Variable cross-section hammer core

Abstract

This utility model discloses a variable cross-section hammer core, comprising a hammer core body separately configured from a piston. The hammer core body comprises n segments with different shaft diameters and coaxiality, where n ≥ 2 is an integer. The n segments of the hammer core body have discontinuous cross-sections, with the upper segment having a larger cross-section than the lower segment. The axial lengths of each segment are similar. The cross-sectional area at the connection between the upper end of the hammer core body and the piston is Sn, and the cross-sectional area at the impact point at the lower end of the hammer core body is S1, where Sn ≥ 2S1. This utility model employs a discontinuous cross-section design to improve the energy transfer efficiency during hammer strikes.

Description

Technical Field

[0001] This utility model relates to an improved invention of a hydraulic pile driver, and more particularly to an improved invention of a variable cross-section hammer core. Background Technology

[0002] Among various piling hammers, hydraulic piling hammers have already occupied an important position in the market due to their own advantages, and it is foreseeable that they will play a key role in the future marine economy. From the perspective of the connection method between the hammer core and piston rod of hydraulic piling hammers, there are mainly two structural designs: 1) Integrated hammer core and piston, such as a rolling pin-shaped hammer core, where the upper small-diameter part also serves as the piston rod; 2) Separate connection of the hammer core and piston, where the hammer core is mostly prismatic or cylindrical, and the piston rod is a separate component.

[0003] Both of the aforementioned mainstream designs have their advantages and disadvantages. However, regardless of the design, during pile driving, in addition to the transfer of kinetic energy from the hammer core to the anvil / pile during the collision between the hammer core and the anvil, other energy losses also occur. This invention addresses the second structural design by introducing a new hammer core design based on the theory of elastic body wave motion, aiming to improve the energy transfer efficiency during hammer impact. Utility Model Content

[0004] The technical problem to be solved by this utility model is to overcome the shortcomings of the prior art and provide a variable cross-section hammer core that can improve the efficiency of impact energy transmission.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: the variable cross-section hammer core includes a hammer core body separately arranged from the piston, characterized in that: the hammer core body includes n segments with different shaft diameters and coaxiality, where n≥2 is an integer, the n segments of the hammer core body have discontinuous cross-sections, and the cross-section of the upper segment is larger than that of the lower segment, the axial lengths of each segment are similar, the cross-sectional area at the connection between the upper end of the hammer core body and the piston is Sn, the cross-sectional area at the impact point of the lower end of the hammer core body is S1, and Sn≥2S1.

[0006] When n≥3, the discontinuous cross-sectional area of ​​each segment of the hammer core body is linearly set.

[0007] The cross-sectional areas of each section of the hammer core body abruptly transition with a circular arc.

[0008] If the total axial length of the hammer core remains constant, but the weight of the hammer core decreases, then the value of n increases.

[0009] The beneficial effect of this utility model is that the improved variable cross-section hammer core, based on the elastic body wave theory, is designed with several segments having discontinuous cross-sections to improve the energy transfer efficiency of the hydraulic pile hammer during construction. Attached Figure Description

[0010] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0011] Figure 1 This is a schematic diagram of the structure before the improvement of this utility model.

[0012] Figure 2 This is a schematic diagram of the improved n=2 structure of this utility model.

[0013] Figure 3 This is a schematic diagram of the improved n=3 structure of this utility model. Detailed Implementation

[0014] The accompanying drawings illustrate the structure of this utility model, and further details will be provided below in conjunction with the drawings. In this embodiment, the variable cross-section hammer core includes a hammer core body that is separately configured from the piston. The hammer core body includes n segments with different shaft diameters and coaxiality, where n≥2 is an integer. The n segments of the hammer core body have discontinuous cross-sections, with the upper segment having a larger cross-section than the lower segment. The axial lengths of each segment are similar. The cross-sectional area at the connection between the upper end of the hammer core body and the piston is Sn, and the cross-sectional area at the impact point at the lower end of the hammer core body is S1, where Sn≥2S1.

[0015] As a further improved implementation, when n≥3, the discontinuous cross-sectional area of ​​each segment of the hammer core body is linearly set to ensure efficient and uniform energy transfer.

[0016] As a further improvement, the cross-sectional transitions of each section of the hammer core body are circular to avoid excessive stress concentration.

[0017] As a further improvement, if the total axial length of the hammer core body remains unchanged, the weight of the hammer core body is reduced, and the value of n is increased. That is, the weight of the hammer core body is reduced by increasing the value of n.

[0018] The following is an excerpt from the literature cited in this utility model:

[0019] Reference [1] Yu Zhanxiang, Modeling and Analysis of Hydraulic Piling Hammer-Pile-Soil System, Master's Thesis, Tongji University, March 2021.

[0020] Literature [2] JD Achenbach, Wave propagation in elastic solids, North-Holland publishing company, 1973.

[0021] Reference [3]: Jonathan A. Kemp, Theoretical and experimental study of wave propagation in brass musical instruments, PhD thesis, University of Edinburgh, 2002.

[0022] According to Reference [1], the best waveform generated by the contacting objects during collision is rectangular, which can more effectively transfer the impact energy to the anvil / stake. This utility model focuses on the design of the hammer core. According to Reference [2], the hammer core is now simplified to a propagation medium only considering longitudinal waves. According to the linear one-dimensional wave theory of elastic solids, at the sudden change (discontinuity) of the solid cross-section, the characteristic impedance of the propagation medium (related to the cross-section) changes, and the wave propagation will be divided into transmitted waves and reflected waves. Let S1 be the cross-sectional area at the lower end of the hammer core where it impacts (i.e., one end of the cross-section discontinuity), and S2 be the cross-sectional area at the other end of the cross-section discontinuity. From the force and wave velocity consistency at this discontinuity, the following longitudinal wave amplitude relationship can be obtained (References [1-3]):

[0023] B / A = (S2 / S1 - 1) / (S2 / S1 + 1), C / A = 2 / (S2 / S1 + 1);

[0024] Where A is the amplitude of the incident wave, B is the amplitude of the reflected wave, and C is the amplitude of the transmitted wave. From the above amplitude relationship, it can be seen that when the pressure wave propagates from S1 to S2, when S1 < S2 (S1 is small enough compared to S2), the reflected wave will be transmitted to the impact point again in the form of a pressure wave, thus prolonging the effective impact time and improving the transfer efficiency of the impact energy.

[0025] Taking the axial simplified sectional view of the hammer core as an example, the schematic diagrams of the two improved schemes before and after improvement are respectively Figure 1 , Figure 2 and Figure 3 ,

[0026] Notes on implementation methods:

[0027] In the first scheme, to increase the amplitude of the reflected wave, while keeping the cross-sectional area of S2 unchanged, it is necessary to consider the impact contact surface and the stake material, and尽可能 reduce S1 as much as possible. The length distribution is referenced as 1:1 and can be appropriately adjusted according to the actual design.

[0028] In Solution 1, while keeping the total axial length of the hammer core unchanged, the mass of the hammer core is reduced. If the mass loss needs to be compensated, the double cross-section change in Solution 2 (S1 < S2 < S3) can be adopted, that is, by utilizing the double reflected waves at different times. However, the amplitude of a single reflected wave is smaller than that in Solution 1. The length distribution is referenced by 1:1:1 and can be appropriately adjusted according to the actual design.

[0029] Solution 1 or 2 can be selected according to the processing cost and design requirements (such as the weight of the hammer core).

[0030] There should be sufficient circular arc transitions at the cross-section mutation points (arrow points in the schematic diagram) to avoid excessive stress concentration.

[0031] In summary, the above are only the preferred embodiments of the present utility model and are not intended to limit the protection scope of the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A variable cross-section hammer core comprising a hammer core body provided separately from a piston, characterized in that: The hammer core body comprises n segments with different shaft diameters and coaxiality, where n≥2 is an integer. The n segments of the hammer core body have discontinuous cross-sections, with the upper segment having a larger cross-section than the lower segment. The axial lengths of each segment are similar. The cross-sectional area at the connection between the upper end of the hammer core body and the piston is Sn, and the cross-sectional area at the impact point at the lower end of the hammer core body is S1, where Sn≥2S1.

2. The variable cross-section hammer core of claim 1, wherein: When n≥3, the discontinuous cross-sectional area of ​​each segment of the hammer core body is linearly set.

3. The variable cross-section hammer core of claim 1, wherein: The cross-sectional areas of each section of the hammer core body abruptly transition with a circular arc.

4. The variable cross-section hammer core of claim 1, wherein: If the total axial length of the hammer core remains constant, but the weight of the hammer core decreases, then the value of n increases.

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