GB2220480A

GB2220480A - Measuring apparatus and its calibration

Info

Publication number: GB2220480A
Application number: GB8914268A
Authority: GB
Inventors: Ali Bindernagel
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-06-22
Filing date: 1989-06-21
Publication date: 1990-01-10
Also published as: GB8914268D0; IT1229161B; FR2633388A1; JPH0246542A; DE3820991A1; IT8920054A0

Description

L _ 2 0 4 7 5 r DIE'SCRIPTION MEASURING APPARATUS AND ITS CALIBRATION The

invention relates to a method of calibrating a measuring apparatus, operating contactlessly using radiation beams, for measuring crosssectional dimensions of elongated work material running through, such as rolled stock. Measuring apparatus of this type not only serve to ascertain and monitor the finished dimensions, but also to regulate and control production plant, such as rolling lines, so that the quality of the work material produced, particularly its range of tolerance, as well as the output of the plant and the utilization of time, may be optimized. In order to achieve this, it is necessary to measure the cross-sectional dimensions of the work material as accurately as possible at one or several points of a plant whilst the work material is running through in order to become aware of any differences immediately. so that suitable counter-measures can be rapidly initiated. Known measuring apparatus, such as those operating contactlessly with laser beams, serve for measurements of this kind.

1n practice, operation with a measuring apparatus of this type gives rise to difficulties in that the position of the zero point of its measured values varies in an undesirable manner. and consequently -2 satisfactory measuring results cannot be obtained. Such displacement of the zero point is generally caused by external influences and is unavoidable in practice. The measuring heads of the measuring apparatus, which transmit and receive the measuring beams, are, in accordance with the type of construction, disposed at a lesser or greater distance from the work material running through, and are held in this position by a holder or a housing which entirely or partially surrounds the work material running through. The housing expands or contracts if the temperature in the production shed, or even in the near proximity of the housing, varies, and hence the position of the measuring heads relative to the longitudinal central axis of the work material running W through changes. whereby the zero point is shifted. According to the type of construction of the measuring apparatus. and according to the nature of the cross-sectional shape of the work material to be measured, the measuring heads are frequently disposed in such a way that they are pivoted about, or rotate around, the longitudinal central axis of the work material. Vibration and forces then occurring may likewise be the cause of variation in the distance between the measuring heads and the longitudinal central axis of the work material, and hence variation A in the position of the zero point. Other uncontrollable external influences also cause displacement of the zero point and result in inaccurate measurement results.

An object of the invention is to provide a method and a device by which more accurate measurement results may be obtained.

In accordance with the invention, a calibration or gauge member with accurately known cross-sectional dimensions is kept in permanent readiness in the vicinity of the measuring point of the measuring apparatus and is introduced into the region of the radiation beams during each or several of the intervals between measurement of the work material, whereupon the dimension indication or measured value output of the measuring apparatus is adjusted to the known cross-sectional dimensions of the gauge member. Hence, while the zero point of a measuring apparatus is normally reset, at all events during installation and in the case of maintenance work carried out at long intervals of time, it is proposed, in accordance with the invention., to perform such calibration very frequently. The frequency with which this should be carried out is dependent upon the type and mode of operation of the plant in which the measuring apparatus is used. In principle, particularly -4accurate measurement results are obtained by carrying out calibration as frequently as possible, since a shift in the zero point which has occurred can possibly exist up to the next calibration operation which soon follows. A gradual drift in the zero point, taking place over a long period of time, to an increasing amount of error is continuously prevented by successive calibration operations effected at short intervals of time. Calibration is effected by repeatedly measuring the gauge member of accurately known cross-sectional dimensions, for which purpose the gauge member is brought into the region of the radiation beams, instead of the work material. The dimension indication or the m;-- asured value output then has to indicate the known dimensions of the gauge member. If it does not do this owing to a shift in the zero point, the calibration device provided on these types of measuring app-aratus n. as to be actuated in such a way that the dimension of the gauge member is indicated or output. A calibration operation of this kind may be performed during any pause in manufacture, although it is also possible to perform the e.libration process whilst the work material continues to run through, the measurement of the work material being, of course, interrupted for the short period of calibration.

The invention also relates to a measuring apparatus capable of being calibrated as described and equipped with at least one measuring head in a housing surrounding the work material running through.

A plurality of measuring heads may be distributed around the periphery and.may be rotatable or pivotable as well as fixed. Furthermore, the housing may be replaced by a suitable holder.

In accordance with the invention. a calibration or gauge member with accurately known cross sectional dimensions is disposed on, or in the vicinity of, the housing and is held by a holding device and may be brought temporarily into the region of radiation beams of the measuring head as required. Consequently, the calibration operation may be performed at low expense within the shortest period of time and may be repeated as frequently as desired, since the gauge member mpy be introduced into, and removed from the region of the measuring beams coaxially with the longitudinal central axis of the work material in a simple and rapid manner.

It is advantageous if the holding device has a tube which surrounds the work material running through and which has radial openings for the radiation beams, and the outside of the tube has an axially displaceable ring serving as the gauge member.

embodiment is particularly suitable for the measurement of heated work material, paritcularly rolled stock from hot-rolling plant, since the tube surrounding the work material considerably reduces the thermal stress on the measuring heads and the gauge ring. Alternatively, the tube may be double-walled, so that it may be cooled by means of coolant flowing through. In this embodiment of the invention, the gauge ring may be rigidly connected to the tube of the holding device and is displaceable with the said tube in an axial direction within, and relative to, the housing. In order to introduce the gauge ring into the region of the radiation beams, it is sufficient to displace the tube in an axial direction together with the gauge ring, which also applies to the removal of the gauge ring from this region. Both these operations may be performed rapidly and without problems. On the other hand, it is also possible for the gauge ring to be longitudinally displaceably guided on the tube of the holding device. In this embodiment, only the gauge ring and no longer the tube, is displaced in an axial direction before and after calibration.

In a further embodiment of the invention, the holding device has at least one pivotable lever to which the gauge member is secured, and the lever holds -7the gauge member selectively at the same position as the work material in the region of the radiation beams or outside this region. This embodiment is particularly suitable for cases of application in which the calibration operation is only performed in the intervals in the runningthrough of the work material. It is thereby also possible for the gauge member to have the cross-sectional dimensions of the work material required at any given time. The calibration operation is then effected directly with the cross-sectional dimensions of the work material which are to be measured, so that particularly accurate calibration is effected.

The invention is further described, by way of example, with reference to the accompanying drawings, in which:- Fig.1 is a longitudinal section through a measuring apparatus during measurement; Fig.2 is a longitudinal section through the measuring apparatus of Fig.1 during calibration; Fig.3 is a cross-section taken on the line III-III of Fig.l; Fig.4 is a longitudinal section through another embodiment of the measuring apparatus; and Fig.5 is a longitudinal section through a third embod-iment of the measuring apparatus.

1 Fig.1 shows a longitudinal portion of elongated work material 1 of circular cross section. However. a circular cross-section is not essential, and the work material 1 may have any cross-sectional shape, comprise a wide variety of materials, and have a high or a low temperature. The work material 1 is surrounded by a tube 2 which, for the sake of simplicity, is only partially shown. The tube 2 is of doublewalled construction, hence resulting in an annular space 3 whose entry end is closed by an end wall 2a sloping towards the work material 1, and whose delivery end is closed by an end wall 2b extending at right angles to the work material 1. Cooling water is supplied to the annular space 3 by way of a water connection 4, and may flow off again by way of the connection 5.

The tube 2 has, at each of a plurality of points on its circumference, two radial openings 6 and 7 through which a measuring head 8 directs measuring beams 9 onto the surface of the work material 1 and receives the reflected measuring beams 9 respectively. The measuring head 8 is held in a housing 11 by means of holders 10. The housing 11 has bearings 12 by means of which it can rotate on the stationary tube 2, or is pivoted.about the longitudinal central axis la of the work material 1. The drives required for this are known and have not 1 1 been shown. Cooling air is admitted to the interior space of the housing 11 by way of a connection 13, and can escape through, inter alia, the radial openings 6 and 7 A gauge ring 14 serving as a calibration member is disposed on the outside of the tube 2 in the immediate vicinity of the radial openings 6 and 7, and is rigidly connected to the tube 2. If the gauge ring 14 serving as the calibration member is to be brought into the region of the measuring beams 9 for the purpose of calibration, it is only necessary to admit pressure medium to a working cylinder 15 on the external wall of the housing 11. The housing 11 is thereby displaced in an axial direction (to the left as viewed in Fig.2) relative to the tube 2, so that the measuring beams 9 impinge on the gauge ring 14 whose diameter is known exactly. If this external diameter is also measured by the measuring head 8, or if the fresh setting is effected in the event of a difference, the calibration position of the housing 11 shown in Fig.2 is cancelled by correspondingly acting upon the working cylinder 15 in the opposite direction, so that the position shown in Fig.1 is reached again and the measurement may be continued.

Fig.3 shows that a plurality of measuring heads 8 may be provided in the housing 11, so that a plurality 1 -10of measurements may be taken simultaneously in order to obtain greater accuracy.

The embodiment of Fig.4 corresponds substantially to the embodiment of Figs. 1 to 3, with the difference that the ring 14 serving as the calibration member is disposed on the tube 2 so as to be longitudinally displaceable and may be brought into, or removed from, the region of the measuring beams 9 by means of the working cylinder 16. It is then unnecessary to displace the housing 11 in an axial direction relative to the tube 2. In Fig.4, the bearings 12 only serve to enable the housing 11 to be rotated about the central longitudinal axis la. The bearings 12 may be omitted if this pivotal or rotary movement should not be required.

In the embodiment of Fig.5, the work material 1 has left the tube 2.. so that the tube has been freed for a gauge bar 17 which serves as a calibration member in this embodiment. The gauge bar is disposed coaxially of the longitudinal central axis la of the work material 1 and., advantageously, but not essentially, has those cross-sectional dimensions which are desired in the work material 1 and which are normally also measured when the measuring apparatus is in order and this also applies to the manufacturing or processing plant of the work material 1.

1 The gauge bar 17 is secured to a holding device 18 so as to be interchangeable. The holding device 18 is equipped with two levers 19 whose end portions are provided with hinges 20, so that the levers can be pivoted. In this manner, it is possible to swing the gauge bar 17 out of the tube 2 into the position shown by dash-dot lines. When in this position, neither the holding device 18 nor the gauge bar 17 impede the run-through of the work material. However. if a calibration operation is to be effected, the gauge bar 17 serving as a calibration member-may be swung very rapidly into its calibration position again within the tube 2 as soon as the work material 1 has left the interior of the tube 2.

1

Claims

1. A method of calibraing a measuring apparatus, operating contactlessly with radiation beams, for measuring cross-sectional dimensions of elongated work material, in which a gauge member with accurately known cross-sectional dimensions is kept in permanent readiness in the vicinity of the measuring point of the measuring apparatus and is introduced into the region of the radiation beams during each or several of the measuring intervals of the work material, whereupon the dimension indication or measured value output of the measuring apparatus is adjusted to the known cross-sectional dimensions of the gauge member.

2. A measuring apparatus having at least one measuring head in a housing surrounding the work material running through, and having a gauge member with accurately known cross-sectional dimensions disposed on, or in the vicinity of, the housing and held by a holding device so that it may be brought temporarily into the region of radiation beams produced by the measuring head as required.

3. A measuring apparatus as claimed in claim 2, in which the holding device has a tube which surrounds the work material running through and which has radial openings for the radiation beams, and the gauge member comprises an axially displaceable gauge ring on the outside of the tube.

4. A measuring apparatus as claimed in claim 3, in which the gauge ring is rigidly connected to the tube of the holding device and is displaceable with the said tube in an axial direction within., and relative to, the housing.

5. A measuring apparatus as claimed in claim 3, in which the gauge ring is longitudinally displaceably guided on the tube of the holding device.

6. A measuring apparatus as claimed in claim 2, in which the holding device has at least one pivotable lever to which the gauge member is secured, and the lever holds the gauge member selectively at the same position as the work material in the region of the radiation beams or outside this region.

7. A measuring apparatus as claimed in claim 6, in which the gauge member has the cross-sectional dimensions of the work material required at any given time.

8. A calibration method substantially as herein described with reference to the accompanying drawings.

9. A measuring apparatus constructed and adapted to be calibrated substantially as herein described with reference to and as illustrated in the accompanying drawings.

Publwlied1959 at The Patent Office. State House. 66'71 High Hollbo-mLondorWCIR4TP Further copies maybe obtained from The Patent Office. Sales Branch, St Mary Cray. Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd. St Mary Cray. Kent. Con- 1187