JPH07269933A - Rotary damper of plurality of vane type for ventilator - Google Patents

Abstract

PURPOSE:To reduce the height of a damper body in order to make its use suitable for a space limited in height by a method wherein a pair of front and rear stopper- cum-seal plates are provided extending in the form of an inwardly facing flange with a suitable width and in contact with the upper surfaces of the outer peripheral parts of large arcuate ends extending over both the ends of rotating shafts of both semicircu lar damper vanes when the dampers are completely closed. CONSTITUTION:On a damper part 2 connected to the lower end of a ventilator 1, a pair of front and rear horizontally rotating shafts 5 are mounted with a suitable space therebetween in such a manner that such shafts are arranged symmetrically about the center of the circular cross section of the damper part and in parallel with each other. In order to improve the sealability of the damper when it is completely closed, within a casing 4U of the damper part 2, front and rear narrow semicircular flange-like seal-cum-stopper plates 13 are provided in a pair extending radially inwardly. Therefore, when the damper part is completely closed, the upper surface of the semi-arcuate outer periphery of each damper 3 comes in contact with the lower surface of a corresponding seal-cum-stopper plate 13 and the linear inner peripheries of the dampers can make contact with each other one above the other with overlap width delta.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-blade rotary damper for a ventilator.

[0002]

2. Description of the Related Art For example, in an engine room of a ship, a damper body 02 is often provided on a lower side of a ventilator 01 as shown in a side view of FIG. Since the die rotary damper has a large diameter, the height H ₀ becomes high.

[0003]

As a result, since the overall height of the ventilation pipe equipped with the damper is increased, in a ventilator room where the space and height of the superstructure are restricted, such as a passenger ship, the Since there are many cases where the height cannot be taken high, it is very difficult to equip this kind of single-blade damper.

The present invention has been proposed in view of such circumstances, and it is difficult to make the height of the damper body as low as possible, and it is difficult to secure a sufficient height because the ventilator compartment is narrow, especially in a passenger ship. It is an object of the present invention to provide a low-height economical multi-blade rotary damper for a ventilator that is suitable for being installed in various compartments.

[0005]

To this end, the invention according to claim 1 provides a damper outer circumference which is loosely coaxially inserted with a slight radial clearance on the same cross-section circle having an inner diameter D of a vertical cylindrical casing. An eccentric point in which a pair of front and rear semi-circular damper blades formed so as to divide the diameter of the circle in the front-rear direction into two equal parts are eccentric by the same distance on the diameter of the front-rear direction and toward the center of the circle of the same cross section. A pair of front and rear semi-circular damper blades that are fixed to eccentric rotation shafts that extend in the left-right direction and that overlap in the left-right diametrical end when fully closed with a slight overlap length δ in the front-rear direction. In a two-blade rotary damper for a ventilator, in which each arc end can be rotated downward by 90 ° around the rotation axis, the two-blade rotary damper is intermittently provided around the inner circumference of the circle of the same cross section, and both of them are closed when fully closed. At both ends of the rotation axis of the semi-circular damper blade A pair of front and rear stoppers / sealing plates that are in contact with the upper surface of the outer circumference of the large arc end and project in an inward flange shape with an appropriate width, and the above-mentioned both damper blades are interlocked with each other around the respective rotation axes. 9 at the end of the arc
A damper blade interlocking device that fully opens downward by 0 ° is provided, and the lower ends of both damper blades project downward from the lower end of the same casing when fully opened.

Further, in the invention of claim 2, the diameter in the left-right direction of the outer circumferential circle of the damper which is loosely coaxially inserted with a slight radial gap on the same cross-section circle of the inner diameter D of the vertical cylindrical casing is defined. As a center line, the width is smaller than the maximum width of the bow-shaped damper blades described later, and the left and right ends are convexly curved with small arcs and are supported rotatably in horizontal and vertical positions by a rotary shaft fixed on the center line in the same horizontal direction. And a front and rear 1 having a center-shaped damper blade of a deformed rectangular shape and a width that divides the length obtained by subtracting the width of the central damper blade from the diameter in the front-rear direction into two equal parts.
A pair of bow-shaped damper blades are fixed to a pair of front and rear eccentric rotary shafts extending in the left and right directions through points on the diameter in the front-rear direction and eccentric to the center of the circle of the same cross section by the same distance. A pair of front and rear bow-shaped damper blades in which the chord ends when fully closed overlap each other with a slight overlap δ in the front-rear direction, and one chord end around each rotation axis, and each arc end is 90 ° downward. In a rotatable three-blade rotary damper for a ventilator, which is intermittently provided on the inner circumference of the circle of the same cross section, and when fully closed, has a large arc end extending over both ends of the rotary shaft of the above-mentioned two bow damper blades. A pair of front and rear large arc stoppers and seal plates which are respectively in contact with the upper surface of the outer peripheral portion and project in an inward flange shape with an appropriate width, and one chord end from the central axis of the left and right arc ends of the irregular rectangular damper blade. On the left and right pair of small arc ends A pair of left and right small arcuate stoppers and seal plates that are in contact with the surface and project inward with an appropriate width, and the above three damper blades are interlocked with each other, and the chord ends and arc ends are provided around the respective rotation axes. And a damper blade interlocking means for fully opening downward by 90 °, and at the time of full opening, at least the lower ends of the bow-shaped damper blades at the front and rear portions respectively project downward from the lower end of the same casing by an equal length.

The invention according to claim 3 is that the diameter of the damper outer circumferential circle, which is loosely coaxially inserted on the same cross-section circle of the inner diameter D of the vertical cylindrical casing with a slight radial clearance, in the front-rear direction. A pair of bow-shaped damper blades on the outer side of the front and rear and a pair of deformed trapezoidal damper blades on the inner side of the front and rear, which are formed so as to divide the circle into four equal parts, respectively, on the diameter in the front-rear direction and at the centers of the circles of the same section, respectively. It is fixed to eccentric rotation shafts that extend in the left-right direction through four points that are eccentric by the same distance toward each other, and the long chord ends and short chord ends are slightly overlapped in the front-back direction when fully closed. A four-blade rotary damper for a ventilator in which four arcuate ends and short chord ends of each of the four vertically overlapping damper blades can be rotated downward by 90 ° about their respective rotation axes. It is installed around the inner circumference intermittently and is raised when fully closed. The upper surface of the outer peripheral portion of each of the pair of small arcs extending from the short arc ends of the arcuate trapezoidal damper blades on the left and right sides of the hypotenuse arc to the ends of the rotation axis of the curved trapezoidal damper blades. 3 front and rear parts, each of which has a uniform width and is protruded in an inward flange shape
The stopper / seal plate of the plate and the above-mentioned four damper blades are interlocked with each other, and the arc ends around the respective rotation axes,
A damper blade interlocking device that fully opens the short chord end downward by 90 ° is provided, and the lower ends of the damper blades project from the lower end of the casing to the same length when fully opened.

[0008]

According to this structure, in the case of the two-sheet type damper, the height of the damper portion is D / the inner diameter D of the casing.
2 or less, about 3/3 or less in the case of a three-plate damper, 4
In the case of a sheet type damper, it can be about D / 4 or less. Also, by supporting each damper blade with an eccentric shaft, all the damper blades can be fully closed all at once when a fire occurs.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment in which the present invention is applied to an engine room of a passenger ship will be described. FIG. 1 is an overall side view showing a two-piece fire damper of the first embodiment, and FIG. 2 is an enlarged view of the damper body, FIG. 3 is a plan view of FIG. 2, FIG. 4 is an enlarged view of IV part of FIG. 2, and FIG. 5 is a link lever mechanism for simultaneously opening and closing the damper of FIG. A) is a side view thereof, FIG. 6B is a plan view thereof, FIG. 6 is a side view and a plan view showing a three-piece type fire protection damper which is a second embodiment of the present invention, and FIG. 7 is a view of the damper blade of FIG. FIG. 8 is a side view showing the interlocking opening / closing mechanism, and FIG. 8 is a side view and a plan view showing a four-sheet fire protection damper according to a third embodiment of the present invention.

First, referring to FIGS. 1 to 3, a pair of front and rear horizontal rotary shafts 5, 5 parallel to each other symmetrically about a center of a circle of a cross section of a damper portion 2 connected to a lower end of a ventilator 1 are appropriately spaced. Install. Semicircular dampers 3 are eccentrically fixed to the rotary shafts 5 at the same eccentricity ratio a / b.
The linear contact surfaces at the inner ends of both dampers 3 have a stacking margin δ with a step on at least one of them to improve the contact and sealability at the time of contact. In such a structure, the damper 3,
When 3 is fully opened to the broken line position (FIGS. 1 and 2) and the air blower 1 is rotated, the air on the exposed deck flows from the air inlet at the front end of the air blower chamber into the ventilation chamber as indicated by the arrow, Once it is deflected upward, it makes a U-turn downward and is discharged from the blower 1 through the ventilation duct 4L into the rear engine room. In addition,
In this embodiment, the mounting positions of the rotary shafts 5 and 5 are l = 1 '(FIG. 2), and when the dampers are fully closed, the inner ends of the dampers 3 move up and down with the overlap margin δ, as shown by the solid line in FIG. Since they are overlapped with each other, the height H of the damper portion is, as will be described later, half or less of the height of the conventional single-sheet damper.

3 to 4, a pair of front and rear semi-circular flanges having a small width inward in the radial direction are formed on the inner surface of the casing 4U of the damper portion 2 in order to improve the sealing performance when the damper is fully closed. A seal / stopper 13 is projected. Therefore, when fully closed, the semicircular arc-shaped outer peripheral upper surface of each damper 3 is a seal / stopper 13 (seal plate).
Of the respective dampers, and the linear inner circumferences of the respective dampers can be in contact with each other by overlapping each other at the overlapping margin δ. The sealing plate not only acts as a stopper when fully closed, but also plays an important role as a sealing plate when the semicircular damper is rotated 90 ° from the fully open position to the fully closed position. This is because the damper 3 is a semi-circular plate, and its rotation shaft 5 is eccentric from the linear inner end by a, so that the left and right ends of the linear inner end side interfere with the inner surface of the casing 4U when the damper is fully opened. There is a fear that it will not be able to rotate. To clear this point,
By making the inner end length Le sufficiently shorter than the length Da that penetrates the casing 4U of the rotating shaft 5, the damper can be fully opened. Then, the semicircular outer circumference of the damper blade 3 when fully closed. Since there is a possibility that a slight clearance will occur between the inner surface of the seal plate and the inner surface of the seal plate, the inward flange-shaped seal plate 13 has a sufficient width to close this clearance.

Further, as shown in FIG. 5, a central fulcrum of the linear lever 7 is fitted to one end of the rotary shaft 5A of the rear damper 3A, and a long hole 9A in the longitudinal direction is bored at its inner end. The fulcrum of the L-shaped lever 8 is fitted to the same side end of the rotary shaft 5F of the front damper 3F, and the long hole 9F in the longitudinal direction formed at the inner lower end of the fulcrum is linear in the rear damper. It is pivotally attached by a long hole 9A of the lever and a pin 10. Therefore, by rotating the linear lever 7 around the rotary shaft 5A by 90 ° in the direction of the arrow from the solid line position to the broken line position, both dampers can be simultaneously opened and closed together. The present invention can also be applied to a damper having three or more blades.

That is, FIG. 6 shows a second embodiment in which the present invention is applied to a three-piece damper, in which front and rear damper blades 16F and 16A have a chord slightly shorter than the inner diameter D of the casing and about 1/3. A pair of identical front and rear arcuate arcuate shapes is formed, and the maximum width W of the central portion is approximately 1 / 3D, and both ends are supported by the casing by a rotational axis that is symmetrical to the front and rear as in the first embodiment. There is. The central damper blade 17 is formed by a parallel string having the same chord length as that of the bow-shaped damper blade and a pair of left and right small arcs having the same curvature that connect the left ends and the right ends of the parallel strings. It has an asymmetrical rectangular shape having a rounded short side and is supported at both ends by a casing by a rotating shaft in the left-right direction passing through the center of the rectangular shape. These three damper blades are supported on the casing by parallel rotating shafts at both ends, and the lever, the chain wheel, and the chain mechanism shown in FIG. 7 open and close the broken line position and the solid line position all at once, as shown in FIG. can do. As for the seal / stopper, as shown in the drawing, the seal / stopper shown in FIGS. 3 to 4 can be provided so as to protrude along the inner surface of the casing to perform sealing and sealing of the damper blade in the fully closed position. According to the second embodiment as described above, the height of the damper portion can be set within about 1/3 or less of the inner diameter of the casing.

Further, FIG. 8 shows a third embodiment in which the present invention is applied to a four-plate damper, and in the three-plate damper of FIG. 6, a pair of front and rear bow-shaped damper blades 16F, 16 are provided.
A is a front and rear bow-shaped damper blade 18F and a rear bow-shaped damper blade 18A with the maximum width of the central portion being about D / 4. Deformed trapezoidal type damper blades 19F, 1
9A. In such a structure, the damper blades are supported at both ends on the casing by rotating shafts in the left-right direction which are parallel to each other, and the damper blades can be simultaneously opened and closed by a lever, a chain wheel, and a chain mechanism. According to the third embodiment as described above, the height of the damper portion can be set within about 1/4 or less of the inner diameter of the casing.

In each of the above-mentioned embodiments, when the number of damper blades is an odd number, a central portion having a relatively narrow width and zero eccentricity is used in the central portion, and all damper blades other than the central damper blade are used. Is relatively wide, and its rotation axis is provided at a position eccentric to the casing center direction with respect to the width of the damper blade. This is because the lower part of the damper blade that is fully opened when fully closed protrudes downward from the lower end of the damper casing and enters the lower ventilation duct 4L, but in the fully closed state, all damper blades are inside the casing of the damper part. Since the height of the casing of the damper portion can be reduced, it is easy to reduce the overall height.

That is, the height H of the damper section is set to 1/2 of the height of the damper section with respect to the rotation axis of each damper blade.
When calculated under the condition of supporting at the height of H, H is inversely proportional to the number of blades N as shown in the equation (1), and
Function of eccentricity ratio r = a / b (see FIGS. 2, 6 and 8) [2
r / (r + 1)]. H = (D / N) × [2r / (r + 1)] (1) For example, if the eccentricity ratio r of the damper blade is r = 1/3, then H = D / 4 (two blades) H = D / 6 (3 blades) H = D / 8 (4 blades), which is the height H of the casing of the damper portion according to the present invention.
And its weight are greatly reduced regardless of whether it is applied to a vertical-axis fan or a horizontal-axis fan. As a result, it can be seen that the transportation cost and installation work cost of the damper part according to the present invention are considerably reduced.

[0017]

According to such a structure, a suitable damper can be obtained in a compartment such as a passenger ship where the ventilation chamber is narrow and the height is not sufficiently high.

In short, according to the first aspect of the present invention, the damper outer circumferential circle is loosely coaxially inserted on the same cross-section circle having the inner diameter D of the vertical cylindrical casing with a slight radial clearance in the front-rear direction. A pair of front and rear semi-circular damper blades formed so as to divide the diameter into two equal parts are provided on the left and right sides through eccentric points which are on the diameter in the front-rear direction and are eccentric by the same distance toward the center of the circle of the same cross section. A pair of front and rear semi-circular damper blades that are fixed to the eccentric rotation shafts that extend in the same direction, and whose left and right diametric ends when fully closed overlap vertically with a slight overlap δ in the front and rear direction around each rotation shaft. A two-blade rotary damper for a ventilator in which each arc end can be rotated downward by 90 °, and the two semi-circular damper blades are intermittently provided around the inner circumference of the circle of the same cross section and are fully closed. Large arc over both ends of the rotation axis of A pair of front and rear stopper / seal plates which are in contact with the upper surface of each of the ends and project inwardly in a flange shape with an appropriate width, and the damper blades are interlocked to form arc-shaped ends around the respective rotation axes. The damper blade interlocking means for fully opening downward by 90 ° is provided so that the lower ends of both damper blades project downward from the lower end of the casing at the time of fully opening. The present invention provides an economical rotary damper for a two-blade type fan, which can be reduced to about 1/4 or less of a single-blade type, can be reduced in weight, and can be easily moved and installed. Above all, it is extremely useful.

According to the second aspect of the invention, the damper outer circumferential circle is loosely coaxially inserted in the horizontal cross-section circle having the inner diameter D of the vertical cylindrical casing with a slight radial gap, in the left-right direction. With the diameter as the center line, which is smaller than the maximum width of the bow-shaped damper blades described below, the left and right ends are convexly curved with small arcs, and can be rotated to horizontal and vertical positions by a rotary shaft fixed on the center line in the left and right direction. The deformed rectangular central damper vane supported by and the pair of front and rear bow-shaped damper vanes each having a width that divides the length obtained by subtracting the width of the central damper vane from the longitudinal diameter into two equal parts. Along the diameter of the direction, passing through points that are eccentric to the center of the circle of the same cross section and extending in the left and right directions, the strings are fixed to a pair of eccentric rotation shafts that extend in the left and right directions. Direction overlap margin δ In a three-blade rotary damper for a ventilator, in which a pair of front and rear bow-shaped damper blades that are vertically overlapped with each other and one chord end and each arc end can be respectively rotated downward by 90 ° , Which are intermittently provided on the inner circumference of the circle of the same cross section, and when fully closed, contact with the upper surface of the outer peripheral portion of each of the large arc ends extending over both ends of the rotation axis of the above-mentioned bow-shaped damper blades, and project in an inward flange shape with an appropriate width. A pair of front and rear large arc stoppers and seal plates are provided, and a pair of left and right small arc ends extending from the center axis of the left and right arc ends of the irregularly shaped rectangular damper blade to one chord end are in contact with the upper surface of a proper width. A pair of left and right small arcuate stoppers / sealing plates protruding inwardly and the above-mentioned three damper blades are interlocked to fully open the chord ends and arc ends 90 ° downward around the respective rotation axes. With damper blade interlocking means, fully open About 1 from the lower end lower end of each said casing bow damper blades of at least the front and rear portions by which is adapted to protrude equal length downward, the single-bladed type having the same diameter of the customary height of the damper unit in
/ 6 or less, the weight can be reduced, and an economical rotary blade damper for a three-blade fan that can be easily moved and installed can be obtained. Therefore, the present invention is extremely useful industrially. is there.

Further, according to the third aspect of the present invention, the front and rear direction of the damper outer circumferential circle which is loosely coaxially inserted with a slight radial clearance on the same cross section circle having the inner diameter D of the vertical cylindrical casing. A pair of bow-shaped damper blades on the outer side of the front and rear portions and a pair of deformed trapezoidal damper blades on the inner side of the front and rear portions, which are formed so as to divide the diameter into four equal parts, respectively, on the diameter in the front-rear direction and having the same cross section circle. Are fixed to eccentric rotation shafts that extend in the left-right direction through four points that are eccentric to the center of the same distance, and the long chord ends and the short chord ends are slightly overlapped in the front-back direction when fully closed. For a ventilator with four damper blades that are vertically overlapped at δ, each arc end and short chord end being able to rotate downward 90 ° about each rotation axis.
In the single-blade rotary damper, the circular arc is intermittently provided on the inner circumference of the same cross section, and when fully closed, the large arc end extending over both ends of the rotation axis of each of the bow-shaped damper blades, the left and right of the irregular trapezoidal damper blade It also serves as a stopper for the front and rear 3 plates that are inwardly flanged and have the same appropriate width and are in contact with the upper surface of the outer peripheral portion of each pair of left and right small arcs extending from the short chord end of the hypotenuse arc to the end of its rotation axis. A seal plate and damper blade interlocking means for interlocking the four damper blades to fully open the arc end and the short chord end downward by 90 ° around the respective rotation axes, and the lower end of each damper blade when fully opened. Since each of them is projected from the lower end of the same casing to the same length downward, the height of the damper part can be reduced to about 1/8 or less of that of the conventional single-blade type having the same diameter, and the weight can be reduced. Together with And because mounting work to gain economical four-blade type ventilators for rotary damper is facilitated, the present invention is the extremely valuable industrial.

[Brief description of drawings]

FIG. 1 is an overall side view showing a two-piece fire protection damper which is an embodiment in which the present invention is applied to an engine room of a passenger ship.

2 is an enlarged view showing the fire damper of FIG. 1. FIG.

FIG. 3 is a plan view of FIG.

FIG. 4 is an enlarged view showing a IV portion of FIG.

5 shows a link lever mechanism for opening and closing the damper shown in FIG. 2, FIG. 5 (A) is a side view thereof, and FIG. 5 (B) is a plan view thereof.

6 (a) and 6 (b) are a side view and a plan view showing a three-piece type fire protection damper according to a second embodiment of the present invention.

7 is a side view showing an interlocking opening / closing mechanism of the damper blade of FIG.

8A and 8B are a side view and a plan view showing a four-plate type fire protection damper which is a third embodiment of the present invention.

FIG. 9 is a side view of a ventilator room showing a fire damper of an engine room of a conventional ship.

[Explanation of symbols]

 1 Ventilator 2 Damper part 3 Two-sheet semi-circular damper 3A Rear damper 3F Front damper 4U Vertical cylindrical casing 4L Ventilation duct 5, 5A, 5M, 5F Rotating shaft 5A Rear damper rotating shaft 5F Front damper rotating shaft 6 Stacking margin δ 7 Lever 8 L-shaped lever 9 Long hole 10 Pin 11 Link lever mechanism 13 Semi-annular seal / stopper (seal plate) 14 Arc-shaped seal / stopper 16F Front damper blade 16A Rear damper blade 17 Center damper blade 18F Front bow damper blade 18A Rear bow damper blade 19F Front inside irregular trapezoidal damper blade 19A Rear inside irregular trapezoidal damper blade D Inner diameter of casing H Height of casing damper N Number of damper blades r Eccentricity of eccentric rotation axis a / b δ Overlap margin

Claims (3)

[Claims] 1. A diameter of a damper outer circumferential circle, which is loosely coaxially inserted with a slight radial clearance on the same cross-section circle having an inner diameter D of a vertical cylindrical casing, is divided into two equal parts. The formed pair of front and rear semi-circular damper blades are fixed to the eccentric rotation shafts extending in the left-right direction through eccentric points that are eccentric by the same distance toward the center of the same cross-section circle on the diameter in the front-rear direction. A pair of front and rear semi-circular damper blades whose top and bottom diameter ends in the left-right direction when fully closed overlap each other with a slight overlapping margin δ in the front-rear direction. ° In a two-blade rotary damper for a ventilator that is rotatable, it is installed around the inner circumference of a circle of the same cross-section intermittently, and when it is fully closed, a large arc extending over both ends of the rotary shafts of the above semicircular damper blades. Touching the upper surface of each outer edge A pair of front and rear stoppers and seal plates protruding inwardly in the shape of an inward flange with a certain width, and the damper blades interlocking the above-mentioned both damper blades so that the arc ends are fully opened downward by 90 ° around each rotation axis. A two-blade rotary damper for a ventilator, characterized in that the lower ends of both damper blades respectively project downward from the lower end of the casing when fully opened. 2. An arched shape whose center line is the diameter in the left-right direction of a damper outer circumference circle which is loosely and coaxially inserted with a slight radial clearance on the same cross-section circle having an inner diameter D of a vertical cylindrical casing. The center part of the odd-shaped rectangle, which is smaller than the maximum width of the damper blades and whose right and left ends are convexly curved with small arcs and is rotatably supported in horizontal and vertical positions by a rotating shaft fixed on the center line in the same horizontal direction. A damper blade and a pair of front and rear bow-shaped damper blades each having a width that divides the length obtained by subtracting the width of the central damper blade from the front-rear diameter on the front-rear diameter and the same cross section, respectively. It is fixed to a pair of front and rear eccentric rotation shafts that extend in the left and right directions through points that are eccentric to the center of the circle and are eccentric by the same distance, and the chord ends when fully closed overlap vertically with some overlap δ in the front and rear direction. A pair of front and rear bow-shaped da A three-blade rotary damper for a ventilator, in which one chord end and each arc end can rotate downward by 90 ° around their respective rotation axes, and is interrupted on the inner circumference of the circle of the same cross section. And a pair of large circles in front of and behind each of the large arcs extending over both ends of the rotation axis of the above-mentioned bow-shaped damper blades, each of which has an appropriate width and projects inward in a flange shape when fully closed. The arc-shaped stopper / seal plate and the left and right ones protruding inward with a proper width in contact with the upper surfaces of the pair of left and right small arc ends extending from the central axis of the left and right arc ends of the irregular shaped rectangular damper blade to one chord end A pair of small arc stoppers and seal plates, and damper blade interlocking means for interlocking the above-mentioned three damper blades to fully open the chord end and the arc end 90 ° downward around their respective rotation axes, and fully open Sometimes at least front and back bow 3 bladed type rotary damper ventilator, characterized in that the lower end of the over blade was made to protrude equal length from the lower end of each of the casing downwards. 3. The diameter of the damper outer circumferential circle, which is loosely coaxially inserted with a slight radial clearance on the same cross-section circle of the inner diameter D of the vertical cylindrical casing, is divided into four equal parts. The pair of outer bow-shaped damper blades formed on the outer side of the front and rear portions and the pair of deformed trapezoidal shaped damper blades formed on the inner side of the front and rear portions are eccentric by the same distance toward the center of the circle of the same cross section on the diameter in the front-rear direction. It is fixed to eccentric rotation shafts that extend in the left-right direction through the four points, and the long chord ends and the short chord ends are slightly overlapped in the front-back direction when fully closed.
In a four-blade rotary damper for a ventilator, in which four arcuate upper and lower damper blades can be rotated downward by 90 ° at each arc end and short chord end about each axis of rotation, The inner circumference of the arc is intermittently provided, and when it is fully closed, the large arc ends that extend across both ends of the rotation axis of each of the bow damper blades,
The pair of left and right small arcuate ends extending from the short chord ends of the left and right hypotenuse arcs of the irregular trapezoidal damper blades are in contact with the upper surface of the outer peripheral portion of each pair of left and right small arcs and project in the shape of inward flanges with the same appropriate width. In addition, a stopper / sealing plate for each of the three front and rear parts, and damper blade interlocking means for interlocking the above-mentioned four damper blades to fully open the arc end and the short chord end downward by 90 ° around each rotation axis, respectively. A four-blade rotary damper for a ventilator, characterized in that the lower end of each damper blade is projected downward from the lower end of the casing by an equal length when fully opened.