Strap length adjustment device

Abstract

Provided in embodiments of the present invention is a strap length adjustment device, which uses the elastic force of a hinge unit and the frictional force of a brake so as to fix or rotate a rotary unit while the brake rotates by being in close contact with or being spaced apart from the inner surface of a side portion of a circular plate through the elastic force of the hinge unit, such that noise generated during strap length adjustment can be reduced.

Description

Strap length adjuster

[0001] The present invention relates to a strap length adjustment device that can reduce noise generated when adjusting the strap length of a head-mounted display device by using the elasticity of a hinge unit and the frictional force of a brake.

[0002] In line with the trend toward lighter and smaller display devices, various wearable devices are being developed. Head-mounted displays (HMDs), a type of wearable device, refer to various devices that users wear on their heads to access multimedia content. Head-mounted displays are categorized into see-through and see-closed types. See-through types are primarily used for augmented reality (AR), while see-closed types are primarily used for virtual reality (VR).

[0003] Augmented Reality (AR) is a technology that superimposes virtual objects onto the user's view of the real world. Because it combines the real world with a virtual world with additional information in real time, it presents a single image, and is also called Mixed Reality (MR). Research and development on hybrid VR systems, which merge real and virtual environments, has been ongoing since the late 1990s, primarily in the United States.

[0004] Head-mounted displays can be worn like glasses, but others are worn on the head like headsets or goggles. These headset- or goggle-style AR or VR head-mounted displays must fit snugly on the head to allow for easy movement and comfort.

[0005] Most current head-mounted displays in the form of headsets / goggles are sized using gear attached to a wearing strap.

[0006] The head-mounted display can be removed by shortening or lengthening the strap, typically by winding the gear clockwise to reduce the size and counterclockwise to increase the size.

[0007] At this time, the gear structure for adjusting the strap length of a general headset / goggle type head-mounted display is equipped with a gear and a pawl that engages with the gear.

[0008] However, in the case of the gear structure provided with the above gear and stopper, a clicking noise is generated depending on the adjustment of the length of the strap. This clicking noise is due to the structure of the gear in which the gear passes over the stopper when rotating the gear, and the gear meshes with the stopper to prevent the gear from rotating when stopping the gear.

[0009] However, due to the nature of the head-mounted display, which adjusts the length of the strap while worn on the head, there is a problem in that the noise described above is generated when the display touches the head, and the noise may be excessively loud and cause discomfort to the wearer.

[0010] Additionally, the clicking noise may cause the wearer to suspect a malfunction, and in quiet environments, the noise can be very distracting.

[0011] In addition, this noise has the problem of reducing the comfort and quality of use when the wearer uses a head-mounted display.

[0012] Therefore, in order to solve the above-described problems, a strap length adjustment device having a structure that can reduce noise generated when adjusting the strap length of a head-mounted display device is required.

[0013] The present invention provides a strap length adjustment device, and more specifically, it aims to provide a strap length adjustment device that can reduce noise generated when adjusting the strap length of a head-mounted display device by using the elasticity of a hinge unit and the frictional force of a brake.

[0014] In addition, the purpose is to provide a strap length adjustment device that can adjust the length of the strap by fixing or rotating the rotation unit while the brake is rotated by being pressed against or separated from the inner surface of the side of the circular plate by the elasticity of the hinge unit.

[0015] In addition, the brake is intended to stably fix the rotating unit by including a rubber member that generates friction with the inner surface of the side of the circular plate, thereby providing a strap length adjustment device that can adjust the length of the strap.

[0016] The problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0017] A strap length adjusting device is provided, comprising: a main body; a pair of straps extending from both sides of the main body and having racks formed at one end; a fixed pad on the back surface on which the racks of the pair of straps are arranged vertically; and a length adjusting unit for adjusting an overlapping length of the pair of straps by horizontally moving the pair of racks, wherein the length adjusting unit comprises: a circular plate coupled to the back surface of the fixed pad and having a side extending rearward on an outer surface; a rotation unit including a pinion positioned between the pair of racks and engaging with the pair of racks and a rotation arm extending from the pinion; a hinge unit including a hinge arm that rotates around the rotation axis of the pinion and is coupled to an end surface by an elastic hinge; and a brake coupled to the hinge arm and fixing or rotating the rotation unit on an inner surface of a side surface of the circular plate.

[0018] The length adjustment unit may include a rotary dial that is rotatably coupled to the circular plate and changes the angle of the hinge arm when rotated.

[0019] The above brake can be brought into close contact with the inner surface of the side of the circular plate by the elastic force of the hinge unit or can rotate away from the inner surface of the side of the circular plate when the angle of the hinge arm changes.

[0020] The above rotary dial includes a first rib that comes into contact with the hinge arm on the front, and the first rib can rotate the hinge arm in a first direction toward the center of the hinge unit when the rotary dial is rotated, thereby reducing the angle of the hinge arm.

[0021] The above hinge arm can be rotated in a second direction opposite to the first direction by the elastic force of the elastic hinge when the rotation of the rotary dial stops, and can be restored to its original state as the angle increases.

[0022] The above rotary dial may include a second rib on the front side that guides the rotation of the brake, and the brake may include a guide protrusion that comes into contact with the inner surface of the second rib.

[0023] The second rib includes a first point and a second point spaced apart from the first point on the side of the circular plate, and the brake is configured to be in close contact with the inner surface of the side of the circular plate when the guide protrusion is positioned at the first point, and to be rotatable spaced apart from the inner surface of the side of the circular plate when the guide protrusion is positioned at the second point.

[0024] The rotary arm of the above rotary unit may include a first rotary arm having a straight shape extending from the pinion to both sides; and a second rotary arm extending from an end of the first rotary arm and provided along an inner surface of a side of the circular plate.

[0025] The above brake may include a coupling projection rotatably coupled to the hinge arm.

[0026] The above brake may include a rubber member that generates frictional force on the inner surface of the side of the circular plate.

[0027] The rotary dial may further include a back cover coupled to the fixed pad on the back side, and the back cover may include an adjustment groove exposing a portion of the rotary dial on at least one of the upper surface and the lower surface.

[0028] The strap length adjustment device according to the present invention can reduce noise generated when adjusting the strap length of a head-mounted display device by using the elasticity of a hinge unit and the frictional force of a brake.

[0029] Additionally, the length of the strap can be adjusted by fixing or rotating the rotation unit while the brake is rotated by being pressed against or separated from the inner surface of the side of the circular plate by the elasticity of the hinge unit.

[0030] Additionally, the brake can stably fix the rotating unit by including a rubber member that generates friction with the inner surface of the side of the circular plate, thereby adjusting the length of the strap.

[0031] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

[0032] FIG. 1 is a perspective view of a strap length adjustment device according to one embodiment of the present invention.

[0033] Figure 2 is an exploded view of a strap length adjustment device according to one embodiment of the present invention.

[0034] FIG. 3 is a drawing showing the shape of a length adjustment unit combined in a strap length adjustment device according to one embodiment of the present invention.

[0035] FIG. 4 is a front view of a rotary dial of a strap length adjustment device according to one embodiment of the present invention.

[0036] FIG. 5 is a drawing showing a shape in which a hinge arm of a hinge unit rotates in a strap length adjustment device according to one embodiment of the present invention.

[0037] FIG. 6 is a drawing for explaining that the brake rotates and rotates the rotation unit when the rotation dial is rotated in a strap length adjustment device according to one embodiment of the present invention.

[0038] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or similar components will be given the same reference numbers and redundant descriptions thereof will be omitted. The suffixes "module" and "part" used for components in the following description are assigned or used interchangeably only for the convenience of writing the specification, and do not in themselves have distinct meanings or roles. In addition, when describing the embodiments disclosed in this specification, if it is determined that a specific description of a related known technology may obscure the gist of the embodiments disclosed in this specification, a detailed description thereof will be omitted. In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

[0039] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0040] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0041] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0042] In this application, terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0043] Fig. 1 is a perspective view of a strap length adjustment device (100) according to one embodiment of the present invention. Fig. 2 is an exploded view of a strap length adjustment device (100) according to one embodiment of the present invention. And Fig. 3 is a drawing illustrating a shape in which a length adjustment unit (200) is combined in a strap length adjustment device (100) according to one embodiment of the present invention.

[0044] A strap length adjustment device (100) according to one embodiment of the present invention is a device for adjusting the length of a strap (120) of a head-worn display device in the form of a headset or goggles worn on the head.

[0045] Referring to FIGS. 1 to 3 together, a strap length adjustment device (100) according to one embodiment of the present invention may include a main body (110) positioned on the face of a wearer, a pair of straps (120) extending from both sides of the main body (110) and having racks (121) formed at one end, a fixed pad (130) having a front side (z-axis direction) positioned on the back of the wearer's head and a rear side (z-axis direction) in which the racks (121) of the pair of straps (120) are arranged up and down (y-axis direction), and a length adjustment unit (200) that adjusts the overlapping length (L) of the pair of straps (120) by moving the pair of racks (121) in a horizontal direction (x-axis direction).

[0046] Here, the wearer can adjust the length of the strap (120) to fit the wearer's head size through the length adjustment part (200) of the present invention.

[0047] More specifically, the length adjusting unit (200) of the strap length adjusting device (100) according to one embodiment of the present invention may include a circular plate (210), a rotation unit (220), a hinge unit (230), and a brake (240).

[0048] First, the circular plate (210) is coupled to the back surface (z-axis direction) of the fixed pad (130) and may include a side portion (211) extending toward the rear (z-axis direction) on the outer surface. And the rotation unit (220) may be positioned between a pair of racks (121) and may include a pinion (221) that engages with the pair of racks (121) and a rotation arm (222) extending from the pinion (221).

[0049] Here, the pinion (221) of the rotation unit (220) may penetrate the circular plate (210) and engage with a pair of racks (121). In addition, the rotation arm (222) of the rotation unit (220) may include a first rotation arm (223) having a straight shape extending from the pinion (221) to both sides, and a second rotation arm (224) extending from an end of the first rotation arm (223) and provided along the inner surface of the side portion (211) of the circular plate (210). At this time, the second rotation arm (224) may be in contact with the side surface of the brake (240) or may be positioned at a predetermined interval therefrom. In addition, the rotation arm (222) of the rotation unit (220) may be positioned on the back surface (z-axis direction) of the circular plate (210).

[0050] Additionally, the hinge unit (230) may include a hinge arm (231) that rotates around the rotational axis of the pinion (221) and is connected to an end with an elastic hinge (232). And the brake (240) may be connected to the hinge arm (231) and may be located on the inner surface of the side (211) of the circular plate (210).

[0051] Here, the brake (240) may include a coupling projection (242) that is rotatably coupled to the hinge arm (231). In addition, the brake (240) may include a rubber member (243) that generates frictional force with the inner surface of the side (211) of the circular plate (210).

[0052] In addition, the length adjustment unit (200) of the strap length adjustment device (100) according to one embodiment of the present invention may include a rotary dial (250) rotatably coupled to a circular plate (210).

[0053] Accordingly, the wearer can rotate the rotary dial (250) by turning the rotary dial (250) with his / her hand. At this time, the rotary dial (250) can change the angle (θ) of the hinge arm (231) illustrated in FIG. 3 when rotating.

[0054] This includes a first rib (251) that comes into contact with a hinge arm (231) on the front of the rotary dial (250), so that when the rotary dial (250) is rotated, the hinge arm (231) rotates together and the angle (θ) of the hinge arm (231) can be changed. In addition, when the angle (θ) of the hinge arm (231) changes, an elastic force can be applied to the elastic hinge (232).

[0055] Additionally, the rotary dial (250) may include a second rib (252) that guides the rotation of the brake (240) on the front, and the brake (240) may include a guide protrusion (241) that comes into contact with the inner surface of the second rib (252).

[0056] Here, the strap length adjustment device (100) according to one embodiment of the present invention can be configured so that the wearer can rotate the rotary dial (250) as described above, and the brake (240) can be brought into close contact with the inner surface of the side (211) of the circular plate (210) by the elastic force of the hinge unit (230) to fix the rotary unit (220), or can rotate away from the inner surface of the side (211) of the circular plate (210) when the angle (θ) of the hinge arm (231) changes to rotate the rotary unit (220).

[0057] And as the rotation unit (220) rotates or is fixed, a pair of racks (121) move in the horizontal direction (y-axis direction) by the pinion (221) of the rotation unit (220), and the overlapping length (L) of a pair of straps (120) can be adjusted.

[0058] That is, the length of the strap (120) can be adjusted to fit the wearer's head size by lengthening or shortening the overlapping length (L) of a pair of straps (120).

[0059] As described above, the gear structure for adjusting the strap length of a general headset / goggle type head-mounted display device is provided with a gear and a pawl that engages with the gear.

[0060] However, in the case of the gear structure provided with the above gear and stopper, a clicking noise is generated depending on the adjustment of the length of the strap. This clicking noise is due to the structure of the gear in which the gear passes over the stopper when rotating the gear, and the gear meshes with the stopper to prevent the gear from rotating when stopping the gear.

[0061] However, due to the nature of head-mounted display devices, which require the length of the strap to be adjusted while worn on the head, the aforementioned noise may be excessively loud and uncomfortable for the wearer, as it is generated when the device touches the head. Furthermore, the clicking noise may cause the wearer to suspect a malfunction, and in quiet environments, the noise may be quite bothersome. Furthermore, this noise can detract from the wearer's sense of comfort and quality when using the head-mounted display device.

[0062] Accordingly, the strap length adjustment device (100) according to one embodiment of the present invention aims to reduce noise generated when adjusting the length of the strap (120) by replacing the structure of the conventional gear and a stopper engaged with the gear to solve the above-described problems, and adjusting the length of the strap (120) by using the elasticity of the hinge unit (230) and the frictional force of the brake (240).

[0063] And, the strap length adjustment device (100) according to one embodiment of the present invention may further include a back cover (260) coupled with a fixed pad (130) on the back surface (z-axis direction) of the rotary dial (250) as shown in FIG. 1.

[0064] Here, the back cover (260) may include an adjustment groove (261) that exposes a portion of the rotary dial (250) on at least one side of the upper or lower surface. Then, the wearer can adjust the length of the strap (120) by rotating the rotary dial (250) exposed in the adjustment groove (261).

[0065] In addition, the back cover (260) can cover the components of the length adjustment unit (200) described above, except for a portion of the exposed rotary dial (250). Therefore, the back cover (260) can act as a soundproofing device against noise that may occur when adjusting the length of the strap (120). This can further reduce noise.

[0066] Additionally, the back cover (260) may house the battery of the head-mounted display device. This is because, if the battery is housed in the main body (110) positioned on the wearer's face as described above with reference to FIG. 1, the weight of the battery may cause the weight to be concentrated on the wearer's face, thereby reducing the wearer's comfort. In other words, by housing the battery in the back cover (260), the center of gravity is prevented from being concentrated on the wearer's face, thereby improving the wearer's comfort.

[0067] Hereinafter, a method of adjusting the length of a strap (120) through a strap length adjusting device (100) according to one embodiment of the present invention will be described in more detail.

[0068] Fig. 4 is a front view of a rotary dial (250) of a strap length adjustment device (100) according to one embodiment of the present invention. Fig. 5 is a drawing showing a shape in which a hinge arm (231) of a hinge unit (230) rotates in a strap length adjustment device (100) according to one embodiment of the present invention. And Fig. 6 is a drawing for explaining that when a rotary dial (250) is rotated in a strap length adjustment device (100) according to one embodiment of the present invention, a brake (240) rotates and rotates a rotary unit (220).

[0069] Here, (a) of FIG. 5 is a drawing showing a shape in which the hinge arm (231) rotates in a first direction toward the center of the hinge unit (230), and (b) of FIG. 5 is a drawing showing a shape in which the hinge arm (231) rotates in a second direction opposite to the first direction. In addition, (a) of FIG. 6 is a drawing showing a case in which the rotary dial (250) does not rotate, and (b) of FIG. 6 is a drawing showing a case in which the dial rotates.

[0070] Meanwhile, the following description will be made based on the assumption that the length of the strap (120) decreases when the rotary dial (250) is rotated clockwise, and the length of the strap (120) increases when the rotary dial (250) is rotated counterclockwise. However, the strap length adjustment device (100) of the present invention is not limited to the above-described direction, and may be configured so that the length of the strap (120) increases when the rotary dial (250) is rotated clockwise, and the length of the strap (120) decreases when the rotary dial (250) is rotated counterclockwise.

[0071] Referring to FIGS. 3 and 4 together, in a strap length adjustment device (100) according to one embodiment of the present invention, a rotary dial (250) may include a first rib (251) that comes into contact with a hinge arm (231) at the front. In addition, the rotary dial (250) may include a second rib (252) that guides the rotation of a brake (240) at the front. Here, the second rib (252) may include a first point (252a) and a second point (252b) that is spaced apart from the first point (252a) on the side (211) of the circular plate (210).

[0072] At this time, referring to FIGS. 4 and 6 together, as illustrated in (a) of FIG. 6, the brake (240) can be brought into close contact with the inner surface of the side (211) of the circular plate (210) when the guide protrusion (241) is positioned at the first point (252a), thereby fixing the rotation unit (220). And as illustrated in (b) of FIG. 6, the brake (240) can be rotated while being spaced apart from the inner surface of the side (211) of the circular plate (210) when the guide protrusion (241) is positioned at the second point (252b), thereby rotating the rotation unit (220). That is, the brake (240) can push the second rotation arm (224) and rotate the rotation unit (220).

[0073] Referring to FIGS. 3 and 5 together, in a strap length adjusting device (100) according to one embodiment of the present invention, a hinge unit (230) may include a hinge arm (231) coupled to an end with an elastic hinge (232), and the hinge arm (231) may rotate and the angle (θ) of the hinge arm (231) may be changed. In addition, when the angle (θ) of the hinge arm (231) changes, an elastic force may be applied to the elastic hinge (232).

[0074] Referring to FIGS. 3 to 6 together, in a strap length adjusting device (100) according to one embodiment of the present invention, when the rotary dial (250) is rotated, the first rib (251) can rotate the hinge arm (231) in a first direction toward the center of the hinge unit (230), thereby reducing the angle (θ) of the hinge arm (231). That is, as shown in (a) and (b) of FIG. 6, due to the rotation of the rotary dial (250), θ2 is smaller than θ1.

[0075] Accordingly, as shown in (b) of FIG. 6, when the rotary dial (250) rotates clockwise, the angle (θ2) of the hinge arm (231) decreases, and the brake (240) can be separated from the inner surface of the side (211) of the circular plate (210) by a distance (d).

[0076] And the guide protrusion (241) of the brake (240) is positioned at the second point (252b) of the second rib (252), and the brake (240) rotates away from the inner surface of the side (211) of the circular plate (210) and pushes the second rotary arm (224) to rotate the rotary unit (220) clockwise.

[0077] And, as described above, by clockwise rotation of the rotation unit (220), the length of the strap (120) can be reduced as the overlapping length (L) of the pair of straps (120) shown in FIG. 3 is shortened.

[0078] And, as shown in (a) of FIG. 6, when the rotation of the rotary dial (250) stops, the hinge arm (231) rotates in the second direction opposite to the first direction by the elastic force of the elastic hinge (232), and as the angle (θ1) of the hinge arm (231) increases, it can be restored to its original state. Accordingly, the brake (240) can be brought into close contact with the inner surface of the side (211) of the circular plate (210) to fix the rotary unit (220) again.

[0079] And referring to FIG. 3 together, when the length of the strap (120) is increased by rotating the rotary dial (250) counterclockwise, the guide protrusion (241) of the brake (240) is positioned at the second point (252b) of the second rib (252), and the hinge arm (231) rotatably coupled to the engaging protrusion (242) of the brake (240) can be rotated in a first direction toward the center of the hinge unit (230). Accordingly, the angle (θ) of the hinge arm (231) can be reduced, and the brake (240) can be spaced apart from the inner surface of the side portion (211) of the circular plate (210).

[0080] And the brake (240) can rotate counterclockwise by rotating away from the inner surface of the side (211) of the circular plate (210) and pushing the second rotary arm (224). Accordingly, the length of the strap (120) can be increased as the overlapping length (L) of the pair of straps (120) increases.

[0081] And, when the rotation of the rotary dial (250) stops, the hinge arm (231) rotates in the second direction opposite to the first direction by the elastic force of the elastic hinge (232) as described above, and the angle (θ) of the hinge arm (231) increases, so that it can be restored to its original state. Accordingly, the brake (240) can be brought into close contact with the inner surface of the side (211) of the circular plate (210) to fix the rotary unit (220) again.

[0082] In particular, in a strap length adjustment device (100) according to one embodiment of the present invention, the brake (240) may include a rubber member (243) that generates frictional force with the inner surface of the side (211) of the circular plate (210), thereby stably fixing the rotation unit (220).

[0083] In addition, the strap length adjustment device (100) according to one embodiment of the present invention replaces the gear structure including a conventional gear and a stopper, and can reduce noise generated when adjusting the length of the strap (120) through the length adjustment unit (200) that utilizes the elasticity of the hinge unit (230) and the frictional force of the brake (240) as described above.

[0084] The above detailed description should not be construed as limiting in any respect and should be considered illustrative only. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are intended to be included within the scope of the present invention.

Claims

1. Main body; A pair of straps extending from both sides of the above body and having a rack formed at one end; A fixed pad on the back side with the racks of the pair of straps arranged vertically; and It includes a length adjusting unit that adjusts the overlapping length of the pair of straps by moving the pair of racks horizontally, The above length adjustment part, A circular plate coupled to the back surface of the above fixed pad and including a side extending rearward on the outer surface; A rotating unit positioned between the pair of racks and including a pinion that engages with the pair of racks and a rotating arm extending from the pinion; A hinge unit including a hinge arm that rotates around the rotational axis of the pinion and is connected to an end with an elastic hinge; and A strap length adjusting device coupled to the hinge arm and including a brake for fixing or rotating the rotation unit on the inner surface of the side of the circular plate.

2. In paragraph 1, The above length adjustment part, A strap length adjustment device characterized by including a rotary dial that is rotatably connected to the above circular plate and changes the angle of the hinge arm when rotated.

3. In paragraph 2, The above brakes are, A strap length adjustment device characterized in that it is brought into close contact with the inner surface of the side of the circular plate by the elastic force of the hinge unit or rotates away from the inner surface of the side of the circular plate when the angle of the hinge arm changes.

4. In paragraph 3, The above rotary dial is, Including a first rib in contact with the hinge arm on the front side, The above first rib, A strap length adjustment device characterized in that when the rotary dial is rotated, the hinge arm is rotated in a first direction toward the center of the hinge unit, thereby reducing the angle of the hinge arm.

5. In paragraph 4, The above hinge arm, A strap length adjustment device characterized in that when the rotation of the above rotary dial stops, the device rotates in a second direction opposite to the first direction by the elastic force of the elastic hinge, and returns to its original state as the angle increases.

6. In paragraph 3, The above rotary dial is, It includes a second rib that guides the rotation of the brake at the front, The above brakes are, A strap length adjustment device characterized by including a guide protrusion that comes into contact with the inner surface of the second rib.

7. In paragraph 6, The above second rib, Including a first point and a second point spaced apart from the side of the circular plate from the first point, The above brakes are, When the above guide protrusion is positioned at the first point, it is in close contact with the inner surface of the side of the circular plate, A strap length adjustment device characterized in that the guide protrusion is rotatable and spaced apart from the inner surface of the side of the circular plate when the guide protrusion is positioned at the second point.

8. In paragraph 1, The rotating arm of the above rotating unit is, A first rotary arm having a straight shape extending from the pinion to both sides; and A strap length adjusting device characterized by including a second rotary arm extending from an end of the first rotary arm and provided along the inner surface of the side of the circular plate.

9. In paragraph 1, The above brakes are, A strap length adjustment device characterized by including a coupling projection rotatably coupled to the hinge arm.

10. In paragraph 1, The above brakes are, A strap length adjustment device characterized by including a rubber member that generates frictional force on the inner surface of the side of the circular plate.

11. In paragraph 2, Further comprising a back cover coupled to the fixed pad on the back of the above rotary dial, The above back cover, A strap length adjustment device characterized by including an adjustment groove exposing a portion of the rotary dial on at least one side of the upper or lower surface.

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