Patent GB-884923-A (GB)
Title: Improvements in fluid-pressure-operated devices for tensioning studs or like tensionmembers
IPC: B25B29/02
Filed: 1960-03-21
Abstract: 884,923. Bolting. BABCOCK & WILCOX CO. March 21, 1960 [March 20, 1959], No. 9979/60. Class 89(1). A device for tensioning a stud 24 (or like tensioning member) comprises fluid-pressureoperated load-applying means to apply a predetermined axial stress to the stud 24 through a tensioning member 53 and compensating means to compensate for misalignment between the axis of application of the load by the load-applying means and the axis of the stud 24 by accommodating relative movement between the load-applying means and the tensioning member 53 (Fig. 2). The loadapplying means may comprise a pedestal 21 disposed with its base receiving a nut 33 on a stud 24, tensioning or pull-rod member 53 having at an end releasable stud-grippnig means 56 gripping the stud 24 in a manner resisting relative axial movement and holding it in axial or substantially axial alignment with the pull-rod 53, and fluid-pressureoperated load-applying means mounted on the pedestal 21 arranged to act on the pull-rod 53 to exert tensile force therein. The pedestal 21 may have side openings 25 to accommodate respective studs and nuts adjacent the tensioned nut and there may be means to rotate the nut 33 on a tensioned stud 24. In the form shown the load-applying meanscomprises a fluidpressure-operated piston-and-cylinder unit 22 with a cylinder 37 connected to the pedestal 21 through which passes a piston rod 47 in coaxial or substantially coaxial manner, connected to the pull-rod means 53 by the compensating means and encircling it with a tapering bore to give a clearance to allow for slight relative tilting thereof. The piston-andcylinder unit comprises a cylinder 37 having partition members 45, defining chambers 42, 43, 44 and in which the piston rod 47 is slidably mounted to carry pistons 48, having outer edges arcuate in cross-section, as are the inner edges of the members 45, both edges providing linear sliding contact with contacted parts. Inlets 49 for pressure fluid occur below the pistons 48 and there are vents, e.g. 51, above the pistons to relieve pressure. The compensating means comprises a washer assembly 55 including a washer 55B (seated on a resilient deformable member 55C on the top piston 48), with an upper part-spherical surface complementary to and slidably engaging a washer 55A supporting the pull-rod 53 against relative downward movement so that relative arcuate sliding of the washers permits the previously-stated tilting. The pull-rod 53 is provided with a thrust nut 54, to resist upward movement of the piston rod 47 relative to the pull-rod 53 and adjustable to vary the latter's axial position relative to the piston rod 47. The stud-gripping or chuck means 56 has a resilient ring-61A around it( attached to the pedestal 21) to hold it normally coaxial or substantially coaxial with respect to the pullrod 53. The nut 33 may be rotated relative to the stud 24 by means of a loosely-mounted nut socket 31 (Fig. 3) formed with gear teeth 31C meshing with a rotatable drive gear 34 mounted on the pedestal 21. The chuck means comprise a chuck housing 57 at the lower end of the pull-rod 53 in which are jaws 58, biased by a spring 59 (Fig. 2) to be normally-closed, adjustable means 60 having cam surfaces acting to open the jaws 58 against the spring action. In a modified form the jaws are so related to the chuck housing that they are closed on upward movement thereof relative to the jaws, and they may engage the housing along an upwardly diverging surface when it can have a downwardly tapering bore, the jaws being liftably mounted therein, complementary to parts of the bore, and biased to open on downward movement of the housing relative thereto. In a further modification the jaws 83 are pivotable about their lower ends (Fig. 5) so that when closed they are upwardly and inwardly inclined, being opened and closed by means of bell-crank levers 87, pivotally-mounted at their apices as shown and having arms 87A pivotally-connecetd to upper parts of the jaws 83 and arms 87B engaging a vertically-movable operating member 90. The jaws of the chuck means have recesses 83B or slots to engage a stud 24 at an end of reduced diameter with annular lands 24C. In the modification of Fig. 6 a spring 102 biases jaws 101 to be normally open, a vertically-movable sleeve 103 being arranged to embrace the jaws 101 when moved down to urge them inwardly to be closed, and vice versa through the spring 102. A final modification has a sleeve and jaws equivalent to the sleeve 103 and jaws 101, respectively, but shaped differently.