Magnet and actuator

Abstract

The present invention provides a magnet, which comprises a body having a first and a second section, and a slide arranged to be movable relative to the body between a first and a second position. The slide comprises a permanent magnet, and a first and a second pole piece that are attached to opposite magnetic pole surfaces of the permanent magnet. The first section comprises a hole that opens into a first cavity of the body, the bottom of the first cavity being delimited at least partly by the second section. The slide is movably arranged in the hole so that the second pole piece is directed towards the bottom of the first cavity, wherein at the first position of the slide, magnetic flux generated by the permanent magnet is short-circuited by the first section, and at the second position of the slide, magnetic flux generated by the permanent magnet is directed through the first and the second section.

Claims

1. A magnet, comprising: a body having a first and a second section, and a slide arranged to be movable relative to the body between a first and a second position, the slide comprising a permanent magnet, and a first and a second pole piece attached to opposite magnetic pole surfaces of the permanent magnet; wherein the first section comprises a hole that opens into a first cavity of the body, bottom of the first cavity being delimited at least partly by the second section, in which hole the slide is movably arranged so that the second pole piece is directed towards the bottom of the first cavity, wherein at the first position of the slide, magnetic flux generated by the permanent magnet is short-circuited by the first section, and at the second position of the slide, magnetic flux generated by the permanent magnet is directed through the first and the second section.

2. The magnet according to claim 1, wherein thickness of the permanent magnet is smaller than thickness of the first pole piece and thickness of the second pole piece.

3. The magnet according to claim 1, characterised in that thickness of the slide is larger than depth of the hole.

4. The magnet according to claim 1, wherein the first and the second section are attached together with a third section of the body, the third section being made of non-magnetic material.

5. The magnet according to claim 4, wherein the third section defines a wall of the first cavity.

6. The magnet according to claim 1, wherein the first and the second section form an integral part.

7. The magnet according to claim 1, wherein the magnet comprises a coil attached to the body, the coil being arranged to generate a magnetic force for moving the slide towards the first or the second position depending on the direction of electric current that is supplied to the coil.

8. The magnet according to claim 7, wherein the magnet comprises means for supplying electric current to the coil.

9. The magnet according to claim 1, wherein the body comprises a fourth section attached to the first sections so that a second cavity is formed in the body, the second cavity being interconnected to the first cavity through the hole.

10. The magnet according to claim 9, wherein the first and the second cavity contain a medium, and the magnet comprises a first conduit for conveying the medium between the first and the second cavity, a first end of the first conduit being arranged in communication with the first cavity and a second end of the first conduit being arranged in communication with the second cavity.

11. The magnet according to claim 9, wherein the first and the second cavity contain a medium, and the body comprises a second conduit for conveying the medium into and out of the first cavity and a third conduit for conveying the medium into and out of the second cavity, a first end of the second conduit being arranged in communication with the first cavity and a first end of the third conduit being arranged in communication with the second cavity.

12. The magnet according to claim 11, wherein the magnet comprises a pump coupled to a second end of the second and the third conduit.

13. The magnet according to claim 10, wherein the medium is gas or liquid.

14. The magnet according to claim 1, wherein the magnet comprises a sealing ring attached around the slide or attached to the wall of the hole.

15. The magnet according to claim 14, wherein the sealing ring is attached to a groove in the first pole piece.

16. The magnet according to claim 14, wherein the slide comprises a cap attached on top of the first pole piece for holding the sealing ring in place.

17. The magnet according to claim 1, wherein the slide comprises a guiding rod extending from the second pole piece to a bore in the bottom of the first cavity.

18. The magnet according to claim 1, wherein the magnet comprises: a magnetic flux sensor configured to measure magnetic flux density in the first section, and means for determining the position of the slide based on the measured magnetic flux density.

19. The magnet according to claim 18, wherein the magnetic flux sensor is one of the following: a Hall sensor, an AMR magnetometer, a MEMS sensor or a reed relay.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the description of specific embodiments when read in connection with the accompanying drawings.

[0048] FIG. 1 illustrates a cross-sectional view of a magnet according to a first embodiment of the invention,

[0049] FIG. 2 illustrates the magnetic field generated by the magnet of FIG. 1, when the slide is at the first position,

[0050] FIG. 3 illustrates the magnetic field generated by the magnet of FIG. 1, when the slide is at the second position,

[0051] FIG. 4 illustrates a cross-sectional view of a magnet according to a second embodiment of the invention, and

[0052] FIG. 5 illustrates a cross-sectional view of a magnet according to a third embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0053] The same reference signs are used of the same or like components in different embodiments.

[0054] FIG. 1 illustrates a cross-sectional view of a magnet according to a first embodiment of the invention. The magnet 100 comprises a cylindrical body 101 that comprises at its one end an attachment surface 102, which is meant to be arranged in contact with an object to be attached.

[0055] The body 101 of the magnet 100 comprises a first and a second section 103, 104 made of magnetic material. The first and the second section 103, 104 are attached together with a third section 105 of the body 101, which third section 105 is made of non-magnetic material. The third section 105 has the form of a sleeve and is attached around the second section 104 that is cylindrical. The first section 103 is attached around the third section 105.

[0056] The first section 103 comprises a hole 106 that opens into a first cavity 107 of the body 101, which first cavity 107 is cylindrical. The bottom of the first cavity 107 is defined by the second section 104, and the wall of the first cavity 107 is defined by the third section 105.

[0057] The magnet 100 comprises a slide 108 that is movably arranged in the hole 106 of the first section 103. The slide 108 is cylindrical and comprises a permanent magnet 109 and a first and a second pole piece 110, 111 that are attached to opposite magnetic pole surfaces of the permanent magnet 109. The second pole piece 111 is directed towards the bottom of the first cavity 107.

[0058] The slide 108 is arranged to be movable relative to the body 101 between a first and a second position. In FIG. 1, the slide 108 is at the first position. At the first position of the slide 108, magnetic flux generated by the permanent magnet 109 is short-circuited by the first section 103, and at the second position of the slide 108, magnetic flux generated by the permanent magnet 109 can be directed to an object to be attached through the first and the second section 103, 104. The position of the slide 108 is determined with a magnetic flux sensor 112 that is arranged inside the first section 103, close to the hole 106.

[0059] The slide 108 comprises a guiding rod 113 that extends from the second pole piece 111 to a bore 114 in the bottom of the first cavity 107. The guiding rod 113 and the bore 114 are dimensioned in such a manner that at least part of the guiding rod 113 stays in the bore 114 all the time.

[0060] The magnet 100 comprises a coil 115 that is arranged to generate a magnetic force for moving the slide 108 towards the first or the second position depending on the direction of electric current that is supplied to the coil 115. The coil 115 is arranged inside the third section 105 and at least partly around the slide 108. The magnet 100 comprises a battery 116 that is connected via a control unit 117 to the coil 115. The control unit 117 controls the amount and the direction of electric current supplied from the battery 116 to the coil 115. The state of the magnet 100, i.e. the position of the slide 108, can be changed with an electric current pulse that has a certain duration, magnitude and polarity.

[0061] FIG. 2 illustrates the magnetic field generated by the magnet of FIG. 1, when the slide is at the first position. The magnetic field is represented by magnetic field lines. At the first position of the slide 108, the permanent magnet 109 and part of the first and the second pole piece 110, 111 are located inside the hole 106. At this position, as can be seen in FIG. 2, essentially all of the magnetic field lines pass from the first pole piece 110 to the second pole piece 111 through a portion of the first section 103 that surrounds the hole 106. The magnet 100 cannot thus attach to an object 200.

[0062] FIG. 3 illustrates the magnetic field generated by the magnet of FIG. 1, when the slide is at the second position. The magnetic field is represented by magnetic field lines. At the second position of the slide 108, the permanent magnet 109 and the second pole piece 111 are located outside the hole 106, and part of the first pole piece 110 is located inside the hole 106. At this position, as can be seen in FIG. 3, essentially all of the magnetic field lines pass from the first pole piece 110 to the second pole piece 111 through the first and the second section 103, 104, and through the object 200 that is in contact with the first and the second section 103, 104 at the attachment surface 102. The object 200 is thus attached to the magnet 100.

[0063] FIG. 4 illustrates a cross-sectional view of a magnet according to a second embodiment of the invention. The magnet of FIG. 4 differs from the magnet of FIG. 1, in that it comprises a second cavity 118 and a first conduit 119 for transferring liquid between the first and the second cavity 107, 118.

[0064] The second cavity 118, which is cylindrical, is defined by a fourth section 120 that is attached to the first section 103. The fourth section 120 is made of non-magnetic material.

[0065] The first conduit 119 is integrated to the body 101. A first end of the first conduit 119 is arranged in communication with the first cavity 107 and a second end of the first conduit 119 is arranged in communication with the second cavity 118. The first conduit 119 allows the liquid to flow between the first and the second cavity 107, 118, when the slide 108 is moved from one position to the other.

[0066] FIG. 5 illustrates a cross-sectional view of a magnet according to a third embodiment of the invention. The magnet of FIG. 5 differs from the magnet of FIG. 1, in that it comprises a second cavity 118, and the means for moving the slide 108 between the first and the second position are different. The magnet of FIG. 5 also comprises a sealing ring 126 that is attached around the first pole piece 110.

[0067] The second cavity 118, which is cylindrical, is defined by a fourth section 120 that is attached to the first section 103. The fourth section 120 is made of non-magnetic material.

[0068] In the magnet of FIG. 5, the position of the slide 108 is changed by transferring liquid from one cavity to the other. The magnet 100 comprises a second and a third conduit 121, 122 that are integrated into the body 101. A first end of the second conduit 121 is arranged in communication with the first cavity 107, and a first end of the third conduit 122 is arranged in communication with the second cavity 118.

[0069] The second and the third conduit 121, 122 extend through the body 101 so that second ends of the conduits 121, 122 open outside the magnet 100. The second end of the second conduit 121 and the second end of the third conduit 122 are connected to a pump 123 with a first and a second pipe 124, 125. By using the pump 123, medium may be transferred from one cavity to the other so that the slide 108 is moved from one position to the other.

[0070] Only advantageous exemplary embodiments of the invention are described in the figures. It is clear to a person skilled in the art that the invention is not restricted only to the examples presented above, but the invention may vary within the limits of the claims presented hereafter. Some possible embodiments of the invention are described in the dependent claims, and they are not to be considered to restrict the scope of protection of the invention as such.