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Apparatus and method for tightening an assembly

  • US 4,344,216 A
  • Filed: 12/10/1979
  • Issued: 08/17/1982
  • Est. Priority Date: 12/10/1979
  • Status: Expired due to Term
First Claim
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1. Apparatus for tightening an assembly including a threaded fastener comprising:

  • driving means for imparting torque and rotation to the fastener to tighten the assembly, the torque-rotation curve which could be plotted for the assembly having a non-linear tightening portion followed by a substantially linear tightening portion;

    means for supplying (1) a first preload signal representative of a predetermined preload which is to be induced in the fastener when the assembly has been tightened to a desired degree, (2) a second preload signal representative of the preload at the onset of said substantially linear tightening portion, and (3) a tension rate signal representative of the tension rate of the assembly;

    torque sensing means responsive to said driving means for developing a torque signal representative of the torque imparted to the fastener;

    angle sensing means responsive to said driving means for developing a first angle signal representative of the rotation imparted to the fastener;

    means responsive to said torque signal and said first angle signal for developing a gate signal at said onset of said substantially linear tightening portion;

    processing means reponsive to said first preload signal, said second preload signal, and said tension rate signal for developing a second angle signal representative of a tightening angle between said onset of said substantially linear tightening portion and said predetermined preload, said tightening angle being related to the difference between said predetermined preload and said preload at said onset of said substantially linear tightening portion divided by said tension rate;

    comparison means responsive to said first angle signal, said second angle signal, and said gate signal for comparing the rotation imparted to the fastener after said onset of said substantially linear tightening portion with said tightening angle and for developing a control signal when said rotation imparted to the fastener after said onset of said substantially linear tightening portion is equal to said tightening angle;

    and control means for supplying said control signal to said driving means to stop said driving means from imparting torque and rotation to the fastener.

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