Magnet

Abstract

The present invention relates to a magnet that comprises a body and a slide arranged to be movable relative to the body between a first and a second position. The movement of the slide is limited by a first and a second section of the body in such a manner that at the first position of the slide, the second pole piece is in contact with the first section, and at the second position of the slide, the second pole piece is in contact with the second section.

Claims

1. A magnet, comprising: a body that comprises a first and a second section made of magnetic material for directing magnetic flux to an object to be attached, the first and the second section being separated and attached to a third section of the body, which third section is made of non-magnetic material, and a slide that comprises a permanent magnet, and a first and a second pole piece attached to opposite magnetic pole surfaces of the permanent magnet, the slide being arranged to be movable relative to the body between a first and a second position in order to alter the path of the magnetic flux generated by the permanent magnet, wherein: the first section comprises a hole that opens at its first end into a cavity of the body, the bottom of the cavity being defined at least partly by the second section, in which hole the slide is movably arranged so that at least part of the first pole piece stays inside the hole and the second pole piece is directed towards the bottom of the cavity, wherein the movement of the slide is limited by the first and the second section in such a manner that at the first position of the slide, the second pole piece is in contact with the first section, and at the second position of the slide, the second pole piece is in contact with the second section.

2. The magnet according to claim 1, wherein diameter of the second pole piece is larger than diameter of the hole.

3. The magnet according to claim 1, wherein the hole and the first pole piece are cylindrical.

4. The magnet according to claim 1, wherein the second pole piece is cylindrical.

5. The magnet according to claim 1, wherein the cavity is cylindrical.

6. The magnet according to claim 1, wherein height of the slide is larger than height of the hole.

7. The magnet according to claim 1, wherein the first section defines the wall of the cavity.

8. The magnet according to claim 7, wherein the third section is a hollow cylinder attached inside the first section, and the second section is attached inside the third section.

9. The magnet according to claim 1, wherein the third section defines the wall of the cavity.

10. The magnet according to claim 1, wherein a second end of the hole is closed by a fourth section of the body.

11. The magnet according to claim 1, wherein the magnet comprises means for transferring a medium into and out of the body in order to move the slide.

12. The magnet according to claim 1, wherein the magnet comprises a coil attached to the body and configured 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.

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

14. The magnet according to claim 13, wherein the sealing ring is attached to a groove in the first pole piece.

15. The magnet according to claim 13, wherein the slide comprises a cap attached on top of the first pole piece for holding the sealing ring in place.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] FIG. 1 illustrates a cross-sectional view of a magnet according to a first embodiment of the invention,

[0065] FIG. 2 illustrates the magnetic field generated by the magnet of FIG. 1, when the slide is at the first position,

[0066] FIG. 3 illustrates the magnetic field generated by the magnet of FIG. 1, when the slide is at the second position,

[0067] FIG. 4 illustrates a cross-sectional view of a magnet according to a second embodiment of the invention,

[0068] FIG. 5 illustrates the magnetic field generated by the magnet of FIG. 4, when the slide is at the first position, and

[0069] FIG. 6 illustrates the magnetic field generated by the magnet of FIG. 4, when the slide is at the second position.

DETAILED DESCRIPTION OF THE DRAWINGS

[0070] The same reference signs are used of the same or like components in different embodiments.

[0071] FIG. 1 illustrates a cross-sectional view of a magnet according to a first embodiment of the invention. The magnet comprises a body 101 and a slide 102 that is arranged to be movable relative to the body 101 between a first and a second position. The magnet comprises at its one end an attachment surface 103, which is meant to be arranged in contact with an object to be attached (not shown in FIG. 1).

[0072] The body 101 comprises a first and a second section 104, 105 that are made of magnetic material for conveying magnetic flux to an object to be attached. The first and the second section 104, 105 are attached together with a third section 106 of the body 101, which third section 106 is made of non-magnetic material. The third section 106 is a ring-shaped section inside which the cylindrical second section 105 is attached.

[0073] The slide 102 comprises a permanent magnet 107, and a first and a second cylindrical pole piece 108, 109 that are attached to opposite magnetic pole surfaces of the permanent magnet 107. The slide 102 also comprises a sealing ring 110 that is mounted in a groove in the first pole piece 108.

[0074] The first section 104 comprises a cylindrical hole 111 that opens at its first end into a cavity 112 of the body 101, which cavity 112 is defined by the first, the second and the third section 104, 105, 106. A second end of the cylindrical hole 111 is closed by a fourth section 113 of the body 101, which fourth section 113 is made of non-magnetic material.

[0075] The slide 102 is movably arranged in the hole 111 in such a manner that part of the first pole piece 108 always stays inside the hole 111, to which part the sealing ring 110 is attached. The second pole piece 109 is directed towards the bottom of the cavity 112, which bottom is defined partly by the second section 105. The diameter of the second pole piece 109 is larger than the diameter of the hole 111. The movement of the slide 102 is mechanically limited by the first and the second section 104, 105 in such a manner that at the first position of the slide 102, the second pole piece 109 engages with the first section 104, and at the second position of the slide 102, the second pole piece 109 engages with the second section 105.

[0076] The slide 102 is moved relative to the body 101 by conveying liquid into and out of the hole 111 and the cavity 112. When liquid is supplied into the cavity 112 and exhausted from the hole 111, the slide 102 moves towards the first position. When liquid is supplied into the hole 111 and exhausted from the cavity 112, the slide 102 moves towards the second position.

[0077] The liquid is conveyed into and out of the hole 111 and the cavity 112 using a hydraulic system 114 that is coupled via a first and a second pipe 115, 116 to a first and a second conduit 117, 118 that are integrated into the body 101. The first end of the first conduit 117 is arranged in communication with the hole 111 through the fourth section 113 that closes the second end of the hole 111. The first end of the second conduit 118 is arranged in communication with the cavity 112 through the wall of the cavity 112. The position of the slide 102 is determined with a magnetic flux sensor 119 that is arranged inside the first section 104, close to the hole 111.

[0078] FIG. 2 illustrates the magnetic field generated by the magnet of FIG. 1, when the slide 102 is at the first position. At this position, the first pole piece 108 and the permanent magnet 107 are located inside the hole 111, and the second pole piece 109 is located inside the cavity 112 and in contact with the first section 104. Essentially all of the magnetic flux (illustrated with magnetic field lines) generated by the permanent magnet 107 passes from the first pole piece 108 to the second pole piece 109 through a portion of the first section 104 that surrounds the hole 111 and through a portion of the first section 104 that is in contact with the second pole piece 109. The first section 104 thus short-circuits the magnetic flux generated by the permanent magnet 107. As a result of this, the holding force of the magnet is very small, and therefore the magnet cannot attach to a metal sheet 201.

[0079] FIG. 3 illustrates the magnetic field generated by the magnet of FIG. 1, when the slide 102 is at the second position. At this position, the second pole piece 109 is in contact with the second section 105 and only part of the first pole piece 108 is located inside the hole 111, whereby essentially all of the magnetic flux (illustrated with magnetic field lines) generated by the permanent magnet 107 passes from the first pole piece 108 through the first section 104 to the metal sheet 201 and therefrom through the second section 105 to the second pole piece 109. As a result of this, the holding force of the magnet is large, and therefore the magnet is tightly attached to the metal sheet 201.

[0080] FIG. 4 illustrates a cross-sectional view of a magnet according to a second embodiment of the invention. The magnet comprises a slide 102 that is arranged to be movable relative to a body 101 between a first and a second position. The magnet is in an OFF state, when the slide 102 is at the first position, and in an ON state, when the slide 102 is at the second position. FIG. 4 shows the magnet in the ON state.

[0081] The slide 102 comprises a permanent magnet 107, and a first and a second cylindrical pole piece 108, 109, which are attached to opposite magnetic pole surfaces of the permanent magnet 107. The slide 102 also comprises a sealing ring 110 that is attached around the first pole piece 108. The body 101 comprises a first and a second section 104, 105, which are made of magnetic material and attached to a third section 106 that is made of non-magnetic material. An object to be attached (not shown in FIG. 4) is meant to be in contact with the bottom sides of the first and the second section 104, 105.

[0082] The first section 104 comprises a cylindrical hole 111 that opens at its first end into a cavity 112 defined by the first, the second and the third section 104, 105, 106. A second end of the hole is closed by the first section 104. The slide 102 is movably arranged in the hole 111 in such a manner that part of the first pole piece 108 always stays inside the hole 111. The sealing ring 110 is attached to the part that always stays inside the hole 111. The second pole piece 109 is directed towards the bottom of the cavity 112, which bottom is defined by the second section 105. The diameter of the second pole piece 109 is larger than the diameter of the hole 111, so that the second pole piece 109 cannot enter the hole 111. The movement of the slide 102 is mechanically limited by the first and the second section 104, 105 in such a manner that at the first position of the slide 102, the second pole piece 109 is engaged with the first section 104, and at the second position of the slide 102, the second pole piece 109 is engaged with the second section 105. When the slide 102 is at the first position, the first pole piece 108 and the permanent magnet 107 are located inside the hole 111. When the slide 102 is at the second position, only part of the first pole piece 108 is located inside the hole 111. The slide 102 is moved relative to the body 101 by conveying air into and out of an airtight space that is formed by the cavity 112 and the hole 111. When air is supplied into the hole 111 and exhausted from the cavity 112, the slide 102 moves towards the second position. When air is supplied into the cavity 112 and exhausted from the hole 111, the slide 102 moves towards the first position.

[0083] The air is conveyed into and out of the hole 111 and the cavity 112 using a pneumatic system 401 that is coupled via a first and a second pipe 115, 116 to a first and a second conduit 117, 118 that are integrated into the body 101. The first end of the first conduit 117 is arranged in communication with the hole 111 through the second end of the hole 111. The first end of the second conduit 118 is arranged in communication with the cavity 112 through the portion of the second section 105 that is in contact with the slide 102, when the slide 102 is at the second position.

[0084] FIG. 5 illustrates the magnetic field generated by the magnet of FIG. 4, when the slide 102 is at the first position. The magnetic field is represented by magnetic field lines. At the first position of the slide 102, the first pole piece 108 and the permanent magnet 107 are located inside the hole 111, and the second pole piece 109 is located inside the cavity 112 and in contact with the first section 104. The magnetic flux generated by the permanent magnet 107 passes from the first pole piece 108 to the second pole piece 109 through a portion of the first section 104 that surrounds the hole 111 and through a portion of the first section 104 that is in contact with the second pole piece 109. Because the magnetic flux generated by the permanent magnet 107 is short-circuited by the first section 104, the holding force of the magnet is negligible, and therefore the magnet cannot attach to a metal sheet 201.

[0085] FIG. 6 illustrates the magnetic field generated by the magnet of FIG. 4, when the slide 102 is at the second position. The magnetic field is represented by magnetic field lines. At the second position of the slide 102, the second pole piece 109 is in contact with the second section 105 and only part of the first pole piece 108 is located inside the hole 111, whereby essentially all of the magnetic flux generated by the permanent magnet 107 passes from the first pole piece 108 through the first section 104 to the metal sheet 201 and therefrom through the second section 105 to the second pole piece 109. The metal sheet 201 that is arranged in contact with both the first and the second section 104, 105 closes the magnetic circuit. The magnet is thus attached to the metal sheet 201.

[0086] 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.