EP0419435B1 - Device for tightening threaded joints - Google Patents

Device for tightening threaded joints Download PDF

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Publication number
EP0419435B1
EP0419435B1 EP19900850316 EP90850316A EP0419435B1 EP 0419435 B1 EP0419435 B1 EP 0419435B1 EP 19900850316 EP19900850316 EP 19900850316 EP 90850316 A EP90850316 A EP 90850316A EP 0419435 B1 EP0419435 B1 EP 0419435B1
Authority
EP
European Patent Office
Prior art keywords
torque
joint
tightening
frequency
power tool
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19900850316
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0419435A3 (en
EP0419435A2 (en
Inventor
Gunnar Christer Hansson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Atlas Copco Industrial Technique AB
Original Assignee
Atlas Copco Tools AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Atlas Copco Tools AB filed Critical Atlas Copco Tools AB
Publication of EP0419435A2 publication Critical patent/EP0419435A2/en
Publication of EP0419435A3 publication Critical patent/EP0419435A3/en
Application granted granted Critical
Publication of EP0419435B1 publication Critical patent/EP0419435B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
    • B25B23/00—Details of, or accessories for, spanners, wrenches, screwdrivers
    • B25B23/14—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers
    • B25B23/147—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers specially adapted for electrically operated wrenches or screwdrivers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
    • B25B23/00—Details of, or accessories for, spanners, wrenches, screwdrivers
    • B25B23/14—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers

Definitions

  • This invention relates to a device for tightening threaded joints in two subsequent steps, namely a first step during which a joint is tightened to a predetermined torque snug level and a second step during which the joint is further tightened up to a final predetermined pretension level, cf. the preamble of claim 1 corresponding to EP-A-0 266 066.
  • the main purpose of the invention is to accomplish a device by which a threaded joint is tightened up to a predetermined pretension level during the second tightening step and by which the stiffness that varies from joint to joint is prevented from causing an undesirable scattering of the obtained pretension level as well as a tiresome jerky reaction torque characteristic to be handled by the operator.
  • a shortcoming of this known method is that the full power application on the screw joint from the start of the second tightening step still causes scattering of the final pretension level. The delivered torque as well as the rotation speed will increase too rapidly to avoid an unacceptable torque overshoot at very stiff joints.
  • the device according to the invention is particularly intended for manually supported tightening tools by which the tiresome and uncomfortable jerks normally occurring at the end of the tightening process are eliminated.
  • the torque growth characteristic depends on a number of factors such as the output power of the tool, the rotation speed of the tool, the characteristic of the threaded joint etc.
  • the output torque growth is always a function of the threaded joint characteristic, such as if the threaded joint has a weak characteristic with a slow torque growth in relation to the angle of rotation or a stiff characteristic with a steep torque growth in relation to angle of rotation, the output torque growth of the tool will vary correspondingly.
  • the optimum torque growth speed from the ergonomic point of view depends on several parameters such as
  • the above problems are solved in that the torque growth speed in the second step is controlled to correspond to man' s ability to respond to the developed reaction torque.
  • suitable torque growth values should be 25-150 Nm/s, whereas in the torque range above 150 Nm 250 Nm/s in combination with short tightening times 0,1 - 0,2 s are suitable. In the latter case, the process time is too short for the operator to react at all.
  • Fig 1 there is shown a three-axes diagram illustrating the relationship between torque designated M, the angle speed designated ⁇ and time t. Following the horizontal time axis, the first tightening step I is illustrated at the left and the second subsequent tightening step II is illustrated at the right.
  • the first tightening step I is commenced in that a constant torque D1 is applied on the threaded joint. D1 represents the torque developed by the power tool, whereas the reaction torque from the threaded joint is illustrated by a curve abc. As the installed torque in the threaded joint, curve abc, has reached a snug level M s , the torque application from the power tool is ceased.
  • the first tightening step is completed.
  • a torque D2 developed by the power tool is successively increased from a level corresponding to the torque level D1 of the first tightening step.
  • the applied torque D2 is gradually increased along a straight line.
  • joint characteristics a, b, and c which represent joints of different stiffness. Curve a represent the stiffest joint and c the weakest joint.
  • the threaded joints are intended to be pretensioned up to a final predetermined level corresponding to a torque M F , and dependent on how stiff the torque/time characteristic of the actual joint the second tightening step will last for different time intervals. This means that the weakest joint c will take the longest time to finish, while joint a with the steepest torque/angle characteristic will be finished in the shortest time t a .
  • the resultant advantage of the new device according to the invention is that for a stiff joint, which reaches its final pretension level very quickly, the angle speed at the end of the tightening process is brought down and the torque overshoot is substantially reduced whereas the end speed at a weak joint c, which reaches its final pretension level less abruptly, is higher. Because of the weak characteristic of the latter, the kinetic energy of the rotating parts will not cause any significant torque overshoot despite a relatively high final angle speed.
  • the device illustrated in Fig 2 comprises an electrically powered tightening tool 10 comprising a brushless AC-motor, a power supply means 11 and a control unit 12.
  • the power supply means 11 comprises an inverter which is fed with DC power from a DC power source 14 and which delivers AC power of variable frequency and voltage amplitude to the tool 10.
  • a power detecting means 15 is provided between the DC power source 14 and the power supply means 11 and is connected to the control unit 12. To the latter there is also connected a torque rate adjusting means 16 by which a desirable value of the torque changing speed may be set.
  • the control unit 12 comprises a programmable processor in which all necessary data for a two-step tightening process are installed.
  • Fig 2 also shows that the power tool carries a sensing means 25 for detecting the actual torque values during operation of the tool.
  • This sensing means 25 is connected to a comparating unit 26 in which the actual sensed torque values are compared to a desired set value. As the actual sensed value reaches the preset value a signal is delivered to the control unit 12.
  • a preferable way to accomplish the above described control of the applied torque when using an inverter drive for an AC-powered tool is to perform the active control on the AC frequency supplied to the tool.
  • the drive frequency which in fact is determining for the angle speed of the tool is increased in a certain way to generate a phase lag in relation to the joint. This phase lag is in turn generative of an increasing drive torque in the motor of the tool.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Details Of Spanners, Wrenches, And Screw Drivers And Accessories (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
EP19900850316 1989-09-22 1990-09-24 Device for tightening threaded joints Expired - Lifetime EP0419435B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8903134A SE8903134L (sv) 1989-09-22 1989-09-22 Metod och anordning foer aatdragning av gaengade foerband
SE8903134 1989-09-22

Publications (3)

Publication Number Publication Date
EP0419435A2 EP0419435A2 (en) 1991-03-27
EP0419435A3 EP0419435A3 (en) 1991-12-04
EP0419435B1 true EP0419435B1 (en) 1995-07-19

Family

ID=20376960

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900850316 Expired - Lifetime EP0419435B1 (en) 1989-09-22 1990-09-24 Device for tightening threaded joints

Country Status (4)

Country Link
EP (1) EP0419435B1 (ja)
JP (1) JP3505175B2 (ja)
DE (1) DE69020994T2 (ja)
SE (1) SE8903134L (ja)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE506118C2 (sv) * 1993-09-02 1997-11-10 Atlas Copco Tools Ab Metod för åtdragning av gängade förband till en önskad förspänningsnivå med hjälp av en manuellt manövrerad kraftmutterdragare innefattande en nedgängningsfas och en förspänningsfas, avkänning av momentmotståndet i förbandet samt avbrytande av rotationen vid uppnådd önskad förspänningsnivå
SE513563C2 (sv) * 1998-03-19 2000-10-02 Atlas Copco Tools Ab Metod för självprogrammering av styrsystem för kraftmutterdragare under initiala åtdragningsförlopp
US6538403B2 (en) 2000-01-07 2003-03-25 Black & Decker Inc. Brushless DC motor sensor control system and method
US7058291B2 (en) 2000-01-07 2006-06-06 Black & Decker Inc. Brushless DC motor
US6975050B2 (en) 2000-01-07 2005-12-13 Black & Decker Inc. Brushless DC motor
DE10133923B4 (de) * 2001-07-12 2015-10-22 Paul-Heinz Wagner Verfahren zur automatischen Steuerung eines Schraubvorgangs
CA2535299C (en) * 2006-02-06 2014-07-22 Dan Provost Method for applying preset torques to threaded fasteners and a power tool therefor
DE102006017193A1 (de) 2006-04-12 2007-10-25 Robert Bosch Gmbh Verfahren zum Anziehen einer Schraubverbindung und Schraubwerkzeug

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5969271A (ja) * 1982-10-13 1984-04-19 第一電通株式会社 誘導電動機を用いたネジ締結装置
NZ214090A (en) * 1985-11-06 1989-01-27 Sps Technologies Pulse width control of ac induction motor

Also Published As

Publication number Publication date
JPH03184775A (ja) 1991-08-12
DE69020994T2 (de) 1996-04-11
DE69020994D1 (de) 1995-08-24
EP0419435A3 (en) 1991-12-04
SE8903134D0 (sv) 1989-09-22
SE8903134L (sv) 1991-03-23
EP0419435A2 (en) 1991-03-27
JP3505175B2 (ja) 2004-03-08

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