Abstract: A heater includes a substrate, a first electrical contact, a plurality of second electrical contacts, a plurality of electrode portions including first electrode portions electrically connected with the first electrical contact and second electrode portions electrically connected with the second electrical contacts, the first electrode portions and the second electrode portions being arranged alternately with predetermined gaps in a longitudinal direction of the substrate, and a plurality of heat generating portions provided between adjacent ones of the electrode portions so as to electrically connect between adjacent electrode portion. The heat generating portions are capable of generating heat by the electric power supply between adjacent electrode portions. A part of the second electrical contacts is selectably electrically connectable with the second terminal. The electrode portions are covered with the heat generating portions so as to be positioned between the substrate and the heat generating portions.

Abstract: A fixing device for fixing an unfixed image onto a recording medium includes a fixing belt, a nip forming member, an opposing rotary member, a heater, and a temperature detector. The fixing belt is formed into a loop to move endlessly and fix the unfixed image on the recording medium. The nip forming member is disposed inside the loop formed by the fixing belt. The opposing rotary member contacts the nip forming member via the fixing belt to form a nip portion therebetween while rotating. The heater heats the fixing belt at a place other than the nip portion. The temperature detector detects a temperature of the surface of the fixing belt. The temperature detector detects the temperature near a place of the fixing belt that easily deforms as the fixing belt is heated by the heater.

Abstract: A heating member for a fusing apparatus includes a resistive heating layer including a base polymer and an electroconductive filler dispersed in the base polymer, where the resistive heating layer generates heat by receiving electric energy, and where a storage modulus of the resistive heating layer is about 1.0 megapascal or greater.

Abstract: A heater includes: a substrate; a first electrical contact; second electrical contacts; first and second electrodes; heat generating portions; a first electroconductive line portion electrically connecting the first electrical contact and the first electrode portions; and a second electroconductive line portion electrically connecting one of the second electrical contacts and a part of the second electrode portions. A cross-sectional area of a portion, of the first electroconductive line portion, into which all of currents flowing through the first electrode portions merge when the currents flow from the first electrode portions toward the first electrical contact is larger than a cross-sectional area of a portion, of the second electroconductive line portion, into which all of currents flowing through the part of the second electrode portions merge when the currents flow from the part of the second electrode portions toward the one of second electrical contacts.

Abstract: The image forming apparatus includes an image forming unit, a fixing unit including a heater, a necessary integral power calculation unit configured to calculate a necessary integral power required for the fixing unit to reach a predetermined fixable temperature, a suppliable integral power calculation unit configured to calculate a suppliable integral power capable of being supplied to the heater in a time elapsing until the recording material reaches the fixing unit, a power source condition detection unit configured to detect a power source condition of a power source for supplying power to the heater, and a controller configured to control a timing to start conveyance of the recording material according to the necessary integral power and the suppliable integral power, wherein the suppliable integral power calculation unit calculates the suppliable integral power according to a resistance value of the heater and the power source condition.

Abstract: A fixing apparatus includes a tubular rotation member including a conductive layer, a helical coil, a resonance circuit, including a resonance capacitor, formed with the rotation member and the coil, a resonance inverter configured to control the resonance circuit, and a control unit configured to control electric power supplied to the resonance inverter, wherein the conductive layer generates heat with electromagnetic induction caused by magnetic flux generated through the coil, wherein the control unit sets a driving frequency of the resonance inverter according to at least one of a size of the recording medium and a temperature of a non-sheet-passing portion of the rotation member, and wherein the control unit changes a resonance frequency of the resonance circuit according to the set driving frequency.

Abstract: A fixing device to fix a toner image on a sheet includes a first rotary member that rotates in a predetermined direction and a second rotary member that contacts an outer circumferential surface of the first rotary member. A stationary member is fixed inside the first rotary member to press the first and second rotary members together to form a nip portion between the rotary members. A reinforcement member is fixedly provided inside the first rotary member and pressed against the stationary member. The fixing device includes heat source to heat the first rotary member and a reflector to reflect heater light emitted from the heat source toward the first rotary member.

Abstract: An endless belt exchangeably usable with an image forming apparatus, the endless belt including a first lubrication layer applied on an inner surface of the endless belt, the first lubrication layer including lubrication particles and lubricant oil; a second lubrication layer provided on the first lubrication layer and including lubrication particles and lubricant oil; wherein a lubricant oil content of the first lubrication layer is larger than a lubricant oil content of the second lubrication layer.

Abstract: A fixing apparatus includes a belt including a ferromagnetic layer, a roller facing the belt, a ferromagnetic plate disposed inside the belt and having a Curie point that is lower than a Curie point of the ferromagnetic layer, an induction heater configured to cause heat generation in the magnetic layer and the ferromagnetic plate, a driving circuit configured to output a high frequency current to the induction heater by switching on and off switching elements thereof, and a controller. The controller is configured to determine whether or not a temperature of the ferromagnetic plate is higher than the Curie point thereof, and control the driving circuit to reduce a level of the high frequency current when the temperature of the ferromagnetic plate is determined to be higher than the Curie point thereof.

Abstract: A heater includes: a substrate; a first electrical contact; a plurality of second electrical contacts; an electroconductive line portion electrically connected with the first electrical contact; a plurality of electrode portions including first electrode portions electrically connected with the first electrical contact through the electroconductive line portion and second electrode portions electrically connected with the second electrical contacts; and a plurality of heat generating portions provided between adjacent ones of the electrode portions. The cross-section of the electroconductive line portion in a side closer to the first electrical contact than the plurality of heat generating portions with respect to the longitudinal direction is larger than the cross-section of a predetermined electrode portion, between adjacent heat generating portions, of the plurality of electrode portions.

Abstract: In a fixing device including a cap member mounted at an end portion of a fixing belt in a rotation shaft direction via a rotation transfer member, an axis center of a support shaft supporting the cap member is made eccentric with respect to a rotation axis center of the fixing belt.

Abstract: A heater control device includes a first voltage conversion part that generates a first voltage based on an external input voltage, a second voltage conversion part that generates a second voltage for supplying power to heater(s) based on the first voltage, a third voltage conversion part that generates a third voltage used at least in driving the heater(s) based on the first voltage, a capacitative element electrically connected to a path that connects the first voltage conversion part to the second voltage conversion part and connects the first voltage conversion part to the third voltage conversion part. The capacitative element is located in a section of the path used for connecting both to the second and to third voltage conversion part, and a control part that performs an operation stop control to stop the operation of at least one heater(s) if the external input voltage has dropped below a first threshold voltage.

Abstract: A fixing device includes a fixing belt, a cap member, a first elastic member, and a second elastic member. The cap member is attached to an end portion of the fixing belt. The first elastic member is mounted in the cap member so as to be opposite to an outer circumferential surface of the fixing belt. The first elastic member is ring-shaped. The second elastic member is mounted in the cap member so as to be opposite to an inner circumferential surface of the fixing belt. The second elastic member is ring-shaped. The first elastic member is in pressed contact with the cap member and with the outer circumferential surface of the fixing belt. The second elastic member is disposed with a space from the inner circumferential surface of the fixing belt and thermally expands toward the inner circumferential surface of the fixing belt.

Abstract: A recording-material cooling device includes a first cooling member, a second cooling member, an approach-and-separation member, and a positioning member. The first cooling member is disposed at a first face side of a recording material to absorb heat of the recording material. The second cooling member is disposed at a second face side of the recording material to absorb heat of the recording material. The approach-and-separation member brings the first cooling member and the second cooling member close to and away from each other. The positioning member positions the first cooling member and the second cooling member relatively brought close to each other by the approach-and-separation member.

Abstract: A fixing device, including a heat roller, a temperature detector member to detect temperature of the heat roller, a supporting member to support the temperature detector member, and a fixer frame to support the heat roller and the supporting member, is provided. The supporting member includes a supporting part to support the temperature detector member, a first part, a second part which is less rigid than the first part, and an attaching part to be attached to an attachable surface of the fixer frame. The attaching part is arranged on one end of the supporting member along the axial direction. The supporting part is arranged in an intermediate position along the axial direction in the supporting member. The first part and the second part are arranged in positions between the attaching part and the supporting part along the axial direction in the supporting member.

Abstract: An image forming apparatus includes a first heater disposed opposite and heating at least a center of a fixing belt in an axial direction thereof and a second heater disposed opposite and heating at least a lateral end of the fixing belt in the axial direction thereof. A power supply supplies power to the first heater and the second heater. A controller that controls the power supply includes a calculator to calculate an elapsed time elapsed after at least one of the first heater and the second heater starts heating the fixing belt. The controller controls the power supply to supply power to the first heater and the second heater such that a power density of the second heater is greater than a power density of the first heater when the elapsed time calculated by the calculator is smaller than a predetermined time.

Abstract: A fixing member includes a substrate and an elastic layer on the substrate. The elastic layer comprises a cured product of a silicone rubber composition containing an anatase titanium oxide particle and an addition-curable silicone rubber, and undergoes cohesive failure in 90° peel test specified in JIS K6854-1: 1999. In the fixing member, an allyl group bound to a silicon atom is present at the interface between the substrate and the elastic layer.

Abstract: A packaged image forming apparatus includes an image forming apparatus, and a packaging member for packaging the image forming apparatus. The image forming apparatus includes a power supply connection unit to which one end of a power cable, the other end of which is connected to an external power source, is detachably connected, a power supply voltage generation unit receiving a voltage via the power cable and generating a power supply voltage, a load circuit operating based on the power supply voltage, a status determination unit determining whether a connection status of the load circuit is normal, and a communication interface unit sending a determination result to the external device. The packaging member includes an access part enabling the one end of the power cable to be connected to the power supply connection unit in a state where the image forming apparatus is packaged.

Abstract: A fixing press member includes a substantially tubular thermal conductive layer containing a resin and a substantially scale-shaped filler having a higher thermal conductivity than the resin, and a surface layer disposed on an outer circumferential surface side of the thermal conductive layer.

Abstract: A heater includes a heater unit and a holder. The heater unit includes a flat and smooth substrate, a linear heat generator provided on a first surface of the substrate, a plurality of electrodes that supply power to the heat generator, and a protective layer disposed to cover a part of each of the electrodes and the heat generator. A second surface of the substrate is bonded to the holder. The substrate is formed of a transparent material. A plurality of positioning marks for determining the relative positions of the heater unit and the holder are disposed on the first surface of the substrate. The holder has through-holes formed at positions opposite to the positioning marks.

Abstract: A heating roller includes: a core bar having a cylindrical shape; a rubber layer arranged on an outer circumferential surface of the core bar; and a release layer arranged on an outer circumferential surface of the rubber layer, wherein when thermally fixing a developer on a recording medium, the heating roller is heated to a temperature within a fixing temperature range including a minute particle-scattering start temperature at which minute particles start to scatter from the rubber layer. The heating roller is arranged inside a casing which is connected to a minute particle density measuring device; then the core bar of the heating roller inside the casing is heated to 230° C. by a heater; and when the density of the minute particles inside the casing is measured after elapse of 20 minutes since start of the heating, the density of the minute particles is less than 2,000 pieces/cm3.

Abstract: Provided is a heating device including a transparent endless pressurizing member that pressurizes a heating target, a contact member that transmits light which is emitted from a light source to heat the heating target, and comes in contact with an inner circumferential surface of the pressurizing member, a support member that supports the contact member within the pressurizing member, and a reflection section that is provided between the contact member and the support member, and reflects light toward a side opposite to the support member.

Abstract: By connecting a first diode between a conductive heating element of a fixing roller and ground, electric charge with the same polarity as the charged polarity of toner can be held on the surface of the fixing roller. Meanwhile, by connecting a second diode between the surface of a pressing roller that does not contact an un-fixed toner image and ground, electric charge with the reverse polarity of the charged polarity of the toner can be held at the surface of the pressing roller. The polarity of the electric charge induced by electromagnetic induction is held at the polarity determined by the two diodes, and as a result the fixing offset can be suppressed without adding a collector member or a charging capacitor.

Abstract: A cooling device cools a continuous resin film, which is transported and onto which a toner image is transferred, after the toner image is heated so that the toner image is fixed to the resin film. The resin film to which the toner image is fixed is cooled in such a manner that an image surface side of the resin film is convexly curved.

Abstract: Provided is an image forming apparatus including an image forming unit that forms an image on a recording medium, and an applying unit that causes powder included in a liquid mixture to be interposed between the recording medium and the image forming unit by applying the liquid mixture to the recording medium, or to the image forming unit which comes into contact with the recording medium, wherein the recording medium includes an image forming layer, an adhesive layer, and a base layer, and the liquid mixture includes the powder reducing adhesion of the adhesive layer and volatile liquid.

Abstract: A thermal eraser for erasing tactile drawing features from a tactile drawing medium, along with methods of erasing tactile drawing features formed on a tactile drawing medium, are disclosed. The thermal eraser has a heated tip that can be heated to a temperature sufficient to cause the tactile drawing feature to flow back into the surface of the tactile drawing medium. The heated tip has a tip temperature that can be controlled by a temperature-regulating circuit. A set-point temperature can be used to set the tip temperature and maintain the tip temperature. The thermal eraser can be controlled by hand or by an electro-mechanical device such as a tactile printer.

Abstract: According to an embodiment, provided is a fixing device that includes: a rotatable fixing member that heats a recording medium on a side carrying an unfixed image; a rotatable pressing member that is pressed and is contacted with the fixing member to form a nip portion between the pressing member and the fixing member; a heat source heating the fixing member; a relay switch provided in an energizing path for the heat source; a temperature detection sensor detecting a temperature of the fixing member; and a control unit that controls energization of the heat source according to the temperature detected by the temperature detection sensor. The control unit keeps the relay switch in an off state if the temperature of the fixing member is equal to or more than a predetermined temperature when the fixing member has stopped rotation.

Abstract: A fixing device capable of incorporating in an image forming apparatus includes a belt unit including a rotatable elastic endless belt having a sleeve shape without a driving shaft and a nip forming member disposed contactable against an inner surface of the endless belt, and a pressing member to form a nip contact portion through which a recording medium passes by pressing against the nip forming member via the endless belt. The endless belt is configured to be removable from the fixing device without contacting the endless belt.

Abstract: An image forming apparatus includes: an image forming station; heating and pressing rollers forming a fixing nip therebetween; a mechanism for changing the relative positional relation between the heating and pressing rollers between a contacting position in which they contact each other, a first spacing position in which they are spaced, and the second spacing position in which they are spaced by a shorter distance; and a controller for controlling the changing mechanism such that in a period after the sheet passes through the fixing nip and before a next sheet reaches the fixing nip, the rollers are brought into the first spacing position when the period is longer than a first predetermined period, and that the rollers are brought into the second spacing position when the period is shorter than the first predetermined period and is longer than a second predetermined period.

Abstract: A fixing device includes an endless fixing belt, fixing-belt holding members which hold the fixing belt at opposite ends, a pressure member to be brought into contact with the fixing belt, a nip forming member arranged inside the fixing belt to form a nip area by contacting the pressure member with the fixing belt, a nip supporting member, side plates where the fixing-belt holding members and the nip supporting member are fixed, and a pressing mechanism which presses the pressure member against the nip forming member. The nip forming member includes at least three layers including a heat absorbing layer contacting the nip supporting member. With no load applied, the nip supporting member assumes a shape protruding at longitudinal center toward the pressure member and is in contact with the nip forming member while having the shape protruding at the center portion.

Abstract: Provided is a member for electrophotography. The member for electrophotography includes: a substrate; an elastic layer containing a cured silicone rubber having a methyl group bonded to a silicon atom; and a fluorine resin release layer bonded to a surface of the elastic layer by an addition-curing-type silicone rubber adhesive. The elastic layer contains a titanium oxide particle having an anatase-type crystal structure.

Abstract: A heating device includes a belt member, plural heating elements, and plural resistance elements. The belt member is rotated. The plural heating elements are arranged in a width direction of the belt member and generate heat so as to heat the belt member. The plural resistance elements having positive temperature coefficients are each connected in series with a corresponding one of the plural heating elements. In the heating device, a temperature of the belt member is reduced by an increase in resistances of the plural resistance elements caused by an increase in temperatures of the plural resistance elements.

Abstract: A fixing device includes: a heating unit; a rotatable body; an urging mechanism; first and second bearings; a frame; first and second positioning members. The first and second bearings support first and second axial end portions of the rotatable body, respectively. The frame supports the heating unit and has two side walls. One of the side walls supports the first bearing, and the other supports the second bearing. Each side wall includes: a first wall portion supporting the first or second bearing; and second and third wall portions supporting the heating unit while interposing the heating unit therebetween. The first and second positioning members extend from the heating unit toward the first and second bearings, respectively. The heating unit is fixed in position relative to the first and second bearings upon engagement of the first and second positioning members with the first and second bearings, respectively.

Abstract: A fixing unit for fixing a toner image includes a fixing device and a guide member. The fixing device includes a fixing roller having a heater inside thereof and a pressing roller disposed opposite the fixing roller. The pressing roller presses against the fixing roller and fixes a toner image formed on a transfer medium. The guide member guides the transfer medium to the fixing device. The guide member includes a metal base member including at least one coating layer.

Abstract: A fixing device includes a heating roller and a pressuring roller, a first holding member, a supporting member and a temperature detecting part. The heating roller and pressuring roller sandwiches and heats a sheet to fix a toner image formed on the sheet onto the sheet. The first holding member has a facing part facing to a circumference face of the heating roller to hold the heating roller. The supporting member is made of material with high heat resisting property as compared with the first holding member, arranged between the facing part of the first holding member and the circumference face of the heating roller so as to face to the circumference face of the heating roller, and formed in an elongated shape along an axial direction of the heating roller. The temperature detecting part is arranged in the supporting member to detect temperature of the heating roller.

Abstract: A fixing device includes a temperature detection unit that detects temperature associated with temperature of an abutting section of a fixing roller and a pressing roller, and a control unit that controls a driving motor based on detection temperature by the temperature detection unit. When the fixing device is activated, if it is determined that detection temperature by the temperature detection unit is not equal to or less than predetermined temperature, the control unit drives the driving motor at a setting speed set in advance, and if it is determined that the detection temperature is equal to or less than the predetermined temperature K, the control unit drives the driving motor at a predetermined low speed lower than the setting speed.

Abstract: The present invention provides a fixing pressure roller exhibiting excellent compression set and having low hardness and low heat capacity, as well as a fixing device including the fixing pressure roller. A pressure roller employed in a fixing unit of a fixing device includes a core, and an elastic layer provided around the core, wherein the elastic layer is formed of a silicone rubber product produced by mixing a silicone rubber raw material with resin microballoons and water, and then curing the silicone rubber raw material; and the silicone rubber product includes therein voids provided by breakage of the resin microballoons through application of pressure, and voids provided through evaporation of the water.

Abstract: On a second surface of a contact member opposite to a first surface in contact with an endless film, a plurality of sheets, each having a thermal conductivity in a planar direction higher than in a thickness direction and having a thickness of less than 100 ?m, are superposed.

Abstract: An image recording device includes a drive roller that conveys a recording medium by rotating, a driven roller that grasps the recording medium between it and the drive roller, a recording unit capable of recording an image on the recording medium arranged further to the downstream side than the drive roller in a first direction which is the recording media conveyance direction, and a control unit that records an image on the recording media while conveying the recording media in the first direction. The control unit, when the conveying of the recording media in the first direction stops, starts conveying the recording media in a second direction which is the reverse direction of the first direction, and stops conveying of the recording media in the second direction in a state with the image recorded on the recording media positioned between the drive roller and the driven roller.

Abstract: An image forming apparatus includes: a fixing unit configured to include at least a first and second radiation heaters capable of heating printing medium; a power supply unit configured to supply power to the first and second radiation heaters; and a controller configured to select either one of the first and second radiation heaters and control to light or turn off the selected radiation heater, wherein a heating width of the printing medium of the second radiation heater is wider than that of the first radiation heater, and the controller determines whether to preheat the second radiation heater based on the number of times of lighting of the first and second radiation heaters and controls to light and turn off the second radiation heater when the controller has determined that it is necessary to preheat the second radiation heater.

Abstract: A photovoltaic power plant includes solar cells and inverters that convert direct current generated by the solar cells to alternating current. The reactive powers generated by the inverters are based on a reactive power generated by a virtual inverter. The virtual inverter has an equivalent impedance representing the impedances of the inverters in the photovoltaic power plant. The reactive power setpoints of the inverters may be received from a local interpreter. The local interpreter may generate the reactive power setpoints from a global reactive power setpoint generated by a grid controller.

Abstract: In an image forming apparatus including a fixing unit having a film and a heater in contact with the inner surface of the film, an electrical breakdown may occur in the protection layer of the heater, when a surge voltage is applied to a power supply line connected to the heater. An arrester is provided on a power supply line connected to the heater of the image forming apparatus.

Abstract: A fixing device includes a light source that radiates a laser beam, a converging member that converges the laser beam, and a roller that is positioned so as to be in contact with the converging member and that transports a recording medium, which enters between the roller and the converging member. The converging member includes a lens that converges the laser beam, which is incident on a first surface of the lens, and emits the laser beam from a second surface of the lens and a holding member made of a material that does not transmit the laser beam, the holding member holding the lens. In the cross-sectional view perpendicular to a rotation axis of the roller, a contact surface in which the roller and the converging member are in contact with each other includes at least a portion of a surface of the holding member and the second surface.

Abstract: A fixing device includes a rotating member, a bearing and a holding member. The rotating member is configured to fix a toner image on a recording medium. The bearing is configured to support the rotating member so that the rotating member is rotatable around a rotation axis. The holding member is configured to hold the bearing. The holding member has a restricting part configured to face an outside face in the rotation axis direction of the bearing at an interval.

Abstract: According to one embodiment, a fixing device includes determination means for determining the size of a medium, heating means for including plural heat-generating members which are two-dimensionally arranged such that the heat-generating members are lined up along two parallel lines or more which are vertical to a transport direction of the medium and divided at locations on the parallel lines, and are disposed so as to come into contact with an inner side of the rotating body, and a switching unit which switches individual conduction, and heats the medium, pressing means for forming a nip by performing pressing and contact at a position of the plural heat-generating members, and heating control means for selecting a group of the heat-generating members which are lined up in the two-dimensional arrangement, conducting the selected group of the heat-generating members, and controlling the heating means.

Abstract: A method and apparatus for providing a relatively short period of time for a fuser assembly to be ready to perform a fusing operation. Included is a fusing assembly having a heat transfer member and a backup member positioned to engage the heat transfer member so as to define a fusing nip therewith; and a controller coupled to the fuser assembly, wherein during a period of time when the fuser assembly is not performing a fusing operation, the controller causes the backup member to rotate at one or more relatively slow speeds relative to a fusing speed of the fuser assembly while activating the heat transfer member. At least one of a beginning and an ending of the period of time being based upon an actual temperature in the fuser assembly.

Abstract: A heater includes a substrate, electrode portions, electrical contact portions, heat generating portions, and electroconductive line portions. The electrode portions include first group electrode portions and second group electrode portions. The electroconductive line portions include a main line portion extending from the electrical contact portions in the longitudinal direction, a first branch line portion branching from the main line portion so as to electrically connect with a first electrode portion of the first group electrode portions, and a second branch line portion branching from the main line portion so as to electrically connect with a second electrode portion of the first group electrode portions. The second electrode portion is spaced farther from the electrical contact portions than the first electrode portion in the longitudinal direction, and the electric resistance of the first branch line portion is larger than the electric resistance of the second branch line portion.

Abstract: A film application system having multiple film application stations. Each film application station has a support for an elongated plastic component (typically vinyl) having an input and an output side. A properly positioned and oriented transfer head includes a heated roller which applies heat and pressure to the elongated film as the component moves through the application station. The roller is most preferably heated with multiple IR heaters controllably energized to achieve a desired roller temperature without too large a gradient of temperature difference across the film application contact surface of the roller.

Abstract: A fixing device includes: a rotatable endless belt type fixing member; a pressurizing member that is opposed to the fixing member and rotates; and a nip forming member that is arranged inside the fixing member, and forms a nip part by contact with the pressurizing member through the fixing member. The nip forming member includes: a heat-uniformizing member having bent portions opposed to each other; a heat-insulating member arranged inside the heat-uniformizing member; a heat-absorbing member arranged on an upper surface of the heat-insulating member; and a sliding sheet that covers a nip side of the heat-uniformizing member, and is held between the bent portions of the heat-uniformizing member and the heat-insulating member. The heat-uniformizing member and the heat-insulating member are fastened to each other by fitting a fitting part formed on the heat-uniformizing member to a fitted part formed on the heat-insulating member.

Abstract: A fixing member, includes: a base layer; and a porous elastic layer provided on the base layer and configured to contain a needle-like filler. The elastic layer has a thermal conductivity, with respect to a longitudinal direction thereof, which is 6 times to 900 times a thermal conductivity with respect to a thickness direction thereof. The elastic layer has an open cell rate larger at longitudinal end portions than at a longitudinal central portion.