Abstract:
In a seal assembly ( 1 ) for sealing a high-pressure side (H) in relation to a low-pressure side (N) with at least one relief bore or relief channel ( 6 ) for pressure relief, a sealing ring ( 2 ) and at least one pre-stressing element ( 3 ) are arranged in a groove space ( 5 ) between two machine parts ( 4   a,    4   b ) that can be displaced towards one another in a translatory manner, in such a way that the pre-stressing element ( 3 ) tensions the sealing ring ( 2 ) with both a radial force component ( 210 ) and an axial force component ( 220 ), and the sealing ring ( 2 ) lies against the second machine part ( 4   b ) and the groove flank ( 51 ) on the low-pressure side by means of defined contact surfaces ( 20, 22 ).

Description:
[0001]    This application is a continuation of 12/227,211 filed Nov. 12, 2008 as the national stage of PCT/DE2007/000706 filed on Apr. 21, 2007 and also claims Paris Convention priority of DE 10 2006 023 157.0 filed on May 16, 2006, the entire enclosures of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention concerns a sealing arrangement between two machine parts that can be moved in a translatory fashion with respect to each other, for sealing a high-pressure side with respect to a low-pressure side, consisting of a viscoplastic sealing ring and at least one rubber-elastic pretensioning element, wherein the sealing ring comprises one or several relief bore(s) or relief channel(s) having openings on the low-pressure side, which face the low-pressure side in the pressurized state of the sealing arrangement, and also openings on the high-pressure side. 
         [0003]    In sealing arrangements between machine parts that can be moved with respect to each other, the medium pressure in the spaces between the individual sealing elements, e.g. a primary and a secondary seal, may build up during operation, i.e. during a translatory motion of the two machine parts with respect to each other. This is caused by unfavorable speed ratios of the machine parts, e.g. of a piston rod relative to the installation space. An increased pressure e.g. on the low-pressure side can damage the machine parts or even destroy them, and thereby cause failure of the entire sealing arrangement. 
         [0004]    A pressure relief sealing arrangement comprises relief bores or channels, which are used for pressure relief comparable to a check valve. A sealing arrangement of this type is disclosed e.g. in DE 101 17 662 C1. In a basic pressure position, in which the sealing arrangement seals a high-pressure side with respect to a low-pressure side, the relief bores or channels provided on a sealing ring are closed, and in a pressure relief position, in other words, in the inverted pressure position, they are released, i.e. opened, such that a pressure that prevails in a space on the low-pressure side can be discharged towards the high-pressure side when an overpressure has been reached. Conventional pressure relief sealing arrangements do not guarantee, for all operating states, that the relief bores or channels are opened only when the pressure relief position has been reached for arbitrary pressure ratios in the system and/or speed ratios of the machine parts. Premature opening or release of the relief bores or channels negates the pressure relief function of the sealing arrangement and a pressurized medium can flow from the high-pressure side to the low-pressure side. 
         [0005]    It is the underlying purpose of the invention to ensure that the relief bores or relief channels of a pressure relief sealing arrangement open exclusively in a pressure relief position. 
       SUMMARY OF THE INVENTION 
       [0006]    This object is achieved in accordance with the invention by a sealing arrangement between two machine parts that can be moved in a translatory fashion, for sealing a high-pressure side with respect to a low-pressure side, consisting of a viscoplastic sealing ring and at least one rubber-elastic pretensioning element, wherein one or several relief bore(s) or relief channel(s) is/are provided in the sealing ring, which have openings on the low-pressure side, which face the low pressure side in the pressurized state of the sealing arrangement, and also openings on the high-pressure side, wherein, when the sealing arrangement is installed in a groove space, the opening(s) on the low-pressure side is/are closed by a groove flank on the low-pressure side of the groove space, which is associated with the low-pressure side in the pressurized state, or by the at least one pretensioning element, or limited by the groove flank on the low-pressure side, a groove bottom of the groove space and the pretensioning element, and in the installed pressure-free state, the sealing ring abuts the groove flank on the low pressure side with an axially oriented force component. 
         [0007]    The force component with axial orientation, i.e. parallel to the direction of the translatory motion of the two machine parts, urges or presses the sealing ring towards the groove flank on the low pressure side to thereby prevent connection between the low-pressure side or a space following the sealing ring on the low-pressure side, and the opening on the low-pressure side of the relief bore or the relief channel. The connection between the space on the low-pressure side and the opening on the low-pressure side is permitted only when there is a corresponding counter force to the axial force component, i.e. in the pressure relief position. 
         [0008]    In a preferred embodiment of the inventive sealing arrangement, the sealing ring comprises one or several partial surfaces that are oriented at an inclination with respect to the groove bottom on its outer surface facing the groove bottom. 
         [0009]    This embodiment is advantageous in that the axial force component is realized by the geometrical design of the outer surface of the sealing ring. The pretensioning element that tensions the sealing ring abuts an inclined partial surface of the sealing ring, thereby urging or pretensioning the sealing ring in an axial direction towards the low-pressure side. The axial force component can be adjusted, i.e. increased or reduced, in accordance with the requirements through suitable profiles of the sealing ring and/or the pretensioning element, in particular, through selection of the inclination of the contact surface between the sealing ring and the pretensioning element. 
         [0010]    In a further preferred embodiment, the pretensioning element abuts the outer surface and at least one high-pressure sided side flank of the sealing ring, which is formed on the high-pressure side. 
         [0011]    The pretensioning element is partially positioned between the side flank of the sealing ring on the high-pressure side and the groove flank on the high-pressure side. The axial overdimension of the pretensioning element with respect to the groove or the groove space generates an axial pressure on the sealing ring and thereby the axial force component for abutment of the sealing ring on the groove flank on the low-pressure side. The pretensioning element is preferably designed as a molded part. 
         [0012]    The sealing arrangement is further characterized by two pretensioning elements. 
         [0013]    Each of the two pretensioning elements that preferably abut a partial surface of the sealing ring, which is oriented parallel to the groove bottom, and a partial surface thereof, which is oriented at an inclination with respect to the groove bottom, generates one of the radial component and the axial component of the force transmitted to the sealing ring by the pretensioning elements. This is advantageous in that standardized pretensioning elements can be used for the inventive sealing arrangement, e.g. O-rings, 4-sided rings, quad rings® (registered trademark of the company Quadion Corporation, Minneapolis, US), which minimizes, in particular, the production costs of the sealing arrangement. 
         [0014]    In another preferred embodiment of the inventive sealing arrangement, in the installed state, the sealing ring abuts the groove flank on the low-pressure side and a groove flank of the groove space on the high-pressure side. 
         [0015]    In this embodiment, the axial force component is provided by the sealing ring itself, which abuts both sides of the groove flank of the groove space on the low-pressure side and the high-pressure side, and is compressed or squeezed in this position. Viewed in the axial direction, the sealing ring is overdimensioned with respect to the groove space. 
         [0016]    The sealing ring also has an additional sealing edge on a side flank on the low-pressure side. 
         [0017]    The design of the additional sealing edge prevents pressure medium, e.g. hydraulic liquid or lubricating oil, from entering into a partial space of the groove space, in which the relief bores or channels terminate on the low-pressure side. 
         [0018]    The first machine part is moreover preferably a cylinder, and the second machine part is a piston rod of a piston guided in the cylinder. 
         [0019]    The inventive pressure relief sealing arrangement is particularly suited for use in a hydraulic system. 
         [0020]    A pressure-free state as defined in accordance with the invention is a state in which the sealing arrangement is installed in a groove space and the pressurized medium does not yet load the sealing arrangement. A pressurized state as defined in accordance with the invention is a state in which the sealing arrangement that is installed in the groove space is loaded with the pressurized medium. 
         [0021]    Further advantages and features of the invention can be extracted from the description and the figures of the drawing. The inventive sealing arrangement is shown in embodiments in  FIGS. 1 through 8 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0022]      FIGS. 1 through 8  each show one exemplary sealing arrangement between two machine parts which can be moved in a translatory fashion with respect to each other. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]      FIG. 1  shows a section through a sealing arrangement  1 , in which a sealing ring  2  and a pretensioning element  3  are disposed between a first machine part  4   a  and a second machine part  4   b.  The second machine part  4   b,  in the present case a piston, is guided along a translatory direction  100  relative to the first machine part  4   a  that is designed as a cylinder, and can be moved in the translatory direction  100 . The two machine parts  4   a  and  4   b  define a groove space  5  having a box-shaped cross-section, with a groove flank  51  on the low-pressure side, an opposite groove flank  52  on the high-pressure side, and a groove bottom  53 . For sealing a low pressure side N and a high-pressure side H, the sealing ring  2  and the pretensioning element  3  are inserted, pressed, deformed and tensioned in the groove space  5  in such a fashion that the pretensioning element  3  exerts a force on the sealing ring  2  along direction  200 . The overall force  200  has a radial force component  210  that causes tight abutment of the sealing ring  2  on the second machine part  4   b  via a sealing edge  20 , and an axial force component  220  that causes tight abutment of the sealing ring  2  on the groove flank  51  on the low-pressure side. The outer surface  21  of the sealing ring  2  is slanted with respect to the groove bottom  53 . This slant generates the axial force component  220 . Due to this axial force component  220  that extends parallel to the translatory direction  100 , the front side flank  22  of the sealing ring  2 , which is formed as a front side, abuts the groove flank  51  on the low-pressure side. Accordingly, the slanted outer surface  21  of the sealing ring  2  defines an inclined partial surface  21  on which the pretensioning element  3  exerts a force. The partial surface  21  extends from the high-pressure sided end H to the low-pressure sided end N of the sealing ring  2 . 
         [0024]    This abutment prevents connection between the low-pressure side N or a space bordering the sealing arrangement  1  at that location, and a relief channel  6 ′ provided in the sealing ring  2 . This connection is released only upon exertion of a corresponding axial counter force and release of contact between the side flank  22  on the high-pressure side and the groove flank  51  on the low-pressure side. An opening  61  of the relief bore  6  on the low-pressure side is closed by the pretensioning element  3  in the illustrated installed state both in the pressure-less state and in a basic pressure position, and is opened only when a pressure relief position has been reached through corresponding displacement and/or deformation of the pretensioning element  3 . An opening  62  of the relief channel  6 ′ on the high-pressure side is provided on a side surface of the sealing ring  2  facing the second machine part  4   b,  which is open in any pressure position. 
         [0025]    As seen in  FIG. 1 , the force  200  exerted by the pretensioning element  3  on the sealing ring  2  has a magnitude and a direction and is accordingly a vector quantity, illustrated by arrow  200 . The arrows  220  and  210  represent the vector decomposition of the force  200  into axial and radial components respectively, i.e. the vector force  200  is the vector sum of its axial  220  and radial  210  components. As indicated by the lengths of arrows  220  and  210 , the magnitude of the radial component  210  exceeds that of the axial component  220 . 
         [0026]      FIG. 2  shows a further embodiment of the sealing arrangement  1 . The sealing ring  2  has a relief bore  6  that extends from the outer surface  21  to a side surface facing the second machine part  4   b,  and a first  23  and a second  24  partial surface on its outer surface  21 . The first partial surface  23  is straight, in other words parallel to the groove bottom  53  of the groove space  5 , and the second partial surface  24  that borders the first partial surface  23  towards the high-pressure side H is inclined with respect to the groove bottom  53 . The sealing ring  2  and the pretensioning element  3  are clamped in the groove space  5  between the first and the second machine part  4   a  and  4   b,  thereby producing a tensioning force that the pretensioning element  3  exerts on the sealing ring  2 . In the illustrated embodiment, the overall tensioning force consists of a first partial force  200 ′ that acts on the first partial surface  23 , and a second partial force  200  that acts on the second partial surface  24 . The axial force component  220  that is required for abutment of the sealing ring  2  on the groove flank  51  on the low-pressure side is exclusively provided by the second force  200 . An inner surface facing the second machine part  4   b  may be slanted, as illustrated, but may also have a symmetrical profile. 
         [0027]      FIG. 3  shows a further embodiment of the sealing arrangement  1 . A pretensioning element  3  that is designed as a quad ring® is disposed in the groove space  5  together with the sealing ring  2  and exerts a force on the latter. The pretensioning element  3  abuts both the groove flank  51  on the low-pressure side and the groove flank  52  on the high-pressure side. A force  200  of the pretensioning element  3  that abuts a slanted second partial surface  24  of the sealing ring  2  produces the axial force component  220 . The opening  61  of the relief bore  6  on the low-pressure side is closed by the pretensioning element  3 . After an interruption, the relief bore  6  continues to extend towards the high-pressure side H in the form of a terminating bore  6 ″, at the end of which the opening  62  on the high-pressure side is provided. 
         [0028]      FIG. 4  shows a sealing arrangement  1  of a sealing ring  2 , a pretensioning element  3  and a further pretensioning element  3 ′. The groove space  5  between the two machine parts  4   a  and  4   b  has a two-step groove bottom  53 . The pretensioning element  3  that closes the relief bore  6  that is formed in the sealing ring  2 , is supported on a flat first partial surface  23  of the sealing ring  2 , which extends parallel to the groove bottom  53 , and clamps it in the radial direction  210 ′. The further pretensioning element  3 ′ abuts an inclined slanted second partial surface  24  of the outer surface  21  and exerts a force on the sealing ring  2 , which acts in a radial direction  210  and in an axial direction  220 . In this embodiment, the inventive sealing arrangement  1  is realized with a sealing ring  2  having a particular profile and with two pretensioning elements  3  and  3 ′ selected as standard elements. The sealing ring  2  has an additional bore  27  via which the pretensioning element  3  can be activated. 
         [0029]      FIG. 5  shows a further embodiment of the sealing arrangement  1 . The pretensioning element  3  that tensions the sealing ring  2  in a radial direction and exerts a force on the sealing ring with an axial force component  220 , is designed as a molded part and abuts the outer surface  21  and a rear side flank  26  of the sealing ring  2 , which faces the high-pressure side H. The pretensioning element  3  that is clamped between the two groove flanks  51  and  52  abuts the rear side flank  26  of the sealing ring  2 , thereby adjusting the axial force component  220  and ensuring abutment of the sealing ring  2  on the groove flank  51  on the low-pressure side. 
         [0030]    The embodiment of the sealing arrangement  1  shown in  FIG. 6  is characterized by a relief channel  6 ′ which extends along the outer surface  21  and the rear side flank  26  of the sealing ring  2  and is not closed by the pretensioning element  3  in the illustrated pressure-free state, but terminates in a partial space  54  of the groove space  5  on the low-pressure side. The partial space  54  is limited by the groove flank  51  on the low-pressure side, the groove bottom  53  and the pretensioning element  3 . The sealing ring  2  abuts the groove flank  51  on the low-pressure side via an additional sealing edge  52 , limits the partial space  54  by this additional sealing edge  25 , and prevents connection between the partial space  54  as well as the relief bore  6  that terminates therein, and a space that joins the low-pressure side N or the low-pressure side N. The sealing ring  2  seals in an axial direction  220  via the additional sealing edge  25  and in a radial direction  210  via the sealing edges  20  and  20 ′ by means of the force  200  exerted on the sealing ring by the pretensioning element  3  that abuts its outer surface  21  that is oriented at an inclination. 
         [0031]      FIG. 7  shows an embodiment of the sealing arrangement  1 , in which the force required for axial abutment is provided through the sealing ring  2  itself or through its position in the groove space  5 . The sealing ring  2  abuts the groove flank  51  on the low-pressure side and the groove flank  52  on the high-pressure side. In other words, it is clamped between the two groove flanks  51  and  52 . An additional groove  27  is provided on the rear side flank  26 , through which the high-pressure side H is connected to a further partial space  54 ′ located behind the pretensioning element  3 . The sealing ring  2 , shown in cross-section, has further, preferably equally spaced, additional grooves along its periphery. The sealing ring  2  has a straight first partial surface  23  on which the pretensioning element  3  abuts or on which it is supported, and a slanted second partial surface  24 . 
         [0032]    In the embodiment of the sealing arrangement  1  shown in  FIG. 8 , the sealing ring  2  abuts both groove flanks  51  and  52 , wherein the rear side flank  26  on the high-pressure side has an extension in which the additional groove  27  is provided. 
         [0033]    Further embodiments of the invention are feasible, which comprise one or several pretensioning element(s) in box-shaped stepped installation spaces, such as groove spaces, between machine parts, which can be moved in a translatory fashion with respect to each other, such as a piston rod or a piston and a cylinder. It is moreover also feasible to provide the full length or at least a partial length of the relief bore or the relief channel in the machine part that comprises the groove space, in particular, in the groove flanks and the groove bottom. 
         [0034]    In a sealing arrangement  1  for sealing a high-pressure side H with respect to a low-pressure side N, comprising at least one relief bore or a relief channel  6  for pressure relief, a sealing ring  2  and at least one pretensioning element  3  are disposed in a groove space  5  between two machine parts  4   a,    4   b  which can be moved in a translatory fashion with respect to each other, such that the pretensioning element  3  tensions the sealing ring  2  both with a radial force component  210  and with an axial force component  220 , and the sealing ring  2  abuts the second machine part  4   b  and the groove flank  51  on the low-pressure side via defined contact surfaces  20 ,  22 .