Torque wrenches for setting tightening forces on threaded nuts, screws or bolts traditionally use a socket spanner and tube assembly. When working with ring or open ended spanners, these are attached to the socket head assembly, which makes a bulky, difficult to use, arrangement.

In industrial situations where large numbers of bolts or the like on machinery and equipment are required to be tightened to predetermined levels of torque, it is the practice to mark the bolt after it has been set by spraying or dabbing it with paint. However, not only is such marking tedious and time consuming, but it is also prone to error. If the operator is distracted, he/she may not recall which nuts have been set when resuming the tightening task. Furthermore, operators tend to set a large number of bolts at a time and one or more can be missed. Also, when the bolts are subsequently marked, the bolts which have been set may not be properly recalled to memory with one or more being marked which have not been set. Clearly, the marking of bolts and the like in such industrial situations is open to many forms of human error.

OBJECTS OF THE INVENTION It is therefore one object of the present invention to provide a torque wrench which obviates the aforementioned bulk problems and permits use in confined

spaces.

Another object of the invention is to provide a torque wrench which automatically marks a bolt, nut or screw as soon as it has been tightened to the required degree of torque.

SUMMARIES OF THE INVENTION According to one aspect of the present invention there is provided a torque wrench comprising a first spanner with a first shank which extends into one end of a principal tube and which is pivotally secured therein by a first head-pin, the first shank having an end which co-acts with a first spring-loaded roller assembly within the tube, and wherein a second spanner with a second shank extends part-way into the other end of the tube, the second shank having an end which co-acts with a second spring-loaded roller assembly within the tube in an opposite direction to the first shank, said second shank being adjustable longitudinally with respect to the principal tube so as to set the tension in a spring, which tensions both the first and second spring- loaded roller assemblies, whereby the torque applied through the first spanner to a nut or the like is set to a predetermined amount.

According to another aspect of the present invention there is provided a torque wrench comprising a spanner with a shank which extends into a tube and which is pivotally secured therein by a head-pin, the shank having an end with co-acts with a spring-loaded roller assembly within the tube, said wrench including a proximity switch and an ink injector which has an associated nozzle extending through the spanner, the construction and arrangement being such that when the spanner shank rocks relative to the tube during the setting of a nut, the proximity switch generates a signal whereby ink is pumped by way of the injector through the

nozzle onto the nut which has been-set.

DETAILED DESCRIPTION OF THE INVENTION The proximity switch can be mounted on the top, side or interior of the torque wrench tube depending on the specific design of the torque wrench and its proposed use. In a preferred embodiment of the invention, the ink injector arrangement is combined with the earlier of the aforementioned two aspects of the invention and, in this case the precision proximity switch is typically mounted on either the side or the top of the torque wrench.

In the earlier aspect of the invention, the second shank of the second spanner can be adjusted longitudinally within the principal tube by fixing it by means of a pivot pin to an extendable portion which can slide relative to the tube. One suitable design for the extendable portion comprises a second tube which slides over the end region of the principal tube. Preferably the second tube has two diameters to limit the amount by which it can slide over the principal tube.

The means for fixing the relative longitudinal position of the second shank with respect to the principal tube can be effected by a locknut on the inner end of the second tube. An associated adjacent torque setting sleeve can be provided to enable appropriate adjustment of the torque when the locknut is loosened or, more preferably, it can provide the means by which the locknut can be rotated to achieve the necessary torque setting.

Preferably, the spring tensioning means is common to both the first and second roller assembly and comprises a coil spring which is axially aligned within the principal tube. Spring guides which fit into the ends of the spring and which contact the respective ends of the first and second shanks, can be provided to ensure

a smooth regular compression/extension of the spring to the required tolerances for setting the torque.

The end-regions of the shanks of the first and second open-end spanners which contact the roller assemblies, in combination with the roller assemblies, can comprises conventional torque applying arrangements.

One such arrangement is wherein the roller assembly projects a sloping face to a complementary sloping face on the end of the shank and is configured and includes means such that when the predetermined torque has been reached, the sloping face on the end of the shank suddenly shifts relative to the position of the indent and collides with the inner side wall of the hollow tube, accompanied by an impact noise and an abrupt reduction in torque which informs the user of the tightening of the bolt or the like.

The torque wrench is also such that different torques can also be applied by extending the spanner mechanism centre from the pivot pin, allowing one torque on one end and a different setting on the other end.

This allows for one spanner to have one torque setting and the other end to be identical or a completely different torque for two different spanner sizes.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a longitudinal cross-section of a torque wrench according to one aspect of the invention, Figure 2 is a partially cut-away side view of a torque wrench according to another aspect of the invention with a switch mounted on top thereof, Figure 3 is a partially cut-away top view of a torque wrench according to yet another aspect of the invention with a switch mounted on the side thereof, and

Figure 4 is a partially cut-away top view of a torque wrench according to still yet another aspect of the invention with a switch mounted inside thereof.

In all of the drawings, like reference numerals refer to like parts.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to Figure 1 of the drawings, the torque wrench comprises a first open end spanner 10 having a first shank 11, and a second open end spanner 12 having a second shank 13, which respectively extend into opposing ends of a principal tube 14.

The first shank 11 is held within the principal tube 14 by means of a pivot pin 20. The second shank 13 is pivoted by means of a pivot pin 21 to a second longitudinally movable tube 22 which is retained on the outer surface of the principal tube 14. The second longitudinal tube 22 has two diameters to limit its movement with respect to the principal tube 14.

The respective ends 15,16 of the shanks of the spanners are angled and co-act with the respective angled faces of roller assemblies 17,18 which are, in turn, held under tension by a common coil spring 19. The angled ends of shanks 15,16 each have an associated pin 24,25. These pins depress the respective roller assemblies 17,18 when under load, enabling the ends of the shanks to rotate about their respective pins 20,21.

The torque setting is adjustable by moving the second tube 22 over the principal tube 14 by means of an adjustable nut 26 which is threaded to the principal tube. An adjacent torque setting sleeve 27 enables one to read off the required setting to which the adjustment is made.

Limit screws 30,31 are located in the respective shanks 11,13 to enable pre-adjustment of the relative degrees of torque indicating movement of the spanners 10,12.

The torque required is proportional to the length"L"of the moment arm from the centre of the spanner 10 to the pin 20 versus the moment arm length"M" from the pin 20 to the roller pin 24 by the spring force.

Increasing the spring tension has the effect of increasing the torque applied to depress the mechanism providing a telltale obvious sound and spanner action indicating the correct torque is reached as preset.

Different torques can be applied also by extending the spanner mechanism centre from the pin allowing one torque on one end and a different setting on the other end. This allows for one spanner to have one torque setting and the other end to be identical or a completely different torque for two different spanner sizes.

The torque read outs are noted on the torque tables adjacent to the spanner and matched against the torque setting sleeves.

Although this embodiment has been directed to a torque wrench having two open end spanners, it will be appreciated that open end ring spanners, closed end spanners, and combinations of all possible spanners, can all equally be used.

The torque wrench utilises an in line compact design suitable for working within confined spaces or on nuts which are not accessible to socket spanners.

Typical of this requirement is the installation of fluid lines such as hydraulic oil or compressed gas where access for socket type torque wrenches are limited.

Referring to Figure 2, the torque wrench comprises a spanner 40, attached shank 41, and guide tube 42 with a conventional rocking mechanism therein. An external precision proximity switch 43 is mounted on the side of the tube and is electrically connected by lead 44 to a pressurized ink reservoir (not shown). An ink injector 45 is fitted to the shank 41 and is connected by way of tube 46 to the ink reservoir. A nozzle 47 projects from the ink injector 45 through the spanner 40 and outlets where a nut to be set will be located.

In operation, when the torque of the nut has been set, the shank 41 rocks and forces sensor arm 48 against a coil in the switch. This alarms the pressurized ink reservoir to disperse ink through nozzle 47 onto the nut, thereby providing an indication on the nut that it has reached a predetermined torque setting.

Figure 3 shows a torque wrench arrangement which is similar in construction and function to that shown in Figure 2. The main difference is that the switch 43 is mounted on the side of the torque wrench.

Figure 4 shows a torque wrench in which the switch 50 is mounted in the interior of the torque wrench. In most other respects the function and operation is similar to that of the Figure 2 embodiment.

Whilst the above has been given by way of illustrative example of the invention, many modifications and variations may be made thereto by persons skilled in the art without departing from the broad scope and ambit of the invention as herein set forth.