Device for testing fluidity of concrete
The concrete flowability testing device, which uses an automated screw, moving plate, and worm gear structure, solves the problems of requiring two people to operate and difficulty in ensuring verticality in existing technologies. It enables single-person operation, good sealing, and vertical lifting, thus reducing test errors.
Patent Information
- Application Number
- CN202511451290.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-11
- Publication Date
- 2026-02-17
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing concrete fluidity testing devices require two operators, which leads to problems such as inadequate compaction, material leakage, and difficulty in ensuring verticality, resulting in large errors in test results.
An automated testing device comprising a lead screw, a moving plate, a motor, and a tamping rod was designed. Through a worm gear self-locking and a return spring ball structure, it enables single-person operation, good sealing, and vertical lifting of the slump cylinder, thus avoiding errors.
It achieves full automation of concrete fluidity testing, saving manpower, preventing material leakage, ensuring verticality, and reducing test errors.
Smart Images
Figure CN121540876A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of concrete testing technology, specifically to a device for testing the fluidity of concrete. Background Technology
[0002] Concrete fluidity is a key parameter in the construction materials field, characterizing the workability of fresh concrete. It refers to its ability to flow and uniformly fill formwork under its own weight or mechanical vibration. Various devices have been developed worldwide for testing concrete fluidity, such as slump cones, flowability testers, remodeling testers, the German flowability test bench, the Kelly ball pressure tester, and the Nash K-probe. Currently, the slump cone test is the most common method for testing concrete fluidity.
[0003] Using existing slump cones to test the flowability of concrete mixtures presents several inconveniences. Firstly, at least two people are required to complete the test: one person holds the slump cone in place by stepping on the foot pedals, while the other loads the concrete. Secondly, the slump cone is not always properly compacted by foot pressure, allowing concrete to leak through gaps. Thirdly, maintaining verticality during the lifting of the slump cone is often difficult, causing the concrete sample to tilt due to lateral and torsional forces during descent, thus introducing errors into the test results. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a device for testing the fluidity of concrete, so as to solve the above-mentioned problems.
[0005] The objective of this invention is achieved through the following technical solution: a device for testing the fluidity of concrete, comprising a test plate, at least two lead screws rotatably mounted on the test plate, a movable plate threaded onto the at least two lead screws, a slump cylinder mounted on the movable plate, a feed hopper detachably mounted on the slump cylinder, a hollow top plate rotatably mounted on the upper end of the at least two lead screws, a tamping rod positioned opposite the slump cylinder and reciprocating towards and away from the slump cylinder between the hollow top plate and the slump cylinder, a first gear for driving the lead screws to rotate, a third sprocket for driving the tamping rod to reciprocate towards and away from the slump cylinder, and a first transmission rod for driving the first gear and the third sprocket to rotate, and a motor for driving the first transmission rod to move on the hollow top plate.
[0006] The first gear is fixedly sleeved on the first transmission rod. A worm gear connected to the lead screw is rotatably arranged inside the hollow top plate. A worm is meshed on one side of the worm gear, and at least two worms are connected to the first gear for transmission.
[0007] A limiting hollow column is fixedly installed on the side of the hollow top plate near the test plate, and the limiting hollow column is rotatably sleeved on the lead screw.
[0008] The first gear has a second gear meshing on both sides. A second transmission rod is provided on the second gear. A first sprocket is fixedly sleeved on the second transmission rod. The first sprocket is connected to the second sprocket via a first chain. A connecting rod is provided on the second sprocket. The worm gear is sleeved on the connecting rod. The outer wall of the connecting rod is provided with multiple sets of first notches along its extension direction. Each set of first notches consists of multiple first notches evenly distributed in a ring with the center of the connecting rod as the center. The inner wall of the worm gear is provided with multiple reset ports that match the positions of the notches. Each reset port is provided with a first reset spring that matches the number and position of the first notches. The end of the first reset spring abuts against a first ball, and the first ball is located inside the first notch.
[0009] It also includes a turntable, a partition plate is provided between the hollow top plate and the slump cylinder, the tamping rod is slidably inserted through the partition plate, a base is provided at one end of the tamping rod near the hollow top plate, a sliding opening is provided on the base, a guide post is provided at the eccentric part of the turntable, the guide post is slidably installed at the sliding opening, and the third sprocket is connected to the turntable for transmission.
[0010] The third sprocket is connected to the fourth sprocket via the second chain drive. The fourth sprocket is connected to the first bevel gear, which meshes with the second bevel gear. The second bevel gear is connected to the fifth sprocket on one side. The fifth sprocket is connected to the sixth sprocket via the third chain drive. The sixth sprocket is rotatably mounted on the support column and connected to the center of the turntable.
[0011] The first transmission rod includes a mother rod rotatably mounted on the inner wall of a hollow top plate and a daughter rod slidably passing through the end of the mother rod. The daughter rod and the mother rod are connected by a spline. The first gear is fixedly sleeved on the mother rod. The daughter rod is threadedly sleeved with a nut. A connecting plate is provided inside the hollow top plate. The nut is rotatably passed through the connecting plate. The third sprocket is located on the side of the nut away from the first gear and is positioned opposite the nut. The nut is elastically engaged with the connecting plate. A snap-fit connector is provided at the end of the daughter rod. A snap-fit interface is provided at the center of the third sprocket, which is detachably engaged with the snap-fit connector.
[0012] The outer wall of the nut has an annular groove, and the inner wall of the annular groove has multiple second recesses. The inner wall of the connecting plate is slidably provided with a sliding rod that matches the position and number of the second recesses one by one. A second ball is movably provided at the end of the sliding rod, and a second return spring is sleeved on the sliding rod. The two ends of the second return spring abut against the second ball and the inner wall of the connecting plate, respectively.
[0013] The diameter of the tamping rod is smaller than the diameter of the small opening at the upper end of the slump cone.
[0014] The beneficial effects of this invention are: (1) By setting screws, moving plates, motors and tamping rods, the present invention realizes the full automation of concrete flowability testing. Only one person is needed to add concrete into the slump bucket, which greatly saves manpower. In addition, during the process of pouring concrete, the slump bucket is tightly sealed to prevent concrete from leaking out from the gaps. Finally, during the process of lifting the slump bucket, it is ensured that it is lifted vertically to avoid errors in the test results.
[0015] (2) By setting up a worm wheel and a worm, the present invention ensures that the lead screw will not rotate spontaneously by using the special self-locking properties of the worm wheel and the worm.
[0016] (3) By setting components such as the first reset spring and the first ball, the connecting rod and the worm gear disengage when the moving plate moves to the limit position, thereby preventing the first gear from continuing to output power to the lead screw while it continues to rotate; and if multiple lead screws wear to different degrees after prolonged use, resulting in different movement distances at each point of the moving plate when rotating one revolution, causing misalignment and jamming, the first reset spring, the first ball and other components can balance the rotation of the lead screws at each point, ensuring that the moving plate moves straight up and down and will not jam.
[0017] (4) By setting components such as a nut, a second return spring, and a second ball, when the motor rotates forward, when the first transmission rod is not connected to the third sprocket, the first transmission rod extends along its extension direction. When the first transmission rod is connected to the third sprocket, the third sprocket is fixed in position and will not move with the extension of the first transmission rod. At this time, the rotation of the first transmission rod drives the third sprocket to rotate and the nut disengages from the connecting plate and rotates with the first transmission rod. When the motor rotates in reverse, the first transmission rod shortens along its extension direction and separates from the third sprocket, no longer driving the third sprocket to rotate. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the present invention; Figure 2 This is a schematic diagram of the sixth sprocket connection of the present invention; Figure 3 This is a schematic diagram of the interior of the hollow roof slab; Figure 4 This is a schematic diagram of a nut connection. Figure 5 This is a cross-sectional view of the first reset spring connection; Figure 6 This is a cross-sectional view of the second reset spring connection; In the diagram, 1. Test plate; 2. Lead screw; 3. Moving plate; 4. Slump cone; 5. Feed hopper; 6. Hollow top plate; 7. Tamping rod; 8. First gear; 9. Third sprocket; 10. First transmission rod; 11. Motor; 12. Limiting hollow column; 13. Worm gear; 14. Worm; 15. Second transmission rod; 16. First sprocket; 17. First chain; 18. Second sprocket; 19. Connecting rod; 20. First notch assembly; 21. First notch; 22. Reset port; 23. First reset spring; 24. First rolling ball. ; 25. Support column; 26. Turntable; 27. Divider plate; 28. Base; 29. Slide opening; 30. Guide column; 31. Second chain; 32. Fourth sprocket; 33. First bevel gear; 34. Second bevel gear; 35. Fifth sprocket; 36. Third chain; 37. Sixth sprocket; 38. Mother rod; 39. Daughter rod; 40. Nut; 41. Connecting plate; 42. Snap connector; 43. Second gear; 44. Annular groove; 45. Second notch; 46. Slide rod; 47. Second ball; 48. Second return spring. Detailed Implementation
[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0020] An apparatus for testing the fluidity of concrete, reference Figure 1 and Figure 2 The system includes a test plate 1 and a hollow top plate 6 arranged parallel to each other. Screws 2 are rotatably mounted at four right angles between the test plate 1 and the hollow top plate 6. A movable plate 3 is threadedly connected to each of the four screws 2. The movable plate 3 is parallel to the test plate 1 and the hollow top plate 6. A slump cone 4, 300 mm high, is fixedly inserted through the center of the movable plate 3. A feed hopper 5 is detachably mounted at the upper opening of the slump cone 4. A support column 25 is mounted on the lower side of the hollow top plate 6. A turntable 26 is rotatably mounted on the front side of the support column 25, and a sixth sprocket 37 is rotatably mounted on the rear side. The center of the sixth sprocket 37 is connected to the turntable 26.
[0021] Hollow limiting columns 12 are installed at the four right angles on the lower side of the hollow top plate 6. The limiting hollow columns 12 are rotatably sleeved on the screw rod 2. The limiting hollow columns 12 and the hollow top plate 6 above them do not rotate synchronously with the screw rod 2. The screw rod 2 is used to support the hollow top plate 6. When the moving plate 3 abuts against the limiting hollow columns 12, the slump cylinder 4 moves upward 300 mm from its lowest position. That is, the maximum distance that the moving plate 3 can move through the screw rod 2 is 300 mm.
[0022] A partition plate 27 is connected to each of the four limiting hollow columns 12 to ensure structural stability. A tamping rod 7 is slidably inserted through the center of the partition plate 27, restricting its movement to vertical motion via openings in the partition plate 27. The tamping rod 7 is connected to the slump cone 4. A base 28 is located at the upper end of the tamping rod 7, with a sliding opening 29 extending from left to right. A guide post 30 is eccentrically positioned on the turntable 26, slidably mounted at the sliding opening 29. A motor 11 is installed at the center of the upper side of the hollow top plate 6. The motor 11 drives the turntable to rotate, causing the eccentrically positioned guide post 30 to slide within the slider 29, thereby driving the tamping rod 7, integrated with the base 28, to reciprocate vertically, thus vibrating the aggregate within the slump cone 4. The diameter of the tamping rod is smaller than the diameter of the small opening at the upper end of the slump cone.
[0023] refer to Figures 3-6 A first transmission rod 10 is rotatably mounted at the center of the hollow top plate 6. The first transmission rod 10 includes a mother rod 38 whose upper end is rotatably connected to the upper inner wall of the hollow top plate 6 and to the output end of the motor 11. A daughter rod 39 is slidably mounted on the lower end of the mother rod 38. The daughter rod 39 is connected to the mother rod 38 via a spline. Rotation of the mother rod 38 can drive the daughter rod 39 to rotate, and the daughter rod 39 can slide up and down within the mother rod 38. A first gear 8 is fixedly sleeved on the mother rod 38 and rotates synchronously with the mother rod 38.
[0024] The first gear 8 has a second gear 43 meshing on both sides. The second gear 43 is provided with a second transmission rod 15. The hollow top plate 6 has a worm gear 13 that is rotatably connected to the lead screw 2 in terms of position and quantity. The worm gear 13 has a worm 14 meshing on one side. The worm 14 is rotatably sleeved on the connecting rod 19. The connecting rod 19 is rotatably set on the inner wall of the hollow top plate 6. The end of the connecting rod 19 is provided with a second sprocket 18. The second transmission rod 15 has a first sprocket 16 that matches the second sprocket 18. The first sprocket 16 and the second sprocket 18 are connected by a first chain 17.
[0025] Multiple sets of first recesses 20 are formed on the outer wall of the connecting rod 19 along its extension direction. Each set of first recesses 20 includes multiple first recesses 21 evenly distributed in a ring around the connecting rod 19. Multiple reset ports 22 are formed on the inner wall of the worm gear 14, which are matched one-to-one with the first recesses 21. A first reset spring 23 is provided in the reset port 22. The end of the first reset spring 23 abuts against a first ball 24. Part of the first ball 24 is located in the first recess 21 and abuts against the inner wall of the first recess 21.
[0026] When the connecting rod 19 is rotating, the worm gear 14 rotates synchronously, driving the turbine 13 and the lead screw 2 to rotate, which in turn drives the moving plate 3 to move up and down.
[0027] like Figure 1 As shown, when the moving plate 3 moves downward, its lowest point is restricted by the frustum-shaped slump cylinder 4. As the moving plate presses down, it presses the slump cylinder 4 tightly onto the test plate 1, ensuring a seal between the slump cylinder 4 and the test plate 1 and preventing the aggregate inside the slump cylinder 4 from flowing out, thus providing a certain sealing effect. When the moving plate 3 moves upward, its highest point is abutted by the limiting hollow column 12.
[0028] When the movable plate 3 is moved to either the highest or lowest point, it will be restricted. When it reaches its limit and can no longer move, the motor 11 continues to rotate, while the lead screw 2 and worm gear 13 stop rotating. Simultaneously, the worm gear 14 also stops rotating. At this point, because the worm gear 14 and the connecting rod 19 are engaged by the first ball bearing 24 and the first spring 23, the force of rotation of the connecting rod 19 is greater than the force of the first spring 23 pressing the first ball bearing 24 against the connecting rod 19. This allows the connecting rod 19 to continue rotating without affecting the worm gear 14. During the normal rotation of the lead screw 2, the first spring 23 presses the first ball bearing 24 against the connecting rod 19. The resulting friction allows the worm gear 14 and the connecting rod 19 to be considered as a single unit. The rotation of the connecting rod 19 will drive the worm gear 14 to rotate, which in turn drives the lead screw 2 to rotate, thus raising and lowering the movable plate 3.
[0029] A connecting plate 41 extending to the left and right is provided inside the hollow top plate 6. A nut 40 is fitted at the center of the connecting plate 41. A third sprocket 9 is rotatably mounted on the bottom wall of the hollow top plate 6. The first transmission rod 10, the nut 40 and the third sprocket 9 are aligned on the same straight line from top to bottom. The third sprocket 9 is connected to a fourth sprocket 32 via a second chain 31. The fourth sprocket 32 is connected to a first bevel gear 33. A second bevel gear 34 meshes with one side of the first bevel gear 33. The second bevel gear 34 is connected to a fifth sprocket 35. The fifth sprocket 35 is connected to a sixth sprocket 37 via a third chain 36. The nut 40 is threaded and rotated on the sub-rod 39. A snap-fit connector 42 is provided at the end of the sub-rod 39. A snap-fit interface is provided at the center of the third sprocket 9 that can be detachably snapped into the snap-fit connector 42. When the snap-fit connector 42 is snapped into the snap-fit interface, the third sprocket 9 rotates with the sub-rod 39.
[0030] like Figure 4As shown, the nut 40 has an I-shaped cross-section. The upper and lower ends of the nut 40 are located on the outside of the connecting plate 41 to prevent the nut 40 from being pulled out of the connecting plate 41. An annular groove 44 is provided on the outer wall of the nut 40. Multiple second recesses 45 are evenly provided on the inner side wall of the annular groove 44 with their centers as the center. A sliding rod 46 is slidably passed through the inner side wall of the annular groove 44, which corresponds to the number and position of the second recesses 45. A second ball 47 is movably provided at the end of the sliding rod 46. The second ball 47 is located in the second recess 45. A second return spring 48 is sleeved on the sliding rod 46. The two ends of the second return spring 48 abut against the second ball 47 and the inner wall of the second recess 45, respectively.
[0031] The sub-rod 39 is threadedly connected to the nut 40. As the sub-rod 39 continues to rotate with the main rod 38, it will continuously rotate downwards or upwards through the thread action of the nut 40. The second return spring 48 keeps pressing the second ball 47 against the inner wall of the second recess 45 of the nut 40. The spring generates friction between the second ball 47 and the nut, so that the nut 40 will not rotate synchronously with the sub-rod 39 as it rotates out. This continues until the sub-rod 39 rotates out to its maximum extent and engages with the third sprocket 9, causing the third sprocket 9 to rotate synchronously. The force of the sub-rod 39 continuing to rotate overcomes the friction, causing the nut 40 to rotate synchronously.
[0032] Motor 11 rotates forward, driving the first transmission rod 10 to rotate, which in turn drives the four lead screws 2 to rotate, causing the moving plate 3 to move downward to the lowest point. When the moving plate 3 reaches the lowest position, the connecting rod 19 disengages from the worm gear 14, and the first transmission rod 10 continues to rotate. Since the sub-rod 39 is threadedly connected to the nut 40, as the sub-rod 39 continues to rotate with the main rod 38, it will continuously unscrew downward through the threaded action of the nut 40. At this point, the sub-rod 39 slides downward until it connects with the third sprocket 9. During this process, the operator can continuously add concrete into the slump cylinder 4. Because the sub-rod 39 is connected to the third sprocket 9, it cannot move further downward after unscrewing to the lowest point. At this point, the sub-rod 39 continues to rotate, and the nut 40 disengages from the connecting plate 41 and rotates with the sub-rod 39. The rotation of the third sprocket 9 drives the tamping rod 7 to reciprocate up and down, thereby tamping the concrete in the slump cylinder 4. After the concrete has been loaded, stop motor 11, remove the feed hopper 5, and remove excess concrete from the slump cylinder 4. Then, motor 11 reverses direction, causing the sub-rod 39 to move upwards and separate from the third sprocket 9. Under the reset action of the second spring 47, the second ball bearing 47 presses against the nut 40, allowing the sub-rod 39 to unscrew smoothly. As the first transmission rod 10 continues to rotate, the connecting rod 9 re-drives the worm gear to rotate, thereby causing the moving plate 3 to move horizontally upwards. When the moving plate 3 reaches its limit position, lift the slump cylinder 4. The internal concrete then flows naturally. The flowability of the concrete is then measured by measuring the difference between the surface of the test plate 1 and the slumped concrete at its highest point.
[0033] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above description or related technical or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.
Claims
1. An apparatus for testing the fluidity of concrete, characterized in that, The test plate (1) is rotatably mounted with at least two lead screws (2). A movable plate (3) is threaded onto the at least two lead screws (2). A slump cylinder (4) is mounted on the movable plate (3). A feed hopper (5) is detachably mounted on the slump cylinder (4). A hollow top plate (6) is rotatably mounted on the upper end of the at least two lead screws (2). A space is provided between the hollow top plate (6) and the slump cylinder (4) with the space positioned opposite to the slump cylinder (4). A tamping rod (7) that moves back and forth towards and away from the slump cylinder (4) is provided inside the hollow top plate (6). A first gear (8) is provided to drive the screw (2) to rotate, a third sprocket (9) is provided to drive the tamping rod (7) to move back and forth towards and away from the slump cylinder (4), and a first transmission rod (10) is provided to drive the first gear (8) and the third sprocket (9) to rotate. A motor (11) is provided on the hollow top plate (6) to drive the first transmission rod (10) to move.
2. The apparatus for testing the fluidity of concrete according to claim 1, characterized in that: The hollow top plate (6) is fixedly provided with a limiting hollow column (12) on the side near the test plate (1), and the limiting hollow column (12) is rotatably sleeved on the screw (2).
3. The apparatus for testing the fluidity of concrete according to claim 1, characterized in that: The first gear (8) is fixedly sleeved on the first transmission rod (10). A worm wheel (13) connected to the lead screw (2) is rotatably arranged inside the hollow top plate (6). A worm (14) is meshed on one side of the worm wheel (13). At least two worms (14) are connected to the first gear (8) in a transmission.
4. The apparatus for testing the fluidity of concrete according to claim 3, characterized in that: The first gear (8) is meshed with the second gear (43) on both sides. The second gear (43) is provided with the second transmission rod (15). The second transmission rod (15) is fixedly sleeved with the first sprocket (16). The first sprocket (16) is connected to the second sprocket (18) through the first chain (17). The second sprocket (18) is provided with the connecting rod (19). The worm gear (14) is sleeved on the connecting rod (19).
5. The apparatus for testing the fluidity of concrete according to claim 4, characterized in that: The outer wall of the connecting rod (19) has multiple sets of first recesses (20) along its extension direction. The first recesses (20) consist of multiple first recesses (21) evenly distributed in a ring with the center of the connecting rod (19) as the center. The inner wall of the worm (14) has multiple reset ports (22) that match the positions of the first recesses (21). The reset ports (22) are provided with first reset springs (23) that match the number and position of the first recesses (21). The end of the first reset spring (23) abuts against a first ball (24). The first ball (24) is partially located in the first recess (21).
6. The apparatus for testing the fluidity of concrete according to claim 1, characterized in that: It also includes a support column (25) set on the hollow top plate (6), a turntable (26) is rotatably set on the support column (25), a partition plate (27) is set between the hollow top plate (6) and the slump cylinder (4), the tamping rod (7) is slidably set through the partition plate (27), a base (28) is set on one end of the tamping rod (27) near the hollow top plate (6), a sliding opening (29) is opened on the base (28), a guide column (30) is set at the eccentric part of the turntable (26), the guide column (30) is slidably installed at the sliding opening (29), and the third sprocket (9) is connected to the turntable (26) for transmission.
7. The apparatus for testing the fluidity of concrete according to claim 6, characterized in that: The third sprocket (9) is connected to the fourth sprocket (32) via the second chain (31). The fourth sprocket (32) is connected to the first bevel gear (33), which meshes with the second bevel gear (34). The second bevel gear (34) is connected to the fifth sprocket (35) on one side. The fifth sprocket (35) is connected to the sixth sprocket (37) via the third chain (36). The sixth sprocket (37) is rotatably mounted on the support column (25) and connected to the center of the turntable (26).
8. The apparatus for testing the fluidity of concrete according to claim 1, characterized in that: The first transmission rod (10) includes a mother rod (38) rotatably mounted on the inner wall of the hollow top plate (6) and a daughter rod (39) slidably passing through the end of the mother rod (38). The daughter rod (39) is connected to the mother rod (38) by a spline. The first gear (8) is fixedly sleeved on the mother rod (38). The daughter rod (39) is threadedly fitted with a nut (40). A connecting plate (41) is provided inside the hollow top plate (6). The nut (40) rotatably passes through the connecting plate. On the connecting plate (41), the third sprocket (9) is located on the side of the nut (40) away from the first gear (8) and is opposite to the nut (40). The nut (40) is elastically engaged with the connecting plate (41). The end of the sub-rod (39) is provided with a snap-fit connector (42). The center of the third sprocket (9) is provided with a snap-fit interface that can be detachably snap-fitted with the snap-fit connector (42). The third sprocket (9) rotates synchronously with the sub-rod through the snap-fit connector (42) and the snap-fit interface.
9. The apparatus for testing the fluidity of concrete according to claim 8, characterized in that: The outer wall of the nut (40) is provided with an annular groove (44), and the inner wall of the annular groove (44) is provided with a plurality of second recesses (45). The inner wall of the connecting plate (41) is slidably provided with a slide rod (46) that matches the position and number of the second recesses (45). A second ball (47) is movably provided at the end of the slide rod (46), and a second return spring (48) is sleeved on the slide rod (46). The two ends of the second return spring (48) abut against the second ball (47) and the inner wall of the connecting plate (41) respectively.
10. The apparatus for testing the fluidity of concrete according to claim 1, characterized in that: The diameter of the tamping rod (27) is smaller than the diameter of the small opening at the upper end of the slump cylinder (4).