Abstract:
A loose flange for connecting pipes, the flange having radially inwardly oriented and elastically deformable oblique surfaces. The clamping force capacity of the loose flange is improved as a result. A method for producing the loose flange is also disclosed.

Description:
FIELD OF THE INVENTION 
     The invention relates to a loose flange for connecting pipes at opposite pipe ends each provided with a collar, having an annular flange body which has a plurality of circumferentially distributed outer through-passage openings for fastening means. 
     The invention also relates to a method of producing a loose flange for a pipe connection, which has a plurality of circumferentially arranged outer through-passage openings. 
     BACKGROUND OF THE INVENTION 
     It is known, for the sealing connection of pipes, to use annular flanges with distributed through-passage openings in the region of pipe ends. The flanges are positioned as loose flanges in each case on an encircling collar of the pipe end and braced by means of bolts, guided through the circumferentially distributed through-passage openings, in conjunction with nuts positioned at free ends of said bolts, with the result that a fixed and sealing connection is produced between the ends of the two pipes. In this case, the loose flanges each butt against a pipe end on a side of the collar of the pipe end which is directed away from the opposite pipe ends. 
     Since the axial bracing forces prevail in the radially outward direction from the collars, it may be the case that the loose flanges move towards one another in an outer region and are thus deformed on a permanent basis. The flanges then have an undesired thrustoconical shaping. During the bracing of such a pipeline flange connection by the tightening of the bolts, the seal and the collars are compressed, the flanges are inverted and the screws are expanded. 
     In particular when loose flanges are used in pipelines made of polymer material, creep of the force-carrying elements, the collars, the seal and the loose flanges in particular, cannot be avoided, with the result that the sealing forces decrease. The clamping bolts or clamping screws, with their small amount of expansion, usually cannot compensate for the creep of the polymer-material parts. Although it would be possible for axially elastic loose flanges to compensate for the creep, such a desirably pliable flange would have the basic disadvantage mentioned above that, in the case of mechanical loading, the flange, in accordance with its low axial rigidity, would deform axially to a pronounced extent and/or be inverted. The effect of the associated conical deformation of the flanges is thereby intensified, which would result in the bearing surfaces for the screws tilting and thus in the screws being subjected to undesired eccentric loading. 
     SUMMARY OF THE INVENTION 
     It is thus an object of the present invention to develop a loose flange for a pipe connection so as to ensure defined axial resilient rigidity and deformability without the screw-bearing surfaces being inclined disadvantageously and the screws being subjected to eccentric loading as a result. 
     In order to achieve this object, the loose flange according to the invention, in conjunction with the preamble of Patent Claim 1, is characterized in that the flange body has an inner ring section and an outer ring section, a radially inner side of the inner ring section having, at least in certain regions, a circumferentially running groove of a predetermined depth. 
     The particular advantage of the loose flange according to the invention is that defined axial rigidity is ensured by the provision of a groove in an inner ring section of the flange body. The groove allows specific elastic deformability of the loose flange in a radially inner region of the same. The axial rigidity of the loose flange decreases from an outer region to an inner region of the same, with the result that an additional fastening means, namely a clamping bolt with a head or a screw, is always retained with predetermined surface-area abutment against the loose flange. 
     It is advantageously possible to prevent undesired “dishing” of the flange body or tilting of the outer ring section as a result of an excessively large tightening torque. Non-uniform bearing of the ends of the fastening means, in particular of a nut and of a screw head, on radial surfaces of the flange body may thus be reliably avoided. 
     According to a preferred embodiment of the loose flange, the groove is of V-shaped design and runs continuously in the circumferential direction. The contour of the groove-forming oblique surfaces may be of planar or curved design here. The shape of the groove depends on the desired deformation characteristics of the inner ring section. The shape of the groove depends on the geometry of the loose flange and/or on the predetermined desired clamping force of the flange connection. 
     In conjunction with a radial surface for the flange parts of the flange body which is directed towards the collar, the groove is shaped such that, with the flange being subjected to nominal loading, the establishing inversion or tilting of the outer ring section is compensated for, the radial surface of the flange body butting against the collar over its surface area, with a relatively low level of surface pressure being formed in the process. 
     According to a development of the loose flange, circumferentially distributed and radially inwardly projecting protuberances are arranged on an inner side of the inner ring section, said protuberances retaining the loose flange with clamping action at the pipe end. It is thus possible for the loose flange to be fixed on the pipe for installation purposes. 
     According to a development of the loose flange, on a side located opposite the oblique surface, the flange parts have radial surfaces with a prism-like surface structure which, when clamping screws are tightened, deform and level out such that when the predetermined tightening torque of the clamping screws is reached, the washers have reached their definitive position and it is no longer possible for them to be lowered any further. It is thus possible to see when the predetermined tightening torque of each screw has been reached by the position of the respective washer. Furthermore, the visibly deformed geometry gives an indication of prior use. 
     According to a development of the loose flange, circumferentially distributed clamping noses are arranged on an inner side of the outer through-passage openings, with the result that clamping screws are retained with clamping action in the through-passage openings. This facilitates, in particular, the vertical installation of the flange connection. These clamping noses, and also the protuberances on the inner side of the inner ring section, preferably consist of an elastic material, namely polymer material. If the loose flanges themselves are produced from polymer material, then the protuberances and/or clamping noses may simply be integrally formed thereon. 
     It is also an object of the present invention to specify a method of producing a loose flange for a pipe connection, with the result that a flange body with a clamping-force capacity which is stable over a long period of time is provided in a manner which is straightforward in production terms. 
     In order to achieve this object, the method according to the invention, in conjunction with the preamble of Patent Claim 18, is characterized in that two identical annular flange parts are formed separately by injection moulding or casting, with a radially inwardly oriented flattened portion being formed in the process, and in that, in a second step, the flange parts are connected to one another in an outer ring section, with a groove produced by the mutually facing flattened portions being formed in the process. 
     The particular advantage of the method according to the invention is the simplicity of production. Preferably identical flange halves are formed separately and then welded to one another with surface-area abutment of radial surfaces of an outer region section. The flange parts or flange halves are thus of straightforward geometrical shape, with the result that they can be produced with a relatively high throughput. 
     According to a preferred embodiment of the method according to the invention, the shaped parts are produced from a polymer material by injection moulding, it being possible for the fixed connection between the same to be easily produced by welding. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention are explained in more detail hereinbelow with reference to the drawings, in which: 
     FIG. 1 shows a plan view of a first flange part, 
     FIG. 2 shows a cross section through the first flange part along line II—II in FIG. 1, 
     FIG. 3 shows a plan view of a second flange part, 
     FIG. 4 shows a cross section through a flange body, formed by the first and second flange parts, along line II—II in FIG. 1, 
     FIG. 5 shows an enlarged part of a detail from FIG. 4, 
     FIG. 6 a  shows a cross section of part of a flange body, provided with a sensor device, in a relieved position, and 
     FIG. 6 b  shows a cross section of part of the flange body according to FIG. 6 a  in a clamping position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The loose flange described hereinbelow serves for connecting pipe ends (not illustrated) each with a collar which butt against one another over their surface area directly or in a state in which they are separated by a seal. Each collar is assigned an annular loose flange, the internal diameter of the loose flange being smaller than the external diameter of the collar. The two loose flanges are aligned coaxially with one another and are braced in the axial direction by fastening means. 
     FIG. 1 illustrates a first flange part  1 , which is joined together with a second flange part  2 , illustrated in FIG. 3, to form a flange body  3 . The flange body  3  is of annular design and serves as a loose flange for butting against the collar. A central through-passage opening  4  has a diameter which is greater than the diameter of the pipes which are to be connected, on the one hand, and is smaller than the external diameter of the collar, on the other hand. The flange body  3  has circumferentially distributed outer through-passage openings  5  into which it is possible to fit in each case one bolt (not illustrated) with a head as fastening means. The bolts are fitted through the outer through-passage openings  5  of a first flange body  3  and are of such a length that the free end of the bolt engages through the corresponding through-passage opening  5  of the identical second flange body  3 . Thereafter, the bolt may be brought into engagement with a nut at the free shank end, with the result that the flange bodies positioned on the collars in each case can be braced in relation to one another. 
     The flange body  3  has an outer ring section  7  and an inner ring section  8 , the outer through-passage openings  5  being arranged essentially in the outer ring section  7 . The flange parts  1  and  2  are fixed to one another in the outer ring section  7 . In the inner ring section  8 , which is adjacent in the radially inward direction, the flange parts  1  and  2  are designed to be spaced apart from one another in a relieved starting position, with the circumferentially running groove  9  being formed in the process. The groove  9  is of cross-sectionally V-shaped design and extends continuously in the circumferential direction on an inner side  10  of the flange body  3 . 
     Alternatively, it is also possible for the groove  9  to be of interrupted design, the groove being arranged at least in a circle cutout of the flange body  3  in which there are no outer through-passage openings  5 . 
     By virtue of the groove  9 , the flange parts  1 ,  2  each form, in the inner ring section  8 , an oblique surface  11  which is of elastically deformable design. The groove  9  is a rotationally symmetrical design and has a foot section  12  which runs along a root circle  6 , the root circle  6  intersecting the outer through-passage openings  5 . Alternatively, it is also possible for the root circle  6  to have a smaller radius, with the result that it is spaced apart radially from the outer through-passage openings  5 . The size of the radius of the root circle  6  depends on the material property of the flange body  3  and/or the desired resilience of the oblique surface  11 . As the radius of the root circle  6  increases, the resilience of the oblique surface  11  decreases, which reduces the prestressing-force compensation for setting the flange connection. 
     The invention advantageously makes it possible, by virtue of the depth of the groove  9 , the thickness of the flange body  3  and the material properties thereof being predetermined, to set a predefined clamping force for the oblique surface  11 , the oblique surface  11  compensating for a considerable amount of the clamping-force losses once it has been compressed in a clamping position of the flange body  3  in a spring-like manner when the flange connection is set. 
     The root circle  6 , at the same time, forms a pivoting axis or a pivoting circle about which the oblique surface  11  can be pivoted. The groove  9  has an opening angle a which is located in a range of between 2° and 20°. The groove  9  preferably has an opening angle of 8°. A diameter d F  of the root circle  6  is smaller than a hole-circle diameter d M  of the flange parts  1 ,  2  and/or of the flange body  3 . The diameter d F  is preferably designed to be smaller, by the diameter of the outer through-passage opening  5 , than the diameter d M . 
     The flange parts  1 ,  2  are of the same thickness, with the result that the flange body  3  is of essentially symmetrical design in relation to a centre plane ME. 
     According to the invention, it is also possible for the groove  9  to be used for signalling a predetermined clamping position of the flange body  3 . The width and the depth of the groove  9  may be coordinated with a predetermined tightening torque, by means of which the bolt is intended to be brought into engagement with the nut. The envisaged clamping position of the flange body  3  is signalled to the fitter in that border edges  13  of the opposite oblique surface  11  come into direct abutment. 
     A further criterion which may be used alternatively or in addition for determining when the envisaged clamping position is reached is constituted by the fact that an outer radial surface  14  of the oblique surface  11  has a prism-like surface structure  16  in certain regions, preferably in the region of a recess  15  for the screw head and/or the nut. The envisaged clamping position is reached in that, following abutment of the screw head and/or of the nut against the recess  15 , which widens the outer through-passage opening  5  on the end side, and application of a clamping force, the prism-like elevations  16  are deformed plastically such that a planar radial surface  14  is formed. The now-reached clamping position corresponds to the predetermined tightening torque of the bolt. 
     The surface structure  16  may be of uniform or irregular design. The essential factor is that the resulting recesses, on average, fill a volume which corresponds to the volume of the rest of the radial regions  17  of the recess  15 . The prism-like surface structure  16  is preferably assigned to a radially inwardly oriented radial region  17  of the recess  15 . 
     The outer radial surfaces  14  are designed such that they diverge in the radially inwardly oriented direction in the initial state, with the result that, following engagement of the clamping bolt and displacement of the same into the clamping position, the head and the nut butt directly, with coaxial orientation, against the radial surfaces  14 . 
     In order to facilitate overhead installation, the outer through-passage openings  5  have, in an edge region in each case, circumferentially offset clamping noses  18 , on which the bolt is retained with clamping action following insertion into the through-passage opening  5 . 
     In order to detect a decreasing clamping force once the flange connection has been set, one embodiment of the loose flange provides a sensor device  19 , which has a pressure sensor  20  which is mounted in a mount  21  which projects essentially axially from an outer radial surface  14  of the oblique surfaces  11 . The mount  21  is preferably integrally formed on the radial surface  14  of the oblique surfaces  11 . The oblique surface  11 , containing the mount  21 , has a through-passage bore  22  through which a sensor bolt  23 , which is connected integrally to the opposite oblique surfaces  11 , can engage. Depending on the opening angle of the oblique surface  11 , the pressure sensor  20  is actuated with abutment of the end surface of the sensor bolt  23 . If the clamping force of the flange body  3  decreases, which is associated with a spreading action of the oblique surface  11 , the sensor bolt  23  is displaced to an extent. If the changing extent exceeds a predetermined desired length outside the tolerance range, this triggers a signal, in the pressure sensor  20 , which, following evaluation in an evaluation unit (not illustrated), serves for signalling a residual sealing force outside the tolerance range. 
     In order to produce the flange body  3 , the flange parts  1  and  2  are produced separately from polymer material by injection moulding. The flange parts  1 ,  2  may consist of a thermoplastic or a preferably glass-fibre-reinforced thermoset polymer material. Alternatively, it is also possible for the flange parts  1  and  2  to consist of metal, in particular sheet metal. 
     In a following step, the two flange parts  1  and  2  are fixed to one another in the outer ring section  7  by welding. For centred positioning of the flange parts  1 ,  2  and/or for aligned arrangement of the outer through-passage openings  5  of the same, the flange parts  1 ,  2  have axially running centring bolts  24  and centring bores  25  in the inner ring section  8 . 
     In order to form the later groove  9 , the flange parts  1 ,  2  each have flattened portions  26  in an inner ring section  8 . Since the flange parts  1 ,  2  are of identical design, they may be produced using a single tool. This reduces the production costs and increases the throughput. 
     In order to facilitate overhead installation, the inner side  10  of the inner ring section  8  has circumferentially distributed protuberances  27 , which project radially inwards and serve for securing the flange body  3  with clamping action at a pipe end. 
     Alternatively, it is also possible for the flange body  3  to be produced in one piece.