Patent Publication Number: US-10774482-B2

Title: Working device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a working device for a ground-processing device having a milling drum with a milling drum tube on whose surface working tools are mounted in a projecting manner and are intended to come into contact with the material to be milled during the milling process, wherein the working device comprises a powertrain for driving the milling drum. 
     2. Description of the Prior Art 
     Ground-processing machines are known in a wide variety of embodiments. For example, DE 201 22 928 U1 (U.S. Pat. No. 7,644,994) discloses a road milling machine as a ground-processing machine. It has a powertrain. This comprises a drive engine, a shifting clutch and a gearbox (what is referred to as the “milling drum gearbox”), and also elements, in particular shafts, toothed or endless drives, which interconnect these units. Within the scope of the invention, a powertrain is to be understood in particular under the above definition. According to DE 201 22 928 U1, use is made of a milling drum which is fitted with working tools on the surface of its milling drum tube. Working tools are to be understood as meaning the constructional units of the milling drum which functionally interact with the material to be milled during the working process. For example, these are milling chisels and the holder systems supporting the milling chisels. Furthermore, working tools frequently mounted on the milling drum are guiding and ejecting tools. These have guiding and conveying functions. 
     When using a machine according to the invention, the work result is decisively influenced by the rotational speed of the milling drum. In this context, the optimal rotational speed is generally dependent on the application. 
     During fine milling of road surfaces, to restore the skid resistance, with a small milling depth, relatively high rotational speeds are required in order to produce a uniform milling pattern. Therefore, only a surface processing takes place here. 
     When removing all or a number of layers of the road structure, lower rotational speeds tend to be more favorable since it has been shown that, as a result, a better milling pattern with a smaller generation of fine particle fragments, and therefore reduced dust generation, can be ensured. Moreover, the wear on the milling tools is considerably reduced at low rotational speeds. Furthermore, with a reduced rotational speed of the milling drum, a reduced output power of the drive is also required and thus a lower fuel consumption is made possible. Overall, it should therefore be sought to achieve a rotational speed of the milling drum which is as low as possible in such applications. 
     In order to meet the various requirements, it is therefore known to be able to variably set the rotational speed of the milling drum in road milling machines. 
     However, if the rotational speed is selected to be too low, the kinetic energy of the milling drum is no longer sufficient to effectively process the material to be milled, there occurring an out-of-round and unsmooth running of the milling drum which is demonstrated, inter alia, by vibrations of the entire ground-processing machine right through to unstable oscillation of the machine, here possibly also resulting in damage to the machine. Furthermore, the work quality suffers as a result of the unsmooth running of the milling drum, and unevenness in the milling pattern can occur. In the extreme case, it is possible for the milling drum to “bog down” if the kinetic energy is not sufficient. 
     A high weight of the ground-processing machine contributes to increasing the running smoothness even at low rotational speeds. However, this is disadvantageous in many respects since as a result, on the one hand, particular requirements must be placed on transportation (large milling machines&gt;40t→heavy transport) and, on the other hand, the use possibilities are restricted to grounds which have statically little load-bearing capacity. 
     It is therefore known to load milling machines for stabilization purposes. For this purpose, additional weights are fastened on the machine. Thus, it is known for example that, in a road milling machine having a total weight of about 4.5 tonnes, 1.3 tonnes can be made available by means of additional weights. In other words, the additional weights make up barely ⅓ of the machine weight. Such a machine can thus be used flexibly but must be loaded with large additional weights for optimal adaptation to the respective task. 
     U.S. Pat. No. 4,006,936 A discloses a ground-processing machine having a milling device. To improve the running smoothness of the milling drum, the use of a milling drum tube which has a greater wall thickness than customary milling drum tubes is recommended. This course of action proves to be disadvantageous particularly during manufacture since the milling drum tubes are rolled from a sheet-like blank. The rolled blank is then welded at its longitudinal-side abutment points. The tube thus manufactured and welded must then be turned. The large material thickness increases the manufacturing expenditure. The use of the relatively thick blank causes a considerable increase in the forming work expenditure. Owing to the large wall thickness, the milling drum tube can be manufactured only with a significant degree of out-of-roundness, with the result that increased machining effort is required during turning. 
     Moreover, in this design of the milling drum tube, flexible adaptation to the respective task cannot occur. 
     SUMMARY OF THE INVENTION 
     It is thus the object of the invention to provide a working device of the type mentioned at the outset which allows optimization of the rotational speed of the milling drum, wherein an optimum cutting pattern can be produced in a simple manner in different applications. 
     This object is achieved in that at least one load weight is arranged, preferably interchangeably, on the powertrain and/or on the milling drum to increase the kinetic energy. 
     The invention is based on the finding that a relatively high running smoothness of the milling drums can be achieved when the kinetic energy in the powertrain and/or the milling drum is increased. The kinetic energy is obtained from the formula
 
 E   rot =½ m r   2 ω 2  
 
where m is the value of the rotating mass and r the distance of this mass from the axis of rotation. The product mr 2  represents the moment of inertia of the moving mass and ω represents the angular velocity (2*π*rotational speed). Since the reduction of the rotational speed is desired, the invention is then concerned with changing the moment of inertia. In this context, one or more load weights are installed on one or more rotating parts of the powertrain or the milling drum.
 
     Tests have revealed that, under otherwise identical conditions, the power consumption during the milling process can be lowered by up to 30% by reducing the rotational speed with a simultaneous increase in the moment of inertia. Consequently, in addition to the fuel requirement, the chisel wear and the coolant requirement are also reduced. In this way, the mass of the entrained coolant (water) can be decreased in favor of a lower machine weight. 
     Moreover, a reduction in the rotational speed also affords the advantage of a longer running time of the machine before it has to be filled with coolant. Furthermore, owing to the lower rotational speed, the dust generation is reduced, which leads to a further reduction in the water requirement. 
     Furthermore, it has been shown that, with an increase in the moment of inertia caused by the weight-loading on the milling drum and/in the powertrain, the same increase in the running smoothness can be achieved as by a considerably higher weight-loading of the entire machine. Here, under otherwise identical circumstances, integral factors can lie in between. 
     Therefore, as a result of the increase in the moment of inertia, there is also the possibility of reducing the entire weight of the machine with the running smoothness remaining the same. Therefore, it is possible to use the machine more flexibly and transportation is simplified. 
     Overall, matching between the rotational speed of the drum and machine weight that is suitable to the application is thus made possible in that a corresponding weight-loading of the milling drum and/or of the powertrain is selected for the respective application. 
     This is particularly advantageous in the case of interchangeable weights since hereby a machine and/or milling drum can be used for different tasks and optimally adapted for these in each case in a simple manner. 
     The load weight can be arranged at any desired point of the powertrain or on the milling drum. Accordingly, it can be positioned, for example, downstream of the drive engine. 
     According to a preferred variant embodiment of the invention, it can be provided that the powertrain has a clutch and a gearbox connected downstream thereof via a belt drive, for example, and that the load weight is arranged downstream of the gearbox or therein on the output side. 
     This arrangement leads to the clutch and gearbox being relieved since the shock factor acting on them is then reduced. If the load weight or weights is/are arranged downstream of the gearbox, this constructional unit can also be effectively relieved. As a result, the service life of the clutch and gearbox is increased. 
     The load weight can be connected fixedly to the powertrain or the milling drum. However, it is preferably interchangeable. In this way, it can then be built onto the ground-processing machine if it is specifically required for the purpose of the desired running smoothness. Thus, weight-optimized adaptation of the machine can also be carried out here. Moreover, the machine transportation is also simplified since the load weight or weights can be separately handled, for example transported. Furthermore, the change of drums is simplified since a lighter drum can be changed and handled more simply. 
     In a particularly preferred manner, it is provided that at least one load weight is arranged in the region of the milling drum. Here, the load weight can be used particularly effectively since it can be arranged at a large distance from the axis of rotation. This leads to a particular increase in the running smoothness since the moment of inertia, and hence the kinetic energy, are a square function of the distance of the mass from the axis of rotation. Thus, the same effect can be achieved with relatively small load weights at a large distance from the axis of rotation as with large load weights at a small distance from the axis of rotation. The arrangement in the region of the milling drum also affords handling advantages. In particular, the load weights are readily accessible here if they are arranged interchangeably. 
     A significant increase in the running smoothness is obtained when it is provided that the load weight or weights has/have a mass which is suitable for increasing the moment of inertia of the milling drum by at least 10%, particularly preferably by at least 20%. Moreover, with an increase by at least 20%, there is obtained the advantage that a considerable lightening in the machine weight is also possible. An experimental design of the inventor revealed that a weight-loading of the milling drum by 100 kg allows a reduction in the overall machine weight by 100 kg with the running smoothness remaining the same. 
     One conceivable variant of the invention is such that the powertrain and/or the milling drum are/is adapted in such a way that the load weights make it possible to increase the weight in two or more stages. In this way, the ground-processing machine can be adapted step by step to the desired work task. Moreover, particularly simple handling is associated with this subdivision of the load weights. 
     A ground-processing machine according to the invention can be such that the powertrain and/or the milling drum have arranged thereon receptacles with fastening means by means of which the load weight or weights can be coupled interchangeably. In this way, the load weights can be positioned and fastened securely and reliably in harsh construction site operation. Here, the load weights can be formed, for example, by segments or rings or similar constructional units. The ground-processing machine may also provide for the storage of the load weights on the chassis and/or on the running-gear units of the machine, on supports provided for this purpose, when the load weights are not in use. 
     It is particularly advantageous if provision is made for the load weight or weights to be mounted in the interior enclosed by the milling drum tube, preferably on the inner side of the milling drum tube. The load weights are then protected from attack by the material to be milled in a simple manner. 
     One possible configuration of the invention can be such that the load weight is formed by a fluid which is held in a fluid reservoir. For example, the fluid used can be water. This can be simply let out again after use. 
     According to the invention, it can also be provided that the milling drum can be releasably mounted on coupling pieces of the powertrain by means of a fastening arrangement, and that the load weights are arranged interchangeably on the fastening arrangement. Here, the load weights are readily accessible particularly when the milling drum has been demounted. 
     Alternatively, to ensure simple accessibility, it is possible for the load weights to be arranged in the axially outer region of the milling drum. This affords the possibility of (de)mounting the additional weights without the milling drum having to be removed from the powertrain for this purpose. 
     Furthermore, it is possible to combine the various fastening possibilities so that a “small” weight-loading can occur without large effort (for example without demounting the milling drum). Moreover, should it be sought to achieve a greater weight-loading, additional weights can be fastened inside the milling drum after it has been demounted. 
     Overall, it is recommended for the benefit of a high running smoothness for the rotating component, for example the milling drum, equipped with the load weight or weights to be designed in such a way that it is balanced. In order to avoid unbalances, it is recommended in this respect for example also to arrange the load weights in a symmetrically distributed manner. 
     One conceivable configuration of the invention is such that a cured casting material, preferably concrete, is used as the load weight. This measure makes it possible to effectively provide the weight-loading in a cost-effective and simple manner. 
     The weight-loading according to the invention is possible not just in mechanical drives with an internal combustion engine. Rather, weight-loading is also possible in other drive variants of the milling drum. For example, it is conceivable for hydraulic or electrical milling drum drives to be weight-loaded on their rotating components and/or the milling drum, where the same advantages can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail below with reference to exemplary embodiments illustrated in the drawings, in which: 
         FIG. 1  shows a ground-processing machine in a perspective view, 
         FIG. 2  shows, in a side view and in section, part of a working device having a milling drum, and 
         FIG. 3  shows a schematic illustration of a milling unit having a powertrain and a milling drum in a sectional view. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a self-propelled ground-processing machine  10 , namely a road milling machine. The ground-processing machine  10  has a chassis  12  which is assigned a driver&#39;s cab. A milling drum  20  is mounted in a milling drum box  41 . The milling drum  20  has a milling drum tube  21  on whose surface  22  work tools  30  are mounted in a projecting manner. The work tools  30  are illustrated only schematically in  FIG. 1 . The work tools  30  usually comprise a chisel holder  32  in which a chisel  31  is arranged interchangeably. The chisel holder  32  can be formed in one piece and, as illustrated in  FIG. 2 , fastened, for example welded, directly to the milling drum tube  21 . Moreover, however, other embodiments are also known for chisel holders  32 ; for example, they can be formed by an upper part and a base part, with the upper part being held interchangeably in the base part, which is fastened to the milling drum tube  21 . One or more chisels  31  can be fastened interchangeably in the chisel holder  32  itself. 
     As has been mentioned above, the milling drum  20  can be installed in the milling drum box  41  of the chassis  12 . For this purpose, the milling drum  20  has a fastening arrangement  24 . This can be designed, for example, in the form of a fastening flange. The milling drum  20  can be connected interchangeably to the ground-processing machine  10  by the fastening arrangement  24 . 
     Finally, as can further be seen from  FIG. 1 , the chassis  10  has running-gear units  13  and a conveying device  11  is provided. For example, the running-gear units  13  can have wheels or crawler track units. In the exemplary embodiment shown, the rear right-hand running-gear unit is arranged pivotably so as, in the folded-in state, to allow milling close to an edge. Here, with the right-hand running-gear unit in the folded-out state, the milling drum  20  is arranged between the running-gear units  13  of the rear axle. At least the rear running-gear units are preferably height-adjustable in order to allow adjustment of the milling depth. 
     In the exemplary embodiment illustrated, the milling drum  20  and the running-gear units  13  are driven via a drive engine  51 . 
     In the case of large milling machines, stabilizers, recyclers and surface miners, it is possible within the scope of the invention for the milling drum  20  to be arranged, for example, between the running-gear unit axes of the front and rear axle. 
     The conveying device  11  can be used to transport away the milled material removed by the milling drum  20 . The conveying device usually has one or more conveyor belts, of which at least the final conveyor belt as seen in the conveying direction can be pivoted relative to the machine frame about a horizontal and a vertical axis. 
       FIG. 2  now shows by way of example the design of the milling drum  20  in section. As can be seen from this illustration, the milling drum  20  has a milling drum tube  21 . This is formed substantially as a hollow cylinder and has an outwardly directed surface  22  and an inner side  23 . The fastening arrangement  24  is mounted in the inner region enclosed by the milling drum  20 , namely being welded to the inner side  23  of the milling drum tube  21 . The fastening arrangement  24  is designed as a fastening flange and has plug receptacles. Coupling pieces  56  of a drive section  58  are inserted through the plug receptacles. The coupling pieces  56  are plug-shaped and have an external thread. A nut can be screwed onto the external thread and the fastening arrangement  24  can thus be connected to the drive section  58 . Here, in the mounted state, the fastening arrangement  24  butts against an end stop  57  of the drive section  58 . Secure support in the axial direction is thus provided here. 
     The drive section  58  is part of a powertrain  50 . The powertrain  50  can, for example, have a drive engine  51  to which a gearbox  53  is connected via a clutch  52  and a belt drive. As can be seen from  FIG. 2 , the drive section  58  is guided through an opening in a bearing wall  42  of the milling drum box  41 . 
     Load weights  25  can be fastened to the milling drum  20 . Here, the load weights  25  are connected, preferably interchangeably, to the milling drum  20 . The interchangeable mounting can also be described as being removably mounted or as a detachable connection. For example, provision can be made in this respect for fastening means  26  to be arranged in a protected manner in the inner region of the milling drum tube  21 . The fastening means  26  are particularly preferably arranged on the inner side  23  of the milling drum tube  21  and/or on the fastening arrangement  24 . 
       FIG. 2  illustrates two examples of the arrangement of load weights  25 . For example, the fastening means  26  can be formed as screw bolts on the fastening arrangement  24 . The load weights  25  can be pushed with fitting fastening receptacles onto said screw bolts. The load weights  25  can then be secured by means of nuts. It is further conceivable that the fastening means  26  comprise receptacles  27  into or onto which load weights  25  are pushed. In  FIG. 2 , by way of example, a receptacle  27  in the form of a pocket is fastened to the inner side  23  of the milling drum tube  21 . The load weight  25  can be pushed into this pocket. Said load weight can then be secured by means of a cover  27 . 1 . The cover  27 . 1  can be screwed for example to the fastening means  26  and/or the milling drum tube  21 . It is also conceivable for the receptacle  27  provided to be a region in the milling drum tube  21  into which segments or rings are inserted. 
     The load weights  25  serve to increase the moment of inertia of the milling drum in favor of improved running smoothness. This has been comprehensively described at the outset. Reference is made to the corresponding statements. The load weights  25  are preferably radially outwardly spaced apart as far as possible and therefore, as shown in  FIG. 2 , advantageously situated in the region of the inner side  23  of the milling drum tube  21 . In this way, the moment of inertia of the milling drum is significantly influenced. Instead of the embodiment, shown in  FIG. 2 , of the load weights  25  as insert parts, for example in the form of iron parts or weights which can be screwed on, provision can also be made for a cavity to be formed on the milling drum  20 , which cavity is filled with a casting material, for example with concrete, or into which cavity a fluid can be filled and let out again. 
     It is also conceivable for the load weights  25  to be fastened, preferably interchangeably, to the drive section  58  since they are readily accessible here when the milling drum  20  has been removed. 
       FIG. 3  shows a further variant embodiment of the invention. This illustration shows the housing  40  of the chassis  12  by way of example. The housing  40  forms the milling drum box  41 . This is partitioned off by means of a bearing wall  42 . On the opposite side to the bearing wall  42 , the milling drum box  41  is closed off by an end wall  43 . A clutch  52  and a gearbox  53  of a powertrain  50  are accommodated outside the milling drum box  41 . However, it is also possible, for example, for the gearbox  53  to be arranged at least partially in the milling drum  20 . A drive engine  51  is coupled to the clutch  52  via a drive shaft  55 . The drive engine  51  is usually a diesel engine which is accommodated in the chassis  12  of the ground-processing machine  10 . The clutch  52  is suited to being coupled to the gearbox  53 , for example by means of a further drive shaft or by means of an endless drive. The gearbox  53  itself is connected on the output side to the milling drum  20 . Here, the connection can be carried out so as to correspond to the fastening shown in  FIG. 2 . As can be seen from  FIG. 3 , the powertrain  50  comprises the drive engine  51 , the clutch  52  and the gearbox  53 . Furthermore, the powertrain  50  includes the drive shaft  55  and the remaining drive shafts or endless drives interconnecting the aforementioned components. 
     The milling drum  20  again has on its external surface  22  the work tools  30  mounted in a projecting manner. Emanating from the gearbox  53 , a drive section  58  is again introduced into the interior of the milling drum  20  and connected to a fastening arrangement  24  of the milling drum  20 . It can now be seen from  FIG. 3  that the rotatable drive section  58  has a hollow chamber as fluid reservoir  54 . A liquid, for example water, can be filled into the hollow chamber via a filler connector  28 . The liquid then serves as a load weight  25 . The filler connector  28  is designed in such a way that, after use of the milling drum  20 , the water can be let out again from the fluid reservoir  54 . 
     In addition, or as an alternative, according to the invention load weights can be mounted at any desired point of the powertrain on the rotating parts.  FIG. 3  shows by way of example the mounting of a load weight  25  in the region of the drive shaft  55 . However, the load weight is advantageously mounted in the region downstream of the gearbox  53  on a rotating part of the powertrain  50 . The shock loading of the gearbox  53  and the clutch  52  is thus minimized. In addition, the damping of interposed drive components, for example belt drives, is then minimized. 
     There are essentially the following possibilities for mounting the load weights  25  which come advantageously into consideration:
         milling drum  20     output side of the gearbox  53  (for example drive section  58 )   input side of the gearbox  53  (for example belt disk upstream of gearbox  53 )   output side of the clutch  52  (for example belt disk downstream of clutch  52 , upstream of belt drive to the gearbox  53 )   input side of the clutch  52     or alternatively in the clutch  52  or in the gearbox  53 .       

     As the above examples show, the load weights  25  can be fixedly or interchangeably connected to the powertrain  50  or the milling drum  20 . Interchangeable fastening offers the advantage that the machine can be flexibly adapted to different boundary conditions and tasks. 
     As the above statements show, the invention relates to a new working device for a ground-processing machine  10  having a milling drum  20 . The milling drum  20  is assigned a powertrain  50  for driving the milling drum  20 . To increase the moment of inertia, load weights  25  are now provided in the region of the powertrain  50  and/or the milling drum  20 .