Structure of horizontal pole and weight of tennis training stand

Abstract

The present invention relates to a tennis training stand in which a horizontal pole (120) is horizontally mounted at a predetermined point of a vertical part (110) of a building or a structure to form a basic frame of the tennis training stand, a string is hung from an end of the horizontal pole of the basic frame toward the ground, a tennis ball is hung on an end of the string, and then the ball is hit with a racket. The training stand can be used for personal purposes. However, the training stand is intended for public use to be mainly installed in a flood plain in the riverside of a city, a school playground, or the like, so that anyone can bring a ball and a racket and practice tennis in a fun and realistic way. Therefore, the height of the training stand from the ground should be quite high. Accordingly, provided is a technology for minimizing problems such as a problem of connecting or separating a ball string at the end side of the horizontal pole (120) at a high position and an unexpected situation in which the ball string (151) is caught on the horizontal pole during hitting practice.

Description

Structure of the crossbar and weights of a tennis practice table

[0001] The present invention relates to a technology for a tennis practice table, which comprises constructing a basic frame of a tennis practice table by installing a horizontal pole (120) at a predetermined point on a vertical surface (110) of a building or structure, hanging a string (151) toward the ground (100) at the end of the horizontal pole, hanging a tennis ball (150) at the end of the string, and then practicing by hitting the ball with a racket.

[0002] That is, when a trainee hits a ball with a racket, the ball flies forward along an upward circular curve with the end of the crossbar as the center, to a certain point in the air, and then falls along a downward circular curve due to gravity, and the practice table repeats the action of hitting the ball again.

[0003] In these tennis practice tables, the height of the crossbar (120) above the ground is very important. That is, if it is too low, the ball's flight trajectory will be minimal, rendering practice useless. However, it must be at least 6.5 m above the ground to enable the player to master the essential hitting posture and hitting technique in a fun, easy, and realistic way.

[0004] However, to achieve the ideal flight trajectory of the ball as described above, the material and weight of the string (151) that suspends the ball are also important considerations. If the material is elastic like a rubber band, or is too thick, inflexible, or heavy, the ball will likely oscillate in the air, making effective hitting practice impossible.

[0005] Accordingly, the string (151) should not be elastic or thick, and should be light and flexible. However, strings made of this material have the difficult problem of having to use special equipment in each situation to reattach the string to the end of the crossbar when the string is inadvertently cut at a very high position, near the end of the crossbar (120), during batting practice due to aging caused by exposure to sunlight or long-term use.

[0006] In another case, if these tennis practice tables are installed in public areas such as riverside areas in cities and are used by the public, users must bring their own balls and rackets with strings so that they can easily hang the strings on the ends of the poles. Also, after practice, they must retrieve the strings and balls and then clean up the tennis practice tables. This is not a simple problem either.

[0007] The present invention relates to a technique for solving the above problem.

[0008] In order to solve the problems raised above in implementing a highly useful tennis practice table, the applicant has filed the following three utility model registration applications.

[0009] A. Tennis practice table for high-level land use (20-04954800000. Kang Chan. Registered on May 30, 2022)

[0010] ~ When connecting the string to the end of the shear connecting string, use a roller and a weight to adjust the rise and fall of the end of the shear connecting string from the end of the crossbar to near the ground.

[0011] B. Wall-mounted tennis practice table (20-2020-0003154. Chan Kang. August 26, 2020. Re-examination underway)

[0012] ~ Using the roller and weight, adjust the rise and fall of the end of the shear link from the end of the crossbar to near the ground.

[0013] D. Tennis practice stand performance tie-down installation structure (20-2021-0002370. Chan Kang. July 27, 2021. Under re-examination)

[0014] ~Using a roller and a pull cord, adjust the end of the shear-end connecting strap to raise and lower it from the end of the crossbar to near the ground. Install an auxiliary strap to prevent the pull cord and ball strap from becoming tangled with each other. That is, by pulling the auxiliary strap, the upper end of the pull cord is moved horizontally below the crossbar to minimize interference with the ball's flight trajectory.

[0015] The results of implementing the three designs above have been met with rave reviews from tennis enthusiasts, who find them fun, easy to practice with, and incredibly helpful for improving their skills. A video of practicing on this tennis practice stand can be found at the URL: https: / / youtu.be / GqdZt17bn7E. Search for "Tennis practice stand. The definitive tennis practice stand" on YouTube.

[0016] However, while the tennis practice tables based on the three designs mentioned above are highly effective, they also present a number of problems. First, the complexity of using the front end connecting strap (hereinafter referred to as the "strap") and the auxiliary strap for the strap. Second, the limitations of the weight function. Third, the safety of the weight. These three issues have emerged as critical issues, necessitating technological advancements to overcome them.

[0017] The three important problems presented above are the tasks that this invention seeks to solve.

[0018]

[0019] First, we seek solutions to the problem of cumbersome use of pull straps and auxiliary straps.

[0020]

[0021] In the above “Da. Tennis practice stand performance string installation structure” (hereinafter “Da” design), the steps are as follows: first, a step of releasing the roller and the auxiliary string; a step of having the trainee pull the string toward the ground, which has the end of the front connecting string tied to the O-ring of the pull string; a step of connecting a ball string to the O-ring of the pull string; a step of winding the roller so that the O-ring of the pull string is in close contact with the O-ring at the end of the crossbar (= guide ring); a step of having the trainee pull the auxiliary string to move the upper part of the pull string horizontally below the crossbar; and after the above steps are sequentially performed, the technique of the trainee hitting the ball hanging from the final ball string is included.

[0022]

[0023] This technology is indeed much more complicated than the technology of adjusting the elevation and descent of the end of the front end connecting string from the end of the crossbar to the ground using only a roller and a weight, which is the technology of the “A. Tennis practice table for high-altitude use” (hereinafter “A” design) and “B. Tennis practice table for wall-mounted use” (hereinafter “B” design).

[0024]

[0025] In order to solve these problems, the present invention provides a technology that excludes the auxiliary string in the above “D” design.

[0026]

[0027] First, an O-ring (121, hereinafter referred to as a crossbar O-ring) at the end of a crossbar (120) is made of a magnetic material, and magnets (122) are densely planted in one or more rows continuously from the adjacent area of ​​the crossbar O-ring to the lower surface (lower surface, hereinafter referred to as the lower surface) of the crossbar. In this tennis practice table, when a trainee rolls the roller (112), the pull string O-ring (132) is pressed against the crossbar O-ring (121). At this time, the pull string O-ring (121) and the upper part (131) of the pull string are automatically attached in one row to the crossbar O-ring (121) and the lower surface of the crossbar by the magnetic force of the crossbar O-ring (121) and the magnet (122) on the lower surface of the crossbar.

[0028]

[0029] Second, we seek solutions to the problem of limitations in the weight function.

[0030]

[0031] In the above “A” and “B” designs, the techniques are implemented in the following steps: first, when the roller is released, the weight attached to the end of the front end connecting string descends to near the ground due to the weight's load; second, a step is to connect a string to the weight; third, a step is to wind the roller so that the weight adheres to the O-ring at the end of the crossbar; and fourth, a step is to have the trainee hit the ball hanging from the string.

[0032]

[0033] This technology is actually much simpler than the technology of adjusting the rise and fall of the end of the front end connecting strap using a roller, a pulling strap, and an auxiliary strap in the above “Da” design.

[0034]

[0035] However, an unexpected situation sometimes occurs that cannot be resolved by relying only on the load of the weight (200) for the rising and falling of the shear connecting string (140). The shear connecting string usually uses a steel wire, and if this wire is bent or wound for a long time at the bend point or roller (112) of the practice stand and then receives a lot of resistance while passing through the inside of the pipe or the crossbar O-ring (121) of the practice stand, or if the ball string (151) of a ball that has been hit very hard gets caught on the crossbar (120), an unexpected situation occurs in which the weight (200) cannot descend to the ground near the ground with its own load alone.

[0036]

[0037] In order to resolve such an unexpected situation, the present invention utilizes a pull string (130) as an auxiliary device. Specifically, first, the end of the front end connecting string (140) sequentially passes through the crossbar O-ring (121) and the pull string O-ring (132), and is then connected to a new O-ring, the front end connecting string O-ring (141). This front end connecting string O-ring is connected to a weight (200).

[0038]

[0039] In addition, the upper end (131) of the pull string is attached in a single row to the crossbar O-ring (121) and the magnet (122) continuously installed on the lower surface of the crossbar, and the middle and lower ends of the pull string are adjacent to the vertical surface (110) of the practice stand and face the ground (100), and the pull string (130) is pulled more strongly to resolve the above-mentioned emergency situation. In this way, a technology for using a pull string (130) to prepare for an emergency situation and a technology for using a weight (200) in the “A” and “B” designs in combination are provided.

[0040]

[0041] Third, we will seek solutions to the safety issues of the weights.

[0042]

[0043] In the above “A” and “B” designs, if the connecting part of the front end connecting string (140) that connects the weight (200) becomes weak and the weight falls and hits the trainee’s head or face, a serious accident may occur if the weight is made of pure metal or stone.

[0044]

[0045] In preparation for such a situation, the present invention provides a technology for a weight (200) in which the outer surface (203, 204, 205) of the weight is made of a soft material such as rubber or silicone rather than iron or stone, or in which the weight (200) increases in weight while reducing the volume of the weight by adding metal or stone to the inner center (206) of the weight whose outer surface is made of a soft material.

[0046]

[0047]

[0048]

[0049] The three important problems presented above are the tasks that this invention seeks to solve.

[0050]

[0051]

[0052] First, we seek solutions to the problem of cumbersome use of pull straps and auxiliary straps.

[0053]

[0054] In the above “Da. Tennis practice stand performance string installation structure” (hereinafter “Da” design), the steps are as follows: first, a step of releasing the roller and the auxiliary string; a step of having the trainee pull the string toward the ground, which has the end of the front connecting string tied to the O-ring of the pull string; a step of connecting a ball string to the O-ring of the pull string; a step of winding the roller so that the O-ring of the pull string is in close contact with the O-ring at the end of the crossbar (= guide ring); a step of having the trainee pull the auxiliary string to move the upper part of the pull string horizontally below the crossbar; and after the above steps are sequentially performed, the technique of the trainee hitting the ball hanging from the final ball string is included.

[0055]

[0056] This technology is indeed much more complicated than the technology of adjusting the elevation and descent of the end of the front end connecting string from the end of the crossbar to the ground using only a roller and a weight, which is the technology of the “A. Tennis practice table for high-altitude use” (hereinafter “A” design) and “B. Tennis practice table for wall-mounted use” (hereinafter “B” design).

[0057]

[0058] In order to solve these problems, the present invention provides a technology that excludes the auxiliary string in the above “D” design.

[0059]

[0060] First, an O-ring (121, hereinafter referred to as a crossbar O-ring) at the end of a crossbar (120) is made of a magnetic material, and magnets (122) are densely planted in one or more rows continuously from the adjacent area of ​​the crossbar O-ring to the lower surface (lower surface, hereinafter referred to as the lower surface) of the crossbar. In this tennis practice table, when a trainee rolls the roller (112), the pull string O-ring (132) is pressed against the crossbar O-ring (121). At this time, the pull string O-ring (121) and the upper part (131) of the pull string are automatically attached in one row to the crossbar O-ring (121) and the lower surface of the crossbar by the magnetic force of the crossbar O-ring (121) and the magnet (122) on the lower surface of the crossbar.

[0061]

[0062] Second, we seek solutions to the problem of limitations in the weight function.

[0063]

[0064] In the above “A” and “B” designs, the technique is implemented as follows: first, when the roller is released, the weight tied to the end of the front end connecting string descends to near the ground due to the weight's load; second, a step is connected to the weight by a string; third, the roller is wound so that the weight adheres to the O-ring at the end of the crossbar; and fourth, the trainee hits the ball hanging from the string.

[0065]

[0066] This technology is actually much simpler than the technology of adjusting the rise and fall of the end of the front end connecting strap using a roller, a pulling strap, and an auxiliary strap in the above “Da” design.

[0067]

[0068] However, an unexpected situation sometimes occurs that cannot be resolved by relying only on the load of the weight (200) for the rising and falling of the shear connecting string (140). The shear connecting string usually uses a steel wire, and if this wire is bent or wound for a long time at the bend point or roller (112) of the practice stand and then receives a lot of resistance while passing through the inside of the pipe or the crossbar O-ring (121) of the practice stand, or if the ball string (151) of a ball that has been hit very hard gets caught on the crossbar (120), an unexpected situation occurs in which the weight (200) cannot descend to the ground near the ground with its own load alone.

[0069]

[0070] In order to resolve such an unexpected situation, the present invention utilizes a pull string (130) as an auxiliary device. Specifically, first, the end of the front end connecting string (140) sequentially passes through the crossbar O-ring (121) and the pull string O-ring (132), and is then connected to a new O-ring, the front end connecting string O-ring (141). This front end connecting string O-ring is connected to a weight (200).

[0071]

[0072] In addition, the upper end (131) of the pull string is attached in a single row to the crossbar O-ring (121) and the magnet (122) continuously installed on the lower surface of the crossbar, and the middle and lower ends of the pull string are adjacent to the vertical surface (110) of the practice stand and face the ground (100), and the pull string (130) is pulled more strongly to resolve the above-mentioned emergency situation. In this way, a technology for using a pull string (130) to prepare for an emergency situation and a technology for adjusting the rising and falling of a front end connecting string (140) as a weight (200) in the “A” and “B” designs are provided.

[0073]

[0074] Third, we will seek solutions to the safety issues of the weights.

[0075]

[0076] In the above “A” and “B” designs, if the connection part of the front end connecting string (140) that connects the weight (200) becomes weak and the weight falls and hits the trainee’s head or face, a serious accident may occur if the weight is made of pure metal or stone.

[0077]

[0078] In preparation for such a situation, the present invention provides a technology for a weight (200) in which the outer surface (203, 204, 205) of the weight is made of a soft material such as rubber or silicone rather than iron or stone, or in which the weight (200) increases in weight while reducing the volume of the weight by adding metal or stone to the inner center (206) of the weight whose outer surface is made of a soft material.

[0079]

[0080] First, in relation to the problem of cumbersome use of the pull strap and auxiliary strap, the technology is provided in which the magnets (122) replace the function of the auxiliary strap in a much more convenient way than using the auxiliary strap in the “Da” design, thereby solving the cumbersome problem of having to operate the auxiliary strap as well.

[0081]

[0082] Second, in relation to the problem of limitations in the weight function, in normal times, the upper part of the pull string (131) is kept attached to the magnets (122) planted on the lower surface of the crossbar, and the rise and fall of the front end connecting string (140) is adjusted only by the roller (112) and the weight.

[0083]

[0084] However, even in the case where an unexpected emergency situation as described above occurs, if the trainee pulls the pull string to first separate the pull string and the pull string O-ring (132) from the magnets, and then continues to pull the pull string toward the ground (100) with a force strong enough to short-circuit the cotton string (151), the front end connecting string O-ring (141) that is caught as a stopper on the pull string O-ring will pull the front end connecting string (140) and lower it toward the ground (100). After resolving the obstacle of the emergency situation in this way, the trainee rolls the roller to return the upper part of the pull string (131) to the normal state where it is attached to the lower surface of the crossbar, thereby providing a technology that enables tennis practice, thereby solving the problem of limitations in the weight function.

[0085]

[0086] Third, with regard to the safety issue of the weight (200), even in the worst case scenario where the weight is short-circuited at the front end connecting strap and falls on the trainee's head, the safety issue will be resolved to the extent that it will only cause some surprise.

[0087]

[0088] Figure 1 is a basic conceptual diagram of a tennis practice table completed according to the present invention. The crossbar O-ring (121) is a magnetic material, and magnets (122) are densely embedded in the lower surface of the crossbar from the adjacent portion of the crossbar O-ring. The end of the front end connecting string (140) that has exited the crossbar O-ring and the ball string (151) are tied to the pull string O-ring (132).

[0089]

[0090] Figure 2 is a conceptual diagram showing a state in which, when a trainee rolls a roller (112) on the tennis practice table in Figure 1, the pull string O-ring (132) and the upper part of the pull string (131) are attached in a single row to the crossbar O-ring and the magnet (122) on the lower surface of the crossbar by the magnetic force of the magnets planted on the crossbar O-ring and the lower surface of the crossbar.

[0091]

[0092] Figure 3 is a conceptual diagram of a tennis practice table in which a front end connecting string (140) that has passed through a crossbar O-ring (121) of the tennis practice table in Figure 1 passes through a pull string O-ring (132) and is then tied to the front end connecting string O-ring (132).

[0093]

[0094] Fig. 4 is a conceptual diagram showing a state in which, when a trainee rolls a roller (112) on the tennis practice table in Fig. 3, the upper part of the pull string (131) is attached to the lower surface of the crossbar, the pull string O-ring (132) is attached to the crossbar O-ring (121), and the front end connecting string O-ring (141) is attached to the pull string O-ring.

[0095]

[0096] Figure 5 is a conceptual diagram showing a weight (200) combined with an O-ring of a front end connecting string on the Figure 3 tennis practice table.

[0097]

[0098] Fig. 6 is a conceptual diagram showing a state in which, when a trainee rolls the roller on the tennis practice table in Fig. 5, the upper part of the pull string (131) is attached to the lower surface of the crossbar, the pull string O-ring (132) is attached under the crossbar O-ring (121), and the front end connecting string O-ring (141) combined with a weight is attached under the pull string O-ring. A ball (150) is hung underneath.

[0099]

[0100] Figure 7 is a cross-sectional view of a weight (200) according to the present invention cut into two equal parts in the vertical direction. The center (206) is made of a hard material such as iron or stone, and the outer peripheral surface (203 204 205) is made of one or more layers of soft material.

[0101]

[0102] Omitted

[0103] (1). Create a basic frame.

[0104] The vertical member (110) can be a steel structure such as a wall surface of a building or a streetlight pole, and the floor surface is usually assumed to be the ground (100). A bracket (111) is installed at a certain point 6.5 m above the ground of the vertical member, and a pipe-shaped crossbar (120) made of duralumin, with an outer diameter of 7 cm and a length of 2.3 m, is installed horizontally in a somewhat rounded shape.

[0105] A roller (112. Small winch winch, hereinafter referred to as roller) is installed at the vertical section's chest height, and a crossbar O-ring (121) is installed at the end of the crossbar. The O-ring is a steel magnetic body with an inner diameter of 3.5 cm and an outer diameter of 5 cm. The repulsive force portion is fixed internally to the inner diameter of the end of the crossbar (120), and the attractive force portion is exposed externally at the end of the crossbar. This is to ensure that the pulling strap O-ring (132) adheres well to the crossbar O-ring (121) when it is pressed against it.

[0106] Neodymium magnets (122) measuring 2 cm wide x 3 cm thick and 7 mm thick are arranged in a single row in an inner frame installed on the lower surface of the crossbar from the point adjacent to the crossbar O-ring to the point where the crossbar meets the vertical part. (Drawing omitted.)

[0107] (2). Select one of the two methods below to install the shear connecting string (140) to the basic frame.

[0108] First, the two methods have in common that the outer end of the shear connection strap (140) (hereinafter referred to as the end of the shear connection strap) starts from the roller at the height of a person's chest, passes through the wall surface or the inside of the pipe-shaped structure of the vertical part of the practice stand and the bracket (111), and then passes through the crossbar O-ring (121). The shear connection strap (140) is composed of 20 m of stainless steel wire with a thickness of 1.5 mm. The constituent materials and specifications of the shear connection strap (140) are the same as below.

[0109] In the first method described above, the end of the front end connecting string (140) that passes through the crossbar O-ring is tied to the pull string O-ring (132) at the end of the pull string. At the same time, the ball string (151) that hangs the ball is tied to the pull string O-ring. In this state, when the roller (112) is wound, the pull string O-ring and the upper part of the pull string are attached to the lower surface of the crossbar from the crossbar O-ring, and the lower part of the pull string and the pull string handle (133) are adjacent to the vertical part and face the ground (100). The trainee practices by hitting the ball hanging below the pull string O-ring (132).

[0110] When you want to retrieve the string (151) and ball (150) after practice, first, switch the roller to the released state, then pull the string handle (133) toward the ground to detach the upper part of the string (131) from the lower surface of the crossbar, and then continue to pull the string toward the ground (100) to detach the string from the string O-ring. In addition, when the trainee leaves the practice stand, it is desirable to wrap the roller (112) to attach the upper part of the string to the lower surface of the crossbar to keep the practice stand tidy.

[0111] The pull string O-ring (132) is made of steel with an inner diameter of 3.5 cm and an outer diameter of 5 cm, and the pull string is composed of 10 m with a thickness of 1.5 mm, and the upper part (131) of the pull string is composed of 2.3 m of steel wire, and the lower part of 7.7 m is composed of stainless steel wire. The material of the string (151) is 1.5 mm thick cotton yarn. The materials and specifications of the pull string, pull string O-ring, and pull string are the same as below.

[0112] In the second method described above, the end of the front end connecting string (140) that passes through the crossbar O-ring (121) passes through the pull string O-ring (132) and is then tied to the front end connecting string O-ring (141). At the same time, the ball string that is hanging the ball is connected to the front end connecting string O-ring. When the roller is wound in this state, the upper end of the pull string is attached to the lower surface of the crossbar, and the middle and lower ends of the pull string are adjacent to the vertical part (110) of the basic frame and face the ground (100). At the same time, the front end connecting string O-ring (141) is pressed under the pull string O-ring (132), and the trainee practices by hitting the ball hanging under the front end connecting string O-ring (141).

[0113] When you want to retrieve the string and ball after practice, first, switch the roller (112) to the released state, and then, while maintaining the state in which the upper part of the pull string is attached to the lower part of the crossbar, pull the string (151) toward the ground to separate the string from the front end connecting string O-ring (141). Then, when the trainee leaves the practice stand, it is desirable to wrap the roller to close the front end connecting string O-ring (141) to the pull string O-ring (132) and tidy up the practice stand.

[0114] Meanwhile, both of the above methods are routinely implemented. However, in an emergency situation, such as when the string (151) of a ball hit with a very strong force as described above gets caught on the crossbar (120), the problem of an emergency situation can be solved by pulling the string (130) toward the ground with a force strong enough to short-circuit the cotton yarn, which is the material of the string.

[0115] The specifications of the shear connection O-ring are the same as those of the crossbar O-ring and the pull strap O-ring (132), with an inner diameter of 3.5 cm and an outer diameter of 5 cm, and its material is stainless steel. The specifications and material of the shear connection O-ring (141) are the same as below.

[0116] (3). Attach a weight (200) to the basic frame.

[0117] In the second method of the above (2), that is, among the methods of installing the shear connecting strap to the basic frame, in the method in which the end of the shear connecting strap (140) that has come out of the crossbar O-ring passes through the pull strap O-ring (132) and is then tied to the shear connecting strap O-ring (141), a weight (200) can be combined or tied to the shear connecting strap O-ring (141).

[0118] When practicing by hanging a string on the O-ring (141) connecting the front end to the weight (200) or the ring on the lower surface of the weight,

[0119] In normal times, the roller is wound so that the pull string O-ring (132) is attached to the crossbar O-ring (121), the front end connecting string O-ring (141) is attached to the pull string O-ring, and at the same time, the upper end (131) of the pull string is attached to the lower surface of the crossbar, and the practice is performed by hitting the ball connected below the front end connecting string O-ring and the weight. In addition, the raising and lowering of the weight (200), which is combined with the front end connecting string, can be adjusted only by the load of the roller (112) and the weight (200), while maintaining the state in which the pull string O-ring is attached to the crossbar O-ring and the upper end (131) of the pull string is attached to the lower surface of the crossbar.

[0120] In the event of an emergency, as described in the above [contents of the invention] and [effects of the invention], the emergency situation can be resolved by strongly pulling the pulling string (130) toward the ground, and then, as in the above ➀ normal times, the string can be re-hooked to the O-ring of the front end connecting string or the hook on the lower surface of the weight, and the above exercise can be continued.

[0121] After practice, it is desirable to release the roller while the pull string O-ring (132) and the upper part of the pull string (131) are still attached to the lower surface of the crossbar, lower the front end connecting string O-ring and the weight, then retrieve the ball and the ball, and then wind the roller to attach the front end connecting string O-ring and the weight to the pull string O-ring (132) to neatly organize the practice stand.

[0122] (4). Minimize the safety risk of the weight (200).

[0123] The weight is independent of the shape, material, or number, and must be able to provide a load to the shear connecting string (140) to lower the shear connecting string toward the ground (100). However, in the present invention, considering the safety risk to the trainee due to the weight (200), it is made of a sphere with an inner diameter of 8.5 cm to 10 cm, and its center (206) is an air layer or a steel ball, and the outer circumference is made of a soft material, and is composed of three multilayer structures in the order of soft silicone (205) - rubber (204) - semi-rigid plastic (203) from the center to the outer circumference, so that the weight is 250 g.

[0124] The outer surface (202) is coated with a UV blocking agent. The upper end connecting strap O-ring is connected with a nut (201), and a round ring (207) is installed on the lower end to connect the strap. If a weight constructed in this way were to fall naturally from a height of 7 m above the ground and land on a person's head, the impact would not cause injury.

Claims

1. A crossbar (120) installed horizontally at a certain point on a vertical section (110) of a building or structure; a crossbar O-ring (121) installed at the end of the crossbar; a shear connection string (140) that starts from a roller (112) installed on a vertical section of the building or the crossbar and penetrates the crossbar O-ring (121); a pull string O-ring (132) that is connected to the end of the shear connection string that penetrates the crossbar O-ring or through which the shear connection string penetrates; when the shear connection string penetrates the pull string O-ring (132), a shear connection string O-ring (141) that functions as a stopper for the pull string O-ring (132) and is connected to the end of the shear connection string; A pull string (130) that is connected to a pull string O-ring (132) and can lower an end of a front end connecting string to the vicinity of the ground by pulling the pull string O-ring toward the ground near the ground (100); a ball (151) that is connected to the pull string O-ring (132) or, when the front end connecting string penetrates the pull string O-ring (132), is connected to the front end connecting string O-ring and is connected vertically downward; a ball (150) that is hung from the lower end of the ball; A tennis practice table structure characterized in that, in a tennis practice table including a crossbar O-ring (121) which is a magnetic body and magnets (122) are densely planted in one or more rows on the lower surface of the crossbar, when the roller is wound so that the pull string O-ring is in close contact with the crossbar O-ring, the pull string O-ring (132) is automatically and sequentially attached to the crossbar O-ring (121) by the magnetic force of the magnetic body or magnet, and the upper part of the pull string (131) is automatically and sequentially attached to the magnets (122) planted on the lower surface of the crossbar, and the middle and lower parts of the pull string are adjacent to a vertical surface of a building, etc., and face toward the ground (100).

2. In the first paragraph, when the end of the front end connecting string (140) passes through the pull string O-ring (132) and is connected to the front end connecting string O-ring (141), when the roller (112) is operated in a released state, the structure of the tennis practice table is characterized in that the weight (200) is installed so that the end of the front end connecting string (140) can be lowered toward the ground by the load applied to the front end connecting string (140) by the weight (200) connected to the front end connecting string O-ring (141) even without pulling the pull string (130) or the ball string (151) from the ground.

3. In the first and second clauses, with respect to the material of the weight (200), first, a part or all of the material of the weight component is not a hard material such as wood, stone or iron, but a soft material such as rubber or silicone, or second, the outer surface (203 204 205) of the weight is made of one or more layers of the above soft material and the center (206) is made of a hard material such as iron, etc., and the structure of a tennis practice table characterized in that one of the weights (200) is installed.

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