Patent Application
20060044097
1. Field of the Invention
The present invention relates to magnet-spaced sensors and in particular magnets and bore holes.
2. Description of the Prior Art
Magnets are used in a wide variety of detectors. For example, magnetostrictive transducers having elongated wave guides that carry torsional strain waves induced in the wave guide when current pulses are applied along the wave guide through a magnetic field are well known in the art. A typical linear distance measuring device using a movable magnet that interacts with the wave guide when current pulses are provided along the wave guide is shown in U.S. Pat. No. 3,898,555.
Devices of the prior art of the sort shown in U.S. Pat. No. 3,898,555 also have the sensor element in a housing which also houses the electronics to at least generate the pulse and receive the return signal. The amplitude of the return signal detected from the acoustical strain pulse is, as well known in the art, affected by many parameters. These parameters include the position magnet strength, wave guide quality, temperature, wave guide interrogation current, and assembly tolerances. In the prior art, the wave guide is connected to a return wire to complete the electrical circuit necessary for the wave guide to generate the pulse which stimulates the return signal.
Several types of magnetic-based sensors are available for measuring linear or rotary position. Magnetic-based sensors have an advantage in that they provide non-contact sensing; so there are no parts to wear out. Examples of magnetic-based sensors are LVDTs, inductive sleeve sensors, and magnetostrictive sensors.
Technical magnets are often made of mechanically very brittle materials, with very simple geometries due to restrictions in the production technologies. In order to install these magnets in machine parts, additional mechanical components are always required for fixing them. These must ensure that the magnets are stressed very little mechanically and that the magnets also remain in a mechanically invariable position in the relevant environment. Additionally, the unavoidable mechanical tolerances of the magnet and of the installation environment must be compensated when mounting. Frequently, these tolerances are relatively high with magnets.
In the art, these requirements are frequently met at relatively high expenditure, by means of sealing compound, elastomers, sheet-metal retainers, screwing, snap rings, etc. In almost all cases, combination of several of the specified auxiliary means is required. Apart from the large quantity of components, the mounting expenditure is also relatively high
It is an object of the present invention to provide a solution for installation of magnet rings securely in bore holes.
The invention is a construction element, which provides a good solution for installation of magnet rings, ring-shaped or circular, generally round, brittle and mechanically sensitive components, e.g. sinter magnets in bore holes.
The elements of the invention include features of:
A Spring element which can compensate tolerances in radial and axial direction.
A spring element which locks the ring magnet axially in a suitable bore hole, by means of spring arms which support the magnet ring against the base of the bore and also support the spring element itself in a groove in the inner surface of the bore whereby the magnet ring is locked definitely in axial direction.
A spring element which fixes the ring magnet in a bore hole in radial direction by means of further spring arms tilted to it, which are located between the surface of the magnet and the inner mantle surface of the bore hole. These spring arms are distributed regularly over the circumference and, in untightened condition, directed at a suitable angle related to the tangent of the surface. When installing the ring magnet and the spring element into the bore hole, these spring arms are slightly distorted, whereby a permanent torsional spring pre-tension is provided. In this way, the magnet ring is definitely locked in radial direction.
By suitable geometrical design of all spring arms, the holding forces must be dimensioned so that they are sufficiently high enough to keep the magnet safely and precisely in radial and axial direction, and on the other hand, so that no unduly high mechanical forces are induced into the magnet ring.
Further construction elements for locking the ring magnet in axial and radial direction are not required.
The spring element is of metal. This ensures that the required defined pre-tension in axial and radial direction can be provided. There are no setting properties, like e.g. with plastics. Thus, the magnet ring is locked in position permanently and precisely and fixed safely. Preferably, the spring element metal should be of non-ferromagnetic material, in order not to affect the magnetic field of the magnet ring in an inadmissible way.
As the spring element is of metal and can be passivated necessary, good fluid compatibility is ensured with normal technical applications, especially oil or water-based hydraulic systems.
The spring element is designed as a punch-bended part and can be supplied preferably as a pre-punched part (
By means of the proposed spring element, the installation procedure of a ring magnet into a bore hole is limited to inserting the magnet into the spring element and to inserting the spring element into the bore hole. As described, no further auxiliary means or elements are required.
Consequently, the installation of a ring magnet into a bore hole is a very low-priced operation.
For a further understanding of the nature and objects of the present invention, reference should be had to the following figures in which like parts are given like reference numerals and wherein:
As shown in
A lock piece 50 is provided and sized to fit within counter bore 25 without the inner surface of locking piece 50 extending into the bore beyond the surface 20. Lock piece 50 includes an outer dog 55 and an inner dog 60. Locking piece 50 is made of spring-type material. Therefore, inner and outer dogs 55, 60 normally bias outwardly and inwardly, respectively, unless they are compressed. Each outer locking dog 55 is sized to fit within grove 40.
As further shown in
In operation, locking mechanism 50 is slid along inner surface 25 of cylinder 20 until outer locking dog 55 falls into or springs into grove 40. Thereafter, magnet 70, usually having its north surface on the inside 80 of the magnet 70, may be slid along the inner side 90 of locking mechanism 50 locking dog 60, depressing inner dog 60 until the end 100 of inner magnet 70 passes past inner locking dog 60 so that it no longer depresses inner locking dog 60. Inner locking dog 60 will then spring up abutting end 100 of magnet 70, thereby holding magnet 70 in place without glue and without cracking elastomers or without cracking or otherwise applying lateral pressure onto magnet 70. The spring force of outer locking dog 55 further acts to center magnet 70 using a support ring 105 formed by to add further lateral support to magnet 70.
On this basis:
A spring element 50 which can compensate tolerances in radial and axial direction.
A spring element 50 which locks the ring magnet 70 axially in a suitable bore hole, by means of spring arms 60 which support the magnet ring 70 against the base 25 of the bore 10 and also support the spring element 50 itself in a groove 40 in the inner surface 25 of the bore whereby the magnet ring 70 is locked definitely in axial direction.
A spring element 50 which fixes the ring magnet 70 in a bore hole 25 in radial direction by means of further spring arms 60 tilted to it, which are located between the surface 100 of the magnet 70 and the inner mantle surface of the bore hole 25. These spring arms are distributed regularly over the circumference and, in untightened condition, directed at a suitable angle related to the tangent of the surface 20. When installing the ring magnet 70 and the spring element 50 into the bore hole, these spring arms 60 are slightly distorted, whereby a permanent torsional spring pre-tension is provided. In this way, the magnet ring 70 is definitely locked in radial direction.
By suitable geometrical design of all spring arms 50, the holding forces must be dimensioned so that they are sufficiently high enough to keep the magnet safely and precisely in radial and axial direction, and on the other hand, so that no unduly high mechanical forces are induced into the magnet ring 70.
Further construction elements for locking the ring magnet 70 in axial and radial direction are not required.
The spring element 50 is of metal. This ensures that the required defined pre-tension in axial and radial direction can be provided. There are no setting properties, like e.g. with plastics. Thus, the magnet ring is locked in position permanently and precisely and fixed safely. Preferably, the spring element metal should be of non-ferromagnetic material, in order not to affect the magnetic field of the magnet ring in an inadmissible way.
As the spring element 50 is of metal and can be passivated, if necessary, good fluid compatibility is ensured with normal technical applications, especially oil or water-based hydraulic systems.
The spring element 50 is designed as a punch-bended part and can be supplied preferably as a pre-punched part (
By means of the proposed spring element 50, the installation procedure of a ring magnet 70 into a bore hole is limited to inserting the magnet 70 into the spring element 60 and to inserting the spring element 50 into the bore hole. As described, no further auxiliary means or elements are required.
Consequently, the installation of a ring magnet 70 into a bore hole 20, 25 is a very low-priced operation.
