A rebound hammer calibration device

Abstract

The present invention relates to a rebound hammer calibration device, comprising a device support, on which a calibration pendulum is rotatably mounted. The calibration pendulum has a pendulum impact portion for being impacted by the rebound hammer, the rotation axis of the calibration pendulum passes through the center of gravity of the calibration pendulum, a pendulum spring is disposed between the calibration pendulum and the device support, and a spring compression adjustment structure is connected to the pendulum spring. The rebound hammer calibration device also includes an angle measurement structure for measuring the swing angle of the pendulum. The present invention provides a rebound hammer calibration device that can achieve rebound hammer calibration without disassembling the rebound hammer.

Description

Technical Field

[0001] The invention relates to a rebound hammer calibration device in the field of calibration and verification. Background Art

[0002] The concrete rebound test uses a spring-driven hammer that strikes the concrete surface through a rod. The concrete surface elastically deforms, absorbing energy, and the hammer rebounds. The energy loss is used to characterize the concrete's hardness. The principle is that the harder the concrete, the less energy it absorbs through elastic deformation, and thus the less energy is lost during the hammer's impact.

[0003] The working process of concrete rebound test hammer is as follows Figure 1 As shown, in order to clearly illustrate the problem, the first state, the second state, the third state, the fourth state and the fifth state occur in chronological order. During operation, the height of the impact hammer 16 is first raised, as shown in the first state, the impact hammer spring 15 stores energy, and the end of the impact rod 2 away from the impact hammer contacts the concrete surface. Subsequently, the impact hammer 16 is released, and the impact hammer moves toward the impact rod under the guidance of the guide rod 19, as shown in the second state; then, the lower end surface 18 of the impact hammer hits the impact rod 2, and the impact rod hits the concrete, as shown in the third state; then, as shown in the fourth state, the impact hammer begins to rebound away from the impact rod; finally, as shown in the fifth state, the impact hammer reaches the highest rebound position.

[0004] In the prior art, the energy loss of the rebound hammer is characterized by the following measurement method, that is, measuring the height difference between the rebound hammer in the first state and the fifth state. The rebound hammer can record the position difference of the rebound hammer before and after the impact, and calculate the rebound value through the change in energy between the two states. The difference between the sum of the gravitational potential energy of the rebound hammer in the first state and the elastic potential energy of the spring in the first state and the sum of the gravitational potential energy of the rebound hammer in the fifth state and the elastic potential energy of the spring in the fifth state is the change in energy between the two states. It can be seen that the accuracy of the rebound hammer mainly depends on the spring inside the rebound hammer. According to the corresponding calibration and verification requirements, the rebound hammer needs to be calibrated regularly. The calibration of the rebound hammer is essentially the calibration of the spring inside it. In the prior art, the calibration method for the rebound hammer is to completely disassemble the rebound hammer, then remove the rebound hammer spring inside the rebound hammer, apply a standard weight to the rebound hammer spring, and judge whether the rebound hammer spring can meet the usage accuracy based on the compressed length of the rebound hammer spring. This calibration method has the following problems: 1) Disassembling the rebound hammer is labor-intensive and increases the difficulty of calibration; 2) After the hammer spring is removed from the rebound hammer, it is no longer in its actual working environment. Even if the spring is calibrated, it is still unknown whether the hammer spring is accurate after being installed in the rebound hammer. Summary of the Invention

[0005] The object of the present invention is to provide a rebound hammer calibration device which can realize the calibration of the rebound hammer without disassembling the rebound hammer.

[0006] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0007] A rebound hammer calibration device includes a device bracket, on which a calibration pendulum is rotatably mounted. The calibration pendulum has a pendulum impact portion for being impacted by the rebound hammer, the rotation axis of the calibration pendulum passes through the center of gravity of the calibration pendulum, a pendulum spring is arranged between the calibration pendulum and the device bracket, and a spring compression adjustment structure is connected to the pendulum spring. The rebound hammer calibration device also includes an angle measurement structure for measuring the swing angle of the pendulum.

[0008] Furthermore, the pendulum spring is a torsion spring or a coil spring.

[0009] Furthermore, the calibration pendulum is a centrally symmetrical structure as a whole.

[0010] Furthermore, the spring compression adjustment structure includes a spring pressure plate connected to one end of the spring and a loading motor driving the spring pressure plate to rotate.

[0011] Furthermore, a rotating shaft is fixed on the calibration pendulum, and the rotating shaft is rotatably matched with the device bracket through a bearing.

[0012] Furthermore, the angle measurement structure includes an encoder arranged corresponding to the rotating shaft.

[0013] Furthermore, the distance between the pendulum impact portion and the axis of the rotating shaft is at least four times the radius of the rotating shaft.

[0014] Furthermore, the device bracket also includes a horizontal placement table for horizontally placing the rebound hammer to be calibrated, and the device bracket also includes a reaction force support, and a rebound hammer placement space is formed between the reaction force support and the pendulum impact part.

[0015] Furthermore, a force sensor is provided between the reaction force support and the rebound hammer, and a rolling body supporting the rebound hammer is provided on the horizontal placement table.

[0016] The beneficial effects of the present invention are as follows: when calibrating a rebound hammer, the rebound hammer is used to strike the pendulum striking portion of the calibration pendulum. After the calibration pendulum is struck by the rebound hammer, the calibration pendulum rotates about its own rotation axis, and the pendulum spring connected to the calibration pendulum stores energy. The swing angle of the calibration pendulum is measured by the angle measurement structure, thereby obtaining the elastic potential energy stored in the pendulum spring. Since the rotation axis of the calibration pendulum passes through the center of gravity of the calibration pendulum, there is no change in gravitational potential energy during the swing of the calibration pendulum. The elastic potential energy of the pendulum spring is the energy lost by the rebound hammer impact, which corresponds to the elastic potential energy of the spring before and after the impact of the hammer in the rebound hammer. Therefore, the rebound hammer can be calibrated without disassembling the rebound hammer, and the calibration process is simple and convenient. The rebound hammer is calibrated in its operating conditions, ensuring that the calibration result is consistent with the actual working conditions of the rebound hammer. The spring compression adjustment structure adjusts the compression of the pendulum spring before the rebound hammer strikes the calibration pendulum to simulate concrete of different hardnesses. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of the background technology of the present invention;

[0018] Figure 2 It is a structural schematic diagram of an embodiment of the present invention;

[0019] Figure 3 yes Figure 2 Top view of the middle pendulum and rebound hammer;

[0020] Figure 4 Figure 1 Side view of;

[0021] In the figure: 1. reaction force support; 2. impact rod; 3. ball; 4. horizontal placement table; 5. rebound hammer; 6. impact rod of rebound hammer; 7. pendulum impact part; 8. calibration pendulum; 9. pendulum spring; 10. spring pressure plate; 11. encoder; 12. bearing; 13. rotating shaft; 14. hollow shaft; 15. impact hammer spring; 16. impact hammer; 18. lower end surface of impact hammer; 19. guide rod; 20. force sensor; 21. loading motor; 22. device bracket. DETAILED DESCRIPTION

[0022] To facilitate understanding of the present invention, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0023] It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0024] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0025] The embodiment of the rebound hammer calibration device of the present invention is as follows: Figures 2-4 The apparatus includes a support 22, on which a calibration pendulum 8 is rotatably mounted. The calibration pendulum 8 has a centrally symmetrical structure, making it easier to determine its center of gravity. One end of the calibration pendulum has a pendulum impact portion 7 for impact by a rebound hammer. In this embodiment, the pendulum impact portion is a ball-shaped head structure designed to engage the rebound hammer's striking rod in point contact.

[0026] The axis of rotation of the calibration pendulum 8 passes through its center of gravity. A rotating shaft 13 is fixed to the calibration pendulum. One end of the rotating shaft rotates with the device bracket 22 via a bearing 12. The distance between the pendulum impact portion 7 and the rotating shaft axis is at least four times the radius of the rotating shaft 13. A pendulum spring 9 is disposed between the calibration pendulum and the device bracket. In this embodiment, the pendulum spring is a coil spring. A spring compression adjustment mechanism is connected to the pendulum spring 9. The rebound hammer calibration device also includes an angle measurement mechanism for measuring the pendulum's swing angle.

[0027] In this embodiment, the spring compression adjustment structure includes a loading motor 21, and a hollow shaft 14 is connected to the output end of the loading motor 21. The angle measurement structure is an encoder 11 arranged corresponding to one end of the rotating shaft 13. The other end of the rotating shaft 13 is rotatably matched with the inner hole of the hollow shaft 14. A spring pressure plate 10 is fixed on the hollow shaft 14. One end of the torsion spring 9 is connected to the pendulum, and the other end of the torsion spring is pressed against the spring pressure plate 10.

[0028] The device bracket also includes a horizontal placement table 4 for horizontally placing the rebound hammer to be calibrated. The device bracket also includes a reaction force support 1. A rebound hammer placement space is formed between the reaction force support 1 and the pendulum impact part. A force sensor 20 is arranged between the reaction force support and the rebound hammer. A rolling body supporting the rebound hammer is arranged on the horizontal placement table. The rolling body in this embodiment is a ball 3.

[0029] When the rebound hammer needs to be calibrated, the spring in the rebound hammer stores energy, and the rebound hammer is placed horizontally on the ball bearing on the horizontal table. The rebound hammer is arranged horizontally. Therefore, before and after the impact of the rebound hammer's impact rod, the rebound hammer in the rebound hammer only moves in the horizontal direction, and the gravitational potential energy of the rebound hammer does not change, which can reduce the influence of the gravitational potential energy of the rebound hammer on the calibration process.

[0030] The loading motor applies pressure to the pendulum spring through the spring pressure plate, thereby adjusting the force exerted by the pendulum spring on the calibration pendulum. This force can be intuitively displayed by the force sensor, and the stiffness of the pendulum spring can be judged. When calibrating the rebound hammer, a multi-point calibration method is generally used, that is, changing the initial force of the pendulum impact part on the impact rod to simulate concrete of different stiffness. For example, first adjust the position of the elastic potential energy of the pendulum spring to zero. At this time, the pendulum impact part contacts the striking rod, and the reading of the force sensor is zero, which means that the pendulum spring is not compressed. At this time, the elastic potential energy of the pendulum spring is zero. Pull the trigger of the rebound hammer manually or mechanically, and the spring in the rebound hammer drives the striking rod to hit the striking rod. Then, the striking rod hits the calibration pendulum. After the calibration pendulum is hit, the calibration pendulum swings around its own rotation axis. The encoder measures the maximum swing angle of the pendulum, and the energy storage of the pendulum spring is calculated based on the swing angle. The energy storage of the pendulum spring corresponds to the energy loss of the rebound hammer during the collision. According to the position of the hammer in the rebound hammer, the difference in elastic potential energy of the rebound hammer before and after the impact is calculated. The difference in elastic potential energy before and after the impact of the rebound hammer is compared with the energy storage of the pendulum spring, and the elastic coefficient of the rebound hammer's spring can be calibrated. The loading motor drives the spring pressure plate to compress the pendulum spring, changing the initial contact force between the pendulum impact part and the striking rod, which can simulate concrete with different stiffness, thereby realizing the calibration process of the rebound hammer under different stiffness states.

[0031] The use of a pendulum structure has two main advantages: 1. The rotation axis of the pendulum passes through the center of gravity of the pendulum. In this way, the gravitational potential energy does not change during the rotation of the pendulum, and the energy loss during the impact of the rebound tester can be obtained through the elastic potential energy of the pendulum spring; 2. The use of a pendulum structure can minimize the influence of the pendulum friction on the conversion of elastic potential energy during the rotation of the pendulum. The farther the impact part is from the rotation axis of the pendulum, the smaller the friction energy consumption during the rotation of the pendulum. The following analysis is performed. The friction coefficient of the bearing is 0.001~0.003. It is assumed that the rolling friction coefficient of the bearing in this embodiment is 0.002. The friction coefficient is represented by μ, the radius of the rotating shaft is r, the distance between the pendulum impact part and the rotating shaft axis is d, the mass of the pendulum is m, the stiffness of the pendulum spring is D, and the angular displacement of the pendulum spring during energy storage is S. The friction force f=mg*μ generated by the gravity of the pendulum, and the friction torque w=mg*μ*r generated by this friction force. This friction torque generates a corresponding reaction force F at the collision point. The reaction force F=mg*μ*r / d. This force produces a deviation in the spring stretching length. The deviation =F / D. This deviation has a relatively small effect on the overall energy loss of the pendulum, and the deviation depends on the r / d value. That is to say, the greater the ratio of the radius of the pendulum impact part to the axis of rotation and the axis of rotation, the smaller the deviation.

[0032] In other embodiments of the present invention: a suitable value of r / d can be selected as needed, and the distance between the impact part and the rotation axis of the rotating connection structure is at least twice the radius of the rotation axis, which can reduce the influence of friction; the pendulum spring can also be a torsion spring or a cylindrical spring; the angle measurement structure can also be other than an encoder, for example, the angle measurement structure includes an arc scale arranged coaxially with the pendulum, and the swing angle of the pendulum is observed through the arc scale, or an indicator is set, and the indicator is guided to move with the arc scale, and the indicator has no direct connection with the calibration pendulum. When the calibration pendulum swings, the indicator can be pushed to move along the arc scale. When the calibration pendulum swings back, the indicator stays on the arc scale to observe the maximum swing angle of the calibration pendulum; the spring compression adjustment structure can also be a manual mode, for example, by screwing a bolt to adjust the compression of the pendulum spring.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A rebound hammer calibration device, characterized by: The device comprises a bracket on which a calibration pendulum is rotatably mounted, the calibration pendulum having a pendulum impact portion for being impacted by a rebound hammer, the rotation axis of the calibration pendulum passing through the center of gravity of the calibration pendulum, a pendulum spring being arranged between the calibration pendulum and the bracket, the pendulum spring being connected to a spring compression adjustment structure, the rebound hammer calibration device also comprising an angle measurement structure for measuring the swing angle of the pendulum, the calibration pendulum being overall centrally symmetrical, the pendulum spring being a torsion spring or a disc spring, a rotating shaft being fixed to the calibration pendulum, the rotating shaft being rotatably fitted with the device bracket through a bearing, the distance between the pendulum impact portion and the axis of the rotating shaft being at least four times the radius of the rotating shaft.

2. The rebound hammer calibration device according to claim 1, characterized in that: The spring compression adjustment structure comprises a spring pressure plate connected to one end of the spring and a loading motor driving the spring pressure plate to rotate.

3. The rebound hammer calibration device according to claim 1, characterized in that: The angle measurement structure includes an encoder arranged corresponding to the rotating shaft.

4. The rebound hammer calibration device according to any one of claims 1 to 3, characterized in that: The device bracket also includes a horizontal placement table for horizontally placing the rebound hammer to be calibrated. The device bracket also includes a reaction force support, and a rebound hammer placement space is formed between the reaction force support and the pendulum impact part.

5. The rebound hammer calibration device according to claim 4, characterized in that: A force sensor is arranged between the reaction force support and the rebound hammer, and a rolling body supporting the rebound hammer is arranged on the horizontal placement table.

Images