Print delay based on media type

A laser printer (10) having a fuser (220) to fix toner on sheets (214) in which the fuser element (225) heated by the power supply (121) of the printer is not capable of drawing enough power from the power supply to cause flicker. Thick or heavy media require more heat energy than paper. At cold-fuser start, the use of thick or heavy media is identified to the control system (14) and the control system adds a predetermined period to the normal delay to start printing. This invention may be implemented by a small addition to control software.

TECHNICAL FIELD

This invention relates to printers and other imaging devices that must be warmed prior to initiating imaging. More specifically, this invention relates to providing for adequate warming for heavy or thick media while not burdening the time to print for common media such as paper. This permits the heater size to be reduced to avoid flicker.

BACKGROUND OF THE INVENTION

Applying high power to an internal heater or heaters of the printer can warm fusers and other elements of printer fairly rapidly. However, such application of power in an ordinary business or office setting may divert power from related systems and cause flicker of lights powered by such systems. Flicker is undesirable as it is distracting and the drain of power evidenced by flicker may interfere with the operation of other apparatus. At least one state in Europe has requirements directed to flicker.

Flicker can be avoided with special apparatus or systems such as coils installed as chokes and surge control circuits. These add expense to the printer and limit initial power to the heater. This invention requires only a control system, which may be only software used with pre-existing elements. This invention delays printing for heavy or thick media, while the use of chokes or surge control delays power to the heater. Delay of power to the heater inherently delays printing since printing is not initiated until the appropriate temperature is reached.

The adding of delays for a printer to reach certain temperatures before launching a sheet to be printed is prior and established in the printer art. This is done in known embodiments by storing a table of the time period to delay or a table of the offset from an operating temperature value normally sensed for. These delays are specific to heavy or thick media in contrast to normal media. The prior art, however, is not known to add to such delays at cold start nor to combine the added delay with a lower power supply to avoid flicker.

DISCLOSURE OF THE INVENTION

In accordance with this invention, a heater in the printer or other imaging device is employed which is of medium power output such that it is not capable of causing flicker when connected to a normal office power source. At turn-on of the printer from a start at which the fuser is not being heated (termed here a cold-fuser start), the control system imposes a delay before initiating printing. The primary purpose for heating of the printer often is to prepare the fuser of a laser printer for operation. As is conventional, a sensor monitors the temperature of the fuser. The delay imposed may be a direct result of monitoring the temperature sensed and launching the media sheet when the fuser reaches a predetermined temperature which assures adequate heat when the sheet reaches the fuser. Alternatively, the delay may be for a predetermined period of time after fuser heating is initiated.

Where heavy or thick media is identified to the control system, in accordance with this invention, at turn-on from a cold-fuser start, the control system imposes a longer delay. Where the temperature sensor is employed to define the delay, the control system launches a sheet at a higher sensed temperature. A typical delay for normal media when this invention is implemented is 30 seconds. Actual line voltages and other factors influencing temperature can vary this. For heavy or thick media, this invention adds 10 to 15 seconds, making the overall delay about 40 to 45 seconds. Delays for heavy or thick media when the device is in operation are much shorter.

By adding this delay, the required heater wattage is reduced to support cold-fuser starts without significant added delay for paper and the like and to support continuous operation once the fuser is warmed for all media. The lower wattage design can avoid flicker.

Identification of the media to be printed as heavy or thick may be defined by code in a communicated print job, but often it will necessarily be defined by the printer operator making an entry in the control panel. Typically, a control panel has several keys that can be used in sequences or combinations or both to define unique entries. Often, use of pre-existing keys can be defined to specify heavy or thick media, since not all entry alternatives have been used.

DESCRIPTION OF THE EMBODIMENTS

Printing System

Referring now to the drawings,FIG. 1shows hardware block diagram of a laser printer generally designated by the reference numeral10. Laser printer10will preferably contain certain relatively standard components, such as DC power supply12which may have multiple outputs of different voltage levels, a microprocessor14having address lines, data lines and control and/or interrupt lines, Read Only Memory (ROM)16, and Random Access Memory (RAM), which is divided into several portions for performing several different functions.

Power supply12receives electrical current by electrical cord plugged into an outlet, such as a standard wall outlet. It is the electrical system supporting the outlet, which is significantly reduced in power when flicker or the like results. The typical source of power to such outlets is limited in capacity, which allows flicker to occur.

Laser printer10will typically contain at least one serial input, parallel input or USB port, or in many cases two types of input ports, as designated by the reference numeral18for the serial port and the reference numeral20for the parallel port. Each of these ports18and20would be connected to a corresponding input buffer, generally designated by the reference numeral22onFIG. 1. USB port18would typically be connected to a USB output port of a personal computer or a workstation that would contain a software program such as a word processor or a graphics package or computer aided drawing package. Similarly, parallel port20could also be connected to a parallel output port of the same type of personal computer or workstation containing the same type of programs, only the data cable would have several parallel lines. Such input devices are designated, respectively, by the reference numerals24and26onFIG. 1.

Once the text or graphical data has been received by input buffer22, it is commonly communicated to one or more interpreters designated by the reference numeral28. A common interpreter is PostScript™, which is an industry standard used by most laser printers. After being interpreted, the input data is typically sent to a common graphic engine to be rasterized, which typically occurs in a portion of RAM designated by the reference numeral30onFIG. 1. Such font pools and caches supply bitmap patterns for common alphanumeric characters so that the common graphics engine30can easily translate each such character into a bitmap using a minimal elapsed time.

Once the data has been rasterized, it is directed into a queue manager or page buffer, which is a portion of RAM, designated by reference numeral34. In a typical laser printer, an entire page of rasterized data is stored in the queue manager during the time interval that it takes to physically print the hard copy for that page. The data within the queue manager34is communicated in real time to a print engine designated by the reference numeral36. Print engine36includes the laser light source within the printhead, and its output results in physical inking on a piece of paper or other media, which is the final print output from laser printer10.

It will be understood that the address, data and control lines are typically grouped in buses, and which are physically communicated in parallel (sometime also multiplexed) electrically conductive pathways around the various electronic components within laser printer10. For example, the address and data buses are typically sent to ROM and RAM integrated circuits, and the control lines or interrupt lines are typically directed to all input or output integrated circuits that act as buffers.

Print engine36contains an ASIC (Application Specific Integrated Circuit)40, which acts as a controller and data manipulating device for the various hardware components within the print engine. The bitmap print data arriving from queue manager34is received by ASIC40, and at the proper moment is sent via signal lines46to the laser, which is designated by the reference numeral48.

ASIC40controls the various motor drives within the print engine36, and also receives status signals from the various hardware components of the print engine. A motor42is used to drive the faceted mirror (see the polygonal mirror116onFIG. 2), and when motor42ramps up to a rotational speed (i.e., its “lock” speed) that is dictated or measured by the frequency of the reference signal (“REF CLK”) at a signal line43, a “Lock” signal will be enabled on a signal line44that is transmitted to ASIC40.

The lock signal may be dictated or controlled by various alternatives. Where the lock speed is to be different for different applications by the same printer10, reference frequencies are supplied to track motor42that supports different lock speeds at different reference frequencies. Where only a single lock speed is to be employed by motor42, the HSYNC signal (discussed below) may be supplied to motor42with a predetermined comparison to motor speed defining lock.

During conventional operation, once ASIC40receives the lock signal from motor42, it transmits a corresponding lock signal (as part of a byte of a digital signal) along one of the data lines64of the data bus62that communicates with ASIC40. Data bus62is either the same as the data bus60that communicates with microprocessor70, or a portion thereof. When this lock status signal is received by microprocessor70, microprocessor70initiates action of printer1leading to printing by printer1in normal course.

FIG. 2provides a perspective partially cut-away view of some of the major components of a printhead100of laser printer10. Starting at the laser light source110, the light travels through a lens112along a pathway130and is redirected by a “pre-scan” mirror114. The redirected light path, designated by a reference numeral132, puts a spot of light on an eight-sided polygonal mirror116. Some of the other major optical components within laser printer10include a lens118, a “post-scan” fold mirror120, a “start of scan” mirror122, an optical sensor mounted to an HSYNC sensor card124, and another lens126that directs the light into a “writing line” designated by the reference numeral140.

A portion of the swept light that creates each raster scan is aimed by the polygonal mirror116, lens118, fold mirror120, and a “start of scan” mirror122to create a light signal that follows the path designated by the reference numeral138. Light that ultimately travels along path138will be directed to impact an optical sensor on the HSYNC sensor card124and the optical sensor is equivalent to the HSYNC sensor52, seen onFIG. 1. InFIG. 2since there are eight (8) facets or sides to polygonal mirror116, each one-eighth rotation of mirror116will create an entire swept raster scan of laser light that ultimately becomes the writing line140. For a small instant at the start of each of these scans, there will be a light beam that travels along path138to impact the HSYNC sensor52on the HSYNC sensor card124. This HSYNC signal will be created during each scan at all times during normal operation of laser printer110when the printhead is running, even during scans in which there are no pels to be printed on the photoconductive drum. Laser source110is controlled such that it will produce no light at all for raster lines that are to be left blank on the final printed page, except for a brief moment at the end of each scan, so that the HSYNC signal will be produced at the beginning of each successive scan.

Major elements of the printer as a whole are illustrated inFIG. 3. Printer10includes a media feed path212for feeding sheets or media214, such as paper, from a media tray216past a photoconductive drum218and a fuser assembly220to an input tray222. Fuser220is nip roller fuser, as is conventional, formed by a heated roller224, which is heated to a high enough temperature to fix particles of electrophotographic toner to the sheets media214by melt flow. Roller226is a backup roller to apply some pressure during the fixing. Heating lamp225is inside roller224and powered by current from power supply12. As is not generally conventional, lamp225in operation does not draw sufficient power from power supply12to cause flicker or the like. Accordingly, fuser220is somewhat slower than are some fusers in reaching operating temperatures. Fuser temperature is sensed by a conventional sensor227in contact with or near heated roller224.

Special media, such as envelopes and index cards, are fed into the media feed path212from an external, front tray228, sometimes referred to as a multi-purpose tray. Special media may also be fed from a separate, external tray (not shown). The photoconductive drum218forms an integral part of a replaceable toner cartridge230inserted in to printer10. A print head100is disposed in the printer10for scanning the photoconductive drum218with a laser beam234so that it ultimately sweeps or “scans” across a “writing line” on the photoconductive drum218as described in the foregoing, thereby creating, in a black and white laser printer, a raster line of either black or white print elements, also known as “pels”. Pivoted roller232feeds sheets from tray216. Other nip rollers shown inFIG. 1are sheet feed rollers to feed paper or other media.

Cold Start Control

This invention is operative in the foregoing embodiment when printer10is turned on from a cold start, which encompasses when the printer is on but the fuser is unheated (often termed “power saver” mode). If printer10is maintained partially warmed, often termed “standby” mode, mirror116is not driven, and another essential delay may be for mirror116to reach “lock” as discussed in the foregoing.

The dominant delay from a cold-fuser start is for fuser220to reach operating temperature. Additionally, where the media is thick or heavy, such as transparencies and many labels, the fuser220must be warmed to more than a lower temperature suitable for paper and the like. It is conventional for the control system, implemented in the embodiment by microprocessor14, to track the fuser temperature and to launch a media sheet so that the sheet arrives at the fuser nip at the same time or soon after the fuser220reaches this desired temperature. The resulting delay typically is about 30 seconds.

In accordance with this invention, when the media to be printed at cold start is identified as heavy or thick, by executing software stored in ROM16the control system implemented by microprocessor adds an additional delay before launching the sheet—with a total delay of 40 to 45 seconds being representative. Accordingly, the launching of the media214from tray216or media from an alternative source is delayed those predetermined amounts regardless of other factors. The additional delay may be by launching media214only when temperature sensed at fuser220is higher than that at which media214is normally launched. Alternatively, the delay may be imposed as a predetermined time period between start of warming and launch of media214. Individual values or tables of values depending on the need for this purpose are stored in ROM16or built into ASIC40. A table of values would be used if different delays are to be imposed on, for example, each of transparencies, card stock and labels. A table might be used for different delays at different print speeds.

In specific situations an even longer delay may be imposed, for example, when mirror116has not reached “lock”.

OPERATOR INPUT

FIG. 4shows a representative control panel300on printer10. It is on the outside, front of printer10and readily accessible to a human operator. In this particular embodiment, the control panel has a variable display302, the information displayed being provided under the control of microprocessor14. With such a display, it is possible to have a list of alternatives for input displayed one at a time on display302, each being presented in a predetermined order by the pressing of a control button304, often termed a “menu” button. To enter control information for thick or heavy paper, the operator presses menu button304until the corresponding term is displayed. In this illustration the term “LABEL” is used as readily recognized and remembered by the operator. When that term appears, the select button306is depressed by the operator, and microprocessor14responds to this information stored in memory32by delaying start as described in the foregoing. The other buttons shown are for various other operator-control entries to printer10.

Entry of the thick-or-heavy media information may be by any available alternative. The print job received by printer10on its ports18and20may have information code (often termed “header” code) that identifies the media. The print job may call for feeding from a tray reserved or unique to heavy or thick media, and therefore may be known to the control system as necessarily being heavy or thick.

This invention combines a heating system not capable of causing flicker or other significant drain of power with a delay at cold start to achieve reliable operation. As it can be implemented by only changing the control code of a microprocessor, tangible costs to practice this invention are generally insignificant. Exact time periods and characteristics of the heating system are a matter of ordinary design, depending upon the details of the printer.