Patent Description:
In recent years, an electric permanent magnetic chuck is used by more and more enterprises. Reversible magnetic material with a reversible polarity is disposed in the electric permanent magnetic chuck. A magnetic pole of the reversible magnetic material may be changed under the control of an external circuit, so as to switch to a working state or a non-working state. In the non-working state, an internal balance is achieved between a magnetic field generated by the reversible magnetic material and a magnetic field generated by permanent magnetic material in the electric permanent magnetic chuck, and thus there is no magnetic field acting on the exterior. In the working state, the magnetic field generated by the reversible magnetic material and the magnetic field generated by the permanent magnetic material are overlapped one another to jointly form magnetic field acting on the exterior, to absorb a material.

In a conventional art, referring to <FIG> is a structural schematic diagram of an electric permanent magnetic chuck in the conventional art.

The chuck includes a housing, a permanent magnetic material, a reversible magnetic material, a pressure plate, and a screw. In the conventional art, it is required to arrange a groove for placing the permanent magnetic material on a side close to an absorbed material in the housing. In order to ensure the magnetic field generated by the whole electric permanent magnetic chuck in the working state to the outside as high as possible, a distance from a bottom of the groove to an outer surface of the housing is required to be very small. As a result, a machining process is very difficult, and the occurrence of an inferior-quality product is frequent. Meanwhile, when the housing is machined subsequently, it is also required to form an inner cavity for placing the reversible magnetic material and the inner cavity for placing a cover plate by cutting. Generally, cross sections of the above-mentioned inner cavities are different in size, and the housing often further needs to be provided with a passage for placing a wire of an excitation coil, which results in that a difficulty in the machining process is very large, a structure of the housing is complex, and a corresponding machining manner is also complex.

The document <CIT> forms the basis for the preamble of claim <NUM> and discloses a one-piece multipole plate for a magnetic holding apparatus. In particular, the document discloses a magnetic holding apparatus for holding ferrous workpieces, comprising: a frame, a plurality of pole pieces each of said which having a ferromagnetic pole member which defines the holding surface part, a reversible magnet, a solenoid located around the reversible magnet and a plate, said plurality of pole pieces extend from said plate and are formed of one piece with said plate, the frame is adapted to contain the plurality of pole pieces laterally and from below and that a through hole for a fastener device extends through the thickness of the pole pieces and part of the thickness of the portion of said frame that acts as a base for the magnetic holding apparatus.

A technical problem to be solved by the invention is to overcome shortages and defects mentioned in the background and to provide an electric permanent magnetic chuck with a simple structure, a small machining difficulty, a good sealing property and a small magnetic loss.

In order to solve the above-mentioned technical problem, the invention provides the following technical solutions, which is set out in the appended set of claims.

An electric permanent magnetic chuck includes a housing in which at least one opened inner cavity is provided. A reversible magnetic material is disposed on a lower portion of the inner cavity. A coil is disposed in the inner cavity and arranged along an outer wall of the reversible magnetic material. A magnetic pole is superimposed and fixed in the inner cavity. An annular groove is provided on a lower surface of the magnetic pole, and permanent magnetic material matching the annular groove is disposed in the annular groove, the magnetic pole is disposed on the reversible magnetic steel, the housing includes an outer shell and a bottom plate, the inner cavity penetrates through the outer shell, the bottom plate is fixedly connected to a lower surface of the outer shell, the magnetic pole is of a barrel-shape, the annular groove is provided on a bottom surface of the barrel-shaped magnetic pole, and a barrel wall of the magnetic pole arranged around the reversible magnetic steel and the coil.

A further improvement of the above-mentioned technical solution may be implemented as following examples.

In one example, the inner cavity does not penetrate through the lower portion of the housing, the coil is fixedly connected to an inner wall of the inner cavity, and the magnetic pole is disposed on the reversible magnetic material.

In one example, the magnetic pole is embedded into the inner cavity of the housing and fixedly connected to an inner wall of the housing, the coil is disposed on a bottom of the inner cavity. The permanent magnetic material is connected to the bottom of the annular groove at a junction by laser welding using a magnetic impermeable material.

In one example, the magnetic pole is embedded into an inner cavity of the housing and fixedly connected to an inner wall of the housing, the coil is disposed on a bottom of the inner cavity. The permanent magnetic material is connected to the bottom of the annular groove at a junction by using a material same as the magnetic pole.

In one example, the magnetic pole is disposed on the reversible magnetic material, the coil is fixedly connected to the inner wall of the inner cavity, the housing includes an outer shell and a bottom plate, the inner cavity penetrates through the outer shell, and the bottom plate is fixedly connected to a lower surface of the outer shell.

In one example, a sealing ring is disposed between the magnetic pole and the annular table.

In one example, the housing is provided with a first threaded hole penetrating through the housing in a vertical direction. The reversible magnetic material is provided with a threaded hole which penetrates through the reversible magnetic material in the vertical direction and cooperates with the first threaded hole of the housing. The magnetic pole is provided with a threaded hole cooperated with the threaded hole of the reversible magnetic material, to fixedly connect the housing, the reversible magnetic material and the magnetic pole to one another by a screw.

In one example, the bottom plate is provided with a first threaded hole and a second threaded hole which penetrate through the bottom plate in a vertical direction. The outer shell is provided with a threaded hole cooperated with the second threaded hole, to fixedly connect the outer shell with the bottom plate by a connecting bolt. The reversible magnetic material is provided with a threaded hole penetrating through the reversible magnetic material in the vertical direction and cooperated with the first threaded hole of the housing. The magnetic pole is provided with a threaded hole cooperated with the threaded hole of the reversible magnetic material, to fixedly connect the housing, the reversible magnetic material and the magnetic pole to one another by a screw.

In one example, the permanent magnetic material is connected to the bottom of the annular groove of the magnetic pole at a junction by a magnetic permeable material or by laser welding using the magnetic impermeable material.

In one example, the housing comprises multiple inner cavities uniformly distributed in the housing, and the multiple inner cavities are distributed in a checkerboard pattern.

In one example, polarities of the reversible magnetic material in any two adjacent inner cavities are different on a same side, and the polarities of the permanent magnetic material in any two corresponding adjacent inner cavities are different on a same side.

In one example, a wiring hole is provided in the housing, and a metal plug is disposed at the wiring hole.

In one example, a wire passing hole in communication with the multiple inner cavities is provided in the housing.

In one example, a border of a barrel edge of the magnetic pole is folded outwards.

Compared with the conventional art, the invention has the following beneficial effects.

According to an electric permanent magnetic chuck provided by the invention, a housing is separated from a magnetic pole portion provided with a permanent magnet, an inner cavity opened from an end surface is provided on the housing, and the magnetic pole portion is detachably mounted in the inner cavity of the housing, so that a traditional housing and magnetic pole integrated machining manner is replaced, the complexity of an internal structure of the housing is greatly reduced, the machining difficulty is lowered, the machining precision is improved, the rejection rate is lowered, and lots of manpower, materials and resources are saved; and meanwhile, an air gap of the housing of the electric permanent magnetic chuck provided by the invention is small, so that the magnetic loss is not generated easily, and the clamping effect is more excellent.

In order to describe the technical solutions in the embodiments of the invention or in the conventional art more clearly, a simple introduction on the accompanying drawings which are needed in the description of the embodiments or conventional art is given below. Apparently, the accompanying drawings in the description below are merely some of the embodiments of the invention, based on which other drawings may be obtained by those of ordinary skill in the art without any creative effort.

List of reference symbols: <NUM>. housing, <NUM>. outer shell, <NUM>. first threaded hole, <NUM>. second threaded hole, <NUM>. bottom plate, <NUM>. wiring hole, <NUM>. metal plug, <NUM>. wire passing hole, <NUM>. reversible magnetic material, <NUM>. coil, <NUM>. magnetic pole, and <NUM>. permanent magnetic material.

In order to facilitate understanding of the invention, a more complete and detailed description is made to the invention below in combination with the accompanying drawings and preferred embodiments of the specification. However, a protection scope of the invention is not limited to the following specific embodiments.

The following embodiments <NUM>, <NUM>, <NUM> and <NUM> are not according to the invention and are present for illustration purpose only.

As shown in <FIG>, an electric permanent magnetic chuck in this embodiment includes a housing <NUM>. The housing <NUM> includes an inner cavity which does not penetrate through a lower portion of the housing <NUM>. Reversible magnetic material <NUM> is disposed on a lower portion of the inner cavity. A coil <NUM> is disposed along an outer wall of the reversible magnetic material <NUM>. The coil <NUM> is fixedly connected to an inner wall of the inner cavity. A skeleton for supporting the coil <NUM> is further disposed out of the coil <NUM>, so that it is assured that the coil has a stable structure. A magnetic pole <NUM> fixedly connected to the inner wall of the inner cavity is disposed on the reversible magnetic material <NUM>. An annular groove is provided on a lower surface of the magnetic pole <NUM>. Permanent magnetic material <NUM> matching the annular groove is disposed in the annular groove. According to the electric permanent magnetic chuck in this embodiment, a housing <NUM> is separated from a magnetic pole <NUM> portion provided with permanent magnetic material <NUM>, and only an inner cavity opened at one end surface and not penetrating through the other end surface needs to be provided on the housing <NUM>. Since a problem for placing the annular permanent magnetic material <NUM> does not need to be considered, a structure of the housing <NUM> is greatly simplified, and the housing <NUM> is machined more easily. The magnetic pole <NUM> only needs to be provided with an annular groove for placing the permanent magnetic material <NUM>, so the structure is also very simple. Such a structure replaces a traditional magnetic pole <NUM> and housing <NUM> integrated machining manner, so that the machining difficulty is greatly reduced, the machining precision is improved, the rejection rate is lowered, and lots of manpower, materials and resources are saved; and without an air gap for disposing a cover plate, the air gap on the housing <NUM> of the electric permanent magnetic chuck is smaller, the magnetic loss is not produced easily and the clamping effect is more excellent.

As shown in <FIG>, in order to guarantee that a magnetic field to the outside is as strong as possible, a junction between the permanent magnetic material <NUM> and a bottom of the annular groove is required to be as thin as possible. In this embodiment, the permanent magnetic material <NUM> is connected to the bottom of the annular groove at the junction by using a material same as the magnetic pole <NUM>. Compared with a previous manner where a copper material serves as the bottom of the annular groove, a magnetic permeable layer having the material same as the magnetic pole <NUM> is machined integrally in machining, thus being more convenient. Moreover, a stress in case of an external force and a temperature change is closer to the magnetic pole <NUM>, so that a condition such as cracking and water ingress caused by misposition is prevented, and a sealing property is better.

In this embodiment, as shown in <FIG>, in order to machine conveniently and in order that a generated magnetic field is a uniform magnetic field, the permanent magnetic material <NUM> is of a circular structure, and the corresponding annular groove is a circular groove. In other embodiments, the permanent magnetic material <NUM> and the annular groove may also be of other shapes, which is not defined herein.

In this embodiment, a place between the permanent magnetic material <NUM> and a lower surface of the magnetic pole <NUM>, namely, an opening place of the annular groove, is sealed by an epoxy resin. Herein, the epoxy resin does not contact with an external working environment, so that the sealing failure caused by aging is not accelerated. In other embodiments, this place may also be sealed in other manners or not sealed, which is not defined specifically herein.

In this embodiment, a cross section of the inner cavity is of a circular shape, the inner cavity includes a first inner cavity and a second inner cavity, the cross section of the second inner cavity is greater than that of the first inner cavity, the first inner cavity is provided with the reversible magnetic material <NUM>, the coil <NUM> is disposed along the outer wall of the reversible magnetic material <NUM>, and the coil <NUM> is fixedly connected to an inner wall of the first inner cavity. The second inner cavity is provided with the magnetic pole <NUM> fixedly connected to an inner wall of the second inner cavity. An upward annular table for supporting the magnetic pole <NUM> is disposed on an upper surface of the first inner cavity, to limit an axial movement of the magnetic pole, and stabilize a fixing position of the magnetic pole <NUM>, so that the sealing property between the magnetic pole <NUM> and the housing <NUM> is further improved. A sealing ring is provided between the magnetic pole <NUM> and the annular table, and a groove having a shape corresponding to the sealing ring is provided on the magnetic pole <NUM> and the annular table, so that the overall sealing property of the electric permanent magnetic chuck is enhanced. In addition, the sealing ring may further be placed on an axial direction and a radial direction.

In this embodiment, the housing <NUM> includes multiple inner cavities, the multiple inner cavities are distributed in a chessboard manner, polarities of the reversible magnetic material <NUM> in any two adjacent inner cavities on a same side are different, and the polarities of the permanent magnetic material <NUM> in any two corresponding adjacent inner cavities on the same side are different. When a workpiece is not absorbed, the electric permanent magnetic chuck exhibits to be non-magnetic to the outside, and a magnetic circuit at this time is as shown in <FIG>. When the workpiece is absorbed, the electric permanent magnetic chuck exhibits to be magnetic to the outside, and the magnetic circuit at this time is as shown in <FIG>. Four adjacent inner cavities are around each inner cavity in this embodiment. In other embodiments, the number of adj acent inner cavities around each inner cavity may be different, which is not defined specifically herein.

In this embodiment, a wiring hole <NUM> is provided in the housing <NUM>, a metal plug <NUM> is disposed at an opening place of the wiring hole <NUM>, and a lead wire for communicating with an external power supply and the coil <NUM> passes through the wiring hole <NUM>, and configured to supply power to the coil <NUM>. By virtue of the wiring hole <NUM>, the coil <NUM> in each accommodation hole can communicate, so that a purpose of controlling the coil <NUM> in each accommodation hole by one electrical signal is achieved. The metal plug <NUM> is disposed at the opening place of the wiring hole <NUM>, so that a cavity generated by the wiring hole <NUM> in the housing <NUM> is prevented from affecting the permeability.

In this embodiment, the housing <NUM> is provided with a first threaded hole <NUM> penetrating through the housing <NUM> in a vertical direction; the reversible magnetic material <NUM> is provided with a threaded hole penetrating through the reversible magnetic material <NUM> in the vertical direction and cooperated with the first threaded hole <NUM> of the housing <NUM>; and the magnetic pole <NUM> is provided with a threaded hole cooperated with the threaded hole of the reversible magnetic material <NUM> , to fixedly connect the housing <NUM>, the reversible magnetic material <NUM> and the magnetic pole <NUM> to one another by a screw. By virtue of screwed connection, the whole electric permanent magnetic chuck is firmer, and a component is not fallen off easily.

In this embodiment, the housing <NUM> is generally made of Q245 material or <NUM># material. Such type of material is a soft magnetic material with good permeability, and excellent wear resistance and corrosion resistance. The magnetic pole <NUM> is often made of a material same as the housing <NUM>. The reversible magnetic material <NUM> is often aluminum-nickel-cobalt magnetic material, and the polarity may change by an external circuit. The coil <NUM> is connected to the inner wall of the inner cavity in a glue filling manner. The permanent magnetic material <NUM> often uses rubidium-iron-boron magnetic material, and configured to generate a stable unchanged magnetic field. The above materials and connection manners may change in other embodiments, and are not defined specifically herein.

This embodiment is basically the same as the embodiment <NUM> and a difference lies in: as shown in <FIG>, in this embodiment, permanent magnetic material <NUM> is connected to a bottom of an annular groove at the junction by laser welding using a magnetic impermeable material. An insulation layer does not cause a magnetic loss, and a laser welding manner may take a good sealing effect. The magnetic impermeable material uses stainless material. In other embodiments, other materials may also be used, which is not defined specifically herein.

This embodiment is basically the same as the embodiment <NUM> and the embodiment <NUM>, and the difference lies in: as shown in <FIG> and <FIG>, when the permanent magnetic material <NUM> in two adjacent accommodation holes is arranged on a same direction, the coils <NUM> in the two accommodation holes after being powered on are on the same direction with the reversible magnetic material <NUM>. When a workpiece is not absorbed, the electric permanent magnetic chuck exhibits to be non-magnetic to the outside, and a magnetic circuit at this time is as shown in <FIG>. When the workpiece is absorbed, the electric permanent magnetic chuck exhibits to be magnetic to the outside, and the magnetic circuit at this time is as shown in <FIG>.

This embodiment is basically the same as the embodiment <NUM>, the embodiment <NUM> and the embodiment <NUM>, and the difference lies in: as shown in <FIG>, in this embodiment, the housing1 includes an outer shell <NUM> and a bottom plate <NUM>; the inner cavity penetrates through the outer shell <NUM>; and the bottom plate <NUM> is fixedly connected to a lower surface of the outer shell <NUM>. That is, the housing <NUM> is further split, and only drilling a through hole on the outer shell <NUM> may form the inner cavity, so that the machining process is simple, the structure of the housing <NUM> is more simplified, the machining difficulty is further lowered, and the manpower, materials and time are saved better.

In this embodiment, the bottom plate <NUM> is provided with a second threaded hole <NUM> and a first threaded hole <NUM> penetrating through the bottom plate <NUM> in a vertical direction; and the housing <NUM> is provided with a threaded hole cooperated with the second threaded hole <NUM>, to fixedly connect the outer shell <NUM> with the bottom plate <NUM> by a connecting bolt.

This embodiment is basically the same as the embodiment <NUM>, and the difference lies in: as shown in <FIG>, in this embodiment, the magnetic pole <NUM> is of a barrel-shape, the annular groove is provided on a bottom surface of the barrel-shaped magnetic pole <NUM>, and a barrel wall of the magnetic pole <NUM> is arranged around the reversible magnetic material <NUM> and the coil <NUM>, so that the contact of the reversible magnetic material <NUM> with the coil <NUM> and the magnetic pole <NUM> is closer. A border of a barrel edge of the magnetic pole <NUM> is folded outwards, so the clamping with the outer shell <NUM> can be better. A wire passing hole <NUM> in communication with the multiple inner cavities is provided in the housing <NUM>, which results in that the coil <NUM> in each accommodation hole can communicate, and a purpose of controlling the coil <NUM> in each accommodation hole by one electrical signal is achieved.

Claim 1:
An electric permanent magnetic chuck, comprising a housing (<NUM>), wherein the housing (<NUM>) is provided with at least one opened inner cavity, a reversible magnetic material (<NUM>) is disposed on a lower portion of the inner cavity, a coil (<NUM>) is disposed in the inner cavity and arranged along an outer wall of the reversible magnetic material (<NUM>), a magnetic pole (<NUM>) is superimposed and fixed in the inner cavity, an annular groove is provided on a lower surface of the magnetic pole (<NUM>), and a permanent magnetic material (<NUM>) matching the annular groove is disposed in the annular groove, wherein the magnetic pole (<NUM>) is disposed on the reversible magnetic material (<NUM>), characterized in that: the housing (<NUM>) comprises an outer shell (<NUM>) and a bottom plate (<NUM>), the inner cavity penetrates through the outer shell (<NUM>), the bottom plate (<NUM>) is fixedly connected to a lower surface of the outer shell (<NUM>), the magnetic pole (<NUM>) is of a barrel-shape, the annular groove is provided on a bottom surface of the barrel-shaped magnetic pole (<NUM>), and a barrel wall of the magnetic pole (<NUM>) is arranged around the reversible magnetic material (<NUM>) and the coil (<NUM>).