Pile driving and drawing apparatus

Abstract

A pile driving and drawing apparatus for use in foundation works, provided with a weight assembly which houses an excitor, and resilient bodies, two of which are interposed between the weight assembly and the head of a pile, another being interposed between said weight assembly and means for suspending the same. The frequency of the excitor is so designed as to coincide with the frequency of the weight assembly, the latter being dependent on one of said resilient bodies interposed between the weight assembly and the pile head, whereby the vibration of the weight assembly imparts downward driving forces to the pile head. The frequency of the excitor is also designed to coincide with the frequency of the weight assembly, the latter frequency being dependent on the other of said resilient bodies interposed between the weight assembly and the pile head as well as the resilient body interposed between said weight assembly and said suspending means, whereby the vibration of the weight assembly imparts upward driving forces to the pile for the drawal thereof.

Description

This invention relates to a pile driving and drawing apparatus for driving and drawing a pile for use in foundation works, which pile is made of concrete, steel or wood and provided in a pole, tubular or sheet form.

Hitherto, known as apparatuses or devices for driving piles for use in foundation works into the ground are a drophammer, diesel hammer, steam hammer, etc. However, those apparatuses or devices only provide driving cycles ranging from 5 to 200 blows/min. On the other hand, a vibration type pile hammer, one of the conventional apparatuses, has at least a pair of weights and utilizes centrifugal forces created thereby, while it provides driving cycles of over 1,000 blows/min. This apparatus, however, dictates the use of an extremely great driving force utilizing the centrifugal force of a pair of weights for directly exerting the head of a pile, with said weights being moved in a vertical direction in synchronism with each other. This in turn results in damages on the pile head, in case the pile is made of a concrete having lower tensile strength.

The present invention is directed to avoiding the drawbacks experienced with the prior art pile driving apparatuses.

According to the one aspect of the present invention, there is provided an apparatus adapted to drive a pile into the ground, comprising a guide member having an `I` shaped cross section and consisting of a rod having flanges, one of which is to be positioned on the head of a pile to be driven into the ground; a weight assembly relatively moving with respect to said guide member, said assembly including a casing having an impinging portion adapted to impinge on one of said flanges of said guide member and a bore portion adapted to slideably receive the rod of said guide member therein, said bore portion being located centrally of said casing and said impinging portion being positioned at the lower end of said bore portion, and an excitor housed in said casing; and a resilient body interposed between one of said flanges and said impinging portion of said casing, the frequency of said excitor being in coincidence with that of said weight assembly, which is dependent on said resilient body.

According to another aspect of the present invention, there is provided an apparatus adapted to draw a pile from the ground, comprising a guide member of an I shaped cross section and consisting of a rod having flanges, one of which is to be secured to the head of a pile; a weight assembly relatively moving with respect to said guide member, said assembly including a casing having a bore portion adapted to slidingly receive said rod and an impinging portion adapted to impinge on one of said flanges and positioned at the upper end of said bore portion, and an excitor housed in said casing; a first resilient body interposed between the top of said weight assembly and supporting means for suspending said weight assembly; and a second resilient body interposed between one of said flanges and said impinging portion of said casing, the frequency of said excitor being in coincidence with that of the weight assembly which is dependent on said first and second resilient bodies.

Before proceeding with the description of the preferred embodiments of the invention, it would aid in better understanding of the present invention to describe the two fundamental principles incorporated in the present invention.

The first principle of the present invention:

Referring to FIG. 1, suppose that a weight W is dropped on a spring from a height h.sub.o above the spring having a free length H.sub.o and a spring constant k, and thereby the spring is compressed a distance y.sub.o acting a force F on a floor, after which the weight W is bounced upwards by means of a restoring force of the spring to its initial position. If a damping force is not present, such upward and downward movements of a spring will be continued permanently, effecting free vibration having a frequency f.

In this case, the following formula will be maintained among those factors such as the weight W of a weight, frequency f, total amplitude A (= h.sub.o + y.sub.o), spring constant k, impact F acting on a floor and acceleration coefficient .xi.(= F/W): spring energy ##EQU1## then, according to the principle of the conservation of energy, ##EQU2## whereas ##EQU3## Suppose that the time required for a weight to effect the free drop from or bouncing upwards to a height h.sub.o is t.sub.1,

from formula, ##EQU4##

The equation of motion during the movement of a weight in contact with the spring will be given as follows: ##EQU5##

This represents simple harmonic oscillation having a vibration center of ##EQU6## wherein H represents the height of a spring when the weight is placed on the spring slowly. The symbol y appearing in formula (4) represents displacement of an object from the vibration center, where t represents the time having the vibration center given as the time original point.

Suppose that t.sub.2 represents the time required for moving up or down between the vibration center H and the free height H.sub.o, and y = W/k and t = t.sub.2, ##EQU7## or ##EQU8##

When the above formula is substituted by y.sub.o = (.xi. W/k) from formula (1), ##EQU9##

Then, suppose that t.sub.3 represents the time required for the weight to move up or down between the vibration center and the maximum compressed point, and formula (4) is substituted by y = y.sub.o - Wk, t = t.sub.3, then ##EQU10##

Suppose that T and f represent total period of vibration and frequency, respectively, then ##EQU11## From formulae (3), (5) and (6), ##EQU12## The total amplitude A will be given as follows:

From formula ##EQU13## From formula (7), ##EQU14##

If the acceleration coefficient .xi.(= F/W) and f are given, then the total amplitude A will be determined from formula (8), while the compressed amount y.sub.o of the spring will be also determined from formula (9).

On the other hand, if the acceleration coefficient .xi., frequency f and weight of a weight W are given, the required spring constant k will be determined from formula (7).

If the free vibration of the weight overcomes a damping force which is inevitably present, to allow the permanent vibration, while an excitor is housed within the weight so as impart continuous vibration or downward impact F of the head of a pile, with the frequency of the excitor being in coincidence with the free frequency f of the weight, then there will arise a resonance phenomenon therebetween, whereby the drive house power of the excitor will be converted into the work of driving a pile into the ground at the maximum efficiency.

FIG. 2 shows a centrifugal weight type excitor having two weights adapted to rotate in opposite directions to each other at a frequency f, thereby producing vibration in a vertical direction. The weight of two weights (2w) and the additional weight accompanied therewith are assumed as being included in the weight of a weight W.

The maximum exciting force q in the vertical direction in this case is given as follows: ##EQU15##

The following prerequisites should be satisfied for starting to move the weight w.

As is apparent from formula (2), the weight w of rotary weights of the excitor is extremely small, as compared with that of the weight W of weight.

The horse power P required for driving the excitor will be given as follows, with the proviso that A represents the total amplitude of the rotary weights: ##EQU16##

wherein:

m : mass of one rotary weight (Two of these rotary weights form an excitor.)

r : radius of gyration of m

.omega. : angular acceleration of m.

The centrifugal force in the case with FIG. 5 acts upwardly and the magnitude thereof will be as follows:

wherein t represents the time origin when the rotary weights having mass m is positioned at the uppermost position.

Accordingly, the centrifugal force is 2mw.sup.2 r cos .omega.t. When the excitor having a weight W vibrates at the total amplitude A or at the half amplitude A/2, and the frequency thereof coincides with that of the R.P.M. of the excitor of a weight 2w, there will be created a resonance. In this case, the phase of vibration of excitor is off-phased by .pi./2 as compared with the phase of the excitor having the rotary weight of a mass m. The vertical displacement of the excitor during the time dt at the time t will be given as follows: ##EQU17##

Accordingly, the work of the excitor during the time dt will be given as follows: e1 ? A ? Aw? ? 2mw.sup.2 r cos .omega.t .sup.. w cos .omega.t.sup.. dt = (2mw.sup.2 r) cos.sup.2 .omega.tdt? 2 2

The work of the excitor during one rotation will be as follows, with the proviso that the period T ##EQU18##

Assume the frequency of f, then the work done during a unit time will be f times as much as the work. If this is assumed as being power P, then ##EQU19## whereas q = 2mw.sup.2 r is the maximum centrifugal force of the excitor, ##EQU20## Further assume that the weight of one rotary weight is w, then,

or

Referring to FIG. 4, if a pile S is driven into the ground at the same frequency as that of the weight having a weight W, yet at the total amplitude A, the apparent amplitude of the weight will be 2A. In other words, when the pile is not sinking, the weight will vibrate at the total amplitude A in a condition (a), while if the pile is sinking, the weight will vibrate in conditions (b) and (c), and thus the total amplitude will be 2 A. The horse power Pmax in this case will be as follows: ##EQU22##

As is apparent from the foregoing description, as shown in FIG. 2, if a resilient body having a spring constant k is secured to a pile S, and a weight having weight W is housed in excitor, with the frequency of said excitor being in coincidence with that of a weight which is dependent on said resilient body, then there will arise a resonance. Accordingly, the drive horse power of the excitor which may be estimated from said Pmax will act on the pile as a driving force of a downward direction.

The second principle of the present invention:

Referring now to FIG. 5, if a weight having weight is suspended by the medium of a resilient body having a spring constant k.sub.1 by means of a supporting body A, and yet an object B is connected by the medium of said resilient body having a spring constant k.sub.2 to said weight, and the weight is subjected to vertical vibration, then the weight will vibrate at a natural frequency f. Suppose that the weight effects downward movement, there will be created a clearance between the stationary object C and the object B, such that the object C will be located in a position shown by the broken line. The weight will move downwardly until the aforesaid clearance reaches the maximum, after which the weight starts moving upwards. While the weight is shifted to an upward movement and the object B contacts the object C, the weight will have maximum kinetic energy. The weight will undergo actions of the resilient body having spring constant k.sub.1 as well as the resilient body having a spring constant k.sub.2.

Accordingly, in case a weight assembly housing an excitor therein consisting of a pair of rotary weights and the vibration of a weight is so designed as to overcome a damping force for continuing vibration, then the object may exert an upward impact on the object C continuously. In addition, the maximum upward impact exerted by the object B on the object C will be achieved by bringing the frequency of said excitor in coincidence with the natural frequency of a weight which is dependent on said two resilient bodies, due to the resultant resonance.

Thus, this permits drawing of a pile by applying an upward force thereto by the medium of the object C integral with a pile. Alternatively, the object C may be the pile itself.

The present invention thus presents a pile driving and/or drawing apparatus utilizing one or both of the aforesaid two principles.

These and other objects and features of the present invention will be apparent from a reading of the ensuing part of the specification, taken in connection with the drawings which indicate embodiments of the present invention, in which:

FIGS. 1 - 4 are diagrams illustrating the first principle of the invention;

FIG. 5 is a diagram illustrating the second principle of the invention;

FIG. 6 is a side elevation of the pile driving and drawing apparatus according to the present invention, showing the supporting means together;

FIG. 7 is a side elevation of the apparatus of the invention which is applied to the drawing operation of a pile;

FIG. 8 is a longitudinal cross-sectional view of the apparatus according to the present invention;

FIGS. 9 and 10 are perspective views of a subsidiary eccentric weight assembly according to the present invention, showing the detailed construction thereof;

FIGS. 11 and 12 are longitudinal cross-sectional views of embodiments of caps each adapted to receive a pile head firmly, according to the present invention;

FIG. 13 is a longitudinal cross-sectional view of another embodiment of the apparatus according to the present invention;

FIG. 14 is a partial, longitudinal cross-sectional view taken along the line 14--14 of FIG. 13;

FIG. 15 is a partial, longitudinal cross-sectional view of the casing of rollers shown in FIGS. 6, 7 and 8, showing the attachment thereof; and

FIG. 16 is a side elevation of an excitor housed in a casing.

Referring to FIG. 6, there is shown at 12 a pile driving and drawing apparatus according to the present invention, which is suspended by a supporting means 10. The supporting means 10 includes an endless track vehicle 14 and a leader 16 pivotted thereto, and a boom 18 whose opposite ends are pivotted to said vehicle and leader, and which is extensible.

The leader 16 is provided with a guide rod 20 disposed lengthwise thereof, with the top of said leader being provided with sheaves 22 and 24. A wire is trained around sheaves 22 and 24 and a sheave 29 which is journaled in a holder 28 having a hook 26.

The pile driving and drawing apparatus 12 includes a casing 32 which houses a plurality of rollers 34 engaging a guide rod 20 secured to the leader 16. The casing 32 is provided with a suspending ring 36 at the top thereof, and the apparatus 12 is suspended by supporting means 10 including wire 30 by the medium of a wire 38 of a ring form, which engages said suspending ring 36 and is adapted to receive the hook 26. The casing 32 is provided with a cap 42 in the lower portion thereof, while the cap 42 is adapted to fit on the head of a pile 44 which is to be driven into the ground.

Referring to FIG. 7, the pile driving and drawing apparatus 12 has suspending ring 36 and hook 26 connected to each other by the medium of a damper 46 including a plurality of springs, while a chuck 48 is provided at the lower end of the casing. The chuck 48 secures the head of a sheet pile 50.

As can be seen from the foregoing, the pile driving and drawing apparatus according to the present invention is used either for driving a pile as shown in FIG. 6 or for drawing a pile as shown in FIG. 7.

The construction of the pile driving and drawing apparatus 12 will be described in more detail with reference to FIG. 8. As shown, the casing 32 consists of an upper portion 32a housing a pair of rotors 54 therein (one of the rotors is shown in FIG. 8.) adapted to be driven and rotated by means of an electric motor 52 and a lower portion 32b housing a guide member 57 of an I shaped cross-section consisting of rods 56 having an upper flange 55a and a lower flange 55b. The pair of rotors 54 in the upper portion 32a of the casing are provided with gears 58 engaging each other and an arcuate weight plates 60 attached to the outer circumference of the rotors 54 in an eccentric manner. The excitor consists of said motor 52 and eccentric weights 60, and said rotors are rotated due to the operation of the motor 52. In this respect, the lateral and horizontal vibration will be off-set due to the rotation of said eccentric weights, leaving a vertical vibration. During the non-operating condition of the motor 52, each rotor maintains eccentric weights positioned still in its lower position as shown.

The lower portion 32b of the casing has an internal space defined so as to house said I shaped member 57 in a manner to permit the relative movement thereof. The lower portion 32b of the casing includes a reduced portion 62 slidingly engaging the rod 56 of the I shaped member 57, upper shoulder portion 64 formed at the upper end of said reduced portion 62, and lower shoulder portion 66 at the lower end of the reduced portion 62.

The lower flange 55b of the rod 56 secures a cap 42 as shown in FIG. 6 and a chuck 48 as shown in FIG. 7, depending on whether a pile is being driven or withdrawn. The casing and the excitor housed in the casing serve as weights which exert a driving force or drawing force to a pile.

The upper shoulder portion 64 and the lower shoulder portion 66 of the casing 32 serve as impinging portions against the upper flange 55a and lower flange 55b of the I shaped member 57 the with respective flanges and shoulder portions have mounted thereon the resilient members 70, 72, 74 and 76 made of rubber-like resilient material. The resilient members 70 and 72 are interposed between the flange portion 55a and the shoulder portion 64 which are to impinge on each other upon drawing the pile. The material and dimensions of the resilient members are designed to have such an elastic modulus such that the vibration frequency of the aforesaid weight assembly will coincide with the frequency of the excitor which is dependent on said resilient bodies constituting a damper 46. On the other hand, the resilient bodies 74 and 76 are interposed between the flange portion 55b and the shoulder portion 66, such that the material and dimensions of the aforesaid resilient bodies are selected so as to have such an elastic modulus that renders the frequency of the weight assembly, which is dependent on the resilient members, coincident with that frequency of the said excitor.

Upon driving a pile into the ground, the apparatus 12 is placed on the head portion of the pile 44, as shown in FIG. 6, the weighted casing 32 is adjusted by means of the cable suspension 30 in relation to the guide member 57 so that only the lower shoulder 66 and the flange 55b will impinge and then the motor 52 of the excitor is energized. This causes the resonance between the excitor and the weight assembly, whereby a downward impact will be applied on the head of the pile. In other words, suppose that the acceleration coefficient .xi. is constant C in formula (7), then ##EQU23## If the elastic modulus of resilient bodies and the weight of a weight assembly are so selected as to render the value of W/g constant, then the impact may be obtained by setting the R.P.M. of the motor 52 to the R.P.M. corresponding to the constant frequency f given thereby. The downward impact F exerted on the head of a pile by means of a weight assembly due to the resonance between the excitor and the weight assembly is extremely great, as compared with the horse power of the motor 52.

When comparing the drive horse power P of the apparatus according to the present invention with the drive horse power P' of the conventional vibrating type pile driver, the following relationship will be obtained: ##EQU24##

From formula (12), P/P' = q/F

while q>W in formula (11), then

Although a>1, a = 2 .about. 4, .xi. = 10 .about. 20 ##EQU26##

Accordingly, the same effect may be achieved with 10 to 40% horse power of the conventional type pile driver. Even if .xi. is 10, the same effect may be achieved with 20% horse power of the conventional vibration type pile driver, with some allowance being taken into consideration.

Next, upon drawing a pile from the ground, as shown in FIG. 7, the chuck is secured to the head of pile 50, and then said weight assembly, i.e., the casing 12 housing the excitor therein is pulled upwards, to an extent that will not cause an initial tension in the pile. This places the weighted casing 32 in such a position relative to the guide member 57 that when the excitor 54 is energized only the upper shoulder member 64 and the upper flange 55a will impinge. Thus, when the weight assembly is vibrated upwardly of the vibration center of the weight assembly, a drawing force may be effectively applied to the pile. Thereafter, the excitor is energized, causing the resonance between the frequency of the excitor and the resilient members and the frequency of the weight assembly which is dependent on the resilient members 70, 72 and 46. However, when the weight assembly is lowered along the I shaped member 57, it will not exert a downward force on the pile, but when the weight assembly is displaced upwardly, then the upper shoulder portion 64 of the casing 12 serving as weights will impinge on the upper flange 55a of the I shaped member 57 which is secured by the medium of chuck 48 to the pile head, thereby exerting an upward force or upward drawing force on the pile head.

The resonance between the weight assembly and the excitor provides great drawing force at lower horse power to a pile while imparting vibration to a pile, thereby reducing a friction force between the outer periphery of the pile and the ground.

The weight of the weight assembly including the casing 32 and the excitor housed in the casing 32 may be varied by removably attaching a suitable subsidiary weight to said weight assembly. It will be understood from the foregoing description that the variation in the weight of a weight assembly dictates the variation in R.P.M. of the motor 52 to insure said resonance. In addition, for insuring the constant R.P.M. for the rotors 54 of the excitor, the subsidiary eccentric weight 78 is attached to the respective rotors 54, as shown in FIG. 9, commensurate to the cycles of the motor electric power source. The eccentric weight, as shown, is made of a metallic material of a half-cylindrical shape, which is formed with two bent edge portions 80 and 82, and fitted on the eccentric weights 60 on the rotors 54 in sliding fashion, as shown in FIG. 10.

The edge portions 80 and 82 of the subsidiary weight 78 engage the respective edge portions 84 of the eccentric weights 60, thereby preventing the detachment thereof due to the rotation of the rotors.

While the I shaped guide member 57 as shown in FIG. 8 mounts cap 42 or chuck 48 for driving or drawing a pile, the typical embodiment of the cap will be described, in reference to FIGS. 11 and 12.

Shown in FIG. 11 is a cap 42 adapted to be fitted on the head of a pile 44 to be driven into the ground. The cap 42 includes a top plate member 86 bolted to the lower flange 55b of the I shaped member 57 and a side plate which is integral with the top plate member 86 and of a cylindrical form, said side plate having a plurality of openings in the periphery thereof. Fixedly fitted by means of bolt-nut fastening means 92 in the openings in the side plate are pile retaining assemblies 90 extending in a radial direction of the cap. Furthermore, a guide ring 94 is secured by means of a bolt 96 to the inner side of the side plate in the lower portion of the side plate 88, said guide ring 94 being adapted to introduce the pile 44 into the cap 42. The pile retaining assemblies 90 consist of a plate member 100 having an extension 98 received in said opening, a finger 104 fastened by means of bolt-nut assembly 102 to said plate member 100, and a coil spring 106, one end of which is secured to the finger 104 and the other end of which is secured to the plate member 100. In this respect, the finger 104 is slidable along the aforesaid extension in the radial direction of the cap, i.e., the pile, depending on the diameter of the pile to be received in the cap 42. The finger 104 and guide ring 94 are formed with tapered surfaces 107 and 108, thereby facilitating positioning and receipt of a pile within the cap.

For coping with the considerable degree of variation in the diameter of the pile, the working length of the boltnut assembly 102 may be varied or a suitable spacer may be inserted between the side plate 98 and the plate member 100 to thereby space the pile retaining assembly 90 from the axial line of the cap 42 in its entirety.

Referring to FIG. 12, the cap 42' fitted on the pile 50 made of a steel angle is rotatably journaled on the shaft 114 attached by the medium of an attaching plate 112 to the base plate 110 which is bolted to the lower flange 55b of the I shaped member 57. Located within the bearing portion 116 of the cap 42' is a ball bearing 118 which surrounds the shaft 114. The ball bearing 118 is held in position by means of a ring 122 held by the nut 120 fitted on said shaft 114.

The cap 42' is formed with a skirt portion 124 under the bearing portion 116, while a pile retaining assembly 126 having a construction similar to that shown in FIG. 11 is provided for the skirt portion 124. The cap 42' is rotatable about the shaft 114, with the pile being received within the skirt portion 124, such that the direction of the pile may be changed as required at a given pile driving position.

Referring to FIGS. 8 and 13, the casing 32 constituting the weights of the pile driving and drawing apparatus 12 effects upward and downward movements relative to the guide member, i.e., the I shaped member 57, due to the operation of the excitor similarly forming weights. However, in this case, the casing 32 causes a lateral impact to the I shaped member, in addition to the vertical impact thereon.

The magnitude of the lateral impact corresponds to about 10% of the vertical impact.

Maximum vertical impact may be achieved by minimizing the lateral impact. FIG. 13 shows an embodiment which is intended to reduce the lateral impact exerted by the weights on the guide member, i.e., the I shaped member 57. A plurality of roller groups 130 are located adjacent to the flange portions 55a and 55b of the I shaped member in a spaced relation along the circumference of the flanges, said roller groups 130 being rotatable relative to the inner wall of the casing 32. The respective roller groups include a plurality of rollers 131 as shown in FIG. 14. Respective rollers normally engage the edge faces 132 of the respective flanges, thereby permitting the smooth relative movement with respect to the guide member of the weight assembly. The rollers are each supported by a shaft 138 by a axial support member 135 which is attached by means of a plurality of bolt-nuts 136 to the flange 134 provided in the lower portion 32b (FIG. 8) of the casing 12. The respective rollers 131 are made of a rubber-like resilient material. In addition, the respective rollers have a configuration of a radius of curvature equal to that of the flange 55a of the guide member. Disposed between the flange 134 of the casing and the roller supporting member 136 are a spacer 140 and a damper 142 which are inserted in an attempt to vary the relative distance between the shaft 138 and the flange 55a. Damping members of a material the same as that of said damping member are attached to the attaching portions of the rollers 34 (FIGS. 6 to 8) to the casing. In other words, as shown in FIG. 15, there are provided damping members 152 and 154 between the base portions of the supporting shaft 146 of the rollers 34 and the outer side surface of casing 32 and between said base portion and the bracket 150 securing the base portion to the casing. The bracket 150 is secured by means of a plurality of bolts 156 to the casing. Oil 158 is contained within the upper portion 32a (FIG. 8) of the casing which houses the motor 52 and the eccentric weight rotors 54 driven by the motor 52, as shown in FIG. 16. The oil serves for the insulating purpose for motor coils as well as for lubricating purpose for gears and motor bearing portions. The casing is provided with a suitable pressure adjusting means 160 to maintain the internal pressure constant, because said oil will be atomized to a mist form due to the rotation of the motor to thereby raise the pressure within the casing. After the stop of the motor, said oil 158 will drop through routes shown by arrows in FIG. 16 onto the lower portion of the upper portion 32a of the casing. More particularly, the oil which has been introduced by the medium of bearing 162 into a motor and the oil which has been introduced between the stator iron core 164 of the motor and the rotor iron core 166 both drop through the openings 168 and 170 provided in the eccentric weights 60, and thus no oil dwells within the motor.

From the foregoing description it is apparent that in FIG. 8, the weight assembly is shown in a neutral position with respect to the guide member 57. In driving a pile, the weight assembly is descended so that the lower shoulder portion 66 strikes only the lower flange portion 55b. On the contrary, in drawing a pile, the weight assembly is pulled upwards so that the upper shoulder portion 64 strikes only the upper flange portion 55a. These are operated by means of the wire 30 (FIG. 6).

The clearance between the shoulder portions and the flange portions is so designed that the clearance is sufficiently larger than the amplitude of the weight assembly depending on the nature of the ground so that the upper shoulder portion 64 does not impinge on the upper flange portion 55a in driving, and the lower shoulder portion 66 does not impinge on the loweer flange portion 55b in drawing the pile. Generally, the amplitude of the weight assembly is mainly determined by the hardness of the ground in which a pile is driven by the action of the weight assembly. Accordingly, said clearance is selected in design to an extent which is sufficiently larger than that of rebound of the weight assembly at the time of striking the pile into the hardest ground, whereby the weight assembly is not limited the amount of its vertical movement along the guide member 57 with anything and effectively exerts downward force in driving and upward force in drawing on the pile, varying its amplitude depending on the nature of the ground. This permits the apparatus to exert a relatively large force in striking the pile when the ground is hard and to exert a relatively small force when the ground is soft.

Claims

I claim:

1. A pile driving and drawing apparatus comprising

a guide member consisting of a rod provided with a flange adapted to be placed on the head of a pile to be driven into the ground;

a weight assembly adapted to effect the relative movement with respect to said guide member, said assembly including a casing provided with a first portion for receiving the rod of said guide member in sliding engagement therewith and a second portion positioned below said first portion and adapted to impinge on said flange, and said assembly further including an excitor provided within said casing; and

a resilient body placed between said flange and second portion of said casing,

the natural frequency of said excitor being so arranged as to coincide with the free frequency of said weight assembly which is dependent on said resilient body.

2. A pile driving and drawing apparatus comprising

a guide member consisting of a rod provided with one end adapted to be secured to the head of a pile to be drawn from the ground and the other end having a flange;

a weight assembly effecting the relative movement with respect to said guide member, said assembly including a casing provided with a first portion for receiving the rod of said guide member in sliding engagement therewith and a second portion positioned above said first portion and adapted to impinge on said flange, said assembly further including an excitor provided within said casing;

a first resilient body interposed between said weight assembly and means for suspending said assembly; and

resilient second resilien body interposed between said flange and the second portion of said casing,

the natural frequency of said excitor being so arranged as to coincide with the free frequency of said weight assembly which is dependent on said first and second resilient bodies.

3. A pile driving and drawing apparatus comprising:

a guide member adapted to be secured to the head of a pile and consisting of a rod provided with upper and lower flanges;

a weight assembly effecting the relative movement with respect to said guide member and including a casing provided with a bore portion adapted to receive the rod of said guide member in sliding engagement therewith and upper and lower shoulder portions which are positioned on opposite sides of said portion and adapted to impinge on said upper and lower flanges, respectively, said assembly further including an excitor housed in said casing;

a first resilient body interposed between said weight assembly and means for suspending said assembly; and

second and third resilient bodies placed between said lower flange and the lower shoulder portion of said casing and between said upper flange and the upper shoulder portion of said casing, respectively;

the frequency of said excitor being so arranged as to coincide with the frequency of said weight assembly which is dependent on said second resilient body for driving a pile and the frequency of said excitor being so arranged as to coincide with the frequency of said weight assembly which is dependent on said first and third resilient bodies for drawing a pile.

4. A pile driving and drawing apparatus according to claim 3, wherein said excitor includes a pair of electromotive rotors and respective rotors are provided with weights positioned in eccentric fashion.

5. A pile driving and drawing apparatus according to claim 4, wherein said rotor is provided with a subsidiary eccentric weight removably attached to said eccentric weight.

6. A pile driving and drawing apparatus according to claim 3, wherein said first resilient body consists of a coil spring assembly, and said second and third resilient bodies are made of rubber-like resilient materials.

7. A pile driving and drawing apparatus according to claim 3, wherein said guide member is provided with a cap member of a cylindrical form at its lower end, said cap member having a plurality of spring biased members placed in a spaced relation around the periphery of said cap member and extending in a radial direction of a pile to be received within said cap member.

8. A pile driving and drawing apparatus according to claim 3, wherein said guide member is provided with a cap member of a cylindrical form pivotally connected to the lower end thereof, said cap member being provided with at least one spring biased member extending in a direction perpendicular to the axis of a pile to be received within said cap member.

9. A pile driving and drawing apparatus according to claim 3, wherein said casing is provided with a plurality of rollers engaging the side of the flange of said guide member.

10. A pile driving and drawing apparatus according to claim 3, wherein the casing, which houses said excitor, contains oil adapted to be circulated within said casing during the operation of said excitor, and said excitor is provided with a pair of rotors and weights disposed in eccentric relation to said rotors, said weights being provided with a plurality of oil vents and said casing having means for adjusting the pressure within said casing.

11. A pile driving and drawing apparatus comprising:

a guide member adapted to be secured to the head of a pile;

a weight assembly movably mounted on said guide member to exert downward or upward force on said pile, said weight assembly including an excitor contained therein;

said guide member including a rod member provided with upper and lower flanges;

said weight assembly defining a casing provided with a bore portion adapted to receive said rod member in sliding engagement therewith;

and upper and lower shoulder portions which are positioned on opposite ends of said bore portion and adapted to impinge on said upper flange in pile drawing and lower flange in pile driving, respectively;

a first resilient body for suspending said weight assembly;

second and third resilient bodies interposed between said lower flange and the lower shoulder portions of said casing and between said upper flange and the upper shoulder portions of said casing, respectively;

the clearance between said flange portions and said shoulder portions being larger than the amplitude of the weight assembly at the time it drives the pile into the hardest ground, and the frequency of said excitor being adapted to coincide with the frequency of said weight assembly which is dependent on said second resilient body for driving a pile and the frequency of said excitor, also being adapted to coincide with the frequency of said weight assembly which is dependent on said first and third resilient bodies for drawing a pile.

12. A pile driving and drawing apparatus comprising:

suspension means to hold a first resilient body;

a weight assembly attached to and suspended from said first resilient body;

said weight assembly defining a casing and having an excitor operatively connected thereto;

said casing having upper and lower compartments with a central bore communicating between said compartments;

said upper compartment having an upwardly facing shoulder about said central bore and including a second resilient body thereabout;

said lower compartment having a downwardly facing shoulder about said central bore and including a third resilient body thereabove;

a guide member within said casing;

said guide member having an upper flange member received in spaced relationship within said upper compartment, an integral rod portion extending in guided relationship through said central bore and a lower flange member received in spaced relationship within said lower compartment;

said upper flange member being opposed to said second resilient body and said lower flange member being opposed to said third resilient body;

the axial length of said rod portion of said guide member being longer than said central bore to define a clearance between said flange portions and said shoulders; said respective flange portions being engageable with said second and third resilient bodies; and

means to connect said lower flange portion of said guide member to a pile;

the clearance between said flange portions and said shoulder portions being larger than the amplitude of the weight assembly at the time it drives the pile into the hardest ground, and the frequency of said excitor being adapted to coincide with the frequency of said weight assembly which is dependent on said second resilient body for driving a pile and the frequency of said excitor, also being adapted to coincide with the frequency of said weight assembly which is dependent on said first and third resilient bodies for drawing a pile.

13. A pile driving and drawing apparatus in accordance with claim 12 wherein:

said casing is provided with a pair of opposing side openings communicating on opposite sides thereof with said upper and lower flanges of said guide member;

means supporting a plurality of rollers in each of said side openings on axes within the plane of said flanges whereby the inner peripheries of each plurality of rollers are engageable with the edges of said flanges; and

dampening means are provided holding said roller supporting means and rollers in said peripheral engagement.

14. A pile driving and drawing apparatus in accordance with claim 12 wherein:

said second and third resilient bodies each comprise opposing pads of rubber-like material affixed to said respective flange members and said shoulders.