Tension balancer

Abstract

This tension balancer comprises: first to n-th cylindrical members; first to (n–1)-th coil springs; a rear hook attached to the first cylindrical member; a front hook attached to the n-th cylindrical member; a first to (n–1)-th front spring washers; first to (n–1)-th rear spring washers; and a stopper fixed to the first cylindrical member. The first cylindrical member contains aluminum as a main component. The second to n-th cylindrical members contain iron as a main component. Details of these configurations are described in the specification.

Description

Tension balancer

[0001] SUMMARY OF THE INVENTION An embodiment of the present invention relates to a tension balancer that can be used on overhead lines.

[0002] Tension balancers are attached to overhead wires such as those used in railways. For example, Patent Documents 1 and 2 disclose a spring-type tension balancer whose basic configuration consists of multiple cylindrical members arranged coaxially and coil springs arranged between the cylindrical members. One end of the spring-type tension balancer is fixed to a support, and the other end is connected to the overhead wire. The coil spring is built into the tension balancer in a compressed state, and the overhead wire can be pulled with the appropriate tension by utilizing the elastic force of the spring as it tries to return to its original length, allowing the overhead wire to always be positioned in a nearly horizontal direction even if expansion and contraction occur due to temperature changes.

[0003] JP 2023-117748 A JP 2021-133822 A

[0004] One of the objectives of the embodiments of the present invention is to provide a tension balancer with a novel structure, or to provide a spring-type tension balancer that is lightweight and does not impose a large load on the support posts that secure the tension balancer.

[0005] One embodiment of the present invention is a tension balancer. The tension balancer includes first to n-th cylindrical members, first to (n-1)-th coil springs, a rear hook attached to the first cylindrical member, a front hook attached to the n-th cylindrical member, first to (n-1)-th front spring washers and first to (n-1)-th rear spring washers, and a stopper fixed to the first cylindrical member. The first to n-th cylindrical members are arranged such that an (m+1)-th cylindrical member selected from the first to n-th cylindrical members is located within an m-th cylindrical member selected from the first to n-th cylindrical members. The first to (n-1)-th coil springs are arranged such that the m-th coil spring selected from the first to (n-1)-th coil springs is sandwiched between the m-th cylindrical member and the (m+1)-th cylindrical member. The first to (n-1)th front spring washers and the first to (n-1)th rear spring washers are arranged such that an mth front spring washer selected from the first to (n-1)th front spring washers and an mth rear spring washer selected from the first to (n-1)th rear spring washers surround the (m+1)th cylindrical member and sandwich the mth coil spring in a direction parallel to the coil axis of the mth coil spring. The stopper is arranged such that the first front spring washer is sandwiched between the first coil spring and the stopper in the above direction. The first cylindrical member contains aluminum as a main component. The second to nth cylindrical members contain iron as a main component. n is a natural number selected from 2 to 5, and m is a variable selected from natural numbers 1 to (n-1).

[0006] 1 is a schematic perspective view of a tension balancer according to an embodiment of the present invention. 2 is a schematic end view of a tension balancer according to an embodiment of the present invention. 3 is a schematic perspective view of a portion of a tension balancer according to an embodiment of the present invention. 4 is a schematic perspective view of a portion of a tension balancer according to an embodiment of the present invention. 5 is a schematic end view of a portion of a tension balancer according to an embodiment of the present invention. 6 is a schematic front view of a portion of a tension balancer according to an embodiment of the present invention. 7 is a schematic end view of a portion of a tension balancer according to an embodiment of the present invention. 8 is a schematic end view of a tension balancer according to an embodiment of the present invention. 9 is a schematic perspective view of a portion of a tension balancer according to an embodiment of the present invention. 10 is a schematic front view of a portion of a tension balancer according to an embodiment of the present invention. 11 is a schematic perspective view of a portion of a tension balancer according to an embodiment of the present invention. 12 is a schematic end view of a tension balancer according to an embodiment of the present invention. 13 is a schematic end view of a tension balancer according to an embodiment of the present invention. 14 is a schematic side view of a portion of a tension balancer according to an embodiment of the present invention.

[0007] Hereinafter, each embodiment of the invention disclosed in this application will be described with reference to the drawings. However, the present invention can be embodied in various forms without departing from the spirit of the invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0008] In order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements having the same functions as those explained in the previous drawings may be assigned the same reference numerals, and duplicate explanations may be omitted.

[0009] In this specification and claims, the expression "a structure exposed from another structure" means a state in which a part of a structure is not covered by another structure, and includes a state in which the part not covered by another structure is covered by yet another structure. The state expressed by this expression also includes a state in which a structure is not in contact with another structure.

[0010] The following describes a tension balancer 100 according to an embodiment of the present invention. The tension balancer 100 can be used to tension an overhead wire with an appropriate tension.

[0011] 1. Overall Structure FIG. 1 shows a schematic perspective view of a tension balancer 100. The tension balancer 100 comprises multiple cylindrical members arranged coaxially and with different outer diameters. The tension balancer 100 shown in FIG. 1 is a two-stage tension balancer comprising a first cylindrical member 120, a second cylindrical member 130, and a third cylindrical member 140. While the tension balancer 100 shown in FIG. 1 has three cylindrical members, there is no restriction on the number of cylindrical members, and the number may be, for example, between two and five, or even five or more. In the tension balancer 100, a cylindrical member with a smaller outer diameter is partially inserted into a cylindrical member with a larger outer diameter. Generally, the tension balancer 100 comprises first through nth cylindrical members (n is a natural number greater than or equal to two), with the outer diameters of the cylindrical members decreasing in order from the first cylindrical member to the nth cylindrical member. The (m+1)th (m is a variable selected from natural numbers greater than or equal to 1 and less than or equal to (n-1)) cylindrical member is arranged so as to be surrounded by the mth cylindrical member, and the (m+1)th cylindrical member reversibly slides inside the mth cylindrical member in the direction of the central axis of each cylindrical member. Below, the explanation will continue using a two-stage tension balancer 100 (i.e., a tension balancer where n is 3).

[0012] A pole-side mounting member (hereinafter referred to as the rear hook) 110 is attached directly or indirectly to one end of the first cylindrical member 120, which has the largest outer diameter. This rear hook 110 can be used to connect the tension balancer 100 to a structure such as a pole. As an optional configuration, a clamp (not shown) for suspending the tension balancer 100 may be provided. Meanwhile, an overhead-line-side mounting member (hereinafter referred to as the front hook) 150, which is connected to the overhead line, is attached directly or indirectly to one end of the cylindrical member (here, the third cylindrical member 140) having the smallest outer diameter. As described below, coil springs are arranged in a compressed state between adjacent cylindrical members, and multiple cylindrical members and multiple coil springs alternate with each other. The elastic force of the coil springs as they expand generates a force that causes the outer cylindrical member to pull the adjacent inner cylindrical member inward. This force allows the overhead line to be tensioned with the appropriate tension.

[0013] Hereinafter, the lengthwise direction of the tension balancer 100 is defined as the x-direction, and the vertical direction when the tension balancer 100 is installed so that the x-direction is horizontal is defined as the z-direction. The direction perpendicular to the x-direction and z-direction is defined as the y-direction. The x-direction is parallel to the central axes of the tension balancer 100 and each cylindrical member, and is the direction in which the second to nth cylindrical members slide. Furthermore, the sides on which the front hook 150 and the rear hook 110 are provided are defined as the front and rear of the tension balancer 100, respectively.

[0014] 2. Cylindrical Member FIG. 2 shows a schematic diagram of an end surface along a chain line A-A' extending in the x-direction in FIG. 1. As shown in FIG. 2, a second cylindrical member 130 and a third cylindrical member 140 are arranged in order of decreasing inner diameter within a first cylindrical member 120, and coil springs (first coil spring 128 and second coil spring 138) are arranged between adjacent cylindrical members. A first back plate 104 forming the bottom surface of the first cylindrical member 120 may be provided at one rear end of the first cylindrical member 120. The rear hook 110 may be attached to the first back plate 104 by welding or bolting, or may be fixed to the first cylindrical member 120 without the first back plate 104. Although not shown, the first cylindrical member 120 may have an opening for discharging water that has entered the interior. A fall-off prevention mechanism is further provided at one rear end of the first cylindrical member 120, which cooperates with the first back plate 104 to prevent the second cylindrical member 130 and the third cylindrical member 140 from falling off. There are no limitations on the structure of the fall-off prevention mechanism, and in the example shown in FIGS. 1 and 2, a U-shaped bar 106 is provided as the fall-off prevention mechanism. A pair of legs of the U-shaped bar 106 extending in a direction perpendicular to the z-direction penetrate the first cylindrical member 120, and a collar 108 provided at the end of the legs prevents the U-shaped bar 106 from falling off. A first coil spring 128 provided between the first cylindrical member 120 and the second cylindrical member 130, and a second coil spring 138 provided between the second cylindrical member 130 and the third cylindrical member 140 are both arranged in a compressed state. Therefore, the elastic force of the first coil spring 128 and the second coil spring 138 returning to their original lengths causes the second cylindrical member 130 and the third cylindrical member 140 to push the first back plate 104 rearward. However, this movement is restricted by the U-shaped bar 106 and the first back plate 104, preventing the second cylindrical member 130 and the third cylindrical member 140 from falling off.

[0015] The first cylindrical member 120 contains aluminum as a main component. That is, the first cylindrical member 120 is made of aluminum or an aluminum alloy. More specifically, the first cylindrical member 120 contains 90% to 100% aluminum. The first cylindrical member 120 may contain elements other than aluminum, such as zinc, magnesium, copper, manganese, and silicon. For example, the first cylindrical member 120 may contain aluminum with a purity of 99% or more, which can be said to be substantially pure aluminum, or may contain an alloy containing aluminum, zinc, magnesium, and copper, such as designated as A7072, A7050, A7075, A7N01, an aluminum-magnesium alloy containing silicon, such as designated as A6061, A6063, A6N01, an aluminum-magnesium alloy, such as designated as A5052, A5056, A5083, A5454, an aluminum-magnesium alloy, such as designated as A4032 or A4043, or an aluminum-manganese alloy, such as designated as A3003, A3005, A3105, etc.

[0016] On the other hand, both the second cylindrical member 130 and the third cylindrical member 140 contain iron as a primary component. More specifically, both the second cylindrical member 130 and the third cylindrical member 140 are made of iron, stainless steel, or invar. If made of iron, the second cylindrical member 130 and the third cylindrical member 140 may contain 98% to 100% iron and 0.1% to 1% carbon as an impurity. Typically, SS400 iron is used. If made of stainless steel, nickel, molybdenum, carbon, and the like may be further contained in addition to iron. For example, austenitic stainless steel, austenitic-ferritic stainless steel, ferritic stainless steel, or martensitic stainless steel may be used. If made of invar, manganese and carbon may be contained in addition to iron. Furthermore, the surfaces of the second cylindrical member 130 and the third cylindrical member 140 may be coated with a metal coating, such as zinc or aluminum.

[0017] 3. Front Spring Washer, Rear Spring Washer, and Coil Spring At the front of the tension balancer 100, i.e., on the front hook 150 side, there is provided a ring-shaped first front spring washer 122 that is sandwiched between the first cylindrical member 120 and the second cylindrical member 130 and surrounds the second cylindrical member 130. The first front spring washer 122 closes a portion of the first cylindrical member 120, and its opening functions as an opening that allows the second cylindrical member 130 to slide inside the first cylindrical member 120 and become partially exposed from the first cylindrical member 120.

[0018] Like the first cylindrical member 120, the first front spring washer 122 may also contain aluminum as a primary component, or may contain iron as a primary component. The first front spring washer 122 is not fixed to the first cylindrical member 120 or the second cylindrical member 130. More specifically, the first front spring washer 122 is not fixed to the first cylindrical member 120 or the second cylindrical member 130 by welding, diffusion bonding, or using fasteners such as screws or bolts. Therefore, in the absence of the elastic force of the first coil spring 128, the first front spring washer 122 can move in the space between the first cylindrical member 120 and the second cylindrical member 130. For this reason, a stopper is provided to prevent the first front spring washer 122 from moving forward and falling off. The stopper is disposed so that the first front spring washer 122 is sandwiched between the stopper and the first coil spring 128 in a direction parallel to the coil axis of the first coil spring 128. There are no restrictions on the configuration of the stopper, but as shown in, for example, Figure 2 and Figure 3, which is a schematic perspective view of the tension balancer 100 as seen from the front, the stopper may include a plurality of bolts 124. In this case, the bolts 124 pass through through holes provided in the first cylindrical member 120, and their heads function as stoppers.

[0019] There are no restrictions on the number of bolts 124, but it is preferably 3 to 8, for example, 6. As will be described later, the first front spring washer 122 is pushed forward by the elastic force of the compressed first coil spring 128, and it is preferable that the first front spring washer 122 be able to evenly resist this elastic force. Therefore, it is preferable to arrange the multiple bolts 124 symmetrically. More specifically, if the number of bolts 124 is k (k is a natural number, for example, 3 to 8), it is preferable that the k bolts 124 are located on a plane perpendicular to the coil axis of the first coil spring 128 and are arranged at the vertices of an imaginary regular k-gon on this plane.

[0020] As can be seen from FIGS. 2 and 3 , when the stopper includes a bolt 124, the head of the bolt 124 is located inside the first cylindrical member 120, and the bolt 124 is fixed to the first cylindrical member 120 by a nut 126. As shown in FIG. 4 , the shape of the head of the bolt 124 (the shape of a surface perpendicular to the axial direction of the bolt 124) is, for example, a polygon (or a polygon with rounded corners; the same applies below), and it is preferable that the straight portion 124 a is arranged so as to be parallel to the main surface of the first front spring washer 122. This arrangement can prevent damage to the first front spring washer 122 due to contact with the head of the bolt 124. The shape of the head is not limited to a regular polygon, and may have straight portions 124 a and 124 b of different lengths, as shown in FIG. 5 . In this case, either the straight portion 124 a or 124 b , preferably the longer straight portion 124 a , is arranged so as to be parallel to the main surface of the first front spring washer 122 .

[0021] Meanwhile, a ring-shaped first rear spring washer 134 is provided at one rear end of the tension balancer 100, sandwiched between the first cylindrical member 120 and the second cylindrical member 130 and surrounding the second cylindrical member 130. The first rear spring washer 134 is fixed to the second cylindrical member 130. The first rear spring washer 134 contains iron as its main component. The first rear spring washer 134 may have the same or substantially the same composition as the second cylindrical member 130. This allows the first rear spring washer 134 to be firmly and easily fixed to the second cylindrical member 130 by welding. However, the first rear spring washer 134 is not fixed to the first cylindrical member 120, but slides relative to the first cylindrical member 120 together with the second cylindrical member 130. 2, the first rear spring washer 134 is provided on the outer circumferential surface (the surface facing the first cylindrical member 120) of the second cylindrical member 130 so as to surround the second cylindrical member 130. However, as shown in FIG. 6, the first rear spring washer 134 does not have to surround the second cylindrical member 130. In this case, the first rear spring washer 134 has an inner diameter equal to or smaller than the inner diameter of the second cylindrical member 130 and an outer diameter larger than the outer diameter of the second cylindrical member 130, and is provided at the end of the second cylindrical member 130. Furthermore, the first rear spring washer 134 may be integrated with the second cylindrical member 130.

[0022] The first coil spring 128 surrounds the second cylindrical member 130 and is disposed between the first front spring washer 122 and the first rear spring washer 134 in the space between the first cylindrical member 120 and the second cylindrical member 130. Therefore, the compressed first coil spring 128 pushes the first front spring washer 122 and the first rear spring washer 134 in opposite directions due to the elastic force of the first coil spring 128 as it tries to expand. The position of the first front spring washer 122 relative to the first cylindrical member 120 is fixed by a stopper, and the first rear spring washer 134 is fixed to the second cylindrical member 130. As a result, the elastic force of the first coil spring 128 generates a force that draws the second cylindrical member 130 into the first cylindrical member 120. This allows tension to be applied to the overhead wire connected to the front hook 150. The first coil spring 128 also contains iron as a main component, and may contain carbon, nickel, cobalt, or the like as secondary components.

[0023] Similar to the first front spring washer 122, a ring-shaped second front spring washer 132 is provided between the second cylindrical member 130 and the third cylindrical member 140. The second front spring washer 132 is surrounded by the second cylindrical member 130 and covers a portion of the second cylindrical member 130. Therefore, the opening of the second front spring washer 132 serves as an opening through which the third cylindrical member 140 slides within the second cylindrical member 130, with a portion of the third cylindrical member 140 exposed from the second cylindrical member 130. However, unlike the first front spring washer 122, the second front spring washer 132 is fixed to the second cylindrical member 130. The second front spring washer 132 may contain iron as its main component and have the same or substantially the same composition as the second cylindrical member 130. Therefore, the second front spring washer 132 can be firmly and easily fixed to the second cylindrical member 130 by welding. In the example shown in Fig. 2, the second front spring washer 132 is fixed to the inner circumferential surface of the second cylindrical member 130 (the surface on the side of the third cylindrical member 140). However, as shown in Fig. 6, the second front spring washer 132 having an outer diameter equal to or smaller than the outer diameter of the second cylindrical member 130 and an inner diameter smaller than the inner diameter of the second cylindrical member 130 may be provided at the end of the second cylindrical member 130. Furthermore, the second front spring washer 132 may be integrated with the second cylindrical member 130.

[0024] Similar to the first rear spring washer 134, a ring-shaped second rear spring washer 144 is provided at the rear of the tension balancer 100. The second rear spring washer 144 is sandwiched between the second cylindrical member 130 and the third cylindrical member 140 and surrounds the third cylindrical member 140. The second rear spring washer 144 is fixed to the third cylindrical member 140. The second rear spring washer 144 may also contain iron as its main component and have the same or substantially the same composition as the third cylindrical member 140. This allows the second rear spring washer 144 to be firmly and easily fixed to the third cylindrical member 140 by welding. However, the second rear spring washer 144 is not fixed to the second cylindrical member 130, but slides relative to the second cylindrical member 130 together with the third cylindrical member 140. Like the first rear spring washer 134, the second rear spring washer 144 does not have to surround the third cylindrical member 140. In this case, the second rear spring washer 144 may be provided at the end of the third cylindrical member 140, and have an inner diameter equal to or smaller than the inner diameter of the third cylindrical member 140 and an outer diameter larger than the outer diameter of the third cylindrical member 140 (FIG. 6). The second rear spring washer 144 may also be integrated with the third cylindrical member 140.

[0025] Like the first coil spring 128, the second coil spring 138 also surrounds the third cylindrical member 140 and is disposed between the second front spring washer 132 and the second rear spring washer 144 in the space between the second cylindrical member 130 and the third cylindrical member 140. Therefore, the elastic force of the compressed second coil spring 138 as it tries to expand pushes the second front spring washer 132 and the second rear spring washer 144 in opposite directions. Because the second front spring washer 132 and the second rear spring washer 144 are fixed to the second cylindrical member 130 and the third cylindrical member 140, respectively, the elastic force of the second coil spring 138 generates a force that draws the third cylindrical member 140 into the second cylindrical member 130. This allows tension to be applied to the overhead wire connected to the front hook 150.

[0026] When the second cylindrical member 130 and the third cylindrical member 140 slide relative to the first cylindrical member 120, the first coil spring 128 and the second coil spring 138 expand and contract. At this time, the first coil spring 128 and the second coil spring 138 rotate about the x-direction, which may result in the second cylindrical member 130 and the third cylindrical member 140 also rotating. For this reason, as an optional configuration, a second back plate 154 with a slit may be provided on the rear side of the tension balancer 100 so as to cover a portion of the third cylindrical member 140, and a plate-shaped guide plate 152 may further be disposed so as to penetrate the slit in the second back plate 154. In this case, the guide plate 152 may function as the rear hook 110, or the rear hook 110 may be fixed to the end of the guide plate 152. By providing a second back plate 154 having a slit and a plate-shaped guide plate 152 that passes through this slit, rotation of the third cylindrical member 140, which is located innermost, is prevented, and therefore rotation of the cylindrical member (here, the second cylindrical member 130) located between the first cylindrical member 120 and the cylindrical member with the smallest diameter (here, the third cylindrical member 140) can also be restricted.

[0027] As described above, the tension balancer 100 has multiple cylindrical members and can tension the overhead wire using multiple built-in coil springs. Furthermore, unlike the other cylindrical members (in the above example, the second cylindrical member 130 and the third cylindrical member 140), the outermost cylindrical member of the tension balancer 100, i.e., the first cylindrical member 120, contains aluminum as its primary component. This allows for a lighter weight tension balancer 100. In fact, the inventors have confirmed that the weight of the two-stage tension balancer 100 can be reduced by 10% or 15% or more compared to a tension balancer having an iron first cylindrical member. Therefore, by applying the embodiments of the present invention, the structure for mounting the tension balancer 100 does not require high strength. This makes it possible to install a lightweight tension balancer at low cost.

[0028] Furthermore, unlike joining or fastening iron by welding, welding aluminum requires advanced technology. Specifically, unlike iron, aluminum forms an aluminum oxide film with a high melting point on its surface, which must be removed before welding. Furthermore, aluminum has a low melting point and high thermal conductivity, making it prone to distortion due to heat. Furthermore, hydrogen is likely to remain in the molten aluminum metal due to the crystal water contained in the aluminum oxide film and moisture in the air. After welding is complete, the aluminum's temperature drops rapidly and solidifies due to its high thermal conductivity. However, if hydrogen remains in the aluminum at this time, the hydrogen can create cavities, which can result in weld cracks. These technical difficulties lead to reduced production yields and increased costs.

[0029] However, as described above, in the tension balancer 100, unlike the second cylindrical member 130 and the third cylindrical member 140, welding to the first cylindrical member 120 is not required. For example, the first front spring washer 122 is not joined or fixed to the first cylindrical member 120; its relative position to the first cylindrical member 120 is simply fixed by a stopper. Furthermore, the processing accuracy of the first cylindrical member 120, the first front spring washer 122, and the stopper is determined by machining accuracy, not welding accuracy. Considering that it is difficult to achieve high processing accuracy when welding aluminum, by applying the embodiments of the present invention, a lightweight tension balancer can be provided at low cost without requiring advanced welding technology.

[0030] Furthermore, the first cylindrical member 120, which contains aluminum as its primary component, accounts for the majority of the outermost surface of the tension balancer 100. As described above, an aluminum oxide coating forms on the aluminum surface due to oxidation by oxygen in the atmosphere, allowing the tension balancer 100 to have high weather resistance without the need for a metal coating such as plating. Furthermore, the formation of surface irregularities caused by plating can be avoided, reducing friction between the first cylindrical member 120 and the first coil spring 128 and, as a result, reducing hysteresis in the stroke-tension characteristics. Furthermore, because there is no need to provide a metal coating, coloring the outer surface of the first cylindrical member 120 is easy.

[0031] The configuration of the tension balancer 100 according to the embodiment of the present invention is not limited to the configuration described above, and various modifications are possible. Modifications will be described below. In the modifications described below, the first cylindrical member 120 contains aluminum as a main component, and therefore the effects described above can be achieved.

[0032] (1) First Front Spring Washer As described above, when the coil spring built into the tension balancer 100 expands or contracts, a force acts on the coil spring, rotating it around the x-direction. For example, when the first coil spring 128 rotates, the first front spring washer 122, which is pressed by the first coil spring 128, also rotates. As a result, friction with the stopper may damage the first front spring washer 122 or the stopper. For this reason, the first front spring washer 122 may be configured to prevent rotation even when the first coil spring 128 rotates. For example, as shown in FIG. 7 and its end view along the chain curve B-B' ( FIG. 8 ), multiple protrusions 122 a may be provided on the front side (opposite the first coil spring 128) of the first front spring washer 122, protruding forward. The number of protrusions 122 a is the same as the number of bolts 124, and one bolt 124 is accommodated between two adjacent protrusions 122 a. This causes the protrusion 122a to interfere with the bolt 124, thereby preventing the first front spring washer 122 from rotating (see the solid arrow).

[0033] (2) Number of Cylindrical Members As mentioned above, there is no restriction on the number of cylindrical members, and the tension balancer 100 may be, for example, a three-stage tension balancer. In this case, as shown in FIG. 9 , a fourth cylindrical member 160 having an outer diameter smaller than the inner diameter of the third cylindrical member 140 is disposed within the third cylindrical member 140, and a third coil spring 148 surrounding the fourth cylindrical member 160 is disposed between the third cylindrical member 140 and the fourth cylindrical member 160. In addition, a third front spring washer 142 is fixed to the inner circumferential surface of the third cylindrical member 140, and a third rear spring washer 164 is fixed to the outer circumferential surface of the fourth cylindrical member 160. The fourth cylindrical member 160, the third front spring washer 142, and the third rear spring washer 164 may contain iron as a primary component. Therefore, by welding, the third front spring washer 142 and the third rear spring washer 164 can be firmly and easily fixed to the third cylindrical member 140 and the fourth cylindrical member 160, respectively. The fourth cylindrical member 160, the third front spring washer 142, and the third rear spring washer 164 can have the same configuration as the third cylindrical member 140, the second front spring washer 132, and the second rear spring washer 144, respectively, and therefore detailed description thereof will be omitted.

[0034] As such, there are no restrictions on the number of stages, i.e., the number of cylindrical members, of the tension balancer 100. Therefore, generally speaking, as described above, the first to nth cylindrical members are arranged so that the (m+1)th cylindrical member selected from the first to nth cylindrical members is located within the mth cylindrical member selected from the first to nth cylindrical members. Also, the first to (n-1)th coil springs are arranged so that the mth coil spring selected from the first to (n-1)th coil springs is sandwiched between the mth cylindrical member and the (m+1)th cylindrical member. Furthermore, the first to (n-1)th front spring washers and the first to (n-1)th rear spring washers are arranged so that the mth front spring washer selected from the first to (n-1)th front spring washers and the mth rear spring washer selected from the first to (n-1)th rear spring washers surround the (m+1)th cylindrical member and sandwich the mth coil spring in a direction parallel to the coil axis of the mth coil spring.

[0035] (3) Stopper As described above, there are no limitations on the configuration of the stopper. Any configuration can be employed as long as it prevents the first front spring washer 122 from falling out forward and allows one or more cylindrical components disposed within the first cylindrical member 120 to slide and be partially exposed from the first cylindrical member 120. Therefore, for example, as shown in FIGS. 10 and 11 , a U-shaped component (U-shaped bar) 112 may be used as the stopper. The U-shaped bar 112 has a pair of legs 112a extending in the z direction that each penetrate the first cylindrical member 120 twice. The pair of legs 112a overlaps the first front spring washer 122 in the x direction, but does not overlap the cylindrical components disposed within the first cylindrical member 120 (the second cylindrical member 130 and the third cylindrical member 140 in the example shown in FIG. 1 ). The pair of legs 112a of the U-shaped bar 112 are provided with collars 114 to prevent them from falling out.

[0036] When the U-shaped bar 112 is used, as a mechanism for preventing rotation of the first front spring washer 122, a pair of grooves 122b capable of accommodating the pair of legs 112a may be provided on the surface of the first front spring washer 122, as shown in Fig. 12. The grooves 122b are provided on the surface opposite the first coil spring 128.

[0037] (4) Insulating Film As described above, in the tension balancer 100, the outermost first cylindrical member 120 contains aluminum as its primary component. Meanwhile, components other than the first cylindrical member 120, such as the first coil spring 128 and the first rear spring washer 134 that contact the first cylindrical member 120, contain iron as their primary component. This creates a difference in ionization tendency between the elements contained in the first cylindrical member 120 and those contained in the other components, which can lead to electrolytic corrosion. This is particularly likely to occur if the tension balancer 100 is installed in a coastal area that is prone to exposure to water or salty water. For this reason, the tension balancer 100 may optionally include an insulating film 116 on the inner surface of the first cylindrical member 120 ( FIG. 13 ). The insulating film 116 may be, for example, a film containing an engineering plastic such as polyamide or polyimide, or a film containing a fluorine-containing polymer such as polytetrafluoroethylene, or a film containing a silicon-containing inorganic compound such as a silicon nitride film or a silicon oxide film, a diamond-like carbon (DLC) film, or a hard chrome plating film.

[0038] (5) Number of Coil Springs In the tension balancer 100, there is no restriction on the number of coil springs arranged between two adjacent cylindrical members, and multiple coil springs may be installed between two adjacent cylindrical members. Generally speaking, one or more of the first through mth coil springs may be configured as multiple coil springs arranged in series in the x direction, which is parallel to the central axis of the cylindrical members, and in contact with each other. The winding directions of adjacent coil springs in the x direction are the same. FIG. 14 shows a schematic end view of a modified example in which the first coil spring 128 includes two coil springs 128-1 and 128-2, and the second coil spring 138 includes two coil springs 138-1 and 138-2. There is no restriction on the number of coil springs arranged between two adjacent cylindrical members, and the number may be two or more and five or less, with the number typically being two or three.

[0039] In this case, at least one end of each coil spring, specifically, the mutually contacting ends of two adjacent coil springs in the x direction, is ground, and each coil spring has a flat surface at the end that is substantially parallel to the yz plane when mounted on the tension balancer 100. For example, if the first coil spring 128 is composed of two coil springs 128-1 and 128-2, as shown in FIGS. 14 and 15, the end of the coil spring 128-1 facing the coil spring 128-2 is ground to form a flat surface 128-1a perpendicular to its coil axis. Similarly, the end of the coil spring 128-2 facing the coil spring 128-1 is ground to form a flat surface 128-2a perpendicular to its coil axis. The two coil springs 128-1 and 128-2 are arranged so that these flat surfaces 128-1a and 128-2a are in contact with each other (see FIGS. 14 and 16). 14, the two coil springs 138-1 and 138-2 that make up the second coil spring 138 are also formed with flat surfaces 138-1a and 138-2a, respectively, and the second coil spring 138 is arranged so that these are in contact with each other. When three or more coil springs are arranged between adjacent cylindrical members, a flat surface may be formed on one end of each of the coil springs at both ends, and flat surfaces may be formed on both ends of the coil springs other than the coil springs at the both ends. Alternatively, flat surfaces may be formed on both ends of all of the coil springs.

[0040] By configuring the coil spring disposed between adjacent cylindrical members with multiple coil springs, it is possible to increase the stroke of the tension balancer 100 when it expands or contracts. This is because when j coil springs (j is a natural number greater than or equal to 2) are connected in series, when a load is applied, all j coil springs expand and contract simultaneously, and they expand and contract j times more than a single coil spring with the same spring constant. Therefore, by applying this modified example, it is possible to apply a greater tension to the overhead wire.

[0041] The above-described embodiments of the present invention may be combined as appropriate as long as they are not mutually inconsistent. Furthermore, even if a person skilled in the art adds or deletes components or modifies the design based on each embodiment, the addition, deletion, or modification of components is included in the scope of the present invention as long as the gist of the present invention is maintained.

[0042] Furthermore, even if there are other effects and advantages different from those brought about by the above-mentioned embodiments, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention.

[0043] 100: tension balancer, 104: first back plate, 106: U-shaped bar, 108: collar, 110: rear hook, 112: U-shaped bar, 114: collar, 116: insulating film, 120: first cylindrical member, 122: first front spring washer, 122a: protrusion, 122b: groove, 124: bolt, 124a: straight portion, 124b: straight portion, 126: nut, 128: first coil spring, 128-1: coil spring, 128-1a: flat surface, 128-2: coil spring, 128-2a: flat surface, 130: second cylindrical member, 132: second front spring washer, 134: first rear spring washer, 138: second coil spring, 138-1: coil spring, 138-1a: flat surface, 138-2: coil spring, 138-2a: flat surface, 140: third cylindrical member, 142: third front spring washer, 144: second rear spring washer, 148: third coil spring, 150: front hook, 152: guide plate, 154: second back plate, 160: fourth cylindrical member, 164: third rear spring washer

Claims

1. A tension balancer comprising: a first to an nth cylindrical member; the first to an (n - 1)th coil spring; a rear hook attached to the first cylindrical member; a front hook attached to the nth cylindrical member; a first to an (n - 1)th front spring washer and a first to an (n - 1)th rear spring washer; and a stopper fixed to the first cylindrical member, wherein the first to the nth cylindrical members are arranged such that a (m + 1)th cylindrical member selected from the first to the nth cylindrical members is located within an mth cylindrical member selected from the first to the nth cylindrical members, the first to the (n - 1)th coil springs are arranged such that an mth coil spring selected from the first to the (n - 1)th coil springs is sandwiched between the mth cylindrical member and the (m + 1)th cylindrical member, the first to the (n - 1)th front spring washers and the first to the (n - 1)th rear spring washers are arranged such that an mth front spring washer selected from the first to the (n - 1)th front spring washers and an mth rear spring washer selected from the first to the (n - 1)th rear spring washers surround the (m + 1)th cylindrical member and sandwich the mth coil spring in a direction parallel to the coil axis of the mth coil spring, the stopper is arranged such that in the direction, the first front spring washer is sandwiched between the first coil spring and the stopper, the first cylindrical member contains aluminum as a main component, the second to the nth cylindrical members contain iron as a main component, n is selected from natural numbers of 2 or more and 5 or less, and m is a variable selected from natural numbers of 1 or more and (n - 1) or less.

2. The tension balancer according to claim 1, wherein the first cylindrical member is made of aluminum or an aluminum alloy.

3. The tension balancer according to claim 1, wherein the second to the nth cylindrical members are made of iron or stainless steel.

4. The (n - 1) rear spring washers from the first one are respectively fixed to the second to the nth cylindrical members, the (n - 1) front spring washers from the second one are respectively fixed to the second to the nth cylindrical members, and the first front spring washer is not fixed to the first cylindrical member and is configured to be movable in the space between the first cylindrical member and the second cylindrical member in the absence of the elastic force of the first coil spring. The tension balancer according to claim 1.

5. The stopper includes a plurality of bolts passing through the first cylindrical member. The tension balancer according to claim 1.

6. The stopper includes k bolts arranged at the vertices of a virtual regular k-sided polygon on a plane perpendicular to the coil axis, where k is selected from natural numbers of 3 or more and 8 or less. The tension balancer according to claim 1.

7. The first front spring washer has a plurality of protrusions protruding in a direction opposite to that of the first coil spring, and one of the bolts is arranged between two adjacent protrusions. The tension balancer according to claim 5.

8. The stopper is a U-shaped member, and a pair of legs of the U shape penetrate the first cylindrical member. The tension balancer according to claim 1.

9. The first front spring washer has a pair of grooves for accommodating the pair of legs on a surface opposite to that of the first coil spring. The tension balancer according to claim 8.

10. The tension balancer according to claim 1 further includes an insulating layer on the inner surface of the first cylindrical member.

11. The second to the nth cylindrical members are coated with a metal film. The tension balancer according to claim 1.

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