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STATEMENT OF RELATED APPLICATIONS 
       [0001]    This application claims priority on and the benefit of German Patent Application No. 10 2010 025 129.1 having a filing date of 25 Jun. 2010 and German Patent Application No. 10 2010 050 490.4 having a filing date of 8 Nov. 2010, both of which are incorporated herein in their entireties by this reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field. 
         [0003]    The invention relates to a process for producing a road covering of asphalt, in particular an asphalt surface or an asphalt road, with a road paver, with material for producing the road covering being supplied to the road paver and said material being homogenized. The invention additionally relates to a road paver, with an undercarriage, with at least one hopper, in particular at least one chamber for holding preferably at least essentially continuously supplied material, with a screed for producing a road covering, and with a conveyor for conveying material to the screed, and with a device for homogenizing the material. The invention also relates to a feeder, with an undercarriage, with at least one hopper for holding material, with a conveyor for preferably continuously supplying material from the hopper to a road paver for laying a road covering, in particular an asphalt layer or asphalt covering. The invention moreover relates to a paving train with at least one road paver, and with at least one feeder, it being possible to produce at least one road covering by the road paver, and for material for producing the surface covering to be supplied by the feeder to the road paver, preferably continuously. 
         [0004]    2. Prior Art. 
         [0005]    Surface coverings or road structures, which can, for example, be walked or driven over, such as in particular road surfacing or road surface layers and in particular roadway pavings, are usually produced from materials such as, preferably, asphalt. So-called road pavers are generally used to produce the layer of material that is applied on top of a subsurface. 
         [0006]    The material is usually at least essentially continuously supplied to the road paver in order to ensure an even application of material that is as uninterrupted as possible. As a buffer for short interruptions in delivery, the road paver generally has a container or hopper that is also known as a material bunker. The material is usually loaded into this hopper from a so-called feeder with the aid of a conveyor. The road paver itself usually also has a conveyor, preferably a scraper conveyor, which serves to remove material from the hopper and supply it to a screed. The screed distributes and compacts the material evenly on the subsurface. The road paver can be designed as a single-layer or multi-layer paver. 
         [0007]    Surface coverings made from rolled asphalt are laid when they are hot. In order to ensure optimum durability of the surface covering produced, it is necessary, on the one hand, to prevent properties of the material from deviating from specifications, such as an optimum working temperature, and differences in the temperature or composition. Mixing devices are usually used for this purpose, which mix a portion of the material to provide it with uniform properties, in particular a uniform temperature, i.e. the material is homogenized before it is laid with the paver. The continuous mixing of the road-surface material entails a high level of energy consumption and causes considerable wear on the required mixing devices. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The object of the invention is to create a process that enables an optimal quality of the road surface material while preventing high energy consumption and wear. 
         [0009]    A process that fulfils this object is a process for producing a road covering of asphalt, in particular an asphalt surface or an asphalt road, with a road paver, with material for producing the road covering being supplied to the road paver and said material being homogenized, characterized in that specifically only such material is used for the homogenizing that deviates in at least one property from predetermined requirements. It is accordingly provided specifically to homogenize such, and preferably only such, material or road-surface material where its properties deviate from predetermined requirements or which does not have the required properties. The material to be homogenized preferably has at least one property that deviates from predetermined requirements. These can, for example, be different physical properties of the material. Meeting predetermined requirements is necessary to achieve optimum quality and durability of the asphalt road. 
         [0010]    The material to be homogenized is preferably separated from the other material at least temporally. This means that the material or at least part of the material which deviates or deviates excessively from the corresponding properties is handled separately. It is thus ensured that the other material has at least essentially the required properties. In particular, the separated part of the material is stored apart from the other material. The material is preferably supplied to a hopper of the road paver and/or the feeder. The separated material is more preferably also supplied to a hopper of the road paver and/or the feeder. This is in particular a preferably separate hopper or an in particular separate section or area or preferably a separate chamber of the hopper. The material to be homogenized is added to the other material preferably in a metered fashion. The material to be homogenized is thus preferably deposited on the other material, in particular in layers or in a layer. The material is usually transported with the aid of a conveyor such as a conveyor belt or scraper conveyor, with the aid of which it is transported in particular as an at least essentially layer-forming stream of material. The separated material is therefore preferably deposited on this stream of material or in the region of the conveyor, or is supplied or added to it. An at least almost even spreading or mixing can thus be achieved. Homogenization thus results. 
         [0011]    The material and/or the separated material is more preferably thoroughly mixed. The material and/or the separated material preferably passes through a mixing device to homogenize the material. At least one conveyor such as, for example, a conveying or mixing auger is provided for the thorough mixing. Alternatively, the material or the separated material can bypass the mixing device. 
         [0012]    Provided for the homogenization of the material is in particular a preferably separate container which is filled with the material to be homogenized. An essentially cylindrical configuration of the container is particularly preferred, especially one having a conically tapering lower end. In order to minimize any heat losses, the container or cylinder is preferably equipped with at least one insulating wall for heat insulation. Positioned in the interior of the container is a mixing device, in particular a rotatably mounted and preferably centrally disposed axis or revolving axis with a plurality of in particular convex and/or concave blades. The blades in this case extend essentially from the central axis to a point near the inner wall of the container. A very preferred arrangement is one with alternating convex and concave blades disposed about the axis, preferably in a plurality of planes. When the mixing device revolves about its axis, the mixture introduced into the container is blended and thus brought to an essentially uniform temperature during the mixing process. Arranged at the lower, conically tapering end region of the container is preferably a removal device. To this end, a slide can be provided, for example, with which a desired quantity of the mix can be released from the container onto the conveyor arranged below, in particular in a continuous manner. The mixing process is preferably executed such that the mixing device, due to the varying concave and convex blade elements, which are preferably arranged in alternating fashion, forces the mix downward during the mixing process along a path which leads from the top end of the cylinder to the lower end and which directs the mix alternately inwards toward the central axis and outwards toward the container wall. In order to raise the temperature of the mixture as a whole a heating element can be additionally provided, for example in the region of the mixing device, such as in the vicinity of the blade elements or the central axis or even the container wall. The heating element can, for example, be powered by electrical means or by a gas heater, for example. 
         [0013]    The temperature of the material is preferably regarded as a relevant value, in particular the average temperature. The material is preferably used for homogenizing depending on its temperature. Material is homogenized that at least in sections has a temperature that deviates from a reference temperature and/or that deviates from the temperature of the other material. The reference temperature or the size of the deviation from the temperature of the other material, in particular its average temperature, can be predetermined for this. A negative deviation preferably results in the separation of at least part of the material, as material temperatures that are too low can cause a reduction in the quality of the material. The material or its properties such as the temperature of the material are preferably homogenized, entailing a selective distributing or thorough mixing. This is achieved by in particular colder material being supplied again to the other material in a preferably metered fashion. However, this happens in such small amounts, or is distributed in such a way that no significant or excessive cooling of the other material is caused by the supplied material. By means of metered addition, relatively small amounts of separated and in particular colder material can thus be supplied to the other material or the stream of material for a homogenization of the temperature. In particular, the temperature of the separated material at least almost matches the temperature of the other material. A homogenization of the temperature is thus all in all achieved. 
         [0014]    Corresponding threshold values or fixed reference temperatures are provided in order to split off or separate part of the material. Part of the material is preferably separated if the temperature of the material falls below a reference temperature. It can additionally or alternatively be provided that the temperature deviation relative to the other material, i.e. for example an average temperature of the material, is at least 5 K, preferably at least 10 K and particularly preferably at least 14 K. (Absolute temperatures are measured in degrees Celsuis, while temperature differences are measured in Kelvin herein.) This means that these deviations are present, on the one hand, relative to the reference temperature and, on the other hand, relative to the temperature of the other material. It has been shown that a deviation of more than 14 K, in particular in the form of colder areas of the material, so-called “nests”, results in a marked deterioration in the quality of the surface covering. 
         [0015]    The temperature of the material is preferably measured by means of a measuring apparatus. The temperature is preferably measured on the road paver and/or on the feeder. The measurement more preferably takes place in the region of a conveyor and/or a hopper for the material. In particular, at least one sensor arrangement is provided with at least one sensor. An infrared sensor is preferably used as a sensor that preferably works in a non-contact fashion. The temperature of the material by sections in individual areas can thus be determined preferably by multiple sensors, preferably arranged at least essentially adjacent to one another, at a suitable distance from the material or stream of material streaming past, in particular on a conveyor. Depending on the temperature, preferably determined at different places, corresponding areas or parts of the material or stream of material can be separated by suitable means. The temperature is preferably measured as averages over flat areas of the material. This is due to the fact that each sensor monitors a specific surface area of the material. Furthermore, the creation of so-called “nests” with too low temperatures and a certain minimum size results in a marked deterioration in the quality of the road covering. The cross section or diameter of these areas is usually at least approximately 5 cm to 10 cm or even 20 cm, but sometimes can even be several decimeters. Substantially smaller nests are normally unproblematic and can accordingly be disregarded. The measuring equipment thus needs to be adapted so that correspondingly small areas are taken into consideration or ignored during the measuring. An imaging process can preferably be provided for determining the temperature distribution of the material, in particular an infrared camera with corresponding analysis. 
         [0016]    A screed is in particular provided on the road paver, serving to apply the supplied material to a subsurface and there compact it. Moreover, a conveying means, in particular a conveying auger or distributing auger, can distribute the material at least essentially evenly over the width of the screed. A conveyor is more preferably provided which supplies the material from a storage means, in particular one of the hoppers or chambers of the screed. Alternatively, the conveyor can, for example, also be loaded directly from the feeder, in order to transport the material to the screed. 
         [0017]    A road paver which fulfils the object of the invention mentioned at the beginning is a road paver, with an undercarriage, with at least one hopper, in particular at least one chamber for holding preferably at least essentially continuously supplied material, with a screed for producing a road covering, and with a conveyor for conveying material to the screed, and with a device for homogenizing the material, characterized in that at least one separate hopper and/or at least one separate chamber is provided for holding material for homogenizing with at least one property that deviates from predetermined requirements. Accordingly, a separate hopper is provided for holding material for homogenizing which has at least one property that deviates from predetermined requirements and/or does not have the required properties. 
         [0018]    The feeder which fulfils the object of the invention mentioned at the beginning is a feeder, with an undercarriage, with at least one hopper for holding material, with a conveyor for preferably continuously supplying material from the hopper to a road paver for laying a road covering, in particular an asphalt layer or asphalt covering, characterized in that at least one measuring apparatus is provided for determining at least one property of the material. Accordingly, a measuring apparatus is provided in order to determine at least one property of the material. 
         [0019]    A paving train which fulfils the object of the invention mentioned at the beginning is a paving train with at least one road paver, in particular according to the invention, and with at least one feeder, in particular according to the invention, it being possible to produce at least one road covering by the road paver, and for material for producing the surface covering to be supplied by the feeder to the road paver, preferably continuously, characterized in that a measuring apparatus is provided for determining at least one property of the material, and/or an additional hopper for holding material for homogenizing. Accordingly, a measuring apparatus for determining at least one property of the material is provided. 
         [0020]    The following detailed embodiments or developments of the invention each relate by analogy to the road paver as well as to the feeder and the paving train. 
         [0021]    The material which has at least one property that deviates from predetermined requirements or does not have the required properties can preferably be specifically homogenized. This means, in particular, that part of the material is split off or can be split off from the other material. Material with deviating properties is thus singled out, as otherwise the quality of the asphalt layer or asphalt overlay produced would be reduced. 
         [0022]    At least part of the material with a temperature that deviates from a reference temperature and/or from that of the other material can, more preferably, be separated off. A separating device for splitting off or separating material is preferably provided. The separating device preferably separates material depending on its temperature. In particular, at least one preferably at least partially pivotable element or guide member is provided which serves to separate the material. This element is, in particular, designed as a guide plate, preferably as a pivotable conveyor. The stream of material can thus be directed in different directions or to different places. Accordingly, the material to be homogenized or to be separated can, for example, be directed into a separate hopper or a separate chamber of a hopper. 
         [0023]    A hopper is preferably provided on the road paver or on the feeder for at least temporarily holding in particular the separated material or material to be homogenized, or the material for homogenizing. The material to be homogenized is preferably supplied to the other material in metered fashion and/or as a layer. The material to be homogenized can thus preferably be removed from the corresponding receptacle, in particular from the separate receptacle, in particular from one of the chambers. The hopper has at least one separate chamber, and preferably two chambers. 
         [0024]    A conveyor such as, for example, a conveying auger or a conveyor belt or a scraper conveyor is in particular provided for the removal of material from the hopper or from the chamber. At least one conveyor, in particular a conveying auger, is more preferably provided to convey and/or mix the material and/or the separated material. The conveyor or conveyors can thus fulfill both functions jointly or separately. The conveyors can be arranged parallel and/or antiparallel to each other but can also be arranged at any angle to each other, although preferably at least almost at right angles to each other. 
         [0025]    In the case of conveying augers, the material is preferably arranged above in a hopper or in one of the chambers. It is transported away or mixed in an essentially horizontal plane. The conveyors particularly preferably serve to add the separated part of the material to the other part of the material, in particular in a metered fashion. This ensures an even distribution of the separated parts of the material. In this way the temperature is matched to the average temperature of the other material. The separated material is particularly preferably added in layers and/or in small amounts to the other material or mixed with it. This ensures optimum heating of the added material, while the other material is only minimally cooled. 
         [0026]    In particular, at least one measuring apparatus is provided for the in particular continuous measurement, at least in sections, of a temperature of the material and/or of the separated material. At least one sensor arrangement is more preferably provided as a measuring apparatus. The sensor arrangement has at least one sensor that works, in particular, in a non-contact fashion. The sensor is preferably an infrared sensor. Three sensors or measuring apparatus are preferably used, which are arranged in particular at least essentially linear and/or in or transverse to the conveying direction. Particularly when assuming a transverse arrangement, the measuring apparatus are distributed over the cross section of the conveyor, preferably evenly. An imaging sensor such as, for example, an infrared camera can also particularly preferably be used. It is thus possible to establish the temperature distributions and local temperature differences or maximum and minimum temperature values in the material or in the stream of material. The temperature of the material is preferably determined in the region of the conveyor. This has the consequence that, when the material is moved continuously through the conveyor and with an essentially fixedly mounted sensor, snapshots of the temperature distribution of the material at the respective point in time can be taken in a corresponding section of the material. Alternatively, the measuring apparatus can be arranged so as to be movable or pivotable. The measuring apparatus is, in particular, provided on the feeder but can also be associated, for example, with the road paver and/or with a separate vehicle having a homogenization device, or with the homogenizer. 
         [0027]    The material can also more preferably be homogenized by a separate device for homogenizing, in particular a preferably self-propelled homogenizer. The device or the homogenizer is, to this end, associated in particular with at least one conveyor and/or at least one hopper. The material can also more preferably be brought together and/or mixed for the homogenizing. The material is preferably supplied to the road paver by a self-propelled feeder. The feeder has for this purpose in particular a conveyor, such as a conveyor belt, a scraper conveyor or the like. The material is supplied to the feeder, for example into a hopper arranged thereon or to a chamber. The conveyor transports the material from the hopper to the region of the road paver. The road paver and the feeder are constituents of the so-called paving train. 
         [0028]    A conveyor belt, a scraper conveyor or the like preferably serves as a conveyor. Particularly preferably, the temperature or the temperature distribution is or can be determined at least in sections on the road paver and/or on the feeder and/or on a homogenizer. The road paver can be designed as a single-layer or multi-layer paver. A multi-layer paver can apply several layers of asphalt to a subsurface in a single operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Preferred embodiments of the invention are described in more detail below with reference to the drawings, in which: 
           [0030]      FIG. 1  shows a paving train with a road paver and a feeder. 
           [0031]      FIG. 2  shows a perspective view of a first embodiment of a road paver with a homogenizer. 
           [0032]      FIG. 3  shows a perspective view of a second embodiment of a road paver with a homogenizer. 
           [0033]      FIG. 4  shows a schematic diagram of the homogenizer in  FIG. 3 . 
           [0034]      FIG. 5  shows a homogenizer according to the invention according to a third embodiment in a front view. 
           [0035]      FIG. 6  shows a top view of the homogenizer according to  FIG. 5 . 
           [0036]      FIG. 7  shows a homogenizer according to the invention according to a fourth embodiment in a front view. 
           [0037]      FIG. 8  shows a top view of the homogenizer according to  FIG. 7 . 
           [0038]      FIG. 9  shows a homogenizer according to the invention according to a fifth embodiment in a front view. 
           [0039]      FIG. 10  shows a top view of the homogenizer according to  FIG. 9 . 
           [0040]      FIG. 11  shows a side view of the homogenizer according to  FIG. 9 . 
           [0041]      FIG. 12  shows a homogenizer according to the invention according to a sixth embodiment in a front view. 
           [0042]      FIG. 13  shows a front view of the homogenizer according to  FIG. 12 . 
           [0043]      FIG. 14  shows a perspective view of the homogenizer according to  FIG. 12 . 
           [0044]      FIG. 15  shows a mixing container with a mixing device. 
           [0045]      FIG. 16  shows a conveyor with two slatted frames. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0046]    A paving train  10  for producing a surface covering or a road of rolled asphalt conventionally comprises at least one road paver  12  and at most one feeder  14 . The road paver  12  serves to apply material supplied to it, such as, for example, asphalt, to a subsurface  38 , to distribute it more or less evenly and to compact it in a suitable manner. At least one layer-forming asphalt roadway paving is thus created. 
         [0047]    In order to move along the subsurface  38  which is to be provided with the road covering, the road paver  12  has an undercarriage  16 , which is often designed as a tracked undercarriage with a drive, as in the present case. The road paver  12  has a so-called screed  18  at its rear end region. The material is supplied to this screed  18  in order to be evenly distributed and compacted on the subsurface  38 . A distributing auger  20 , not visible in detail here, is usually provided in the region of the screed  18  for at least coarse distribution. The undercarriage  16  of the road paver  12  stands on the subsurface  38  and not on the fresh road surface. When operating, in other words during the production of the road surface, it travels away from the edge of the road surface that has just been produced. 
         [0048]    The road paver  12  has a hopper  22  for the material at a front end region. While the road paver  12  is operating, the material is successively removed from this hopper  22  and transported through the inner, in particular the lower, region of the road paver  12  near the ground into the region of the screed  18 . A conveyor  24 , in particular a scraper conveyor, is provided for this transporting. A drive unit  26 , which here has an internal combustion engine, is provided to drive the components, in particular the undercarriage  16 , the conveying devices etc of the road paver  12 . The road paver  12  can be controlled, in particular by manual intervention, in the region of the operating platform  28  with operating elements  30 . At least one seat  32  and one roof  34  for protection from the weather are provided for an operator. 
         [0049]    The material is supplied to the hopper  22  by a feeder  14 . For this purpose, the feeder  14  has a conveyor boom  40  with a conveyor  42  extending along it. The conveyor boom  40  is articulated at a rear end region of the feeder  14 . A pivoting device  44  is provided for the height adjustment and lateral adjustment of the conveyor boom  40 . The pivoting device  44  can be automatically controlled, in particular pivoted, by an operator. It can thus be ensured that the material transported with the aid of the conveyor  42  lands in the hopper  22  of the road paver  12  in every case. To this end, the conveyor boom  40  tracks the road paver  12  during the process in a suitable manner. This is necessary in particular when the road paver  12  and the feeder  14  are operating together. The direction of travel  36  of the road paver  12  or the entire paving train  10  including the feeder  14  during operation, in other words when a road covering is being produced, is in the direction of the arrow of direction of travel  36 , in other words to the left in the plane of the drawing or plane of the sheet of paper in  FIG. 1 . 
         [0050]    To move, the feeder  14  has an undercarriage  46  that is designed here as a tracked undercarriage. The feeder  14  has its own drive unit  48 , typically with an internal combustion engine, as a drive for the undercarriage  46  and the different units of the feeder  14 . An operating platform  50  with operating elements  52  is provided for controlling the feeder  14 , in other words in particular the undercarriage  46 , the conveyor  42  and the conveyor boom  40 . At least one seat  54  and one roof  56  serve to improve the working conditions of the at least one operator and to protect the operating platform from the weather. 
         [0051]    The feeder  14  has a hopper  58  at its front end region. A transport vehicle such as, for example, a lorry with, for example, a tippable loading area can pour a quantity of the material into this hopper  58 . The material is preferably removed from the hopper  58  with the aid of a conveyor  60  such as, for example, a scraper conveyor. To this end, the conveyor  60  extends from the region of the hopper  58  as far as the region of the conveyor boom  40 . The material is there reloaded onto a conveyor  42 , for example by falling down onto it. The conveyor  42  then transports the material further along the conveyor boom  40 . At its free end region with a tensioning roller  62 , it then falls down from the conveyor  42 . Because of the transporting speed of the conveyor  42  the material usually falls downwards and forwards, in the opposite direction to the direction of travel  36 , forming a parabola or arc. The free end of the conveyor boom  40  must thus be arranged at such a distance from the hopper  22  in the direction of travel  36  of the paving train  10  that the material lands on the hopper  22  on the road paver. Alternatively, a continuous conveyor can also be provided instead of the two separate conveyors  42  and  60  so that there is no need for reloading. 
         [0052]    The pivoting device  44  usually has a hydraulic design. It can adjust the horizontal and vertical orientation or position of the free end of the conveyor boom  40  relative to the feeder  14  and thus also relative to the road paver  12 . A movable deflection member  80 , such as a guide plate, is additionally provided here at the free end of the conveyor boom  40 . This can in a simple manner move the stream of material laterally or forwards and backwards, depending on the arrangement of deflection member  80  transversely to or in the direction of travel  36  of the feeder  14 . To do this, the deflection member  80  must be pivoted or adjusted slightly. 
         [0053]    The first embodiment of a road paver  12  according to the invention shown in detail in  FIG. 2  is designed to be self-propelled and accordingly also has an undercarriage  16 . A drive unit  26  with an internal combustion engine is provided to drive the undercarriage  16  and the other components. An operating platform  28  with a roof  34  provides protection from the weather. The operating platform  28  houses operating elements  30  for an operator to control the road paver  12 . 
         [0054]    The road paver  12  has a hopper  22  at its front end region. The hopper  22  serves, on the one hand, to hold the material or asphalt to be used as the road covering. On the other hand, the hopper  22  simultaneously serves to homogenize material by means of corresponding equipment, in other words serves as a homogenizer  72 . Guide plates  64  and  66  are arranged inside the hopper  22  and serve to deflect the stream of material inside the hopper  22 . They are particularly suited to partitioning the chamber  68 ,  70  of the hopper  22  at least roughly into a left and a right half. To this end, the guide plates  64  have a roof-like design, in particular in the middle region of the hopper  22 . The laterally arranged guide plates  66  are designed as essentially plane sheets. They extend respectively along the entire length of the hopper  22 . They run obliquely downwards from the side wall  104  of the hopper  22 . 
         [0055]    Moreover, in the lower region of the hopper  22 , two conveying augers  74  are arranged here which serve predominantly to transport or convey the material from the hopper  22  onto the conveyor  24 . At the same time, they at least partially serve to thoroughly mix the material. Because the conveying augers  74  can be controlled individually, differing amounts of the material can be transported from the left chamber  68  or the right chamber of the hopper  22  onto the conveyor  24  arranged beneath the operating-platform end of the conveying auger  74 . The conveyor  24  serves to transport the material to the rear end of the road paver  12  in the region of the operating platform  28 . The material is there applied to the subsurface by the screed  18 . 
         [0056]    The hopper  22  here has three wheels  76  for supporting it on a subsurface  38 , so that the weight of the hopper  22  is not supported exclusively by the undercarriage  16  of the road paver  12 . 
         [0057]    The road paver  12  described here can be operated in an alternative embodiment also as a separate, in particular self-propelled homogenizer  72  or as a homogenizing system. For this, the screed  18  is removed at the rear end of the road paver  12  and replaced by a coupling and/or an additional conveyor, in order to transfer the material to, for example, a road paver  12  or feeder  14 . 
         [0058]    The hopper  22  of the road paver  12  can be exchanged for alternative embodiments of the hopper  22 . In particular, the different embodiments in  FIGS. 3 to 6  may be considered. The description of identical constituents or components of the different embodiments is thus in part not repeated. 
         [0059]      FIG. 3  shows an alternative embodiment of a road paver  12  according to the invention. The road paver  12  shown here essentially corresponds to that described above as the first embodiment. Only the hopper  22  has been modified. 
         [0060]    In the present case, two chambers  68  and  70  are arranged one behind the other inside the hopper  22 , in the direction of travel  36  of the road paver  12 . The chamber  68  is designed to be significantly larger than the chamber  70 . Accordingly, the chamber  68  in the present case contains about four times more material as its volume is about four times as large. A partition wall  78 , which is arranged transversely to the direction of travel, serves to divide the hopper  22  into the two chambers  68  and  70 . Lateral guide plates  66  are arranged inside the two chambers  68  and  70 , and roof-shaped guide plates  64  are arranged in the central region, to deflect the material. In an alternative embodiment, these guide plates  64  and  66  can, however, be omitted. 
         [0061]    The larger chamber  68  serves to hold the material that is at the correct temperature. In the smaller chamber  70 , on the other hand, the material to be homogenized or colder material is stored. 
         [0062]    The hopper  22  or homogenizer from  FIG. 3  is shown in  FIG. 4  with a portion of the conveyor  24  in a schematic diagram. The conveyor  24  has a scraper belt  100  that is guided around a tensioning roller  102 . The upper section of the scraper belt  100  facing the chambers  68  and  70  moves to the left in the plane of the drawing and thus in the opposite direction to the direction of travel  36  of the road paver  12 , in other words in a running direction  86 . 
         [0063]    It can be observed how the two chambers  68  and  70  are arranged relative to the conveyor  24 . The material from the chamber  68  is deposited on the conveyor  24  with the aid of the conveying auger  74  as a first layer  82 . An opening  96  is present for this purpose in the bottom of the hopper  22  or the chambers  68 ,  70 . As long as there is also material in the chamber  70 , it is added as a comparatively thin second layer  84  on top of the first layer  82 . Accordingly, the chamber  70  is arranged behind the chamber  68 , in the running direction  86  of the conveyor  24 , in other words in the opposite direction to the direction of travel  36 . It is hereby ensured that the material from the chamber  70  can be added to the material from the chamber  68 . Because only a relatively thin layer  84  of the colder material from the chamber  70  is used in comparison with the layer  82 , the temperature of the colder material can be matched to that of the warmer material. All in all, a homogenization of the temperature is achieved that approaches the optimum surfacing temperature. 
         [0064]    The upper layer  84  can but does not have to be applied as a continuous layer on top of the lower layer  82 . In particular, if the chamber  70  is empty or also for a better distribution of the material, an interrupted addition, or addition in sections, of the colder material can also take place. The layer  84  is then not formed as a continuous layer as shown in  FIG. 4  but has interruptions. As a distributing auger  20  is arranged in the region of the screed  18 , a corresponding mixture is nevertheless ensured. Additionally, however, another mixing system and/or an additional mixing device can be arranged at the end of the conveyor  24 , which effects an additional thorough mixing. The conveying augers  74  at the same time serve as mixing and conveying augers. Viewed from above, they are arranged parallel to each other. 
         [0065]    In the embodiment in  FIGS. 7 and 8 , the homogenizer  72  has four conveying augers  74  which are arranged transversely to the direction of travel or to the mounting direction. The conveying augers  74  in each pair are arranged parallel to each other. They serve to supply the material, in particular in counterrotating fashion, for the purpose of thorough mixing. Because chambers  68  and  70  on either side of the hopper  22  are divided by the guide plates  64 , materials at different temperatures can be poured into the two chambers  68  and  70 . By controlling the conveying augers  74  beneath the respective chambers  68  and  70 , the material contained in each case can be conveyed in a metered fashion into the region of the conveyor  24  arranged beneath the hopper  22 . When, for example, one chamber  68  contains the material at the right temperature, this material can be supplied to the conveyor  24  as a base material or lower layer  82 . A metered supply of comparatively small amounts of the colder material from the chamber  70  as a second layer  84  results in an only slight cooling of the base material and a sufficient heating up of the added material from the chamber  70 . All in all, a suitable temperature of the material for producing a roadway paving is thus ensured. 
         [0066]    A further alternative embodiment is shown in  FIGS. 9 to 11 . Here the two chambers  68  and  70  are arranged next to each other in the direction of travel above the wheels  76 . A mixing chamber  88  is situated behind. Two conveying augers  74  for metering the addition of material into the mixing chamber  88  are arranged in the region of the chambers  68  and  70 . A total of four conveying augers  74 , which serve to convey or mix the material, are arranged in the lower region of the mixing chamber  88 . A deflecting flap or a deflecting member  80 , or alternatively a conveyor belt, is arranged above the chambers  68  and  70 . The deflecting flap  80  or the conveyor belt serve to guide the material laterally into the different chambers  68  and  70 . The chamber  68  contains the warmer material at the right temperature, and the chamber  70  contains the colder material. 
         [0067]    The embodiment in  FIGS. 12 to 14  shows a hopper  22  in which a bucket  90  is arranged. This bucket  90  overall has a conical shape with a circular cross section. It is arranged with its feeding end pointing downwards. A plurality of holes  94  are arranged in the side wall  92  of the bucket  90 . The opening  96  in the bottom here also serves to discharge material onto the conveyor  24 . 
         [0068]    The homogenizer  72  of this embodiment that is shown functions as follows: the material at the correct temperature is poured into the inside of the bucket  90 . The material that is too cold or which is separated is added into the hopper  22  beneath the bucket  90 . While material is discharged through the opening  96  in the bottom onto the conveyor  24 , the filling level inside the hopper  22  or in the chamber  68  falls so that a growing number of holes  94  are present above the material. As soon as material outside the bucket  90  has a higher filling level, this material flows laterally through the holes  94  into the bucket  90  and onto the warmer material situated therein. However, this happens only in metered proportions as the amount of the material flowing in is determined by the filling level in the bucket  90 . As soon as more warmer material is added, its filling level may exceed the filling level outside the bucket  90  so that cold material can no longer flow into the inside of the bucket  90 . Moreover, not only is the cold material in the bucket  90  covered with new material, but also material from the inside of the bucket  90  flows out through the holes  104 . All in all, this results in a thorough mixing of warm and cold material. 
         [0069]    The process according to the invention functions as follows: 
         [0070]    The temperature of the material supplied from the feeder  14  is determined. To do this, for example a measuring apparatus  98  is provided, such as at least one heat sensor or infrared sensor or even an infrared camera. In order to scan the entire stream of material simply, the measuring apparatus  98  is arranged above the conveyor  42  on the feeder  14 . It is also possible to provide a plurality, at least two, but preferably three measuring apparatus  98  and/or a measuring apparatus  98  having at least two, but preferably three sensors. The sensors or measuring apparatus  98  are preferably distributed in linear fashion along the conveying path of the conveyor boom  40 . 
         [0071]    As soon as it is established that at least part of the material or the stream of material has material that is too cold, the corresponding part of the material is separated, for example with the aid of a deflecting member  80  or with the aid of a guide plate. This part of the material to be homogenized is thereby guided away into the separate chamber  70 . 
         [0072]    The other material, which is at the correct temperature, passes into the chamber  68 . Material is removed from these two chambers  68  and  70  in order to be supplied to the road paver  12  or the screed  18  to produce an asphalt layer. In this way, the colder material from the chamber  70  is supplied to the material at the correct temperature from the chamber  68  only in the proportion that causes no excessive cooling of the material at the correct temperature and, on the other hand, that the material which is too cold is heated up sufficiently. 
         [0073]    As so-called “nests” of cold material, which are usually only local, are present in the stream of material, for example on the conveyor  24  of the road paver  12  or also on the conveyor  42  of the feeder  14 , a suitable spatial resolution of the measuring apparatus  98  must be provided. The resolution should be provided such that, on the one hand, the nests are recognized and, on the other hand, no colder areas are ignored, creating no problems. This is, for example, ensured by three sensors or also an infrared camera system. 
         [0074]    The measuring apparatus  98  for determining the temperature can be provided, for example, on the feeder  14 . Alternatively, the arrangement can also, however, be situated in the region of the road paver  12 . The device for homogenizing the material, in other words in particular the homogenizer  72 , can be substituted for the hopper  22  of the road paver  12 . Alternatively, a separate, in particular self-propelled homogenizer can also be used. It is also possible to substitute the hopper  22  on the feeder  14  for a corresponding device for homogenizing. The apparatus for measuring the temperature must accordingly be arranged in front of the corresponding device for separating the material. 
         [0075]    In the following, a further exemplary embodiment of the invention will be described with reference to  FIGS. 15 and 16 : 
         [0076]    As in the previous exemplary embodiment, the hopper  120  serves to accommodate the mix which has the correct temperature. Shown in  FIG. 16  is the conveyor  122  with the two slatted frames  140 . An additional mixing container  124  is arranged downstream with respect to the conveyor  122 , i.e. in the direction of the screed (not shown) to the right. This mixing container  124  has a (horizontal) cross-section which is circular in shape. Correspondingly, it assumes an essentially cylindrical configuration. In this arrangement, the mixing container  124  assumes an upright or vertical alignment. Located at its top end is a circular filling opening  126 , which has essentially the same cross-section as the mixing container  124 . Located at the lower end is a conically tapering region  128 , at the bottom of which a discharge opening  130  is provided. The discharge opening  130  is located above the conveyor  122  and thus above the material flow of the mixture as it is conveyed by the conveyor  122  out of the hopper  120 . Accordingly, the mixture discharged from the mixing container  124  is added to the other mixture on the conveyor  122 . 
         [0077]    The mixing container  124  has a mixing device  150  with a central rotational axis  132 , about which a plurality of wings or blades  134 ,  136  is arranged. In this arrangement the blades  134 ,  136  extend essentially from the rotational axis  132  almost to an inner wall  138  of the mixing container  124 . In the present case, the blades  134 ,  136  are configured as alternating concave blades  134  and convex blades  136 . When the mixing device  150  revolves about its rotational axis  132 , this ensures that the mixture located between the blades  134  and  136  is moved alternately along the path of the mixture from the upper filling opening  126  to the lower discharge opening  130  and from the inner wall  138  toward the rotational axis  132  and vice versa. This ensures that the mixture is moved in an essentially oscillating manner and is thus blended quite effectively. 
         [0078]    In order for asphalt too cold for incorporation into an asphalt layer to be brought to the correct temperature, the mixing container  124  has a heating element (not shown). In this arrangement, the blades  134  and  136  can be heated by an electric or gas powered heating element. Alternatively, or as a supplement, the inner wall  138  of the mixing container  124  can also be heated. Provided in the outer wall of the mixing container  124  is a flue  148 . In case a gas heater is employed, the flue  148  serves as an channel for discharging combustion gases or as a general discharge conduit for gases escaping from the mixture. 
         [0079]    In order to determine the temperature or temperature distribution of the mixture in the mixing container  124 , a plurality of temperature sensors  146  are disposed at least in the lower region of the mixing container  124  at different heights or even arranged one above the another in a vertical alignment. Here the temperature sensors  146  are positioned on opposing sides of the mixing container  124  at different heights. Accordingly, as soon as the temperature lies within a predetermined range or matches the temperature of the mixture in the main hopper  120  within the tolerance limits, the discharge opening  130  at the lower end of the mixing container  124  can be opened to discharge at least part of the homogenized mixture. Provided for this is a sliding or revolving closure  142 . 
         [0080]    In order to provide an additional means for regulating the overall flow of material, a further closure  144  is arranged above the conveyor  122  for adjusting the total volume of the mixture discharged on the conveyor. 
         [0081]    The foregoing detailed description of the preferred embodiments and the appended figures have been presented only for illustrative and descriptive purposes. They are not intended to be exhaustive and are not intended to limit the scope and spirit of the invention. The embodiments were selected and described to best explain the principles of the invention and its practical applications. One skilled in the art will recognize that many variations can be made to the invention disclosed in this specification without departing from the scope and spirit of the invention. 
       List of Designations: 
       [0000]    
       
           10  paving train 
           12  road paver 
           14  feeder 
           16  undercarriage 
           18  screed 
           20  distributing auger 
           22  hopper 
           24  conveyor 
           26  drive unit 
           28  operating platform 
           30  operating elements 
           32  seat 
           34  roof 
           36  direction of travel 
           38  subsurface 
           40  conveying boom 
           42  conveyor 
           44  pivoting device 
           46  undercarriage 
           48  drive unit 
           50  operating platform 
           52  operating elements 
           54  seat 
           56  roof 
           58  hopper 
           60  conveyor 
           62  tensioning roller 
           64  guide plate 
           66  guide plate 
           68  chamber 
           70  chamber 
           72  homogenizer 
           74  conveying auger 
           76  wheel 
           78  partition wall 
           80  deflecting member 
           82  layer 
           84  layer 
           86  running direction 
           88  mixing chamber 
           90  bucket 
           92  side wall 
           94  hole 
           96  opening 
           98  measuring apparatus 
           100  scraper belt 
           102  tensioning roller 
           104  side wall 
           120  hopper 
           122  conveyor 
           124  mixing container 
           126  filling opening 
           128  conically tapering region 
           130  discharge opening 
           132  rotational axis 
           134  blade 
           136  blade 
           138  inner wall 
           140  slatted frame 
           142  closure 
           144  closure 
           146  temperature sensor 
           148  flue 
           150  mixing device

Summary:
A process for producing an asphalt layer in which material with properties that deviate from predetermined requirements is specifically homogenized, and a paving train ( 10 ), a road paver ( 12 ) and a feeder ( 14 ) for carrying out the process.