Abstract: An electrophotographic printer (11) including a fuser (16, 17) for fusing a toned image onto an envelope (13) passing through a fuser nip (14). Wrinkling and treeing of the envelope (13) is substantially eliminated by removing the pressure on the envelope (13) in the fuser nip (14) for one or more brief intervals during the fusing process. To do this, a solenoid (21) is intermittently driven to remove the force of a spring (18) urging the fuser rolls (16, 17) together.

Abstract: A low profile tactile keyswitch including a horizontally positioned elastic column spring which buckles under an axial load to provide a tactile feel for the keyswitch. The ends of the spring are maintained between two spring holders which are urged together as the keybutton is depressed. Stabilizing arms pivotally attached to the keybutton are used to stabilize the keybutton and also to carry extensions which engage the spring holders to move them together as the keybutton is depressed. The keyswitch is operable to be placed in an inactive configuration in which the keybutton is lowered without placing the spring under added compression.

Abstract: A memory management system for a page printer controller (11) which includes random access memory (17) allocated among bit map memory (30), page buffer memory (29), and user memory (28). The memory management system allocates the random access memory to provide either a large bit map memory or, responsive to needs of the controller (11) for increased memory for other uses, for allocating the random access memory (17) to provide a small bit map memory and place more memory in the page buffer memory (29) and user memory (28).

Abstract: A page printer (101) which rasterizes a page utilizing partial page bit map swaths. Received data to be printed is stored in packets (12-17) in a page buffer in random access memory (105). Data within each packet is arranged in printing order down the page to be printed, but the packets themselves are arranged in the order received, and are not indexed or linked. As each swath (11) is rasterized, each packet is examined, and packets containing data falling at least in part within the active swath are processed. The printer is controlled by a programmed microprocessor, and logic hardware assistance is provided for translating data addresses from logical addresses (54) to physical addresses (52). Logic hardware assistance is also provided for making the determination of whether or not a given data address lies within the active swath.

Abstract: An electrophotographic printer (11) having a base (13) and a top (12), the top (12) being pivotable about an axis (23) between a closed position and an open position. The printer (11) receives a supply cartridge (14) on a shelf (22) which is pivotable about the same axis (23) as the top (12) of the printer (11). A counterbalance spring (34) helps to support the shelf (22) and the cartridge (14) below the top (12) of the printer (11) and above the printer base (13) when the top (12) of the printer (11) is in its open position. When the top (12) of the printer (11) is closed, the cartridge (14) is urged into a position adjacent the printer base (13) and locked into an operative position.

Abstract: A timing circuit in which an output can be held at a certain level or state for a particular time after the circuit is enabled. The time is established by an external resistor and capacitor. The timing circuit is self-biasing to permit operation after associated power supplies have dropped to zero. The timing of the circuit is independent of supply voltage and substantially independent of temperature variations. The timing circuit includes a number of MOSFET's which are diode connected between two nodes, and another MOSFET having a gate and one conduction electrode connected across the two nodes. The voltage between the two nodes at the beginning of the timing interval is the sum of the threshold voltages of the diode connected MOSFET's. At the end of the timing interval, the voltage between the two nodes has fallen to the threshold voltage of the single MOSFET.

Abstract: A printer having a print engine (13) and a bit map memory (12) including a number of page image areas (31) into which information to be printed is rasterized and from which information for the print engine is serialized. A digital processor (11) controlling the print engine is operable to reduce a page image area (31) to a modified page image area (37) based upon the highest and lowest addresses at which information has been written into the page image area. The digital processor (11) is also operable to begin rasterization of a new page image area when a sufficient amount of an existing page image area (41) has been serialized to make available the requisite bit map memory for the new page.

Abstract: A printer control system which enables the using application program to automatically selectively alter printer default parameters, to automatically selectively delete previously downloaded fonts and macros, and to enable the printer to operate from one of several datastream formats. The system allows the printer to initialize default parameters for a succeeding job during the printing of a current job as long as the datastream format is unchanged, and allows the deletion of downloaded fonts as long as they are not needed for the current or future pages being printed for the current job.

Abstract: A computer system operating under software control to provide output to a printer for printing. The computer system sets printer parameters to accommodate different forms of output to the printer. A word processing program stored in the computer memory is executed to couple information for printing to the printer with the printer in a first set of printer states. A typewriter emulator program stored in the computer memory is executable to couple information for printing to the printer and to set the printer states. The word processing program is interrupted by a hot key depressed by an operator, and the typewriter emulator program is entered, with the printer states being set in dependence upon printer state information for the typewriter emulator. When the typewriter emulator is interrupted by a hot key, the then-current printer states are stored and a set of default printer states for the word processor are restored prior to returning to execution of the word processing software.

Abstract: A page printer including a print engine (15) and a controller (11) which includes a non-volatile memory (16) having an EEPROM (17) and a chip RAM (18). A microprocessor (12) under program control manages the placement of data in the EEPROM (17) of the non-volatile memory (16). The EEPROM (17) and the associated chip RAM (18) are structured to have a control block (31) and a data storage portion (32-39). The control block (31) includes pointers (41-47) indicating the locations in the non-volatile memory where data is stored. If a data location becomes faulty, the value of the pointer to that location is changed so that the pointer points to a previously unused portion of the non-volatile memory.

Abstract: A printer receives and stores coded text character data (22, 23) and also receives graphic image commands in the same datastream. The printer creates a raster image (24) of the graphic image commands and stores the resultant raster image. When rasterizing a page (21), the printer rasterizes the text character data utilizing stored raster fonts and rasterizes the graphic image data from the stored raster image.

Abstract: A continuous form and cutform feeding unit for a printer. The feeding unit permits feeding a continuous form and cutforms utilizing a cutform feeding arrangement and a continuous form tractor feed. In order to permit either type of form to be fed to a main body of a printer, through a single form feeding passage, a cutform feeding passage and a continuous form feeding passage are provided upstream of the single form feeding passage. In the continuous form feeding passage, a continuous form cutting apparatus is operable to cut a continuous form in response to a signal such as for the beginning of the feeding of cutforms.

Abstract: A matrix keyboard system for producing key codes in response to the actuation of key switches. The keyboard system includes ghost key condition detection. In the keyboard system, a group of parallel drive lines and a group of orthogonal parallel sense lines form a matrix, with a key switch being associated with each of the intersection points on the matrix. The drive lines are sequentially activated, and the actuation of a key switch along an activated drive line results in the coupling of a drive signal to the associated sense line. A ghost key condition arises when three of the four corners of a notional rectangle in the matrix contain an actuated key switch. The ghost key condition detector senses the presence of drive signals not only on the sense lines but also on the drive lines, with a ghost key condition being identified if a drive signal is sensed on two or more sense lines and two or more drive lines simultaneously.