Patent Publication Number: US-10315478-B2

Title: Bonded guide tube and bellow assembly for air spring

Description:
FIELD 
     This invention relates to a pneumatic spring or air spring for a vehicle and, in particular, to a bellow molded into a guide tube of the air spring. 
     BACKGROUND 
     A conventional air spring is a device that is arranged between a vehicle body and chassis. The typical air spring has at least one working space that is filled with compressed air, wherein at least one working space is, in each case, delimited at least partially by movable walls in the form of roll-type or fold-type bellow. The working spaces are connected to one another via flow ducts, and the flow ducts have throttle valves. 
       FIG. 1  shows a portion of a conventional air spring, generally indicated at  10 , for a motor vehicle. The air spring  10  has a working chamber  12  filled with compressed air that is at least partially delimited by rolling bellow  14 , which forms a rolled fold  14   a . When the vehicle experiences spring compression and spring extension, the rolling bellow  14  rolls both on a rotationally symmetrical contour of a roll-off piston  16  and on the inner surface of a guide tube  18 . At its ends  20 ,  22 , the rolling bellow  14  is fastened to the connecting parts by clamping rings  24 ,  26 . The air spring  10  has a centrally arranged hydraulic damper including a piston rod  28  connected via and by the air spring cover (not shown) to the bodywork. The piston rod  28  is connected to a damper cylinder  30  that is connected, via a connecting flange (not shown) to a wheel support of the chassis in the conventional manner. 
     The guide tube  18  is fastened directly to the rolling bellow  14  by being crimped to a support ring  32 . Thus, the rolling bellow  14  is thus firmly positioned and fixed relative to the guide tube  18 . However, this process step requires preassembly steps and an additional part (support ring), which increase cost and assembly time. 
     Thus, there is a need to eliminate the crimping process of the guide tube and eliminate a support ring by bonding the rolling bellow directly onto the guide tube during molding of the bellow. 
     SUMMARY 
     An objective of the invention is to fulfill the need referred to above. In accordance with the principles of an embodiment, this objective is achieved by an air spring that includes a bellow at least partially delimiting at least one working chamber that is constructed and arranged to be filled with compressed air. A guide tube surrounds at least a portion of the bellow. A bonding agent solely fixes a portion of the bellow to the guide tube. A piston is associated with the bellow. The bellow is constructed and arranged to roll with respect to an outer surface of the piston and an inner surface of the guide tube. 
     In accordance with another aspect of an embodiment, a method secures a portion of a bellow to a guide tube of an air spring. The method places the bellow, in an unformed state, in an outer mold form along with the guide tube. A bonding agent is provided on a portion of an inner surface of the guide tube at a location where the bellow is to be fixed to the guide tube. The bellow is pressed against the outer mold to form the bellow and the bellow is pressed against a portion of the guide tube so that the bonding agent contacts the guide tube and a portion of a peripheral surface of the bellow. The bellow and bonding agent are cured. After curing, the outer mold form is removed, with the bonding agent fixing the formed bellow directly to the guide tube. 
     Other objectives, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which: 
         FIG. 1  is a view of a conventional air spring having a guide tube crimped to a support ring, thereby fixing a rolling bellow to the guide tube. 
         FIG. 2  is a view of an air spring having the rolling bellow bonded directly onto the guide tube in accordance with an embodiment. 
         FIG. 3  is a view of the rolling bellow and guide tube in an outer mold form in accordance with an embodiment. 
         FIG. 4  is a view of the rolling bellow of  FIG. 3  now shown pressed against the outer mold, with the guide tube acting as an outer mold during a curing process and with the rolling bellow bonded to the guide tube in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     With reference to  FIG. 2 , a portion of an air spring is shown, generally indicated at  10 ′, for a motor vehicle. The air spring  10 ′ can be of the type disclosed in U.S. Pat. No. 8,474,798, the content of which is hereby incorporated by reference into this specification. Thus, the air spring  10 ′ has at least one working chamber  12  filled with compressed air, which is at least partially delimited by an elastomer rolling bellow  14  that forms a rolled fold  14   a . When the vehicle experiences spring compression and spring extension, the rolling bellow  14  rolls both on a rotationally symmetrical outer surface  15  of a roll-off piston  16  and on an inner surface  17  of a preferably metal guide tube  18 ′. Thus, the guide tube  18 ′ surrounds a portion of the rolling bellow  14 . At its ends  20 ,  22 , the rolling bellow  14  is fastened to the connecting parts by clamping rings  24 ,  26 . The air spring  10 ′ has a centrally arranged hydraulic damper structure, generally indicated at  27 , including a piston rod  28  preferably connected via an air spring cover (not shown) to the bodywork. The piston rod  28  is connected to a damper cylinder  30  that is connected, via a connecting flange (not shown) to a wheel support of the chassis in the conventional manner. The conventional cardanic fold  33  of the bellow  14  is adjacent to an end  34  of the guide tube  18 ′. 
     Instead of crimping the guide tube  18 ′ to a support ring to fix the rolling bellow  14 , the bellow  14  is fixed directly to the guide tube  18 ′ solely by a bonding agent  36 , generally adjacent to the cardanic fold  33 . The bonding agent  36  can be any suitable agent such as adhesive, epoxy, rubber cement, etc. The bonding area is shown at A in  FIG. 2 . With the embodiment, advantageously, the support tube  32  of  FIG. 1  is no longer required, nor is a crimping step. Conventionally, the bellow  14  is molded in a manufacturing step. Thus, the embodiment makes use of this molding step to bond the bellow  14  to the guide tube  18 ′ as explained below. 
     With reference to  FIG. 3 , the unformed bellow  14  is placed in a conventional outer mold form  38  along with the guide tube  18 ′. The bonding agent  36  is provided on a portion of an inner surface  40  of the guide tube  18 ′ at a location where the bellow  14  is to be fixed to the guide tube  18 ′. As shown in  FIG. 4 , the bellow  14  is pressed by an inflatable portion  41  of a mold member  42  against the outer mold form  38  in the conventional manner to from the bellow and, in accordance with an embodiment, the bellow  14  is also pressed against a portion of the guide tube  18 ′ so that the bonding agent  36  contacts the guide tube  18 ′ and a portion of a peripheral surface  44  of the bellow  14 . The bellow and bonding agent  36  is then cured, with the guide tube  18 ′ acting as an outer mold during the curing process. Once cured, the outer mold form  38  is removed, with the bonding agent  36  fixing the formed bellow  14  directly to the guide tube  18 ′. 
     Thus, the use of the bonding agent  36  during the bellow molding process eliminates the need for the conventional support ring and crimping process, thereby reducing parts and cost and also reducing a cumbersome manufacturing process of an air spring. 
     The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the scope of the following claims.