PROBE DEVICE FOR A ROTATING HEAD WITH BENDING SPRING, SUPPORT ARM AND TESTING DEVICE

Description

[0001] The present invention relates to a probe device for a rotating head, comprising at least one support arm mounted for rotation about a rotation axis, at least one probe connected to the support arm, and at least one spring element that can be supported on the rotating head and engages the support arm. The spring element is provided for exerting a force on the support arm, which, as a result of this force, experiences a torque with respect to the rotation axis. Furthermore, the invention relates to a rotating head with at least one such probe device and a testing device with at least one such probe device and / or with at least one such rotating head.

[0002] Testing devices designed as rotating systems are used, particularly for the inspection of rod-shaped, round metallic semi-finished products for defects such as cracks and cavities using eddy current or flux leakage methods. In such rotating systems, probe devices are mounted on rotating heads of the testing device. As the rotating head, along with the attached probe devices, rotates while an elongated test piece is pushed through a central opening in the rotating head, the probe devices move along a helical path relative to the test piece. In order to detect magnetic field changes resulting from defects in the test piece, the probes of the probe devices intended for the eddy current method must be located at a specified distance or as close as possible to the surface of the test piece.In the flux leakage method, however, the probes are in contact with the test piece and rub against its surface. They wear out and must be replaced regularly. For this reason, the contact pressure of the probes on the surface of the test piece should be as low as possible without the probes lifting off the test piece, as lifting the probe would disrupt or even prevent the test.

[0003] For example, DE 10 2012 108 241 A1 discloses a probe device or probe carrier for a rotating testing device for non-destructive testing of an elongated test specimen using flux leakage or eddy currents. The probe carrier is modular and pluggable, allowing the testing device to be quickly adapted to a changed test specimen diameter.

[0004] Other known probe devices, such as the probe device shown in DE 10 2015 214 232 A1, have a support arm mounted so as to be freely movable around a pivot point. The probe is arranged at one end of the support arm, which is mounted like a two-sided lever, and a counterweight is provided at the opposite end of the support arm. A tension spring acting on the support arm and attached to the rotating head exerts a force and thus a torque on the support arm. If, for example, a test specimen moves irregularly through the passage opening of the rotating head, the probes can deflect accordingly due to the rotatable mounting of the support arm.By means of the counterweight and the tension spring acting on the support arm, a position of the probe can be set at a predetermined distance from the surface of the test piece and, if necessary, a contact force of the probe on the test piece can be set at a predetermined speed of the rotating head and a predetermined diameter of the test piece.

[0005] DE 41 21 948 A1 relates to a probe carrier for eddy current materials testing, which can be attached to a test rotor and carries at least two pivoting probe levers. The probe levers are preloaded into a rest position by a tension spring.

[0006] DE 29 45 586 A1 discloses a multiple mount for ultrasonic probes. Each probe is gimbal-mounted in a double arrangement at each free end of a pivoting rocker.

[0007] As the rotating head rotates, the spring element is subjected to centrifugal forces. Depending on the speed of the rotating head and the position of the support arm, the force exerted by the spring element on the support arm changes, and thus the torque acting on the support arm around the rotation axis also changes. This particularly influences the contact force and the position of the probes in relation to the test piece. If the contact force of the probe on the test piece increases, probe wear increases. If, on the other hand, the contact force decreases, the probes can lift off the test piece or increase their distance from the test piece, depending on whether the test is a flux leakage or eddy current method, which disrupts the test or makes it impossible to perform it altogether.

[0008] To prevent the probes from lifting off the surface of large test pieces and corresponding rotating head speeds, which would interrupt the testing process during the flux leakage test, the spring force and thus the contact pressure of the probe on the test piece are often excessively high, or the rotating head speed is reduced. However, a high contact pressure leads to increased wear on the probes rubbing against the test piece's surface, while a reduction in the rotating head speed leads to a reduced throughput of the test piece. Correctly setting the distance of the probes from the test piece's surface in the eddy current test is also generally difficult in practice due to the influences of the speed and the diameter of the test piece.

[0009] It is therefore the object of the present invention to provide a probe device, a rotating head and a testing device which enable an adjustment of probes with respect to a test object independent of centrifugal forces.

[0010] This object is achieved by the probe device having the features of claim 1, by the rotating head having the features of claim 9 and by the testing device having the features of claim 10.

[0011] While in known probe devices, the spring element is usually designed as a tension spring that engages the support arm at a point spaced from the rotational axis, so that the contact pressure of the probe on the test piece varies with the rotational speed of the rotating head or with the test piece diameter, the support arm of the probe device according to the invention has at least one receptacle for the spring element concentric with the rotational axis. The spring element is arranged on the receptacle and is wound around the receptacle with at least one winding and is curved around the rotational axis. In other words, the rotational axis is wrapped around the spring element, or the spring element is looped or wound around the rotational axis.

[0012] The spring element can wrap around the mount or the rotational axis with at least one or more windings, or be wound one or more times around the mount or the rotational axis. The spring element, curved or wound around the rotational axis, engages the support arm at a point spaced from the rotational axis. This point can be located on the mount, but it can also be spaced from the mount.

[0013] In general, the support arm can have a longitudinal axis, whereby the longitudinal axis and the rotational axis can be skewed relative to each other. However, the support arm or its longitudinal axis can also intersect the rotational axis. Furthermore, the probe can be attached to the ends of two or more parallel support arms, all of which are rotatably mounted about the same rotational axis. In addition, at least one counterweight can be arranged on the support arm to adjust the contact force or position of the probe; its position can advantageously be adjustable along the support arm.

[0014] Because the spring element is curved or wound around the holder, which is concentric with the axis of rotation and thus also around the axis of rotation, the spring element is pressed against the holder when subjected to centrifugal forces without generating bending stresses in the spring element. This means that the spring element cannot exert any forces caused by centrifugal forces on the support arm and consequently cannot induce any torque on it. Rather, the support arm remains balanced for any rotating head speed and any test piece diameter. The probes cannot be lifted off or removed from the test piece, even when the rotating head speed is high. Because the contact force is always set to the optimal or lowest possible level, probe wear is also reduced, significantly extending probe service life and maintenance intervals.Since the contact pressure of the probe is generated exclusively by spring force and the support arm only needs to be balanced once, for example, using suitable counterweights, there is no need to rework counterweights to adjust the contact pressure of the probes against or the distance of the probes from the surface of the test specimen. Such subsequent adjustment of counterweights is only necessary if probes of different weights are used. In particular, a diameter-dependent adjustment of the counterweight or even a forced reduction of the line speed is no longer necessary. Because the required rotational speeds of the rotating head can always be achieved, the productivity of testing devices with probe devices according to the invention is also increased.

[0015] The spring element can in particular be a spiral spring such as a spiral, elliptic, parabolic, wave, wire or leg spring. Spiral springs are generally referred to as bodies that can be elastically deformed when bent under a bending moment, whereby bending stress is generated in the body. Examples of spiral springs include spiral springs, i.e. strongly curved metal strips wound in a helical line in one plane. Elliptical springs, on the other hand, consist of slightly curved leaf springs, which are usually mounted in pairs as spring assemblies with individual spring leaves lying on top of one another. In parabolic springs, leaf springs with a strength that decreases parabolically from the center to the ends are used instead of a stepped spring assembly. Wave springs, on the other hand, are rings of corrugated flat wire in which waves are bent out when loaded.Wave springs can be stacked on top of each other in stacks or used in single layers. Unlike leaf springs with a rectangular cross-section, wire springs are made of wires. Wire springs include torsion springs, which are helically wound or coiled wire springs with protruding straight ends or legs that serve to introduce a torque that bends the wire.

[0016] In principle, the spring element can be firmly or detachably connected to the support arm or fixed thereto. Accordingly, the spring element can be supported on the rotating head by being firmly or detachably connected to a suitable point on the rotating head or to an element of the rotating head provided for this purpose. However, an embodiment of the probe device is preferred in which the spring element is not connected to the rotating head but instead has a support section, for example an end section, for supporting on or for contacting a stop on the rotating head. Such an embodiment has the particular advantage that the individual spring element can be easily replaced when the spring element is on the support arm oris not mounted on its mount, or that, whether the spring element is mounted firmly or loosely on the support arm, the support arm or even the entire probe assembly can be replaced without having to loosen or separate the spring element from the rotating head. Installing a new spring element, support arm, or probe assembly is just as easy.

[0017] The probe device according to the invention is suitable for any rotation system, even those in which probes are movably suspended from support arms. Even for non-contact testing methods, a mechanical rotation angle limiter for the support arm and / or the probe can be provided. The support arm or probe rests against this limiter with slight pressure, allowing it to deflect as easily as possible. This reduces the impact energy of the test specimen on the probe deflectors.

[0018] Since the probe of the probe device requires a connection to the evaluation unit in order to transmit measurement signals to the evaluation unit, for example, probe cables are routed from the probe through the support arm. Probe cables often run as cable bends or loops from a connection or inlet on the rotating head to the probe device and, in a cable guide, via a support arm of the probe device to the probe to ensure the mobility of the support arm. Like the spring elements of conventional probe devices, these cable bends also experience a centrifugal force when the rotating head rotates and thus exert a torque on the support arm, which influences the contact force or the position of the probes in relation to the test object.

[0019] To reduce or avoid such torques, the probe device preferably has at least one cable guide for guiding a probe cable, wherein the cable guide has a first end section running along the support arm from the probe to the axis of rotation and a second end section extending substantially from the axis of rotation. In other words, both the first end section and the second end section essentially lie with one of their ends on the axis of rotation or one of their respective ends is positioned substantially 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 section and the second end section thus enclose an angle with the axis of rotation. This has the effect that a probe cable is fed to or led away from the probe device or its probe at the level of the axis of rotation of the support arm.As a result, the probe cable cannot exert any torque on the support arm when both the probe assembly and the probe cable are rotated as part of a rotating head of a rotating system and are subjected to centrifugal force. Thus, the probe cable cannot exert any influence on the adjustment of the probe position or its contact force on the surface of the test specimen.

[0020] Embodiments of the probe device are possible in which the first end section and the second end section are directly connected to one another. In these cases, the two end sections essentially merge at the pivot point of the support arm. In other embodiments of the probe device, a cable guide section running along the axis of rotation connects the first end section and the second end section. For example, the first end section can lead from the probe to the axis of rotation or to the pivot point of the support arm, where it opens into the cable guide section parallel to the axis of rotation, which in turn leads along the axis of rotation away from the pivot point of the support arm and opens into the second end section at a distance from the pivot point.

[0021] In the probe device according to the invention, the support arm can be mounted in the manner of a single-sided or double-sided lever. In both cases, the probe can be connected to the support arm at one end or end section. If the support arm is mounted in the manner of a double-sided lever, preferably at least one counterweight is attached to the support arm in addition to the probe, with the probe and counterweight being located on opposite sides of the support arm's rotational axis, preferably at opposite ends or end sections of the support arm.

[0022] A rotating head according to the invention advantageously comprises at least one probe device according to the invention. By appropriately selecting the spring constant of the spring element, the position of the probe relative to the test piece or the contact force of the probe against the test piece can be adjusted.

[0023] A testing device according to the invention preferably has at least one pair of probe devices whose probes are arranged facing each other. If a test specimen is placed between the probes or pushed through them, the probes can simultaneously test two opposite sides of the test specimen.

[0024] The invention is explained in more detail below with reference to the drawings. They show: Figure 1 shows a rotating head according to the prior art with two probe devices; Figure 2 shows a probe device according to the prior art; Figure 3 shows a schematic side view of the probe device of the Figure 2 ; Figure 4 shows a schematic side view of a probe device according to the invention; Figure 5 shows a spatial representation of a probe device according to the invention; Figure 6 shows a spatial representation of a probe device with a cable guide.

[0025] In the Figure 1A known circular rotating head 1 of a testing device designed as a rotating system is shown. The rotating head 1 has a central through-hole 2 and two essentially identically designed probe devices 3 and 4.

[0026] The probe device 3 is in the Figure 2 enlarged and in the Figure 3 in a schematic side view. It comprises two elongated support arms 5 and 6, which are arranged parallel to each other and are connected by means of a substantially centrally arranged central web 7. At the height of the central web 7, the support arms 5 and 6 are pivoted in the manner of a two-sided lever around a Figure 2rotatably mounted on a rotation axis 8 shown in dashed lines. A probe 9 extending between the support arms 5 and 6 is held by 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 guide with a first end section 11 extending from the probe 9 and along the support arm 5 and a second end section 12 adjoining the first end section 11, wherein the second end section 12 neither intersects the rotation axis 8 nor originates from it. The cable guide is provided to accommodate a probe cable, not shown in the figures for reasons of clarity.Finally, a helical tension spring or coil spring 13 acts at a point between the central web 7 and the counterweight 10 on the support arm 5, thus on an end section of the support arm 5 facing away from the probe 9.

[0027] The probe device 4 is essentially the same in its construction as the probe device 3. In particular, the probe device 4 also has a probe 14 which is attached to end sections of its support arms. A counterweight 15 is provided at an end of a support arm of the probe device 4 opposite the probe 14. From the spatial perspective of the Figure 1 Only the second end section 16 of the cable guide of the probe device 4 is visible. A coil spring 17 engages with one end on an end section of the support arm of the probe device 4 facing away from the probe 14 at a point between the second end section 16 of the cable guide and the counterweight 15 on the support arm.

[0028] 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 opposite each other with respect to the through hole 2.

[0029] During operation of the testing device, an elongated test piece 18 to be tested by the probes 9 and 14 is pushed through the through hole 2, while the rotating head 1 rotates around the test piece 18. By appropriately selecting the counterweights 10 and 15 of the probe devices 3 and 4 as well as the helical springs 13 and 17 acting on the probe devices 3 and 4, the contact force with which the probes 9 and 14 press onto the surface of the test piece 18 can be adjusted. The distance to the test piece 18 is controlled in non-contact methods by means of mechanical rotation angle limitations, such as the Figure 2The limiter 36 shown for the probe device 3 is set. In contact processes, the limiter 36 serves to hold back the support arm 5 so that the path for the test piece 18 is not blocked. The distance to the test piece 18, however, is influenced by the counterweight 10 and coil spring 13 in such a way that the probe 9 lifts off the test piece 18 in contact processes, or in non-contact processes, contact with the limiter 36 is lost.

[0030] During rotation of the rotating head 1, the coil springs 13 and 17 are subjected to centrifugal forces. These centrifugal forces influence the spring tensions of the coil springs 13 and 17 and thus the forces and torques exerted by the coil springs 13 and 17 on the respective support arms. For this reason, the preset distance of the probes 9 and 14 from the surface of the test piece 18, or their contact force on the surface of the test piece 18, is influenced. This influence also depends on the respective rotation speed of the rotating head 1.

[0031] To avoid this influence of centrifugal forces, the probe device 19, which is located in the Figure 4 in a schematic side view and in the Figure 5shown in a three-dimensional view, a curved spring element is provided instead of a helical spring. In the present case, this is a leg spring 20. Like the previously described probe device 3, the probe device 19 also has support arms 21 for a probe 22, which are rotatably mounted about the axis of rotation 8. A receptacle 23 for the leg spring 20 is provided concentrically to the axis of rotation 8 on each of the support arms 21. The leg spring 20 is arranged on the receptacle 23 and wound several times around the receptacle 23. With an end section 24, the leg spring 20 rests against a protruding stop or stop pin 25 of the rotating head 1 and is thus supported thereon. In addition, the leg spring 20 engages the support arm 21 at a point spaced from the axis of rotation 8, wherein in the present case it is fixed at this point by means of a fastening 26 on the support arm 21.

[0032] As a result of the end section 24 of the leg spring 20 pressing against the stop pin 25 and its fixation by means of the fastening 26, through which it engages the support arm 21, the leg spring 20 is able to exert forces and torques on the support arm 21. However, the centrifugal forces occurring during operation of the rotating head 1 are unable to increase the bending stress of the leg spring 20 and thereby influence the forces and torques acting on the support arm 21 by the leg spring 20, since the leg spring 20 is arranged concentrically to the rotation axis 8. Instead, the centrifugal forces press the leg spring 20 against the receptacle 23 without influencing its bending stress. For this reason, the contact pressure of the probe 22 against the surface of the test piece 18 or their distance from each other is independent of the rotation speed of the rotating head 1 and the diameter of the test piece 18.

[0033] When the rotating head 1 rotates, the probe cables, which are accommodated in the cable guides of the known probe devices 3 and 4 and which, after exiting their second end sections 12 and 16, extend in a curved manner to a connection or inlet of the rotating head 1, also experience centrifugal forces. These centrifugal forces, in turn, exert a lever effect on the rotatably mounted probe devices 3 and 4, thereby influencing the preset distance of the probes 9 and 14 from the surface of the test piece 18 or their contact force on the surface of the test piece 18.

[0034] Figure 6now shows a probe device 27 in which this problem has also been 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 a one-piece component. Both support arms 28 and 29 are rotatably mounted about the same axis of rotation, with their rotation being influenced by a leg spring 30 in the manner described above. A probe 31 extending between the support arms 28 and 29 is held at one end of the support arms 28 and 29, while a counterweight 32 is arranged at the opposite end of the support arm 29.

[0035] The probe device 27 differs from the previously described probe devices 3 and 4 not only in its one-piece support arms 28 and 29, but also in its cable guide for accommodating probe cables. Thus, the cable guide of the probe device 27 has a first end section 33 running along the support arm 28 from the probe 31 to the axis of rotation. A second end section 34 essentially originates from the axis of rotation or forms an angle with it. The first end section 33 and the second end section 34 are connected by means of a cable guide section 35, which, designed as a hollow shaft, runs along the axis of rotation. When the probe device 27 is installed in the rotating head 1, the second end section 34 is fixed or immovable relative to the rotating head 1, while the support arms 28 and 29 are rotatable about the axis of rotation and can thus perform a rotational movement relative to the second end section 34.Within the hollow cable guide section 35, a probe cable can rotate flexibly when the support arms 28 and 29 are tilted, without significantly changing its position or distance relative to the rotation axis. A cable guide corresponding to the cable guide of the support arm 28 is provided on the support arm 29.

[0036] Due to the special cable routing with the first end section 33 converging toward the rotation axis, the second end section 34 extending from the rotation axis, and the cable guide section 35 parallel to the rotation axis, a probe cable can be guided in such a way that the influence of centrifugal force on the probe device 27 can be minimized when the rotating head 1 rotates. In particular, there are no cable bends in the probe device 27 that would be exposed to such centrifugal force and would transmit it to the support arms 28 and 29. When, for example, the support arm 28 rotates about the rotation axis, the probe cable can twist freely within the hollow cable guide section 35 without changing its shape or moving away from the rotation axis, so that it cannot exert any forces on the probe device 27 as a result of the rotation of the rotating head 1.This allows the probe assembly 27 to be balanced once via the counterweight 32 according to the weight of the probe 31. The balanced probe assembly 27 then functions equally across the entire diameter and speed range of the rotating head 1. The contact force on the test piece 18 or the distance of the probe 31 from its surface is thus independent of the centrifugal force.

[0037] In another embodiment of a probe device according to the invention, a hollow cable guide section is omitted and the first end section is directly connected to the second end section. List of reference symbols

[0038] 1.Rotating head 2.Through hole 3.Probe assembly 4.Probe assembly 5.Support arm 6.Support arm 7.Center bar 8.Rotation axis 9.Probe 10.Counterweight 11.First end section 12.Second end section 13.Coil spring 14.Probe 15.Counterweight 16.Second end section 17.Coil spring 18.Test piece 19.Probe assembly 20.Leg spring 21.Support arm 22.Probe 23.Receptacle 24.End section 25.Stop pin 26.Fastener 27.Probe assembly 28.Support arm 29.Support arm 30.Leg spring 31.Probe 32.Counterweight 33.First end section 34.Second end section 35.Cable guide section 36.Limiter

Claims

1. Probe device (19, 27) for a rotary head (1) which has a central through-hole (2), the probe device having at least one carrier arm (21, 28, 29) mounted rotatably about an axis of rotation (8), at least one probe (22, 31) connected to the carrier arm (21, 28, 29) and held on an end of the carrier arm (21, 28, 29) facing towards the through-hole (2), and at least one spring element (20, 30) which can be supported on the rotary head (1) and engages on the carrier arm (21, 28, 29) and is provided to exert a force on the carrier arm (21, 28, 29), which as a result of this force experiences a torque with respect to the axis of rotation (8), wherein the carrier arm (21, 28, 29) has at least one receptacle (23), concentric with the axis of rotation (8), for the spring element (20, 30), and wherein the spring element (20, 30) is arranged on the receptacle (23) and is wound with at least one winding around the receptacle (23) and is curved about the axis of rotation (8).

2. Probe device (19, 27) according to Claim 1, wherein the spring element (20, 30) is a flexural or spiral or elliptical or parabolic or wave or wire or leg spring.

3. Probe device (19, 27) according to Claim 1 or 2, wherein the spring element (20, 30) has a support portion (24) for supporting on a stop (25) of the rotary head (1).

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

5. Probe device (27) according to any one of the preceding claims, having at least one cable guide for guiding a probe cable, wherein the cable guide has a first end portion (33) running along the carrier arm (28, 29) from the probe (31) to the axis of rotation and a second end portion (34) starting substantially from the axis of rotation.

6. Probe device (27) according to Claim 5, wherein the first end portion (33) and the second end portion (34) are directly connected to each other, or wherein a cable guide portion (35) extending along the axis of rotation connects the first end portion (33) and the second end portion (34) to each other.

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

8. Probe device (19, 27) according to any one of the preceding claims, having at least one counterweight (32) arranged on the carrier arm (21, 28, 29).

9. Rotary head (1) having at least one probe device (19, 27) according to any one of the preceding claims.

10. Test apparatus having at least one probe device (19, 27) according to any one of Claims 1 to 8 and / or having at least one rotary head (1) according to Claim 9.

11. Test apparatus according to Claim 10, having at least one pair of probe devices (19, 27), the probes (22, 31) of which are arranged facing each other.