GB2054429A - Angle measuring wrench - Google Patents

Abstract

A wrench, particularly for setting threaded elements to a predetermined loading by applying a predetermined degree of angular rotation, incorporates a drive formation 10 with a handle 11 operated for direct rotation of the element and a reference member having a knob 16 or other hand grip and which is independently angularly movable about the axis of the element. A pointer 18 of the reference member is read against an angular scale 12 carried by the drive formation, the reference member being held stationary by one hand of a user while leverage is applied to the handle with the other hand. Conveniently the reference member is spring loaded to return automatically to a zero position and a movable stop 15 may be provided to determine the required degree of movement. <IMAGE>

Description

SPECIFICATION Wrench This invention refers to wrenches for tightening threaded elements.

Use of torque wrenches for setting threaded elements to a predetermined load is well known, however, loading by assessment of applied torque is not always entirely satisfactory due to varying conditions (e.g. state of lubrication of threaded element) and the danger that a torque reading will not show that a bolt our otherthreaded element has actually been tightened past its yieid point, once it starts to yield its torque resistance does not necessarily rise.

For this reason the "turn of the nut method" is now specified for certain applications of threaded elements, e.g. in automobile engineering. In employing this method measured torque is applied up to a predetermined level somewhat lower than the required final tightness in conventional manner, then a final measured tightening is effected by further turning the threaded element through a predetermined angle of rotation (regardless of torque) which has been computed to give the required stressing.

Various forms of wrench have been proposed to give a facility for measurement of the angle of rotation of the threaded element but they have often been designed onlyfora particular application. The need for an operatively stationary datum against which the angle can be measured has involved proposals for complex inertia or like devices carried on the wrench, or the need to mount some part of the device on adjoining structure to provide a fixed datum. This kind of arrangement does not lend itself to use by non-specialist mechanics or owners doing their own maintenance and, even if the equipment is available, the time and trouble needed to set it up may mean that an operator will not be troubled to use it so that the final tightening will either be guessed at or omitted.

The object of the invention is to provide a wrench incorporating the facility for setting by the "turn of nut method" which is particularly simple and adaptable in use, durable, and inexpensive to provide and maintain and which will readily give results well within acceptable tolerances.

According to the invention there is provided a wrench having a drive formation for connection to a threaded element, a drive handle by which torque is applied through said formation about the axis of rotation of said element in use, a reference member mounted for angular movement about said axis relative to the drive formation and provided with a hand grip enabling said member to be held stationary as said torque is applied, and reference means by which the angular displacement of the drive formation relative to said member while held stationary can be read.

Preferably the reference means incorporates a pointer and graduated scale, the latter conveniently being provided with a movable stop to be abutted by the pointer when the required angular movement has taken place so enabling operation to be sensed by feel as well as sight. It is also preferred that the wrench incorporates resilient means urging the reference member to a zero or starting position.

One way of carrying out the invention is now described in detail with reference to the accompanying drawings illustrating a specific embodiment, in which: Figure 1 is a side elevation of a wrench and Figure 2 is a plan view thereof.

The wrench comprises a conventional square drive formation 10 for mounting standard sockets or other accessories through which drive is applied to nuts, bolts or other threaded elements, formation 10 being fast with a conventional lever drive handle 11 (part shown broken away).

A reference plate 12 is fixed to a face of handle 11 an the opposite side to formation 10 and is graduated in tens of degrees about the centre axis 13 of formation 10. Associated with each graduation is an aperture 14 in which a movable stop 15 can be selectively located.

A hand grip in the form of a part spherical knob 16 atthe end of a stem 17 extendsfrom plate 12and is mounted for rotation relative thereto about axis 13.

Stem 17 carries a radially projecting pointer 18 so that said relative angular movement is limited between a zero position (defined by a fixed stop 19) and a position defined by the location of stop 15.

A torsion or other spring within stem 17 urges the hand grip to the zero position.

In use, to carry out then "turn of the nut method" of tightening the threaded element is set by a conventional torque wrench to the specified initial tightness and then the wrench of the invention is applied with stop 15 set to the required final tightening angle.

The user's right hand turns drive handle 11 while the left hand grips knob 16to hold it and pointer 18 stationary. Handle 11 is displaced until stop 15 is brought up against pointer 18, a condition which can be felt as well as seen so that the wrench can be used in conditions of poor visibility or accessibility. The userthen knowsthatthe required angulardisplace- ment has been effected to give tightening according to specification. On release of knob 16 the pointer is sprung back to zero ready for further use.

Though it is envisaged that the invention might be incorporated in a ratchet or, possibly, a torque wrench (in the latter case enabling the one tool to carry out both stages of the "turn of the nut method") the use of a separate tool is, in most applications, just as convenient particularly as the construction is simple and cheap to provide. For example, when tightening down a set of cylinder head nuts a torque wrench would be applied to each in turn to set them to the first stage of tightness then the wrench of the invention would be applied to each for final tightening.

Other versions of the invention are possible, for example stem 17 could carry a graduated scale for cooperation with a pointer or stop fast with handle 11, or instead of a stop which can be selectively set by predetermined increments a sliding stop or pointer which can be selectively clamped in position might be used. For most applications increments of 10' are within the tolerance range, and it is found in practice that knob 16 can easily be held stationary within acceptable tolerances although no fixed or artificial datum is provided.

Claims (9)

1. Awrench having a drive formation forconnection to a threaded element, a drive handle by which torque is applied through said formation about the axis of rotation of said element in use, a reference member mounted for angular movement about said axis relative to the drive formation and provided with a hand grip enabling said member to be held stationary as said torque is applied, and reference means by which the angular displacement of the drive formation relative to said member while held stationary can be read.

2. Awrench as in claim 1 wherein the reference means incorporates a pointer and a graduated scale.

3. A wrench as in claim 1 or 2 wherein the reference means incorporates a movable stop which can be positioned for abutment limiting said relative annuiar displacement to a preselected degree.

4. A wrench as in claim 3 wherein the reference means incorporates a plate having a series of apertures in which the movable stop is selectively located.

5. Awrench as in claim 4wherein said apertures are positioned at intervals of 10 degrees.

6. A wrench as in anyone preceding claim incorporating resilient means urging the reference member to a zero or starting position.

7. A wrench as in claim 6 wherein said zero or starting position is defined by a fixed stop.

8. A wrench as in any one of the preceding claims wherein the hand grip is a knob centered on said axis of rotation.

9. A wrench substantially as hereinbefore described with reference to and as shown in the accompanying drawings.