Abstract:
A stop damper including a damper member with a cylinder. A piston is moveably guided inside a receiving space of the cylinder. The cylinder has a sliding surface against which the piston rests with a sealing element. A braking force that acts upon the piston can be applied using the air pressure generated in the receiving space because the piston is displaced, the receiving space being connected to the environment via an air-conducting connection to reduce the air pressure. In order to improve the braking effect of the sliding element, the sealing element of the piston and the sliding surface of the cylinder can contact each other in at least some areas via a defined rubbing surface geometry, the peak-to-valley height of the sliding surface being &lt;1 μm and the peak-to-valley height of the facing surface of the sealing element being=4.5 μm in at least some areas.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates an end stop damper with a damper body having a cylinder, wherein a piston is displaceably guided inside a reception chamber of the cylinder, the cylinder has a sliding surface against which the piston rests with a sealing element, wherein as a result of the displacement of the piston, a braking force acting on the piston can be exerted by the air pressure formed in the reception chamber, and for releasing the air pressure, the reception chamber is connected with the surrounding space via an air guidance connection. 
         [0003]    2. Discussion of Related Art 
         [0004]    An end stop damper is known from German Patent Reference DE 103 13 659 B3. The end stop damper has a cylinder, in which a piston is guided in a linearly displaceable manner. In this case, the piston is sealingly conducted on the interior wall of the cylinder, so that two pressure chambers are formed inside the cylinder. 
         [0005]    In the course of retracting the piston, air is compressed in an overpressure chamber. At the same time, a pressure which is less than the pressure in the overpressure chamber is generated in an underpressure chamber. 
         [0006]    Overflow channels of reduced cross section are provided for permitting a continuous pressure equalization between these two pressure chambers. 
         [0007]    The air from the overpressure chamber flows into the underpressure chamber through the overflow channels. 
         [0008]    The piston has a bellows section for increasing the braking force, which is expanded by a pressure difference existing between the overpressure chamber and the underpressure chamber. In the process, it comes to rest against the interior wall of the cylinder and thus increases the friction of the piston. The bellows section is made in the form of a sleeve made of a flexible material. The piston is designed in two parts for fixing the bellows section in place, and the bellows section is clamped between the piston parts. 
         [0009]    This known end stop damper requires a large parts outlay. 
       SUMMARY OF THE INVENTION 
       [0010]    It is one object of this invention to provide an end stop damper of the type mentioned above but which has an improved braking effect. 
         [0011]    This object of this invention is attained with a sealing element of the piston and the sliding surface of the cylinder that touch at least over a friction surface of a defined geometry, wherein the peak-to-valley height of the sliding surface Ra &lt;1 μm and the peak-to-valley height of the facing surface of the sealing element is ≧4.5 μm, at least in parts. 
         [0012]    An ideal damping behavior occurs with this pairing of the friction surfaces. In this case friction, both at high, as well as low retraction speed of the piston, is always such that the retraction movement is not hindered by any impermissibly large adhesive friction portions. 
         [0013]    However, the air removal from the reception chamber is optimized as a result of the pairing of the friction surfaces. A clearly higher peak-to-valley height would lead to a strong air removal between the sealing element and the sliding surface, which results in a clear reduction of the damping effect. 
         [0014]    This object of this invention is achieved with a surface peak-to-valley height of the sealing element and/or of the sliding surface which is created by a periodic structure, for example a groove structure. 
         [0015]    A good guidance of the sealing element during the displacement movement of the piston results with this design. The guidance can be optimized if the linear extension of the grooves of the groove structure are arranged transversely to the movement direction of the piston. In this case, the grooves of the groove structure can be cut into the sliding surface encircling it and transversely in relation to the movement direction of the piston, wherein the grooves extend at an angle of ≧0 and &lt;90° in relation to the movement direction of the piston. The angle advantageously lies in a range between ≧0 and &lt;5°. Such a structure can be simply created with lathe technology. The surface geometry then being created has characteristic peak-to-valley values which optimally affect the wear characteristics. During this, it is possible for the angle of attack to be selected so that over its entire circumference the annularly encircling sealing element only extends over a small number of grooves at the same time. In this way, only a groove cross section is available which, as a function of the elasticity of the sealing element, forms defined air flow-through gaps. 
         [0016]    In one embodiment of this invention, for the sealing element made of a flexible material, for example an elastomer, the surfaces of the sealing element have a peak-to-valley height Ra ≧0.4 μm in the area facing the sliding surface. The elastomeric material can offer good material properties for the intended sealing job. However, in the present application this material has a tendency to make too strong of a bond with the sliding surface of the piston at a peak-to-valley height of ≧0.4 μm. In the end, this leads to bad damping characteristics obtained. In this case, the sealing element is made of a thermoplastic elastomer. This material can be cost-effectively worked by an injection molding process. It is possible to reduce the costs for the material by employing a thermoplastic material on an olefin basis. 
         [0017]    An end stop damper in accordance with this invention has the sliding surface of the cylinder with a peak-to-valley height Ra ≧0.05 μm, at least in parts. 
         [0018]    In contrast to the sliding surface which is hard in comparison with the sealing element, this represents a peak-to-valley range in which the adhesion of the sealing element because of the influence of cohesion is effectively prevented. 
         [0019]    In one embodiment of this invention, the piston has a bellows section which, as a function of the pressure conditions in the reception chamber, is in an active connection with the cylinder. During the push-in movement of the piston into the cylinder, the bellows section expands as a result of the interior pressure existing in the cylinder and is placed against the sliding surface of the cylinder, and in the process aids the braking effect. 
         [0020]    The bellows section can have areas of different expansion capabilities, at least in the active area which is in contact with the cylinder. 
         [0021]    It has been determined that in the direction of the displacement movement the bellows section needs a certain amount of inherent stiffness, so that it is not impermissibly deformed by the braking forces occurring during the braking process. On the other hand, with a bellows section having a high degree of inherent stiffness, a large portion of energy is destroyed because of the expansion process. Because the bellows section has areas of differing expandability, the expansion of the bellows in the areas of great expandability can occur with reduced energy consumption. With this the built-up interior pressure in the reception chamber can be effectively converted into braking work. At the same time the areas of little expandability sufficiently stiffen the bellows section so that it is not impermissibly deformed as a result of the acting braking forces. 
         [0022]    In this case, such an end stop damper can be realized with less costly parts, if the areas of differing expandability are formed by portions of the bellows section having different wall thicknesses. The bellows section can then be embodied in one piece. 
         [0023]    It is possible to have large expansion sections in a simple manner if the bellows section has groove-shaped cutouts forming a change in the cross section of the bellows section. If the end stop damper is designed so that the cutouts extend in the direction of the displacement movement of the piston, or at an angle of less than 90° relative to the direction of the displacement movement, or spirally, the inherent stiffness of the bellows section in the direction of the displacement movement is maintained. 
         [0024]    In one embodiment of this invention, a displacement arrangement of the piston can be actuated as a function of the size of the air pressure, and the displacement arrangement brings a braking section into active connection with the cylinder for damping the displacement movement of the piston. 
         [0025]    Thus, the braking section is switched via the displacement arrangement as a function of the air pressure. Thus it is possible to increase the braking effect of the piston. 
         [0026]    Thus it is possible for the piston to be connected to a piston rod, and for the displacement arrangement to be actuated by the piston rod. In this case, the force introduced into the piston rod can be used for the actuation of the displacement arrangement. 
         [0027]    A simple and particularly effective braking arrangement results if, when the displacement arrangement is actuated, the cross sectional dimension of the braking section can be changed. In accordance with one embodiment of this invention, the bellows section and the piston can be connected to form one part with each other, and/or the piston rod can be formed as one part on the piston. With the single piece bellows section and the piston, the cost outlay for parts and assembly is reduced. 
         [0028]    The cost outlay for sealing, which is required with the prior art for sealing the bellows section in respect to the bellows, is reduced. 
         [0029]    With this invention it is possible to combine the components of the bellows section and the piston, which customarily have different materials and are employed for completely different purposes, into one unit. 
         [0030]    The structural cost outlay can be still further reduced if the piston rod is formed on the piston as one part. 
         [0031]    In one embodiment of this invention, a support body is assigned to the piston rod, or it has one so that the support body has an impact side arranged outside the damper body, and the support body is supported on the piston by a shoulder. 
         [0032]    Depending on the design, the piston rod can be stiffened by the support body. It is simultaneously possible to absorb the impact force of, for example, an impacting door or flap, by the support body, and it can be transferred at least partially to the piston. 
         [0033]    This is an advantage if the piston and the bellows section are made of a flexible material. In that case, the impact force acts on the piston in a spring-elastic manner, and thus a portion of the impact force is destroyed by hysteresis. 
         [0034]    With the flexible embodiment of the piston and bellows section it is possible for a pairing of material with the cylinder, which permits strong damping through large coefficients of friction. 
         [0035]    If the piston rod is also made of a flexible material, for reasons of sturdiness the piston rod is stiffened by a sheath element. 
         [0036]    In one embodiment of this invention, on a side facing away from the piston, the piston rod forms an impact element made of a flexible material. The impact force can be absorbed by the impact element and can be partially damped. 
         [0037]    If the bellows section has a cylinder-shaped portion, which is maintained at a distance from the interior wall of the cylinder, and the area surrounded by the cylinder-shaped portion is assigned to a pressure chamber of the cylinder, the bellows section, when charged with pressure, can be placed circumferentially against the interior wall of the cylinder and can there cause an even and extensive braking effect. 
         [0038]    It is possible to achieve an effective conversion of the pressure into a braking force in a useful way if the areas of different expansion capability are arranged in the cylinder-shaped portion of the bellows section. 
         [0039]    The functionality of the bellows section can be increased if the cylinder-shaped portion of the bellows section forms a spring receptacle, in which a spring is at least partially received, and the spring supports the piston on the cylinder in a direction opposite the push-in movement of the piston into the cylinder. 
         [0040]    A further structural simplification results if the sealing element formed on the bellows section seals a pressure chamber and an underpressure chamber of the cylinder against each other. 
         [0041]    If the areas of differing expansion capability extend as far as the formed-on sealing element, large-surfaced expansion areas result. 
         [0042]    The braking effect of the end stop damper can be increased if the underpressure chamber and/or the pressure chamber are in an air guidance connection with the surroundings by at least one opening. 
         [0043]    This is possible if the openings, or throttle members assigned to the openings, are designed so that a metered airflow is achieved. 
         [0044]    It is possible to achieve an air volume flow for a controlled pressure reduction, and simultaneously good damping, if at least one of the openings has a diameter D &lt;0.2 mm, preferably &lt;0.1 mm. Diameters &lt;0.1 mm display a good throttle effect for use in furniture construction. 
         [0045]    This damping can also be satisfactorily achieved if the ratio of the cross-sectional surface of the piston in the area facing the hollow space to the opening cross section of the opening is greater than 4,000/1. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0046]    This invention is explained in greater detail in view of an exemplary embodiment represented in the drawings, wherein: 
           [0047]      FIG. 1  shows an end stop damper in a lateral view and in section; 
           [0048]      FIG. 2  shows a detailed representation marked by “A” in  FIG. 1 ; 
           [0049]      FIG. 3  shows a further embodiment of an end stop damper in a lateral view and in section; 
           [0050]      FIG. 4  shows a detailed representation marked by “A” in  FIG. 3 ; 
           [0051]      FIG. 5  shows a detailed representation marked by “B” in  FIG. 3 ; 
           [0052]      FIG. 6  shows a component of the end stop damper including a piston rod and a piston, in a lateral view; 
           [0053]      FIG. 7  shows the component in accordance with  FIG. 5  in section taken along line VII-VII of  FIG. 6 ; 
           [0054]      FIG. 8  shows an alternative embodiment of the component in accordance with  FIGS. 6 and 7 ; 
           [0055]      FIG. 9  shows the component in accordance with  FIG. 8  taken along line VIII-VIII of  FIG. 8 ; 
           [0056]      FIG. 10  shows a combination of the component in accordance with  FIGS. 8 and 9 , having a sheath element, in a lateral view; 
           [0057]      FIG. 11  shows the representation in accordance with  FIG. 10  in section taken along line IX-IX of  FIG. 10 ; and 
           [0058]      FIG. 12  shows a portion of a cylinder of the end stop damper in accordance with  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0059]    An end stop damper with a linearly extending damper body  10  is represented in  FIG. 1 . The damper body  10  forms a cylinder  11 . The cylinder  11  surrounds a reception chamber  11 . 1 , in which a piston  43  of a sliding element  40  is maintained in a linearly displaceable manner. 
         [0060]    A spring guidance device  14  projects into the reception chamber  11 . 1  which is formed in one piece on a bottom  13  of the damper body  10  in the shape of a hollow cylinder. The spring guidance device  14  has an opening  16  in the form of a bore in the area of or near a side facing away from the bottom  13 . The opening  16  creates a spatial connection between the reception chamber  11 . 1  and an air guidance channel  15 , which is surrounded by the spring guidance device. Here, the diameter of the opening is &lt;0.1 mm in order to make a metered air exchange between the reception chamber  11 . 1  and the air guidance channel  15  possible. In place of the bore it is also possible to realize any arbitrary other opening cross section. 
         [0061]    Good damping results are achieved if the cross-sectional surface of the piston  43  in an end area facing the reception chamber  11 . 1  has a ratio of 4,000/1 in respect to the opening cross section of the opening. 
         [0062]    The air guidance channel  15  terminates in a hollow space  17  formed by a cylinder-shaped end section of the damper body  10 . The damper body  10  is made as an injection-molded part. The interior surface of the cylinder  11  is embodied as a sliding surface  18 . For the purpose of taking it out of the mold, it has slight opening cone, so that the reception chamber  11 . 1  slightly widens toward the area of the inlet opening located opposite the bottom  13 . 
         [0063]    As mentioned above, a sliding element  40  is guided in the reception chamber  11 . 1 . The sliding element  40  is embodied in one piece and is comprised of the piston rod  42 , the piston  43  and the bellows section  44 . The sliding element  40  is also made as an injection-molded part and is of a flexible material, for example an elastomer on olefin basis, in particular a TPE material, to which slip agents can also be added for improving the friction properties. 
         [0064]    But the cylinder is made of a thermoplastic material, for example of ABS, with or without a slip agent, or of POM. 
         [0065]    The piston rod  42  is formed on the piston  43  on the side located opposite the bellows section  44 . It is cylinder-shaped in cross section and protrudes out of the reception chamber  11 . 1  of the damper body  11 . At its end it has an impact element  41  designed as an end cap. 
         [0066]    In an alternative embodiment, it is possible to omit the piston rod  42  formed on the piston  43 . In this case, the piston rod is formed by the support body  30  alone. In the present construction there is no mechanical connection between the piston  43  and the support body  30  required. However, in this case the centering of these two components is advantageous. 
         [0067]    The piston rod  42  is surrounded by a support body  30 . Thus, the latter has a hollow-cylindrical receptacle, with a cross section matched to the exterior cross section of the piston rod  42  and formed by a sheath element  31 . The material of the support body  30  is rigid, so that the piston rod  42  is stiffened. As  FIG. 1  clearly shows, the support body  30  is supported on the piston  43  by means of a radially widened shoulder  32 . The shoulder  32  can guide the piston  43 . In that case it is radially expanded in such a way that, together with the interior wall  19  of the reception chamber  11 . 1 , it forms a guidance. Depending on the design of the shoulder  32 , it is possible to minimize a danger of tilting of the piston  43 . 
         [0068]    The bellows section  44  protrudes into the reception chamber  11 . 1  and is embodied as a hollow cylinder, preferably with a constant wall thickness, so that it has the same material properties over its circumference, in particular a uniform expansion behavior. 
         [0069]    However, the wall can also be crowned or, to achieve a varying force, can have a changing cross section. For example, a cross section of a reduced cross section can be used. The bellows section  44  has a circumferential sealing element  45  at a free, an open end, which sealingly rests with a sealing lip against the sliding surface  18  of the reception chamber  11 . 1 . The sealing element  45  is embodied so that it seals over the entire sliding area and, based on the elasticity of its material, compensates the opening cone of the reception chamber  11 . 1 . 
         [0070]    The peak-to-valley height Ra of the sliding surface  18  lies in the range between 0.05 and 1 μm. The peak-to-valley height of the sealing element  45  in the contact area with the sliding surface  18  lies in the range between 0.4 and 4.5 μm. These pairings of the peak-to-valley heights result in ideal dampening behavior. For use as end stop dampers for furniture, good damping power under the conditions can occur at a peak-to-valley height Ra of 0.05 and 0.2 μm of the sliding surface  18  and Ra=0.5 to 3 μm of the sealing element  45 . In this case, the peak-to-valley height of the surface is provided by a groove structure as represented in  FIG. 12 . Here, the linear extension of the grooves  18 . 1  extends transversely to the movement direction of the piston  43  (v=see  FIG. 1 ). In this case, the groove structure is predetermined by the tool shape, the injection molding tool. A groove structure is preferably created over the entire surface by a lathe, so that the grooves  18 . 1  circulating on the interior wall of the cylinder are at an angle (α), for example 0.2° to 5°, in relation to the movement direction of the piston  43 . The angle (α), advance, is sufficiently small here, so that the lip-shaped sealing element always only passes over a small number of grooves  18 , &lt;20 grooves ( 18 ), at the same time. 
         [0071]    The groove structure illustrated in  FIG. 12  assures a sufficient sealing effect, so that the sealing element assures the pressure build-up. 
         [0072]    The groove structure, the negative contour of the tool, can be polished, to produce the surface structure represented in  FIG. 12 . This groove structure has a large support component, by which the sliding properties can be influenced. 
         [0073]    The detailed plan view in accordance with  FIG. 2  makes it possible to accurately see the exact embodiment of the sealing element  45 . 
         [0074]    The bellows section  44  surrounds a spring receptacle  46 , into which a spring  50  is inserted. Here, the spring receptacle  46  is dimensioned so that it prevents the spring  50  from buckling. 
         [0075]    The spring  50  is supported on the piston  43  with one of its ends. The other spring end rests against the bottom  13 . The spring  50  is placed atop the spring guidance device  14 , which also prevents bulging of the spring  50 . The spring guidance device  14  is designed so that while pushing the sliding element  40  in, there is room in it for the spring guidance device  14  and the spring  50 , and the piston movement is not hampered. 
         [0076]    An end stop element  20  is used for fixing the sliding element  40  in place in the extended end position represented in  FIG. 1 . It is designed as a ring and has a circumferential bead-shaped snap-in shoulder  21  on its exterior circumference. The end stop element  20  has a hollow-cylindrical passage  22 , through which the sheath element  31  of the support body  30  is guided. In this case, the exterior diameter of the sheath element  31  is matched to the interior diameter of the passage, so that a stable linear guidance of the support body  30  results. Here, the pairing of materials between the support body  30  and the end stop element  20  is selected so that smooth seating results. 
         [0077]    During assembly, the end stop element  20  can be easily inserted into the reception chamber  11 . 1  through an insertion widening  19 . 3  in the damper body  10 . In this case, the insertion movement is limited by a shoulder  19 . 1  of the damper body  10 . In its assembly position, the end stop element  20  snaps with its snap-in shoulder  21  into the snap-in receptacle  19 . 2 . 
         [0078]    In the end position represented in  FIG. 1 , the end stop element  20  supports the support body  32 , and therefore the piston  43 , on the shoulder  32  against the bias of the spring  50 . 
         [0079]    The mode of functioning of the end stop damper, which for example is employed in a piece of furniture with a hinged flap, is now briefly described. The furniture body of the piece of furniture customarily has a receiver bore, into which the damper body  10  with its cylindrical exterior contour can be inserted. Here, the flange  12  of the damper body  10  rests against the furniture body in the area of or near the receiver bore. 
         [0080]    The closing flap initially impacts on the impact element  41  of the piston rod  42 . The impact noise of the flap is compensated by the resilient properties of the material of the impact body  41 . The impact body  41  is deformed as a function of the impact energy of the flap. With a strong impact, the impact body  41  is completely deformed into the sheath element  31 , and the flap comes into contact with the free end of the sheath element  31 . The force is transferred to the piston  43  via the piston rod  42 , of the sheath element  31 . Here, the ring-shaped contact of the shoulder  32  against the piston  43  assures an even force distribution. A portion of the energy can be damped by the elastic deformation of the piston  43 , depending on the strength of the impact energy. 
         [0081]    The piston  43  is displaced into the reception chamber  11 . 1 . During this pressure is built up in the reception chamber  11 . 1 , aided by the sealing effect of the sealing element  45 . The pressure is simultaneously dissipated via the opening  16 . If the pressure build-up takes place over a short period of time, the pressure dissipation takes place slowly and continuously via the opening  16 . A damping overpressure is created in the reception chamber  11 . 1  and acts on the bellows section  44 . Since ambient pressure prevails in the space between the interior wall  18  and the exterior surface of the bellows section  44 , a pressure drop is created. 
         [0082]    This expands the bellows section  44 , so that it is placed against the interior wall  18 . In the process, it aids damping because of sliding friction. The friction is correspondingly great because of the flexible properties of the material of the bellows section  44 . The groove structure represented in  FIG. 12  assures that the bellows section does not additionally adhesively stick too strongly to the interior wall  18 . Thus a very strong sliding friction can be created, which leads to heavy wear on the bellows section  44 . In this case, the groove structure effectively aids an advantageous, even damping behavior, along with a simultaneous optimization of wear. Once the pressure drop is reduced, the bellows section  44  again returns into its initial position. 
         [0083]    After the piston rod  42  is relieved, the piston  43 , aided by the spring  50 , again returns into its initial position as shown in  FIG. 1 . In the process, ambient air is drawn into the reception chamber  11 . 1  via the opening  16 . 
         [0084]    The opening is dimensioned so that the following properties of the end stop dampers are provided: controlled, slow pressure reduction for achieving satisfactory damping; and rapid pressure equalization during the restoring movement of the piston  43 . 
         [0085]    These properties can be optimally provided by the conditions described in the claims and in this specification. 
         [0086]    A further embodiment variation of an end stop damper is represented in  FIGS. 3 to 6 . The construction shown substantially corresponds to the design in accordance with  FIGS. 1 and 2 , so that reference is made to the above remarks, and only the differences are addressed. 
         [0087]    As the detail “A” in accordance with  FIG. 2  illustrates, a seal  23  is provided in the area of the end stop element  20 , which seals the exterior circumference of the sheath element  31 . In this way an underpressure chamber  22 , which is sealed against the surroundings, is created in cooperation with the seal  45  of the bellows section  44 . The seal  23  could be arranged at any arbitrary other location to achieve this purpose. 
         [0088]    The underpressure chamber is in spatial connection with the surroundings via an opening  16 . 1 , such as shown in  FIG. 5 . For a controlled pressure equalization, the opening  16 . 1  has the shape described in the claims and in this specification. While pushing the piston  43  in, a pressure is created in the underpressure chamber  22 , which is reduced in comparison to the surroundings. In the process, a pressure drop is created between the reception chamber  11 . 1  and the underpressure chamber  22 , which leads to the expansion of the bellows section  44  with a strong braking effect. 
         [0089]    A functioning of the end stop damper is also assured in accordance with this invention if an underpressure chamber  22  is created in accordance with the exemplary embodiment of  FIGS. 3 and 5 , and ambient pressure always prevails in the reception chamber  11 . 1 , for example if the opening  16  is dimensioned correspondingly large. 
         [0090]    Two embodiments of the sliding element  40  are represented in detail in  FIGS. 6 to 9 . As explained above, the sliding element  40  has a piston  43  with a bellows section  44 . As  FIG. 7  shows, the bellows section  44  has groove-shaped cutouts  47  that extend, starting at the connection area of the piston  43  with the piston rod  42 , as far as the bellows section  44  areas of different wall thickness. Thus the bellows section  44  is divided into areas of different wall thickness. 
         [0091]    When the cylinder is charged with overpressure in the reception chamber  11 , the bellows section  44  is expanded more in the area of the cutouts  47  than in the remaining areas of the bellows section  44 . 
         [0092]    As  FIG. 7  shows, the cutouts  47  of the bellows section  44  extend over a relatively large circumferential area. The areas of the bellows section of reduced expanding capability remaining between the individual cutouts  47  stiffen the bellows section  44  in the direction of the center linear axis of the piston  43 . 
         [0093]      FIGS. 8 and 9  show another embodiment of the sliding element  40  represented in  FIGS. 6 and 7 . As these drawings disclose, the cutouts  47  are designed as grooves which are V-shaped in cross section. Thus, the extent of expandability of the bellows section  44  can be adjusted by the size and the shape of the cutouts  47 . 
         [0094]      FIGS. 10 and 11  show a further embodiment of the sliding element  40 . The sliding element  40  is substantially constructed in the same way as the sliding element  40  represented in the previously explained drawings. 
         [0095]    No cutouts  47  are provided in the sliding element  40  in accordance with  FIGS. 10 and 11 , so that the bellows section  44  shows a uniform expansion behavior. 
         [0096]    However, within the scope of this invention it is possible to employ a bellows section  44  with areas of differing expansion behavior, in particular in accordance with the embodiments shown in  FIGS. 6 to 9 . 
         [0097]    As  FIG. 11  makes clear, and as represented in  FIGS. 1 to 5 , the piston rod  42  is surrounded and stiffened by a sheath element  31  of a support body  30 . The support body  30  has a shoulder  32 . An annularly circulating protrusion  32 . 1  is formed on the shoulder  32 . This protrusion  32 . 1  acts on the piston bottom of the piston  43 . If a counter-pressure is generated in the reception chamber  11 . 1  as a result of a displacement of the piston  43 , and a force is introduced into the piston rod  42 , for example by a furniture flap or a drawer, the protrusion  32 . 1  displaces the piston bottom in the direction of the displacement movement of the piston  43 . Because of the displacement of the piston bottom, the area of the piston  43  is radially outwardly displaced in the transition area between the piston bottom and the bellows section  44  by the bending moment, so that a ring-shaped widening of the sliding element  40  results in this area. Thus, the piston bottom and the thickened area form a displacement arrangement. The exterior wall area of the thickened area forms a braking section, which rests against the interior wall of the reception chamber  11 . 1 . With this braking section, it is possible to effectively brake the displacement movement of the sliding element  40 .