EP0266066B1 - Outil de serrage moteur - Google Patents

Outil de serrage moteur Download PDF

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Publication number
EP0266066B1
EP0266066B1 EP19870308677 EP87308677A EP0266066B1 EP 0266066 B1 EP0266066 B1 EP 0266066B1 EP 19870308677 EP19870308677 EP 19870308677 EP 87308677 A EP87308677 A EP 87308677A EP 0266066 B1 EP0266066 B1 EP 0266066B1
Authority
EP
European Patent Office
Prior art keywords
torque
power tool
drive
power
datum
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
Application number
EP19870308677
Other languages
German (de)
English (en)
Other versions
EP0266066A1 (fr
Inventor
Joshua Nee Adjah Okunor
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.)
Air Compressors and Tools Ltd
Original Assignee
Desoutter Ltd
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 Desoutter Ltd filed Critical Desoutter Ltd
Publication of EP0266066A1 publication Critical patent/EP0266066A1/fr
Application granted granted Critical
Publication of EP0266066B1 publication Critical patent/EP0266066B1/fr
Expired 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
    • B25B23/1415—Break members; Arrangements specially adapted for break-bolts

Definitions

  • This invention relates to power tools and in particular to power tools equipped with a device for cutting-off drive before the torque across the tool holder has reached a maximum desired torque such that a relatively low residual inertia of the tool holder remains after the cutting-off of the drive.
  • a power tool which has a device for cutting-off drive is described in United Kingdom Patent No. 2 096 510B.
  • the device is in the form of a clutch operatively connected between a motor and a tool holder.
  • the clutch comprises torque sensitive clutch members which move axially relative to each other when a torque above a preset value is transmitted across the clutch. This relative movement gives rist to relative movement between members of a Hall effect device which causes the motor to be cut-off.
  • the clutch disenages the tool holder from the motor.
  • a compression spring in the clutch can be adjusted by being tightened or loosened.
  • This power tool is disadvantageous in that it operates at full power regardless of the torque setting which gives rise to a significant amount of inertia in the motor, gearing and the tool holder because full power is being supplied to the motor prior to cut-off. This gives rise to an indeterminate torque across the tool holder after cut-off, the value of this torque and rate at which it decays depending upon the friction between the tool and the workpiece, the inertia of the tool, tool holder, motor and gearing at cut-off.
  • the indeterminate torque gives rise to an undesirable degree of unpredictability in the operating characteristics of the power tool.
  • a previously proposed solution is to provide a power tool which has a variable free running speed, the cut-off being effected by means of a clutch or by current measurement as described above.
  • Such power tools are disadvantageous because they cannot achieve high torques at low speeds.
  • a power tool comprising: drive means for driving a tool holder; a speed select for selecting a free-running speed of the drive means and a torque datum (T d ), the free-running speed being such that the running speed of the drive means is substantially zero when a torque equal to the torque datum (T d ) is applied across the tool holder; generator means for generating a signal indicative or torque across the drive means; electronic means for switching full power to the drive means when the torque across the drive means is equal to the torque datum (T d ); and clutch means for cutting off the drive to the tool holder after the full power is supplied to the drive means and when a set torque (P) is reached bythe tool holder; whereby the residual inertia of the tool holder is relatively low after the cutting off of the drive at the set torque (P).
  • the torque datum may be the value of the torque across the drive means when the speed of the drive means is substantially equal to zero due to loading on the tool holder.
  • Setting means may be provided for setting the value of the torque datum in dependence upon the free-running speed of the drive means.
  • Switch means may be operatively associated with the clutch means for switching off the power to the drive means when the clutch means cuts-off the drive to the tool holder.
  • the switch means may be in the form of a Hall effect switch or a lever type switch.
  • the drive means may comprise an electric motor and the torque across the drive means may be measured in dependence upon current supplied to the electric motor.
  • the clutch means is preferably adjustable so that the torque at which it is operative for cutting-off the drive can be maintained greater than the torque datum.
  • a programmable microprocessor is preferably operative for determining the torque datum which corresponds to a given free-running speed by way of inspection of a pre-programmed set of corresponding torque data and free-running speed values.
  • the programmable microprocessor may be operative for comparing the signal indicative of the torque across the drive means with the preset torque datum and for switching the drive means to full power when the torque is equal to or greater than the preset torque datum.
  • the switch means may be incorporated into the microprocessor so that the microprocessor switches off the power supply to the motor immediately before the clutch means cuts-off drive to the tool holder.
  • Programming switches may be associated with the programmable microprocessor for setting an operating mode of the power tool, for example, for setting the tool to be switched on/off in response to axial movement of the holder instead of by a manual switch. Additionally, the programming switches may provide means for switching the power tool to operate in forward or reverse functions.
  • the curve a shows torque variations when the screwdriver is used to tighten a screw into a hard stop, the torque across the motor rises steeply as the screw is tightened.
  • the torque across the electric motor is proportional to the electric current supplied to the motor and so by measuring the current an indication of the torque can be derived.
  • Tp the power to the electric motor is switched off.
  • the screwdriver however continues to turn due to inertia of the rotating parts (ie, tool holder, gearing and electric armature).
  • the torque across the electric motor continues to rise for a short time after the cut-off and then decays to zero as the speed of the screwdriver reaches zero.
  • Curves b, c, and d show different profiles of torque variation in the case where the screwdriver is used to drive in screws into softer materials.
  • Figure 2 illustrates how the torque varies with speed of the power tool for four different free-running speeds e to h.
  • the free-running speed of the screwdriver may be 1000 revolutions per minute (r.p.m). If a steadily increasing torque is applied across the electric motor, the speed of the screwdriver will steadily decrease until the electric motor stalls.
  • the torque at which the electric motor stalls represents the maximum torque T," which the power tool is capable of supplying. If the initial free-running speed of the electric motor is 800 revolutions per minute then the maximum torque which can be supplied by the power tool is correspondingly lower (line f).
  • the free-running speed of the electric motor by varying the free-running speed of the electric motor, the maximum torque which can be supplied by the power tool can be varied accordingly. If it is desired to have a preset torque datum T d , then this may be achieved by setting the power tool to run at its maximum free-running speed of 1000 rpm and then cutting-off the power supply to the electric motor or disengaging the screwdriver and tool holder from the motor when the required torque datum T d is reached. However, in this case the speed of the screwdriver at cut-off is 850 rpm and so considerable inertia remains in the system.
  • the free-running speed may be set at 200 rpm (see line h of Figure 2) and so when the torque across the electric motor has reached the required torque datum T d , the speed of the screwdriver is substantially equal to zero and so very little inertia remains. Hence, if the screwdriver and tool holder is disengaged from the electric motor when this point is reached the inertia remaining in the motor and tool holder is much smaller.
  • the actual initial free-running speed may be set slightly higher than the theoretical value, say 220 rpm for the torque datum T d . This is due to resistive and frictional effects of gearing etc.
  • FIG 3 there is shown a schematic diagram of a power tool embodying the present invention.
  • an electric motor 2 is powered by a power amplifier 4 which is coupled to a microprocessor 6.
  • the microprocessor 6 is operative for controlling the power supplied to the electric motor 2 by hhe power amplifier 4 in dependence upon the torque across the electric motor 2.
  • An AD converter 8 receives a signal representative of the current i supplied to the electric motor and generates a digital signal indicative of the torque across the electric motor 2 and supplies this to the micropcocessor 6.
  • a setting means which in this case is a speed select switch 10, sets the free running speed of the motor 2 and the datum torque T d (that is, the datum torque at which full power is to be switched on).
  • the microprocessor 6 comprises a data memory 12 which may be in the form of a read only memory (ROM) which stores tables of torque data corresponding to different free-running speeds.
  • the microprocessor 6 is operative for comparing the digital signal representative of the torque across the electric motor 2 received from the AD converter 8 with the value of the preset torque datum T d which corresponds to the speed selected by the speed select switch 10.
  • the microprocessor 6 switches the power amplifier 4 to supply full power to the electric motor 2.
  • a mechanical clutch 14 responds immidiately to the sudden increase in torque across the electric motor 2 so as to disengage the electric motor from a tool holder 15.
  • a Hall effect switch (not shown), which is associated with the mechanical clutch 14, generates a signal which is fed to the microprocessor 6.
  • the microrocessor 6 switches off the power supply to the electric motor 2.
  • Figure 4 shows an example of torque against time for an embodiment of the invention where the torque datum has been set at T d and the maximum torque desired is T max'
  • T d the torque datum
  • T max the maximum torque desired
  • Embodiments of the present invention are advantageous in that the relatively low residual inertia of the tool holder 15 after disengagement enables a more precise determination of torque and provides for the possibility of obtaining a high torque at a relatively low speed.
  • a touch switch pad 16 may be provided on the tool and is connected to the microprocessor 6 in order to provide an on/off switch for the power tool.
  • An overload detecting means 18 is also associated with the microprocessor 6 in order electrically to disconnect the electric motor 2 from the tool holder and/or to disconnect the power supply from the power amplifier 4 in the case where there is an overload due to over-heating or the like.
  • Four programming switches 20 may be coupled to the microprocessor 6 to enable the power tool to be programmed to operate in any one of up to sixteen modes.
  • one switch may be operative for setting the microprocessor to be switched on/off in response to axial movement of the tool holder instead of by the touch switch pad 16.
  • one of the programming switches may be operative for providing a slow start feature. Such a feature is useful in the case where the screwdriver is intended for delicate work where it may be desired to start the screwdriver slowly (thereby giving the operator time to locate the screwdriver accurately in the screw head) and to increase speed gradually.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Details Of Spanners, Wrenches, And Screw Drivers And Accessories (AREA)

Claims (12)

1. Outil à moteur comprenant: un moyen d'entraînement (2) pour entraîner un porte-outil (15); un sélecteur de vitesse (10) pour sélectionner une vitesse de march libre du moyen d'entraînement (2) et une valeur de couple donnée (Td), la vitesse de marche libre étant telle que la vitesse de marche du moyen d'entraînement (2) est substantiellement nulle lorsqu'un couple égal à la valeur de couple donnée (Td) est appliqué sur le porte-outil; un moyen générateur (G) pour engendrer un signal indicateur du couple sur le moyen d'entraînement (2); un moyen de commutation électronique (6) pour communiquer la pleine puissance au moyen d'entraînement (2) lorsque le couple sur le moyen d'entraînement (2) est égal à la valeur de couple donnée (Td); et un embrayage (14) pour couper l'entraînement du porte-outil (15) une fois que la pleine puissance est fournie au moyen d'entraînement (2) et qu'un couple de consigne (P) est atteint par le porte-outil; si bien que l'inertie résiduelle du porte-outil (15) est relativement faible une fois qu'a été coupé l'entraînement du moyen d'entraînement (2) au couple de consigne (P).
2. Outil à moteur selon la revendication 1, dans lequel le moyen de commutation est associé en fonctionnement au moyen d'embrayage (14) pour couper la fourniture d'énergie au moyen d'entraînement (2) lorsque le moyen d'embrayage (14) coupe l'entraînement du porte-outil (15).
3. Outil à moteur selon la revendication 2, dans lequel le moyen de commutation est un commutateur à effet de Hall ou un commutateur à levier.
4. Outil à moteur selon l'une quelconque des revendications précédentes, dans lequel le moyen d'entraînement (2) comprend un moteur électrique, et le couple sur le moyen d'entraînement (2) est mesuré en fonction du courant fourni au moteur électrique.
5. Outil à moteur selon l'une quelconque des revendications précédentes, dans lequel le moyen d'embrayage (14) est réglable de sorte que le couple auquel le moyen d'embrayage
(14) est capable de couper l'entraînement puisse être maintenu supérieur à la valeur de couple donnée.
6. Outil à moteur selon l'une quelconque des revendications précédentes, dans lequel un microprocesseur programmable est pourvu pour déterminer la valeur de couple donnée qui correspond à la vitesse de marche libre sélectionnée.
7. Outil à moteur selon la revendication 6, dans lequel la valeur de couple donnée est déterminée par surveillance d'un ensemble de valeurs de couple données et de vitesse de marche libre pré- programmées.
8. Outil à moteur selon la revendication 6 ou 7, dans lequel le microprocesseur programmable sert à comparer le signal indicateur du couple sur le moyen d'entraînement (2) avec la valeur de couple donnée (Td) et à commuter le moyen d'entraînement (2) à la pleine puissance lorsque le couple est égal à la valeur de couple donnée (Td).
9. Outil à moteur selon l'une quelconque des revendications 6 à 8, dans lequel des commutateurs de programmation (20) sont associés au microprocesseur programmable (6), lesquels commutateurs servent à établir un mode de fonctionnement de l'outil à moteur.
10. Outil à moteur selon la revendication 9, dans lequel les commutateurs de programmation (20) fournissent un moyen pour commuter l'outil à moteur pour un fonctionnement avant ou arrière.
11. Outil à moteur selon l'une quelconque des revendications 6 à 10, lorsque rattachée à la revendication 2, dans lequel le moyen de commutation est incorporé dans le microprocecesseur programmable de sorte que le microprocesseur serve à couper l'alimentation en énergie du moyen d'entraînement (2) immédiatement avant que le moyen d'embrayage (14) coupe l'entraînement du porte-outil (15).
EP19870308677 1986-10-01 1987-09-30 Outil de serrage moteur Expired EP0266066B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8623549A GB2195569B (en) 1986-10-01 1986-10-01 Power tools
GB8623549 1986-10-01

Publications (2)

Publication Number Publication Date
EP0266066A1 EP0266066A1 (fr) 1988-05-04
EP0266066B1 true EP0266066B1 (fr) 1991-01-16

Family

ID=10605067

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19870308677 Expired EP0266066B1 (fr) 1986-10-01 1987-09-30 Outil de serrage moteur

Country Status (3)

Country Link
EP (1) EP0266066B1 (fr)
DE (1) DE3767437D1 (fr)
GB (1) GB2195569B (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE464960B (sv) * 1990-03-09 1991-07-08 Nobelpharma Ab Vridaatdragare foer benfoerankrings- eller implantatelement/-verktyg
GB2269025B (en) * 1992-07-24 1995-08-16 Delco Chassis Overseas Corp Torque controller for electrical tool
DE4330481A1 (de) * 1993-09-09 1995-03-16 Bosch Gmbh Robert Verfahren zum Herstellen einer Fügeverbindung, insbesondere einer Schraubverbindung
GB2315885A (en) * 1996-08-01 1998-02-11 Derek Pattinson Controlling electric motors dependent on load
CN100366399C (zh) * 2005-06-16 2008-02-06 朝程工业股份有限公司 电动工具扭力控制装置

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3892146A (en) * 1973-08-31 1975-07-01 Shibaura Engineering Works Ltd Electric control for an electric motor operated nut fastening tool
DE2835382C2 (de) * 1978-08-12 1987-11-12 C. & E. Fein Gmbh & Co, 7000 Stuttgart Schaltungsanordnung für eine elektronische Drehmomentabschaltung eines Schlagschraubers
DE3274631D1 (en) * 1981-04-13 1987-01-22 Desoutter Ltd Motor driven power tool
GB2098740A (en) * 1981-05-18 1982-11-24 Ford Motor Co Monitoring threaded joint tightening

Also Published As

Publication number Publication date
EP0266066A1 (fr) 1988-05-04
GB8623549D0 (en) 1986-11-05
GB2195569A (en) 1988-04-13
GB2195569B (en) 1990-04-04
DE3767437D1 (de) 1991-02-21

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