JP2689321B2 - Crusher for concrete crushing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is equipped with an electromagnet device for suction-adsorbing and collecting rebar scraps, iron pieces, etc. generated in the process of crushing a reinforced concrete block accompanying the dismantling of a building, and the magnetic line of force is provided by the electromagnet device. The present invention relates to a crusher for crushing concrete that allows a strong suction force to be obtained by making a non-magnetic lid reach far outside.

[0002]

2. Description of the Related Art Generally, the crushing and crushing work of reinforced concrete blocks generated when a building is demolished is carried out by a concrete crusher (generally called a crusher) attached to the arm tip of a backhoe and a bucket link. A large amount of iron scraps such as reinforcing bars are generated. These iron scraps come in various lengths and shapes, and small iron pieces such as bolts and nuts are also mixed. Further, as a crusher, a model equipped with a rebar cutting cutter blade is also commonly used, and the rebar may be cut into short pieces during crushing work of concrete with this cutter blade.

[0003] Among these iron scraps, long rebars and the like can be collected by the crusher itself, further bent or bundled, loaded into a truck, and taken out as it is. On the other hand, since a large amount of short rebar scraps and small iron pieces such as bolts that cannot be bundled with a crusher are also generated, these are conventionally collected manually, but this collection work requires considerable labor and labor costs. doing.

For this reason, an electromagnet device is attached to a crusher, and the crusher is used to perform normal work such as smashing concrete blocks and bundling rebars, while short rebars and small iron scraps are adsorbed to the electromagnet device. The method of collecting and collecting is adopted. As examples of attaching an electromagnet device to a crusher, there are JP-A-4-155068 and JP-A-6-67700.

[0005]

The conventional electromagnet device mounted on the crusher typically has the structure shown in FIGS. 9 and 10, and the adsorbing surface of the electromagnet 70 has a concentric circular shape. A magnetic core material 71 having a diameter of about 10 cm is located at the center. The surface of the magnetic core material 71 is the attracting surface 72 at the magnetic pole end of either the S pole or the N pole, and the electromagnetic coil 74 is provided outside thereof.
And the other magnetic pole from the rear of the magnetic core material 71 to the coil 7
4, the magnetic pole end face 73 faces the same direction as the one magnetic pole end face 72. The electromagnet 70 is cylindrically housed and held in a cylindrical case 75 having a flange 76 projectingly formed on the periphery thereof, and the flange portion 76 of the case is attached to the bottom surface of the fixed arm by a bolt 77. Further, the electromagnet 70 is fed from the hydraulic excavator side to the electromagnetic coil 74 by a cable 78 via the inside of the crusher.

In this type of electromagnet 70, the width of the attraction surface 72 at the center magnetic pole end is structurally small, and the outer periphery of the attraction surface and the attraction surface 73 at the magnetic pole end of the other pole are close to each other. Therefore, there is a defect that the magnetic flux of the external magnetic field line passing between both poles is concentrated near the surface of the adsorption surface, the magnetic flux density is rapidly reduced at the position away from the surface, and the magnetic field line does not reach far.

For this reason, even a small piece of iron scrap can hardly be attracted if the position of the magnetic pole surface is far from the magnetic pole surface, and the central magnetic pole attracting surface is covered only by attracting a few thick rebars.
When most of the magnetic flux passes through the inside of the adsorbate, the lines of magnetic force that permeate to the outside of the adsorbing rebar almost disappear, and neither attraction nor adsorption becomes possible. That is, since the magnetic field lines spreading to the outside cannot reach far away, the electromagnet 70 has a weak attracting force, and it is necessary to press it against the iron scraps scattered on the ground.
The impact of the pressing may cause the iron scraps that have once been adsorbed to fall apart, which has the disadvantage that the amount of iron scraps that can be adsorbed is small and the work efficiency is poor.

The present invention proposes an electromagnet device installed in a crusher for crushing concrete, which has an improved capability of attracting distant ones to enhance the work efficiency of collecting rebar scraps and the like. An object of the present invention is to provide a magnetic field line to a wide range and reach far, and by providing an electromagnet device capable of adsorbing more rebar scraps, the magnetic field line can reach far outside the non-magnetic lid to generate a strong attractive force. The object is to provide a crusher for crushing concrete.

[0009]

[Means for Solving the Problems] In order to solve the above problems, a crusher 1 for concrete crushing according to the present invention (FIG. 1)
Is attached to the tip of the movable arm 51 of the work truck such as the backhoe 50 illustrated in FIG. The crusher to which the present invention is applied may be composed of a pair of movable arms (not shown) instead of the combination of the fixed arm 3 and the movable arm 5. In a crusher having a pair of movable arms, an opening is provided on the back surface of one of the movable arms. A non-magnetic lid 34 is attached to the opening as in the above, and the electromagnet device 30 is installed inside the lid.

As shown in FIGS. 2 to 4, the crusher 1 is provided with an opening 21 longer than the frame width on the lower rear surface of the frame 2 or the rear surface of the fixed arm 3, and the nonmagnetic lid is provided in the opening 21. It may be covered with 34 and fixed with bolts or the like. Lid 3
Reference numeral 4 is a generally flat plate body as shown in FIGS. 1 and 2, and bolt holes 40 are provided around the plate body. Opening 21
The plane shape of can be a rectangle, an ellipse, or any other irregular plane, and the material of the lid 34 to cover this is substantially non-magnetic alloy metal such as stainless steel, copper or aluminum. It may be plastic such as FRP.

Inside the lid 34, the horizontally long electromagnet device 3 is provided.
Set 0 with bolts. The electromagnet device 30 is approximately U
It is composed of a magnetic core material 31 on the side surface of a letter and an electromagnetic coil 33 wound around the magnetic core material, all of which are known materials. As is clear from FIG. 4, it is preferable to dispose both magnetic pole end portions 31a and 31b of the magnetic core material 31 on the inner wall surface of the lid 34 so as to be spaced apart from each other. For example, they are arranged so as to be substantially orthogonal to the inner wall surface of the lid 34. Generally, a magnetic core material 3 having a substantially U-shaped side surface
In No. 1, it is preferable that the electromagnetic coil 33 is wound around the central portion thereof and the bent end portion of the magnetic core body is wider than the central portion.

In addition, as shown in FIGS. 6 and 7, an opening 80 is formed in the lower rear surface of the frame 2 or the rear surface of the fixed arm 3.
Alternatively, the electromagnet device 81 may be housed in the opening, and then the nonmagnetic lid 82 may be covered and fixed to the opening 80.
In the electromagnet device 81, one magnetic pole end portion 85 of the magnetic core member 83 is arranged in contact with the inner wall surface of the non-magnetic lid 82, and the other magnetic pole end portion 86 is arranged in contact with the frame 2 or the fixed arm 3. The frame 2 or the fixed arm 3 is entirely configured to have the other magnetic pole.

Instead of the flat lid 34, in the lid 43 shown in FIGS. 3 and 4, a through hole 41 is provided in a portion facing one or both magnetic pole end surfaces of the electromagnet device 30, and one or both of the magnetic pole end portions are provided. Is closely inserted into the through hole 41. Further, as shown in FIG. 5, a magnetic material 42 such as steel is provided in the through hole 41.
May be inserted and fixed. The planar shape of the through hole 41 or 87 needs to face one or both of the magnetic pole end surfaces of the magnetic core material, and is usually the same shape as the both magnetic pole end surfaces.
When the magnetic material 42 is inserted, it may be slightly larger than the end faces of both magnetic poles. The power cable 37 of the electromagnet device 30 or 81 passes from the inside of the frame 2 of the crusher 1 through the bracket portion 4 to the backhoe 50 (FIG. 8).
The arm 51 and the boom 56 are guided to the operator cab 57 of the backhoe. In the operator's cab 57, a controller (not shown) installed therein is relayed and connected to a power source such as a battery, and a switch installed in the controller can turn on / off power supply to the electromagnet device 30 or 81. To do.

[0014]

The crusher 1 can be moved to a predetermined position on the dismantling site by the backhoe 50, for example, and the non-magnetic lid 34 located on the rear surface of the fixed arm 3, that is, the attracting surface of the electromagnet device 30, is scattered with the reinforcing bar scraps and the like. Close to the ground where it is. Then, turn on the switch of the controller in the backhoe cab 57.
N, the electromagnet device 30 is excited to absorb the rebar scraps by suction,
The backhoe 50 is operated again to move the crusher 1 to the place where the reinforcing bar scrap is collected. If the switch of the controller is turned off here, the magnetic force of the electromagnet device 30 disappears, and the reinforcing bar scraps of the adsorbed material fall.

The non-magnetic lid 34 has a laterally long dimension in order to cover and fix the lower rear surface of the frame 2 to the opening 21 longer than the frame width (see FIG. 3). Moreover, since the electromagnet device 30 is installed laterally inside the lid 34, the gap between the magnetic pole ends 31a and 31b of the magnetic core material 31 is relatively wide, and the magnetic field lines extending from the magnetic pole ends 31a and 31b to the outside are provided. A strong magnetic flux extends in an arc shape at a long distance, and the magnetic pole end 31
Reinforcing bar scraps separated from a and 31b can also be sucked well. Also,
Since both the magnetic pole end portions 31a and 31b are designed to be wide,
A wide range of magnetic force lines can be blown, and even if rebar scraps have already been adsorbed, the magnetic force lines fly from the part that is not blocked by them, so the suction capacity does not decrease significantly, and a large amount of rebar scraps are sucked and adsorbed at one time. To do.

In the electromagnet device 30, since the lid 34 covering both end faces of the magnetic pole is a non-magnetic material, the magnetic force lines are not obstructed or weakened by the lid 34, and the magnetic force lines can pass without any trouble. . In addition, FIG.
As shown in FIG. 2, both magnetic pole end portions 31a and 31b of the magnetic core material 31 are
However, if the magnetic material 42 is exposed to the outside through the through holes 41, 41 provided in the non-magnetic lid 34, or the magnetic material 42 is fitted and fixed in the both through holes 41, 41, the magnetic pole of the electromagnet device 30 is The end plate has a fixed arm 3 of the crusher 1 or a back plate 1 of the frame 2.
The magnetic flux radiated from the magnetic pole end faces is attracted to the back plates 18 and 19 of the crusher 1 and is not effectively radiated without being attenuated. Since it is in close proximity to or in direct contact with an object, the reinforcing bar scraps are more strongly adsorbed, do not separate during movement, and can adsorb a large amount.

[0017]

Embodiments of the present invention will now be described with reference to FIGS. FIG. 1 shows an overall side surface of a crusher 1 equipped with an electromagnet device 30 according to the present invention. In FIG. 1, a chain double-dashed line shows a state in which a movable arm of the crusher is closed.

In the crusher 1, the tip of the movable arm 51 of the backhoe 50 and the tip of the bucket link 52 at the tip of the movable arm 51 are pin-connected to the connecting pin holes 10 provided in the bracket portion 4 above the frame 2. To do. Arm 51 of backhoe 50, bucket link 5
2, the crusher 1 is attached by the expansion and contraction operation of each cylinder of the boom 56 so as to be freely movable and rotatable in the vertical and vertical directions along the vertical plane including the arm 51 of the backhoe 50 and the boom 56, and The operation of turning and running allows the work to be performed at any position and angle.

Below the frame 2 of the crusher 1, a fixed arm 3 is provided so as to project toward the front, and a movable arm 5 is arranged so as to face the fixed arm 3, and a base end portion of the movable arm is fixed by a pin 6. It is rotatably supported by the base of the frame 2. The tip of the movable arm 5 is rotatably connected to a piston rod of a hydraulic cylinder 9 by an arm pin 8, and the hydraulic cylinder is rotatably supported on the frame 2 by a pin 7. By extending and contracting the hydraulic cylinder 9, the tip of the movable arm 5 can be opened and closed with respect to the fixed arm 3.

The hydraulic oil of the hydraulic cylinder 9 also serves as the oil of the hydraulic pump (not shown) for driving the backhoe 50,
A pipe (not shown) attached along the boom 56 and the arm 51 of the backhoe 50, a relay hydraulic connection 24 attached to the frame 2 of the crusher 1, and a hydraulic pressure connecting the hydraulic connection 24 and the hydraulic cylinder 9. It is supplied via a hose (not shown).

On the inner side surface of the movable arm 5, arm tip teeth 11, large crushing teeth 12, small crushing teeth 13 and the like are provided upright. Further, a wedge tooth 14 is attached to the front end of the fixed arm 3 so as to face forward so as to intersect the front tooth 11 of the arm 5. Cutter blades 15 and 16 are fixed near the base ends of the movable arm 5 and the fixed arm 3 so as to intersect with each other when the movable arm is closed.

In the back side plate of the crusher 1, between the rear end of the bottom member 18 of the fixed arm 3 and the lower end of the back member 19 connecting the left and right side plates forming the frame 2, A wide opening 21 is formed between the side plates. The planar shape of the opening 21 is rectangular, and a screw hole 23 for mounting a bolt is provided around the rectangular shape. The internal reinforcing member 17 of the fixed arm 3 is provided with a cutout portion 22 (see FIG. 1) cut out in the vicinity of the opening portion 21, and the electromagnet device 30 is provided in a space portion formed by the opening portion 21 and the cutout portion 22.
To store.

As shown in FIGS. 2 and 4, the electromagnet device 30 is composed of a magnetic core material 31 having a substantially U-shaped side surface and a wide cross-section, and a wound frame body 32 attached to the central portion of the magnetic core material. The electromagnetic coil 33 is wound around. The connection terminal 36 of the electromagnetic coil 33 is attached to the outside of the frame 32. Power is supplied to the electromagnetic coil 33 from a cable 37 connected to a connection terminal 36 of the electromagnetic coil 33. This cable 37
Goes out through the inside of the frame 2 of the crusher 1,
A controller (not shown) installed in the operator's cab 57 is relayed along the arm 51 and the boom 56 of the backhoe 50 (FIG. 8) and connected to a power supply device (not shown) such as a battery, and an electromagnet is switched by a switch of the controller. The device 30 can be excited and demagnetized.

In the electromagnet device 30, both end portions of the magnetic core material 31 are bent substantially at right angles in the same direction so that both lateral widths of both end portions (magnetic pole end portions) of the magnetic core material and a gap between both poles are widened. On the other hand, the non-magnetic stainless steel lid 34 is a flat plate body, and a plurality of bolt holes 40 are formed in the periphery of the lid 34 at predetermined intervals, and L is integrally fixed to the inside of the lid. Via the letter-shaped member 38, the magnetic pole ends 31a and 31b of the electromagnet device 30 are fixed with bolts 39 so that they come into contact with the lid surface. The electromagnet device 30 is arranged inside the crusher frame 2 and both magnetic pole ends 31a,
So that 31b is in a posture to face outward through the lid 34,
Bolts 35 (FIG. 1) are inserted into the bolt holes 40 of the lid 34 to fasten the lid to the screw holes 23 around the opening 21.

Next, the crushing work by the crusher 1 and the reinforcing bar scrap collection work will be described with reference to FIG. Generally, the primary crushed concrete block 54 is bitten between the fixed arm 3 and the movable arm 5 of the crusher 1 and the movable arm 5 is closed by the hydraulic cylinder 9 to successively crush it into small pieces, Furthermore, it is thrown into a crusher for fine crushing and finely crushed to be reused as an aggregate for roadbed materials and backfilling. In this case, if a foreign substance such as a reinforcing bar is mixed in the concrete block 54, the cleaving process cannot be performed as it is, and it is necessary to separate these.

The concrete block 54 coming out of the dismantling site contains iron scraps such as reinforcing bars 55 and bolts inside,
It is necessary to separate and separate these during the crushing process.
Since these iron scraps are used as recycled raw materials, long ones may be grasped by the fixed arm 3 and the movable arm 5 of the crusher 1, folded and bundled, and loaded on a truck and carried out. On the other hand, short-sized reinforcing bar scraps and bolts cut by the cutter blades 15 and 16 during the crushing and other processing steps cannot be dropped from the crusher 1 and collected, and the crushed concrete lumps and the ground lumps can be collected on the ground. You will be left behind.

With respect to iron scraps such as short rebars and bolts left on the ground, the backhoe 50 is operated to make the electromagnet device 30 of the crusher 1 face the ground as shown in FIG. The switch of the controller installed in the chamber 57 is turned on to excite the electromagnet device 30. Magnetic lines of force that cross between both magnetic poles of the electromagnet device 30 are generated outside the lower lid 34 of the crusher 1, and iron scraps 53 such as reinforcing bars scattered on the ground are attracted by the electromagnet device 30 and adsorbed to the outer surface of the lid 34. . In this adsorption state, the backhoe 50 is operated to move the adsorption object 53 to a desired location such as on the truck bed, and when the switch is turned off, the electromagnet device 30 is demagnetized and the adsorption object is dropped to the intended position. You can

In the electromagnet device 30, the magnetic pole end portions 31 a,
The U-shaped magnetic core material 31 is used so that 31b is formed wide as shown in FIG.
Therefore, the magnetic force line from the electromagnet device 30 has a wide magnetic flux width, and the arc of the magnetic force line emitted in an arc shape between the magnetic pole end faces reaches a long distance, so that a large attraction force acts even if it is far from the electromagnet device 30. Can absorb a larger amount of scrap metal.

Next, a modified example of the non-magnetic lid used in the present invention will be described. In the lid 43 shown in FIGS. 3 and 4, through holes 41, 41 are provided in a portion of the electromagnet device 30 facing the magnetic pole ends 31a, 31b, and the magnetic pole ends 31a, 31b are closely inserted into the through hole 41. . Magnetic pole end portions 31a, 31
When b is inserted into the through hole 41 and its tip end surface is exposed to the outside of the lid 34, the magnetic pole end surface is more than the opening 21 at the ends of the fixed arm 3 of the crusher 1 or the back plates 18, 19 of the frame 2. Has a state in which the magnetic flux radiated from the magnetic pole end surface is attracted to the surrounding back plates 18 and 19 and the side plates of the frame 2 without being attenuated, and a strong magnetic line of force extends to a distance. Since the magnetic pole end faces can be closer to or directly in contact with the object to be attracted, they can be more strongly attracted.

Instead of inserting the magnetic core material itself into the through hole 41 of the lid 34 as described above, the magnetic material 42 may be fitted and fixed in the through hole 41. In this case, the magnetic force lines emitted from the electromagnet device 30 pass through the inside of the magnetic materials 42, 42, and the outer end surfaces of the magnetic materials 42, 42 act as magnetic poles, resulting in the same function as described above.

In FIGS. 6 and 7, as a modified example of the present invention, a substantially square flat opening 80 is provided on the lower rear surface of the frame 2 or the rear surface of the fixed arm 3 in the crusher 79.
An electromagnet device 81 is housed in a space formed between the reinforcing partition plates in the opening. The electromagnet device 81 includes a substantially columnar magnetic core material 83 and an electromagnetic coil 84 wound around the magnetic core material. The electromagnet device 81 is located in a space formed by the reinforcing partition plate inside the opening 80, and the rear portion thereof is bolted to the inner wall surface of the frame 2 or the fixed arm 3 and then the lid having a substantially square plane. 82 is put on the opening 80 and bolted. The through hole 8 for exposing one magnetic pole 85 of the electromagnet device 81 is formed in the center of the non-magnetic lid 82.
7 and the material and function of the lid are similar to the lid 34 described above.

After housing the electromagnet device 81 in the opening 80, one magnetic pole end portion 85 of the magnetic core material 83 is fitted into and closely fitted in the through hole 87 of the non-magnetic lid 82. Electromagnet device 8
1, the other magnetic pole end portion 86 is arranged in contact with the frame 2 or the fixed arm 3 so that the entire frame 2 or the fixed arm 3 serves as the other magnetic pole.

In the crusher 79, one magnetic pole end 85 of the electromagnet device 81 is located at the center of the non-magnetic lid 82 on the opening 80, while the other magnetic pole is formed on the entire frame 2 or fixed arm 3. Therefore, the distance between both magnetic poles becomes longer. Therefore, the external magnetic field lines extending over both magnetic poles are broadly radiated in an arc shape between the center of the opening 80 and the vicinity of the inner peripheral edge and far, and act as an electromagnet having a large magnetic field line area. The electromagnet device 81 can well suck rebar scraps away from the non-magnetic lid 82 and can adsorb a large amount of rebar scraps at the same time, and at the time of adsorbing / moving the rebar scraps, the impact of the operation of the crusher 79 or the rebar scraps. It is possible to efficiently carry out safe work by eliminating the drop of reinforcing bar scrap due to extrusion due to mutual interference.

[0034]

In the crusher of the present invention, since the magnetic pole end faces of the electromagnet device are wide and the distance between the magnetic pole end faces is long, the range of magnetic force lines is widened and the magnetic poles are blocked by a small amount of the attracted substance. It will not be lost. Compared to conventional magnet devices, this electromagnet device not only attracts and absorbs more reinforcing bars and scraps at once, but also the lines of magnetic force extend far,
Even if the crusher is not grounded on the ground, it is possible to suck the distant object well, which makes it easy to monitor the suction operation state and increases the work efficiency.

In the electromagnet device used in the present invention, the distance between both magnetic pole end faces is large, so that even after adsorption, a long object is unlikely to be separated by a slight impact. During the work of adsorbing / moving an object to be adsorbed, such as rebar scraps, the object to be adsorbed may not easily drop even by turning, undulating, or rotating with a backhoe, and the object to be adsorbed may be extruded due to interference between rebar scraps. Has been eliminated, and safe work can be achieved extremely efficiently, and operability and reliability are high.

Further, the non-magnetic lid used in the present invention is a member that intervenes so as to bridge both magnetic pole end surfaces of the electromagnet device, and since it is a non-magnetic material, it does not have the property of attracting magnetic lines of force from the electromagnet device. The generated magnetic field lines are not disturbed or attenuated. This non-magnetic lid serves to protect the electromagnet device from dirt and dust, and also serves to prevent abrasion damage of the magnetic pole tip surface, thereby contributing to the improvement of the durability of the electromagnet device.

[Brief description of the drawings]

FIG. 1 is an overall side view showing a notch of a mounting portion of an electromagnet device in a crusher according to the present invention.

FIG. 2 is a perspective view showing an electromagnet device used in the present invention.

FIG. 3 is a plan view showing another example of a non-magnetic lid on which the electromagnet device is installed.

FIG. 4 is a vertical cross-sectional view of the non-magnetic lid shown in FIG. 3 taken along the line AA of FIG. 3 together with the electromagnet device.

FIG. 5 is a partial cross-sectional view of an electromagnet device showing another example of a non-magnetic lid.

FIG. 6 is an overall side view similar to FIG. 1, showing a modification of the electromagnet device.

FIG. 7 is a plan view seen from the ZZ direction in FIG.

FIG. 8 is a side view showing a state in which the crusher according to the present invention is attached to a backhoe to adsorb iron scraps such as reinforcing bars.

9 is an overall side view similar to FIG. 1 of a conventional crusher.

FIG. 10 is a plan view seen from the XX direction in FIG. 9.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crusher 2 Frame 3 Fixed arm 5 Movable arm 21 Opening 30 Electromagnet device 31 Magnetic core material 33 Electromagnetic coil 34 Non-magnetic lid 42 Magnetic material

Claims (5)

(57) [Claims] 1. A bracket removably attached to a working portion of a self-propelled work cart, a frame integrally formed with the bracket, a fixed arm or one movable arm protruding from a lower portion of the frame, and the fixed arm or In a crusher equipped with the other movable arm that is rotatably supported by the frame so as to face the one movable arm, and a hydraulic cylinder that is arranged in the frame to open and close one or both of the movable arms, An opening having a lateral width longer than the frame width is provided on the lower rear surface of the frame or the rear surface of one of the movable arms, and a non-magnetic lid having an oblong electromagnet device installed inside is fixed to the opening and the electromagnet device is fixed. Is composed of a magnetic core material having a substantially U-shaped side surface and an electromagnetic coil wound around the magnetic core material. The magnetic pole end portions of the magnetic core material are separated from each other on the inner wall surface of the non-magnetic lid. A crusher for concrete crushing that generates magnetic lines of force even far outside the non-magnetic lid by arranging them in place. 2. The crusher according to claim 1, wherein in the magnetic core material having a substantially U-shaped side surface, an electromagnetic coil is wound around the central portion thereof, and the bent end portion of the magnetic core material is wider than the central portion. 3. A bracket removably attached to a working portion of a self-propelled work cart, a frame integrally formed with the bracket, a fixed arm or one movable arm protruding from a lower portion of the frame, and the fixed arm or In a crusher equipped with the other movable arm that is rotatably supported by the frame so as to face the one movable arm, and a hydraulic cylinder that is arranged in the frame to open and close one or both of the movable arms, An opening is provided on the lower back surface of the frame or on the back surface of one of the movable arms, the electromagnet device is housed in this opening, and the opening is covered with a non-magnetic lid to be fixed. It is composed of a magnetic core material and an electromagnetic coil wound around the magnetic core material, and one magnetic pole end portion of the magnetic core material is disposed in contact with the inner wall surface of the non-magnetic lid, and the other magnetic pole end portion is flared. A crusher for crushing concrete in which the frame or the fixed arm is configured so that the whole of the frame or the fixed arm serves as the other magnetic pole by being placed in contact with the column or the fixed arm. 4. A non-magnetic lid is provided with a through hole in a portion facing one or both magnetic pole end surfaces of the electromagnet device, and one or both of the magnetic pole end parts are inserted into the through hole to thereby remove the electromagnet device. The crusher according to claim 1 or 3, wherein one or both magnetic pole end surfaces are exposed to the outside of the crusher. 5. A non-magnetic lid is provided with a through hole in a portion facing one or both of the magnetic pole end surfaces of the electromagnet device, and a magnetic material is fitted and fixed in the through hole to form a magnetic pole end portion of the electromagnet device. The crusher according to claim 1 or 3, wherein one or both magnetic pole ends of the electromagnet device generate magnetic lines of force outside the crusher through the magnetic material of the non-magnetic lid when brought into contact with each other.