JPH08338652A - Ventilation fan for duct - Google Patents

Abstract

PURPOSE: To enable a main body frame to be easily coupled to a fixing plate in which the main body frame is coupled to the fixing plate and fixed there. CONSTITUTION: A fixing plate 11 is provided with a resiliently deformable engaging projection 16, a main body frame 12 is provided with an engaging groove 21, the main body frame 12 is inserted and passed through a ceiling opening from a lower side, the engaging groove 21 is slidingly engaged with the engaging projection 16, thereby the main body frame 12 can be coupled not only to the fixing plate 11 but also the main body frame 12 is moved toward the fixing plate 11 while it is being inserted, thereby the main body frame 12 can be coupled to the fixing plate 11 even by press fitting the engaging groove 21 to the main body frame 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duct ventilation fan having an improved structure for connecting a main body frame to a mounting plate.

[0002]

2. Description of the Related Art Conventionally, in this type of duct ventilation fan, its attachment has been performed by the structure shown in FIGS. That is, the mounting plate 4 having the ventilation port 3 is mounted on the edge portion (the edge portion of the wooden frame 1) of the opening 2 formed in the ceiling (not shown) by the wooden frame 1, whereby the mounting plate 4 is attached. Is erected on the back of the ceiling, and a duct (also not shown) is connected to the vent 3 in the back of the ceiling.

On the other hand, a main body frame 6 having a fan device 5 inside is inserted from below into an opening 2 in the ceiling where the mounting plate 4 is mounted, and is folded and formed in advance on both left and right sides of the mounting plate 4. Into the engaging groove portions 7 which are opened facing each other, engaging convex portions 8 which are also formed in advance on opposite sides of the corresponding surface portion of the main body frame 6 and which project in opposite directions are inserted from below and are slidably engaged. Thus, the main body frame 6 is positioned on the back of the ceiling and communicated with the ventilation port 3 to be coupled to the mounting plate 4, and in this state, the main body frame 6 is attached to the opening 2 (the wooden frame 1) of the ceiling.
Is fixed by screws or the like.

[0004]

In the case of the above-mentioned conventional one, when the main body frame 6 is coupled to the mounting plate 4, the left and right engaging groove portions 7 of the mounting plate 4 at the height of the ceiling are provided with the main body frame 6. It was necessary to insert the left and right engaging projections 8 from below to make a sliding engagement, and this work was difficult. Further, in the case of this, even if it is noticed that the engaging convex portion 8 of the main body frame 6 is not engaged with the engaging groove portion 7 of the mounting plate 4 during the insertion of the main body frame 6, in order to correct it, It was troublesome to remove all the main body frame 6 and re-engage the engaging convex portion 8 of the main body frame 6 with the engaging groove portion 7 of the mounting plate 4.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a ventilation fan for a duct in which a main body frame can be easily connected to a mounting plate.

[0006]

In order to achieve the above object, in a duct ventilation fan according to the present invention, firstly, a lower end portion is attached to an edge portion of an opening formed in a ceiling so that it is attached to the back of the ceiling. It is provided upright and has a plastic mounting plate having a vent for connecting a duct at the back of the ceiling and a fan device inside, and is inserted into the opening of the ceiling from below and positioned at the back of the ceiling. A plastic main body frame which is communicated with the vent hole and is fixed to the opening of the ceiling in this state, and an engaging protrusion is provided on both left and right sides of one of the mounting plate and the main body frame. Provided on both the left and right sides of the other, the engaging convex portion and an engaging groove portion which can be slidably engaged when the ceiling opening portion of the main body frame is inserted, and one of the engaging convex portion and the engaging groove portion is provided. On the other hand, elasticity that can be press-fitted by moving the main frame to the mounting plate side Characterized the formed it to have.

In the duct ventilation fan of the present invention, the second
In addition, it is characterized in that the above-mentioned engaging convex portion is formed in a vertically long ridge shape. In the duct ventilation fan according to the present invention,
In addition, it is characterized in that the engaging convex portion is formed in a protrusion shape at least in the upper and lower portions. Fourthly, the duct ventilation fan according to the present invention is characterized in that the engaging convex portion is formed to be inclined with respect to the press-fitting direction with respect to the engaging groove portion.

In the duct ventilation fan of the present invention, the fifth aspect
In addition, the engaging convex portion is formed to have a hook-shaped head. Sixthly, the duct ventilation fan according to the present invention is characterized in that the engaging protrusion is formed to have an arrowhead-shaped head.

In the duct ventilation fan of the present invention, the seventh aspect
A lower end portion is attached to an edge portion of an opening formed in the ceiling, is installed upright on the back of the ceiling, and has a plastic mounting plate having a vent for connecting a duct on the back of the ceiling, and a fan device inside. And a plastic main body frame that is inserted into the opening of the ceiling from below and is located in the back of the ceiling and communicates with the vent, and is fixed to the opening of the ceiling in this state. By providing the engaging projections on the left and right sides of the mounting plate and the elastic fins on the left and right sides of the body frame, the engagement projections can be slidably engaged when the ceiling opening of the body frame is inserted. Moreover, an engaging groove portion which can be press-fitted by moving the main body frame to the mounting plate side is formed.

[0010]

According to the first means, the mounting plate and the body frame are
Not only is the engaging protrusion and the engaging groove slidably engaged, but also the elasticity of one of them is used to press-fit the engaging protrusion and the engaging groove by moving the main body frame to the mounting plate side. You can also combine them. According to the second means, the length of the engaging convex portion can increase the coupling dimension between the mounting plate and the main body frame. or,
In this case, the airtightness of the connecting portion between the mounting plate and the main body frame can be increased by the length of the engaging convex portion.

According to the third means, since the engaging convex portion is in the form of a protrusion, it is easy to press fit the engaging convex portion and the engaging groove portion by moving the main body frame to the mounting plate side. You can According to the fourth means, the engaging convex portion can be pressed against the side surface of the engaging groove portion due to its inclination, and the degree of coupling between the mounting plate and the main body frame can be increased. According to the fifth means, since the head portion of the engaging convex portion has a hook shape, the engagement with the engaging groove portion can be strengthened.

According to the sixth means, since the head portion of the engaging convex portion has an arrowhead shape, the engagement with the engaging groove portion can be strengthened as described above. According to the seventh means, the mounting plate and the main body frame are not only slidably engaged with the engaging convex portion by the engaging groove portion, but also the elasticity of the elastic fin portion of the engaging groove portion is used to move the engaging plate to the mounting plate side. It is also possible to press the engaging groove portion into the engaging convex portion by the movement of the main body frame so as to be joined.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. First, FIG. 3 shows the mounting plate 11 and the main body frame 12. Among them, the mounting plate 11 is made of plastic, has a vent hole 13 in a central portion, has flange portions 14 directed to the main body frame 12 side at upper edge portions and both left and right edge portions, and a lower edge portion ( The lower end portion) has a flange portion 15 directed toward the side opposite to the main body frame 12.

Further, as shown in FIGS. 4 and 1 and 2, engaging projections 16 are integrally formed on both left and right sides of the mounting plate 11. More specifically, the engagement protrusion 16 is hollow and has a pillar portion 16a that is open to the outside of the mounting plate 11 on the side opposite to the main body frame 12, and that is located at the tip of the pillar portion 16a and has a diameter larger than the width of the pillar portion 16a. An elastically deformable one having a large circular bag-shaped head portion 16b, which is vertically long as a whole,
In particular, the mounting plate 11 is formed in a ridge shape over the entire vertical length.

On the other hand, the body frame 12 is also made of plastic and has a fan device 17 inside. The fan device 17 is composed of a fan 18 which is rotationally driven by a motor (not shown), and a casing 19 which surrounds the fan 18. The air is exhausted from the side exhaust port 20.

Further, engaging groove portions 21 are formed on both left and right side portions of the side surface portion of the body frame 12 on the side of the mounting plate 11. The engaging groove portion 21 is the engaging convex portion 16 of the mounting plate 11.
The engaging projection 16 is slightly larger than the engaging projection 16 and has substantially the same shape as that of the engaging projection 16. A guide section 22 having a funnel-shaped cross section is formed on both sides of the opening on the mounting plate 11 side. ing. In addition, the flange portion 2 is provided on the peripheral portion of the lower end of the main body frame 12.
3 (see FIG. 1).

In the case of the above structure, the ventilation fan is attached as shown in FIG. 5 or 6. In FIGS. 5 and 6, an opening 2 for attaching a ventilation fan is provided on a ceiling (not shown).
4 shows a wooden frame 25 in which 4 is formed. First, the flange portion 15 of the mounting plate 11 is attached to the edge of the wooden frame 25 which is the edge of the opening 24 by screwing or the like, and the mounting plate 11 is mounted on the ceiling. Set up on the back. At this time, the mounting plate 11 has the engaging projections 16
Is located on the side of the opening 24, and the vent 13 is connected to the opposite opening 24.
It is located on the side, and a duct (also not shown) is connected to the ventilation port 13 at the back of the ceiling.

Next, the main body frame 12 is inserted into the opening 24 from below, and this folding is performed so that the engaging groove portion 21 is engaged with the engaging convex portion 16. There are two methods for this engagement. One of them is a method in which the engaging groove portion 21 is fitted into the engaging convex portion 16 from its lower end as shown in FIG. 5, and the main body frame 12 is inserted and slid as shown by an arrow B so as to be engaged. Another is a method in which, as shown in FIG. 6, the engaging groove portion 21 is press-fitted into the engaging convex portion 16 by moving the main body frame 12 to the mounting plate 11 side as shown by an arrow C after being inserted. In this latter method, due to the elasticity of the engaging projection 16 due to its hollow structure, the engaging projection 16 and in particular the head 16 thereof.
b is contracted and deformed during the press fitting of the engaging groove portion 21, and the engaging groove portion 2
The engaging groove 21
Pressure contact with.

Thus, the main body frame 12 is connected to the mounting plate 11, and at the same time, the main body frame 12 is positioned in the back of the ceiling so that the exhaust port 2
0 is communicated with the ventilation port 13 of the mounting plate 11, and in this state, the flange portion 23 of the main body frame 12 is fixed to the opening 24 (the wooden frame 25) of the ceiling by screwing or the like.

As described above, according to this configuration, the mounting plate 11 and the main body frame 12 not only slide-engage the engaging groove portion 21 with the engaging convex portion 16, but also the engaging convex portion 16 among them.
By utilizing the elasticity of, the main body frame 12 is moved toward the mounting plate 11 side, and the engaging groove portion 21 can be press-fitted into the engaging convex portion 16 so that they can be joined. In particular, by adopting the latter method, Positioning of the upper end of the engaging groove portion 21 with respect to the lower end of the engaging convex portion 16 from the beginning of the insertion of the main body frame 12 into the opening 24 can be eliminated, and the work can be facilitated.

Further, according to this structure, the engaging convex portion 16
The main body frame 1 intended to be slidably engaged with the engaging groove portion 21
When it is noticed that the engaging groove portion 21 is not engaged with the engaging convex portion 16 during the insertion of 2, the body frame 12 is immediately moved to the mounting plate 11 side so that the engaging groove portion 21 is not moved. The engagement groove portion 21 can be re-engaged with the engagement convex portion 16 by press-fitting into the engagement convex portion 16.
There is no need for the troublesome work of the related art such as taking out all 2 and re-engaging the engaging groove portion 21 with the engaging convex portion 16 from the lower end.

Further, according to this structure, the main body frame 12
Even when it is inserted diagonally as shown in FIG. 6, the engaging groove portion 21 can be press-fitted to the engaging convex portion 16 by moving it to the mounting plate 11 side. In comparison, the workability of mounting can be further improved.

In addition, particularly in the above-mentioned structure,
The engaging convex portion 16 is formed in a vertically long ridge shape in conformity with the engaging groove portion 21, and the length of the engaging convex portion 16 can increase the coupling dimension between the mounting plate 11 and the main body frame 12. Therefore, the binding can be made more reliable. Also, in this case,
The head 16b of the engaging convex portion 16 having a long convex strip above and below
By press-contacting the inner part of the engaging groove portion 21 with each other, the airtightness of the joint portion between the mounting plate 11 and the main body frame 12 can be increased, and the main body frame 1
It is possible to more reliably prevent air from leaking from the second exhaust port 20 to the duct connected to the ventilation port 13 of the mounting plate 11.

In contrast to the above, FIG. 7 shows a second embodiment of the present invention, in which the engaging projections 26 are replaced by the above-mentioned engaging projections 16 and the upper and lower parts of the mounting plate 11 are shaped like a protrusion. It shows what was formed in. In this case, the support projections 26a and the head portion 26b of the engagement protrusions 26 are hollow like the engagement protrusions 16 and are elastically deformable. According to this, since the engaging convex portion 26 has a projecting shape, it is easy to press-fit the engaging groove portion 21 in the engaging convex portion 26 by moving the main body frame 12 toward the mounting plate 11 side. Therefore, the workability of mounting can be further improved. In this case, the engaging protrusion 2
6 may be provided at least at the upper and lower portions of the mounting plate 11, and one or more may be provided at other intermediate portions.

FIGS. 8 and 9 show a third embodiment of the present invention, in which the engaging projection 27 is replaced with the engaging projection 26 described above, and an angle α is formed with respect to the press fitting direction with respect to the engaging groove 21. The thing formed inclining is shown. Further, the engagement convex portion 27 in this case also has the column portion 27a and the head portion 26b, and particularly in this case, the column portion 27a is elastically deformable.

According to this, when the engaging convex portion 27 (the strut portion 27a) is press fitted into the engaging groove portion 21, it is bent from its inclined state and elastically deformed as shown in FIG. Since the pressure contact force is applied to the side surface of the mating groove portion 21, the degree of coupling between the mounting plate 11 and the body frame 12 can be increased by this pressure contact force, and the body frame 12 can be mounted more reliably.
Further, in the configuration in which the engaging convex portion 27 has a vertically long ridge shape,
Since the airtightness of the connecting portion between the mounting plate 11 and the main body frame 12 can be increased by the above-mentioned pressure contact, the exhaust port 20 of the main body frame 12
It is possible to more reliably prevent the air from leaking from the air to the duct.

FIG. 10 and FIG. 11 show a fourth embodiment of the present invention, in which the engaging projection 28 and the above-mentioned engaging projection 27 are provided.
Instead, a hook-shaped head portion 28b is attached to the tip of the column portion 28a.
Is formed so as to have. Further, in this case, the engaging convex portion 28 is capable of elastically deforming both the column portion 28a and the head portion 28b. Further, the engagement groove portion 29 in this case is formed so as to have a step portion 29a corresponding to the head portion 28b of the engagement convex portion 28 in place of the above-mentioned engagement groove portion 21.

According to this, when the engaging convex portion 28 is press-fitted into the engaging groove portion 29, the column portion 28a and the head portion 28b are bent and elastically deformed, and the restoring force thereof causes the head portion 28b to engage the engaging groove portion. As shown in FIG. 11, the stepped portion 29a of 29 is pressed and brought into contact with the stepped portion 29a, so that the engaging groove portion 29 can be strongly hooked and the main body frame 12 can be attached more reliably. Also in this case, in the configuration in which the engaging convex portion 28 has a vertically long ridge shape, the mounting plate 11 is pressed by the pressure contact of the head portion 28b of the engaging convex portion 28 with the step portion 29a of the engaging groove portion 29. The airtightness of the connecting portion between the main body frame 12 and the main body frame 12 can be increased, and the leakage of air from the exhaust port 20 of the main body frame 12 to the duct can be further reliably prevented.

12 and 13 show a fifth embodiment of the present invention, in which the engaging projection 30 is further replaced by the engaging projection 28 described above.
Instead, the pillar 30a is formed to have an arrowhead-shaped head portion 30b at the tip. Further, in this case, the engaging projection 30 makes the head portion 30b elastically deformable. Further, the engagement groove portion 31 in this case is formed so as to have the step portions 31a on both sides corresponding to the head portion 30b of the engagement convex portion 30 in particular.

According to this, when the engaging convex portion 30 is press fitted into the engaging groove portion 29, the head portion 30b is flexed and elastically deformed as shown in FIG. 13, and the head portion 30b is restored by the restoring force.
Is engaged with the stepped portions 31a on both sides of the engagement groove portion 31, so that the engagement groove portion 31 can be strongly engaged and the main body frame 12 can be attached more reliably. Also in this case, the engaging projection 3
In the configuration in which 0 is vertically long and long, the head portions 30b of the engaging protrusions 30 are pressed against both inner side surfaces of the engaging groove portion 31 to hermetically seal the joint between the mounting plate 11 and the main body frame 12. Therefore, it is possible to more reliably prevent air from leaking from the exhaust port 20 of the main body frame 12 to the duct.

FIGS. 14 and 15 show a sixth embodiment of the present invention, in which engaging protrusions having a solid head portion 32b as well as a solid support portion 32a on both left and right sides of the mounting plate 11. 32
On the other hand, step portions 33 are provided on both left and right sides of the main body frame 12, half groove portions 34 are provided therein, and the elastic fin portions 3 are provided.
It is shown that the engaging groove portion 36 is formed by providing 5 in the upper and lower portions.

Also in this case, similarly to the first embodiment described above, not only the engaging groove portion 36 is slidably engaged with the engaging convex portion 32, but also the elasticity of the elastic fin portion 35 is utilized to make the mounting plate 11 side. By moving the main body frame 12 to the engaging convex portion 32, the engaging groove portion 3
Since the body frame 12 can be joined to the mounting plate 11 by press-fitting 6, the workability of mounting can be improved as in the first embodiment.

In this case, the elastic fins 35 may be provided not only on the upper and lower portions of the main body frame 12 but also over the entire vertical length thereof, or they may be provided flush with the front and rear surfaces of the main body frame 12, respectively. Is also good. Further, as shown in the sixth embodiment, regarding the elasticity of the engaging convex portion and the engaging groove portion,
The engaging groove portion may have elasticity instead of the engaging convex portion. Further, as for the engagement protrusion and the engagement groove, the engagement protrusion may be provided on the main body frame and the engagement groove may be provided on the mounting plate. The fan device 17 may be for intake instead of exhaust. In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and may be appropriately modified and implemented without departing from the scope of the invention.

[0034]

The duct ventilation fan of the present invention is as described above, and has the following effects. Firstly, a lower end is attached to the edge of the opening formed in the ceiling and is installed upright in the back of the ceiling, and a plastic mounting plate having a vent for connecting a duct in the back of the ceiling, and Has a fan device,
The mounting plate includes a plastic main body frame that is inserted into the opening of the ceiling from below and is located in the back of the ceiling and communicates with the vent, and is fixed to the opening of the ceiling in this state. Engaging projections are provided on both left and right sides of one of the main body frame and the engaging frame, and engaging groove portions that can be slidably engaged when the ceiling opening of the main body frame is inserted are provided on the other left and right sides. By providing one of the engaging convex portion and the engaging groove portion so as to have elasticity that can be press-fitted to the other by the movement of the main body frame to the mounting plate side, the main body with respect to the mounting plate is provided. The frame can be easily connected, and the workability of mounting can be improved.

Secondly, by forming the engaging convex portion in the shape of a long convex strip in the vertical direction, the main body frame can be more surely connected to the mounting plate, and the airtightness of the connecting portion is increased. This makes it possible to more reliably prevent air from leaking from the body frame to the duct.

Thirdly, since the engaging projections are formed in a projecting shape at least in the upper and lower portions, the main body frame can be more easily connected to the mounting plate, and the workability of mounting can be further improved. it can. Fourthly, since the engaging protrusion is formed to be inclined with respect to the press fitting direction other than the engaging groove, the degree of coupling between the mounting plate and the body frame can be increased,
The body frame can be attached more reliably.

Fifth, since the engaging projection is formed to have a hook-shaped head, the engaging projection can be strongly hooked to the engaging groove, so that the body frame can be mounted more securely. it can. Sixthly, by forming the engaging convex portion to have an arrowhead-shaped head, the engaging convex portion can be strongly hooked to the engaging groove portion as in the above, and the attachment of the main body frame can be more surely performed. You can

Seventh, a plastic mounting plate having a lower end attached to an edge of an opening formed in the ceiling and erected upright on the back of the ceiling and having a vent for connecting a duct on the back of the ceiling. A plastic body that has a fan device inside, is inserted into the opening of the ceiling from below, is located in the back of the ceiling, and communicates with the vent, and is fixed to the opening of the ceiling in this state A frame is provided, engaging protrusions are provided on both left and right sides of the mounting plate, and elastic fins are provided on both left and right sides of the main body frame so that the engaging protrusions are inserted into the ceiling opening of the main body frame. By forming the engaging groove portion which can be slidably engaged and can be press-fitted by the movement of the main body frame to the side of the mounting plate, the workability of mounting can be improved similarly to the first effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is an enlarged view of part A of FIG.

FIG. 3 is an exploded perspective view

FIG. 4 is a perspective view of a single mounting plate.

[Fig. 5] Side view in vertical section during installation

FIG. 6 is a vertical sectional side view showing a different mounting state.

FIG. 7 is a view corresponding to FIG. 4, showing a second embodiment of the present invention;

FIG. 8 is an exploded view of a portion corresponding to FIG. 2 showing a third embodiment of the present invention.

FIG. 9 is a view corresponding to FIG.

FIG. 10 is a view corresponding to FIG. 8 showing a fourth embodiment of the present invention.

FIG. 11 is a view corresponding to FIG.

FIG. 12 is a view corresponding to FIG. 8 showing a fifth embodiment of the present invention.

FIG. 13 is a view corresponding to FIG.

FIG. 14 is a view corresponding to FIG. 3 showing a sixth embodiment of the present invention.

FIG. 15 is a view corresponding to FIG.

FIG. 16 is a perspective view showing a conventional example in the middle of mounting.

FIG. 17 is a view equivalent to FIG.

[Explanation of symbols]

11 is a mounting plate, 12 is a main body frame, 13 is a vent, 16 is an engaging protrusion, 17 is a fan device, 21 is an engaging groove, 24 is an opening, 26, 27 and 28 are engaging protrusions, α Is an inclination angle of the engaging convex portion, 28b is a head portion, 29 is an engaging groove portion, 30 is an engaging convex portion, 30b is a head portion, 31 is an engaging groove portion, 32 is an engaging convex portion,
Reference numeral 35 is an elastic fin portion, and 36 is an engaging groove portion.

Claims (7)

[Claims] 1. A mounting plate made of plastic, having a lower end attached to an edge of an opening formed in the ceiling, standing upright in the back of the ceiling, and having a vent for connecting a duct in the back of the ceiling; A plastic main body frame that has a fan device, is inserted into the opening of the ceiling from below, is located on the back of the ceiling, and is in communication with the ventilation port, and is fixed to the opening of the ceiling in this state; The engaging projections are provided on both left and right sides of one of the mounting plate and the main body frame, and the sliding projections are inserted into the other left and right sides of the engaging projection and the ceiling opening of the main body frame. The engaging groove portion that can be fitted is provided, and one of the engaging convex portion and the engaging groove portion is formed to have elasticity so that it can be press-fitted to the other by moving the main body frame toward the mounting plate side. A ventilation fan for ducts that is characterized by that. 2. The ventilation fan for a duct according to claim 1, wherein the engaging projection is formed in a vertically long ridge shape. 3. The ventilation fan for a duct according to claim 1, wherein the engaging projections are formed in a projecting shape at least in upper and lower portions. 4. The duct ventilation fan according to claim 1, wherein the engaging convex portion is formed to be inclined with respect to the press fitting direction with respect to the engaging groove portion. 5. The duct ventilation fan according to claim 1, wherein the engaging projection is formed to have a hook-shaped head. 6. The duct ventilation fan according to claim 1, wherein the engaging protrusion is formed to have an arrowhead-shaped head. 7. A plastic mounting plate having a lower end attached to an edge of an opening formed in the ceiling, standing upright on the back of the ceiling, and having a vent for connecting a duct on the back of the ceiling; A plastic main body frame that has a fan device, is inserted into the opening of the ceiling from below, is located on the back of the ceiling, and is in communication with the ventilation port, and is fixed to the opening of the ceiling in this state; The engaging projections are provided on both left and right sides of the mounting plate, and the elastic fins are provided on both left and right sides of the main body frame, so that the engaging projections are slidable when the ceiling opening of the main body frame is inserted. A ventilating fan for a duct, characterized in that an engaging groove portion which can be fitted and which can be press-fitted by the movement of the main body to the mounting plate side is formed.