A rebound hammer

Abstract

The present invention relates to a rebound instrument, which includes a rebound instrument frame provided with a striker rod. An impact hammer is further provided on the rebound instrument frame. An impact hammer spring for driving the impact part of the impact hammer to strike the striker rod is connected to the impact hammer. A measuring device for measuring the speed change of the impact hammer before and after striking the striker rod is provided on the rebound instrument frame. The rebound instrument frame includes a rebound instrument frame body and an adjusting sleeve threadedly connected to the rebound instrument frame body. The adjusting sleeve has a striker rod guiding hole, and the striker rod is guidingly and movably assembled in the striker rod guiding hole. The adjusting sleeve is provided with a striker rod limiting structure for limiting the movement range of the striker rod in a limiting fit with the striker rod. The present invention solves the technical problem in the prior art that it is difficult to find the zero potential energy point of the spring when determining the energy loss of the impact hammer through kinetic energy loss.

Description

Technical Field

[0001] The present invention relates to a rebound hammer in the field of concrete hardness detection. Background Art

[0002] A concrete rebound hammer is a device that uses a spring to drive a striker. The striker impacts the concrete surface through a striker rod. The concrete surface undergoes instantaneous elastic deformation to absorb energy, and the striker rebounds. The hardness of the concrete is characterized based on the energy loss. The principle utilized is that the harder the concrete, the less energy it absorbs through elastic deformation, and thus the less energy is lost during the impact of the striker.

[0003] The working process of the concrete rebound hammer is as Figure 1 shown. For the sake of clearly demonstrating the problem, the first state, the second state, the third state, the fourth state, and the fifth state occur in chronological order. During operation, first, the height of the striker 16 is lifted. As shown in the first state, the striker spring 15 stores energy, and the end of the striker rod 2 away from the striker contacts the concrete surface. Subsequently, the striker 16 is released. Under the guiding action of the guide rod 19, the striker moves towards the striker rod, as shown in the second state. Then, the lower end surface 18 of the striker impacts the striker rod 2, and the striker rod impacts the concrete, as shown in the third state. Immediately afterwards, as shown in the fourth state, the striker starts to rebound away from the striker rod. Finally, as shown in the fifth state, the striker reaches the highest rebound position.

[0004] In the prior art, there are basically two measurement methods to characterize the energy loss of the striker. The first method is to measure the height difference of the striker in the first state and the fifth state, and calculate the rebound value based on the energy change between the two states. The difference between the sum of the gravitational potential energy of the striker 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 striker in the fifth state and the elastic potential energy of the spring in the fifth state is the energy change between the two states. This method obviously has the following disadvantages: 1), the change from the first state to the fifth state is not only the change in gravitational potential energy and elastic potential energy. There is a sliding friction force between the striker and the guide rod, and this friction force will also cause energy loss, which cannot be ignored and will affect the accuracy of the rebound value characterization; 2), since the gravitational potential energy of the striker needs to be considered, the impact angle of the striker rod on the concrete surface is very critical, and the entire operation process has relatively strict requirements.

[0005] The second method is to measure the impact velocity V of the striker when it impacts the striker rod 0 , and measure the rebound velocity V of the striker when it just detaches from the impact rod R, the energy loss of the impact hammer is characterized by the kinetic energy loss of the impact before and after, and then the rebound value is calculated. This method has the following disadvantages: 1) Due to the existence of the spring, it is not a complete kinetic energy loss in the two states. Only when the elastic potential energy of the spring is exactly at the zero potential energy point at the moment of impact, the kinetic energy loss can accurately characterize the energy loss of the impact hammer. However, it is difficult to ensure that the spring is exactly at the zero potential energy point at the moment of impact; 2) The frictional force between the impact hammer and the impact rod is still a non-negligible energy loss factor in the energy calculation process; 3) Dynamic speed measurement is not so easy and stable.

[0006] Of course, whether it is the first method or the second method, there is still a problem: the lower end surface of the impact hammer is a plane. In an ideal state, the lower end surface of the impact hammer directly contacts the upper end surface of the impact rod once to complete the measurement of the hardness of the concrete. However, due to the guiding fit tolerance between the impact hammer and the guiding rod, during the movement of the impact hammer, it cannot be guaranteed that its lower end surface is completely perpendicular to the axis of the guiding rod. When the lower end surface of the impact hammer is not perpendicular to the axis of the impact rod, the tip of the impact hammer will first hit the impact rod once, and then hit the impact rod a second time. If two impacts occur, part of the energy will be absorbed by the impact rod, and the entire measurement process will be inaccurate. Summary of the Invention

[0007] The purpose of the present invention is to provide a rebound instrument to solve the technical problem of difficult finding of the zero potential energy point of the spring when determining the energy loss of the impact hammer by kinetic energy loss in the prior art.

[0008] To solve the above technical problems, the technical solution of the present invention is as follows:

[0009] A rebound instrument includes a rebound instrument frame provided with an impact rod. An impact hammer is also provided on the rebound instrument frame. An impact hammer spring for driving the impact part of the impact hammer to impact the impact rod is connected to the impact hammer. A measuring device for measuring the speed change of the impact hammer before and after impacting the impact rod is provided on the rebound instrument frame. The rebound instrument frame includes a rebound instrument frame body and an adjusting sleeve threadedly connected to the rebound instrument frame body. The adjusting sleeve has an impact rod guiding hole, and the impact rod is guidingly and movably assembled in the impact rod guiding hole. An impact rod limiting structure for limiting the movement range of the impact rod by limiting cooperation with the impact rod is provided on the adjusting sleeve.

[0010] Furthermore, the adjusting sleeve includes an outer sleeve threadedly connected to the rebound instrument frame body and a striking rod guide sleeve fixed on the inner side of the outer sleeve, the inner hole of the striking rod guide sleeve constitutes the striking rod guide hole, a limiting outward edge is provided on the striking rod, the striking rod limiting structure includes an adjusting sleeve inward edge located on the upper side of the limiting outward edge on the striking rod guide sleeve, the striking rod limiting structure also includes an upper end surface of the striking rod guide sleeve, and the upper end surface of the striking rod guide sleeve is located on the lower side of the limiting outward edge.

[0011] Furthermore, a striking rod verticalizer is installed on the adjusting sleeve, and the striking rod verticalizer includes a verticalizer floating spring and a verticalizer guide sleeve. The verticalizer guide sleeve cooperates with the adjusting sleeve for guiding movement. The verticalizer floating spring is arranged between the verticalizer guide sleeve and the adjusting sleeve. The lower end surface of the verticalizer guide sleeve is a plane of the vertical striking rod axis.

[0012] Furthermore, the impact hammer is a pendulum connected to the rebound tester frame through a rotating connection structure, and the rotation axis of the rotating connection structure passes through the center of gravity of the pendulum.

[0013] Furthermore, the impact hammer spring is a disc spring or a torsion spring.

[0014] Furthermore, the measuring device measures the change in the swing angle before and after the impact hammer impacts the impact rod.

[0015] Furthermore, the rotating connection structure includes a bearing mounted on the rebound tester frame and a rotating shaft rotatably matched with the bearing, and the pendulum is fixed together with the rotating shaft.

[0016] Furthermore, the measuring device is an absolute value encoder for detecting the rotation angle and rotation speed of the rotating shaft.

[0017] The beneficial effects of the present invention are as follows: when in use, gently flick the impact hammer spring, and when the impact hammer automatically resets, it is the zero elastic potential energy position of the impact hammer spring. At this time, press the impact rod upward with your hand to move the impact rod relative to the adjusting sleeve to the upward movement limit position, and the adjusting sleeve rotates relative to the rebound instrument frame body, and adjusts the height of the adjusting sleeve so that the upper end of the impact rod contacts the impact part of the impact hammer, and then stops adjusting the adjusting sleeve. At this time, when the impact hammer spring stores energy and then releases it, the impact hammer spring carries the impact hammer to impact the impact rod. At the moment when the impact part contacts the impact rod, the elastic potential energy of the impact hammer spring is zero. When there is no impact hammer spring force involved, the energy loss before and after the pendulum impact can be easily obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the background technology of the present invention;

[0019] Figure 2 1 is a schematic structural diagram of Embodiment 1 of the rebound tester in the present invention;

[0020] Figure 3 is Figure 2 a schematic diagram of the cooperation of the pendulum, the rotating shaft and the impact hammer spring in

[0021] Figure 4 is Figure 1 the top view of

[0022] Figure 5 a schematic structural diagram of the pendulum in the energy storage state in Embodiment 1

[0023] Figure 6 a schematic structural diagram of Embodiment 2 of the rebound instrument in the present invention

[0024] In the figure: 1. Vertical guide sleeve; 2. Impact rod; 3. Vertical floating spring of impact rod; 4. Impact rod guide sleeve; 5. Adjusting sleeve; 6. Rebound instrument frame; 7. Impact part; 8. Impact hammer; 9. Impact hammer spring; 10. Rotating shaft; 11. Vertical of impact rod; 12. Bearing; 13. Absolute encoder; 14. Pendulum limit block; 18. Lower end face of impact hammer; 19. Guide rod; 20. Limit outward flange; 21. Inner flange of adjusting sleeve. Detailed implementation manners

[0025] For ease of understanding of the present invention, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments. The 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. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of the present invention more thorough and comprehensive.

[0026] It should be noted that unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not used to limit the present invention.

[0027] The following will describe each embodiment of the present invention in detail with reference to the accompanying drawings.

[0028] Embodiment 1 of a rebound instrument according to the present invention is as shown in Figures 2 - 5As shown: It includes a rebound hammer frame 6 provided with a striking rod 2. A striking hammer is rotatably assembled on the rebound hammer frame 6 through a rotational connection structure. Since the striking hammer in the present invention outputs a striking force through swinging, the striking hammer 8 can be called a pendulum hammer. The pendulum hammer as a whole is a centrosymmetric structure. One end of the pendulum hammer is a striking portion 7 for striking the striking rod. The striking portion is a ball head structure for point contact and cooperation with the striking rod. Since the pendulum hammer as a whole is a centrosymmetric structure, the other end of the pendulum hammer is also the same ball head structure. The pendulum hammer as a whole adopts a centrosymmetric structure, which makes it easier to determine the center of gravity of the pendulum hammer. The axis of the rotational connection structure passes through the center of gravity of the pendulum hammer. In this embodiment, the rotational connection structure includes a rotating shaft 10. The rotating shaft is rotatably matched with the rebound hammer frame 6 through a bearing 12. The pendulum hammer is fixedly connected to the rotating shaft 10. The axis of the rotating shaft constitutes the axis of the rotational connection structure. Therefore, the axis of the rotating shaft 10 passes through the center of gravity of the pendulum hammer.

[0029] The rebound hammer further includes a pendulum hammer driving structure for driving the pendulum hammer to strike towards the striking rod. In this embodiment, the pendulum hammer driving structure is a striking hammer spring 9 connected to the pendulum hammer. The striking hammer spring 9 is a torsion spring. One end of the striking hammer spring is connected to the pendulum hammer, and the other end of the striking hammer spring is connected to the rebound hammer frame 6.

[0030] The rebound hammer further includes a measuring device for measuring the change in the swinging speed and the change in the swinging angle of the pendulum hammer before and after striking the striking rod. In this embodiment, the measuring device is an absolute encoder 13 for detecting the rotation angle and rotation speed of the rotating shaft. The absolute encoder 13 can detect the rotation angle of the rotating shaft 10 and can also detect the angular velocity of the rotating shaft.

[0031] The rebound hammer frame includes a rebound hammer frame body and an adjusting sleeve 5 connected to the rebound hammer frame body. The adjusting sleeve 5 includes an outer sleeve threadedly connected to the rebound hammer frame. The adjusting sleeve further includes a striking rod guide sleeve 4 fixed to the inner side of the outer sleeve. The inner hole of the striking rod guide sleeve 4 forms a striking rod guide hole. The striking rod 2 is in guiding movement cooperation with the inner hole of the striking rod guide sleeve 4. A limiting outward flange 20 is provided on the striking rod 2. An adjusting sleeve inward flange 21 for blocking and cooperating with the limiting outward flange 20 to limit the upward movement limit of the striking rod relative to the adjusting sleeve is provided on the adjusting sleeve 5. The upper end surface of the striking rod guide sleeve 4 is used for blocking and cooperating with the lower end of the limiting outward flange to limit the downward movement limit of the striking rod. The adjusting sleeve inward flange and the upper end surface of the striking rod guide sleeve constitute a striking rod limiting structure for limiting the movement range of the striking rod by limiting cooperation with the striking rod.

[0032] The adjusting sleeve 5 is used to adjust the moment when the pendulum hits the impact rod to the moment when the impact rod spring has zero elastic potential energy. The specific use process is to gently turn the impact rod spring. When the pendulum automatically resets, it is the zero elastic potential energy position of the impact rod spring. At this time, press the impact rod upward by hand so that the limit outward edge of the impact rod is always in contact with the inward edge of the adjusting sleeve. The adjusting sleeve rotates relative to the rebound instrument frame body, and the height of the adjusting sleeve is adjusted so that the upper end of the impact rod contacts the impact part of the pendulum, and then the adjustment of the adjusting sleeve is stopped. At this time, when the pendulum is rotated upward, the impact rod spring accumulates energy, and the impact rod spring carries the pendulum to hit the impact rod. At the moment when the impact part contacts the impact rod, the elastic potential energy of the impact rod spring is zero. In this embodiment, an observation window can be opened at the corresponding position of the rebound instrument frame and the upper end of the impact rod. The observation window is blocked by a transparent material, and the upper end of the impact rod is observed through the observation window to see whether it contacts the impact part.

[0033] The adjusting sleeve 5 is provided with a vertical device 11 for the impact rod, which is used to ensure that the impact rod is perpendicular to the concrete surface. The vertical device of the impact rod includes a vertical device floating spring 3 and a vertical device guide sleeve 1. The vertical device guide sleeve is matched with the guiding movement of the adjusting sleeve. The vertical device floating spring 3 is arranged between the vertical device guide sleeve 1 and the adjusting sleeve 5. The lower end surface of the vertical device guide sleeve is a plane perpendicular to the axis of the impact rod. When in use, the lower end surface of the vertical device guide sleeve contacts and cooperates with the concrete surface to be tested, and the adjusting sleeve is pressed until the lower end surface of the impact rod also contacts and cooperates with the concrete surface. At this time, the limit outward edge on the impact rod is blocked by the inward edge of the adjusting sleeve on the adjusting sleeve. The rebound value test can be carried out, the pendulum is rotated upward, the impact hammer spring stores energy, and then the pendulum is released. Under the drive of the impact hammer spring, the impact part of the pendulum hits the impact rod. After the impact, the concrete absorbs energy and the pendulum loses energy. The pendulum limit block 14 in the figure is used to limit the clockwise rotation limit of the pendulum.

[0034] The absolute value encoder in the present invention can measure the rotation angle of the rotating shaft, and can also measure the rotation angular velocity of the rotating shaft. When the rotation angle of the rotating shaft is selected as the measurement data, the energy loss before and after the pendulum impact can be calculated through the potential energy loss. Moreover, it is simple and convenient because during the entire impact process, the gravitational potential energy of the pendulum does not change, and only the elastic potential energy of the impact hammer spring changes. Therefore, it is not limited to the impact angle of the impact rod and has nothing to do with the impact angle. It is easy to operate, and the energy loss before and after the pendulum impact can be easily obtained, and then the rebound value can be obtained.

[0035] When the rotational angular velocity of the rotating shaft is selected as the measurement data, the energy loss before and after the pendulum hammer impacts can be calculated through the kinetic energy loss. The velocities of the impact part before and after it impacts the impact rod can be obtained by converting through the angular velocity of the rotating shaft. Since the elastic potential energy of the impact hammer spring is zero when the impact part impacts the impact rod and the pendulum hammer moves at a constant speed without the intervention of the impact hammer spring force, the energy loss of the pendulum hammer before and after the impact can be easily obtained, and then the rebound value can be obtained. The present invention can calculate the energy loss of the pendulum hammer either using potential energy or kinetic energy.

[0036] Since it is guided by the rotational connection structure, the guiding structure does not need to penetrate the pendulum hammer. Therefore, the impact part can be a ball head structure for point contact and cooperation with the impact rod. The impact between the impact part and the impact rod completes the test once, ensuring the accuracy of the test.

[0037] After the rotating pendulum hammer impacts the impact rod, the rotating shaft fixed to the pendulum hammer has the same angular velocity as the pendulum hammer. Compared with the linear velocity measurement in the prior art, the measurement of the rotational speed of the rotating shaft is simple and convenient.

[0038] Moreover, whether calculating the energy loss of the pendulum hammer before and after the impact using potential energy or kinetic energy, due to the adoption of the pendulum hammer structure, the work done by the friction force at the rotating shaft can be almost ignored. The principle is as follows: the friction coefficient of the rotating bearing is 0.001 - 0.003. In this embodiment, it is assumed that the rolling friction coefficient of the bearing is 0.002. The friction coefficient is represented by μ, the radius of the rotating shaft is r, the distance from the impact part to the axis of the rotating shaft is d, the mass of the pendulum hammer is m, the stiffness of the impact hammer spring is D, and the impact angular displacement of the impact hammer spring from the self - energy storage state to the zero elastic potential energy state is S. Then the friction force f generated by the gravity of the pendulum hammer is f = mg * μ, the friction torque w generated by this friction force is w = mg * μ * r. This friction torque generates a reaction force F at the collision point, and this reaction force F = mg * μ * r / d. This force generates a deviation in the spring stretch length, and this deviation = F / D. This deviation has a relatively small impact on the overall energy loss of the pendulum hammer, and this deviation depends on the r / d value. That is to say, the larger the ratio of the distance from the impact part to the axis of rotation to the radius of the rotating shaft, the smaller this deviation.

[0039] Below, it is assumed that D = 785 N / m, S = 75mm, m = 0.37kg, μ = 0.002, r = 5mm, d = 86mm. The frictional force f generated by the gravity of the pendulum bob is f = 0.37 * 10 * 0.002 = 0.0074N, and the frictional torque w generated is w = 0.0074N * 0.005 = 0.000037 Nm. This frictional torque corresponds to a reaction force F = 0.000037 Nm / 0.086 = 0.00043 N at the collision point. This force generates a deviation in the spring stretch length: 0.00043 N / 785 N / m = 0.00000055 m = 0.00055 mm. The influence of this length deviation on the energy loss caused by the pendulum bob impact is relatively small, resulting in a deviation of less than 2 / 10000 at most.

[0040] In other embodiments of the present invention, a suitable value of r / d can be selected as needed. The distance between the impact part and the rotation axis of the rotation connection structure is at least twice or more the radius of the rotation shaft, which can all achieve the effect of reducing the influence of frictional force. When only the kinetic energy is needed to calculate the energy loss value of the pendulum bob, the measuring device only needs to measure the change in the speed of the pendulum bob before and after it impacts the impact rod, and does not need to measure the change in the swing angle of the pendulum bob before and after the impact. The swing spring can also be a torsion spring or a cylindrical spring, etc. The impact rod limiting structure can also be in other forms. For example, a long groove extending along the axial direction of the impact rod is provided on the impact rod. The impact rod limiting structure includes a limiting rod fixed to the adjusting sleeve. One end of the limiting rod extends into the long groove. When the lower end of the long groove abuts against the bottom of the limiting rod during the movement of the impact rod, the impact rod moves to the upper limit position relative to the adjusting sleeve. When the upper end of the long groove abuts against the top of the limiting rod, the impact rod moves to the lower limit position relative to the adjusting sleeve.

[0041] Example 2 of the rebound hammer is as Figure 6 shown: The difference between Example 2 and Example 1 is that the impact hammer 8 is not a pendulum bob. The impact hammer 8 is guided and movably assembled on the rebound hammer frame 6 in a straight line direction. The impact hammer spring 9 is a compression spring disposed between the impact hammer and the rebound hammer frame 6. The impact hammer outputs an impact force to the impact rod 2 through linear motion.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rebound hammer, comprising a rebound hammer frame provided with a striker rod, a striking hammer is further provided on the rebound hammer frame, a striking hammer spring for driving the striking part of the striking hammer to strike the striker rod is connected to the striking hammer, and a measuring device for measuring the speed change of the striking hammer before and after striking the striker rod is provided on the rebound hammer frame. Characterized in that: The rebound hammer frame includes a rebound hammer frame body and an adjusting sleeve threadedly connected to the rebound hammer frame body. The adjusting sleeve has a striker rod guiding hole, and the striker rod is guidingly and movably assembled in the striker rod guiding hole. An striker rod limiting structure for limiting the movement range of the striker rod by limiting cooperation with the striker rod is provided on the adjusting sleeve. A striker rod perpendicularizer is installed on the adjusting sleeve. The striker rod perpendicularizer includes a perpendicularizer floating spring and a perpendicularizer guiding sleeve. The perpendicularizer guiding sleeve is guidingly and movably matched with the adjusting sleeve. The perpendicularizer floating spring is arranged between the perpendicularizer guiding sleeve and the adjusting sleeve. The lower end surface of the perpendicularizer guiding sleeve is a plane perpendicular to the axis of the striker rod. The striking hammer is a pendulum hammer connected to the rebound hammer frame through a rotational connection structure. The rotational axis of the rotational connection structure passes through the center of gravity of the pendulum hammer. The striking hammer is a pendulum hammer, and the whole pendulum hammer is a centrosymmetric structure.

2. The rebound hammer according to claim 1, Characterized in that: The adjusting sleeve includes an outer sleeve threadedly connected to the rebound hammer frame body and a striker rod guiding sleeve fixed to the inner side of the outer sleeve. The inner hole of the striker rod guiding sleeve constitutes the striker rod guiding hole. A limiting outward flange is provided on the striker rod. The striker rod limiting structure includes an adjusting sleeve inward flange provided on the striker rod guiding sleeve and located above the limiting outward flange. The striker rod limiting structure further includes the upper end surface of the striker rod guiding sleeve, and the upper end surface of the striker rod guiding sleeve is located below the limiting outward flange.

3. The rebound hammer according to claim 1, Characterized in that: The striking hammer spring is a disc spring or a torsion spring.

4. The rebound hammer according to claim 1, Characterized in that: The measuring device measures the change in the swing angle of the striking hammer before and after striking the striker rod.

5. The rebound hammer according to claim 1, Characterized in that: The rotational connection structure includes a bearing installed on the rebound hammer frame and a rotating shaft rotatably matched with the bearing. The pendulum hammer is fixed to the rotating shaft.

6. The rebound hammer according to claim 5, Characterized in that: The measuring device is an absolute encoder for detecting the rotation angle and rotation speed of the rotating shaft.

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