Parallel spring tape measure

Abstract

To provide a parallel spring tape measure capable of reducing the size of the tape measure by connecting springs that drive a rotary shaft in parallel to reinforce the rotating force.SOLUTION: A parallel spring tape measure comprise: a housing; a rotary shaft rotatably mounted in the housing; a bobbin that rotates in conjunction with the rotary shaft in the housing; a blade wound around a winding surface of the bobbin and pulled out to the outside or retracted into the inside through an entrance in the housing; a side spring interposed between the housing and the bobbin on one side of the bobbin, one end being fixed to the housing and the other end being fixed to the rotary shaft; and an inner spring interposed between the rotary shaft and the bobbin inside the bobbin, one end being fixed to the housing and the other end being fixed to the rotary shaft.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a miniaturized tape measure, and more particularly to a parallel spring tape measure that can reduce the size of the tape measure by connecting springs that drive rotary shafts in parallel to increase the rotational force. [Background technology]

[0002] A conventional tape measure includes a housing, a bobbin, a blade wound on the outside of the bobbin, and a spring to return the bobbin and blade to their original position. The spring is built into the housing and returns the blade to its original position, and a hook attached to the end of the blade stops the end of the blade at the desired position.

[0003] Since the blade of a tape measure is associated with the maximum measurable length and easy scale reading, it is difficult to reduce its length and width, and therefore, a method of realizing miniaturization through a spring can be considered.

[0004] U.S. Patent No. 11,226,187 proposes removing the spring between the tape reel and the rotating shaft and placing it on both sides. However, moving the spring to both sides can result in the springs on the sides not providing sufficient force. Also, increasing the width of the springs on the sides can re-emerge as a problem that makes it difficult to make the tape measure smaller. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a parallel spring tape measure that can reinforce the force of the spring while arranging the spring of the tape measure to the side.

[0006] The present invention provides a parallel spring tape measure that can strengthen the spring force by connecting two or more springs in parallel to one rotating shaft.

[0007] The present invention provides a compact parallel spring tape measure that efficiently utilizes the space inside the housing.

[0008] The present invention provides a parallel spring tape measure in which two or more springs are connected in parallel to one rotating shaft, and the springs are balanced to prevent the rotating shaft from being overloaded. [Means for solving the problem]

[0009] According to an exemplary embodiment of the present invention, the parallel spring tape measure may include a housing, a rotating shaft rotatably mounted within the housing, a bobbin that rotates within the housing in conjunction with the rotating shaft, a blade that is wound around the winding surface of the bobbin and is pulled out to the outside through an inlet of the housing or retracted inside, a side spring that is interposed between the housing and the bobbin on one side of the bobbin, one end of which is fixed to the housing and the other end of which is fixed to the rotating shaft, and an internal spring that is interposed inside the bobbin between the rotating shaft and the bobbin, one end of which is fixed to the housing and the other end of which is fixed to the rotating shaft.

[0010] The rotating shaft is rotatably mounted within the housing, and at least one side spring and at least one internal spring can be connected in parallel to one rotating shaft. Two types of springs can connect one rotating shaft to the housing, and are appropriately arranged in the side space and the internal space of the bobbin, minimizing the spring space and contributing to the miniaturization of the tape measure.

[0011] In this embodiment, the winding direction of the side spring and the inner spring may be the same, and they can compensate for each other's force by winding and unwinding in the same direction.

[0012] The side springs and the inner spring may be fixed to the housing, which means that the ends of the springs are fixed to the housing, and the housing and the ends of the springs may be directly or indirectly connected to each other.

[0013] To reduce the spring space, a spring with a larger elastic modulus can be used, and by using a stronger spring or combination of springs, the number of spring rotations can be reduced compared to the number of bobbin rotations (i.e., blade length).To this end, a gear train can be included on the other side of the bobbin between the housing and the bobbin to link the rotating shaft and the bobbin, and the ratio of the bobbin rotation to the rotating shaft rotation can be made greater than 1 through the gear train.

[0014] For example, the gear train may include a first gear that directly meshes with the rotary shaft, a second gear that is mounted on the housing and meshes with the first gear, and a third gear that meshes with the second gear and transmits rotation to the bobbin, and the reduction ratio may be determined through the first to third gears. The second gear may be fixed to the housing, and in this case, a gear train different from a planetary gear may be formed.

[0015] The housing may be provided by using a first housing that covers one side of the bobbin and a second housing that covers the other side of the bobbin. The first housing may cover the side on which the side spring is disposed. The main body of the first housing may be formed with a hollow cylinder hub that is inserted into the inner surface of the bobbin, and a housing cover may cover the outside of the first housing main body and cover the part where the internal spring, side spring, and rotating shaft are attached.

[0016] An internal spring is inserted inside the cylinder hub to connect the first housing to the rotary shaft, and a side spring is disposed inside the housing cover to connect the first housing to the rotary shaft.

[0017] The rotating shaft may enter from the outside of the first housing and be positioned at the center of the bobbin through the cylinder hub, the distal end of the rotating shaft may pass through a through-hole formed in the cylinder hub and enter the space between the first housing and the second housing, and the proximal end may be rotatably attached to the housing cover.

[0018] The distal end of the rotating shaft passing through the cylinder hub can be directly connected to the bobbin to transmit the rotation, or can be connected to the bobbin through a gear train.

[0019] The rotating shaft may include a flange that separates the space in the cylinder hub where the internal spring is disposed from the space inside the housing cover where the side spring is disposed, or the spaces for the internal spring and the side spring may be separated from each other.

[0020] The rotation shaft, the inner spring, and the side spring may be provided in one spring module. To this end, the spring housing forming the spring module may include a hollow cylinder portion inserted into the cylinder hub and a hollow disk portion integral with the cylinder portion.

[0021] The rotation shaft, the inner spring, and the side spring can be assembled into a package through the spring module, and can be assembled into the first housing together with one module T from outside the first housing.

[0022] According to another embodiment, the spring module may be assembled to the first housing without a hollow cylinder hub, with the first housing as a part, so that the spring module is inscribed on the bobbin. That is, the rotating shaft, the inner spring, and the side spring are packaged within the spring housing mounted on the first housing, and the spring housing may include a hollow cylinder portion inserted into the inscribed surface of the bobbin, a hollow disk portion integral with the cylinder portion, and a housing cover that covers the outside of the first housing.

[0023] An internal spring is inserted into the cylinder portion to connect the first housing to the rotary shaft, and a side spring is disposed inside the disk portion and the housing cover to connect the first housing to the rotary shaft.

[0024] The spring module can modularize the rotating shaft, inner spring, side spring, and spring housing, and can be removably attached to the first housing. Therefore, when the force of the spring decreases, a new spring module can be installed to maintain the performance of the tape measure for a long time. Of course, it can also be installed permanently without being replaced.

[0025] The spring housing may be formed using a metal sheet material, and may have a T-shaped cross section as a whole due to the hollow cylinder portion and the disk portion. The spring housing includes an inner spring, a rotating shaft, and a side spring, and one end of the spring is fixed to the spring housing, and the spring housing is fixed to the first housing, thereby achieving the effect of fixing the spring to the housing. Structurally, a slit connecting the cylinder portion and the disk portion may be formed in the spring housing, and one end of the internal spring or the side spring may be fastened to the slit.

[0026] When connecting the internal spring and side spring to the rotating shaft, the internal spring and side spring can be connected at 180 degrees apart from each other around the rotating shaft. By pulling the rotating shaft in different directions, they can be balanced. If there are three springs, they can be equally spaced at 120 degrees apart or appropriately distributed according to the force distribution.

[0027] The maximum outer diameter of the side spring is set to approximately 60 to 95% of the maximum outer diameter of the bobbin, thereby enabling the tape measure housing to be made compact, and the ratio of the bobbin's winding head to the outer diameter of the rotating shaft can be maintained at approximately 200 to 600%.

[0028] The bobbin winding mirror must maintain a minimum size to ensure space for the internal spring, but if the winding mirror is too small, it could actually cause damage to the blade. Therefore, it is sometimes desirable to design the bobbin winding mirror so that it maintains approximately 200 to 600% of the rotation axis.

[0029] It is preferable that the thickness (Ts) of the side springs is thicker than the thickness (Ti) of the inner springs, and it may be preferable that the average thickness (Ts) of the side springs is approximately 2 to 4 times the average thickness (Ti) of the inner springs.

[0030] It may be desirable to form the inner spring with a width approximately 2 to 5 times the width of the side spring. [Effects of the Invention]

[0031] The parallel spring tape measure of the present invention has a side spring disposed on the side of the bobbin, while securing a minimum space between the bobbin and the rotating shaft, and an internal spring disposed in that space to increase the pulling force of the spring. In this case, the side spring can be connected to the rotating shaft in parallel with the internal spring, or conversely, it can be connected directly or indirectly to the housing.

[0032] The rotating shaft can be connected to the bobbin either directly or through a gear train. By making the rotation speed of the rotating shaft lower than that of the bobbin, the space occupied by the spring can be kept smaller, and although the springs are connected in parallel, the internal spring can be actively used.

[0033] In particular, the internal spring can connect the rotary shaft and the housing for parallel connection, rather than connecting between the rotary shaft and the bobbin. In this way, the parallel spring tape measure of the present invention can connect two or more springs in parallel to one rotary shaft, thereby strengthening the spring force.

[0034] The parallel spring tape measure of the present invention can be made compact by efficiently utilizing the space inside the housing, and the springs can be arranged in opposite directions or at equal intervals around the rotation axis to balance the forces between the springs. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a diagram illustrating a parallel spring tape measure according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram for explaining the AA cross section of the parallel spring tape measure of FIG. [Figure 3] FIG. 3 is a diagram illustrating the exploded structure of the parallel spring tape measure of FIG. [Figure 4] FIG. 4 is a diagram for explaining the spring module of the parallel spring measuring tape of FIG. [Figure 5] FIG. 5 is a diagram for explaining the spring module of the parallel spring measuring tape of FIG. [Figure 6] FIG. 6 is a diagram for explaining the spring housing of FIG. [Figure 7]FIG. 7 is a diagram illustrating the connection between a rotating shaft and a spring in a parallel spring tape measure according to an embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view of a parallel spring tape measure according to an embodiment of the present invention. [Figure 9] FIG. 9 is a diagram illustrating the exploded structure of the parallel spring tape measure of FIG. [Figure 10] FIG. 10 is a diagram illustrating the exploded structure of the parallel spring tape measure of FIG. [Figure 11] FIG. 11 is a view for explaining the coupling of the first housing and the spring module of FIG. [Figure 12] FIG. 12 is a diagram for explaining the replacement of spring modules of the parallel spring measuring tape of FIG. [Figure 13] FIG. 13 is a diagram for comparing spring modules of a parallel spring tape measure according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to or construed as being limited by the embodiments. In this description, the same numbers refer to substantially the same elements, and under this rule, the contents described in other drawings may be referred to and described, and contents that are deemed obvious to those skilled in the art or that are repeated may be omitted.

[0037] FIG. 1 is a diagram illustrating a parallel spring tape measure according to one embodiment of the present invention, FIG. 2 is a diagram illustrating a cross section AA of the parallel spring tape measure of FIG. 1, FIG. 3 is a diagram illustrating an exploded structure of the parallel spring tape measure of FIG. 1, FIGS. 4 and 5 are diagrams illustrating the spring module of the parallel spring tape measure of FIG. 1, and FIG. 6 is a diagram illustrating the spring housing of FIG. 4.

[0038] 1 to 6, the parallel spring tape measure 100 according to this embodiment may include a housing 105, a rotating shaft 150, a bobbin 140, a blade 130, a side spring 170, an internal spring 175, and a gear train 190. The blade 130 is wound on a winding surface 142 of the bobbin 140 and may be pulled out through an entrance of the housing 105 for length measurement, or may be wound around the outer surface of the bobbin 140 and stored while being pulled in for storage. As in the past, a spring may be used to pull the blade 130 into the housing 105.

[0039] The housing 105 may be provided using a first housing 110 and a second housing 120. The first housing 110 may cover one side of the bobbin 140 and cover the side where the side spring 170 is disposed, and the second housing 120 may cover the other side of the bobbin 140 and cover the side where the gear train 190 is disposed. The first housing 110 and the second housing 120 may be coupled to each other to form a single housing 105.

[0040] The rotating shaft 150 is rotatably mounted at the center of the housing 105 and is connected to the side spring 170 and the internal spring 175 along the axial direction, and the distal end 154 of the rotating shaft 150, which is far from the side spring 170, can be coupled to the bobbin 140 via a gear train 190.

[0041] The side spring 170 may be provided on one side of the bobbin 140 where the first housing 110 is located, and may be interposed between the housing 105 and the bobbin 140. One end of the side spring 170 may be fixed to the first housing 110, and the other end may be fastened to the rotation shaft 150.

[0042] In addition, the internal spring 175 may be located inside the bobbin 140 and interposed between the bobbin 140 and the rotary shaft 150. One end of the internal spring 175 may be fixed to the first housing 110, and the other end may be fastened to the rotary shaft 150.

[0043] In this embodiment, the side spring 170 and the inner spring 175 are located inside the spring housing 180 of the spring module 160 and are fastened to the spring housing 180, which may be fixed to the housing 105. Therefore, the side spring 170 and the inner spring 175 may be indirectly fixed to the first housing 110 through the spring housing 180.

[0044] In this embodiment, one side spring 170 and one internal spring 175 are connected to one rotating shaft 150, but in some cases, multiple identical or similar side springs or internal springs may be provided. In this case, each side spring and internal spring may be connected in parallel to the rotating shaft 150 and the housing 105, and the forces of the springs may be mutually reinforced through the mutual parallel connection.

[0045] The internal spring 175 assists the force, thereby reducing the width of the side spring 170 and efficiently utilizing the otherwise empty internal space of the bobbin 140. The internal spring 175 allows the side space for the side spring 170 and the internal space of the bobbin 140 to be efficiently utilized, contributing to the overall miniaturization of the tape measure.

[0046] In addition, because the blade 130 is wound from the winding surface 142, if the diameter of the winding surface 142 is too small, it may actually damage the blade 130. Therefore, in order to protect the blade 130, it is preferable that the outer diameter of the winding surface 142 is at least twice the outer diameter of the rotating shaft 150. When the outer diameter of the winding surface 142 is formed to be 2 to 6 times the outer diameter of the rotating shaft 150, a space may be generated between the rotating shaft 150 and the bobbin 140, but by disposing the internal spring 175 in this space, the internal spring 175 can assist the force that the side spring 170 would otherwise have to handle.

[0047] In this embodiment, the side spring 170 and the internal spring 175 can be wound in the same direction relative to the rotating shaft 150. In addition, the winding of the rotating shaft 150 is applied to the side spring 170 and the internal spring 175 simultaneously, and when either one is completely unwound or cannot be wound any further, the entire rotating shaft 150 may not move.

[0048] As described above, in this embodiment, the side spring 170 and the inner spring 175 may be indirectly fixed to the first housing 110 through the spring housing 180 of the spring module 160 .

[0049] The spring module 160 is configured by packaging a spring housing 180, a rotating shaft 150 mounted inside the housing cover 116, an internal spring 175, and a side spring 170. The spring housing 180 may be formed of a metal plate, may be formed by a hollow cylinder portion 182 and a hollow disk portion 184, and may have an overall T-shaped cross section.

[0050] The rotation shaft 150 is disposed through the center of the spring housing 180, and the internal spring 175 is accommodated in a hollow cylinder portion 182, with one end fixed to the rotation shaft 150 and the other end fixed to the inner wall of the hollow cylinder portion 182. In addition, the side spring 170 is accommodated in a hollow disk portion 184, with one end fixed to the rotation shaft 150 and the other end fixed to the inner wall of the hollow disk portion 184.

[0051] In this embodiment, a slit 186 passing through the cylinder portion 182 and the disk portion 184 may be formed along the inner wall of the screen housing 105, and the ends of the inner spring 175 and the side spring 170 may be fixed using this slit 186.

[0052] With the springs housed in the screen housing 105, the housing cover 116 may cover the open side of the screen housing 105 to form a spring module 160. In this embodiment, the spring module 160 may be inserted from the outside of the first housing 110 and fixed.

[0053] For this purpose, the first housing 110 may be formed with a hollow cylinder hub 114 protruding from the center into which the main body 112 and the spring module 160 can be inserted, and the inside of the cylinder hub 114 may be in close contact with the cylinder portion 182 of the spring module 160, allowing the internal spring 175 and the rotating shaft 150 to enter the inside of the bobbin 140.

[0054] A through-hole through which the distal end 154 of the rotating shaft 150 can protrude is formed at the end of the cylinder portion 182 of the spring housing 180, and the distal end 154 of the rotating shaft 150 can be exposed through the through-hole. As the spring module 160 is coupled to the first housing 110, the distal end 154 of the rotating shaft 150 can also pass through the hollow cylinder hub 114 and enter the inside of the first housing 110 and the second housing 120.

[0055] The rotating shaft 150 may further include a flange 152 for dividing the cylinder portion 182 and the disk portion 184 of the spring housing 180. The flange 152 may divide the space of the spring housing 180 into two spaces 183 and 185.

[0056] A protrusion 188 may be formed on the outer surface of the spring housing 180, and the spring housing 180 may be coupled to the first housing 110 or the housing cover 116, thereby fixing the spring housing 180 so that it does not rotate relative to the first housing 110. By fixing the spring housing 180 to the first housing 110 in this manner, the side spring 170 and the internal spring 175 may be fixed to the housing 105.

[0057] The distal end 154 of the rotating shaft 150 passes through the cylinder hub 114 of the first housing 110 and may be connected to a gear train 190 provided between the second housing 120 and the bobbin 140. The distal end 154 of the rotating shaft 150 may be formed in a non-circular shape and may be connected to a first gear 192 located at the center of the gear train 190. In the gear train 190, the first gear 192 may be connected to a second gear 194 located at the periphery thereof, and the second gear 194 may be connected to a third gear 196 that interfaces with the bobbin 140. In this embodiment, the third gear 196 is integrally formed on one side of the bobbin 140 and can be coupled to the second gear 194 while the bobbin 140 is attached to the cylinder hub 114 and the second housing 120 is coupled to the first housing 110. In this embodiment, the second gear 194 is fixed to the second housing 120 and can only rotate without changing its position.

[0058] The second housing 120 may include a gear cover 122 for protecting the first gear 192 and the second gear 194, and a hole may be formed in the center of the gear cover 122 through which the third gear 196 of the bobbin 140 and the distal end 154 of the rotating shaft 150 can enter.

[0059] The gear train 190 can be designed so that the rotation speed of the bobbin 140 is greater than the rotation speed of the rotating shaft 150. Even if the rotation speed of the rotating shaft 150 is reduced, a strong parallel spring combination is formed to prevent a weak force, and the spring space can be further reduced compared to conventional methods by using the strong parallel spring combination.

[0060] In this embodiment, the bobbin 140 and the rotary shaft 150 may be directly connected without a spring through the gear train 190. However, in some cases, the bobbin and the rotary shaft may be directly connected one-to-one without any reduction gear, and the structure for connecting the rotary shaft and the bobbin may be various other methods such as a belt instead of a gear.

[0061] The first housing 110 rotatably supports the bobbin 140 using the cylinder hub 114, and the spring module 160 can be inserted and fixed from the outside of the first housing 110. Alternatively, a spring housing 180 can be provided separately, and the internal spring 175 can be fixed to the first housing 110 through the spring housing 180.

[0062] Since the spring module 160 includes the rotating shaft 150, the internal spring 175, and the side spring 170 as a package, if the spring function is reduced or broken, the spring module 160 can be easily separated from the first housing 110 and repaired or replaced.

[0063] FIG. 7 is a view illustrating a rotation axis and a spring connection in a parallel spring tape measure according to an embodiment of the present invention.

[0064] Referring to FIG. 7, the inner spring 175 of the rotating shaft 150 can be fixed to the side where the distal end 154 is located around the flange 152, and the side spring 170 can be fixed to the side where the proximal end is located around the flange 152.

[0065] The average thickness (Ts) of the side spring 170 may be thicker than the average thickness (Ti) of the inner spring 175. The width (Wi) of the inner spring 175 may be 2 to 5 times the width (Ws) of the side spring 170.

[0066] The side spring 170 and the internal spring 175 may be connected to the same side of the center of the rotation shaft 150 (a), or the side spring 170 and the internal spring 175 may be connected to the rotation shaft 150 in opposite directions (b). When there are three side springs or internal springs, they may be appropriately arranged so that the angle is approximately 120 degrees or the force from the springs is evenly distributed.

[0067] In this embodiment, the side spring 170 can generate sufficient force by having a maximum outer diameter (Ds) of approximately 60 to 95% of the maximum outer diameter (Db) of the bobbin 140, and for this purpose, the width (Ws) and thickness (Ts) of the side spring 170 can be appropriately adjusted. Through this process, it is not necessary for the outer diameter of the side spring 170 to be expanded to be equal to the outer diameter of the bobbin, and therefore, a condition can be provided in which the inner spring 175 does not expand the outer diameter of the side spring 170 more than necessary.

[0068] In addition, by making the outer diameter (Ds) of the side spring 170 smaller than the outer diameter (Db) of the bobbin 140, the center of the housing can be made a little thicker than the periphery, allowing the housing to be designed to be easier for the operator to grip with their hands. In this embodiment, the ratio of the diameter (Dw) of the winding surface 142 of the bobbin 140 to the outer diameter (Dx) of the rotating shaft 150 can be maintained at approximately 200 to 600%. This allows a space to be formed between the winding surface 142 and the rotating shaft 150, and the effects of preventing damage to the blade and spring reinforcement through the internal spring 175 can be expected.

[0069] FIG. 8 is a diagram illustrating a cross section of a parallel spring tape measure according to one embodiment of the present invention, FIGS. 9 and 10 are diagrams illustrating the disassembled structure of the parallel spring tape measure of FIG. 8, FIG. 11 is a diagram illustrating the connection of the first housing and spring module of FIG. 9, and FIG. 12 is a diagram illustrating the replacement of the spring module of the parallel spring tape measure of FIG. 8.

[0070] 8 to 12, the parallel spring tape measure 200 according to this embodiment may include housings 210 and 220, a rotating shaft 250, a bobbin 240, a blade 230, a side spring 270, an internal spring 275, and a gear train 290. The blade 230 is wound around a winding surface 242 of the bobbin 240 and can be pulled out or retrieved through an opening in the housing.

[0071] The housing is provided using a first housing 210 and a second housing 220. A spring module 260 can be attached to the first housing 210. With the spring module 260 attached, the rotating shaft 250 is rotatably attached at the center of the housing and is simultaneously connected to a side spring 270 and an internal spring 275 along the axial direction. A distal end 254 of the rotating shaft 250 can be coupled to the bobbin 240 via a gear train 290 so as to be movable with the bobbin 240.

[0072] In this embodiment, the spring module 260 is directly coupled to the first housing 210 without a cylinder hub, and can rotatably support the inscribed surface of the bobbin 240. That is, the spring housing 280 serves as the housing of the spring module 260, and serves as a medium for fixing the inner spring 275 and the side spring 270 to the first housing 210, and can itself serve as a center for rotation of the bobbin 240.

[0073] As shown in FIG. 13, the cylinder portion 282 of the spring module 260 of this embodiment may have a relatively larger diameter than the cylinder portion 182 of the previous embodiment, which may serve to relatively further reinforce the internal spring 275 or, conversely, to reduce the internal spring space and overall tape measure size.

[0074] The internal spring 275 can assist with a larger force, the width of the side spring 270 can be further reduced, and the internal space of the bobbin 240, which may otherwise be empty space, can be more efficiently utilized.

[0075] As shown in FIG. 9, when first assembled, the first housing 210 and the spring housing 280 can be provided in a state of being connected together as a single unit, and the tape measure can be easily assembled by connecting the first housing 210 and the second housing 220 around the bobbin 240 on which the blade 230 is wound.

[0076] Also, if the proximal end of the rotating shaft 250 exposed at the center of the housing cover 216 is tightened with a wrench while assembling the first housing 210 and the second housing 220, the assembly can be performed with the spring tensioned. In some cases, if the spring becomes loose, the housings can be separated and the rotating shaft 250 can be rotated in the tightening direction to reinforce the loosened force.

[0077] The spring module 260 may be provided in a package including a spring housing 280, a rotating shaft 250, an inner spring 275, a side spring 270, and a housing cover 216, and a detailed description thereof may refer to the description of the previous embodiment.

[0078] The rotation shaft 250 is disposed through the center of the spring housing 280, the inner spring 275 is accommodated in a hollow cylinder portion 282, the side spring 270 is accommodated in a hollow disk portion 284, and the outer ends can be bent and fixed through slits 286.

[0079] For this purpose, the first housing 210 has a hole 212 through which the spring module 260 can enter without a cylinder hub, and the inner spring 275 and the rotary shaft 250 can enter the bobbin 240 together with the spring module 260 .

[0080] The distal end of the rotary shaft 250 protrudes from the end of the cylinder portion 282 of the spring housing 280 , and the distal end of the rotary shaft 250 passes through the bobbin 240 and can be combined with the gear train 290 of the second housing 220 .

[0081] A protrusion 288 or a bent portion may be formed on the outer surface of the spring housing 280, and the spring housing 280 may be coupled to the first housing 210 or the housing cover 216. By fixing the spring housing 280 to the first housing 210, the side spring 270 and the internal spring 275 may be fixed to the housing. The distal end 254 of the rotary shaft 250 is connected to a gear train 290 in the second housing 220, and the rotary shaft 250 and the bobbin 240 can be linked together without a spring through a first gear 292, a second gear 294, and a third gear 296.

[0082] The gear train 290 can be designed so that the rotation speed of the bobbin 240 is much higher than the rotation speed of the rotary shaft 250. Even if the rotation speed of the rotary shaft 250 is reduced, a strong parallel spring combination is formed to prevent a weak force, and the spring space can be further reduced compared to conventional methods by using the strong parallel spring combination.

[0083] As mentioned above, the present invention has been described with reference to a preferred embodiment, but it will be understood by those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. [Explanation of symbols]

[0084] 100 Tape Measure 110 First Housing 114 Cylinder hub 116 Housing cover 120 Second Housing 130 blades 140 bobbins 150 rotation axis 160 Spring Module 170 Side spring 175 Internal spring 180 spring housing 190 gear train

Claims

1. Housing and a rotating shaft rotatably mounted within the housing; a bobbin that rotates in conjunction with the rotary shaft within the housing; a blade wound on a winding surface of the bobbin and pulled out to the outside or retrieved into the housing through an inlet of the housing; a side spring, which is interposed between the housing and the bobbin on one side of the bobbin, one end of which is fixed to the housing and the other end of which is fixed to the rotary shaft; an internal spring interposed between the rotary shaft and the bobbin inside the bobbin, one end of which is fixed to the housing and the other end of which is fixed to the rotary shaft; The housing is provided using a first housing covering one side of the bobbin and a second housing covering the other side of the bobbin, the first housing including a hollow cylinder hub inserted into an inner surface of the bobbin, and a housing cover covering the outside of the first housing on which the cylinder hub is formed; The parallel spring tape measure is characterized in that the internal spring is inserted into the cylinder hub to connect the first housing and the rotary shaft, and the side spring is disposed inside the housing cover to connect the first housing and the rotary shaft.

2. 2. The parallel spring tape measure of claim 1, wherein the side spring and the inner spring are wound in the same direction.

3. 2. The parallel spring tape measure according to claim 1, further comprising a gear train interposed between the housing and the bobbin on the other side of the bobbin to link the rotary shaft and the bobbin, wherein a ratio of the rotation of the bobbin to the rotation of the rotary shaft caused by the gear train is greater than 1.

4. 4. The parallel spring tape measure of claim 3, wherein the gear train includes a first gear that directly meshes with the rotary shaft, a second gear that is attached to the housing and meshes with the first gear, and a third gear that meshes with the second gear and transmits rotation to the bobbin, and the second gear is fixed to the housing.

2. The parallel spring tape measure of claim 1.

5. 2. The parallel spring tape measure of claim 1, wherein the rotating shaft is located at the center of the bobbin through the cylinder hub outside the first housing, the distal end of the rotating shaft passes through the cylinder hub and enters the space between the first housing and the second housing, and the proximal end is rotatably fastened to the housing cover.

6. 6. The parallel spring tape measure according to claim 5, wherein the rotation axis includes a flange that divides the space in the cylinder hub where the inner spring is disposed and the space inside the housing cover where the side spring is disposed.

7. a spring housing including a hollow cylinder portion inserted into the cylinder hub and a hollow disk portion integral with the cylinder portion, 6. The parallel spring tape measure of claim 5, wherein the rotating shaft, the inner spring, and the side spring are packaged within the spring housing and assembled together to the first housing outside the first housing.

8. A parallel spring tape measure as described in Claim 7, characterized in that the rotating shaft, the internal spring, the side spring and the spring housing are interchangeably attached to the first housing as a single spring module.

9. A housing, a rotating shaft rotatably mounted within the housing; a bobbin that rotates in conjunction with the rotary shaft within the housing; a blade wound on a winding surface of the bobbin and pulled out to the outside or retrieved into the housing through an inlet of the housing; a side spring, which is interposed between the housing and the bobbin on one side of the bobbin, one end of which is fixed to the housing and the other end of which is fixed to the rotary shaft; an internal spring interposed between the rotary shaft and the bobbin inside the bobbin, one end of which is fixed to the housing and the other end of which is fixed to the rotary shaft; The housing is provided using a first housing covering one side of the bobbin and a second housing covering the other side of the bobbin, The rotation shaft, the inner spring, and the side spring are packaged in a spring housing attached to the first housing, the spring housing includes a hollow cylinder portion inserted into the inner circumferential surface of the bobbin, a hollow disk portion integral with the cylinder portion, and a housing cover covering the outside of the first housing, The parallel spring tape measure is characterized in that the internal spring is inserted into the cylinder portion to connect the first housing and the rotating shaft, and the side spring is disposed inside the disk portion and the housing cover to connect the first housing and the rotating shaft.

10. a distal end of the rotating shaft passes through the cylinder portion and enters the space between the first housing and the second housing, and a proximal end of the rotating shaft is rotatably fastened to the housing cover; 10. The parallel spring tape measure of claim 9, wherein the rotating shaft includes a flange that separates the cylinder portion from the disk portion.

11. 10. The parallel spring tape measure according to claim 9, wherein the rotation shaft, the inner spring, the side spring, and the spring housing are interchangeably mounted in the first housing as one spring module.

12. 12. The parallel spring tape measure according to claim 11, wherein the spring housing includes a slit formed to connect the cylinder portion and the disk portion, and one end of the internal spring or the side spring is fastened to the slit.

13. 2. The parallel spring tape measure according to claim 1, wherein the inner spring and the side spring are fixed in different directions around the rotation axis.

14. 2. The parallel spring tape measure according to claim 1, wherein the maximum outer diameter of the side spring is 60 to 95% of the maximum outer diameter of the bobbin.

15. 2. The parallel spring tape measure according to claim 1, wherein the ratio of the wound head of the bobbin to the outer diameter of the rotary shaft is 200 to 600%.

16. 2. The parallel spring tape measure of claim 1, wherein the thickness (Ts) of the side spring is greater than the thickness (Ti) of the inner spring.

17. The parallel spring tape measure according to claim 1, wherein the thickness (Ts) of the side spring is 2 to 4 times the thickness (Ti) of the inner spring.

18. 2. The parallel spring tape measure of claim 1, wherein the width of the inner spring is 2 to 5 times wider than the width of the side spring.

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