number  37  and the intermediate wall is denoted by the reference number  38 . The portions  26  and  14  are defined by the ends of the flanges  37  that protrude beyond the wall  38  in a direction orthogonal to the axes  13 , 16 , 17 . Preferably, the same arrangement is provided for the portions  15  and  31 . 
         [0019]    The jack  1  further comprises a screw/nut-screw device  39  which connects the arms  11 , 12  and is manually operated to make the portion  14  slide along the guide  20  and then to lower/raise the plate  27 . 
         [0020]    In particular, the device  39  comprises a bracket  40 , which is coupled to the portion  15  of the arm  12  so as to remain angularly fixed about the direction  7  and to be angularly rotatable about an axis  41  parallel to axis  17 , or eventually coinciding with the axis  17 . 
         [0021]    The device  39  further comprises a screw  42 , which preferably has a right-hand thread, extends along an axis  43  orthogonal to the axes  17  and  41 , and has a back end coupled to the bracket  40  by means of a center bearing  44  in order to have, as an only degree of freedom, the rotation about the axis  43 . The screw  42  has, then, a front end  45  defining an attachment point for fixing a crank or ratchet handle in a releasable manner  46  ( FIG. 1 ). 
         [0022]    The device  39  finally comprises a nut-screw  47 , which is screwed on the screw  42  and is coupled to the arm  11  in an angularly fixed manner about an axis  43  and angularly rotatable about an axis  48  which is parallel to the axis  13 , is fixed with respect to arm  11  and is advantageously arranged higher than the axis  41 . Preferably, the axis  48  is arranged in intermediate position between the axes  13  and  16 . 
         [0023]    The above defined positions of the constraint points allow to have essentially the following advantages:
       the axis  43  varies its inclination with respect to the direction  7  as the angle between the arms  11 , 12  changes, thus the end  45  progressively moves away from the base  6  during the lifting so as to facilitate the use of the crank or ratchet lever  46  ( FIG. 1 );   despite the arm  12  being constrained to the device  39  at the axis  41 , it is free to rotate about the axis  17  and helps to support the loads applied to the plate  27 , by transferring such loads on the base  6  exactly at the axis  17 , while the arm  11  transfer them on the axis  16 .       
 
         [0026]    With reference to  FIG. 1 , when the plate  27  is lowered, the jack  1  assumes a closed configuration, wherein the arm  11  houses the arm  12  and, in turn, remains housed between the flanges  9  of the base  6 . In particular, the length of the arm  11  is such that the flanges  37  are aligned with the guide  20  in the closed configuration. Also in this closed configuration, the device  39  remains housed in a cavity defined at the top and at the side by the arms  11 , 12  and at the bottom by the wall  8 , except for the free end  45 , which remains accessible above the pin  22 . 
         [0027]    By operating the device  39  by means of the crank  46 , with left-hand rotation, the portion  14  is pushed towards the arm  12  and the jack  1  tends to assume an extended configuration ( FIG. 2 ) wherein the axis  16  approaches the axis  17  and the plate  27  is raised to lift, in turn, the chassis  4 . 
         [0028]    From the foregoing it appears obvious how the jack  1 , in the closed configuration, has an extremely limited overall dimension in the vertical direction and therefore can be inserted below the chassis  4  in an easy manner to locally raise the motor vehicle  3 , and perform the wheel  2  replacement operations. 
         [0029]    Also, thanks to the reduced dimensions, the jack  1  can be housed and transported easily in a special accessories compartment (not shown) of the motor vehicle  3 . The jack  1  is extremely compact and lightweight also for the fact that the plate  27  and the arm  12  can be designed to have relatively small overall dimensions. 
         [0030]    Despite the simplicity and lightness of the jack  1 , the characteristics of its components are such as to provide a relatively high rigidity and resistance. 
         [0031]    Furthermore, the plate  27  is oriented automatically about the axis  29  during the lifting, so as to obtain a stable support against the chassis  4 , regardless of the lifting degree of the pantograph  10 . 
         [0032]    As mentioned above, the positions of the attachment points provided on the arms  11 , 12  for the device  39  allow primarily to obtain a variation in the angle of the axis  43  that during the lifting progressively facilitates the maneuvering of the crank or ratchet lever  46 . 
         [0033]    The base  6  provides safe rest with respect to rough terrain and acts as a guide on the arm  11 , thus increases the breakdown resistance of the arms  11 , 12  of the pantograph  10 . Finally, from the above, it is evident that the jack  1  described can be subject to modifications and variations which do not depart from the scope of protection of the present invention, as defined by the attached claim. 
         [0034]    For example, the plate  27  could be replaced by a support element having a different shape and/or size; and/or the device  39  could be coupled to the arms  11 , 12  at attachment points different from those indicated by way of example. 
         [0035]    The base  6  may be reduced in longitudinal dimensions or completely replaced by wheels or rollers which are arranged at the axes  16  and/or  17  and define resting points movable on the ground. 
         [0036]    Finally, the components of the jack  1 , although normally made of metallic material, could be made of different materials.