Free-fall impact test equipment

Abstract

To provide a device capable of performing drop impact testing with a high reproducibility that matches the actual phenomena.SOLUTION: A free fall impact testing device which makes a falling object free fall and collide with an impact receiving plate includes: a cover which surrounds the falling object from outside in a horizontal direction, independent of the falling object; and a guide which guides the cover free falling with the falling object in a vertical direction. The cover has a lower opening larger than the falling object as viewed from the vertical direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a free-fall impact test device used in a test in which a falling object is allowed to freely fall and collide with an impact receiving plate. [Background technology]

[0002] Patent Document 1 discloses a drop impact testing device that allows a test object to freely fall while maintaining a constant posture, causing the test object to collide with a collision receiving plate. In this device, a tapered holder that holds the test object falls along a linear rail. The test object collides with the collision receiving plate through a lower opening of the tapered holder, and the tapered holder collides with an impact absorbing material below the collision receiving plate and stops. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-166922 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device of Patent Document 1, the lower opening of the holder is smaller than the test object, and the test object is held in the holder, so the test object may fall at a speed different from the actual falling speed, and it may not be possible to reproduce a free fall that matches the actual phenomenon.

[0005] Therefore, one aspect of the present disclosure aims to provide an apparatus capable of conducting a drop impact test with high reproducibility that matches actual phenomena. [Means for solving the problem]

[0006] A free-fall impact test apparatus according to one aspect of the present disclosure is a free-fall impact test apparatus used in a test in which a falling object is allowed to freely fall and collide with an impact receiving plate, Separation possiblea cover that surrounds the falling object from the outside in the horizontal direction; and a guide that guides the cover that falls freely together with the falling object in the vertical direction. at least one stopper that prevents the cover from falling when a lower end of the cover that has fallen together with the falling object reaches a specific position that is a predetermined height above the impact receiving plate; The cover has a lower opening that is larger than the dropped object when viewed in the vertical direction. and a slit extending upward from the bottom end. With The at least one stopper applies an external force to the cover so that the lower opening widens when the lower end of the cover reaches the specific position. do It is something . A free-fall impact testing device according to another aspect of the present disclosure is a free-fall impact testing device used in a test in which a falling object is allowed to freely fall and collide with an impact receiving plate, and further comprises a cover that surrounds the falling object from the horizontal outside so as to be able to be separated from the falling object, a guide that vertically guides the cover that free falls together with the falling object, and a tapered wall that protrudes above the impact receiving plate, wherein the cover has a lower opening that is larger than the falling object when viewed vertically and a slit extending upward from its lower end, and the tapered wall guides the inner surface of the cover so that the lower opening widens before the falling object that has fallen together with the cover collides with the impact receiving plate. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, the cover free-falls along with the falling object, and the falling object free-falls independently of the cover, thereby reproducing the free fall of a falling object that matches a real phenomenon. Thus, a drop impact test with high reproducibility that matches a real phenomenon can be performed in the free-fall impact test device. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a free-fall impact testing device according to the first embodiment. [Figure 2] FIG. 2 is a vertical cross-sectional view of the cover and its vicinity shown in FIG. [Figure 3] FIG. 3 is a perspective view of the cover of FIG. [Figure 4] FIG. 4 is a horizontal cross-sectional view of the cover and its vicinity shown in FIG. [Figure 5] 5 is a vertical cross-sectional view of the impact force receiving plate of FIG. 1 and the vicinity thereof immediately before a falling object collides with the impact force receiving plate. [Figure 6] FIG. 6 is a vertical cross-sectional view of a free-fall impact testing device according to the second embodiment, corresponding to FIG. [Figure 7] FIG. 7 is a vertical cross-sectional view of a free-fall impact testing device according to a third embodiment, corresponding to FIG. [Figure 8] FIG. 8 is a vertical cross-sectional view of a free-fall impact testing device according to a fourth embodiment, corresponding to FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment will be described with reference to the drawings.

[0010] (First embodiment) FIG. 1 is a perspective view of a free-fall impact testing apparatus 1 according to a first embodiment. As shown in FIG. 1, the free-fall impact testing apparatus 1 performs a test in which a falling object 10 is allowed to freely fall and collide with the upper surface of an impact receiving plate 11. The falling object 10 may be the test object, or the impact receiving plate 11 may be the test object. The falling object 10 and the impact receiving plate 11 are not particularly limited and are determined according to the purpose of the test. As an example, if the test object simulating an aircraft wing is the impact receiving plate 11, the falling object 10 may be a gelatin sphere simulating a bird, or a round piece of ice. In this embodiment, an example will be described in which the falling object 10 is a sphere and the impact receiving plate 11 is a horizontal plate.

[0011] The free fall impact testing device 1 includes a base 2 , at least one load cell 3 , a stand 4 , a guide 5 , a cover 6 , at least one stopper 7 , and a video camera 8 .

[0012] The base 2 is a plate placed on the ground. At least one load cell 3 is placed on the base 2. The load cell 3 may be a load cell. In this embodiment, the at least one load cell 3 includes a plurality of (for example, four) load cells 3 distributed over the base 2. The load cells 3 support the impact receiving plate 11 from below. That is, the load cells 3 measure the load applied to the impact receiving plate 11 from above. The base 2 may be omitted and the load cells 3 may be placed directly on the ground.

[0013] The stand 4 has a plurality of legs 4a and a support plate 4b. The legs 4a are installed on the ground or on the base 2. The support plate 4b is horizontally disposed above an impact receiving plate 11 supported by the load meter 3, and is supported from below by the legs 4a. The support plate 4b has a passage hole H that opens in the vertical direction. The collision space S surrounded by the plurality of legs 4a may be surrounded from the side by a transparent plate.

[0014] The guide 5 is supported by the support plate 4b of the stand 4. The guide 5 extends upward from the support plate 4b. The guide 5 guides the cover 6, which falls freely together with the falling object 10, in the vertical direction. The guide 5 is, for example, a pipe having an axis extending in the vertical direction. When viewed from the vertical direction, the inner surface 5a of the guide 5 has a shape similar to the shape of the outer surface 6e of the cover 6. The horizontal cross section of the guide space G inside the guide 5 has a constant shape and size along the vertical direction. In this embodiment, the guide 5 is a round pipe, and the horizontal cross section of the guide space G is circular.

[0015] The cover 6 has an internal space in which the falling object 10 is placed. The cover 6 has an inner surface 6d that surrounds the falling object 10 from the horizontal outside. The cover 6 can be freely separated from the falling object 10 and is a member independent of the falling object 10. The inner surface 6d of the cover 6 has a shape similar to the outer shape of the falling object 10 when viewed in the vertical direction. The cover 6 has an outer surface 6e that is similar to the outer shape of the horizontal cross section of the guide space G. In other words, the cover 6 has an outer surface 6e that is similar to the inner surface 5a of the guide 5. The cover 6 is, for example, a tube. The tube is not limited to a cylindrical tube and may be a polygonal tube. The cover 6 is flexible. The cover 6 is made of, for example, resin. The cover 6 is, for example, transparent or translucent.

[0016] At least one stopper 7 prevents the cover 6 from falling when the lower end of the cover 6, which has fallen freely together with the falling object 10, reaches a specific position P (see FIG. 5 ), which will be described later. In this embodiment, the at least one stopper 7 includes a pair of stoppers 7. The pair of stoppers 7 is, for example, a string. One end of the stopper 7 is connected to the upper end of the cover 6, and the other end of the stopper 7 is fixed to a member 15 located above the upper end of the cover 6 that has reached the specific position P, which will be described later. The stopper 7 descends through the guide space G of the guide 5 along with the freely falling cover 6. The member 15 may be a fixed fixture separate from the free fall impact test apparatus 1, or may be the upper end of the guide 5, or may be a reel installed on the fixed fixture or the guide 5.

[0017] The video camera 8 is positioned so as to be able to capture images of the impact receiving plate 11 and the collision space S from the side. The video camera 8 is, for example, a high-speed camera. Although FIG. 1 shows an example in which both the load meter 3 and the video camera 8 are used, only the load meter 3 or only the video camera 8 may be used. The measuring devices used in the test are not limited to the load meter and the video camera, and other devices (for example, strain gauges, etc.) may also be used.

[0018] FIG. 2 is a vertical cross-sectional view of the cover 6 and its vicinity in FIG. 1. As shown in FIG. 2, the cover 6 is, for example, a cylinder that opens in the vertical direction. The cover 6 has a lower opening 6a that opens the internal space downward and an upper opening 6b that opens the internal space upward. A gap is provided between the inner surface 5a of the guide 5 and the outer surface 6e of the cover 6. A gap is also provided between the inner surface 6d of the cover 6 and the outer surface of the falling object 10. A lubricant such as grease is applied to the interface between the cover 6 and the guide 5. A lubricant such as grease is also applied to the interface between the falling object 10 and the cover 6. Specifically, a lubricant is applied to the inner surface 6d and the outer surface 6e of the cover 6. Note that the lubricant may be applied partially or not at all.

[0019] In the ready-to-drop state, the falling object 10 is inserted into the cover 6 and the lower end of the cover 6 is inserted from above into the guiding space G of the guide 5. In the ready-to-drop state, the cover 6 and the falling object 10 are stationary, for example, by being held by the operator's hands. In the ready-to-drop state, the lower end of the falling object 10 is spaced a predetermined distance L above the lower opening 6a of the cover 6. Note that the lower part of the falling object 10 may protrude downward from the lower opening 6a of the cover 6.

[0020] FIG. 3 is a perspective view of the cover 6 of FIG. 2. As shown in FIG. 3, the cover 6 has a slit 6c extending upward from its lower end. In this embodiment, the slit 6c extends from the lower end to the upper end of the cover 6. That is, the cover 6 has a C-shaped horizontal cross section. Note that the slit 6c does not have to extend from the lower end to near the upper end of the cover 6 and reach the upper end of the cover 6. That is, the slit 6c only needs to be formed so that the lower opening 6a can expand due to elastic deformation of the cover 6. One end, i.e., the lower end, of the pair of stoppers 7 is connected to both sides of the slit 6c at the upper end of the cover 6.

[0021] FIG. 4 is a horizontal cross-sectional view of the cover 6 and its vicinity in FIG. 2. As shown in FIG. 4, the inner surface of the cover 6 is larger than the outer shape of the falling object 10 when viewed vertically. That is, the lower opening 6a of the cover 6 (see FIG. 2) is larger than the outer shape of the falling object 10 when viewed vertically. The inner surface 6d of the cover 6 does not overlap with the falling object 10 when viewed from below. The falling object 10 is not supported from below by the cover 6. The impact receiving plate 11 is arranged to encompass the guiding space G of the guide 5. That is, the impact receiving plate 11 is arranged to encompass the falling object 10 when viewed vertically. The impact receiving plate 11 has an area larger than that of the falling object 10 when viewed vertically. Note that the impact receiving plate 11 may have an area smaller than that of the falling object 10 when viewed vertically.

[0022] 5 is a vertical cross-sectional view of the impact receiving plate 11 in FIG. 1 and the vicinity thereof immediately before the falling object 10 collides with the impact receiving plate 11. As shown in FIG. 5, when the worker releases the falling object 10 and the cover 6 from the ready-to-drop state (see FIG. 2), the cover 6 together with the falling object 10 falls freely along the guide 5. That is, the inner surface 6d of the cover 6, which also falls freely, is present to the side of the falling object 10. Therefore, the falling object 10 does not come into direct contact with the inner surface 5a of the guide 5 during free fall. Then, when the lower end of the cover 6 reaches a specific position P that is a predetermined height H1 above the impact receiving plate 11, the stopper 7 stops the cover 6 from falling.

[0023] Specifically, the stopper 7 has a length that generates tension when the lower end of the cover 6 reaches the specific position P. As a result, the stopper 7 holds back the cover 6 when the lower end of the cover 6 reaches the specific position P, so that the cover 6 does not move downward beyond the specific position P toward the impact receiving plate 11. The falling object 10, which is falling freely, passes downward through the lower opening 6a of the cover 6 that has been prevented from falling, and moves toward the impact receiving plate 11.

[0024] The height H1 of the specific position P relative to the upper surface of the impact receiving plate 11 is greater than the maximum height dimension D of the falling object 10. The height H1 of the specific position P is less than the height H2 from the upper surface of the impact receiving plate 11 to the lower end of the guide 5. The specific position P is located above the shooting range of the video camera 8. The specific position P is set above the height at which the falling object 10 is expected to bounce upward after colliding with the impact receiving plate 11.

[0025] The specific position P may be set so that the upper end of the cover 6 is positioned in the guide space G of the guide 5 when the lower end of the cover 6 reaches the specific position P. This allows the cover 6 to be easily guided upward through the guide space G when the stopper 7 is rolled up and the cover 6 is pulled upward for the next test. Note that if the lower part of the guide space G of the guide 5 is shaped to expand horizontally, the specific position P may be set so that the lower end of the cover 6 is positioned in the guide space G of the guide 5 when the lower end of the cover 6 reaches the specific position P. In other words, the specific position P may be set so that at least the upper end of the cover 6 is positioned in the guide space G of the guide 5 when the lower end of the cover 6 reaches the specific position P.

[0026] The stoppers 7 apply an external force to the cover 6 so that the lower opening 6a expands horizontally when the lower end of the cover 6 reaches the specific position P. Specifically, the lower ends, which are one end of the pair of stoppers 7, are connected to both sides of the slit 6c at the upper end of the cover 6, and therefore the tension of the pair of stoppers 7 acts on the upper end of the cover 6, generating a load that expands the lower part of the slit 6c horizontally. This expands the lower opening 6a of the flexible cover 6, making it less likely that a falling object 10 will come into contact with the cover 6 when passing downward through the lower opening 6a.

[0027] In this embodiment, when the lower end of the cover 6 reaches the specific position P, the pair of stoppers 7 extend in directions that approach each other as they extend upward. Note that when the lower end of the cover 6 reaches the specific position P, the pair of stoppers 7 may extend upward in parallel.

[0028] The falling object 10 passes downward through the lower opening 6a of the cover 6, which has been prevented from falling, and collides from above with the impact receiving plate 11. The load meter 3 measures the load received by the impact receiving plate 11 from the falling object 10. The video camera 8 captures images of the behavior of the falling object 10 colliding with the impact receiving plate 11.

[0029] According to the configuration described above, the cover 6 free falls together with the falling object 10, and the falling object 10 free falls independently of the cover 6. Therefore, even if the falling object 10 comes into contact with the cover 6 during free fall, vertical resistance is unlikely to occur to the falling object 10, and a free fall that matches a real phenomenon can be reproduced. Therefore, the free fall impact test device 1 can perform a drop impact test that matches a real phenomenon and has high reproducibility.

[0030] The lower opening 6a of the cover 6 is larger than the falling object 10, and the impact receiving plate 11 has an area larger than the falling object 10. Therefore, compared to when the impact receiving plate 11 has an area smaller than the falling object 10, a collision behavior that matches the actual phenomenon can be reproduced.

[0031] When the lower end of the cover 6 that has fallen together with the falling object 10 reaches a specific position P that is a predetermined height H above the impact receiving plate 11, the stopper 7 prevents the cover 6 from falling. Therefore, when the falling object 10 collides with the impact receiving plate 11, the falling object 10 is not surrounded by the cover 6. This makes it easier to reproduce a collision behavior that matches the actual phenomenon, and also makes it easier to visually confirm the collision behavior of the falling object 10.

[0032] The stopper 7 applies an external force to the cover 6 so that the lower opening 6a widens when the lower end of the cover 6 reaches the specific position P. Therefore, the cover 6 is less likely to come into contact with the falling object 10 just before the falling object 10 collides with the impact receiving plate 11, and the collision posture of the falling object 10 can be stabilized.

[0033] The pair of stoppers 7 has a length that generates tension when the lower end of the cover 6 reaches the specific position P. Therefore, when the lower end of the cover 6 reaches the specific position P, both sides of the slit 6c at the upper end of the cover 6 are pulled upward, widening the lower opening 6a of the cover 6. Therefore, the cover 6 is less likely to come into contact with the falling object 10 just before the falling object 10 collides with the impact receiving plate 11, and the impact posture of the falling object 10 can be stabilized.

[0034] A lubricant is applied to the interface between the cover 6 and the guide 5. Therefore, even if the cover 6 comes into contact with the guide 5 during falling, vertical resistance is unlikely to occur on the cover 6, so a decrease in the falling speed of the cover 6 is suppressed, and a relative speed difference is unlikely to occur between the falling object 10 and the cover 6. Therefore, even if the falling object 10 comes into contact with the cover 6 during falling, vertical resistance is unlikely to occur on the falling object 10, and a free fall that matches the actual phenomenon can be reproduced.

[0035] A lubricant is also applied to the interface between the falling object 10 and the cover 6. Therefore, even if the falling object 10 comes into contact with the cover 6 during falling, vertical resistance is unlikely to occur in the falling object 10, so a decrease in the falling speed of the falling object 10 is suppressed, and a free fall that matches the actual phenomenon can be reproduced.

[0036] The guide 5 is not limited to a pipe, but may be anything that can guide the cover 6 so as to maintain its posture as it falls freely. For example, the guide 5 may be a plurality of vertical rods that are horizontally distributed so as to surround the path of the cover 6 as it falls freely, with some play. The guide 5 may also be a vertical rail that guides the cover 6 downward with some play. The cover 6 may also be a cylindrical shape with a closed bottom and an upper opening 6b that is closed.

[0037] (Second embodiment) 6 is a vertical cross-sectional view corresponding to FIG. 5 of a free-fall impact testing apparatus 101 according to a second embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted. As shown in FIG. 6, the free-fall impact testing apparatus 101 of the second embodiment differs from that of the first embodiment in the stopper 107. The stopper 107 closes the outer periphery of the guide space G from below at the lower end of the guide space G of the guide 5.

[0038] The stopper 107 protrudes inward from the inner surface 5a of the guide 5 when viewed vertically. The stopper 107 protrudes inward from the outer surface 106e of the cover 106 when viewed vertically. The stopper 107 has a passage hole H that communicates with the guide space G of the guide 5. The passage hole H of the stopper 107 is smaller than the horizontal cross section of the guide space G of the guide 5. The cover 106 is cylindrical, but does not have the slit 6c (see Figure 3) of the first embodiment. However, the cover 106 may have the slit 6c.

[0039] When the lower end of the cover 106 reaches a specific position P above the impact receiving plate 11, the cover 106 is received from below by a stopper 107, which prevents the cover 106 from falling. The freely falling falling object 10 passes downward through the lower opening 106a of the cover 106, which has been prevented from falling, and heads toward the impact receiving plate 11. This configuration also makes it possible to carry out a drop impact test with high reproducibility that matches actual phenomena. Note that the other configurations are the same as those of the first embodiment described above, so a description thereof will be omitted.

[0040] (Third embodiment) 7 is a vertical cross-sectional view corresponding to FIG. 5 of a free-fall impact testing apparatus 201 according to a third embodiment. Note that the same reference numerals are used to designate components common to the first embodiment, and descriptions thereof will be omitted. As shown in FIG. 7, the free-fall impact testing apparatus 201 according to the third embodiment is provided with a stopper 207 and a tapered wall 220. The stopper 207 is disposed between the guide 5 and the impact receiving plate 11. The stopper 207 prevents the cover 6 from falling when the lower end of the cover 6 reaches a specific position P that is a predetermined height H3 above the impact receiving plate 11.

[0041] The tapered wall 220 protrudes above the impact bearing plate 11. Specifically, the tapered wall 220 protrudes upward from the inner end of the stopper 207. The tapered wall 220 has a shape that widens horizontally from top to bottom. The tapered wall 220 may be, for example, a truncated cone shape. The upper end of the tapered wall 220 is located inward from the inner surface 5a of the guide 5 when viewed vertically. The upper end of the tapered wall 220 protrudes inward from the inner surface 6d of the cover 6 when viewed vertically.

[0042] The cover 6, which has fallen freely together with the falling object 10 and passed downward through the guide 5, has its inner surface 6d guided horizontally outward by the tapered wall 220, widening the lower opening 6a of the cover 6. The cover 6, with its lower opening 6a widened, is then received by the stopper 207. The falling object 10, which has passed downward through the lower opening 6a of the cover 6 and whose fall has been prevented, collides with the impact receiving plate 11 from above. This configuration also makes it possible to carry out a drop impact test with high reproducibility that matches actual phenomena. Note that the other configurations are the same as those of the first or second embodiment described above, and therefore a description thereof will be omitted.

[0043] (Fourth embodiment) FIG. 8 is a vertical cross-sectional view corresponding to FIG. 5 of a free-fall impact testing apparatus 301 according to a fourth embodiment. As shown in FIG. 8, the free-fall impact testing apparatus 301 according to the fourth embodiment does not have a stopper above the impact receiving plate 11 to prevent the cover 306 from falling. The cover 306 is a combination of a pair of separable cover halves 306a and 306b. Each of the cover halves 306a and 306b is a semi-cylinder, and the cover 306 as a whole has a substantially cylindrical shape. That is, the cover 306 has a pair of slits 306c extending from the lower end to the upper end of the cover 306.

[0044] A tapered wall 320 protrudes upward above the impact bearing plate 11. The tapered wall 320 protrudes upward from, for example, the base 2. The tapered wall 320 has a shape that widens horizontally from top to bottom. The tapered wall 320 may have, for example, a truncated cone shape. The upper end of the tapered wall 320 is located inward from the inner surface of the guide 5 (see FIG. 7) when viewed vertically. The upper end of the tapered wall 320 protrudes inward from the inner surface of the cover 306 when viewed vertically.

[0045] The cover 306, which falls freely together with the falling object 10, has its inner surface guided horizontally outward by the tapered wall 320, causing the pair of cover halves 306a, 306b to move horizontally away from each other. Therefore, the falling object 10 that strikes the impact receiving plate 11 from above is unlikely to come into contact with the cover 306. This configuration also makes it possible to carry out a drop impact test with high reproducibility that matches actual phenomena. Note that the other configurations are the same as those of any of the first to third embodiments described above, and therefore a description thereof will be omitted.

[0046] As described above, the above-described embodiments have been described as examples of the technology disclosed in this application. However, the technology of the present disclosure is not limited to these embodiments and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, the components described in the above-described embodiments can be combined to create new embodiments. For example, some configurations or methods in one embodiment may be applied to other embodiments, and some configurations in one embodiment may be separated from other configurations in that embodiment and extracted as desired. Furthermore, the components described in the accompanying drawings and detailed description include not only components essential for solving the problem, but also components that are not essential for solving the problem, and are used to illustrate the technology. [Explanation of symbols]

[0047] 1,101,201,301 Free fall impact test equipment 5 Guide 6,106,306 covers 6a,106a Lower opening 6c,306c slit 7,107,207 Stopper 10 Falling Objects 11 Impact receiving plate 15 Components 220,320 Tapered wall P Specific position

Claims

1. A free-fall impact test device used in a test in which a falling object is allowed to freely fall and collide with an impact receiving plate, a cover that surrounds the falling object from the horizontal outside so as to be spaced apart from the falling object; a guide that guides the cover, which falls freely together with the falling object, in a vertical direction; and at least one stopper that prevents the cover from falling when a lower end of the cover that has fallen together with the falling object reaches a specific position that is a predetermined height above the impact receiving plate, the cover has a lower opening that is larger than the fallen object when viewed in the vertical direction, and a slit that extends upward from the lower end, The at least one stopper applies an external force to the cover so as to widen the lower opening when the lower end of the cover reaches the specific position.

2. the at least one stopper includes a pair of stoppers; the pair of stoppers have one end connected to portions on both sides of the slit at the upper end of the cover, and the other end fixed to a member located above the upper end of the cover at the specific position, 2. The free-fall impact testing device according to claim 1, wherein the pair of stoppers have a length that generates tension when the bottom end of the cover reaches the specific position.

3. A free-fall impact test device used in a test in which a falling object is allowed to fall freely and collide with an impact receiving plate, a cover that surrounds the falling object from the horizontal outside so as to be spaced apart from the falling object; a guide that guides the cover, which falls freely together with the falling object, in a vertical direction; a tapered wall protruding above the impact receiving plate; The cover has a lower opening that is larger than the fallen object when viewed vertically, and a slit that extends upward from the lower end of the lower opening, The tapered wall guides the inner surface of the cover so that the lower opening widens before the object that falls together with the cover collides with the impact receiving plate.

4. The free-fall impact testing device according to claim 1 , further comprising a lubricant applied to an interface between the cover and the guide.

5. The free-fall impact testing device according to claim 1 , further comprising a lubricant applied to an interface between the fallen object and the cover.

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