Abstract:
The subject of the invention is an assembly and clamping bolt to be employed under tension, having a shank and a head, wherein the head, situated at a first end of the shank, is provided with a clamping tensioning means with a hydraulic cylinder mounted permanently on the bolt, clamping taking place between a rear shoulder device and the hydraulic cylinder, the rear shoulder device being disposed at a second end of the shank.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the National Stage of International Application No. PCT/EP2015/055093, having an International Filing Date of 11 Mar. 2015, which designates the United States of America, and which International Application was published under PCT Article 21(2) as WO Publication No. 2015/135998 A1, and which claims priority from and the benefit of French Application No. 1452084, filed 13 Mar. 2014, the disclosures of which are incorporated herein by reference in their entireties. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The presently disclosed embodiment concerns the field of bolted connections and more particularly bolted connections of large diameter, notably greater than M24, and high tightening torque, such as those used in the automotive, railway, maritime and even undersea, offshore, nuclear, etc. industries. 
         [0004]    2. Brief Description of Related Developments 
         [0005]    In these applications, a high level of safety and of reliability of the connection is required, which means in particular good reproducibility and repeatability of the residual tension after tightening. Also a certain ease and rapidity of use, even and above all in difficult environmental surroundings and under difficult environmental conditions, whether this be for reasons of accessibility, corrosion or nuclear radiation. 
         [0006]    Three techniques are known for tightening bolted connections: torque tightening, thermal tightening, mechanical traction tightening. 
         [0007]    Overall, the correct strength of a bolted connection is linked directly to the value of the residual tension in the connection after tightening. 
         [0008]    The best known tightening method, which consists in tightening the connection by applying a torque to it by screwing action via the screwthread, is associated with a very wide dispersion of this residual tension. It is accepted that this dispersion is +/−20% in the best case scenario—with good control of the tightening torque—but is more generally ±/−60%. 
         [0009]    What is more, torque tightening induces unwanted effects in the bolts, for example: torsion effects, which render the connection even more uncertain. 
         [0010]    Also, torque tightening implies friction between screwthreads, which gradually degrades the surfaces in contact and limits the possibility of effecting a plurality of successive tightenings/loosenings. 
         [0011]    Finally, torque tightening generally does not make possible the simultaneous tightening of a plurality of connections, which further limits the fastening efficacy that it might be hoped to achieve. 
         [0012]    Because of this, an alternative to torque tightening was invented a long time ago: tension tightening, with a first variant consisting in thermal tightening that employs thermal and/or differential expansion. However, given all the constraints associated with the use of heating to a high temperature, its use is limited. 
         [0013]    Tension tightening is more simply effected by applying mechanical tension to the bolt. 
         [0014]    Of these tensioning methods, of concern here is tensioning by hydraulic traction that makes it possible to control the residual tension in the shank by application of a pure traction force and makes a small dispersion possible. 
         [0015]    In the field of hydraulic tensioning of threaded rods by pure traction, a plurality of methods exist. 
         [0016]    There exists firstly a tightening method using a hydraulic tensioner. The tensioner is fitted to a standard bolt already mounted and pre-tightened or to a nut already in contact. The actuator stretches the bolt by hydraulic pressure and the nut is returned to contact with the parts to be clamped, which maintains the stretching of the bolt and produces the residual tension therein after relaxation. 
         [0017]    The actuator is then removed, only the standard bolt remaining in place. The use of this type of technology also offers the possibility of tightening multiple connections simultaneously and therefore of obtaining a better distribution of the tensions in flanged connections. 
         [0018]    There also exists a tightening method using a hydraulic nut. The hydraulic nut functions in accordance with the same principle as the hydraulic tensioner, the difference being that it replaces the standard nut on the bolt and therefore remains in place after tightening. Research has also been conducted into integrating a hydraulic piston into a bolt in order to stretch it. Placing the nut on the stretched bolt and releasing the pressure then produces the residual tension in the bolt. 
         [0019]    In fact numerous devices, in particular hydraulic devices, are commercially available enabling tension tightening to be used, but it is clear that they may be complicated to use. 
         [0020]    In fact this necessitates: 
         [0021]    placing the bolt and the nut on the parts to be assembled; 
         [0022]    placing the hydraulic tensioner and its hydraulic feed; 
         [0023]    tensioning the bolt; locking the bolt; 
         [0024]    verifying the tightening; 
         [0025]    demounting the tensioner. 
         [0026]    In an aggressive environment, for example a radioactive or deep water environment, or merely for economic reasons, it would be desirable to reduce these operating times, even to automate tightening and loosening when there is a requirement to assemble and to disassemble several times. 
       SUMMARY 
       [0027]    The presently disclosed embodiment therefore relates to an integrated assembly device of the type employing a bolt under tension that makes possible simplification of the operations that must be carried out by the operators at the same time as ensuring control of the assembly and the quality thereof. 
         [0028]    The principle of the disclosed embodiment consists in integrating a hydraulic actuator permanently into the bolt to be tightened. 
         [0029]    A shoulder device, for example a nut, is fixed to the end of the bolt opposite that carrying the hydraulic actuator. 
         [0030]    To be more precise the presently disclosed embodiment proposes an assembly and clamping bolt to be used under tension including a shank and a head the head of which, situated at a first end of the shank, includes hydraulic actuator tightening tensioning means permanently mounted on the bolt, tightening being effected between a rear shoulder device and the hydraulic actuator, the rear shoulder device being disposed at a second end of the shank. 
         [0031]    The actuator preferably includes a cylinder facing the rear shoulder device, parts being clamped between an annular rear face of the cylinder and the rear shoulder device. 
         [0032]    The bolt advantageously includes a device for locking the tightening tension once the actuator of the tensioning means has been actuated. 
         [0033]    The shoulder device preferably includes at least one stop nut, the shank including a thread receiving said stop nut over at least a part of said second end. 
         [0034]    The head advantageously includes a bearing surface for means for loosening the bolt. 
         [0035]    The actuator may notably include a piston formed by a flange on the shank. 
         [0036]    The actuator may include a hydraulic feed discharging into a face of the piston facing an internal face of the cylinder surrounded by a first skirt itself surrounding the piston in a sealed manner. 
         [0037]    The cylinder advantageously includes an annular cylinder body mounted to slide on the shank and including sealing means between the shank and the cylinder. 
         [0038]    Return springs of the cylinder are preferably disposed between a flange screwed to the shank and a rear face of the cylinder body. 
         [0039]    The rear face of the cylinder may be annular and consist of the free end of a second skirt extending from the cylinder body and surrounding the springs. 
         [0040]    The hydraulic actuator tightening tensioning means are advantageously connected to a pipe from a hydraulic source by means of connectors mounted on rotary turrets which make it possible to move the bolt in rotation while the pipe remains in the same orientation. 
         [0041]    The turrets are advantageously disposed along a longitudinal axis perpendicular to the body of the bolt and free to rotate about their longitudinal axis whereas the connectors themselves are oriented at 90° to the axis of the turrets, which makes it possible to orient the connectors angularly relative to the axis of the bolt. 
         [0042]    The head advantageously includes an angular engagement area that makes manual loosening of the bolt possible with nuts at the level of the rear shoulder. 
         [0043]    The bolt advantageously includes releasable coupling means between the device for locking the tension and a ring driving that device, said means being designed to allow the ring to drive the device in the absence of resisting force. 
         [0044]    The disclosed embodiment further concerns an assembly device wherein the bolt is advantageously received in a grooved first support allowing rotation of the bolt and movement in translation of the bolt parallel to itself. 
         [0045]    The assembly device may include a second support for temporary retention of the bolt in a waiting position. 
         [0046]    It may include a spring clamp type third support for retaining the bolt in an operating position. 
         [0047]    The disclosed embodiment further provides an assembly system including is plurality of assembly devices in accordance with the disclosed embodiment and wherein the bolts of the assembly devices are connected in alternating groups to separate pressure sources. 
         [0048]    The disclosed embodiment finally provides a method of assembling parts by means of at least one bolt of the invention and wherein
       a distance D between the bolt head and the rear shoulder device is adjusted,   the bolt is put in place,   the bolt is put under hydraulic pressure so as to clamp the parts to be fixed between the head and the rear shoulder device,   the bolt is mechanically locked by tightening a   tightening tension locking device.       
 
         [0054]    The device including a correct tightening marker, a ring of the tightening tension locking device is turned until said marker appears. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0055]    Other features and advantages of the disclosed embodiment will be apparent on reading the following description of one nonlimiting aspect of the disclosed embodiment with reference to the drawings which show: 
           [0056]      FIG. 1  is a side view of a longitudinal section of a bolt in accordance with the disclosed embodiment; 
           [0057]      FIGS. 2A, 2B, 2C  are side views of an assembly device in accordance with the disclosed embodiment in three positions; 
           [0058]      FIG. 3  is a partial view of an assembly system of the disclosed embodiment and parts assembled by means of such a system; 
           [0059]      FIGS. 4A and 4B  are two side views of a constructional detail of a bolt in accordance with one particular aspect of the disclosed embodiment; 
           [0060]      FIGS. 5A and 5B  are two views in section of a detail of a device for verifying and showing the correct position of the bolt of the disclosed embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0061]      FIG. 1  represents an integrated assembly device in accordance with the disclosed embodiment of the type employing a bolt under tension that makes it possible to simplify the operations that must be carried out by the operators to clamp parts with the bolt at the same time as ensuring control of assembly and the quality thereof. 
         [0062]    The device constitutes a hydraulic bolt  1  that includes a shank  10  including a first end on which is disposed an actuator cylinder  11  retained by a flange  14  screwed onto a thread at said first end of the shank  10  and return springs  13 . 
         [0063]    The shank  10  in this example includes at a second end a screwthread onto which there is screwed a device with a nut  21  and locknut  22 , the nut  21  further carrying a washer  23  integral with it. 
         [0064]    The parts to be clamped are positioned between a face  11   a  of the cylinder  11  of the actuator and the washer  23 . 
         [0065]    A nut for maintaining the tension  12  with a verification device including a ring  15  is screwed onto a rear body  101  forming the head of the bolt behind a skirt  11   b  of the cylinder  11 . A hydraulic liquid inlet connector  16  communicates with feed pipes  18  feeding hydraulic fluid into the body  101  of the bolt and discharging into a face  103  of a flange  102  facing the rear of the cylinder  11  of the actuator. 
         [0066]    The flange  102  therefore constitutes a piston of the actuator, to which the shank  10  is rigidly connected. Injecting hydraulic fluid into the feed pipes drives movement of the cylinder  11 , the fluid filling the space delimited by the face  103  and the cylinder  11  inside the skirt  11   b  surrounding the flange/piston  102 . 
         [0067]    In this configuration the actuator is special in that the hydraulic fluid feed is effected through the piston and in that both the cylinder  11  and the flange/piston  102  are able to move, the cylinder moving provided that its face  11   a  and the nut  23  are not in contact with the parts to be clamped and the piston moving to stretch the shank  10  from the moment at which clamping of the parts between the cylinder  11  and the nut  23  begins. 
         [0068]    To make tightening a plurality of bolts equipped with the device possible, an outlet connector  17  receives a hydraulic fluid return from the interface between the body of the bolt and the actuator via a pipe  19 . 
         [0069]    In this example the inlet connector  16  and the outlet connector  17  are mounted on rotary turrets  20   a,    20   b.    
         [0070]    In this example the turrets are disposed along a longitudinal axis perpendicular to the body of the bolt and free to rotate about their longitudinal axis, whereas the connectors themselves are oriented at 90° to the axis of the turrets, which makes it possible to orient the connectors angularly relative to the axis of the bolt. 
         [0071]    The hydraulic bolt is based on the operation of a standard actuator, the cylinder  11  of the actuator embodying the function of the screwthread of a bolt. 
         [0072]    Here the fixing is effected between the cylinder of the actuator and the nut  21 . 
         [0073]    The distance D between the bolt head and the nut identified in  FIG. 2 b    is adjusted before installing the bolt. The distance D is defined to be compatible with the stroke of the actuator, for example 5 mm, and once adjusted this distance makes tightening possible without manual intervention up to the stage of placing the nut  12  for maintaining the tension. When the actuator is pressurized, the cylinder  11  is moved into contact with the parts to be clamped between the cylinder and the nut, after which a pressure force is generated that by reaction triggers the stretching of the shank  10  because of the thrust on the rear body  101 . 
         [0074]    These movements generate a clearance between the skirt  11   b  of the cylinder and the nut  12  for maintaining the tension corresponding to the stroke that moves the cylinder into contact with the parts to be clamped and to the stretching of the shank. This nut  12  is then brought into contact with the skirt  11   b  of the cylinder  11 , which locks the bolt and maintains the stretching of the shank  10 . The bolt is therefore mechanically locked by the contact of the nut for maintaining the tension with the cylinder of the actuator. 
         [0075]    Placing the nut for maintaining the tension is a delicate operation. At a pressure of 700 bar the stretching of the shank  10  is of the order of 0.2 mm for a shank of 30 mm diameter, which implies the necessity of placing the nut  12  for maintaining the tension in perfect contact. 
         [0076]    The hydraulic bolt integrates a device for verifying and showing correct positioning of the bolt. 
         [0077]    The display device includes openings  30   a  represented in  FIGS. 4A and 4B  enabling correct placement of the nut for maintaining the tension in that a colored marker  30   b  appears in the openings  30   a  only when the movement of the nut  12  is sufficient. 
         [0078]    This verification device is designed to make it possible to lock the nut for maintaining the tension, to show locking thereof, and to show a locking defect if the locking surface of the nut  12  on the skirt  11   b  is polluted by a foreign body  25  of shaving type as represented in  FIG. 5B . 
         [0079]    Operation is based on the use of releasable coupling means between the nut  12  for maintaining the tension and the ring  15 . These means are designed to allow the ring to drive the nut in the absence of resisting force and in particular until the skirt  11   b  comes into contact with the front face of the nut  12 . 
         [0080]    Once the nut  12  is in contact with the skirt  11   b,  the coupling means, here in this nonlimiting example a system with balls  32  pushed forward by springs  33  and received in housings  31 , are released. In the example shown, the balls push back the springs and leave the housings, which allows the ring to turn on the nut to place a marker  30   b  indicative of correct positioning in front of a window  30   a,  as represented in  FIG. 5A . 
         [0081]    If debris such as a shaving is wedged between the ring  15  and the skirt  11   b  as represented in  FIG. 5B , the ring is immobilized and the nut  12  does not come into contact with the skirt  11   b.  In this case, the coupling means cannot be released and the correct position marker does not appear in the window  30   a.    
         [0082]    Once the nut for maintaining the tension is brought into contact with the skirt  11   b  of the cylinder  11  of the actuator it is then possible to release the pressure in the hydraulic circuit whilst maintaining the stretching of the shank. 
         [0083]    In accordance with the example represented in  FIGS. 2A to 2C , using the device entails pivoting the bolts  1 . In accordance with this example, the parts  41 ,  42  to be clamped include cut-outs  43 ,  44  formed by a cylindrical cut-out of the bore type extended on one side to form a slot with a rounded bottom making it possible to move the bolt into position laterally with the locknut  21  already mounted in position. 
         [0084]    In  FIG. 2A , the bolt  1  is positioned in a first support  50  including an oblong opening receiving the shafts  201  at the end of the turrets  20   a,    20   b  carrying the inlet/outlet connectors  16 ,  17 . 
         [0085]    In  FIG. 2B , the bolt has been rotated to assume a position parallel to the slots  43 ,  44  of the parts  41 ,  42  to be clamped. The nut  21 , locknut  22  and washer  23  on the bolt are positioned beforehand with a distance D between the face  11   a  of the cylinder and the washer  23  of the nut  21 . The distance D takes account of the clearances necessary for triggering the device and makes it possible to eliminate any manipulation at the level of the nut/locknut. 
         [0086]    In  FIG. 2C , the bolt is in position and clipped into a spring collar  51  to make it possible to clamp the parts. 
         [0087]      FIG. 3  represents parts  41 ,  42  with a plurality of slots  43 ,  44  for fastening them. 
         [0088]    In the inclined waiting position, the bolt  1   a  is retained at the level of its shank  10  by a clamp  52 . 
         [0089]    This FIGURE makes it possible to see the bolts connected to hydraulic pressure circuits with the general references  61 ,  62 ,  63  with suffixes a, b, c. In this example three independent circuits each connect a plurality of bolts by their branches  61   a,    61   b,    61   c,    62   a,    62   b,    63   a,    63   b,  . . . which makes it possible to alternate the pressure circuits and to balance the pressures in the bolts fed by the same circuit and to alleviate a defective pressure circuit. 
         [0090]    By design, a tightening device of this kind is reversible since it suffices to depressurize the bolt, unscrew the retaining nut  12  and then release the pressure to demount the bolt. 
         [0091]    According to  FIG. 3 , the bolt is received in its spring collar  51  in the tightening position while the other bolts that can be seen are in the waiting position temporarily retained in second supports  52 . 
         [0092]    The device of the disclosed embodiment makes possible tightening without the presence of an operator and/or improved ergonomics because of the reduction of the necessary operator forces and assembly without tools. It makes possible good control of the accuracy and repeatability of the residual tension. It further makes possible a lengthening of the service life of the assembly devices, thanks to tightening under tension, verifying the residual tension; secure tightening, enabling reversion to a stable state (opening of the connection) from any degraded state (jamming, deterioration, fire, . . . ); to prevent manipulation errors and to optimize the operating times. 
         [0093]    The concept of operation by pivoting makes it possible to optimize operating times and the times of exposure to aggressive environments, the manipulation of the hydraulic pump effecting the tensioning is effected remotely. 
         [0094]    This optimization is achieved by the fact that tightening necessitates no intervention at the level of the nut of the bolt and that the operation proceeds without necessitating additional tools such as wrenches. 
         [0095]    By adding a system for driving the pivoting and the positioning of the bolts and a system for driving the position of the nut  12  for maintaining the tension, tightening can be carried out without the presence of an operator. 
         [0096]    The ergonomics and the use of this type of equipment are improved in the sense that the operators do not require to use any equipment. 
         [0097]    Moreover, the pivoting support for the bolt is designed to absorb the loads when it is manipulated. 
         [0098]    The solution makes it possible to eliminate entirely torque tightening and the high levels of uncertainty linked to friction. The residual tension obtained in the shank is generated entirely by pure traction and the tension is therefore controlled, accurate and repeatable. 
         [0099]    The use of high-torque bolted connections generates risks of deterioration of the thread and therefore of jamming. 
         [0100]    The hydraulic bolt entirely eliminates these risks linked essentially to the torque tightening method. 
         [0101]    The hydraulic bolt integrates a device for showing correct placing of the nut for maintaining the residual tension. 
         [0102]    In conjunction with input and output pressure monitoring, this device makes it possible to verify that the residual tension in the shank is correct. 
         [0103]    The hydraulic bolt of the disclosed embodiment is designed to integrate safety devices making it possible to revert to a stable state (opening of the connection) from a degraded state (jamming, damage by fire, . . . ). 
         [0104]    It is in particular possible to loosen the bolt because the head includes an angular engagement area or surface  34  represented in  FIG. 1  and in  FIG. 4B , this area being provided by a square rod in  FIG. 4B . It is therefore possible by retaining the bolt by means of the square rod  34  to loosen it by turning the locknut  22  and then the nut  21  in an unscrewing direction. 
         [0105]    Manipulation errors and numerous risks are also addressed by the safety devices (monitoring of incorrect placement of the nut for maintaining the residual tension, impossibility of placing the maintaining nut in the presence of pollution). 
         [0106]    In some sensitive environments (fire risk) it is possible to drive the pivoting bolt not by means of oil but by means of water containing glycol. 
         [0107]    The device of the disclosed embodiment may be adapted to any industry and to all fields requiring high-tension or high-torque tightening: automotive, railway, maritime, . . . , it is particularly suitable for use on flanged connections. 
         [0108]    Its ability to function in aggressive environments including undersea environments and its safety level and its ergonomics and in particular its short manipulation time, low operator exposure, makes it particularly suitable for hazardous environments that are difficult to access such as for example in the nuclear, chemical, gas, petroleum, wind turbine, undersea pipe fields.