Abstract:
A pair of tongs is disclosed that includes first and second spaced apart members each having a first end having a jaw-like part and a second end, the second ends of the first and second members being movable toward and away from each other by the use of one hand. A first connecting element with a first straight toothed surface extends from a point on the first member between its first and second ends and a second connecting element having a second straight toothed surface facing the first straight toothed surface extends from a point on the second member between the first and second ends of the second member for releasably engaging the first connecting element. The first toothed surface includes first and second rows of teeth and the second row of teeth is displaced relative to the first row of teeth.

Description:
FIELD OF INVENTION 
     The present invention relates to a hand tool to lockably apply a compressive or separating force on a workpiece, said tool comprising two shafts pivotable in relation to each other, the ends of which form two jaws for cooperation with the workpiece and which, spaced from these ends, are joined together by a spring element with an action corresponding to a compressible compression spring, and a locking device between said spring element and said jaws, said locking device comprising a toothed locking element protruding from one of the shafts and a locking device on the other shaft arranged by engagement with the toothed locking element to releasably lock the position of a joint about the spring element. 
     DESCRIPTION OF THE PRIOR ART 
     Patent specification EP 0403517 describes a tool according to the above, comprising two shafts with jaws, a spring element and a locking device, which locking device produces a movable joint. The movable joint enables a combination of high clamping force and large working range. To obtain a high clamping force on workpieces of varying thicknesses the possible locked positions for the joint must be as close together as possible. The above patent suggests different designs of locking devices which can be divided into two main groups: shape-dependent and friction-dependent locking devices. Friction-dependent locking devices allow in principle stepless adjustment of the position of the joint, but have the drawback that they require considerable contact forces. These large contact forces require the locking element and locking member to be manufactured of high-strength material, thereby greatly increasing manufacturing costs. In practice, therefore, shape-dependent locking devices have come to be used for this type of hand tool, said locking devices comprising a toothed locking element protruding from one of the shafts and a locking member in the form of a catch on the other shaft, arranged by engagement in the toothed locking element to releasably lock the position of the joint. It has been found that a catch that is pivotably suspended in the second shaft offers particularly good function. The drawback with this type of locking device is that the teeth on the locking element can hardly be closer together than 2.5 mm if they are manufactured of metal with high precision, if a reliable locking function is to be obtained. This means that greater amplification than approximately 3 times the force cannot be obtained if an acceptable clamping function is to be obtained on workpieces of varying thicknesses when the tool is operated. with one hand. There has hitherto been no satisfactory solution to this limitation in force amplification. Furthermore, due to the demand for locking positions close together, and thus small teeth, it has hitherto been impossible to achieve a reliable locking device made from plastic, which is desirable since the tool can then be produced more cheaply. 
     SUMMARY OF THE INVENTION 
     The main object of the present invention is to provide a hand tool as described above consisting of two shafts with jaws, a spring element and a shape-dependent locking device which produces a movable joint, said locking device combining reliable locking function and tightly spaced locked positions for the joint. 
     This object is achieved with a hand tool to lockably apply a compressing or separating force on a workpiece, said tool comprising two shafts pivotable in relation to each other, the ends of which form two jaws for cooperation with the workpiece and which, spaced from these ends are joined together by a spring element with an action corresponding to a compressible compression spring, and a locking device between said spring element and said jaws, said locking device comprising a toothed locking element protruding from one of the shafts and a locking device on the other shaft arranged by engagement with the toothed locking element to releasably lock the position of a joint about which the shafts can pivot in relation to each other under influence of the spring element, said locking device comprising two or more catches and/or said locking element comprising two or more rows of teeth. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in more detail with reference to the accompanying drawings which are intended to explain and to not limit the invention, in which 
     FIG. 1 is a side view showing the construction of the tool in principle, 
     FIG. 2 is intended to explain the relationship between force amplification and the movement of the locking device during compression of the spring, 
     FIG. 3 is a side view of a preferred embodiment of a tool made from plastic material, 
     FIG. 4 is a partial view, partly in section, showing the tool according to FIG. 3 from above, 
     FIG. 5 is a side view or the tool according to FIG. 3, with the jaws in engagement with a workpiece, 
     FIGS. 6 and 7 are side views showing the tool according to FIG. 5 with the spring element in varying degrees of compression, 
     FIG. 8 is a side view showing an alternative embodiment of the locking device with two catches controlled to linear movement, 
     FIG. 9 is a side view showing a toothed locking element with two different rows of teeth and catches pertaining thereto, 
     FIG. 10 is a view from the front of the device according to FIG. 9, 
     FIG. 11 is a side view showing a locking element with two rows of teeth which can be turned in relation to each other. 
     FIG. 12 shows the tool provided with tiltable collet jaws. 
     FIG. 13 is a view from above of the tool according to FIG. 12, showing the lateral extension of the collet jaws. 
     FIG. 14 shows the tool in squeezed position, provided with collet jaws for securing at right angles. 
     FIG. 15 shows the tool in squeezed position, provided with collet jaws for securing at right angles. 
     FIG. 16 shows the tool provided with fixed collet jaws for metal objects. 
     FIG. 17 shows the tool in squeezed position, provided with extended collet jaws. 
     FIG. 18 shows a side view of extended collet jaws connected together. 
     FIG. 19 shows the tool in squeezed position, provided with collet jaws for suspension from a hook. 
     FIG. 20 shows the tool provided with contact jaws with an electric conductor between. 
     FIG. 21 shows the tool provided with contact jaws without an electric conductor between. 
     FIG. 22 shows the tool provided with crossing collect jaws for pressing apart two surfaces. 
     FIG. 23 shows the tool provided with collet jaws pointing downwards. 
     FIG. 24-26 show partial side view of a coupling arrangement between jaw and shaft. 
     FIG. 27-28 show partial side view of a coupling arrangement between jaw and shaft. 
     FIG. 29 is a side view of a tool with coupling arrangements for jaws. 
     FIG. 30 shows side views of various types of jaws to fit the tool according to FIG.  29 . 
     FIG. 31-32 are side views of tools according to FIG. 29 with applied jaws in various forms according to FIG.  30 . 
     FIG. 33 shows side views of a tool and separate variations of jaws with alternative coupling arrangements. 
     FIG. 34 shows side views of a tool according to FIG. 33 with various jaws fitted. 
     FIG. 35 is a side view of a tool in which the lower jaw is adjustable for two different working ranges. 
     FIG. 36 is a side view of the tool according to FIG. 35 with the lower jaw removed. 
     FIG. 37 is a side view of adjustavle lower jaw according to FIG.  35 . 
     FIG. 38 is a view from above of the jaw according to FIG.  37 . 
     FIG. 39 is a side view of two jaws with tiltable collet jaws in contact with a workpiece, revealing elements for securing the collet jaws in the jaws. 
     FIG. 40 is a side view of a jaw according to FIG. 39 with a long collet jaw in its position of rest. 
     FIG. 41 is a side view of a jaw according to FIG. 39 with a long collet jaw turned to its outermost position. 
     FIG. 42 is a side view of a jaw according to FIG. 39 with a short collet jaw in its position of rest. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In its basic design, the tool is constructed in accordance with FIG. 1 with two shafts  1  and  2  provided at their ends with jaws  3  and  4 . The shafts are joined by a spring element  5  at the opposite ends. Between the jaws and the spring element is a locking device  6  comprising a toothed locking element  7  protruding from the shaft  2 , and a locking member  8  comprising a catch  11  pivotably suspended in the joint  10  on the shaft  1 , a spring element  15  that presses the catch against the toothed locking element, and a lever  13  to release the catch from the locking element  7 . In its non-deformed state the spring element  5  defines the rest position of the shafts in relation to each other. The jaws  3  and  4  are then preferably spaced from each other so that a workpiece can easily be inserted between them. The exterior of the shafts is provided with grips between the spring element  5  and the locking device  6 , to enable convenient manipulation with one hand. When a work-piece is to be gripped, the gripping portions are pressed together. The jaws of the shafts are thus pivoted in relation to each other and the spring element  5  is bent somewhat, without noticeable compression. Upon such a pivoting movement the catch  11  slips over the teeth of the locking element  7 . When the jaws come into contact with the workpiece the compressive force is increased and the spring element  5  is thus compressed. During this compression phase, the catch  11  slips ever another few teeth on the locking element  7 . When the gripping portions are then released, the catch will be in locked position. The force from the compressed spring element  5  will then strive to swing the shafts  1  and  2  in relation to each other around the joint  9 , in practice around both the joints  9  and  10 . A clamping force then arises on the workpiece, the magnitude of which depends on the position of the joints  9  and  10  between the spring element  5  and the jaws  3  and  4 . A force amplification will occur if the joints  9  and  10  are nearer the jaws than the spring element. The account above is substantially an account of known technology according to EP 0403517. Referring now to FIG. 2, the limitations of this technology will be discussed, paying particular attention to the function of the locking device. The Figure shows two triangles of similar shape, ADE and ACB. Point A represents the contact point of the jaw  3  with the workpiece. This is the point around which the shaft  1  pivots when the spring element  5  is compressed the distance CG. The force from the spring element  5  is assumed to operate along the line BC. During the compression phase the shaft  1  is moved from position AC to position AG. The catch  11  is thus moved the distance DF. The fundamental limitation is the working range of the human hand. An average hand can comfortably achieve a force grip with a distance between the two gripping portions that can vary from 50 mm up to maximally 80 mm. The maximum compression distance CC for the spring element is thus approximately 30 mm. If twice the force amplification is to be achieved, the distance EB must be twice the distance AE. The distance AB will therefore be three times greater than AE. Since the triangles are similar, this results in the distance DF being one third of the distance CG. The conclusion is, therefore, that the displacement of the catch  11  during the compression phase will be only 10 mm. In the same way, three times the force amplification will result in the distance DF being reduced to one fourth of the distance CG. To obtain acceptable function of the tool, at least three locked positions for joint  9  are required during the compression phase. At least two different levels of squeezing force can then be applied to the workpiece and ⅔ of the maximum squeezing force is always available. 
     If this is to be achieved with three times the force amplification, the distance between the locked positions for the joints must be at most 2.5 mm. The teeth on the locking element  7  must then necessarily be small and must be manufactured with high precision in metal in order to ensure reliable engagement of the catch  11  in the locking element, without risk of breaking when the locking device is subjected to considerable forces under the influence of the spring element  5 . For the above reason it is impossible to increase the force amplification any more with a shape-dependent locking device according to known technology. Neither is it possible to manufacture a locking device of plastic material, which would be preferable since this would greatly reduce the manufacturing costs. To obtain a reliable lock in plastic the tooth distance would have to be about 8 mm. Even if a force amplification of about 1.6 times is accepted, conventional technology does not permit greater distance between the teeth than about 4 mm. 
     FIGS. 3 and 4 show the solution to the problem defined in the paragraph above, in a preferred embodiment of a tool according to the invention, manufactured mainly of plastic material. The shafts  1  and  2  are made in one piece with the jaws  3  and  4 , respectively, from reinforced plastic material. The shafts  1  and  2  are provided externally with gripping portions. A toothed locking element  7  with a tooth distance of about 8 mm protrudes from the shaft  2  and in one piece therewith. The locking element  7  cooperates with a locking member  8  on the shaft  1 . This locking member comprises two catches  11  and  12 , pivotably suspended in the joint  10  consisting of the pin  14  in the shaft  1 . The catches, also, are made of a reinforced plastic material and characterized in that they are displaced in relation to each other by approximately half a tooth distance, so that they do not engage simultaneously in the teeth of the locking element  7 . The locking member  8  also includes the spring elements  15  and  16  which press the catches  12  and  11 , respectively, against the toothed locking element  7 . The locking member  8  also comprises a lever  13  to be manipulated with the thumb in order to release the catches  11  and  12  from their locked position. The lever  13  is manufactured in one piece with the catch  11 . Some form of driver is required on the catch  11  to enable manipulation of the catch  12  with this lever  13 , and a corresponding groove in the catch  12 , which is not shown in the figure. The shafts  1  and  2  with their jaws and locking parts are retained in rest position by means of a spring element  5 , preferably in the form of a plate spring made of steel. The spring element  5  is preferably embedded at each end into the shafts  1  and  2 . When the gripping portions  31  and  32  of the shafts  1  and  2  are pressed together, the jaws  3  and  4  will swing towards each other without noticeable compression of the spring element  5 , whereupon the highest points  41  and  42  are at approximately the same distance from each other. This is illustrated in FIG. 5 where the jaws  3  and  4  are in initial contact with a workpiece  17  and the catch  11  engages with a tooth in the locking element  7 . If the gripping portions  31  and  32  are subjected to increased compressive force, the spring element  5  will be compressed and the locking member  8  is moved in relation to the locking element  7 . This is illustrated in FIG. 6 where the locking member has moved half a tooth distance and the catch  12  engages with the same tooth of the locking element  7  as was previously in engagement with the catch  11 . Upon further compression of the gripping parts  31  and  32  the catch  11  engages in the next tooth of the locking element  7 , as shown in FIG.  7 . 
     The compression phase is now complete and when the gripping portions are released the force from the spring element  5  will endeavour to pivot the shafts  1  and  2  around the joint  9 , thus producing reinforced clamping pressure on the workpiece  17 . During the compression phase the joint  9  has been displaced approximately 8 mm in two steps. Thanks to the arrangement with double catches, both these positions of the joint  9  have been reliably locked. The tooth distance is approximately 8 mm and the teeth on the locking element  7  can therefore be made of plastic material and still be dimensioned to withstand protracted loading. Furthermore, the engagement distance is sufficiently long to prevent risk of the catches  11  and  12  slipping out of their locked positions. In the embodiment according to FIGS. 3-7 the catches  11  and  12  operate beside each other on half the width of the teeth  7  in the locking element. To avoid uneven loading the catches may instead be arranged in the form of an inner and an outer catch, the outer catch being provided with two gripping surfaces, one on each side of the inner catch. 
     In FIG. 8, illustrating the principle of the invention, the catch  11  is placed above the catch  12 . This allows them to operate across the whole width of the teeth in the locking element  7 . The catches are here controlled to linear movement by the pin  20 . As previously, the catches are pressed against the teeth of the locking element  7  by the spring elements  15  and  16 . To allow space for the guides and the material thickness required for strength, the distance between the engagement surfaces of the catches has been increased to 1.5 of the tooth distance. 
     FIGS. 9 and 10, illustrating the principle of the invention, show another embodiment of the locking device. In the same way as in FIGS. 3 to  7 , the catches  11  and  12  operate beside each other. The difference is that their engagement surfaces are not displaced in relation to each other. Instead, the locking element  7  is provided with two rows of teeth  18  and  19 . Each of these rows consists of evenly spaced teeth, but the rows are displaced half a tooth distance from each other. The catch  11  thus operates against the tooth row  18  and the catch  12  against the tooth row  19 . 
     FIG. 11, illustrating the principle of the invention, shows yet another feasible embodiment of the locking device according to the invention. In this embodiment also, the locking element  7  is provided with two rows of teeth  18  and  19 , displaced half a tooth row. These can be turned in relation to each other around the joint  21  and thus operate alternately against half the width of a fixed catch  11 . This occurs under the influence of spring elements which, like the operating lever, are not shown in the Figure. 
     Various embodiments of the present invention have been described here. Common to all of them is that the locking member  8  comprises two catches and/or that the locking element  7  comprises two rows of teeth. When these catches and/or rows of teeth are displaced in relation to each other, the desired combination is achieved—reliable locking function and locked positions for the joint situated close together. The invention can of course be varied in many different ways. A locking member is possible, for instance, having more than two catches and/or a locking element having more than two rows of teeth, thus enabling ever larger teeth and/or locked positions of the joint even closer together. Other forms of locking surfaces than teeth are also possible. The catches of the locking member  8  may be replaced by pins, for instance, operating against hole patterns in the locking element  7 . These and other embodiments obvious to one skilled in the art are deemed to lie within the scope of the invention as defined in the following claims. 
     FIGS  12  through  42  show further developments of the invention, relating to connection means for connecting the rear, hand-held parts of the tool with jaws, as well as means for connecting the jaws of the tool with collet jaws or similar elements for manipulating objects. 
     Conventional pliers have the drawback that the hand-held shafts and the forward portions affecting the object are integrated in one piece. For this reason the shape of the jaws cannot be easily varied. Common to all tong-like tools, and particularly clamping and retaining tools, is that it should preferably be possible to use them in as many contexts as possible. This preference places incompatible demands on the design of the jaws. Short but wide jaws may be required for one workpiece, for instance, C-shaped jaws for another workpiece, jaws with a large opening for a third, and so on. No satisfactory solution has hitherto been found to this problem. Tool manufacturers have provided tools with a small number of different jaws designs, depending on the high cost of production tools and storage of the finished products. In practice the user converts the tools by welding on the desired jaws. This is particularly usual with welding tongs. Similar problems exist as regards collet jaws and the like. The most usual types are soft, designed to protect the workpiece from damage caused by the jaws. Common to such known soft collet jaws is that they are fitted onto the jaw from the front, like shoes, partially enclosing the forward part of the jaws. The drawback with such a connection is that the collet jaws easily become detached and are lost. Another type of collet jaw often used is foldable, designed to present parallel clamping surfaces in all positions of the jaws. Such foldable collet jaws are provided with flanges between which the forward part of the jaw is inserted. Collet jaw and jaw are held together with a rivet or the like, inserted through a hole in the flanges and the jaw, around which rivet the collet jaw can tilt. The drawback with this connection is that it is relatively expensive to manufacture. A serious drawback is that the connection is permanent and the collet jaws cannot easily be exchanged for collet jaws more suitable to other workpieces. Long, straight collet jaws are desirable for clamping long workpieces such as beading. Conventional clamping tools cannot easily be provided with such collet jaws and an intermediate rod must be applied, which is time-consuming. Another known need is to secure two workpieces parallel or at an angle to each other. This need cannot easily be satisfied by tong-like tools on the market since they are not designed to be connected together. 
     DESCRIPTION OF FURTHER DEVELOPMENT OF THE INVENTION. 
     The main object of the further development of the invention is to provide a device and a method relating to hand tools that employ a pair of jaws to receive a workpiece between them, said device and method permitting simple and inexpensive manufacture of tools with different jaws and collet jaws. 
     Another object is to provide a device and method permitting jaws and/or collet jaws to be easily exchanged and combined. 
     Another object is to provide a device and enable simple adjustment of various work areas. 
     Another object is to provide a device that permits simple combination of several tools parallel or at a desired angle to each other. 
     Yet another object is to provide a means that enables a reliable connection, particularly for soft collet jaws. 
     These objects are achieved with a coupling arrangement between shaft and jaw, and between jaw and collect jaw, respectively, comprising grooves and ridges located substantially perpendicular to the longitudinal direction of the tool. 
     Although the further development of the invention will be described in the following with reference to a hand-operated clamping tool, it is implicit that the invention also relates to all other types of tong-like tools, with or without crossing shafts, as well as screw clamps and the like where one jaw can be moved along a rod. 
     FIGS. 12 through 17 and  19  through  23  show further development of the invention relating to application of exchangeable collet jaws. This is illustrated on an embodiment of the tool comprising two shafts  1  and  2 , jaws  3  and  4 , spring element  5  and locking element  7 ,  10 ,  11 ,  12 ,  15 , as previously. The shafts in this embodiment are injection-moulded from reinforced plastic and made in the shape of U-sections turned so that their open sides are facing each other. The Figures show sectional views, with the waist of the U-sections and reinforcing ribs in section and the rear flanges of the U-sections visible. Through-running, grooves  26  are arranged in the forward end parts of the jaws, arranged substantially perpendicular to the longitudinal direction of the tool. The openings of the channels are preferably smaller than their greatest width, and facing each other. Collet jaws  43 , provided with ridges  25  the same shape as the grooves  26  can thus be inserted into the grooves  26  and remain there, as shown in FIGS. 12 and 13. When squeezing force is applied the collet jaws are pressed against the grooves. The fact that the grooves and ridges face each other and are oriented transverse to the longitudinal direction of the tool ensures that the collet jaws will remain securely in place at all normal handling, although they can easily be exchanged. They are normally affected so little laterally that they can be locked with a friction element such as a spring and can therefore be exchanged without the need for tools. The groove shape may of course be reversed so that the collet jaws  43  are provided with grooves surrounding ridges on the end parts of the jaws. Since the grooves  26  are through-running, the collet jaws  43  may have the same cross section and can therefore be manufactured cost effectively by extruding plastic or aluminium. This method of manufacture ensures straight ridges  25  and clamping surfaces, which is necessary for good function. Collet jaws of different lengths can also be easily manufactured, e.g. protruding from both sides of the tool, thus enabling long workpieces to be clamped in a simple and reliable manner. The design of the ridges and grooves  25  and  26  also enables connection of several tools on the same collet jaw  43 , thus enabling the desired pressure to be achieved even with long collet jaws. The cross-sectional shape of the ridges and grooves  25  and  26  may be circular or non-circular. 
     A circular cross section allows tiltable collet jaws to be easily fitted so that parallel clamping surfaces are obtained in all jaw positions. The cross section may also be toothed so that the desired angle between jaw and collet jaw can be achieved. FIG. 14 shows a collet jaw  44  fitted in the tool, with a right-angled bracket to securely clamp round objects  35 . If the collet jaw  44  is long, several tools can be combined on the same collet jaw  44 . If the collet jaw  44  is produced by extruding aluminium, for instance, and is therefore of high quality with regard to cross-sectional shape and straightness, such a combination enables several workpieces to be easily  10  secured parallel to each other. FIG. 15 shows the tool with collet jaws  45  and  46  inserted in the grooves  26 , said jaws retaining workpieces  33  and  34  at right angles. FIG. 16 shows the tool with collet jaws  47  provided with transverse fluting to hold workpieces securely without their turning. FIG. 17 shows the tool with collet jaws  49  intended to increase the clamping height so that tall workpieces  36  and  37  can be gripped. The clamping surfaces of the collet jaws  49  are provided with grooves  26  into which collet jaws  48  are inserted. These collet jaws are extruded from a thermoplastic material and provide a yielding clamping surface so that soft workpieces can be retained without risk of damage. Since the collet jaws are provided with ridges and grooves  25  and  26 , respectively, they can be connected together to add additional clamping height, as illustrated in FIG.  18 . FIG. 19 shows the tool with a collet jaw  50  provided with an upwardly directed part having a hole for a hook  38 . A workpiece  36  can thus be suspended in a transport system, for instance. FIGS. 20 and 21 show the tool provided with contact jaws  51  and  52 . A conductor  39  for electric current is connected to jaw  51 . Jaws  51  and  52  are suitably made of copper and joined to the current conductor  40 . At low current strengths the device can be simplified to have only a current-conducting contact jaw  51  according to FIG.  21 . If a force is required to separate two surfaces, the tool may be provided with crossing collet jaws  53  and  54  according to FIG.  22 . One collet jaw can then be shaped with two fork legs between which the other collet jaw can move freely. The clamping surfaces are provided with grooves into which soft collet jaws  48  are inserted. When fitting false ceilings, for instance, a clamping function is required at a different level from the clamping tool. 
     This requirement can be satisfied using collet jaws  55  and  56  according to FIG. 23, these being provided as before with soft collet jaws  48 . 
     Many different variations, intended for varying purposes, are also feasible besides the collet jaws described in the paragraph above. The shared idea is that, thanks to the transverse ridges and grooves  25  and  26 , the collet jaws remain in place, are tiltable if desired, and can easily be exchanged by the operator without the use of tools and, finally, that they can be combined in many ways. 
     The same inventive concept can be advantageously applied to tool jaws, as will now be described in more detail. It is desirable, with one and the same jaw, to be able to manufacture a clamping tool for different working ranges. This is possible with an arrangement according to FIGS. 24 to  26 . FIG. 24 shows the forward part of the lower shaft  2  of the tool, provided with transverse grooves  26 , spaced equally apart. A loose jaw  57  is provided with rearwardly facing ridges  25  to fit the grooves  26  so that the jaw  57  can be inserted in different positions, as shown in FIGS. 25 and 26. The jaw may be permanently secured in some position, e.g. the ridges  25  being upset at both ends, or may be movable to a desired position by the operator. FIGS. 27 and 28 show a coupling arrangement between the shaft  2  and a jaw  58 , which is reliable but at the same time can be dismantled. The forward part of the shaft  2  is provided with a recessed groove  30  and a pivotable yoke  29 . The rear part of the jaw  58  is provided with two ridges  27  and  28 . During assembly the ridge  27  is hooked into the groove  30 , after which the yoke  29  is swung over the ridge  28 , as shown. in FIG.  28 . In locked position the yoke  29  and corresponding forward end of the shaft  2  form a groove for the ridge  28 . 
     The advantage of this dismantlable coupling is that, besides withstanding clamping forces, it is also firmly ensconced to withstand lateral forces. 
     FIG. 29 shows a clamping tool with shafts  1  and  2  and an intermediate spring  5 , manufactured in one piece from an extruded aluminium profile. As previously, the tool comprises a locking device  5 ,  7 ,  10 ,  11  and  13 . The forward parts of the shafts are provided with arrangements for jaws comprising T-shaped channels  26 . T-shaped ridges  25  on desired jaws according to FIG. 30 can be inserted into these channels  26 . FIG. 30 also shows collet jaws with external circular grooves  25  that can cooperate with corresponding forward circular grooves  26  on a jaw. FIGS. 31 and 32 show the tool according to FIG. 29 combined with different combinations of jaws  3  and  4  from FIG.  30 . The jaws are thus inserted in laterally running grooves and can then be permanently secured by means of upsetting, without the need for any other connection elements. It is extremely advantageous in this case to use shortened aluminium sections for the jaws as well, since the connection surfaces  25  and  26  can then be manufactured with high quality as regards shape and parallellity, at low cost. The connection is thus free from play and ensures that the shaft and jaw are parallel. In this way a large number of different clamping tools can be produced, starting from the same basic tool. Since these different jaws can be manufactured with high quality from shortened, extruded aluminium sections, the cost of production tools will be low and a large number of different jaws can be produced at reasonable cost. The coupling arrangement also allows jaws to be easily combined, so that even a small number of jaw variants enables a large number of different tools to be manufactured. Finally, the cost of stocking will be low since one and the same basic tool can be completed to form the desired tool. Even a small number of clamping tools with a particular jaw configuration can therefore be manufactured and supplied without unreasonable expense. 
     FIG. 33 shows an alternative embodiment of the basic tool with shafts  1 ,  2  and spring  5  manufactured in one piece from an aluminium section, and various jaws, turned for connection with the lower shaft  2 . The Figure also shows two different collet jaws with ridges  25  designed for insertion into corresponding grooves in the forward part of two of the jaw variants shown. The coupling arrangement on the forward part of the shafts comprises two grooves  26 , an outer and an inner, and a ridge  25 . The ridge  25  cooperates with the outer groove  26  on a jaw. The outer groove  26  on the shaft  2  also cooperates with the corresponding ridge  25  on a jaw. The inner groove  26  on the shaft and the inner groove  26  on the jaw combine to form a circular hole into which a circular pin  22  is inserted at assembly according to FIG. 34, whereupon shaft and jaw are secured held together. FIG. 34 shows the tool with three different jaw configurations fitted. The tool is shown both in open and closed position. The circular pin  22  used at assembly may be a rivet, for instance, or a springy tension pin. The advantage of this type of connection is that the tolerance requirements at manufacture of the ridge and groove surfaces  25  and  26  may be relatively low and still provide an lay-free connection that can be dismantled. The inner grooves  26  may naturally form a non-circular channel for cooperation with a pin having a corresponding cross section. The advantage with a circular channel is that inexpensive standard pins can be used. 
     Besides those described above, the inventive concept naturally encompasses many other possible ways of securely combining shafts with the desired jaws. 
     FIGS. 35-38 show yet another embodiment of the invention. The tool is manufactured from injection moulded reinforced plastic, the shafts  1 ,  2  and upper jaw  3  constituting a coherent part with a steel spring  5  embedded at its ends. A soft collet jaw  48  is inserted in an inner groove  26  in the forward part of the jaw  3 . A locking element  7 ,  10 ,  11 ,  12  and  13  is provided as previously. FIG. 35 shows the tool with a lower jaw  59 , and collet jaw  48 . The jaw can be set by the operator in two positions, the lower position being indicated in dotted lines. The working range of the tool has thus been doubled as regards height of the opening, which is extremely advantageous. FIG. 36 shows in detail the coupling arrangement on the forward part of the shaft  2 . This forward part of the shaft  2  comprises a forward-pointing wing with protruding ribs on both the right-hand and the left-hand side of the tool, forming channels  62  and  63 . The channel  63  forms a fulcrum around which the jaw  59  can be pivoted when setting the two positions. These positions are defined by the channels  62  which partially surround ribs  61  on the jaw  59  according to FIGS. 37 and 38. The jaw  59  is manufactured from a piece of injection-moulded reinforced plastic. At its forward end a soft collet jaw  48  is inserted into a channel. The rear part of the jaw is provided with two fork legs  64 , right and left. Each leg  64  is provided on the inner side with a circular shoulder  60  and a rectangular rib  61 . The shoulder  60  and rib  61  form external grooves intended on the right and left sides to cooperate with corresponding internal grooves  63  and  62 . Basic assembly is performed at manufacture by pushing the shoulders  60  on the jaws  59  over the bevels  72  on the shaft  2 . The fork legs  64  thus yield outwards and then return to their original shape. The shoulders  60  are thus inside the recesses defined by the grooves  63  and the jaw is hooked permanently into the tool. The operator sets the desired working range by pulling the jaw forward so that the shoulders  60  are moved as far forward as possible in the surrounding recesses. The rib  61  on the jaw  59  can then be swung past the channels  62  on the shaft  2 . The jaw  59  is thereafter inserted into the desired position and the rib thus hooks into the upper or lower of the channels  62 . Setting is completed by turning the jaw downwards in the clamping direction. The shoulders  60  then snap into corresponding channels  63 . If the connection parts are manufactured with good precision, which can easily be achieved with injection moulding, the connection will be play-free. The channels  62  can also be shaped to partially surround the ribs  61  rearwardly, so that a snap function is obtained ensuring that the jaw cannot involuntarily become detached from the set position. The connection between jaw and shaft described above provides a reliable connection in the event of influence by clamping forces, i.e. if the jaw is turn counter-clockwise. The jaw is also secure against lateral forces and forces along the tool. The operator can easily change the working range by pressing the jaw  59  upwards towards the upper jaw  3 , or by turning the jaw  59  in clockwise direction. The jaw is then turned about the centre of the grooves  63  and the ribs  61  are released from the corresponding channels  62 , after which the jaw can be pulled forward and swung into the second position. 
     FIGS. 39-42 show a device for detachably locking collet jaws  66  to jaws  65 . A wire spring  68  is used as locking element. This spring is shaped as a U. both ends being bent inwards towards each other and then bent outwards, the ends thus forming two hooks. The hooks are bent to V-shape and form external channels which are pressed from right and left into internal channels  67  on the jaw. With correct dimensioning and soft jaw material such as aluminium, the V-shape of the hooks will cause their free ends to cut into the channels  67  of the jaw  65  and the wire spring  68  will therefore be securely connected to the jaw  65  even under the influence of lateral forces. The closed part of the wire spring  68  cooperates with a wing  70  on the collet jaw  66 . As previously, collet jaw  66  is provided with a ridge  25  inserted into a groove  26  in the jaw  65 . The ridges and grooves have circular cross section and the collet jaw is therefore tiltable. FIG. 39 shows two workpieces  36  and  37  being clamped. The jaws  65  are provided at the rear ends with ridges  25  to cooperate with grooves in the shaft, not shown. 
     Since the collet jaws  66  are tiltable, this ensures that they are parallel regardless of the height of the opening. FIG. 40 shows a long collet jaw  66  influenced by the wire spring  68 . Since the collet jaw is longer than the width of the wire spring, its rear part rests on the wing  70  and the collet jaw  66  is thus pressed clockwise to a stop position. The friction between the wire spring  68  and collet jaw  66  and also between the jaw  65  and collet jaw  66  causes the collet jaw to be secured in the desired position in relation to the jaw. The friction force can be made sufficiently great to ensure reliable securing at normal use without preventing quick exchange of the collet jaw. If the forward parts of the collet jaw  66  and jaw  65  are also provided with wedge-shaped cooperating surfaces, the collet jaw can also be wedged in its rest position, with even more reliable securing as a result. If the collet jaw  66  is turned counter-clockwise according to FIG. 41 the wire spring  68  will be tensioned further but the collet jaw will detach from its wedged position and can easily be pushed to the side to the desired position, or exchanged. FIG. 42 shows a short collet jaw  69  in which the wing  70  is surrounded by the rear part of the wire spring  68 . This rear part rests instead on a second wing  71  on the collet jaw  69  so that the collet jaw  69  is pressed clockwise to a stop position. The wire spring thus locks the collet jaw in the desired side position, thereby further securing the collet jaw. The collet jaw can easily be replaced, however, without the use of tools, by lifting the rear part of the wire spring  68  towards the inner side of the jaw so that the wing  70  is free and the collet jaw can be pushed out.