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机械扳手的新设计 全联盟的石油机械研究机构解释了基于不同设计的机械扳手传递扭矩的规律性,由此明确的一点就是通过扳手咬合施加力所产生的3040KNm扭矩足够用来传递更高的扭矩（80KNm）。由此及彼，通过减少与扭矩成正比例管子上扳手颚的强度使得减少扳手的重量并且增加它们的可靠性成为可能。当然，在产生夹紧力的初期我们必须保证扳手不能滑动。然而，传统设计的机械扳手不能保证在扳手扭动过程中力变化的规律性。基于不同设计下扳手强化机构的特征表述在1 在脑海中我们应该记住的就是扳手和管子的接触在很大程度上与杠杆的旋转角度有关。然后，随着扳手杠杆外力的增加，这个角度变得越来越小，从左到右加紧螺纹的整个过程见图1 强化机构最有效率的结合可以由联动机构和铰链机构得到。当管子第一次被加紧的时候，链接机构就开始工作了（曲线1）；它的工作区域由杠杆切缝的尺寸来限制，然后就转到由四连杆机构操作（曲线2）来确定最高强化系数。当杠杆最末端那一面上升到最终夹紧连接时，强化机构便从曲柄设计和通过不同长度杆来连接的连接杆机构（曲线4）中得到收益。因此，在经过考虑的这个例子中，扳手连接在管子上的强度开始的强化系数是i1820，增至i4245，并且以i1213结束。 通过铰链设计的扳手加紧过程以强化系数i25（曲线2，3）结束。这也就解释了为什么这些扳手会比联动机构和铰链机构的扳手重20。 联动机构和铰链机构的另一个明显的优势应当被提及：杠杆工作有着大范围的旋转角度：-15 度 30 度 。 我们调查的结果被用来作为计算有着转矩极限的混合铰链机构KMB1082112的基础。这些扳手设计的特殊之处就在于在管子上扳手夹紧过程中减少了1/2或者1/3的强化系数。这就是依靠特殊转矩极限应用到最末端表面杠杆制动力的结果。 扳手控制联动机构和铰链机构。扭矩极限，楔形断面的一部分，铰接到扳手的加紧部分。在杠杆最末端表面有一个相同截面的架子作为扭矩极限的凹槽。 扳手开始的时候是由铰链机构来操控；当动作限制在滑动槽的时候，就开始由铰接四连杆机构来控制，当大约达到所能达到最大夹紧力的一般时，就由紧紧镶嵌在扭矩限制槽里面的杠杆架来操控。 由于有着最末级扳手杠杆的制动影响，它所形成的夹紧部分的动力链接中两杠杆大约等于三杠杆的效果，这一点与第五设计的强化系数（看图1）相符。因此，在扳手KMB108212中，一个合理的操作过程形成了：进程开始时大的强化系数（i80 kNm). In connection with that it therefore becomes possible to reduce the weight of the wrenches and increase their reliability by reducing the intensity of the clamping of the spanner jaws on the pipes in proportion to the increase of torque. Of course, at the initial stage of loading a clamping force has to be ensured that makes slippage of the wrench impossible. However, machine wrenches of traditional design do not ensure the necessary regularity of the change of forces in the gripping links of the wrench. The characteristics of the intensifying mechanisms of wrenches based on different schemes are presented in i.It should be borne in mind that contact of the wrench with the pipe occurs at large values of the angles of rotation of the lever. Then, as the drawing force on the lever of the wrench increases, the angle becomes smaller, i.e., the process of tightening the thread proceeds from right to left (see Fig. i).The most efficient combination of intensifying mechanisms can be obtained in wrenches with link gear and hinged mechanism. When the pipe is gripped first, the link mechanism acts (curve i); its zone of action is limited by the size of the slit in the lever. Then comes the transition to operation by the hinged four-link mechanism (curve 2) ensuring the highest coefficients of intensification. When the end face of the lever comes up against the final gripping link, intensification proceeds by the scheme of the crank and connecting rod mechanism (curve 4) with a connecting rod of variable length. Thus, in the case under consideration, tightening of the wrench links on the pipe begins at an intensification coefficient i = 18-20, which increases to i = 42-45, and ends with i = 12-13.With wrenches with hinged scheme the process of tightening ends with the coefficient of intensification i 25 (curves 2, 3). This also explains why these wrenches weigh 20%2 more than wrenches with link gear and hinged mechanism.Another substantial advantage of the link gear and hinged wrench should be mentioned: the wider range of working angles of rotation of the lever: -15 e 30 .For wrenches with the hinged scheme -5 18 because of the unreliable gripping with i 18-20 at the onset of the process and the better operation of such wrenches by the scheme of the crank and connecting rod mechanism (curve3).The results of our investigations were made the basis for working out the multihinge machine wrench KMB 108-2112 for drilling pipes with torque limiter 3. The special feature of the design of these wrenches consists in the reduction of the coefficient of intensification to one-half or one-third when the process of tightening the wrench on the pipe is concluded; this is the result of a braking force being applied to the end face of the lever by means of a special torque limiter.The wrench operates on the link gear and hinge mechanism scheme. The torque limiter, a part with a groove of wedge-shaped section, is hinged to the drawing link of the gripping part of the wrench. On the end face of the lever there is a rack with the same section as the groove of the torque limiter.The wrench begins to operate by the link gear scheme; when the motion is limited in the slide groove, it operates by the scheme of the hinged four-link mechanism, and when approximately half the maximal drawing force is attained, it operates by a scheme where the rack of the lever fits tightly into the groove of the torque limiter.Thanks to the effective braking of the wrench lever at the last stage, it forms with the drawing link of the gripping part a two-armed lever with the ratio of the arms approximately equal to three, which corresponds to the coefficient of intensification of the fifth scheme (see Fig. i). Thus in the wrench KMB 108-212 a rational combination of the operating regimes was effected: with large intensification (i _ 45) at the beginning of the process with small drawing loads on the lever (to attain reliable cohesion between the wrench and the pipe) and with considerable reduction of the intensification when high drawing loads are attained (to prevent overloading of the wrench). Strain-gauge measurements showed that in that case the maximal stresses in the links of the wrench are reduced by one third to one half.A prototype of the wrench KMB 108-212, calculated for a nominal torque of 80 kN was tested on a test bench of the Azerbaidzhan Institute of Petroleum Machinery with a torque of 207.5 kN-m. The efficiency of the wrench was not impaired in any way. In 1985 series production of the wrenches KMB 108-212 started. However, production to full capacity of these tools is prevented by the unstable quality of cast blanks for the wrench.
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