Abstract:
A bead breaking unit for tire changing machines includes an arm having an adjustable supporting device for the pad against which a tire can be positioned, the adjustable supporting device including a first body mounting the pad, a second body attached to the base of the tire changing machine, and first and second rods extending through lateral slots in the bodies to control horizontal telescopic movement of the first body relative to the second body and the slant of the pad relative to the base.

Description:
BACKGROUND OF THE INVENTION 
     The present invention refers to a bead breaking unit for tire changing machines. 
     THE PRIOR ART 
     Tire changing machines are normally used to fit/remove tires in/off their seat on rims. 
     As is common knowledge, before a tire can be removed completely from its rim, it is necessary to detach the beads from their bead clipping edges around the rim. 
     This operation is done by means of a suitable bead breaking unit, normally present on the tire changing machine, which comprises an arm, located on the side of the main support or base, which has a first end hinged to the support according to a substantially vertical axis, and a second end associated to a bead breaking tool, otherwise called small shovel. 
     An automatic linear actuator is placed in between the above mentioned arm and the base of the machine that allows the arm to rotate on a horizontal plane and, in particular, its oscillating movement between a working position, wherein the bead breaking tool is in proximity of the machine and in contact with the wheel, and a home position, wherein the bead breaking tool is kept away from the main support. 
     Near the bead breaking tool a stop is positioned on the base used for resting the rim on and to ensure it is correctly placed during bead breaking; this stop has a resting surface at the front, also called pad, made of a suitable material and usually knurled so as to increase the friction coefficient. 
     However, the known bead breaking units have some drawbacks, in particular, because of the huge variety of modern tires in terms of size and rigidity characteristics, they would require greater adaptability of the machine; as a matter of fact, the variability of these parameters inevitably affects the good outcome of the bead breaking operation, often making it very difficult with the possibility of damaging the wheel or the rim during the procedure. 
     Alternatively, there are machines where the bead breaking units are equipped with a pad mounted on a telescopic support, the sliding axis of which is positioned horizontally and crosswise with respect to the main support formed by the tire changing machine frame. This telescopic support can be adjusted based on the size of the wheel that requires bead breaking and, in particular, it lets the small shovel exert pressure on the tire at approximately the same angle, regardless of the size of the wheel. 
     However, this invention is susceptible to additional upgrading. 
     In particular, in this specific sector the need is felt to overcome this technical problem by using a bead breaking unit with mechanical characteristics that render it suitable for bead breaking different types of tire. 
     The main aim of this invention is to provide a bead breaking unit that improves the effectiveness of the bead breaking operation of the tires by implementing an apparatus that can adapt to almost the entire range of tires as far as rigidity and size are concerned. 
     Within the scope of such technical aim, another object of the present invention is to cater for the above aims with a simple structure, of relatively practical implementation, safe to use and with effective operation, as well as having a relatively low cost. 
     SUMMARY OF THE INVENTION 
     The above mentioned objects are all achieved by this bead breaking unit for tire changing machines, of the type comprising an arm with a first end jointed to the base of a tire changing machine on a substantially vertical axis and a second end associated to a bead breaking tool, the arm being suitable for oscillating between a home position, wherein the bead breaking tool is placed away from the base, and a working position, wherein the bead breaking tool is placed in contact with a wheel that has to undergo bead breaking resting against at least one side pad protruding at least in part from base, characterised in that it includes an adjustment device for adjusting the slant of the resting surface of the pad suitable for defining at least two working configurations. 
     Further characteristics and advantages of the present invention will appear even more evident from the detailed description of a preferred, but not exclusive, embodiment of a bead breaking unit for tire changing machines, illustrated indicatively by way of non limiting example, in the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view from the top of a tire changing machine on which the bead breaking unit is mounted, according to the invention, in the working position with the telescopic element closed; 
         FIG. 2  is a view from the top of a tire changing machine on which the bead breaking unit is mounted, according to the invention, in the working position with the telescopic element open; 
         FIGS. 3 and 5  are side and partial views of the telescopic element of the bead breaking unit according to the invention in the closed position; 
         FIG. 4  is a front and partial view of the telescopic element of the bead breaking unit according to the invention in the closed position; 
         FIGS. 6 and 8  are side and partial views of the telescopic element of the bead breaking unit according to the invention in the open position; and 
         FIG. 7  is a front and partial view of the telescopic element of the bead breaking unit according to the invention in the open position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With special reference to such figures, a tire changing machine for fitting and removing a tire P onto and from the rim C of a wheel R, has been globally and schematically designated by reference number  1 . 
     The tire changing machine  1  has a base  2  on which the swivel locking plate and the tool for removing the tire P from the wheel R are housed; the locking plate and the tool for removing are not illustrated in detail in the figures. 
     On one of the sides of the base  2  is a bead breaking unit  3  having a connecting appendage  4  that is fixed to a rib  5  on the side of the base  2 . 
     The connecting appendage  4  is crossed vertically by a hinging pivot  6  that supports a first end of a swivel arm  7 . 
     The arm  7  has a second end, opposite the first, on which a bead breaking tool  8  is mounted of the known shape, that can be made to turn, with respect to the arm  7 , around a horizontal and cross axis to the arm  7  by means of a lever  9 . 
     The rotation of the arm  7  around the hinging pivot  6  occurs due to the action of a pneumatic cylinder  10 , fixed at one end to the base  2  and at the other end to the substantially median portion of the arm  7 . 
     In actual facts, the operation of the pneumatic cylinder  10  allows the arm  7  to swing between a home position, wherein the bead breaking tool  8  is placed away from the base  2  so the wheel R can be positioned properly, and a working position wherein it is near the base  2  and in contact with the tire P of the wheel R to execute bead breaking. 
     During bead breaking the rim C of the wheel R is arranged so it is resting against a side pad  11  whose contact surface is made of a non-slip material and has a high friction coefficient. 
     Usefully, the bead breaking unit  3  has an adjustment device for adjusting the slant of the resting surface of the pad  11 , suitable for defining at least two working configurations. 
     The adjustment device is composed of a telescopic element  12  with a substantially horizontal sliding axis, which is associated to the side of the base  2  and on the head of which the pad  11  is fixed. 
     The telescopic element  12 , in detail, is composed of a first hollow body  13  that supports the pad  11 , and a second hollow body  14  fixed to the base  2  crosswise to the rib  5  and inside of which the first body  13  is housed in a slidable way. 
     In practice, the sliding of the first body  13  inside the second body  14  is suitable for defining a closed position of the telescopic element  12 , wherein the pad  11  is positioned in proximity to the base  2 , and an open position wherein the pad  11  is positioned away from the base  2 . 
     The first body  13  has two lateral sides  15  substantially parallel with the sliding direction of the telescopic element  12 , one of which is longer than the other allowing to give the pad  11  a slant of about ± three sexagesimal degrees with respect to a vertical plane parallel with the side of the base  2  on which the bead breaking unit  3  is mounted; in addition, the shorter lateral side  15  has, advantageously, a portion of the end  16  folded in towards the inside of the telescopic element  12 . 
     The forward and backward strokes of the pad  11  are entrusted to a kinematic coupling between the bodies  13  and  14 , which comprises two rods  17  overlapping parallel with each other and arranged horizontally. 
     The ends of the rods  17  are individually received, according to a free sliding coupling, in first slots  18  created in the lateral sides  15  of the first body  13  and in second slots  19   a ,  19   b ,  20   a  and  20   b  created in the lateral sides  21  of the second body  14 . 
     The rods  17  protrude from both the lateral sides  21  of the second body  14 , enough to be blocked by a stopping system, of the known type. 
     In addition, the rods  17  are connected together by means of two small connecting rods  22 , vertical and opposite, positioned close to the lateral sides  15  of the first body  13  inside the telescopic element  12 . 
     The first slots  18  created on the first body  13  are rectilinear and aligned according to a vertical direction. 
     The second slots  19   a ,  19   b ,  20   a  and  20   b  on the second body  14  start and end in the same point as the first slots  18  and have shapes and slant different from one another. 
     In detail, the second slots  19   a  and  19   b  created on the lateral side  21  of the second body  14  opposite the hinged end of the arm  7  comprise an upper first section that slants downwards and towards the pad  11 , and a lower second section that extends from the first section towards the bottom but on the opposite side with respect to the pad  11 . 
     The second slots  20   a  and  20   b  which, instead, are on the lateral side  21  facing towards the hinged end of the arm  7 , comprise an upper first section that slants downwards and towards the pad  11 , and a lower vertical second section. 
     Advantageously, the pair of second slots  19   a  and  20   a , both reciprocally facing each other and along which the top rod  17  is engaged, have a short initial section, substantially horizontal of a size sufficient to house the above rod in safe conditions, with the purpose of avoiding an uncontrolled disengagement of the rod from its housing during the various bead breaking operations. 
     The slant of the oblique sections of the second slots  19   a ,  19   b ,  20   a  and  20   b  can vary in alternative implementations of the invention where one wishes to vary the stroke of the telescopic element  12 . 
     It will be obvious to a technician in the sector that the correspondence, as described here, between the slots  18 ,  19   a ,  19   b ,  20   a  and  20   b  and the telescopic element  12  is only an example and not binding; it is, in fact, possible to obtain the same technical results also by creating the vertical slots on the second body  14  and the oblique ones on the first body  13 , but in this case the slant must necessarily be contrary to that described. 
     Conforming to the invention, the pad  11  can engage two different working configurations, illustrated clearly in the  FIGS. 1 and 2  respectively, the positions of which ensure an excellent bead breaking of any type of tire. 
     The forward/backward strokes of the pad  11  are entrusted to the lifting/lowering of the rods  17 , action which can be done using an operating device of the manual type constituted, for example, by a handle  23  fastened integral with one of the ends of the rods  17 , or using an operating device constituted by a linear actuator positioned inside the bodies  13  and  14 , with one end fastened to the base  2  and the other to one of the rods  17 . 
     The particular conformation of the invention, in particular as regards to the asymmetry of the second slots  19   a ,  19   b ,  20   a  and  20   b  that cause the rods  17  to block on unaligned points with a horizontal axis parallel with the rib  5  when the telescopic element  12  is in the open position, and the folding of the end portion  16  of the first body  13 , lets the pad  11  not only slide with a forward and backward motion but also, and above all, to be able to vary the angle of the resting surface with respect to a vertical axis. 
     The pad  11 , in fact, can go from an initial working configuration in which the telescopic element  12  is closed and its resting surface is slanted due to the different length of the lateral sides  15  of the first body  13 , to a final working configuration in which the telescopic element  12  is open and the resting surface of the pad  11  finds itself turned around a vertical axis with respect to the initial working configuration. 
     This variation in the slant of the resting surface, together with a translation of the pad  11 , determines an effect that leads to a notable change in the angle of incidence of the bead breaking tool  8  on the tire P in the passage between the two operating configurations. 
     This allows a correct approach both on hard and soft tires and, in general, on all types of tire. 
     It has in practice been found how the described invention achieves the intended objects. 
     In particular, it must be pointed out the considerable adaptability capacity of the bead breaking unit according to the invention, making it possible to adjust the relative position between the wheel and the bead breaking tool and to work in optimum conditions on any type of tire. 
     The invention thus conceived is susceptible of numerous modifications and variations, all of which falling within the scope of the inventive concept. 
     Furthermore, all the details may be replaced by other elements which are technically equivalent. 
     In practice, the contingent shapes and dimensions may be any according to requirements without because of this moving outside the protection scope of the following claims.