Patent Publication Number: US-2004040151-A1

Title: Piston-rod scraping ring accommodated in a groove in a dashpot cap, and method of inserting such a ring in such a groove

Description:
[0001] The present invention concerns, first, a piston-rod scraping ring accommodated in a groove in a dashpot cap as recited in the preamble to claim 1, and, second, a method of inserting such a ring in such a groove.  
       [0002] Piston-rod scraping rings of elastic materials, especially intended for scraping water and dirt off piston rods, and accommodated in a groove in a dashpot cap are known from German 3 443 370 C2.  
       [0003] There are many many ways of securing such piston-rod scraping rings to the upper cap of a dashpot. One way is disclosed in German 3 443 370 C2. The cap is secured by means of a groove that is open radially and, in one direction, axially, by a sleeve that axially and radially encloses the rim around the ring and is forced into a bore in the groove. The compression secures the sleeve and hence the ring. There is a drawback to this approach in that the sleeve necessitates additional material and work.  
       [0004] Another approach to attaching such a cap to a dashpot is known from German Patent 1 140 705. The piston-rod scraping ring is again inserted in a groove that is open radially and, in one direction, axially, and secured there radially by compression at the end of the outer cylinder. One drawback to this approach is that the ring remains loose and can accordingly get lost before it is finally secured in place. Furthermore, to protect it from deformation or eccentricity, the cap must be inserted very precisely in the groove before the dashpot is assembled.  
       [0005] German 19 921 696 A1 discloses a seal accommodated in an inward-opening groove in a cap. The actual sealing mass employed in such seals must be well inserted axially in the groove. Furthermore, the mass must be secured in the nut somehow or radially tensioned, making the groove difficult to machine precisely and necessitating an additional component.  
       [0006] The object of the present invention is accordingly a piston-rod scraping ring and a groove in a dashpot cap improved to the extent that the ring can easily be inserted into the groove and secured there until the overall dashpot is assembled.  
       [0007] This object is attained in accordance with the present invention as recited in the body of claim 1. Claims 2 through 4 address methods of inserting a piston-rod scraping ring in a groove in a dashpot cap.  
     
    
    
     [0008] The advantages of the present invention are that the ring can be fastened to the cap by simple means and with low expenditure and-before the dashpot is finally assembled. Embodiments of the present invention will now be specified with reference to the accompanying drawing, wherein  
     [0009]FIG. 1 is a transverse section through the dashpot cap and its associated components,  
     [0010]FIG. 2 is a larger-scale depiction, representing the situation before the ring has been secured, of the groove that accommodates the ring,  
     [0011]FIG. 3 is an illustration similar to FIG. 2 representing the situation after the ring has been inserted,  
     [0012]FIG. 4 depicts an alternative embodiment in the situation illustrated in FIG. 2, and  
     [0013]FIG. 5 depicts the same embodiment in the situation illustrated in FIG. 3. 
    
    
     [0014] Piston rods usually extend out of dashpots through caps that close off the dashpots&#39; open ends. FIG. 1 shows such a piston rod  1  and dashpot cap  2 . At its outer circumference  2 , the cap is sealed off against an unillustrated outer dashpot cylinder by an O ring  3 . Such caps can be fastened to the cylinders in various ways.  
     [0015] Cap  2  is provided with various components that center and seal rod  1  as it travels into and out of the cylinder. These components are positioned in the vicinity of a bore that extends through cap  2 . Positioned at the bottom of cap  2  is a low-friction bushing  4  that centers rod  1 . Above bushing  4 , a gasket  5  is accommodated in an inward-opening groove and provided with the requisite radial tension by a compression ring  6 .  
     [0016] At the top of cap  2  is a ring  7  that scrapes water and dirt off the section of piston rod  1  outside the cylinder as the rod enters it.  
     [0017] The rim  8  around piston-rod scraping ring  7  is accommodated in an inward opening groove  9  in dashpot cap  2 . Prior to assembly of the dashpot, rim  8  is more or less uniformly high. Furthermore, as will be evident from FIG. 2, the height  10  of groove  9  is also more or less uniform.  
     [0018] The height of the rim  8  around piston-rod scraping ring  7 , which is not illustrated in FIG. 2, approximately equals the height  10  of groove  9 . Once piston-rod scraping ring  7  has been positioned with its rim  8  in groove  9 , the groove&#39;s outer wall  11  is forced against its inner circumference  12  by a separate tool, a press for instance, compressing height  10  in the vicinity of the inner circumference.  
     [0019] A similar deformation is induced in the embodiment illustrated in FIGS. 4 and 5.  
     [0020] When the conditions wherein piston-rod scraping ring  7  will be employed prescribe that it be forced even more firmly into groove  9 , both the groove and the rim  8  around the ring can in their original shape be higher toward the center. When outer wall  11  is deformed such that the height  10  of groove  9  decreases as it approaches inner circumference  12 , the rim  8  around the ring will accordingly be more powerfully compressed.  
     [0021] It is also possible for the height of the rim  8  around piston-rod scraping ring  7  to increase outwards, in which event its maximal height will approximately equal the height  10  of groove  9 . The seating of piston-rod scraping ring  7  will then be secured, once outer wall  11  has been deformed, by the interlocking structures and by additional axial compression.