Mounting means for movable carriage on an offset press

An offset printing press comprising:

• a mainframe including paper handling means, the paper handling means defining a paper handling path extending between a paper feed input and a paper delivery output;
• a printer head mounted on and fixed to the mainframe and engageable with the paper handling path at a location generally intermediate the paper feed input and the paper delivery output, the printer head including a single blanket cylinder and a pair of plate cylinders, the plate cylinders being simultaneously engageable with the blanket cylinder, the plate cylinders and blanket cylinder being adjacent to each other and rotatably mounted on the printer head along generally parallel axes, the blanket cylinder being adapted to simultaneously transfer images from the plate cylinders to paper provided by the paper handling means;
• a movable carriage mounted on the mainframe and located generally adjacent to the printer head, the carriage being substantially linearly movable along a generally straight line to and from the printer head, the carriage having a rectangular base including four linear motion ball bushings and located at a respective one of the four corners of the rectangular base, the mainframe including a pair of parallel rails upon which the ball bushings ride, the ball bushings engaging the rails to substantially eliminate carriage movement in directions generally perpendicular to the straight line along which the carriage moves, the carriage being positively lockable at predetermined positions along the generally straight line of linear movement;
• a first set of dampening and inking rollers rotatably mounted on and fixed to the printer head and engageable with one of the plate cylinders;
• and
• a second set of dampening and inking rollers rotatably mounted on and fixed to the carriage and engageable with the other of the plate cylinders when the carriage is moved toward the printer head to an engagement position.