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Title:
A TYRE-REMOVING METHOD AND A TYRE-CHANGING MACHINE
Document Type and Number:
WIPO Patent Application WO/2009/138322
Kind Code:
A1
Abstract:
A method and a machine for removing a tyre (100) from a rim (101) using a demounting tool (7) which is mobile on a support body (5, 51) between a first operating position and a second operating position, to which operating positions correspond different inclinations of the demounting tool (7) with respect to an axis (A) of the rim (101); the method including a stage of inserting the demounting tool (7), which is in the first operating position, between a side of the tyre (100) and an edge of the rim (101), and subsequently moving the demounting tool (7) from the first operating position to the second operating position, by means of a movement of the support body (5, 51) towards the axis (A) of the rim (101), such that the edge of the rim (101) pushes the demounting tool (7) towards the second operating position.

Inventors:
CORGHI GIULIO (IT)
Application Number:
PCT/EP2009/055189
Publication Date:
November 19, 2009
Filing Date:
April 29, 2009
Export Citation:
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Assignee:
CORGHI SPA (IT)
CORGHI GIULIO (IT)
International Classes:
B60C25/138
Foreign References:
US20020162633A12002-11-07
EP1625954A22006-02-15
EP1623850A12006-02-08
EP1714807A12006-10-25
Attorney, Agent or Firm:
CORRADINI, Corrado et al. (4 Via Dante Alighieri, Reggio Emilia, IT)
Download PDF:
Claims:
CLAIMS

1 ). A method for removing a tyre (100) from a rim (101 ) using a demounting tool (7) which is mobile on a support body (5, 51 ) between a first operating position and a second operating position thereof, to which operating positions correspond different inclinations of the demounting tool (7) with respect to an axis (A) of the rim (101 ), the method including a stage of inserting the demounting tool (7), which is in the first operating position, between a side of the tyre (100) and an edge of the rim (101 ), and subsequently moving the demounting tool (7) from the first operating position to the second operating position, characterised in that the stage of moving the demounting tool (7) between the first operating position and the second operating position is performed by means of a movement of the support body (5, 51 ) towards the axis (A) of the rim (101 ), such that the edge of the rim (101 ) pushes the demounting tool (7) towards the second operating position. 2). The method of claim 1 , characterised in that the demounting tool (7) in the first operating position is substantially parallel to the axis (A) of the rim (101 ), or oriented toward the axis (A) of the rim (101 ). 3). The method of claim 1 , characterised in that the demounting tool (7) in the second operating position is oriented in an opposite direction with respect to the axis (A) of the rim (101 ). 4). The method of claim 1 , characterised in that it comprises keeping the demounting tool (7) blocked in the first operating position during the stage of inserting the demounting tool (7) between the tyre (100) and the edge of the rim (101 ); unblocking the demounting tool (7) before the movement of the support body (5, 51 ) towards the axis (A) of the rim (101 ); and blocking the demounting tool (7) in the said second operating position.

5). The method of claim 4, characterised in that at least the stage of unblocking the demounting tool (7) is performed manually.

6). The method of claim 4, characterised in that the demounting tool (7) is blocked by means of a control connecting rod (8) which is hinged to the demounting tool (7), to which control connecting rod (8) coupling means are associated which engage with corresponding blocking means (52) which are solidly constrained to the support body (5, 51 ), in such a way that the control connecting rod (8) can be blocked in two distinct positions, to which positions the first and the second operating positions of the demounting tool (7) correspond, the control connecting rod (8) being provided with a grip (80) which can be held by a user at least to free a coupling thus achieved. 7). The method of claim 6, characterised in that the coupling means associated to the control connecting rod (8) comprise two distinct cavities (82, 83) afforded in the control connecting rod (8), and in that the corresponding blocking means (52) which are solidly constrained to the support body (5, 51 ) comprise a fixed pin (52), which alternatively couples in each of the cavities (82, 83) of the control connecting rod (8).

8). The method of claim 1 , characterised in that the relative movement of the support body (5, 51 ) towards the axis (A) of the rim (101 ) is obtained by means of a total movement of the rim (101 ) towards the support body (5, 51 ). 9). The method of claim 1 , characterised in that the relative movement of the support body (5, 51 ) towards the axis (A) of the rim (101 ) is obtained by means of a total movement of the support body (5, 51 ) towards the rim (101 ). 10). A machine for removing a tyre (100) from a rim (101 ), comprising wheel-bearing means (4) for the rim (101 ) coupled to the tyre (100), a demounting tool (7) which is mobile on a support body (5, 51 ) between a first operating position and a second operating position, to which first and second operating positions different inclinations of the demounting tool (7) correspond with respect to an axis (A) of the rim (101 ) mounted on the wheel-bearing means (4), characterised in that the demounting tool (7) is joined to the support body (5, 51 ) by connecting means which enable the demounting tool (7) to move between the first operating position and the second operating position thereof, following a relative movement of the support body (5, 51 ) toward the axis (A) of the rim (101 ) mounted on the

bearing means (4), such that an edge of the rim (101 ) pushes the demounting tool (7) towards the second operating position. 11 ). The machine of claim 10, characterised in that in the first operating position thereof the demounting tool (7) is substantially parallel to the axis (A) of the rim (101 ), or is oriented towards the axis (A) of the rim (101 ).

12). The machine of claim 10, characterised in that in the second operating position thereof the demounting tool (7) is oriented in an opposite direction with respect to the axis (A) of the rim (101 ). 13). The machine of claim 10, characterised in that the demounting tool (7) is hinged to the support body (5, 51 ) in such a way as to be capable of moving between the first operating position and the second operating position by rotating on a hinge axis (D) which is substantially perpendicular to the axis (A) of the rim (101 ) which is mounted on the bearing means (4). 14). The machine of claim 10, characterised in that it comprises blocking means (8, 52) for selectively blocking the demounting tool (7) in the first operating position and in the second operating position. 15). The machine of claim 14, characterised in that the blocking means (8, 52) can be manually operated. 16). The machine of claim 14, characterised in that the blocking means (8, 52) comprise a control connecting rod (8) which is hinged to the demounting tool (7), to which control connecting rod (8) coupling means are associated which give rise to a coupling with the corresponding blocking means (52) solidly constrained to the support body (5, 51 ), in such a way as to be capable of blocking the control connecting rod (8) in two distinct positions, to which two distinct positions correspond the first operating position and the second operating position of the demounting tool (7) respectively. 17). The machine of claim 16, characterised in that the control connecting rod (8) comprises a grip (80) which can be held by a user at least to free the coupling. 18). The machine of claim 16, characterised in that the control connecting rod (8) is associated to automatic means (84) at least to free the coupling.

19). The machine of claim 16, characterised in that the coupling means associated to the control connecting rod (8) comprise two distinct cavities (82, 83) afforded in the control connecting rod (8), and characterised in that the corresponding blocking means which are solidly constrained to the support body (5, 51 ) comprise a fixed pin (52) which can couple alternatively with each of the cavities (82, 83) of the control connecting rod (8). 20). The machine of claim 16, characterised in that the control connecting rod (8) is associated to a spring (9) which pushes the connecting rod (8) in a direction which maintains the coupling between the coupling means (82, 83) associated to the connecting rod (8) and the blocking means (52) associated to the support body (5, 51 ).

21 ). The machine of claim 10, characterised in that it comprises motohsed means (22) for moving the bearing means (4) of the rim (101 ) towards the support body (5, 51 ) of the demounting tool (7), in such a way as to obtain the relative movement of the support body (5, 51 ) towards the axis (A) of the rim (101 ) mounted on the bearing means (4).

22). The machine of claim 10, characterised in that it comprises motohsed means for moving the support body (5, 51 ) of the demounting tool (7) toward the bearing means (4) of the rim (101 ), such as to obtain the relative movement of the support body (5, 51 ) towards the axis (A) of the rim (101 ) which is mounted on the bearing means (4).

23). The machine of claim 10, characterised in that the demounting tool (7) is associated to elastic return means (85) which bring the demounting tool (7) back from the second operating position into the first operating position.

Description:

A TYRE-REMOVING METHOD AND A TYRE-CHANGING MACHINE

Technical Field

The invention concerns a method for removing tyres from relative rims, and a tyre-changing machine designed to implement this method. Background Art

As is known, tyres are removed from rims using tyre-changing machines which schematically comprise a wheel-bearing chuck which is capable of coaxially bearing a rim and its tyre, and a demounting tool which hooks onto the bead of the tyre, in such a way as to lift the bead completely out of the bead seating when the wheel-bearing chuck is rotated. In particular, tyre-changing machines are known which enable the tyre to be removed from the rim without an operator actively intervening.

These tyre-changing machines comprise a tool-bearing arm which extends radially with respect to the axis of rotation of the wheel-bearing chuck, to which tool-bearing arm a tyre-changing tool is hinged, having a substantially hook-shaped end which is capable of hooking onto the bead of the tyre. This tyre-removing tool rotates on the tool-bearing arm between an operating position in which it is either substantially parallel to the axis of rotation of the wheel-bearing chuck, or oriented with the hook-shaped end slightly inclined towards the axis of rotation, and a second operating position, in which it is oriented in the opposite direction. Tyre-changing machines of this type are provided with first motorised means which move the tool-bearing arm and the wheel-bearing chuck reciprocally closer and further away in a direction which is parallel to the axis of rotation of the wheel-bearing chuck; second motorised means which cause a relative movement between the wheel-bearing chuck and the tyre-changing tool in a radial direction; and third motorised means which move the tyre-changing

tool with respect to the tool-bearing arm between the first operating position and a second operating position.

In the demounting procedure implemented by these machines, the tyre is initially deflated and debeaded, that is, the bead of the tyre is detached from the relative bead seating on the rim edge. This preliminary stage can be implemented before fixing the rim on the wheel-bearing chuck, or after the fixing operation, by means of a suitable bead-breaking tool tool which can be installed on the tool-bearing arm of the tyre-changing machine, together with the demounting tool. After having debeaded the tyre and fixed the rim on the wheel-bearing chuck, the demounting tool is arranged in the first operating position and, via activation of the second motohsed means, is radially aligned with the portion of the side of the tyre which is near the edge of the rim. At this point, the first motorised means start functioning, initially moving the tool-bearing arm and the wheel-bearing chuck reciprocally closer until the demounting tool penetrates between the side of the tyre and the edge of the rim, and then moving them apart in an opposite direction, in such a way that the demounting tool hooks onto a portion of the bead of the tyre and pulls the portion towards the outside of the rim. When the portion of the bead is substantially flush with the edge of the rim, the third motorised means rotate the demounting tool from the first operating position to the second operating position, in such a way that the portion of the bead goes beyond the edge of the rim, at the same time moving closer to the axis of rotation of the wheel-bearing chuck, and thus reducing the tensional stresses to which the tyre is subjected.

Finally the wheel-bearing chuck is rotated such that the bead of the tyre, sliding on the surface of the bead-breaking tool, is completely extracted from the seating of the relative rim. This automatic demounting system is extremely efficient at removing tyres having somewhat flexible sides, typically tyres of light vehicles such as motor cars and motor cycles, while it encounters some difficulty in removing tyres with rigid sides, because of the greater resistance opposed by the tyre during

the movement of the demounting tool from the first operating position to the second operating position.

In particular, when this demounting system is applied to machines for removing heavy duty tyres - that is to say, tyre-changing machines which are designed to operate with large-sized and very large-sized wheels, such as those of trucks and agricultural tractors - the third motohsed means, which move the demounting tool from the first to the second position must be capable of exerting much greater force, thus requiring the adoption of a rather more complicated constructional solution which is bulkier and more expensive than those applied in light-duty tyre-changing machines. Disclosure of Invention

An aim of this invention is to make available a tyre-changing method which obviates the above-mentioned drawbacks in the prior art, while maintaining the functional advantages thereof. A further aim of the invention is to provide a method which can be implemented via a tyre-changing machine which is simpler, more rational and more economical than those in the prior art.

These aims are achieved by the characteristics which are delineated in the independent claims. The dependent claims delineate preferred and/or particularly advantageous aspects of the invention.

The method of the invention, like known systems, uses a demounting tool which is mobile on a support body between a first operating position and a second operating position, to which positions different inclinations of the demounting tool correspond with respect to the axis of the rim, and also includes the stages of inserting the demounting tool, which is in the first operating position, between the side of the tyre and the edge of the rim, and subsequently moving the demounting tool from the first operating position to the second operating position. Differently from known systems, in the method of the invention the stage of moving the demounting tool between the first operating position and the second operating position is effected via a relative movement of the support

body towards the axis of the rim, such that the edge of the rim pushes the demounting tool towards the second operating position.

Thanks to this solution, tyre-changing machines which apply the method of the invention do not require third motohsed means to move the demounting tool from the first operating position to the second operating position, since this movement can be obtained for example using the second motohsed means, which are capable of moving the rim and the demounting tool reciprocally closer in a radial direction.

These tyre-changing machines are therefore simpler and more economical than those which are at present in use, and can operate efficiently even with tyres having very rigid sides, such as those of wheels of large dimensions, since generally speaking, increasing the power of the second motorised means does not pose significant technical problems.

In a preferred aspect of the invention, the method includes keeping the demounting tool blocked in the first operating position during the stage of inserting the demounting tool between the tyre and the edge of the rim; unblocking the demounting tool before the relative motion of the support body towards the axis of the rim; and then blocking the demounting tool in the second operating position, before setting the wheel in rotation and completely debeading the tyre.

Preferably, the stage of blocking the demounting tool in the first and second operating positions is obtained via blocking means which can be activated manually, at least to unblock the demounting tool.

Brief description of the Drawings Further characteristics and advantages of the invention will emerge from the description herein below, which is a non-limiting example, with the aid of the figures of the appended drawings.

Figure 1 is a plan view of a heavy-duty tyre-changing machine which is equipped to implement the method of the invention. Figure 2 is an enlarged detail of the demounting tool which enables the machine of figure 1 to implement the method of the invention.

Figure 3 is a section view along section line Ill-Ill indicated in figure 2.

Figures 4 to 10 show a corresponding number of stages of the demounting method of the invention.

Figure 11 shows an alternative embodiment of the demounting tool of figure

2. Best Mode for Carrying Out the Invention

The machine 1 shown in the appended figures is a heavy-duty tyre-changing machine, that is to say, a machine designed to operate with wheels of large and extra-large dimensions, such as those with which trucks and agricultural tractors are normally fitted, without thereby excluding that the invention may be applied in the same way to any type of tyre-changing machine, including those operating on the wheels of motor cars or motor cycles.

The tyre-changing machine 1 comprises a solid base 2 resting on the ground, upon which a wheel-bearing chuck 4 is installed which rotates about a horizontal axis of rotation A. The wheel-bearing chuck 4 comprises a self-centring group, which is capable of blocking a wheel while keeping it coaxial with the axis of rotation A.

The self-centring group comprises four identical blocking claws 40, which are distributed in an angularly equidistant way on a circumference which is centred on the axis of rotation A of the chuck 4, in such a way as to be in direct contact with, and press from the inside outwardly against, the rim of the wheel.

The blocking claws 40 are borne at the end of respective oscillating arms 41 , which are moved by a single drive system (not shown), such that the blocking claws 40 are capable of moving contemporaneously further from or closer to the axis of rotation A, performing identical radial movements, and always remaining arranged on a circumference which is centred at the axis of rotation A.

The wheel-bearing chuck 4 is of a known type and is therefore not described in greater detail. The wheel-bearing chuck 4 is rotatably installed on a sliding carriage 20, the sliding carriage 20 being associated to a sturdy bearing arm 21 , on which the

sliding carriage 20 is guided to slide in a direction Y, which is perpendicular to the axis of rotation A of the wheel-bearing chuck 4, by a hydraulic jack 22.

The bearing arm 21 is projectingly attached to a slide 23 which in turn is slidingly coupled to a horizontal straight guide 24, which horizontal straight guide 24 is parallel to the axis of rotation A of the wheel-bearing chuck 4, and is associated to the base 2.

The tyre-changing machine 1 further comprises a tool-bearing turret 5 comprising a tubular support body 50, the axis C of which tubular support body 50 is perpendicular to the axis of rotation A of the wheel-bearing chuck 4, and is parallel to the direction of sliding Y of the sliding carriage 20, in such a way as to always be coplanar with the axis of rotation A in any position of the wheel-bearing chuck 4 on the bearing arm 21.

The free end of the tubular body 50 bears a head element 51 on which both a bead-breaking tool 6 and a tyre-demounting tool 7 are mounted, which are arranged in a diametrically oppositely of the axis C of the tool-bearing turret

5.

The bead-breaking tool 6 is of a known kind and is not described in greater detail herein.

As shown in figure 2, the tyre-demounting tool 7 is substantially lever-shaped and is hinged at an intermediate point in the manner of a rocker arm to the head element 51 of the tool-bearing turret 5, on a hinge axis D which is perpendicular to the axis of rotation A of the wheel-bearing chuck 4.

The tyre-demounting tool 7, which exhibits a first end 70 which faces radially outwardly with respect to the tool-bearing turret 5, is substantially hook- shaped and capable of hooking onto the bead of the tyre.

The opposite end of the tyre-demounting tool 7 is hinged to the end of a control connecting rod 8, on a hinge axis E which is parallel to the hinge axis

D with the head element 51.

The control connecting rod 8 is defined by a shaped plate which extends substantially parallel along the outer lateral side of the tubular support body

50 of the tool-bearing turret 5 (see figure 3), the opposite end of which control

connecting rod 8 exhibits a transversal grip 80 which an operator can hold to manoeuvre the control connecting rod 8.

An intermediate tract of the control connecting rod 8 affords a shaped opening 81 , in which a blocking pin 52 engages, which blocking pin 52 is solidly constrained to the outer lateral side of the tubular body 50 of the tool- bearing turret 5.

The shaped opening 81 affords a longitudinal slit in which the blocking pin 52 can freely slide, and two distinct blocking cavities 82, 83 open within the longitudinal slit, each of which is situated at a different distance with respect to the hinge axis E between the control connecting rod 8 and the tyre- demounting tool 7.

Each of the blocking cavities 82, 83 can snugly receive the blocking pin 52, thereby giving rise to a coupling which prevents rotation of the tyre- demounting tool 7 with respect to the hinge axis D with the head element 51 , thus blocking the tyre-demounting tool 7 in a first and a second operating position respectively, with different inclinations of the tyre-demounting tool 7 corresponding to these positions, with respect to the axis of rotation A of the wheel-bearing chuck 4. In detail, in the first operating position, which is shown in figures 2 and 4, the tyre-demounting tool 7 is substantially parallel to the axis of rotation A of the wheel-bearing chuck 4, or is oriented with the hook-shaped end 70 slightly inclined towards the axis of rotation A, while in the second operating position, which is shown in figure 9, the tyre-demounting tool 7 is oppositely oriented, the hook-shaped end 70 being oppositely inclined with respect to the axis of rotation A of the wheel-bearing chuck 4.

As shown in figure 2, a leaf spring 9 acts on the lateral edge of the control connecting rod 8, alternately pushing each of the blocking cavities 82, 83 to engage with, and remain engaged with, the blocking pin 52. The leaf spring 9 is borne on a bearing block 90, which is hinged to the head element 51 of the tool-bearing turret 5, on a hinge axis F which is parallel to the hinge axis E between the control connecting rod 8 and the tyre- demounting tool 7, the bearing block 90 being blocked by a fixing screw 91

which screws into the head element 51 passing through a slot 92 of the bearing block 90, which slot 92 has a circular extension centred on the hinge axis F.

In this way, by loosening the fixing screw 91 , and modifying the angular position of the bearing block 90 with respect to its own hinge axis F, it is possible to regulate the preload of the leaf spring 9 and thus the elastic force which the leaf spring 9 exerts on the control connecting rod 8. The tool-bearing turret 5 can be rotated about its own axis C in such a way as to be selectively blocked in a first operating position (not shown), in which it directs the bead-breaking tool 6 towards the wheel-bearing chuck, or in a second operating position (shown in figure 1 ) in which the positions of the bead-breaking tool 6 and of the tyre-demounting tool 7 are inverted, the tyre- demounting tool 7 facing towards the wheel bearing chuck 4. This rotation of the tool-bearing turret 5 can be obtained manually by an operator, or by using suitable automatic drive means of a known type.

The tool-bearing turret 5 is mounted on a slide 25 which in turn is slidingly coupled to a straight horizontal guide 26 associated to the base 2, the tool- bearing turret 5 being parallel to the straight guide 24 upon which the slide 23 of the wheel bearing chuck 4 slides. The slides 23 and 25 are associated to first motohsed drive means, in this case a hydraulic jack 27, which move the two slides 23 and 25 reciprocally closer to or further from each other at the same time, in the horizontal direction defined by the respective guides 24 and 26, that is, parallelly to the axis of rotation A of the wheel-bearing chuck 4. In an alternative embodiment of the tyre-changing machine 1 , only one of the two slides 23 or 25 moves towards the other slide 25 or 23, which can instead be fixed.

Operation of the tyre demounting machine 1 includes coaxially blocking a deflated wheel to be treated on the wheel bearing chuck 4 with the aid of suitable lifting devices while the slides 23 and 25 are arranged at the maximum reciprocal distance.

The tool-bearing turret 5 is initially blocked in the first operating position, in which it positions the bead-breaking tool 6 facing towards the lateral wall of the tyre of the wheel which is mounted on the wheel-bearing chuck 4. The wheel-bearing chuck 4 is then set in rotation and the slides 23 and 25 are moved reciprocally closer in direction X, such that the bead-breaking tool 6 is pressed against the side of the tyre, pushing the tyre toward the inside of the seating of the rim until the bead of the tyre is detached from the edge of the rim. The bead-breaking tool 6 operates in a known way and is therefore not described in greater detail herein.

When the tyre is completely debeaded, the wheel-bearing chuck 4 is halted, and the slides 23 and 25 are moved apart again.

As shown in figure 4, the tool-bearing turret 5 is then rotated upon itself around the axis C, and blocked in the second operating position, in which it orients the tyre-demounting tool 7 towards the detached bead of the tyre 100. The tyre-demounting tool 7 is now in the first operating position, in which it is substantially parallel to the axis of rotation A of the wheel-bearing chuck 4 (and therefore to the rim 101 of the wheel): it is blocked in position by the control connecting rod 8, since the blocking cavity 82 of the control connecting rod 8 which is proximal to the hinge axis E with the tyre-changing tool 7 is coupled with the blocking pin 52 which is attached to the tool-bearing turret 5.

At this point, the slides 23 and 25 are moved reciprocally closer together in direction X, in such a way (see figure 5) that the tyre-demounting tool 7 pushes the side of the tyre 100 in an axial direction towards the inside of the seating of the rim 101 , until the hook-shaped end 70 goes beyond the bead of the tyre 100, inserting itself between the bead of the tyre and the edge of the rim 101. As shown in figure 6, the slides 23 and 25 are subsequently moved apart in direction X, in such a way that the tyre-demounting tool 7 is progressively extracted from the seating of the rim 101 , drawing with it the portion of the bead of the tyre 100 which it hooked onto earlier.

When the portion of bead is substantially flush with the edge of the rim 101 , as shown in figure 7, an operator manually holds the grip 80 of the control connecting rod 8, and acting contrastingly against the leaf spring 9 (see the arrow Z) disengages the blocking cavity 82 from the blocking pin 52. In the alternative embodiment shown in figure 11 , the movement of the control connecting rod 8 contrasting with the leaf spring 9 can be obtained automatically, in the illustrated example by installing a pneumatic jack 84 on the tool-bearing turret 5, an end of which pneumatic jack 84 is hinged to the grip 80, while the opposite end is hinged to the tubular support body 50. In both cases, the tyre-demounting tool 7 is now free to rotate with respect to the head element 51 about the hinge axis D, to move from the previously described first operating position to the second operating position, in which the hook-shaped end 70 is facing in the opposite direction with respect to the axis of rotation A of the wheel-bearing chuck 4 (and therefore of the rim 101 of the wheel).

As shown in figure 8, this movement is obtained thanks to the action of the hydraulic jack 22 (see also figure 1 ), which moves the sliding carriage 20 on the bearing arm 21 , in such a way as to move the wheel-bearing chuck 4 together with the wheel mounted upon it, in the radial direction Y, moving the wheel-bearing chuck 4 progressively closer to the demounting tool 2, which remains immobile.

In this way, the edge of the rim 101 first comes into contact with the end of the tyre-demounting tool 7, and subsequently pushes the tool 7 to rotate about its own hinge axis D until it reaches the second operating position of figure 8, while the blocking pin 52 slides in the longitudinal slit of the control connecting rod 8.

During this movement, the tyre-demounting tool 7 acts as a lever against the edge of the rim 101 , forcing the bead of the tyre 10 to go beyond the edge of the rim 101 and move slightly closer to the axis of rotation A, in such a way as to reduce the stresses to which the tyre 100 is subjected.

If it is necessary to maintain contact between the edge of the rim 101 and the demounting tool 7 during the displacement of the demounting tool 7 towards

-liĀ¬

the second operation position, the demounting tool 7 and the rim 101 can be slightly neared to one another in direction X also.

When the demounting tool reaches the second operating position, the operator can release the grip 80 of the control connecting rod 8 which, by effect of the leaf spring 9 (see arrow Q in figure 9) moves to the position in which it engages the blocking cavity 83, distal to the hinge axis E, with the blocking pin 52, in such a way as to block the tyre-demounting tool 7 in the said second operating position. As shown in figure 10, the slides 23 and 25 are then further distanced in an axial direction X, in such a way as completely to remove the portion of the bead previously hooked onto, and if necessary, the wheel bearing chuck 4 can be moved further in a radial direction Y, in such a way as further to reduce stresses in the tyre 100. After having reached the configuration shown in figure 10, the wheel-bearing chuck 4 is set in rotation, in such a way that by sliding on the tyre- demounting tool 7, the bead of the tyre 100 is entirely extracted from the rim 101.

When the tyre 100 has been completely removed, the wheel is dismounted from the wheel-bearing chuck 4, and the tyre-demounting tool 7 is brought back into the first operating position.

This operation is performed manually by the operator, who manually grips the grip 80 of the control connecting rod 8, and acting contrastingly with the leaf spring 9, first disengages the blocking cavity 83 from the blocking pin 52, and then pulls the connecting rod 8 axially and backwards, which connecting rod 8, being guided by the blocking pin 52 sliding in the longitudinal groove of the opening 81 , engages the tyre-demounting tool 7 to rotate towards the first operating position.

In the alternative embodiment shown in figure 11 , in addition to the jack 84, which pushes the control connecting rod contrastingly against the leaf spring 9 to disengage the blocking cavity 83 and the blocking pin 52, a return spring 85 is also provided, which pulls the control connecting rod 8 axially and

backwardly, in such a way as to bring the tyre-demounting tool 7 automatically back to the first operating position.

An end of the return spring 85 is attached to the blocking pin 62 while an opposite end thereof is attached to a hook 86 which is fashioned in the control connecting rod 8, in such a way that the return spring 85 extends as the control connecting rod 8 moves due to the rotation of the tyre-demounting tool 7 towards the second operating position, thus generating a return force which is subsequently sufficient to bring the control connecting rod 8 and the tyre-demounting tool 7 back into the initial position. With reference to this embodiment, note that the jack 84 could be a double- acting jack, and therefore be capable not only of disengaging the blocking cavities 82, 83 of the control connecting rod 8 when the tyre-demounting tool 7 is in the first or the second operating position, but also of giving rise to the engagement when the tyre-demounting tool 7 is in the first or in the second operating position, thus enabling elimination of the leaf spring 9.

Obviously a technical expert in the sector might make numerous modifications of a technical-applicational nature to the tyre-changing machine as described herein, without its forsaking the ambit of the invention as claimed herein below. In particular, although the present description relates to a tyre-changing machine 1 in which the wheel-bearing chuck 4 (and thus the rim 101 ) is provided with a total motion in direction Y with respect to the tyre-demounting tool 7, an alternative embodiment of the invention includes providing the tool- bearing turret 5 with a total motion in a parallel direction to the axis C (parallel to direction Y) while keeping the wheel-bearing chuck 4 stationary, such as still to be able to realise a reciprocal movement between the rim 101 and the demounting tool 7 which moves the demounting tool 7 from the first operating position into the second operation position as described herein above.