Abstract: The device serves to suspend heating elements in the interior of a receptacle drum of a drier. The drier is provided with a rotary drive for the drum, and the heating elements exhibit a tubular conformation. The heating elements are guided in a support comprising a basic element and a clamping element positionable relative to the basic element. Both the basic element and the clamping element are provided with guidance recesses for the heating elements. The heating elements extend through the guidance recesses. The clamping element is arranged adjustable in a radial direction with respect to the longitudinal axis of the drum.

Abstract: A drum made from a wire mesh is axially rotatable whereby wet clothes in the drum tumble when the drum is rotated. A motor is mounted on a platform beneath the drum. The motor has fan blades mounted on its shaft that provide a flow of air to the drum when the shaft rotates. A friction coupling of the drum to the motor is used to rotate the drum. When the shaft does not rotate, power is provided to the motor through two capacitors that are in parallel. When the motor starts, a sail switch causes a break in an ohmic connection between one of the capacitors and the motor.

Abstract: A machine for producing a material web is provided having at least one smooth roll at least partially wrapped by the material web. The machine includes an air blowing device arranged for ventilating the material web with at least one discharge stream, wherein the at least one discharge stream is directed into a wedge-shaped opening formed between the at least one at least one roll and the material web leaving the roll.

Abstract: The present invention relates to cleaning sheets that resist folding, especially refolding upon themselves even after an initial fold has been formed in the sheet.

Abstract: A method for decontaminating both soil and mixed waste water polluted by hydrocarbons in a single integrated process is disclosed. Contaminated mixed waste fluid is separated into water and hydrocarbons which are then used in the thermal decontamination of polluted soil through the volatilization of hydrocarbon contaminants. Flue gases containing the volatilized hydrocarbons from the thermal soil decontamination undergo oxidation. Thermal energy from the soil decontamination process and the thermal oxidization of the flue gases can be recovered and used to facilitate the separation of hydrocarbons and water. In this integrated system, every by-product of each step is either decontaminated or consumed in another operation of the system. Energy conservation within this system is also realized by the use of heat exchangers to transfer energy from where it is created by the process to where it is used elsewhere to enhance efficiency within the process.

Abstract: A flighted, horizontally inclined rotary retort, heated externally by flame, hot gases, steam or other sources of heat. The retort shall have sufficient flight area to transport the coal through the retort in the predetermined time. The coal being processed in this retort is prevented from becoming exothermic by provision for a countercurrent flow of blanket gas, heated to a predetermined temperature below exotherm, to prevent coal surface temperatures from rising above the ignition temperature. The retort accommodates oversize pieces of raw coal by having alternating long and short flights, thus allowing greater space between long flights and allowing the larger pieces to be carried over the center pipe by the wiping action of the long flights. The retort will also be provided with an internal pipe, mounted on the center line of the shell.

Abstract: A tobacco treatment system comprising a rotatable cylinder and a plurality of axially directed flights, with each flight having a forward side and a back side relative to the rotational motion of the cylinder, with both the forward and back sides being concave-open in a direction toward the interior of the cylinder.

Abstract: A rotatable drum arrangement, wherein the drum is mounted on support rings such that circumferential expansion and contraction of the drum relative to said support rings does not adversely affect the mounting. In a preferred embodiment, drum blocks are mounted to the drum, and corresponding ring blocks are mounted to the support ring. The side surfaces of adjacent drum blocks and ring blocks support the weight of the drum on the ring. In this arrangement, gaps may be maintained between the drum and support ring that allow for expansion and contraction of the drum. In the preferred embodiment, there is also a drive sprocket mounted on the drum with a sprocket mounting arrangement that also accommodates expansion and contraction of the drum.

Abstract: A drying apparatus comprising a cylindrical drum (1) for drying, on the outside surface of the drum (1), pulp-shaped and viscous substances, such as for instance coffee milk powder, or band-shaped products, such as for instance paper, cardboard or textile, the apparatus comprising means for heating the drum (1) from the inner space of the drum (1), the means for heating the drum from the inner space of the drum (1) comprising a number of gas burners (2) juxtaposed in axial direction of the drum and controllable independently of one another. In furher elaboration of the invention, the gas burners are radiant burners.

Abstract: A description is given of a rotary drum, as for example a rotary kiln, which is suspended within a live-ring by means of axially extending brackets which are retained by the live-ring and bearing, at their free ends, against retaining elements fixed to the rotary drum, in such a way that the vertical load of the drum relative to the drum shell is transmitted tangentially to the live-ring. The brackets are evenly distributed over the circumference of the live-ring fixed to its side faces. Hereby, the live-ring can be made with a smooth cylindrical inner face without teeth, which, besides being advantageous from an economic perspective, also makes it possible to use existing live-rings of the migrating type. Further, all parts of the device will be more readily accessible in connection with inspection and maintenance work in that none of the parts are concealed under the live-ring.

Abstract: A treatment system and method is disclosed for heat treating aggregate, for example, an aggregate dryer of the type which uses a burner and rotating drum for veiling aggregate into a thermal flow path. The invention provides a plurality of mixers which safely mix fuel and oxidant into a premix which is delivered to a reaction chamber The premix is combusted and recirculated within the reaction chamber to insure uniform and complete combustion, resulting in lower emissions of pollutants such as carbon monoxide, volatile organic compounds, and nitrogen oxides and also lower combustion roar. This uniform and complete combustion results in a more uniform thermal profile within the rotating drum, resulting a greater throughput of processed aggregate and a more efficient consumption of energy.

Abstract: Apparatus for drying and/or treating powdered, granular, or flaked material in combination with a containment room or glove box under controlled atmospheric conditions, which may have an oven in the room with a chamber with a vessel therein to carry material, the chamber having a door to seal it off and vacuum creation and gas supplying features directly therefor, the vessel which carries material for drying and/or treating is supported on a frame with provisions for rotation by motor equipment, with heater elements around the outside of the chamber to provide heat if required, and vanes inside the vessel to fluidize the material upon rotation and the application to the vessel of vacuum, heat, and/or gas for drying and/or treating the material as required.

Abstract: An idler pulley assembly for tensioning a belt drive for a clothes dryer or other belt driven appliance. The idler pulley assembly provides a spring steel support anchored to a base of the clothes dryer, a Y-shaped bracket connected to the spring steel support and holding an idle pulley at an opposite end. The idle pulley is mounted on an open cross section, C-shaped shaft which is fixed at opposite arms of the Y-shaped bracket. An oil impregnated wick is inserted into the shaft which deposits oil on an inside surface of the idler pulley journaling the shaft.

Abstract: A roll used for tensioning a canvas belt used to hold paper against a dryer. The roll includes a main cylindrical body formed of steel. A layer formed of a metal harder than steel is disposed over the outer surface of the main body. The metal layer is formed with a channel around its center so as to define two spaced roll end sections of a common diameter. A fluororesin layer is disposed in the metal layer channel and is shaped so as to have an outer surface of a diameter equal to that of the metal layer end sections.

Abstract: A rotating seal device for a rotary drum kiln. A rotating seal member is welded about the drum near each of its ends, each sealing against a rotationally stationary seal member joined with the associated kiln end hood through a flexible gas tight bellows. The stationary seal rides on a pair of rollers each bearing upon a track, preventing its rotation. The bellows accommodates longitudinal expansion and contraction of the drum. Hanging weights are used with pulley wheels and flexible cables to urge the non-rotating members against the rotating members with unvarying force.

Abstract: The present invention is a graphite lubrication apparatus for lubricating the support rollers of a drying kiln, dryer or the like by dispensing graphite powder across the surface of the rollers. It has a graphite storage means for storing the graphite powder to be used for lubrication; a dispensing pipe adjacent the graphite storage means and having a top and bottom and a plurality of receiving holes in the top thereof the receiving holes permitting communication of the graphite from the storage means into the dispensing pipe. The dispensing pipe also having a plurality of discharge holes positioned adjacent the roller. The discharge holes permit the discharge of graphite onto the roller. A discharge means discharges graphite from the dispensing pipe onto the roller.

Abstract: Both indirect and counterflow direct heating are utilized in a dryer to achieve improved efficiency with a reduced tendency to char or damage the treated material. A horizontal drum has a first segment of aluminum and a second section of stainless steel and is disposed within a heating chamber which is divided into two sections by a baffle. Hot combustion gases are introduced to the chamber and flow to the end of the heating chamber to the rear of the drum and enter the drum. The gases counterflow through the drum in a direction opposite to material moving through the drum to exchange heat. The gases remove moisture from the material and exit the drum into a preheat zone of the chamber where the moisture laden gases condense on the drum's surfaces. The exhaust gases then proceed up two stacks. The interior surfaces of the heating chamber and the preheat chamber are insulated to increase thermal efficiency.

Abstract: An improved latching configuration for a side swing door includes a cabinet enclosure with at least one side wall. An opening is formed in the side wall to provide access to an interior of the cabinet. A door is pivotably attached to the side wall to selectively open and close the opening upon a pivoting movement of the door. A latch assembly is provided on the door and/or the side wall for securing the door to the side wall in a closed position. The latch assembly is positioned between a location of attachment of the door to the side wall and a free edge of the door opposite the attachment location, preferably midway between those points.

Abstract: A hollow shaft bearing for a drying cylinder of a paper machine. The hollow shaft bearing is provided with thermal insulation between the interior of the hollow shaft and the surface of the journal on which a bearing is supported. The insulation is formed by a coaxial annular space formed between the inside wall of the hollow shaft and the outside wall of the hollow shaft which supports the bearing.

Abstract: In a bearing arrangement for a rotary drum, the ends of two cradles are attached to load-carrying rollers which rotate freely over a surface area of a race of the rotary drum. The cradles run in self-aligning bearings in a load-bearing structure via intermediate cradles. Each load-carrying roller runs in bearings at the end of its respective cradle, in a manner which avoids slanting and which is free of axial clearance. Each cradle runs in rocker bearing located between its two load-carrying rollers, without bearing clearance at the end of an intermediate cradle. One of the intermediate cradles runs in a journal bearing with an axial clearance equal to or larger than the axial dislocation of the load-carrying rollers in the load bearing structure when the rotary drum is in operation.

Abstract: A dryer drum for drying bulk material including a rotating drum having an inlet for material to be dried at one end and an outlet for dried material at the other end, a center shaft extending therethrough, vanes mounted on the shaft circumferentially spaced from each other and axially spaced along the shaft, the vanes having a first panel extending substantially in a radial plane parallel to the axis of the shaft, a second panel attached to the first panel and facing in a downstream direction and a third panel attached to the second panel; wherein the bulk material to be dried moves in sliding movement over the panels and is mechanically conveyed toward the dryer inlet.

Abstract: A door bar handle for a clothes dryer having a front loading glass door. The door bar attaches to opposite sides of the door frame and spans across in front of the glass to prevent it from being struck by laundry carts and the like. A portion of the door bar is spaced from the glass so as to provide a handle for opening and closing the door, but the remainder of the mid-portion of the door bar is close to the glass so that it won't be used as a hanger rod.

Abstract: An insulating apparatus is disclosed for thermally insulating a dryer head journalled in a dryer section of a papermaking machine. The apparatus includes a stationary insulator having a disc-shaped configuration. The insulator defines a central bore for the rotatable reception therein of the journal. A peripheral seal extends circumferentially around the insulator for inhibiting the flow of convection currents past the periphery of the insulator thereby reducing thermal losses through the head.

Abstract: A rotatable hollow drum for a dehydrator has an inlet at one end and an outlet at the other end. A longitudinal shaft extends axially from one end of the drum to the other. A plurality of circumferentially-spaced, longitudinally extending flights are mounted to the inner side of the hollow drum. A plurality of circumferentially-spaced flights is also mounted to the shaft with each of these flights also extending along the shaft. The flights on both the drum and shaft uniquely comprise a plurality of tines which may have their ends bent, at progressively increasing angles, for intercepting, turning, separating and enhancing the conveyance of pieces of material being dried in the dehydrator as the pieces travel from one end to the other as the dehydrator rotates. This action promotes constant movement of the material in the dehydrator to provide uniform drying of individual pieces while reducing the likelihood of blockage caused by the accumulation of pieces.

Abstract: The invention is a fluid heated drum especially well adapted for use with a drum press in which high press roll nip loading and high heat flux to a pressed web are both encountered. A press of this type is disclosed in detail. However, the drum is more broadly useful in any application combining heavy mechanical drum loading and high heat flux through the drum surface. The drum is constructed with a thin outer shell spaced radially apart from an inner cylindrical body. Radial supports provide load bearing connections between the two. The annulus between the shell and inner body may be arranged in various patterns as a conduit for the flow of heating fluid. By using a thin outer shell which does not have to sustain high bending stresses a high rate of heat transfer is permitted. The outer shell may be made of copper or other high thermal flux but lower strength metal to obtain additional heat transfer advantages.

Abstract: A kiln is disclosed which includes an elongated housing formed by a plurality of interconnected longitudinally extending sections each forming an independent housing module. Each housing module has support means for rotatably supporting that housing module independently of any other module and power means for moving the support means of each housing module into contact engagement therewith for compensating for load variations applied to the support means and uniformly distributing the loading forces imposed thereon by the housing modules and their respective contents.

Abstract: A system for pyrolysing/drying biological sludge by indirectly heating the same by means of hot fumes, characterized by the fact that it incorporates a rotary furnace secured angularly to a cover skirt and defining, with the same, a cavity in which to circulate the aforementioned heating fumes; the aforementioned skirt being supported in rotary manner on powered rollers and connection to the utility pipes and to the sludge loading/unloading means fixed to the floor being made by means of devices consisting of a first frame turning together with the furnace and the respective skirt and supporting, in idle manner by means of rolling bodies, and a second frame connected to the aforementioned pipes.

Abstract: A mounting structure for use in rotationally supporting a rotatable drum dryer is provided which prevents spauling, flaking and pitting of the dryer tracks, which supports the rotational movement of the dryer, and which prevents axial shifting of the dryer. The mounting structure preferably includes a fixed base, at least a pair of proximal, continuous, annular tracks fixedly secured to the dryer, and a corresponding pair of trunnion rollers rotatably coupled with the base and adapted for contacting the faces of the tracks respectively. The mounting structure also advantageously includes at least one thrust wheel for engaging the side of one of the tracks to prevent axial shifting of the dryer. More particularly, two mounting structures are provided, one for each end of the dryer, and each mounting structure includes two pairs of thrust wheels, one pair engaging the side of each track and opposedly configured to prevent axial shifting of the dryer in either direction.

Abstract: A roller for supporting the rotating drum of a clothes drier or similar appliance includes a hub which is molded from a suitable polymer and a rubber tire which fits around and is interlocked with the hub. The tire is of uniform cross-sectional configuration and is stressed so that it remains in intimate contact with the hub rim, even after substantial use. To manufacture the roller, the tire, which is molded in a separate operation, is placed in a mold cavity that is configured to seal against the side walls of the tire and yet permit the tire to expand radially, maintaining the seals along the tire side walls throughout the expansion. Once the mold is closed, a polymer in a plastic state is injected into the region of the cavity surrounded by the tire, there being enough polymer forced into the mold to expand the tire radially against an outer surface of the cavity.

Abstract: A sieve drum is disclosed that is particularly useful in textile processing equipment, such as a suction drum dryer, for heat-treating of continuous web material. The sieve drum is constructed having a single layer of a close mesh screen cylindrically formed between a pair of end heads to provide support for and transmit torque to web material being processed. The close mesh screen is composed of a plurality of longitudinal and transverse wire lengths of relatively heavy gauge than are sinusoidally woven into a lattice having a multitude of small interstitial openings each with rounded edges to provide smooth, unabrasive support to the web material. The multitude of small openings the aggregate area of which comprises less than 50% of the screen surface provides an even distribution of heated air over the surface of the drum and exposes a high percentage of the supported web to the air for a fast, energy efficient heat-treating process.

Abstract: A rotary cylindrical drying drum comprising in axial direction a series of vaned sections, with air and material passages, and in which material to be dried can enter each section via an annular slot disposed along the drum wall and be transported by the vanes in radial direction, and material transporting vanes on either side of each section disposed against the drum wall for axially transporting the material to be dried. According to the invention, each section (7) includes two double-walled, frusto-conical portions whose apices are directed towards one another, the apices of the outer cones (1) being interconnected to form an air and material passage (4), with the edges of the base circles being connected to the drum wall (8) and the inner cones 2 being connected to the outer cones (1) by means of spacers.

Abstract: A drum for a clothes drier formed from a cylindrical sleeve into which is inserted a pair of opposed head structures, each provided with a seat snugly received in the adjacent end of the sleeve and terminated by an abutment to limit the penetration of the head into the sleeve. Axially extending projections are provided at each end of the sleeve and these projections are bent around their adjacent seats thereby to hold the heads and sleeve together.

Abstract: In a mixer having an elongated rotatable drum surrounded by coaxial front and rear tires, the invention facilitates adjustment of the positions of the two trunnion units that supportingly and drivingly engage each tire. Each trunnion unit comprises a base member horizontally shiftably slidable on the mixer frame and a tire engaging roller confined to rotation relative to the base member. Opening to front and rear ends of each trunnion unit are holes that are coaxial with its roller axis. Fixed to one side of the mixer frame are two locating fixtures, each having holes opening to front and rear end surfaces thereon, all of those holes having coinciding axes. Three U-shaped gages are provided, each having tangs which are closely receivable in said holes and which project laterally from opposite ends of an elongated lengthwise adjustable body portion. Two of the gages are used with the locating fixtures to position their adjacent trunnion units.

Abstract: An improved flighting for dryers is the subject of the present invention. An elongated drying drum is disposed for rotation about its longitudinal axis. The inner surface of the drum is provided with a plurality of material distributing vanes in circumferentially spaced relationship. The vanes are characterized by first surface extending generally transverse to a tangent to set body at the point of attachment and a second wedge-shaped surface intersecting the first surface. The wedge-shaped surface may also be provided with a lip extending circumferentially therefrom. A plurality of interference structures are disposed from a central longitudinal support and provide means for distributing material gravitating from the outer peripheral vanes. A plurality of return flighting members are disposed along the inner surface of the drum between the afore described material distributing vanes. These flighting members are disposed at an angle and conform generally to the curvature of the inner surface.

Abstract: A rotary kiln construction wherein the kiln cylinder has an annular bearing ring for supporting the kiln in rotation with spacer plates located between the ring and the outer surface of the cylinder and circumferentially spaced from each other with supporting assemblies at each axial side of the bearing ring secured to the outer surface of the cylinder having retaining elements projecting on both circumferential sides of the plates and being radially outward of the plates to provide a radial inward support to the plate ends constructed for retaining the plates and for ease of replacement and removal without rewelding the full plate assembly on the cylinder.

Abstract: A rotary drum having a toothed rim arranged on the drum casing and supported at several peripheral points on the drum casing by evenly distributed bridge members. Each bridge member includes two clips axially spaced from one another and welded to the drum casing and a cross plate which connects the clips and is radially spaced from the drum casing. Each cross plate is rigidly connected to one clip and slideably connected in the axial direction to the other clip so that differing degrees of thermal expansion and resulting deformation of the cross plates and further strain on the cross plates, clips and connection points can be compensated for.

Abstract: A belt drive system preferably for a clothes dryer has a high ratio of diameters between driving and driven members and has a pair of idler pulleys positioned close to the smaller member and mounted on a tensioning member to keep the belt in tension, and the closer adjacent faces of the idler pulleys are spaced apart by a distance not materially different from the diameter of the smaller member.

Abstract: A Yankee Dryer used in drying a web of paper or like materials in which all structural components are fabricated of weldments of steel plate and forgings and in which the outer shell is formed of a weldment of steel plates expanded to roundness and machined to final dimensions. All primary welds are subject to X-ray inspection. The dryer is of lighter weight than the usual cast iron Yankee Dryers, yet designed to withstand substantially higher steam pressure within the shell.

Abstract: A rotary drum comprising a bearing ring loosely arranged on the drum shell and spacer plates arranged between the ring and the shell, a pair of elements for axially holding a spacer plate in position being provided at one end of each spacer plate, one retaining element being arranged on the drum shell and the other retaining element being arranged on the spacer plate. This construction enables the spacer plates to be readily replaced and the radial clearance to be changed without any need to loosen a retaining element fixed on the drum shell.

Abstract: A paper machine dryer cylinder mounts a plurality of circumferentially spaced stud clamps which project from the inside face of the panel, each stud clamp constituting a slotted, arcuate body with a screw spanning the slot to reduce the diameter of a central opening within the body and to which a dryer bolt head is clamped to fix the panel to the end face of the dryer cylinder to reduce heat loss axially of the cylinder.

Abstract: Bucket-type material lifters are adjustably mounted on the inner peripheral surface of a drier drum between pairs of spaced plates carried by the drum, so that the position at which each lifter starts to discharge material during rotation of the drum and the position at which it completes its discharge can be selectively changed.

Abstract: A rotatable drum apparatus for use with a drying kiln or a dry grinding mill has a large gear wheel secured to the periphery of the drum, the drum being heated. In order to minimize the generation of undue stresses between gear wheel and drum due to thermal gradients, the apparatus includes a stationary heat shield extending about the gear in thermal stabilizing relation therewith. The arrangement includes air pressurization within the shield and seal means between stationary and rotary components, to limit the loss of heated air from the enclosure, and to preclude the ingress of air and foreign particles into the enclosure.

Abstract: A belt tensioning assembling for use in a clothes dryer positions a drive belt in tensioned relation about a rotatable drum and a drive pulley mounted within the dryer housing. The belt tensioning assembly includes an idler pulley and a resilient mounting bar. The mounting bar is preferably pre-stressed to maintain the belt in aligned tensioned relation about the pulleys. The mounting bar includes a torsion arm member, a moment arm member, and a cantilevered positioning arm member onto which the idler pulley is rotatably mounted. The moment member joins one end of the positioning member to one end of the torsion member. The torsion member is secured in positioned load transfer relation with the housing. This locates the positioning member in predetermined spaced relation to the main axis of the drive pulley so that the idler pulley may be mounted thereon. Once mounted, the idler pulley may be moved to receive the belt thereover so as to provide tension thereto.

Abstract: An apparatus for carbonizing an agricultural product utilizes a horizontally rotatable cylindrical vessel in which a pair of helical barriers are used to cause hot gases and combustion air to turbulate in a vortex about a central support member to cause various volatile constituents and organic matter of the agricultural product to evolve leaving the carbon constituents remaining on the skeletal silica through controlled burning at a temperature below the fusion point of the skeletal silica of the agricultural product.

Abstract: A relatively large drum which is supported by rotation about a horizontal axis of rotation is driven by a drive mechanism. The above mechanism includes an energizable rotor that is resiliently and rotatably supported, and in frictional contact with the circumference of the drum, so as to rotate the drum when energized.

Abstract: A rotary drum for the heat treatment of bulk goods, with the drum being mounted by means of thrust rings. Wedges are arranged on the outer periphery of the shell of the rotary drum, the wedges being disposed opposite to one another at a spacing corresponding approximately to the width of the thrust ring. Those inclined surfaces of the wedges which inclined surfaces face toward each other cooperate with insert pieces, the insert pieces being fastened on the thrust ring and being provided with counterwedge surfaces. The inclined surfaces of the wedges and the counterwedge surfaces are arranged on the outer periphery of the shell of the rotary drum successively flip symmetrically.

Abstract: A damper structure for a clothes dryer vent is disclosed. The damper structure comprises a support member adapted to be inserted inside the dryer vent adjacent the inside wall of a house, and a damper plate mounted on the support member, so as to form a closed air space between the damper plate and the regular closure damper of the dryer vent for minimizing heat losses through the dryer vent. In order to fit a dryer vent of circular cross-section, the damper structure comprises a central damper element hinged at the top of the support structure and two lateral damper elements hinged one on each side of the central damper element for allowing full opening of the damper plate into the tubular dryer vent.

Abstract: Method and apparatus are disclosed for eliminating wet streaks in fibrous sheets or webs by infra-red radiation, the method providing means for determining where, lengthwise of the dryer section such radiation should be applied, and the apparatus providing one or more units to be there incorporated and capable of control in a manner such as to enable the radiation to be applied wherever widthwise of the web the moisture content of the web is excessive.

Abstract: The apparatus consists of a hollow cylindrical case arranged at an angle to the horizontal axis of its rotation. Disposed in a space inside the case are coils each bent into a helix of suitable shape, arranged coaxially relative to other coils and connected to manifolds which are attached to an internal wall of the case, each with only one of its ends and are connected to a space between the walls of the case passing wherethrough is a heat carrier. The points where the coils are connected to the manifolds are separated from the internal wall of the case by a distance anywhere between 1/3 and 1/2 of the internal diameter of the case of the drier.

Abstract: In a laundry machine having a horizontal axis rotatable drum and a door for access into the drum there is provided an air vent including a duct having one end in air flow communication with the interior of the drum and the opposite end in air flow communication with air outside the machine. The air vent also includes a flexible flap within the duct having one end free and movable from a vertical first position to a second position and the opposite end of the flap is secured to the duct. The flap has a dimension less than the inside lateral cross section of the duct. There is also a partition spaced from the free end of the flap when the flap is in the first vertical position and the partition has an opening smaller than the flap whereby the opening is covered when the machine is in operation and the flap is in the second position.