(19)
(11)EP 1 632 755 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
07.05.2014 Bulletin 2014/19

(21)Application number: 05255332.8

(22)Date of filing:  31.08.2005
(51)International Patent Classification (IPC): 
G01D 11/24(2006.01)
H02K 1/18(2006.01)

(54)

Construction element for locking ring magnets in bore holes

Bauelement zur Befestigung von Ringmagneten in Bohrlöchern

Elément de construction pour fixer des aimants annulaires dans des puits de forage


(84)Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR

(30)Priority: 01.09.2004 US 931484

(43)Date of publication of application:
08.03.2006 Bulletin 2006/10

(73)Proprietor: MTS SYSTEMS CORPORATION
Eden Prairie, MN 55344-2290 (US)

(72)Inventor:
  • Garneyer, Birgit
    58097 Hagen (DE)

(74)Representative: Boult Wade Tennant 
Verulam Gardens 70 Gray's Inn Road
London WC1X 8BT
London WC1X 8BT (GB)


(56)References cited: : 
US-A- 5 057 730
US-A1- 2004 041 487
US-A- 5 481 148
US-A1- 2004 104 636
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND OF THE INVENTION


    FIELD OF THE INVENTION



    [0001] The present invention relates to magnet-spaced sensors and in particular magnets and bore holes.

    DESCRIPTION OF THE ART



    [0002] 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. Patent No. 3,898,555.

    [0003] Devices of the prior art of the sort shown in U.S. Patent 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.

    [0004] 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.

    [0005] 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.

    [0006] 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

    [0007] It is an object of the present invention to provide a solution for installation of magnet rings securely in bore holes.

    SUMMARY OF THE INVENTION



    [0008] According to the present invention, there is provided a magnet assembly comprising: a mounting form having a borehole; a magnet; and a spring element having: a first spring arm and a second spring arm locking the mounted magnets axially in the borehole; and third spring arms pressing against the borehole and supporting the mounted magnets radially apart from the borehole, wherein: the borehole comprises a groove and a shoulder; the first spring arm extends into the groove; and the second spring arm holds the magnet against the shoulder.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0009] 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:

    Figure 1 is a side cross-sectional view of a bore hole in which the magnet ring is installed by means of the preferred embodiment of the present invention; and

    Figure 2 is a side cross-sectional view taken along lines 2-2 of Figure 1; and

    Figure 3 is an illustration of a pre-punched part for a spring element of the preferred embodiment.


    DESCRIPTION OF THE PREFERRED EMBODIMENTS



    [0010] The following describes 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.

    [0011] The construction element includes the features of:

    [0012] A Spring element which can compensate tolerances in radial and axial direction.

    [0013] 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.

    [0014] 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.

    [0015] 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.

    [0016] Further construction elements for locking the ring magnet in axial and radial direction are not required.

    [0017] 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.

    [0018] 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.

    [0019] The spring element is designed as a punch-bended part and can be supplied preferably as a pre-punched part (Fig. 3), such as a single element within a band of any length on rolls. Dependent of the number of spring elements which are cut off in one piece from the band, the spring elements can be used for magnet rings of various diameters.

    [0020] 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.

    [0021] Consequently, the installation of a ring magnet into a bore hole is a very low-priced operation.

    [0022] As shown in Figure 1, a cylindrical mounting form or cylinder 10 to support mounting a magnet therein is shown. Cylindrical form 10 has an outer cylindrical surface 15 and an inner cylindrical surface 20. Inner cylindrical surface 20 forms the bore for the cylinder 10. A counter bore 25 is formed having a larger diameter than the bore having surface 20 and terminating at shoulder 35. A cylindrical grove 40 is formed in the inner surface of counter bore 25.

    [0023] 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 groove 40.

    [0024] As further shown in Figure 1, a magnet 70 is sized to fit within the counter bore 25 without the inner surface 80 of the magnet 70 extending into the bore beyond the surface 20 when magnet 70 is locked in place. Thus magnet 70 has a thickness such that its inner surface 80 is flush with the inner surface 20 of cylinder 10 when magnet 70 is locked in place.

    [0025] In operation, locking mechanism 50 is slid along inner surface of cylinder 10 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.

    [0026] On this basis:

    [0027] A spring element 50 which can compensate tolerances in radial and axial direction.

    [0028] A spring element 50 which locks the ring magnet 70 axially in a suitable bore hole, by means of spring arms 55, 60 which support the magnet ring 70 against the shoulder 35 of the bore 25 and also support the spring element 50 itself in a groove 40 in the inner surface of the bore whereby the magnet ring 70 is locked definitely in axial direction.

    [0029] A spring element 50 which fixes the ring magnet 70 in a bore hole 25 in radial direction by means of further spring arms 5 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. When installing the ring magnet 70 and the spring element 50 into the bore hole, these spring arms 5 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.

    [0030] 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.

    [0031] Further construction elements for locking the ring magnet 70 in axial and radial direction are not required.

    [0032] 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.

    [0033] 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.

    [0034] The spring element 50 is designed as a punch-bended part and can be supplied preferably as a pre-punched part (Fig. 3), such as a single element 50 within a band of any length on rolls. Dependent of the number of spring elements 50 which are cut off in one piece from the band, the spring elements can be used for magnet rings of various diameters.

    [0035] 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 50 and to inserting the spring element 50 into the bore hole. As described, no further auxiliary means or elements are required.

    [0036] Consequently, the installation of a ring magnet 70 into a bore hole 20, 25 is a very low-priced operation.


    Claims

    1. A magnet assembly comprising:

    a mounting form (10) having a borehole (25);

    a magnet (70); and

    a spring element (50) having:

    a first spring arm (55) and a second spring arm (60) locking the mounted magnets axially in the borehole; and

    third spring arms (5) pressing against the borehole (25) and supporting the

    mounted magnets radially apart from the borehole (25),

    wherein:

    the borehole (25) comprises a groove (40) and a shoulder (35);

    the first spring arm (55) extends into the groove (40); and

    the second spring arm (60) holds the magnet against the shoulder (35).


     
    2. The assembly of claim 1, wherein the magnet (70) forms a ring and said third spring arm (5) biases the ring radially apart from the borehole (25).
     
    3. The assembly of claim 1or claim 2, wherein the magnets are sintered magnets and said spring element (50) minimizes stress on the magnet (70).
     
    4. The assembly of any preceding claim, wherein the first spring arm includes a first dog seated in the groove (40) radially biasing the mounted magnet (70) relative to the borehole (25).
     
    5. The assembly of claim 4, wherein the second spring arm (60) includes a second dog abutting the end of the magnet (70), thereby locking the mounted magnet (70) axially within the borehole (25).
     
    6. The assembly of claim 5, wherein said first and second dogs are spaced apart so that said first dog is situated in the groove (40) when said second dog abuts the end of the magnet (70).
     
    7. The assembly of claim 6, wherein said first dog is spring biased to extend into the groove (40).
     
    8. The assembly of claim 7, wherein said second dog is spring biased to abut the end of the mounted magnet (70) when the mounted magnet (70) is positioned in the borehole (25).
     
    9. The assembly of claim 1, wherein said spring element (50) is made of metal.
     
    10. The assembly of claim 1, wherein said spring element (50) includes a punch bended part.
     


    Ansprüche

    1. Magnetbaugruppe umfassend:

    eine Montageform (10), welche ein Bohrloch (25) aufweist;

    einen Magneten (70); und

    ein Federelement (50), welches

    einen ersten Federarm (55) und einen zweiten Federarm (60), welche die montierten Magneten axial in dem Bohrloch sperren; und

    dritte Federarme (5) aufweist, welche gegen das Bohrloch (25) pressen und welche die montierten Magnete von dem Bohrloch (20) radial getrennt tragen,

    wobei: das Bohrloch (25) eine Nut (40) und eine Schulter (35) umfasst;

    der erste Federarm (55) sich in die Nut (40) erstreckt; und

    der zweite Federarm (60) den Magnet gegen die Schulter (35) hält.


     
    2. Baugruppe nach Anspruch 1, wobei der Magnet (70) einen Ring bildet und der dritte Federarm (5) den Ring radial getrennt von dem Bohrloch (25) vorspannt.
     
    3. Baugruppe nach Anspruch 1 oder Anspruch 2, wobei die Magnete gesinnte Magnete sind und das Federelement (50) einen Stress an dem Magnet (70) minimiert.
     
    4. Baugruppe nach einem der vorhergehenden Ansprüche, wobei der erste Federarm einen in der Nut (40) sitzenden ersten Mitnehmer umfasst, welcher den montierten Magnet (70) relativ zu dem Bohrloch (25) radial vorspannt.
     
    5. Baugruppe nach Anspruch 4, wobei der zweite Federarm (60) einen zweiten Mitnehmer umfasst, welcher an dem Ende des Magnets (70) anstößt, wodurch der montierte Magnet (70) axial innerhalb des Bohrlochs (25) gesperrt wird.
     
    6. Baugruppe nach Anspruch 5, wobei der erste und zweite Mitnehmer voneinander derart beanstandet sind, dass der erste Mitnehmer sich in der Nut (40) befindet wenn der zweite Mitnehmer an das Ende des Magnets (70) anstößt.
     
    7. Baugruppe nach Anspruch 6, wobei der erste Mitnehmer mittels einer Feder vorgespannt ist, um sich in der Nut (40) zu erstrecken.
     
    8. Baugruppe nach Anspruch 7, wobei der zweite Mitnehmer mittels einer Feder vorgespannt ist, um an dem Ende des montierten Magnets (70) anzustoßen, wenn der montierte Magnet (70) in dem Bohrloch (25) positioniert ist.
     
    9. Baugruppe nach Anspruch 1, wobei das Federelement (50) aus Metall hergestellt ist.
     
    10. Baugruppe nach Anspruch 1, wobei das Federelement (50) ein stanzgebogenes Teil umfasst.
     


    Revendications

    1. Ensemble aimant comprenant :

    une forme de montage (10) ayant un trou de forage (25) ;

    un aimant (70) ; et

    un élément élastique (50) ayant :

    un premier bras élastique (55) et un deuxième bras élastique (60) verrouillant les aimants montés axialement dans le trou de forage ; et

    des troisièmes bras élastiques (5) appuyant sur le trou de forage (25) et supportant les aimants montés radialement loin du trou de forage (25),

    dans lequel :

    le trou de forage (25) comprend une rainure (40) et un épaulement (35) ;

    le premier bras élastique (55) s'étend dans la rainure (40) ; et

    le deuxième bras élastique (60) maintient l'aimant contre l'épaulement (35).


     
    2. Ensemble de la revendication 1, dans lequel l'aimant (70) forme un anneau et ledit troisième bras élastique (5) sollicite l'anneau radialement loin du trou de forage (25).
     
    3. Ensemble de la revendication 1 ou 2, dans lequel les aimants sont des aimants frittés et ledit élément élastique (50) réduit au minimum la contrainte sur l'aimant (70).
     
    4. Ensemble de l'une des revendications précédentes, dans lequel le premier bras élastique comporte un premier taquet placé dans la rainure (40) sollicitant radialement l'aimant monté (70) par rapport au trou de forage (25).
     
    5. Ensemble de la revendication 4, dans lequel le deuxième bras élastique (60) comporte un deuxième taquet venant en butée contre l'extrémité de l'aimant (70), ce qui permet de verrouiller l'aimant monté (70) axialement à l'intérieur du trou de forage (25).
     
    6. Ensemble de la revendication 5, dans lequel lesdits premier et deuxième taquets sont espacés l'un de l'autre de sorte que ledit premier taquet soit situé dans la rainure (40) lorsque ledit deuxième taquet vient en butée contre l'extrémité de l'aimant (70).
     
    7. Ensemble de la revendication 6, dans lequel ledit premier taquet est sollicité par un ressort pour s'étendre dans la rainure (40).
     
    8. Ensemble de la revendication 7, dans lequel ledit deuxième taquet est sollicité par un ressort pour venir en butée contre l'extrémité de l'aimant monté (70) lorsque l'aimant monté est positionné dans le trou de forage (25).
     
    9. Ensemble de la revendication 1, dans lequel ledit élément élastique (50) est réalisé en métal.
     
    10. Ensemble de la revendication 1, dans lequel ledit élément élastique (50) comporte une partie pliée par poinçon.
     




    Drawing








    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description