Electromagnetic brake

Abstract

To provide an electromagnetic brake including a structure suitable to automatize work for inserting a coil spring therein.SOLUTION: The electromagnetic brake includes a yoke 1, a coil 2 provided on the yoke 1, and a coil spring 10 provided on the yoke 1, where the excitation force of the coil 2 and the spring force of the coil spring 10 are used for switching the ON / OFF state of the brake, the yoke 1 including an inner periphery side yoke part 101, and a spring storage part 103 being on the outer periphery site of the inner periphery side yoke part 101 and having a spring hole 131, the spring storage part 103 being mountable on the outer periphery site of the inner periphery side yoke part 101 in the state of storing the coil spring 10 in the spring hole 131.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an electromagnetic brake that is widely used for braking a rotating body, etc. [Background technology]

[0002] BACKGROUND ART Known electromagnetic brakes are of the non-excitation type, which generate braking force by the torque of a coil spring (see, for example, Patent Document 1).

[0003] As shown in FIG. 11, this patent document 1 includes a yoke 1, a coil 2 provided on the yoke 1, and a coil spring 10 provided on the yoke 1, and the armature 4 can be moved back and forth by the excitation force of the coil 2 and the spring force of the coil spring 10. When not excited, the coil spring 10 moves the armature 4, sandwiching a disk 5 between the armature 4 and the side plate 7, thereby transmitting the braking force of the disk 5 to the motor shaft 11, and when excited, the electromagnetic force pulls the armature 4 away from the side plate 7, thereby releasing the motor shaft 11 through the disk 5. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-220504 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the coil spring of a conventional electromagnetic brake is housed in a flat-bottomed spring hole 1x machined into the yoke 1, as shown in FIG.

[0006] However, when attempting to insert the coil spring 10 into a spring hole 1x of this shape, the spring hole 1x opens in only one direction (the up and down direction in FIG. 11), so the coil spring 10 can only be inserted from that direction. For this reason, the spring insertion work must be performed strictly by hand or by a robot.

[0007] With such a spring housing structure, in particular when inserting the coil spring 10 using a robot, the coordinates of the spring hole 1x, which varies depending on the model, must be individually set on the robot or detected each time, which requires complex settings and has hindered the automation of spring insertion work using a robot.

[0008] The present invention has been made in light of these problems, and has as its object to provide an electromagnetic brake having a structure suitable for automating the insertion of a coil spring. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention takes the following measures.

[0010] That is, the electromagnetic brake of the present invention comprises a yoke, a coil provided on the yoke, and a coil spring provided on the yoke, and switches the brake between ON / OFF states by the excitation force of the coil and the spring force of the coil spring, wherein the yoke comprises an inner circumferential yoke portion and a spring accommodating portion located on the outer periphery of the inner circumferential yoke portion and having a spring hole, and the spring accommodating portion can be attached to the outer periphery of the inner circumferential yoke portion with the coil spring accommodated in the spring hole. premise Let's say.

[0011] In the past, the spring accommodating portion was integrated with the inner yoke portion and other components to form a yoke. In contrast, with the configuration of the present invention, a coil spring can be accommodated in the spring hole of the spring accommodating portion before the spring accommodating portion is positioned on the outer periphery of the inner yoke portion. Therefore, by designing the spring accommodating portion in a shape that makes it easy to insert a coil spring, it is possible to eliminate the need for a robotic process that begins with setting and locating the position of the spring hole, and then inserting the coil spring by aiming at the spring hole from the direction of its opening.

[0012] Based on the above premise, the electromagnetic brake of the present invention is as follows: The spring accommodating portion is preferably an elongated rod-like shape, has a spring hole opening at one side edge, and a coil spring can be inserted into this opening from the side. The spring accommodating portion is bent so that the opening faces the inner periphery, thereby narrowing the opening and deforming it into a circular or partially circular shape, and is attached to the outer periphery of the inner periphery side yoke portion. Characterized by .

[0013] In this way, the coil spring can be inserted into the spring hole of the spring receiving portion from the side before the spring receiving portion is attached to the outer periphery of the inner yoke portion, so that a process can be adopted in which the coil spring is efficiently placed into the spring hole using a parts feeder or other parts supply device without having to precisely aim for the position of the spring hole. Moreover, because the coil spring is rod-shaped before being bent, it requires less storage space and is easier to handle.

[0014] Furthermore, the electromagnetic brake of the present invention, under the above premise, A fall prevention portion is provided near the bottom of the spring hole to prevent the coil spring from falling off. Characterized by .

[0015] In this way, even if the spring hole is penetrated, it is possible to effectively prevent the coil spring from falling off the bottom of the spring accommodating portion before the spring accommodating portion is attached to the outer periphery of the inner yoke portion.

[0016] Furthermore, the electromagnetic brake of the present invention, under the above premise, The yoke Coils are provided on the outer periphery The inner yoke part and this Coil included The inner yoke has a spring hole on the outer periphery. , a separate body from the inner yoke portion A spring accommodating portion is provided. Characterized by .

[0017] A specific embodiment is one in which an outer yoke portion is provided on the outer periphery of the spring accommodating portion, and the spring accommodating portion is inserted axially into an annular gap formed between the inner yoke portion and the outer yoke portion. In this way, the spring accommodating portion can be attached to the yoke body, which is made up of the inner yoke portion and the outer yoke portion, simply by inserting the spring accommodating portion into the annular gap from the axial direction.

[0018] Furthermore, the electromagnetic brake of the present invention, under the above premise, The spring accommodating portion has an outer yoke portion separate from the inner yoke portion at the outer periphery thereof, the spring accommodating portion is located at the outer periphery of the inner yoke portion, and the outer yoke portion is fitted to the outer periphery of the spring accommodating portion. Characterized by .

[0019] In this way, the spring accommodating portion can be fitted or wound around the outer periphery of the inner yoke portion, and then the outer yoke portion can be fitted around the outer periphery of the spring accommodating portion to complete the attachment of the spring accommodating portion to the yoke body composed of the inner yoke portion and the outer yoke portion. Of course, it is also possible to first fit the outer yoke portion around the outer periphery of the inner yoke portion and then insert the spring accommodating portion between the inner and outer yoke portions.

[0020] Furthermore, the electromagnetic brake of the present invention, under the above premise, An intermediate wall that forms part of the yoke is provided on the outer periphery of the inner yoke portion, and the spring accommodating portion is attached to the outer periphery of the intermediate wall. Characterized by .

[0021] In this way, the intermediate wall constitutes the yoke body together with the inner circumferential yoke portion, and can also contribute to the stable installation of the spring accommodating portion.

[0022] In the above, it is preferable that the spring accommodating portion is made of a resin material.

[0023] This makes it easier to fit the spring accommodating portion into the iron core material, which also contributes to reducing the weight of the yoke. [Effects of the Invention]

[0024] According to the present invention as described above, it is possible to provide an electromagnetic brake having a structure suitable for automating the insertion of a coil spring. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view showing an electromagnetic brake according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a yoke portion that constitutes the electromagnetic brake in FIG. 1. [Figure 3] FIG. 3 is a diagram showing the yoke portion of FIG. 2 in a state before assembly. [Figure 4] FIG. 4 is an explanatory diagram of a spring accommodating portion used in the embodiment. [Figure 5] FIG. 4(b) is an enlarged view of a part of FIG. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. 10 is a diagram showing another modified example of the present invention. [Figure 9] FIG. 10 is a diagram showing yet another modified example of the present invention. [Figure 10] FIG. 10 is a diagram showing another modified example of the present invention. [Figure 11] FIG. 10 is a diagram showing the structure of a conventional spring housing portion. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0027] This electromagnetic brake is basically the same as the one shown in Figure 8 of the patent document. That is, as shown in Figure 1, it includes a yoke 1, a coil 2 attached to the yoke 1, and a coil spring 10 attached to the yoke 1, and the excitation force of the coil 2 and the spring force of the coil spring 10 allow the armature 4 to advance and retreat in the axial direction. When de-excited, the coil spring 10 moves the armature 4 to sandwich a disk 5 between the armature 4 and a side plate 7, thereby transmitting a braking force to the motor shaft 11 through the frictional force and holding force of the disk 5. When excited, the electromagnetic force separates the armature 4 from the side plate 7, thereby releasing the motor shaft 11 through the disk 5. The right half of Figure 1 is a cross-section of the electromagnetic brake taken along a line passing through the coil spring 10, and the left half is a cross-section of the electromagnetic brake taken along a line passing through a screw 9, which will be described later and is used to assemble the electromagnetic brake.

[0028] Specifically, yoke 1 is fixed to a stationary frame 3 or the like of the motor to which this electromagnetic brake is attached. Yoke 1 houses a current-carrying coil 2, and forms a magnetic path Φ between yoke 1 and armature 4, which is disposed axially on motor shaft 11. Disk 5 is adjacent to armature 4, and disk 5 is fitted with hub 6, restricting its rotational direction and allowing it to slide axially. Side plate 7 is fixed to yoke 1 via collar 8 with screws 9 or the like. Multiple coil springs 10 are housed in yoke 1. Hub 6 is restricted in its rotational direction on motor shaft 11 with key 13 and is fixed via retaining ring 12 or the like. Alternatively, hub 6 may be fixed to motor shaft 11 by press-fitting or adhesive. A predetermined gap is provided between side plate 7 and yoke 1 due to the dimensions of collar 8, allowing armature 4 and disk 5 to move axially within this gap. When the current to the coil 2 is turned off, the pressing force of the multiple coil springs 10 housed in the yoke 1 presses the disc 5 against the side plate 7 via the armature 4, and the disc 5 generates torque due to the frictional force at the contact surface between the armature 4 and the side plate 7, putting the brake into an applied state. When the current is turned on to the coil 2, a magnetic path Φ is formed between the yoke 1 and the armature 4, generating a magnetic attractive force, which overcomes the pressing force of the coil springs 10 and attracts the armature 4 to the yoke 1, releasing the disc 5 and releasing the applied brake.

[0029] In an electromagnetic brake having such a configuration, in this embodiment, as shown in the yoke assembly diagram of FIG. 2 and the partial exploded view of the yoke in FIG. 3, the portion of the yoke 1 structure that houses the coil spring 10 is separated from the yoke body 100 as spring accommodating section 103, thereby improving the ease of installation of the coil spring 10.

[0030] Specifically, this electromagnetic brake has a yoke 1 that includes at least an inner yoke portion 101 and a spring accommodating portion 103 located on the outer periphery of the inner yoke portion 101 and having a spring hole 131, and this spring accommodating portion 103 can be attached to the outer periphery of the inner yoke portion 101 with a coil spring 10 accommodated in the spring hole 131.

[0031] The yoke body 100, which forms the main body of the yoke 1, is constructed using an iron core material so that the inner yoke portion 101 and the outer yoke portion 102 are integral with each other, and has an annular gap 100a (a bottomed groove in this embodiment) on its upper surface. The coil 2 held by a coil holding member 2a is attached to the inner periphery of the annular gap 100a, and the spring housing portion 103 is inserted from above (axially) between the coil 2 and the outer yoke portion 102, as shown in FIG. 2. Of course, the coil may be of a type that does not have a "coil holding member 2a," i.e., an "air-core coil type."

[0032] The spring accommodating portion 103 is made of a resin part, and when the yoke 1 in FIG. 1 is viewed from the axial direction, the spring accommodating portion would normally correspond to a circular region as shown in FIG. 4(a). Line AA in FIG. 4(a) indicates that FIG. 1 is a cross section taken along that line. The spring accommodating portion 103 in this embodiment has a shape similar to that obtained by cutting out this circular region. In the unfolded state, the spring accommodating portion 103 is configured to have an elongated rod-like shape as shown in FIG. 4(b).

[0033] The spring accommodating section 103 has a spring hole 131 opening on one side edge corresponding to the position of the spring hole 1x in Fig. 4(a), and the coil spring 10 can be inserted into this opening from the side. The spring accommodating section 103 is bent so that the opening of the spring hole 131 faces inward, thereby narrowing the opening and deforming it into an annular shape, as shown in Fig. 4(c), 5(a), and 5(b), so that the spring accommodating section 103 can be inserted from above (axially) into the annular gap 100a in the yoke body 100, as shown in Fig. 3. The spring hole 131 has a U-shaped groove shape in the unfolded state shown in Fig. 4(b).

[0034] Furthermore, V-shaped notches 132 are provided between the spring holes 131, 131 to make it easier to bend the spring accommodating portion 103. In other words, the spring accommodating portion 103 is made up of a number of divided spring accommodating portions (portions in which the spring holes 131 are formed), and the spring accommodating portions are thinly connected by the groove bottom portions of the notches 132.

[0035] Therefore, when the spring accommodating portion 103 is in the expanded state shown in Figure 4(b), the coil spring 10 is inserted into the spring hole 131 opening on one side edge from the side (i.e., in a direction approximately perpendicular to the axial direction of the coil spring 10 accommodated in the spring hole 131), and then the spring accommodating portion 103 is bent into a circular shape as shown in Figures 4(c) and 5(a)-(b), and this spring accommodating portion 103 is then inserted from above into the circular gap 100a of the yoke body 100 as shown in Figure 3, thereby completing the attachment of the coil spring 10 to the yoke body 100.

[0036] The spring accommodating portion 103 also has an opening 133 for the fixing screw 9 used when assembling the brake as shown in Fig. 1 (see Figs. 4 and 5). The opening 133 is also provided at a position corresponding to the spring insertion groove 1y in Fig. 4(a), and by providing an opening on the inner circumferential side, it is possible to accommodate bending deformation toward the inner circumferential side.

[0037] A part of the collar 8 in FIG. 1 is in contact with the yoke 1 (the part indicated by P in the drawing), thereby reducing the force applied to the spring accommodating portion 103 when the screw is tightened.

[0038] As described above, the electromagnetic brake of this embodiment includes yoke 1, coil 2 attached to yoke 1, and coil spring 10 attached to yoke 1, and switches the brake between ON and OFF states using the excitation force of coil 2 and the spring force of coil spring 10. Yoke 1 includes inner yoke portion 101 and spring accommodating portion 103 located on the outer periphery of inner yoke portion 101 and having spring hole 131, and spring accommodating portion 103 can be attached to the outer periphery of inner yoke portion 101 with coil spring 10 housed in spring hole 131.

[0039] In the conventional structure shown in FIG. 11 , the spring accommodating portion 103 is an integral part of the yoke 1. In contrast, in this embodiment, the spring accommodating portion 103 is separated from the yoke 1, allowing the coil spring 10 to be accommodated in the spring hole 131 of the spring accommodating portion 103 before the spring accommodating portion 103 is positioned on the outer periphery of the inner yoke portion 101. Therefore, by designing the spring accommodating portion 103 to facilitate insertion of the coil spring 10, the conventional problem shown in FIG. 11 is eliminated, namely, the robotic process of setting and locating the spring hole position, and then inserting the coil spring into the spring hole by aiming it from the direction of its opening. This reduces the work time. Naturally, similar effects can be achieved when the work is performed manually.

[0040] The spring accommodating portion 103 has an elongated rod-like shape, with a spring hole 131 opening at one side edge, into which the coil spring 10 can be inserted from the side, and then the opening is bent so that it faces the inner periphery, thereby narrowing the opening and deforming it into a circular ring shape, so that it can be attached to the outer periphery of the inner yoke portion 101.

[0041] As a result, the coil spring 10 can be inserted into the spring hole 131 of the spring accommodating portion 103 before the spring accommodating portion 103 is attached to the outer periphery of the inner yoke portion 101, eliminating the need to precisely aim the position of the spring hole 131 and making it possible to employ a process of efficiently placing the coil spring into the spring hole using a parts supply device such as a parts feeder. Furthermore, by making the spring accommodating portion 103 rod-shaped, the space on the inner periphery side does not become dead space compared to when the spring accommodating portion is configured to be annular from the start, so less storage space is required and it is more convenient for transportation and for configuring a coil spring loading device.

[0042] In addition, an outer yoke portion 102 is provided on the outer periphery of the spring accommodating portion 103, and the spring accommodating portion 103 is configured to be inserted axially into an annular gap 100a formed between the inner yoke portion 101 and the outer yoke portion 102.

[0043] Therefore, simply by inserting the spring accommodating portion 103 into the annular gap 100a from the axial direction, the spring accommodating portion 103 can be attached to the yoke body 100, which is composed of the inner yoke portion 101 and the outer yoke portion 102.

[0044] In addition, in this embodiment, the spring accommodating portion 103 is made of a resin material, which makes it easier to fit the spring accommodating portion 103 into the yoke body 100, which is made of an iron core material, and by making a portion of the yoke 1 out of resin, it also contributes to reducing the weight of the entire yoke 1.

[0045] Although one embodiment of the present invention has been described above, the specific configuration of each part is not limited to the above-described embodiment.

[0046] For example, as shown in FIG. 6, a drop-out prevention portion 131a for preventing the coil spring 10 from dropping out may be provided near the bottom of the spring hole 131.

[0047] In this way, even if the spring hole 131 penetrates in the vertical direction, it is possible to effectively prevent the coil spring 10 from falling off from the bottom of the spring accommodating portion 103 during movement when positioning the spring accommodating portion 103 at the outer periphery of the inner yoke portion 101.

[0048] It is also effective to provide a recess 133a and a protrusion 133b in the fixing screw relief hole 133, as shown in FIG. 7 . These recesses 133a and protrusions 133b are provided on both sides of the opening edge of the fixing screw relief hole 133, so that when the fixing screw is bent, one recess 133a fits into the other protrusion 133b, allowing the fixing screw relief hole 133 to close in a desirable shape. This shape eliminates gaps in the cutouts of the relief hole 133 for the fixing screw 9, for example, as shown in FIG. 5(b). This allows the screw to evenly press the periphery of the relief hole 133 when tightened, reducing deformation of the spring accommodating portion 103 due to the tightening force of the screw. This configuration is effective when the spring accommodating portion 103 is made of a soft material such as resin.

[0049] Also, as shown in FIG. 8, a structure can be adopted in which an outer yoke portion 102 separate from an inner yoke portion 101 is provided at the outer periphery of the spring accommodating portion 103, the spring accommodating portion 103 is positioned at the outer periphery of the inner yoke portion 101, and the outer yoke portion 102 is fitted to the outer periphery of the spring accommodating portion 103.

[0050] In this manner, spring accommodating portion 103 can be fitted or wound around the outer periphery of inner yoke portion 101, and then outer yoke portion 102 can be fitted around the outer periphery of spring accommodating portion 103 to complete the attachment of spring accommodating portion 103 to yoke body 100, which is made up of inner yoke portion 101 and outer yoke portion 102. Of course, spring accommodating portion 103 can also be inserted between inner yoke portion 101 and outer yoke portion 102 after fitting outer yoke portion 102 into inner yoke portion 101.

[0051] 9(a), an intermediate wall 104 forming part of the yoke 1 may be provided on the outer periphery of the inner yoke portion 101, and the spring accommodating portion 103 may be attached to the outer periphery of the intermediate wall 104.

[0052] In this way, intermediate wall 104, together with inner yoke portion 101, constitutes yoke body 100 and also contributes to the stable installation of spring accommodating portion 103. In this case, spring accommodating portion 103 can be fixed by fitting outer yoke portion 102 onto the outside of spring accommodating portion 103. In this case, outer yoke portion 102 does not necessarily have to be made of an iron core material because intermediate wall 104 forms a magnetic path.

[0053] In addition, in the structure of FIG. 9(a), the intermediate wall 104 is configured integrally with the inner yoke portion 101, but it may also be attached as a separate body from the inner yoke portion 101, as in the intermediate wall 104' of FIG. 9(b).

[0054] Alternatively, as shown in FIG. 10(a), if the spring accommodating portion 103 can be stably mounted, the outer circumferential yoke portion can be omitted.

[0055] 10(b), a spacer 8 that keeps a constant distance between the side plate 7 and the yoke 1 may be integrally formed in the spring accommodating portion 103 in the portion where the fixing screw relief hole 133 for assembling the brake is provided. In this way, the number of parts can be reduced.

[0056] Furthermore, the spring accommodating portion is not necessarily limited to a circular ring shape, but may be configured as a partial ring shape by assembling two or more parts to form a circular ring shape.

[0057] Alternatively, the spring accommodating portion may be configured in a continuous, long state, for example wound up like a reel, and then cut to the required length for use.

[0058] Furthermore, if convenience in storage or the like is not required, there is nothing to prevent the spring accommodating portion from being formed in a circular ring shape from the beginning.

[0059] Other configurations can also be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0060] 1. York 2...Coil 10...Coil spring 100a...Circular gap 101...Inner yoke part 102...Outer yoke part 103...Spring housing 104...Intermediate wall 131...Spring hole 131a... Falling prevention part

Claims

1. A brake device comprising a yoke, a coil provided on said yoke, and a coil spring provided on said yoke, wherein the ON / OFF state of the brake is switched by the excitation force of said coil and the spring force of said coil spring, The yoke comprises an inner yoke portion and a spring accommodating portion located on the outer periphery of the inner yoke portion and having a spring hole, and the spring accommodating portion can be attached to the outer periphery of the inner yoke portion with a coil spring accommodated in the spring hole, the spring accommodating portion has an elongated rod-like shape, a spring hole opening at one side edge, a coil spring can be inserted into this opening from the side, and the spring accommodating portion is attached to the outer periphery of the inner yoke portion in a state where the opening is narrowed by bending the spring accommodating portion so that the opening faces the inner periphery and the spring is deformed into a circular or partial circular shape.

2. A brake device comprising a yoke, a coil provided on the yoke, and a coil spring provided on the yoke, in which the ON / OFF state of the brake is switched by the excitation force of the coil and the spring force of the coil spring, The yoke comprises an inner yoke portion and a spring accommodating portion located on the outer periphery of the inner yoke portion and having a spring hole, and the spring accommodating portion can be attached to the outer periphery of the inner yoke portion with a coil spring accommodated in the spring hole, An electromagnetic brake characterized in that a fall-off prevention portion is provided near the bottom of the spring hole to prevent the coil spring from falling off.

3. A brake device comprising a yoke, a coil provided in the yoke, and a coil spring provided in the yoke, in which the ON / OFF state of a brake is switched by the excitation force of the coil and the spring force of the coil spring, an electromagnetic brake, characterized in that the yoke comprises an inner yoke portion having a coil provided on its outer periphery, and a spring accommodating portion separate from the inner yoke portion, the spring accommodating portion having a spring hole located on the outer periphery of the inner yoke portion including the coil, and the spring accommodating portion can be attached to the outer periphery of the inner yoke portion with a coil spring accommodated in the spring hole.

4. 4. The electromagnetic brake according to claim 3, further comprising an outer yoke portion on an outer periphery of the spring accommodating portion, the spring accommodating portion being inserted in the axial direction into an annular gap formed between the inner yoke portion and the outer yoke portion.

5. A brake device comprising a yoke, a coil provided on the yoke, and a coil spring provided on the yoke, in which the ON / OFF state of the brake is switched by the excitation force of the coil and the spring force of the coil spring, The yoke comprises an inner yoke portion and a spring accommodating portion located on the outer periphery of the inner yoke portion and having a spring hole, and the spring accommodating portion can be attached to the outer periphery of the inner yoke portion with a coil spring accommodated in the spring hole, An electromagnetic brake characterized in that the electromagnetic brake has a structure in which an outer yoke portion separate from the inner yoke portion is provided on the outer periphery of the spring accommodating portion, the spring accommodating portion is located on the outer periphery of the inner yoke portion, and the outer yoke portion is fitted onto the outer periphery of the spring accommodating portion.

6. A brake device comprising a yoke, a coil provided on the yoke, and a coil spring provided on the yoke, in which the ON / OFF state of the brake is switched by the excitation force of the coil and the spring force of the coil spring, The yoke comprises an inner yoke portion and a spring accommodating portion located on the outer periphery of the inner yoke portion and having a spring hole, and the spring accommodating portion can be attached to the outer periphery of the inner yoke portion with a coil spring accommodated in the spring hole, An electromagnetic brake comprising an intermediate wall forming a part of the yoke at an outer periphery of the inner yoke portion, and the spring accommodating portion attached to an outer periphery of the intermediate wall.

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