Tools – Wrench – screwdriver – or driver therefor – Responsive to torque on work
Utility Patent
1999-02-26
2001-01-02
Gerrity, Stephen F. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Responsive to torque on work
C081S429000, C073S862230
Utility Patent
active
06167788
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a torque wrench having an electronic evaluation device for measurement values from sensors for detecting the torque and a rotary angle.
Such a torque wrench is known from EP 0,133,557. In the torque wrench there, a microprocessor is provided, which has a keyboard by way of which data required in each particular case, such as desired values, limit values or the like, selected as presettings, can be entered for the purpose of the tightening operation. The tightening operation, for example the tightening of a screw, is monitored according to these presettings. In this case, when specific limit values are reached, these values which are reached are stored automatically. It became clear that one disadvantage there was the transmission technology for the measurement values of the rotary-angle measuring arrangement, which consists substantially of a pulse wheel and a reflex probe. This transmission technology is very costly and, for example, is highly susceptible to contamination. Furthermore, the geometry of the wrench is substantially determined by the pulse-wheel/reflex-probe arrangement.
SUMMARY OF THE INVENTION
There is, therefore, the technical problem of improving, which is an object of the present invention, the transmission technology for detecting the rotary angle, and to improve the torque wrench.
According to the invention the evaluation device (
5
) is programable with a starting torque (M
s
) and determines a deflection angle (&bgr;) when the starting torque (M
s
) is reached. The type of time integration depends on the overall design of the evaluation device and, in particular, also on the output of measurement values from the acceleration sensor. Thus, integration may take place in a way known per se by means of differential amplifiers, if the evaluation of the measurement values is carried out by analog means. If, for example, a microprocessor is provided, evaluation may also be carried out digitally and, for this purpose, there are various numerical integration methods available, by means of which the microprocessor can then be programmed. Suitable acceleration sensors are known and are commercially available. Preferably, those acceleration sensors are used which are disposed at a specific distance from the pivot axis in the torque wrench and for which the pivot axis in the torque wrench serves as a virtual fixed point. This distance depends on the type of acceleration sensor used and must also be adjusted accordingly. In contrast to acceleration sensors for detecting rotary-angle accelerations which are arranged, for example, annularly about an axis of rotation, the preferred arrangement has the advantage that, here, no measurement takes place between components fixed relative to the axis of rotation and components fixed relative to the wrench. A deflection angle is to be understood below as referring to that fraction of the rotary angle which normally begins to be measured from specific initial conditions of a zero angle position, such as, for example, a spatial position of the torque wrench relative to a housing, and likewise then ends with the termination of the tightening operation or monitoring operation. As a result, in addition to the measurement of the torque, the secure tightening of, for example, a screw is also detected by means of the deflection angle. Such a zero angle position may, for example, be entered manually in the torque wrench. Usually, however, a torque wrench of the type mentioned in the introduction is used for monitoring the tightening of, for example, screws for a multiplicity of identical screw connections during mass production. In this case, it proved expedient for the evaluation device to be preprogrammable with a starting torque and for a deflection angle to be determined from the moment when the starting torque is reached. As a result, initially, the detection of the torque is linked to the detection of the rotary angle in order to determine the deflection angle. The consequence of this is that the beginning of the determination of the deflection angle is, as it were, automated. According to the invention, the acceleration sensor detects a rotary-angle acceleration which may be both positive and negative in the tightening direction of, for example, a screw, the screw nevertheless being tightened with a positive torque. If, however, the torque or the angular speed becomes negative when a ratchet or lever brace is used, specifically during the return of the torque wrench opposite to the tightening direction, this angular range covered by the torque wrench should not be taken into account, since it does not contribute to the tightening of the screw. It is therefore expedient for the measurement values from the acceleration sensor to be evaluated only in a predeterminable direction of rotation. In a further embodiment, there is provision for the evaluation device to be preprogrammable in each case with a lower and an upper limit value for the torque and with a deflection angle and for the evaluation device to indicate actual values lying between the respective limit values. This results in double monitoring of the tightening operation as to whether a predetermined range both of the torque and of the deflection angle has been reached. Furthermore, there may also be provision for the evaluation device to indicate that the lower limit value of the torque and/or of the deflection angle has already been exceeded. The user is thereby advised that the operation of tightening, for example, a screw is approaching the end and he must then also monitor the upper limit values to ensure that these are not exceeded. The exceeding of the upper limit value of the torque and/or of the deflection angle is likewise indicated by the evaluation device, thereby signalling that this tightening operation has not been properly concluded. It proved expedient to effect such an indication that limit values are reached or exceeded by means of at least one light-emitting diode. In this case, there is a multiplicity of indicating possibilities, for example the exceeding of the limit values of the torque or of the deflection angle may be signalled by a colour change or flashing. Final values reached are jointly indicated in a conventional way on an LCD display or a change-over of the measuring mode may also take place and a reversible alternative indication of the final torque and/or of the final deflection angle may be effected. These final values may be stored by the microprocessor, transmitted to a computer by means of a corresponding interface or output directly to a printer.
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Humme Frank
Schonberger Heinz
Farber Martin A.
Gerrity Stephen F.
Saltus-Werk Max Forst GmbH
Shakeri Hadi
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