TIGHTENING DEVICE FOR AUTOMATICALLY TIGHTENING BOLTS AND THE LIKE

• US 3,693,726 A
• Filed: 09/17/1970
• Issued: 09/26/1972
• Est. Priority Date: 09/17/1970
• Status: Expired due to Term

• Current Assignee: Rudolf Hornig, Siegfried Sailer
• Original Assignee: Rudolf Hornig, Siegfried Sailer
• Inventors: Hornig, Rudolf, Sailer, Siegfried
• Primary Examiner(s): Purser, Ernest R.
• Application Number:
  US05/072,978
• Time in Patent Office: 740 Days
• Field of Search: 173/12 29/240
• US Class Current: 173/179
• CPC Class Codes: B25B 23/147 specially adapted for electrically operated wrenches or screwdrivers
• CPC Class Codes: Y10T 29/53687 by rotation of work part

Abstract

A device for automatically tightening threads of a threaded connection, in which the threads of, for example, bolts are adapted to be tightened in such a manner that a yielding of the material occurs in the shanks of the bolts; the device is provided with a measuring installation which measures, when the yield point is reached, by the change of the tightening torque of as function of the change of the rotation of the bolt and then turns off the device for tightening the bolt.

Claims

1. A tightening device for automatically tightening the threads of a threaded connection, which threads are adapted to be tightened in such a manner that a yielding of the material occurs in the parts containing the threads, characterized in that the device includes measuring means operable to determine the approach to the yield point by measuring the change of the tightening torque in dependence on the change of the relative rotation of the threads, and means operatively associated with said measuring means for turning off the tightening device when the yield point is substantially reached.

2. A device according to claim 1, characterized in that the part containing the threads is the shank of a bolt or the like.

3. A device according to claim 2, characterized in that an elastic means is provided between a drive means for the device and the bolt head and in that the measuring means measures the change of the twist of said elastic means.

4. A device according to claim 3, characterized in that the measuring means includes at least one rotational speed measuring device which measures the change of thE twist of the elastic means in front of and to the rear of the elastic means against the rotational speed changes.

5. A device according to claim 4, characterized in that several rotational speed measuring devices are provided.

6. A device according to claim 4, characterized in that the measuring means includes switch means operable to start the measurement of the change of the twist in dependence of a predetermined tightening torque.

7. A device according to claim 4, characterized in that the measuring means includes a switch means operable to start the measurement of the change of the twist in dependence of a predetermined twist of the elastic means.

8. A device according to claim 4, characterized in that the measuring means included a limit switch means which responds to an excessive increase of the tightening torque.

9. A device according to claim 8, characterized in that the measuring means includes a warning means that responds to an excessive increase of the tightening torque.

10. A device according to claim 3, characterized in that the measuring means includes a warning means that responds to an excessive increase of the tightening torque.

11. A device according to claim 4, characterized in that the measuring means is constructed as an input apparatus adapted to be series-connected in the input of the tightening device.

12. A device according to claim 3, characterized in that the measuring means includes a gear means which engages in front of and to the rear of the elastic means and produces a rotational speed changing with the twist, which is monitored by way of a rotational speed measuring means operable to produce upon reaching an intended value a signal causing said device to be turned off.

13. A device according to claim 3, characterized in that a switch means is connected to the output of a gear means engaging in front of and to the rear of the elastic means, said switch means being adjustable to a predetermined intended value.

14. A device according to claim 13, characterized in that said switch means is a centrifugal switch.

15. A device according to claim 13, characterized in that said switch means is an acceleration switch.

16. A device according to claim 13, characterized in that said gear means engages said elastic means by way of further speed-change reduction gear means.

17. A device according to claim 13, characterized in that said gear means engages at the output of said elastic means by way of further speed increase gear means.

18. A device according to claim 3, characterized in that the measuring means includes two rotational speed measuring devices which measure the angular velocity in front of and to the rear of the elastic means, the outputs of said rotational speed-measuring devices being fed to an analog computer operable to compare a value obtained from the angular velocities with an intended value.

19. A device according to claim 3, characterized in that the output of a gear means engaging in front of and to the rear of the elastic means as well as a place located to the rear of the elastic means are operatively connected with a pulse transmitter means which feeds the pulses by way of a pulse shaper means to a counter means operable to count the pulses associated with the twist angle, and which carries out a comparison with a correspondingly stored limit value by each pulse associated with the over-all rotation, and subsequently is erased and started anew.

20. A device according to claim 3, characterized in that the output of a gear means operatively connected in front of and to the rear of the elastic means is operatively connected with a pulse transmitter means which feeds the pulses thereof by way of a pulse shaper means to a counter means as canceling and starting pulses, said counter means counting the pulses which are fed thereto by way of a pulse transmitter means connected to the rear of the elastic means and fed thereto by way of an interposed pulse shaper means and which is operable To turn off the device in case of overrun.

21. A tightening device according to claim 20, characterized in that the overrun of the counter means is adjustable.

22. A device according to claim 3, characterized in that the measuring means includes switch means operable to start the measurement of the change of the twist in dependence of a predetermined tightening torque.

23. A device according to claim 3, characterized in that the measuring means includes a switch means operable to start the measurement of the change of the twist in dependence of a predetermined twist of the elastic means.

24. A device according to claim 1, characterized in that the measuring means includes a limit switch means which responds to an excessive increase of the tightening torque.

25. A device according to claim 1, characterized in that the measuring means includes a warning means that responds to an excessive increase of the tightening torque.

26. A device according to claim 1, characterized in that the measuring means is constructed as an input apparatus adapted to be series-connected in the input of the tightening device.

27. A tightening device for automatically tightening the threads of a threaded connection between two threaded parts in such a manner that a yielding of the material occurs in the parts containing the threads;

said device comprising;

tightening means for applying a tightening moment to the threaded connection, measuring means for determining when said threaded connection is approaching the yield point, said measuring means including means for determining the first derivative of the tightening moment with respect to the relative angular rotation of the threaded parts, and means responsive to said measuring means for turning off the tightening means when a predetermined first derivative corresponding to the yield point of the threaded connection is substantially reached.

28. A device according to claim 27, wherein the measuring means includes switch means operable to start the measurement of the first derivative after a predetermined tightening torque is reached, whereby the inadvertent turning off of the tightening means upon the first occurrence of the predetermined first derivative is prevented, said first occurrence occurring at a significantly lower tightening torque than the torque corresponding to the yield point.

29. A device according to claim 27, wherein an elastic means is interposed between said tightening means and one of the parts of the threaded connection, said measuring means including means for measuring the change of the twist of said elastic means.