EP0403460B1 - Power wrench for tightening screw joints - Google Patents

Power wrench for tightening screw joints Download PDF

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Publication number
EP0403460B1
EP0403460B1 EP19900850234 EP90850234A EP0403460B1 EP 0403460 B1 EP0403460 B1 EP 0403460B1 EP 19900850234 EP19900850234 EP 19900850234 EP 90850234 A EP90850234 A EP 90850234A EP 0403460 B1 EP0403460 B1 EP 0403460B1
Authority
EP
European Patent Office
Prior art keywords
tightening
power
torque
motor
power supply
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
EP19900850234
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0403460A1 (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 EP0403460A1 publication Critical patent/EP0403460A1/en
Application granted granted Critical
Publication of EP0403460B1 publication Critical patent/EP0403460B1/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
    • B25B21/00—Portable power-driven screw or nut setting or loosening tools; Attachments for drilling apparatus serving the same purpose
    • B25B21/008—Portable power-driven screw or nut setting or loosening tools; Attachments for drilling apparatus serving the same purpose with automatic change-over from high speed-low torque mode to low speed-high torque mode

Definitions

  • This invention relates to a power wrench intended for two-step tightening of screw joints, cf. e.g. EP-A-0 271 903 and the preamble of claim 1.
  • a problem inherent in previously known power wrenches is either that the interruption of the delivered torque is not fast enough and that by these power wrenches a torque overshoot is not avoidable when tightening very stiff joints or that extra wiring communication with the tool is needed for connection of speed sensing means on the tool to the power supply means.
  • E.P. 271903 there is described an electrically powered two-step tightening apparatus in which the snug level is detected by a speed sensor mounted in proximity to one of the parts rotated by the motor.
  • This sensor emits pulses as the motor rotates, and the frequency of these pulses is converted to a voltage which is reflective of the rotational speed of the motor.
  • a differential amplifier By means of a differential amplifier the derivative of the speed reflecting voltage is formed. A positive derivative indicates an acceleration of the motor speed, and a negative value of the derivative indicates a retardation.
  • This known apparatus has a less favourable feature in that the speed sensor arrangement requires extra wiring for communication with the control and power supply unit. This will make hand held tool versions more akward to handle and more exposed to damage on the part of the wiring and, consequently, the snug level detecting function as well.
  • a solution to the wiring problem that might seem feasible is to provide a speed sensor in the form of a motor frequency sensitive means incorporated in the power supply unit and to have decelerations of the motor speed calculated.
  • this is not a fast enough method to accomplish a snug level signal, because when for example using an asynchronous induction motor, there is a slip between the driving frequency and the motor speed.
  • This slip which is a sort of "lost motion" would cause an undesirable delay in the frequency change signal and, accordingly, a late interruption of the torque delivery.
  • the invention For accomplishing a fast reacting power shut-off initiating means intended for interrupting the first, high speed tightening step, the invention employs a mechanical retardation responsive activating means of a type similar to those previously used in impact wrenches. See for instance US 2,768,546.
  • the invention concerns an electric power wrench supplied with power from a power converter with variable voltage and frequency output, and current responsive means are comprised in the power converter to accomplish a power shut-off as a desired final tightening level is reached.
  • This belongs to prior art in itself and is marketed by Atlas Copco under the name: Tensor A-CC-Drive.
  • the main object of the invention is to accomplish an electric power wrench for two-step tightening of screw joints in which a torque overshoot even at very stiff screw joints is safely avoided. This is obtained by means of the features of claim 1.
  • the invention comprises a combination of a retardation responsive switch means associated with the motor rotor of the tool for initiating interruption of the initial tightening step, and a current responsive power shut-off means associated with the power converter for discontinuing the final tightening step.
  • the power wrench illustrated in the drawing figures is of the angle nut runner type intended for two-step tightening of threaded joints and powered by an electric AC motor 10.
  • the motor 10 which is of the asynchronous induction type, is supplied with electric power from a control and power supply unit 11.
  • the supply unit is of a prior art type known as Tensor A-CC-Drive marketed by Atlas Copco.
  • This control and supply unit comprises a solid state inverter 51 for delivering an AC current of variable frequency and voltage to the motor 10 as well as means for controlling the inverter in response to signals obtained by a current sensing means within the unit 11 and by a switch 12 mounted in the tool housing 13.
  • the control and power supply unit 11 is located remotely from the tool and communicates with the latter via power supply conduits 15, 16 connected to the motor 10 and signal wires 17, 18 connected to the switch 12.
  • a manually operable switch 19 (just schematically illustrated in the drawing figures) is mounted on the tool housing 13 for operator controlled start of the power supply to the motor 10. The switch 19 is operated by a lever 20 and is connected to the control and power supply unit 11 via wires 21, 22.
  • the control and power supply unit 11 is of a previously known type and does not in itself constitute a part of the present invention. Therefore, it is not described in great detail.
  • the main parts of the unit 11, however, as illustrated in Fig 4, comprise a rectifier 50, which is connected to an external AC power source, and a computerized inverter 51 connected to the rectifier 50 as well as to the power wrench via the conduits 15-18, 21, 22.
  • a low ohmic resistance 52 is provided in the DC section between the rectifier 50 and the inverter 51, and the voltage drop across the resistance 52 is sensed as being indicative of the motor current and, thereby the delivered torque of the motor 10.
  • the power wrench comprises an angle head 23 journalling an output shaft 24 with a square end for connection of a nut socket.
  • the rotor 25 of the motor 10 is formed with a central coaxial bore 26 in which a spindle 27 is rotatable as well as axially displaceable.
  • a spindle 27 On the spindle 27 there is rigidly secured an inertia member in the form of a flywheel 28.
  • two axially extending pins 29 which act as cam followers as they are arranged to engage a pair of cam surfaces 30 on the rear end of the rotor 25.
  • Each of the cam surfaces 30 has a top portion 31 with 90 degrees inclination. This portion 31 serves as a stop means to prevent the cam followers 29 from riding over the cam top.
  • a spring 32 acts between a shoulder 33 in a coaxial bore 34 in the housing 13 and a sleeve 35, thereby exerting an axial bias force on the latter.
  • the sleeve 35 which is displaceably guided in the bore 34 rests via a ball 36 against the centre of the flywheel 28 to, thereby, transfer the axial bias force of the spring 32 to the flywheel 28.
  • An axially displaceable actuating pin 38 rests with its one end against the ball 36, whereas the opposite end of the pin 38 engages the activation arm 39 of the switch 12.
  • the actuating pin 38 is displaceably guided in a bush 40 mounted in the housing 13.
  • the switch 12 is secured to a plate 41 which is mounted in the housing 13 by means of a stud 42 and a fixing screw 43. The latter extends through an elongate opening 44 in the plate 41 which provides for a certain adjustability of the switch 12.
  • the tool is fitted with a nut socket and is applied on a screw joint to be tightened, while the control and power supply unit 11 connects the tool to a power source.
  • the tightening process is commenced by the operator pressing the lever 20, thereby making the switch 19 deliver a signal to unit 11 which immediately starts supplying a power current to the motor 10 via conduits 15, 16.
  • the torque resistance in the screw joint is very low and the speed of the tool is high.
  • the flywheel 28 and the spindle 27 remain in their forward positions as shown in Fig 1, biassed by the spring 32 via the sleeve 35 and the ball 36.
  • the flywheel 28 tends, due to its inertia, to uphold the speed, whereby a relative rotation between the flywheel 28 and the rotor 25 occurs. Then, the cam following pins 29 slide along the cam surfaces 30, thereby accomplishing an axial displacement of the flywheel 28, the spindle 27, the ball 36 and the actuating pin 38. The latter activates the switch 12 which in turn delivers a signal to the control and power supply unit 11 via wires 17, 18.
  • control unit 11 Upon receiving a signal from the switch 12, the control unit 11 is programmed to shut off the power supply to the motor in the tightening direction and, instead initiate electrical braking of the motor so as to effectively absorb the remaining kinetic energy of the rotating parts of the tool and prevent the inertia forces of these parts from causing a torque overshoot.
  • the flywheel 28, the spindle 27 and the actuating pin 38 are returned to their original positions by the spring 32.
  • This torque level corresponds to a certain current magnitude set as a reference value in the inverter 51, and the final tightening step is discontinued automatically as the current level indicated as a voltage drop across the resistance 52 reaches that value.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Details Of Spanners, Wrenches, And Screw Drivers And Accessories (AREA)
EP19900850234 1989-06-12 1990-06-11 Power wrench for tightening screw joints Expired - Lifetime EP0403460B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8902101 1989-06-12
SE8902101A SE8902101L (sv) 1989-06-12 1989-06-12 Mutterdragare foer aatdragning av skruvfoerband

Publications (2)

Publication Number Publication Date
EP0403460A1 EP0403460A1 (en) 1990-12-19
EP0403460B1 true EP0403460B1 (en) 1995-08-16

Family

ID=20376244

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900850234 Expired - Lifetime EP0403460B1 (en) 1989-06-12 1990-06-11 Power wrench for tightening screw joints

Country Status (4)

Country Link
EP (1) EP0403460B1 (sv)
JP (1) JP2824125B2 (sv)
DE (1) DE69021647T2 (sv)
SE (1) SE8902101L (sv)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE59605901D1 (de) * 1995-03-24 2000-10-26 Marquardt Gmbh Verfahren und Schaltungsanordnung zum Betrieb eines Elektromotors
DE29816673U1 (de) * 1998-09-17 1999-10-21 Atlas Copco Electric Tools Handgeführtes Werkzeug
WO2015018555A1 (en) * 2013-08-08 2015-02-12 Atlas Copco Industrial Technique Ab Power tool with flywheel and gear for accelerating said flywheel
US10099351B2 (en) * 2013-08-08 2018-10-16 Atlas Copco Industrial Technique Ab Torque delivering power tool with flywheel

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2768546A (en) * 1954-04-26 1956-10-30 Chicago Pneumatic Tool Co Torque control for impact wrenches
JPS4521198Y1 (sv) * 1966-10-03 1970-08-24
SE348395B (sv) * 1969-07-07 1972-09-04 Saab Scania Ab
SE461510B (sv) * 1986-11-27 1990-02-26 Atlas Copco Ab Aktiveringsarrangemang vid elektrisk skruvdragare
JPH01127280A (ja) * 1987-11-10 1989-05-19 Matsushita Electric Ind Co Ltd ねじ締め装置

Also Published As

Publication number Publication date
DE69021647T2 (de) 1996-05-02
JPH04176574A (ja) 1992-06-24
EP0403460A1 (en) 1990-12-19
DE69021647D1 (de) 1995-09-21
JP2824125B2 (ja) 1998-11-11
SE8902101D0 (sv) 1989-06-12
SE8902101L (sv) 1990-12-13

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