Electrophotography – Internal machine environment – Temperature
Reexamination Certificate
2001-07-17
2002-09-03
Grimley, Arthur T. (Department: 2852)
Electrophotography
Internal machine environment
Temperature
C399S092000
Reexamination Certificate
active
06445892
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention.
This invention generally relates to printer/scanner units. More particularly, it is concerned with combined printer/scanner units wherein a scanner is stacked on top of a printer.
2. Description of Related Art.
As use of personal computers and their peripheral equipment has proliferated, the available space on user desktops has become extremely crowded and, hence, valuable. The term “footprint” has, in part, arisen out of concerns for conserving desktop space. Computer and peripheral equipment manufacturers have used various approaches in addressing the desktop crowding problem. These approaches have included stacking schemes (such as stacking a monitor or printer on top of a computer's chassis), combining a mouse and a keyboard in an integral unit and by simply making computers and peripherals narrower and taller.
Manufacturers of scanners also have made strides in reducing the footprints of their products. One approach has been to combine a printer and a scanner in a stacked relationship to create a combined printer/scanner unit. Owing to its size, weight and relative frequency of use, the printer component of a combined printer/scanner unit usually serves as its base. That is to say that the scanner is normally stacked on top of the printer. This stacked relationship presents at least one problem in the case of those printers that employ fuser units (e.g., electrophotographic printers). These fuser units can create heat flux that is large enough to interfere with optimal operation of a stacked scanner. That is to say that stacked output media that has been heated by a fuser can contribute greatly to the heat flux entering a stacked scanner.
Since electrophotographic printers are the most common example of printers having such fuser units, an electrophotographic printer will be used to further illustrate the present invention. Generally speaking, electrophotographic printers employ a laser beam to form an electrical latent image on a charged photoconductor drum. The latent image is then developed with a toner. The resultant toner image is then transferred to a print media substrate such as a sheet of paper. Electrophotographic printers also are especially characterized by the fact that they employ heater/pressure devices (commonly referred to as “fuser units” or “fusers”). Such fuser units normally comprise two opposing rollers that roll over each other in a pressured, rolling contact-creating, relationship. At least one of the two opposing rollers normally contains a heating device such as an electrically powered inductive heater element or halogen tube.
The heat generated by such a fuser unit does not significantly effect the operation of a scanner unit that is separate, distinct and laterally positioned from a fuser-employing printer. It is however well known that the quality of electrophotographic scanning processes can suffer when relatively high temperatures from a printer's fuser are transferred to the scanning cavity of a scanner that is stacked on top of an electrophotographic printer. Thus, when a scanner is stacked on an electrophotographic printer in order to create a footprint-saving printer/scanner unit, the heat generated by the printer's fuser must be dissipated before it reaches the scanner cavity where the actual scanning operation is carried out. Heretofore, such fuser heat dissipation operations have been accomplished through use of cooling fans placed in the vicinity of the fuser within the printer. In effect, these fans expel heat from a printer's inner cavity after that heat has served to soften the toner, but before it has an opportunity to rise (by natural convection) and impinge upon the bottom of a scanner unit that is stacked on top of the printer unit.
This method of preventing fuser-generated heat from reaching a stacked scanner has several drawbacks. For example, the fan(s) used to cool the printer cavity are costly to purchase, install and operate. They also take up valuable printer cavity space. Moreover, they do not adequately deal with another source of heat that reaches a scanner unit that is stacked on a fuser-equipped printer—namely heat from the print media itself. That is to say that a stack of recently fused sheets of print media (e.g., a stack of paper) is itself a significant source of heat. Such a stack of heated print media is generally located outside of the printer cavity (and hence beyond the cooling action of the printer's fan) but, to a large degree, directly underneath the scanner. Thus, heat rises from a stack of recently fused print media and is taken up into the scanner cavity through the bottom of the scanner unit. Again, the presence of relatively high temperatures (e.g., above 150° F.) in a scanner's scanning cavity region serves to lower the print quality performance of such a scanner.
SUMMARY OF THE INVENTION
The present invention provides a stacked printer/scanner unit with improved scanning performance, lower manufacturing costs and lower space and power requirements relative to those stacked printer/scanner units that employ fans to cool their printer cavity. These attributes are attained through applicant's use of one or more passive heat shields. These shields serve to produce scanner cavity operating temperatures that produce relatively high quality scanning operations. Preferably, the scanner cavity of a scanner component of applicant's stacked printer/scanner unit is provided with operating temperatures of less than about 150° F. Scanner cavity operating temperatures of less than 100° F. are even more preferred—and attainable through practice of the present invention. In the more preferred embodiments of this invention, these scanner cavity operating temperatures are produced without the aid of a fan in the printer cavity where the fuser is located, or in the scanner cavity itself. If, however, such fans are employed in applicant's printer/scanner units, they can be relatively smaller than those used in printers that do not follow the teachings of the present invention.
These preferred scanner cavity operating temperatures are provided by hindering entry of fuser-generated heat flux into a stacked scanner's scanner cavity. This heat flux hindering action is obtained by applicant's use of at least one strategically positioned passive heat shield. Such a passive heat shield is located between the printer's fuser unit and a scanning cavity of a scanner that is stacked on top of the printer in order to form a combined printer/scanner unit. For the purposes of this patent disclosure, the term “passive heat shield” can be taken to mean a heat shield that does not have an electrical power input requirement. It also should be appreciated that, for the purposes of this patent disclosure, the term “passive heat shield” should not be taken to mean a housing component of the printer, nor a housing component of the scanner, if in fact such housing(s) are employed in the construction of applicant's combined printer/scanner unit. Hence, a housing bottom (and especially a metallic housing bottom) of a scanner unit or a housing top (and especially a metallic housing bottom) of a printer unit should not be considered a “passive heat shield” under the teachings of this patent disclosure.
Applicant's passive heat shield(s) can comprise a single layer of heat insulating material. A second, third, etc. passive heat shield also can be employed in the practice of this invention as well. These passive heat shields also can comprise two or more distinct layers of heat insulating material. Moreover, any two or more such layers of heat insulating material also can be provided with a gas-containing cavity between such layers. In some of the more preferred embodiments of this invention, the heat shield(s) will form a heat barrier that hinders or prevents heat carrying air currents from arising directly from the fuser to the underside of the scanner cavity. That is to say that applicant's passive heat shield(s)
Grimley Arthur T.
Hewlett--Packard Company
Ngo Hoang
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