Xerographic fusing apparatus with input sheet guide

#The present invention relates to a fusing apparatus, such as used in electrostatographic printing.

#In electrostatographic printing, commonly known as xerographic or printing or copying, an important process step is known as “fusing.” In the fusing step of the xerographic process, dry marking material, such as toner, which has been placed in imagewise fashion on an imaging substrate, such as a sheet of paper, is subjected to heat and/or pressure in order to melt or otherwise fuse the toner permanently on the substrate. In this way, durable, non-smudging images are rendered on the substrates.

#Currently, the most common design of a fusing apparatus as used in commercial printers includes two rolls, typically called a fuser roll and a pressure roll, forming a nip therebetween for the passage of the substrate therethrough. Typically, the fuser roll further includes, disposed on the interior thereof, one or more heating elements, which radiate heat in response to a current being passed therethrough. The heat from the heating elements passes through the surface of the fuser roll, which in turn contacts the side of the substrate having the image to be fused, so that a combination of heat and pressure successfully fuses the image.

#FIG. 1 is a simplified elevational view showing the essential portions of an electrostatographic printer, such as a xerographic printer or copier, relevant to the present invention.

#FIGS. 2 and 3 are elevational views of a print sheet passing from a charge receptor to a fusing apparatus.

#FIG. 4 is a perspective view showing, in isolation, fuser rolls and a pivotably mounted guide member.

#FIG. 1 is a simplified elevational view showing the essential portions of an electrostatographic printer, such as a xerographic printer or copier, relevant to the present invention. A printing apparatus 100, which can be in the form of a digital or analog copier, “laser printer,” ionographic printer, or other device, includes mechanisms which draw substrates, such as sheets of paper, from a stack 102 and cause each sheet to obtain a toner image from the surface of a charge receptor 104. The toner image is transferred from the charge receptor 104 to the sheet by a transfer corotron 106, and the sheet is detached from the surface of the charge receptor 104 by a detack corotron Once a particular sheet obtains marking material from charge receptor 104, the sheet is caused to pass through a fusing apparatus such as generally indicated as 10. (Although a charge receptor, as would be used in an electrostatographic printer, is shown, other types of “marking station,” such as including a ink-jet printhead and/or an intermediate transfer member, can be contemplated in conjunction with the claimed invention.) Depending on a particular design of a printing apparatus, fusing apparatus 10 according to the invention may be in the form of a fuser module which can be readily removed and installed, in modular fashion, from the larger apparatus 100.

#A typical design of a fusing apparatus 10 includes a fuser roll 12 and a pressure roll 14. Fuser roll 12 and pressure roll 14 cooperate to exert pressure against each other across a nip formed therebetween. When a sheet passes through the nip, the pressure of the fuser roll against the pressure roll contributes to the fusing of the image on a sheet. Fuser roll 12 further includes means for heating the surface of the roll, so that heat can be supplied to the sheet in addition to the pressure, further enhancing the fusing process. Typically, the fuser roll 12, having the heating means associated therewith, is the roll which contacts the side of the sheet having the image desired to be fused.

#Generally, the most common means for generating the desired heat within the fuser roll 12 is one or more heating elements within the interior of fuser roll 12, so that heat generated by the heating elements will cause the outer surface of fuser roll 12 to reach a desired temperature. Basically, the heating elements can comprise any material which outputs a certain amount of heat in response to the application of electrical power thereto: such heat-generating materials are well known in the art.