Patent Publication Number: US-2016236524-A1

Title: Supporting plate for self-centring chucks

Description:
TECHNICAL FIELD 
     The present invention relates to a supporting plate for self-centring chucks used in tyre-changing machines 
     BACKGROUND ART 
     The use is known of tyre-changing machines for fitting and removing tyres to and from relative wheel rims. 
     Such tyre-changing machines comprise a base supporting a rim gripping and rotation unit, having a self-centring device, and a tool-carrying arm having a tool for removing and/or fitting the tyre. 
     The above device is a particular type of self-centring chuck also called “self-centring plate”. 
     Such device is composed of a supporting plate for the rim, comprising grooves in which jaws run in a radial direction to lock the inner edge of the rim for its automatic centring. 
     The device is keyed on a shaft of the gripping unit, so that the rim, once locked, can be made to rotate to fit or remove the tyre, with the cooperation of the above-mentioned tool. 
     The known supporting plates can have different shapes, typically circular, square or “flower like” but, whatever the chosen shape, they are made from a single piece of metal. 
     Such plates are made up of a single metal slab with constant thickness, shaped by means of laser technology, in order to achieve enough structural strength to offset the stresses developed during the fitting/removal operations. 
     This aspect nevertheless makes known plates particularly heavy and therefore inconvenient to fit for operators. 
     Furthermore, known plates are expensive due to the fairly large quantity of raw material used. 
     DESCRIPTION OF THE INVENTION 
     The main aim of the present invention is to provide a supporting plate for a self-centring chuck which, though lighter and cheaper than those of prior art, is at least equally resistant. 
     Within this aim, one object of the present invention is to provide a supporting plate for a self-centring chuck that can be manufactured in different shapes at lower costs compared to prior art. 
     Another object of the present invention is to provide a supporting plate for a self-centring chuck which can overcome the above mentioned drawbacks of the prior art in the ambit of a simple, rational, easy and effective to use as well as low cost solution. 
     The above mentioned objects are achieved by the present supporting plate for a self-centring chuck made according to claim  1 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the present invention will become better evident from the description of a preferred, but not exclusive, embodiment of a supporting plate for a self-centring chuck, illustrated by way of an indicative, but not limitative example in the accompanying drawings in which: 
         FIG. 1  is an axonometric view of a tyre-changing machine on which the plate according to the invention is installed; 
         FIG. 2  is an axonometric view of the chuck comprising the plate according to the invention; 
         FIG. 3  is an axonometric view of the plate according to the invention; and 
         FIG. 4  is an exploded axonometric view of the plate according to the invention. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     With special reference to these figures, globally indicated by  1  is a supporting plate meant to be used in a self-centring chuck  2  of the type also called “self-centring chuck”. 
     The chuck  2  which comprises the plate  1  of the invention is meant to support and lock the rim of a vehicle wheel on a tyre-changing machine  3  like the one shown in  FIG. 1 . 
     The function of plate  1  is to support the wheel locked or to be locked on the chuck  2  included in a gripping and rotation unit  5  installed on the machine  3 . 
     The machine  3  can be of the type having a base  4  on which the gripping unit  5  is mounted in front position, behind which unit  5  is a post  6  supporting a tool-carrying arm  7  which has the tool for fitting and removing tyres to and from a rim. 
     The plate  1  comprises a main element  8 , in turn comprising a central coupling  9  which is keyed on the shaft of the gripping unit  5 . 
     The main element  8  also comprises a plurality of spokes  10 , each having a groove  11  wherein can slide respective jaws  12  of the chuck  2 , to lock and automatically centre the rim, in ways in themselves known and which are not therefore detailed here. 
     In detail, the grooves  11  are full-thickness passages obtained centrally to each spoke  10 , to define in this two prongs  13 , i.e., a pronged shape. 
     Preferably, the main element  8  comprises a metal slab, made in a single body piece, which shapes the above-mentioned spokes  10  and which can have a constant thickness. 
     In the embodiment shown in the illustration, such slab  8  is cross-shaped and comprises four spokes  10  angularly equally distanced. 
     The plate  1  also includes a plurality of peripheral sectors  14 , in the number of four in the illustrated example, with substantially planar extension. Each sector  14  is fixed to the main element  8  between two of its spokes  10 , e.g., by welding, to define with it a single product. 
     The sectors  14  can be arranged in the plate  1  angularly equally distanced, substantially like the petals of a four-leafed clover or the like. 
     The sectors  14  are separated the one from the other from the main element  8  which is arranged in central position to define sort of quadrants occupied by respective sectors  14 . 
     Preferably, each sector  14  is made of metal and in a single body piece. 
     The sectors  14  and the main element  8  are joined to one another in correspondence to respective perimeter edges  15 ,  16 . 
     In detail, one or more perimeter edges  15  of the sectors  14  are fastened to the outer side edges  16  of the spokes  10  so as to fill the spaces between the prongs  13  of two consecutive spokes  10 , defining an equal number of continuous angular portions of the plate  1 . 
     Preferably, the plate  1  is interrupted only in correspondence of the grooves  11  and of a central hole  17  obtained in the central coupling  9  to accommodate the above shaft of the gripping unit  5 . 
     Advantageously, the thickness of each of the sectors  14  is greater than that of the main element  8 , e.g., it can be substantially double. 
     Nevertheless, the thickness of the sectors  14  does not coincide with the thickness of the walls of the lamina from which it is made. 
     In fact, each sector  14  comprises an upper contact side  18 , meant to receive in support the rim, and a lower side  19  opposite the former and concave, like an overturned tray. 
     To be more precise, the lower side  19  has a concavity which is laterally contained in a perimeter frame, the width of which defines the thickness of the relative sector  14  and the outer surface of which identifies the above-mentioned edge  15  of the sector  14  (see  FIG. 4 ). 
     Preferably, the frame extends crossways to the surface of the upper side  18 , which is substantially flat. 
     Consequently, the difference appears clear between the thickness of the sector  14 , which is the width of its side edge  15 , and the thickness of the lamina or foil from which it is made. 
     The thickness of the sector  14  is greater than that of the main element  8 , while the thickness of the lamina is smaller than this. 
     Advantageously, the invention provides a plate  1  having a main element  8  consisting of a rather thick slab, e.g., 15 mm like the known plates, which gives the plate  1  its structural strength and enables it to offset the stresses produced during use. 
     The thickness of the main element  8  can be between 10 and 20 mm and preferably, as said, is 15 mm 
     On the other hand, the plate  1  is completed by the sectors  14  made from a lamina or sheet thinner than the main element  8  to which they are joined, to give the plate  1  a lightness and cheapness far superior to those of the plates of prior art. 
     Despite this, the plate  1  of the invention is surprisingly more resistant to lateral bending stresses compared to known ones, because the thickness of the sectors  14 , which are the components that withstand such bending, is greater than that of the slab from which the plates of prior art are made in their entirety. 
     The thickness of the sectors  14  can be between 25 and 35 mm and is preferably 30 mm. 
     In the preferred embodiment of the invention, each side edge  13  of the spokes  10  is joined to a respective edge  15  of a sector  14  in a median position with respect to the thickness of the latter. 
     The edges  15  of the sectors  14  can be lightened by the through holes  20 . 
     In the shown embodiment, the sectors  14  have a generically triangular shape or approximately of circular sectors  14 . 
     Nevertheless, the invention can envisage these having a shape with external angles, e.g., right angles, opposite the edges  15  which join to the main element  8 , to define a plate  1  with a substantially quadrangular shape. 
     Or the sectors  14  can have a substantially V shape, to define “flower-shaped” plates. 
     Generally, the plates  1  of the invention can have all the shapes of known plates and others still, inasmuch as sectors  14  of the most different shapes can be fastened to the main element  8 . 
     In fact, main elements  8  of the same shape can be used to make plates  1  of any shape, thus considerably cutting production costs. 
     It has in fact been ascertained that the invention provides a plate  1  for self-centring chucks of tyre changing machines which is lighter but as equally resistant as known plates, cheaper and which more effectively withstands lateral bending stresses.