GB2182592A

GB2182592A - Hydraulic torque wrench

Info

Publication number: GB2182592A
Application number: GB08625129A
Authority: GB
Inventors: Olaf Blokisch
Original assignee: Hydra Tight Ltd
Current assignee: Hydra Tight Ltd
Priority date: 1985-10-22
Filing date: 1986-10-20
Publication date: 1987-05-20
Also published as: EP0246262A1; WO1987002610A1; GB8525983D0; GB8625129D0

Abstract

A hydraulic torque wrench has a hollow piston with a slot in its sidewall through which an actuator arm projects into the interior of the piston, to which it is connected only through a linkage between the piston at one end and the arm at the other end.

Description

SPECIFICATION Improved power tools Fieldoftheinvention This invention relates to torque wrenches. In particular it is concerned with a torque wrench which is hydraulically-operated bya piston and cylinderdevice and also includes a ratchet mechanism.

Successive operations of the piston and cylinder device allied to operation of the ratchet on the return stroke of the latter enable a nut or boltto betightened (or untightened) without removing the tool from the nut (or bolt) and without need for manual re-setting between successive power strokes of the piston and cylinder.

Discussion ofthe prior art Many forms of hydraulic torque wrench incorporating a ratchet are known. For example European patent specification Number 621 95A shows a wrench in which a form of knee joint linkage is used to transmit pressure from a piston in one part ofthe wrench to another part ofthe wrench, so that relative movement takes place between the two parts, thereby turning a nut (or bolt) - engaging socket. A similar knee joint is used in association with a pawl and ratchet mechanism, to facilitate the return of the two wrentch parts to their starting point, for the next power stroke of the piston and cylinder device.

Object ofthe invention It is an object of the invention to produce a ratchettype hydraulictorque wrench of relatively simple construction.

Brief discussion ofthe invention According to this invention, a hydraulictorque wrench of the kind comprising two parts which are relatively movable about a common axis of rotation with an associated ratchet and pawl mechanism, underthe influence of a piston and cylinder device, is characterised in that the piston and cylinder device includes a hollow piston having a slot defined in a sidewall thereof and a distal portion of one of said relatively movable parts projects through said slot and through a corresponding slot in the cylinder into the hollow piston, to which it is operably connected onlythrough a linkage between the piston at one end and said distal portion at the other end.

"Operably connected" means for present purposes that the linkage is not necessarily positively attached to the piston, for example by a pin, orto the distal portion, orto both of these. In some embodiments it may be more convenient to have no such positive connection between the linkage and the piston. For example, the otherwise free end ofthe linkage may be located within a recess or hollow in the piston. Operably-connected means in this case that the linkage can exert positive pressure in only one direction. For practical purposes this may be all that is actually necessary.

The hollow piston may be of unitary construction, closed at both ends. The return stoke of the piston and cylinder (priorto the next power stroke) may in this case be accomplished by applying hydraulic pressure to that end ofthe piston opposite to the end operably connected to the linkage.

However, it is also possible for that one end just mentioned to be open. In this case, a second independant and oppositely-directed piston may be provided in back-to-back relation to the first piston. The oppositely-directed piston may be constructed to apply pressure directly against the open end of the first piston, to cause the latter to make the return stroke. Alternatively, the oppositely directed piston may be operably connected to the same distal portion of one of the movable parts only through a linkage operably connected to the second piston at one end and to the distal portion at the other end.

Description of preferred embodiments Figure 1 ofthe accompanying drawings illustrates the features of a torque wrench constructed in accordance with the invention. The drawing is a side elevation, partly in section, from which aspects not directly relevant to the invention have either been omitted, or are not shown in great detail.

Awrench body (1 ) with hydraulicfluid connectors (2) and a carrying handle (3) contains a pawl foot (4) and ratchetwheel (5), the latter driving a sockettool (6). The socket (6) is accessible through the wrench body; the pawl foot (4) is spring biassed in conventional manner (7) into wedging engagement with the ratchet wheel (5), with the aid of a cam surface (8) constituted by one side of an opening in a relatively movable member (9) located insidethewrench body (1). The member (9) has a distal portion (10). The body (1 ) also contains a piston (11) in a cylinder (12).

The piston is hollow, with a piston head (13), (14) at each end. The piston is in two parts (15), (16) united byascrew-threadedconnection (17).Annularseals (18) are provided adjacent each piston head; each of the two fluid connectors (2) communicates with its own respective end of the cylinder (12).

Both the piston and the cylinder have slots machined in them (not explicity shown, but in the region 19) to aIIowthe distal portion (10)toprojectintothe hollow piston. The free end of the distal portion has one end of a linkage (20) pivotally attached to it. The opposite end of the linkage is connected to the inside of the piston head (13), by a pivot pin, (21).

In use, pressure applied to the piston head (13) causes the piston to move to the right. This in turn movesthe linkage (20) andwith itthe distal portion (1O).Th e I atter causes the member (9) to rotate clock- wise about the axis of the socket (6). This movement, plus the action of the cam surface (8) and spring (7), wedges the pawl foot (4) into engagement with the ratchet wheel (5) so the latterturns with the member (9), forcing the socket (6) to do likewise, provided that the body (1 ) is not also free to rotate aboutthe same axis.Normally this is accomplished by ensuring that there is engagement between the body and a fixed abutment on the hardware associated with the nut (or bolt) on which the socket is seated and which isto be tightened, or released by use of the wrench.

For example, the regions (22) or (23) of the body (1) may be abutted against the next nut in a series which are to be tightened (or released).

Afterthecompletion ofthefirstpiston stroke, the fluid pressure, or at least some of it, can be applied at the other end of the cylinder, to piston head (13). This then moves to the left in the figure, causing the distal portion (10) to do the same. This rotates the member (9) anti-clockwise; this in turn releases the pawl foot (4) from the cam surface (8) so that onlythe spring (7) holds it against the ratchet wheel. Provided that the nut (or bolt) engaged in the socket (6) is not actually loose, the pawl foot (4) will iift off the ratchetwheel allowing the member (9) to return to its starting position. The operation is repeated as desired.

It will be appreciated that the same tool can be used for both clockwise and anti-clockwise rotation of a nut/bolt, by simply turning the tool over.

Figure 2 ofthe accompanying drawings shows a further embodiment ofthe invention. In this version, two separate pistons, 40 and 41 are provided and there are two linkages 42,43 corresponding to the single linkage 20 of Figure 1. However, these linkages are pivotally connected to the distal portion 10 ofthe common member 9. (It should be noted that common reference numerals have been used in both figures, asfaras possible).

Because ofthe symmetrical construction, it is not necessary to secure the linkages 42,43 to their respective pistons 40 and 41. The operable connection is in each case provided by co-operating ball (44,45) and socket (46,47) joints. The operation of this tool is otherwise generally similar to that of the first embodiment; it need not be described further here.

Figure 3 ofthe accompanying drawings illustrates a modification ofthetwo piston arrangement shown in Figure 2 For ease ofunderstanding,onlythe link- ages 42,43 are shown, on an enlarged scale. In order to urge the linkages towards one another and into contact with the actuator (10, in Figure 2) a coil spring 50 is provided. The spring extends into bores 51,52 in the respective linkages and the ends ofthe spring are retained by set screws 53,54 respectively, so that the spring is undertension. The linkages are thus bi assed towards one another and against the actuator 10. Whilst only one spring has been shown, it will be appreciated that a second spring diametrically opposite to the first one will usually be used, to ensure thatthe biassing force is symmetrically disposed aboutthecommon axis of the linkages.

Claims

1. A hydraulic torque wrench ofthe kind comprising two parts which are relatively movable about a common axis of rotation with an associated ratchet and pawl mechanism, under the influence of a piston and cylinder device, characterised in that the piston and cylinder device includes a hollow piston having a slot defined ina sidewall thereof and a distal portion of one of said relatively movable parts projects through said slot and through a corresponding slot in the cylinder into the hollow piston, to which it is operably connected (as defined) only through a linkage between the piston at one end and said distal portion at the other end.

2. A wrench accordingtoClaim 1 wherein the hollow piston is of unitary construction and closed at both ends.

3. AwrenchaccordingtoClaim 1 orClaim2 wherein fluid pressure may be applied to either end of the piston, for reciprocating movement in said cylinder.

4. A wrench according to Claim 1 including a second, independantand oppositely-directed piston in back-to-back relation to the first piston, said second piston being adapted to apply pressure to the end of the first piston to cause the latterto make a return stroke.

5. A wrench according to Claim 1 including a second, independent and oppositely-directed piston in back-to-back relation to the first piston, wherein the second piston is operably connected to the same distal portion asthefirst piston only through a second linkage operably connected to the second piston at one end and to the distal portion at the other end.

6. A wrench according to Claim wherein said first and second linkages are operably biassed towards one another by spring means.

7. Awrench according to any preceding Claim, wherein movement of the hollow piston in one direction causesthe pawltoengagethe ratchetthereby rotating an associated drive tool about said common axis.