Jaw, wheel-holder unit and tyre changing apparatus

A wheel-holder unit for a tyre changing apparatus, the wheel-holder unit comprising a head, the head being rotatable about an axis of rotation, and a lift actuator, connected to the head to move it along a trajectory having at least a vertical component, parallel to the weight force, wherein the head includes a plurality of jaws which are angularly spaced around the axis of rotation and which are movable towards and away from each other between a position where they are distal from, and a position where they are proximal to, the axis of rotation of the head, wherein each jaw of the plurality of jaws is a jaw for clamping a wheel rim in a tyre changing apparatus provided with a wheel-holder unit having a head, the jaw comprising a body extending along a longitudinal orientation, the body including:

• a connecting portion configured to be connected to the head of the wheel-holder unit;
• a base portion extending along the longitudinal orientation;
• a first abutment wall, extending from the base portion along a clamping orientation, perpendicular to the longitudinal orientation, in a spacing-apart direction, and along a transverse orientation, the transverse orientation being perpendicular to the longitudinal orientation and to the clamping orientation;
• a second abutment wall extending from the base portion along the clamping orientation in the spacing-apart direction, along the transverse orientation and longitudinally spaced from the first abutment wall by a working distance;
• an abutment surface, longitudinally interposed between the first abutment wall and the second abutment wall and smoothly connected thereto to delimit the body in the spacing-apart direction, between the first abutment wall and the second abutment wall,
• wherein the abutment surface comprises a first portion, smoothly connected to the first abutment wall, and a second portion, smoothly connected to the first portion and to the second abutment wall and including an inclined portion inclined relative to the first portion and relative to the longitudinal orientation,
• wherein the second portion of the abutment surface is located at an advanced position relative to the first portion in the spacing-apart direction of the clamping orientation, to come into contact with the wheel rim,
• wherein the second portion is spaced from the first abutment wall along the longitudinal orientation by a first abutment distance, greater than 30% of the working distance.

A method for mounting or demounting a wheel tyre on or from the corresponding rim, comprising the following steps:

• preparing a tyre changing apparatus, including a wheel-holder unit comprising a head, which rotates about an axis of rotation. and a plurality of jaws, which are angularly spaced around the axis of rotation of the head;
• moving the head and the wheel rim towards each other along a longitudinal orientation parallel to the axis of rotation to position the plurality of jaws inside the wheel;
• moving the jaws along a clamping orientation perpendicular to the axis of rotation towards or away from each other between a position distal from, and a position proximal to, the axis of rotation of the head;
• clamping the wheel rim with the plurality of jaws, where the rim is in contact with each jaw at an abutment surface thereof which is interposed along the longitudinal orientation between a first abutment wall and a second abutment wall, which are spaced from each other by a working distance;
• wherein the abutment surface comprises a first portion and a second portion, including an inclined portion that is inclined relative to the first portion, and wherein, in the step of clamping, the second portion is interposed along the clamping orientation, between the first portion and the rim, to come into contact with the wheel rim before the first portion does,
• and wherein the second portion is spaced from the first abutment wall, along the longitudinal orientation, by a first abutment distance, greater than 30% of the working distance.