Abstract:
A system for the contactless sealing of a rotatably mounted shaft with respect to a housing, and a gear unit, oil being provided in the interior of the housing, in particular, the rotating shaft protruding from the interior into the outer area; a centrifugal disk, joined in rotatably fixed manner to the shaft, having at least partially radially extending bores that connect oil from a centrifugal chamber to a collection chamber surrounding the centrifugal disk.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 13/255,067, filed on Sep. 6, 2011, which is a national phase of PCT International Application No. PCT/EP2010/001242, filed on Mar. 1, 2010, which claims priority to German Patent Application No. 10 2009 011 124.7, filed on Mar. 3, 2009, each of which is expressly incorporated herein in its entirety by reference thereto. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a system for the contactless sealing of a rotatably mounted shaft with respect to a housing, and a gear unit. 
     BACKGROUND INFORMATION 
     In sealing systems having shaft sealing rings, it is well-known that friction losses increase as the rotational speed increases. 
     German Published Patent Application No. 602 16 474 describes a contactless sealing in which a centrifugal disk, having radial bores as slinger ports (FIG. 1 there, reference 44), is provided on a shaft. The radial bores permit lubricating oil, which was accumulated in a radially inner centrifuging chamber, to flow out, the bores then centrifuging the oil off at their other end area into a collection chamber. The centrifugal disk has an axial gap with respect to a non-rotating part, the gap joining the centrifuging chamber to the collection chamber. 
     A labyrinth seal is described in German Published Patent Application No. 479 388. 
     U.S. Pat. No. 2,598,381 describes connecting an interior space of a gear unit, partially filled with lubricating oil, via an air channel (FIG. 1 there, reference numeral 9) to the outside air, for example, for compressed-air compensation. In that case, oil is conveyed radially and axially inward by centrifugal force, by providing a suitable bevel. Independently of this air channel, a contactless sealing is achieved by a centrifugal edge which, during rotational movement, centrifuges the oil off into a collection chamber (FIG. 1 there, reference numeral 13) that is connected by a downward running bore to the oil-pan space. 
     German Published Patent Application No. 10 2007 014 657 describes a shaft sealing device in which oil, likewise centrifuged off, is recirculated. 
     German Published Patent Application No. 698 18 914 describes a shaft sealing system in which a shaft sealing ring is provided. 
     A sealing ring for a water-pump bearing is described in German Published Patent Application No. 601 30 871. 
     German Published Patent Application No. 42 20 754 also describes a sealing system that functions in non-contact fashion during rotational movement of the shaft of a gear unit, in which oil, likewise centrifuged off, is recirculated. 
     German Published Patent Application No. 39 30 280 likewise describes such a sealing system functioning in non-contact fashion during rotational movement of the shaft. 
     A sealing system acting in contacting fashion is described in German Published Patent Application No. 35 44 783. 
     A sealing system that functions in non-contact fashion during rotational movement of the shaft, in which oil, likewise centrifuged off, is recycled is also described in German Published Patent Application No. 33 30 473. 
     German Published Patent Application No. 11 2004 000 627 also describes a sealing system that functions in non-contact fashion during rotational movement of the shaft, and in which oil spun off by a plurality of shaft grooves is likewise recycled. 
     A sealing system that functions in non-contact fashion during rotational movement of the shaft and in which oil spun off by pointed edges is likewise recirculated is described in German Published Patent Application No. 470 121, as well. 
     U.S. Pat. No. 5,538,258 describes a contactless sealing in which a centrifugal disk, having radial bores as slinger ports (FIG. 1 there, reference numeral 44), is provided on a shaft. The radial bores permit lubricating oil, which was accumulated in a radially inner centrifugal chamber, to flow out, the bores then ejecting the oil at their other end area into a collection chamber. The centrifugal disk has an axial gap with respect to a non-rotating part, the gap joining the centrifugal chamber to the collection chamber. 
     SUMMARY 
     Example embodiments of the present invention reduce maintenance costs and losses in the case of a sealing system. 
     Among features of example embodiments of the present invention with regard to the system are that it is provided for the contactless sealing of a rotatably mounted shaft with respect to a housing, oil being provided in the interior of the housing, in particular, the rotating shaft protruding from the interior into the outer area, wherein a centrifugal disk, joined in rotatably fixed manner to the shaft, has at least partially radially extending bores that connect oil from a centrifugal chamber to a collection chamber surrounding the centrifugal disk. 
     In particular, a centrifugal disk, joined in rotatably fixed manner to the shaft, thus has bores extending at least partially in the radial direction, so that lubricating oil is able to be conveyed from a centrifugal chamber to a collection chamber surrounding the centrifugal disk, the bores opening through with their radially inner end area into the centrifugal chamber, and opening through with their radially outer end area into the collection chamber, between the centrifugal disk and a flange part of the housing, a gap region being provided which
         connects the centrifugal chamber to the collection chamber and   into which a bore leads with its first end area, the bore opening through with its other end area into a further collection-chamber area, so that lubricating oil, centrifuged off into the further collection-chamber area by a centrifugal edge joined in rotatably fixed fashion to the shaft, is able to be collected and fed through the bore to the gap region, a gap region connecting the further collection-chamber area to the centrifugal chamber.       

     The bore between the gap region and the further collection-chamber area preferably extends axially. 
     Of advantage is that the oil is able to be conveyed out of a centrifugal chamber—which at least partially surrounds the centrifugal disk and is bounded by housing parts and the shaft or centrifugal sleeve provided on the shaft—through the centrifugal disk, namely, through bores in the centrifugal disk. Thus, effective emptying of the centrifugal chamber is attainable. In so doing, the oil is emptied out not into the oil-pan area or the interior space, e.g., into the interior of the gear unit, but rather into a collection chamber, therefore, a spatial area which is bounded by the flange parts and the rotating part, thus, the shaft or a centrifugal sleeve provided on the shaft. 
     In this manner, it is possible to avoid wear to the seal, particularly in comparison to shaft sealing rings which are subject to wear. Furthermore, maintenance costs are improved and reliability is likewise improved. 
     It is further advantageous that oil, which is caught in a collection chamber situated axially further outside, is able to be fed into the gap region between the co-rotatable centrifugal disk and the stationary flange part. Since this gap region extends radially, a pressure gradient exists between the centrifugal chamber and the collection chamber that has a conveying effect which acts as return. Thus, even if oil on the centrifugal disk were to arrive further axially to the outside, a return from a downstream collection chamber would be made possible through the bore between the gap region and the collection-chamber area. 
     An advantage is that an active pumping action is attainable, accompanied by a contactless sealing. 
     In example embodiments, the centrifugal disk is secured on a centrifugal sleeve which is provided on the shaft. This is advantageous because assembly is easy, and in addition, diameter variations, such as an axial area with increasing or decreasing diameter, may be produced in an inexpensive and uncomplicated manner. The reason is the centrifugal sleeve does not pass any substantial torque through, the centrifugal disk being secured on the centrifugal sleeve, however. Thus, centrifugal grooves are able to be provided easily and inexpensively in the centrifugal sleeve, as well. 
     In example embodiments, the centrifugal chamber is bounded at least partially by a channel running round on the centrifugal disk, the channel being formed as the local maximum of the radial distance of the surface of the centrifugal disk; thus, in particular, the radial distance of adjacent surface areas of the centrifugal disk increases with decreasing axial distance toward the channel. This offers the advantage that oil propelled by the centrifugal force is driven into this channel, and from there, is then conveyed away with the aid of the bores. 
     In example embodiments, at least in one axial partial area, the outside diameter of the centrifugal sleeve increases toward the centrifugal disk, particularly with the aid of a chamfer provided on the centrifugal sleeve, especially so that oil is conveyed in the direction of the centrifugal disk, especially in the direction of the channel of the centrifugal disk. The advantage in this context is that a conveying action is able to take place in the direction of the channel, and therefore the oil is able to be discharged, especially in an easy manner, via the associated bore in the centrifugal disk, into the collection chamber. 
     In example embodiments, provided between the centrifugal disk and a flange part of the housing is a gap region, especially a radially extended gap region, into which a bore leads that is connected to a collection groove, thus a collection-chamber area, provided in the flange part, in particular, the bore being situated at smaller radial distance than the radial distance of the end area of the gap region, which opens through into the collection chamber, in particular, the collection groove being provided axially further outside than the centrifugal disk. The advantage in this case is that a pumping action is attainable in the gap region, since the gap region is bounded at a first lateral surface by the centrifugal disk, and at the lateral surface opposite this first lateral surface, by the housing part that does not co-rotate, thus, especially the outer flange part. Therefore, an underpressure is obtained for emptying the bore leading in, in the direction of the collection chamber connected at greater radial distance. 
     In example embodiments, a gap is provided between the centrifugal sleeve and a further flange part joined to the flange part, the gap being implemented as a radial gap in a first partial area, and as an axial gap in a further partial area. This is advantageous in that oil must traverse the radial gap coming from outside to the inside, since the end area of the radial gap with greater radial distance is disposed toward the interior, and the end area of the radial gap with smaller radial distance must first be reached against the centrifugal force. 
     In example embodiments, the gap opens through into a collection groove that is provided in the further flange part and is connected to the collection chamber via a further gap which is situated between the further flange part and the centrifugal sleeve. The advantage here is that the gap represents a further barrier for penetrating oil. In particular, it may be implemented as a capillary gap, and therefore also represents a barrier very difficult to overcome. 
     In example embodiments, the collection chamber is connected in its lower area via a bore to the interior of the housing, especially to the oil-pan area. This is advantageous because oil which has penetrated or been caught in the collection chamber is able to be evacuated to the oil pan, especially driven by the force of gravity. 
     In example embodiments, the flange parts are screw-connected and a seal, especially an O-ring seal, is disposed between them. The advantage here is that the housing may be made strong and leak-proof. In particular, the joint of the two flange parts is sealed up, so that the O-ring seal lies further inside in the joining surface and the screw connection lies further outside. Therefore, no oil penetrates from the interior space via the joining surface, thus the contact surface, to the thread area of the screw, and from there into the outer area.  FIG. 1  shows a screw passing through from the outer area through the outer and the inner flange part. In a further improved exemplary embodiment, the screw does indeed penetrate through the outer flange part, but is screwed into a non-through bore in the inner flange part. 
     In example embodiments, a first baffle area having a first drainage channel is disposed on the further flange part, in particular, a second baffle area having a second drainage channel being disposed on the further flange part, the baffle area and drainage channel in particular being axially symmetric. This offers the advantage that each baffle area is able to be provided combined with a corresponding drainage channel, so that the liquid portions which have struck are able to be carried away quickly and easily. Therefore, the main quantity of the oil sprayed around during operation above the oil level is able to be collected and recirculated, particularly at the periphery of the overall sealing system. 
     In example embodiments, in each case a centrifugal groove is disposed on the centrifugal sleeve, radially opposite the collection groove(s). This is advantageous, because the centrifugal groove may be produced easily and inexpensively. 
     In example embodiments, the gap regions are each implemented as capillary gap regions. The advantage here is that the resistance to flow for oil is very high, and this is therefore hindered in respect to the at least rapid flow through the gap. 
     In example embodiments, a dust protector, which is in contact with the flange part, is disposed on the shaft. The advantage in this case is that the functioning method of the sealing system is not disturbed, for in the event great quantities of dust penetrate, a bore could be stopped up, for example. The spatial area protected by the dust protector is connectable directly or with the aid of a gap to a collection groove or to some other collection area such as the collection chamber, for instance. 
     The dust protector does not contribute to the actual sealing action of the sealing system, for it protects only against penetrating dust and contacts the flange part, belonging to the housing, at its outer surface. 
     In example embodiments, the oil level lies below—thus below in the gravitational direction—the system when the gear unit is at rest. The advantage in this context is that in the state of rest, there is no possibility that oil will pass through the sealing system, and then penetrate into the outer area. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Shaft 
           2  Axial gap, capillary cap region 
           3  Entry labyrinth, including radially extended gap section, capillary cap region 
           4  Drainage channel 
           5  Calming space 
           6  Baffle surface 
           7  Collection groove 
           8  Drainage channel 
           9  Baffle surface 
           10  Collection chamber 
           11  Centrifugal bore 
           12  Gap, particularly radial gap, capillary cap region 
           13  Collection groove, further collection-chamber area 
           14  Third centrifugal groove 
           15  Second centrifugal groove 
           16  First centrifugal groove 
           17  Dust protector 
           18  Inner return bore 
           19  Flange, outer sealing flange 
           20  Retaining screw 
           21  Outer return bore 
           22  Centrifugal disk 
           23  Inner sealing flange, further flange apart 
           24  Drain bore 
           25  Centrifugal sleeve 
           26  O-ring seal 
           27  Centrifugal chamber 
           28  Chamfer 
           29  Widening 
       
    
     Example embodiments of the present invention are explained in greater detail with reference to the Figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a system according to an example embodiment of the present invention. 
         FIG. 2  is an enlarged cross-sectional view of the system illustrated in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     A system according to an example embodiment of the present invention is shown schematically in  FIG. 1 . An enlarged section is shown in  FIG. 2 . 
     According to example embodiments of the present invention, a contactless sealing is attained between a rotating shaft  1  and a housing. 
     In this context, disposed on shaft  1  is a centrifugal sleeve  25  on which, in addition, a centrifugal disk  22  is situated, in particular, joined with material locking or as a press-fitted connection. 
     An outer sealing flange  19  and an inner sealing flange  23  are provided on the housing, the centrifugal disk being set apart from outer sealing flange  19  by a gap  12 , and centrifugal sleeve  25  being set apart from inner sealing flange  23  by a gap, including entry labyrinth  3  and axial gap  2 . 
     The sealing system is set up in multiple stages, and in this manner, the oil passing through each obstacle is in each instance met with a further obstacle. 
     The entire sealing system is disposed above the oil level which sets in when shaft  1  is at rest. During operation of shaft  1 , oil foam or spraying oil may be produced, for example, by gear wheels connected directly or indirectly with the shaft. Preferably, this oil level is below return bore  21 . 
     The oil striking against baffle surface  9  is drained off via an annularly formed drainage channel  8 , and downward toward the oil pan. 
     Provided axially somewhat further inside, but radially deeper, is baffle surface  6 , which is bounded radially to the inside by an annular calming space  5  that has a drainage channel  4  situated radially inside. Entry labyrinth  3 , which is provided between centrifugal sleeve  25  and inner sealing flange  23 , begins directed inwards in the axial direction, then goes over into a radially running section and ends as axial gap  2  situated radially further inside, which then runs directed outwards in the axial direction, and at its end area, widens in the direction of collection groove  7 . The flaring, thus the widening denoted by reference numeral  29 , is realized by a suitable chamfer, so that the capillary effect is interrupted in this area. A centrifugal groove  16  is disposed on centrifugal sleeve  25 , opposite collection groove  7 , and is provided to spin oil off in the direction of collection groove  7 . At the lower area of collection groove  7 , a drain bore is provided that is aligned in the axial direction and leads into a collection chamber  10 , which in turn returns oil via a bore, namely, outer return bore  21  in inner sealing flange  23 , back into the oil pan. 
     Between centrifugal sleeve  25  and inner sealing flange  23 , a gap is provided that connects collection groove  7  to collection chamber  10 . 
     A centrifugal groove  15  is again disposed in the axial region of collection chamber  10 , so that oil which penetrates via the indicated gap is centrifuged off. 
     In addition, provided axially following is centrifugal disk  22  that likewise centrifuges oil off into collection chamber  10 . 
     Axially following centrifugal disk  22 , a further centrifugal groove  14  is again provided, opposite which a collection groove  13  is located on flange part  19 . Thus, oil is spun off from the edges of centrifugal groove  14  into collection groove  13 . 
     Centrifugal sleeve  25  is implemented with a chamfer  28  such that its outside diameter increases in an axial area which is located between centrifugal groove  14  and centrifugal disk  22 , and specifically, increases with decreasing distance to centrifugal disk  22 , so that oil possibly appearing is conveyed in this direction, thus, toward centrifugal disk  22 . Therefore, chamfer  28  contributes in connection with the return flow. The oil is then conveyed into centrifugal chamber  27 , which is emptied into collection chamber  10  with the aid of centrifugal bores  11  that are introduced into centrifugal disk  22  in the radial direction. A plurality of such centrifugal bores  11 , especially between four and twenty, are provided at the periphery of the centrifugal disk. 
     Collection groove  13 , situated axially further to the outside, has at its lower region, especially including the deepest point, a bore  18  directed axially toward the gap region, thus, gap  12 , which is provided between centrifugal disk  22  and outer flange  19 . Collection groove  13  is assigned a centrifugal groove  14 , which is provided on centrifugal sleeve  25 . 
     This gap region of gap  12  is open toward collection chamber  10 . Since bore  18  discharges into gap region  12  at a radial distance that is smaller than the radial distance of radially outside end area of gap region  12 , where gap region  12  discharges into collection chamber  10 , a conveying effect is provided. The reason is that due to the rotational movement, an underpressure is generated, which causes bore  18 , and therefore collection groove  13 , to be pumped out. 
     Thus, not only is the well-known centrifuging provided for the discharge, but also the pumping effect of a gap region  12 . 
     Collection grooves  7  and  13  are therefore emptied into collection chamber  10 , and not directly into the interior and/or the oil-pan area. To that end, bore  24  connects collection groove  7  to collection chamber  10 . 
     Inner sealing flange  23  and outer sealing flange  19  are joined to each other, sealed off by an O-ring seal  26 , a plurality of successive retaining screws  20  in the circumferential direction joining the two sealing flanges. Thus, a one-piece construction of the two sealing flanges  19  and  23  is also possible. A dust protector  17  is just provided externally. 
     A further collection-chamber area is formed by collection groove  13 , that is situated separate from collection chamber  10  and is provided further axially outwards.