Abstract:
The invention relates to a mobile work machine, in particular a truck-mounted concrete pump, comprising a vehicle-mounted support structure and at least one swivel arm that is hinged to the support structure and is provided with two bearing brackets which project like forks and are mounted by means of a supporting bore so as to be able to rotate horizontally on a swivel arm bolt retained on the support structure. According to the invention, the bearing region between the swivel arm bolt and the bearing brackets is sealed by flexible profiled ring seals.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of PCT/EP2015/060841, filed May 18, 2015, which claims priority to DE 10 2014 210 573.0, filed Jun. 4, 2014, both of which are hereby incorporated herein by reference in their entireties. 
     
    
     BACKGROUND 
       [0002]    The invention relates to a mobile work machine, in particular a truck-mounted concrete pump, comprising a supporting structure fixed to a vehicle, in particular for a concrete distribution mast, and at least one swivel leg which is hinged to the supporting structure and has two bearing brackets which protrude in the manner of forks and are each mounted by means of a bearing bore, so as to be able to rotate horizontally, on a swivel leg bolt held on the supporting structure. 
         [0003]    The hinging of the swivel legs onto mast blocks of truck-mounted concrete pumps resembles in its structure two links of a bicycle chain which are connected together via a bolt. Thus the swivel leg forms one “chain link” and the supporting structure the other. The swivel leg bolt connects the two parts together such that the legs can swivel out laterally about the vertical bolt axis. In contrast to a bicycle chain, the articulated connection of the swivel leg and supporting structure is loaded transversely to the connection, i.e. in the vertical direction, by transverse forces and moments. In the travelling state, the swivel leg lies on its lower bearing bracket, wherein a gap appears in the bearing region of the upper bearing bracket, while in the supporting state the reverse applies. Also, on swiveling and in pumping mode, radial and axial movements occur in the bearing region. This requires stable and precise fits which can be achieved via correspondingly machined bearing points, in some cases using bearing bushes. The bearing points lie in an exposed region where they are not protected from weather influences and corrosive media such as precipitation water and splash water during travelling or from the use of high pressure cleaners. The problem of corroded bearing points has been known for a long time, but so far no remedy has been found. 
       SUMMARY 
       [0004]    This disclosure further improves work machines known from the prior art, and with simple measures create a reliable protection for the bearing points of swivel legs. 
         [0005]    This disclosure is based on the concept of using commercial sealing elements to protect the bearing points from the ingress of corrosive media. Consequently, according to this disclosure it is proposed that the bearing region between the swivel leg bolt and the bearing brackets is sealed by flexible profiled ring seals. Although the use of sealing elements initially appears unfeasible because of the particular peripheral conditions, surprisingly, problems could be overcome and a configuration of elastic profiled ring seals created which is adapted to the environmental and installation conditions, the functional capacity of which is not adversely affected by aggressive ambient media, so as to provide a sustained and low-maintenance functionality. Because of the flexibility of the elastic profiled ring seals, installation is easily possible without the use of special tools. 
         [0006]    Advantageously, the elastically deformable profiled ring seals are held under pretension in a respective sealing ring seat, so as to retain a position adapted to the sealing gaps occurring, even during movements. 
         [0007]    One embodiment provides that at least one profiled ring seal is held on each bearing bracket in a peripheral recess of the swivel leg bolt. This groove-like sealing ring seat is thus formed on the bolt and not on the bearing bracket, so that a compact construction is achieved and the bearing surface of the bearing brackets for the necessary force absorption is not restricted. 
         [0008]    The bearing region is formed by a cylindrical bearing gap between the bearing bracket and the swivel leg bolt. This results in an exposed bearing point which is reliably sealed on both sides of the bearing bracket by the profiled ring seals. 
         [0009]    In order to optimize the gap seal, in particular on axial bearing movements and also in the case of production tolerances, it is favorable if a V-ring as a profiled ring seal is arranged on each of the mutually facing insides of the bearing brackets. The pretensioned V-seal absorbs axial movements of the bolt and nonetheless seals this against the bearing bracket. It is particularly favorable if the V-ring has a sealing lip which can be pressed against the bearing bracket. 
         [0010]    In order to maintain the sealing effect under widely varying conditions of use, it is advantageous if a sealing ring seat which widens conically towards a respective bearing bracket is formed on each end portion of the swivel leg bolt. The conical shape allows the V-ring to lie optimally in the seat, wherein because of the conically increasing diameter and the associated pretension, the sealing effect in the direction of the bearing point to be sealed is constantly increased. 
         [0011]    A further improvement in retaining the desired sealing position can be achieved if the conical sealing ring seat has a stepped edge on its flank facing away from the associated bearing bracket. 
         [0012]    For protection and design reasons, the swivel leg bolt is coated with a paint coating, wherein damage to the painted parts can advantageously be avoided if the paint coating ends at a paint edge in the region of the conical sealing ring seat, so that the paint edge remains protected from flaking off, and the unpainted region is protected from corrosion by the V-ring. 
         [0013]    According to a further embodiment, an O-ring as a profiled ring seal is arranged on the outsides of the bearing brackets facing away from each other. Surprisingly, by use of an O-ring which is normally used only as a static seal, under the conditions of use occurring in a truck-mounted concrete pump, nonetheless a good axial and radial sealing effect can be achieved. Here it is particularly favorable if the swivel leg bolt is held at both ends on two retaining plates fixed to the vehicle, and if the O-ring is arranged in each case between the paired adjacent retaining plates and bearing brackets. Thus a reliable seat can be achieved even in the restricted installation space. 
         [0014]    A further improvement in this regard can be achieved if the retaining plates and bearing brackets are supported against each other in pairs by sliding disks, and a gap region between the sliding disks is sealed by the O-ring. 
         [0015]    To further improve the centering at the sealing gap, it is advantageous if the sliding disks are chamfered on their mutually adjacent peripheral edges, and in the chamfer region form a sealing ring seat for the O-ring. 
         [0016]    Advantageously, a bearing bushing sealed by the profiled ring seals against the ingress of corrosive media is inset into the bearing bore of the bearing brackets. 
         [0017]    With a view to cost-efficient design with nonetheless unrestricted functional capacity, it is advantageous if the swivel leg bolt comprises two cylindrical end portions and a center portion that widens as a double cone towards the end portions, and a profiled ring seal is arranged in each of the transitional regions between the center portion and the end portions. 
         [0018]    In order to further increase the benefits in use by suitable choice of material, the profiled ring seals should be formed from a nitrile rubber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: 
           [0020]      FIG. 1  shows a swivel leg of a truck-mounted concrete pump with a hinge connection to a supporting structure fixed to the vehicle, as a partly cut-away side view; 
           [0021]      FIG. 2  shows an enlarged depiction of the hinge connection from  FIG. 1 ; 
           [0022]      FIG. 3  shows a sealing arrangement of the hinge connection in a further enlarged extract from  FIG. 2 ; and 
           [0023]      FIG. 4  shows an O-ring of the sealing arrangement in an enlarged extract from  FIG. 3 . 
       
    
    
     DESCRIPTION 
       [0024]    The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure. 
         [0025]    It should be understood that the terms “horizontal” and “vertical” are generally used herein to establish positions of individual components relative to one another rather than an absolute angular position in space. Further, regardless of the reference frame, in this disclosure, terms such as “vertical,” “parallel,” “horizontal,” “right angle,” “rectangular” and the like are not used to connote exact mathematical orientations or geometries, unless explicitly stated, but are instead used as terms of approximation. With this understanding, the term “vertical,” for example, certainly includes a structure that is positioned exactly 90 degrees from horizontal, but should generally be understood as meaning positioned up and down rather than side to side. Other terms used herein to connote orientation, position or shape should be similarly interpreted. Further, it should be understood that various structural terms used throughout this disclosure and claims should not receive a singular interpretation unless it is made explicit herein. By way of non-limiting example, the terms “swivel leg,” “ring seal,” and “bearing bracket,” to name just a few, should be interpreted when appearing in this disclosure and claims to mean “one or more” or “at least one.” All other terms used herein should be similarly interpreted unless it is made explicit that a singular interpretation is intended. 
         [0026]    The truck-mounted concrete pump  10  shown only as an extract in  FIG. 1  has a supporting structure  12  fixedly mounted on a chassis of a vehicle. The supporting structure  12  forms a bearing block  14  for a concrete distribution mast (not shown) rotatable about a vertical rotation axis, and which is connected in articulated fashion via a hinge connection or hinge point  16  onto two horizontally swiveling rear swivel legs  18  mounted on the long vehicle sides, while two front telescopic legs  20  can be extended telescopically. The legs  18 ,  20  can thus be brought from a travelling position into a supporting position further out from the vehicle longitudinal axis, in order to guarantee the safety and stability of the vehicle even on movements of the concrete distribution mast. The swivel legs  18  are swiveled outward via hydraulic cylinders  21  which act on the horizontal support leg arm  22 . To compensate for unevenness of the ground, vertically extending hydraulic supporting cylinders  23  are arranged on the ends of the legs  18 ,  20  and are able to lift the chassis from the ground. 
         [0027]    Each hinge point  16  of the swivel legs  18  has a swivel leg bolt  24  which is held on the supporting structure  12  and defines a vertical pivot axis. The swivel leg bolt  24  is tapered in its center region  25  in the manner of a double cone, as described in more detail in DE-A 102013205888. With regard to the general configuration of a truck-mounted concrete pump with supporting structure and distribution mast, reference is hereby made in full to DE-A 102013205888. 
         [0028]    As shown most clearly from the axial section through the swivel leg bolt  24  in  FIG. 2 , each swivel leg  18  on its end close to the vehicle has two bearing brackets  26  which protrude in the manner of forks and are spaced vertically from each other, and which are mounted via co-aligned bearing eyes or bearing bores  28  on the cylindrical end portions  30  of the swivel leg bolt  24  so to be able to rotate horizontally. The two bearing brackets  26  have outsides facing away from each other and insides facing towards each other. The swivel leg bolt  24  is held at both ends on two retaining plates  32  which are fixedly connected to the supporting structure  12  and overlap in pairs with the bearing brackets  26 , wherein an axle holder in the form of a covering end plate  34  bolted to the upper end face of the swivel leg bolt  24  ensures a rotationally stationary and axially displaceable fixing. 
         [0029]    The bearing region formed by the annular cylindrical bearing gap between the swivel leg bolt  24  and the bearing brackets  26  is in each case sealed by flexible profiled ring seals  36 ,  38  so as to prevent the ingress of corrosive media. The elastically deformable profiled ring seals  36 ,  38  are here held under pretension in order to achieve an optimum sealing effect. 
         [0030]      FIG. 3  shows an enlarged extract of the arrangement of the profiled ring seals  36 ,  38  on the upper end portion  30  of the swivel leg bolt  24 . The lower end portion is sealed symmetrically to this. On the insides of the bearing brackets  26  facing each other, a fully rubberized V-ring  40  is arranged as a profiled ring seal  36  in a peripheral recess of the swivel leg bolt  24 , wherein the profile of the V-ring  40  has a flexible sealing lip  42  pressing axially against the bearing bracket  26  and a supporting body  44  connected to the sealing lip  42  in the manner of a hinge, leaving a V-shaped gap. To secure the position, the V-ring  40  is drawn onto a conical sealing ring seat  46  which expands towards the bearing bracket  26  to be sealed, and has a stepped edge  48  in its tapered region facing away from this. This prevents the V-ring  40  from slipping into the small diameter region of the swivel leg bolt  24 . 
         [0031]    In the region between the swivel leg bolt  24  and the bearing bracket  26 , a bearing bushing  50  is inserted between bright metal faces to improve the bearing properties. The V-ring  40  as a gap seal serves to seal against dirt, dust and water, and a mixture of these corrosive media. The sealing lip  42  allows a degree of axial play of for example 3 to 6 mm, so that the sealing effect is retained even under loads in travelling mode or on extension of the supporting cylinder  23 . The chamfer of the supporting body  44 , transforming into the conical region of the swivel leg bolt  24 , supports the outflow of fluidic media. As already mentioned, the swivel leg bolt  24  in its cylindrical end portion  30  remains bright for reasons of fit precision, while the double conical center region has a paint layer  52  on the casing side for design reasons. Suitably, this paint layer  52  ends at a paint edge in the region of the conical sealing ring seat  46 . 
         [0032]    The bearing brackets  26  and retaining plates  32  are supported against each other in pairs by annular sliding disks  54 ,  56 . On the periphery, these are fixed via weld seams to the respective adjacent connecting partner. An integral molding of sliding disks on the respective bearing brackets  26  or retaining plate  32  is also conceivable. 
         [0033]    As shown in  FIG. 4 , the gap region  58  between the sliding disks  54 ,  56  is sealed by a further profiled ring seal  38  formed as an O-ring  60 . Suitably, the sliding disks  54 ,  56  are chamfered on their peripheral edges adjacent to each other, and thus in the chamfer region form a sealing ring seat  62  for the O-ring  60 . Further centering is achieved by fillet welds  63  with which the sliding disks  54 ,  56  are fixed rotationally stationarily to the bearing brackets  26  and retaining plate  32 . The sliding disks  54 ,  56  indeed move relative to each other on extension of the swivel leg  18 ; the angular ranges are however small and the rotary movements slow and also infrequent. It was therefore found that a quasi-static sealing situation exists in which an O-ring can still be used without problems. In order to ensure a reliable radial sealing effect, the ring diameter of the O-ring  60  is selected significantly smaller (e.g. by 10 mm) than the diameter of the sliding disks  54 ,  56 , so that it sits under a strong pretension in the installation position. The profile diameter of the O-ring  60  is dimensioned sufficiently large to be able to seal the axial expansions of the gap region  58  occurring at any time during travel and in pumping mode. 
         [0034]    The two profiled ring seals  36 ,  38  consist of nitrile rubber which has a high flexibility, elasticity and resistance to weather, oil and solvents, and the properties of which can be optimized further by suitable application-specific additives. 
         [0035]    While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.