BLIND

Abstract

To provide a blind which can reduce failures when winding a lifting cord on a winding drum.SOLUTION: A blind 100 comprises a winding drum 120 on which a lifting cord 110 is wound. The winding drum 120 comprises a winding surface 123 on which the lifting cord 110 is wound from a winding start part 121 of the lifting cord 110 to a connection part 122 to which one end of the lifting cord 110 is connected. The winding surface 123 comprises: a plurality of first ribs 124 which extend in an axial direction from the winding start part 121 side and are gradually reduced in diameter of a circumference connecting an apex from the winding start part 121 side; and a plurality of second ribs 125 which extend in the axial direction from the connection part 122 side. The first and second ribs 124 and 125 are at different positions different from each other in a circumferential direction, and formed to partially overlap with each other in the axial direction. Thus, failures when winding the lifting cord on the winding drum can be reduced.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a blind equipped with a winding drum for winding up a lifting cord. [Background technology]

[0002] A conventional blind equipped with a winding drum for winding up a lifting cord is disclosed in Japanese Patent Publication No. 6906096 (Patent Document 1). The blind disclosed in this document has a winding drum with a connecting portion at one end to which one end of the lifting cord is connected, a winding start portion for the lifting cord located at the other end closer to the connecting portion, a winding surface for winding up the lifting cord from the winding start portion to the connecting portion, and multiple ribs extending in the axial direction of the winding drum. The winding drum has a circumferential diameter that gradually decreases from the winding start portion toward the winding surface. The winding surface is composed of the surfaces of multiple ribs and a bottom surface portion formed between each rib. The height of each rib is such that the circumference of a circle connecting the apexes of each rib remains constant from the winding start portion toward the connecting portion. The bottom surface gradually decreases in height from the winding start portion toward the connecting portion.

[0003] This configuration can reduce problems caused by loosening of the wound lift cord. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6906096 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned blinds, the lifting cord slides sideways on the take-up drum while being wound up, which can cause a phenomenon known as "stick-slip," in which the lifting cord does not slide smoothly sideways but instead shifts sideways and stops intermittently, due to frictional resistance and the tightening force of the lifting cord. Stick-slip can cause problems such as abnormal noise when the lifting cord is wound up, so there was an issue that needed improvement.

[0006] The present invention has been made in consideration of such problems, and its object is to provide a blind that can reduce problems that occur when winding the lifting cord onto the winding drum. [Means for solving the problem]

[0007] In order to solve the above problem, according to the present invention, there is provided a blind having a winding drum that winds up a lifting cord, wherein the winding drum has a winding surface that winds up the lifting cord from the winding start portion of the lifting cord to a connecting portion where one end of the lifting cord is connected, and the winding surface has a plurality of first protrusions that extend axially from the winding start portion side and have a circumference connecting vertices whose circumferential diameter gradually decreases from the winding start portion side, and a plurality of second protrusions that extend axially from the connecting portion side, and the first protrusions and the second protrusions are located at different positions from each other in the circumferential direction and are formed so as to partially overlap each other in the axial direction.

[0008] This configuration reduces the contact area of ​​the lifting cord with the winding drum. This reduces frictional resistance, allowing the lifting cord to slide smoothly. As a result, stick-slip can be prevented, and problems such as abnormal noise that occur when the lifting cord is wound onto the winding drum can be reduced.

[0009] Furthermore, because the first and second protrusions are positioned at different locations in the circumferential direction and partially overlap in the axial direction, the lift cord is less likely to slip sideways at the axial position where the slope changes from the first protrusion to the second protrusion, which makes it possible to maintain smooth sideways sliding even with a large number of turns of the lift cord.

[0010] The present invention is applicable in a variety of ways. The following application examples can be combined as appropriate. For example, the first protrusions and the second protrusions may be formed alternately in the circumferential direction. Furthermore, the first protrusions and the second protrusions may be formed so as to extend in the axial direction while tapering. Furthermore, the second protrusions may be formed so that the circumference connecting the apexes has a constant diameter. With this configuration, the contact pressure of the lifting cord against the winding drum is dispersed, allowing the lifting cord to slide smoothly sideways and preventing the stick-slip phenomenon from occurring.

[0011] Furthermore, the winding surface may be made up of surfaces of the first protrusion and the second protrusion and a bottom surface portion formed between the protrusions, and the bottom surface portion may have a circumference whose diameter gradually decreases from the winding start portion toward the connecting portion. With this configuration, the winding drum can be easily removed from the processing mold during molding, and a winding drum that can obtain the above-mentioned effects can be manufactured using an existing manufacturing method that makes it easy to mold ribs.

[0012] The first protrusion may be formed by the vertices of a regular polygon. In addition to the above-mentioned effects, this configuration has a simple structure and can be easily processed. [Effects of the Invention]

[0013] According to the present invention, a blind is provided that can reduce problems that occur when winding the lifting cord onto the winding drum. Other effects of the present invention will be described in the detailed description of the invention below. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram schematically illustrating the overall configuration of a blind 100 according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of a winding drum 120. [Figure 3] FIG. 2 is a front view of the winding drum 120. [Figure 4] FIG. 2 is a side view of the winding drum 120. [Figure 5] 4A is a cross-sectional view taken along line AA in FIG. 3; FIG. 4B is a cross-sectional view taken along line BB in FIG. 3; and FIG. 4C is a cross-sectional view taken along line CC in FIG. [Figure 6] 5A and 5B are diagrams for explaining the winding drum 120, in which (a) is a cross-sectional view taken along line DD in FIG. 4, and (b) is a cross-sectional view taken along line EE in FIG. [Figure 7] 10A and 10B are schematic diagrams showing the contact pressure distribution of the lifting cord, in which (a) is the existing winding drum MD and (b) is the winding drum 120 of this embodiment. [Figure 8] 10A and 10B are diagrams showing a state in which a lifting cord is wound onto a winding drum, in which (a) is an existing winding drum MD and (b) is a winding drum 120 of this embodiment. [Figure 9] FIG. 10 is a perspective view of a winding drum 220 according to a second embodiment. [Figure 10] FIG. 10 is a front view of a winding drum 220 according to a second embodiment. [Figure 11] 10. It is a figure for demonstrating the winding drum 220, (a) is a sectional view taken along line FF in FIG. 10, (b) is a sectional view taken along line GG in FIG. 10, and (c) is a sectional view taken along line HH in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0016] (First embodiment) A first embodiment of the present invention will be described. First, the overall configuration of a blind 100 of this embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the overall configuration of the blind 100. The blind 100 of this embodiment is a blind equipped with a winding drum 120 that winds up a lifting cord 110. The configuration of each part will be described in detail below.

[0017] As shown in Figure 1, the blind 100 comprises a head box 130, a lifting cord 110 hanging down from the head box 130, a plurality of slats 140 that are raised and lowered by the lifting cord 110, a ladder cord 150 that supports the plurality of slats 140 in an aligned state, and a bottom rail 160 that is provided below the row of the plurality of slats 140 and to which the lower end of the lifting cord 110 and the lower end of the ladder cord 150 are connected.

[0018] The head box 130 is fixed via brackets to an opening in a window frame, ceiling, or the like. As shown in FIG. 1 , a rotary shaft 132 extending in the longitudinal direction of the head box 130 is rotatably supported within the head box 130. Drum receivers 133 that rotatably support the winding drums 120 are arranged in the head box 130 at three locations in the longitudinal direction. The rotary shaft 132 passes through each winding drum 120 and rotates integrally with each winding drum 120. The head box 130 is also provided with a motor 134 that rotationally drives the rotary shaft 132, a control unit 136 that controls the drive of the motor 134, and an encoder 138 that detects the rotation angle of the motor 134.

[0019] The lifting / lowering cord 110 raises and lowers the slats 140. As shown in Fig. 1, the upper end of the lifting / lowering cord 110 is connected to a winding drum 120 in the head box 130 so as to be capable of being wound and unwound. The lower end of the lifting / lowering cord 110 hangs down from the head box 130, passes through multiple slats 140, and is connected to a bottom rail 160.

[0020] The slats 140 are capable of closing the opening. As shown in FIG. 1, a plurality of slats 140 are arranged in parallel in the vertical direction below the head box 130.

[0021] The ladder cord 150 supports the multiple slats 140 in an aligned state. As shown in FIG. 1, the upper end of the ladder cord 150 is connected to a rotating drum (not shown) that rotates integrally with the winding drum 120. The lower end of the ladder cord 150 is connected to a bottom rail 160. The ladder cord 150 tilts with the rotation of the rotating drum, causing the slats 140 to rotate.

[0022] The bottom rail 160 applies tension to the lifting / lowering cord 110 and the ladder cord 150. As shown in FIG. 1, the bottom rail 160 is disposed below the lowest slat 140. As described above, the lower ends of the lifting / lowering cord 110 and the ladder cord 150 are connected to the bottom rail 160. When the winding drum 120 winds up the lifting / lowering cord 110 and the lifting / lowering cord 110 rises, the bottom rail 160 rises and folds up the slats 140 one by one, starting from the lowest slat 140.

[0023] Next, the winding drum 120, which is a characteristic configuration of this embodiment, will be described with reference to Figs. 2 to 5. Fig. 2 is a perspective view of the winding drum 120. Fig. 3 is a front view of the winding drum 120. Fig. 4 is a side view of the winding drum 120. Fig. 5 is a diagram for explaining the winding drum 120, where (a) is a cross-sectional view taken along line AA in Fig. 3, (b) is a cross-sectional view taken along line BB in Fig. 3, and (c) is a cross-sectional view taken along line CC in Fig. 3.

[0024] As shown in FIG. 2, the winding drum 120 has a winding surface 123 that winds the lifting cord 110 from a winding start portion 121 of the lifting cord 110 to a connecting portion 122 to which one end of the lifting cord 110 is connected. The winding surface 123 has a plurality of first ribs (first protrusions) 124 that extend in the axial direction from the winding start portion 121 side and have a circumference connecting vertices whose circumferential diameter gradually decreases from the winding start portion 121 side, and a plurality of second ribs (second protrusions) 125 that extend in the axial direction from the connecting portion 122 side. The first ribs 124 and the second ribs 125 are located at different positions from each other in the circumferential direction and are formed so as to partially overlap each other in the axial direction. The configuration of each portion will be described in detail below.

[0025] 2, the winding start portion 121 is one end of the winding drum 120 and is located approximately vertically above the connection position of the lifting cord 110 with the bottom rail 160. The connection portion 122 is located at the other end of the winding drum 120. A winding surface 123 is formed from the winding start portion 121 to the connection portion 122.

[0026] As shown in FIG. 2, the winding surface 123 is made up of the surfaces of a plurality of first ribs 124 and second ribs 125, and a bottom surface portion 126 formed between each rib (between adjacent first ribs 124, between adjacent second ribs 125, and between the first rib 124 and the second rib 125). As shown in FIGS. 3 and 4, the plurality of first ribs 124 and second ribs 125 are formed alternately in the circumferential direction of the winding drum 120. As shown in FIG. 3, the tips of the first ribs 124 and the second ribs 125 partially overlap each other in the axial direction. As shown in FIG. 4, the first ribs 124 and the second ribs 125 are arc-shaped. As shown in FIG. 5, the bottom surface portion 126 is configured so that the circumferential diameter gradually decreases from the winding start portion 121 toward the connecting portion 122.

[0027] As shown in Fig. 3, the first rib 124 extends from the winding start section 121 side to just under half the length in the axial direction of the winding drum 120. As shown in Figs. 4 and 5, the first rib 124 is configured so that the circumferential diameter X of the circumference connecting the vertices of the end portion on the winding start section 121 side is larger than the circumferential diameter Y of the circumference connecting the vertices of the second rib 125. The first rib 124 is an inclined rib formed so that the circumferential diameter of the circumference connecting the vertices gradually decreases from the winding start section 121 side. Furthermore, the first rib 124 is formed so as to taper as it extends in the axial direction.

[0028] As shown in Fig. 3, the second rib 125 extends in the axial direction from the connecting portion 122 side to the vicinity of the winding start portion 121. As shown in Fig. 5, the second rib 125 is a parallel rib formed so that the circumferential diameter Y of the circumference connecting the vertices is constant over the entire axial length. In addition, the second rib 125 is formed so as to taper as it extends in the axial direction.

[0029] The circumferential diameters of the first rib 124 and the second rib 125 will be described with reference to Fig. 6. Fig. 6 is a diagram for explaining the winding drum 120, where (a) is a DD cross-sectional view of Fig. 4 and (b) is an EE cross-sectional view of Fig. 4. As shown in Fig. 6, the first rib 124 has a circumferential diameter of X at the end on the winding start portion 121 side, but the circumferential diameter at the tip is smaller than Y. The portion of the first rib 124 closer to the connecting portion 122 than the tip thereof forms a bottom surface portion 126.

[0030] 6, the second rib 125 has a circumferential diameter Y from the connecting portion 122 side to the vicinity of the winding start portion 121. Since the circumferential diameter Y of the second rib 125 is larger than the circumferential diameter Z of the end portion of the bottom surface portion 126 on the connecting portion 122 side, the end portion of the second rib 125 on the connecting portion 122 side protrudes the most from the bottom surface portion 126 and becomes smaller toward the winding start portion 121.

[0031] The contact pressure of the lift-down cord 110 when wound around the winding drum 120 of this embodiment and when wound around a conventional winding drum MD will be compared and explained with reference to Fig. 7. Fig. 7 is a schematic diagram showing the contact pressure distribution of the lift-down cord, where (a) is the conventional winding drum MD and (b) is the winding drum 120 of this embodiment. The thick line CP and black circle in the figure schematically show the contact pressure of the lift-down cord.

[0032] In the case of a conventional winding drum MD, as shown in FIG. 7(a), only a rib RB corresponding to the second rib 125 of this embodiment is provided, and no rib RB is provided at a position corresponding to the winding start portion 121 of this embodiment. Therefore, because the lifting cord is wound around the cylindrical winding start portion WS, the contact pressure (thick line CP in the figure) near the winding start portion WS is not dispersed. This increases the frictional resistance when the lifting cord slides sideways. Because the lifting cord slides sideways while being wound on the winding drum MD, frictional resistance and the tightening force of the lifting cord can cause a phenomenon known as "stick-slip," in which the lifting cord does not slide smoothly sideways but instead intermittently shifts sideways and stops.

[0033] In contrast, in the case of the winding drum 120 of this embodiment, as shown in Fig. 7(b), a first rib 124 is provided at the winding start portion 121. Therefore, at the winding start portion 121, the lift-up cord 110 wound around the winding surface 123 mainly comes into contact with the first rib 124. This distributes the contact pressure of the lift-up cord 110 near the winding start portion 121 (black circles in the figure), reducing frictional resistance against the tightening force of the winding of the lift-up cord 110 and allowing the lift-up cord 110 to slide smoothly.

[0034] At the position where the first rib 124 and the second rib 125 overlap, the first rib 124 and the second rib 125 come into contact with each other. Generally, the contact pressure between the first rib 124 and the second rib 125 is greater on the side with a larger circumference, and is approximately the same at position a where the circumferences are approximately the same. By alternately arranging the first ribs 124 and the second ribs 125 in this way, which distributes the contact pressure, it is possible to reduce the retention of sliding of the lift-up cord 110 at the axial position where the slope changes from the first rib 124 to the second rib 125. Note that because frictional resistance when the lift-up cord 110 slides also has an effect, the position where the contact pressure between the first rib 124 and the second rib 125 is equivalent may deviate from position a where the circumferences of the first rib 124 and the second rib 125 are the same, but the lift-up cord 110 continues to slide smoothly.

[0035] The configuration of the blind 100 of this embodiment has been described above. Next, the operation of the blind 100 will be described with reference to Fig. 8. Fig. 8 is a diagram showing a state in which the winding drum is wound around the lifting cord, where (a) is an existing winding drum MD and (b) is the winding drum 120 of this embodiment.

[0036] In the case of a conventional winding drum MD, as shown in Figure 8(a), when the lifting cord LC is wound from the winding start part WS, it is wound onto a part where the rib RB is not provided. Then, the lifting cord LC is wound while sliding sideways on the winding drum MD in the direction indicated by arrow b, causing intermittent lateral displacement (stick-slip) as indicated by the dashed-dotted line. Therefore, stick-slip occurs due to the frictional resistance when the lifting cord LC slides sideways and the tightening force when the lifting cord LC is wound, which may cause an abnormal "knocking" noise.

[0037] In contrast, in the case of the winding drum 120 of this embodiment, as shown in FIG. 8(b), the lift-up cord 110 wound from the winding start portion 121 first comes into contact primarily with the first rib 124, and then smoothly slides in the direction indicated by arrow c, coming into contact with the first rib 124 and the second rib 125. This reduces the likelihood of the lift-up cord 110 staying in the axial direction at the point where the slope changes from the first rib 124 to the second rib 125. This makes it possible to maintain smooth sliding even with a large number of turns of the lift-up cord 110. In this way, frictional resistance to the tightening force of the winding when the lift-up cord 110 slides is reduced, preventing stick-slip from occurring.

[0038] (Effects of the first embodiment) As described above, according to this embodiment, the contact area of ​​the lift-up cord 110 with the take-up drum 120 is reduced. This reduces frictional resistance, allowing the lift-up cord 110 to slide smoothly sideways. As a result, the stick-slip phenomenon can be prevented, and problems such as abnormal noise that occur when the lift-up cord 110 is taken up onto the take-up drum 120 can be reduced.

[0039] Furthermore, the first rib 124 and the second rib 125 are positioned at different positions in the circumferential direction and are formed to partially overlap each other in the axial direction, which reduces the likelihood of the lift-up cord 110 slipping sideways at the axial position where the slope changes from the first rib 124 to the second rib 125. This makes it possible to maintain smooth sliding even when the number of turns of the lift-up cord 110 is increased.

[0040] Furthermore, since the contact pressure of the lifting cord 110 against the take-up drum 120 is dispersed, the lifting cord 110 can slide smoothly sideways, preventing the stick-slip phenomenon from occurring.

[0041] In addition, the winding surface 123 consists of the surfaces of the first rib 124 and the second rib 125 and a bottom surface portion 126, and the bottom surface portion 126 is configured so that the circumference diameter gradually decreases from the winding start portion 121 toward the connecting portion 122, making it easier to remove the winding drum 120 from the processing mold during molding processing, and a winding drum 120 that can achieve the above-mentioned effects can be manufactured using an existing manufacturing method that makes it easy to mold ribs.

[0042] (Second embodiment) A second embodiment of the present invention will be described. First, the configuration of the winding drum 220 of the blind according to this embodiment will be described with reference to Figs. 9 to 11. Fig. 9 is a perspective view of the winding drum 220 of the second embodiment. Fig. 10 is a front view of the winding drum 220 of the second embodiment. Fig. 11 is a diagram for explaining the winding drum 220. This embodiment differs from the first embodiment in the configuration of the winding drum 220, but other configurations are similar to those of the first embodiment. In this embodiment, differences from the first embodiment will be mainly described. Components having substantially the same functional configurations will be assigned the same reference numerals, and redundant description will be omitted.

[0043] 9 and 10, the portion of the winding drum 220 corresponding to the first rib 124 of the first embodiment is configured as the apex 224 of a 24-sided pyramid, and the apex (first protrusion) 224 is disposed between adjacent second ribs 225. The circumference of the circle connecting the apexes 224 is largest on the winding start portion 121 side and becomes smaller toward the connecting portion 122, with the tip formed to be the same size as the circumference of the bottom surface portion 226. Note that although a 24-sided pyramid is used in this embodiment, any design may be used as long as the apex has an obtuse angle.

[0044] The vertices 224 are rounded. The rounded vertices 224 have the same radius as the first ribs 124 of the first embodiment. Therefore, the vertices 224 allow the lifting cord 110 to slide in the axial direction and the winding direction, just like the first ribs 124. The space between adjacent vertices 224 is formed flat.

[0045] 9 and 10, the winding surface 223 is composed of an apex 224, a second rib 225 having the same configuration as in the first embodiment, and a bottom surface 226. Where the apex 224 and the second rib 225 overlap, a ridge line 223a is formed by a flat surface 227 of the 24-sided pyramid and the cylindrical surface of the bottom surface 226. FIG. 11 is a diagram for explaining the winding drum 220, where (a) is an FF cross-sectional view of FIG. 10, (b) is a GG cross-sectional view of FIG. 10, and (c) is an HH cross-sectional view of FIG. 10. As shown in FIG. 11(a), the circumference of the apex 224 of the winding start portion 121 connecting the apex 224 and the apex 224 has the largest circumference within the winding surface 223. 11(b), the circumference of the vertex 224 becomes smaller as it approaches the connecting portion 122, and near the tip, the circumference of the second rib 125 and the circumference of the circumference become the same as Y. The circumference of the vertex 224 further becomes smaller as it approaches the connecting portion 122, and the tip becomes the same size as the circumference of the bottom surface portion 226.

[0046] As described above, the second rib 225 has the same configuration as in the first embodiment. That is, as shown in Fig. 11(c), the second rib 225 is a parallel rib whose circumference connecting the vertices on the connecting portion 122 side is Y, and whose circumference remains Y all the way to the tip on the winding start portion 121 side.

[0047] In this embodiment, the vertex 224 is rounded, but since the vertex of the 24-sided pyramid has an obtuse angle, the effect on the lift cord 110 is small even if the rounding is not performed, so the rounding is not necessarily required.

[0048] The operation of the blind 200 of this embodiment is substantially the same as that of the first embodiment. That is, the lifting / lowering cord 110 wound from the winding start portion 121 first comes into contact mainly with the apex 224, and then slides sideways to come into contact with the apex 224 and the second rib 225. This reduces the frictional resistance against the tightening force of the winding when the lifting / lowering cord 110 slides sideways, preventing stick-slip from occurring.

[0049] (Effects of the second embodiment) As described above, according to this embodiment, the vertices 224 are formed from the vertices of a regular polygon, which results in a simple structure and allows for easy processing.

[0050] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that these modifications and alterations also fall within the technical scope of the present invention.

[0051] For example, in the first embodiment, the first ribs 124 and the second ribs 125 are alternately formed in the circumferential direction, but the present invention is not limited to this example. Any design is possible as long as the frictional resistance of the lifting cord is reduced and the lifting cord can slide smoothly sideways. For example, the first protrusions and second protrusions may be arranged at multiple intervals in the circumferential direction, such as every third protrusion. The same applies to the second embodiment.

[0052] In the first embodiment, the first rib 124 and the second rib 125 are formed so as to taper and extend in the axial direction, but the present invention is not limited to this example. Any design may be used as long as the frictional resistance of the lifting cord is reduced and the lifting cord can slide smoothly sideways. For example, the first protrusion and the second protrusion may have a constant width along their entire length or may widen toward their tips. This also applies to the second embodiment.

[0053] In the first embodiment, the second rib 125 is formed so that the circumference connecting the vertices has a constant diameter, but the present invention is not limited to this example. Any design is possible as long as the frictional resistance of the lifting cord is reduced and the lifting cord can slide smoothly sideways. For example, the second protrusion may be formed so that the circumference connecting the vertices gradually decreases from the connecting portion side. This also applies to the second embodiment.

[0054] In the first embodiment, the winding surface 123 is composed of the surfaces of the first rib 124 and the second rib 125 and the bottom surface 126 formed between the first rib 124 and the second rib 125, and the circumference of the bottom surface 126 gradually decreases from the winding start portion 121 toward the connecting portion 122. However, the present invention is not limited to this example. Any design is possible as long as the frictional resistance of the lifting cord is reduced and the lifting cord can slide smoothly sideways. For example, the circumference of the bottom surface may not change over the entire length from the winding start portion to the connecting portion. The same applies to the second embodiment.

[0055] The above-described embodiments, applications, and modifications can be implemented in any combination. [Explanation of symbols]

[0056] 100, 200 blinds 110 Lifting cord 112 Rotation axis 113 Drum holder 114 Motor 116 Control Unit 118 Encoder 120, 220 winding drum 121 Winding start part 122 Connection section 123, 223 winding surface 124 First Rib 125, 225 Second Rib 126, 226 Bottom part 130 headbox 140 slats 150 Ladder Code 160 bottom rail 223a Ridgeline 224 Vertices MD take-up drum RB Rib WS winding start section LC Lifting Cord

Claims

1. A blind equipped with a winding drum for winding up a lifting cord, the winding drum has a winding surface that winds the lifting cord from a winding start portion of the lifting cord to a connecting portion to which one end of the lifting cord is connected, the winding surface includes a plurality of first protrusions extending in the axial direction from the winding start portion side, the circumference of which connecting vertices gradually decreases from the winding start portion side, and a plurality of second protrusions extending in the axial direction from the connecting portion side, the first protrusion and the second protrusion are located at different positions in the circumferential direction and are formed to partially overlap with each other in the axial direction, The first protrusion has a larger circumference than the second protrusion at the end on the winding start portion side, and the tip of the first protrusion has a smaller circumference than the second protrusion at the portion overlapping with the second protrusion.

2. The blind according to claim 1 , wherein the first protrusions and the second protrusions are formed alternately in the circumferential direction.

3. The blind according to claim 1 or 2, wherein the first protrusion and the second protrusion are formed so as to extend in the axial direction while tapering.

4. The blind according to any one of claims 1 to 3, wherein the second protrusion is formed so that the circumference of a circle connecting the apexes has a constant diameter.

5. the winding surface is made up of surfaces of the first protrusion and the second protrusion and a bottom surface portion formed between the protrusions, The blind according to any one of claims 1 to 4, wherein the bottom surface portion has a circumference that gradually decreases in diameter from the winding start portion toward the connecting portion.

6. The blind according to any one of claims 1 to 5, wherein the first protrusion is formed by a vertex of a regular polygon.

Images