Abstract: A printer has dual opposing printheads which can print in tandem on two sides of paper fed along a printing plane. The dual opposing printheads can print the same information on each side of two paper sheets fed in back-to-back (two-ply) fashion, thereby providing a document and copy simultaneously. The printer can also print different information on two sides of the same paper sheet or on each side of two paper sheets, thereby doubling the printing speed as compared to a single printhead. In a preferred embodiment, the dual opposing printheads are mounted in carriages driven reciprocatingly in tandem by one drive belt. Tandem paper feed mechanisms are arranged at one side of the printer and have respective clutch spring devices which are actuated alternately by cam surfaces on the printhead carriages so as to drive a pair of paper feed rollers with the paper fed in between them.

Abstract: A disposable safety needle and syringe assembly includes a needle shield movably positioned within a syringe housing. Movement of the needle shield from the housing is effected by movement of the syringe plunger and plunger piston following completion of an injection whereby the needle shield envelopes the needle extending from the housing to prevent accidental needle sticks. The plunger piston is disengagable from the plunger at a limit of travel upon retraction of the plunger, thus maintaining the shield in a locked position enveloping the needle. The syringe and needle assembly can then be safely handled for disposal, and the possibility of inadvertent reuse of the needle is eliminated.

Abstract: A locking device is capable of being retrofitted by insertion into a standard plastic syringe. The syringe is of the type having a cylindrical inner wall made of plastic material, a closed, distal end, and an open, proximal end for movement of a plunger therein. The plunger has a plunger stem made of plastic material with longitudinal ribs in an "X" shaped cross-section. The locking device has a clip-type body portion formed with a U-shaped channel for clipping onto one longitudinal rib, a first set of barbed points angled toward the plunger stem for engaging the plunger stem when it is depressed toward the distal end after a first retraction movement toward the proximal end of the syringe, and a second set of barbed points angled toward the inner wall of the syringe for engaging the inner wall in order to lock the plunger stem from a second retraction movement, thereby preventing reuse of the syringe.