AU2012101315A4 - Apparatus for Forming Bends in Thermoplastic Pipe and Method of Use - Google Patents

Abstract

An apparatus for forming a bend in a section of thermoplastic pipe, the apparatus comprising: a. a bending jig including a working surface, a pivotable circle vector member mounted beneath the working surface, and a collar mounted at an end of the working surface for receiving an end of the pipe section and holding the pipe section in contact with the working surface, wherein the collar pivots on the same axis as the circle vector member, b. a flexible but incompressible mandrel of substantially the same internal diameter as the pipe section, c. a mechanism for driving the mandrel into the pipe section, advancing the mandrel and pipe section into engagement with the collar of the bending jig, and for retraction of the mandrel from the pipe section after bending the pipe section, and d. a mechanism for pivoting the circle vector member of the bending jig so that a point on the working surface moves at substantially the same rate as the pipe section when being advanced.

Description

APPARATUS FOR FORMING BENDS IN THERMOPLASTIC PIPE AND METHOD OF USING SAME TECHNICAL FIELD 100011 The present invention relates to thermoplastic pipe. In particular, the invention relates to apparatus which can be used for forming bends in thermoplastic pipe. The invention also relates to the forming of a bend in thermoplastic pipe using the apparatus of the invention. BACKGROUND ART 100021 Thermoplastic piping is now widely used for water and sewage reticulation and for gas supply. Such piping can be supplied as discrete lengths but in some instances is provided as rolls allowing continuous laying of pipe over long distances. 100031 Irrespective of the length of the sections used to make up a piping system, bends are invariably required. Bends are typically required at all angles between 110 and 900 in centreline radii of curvature varying from 2 to 3 times diameter. 100041 To be incorporated into the piping system the bends must be connected to the adjacent pipe sections in the same fashion as the pipe sections per se must be joined. Thermoplastic pipe sections are commonly connected by electrofusion or butt welding. In some cases, a butt flange may be provided between sections but each half of the butt flange must be connected to a section using the foregoing methods. 100051 So that a join can be formed that is commensurate with the pressure rating of the pipe, it is important that the ends of pipe sections to be joined are both circular. That is, if one section has a circular end while the other end has a slightly oval end, an inferior joint will be produced. 100061 According to generally accepted practice, bends are formed in sections of thermoplastic pipe by supporting a section of softened pipe at its ends and applying pressure at the centre of the section to form the desired bend. 100071 A disadvantage of the foregoing method for forming bends in thermoplastic pipe is that the pipe is stretched preferentially in the middle of the arc during the bending process. This is particularly the case with the outside wall of the bend. The stretching weakens the pipe wall and leads to derating of the pressure rating of the bend.

100081 In UK patent application no. GB 2 351 936 A, there is disclosed a method and apparatus for forming bends in thermoplastic pipe. This disclosure overcomes the disadvantages of the methods that existed at the filing date of that application. An improved apparatus is disclosed in Australian Patent No. 2003203314. However, a particular apparatus according to either of these disclosures can be used to form bends in thermoplastic pipe usually of only one size. That is, a specific apparatus has to be constructed for each size of pipe in which a bend is to be made. It would therefore be desirable to have available apparatus that can be used with thermoplastic pipe of a range of sizes. 100091 The publications referred to in the previous paragraph are incorporated herein by cross-reference. It will be clearly understood however that this cross-referencing does not constitute an admission that the publications form part of the common general knowledge in the art in Australia or in any other country. SUMMARY OF THE INVENTION 100101 The object of the invention is to provide apparatus for forming bends in thermoplastic pipe, which apparatus can be used with pipe of various sizes-that is, of any diameter-and which provides a bend with minimal changes to the pipe wall. [00111 In one aspect, the invention resides broadly in An apparatus for forming a bend in a section of thermoplastic pipe, the apparatus comprising: a. a bending jig including a working surface, a pivotable circle vector member mounted beneath the working surface, and a collar mounted at an end of the working surface for receiving an end of the pipe section and holding the pipe section in contact with the working surface, wherein the collar pivots on the same axis as the circle vector member, b. a flexible but incompressible mandrel of substantially the same internal diameter as the pipe section, c. a mechanism for driving the mandrel into the pipe section, advancing the mandrel and pipe section into engagement with the collar of the bending jig, and for retraction of the mandrel from the pipe section after bending the pipe section, and d. a mechanism for pivoting the circle vector member of the bending jig so that a point on the working surface moves at substantially the same rate as the pipe section when being advanced.

100121 In a broad format, the invention provides apparatus for forming a bend in a section of thermoplastic pipe, said apparatus comprising: (a) a bending jig comprising: (i) an elongate working surface comprising a plurality of abutted lateral bars which are held together by a flexible and tensionable cable; (ii) a channel or channel members within which said working surface can slide; (iii) a circle vector member mounted beneath said working surface which pivots on an axis normal to a longitudinal central plane of said working surface, wherein at least a leading end of the arced extremity of said member is in contact with the underside of said working surface at the leading end of said surface, and wherein the sum of the radius of said circle vector member plus the thickness of a bar of said working surface is equal to the inner radius of the pipe section when bent; and (iv) a collar mounted at the leading end of said working surface for receiving an end of said pipe section and holding said section in contact with said working surface, wherein said collar mounting pivots on the same axis as said circle vector member; (b) a flexible but incompressible mandrel of substantially the same internal diameter as said pipe and of at least the same length as said pipe section; (c) a support for said bending jig, said mandrel, and a said pipe section, with said pipe section positioned between said bending jig and said mandrel, wherein said circle vector member and collar of the bending jig are mounted to the support so that said circle vector member and collar can rotate away from a position where said collar is aligned with axes of said pipe section and said mandrel; (d) a mechanism for driving said mandrel into said pipe section, advancing said mandrel and pipe section into engagement with said collar of the bending jig, and for retraction of said mandrel from said pipe section after bending said pipe section; and (e) a mechanism for rotating said circle vector member of the bending jig so that a point on the working surface moves at the same rate as the pipe section when being advanced. 100131 The invention also includes within its scope use of the apparatus for forming a bend in a section of thermoplastic pipe. 100141 The term 'comprising' and variants of the term such as 'comprise' and 'comprised', are used herein to donate the inclusion of a stated integer or integer but do not necessarily denote the exclusion of other integers unless in the context of usage on exclusive interpretation is required.

1+ 100151 The term 'thermoplastic' as used herein applies particularly to polyolefins such as polyethylene and polypropylene. 100161 The term 'inner radius' is used herein to denote the distance between the centre of the arc of the bent section of pipe and the surface of the bent section closest to the centre of the arc. [00171 The circle vector member is typically configured so that it can subtend an angle at the anvil working surface of up to about 1000. This permits the formation of a bend in the section of pipe of 900. Bends of less than 900 can be formed by limiting the rotation of the circle vector member this will be explained in greater details below. 100181 In a preferred embodiment, the mandrel includes a plurality of openings on its outer surface through which a liquid can be pumped during the cooling of the bent pipe section (see below). The liquid is fed to the openings from channels within the mandrel that are connected to a source of the liquid. [00191 Apparatus according to the invention can be used for forming bends in thermoplastic pipe sections of any diameter including diameters of 90 mm up to 1000 mm. It will be appreciated, however, that certain apparatus components must be appropriately sized for the diameter of the section of pipe in which the bend is to be formed. 100201 In another aspect, the invention resides broadly in a method for forming a bend in a section of thermoplastic pipe, the method comprising the steps of: a) heating the section of pipe to approximately its Vicat softening temperature to form a heated section; b) loading the heated section onto an apparatus for forming a bend in a section of thermoplastic pipe; c) driving a mandrel into the heated section; d) advancing the heated section into contact with a working surface; and e) pivoting a circle vector member to form the bend in the heated section. [00211 In a preferred embodiment of the invention, step d) of the method further includes advancing the mandrel with the heated section into contact with the working surface. 100221 In some embodiments, the method may further include the step of cooling the heated section to below its Vicat softening temperature while the heated section is still in contact with the working surface.

D [00231 In yet another embodiment of the invention, the method may include the further step of withdrawing the mandrel from the section of pipe. 100241 It is envisaged that once the mandrel is withdrawn from the section of pipe, the section of pipe may be removed from the apparatus. [00251 In a preferred embodiment of the invention, the apparatus for forming a bend in a section of pipe is the same apparatus as described in previous aspects of the present application. 100261 Utilisation of apparatus according to the invention is generally in accordance with the methods described in GB 2 351 936 A and AU 2003203314 with appropriate modification as will be detailed below. In summary, the steps are as follows: (i) the pipe section is heated to the Vicat softening temperature thereof; (ii) the mandrel is driven into the section of pipe; (iii) the mandrel and pipe section are advanced into contact with the working surface of the bending jig; (iv) the circle vector member is rotated to form the bend in the pipe; (v) the pipe section is cooled to below its softening temperature while still in contact with the now curved working surface of the bending jig; and (vi) the mandrel is withdrawn from the pipe section allowing further internal cooling until the bent section of pipe is in a sufficient condition for removal from the apparatus. 100271 In a preferred embodiment, in step (v) as outlined above, the pipe section is cooled to a temperature that is significantly below its softening temperature. 100281 In the foregoing method, the section of thermoplastic pipe can be softened using any of the methods known to those of skill in the art. 100291 Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0030] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings briefly described hereafter.

0 [00311 Figure 1 is a side view of an apparatus according to the invention. 100321 Figures 2A and 2B are side and end views, respectively, of the bending jig portion of the apparatus depicted in Figure 1. [00331 Figures 3 is another side view of the bending jig portion of the apparatus depicted in Figure 1. 100341 Figure 4 is a perspective view of a portion of the apparatus depicted in Figure 1. DETAILED DESCRIPTION OF THE INVENTION 100351 Reference throughout this specification to 'one embodiment' or 'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or 'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Further more, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations. 100361 Apparatus according to the invention, appropriately configured, can be used for forming bends in pipe of any diameter but is particularly suited for forming bends in a section of pipe having a diameter in the range of 110 to 250 mm. The apparatus to be described below is configured for forming bends in sections of pipe having a diameter in the range of 125 to 250 mm. 100371 With reference to Figure 1, there is broadly depicted apparatus 1 comprising a support frame 2 to which is mounted bending jig 3 which will be described in greater detail below. There is also shown in Figure 1 hydraulic ram 4, the piston 5 of which extends from cylinder 6 of the ram where it can be connected to mandrel 7 via a mandrel pulling box (see below). A power pack for delivering hydraulic fluid to ram 4 is generally depicted as item 'A' in the figures. This power pack also drives other hydraulic components of the apparatus. 10038] With reference to bending jig 3 of Figure 1, this component of apparatus 1 is shown in greater detail in Figures 2A and 2B together with other components of the apparatus. Referring now to the last-mentioned figures, there is shown bending jig 3 which comprises working surface 8 which comprises a plurality of lateral bars, one of which is item 9. These bars are approximately 300 by 25 mm and 25 mm thick. The bars are held together by wire cables which are tensionable. The cables pass through holes near each end of a bar. A convenient manner of tensioning the cables is by providing a threaded portion at an end of a cable which extends beyond the final bar of the working surface, which threaded portion has a coil spring positioned between a nut on the threaded portion and the bar. The bars are retained within bending jig 3 by being located within a channel or channel members affixed to support frame 2 of apparatus 1. [00391 The circle vector member of bending jig 3 is mounted beneath working surface 8. The circle vector member of the exemplified apparatus actually comprises two members, 10 and 11, at each side of the working surface which are pivotally mounted to vertical members 12 and 13 of the apparatus frame. It can be seen that the leading ends of the circle vector members, one of which ends is item 14, are aligned with the leading edge 15 of working surface 8. ('Leading edge' in the foregoing context is the edge that advances with the advancement of the mandrel during the pipe bending process.) 100401 Bending jig 3 also includes a collar 16 which is pivotally mounted at the same point 17 as the circle vector members. Collar 16 receives the leading end of the section of pipe to be bent and has an internal diameter which allows the pipe section to fit thereto as a clearance fit. Rotation of circle vector members 10 and 11 and hence progression of working surface 8 is effected by hydraulic ram 18 which is driven by power pack A. [00411 Circle vector members 10 and 11 and the arms 19 and 20 which support collar 16 can be mounted to the apparatus at differing pivot points-see for example item 21 of Figure 2A. This permits the formation of bends of differing radii. 100421 Also visible in Figure 2A is a sliding cup 22 which like collar has an internal diameter which is a clearance fit with respect to the section of pipe to be bent. When a section of pipe is loaded for bending, a lip at the distal end of sliding cup 22 abuts the end of the section distal the leading end. Further visible in the foregoing figure is a mandrel pulling box 23 which abuts sliding cup 22 when the mandrel has been inserted into the section of pipe. Mandrel pulling box 23 is connected to piston 5 of hydraulic ram 4 (see Figure 1). Pulling block 23 has a shape that allows it to receive the end of mandrel 7 distal the leading end of the mandrel. 100431 The disposition of bending jig components and other components referred to in immediately preceding paragraphs can be appreciated from Figure 3. In this figure, bending jig 3 is shown after a nominal 900 bend has been formed in a section of pipe 24. Two hydraulically driven pins are mounted to a support frame 2 of apparatus I in the region of bending jig 3. One of these pins and its associated hydraulic cylinder are items 25 and 26, respectively in the figure.

6 On forming the bend, the rams are activated such that the pins extend and lock into sliding cup 22. This then locks the bent section of pipe into the position shown in the figure and permits withdrawal of mandrel 7. 10044] The manner in which components such as sliding cup 22 and mandrel pulling block 23 can proceed along members of the apparatus frame can be appreciated from Figure 4. In this figure, there are shown top rails 27 and 28 of apparatus frame 2 and mandrel pulling box 23. It can be appreciated from the drawing that mandrel pulling box 23 has a rectangular internal cross section so that it can closely mate with the end of mandrel 7 received by the pulling box 23. It can be further appreciated from Figure 4 that members 29 and 30 are provided on each side of mandrel pulling box 23 which act as slides. The lower surfaces of each of these member can have a material fitted to reduce the friction between the members and the rails. Such a material is item 31 of Figure 4. Rods 32 and 33 extend from mandrel pulling block 23 through corresponding openings in sliding cup 22 (not shown in Figure 4). These rods are used to limit the intrusion of the mandrel into shorter lengths of heated pipe corresponding to angles less than 900. In addition, the rods assist in the feeding and retraction of the sliding cup 22. [00451 For clarity, components of the apparatus such as hydraulic fluid supply lines and electrical control circuitry have been omitted from the drawings. Other optional features of the apparatus that have not been shown in drawings include a gantry above the apparatus The gantry can be used for affixing an electric winch to aid loading the mandrel and/or the section of pipe to be bent. The electric winch can also be used for removing the bent section of pipe from the apparatus once the cooling process has been completed (see below). 100461 Another optional component not shown in the drawings is a fluid supply system for cooling the bent section of pipe. This system can include an open-topped tank beneath the bending jig to catch the cooling fluid and an enclosure chamber over the bending jig to prevent cooling fluid escaping from the apparatus. 100471 Use of the apparatus as described above for bending a section of pipe will now be described. As indicated above, the pipe section to be bent is first heated to its Vicat softening point. This is most conveniently done in a bath such as that described in, for example, Australian Patent No. 2003203314. The softened pipe section is then loaded onto the apparatus in the region indicated as 'B' of Figure 1. If necessary, the mandrel is also loaded onto the apparatus but in most instances it will already be present on the apparatus, having been withdrawn from a bent section of pipe as part of a previous bending cycle. The mandrel prior to being driven into the section of pipe lies in the region of the apparatus marked as 'C' in Figure 1. [00481 Further preferred steps in the bending cycle, with reference to drawings as indicated, are as follows: (a) Hydraulic ram 4 is activated to drive mandrel 7 through sliding cup 22 (see Figure 3) into the section of pipe (see also Figure 1). (b) The section of pipe with mandrel 7 therein is then driven into collar 16 (see Figures 1, 2A and 2B). (c) Advancement of the combined mandrel 7, section of pipe, mandrel pulling block 23 and sliding cup 22 is continued but simultaneously with rotation of circle vector members 10 and 11 until the desired angle is formed in the section of pipe. (d) Sliding cup 22 is locked to the support frame (see Figure 3). (e) The cooling system is activated to cool the section of pipe to below its softening point. (f) Mandrel 7 is withdrawn via the linkage of hydraulic ram 4 to mandrel pulling block 23. (g) If desired, cooling of the interior and exterior of the bent section of pipe can be continued. (h) Hydraulic locking pins disengage from the sliding cup. (i) Sliding cup 22 is withdrawn from the bent section of pipe (preferably via the rods 32, 33 connected to the mandrel pulling box 23). (j) The bent section of pipe is removed form the apparatus. (k) The bending cycle is then repeated as necessary. [0049] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.

Claims (5)

1. An apparatus for forming a bend in a section of thermoplastic pipe, the apparatus comprising: a. a bending jig including a working surface, a pivotable circle vector member mounted beneath the working surface, and a collar mounted at an end of the working surface for receiving an end of the pipe section and holding the pipe section in contact with the working surface, wherein the collar pivots on the same axis as the circle vector member, b. a flexible but incompressible mandrel of substantially the same internal diameter as the pipe section, c. a mechanism for driving the mandrel into the pipe section, advancing the mandrel and pipe section into engagement with the collar of the bending jig, and for retraction of the mandrel from the pipe section after bending the pipe section, and d. a mechanism for pivoting the circle vector member of the bending jig so that a point on the working surface moves at substantially the same rate as the pipe section when being advanced.

2. An apparatus according to claim I wherein the working surface comprises one or more abutted lateral bars that are retained together by a cable.

3. An apparatus according to any claim 1 or claim 2 wherein the circle vector member pivots on an axis normal to a longitudinal central plane of the working surface.

4. An apparatus for forming a bend in a section of thermoplastic pipe, said apparatus comprising: (a) a bending jig comprising: (i) an elongate working surface comprising a plurality of abutted lateral bars which are held together by a flexible and tensionable cable; (ii) a channel or channel members within which said working surface can slide; (iii) a circle vector member mounted beneath said working surface which pivots on an axis normal to a longitudinal central plane of said working surface, wherein at least a leading end of the arced extremity of said circle vector member is in contact with the underside of said working surface at the leading end of said working surface, and wherein the sum of the radius of said circle vector member plus the thickness of one of the bars of said working surface is equal to the inner radius of the pipe section when bent; and S1I (iv) a collar mounted at the leading end of said working surface for receiving an end of said pipe section and holding said section in contact with said working surface, wherein said collar mounting pivots on the same axis as said circle vector member; (b) a flexible but incompressible mandrel of substantially the same internal diameter as said pipe and of at least the same length as said pipe section; (c) a support for said bending jig, said mandrel, and a said pipe section, with said pipe section positioned between said bending jig and said mandrel, wherein said circle vector member and collar of the bending jig are mounted to the support so that said circle vector member and collar can rotate away from a position where said collar is aligned with axes of said pipe section and said mandrel; (d) a mechanism for driving said mandrel into said pipe section, advancing said mandrel and pipe section into engagement with said collar of the bending jig, and for retraction of said mandrel from said pipe section after bending said pipe section; and (e) a mechanism for rotating said circle vector member of the bending jig so that a point on the working surface moves at the same rate as the pipe section when being advanced.

5. A method of forming a bend in a section of thermoplastic pipe, the method comprising: (i) heating the section of pipe to the Vicat softening temperature thereof; (ii) loading the heated section onto an apparatus according to any one of claims 1 to 12; (iii) driving said mandrel of said apparatus into the section of pipe; (iv) advancing the mandrel and pipe section into contact with the working surface of the bending jig of the apparatus; (v) rotating the circle vector member of the bending jig to form the bend in the section of pipe; (vi) cooling the section of pipe to below its softening temperature while still in contact with the curved working surface of the bending jig; and (vii) withdrawing the mandrel from the pipe section and removing the section of pipe from the apparatus.