Abstract: The present invention provides for a refrigerator-oven complex based on the principle of the operative circuitry of the conventional refrigerator or freezer, specifically it means the additional incorporation of an empty box with temperature conservancy equipments at a suitable quarter of the conventional refrigerator or freezer, the said additional empty box will be referred to as the oven hereafter, the high temperature evaporation tube as the exhaust of the compressor of the refrigerator or the freezer is extended into the oven, the calorific power is diffused in the oven by means of several curved tubeworks and various ways of heat-diffusion so as to afford heating for objects such as foods or temperature conservation for them.

Abstract: A heat pipe device has been developed which permits completely passive ice formation and periodic release of ice without requiring the ambient temperature to rise above the melting point of water. This passive design enables the maximum amount of cooling capacity to be stored in the tank.

Abstract: An automatic car-cooler clutch control apparatus such that the compressor can forcedly be engaged with the engine when a predetermined period of time has elapsed after the compressor is disengaged or when the vehicle speed reaches a predetermined value, in addition to when a vacuum pressure within the intake manifold is more than a predetermined value, that is, a relatively light load is applied to the engine. The automatic car-cooler clutch control apparatus of the present invention comprises a timer or a speed indicator including one or two switch circuits for energizing the clutch relay to engage the compressor with the engine, regardless of a vacuum pressure within the intake manifold, in addition to a vacuum pressure switch and a vacuum pressure chamber communicated with the intake manifold.

Abstract: A dial and sleeve type combination lock is provided with a shift member to move the sleeves out of coupling engagement with the dials for changing the combination of the lock. The shift member includes a manual actuator extending through an opening in the face plate of the lock which opening extends transversely to the axis of the sleeves and movement of the actuator in the opening in the transverse direction effects axial movement of the sleeves by means of an oblique camming surface on the shift member.

Abstract: There is disclosed a tube bending machine with a rotatable die having a tubing clamp associated therewith and a stationary wiper block to bend a tubing work piece around the die as it rotates. The wiper block and tubing clamp are placed into and locked in operative position with similar toggle linkages which are adjustable to accommodate different bending dies and wiper blocks. The die is rotated by a fluid pressure linear actuator chain driving a sprocket secured to a common shaft with the die; the chain is pinned at one end to the sprocket and the sprocket has a torsion spring connected thereto applying tension to the chain and causing the die to return when the actuator moves to slacken the chain. An adjustable stop limits the travel of the actuator shaft and a pointer which moves with the stop reads against a scale to directly indicate degree of bend.

Abstract: A method and apparatus for uncoiling material such as wire, from a coil supported about a horizontal axis by a drum, including separating a loop from the coil, and bending the leading end of the material upon its exit from a pinch roll unit so that it takes a path generally parallel to that of a predetermined passline, and straightening the material once the leading end passes through the straightener roll area. An end bender roll and two of the straightener rolls are mounted on a pivotal frame connected to a piston cylinder assembly which causes the frame to be rotated through an arc in a direction to either bring the end bender roll into an operative position while the two straightener rolls are in an inoperative position, or to bring the end bender roll into an inoperative position while the two straightener rolls assume a nested relationship with a fourth roll in an operative position.

Abstract: This disclosure relates to a hold down mechanism which is particularly adapted to apply a preselected hold down pressure on an element. It employs a bar which is pivotally mounted on a support member with the bar having a hold down surface thereon so positioned that when the bar is pivoted in a selected direction the hold down surface will engage the element in clamping relation and further pivoting of the bar in the same direction will result in the shifting of the pivot point for the bar from the pivot member to the hold down surface. The pivot member is spring loaded for lifting movement at this time with an associated spring pack providing for a controlled loading by the hold down surface against the element. A movable cam member having a wedge shaped lower end moves between a cam follower carried by the arm and a fixed cam follower to effect the controlled pivoting of the bar.

Abstract: A bending device for metal pipe with and without plastic jacketing has a short cylindrical segment including a circumferential groove which determines the bending radius of the pipe to be bent and a support for holding the pipe to be bent tangentially with respect to the groove. A lever is mounted for concentric pivotable movement about the segment and a pressing block is mounted on the lever for pivotal movement about an axis parallel to the segment axis. The pressing block has a working surface which has an approximately semicircular, concave cross section in a plane disposed parallel to the pivot axis of the pressing block and the segment axis and a concave cross section in a plane disposed perpendicular to those axes.

Abstract: An apparatus is provided for manufacturing a cylindrical member utilizing a pair of dies each of which has a semi-cylindrical recess formed therein and which are adapted to be brought into abutment against each other to form a material disposed within the recesses into a cylindrical form. The abutting surfaces of the pair of dies are offset from a plane which includes the axis of a cylindrical member to be formed within the recesses of the dies and which is perpendicular to the direction of movement of one or both of the dies. In this manner, the formation of a bulge or flash on the outer periphery of the cylindrical member can be prevented which may be formed if the abutting surfaces lie in said plane.

Abstract: A press is disclosed having an upper set and a lower set of dies which open and close simultaneously during the operating cycle. An upright body frame member carries the lower die of each of the upper and lower sets of dies. A sliding member is mounted for reciprocal vertical movement and carries the top die for each of the upper and lower dies sets. The sliding member is provided with a recess for receiving an eccentric cam for actuating the slide.

Abstract: A metal rivet, a two-piece rivet assembly, and a joint including the assembly. The metal rivet includes a preformed head at one end of a solid shank. At the other end there is a tubular upsettable portion which is circularly cylindrical with a recess which terminates at a base opening at said other end of the solid shank. The tubular upsettable portion is so proportioned as to form a proper upset head. At least a part of a core pin fits in the tubular upsettable portion and is retained therein after the rivet is set. During setting it prevent internal buckling of the tubular upsettable portion, and after setting it reinforces the upset head to prevent rollout as a consequence of axial separative forces. As an optional feature, at the terminal part of the forming of the upset head, the core pin can be pressed against the base to swell the solid shank and create a closer, or even an interference, fit for the shank in a workpiece.

Abstract: A damping force produced by a shock absorber being tested is detected and converted into an electric analog signal for deciding whether the damping force is acceptable or not. The shock absorber is mounted between a slider operatively connected to a motor for reciprocating movement and a free end of a load detection beam. A potentiometer and so on detect an amount of displacement of the free end of the load detection beam on reciprocation of the slider, and produces the electric analog signal for electrically deciding whether to accept the damping force tested of the shock absorber.

Abstract: A gas measurement and analysis system having a gas chromatograph which converts a gas mixture from a source to a time varying continuous signal. This signal is sampled and converted to digital form by an analog to digital converter which provides a stream of amplitude dependent digital values at equally spaced time intervals. These sampled signals are applied to a rate of change estimator system which provides an accurate estimate of the time derivative of the sampled signal by means of recursive digital feedback. The output of the estimator system is applied to a processor.

Abstract: The invention relates to a device for detecting combustion defects in an internal combustion engine which are in the form of pinking. The device comprises a detector placed on the cylinder head of the engine and a system for utilizing the signals of the detector. The system comprises means for converting the analog data delivered by the detector into digital data, means for temporarily storing, in the course of each cycle, the digital data relating to each cylinder of the engine, and means for comparing the data relating to each cylinder, stored in succession in the course of a cycle, with corresponding data obtained in the course of the following cycle.The device is applicable in particular in devices for initiating the ignition of an engine.

Abstract: An apparatus for sequentially measuring the physical properties of air-permeable rod-like articles such as cigarettes or filter rods. The apparatus is self contained and includes stations for measuring the circumference, weight and pressure drop of each article. The measurement of circumference and pressure drop are carried out pneumatically. An indexing drum is provided to transfer each article to the subsequent measuring station.

Abstract: In a steam generator an ultrasonic probe is used to measure the accumulation of sludge between the tubes. A ribbon-like probe carrier is fed into the vessel and deflected by a carriage placed in alignment with a lane of tubes at 90.degree., the probe head being advanced in the lane to measure vertically and sideways the distance to the surface of the sludge. The probe carrier consists of two steel tapes held face-to-face by a plastic tube which has been heat shrunk. The conductors for the transducers are contained in the space between concave tapes. An adaptor mounted at the end of the probe carrier is amovably connected to the probe head. Probe head, adaptor and probe carrier are sealed so that measurement can be conducted inside the steam generator supposedly filled with water.

Abstract: A circuit for compensating the temperature dependence of the deformation properties of a pressure transducer sensor, having four basic parts: a current source having an output proportional to the sensor temperature, a constant voltage source, a Norton divider, and an operational amplifier. One brach of the Norton divider is a variable conductance ladder having an output current which increases at a programmed rate as the current from the temperature dependent source increases. The programmed rate is based on the temperature-dependent characteristic of the transducer sensor. The two branches of the Norton divider are connected as inputs to the operational amplifier. The operational amplifier provides the output of the compensating circuit, which is the difference between the reference voltage of the voltage source and the voltage at the output of the variable conductance ladder.

Abstract: A non-destructive testing device and method is provided wherein a test piece is held in a test stand located in a test enclosure. The test enclosure is evacuated. The test stand and test piece held therein is then vibrated, immediately after which the test piece is irradiated by at least one beam of collimated radiant energy, preferably ultraviolet light, which is scanned over the test piece in a systematic pattern. Measurements of exo-electrons given off by the test piece responsive to the irradiation of the test piece are recorded for correlation with other exo-electron measurements made of the test piece throughout the life of the test piece. For metal test pieces not sensitive to this technique, a selected gas or gases (mixed or in sequence) may be introduced into the evacuated chamber for forming a surface compound of gas and metal on the surfaces of the test piece. The test enclosure is then evacuated and the test piece is vibrated and scanned by radiant energy and measurements taken.

Abstract: A fluid sampling probe includes a fluid sampling conduit surrounded by a sheath. Cooling fluid passes through the annulus between the fluid sampling conduit and the sheath to cool the fluid samples passing through the fluid sampling conduit. A thermocouple has its sensing end located in the annulus to monitor the temperature of the cooling fluid.

Abstract: A centrifugal brake for a gyroscope with Cardan suspension in a fixed housing on a mobile support includes two weights, identical, of C shape, mounted in opposition on two, diametrically opposed cylindrical articulation pins or axles. The two weights form, by their construction, a ring in two identical parts permanently bearing on one another under the action of a spring. The weights are freely articulated, forming by simple construction an autocompensated brake against the inertial forces generated by combined accelerations of the support.

Abstract: A magnetic gyroscope includes a flexible rotating disk having a plurality of magnetic regions formed in or on the periphery of the disk. Typically four pairs of magnetic sensors are disposed about the disk at 90.degree. angles with respect to each other to detect the magnetic regions as the disk rotates, each sensor pair including a sensor above the disk and one below it. The sensors detect changes in the separation of the disk from the sensors and supply this information to an amplifier to control the gyroscope or the structure within which the gyroscope is mounted.

Abstract: A scavenging gear pump for use in a final drive comprising a drive gear and a driven gear, each being mounted for rotation and in mesh with each other. The drive gear is coupled with an input shaft and rotated thereby and has formed therein a fluid passage for communicating an outlet port of the pump with a fluid chamber formed in the input shaft. A plurality of guide passages are formed in the input shaft for supplying lubricant from the fluid chamber to rotary components, such as bearings and gears.

Abstract: A device for supporting a shift lever in a manual transmission for an automobile which includes the shift lever having a large spherical portion and a small spherical portion, a shift lever retainer supporting the large spherical portion of the shift lever, a resin bush having a cylindrical outer surface spherically engaging with the small spherical portion of the shift lever and a shift lever housing fixed to an operation lever shaft extending toward the transmission. The device comprises a cylindrical vibration preventing bush interposed between the cylindrical outer surface of the resin bush and the inner surface of a hole in the shift lever housing.

Abstract: A predetermined limit in the rotation of a manually rotatable control shaft is established by a special knob having a speed nut which secures the knob to the shaft, and an interrupted circular slot in the knob, concentric with the shaft, for cooperating with a fixed projection extending parallel to the shaft and into the circular slot. The device is described as usable in a thermostatically controlled heating system with an auxiliary control for improving efficiency.

Abstract: A single-operation cam mechanism includes a cam body with a cam surface extending along the body from an entrance location to an exit location. A cam follower is retained in a waiting position adjacent a part of the cam body at which the exit location is found. When the cam follower is moved free of the retainer, a spring forces the cam follower to the part of the cam where the entrance location is found. Then, as the cam rotates, the cam surface engages the follower and forces it back through the exit location and past a resilient trap to the waiting position. The trap snaps shut after the follower has been forced past it, and the surface of the trap then prevents the follower from moving back into engagement with the cam surface except by way of the entrance location.

Abstract: A reciprocable plunger fuel injection pump has a plunger extending from a pump barrel. A spring abutment is mounted at the outer end of the plunger and carries a thrust member engageable with the radiussed end of the plunger and by an actuating device such as a cam. A ring is carried by the plunger for engagement with an annular surface in a bore in the abutment through which the plunger extends. The abutment and the thrust member can rock about the end of the plunger to absorb side thrust applied by the actuating device.

Abstract: A continuously variable ratio transmission of the rolling friction type has a hydraulic control circuit including an end loading device for the transmission located upstream of a double sided piston used to balance roller reaction torque, and a valve for controlling the force exerted by the double sided piston. The valve has two outlets each feeding one side of the piston and communicating with the transmission's sump by way of a device for equalizing the flow rates from the two outlets to the sump. A feedback arrangement provides that the force exerted on the spool of the control valve is always proportional to the force exerted by the piston. The piston travel is limited by hydraulic end stops, upstream of which is provided a pressure relief valve to eliminate damaging transient overloads being exerted by the end loading device. The circuit also includes a facility whereby normal electrical/electronic control of the control valve can be overridden in an emergency.

Abstract: A tool turret according to the invention comprises a turret head which is shiftable between a rotational position and a working position, drive means adapted to rotate the turret head in the rotational position and being in permanent engagement with the turret head, fixation means for locking the turret head in the working position, and a transducer sensing the position of the turret head.The turret head is rotatable with respect to a non-rotary body which is axially displaceable with the turret head and which has a circumferential projection serving as a piston and being mounted axially displaceable in an annular recess serving as a cylinder and formed in a seat, receiving the body, of a member supporting the body. The projection and the annular recess cooperate with each other to ensure axial displacement of the body with the turret head between the rotational position and the working position.

Abstract: This invention relates to a safety switch for a small transmission to prevent operation of an engine when the transmission is in gear. The transmission can have an H-shaped shifting pattern with the engine being capable of starting only when a gear shift lever of the transmission is in neutral. The switch and preferably being made mostly of plastic material.

Abstract: In order to diminish the lurching which occurs when automatic transmissions of motor vehicles perform gear changes, the invention describes apparatus for gradual changes of the engine torque at or near the onset of the gear change as well as at or near the time of gear reengagement. The engine torque may be changed by altering the fuel metering characteristics and/or the ignition timing in a gradual and controlled manner.

Abstract: A chain saw bar attachment is disclosed for a conventional chain saw bar which has a peripheral track for guiding a saw chain and which is detached from a chain saw. The attachment includes an elongated body, a mounting mechanism for mounting the body to the bar with a free end projecting outwardly beyond the connecting end of the bar, and a saw chain guiding member defining an arcuate guideway for receiving and guiding a saw chain carried by the bar from the track at one side edge of the bar, about the connecting end of the bar, and to the track at the other side edge of the bar as the saw chain is sharpened. In one form, the saw chain guiding member may comprise a sprocket wheel having teeth which engage links of a saw chain and a mechanism for turning the sprocket wheel to move the saw chain about the bar. In alternate forms, the guiding member may comprise a slotted roller wheel rotatably connected to the body or a stationary arcuate guideway defining member.

Abstract: A modified Phillips-type cruciform recess in a screw or the like, which provides a cling-fit with a driver by causing deflection of the flutes of the driver against the walls of the slot in the recess, comprises a central socket portion and radially extending slots adapted to receive the flutes of a suitable driving tool. Each slot is defined in part by a bottom surface of substantially uniform width which slopes radially inwardly and downwardly along the axis of the screw. The bottom surface joins two opposing surfaces which form the walls of the slot. The pairs of opposite slots in the cruciform pattern are not symmetrically located relative to a plane including the longitudinal axis of the screw, but are offset laterally in opposite directions with respect to such a plane. On insertion of a standard driver into the recess, the flutes of the driver are caused to flex into frictional engagement with the walls of the slots, thereby achieving the desired cling-fit.

Abstract: A portable turning tool for removing material from a worn component of a device such as a motor generator. The portable turning tool has a support member which is fixedly secured to the device in such a position so as to have a centrally located opening therein aligned with an opening formed in the support structure of the device. A rod having a cutter bit at one end and an actuator at the other end is passed through the pair of openings thereby positioning the cutter bit adjacent the worn component. By providing means on the support member for permitting the rod to slide but not rotate with respect thereto, sliding movement of the rod and thereby the cutter bit across the worn component while simultaneously rotating the component allows material to be removed from the component without disassembling the device during the turning operation.

Abstract: A web sectioning apparatus wherein web sectioning occurs through engagement or interference of the cutting edges of a rotatable knife assembly with the surface of a drum and wherein an indicator is provided for generating a signal indicative of the force resulting from such interference.

Abstract: An apparatus for detecting lateral deviations of a bandsaw blade has a follower which is in contact with and follows lateral movement of the blade. A sensing circuit, which is connected to the follower, generates deviation signals representing movement of the follower. A control circuit which is responsive to the deviation signals stops the bandsaw when the lateral movement of the blade has deviated beyond established limits.

Abstract: An apparatus for removing the wire-reinforced inside rim cores of automobile tires and the like so as to permit shredding for fuel or other use of the remaining carcass, such apparatus principally featuring axially aligned reciprocative action tubular cutters, associated tire positioning and centering mechanism including conjointly actuated centering arms, an annular tire support platform that yieldably supports the tire at a level initially above the lower cutter, and a centering cone member that precisely centers the tire as the upper cutter approaches cutting engagement with the tire, and further featuring an upper cutter assembly that carries a stripper that presses the severed or partially severed cores through the interior of the lower cutters and in the process thereof completes the severance of tire wall material over the edge of the lower cutter.

Abstract: A sawing device for translating the shape on a template to an accompanying sawing blade which gauges the workpiece to cut the workpiece in the desired shape and includes a table which detachably supports a pattern or template. The template is securable at one edge of the table surface. A track is supported at opposite edges of the table in a carriage assembly. The carriage assembly permits the entire track assembly to be moved in the X-X axis or longitudinally along the table. The carriage comprises a cylindrical sleeve secured to the end of the track which receives a longitudinal rod mounted to the table by appropriate brackets. The track defines a groove and supports a motor. The motor has a lip engaging the groove so the motor may be moved in the Y-Y axis or transversely of the table. The motor drives a vibrating or oscillatory blade which depends from the motor through the slot. The guide member also depends from the motor and is received in a groove in the subjacent template.

Abstract: The invention relates to a pair of shears for shearing sheet metal. Known shears, for example power shears, require relatively great forces, which cannot be produced except by special gear means. For rendering it possible to manually shear even relatively thick sheets, according to the invention it is proposed that the movable blade (22) of the shears is connected to a drive mechanism (13,15,17) and is located above the stationary blade (6) of the shears in its starting position for shearing, and that the drive mechanism is supported in the stand (1) of the shears for vertical movement, whereby the dead load of the drive mechanism and of the movable blade is utilized by gravity action for the shearing work.

Abstract: An electronic musical instrument equipped with multiple musical tone signal generating channels, with an automatic play system which controls the tone generation of the musical tone signal generating channels on the basis of the automatic play data recorded in a memory so as to successively and automatically generate musical tones. The instrument also has a manual play system which controls the tone generation of the musical tone signal generating channels by the keyboard and other performance controls so as to generate musical tones by control of the tone generation of the multiple musical tone signal generating channels by the joint use of the automatic play system and the manual play system.

Abstract: A reed construction for a musical instrument fabricated from a plurality of fibers combined with a binding agent and a filler material of lower density than the binding agent, so as to produce an acoustic impedance comparable to that of the natural cane reed.

Abstract: Series resistance is added to the projectile current loop to assure there will be no premature launching or excessive heating of the projectile armature during the energizing cycle.

Abstract: A new, lightweight armor plating for important installations or control cers is disclosed whereupon being struck by a projectile restricts the ensuing shock wave to a narrow beam-like path always perpendicular to patterns of striation engrained in said armor. This response dissipates the projectile's kinetic energy more rapidly. The new armor is lighter than traditional forms of armor.

Abstract: A dual rate of fire mechanism in an automatic weapon absorbs and dissipates portion of the recoil energy to produce a slow firing rate and inactivates the energy absorbing elements to produce a rapid firing rate. Compression of a recoil spring stores the recoil energy of the weapon bolt and normally returns substantially all of the energy to the bolt in a counter recoil portion of the cycle. In slow firing mode, some of the energy stored in the recoil spring is dissipated in a positioning spring thus providing less energy to the counter recoil action and slowing the rate at which succeeding rounds are fired.

Abstract: A pneumatic reciprocating mechanism comprising a working member (11) reciprocably powered in a housing (10) and forming together with a vibration absorbing reaction support member (12) and an elastic seal element (47) a working chamber (49) which is supplied with pressure via an air feed valve (54,55). The latter is positively coupled to the working member (11) and controls the air flow through openings (54) in the reaction support member (12) in response to the relative positions of the working member (11) and the reaction support member (12).The elastic seal element (47) is associated with the working member (11) and has an annular valve collar (48) which is arranged to establish sealing contact with a diverging peripheral wall (52) of the reaction support member (12) by radial expansion due to the air pressure in the working member (49).

Abstract: A load check valve is normally employed in association with a double-acting hydraulic cylinder, such as the type used to raise and lower the boom of a construction vehicle. Conventional check valves of the poppet type are difficult to modulate whereas check valves of the spool type generally do not insure leakage control at an acceptable rate during normal operation. The spool-type load check valve (20) of this invention, used in conjunction with additional check valves (60,61), overcomes the latter problem by providing a series of interconnecting passages and chambers (36) for communicating equalized fluid pressure from a cylinder (11) to either end of the spool (27) thereof to provide for minimal leakage.

Abstract: A valve driving apparatus comprising a case proper provided in the interior thereof with a movement conversion-transmission mechanism, a cylinder mechanism freely detachably fixed to one end of the case proper and a piston rod supporting mechanism freely detachably fixed to the other end of the case proper so as to be applicable to any kind of valve merely by the replacement of the mechanisms between which the case proper intervenes.

Abstract: A mounting pin for a pivoted damper blade is disclosed which comprises a cylindrical shaft having a cenrtrally positioned hole extending therethrough, this hole being surrounded on one side of the pin with an upstanding flat seat. This hole is longer than it is wide so that it extends longitudinally of the pin. Also, the pin at one side of the seat is formed to include longitudinal depressions which provide a plurality of circumferentially spaced arc segments which form an interrupted circle. This pin is mounted on a blade at a side margin thereof by means of a bolt extending through a hole in the blade and through the hole in the pin, and a nut is associated with the bolt, the nut locking against the flat seat of the pin. A resilient gasket is interposed between the head of the bolt and the rear face of the blade so that the bolt need not be held while the nut is tightened. Also, a locking washer is desirably interposed between the nut and the seat.

Abstract: A barn ventilating system includes an inlet located centrally of the peak of the roof for admitting fresh air to a manifold, which distributes the air to each side of the barn, wherein fans blow the air into elongated, perforated plastic tubes for carrying the air along the length of the barn; and a pair of outlets also located at the peak of the roof, one at each end thereof, for discharging stale air from the barn.

Abstract: There is disclosed an electric hot dog cooker also suitable for cooking individual portions of sausages, shishkabob or the like, including a stand supporting an electric heating coil in the form of a helix extending horizontally; inside the helical heating coil is a hollow bushing member arranged so that a rotisserie spit rod will extend through the bushing and engage a rotisserie motor element, all essentially co-axial with the helical electric heating element. Secured only to the outer end of the rotisserie spit is a circular arrangement of nine cylindrical open-wire cages about two inches in diameter and about nine inches long, capable of accepting a hot dog, sausage or similar shaped food portion and large enough so that the hot dog will roll in the cage while the circular arrangement of cages is rotated around the heating coil by the rotisserie motor. The motor is shielded from the heating element by a metal shield having a horizontal turned-down portion at the top thereof serving as a warming shelf.

Abstract: A barbecue oven is provided for cooking and smoking food. The oven includes a grease control system for the door of the oven comprising an inset portion and a door grease deflector cooperating to direct grease and moisture deposited on the inner door surface during cooking to the bottom interior surface of the oven. The oven also includes an electrical heating element support and wood tray assembly. An electrical heating element is supported within the assembly and protected from contact with grease or moisture within the oven. The heating element support confines heat generated by the heating element to create an area beneath the top surface of the heating element support having a relatively elevated temperature. This elevated temperature enhances the natural convection within the oven to uniformly heat the cooking area and also causes the wood within the wood tray assembly to smoulder. Multiple apertures in the assembly aid the convection flow for efficient heat transfer to the oven.