EP0918978A1

EP0918978A1 - Method and device for the measuring of the overlap width of a lap joint where two work pieces lie flat upon each other

Info

Publication number: EP0918978A1
Application number: EP97942835A
Authority: EP
Inventors: Hans-Dieter Gall; Martin Koch
Original assignee: Thyssen Stahl AG
Current assignee: Thyssen Stahl AG
Priority date: 1996-08-14
Filing date: 1997-07-30
Publication date: 1999-06-02
Also published as: DE19632696C1; WO1998007000A1

Abstract

The invention relates to a method and a device for the measuring of the overlap width of a lap joint where two work pieces (b1, b2) lie flat upon each other. The distance (x1, x2) from the edges (K1, K2) of the joint to a common reference spot or two reference spots (N1, N2) with a defined distance (xN) is determined and the overlap width (ul) calculated from these values with two transducers (1, 2) working in particular according to the light-section and triangulation procedure.

Description

Method and device for measuring the overlap width of an overlap joint of two workpieces lying flat on top of one another

For the control of a joining process, in particular a welding process for overlapping boards or strips, in particular made of sheet steel, it is important to control the overlap width of the overlap joint in order to, depending on the measured values determined, the production system, in particular the course of the strips to control. Knowledge of the overlap width is also important for assessing the quality of interconnected workpieces.

A difficulty in determining the overlap width is that the abutting edges of the two workpieces can only be detected from different sides. Another difficulty is to quickly determine the position of the butt edges with high accuracy so that they can be used to control a feed device and / or a welding device. In order to detect the overlap width of two material webs conveyed transversely to overlap joints, it is known (DE 692 06 747 T2, * JP 62-98 210 A. In: Patents Abstract of Japan P-623 October 6, 1987 vol. 11 / no. 305 ), two sensors responsive to the material web edges, in particular laser sensors, to be arranged exactly opposite one another on opposite sides of the material web. When the overlap bumps pass through the barrier formed in this way, these sensors, depending on the overlap width, emit signals with a time delay to an evaluation device which also receives a signal for the material web speed. The overlap width can then be calculated from these signals. If two pairs of these sensors are arranged offset transversely to the web running direction and also lie in the same plane arranged transversely to the web running direction, an offset angle of the edges can also be determined with this method and this device. In both cases, however, the measurement accuracy depends on the exact alignment of the sensors to one another and further on that the path speed is constant in the phase between the first signal for the leading edge and the second signal for the trailing edge. It goes without saying that measurement errors can occur because of these requirements. Furthermore, this method and this device are limited to measurements in which the material web is moved past the sensors with a transverse overlap joint.

Furthermore, a method for measuring the overlap width of an overlap shock of a tape section wound on a drum is known (DE 41 29 465 AI). For this purpose, the front end of the drum is simultaneously wound on the one hand Material web section and on the other hand, the associated angular position of the drum is detected. After winding up the material web section, the rear end of the material web section and, on the other hand, the associated angular position of the drum are detected at the same time. The overlap width can be drawn directly from the differential value of the angular positions of the drum. The measurement result can be used to control an upstream feed device for the material web strips in such a way that the length of the material web sections to be fed in is corrected if the actual value for the overlap deviates from the target value.

The so-called light-section triangulation method has proven itself in order to precisely capture the edges of, in particular, moving profiles (DE 44 31 922 AI).

The invention is based on the object of developing a method and a device for measuring the overlap width of an overlap joint of two workpieces lying flat one above the other, which enables rapid, exact detection of the overlap width of two workpieces lying flat on one another.

According to the invention, this object is achieved in that the distance between the edges of the workpieces from a common reference point or from two reference points having a defined distance from one another is measured without contact and the overlap width is calculated from these measured values. The distances are preferably measured using a measuring line running across the respective edge. This measurement along the measurement line can be carried out, for example, according to the known light section Triangulation method. In another contactless method, the measuring line is formed with an air jet, which is generated with the aid of a slot-shaped nozzle. If the air jet blows onto a sheet metal surface, a dynamic pressure is generated. If a sheet whose edge lies within the impact surface of the air jet is moved parallel to the direction of the measuring line, the dynamic pressure of the air jet changes since it is covered differently. There is thus a clear connection between the position of the sheet edge and the dynamic pressure. The edge position can thus be determined with the aid of a dynamic pressure measurement.

The method according to the invention, which works without contact, initially provides two measured values for the position of the edge in relation to a fixed reference location or reference locations. In any case, the overlap width can be calculated from this purely geometric data. In addition, the spatial position of the edge in relation to the reference point can be determined via the distance between the edges, which is crucial for knowing the course of the edges.

The defined distance from two reference points can be determined in a simple manner by measuring the .distances of the reference points from a common measuring edge lying in the measuring range.

In order to determine the course of the individual edges, in particular when the edges are skewed, it is provided according to a further embodiment of the invention to measure the distances of the edges from the reference point (s) at the points offset in the axial direction in order to compare these measured values a possible change in the overlap width and / or the degree of a possible one Determine the misalignment of one or both workpieces. The measurement is carried out either with a time shift in the case of workpieces moving parallel to the axial direction or at the same time at points offset in the axial direction, in which case, however, the distance from the measurement location to a parallel in the axial direction is either the same at both locations or must be taken into account in the measurement if the distance is different. The method according to the invention is universally applicable and is therefore not restricted to the movement of the workpieces in a specific direction.

Depending on a target / actual value comparison, a target / value deviation of the overlap width or the skew is preferably stored in a location-specific manner and / or the workpieces are marked at the fault locations.

The measurement method according to the invention is suitable for a method for bringing together two workpieces to be connected in an overlapping manner, the measurement result being used to control actuators of a device for bringing the workpieces together or a welding device.

The invention also relates to a device for measuring the overlap width of two workpieces lying flat on top of one another, each with at least one measuring transducer directed towards the overlap joint and contactlessly measuring the distance between the edges and a reference point on each side of the workpieces lying on top of each other and with an evaluation unit for the measurement results the transducer, taking into account the position of the reference locations and the measured distances, an output signal for the overlap width and / or an output signal as an actuating signal for a marking unit and / or a Supply unit for the workpieces to be brought together or a welding device. The evaluation unit supplies the control signals in the event of a target / actual value • deviation.

With the device according to the invention it is also possible to determine the edge position of one or both workpieces, in particular the workpiece, which is responsible for a possible misalignment in the case of non-parallel edges, instead of or in addition to the overlap width.

The invention is explained in more detail below with reference to a drawing which represents an exemplary embodiment. In detail show:

L two workpieces lying flat one above the other, forming an overlap joint, in an isometric representation,

2 the determination of a defined distance from two reference points (zero lines) associated with measuring sensors in a schematic representation in axial cross section,

3 the determination of the overlap width at two reference points (zero line) in a schematic representation in the axial cross section,

4 the detection of the overlap width during a relative axial movement between the overlapping workpieces on the one hand and the measuring device with two assigned measurement sensors on the other, in supervision, 5 shows diagrams for the overlap widths determined in the measurement according to FIG. 4 in the axial direction of the overlap joint,

6 shows the detection of the overlap width of two workpieces lying on one another in an inclined position with respect to one another with two pairs of measuring sensors offset in the axial direction,

Fig. 7 diagrams for the distances of the edges of the two workpieces from reference points at points offset in the axial direction and the overlap widths and calculated from it

Fig. 8 shows a measuring device in the form of a block diagram.

1, two workpieces b _lf b ₂ lie flat on one another with overlap. The upper workpiece b_ has a butt edge K and the lower workpiece b _{2 has} an butt edge K ₂ . The distance between these abutting edges K ^ K _j is equal to the overlap width ul. Each butt edge K _{1 (} K ₂ is assigned at least one, in the exemplary embodiment two, transducers _1, ₂ , 3, 4, which are offset one behind the other in the axial direction. In an embodiment of the invention, these transducers _1, ₂ , 3, 4 work according to the known light section Triangulation method, which allows the position of a butt edge on a measuring line to be recorded transversely to the course of the butt edges K _lr K ₂ without contact and with high accuracy.

In another embodiment of the invention, the line-shaped measuring line is formed by a streak-shaped air jet and the sensors are Pressure sensors that measure the dynamic pressure in the measuring beam. With such a measuring arrangement, the position of a butt edge within the measuring line can also be measured transversely to the course of the butt edges K _X , K ₂ quickly and with high accuracy without contact.

The invention is described below using the example of the light section triangulation method. Since the method of the light section triangulation method is well known, it only needs to be dealt with to the extent necessary for the implementation of the method according to the invention.

It is thus possible to measure a reference point (zero line) N _{1 (} N ₂ ) to a fixed reference point (zero line) N _{1 (} N ₂ ) in the measuring device of the measuring _transducer 1, _2, _{3, 4.} Since in the method _according to the invention both in the same vertical axial plane the position of the abutting edge K. as well as the position of the abutting edge K _{2 is} detected by transducers 1, _2, 3, 4 arranged on different sides, it is necessary before the start of the measurement of the overlap width ul to maintain the predetermined one and later also during the measurement. distance x _N of reference points N _lr N ₂ to determine this purpose is in the dimension L _ü overlapping measurement ranges L ^ _L;... shows a sheet placed both transducers 1,2 Mk with sharply defined measuring edge as shown in Figure 2 Because of the are sharply defined measuring edge, the edges a, B of the measuring edge exactly one above the other. the upper measuring sensor 1 measures for the measuring edge then a distance 1 from its reference point N _{1 (while} the lower transducer 2 f r measures the measuring edge a distance 1 ₂ from its reference location N _2. The sum of these distances 1 _{1 (} 1, is then equal to the distance x _N. With this defined distance x _N , the overlap uel can then be calculated using the following formula in the case of workpieces overlapping one another ül = x _n - (χ .. + x ₂ ),

where x ₁₇ x _{2 are} the distances of the measuring locations from the reference locations N _{1 #} N ₂ of the transducers _1, ₂ , as shown in FIG. 3.

It is understood that the defined distance of the reference locations N _X , N ₂ for the transducers 3, 4 in FIG. 1 is determined in a corresponding manner.

FIGS. 4 and 5 relate to the measurement of the overlap width ul of two workpieces b _lf b ₂ _lying one above the other as boards, each with a _{measuring transducer 1,} ₂ arranged on the top and one on the bottom, working according to the light section triangulation method. With this measuring method, there is a relative movement in the axial direction of the edges between the blanks b _{1 (} b ₂ and the transducers _1, ₂ , as is the case, for example, when welding. When passing through the blanks b ^ b _j one obtains for the overlap width ül at location n

^u - * - (n) = * ~ ( ^χ ι (n) ^{+ X} 2 (n)) •

5 shows these measured values in an upper diagram. They can be stored in a location-specific manner, in order for the workpieces b _1; b ₂ to have a measurement report. An average value can be formed from the measured values in the upper diagram, which is shown in the lower diagram. The lower diagram shows a large number of such measured values for welded workpieces according to FIG. 4.

The embodiment of FIGS. 6 and 7 differs from that of FIGS. 4 and 5 in that in this case the upper board b. to the lower board b _{2 has} an imbalance. In order to be able to record this misalignment, the overlap width ül _A and ül _{E is} measured at two points offset in the axial direction. The measurement of the misalignment can be derived from these measurement results. In addition, the distance values x _1A and x _1B and x _2A and x _{2B can} also be used to determine which of the two boards b _! , b _{2 is} responsible for the imbalance. This is clear from the diagrams of FIG. 7, which show at the bottom left that the lower board b _{2 has the} desired dimension with its edge at both measuring locations, while the upper board b- _^ deviates from the target dimension at both measuring locations. The diagrams on the right show the measurement results from different boards or the measurement results when moving through strips.

The measuring device according to FIG. 8 comprises two pairs of transducers 1, 2, 3, 4 for detecting the upper and lower edges of an overlap joint at points offset in the direction of the abutting edges. In this respect, it corresponds to the representations of FIGS. 1 and 6. The transducers 1 to 4 operate according to the light section triangulation method, that is to say that they supply measured values for the distances from abutting edges, for example, from reference points or reference lines specified by the device. In a converter 5, the analog measured values are converted into digital measured values and fed to a PC, which can process them into different measured values, in order to determine the

Overlap width, for determining the position of the edges with respect to a predetermined location, in particular for determining the skew or for generating an actuating signal for a marking unit M or for controlling a welding device and / or belt guiding device. The transducers can be arranged in a stationary manner, but they can also be moved along the abutting edges, for example with a welding device moving along the abutting edge. Then it is important however, that the relative distance between the reference points (zero lines) of the assigned transducers is kept constant.

Claims

Expectations

1. Method for measuring the overlap width of an overlap joint of two workpieces lying flat on top of each other, so that the distance of each edge of the workpieces from a common reference location or two reference locations having a defined distance from one another is measured without contact and the overlap width is calculated from these measured values.

2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the distances are measured with the aid of at least one measuring line running across the respective edge.

3. The method of claim 1 and 2, d a d u r c h g e k e n n z e i c h n e t that the measurement is carried out according to the light section triangulation method.

4. The method according to claim 1 and 2, characterized in that the measurement is carried out by means of an air jet directed at the sheet surface with strichför iger impact surface, the position of which is detected via the dynamic pressure with the edge lying within the impact surface.

5. The method according to any one of claims 1 to 4, so that the distances of the reference locations are measured from a common measuring edge lying in the measuring range in order to determine the defined distance between the two reference locations.

6. The method according to any one of claims 1 to 5, characterized in that the distances of the edges from the or the common reference points are measured at points offset in the axial direction and a possible change in the overlap width and / or the degree of a possible skew from the comparison of these measured values one or both workpieces is determined.

7. The method according to any one of claims 1 to 6, so that the measured values for the overlap width and / or skew are stored in a location-specific manner and / or the workpieces are marked at the fault locations.

8. The method according to any one of claims 1 to 7, that the measurement result is used to control actuators of a device for merging two overlapping workpieces to be joined together and / or a welding device.

9. Device for measuring the overlap width of two workpieces lying flat one on top of the other (b _{1 (} b ₂ ), each with at least one contactless point of the overlap joint, the distance (x ^ x,) to a reference point (N _{1 (} N ₂ ) measuring transducers ( _{1, 2, 3, 4} ) on each side of the workpieces and an evaluation unit (PC) for the measurement results of the measuring transducers ( _{1, 2, 3, 4} ), taking into account the position of the reference locations (N _X , N ₂ ) and the measured distances (x.-_, x. ₂ ) indicates an output signal for the overlap width (ül).

10. The apparatus of claim 9, d a d u r c h g e k e n n z e i c h n e t that the evaluation unit (PC) delivers as an output signal, a control signal for a marking unit (M) or a guide unit for the workpieces or a welding device.

11. The device according to claim 9, characterized in that the evaluation unit (PC) individually indicates the distances X _1A , X _1E , X _2A and X _2E as the output signal.

12. The apparatus according to claim 11, characterized in that the distances X _1A , X _1E , X _2A and X _2E are indicated graphically or numerically.

13. The apparatus according to claim 12, characterized in that the specification of the distances X _1A , X _1E , X _2A and X _2S allows the statement which workpiece or whether both workpieces are responsible for an existing skew or are.