Tension spring

Abstract

To provide a tension spring which can be stabilized in a shape even if the initial tension of the tension spring is raised.SOLUTION: A tension spring comprises a coil-shaped outer coil part 3 having a plurality of winding parts 3a in an axial direction, and an inner coil part 5 having a plurality of winding parts 5a in the axial direction, formed into a coil shape having a diameter smaller than that of the outer coil 3, and arranged in the outer coil 3. By the fitment of the winding parts 5a, 3a corresponding to the other of the outer coil part 3 and the inner coil part 5 into a clearance between the adjacent winding parts 3a, 5a of either of the outer coil 3 and the inner coil 5, a clearance between the adjacent winding parts 3a, 5a of at least either of the outer coil part 3 and the inner coil part 5 is expanded from a free state within a range smaller than a line diameter of the other of the outer coil part 3 and the inner coil part 5, and deformations of the winding part 3a of the outer coil part 3 and the winding part 5a of the inner coil part 5 caused by the initial tension can be suppressed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tension spring used in the arms of lighting equipment, balancers of robot arms, etc. [Background technology]

[0002] An example of this type of tension spring is disclosed in Patent Document 1, which is used in the balancer of a robot arm and applies a tensile force in the opposite direction to the load caused by the weight of the arm, thereby reducing the load on the drive source.

[0003] Tension springs used in such balancers and the like may be required to have a large initial tension (a force that constantly keeps the coil wires in close contact with each other even when there is no load), such as a zero-length spring.

[0004] However, with a typical tension spring, if the initial tension is increased, the coiled portion may be displaced in the radial direction, causing the shape to become unstable. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-13168 A Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved was that if the initial tension was too large, the shape might become unstable. [Means for solving the problem]

[0007] The present invention comprises an outer coil portion which is coiled and has a plurality of windings in the axial direction, and an inner coil portion which is coiled and has a smaller diameter than the outer coil portion and is disposed within the outer coil portion, and by fitting a corresponding winding portion of the other of the outer coil portion and the inner coil portion between adjacent winding portions of one of the outer coil portion and the inner coil portion, at least the space between adjacent winding portions of one of the outer coil portion and the inner coil portion is expanded from a free state within a range smaller than the wire diameter of the other of the outer coil portion and the inner coil portion, generating an initial tension, and suppressing radial displacement of the winding portions of the outer coil portion and the inner coil portion due to the initial tension. At least one of the outer coil portion and the inner coil portion has hooks at both ends in the axial direction. Provide a tension spring. Effect of the Invention

[0008] According to the present invention, the shape of the tension spring can be stabilized even if the initial tension of the tension spring is increased. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing a tension spring according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a cross section of a winding portion of the tension spring of FIG. [Diagram 3] 3A is a schematic cross-sectional view showing a cross section of a winding portion of an outer coil portion of the tension spring of FIG. 2, and FIG. 3B is a schematic cross-sectional view showing a cross section of a winding portion of an inner coil portion of the same. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a cross section of a winding part of a tension spring according to a second embodiment of the present invention. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing a state in which the tension spring of FIG. 4 is rotated by 90 degrees. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a cross section of a winding part of a tension spring according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The objective of making it possible to stabilize the shape even when the initial tension of the tension spring is increased is achieved by using a tension spring consisting of inner and outer coil portions.

[0011] That is, the tension spring (1) includes an outer coil portion (3) and an inner coil portion (5). The outer coil portion (3) is coiled and has a plurality of winding portions (3a) in the axial direction. The inner coil portion (5) is coiled and has a smaller diameter than the outer coil portion (3) and has a plurality of winding portions (5a) in the axial direction, and is disposed within the outer coil portion (3). Between adjacent winding portions (3a, 5a) of one of the outer coil portion (3) and the inner coil portion (5), the corresponding winding portions (5a, 3a) of the other of the outer coil portion (3) and the inner coil portion (5) are fitted.

[0012] As a result, the distance between at least the adjacent winding portions (3a, 5a) of the outer coil portion (3) and the inner coil portion (5) is expanded from the free state within a range smaller than the wire diameter of the other of the outer coil portion (3) and the inner coil portion (5), generating an initial tension and suppressing radial displacement of the winding portion (3a) of the outer coil portion (3) and the winding portion (5a) of the inner coil portion (5) due to the initial tension.

[0013] An adjacent winding portion (3a, 5a) of one of the outer coil portion (3) and the inner coil portion (5) and a corresponding winding portion (5a, 3a) of the other of the outer coil portion (3) and the inner coil portion (5) come into contact with each other by fitting, and the contact position of the winding portions (3a, 5a) may be set by the wire diameter of the winding portion (3a) of the outer coil portion (3) and the winding portion (5a) of the inner coil portion (5) and the coil diameter of the outer coil portion (4) and the inner coil portion (5), depending on the force that radially displaces the winding portion (3a) of the outer coil portion (3) and the winding portion (5a) of the inner coil portion (5) due to the initial tension.

[0014] At least one of the outer coil portion (3) and the inner coil portion (5) may be configured to have hooks (3c, 5c, 7) provided at both axial ends.

[0015] The hooks (3c, 5c) may be integrally provided on both axial ends of the outer coil portion (3) and the inner coil portion (5).

[0016] Alternatively, the hook (7) may be configured to be attached to both axial ends of the outer coil portion (3), each of which includes a base portion (9) positioned at the end opening (3d) of the outer coil portion (3), and a hook portion (11) attached to this base portion (9). EXAMPLES

[0017] FIG. 1 is a cross-sectional view showing a tension spring according to a first embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing a cross-section of a winding portion of the same, FIG. 3(A) is a schematic cross-sectional view showing a cross-section of the winding portion of an outer coil portion of the tension spring in FIG. 2, and FIG. 3(B) is a schematic cross-sectional view showing a cross-section of the winding portion of an inner coil portion of the same.

[0018] The tension spring 1 of this embodiment is used in devices that require initial tension (a force that constantly keeps the coil wires in close contact with each other even when there is no load), such as the arms of lighting equipment and the balancers of robot arms.

[0019] The tension spring 1 is composed of an outer coil portion 3 and an inner coil portion 5.

[0020] The outer coil portion 3 and the inner coil portion 5 are each made of a coil spring, and are coiled with multiple windings 3a, 5a in the axial direction. In this embodiment, the outer coil portion 3 has axial gaps 3b between adjacent windings 3a in a free state, and the inner coil portion 5 is made of a tightly packed spring in which adjacent windings 5a are in close contact with each other in the axial direction in a free state.

[0021] The axial direction refers to the direction along the axis of the tension spring 1, and the radial direction refers to the direction along the diameter of the coil of the tension spring 1 (the same applies below). However, the axial direction and radial direction do not need to be interpreted strictly, and the axial direction includes a direction slightly inclined with respect to the axis of the tension spring 1, and the radial direction includes a direction slightly inclined with respect to the diameter of the coil.

[0022] The axial dimension (pitch) of the gap 3a of the outer coil portion 3 is constant. However, the pitch may be varied. The inner coil portion 5, which is a contact spring, may have an initial tension in a free state, depending on the characteristics required of the tension spring 1. The inner coil portion 5 of this embodiment does not have an initial tension in a free state.

[0023] The materials of the outer coil portion 3 and the inner coil portion 5 can be any appropriate material such as metal, resin, etc. The cross-sectional shapes of the wires (winding portions 3a, 5a) of the outer coil portion 3 and the inner coil portion 5 are circular and have the same wire diameter.

[0024] However, this cross-sectional shape is not limited to a circle, and may be a semicircle, an ellipse, etc. Furthermore, the cross-sectional shapes, wire diameters, materials, etc. of the outer coil portion 3 and the inner coil portion 5 may be different from each other.

[0025] The inner coil section 5 has a coil shape with a smaller diameter than the outer coil section 3, and is disposed within the outer coil section 3. Here, small diameter means that the coil diameter of the inner coil section 5 is smaller than the coil diameter of the outer coil section 3.

[0026] The coil diameter of the inner coil portion 5 and the outer coil portion 3 may be any one of the outer diameter, inner diameter, and center diameter. In this embodiment, the coil diameter of the inner coil portion 5 and the outer coil portion 3 is constant from one end to the other end in the axial direction, but may vary in the axial direction.

[0027] The outer coil section 3 and the inner coil section 5 have adjacent winding portions 3a, 5a between which corresponding winding portions 5a, 3a of the other are fitted. That is, the corresponding winding portions 5a of the inner coil section 5 are fitted from the inside between the adjacent winding portions 3a of the outer coil section 3, and the corresponding winding portions 3a of the outer coil section 3 are fitted from the outside between the adjacent winding portions 5a of the inner coil section 5.

[0028] This fitting causes the winding portion 3a of the outer coil portion 3 to come into contact with the adjacent winding portion 5a of the inner coil portion 5, and spreads the space between the adjacent winding portions 5a in the axial direction according to the difference in the coil diameters. This creates a gap 5b between the adjacent winding portions 5a of the inner coil portion 5 that is smaller than the wire diameter of the outer coil portion 3, and generates an initial tension in the tension spring 1 due to the elasticity of the inner coil portion 5.

[0029] That is, the tension spring 1 is configured such that the space between the windings 5a of the inner coil portion 5 is expanded from a free state within a range smaller than the wire diameter of the outer coil portion 3, generating an initial tension. The amount of expansion between the windings 5a can be set by the difference in the coil diameters of the outer coil portion 3 and the inner coil portion 5, and the difference in wire diameters of the outer coil portion 3 and the inner coil portion 5. In this embodiment, since the wire diameters of the outer coil portion 3 and the inner coil portion 5 are the same, the amount of expansion between the windings 5a is set by the difference in the coil diameters of the outer coil portion 3 and the inner coil portion 5.

[0030] The initial tension can be set by any one, more than one, or all of the following: the amount of expansion, the pitch of the outer coil in a free state, and the materials of the inner coil portion 5 and the outer coil portion 3. To generate the initial tension, it is sufficient that the gaps 3b, 5b of at least one of the inner coil portion 5 and the outer coil portion 3 are expanded from their free states. To this extent, the inner coil portion 5 does not have to be a contact spring, and may have gaps between the windings 5a in a free state.

[0031] The outer coil portion 3 may be configured to have a tight spring or a small gap 3b so that the windings 3a can be expanded from the free state. In this case, the inner coil portion 5 may be configured not only so that the windings 5a can be expanded from the free state, but also so that they do not expand from the free state by setting the pitch, etc.

[0032] The contact between the adjacent windings 3a, 5a of the outer coil section 3 and the inner coil section 5 and the corresponding windings 5a, 3a of the other coil section 5 is made in the range where the windings 3a, 5a partially overlap in the radial direction. This contact allows the windings 3a of the outer coil section 3 and the windings 5a of the inner coil section 5 to mutually suppress radial displacement caused by initial tension.

[0033] Therefore, even if the initial tension of the tension spring 1 is large, radial displacement of the windings 3a and 5a of the outer coil portion 3 and the inner coil portion 5 due to the large initial tension is suppressed, and the shape is stable. Note that radial displacement refers to displacement of the coil centers of the windings 3a and 5a of the outer coil portion 3 and the inner coil portion 5 from the axes of the outer coil portion 3 and the inner coil portion 5 beyond an allowable range such as a tolerance.

[0034] The contact positions between adjacent winding portions 3a, 5a of the outer coil portion 3 and the inner coil portion 5 and the corresponding winding portions 5a, 3a of the other coil portion 5 are on an imaginary line S connecting the cross-sectional center of the winding portion 3a and the cross-sectional center of the winding portion 5a.

[0035] This contact position is set according to the wire diameters of the winding portion 3a of the outer coil portion 3 and the winding portion 5a of the inner coil portion 5 and the coil diameters of the outer coil portion 3 and the inner coil portion 4, in accordance with the force (hereinafter referred to as the "displacement force") that radially displaces the winding portion 3a of the outer coil portion 3 and the winding portion 5a of the inner coil portion 5 due to the initial tension. By setting this contact position, radial displacement of the winding portions 3a and 5a can be reliably suppressed, and the shape of the tension spring 1 can be stabilized.

[0036] This makes it easy to adjust the contact position of the windings 3a and 5a, which affects the stabilization of the shape, and to adjust the initial tension based on the amount of spread between the adjacent windings 5a. The contact position is set according to the displacement force as described above, and in this case, the angle θ between the imaginary lines S is set to be close to 60°. This is because when the angle θ is around 60°, the shape of the tension spring 1 tends to be stabilized. EXAMPLES

[0037] Fig. 4 is a schematic cross-sectional view showing a cross section of a wound portion of a tension spring according to Example 2 of the present invention. Fig. 5 is a schematic cross-sectional view showing a state in which the tension spring of Fig. 4 is rotated 90 degrees. Note that Figs. 4 and 5 show cross sections of the wound portion excluding the hook. In addition, since Example 2 has a basic configuration in common with Example 1, the same reference numerals are used for configurations corresponding to those of Example 1, and duplicated explanations will be omitted.

[0038] In the second embodiment, integral hooks 3c, 5c are provided on both axial ends of the outer coil section 3 and the inner coil section 5. It is sufficient to provide a hook on at least one of the outer coil section 3 and the inner coil section 5, and it is also possible to omit one of the hooks 3c, 5c. The rest is the same as the first embodiment.

[0039] The hooks 3c, 5c are formed by bending both ends of the outer coil portion 3 and the inner coil portion 5. As a result, the hooks 3c, 5c are formed as one-piece parts that are continuous with the winding portions 3a, 5a located at the ends without any breaks. The hooks 3c, 5c may be attached to the winding portions 3a, 5a at the ends by welding or the like. The shape of the hooks 3c, 5c is a round hook in this embodiment, but may be any shape appropriate for the purpose, etc.

[0040] The tension spring 1 having such a configuration can be attached to other members by the hooks 3c, 5c of the outer coil portion 3 and the inner coil portion 5. Furthermore, by providing hooks 3c, 5c on both the outer coil portion 3 and the inner coil portion 5, both the outer coil portion 3 and the inner coil portion 5 are tensioned. Therefore, the tension spring 1 is well-balanced and has a stable shape even when tensioned. Additionally, the second embodiment can achieve the same effects as the first embodiment. EXAMPLES

[0041] 6 is a schematic cross-sectional view showing a wound portion of a tension spring according to Example 3 of the present invention. Since Example 3 has a basic configuration in common with Example 1, the same reference numerals are used for configurations corresponding to those in Example 1, and duplicated explanations will be omitted.

[0042] In the third embodiment, separate hooks 7 are attached to both axial ends of the outer coil portion 3. The rest is the same as the first embodiment.

[0043] Each hook 7 includes a base portion 9 located at an end opening 3d of the outer coil portion 3, and a hook portion 11 attached to the base portion 9.

[0044] The base portion 9 is formed in a plate shape and abuts against the end of the outer coil portion 3. As a result, the base portion 9 is positioned at the end opening 3d of the outer coil portion 3 and closes the end opening 3d. The base portion 9 may be strip-shaped or rod-shaped, which does not close the end opening 3d but leaves part of the end opening 3d open. A side wall portion 9a is provided on the outer periphery of the base portion 9.

[0045] The base portion 9 is fixed to the outer coil portion 3 with the side wall portion 9a engaged with the outer periphery of the end of the outer coil portion 3. The base portion 9 can also be fixed to the inner coil portion 5 in addition to the outer coil portion 3. Any suitable fixing method such as welding, bonding, fastening, etc. can be used. In the case of fastening, in addition to pins and screws, a female threaded portion can be provided on the outside of the side wall portion 9a and screwed into the inner periphery of the inner coil portion 5, or a female threaded portion can be provided on the inside of the side wall portion 9a and screwed into the outer periphery of the outer coil portion 3.

[0046] The hook portion 11 is connected to the base portion 9 at the center of the coil shape of the tension spring 1. The shape of the hook portion 11 is annular in this embodiment, but may be any appropriate shape depending on the application, etc.

[0047] In the tension spring 1 having such a configuration, even if the hook 7 is attached only to the outer coil portion 3, the end opening 3d is closed by the hook 7, so that it is possible to prevent the inner coil portion 5 from coming loose in the axial direction. As a result, the shape of the tension spring 1 is stable when tensioned. In addition, the third embodiment can achieve the same effects as the second embodiment. [Explanation of symbols]

[0048] 1. Tension spring 3. Outer coil section 3a winding part 3b Gap 3c, 5c, 7 hooks 5 Inner coil section 5a winding part 5b Gap

Claims

1. An outer coil portion having a coil shape with a plurality of windings in an axial direction; an inner coil portion having a plurality of windings in the axial direction, a coil shape having a smaller diameter than the outer coil portion, and disposed within the outer coil portion; By fitting one of the adjacent winding portions of the outer coil portion and the inner coil portion between the corresponding winding portion of the other of the outer coil portion and the inner coil portion, at least the space between the adjacent winding portions of the outer coil portion and the inner coil portion is expanded from a free state within a range smaller than the wire diameter of the other of the outer coil portion and the inner coil portion, generating an initial tension, and suppressing radial displacement of the winding portion of the outer coil portion and the winding portion of the inner coil portion due to the initial tension, At least one of the outer coil portion and the inner coil portion is provided with hooks at both ends in the axial direction. Tension spring.

2. 2. The tension spring of claim 1, An adjacent winding portion of one of the outer coil portion and the inner coil portion and a corresponding winding portion of the other of the outer coil portion and the inner coil portion come into contact with each other by the engagement, and the contact position of the winding portions is set by the wire diameters of the winding portions of the outer coil portion and the inner coil portion and the coil diameters of the outer coil portion and the inner coil portion in response to a force that displaces the winding portions of the outer coil portion and the inner coil portion in the radial direction due to the initial tension. Tension spring.

3. The tension spring according to claim 1 or 2, The hooks are integrally provided at both ends in the axial direction of both the outer coil portion and the inner coil portion, Tension spring.

4. The tension spring according to claim 1 or 2, The hook is attached to both ends of the outer coil part in the axial direction, and includes a base part located at an end opening of the outer coil part, and a hook part attached to the base part. Tension spring.

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