Patent Publication Number: US-2010109257-A1

Title: Method for the production of flat seals, and flat seal

Description:
The invention relates to a method for the mechanical connecting of flat gaskets having at least two layers. 
     A metallic gasket can be learned from DE 198 51 066 A1, which is designed such that it is located between opposite surfaces of a cylinder block and a cylinder head. The metallic gasket comprises a pair of elastic metal plates, which are furnished with first boring holes designed corresponding to the cylinder bore and beads formed along the circumferences of the first boring holes. In addition, a compensating element is provided, which is furnished with the first boring holes opposite the second boring holes and which is laminated between the elastic metal plates. The elastic metal plates have connection elements, in which the metal plates and the compensating element are connected to each other by caulking. A punch is applied, which mechanically deforms the material in the respective connecting area of the metal plates as well as of the compensating element. With the aid of another punch an outwardly effective plastic yielding can be generated in the area of the respective layers, through which a firm connection of the individual layers is generated. 
     The invention is based on the task of providing a method for the mechanical connecting of flat gaskets, such as cylinder head gaskets, flange gaskets or the like, having at least two sites, in which the connection can be realized in the simplest manner without additional materials or connection elements. 
     Furthermore, a flat gasket, particularly a multi-layered metallic cylinder head gasket, should be provided, in which a detachable connection of the individual layers to one another should be possible. 
     The task is solved by a method for the mechanical connecting of flat gaskets, having at least two layers, while the individual layers are positioned in the area of a tool, at least one piercing punch with an approximately circular cross section that partially cuts the layers in defined sites of the respective connection area and outside of the respective cutting area at least parts of the residual material are deformed with formation of bending areas, in such a way, that the respective cutting area is designed rounded and the respective bending area is designed linearly, in which in the cutting area are formed burrs of at least one of the layers are brought into mechanical connection for the formation of a detachable clamp connection with the material of at least another layer. 
     Advantageous further developments of the method according to the present invention can be learned from the associated methodological subsidiary claims. 
     This task is also solved by a flat gasket, comprising at least two layers, which have similar hole patterns, in which the individual layers are connected to each other in a detachable manner by clamping, in which the respective connection area has an approximately circular cross section and in defined sites has cutting areas and outside of the cutting areas bending areas, in which the respective cutting area is designed rounded and the respective bending area is designed linearly and in the cutting areas are formed burrs of at least one of the layers impressed into the material of at least one other layer, are interlocked respectively with other burrs of the other layer. 
     Advantageous further developments of the flat gasket according to the present invention can be learned from the associated objective subsidiary claims. 
     In comparison to the prior art according to DE 198 51 066 A1, a detachable connection of the individual layers of the flat gasket produced by clamping, particularly of a cylinder head gasket, thus operates, so that during the production process of the flat gasket, particularly of the cylinder head gasket, if necessary, existing defective layers can be replaced, without the layers, which are technically sound, having to be disposed of. 
     The individual, particularly metallic, layers of the flat gasket are connected mechanically to each other in a kind of punching process, however, can be detached in pre-definable sites. For this a piercing punch is flattened and rounded off in several sites (preferably three sites), so that no cuts can take place at these sites. In these flattened and rounded off areas the material in the respective connection area is merely clamped and mechanically deformed. In the residual areas of the piercing punch the respective layer is cut during the pressing process at defined sites (preferably three sites), in such a way, that burrs still remain, which are pressed either under pressure effect into another layer, or come into mechanical connection with burrs of another layer. Through both processes a clamping connection of the individual layers is achieved. The cutting areas are shaped by their dimensioning, so that they are designed as a percentage smaller or maximally equally large, as the bending area running essentially linearly. 
     It is ensured contingent on this cutting process, that the diameter of the piece punched out of one of the layers is somewhat larger than the boring of another layer, so that the aforesaid clamping of the piece punched out occurs in the other layer. 
     With the method according to the present invention up to six (metallic) layers can be connected to each other in a detachable manner, in which the connection of the layers is implemented at different sites of the flat gasket in a process step. 
     As already addressed, the connection of the individual layers can be detached again temporarily, so that after replacement of a defective by a technically sound layer the connection can be subsequently reproduced under pressure effect. 
    
    
     
       The object of the invention is depicted by means of a preferred embodiment and is described as follows: 
         FIG. 1  shows schematic diagrams of the tool which can be used for the production of a connection area in different views or sections; 
         FIG. 2  shows a single depiction of the respective cutting area and bending area in a connection area. 
     
    
    
       FIG. 1  shows the schematic design of an individual cutting tool  1  in a partial perspective depiction. The cutting tool  1  comprises an elongated piercing punch  2  with an approximately circular lower hole surface  3 . Through arrangement of several such piercing punches  2  in the area of a step-up station connection areas can be produced at several sites of the flat gasket, such as, for example, of a cylinder head gasket, not depicted here. The piercing punch  2  is flattened on three sides  4 ,  5 ,  6  and rounded off at three other sides  7 ,  8 ,  9 . Each connection area thus forms on the one hand cutting areas  7  to  9  and on the other hand bending areas  4  to  6 . 
       FIG. 2  shows a partial view of a flat gasket  13  consisting in this example of three metallic layers  10 ,  11 .  12 , designed as a cylinder head gasket. With the method according to the present invention up to six layers can be brought into mechanical connection to each other. The cylinder head gasket  13  comprises combustion chamber through-borings, media through-borings as well as screw through-borings, which are not depicted. The metallic layers  10  to  12  of the cylinder head gasket  13  are connected mechanically with each other at different sites  14  by clamping, however, are detachable. The individual connection area  14  distinguishable here comprises cutting areas  7  and bending areas  4 , in which this connection area  14  has in each case three cutting areas  7  to  9  as well as three bending areas  4  to  6  in alternating arrangement. 
     In the respective connection area  14  a mechanical bracing of materials (burrs  7 ′) of the layers  10  to  12  takes place, in which the individual layers  10 ,  11 ,  12  are connected to each other in a detachable manner by clamping. Furthermore, the piercing punch  2  is distinguishable with the cutting area  7  as well as the bending area  4 . With the reference numeral  2 ′ a lower tool element is designated, which has a corresponding recess  15 . Through pressure effect (arrow) the respective connection area  14  is generated in such a way that the layers  10  to  12  are pressed into the recess  15 , in which at the same time the rounded cutting areas  7  to  9  and the bending areas  4  to  6  running linearly are generated. 
     If during the manufacture of the cylinder head gasket it emerges that an individual layer of the connection is defective, the layers  10 - 12  can be separated without any difficulty. The defective layer is replaced by a technically sound layer and connected again to the other layers through pressure effect.