Abstract:
In order to improve a control plate ( 10 ) for mounting between two hydraulic units ( 62, 64 ), in particular between two hydraulic units of a transmission, including an intermediate layer ( 12 ) having apertures ( 32, 34 ) for guiding fluid, and metal sealing layers ( 22, 24 ) that are arranged on either side of the intermediate layer and have apertures for guiding fluid, and sealing beads ( 112, 114, 116, 118 ) which run linearly between the apertures, for sealing between the intermediate layer and the opposing hydraulic units on either side thereof, such that an optimum seal is possible between the intermediate layer and the hydraulic units, it is proposed that, for sealing, the sealing beads abut by means of their bead feet ( 132, 134 ) against the intermediate layer and have on their side remote from the intermediate layer a bead crest ( 152 ) for linearly sealing to the respective hydraulic unit, and in that the sealing beads in the sealing layers are formed such that when the sealing beads are compressed in the course of installing the control plate between the hydraulic units a plasto-elastic deformation is established, at least in certain regions, and a sealing force above a predetermined minimum sealing force is achieved over the entire linear extent of the respective bead crest.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application is a continuation of International application No. PCT/EP2014/055628 filed on Mar. 20, 2014. 
         [0002]    This patent application claims the benefit of International application No. PCT/EP2014/055628 of Mar. 20, 2014 and German application No. 10 2013 205 220.0 of Mar. 25, 2013, the teachings and disclosure of which are hereby incorporated in their entirety by reference thereto. 
       BACKGROUND OF THE INVENTION 
       [0003]    The invention relates to a control plate for mounting between two hydraulic units, in particular between two hydraulic units of a transmission, including an intermediate layer having apertures for guiding fluid, and metal sealing layers that are arranged on either side of the intermediate layer and have apertures for guiding fluid, and sealing beads which run linearly between the apertures, for sealing between the intermediate layer and the opposing hydraulic units on either side thereof. 
         [0004]    Control plates of this kind are known from the prior art. 
         [0005]    However, in those there is a continual requirement to optimise the seal between the intermediate layer and the hydraulic units. 
         [0006]    The object of the invention is therefore to improve a control plate of the type mentioned in the introduction such that an optimum seal is possible between the intermediate layer and the hydraulic units. 
       SUMMARY OF THE INVENTION 
       [0007]    This object is achieved according to the invention with a control plate of the type mentioned in the introduction in that, for sealing, the sealing beads abut by means of their bead feet against the intermediate layer and have on their side remote from the intermediate layer a bead crest for linearly sealing to the respective hydraulic unit, and in that the sealing beads having the sealing layers are formed such that when the sealing beads are compressed in the course of installing the control plate between the hydraulic units a plasto-elastic deformation is established, at least in certain regions, and a sealing force above a predetermined minimum sealing force is achieved over the entire linear extent of the respective bead crest. 
         [0008]    The advantage of the solution according to the invention can thus be seen in the fact that, as a result of the configuration of the shape of the sealing beads and the choice of material of the sealing layers, it is possible to achieve a behaviour of the sealing beads that makes a predetermined minimum sealing force achievable with the sealing beads, with a plasto-elastic deformation when the control plate is installed between the hydraulic units, regardless of the location at which the seal is to be made. 
         [0009]    Here, it is particularly advantageous if the minimum force is 5 N/mm 2 . 
         [0010]    Further, it is preferably provided for the level of the sealing force that occurs when the control plate is installed to be limited such that the sealing force is preferably 100 N/mm 2  or less. 
         [0011]    This restriction on large values for the sealing force has the advantage that in this way excessive deformation of the hydraulic units as the control plate is installed between them can be avoided. 
         [0012]    As an alternative or in addition to the solution described, the object stated in the introduction is also achieved according to the invention with a control plate of the type mentioned in the introduction in that, with a deformation of the respective sealing bead to a bead height that is  5  pm greater than the bead height on complete compression, the sealing force is in a range of from 40 N/mm 2  to 80 N/mm 2 . 
         [0013]    As an alternative or in addition thereto, a further solution to the object according to the invention provides, with a compression of the sealing beads to a bead height that is 50 μm above the bead height on complete compression, for the sealing force to be in a range of from 5 N/mm 2  to 20 N/mm 2 . 
         [0014]    Further, as an alternative or in addition, with a further solution to the object according to the invention it is provided, after the plasto-elastic deformation for achieving the provided minimum sealing force, for the sealing beads to have a rebound travel of 10 μm or more—that is to say that despite the plasto-elastic deformation the sealing beads are still resilient and ensure a rebound of 10 μm or more. 
         [0015]    A behaviour of this kind in the sealing beads is important so that the sealing beads can still follow deformations of the hydraulic units, where appropriate also in the region of the carrier plate, that occur in operation as a result of the effects of heat or pressure. 
         [0016]    It is even more advantageous if, after the plasto-elastic deformation for achieving the minimum sealing force, the sealing beads still have a rebound travel of 15 μm or more. 
         [0017]    In order in particular to achieve sufficient long-term loading capacity of the sealing beads, it is preferably provided, after at least 1.5 million deflection cycles, for the sealing beads still to have a rebound travel of 10 μm or more and the designated minimum sealing force. 
         [0018]    As regards the formation of the sealing beads themselves, more detailed statements have not been made in the context of the explanation hitherto of the individual exemplary embodiments. 
         [0019]    Thus, an advantageous solution provides for the bead height of the not yet deformed sealing beads in the sealing layer to be 10 μm or more. 
         [0020]    It is even better if the bead height of the not yet deformed sealing beads in the sealing layer is 20 μm or more. 
         [0021]    In order to achieve the advantageous properties of the sealing beads, it is preferably provided for the bead height of the beads not to be excessively great. 
         [0022]    For this reason, it is preferably provided for the bead height of the not yet deformed sealing beads in the sealing layer to be 150 μm or less. 
         [0023]    Further, more detailed statements have not yet been made as regards the bead width either. 
         [0024]    Thus, an advantageous solution provides for the bead width of the not yet deformed sealing beads to be 0.5 mm or more. 
         [0025]    A bead width of the sealing bead of this kind is partially responsible for the behaviour, in particular the plasto-elastic behaviour, of the sealing beads, and also contributes to ensuring the necessary rebound travel after the plasto-elastic deformation. 
         [0026]    However, the bead width should moreover not be too great, and for this reason it is preferably provided for the bead width of the not yet deformed sealing beads to be 1.5 mm or less. 
         [0027]    Further, more details have not yet been specified as regards the material thickness of the sealing layers either. 
         [0028]    For this reason, it is preferably provided for the material thickness of the sealing layers to be 150 μm or more. 
         [0029]    Preferably, however, the material thickness of the sealing layer should not be chosen to be excessively great, and for this reason it is favourably provided for the material thickness of the sealing layer to be 300 μm or less. 
         [0030]    The sealing layer may at the same time be formed from the greatest variety of materials. 
         [0031]    Thus, an advantageous solution provides for the sealing layer to be formed from steel, in particular carbon steel. 
         [0032]    Further, the sealing layer is preferably formed from a material that has a modulus of elasticity of 500 N/mm 2  or less. 
         [0033]    As an alternative or in addition to the solutions described above, a further solution of the object according to the invention provides for the sealing beads of the respective sealing layer to be provided on their side facing the respective hydraulic unit with an elastomer coating. 
         [0034]    An elastomer coating of this kind provides the possibility of compensating for unevennesses in the surface of the hydraulic units in the region of their end faces facing the sealing layer and hence improving the sealed closure between the end face of the respective hydraulic unit and the respective sealing bead. 
         [0035]    As an alternative or in addition, further, in the case of a solution to the object according to the invention, it is provided for the bead feet of the respective sealing layer to be provided on their side facing the intermediate layer with an elastomer coating. 
         [0036]    An elastomer coating of this kind also provides the possibility of improving the seal between the sealing bead and the intermediate layer, in particular also as regards the seal in the event of unevennesses in the surface of the intermediate layer. 
         [0037]    More detailed statements have not yet been made as regards the thickness of the elastomer coating, and in this case an advantageous solution provides for the elastomer coating to have a thickness of  10  μm or more. 
         [0038]    In order that the thickness of the elastomer coating should not become excessively great, it is preferably provided for the elastomer coating to have a thickness of 50 μm or less. 
         [0039]    In the context of the description hitherto of the individual exemplary embodiments of the control plate, the manner in which the intermediate layer is to be formed has not yet been discussed in more detail. 
         [0040]    Thus, it has proved favourable for achieving the object stated in the introduction if the intermediate layer has a thickness of 800 μm or more in order to give the intermediate layer sufficient stability. 
         [0041]    In particular, sufficient stability is required in order to ensure that the sealing beads have sufficient support relative to one another, for example if the sealing beads are arranged non-congruently on different sides of the intermediate layer. 
         [0042]    In order that the material thickness of the intermediate layer should not become excessively great, it has proved advantageous if the intermediate layer has a material thickness of 2600 μm or less. 
         [0043]    Moreover, more detailed statements have not been made as regards the material of the intermediate layer. 
         [0044]    Thus, a favourable solution provides for the intermediate layer to be made from material that is free from spring steel. 
         [0045]    Preferably, in this case the intermediate layer is formed from steel. 
         [0046]    A favourable steel grade for forming the intermediate layer is carbon steel. 
         [0047]    As an alternative thereto, however, it is also possible for the intermediate layer to be formed from aluminium. 
         [0048]    In particular, it is preferably provided for the intermediate layer to be formed from an aluminium alloy. 
         [0049]    A further alternative provides for the intermediate layer to be formed from AlMg 3  or AlMg 4.5 Mn 0.7 . 
         [0050]    Also as regards the material properties of the intermediate layer, it has proved favourable if the intermediate layer is formed from a material that has a modulus of elasticity of 700 N/mm 2  or less. 
         [0051]    Further features and advantages of the invention form the subject matter of the description below and the graphical representation of some exemplary embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0052]      FIG. 1  shows a perspective exploded illustration of a control plate according to the invention; 
           [0053]      FIG. 2  shows a detail illustration of the control plate that is arranged between two hydraulic units, in a partial region defined by the section along line  2 - 2  in  FIG. 1 ; 
           [0054]      FIG. 3  shows a detail illustration of the control plate that is arranged between two hydraulic units, in a partial region defined by the section along line  3 - 3  in  FIG. 1 ; 
           [0055]      FIG. 4  shows an illustration on a larger scale, of a bead between an intermediate layer and a hydraulic unit, in the not yet deformed condition; 
           [0056]      FIG. 5  shows an illustration similar to  FIG. 4 , of the bead in the deformed, installed condition; 
           [0057]      FIG. 6  shows a graph which represents a plasto-elastic behaviour of the beads on being deformed during installation, in its relationship with the sealing force generated by the beads; 
           [0058]      FIG. 7  shows an illustration similar to  FIG. 6 , with a correlation of the individual locations of deformation of the sealing beads in connection with an illustration of the sealing bead according to  FIG. 2 ; 
           [0059]      FIG. 8  shows an enlarged section of a sealing bead, similar to  FIG. 4 , of a second exemplary embodiment of a control plate according to the invention, with a complete elastomer coating of the sealing layer, and 
           [0060]      FIG. 9  shows an enlarged section through a sealing bead similar to  FIG. 4 , having an elastomer coating of the sealing layer in the form of strips. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0061]    A first exemplary embodiment, illustrated in  FIG. 1 , of a control plate  10  according to the invention for mounting between two hydraulic units, in particular between two hydraulic units of a transmission of a motor vehicle, includes an intermediate layer  12  which is designated  12  as a whole and extends flat, and which has a first flat side  14  and a second flat side  16  on each of which a metal sealing layer  22  and  24  respectively is placeable as a functional layer. 
         [0062]    In this arrangement, the intermediate layer is provided for example with a plurality of in particular differently shaped apertures  32  and  34  respectively, which allow a fluid to pass through the intermediate layer  22 . 
         [0063]    In a manner corresponding to the apertures  32  and  34 , the first sealing layer  22  is also provided with correspondingly arranged apertures  42  and  44 , and the second sealing layer  24  is also provided with apertures  52  and  54  respectively, corresponding to the apertures  32  and  34 , with the overall result that a fluid, preferably a hydraulic fluid, can pass through the entire control plate  10 , wherein this fluid then passes through the control plate  10  for example in the region of the apertures  42 ,  32  and  52 , or passes through the control plate  10  for example in the region of the apertures  44 ,  34  and  54 . 
         [0064]    As illustrated in  FIGS. 2 and 3 , a control plate  10  of this kind is arranged between two hydraulic units  62  and  64 , which in  FIGS. 2 and 3  are illustrated only by a partial region that adjoins a partial area of the control plate  10  and in each case lies between two connection screws  72  and  74  or  76  and  78 . 
         [0065]    So that the two hydraulic units  62  and  64  can be connected by means of the connection screws  72 ,  74 ,  76 ,  78 , both the intermediate layer  12  and the first sealing layer  22  and the second sealing layer  24  for this purpose have, in addition to the apertures  32  and  34 ,  42  and  44  and  52  and  54 , screw apertures  82 ,  84  and  86 ,  88  respectively in the intermediate plate  12 ,  92 ,  94  and  96 ,  98  respectively in the first sealing layer  22 , and  102 ,  104  and  106 ,  108  respectively in the second sealing layer  24 , all of which are flush with one another such that the connection screws  72  and  74  and  76  and  78  respectively can reach through these screw apertures  82  to  88 ,  92  to  98  and  102  to  108  in order to connect the hydraulic units  62  and  64  firmly to one another. 
         [0066]    In order to provide a seal on the one hand to the hydraulic units  62  and  64  and also to the intermediate layer  12  in the region of the apertures  32  and  34 ,  42  and  44  and  52  and  54 , the sealing layers  22  and  24  are provided with sealing beads  112  and  114  that run in a line around the apertures  32  and  34  in the first sealing layer  22 , and sealing beads  116  and  118  in the second sealing layer  124 , wherein—as illustrated in FIG.  2 —the sealing beads  112  creates a seal between the first flat side  14  of the intermediate layer  12  and an end face  122  of the first hydraulic unit  62  that faces the control plate  10 , and the sealing bead  114  creates a seal between the first flat side  14  of the intermediate layer  12  and the end face  122  of the first hydraulic unit  62 . 
         [0067]    Further, the sealing bead  116 , as illustrated in  FIG. 2 , creates a seal between the second flat side  16  of the intermediate layer  12  and an end face  124  of the second hydraulic unit  64  that faces the control plate  10 . 
         [0068]    Moreover, the sealing bead  114 , as illustrated in  FIG. 3 , creates a seal between the first flat side  14  of the intermediate layer  12  and the end face  122  of the first hydraulic unit  62 . 
         [0069]    In the same way, the sealing bead  118 , as illustrated in  FIG. 3 , creates a seal between the second flat side  16  of the intermediate layer  12  and the end face  124  of the second hydraulic unit  64 . 
         [0070]    In  FIGS. 2 and 3 , the deformation of the hydraulic units  62  and  64  between each pair of screws  72  and  74 , and  76  and  78 , that connect them is illustrated in exaggerated manner, wherein in each case in the region of the connection screws  72  and  74 , and  76  and  78 , the hydraulic units  62  and  64  act by means of their end faces  122  and  124  with maximum force on the sealing layer  22  and  24 , with the result that even a bead that runs in the region around the connection screws  72  and  74 , and  76  and  78 , such as the bead  112  and  116  respectively, is pressed more or less flat, while the end faces  122  and  124  of the hydraulic units  62  and  64  in the regions between the connection screws  72  and  74 , and  76  and  78 , move increasingly away from one another, with the result that the end faces  122  and  124  have the greatest spacing from one another in an approximately central region between each pair of connection screws  72  and  74 , and  76  and  78 . 
         [0071]    For this reason, the deformable sealing beads  112  and  114 , and  116  and  118 , are also required in order to achieve a reliable seal between the flat sides  14  and  16  of the intermediate layer  12  and the end faces  122  and  124  respectively of the hydraulic units  62  and  64  in the entire region between a pair of connection screws  72  and  74 , and  76  and  78 . 
         [0072]    The sealing beads  112  and  114 , and  116  and  118 , thus always ensure that there is a reliable seal between the hydraulic units  62  and  64  and the intermediate plate  12 , regardless of how far away the respective location of the seal is from the regions in which connection screws  72  and  74 , and  76  and  78 , pass through the control plate  10 . 
         [0073]    The sealing beads  112  and  114 , and  116  and  118 , could in theory be half beads. 
         [0074]    However, it is particularly advantageous if the sealing beads  112 ,  114 ,  116  and  118  are full beads, as illustrated in  FIG. 4  by the example of the sealing bead  114 . 
         [0075]    Each of the sealing beads  112 ,  114 ,  116  and  118  includes two bead feet  132  and  134  which adjoin a flat region  136  of the respective sealing layer  22  and  24  and form a bead foot kink  142  and  144  respectively, from which the respective bead rises by means of bead flanks  146  and  148  to a bead crest  152 , with the two bead flanks  146  and  148  merging with one another in the region of the bead crest  152  ( FIG. 4 ). 
         [0076]    A load on the respective sealing bead, for example the bead  114 , by the end face  122  of the first hydraulic unit  62  now results, in the region of the bead crest  152 , in a linear seal between the bead  114  and the end face  122  of the respective—for example the first—hydraulic unit  62  on the one hand, and on the other hand in a linear seal, in the region of the first flat side  14  of the intermediate layer  12 , in the region of the bead foot kinks  142  and  144 , wherein—as illustrated in FIG.  5 —the bead feet  132  and  134  are lifted slightly away from the first flat side  14  at their regions remote from the bead flanks  146  and  148 , with the result that only in the region of the bead foot kinks  142  and  144  is the linear seal with the first flat side  14  of the intermediate layer  12  produced, as illustrated in  FIG. 5 . 
         [0077]    As illustrated in  FIG. 4 , the sealing beads  112 ,  114 ,  116  and  118  have a bead height H in the undeformed condition which is in a range greater than or equal to 0.02 mm and less than or equal to 0.10 mm. 
         [0078]    Further, the sealing beads have a bead width B in the undeformed condition—according to FIG.  4 —which is in a range greater than or equal to 0.5 mm and less than or equal to 1.5 mm. 
         [0079]    In order to achieve optimum deformation characteristics in the sealing beads  112 ,  114 ,  116  and  118 , preferably the first sealing layer  22  and the second sealing layer  24  are made from a material which, even with a small deformation of the sealing beads, in particular in the central regions between each pair of connection screws  72  and  74  or  76  and  78 , still always has sufficient minimum sealing force, wherein the minimum sealing force is to be 5 N/mm 2 . 
         [0080]    The behaviour of the material of the sealing layers  22  and  24  is illustrated schematically in  FIG. 6 , wherein  FIG. 6  shows the sealing force KD over the height of the sealing beads HD in the deformed condition. 
         [0081]    If for example a sealing bead having the height H is deformed, for example to the height HD 1 , then the sealing force KD increases to the value KD 1 . 
         [0082]    In this arrangement, the deformation of the sealing bead from the height H in the undeformed condition to the height HD 1  in the deformed condition is a plasto-elastic deformation, which can be seen from the fact that, in  FIG. 6 , on rebounding again from the height HD 1  of the deformed sealing bead the height H is no longer achieved, but at most a height H′ that is smaller than the height H in the undeformed starting condition of the bead is achieved. 
         [0083]    If, from the undeformed starting condition according to  FIG. 4 , the sealing bead having the height H is deformed for example to the height HD 2 , which is smaller than the height HD 1 , and can then rebound, the resulting bead height H″ is again smaller than the starting height H and even smaller than the height H′. 
         [0084]    The sealing bead can also be brought to the height HD zero, that is to say be completely compressed, when the bead is in a region around one of the connection screws  72  or  74 , or  76  or  78 . In this case the force KD increases asymptotically towards infinity. 
         [0085]    A characteristic feature of the behaviour of the material of the sealing layers  22  and  24  is the sealing force KD which is achievable if the respective bead  112 ,  114 ,  116 ,  118  is deformed plasto-elastically to a height that is greater by a defined value than the height HD zero—that is to say the height HD when the sealing bead is compressed completely. 
         [0086]    If for example the sealing bead is deformed such that its height HD is still 50 μm above the bead height HD on complete compression, the sealing force should be in the range from 5 N/mm 2  to 20 N/mm 2 . 
         [0087]    If by contrast the sealing bead is compressed to a bead height HD which is 5 μm greater than the bead height HD on complete compression, the sealing force should be in the range from 40 N/mm 2  to 80 N/mm 2 . 
         [0088]    Further, the plasto-elastic deformation should be such that the sealing bead still has a rebound travel of 10 μm or more, preferably 15 μm or more, at the minimum sealing force, which should for example be around 5 N/mm 2  or more. 
         [0089]    Moreover, in addition high demands are to be made of the cycling stability of the material of the sealing layer  22 ,  24 . 
         [0090]    Thus, it is preferably provided for the respective sealing bead, after at least 1.5 million deflection cycles, still to have a rebound travel of 10 μm or more and the designated minimum sealing force. 
         [0091]      FIG. 7  once again illustrates the behaviour of the sealing force KD in relation to the height HD of the deformed sealing bead, and shows the relationship of these to the respective location of the seal between two connection screws  72  and  74 . 
         [0092]    Here, it is for example the case that, between the two connection screws  72  and  74 , approximately centrally between these, the sealing bead undergoes a deformation that results for example in a bead height HD of  50  pm above the bead height HD on complete compression, that is to say a theoretical bead height of zero. 
         [0093]    This is for example the bead height HD 1 , and at this bead height HD 1  there is for example a sealing force KD of approximately 10 N/mm 2 . If the sealing bead undergoes a more pronounced deformation, for example in the region close to the connection screw  72 , then the sealing force KD increases as the bead height decreases, wherein at a bead height HD of for example 5 pm above complete compression there is a sealing force of approximately 45 N/mm 2 . 
         [0094]    As regards the material thickness of the sealing layers  22  and  24 , more detailed statements have not yet been made. 
         [0095]    Thus, it is preferably provided for a material thickness MD of the sealing layers  22 ,  24  to be for example  150  μm or more. 
         [0096]    Preferably, a material thickness MD of the sealing layers  22 ,  24  of greater values is limited such that the material thickness is  300  μm or less. 
         [0097]    Similarly, as regards the materials for the sealing layers  22  and  24 , more detailed statements have not been made. 
         [0098]    Preferably, it is provided here for the sealing layers  22 ,  24  to be formed from carbon steel. 
         [0099]    Advantageously, the material of the sealing layers in this case has a modulus of elasticity of 500 N/mm 2  or less. 
         [0100]    As regards the formation of the intermediate layer  12 , in conjunction with the explanation above of the individual exemplary embodiments more detailed statements have not been made. 
         [0101]    Thus, it is for example provided for the intermediate layer to have a material thickness MZ of 800 μm or more, wherein the material thickness MZ is preferably limited to values of 2600 μm or less. 
         [0102]    Advantageously, the material from which the intermediate layer  12  is made is a material free from spring steel. 
         [0103]    For example, the intermediate layer  12  is made from steel, wherein the steel is in particular a carbon steel. 
         [0104]    As an alternative to forming the intermediate layer  12  from steel, it is also conceivable for the intermediate layer to be formed from aluminium or from AlMg 3  or from AlMg 4.5 Mn 0.7  or another aluminium alloy. 
         [0105]    As regards the modulus of elasticity of the intermediate layer  12 , it is favourable if the modulus of elasticity thereof is 700 N/mm 2  or less. 
         [0106]    An additional improvement in the sealing behaviour of the sealing beads  112 ,  114 ,  116 ,  118  can be achieved in a second exemplary embodiment of the control plate  10 ′, as illustrated for example in  FIG. 8 , in that the sealing beads, for example the sealing beads  114 ′, is provided in the region of its bead feet  132 ,  134  and thus also in the region of the bead foot kinks  142 ,  144  with an elastomer coating  152 ,  154  on its side facing the intermediate layer  12 , such that in this case the bead foot kinks  142  do not lie directly on the first flat side  14  of the intermediate layer  12  but only directly by way of the elastomer coating  152 ,  154 , which creates the possibility of improving the seal tightness with the first flat side  14  of the intermediate layer  12  in that the elastomer coatings  152  and  154  are each also capable of compensating for unevennesses in the surface. 
         [0107]    For example, in this case the elastomer coatings  152  and  154  have a thickness of 10 μm or more, wherein the thickness is favourably limited to 50 μm or less. 
         [0108]    Further, it is also preferably provided for the bead  114 ′ to be provided in the region of its bead crest  152  with an elastomer coating  166  which is arranged on the side of the bead crest  152  facing the end face  122  of the first hydraulic unit  62 , with the result that the bead crest  152  abuts by means of the elastomer coating  166  against the end face  122  of the first hydraulic unit  62 . 
         [0109]    In this arrangement, the elastomer coatings  162  and  164  and  166 , as illustrated in  FIG. 8 , may be elastomer coatings that cover the entire surface of the sealing layers  22  and  24 . 
         [0110]    As regards the remaining features and the operation of the second exemplary embodiment, the statements made in respect of the first exemplary embodiment are included by reference in their entirety, with the same elements in each case being provided with the same reference numerals. 
         [0111]    However, an alternative embodiment, explained in conjunction with a third exemplary embodiment of the control plate  10 ″, for example illustrated in  FIG. 9 , provides for the elastomer coatings  162 ,  164  and  166  to be formed by elastomer strips  172 ,  174  and  176  respectively, which run along the respective sealing bead, for example the sealing bead  114 ″, and may be applied to the respective side of the sealing layers  22  and  24 , for example by a printing method. 
         [0112]    As regards the remaining features and the operation of the third exemplary embodiment, the statements made in respect of the first exemplary embodiment are included by reference in their entirety, with the same elements in each case being provided with the same reference numerals. 
         [0113]    In the second or third exemplary embodiment, preferably elastomer coatings made from ACM, AEM, FPM, MBA are used.