world news

Earphone device

An earphone device includes a housing having a driver unit, and a sound guide tube mounted on a front surface of the housing to protrude from the front surface, in which the sound guide tube is disposed at a position deviated from a center position of the housing.




world news

Saddle-ride type vehicle

A saddle-ride type vehicle which includes catalyst devices in left and right exhaust flow passages can suppress effect of the catalyst devices on the reach to the ground even if the sizes of catalysts are large. The vehicle includes: exhaust flow passages connected to a multi-cylinder engine and disposed independently on left and right sides of a vehicle body; a first catalyst device provided in a middle of the left exhaust flow passage; a second catalyst device provided in a middle of the right exhaust flow passage; a swing arm pivotally supporting a rear wheel such that the rear wheel is swingable, the saddle-ride type vehicle includes silencers connected to portions of the exhaust flow passages downstream of the first catalyst device and the second catalyst device, and the first catalyst device and the second catalyst device are arranged side by side below the swing arm.




world news

Anchoring of septums in acoustic honeycomb

A honeycomb structure dial includes cells in which septums are located to provide acoustic dampening. The cells are formed by at least our walls wherein at least two of the walls are substantially parallel to each other. The septums include warp fibers and weft fibers that are substantially perpendicular to each other. The septums are oriented in the honeycomb cells such that the weft fibers and/or warp fibers are substantially perpendicular to the parallel walls.




world news

Deghosting using measurement data from seismic sensors

Measurement data is received from first and second seismic sensors, where the first and second seismic sensors are oriented in opposite directions. Each of the first and second seismic sensors has a sensing element responsive to pressure and particle motion. The signals can be combined to remove the particle motion component of the measurement data and obtain pressure-only data. Alternatively, the signals can be combined to deghost the received measurement data.




world news

Bone conduction device having an integrated housing and vibrator mass

A bone conduction hearing aid device comprising a vibrator configured to vibrate in response to sound signals received by the device. The device further comprises a housing mass forming a housing for one or more operational components of the device, wherein the housing mass is attached to the vibrator so as to move in response to the vibration. The device also comprises a coupling configured to attach the device to a recipient so as to deliver the generated mechanical to the recipient's skull.




world news

Muffler equipped with catalytic converter

A muffler is capable of stably supporting the catalytic converter in a muffler box with a pair of partitions. The muffler box includes first and second box halves joined together with open surfaces thereof abutting each other, and first and second partition plates interposed between the first and second box halves and overlapping each other to separate inside of the muffler box into first and second silencing chambers and define a third silencing chamber between the first and second partition plates, one end opening of a cylindrical holding tube housing and holding the catalytic converter is connected to the exhaust inlet pipe, the pair of partition plates support the holding tube in such a way as to wrap an outer peripheral surface thereof, and another end opening of the holding tube is communicated with the exhaust outlet pipe through the first, second, and third silencing chambers in this order.




world news

Adjustable sound-absorbing panel and assembly of adjustable sound-absorbing panels

A directable sound-absorbing panel comprising a sound-absorbing panel, a fixing member which can be fixed to said sound-absorbing panel, an arm and an articulated joint between said fixing member and said arm, is described. An assembly of directable sound-absorbing panels is also described, said assembly comprising a plurality of sound-absorbing panels, a corresponding plurality of fixing members, a corresponding plurality of arms, a corresponding plurality of articulated joints between each arm and each fixing member, and a fixing bar to which at least a part of said plurality of arms is fixed.




world news

Image forming apparatus having a member for forming an image

An image forming apparatus includes a drive source configured to drive a member for forming an image on a recording material, a frame of the image forming apparatus including a planar portion on which the drive source is mounted, wherein a plurality of through holes is formed on the entire planar portion of the frame, and a sheet member configured to cover at least a portion of the plurality of through holes.




world news

Electro-pneumatic sound alarm

Herein described is an electro-pneumatic sound alarm, to be fitted on a two or four wheeled vehicle, constituted by an electro-compressor (2), having the function of drawing atmospheric air, compressing it and conveying it to an acoustic group (3). Such sound alarm (1) is characterized in that the electro-compressor (2) and the acoustic group (3) are mutually held by means of removable fit-coupling; furthermore, the coupling elements are rigid and integral with the aforementioned two components (FIG. 1).




world news

Systems and methods for optimizing low frequency output from airgun source arrays

Systems and methods for optimizing low frequency output of marine sources are described. The marine source arrangements and associated methods disclosed herein seek to fully frequency lock bubbles emitted by airguns in close proximity to one another. In this manner, larger effective bubble volumes can be achieved, thus increasing low frequency output.




world news

Audio performance system

An audio performance system for use during an event including a shipping container containing at least a first electroacoustic device. A lifting device forms a first portion of the shipping container, the lifting device configured to movably secure the first electroacoustic device between a first position for transport of the container and a second position for the event. A second portion of the shipping container is configured to be manually removable. A third portion of the shipping container is configured to positionably secure a second electroacoustic device for the event.




world news

Hearing assistance device and method

A device and attendant method to assist the hearing of a user by being removably connected to and disposing a user's ear in an enhanced hearing orientation. The device includes an elongated base, which may be disposable, and has a sufficient length to be disposed in an operative position behind the user's ear. Opposite ends of the base include an adhesive material secured to a common side thereof, wherein different ones of said opposite ends are respectively disposed and maintained in confronting engagement with a rear surface of the ear and adjacently disposed portion of the user's head. The base further includes biasing capabilities disposed and structured to exert a sufficient, forwardly and outwardly directed force on the user's ear to dispose and maintain it in the enhanced hearing orientation, when the base is in the operative position.




world news

Speaker diaphragm, speaker, and production method of speaker diaphragm

A speaker diaphragm contains a material obtained by adding a cycloolefin polymer resin to a carbon fiber-reinforced liquid crystal polymer. The speaker diaphragm having high sound velocity, a speaker, and a production method of the speaker diaphragm can thereby be obtained.




world news

Bonding structure of diaphragm for microspeaker

The present invention relates to an assembly structure of a diaphragm for a microspeaker. The present invention discloses a bonding structure of a diaphragm for a microspeaker, the boding structure comprising: a suspension including a central portion, an outer peripheral portion, and a connecting portion connecting the central portion and the outer peripheral portion; and a side diaphragm including an inner peripheral portion and an outer peripheral portion, which are attached to the central portion and outer peripheral portion of the suspension, respectively, and a dome portion, which projects between the inner peripheral portion and the outer peripheral portion, wherein the suspension and the side diaphragm are attached by thermal compression.




world news

Protective enclosure for enhancing sound from an electronic device

A protective enclosure for an electronic device can include a waveguide to direct and enhance sound waves emanating from a speaker of an electronic device when installed in the protective enclosure. The waveguide can include a first end and a second end. The first end of the waveguide can be located proximate the speaker of the electronic device. The waveguide can increase in cross-sectional area between the first end and the second end.




world news

Synthetic jet muffler

A synthetic jet muffler includes an exit end, a propagation path for conducting a first sound wave emitted by a synthetic jet generator to the exit end, and a shroud for conducting a second sound wave emitted from the synthetic jet generator in a direction opposite to the first sound wave to the exit end, wherein the shroud is disposed so that the first and second sound waves travel different distances to effect noise cancellation at the exit end.




world news

Acoustic container

Methods and devices are disclosed for a gaseous liquid to audibly deform the shape of a closed container. One embodiment includes pushing inward to depress a plurality of deformations integral with an exterior of the plastic container having a bottom, a top, the exterior, and an interior, wherein the top is at least partially opened. Further, the method includes sealing, subsequent to the depressing, the top to close the plastic container. Further still, the method includes pushing outward, subsequent to the sealing, by carbonation from a carbonated liquid contained within the interior, on the plurality of deformations. Yet further, the method includes deforming, by the pushing outward, at least two of the plurality of deformations to displaced positions. The method also includes creating two or more sounds and/or movement by the deforming.




world news

Coating and its manufacturing process

A coating composition has a natural fiber-bearing dry matter mixture, as well as cellular plastic grains, mixed into water. By spreading this composition onto any base, particularly by spraying, and by hardening it, particularly through drying, the coating is formed from the coating composition, which coating provides extremely good acoustic properties. If a special fiber base plate based on chemical pulp is used as the base of the coating, the plate-like acoustic element is obtained.




world news

Sound-absorbing member lamination structure

There is provided a sound absorbing member lamination structure in which the functions by the sound field adjustment can effectively be achieved by preventing the sound reflection against an intension of design in a boundary between the sound absorbing member and the other layer, when the sound absorbing member and the other layer are laminated into a united body. When the sound absorbing member and the other layer are placed in a stacked state, they are bonded with the use of a pressure-sensitive adhesive, so that the sound absorbing member and the other layer are combined together, with the pressure-sensitive adhesive kept uncured in a stacked state of the sound absorbing member and the other layer. Thus, such an uncured pressure-sensitive adhesive does not become a reflection portion of a sound. It is therefore possible to cause the sound to pass through appropriately the boundary between the respective layers.




world news

Enhanced, lightweight acoustic scrim barrier

An enhanced, lightweight acoustic absorber is provided. The acoustic absorber is bounded by the at least one scrim layer without need for additional layers, such as melt-blown or nonwoven layers. The at least one scrim layer includes at least one non-planar, folded scrim layer bonded to itself or another scrim layer to form a plurality of air spaces between folded portions of the at least one scrim layer. The at least one scrim layer establishes a thickness of the acoustic absorber extending across opposite exposed sides of the acoustic absorber.




world news

Acoustic sensor assembly

An acoustic sensor is configured to provide accurate and robust measurement of bodily sounds under a variety of conditions, such as in noisy environments or in situations in which stress, strain, or movement may be imparted onto a sensor with respect to a patient. Embodiments of the sensor provide a conformable electrical shielding, as well as improved acoustic and mechanical coupling between the sensor and the measurement site.




world news

Vertical line array loudspeaker mounting and adjustment system

The invention relates to a loudspeaker mounting and adjustment system and method for installing and operating a professional audio system used in a stadium, concert hall or the like. The system comprises a vertical array of loudspeaker cabinets that can be suspended from a ceiling and that enables the horizontal and vertical angle of the sound dispersion field to be adjusted remotely and/or automatically while the system is suspended. Each loudspeaker cabinet is connected to a vertically adjacent loudspeaker cabinet via a pair of levers located on either side of the cabinet that control the angle between adjacent loudspeaker cabinets. A linear actuator is connected to each lever for controlling the lever position. Each loudspeaker cabinet also comprises a waveguide with at least one actuator for modifying the waveguide angle and thus the horizontal angle of the sound dispersion field.




world news

Protective enclosure for enhancing sound from an electronic device

A protective enclosure for an electronic device can include a waveguide to direct and enhance sound waves emanating from a speaker of an electronic device when installed in the protective enclosure. The waveguide can include a first end and a second end. The first end of the waveguide can be located proximate the speaker of the electronic device. The waveguide can increase in cross-sectional area between the first end and the second end. The second end of the waveguide can be located proximate a front surface of the protective enclosure and can direct sound waves toward a user of the electronic device.




world news

Sound suppressor device for an air drying unit of a compressed-air supply system

A sound suppressor device for an air drying unit of a compressed-air supply system having a sound suppressor housing on which is arranged an inlet opening for the supply of condensate-laden compressed air to be discharged from the air drying unit and at least one outlet opening for the discharge of the condensate-laden compressed air to the outside, wherein the inlet opening issues into at least one pre-chamber of the sound suppressor housing, which pre-chamber issues into post-chambers which are connected in parallel and which are arranged around a heating rod arranged centrally in the sound suppressor housing.




world news

Sound absorption material and method of manufacturing sound absorption material

Described embodiments relate to a method of manufacturing a sound absorption material. The method comprises: forming a low density fibrous web to act as porous bulk absorber, the fibrous web containing a proportion of bi-components fibers, each bi-component fiber having a core material and a sheath material around the core material; applying a thin facing later to the low density fibrous web, wherein the facing layer is adhesively compatible with the sheath material; heating the fibrous web to a temperature sufficient to soften the sheath material of at least some of the bi-component fibers; and pressing the facing layer and fibrous web together under low pressure such that at least part of the facing layer contacts the softened sheath material of at least some of the bi-component fibers to form an adhesive bond between the facing layer and the fibrous web.




world news

Optimized pattern of a damping layer for wall, floor, and ceiling constructions

An acoustic damping article includes a substrate, wherein the substrate has a surface area S. The acoustic composition further includes a polymer resin. The polymer resin coats partially the surface area with a set of areas. The ratio of the coated areas over the surface area S is less than 1 and the polymer resin coverage is not greater than about 500 g/m2.




world news

Garnish double ring for speaker seal

An adaptive speaker panel is provided. The speaker panel can have a speaker opening and a pair of concentric sealing ribs proximate to the speaker opening, the pair of sealing ribs having a first sealing rib and a second sealing rib towards a center of the speaker opening from the first sealing rib. The first sealing rib is first sealing rib dimensioned to seal against a first speaker basket and the second sealing rib dimensioned to seal against a second speaker basket that is smaller than the first speaker basket. Also, the first sealing rib and the second sealing rib are operatively arranged such that without modification to the speaker panel the first speaker basket or the second speaker basket can be attached to and sealed against the panel.




world news

Neutrally-buoyant borehole investigation tools and methods

Neutrally-buoyant tools for seismic data collection are provided that may range from several hundred meters to several kilometers in length and have integrated sensors which move along with the borehole fluid in response to a passing seismic wave. The disclosure also provides methods of deploying neutrally-buoyant tools, which includes using a tractor, adding a weight or both to the tool in order to overcome the difficulty of lowering a neutrally buoyant tool into a borehole, and optionally occasionally clamping the tool to the borehole to alleviate tension in the tool. This disclosure also provides methods of acquiring seismic data, which involves positioning a neutrally-buoyant tool in a borehole such that the tool is able to move relatively freely along with the borehole fluid in response to a seismic wave passing through the fluid, firing a seismic source, and using the sensors to collect seismic data generated thereby.




world news

Broadband flex joint isolator for acoustic tools

An acoustic attenuator assembly for an acoustic tool for performing acoustic investigation of a subterranean formation is disclosed. The acoustic attenuator assembly includes a first end portion (205) and a second end portion (210) having a bore therethough to enable passage of an electrical line. The acoustic attenuator assembly further includes a fiber portion (230) disposed between the first and second end portion so that the fiber portion attenuates at least a portion of acoustic energy when the acoustic energy is received by one or both of the first (205) and second (210) end portions. The fiber portion (230) includes a continuous flexible portion that allows relative deflection of the first (205) and second (210) end portions.




world news

Sound absorbing body and printing device

A sound absorbing body includes a fibrillated part fibrillated into fiber form, and an unfibrillated part that is not fibrillated into fiber form. The unfibrillated part is dispersed inside the single sound absorbing body.




world news

Sound absorbing body and printing device

A printing device includes a case, a printing unit arranged inside the case, and a sound absorbing body arranged inside the case. The sound absorbing body has parts with different densities including a dense part with a higher density and a non-dense part with a lower density. The non-dense part includes a fibrillated part that is fibrillated into fiber form, and an unfibrillated part that is not fibrillated into fiber form.




world news

Sound absorbing body and electronic device

A sound absorbing body includes parts of different densities including a plurality of non-dense parts of lower density and a plurality of dense parts of higher density. The non-dense parts and the dense parts are alternately laminated obliquely.




world news

Firearm suppressor

Embodiments of a firearm suppressor are disclosed herein. According to various embodiments, the firearm suppressor can include a housing. The housing can include an outer surface, an inner cavity, and an attachment mechanism that attaches the housing to a barrel of a firearm. The inner cavity can accommodate a baffle. The firearm suppressor also can include a lighting attachment. The lighting attachment can include a power source and a lighting mechanism.




world news

Firearm silencer

A firearm silencer for suppressing sound intensity generated by the discharge of a firearm, the discharge generating propellant gases, is disclosed. The firearm silencer includes an outer tube. The outer tube is generally hollow and generally cylindrical. The firearm silencer also includes a monolithic baffle stack inserted within the outer tube, and the monolithic baffle stack positions and constrains the outer tube coaxially and axially at a first and second end of the outer tube relative to a first and second end of the monolithic baffle stack using seals and retention seals, with such seals also providing an atmospheric sealing function. The monolithic baffle stack includes a first end that includes a first hole. The monolithic baffle stack also includes a second end that includes a second hole. The second end is located opposite the first end of the monolithic baffle stack. The monolithic baffle stack further includes a plurality of chambers in fluid communication with each other via a plurality of holes and annular void. The monolithic baffle stack also includes a plurality of recesses in fluid communication with the plurality of chambers via a plurality of through holes and annular void. The monolithic baffle stack also further includes plurality of protrusions and plurality of lands within the plurality of chambers where said lands and plurality of holes in chambers form an equivalent cylindrical bore dimension. Moreover, the firearm silencer includes a path extending from the first hole adjacent the first end of the monolithic baffle stack through the first hole adjacent the second end of the monolithic baffle stack. The plurality of chambers, the plurality of recesses, the plurality of through holes, the plurality of protrusions, the plurality of lands, the annular void, and the path are configured to allow propellant gases to travel there through.




world news

Hybrid silencer with gas-liquid separating function in fuel cell system

A hybrid silencer in a fuel cell system includes an expansion chamber connected to a predetermined apparatus of the fuel cell system, where the expansion chamber reduces acoustic noise of a fluid discharged from the predetermined apparatus, a water-absorber disposed inside the expansion chamber, where the water-absorber absorbs a liquid component of a fluid which flows into the expansion chamber; and a perforated silencer which discharges the fluid from which the liquid component is removed by the water-absorber while reducing acoustic noise of the fluid discharged therefrom.




world news

Acoustic cover assembly

An acoustic protective cover assembly comprising a porous membrane and an acoustic gasket is disclosed. The porous membrane is bonded to the acoustic gasket at a peripheral region, the membrane is left unhanded at a central region. The acoustic gasket comprises a composite of a porous polytetrafluoroethylene (PTFE) polymer matrix of polymeric nodes interconnected by fibrils, resilient expandable microspheres embedded within the matrix.




world news

Thermal-acoustic sections for an aircraft

Embodiments of thermal-acoustic sections for an aircraft for reducing noise along an acoustic path produced from an acoustic source are provided herein. The thermal-acoustic section comprises a first porous layer having a first characteristic acoustic impedance. A second porous layer is disposed adjacent to the first porous layer and has a second characteristic acoustic impedance that is greater than the first characteristic acoustic impedance. The thermal-acoustic section is configured to be positioned along the acoustic path such that at least a portion of the noise from the acoustic source is directed through the first porous layer to the second porous layer to promote absorption of the noise.




world news

Coaxial passive radiation monomer

A coaxial passive radiation monomer apparatus is disclosed. In accordance with an aspect of the present disclosure, there is disclosed a dynamic speaker monomer combined with a passive radiator in a single unitary structure located in spatial proximity with respect to one another to thereby and further comprising an elastic material at the base of the speaker assembly for enhanced and optimized resonance frequencies for the active and passive components of the overall device.




world news

Method for optimizing performance of a multi-transducer earpiece and a multi-transducer earpiece

There is provided a method for optimizing performance of a multi-transducer earpiece, where the multi-transducer earpiece includes a perpendicular flange that partitions the cross sectional area of the acoustic delivery channel in a manner where mixing of signals from both the high frequency transducer and the mid/low frequency transducer is carried out in the ear canal of a user during reproduction of audio signals.




world news

Gun dog training tool and method

A gundog training tool prevents gun shyness by gradually allowing a pup to adapt to the sound of a gunshot. A pop gun shoots treats upon creating a simulated gunshot so that the dog grows used to the sound of a gunshot and creates positive reinforcement rewarded by the treat. As the pup learns, a charge in a housing is introduced to provide a simulated gunshot that expels a treat that trains the dog to feel excitement at the sound and smell of a gunshot. The size of the charge adjusts to create louder simulated gunshots as the pup learns so that the pup is prepared for introduction to actual gunshots, such as from a shotgun shooting at a bird.




world news

Tethering stakes

Tethering stakes of the nature intended to be pounded flush with or below ground level. Certain of the tethering stakes include a cap on the pounding end which is adapted for ease of placement and release of a tethering line. Accordingly, the tethering line can be removed from the stake when it is to be pounded into the ground and then engaged with the stake only when tethering is desired. Certain of the embodiments include caps having uniquely shaped apertures for securing the tethering line. Another includes an aperture in communication with an aperture in the stake such that a lead cable or the like may be moved out of the way when the stake is pounded into the ground and may be fully received within the stake when tethering is not desired. Another embodiment employs a coupler passing through an aperture directly beneath the pounding surface to facilitate ease of attachment and removal of the tethering line.




world news

Tethering stake

A tethering stake includes a rod having a point at one end thereof and a driving cap at an opposite end. A collar is fixed to the rod adjacent to and spaced from the driving cap, thus providing a neck to receive a tether line or chain. A cap cover is slidingly received upon the rod and is adapted to be selectively engaged with the collar. The cap cover includes a central circular aperture with a radial slot extending therefrom. The centrally positioned aperture and slot allow the cover to assume a position substantially parallel to the rod during shipment and storage, while allowing it to take a position substantially orthogonal to the rod when the rod is driven into the ground.




world news

Dog vest with integrated flexible bumper

A vest can be worn by a visually impaired pet, such as a dog, to help the pet navigate without hurting themselves by bumping into walls or objects. The vest includes plastic tubing with wire woven therein. The tubing is shaped like a halo that surrounds the front and sides of the pet's head. Should the visually impaired pet run into an object or wall, the halo will hit before their head hits and the pet will turn away before injuring themselves. The vest can be worn about their torso with their front legs fitting in leg holes of the vest. The vest can be adjustable to fit a range of pet sizes. The halo can also be adjustable to provide safe navigation of the pet. Typically, the vest is designed for dogs, but other visually impaired pets or animals may benefit by using the vest.




world news

Animal identification system and related method

A system for identifying an animal comprises an identification tag/transponder device surgically implanted into tissue of the animal and a scanning unit. As the animal passes in a vicinity of a scanning unit, the system causes the identification device to send a signal to a receiving portion of the scanning unit, and processes the signal, and identifies the animal from the signal. The system is of particular benefit to veterinary surgeries in assisting their smooth operation.




world news

Quick release horse lead clip assembly

A horse lead clip assembly for connection between horse tack that includes an upper clasp section with a hook and bolt closure and a lower quick detachable end that allows for the replacement of a broken clip with a new clip portion when excess stress is placed upon the hook of the clasping section. The assembly further includes a sleeve that when actuated laterally, allows for the introduction or removal of a new clasp section from the receiving end of the detachable portion. The assembly provides easy replacement of a broken clip, prevents the user from discarding the rope due to the broken clip, and allows a user to leave the clip hooked on one object while detaching it from the other.




world news

Modular fire prevention flooring

A modular fire prevention flooring system includes a plurality of fire prevention flooring planks. Each plank is generally tubular and forms a drain channel. Fluids spilled onto the upper surface of the flooring system may drain through a plurality of drain holes formed in the upper surface of the planks. The planks may further include a metal filler positioned within the drain channels to stop combustion of burning fluids spilled into the drain channels. The metal filler may break up burning liquids and remove heat therefrom. In some embodiments, a purging fluid may be flowed through the planks to purge any spilled fluids therefrom.




world news

Method for using a rat guard

A rat guard and method utilizing a flexible shield affixed to a plastic sheath positioned on a mooring line to prevent entry onto or exit from the ship by vermin. An electric grid is positioned on an insulated pad on the sheath which is electrically connected to the shield for receiving power from an acoustical generator also connected to the shield and spaced therefrom. The acoustical generator directs ultrasonic acoustic signals in a variable frequency range toward the shield to frighten rats or other vermin therefrom. Should the acoustical signals not deter the vermin, the electric grid will shock any vermin making contact therewith to cause harm and frighten. The shield provides another obstacle to prevent advancement and is affixed to the sheath on the mooring line. The shield is flexible and remains in place during high winds and other adverse weather conditions.




world news

Absorbent composition for mitigating fecal odor

The present invention is directed towards an absorbent composition and its method of production and use. More specifically, the present invention relates to an absorbent composition comprising a liquid absorbing material, at least one alkaline earth metal peroxide, and an acidic material. The acid maintains a high hydrogen peroxide release profile under acidic conditions, such that the composition is found surprisingly effective in mitigating fecal odor.




world news

Lightweight clumping animal litter and method thereof

Animal litter having up to a sixty percent reduction in bulk density can be produced by combining flat-shaped cellulosic materials and sodium bentonite clay. Not only is the resulting litter lighter, but it also maintains a high clump strength as compared to clay-based animal litters that contain greater than ninety percent by weight sodium bentonite clay.




world news

Animal keeping installation

Animal keeping installation comprising a floor (11) provided with a mat (12) on which the animal treads when setting foot on the floor (11) and which mat (12) is arranged to be intermittently propelled by a drive roll (13) placed internally in relation to the mat (12), wherein the drive roll (13) is connected to and mounted in bearing journals (15) for rotation about its center axis in a pendulum (14) which allows the drive roll (13), on the one hand, to bear against the inner side of the mat (12) and, on the other hand, to be released from the said bearing contact in dependence on the position of the pendulum (14), and wherein the drive roll (13) is connected to a drive member (18, 19, 51, 62) for driving the roll (13) at least into a position where the drive roll (13) bears against the mat (12).