Carriage guide mechanism for use in scanning device

A carriage guide arrangement for use in a device for scanning a surface of a recording medium supported by a cylindrical drum, said arrangement comprising:

• a carriage capable of bidirectional linear movement along a path having at least a portion thereof parallel to said surface;
• an image transducing head mounted on said carriage;
• an enlongated first guide member extending in the direction of linear movement of said carriage,
• said carriage being bidirectionally rotatably and translatably mounted on said first guide member;
• a second guide member in juxtaposition with said first guide member for defining a first rotational position of said carriage in the region adjacent said record medium surface and a second rotational position of said carriage in the region beyond the ends of said drum;
• means for biasing said carriage toward said second guide member so that said carriage rotates between said first and second rotational positions as said carriage traverses the ends of said drum;
• and
• a carriage bearing member mounted on said carriage for engaging said second guide member to keep said transducing head at a desired distance from said record medium surface, corresponding to said first rotational position, between the ends of said drum, and for keeping said transducing head at said second rotational position beyond the ends of said drum.