Production of pipe couplings

Abstract: A method of producing a coupling for pipes, includes the steps of subjecting a predetermined length of desired cross sectional profile to a bending process to form an items of semi-circular side view, forming or pre-forming bent over ends of predetermined size; and then coining these ends to lie in the same horizontal plane as the horizontal diameter of the item, the coining operation being accompanied by forcing excess material into the zone between the semi-circular portion and the bent-over ends.

Description: FIELD OF THE INVENTION This invention relates to metal couplings for shoulder ended and grooved-ended pipes in particular and to pipes in general. BACKGROUND OF THE INVENTION The couplings for such pipes are cast in two portions which are linked by means of nuts and bolts. The casting process is not ideal and is often subject to inaccuracies and is expensive. It is an object of the present invention to provide a method of producing couplings which is not only more accurate and easy but is also less expensive than prior art methods. JP-A-6 132 741 discloses a method of forming a semi-circular item with bent-over ends formed by pressure forming. This method could be used with a metallic material. However, the item is used as an inner lining of composite pipe. THE INVENTION According to the invention a method for producing a metal coupling for pipes including the steps of subjecting a predetermined length of desired cross sectional profile to a bending process in a mould having a semi-circular portion to form a symmetrical item comprising a semi-circular portion continuated by formed or pre-formed bent-over ends of a predetermined size; characterised in that the bent over ends are coined to lie in the same horizontal plane as the horizontal diameter of the item and at the same time to force excess material from the bent-over ends into a zone in the mould between the semi-circular portion of the mould and the bent over ends, the zone corresponding to a gusset for the coupling. In one form of the invention the profiled length is first subjected to a cold bending process to form the bent-over ends of predetermined size. The item which results can then be subjected to hot bending process to form the semi-circular item with continuated bent-over ends and the latter are coined to lie in the same horizontal plane as the horizontal diameter of the item, the coining operation being accompanied by forcing excess material into a zone in the mould between the semi-circular portion of the mould and the bent over ends, the zone corresponding to a gusset for the coupling. The spreading action may be accompanied by the formation of orifices through the bent-over ends (or ears) and there may also be a finishing operation for the ends of the ears, so that the finished coupling emerges from the die. EMBODIMENT OF THE INVENTION Embodiments of the invention are described below with reference to the accompanying drawings in which: Figure 6 is a side view of a predetermined length of profiled metal; Figure 7 is a cross section view of the profile of Figure 6 after forming bent-over ends; Figure 8 is a diagrammatic section representation of the first step of bending the length of metal to form the item having a semi-circular portion and continuated bent-over ends; Figure 9 is a diagrammatic sectional representation of the coining operation; Figure 10 is a sectional representation of portion of the mould with a zone for receiving excess metal; Figures 11 to 13 are diagrammatic representations of a tool set useful in the method of the invention; Figure 14 is a diagrammatic representation of a feeder device for the tool set of Figure s 11 to 13; Figure 15 is an isometric view of a mould for forming the gussets; and Figure 16 is an isometric view of a gusset produced by the mould in Figure 15. In Figure 6 a predetermined length 60 of a desired profile is cut and holes 62 are pierced at either end. Figure 7 is a side view of this length after being subjected to a cold bending process which results in the formation of bent-over ends (ears) 64. The next step is illustrated by Figure 8 which is a side view of a semi-circular item 66 formed by a hot bending process as described above. The coupling is completed by coining and trimming the ears, resulting in the final item shown in Figure 9. The coining and trimming process results in a ideal seating surface. The coining process results in the formation of excess material and in Figure 10, which is an enlarged view of the zone between the semi-circular portion and an ear, this excess material being forced thereinto to form a gusset 68 which adds significantly to the strength of the coupling. Referring to Figures 11 through 13, a profiled length 70 is heated to a temperature in excess of its Curie temperature level (about 90°C) and placed on the die 72. The press 74 has a double action movement. The punch 76 is mounted through bolts 78 to a pressure plate 80, the bolts 78 being spring-loaded to a predetermined tonnage. The downward stroke distance of the die set is limited according to the load applied by the press, the first downward movement ensuring the formation of the semi-circular portion whilst maintaining an angle of about 55° to 65° for the bent-over ends. During this stage the punch 76 is not fully depressed so that there is a gap between it and the pressure plate 80 (see Figure 12). This gap is necessary so that metal can flow within the whole profile during the first bending stage, especially in the critical zone between the bent-over end and the semi-circular portion. In the second stage, the load is increased until the die set is completely closed. In this stage the downward stroke of the punch 76 is not repeated but merely extended by the upward movement of the pressure plate (see Figure 13). During the second stage the profile is coined to meet the dimensional requirements of the specific coupling size - for example the cavity height which ensures the snug fit of a rubber gasket; the key height to the exact height (grooved couplings have a shorter key than shouldered couplings; it being appreciated that the final key height can be determined by suitable adaptions in the first stage; the ears are flat to ensure a perfectly round coupling; reinforcing gussets are formed bridging the ears to the semi-circular portion. Both stages are completed before the profile cools to temperature at which structural change takes place. The dies are made about 0,8 percent larger than the optimal size to allow for shrinkage on cooling. As the die set is opened, the cushion of the press, which has been forced down by the die set, returns to its original position. Referring now to Figure 14 a feeder device 90 is provided for the profiled metal 92. In a first stage operation 94 a predetermined length of the metal profile is cut and also pierced at either end to form the orifices for the ears. From this first stage the lengths of profiled metal are moved to the second stage 96 as in Figures 11 through 13. As each stage involves two operations it will be appreciated that they can be arranged for a complete part to be ejected from the second stage at every stroke of the common press 98. In Figure 15 a mould portion for creating gussets is illustrated and the resulting gussets are shown in Figure 16. The mould portion 100 includes a semi-circular portion 102, flat portions 104 and pockets 106 into which excess material will flow during the coining operation. The pockets 106 produce gussets 108 in the item 110.

Claims: A method for producing a metal coupling for pipes including the steps of subjecting a predetermined length (60) of desired cross sectional profile to a bending process in a mould having a semi-circular portion to form a symmetrical item comprising a semi-circular portion (66) continuated by formed or pre-formed bent-over ends (64) of a predetermined size; characterised in that the bent over ends (64) are coined to lie in the same horizontal plane as the horizontal diameter of the item and at the same time to force excess material from the bent-over ends (64) into a zone in the mould between the semi-circular portion of the mould and the bent over ends, the zone corresponding to a gusset (68) for the coupling. The method of claim 1 characterised in that the profiled length (60) is first subjected to a cold bending process to pre-form the bent-over ends (64) of predetermined size. The method of claim 2 characterised in that the profiled length (60) with bent-over ends (64) of predetermined size is subjected to a hot bending process to form the symmetrical item comprising a semi-circular portion (66) continuated by the bent-over ends (64), and the bent-over ends (64) are then coined to lie in the same horizontal plane as the horizontal diameter of the item and at the same time to force excess material from the bent-over ends into a zone in the mould between the semi-circular portion of the mould and the bent over ends, the zone corresponding to a gusset (68) for the coupling.

Inventors: CORBETT MICHAEL ROBERT, CORBETT, MICHAEL ROBERT
Applicants: CORBETT MICHAEL ROBERT, CORBETT, MICHAEL ROBERT
Application year: 1993
Main classification: F16L9
IPC codes: B21K1, F16L21