Ing C. Olivetti C., S.p.a.

Marcello Boella

Paolo Rivera

Mario Figini

Ugo Carena

Ferruccio Mariotti

A print unit for an electronic typewriter comprising a removable character-carrying disc with flexible spokes which is operated by a selector motor which in turn is controlled by a control circuit. The character-carrying disc is provided with a plurality of reflective identification plates and a recognition circuit detects the pattern of the reflective plates present in selected ones of a series of predetermined angular sectors of the disc to identify some characteristics of the disc, e.g. typing pitch and character set. The angular position of the disc is detected by a position transducer which generates a position signal for the control circuit having a period which is double the angular distance between two contiguous character-carrying spokes discriminating the spokes at even positions from those at odd positions. In an initialization phase, a zeroing circuit coarsely positions the character-carrying disc in a zero area defined by a synchronization plate adjacent a plate-free gap and activates the control circuit to stop the character-carrying disc in a zero position in respect of a spoke having a predetermined parity. The print unit is provided with phase regulation elements for the position transducer and for the circuit for recognition of the reflective plates on the character-carrying disc.

Rotary character-carrying member and selector device therefor for a

An optical transducer for detecting the position of a rotary or translatory member comprises a light source, a photodetector group, and a shutter provided with a series of transparent elements spaced by opaque regions and interposed between the light source and the photodetector group. The photodetector group comprises an integrated circuit, on a surface of which is disposed a plurality of photovoltaic cells, each having an area which is a fraction of the area of each transparent element. The cells are divided into four groups to generate as many electrical signals which are out of phase relative to each other by 90.degree. and which are indicative of the position of the shutter with respect to the position of the photodetector group and the light source. The cells are disposed symmetrically with respect to a central radially extending optical axis, and in such a way that the barycenter of the areas of each of the four groups is included in the central optical axis. The sum of the four electrical signals is also used as feedback for controlling the power supply for the light source.

Optical position transducer having a plurality of photodetector cells of

A device for controlling the rotary movement of a platen roller of a typewriter comprises a bidirectional electric motor coupled to the platen by a worm gear and gear wheel and a pair of knobs which are disposed at the sides of the platen and which are rotatable with respect thereto. The knobs are fixed to a bar which extends rotatably through the platen roller and carries the gear wheel. Selective bidirectional rotation of the knobs causes corresponding rotary movement of a disc in a transducer. The disc has a toothed sector in mesh with the gear wheel and is the moving part of a rotary switch which generates electrical signals which determine both the power supply to the electric motor and the direction of rotation thereof. Small degrees of rotary movement of the knobs against a first spring force establish continuous rotary movement of the platen roller at low speed. A further slight rotary movement of the knobs against a stronger spring force establishes rotary movement of the platen at high speed.

Device for controlling the rotary movement of a platen

A direct-current electric motor (29) used for, for example, positioning a printing device in an office machine, is controlled by an arrangement comprising a microprocessor (40) which causes the motor digitally to perform accelerations and/or decelerations to maintain it close to a desired speed programmed in relation to the distance to be completed. Control between the actual speed of the motor and the desired speed is effected utilizing the timing signals (FTA, STB) generated by a transducer (35) connected to the motor. During a first phase, the microprocessor compares the times taken to complete a series of angular steps of rotation, the steps following a schedule of decreasing size with stored reference times and effects accelerations and decelerations of durations proportional to any discrepancies. Once the motor is near enough to its target position to be on a monotonic segment of one of the timing signals (FTA) which is sinusoidal, control switches to a position feedback loop bringing the motor to a standstill with FTA zero.

Arrangement for controlling the speed and positioning of an electric

An optical transducer for detecting the angular position of a rotary member with respect to a fixed structure comprises a disc 13 mounted rotatably within a casing. The disc is provided with a plurality of opaque radial regions 19 which are spaced by transparent regions 18 which transmit the light emitted by a light source mounted on the casing. The light is received by a photodetector element 25 comprising a support plate 28 on which is disposed a multiplicity of photovoltaic cells 26 each having an area which is fraction of the area of each transparent region of the disc. The cells are subdivided into the groups A, B and C with different functions and phase positions and are distributed diffusely over the area encountered by the beam of light from the light source. The cells of each group are connected together in parallel to generate three electrical signals, one of which provides pilot control for the feed to the light source to stabilize the signals of the other two groups of photoelectric cells.

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Loranze, Italy

Marcello Boella