Abstract:
An end-stop damper including a damper body in the form of a cylinder, wherein a piston is guided so that it is displaceable in the cylinder receiving chamber. An air pressure is formed in the receiving chamber produces a braking force acting on the piston during its displacement. The receiving chamber includes at least one pressure reducing opening and the piston includes a bellows section which is actively connected to the cylinder according to pressure conditions in the receiving chamber. This invention substantially simplifies the structural design of the end-stop damper because the piston and the bellows section are connected to each other so that they are formed in one piece.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an end-stop damper with a damper body having a cylinder, wherein a piston is displaceably guided in a receiving chamber of the cylinder, a braking force acting on the piston is exerted by air pressure generated in the receiving chamber during displacement of the piston, the receiving chamber has at least one opening for relieving the air pressure, and the piston has a bellows section in operational connection with the cylinder as a function of the pressure conditions in the receiving chamber. 
     2. Discussion of Related Art 
     An end-stop damper is taught by 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. Here, the piston is sealingly conducted on the inner wall of the cylinder, so that two pressure chambers are formed in the cylinder. 
     When retracting the piston, air is compressed in an overpressure chamber. At the same time an air pressure, which is less than the pressure in the overpressure chamber, is generated in an underpressure chamber. For allowing a continuous pressure compensation to occur between these two pressure chambers, overflow conduits of a narrow cross section are provided. 
     Air flows through these conduits from the overpressure chamber to the underpressure cylinder. For increasing the braking force, the piston has a bellows section which is inflated because of a difference in pressure existing between the overpressure chamber and the underpressure chamber. During this it rests against the inner wall of the cylinder and thus increases the friction of the piston. The bellows section is made as a sleeve 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 parts of the piston. 
     The known end-stop damper has a multitude of parts and the assembly is complicated. 
     SUMMARY OF THE INVENTION 
     It is one object of this invention to provide an end-stop damper of the type mentioned above but which has a simple construction. 
     This object is achieved if the piston and the bellows section are connected with each other in one piece. The one-piece embodiment of the bellows section and the piston reduces the cost outlay for parts and assembly. In particular, the cost outlay for sealing required for sealing the bellows section against the piston, is reduced in comparison with the prior art. 
     This invention recognizes the structural elements of bellows section and the piston, which customarily are made of different materials and are employed for completely different purposes, can be combined into one unit. 
     The structural cost outlay can be even more reduced if the piston rod is formed in one piece on the piston. 
     In one embodiment of this invention, a support body is assigned to the piston rod or has a support body. The support body has a detent side arranged outside the damper body. The support body is supported on the piston by a shoulder. Depending on the layout, the piston rod can be stiffened by the support body. At the same time, it is possible to absorb the impact force, of a striking door or a leaf, for example, and to transmit it at least in part directly to the piston. 
     This is a particular advantage if the piston and the bellows section include a flexible material. In that case, the piston is charged by the impact force in a spring-elastic manner, and a portion of the impact force is destroyed by hysteresis. 
     The flexible embodiment of the piston and the bellows section also make possible a pairing with the materials of the cylinder, which allow strong damping because of large coefficients of friction. If the piston rod is made of a flexible material, for reasons of rigidity, the piston rod is stiffened by a sheath element. 
     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 through the impact element and can be partially damped. 
     If the bellows section has a cylinder-shaped portion maintained a distance away from the inner 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 can rest continuously against the inner wall of the cylinder when charged with pressure, and can create a uniform and large braking force. 
     The functionality of the bellows section can also be increased if the cylinder-shaped portion of the bellows section forms a spring receptacle, in which a spring is at least partially received. The spring can support the piston against the cylinder in a direction opposite the insertion movement of the piston into the cylinder. 
     A structural simplification results if the bellows section supports a sealing element formed on it, which seals a pressure chamber and an underpressure chamber of the cylinder against each other. 
     The braking effect of the end-stop damper can be increased if both the underpressure chamber and the pressure chamber are in an air-conducting connection with their surroundings by at least one opening. 
     This is possible if the openings, or damping members assigned to the openings, are designed to achieve a metered air flow. 
     For example, it is possible to achieve an air volume flow for 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, in particular, have a good damping effect for application in furniture construction. 
     It is possible to achieve this damping satisfactorily if the ratio of the cross-sectional surface of the piston in the area facing the hollow chamber, to the opening cross section of the opening is greater than 4000/1. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This invention is described in greater detail in view of an exemplary embodiment represented in the drawings, wherein: 
         FIG. 1  shows an end-stop damper in a lateral sectional view; 
         FIG. 2  shows a detailed sectional view, identified by “A” in  FIG. 1 ; 
         FIG. 3  shows a further embodiment of an end-stop damper in a lateral sectional view; 
         FIG. 4  shows a detailed view, identified by “A” in  FIG. 3 ; and 
         FIG. 5  shows a detailed view, identified by “B” in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An end-stop damper with a longitudinally extending damping body  10  is shown in  FIG. 1 . The damping body  10  comprises a cylinder  11 . The cylinder  11  surrounds a receiving chamber  11 . 1 , in which a piston  43  of a sliding element  40  is maintained in a linearly displaceable manner. A spring guide element  14 , which is formed as one piece on a bottom  13  of the damping body  10 , protrudes into the receiving chamber  11 . 1 . In the area of or near its side facing away from the bottom  13 , the spring guide element  14  has an opening  16  in the form of a bore. The opening  16  creates a spatial connection between the receiving chamber  11 . 1  and an air-guidance channel  15  surrounded by the spring guide element. 
     In this case, the diameter of the opening is less than 0.1 mm in order to permit a metered air exchange between the receiving chamber  1 . 1  and the air-guidance channel  15 . However, in place of a bore, any desired other opening or cross section can be used. Good damping results are achieved if the cross-sectional surface of the piston  43  in the end area facing the receiving chamber  11 . 1  to the opening cross section of the opening has a ratio of 4000/1. 
     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 embodied as an injection-molded part. For reasons of removal from the mold, the inner wall  18  of the cylinder  11  has a slight opening cone, so that the receiving chamber  11 . 1  slightly widens in the direction toward the inlet opening located opposite the bottom  13 . 
     As mentioned above, a sliding element  40  is guided in the receiving chamber  11 . 1 . The sliding element  40  is of one-piece construction and comprises a piston rod  42 , the piston  43  and a bellows section  44 . The sliding element  40  is also embodied as an injection-molded part and is made of a flexible material, for example a TPE material. 
     The piston rod  42  is formed on the piston  43  on the side located opposite the bellows section  44  and projects out of the receiving chamber  11 . 1  of the damper body  11 . On an end it has an impact element  41  embodied as an end cap. 
     In an alternative embodiment, it is possible to omit the piston rod  42  formed on the piston  43 . In that case, the piston rod  42  is formed by the support  30  alone. 
     A mechanical connection between the piston  43  and the support body  30  is not required with the present structure. However, centering of these two components can be advantageous. The piston rod  42  is enclosed in a support body  30  and can have a hollow-cylindrical receptacle, with a cross section matched to the exterior cross section of the piston rod  42 . It is formed by a sheath element  31 . The material of the support body  30  is rigid, so that the piston rod  42  is stiffened. As shown in  FIG. 1 , a radially widened shoulder  32  of the support body  30  supports it on the piston  43 . The shoulder  32  can guide the piston  43 . In that case, it is radially widened so that, together with the inner wall  18  of the receiving chamber  11 . 1 , it forms a guide. Depending on the layout of the shoulder  32 , it is possible to minimize the danger of tilting of the piston  43 , in particular. The bellows section  44  projects into the receiving chamber  11 . 1 . It is formed as a hollow cylinder, preferably of constant wall thickness, so that it has identical workpiece properties over its circumference, in particular a uniform expansion behavior. However, the wall can also be embodied to be spherical or, for achieving a varied force, can have a variable cross section. For example, a reduced cross section can be employed. On its free open end, the bellows section  44  has a circumferential sealing element  45 , which sealingly rests against the inner wall  18  of the receiving chamber  11 . 1  with a sealing lip. In this case, the sealing element  45  is embodied so that it provides sealing over the entire sliding area and, based on the elasticity of its material, compensates the opening cone of the receiving chamber  11 . 1 . 
     The detailed representation of  FIG. 2  shows the exact design of the sealing element  45 . The bellows section  44  encloses a spring receptacle  46 , into which a spring  50  is placed. The spring receptacle  46  is dimensioned so that it prevents kinking of the spring  50 . 
     With one of its ends, the spring  50  is supported on the piston  43 . The other spring end rests on the bottom  13 . The spring  50  is placed over the spring guide element  14 , which also prevents kinking of the spring  50 . The spring receptacle  46  is embodied so that, during insertion of the sliding element  40 , the spring guide element  14  and the spring  50  are accommodated in it and the piston movement is not thus hindered. 
     A detent element  20  is used for fixing the sliding element  40  in place in the extended end position represented in  FIG. 1 . This is embodied as a ring and has a circumferentially extending bead-like shoulder  21  on its outer circumference. The detent element  20  has a hollow-cylindrical passage  22 , through which the sheath element  31  of the support body  30  is passed. In this case, the outer diameter of the sheath element  31  is matched to the inner diameter of the passage, so that a stable linear guidance for the support body  30  results. Here, the pairing of the material of the support body  30  and the detent element  20  is selected so that a smooth-running seating results. During assembly, the detent element  20  can be easily inserted into the receiving chamber  11 . 1  via an insertion widening  19 . 3  of the damper body  10 . The insertion movement is limited by a shoulder  19 . 1  of the damper body  10 . In its assembled position, the detent element  20  snaps into the snap-in receptacle  19 . 2  with its snap-in shoulder  21 . 
     In the end position represented in  FIG. 1 , the detent element  20  supports the support body  30  against the shoulder  32 , and thus the piston  43  against the pretension of the spring  50 . 
     The mode of functioning of the end-stop damper, which is for example employed in a piece of furniture with a leaf hinged on it, will now be briefly described. 
     The furniture body of the piece of furniture customarily has a receiver bore into which the cylindrical outer contour of the damper body  10  can be inserted. During this, the flange  12  of the damper body  10  rests against the furniture body in the area of or near the receiving bore. 
     The closing leaf first impacts the impact element  41  of the piston rod  42 . The mechanical impact noise of the leaf is compensated because of the resilient material properties of the impact body  41 . The impact body  41  is deformed as a function of the impact energy of the leaf. With a strong impact, the impact body  41  is completely deformed into the sheath element  31  and the leaf comes into contact with the free end of the sheath element  31 . The force is transmitted to the piston  43  via the piston rod  42 , or the sheath element  31 . The annular contact of the shoulder  32  with the piston  43  assures an even force introduction. Depending on the strength of the impact energy, a portion of the energy can be damped as a result of the elastic deformation of the piston  43 . The piston  43  is displaced into the receiving chamber  11 . 1  and pressure is built up in the receiving chamber  11 . 1 , which is aided by the sealing effect of the seal  45 . The pressure is simultaneously relieved via the opening  16 . If pressure is built up in a short period of time, pressure relief does not take place in the same amount in which it is relieved via the opening  16 . 
     A damping overpressure is generated in the receiving chamber  11 . 1 . This overpressure acts on the bellows section  44 . Because ambient pressure exists in the space between the inner wall  18  and the outer surface of the bellows section  44 , a pressure gradient is created. This inflates the bellow section  44  so that it rests against the inner wall  18 . In the process, it aids damping because of sliding friction. The friction is comparatively large because of the flexible material property of the bellows section  44 . 
     The bellows section  44  returns into its starting position when the pressure gradient drops. Following the relief of the piston rod  42 , the piston  43  returns into its initial position in accordance with  FIG. 1 , aided by the spring  50 . During this, ambient air is aspirated into the receiving chamber  11 . 1  through the opening  16 . 
     The opening is of such dimensions that properties of the end-stop damper are met, including controlled, slow pressure reduction for achieving proper damping, and rapid pressure equalization during return movement of the piston  43 . 
     These properties can be optimally achieved under the conditions described in this specification and in the claims. 
     In another embodiment, an end-stop damper is shown in  FIGS. 3 to 5 . The structure substantially corresponds to the embodiment in accordance with  FIGS. 1 and 2 , so reference is made to the above explanations, and only the differences are addressed. 
     As the detail “A” in accordance with  FIG. 2  shows, a seal  23  is provided in the area of or near the detent element  20 , which seals the outer circumference of the sheath element  31  of the support body  30 . Together with the seal  45  of the bellows section  44 , an underpressure chamber  22  is created, which is sealed with respect to the surroundings. The seal  23  can be arranged at any other desired location for this purpose. 
     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  is designed as described in this specification and in the claims. While introducing the piston  43 , a pressure, which is less than that of the surroundings, is formed in the underpressure chamber  22 . Thus, a pressure gradient is created between the receiving chamber  11 . 1  and the underpressure chamber  22 , which results in an expansion of the bellows section  44  with a strong braking effect. 
     In accordance with this invention, functioning of the end-stop damper is assured if, in accordance with the exemplary embodiment according to  FIGS. 3 to 5 , an underpressure chamber  22  is created and ambient pressure always exists in the receiving chamber  11 . 1 , for example if the opening  16  has correspondingly large dimensions.