GB2294280A

GB2294280A - Impact transmitting apparatus for a pile driver

Info

Publication number: GB2294280A
Application number: GB9518304A
Authority: GB
Inventors: Victor Alexandrovich Kuvshinov; Vladimir Mikhailovich Ermolaev
Original assignee: AKTSIONERNOE OBSCHESTVO ZAKRYT
Current assignee: AKTSIONERNOE OBSCHESTVO ZAKRYT
Priority date: 1994-10-20
Filing date: 1995-09-07
Publication date: 1996-04-24
Also published as: NL1001122C2; CN1121130A; GB9518304D0; NL1001122A1; DE19534115A1; RU94039661A; JPH08177050A; RU2078175C1

Description

1 2294280 1 APPARATUS FOR TRANSMITTING IMPACT ENERGY FROM A STRIKING MASS

TO A DRIVEN MEMBER

The present invention relates to the field of constructing pile foundations of buildings, bridges, ports, marine gas and oil producing platforms, etc.

The present invention can be most successfully utilized in machines of impact action, and more particularly in hammers for driving any kinds of piles, such as reinforced concrete piles, steel tubular piles and piles of other profiles.

Owing to the wide use of piles in the construction industry, it has become necessary to protect piles against failure or plastic deformation occurring when they are being driven into the ground under a striking mass action.

Currently, the problem of protecting piles against failure is solved by using shock-absorbing elements disposed between a striking mass and a pile end. Generally, the shock-absorbing elements are made of materials softer than steel, such as hard and durable kinds of wood, asbestos, felt, plastics, etc. The shock-absorbing elements, however, are short-lived and rapidly fail. Their failure is accelerated by overheating in operation due to the low thermal conductivity of the material from which the shock-absorbing elements are made. In addition, the overheating reduces the elastic characteristics of the material, and this prevents the attainment of stable shock-absorbing properties and can even cause combustion of the shock-absorbing element. The short service life of the shock-absorbing element reduces the total efficiency of the operations involved in driving piles into the ground.

An attempt to improve the durability of the shock-absorbing element resulted in an apparatus for transmitting impact energy from a striking mass to a driven member (DE patent No. 3006234). lbs known apparatus is designed for use in hammers for driving piles into the ground. It comprises three parts. The apparatws is made entirely of steel and is provided with a massive upper part, known as a drivehead, having a spherical impact surface facing a hammer 2 striking mass. The drivehead is integrally joined to a tubular section, the diameter of which increases with the distance from the drivehead. In the lower part the tubular section merges to a support element made in the form of a massive ring opposite to the drivehead and designed to interact with a c1riven member, such as a pile. All parts of the apparatus are arranged in alignment. In this apparatus, the shock- absorbing element is a tubular section connecting the drivehead to the support ring, the shock absorbing properties thereof being provided by elastic deformation under the action of impact force. The required magnitude of the deformation is ensured by selection of an appropriate length of the tubular section. The tubular section has a uniform cross section along the entire length thereof, the cross section value being selected so as to provide a required strength.

In the aforementioned apparatus the shock-absorbing element in the form of a cone-shaped tubular section is made of steel, which substantially improves the durability of the apparatus as a whole, making its service life practically unlimited.

However, to achieve. appropriate shock-absorbing properties, the tubular section should have a large length, as a result of which the apparatus is several tinies longer than a corresponding analog having soft shockabsorbing inserts. This results in a substantial increase of the axial dimension of the apparatus for transmitting impact energy, and, hence, of the entire hammer, which is not always acceptable. In practice, the apparatus of the aforementioned design has found application only in special-purpose marine hydraulic hammers of the MHU model, manufactured by FERROSTAAL AG. (BRD) and designed solely for driving long steel tubular piles into the seabed. In this case, an increase of hammer length is admissible because of the use of cranes installed on special ships, the hook elevation height thereof being 70 m and more. Furthermore, relatively more rigid apparatuses, i.e. possessing a lower degree of elastic deformation, and, therefore, being shorter, can be used in marine 3 hammers, since a long pile per se is a good shock absorber due to the considerable elastic deformation thereof at impact. However, the shockabsorbing element of the construction described above has not found application in hammers for driving reinforced concrete piles, constituting an absolute (overwhelming) majority in all pile-driving machines used worldwide. This is due to the fact that a reinforced concrete pile can be considered to be absolutely rigid, failing to provide a shock-absorbing action at impact. As a consequence and also due to the lower strength of a reinforced concrete pile as compared to a pile made of steel, an apparatus for transmitting impact energy to a pile should possess substantially greater elastic deformation than a similar apparatus used in marine hammers. This makes it necessary to substantially increase the tubular section length, increasing thereby the length and weight of the hammer which is generally of a pile-driver type, i.e. such as to be suspended from the guide of a pile driver, the guide acting as a guiding member. Therefore, a pile driver guide should provide for the disposal of a reinforced concrete pile with a hammer put thereon. With a substantial increase (up to 1.5 times) of hammer length, the length of a standard guide of pile drivers manufactured worldwide fails to provide sufficient space for a standard pile with a hammer, which is the main reason why the apparatus according to DE patent No. 3006234 is not used in hammers of pile drivers.

It is an object of the present invention to provide an apparatus for transmitting impact energy from a striking mass to a driven member, wherein the axial dimension of the apparatus is substantially reduced due to the design of the shock-absorbing element, while a large length of the latter is maintained.

It is another object of the invention to reduce the axial dimension of an apparatiLs for transmitting impact energy, while maintaining hardne%, of tile sh ock -absorbing element.

4 It is still another object of the invention to simplify the process for manufacturing the apparatus. Still one more object of the invention is to protect a pile end against failure.

With these and other objects in view, the essence of the present invention resides in that in an apparatus for transmitting impact energy from a striking mass to a driven member, the apparatus comprising three aligned elements, the first of which, adapted to interact with the striking mass, is massive, the second element, adapted to interact with the driven member, is opposite to the first element and acts as a support, and the third, a shock-absorbing element, is connected to the first and second elements, wherein according to the present invention, the shock- absorbing element comprises successively connected central bar and at least two concentrically disposed tubular members, the central bar being connected to the first element and the outer tubular member being connected to the second element.

Owing to such a design of the apparatus, the latter has a small axial dimension, while maintaining high elasticity due to the large overall length of the shock-absorbing element. This makes the apparatus suitable for use in pile driver hammers for driving both steel and reinforced concrete piles.

It is recommended that the cross section areas of the central bar and each tubular member be made substantially equal.

The necessity for this feature is to ensure equal strength of the central bar and the tubular members, while maintaining a predetermined elasticity of the apparatus.

Each connection between the first element and the central bar, the central bar and the inner tubular member, between tubular members themselves and between the outer tubular member and the second element, is preferably made nondetachable.

This feature ensures maximum strength and durability of the apparatus.

Each nondetachable connection is preferably formed by a weld.

This feature satisfies the requirement for a rigid connection, and the apparatus is simple and inexpensive to manufacture.

Each nondetachable connection can alternatively be made by shrink fit.

This can be preferred over the weld connections in the case when the apparatus has large overall dimensions.

It is advisable that the second element, at the side facing the driven member, has a spherical surface.

Such a design is preferably used in pile driver hammers for driving reinforced concrete piles since the spherical surface essentially compensates misalignment between the force vector of a striking mass and the longitudinal axis of a pile, which prevents failure of the end of the latter.

Alternatively, the central bar of the shock-absorbing element can be provided with an inner cavity, such as a cylindrical axial bore.

This may be advantageous from structural considerations, namely, in order to ensure the selection of the best relationship of lateral dimensions of separate elements, and from technological considerations, in order to reduce the cost of manufacture or to improve strength of the apparatus.

Other objects and advantages of the present invention will become more apparent from the following description of specific examples of practicing the invention, taken in conjunction with accompanying drawings, in which:

Fig. I is a schematic isometric longitudinal section view of an apparatus for transmitting impact energy from a striking mass to a driven member, for example, a pile, in accordance with the present invention.

Fig. 2 is a longitudinal section view of an apparatus in accordance with the present invention wherein the nondetachable connections of the elements are made by welding.

Fig. 3 is a longitudinal section view of an apparatus in accordance with the present invention wherein the nondetachable connections of the elements are made by shrink fit.

6 Fig. 4 is a schematic longitudinal section view of a harnmer for driving piles with the apparatus in accordance with the present invention.

Fig. 5 is a schematic longitudinal section view of the same as in Fig. 4, but with an embodiment of the apparatus in accordance with the present invention.

Referring to Fig. 1, an apparatus 1 is shown for transmitting impact energy from a striking mass to a driven member, according to the present invention. The apparatus comprises three aligned elements 2, 3 and 4. The first element 2, adapted to interact with a striking mass (not shown), is massive and is referred to as a drivehead. The latter has a plane or convex impact surface 2a. The second support element 3, adapted to interact with a driven member (not shown), is opposite to the drivehead 2, and formed, for example, as a massive ring or a solid plate. Ilie third, shock-absorbing element 4 is connected to the drivehead and massive ring. Element 4 comprises successively connected central bar 5 and at least two concentrically disposed tubular members 6, 7. Mie central bar 5 is made, for example, solid (monolithic), as shown in Fig. 1, or has an inner cavity (Figs. 4, 5). One end Sa of the latter is rigidly (nondetachably) connectd to the drivehead 2, and the other end 5b thereof is connected to one end 6a of the inner tubular member 6, the other end 6b of which is rigidly (nondetachably) connected to an end 7a of the outer tubular member 7. the other end 7b of the outer tubular member 7 being rigidly (nondetachably) connected to the second support element 3. Ilie rigid (nondetachable) connections of the abovementioned members 2, 5, 6, 7 and 3 are made by welds 8, as shown in Fig. 2, or by shrink fit 9, as shown in Fig. 3. Ilie central bar 5, inner tubular member 6 and outer tubular member 7 have essentially equal cross-section areas, providing equal strength of those members while maintaining a desired elasticity of the shock-absorbing element 4. A successive connection of the central bar 5, ir-mer tubular member 6 and outer tubular member 7 provides a shockabsorbing element 4 having a large overafl 7 length, which improves the shock-absorbing ability of the apparatus as a whole, the axial dimension thereof being small. Where necessary, the shock-absorbing ability of the apparatus 1 can be improved over a wide range by increasing the overall length of the elastic member 4 by increasing the number of tubular members, for example, to four. In this case the axial dimension of the apparatus 1 can be maintained unchanged.

Fig. 4 illustrates the use of an apparatus 1, made in accordance with the present invention, in a hammer for driving steel tubular piles. The hammer comprises a housing 10 accomodating a longitudinally movable striking body 11 which is connected through a rod 12 to a hydraulic motor 13 driven by a pump (not shown). An end 14 of the st body 11, facing the apparatus 1, is spherical. The apparatus 1, adapted to move longitudinally, is disposed within a lower part of the housing 10 and rests by a support element 3 on an end of a steel tubular pile 15. A Ode 16, joined to the housing 10, is provided to facilitate mounting of the hammer on the pile 15. A damper 17 is provided to increase durability of the housing 10 and apparatus 1.

The hammer as described above operates as follows. When the hammer is set on a pile 15, the apparatus 1 for transmitting impact energy rests closely on the upper end of the pile 15, the striking body 11 rests on the apparatus 1, and the damper 17 is compressed by the weight of the housing 10. When the hydraulic motor 13 of the hammer is activated, the striking body 11 is lifted by the rod 12 to a predetermined height required to produce a predetermined impact energy. When the striking body 11 falls, it interacts with the end surface 2a of the drivehead of the apparatus 1 via the spherical surface 14. The apparatus 1 damps the impact by elastic deformation of the element 4, extending the duration of impact and thereby eliminating the hardness of impact. An appropriate length of the shock-absorbing element 4 provides the required elasticity thereof, allowing strains to be generated in the pile end which do not exceed permissible levels. As a result of transmaing impact 1 8 energy from the striking body I I via the apparatus I to the pile 15, the latter sinks into ground, relieving the damper 17. At the moment fonowing the impact, the striking body is lifted upwards, relieving the load from the apparatus 1. The damper 17 protects apparatus I from failure when the housing 10 falls on apparatus I after impact. Further, the cycle is repeated.

When a pile driver hammer is used for driving reinforced concrete piles, the construction of the apparatus for transmitting impact energy is modified to a certain extent. The apparatus I (Fig. 5) is made similar to that described above. A distinction is that the second support element 3, at the side facing a reinforced concrete pile 18, has a spherical or otherwise shaped convex surface 19 to compensate misalignment between the force vector of the striking body I I and longitudinal axis of the pile 18. A plate 20 having a guide 21 is provided to distribute the impact load uniformly across the end of the pile 18.

The haminer operates in a manner similar to the hammer described above.

The present invention makes it possible to produce an integral steel apparatus having shock -absorbing properties exceeding those of widely used analogs with soft shock-absorbing inserts. The axial dimension of the apparatus in accordance with the present invention does not exceed the axial dimension of the corresponding analog, and its durability is practically unlimited. This results in a substantial improvement of efficiency and reduction of costs for driving piles due to the elimination of time losses and expenditures for replacement of destructible soft shock-absorbing inserts. Thousands of pile driver hammers used worldwide can be efficiently equipped with apparatuses according to the present invention.

The apparatus for transmitting impact energy to a steel or reinforced concrete pile has an axial dimension equal to about 500 min with a maximum impact energy of 100 kj and length of the shock-absorbing member equal to about 700 nim.

The proposed apparatus in accordance with the invention can successfully be used in marine hammers having an impact energy of 400-16M kj.

When piles which are at a small distance from each other are driven, the diameter of the hammer housing is limited. This may entail making the central bar of the shock-absorbing member solid, while the cross-section areas of the solid bar and the tubular members are maintained equal.

The central bar can be made together with the drivehead from one blank.

The proposed apparatus for transmitting impact energy is technological and inexpensive in production.

1

Claims

An apparatus for transmitting impact energy from a striking mass to a driven member, comprising three aligned elements, the first of which is adapted to interact with a striking mass and is massive, the second of which is adapted to interact with a driven member, is opposite to the first element and acts as a support, and the third of which is a shockabsorbing element connected to the first and second elements and comprisingsuccessively connected, a central bar and at least two concentrically disposed tubular members, the central bar being connected to said first element, and the outer said tubular member being connected to said second element.
2. An apparatus according to claim 1 wherein the cross-section area of the central bar is substantially equal to the cross-section area of each said tubular member.
3. An apparatus according to claims 1-2, including nondetachable connections between:- the central bar and the first element and the inner tubular member, between said tubular members themselves, and between said outer tubular member and the second element.
4. An apparatus according to claim 3, wherein each said nondetachable connection is formed by a weld.
5. An apparatus according to claim 3, wherein each said nondetachable connection is formed by shrink fit.
6. An apparatus according to any one of the preceding claims, wherein the second element, at the side facing the driven member, has a spherical surface.
7. An apparatus according to any one of claims 1 to 6, wherein the central bar is made hollow.
8. An apparatus for transmitting impact energy from an impact mass to a driven member, substantially as hereinbefore described in the description with reference to Figs. 1-5.