Clamping mechanism for use on a rotatable plotter drum

A system for plotting on a medium, the system comprising:

• a rotatable drum having a circumferential surface and an end disk having a receptacle;
• clamping means for holding the medium to the drum surface, the clamping means having an open mode, in which the medium may be mounted on the drum, and a clamped mode, in which the medium is clamped to the drum surface;
• and
• activation means, mounted adjacent the end disk, for urging the clamping means into its open mode, the activation means having an extendable member, disposed so that, when the member is extended and engaged by the receptacle, the drum is locked in position.

A clamping system comprising:

• a mounting member having a mounting surface and a passage, the mounting surface having a groove;
• a slidable member extending through the passage, the slidable member including, at one end, a finger, which is disposed adjacent the mounting surface so as to permit clamping between the finger and the surface;
• means for urging the slidable member so as to force the finger towards the drum surface;
• actuation means, for, in a first mode, forcing the slidable member so as to move the finger away from the mounting surface and, in a second mode, permitting the finger to be urged against the mounting surface by the urging means;
• and
• means for causing the slidable member to turn so that, every other time the actuation means goes into its second mode, the finger does not go into the groove, and the remaining times the actuation means goes into its second mode, the finger is urged into the groove, the turning means including
• cylindrical cam means, located in the passage around the slidable member, for providing shaped notches, and
• pin means, located in the passage adjacent the slidable member, for engaging the notches as the actuation means switches between modes,
• wherein the notches are shaped so that, as the pin means engages the notches, the slidable member is turned.