Tyre-changing machine and a relative bead-breaking method

1. A tyre-changing machine comprising support means ( 4 ) for a wheel, a tool-bearing arm ( 50 ) at an end of which a bead-breaking tool ( 6 ) is hinged according to a hinge axis (E) which is perpendicular to an axis (A) of the wheel, and first motorised means ( 32 , 33 ) for causing a relative movement, in a parallel direction to the axis (A) of the wheel, between the support means ( 4 ) and the tool-bearing arm ( 50 ), such as to press the bead-breaking tool ( 6 ) against a flank of a tyre on the wheel, wherein said machine comprises second motorised means ( 64 ), able to activate independently from the first motorised means ( 32 , 33 ), which second motorised means ( 64 ) are destined to rotate the bead-breaking tool ( 6 ) about the hinge axis (E) with the tool-bearing arm ( 50 ), in order to vary an inclination of the bead-breaking tool ( 6 ) with respect to the axis (A) of the wheel which is mounted on the support means ( 4 ), wherein the second motorised means ( 64 ) are controllable such as to be able to rotate the bead-breaking tool ( 6 ) continuously between two extreme end positions in both directions and to be able to stop the bead-breaking tool ( 6 ) in intermediate positions between the end positions,

wherein a tyre-demounting tool ( 7 ) is further mounted on the tool-bearing arm ( 50 ), and wherein the second motorised means ( 64 ) rotate the bead-breaking tool ( 6 ) between two extreme end positions, in at least one of which the bead-breaking tool ( 6 ) is at a minimum radial distance from the axis (A) of the wheel mounted on the support means ( 4 ), which is greater than the minimum radial distance separating the axis (A) of the wheel from the tyre-demounting tool ( 7 ), wherein the bead-breaking tool ( 6 ) and the tyre-demounting tool ( 7 ) are both coupled to a tool-bearing turret ( 5 ) and are oriented in different directions, wherein the tool-bearing turret ( 5 ) is rotatable about an axis (B) perpendicular to the hinge axis (E), to be locked in a first operative position, in which the bead-breaking tool ( 6 ) faces the support means ( 4 ) and the tyre-demounting tool ( 7 ) faces away from the support means ( 4 ), and a second operating position, in which the tyre-demounting tool ( 7 ) faces the support means ( 4 ) and the bead-breaking tool ( 6 ) faces away from the support means ( 4 ), whereby the bead-breaking tool ( 6 ) and the tyre-demounting tool ( 7 ) are selectively activated by rotation of the tool-bearing turret ( 5 ).

2. The machine of claim 1 , wherein the motorised means ( 64 ) are destined to rotate the bead-breaking tool ( 6 ), when the bead-breaking tool ( 6 ) is in contact with the flank of the tyre on the wheel mounted on the support means ( 4 ).

3. The machine of claim 1 , wherein the second motorised means ( 64 ) are associated to manual control means which are destined to activate the second motorised means ( 64 ) in order to cause rotation of the bead-breaking tool ( 6 ).

4. The machine of claim 1 , wherein the second motorised means ( 64 ) are associated to automatic control means.

5. The machine of claim 1 , wherein the second motorised means comprise a double-acting jack ( 64 ).

6. A bead-breaking method using a tyre-changing machine as in claim 1 , comprising stages of blocking a wheel on the support means ( 4 ), causing a relative movement, in a parallel direction to an axis (A) of the wheel, between the support means ( 4 ) and the tool-bearing arm ( 50 ), such as to press the bead-breaking tool ( 6 ), hinged to said tool-bearing arm ( 50 ), against a flank of the tyre of the wheel, characterised in that it comprises a stage of rotating the bead-breaking tool ( 6 ) about a hinge axis (E) with the tool-bearing arm ( 50 ), while the bead-breaking tool ( 6 ) is in contact with the tyre, such as to exert an action which tends to distance the tyre bead from the rim edge in such a way as to be able to stop the bead-breaking tool ( 6 ) in intermediate positions between the end positions.

7. The method of claim 6 , characterized in that the rotation of the bead-breaking tool ( 6 ) is done during relative movement in an axial direction between the tool-bearing arm ( 50 ) and the wheel.

8. The method of claim 6 , characterised in that the rotation of the bead-breaking tool ( 6 ) is performed while the tool-bearing arm ( 50 ) is axially stationary with respect to the wheel.

9. The method of claim 6 , characterised in that the rotation of the bead-breaking tool is done while the wheel mounted on the support means ( 4 ) is rotating about the axis thereof (A).

10. The machine of claim 1 , wherein the bead-breaking tool ( 6 ) and the tyre-demounting tool ( 7 ) are oriented in opposite directions facing away one from the other.

11. The machine of claim 1 , wherein the tyre-demounting tool ( 7 ) is hinged to the tool-bearing turret to oscillate between end positions.

12. The machine of claim 11 , wherein the tyre-demounting tool ( 7 ) is connected to a double-acting jack to be controlled in its oscillation.

13. The machine of claim 1 , wherein the bead-breaking tool ( 6 ) is connected to a double-acting jack configured to control its oscillation about axis (E).