Abstract: A heat roll fixing unit for fusing a toner image on a recording sheet in an image recording device is provided with a heat roller and a backup roller arranged oppositely to the heat roller. The recording sheet bearing a toner image is fed between the backup roller and the heat roller. At least one of the heat roller and the backup roller has a plurality of slits at an end thereof and a gear member having a plurality of protrusions on the inner periphery thereof is provided. The protrusions are fitted in the slits, respectively, and driving means for driving the gear member to rotate the rollers is also provided.

Abstract: A heating apparatus includes a heater generating heat upon electric power supply thereto; a film, wherein an image on a recording material is heated by heat from the heater through the film; wherein the film comprises a high resistance layer at a side remote from the recording material and a low resistance layer at a side remote from the heater; and wherein an area of the high resistance layer is larger than an area of the low resistance layer.

Abstract: A method of heat fixing a toner image comprises heat fixing a toner image on a recording material with a heating member fixed and supported and a pressurizing member which is opposed to, in pressure contact with said heating member and adapted to bring said recording material into pressure contact with said heat member through a film, wherein said toner image is formed of a toner, said toner comprises a binder resin and a colorant, said binder resin has a melt viscosity of 0.1 to 10.sup.7 centipoise at 140.degree. C. and the gradient (.theta.) of the straight line represented by the following formula comprising the reciprocal number (1/T) of the absolute temperature when the toner is melted by heating with the heating member and the logarithm (log .eta.) of the melt viscosity of the binder resin at this time is 10.sup.2 to 3.times.10.sup.3 :log .eta.=.theta..multidot.

Abstract: A fixing mechanism is provided including a heated roller. The heated roller includes a core made of a high thermally conductive metallic material, and a gudgeon for supporting such a core. The gudgeon is made from powder metal stainless steel material that has an interconnected porosity of 20%.

Abstract: A fixing apparatus includes rotatable member contactable to a material carrying a toner image to fix the toner image thereon, a first contacting member in sliding contact with a surface of the rotatable member, the first contacting member is reciprocable in a direction of a generating line of the rotatable member, a second contacting member in sliding contact with the surface of the rotatable member at a position different from the first contacting member in a rotational direction, the second contacting member being reciprocable in a direction of generating line of the rotatable member, wherein the first contacting member having a reciprocable movable range without overlapping with a reciprocable movable range of the second contacting member.

Abstract: A device for fusing and fixing electrophotographic toner powder to a receiver sheet and a method for using the same. The device comprises a first fusing member, such as a fusing roll, having a resilient surface for pressure contact with thermoplastic toner on the receiver sheet. A second member, which can be a non-resilient pressure roll, presses the toner into contact with the resilient surface. The device also is designed to heat the toner. The fusing member has a layer of an elastomeric, amorphous silarylene-siloxane alternating or random copolymer which is thermally stable, has good wear resistance, and good thermal conductivity and exhibits little or no swelling when contacted with poly(dimethylsiloxane) release oils.

Abstract: A temperature measuring arrangement for a revolving roll which includes a contactless temperature sensor by means of which the temperature of an annular peripheral zone of the roll situated outside the operating zone of the roll is measured contactlessly. Upon detection of a deviation from a given temperature or given time response of the temperature, a contact temperature sensor which is active only briefly is, by means of a control unit, brought into abutment, using a movement drive, at a point inside the operating zone of the roll.

Abstract: An elastic rotatable member conveniently usable as an image fixing member has a base member, a first primer layer, an elastic layer, a second primer layer and a resin layer in the order named. The first primer layer has a thermal conductivity higher than that of the second primer layer. Using the elastic rotatable member, its sheet conveying properties, releasability, wear resistance and durability are improved. When used for an image fixing rotatable member, its image fixing properties are improved.

Abstract: A fixing method for a wet process copier which develops an electrostatic latent image by using a heat-bridging type toner, transfers the resulting toner image to a paper sheet, and fixes the toner image transferred on the paper sheet by transporting the paper sheet through a nipping section defined by a heating roller and a pressing roller such that the side of the paper sheet carrying the toner image directly contacts the heating roller. At least a surface portion of the heating roller is made of either one of monomeric, additive-free RTV (Room Temperature Vulcanized) and LTV (Low Temperature Vulcanized) silicone rubbers. The heating roller has average surface roughness of less than 3 microns.

Abstract: A system for fixing a toner image to a paper has a first rotatably mounted roller having a peripheral surface for contact with the side of the paper having the toner image therein, a second rotatably mounted roller having a peripheral surface for contact with the other side of the paper in pressure engagement with the peripheral surface of the first roller, and means for rotating the first and second rollers for driving the peripheral surfaces at different velocities, the velocities differing by an amount at least sufficient to provide a slippage between the first roller and the paper held between the first and second rollers to minimize paper rucking, but differing by an amount insufficient to effectively distort the toner image.

Abstract: An image forming apparatus has upper and lower frames. A fixing unit detachably mounted on one frame is provided with a heated roller and a pressure roller. One end of a lever is positioned to be pushed by the other frame when the frames are in a closed condition, and the other end of the lever pushes the pressure roller at both ends of its shaft transversally towards the heated roller so as to pinch therebetween and heat a sheet having a toner image thereon. When the frames are disengaged and moved to their opened condition the pressure on the lever is released, whereupon the pressure roller separates from the heated roller so that the pressure on the sheet is released to facilitate easy removal of the sheet.

Abstract: A fluororesin-containing composition comprising a fluororesin, a fibrous material coated by an electrically conductive oxide, an acrylic resin and a liquid medium wherein the weight ratio of the fluororesin to the fibrous material is from 95:5 to 50:50, and the weight ratio of the fluororesin to the acrylic resin is from 100:0 to 85:15. The coating formed form the composition has good heat, chemical and weather resistance and non-tackiness properties.

Abstract: A low pressure heat fixing device for fixing toner images to multilayer paper as well as to ordinary copy paper. The device has a heat fixing roller having a metal roller body, an elastic intermediate layer formed on the surface of the metal roller body, and a thin resin film formed on the surface of the intermediate layer and having a releasing property and thickness less than the intermediate layer, a pressure roller in contact with the heat fixing roller and having a metal roller body, an elastic layer formed on the surface of the metal roller body, and a pressing member for pressing the heat fixing roller and the pressure roller together along a nip line at a total pressure of less than 20 kg to thereby thermally fix an image to a paper passed between the rollers.

Abstract: A heating roller having a surface layer of Teflon.RTM. and a pressing roller having a surface layer of an elastomeric material are held rotatably against each other for fixing a full-color toner image to a toner carrier therebetween. The ratio (1/V) between the nip width 1 of the heating and pressing rollers and the peripheral speed V of the rollers is selected to be at least 0.06, and the pressure of contact per unit area between the heating and pressing rollers at their nip region is selected to be at least 7 kg/cm.sup.2, for increasing a temperature range corresponding to the rubber range of toners used. The toners which have a small molecular weight and a small molecular weight distribution are prevented from being offset before the toners are fixed. Teflon.RTM. with desirable features can therefore be used as the surface layer of the heating roller.

Abstract: In a toner image fixing apparatus for an image forming machine, toner image transferred on a paper is heated at a predetermined fixing temperature. The fixing temperature is set to be larger than or equal to the toner melting temperature plus 10 [.degree.C.], and smaller than or equal to the toner melting temperature plus 20 [.degree.C.], in order to prevent rumples from forming on the paper. The paper is run at a predetermined speed slightly lower than the transfer speed of 60 mm/sec or less. Two cylindrical rollers are used to press the paper. The hardness of the surface of one of the rollers is set at 40.degree. or more. The fixing length of the portion where the rollers are in contact with one another is set at 2.5 mm or less. The distance between the fixing apparatus and the edge of a guide plate is set to be larger than or equal to 0.2 times the diameter of one of the rollers. Another aspect of the invention is setting the fixing speed higher than or equal to 1.

Abstract: An image fixing apparatus includes a couple of rotatable rollers press-contacted to each other, for fixing a toner image by passing a toner image carrying material carrying the toner image, through a nip formed between the rotatable rollers, at least one of the rollers including a surface coating of anodized aluminum having fine pores filled with perfluoroalkyl compound material.

Abstract: An elastic rotatable member usable for image fixing includes an elastic layer having a roughened surface, a resin layer formed by applying a liquid resin on the surface of the elastic layer and heating it up to a temperature not lower than its crystalline melting point and then quickly cooling it, wherein the resin layer has a side near the elastic layer, having a number of fine concave and convex portions, and wherein the convex portions are in concave portions of the surface of the elastic layer, and the concave portions of the resin layer is pressed by the convex portions of the elastic layer.

Abstract: An apparatus for processing a warp sheet of synthetic multifilament yarns is disclosed, and wherein the yarns may be withdrawn from supply packages and advanced along a path of travel in warp sheet form, heated and drawn while in advancing warp sheet form to orient the filaments, and then wound for example on a warp beam. Upon detection of a yarn break, the advance of the warp sheet is terminated, and means are provided for interrupting the application of heat to the sheet while the advance is terminated so as to avoid damage to the remaining yarns from a continued application of heat.

Abstract: A fixation device which comprises a roller comprising a core member, a fluororesin-containing rubber layer on the core member and a fluororesin surface layer. The fluororesin surface layer has a thickness from 2 to 100 .mu.m, preferably 5 to 30 .mu.m, and surrounds and contacts the outside of the rubber layer.

Abstract: A thermally developing apparatus for a light and pressure sensitive material. The exposed material is inserted between a rotating heated roller and an endless belt wrapped partially around the roller. Additionally, a temperature sensor detects abnormally high temperatures and, as a result, removes the material from the heated roller.

Abstract: A heating roller having a surface layer of Teflon and a pressing roller having a surface layer of an elastomeric material are held rotatably against each other for fixing a full-color toner image to a toner carrier therebetween. The ratio (1/V) between the nip width 1 of the heating and pressing rollers and the peripheral speed V of the rollers is selected to be at least 0.06, and the pressure of contact per unit area between the heating and pressing rollers at their nip region is selected to be at least 7 kg/cm.sup.2, for increasing a temperature range corresponding to the rubber range of toners used. The toners which have a small molecular weight and a small molecular weight distribution are prevented from being offset before the toners are fixed. Teflon with desirable features can therefore be used as the surface layer of the heating roller.

Abstract: A thermal roller for fixing a powdered toner image onto an image receiving sheet is provided with a sub-surface resistive heat generating layer adjacent the outer surface of the roller. The thickness of the heat generating layer or the materials that constitute the layer are controlled so that the resistance per unit length of the thermal roller increases gradually in the axial direction from the center portion thereof toward and to both ends. Electrical energy passed through the heat generating layer generates a desired temperature distribution profile along the roller to provide appropriate fixing temperatures, without excessively increasing the temperature at both ends of the roller.

Abstract: A heat-fixing apparatus comprising a heating roll to be brought into contact with a toner image borne on a sheet member, a pressure roll in pressed contact with the heating roll to provide a nip portion therebetween, each of the heating roll and the pressure roll being constituted by a cylindrical core coated with a heat-resistant, resilient layer and a resin surface layer having release properties, the heating roll and the pressure roll having such surface hardness as to make the nip portion substantially flat and also having substantially the same outer diameter, and the contact pressure of the rolls being such that the nip portion has a width within the range of providing good fixing capability. This heat-fixing apparatus can perform toner image fixing even on sheet members of a plurality of plies such as envelopes without creasing.

Abstract: An elastomer roll comprising a roll core, a first layer of a cured organopolysiloxane composition, and a second thin layer of a fluorine resin formed in this order. The organopolysiloxane composition is comprised of an organopolysiloxane, a finely divided silica filler, an organosilicon material having at least one hydrogen atom bonded to the silicon atom in one molecule, iron oxide, a fluorine resin, and an organic peroxide in defined amounts.

Abstract: An improved full color electrophotographic print engine using flexible belts to carry a photosensitive electrostatic image developer and a transfer belt for building up composite developed images. Each belt, and an optical scanner, are driven by mechanically independent motors which are synchronized by an electronic digital controller implementing precise servos. The use of the flexible belts allows the machine to be relatively inexpensive, very small compared to previous full color print engines, and yet maintain precise registration of color composite images. An improved fuser mechanism with increased dwell time at constant machine speed is also shown. The fuser includes a pair of spaced-apart rollers, both of which urge a sheet of image receptor against the heated roller over a predetermined angular portion of the roller. The machine is specifically designed to be used interchangeably with an optical bench source as a copier or with a laser bench as a laser printer.

Abstract: A pressure device for applying pressure between an upper fixing roller and a lower fixing roller, the pressure applying device being disposed at each end of the lower fixing roller and including a bearing member for supporting a rotary shaft mounted in the lower fixing roller and a biasing spring for biasing the bearing member upwards. The upper and lower fixing rollers are held in pressure contact with each other through depression of the upper fixing roller towards the lower fixing roller, under the influence of the pressure device.

Abstract: Heat and pressure fusing apparatus for fixing color toner images to various types of copy substrates. The apparatus includes three roll members which cooperate to form a pair of nips. All substrates pass through a first nip and a deflector plate directs certain types of substrates through the second nip. Passage of the substrates through the first nip causes the images carried thereon to contact a conformable elastomeric surface while passage through the second nip casues them to contact a relatively rigid surface. Thus, glossy and matt color copies on substrates such as plain paper and high chroma transparencies are suitably produced in a color reproduction apparatus incorporating this fuser. Matt color copies are produced by passing the substrate through only the first nip while glossy color copies and high chroma transparencies are produced by passing the substrates through both nips.

Abstract: A fixing unit for shell-type image formation apparatuses comprising: a pair of fixing rollers, one of which is an upper roller contained in an upper housing and the other of which is a lower roller contained in a lower housing, said housings being pivotally held by a shaft that is parallel to said pair of fixing rollers, and a lever that can be rotated at the opening edge of said lower housing, said lever being rotated so that it holds the upper housing to the lower housing in its first position, and being able to be released from the first position so that it switches to the second position where it holds the lower housing to the body of the image formation apparatus in a prescribed position.

Abstract: Disclosed is a toner thermal fixing roller comprised of the following; a heating unit internally provided with a heating source: a roller pressed against said heating roller; and several member parts preventing reflective heat from heating the heating source, while these member parts are provided inside the bearing parts which are set to both ends of the heating source, the bearing parts being set to both ends of the heating roller and installed inside the hollow portion of the heating roller.

Abstract: An apparatus, a process and a processing sheet for improving qualities of an image in sharpness, density and/or glossiness. A copy or printed sheet having an image is coated with a thin sheet at the image bearing side of the copy. The copy is then pressed together with the thin sheet, and simultaneously heated so as to soften or fuse at least the surface of the image on the copy. Then, the sheet is peeled off the image after the image is cooled sufficiently. Surprisingly, the qualities of the image are improved as compared with the image before processing.

Abstract: A heat and pressure roll fusing apparatus for fixing toner images to copy substrates, the toner comprising a thermoplastic resin. The apparatus includes an internally heated fuser roll cooperating with an unheated bare metal backup or pressure roll to form a nip through which the copy substrates pass with the images contacting the heated roll. The heated fuser roll is characterized by a comformable outer layer or surface which by way of example is fabricated from a silicone rubber or "Viton" material to which a low viscosity polymeric release fluid is applied. Release fluid is contained in a sump and the pressure roll is partially immersed in the fluid. Thus, the release fluid is applied to the surface of the internally heated fuser roll via the bare metal pressure roll. The roll structures are such as to provide maximum area of contact in the nip, while minimizing the area of contact between the pressure roll and the copy substrates.

Abstract: An electrophotographic hot roll fuser is manually movable from an operative position within an electrophotographic reproduction device, to an inoperative position where the fuser is available for cleaning, inspection or sheet jam clearance. When the fuser is in its inoperative position, a manually operable handle is accessible for operation. Operation of this handle moves various operating components, such as sheet guides, apart, thereby facilitating manual sheet jam clearance. Subsequently, when the handle is manually returned to its original position, all sheet guides and like components are accurately relocated to their original operative positions.

Abstract: An image reproducing apparatus wherein a heat generating member is disposed in the proximity of a roller fixing device at the side of a charge receptor from which a transfer sheet is introduced to the fixing device. The roller fixing device is a heat roller fixer and the heat generating member is a plate-shaped heat generating member disposed at the lower side of conveying path for the transfer sheet.

Abstract: An electrostatic printing apparatus capable of printing both normal sheets of paper and composites such as envelopes. In accordance with a mode in which normal sheets are printed and with the other mode in which envelopes are printed, transfer current applied to a transfer charger, fixing pressure applied to between a pair of fixing rollers, and heat generation of the heat source(s) in the fixing roller(s) can be changed respectively to those suitable for the sort of a transfer member. This change can be performed manually, or controlled automatically based on a signal issued from a member sorting sensor disposed in a paper supply portion.

Abstract: A device for fixing a toner image on an image forming medium in an image forming apparatus includes a heating roller and a supporting roller for supporting the sheet of paper and transporting the paper, the heating roller having an inner peripheral surface, and at least one electrically resistive layer on the inner surface of the heating roller for fixing the toner image on the paper and reducing heat loss from the heating roller. Further, the device includes a pair of electrodes at opposite ends of the resistive layer for transmitting electrical power to the resistive layer.

Abstract: An electrophotographic reproduction device includes a pressure roll fuser whereat toner carried by a sheet of paper is fused onto the paper's surface by the application of both heat and pressure as the sheet passes through a pressure fusing nip. The pressure nip is formed by pressure engagement of a heated fusing roll to an unheated backup roll. A multilayer cloth wick rubs against a portion of the hot roll's toner engaging surface, and thereby supplies release oil to this surface. When the wick's outer cloth layer becomes contaminated with toner and the like, the operator acitvates a manually releasable stitch which is associated with the wick's multiple layers. This action allows manual removal of the wick's top contaminated layer, thereby exposing a clean cloth surface for subsequent engagement to the hot roll's toner engaging surface.

Abstract: A reproducing machine in which a liquid image including a liquid carrier having pigmented particles dispersed therein is transferred to a sheet of support material. In the operative mode, when the sheet of support material having the liquid image thereon is present, a fuser applies heat thereto to remove liquid carrier therefrom so as to dry the sheet of support material, and fuse the pigmented particles thereto in image configuration. In the standby mode, when the sheet of support material is not present, the fuser still generates heat. The liquid carrier removed from the sheet of support material by the fuser is collected in a condenser. Air flowing from the condenser passes through a filter to remove residual liquid carrier therefrom, in the standby mode, heated air from the fuser is directed to the filter to regenerate the filter.

Abstract: An electrophotographic printing machine in which an electrostatic latent image recorded on a photoconductive member is developed with a liquid developer material having at least a liquid carrier with pigmented particles dispersed therein. The developed image is transferred from a photoconductive member to a sheet of support, material. Heat and pressure are applied to the developed image on the sheet of support material to vaporize substantially all of the liquid carrier transferred to the sheet of support material and to substantially permanently fuse pigmented particles to the sheet of support material in image configuration.

Abstract: The present invention is concerned with an instant-on fuser having a cylindrical, relatively thin metal cylinder supporting a resistance heating foil or printed circuit secured on the inside surface of the cylinder by a high temperature adhesive. The interior of the cylindrical tube is filled with air. The heating foil or printed circuit is carried on a fiber glass substrate and the heating elements is connected to electrical leads extending through caps on the ends of the cylindrical support. The relatively low thickness, low mass fuser and high temperature materials permit a relatively fast instant-on fuser.

Abstract: A heater drum has an outer cylindrical wall centered on and rotatable about an axis, an inner cylindrical wall fixed concentrically within the outer wall and defining therewith an annular chamber, and a body of a heat-transmitting fluid in the chamber in heat-transmitting contact with both walls. A core body fixed nonrotatably about the axis inside the inner wall is heated to a high treatment temperature. This heat is transmitted radially from the core body to the inner wall. The walls are rotated jointly about the axis relative to the core body to distribute the heat of the inner wall via the fluid body to the outer wall. The chamber is at subatmospheric pressure and the fluid is partly vaporized and partly liquid at the high treatment temperature. The core body is of part-cylindrical section generally centered on the axis and has an outer surface spaced slightly radially inward of the inner wall.

Abstract: One or two auxiliary rollers of relatively small diameter are pressed against the peripheral surface of a main rotatable body which is heated. Where the two auxiliary rollers are employed, they are spaced apart from each other and are rotated in one direction at the same peripheral speed as that of the main rotatable body. A sheet carrying an unfixed toner image is fed by being gripped between the main rotatable body and the auxiliary rollers, during which the toner is heated and dried, and fixed to the sheet with the solvent evaporated. Thereafter, the sheet is discharged toward a next process. The sheet auxiliary sheets are relatively disposed under certain positional conditions for keeping the sheet in intimate contact with the main rotatable body to achieve proper toner fixing and sheet feeding operations.

Abstract: A contact fixing device primarily used in electrophotographic copiers is provided with a driven and heated fixing surface which is made from a partially resilient material and a driven pressure surface which presses against the fixing surface forming a fixing zone through which copy material can be fed for fixing a toner image thereon. It also has a hollow perforated cleaning roller which while rotating in contact with the fixing surface takes up toner from the fixing surface. To prevent contamination of the device due to toner material flowing over the ends of the cleaning roller, the device is provided with a disc roller near each end of the cleaning roller which presses against the cleaning roller and is thereby rotationally driven.

Abstract: A method and a device are provided for determining the moment that a layer of tacky material needs to be rejuvenated. Typically, the layer is present on a cleaning member for removing contaminants such as paper dust and softened toner material from a fusing surface. The method includes measuring the light reflection value of the layer of tacky material, comparing the measured light reflection value with a reference value and rejuvenating the layer of tacky material as soon as the measured light reflection value differs by a predetermined value from the reference value. The device implements the method of the present invention.

Abstract: A drying cylinder (A) is mounted for rotation about its central axis (44). A burner assembly (B) oxidizes fuel interior to the shell, generally along the central axis. A recirculating fan (C) urges the hot combustion gases from the burner into a nozzle box assembly (D). The nozzle box assembly includes a plurality of peripherally spaced, longitudinally extending boxes (80) which have an array of nozzles (82) therein. The nozzles direct jets of hot combustion gases against an interior surface of a cylindrical dryer shell (30) for transferring heat thereto. Hot combustion gases which have impinged upon the shell are recirculated through passages (84) and are in part reheated by the burner and in part discharged through an exhaust aperture (90) and an exhaust duct (92). In one embodiment, the direct fired dryer is mounted in one of the dryer sections of a Fourdrinier paper production line.

Abstract: An image forming apparatus wherein an unfixed image is formed on a recording material at an unfixed image forming station, such as an image transfer station or a station for developing an electrostatic latent image. The unfixed image is fixed by a fixing device including a couple of fixing rollers, one of which is substantially frustoconical. The present invention is effective to avoid the possible disturbance to the image caused by the frustoconical shape of the roller. The preferable arrangement is such that the distance between the image forming station and the nip formed between the rollers is shorter than the length of the recording material, and that the nip is non-parallel with respect to the leading edge of the on-coming recording material. Further, the small diameter side of the conical roller receives the leading edge of the sheet earlier than the large diameter side of the frustoconical roller.

Abstract: A dryer for paper and similar fibrous web materials including a dryer roll having an outer cylindrically-shaped wall, a radiant heat source within the dryer roll adapted to heat the wall substantially uniformly about the entire periphery thereof, and nip-forming means forming a pressure nip with the dryer roll.

Abstract: Apparatus is disclosed for feeding a support web between a pair of fusing rollers, at least one of which is heated. Heat conductive skive means is supported in contact with the heated roller for stripping the web material from the roller. Temperature sensitive means in heat-conducting contact with the skive means senses the temperature change of the roller by conduction along the skive means. The temperature sensitive means generates an electrical signal representative of the temperature change, and the signal is coupled to temperature control means operative in response to the generated signal to control the temperature of the heated roller so that the temperature transferred to the web material is maintained within preferred temperature limits.

Abstract: In a fixing device wherein a toner image formed on a copying paper by an electrophotographic copying machine is fixed while the copying paper is maintained in contact with the periphery of a heated fixing roller. Pressure is applied to the copying paper by a pressure applying device including an endless belt supported by a pair of spaced rollers which are mounted on a slidable plate. The slidable member is normally clamped at an operating position by a clamping member. When the clamping member is released, the slidable plate can be slid laterally to separate the endless belt from the fixing roller thereby enabling removal of jammed copying paper, exchange, repair and inspection of various elements of the fixing device.

Abstract: A rotary cylindrical drum used in a commercial laundry flatwork finisher, having a jacket type construction so as to provide an annular fluid cavity for uniformly heating the exposed surface of the drum. The flatwork finisher includes fluid circulating system providing a temperature sensing probe exteriorly of the drum for measuring and regulating the temperature of the circulated fuel by controlling the operation of a heating element associated therewith.

Abstract: A heat-fixing apparatus comprising a heating roll to be brought into contact with a toner image borne on a sheet member, a pressure roll in pressed contact with the heating roll to provide a nip portion therebetween, each of the heating roll and the pressure roll being constituted by a cylindrical core coated with a heat-resistant, resilient layer and a resin surface layer having release properties, the heating roll and the pressure roll having such surface hardness as to make the nip portion substantially flat and also having substantially the same outer diameter, and the contact pressure of the rolls being such that the nip portion has a width within the range of providing good fixing capability. This heat-fixing apparatus can perform toner image fixing even on sheet members of a plurality of plies such as envelopes without creasing.