Abstract:
A rotary seal arrangement has a rotatable component ( 2 ) supported within a machine component ( 3 ), the machine component ( 3 ) forming a housing structure for a sealing means ( 23 ) which acts to seal off a high-pressure area ( 10 ) between the components ( 2,3 ) to allow the passage of high pressure fluid therebetween. The seal arrangement includes a holding element ( 30 ) for mounting in the machine component ( 3 ) to support spaced sealing members ( 23 ) therein to define said high pressure area ( 10 ) therebetween. The arrangement is particularly suitable for use where the rotatable component ( 2 ) is formed as a rotatable shaft and the holding element ( 30 ) and sealing members ( 23 ) are arranged around the shaft such as, for example, in a vehicle tyre pressure changing system for use on an agricultural tractor. The spaced sealing members ( 23 ) are provided with support elements ( 20 ) which extend generally radially relative to the rotatable component ( 2 ) to provide support for the sealing members ( 23 ) against the high pressure fluid, the holding element ( 30 ) and support elements ( 20 ) forming a cartridge like arrangement which encloses the sealing members ( 23 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The invention relates to a rotary seal arrangement having a rotatable component supported within a machine component, wherein the machine component forms a housing structure for a sealing means which acts to seal off a high pressure area between the components to allow the passage of high pressure fluid therebetween. 
         [0003]    2. Description of Related Art 
         [0004]    Generic rotary seals are used, for example, for sealing off rotary feed-throughs. The high-pressure area is then formed by a rotary feed-through area between the two components. The rotary seal is thereby also referred to as a rotary feed-through seal. The rotary feed-through allows fluids, i.e. gases of liquids, to pass between the fixed machine component and a rotatable component in a sealed manner. Usually, the fixed machine component is designed with the housing structure for the seal and the rotatable component is designed as a shaft rotatably supported therein. Rotary feed-throughs of this kind are used, for example, in hydraulic applications or for feeding in hot gas to heat a roller. 
         [0005]    Known rotary feed-through seals are, for example, designed as sliding rings (rotating mechanical seals), wherein the sliding ring usually has a sealing ring made of polytetrafluoroethylene (PTFE). 
         [0006]    An example of a rotary feed-through seal is designed in such a way that as little as possible of the fluid under excess pressure gets from the high pressure rotary feed-through area to the surrounding low-pressure area, i.e. that there is little leakage. However, the less leakage there is, the greater is the frictional force occurring between the sealing area of the rotatably supported machine component and the rotary feed-through seal. The abrasive wear of the rotary feed-through seal is correspondingly increased and a relatively large amount of drive energy is expended against the said frictional force. In particular, with shafts rotating with high rotational speeds and with fluids under high pressure, the service life of a known rotary feed-through seal of this kind is therefore low. 
         [0007]    Furthermore, the rotary seal must be prevented from rotating concurrently with the shaft. To this end, the sealing ring is often pressed into a holding element manufactured from steel, for example, and also ring-shaped. The holding element is fitted tight against torsion in the housing structure for the seal. A rotary feed-through seal of this kind is, however, relatively complicated to produce. For a fitting which is tight against torsion, anti-twist protection must be provided on the housing structure for the seal is not possible due to the rigidity of the holding element. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The object forming the basis of the invention is to provide a rotary seal arrangement which avoids the disadvantages of the prior art, wherein, in particular, the rotary seal is to be able to easily fit between the components. 
         [0009]    This object is achieved by the subject-matter claimed in claim  1  and the dependent claims constitute preferred embodiments of the invention. 
         [0010]    Thus in accordance with the present invention there is provided a rotary seal arrangement having a rotatable component supported within a machine component, the machine component forming a housing structure for a sealing means which acts to seal off a high-pressure area between the components to allow the passage of high pressure fluid therebetween, the seal arrangement being characterised by including the combination of a holding element for mounting in the machine component to support spaced sealing members therein to define said high pressure area therebetween and support elements which extend generally radially relative to the rotatable component to provide support for the sealing members against the high pressure fluid, the holding element and support elements forming a cartridge like arrangement which encloses the sealing members. 
         [0011]    Such a seal arrangement is particularly suitable for use where the rotatable component is formed as a rotatable shaft supported in the machine component with the holding element and sealing members are arranged around the shaft. One such application is a part of a tyre pressure changing system on an agricultural or commercial vehicle, such as a tractor, so that the tyre pressure can be increased for an intended driving on an asphalt road compared to the tyre pressure for driving on a soft field. 
         [0012]    The cartridge like arrangement can be particularly easily fitted in its operation position in the machine component. 
         [0013]    The holding element and support elements may be held together in the cartridge-like arrangement by resilient abutment bodies located between each sealing member and its associated support element, the abutment bodies being bonded to the holding element and the associated support elements. 
         [0014]    The holding element may be a sleeve-like element which encloses the arrangement and which includes a hole therein to provide communication with the high pressure area. 
         [0015]    Two holding elements and associated sealing members may be mounted side by side to seal two high pressure areas between the components. 
         [0016]    Axially outboard of the holding element, or a pair of holding elements may be located a pair of oil seals to prevent ingress of oil into the high pressure area or areas. 
         [0017]    Each oil seal may have its own outer fixing structure for easy mounting in its operational position. 
         [0018]    The invention also provides a vehicle tyre pressure changing system which uses a seal arrangement as described above. 
         [0019]    The holding element can be designed as a sleeve abutting on the housing structure for the seal, preferably wherein the abutment body has a foot-like enlargement which is preferably integrally moulded to the sleeve. These embodiments are particularly suitable for arranging a plurality of rotary seals designed according to the invention fixed opposite one another between the machine components. For example, four rotary seals formed according to the invention can be used in pairs mirror-symmetrically with respect to one another, in order to seal off a paired rotary feed-through. In this way, a multiple rotary seal of this kind can be easily fitted between the two machine components. 
         [0020]    If two rotary seals are preferably mirror-symmetrically arranged around the, or a, rotary feed-through area, the rotary feed-through area will be reliably sealed off on both sides. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The invention will be explained in more detail below by means of exemplary embodiments with reference to the drawings. 
           [0022]      FIG. 1  shows an embodiment of a rotary seal arrangement according to the invention in a cross-section. 
           [0023]      FIG. 2  shows a paired rotary feed-through with a rotary seal arrangement according to the invention. 
           [0024]      FIGS. 3   a  to  3   f  show embodiments of rotary seals of a rotary seal arrangement according to the invention. 
           [0025]      FIG. 4  shows part of a rotary seal arrangement according to the invention. 
           [0026]      FIG. 5  shows part of a further form of rotary seal arrangement according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    The illustrations in the drawings show the subject-matter according to the invention very schematically and are not to be interpreted as being to scale. The individual components of the subject-matter according to the invention are illustrated so that their construction can be shown well. 
         [0028]    In  FIG. 1  an embodiment of a rotary seal arrangement  1  according to the invention is illustrated in a cross-section. Rotary seals  5  are fitted between a rotatable component in the form of a wheel drive shaft  2  and a component forming a support for the rotatable shaft  2  in the form of a vehicle axle housing  3 . The seals  5  have a ring-shaped form which is symmetrical to the shaft centre. The rotatability of the shaft is represented in the figure by a curved double arrow X. The rotational symmetry axis  6  of the rotary seals  5  coincides with the rotational axis of the shaft. 
         [0029]    The seals  5  are inserted in a housing structure formed in axle housing  3 . This housing structure may simply be a surface on which the seal is positioned. The shaft  2  has a surface forming a sealing area  7 . The seating of the rotary seals  5  is secured by a washer  8 , which in turn is fixed by means of a spring ring  9  engaging in a groove  3   c.    
         [0030]    A high-pressure area  10 , formed as a rotary feed-through area between housing  3  and shaft  2  is sealed off against a low-pressure area  11  by means of the seals  5 . Through the rotary feed-through area  10  a fluid, such as high pressure air, which is under excess pressure compared to the low-pressure area  11  with the low pressure P N , can be conducted from the housing  3  through the sealing area  7  into the rotatable shaft  2 . The low pressure P N  can, for example, be the normal atmospheric pressure. In addition, a hole  14  is provided in the fixed component  3 , which leads into the rotary feed-through area  10 . The rotatable component  2  also has holes  14  which lead into the rotary feed-through area  10  and connect the rotary feed-through area  10  for feeding through the fluid to a shaft end of the rotatable machine component  2 . Thus, the fluid can be conducted from the fixed machine component  3  through the holes  14  into the rotatable machine component  2 , which is represented in the figure by arrows  16 . 
         [0031]    There are two rotary seals  5  arranged mirror-symmetrically around the high-pressure area  10  or the rotary feed-through area. Each of the rotary seals  5  has a support element  20  which is essentially rigid and essentially arranged in a stable position with respect to the first machine component  3 , an abutment body  21  which can be deformed in a rubbery-elastic manner and is adjacent to the support element  20  on the rotary feed-through area side, and a sealing ring  23  which has a sealing edge  22  and loosely abuts on the abutment body  21 . The sealing ring  23  is thus not firmly connected to the abutment body  21  but only abuts on it. Intermediate spaces can also be present. The support element  20  is a component which is separate from the machine components  2 ,  3 . The sealing edge  22  of the sealing rings  23  is in each case arranged on a load area of the respective sealing ring  23  protruding beyond the support element  20  and the abutment body  21 , lying in between, in the direction of the sealing area  7 . In particular, the position of this load area varies when pressure is applied in the high-pressure area  10 . The load area is thus deformed, when pressure is applied, in such a way that the sealing edge  22  is pressed against the sealing area  7 . 
         [0032]    The sealing rings  23  are pushed away in each case from the sealing area  7  by the associated abutment body  21 . The latter is represented by arrows  25  in the figure. The pushing away action occurs by means of the rubbery-elastic properties of the abutment bodies  21 . The sealing rings  23  in each case have a cross-section which is at a concave angle to the rotary feed-through area  10 . The rotary feed-through area  10  is thereby bounded by the sealing rings  23  and the sealing area  7  in such a way that an obtuse angle exists between the rotary feed-through side surfaces of the sealing rings  23  and the sealing area  7 . The abutment bodies  21  are supported against the respectively associated supporting element  20 . 
         [0033]    If a fluid under high pressure P H  is introduced into the rotary feed-through area  10 , then, as represented by curved arrows in the figure, a force is exerted on the rotary feed-through area side surfaces of the sealing rings  23 . This force leads to the abutment bodies  21  being compressed against their inner rubbery-elastic actuating forces pushing the sealing ring  23  away from the sealing area  7 . As a result, the sealing edges  22  are pressed onto the sealing area  7 , so that the rotary feed-through area  10  is sealed off essentially leakage-free against the low-pressure area  11 . 
         [0034]    In the illustrated embodiment, a holding element  30 , made of steel for example, is provided for fixing the position of the rotary seals  5  in the housing structure for the seal. The two rotary seals  5  are arranged in a stable position with respect to one another by the holding element  30  and the support elements  20  which are bonded to the resilient abutment bodies  21  to form a cartridge-like arrangement. Thus, a seal pair is easily assembled into the operational position in component  3 . The holding element  30  forms a sleeve engaging the housing structure bore  3   a  for the seal, and each of the abutment bodies  21  has a foot-like enlargement  21   a  which is integrally moulded to the sleeve  30 . The sleeve  30  has a hole  31  in the region of the rotary feed-through area  10 , so that the fluid can flow through the hole  31  of the sleeve  30 . The entire seal contained between the support elements  20  and sleeve  30  is held against a simple shoulder  3   b  on component  3  by the simple spring ring  9  which engaged groove  3   c.  No complex sealing surfaces are required for mounting the entire seal in its operational position. 
         [0035]    In  FIG. 2 , a paired rotary feed-through having a rotary seal arrangement  1  according to the invention is illustrated, as is applicable in particular for use in a tyre pressure variation system. A paired rotary feed-through is understood to mean a rotary feed-through arrangement, in which two rotary feed-throughs  40 , sealed against each other and against at least one low-pressure area  11 , are present with their respective associated rotary feed-through areas  10 . The rotary feed-through areas  10  are also here at least periodically under high pressure P H  compared to the low pressure P N  available in the low-pressure area  11 . As a result, a fluid (such as air) can be conducted in a controlled manner from the fixed machine component  3  into the machine component  2 , rotatable therein, and conducted out again. By way of example, in addition flow directions  42  of the fluid in holes  14  connected to the rotary feed-through areas  10  into the machine components  2 ,  3  are represented by arrows. In the second rotatable machine component  2 , two holes  14  separate from one another are present, i.e. a separate channel is formed for each rotary feed-through, which is simply represented by a double arrow in the figure. The rotary seal arrangement components corresponding to  FIG. 1  are indicated with the same reference symbols in  FIG. 2 . 
         [0036]    Each of the rotary feed-through areas  10  is sealed off against the low-pressure area  11  by means of a seal pair according to  FIG. 1 . 
         [0037]    In addition to the illustration in  FIG. 1 , a lubricating seal  50  is provided in each case between the low-pressure area  11  and the seal pairs, though which penetration of lubricant from the low-pressure area  1  into the rotary feed-through areas  10  is prevented. The latter is particularly necessary if the pressure of the fluid in one of the rotary feed-through areas  10  is not sufficient to press the sealing rings  23 , which are associated with the corresponding seal pair, sufficiently strongly against the sealing area  7 . 
         [0038]    The lubricating seals  50  in each case have rubbery-elastic seal bodies  52 , in each case having a sealing lip  51 , and fixing structures  54  fixing the seal bodies  52 . The sealing lips  51  are pressed against the sealing area  7  by means of spring rings  55  made, for example, of steel. The angularly formed element  54   a,  which reaches up to the sealing area  7  between the fixing structures  54  in each case forms an additional, particularly tightly jammed sealing ring, e.g. made of PTFE. 
         [0039]    In  FIGS. 3   a  to  3   f , axial cross-sections of different embodiments of rotary seals of a rotary seal arrangement according to the invention are illustrated. The embodiments essentially correspond to the rotary seal according to  FIG. 1 . Therefore, only special details are concentrated on below. In the figures, the rotary arrangement seal components corresponding to  FIG. 1  are indicated with the same reference symbols. The abutment bodies  21  of the illustrated rotary seals in each case have a foot-like enlargement  21   a  on the housing structure side for the seal. The abutment body extends in the radial direction of the rotary seal  5  between the sealing ring  23  and the housing structure for the seal, and the abutment body  21  has an area which is adjacent to the sealing ring  23  on the high-pressure area side in the axial direction of the rotatably supported machine component  2 . The latter area stretches to different extents in the direction of the sealing edge. In this way, the edge of the sealing ring  23  facing radially away from the sealing area is arranged in a recess of the abutment body  21 . 
         [0040]    The abutment bodies  21  in each case have at least one pointed end  60  on the housing side for the seal. These ends  60  are in each case pressed against the housing structure for the seal in such a way that the abutment body  21  is elastically deformed and the sealing ring  23  is thereby pre-stressed. The latter is represented by the dashed outline of the ends  60 . The edge of the sealing ring  23  facing radially away from the sealing area is also, thereby, in each case elastically jammed in the recess in the abutment body  21 . In  FIG. 3   b , an edge  70  bridging a gap is formed as a result. The illustrated rotary seals also differ in the formation of the support elements  20 , the sealing rings  23  and the areas of the abutment bodies  21  lying in between. 
         [0041]    In  FIGS. 3   a  to  3   e , the support elements  20 , the sealing rings  23  and the areas of the abutment bodies  21  laying in between in each case have a cross-section which is at a concave angle to the high-pressure area. In the exemplary embodiments of  FIGS. 3   c  to  3   e , the area of the abutment body  21 , arranged between the support element  20  and the sealing ring  23 , is thereby conically widened in the direction of the sealing edge. In  FIG. 3   f , the cross-section of the support element  20 , the sealing ring  23  and the area of the abutment body  21  lying in between is, in contrast, not angled. 
         [0042]    The sealing ring  23  being pre-stressed radially in the direction of the second machine component  2  (not illustrated) in each case by an elastic restoring force of the abutment body  21  is common to all the illustrated embodiments. Due to the fact that in each case at least in one supporting area the support element  20  runs at an angle to the axial direction of the rotatably supported machine component (not illustrated), the abutment body  21  is compressed in this area between the support element  20  and the sealing ring by the said pre-stressing. As a result, the sealing ring  23  is in turn pushed away from the sealing area in the supporting area by the abutment body  21 . The abutment body  21  is thereby in each case arranged radially between the respective support element  20  and the associated sealing ring  23 . 
         [0043]    In  FIG. 4 , an embodiment of an abutment body  21  of a rotary seal arrangement according to the invention is illustrated in an axially directed plan view. The sealing ring side surface of the abutment body  21  is therefore shown. Although the abutment body can also have a level surface on the sealing ring side, in this exemplary embodiment the surface has projections  80  in the direction of the sealing ring, so that a gap also remains between the abutment body  21  and the sealing ring when the abutment body  21  is compressed. 
         [0044]      FIG. 5  shows an alternative embodiment of the invention described in  FIG. 2  whereby similar numbers are unaltered. 
         [0045]    Lubricating seals  50  are also fixed in holding element  130 . The seating of the holding element  130  is secured by a washer  100 , which in turn is fixed by means of a spring ring  90  engaging in respective grooves. 
         [0046]    The present invention provides a rotary sealing arrangement which with its use of the holding element  30  enables the entire sealing arrangement required to seal a high pressure area between relatively rotatable components to be mounted in position as a single cartridge-like component on simple mating surfaces on the two relatively rotatable components. This greatly simplifies production of the mating surfaces on the relatively rotatable components and ensures that no components of the sealing arrangement are left out when the sealing arrangement is mounted in its operating position. 
         [0047]    The invention is not restricted to the abovementioned specified exemplary embodiments. In fact, a number of alternatives are conceivable, which also make use of the features of the invention in a basically different implementation.