Abstract:
A shock absorber with a shock absorber body having a cylinder. A piston is moveably guided in a receiving space of the cylinder. When the piston is moved, an air pressure generated in the receiving space exerts a braking force that acts on the piston. For air pressure reduction, the receiving space has at least one opening that produces an air-carrying connection between the receiving space and the environment. The shock absorber body has a simple design if the piston or the cylinder contains a receptacle into which an insert piece is inserted in a frictionally engaging fashion and if the opening is positioned between the insert piece and the wall of the receptacle that is touched by the insert piece.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a shock absorber with a shock absorber body having a cylinder, a piston guided in a movable fashion in a receiving space of the cylinder, when the piston is moved an air pressure generated in the receiving space exerts a braking force that acts on the piston, and for air pressure reduction, the receiving space has at least one opening that produces an air-carrying connection between the receiving space and the environment. 
   2. Discussion of Related Art 
   A shock absorber is taught by German Patent Reference DE 20 107 426 U1, and uses a shock absorber body equipped with a cylinder. The cylinder encompasses a receiving space in which a piston is guided in a movable fashion. Extending from the receiving space of the cylinder, a bore leads into the piston bottom. The bore is connected to a cross bore. 
   This produces an air-carrying connection between the receiving space and the environment. A spring and a ball are inserted into the bore to produce a check valve. In order to secure the ball in captive fashion, the bore is tapped with an internal thread into which a screw is tightened. The screw has a sealing seat against which the ball rests in a sealing fashion. Downstream from the sealing seat, the screw contains a through bore. When the piston is traveling inward, an excess pressure is generated in the receiving space. A ball thus moves in the bore until air can escape into the environment through the cross bore. Once the pressure difference is balanced, then the ball closes the air-carrying connection again. 
   This known shock absorber is encumbered by a complex design with many parts. In addition, it does not achieve a satisfactory damping action. As soon as the ball lifts away from the sealing seat in the presence of an excess pressure, an abrupt pressure drop occurs. With shock absorbers used in furniture construction, however, a delayed pressure decrease is required for an optimum shock absorbing action. Due to production tolerances or temperature fluctuations, it is not possible to uniformly determine the lift-off time of the ball. 
   SUMMARY OF THE INVENTION 
   One object of this invention is to provide a shock absorber that has a uniformly favorable damping characteristic while having a simple design. 
   This object is attained according to this invention, because the piston or the cylinder contains a receptacle into which an insert piece is inserted in a frictionally engaging fashion. An opening between the insert piece and the wall of the receptacle is touched by the insert piece. 
   With this embodiment, a continuous pressure decrease requires a very small opening cross-section. This can be simply and reproducibly achieved by the embodiment disclosed according to this invention. The frictionally engaged connection between the insert piece and the receptacle assures a good seal between the insert piece and the receptacle everywhere, except for the opening. This seal is maintained in spite of temperature fluctuations and different expansions of the insert piece and receptacle. This makes the shock absorber very operationally reliable. Also, the shock absorber is easy to produce because forming the opening requires only that the insert body be placed into or against the receptacle. 
   According to one embodiment of this invention, the receptacle is a bore into which the insert piece embodied in the form of a cylinder or ball is inserted. The cylinder and the ball can be inexpensive, true-to-size, mass-produced parts. 
   If the receptacle is in the form of a bore and is adjoined by a cross sectionally reduced passage, which forms a shoulder, and the shoulder forms a stop for the insert piece, then this limits the inserting motion of the insert piece into the receptacle in a simple fashion. This also permits a precisely fit positioning of the insert piece. 
   If a material pairing is selected in which the material of the insert piece and the material of the receptacle are of different hardnesses, then the softer component rests against the harder component in a sealed fashion, producing a definite seal. 
   In particular, it is possible for the insert piece to be of metal and for the material comprising the receptacle to be a plastic, preferably a thermoplastic. 
   Production is facilitated if the shock absorber is embodied so that the opening is formed by a groove, which leads into the material of the receptacle, extends in a direction of the central longitudinal axis of the receptacle, and has a region oriented toward the receptacle that is covered by the insert piece. 
   In particular, the component forming the receptacle can also be produced as a true-to-size injection-molded component. 
   In one embodiment, the piston has a bellows section operationally connected to the cylinder as a function of the pressure ratios within the receiving space. The bellows section helps boost the braking force and is inflated when there is a pressure difference between the receiving space and the environment, an excess pressure in the receiving space. The bellows section then rests against the inner wall of the cylinder, thus increasing the friction of the piston. Thus, a particularly simple construction is achieved if the piston and the bellows section are integrally joined to each other because this reduces the sealing complexity. 
   The structural complexity can be further reduced if the piston rod is integrally formed onto the piston. 
   In one embodiment of this invention, the piston rod is associated with or has a supporting body and the supporting body has a stop surface situated outside the shock absorber body and the supporting body is supported against the piston via a shoulder. 
   Depending on the design, the supporting body can brace the piston rod. At the same time, the supporting body can also absorb the impact force, for example of a closing door or cover, and transmits at least part of it directly to the piston. 
   This is particularly advantageous if in addition, the piston and the bellows section are of soft elastic material. Then, the impact force impinges on the piston in a spring-elastic fashion and a portion of the impact force is canceled out by hysteresis. 
   The soft elastic embodiment of the piston and bellows section also makes it possible to achieve a material pairing with the cylinder that enables powerful damping by high coefficients of friction. If the piston rod is of a soft elastic material, then for strength reasons, the piston rod is braced by a casing part. 
   One alternative embodiment of this invention can be for the end of the piston rod oriented away from the piston to form an impact piece made of soft elastic material. The impact piece can absorb the impact force and immediately damp a portion of the impact. 
   If the bellows section has a cylindrical part that is kept spaced apart from the inner wall of the cylinder and the region encompassed by the cylindrical part is associated with a pressure chamber of the cylinder, then when subjected to pressure, the bellows section can rest against the inner wall of the cylinder on all sides, thus generating a uniform, powerful braking force. 
   The functionality of the bellows section can be further increased if the cylindrical part of the bellows section forms a spring receptacle that at least partially accommodates a spring and the spring supports the piston in relation to the cylinder, to counteract an inserting motion of the piston into the cylinder. 
   The construction is further simplified if the bellows section supports a sealing element formed onto it, which produces a seal between a pressure chamber and a negative pressure chamber of the cylinder. 
   The braking action of the shock absorber can be further increased if both the negative pressure chamber and the pressure chamber communicate with the environment in an air-carrying fashion by at least one opening. 
   This is possible particularly if the openings or the throttle elements associated with the openings are embodied so that they achieve a metered flow of air. 
   For example, a volumetric flow of air can be used to achieve a controlled pressure decrease and simultaneously, a favorable damping if at least one of the openings has a diameter D &lt;0.2 mm, preferably &lt;0.1 mm. In particular, diameters &lt;0.1 mm achieve a favorable throttling action for use in furniture construction. 
   This damping can be achieved in a particularly satisfactory fashion if, in the region oriented toward the cavity, the ratio of the cross-sectional area of the piston to the opening cross section of the opening is greater than 4000/1. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This invention is explained in view of an exemplary embodiment shown in the drawings, wherein: 
       FIG. 1  is a side view of a shock absorber; 
       FIG. 2  is a section taken through the shock absorber, along line II-II shown in  FIG. 1 ; 
       FIG. 3  is a view of a detail that is labeled III in  FIG. 2 ; and 
       FIG. 4  is a sectional view taken along the cutting line labeled IV-IV in  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  show a shock absorber with an elongated shock absorber body  10 . The shock absorber body  10  forms a cylinder  11 . The cylinder  11  encompasses a receiving space  11 . 1  in which a piston  43  of a sliding element  40  is contained in a linearly moving fashion. 
   A spring guide  14  in the form of a hollow cylinder, which is integrally formed onto a bottom  13  of the shock absorber body  10 , protrudes into the receiving space  11 . 1 . In the region of or near an end oriented away from the bottom  13 , the spring guide  14  has an opening  16  in the form of a bore that will be explained in greater detail below in view of  FIG. 3 . The opening  16  provides a spatial connection between the receiving space  11 . 1  and an air conduit  15  encompassed by the spring guide. The diameter of the opening is &lt;0.1 mm in order to permit a metered exchange of air between the receiving space  11 . 1  and the air conduit  15 . In lieu of a bore, any other form of opening cross section can also be provided. Favorable damping properties are achieved if, in the end region oriented toward the receiving space  11 . 1 , the ratio of the cross-sectional area of the piston  43  to the opening cross section of the opening is 4000/1. 
   The air conduit  15  extends in a cavity  17  formed by a cylindrical end section of the shock absorber body  10 . The shock absorber body  10  is produced in the form of an injection-molded component. For demolding reasons, the inner wall  18  of the cylinder  11  is embodied with a slight opening cone so that the receiving space  11 . 1  expands slightly toward the region of the inlet opening oriented away from the bottom  13 . 
   As mentioned, a sliding element  40  is guided in the receiving space  11 . 1 . The sliding element  40  is one piece, including a piston rod  42 , the piston  43 , and a bellows section  44 . The sliding element  40  can be embodied in the form of an injection-molded component and is of a soft elastic material, for example a TPM material. 
   The piston rod  42  is formed onto the end of the piston  43  oriented away from the bellows section  44 . It is cylindrical in cross section and protrudes out from the receiving space  11 . 1  of the shock absorber body  10 . At the end, it has an impact piece  41  embodied in the form of an end cap. 
   In an alternative embodiment, it is possible to eliminate the piston rod  42  formed onto the piston  43 . The piston rod  42  is then solely formed by the supporting body  30 . There does not necessarily have to be a mechanical connection between the piston  43  and the supporting body  30  in this embodiment. However, it is then advantageous to center these two components. 
   The piston rod  42  is encompassed by a supporting body  30 . Thus, the supporting body  30  has a hollow, cylindrical receptacle with a cross section adapted to the outer cross section of the piston rod  42  and is comprised of a casing part  31 . The material of the supporting body  30  is flexurally resistant so as to brace the piston rod  42 . As shown in  FIG. 1 , the supporting body  30  is supported against the piston  43  with a radially thickened shoulder  32 . The shoulder  32  can be used to guide the piston  43  and can be thickened radially so that it forms a guide along with the inner wall  18  of the receiving space  11 . 1 . Depending on the design of the shoulder  32 , it is possible to minimize the risk of the piston  43  tilting. 
   The bellows section  44  protrudes into the receiving space  11 . 1  and is embodied in the form of a hollow cylinder, preferably with uniform wall thickness, so that it has uniform work piece properties over its entire circumference, in particular a uniform expansion behavior. The wall can also be embodied as spherical or with a changing cross section in order to achieve a varying force. For example, it is possible to use a cross section that has a reduced cross section in the middle region. At its free, open end, the bellows section  44  has a circumferential sealing element  45  with a sealing lip that rests against the inner wall  18  of the receiving space  11 . 1  in a sealed fashion. The sealing element  45  can be embodied so that it produces a seal over the entire sliding range and, due to its material elasticity, compensates for the opening cone of the receiving space  11 . 1 . 
   The bellows section  44  encompasses a spring receptacle  46  that contains a spring  50 . The spring receptacle  46  is dimensioned so that it prevents the spring  50  from buckling. The spring  50  is supported with one end against the piston  43 . The other end of the spring  50  rests against the bottom  13 . The spring  50  is placed over the spring guide  14  that likewise prevents the spring  50  from buckling. The spring receptacle  46  is embodied so that the spring guide  14  and the spring  50  are accommodated in it upon insertion of the sliding element  40  and do not hinder the piston movement. 
   A stop element  20  fixes the sliding element  40  in the retracted end position shown in  FIG. 1 . The stop element  20  is embodied in the form of a ring and has a circumferential, bead-shaped detent projection  21  on its outer circumference. The stop element  20  has a hollow cylindrical passage  22  through which the casing part  31  of the supporting body  30  is guided. The outer diameter of the casing part  31  is adapted to the inner diameter of the passage so that a stable, linear guidance for the supporting body  30  is achieved. The material pairing between the supporting body  30  and the stop element  20  is selected so that a smooth support is achieved. 
   During assembly, the stop element  20  can be easily inserted into the receiving space  11 . 1  via a flared insertion opening  19 . 3  of the shock absorber body  10 . The insertion movement is limited by a shoulder  18 . 1  of the shock absorber body  10 . In its installed position, the detent projection  21  of the stop element  20  engages in detent fashion in the detent recess  19 . 2 . 
   In the end position shown in  FIG. 1 , the stop element  20  supports the supporting body  30  at its shoulder  32  and thus supports the piston  43  in opposition to the prestressing force of the spring  50 . 
     FIG. 3  shows an enlarged detail of the end of the spring guide  14  oriented away from the bottom  13 . As shown in the drawing, a bore-shaped receptacle  16 . 3  leads into the free end of the spring guide  14  and the receptacle  16 . 3  transitions into a similarly bore-shaped passage  16 . 4 . The passage  16 . 4  is concentric to the receptacle  16 . 3  but has a smaller diameter, thus forming a shoulder  16 . 5 . 
   The receptacle  16 . 3  has a lateral groove let into it, which extends in a direction of the central longitudinal axis of the receptacle  16 . 3 . The groove forms the opening  16 , as shown in  FIG. 4 . The groove extends into the region of the passage  16 . 4  through opening  16 . 1  so that an air-carrying connection is produced between the receiving space  11 . 1  and the environment. The open side region of the groove is covered by an insert piece  16 . 2 , thus producing the opening  16  shown in  FIG. 4 . The insert piece  16 . 2  in this embodiment is of a metal ball press-fifed into the receptacle  16 . 3  so that it is secured in the receptacle  16 . 3  in a frictionally engaging fashion. 
   The frictionally engaging connection also causes a deformation of the material of the receptacle  16 . 3  so that a seal is produced between the insert piece  16 . 2  and the receptacle  16 . 3 . 
   A brief description of the function of the shock absorber follows, which is used, for example, in a piece of furniture with a hinge-mounted cover. Usually, the body of the piece of furniture has a receiving bore into which the cylindrical outer contour of the shock absorber body  10  can be inserted. When inserted, the flange  12  of the shock absorber body  10  comes to rest against the body of the piece of furniture in the region of the receiving bore. 
   The closing cover first comes into contact with the impact piece  41  of the piston rod  42 . The mechanical impact noise of the cover is compensated for, by the elastic material properties of the impact by  41 . The impact body  41  is deformed as a function of the impact energy of the cover. With a powerful impact, the impact body  41  is deformed completely into the casing part  31  and the cover comes into contact with the free end of the casing part  31 . The piston rod  42  and the casing part  31  transmit the force to the piston  43 . The annular contact of the shoulder  32  against the piston  43  assures a uniform introduction of force. Depending on the intensity of the impact energy, a portion of the energy can be damped by elastic deformation of the piston  43 . 
   The piston  43  is slid into the receiving space  11 . 1 . As a result, a pressure builds up in the receiving space  11 . 1 , assisted by the sealing action of the seal  45 . The pressure simultaneously increases via the opening  16 . 
   If the pressure increase occurs in a shorter time span, then the pressure decrease does not occur to the same degree to which it occurs via the opening  16 . An excess pressure with a damping action is thus generated in the receiving space  11 . 1  This excess pressure acts on the bellows section  44 . Because atmospheric pressure prevails in the intermediate space between the inner wall  18  and the outer surface of the bellows section  44 , a pressure difference arises. This causes the bellows section  44  to inflate so that it rests against the inner wall  18  and reinforces the damping action due to its sliding friction. The soft elastic material property of the bellows section  44  generates a correspondingly large amount of friction. If the pressure difference decreases, then the bellows section  44  returns to its initial position. 
   After the force acting on the piston rod  42  is released, the piston  43  returns to its initial position as shown in  FIG. 1 , assisted by the spring  50 . This movement draws air from the environment into the receiving space  11 . 1  via the opening  16 . 
   The opening is dimensioned so that the following properties of the shock absorber are achieved: controlled, slow pressure decrease to achieve a favorable damping action; and rapid pressure compensation in the return motion of the piston  43 . 
   These properties can be achieved with the ratios described in this specification and in the claims. 
   German Patent Reference 10 2005 020 476.7-12, the priority document corresponding to this invention, and its teachings are incorporated, by reference, into this specification.