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Dokumentenidentifikation EP0363587 07.03.1996
EP-Veröffentlichungsnummer 0363587
Titel Anziehdrehmoment-Kontrollvorrichtung für Schraubenschlüssel
Anmelder Fuji Kuuki K.K., Osaka, JP
Erfinder Ohkubo, Masaaki, Osaka-shi Osaka, JP;
Fukada, Ryo, Osaka-shi Osaka, JP
Vertreter derzeit kein Vertreter bestellt
DE-Aktenzeichen 68925507
Vertragsstaaten DE, FR, GB, IT, SE
Sprache des Dokument En
EP-Anmeldetag 31.07.1989
EP-Aktenzeichen 891141251
EP-Offenlegungsdatum 18.04.1990
EP date of grant 24.01.1996
Veröffentlichungstag im Patentblatt 07.03.1996
IPC-Hauptklasse B25B 23/145

Beschreibung[en]

This invention relates to torque wrenches such as an impact wrench and a hydraulic wrench.

In utilization of an impact wrench, it is necessary to detect the striking state in order to accurately control the tightening torque or accurately grasp the number of tightened nuts. Conventionally, the striking state is detected by detecting the reverse rotation of the main shaft of an air motor using a sensor mounted to this main shaft. However, since this method requires the sensor to detect the forward and reverse rotations of the main shaft disposed within the impact wrench, it has disadvantages in that the machine would be enlarged and its cost would be increased.

For solving such problem, it can be considered to employ a system which detects the admitted pressure and detects the striking state as the impact wrench being activated when the admitted pressure falls below a reference level. With the use of this system, however, it is not possible to discriminate whether the impact wrench is in the free-running (no-load rotating) state or striking state. This is because the difference between the pressures generated in free-running state and striking state is smaller than a variation in pressure which is inevitably caused in the pressure source, thus making it impossible to distinguish one state from the other.

FR-A-1 517 360 discloses a tightening control apparatus for a torque wrench with the features included in the first part of claim 1. In Figure 2 of that document, a fluid line including a restriction is connected in parallel to a main valve inserted in the pressure supply line from a pressure source to the wrench. When the actuating lever on the wrench is depressed, a change at the downstream side of the restriction occurs and the thus produced pressure difference between the upstream and downstream sides of the restriction is used to close a switch which causes the main valve to be opened and pressure to be applied to the wrench, and further causes an electrical timer to start. Upon lapse of the time interval set by the timer, the main valve is closed. The known control apparatus again does not distinguish between the free running state and the actual striking state of the wrench.

US-A-3 590 582 describes another control apparatus for a torque wrench in which the difference between the line pressure and the pressure occurring at the input of the tool is detected in order to determine the start or the striking condition of the tool. The known apparatus requires the line pressure to be maintained at a substantially constant value.

In a further control apparatus disclosed in US-A-3,732,932, a predetermined time interval, during which pressure fluid is applied to a wrench, is started when the wrench is actually starting to do work to overcome an increased resistence. The control apparatus of this document, however, requires more than one pressure sensor, each associated with a pressure reservoir, and is therefore bulky and expensive.

It is an object of the invention to provide a tightening control apparatus for a torque wrench which can accurately detect the striking state of the wrench by means of a simple arrangement.

This object is met by the features included in claim 1.

During free-running, the admission pressure is kept at a specific level and does not vary with time, so that the striking signal will not be produced. In the striking state, however, a certain minimum degree of change occurs in the admitted pressure for each striking and the striking signal is produced in accordance with the change. An advantage of this is that, unlike the conventional system of detecting the admitted pressure, the striking state is detected from a change in pressure, thus ensuring the accurate detection of the striking state with a simple structure.

In preferred embodiments, the number of produced striking signals is counted (claim 3), or the time during which the striking signal is continuously produced is measured (claim 4). According to either embodiment, when the count value or the measured time reaches a set value, the admission of pressure is stopped, thereby to ensure the accurate tightening torque control. By providing signal output time altering means (claim 2), the detecting systems of these embodiments may be switched from one to the other as needed. This further improves the accuracy of the torque control.

According to another modification (claim 5), the tightening control apparatus can measure the number of tightened nuts and can detect that this number reaches a set number, thus ensuring an accurate management of tightened nuts numbers in addition to an accurate torque control.

The foregoing objects, advantages and other features will become more apparent from the detailed description of a preferred embodiment of this invention with reference to the accompanying drawings in which:

  • Fig. 1 is a diagram illustrating the general arrangement of a tightening control apparatus for a torque wrench according to the preferred embodiment;
  • Fig. 2 is a block diagram illustrating a control system of the apparatus; and
  • Fig. 3 is a time chart illustrating operational states of the control system.

In Fig. 1 illustrating the general arrangement of the present apparatus, reference numeral 1 denotes an admission source, reference numeral 2 an air hose, and reference numeral 3 an impact wrench. The air hose 2 is provided with an electromagnetic valve 4, a check valve 5 and a pressure transducer 6 in order from the side of the admission source 1. The check valve 5 serves to prevent troubles originating from reduction in pressure at the part of the admission source 1. Referring to the same diagram, reference numeral 7 denotes a controller 7, which comprises an input port 8 coupled to the pressure transducer 6, an output port 9 coupled to the electromagnetic valve 4, a plurality of input ports 10 &peseta;&peseta; which receive data with respect to a set number, and output ports 11 and. 12 which respectively output a predetermined-number tightening end signal and an NG signal.

Fig. 2 is a functional block diagram of the controller 7. A pressure signal from the pressure transducer 6 is input to a pressure signal amplifier 21 and is supplied therefrom to a pressure change detector 22 and a striking signal output section 23. The striking signal output section 23 has a detection level setting section 24, a signal output time altering section 25 and a reset level setting section 26, and it outputs a striking signal. (The function of this section 23 will be described later.) The number of the striking signals output from the section 23 is measured by a counter 27 and the time during which the striking signal is continuously output is measured by a timer 28. When the measured values reach values set in associated setting sections 29 and 30, a tightening end signal is output. Based on the tightening end signal, an electromagnetic valve shutoff section 31 closes the electromagnetic valve 4.

The controller 7 further comprises a number setting section 32 constituted by digital switches and a counter section 33 which counts the tightening end signal. When the count value reaches a value set in the section 32, a predetermined-number tightening end signal is output from the counter section 33, thereby to stop a sequence of a tightening operation. Reference numeral 34 denotes a remaining-number indicator, which indicates how many nuts are left to be tightened by means of LEDS (light-emitting diodes). The number setting section 32 may be one or more than one in quantity. The controller 7 further has a timer section 35 which is reset by a start signal produced at the time a sequence of a tightening operation starts. When no predetermined-number tightening end signal is output within a predetermined time after the timer section 35 is reset, an NG signal is produced. Reference numeral 36 denotes a timer adjusting section and reference numeral 37 a power source.

Referring to Fig. 3, the operation states of the above-described controller 7 will be explained below. Referring to (a) in Fig. 3 illustrating the output signal from the pressure transducer 6, the pressure change detector 22 extracts an AC component only from this output signal as a pressure change signal. This pressure change signal has such a characteristic that it does not vary when the impact wrench is stopped, has a large negative variation when the lever is open, has a minute positive and negative variation when the impact wrench is in free running state, and repeats a large positive variation and a small negative variation for each striking (as can be seen in (b) of Fig. 3). In this connection, when the negative variation caused upon opening of the lever reaches a reset level set in the reset level setting section 26, the striking signal output section 23 resets the counter 27 or timer 28 and starts detecting the striking state.

A description will now be given with respect to the case where the counter 27 counts the number of strikes. When a positive variation equal to or greater than the detection level set in the detection level setting section 24, i.e., when striking occurs, the striking signal output section 23 outputs the striking signal for a predetermined time T&sub4; as shown in (c) of Fig. 3. Assume now that this signal output time T&sub4;, which is set by the signal output time altering section 25, is set shorter than a striking interval T&sub3;. The number of the striking signals output is counted by the counter 27. When the count value reaches the set value, the tightening end signal is output from the counter 27, thereby to close the electromagnetic valve 4 followed by the closing of the lever (see (d) and (e) of Fig 3). Upon the lapse of a predetermined time T&sub2; after the electromagnetic valve 4 is closed, this valve 4 is automatically opened. When the above tightening operation is repeated by a predetermined number of times and the number of the tightening end signals counted by the counter section 33 reaches the set value, the predetermined-number tightening end signal is output from the section 33. This completes a tightening operation sequence.

A description will now be given with respect to the case where the signal output time T&sub4; is set greater than the striking interval T&sub3; in the signal output time altering section 25. In this case, the striking signal is output as a continuous signal from the first striking. Thus, when the continuous signal output time measured in the timer 28 reaches the set time T&sub1;, the tightening end signal is output from the timer 28. The operation state thereafter is the same as described in the previous case.

The foregoing description discusses the tightening control apparatus for a torque wrench according to one embodiment of this invention. Needless to say, the present apparatus is in no way restricted to this particular embodiment, but may be modified in various manners within the scope of the appended claims. For instance, some modification may be made in such a way that when the striking interval T&sub3; is detected to be greater than a reference time, this event is discriminated to be a disturbance, not an occurrence of striking, and countermeasure can be taken by resetting the counter 27 or timer 28.


Anspruch[de]
  1. Festzieh-Steuervorrichtung für einen Drehmomentschlüssel, umfassend

       eine Einrichtung (22) zum Erfassen einer Änderung in dem an dem Schlüssel (3) angreifenden Druck,

       eine Einrichtung (23) zur Abgabe eines Schlagsignals während der Betätigung des Schlüssels (3), und

       eine Einrichtung (31) zum Schließen der Druckzuleitung zu dem Schlüssel (3) bei Empfang eines Festzieh-Endsignals,

       dadurch gekennzeichnet,

       daß die Druckänderungs-Erfassungseinrichtung (22) mit einem Druckamplitudensignal aus einer Einrichtung (6), die den an dem Schlüssel (3) angreifenden Druck mißt, beaufschlagt ist, um das Maß der Änderung im Ausgangssignal der Druckmeßeinrichtung (6) zu erfassen, und

       daß die das Schlagsignal abgebende Einrichtung (23) gestartet wird, wenn das Maß der Druckänderung einen Bezugswert erreicht.
  2. Vorrichtung nach Anspruch 1, wobei die das Schlagsignal abgebende Einrichtung (23) so ausgelegt ist, daß sie ein Schlagsignal mit vorgegebener Impulsbreite erzeugt, sooft das Maß der Druckänderung den Bezugswert erreicht, und wobei die Vorrichtung ferner eine Einrichtung (25) zur Änderung der Impulsbreite aufweist.
  3. Vorrichtung nach Anspruch 2 mit einem Zähler (27) zum Zählen der Schlagsignalimpulse, wenn die Impulsbreite kürzer ist als das Schlagintervall des Schlüssels (3), und zur Abgabe des Festzieh-Endsignals, wenn ein vorgegebener Zählwert erreicht ist.
  4. Vorrichtung nach Anspruch 2 mit einem Zeitglied (28) zur Messung der Zeit, während der das Schlagsignal kontinuierlich abgegeben wird, wenn die Impulsbreite größer ist als das Schlagintervall des Schlüssels (3), und zur Abgabe des Festzieh-Endsignals, wenn eine vorgegebene Meßzeit erreicht ist.
  5. Vorrichtung nach einem der Ansprüche 1 bis 4 mit einem Zähler (33) zum Ermitteln, wie oft das Festzieh-Endsignal aufgetreten ist, und zur Beendigung einer Folge von Festzieh-Vorgängen, wenn der Zähler (33) einen vorgegebenen Zählwert erreicht.
Anspruch[en]
  1. A tightening control apparatus for a torque wrench, comprising

       means (22) for detecting a change in the pressure applied to said wrench (3),

       means (23) for outputting a striking signal during actuation of said wrench (3), and

       means (31) for closing the pressure admission path to said wrench (3) upon receipt of a tightening-end signal, characterized in

       that said pressure change detecting means (22) is supplied with a pressure amplitude signal outputted by means (6) detecting the pressure applied to said wrench (3), so as to detect the degree of change in the output signal of said pressure detecting means (6), and

       that said striking signal outputting means (23) is started when the degree of said pressure change reaches a reference value.
  2. The apparatus of claim 1, wherein said striking signal outputting means (23) is adapted to produce a striking signal with a predetermined pulse width whenever said degree of pressure change reaches said reference value, said apparatus further comprising means (25) for altering said pulse width.
  3. The apparatus of claim 2, further comprising a counter (27) for counting said striking signal pulses, when said pulse width is shorter than the striking interval of said wrench (3), and for outputting said tightening-end signal when a predetermined count value is reached.
  4. The apparatus of claim 2, further comprising a timer (28) for measuring the time during which said striking signal is continuously output, when said pulse width is greater than the striking inverval of said wrench (3), and for outputting said tightening-end signal when a predetermined measured time is reached.
  5. The apparatus of any of claims 1 to 4, further comprising a counter (33) for counting the number of occurrences of said tightening-end signal and completing a tightening operation sequence when the counter (33) reaches a predetermined count value.
Anspruch[fr]
  1. Appareil de commande de serrage pour une clé dynamométrique à déclenchement, comprenant :

       des moyens (22) pour détecter un changement de la pression appliquée à ladite clé (3), et

       des moyens (23) pour délivrer en sortie un signal d'impact durant l'actionnement de ladite clé (3), et

       des moyens (31) pour fermer le trajet d'admission de pression sur ladite clé (3) lors de la réception d'un signal de fin de serrage,

       caractérisé en ce que

       lesdits moyens de détection de changement de pression (22) reçoivent un signal d'amplitude de pression délivré en sortie par des moyens (6) détectant la pression appliquée à ladite clé (3), de façon à détecter le degré de changement de signal de sortie desdits moyens de détection de pression (6), et

       en ce que lesdits moyens de délivrance de signal d'impact (23) commencent à être actionnés lorsque le degré dudit changement de pression atteint une valeur de référence.
  2. Appareil selon la revendication 1, dans lequel lesdits moyens de délivrance de signal d'impact (23) sont adaptés pour produire un signal d'impact avec une largeur d'impulsion prédéterminée à chaque fois que ledit degré de changement de pression atteint ladite valeur de référence, ledit appareil comportant de plus des moyens (25) pour modifier ladite largeur d'impulsion.
  3. Appareil selon la revendication 2, comportant de plus un compteur (27) pour compter lesdites impulsions de signal d'impact, lorsque ladite largeur d'impulsion est plus courte que l'intervalle d'impact de ladite clé (3), et pour délivrer en sortie ledit signal de fin de serrage lorsqu'une valeur de comptage prédéterminée est atteinte.
  4. Appareil selon la revendication 2, comportant de plus un minuteur (28) pour mesurer le temps durant lequel ledit signal d'impact est délivré en sortie de façon continue, lorsque ladite largeur d'impulsion est supérieure à l'intervalle d'impact de ladite clé (3), et pour délivrer en sortie ledit signal de fin de serrage lorsqu'un temps mesuré prédéterminé est atteint.
  5. Appareil selon l'une quelconque des revendications 1 à 4, comportant de plus un compteur (33) pour compter le nombre d'apparitions dudit signal de fin de serrage et pour terminer une séquence d'opération de serrage lorsque le compteur (33) atteint une valeur de comptage prédéterminée.






IPC
A Täglicher Lebensbedarf
B Arbeitsverfahren; Transportieren
C Chemie; Hüttenwesen
D Textilien; Papier
E Bauwesen; Erdbohren; Bergbau
F Maschinenbau; Beleuchtung; Heizung; Waffen; Sprengen
G Physik
H Elektrotechnik

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