Probe device with spiral spring, rotating head, and test apparatus

Abstract

To provide a probe device, a rotary head, and a test device capable of adjusting a probe for a test piece independent of centrifugal force.SOLUTION: A probe device 19 for a rotating head 1 has: at least one support arm 21 that is mounted so as to rotate around an axis of rotation; a probe 22 that is joined to the support arm 21; and at least one spring element 20 that can be supported on the rotating head 1, engages with the support arm 21, is provided for exerting force on the support arm 21, and, as a result of this force, receives torque with respect to the axis of rotation. The support arm 21 has at least one mount 23 which is concentric with the axis of rotation, for the spring element 20. When arranged on the mount 23, the spring element 20 is bent at least in part around the axis of rotation. As a consequence, centrifugal force that acts on the spring element 20 when the rotating head 1 is in operation, has no influence on tension of the spring element 20.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a probe device for a rotating head, which has at least one support arm mounted for rotation about an axis of rotation, at least one probe connected to the support arm, and at least one spring element capable of being supported on the rotating head and engaging the support arm and provided for exerting a force on the support arm, which as a result of this force is subjected to a torque relative to the axis of rotation. Furthermore, the present invention relates to a rotating head comprising at least one probe device of this kind, as well as a test apparatus comprising at least one probe device of this kind and / or at least one rotating head of this kind. [Background technology]

[0002] Testing devices designed as rotating systems are increasingly being used for the inspection of bar-shaped round semi-finished metal products for defects such as cracks and blow-throughs with the eddy current and magnetic leakage methods, in which the probe device is arranged on a rotatable rotary head of the testing device. By rotating the rotary head with the probe device arranged thereon and inserting an elongated test piece through a central opening through the rotary head, the probe device moves along a helical path relative to the test piece. In order to be able to detect changes in the magnetic field due to the location of defects in the test piece, the probe provided in the probe device of the eddy current method must be arranged at a given distance from the surface of the test piece or as close as possible to it. In contrast, in the magnetic leakage method, the probe comes into contact with the test piece and rubs along its surface. In this case, the probe wears out and has to be replaced periodically. For this reason, the contact pressure of the probe on the surface of the test piece must be as small as possible without lifting the probe from the test piece, since lifting the probe would interrupt the inspection or prevent it from being performed at all.

[0003] Thus, from DE 10 2012 108 241 A1, a probe device or probe carrier for a test arrangement designed as a rotating system for non-destructive testing of elongated test pieces by means of leakage flux or eddy currents is known, the probe carrier being designed in a modular and plug-in manner so that adaptation of the test arrangement to changed diameters of the test pieces can be performed quickly.

[0004] Other known probe devices, for example the probe device shown in DE 10 2015 214 232 A1, have a support arm mounted so as to move freely around a pivot point. The probe is arranged at one end of the support arm which is mounted like a bilateral lever, the opposite end of which is provided with a counterweight. A tension spring arranged in the rotating head engages the support arm, exerting a force on the support arm and thus a torque on the support arm. Insofar as the test pieces move irregularly, for example through the through openings in the rotating head, the rotatable mounting of the support arm carrying the probe makes it possible for the probe to avoid them. The counterweight as well as the tension spring engaged in the support arm makes it possible to adjust the position of the probe at a given distance from the surface of the test piece and, if necessary, also to adjust the contact pressure of the probe on the test piece for a given speed of rotation of the rotating head and a given diameter of the test piece.

[0005] During rotation of the rotating head, the spring element is subjected to a centrifugal force. Depending on the speed of rotation of the rotating head and the position of the support arm, the force that the spring element exerts on the support arm varies, as does the torque acting on the support arm around the axis of rotation. In particular, the contact pressure or the position of the probe on the test piece is thus affected. An increase in the contact pressure of the probe on the test piece leads to increased wear of the probe. Conversely, a decrease in the contact pressure may cause the probe to lift off the test piece or to move further away from it, depending on whether magnetic flux or eddy current methods are involved, with the result that the test may be interrupted or completely impossible.

[0006] In the case of large test pieces and the corresponding speed of rotation of the rotating head, in order to prevent the probe from lifting off the surface of the test piece, which results in the interruption of the inspection operation in the leakage flux method, in practice, it is inclined to design a spring force, thereby making the contact pressure of the probe on the test piece excessively high, or to slow down the speed of rotation of the rotating head. However, the high contact pressure will increase the wear of the probe rubbing the surface of the test piece, and slowing down the speed of rotation of the rotating head will reduce the throughput of the test piece. Also, considering the effects of the speed of rotation and the diameter of the test piece, it is found that it is difficult to accurately adjust the distance of the probe from the surface of the test piece in the eddy current method.

[0007] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to manufacture a probe device, a rotating head, and a test apparatus that enable adjustment of a probe to a test piece independent of centrifugal force. Summary of the Invention [Means for solving the problem]

[0008] This object is achieved by a probe device having the features of claim 1, a rotating head having the features of claim 9 and a test apparatus having the features of claim 10.

[0009] Whereas in known probe devices the spring element is generally designed as a tension spring which engages at a point on the support arm remote from the axis of rotation such that the contact pressure of the probe on the test piece varies depending on the speed of rotation of the rotating head or the diameter of the test piece, the support arm in the probe device according to the invention has at least one mount for the spring element which is concentric with the axis of rotation, the spring element being at least partially curved about the axis of rotation when it is placed on the mount. In other words, the axis of rotation is at least partially surrounded by the spring element or the spring element is at least partially coiled or wound around the axis of rotation. In this way, the spring element can be coiled around the mount or around the axis of rotation at least one turn or several turns or can be wound around the mount or around the axis of rotation once or several times. In this case the spring element curved or wound around the axis of rotation engages at a point on the support arm remote from the axis of rotation. This point can in particular be located on the mount, but it can also be placed away from the mount.

[0010] Quite generally, the support arm may have a longitudinal axis, and it is possible that the longitudinal axis and the axis of rotation are designed to be oblique with respect to each other. However, the support arm or its longitudinal axis may also intersect the axis of rotation. Furthermore, the probe may be fixed to the end of two support arms or to several support arms arranged parallel to each other, all mounted to rotate around the same axis of rotation. Furthermore, at least one counterweight may be arranged on the support arm, the position of which can be advantageously moved along the support arm, in order to adjust the contact pressure or the position of the probe.

[0011] Since the spring element is curved or wound around the mount, which is concentric with and also around the axis of rotation, the spring element is pressed against the mount under the action of the centrifugal force, which does not result in any bending stress on the spring element. The spring element is therefore also unable to exert forces caused by centrifugal force on the support arm, and as a consequence no torque is generated on it. Instead, the support arm is balanced for any speed of rotation of the rotating head and for any diameter of the test piece. No lifting or detachment of the probe from the test piece occurs, even in the case of high speeds of rotation of the rotating head. Since the contact pressure is always adjusted to the optimum or to the minimum possible, the wear of the probe is reduced, and as a result, the service life of the probe and its maintenance intervals are significantly increased. Since the contact pressure of the probe occurs only by the force of the spring and the support arm needs to be balanced only once by a suitable counterweight, it is possible to omit subsequent manipulations of the counterweight, for example for adjusting the contact pressure of the probe on the surface of the test piece or for adjusting the distance of the probe from the surface of the test piece. Such a subsequent adjustment of the counterweight is only necessary if probes of different weights are used. In particular, a diameter-dependent adjustment of the counterweight or even a forced reduction in the linear speed is no longer necessary. The productivity of an inspection device having a probe device according to the invention is increased, since the required speed of rotation of the rotary head can always be ensured.

[0012] The spring elements may in particular be torsion springs, such as helical springs or elliptical springs or parabolic springs or wave springs or wire springs or leg springs. Torsion springs generally refer to elements that can be elastically deformed by bending with a bending torque, resulting in bending stresses in the element. Torsion springs include, for example, helical springs, i.e. tightly curved metal bands that are wound in a spiral shape in a plane. In contrast, elliptical springs consist of slightly curved leaf springs, which are generally attached in pairs to each other, as spring assemblies containing individual spring leaves lying on top of each other. In the case of parabolic springs, instead of layered spring assemblies, leaf springs are used that decrease in strength parabolically from the center to the ends. Wave springs, in turn, are rings made of wavy flat wire, which curve in waves when loaded. Wave springs can be used one above the other in an assembly, or in other single layers. Leaf springs have a rectangular cross section, whereas wire springs consist of wire. Wire springs include, among others, leg springs, which are coiled or spirally wound wire springs with protruding straight ends for introducing torque to bend the wire.

[0013] It is basically possible for the spring element to be connected or fixed to the support arm in a permanent or removably manner. Correspondingly, the spring element can be supported on the rotating head by connecting it in a permanent or removably manner at a suitable point of the rotating head or at an element of the rotating head intended for this purpose. Preferred, however, are embodiments of the probe device in which the spring element is not connected to the rotating head, but rather has a support segment, for example an end segment, for supporting it or for resting it against a stop of the rotating head. This kind of embodiment has the special advantage that a simple exchange of individual spring elements is possible, if the spring elements are not attached to the support arm or its mount, or even an exchange of the entire support arm or probe device is possible, if the spring elements are permanently or removably attached to the support arm, without the need to remove or separate the spring elements from the rotating head for this purpose. The installation of new spring elements or support arms or probe devices is likewise simple.

[0014] The probe device according to the invention is suitable for any rotation system, i.e. one in which the probe is movably suspended on a support arm. It is also possible to provide mechanical delimiters for limiting the angle of rotation of the support arm and / or the probe in a non-contact testing method, on which the support arm or the probe can come to rest with a slight pressure, so that it can be released as easily as possible. In this way, the energy of the impact of the test piece on the probe deflector can be reduced.

[0015] Since the probe of the probe device must have a connection with the evaluation unit in order to be able to transmit the measurement signal to the evaluation unit, for example the probe cable is guided from the probe via a support arm. The probe cable often runs as a cable bend or loop from a connection terminal or inlet on the rotating head to the probe device and is guided in a cable conduit of the latter via the support arm of the probe device to the probe in order to ensure the mobility of the support arm. Like the spring elements of the known probe devices, these cable bends are also subjected to centrifugal forces when the rotating head rotates and as a result exert a torque on the support arm, as a result of which they affect the contact pressure or position of the probe on the test piece.

[0016] To reduce or prevent this type of torque, the probe device preferably has at least one cable conduit for guiding the probe cable, with the cable conduit having a first end segment extending along the support arm from the probe to the axis of rotation and a second end segment starting substantially from the axis of rotation. In other words, both the first end segment and the second end segment are substantially at one of their ends relative to the axis of rotation, or the other one of their respective ends is substantially located on the axis of rotation, or one of their respective ends is located at the level of the axis of rotation. Both the first end segment and the second end segment thus enclose an angle with the axis of rotation. In this way, it is provided that the probe cable is guided to or away from the probe device at the level of the axis of rotation of the support arm. As a result, the probe cable cannot generate any torque on the support arm when both the probe device and the probe cable rotate as part of the rotating head of the rotating system and are subjected to centrifugal forces. Thus, the probe cable also cannot have any influence on the adjustment of the position of the probe or its contact pressure on the surface of the test piece.

[0017] In embodiments of the probe device, it is possible for the first and second end segments to be directly connected to each other. In these cases, the two end segments transition directly to each other substantially at the pivot point of the support arm. In other embodiments of the probe device, a cable duct segment extending along the axis of rotation connects the first and second end segments to each other. For example, the first end segment can be led from the probe to the axis of rotation or to the pivot point of the support arm, where it leads to a cable duct segment parallel to the axis of rotation, and then led away from the pivot point of the support arm along the axis of rotation and leads to the second end segment away from the support arm.

[0018] In the probe device according to the invention, the support arm can be mounted as a kind of one-sided or two-sided lever. In both cases, the probe can be connected to it at the end or end segment of the support arm. If the support arm is mounted as a kind of two-sided lever, preferably at least one counterweight is fixed to the support arm besides the probe, the probe and the counterweight being arranged on opposite sides relative to the axis of rotation of the support arm, i.e. preferably at both ends or end segments of the support arm.

[0019] Advantageously, the rotating head according to the invention comprises at least one probe device according to the invention. A suitable selection of the spring constant of the spring element can contribute to adjusting the position of the probe relative to the test piece or the contact pressure of the probe on the test piece.

[0020] The test apparatus according to the present invention preferably comprises at least one pair of probe devices, the probes of which are arranged opposite each other, such that when a test piece is placed or inserted between the probes, the probes can simultaneously test two opposing sides of the test piece. [Brief description of the drawings]

[0021] The present invention will now be described in detail with reference to the accompanying drawings.

[0022] [Figure 1] 1 shows a prior art rotating head with two probe devices.

[0023] [Diagram 2] 1 shows a probe device according to the prior art;

[0024] [Diagram 3] FIG. 3 is a schematic side view of the probe device of FIG. 2.

[0025] [Figure 4] 1 shows a schematic side view of a probe device according to the present invention;

[0026] [Diagram 5] 1 shows a spatial representation of a probe device according to the present invention;

[0027] [Figure 6] 1 shows a spatial representation of a probe device with a cable conduit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] 1 shows a known circular rotating head 1 of a test apparatus designed as a rotating system. The rotating head 1 has a central through hole 2 and two substantially identically designed probe devices 3 and 4.

[0029] The probe device 3 can be seen in an enlarged view in FIG. 2 and in a schematic side view in FIG. 3. They are arranged parallel to one another and are connected to one another by a central connecting piece 7 located substantially in the middle. At the level of the central connecting piece 7, the support arms 5 and 6 are mounted to rotate like a kind of double-sided lever around an axis of rotation 8 shown in dashed lines in FIG. 2. A probe 9 extending between the support arms 5 and 6 is held at the ends of the support arms 5 and 6 facing the through-hole 2, while a counterweight 10 is arranged at the end of the support arm 5 facing away from the through-hole 2. Furthermore, the probe device 3 has a cable duct with a first end segment 11 starting from the probe 9 and running along the support arm 5 and a second end segment 12 adjacent to the first end segment 11, the second end segment 12 not intersecting the axis of rotation 8 and not starting from it. A cable duct is provided for mounting the probe cable, which is not shown for the sake of clarity. Finally, a coil tension spring or coil spring 13 engages at a point between the central connecting piece 7 and the counterweight 10 on the support arm 5 , and thus at the end segment of the support arm 5 facing away from the probe 9 .

[0030] In its structure, the probe device 4 substantially corresponds to the probe device 3. In particular, the probe device 4 also has a probe 14 fixed to an end segment of its support arm. At the end of the support arm of the probe device 4 facing the probe, a counterweight 15 is provided. From the spatial perspective of FIG. 1, only the second end segment 16 of the cable conduit of the probe device 4 is visible. A coil spring 17 engages with one end of the end segment of the support arm of the probe device 4 facing away from the probe 14, at a point between the second end segment 16 of the cable conduit and the counterweight 15 on the support arm.

[0031] In the rotating head 1 the two probe devices 3 and 4 are arranged such that their respective probes 9 and 14 are substantially diametrically opposed to each other with respect to the through-hole 2 .

[0032] In operation of the test device, one of the probes 9 and 14 is then inserted through the hole 2 towards the elongated test piece 18 to be tested, while the rotating head 1 is rotated around the test piece 18. By appropriate selection of the counterweights 10 and 15 of the probe devices 3 and 4 and the coil springs 13 and 17 on the probe devices 3 and 4, it is possible to adjust the contact pressure with which the probes 9 and 14 press against the surface of the test piece 18. The distance from the test piece 18 is adjusted in a non-contact manner by a mechanical delimitation of the angle of rotation, for example the delimiter 36 depicted in FIG. 2 for the probe device 3. In a contact manner, the delimiter 36 serves to hold the support arm 5 so that the path for the test piece 18 is not interrupted. In contrast, the distance from the test piece 18 is influenced by the counterweight 10 and the coil spring 13 to the extent that in a contact manner the probe 9 lifts off the test piece 18, or in a non-contact manner the contact to the delimiter 36 is lost.

[0033] During rotation of the rotating head 1, the coil springs 13 and 17 are subjected to centrifugal forces. These centrifugal forces affect the spring tensions of the coil springs 13 and 17 and therefore the forces and torques exerted by the coil springs 13 and 17 on the respective support arms. Because of this, the pre-adjusted distance of the probes 9 and 14 from the surface of the test piece 18 or their contact pressure on the surface of the test piece 18 is affected. Moreover, this effect depends on the speed of the respective rotation of the rotating head 1.

[0034] In order to prevent this effect of centrifugal force, a curved spring element is provided in the probe device 19 instead of a coil spring, which is depicted in a schematic side view in FIG. 4 and in a schematic side view in FIG. 5. In this embodiment, a leg spring 20 is involved. As in the case of the previously described probe device 3, the probe device 19 also has a support arm 21 for the probe 22, which is rotatably mounted around the axis of rotation 8. A mount 23 for the leg spring 20 is provided in each case on one of the support arms 21 and is concentric with the axis of rotation 8. The leg spring 20 is placed on the mount 23 and is wound around it several times. By means of an end segment 24, the leg spring 20 rests against and is thereby supported by a protruding stop or stop pin 25 of the rotating head 1. Furthermore, the leg spring 20 engages at a point on the support arm 21 spaced from the axis of rotation 8, which in this case is fixed in place on the support arm 21 by a fastener 26.

[0035] As a result of the fact that the end segments 24 of the leg springs 20 press against the stop pins 25, which are fixed in place by fasteners 26 engaging the support arms 21, it is possible for the leg springs 20 to exert forces and torques on the support arms 21. In contrast, since the leg springs 20 are arranged concentrically with the axis of rotation 8, it is not possible during the operation of the rotating head 1 for centrifugal forces to arise that would increase the bending stress of the leg springs 20 and thereby affect the forces and effective torques acting on the support arms 21 through the leg springs 20. Instead, the leg springs 20 are pressed against the mounts 23 by centrifugal forces without affecting their bending stress. For this reason, the contact pressure of the probes 22 against the surface of the test piece 18 or their distance from each other does not depend on the speed of rotation of the rotating head 1 and also on the diameter of the test piece 18.

[0036] When the rotating head 1 rotates, the probe cables, which are housed in the cable conduits of the known probe devices 3 and 4 and which, after emerging from their second end segments 12 and 16, run in an arc to the connection terminals or inlets of the rotating head 1, are subjected to centrifugal forces. These centrifugal forces then exert a lever effect on the rotatably mounted probe devices 3 and 4, as a result of which the pre-adjusted distance of the probes 9 and 14 from the surface of the test piece 18 or their contact pressure on the surface of the test piece 18 is influenced.

[0037] Figure 6 shows a probe device 27 in which this problem is also overcome. In contrast to the known probe devices 3 and 4 described above, the probe device 27 comprises two support arms 28 and 29, which are designed as one piece. The two support arms 28 and 29 are mounted rotatably about the same axis of rotation, the rotation being influenced by a leg spring 30 as described above. At one end of the support arms 28 and 29 a probe 31 is held which extends between the support arms 28 and 29, while at the opposite end of the support arm 29 a counterweight 32 is arranged.

[0038] The probe device 27 differs from the previously described probe devices 3 and 4 not only in the integral design of the support arms 28 and 29, but also in its cable duct for mounting the probe cable. The cable duct of the probe device 27 thus has a first end segment 33 which extends along the support arm 28 from the probe 31 to the axis of rotation. The second end segment 34 extends substantially from the axis of rotation or surrounds an angle with it. The first end segment 33 and the second end segment 34 are connected by a cable duct segment 35 which is designed as a hollow shaft and extends along the axis of rotation. In the mounting state of the probe device 27 on the rotating head 1, the second end segment 34 is permanently or detachably arranged with respect to the rotating head 1, while the support arms 28 and 29 are rotatable around the axis of rotation and can therefore perform a rotational movement with respect to the second end segment 34. Inside the hollow cable conduit segment 35, the probe cable can be flexibly twisted without its position or its distance changing significantly when the support arms 28 and 29 are tilted. Provided on the support arm 29 is a cable conduit corresponding to the cable conduit of the support arm 28.

[0039] As a result of the special cable duct, where the first end segment 33 runs up to the axis of rotation, the second end segment 34 starts from the axis of rotation and the cable duct segment 35 is parallel to the axis of rotation, the probe cable can be guided in such a way that it minimizes the effect of centrifugal forces on the probe device 27 when the rotating head 1 rotates. In particular, in the case of the probe device 27, no cable bends occur that would be subjected to this kind of centrifugal force and transmit this centrifugal force to the support arms 28 and 29. For example, when the support arm 28 rotates about the axis of rotation, the probe cable can twist freely inside the hollow cable duct segment 35 without changing its shape or moving away from the axis of rotation, so that it cannot exert any forces due to the rotation of the rotating head 1 on the probe device 27. Thus, the probe device 27 can be balanced in one go by the counterweight 32 depending on the weight of the probe 31. The balanced probe device 27 then functions uniformly over the entire range of diameters of the rotating head 1 and the range of rotation speeds. Therefore, the contact pressure on the test piece 18 or the distance of the probe 31 from its surface is independent of the centrifugal force.

[0040] In another embodiment of the probe device according to the invention, the hollow cable duct segment is dispensed with and the first end segment is directly connected to the second end segment. Reference Number List 1. Rotating head 2.Through holes 3. Probe Device 4. Probe Device 5. Support arm 6. Support arm 7. Central connecting piece 8. Axis of rotation 9. Probe 10. Counterweight 11. First end segment 12. Second end segment 13. Coil spring 14. Probe 15. Counterweight 16. Second end segment 17. Coil spring 18. Test Piece 19. Probe Device 20. Leg Spring 21. Support arm 22. Probe 23. Mount 24. End Segment 25. Locking pin 26. Zipper 27. Probe Device 28. Support arm 29. Support arm 30. Leg Spring 31. Probe 32. Counterweight 33. First end segment 34. Second end segment 35. Cable conduit segment 36. Delimiter

Claims

1. A probe device (19, 27) for a rotary head (1), comprising: at least one support arm (21, 28, 29) mounted for rotation about an axis of rotation (8); At least one probe (22, 31) connected to said support arm (21, 28, 29); at least one spring element (20, 30) capable of being supported on said rotating head (1) and adapted to engage said support arms (21, 28, 29) and to apply a torque to said support arms (21, 28, 29) relative to said axis of rotation (8); A probe device (19, 27), wherein the support arm (21, 28, 29) has at least one mount (23) for the spring element (20, 30) that is concentric with the axis of rotation (8), the spring element being arranged wound one or more times around the mount (23) or around the axis of rotation (8).

2. The probe device (19, 27) of claim 1, wherein the spring element (20, 30) is a torsion spring or a spiral spring or a wire spring or a leg spring.

3. A probe device (19, 27) according to claim 1 or 2, wherein the spring element (20, 30) has a support segment (24) for supporting it at a stop (25) of the rotating head (1).

4. Probe device (19, 27) according to any one of the preceding claims, comprising at least one mechanical delimiter (36) for limiting the angle of rotation of the support arm (21, 28, 29) and / or the probe (22, 31).

5. A probe device (27) according to any one of claims 1 to 4, comprising at least one cable duct for guiding a probe cable, said cable duct having a first end segment (33) extending along said support arm (28, 29) from said probe (31) to said axis of rotation, and a second end segment (34) starting substantially from said axis of rotation.

6. 6. The probe device (27) of claim 5, wherein the first end segment (33) and the second end segment (34) are directly connected to each other or a cable conduit segment (35) extending along the axis of rotation connects the first end segment (33) and the second end segment (34) to each other.

7. Probe device (19, 27) according to any one of the preceding claims, wherein said support arms (21, 28, 29) are mounted in the manner of a one-sided or two-sided lever.

8. A probe device (19, 27) according to any one of the preceding claims, comprising at least one counterweight (32) arranged on said support arm (21, 28, 29).

9. A rotating head (1) having at least one probe device (19, 27) described in any one of claims 1 to 8.

10. A test apparatus having at least one probe device (19, 27) according to any one of claims 1 to 8.

11. A test device having at least one rotating head (1) as described in claim 9.

12. 12. Test apparatus according to claim 10 or 11, comprising at least one pair of probe devices (19, 27) in which the probes (22, 31) are arranged opposite each other.

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