WO2004099807A1

WO2004099807A1 - The assembling method and conveying tool for magnetic device

Info

Publication number: WO2004099807A1
Application number: PCT/EP2004/004988
Authority: WO
Inventors: Cheng Ni; Ting Qiang Xue
Original assignee: Siemens Aktiengesellschaft
Priority date: 2003-05-09
Filing date: 2004-05-10
Publication date: 2004-11-18
Also published as: CN1548980A; CN100504429C

Abstract

This invention relates to an assembling method and tool of permanent magnetic column in a permanent magnetic field generating device which is used to manufacture magnetic resonance imaging equipment's, includes following steps: conveying a permanent magnetic column into the space between surfaces of a pole plate through an extension plate which is mounted on the peripheral of the pole plate; coating glue or beforehand coating glue on at least one side surface of the above permanent magnetic column; fixing the above permanent magnetic column on the permanent magnetic columns which have been mounted on the pole plate previously to form a whole; repeating the above steps until assembling the permanent magnetic field generating device is complete. The advantages of this method are the permanent magnetic column is moved much more easily and laborsaving even if it is near the edge of the pole plate. The extension plate augments the assembling work surface of the permanent magnetic column, so it becomes convenient for the assembling operation. This invention also relates to a conveying tool of the permanent magnetic column.

Description

THE ASSEMBLING METHOD AND CONVEYING TOOL FOR MAGNETIC DEVICE

The Assembling Method of and the Tool for Conveying the Permanent Magnetic Material in the Permanent Magnetic Field Generating Device

(1) Technical field

The present invention relates to the assembling method and the tool for conveying the permanent magnetic material in the making of permanent magnetic field generating device, and particularly to the assembling method of the permanent magnetic field generating device in a magnetic resonance imaging/Nuclear Magnetic Resonance (MRI/NMR) equipment and the tool used therein, and to assembling permanent magnetic column on the pole plate during the manufacturing process of the magnetic resonance imaging equipment.

(2) Background Art

Magnetic field is widely used in measuring and imaging techniques, for example, the permanent magnetic field generated by using permanent magnet material in various types of magnetic resonance imaging apparatus. Take an open C-shaped permanent magnet of MRI/NMR equipment of as an example, its main mechanical structure is shown in Fig. 1. An open C-type MRI/NMR equipment comprises a C-shaped yoke 1 using as the magnetic conducting path; the upper press plate 2 and the lower press plate 21 are respectively mounted on the top and bottom ends of the opening of the C-shaped yoke, the upper pole plate 3 and the lower pole plate 31 are respectively located in the opening of the C-shaped yoke and are arranged opposite to each other; an upper gradient coil plate 11 and a lower gradient coil plate 111 are provided respectively opposite to the surface of the upper pole plate 3 and the surface of the lower pole plate 31, the Rose Rings 4 and 41 are respectively mounted around the edges of the upper pole plate 3 and the lower pole plate 31; the magnetic field generating source 10 is provided between the upper press plate 2 and the upper pole plate 3 and in the space within the lower press plate 21 and the lower pole plate 31. The above magnetic field generating source is formed by adhering multiple numbers of permanent magnets 5.

The above magnetic field generating device is an important component of the magnetic resonance imaging equipment. The magnetic field generating sources 10 are provided between the pole plate and press plate at the opening of the open type magnetic resonance imaging equipment corresponding to each other, so as to generate a magnetic field of up to 0.5 Tesla for the magnetic resonance of the whole human body or to generate a magnetic field of up to 1 Tesla for the magnetic resonance diagnosis on parts of the human body or on animals and for the magnetic resonance or nuclear magnetic resonance for industrial purpose or for other applications of the magnetic field generated by permanent magnet materials. The above magnetic generating device is formed by adhering multiple numbers of permanent magnet columns. Usually, there are two methods of forming permanent magnet columns, i.e., magnetizing after assembling in the pole and assembling in the pole after magnetizing. When assembling after magnetizing is adopted, the permanent magnet columns are formed by superposing a plurality of magnetized magnetic columns and the magnetic columns are bound with glue to form a whole. Comparatively, magnetizing the whole pole after assembling needs a magnetizer of large power, while for assembling after mag- netizing, since the sizes of the magnetic blocks are relatively small, magnetizer of large power is not required. In addition, in the method of magnetizing after assembling, permanent magnet of large size could be adopted theoretically to save the time for assembling, but since it is difficult for permanent magnets of large size to have uniform magnetic properties and mechanical properties, permanent magnet columns of small size are usually adopted in the method of magnetizing after assembling, and thereby the advantages of the method of magnetizing after assembling are limited.

In the method of assembling after magnetizing, when the per- manent magnetic column 5 is set to between the pole plate and the press plate, it will be affected by the strong magnetic force because the magnetic conductivity of the pole/press plate or ferromagnetic C-shaped yoke is far greater than the air, and thus the permanent magnet column will be attracted to fly to the pole/press plate or the C-yoke by the strong magnetic field. When a certain number of permanent magnet columns have been assembled between the pole plate and the press plate, the permanent magnet column will be forced out from the pole plate under the effect of the strong magnetic repelling force due to the reason that two magnets with the same polarity repel each other, or the permanent magnetic column will rotate and turn upside down under the effect of the repelling force. All these processes will cause collision between the permanent magnetic column and the pole plate, between the magnetic blocks of the permanent magnetic column and between the permanent magnetic column and the yoke. Since the permanent magnetic material, for example, NdFeB, of the permanent magnetic column is hard and brittle, the edges and corners of the permanent magnetic column will easily be damaged after collision and thus result in a non-uniform magnetic field and thereby affect the quality of the images. Therefore, the damaged permanent magnet column needs to be replaced frequently.

In order to solve the above problem, the technology of magnetizing the whole pole after assembling has been employed by- Oxford Magnet Technology (OMT) , wherein the non-magnetized permanent magnetic columns are fixed to the predetermined position on the pole plate, and the whole pole is magnetized after assembling by superconducting technology. Since there is no magnetic field during the assembling, the permanent magnetic material column is not affected by magnetic force, thus the assembling becomes easier and the permanent magnetic material column is not liable to be damaged, but the disadvantage thereof is that superconducting magnetizing is very- expensive .

EP 0 978 727 A2 disclosed another method, wherein a predetermined number of permanent magnetic columns that have been magnetized are assembled on the pole plate or the press plate before the pole plate or press plate is mounted to the yoke, and then the pole plate is assembled onto the yoke. The advantage of such method is that no magnetic path is formed since the yoke and the pole/press plates are not yet in the corresponding positions, and therefore, the magnetic force on the permanent magnetic columns is relatively weaker and thereby it is relatively easier to some extend for the mounting of the permanent magnetic columns. However, when the permanent magnetic columns have already been mounted on the pole plate, the mounting of the pole plate to the yoke will be under extremely strong attraction force and the permanent magnetic columns will fly to collide the press plate or pole plate .

Another method is to mount the magnetized permanent magnetic columns one by one after assembling the pole plate, the press plate and the yoke, but the disadvantage thereof is that it is difficult to move and mount magnetized magnetic column on the pole plate due to the effect of the strong magnetic force, and it is especially difficult to mount and position the permanent magnetic columns around the edge of the pole plate or near the yoke side. Although a majority of manufacturers tend to employ permanent magnetic column mounting methods similar to this one, the problem is that the permanent magnetic column is difficult to be mounted under the existence of magnetic force, especially around the edge of the pole plate. Therefore, people are always expecting a new mounting method that could overcome the above defects. (3) Contents of the invention

The object of the present invention is to provide a method of assembling the permanent magnetic material in the permanent magnetic field generating device for the use of manufacturing, for example, magnetic resonance equipment. The above method is easy to operate and have a low cost and could greatly improve the situation in the prior art that the permanent magnetic columns are difficult to be assembled due to the effect of the magnetic force.

Another object of the present invention is to provide a tool of assembling the permanent magnetic material in the permanent magnetic field generating device that has a simple structure and could accurately convey the permanent magnetic column onto the pole plate.

One object of the present invention is achieved by the method of claim 1, i.e., an assembling method of permanent magnetic material in a permanent magnetic field generating device for manufacturing equipment with permanent magnetic field generating device includes the following steps: (1) conveying step: conveying a permanent magnet column into the space between surfaces of the above pole plate and the above press plate through an extension plate which is mounted on the peripheral of the press plate and the pole plate respectively; (2) coating glue step: coating glue or beforehand coating glue on at least one side surface of the above permanent magnetic column; (3) fixing step: fixing the above permanent magnetic column on the permanent magnetic columns which have been mounted on the pole plate previously to form a whole; (4) repeating the steps from (1) to (3) until assembling the permanent magnetic field generating device is complete.

According to one aspect of the present invention, the extension plate mounted in the above conveying step is made of ferromagnetic material, and the extension plate is re-movably mounted on the peripheral of the above pole plate, and the mechanical fixing methods like stud, dowel, and clamps, etc. are employed. The surface of the extension plate and the surface of the above pole plate together form a magnetic conducting surface. Since the surface of the extension plate forms an extension of the magnetic conducting surface of the pole plate, the permanent magnetic column could be smoothly- slid from the surface of the extension plate to the surface of the above pole plate.

According to another aspect of the present invention, in the above conveying step, the above extension plate extends from partial peripheral of the above pole plate, or from whole peripheral of the above pole plate, thus the permanent mag- netic column could enter the surface of the pole plate from all directions. When it reaches the predetermined position, the above permanent magnetic column is adhered to the previously mounted permanent magnetic column with their side surfaces opposite to each other in the fixing step.

According to another aspect of the present invention, in the above conveying step, the extension plate is re-movably mounted on the peripheral of the above press plate, and the mechanical fixing methods like stud, dowel, and clamps, etc. are employed. The surface of the extension plate and the surface of the above press plate together form a magnetic conducting surface. Since the surface of the extension plate forms the extension of the magnetic conducting surface of the press plate, the permanent magnetic column could be smoothly slid from the surface of the extension plate to the space between the above pole plate and the above press plate. The above extension plate extends from partial or whole peripheral of the above press plate, and the extension plate is at least partially confronting another extension plate on the peripheral of the above pole plate. According to another aspect of the present invention, in the conveying step, the above extension plate is made up of several separated components. For example, the above extension plate is assembled by four separate components, and after assembly, the shape of outer peripheral of the extension plate appears square, rectangular, polygonal or arc and the shape of the inner peripheral of it corresponds to the peripheral shape of the above press plate and /or the above pole plate .

Another object of the present invention is achieved by the solution of claim 9, i.e., a conveying tool of permanent magnetic material, for carrying out the assembling method described in any of claims 1 to 8 , including: a tunnel for guiding the above permanent magnetic columns, whose output port is re-movably mounted on the extension plate; and a feeder having a holder that drives the above permanent magnetic column forward inside the above tunnel.

According to one aspect of the conveying tool of the present invention, there is a flange and a guide accessory on the output port of the tunnel, the shape and size of the cross section of the inner cavity of the tunnel are basically the same as that of the above permanent magnetic column to be conveyed, one end of the tunnel could be fixed on the extension plate by means of stud, clamps, pins or other mechanic means.

According to another aspect of the conveying tool of the present invention, the above feeder has a screw rod that is rotatablely mounted at one of its ends on the holder and fixed at its another end with a crank, and a nut is mounted on the flange of the tunnel by means of a cover plate. The above holder contains the permanent magnetic column and could be slid within the tunnel and the permanent magnetic column could be sent to the predetermined position by rotating the above crank. As one of the substitute solutions, the above feeder could also be replaced by a hydraulic pressure cylinder and there is a holder on the end of its holder rod.

By using an extension plate in the present invention, in the assembling process of the permanent magnetic field generating device, the force status of the permanent magnetic column is temporarily changed so that the permanent magnetic column could be conveniently moved to any position on the pole plate or the press plate. The magnetic force acting upon the perma- nent magnetic column is magnificently reduced, especially near the edge of the pole plate or press plate, and the force status thereof is similar to that when assembling the columns away from the edge of pole/press plate, and the above assembling method is flexible, labor-saving, safe and efficient. In addition, by using the extension plate, the assembling working surface of the permanent magnetic column is enlarged, so it does not need to frequently change the mounting position of the permanent magnetic column conveying tool.

(4) Description of figures

In order to better understand the present invention, some embodiments of the present invention are introduced in the following with reference to the figures, wherein Fig. 1 shows the main mechanical structure of the magnetic resonance imaging equipment of an open C-shaped permanent magnet ;

Fig. 2 shows a method according to the embodiment of the present invention, and it shows the situation of preparing to assemble a permanent magnetic field generating device of the magnetic resonance imaging equipment, wherein the extension plate composed of separated components is employed; Fig. 3 shows the situation that after the mounting of the extension plate, the permanent magnetic columns are conveyed to the space between the press plate and the pole plate as shown in the embodiment illustrated by Fig. 2; Fig. 4 shows an embodiment of the permanent magnetic column conveying tool according to the present invention, and shows the situation in which the above conveying tool is conveying permanent magnetic column to the space between the upper pole plate and the upper press plate;

Fig. 5 is a perspective drawing of the tunnel of the above conveying tool of the embodiments as illustrated in Fig. 4 ; Fig. 6 shows a perspective drawing of the feeder of the above conveying tool of the embodiments as illustrated in Fig. 4; Fig. 7 shows the permanent magnetic generating device having the magnetic resonance imaging equipment assembled by using the method of the present invention.

(5) Specific embodiments

According to one embodiment of the present invention, a method of assembling permanent magnet in the permanent magnetic field generating device of the open C-shaped magnetic resonance imaging equipment, wherein the special extension plate of the present invention has is used as shown in Fig. 2 and Fig. 3. Nevertheless, these embodiments are not limitative, so the present invention is not limited to magnetic resonance magnet and neither is it limited to the open C-shaped permanent magnet structure.

As shown in Fig. 2, the upper and lower press plate 2 and 21, upper and lower pole plate 3 and 31 as well as the Rose rings 4 and 41 have already been assembled, and the permanent magnetic field generating device 10 is to be mounted, but before the mounting of the above device, the separate type extension plate 6 has to be mounted on the peripheral of the above press plate 2 and 21 and the above pole plate 3 and 31. The above extension plate 6 is composed of four separate components 61, 62, 63 and 64, and after assembling by mechanical means such as stud, clamp, dowel or pin, etc., the external boundary of the extension plate 6 becomes a square (or any other shapes) and its inner boundary has the same shape of the peripheral of the press plate 2 and 21 and the pole plate 3 and 31. Likewise, an extension plate 6 is also mounted on the peripheral of the lower press plate 21 and lower pole plate 31. The above extension plate 6 is made of ferromagne- tic material.

As shown in Fig. 3, the extension plate 6 has been mounted on the whole peripheral of the press plate 2 and 21 and the pole plate 3 and 31, and some permanent magnetic columns have been mounted in the space between the upper press plate 2 and the upper pole plate 3, and are fixed therein to form a whole 5' by gluing. A permanent magnetic column 5 to be mounted is slid to the surface of the pole plate 3 through the extension plate 6 mounted on the peripheral of the upper press plate 2 and upper pole plate 3, and then moves to the predetermined position; at least one side surface of the above permanent magnetic column 5 is coated with glue or beforehand coated with glue; the above permanent magnetic column 5 is glued together with the permanent magnetic column 5' that has pre- viously been mounted on the pole plate 3; these steps are repeated until the upper permanent magnetic field generating source 10 is full is mounted. In the space between the above lower press pole 21 and the above lower pole plate 31, the procedure of mounting the permanent magnetic column is com- pletely the same as the procedure with the upper press plate 2 and the upper pole plate 3, and the above mounting could be performed before, after or at the same time with the mounting of the upper permanent magnetic field generating source. After all permanent magnetic field generating source 10 are mounted, the extension plate 6 is removed, and the next step of mounting will be performed on the magnetic resonance imaging equipment .

The assembling method of the permanent magnetic column of the present invention is based on the following principles: after some permanent magnets are mounted on the pole plate 3 and 31 of the permanent magnet, the magnetic field will be generated subsequently. Since the magnetic conductivity of pole plate, press plate and the magnetic yoke is far greater than the air, a strong magnetic force will act on the permanent magnetic column at and near the interface of the air, the pole plate and the press plate, while the magnetic force in the center of the pole plate is relative weak and the magnetic force near the edge of the pole plate is relative strong. Therefore, in the process of mounting the permanent magnetic column 5 starting from the center of the pole plate then expanding to the edges thereof, the permanent magnetic column will be affected by the magnetic force that is stronger and stronger near the edge of the pole plate, and hence, moving, positioning and gluing will become very difficult; and this is quite different from the situation when the per- manent magnetic column is in the center of the pole plate and magnetic force worked thereon is weak so that moving and positioning is easy. The present invention just takes advantage of this to mount an extension plate 6 on the peripheral of the press plate 2 and 21 and pole plate 3 and 31. The surface of the extension plate 6 and the surface of the above press plate combine into an enlarged magnetic conducting surface, and similarly, the surface of the extension plate 6 and the surface of the above pole plate also combine into an enlarged magnetic conducting surface. On these larger magnetic conductive surfaces, the peripheral of the above press plate 2 and 21 is no longer in the position of the edge; similarly, the peripheral of the above pole plate is no longer in the edge, neither. Therefore, only a weak magnetic force needs to be overcome when mounting and positioning the permanent mag- netic column on the edges of the above press plate and pole plate, thereby the mounting becomes relatively easy. Hence, the difficulty in mounting the permanent magnet on the edge of the pole plate existing in the prior art is much reduced.

In the embodiments shown in Figs. 2 and 3, the separate type extension plate 6 is employed, which further has the advantages of flexible removing and convenient adjusting in addi- tion to the above excellent effects. Furthermore, extension plates are mounted on the whole peripheral of the above press plate and the above pole plate, so that the permanent magnetic column could be conveyed to the space between the above press plate and pole plate from all directions. Meanwhile, the surface of the mounting work is enlarged and thereby the operation of the permanent magnetic column conveying tool becomes convenient .

According to an embodiment of the present invention that is not shown, in the mounting process of the permanent magnetic column 5, the extension plate 6 is only extended from a part of the edge of each press plate 2 and 21, and the above extension plate is also mounted on the peripheral of each of the pole plate 3 and 31 at the substantially corresponding position, so that the upper and lower extension plates are opposite to each other for conveying the permanent magnetic column into the pole plate.

According to the method of the present invention, after the extension plate 6 is provided, the force worked on the permanent magnetic column near the peripheral of the press plate 2 and 21 and pole plate 3 and 31 is reduced, while on the contrary, the force acting on permanent magnetic column near the external edge of the extension plate 6 becomes relatively strong. In order to help permanent magnetic column to overcome the strong magnetic force at the end of the extension plate and to enter the space between the press plate and the pole plate smoothly, the present invention also provides a conveying tool for the permanent magnetic column.

Figs. 4, 5 and 6 show a specific embodiment of the conveying tool for the permanent magnetic column of the present invention, which includes: a tunnel 8 and a feeder 9, the output port of the above tunnel 8 is re-movably mounted on the extension plate 6 with stud, clamp, dowel or pin, and is con- veying the permanent magnetic column to the space between the upper press plate 2 and the upper pole plate 3.

As shown in Fig. 5, the output port of the above tunnel 8 has a guide accessory 81 and a flange 82, the above guide accessory 81 could insert between the confronting extension plates 6 and leads the permanent magnetic column thereinto. The above flange 82 could have some mounting holes for fixing the above tunnel 8 re-movably to the extension plate 6 so as to perform the conveying. There is also a flange 83 at the other end of the above tunnel 8 for fixing the nut 94. The shape and size of the cross section of the inner cavity of the above tunnel 8 are basically the same as that of the holder 91 so as to contain the permanent magnetic column 5 and let it go through.

It can be seen from Fig. 6 the feeder 9 of the permanent magnetic column conveying tool 7, which has a screw rod 92 which is rotatablely mounted at one of its end on the holder 91 and fixed at its another end with a crank (95) , and a nut 94 that is mounted on the flange (83) of the tunnel (8) by means of a cover plate (93) . The method of connecting could be using stud, clamp, dowel, pin, etc.

The working process of the permanent magnetic column conveying tool 7 is shown in Fig. 4. When the above tunnel 8 is filled with the above permanent magnetic column 5, the guide accessory 81 of the output port of the above tunnel 8 inserts to the space between the confronting extension plates 6 and the above tunnel 8 is fixed to the extension plate 6 by means of the flange 82. Making the holder 91 to move towards the output port under the function of the screw rod 92 by rotating the crank 95, and the permanent magnetic column 5 in the tunnel 8 is pushed to the space between the above extension plates 6 through the guide accessory 81, and thereby it continues to move to the predetermined position on the pole plate, wherein it is positioned and glued together with the previously mounted permanent magnetic column 5' .

In another embodiment of the conveying tool of the permanent magnetic column of the present invention, a hydraulic pressure cylinder and there is a holder on the end of its holder rod.

Although the conveying tool of the permanent magnetic column of the present invention is simple in structure, it could enable the permanent magnetic column 5 to easily overcome the strong magnetic force near the edge of the extension plate 6 and to enter the pole plate, and thereby the efficiency of the mounting work is greatly improved.

Claims

Patent claims

1. An assembling method of permanent magnetic material in a permanent magnetic field generating device for manufactu- ring equipment with permanent magnetic field generating device includes the following steps:

(1) conveying step: conveying a permanent magnetic column (5) into the space between surfaces of the above pole plate (3, 31) and the above press plate (2, 21) through an extension plate (6) which is mounted on the peripheral of the press plate (2, 21) and the pole plate (3, 31) respectively;

(2) coating glue step: coating glue or beforehand coating glue on at least one side surface of the above permanent magnetic column (5) ;

(3) fixing step: fixing the above permanent magnetic co- lumn (5) on the permanent magnetic columns (5') which have been mounted on the pole plate (3, 31) previously to form a whole;

(4) repeating the steps from (1) to (3) until assembling the permanent magnetic field generating device is complete .

2. The assembling method as described in claim 1, characterized in that in the above conveying step, the above extension plate (6) mounted is made of ferromagnetic material .

3. The assembling method as described in claim 2, characterized in that in the above conveying step, the extension plate (6) is re-movably mounted on the peripheral of the above pole plate (3, 31) in such way that the surface of the extension plate (6) and the surface of the above pole plate (3, 31) together form a magnetic conducting surface.

4. The assembling method as described in claim 3, characterized in that in the above conveying step, the above extension plate (6) extends from partial peripheral or whole peripheral of the above pole plate (3, 31) .

5. The assembling method as described in claim 2, characterized in that in the above conveying step, the extension plate (6) is re-movably mounted on the peripheral of the above press plate (2, 21) in such way that the surface of the extension plate (6) and the surface of the above press plate (2, 21) form a magnetic conducting sur- face.

6. The assembling method as described in claim 5, characterized in that in the above conveying step, the above extension plate (6) extends from partial or whole peripheral of the above press plate (2, 21) .

7. The assembling method as described in one of claims from 1 to 7, characterized in that in the above conveying step, the above extension plate (6) is made up of several separate components.

8. The assembling method as described in claim 7, characterized in that in the above conveying step, the above extension plate (6) is assembled by four separate components (61, 62, 63, 64), after the assembly, the shape of outer peripheral of the extension plate (6) appears square, rectangular, polygonal or arc and the shape of the inner peripheral of it corresponds to the peripheral shape of the above press plate (2, 21) and /or the above pole plate (3, 31) .

9. A conveying tool of permanent magnetic material, for carrying out the assembling method described in any of claims 1 to 8 , including: a tunnel (8) for guiding the above permanent magnetic columns, whose output port is re-movably mounted on the extension plate (6) ; and a feeder (9) having a holder (91) that drives the above permanent magnetic column (5) forward inside the above tunnel (8) .

10. The conveying tool as described in claim 9, characterized in that there is a flange (82) and a guide accessory (81) on the output port of the tunnel (8) , the shape and size of the cross section of the inner cavity of the tunnel (8) are basically the same as that of the above permanent magnetic column (5) to be conveyed.

11. The conveying tool as described in claim 9, characterized in that the above feeder (9) has a screw rod (92) that is rotatably mounted at one of its ends on the holder (91) and fixed at its another end with a crank (95) , and a nut (94) is mounted on the flange (83) of the tunnel (8) by means of a cover plate (93) .

12. The conveying tool as described in claim 9, characterized in that the above feeder (9) uses a hydraulic pressure cylinder and there is a holder on the end of its holder rod.