Abstract:
A pipe section provided with a socket end part for accommodating a spigot end part of a second pipe section, the spigot end part having a sealing ring and the socket end part configured with an obliquely tapered part having areas of varying dimension for deforming the sealing ring to differing extent along the circumference of the sealing ring when the socket end part engages the spigot end part.

Description:
BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The invention relates to a pipe section provided with a socket end part which is intended for accommodating a spigot end part of a second pipe section, the exterior of the spigot end part being provided with a sealing ring and the interior of the socket end part, viewed from the end edge, having a part obliquely tapering towards the centre axis of the socket end part for deforming the sealing ring when the spigot end part and an adjoining cylindrical part are inserted into the socket end part, the part of the socket end part obliquely tapering towards the centre axis having at least two areas distributed regularly over the circumference in which the angle of the obliquely tapering part varies relative to the centre axis of the socket end part in the circumferential direction, in such a manner that in each area, along the sides of the area, the obliquely tapering part, viewed in the circumferential direction, is at a first angle relative to the centre axis of the socket end part and, in the centre of the area, is at least partly at a second angle relative to the centre axis of the socket end part which is smaller than the first angle. 
   A pipe section of this type is known from U.S. Pat. No. 3,831,954, in particular FIGS. 8 and 10. 
   Well-known pipe sections, in which the obliquely tapering part extends parallel to a plane at right angles to the centre axis of the pipe section, have the disadvantage that when a spigot end part which is provided with a sealing ring is inserted into the socket end part, the insertion force is in many cases considered to be undesirably great. The great insertion force results from the fact that when the spigot end part is inserted, the sealing ring has to be deformed over the entire circumference at the same time, which generally involves having to reduce the sealing ring&#39;s outer diameter. U.S. Pat. No. 3,831,954 (FIG. 8-10) proposes two solutions to this problem. With the first solution (FIG. 9), the axial position of the obliquely tapering part varies over the circumference of the socket end part. The obliquely tapering part is corrugated in the axial direction. With the second solution (FIG. 10), the pitch varies and thus also the length of the obliquely tapering part over the circumference of the socket end part. 
   BRIEF SUMMARY OF THE INVENTION 
   It is an object of the invention to provide an improved pipe section of the type mentioned in the introduction. 
   This object is achieved according to the invention with a pipe section of the type mentioned in the introduction by the fact that, between the sides and the centre of each area, the obliquely tapering part is at the first angle in a part which is situated on the side of the end edge of the socket end part and at the second angle in an adjoining part on the side of the cylindrical part of the socket end part relative to the centre axis, the axial length of the part at the second angle gradually increasing from the sides towards the centre of the area. 
   Through the measures according to the invention, the insertion force required for inserting the spigot end part into the socket end part is reduced further. In addition, the pipe section can be produced using a simpler die than in the case of the pipe sections with socket end parts according to FIG. 8-10 of U.S. Pat. No. 3,831,954. 
   Preferred embodiments of the pipe section according to the invention are defined in the subclaims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in more detail below by way of a number of exemplary embodiments with reference to the drawing, in which: 
       FIG. 1  shows a longitudinal view of a specific embodiment of a socket end part of a pipe section according to the invention and an associated spigot end part of a second pipe section; 
       FIG. 2  shows a head end view of the socket end part from  FIG. 1 , viewed in the direction of the arrow II in  FIG. 1 ; 
       FIG. 3  shows the socket end part from  FIG. 1  in a longitudinal view along the line III-III in  FIG. 2 ; 
       FIG. 4 to 7  inclusive show an end part of the wall of the socket end part from  FIG. 1  in longitudinal sections along the lines IV-IV, V-V, VI-VI and VII-VII in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a longitudinal view of a specific embodiment of a socket end part  1  of a first pipe section according to the invention and an associated spigot end part  2  which has to be inserted into the socket end part  1  in order to form a pipe connection between the first pipe section and the second pipe section. 
   In the embodiment shown, the spigot end part  2  is an end part of a pipe section with a relatively thin wall  3  which is provided on the outside with circumferential ribs  4 . A sealing ring  5  is arranged between two ribs  4 . However, the spigot end part may also have another shape, for example be designed to have a thick wall, in which case the sealing ring is disposed in a circumferential groove arranged on the exterior in the wall. 
   The interior of the socket end part  1  has, viewed from the end edge  11 , a part  13  obliquely tapering towards the centre axis  12  of the socket end part  1  in order to reduce the outer diameter of the sealing ring  5  when the spigot end part  2  and an adjoining cylindrical part  14  are inserted into the socket end part  1 . 
   The obliquely tapering part  13  of the socket end part  1  has at least two areas  15  distributed regularly over the circumference in which the angle of the obliquely tapering part  13  varies relative to the centre axis  12  of the socket end part  1  in the circumferential direction. In each area  15 , along the sides  16  and  17  of the area  15 , the obliquely tapering part  13 , viewed in the circumferential direction, is at a first angle α 1  relative to the centre axis  12  of the socket end part  1  (see  FIG. 4 ) and, in the centre  18  of the area  15 , is at least partly at a second angle α 2  relative to the centre axis  12  of the socket end part  1  which is smaller than the first angle α 1  (see  FIG. 7 ). In the embodiment shown, the obliquely tapering part is at the second angle α 2  relative to the centre axis  12  of the socket end part  1  in the centre  18  of each area  15 . 
   Between the sides  16  and  17  and the centre  18  of each area  15 , the obliquely tapering part is in a part  19  situated on the side of the end edge  11  of the socket end part  1  at the first angle α 1  and in an adjoining part  20  situated at the side of the cylindrical part  14  of the socket end part  1  at the second angle α 2  relative to the centre axis  12  (see  FIGS. 5 and 6 ). In this case, the axial length l of the part  20  which is at the second angle α 2  gradually increases from the sides  16  and  17  towards the centre  18  of the area  15 . 
   Between the areas  15  with a varying angle, there are areas  21  in which the obliquely tapering part is at the first angle α 1  relative to the centre axis  12 . 
   The following applies with regard to the dimensions of the areas  15  of the socket end part  1  (see  FIG. 2 ). With an internal diameter D 1  of the cylindrical part  14  of the socket end part  1  and an internal diameter D 2  of the obliquely tapering part  13  at the location of the end edge  11  with the configuration of the angles α 1  and α 2  described above, the part which is at an angle α 2  at the location of the end edge  11  has a radius R 1 . The radius R 1  starts from a point which is at a distance R 22  from the centre axis  12  of the socket end part. In this case, the following applies: 
   R 1 =(0.25 to 0.5)D 1 , preferably (0.3 to 0.35)D 1 , at the end edge  11  of the socket end part, 
   α 2 =(0.3 to 0.5) α1, 
   R 1 +R 2 =0.5D 2 , 
   the areas  21  which are at an angle α 1  should occupy less than 30% of the circumference of the socket end part (this obviously depends on the choice for R 1 ), 
   preferably, the transition from the obliquely tapering part  13  to the cylindrical part  14  is provided with a rounding having a radius of 3 to 10 mm. 
   Using the above-described socket end part results in the sealing ring  5  being deformed in sections when the spigot end part  2  is being inserted and, in the embodiment shown, the outer diameter of the sealing ring  5  is reduced in sections, as a result of which the associated required force can be applied distributed over time and the required insertion force can be reduced. 
   The socket end part  1  may be of a different design to that described above while still remaining within the scope of the attached claims.