Printer and method for saving power

Abstract: A system using a printer with a fuser-heater has control means for turning off the fuser-heater during times when no printing is required, while leaving the rest of the printing system operable. Time between print requests is monitored, and the fuser-heater is turned off when a preset time is reached without a print request. A next request turns the fuser-heater back on again. Data is accepted at a reduced rate while a heater warms up.

Description: Field of the Invention This invention is in the field of apparatus and methods for controlling a nonimpact laser printer or laser-type printer, and has particular application as a power saving device. Background of the Invention As printing technology becomes more sophisticated and printers more capable of producing text and graphics with quality that is acceptable for almost any intended application, printers are becoming more available to all computer users. The most popular printer for its ease of use and quiet, dependable operation is the laser-type electrostatic printer, which produces a superior print quality and is faster and quieter than printer types that predate it, such as the dot matrix, daisy wheel, thermal, and ink-jet. For purposes of this specification printers that write on a drum by LED or LCD instead of a laser, and use a fuser-heater to fuse toner to the paper, are included as laser-type printers. The laser-type printer uses a mechanism similar to that of a photocopy machine. The image is written on a photosensitive drum by a laser in the case of a laser printer. In other printers the image is written by an LED bar or an LCD shutter. Toner is attracted to the areas on the drum that have been written. The toner is then heated by the fuser-heater to fuse it to the paper to produce the printout. Because laser-type printers print an entire page at a time and the drum may be scanned quickly, they are much faster than most other printer types. Typically such a printer has an electronic buffer that can store a page or several pages of data depending on the amount of memory it has available for use. In a network comprising several computers and printers, printer buffers are inclined to be rather large and a network server, if present, usually means that a more than adequate amount of memory is available. A print request sent by a computer is received by the printer buffer and scheduled for printing, which typically commences when the buffer contains a full page and a "not busy" message is received from the printer. The process of printing is one of processing pages sent by the computer to the printer that are held in the printer's buffer. If the amount of material being sent to the printer is greater than the size of the buffer, the host computer is forced to hold until the buffer is cleared and can again accept print input, and so on until all pages are printed. In a typical working environment, the printers are left on all the time as a convenience to users and are consequently consuming power in order to keep the fuser-heater at the proper operating temperature and the printer ready to print in response to instructions from a connected computer, i.e. a print request. The fuser-heater is the principal consumer of power in a laser-type printer and typically a fan for dissipating heat from the fuser-heater is the main source of noise. If a printer is allowed to run continually and no printing instructions are received, the fuser-heater will be kept at a certain set temperature, the fan will continue to operate to cool the rest of the printer, and the printer will be in a ready state. If the printer is turned off when not being used, it will require a certain amount of time to bring the fuser-heater up to a proper temperature and begin carrying out instructions from the computer when it is turned on again in response to a print command. The amount of time required for a fuser-heater to reach operating temperature is dependent on several factors that are unique to each printer. The wait that is necessarily involved is awkward and costly in a multi-user environment. With several computers and one or more printers running in an enclosed area, there may be a heat build-up that must be eliminated through climate control equipment to maintain a successful operation. If the principle heat-producing element in a laser-type printer, the fuser-heater, could be turned off for times of non-use, this problem would be considerably reduced. What is clearly needed is an automatic management system for shutting down a printer fuser-heater during periods of inactivity without disrupting operations, and that is compatible with existing systems. One such system is, for example, disclosed in PATENT ABSTRACTS OF JAPAN, vol.16. no.301 (P-1379) [5344], 3rd July 1992 & JP-A-0481914 (CANON, INC.), 16th March 1992. Brief Description of the Drawings Fig. 1 is a view of a laser-type printer as used with the present invention. Fig. 2 is a drawing of a laser-type printer operated according to the present invention on a network with several computers. Fig. 3 is a flow chart of the printing process according to the present invention. Summary of the Invention The invention provides a printer comprising a fuser heater; receiving circuitry for receiving data and print requests from a host computer; a data buffer coupled to the receiving circuitry for storing data to be printed; characterised by control circuitry having a timer for measuring periods of inactivity of the receiving circuitry and the control circuitry being configured for reducing power to the fuser-heater in response to a period of inactivity of the receiving circuitry and also for reducing the rate of data transfer to the buffer in response to the fuser heater being on but not at operating temperature. The control circuitry may receive power management instructions from a remote computer system. Power management may be accomplished by executing control routines that are installed and executed in the control circuitry in the printer. A computer system may comprise a printer according to the invention and a computer connected by a data link to the printer. The invention also provides a method as claimed in claim 12. The invention is useful in the event of a single printer operated by a single computer, or in network situations where several computers are connected to and sharing one or more printers. In one embodiment, the invention is implemented entirely integral to a printer with a fuser-heater. The invention allows printing requirements to be carried out with a minimum power usage, and without disrupting printing operations. Description of the Preferred Embodiments Fig. 1 is an isometric drawing of a laser-type printer 13 operable according to the present invention, and which contains a fuser-heater 15, a drum, a fan, a buffer (not shown) and a cable connection 23 that joins the printer to a host computer or a to a network. The fuser-heater is responsible for heating the toner applied to the drum after an image has been written to the dram has written a page to be printed, to fuse the toner to the paper. Instructions sent by a computer what is written, and the entire process is managed by control routines. The fan (if used) in the printer is powered on at start up and is usually controlled by a heat-sensing mechanism that reacts to internal temperature and runs in reaction to cool mechanical and electronic elements of the printer. The majority of printers have a memory buffer that electronically stores composed pages transmitted by the control routines and sends the data to the processing unit of the printer as the printer is ready to accept it. When the buffer has emptied its contents to the printer and all instructions from the computer have been carried out, the printer waits for further input and maintains all of its components in a state of readiness. Actual operation can vary from printer to printer according to the type and speed of the printer and the size of the printer buffer. It is not the intent of the present description to present a detailed description of laser-type printing, but rather to present an example of a relatively common printing function and demonstrate its functional components in the context of the present invention. The embodiment of the present invention as shown in Fig. 2 demonstrates laser-type printer 13 operating within a networked environment of other computers 25 and possibly other printers and with a network server computer 27. The present invention provides a means to keep the printer operating and prepared to print but to save power by turning off the fuser-heater portion of the laser-type printer. In response to a reduction in heat created by turning off the fuser-heater, the fan will shut down and run only infrequently, if at all, in response to ambient heat from other sources. The connection to a computer or computers is never broken. The turning off of the fuser-heater significantly lessens power consumption and heat dissipation requirements. Control routines that are a part of the invention can be installed on any computer that uses a printer that uses a fuser-heater or can be installed solely on network server, such as server 27 in Fig. 2, or may be installed preferably in the printer. The system of the invention comprises a means of turning off fuser-heater 15 (Fig. 1) in laser-type printer 13 after a set amount of time has passed without any input from the network server or from the connected computer or computers, and to turn it back on again when the connection is initialized (such as when a computer on the network is turned on) or a print request is sent from an attached network server or single computer. The printer stays on all the time, and only the fuser-heater element is turned off. When the fuser-heater is turned back on after being powered down, it requires a certain amount of time to reach the correct operating temperature. During this time, the printer buffer is fully active and still accepts input but does so more slowly than usual until the fuser-heater is at operating temperature. This slower data acceptance rate avoids software timeouts, such as might occur when printing from DOS. A user will seldom notice slower operation and will not be aware that an element in the printer has been turned off or conversely, turned back on again. The system performs this function automatically. In a preferred mode of operation the reduced data acceptance rate is set to be equal to or smaller than the buffer size divided by the warm-up time. In some embodiments the control routines can further be manipulated to manually turn the fuser-heater on or off at any time. Fig. 3 is a flow diagram illustrating the operation of the present invention to control laser-type printer functions and thereby save power and decrease noise. An INIT signal (point 26) is received from a host system when the system starts up, such as after an intentional downtime. INIT turns on fuser-heater 15 at point 31 as a consequence of turning on the printer itself. The INIT signal or similar signal is also received when a laser-type printer is turned on directly. After start-up, the system responds to print requests from the server 27 or any one of the computers 25 on the network (Fig. 2). The system receives a print request at point 24 and determines whether the fuser-heater is on, off, or in a warm-up mode (point 29). If the fuser-heater is on and at operating temperature when a print request is received, data is accepted by the buffer at maximum rate (37). The rate for a particular printer buffer is unique to each laser-type printer. The printer fuser-heater is managed by monitoring the time between print requests (41). This time is designated t WI , for time without input, and is measured by a timer in the control circuitry. The timer is reset to zero (43) each time a print request is received and the printer is determined to be initialized and at operating temperature. A trigger time, T TRIG , is set (39) for a maximum period between print requests, and the fuser-heater is shut off (45) when t WI = t TRIG . In some embodiments the trigger time may be set in the software and not accessible as a variable to a user. If, when a print request is received, the fuser-heater is in a warm-up mode (35), data from a print request is accepted at a slower rate than the maximum data transfer rate available. Data is accepted at the maximum rate after the fuser-heater is at operating temperature. If when a print request is received the fuser-heater is off, the control system turns it on (31), putting the fuser-heater in warm-up mode, and the printer buffer accepts data more slowly until the fuser-heater is at operating temperature. The amount of time it takes for the fuser-heater to warm up is dependent upon the particular printer, and can vary Additional contributing factors to the length of warm-up time include the difference between a printer being powered on after an intentional downtime, in which the length of time it takes to warm up is naturally greater, and the case when a print request has been handled only moments before, requiring only a short warm-up. In an alternative, and somewhat more sophisticated embodiment of the invention, there is more than one trigger time, and the fuser-heater is only partially shut down in some instances. For example, the control routines may be written and hardware included in a printer, so the fuser-heater, after a first period of 5 minutes, would be reduced to 2/3 power. If no print request is received after 30 minutes, the power would be reduced to 1/3, and if no request is received after 1 hour, the power would be shut off. This embodiment addresses the possible reasons for no print requests. The 5 minute trigger addresses the ongoing situation that assumes that the users have only periodic need for the printer, and allows for rapid warm up when a new request is received. The 30 minute trigger anticipates situations like lunch time and shift change, and still allows for a shorter warm up than a complete shut down. The one hour trigger anticipates everyone has gone home for the day or the weekend, and shuts off the power completely. In this embodiment, the times may be adjusted empirically to provide the minimum power usage for the demand pattern of a particular organization, and in other embodiments more or fewer trigger times might be useful. The invention is not limited to any particular computer, network server, or printer. Computers or printer with fuser-heaters of any manufacture can be used providing control routines are written in the languages that the computers and printers require. The present invention can also be used to control several printers that are connected together into a network, and still allow manual operation of any one of the printers. The invention is broadly applicable to any system using printers that have fuser-heaters. It is seen, then, that there are many alterations that may be made without departing from the scope of the appended claims.

Claims: A printer (13) comprising: a fuser heater (15); receiving circuitry for receiving data and print requests from a host computer; a data buffer coupled to the receiving circuitry for storing data to be printed; characterised by control circuitry having a timer for measuring periods of inactivity of the receiving circuitry and the control circuitry being configured for reducing power to the fuser-heater (15)in response to a period of inactivity of the receiving circuitry and also for reducing the rate of data transfer to the buffer in response to the fuser heater being on but not at operating temperature. A printer as claimed in claim 1 wherein the control circuitry is adapted to receive power management instructions from a remote computer system (25, 27). A printer as claimed in claim 1 wherein power management is accomplished by executing control routines that are installed and executed in the printer (13). A printer as claimed in any one preceding claim, and further comprising means for monitoring the status of the fuser heater (15), including power levels, and temperature A printer as claimed in any one preceding claim wherein the control circuitry is configured for reducing power to the fuser heater (15) to a partial power level in response to a first period of inactivity of the receiving circuitry, and for suspending power to the fuser heater (15) in response to a second period of inactivity of the receiving circuitry. A computer system comprising a printer as claimed in any one preceding claim and a computer (25, 27) connected by a data link (23) to the printer (13). A computer system as claimed in claim 6 and comprising: a) means for initialising the printer (13) by turning on the fuser heater (15) and readying the printer to accept print requests (41) and data; b) means for ascertaining when a print request (41) is received by the receiving circuitry whether the printer is initialised, if so, whether the power to the fuser heater (15) is suspended, and if not, whether the fuser heater is on but not at operating temperature, or on and at operating temperature; c) means for restoring full power to the fuser heater in response to a condition where a print request (41) and data is received by the receiving circuitry, the printer is initialised, and power to the fuser heater (15) is suspended; and d) means for limiting a data acceptance rate at the buffer to a rate less than a maximum rate in response to a condition where the printer is initialised, power to the fuser heater (15) is not suspended, and the fuser heater is on but not at operating temperature, and for accepting data at the buffer at the maximum rate in response to a condition where the printer is initialised, power to the fuser heater is not suspended, and the fuser heater is on and at an operating temperature. A system as claimed in claim 6 or 7 as appended to claim 1, 2, 4, 5 and 6 only, wherein power management control routines are installed and executed on the computer (25, 27) connected to the printer. A system as claimed in any one of claims 6 to 8 wherein the computer system comprises a local area network system wherein network stations (25) share the printer (13). A system as claimed in claim 9 as appended to claim 8 only, wherein power management control routines are installed and executed on a network server (27) computer connected in the local area network. A computer system as claimed in any one of claims 6 to 10 wherein the limited data acceptance rate is no greater than a size of the buffer divided by a warm up time from ambient to operating temperature of the fuser heater (15). A method for saving power in operation of a printer (13) having a fuser heater (15) and a data buffer storing data to be printed and a timer for measuring periods of inactivity in the data transfer, characterised by , monitoring data transfer to the buffer; reducing power to the fuser heater (15) in response to detection of a period of inactivity in the data transfer, and reducing the rate of data transfer to the buffer in response to the fuser heater (15) being on but not at operating temperature. A method for conserving power in operation of a printer as claimed in claim 12, further comprising monitoring fuser heater (15) status, including power levels and temperature.

Inventors: DORNIER PASCAL, DORNIER, PASCAL
Applicants: ELONEX TECHNOLOGIES INC, ELONEX I.P. HOLDINGS LIMITED
Application year: 1993
Main classification: G01D15
IPC codes: G03G15, G09G5, G06F1, G06K15