Abstract: A method and apparatus for determining the position of a sensor with respect to a color screen are disclosed. The screen is colored with first and second colors in such a way that the intensity of each color varies from a minimum to maximum along a respective direction lying in the plane of the screen, the two respective directions being oblique to each other. As a result, each point on the screen is characterized by a unique pair of color intensities. The sensor is provided with means for measuring the intensity of each color at the point on the colored surface corresponding to the location of the sensor. In one advantageous application of the invention, one surface of a screen is colored as described above, and the screen is placed over an object to be ultrasonically inspected.

Abstract: An apparatus for pressure measurement employs fiber optics to transport a broadband beam light to and from a remote electrically passive sensing head. In the sensing head, a linearly polarized beam is phase shifted in a birefringent plate, then passed through a photoelastic pressure sensor and a polarization analyzer. The wavelength for which the output light has an intensity minimum is a measure of the applied pressure.

Abstract: A measuring system includes a plurality of resistors and circuitry connected thereto which generates first and second signals each containing different information about one or more of the resistors. Each information is possibly contaminated by error but only by substantially the same error contaminating the other information. Subtraction of two such informations thus gives error-free information because the like errors cancel.

Abstract: A transducer device for measuring the internal pressure in pipe comprises a housing made of two parts, a connecting element which acts for a hinge connection between the housing parts, and a chucking device for clamping the housing parts onto the pipe. To enable a simple handling and mounting of the device and to avoid effects on the measuring signals resulting from mechanical vibrations of the pipe, the chucking device is performed as a snapping catch and comprises a clamp and a spring clip. The clamp is hinged supported at that side of one of the housing parts being opposite the connecting element. The spring clip is hinged supported at the clamp and coacts in locked position of the chucking device with a notch arranged on the other one of the housing parts.

Abstract: A mechanical timber grading machine comprises inlet and outlet clamping stations for a length of timber. Each clamping station comprises a number of support and clamping rolls. Midway between the clamping stations is an oscillating station also comprising clamping and support rolls carried in a sub-frame. A push rod applies a vertical oscillating force to the sub-frame (which is carried on a swinging frame). A pair of strain guages are provided on the pushrod to detect the reaction of the timber plank. This plank is moved through the machine by causing the support rolls at the clamping stations to rotate. The oscillating forces is preferably applied at between 20 and 100 Hz. and are applied both positively and negatively.

Abstract: An apparatus for measuring fluid flow velocity includes an oscillation generator triggered by a circuit driver and a receiver which are disposed in oblique, opposed relation with respect to the direction of flow of the fluid, and an analyzing circuit for the determination of the transit time of the oscillations through the fluid, which analyzing circuit is made up by an exclusive OR-circuit connected on the input side of the receiver and to the oscillation generator operating with constant frequency and constructed as a square-wave impulse generator, a low-pass filter following it, and circuit means for detecting the differential value between a reference voltage and the voltage at the low-pass filter. The apparatus measures the phase-shift between the emitted and received signals, as a result of which a high accuracy is achieved even in case of short measuring distances and the apparatus can be constructed at very low costs.

Abstract: An improved ton-mile recorder for accurately measuring the work done by a cable of a drawworks system. Analog signals representing weight applied to the cable and pulse signals representative of cable movement are integrated electronically to provide electrical gate pulse signals that represent work done by the cable. A high degree of accuracy of the resulting work indicating pulse signals is accomplished by synchronizing a gate pulse of predetermined duration with a pulse train, the frequency of which is representative of weight applied to the cable. A proximity detector is employed to detect the various evenly spaced bolts of a bolt circle of the typical drawworks clutch which rotates along with the cable drum. As each bolt passes the proximity detector, a pulse signal is transmitted which indicates a segment of drum movement and thus a segment of cable movement.

Abstract: A well pump having a walking beam operated by a pitman and crank, the latter of which has a main counter weight connected to its end for counter balancing the weight of the rod string and one-half of the weight of the fluid pumped. An auxiliary counter weight is coupled to the crank between its driving shaft and the main counter weight and is rotated relative to the crank to aid in counter balancing the remaining portion of the fluid pumped.

Abstract: A power transmission device adapted to be employed with a chain saw for providing a rotary output in a plurality of directions. The device includes a housing having an input shaft coupled with an output shaft where the input and output shafts are right angles to one another. The housing serves as the support for the driven mechanism and provides mounting flanges about both the input and output shafts. The mounting flange associated with the input shaft cooperates with a chain guideplate to adjustably mount the housing to the chain saw. By simply loosening two screws, the orientation of the output shaft relative to the chain saw can be changed by up to substantially 180 degrees. The mounting flange around the output shaft is designed to allow a 360-degree range in orientation of the driven device about an axis coincident with the axis of the output shaft.

Abstract: A stepping motor causes a driving pinion to rotate by steps of 90.degree., he stopping position being such that a driven pinion is blocked with a very small backlash by the pressure of a tooth of the driven pinion against the top face of one of the teeth of the driving pinion. Both pinions have simple teeth with conventional profiles capable of being cut by means of a worm-hob. The pitch of the driving pinion is between one and two times that of the driven pinion, and the layouts of the teeth are such that the arc along which a tooth of the driving pinion engages the teeth of the driven pinion includes a portion tranversed freely and a portion along which the driving pinion rotates the driven pinion by one step of its toothing.

Abstract: A motion transmitting remote control assembly of the type for transmitting motion along a curved path by a flexible motion transmitting core element supported within a conduit. The motion transmitting assembly includes a flexible conduit extending from and attached within an end fitting and a swivel member pivotally attached to the end fitting at a swivel joint. A flexible motion transmitting core element is supported within the assembly. A sleeve surrounds the core element and extends from within the end fitting, through the swivel joint and into the swivel member for reducing friction of linear movement of the core element within the assembly and for providing a seal throughout the swivel joint. The swivel member includes a wiper cap for preventing foreign matter on the extended length of the core element from entering the assembly.

Abstract: The specification discloses a safety device for presses and other similar machines in which stock material is manually inserted between converging machine parts. A ram and sleeve arrangement cooperates with a collar mounted on the moving portion of the machine to insure that the operator's hands are drawn completely back to the safety position prior to the commencement of the machine stroke. In the event that the ram does not operate at the commencement of the press cycle, the collar abuts the sleeve on the downward stroke of the press, and moves the pull-back mechanism therewith to the safety position.

Abstract: In a speed reducer, a reaction sun is fixed to a frame and an output sun is coaxial with the reaction sun. An idler carrier assembly, rotatable about the common axis of the two suns, carries a planet shaft supporting a reaction planet and an output planet for conjoint rotation and in radial alignment, respectively, with the reaction sun and the output sun. Rotation of the idler carrier assembly effects orbiting of the planet shaft and its planets about the common axis of the suns. Endless loop force-transmitting elements connect corresponding suns and planets. Rotary input power is applied to the planet shaft effecting conjoint rotation of the planets and orbiting of the planets about the suns' axis. The epicyclic motion of the output planet effects rotation of the output sun.

Abstract: A process for the production of drawing die bores, especially in hard metal or carbide wire drawing dies, wherein each bore has an inlet cone portion on the feed side of the die and a cylindrical calibrating portion along a common axis, the process being a two-step grinding and finishing procedure with a cross-grinding of the inlet cone in a first step and a calibrating grinding and finishing of the cylindrical portion in a second step. Especially preferred apparatus is described for each of these steps, with devices to operate in an automatic or semi-automatic manner to manufacture the finished drawing dies.

Abstract: For use in connection with the adjusting spindle of a vehicle wheel brake of the kind wherein the adjusting spindle is accessible through at least one slot formed in the wheel hub, a tool adapted to be temporarily secured to the wheel hub and in such condition maintain the adjusting lever and star wheel out of engagement whereby both hands of the mechanic are free for turning the wheel and for adjusting the star wheel.

Abstract: An automatic bar puller for a numerically controlled turret lathe, the puller being mounted on one station of the turret and have a detent actuated jaw that grips the end of a chuck mounted workpiece on triggering of a contact stop on the puller by the workpiece, and, the lathe controlling displacement of the workpiece and release of the jaw.

Abstract: A tool holder for retaining a cutting tool, the toolholder including a body portion, a clamp portion operably connected to the body portion, the body portion having a first jaw portion, the clamp portion having a second jaw portion, the jaw portions being adapted to receive the cutting tool therebetween, and a holding strap pivotally mounted on one of the jaw portions, the holding strap having a flat surface for engagement with a surface of the cutting tool.

Abstract: A continuous cold cut slicing system utilizing a slicing machine having a conveyor which feeds a loaf into engagement with a series of drums located on each side of the slicing machine channel; the drums are driven by a variable speed motor with the rotation of the drums providing a feed mechanism of the product to the slicing blade. A gripper assembly is provided which rides on a guide shaft adjacent the channel with the movement of the gripper in the channel constantly being monitored by an encoder and clutch arrangement connected thereto. As the gripper approaches the knife, the encoder and clutch arrangement provide for a drag on the gripper thereby controlling the feed of the product compensating for pull on the knife. Also, since the encoder and clutch arrangement are constantly monitoring the position of the gripper the exact location of the tail end of the loaf being sliced is readily determinable so that a profile compensation control system may be effectively incorporated into the system.

Abstract: There is provided herein a method and associated apparatus for processing groups of elongated cylindrical members such as tubing or the like. The cylindrical members are arranged and transversely clamped in a substantially flat array by a reciprocating clamp which operates to advance the array of cylindrical members a predetermined distance toward operation performing apparatus whereupon a second clamp engages the members and maintains them in the generally flat array while an operation is performed upon each of the members. Additional apparatus is provided which receives the cylindrical members longitudinally from the operation performing means and delivers the array transversely to other apparatus. Hold down apparatus are also provided on this additional apparatus as well as on the operation performing device and reciprocating clamp device which are designed for rapid accurate adjustment to accommodate different diameter cylindrical members.

Abstract: A tension adjustment for a band saw having a band saw blade (30) encircling upper and lower band wheels (26, 28) disposed on opposite sides of the cutting table (12), with the lower band wheel (28) and the drive motor (66) being supported by a housing (50) which is pivotally mounted to the frame structure (10) of the band saw and which can be moved toward and away from the upper band wheel (26) by means of a threaded rod (84) extending between the frame (10) and the housing (50) so that the tension in the band saw blade can be adjusted by pivotal movement of the housing (50) supporting the lower band wheel (28).

Abstract: An electronic musical instrument having a plurality of keys is provided with a depressed key detector which detects depressed keys and produces key identifying signals; a highest signal detector which detects a highest one among the key identifying signals having a highest priority in accordance with a predetermined order of priority; a musical tone producing unit responsive to the detected highest signal for producing a musical tone of a tone pitch corresponding to the highest signal; a reference memory device for storing the detected highest signal in accordance with a predetermined condition; and a controller for inhibiting the musical tone producing unit from producing the musical tone according to a relationship between the detected highest signal and an output of the reference memory device.Thus the progression of simultaneous plural key depressions provides a melody performance including rests.

Abstract: An electronic musical instrument comprises a power source switch, a keyboard including a plurality of key switches corresponding to a plurality of keys, a signal generator for generating a musical tone signal corresponding to a note of a depressed key, and a loudspeaker driven by an output of the signal generator for producing a musical tone. In the instrument, the power source switch is interlocked with the key depression operation so as to supply power to the electronic musical instrument only when a key is depressed.

Abstract: A musical instrument for cooperation with an electronic synthesizer having a parallel-control fretboard on a mountable neck member. Electronics associated with the neck member provide accurate volume, gate and frequency control signals for a synthesizer while still permitting normal guitar playing nuances such as hammer-offs, hammer-ons, slides, muting, and bends. A preferred embodiment employs a micro-processor and a multiple string fretboard.

Abstract: An electronic device for use in aiding the instruction of musical students. The device is comprised of a metronome and a plurality of tone generators, all under the control of a microprocessor computer. Input devices for the system take the form of a musical keyboard and a microphone. The metronome produces an audible regularly repeated sound in the loudspeaker of the device and causes a visual display of a plurality of indicator lights to be lit simultaneously. Pitch error information is displayed on a plurality of indicator lights which indicate musical sharp, flat or correct pitch. The tone generators produce tones in the loudspeaker under the control of the program in the microprocessor. The device has the capability of interacting with the student to exchange musical responses which each is capable of understanding and judging.

Abstract: A composite fishing line comprising a core and braided jacket the core being made of material which will break under a predetermined tensile loading of the line, said braided jacket being made of a different material which does not break under said predetermined tensile loading and having a braid tightness which permits reoccurrent breaks in the core under the reoccurrence of said tensile loading without affecting the utilization of the line.

Abstract: The invention relates to a drive-assisting device comprising at least a fluid relief engine, a source of pressurized fluid, an engine supply pipe connecting the delivery connector of the fluid source to the inlet connector of the engine, and a calibrated discharge valve, shunt-connected to the supply pipe and provided with means for adjusting its calibration, the control of which is deliberate.

Abstract: In a pulser for transmitting the reciprocating motion of a piston to a fluid contained in a chamber such as a solvent extraction column, at least one pulsation diaphragm having the shape of a hollow torus is joined to the piston and to a rim of the duct in leak-tight manner, means being provided for applying a pressure which compensates for the static pressure of the fluid on the piston and the pulsation diaphragm. The difference between the pressure exerted on the internal wall of the diaphragm on the fluid side and the pressure exerted on the external diaphragm wall is minimized during operation but maintained at a positive value.

Abstract: A sheet metal cabinet supports a gas burner assembly below the forward portion of a shield, over which are a pair of removable primary cooking gridirons, having spaced, parallel, transversely extending U-shaped grids which cover the upper opening of the grill cabinet, the U-shaped grids having holes in their end portions so that the grease may drip onto a drip pan or grease tray which extends rearwardly of the burner assembly. A secondary gridiron or bake rack, is supported by a tubular upright rectangular hood assembly above the drip pan and over the rear portion of the primary gridirons. The hood has a front L-shaped access door hinged at the top of the hood by a transverse hinge. The burner assembly has tandem arranged burners with upwardly open, plenum boxes, the top portions of which are covered by a plurality of ceramic, juxtaposed, rectangular, foraminous, radiant burner elements.

Abstract: An apparatus for preparing a food product having at least a cooked batter outer shell and a filling material contained therein. The apparatus is comprised of an conventionally controlled, motor-driven, continuous conveyor belt mounted on a frame; an oil container and associated wick which oil the surface of the belt; a batter dispenser for dispensing batter to the surface of the belt; heating griddles for cooking the batter; a filling material dispenser for dispensing filling material onto the batter; a plurality of side folding spades for folding over side portions of the batter; a rolling mechanism for rolling the batter and filling material over onto itself; and, controls for controlling the operation of the apparatus. The side folding spades are arcuately configured and tapered from one end to the other end. The rolling mechanism is a power driven roller having an abrasive surface in association with a rolling spade.

Abstract: A device for use with a conventional deep fat frying basket to facilitate the frying of a porous mass of a food product, such as onion rings, located within the basket. The device comprises an apertured cover plate arranged for disposition over the mouth of the basket to lock the food product within the basket. Projecting downward from the underside of the cover plate are a pair of projecting members which extend for substantially the full depth of the basket. The members are rod-like and each includes a longitudinally extending, concavely relieved face. A handle is secured to the upper surface of the cover plate. The device is coated with a non-stick material.

Abstract: A cheese making vat comprising a closed vessel having a vertical shaft mounted for rotation within the vessel. The shaft carries a frame that extends radially outward from the shaft, and a series of vertical blades are mounted on the frame and are designed so that when the shaft is rotated in one direction, the blades act to cut the cheese curds and when the shaft is rotated in the opposite direction the blades act to stir or agitate the curds. During the agitation cycle, whey is continuously withdrawn from the upper end of the vessel and circulated through a heat exchanger to increase the temperature of the whey. The heated whey is then re-introduced into the lower end of the vessel. The circulation of whey, in combination with the movement of the agitator blades, provides a gentle agitation for the curds.

Abstract: In the production of cottage and similar fresh cheese, of the kind in which a milk coagulate is cut to curd granules of suitable size, the granular structure of the curd is maintained by stirring the cheese curd-whey mixture, the curd granulate is scalded by heating, and the curd granulate thus treated, after extraction of the whey in the meantime, is washed and cooled in water and iced water, the improvement that the cheese-whey mixture is subjected to successive processing operations in a continuous flow.

Abstract: Batch method and apparatus for treating foodstuffs, especially dried proteinaceous products such as shrimp, with a liquid, especially with an aqueous rehydration medium under automatically controlled conditions of temperature, pressure and time.

Abstract: Apparatus for continuously processing produce such as fruits and vegetables. The produce is heated by being fed into a pipe coil immersed in hot water and is sucked from the coil by vacuum into an expansion chamber where it is subjected to cold water which then travels with the treated produce under the influence of the vacuum. The cold water traveling with the treated produce is thereafter separated from the produce and is returned to the cold water source.

Abstract: The machine comprises a series of egg cracking and contents separating heads carried on bracket plates which are connected to form a continuously traveling chain conveyor advancing in a horizontal path along which there are means for actuating the cracking and separating mechanisms on each head, with the cracking mechanisms being activated at a transfer station so as to receive a group of eggs from a feed conveyor and while advancing to crack and open the shell portions at a dumping area where each egg contents is dropped into the associated, swingably mounted separating mechanism, comprising a yolk cup and an albumen collecting pan, which is disposed beneath the cracking mechanism and which is advanced to a discharge area where the assembly is tilted so as to discharge the yolk and the albumen into separate receptacles, there being means enabling an operator to inspect and manually discharge a whole egg contents into a collecting receptacle or a spoiled egg into another collecting receptacle when the egg yol

Abstract: In treating nuts which are supplied by way of transport means and which are held between two conveyor belts, a groove of uniform depth is milled into the shell of the nut by means of overlapping milling discs, which groove permits the shell of the nut to be broken open by a subsequent splitting means.On the transport means, the nuts are separated and aligned by vibration and the configuration of the guide tracks. A spiral conveyor with a baffle is also provided for this purpose.The conveyor belts are adapted to the different thicknesses of the nuts by means of vertically adjustable rollers.The depth of the groove which is less than the thickness of the shell of the nut is restricted by toothed rings on the milling discs and annular shoulders which are arranged at a displaced position relative thereto radially with respect to the axis of rotation.

Abstract: This invention is an improved breather bag apparatus used with a sealed storage bin such as a silo allowing for expansion and contraction of the air within the sealed structure due to changes in the air temperature in the sealed storage bin. As a material with a high moisture content is normally being stored, the connector pipe between the improved breather bag structure is inclined back into the storage bin for any condensed fluid to flow back into the storage bin to keep the stored material moist. This improved breather bag apparatus is mountable on the sidewall of an existing silo within a protector shell member and having a bag member that is readily observable from adjacent the silo to ascertain whether such is operating properly and having a drain valve to release fluid from the bag member. The protector shell member is provided with a bottom wall with an access door to allow one entrance to the drain valve for operation thereof.

Abstract: An electro-mechanical latch apparatus is provided for selectively and sequentially moving and locking a latch member into a desired position, and then unlocking and returning said latch member to its original position, by energizing an electrical pulse means in contact with said latch apparatus.

Abstract: A rotary type rubber stamp of the present invention comprises an assembly of an endless rubber stamp belt, a pair of guide pulleys mounted on shafts for rotating stamp belt, the shafts being spaced apart from each other and mounted on the inner side walls of a case, the stamp belt having a plurality of unit stamp portions connected with each other through a relatively thin hinge portion of the stamp belt, each of said unit stamp portions having on its back surface widthwise of the stamp belt a ridge-like projection to be engaged with mating grooves formed respectively on the pulleys, one of which pulleys being substantially square in section and the other being circular in section, and cooperating projections and recesses on the square pulley and inner side walls of the case, respectively, for releasably retaining the stamp in position during use.

Abstract: Drive for cylinders of an offset printing machine having a gear train constructed of spur gears disposed as drive gears on respective shafts of the cylinders, and including clamping devices for synchronizing rotation of the cylinders, the clamping devices being rotatable with the spur gears respectively associated therewith and having respective gear rims deformable more or less in accordance with an adjustment thereof, including a clamping plate respectively disposed coaxially to the spur gears, the spur gears being helically toothed, and at least two of the clamping devices mounted on the clamping plates, respectively, and acting in radial direction upon the gear rim of the spur gear respectively associated therewith.

Abstract: A method for limiting the diffusion of ink through a planographic plate comprising a polymetric matrix containing liquid, as for example an agar matrix, is described. Incorporated in the matrix is a diffusion inhibitor which has a binding affinity for the water soluble dye comprising the ink. The additives are cationic or anionic surfactants and the dyes employed are anionic or cationic. When an anionic surfactant a cationic dye is used and vice-versa.

Abstract: A passive target detecting system for discriminating against both doppler d continuous wave off-target radars. A signal from the missile guidance system representing the pulse repetition frequency of the target being tracked is combined in a coincidence circuit with the signals received by the target detecting device. Doppler signals are compared directly while CW signals are processed through a chopper amplifier circuit to simulate doppler signals before comparison.

Abstract: Apparatus for automatically unloading a hopper type car having at least one pair of doors whose individual doors swing open in opposite directions, each door having an end of a connecting rod attached thereto so that the rod is moved in the same direction as the doors of a pair are opened. The rod operates a control lever which acts against a return lever which is biased by a spring, the return force of the spring decreasing as the doors move further open such that the doors stay open of their own weight.

Abstract: A generally rectangular modular table unit is disclosed which is adapted to being stacked to create larger furniture assemblies but is also capable of being assembled so as to stand alone. Each table unit includes four legs (20, 22), a pair of side bars (30, 32) extending along the sides of the unit, and a planar member (44) to form the top of the unit. A pair of top and bottom cross bars (24, 26) extend across the ends of each of the units. The cross bars (24, 26) have rabbetted recesses (28) formed at each of their ends and each is fastenable to the adjacent legs (20, 22) in one of two configurations, one configuration being adapted for interlocking with adjacent table units in a stack while the other configuration is adapted for table units which are intended to stand alone.

Abstract: A collapsible frame includes a plurality of legs adapted to engage a floor. The legs are connected by braces to rigidify the legs in an upstanding position. A plurality of arms are connected to the legs to form a plurality of vertically spaced support platforms. Each support platform is formed by a pair of the arms positioned in spaced parallel, horizontal relationship. The pairs of arms are located at selected elevations to provide upper and lower support platforms with at least one intermediate support platform between the upper and lower support platforms. The legs are suitably connected to facilitate assembly and disassembly of the music stand for storage and transportation. The support platforms are adapted to support musical instruments and related accessories, such as percussion instruments, for movement on the music stand to permit the instruments to be placed in selected positions and combinations for playing by the musician.

Abstract: A support structure for use in furniture which is comprised of upper and lower support assemblies that are spatially separated one from the other by an even number of connecting panels. Alternate pairs of the panels converge with respect to the upper support assembly and alternate pairs of the panels converge with respect to the lower support assembly.

Abstract: A structure for impounding liquid is disclosed below the combustion chamber of a steam generator. The structure divides the impounded liquid in two sections, or pools. The first section, or pool, receives the hot residue gravitated from the combustion chamber and absorbs the thermal and mechanical shock of the residue. The second section, or pool, is connected to the first pool through a gate valve and contains a continuous conveyor which transports the cooled residue, received from the first pool, to a point of ultimate disposal.

Abstract: A continuous gasification furnace and method of operation. The charge is fed into the furnace chamber between two rolls at least one of which is driven. The furnace chamber can be sealed from the ambient atmosphere. The bed of the furnace contains three zones from top to bottom, these zones are; a volatilization zone, a char reaction zone and an ash zone. Additionally, there can be a drying zone above the volatilization zone. Fuel, air, and steam enter the lower portion of the furnace through strategically located inlet ports. Fuel is used to start up the burning bed while carefully controlled steam to air ratio is used during continuous operation of the furnace. Simultaneously controlled steam cooling effects and exothermic reactions occur in the char reaction zone whereby all or controlled amounts of the oxygen is consumed so that pyrolysis can occur in the volatilization zone without the danger of combustion in that zone or combustion of the fumes leaving the bed.

Abstract: A cremator is provided with a primary cremation chamber and a secondary cremation chamber adjacent to and in communication with the first chamber. A method of cremating bodies utilizing the apparatus disclosed wherein a body is eighty percent consumed in the primary chamber and is then moved to the secondary chamber wherein it is consumed together with the by-products of the cremation of a second body in the primary chamber. Cremation in the secondary chamber utilizes the heat of combustion of the second body in the primary chamber to increase the efficiency of the system.

Abstract: A furnace for consuming solid fuel, wherein a horizontal or slanting feeding plane is used to feed fuel into the fire chamber. The feeding plane is attached to a vertical or nearly vertical channel surface, against which the fuel is pressed either with special feeding apparatus or by utilizing the force of gravity. Primary air is led into the lower part of a channel surface after which it rises further upwards along passages formed between the channel surface and the layer of fuel. Secondary air openings are provided on the upper part of the channel surface so that secondary air can be led up from behind the channel surface and through the channel surface onto its front side.