Abstract: An interference-reducing optoelectronic device determines the value of a current data bit in an optical data stream. A receiver receives the optical data stream, which is converted to a series of samples by a D/A converter. A set of adaptive filters, each filter corresponding to a unique possible value for one or more prior data bits, filters the series of samples utilizing variable tap coefficients to generate filtered output values. The variable tap coefficients are at least partially different than the variable tap coefficients of another adaptive filter. Comparators compare the filtered output values against filter-specific adaptive threshold values to generate tentative values for the current data bit. A delay mechanism delays a determined value for the prior data bits, and a selection mechanism determines the value of the current data bit by selecting the tentative value corresponding to the delayed determined value of the prior data bits.

Abstract: A method of reducing interference in a data stream includes filtering the data stream using a first equalizer to output a first filtered data stream. Also, the data stream is filtered using a second equalizer to create a second filtered data stream. Then, one or more error rates based on the first filtered data stream and the second filtered data stream are determined. Based at least in part on those error rates, a filtered data stream is selected from among the first filtered data stream and the second filtered data stream. A threshold value is determined, and then compared against the selected filtered data stream to generate a data bit.

Abstract: An optical transmitter of a subscriber optical interface and an optical receiver of a laser transceiver node can be designed to a frequency of data that is formatted according to a predetermined network protocol, that is encoded with a predetermined coding scheme, and that is transmitted according to a predetermined data transmit timing scheme. The frequency of data is an occupied frequency of a protocol when the data comprises a maximum number of like bits permitted by the protocol. An optical transmitter and optical receiver can be designed to a lowest occupied frequency of data that is encoded with 8B/10B encoding, and that is propagated upstream according to time division multiple access (TDMA). In this way, upstream optical communications can be maximized for speed.

Abstract: Aspects of the invention provide a method and system for synchronizing a transceiver and a framer in an optical transmission network. Subsequent to achieving synchronization of an inbound data stream, an internal framer may be adapted to inform a downstream device such as a full framer, that synchronization has already been attained. Accordingly, the downstream device may not need to perform resynchronization of the inbound data and can immediately start processing the inbound data. Advantageously, the internal framer may provide expedited error checking, handling and reporting prior to receipt of the data by the downstream device.

Abstract: Disclosed is a wavelength-division multiplexing optical transmission system in which an optical lossy medium, optical amplifiers and Raman amplifiers for compensating for loss in the optical lossy medium are cascade-connected. The system includes power-level equalizing means for equalizing optical power levels input to an optical amplifier of a succeeding stage by adjusting excitation ratio of a Raman amplifier; optical-SNR equalizing means for adjusting power levels at a transmitting end to equalize optical SNRs at a receiving end; and correction-value acquisition means for acquiring a correction value that represents an amount of change in power of each wavelength before and after optical-SNR equalization control.

Abstract: An optical binary code transmission system comprising a sender comprising: means for generating a light beam; phase-shifter means; attenuator means whereby the intensity of the lateral modes is sufficiently low for there to exist at the most only one photon in the lateral modes. The phase-shifter means of the sender impose a phase-shift that is chosen randomly to be equal either to 0 or to &pgr;/2 for a first bit value or either to &pgr;/or to 3&pgr;/2 for a second bit value, and the receiver comprising means for detecting the presence of a photon in the first lateral mode and means for detecting the presence of a photon in the second lateral mode, a first bit value being detected if the presence of a photon is detected in the first lateral mode and a second bit value being detected if the presence of a photon is detected in the second lateral mode.

Abstract: A method and apparatus is provided that yields improved performance of both single channel and WDM long-distance optical transmission systems by synchronously modulating of the transmitted signal's amplitude. An amplitude modulator receives an optical signal onto which data has been modulated at a predetermined frequency. The modulator re-modulates the amplitude of the optical signal in a continues fashion with a waveform that is periodic, whose fundamental frequency is equal to the same predetermined frequency at which the data is modulated onto the optical signal. The resulting signal (which is neither a pure NRZ or RZ signal) is more tolerant to the distortions usually found in lightwave transmission systems, thus giving superior transmission performance.

Abstract: In an adaptive optics module, wavefront sensing and data detection are implemented in a single device. For example, an optical-to-electrical converter converts a data-encoded optical beam to an intermediate electrical signal, which contains both the data encoded in the beam and also wavefront information about the beam. The data and wavefront information are later separated, for example by frequency filtering.

Abstract: A receiver for an optics telecommunication system, the receiver comprises a first receiving device and means for focusing a received light beam carrying a signal towards such first receiving device. The receiver is characterized in that it further comprises at least a second receiving device and a beam splitter for splitting the focused light beam partially towards the first receiving device and partially towards the at least second receiving device. Tipically, the first receiver device is an APD diode while the second receiver device is a PIN diode. The telecommunication system is a Free Space Optics telecommunication system. A method is also described. The invention results in a high dynamic receiver. The dynamic of the invention receiver could be up to the sum of the dynamics of receivers provided with single receiving device (APD or PIN).

Abstract: By executing a storage control program, a CPU core stores in a time series detection signals from sensors, operation signals outputted to operating members, and error detection results in a ring buffer of a RAM whenever a change occurs in any of these data. The CPU core outputs the data stored in the ring buffer to a personal computer, for example, based on an output program. Accordingly, an operator can view the history of detection signals outputted from the sensors and the operation signals outputted to the operating members up to the point that the error is generated on the CRT screen of the personal computer. The operator can easily analyze the cause of the generated error.

Abstract: An image forming apparatus of the present invention includes a paper sensor disposed in a fixing device downstream of a fixing roller pair in a direction of paper conveyance. When a jam occurs in the fixing device without the paper sensor sensing a paper sheet and if the fixing device is not pulled out of the apparatus body, it is determined that a paper left in the fixing device has not been removed. The apparatus is then inhibited from resuming its operation with a jam status being maintained.

Abstract: After a laser printer has been inactive for a long period of time, the CPU in the laser printer compares the remaining toner status determined based on a detection by a toner sensor during a warm-up operation prior for performing a printing operation and the last remaining toner status that was determined during a printing operation and that is stored in memory, and displays the larger of the two.

Abstract: A controller for a moisture adjusting device of the present invention reads out a target moisture content set in advance in a data table in accordance with a type of a planographic printing plate; determines, every predetermined control period, a moisture content of an overcoat layer (measured moisture content) based on a measured signal SW; and calculates a difference (deviation) between the measured moisture content and the target moisture content. For example, if the measured moisture content of the overcoat layer is lower than the target moisture content, the controller sets an adjusted moisture content which is higher than the measured moisture content and controls the humidity and the temperature within a humidity conditioning zone so that an interposing paper web (protective sheet material) attains the adjusted moisture content within the humidity conditioning zone.

Abstract: A method of aligning and registering duplex images using an imaging device, such as a printer including the steps of applying a first image to a first side of a media, modifying one or more imaging parameters of the imaging device after the first image is applied, and applying a second image to a second side of the media using the modified imaging parameters.

Abstract: A voltage generated when a predetermined electric current is applied to a transfer roller is measured, and a sheet transport speed is determined based on the measured voltage, a sheet type, and a sheet width. The transport speed is reduced when current leakage tends to occur due to a narrow sheet width or low resistance in the transfer roller, so that the electric charge per unit area applied to the sheet is maintained constant without increasing a transfer bias to be applied to the transfer roller.

Abstract: A method of determining when liquid electrophotographic toner has been depleted using a means of detecting signals indicating the conductivity provided by toner solids in a liquid carrier and determining their concentration in relationship to the liquid dielectric carrier solvent.

Abstract: A developing device for developing a latent image formed on an image carrier with a developing liquid includes a liquid storing section for storing the liquid consisting of a developing substance and a carrier liquid. A developer carrier deposits the liquid fed from the liquid storing section thereon. A float type liquid level sensor senses a liquid level in the liquid storing section. The liquid level sensor includes a magnetic force generating member for generating a magnetic force, a magnetic force sensing device for sensing the magnetic force, and floats movable up and down in accordance with the liquid level in the liquid storing section. A distance between the magnetic force generating member and the magnetic force sensing device varies in accordance with the movement of the floats, allowing the liquid level to be determined on the basis of the output of the magnetic force sensing device. An image forming apparatus including the developing device is also disclosed.

Abstract: An image forming apparatus is provided, which causes a large flicker not to be occurred during activating of heater lamps even if such a fixing heat roller is used as having incorporated therein a heater lamp having a larger power consumption.

Abstract: A toner fixing device that includes a fixing member and a member formed opposite the fixing member so as to form a nip between the fixing member and the opposite member. The device is supplied with power from a main power source. A charger connects an electric double-layer capacitor to the main power source. A fixing member heater is powered by the electric double-layer capacitor and heats the fixing member. A controllable switch is disposed between the electric double-layer capacitor and the fixing member heater. A fixing member temperature sensor is in contact with the fixing member. A controller controls the switch such that the electric double-layer capacitor connects to or disconnects from the heater based on comparing a temperature sensed by the fixing member temperature sensor to a temperature threshold value so that a toner image is more efficiently fixed onto a recording medium passing through the nip.

Abstract: An image fixing apparatus includes a first rotatable member for being heated by a first heater; a first temperature detecting element for detecting a temperature of the first rotatable member; first control means for controlling electric energy supply through the first heater so as to maintain a detected temperature of the first temperature detecting element at a first target temperature; a second rotatable member for being heated by the second heater, the second rotatable member constituting a fixing nip with the first rotatable member; a second temperature detecting element for detecting a temperature of the second rotatable member; a second control means for controlling electric energy supply to the second heater so as to maintain the detected temperature of the second temperature detecting element at a second target temperature; and phase control means for controlling electric energy supply phase so as to avoid overlapping of a phase of an electric power supply to the first heater and a phase of an electr

Abstract: In a fixing device of an image forming apparatus including a heating roller and a temperature detecting device spaced apart from the roller, having a first sensor for detecting the surface temperature of the roller, and a second sensor for detecting the ambient temperature, the first sensor being placed at a first position in a casing having an opening through which the heat radiation of the roller is directly incident and the second sensor being enclosed by the casing and placed at a second position to which the heat radiation of the roller is not directly incident, the temperature is calculated on the basis of the outputs of the two sensors, and the opening is disposed so as not to enter a region between the vertical plane containing the central axis of the roller and a tangential plane to the circumferential surface of the roller parallel to the vertical plane.

Abstract: Sensitive consumable components of printing devices involved in the process of transferring and fixing an image with toner onto a print medium are protected from harmful exposure to the environment and handling through designating and consistently positioning non-use regions of the components toward exposure gaps in their protective housings upon the completion of every printing process. The need for shutter mechanisms on consumable housings to cover up exposure gaps to protect consumables while in a general handling environment is therefore reduced.

Abstract: An image formation apparatus has developing agent charging means situated downstream in the direction of motion of a photosensitive drum from a transfer roller and upstream from a charging roller, for charging residual developing agent remaining on the photosensitive drum. Applying AC voltage to the charging roller is started before a portion on the face of the photosensitive drum where application of voltage to the developing agent charging means has started reaches a position of coming into contact with the charging roller, and applying AC voltage to the charging means is ended after the portion on the face of the photosensitive drum where application of voltage to the developing agent charging means has ended reaches a position of coming into contact with the charging roller. This configuration prevents adhesion of developing agent to the photosensitive drum and charging roller, avoids resultant substandard images, and provides high-quality images for prolonged periods.

Abstract: Provided is an image forming apparatus, which includes a photosensitive drum, a charging roller, a transfer roller, and a toner charging brush, reciprocates the toner charging brush in a longitudinal direction of the photosensitive drum. In the image forming apparatus, when a number of rotations per a unit time of the image bearing member is assumed to be “a” and a number of times of reciprocation per unit time of the toner charging brush is assumed to be “b”, assuming that R=b/a, R is set to be in a range of {fraction (1/25)}≦R≦3. However, R=m/n (m and n are integers of 5 or less) is excluded. Consequently, generation of a periodic attachment pattern appearing on the photosensitive drum is eliminated.

Abstract: A belt drive control device of the present invention is constructed to sense the angular displacement or the angular velocity of a driven roller, separates from the angular displacement or the angular velocity sensed an AC component having a frequency that corresponds to the periodic thickness variation of an endless belt in the circumferential direction, and then controls the rotation of a drive roller in accordance with the amplitude and phase of the AC component.

Abstract: A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, wherein the main assembly includes a motor, a main assembly side gear for receiving driving force from the motor, a hole defined by twisted surfaces, the hole being substantially coaxial with the gear, and a main assembly side grounding contact provided in the hole, the process cartridge includes an electrophotographic photosensitive drum; process mechanisms actable on the photosensitive drum; and a projection engageable with the twisted surfaces, the projection being provided at a longitudinal end of the photosensitive drum, wherein when the main assembly side gear rotates with the hole and projection engaged with each other, rotational driving force is transmitted from the gear to the photosensitive drum through engagement between the hole and the projection; and a cartridge side grounding contact electrically connected with the electrophotographic photosensitive drum for electrically grounding the

Abstract: An image forming apparatus has a developing device containing therein a developer including a toner and a carrier, the developing device having a first chamber for developing an electrostatic image formed on an image bearing member, and a second chamber constituting a developer circulating route between it and the first chamber, a carrying member rotatably provided in the second chamber for carrying the developer, a rotary member holding the developing device and rotatable in a route including a developing position, a supplying device for supplying the developer to the developing device when at the developing position, an opening provided in the second chamber for outwardly discharging therethrough any excess developer resulting from the supply of the developer, and a wall portion provided in the second chamber for suppressing the developer flowing out through the opening with the rotation of the rotary member.

Abstract: An apparatus for assisting in the removal or waste or excess ink and a method for disposal of ink from electrophotographic printers comprises providing electrophotographic ink from a source, combining the ink with an absorbable material in a container to form a solid within the container, and closing the container so that the container with the solid inside may be disposed of without ink flowing from the container.

Abstract: A toner supply roll free from occurrence of an imaging failure. The toner supply roll comprises a shaft (1) and a urethane foam layer (2) provided on an outer peripheral surface of the shaft (1), wherein when the urethane foam layer is compressed to a depth of 1 mm from an outermost surface thereof during compression thereof to a depth of 2 mm, a stress F0 occurs in the urethane foam layer and when the urethane foam layer is decompressed to a depth of 1 mm after the compression thereof to a depth of 2 mm, a stress F1 occurs in the urethane foam layer, the urethane foam layer satisfies a relation represented by the following expression (1) at a temperature of 23±° C.

Abstract: Printers wherein a stub pulley gripping the conveyor belt from below changes contact force, a first register error occurs; and due to change of the spacing between the image lines on the sheet change, a second register error occurs. To prevent the first register error, time-lags of the first start signals (START OF FRAME) for the application of image lines are changed; and to prevent a second register error, time-lags of the second start signals (START OF LINE) for the application of image frames or frames are changed.

Abstract: An electrophotographic imaging apparatus has a first toner accepting layer and an intermediate transfer member. The first toner accepting layer is positioned in electrical contact with a) a charge provider, b) an irradiation source that activates photoconductivity in the first toner accepting layer, and b) at least one toner applicator, so that a first toner image can be formed on the first toner accepting layer. The first toner layer is movable (after interaction with a), b) and c)) into contact with the intermediate transfer layer from which the first toner image can be transferred to an image bearing member. The intermediate transfer member comprises a non-conductive flexible film layer, a layer of an electrically conductive material affixed to a first surface of the non-conductive flexible film layer, and the electrically conductive material layer has an electrically resistive polymeric coating thereon.

Abstract: An image forming apparatus includes a fusing device comprising of a fuser roller, which fuses toner on a sheet of paper, and a pressure roller getting into contact with the fuser roller to form a nip between them where the sheet of paper passes through. A fuser-side external heat roller having an internal heater comes into contact with the fuser roller. A pressure-side heat roller having an internal heater comes into contact with the pressure roller. The fuser roller and the pressure roller have approximately same outer diameter and are both composed of an elastic material. An approximate radius of the nip formed between the two rollers is set to be equal to or larger than a radius of the fuser roller or the pressure roller. In another construction, the rollers are different in outer diameter, but each composed of an elastic material and a nip between them is set to be equal to or larger than 1.25 times as large as the radius of either the fuser roller or the pressure roller with smaller outer diameter.

Abstract: To produce an electrophotographic print with high image quality and good texture and with minimized curling, a method produces an electrophotographic print by fixing a toner image on an image bearing surface of an electrophotographic image-receiving sheet using a belt fixing and smoothing apparatus including a hot-pressing device, a belt member, a cooling device, and a cooling-releasing section, smoothing the toner image, and releasing the sheet, in which an amount of curling C (mm) of the electrophotographic print is controlled to be more than-0.10 L and less than +0.05 L, wherein L is a length (mm) of a short side of the electrophotographic print; a negative value (−) of the amount of curling C means that the electrophotographic print curls toward its back side not bearing the image; and a positive value (+) of the amount of curling C means that the electrophotographic print curls toward its image-bearing surface.

Abstract: An image stripping apparatus includes: a stripping roller which strips an image forming material from an image recording medium by contacting the image forming material on the image recording medium; a cleaning roller for removing, from the stripping roller, the image forming material which has been transferred to the stripping roller; and a cleaning blade stripping the image forming material from the cleaning roller. The stripping roller has a surface layer made of a material having affinity and releasability with respect to the image forming material and the image recording medium. Thus, the stripping roller exhibits peelability required for stripping of the image forming material from the image recording medium and releasability required for removal of a transferred image forming material from the stripping roller.

Abstract: A conductive brush comprises a substrate of a belt shape and a plurality of pile yarns extended from the substrate. The substrate and the pile yarns are formed of a same kind of synthetic resin and the pile yarns are adhered to the substrate by a ultrasonic wave. Conductivity is applied to at least a part of the substrate and the pile yarns by including a conductive material in the synthetic resin.

Abstract: Printers such as electrophotographic printers are provided with multipaths for facilitating different kinds of printing operations (simplex, duplex). The multipaths are utilized through use of a sheet diverter and a sheet pickup mechanism.

Abstract: A printer has a main body, a back delivery unit, and a media turnover guide that is detachably or tiltably mounted on the main body. When mounted in an operable position, the media turnover guide delivers printed media face-down onto the top cover of the main body, where they can be easily retrieved. When the media turnover guide is mounted in an inoperable position or is detached, the printed media are delivered face-up to the back delivery unit. The media turnover guide may have a simple structure with a curved surface formed by a back wall and roof. The printer may also have a stacker for stacking the printed media delivered face-down.

Abstract: A personal digital assistant (901) stores personal information in an electronic and transportable from. The digital assistant includes a body section (902) connected to a display screen (904). The body (902) houses a memory, control circuitry for operating the personal digital assistant and an internal printer (500) for printing stored and/or displayed information. The printer (500) has a removable ink/print media cartridge (504) disposed in the hinge joint (905) connecting the body section (902) and the display screen (904).

Abstract: A thermal transfer overcoating technology for reducing overcoat tags. Skewing the interface between a carrier ribbon to coated document at the peeling of the carrier from the coated document concentrates the forces at the interface to a smaller region of the document edge. Moreover, tensioning the document at the interface changes the forces at the interface from peeling type to tensile type.

Abstract: A standard keyboard includes a plurality of function keys having a second function hierarchy defined to support multimedia functions, and a setting key adapted to work with the function keys to form different key combinations. The function keys are electrically connected to a scan matrix inside the keyboard to enable conversion of a state flag of a micro central processing unit of the keyboard through interlocking of two keys and change of scan codes of the function keys, so that application programs obtained from database and application program interface under Windows may be used to run a selected multimedia function by manipulating the function keys and the setting key directly on the standard keyboard without the need of adding any new key thereto. And, an actual state of the switched keyboard is indicated by a light-emitting diode provided on the keyboard.

Abstract: A keyboard arrangement that assigns alphanumeric and special character symbols to keys based upon the shapes of the symbols in order to facilitate learning to type. Attribute classes are defined according to the number, position, direction, or contours of the line segments that comprise the symbols. As an aid to memorization of a keyboard arrangement, symbols are assigned to keys such that a substantial number of keys in a column of keys belong to the same attribute class. To convert any prior art or other kind of electronic keyboard to a keyboard arrangement within the scope of the invention, hardware and/or software components are provided that reassign the keys so that substantially all keys within the same column will correspond to symbols within the same attribute class.

Abstract: A writing implement ensuring a non-slip grip on a barrel when it is grasped and a good fit between the grip and fingers, thus providing a comfortable grasping touch. In the writing implement having a grip made of elastic resin material fitted on an outer circumferential surface in a grasped area of a barrel, the grip is formed into a cylinder whose inner circumferential surface is fitted on the outer circumferential surface in the grasped area of the barrel, with hollows axially passing through a peripheral wall of the cylinder and with the plurality of hollows circumferentially arranged in parallel, and the grip is fitted on the barrel so as to form a vent passage for communication between the hollows and the outside at an end of the grip.

Abstract: A holder includes a main body having two ends that hold cosmetic tools substantially parallel to a central axis of the tool, and it can also include caps for placement over the cosmetic tools. The caps can have a reflective outer surface for use as a mirror. The ends can be configured to hold cosmetic tools having variable dimensions by using a chuck mechanism or a compressible material in the ends of the holder. With cosmetic tools held in place and the caps installed, the holder provides for a way to carry and use a variety of cosmetic tools such as lipstick, lip liner, eye liner, eye shadow, or other tools.

Abstract: A unique writing instrument is described. Preferred is a writing instrument with an application of decorative beads to the surface of the instrument or within the clear barrel of a writing instrument. A method of producing the beaded writing instrument is also described.

Abstract: A stylized writing instrument is disclosed which is shaped like a proprietary and/or familiar object. In general, embodiments of the invention include a housing shaped like the proprietary and/or familiar object, a writing implement, and internal mechanisms provided within the housing for extending the writing implement from, and retracting the writing implement into, the housing. The internal mechanisms may comprise a wide variety of actuation systems for extending and retracting the writing implement, including a cam actuation assembly, an edge slide actuation assembly, a gravity actuation assembly, a pressure actuation assembly and a push button actuation assembly.

Abstract: Cleaning compositions, pads, wipes, and implements provide effective cleaning of hard surfaces.

Abstract: An applicator for an anti-microbial solution includes an aerosol container and an applicator pad assembly having a hollow arm. The hollow arm has a proximal end attached to an aerosol cap and a distal end having a flanged arm plate to receive a foam applicator pad. The aerosol cap is removably attached to the aerosol container. A solution flow control is in communication with the aerosol container for selectively dispensing the anti-microbial solution. The aerosol container holds the anti-microbial solution under pressure and flow is controlled by a pressure-sensitive flow control tab. The control tab activates the flow of the anti-microbial solution from the aerosol container through the hollow handle to the foam pad and then to the patient. The control tab may be actuated by touch or by pressure applied to the applicator pad. An optional flow control feature, in addition to the control tab, is a slit formed in the foam pad.

Abstract: A device for sweeping a substantially horizontal surface is provided which includes a broom having a handle and a head, a valve disposed on the device, and a spray bar movably disposed on the head for directionally spraying a liquid that is supplied to the valve, wherein the valve regulates the pressure of liquid sprayed by the spray bar. The valve can be spring-loaded and/or hand-controlled. The device may include tubing between the valve and the spray bar, which tubing may be positioned internal to the handle or external to the handle. The handle may be used to convey liquid, such as that from a garden hose, from the valve to the spray bar. In an embodiment, the head may include water channels and the spray bar may be made integral to the head. The spray bar may oscillate and may take a variety of shapes, including elliptical, u-shaped and straight shapes. The device may further include a reservoir for holding an agent for treating the horizontal surface.

Abstract: A binder that can be opened/closed relatively easily by manually handling the tops of binding rings includes a holding member having a sufficient length to allow binding rings to be arranged with a spacing therebetween, and an operating member fixed movably to the inner side of the holding member such that the binding rings anchored to the surface thereof are fixed to the holding member. The operating member includes a pair of operating pieces movable along the longitudinal direction of the holding member within the holding member, and a pivot shaft formed along the abutting edges of the pair of operating pieces. Further, an opening/closing member is provided to move the operating pieces within the holding member in the longitudinal direction of the holding member while rotating the pair operating pieces around the pivot shaft in the directions to open the binding rings.

Abstract: A plug-in coupling for removably interconnecting a first structural member and a second structural member comprises a resiliently deformable female coupling part adapted to be inserted into a socket at the first structural member such that it is retained therein. The female coupling part comprises a ball-shaped cup, an intermediate annular wall integral with said ball-shaped cup and serving as a guide portion, and a tubular external wall integral with said annular intermediate wall. The external wall surrounds at least a part of the ball-shaped cup in spaced relation thereto and engages a peripheral wall of the socket when the female coupling part is inserted into the socket. A male coupling part comprises a ball-shaped head and a fixing portion for securing the male coupling part to the second structural member. The intermediate annular wall of the female coupling part is of an undulated shape at least in a certain area thereof.