TW201621954A - Electromagnetic contactor and method for assembling the same - Google Patents

Abstract

An electromagnetic contactor includes: a polarized electromagnet (2); a receivable carrier, on which a movable contactor can be mounted, being amounted on a first movable iron core plate (10a); a case, on which a fixed contactor can be amounted, covering the receivable carrier; and rear case accommodating the polarized electromagnet (2) and connecting to the case. An upper surface of a coil bobbin (9) is provided with a first engaging protrusion, and the case includes: a second engaging protrusion, which is opposite to and spaced from the first engaging protrusion with a clearance having a pre-determined distance while the receivable carrier is mounted to the first movable iron core plate (10a).

Description

Electromagnetic contactor and electromagnetic contactor assembly method

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 has a polarized electromagnet in which a permanent magnet and a coil are combined, a carrier that can mount a movable contact, and a contact with a movable contact. A contact case, a rear case that houses the polarized electromagnet, and a case that covers the connectable bracket and is engaged with the back cover. The polarized electromagnet has a coil formed by winding a wire, a coil bobbin for winding a coil, a movable iron core that penetrates the bobbin in the axial direction, and a U-shaped fixing that faces the movable iron core. The iron core, the magnetic pole plate disposed opposite to the coil, and the permanent magnet disposed on the fixed iron core. The connectable bracket provided with the movable contact is mounted to the movable core plate, and the movable contact is displaced by the same amount as the movable iron core is displaced.

In the electromagnetic contactor disclosed in Patent Document 1, the movable iron core is sucked by the magnetic force of the permanent magnet without exciting the coil. Attached to the magnetic pole plate, the state in which the movable contact is separated from the fixed contact is maintained. When the coil is excited, a magnetic field that cancels the magnetic field of the permanent magnet is generated between the movable iron core and the fixed iron core, so that the movable iron core plate is displaced toward the fixed core plate side, and the movable contact is in contact with the fixed contact. status.

[Previous Technical Literature]

(Patent Literature)

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

When the foreign matter is caught in the drive unit of the electromagnetic contactor, the operation is poor, and if the foreign matter is caught between the contacts of the electromagnetic contactor, the contact life is shortened. The electromagnetic contactor must prevent foreign matter. Invade and remain inside the product. Therefore, the electromagnetic contactor must use a frame having no opening as much as possible, and must be assembled in such a manner that no foreign matter remains in the casing as much as possible.

However, Patent Document 1 does not disclose an assembly step in consideration of an electromagnetic contactor that prevents intrusion of foreign matter and remains.

Further, in the electromagnetic contactor disclosed in Patent Document 1, the polarizable electromagnet is lifted by holding the outer casing while inserting the detachable bracket provided with the movable contact into the outer casing and mounting the polarized electromagnet to the outer casing. The connectable bracket will drop due to the weight of the polarized electromagnet. Once the connectable bracket is lowered due to the weight of the polarized electromagnet, the movable contact will be made larger than the equal Since the displacement amount of the movable bracket is displaced from the fixed contact, the movable contact is deformed.

In order to prevent deformation of the movable contact, it is necessary to hold the outer casing and the polarized electromagnet at the same time, but with the outer casing and the polarized electromagnet held by both hands, the work efficiency of the assembly work is lowered. Therefore, it is necessary to have a structure in which the outer casing of the entire structure except the back shell is brought into contact with the polarized electromagnet without bringing the movable contact into contact with the fixed contact.

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

In order to solve the above problems, an object of the present invention is to provide a polarizable electromagnet; a movable carrier that can be mounted with a movable contact and attached to a first movable core plate of a polarized electromagnet; a case in which a fixed contact is attached and covers the attachable bracket; and a rear case in which the polarized electromagnet is housed and coupled to the outer casing, wherein the polarized electromagnet is provided with: a coil formed by winding a wire around a coil bobbin; forming a U-shaped end plate portion extending from both ends of the side plate portion, and having one end plate portion facing one end of the coil, The other end plate portion and the other end of the coil are opposed to each other with the other end of the coil facing each other, and the side plate portion and the outer peripheral portion of the coil are opposed to each other, and the coil is disposed inside the U-shaped fixed iron core; and the U-shaped fixed iron core is disposed. One of the inner side of the side plate portion is opposite to the permanent magnet; and at one end of the iron core rod inserted through the coil, the first movable iron core plate is disposed outside the one end plate portion of the U-shaped fixed iron core, and the other of the iron core rod One end is provided with a movable iron core of a second movable core plate between the other end of the coil and the other end plate portion of the U-shaped fixed iron core; the bobbin is provided with a first engaging projection on the upper surface, and the outer casing is provided with a first engaging projection The second engagement projection that faces the first engagement projection with a clearance of a predetermined distance in a state in which the attachable bracket is attached to the first movable core plate is provided.

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

1‧‧‧Electromagnetic contactor

2‧‧‧Polarized electromagnet

3‧‧‧ Shell

3a‧‧‧lower surface

3b, 3c‧‧‧Second card joint protrusion

3d‧‧‧ paragraph difference

4‧‧‧Connectable bracket

4a‧‧‧Clock Department

5‧‧‧Fixed contact

6‧‧‧ movable contact

7‧‧‧ Back shell

8‧‧‧ coil

8a, 8b‧‧‧

8c‧‧‧The outer part

9‧‧‧ coil holder

9a‧‧‧Upper surface

9b, 9c‧‧‧ first card joint protrusion

10‧‧‧ movable iron core

10a‧‧‧First movable core plate

10b‧‧‧Second movable core plate

10c‧‧‧ gap

10d‧‧‧ iron heart stick

10d1, 10d2‧‧‧

11‧‧‧Fixed core plate

12‧‧‧U-shaped fixed iron core

12a, 12b‧‧‧ End Plate Department

12c‧‧‧Side plate department

13‧‧‧ permanent magnet

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

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

Fig. 3 is a cross-sectional view showing a polarized electromagnet of the electromagnetic contactor of the embodiment.

Fig. 4 is a perspective view showing a polarizing electromagnet of the electromagnetic contactor of the embodiment.

Fig. 5 is a perspective view showing the attachable bracket of the electromagnetic contactor of the embodiment.

Fig. 6 is a perspective view showing the outer casing of the electromagnetic contactor of the embodiment.

Fig. 7 is a perspective view showing the outer casing of the electromagnetic contactor of the embodiment.

Fig. 8 is a cross-sectional view showing a portion of the electromagnetic contactor of the embodiment in which the engaging portion of the attachable bracket is passed through the notch provided in the movable core plate except for the back shell.

Fig. 9 is a cross-sectional view showing a portion of the electromagnetic contactor of the embodiment in a state in which the outer casing into which the detachable bracket is inserted is swept in the +z direction, except for the back shell.

Fig. 10 is a cross-sectional view showing a portion other than the back shell in a state in which 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.

Figure 13 is a cross-sectional view showing the inside of the outer casing of the electromagnetic contactor of the embodiment.

Fig. 14 is a cross-sectional view showing a portion other than the back shell in a state where the outer casing of the electromagnetic contactor of the embodiment is picked 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.

Figure 17 is a cross-sectional view showing the inside of the outer casing of the electromagnetic contactor of the embodiment.

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

Implementation form.

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

The electromagnetic contactor 1 has a polarized electromagnet composed of a permanent magnet and a coil, a connectable bracket 4 to which the movable contact 6 can be attached, a fixed contact 5 that contacts/separates the movable contact 6, and a receiving pole. The cylindrical back shell 7 of the electromagnet 2 is used. Furthermore, the electromagnetic contactor 1 also has a housing 3 covering the dockable bracket 4. A fixed contact 5 can be mounted in the outer casing 3.

Fig. 3 is a cross-sectional view showing a polarized electromagnet of the electromagnetic contactor of the embodiment. The polarized electromagnet 2 has a coil 8 formed by winding a wire around a bobbin 9 and a pair of U-shaped fixed iron cores 12, and the pair of U-shaped fixed iron cores 12 are configured such that the coil 8 is internally: One end plate portion 12a faces the one end 8a of the coil 8, and the other end plate portion 12b faces the other end 8b of the coil 8 with a space therebetween, and the side plate portion 12c faces the outer peripheral portion 8c of the coil 8. . Further, the polarized electromagnet 2 further has: one 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 to be provided The first movable core plate 10a located outside the one end plate portion 12a of the U-shaped fixed iron core 12, and the other of the iron core bars 10d The one end 10d2 is provided with a movable iron core 10 of the second movable core plate 10b to be positioned between the other end 8b of the coil 8 and the other end plate portion 12b of the U-shaped fixed iron core 12. Further, the polarized electromagnet 2 is provided with a fixed core plate 11 made of a magnetic material inside the permanent magnet 13. The distance between the second movable core plate 10b and the other end plate portion 12b of the U-shaped fixed iron core 12 is L2. That is, the movable core 10 has a displacement amount of the distance L2.

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

Fig. 4 is a perspective view showing a polarizing electromagnet of the electromagnetic contactor of the embodiment. Fig. 5 is a perspective view showing the attachable bracket of the electromagnetic contactor of the embodiment. 6 and 7 are perspective views of the outer casing of the electromagnetic contactor of 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 attachable bracket 4 has an engaging portion 4a by which the engaging portion 4a of the attachable bracket 4 is carded. The notch 10c of the first movable core plate 10a is attached to the first movable core plate 10a. As shown in Fig. 4, the upper surface 9a of the bobbin 9 of the polarized electromagnet 2 is formed with first engaging projections 9b, 9c. As shown in Fig. 6, the lower surface 3a of the outer casing 3 is formed with 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 for preventing the engagement between the first engagement projection 9c and the second engagement projection 3c in a state in which the second engagement projection 3c is engaged with the first engagement projection 9c.

The state in which the coil 8 is not excited as shown in Fig. 2 Then, the second movable core plate 10b is attracted to the fixed core plate 11 by the magnetic force of the permanent magnet 13, so that the movable contact 6 and the fixed contact 5 are maintained at a distance L1 apart.

After the coil 8 is excited, the magnetic field of the magnetic field generated by the permanent magnet 13 is applied between the movable iron core 10 and the U-shaped fixed iron core 12, and the movable iron core 10 is displaced toward the U-shaped fixed iron core 12 by the distance L2. . As a result, the movable contact 6 is in contact with the fixed contact 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, the assembly procedure of the electromagnetic contactor of the embodiment will be described. In the first step, the movable contact 6 is mounted on the splicable bracket 4, and the splicable bracket 4 is inserted into the outer casing 3. The second step is to attach the fixed contact 5 to the outer casing 3, and perform dust removal by air blow. The third step attaches the polarized electromagnet 2 to the dockable bracket 4. In the fourth step, the polarized electromagnet 2 of the structure assembled by the first, second and third steps is inserted into the barrel of the back shell 7 to fit the outer shell 3 and the back shell 7. In the above-described assembling step, the step of inserting the polarized electromagnet 2 into the cylinder of the back shell 7 is used as a final step, and the structure in which the foreign matter generated during the assembly does not remain in the back shell 7 is achieved.

That is, in the electromagnetic contactor 1 having the polarized electromagnet 2, by inserting the detachable bracket 4 provided with the movable contact 6 into the outer casing 3, the fixed contact 5 is mounted while being polarized The electromagnet 2 and the attachable bracket 4 are engaged with the outer casing 3 to perform dust removal, and finally the outer casing 3 and the back shell 7 are combined to realize a small number of assembly steps of foreign matter remaining.

In the above-described assembly step, it is also conceivable to perform dust removal by blowing air after the assembly, but since the foreign matter is prevented from intruding from the outside, the opening portion is not provided in the back shell 7, so that the outer casing 3 and the back shell 7 cannot be combined. Dust removal.

Next, an assembly procedure of the structure including the outer casing 3, the attachable bracket 4, the fixed contact 5, and the movable contact 6 and the polarizing electromagnet 2 will be described. First, the fixed contact 5 is attached to the detachable bracket 4, and then the detachable bracket 4 is inserted into the outer casing 3. Next, the outer casing 3 into which the attachable bracket 4 is inserted is moved in the -y direction so that the engaging portion 4a of the attachable bracket 4 passes through the notch 10c provided in the first movable core plate 10a. Fig. 8 is a cross-sectional view showing a portion of the electromagnetic contactor of the embodiment in which the engaging portion of the attachable bracket is passed through the notch provided in the movable core plate except for the back shell.

After the engaging portion 4a is passed through the notch 10c, the outer casing 3 into which the detachable bracket 4 is inserted is slid in the +z direction, thereby engaging the detachable bracket 4 with the first movable core plate 10a, thereby making it possible to connect The bracket 4 is coupled to the polarized electromagnet 2. Through the above assembly steps, the structure including the polarized electromagnet 2, the outer casing 3, the connectable bracket 4, the fixed contact 5, and the movable contact 6 is removed, that is, after the back shell 7 is removed from the electromagnetic contactor 1. The structures are grouped together.

Fig. 9 is a cross-sectional view showing a portion of the electromagnetic contactor of the embodiment in a state in which the outer casing into which the detachable bracket is inserted is slid in the +z direction, except for the back shell. The upper surface 3b1 of the second engaging projection 3b and the lower surface 9b1 of the first engaging projection 9b are opposed to each other in the y direction by sliding the outer casing 3 into which the detachable bracket 4 is inserted in the +z direction, so that the second Clamp The upper surface 3c1 of the projection 3c faces the lower surface 9c1 of the first engagement projection 9c in the y direction.

Fig. 10 is a cross-sectional view showing a portion other than the back shell in a state in which 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 showing a portion A and its surroundings in Fig. 10, and Fig. 12 is an enlarged view showing a portion B in Fig. 10 and its surroundings. Figure 13 is a cross-sectional view showing the inside of the outer casing of the electromagnetic contactor of the embodiment. In a state in which the outer casing 3 into which the detachable bracket 4 is inserted is slid in the +z direction, since the second engaging projection 3b and the first engaging projection 9b are not completely engaged, the electromagnetic contactor 1 is assembled. The state between the upper surface 3b1 of the second engagement projection 3b and the lower surface 9b1 of the first engagement projection 9b, and the upper surface 3c1 of the second engagement projection 3c and the lower surface 9c1 of the first engagement projection 9c In the meantime, there is a clearance of distance L3 as shown in Fig. 12. The gap distance L3 is smaller than the distance L2 shown in FIG. 2 and has a relationship of L3 < L2. Further, the gap distance L3 is smaller than the distance L1 between the movable contact 6 and the fixed contact 5 in a state where the coil 8 is not excited, and has a relationship of L3 < L1.

Fig. 14 is a cross-sectional view showing a portion other than the back shell in a state where the outer casing of the electromagnetic contactor of the embodiment is picked up. 15 and 16 are partial enlarged views of the electromagnetic contactor of the embodiment. Fig. 15 is an enlarged view showing a portion C and its surroundings in Fig. 14, and Fig. 16 is an enlarged view showing a portion D in Fig. 14 and its surroundings. Figure 17 is a cross-sectional view showing the inside of the outer casing of the electromagnetic contactor of the embodiment.

When the attachable bracket 4 is engaged with the first movable core plate 10a, the outer casing 3 is picked up in the +y direction, and the lower surface 9b1 of the first engaging projection 9b and the second engaging projection 3b are When the upper surface 3b1 abuts, the lower surface 9c1 of the first engaging projection 9c abuts against the upper surface 3c1 of the second engaging projection 3c, and the second engaging projections 3b, 3c are completely identical to the first engaging projections 9b, 9c. Engage. Therefore, the outer casing 3 is picked up in the +y direction, and the polarized electromagnet 2 having the bobbin 9 is hung under the outer casing 3.

In the electromagnetic contactor 1 of the embodiment described above, the first engaging projections 9b and 9c of the upper surface 9a of the bobbin 9 and the second engaging projections 3b and 3c provided on the lower surface 3a of the outer casing 3 are not When the outer casing 3 is picked up in the +y direction, it is not completely engaged. With such a configuration, the electromagnetic contactor 1 can be easily assembled by sliding the attachable bracket 4 in the +z direction after the engageable bracket 4 is engaged with the first movable core plate 10a. Moreover, since the tool is not required when the electromagnetic contactor 1 is assembled or disassembled, the man-hour can be eliminated as compared with the case of locking with a screw or fitting the hook.

The first engaging projections 9b, 9c of the bobbin 9 are in contact with the second engaging projections 3b, 3c of the outer casing 3 only when the polarizing electromagnet 2 is lifted while picking up the outer casing 3, and in the assembled state, The first engaging projections 9b, 9c do not interfere with the second engaging projections 3b, 3c.

When the first engaging projections 9b, 9c and the second engaging projections 3b, 3c are in contact with each other in the assembled state, there is a displacement of the movable contact 6 when the coil 8 is excited to move the movable core 10. The possibility that the amount is different from the design value and affects the performance of the product. Relative to this, Since the first engagement projections 9b, 9c and the second engagement projections 3b, 3c do not interfere with each other in the assembled state, the first engagement projections 9b, 9c and the second card are provided. The combination of the projections 3b, 3c also reduces the possibility of deterioration in product performance.

By making the gap L3 shorter than the distance L1 between the movable contact 6 and the fixed contact 5 of the unexcited state of the coil, it is possible to prevent the movable contact 6 from being caused by the self-weight of the polarized electromagnet 2 during the assembly operation. 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 breakage. Therefore, it is possible to prevent a defective product from being generated due to deformation of the movable contact 6 during the assembly work, resulting in a decrease in yield. Moreover, since the assembly time is shortened, the energy consumption in the production process can be suppressed.

By providing the second engagement projection 3c for holding the first engagement projection 9c to the outer casing 3, the step of disengaging the first engagement projection 9c from the second engagement projection 3c is prevented from being separated by 3d, and can be hung The state of the polarized electromagnet 2 causes the outer casing 3 to be inclined, and prevents the engagement between the first movable core plate 10a and the attachable bracket 4 from being separated by the self-weight of the polarized electromagnet 2. Here, the configuration in which the step 3d is provided only in the second engaging projection 3c is taken as an example. However, at least one of the second engaging projections 3b and 3c is provided with a step for holding the first engaging projections 9b and 9c. It is possible to prevent the engagement of the first movable core plate 10a and the attachable bracket 4 from being separated by the own weight of the polarized electromagnet 2.

As described above, the electromagnetic contactor 1 of the embodiment is attached until the polarized electromagnet 2 is assembled to the upper casing 3, Since the upper outer casing 3 is assembled to the back shell 7, it is possible to achieve an assembly method in which the foreign matter generated during assembly is not left in the back shell 7. Moreover, since the electromagnetic contactor 1 can hang the polarizing electromagnet 2 by the outer casing 3, it is easy to assemble. Further, since a certain gap is provided between the first engaging projections 9b and 9c and the second engaging projections 3b and 3c, even if the outer casing 3 is picked up and the polarizing electromagnet 2 is hung, the movable contact 6 and the movable contact 6 are The fixed contact 5 does not come into contact with each other, and deformation and breakage of the movable contact 6 can be prevented.

The configuration disclosed in the above embodiments is an example of the content of the present invention, and may be combined with other known techniques or a part of the configuration may be changed without departing from the spirit of the present invention. Omitted.

2‧‧‧Polarized electromagnet

8‧‧‧ coil

8a, 8b‧‧‧

8c‧‧‧The outer part

9‧‧‧ coil holder

10‧‧‧ movable iron core

10a‧‧‧First movable core plate

10b‧‧‧Second movable core plate

10d‧‧‧ iron heart stick

10d1, 10d2‧‧‧

11‧‧‧Fixed core plate

12‧‧‧U-shaped fixed iron core

12a, 12b‧‧‧ End Plate Department

12c‧‧‧Side plate department

13‧‧‧ permanent magnet

Claims (4)

An electromagnetic contactor comprising: a polarized electromagnet; and a coil formed by winding a wire around a bobbin; and forming a U-shape extending from both ends of the side plate portion, and causing one of the foregoing The end plate portion faces the one end of the coil, and the other end plate portion faces the other end of the coil, and the side plate portion faces the outer peripheral portion of the coil so that the coil is disposed a pair of U-shaped fixed iron cores; one pair of permanent magnets disposed on an inner side of the side plate portion of the U-shaped fixed iron core; and one end of the iron core rod inserted through the coil, and the U-shaped fixed iron core a first movable core plate on the outer side of one end plate portion, and a second movable iron core located between the other end of the coil and the other end plate portion of the U-shaped fixed iron core at the other end of the iron core rod The movable iron core of the board; the connectable bracket is configured to be provided with a movable contact and is mounted to the first movable iron core board; the outer casing is capable of being provided with a fixed contact and covering the connectable bracket; And the back shell is configured to receive the polarized electromagnet and is coupled to the outer casing, wherein the bobbin includes a first engaging projection on an upper surface thereof, and the outer casing is provided to attach the attachable bracket to the front In the state of the first movable core plate, the second engagement projection is opposed to the first engagement projection via a gap of a predetermined distance. The electromagnetic contactor according to claim 1, wherein the gap is smaller than a distance between the movable contact and the fixed contact in a state where the coil is not excited. The electromagnetic contactor according to the first aspect of the invention, wherein the second engagement projection has the first engagement projection and the second engagement projection in a state of being engaged with the first engagement projection. The difference between the engagement and the disengagement. A method of assembling an electromagnetic contactor according to any one of claims 1 to 3, comprising the steps of: attaching the movable contactor to the movable bracket; The movable bracket provided with the movable contact is inserted into the outer casing; the fixed contact is mounted on the outer casing into which the connectable bracket is inserted; and the connectable bracket provided with the fixed contact is dusted; Engaging the connectable bracket with the first movable core plate to connect the connectable bracket to the polarized electromagnet; and inserting the polarized electromagnet into the back shell to make the back shell and the back shell The aforementioned outer casings are coupled.