Abstract: A double walking beam furnace for the heat treatment of individual articles which includes a transport apparatus for conveying the part to be treated through the furnace, the transport apparatus including two groups of longitudinal beams which alternately transport the parts in a stepwise manner. The longitudinal beams are alternately arranged in spaced relationship to one another, and a sub-structure is provided beneath each beam to carry the beam and move together therewith. The sub-structure effect both a perpendicular movement and a horizontal movement, in the longitudinal direction of the furnace, of the longitudinal beams. A fixed water trough is provided between each two adjacent sub-structures, which extends approximately over the entire length of the furnace or hearth and is not movable together with the sub-structures, which extends approximately over the entire length of the furnace or hearth and is not movable together with the sub-structure.

Abstract: A rider for use with lengthwise generally horizontal supports in a furnace is formed from an anchor block and a cover block and a locking means. The anchor block is secured to the lengthwise generally horizontal support surface. The cover block fits vertically onto the anchor block and can be moved forwardly into a locking position which prevents vertical, forward, or lateral movement of the cover block. A locking means between the anchor block and the cover block prevents rearward movement of the cover block. The cover block is replaceable without requiring removal and replacement of the anchor block.

Abstract: Independent installation for discharging, storing and transferring products, such as steelworks products, which comprises fixed beams on which rest the products to be handled, and moveable beams placed between the fixed beams and driven in a rectangular cycle of displacement, each moveable beam comprises, at one of its ends, a discharging arm or fingers so that when a product taken from among those stored on the fixed beams is being transferred, said product rests on the end of said fingers and can be displaced and transferred to a discharging or removal zone in a manner entirely independent of the products which remain stored on said fixed beams.

Abstract: A furnace for heating glass sheets moving along the axis of the furnace has at least one differentiated heating cell, the heating elements of which disposed at the vault side are constituted of sets of electrical resistors controlled in temperature or in power and adjustable in height independently for each set. A portion of the electrical resistors are mounted parallel to the axis of the furnace, the other heating cells each constituting a longitudinal heating zone independent of the other longitudinal zones and having, at the vault side, heating elements composed of sets of electrical resistors subdivided into several independent transverse sub-zones, in which the electrical resistors are mounted perpendicularly to the axis of the furnace. The invention is applicable to the manufacture of curved and toughened panes.

Abstract: A plurality of semiconductor chips are sequentially mounted on a rotary table, heated on the rotary table for a predetermined time, and ejected from the rotary table. The semiconductor chips ejected from the rotary table are fed to a bonding apparatus. The semiconductor chips are heated while the rotary table is stationary and are held to the rotary table by a vacuum chuck. The position of a semiconductor chip is adjusted before the semiconductor chip is ejected from the rotary table.

Abstract: The invention is directed to an arrangement of high thrust burners with control systems for a heating furnace which heat metal or similar product, in order to erase developing cold skid marks. The location of these burners is specified, transversely and longitudinally as well as their position with the product face. This invention considers the flow of gases inside of the furnace and the necessary burner characteristic required for the application of these burners to the developing skid marks and the reasons for the specifications. The burners are required to be such that the maximum available heat in the flame is applied at the spot required in order to heat those spots at a faster rate than the cooling effect of the water cooled parts, which are the initial causes of the cold spots. Moreover, it is specified as to the control systems and to the part in which they play in the operation of the skid mark erasure burners.

Abstract: A furnace assembly for automatically transporting circuit board of varying sizes through a firing chamber and for maintaining heat within the firing chamber and preventing ambient air from entering into the firing chamber by having an adjustable twin-track rail assembly for housing and positioning conveyor belts which secure the circuit boards and by having baffle gate chambers in which a series of baffle gates maintain a constant atmosphere at the open ends of the firing chamber.

Abstract: A heating apparatus comprising a heating chamber the inside of which is heated to a fixed temperature and which is provided with an entrance and an exit through which articles to be heated are taken in and out of the heating chamber, a support on which the articles are supported inside and outside of the heating chamber, a conveyer which moves vertically and horizontally so that the top surface of the conveyer is above and below the top surface of the conveyer is above and below the top surface of the support and that the conveyer reciprocates in the direction in which the articles are conveyed, and a pair of doors for opening and closing the entrance and exit of the heating chamber, whereby the articles are successively moved over a fixed distance by the conveyer toward the heating chamber, thereby providing a heating apparatus with a simple structure in which articles such as semiconductor devices are conveyed to the heating chamber without vibration and then properly heated in the heating chamber.

Abstract: The invention relates to an apparatus for automatically feeding each of a sequence of crucibles (3), which are arranged on a conveyor, to a test oven (12) for vaporization and content analysis of a sample contained in each crucible. For cradling each crucible, a gripper head (13) is provided. In order to provide an apparatus in which the number of mechanically moving parts is minimized, the gripper head is rigidly mounted on the end of an operating piston (7). The gripper head preferably comprises two spaced, co-linear crosspieces (16) which face each other and engage under an outwardly extending circumferential flange (17) on the top of each crucible (3). The operating piston (7) and a lifting piston (6) are oriented vertically and connected together at their tops by a transverse crossbar (10). Lifting piston (6) is rotated about its axis (8) by a drive motor, thereby revolving operating piston (7) along a circle (11).

Abstract: An oven (20) includes an oven enclosure (24) having a conveyor (40) mounted therein for transporting food products through the oven. A plurality of ribbon burners (100) are mounted within the oven interior (32) adjacent the path of the conveyor to heat the interior of the oven. Heated gases generated by operation of the ribbon burners are received through inlet plenums (140) under operation of a circulation fan (146) and are discharged through discharge tubes (154) extending adjacent portions of the conveyor (40) remote from the locations of the ribbon burners (100). Exhaust gases are removed from the oven interior through discharge ports (180) by exhaust blower assemblies (184) which are operated to remove exhaust gases from the oven interior at a rate proportional to the flow rate of combustion air and gaseous fuel into the ribbon burners.

Abstract: Apparatus is provided for heating powder material charges to high temperatures at a fast rate, and for moving the charges through process operations, and for maintaining the temperatures of preheated charges and protecting the charges against contamination as they are moved through process operations. Such apparatus includes: a charge enclosing heated enclosure body having two or more separate sections; an internal wall in the enclosure body sections that has an internal cavity having a configuration shaped to hold a desired charge configuration; heating means for the internal cavity wall to heat it to desired temperature.Apparatus is also provided for heating metal, ceramic and similar material charges to high temperatures at a fast rate, and for moving the charges through heating and process operations, and for controlling the temperatures of preheated charges and protecting the charges against contamination as they are moved through process operations.

Abstract: A walking beam furnace with a hearth of fixed beams and of walking beams arranged on supports passing through slots in the floor of the furnace in which, so as to avoid heat loss and undesired heating of the supports in the region of the floor slots, covers are provided for the floor slots that are movable with the supports in at least the feed direction.

Abstract: In a method for ceramising glass plates, in which the plates to be ceramised are hung vertically, a plurality of plates are hung transversely of the transport direction so that they form a plate package. This plate package is passed through a plurality of chambers of an oven in which it is subjected to a direct succession of different temperatures.

Abstract: An improved walking beam furnace insulation in which the leg openings through the furnace floor are provided with insulation to limit the heat losses therethrough and such insulation includes an insulating cap secured to the leg within the furnace and positioned to engage the insulating material surrounding the leg openings in the furnace floor during a substantial portion of the time. Additionally a pipe is secured to said leg to circulate water therethrough.

Abstract: A method, and a kiln, by and in which to fire ceramic tiles (8), or similar items, which are taken along a given path each stage of which is singular in terms of temperature level and other parameters governing the firing cycle. Travelling forward along the path, the tiles are subjected to a succession of alternating forward and reverse movements (30, 31) sequenced in such a way that each passage forward is followed by a shorter movement in reverse.

Abstract: A walking beam type reheating furnace which is provided with a furnace housing, stationary beams fixedly mounted in the furnace housing, first movable beams arranged on the charge side in the furnace housing, second movable beams arranged separately from the first movable beams on the discharge side in the furnace housing and a steel workpiece transfer device capable of transferring a steel workpiece which is placed in a zone where the first movable beams are located to a predetermined position in the vicinity of a separating portion of the first and second movable beams by passing the steel workpiece over the stationary beams and the first movable beams, wherein the first and second movable beams can be independently driven from each other.

Abstract: The process involves producing a monocrystal from the ferroelectric compound, annealing the monocrystal and cooling the latter in a zero longitudinal temperature gradient. The apparatus comprises means for producing the monocrystal, and heating means for annealing the monocrystal in a zero temperature gradient, as well as for cooling the monocrystal in a zero longitudinal temperature gradient after annealing. The strain-free monocrystals may be used in the production of surface wave filters, modulators and optical amplifiers.

Abstract: A walking beam type reheating furnace which is provided with a furnace housing, stationary beams fixedly mounted in the furnace housing, first movable beams arranged on the charge side in the furnace housing, second movable beams arranged separately from the first movable beams on the discharge side in the furnace housing and a steel workpiece transfer device capable of transferring a steel workpiece which is placed in a zone where the first movable beams are located to a predetermined position in the vicinity of a separating portion of the first and second movable beams by passing the steel workpiece over the stationary beams and the first movable beams, wherein the first and second movable beams can be independently driven from each other.

Abstract: At least two successive assemblies are formed by respective walking beams and actuatable independently of one another to advance articles through an oven, with a respective hydraulic jack connected to each of the assemblies for horizontally displacing each assembly. A respective pump is connected to each of the jacks in a respective circuit having two sides, with a respective nonreturn valve provided on one of the sides of each of the circuits between each jack and the respective pump. A pair of distributors are provided in the other side of one of the circuits between one of the jacks and the respective pump, with a respective distributor provided in each of the sides of the other circuit between another of the jacks and the respective pump, and hydraulic lines connecting the distributors of the circuits.

Abstract: Apparatus is provided for heating powder material charges to high temperatures at a fast rate, and for moving the charges through process operations, and for maintaining the temperatures of preheated charges and protecting the charges against contamination as they are moved through process operations.

Abstract: A workpiece charging unit for a walking beam furnace has an entry table and a charging conveyor positioned exteriorly and interiorly of the entry end opening of the furnace. The charging conveyor can undergo a movement along a generally rectangular path for the receipt of the workpiece from the entry table and for the subsequent transfer of the workpiece onto the fixed beams or rails within the heating chamber where it can be picked up by the walking beam conveyor unit for the passage through the heating chamber. The charging conveyor includes charging beams, a plurality of support posts for the support of the charging beams and frame structure coupled with the horizontal and vertical drive mechanisms.

Abstract: A walking beam furnace comprises a hearth formed by fixed and walking beams disposed with their axes in the feed direction. Both the walking beams and the fixed beams are divided at positions spaced apart in the feed direction into sections, and each section of each beam is staggered relative to the adjacent section. As a result, the material to be annealed comes into contact with the cooled fixed beams at different positions at each of the conveying pauses and temperature balancing takes place at the points of contact.

Abstract: A loading device for a horizontal continuous furnace for the heating of glass plates comprises a roller conveyer (6) as part of a continuous conveying system. Support strips (12-15, 32-35) can be lowered and are arranged between conveying rollers (7) of the roller conveyer at a feed station (A). The glass plates (2, 3, 4, 5) are placed on the raised support strips (12-15, 32-35) and are lowered onto the conveying rollers at a preset time by simultaneous lowering of all support strips. Each support strip (12-15, 32-35) is supported independently of the other support strips on separate lifting devices (16-19, 36-39). These lifting devices (16-19, 36-39) are controlled by reflecting photoelectric barriers (22-25, 42-45) respectively dedicated to each support strip such that each support strip (12-15, 32-35) is individually raised to an upper position as soon as a glass plate transferred to the conveying rollers (7) has left the area of that support strip.

Abstract: A walking beam type heating furnace for steels has a conventional skid pipe through which a coolant flows, a skid button made of a ceramic material, a base fixed to an upper portion of the skid pipe, an attachment frame attached to the base for holding the skid button in its supporting position, and a thermal insulating material placed at a bottom portion of the skid button for supporting the skid button. The thermal insulating material has a high strength, high density, low thermal conductivity and high coefficient of thermal expansion such as quartz glass, vycol glass, hard glass and soda lime glass.

Abstract: A glass furnace, e.g. for annealing or tempering glass, has a roller conveyor whose fused rollers rest upon stub rollers overshot by a belt which alternately overshoots and undershoots the stub rollers. A drive for the belt advantageously is controlled by a computer allowing display of the heater parameters etc. and includes a pair of motors connected to the belt with overrunning clutches and driven in opposite senses to alternately drive the belt and thereby prevent play in the movement of the latter. The heater overlying the conveyor has a matrix array of individually or collectively controllable infrared heaters.

Abstract: A multi-zone furnace having one or more walking beam conveyors operative in association with movable isolation doors to provide selective isolation of furnace zones and efficient transport and processing of a product through successive furnace zones.

Abstract: This invention relates to a method of and a walking beam furnace for the intermediate heating of pipes, or the like, in hot rolling mills, by means of a furnace located between the plug-mill and the sizing mill. According to the invention, in a forehearth (17) of the intermediate heating furnace, at the inlet side thereof, there is maintained a temperature which is lower than that at the outlet side, and which, anyway, is such that the hottest pipes will be cooled down and the coldest pipes will be heated up whereby, when exiting from said forehearth (17) of the furnace, the difference between the temperatures of the various pipes is zero or, at least, is small and, in any case, is smaller than that at the inlet, whereas in the successive chamber (18) of the furnace there is maintained such a temperature as to give the pipes the desired temperature when exiting from the furnace.

Abstract: A walking-beam furnace in the heating of metal bodies without bending in which at least a pair of walking beams straddle a stationary beam whose width is greater than that of the walking beams. The stationary beam is formed with a plurality of rectangular recesses opening at a support surface of the stationary beam upon which the metal bodies come to rest and communicate from below with a source of combustion gases so that the hot gas rises to contact the bottom of the metal bodies and the bottom of the metal bodies is subject to heating by radiation from the walls of the recess which converges downwardly to a duct supplying the hot gas. The width of the recess is greater than the widths of the portions of the fixed beam laterally flanking, while the length of the recesses is greater than its width.

Abstract: A wafer handling method and apparatus insures proper centering of a wafer at a work station and controls the heat transferred to the wafer in a baking operation. The amount of heat transferred and the rate at which the heat is transferred to the wafer are regulated by controlling the distance between the wafer and a hot plate. The hot plate is maintained at a constant temperature higher than the bake out or equilibrium temperature to which the wafer is to be heated.

Abstract: This invention relates to the walking beam furnaces--particularly of the bilateral-heating type, with fixed and/or walking beams (1, 2) cooled by means of water or other fluid--for the heating of metallurgical products (B), such as billets, blooms or the like. The invention aims to eliminate or minimize the localized cooling effect on metallurgical products where they contact the cooled beams, which cooling generates the so-called skid marks on said metallurgical products.For this purpose, the invention provides a method wherein each metallurgical article is turned over 180.degree. at least once around its longitudinal axis at a region in the furnace which is near the discharge end (18) of the furnace.

Abstract: A conveyor for removing billets from an induction heating furnace and for separating them from following billets to which they may have become adhered employs a roller having a contoured surface. The roller is rotatably mounted about an axis skewed relative to its central axis so that it wobbles as it rotates, imparting a reciprocating force on the billet to separate it from the following billet to which it is adhered.

Abstract: The invention relates to a walking beam furnace wherein the walking beams can be lowered beyond their operative stroke to a maintenance position. The actuating device for the walking beams comprises a hydraulic, pneumatic or electric assembly (10) and a wheel (16) rotatably mounted around a stationary axis and a preferably flexible drive-transmitting member (20) which is formed, for example, by a cable, a sprocket chain or the like, and is pivotably connected to said wheel (16). The flexible drive-transmitting member can rest on the peripheral surface of the wheel (16) both during the operative stroke of the walking beams (7) and during their lowering stroke to the maintenance position. The ramps, whereon the lifting rollers (6) for the walking beams (7) run, comprise a less-inclined upper stretch (3) and a successive more-inclined stretch (4).

Abstract: The improvement in a walking beam oil country tube reheat furnace comprises a first row of burners positioned in spaced relationship and transverse the furnace hearth with each of the burners containing a refractory housing positioned in the limited space between the walking beam pass line and the hearth of the furnace. The burner includes a burner body and a centrally disposed fuel tube so as to define an annular air chamber thereabout. The burner includes a 90.degree. bend so as to fire in parallel relationship to the pass line. The method of retrofitting a top fired walking beam furnace includes inserting at least one unitized bung of said spaced burners through the furnace floor and into the space between the pass line and floor and firing the burners in parallel relationship with the pass line.

Abstract: A pusher-type furnace for heating slabs is disclosed having lift rails in its soak zone for periodically raising slabs out of contact with skid rails along which the slabs travel through the furnace. The controlled raising and lowering of the lift rails in the soak zone alternates with extraction of slabs from the furnace discharge end and pushing of slabs along the skid rails, and reduces or eliminates soak zone skid marks on the bottom surface of the slabs without the need for a soak hearth. The lift mechanism comprises an open structure of rails and supporting members to facilitate heating as well as soaking of the slabs in the furnace soak zone, thus promoting efficient use of fuel.

Abstract: In the walking beam furnaces, in order to heat metallurgical materials such as billets, bars and the like, having different temperatures of introduction into the furnace and/or different cross sections, so as to discharge materials at uniform temperatures from the furance, said materials are selected according to their temperature and/or cross section, and are introduced into the furnace through a plurality of side inlet doors while said materials are conveyed along the furnace by means of an external side conveyor, and/or they are discharged from the furnace through a plurality of side outlet doors and are then advanced outside along the furnace by means of an external side conveyor.

Abstract: A transfer apparatus of vessels in a tunnel furnace with a built-in heating apparatus is disclosed, comprising a horizontally reciprocative apparatus for carrier apparatus and vertically reciprocative apparatus for vessels. The vessels forward one stroke together with the carrier apparatus when the carrier apparatus forwards, and the vessels are lifted up during returning the carrier apparatus to the former portion, then the vessels are felled on the returned carrier apparatus. The vessels forward one stroke at every one reciprocation movement of the carrier apparatus during backing or heating treatment of material contained in the vessels in the furnace.

Abstract: In a slab heating furnace of walking beam- or pusher-type, particularly for the heating of steel prior to the hot working of the steel, skid beams are supported by water-cooled posts. In order to reduce the number of the water-cooled posts from that in the prior art, a post head having a trough shaped portion is stationarily located on each of the posts. The length of the post head is longer than the outer diameter of the post provided with said post head. The total withdrawal of heat from heated steel to all of the post heads is considerably small, because the number of posts is reduced from that of the prior art due to the structure of the post heads. The posts are preferably arranged in a zigzag pattern.

Abstract: A heating furnace in which radiant tubes are extended widthwise into the furnace so that the products of combustion are discharged into the furnace, whereby intermediate shapes such as slabs which are transported through the furnace are heated to desired rolling temperatures.

Abstract: The invention relates to a walking beam furnace, the hearth of which consists, at least partially, of longitudinal beams arranged side by side and alternately formed as fixed beams and walking beams. Each walking beam is lifted and lowered with the aid of lifting rollers, which run on ramps. The ramps are prolonged downwards by a longer distance than is required for the working lift of the walking beams. The walking beams are depressed, step by step, into a repair and maintenance plane which lies appreciably below the plane of the hearth, by moving down the lifting rollers into the region of the lower prolongation of the ramps.

Abstract: This disclosure is directed to a tire retreading machine which includes a chamber adapted to receive therein a plurality of stacked tires adapted to be retreaded therein, the chamber having an inner surface, and inwardly therefrom there being a radiant heater, a porous or perforated shield, and an imperforate or nonporous shield with the latter being axially shorter than the former and both shields being spaced from a bottom surface of the chamber such that upon heat being generated by the radiant heater, hot air convection currents are set up within the chamber flowing generally upwardly adjacent the chamber inner surface and flowing generally downwardly between the imperforate shield and tires within the chamber to create substantially uniform curing or retreading temperature throughout the chamber, lessening temperature gradients or hot spots, and also allowing radiant heat to pass through a lower portion of the porous shield adjacent the bottom surface of the chamber to augment temperature uniformity thro

Abstract: Walking beam assemblies used to advance workpieces in a reheat furnace include upper and lower runs of coolant pipes spaced and joined together by web plates to extend along each of the opposite lateral sides of a body of refractory that contacts the workpieces. The web plates support clip members that have a bent midportion to wrap around the upper run of the coolant pipe. A leg section of each clip member extends along the side of the refractory material to an elevation spaced below the workpiece-engaging face of the refractory. Support members including gusset plates are carried by the refractory support member to engage the lower run of the coolant pipe and extend along the web plates for support.

Abstract: The invention relates to a method of reheating, storing and conveying metal bars or rounds cast by continuous casting processes whereby uniform bar temperature is achieved, lengthwise and cross sectionally, prior to rolling, cutting and other secondary operations, and discloses apparatus for practicing the novel process concepts. Cast metal bars having varying heat content throughout their length and cross section have their local heat content restored by heaters at a variable rate proportional to the energy required to produce a substantially uniform temperature throughout the bar length end cross section. The reheated bars are stored in a inventory control and soaking furnace for a duration at least sufficient to permit the energy absorbed by the bars during reheating to uniformly dissipate throughout the bars, and and bars of uniform temperature are released from the furnace at a controlled rate for subsequent processing.

Abstract: A method of heating a fleece comprises supporting the fleece on a perforate fleece carrier and passing a heated gas through the fleece and fleece carrier, preferably in that sequence to assist compaction of the fleece. Apparatus for performing this method comprises two chambers between which the fleece is passed on the carrier, the chambers being maintained at different pressures by a fan to create the flow through the fleece and through a radiator for heating the gas. The gas may be recirculated and may be filtered and/or augmented by a further supply. A roller at the exit end of the chambers compresses the heated fleece, preferably from above. The fleece carrier may be preheated upstream of the heating station, for example by induction heating in the case of a metal fleece carrier. A freely running roller having adjustable height rests on the fleece and seals the entry to the heating station.

Abstract: A furnace having a flue through which plates bearing products to be fired are advanced. A plurality of rams are mounted below the plates for lifting the plates off of supports in the flue. A mechanism is also provided to move the rams parallel to the direction of advance. To advance the products along the flue, the rams lift the plates. The rams are then advanced in a forward direction, after which the plates are lowered onto a flue supports. The rams are then returned to their original position and the cycle is repeated.

Abstract: Pass-through heating device for vacuum coating apparatus having a heating chamber with at least one heating device, a thermal barrier positioned between the walls of the heating chamber and the heating device parallel to the longitudinal axis of the coating apparatus.

Abstract: A vacuum electric furnace is disclosed for operation with a hostile environment therein which may be above the melting temperature of most metals, other than refractory metals, with apparatus in the furnace for advancing the work, the advancing apparatus being a walking beam with provisions for protecting the exposed portions of the walking beam by the use of graphite and with work supporting buttons of molybdenum to prevent the work from reacting with the graphite at high temperatures, and with separation and shielding of portions of the walking beam from the hot zone and with liquid cooling of the shielded portions.

Abstract: A continuous heating or pusher-type furnace for the heat treatment of small arts, by which in a closed furnace chamber glide tracks are provided for the intermittent feeding of basket cars in a row between a loading station and a discharge station which is connected gas-tight to the furnace chamber, in the vicinity of which stations there is arranged respectively a reversing device for the translation of the individual baskets from one glide track to the other glide track, whereby the filled baskets automatically can be inserted into the discharge station, and can be emptied by a tipping device with a connecting gravity chute into a quenching bath. The glide tracks with the loading station and the discharging station lie on one plane and at least two glide tracks are provided for the transportation of the filled baskets, the two glide tracks being symmetrically arranged relative to a glide track provided for the return transportation of the emptied baskets.

Abstract: A grate is formed of a plurality of grate elements each in turn having a horizontal elongated support tube extending above and parallel to a supply tube. One end of the supply tube is connected via an upright connector tube or the corresponding end of the support tube and a plurality of posts extend vertically down from the support tube to the supply tube with their lower ends connected to the support tube. One end of the supply tube is fixed and the rest of the supply tube can move relative to its fixed end so when a heat-exchange fluid is passed through the supply tube, connector tube, and support tube the supply and support tubes will expand or contract thermally and displace the upper and lower ends of the connector tube and posts to the same extent.

Abstract: A multiple beam furnace in which the beams can be selectively interconnected for removal as a single unit from the furnace and for replacement into the furnace as a single unit. The movable beams can be raised to a higher position above their normal operating height for engagement of an intermediately disposed fixed beam such that the engaged beams are laterally removable as a single unit from the furnace.

Abstract: A glass furnace, e.g. for annealing or tempering glass, has a roller conveyor whose fused rollers rest upon stub rollers overshot by a belt which alternately overshoots and undershoots the stub rollers. A drive for the belt advantageously is controlled by a computer allowing display of the heater parameters etc. and includes a pair of motors connected to the belt with overrunning clutches and driven in opposite senses to alternately drive the belt and thereby prevent play in the movement of the latter. The heater overlying the conveyor has a matrix array of individually or collectively controllable infrared heaters.