Abstract: Hopper plug (143) vents out air pressure build-up which cause toner leaks. One side of the plug has a series of entrance openings (491) which communicate with the inside of the hopper (61). Air, potentially containing some toner particles, passes through those openings and enters a first chamber (507). The first chamber has exit holes (499) which do not face the entrance openings. Air passing through the exit holes of the first chamber enters a second chamber (509). The second chamber has exit holes (495) which are at the opposite end and do not face the entrance openings. Third chamber (511) of this labyrinth faces a mat toner filter (501) which leads to exit holes (503).

Abstract: A toner cartridge (1) contains a photoconductive drum (43) having a central shaft (47). The shaft extends outward from the sides of the cartridge so that it can be lowered on a V-shaped locator (301) in the printer. An assembly of a hopper (61), toner adder roller (45) and developer roller (43) is attached to an assembly carrying the photoconductive drum through springs (132a, 132b). The hopper assembly has center locating surfaces (29a, 29b) to receive a downward pressing member from the printer and flat ledges (161a, 133a) to contact rollers in the printer, which permits adjustment of the contact between the drum and the developer roller while positively locating the drum. The cover assembly also has flat locating surfaces (449, 451) near the hopper to rest on the printer frame.

Abstract: The door (3) of a laser printer (1) is pivoted to the frame (1c) of the printer by a pin (21) of hinge (19). When the door is shut, link (33) is rotatably connected to the hinge at a location above the pin. Link 33 has an elongated slot (33a) at its end opposite the hinge in which a pin (51) does not encounter the edge of the slot when the door is closed. Spring (31) therefore rotates U shaped link 11 around its pivot point (15) to the frame to bring charge roller (9) into contact with photoconductor drum (5). When the door is manually opened, spring 31 provides an upward force, link 33 is moved forward where the slot engages pin 51, which pivots both link 13 and door 3 upward. Force of the charge roller against the drum is by the spring as the only active element, thereby providing a controlled force.

Abstract: A dot matrix printhead is adjusted automatically or manually with respect to a platen in accordance with the thickness of a recording medium on which printing is to occur. When a host data processor sends a control signal to a printer microprocessor to indicate that a recording medium of a different thickness is to be printed, a carrier, which has a first portion supporting the printhead and pivotally and slidably mounted on a front guide rail, is moved so that a shift arm on the carrier engages a right side plate of the frame. This disconnects a ribbon drive motor gear from a ribbon drive gear and moves the ribbon drive motor gear into engagement with a gear train. Rotation of the gear train rotates a gear, which has a threaded shaft and is rotatably supported by a second portion of the carrier slidably mounted on a rear guide rail, to cause pivoting of the first portion of the carrier about the front guide rail to change the gap of the printhead from the platen.