Abstract: Method in manufacturing a heat insulated tube includes a tube (17) for conducting fluid and a sheath (12) enclosing said tube, a heat insulating material (15) being disposed between the fluid tube and the sheath. The sheath is being extruded in an angle extruder die (10) while the fluid tube and the heat insulating material enclosing said tube are being fed axially through the angle extruder die as the sheath is being extruded around the heat insulating material. Then the sheath (12) extruded from the angle extruder die is kept spaced from the heat insulating material (15) enclosing the fluid tube (17), over an initial length of the axial movement thereof up to chains of chill molds (13) for imparting to the sheath a corrugated shape by forming the sheath against the chains of chill molds under the influence of negative pressure. The invention also relates to a device in extruders having an angle extruder die (10) for the manufacture of the heat insulated tube.

Abstract: A pinch-off clamp 20, built into a top 12 of a hollow core 11 within a blow molding machine 10, has jaws 21 and 22 that open to receive a leading end 18 of a parison 15, which descends into the hollow core. Then jaws 21 and 22 close together to pinch off and hold a leading region of parison 15 at top of core 11. Once parison 15 is pinched off and held closed, it can be ballooned and draped over core 11 and then blown into a double-walled box formed between the core and cavity mold parts closed around the core.

Abstract: A process for the production of a laminate of thermoplastic material with a multi-layer wall by co-extrusion provides that added to the material for forming at least one of the layers of the laminate is a substance which makes it possible for that layer to be rendered recognizable in the laminate by the action of physical and/or chemical means. The added substance may be a fluorescing, phosphorescing or luminescing substance so that the layer containing that substance can be rendered visible in the wall of the laminate by the action of UV radiation of appropriate wavelength.

Abstract: In the forming of an article by blow molding parisons into conformity with cavities of an array of mold sections wherein parisons in the form of tubes are extruded from an extruder into an array of neck molds on a head, the head is moved axially away from the extruder to define the parisons, mold sections are closed about the parisons, and the parisons are blown outwardly, an apparatus for application of labels to the hollow blown plastic articles which comprises an array of vacuum cups mounted on the head and movable with the head and a mechanism operable to move the vacuum cups outwardly to engage labels on magazines and move the labels inwardly toward the head and to thereafter move the labels outwardly and deposit them in the mold cavities when the head moves adjacent the mold cavities.

Abstract: A method for manufacturing a blow-molded body employs a two-part blow-mold. A tubular preform is introduced, with the material in a thermoplastic state, into the opened blow-mold halves, and a reinforcing element is supported inside the preform by a displaceable holding device. During closing of the blow-mold halves, pressure is exerted on the wall regions of the preform that are adjacent to the reinforcing element. This pressure results in a reduced cross section of the preform wall in the region of the reinforcing element, and thermoplastic material is displaced. The interior of the preform is subjected to a blowing-pressure no later than when the pressure is applied from the exterior, and the blowing pressure causes the preform to inflate inside the mold. The displaced material anchors the reinforcing element inside the blow-molded body, and preferably forms bridges which extend across the blow-molded body and which cover the sides of the reinforcing element.

Abstract: An apparatus for producing a finned tube from synthetic plastics material has a moulding chamber which moves in the direction of production. Molten synthetic plastics charge enters this moulding chamber from which fins are moulded one after another, the fins being in each case formed individually one after another. In order to ensure this procedural measure, there are constructed in the surface of the molten plastics material present in the moulding chamber annular raised portions with conveying surfaces trailing in the direcetion of production. Corresponding conveying grooves are constructed in the half moulds which bound the molding chamber. These measures ensure an accurate contour of the tube which is to be produced, ensuring that a reverse flow of molten plastics charge and its combustion will be prevented.

Abstract: A blow molding parison (10) being draped around a generally rectangular mold part (12) is spread from its extruded cylindrical shape into a generally rectangular shape (14), as it descends from an extrusion head (11). Before the open bottom (20) of the parison reaches a clamp (25) on the mold part, a jet of air is blown downward through the open bottom to draw in the parison's side and end regions (21 and 22 respectively). This reduces the size of parison (10) and helps it fit within the clamp and also forms the end regions (22) of the parison into a pair of opposed pleats (23) extending inward from the ends of the pinch-off line when clamp (25) closes. Further descending of the parison unfolds the pleats into gussets (24) extending toward corner regions (27) of mold part (12) so that the parison can drape around the mold part corners.

Abstract: A method for producing thermoplastic tubular containers having a tubular wall section, open neck, and integral sealed bottom where a thermoplastic disc, is sealed to the inner wall of the tubular wall section, and the disc, while in a moldable state, is formed into a bottom wall by application of either a vacuum to the exterior surface of the disc or a fluid pressure to the interior of the tubular wall section, or both, to mold the disc in a mold cavity to a desired shape. A supporting sleeve surrounds the tubular wall section during application of the fluid pressure. Thermoplastic containers can be formed from a single thermoplastic material or from laminates, such as a laminate material containing an oxygen impermeable layer.

Abstract: A method of fabricating a multi-layered parison having adjacent layers of different polymeric resins with incompatible melt flow temperatures without degrading the polymeric resin having the lower melt flow temperature.

Abstract: A barrier structure liner for food packages comprises two layers of EVOH (ethylene-vinyl alcohol copolymers), one of which is interposed between two moisture barriers. The inner layer of EVOH (in contact with the packaged food) functions as a solvent barrier which reduces the loss of flavor components from the foods, while the buried EVOH layer, protected from moisture from the packaged food and the outside atmosphere, serves as an oxygen barrier to prevent oxygen from outside the package from oxidizing the foods within the container. The barrier structure may be used in paper cartons, plastic bottles, bags and the like.

Abstract: In a process for producing a hollow body with a wall which partially comprises foamed thermoplastic material by an extrusion blow molding procedure, a preform which comprises at least first and second layers of which at least one comprises foamable plastics material is first extruded, the layer of foamable material is foamed, and then the preform is expanded in a blow molding mold by the application of an internal pressure. The hollow body may have a welded seam at a region of the hollow body at which an operation of squeezing off excess material has been carried out, the seam being in the form of an outwardly projecting flange web portion and the thickness thereof being such that the layer of foamable material is compressed at least to such an extent that it is not thicker than in the unfoamed condition.

Abstract: Polyvinyl alcohol films are provided which are gelled, non-tacky, bubble-free and resistant to water at ambient temperatures. The polyvinyl alcohol film is obtained by plasticizing (fluxing) and melting granules of pure polyvinyl alcohol containing from 25 to 35% by weight of water at a temperature at least 100.degree. C. above the equilibrium melting point of the granules and less than or equal to 220.degree. C., and extruding the melted granules through a die at a temperature at least 5.degree. C. above the equilibrium melting point of the granules and less than or equal to 98.degree. C., optionally followed by monoaxial stretching or biaxial stretching of the unstretched film obtained. The stretched or unstretched film may be heat-treated to improve its properties. The polyvinyl alcohol film can be used to prepare with thermoplastic films composite films or sheets having a high gas impermeability.

Abstract: An extrusion molding equipment for a multi-layer parison which includes an operation position detecting device for detecting an operation position of an accumulator extruding an layer of resin material invisible from outside the parison. A pressure detecting device is provided for detecting pressure of the inner resin material in an inner resin conduit. An extrusion amount control device for the inner resin material is also provided for controlling an extrusion amount of the inner resin by the use of a signal indicating the operation position from the operation position detecting device, and a signal indicating the pressure from the pressure detecting device.

Abstract: The invention relates to a method and an apparatus for the extrusion of plastic pipes. Today, plastic pipes are provided with a sleeve in such a manner that the end of the pipe is heated, whereafter the end is expanded by means of a mandrel or a pressure medium. This step requires a separate sleeve machine, and it also takes plenty of time and consumes thermal energy. According to the invention a sleeve (22) is formed in connection with the extrusion of a pipe in an apparatus in which a mandrel (8) is surrounded by chill moulds (1, 2) moving in the axial direction of the apparatus. The sleeve is formed by providing some of the chill moulds with a recess (16) the shape of which corresponds to that of the sleeve (22) and by pressing a plasticized plastic hose (11) extruded through a nozzle (10) against the walls of the recess in the area thereof by means of pressure air.

Abstract: Long lengths of a heat-shrinkable sleeve for use in splicing electrical cables and the like are manufactured by providing an elongated impermeable core having a smooth outer surface, extruding an elongated sleeve around and in contact with the core, the sleeve having a smooth inner surface conforming to the outer surface of the core, and effecting an initial expansion of a portion of the sleeve to a larger diameter in an expansion zone so that the sleeve separates from the core and leaves a space between the sleeve and core. A fluid is introduced into the space under pressure via a fitting at the downstream end of the sleeve while continuously advancing the sleeve and core through the expansion zone. To begin the process, a permeable core is used, and the sleeve is extruded around and in contact with the permeable core.

Abstract: A process for the preparation of a multilayer plastic container in which an inner and an outer layer, one of which is in the melt phase, are introduced into an opened mold. Before the mold is closed, the inner layer is inflated by a pressurized medium until the facing surfaces of the inner and outer layers are in contact over almost all their respective surface areas. The mold is then closed and the first and second layers are forced against the mold wall by a pressurized medium.

Abstract: In the forming of an article by blow molding parisons into conformity with cavities of an array of mold sections wherein parisons in the form of tubes are extruded from an extruder into an array of neck molds on a head, the head is moved axially away from the extruder to define the parisons, mold sections are closed about the parisons and the parisons are blown outwardly and a take out mechanism grasps and removes the containers after the mold sections are opened, the apparatus for application of labels to the hollow blown plastic articles which comprises a label carrier mounted for reciprocating movement between the open mold sections and supporting an array of spaced vacuum pick up devices.

Abstract: A method of forming a container having upper and lower portions, the lower portion having self-supporting side walls and a bottom wall. The upper portion is flexible and non-self-supporting. Preferably, the upper and lower portions are formed of plastic material with the upper portion forming a integral continuation of the lower portion. The entire container may be formed using blow molding techniques or other conventional means such as co-extrusion.

Abstract: A double-walled plastic box 20 is molded from a single parison 50 in an unlimited depth by closing the bottom of parison 50 and draping it downwardly over a core 60 so that a leading part of the parison forms an inside wall of the box and a following part of the parison forms an outside wall of the box. After parison 50 is draped over core 60, outer mold parts 61 close around the core and the draped parison; and the box is blown in a cavity between the core and the outer mold parts. The parison can be ballooned while draping down over the core to enlarge the parison to stand out from and surround the core, which can be raised during the draping process. Parison 50 can also be deballooned after draping to stay within the confines of outer mold parts 61 while core 60 raises and while the outer mold parts close.

Abstract: A float switch assembly for selectively energizing and deenergizing a fluid pump or other electronic equipment responsive to the rise and fall of a fluid level within a reservoir and a method of manufacturing or assembling the float switch assembly. The assembly includes a hollow tube having an open end wherein a mercury tilt switch is fixed. A plurality of conductors covered with a non-conductive material extend within the tube open end and are connected to the switch so that a current path may be provided between the conductors responsive to the angle of the switch. Ridges are provided on the outer surface of the tube near the open end and, a float bulb is provided substantially surrounding the tube below the ridges and sealingly connected upon the ridges. A potting epoxy compound surrounds the switch and the conductors within the tube so that electrical contact with a fluid through the open end is prevented. A cap is placed on the tube open end and is locked into place.

Abstract: An air cleaner and method of making same, the air cleaner comprises: a one piece, moulded housing, including domed first and second outer portions integrally formed about a common circumferential first edge, defining therein a chamber, an inlet and an outlet extending therefrom in communication with the chamber. A panel filter is secured within the housing, during the moulding thereof, at the common edge for dividing the chamber into first and second aerodynamically shaped compartments in communication with the inlet and outlet respectively.

Abstract: A process for coextrusion blowmolding of multilayer polymer articles, wherein a multilayer parison is extruded through a die, introduced into a mold, and blowmolded, the flow of multilayer plastic material being periodically interrupted, and additional plastic material being injected into the extrusion die at timed intervals, so that this additional material forms portion of the parison which later are trimmed from the molded article and reprocessed for reuse.

Abstract: A method of manufacturing interior trimmings characterized in that an integral portion is extended from the circumferential rim of a skin material in die half, that the substantially whole of this extended portion is sandwiched and fixed between a holder member and that face of the die half which is combined with that of the other die half, that the paired die halves are thus combined with each other to mold a resin body, and that when the resin body thus molded is divided, the extended portion of the skin material is folded round the divided end of its corresponding resin body and fixed to the inner face of this resin body.

Abstract: A process for forming a separable laminate container includes the steps of coextruding at least two substantially non-adhering thermoplastic compositions to form a tubular parison having a relatively thick outer layer and a relatively thin inner layer. The parison is subsequently blow molded and trimmed to provide an open-ended container body and an inner liner which is separable along the interior walls of the container body to permit closing and/or sealing of the liner, independent of the container. A lid may also be applied to the container body.

Abstract: The tube of the present invention has no or very small local minute nonuniformity in thickness of EVOH layer, and therefore drawn-formed articles such as blow bottle obtained by draw molding the tube have no streaks and are superior in appearance.

Abstract: A modular extrusion head is disclosed including a plurality of cross head die modules, each including a flow path for a single resin. Molten resin layers are flowed from the modules onto a stepped mandrel and then along the mandrel and out an extrusion die to form a multi-layer parison. The layers are thin, with a uniform thickness and hole free. The modules are temperature zoned to permit flowing of a low temperature resin to and along the mandrel in contact with a high temperature resin without impairing the properties of the low temperature resin.

Abstract: Method in extruding a double-walled plastic tube by using plastic materials of different colors for the inner layer and the outer layer, a portion of the material for the inner layer being diverted to form a longitudinal strip of the outer layer on the outside surface of the tube. The invention also relates to an extrusion tool for working the method, wherein an element (21) is provided inside the tool to divert material from a passage (19) for material for the inner layer to a passage (16) for material for the outer layer.

Abstract: A heat-softening plastic material is extruded such that the plastic material forms a pine-shaped outer member and at least one rod-shaped core member is positioned in the inside space of the pipe-shaped outer member. Divided forming molds are disposed about the extruded plastic material except for an entrance opening for introducing gas such that only the pipe-shaped outer member is expanded by the pressurized gas and the thus formed container is subsequently cooled and hardened. The thus formed hollow container has at least one rod-shaped support extending between the upper and lower ends on the inside of the hollow container. The container will not expand and remains stable even if a high pressure fluid is introduced into the inside of the container.

Abstract: Disclosed is a protective patch for biaxially a heat shrinkable, thermoplastic vacuum bag for protecting the bag from puncture by sharp protruding bones in bone-in cuts of meat which are vacuum packaged within the bags. The patch is made from multi-layer film and preferably comprises outer layers of a blend of linear low density polyethylene and ethylene vinyl acetate copolymer and inner layers of ethylene vinyl acetate copolymer. The patch is heat shrinkable with the bag. A method of making the patch is also disclosed.

Abstract: A double-walled plastic box 20 is molded from a single parison 50 in an unlimited depth by closing and holding a bottom region of the parison at the bottom of a cavity 30, bringing together parts of a core 40 above the cavity to close off an upper region of the parison, moving the core, the cavity, or both vertically to position the core within the cavity and invert the parison so that a lower region of the parison forms an outside wall of the box against an inside surface of the cavity and an upper region of the parison forms an inside wall of the box against an outer surface of the core. The parison is then blown into a double-walled box 20 in the shape of an enclosed space between the cavity and the core.

Abstract: Disclosed is a protective patch for biaxially a heat shrinkable, thermoplastic vacuum bag for protecting the bag from puncture by sharp protruding bones in bone-in cuts of meat which are vacuum packaged within the bags. The patch is made from multi-layer film and preferably comprises outer layers of a blend of linear low density polyethylene and ethylene vinyl acetate copolymer and inner layers of ethylene vinyl acetate copolymer. The patch is heat shrinkable with the bag. A method of making the patch is also disclosed.

Abstract: A multilayer film useful in the packaging of high acid food products at elevated temperatures comprises a core layer of ethylene vinyl alcohol copolymer, two intermediate layers each comprising a polyamide; outer blend layers of linear low density polyethylene and anti-blocking agent, and adhesive polymeric materials to adhere the outer blend layers to the respective intermediate polyamide layers.

Abstract: The present invention provides an injection and blow molding machine which comprises a machine bed having five operating sections, i.e., an injection molding section, a temperature control section, a stretching and blow section, a secondary working and releasing section and a releasing section, a base plate mounted in a peripheral portion above and parallel to said machine bed, a rotary disk rotatably mounted on the under-surface of said base plate and having neck molds of the same number as that of the operating sections, and a drive means fixedly mounted on the central portion of the base plate to intermittently turn the rotary disk with respect to the respective operating sections. It is of course that between the rotary disk and the machine bed, there are provided an injection mold disposed movably up and down, a temperature control member, a blow mold and a mechanism for opening and closing the blow mold, which are disclosed in U.S. Pat. No.

Abstract: In a process for making a gasket with a tubular shape, a tubular blank of elastomeric material is extruded and zones are marked along its length, the zones corresponding to a location along the length of the gasket which is to undergo a change of shape, dimension, or orientation through a shaping operation. The shaping operation involves a preliminary step of attaching a U-clip to the blank and introducing the blank, with the U-clip attached to it, into a shaper passage which has a guide element extending into the passage, and guiding the blank through the shaper passage while the guide element extends into the U-clip.

Abstract: Mold and method for molding a plastic headrest core member which has an insert partially embedded therein. The mold comprises two halves one of which is integrally formed at its shaped inner surface with a projection which is constructed and arranged to contact an end of the insert to suppress undesirable inward movement of the same during cooling of the molded headrest core member in the closed mold.

Abstract: Polyvinyl alcohol films are provided which are gelled, non-tacky, bubble-free and resistant to water at ambient temperatures. The polyvinyl alcohol film is obtained by plasticizing (fluxing) and melting granules of pure polyvinyl alcohol containing from 25 to 35% by weight of water at a temperature at least 100.degree. C. above the equilibrium melting point of the granules and less than or equal to 220.degree. C., and extruding the melted granules through a die at a temperature at least 5.degree. C. above the equilibrium melting point of the granules and less than or equal to 98.degree. C., optionally followed by monoaxial stretching or biaxial stretching of the unstretched film obtained. The stretched or unstretched film may be heat-treated to improve its properties. The polyvinyl alcohol film can be used to prepare with thermoplastic films composite films or sheets having a high gas impermeability.

Abstract: Seamless, molded, thermoplastic articles having a laminar, multi-component composition with a heterogeneous blend of incompatible polymers--at least one as a matrix and at least one as a discontinuous phase, are manufactured by (1) heating the blend above the melting point of the highest melting polymer component, and (2) molding the melted blend to have a knit line curved through the thickness of the article resulting from such molding.

Abstract: An air cushion shoe sole which is preferably blow molded of elastomeric material and has at least one cavity which in cross-section is substantially rectilinear. The cavity has a number of depressions and each cavity has an air valve for introducing a shock absorbing material, namely gas, liquid, or a combination thereof into that cavity. Each air valve has means in it for automatically bleeding off a portion of the shock absorbing material introduced into the cavity once the pressure of that material reaches a predetermined level.

Abstract: A synthetic resin product contains various substances such as perfumes, insectifuges/insecticides, mold/mildew-proofing agents and anti-fungi agents which are inactivated by forming an inclusion compound thereof in cyclodextrin and coating them with glycitol(s) to thereby prolong the duration period of the substance. A process for the production of the same is further disclosed wherein the glycitol is provided in the form of reduced millet jelly or reduced cyclodextrin millet jelly.

Abstract: This invention relates to a method and an apparatus for the production of ribbed pipes. The apparatus comprises a core which together with an extrusion sleeve forms a nozzle through which a plastic material is fed into a moulding space defined between a conically-enlarging mandrel and chill moulds moveable with respect to the mandrel. The volume of a moulding space defined between a plane at an end face of the extrusion sleeve, a surface of the mandrel, and a cylindrical plane projection from the surface of a kernel on the mandrel equals the combined volume of the grooves positioned at the mandrel at the mandrel at each particular moment. The method feeds a volume of the plastic material per unit time equal to volume of the pipe wall and ribs produced in that unit time.

Abstract: In disposing an insert or inserts within a blow-molded product, before the blow molding step is started, an inner supporting device supporting the insert at an end thereof is inserted into a parison and then the mold is closed so that the insert is made into contact with the parison. Thereafter the blow molding is effected so that the insert is securely welded to the parison.

Abstract: A method and an apparatus for making blow-moulded bottle from a preform consisting of at least three layers. For making the preform a tube section heated at one end is shaped by pushing into a closed bottom mould to form a bottom and pressure is exerted in the axial direction on the center bottom region to close the still present gaps in an outer layer as soon as an inner layer has flowed together.

Abstract: A foam acoustic absorption member having a stabilizing layer with perforations and, in order to obtain a simple, stable structural shape of homogeneous resistance to flow, the stabilizing layer (2) is a wide-side wall of a hollow body (K) which wall is pressed, under thermal deformation, against the foam layer (1), the openings in said hollow body consisting of holes (9) punched from the foam side.

Abstract: Disclosed is a coated oriented plastic vessel formed by subjecting a parison, preform or sheet comprising a molecularly orientable thermoplastic resin substrate and a coating layer of a vinylidene chloride copolymer formed on at least one surface of said substrate to a draw-molding operation such as biaxial draw-blow-molding or draw-forming, wherein the coating layer of the vinylidene chloride copolymer has such a molecular orientation tht the sum of two-dimensional orientation coefficients (l+m) in the axial direction and circumferential direction is at least 0.03 as measured according to the polarized light fluorometry and the coating layer is not substantially peeled at the low-temperature burst test conducted at -5.degree. C.

Abstract: A plastic container with an integral handling ring is formed in a mold having a pair of side sections movable toward each other and a pair of co-planar end sections movable toward each other and toward said side sections, by placing molten extrudate in a mold between the side and end sections, so that a handling ring can be formed and compression joined to the container at the same time the container is being formed by blow-molding.

Abstract: A multi-layer laminate structure comprises a separate layer of scrap produced from the several thermoplastic resins used in making the laminate structure. In a preferred construction, the multi-layer laminate structure comprises an outer thermoplastic polyolefin layer, an inner thermoplastic polyolefin layer and an intermediate oxygen barrier layer preferably made of ethylene-vinyl alcohol copolymer. An adhesive layer bonds the barrier layer to the inner polyolefin layer and a separate scrap layer is disposed interiorly of the outer polyolefin layer. A second adhesive layer bonds the scrap layer to the intermediate barrier layer. Containers having excellent oxygen barrier properties and good transparency are made by forming a parison from the multi-layer laminate structure and blow molding the parison to the desired container shape.

Abstract: This relates to a method of forming a thermal/collapse-resistant highly oriented polyester container for use in hot fill applications. In accordance with the method of a polyester preform is reheated and then placed in a blow mold cavity whereat the preform is distended to match the blow mold cavity to form an intermediate article including a container having an oriented end unit receiving finish of a diameter materially greater than the diameter of the preform. The method is characterized in that in providing the preform the composition of the polyester, the draw ratio during distending of the preform and reheat conditions are all controlled to provide a container with a sidewall and finish density in the range of 1.350 to substantially but less than 1.370 grams/cubic centimeter.

Abstract: A hollow thermoplastic container having an annular closure receiving insert embedded in the wall thereof made by blowing a hollow preform radially outwardly against the confines of a mold wherein a cone-shaped mandrel is positioned on the wall of the mold and supports the insert on the wall of the mold with the apex extending inwardly such that as the preform is blown outwardly, the plastic material is deflected and caused to form about the periphery of the insert.

Abstract: A method and apparatus for manufacturing a hollow plastic product is provided. In accordance with one aspect, into a mold half having a tubular groove portion and a projecting groove portion which projects outwardly from the tubular groove section is supplied a parison into the tubular groove portion and a clump of molding material into the projecting groove portion. When blow molding is carried out by introducing a pressurized gas into the parison, the clump becomes integrated with the parison thereby providing a hollow plastic product of unitary structure. In accordance with another aspect of the present invention, a parison extrusion nozzle is provided with at least two passages each of which is connected, preferably through a valve, to a corresponding dispensing unit for dispensing a desired molding material. A control unit is provided as connected to each of the dispensing units to control the supply of molding material so that there is obtained a parison having regions of different molding materials.

Abstract: An apparatus for producing a sheet having many hollow bodies from thermoplastic material such as polyethylene, used for cushioning and insulation, is disclosed. Film extruded from a T die, after being cooled, is heated by an induction heating roller with a jacket and inner cooling means.The induction heating roller with a jacket and inner cooling means has, along with the jacket within a rollershell, an induction coil for heating, and a hermetically sealed heat transfer medium between the jacket and the induction coil. The characteristic feature of the present invention is a cooling means provided to cool the heat transfer medium, with advantages of rapid temperature rise and fall, and uniform temperature distribution on the circumference and longitudinal axis of the roller.Using this apparatus, a sheet having many hollow bodies, with high transparency and high product yield without defects such as partial inferior fusing, can be produced.