Measuring and testing – Inspecting
Reexamination Certificate
2001-01-11
2004-08-31
Raevis, Robert (Department: 2856)
Measuring and testing
Inspecting
Reexamination Certificate
active
06782769
ABSTRACT:
The present disclosure relates to the subject matter disclosed in German patent application No. 100 00 954.9 of Jan. 17, 2000, the entire specification of which is incorporated herein by reference.
The invention relates to a monitoring device for checking for a predefined position of a body or for checking for the presence of a body, comprising a pivotal checking element, a motor for driving the checking element and a control device for controlling the pivotal movement of the checking element.
Monitoring devices of this type are known from DE 30 03 431 C2, DE 43 10 872 A1 or DE 196 08 628 A1.
They are employed in machine tools for example in order to check whether a tool, such as a drill for example, is still in a predefined position or, for example, has broken off, or for checking as to whether a “foreign body” has entered a region in which such a body would constitute a disturbance.
In DE 30 03 431 C2, it is proposed, for the purposes of setting the sensitivity or impact weight, on the tool or workpiece being monitored, of a sensing needle which is seated in the checking element, that the rotational speed of a dc motor and hence the pivotal speed of the sensing needle be altered.
Commencing from the state of the art, the object of the invention is to improve a monitoring device of the generic kind in such a manner that the monitoring device will be universally employable in a simple manner and in particular that damage to a body being monitored will, to a large extent, be avoidable when rapidly executing a monitoring operation.
In accordance with the invention, this object is achieved in a monitoring device of the type described hereinabove in that the checking element is adapted to be pivoted commencing from a starting position through a transition region into a monitoring region in which the predefined position of the body lies or in which the presence of a body should be monitored, and in that the control device limits the torque of the checking element in such a manner that the maximum possible torque in the monitoring region is reduced relative to that in the transition region.
By virtue of the inventive concept, it is firstly ensured that the checking element will reach the monitoring region quickly, i.e. that it can pass through the transition region with a high torque value. Secondly, in the monitoring region, the checking element will strike a body that is possibly located therein with a small amount of torque since the maximum possible torque has been reduced. The checking element will exert a force on the body even when its speed is zero i.e. it is resting on the body. By reducing the torque limit, it is ensured, in accordance with the invention, that this force will not be too large and, in particular, will not exceed a force which could destroy the body, such as a tool for example.
Account should be taken of the fact that, if the pivotal movement of the checking element is stopped by a body in the monitoring region, the control device will attempt to counteract this, i.e. the torque will be increased for a short period despite the reduction in speed. The body, on which the checking element then rests, may thereby be subjected to an increased load. Since the control process for the pivotal movement of the checking element has a certain time constant, such a short term rise in torque cannot generally be prevented. However, by virtue of the solution in accordance with the invention, whereby there is a predefined upper limit for the torque in the monitoring region, this being reduced relative to the upper limit in the transition region, the torque will be prevented from exceeding a certain value and hence the force on the body will also be prevented from exceeding a certain value.
A sensing needle is preferably arranged on the checking element. The torque will alter in correspondence with the differing lengths of the sensing needle. However, by virtue of the solution in accordance with the invention, it is always ensured that the torque will not exceed an upper limiting value independently of its actual value.
Furthermore, in accordance with the invention, provision may be made for a seal to be arranged between the checking element and the housing. A frictional moment is exerted by this seal which counteracts the torque of a shaft which is driven by the motor.
The absolute value of the torque may thereby alter in this case too. However, in accordance with the invention, it is always ensured that an upper limit for the torque will not be exceeded.
It is especially very advantageous if the motor is a dc motor and if the control device limits the supply of current to the motor. The torque, which the motor can exert, is set by the current through the motor. If the supply of current is limited, then the maximum permissible amount of torque can be set in a simple manner, and, in particular, the maximum permissible torque in the monitoring region can be correspondingly reduced by reducing the supply of current.
It is especially very expedient if the pivotal movement of the checking element is controlled by means of a combined position, speed and torque controlling. The pivotal movement can then be matched to the demands, and in particular, the transition region can be passed through quickly and the predefined position of a body in the monitoring region can be monitored without fear of damaging or even destroying the body.
It is expedient for the speed of the checking element to be reducible during its passage from the transition region into the monitoring region so as to produce the requisite control and regulation of the monitoring process in the monitoring region.
It is especially very expedient if the reduction of the torque limit is effected after the reduction in the speed of the checking element. On the one hand, it is thereby ensured that the speed of the checking element will be reduced in the monitoring region and, in particular, that the reduction of the torque limit will not prevent the speed sinking to a predefined value, but, on the other hand, it is nevertheless ensured that the checking element will not strike against a body in the monitoring region with too great a torque.
It is especially very advantageous if the control device comprises an angle transmitter. This may, in particular, be an incremental transmitter. The pivotal movement of the checking element can then be controlled in a simple manner.
It is expedient if the transition region comprises an acceleration region in which the speed of the checking element is increased commencing from the starting position. Commencing, in particular, from a static position of the checking element, this thereby permits its speed to increase rapidly so that it can pass quickly through the transition region.
Moreover, it is advantageous if the transition region comprises a braking region in which the speed of the checking element is reduced. In a simple manner, this arrangement permits the checking element to be pivoted in the monitoring region at a lower speed than in the transition region so as to prevent a hard impact between the checking element and the body that is to be monitored.
It is expedient for the speed of the checking element to be maintained substantially constant between an acceleration region and a braking region of the transition region. This thereby results in improved control and regulating possibilities since the pivotal angle is proportional to time in this region, and improved control and regulating possibilities are also created since non-linear calculations do not need to be carried out in this region whereby the adjusting behaviour for the controlled value when such controlling is required will then be improved because of the linear relationship between the pivotal angle and the time.
It is also particularly advantageous if the speed of the checking element is maintained substantially constant in the monitoring region. In essence, the reasons for this are the same as were indicated immediately above.
It is especially expedient for the control of the pivotal movement, if the control device c
Middex-Electronic GmbH
Raevis Robert
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