Mechanical assembly for urging the circumferential segments of a tire-building drum into fully-expanded positions

In a tire-building drum having a hollow main shaft having an end which is mountable upon a support for supporting the drum in a cantilevered condition above a floor, a plurality of circumferential segments about which a tire carcass can be constructed and which are movable between collapsed positions at which the drum is in a radially-collapsed condition and fully-expanded positions at which the drum is in a radially and fully-expanded condition, a drive rod which is positioned within and is axially movable along the length of the main shaft between a first condition and a second condition and so that the drive rod is movable from the first condition to the second condition upon application of an axial force applied thereto, and a swing arm which surrounds the main shaft and is connected between the circumferential segments and the drive rod so that axial movement of the drive rod along the length of the main shaft from the first condition to the second condition effects a rotation of the swing arm about the main shaft from a first position thereabout at which the drum is in its radially-collapsed condition to a second position at which the drum is in its radially and fully-expanded condition, the improvement comprising:

• a mechanical assembly for acting between the swing arm and the main shaft so that upon rotation of the swing arm about the main shaft to its second position thereabout, the mechanical assembly biases the swing arm about the main shaft in a rotational direction with respect thereto which corresponds with the direction of rotation of the swing arm about the main shaft from its first position toward its second position to thereby continually urge the circumferential segments toward the fully-expanded positions, even after an axial force which has been applied to the drive rod for moving the drive rod axially along the length of the main shaft to the second position has been relieved.

In a tire-building drum having a hollow main shaft having an end which is mountable upon a support for supporting the drum in a cantilevered condition above a floor, a plurality of circumferential segments about which a tire carcass can be constructed and which are movable between collapsed positions at which the drum is in a radially-collapsed condition and fully-expanded positions at which the drum is in a radially and fully-expanded condition, a drive rod which is positioned within and is axially movable along the length of the main shaft between a first condition and a second condition and so that the drive rod is movable from the first condition to the second condition upon application of an axial force applied thereto, and a swing arm which surrounds the main shaft and is connected between the circumferential segments and the drive rod so that axial movement of the drive rod along the length of the main shaft from the first condition to the second condition effects a rotation of the swing arm about the main shaft between a first angular position thereabout at which the drum is in its radially-collapsed condition and a second angular position at which the drum is in its radially and fully-expanded condition, the improvement characterized in that:

• the main shaft has an outer surface, and the drum includes means defining a detent adjacent the outer surface, and
• the drum includes a mechanical assembly connected to the swing arm for acting between the detent of the detent-defining means and the swing arm so that upon rotation of the swing arm relative to the main shaft to the second angular position thereabout, the mechanical assembly cooperates with the detent as a cam and cam follower to bias the swing arm from its first angular position toward its second angular position to thereby continually urge the circumferential segments to the fully-expanded positions, even after the axial force which has been applied to the drive rod axially along the length of the main shaft for moving the swing arm to the second angular position has been relieved.