EXTRACTION APPARATUS

Abstract: Extraction apparatus (10) for tubes and like elongated articles comprises a tiltable gripping collar (64) of fixed internal dimensions, to engage and grip the article to be extracted. The collar has internal dimensions slightly larger than those of the article to be gripped and is mounted so as to tilt in use and engage and grip the article. The collar can be used either as non-return means for the article being extracted, or for applying the extraction load to it. A collet assembly applies the extraction load to the article from a hydraulic ram. The coller jaws (48) are axially spaced from tht end of the tubular piston rod (34) of the ram and connected to it by a collet head (38) whereby the assembly is removable on a quick-attach basis for servicing.

Description: EXTRACTION APPARATUS This invention relates to extraction apparatus for tubes and like elongated articles. An example of the application of the invention is to tube extraction apparatus suitable for removing condenser and heat exchanger tubes from their mountings in electrical power generation stations. The invention has many other applications. Apparatus for extracting tubes from heat exchangers and the like has already been proposed. An example of such apparatus is disclosed in GB 2,113,598A. However, such apparatus is of relatively elaborate and complex structure, and this is reflected in the complexity of the mode of operation of the apparatus. Accordingly, improvements are desirable in relation to the simplifying the construction and operation of the apparatus, its cost, its space requirements, particularly axial length, and indeed its reliability. An area in such prior apparatus which particularly calls for improvement concerns the method of gripping the article to be extracted, and the present invention is particularly, though not exclusively, concerned with providing improvements in this respect. Accordingly, an object of one aspect of the present invention is to provide extraction apparatus for tubes and like elongated articles providing improvements in relation to one or more of the matters discussed above or generally. According to a first aspect of the invention there is provided extraction apparatus for tubes and like elongated articles as defined in claim 1 of the accompanying claims. A second aspect of the invention concerns the means for applying extraction load to the article concerned. Prior proposals in this regard include the use of a collet assembly mounted within the tubular piston rod of the hydraulic ram assembly, whereby extraction load is transferred radially inwards through a collet head or chuck to the collet jaws, and thus to the article. While this prior proposal may well operate satisfactorily in laboratory test conditions, it is found that in actual normal use conditions, it is subject to significant problems and shortcomings. These concern not only the size and weight of the apparatus, but also a tendency to cease-up and jam in use, whereby the apparatus becomes unusable, service is imperative, and it is then found that it is extremely difficult to detach the jammed collet assembly for servicing purposes, and later to replace it. Accordingly, it is an object of this second aspect of the present invention to provide improvements in relation to one or more of the matters discussed and disclosed herein, or generally. According to this second aspect of the invention there is provided extraction apparatus for tubes and like elongated articles as defined in claim 14 of the accompanying claims. An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig 1 shows an axial section through extraction apparatus for tubes and like elongated articles; Fig 2 shows an end elevation view of the apparatus of Fig 1, the direction of viewing being indicated by arrow II in Fig 1; Fig 3 shows an end elevation view of the opposite end of the apparatus of Fig 1, the direction of viewing being indicated by arrow III in Fig 1; Fig 4 shows the apparatus of Fig 1 on a larger scale so as to illustrate, for the purpose of describing the primary article gripping means therein, the structure and arrangement and relative dispositions of the component parts thereof; Fig 5 shows a section through a modified gripping collar or lockplate for use in the preceding embodiments; and Fig 6 shows an end elevation view of the collar of Fig 5, as viewed in the direction of arrow VI in Fig 5. As shown in the drawings, extraction apparatus 10 for tubes and like elongated articles comprises primary and secondary article gripping means, 12, 14, and thrust means 16 to apply an extraction load to the article. Broadly speaking, the apparatus 10 operates by causing primary article gripping means 12 to engage and grip the article to be extracted (not shown), and to apply to it an extraction load generated by thrust means 16. The article is moved in the direction from left to right in Fig 1. In this direction, secondary article gripping means 14 permits the article to move through it, while reaction thrust is applied to the tube assembly by a reaction collar 18. After one stroke of the thrust means, it returns to take a second stroke. During this period the secondary article gripping means prevents return movement (in the right to left direction in Fig 1) of the article being extracted. This extraction cycle is repeated to provide stepwise extraction of elongated articles. Looking now at the general structure of apparatus 10, it will be seen that it comprises a cylinder 20 having an internal bore 22 in which a piston 24 slides. The piston is annular in form and has an internal periphery 26 slidingly and sealingly engaging the outer periphery of a centre tube or stem 28. Piston 24 has annular seals 30, 32 at both its outer an inner peripheries. Piston 24 has a tubular rod or stem 34 which likewise slides on centre tube 28 and is formed with a screw- threaded portion 36 of slightly reduced external diameter on which a cylindrical head 38 is scr e w-thr eadedly received, and locked in position by a grub screw 40. Piston rod 34 slides in a cylinder end block 42 which is axially fixed within cylinder 20 and provided with seals so as to define a fluid tight annular rod-side chamber 44, whereby piston 24 can be actuated in a double-acting 0 manner. Cylinder 20 has an extension portion 46 in which head 38 is freely received in the fully-retracted position shown in Fig 1. A collet 48 is mounted within the tapering internal periphery 50 of head 38 and has a complementary tapering external periphery 52 to co-operate therewith. Axially- extending springs 54 are received in bores in the collet and act against an end plate 56 retained by a cap 58 which is screw-threaded on head 38. Springs 54 load the separate portions of collet 48 axially inwards and, by virtue of the ramp effect of the tapering profiles 50, 52, the collet is thus biased inwardly to engage and grip a tube or other article to be pulled. Referring now to Fig 4, the structure and arrangement of the primary article gripping means 12 in relation to piston 24 and the rod or stem 34 thereof in particular, will now be considered in more detail in relation to Fig 4. It will be seen that extraction load applied to the head side of piston 24 is transferred via piston rod 34, screw-threads 36, collet head or chuck 38, ramp 52, and thus to the collet elements or jaws 48 themselves. Head 38 constitutes mounting means for elements 48. It is quickly attachable/detachable by virtue of the screw-thread 36 and the grub screw 40, whereby the entire collet assembly can be quickly attached/detached for servicing purposes. It can be clearly seen from Fig 4 that the collet elements 48 are located such that they are axially spaced from the axially outer end 59 of the piston rod or stem 34. Fig 4 shows the fully axially retracted position of the elements 48, in which their axially inner ends 61 are spaced apart from piston rod end 59 by a discrete distance. For the purpose of the invention, it would not be out of the question for actual contact to be made. The space 63 between the ends 59 and 61 has a particular significance in relation to this aspect of the present invention, namely that it illustrates the extremely limited volume available within the apparatus, between the end of the piston and the collet jaws or elements 48, in which any foreign matter could conceivably accumulate, though in practice in the present design, such accumulation may not occur at all. In previously proposed apparatus, in which the collet assembly is located entirely radially within the tubular stem or rod of the piston of the ram assembly, the piston rod is necessarily of very greatly increased diameter as compared with that of the present embodiment, and this leads to large voids within the rod in which scale and other foreign matter from the tube being pulled can accumulate. This build-up occurs relentlessly until the pressure thereby exerted produces a distorting effect on the piston rod itself whereby it can no longer slide freely in the bearing corresponding to bearing or block 42, and the assembly jams. When jamming occurs, it is extremely difficult to remove the collet assembly from within the confines of the tubular piston stem. In the present embodiment, removal of the collet assembly for servicing purposes is very readily accomplished. Cylindrical extension portion 46 is readily removed by virtue of screw-threads 65, thereby leaving collet head 38 exposed. The latter is released by means of grub screw 40 and screw-threads 36, thereby removing the collet assembly in one action. It can be quickly replaced by a previously serviced assembly. Centre tube or stem 28 is axially fixed in the outward direction (left to right in Fig 1) by mutual engagement of stepped diameter portions 60 thereon with corresponding stepped internal diameter portions on the cylinder. The cylindrical internal surface 62 is to slidingly receive a mandrel (not shown) and subsequently the external surface of a tube or other article being extracted. Secondary article gripping means 14 will now be described in more detail. The secondary article gripping means 14 comprises a gripping collar or plate 64 having a cylindrical internal periphery 66 of which the diameter is slightly larger, by approximately one millimetre, than the diameter of the article to be extracted, and of the associated extraction mandrel (not shown). Thus the gripping collar has fixed internal dimensions which are slightly larger than the external dimensions of the article to be extracted. Moreover, the collar is mounted in a housing 68 so as to be tiltable relative to the article to be extracted. Gripping collar 64 is located in housing 68 on a support 70 and between a spring or hydraulically-loaded plunger 72 and a hardened heel pin indicated diagrammatically at 74. Thus, the mounting of the gripping collar is such that it is biased by plunger 72 to a tilted position in which its internal diameter 66 engages and grips the article to be extracted. The axially outer ends of its cylindrical internal diameter are not machined to a sharp edge, but are slightly radiused. A latch 76 biased by a spring 78 to a latched condition engages a corresponding latch member 80 on cylinder 20 and serves to retain gripping collar 64 and provide access thereto for releasing same if jammed and for replacing it with an alternative collar of different dimensions for different tube sizes. Operation of apparatus 10 will now be described. First a mandrel (not shown) in the form of a cylindrical rod having a tapered helical thread at one end and a drive boss at the other is offered up to a tube to be extracted and screwed into same by means of a torque wrench. Then, apparatus 10 is offered up to the projecting mandrel and the shank of the latter is inserted into reaction collar 18 and hence through gripping collar 64 and through centre tube 28 until it reaches collet 48. By sufficiently loading the apparatus 10 against the mandrel, the collet and the entire assembly of head 38, piston rod 34 and piston 24 are moved axially outwards until the collet can ride up tapering periphery 52 of the head 38 and allow the mandrel to pass through it. In this condition, the apparatus 10 is held with reaction collar 18 firmly against the plate or body (not shown) in which the tube to be extracted is mounted. Then, fluid pressure is applied to the head side of piston 24, exerting a thrust on the assembly from left to right as seen in Fig 1. This thrust is applied to the tube via collet 48, and the thrust increases until it is sufficient to break the anchorage of the tube, and the latter then moves from left to right as seen in Fig 1 while cylinder 20 and collar 18 remain axially fixed. At the end of a stroke of about two and a half inches, the piston is recycled by application of pressure to rod- side chamber 44, and collet 48 allows the mandrel to pass through it in the outward direction. When the piston reaches the Fig 1 position again, the cycle is repeated, and so on. During the return movement of the piston to the Fig 1 position, gripping collar 64 operates to provide two functions. Firstly it provides a non-return function for the tube being extracted. The tube itself has a degree of resilience and tends to return from right to left as soon as the load is released. Such return movement is prevented by the collar which tilts and engages and grips the tube, and the load is transferred to cylinder 20 and thence to reaction collar 18 via heel pin 74. Secondly, the gripping collar provides the function of preventing the rear of the apparatus (reaction collar 18) moving forward on the return stroke ie no manual assistance is needed to hold collar 18 against the tube plate from which the tube is being extracted. Otherwise, the cylinder 20 might reciprocate. Amongst other advantages provided by the above embodiment, it will be noted that gripping collar 64 is of very simple construction, very easy to use, and occupies a minimum of axial space. In this latter regard it is to be compared with collet 48, which is a relatively complex structure requiring springs and tapered surfaces, and a significant number of associated components. The advantages of the collet assembly 38, 48 have already been discussed above. Amongst other modifications which could be provided in the above embodiment is the use of a gripping collar corresponding to collar 64 at the opposite end of the apparatus, in place of the collet 48. Indeed the collar can be used at either or both ends of the apparatus. It will be noted that the degree of tilt of the gripping collar is relatively small. This corresponds to the small difference in diameters of the parts concerned. This may be varied to suit different applications of the invention. The collar need not necessarily have a cylindrical internal surface but may be adapted as necessary or desirable to grip articles of differing forms and sizes. In the embodiment of Figs 5 and 6 there is shown in more detail a gripping collar or lockplate 100 suitable for use in the preceding embodiments. The collar comprises an inner hub 102 which fits within an outer collar or lockplate body 104 having a radial flange portion 106 engageable with plunger 72. Hub 102 is removably secured within body 104 by means of a series of grub screws 108 having reduced diameter end portions 109 entering and locating in an annular groove 110 formed in hub 102. In this way, the hub can be removed and replaced in order to accommodate tubes of differing diameters, or rotated in flange portion 106 to present a new locking edge to the tube, when worn. Fig 5 shows the relationship between the hub 102 and an associated tube 112, to be extracted. The hub is indicated in two positions, angularly inclined with respect to each other, these indicating the relative angular inclination sufficient to cause gripping or locking by the collar 100. The inclined grippng or locking position is indicated merely by the broken line 111 in Fig 5, which represents the attitude of face 113 of flange 106 in the inclined position of the hub. In use, this embodiment functions substantially identically to the previously described embodiments. It will be noted that the internal surface 114 of hub 102 has a bevelled face 116 at one end and a slightly relieved annulus 118 at its other axial end, whereby the gripping action of the hub with respect to a tube 112 is exerted by the cylindrical inner face 114 and its end edges 120, 122. The degree of lock can be varied by supplying a hub with a pre-defined distance between edges 120 and 122 and a pre-defined clearance between the tube to be acted on and the hub internal diameter.

Claims: CLAIMS 1 Extraction apparatus for tubes and like elongated articles, the apparatus comprising article gripping means, and thrust means to apply an extraction load to the article, said article gripping means comprising a gripping collar to encircle and engage the article, characterised in that said gripping collar is of fixed internal dimensions, said dimensions being slightly larger than the external dimension of said article, and said gripping collar being mounted so as to be tiltable relative to said article, whereby in use said collar can tilt and engage and grip the article at the inner periphery of the collar and thus inhibit relative movement between the collar and the article in the lengthwise direction of the latter. 2 Extraction apparatus for tubes and like elongated articles comprising a gripping collar of fixed internal dimensions and arranged to be tiltable relative to an article to be extracted so as to engage and grip the article at the inner periphery of the collar. 3 Apparatus according to claim 1 or claim 2 characterised in that resilient means is provided to bias the collar towards its tilted position. 4 Apparatus according to claim 3 characterised in that said resilient means engages the collar in the region of the outer periphery thereof. 5 Apparatus according to any one of the preceding claims characterised in that said mounting means for the collar comprises pivot means adapted to promote tilting of the u collar. 6 Apparatus according to claim 5 characterised in that said pivot means comprises a hardened pin or the like to engage the collar in the region of the outer periphery thereof. 7 Apparatus according to claim 6 when dependent upon claim 3 or claim 4 cha acterised in that said pivot means is located diametrically opposite said resilient means, or within an arc of 45 degrees diametrically opposite thereof. 8 Apparatus according to any one of the preceding claims characterised in that said gripping means is arranged to provide for non-return of said article being pulled. 9 Apparatus according to any one of the preceding claims characterised in that said gripping means is arranged to apply said extraction load to said article. 10 Apparatus according to any one of the preceding claims characte ised in that said gripping collar has a generally circular internal periphery. 11 Extraction apparatus for tubes and like elongated articles, the apparatus comprising article gripping means to apply an extraction load to the article, said article gripping means comprising gripping elements movable inwardly to grip the article, said apparatus further comprising fluid actuatable piston and cylinder means to generate said extraction load and mounting means for said gripping elements engageable with the piston means in the region of one axial end of said piston means to transfer said extraction load to said gripping elements, characterised in that said mounting means locates at least part of said gripping elements at a location axially spaced from said one axial end of the piston. 12 Apparatus according to claim 11 characterised in that said gripping elements comprise two or more collet or jaw elements and said mounting means comprises a head or chuck of generally tubular form in which said elements are located, said head overlapping said one axial end of the piston and being detachably fixable thereto and then extending axially away from said one axial end. 13 Apparatus according to claim 12 characterised by quick attach means to connect said head to said piston. 14 Apparatus according to claim 13 characterised in that said quick attach means comprises screw-threaded means provided on the outer surface of a tubular end portion of said piston at said one end and on a corresponding inner surface of said head. 15 Apparatus according to any one of claims 11 to 14 characterised in that said mounting means and said gripping elements are removable as an assembly from said piston, and are likewise replaceable as an assembly. 16 Apparatus according to any one of claims 11 to 15 characterised by a removable and replaceable extension portion of said cylinder means to enclose at least partially said mounting means and said gripping elements. 17 Apparatus according to any one of claims 11 to 16 characterised in that individual axially extending compression springs are provided for said gripping elements acting between structure connected to said head and the gripping elements to bias the latter inwardly by virtue of ramp means.

Inventors: BEARD JAMES HENRY, BEARD, JAMES, HENRY
Applicants: WICKSTEED ENGINEERING LIMITED
Application year: 1989
Main classification: B23P19
IPC codes: B23P19, B25B5, B25B27