Torque wrench

Abstract: A torque wrench comprises an elongate body portion (2) including a hydraulic piston-cylinder assembly and a drive mechanism (4) actuated by said assembly to rotate an associated component about a first axis extending perpendicular to the line of action of the piston-cylinder assembly. A reaction member (6) is mounted to the body portion (2) to be pivotal relative thereto about a second axis extending parallel with the first axis between different positions extending angularly outwardly of the body portion (2).

Description: This invention relates to torque wrenches according to the preamble of claim 1, such wrenches incorporating reaction members for engagement with a fixed component during the tightening or untightening procedure. When torque tightening a nut or bolt of a series of nuts and bolts using a torque wrench provided with a reaction member, whether an arm or a foot, the wrench can usually be positioned whereby the reaction member reacts from the nut or bolt to either side of the one being tightened - ie. the wrench can be located either behind or in front of the row of nuts and bolts. In certain circumstances, however, there may be restricted access either behind or in front of the row of nuts and bolts whereby a torque wrench can only be located in front of or behind said row. Such a situation can arise, for example, when attaching or removing the individual blades of a ship's propeller to the central hub, and when dealing with the individual blades of a turbine. Thus it will be appreciated that, when the last bolt in a line of bolts is reached, there is no reaction point available to the torque wrench. Attempts have been made to overcome this problem of restricted access by providing a torque wrench incorporating a pair of driving heads adapted to tighten two bolts simultaneously, each bolt being tightened also being reacted upon. However, such a tool has a number of disadvantages. It is a complex, expensive piece of equipment that is dedicated to a particular use and cannot be used for tightening individual bolts. It cannot be used for an uneven number of bolts, while the actual load applied to a bolt may vary in each bolt being tightened, as maximum torque is applied to the tightest bolt. Further, such a wrench cannot cater for differing bolt pitches because of the fixed nature of the driving heads. US specification no. 4513645 discloses a torque wrench according to the preamble of claim 1 and including a reaction arm pivotally mounted to the body of the wrench, the end of the reaction arm remote from the body of the wrench having a socket therein for location over a fixed component to provide reaction for the wrench in use. It would be desirable to be able to provide a torque wrench of simple construction capable of accommodating restricted access to nuts and bolts to be tightened or unfastened thereby, capable of use under normal circumstances regardless of pitch variations in the nuts and bolts, and which provides additional restraint for absorbing reaction forces compared with the known arrangements. According to the present invention there is provided a torque wrench comprising an elongate body portion including a piston-cylinder assembly, a drive mechanism actuated by said assembly and having an output shaft rotatable about a first axis extending perpendicular to the line of action of the piston-cylinder assembly, means on said output shaft for engaging an associated component to be rotated whereby, on actuation of the piston-cylinder assembly, said component is rotated about said first axis, and a reaction member mounted to the body portion to be pivotal relative thereto about a second axis extending parallel with the first axis between different positions extending angularly outwardly of the body portion, the reaction member including, at or adjacent its free end remote from the pivotal mounting, a socket, characterised in that the reaction member comprises first and second arm portions located in a plane perpendicular to those containing the first and second axes, said first and second arm portions extending in opposite directions from the pivotal mounting of the reaction member, each arm portion including, at or adjacent its free end remote from said pivotal mounting, a socket so positioned that, on pivoting movement of the reaction member about the second axis, either one of the sockets can be aligned with said output shaft of the drive mechanism for location, in use of the wrench, over the component to be rotated, the other of the sockets, in such position of the reaction member, being aligned with, for location over, a separate fixed component spaced from the component to be rotated. The body portion may house therein a separate hydraulic piston-cylinder assembly or the body portion may comprise the cylinder of the hydraulic piston-cylinder assembly. Each arm portion of the reaction member may further include, intermediate the socket at or adjacent its free end and the pivotal mounting, one or more further sockets adapted to locate over fixed components. The reaction member may be mounted directly to the body portion and may comprise opposed, interconnected plates one to each side of the body portion and each including aligned sockets therein. By way of example only, an embodiment of the invention will now be described in greater detail with reference to the accompanying drawing which shows a torque wrench according to the invention. Referring to the drawing there is shown a low profile torque wrench of relatively conventional construction and including a generally cylindrical body portion 2 housing a hydraulic piston-cylinder assembly. To the front of the body portion 2 there is a housing 4 containing a drive mechanism which, in the case of a conventional wrench, comprises a pivotal drive lever carrying a square drive shaft and to which can be attached sockets of varying sizes, all in conventional manner. Heretofore torque wrenches have been provided with reaction arms and/or reaction feet adapted to react against a fixed member, conveniently an adjacent nut or bolt head, during a tightening procedure. However, such reaction arms and/or feet, once mounted on the wrench, are fixed relative thereto and project therefrom in a given direction. There are situations, as mentioned above, where the access to a row of bolts may be restricted to one side of the row and whereby the torque wrench, because of its physical size, cannot be positioned to that one side of the row. Consequently one or more of the bolts of the row may not be able to be tightened by the torque wrench because there is no suitably-positioned fixed member for the reaction member of the wrench to react against with the wrench positioned to the only side of the row of bolts available to it. In order to overcome this problem, the wrench of the invention includes a housing 4, containing a pivotal drive lever in which is formed a hexagonal socket 32, and a reaction arm indicated generally at 6 which is pivotally mounted to the body portion 2 to be movable between first and second angularly-displaced positions show in full lines and in dotted lines respectively in the drawing. The resultant arrangement is thus such that any bolt can be tightened by reaction against an adjacent bolt to either side thereof and without the necessity for the wrench to be located in the region of restricted access. More particularly, the reaction arm 6 comprises opposed, interconnected plated 6a, 6b one to each side of the wrench. Each plate 6a, 6b includes a first arm portion 36 and a second arm portion 38 integral with the first arm portion 36, said arm portions 36, 38 extending in opposite directions from the pivotal mounting of the reaction arm 6 to the body 2. The arm portions 38 are substantially mirror images of the associated arm portions 36, each portion 36 including a cylindrical socket 34 adjacent its free end and each portion 38 including a cylindrical socket 40 adjacent its free end. The arrangement is such that, in the first operative position of the torque wrench shown in full lines in the drawings, the socket 34 locates over a fixed reaction component spaced to one side of the nut or bolt to be tightened, while the socket 40 locates over the socket actually used to tighten the nut or bolt in question. Thus it will be appreciated that the provision of the socket 40 provides additional restraint for absorbing reaction forces than would be the case if the reaction arm 6 included portion 36 only. If the wrench is to react against a fixed component to the other side of the nut or bolt to be tightened, the reaction arm 6 is pivoted to the second operative position shown in dotted lines in the drawing in which the socket 34 locates over the component to be tightened, while the socket 40 locates over the fixed component to the other side of the nut or bolt to be tightened. The reaction arm 6 is provided with additional apertures or sockets 42 therein intermediate the sockets 34 and 40 which may be of different sizes. These additional sockets 42 can be located over additional or other fixed components thereby increasing the versatility of the tool and enabling different bolt pitches and/or different bolt sizes to be accommodated by a single tool. Thus there is provided a torque wrench of relatively simple construction which is capable of accommodating restricted access to nuts and bolts to be tightened or slackened but which can also be used in conventional situations for different pitch variations in the nuts and bolts, and which provides for additional restraint for absorbing reaction forces in view of the co-operation between one of the arm portions and the nut or bolt to be tightened.

Claims: A torque wrench comprising an elongate body portion (2) including a piston-cylinder assembly, a drive mechanism actuated by said assembly and having an output shaft rotatable about a first axis extending perpendicular to the line of action of the piston-cylinder assembly, means (32) on said output shaft for engaging an associated component to be rotated whereby, on actuation of the piston-cylinder assembly, said component is rotated about said first axis, and a reaction member (6) mounted to the body portion (2) to be pivotal relative thereto about a second axis extending parallel with the first axis between different positions extending angularly outwardly of the body portion (2), the reaction member (6) including, at or adjacent its free end remote from the pivotal mounting, a socket (34, 40), characterised in that the reaction member (6) comprises first and second arm portions (36, 38) located in a plane perpendicular to those containing the first and second axes, said first and second arm portions (36, 38) extending in opposite directions from the pivotal mounting of the reaction member (6), each arm portion (36, 38) including at or adjacent its free end remote from said pivotal mounting, a socket (34, 40) so positioned that, on pivoting movement of the reaction member about the second axis, either one of the sockets (34, 40) can be aligned with said output shaft of the drive mechanism for location, in use of the wrench, over the component to be rotated, the other of the sockets (34, 40), in such position of the reaction member (6), being aligned with, for location over, a separate fixed component spaced from the component to be rotated. A torque wrench as claimed in claim 1 in which the body portion (2) houses therein a separate hydraulic piston-cylinder assembly. A torque wrench as claimed in claim 1 in which the body portion (2) comprises the cylinder of the hydraulic piston-cylinder assembly. A torque wrench as claimed in any one of claims 1 to 3 in which each arm portion (36, 38) of the reaction member (6) further includes, intermediate the socket (34, 40) at or adjacent its free end and the pivotal mounting, one or more further sockets (42) adapted to locate over fixed components. A torque wrench as claimed in any one of claims 1 to 4 in which the reaction member (6) is mounted directly to the body portion (2). A torque wrench as claimed in claim 5 in which the reaction member (6) comprises opposed, interconnected plates (6a, 6b) one to each side of the body portion (2) and each including aligned sockets (34) therein.

Inventors: WALTON JOHN NIGEL, WALTON, JOHN NIGEL
Applicants: HEDLEY PURVIS LTD, HEDLEY PURVIS LIMITED
Application year: 1991
Main classification: B25B23
IPC codes: B25B21, B25B23