TWI610326B - Electromagnetic contactor and method for assembling the same - Google Patents

Abstract

The electromagnetic contactor is provided with: a polarized electromagnet (2); a movable contactor can be installed and connected to the first movable core plate (10a); a fixed contactor can be installed; and the cover can be mounted A housing of the frame; and a back housing that houses the polarized electromagnet (2) and is connected to the housing. The upper surface of the coil bobbin 9 is provided with a first engaging protrusion, and the housing is provided with: In a state of the movable iron core plate (10a), a second engaging protrusion facing the first engaging protrusion through a gap of a predetermined distance.

Description

Electromagnetic contactor and assembly method of electromagnetic contactor

The present invention relates to an electromagnetic contactor having a polarized electromagnet composed of a permanent magnet and a coil, and an assembly method thereof.

The electromagnetic contactor disclosed in Patent Document 1 includes a polarized electromagnet composed of a permanent magnet and a coil, a carrier capable of attaching a movable contactor, and a fixing for contacting / separating the movable contactor. A contactor, a rear case that houses the polarized electromagnet, and a case that covers the bracket and can be engaged with the back case. The polarized electromagnet has a coil formed by winding a wire, a coil bobbin for winding the coil, a movable iron core penetrating the coil frame in the axial direction, and a U-shaped fixing provided facing the movable iron core. An iron core, a magnetic pole plate arranged opposite to the coil, and a permanent magnet provided on the fixed iron core. When the movable bracket equipped with the movable contactor is mounted on the movable iron core plate, the movable contactor will be displaced by the same amount as the movable iron core is displaced.

In the electromagnetic contactor disclosed in Patent Document 1, when the coil is not excited, the movable core is attracted by the magnetic force of the permanent magnet. It is attached to the magnetic pole plate, so the movable contactor is separated from the fixed contactor. Once the coil is excited, a magnetic field that cancels the magnetic field of the permanent magnet will be generated between the movable iron core and the fixed iron core, so the movable iron core plate will be displaced to the side of the fixed iron core plate and become the contact between the movable contactor and the fixed contactor. status.

[Prior technical literature]

(Patent Literature)

(Patent Document 1) Japanese Patent Laid-Open No. 2010-62079

From the viewpoints that if a foreign object is caught in the driving part of the electromagnetic contactor, it will cause malfunction, and if a foreign object is caught between the contacts of the electromagnetic contactor, the contact life will be shortened. Intrude and remain inside the product. Therefore, the electromagnetic contactor must be assembled with a frame that has as few openings as possible, and must be assembled in a manner that no foreign matter remains in the frame as much as possible.

However, Patent Document 1 does not disclose a step of assembling an electromagnetic contactor that takes into consideration the prevention of intrusion and residue of foreign matter.

In addition, in the electromagnetic contactor disclosed in Patent Document 1, in a state where a connectable bracket provided with a movable contactor is inserted into the housing, and the polarized electromagnet is mounted on the housing, the polarized electromagnet is lifted by holding the housing. , The accessible bracket will drop due to the weight of the polarized electromagnet. Once the accessible bracket is lowered due to the weight of the polarized electromagnet, the movable contactor will be larger than Because the displacement amount of the movable bracket is displaced and comes into contact with the fixed contactor, the movable contactor is deformed.

In order to prevent deformation of the movable contactor, it is necessary to hold the casing and the polarized electromagnet at the same time, but holding the casing and the polarized electromagnet with both hands will reduce the work efficiency of the assembly operation. Therefore, it is necessary to have an engaging structure of the polarized electromagnet with the case of the entire structure except the back case being lifted without bringing the movable contactor into contact with the fixed contactor when the case is picked up.

The present invention has been made in view of the problems described above, and an object thereof is to provide a structure in which all the structures other than the back shell can be picked up without bringing the movable contactor into contact with the fixed contactor when the housing is picked up. Electromagnetic contactor with engaging structure of shell and polarized electromagnet.

In order to solve the above-mentioned problems and achieve the purpose of the present invention, the present invention is provided with: a polarized electromagnet; a movable carrier capable of mounting a movable contactor and being mounted on the first movable iron core plate of the polarized electromagnet; ; A fixed contact may be installed and cover a case that can be connected to the bracket; and a rear case that houses a polarized electromagnet and is connected to the case, wherein the polarized electromagnet is provided with: A coil formed by winding a wire around a coil bobbin; a U-shape in which the end plate portion extends from both ends of the side plate portion, and one end plate portion faces one end of the coil, The other end plate portion and the other end of the coil are opposed to each other with a gap therebetween, and the side plate portion and the outer peripheral portion of the coil are opposed to each other. A pair of U-shaped fixed iron cores are arranged inside the coil; they are arranged on the U-shaped fixed iron core. One pair of permanent magnets on the inner side of the side plate portion; and one end of the iron core rod inserted through the coil is provided with the first movable iron core plate on the outer side of one end plate portion of the U-shaped fixed iron core, and One end is provided with a movable core of a second movable core plate located between the other end of the coil and the other end plate portion of the U-shaped fixed core; the coil frame is provided with a first engaging protrusion on the upper surface, and the casing The second engaging protrusion is provided opposite to the first engaging protrusion with a clearance of a predetermined distance in a state where the connectable bracket is attached to the first movable core plate.

According to the electromagnetic contactor of the present invention, when the housing is lifted, the movable contactor can be brought into contact with the fixed contactor, and the entire structure other than the back shell can be lifted up.

1‧‧‧ electromagnetic contactor

2‧‧‧ Polarized Electromagnet

3‧‧‧ shell

3a‧‧‧ lower surface

3b, 3c ‧‧‧ second engagement protrusion

3d‧‧‧step difference

4‧‧‧ can be connected to the bracket

4a‧‧‧ Engagement Department

5‧‧‧ fixed contact

6‧‧‧ movable contactor

7‧‧‧back shell

8‧‧‧ Coil

8a, 8b‧‧‧

8c‧‧‧ Peripheral

9‧‧‧ Coil Frame

9a‧‧‧upper surface

9b, 9c ‧‧‧ first engagement protrusion

10‧‧‧ Movable iron core

10a‧‧‧The first movable core plate

10b‧‧‧Second movable iron core plate

10c‧‧‧ gap

10d‧‧‧Iron Core Stick

10d1,10d2‧‧‧end

11‧‧‧ fixed iron plate

12‧‧‧U-shaped fixed iron core

12a, 12b‧‧‧End plate section

12c‧‧‧Side panel

13‧‧‧permanent magnet

Fig. 1 is a perspective view of an electromagnetic contactor according to an embodiment of the present invention.

Fig. 2 is a sectional view of an electromagnetic contactor according to an embodiment of the present invention.

Fig. 3 is a sectional view of a polarized electromagnet of an electromagnetic contactor according to an embodiment.

Fig. 4 is a perspective view of a polarized electromagnet of an electromagnetic contactor according to an embodiment.

Fig. 5 is a perspective view of a bracket that can be connected to the electromagnetic contactor according to the embodiment.

Fig. 6 is a perspective view of a housing of the electromagnetic contactor according to the embodiment.

Fig. 7 is a perspective view of a housing of the electromagnetic contactor according to the embodiment.

FIG. 8 is a cross-sectional view of a portion of the electromagnetic contactor of the embodiment other than the back shell in a state where the engaging portion of the connectable bracket passes through a notch provided in the movable core plate.

Fig. 9 is a cross-sectional view of a portion of the electromagnetic contactor of the embodiment other than the back case in a state where the housing with the attachable bracket inserted is slid in the + z direction.

Fig. 10 is a cross-sectional view of a portion other than the back shell in a state where the electromagnetic contactor of the embodiment is assembled.

Fig. 11 is a partially enlarged view of the electromagnetic contactor of the embodiment.

Fig. 12 is a partially enlarged view of the electromagnetic contactor of the embodiment.

Fig. 13 is a sectional view of the inside of the housing of the electromagnetic contactor of the embodiment.

Fig. 14 is a sectional view of a portion of the electromagnetic contactor according to the embodiment other than the back shell in a state where the outer shell is lifted up.

Fig. 15 is a partially enlarged view of the electromagnetic contactor of the embodiment.

Fig. 16 is a partially enlarged view of the electromagnetic contactor of the embodiment.

Fig. 17 is a sectional view of the inside of the housing of the electromagnetic contactor of the embodiment.

Hereinafter, an electromagnetic contactor according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited by this embodiment.

Implementation form.

Fig. 1 is a perspective view of an electromagnetic contactor according to an embodiment of the present invention. Fig. 2 is a sectional view of an electromagnetic contactor according to an embodiment of the present invention. In the following description, the direction shown by the arrow x in the figure is the x direction, the direction shown by the arrow y is the y direction, and the direction shown by the arrow z is the z direction. The same direction as the arrow is +, and the opposite direction is-. For example, the same direction as the arrow x is the + x direction, and the direction opposite to the arrow x is the -x direction. The figure showing only a part of the constituent elements of the electromagnetic contactor 1 is indicated by arrows x, y, and z in the orientation in the assembled state shown in FIG. 1.

The electromagnetic contactor 1 has: a polarized electromagnet composed of a permanent magnet and a coil 2, a connectable bracket 4 capable of installing a movable contactor 6, a fixed contactor 5 in contact with / detached from the movable contactor 6, and a receiving pole The cylindrical back case 7 of the electromagnet 2. In addition, the electromagnetic contactor 1 also has a housing 3 covering the connectable bracket 4. A fixed contact 5 may be installed in the housing 3.

Fig. 3 is a sectional view of a polarized electromagnet of an electromagnetic contactor according to an embodiment. The polarized electromagnet 2 includes: a coil 8 formed by winding a lead wire around a coil bobbin 9; and a pair of U-shaped fixed iron cores 12 which are arranged in the coil 8 such that One end plate portion 12 a is opposed to one end 8 a of the coil 8, the other end plate portion 12 b is opposed to the other end 8 b of the coil 8 at a distance, and the side plate portion 12 c is opposed to the outer peripheral portion 8 c of the coil 8. . In addition, the polarized electromagnet 2 further includes a pair of permanent magnets 13 disposed on the inner side of the side plate portion 12c of the U-shaped fixed iron core 12, and one end 10d1 of the iron core rod 10d inserted through the coil 8 and provided with The first movable core plate 10a located outside the one end plate portion 12a of the U-shaped fixed core 12 is separated from the other of the core rod 10d. One end 10d2 is provided with a movable core 10 of a second movable core plate 10b to be located between the other end 8b of the coil 8 and the other end plate portion 12b of the U-shaped fixed core 12. The polarized electromagnet 2 includes a fixed core plate 11 made of a magnetic material disposed inside the permanent magnet 13. The distance between the second movable iron core plate 10b and the other end plate portion 12b of the U-shaped fixed iron core 12 is L2. That is, the movable iron core 10 has a displacement amount of the distance L2.

The U-shaped fixed iron core 12 has a U-shape that extends from the two ends of the side plate portion 12c to the end plate portions 12a and 12b. The shape of the U-shaped fixed iron core 12 in a cross section perpendicular to the x direction, that is, the shape of a cross section including a plane extending in the y direction and the z direction is a U shape.

Fig. 4 is a perspective view of a polarized electromagnet of an electromagnetic contactor according to an embodiment. Fig. 5 is a perspective view of a bracket that can be connected to the electromagnetic contactor according to the embodiment. Figures 6 and 7 are perspective views of the housing of the electromagnetic contactor according to the embodiment. As shown in FIG. 4, the first movable core plate 10a is provided with a notch 10c. As shown in FIG. 5, the connectable bracket 4 has an engaging portion 4a, and the engaging portion 4a of the connectable bracket 4 is locked. The notch 10c that fits in the first movable iron core plate 10a can be used to mount the connectable bracket 4 to the first movable iron core plate 10a. As shown in FIG. 4, first engagement protrusions 9 b and 9 c are formed on the upper surface 9 a of the bobbin 9 of the polarized electromagnet 2. As shown in FIG. 6, the lower surface 3a of the case 3 is formed with the second engaging projections 3b, 3c. The second engaging projection 3c is provided with a step 3d for holding the first engaging projection 9c. The step 3d is used to prevent the engagement between the first engagement protrusion 9c and the second engagement protrusion 3c in a state where the second engagement protrusion 3c is engaged with the first engagement protrusion 9c.

In a state where the coil 8 is not excited as shown in FIG. 2 Next, the second movable iron core plate 10b is attracted to the fixed iron core plate 11 due to the magnetic force of the permanent magnet 13, so the movable contactor 6 and the fixed contactor 5 maintain a state of being separated by a distance L1.

After the coil 8 is excited, the magnetic field that cancels the magnetic field generated by the permanent magnet 13 will act between the movable iron core 10 and the U-shaped fixed iron core 12, and the movable iron core 10 will be displaced by the distance L2 to the U-shaped fixed iron core 12 side. . As a result, the movable contactor 6 is brought into contact with the fixed contactor 5. Therefore, the distance L2, which is the displacement amount of the movable iron core 10, is larger than the distance L1 and has a relationship of L2> L1.

Next, an assembling procedure of the electromagnetic contactor according to the embodiment will be described. The first step is to install the movable contactor 6 on the connectable bracket 4 and insert the connectable bracket 4 into the casing 3. The second step is to mount the fixed contactor 5 to the casing 3 and perform dust removal by air blow. The third step is to attach the polarized electromagnet 2 to the connectable bracket 4. The fourth step is to insert the polarized electromagnet 2 of the structure assembled through the first, second, and third steps into the cylinder of the back shell 7 to combine the outer shell 3 and the back shell 7 together. The above-mentioned assembly step is to realize a structure in which the foreign matter generated during assembly is not left in the back shell 7 by taking the step of inserting the polarized electromagnet 2 into the cylinder of the back shell 7 as a final step.

That is, in the electromagnetic contactor 1 having the polarized electromagnet 2, the fixed contactor 5 is installed after inserting the accessible bracket 4 provided with the movable contactor 6 into the housing 3, and the polarized The electromagnet 2 and the connectable bracket 4 are engaged with the outer shell 3 for dust removal, and finally the outer shell 3 and the back shell 7 are combined to achieve an assembly step with few foreign matter residues.

In the above assembly step, it is also possible to perform dust removal by blowing air after the assembly, but since it is necessary to prevent foreign matter from invading from the outside, an opening is not provided in the back shell 7, so it is not possible to combine the outer shell 3 with the back shell 7 Perform dust removal.

Next, the assembly steps of the structure including the housing 3, the connectable bracket 4, the fixed contact 5 and the movable contact 6 and the polarized electromagnet 2 will be described. First, the fixed contact 5 is mounted on the connectable bracket 4, and then the connectable bracket 4 is inserted into the housing 3. Next, the housing 3 in which the connectable bracket 4 is inserted is moved in the -y direction so that the engaging portion 4a of the connectable bracket 4 passes through the notch 10c provided in the first movable core plate 10a. FIG. 8 is a cross-sectional view of a portion of the electromagnetic contactor of the embodiment other than the back shell in a state where the engaging portion of the connectable bracket passes through a notch provided in the movable core plate.

After the engaging portion 4a passes through the notch 10c, the housing 3 inserted with the connectable bracket 4 is slid in the + z direction, so that the connectable bracket 4 is engaged with the first movable core plate 10a to make the connectable bracket 4 accessible. The bracket 4 is connected to the polarized electromagnet 2. Through the above assembly steps, the structure including the polarized electromagnet 2, the housing 3, the connectable bracket 4, the fixed contactor 5, and the movable contactor 6, that is, the back shell 7 is removed from the electromagnetic contactor 1. The structures are assembled.

Fig. 9 is a cross-sectional view of a portion of the electromagnetic contactor other than the back shell in a state where the housing with the attachable bracket inserted is slid in the + z direction. By sliding the housing 3 into which the attachable bracket 4 is inserted in the + z direction, the upper surface 3b1 of the second engaging projection 3b and the lower surface 9b1 of the first engaging projection 9b face each other in the y direction, so that the second Snap The upper surface 3c1 of the projection 3c and the lower surface 9c1 of the first engagement projection 9c face each other in the y direction.

Fig. 10 is a cross-sectional view of a portion other than the back shell in a state where the electromagnetic contactor of the embodiment is assembled. 11 and 12 are partial enlarged views of the electromagnetic contactor of the embodiment. FIG. 11 is an enlarged view of Part A and its surroundings in FIG. 10, and FIG. 12 is an enlarged view of Part B and its surroundings in FIG. 10. Fig. 13 is a sectional view of the inside of the housing of the electromagnetic contactor of the embodiment. After the housing 3 with the attachable bracket 4 inserted is slid in the + z direction, since the second engagement protrusion 3b and the first engagement protrusion 9b are not completely engaged, the electromagnetic contactor 1 is assembled. Between the upper surface 3b1 of the second engaging projection 3b and the lower surface 9b1 of the first engaging projection 9b, and between the upper surface 3c1 of the second engaging projection 3c and the lower surface 9c1 of the first engaging projection 9c. There is a clearance of a distance L3 as shown in FIG. 12. The distance L3 of the gap is smaller than the distance L2 shown in FIG. 2 and has a relationship of L3 <L2. The distance L3 of the gap is smaller than the distance L1 between the movable contactor 6 and the fixed contactor 5 in a state where the coil 8 is not excited, and has a relationship of L3 <L1.

Fig. 14 is a sectional view of a portion of the electromagnetic contactor according to the embodiment other than the back shell in a state where the outer shell is lifted up. 15 and 16 are partial enlarged views of the electromagnetic contactor of the embodiment. FIG. 15 is an enlarged view of part C and its surroundings in FIG. 14, and FIG. 16 is an enlarged view of part D and its surroundings in FIG. 14. Fig. 17 is a sectional view of the inside of the housing of the electromagnetic contactor of the embodiment.

In a state where the connectable bracket 4 is engaged with the first movable core plate 10a, when the housing 3 is picked up in the + y direction, the lower surface 9b1 of the first engagement protrusion 9b and the second engagement protrusion 3b The upper surface 3b1 abuts, the lower surface 9c1 of the first engaging protrusion 9c will abut the upper surface 3c1 of the second engaging protrusion 3c, and the second engaging protrusions 3b, 3c will completely contact the first engaging protrusion 9b, 9c. Snap. Therefore, when the housing 3 is picked up in the + y direction, the polarized electromagnet 2 with the coil bobbin 9 is suspended under the housing 3.

In the electromagnetic contactor 1 of the embodiment described above, the first engaging projections 9b, 9c of the upper surface 9a of the coil bobbin 9 and the second engaging projections 3b, 3c provided on the lower surface 3a of the case 3 are not When the housing 3 is picked up in the + y direction, the system is not fully engaged. With such a configuration, as long as the connectable bracket 4 is engaged with the first movable core plate 10a and the connectable bracket 4 is slid in the + z direction, the electromagnetic contactor 1 can be easily assembled. In addition, no tool is required when assembling or disassembling the electromagnetic contactor 1, and therefore, compared with the case of tightening with screws or the case of fitting the claws, the number of man-hours can be reduced.

The first engaging protrusions 9b, 9c of the coil bobbin 9 are in contact with the second engaging protrusions 3b, 3c of the housing 3 only when the case 3 is lifted and the polarized electromagnet 2 is suspended. The first engaging protrusions 9b, 9c and the second engaging protrusions 3b, 3c do not interfere with each other.

If the first engaging protrusions 9b, 9c and the second engaging protrusions 3b, 3c are in contact with each other in the assembled state, the movable contactor 6 will be displaced when the coil 8 is excited and the movable core 10 is moved. The possibility that the quantity and design value will affect the performance of the product. In contrast, real The electromagnetic contactor 1 in this embodiment does not interfere with the first engagement protrusions 9b, 9c and the second engagement protrusions 3b, 3c in the assembled state, so even if the first engagement protrusions 9b, 9c and the second card are provided, The combination of the protrusions 3b and 3c can also reduce the possibility of product performance degradation.

By making the distance L3 of the gap shorter than the distance L1 between the movable contactor 6 and the fixed contactor 5 in the non-excited state of the coil, it is possible to prevent the movable contactor 6 and The amount of reduction in the distance between the fixed contacts 5 becomes equal to or greater than the distance L1, causing the movable contact 6 to come into contact with the fixed contact 5 and break. Therefore, it is possible to prevent a defective product from being generated due to the deformation of the movable contactor 6 during the assembly operation, which may cause a decrease in the yield. Moreover, since the assembly time is shortened, energy consumption in the production process can be suppressed.

By providing the second engaging protrusion 3c for holding the first engaging protrusion 9c to the housing 3, the step of preventing the first engaging protrusion 9c from detaching from the second engaging protrusion 3c from being separated by 3d can be suspended. When the state of the polarized electromagnet 2 tilts the casing 3, the engagement between the first movable core plate 10a and the attachable bracket 4 is prevented from detaching due to the weight of the polarized electromagnet 2. Although the configuration in which the step difference 3d is provided only on the second engagement protrusion 3c is taken as an example here, as long as at least one of the second engagement protrusion 3b, 3c is provided with a step difference to hold the first engagement protrusion 9b, 9c, This prevents the engagement between the first movable iron core plate 10a and the attachable bracket 4 from detaching due to the weight of the polarized electromagnet 2.

As described above, the electromagnetic contactor 1 of the embodiment is assembled after the polarized electromagnet 2 is assembled to the upper case 3, Only the upper shell 3 is assembled to the back shell 7, so a method of assembling as much as possible so that the foreign matter generated during assembly does not remain in the back shell 7 can be realized. Moreover, since the electromagnetic contactor 1 can suspend the polarized electromagnet 2 using the housing 3, it is easy to assemble. Moreover, since a certain gap is provided between the first engaging protrusions 9b, 9c and the second engaging protrusions 3b, 3c, even if the polarizing electromagnet 2 is suspended while the housing 3 is picked up, the movable contactor 6 and The fixed contacts 5 do not touch each other, and deformation and breakage of the movable contacts 6 can be prevented.

The configuration disclosed in the above embodiment is an example of the content of the present invention. In addition, the configuration may be combined with other known technologies or a part of the configuration may be changed without departing from the gist of the present invention. , Omitted.

2‧‧‧ Polarized Electromagnet

8‧‧‧ Coil

8a, 8b‧‧‧

8c‧‧‧ Peripheral

9‧‧‧ Coil Frame

10‧‧‧ Movable iron core

10a‧‧‧The first movable core plate

10b‧‧‧Second movable iron core plate

10d‧‧‧Iron Core Stick

10d1,10d2‧‧‧end

11‧‧‧ fixed iron plate

12‧‧‧U-shaped fixed iron core

12a, 12b‧‧‧End plate section

12c‧‧‧Side panel

13‧‧‧permanent magnet

Claims (3)

An electromagnetic contactor includes: a polarized electromagnet including a coil formed by winding a lead wire around a bobbin; a U-shaped end plate portion extending from both ends of a side plate portion; The end plate portion is opposed to one end of the coil, the other end plate portion is opposed to the other end of the coil at a distance, and the side plate portion and the outer peripheral portion of the coil are arranged to face each other. One pair of U-shaped fixed iron cores inside; one pair of permanent magnets arranged inside the side plate portion of the U-shaped fixed iron core; and one end of the iron core rod inserted through the coil is provided with an U-shaped fixed iron core A first movable core plate on the outside of one end plate portion is provided with a second movable core between the other end of the coil and the other end plate portion of the U-shaped fixed core on the other end of the core rod. The movable iron core of the board; the movable bracket can be connected with the movable contactor and is mounted to the first movable iron core board; the shell can be fixed with the movable contactor and covers the aforementioned movable bracket; The back shell is configured so that the polarized electromagnet is inserted in the first direction to accommodate the polarized electromagnet, and is connected to the housing, wherein the coil bobbin is provided with a first engaging protrusion on an upper surface. The housing is provided with a state in which the connectable bracket is mounted on the first movable core plate, and the housing is preliminarily disposed across the first direction. The gap of the set distance is opposite to the second engagement protrusion of the first engagement protrusion, and the gap is between the movable contactor and the fixed contactor in the first state in a state where the coil is not excited. The distance in the direction is small. The electromagnetic contactor according to item 1 of the scope of patent application, wherein the second engagement protrusion has a state that prevents the first engagement protrusion and the second engagement protrusion from being engaged with the first engagement protrusion. The gap between the engagement and the separation. A method for assembling an electromagnetic contactor, which is the method for assembling an electromagnetic contactor described in item 1 or 2 of the patent application scope, including the following steps: installing the movable contactor to the movable bracket; and installing the aforementioned The aforementioned movable bracket of the movable contactor is inserted into the aforementioned casing; the aforementioned fixed contactor is installed in the casing into which the aforementioned accessible bracket is inserted; the aforementioned accessible bracket with the aforementioned fixed contactor is dust-removed; The bracket is engaged with the first movable iron core plate, so that the connectable bracket is connected with the polarized electromagnet; and the polarized electromagnet is inserted into the back shell, so that the back shell is connected with the outer shell .