Abstract: The apparatus makes it possible to restore operation of the nozzles of a print head by removing blockages and eliminating any bubbles of air or gases which may have formed in the ink jet printing elements of a dot printer. In the ink jet printing elements of the self-cancelling type in which the parasitic oscillations in the pressure of the ink are damped by the control circuit itself, blockages and air bubbles are eliminated by means of the control circuit which is caused to operate at a higher frequency than that used for the printing operation, under control of a microprocessor electronic selector switch and frequency generator. This is effected simultaneously with the application of a suction effect on the ink in the nozzles. The suction effect is produced by means of a suction pump connected to a resilient cup fitted in front of the nozzles in a parking position of the head beyond the platen.

Abstract: Each print element is connected to the head by means of a resilient blade pivoted on the head and is movable in two directions, respectively parallel and perpendicular to the direction of movement of the head, to vary the relative position of the nozzles. The nozzles of the print elements are disposed along a straight line which is inclined with respect to the direction of movement of the head. The head can be rotated to vary the inclination of the nozzles, thereby to provide different print definitions. A parking station is further provided for the head to clean and keep the nozzles in contact with an atmosphere saturated with a solvent for the ink, to prevent the ink from drying out in the nozzles.

Abstract: An optical transducer for detecting the angular position of a rotating member with respect to a fixed structure comprises a shell formed by two half shell portions which are assembled together by positioning projections which are provided integrally on one of the two half shell portions and which can be precisely connected to corresponding openings provided in the other of the two half shell portions. Arranged within the shell, with play, are a disc which is provided with radial openings, a hub having a plate portion for fixing the disc, a single light emitting means and a plurality of photovoltaic cells for detecting the passage of light through the openings in the disc. Two fixed masks provided with openings are interposed, one between the light emitting means and the disc and the other between the disc and the photovoltaic detection cells.

Abstract: An angular position transducer for a rotating member comprising a notched disc connected to said member, an opto-electronic pair for sensing the angular position of said disc and a supporting shell for said pair which is fixable on the support of the rotating member coaxially to said member. The disc is fixable directly to the rotating member at a predetermined position with respect to the shell, and comprises a thin flexible lamina guided on its periphery by a guiding element adjacent to the notches. The flexibility of the lamina compensates for any disalignment and axial displacement of the rotating member. The position signal is periodic and is sent to the terminals of a reference resistor. A control circuit modifies the value of the resistor in order to stabilize the peak value of the position signal within predetermined narrow tolerance limits.

Abstract: An angular position transducer for a rotating member comprising a notched disc connected to said member, an opto-electronic pair for sensing the angular position of said disc and a supporting shell for said pair which is fixable on the support of the rotating member coaxially to said member. The disc is fixable directly to the rotating member at a predetermined position with respect to the shell, and comprises a thin flexible lamina guided on its periphery by a guiding element adjacent to the notches. The flexibility of the lamina compensates for any disalignment and axial displacement of the rotating member. The position signal is periodic and is sent to the terminals of a reference resistor. A control circuit modifies the value of the resistor in order to stabilize the peak value of the position signal within predetermined narrow tolerance limits.