Abstract: Improving the connective heat transfer of a tunnel type cryogenic freezer by positioning the circulating fan blades upside down and closer to the articles moving through the tunnel.

Abstract: Method and apparatus for quick freezing particles with surface moisture by immersion in liquid cryogen to produce a frozen crust or layer on the particles followed by agitation in content with the vaporized cryogen to complete freezing and prevent clumping of the particles.

Abstract: An apparatus for freezing foodstuffs includes a drum 1 mounted for rotary movement at an angle to the horizontal such that individual compartments 12 in the drum 1 successively descend into and rise from a vessel 11 containing cryogenic fluid. Frozen products tumble under gravity towards a central outlet 5 in one surface 4 of the drum, guided by the curved partitions 14 defining individual compartments 12.

Abstract: A cooling tunnel for baked tortillas and the like, the tunnel having a housing defining a cooling space, an aperatured product conveyor for moving the product to be cooled through the cooling space, means for moving cooling gas over the tortillas in the cooling space, closed loop flexible hold down chains, supports for positioning the hold down chains in the cooling space for resting on the conveyor, and a drive for moving the hold down chains through the cooling space along with the conveyor with the tortillas between the hold down chains and the conveyor.

Abstract: Refrigeration apparatus for cooling or freezing products such as protein materials includes a drum through which heat transfer fluid is circulated. A belt is wrapped around part of the drum surface and the product to be refrigerated is applied to the drum surface, being pressed thereagainst by the belt. Either liquid or triple point carbon dioxide is circulated through the drum to cool the product in contact therewith. Other heat transfer fluids such as D-Limonene or DOWTHERM may also be circulated through the drum. A tank and related apparatus for cooling the heat transfer fluid is also disclosed.

Abstract: An apparatus for chilling and shrinking workpieces being conveyed to a workstation on an assembly line comprises, a chilling chamber, a conveyer for transporting workpieces, at least one generally vertical conduit for transporting cryogenic liquid out of a bath to an outlet above the bath, wells for storing cryogenic fluid bath, baffles for slowing the counterflow of cryogenic vapor and a lid for maintaining vapor in the chilling chamber. The workpieces first go through the pre-cooling process where cryogenic vapor flows in a counterflow to chill the workpieces. The workpieces move through openings in the baffles, and after the pre-cooling process, the conveyer transports the workpieces to the cooling stage where baths of cryogenic liquid are stored in wells. Generally vertical conduits are immersed in the wells. The density of cryogenic fluid in the conduit is reduced by warm vapor, enabling the cryogen to flow up the conduit.

Abstract: Method and apparatus for controlling the cooldown and steady-state operation of a tunnel type cryogenic freezer by providing auxiliary cryogen to one or more gas recirculating zones of the freezer and controlling the supply of the auxiliary cryogen by sensing the temperature of the gas recirculating zone and comparing the temperature to a pre-set level.

Abstract: According to the process, there is maintained in a conduit (3), on the downstream side of a valve (5), up to the vicinity of the point A of injection of the CO.sub.2, an intermediate pressure (PI) higher than the pressure (PT) of the triple point of the CO.sub.2. Application in the treatment of waste waters or the deep freezing of food.

Abstract: In an apparatus for the cooling of softly packaged food-stuffs, such as pouches with foods, said pouches are immersed inside a tank (52) into a cooling liquid with a density that is lower than that of the pouches. A floor is arranged inside the tank above the tank bottom so as to support the pouches, which floor comprises a grid (14). At least one jet (15) is arranged between the tank floor and the grid, said jet being adapted to eject liquid in a generally upward direction, and said jet during the ejection being moved so as to vary the flow pattern inside the tank. The motion of the jet provides an exceptionally good cooling effect, which is believed to be attributable to a combination of advantageous circumstances, viz. that no pouch is constantly stationary and that the pouches do not cover the surfaces of other pouches.The motion of the jets can be provided by a mechanically relatively simple arrangement, in which the jets are mounted on arms (16), which arms are rotated around a vertical axis (17).

Abstract: A tunnel for freezing scrap is adapted to reduce consumption of volatile liquid cryogens. The tunnel is supported in an inclined orientation and rotated to move scrap from a scrap inlet to a scrap outlet. A liquid cryogen is injected into the tunnel. The scrap inlet may incorporate a screw drive or other mechanism to reduce loss of gaseous cryogenic material. An exhaust conduit permits discharge of spent gaseous cryogen. The temperature of the spent gas is sensed and indicated, and the rate at which spent cryogen is exhausted and fresh cryogen is introduced is varied with the temperature. A discharge end of the tunnel contains an annular plate which prevents free discharge of liquid cryogen. A longitudinal rib attached to the interior surface of the tunnel adjacent the plate lifts scrap from liquid cryogen accumulating at the plate and drops the scrap through the central opening.

Abstract: Method and apparatus for opening a mollusk (e.g., oysters) by rapidly cooling said mollusk to a surface temperature of about -100.degree. F. followed by mechanically agitating said mollusk whereby the mollusk shell opens and at least one eye of the mollusk meat is detached from the shell. Subsequent to cooling and prior to agitating, the mollusk can be rapidly immersed in a water bath to raise the surface temperature of the mollusk to no more than about -50.degree. F. Individually quick frozen mollusk meat can be prepared rapidly either as an individual portion of meat or on the half shell.

Abstract: A freezing device having a substantially closed container is shown and described. The top part of the container has a feed opening and a discharge opening. These openings are located above a maximum level of cooling medium in a container, which cooling medium in a gaseous stage is heavier than air. A first tube extends through an additional opening in the top side of the container and forms an overflow. By means of this device, the level of the cooling medium is maintained constant in the container and excess cooling medium is removed by means of a second tube and pipe connected to it.

Abstract: A cryogenic freezer having an insulated cabinet forming an interior vessel with a bottom and sloping sides. A shallow liquid nitrogen bath is maintained in the vessel at a predetermined level. A conveyor assembly having a medial portion shaped to conform to the profile of the vessel is pivotally mounted at one end so that the medial portion is submerged in liquid nitrogen. An endless conveyor belt is mounted on the conveyor assembly by means of support rollers and guides to maintain a tensioned relationship. A jack is provided on the conveyor assembly to rotate the assembly about its pivot. An exhaust system is connected to the cabinet to remove evolved nitrogen gas.

Abstract: A cryogenic freezer apparatus for food products, including a thermally insulated enclosure and conveyor means for conveying products through the enclosure. A cryogen unit in the enclosure produces cryogen vapor near the enclosure entrance, and a blower unit is located in the enclosure adjacent the entrance thereof. The blower unit is selectively reconfigurable in response to a blower control signal to selectively direct cryogen vapor in varying directions, drawing cryogen vapor away from a first portion of the enclosure and blowing cryogen vapor toward a second portion of the enclosure. A photocell unit outside the enclosure, adjacent the entrance thereof, detects cryogen vapor exiting the enclosure entrance and generates at least one sensor output signal in response thereto, being indicative of the amount of cryogen vapor exiting.

Abstract: A cooling device which includes a conveyer belt to carry food products thereinto is provided with improvements in which a spraying device for spraying a cold salt solution onto the belt includes a first and second spraying unit provided above and below the conveyer belt so that a salt solution can be sprayed both directly onto the food products and onto the bottom side of the belt when the food products are covered or packaged, or sprayed onto the bottom side of the belt only when the food products are not covered or packaged. A secondary cooling unit operating with a cooling medium coming from an evaporator of the cooling device includes a tray-like member divided by a heat transfer plate into an upper chamber for receiving the salt solution after being sprayed and a lower chamber for receiving the cooling medium.

Abstract: A cryogenic freezer apparatus for food products includes a conveyor within a thermally insulated enclosure. A cryogen injecting unit is located in said enclosure adjacent the opening thereof, and responsive to a cryogen control signal for introducing liquid cryogen in said enclosure. A blower unit in said enclosure directs cryogen vapor away from said enclosure opening toward the interior of said enclosure. The output of said blower unit being controllable by a blower control signal. A sensing unit within said enclosure senses the cooling capacity of the cryogen vapor at the enclosure opening and generates a sensor output signal which is indicative of the amount of cryogen vapor escaping out of said opening. A control unit, coupled to said sensing unit, said injecting unit, and to said blower unit generates a cryogen control signal and a blower control signal in response to the sensor output signal.

Abstract: A freezer includes an insulated enclosure for maintaining low temperatures therewithin and a conveyor belt that carries food products throughout the enclosure. The conveyor belt includes a straight-line path section and at least one helical path section and is driven by vertical drive elements carried by a rotating drum about which the conveyor helical path section is located. Upon entering a helical path section from a straight-line path section, the conveyor belt undergoes expansion only, with the inner ends of its transverse rods maintaining a precise spacing which allows smooth interengagement between heads at the inboard ends of the rods and the leading surfaces of the vertical drive elements that are located along the circumference of the rotating drum which defines the curved helical path. Because of the improved arrangement, both an ascending helical path and a descending helical path can be established within a single freezer with both rotating drums simply driven by a single motor.

Abstract: A closed pressure vessel is provided having a cryogenic liquid bath therein utilizing a bath liquid having a low boiling point temperature.

Abstract: A multi-tier refrigeration tunnel of modular construction, with lateral doors, in which fans are disposed between each tier, in which they are driven by shafts extending from ceiling to floor of the tunnel, and in which the shafts are driven by top mounted fan motors. A multi tier refrigeration tunnel, not of modular construction and without lateral doors, in which fans are disposed between each tier, in which the fans are driven by shafts extending from the floor of the tunnel and from the ceiling of the tunnel, in which the shafts are driven by top mounted and bottom mounted fan motors. A multi tier refrigeration tunnel, and by extension also a single tier refrigeration tunnel, in which two products of different required processing times can be processed simultaneously. A multi tier refrigeration tunnel, preferably without lateral doors but not necessarily, in which fans are disposed above the upper tier and in which fans are disposed next to, and to the side of, the lower tiers.

Abstract: An apparatus and method for cooling a strip of moving metal in a hot strip mill, or the like, is disclosed. The apparatus utilizes an infrared sensor for measuring a temperature profile across a transverse section of the strip. A coolant manifold is utilized to apply coolant to the metal strip after the temperature is measured from a plurality of independently controllable outlets in the manifold transversely spaced across the strip. A controller adjusts the flow of coolant of the outlets in response to the transverse temperature measurements to selectively cool the strip in order to establish an uniform temperature profile.

Abstract: A process and apparatus for extracting musts from fruit by rapid cooling said fruit to a temperature below 0.degree. C. followed by homogenizing the temperature of batches of said fruit prior to processing. The apparatus includes a cryogenic tunnel freezer in combination with a homogenizing/discharge hopper with refrigeration provided by a liquid cryogen such as nitrogen.

Abstract: A counter-flow food chiller provided with an oscillating screw-feed so that the food, while being pushed through the chill tank in a direction contrary to the water flow is also agitated and oscillated, improving the heat exchange and preventing ice formation on the walls of the tank which are cooled by refrigeration.

Abstract: A freezing system combining a cryogenic freezer and a mechanical refrigeration freezer, with the cryogenic vapor from the cryogenic freezer being used to lower the temperature of the air in the refrigeration freezer. The cryogenic vapor from the cryogenic freezer is passed through a heat exchanger in the refrigeration freezer with the heat exchanger positioned downstream of the evaporator coil of the refrigeration freezer and upstream of the product conveyor belt.

Abstract: This invention pertains to a method and apparatus for cooling and freezing of organic-comprised articles which makes use of liquid cryogen and of chilled gases from a mechanical refrigeration system to provide an economical process for reducing the temperature of the article. The article is contacted with a liquid cryogen and subsequently contacted with circulating cold gases in the mechanical refrigeration system. The improvement relates to the method and apparatus for producing the cold gases which are used in the mechanical refrigeration system; the method comprises using the cryogen vapors generated upon contact of the articles with the liquid cryogen as an indirect heat exchange fluid for removing heat from heat exchange fluids used in the mechanical refrigeration system. This indirect heat transfer using cryogen vapors supplements cooling of the mechanical refrigeration system cold gases by the mechanical refrigeration system chiller.

Abstract: The present invention comprises a method and apparatus to be used in the cryogenic fast freezing of organic comprised articles such a biologicals and foodstuffs. The method enables control of the time-temperature profile of an article as it progresses through the freezing process, and thus provides the highest quality frozen article. The method requires at least two applications of liquid cryogen to the surface of the article during the freezing process, wherein the applications of liquid cryogen are spaced in time in a manner which essentially prevents thermal cracking and embrittlement of portions of the article, while simultaneously ensuring that a frozen crust which operates as a barrier to water conduction or transmission out of the article remains on the articles throughout the freezing process. In addition, the method and apparatus provide an improved efficiency of operation in terms of utilization of the cryogenic medium within the freezing process.

Abstract: A conveyor line system for carrying frozen comestibles in which the conveyor line support rail is formed of an elongated aluminum extrusion having incorporated within it a fluid passage extending along its length with radially and longitudinally spaced orifices for washing the conveyor line assembly during a cleaning cycle.

Abstract: A food freezing tunnel has an inner trough member and a roof member. In order to gain access to the interior of the tunnel, for example for purposes of cleaning the tunnel, the inner trough member is able to be raised and lowered. The tunnel has a spray header for liquid nitrogen and fans for circulating resulting cold nitrogen vapor. The tunnel has an inner trough member spaced from the outer trough member. The inner trough member has a floor extending underneath the upper run of a conveyor passing through the tunnel and has sides which prevent direct impingement of liquid nitrogen onto the outer trough member and which co-operate with the roof member to inhibit the passage of cold gas from within the trough member over the sides.

Abstract: Method and apparatus for controlling gaseous cryogen flow through a continuous tunnel type freezer wherein the cryogen and product to be frozen travel in counterflow heat exchange relation to minimize egress of cryogen from, or ingress of ambient air into the product discharge opening in the freezer.

Abstract: Products to be cooled are brought in the form of individual portions at least partially into contact with a refrigerant liquid for a sufficient time so that the liquid is almost completely evaporated when the portion has reached its required cooling temperature.

Abstract: A chiller has a series of moving rakes for advancing poultry carcasses through a tank of chilling liquid for cooling the carcasses down to an acceptable temperature. The chiller includes a loader which permits loading of the carcasses into an end of the tank without subsequent damages to the carcasses by the rakes. The loader includes a gate which is biased open for permitting feeding of the carcasses through an inlet and onto a ramp in the loading end of the tank when the rakes are remote from the inlet, and is closed as the rakes approach the inlet so as to prevent pinching of the carcasses between the rakes and the ramp.

Abstract: A cryogenic freezer having a thermally insulated tunnel-like enclosure with an entrance and an exit and means for conveying products being frozen therethrough. Products are contacted with liquid cryogen at a region generally near the entrance and a blower located closer to the entrance than to the exit controls flow of cryogen vapor. Upstream and downstream baffles and dampers associated with blower are linked together for complementary movement to selectively regulate the upstream and downstream flow of vapor discharged from the blower. Additional blowers circulate the cold cryogenic vapor transverse to the direction of the conveying means. The temperature of vapor leaving the region of the entrance is monitored the orientation of the baffle and damper arrangement is adjusted in accordance with the temperature monitored. The food products can be contacted by liquid nitrogen in a reservoir facilitates cleaning and retards inefficient vaporization.

Abstract: A food freezing tunnel has a trough member and a roof member. In order to gain access to the interior of the tunnel, for example for purposes of cleaning the tunnel, the trough member is able to be raised and lowered. Jack means housed in the respective legs of the tunnel are driven by for example an electric motor to lower and raise the tunnel. The trough has counterweights. Typically the jack includes a rotary screw-threaded shaft which carry a nut connected to a chain which travels over pulleys and which is secured to the trough member.

Abstract: In a method of manufacturing shoes, shoes which are integrated by securing bottoms to ones assembled by joining the edges of uppers and insoles fitted to shoe lasts, are taken in a rapid freezing atmosphere cooled by liquefied gas, in which the surfaces thereof are cooled rapidly. The effect of rapid cooling makes it possible to manufacture shoes which maintain their shape when fitted in correspondence to the shoe lasts without causing any disfigurement thereafter as well as shortening the manufacturing time.

Abstract: In a process for freezing liquid or semiliquid food products in the form of essentially uniform pellets, the nonfrozen food product is introduced into a container. The product is agitated within the container, while a liquid cooling gas is sprayed over the product. The partially frozen food product is then removed from the container before it is completely frozen and after formability has been achieved, and is formed into essentially uniform pellets which are completely frozen outside the container. An apparatus for carrying the process into effect comprises a container, an agitator mounted within said container, spray nozzles opening into the upper part of the said container for spraying the underlying food product in the container with a liquid cooling gas, a forming device for forming the partially frozen food product removed from said container into essentially uniform pellets, and a freezer for completely freezing the pellets thus formed.

Abstract: Liquid carbon dioxide is injected through one end into the upper compartment (14) of the tunnel. The gaseous CO.sub.2 is circulated in the lower compartment (13) partly in a countercurrent manner and partly in a cocurrent manner relative to the objects (22) to be cooled, by a central fan (9). Application in the temporary hardening of products of rubber and plastics material and in the precise cooling of food products.

Abstract: A method is described for cooling or heating hot filled containers, such as metallic cans. The apparatus employs countercurrent flow between the containers and a water trough and uses axial shaking and the physics of the containers to promote cooling or heating.

Abstract: A video camera or other scanning device is employed to monitor the loading with articles to be frozen of an endless belt which passes through a freezing apparatus so as to freeze such articles typically by contact with liquid nitrogen or its cold vapor. The video camera is associated with electronic circuits that generate a signal representative of the belt loading and compare it with a signal representative of an optimum belt loading. If the difference between the signals is greater than a chosen threshold the belt speed is adjusted so as to reduce or eliminate the difference. By this means an improvement is made possible in the efficiency with which the liquid nitrogen is utilized.

Abstract: Semiconductor devices such as integrated circuits and discrete transistors are mounted on cards and the cards are installed on raised racks extending up from the bottom of a tank forming a burn-in chamber. The racks are individually lowered to immerse the cards and operating devices in a bath of liquid heat exchange medium at an elevated temperature. The racks are individually accessible through aligned segments of a segmented cover to reduce the intrusion of room water vapor into the burn-in chamber. The elevated temperature of the medium is maintained during the procedure by pumping the medium over mechanical cooling coils to remove excess heat produced by the operating devices. A lead screw and lever mechanical combination provide variable speed pumping, to accommodate changes in medium viscosity, from a fixed speed motor. The pumping also mixes the medium around the cards and devices to produce uniformity in the medium temperature.

Abstract: An upper transverse chamber and a lower transverse chamber have apertures for the passage of cooling agent to a product passing between them. At least the upper chamber is divided into a central compartment corresponding to the central zone of the product, and two lateral compartments, corresponding respectively to the two edge zones of the product. The division into compartments is achieved by partitions which are perpendicular to the bottom of the upper chamber. The partitions form, inside of the upper chamber, a channel converging in the direction of motion of the product.

Abstract: The tunnel comprises a tube (1) in which are stacked parts (A) to be cooled, and an intermediate chamber (7) which surrounds the tube and around which is disposed a heat exchanger (3). Liquid nitrogen is vaporized upwardly in the exchanger, redescends in the chamber (7) and rises in the tube (1). The supply of liquid nitrogen is controlled by a temperature probe (17). Application in the cold fitting of parts in the mechanical industry.

Abstract: Eviscerated poultry is conveyed upon a shackle through a refrigerated space in a compact configuration for a time sufficient to chill birds so as to cause them to self-retain the compact configuration when delivered to a bird packaging station for packing in the same configuration. The shackle itself has a basket pivotably mounted to a lower portion of a hanger bar and a canopy mounted to an upper portion of the bar.

Abstract: A process is provided for carrying out the cryogenic cooling of a material which comprises introducing material to be cooled into an elongated cryogenic tunnel housing on means for conveying said material from an inlet end to an outlet end, spraying liquid cryogen onto said material as it travels through said tunnel at a position proximate said outlet end, passing vapor or gas derived from said liquid cryogen in counter-current flow over said material passing through the tunnel, removing from said tunnel at a position proximate said inlet end an exhaust comprising said vapor or gas and atmospheric air entrained thereby through said inlet end, determining the rate of flow of the exhaust and the content of molecular oxygen in said exhaust, and calculating from the rate of flow of the exhaust and its oxygen content the rate of consumption of said liquid cryogen.

Abstract: When cooling hot metal strip, it is known to employ headers which apply continuous curtains of water across the width of the strip. The headers above the strip are inclined to each other so that the curtains extend across the width of the strip and are spaced apart horizontally by a greater distance at one edge of the strip than at the other edge.

Abstract: A method of holding an polishing a workpiece whereby a liquid such as water is applied between the workpiece and a support member and the liquid is frozen to secure the workpiece to the support member. A polishing member is positioned in contact with the workpiece in a grinding liquid and the polishing member and the workpiece are moved relative to each other to polish the workpiece. Grooves or through holes may be provided in a surface of the support member to hold the water or other suitable liquid. The liquid to be frozen further may be impregnated into a liquid absorbing material.

Abstract: Tunnel freezer for freezing products which are transported through the tunnel freezer from an infeed end to an outfeed end. Close to the outfeed end of the tunnel spray nozzles are provided for spraying the products with liquified nitrogen or similar cryogenic liquid. The tunnel comprises circulation fans positioned upstream of the nozzles. The circulation fans comprise at least one paddle wheel positioned immediately above the products. The paddle wheel has paddles, the radial length of which is 20 to 60%, preferably 50%, of the radius of the fan wheel. Preferably also a fan wheel is arranged below the conveyor between the two paths of the conveyor, whereby the paddle wheel is driven by e.g. a chain or belt transmission. Moreover, the tunnel is divided in compartments by partitions, whereby the partition positioned at the infeed end of the fan wheel is positioned closer to the fan wheel than the partition which is positioned at the outfeed end of the fan wheel.

Abstract: A cooling apparatus for cooling food products to be frozen from their both sides by putting said products between plural, vertically arranged cooling means comprises a rotary conveyor, a cooling means placed below the upper belt of the rotary conveyor and containing a low temperature cooling fluid to thereby cool the upper belt and at least one cooling vessel placed above the rotary conveyor so as to be vertically movable.

Abstract: A packing plant by-products chiller includes an elongated tank having an inlet end for introducing fresh animal by-products and an outlet end for removing chilled by-products. The tank is rotatably supported on a set of trunnion wheels and is rotated by a chain and sprocket assembly operatively connected to a motor. A liquid coolant supply line from a coolant source introduces low temperature coolant into the tank. An elongated trough is positioned beneath the tank for receiving warmed coolant which drains from the tank through a plurality of apertures therein. A pump is operatively connected to the trough for recirculating the coolant back to the coolant source.The method of chilling fresh animal by-products comprises introducing the by-products and liquid coolant from the coolant source into the chilling tank located at the slaughter location and rotating the tank such that the by-products therein are tumbled for complete exposure to the coolant.

Abstract: A packing plant by-products chiller includes an elongated tank having an inlet end for introducing fresh animal by-products and an outlet end for removing chilled by-products. The tank is rotatably supported on a set of trunnion wheels and is rotated by a chain by sprocket assembly operatively connected to a motor. A liquid coolant supply line from a coolant source introduces low temperature coolant into the tank. An elongated through is positioned beneath the tank for receiving warmed coolant which drains from the tank through a plurality of apertures therein. A pump is operatively connected to the through for recirculating the coolant back to the coolant source. The method of chilling fresh animal by-products comprises introducing the by-products and liquid coolant from the coolant source into the chilling tank located at the slaughter location and rotating the tank such that the by-products therein are tumbled for complete exposure to the coolant.

Abstract: A method and apparatus are provided for rapidly and efficiently cooling a flow of a food substance such as ground chicken meat while simultaneously conveying the food substance along a relatively short, upwardly inclined travel path that is defined by an inner chamber of an elongate housing assembly. A power driven auger extends along the travel path and is journaled by the housing assembly for rotation within the inner chamber. An inlet hopper is provided for introducing a flow of relatively warm food substance into a lower end region of the inner chamber. A discharge spout is provided for discharging a cooled flow of the food substance from an upper end region of the inner chamber. Cooling of the food substance as it is conveyed along the travel path is effected by providing the housing assembly with a refrigerant chamber that surrounds but is segregated from the inner chamber.

Abstract: A freezing apparatus is disclosed wherein a first and a second endless belt conveyor are disposed substantially horizontally put one upon another with a predetermined gap being left between the confronting runs of the conveyors, the conveyor belts being adapted to be separately cooled at their rear surfaces by means of cooled brine, and adapted so that products-to-be-frozen can be supplied into the gap from one end with their upper and lower surfaces being kept in contact with the exterior surfaces of the confronting runs of the moving belts to be conveyed towards the other end of the gap, whereby the products are quickly frozen by simultaneous cooling of their upper and lower surfaces. In this case, at least one of the belt conveyors is preferably composed of a flexible belt conveyor made of e.g. a thin rubber sheet.