GB2107964A

GB2107964A - Apparatus for making internally coated hollow baked products

Info

Publication number: GB2107964A
Application number: GB08225337A
Authority: GB
Inventors: Snr Franz Haas; Franz Haas
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-09-07
Filing date: 1982-09-06
Publication date: 1983-05-11
Also published as: SE8205045D0; BR8205166A; IT1189345B; FR2512328A1; NL8203466A; DE3232824A1; FR2512328B1; NO823009L; CA1178847A; NZ201819A; ES515513A0; FI823030A0; DE3232824C2; AU8804382A; SU1512470A3; GB2107964B; YU199382A; FI823030L; AT375005B; JPS58134935A

Abstract

A hollow baked product, e.g. a wafer, is formed by winding a baked strip (1) with overlapping convolutions around rotating mandrel (2) and pressed thereon by roller (3). The wafer is shaped and cut into desired lengths by cutter (5) remote from the mandrel. An edible coating material is applied to at least part of the inside surface of the wafer through passages (36, 35) to form layer (56). A particulate solid filler may be supplied from bin (14) through central bore (7) onto coated wafer; the coating having been supplied to wafer via passages (13, 11) and annular groove (10). Two separate coatings may be applied to the wafer before applying a filler. <IMAGE>

Description

SPECIFICATION Process and apparatus for making a hollow baked product which is coated on at least part of its inside surface This invention relates to the making of a hollow baked product which comprises a body formed by a wound baked strip consisting preferably of a wafer strip and coated on at least part of its inside surface and optionally containing a filling material in at least part of its cavity.

Various baked wafer products made by machine are known, inter alia, in the foodprocessing industry. These baked wafer products are placed on the market in a filled or unfilled state and are generally known as luxury foods. Such products of the wafer-baking industry are, e.g., wafer cones, wafer cups, wafer plates, flat wafer discs, low hollow wafers, hollow sticks, wafer rolls, icecream cones, filled wafers, icecream wafers, small filled wafer sticks, wafer slices and the like. These baked wafer products made by baking a wafer dough are crisp and brittle and break easily. They are baked to be as dry as possible and have a very low moisture content.

The various baked wafer products can be made in various ways. Some wafer products are baked in their final shape. This applies, e.g., to wafer cones, wafer cups, wafer discs, low hollow wafers and the like.

In the manufacture of other baked wafer products, a wafer sheet or an endless wafer strip is baked first and is given its final shape when it is still soft after the baking operation. In that final shape the baked wafer product is permitted to cool and to assume a crisp and brittle consistency.

Examples of such baked wafer products are sugarcontaining icecream cones, hollow sticks, sugarcontaining wafer rolls and the like.

Other kinds of baked wafer products are made in that a plurality of wafer sheets are baked, cooled, coated with cream, and stacked to form a wafer block. That cream-filled wafer block is subsequently cut into small handy pieces of uniform size, which are then packaged in units consisting of one or more pieces, possibly in vacuum packages, and are placed on the market in that form.

Various baked wafer products may be provided with coatings consisting, e.g., of sugar or chocolate, or may contain various filling materials, such as icecream, various other creams, chocolates or the like.

The wafer products described hereinbefore differ from waffles, which are usually baked by housewives in waffle irons and constitute a soft baked product, which is similar to rolls or pancakes. These waffles made by housewives do not resemble at all the above-mentioned baked wafer products of the wafer industry as regards consistency and use.

It is known from Austrian Patent Specification 262,187 to make a tubular wafer body in that a baked wafer strip which is delivered by a continuously operating wafer-baking machine and is still in a warm, soft state is continuously wound on a winding mandrel in overlapping helical convolutions so as to form an endless tubular body, which is rotating as a result of the winding operation. The winding mandrel may be stationary or may be rotatably mounted and adapted to be driven and has a longitudinal bore, which opens at the free end of the winding mandrel and tapers there to form a spray nozzle. Fat or chocolate is sprayed through that nozzle onto the inside surface of the tubular body. When the tubular body and the coating material sprayed on it have hardened, the tubular body is sawn through with a circular saw.Only coating materials which are sprayable or which have been rendered sprayable by heating can be used in that known process. An entraining fluid, such as air, is required for a fine division of the sprayed coating material. If the fat or chocolate to be applied is liquefied by heating so that it is rendered sprayable, the danger of an overheating of the fat or chocolate will impose a restriction on the liquefaction so that it will also be necessary to admix air as an entraining fluid. In that connection it has been found that a disadvantage resides in that the quantity which can be applied by spraying is restricted by the fact that the entraining air escaping from the wound wafer body during the cutting operation will inevitably destroy the wafer body.It is not possible to liquefy coating materials by dissolving them in a solvent or by mixing them with other liquids so that the coating material can be sprayed because the coating material can be sprayed because the coating material will not adhere to the inside surface of the tubular body unless the solvent or the liquid vehicle either evaporates or is absorbed by the wafer body. The cavity inside of the wafer body is much too small and the time available until the tubular body is severed is much too short to permit of an evaporation of the solvent or of the liquid vehicle. In no case must the solvent or the liquid vehicle be absorbed by the wafer body because the latter would be destroyed in that case.Another disadvantage of the spraying of fat or chocolate onto the inside surface of the tubular body resides in that the cavity of the endless tubular wafer body will then be filled with a fog consisting of the spray and that fog will soil the circular saw used to sever the body. As a result, the circular saw will become inoperative in the course of time and must be cleaned frequently so that the manufacture of the wafer body will be interrupted. Besides, the fog which has been formed will escape from the interior of the wafer body into the environment during the cutting operations and will then soil the entire environment. Another disadvantage involved in the spraying of the coating material resides in that only a single coating material can be applied.If the tubular wafer bodies made by that known process are to be filled, the tubular body must first be sawn into discrete pieces because the filler can be introduced only into the discrete tubular wafer bodies without a risk of a mixing of the filler with the fat or chocolate which has been sprayed. The subsequent filling of discrete tubular wafer bodies involves a high handling expenditure because each piece which has been sawn ofi must be suitably received and then fed to a separate filling apparatus.

From Austrian Patent Specification 304,245 it is known to make a filled hollow baked product, which has a tubular wafer body, in a process in which a baked wafer strip which is still soft after the baking operation is continuously wound on a winding mandrel in overlapping helical convolutions to form an endless tubular body, which is completely filled with a creamlike material supplied through a longitudinal bore in the winding mandrel and is sheared into pieces of desired length before the filler and the creamlike material have hardened. The tubular body is sealed on its sides in that steam is supplied to the several convolutions of the wafer band before said convolutions overlap so that said convolutions will adhere to each other, possibly under pressure.The wafer strip used for that purpose contains 30 to 60% sucrose, glucose or malt products, which under the action of heat in the presence of moisture are quickly dissolved to become tacky.

As that known hollow baked product has no coating on the inside surface of the tubular wafer body, the filling material must consist of a substance which will not soften the wafer strip because this would adversely affect the strength and quality of the wafer body.

As the known hollow baked product is filled immediately after the wafer strip has been wound and the filling material is supplied through the winding mandrel, it is not possible at all to coat the wound tubular body on its inside surface before it is filled, e.g., to provide a sealing layer between the filling material and the wafer body.

Austrian Patent Specification 327,129 discloses apparatus for making a hollow baked product which is adapted to receive a soft filling material in a process in which a baked strip is provided on one side with a coating of a material, such as chocolate, which acts as a sealant for the filling material, and the baked strip is then continuously wound on a winding mandrel with overlapping helical convolutions to form an endless tubular body which is coated on its inside surface. The sealing coating is applied to the baked strip by spraying, squirting or pouring and the filling material is supplied through the central longitudinal bore of the winding mandrel into the hollow baked product thus obtained.In the operation of that apparatus, the materials which can be applied to the baked strip are substantially restricted to materials which can be sprayed, squirted or poured at room temperature or at a temperature to which they may be heated.

Whereas in the operation of that apparatus the air which is admixed to permit the spraying or squirting of the coating material can escape and materials which can be liquefied by heating need be heated only to a temperature at which they can be poured, the materials which have been applied must be so elastic that they continue to adhere to the baked strip and can be deformed with the latter as it is wound. Besides, said materials must retain an adequate bond strength during the winding of the baked strip so that they will adhere to the inside surface of the resulting tubular body.

Moreover, the material which has been applied must retain its sealing capacity when the coating is upset during the winding operation. Where coating substances are used which can be liquefied by heating, this requirement will be met by the contact of the coating material with the surface of the baked strip, provided that the latter is at a sufficiently high temperature. Materials which cannot be sprayed or squirted or poured or which do not melt as they contact the baked strip cannot be used to form a coating in this manner.

It is an object of the invention to eliminate the above-mentioned disadvantages and deficiencies.

In a process of making a hollow baked product which comprises a body formed by a wound baked strip consisting preferably of a wafer strip and coated on at least part of its inside surface and optionally containing a filling material in at least part of its cavity, wherein a baked strip, particularly a baked wafer strip which is still soft after the baking operation, is continuously wound in overlapping convolutions on a winding mandrel having a forward end to form a rotating endless tubular body which advances toward and beyond said forward end of the mandrel and is coated on its inside surface with an edible coating material and is subsequently severed into discrete pieces of finite length and the coating material is supplied through the mandrel toward the forward end thereof and is applied to the inside surface of the endless tubular body adjacent to said forward end of the mandrel, that object is accomplished in that one or more coating materials in a pasty or liquid or spreadable state are applied to the inside surface of the endless tubular body through one or more openings which are formed in the mandrel in its forward end face or succeed the forward end of the mandrel when seen in the direction in which the tubular body is conveyed along the mandrel and/or are caused to emerge through one or more openings provided in the periphery of the mandrel and/or at the transition from the forward end face of the mandrel to its periphery, the coating material or materials are optionally spread on at least part of said inside surface to which they have been applied, and a particulate solid material and/or a filling material is supplied through the mandrel or an extension of the mandrel and introduced into the endless tubular body after the coating material or materials have been applied.

In the process according to the invention, at least one coating is formed on the inside surface of the endless tubular body in that coating material supplied through the winding mandrel is applied in the form of at least one coherent stream to the inside surface of the endless tubular body adjacent to the forward end of the winding mandrel. The phrase "at least one coherent stream" includes a continuous coherent stream, a plurality of parallel continuous coherent streams and a plurality of consecutive coherent streams of finite length.

In the process according to the invention, any undesired adverse effect in the cavity of the tubular body or on the severing device will be avoided because the coating materials are not atomized so that no fog is formed in the cavity of the tubular body. The process according to the invention may be used to apply liquid substances and/or substances which cannot be liquefied even by heating. If the process according to the invention is used to coat the baked strip with materials having a melting point above the temperature of the baked strip during the winding operation, it will be sufficient to heat these materials to such a temperature that they will be just tacky as they are applied.Within the scope of the invention the application of the coating materials can be assisted in that the coating material which has been applied to the inside surface of the tubular body is spread on said surface. The spreading of the material which has been applied will result in an intimate contact of the coating material with the baked strip. The consistency of the material to be spread is selected so that the forces required to spready the material on the inside surface of the wound body will not adversely affect the latter.

In the process according to the invention, a particulate solid material can be applied to the coated inside surface of the tubular body. That particulate solid material is supplied through the mandrel and applied to the coating, e.g., when the latter is still tacky. As a result, the roughness of the inside surface of the coated tubular body is increased so that any filling material which may subsequently be introduced will be more firmly held in the hollow baked product. The particulate solid material which is applied to the coating may preferably be granular and may consist in that case of crystalline sugar, croquant, comminuted nuts or sugar-containing grits, or may consist of a powder, such as powdered sugar or the like.

In the process according to the invention, a filling material may be introduced through the mandrel into the interior of the tubular body before the latter is severed into length sections if a sealing layer which is required between the baked strip and the filling material has previously been applied to the inside surface of the tubular body. In that case, each piece which is severed from the endless tubular body will constitute a complete hollow baked product, which is coated on its inside surface and contains a filling material and can then be packaged.

Because the coating is formed on the wound tubular body, the convolutions of the wound baked strip consisting of a wafer strip may be adhered to each other, e.g., in that steam is supplied to the subsequently overlapping regions of the convolutions of the strip so that the coating material applied to the inside surface need not comply with such high requirements as are to be met, e.g., when a layer applied to the baked strip is wound with the latter. In the process according to the invention, the quantity of the coating material which is applied may be restricted to the quantity which is absolutely required for the desired sealing.

In one embodiment of the process, one or more coating materials are discharged through openings formed in the forward end face of the mandrel or succeeding the forward end of the mandrel in the direction in which the tubular body is conveyed and are permitted to descend from said opening or openings substantially only by gravity. That embodiment of the process will be of special advantage with coating materials which are liquid or can easily be liquefied because a splashing or spraying of the coating materials will be avoided.

In another embodiment of the process, one or more coating materials are caused to emerge through one or more openings provided at the periphery of the mandrel under such a pressure that the tubular body is temporarily expanded in the radial direction by not more than the approximate thickness of the coating to be formed. In that case it will be possible to apply a coating material which is merely spreadable or pasty and for this reason must be conveyed under a relatively high pressure and the thickness of the coating to be applied can simply be controlled by a change of the pressure under which the coating material is conveyed and of the pressure under which it is discharged.

The invention provides also apparatus for carrying out the process. That apparatus comprises a winding device, which is associated with at least part of the mandrel, means for continuously feeding the baked strip to the winding device, coating material supply means for supplying a coating material, comprising at least one supply passage, which extends through the mandrel toward its forward end and has at least one outlet opening, and means for severing the tubular body into individual pieces.That apparatus is characterized in that the outlet opening or openings formed in the mandrel or in extensions thereof are provided in the forward end face of the mandrel or of said extensions or in the periphery of the mandrel or in a transitional portion between the forward end face and the periphery of the mandrel and have a cross-section which is sufficiently large to prevent a spraying of the coating material supplied by said coating material supply means, any device for introducing a filling material comprises also at least one passage which extends through the mandrel and/or through extensions thereof and is separate from the supply passage or passages for the coating material or materials and has one or more outlet openings which in the direction of conveyance of the tubular body succeed the outlet opening or openings for the coating material or materials, the passage for the filling material optionally contains a conveying device, and at least one device for spreading at least part of the coating material or materials applied to the inside surface of the tubular body is optionally provided.

With that design, the outlet openings can be arranged close to that portion of the tubular body to which the coating material is to be applied.

In the apparatus according to the invention, the means for introducing the filling material may be so designed that the filling material is introduced into the interior of the tubular body with an optimum orientation for the filling operation.

Another advantage of the apparatus according to the invention resides in the provision of means for conveying the filling material in the passage for the filling material. In that case even a filling material which can be conveyed only with great difficulty can be introduced into the interior of the tubular body. Within the scope of the invention, the means for conveying the filling material may have separate drive means, which are independent from the means for driving the winding device or for driving the mandrel. In that case the means for conveying the filling material can be operated to convey the filling material under optimum conditions at a volumetric rate or speed which is independent of the speed at which the baked strip is wound and of the rate at which a coating material is applied.

Also within the scope of the invention, the outlet opening or openings may consist of one or more annular channels, slots or holes and may be formed in the mandrel in a coating section, which succeeds the winding section of the mandrel in the direction of conveyance of the tubular body.

That feature permits a very compact design of the entire apparatus.

Within the scope of the invention the coating section of the mandrel may consist of a separate coating head. This will permit a simple alteration of the mandrel, e.g., from the application of only one coating material to the application of a plurality of coating materials in that one coating head is replaced by another. The mandrel is formed in its winding section with all passages which are required for one coating head and the other.

Within the scope of the invention, at least one tube extends through the mandrel in its longitudinal direction and may be used to feed the filling material through the mandrel and is not rotated in unison with a rotatable mandrel. That tube may be fitted in a bore which is formed in the mandrel and may be in snug contact with the tube, or a clearance left between the outside surface of the tube and the inside surface of the bore in the mandrel may be used as a passage for feeding a coating material or filling material.

Within the scope of the invention, the mandrel may consist of a sleeve and the tube fitted into the mandrel may preferably consist of a material of low thermal conductivity and may be in substantially snug contact with the inside surface of the sleeve and on the outside of that portion which contacts the inside surface of the sleeve may have one or more flats or one or more grooves, which together with the sleeve define one or more supply passages for one or more coating materials, which supply passage or passages communicate with the outlet opening or openings formed in the sleeve for the discharge of the coating material or materials whereas the bore of the tube constitutes a passage for a filling material.In that embodiment of the invention, the interior of the tubular body formed by winding the baked strip may be supplied with a filling material which when introduced into the tubular body must be at a predetermined temperature above or below the temperature required for the winding of the baked strip. In that case the filling material may be introduced into the tubular body at a temperature which is optimum for said introduction and said temperature will not be affected by the temperature of the baked strip, which during the winding and coating operations may be at optimum temperature for these operations.

If the baked strip is wound at a temperature which is much higher than the temperature of the filling material, the outlet opening of the heatinsulating tube is suitably spaced a sufficiently large distance from the outlet openings provided on the periphery of the mandrel for the discharge of the coating material so that the baked strip which has been wound to form a tubular body can cool down before the cold filling material contacts the coating on the inside surface of the tubular body formed by winding a baked strip.

Also within the scope of the invention, at least one length section of the mandrel may consist of two concentric tubes which define between them a supply passage for a coating material in an arrangement in which the inner tube extends beyond the forward end of the outer tube and is provided at its forward end with a flange, which together with the forward end face of the outer tube defines an annular channel which constitutes an outlet opening for the coating material. In that case the supply passage may have a large crosssection so that the coating material can be conveyed through the mandrel at a high rate and a tubular body which is internally coated can be produced at a high rate.If the inner tube has a sufficiently small wall thickness, filling material at a high rate, corresponding to the high production rate of the tubular body, can be fed through the interior of the inner tube.

Within the scope of the invention the outer and inner tubes may be rotatable relative to each other so that the filling material can be introduced into the hollow baked product through the inner tube which is stationary while the outer tube is rotating.

Alternatively, the inner tube may be rotated at a higher speed than the outer tube so that that portion of the coating head which succeeds the outlet opening or openings for the coating material will spread the coating material.

Also within the scope of the invention, recesses and elevations may be formed on the surface of the passage for the filling material so that the surface of the passage acts to convey the filling material, particularly if the latter consists of a particulate solid material. If the surface of the passage is formed by the inside surface of the inner tube and the latter is rotatable relative to the outer tube, the velocity at which the filling material is conveyed may be controlled independently of the winding speed of the mandrel.

Also within the scope of the invention, the passage for the filling material may contain a conveyor screw, which is preferably adapted to be driven independently of the mandrel. With that design the rate or velocity or pressure at which the filling material is conveyed can be selected in dependence on the nature of the filling material.

Because the conveyor screw is driven independently of the mandrel, these parameters can be selected in dependence on the production rate of the tubular body. In case of a change of the filling material, it will be sufficient to exchange the conveyor screw so that optimum filling conditions will be obtained even when an entirely different filling material is employed.

The invention will subsequently be explained with reference to a hollow baked product which is made in a process in which the tubular body is made from a baked strip consisting of a wafer strip which is still soft after the baking operation as it is wound around the mandrel. It will be understood that the invention is not restricted to the use of a baked strip made from wafer dough. The dough may consist of a wafer dough having a low sugar content or of a wafer dough which has a high sugar content so that the baked strip will be plastic when it is still soft from baking and will harden as it is cooled, or of other baked doughs which can be made in the form of continuous strips.

Illustrative embodiments of the apparatus according to the invention are shown on the accompanying drawings, in which Figure 1 is a diagrammatic side elevation showing a first embodiment of apparatus according to the invention and Figure 2 is a sectional view taken on line Il-Il in Figure 1.

Figures 3 to 5 are longitudinal sectional views showing additional embodiments of apparatus according to the invention.

Figures 6a, 6b, 7, 8a, 8b, 9a, 9b and 10 show various embodiments of a mandrel which may be used within the scope of the invention to apply only one coating material to the inside surface of the tubular body, or of the coating section of such mandrel.

Figures 11 a and 1 b show another embodiment of a mandrel which may be used within the scope of the invention to apply up to three different coating materials.

Figures 1 2a and 1 2b show another embodiment of a mandrel which may be used within the scope of the invention for applying only one coating material, Figure 13 shows another embodiment of a mandrel which may be used within the scope of the invention to apply one coating material or two different coating materials, Figures 14, 1 spa, 1 sub show two embodiments of a mandrel for applying two different coating materials, Figures 1 6a, 1 6b, 1 7a, 1 7b, 1 8a, 1 8b, 19, 20, 21 a, 21 b, 21 c, 22, 23a, 23b, 23c show various embodiments of a mandrel which may be used within the scope of the invention to coat the tubular body on its inside surface and to introduce a filling material or a particulate solid material into the interior of the tubular body, Figure 24 shows the applying section of a mandrel, which applying section consists of a plurality of concentric tubes and serves to apply two coating materials and to introduce a filling material or a particulate solid material into the interior of the tubular body, Figure 25 shows an embodiment of a mandrel provided with two applying heads for applying two coating materials, Figures 26a, 26b, 27a, 27b show two more embodiments of a mandrel which may be used within the scope of the invention and has a heatinsulating core, and Figures 28 to 31 are longitudinal sectional views showing four different embodiments of a hollow baked product made in accordance with the invention.

In the embodiment shown in Figures 1 and 2 a baked strip 1 consisting, e.g., of a wafer strip which is still soft from baking is supplied to a driven mandrel 2 at an oblique angle to its axis of rotation and is urged against the winding section 4 of the mandrel 2 by a feeding and pressureapplying roll 3, which is also driven. The feeding and pressure-applying roll 3 is axially parallel to the rotating mandrel 2 and is provided on its periphery with screw threads, which tend to advance the wafer band that is supplied at an oblique angle to the axis of the mandrel 2. The mandrel 2 is succeeded by a severing device 5 for severing the baked strip 1 when the same has been wound on the mandrel to form a tubular body. The severing device may consist of a shearing machine or of a travelling circular saw or the like.The winding apparatus consisting of the feeding and pressure-applying roll 3 and the mandrel 2 is supplied with the baked strip 1, e.g., from a continuously operating wafer-baking machine, and winds the strip around the mandrel to form a tubular body, which is advanced along the mandrel and rotates as it is advanced. The overlapping edges of the baked wafer strip will stick together if the subsequently overlapping portions of the baked wafer strip that has not yet been wound are supplied with steam from a steam discharge nozzle 6, which extends substantially tangentially to the mandrel 2 (Figure 2). Steam may also be supplied to the baked strip 1 in that water is continually fed at a low rate to a hot metal plate or the like which is disposed under the path of the baked strip.The winding section 4 of the mandrel 2 is succeeded toward the free end of the mandrel by a coating section 9, which is formed in its periphery with an annular groove 10 near the free end of the mandrel. The annular groove is defined toward the free end of the mandrel by a sizing shoulder 38, which is smaller in diameter than the mandrel by an amount which is approximately twice the thickness of the coating to be applied. The coating material 56 is supplied to the annular groove 10 through radial passages 35 from a supply passage 36 that extends centrally in the mandrel 2. The coating material 56 completely fills the annular passage which is defined by the annular groove 10 and the tubular body 39 and the coating material contacts the inside surface of the tubular body 39 throughout the periphery of the mandrel.Moving relative to the mandrel 2, the tubular body takes from the mandrel the coating material, which sticks to the inside surface of the tubular body. The sizing shoulder 38 will scrape surplus coating material from the inside surface of the tubular body 39 so that the thickness of the coating applied to the inside surface of the tubular body 39 will be determined by the annular clearance between the tubular body 39 and the sizing shoulder 38. If the sizing shoulder 38 is cylindrical, the coating of the tubular body 39 will have a cylindrical inside surface.

The coating on the inside surface will be formed with radially inwardly protruding ribs if the sizing shoulder 38 has axial grooves conforming to the desired cross-section of the ribs, or with grooves, if the sizing shoulder 38 is formed with corresponding radially protruding ribs.

In the embodiments shown in Figures 3 to 5, the winding section 4 of the mandrel 2 is succeeded by a coating section, which at the periphery of the mandrel is also formed with an annular groove 10. Supply passages 11 extend longitudinally through the mandrel and serve to supply the annular groove with a coating material that is to be applied to the inside surface of the tubular body. The supply passages 11 for the coating material extend through the winding section 4 of the mandrel 2 near the periphery thereof and open laterally into the annular groove 10. The supply passages extend from a manifold 12, which is disposed behind the roll 3 and is fed with the coating material through a conduit 1 3 from a supply bin or a pump (not shown).The mandrel 2 has a central bore 7, which extends throughout the length of the mandrel 2 and serves to supply a filling material 8 into the interior of the tubular body.

A passage 15 extends from a supply bin 14 for filling material to that end of the bore 7 which is disposed at the rear end of the mandrel 2. A blast nozzle 1 6 which is coaxial to the mandrel 2 opens into the passage 1 5 (Figure 3). A particulate solid filling material which is delivered from the supply bin 14 through the passage 1 5 is blown by the blast nozzle 1 6 through the bore 7 into the interior of the tubular body to fill the same in part. If the particulate solid material, such as comminuted nuts, crystalline sugar, croquant, sugar-containing grits or the like should be deposited only in a small quantity on the coated inside surface of the tubular body, the bore 7 suitably flares toward the free end of the mandrel 2 (Figure 20).

In another embodiment (Figure 4), a conveyor screw 1 7 is mounted in the bore which extends through the mandrel 2 and is supplied from the supply bin 14 with the filling material that is to be conveyed. The conveyor screw 1 7 terminates at the forward end of the mandrel 2 and is driven by the screw shaft at the rear end of the mandrel 2.

That concept may be adopted in conjunctions with a driven or stationary mandrel because the filling rate will be determined by the variable speed of the conveyor screw, independently of the rotation of the mandrel. Alternatively, the conveyor screw may be non-rotatably connected to a rotating mandrel so that the speed of the latter will also determine the rate at which the filling material is supplied.

As is apparent from the embodiment shown in Figure 5, a rotating mandrel 2 may be used directly to convey the filling material through the central bore 7 of the mandrel 2. For this purpose, individual helical ribs 1 8 are provided on the surface which defines the bore 7. These ribs 18 may constitute a single, continuous rib.

Figures 6 to 11 show various embodiments of mandrels 2 having applying sections 9 for applying only one coating material to the inside surface of the tubular body.

The embodiment shown in Figure 6 differs from the mandrels shown in Figures 3 to 5 only in that there is no central bore for the filling material. The design of the coating section 9 of the mandrel 2 is common to these four embodiments. Between the annular groove 10 and the forward end face of the mandrel 2, the latter has a portion that is equal in diameter to the body of the mandrel 2. If such a coating sectiQn 9 is used, the coating material will be delivered into the annular groove 10 under such a pressure that the tubular body is temporarily locally inflated adjacent to the annular groove.

In the embodiment shown in Figure 7, the coating section 9 of the mandrel 2 is conically tapered at 33. At the transition from the cylindrical portion of the mandrel to its conically tapered portion 33, the mandrel 2 is formed at its periphery with four outlet openings 34, which are equally spaced around the periphery of the mandrel and communicate through radial passages 35 with an axial passage 36 for supplying the coating material. The outlet openings 34 consist of slots, each of which extends along the mandrel partly in its cylindrical portion and partly in its conically tapered portion.

Owing to that design the coating material supplied through passages 35, 36 emerges from the outlet openings 34 in part at the periphery of the mandrel and in part towards its forward end face.

The selection of the taper and of the distance over which the outlet openings extend into the conically tapered portion 33 will depend on the desired thickness of the coating.

In this embodiment, a helical strip of coating material is applied from each outlet opening to the inside surface of the tubular body. The lead of the helical strips will depend on the ratio of the rotational movement to the axial movement of the tubular body relative to the stationary or rotating mandrel 2. In the embodiment shown in Figure 7, four separate helical strips will be formed on the inside surface of the mandrel if the tubular body is axially moved at a high velocity and is only slowly rotated relative to the mandrel or four helical strips having overlapping edges will be formed. This will depend on the lead of the helical strips and on the length of the outlet openings 34 measured at right angles to the helix.

If the mandrel rotates in synchronism with the tubular body, parallel longitudinal strips of the coating material will be formed on the inside surface of the tubular body.

The outlet openings for delivering the coating material may alternatively consist of slots 40, which extend at an oblique angle to the axis of the mandrel and open at the periphery of the mandrel and may also open at its forward end face.

In the embodiment shown in Figures 8a, 8b the slot 40 is so arranged that its ends 41 lie on the periphery of the mandrel on a straight line which intersects the axis of the mandrel at an oblique angle. In the embodiment shown in Figures 9a, 9b the ends 41 of the slot 40 lie on a straight line which intersects the axis of the mandrel at right angles.

Each slot communicates at its bottom with a central supply passage 36 formed in the mandrel 2. With that design, the coating material can be applied at a high rate.

In the embodiment shown in Figure 10, the coating section 9 is provided at the forward end face of the mandrel with outlet openings 1 9, which communicate through passages 11 with one or more feeders for supplying one or more coating materials. Each of these feeders comprises a feed conduit 13 and a manifold 12. The coating material emerges through these outlet openings from the forward end face of the mandrel and in dependence on the consistency of the coating material may be squirted from said outlet openings as a thick jet onto the inside surface of the tubular body or may be applied under pressure as an extrusion to the inside surface of the tubular body.As the coating material emerges from the outlet openings in a substantially liquid state, it will spread on the inside surface of the tubular body as soon as it has been applied thereto and will thus form a coherent coating or a plurality of helical strips, which merge only in part or are entirely separate from each other. This will depend on the velocity at which the tubular body is advanced along the mandrel.

From a stationary mandrel, the coating material will fall by gravity on that portion of the inside surface of the tubular body which is substantially vertically below the respective outlet opening.

When it is desired, for instance, to apply a plurality of different coating materials to the inside surface of the tubular bodies in superimposed or juxtaposed layers, another embodiment of the invention may be adopted in which the mandrel 2 has a plurality of axial passages which open in the forward end face of the mandrel. To ensure a separation of the several coating materials, the passages extend through respective extensions, which protrude from the forward end face of the mandrel, and the openings of the several passages are spaced different distances from the forward end face of the mandrel. Said extensions which protrude from the end face of the mandrel may suitably consist of tubes, which are fitted in bores formed in the coating section of the mandrel.

Alternatively, said extentions may consist of tubes which extend through a sleevelike mandrel and protrude different distances from the forward end face of the mandrel (Figure 12).

In another embodiment the outlet openings 19 are provided in the forward end face of the mandrel 2 in a circular annular region 20 which is close to the periphery of the mandrel and is adjoined toward the axis of the mandrel by an extension 21, which protrudes from the forward end face of the mandrel 2 and has a radially outer boundary surface 22, which axially adjoins the outlet openings 19. The boundary surface 22 ensures that the coating material emerging from the outlet openings 1 9 in the forward end face will be confined closely to the inside surface of the tubular body, which is sliding along the periphery of the mandrel 2, so that the coating material applied to the inside surface of the tubular body will form a coating of uniform thickness (Figures 1 1a, 1 1b).

If the mandrel 2 is stationary or rotates at low speed, the cylindrical boundary surface 22, which may be formed with recesses axially adjoining the outlet openings 19, if required, will prevent a premature sagging of the coating material which has emerged from an outlet opening 1 9.

If the mandrel 2 is rotating, the boundary surface of the extension at the forward end of the mandrel will promote the spreading of the coating material emerging from the several outlet openings 1 9 so that a continuous coating of uniform thickness will be formed. In that embodiment the coating material may emerge from the forward end face of the mandrel at a low velocity relative to the tubular body. For instance, the mandrel and the tubular body wound on the mandrel may rotate about the axis of the mandrel substantially at the same angular velocity. In that case, the tubular body will perform only a longitudinal movement relative to the mandrel and it will no longer be necessary to impart a rotation to the coating material as it reaches the inside surface of the tubular body.The outlet openings 19, which are angularly spaced apart in the circular annular region 20, and the boundary surface 22 of the extension 21 will then ensure that the coating has a uniform thickness throughout the periphery of the inside surface of the tubular body.

The extension 21 may be integral with the mandrel 2 or may consist of a sealing plug, which is fitted in a bore of the mandrel 2 (Figure 11 a).

The extension 21 may be integrally formed with a sealing plug 23, which seals a bore 7 extending through the mandrel 2. The supply passages 11 terminate in outlet openings 19, which are formed in the forward end face of the mandrel 2 and disposed radially outwardly of the plug 23. Such a mandrel can be used for numerous purposes.

When the sealing plug 23 has been inserted, the mandrel 2 can be used to coat the inside surface of the tubular body with coating material emerging from outlet openings 1 9 formed in the forward end face of the mandrel whereas no filling material is introduced into the interior of the tubular body. When the sealing plug 23 is replaced by a plug which has a through bore, the same mandrel 2 can also be used to introduce filling material into the interior of the tubular body.

In another embodiment, shown in Figure 13, the sealing plug 23 is replaced by a coating head 24 and the supply passages 11 open into an annular channel 26, which is defined by the forward end face of the mandrel 2 and a shoulder 25 of the coating head. The shoulder 25 tapers toward the forward end of the coating head 24 and is formed with another annular groove 27, which communicates through radial passages 28 with a blind hole 29, which continues the bore 7 of the mandrel. In that case the bore 7 of the mandrel 2 constitutes a passage for supplying a second coating material, which flows through the annular groove 27 and is applied to the coating formed by the first coating material, which has been applied from the annular channel 26 to the inside surface of the tubular body.

The thickness of the coating formed by the first coating material and the thickness of the coating formed by the second coating material are respectively controlled by the largest and smallest diameters of the shoulder 25 and by the pressures applied to the coating materials in the annular channels 26 and 27.

In another embodiment of the coating head, the shoulder 25 is adjoined by a step 30 and the supply passages 31 communicating with the bore 7 of the mandrel 2 have outlet openings 19 in the forward end face of the step 30 (Figures 1 5a, 15b). From that coating head, one coating material emerges through the annular channel 26 disposed at the periphery of the mandrel and the second coating material emerges through the outlet openings 1 9 formed in the forward end face of the mandrel 2 or of its coating section.

In the embodiment shown in Figures 16a,16b, the outlet openings 34 are arranged like those of Figure 7 but communicate with respective supply passages 35, which extend axially near the periphery of the mandrel. In this embodiment, different coating materials can be supplied to respective outlet openings or a single coating material can be supplied through all supply passages. A bore or passage 37 extending through the mandrel can be used to introduce a filling material or a particulate solid material into the interior of the tubular body which has been coated on its inside surface.

In the embodiment shown in Figures 17a, 17b, the outlet opening consists of a slot 40, which is similar to that shown in Figures 8a, 8b and has ends 41 which are disposed on the periphery of the mandrel on a straight line which intersects the axis of the mandrel at an oblique angle. In the embodiment shown in Figures 21 a, 21b, 21e the outlet opening consists of a slot 40, which is similar to that shown in Figures 9a, 9b and has ends 41 which are disposed on the periphery of the mandrel on a straight line which intersects the axis of the mandrel at right angles.In these two embodiments the mandrel has a centrally disposed passage 42 for a filling material or for a particulate solid material, the slot is separated at its bottom from that passage by a wall (Figures 1 7b, 21 b) and the supply passages 35 of the mandrel open in the side walls of the slots 40 (Figures 17a, 17b,21a).

In the embodiments shown in Figures 8a, 8b and 17a, 17b, the slots 40 open at the periphery of the mandrel and the opening of the slots 40 extends around one-half of the periphery of the mandrel.

In the embodiments shown in Figures 21 a, 21 b, 21 c, 9a and 9b the slot 40 extends into a step 43, which is directed toward the forward end of the mandrel 2. Part of the opening of the slot is open toward the forward end of the mandrel 2.

Rather than through a plurality of supply passages 35, which are provided in the mandrel 2 near its periphery and open in the side walis of the outlet opening or openings, which may consist of one or more annular channels or slots, a single passage defined by coaxial cylindrical surfaces may be sued to supply coating material (Figures 14, 19and25).

That passage may be defined by an outer tube 44 and a cylindrical rod coaxially extending in said tube. The tubular body slides on the outside of the outer tube 44. The cylindrical rod protrudes from the forward end of the outer tube and has a flange 46, which is disposed outside the outer tube and together with the forward end face 47 of the outer tube 44 defines an annular channel, which constitutes an outlet opening. The flange 46 of the rod constitutes a sizing shoulder for the application of the coating material.

The cylindrical rod may have a longitudinal bore, which serves as a supply passage leading to a coating head 48, which is mounted on the forward end of the rod. In this embodiment, shown in Figure 14, two coating materials can be applied in succession. One coating material is applied through the coating head 48 and the second coating material emerges from the annular channel defined by the forward end face 47 of the outer tube 44 and the coating head 48.

The embodiment shown in Figure 14 may also be used to apply a single coating material by means of the coating head 48, which is rotated independently of the mandrel 2 so that the coating material will be spread and the irregularities which will occur when the coating head is stationary will be avoided.

To permit a coating of the tubular body and an introduction of a filling material or a particulate solid material into said tubular body, the rod of the mandrel 2 is replaced in the embodiments shown in Figures 19, 22, 23a, 23b, 23c by an inner tube 45, which extends in the outer tube 44. The inner tube 45 carries at its forward end a flange 46, which together with the forward end face 47 of the outer tube constitutes the coating section of the mandrel. The bore of the inner tube 45 serves as a passage for supplying the filling material or the particulate solid material and may contain a conveyor screw 1 7 for conveying the filling material or the particulate solid material (Figure 22).

In another embodiment, the inner tube 45 is provided on its inside surface with a continuous helical rib (Figures 23a, 23b, 23c).

In the embodiment shown in Figure 24 the coating section 9 of the mandrel consists of a plurality of concentric tubes, which define supply passages between them. An inner tube 45 is provided at its forward end with a coating head 48 and is inserted into the outer tube 44. The coating head 48 consists of a cylindrical flange, which protrudes from the inner tube 45 and is formed between its two end faces with a peripheral groove 49, which communicates through radial passages with the interior of the inner tube 45.

Another concentric tube 50 is fitted in the coating head 48 and extends from the forward end face of the coating head 48 and together with the inner tube 45 defines the passage for supplying the coating material which emerges from the coating head. The interior of the tube 50 serves as a passage for supplying the filling material or the particulate solid material or is used as a passage for supplying the coating material to another coating head 48' (Figure 25). The rear end face of the first coating head 48 and the forward end face 47 of the outer tube 44 define another annular channel, through which a coating material emerges.

In the embodiments shown in Figures 27a, 27b, 26a, 26b the mandrel consists of a cylindrical sleeve 51, which contains a tubular insert 52, which is in snug contact with the inside surface of the tube and is formed in its outside peripheral surface with a flat 53, which together with the inside surface of the sleeve 51 defines a passage for supplying a coating material. That supply passage terminates just as the flat 53 near the forward end face of the sleeve 51. The insert 52 is provided with a collar 54, which is disposed closely beyond the forward end of the flat 53 and together with the forward end face of the sleeve 51 defines an annular channel 55. The passage defined by the flat 53 opens laterally into said annular channel.That passage may alternatively be formed by one or more longitudinal grooves formed in the outside peripheral surface of the insert but the flat is preferably to the longitudinal groove because the contact surface between the coating material fed in the passage and the heatinsulating material is smaller than the contact surface between the coating material fed in the passage and the mandrel sleeve 51.

As a result, more heat will be transferred through the winding mandrel to the coating material than is dissipated through the insulating material.

The insert 52 may consist of heat-insulating material and may terminate at a large distance from the annular channel 55. This will be the case, e.g., when a tubular body formed by winding a wafer strip is to be filled with icecream. In that case a coating material such as chocolate which seals the wafer strip against an absorption of moisture is applied through the annular channel 55 to the inside surface of the tubular body and the internally coated wafer body is cooled so that the icecream fed through the tubular insert 52 reaches a wafer body which is cooler than during the winding operation and which is completely sealed. In a length section which corresponds to the desired length of the hollow baked product the endless tubular wafer body is completely filled with icecream and that length section is then severed from the endless wafer body.

Figures 28 to 31 are longitudinal sectional views showing some examples of hollow baked products which have been made by the process according to the invention.

Figure 28 shows a hollow stick 57, which has been formed by winding a wafer strip and a has a chocolate coating 56a on its inside surface. Within the scope of the invention that chocolate coating 56a may be continuously applied throughout the periphery of the inside surface of the hollow stick.

Alternatively, a plurality of helical chocolate strips may be applied, which merge to form a coherent coating. The several chocolate strips may consist of different chocolate compositions.

Alternatively, part of the helical strips may consist of a fat icing or part of the inside surface of the hollow stick may remain uncoated.

In another embodiment of the process according to the invention the coating material is applied to the inside surface of the hollow stick 57 in the form of narrow ribs or winding strips, which may be helical and may cross each other.

Said strips of chocolate or deposited ribs may be applied to extend parallel to the longitudinal axis of the hollow sticks.

Figure 29 shows a hollow stick in which a particulate solid material 8, such as nuts, croquant or the like has been applied on a coating 58 consisting of one or more layers of chocolate or fat icing.

Before the solid particulate material 8 is applied, jam may be applied in discrete strips to the coating consisting of chocolate or fat icing.

Figure 30 shows an internally coated hollow stick 57, which has been completely filled with a nougat composition 59 or with icecream or with a cream.

Figure 31 shows a hollow stick 57 which has been coated on its inside surface with chocolate and with a second coating material 60 consisting of nougat, whereafter a particulate solid material 8 consisting of croquant has been applied to the nougat layer.

Chocolate, fat icings, nougat or jam have been mentioned hereinbefore as coating materials. It will be understood that other materials of cream like to pasty consistency can be applied by the process according to the invention. Such substances may include marzipan or a caramel composition.

The mandrel may consist of surface-hardened metal or of a metal sleeve and a plastic core or entirely of plastic. The coating heads may consist of plastic material.

It will be understood that the present invention is not restricted to the illustrative embodiments described hereinbefore. The several features of the various embodiments of the mandrels used within the scope of the invention and of the coating sections of said mandrels may be combined in any desired manner without departing from the scope of the invention. For instance, mandrels which are shown to be integral may alternatively be composed of two or more elements. Besides, the coating heads may be integral with the mandrel or may consist of units which are screwed to the mandrel.

Each of the mandrels described, which may be used within the scope of the invention, or of the coating sections or coating heads of such mandrels, may be used in any of the embodiments of the apparatus shown in Figures 1 to 5.

Claims

1. A process of making a hollow baked product which comprises a body formed by a wound baked strip consisting preferably of a wafer strip and coated on at least part of its inside surface and optionally containing a filling material in at least part of its cavity, wherein a baked strip, particularly a baked wafer strip which is still soft after the baking operation, is continuously wound in overlapping convolutions on a winding mandrel having a forward end to form a rotating endless tubular body which advances toward and beyond said forward end of the mandrel and is coated on its inside surface with an edible coating material and is subsequently severed into discrete pieces of finite length and the coating material is supplied through the mandrel toward the forward end thereof and is applied to the inside surface of the endless tubular body adjacent to said forward end of the mandrel, characterized in that one or more coating materials in a pasty or liquid or spreadable state and in the form of at least one coherent stream are applied to the inside surface of the endless tubular body through one or more openings which are formed in the mandrel in its forward end face or succeed the forward end of the mandrel when seen in the direction in which the tubular body is conveyed along the mandrel and/or are caused to emerge through one or more openings provided in the periphery of the mandrel and/or at the transition from the forward end face of the mandrel to its periphery, the coating material or materials are optionally spread on at least part of said inside surface to which they have been applied, and a particulate solid material and/or a filling material is supplied through the mandrel or an extension of the mandrel and introduced into the endless tubular body after the coating material or materials have been applied.

2. A process according to claim 1, characterized in that one or more coating materials are discharged through openings formed in the forward end face of the mandrel or are disposed behind the forward end of the mandrel in the direction in which the tubular body is conveyed are permitted to descent substantially only by gravity.

3. A process according to claim 1, characterized in that one or more coating materials are caused to emerge through one or more openings provided at the periphery of the mandrel under such a pressure that the tubular body is temporarily expanded in the radial direction by not more than the approximate thickness of the coating to be formed.

4. A process according to any of claims 1 to 3, characterized in that the inside surface of the tubular body is covered in part or is completely covered with one or more continuous layers by the application of a coating material.

5. A process according to any of claims 1 to 3, characterized in that the inside surface of the tubular body is covered in part or is completely covered with one ore more continuous layers by the application of a plurality of coating materials.

6. A process according to claim 5, characterized in that the or each layer is formed from a plurality of coating materials.

7. A process according to any of the preceding claims, characterized in that the coating material or materials are applied to form one or more helical or longitudinal strips.

8. A process according to claim 7, characterized in that the helical strip or strips are applied so that their convolutions overlap each other.

9. A process according to claim 7, characterized in that the helical or longitudinal strips are applied so that their convolutions overlap each other at least in part.

10. A process according to any of claims 7 to 9, characterized in that one or more coating materials are applied to form helical or longitudinal strips and the coating material or materials forming at least one of the helical or longitudinal strips are distributed over part of the inside surface of the tubular body when said coating material or materials have reached said inside surface.

11. A process according to any of claims 1 to 6, characterized in that a coating which completely covers the inside surface of the tubular body is formed in that the coating material is applied continuously throughout the periphery of the inside surface and part of the thickness of the resulting coating is subsequently scraped from the inside surface at least in part of its periphery or in a helical strip.

12. A process according to any of the preceding claims, characterized in that a particulate solid material is introduced, e.g., by blowing into the interior of the tubular body and is deposited on the coating material which has been applied.

1 3. Apparatus for carrying out the process according to any of the preceding claims, comprising a winding device, which is associated with at least part of the mandrel, means for continuously feeding the baked strip to the winding device, coating material supply means for supplying a coating material, comprising at least one supply passage, which extends through the mandrel toward its forward end and has at least one outlet opening, and means for severing the tubular body into individual pieces, characterized in that the outlet opening or openings formed in the mandrel or in extensions thereof are provided in the forward end face of the mandrel or of said extensions or in the periphery of the mandrel or in a transitional portion between the forward end face and the periphery of the mandrel and have a cross-section which is sufficiently large to prevent a spraying of the coating material supplied by said coating material supply means, any device for introducing a filling material comprises also at least one passage which extends through the mandrel and/or through extensions thereof and is separate from the supply passage or passages for the coating material or materials and has one or more outlet openings which in the direction of conveyance of the tubular body succeed the outlet openings or openings for the coating material or materials, the passage for the filling material optionally contains a conveying device, and at least one device for spreading at least part of the coating material or materials applied to the inside surface of the tubular body is optionally provided.

14. Apparatus according to claim 13, characterized in that the or each passage communicates with an outlet opening which consists of an annular channel, a slot or a hole.

1 5. Apparatus according to claim 13, characterized in that the or each passage communicates with a plurality of outlet openings.

1 6. Apparatus according to claim 13, characterized in that a plurality of passages communicate with a common outlet opening, which consists of an annular channel or a slot.

17. Apparatus according to any of claims 13 to 1 6, characterized in that the outlet opening or openings consisting of one or more annular channels, slots or holes are formed in a coating section of the mandrel and said coating section succeeds the winding section of the mandrel in the direction of conveyance of the tubular body.

1 8. Apparatus according to claim 17, characterized in that one or more outlet openings consisting of one or more annular grooves, slots or holes are formed in a separate coating head, which constitutes the coating section of the mandrel.

1 9. Apparatus according to claim 18, characterized in that a separate coating head is provided for each coating material and has outlet openings which communicate through separate passages with separate supply passages of the mandrel.

20. Apparatus according to any of claims 1 3 to 19, characterized in that at least one of the outlet openings for the coating material or materials is succeeded by means for spreading the coating material which emerges from said outlet opening.

21. Apparatus according to claim 20, characterized in that the means for spreading the coating material comprise a shoulder formed on the mandrel or coating head and succeeding the outlet opening or comprises the forward boundary of the outlet opening in the direction of conveyance of the tubular body.

22. Apparatus according to any of claims 13 to 21, characterized in that at least one tube extends through the mandrel in its longitudinal direction.

23. Apparatus according to claim 22, characterized in that the mandrel consists of a sleeve, the tube inserted into the mandrel preferably consists of a material which has a low thermal conductivity, said tube is in snug contact with the mandrel substantially throughout its periphery and on the outside of that portion of the tube which contacts the inside surface of the sleeve is formed with a flat or a groove which together with the sleeve defines a supply passage for the coating composition, said passage communicates with the outlet openings formed in the sleeve for discharging the coating material, and the bore of the inserted tube constitutes a passage for the filling material.

24. Apparatus according to any of claims 13 to 22, characterized in that at least part of the mandrel consists of two concentric tubes, the inner tube carries at its forward end a coating head, and the bore of the inner tube constitutes a supply passage for delivering the coating material to the outlet opening or openings of the coating head.

25. Apparatus according to claim 24, characterized in that the clearance between the concentric tubes constitutes also a supply passage for a coating material, the inner tube protrudes from the forward end face of the outer tube and at its forward end is provided with a flange, which together with the forward end face of the outer tube defines an annular channel, which constitutes an outlet opening for that coating material.

26. Apparatus according to claim 25, characterized in that another concentric tube is inserted into the inner tube and defines an internal passage for the filling material and together with the inner tube defines a supply passage for a coating material.

27. Apparatus according to claim 25 or 26, characterized in that the outer tube and the inner tube or tubes are rotatable relative to each other.

28. Apparatus according to claim 27, characterized in that the outer tube and the inner tube or tubes are non-rotatably mounted.

29. Apparatus according to any of claims 1 3 to 28, characterized in that the conveyor provided in the passage for the filling material is formed by recesses or elevations formed on the surface which defines the passage.

30. Apparatus according to claim 29, characterized n that one or more helical grooves or ribs are provided on the surface defining the passage.

31. Apparatus according to any of claims 13 to 28, characterized in that one or more conveyor screws are provided in the passage for the filling material and are adapted to be driven preferably independently of the mandrel.

32. Apparatus according to any of claims 13 to 31 , characterized in that the several tubes consist of heat insulating material or are designed to be heat-insulating.