Abstract:
A bowl mill transmission which has a high overall transmission ratio with a large output torque, is of compact construction and is simple to assemble. The transmission includes a vertically arranged bevel-gear stage for the power input and a multi-stage power-splitting epicyclic transmission arrangement for power output into a thrust ring of the bowl mill.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to bowl mill transmissions, and particularly to a bowl mill transmission with a vertically arranged bevel-gear stage for power input and a multi-stage epicyclic transmission arrangement for power input to a thrust ring of a bowl-mill crusher. 
     2. Description of the Related Art 
     The invention is based on bowl mills which are driven by vertical bevel-gear transmissions. 
     The prior art includes drives of this kind (e.g., Renk Tacke company publication Kegelrad-Planetengetriebe KPAV fürvertikale Wälzmühlen [Epicyclic bevel-gear transmissions for vertical roller mills]) in which the bevel-gear stage outputs power into the sun gear of an epicyclic transmission with a fixed annulus. In such transmissions, power output to the grinding bowl is via the planet carrier, which accommodates a plurality of planet gears for power transmission. 
     The grinding process in such mills requires high power transmission to the grinding stock at low speeds of rotation and high torque. The high transmission ratios required for this purpose are limited by the maximum possible diameter of the transmission stage and the diameter of the horizontal bevel gear. The diameter of the epicyclic stage is limited by the transmission housing which passes the grinding forces into the mill foundation by direct force transmission. 
     Developments of such drives embody two epicyclic stages. Here, the bevel-gear transmission drives a first sun pinion of a first epicyclic transmission stage. A second epicyclic transmission stage is driven by means of a rotationally fixed connection of the planet carrier, which rotates in the fixed annulus, to a further sun gear, which is arranged axially above the first sun gear. This second epicyclic stage is arranged axially above and concentrically to the first. By way of a further planet carrier, which revolves in a further fixed annulus by means of its planet gears, which are provided for power splitting, it outputs power into the grinding bowl. 
     The prior-art transmissions consume high input power to move the large revolving masses. A considerable outlay for bearings is furthermore required and assembly of the many individual parts is difficult. Furthermore, the bearings installed in revolving planet carriers can be monitored only with extreme difficulty. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the present invention to provide a transmission which has a high overall transmission ratio with a large output torque, is of compact construction, and is simple to assemble. 
     According to an aspect of the invention, this object is achieved by a bowl mill transmission that inputs power through a bevel-gear transmission stage and through a sun pinion into an epicyclic transmission arrangement in which the power is split. The power output is then summed in two annulus toothings of an annulus body. 
     In each of its various overall sizes, the transmission design according to the invention covers a broader power range than the prior art and extends the power spectrum upwards. 
     By virtue of the compact epicyclic-stage unit according to the invention, the transmission can to a very large extent be preassembled, making assembly easier. 
     While maintaining grinding performance, more compact plants with a significantly lower weight can be achieved with the transmission arrangement according to the invention. 
     By virtue of the advantageous drive configuration, the transmission according to the invention can be constructed on a modular basis. 
     With the advantageous integration of the power output stage into the interior of the thrust plate, it is possible to achieve lower overall heights by means of the invention. 
     By virtue of the advantageous drive configuration, the number of components is reduced, thereby allowing transmissions according to the invention to be produced at lower cost. 
     Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein like reference numerals denote similar elements: 
     FIG. 1 shows a longitudinal section through a transmission according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a longitudinal section through a transmission according to the invention. It is constructed with its housing  47  on the base plate  37 . Power input is by means of the drive shaft  33 , which is connected at one end to an electric motor, for example, and carries a bevel gear  32  at its other end. The drive motor has not been shown here. The drive shaft  33  is installed with a complete bearing unit  34  in an insert in the housing  47 . By means of tooth engagement with the horizontal bevel gear  35 , the driving power is transmitted to the vertical bevel-gear shaft  36  of the angular transmission. To support the axial and radial forces resulting from the tooth engagement and the forces introduced via the sun-gear shaft  31 , the vertical bevel-gear shaft  36  is held at its lower end by a bearing  38 , which is secured on the base plate  37  by a housing part. A further bearing  39  is arranged in such a way at its upper shaft end that the bevel-gear shaft  36  projects somewhat and can be connected in a rotationally fixed manner to the sun-gear shaft  31  by a releasable coupling  40 . This coupling  40  is preferably a toothed coupling. 
     The sun-gear shaft  31  is supported axially on the bevel-gear shaft  36  and, at the lower end, is guided in the radial direction by the coupling  40 . By means of the sun pinion  53  attached to the other end of the sun-gear shaft  31 , the sun pinion  53  being centered in an overhung manner between the planet gears  51 , the sun-gear shaft  31  is guided radially at its upper shaft end. The revolving planet gears  51  are mounted rotatably in the planet carrier  54  by means of bearings  52 . The planet carrier  54  is guided in the radial direction by means of the planet gears  51 , which mesh with the annulus toothing  50 , and its entire weight is supported on the sun-gear shaft  31  by means of a thrust bearing  57  bearing down above the sun pinion  53 . The planet carrier  54  is connected in a rotationally fixed manner to the sun gear  41 , which is arranged under it on the same axis of rotation. The sun gear  41  is bored out so that, once assembled with the planet carrier  54 , it can be mounted over the preinstalled sun pinion  53 . With its toothing, the sun gear  41  meshes with the planet gears  43 , which are guided on spindles of the planet carrier  58  by means of bearings  42 ,  45 . The planet carrier  58  is connected in a rotationally fixed manner to the housing partition. The power flows from the sun-gear shaft  31 , via the sun pinion  53 , into the revolving planet gears  51 , which deliver some of the power via the annulus toothing  50  to the likewise revolving annulus body  46 . The remainder of the power is introduced into the second epicyclic transmission stage  41 ,  43 ,  44 , arranged below the first, via the planet carrier  54  which carries the planet gears  51  and is connected in a rotationally fixed manner to the sun gear  41 . The planet gears  43  fixed to the housing mesh with the annulus toothing  44 , which, like the annulus toothing  50  of the first epicyclic transmission stage  53 ,  51 ,  50 , is attached in a rotationally fixed manner to the annulus body  46 . By means of these toothings  44 ,  50 , the component power flows are summed in the annulus body  46 , which is connected by a shrink fit and additional keys  56  to the thrust ring  49  in the interior of the latter. Power output from the annulus body  46  takes place directly into the thrust ring  49 . 
     The bowl mill  30  is mounted on the thrust ring  49 . The very large grinding forces which act in the axial direction on the thrust ring  49  are introduced by means of thrust bearings  48  into the housing  47 , from where they are introduced into the foundation by direct force transmission via the base plate  37 . The thrust bearings  48  are embodied as hydrodynamic or hydrostatic bearings or as a combination of the two types of bearing, depending on the size of the mill and the grinding pressure which arises. 
     The thrust ring  49  with the bowl mill  30  arranged on it is supported radially by the annulus body  46 , which is guided on the inside by a bearing  55  via various intermediate washers. The bearing  55  is connected to the housing  47  by the planet carrier  58  of the lower epicyclic transmission stage  41 ,  43 ,  44 , the planet carrier  58  being fixed to the housing  47 . Oil sump lubrication is provided for the lower epicyclic transmission stage  41 ,  43 ,  44  with the planet gears  43  fixed to the housing. The operation of the bearings  42 ,  45  of these planet gears  43  fixed to the housing can be monitored in a simple manner by measurements of structure-borne noise. 
     In another variant (not shown) of the housing, a complete module  59  of the bevel-gear transmission stage  32 ,  35  is provided with its own, vertical housing secured on the base plate  37 . 
     A complete module of this kind can be inserted through a tunnel leading radially into the housing  47  and can be positioned under the raised sun-gear shaft  31 . 
     By lowering the shaft  31  with the sun pinion  53 , which, as with the process of raising, is performed from above by means of lifting gear, the sun-gear shaft  31  is connected to the bevel-gear shaft  36  by the coupling  40 . 
     In another design configuration, such a module  59  of the bevel-gear transmission stage  32 ,  35  includes a flanged housing  60 . This flanged housing is flanged as a compact unit to the housing partition beneath the second epicyclic transmission stage  41 ,  43 ,  44 , and the coupling  40  connects the bevel-gear shaft  36  to the sun-gear shaft  31 . 
     The vertical housing  59  and the flanged housing  60  are of multi-part design and also allow partial disassembly after installation. 
     Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps,which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.