Electricity: measuring and testing – Magnetic – Combined
Reexamination Certificate
1999-05-25
2002-02-05
Snow, Walter (Department: 2862)
Electricity: measuring and testing
Magnetic
Combined
C324S262000
Reexamination Certificate
active
06344740
ABSTRACT:
The invention relates to a guide device for guiding elongated objects, particularly wires, which are movable in a passage direction along a passage axis relative to the guide device.
Elongated objects, such as metal wires, rods, bars or tubes, can be starting materials for high-value end products and are frequently subject to the highest quality requirements. Tests for surface defects are an important part of the quality control for such products. One objective is inter alia an uninterrupted and complete testing or inspection of the surfaces with high resolution, even for small defects, e.g. cracks, preferably in the cycle and speed of the manufacturing process. Nowadays such tests are frequently carried out using magnetic methods, particularly eddy current technology performed on a continuous basis, in which the object to be tested or inspected is guided at high speed through an axial test section of a test device e.g. equipped with a rotary test head with eddy current probes and the probes test the surface of the object, preferably in contactless manner.
In the passage direction upstream of the area of the test probes, such a test device normally has a so-called inlet nozzle and behind it an outlet nozzle. These guide devices, also known as protective nozzles fulfil a double function. They protect the test heads against damage, particularly during the entry and exit of the test material. They also limit the maximum eccentricity of the moving test material within the test section to a narrow, confined amount, within which the spacing compensation of the test device can cancel out the sensitivity fluctuations strongly dependent on the spacing between the test object surface and the test probe.
A guide nozzle known from DE 40 07 471 has for the damping of vibrations of the transiting objects a damping device with three guide elements directed onto the surface of the object and whereof each has a sliding body with wear-resistant surface for sliding contact with the test product and which is carried by a damping member made from a rubber-like material. Such test devices generally operate in a completely satisfactory manner.
However, particularly in the case of high passage or transit speeds and very thin, transiting testpieces, such as e.g. highly polished wires for the medical sector with diameters of approximately one or a few mm, very high disturbance levels have been observed, which impair the measuring accuracy. In addition, the metallic sliding bodies can damage sensitive surfaces.
The problem of the invention is to propose a guide device making it possible to increase the measuring accuracy of in particular test devices operating in contactless manner in the case of gentle material guidance.
According to the invention this problem is solved.
A guide device according to the invention can in particular be used with advantage in a test device for the preferably magnetic, non-destructive testing of elongated objects in a continuous process. It has a damping device for damping vibrations, particularly transverse vibrations of the transiting objects. The damping device has a plurality of elastic damping members for direct, preferably sliding contact with the transiting object and which are able to absorb vibration energy.
Such damping members acting directly on the test product and whereof there can be 10, 50, 100 or 1000, absorb vibration energy at numerous points, particularly in the range of maximum transverse deflection, i.e. in the area of a vibration antinode and have a damping counteracting effect on the object deflection. A large number of damping members can lead to each individual damping member acting on the test product only exerting a limited pressure force on the test product surface, so that the test product can be guided in a gentle manner. An advantageously statistical distribution of the damping members assists a damping in a wide, continuous vibration frequency spectrum. It has been found that in particular in the case of thin wires tested at high passage speeds wire vibrations can occur in the vicinity of the test probes, which give rise to high disturbance levels for the test signals and therefore impair the measuring accuracy, especially for the detection of small defects. A guide device with the inventive damping device guiding in surface-protecting manner can counteract such vibrations and ensure a particularly quiet running, with no or only limited transverse vibrations, of the test material in the vicinity of the test probes.
In a preferred embodiment, the damping device has a brush arrangement and is in particular formed by the latter. The bristles or fibers of a brush arrangement can engage in gently sliding manner on a transiting object and form the damping members. Vibrations of the object lead to a deflection, particularly a bending of fibers and/or a rubbing against one another of adjacent fibers deflected to a varying degree. Both the substantially elastic fiber bending and also the reciprocal rubbing of fibers require energy, which is deducted from a vibration of the object, so that its vibration is damped. Flexible bristles engaging gently on the guided object also facilitate the introduction and passage of the objects to be guided into or through the guide device and only very limited friction losses occur.
In addition to the damping action, a brush arrangement can also be used for cleaning a transiting object and/or it can act in the manner of a brush seal as a sealing device and seal the axial area following in the damping device transit direction against the introduction of dirt.
As a result of the flexibility of the bristle fibers, a single brush arrangement of given dimensions can be used for test objects of different diameters from an appropriate diameter range. There is an automatic diameter adaptation of the damping device in that, in accordance with the thickness of the transiting object, the bristle fibers are deflected or bent to a greater or lesser extent. Thus, it is e.g. possible to create guide devices with nominal sizes or internal diameters of e.g. between 1 mm and approximately 130 to 140 mm, each guide device with a brush arrangement being able to cover a certain diameter range of e.g. between 1 and 10 mm, particularly between 2 and 5 mm range width. A test device suitable for different diameters consequently only requires far fewer guide devices of this type than one having conventional guide devices.
As a function of the intended use the fibers can be hard or soft, thick or thin, more or less flexible, bending-resistant, buckling-resistant and/or abrasion-resistant. Thus, the fibers can be wire, synthetic or natural fibers. For guiding thin, particularly superfinished wires for the medical sector or other test objects having sensitive surfaces soft natural or synthetic fibers having a good sliding action on metals have proved very satisfactory. A brush arrangement can also have a uniform or statistical mixture of several different fibers or fiber types.
A brush arrangement can e.g. have at least one circular brush with e.g. substantially radially inwardly directed bristles. A preferred embodiment is characterized in that the brush arrangement has at least one and preferably several axially directed strip brushes distributed more particularly in symmetrical manner around the guide device surface. It is e.g. possible to provide three strip brushes in each case mutually displaced in the circumferential direction by 120° and whose bristles define with their free ends an e.g. triangular passage for a transiting object. A circumferentially symmetrical arrangement of vibration-damping fibers with their free ends oriented radially and partly tangentially to the test object has proved to be particularly advantageous for vibration damping purposes. In addition, an improved centering of the transiting objects compared with conventional guide nozzles has been observed.
A format or diameter change is more particularly facilitated in a preferred embodiment in that the damping members or the at least one brush of the brush arrangement i
Duane Morris LLP
Institut Dr. Friedrich Forster Prufgeratebau GmbH & Co. KG
Snow Walter
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