Abstract:
A clamping ring for pipe couplings, in particular for the axial tension-proof connection of smooth-ended pipes is supported on a housing and on the pipe to be connected, where the clamping ring has teeth which can be caused to engage the pipe, the total number of teeth being divided into repeating groups of teeth, at least one group having at least two teeth differing from one another.

Description:
BACKGROUND  
       [0001]     The invention relates to a clamping ring for pipe couplings, in particular for the axially tension-proof connection of smooth-ended, metallic pipes, the pipe couplings having a housing which can be clamped around the pipes to be connected and having at least one sealing element preferably consisting of an elastomer and, in the clamped state of the pipe coupling, at least one clamping ring being supported axially and/or radially on the one hand on the housing and on the other hand on one pipe end, the clamping ring having on its inside teeth which can be made to engage the pipe.  
         [0002]     The penetration of the teeth into the pipe wall results in an interlocking connection which permits secure clamping of the pipes to be connected in the pipe coupling. In the pipes used today in pipeline construction, different pipe materials and pipe wall thicknesses are used depending on the application. For example, in lightweight construction for aircraft or other vehicles, aluminium alloys and other light metals are used, whereas, for example, very hard titanium alloys are used in the case of higher requirements, also regarding corrosion. Particularly in the case of such pipes of titanium alloys or chromium nickel steels, engagement of the clamping rings known to date is problematic in some cases.  
         [0003]     EP 211158 A1 discloses a pipe coupling whose clamping rings have a concave, in particular V-shaped, profile on their end face on the engaging side. The individual teeth are preferably produced by punching. The mode of action of this V-shaped profile consists in the fact that one edge of the end face forms a cutting edge which penetrates into the pipe surface on clamping, while the second edge forms a type of depth stop which limits the penetration of the cutting edge into the pipe surface.  
         [0004]     EP 940618 A1 discloses a further pipe coupling whose clamping rings have an asymmetric profile. The asymmetric profile results in the formation of an acute wedge angle which is intended to improve the penetration of the clamping ring into the pipe surface. However, in contrast to the subject of EP 211158 A1, the penetration of the clamping ring into the pipe surface is not limited.  
         [0005]     EP 931966 A1 starts from a prior art according to EP 940618 A1, an indentation which is intended to lead to an improvement in the material or the cutting geometry being made laterally in all teeth.  
         [0006]     Common to all three EP-A1 documents mentioned is that all teeth over the entire circumference of the clamping ring are identically formed.  
         [0007]     Particularly for extreme materials, i.e. particularly soft or particularly hard materials, problems may arise in the case of the known clamping rings in that the clamping ring penetrates either too strongly or not at all into the pipe surface.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with one or more aspects of the invention, a clamping ring is provided for pipe couplings which permits optimal adaptation to the respective pipe material without substantial additional effort.  
         [0009]     According to the invention, this is achieved if the total number of teeth is divided into repeating groups of teeth, at least one group having at least two teeth differing from one another, or if at least two groups of teeth which differ from one another are present.  
         [0010]     As a result of the different formation of teeth, these engage the pipe material completely, only partly or not at all. Thus, for example for hard materials, the number of teeth engaging the pipe can be reduced compared with the prior art to date. This leads to higher loads on the engaging teeth, both on the tooth and on the pipe material, so that these teeth can better penetrate in the case of hard pipe surfaces and do not slip on the pipe surface.  
         [0011]     In an expedient embodiment, at least one group consists of X teeth, the quantity X being between 2 and 10, between 3 and 6 or between 4 and 5. Such groups of teeth may be formed, for example, by means of a punching tool, in which a plurality of teeth are simultaneously punched out of the profiled strip material. The number of teeth per group may also differ in the case of different coupling sizes.  
         [0012]     In an advantageous solution, the groups of teeth consist of a number n of A teeth and a number m of B teeth, the clamping edge being slightly recessed in the radial and/or axial direction in the case of the B teeth relative to the A teeth. The A teeth are therefore those which first engage the pipe wall on clamping the pipe coupling. The B teeth recessed relative to the A teeth may engage the pipe surface later or not at all. These B teeth may also be blunt and/or perform the function of a stop limiting the depth of penetration. The sum n+m gives the quantity X of the total number of teeth per group.  
         [0013]     The A teeth expediently have a cutting edge on their end face. This cutting edge may run in the circumferential direction of the pipe or, as disclosed, for example, in EP-A1-211158, may be at least partly angled. The first variant results in a linear engagement of the clamping ring with the pipe surface. In the second variant, the engagement of the individual teeth tends to be point-like.  
         [0014]     In an advantageous embodiment, the cutting edge is asymmetrical. By means of the asymmetrical cutting form, relatively acute wedge angles can be formed and hence the penetration of the teeth in the pipe material can be facilitated.  
         [0015]     Particularly in the case of soft pipe materials, the penetration of the teeth should be limited in order to avoid excessive reduction of the pipe wall thickness. It is therefore expedient if the A teeth have a concave, preferably V-shaped profile on their end face.  
         [0016]     The number of teeth can in principle be chosen as desired. However, it is advantageous if the number n is at least 1 and if n is preferably less than the number m. Thus, the number of projecting A teeth is in the minority compared with the B teeth recessed in the axial and/or radial direction. This means that the clamping via a reduced number of teeth is distributed over the circumference.  
         [0017]     In an expedient embodiment, A and B teeth are arranged so as to be uniformly distributed within a group or over the entire circumference. Thus, the clamping forces are also uniformly distributed over the circumference or within a group.  
         [0018]     In a further advantageous embodiment, the A teeth and the B teeth are arranged so as to be asymmetrically distributed within a group or over the entire circumference. However, in the asymmetrical arrangement, for example, identically formed teeth may be located adjacent to one another and the load thus distributed over a plurality of teeth.  
         [0019]     It is expedient if the B teeth are compressed by a material-forming process or are processed by a material-abrading process. The compression of the teeth can be produced, for example, by a cold forming process. As a result, the formed material can, for example, simultaneously serve as a stop limiting the depth of penetration. A suitable material-abrading process is, for example, grinding or milling. Both processes can, for example, also be effected in combination with a punching process.  
         [0020]     In an advantageous embodiment, the A teeth are stretched by a forming process or are formed by material application. The stretching of the teeth can be effected, for example, by cold working in a pressing process. Material application can be carried out, for example, by one or more welding processes.  
         [0021]     On clamping of the pipe coupling, the clamping ring is reduced in circumference and hence its internal diameter is reduced. The teeth slide over the circumference of the pipe surface. In order to permit this movement, it is advantageous if the lateral flanks of the teeth are bevelled. This avoids the formation of sharp corners which can hook into the pipe surface on clamping of the pipe coupling, making the equilibration over the circumference of the clamping ring difficult or impossible. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The invention is to be explained in more detail below with reference to the drawings representing them by way of example. The list of reference numerals and  FIG. 1  to  FIG. 12 , together with the subjects described or protected in the Claims, are an integral part of the disclosure of this Application.  
         [0023]     The figures are described in relation to one another and as a whole. Identical reference numerals denote identical components, and reference numerals with different indices indicate components having the same function.  
         [0024]      FIG. 1  shows a pipe coupling having a clamping ring according to the invention, partly in longitudinal section;  
         [0025]      FIG. 2  shows an end view of the pipe coupling shown in  FIG. 1 ;  
         [0026]      FIG. 3  shows a first embodiment of the clamping ring according to the invention;  
         [0027]      FIG. 4  shows a variant of the clamping ring shown in  FIG. 3 ;  
         [0028]      FIG. 5  shows a variant of the clamping ring shown;  
         [0029]      FIG. 5  shows a variant of the clamping ring;  
         [0030]      FIG. 6  shows a further variant of the clamping ring;  
         [0031]      FIG. 7  shows a section of a variant of the pipe coupling shown in  FIG. 1 ;  
         [0032]      FIG. 8  shows a further section through the pipe coupling shown in  FIG. 7 ;  
         [0033]      FIG. 9  shows a further section of a variant of the pipe coupling shown in  FIG. 1 ;  
         [0034]      FIG. 10  shows a further section through the pipe coupling shown in  FIG. 9 ;  
         [0035]      FIG. 11  shows the section of a clamping ring according to the invention, as a view, and  
         [0036]      FIG. 12  shows a variant of the clamping ring shown in  FIG. 11 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]     The pipe coupling shown in  FIGS. 1 and 2  has a substantially cylindrical housing  1  provided with a longitudinal slot  2 , the free ends of the housing  1  being in the form of bent-over straps  3   a ,  3   b . Cylindrical locking pins  4  are arranged in the straps  3   a ,  3   b . The housing  1  can be radially clamped by means of locking bolts  5  which pass through the locking pins  4 , it being possible for the longitudinal slot  2  to become narrower. A sealing sleeve  6  preferably consisting of an elastomer and intended for sealing the pipes to be connected is arranged in the housing  1 . The sealing sleeve  6  has elastically deformable sealing lips  7   a ,  7   b  for this purpose. Present at both ends of the sealing sleeve  6  are clamping rings  8 , which are preferably installed at about 45° to the longitudinal axis of the pipe coupling and are supported on the housing  1  in the corner of the side walls of the housing  1  which are directed radially inwards.  
         [0038]     As shown in particular in  FIG. 2 , the clamping rings  8  are provided with teeth  9   a ,  9   b  on their free end face. The teeth  9   a ,  9   b  are differently formed, the teeth  9   a  projecting radially inwards beyond the teeth  9   b .  FIG. 1  shows two pipes  10 ,  11  to be connected to one another. In the region of the pipe, the pipe coupling is shown in the unclamped state. The sealing lip  7   a  and the clamping ring  8   a  do not as yet touch the surface of the pipe  10 . In the clamped state of the pipe coupling, shown in the right half, the sealing lip  7   b  has been placed so as to provide a seal against the surface of the pipe  11 , and the teeth  9   a  of the clamping ring  8   b  have partly penetrated into the surface of the pipe  11 .  
         [0039]      FIG. 3  to  FIG. 6  show different embodiments of clamping rings.  
         [0040]     The clamping ring  12  shown in  FIG. 3  has, on its inside, groups of in each case two differently formed teeth. The teeth  13  designated as A teeth project radially inwards beyond the teeth  14  designated as B teeth. In the clamping ring  12 , the A teeth  13  and the B teeth  14  are arranged alternately side by side. In other words, the clamping ring  12  has approximately the same number of A teeth  13  and B teeth. In  FIG. 3 , the tooth width is denoted by “a” and the width of the gaps present between the individual teeth is denoted by “b”.  
         [0041]     Assuming that, in the clamped state of the pipe coupling, the clamping ring  12  extends over the entire circumference, the general formula for the bearing circumferential fraction CF is applicable:  
         CF   ⁡     [   %   ]       =         (     n     n   +   m       )     ·     (     a     a   +   b       )     ·   100     ⁢   %         
 
         [0042]     Since the number n of A teeth and the number m of B teeth are each equal to  1  in the example of the clamping ring  12  shown in  FIG. 3 , the bearing circumferential fraction (CF) is therefore:  
           (     1     1   +   1       )     ⁢     (     a     a   +   b       )       =       1   2     ⁢     (     a     a   +   b       )           
 
 i.e. the bearing circumferential fraction in this example is only half that of conventional clamping rings having teeth formed uniformly over the entire circumference. 
 
         [0044]     In the case of the clamping ring  15  shown in  FIG. 4 , a repeating group consists in each case of one A tooth  16  and two B teeth  17  recessed relative to said A tooth. Over the entire circumference, the clamping ring  15  thus has one third A teeth  16  and two thirds B teeth. The bearing circumferential fraction is reduced to one third of that of conventional clamping rings. Such clamping rings  15  are preferably used for relatively hard pipe materials.  
         [0045]     The clamping rings  18  and  21  shown in  FIGS. 5 and 6  differ from the embodiments according to  FIGS. 3 and 4  through the proportions of A teeth  19  and  22  and B teeth  20  and  23 .  
         [0046]     In the case of the clamping ring shown in  FIG. 5 , the bearing circumferential fraction CF is:  
             (     2     2   +   1       )     ⁢     (     a     a   +   b       )       =       2   3     ⁢     (     a     a   +   b       )         ,       
 
 i.e. the bearing circumferential fraction in this example is ⅔ of that of conventional clamping rings having teeth formed uniformly over the entire circumference. 
 
         [0048]     In the case of the clamping ring  21  shown in  FIG. 6 , the bearing fraction is, considered purely mathematically, equal to that in the case of the clamping ring  12  in  FIG. 3 . However, the distribution differs in that two A teeth  22  and two B teeth  23  are always arranged side by side. This can result in more advantageous engagement conditions for certain pipe materials.  
         [0049]     Common to these clamping rings is the fact that they have groups repeating over the circumference and comprising differently formed teeth. However, it is also possible for a plurality of different groups of teeth to be arranged so as to be distributed over the circumference. The bearing circumferential fraction can thus be reduced stepwise or digitally and adapted to the respective pipe material through the choice of the number of A teeth and B teeth per group.  
         [0050]     Those sections of a pipe coupling which are shown in  FIGS. 7 and 8  have a clamping ring  24  clamped between the housing  1  and the pipe  10 . The clamping ring  24  has a concave, approximately V-shaped profile on its end face and is provided with sharp A teeth  25  and B teeth  26  recessed, for example, by cold forming. The B teeth  26  can serve as a stop limiting the penetration of the A teeth  25  into the pipe surface of the pipe  10 .  
         [0051]     The embodiment shown in  FIGS. 9 and 10  differs from the embodiment shown in  FIGS. 7 and 8  in the cross-section of the clamping ring  27 . The clamping ring  27  has an asymmetrical profile. Blade-like A teeth  28  are formed thereby. The B teeth  29  recessed relative to the A teeth  28  can be produced, for example, by a grinding process. The B teeth  29  can likewise limit the penetration of the A teeth  28  into the surface of the pipe  11 .  
         [0052]      FIGS. 11 and 12  show the unshaped, strip-like profile of clamping rings  24  and  27 , the A teeth  25  and  28  and the B teeth  26  and  29  being produced by recesses  30  and  31 . The recesses  31  and  32  are formed in such a way that side walls make acute angles a and B. This prevents the corners of the recesses  31  and  32  from hanging in or hooking in at the pipe surface, when the pipe coupling is clamped, with the result that equilibration of the clamping ring over the entire pipe circumference is hindered or rendered impossible.  
         [heading-0053]     List of Reference Numerals 
         [none]    
       
           1  Housing  
           2  Longitudinal slot  
           3   a, b  Strap  
           4  Locking pin  
           5  Locking bolt  
           6  Sealing sleeve  
           7   a, b  Sealing lip  
           8   a, b  Clamping ring  
           9   a, b  Teeth  
           10  Pipe  
           11  Pipe  
           12  Clamping ring  
           13  A tooth  
           14  B tooth  
           15  Clamping ring  
           16  A tooth  
           17  B tooth  
           18  Clamping ring  
           19  A tooth  
           20  B tooth  
           21  Clamping ring  
           22  A tooth  
           23  B tooth  
           24  Clamping ring  
           25  A tooth  
           26  B tooth  
           27  Clamping ring  
           28  A tooth  
           29  B tooth  
           30  Recess  
           31  Recess 
       
     
         [0085]     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.