| 摘要 |
1,197,853. Tensioning spokes. ATELIERS DE LA MOTOBECANE. 26 Feb., 1968 [27 Feb., 1967], No. 9227/68. Heading B7C. [Also in Division G1] In the trueing of a wire-spoke wheel by applying torque to each spoke nut to tension the spoke, the torque is applied in dependence on the natural frequency of vibration of the spoke. After initial pretensioning of the spokes, the wheel is fixed on a support 1a (Fig. 1) and an electromagnetic vibration exciter 5, detector 6 and a pneumatic wrench 3 for tightening the spoke nut 3a are provided for each spoke. A first exciter 5 1 previously energized by a pulse caused by the discharge of capacitor 7 when voltage source 91 is connected to fire thyristor 10, causes a spoke 2 1 to vibrate at its natural frequency, which is sensed by detector 6 1 , converted into a square wave signal of constant amplitude and fed to a comparator 20, where the frequency is compared with a reference frequency from an oscillator (not shown). If the tension in the spoke is below the desired value, a pulse is emitted by comparator 20, stretched in circuit 23 and, after a preset time delay provided by circuit 24 1 , is applied to the control 11 1 of pneumatic winch 3 1 . The tensioning of each spoke is carried out three times with increasing reference frequencies, so that the tensions finally lie within a narrow band corresponding to the highest frequency. The cyclic operation is effected by three switch banks A, B, C, driven by a motor 13, each having the same number of contacts 16, 19, 22 as there are spokes. The contacts on unit A for any one spoke are advanced by one in relation to the corresponding contacts on unit B so that while vibration of one spoke is being excited, the vibrations of the previously excited spoke are being detected and its tension adjusted, after a further slight delay at unit C. The cyclic operation may be effected electronically (Fig. 2) utilizing a pulse distributer 30 feeding pulses in sequence to pulse modifier 32, corresponding to unit A, and AND gates 33, 34, corresponding to units B, C. There are the same number of circuits 32, 33, 34 as there are spokes, and the gates 33, 34 for one spoke are energized by the pulse following that which is fed to the corresponding pulse modifier 32. |
