JPH1060891A - Buffer for vibratory driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to absorb the vibration of a vibratory hammer with high efficiency and to be unsusceptible to damages even when a large downward impact is inflicted and expand the service weight range of the vibratory hammer. SOLUTION: In a buffer of a vibratory pile driver, two sets of two slide shafts 16 whose respective lower ends are mounted on a vibratory hammer 20, are housed respectively in a spring case 21. The upper end of each slide shaft 16 housed in the spring case is interconnected to each other with a connector 17. Each slide shaft 16 is provided respectively with a first compression spring 13 which is energized upward when each slide shaft 16 is towed downward. When each first compression spring 13 is compressed by a specific amount with the connector 17, each connector 17 will be energized upward by a second compression spring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for absorbing the vibration of a vibratory hammer attached to the upper end of a casing pipe when forming a sand pile on soft ground. The present invention relates to a shock absorber for a vibratory pile driver provided in a vehicle.

[0002]

2. Description of the Related Art In a sand drain method in which a sand pile is formed on a soft ground to quickly remove excess pore water in the soft ground, usually, a casing pipe is driven into the soft ground, and sand is poured into the driven casing pipe. After filling, sand pipes are formed on the soft ground by pulling out the casing pipe. In such a sand drain construction method, for example, a vibratory hammer is used to pull out a casing pipe that has been driven into soft ground. The vibrating hammer is attached to the upper end of the casing pipe to vibrate the casing pipe, and the vibrating hammer is pulled upward by a crane or the like in a vibrated state, so that the casing pipe is Pulled out from soft ground.

In this case, a shock absorber is attached to the vibratory hammer so that the vibration of the vibratory hammer is not transmitted to a crane or the like.

FIG. 6A is a front view showing an example of a vibratory pile driver in which a shock absorber is attached to a vibratory hammer.
FIG. 6B is a side view thereof. The shock absorber 40 is connected to a vibratory hammer 30 attached to the upper end of the casing pipe, and a pulley 41 on which a rope suspended by a crane or the like is wound.
The support 41 provided with a is provided. Support 4
1, a pair of buffer mechanisms 42 are suspended vertically so as to be parallel to each other.

Each buffer mechanism 42 has four tension springs 42a vertically arranged so as to be parallel to each other, and each tension spring 42a has two vertically extending traction arms. 43 are respectively attached to the upper ends. A clamp mechanism 44 for clamping the vibratory hammer 30 is attached to the lower end of each towing arm 43, and each clamp mechanism 44 clamps the vibratory hammer 30.

In the vibratory pile driver having such a configuration, after the casing pipe is driven into the soft ground and sand is filled, the vibratory hammer 30 clamped by the shock absorber 40 is provided at the upper end of the casing pipe. It is attached.
The shock absorber 40 is suspended by a crane or the like, and the shock absorber 40 is pulled upward by a crane or the like while the casing pipe is vibrated by the vibrating hammer 30. Thereby, the casing pipe is sequentially pulled upward while being vibrated by the vibrating hammer 30 pulled upward. In this case, the vibration of the vibration type hammer 30 is applied to each of the shock absorbers 4 in the shock absorber 40.
It is absorbed by the two four extension springs 42a.

[0007]

When the tip of the casing pipe that has been driven into the soft ground reaches a hard ground such as rock, a large pressure is applied from the outer peripheral surface of the casing pipe at the tip. . Also, since the inside of the casing is filled with sand,
A large pressure is applied to the inner peripheral surface and the outer peripheral surface at the tip of the casing pipe. In such a state, when the casing pipe is pulled out, a large resistance is applied to the casing pipe, and a large downward pulling force may be applied to the shock absorber 40 that pulls the vibrating hammer 30 upward. The shock absorbing device 40 is provided with a pair of shock absorbing mechanisms 42 each constituted by four tension springs 42a. When a large impact is applied to the shock absorbing device 40 due to the peripheral surface resistance of the casing pipe, each of the tension springs 42a. 4
2a cannot sufficiently cope with the tension spring 42a.
a may be damaged.

Further, such a shock absorber 40 has a problem that the load range in which vibration can be efficiently absorbed is limited. FIG. 7 is a graph showing the vibration transmission rate (absorption rate) with respect to the load (percentage of the maximum allowable load) applied to the shock absorber 40. In the shock absorber 40, as the load increases from the unloaded state, the vibration transmission rate decreases and the vibration absorption rate increases, but the load applied to the shock absorber 40 can effectively absorb the vibration. The range is narrow.
Typically, the vibratory hammer 30 is mounted on the shock absorber 40 so as to have a weight within a range that allows the shock absorber 40 to absorb vibrations most effectively.
Is limited within the range, and the vibratory hammer 30 having a weight smaller than the range cannot be used.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to be able to efficiently absorb the vibration of a vibrating hammer, and to be likely to be damaged even if it receives a large downward impact. Another object of the present invention is to provide a shock absorber for a vibratory pile driver in which the usable weight of a vibratory hammer is increased.

[0010]

SUMMARY OF THE INVENTION A shock absorber for a vibratory pile driver according to the present invention is provided with a structure in which a vibratory hammer attached to an upper end of a casing pipe is pulled upward to form a sand pile. This is a shock absorber for a vibratory pile driver provided to absorb the vibration of the vibratory hammer, and two sets of two slide shafts each having a lower end attached to the vibratory hammer. And a pair of connecting members for connecting the upper ends of the sliding shafts forming a pair, respectively, and four first compression springs respectively fitted to the sliding shafts so as to urge the connecting members upward, respectively. And a second compression spring that is compressed to bias each coupling body upward when the pair of first compression springs are compressed by a predetermined amount by each coupling body. And

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1A is a front view showing an example of an embodiment of a vibratory pile driver provided with a shock absorber according to the present invention,
FIG. 1B is a side view thereof. This vibratory pile driver is used, for example, to pull out a casing pipe that has been driven into soft ground to form a sand pile in soft ground. The sand pile is formed by driving a casing pipe into soft ground, filling the casing pipe with sand, and pulling out the sand-filled casing pipe.

A vibration type pile driver shown in FIGS. 1A and 1B includes a shock absorber 10 suspended by a crane or the like,
The vibratory hammer 3 connected to the lower side of the shock absorber 10
0.

The vibrating hammer 30 is attached to the upper end of the casing pipe to be withdrawn, and applies vibration to the casing pipe.

FIG. 2A is a partially cutaway front view showing the shock absorber 10 on an enlarged scale, and FIG. 2B is a partially cutaway side view thereof. At the upper center of the shock absorber 10, a support 11 suspended by a crane or the like is provided.
Three pulleys 11a around which ropes hung by a crane or the like are wound
Is provided. Each pulley 11a is rotatably supported in a vertical state.

A spring case 12 is provided on each of the left and right sides of each support 11 with each support 11 interposed therebetween. Each spring case 12 has a thin rectangular parallelepiped shape along the support 11 and is supported vertically with respect to the support 11.

FIG. 3 is a sectional view showing the internal structure of one spring case 12. Each spring case 12 has a longitudinal direction orthogonal to the width direction along the pulley 11a, and a pair of first compression springs 13 in each side thereof.
At an appropriate distance from each other, each is arranged vertically. The second compression springs 14 are vertically arranged between the first compression springs 13.

Each of the first compression springs 13 is a cylindrical lower spring seat 1 mounted on the bottom surface 12a of the spring case 12.
5, each lower end is supported. A slide shaft 16 is inserted into each first compression spring 13 in a fitted state. Each slide shaft 16 is connected to each first compression spring 1.
By passing through the bottom surface 12a of the spring case 12 through the inside of the lower spring seat 15 that supports the lower end portion of the third case 3, it is in a state of extending below the spring case 12. The upper ends of the slide shafts 16 are connected to each other in a horizontal state.
7 are connected. Each slide shaft 16 is bolted to each end of the connector 17.

At the lower end of each slide shaft 16 extending downward from the bottom surface 12a of the spring case 12, a clamp mechanism 26 for clamping the vibratory hammer 30 is mounted. Each clamp mechanism 26 clamps the vibrating hammer 30. Each slide shaft 1
A tension spring 18 is fitted to the lower part of each 6. The upper end of each tension spring 18 is attached to the bottom surface 12 a of the spring case 12 via a bush sleeve 19. Each of the extension springs 18 is fitted in a protective cylinder 21 attached to the bush sleeve 19 except for a lower end thereof. The lower end of each extension spring 18 is connected to the vibrating hammer 30 via a bush sleeve 25. Is attached to a clamp mechanism 26 that clamps the upper end of the.

The second compression spring 14 provided at the center in the spring case 12 has an axial length of about 1/2 of the first compression spring 13, and is located at the center of the bottom surface 12 a of the spring case 12. It is housed in the attached sleeve 22. Second compression spring 1 housed in sleeve 22
4 is slightly compressed in the sleeve 22. A pressing shaft 23 extending upward from the upper end surface of the sleeve 22 is attached to the upper end of the second compression spring 14. The elastic member 2 such as rubber is attached to the upper end of the pressing shaft 23.
4 is attached in a state of projecting upward.

As shown in FIG. 2 (b), three compression amount sensors 27a are provided at the center of the side surface of one spring case 12 on the side of the support 11 with an appropriate interval in the vertical direction.
27b and 27c are provided in order from the upper side. Each compression amount sensor 27a, 27b, 27c
The vertical position of each is detected,
Based on the detection results of the compression amount sensors 27a, 27b, 27c, the compression amount of the pair of first compression springs 13 provided in the spring case 12 is detected.

The shock absorber 10 having the above-described structure includes a clamp mechanism 26 attached to the lower end of the slide shaft 16.
The ropes attached to the upper end of the vibrating hammer 30 and suspended by a crane are wound around each pulley 11 a provided on the upper part of the support 11. Then, the rope wound around each pulley 11a is suspended by a crane, so that the vibration type hammer 30
Is suspended from the crane via the shock absorber 10.

In such a state, the vibrating hammer 30 is attached to the upper end of the casing pipe to be pulled out. Then, the vibratory hammer 30 is driven, and the vibratory hammer 30 is pulled upward by the crane via the shock absorber 10. In this way,
Vibrating hammer 30 vibrating casing pipe
Is pulled upward, the casing pipe vibrated by the vibrating hammer 30 is pulled out of the soft ground.

At this time, the vibration of the vibratory hammer 30 is
The power is transmitted to each slide shaft 16 of the shock absorber 10, and each slide shaft 16 is vibrated in the vertical direction. Each spring case 12
When the pair of slide shafts 16 housed in the inside are vibrated in the vertical direction, the lower end of each slide shaft 16 and the spring case 12 are moved.
The tension spring 18 provided between the spring body 1 and the bottom surface 12a expands and contracts.
Each first compression spring 13 provided between the first compression spring 13 and the second bottom surface 12a
Are contracted and elongated. Thereby, each slide shaft 1
6 is absorbed by each of the first compression springs 13 and each of the extension springs 18 and is not transmitted to each of the spring cases 12, and therefore, the support 11 to which each of the spring cases 12 is attached, and the support 11 The vibration of the vibratory hammer 30 is not transmitted to the rope that suspends the hammer.

When the tip of the casing pipe reaches the inside of a hard ground such as a bedrock, a large pull-out resistance is applied to the casing pipe due to the peripheral surface resistance at the tip of the casing pipe. As a result, a large downward impact may be applied to the vibrating hammer 30 that vibrates the casing pipe. In this case, the respective slide shafts 16 are instantaneously largely pulled downward, and the respective slide shafts 16 accommodated in the respective spring cases 12 are greatly advanced downward from the respective spring cases 12. Thereby, the connecting body 17 that connects the upper ends of the pair of slide shafts 16 in each spring case 12 is pulled downward.

The downward pulling force of the connecting body 17 is generated by each of the first compression springs 13 being compressed, and
The tension springs 18 provided between the spring case 12 and the lower ends of the slide shafts 16 are absorbed by the extension, and are absorbed. However, each of the first compression springs 13 and each of the tension springs 1 are absorbed.
8, the connecting body 1 connects the upper ends of the slide shafts 16 as shown in FIG.
7 is a second compression spring 1 located between the first compression springs 13
The second compression spring 14 is compressed by contacting the elastic body 24 connected to the upper end of the fourth compression spring 4. Thereby, each first compression spring 13
In addition, the downward pulling force of each slide shaft 16 that is not absorbed by each tension spring 18 is absorbed.

Therefore, even when a large downward impact is applied to the vibration hammer 30, the shock is absorbed by the second compression spring 14, so that the damping device 10 is prevented from being damaged. Also, there is no possibility that a large impact is applied to a crane or the like that pulls the shock absorber 10 upward.

The large downward impact on each slide shaft 16 is detected by each of the compression amount sensors 27a, 27b, and 27c. , 27b and 27c detect that a large downward impact has been applied, the vibration of the vibratory hammer 30 is stopped.
Thereby, the damage of the shock absorber 10 is more reliably prevented.

FIG. 5 is a graph showing the relationship of the vibration transmission rate (vibration absorption rate) to the load (shown as a percentage of the maximum allowable load) applied to the shock absorber 10 of the present invention. FIG.
In comparison with the graph of the conventional shock absorber 40 shown in FIG. 5, the shock absorber 10 of the present invention has a sharp decrease in the vibration transmissibility as the load increases from the unloaded state. On the other hand, the vibration is efficiently absorbed. Moreover, the usable load range having the smallest vibration transmissibility is wider than the usable range of the conventional shock absorber 40, and the usable weight range of the vibratory hammer 30 is widened.

[0030]

As described above, according to the shock absorber of the vibratory pile driver according to the present invention, the vibration of the vibratory hammer connected to each slide shaft is efficiently absorbed by each first compression spring, and Even when a large downward impact is applied to the type hammer, the impact is absorbed by the second compression spring. Therefore, even if a large downward impact is applied to the vibratory hammer, the shock absorber is not likely to be damaged. Further, since the weight range of the vibratory hammer attached to the shock absorber is widened, versatility is also improved.

[Brief description of the drawings]

FIG. 1A is a front view showing an example of an embodiment of a vibration type pile driver having a shock absorber according to the present invention, and FIG. 1B is a side view thereof.

FIG. 2A is a partially cutaway front view showing an enlarged view of a shock absorber of the vibratory pile driver, and FIG. 2B is a partially cutaway side view thereof.

FIG. 3 is an enlarged sectional view showing a main part of the shock absorber.

FIG. 4 is a sectional view for explaining the operation of the shock absorber.

FIG. 5 is a graph showing the relationship between the load applied to the shock absorber and the vibration transmissibility.

FIG. 6 (a) is a front view showing a vibration type pile driver having a conventional shock absorber, and FIG. 6 (b) is a side view thereof.

FIG. 7 is a graph showing the relationship between the load applied to the shock absorber and the vibration transmissibility.

DESCRIPTION OF SYMBOLS 10 Shock absorber 11 Support 12 Spring case 13 First compression spring 14 Second compression spring 16 Slide shaft 17 Connecting body 18 Extension spring 21 Protective cylinder 26 Clamp mechanism 30 Vibratory hammer

Claims (1)

[Claims] 1. A vibratory pile provided to absorb the vibration of a vibratory hammer attached to an upper end of a casing pipe when the vibratory hammer is pulled upward to form a sand pile. A shock absorber for a striker, wherein each lower end is attached to a vibrating hammer.
A pair of slide shafts, one pair of slide shafts, a pair of connecting members respectively connecting the upper end portions of each pair of slide shafts, and each slide shaft so as to urge each connecting member upward. The four first compression springs fitted respectively, and when the pair of first compression springs are compressed by a predetermined amount by the respective coupling bodies, the respective first compression springs are compressed so as to urge the respective coupling bodies upward. 2. A shock absorber for a vibratory pile driver, comprising: a compression spring;