Torque wrench with variable-arm clicker mechanism

Abstract: A torque wrench (40) with a variable-arm clicker mechanism, comprises a substantially tubular body (41), equipped with a handgrip (18) from which protrudes a ratchet gear element (4), suited for engaging with the blocking device which must be tightened. Inside the tubular body (41) is the clicker mechanism, which comprises a main lever (2) ending with the ratchet gear element (4), with fulcrum on the same tubular body (41) by means of a pin (3). The clicker mechanism has a pair of parallel intermediate levers (6), hinged on a fulcrum (10), integral with a mobile carriage (9), where the parallel intermediate levers (6) extend within the carriage (9) through slots (31, 32) which act as guides for the levers and are connected by means of a pin (12) to small levers (22) which command a push rod (20) that operates a spring (16).

Description: The present invention relates to a torque wrench with variable-arm clicker mechanism according to the preamble portion of claim 1. Such a torque wrench is known for example from DE-A-37 18 143. As is known, there are various torque wrenches in existence, in particular equipped with a variable-arm clicker mechanism, which are used for applying a pre-established tightening torque on fastening devices such as bolts, nuts and similar. Torque wrenches generally have a tubular body, equipped with a handgrip, on which is applied a ratchet gear mechanism having, on one face, a suitable protruding part or cavity which allows it to mate with the fastening device that is to be tightened. This purpose of this ratchet gear is to form a solid connection, only in the tightening direction, with a portion of the mechanism which mates with the fastening device and with the tubular body, thus tightening the fastening device. Inside the tubular body is a so-called "clicker" mechanism which, when the pre-established tightening torque has been applied on the fastening device, allows a further limited rotation of the tubular body in the tightening direction without this additional rotation having any effect on the fastening device. In this way, when the user feels this clicking rotation in the tightening direction, he understands that the desired torque has been applied on the fastening device. An example of these torque wrenches is described in the patent for an industrial invention No. IT 1191798. It presents, among other things a torque wrench clicking and resetting mechanism, operated by a spring, for determining the clicking movement of the above-mentioned clicker mechanism. The torque wrench reset mechanism comprises a first transmission lever, which is hinged on a pin arranged substantially at the same height as a second pin on which is hinged a second transmission lever. When the pre-established tightening torque is applied on the nut or bolt to be tightened, one of the above-mentioned levers rotates in the opposite direction to the tightening direction, causing consequent rotation of the second lever and these rotations take place with a clicking movement, thus preventing further tightening of the nut or bolt once the pre-established tightening torque has been applied on them. Although a torque wrench such as the one described is able to perform the function for which it was designed, some interesting and important improvements may be made. In this torque wrench there are in fact a high number of components which are used to realise the linkages necessary to make the clicking and reset of the wrench. Moreover some components are difficult to make and are therefore expensive, and are also subject to premature wear because they have areas with concentrated loads that are too high. The aim of the present invention is therefore to realise a torque wrench with a variable-arm clicker mechanism, with a distinctly simpler construction than the prior art. A further aim of the present invention is to realise a torque wrench with a reduced number of components. Another aim of the present invention is to indicate a torque wrench with high repeatability, reliability and long life. Not the least aim of the present invention is to indicate a torque wrench that is easy to realise and therefore with low costs. These and other aims are achieved by a torque wrench with a variable-arm clicker mechanism, according to claim 1, to which reference is made for brevity's sake. Further characteristics of the present invention are also defined in the subsequent claims. Further aims and advantages of the present invention will be clear from the following description and from the annexed drawings, supplied purely as an illustrative example, without limitation, in which: figure 1 shows a longitudinal section of the torque wrench in the invention, with mechanism at rest and minimum torque position; figure 2 is a plan view of the torque wrench in the invention; figure 3 is a longitudinal section, similar to figure 1, but with the mechanism at end of stroke after the click; figure 4 is a longitudinal view, partly in section, in which the mechanism regulated at maximum torque is visible; figure 5 is a section plan view showing the main components of the torque wrench in the invention; figure 6 is an enlarged section of the blocking device belonging to the torque wrench in the invention; figure 7 is a cross section, through the plain VII-VII of figure 5, showing the form of the main lever and of two intermediate levers; figure 8 is a partial longitudinal section showing a blocking device of the wrench, housed in a receding position; and figure 9 is a cross section, through the plain IX-IX of figure 8, showing the folded tabs of a graduated scale, as well as the shape of the catch on the handgrip and that of the spacer. With particular reference to the figures mentioned, it is noted how the structure of the torque wrench, indicated overall with the reference number 40, is composed of a single tube 41, with a substantially rectangular section, within which is inserted on one side a main lever 2, with fulcrum on the same tube 41, by means of the pin 3. The main lever 2 ends with a ratchet mechanism 4 (or jack), suited to engage with the blocking device which must be tightened. A portion of the main lever 2, inside the tube 41, is shaped, in cross section, like an upside-down T and at its end 5 it is made in such a way as to be able to activate a pair of parallel intermediate levers 6, practically rolling on them, therefore with practically negligible friction. The intermediate levers 6 are hinged on a fulcrum 10, which is integral with a carriage 9; the intermediate levers 6 protrude from the mobile carriage 9 so that they are arranged next to the main lever 2 and then move with respect to it to vary the using torque of the torque wrench 40. Moreover, the intermediate levers 6 present a nib 7 which stops the stroke of the carriage 9 when it is shifted to obtain maximum torque. It should be noted that the intermediate levers 6 extend inside the carriage 9 through the slots 31 and 32 which act as guides for the levers themselves, so as to keep them parallel to the main lever 2. The intermediate levers 6, ending with a portion 13, arrive in a hollow 23, where they are connected by means of a pin 12 to small levers 22. The small levers 22 are hinged (in 21) onto a roller 15 which supports the transverse thrust, reducing friction during operation of the torque wrench 40. Moreover, the small levers 22 command a push rod 20 that operates a spring 16 which may be calibrated; the spring 16 is regulated by means of the nut 33 only in the final calibration phase of the wrench 40, through a hole 30. A suitable handgrip 18 closes the final part of the tube 41 and, by means of a protrusion 19, determines stopping at end of stroke of the carriage 9, when the torque wrench 40 is regulated at minimum torque. The carriage 9 therefore comprises all the mechanisms that make up the clicking device of the torque wrench 40. It also comprises a graduated scale 11 and a blocking device 14 that blocks the carriage 9 in the desired position. The graduated scale 11, not represented in detail, is visible by means of the through slot 8 in the tubular body 41; there is also a lens 36 which facilitates reading of the graduated scale 11. The position of the carriage 9 (depending on the torque regulation) is fixed by means of a blocking device 14 formed by a special nut (34), having a base (26) with a square section, and a round hub 25 which, passing through the graduated scale 11, pulls the scale together with the carriage 9. A screw with a large head 24 then blocks the device 14. As may be noted, the special nut 34 presents a seat 27 to contain the end of the screw which is lightly riveted to avoid its complete unscrewing and therefore the possibility of being lost. The blocking device 14 is fitted in one of the two seats 17 present in the carriage 9 and is inserted in the tube 41, together with the carriage 9 and the graduated scale 11, through the slot 8 in the tube 41. The blocking device 14 is fitted in the front seat, as indicated in figure 1, for wrenches that reach a maximum capacity of about 200 Nm and so the total length of the wrench 40 is such that the force to be applied on the handgrip, to reach maximum torque, assumes a reasonable value. Obviously, the graduated scale 11 will move together with the blocking device 14. The operation of the torque wrench 40, according to the present invention, is briefly illustrated below. The ratchet gear element 4 is engaged with the blocking device which is to be tightened and, by means of the handgrip 18, the user performs a rotation of the tubular body 41 of the torque wrench 40. Following this movement, the main lever 2, by means of its end 5, activates the pair of intermediate levers 6, rolling on them. The intermediate levers 6 rotate around the fulcrum 10, moving the small levers 22, which in turn rotate around the pin 21 until the pin 12 is substantially aligned with the pin 21 and with the fulcrum 10; this position is represented in figure 3 and is the position in which the mechanism described is at the end of stroke after having made one click. In this situation, the pre-established tightening torque has therefore been applied on the device to be tightened. In this situation, the spring 16 is temporarily compressed and allows the small levers 22 to perform an anti-clockwise rotation to go near the position in which the pins 12 and 21 and the fulcrum 10 are substantially aligned. The spring 16, in this condition, once the action of the torque exerted by the main lever 2 has ceased, is extended in the initial position, bringing the small levers 2 back to their initial position. The using torque of the torque wrench 40 may be varied, within certain limits, according to requirements, by shifting the mobile carriage 9, thus varying the distance between the fulcrum 10 and the end 5 of the main levers 2 on which the intermediate levers 6 act. The nib 7 allows the stroke of the carriage 9 to be stopped when it is shifted to obtain maximum torque. As indicated previously, the position of the carriage 9 (and therefore the torque regulation) is fixed by means of the blocking device 14, acting on the screw 24. Also the resistant force of the spring 16 may be calibrated by means of the nut 33, turning it through the hole 30. To obtain wrenches with a more reduced maximum torque, the regulation of the contrast spring 16 may be adjusted, or the spring 16 may be replaced with a spring that has a lower load. To obtain wrenches with a higher torque up to about 300-350 Nm, the main lever 2 must be replaced with a lever on which the part inside the tube 41 is suitably longer, so as to increase the arm on which the intermediate levers 6 act. For this purpose there is also a spacer 35 which, among other things, supports the graduated scale 11, on which there are two folded tabs 29 which pull the spacer 35, as far as a stop 28, during the regulating stroke of the wrench 40. For example, if the extension is 50%, the torque too will increase by about the same amount, but obviously the total length of the wrench 40 will increase in a much smaller proportion, and so the force that must be exerted on the handgrip to obtain the maximum torque will be too high and the wrench will therefore lose functionality. To avoid this problem, the blocking device 14 is inserted in the second seat 17 in the carriage 9. As may be seen, the rectangular-section tube of the torque wrench 40 must be extended, not only the difference of the length of the main lever 2, but also by an amount equal to the distance between the first and the second seat of the blocking device 14. The length of the wrench 40 is therefore again proportional to the maximum torque that it must develop and so the force to be exerted on the handgrip becomes acceptable again. Obviously, along with the blocking device 14 the graduated scale 11 also moves and, in order to be able to stop the movement of the carriage 9, towards minimum torque position, a spacer 35 is inserted which also supports the gradual scale 11, on which there are two folded tabs 29 which pull the spacer 35 during the regulating stroke of the wrench 40. As may be seen, the various components of the torque wrench 40 are simple, easy to make and to assemble, and so the costs of making it become quite low. From the description given, the characteristics of the torque wrench to which the present invention refers are clear, just as its advantages are clear. To define these advantages more precisely, the following considerations are now made. The torque wrench 40 in the invention allows a considerable reduction of the number of components, it has very simple components and considerable repeatability and reliability. The invention offers the possibility of realising a torque wrench with a relatively high capacity, modifying the total length of the torque wrench by an amount higher than the variations of the main lever, changing the seat 17 in which the fixing device 14 is inserted from front to rear, so as keep the same working of the tube in the rear area thus containing the length of the hollow. The formation of the end of the main lever and the arrangement of the changes of rotation, both of the main lever 2 and of the intermediate levers 6, allow a positioning to be held with minimum rubbing and practically no axial reaction. It is possible to pre-assemble the fixing device 14 so as to lightly rivet the end part of the screw, thus preventing total unscrewing with loss of the screw itself. The fixing device 14 is realised with a special nut and bolt obtained from a square-section bar, so as not to have to make any additional working apart from turning. The cylindrical hub of the above-mentioned nut passes through a hole made in the graduated scale 11 so as to pull it during the torque adjustment phase. The graduated scale 11 presents an end provided with folded tabs to pull the stop spacer which also acts as support for the graduated scale. The formation of the intermediate lever is such as to realise also the stop for axial regulation against the end part of the main lever. Although a particular embodiment of the invention has been described in detail for purposes of illustration, it is recognized that modifications and variations may readily occur to those skilled in the art, the scope of protection being determined by the appended claims.

Claims: Torque wrench (40) with a variable-arm clicker mechanism, comprising a substantially tubular body (41), equipped with a handgrip (18) from which protrudes a ratchet gear element (4), suitable for engagement with a fastening device intended to be tightened, where inside said tubular body (41) there is said clicker mechanism, which comprises a main lever (2) ending with said ratchet gear element (4), with fulcrum on the same tubular body (41) by means of a pin (3), characterised in that said clicker mechanism has a pair of parallel intermediate levers (6), hinged on a fulcrum (10), integral with a movable carriage (9), said parallel intermediate levers (6) extend within said carriage (9) through slots (31, 32) which act as guides for the levers and are connected by means of a pin (12) to additional small levers (22) which command a push rod (20) that operates elastic means (16). Torque wrench (40), according to claim 1, characterised in that said small levers (22) are hinged (in 21) onto a roller (15) which supports the transverse thrust of said intermediate levers (6). Torque wrench (40), according to claim 1, characterised in that the position of said carriage (9) is fixed by means of a blocking device (14), formed by a special nut (34), having a base (26) with a square section and which may be secured by means of a screw with a large head (24) Torque wrench (40), according to claim 3, characterised in that it has a graduated scale (11), visible by means of a through slot (8) in said tubular body (41). Torque wrench (40), according to claim 3, characterised in that said blocking device (14) has a round hub (25) which, passing through said graduated scale (11), pulls the scale together with said carriage (9). Torque wrench (40), according to claim 3, characterised in that it has a lens (36) which facilitates reading of the graduated scale (11). Torque wrench (40), according to claim 1, characterised in that it has means for calibrating the resistant force of the elastic means (16). Torque wrench (40), according to claim 1, characterised in that said handgrip (18) closes the end part of said tubular body (41) and has a protrusion (19) to determine stopping at end of stroke of the carriage (9), when the torque wrench (40) is regulated at minimum torque. Torque wrench (40), according to claim 1, characterised in that said intermediate levers (6) present a nib (7) which stops the stroke of the carriage (9) when it is shifted to obtain maximum torque. Torque wrench (40), according to claim 3, characterised in that said blocking device (14) may be housed in one of at least two seats (17) present in said carriage (9). Torque wrench (40), according to claim 10, characterised in that a spacer (35) is inserted in the tubular body (41) between the carriage (9) and the handgrip (18) to stop the movement of said carriage (9), when the torque wrench (40) is regulated at minimum torque and to support said gradual scale (11). Torque wrench (40), according to claim 11, characterised in that said spacer (35) is pulled during regulation by means of a folded tab (29) of the graduated scale (11).

Inventors: GAMBARINI LORENZO, GAMBARINI, LORENZO
Applicants: TECNOGI S R L, TECNOGI S.R.L.
Application year: 2001
Main classification: B25B23
IPC codes: B25B23