Magnetic substance holding device

A magnetic substance holding device includes: a first pole piece assembly comprising at least one first pole piece, at least two second pole pieces, and at least two first permanent magnets; a second pole piece assembly comprising at least one third pole piece, at least two fourth pole pieces, and at least two second permanent magnets; a coil; and a control device. The first pole piece assembly and/or the second pole piece assembly is configured to be movable such that they are switched between a first arrangement in which the second faces of the first pole piece assembly are spaced apart from the first faces of the second pole piece assembly, and a second arrangement in which the second faces of the first pole piece assembly come in contact with the first faces of the second pole piece assembly. The control device controls holding and detaching of a workpiece on and from the first faces of the first pole piece assembly or the second faces of the second pole piece assembly, by way of controlling electric current applied to the coil to switch between the first arrangement and the second arrangement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No. 10-2015-0010094 filed on Jan. 21, 2015, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a magnetic substance holding device, and more particularly to a magnetic substance holding device that controls magnetic fluxes from permanent magnets to thereby obtain strong holding force, to easily switch between holding and detaching, and to minimize residual magnetism.

Description of the Related Art

A magnetic substance holding device such as a permanent magnet workholding device is used to attach thereto a workpiece made of a magnetic material such as iron using magnetic force. Nowadays, such a magnetic substance holding device is widely used as an internal device attached to a mold clamping unit of an injection molding machine, a mold clamping unit of a press machine, a chuck of a machine tool, and so on.

The basic principle of such a magnetic substance holding device is that it attaches a magnetic workpiece to a holding face using strong magnetic force from a permanent magnet, and detaches the magnetic workpiece from the holding face by controlling the magnetic flux from the permanent magnet so that no magnetic flux flows through the holding face.

The method for controlling the magnetic flux from the permanent magnet may include rotating another permanent magnet which is rotatably installed to control the magnetic flux, employing an additional electromagnet to control the magnet flux, or the like.

The applicant of the present invention has already proposed a magnetic substance holding device employing an additional electromagnet (see Korean Patent No. 1319052, titled “MAGNETIC SUBSTANCE HOLDING DEVICE USING PERMANENT MAGNET ENERGY CONTROL,” published on Oct. 17, 2013). In addition, the applicant of the present invention has proposed an improved magnetic substance holding device (see Korean Patent Laid-open Publication No. 10-2014-0124739, titled “MAGNETIC SUBSTANCE HOLDING DEVICE,” published on Oct. 27, 2014).

The magnetic substance holding device disclosed in the Korean Patent No. 1319052 to the applicant of the present invention includes coils around pole pieces instead of an additional electromagnet, and accordingly has advantages in that strong holding force can be obtained in a simple structure, magnetic force from a permanent magnet can be controlled with small electric current at the time of switching between holding and detaching, and strong holding force can be obtained in a smaller space.

However, there is still a challenge for such a magnet substance holding device to minimize residual magnetism that attracts a workpiece even after it is detached.

In short, as more permanent magnets are used for increasing holding force, it becomes more difficult to control magnetic fluxes and residual magnetism becomes lager, thereby harming the usability.

SUMMARY OF THE INVENTION

In view of the above, an object of the present invention is to provide a magnetic substance holding device that controls magnetic fluxes from permanent magnets to thereby obtain strong holding force, to easily switch between holding and detaching, and to minimize residual magnetism.

It should be noted that objects of the present invention are not limited to the above-mentioned object; and other objects of the present invention will be apparent to those skilled in the art from the following descriptions.

According to an aspect of the present invention, there is provided a magnetic substance holding device for holding and detaching a workpiece that is a magnetic substance, the device comprising: a first pole piece assembly comprising at least one first pole piece having a first face and a second face, the first pole piece being a magnetic substance, at least two second pole pieces, each of the second pole pieces having a first face and a second face and being a magnetic substance, and at least two first permanent magnets, one of an N-pole and an S-pole of each of the first permanent magnets being in contact with the first pole piece while the other of the N-pole and the S-pole thereof being in contact with the second pole pieces, respectively; a second pole piece assembly comprising at least one third pole piece having a first face and a second face, the third pole piece being a magnetic substance, at least two fourth pole pieces, each of the fourth pole pieces having a first face and a second face and being a magnetic substance, and at least two second permanent magnets, their each pole of opposite polarity to that of the poles of the first permanent magnets in contact with the first pole piece is in contact with the third pole piece while the pole of same polarity to that of the poles of the first permanent magnets in contact with the first pole piece is in contact with the fourth pole pieces, respectively; wherein the first face of the third pole piece faces the second face of the first pole piece while the first face of each of the fourth pole pieces faces the second face of a respective one of the second pole pieces; at least one coil wound around the first pole piece and/or the third pole piece; and a control device controlling electric current applied to the coil, wherein the first pole piece assembly and/or the second pole piece assembly is configured to be movable such that they are switched between a first arrangement in which the second faces of the first pole piece assembly are spaced apart from the first faces of the second pole piece assembly, and a second arrangement in which the second faces of the first pole piece assembly come in contact with the first faces of the second pole piece assembly, and wherein the control device controls holding and detaching of a workpiece on and from the first faces of the first pole piece assembly or the second faces of the second pole piece assembly, by way of controlling electric current applied to the coil to switch between the first arrangement and the second arrangement.

The device may further comprise: a base having a contact face and being a magnetic substance, the contact face facing the first faces of the first pole piece assembly. The first faces of the first pole piece assembly come in contact with the contact face of the base when the first pole piece assembly and the second pole piece assembly are in the first arrangement, and the first faces of the first pole piece assembly are spaced apart from the contact face of the base when the first pole piece assembly and the second pole piece assembly are in the second arrangement.

The device may further comprise: a base having a contact face and being a magnetic substance, wherein the base is disposed such that its contact face is in contact with the first faces of the first pole piece assembly.

According to an aspect of the present invention, there is provided a magnetic substance holding device for holding and detaching a workpiece that is a magnetic substance, the device comprising: a first pole piece assembly comprising at least one first pole piece having a first face and a second face, the first pole piece being a magnetic substance, at least two second pole pieces, each of the second pole pieces having a first face and a second face and being a magnetic substance, and at least two first permanent magnets, one of an N-pole and an S-pole of each of the first permanent magnets being in contact with the first pole piece while the other of the N-pole and the S-pole thereof being in contact with the second pole pieces, respectively; a second pole piece assembly comprising at least one third pole piece having a first face and a second face, the third pole piece being a magnetic substance, at least two fourth pole pieces, each of the fourth pole pieces having a first face and a second face and being a magnetic substance, and at least two second permanent magnets, their each one pole of opposite polarity to that of the poles of the first permanent magnets in contact with the first pole piece is in contact with the third pole piece while the pole of same polarity to that of the poles of the first permanent magnets in contact with the first pole piece is in contact with a respective one of the fourth pole pieces; wherein the first face of the third pole piece faces the second face of the first pole piece while the first face of each of the fourth pole pieces faces the second face of a respective one of the second pole pieces; a connection pole piece assembly comprising at least one first connection pole piece having a first face and a second face and being a magnetic substance, and at least two second connection pole pieces, each of the second connection pole pieces having a first face and a second face and being a magnetic substance; wherein the second face of the first connection pole piece faces the first face of the first pole pieces, and the second face of each of the second connection pole pieces faces the first face of the respective one of the second pole pieces; at least one coil wound around the first pole piece and/or the third pole piece; and a control device controlling electric current applied to the coil, wherein at least one least one of the first pole piece assembly, the second pole piece assembly and the connection pole piece assembly is configured to be movable such that they are switched between a first arrangement in which the second faces of the first pole piece assembly are spaced apart from the first faces of the second pole piece assembly while the first faces of the first pole piece assembly come in contact with the second faces of the connection pole piece assembly, and a second arrangement in which the second faces of the first pole piece assembly come in contact with the first faces of the second pole piece assembly while the first faces of the first pole piece assembly are spaced apart from the second faces of the connection pole piece assembly, and wherein the control device controls holding and detaching of a workpiece on and from the first faces of the connection pole piece assembly or the second faces of the second pole piece assembly, by way of controlling electric current applied to the coil to switch between the first arrangement and the second arrangement.

The first faces of the connection pole piece assembly and the second faces of the second pole piece assembly may be configured to hold and detach a single workpiece.

The first pole piece assembly may be movable along a plane extended from the second faces of the second pole piece assembly and the first faces of the connection pole piece assembly.

At least two first permanent magnets may be disposed between the first pole piece and each of the second pole pieces, and at least two second permanent magnets may be disposed between the third pole piece and each of the fourth pole pieces.

The first permanent magnets may be disposed in a line between the first pole piece and each of the second pole pieces, and the second permanent magnets may be disposed in a line between the third pole piece and each of the fourth pole pieces.

The first pole piece assembly may comprise at least two first pole pieces, the second pole piece assembly may comprise at least two third pole pieces, at least one first permanent magnet may be disposed between each of the first pole piece and a respective one of the second pole pieces, and at least one second permanent magnet may be disposed between each of the third pole piece and a respective one of the fourth pole pieces.

An area of the first face of each of the fourth pole pieces may be smaller than an area of the second face of a respective one of the second pole pieces, and the area of the second face of each of the fourth pole pieces may be smaller than an area of the first face of a respective one of the fourth pole pieces.

The device may further comprise: a rail bolt fixed to the first pole piece assembly and to the base while penetrating the second pole piece assembly so that the second pole piece assembly slides along the rail bolt.

The device may further comprise: a rail bolt fixed to the first pole piece assembly and to the connection pole piece assembly while penetrating the second pole piece assembly so that the second pole piece assembly slides along the rail bolt.

According to the magnetic substance holding device of the present invention, residual magnetism when a workpiece has been detached therefrom can be minimized. In addition, by disposing coils around pole pieces instead of an additional electromagnet, strong holding force can be obtained in a simple structure, magnetic force from a permanent magnet can be controlled with small electric current at the time of switching between holding and detaching, and strong holding force can be obtained in a smaller space.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Advantages and features of the present invention and methods to achieve them will become apparent from the descriptions of exemplary embodiments herein below with reference to the accompanying drawings. However, the present invention is not limited to exemplary embodiments disclosed herein but may be implemented in various different ways. The exemplary embodiments are provided for making the disclosure of the present invention thorough and for fully conveying the scope of the present invention to those skilled in the art. It is to be noted that the scope of the present invention is defined only by the claims.

The figures, dimensions, ratios, angles, numbers of elements given in the drawings are merely illustrative and are not limiting. Further, in describing the present invention, descriptions on well-known technologies may be omitted in order not to obscure the gist of the present invention. It is to be noticed that the terms “comprising,” “having,” “including” and so on, used in the description and claims, should not be interpreted as being restricted to the means listed thereafter unless specifically stated otherwise. Where an indefinite or definite article is used when referring to a singular noun, e.g. “a,” “an,” “the,” this includes a plural of that noun unless specifically stated otherwise.

In describing elements, they are interpreted as including error margins even without explicit statements.

In describing positional relationship, such as “an element A on an element B,” “an element A above an element B,” “an element A below an element B” and “an element A next to an element B,” another element C may be disposed between the elements A and B unless the term “directly” or “immediately” is explicitly used.

As used herein, a phrase “an element A on an element B” refers to that the element A may be disposed directly on the element B and/or the element A may be disposed indirectly on the element B via another element C. Like reference numerals denote like elements throughout the descriptions.

Although terms such as first, second, etc. are used to distinguish arbitrarily between the elements such terms describe and these terms are not necessarily intended to indicate temporal or other prioritization of such elements. Theses terms are used to merely distinguish one element from another. Accordingly, as used herein, a first element may be a second element within the technical scope of the present invention.

The drawings are not to scale and the relative dimensions of various elements in the drawings are depicted schematically and not necessarily to scale.

Features of various exemplary embodiments of the present invention may be combined partially or totally. As will be clearly appreciated by those skilled in the art, technically various interactions and operations are possible. Various exemplary embodiments can be practiced individually or in combination.

Hereinafter, magnetic substance holding devices according to exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

At first, the basic configuration and operating principle of a magnetic substance holding device of the present invention will be described.

FIGS. 1A to 1Fare schematic cross-sectional views of a magnetic substance holding device according to an exemplary embodiment of the present invention. In particular,FIGS. 1E and 1Fare schematic cross-sectional views of a magnetic substance holding device according to a variant of the magnetic substance holding device shown inFIGS. 1A to 1D.

Referring toFIGS. 1A to 1D, the magnetic substance holding device1000includes a first pole piece assembly1100, a second pole piece assembly1200, coils1300, a base1400, and a control device (not shown).

The first pole piece assembly1100includes at least one first pole piece1110, at least two second pole pieces1120, and at least two first permanent magnets1130. The first pole piece1110is a magnetic substance and has a first face1111and a second face1112. Further, each of the second pole pieces1120is a magnetic substance and has a first face1121and a second face1122. The N-pole or the S-pole of each of the first permanent magnets1130is in contact with the first piece1110while the S-pole or the N-pole thereof is in contact with the respective second pole pieces1120. For example, as shown inFIGS. 1A to 1D, the N-pole of each of the first permanent magnets1130may be in contact with the first pole piece1110while the S-pole thereof may be in contact with the respective second pole pieces1120. The poles of the first permanent magnets1130may be disposed in the opposite direction.

The second pole piece assembly1200includes at least one third pole piece1210, at least two fourth pole pieces1220, and at least two second permanent magnets1230. The third pole piece1210is a magnetic substance and has a first face1211and a second face1212. Further, each of the fourth pole pieces1220is a magnetic substance and has a first face1221and a second face1222. Between the N-pole and the S-pole of each of the second permanent magnets1130, the pole of opposite polarity to that of the poles of the first permanent magnets in contact with the first pole piece1110is in contact with the third pole piece1210while the other pole is in contact with a respective one of the fourth pole pieces1120.

The first pole piece assembly1100and the second pole piece assembly1200are arranged so that the first face1211of the third pole piece1210can come in contact with and be spaced apart from the second face1112of the first pole piece1110(i.e., they face each other) while the first face1221of each of the fourth pole pieces1220can come in contact with and be spaced apart from the second face1122of a respective one of the second pole pieces1120(i.e., they face each other).

The coils1300may be wound around the first pole piece1110and/or the third pole piece1210. Coils1310and1320may be wound around the first pole piece1110and the third pole piece1210, respectively, as shown inFIGS. 1A to 1D, or may be wound around only the first pole piece1110or only the third pole piece1210, although not shown in the drawings.

The coils1310and1320are wound around magnetic substances and affect magnetic fluxes in the magnetic substances by magnetizing the magnetic substances upon application of electric current. The coils1310and1320are disposed so that they can affect a magnetic flux passing through the first face1111of the first pole piece1110and a magnetic flux passing through the second face1212of the third pole piece1210, respectively. The coil1310may be disposed closer than the first permanent magnet1130to the first face1111of the first pole piece1110as shown inFIG. 1A to 1D, or may be disposed more distant than the first permanent magnet1130from the first face1111of the first pole piece1110. The coil1320may be disposed closer than the second permanent magnet1230to the second face1212of the third pole piece1210as shown inFIG. 1A to 1D, or may be disposed more distant than the second permanent magnet1230from the second face1212of the third pole piece1210.

Although each of the coils1310and1320is wound around the first and third pole pieces, respectively, inFIGS. 1A to 1D, two or more coils may be wound around the first and third pole pieces, respectively.

In addition, it is beneficial to dispose the coils1310and1320between the second permanent magnets1230and the second faces1212and1222of the second pole piece assembly1200for the purpose of controlling magnetic flux. In addition, coils1310and1320may be disposed between the first permanent magnets1130and the first faces1111and1121of the first pole piece assembly1100. Such disposal of the coils1310and1320may be applied to other exemplary embodiments.

The coils1310and1320are connected to the control device. The control device controls (the direction or intensity of) electric current applied to the coils1310and1320. As used herein, electric current refers to direct current (DC).

The base1400has a contact face1401and is a magnetic substance. The base1400is disposed so that it can come in contact with and be spaced apart from the first faces1111and1121of the first pole piece assembly1100(i.e., they face each other). The contact face1401of the base1400may be in contact with the first faces1111and1121of the first pole piece assembly1100so that the base1400may move together with the first pole piece assembly1100or may be stationary.

At least one of the first pole piece assembly1100, the second pole piece assembly1200and the base1400is movable, so that a first arrangement in which the second faces1112and1122of the first pole piece assembly1100are spaced apart from the first faces1211and1221of the second pole piece assembly1200, respectively, while the first faces1111and1121of the first pole piece assembly1100come in contact with the contact face1401of the base1400(the arrangement shown inFIGS. 1C and 1D), and a second arrangement in which the second faces1112and1122of the first pole piece assembly1100come in contact with the first faces1211and1221of the second pole piece assembly1200, respectively, while the first faces1111and1121of the first pole piece assembly1100are spaced apart from the contact face1401of the base1400(the arrangement shown inFIGS. 1A and 1B) are switched between each other. Specifically, only the first pole piece1100or only the second pole piece1200may be movable, or both of the first and second pole pieces1100and1200may be movable. In the following descriptions, only the first pole piece assembly1100is movable in exemplary embodiments for the sake of convenience in description. However, it is to be understood that the present invention is not limited thereto.

Referring toFIGS. 1A to 1D, rail bolts1001and1002are fixed to the first pole piece assembly1100and to the base1400and penetrate the second pole piece assembly1200, so that the second pole piece assembly1200slides along the rail bolts1001and1002by magnetic force. Namely, the first pole piece1110may slide along the rail bolt1001in the axial direction, as the rail bolt1001is fixed to the base1400and to the third pole piece1210while passing through the first pole piece1110. Further, the second pole pieces1120may slide along the rail bolts1002, as the rail bolts1002fixed to the base1400and to the fourth pole pieces1220pass through the second pole pieces1120. The rail bolts1001and1002are non-magnetic substances and thus no magnetic flux may be created through the rail bolts1001and1002. The rail bolts1001and1002may be fixed to the first pole piece assembly1100and to the base1400by screwing them thereinto. On the other hand, the rail bolts1001and1002may be fixed to at least one of the first pole piece assembly1100, the second pole piece assembly1200and the base1400, so that the others may slide along the rail bolts1001and1002.

The control device adjusts (the direction or amplitude of) electric current applied to the coils1310and1320to thereby control the direction and the intensity of magnetic fluxes passing through the coils1310and1320.

Referring toFIG. 1A, when the first pole piece assembly1100and the second pole piece assembly1200are in the second arrangement in which they are in contact with each other, with no electric current applied from the control device to the coils1310and1320, a magnetic flux flows inside the magnetic circuit through the second faces1112and1122of the first pole piece assembly1100and the first faces1211and1221of the second pole piece assembly1200, as indicated by the dashed lines. In this instance, almost no magnetic flux passes through the first faces1111and1121of the first pole piece assembly1100and the second faces1212and1222of the second pole piece assembly1200. The magnetic fluxes passing through the first faces1111and1121of the first pole piece assembly1100and the second faces1212and1222of the second pole piece assembly1200are proportional to the difference in magnetic forces (magnetic energies) between the first permanent magnets1130and the second permanent magnets1230. Therefore, in the arrangement shown inFIG. 1A, attractive forces between the first faces1111and1121of the first pole piece assembly1100and the base1400are minimized, and a workpiece, which is a magnetic substance, is not held on the second faces1212and1222of the second pole piece assembly1200(Throughout the drawings, a workpiece that is not held by the device is indicated by a dashed line).

On the other hand, when the control device applies electric current to the coils1310and1320as shown inFIG. 1B, the magnetic fluxes between the first permanent magnets1130and the second permanent magnets1230through the second faces1112and1122of the first pole piece assembly1100and the first faces1211and1221of the second pole piece assembly1200become weak and are eventually disconnected.

When this happens, the first pole piece assembly1100slides along the rail bolts1001and1002by magnetic force, so that the first faces1111and1121of the first pole piece assembly1100come in contact with the contact face1401of the base1400, while the second faces1212and1222of the second pole piece assembly1200come in contact with a workpiece1which is a magnetic substance. As a result, magnetic fluxes passing through the base1400and the workpiece1are created as indicated by the dashed lines inFIG. 1C, so that the base1400is attached to the first faces1111and1122of the first pole piece assembly1100by stronger magnetic force, while the workpiece1is held on the second faces1212and1222of the second pole piece assembly1200.

Thereafter, as shown inFIG. 1C, the magnetic fluxes once formed through the base1400and the workpiece1are not broken but remain even if electric current is no more applied to the coils1310and1320. Further, since no magnetic flux is formed passing through the second faces1112and1122of the first pole piece assembly1100and the first faces1211and1221of the second pole piece assembly1200, the first pole piece assembly1100and the second pole piece assembly1200can be spaced apart from each other.

Later on, as shown inFIG. 1D, by applying electric current to the coils1310and1320in the opposite direction to that shown inFIG. 1B, it is possible to detach the base1400and the workpiece1from the first pole piece assembly1100and the second pole piece assembly1200again. When electric current is applied to the coils1310and1320in the direction shown inFIG. 1D, the magnetic fluxes passing through the first faces1111and1121of the first pole piece assembly1100and the second faces1211and1222of the second pole piece assembly1200become weak and are eventually disconnected. Accordingly, the first pole piece assembly1100slides along the rail bolts1001and1002by magnetic force, so that the first pole piece assembly1100and the second pole piece assembly1200are switched to the second arrangement as shown inFIG. 1A, and the magnetic flux as shown inFIG. 1Acan be restored.

In addition, the separation distance by which the base1400in the first arrangement is spaced apart from the first faces1111and1121of the first pole piece assembly1100also has to be determined appropriately. If the distance is too distant, the base1400may not be attached to the first faces1111and1121of the first pole piece assembly1100even when electric current is applied to the coils1310and1320. On the other hand, if the distance is too close, the base1400may be attached to the first faces1111and1121of the first pole piece assembly1100even when electric current is not applied to the coils1310and1320. Therefore, in view of the above, the separation distance between the base1400in the first arrangement and the first faces1111and1121has to be adjusted such that the base1400is attached to the first faces1111and1121of the first pole piece assembly1100only when certain amount of electric current is applied to the coils1310and1320. The distance may be adjusted empirically or experimentally, taking into account the intensity of the magnetic force induced by the coils1310and1320, or the like.

In short, the control device adjusts electric current applied to the coils1310and1320to thereby control the direction and intensity of the magnetic fluxes passing through the coils1310and1320. By doing so, the first pole piece assembly1100, the second pole piece assembly1200and the base1400can be switched between the first arrangement and the second arrangement, and the direction and intensity of the magnetic fluxes passing through the first faces1111and1121of the first pole piece assembly1100and the second faces1212and1222of the second pole piece assembly1200can be controlled. As a result, the workpiece1, which is a magnetic substance, can be held on and detached from the second faces1212and1222of the second pole piece assembly1200.

Referring back toFIG. 1A, when the workpiece is detached from the magnetic substance holding device1000thus configured, the magnetic fluxes from the permanent magnets1130and1230flow only inside the magnetic circuit, so that it is possible to leave almost zero or completely no residual magnetism toward the outside. (This effect can be maximized when the first permanent magnets1130and the second permanent magnets1230have the equal magnetic force (magnetic energy).) Further, in this structure, permanent magnets can be placed closely together, and thus stronger holding force can be obtained.

Referring toFIGS. 1E and 1F, at least two first pole pieces1110′ and at least two third pole pieces1210′ can be disposed. In this instance, at least one first permanent magnets1130′ may be disposed between a first pole piece1110′aand the respective one of the second pole pieces1120′ while at least one first permanent magnet1130′ may be disposed between a first pole piece1110′band the respective one of the second pole pieces1120′. Further, at least one second permanent magnets1230′ may be disposed between a third pole piece1210′aand the respective one of the fourth pole pieces1220′ while at least one first permanent magnet1230′ may be disposed between a third pole piece1210′band the respective one of the fourth pole pieces1220′. With this configuration, magnetic fluxes in each of the first pole pieces1110′aand1110′band each of the third pole pieces1210′aand1210′bare not superposed on one another. Namely, magnetic fluxes each created from the first permanent magnets1130′ or the second permanent magnets1230′ may be formed so that they are not superposed on one another in any of the pole pieces1110′a,1110′b,1210′aand1210′b. Further, each of the rail bolts1001′ penetrates a respective one of the first pole pieces1110′ and is fixed to a respective one of the third pole pieces1210′, thereby guiding the movement of the first pole piece assembly1100′.

The first pole pieces1110′aand1110′bmay be spaced apart from each other, and the third pole pieces1210′aand1210′bmay be spaced apart from each other, as shown inFIGS. 1E and 1F. However, they may be in contact with each other.

Further, the magnetic substance holding device1000according to this exemplary embodiment may further include means for further reducing residual magnetism. The means for further reducing residual magnetism will be described in detail below.

When the first pole piece assembly1100and the second pole piece assembly1200are in the second arrangement as shown in FIG.1A, residual magnetism is created in a such manner that a part of the magnetic flux flowing in the magnetic circuits (indicated by the dashed lines) comes out of the circuits to affect the workpiece1. Therefore, in order to eliminate residual magnetism, it is necessary to enhance the magnetic circuits as shown inFIG. 1Awhile making it difficult for magnetic fluxes to come out of the circuit.

Referring toFIGS. 1A to 1D, the area of the first faces of the four pole pieces1220may be smaller than the area of the second faces1122of the second pole pieces1120, and the area of the second faces1222of the fourth pole pieces1220may be smaller than the first faces1221of the fourth pole pieces1220. In other words, the thickness of the second pole pieces1120close to the second faces1122may be larger than the thickness of the four pole pieces1220close to the first faces1221, and the thickness of the fourth pole pieces1220close to the second face1222may be smaller than the thickness of the four pole pieces1220close to the first faces1221. With this configuration, the magnetic flux from the second permanent magnet1230is facilitated more toward the first faces1211and1221of the second pole piece assembly1200than toward the second faces1212and1222.

Namely, it is possible to eliminate residual magnetism by way of making it difficult to form magnetic fluxes toward the second faces1212and1222of the second pole piece assembly1200. It is to be understood that such features can be applied to other exemplary embodiments.

On the other hand, it is desirable to shape inner faces of the third pole piece1210and the fourth pole pieces1220to be straight, to facilitate magnetic fluxes between the second permanent magnets1230and the workpiece1so that attaching force can be enhanced.

Hereinafter, various exemplary embodiments of the present invention which are modifications of the structure shown inFIGS. 1A to 1Dwill be described.

FIG. 2is a schematic cross-sectional view of a magnetic substance holding device according to another exemplary embodiment of the present invention.

Referring toFIG. 2, the magnetic substance holding device2000includes a first pole piece assembly2100, a second pole piece assembly2200, coils2300, and a control device (not shown).

The first pole piece assembly2100, the second pole piece assembly2200and the coils2300are identical to the first pole piece assembly1100, the second pole piece assembly1200and the coils1300shown inFIGS. 1A to 1D; and, therefore, the redundant descriptions will be omitted. The magnetic substance holding device2000according to this exemplary embodiment is different from the magnetic substance holding device1000shown inFIGS. 1A to 1Din that the base1400has been eliminated and that a workpiece2can also be held on and detached from the first faces2111and2121of the first pole piece assembly2100.

The first pole piece assembly2100and the second pole piece assembly2200is movable so that they can be switched between the first arrangement in which they are spaced apart from each other and the second arrangement in which they come in contact with each other. The first pole piece assembly2100and the second pole piece assembly2200may move in various manners known in the art, such as by using bolts and counter-bores. When the first pole piece assembly2100and the second pole piece assembly2200are in the first arrangement, the workpieces1and2are detached from the device. When the first pole piece assembly2100and the second pole piece assembly2200are in the second arrangement, the workpieces1and2are held on two sides of the device.

FIGS. 3A to 3Care schematic cross-sectional views of a magnetic substance holding device according to yet another exemplary embodiment of the present invention.

Referring toFIGS. 3A to 3C, the magnetic substance holding device3000includes a first pole piece assembly3100, a second pole piece assembly3200, coils3300, a connection pole piece assembly3400, and a control device (not shown).

The first pole piece assembly3100, the second pole piece assembly3200and the coils3300are identical to the first pole piece assembly1100, the second pole piece assembly1200and the coils1300shown inFIGS. 1A to 1D; and, therefore, the redundant descriptions will be omitted.

The connection pole piece assembly3400includes at least one first connection pole piece3410, and at least two second connection pole pieces3420. The first connection pole piece3410is a magnetic substance and has a first face3411and a second face3412. Further, each of the second connection pole pieces3420is a magnetic substance and has a first face3421and a second face3422.

The connection pole piece assembly3400is arranged so that the second face3412of the first connection pole piece3410can come in contact with and be spaced apart from the first face3111of the first pole piece3110(i.e., they face each other) while the second face3422of each of the second connection pole pieces3420can come in contact with and be spaced apart from the first face3121of a respective one of the second pole pieces3120(i.e., they face each other).

At least one of the first pole piece assembly3100, the second pole piece assembly3200and the connection pole piece assembly3400are movable so that the first faces3111and3121of the first pole piece assembly3100come in contact with the second faces3412and3422of the connection pole piece assembly3400, respectively, for a first arrangement in which the first pole piece assembly3100is spaced apart from the second pole piece assembly3200(the arrangement shown inFIG. 3C), while the first faces3111and3121of the first pole piece assembly3100are spaced apart from the second faces3412and3422of the connection pole piece assembly3400, respectively, for a second arrangement in which the first pole piece assembly3100comes in contact with the second pole piece assembly3200(the arrangement shown inFIGS. 3A and 3B).

Referring toFIGS. 3A to 3C, rail bolts3001and3002are fixed to the first pole piece assembly3100and the connection pole piece assembly3400and penetrate the second pole piece assembly3200, so that the second pole piece assembly3200slides along the rail bolts3001and3002by magnetic force. Namely, the first pole piece3110may slide along the rail bolt3001in the axial direction, as the rail bolt3001is fixed to the connection pole piece assembly3400and to the third pole piece3210while penetrating the first pole piece3110. Further, the second pole pieces3120may slide along the rail bolts3002in the axial direction, as the rail bolts3002are fixed to the connection pole piece assembly3400and to the fourth pole pieces3220while penetrating the second pole pieces3120. On the other hand, the rail bolts3001and3002may be fixed to at least one of the first pole piece assembly3100, the second pole piece assembly3200and the connection pole pieces assembly3400, so that the others may slide along the rail bolts3001and3002.

Referring toFIG. 3A, when the first pole piece assembly3100and the second pole piece assembly3200are in the second arrangement, with no current applied to the coils3310and3320, a magnetic flux flows inside the magnetic circuit in the first pole piece assembly3100and the second pole piece assembly3200and does not pass through the first faces3111and3121of the first pole piece assembly3100and the second faces3212and3222of the second pole piece assembly3200, and thus workpieces cannot be held on neither upper side nor lower side of the device.

Then, when electric current in the direction indicated inFIG. 3Bis applied to the coils3310and3320, the magnetic flux between the first pole piece assembly3100and the second pole piece assembly3200is disconnected, and a magnetic flux passing through the second faces3212and3222of the second pole piece assembly3200becomes strong, so that the workpiece2can be held on the side close to the second pole piece assembly3200. On the contrary, since the first pole piece assembly3100is spaced apart from the connection pole piece assembly3400, a magnetic flux passing through the first faces3411and3421of the connection pole piece assembly3400is almost zero, and thus a workpiece can hardly be held on the first faces3411and3421of the connection pole piece assembly3400.

Thereafter, when the amplitude of the electric current applied to the coils3310and3320in the direction indicated inFIG. 3Brises above a predetermine value, the first pole piece assembly3100slides along the rail bolts3001and3002by magnetic force to be in contact with the connection pole piece assembly3400. As a result, the first pole piece assembly3100and the second pole piece assembly3200are in the first arrangement. When the first pole piece assembly3100is in the first arrangement as shown inFIG. 3C, magnetic fluxes from the first permanent magnets3130pass through the workpiece1, and thus the workpiece1can be held on the upper side as well.

Then, the magnetic fluxes once formed remain even if electric current is no more applied to the coils3310and3320, as indicated by the dashed lines inFIG. 3C. Accordingly, the workpiece1is held on the first faces3411and3421of the connection pole piece assembly3400while the workpiece2is held on the second faces3212and3222of the second pole piece assembly3200.

In order to detach the workpieces1and2from the first pole piece assembly3100and from the second pole piece assembly3200, respectively, by applying electric current in the opposite direction to that ofFIG. 3Bto the coils3310and3320so that the first pole piece assembly3100slides along the rail bolts3001and3002by magnetic force, the first pole piece assembly3100and the second pole piece assembly3200are placed in the second arrangement as shown inFIG. 3Ato thereby restore the magnetic flux shown inFIG. 3A.

The magnetic substance holding device3000according to this exemplary embodiment has an advantage in that it can hold workpieces1and2on both sides. In addition, at the time of detaching as shown inFIG. 3A, the connection pole piece assembly3400is spaced apart from the first pole piece assembly2100, and a magnetic flux flows only inside the magnetic circuit in the first pole piece assembly3100and the second pole piece assembly3200, leaving almost no residual magnetism.

In short, the control device adjusts electric current applied to the coils3310and3320to thereby control the direction and intensity of the magnetic fluxes passing through the coils3310and3320. By doing so, the first pole piece assembly3100, the second pole piece assembly3200and the connection pole piece assembly3400can be switched between the first arrangement and the second arrangement, and the direction and intensity of the magnetic fluxes passing through the first faces3111and3121of the first pole piece assembly3100and the second faces3211and3221of the second pole piece assembly3200can be controlled. As a result, the workpieces1and2, which are magnetic substances, can be held on and detached from the second faces3212and3222of the second pole piece assembly3200and the first faces3411and3421of the connection pole piece assembly3400.

Although not shown in the drawings, at least two first connection pole pieces1410′ may be disposed, like the first pole pieces1110′ or the third pole pieces1210′ shown inFIG. 2. By doing so, magnetic fluxes in the first connection pole pieces1410′ may not be superposed with each another. Namely, magnetic fluxes each created from the first permanent magnets1130′ or the second permanent magnets1230′ may be formed so that they are not superposed on one another in any of the first connection pole pieces1410′. The first connection pole pieces1410′ may be spaced apart from each other or may be in contact with each other.

FIGS. 4A to 4Dare a schematic perspective view and side cross-sectional views of a magnetic substance holding device according to another exemplary embodiment of the present invention; andFIGS. 5A and 5Bare schematic, side cross-sectional views of a magnetic substance holding device according to variants of the magnetic substance holding device shown inFIGS. 4A to 4D. Specifically,FIG. 4Ais a perspective view conceptually showing the magnetic substance holding device shown inFIGS. 4B to 4DandFIGS. 5A and 5B.FIGS. 4B(a),4C(a),4D(a),5A(a) and5B(a) are cross-sectional views taken along line A-A ofFIG. 4A.FIGS. 4B(b),4C(b),4D(b),5A(b) and5B(b) are cross-sectional views taken along line B-B ofFIG. 4A.FIGS. 4B(c),4C(c),4D(c),5A(c) and5B(c) are cross-sectional views taken along line C-C ofFIG. 4A.

Referring toFIGS. 4A to 4D, the magnetic substance holding device4000according to this exemplary embodiment includes a first pole piece assembly4100, a second pole piece assembly4200, coils4300, a connection pole piece assembly4400, and a control device (not shown).

The first pole piece assembly4100, the second pole piece assembly4200, the coils4310and4320the connection pole piece assembly4400are identical to the first pole piece assembly3100, the second pole piece assembly3200, the coils3310and3320and the connection pole piece assembly3400shown inFIGS. 3A to 3C; and, therefore, redundant descriptions thereon will be omitted. The feature of this exemplary embodiment lies in the locations of the first pole piece assembly4100, the second pole piece assembly4200and the connection pole piece assembly4300, which are different from the locations of the first pole piece assembly3100, the second pole piece assembly3200and the connection pole piece assembly3300shown inFIGS. 3A to 3C.

The first pole piece assembly4100, the second pole piece assembly4200and the connection pole piece assembly4400all are adapted to hold and detach a single workpiece1. In this exemplary embodiment, the first faces4411and4421of the connection pole piece assembly4400and the second faces4212and4222of the second pole piece assembly4200are configured to have a plane shape. However, they may have different shapes depending on the shape of the workpiece1.

Further, the first pole piece assembly4100is movable along a plane extended from the second faces4212and4222of the second pole piece assembly4200and the first faces4411and4421of the connection pole piece assembly4400. In other words, the first pole piece assembly4100is movable in the horizontal direction.

The second faces4212and4222of the second pole pieces assembly4200may be perpendicular to the first faces4211and4221of the second pole piece assembly4200. Further, the first faces4411and4421of the connection pole piece assembly4400may be perpendicular to the second faces4412and4422of the connection pole pieces assembly4400. As shown inFIGS. 4A to 4D, the second faces4412and4422of the connection pole piece assembly4400face the first faces4211and4221of the second pole piece assembly4200, respectively, with the first pole piece assembly4100therebetween.

Referring toFIG. 4B, when the first pole piece assembly4100and the second pole piece assembly4200are in the second arrangement in which they are in contact with each other, with no electric current applied from the control device to the coils4310and4320, a magnetic flux flows inside the magnetic circuit through the second faces1112and1122of the first pole piece assembly1100and the first faces1211and1221of the second pole piece assembly1200, as indicated by the dashed lines shown inFIGS. 4B(b) and4B(c). Therefore, in the arrangement shown inFIG. 4B, a workpiece is held neither on the first faces4411and4421of the connection pole piece assembly4400nor on the second faces4212and4222of the second pole piece assembly4200.

On the other hand, when the control device applies electric current to the coils4310and4320as shown inFIG. 4C, the magnetic fluxes passing through the second faces4112and4122of the first pole piece assembly4100and the first faces4211and4221of the second pole piece assembly4200are disconnected, and magnetic fluxes passing through the second faces4212and4222of the second pole piece assembly4200become strong, so that the workpiece1can be held on the side close to the second pole piece assembly4200. On the contrary, since the first pole piece assembly4100is spaced apart from the connection pole piece assembly4400, magnetic fluxes passing through the first faces4411and4421of the connection pole piece assembly4400are almost zero, and thus a workpiece can hardly be held on the first faces4411and4421of the connection pole piece assembly4400.

Thereafter, when the amplitude of the electric current applied to the coils3310and3320in the direction indicated inFIG. 4Crises above a predetermine value, the first pole piece assembly4100moves along the rail bolts4001and4002by magnetic force to be in contact with the connection pole piece assembly4400. As a result, the first pole piece assembly4100, the second pole piece assembly4200and the connection pole piece assembly are in the first arrangement. When the first pole piece assembly4100is in the first arrangement as shown inFIG. 4D, magnetic fluxes from the first permanent magnets4130pass through the workpiece1, and thus the workpiece1can be held on the first faces4411and4421of the connection pole piece assembly4400as well.

Then, the magnetic fluxes once formed remain even if electric current is no more applied to the coils4310and4320, as indicated by the dashed lines inFIG. 4D. Accordingly, the workpiece1is held on the second faces4212and4222of the second pole piece assembly4200and the first faces4411and4421of the connection pole piece assembly4400.

The magnetic substance holding device4000according to this exemplary embodiment has an advantage in that it can hold workpieces1and2on both sides. In addition, at the time of detaching as shown inFIG. 4B, the connection pole piece assembly4400is spaced apart from the first pole piece assembly4100, and a magnetic flux flows only inside the magnetic circuit in the first pole piece assembly4100and the second pole piece assembly4200, leaving almost no residual magnetism.

In addition, the magnetic substance holding device4000according to the present invention may be modified to have stronger holding force by disposing multiple permanent magnets4130and4230on one another.

Referring toFIG. 5A, at least two first permanent magnets4130′ may be disposed between the first pole piece4110′ and each of the second pole pieces4120′, and at least two permanent magnets4230′ may be disposed between the third pole piece4210′ and each of the fourth pole pieces4220′.

The first permanent magnets4130′ in contact with the respective second pole pieces4120′ are disposed such that their the poles of the same polarity are in contact with the same pole piece(s) (the first pole piece4110′ or the second pole pieces4120′). The first permanent magnets4130′ in contact with the respective second pole pieces4120′ may be disposed on one another so that they can generate a strong magnetic flux as if they were a single permanent magnet.

Further, the second permanent magnets4230′ in contact with respective the fourth pole pieces4220′ are disposed such that their poles of the same polarity are in contact with the same pole piece(s) (the third pole piece4210′ or the fourth pole pieces4220′). Further, the second permanent magnets4230′ in contact with the respective fourth pole pieces4220′ may be disposed on one another.

The permanent magnets4130′ and4230′ with their poles of the same polarity in contact with the same pole pieces may be disposed in a quadrangular shape as shown inFIG. 5Aor may be disposed in a line as shown inFIG. 5B. The numbers and layouts of the permanent magnets4130′,4230′,4130″ and4230″ are not limited to those shown inFIGS. 5A and 5B, but may vary depending on design choices.

As described above, the magnetic substance holding devices4000′ and4000″ according to the variants may have more permanent magnets4130′,4230′,4130′ and4230′ per volume, so that holding force can be increased.

According to the magnetic substance holding devices (1000to4000) of the present invention, residual magnetism can be minimized when a workpiece is detached. In addition, by disposing coils around pole pieces instead of an additional electromagnet, strong holding force can be obtained in a simple structure, magnetic force from a permanent magnet can be controlled with small electric current at the time of switching between holding and detaching, and strong holding force can be obtained in a smaller space.

Thus far, exemplary embodiments of the present invention have been described in detail with reference to the accompanying drawings. However, the present invention is not limited to the exemplary embodiments, and modifications and variations can be made thereto without departing from the technical idea of the present invention. Accordingly, the exemplary embodiments described herein are merely illustrative and are not intended to limit the scope of the present invention. The technical idea of the present invention is not limited by the exemplary embodiments. Therefore, it should be understood that the above-described embodiments are not limiting but illustrative in all aspects. The scope of protection sought by the present invention is defined by the appended claims and all equivalents thereof are construed to be within the true scope of the present invention.