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Publication numberUS3262507 A
Publication typeGrant
Publication dateJul 26, 1966
Filing dateOct 14, 1963
Priority dateOct 17, 1962
Also published asDE1484428A1
Publication numberUS 3262507 A, US 3262507A, US-A-3262507, US3262507 A, US3262507A
InventorsFrode Hansen
Original AssigneeChristiani And Nielsen Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Driving and extraction of piles and/or encasing structures
US 3262507 A
Abstract  available in
Images(5)
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Claims  available in
Description  (OCR text may contain errors)

July 26, 1966 F. HANSEN 3,262,507

DRIVING AND EXTRACTION OF FILES AND/OR ENCASING STRUCTURES Filed Oct. 14, 1963 5 Sheets$heet l ELQL PILOT VALVE n":

CONTROL f COM/019,94 Tax lnvenlor FRO DE HANSEN BY 9mm:-

A ttorneys July 26, 1966 F. HANSEN 3,262,507

DRIVING AND EXTRACTION 0F FILES AND/OR ENCASING STRUCTURES Filed Oct. 14, 1963 5 Sheets sheet 2 2""\ x 3 $2M 5 6a L 1 Inventor FRODE HANSEN Attorneys July 26, 1966 F. HANSEN 3,262,507

DRIVING AND EXTRACTION OF PILES AND/OH ENCASING STRUCTURES Filed 001;. 14. 1963 5 Sheets-Sheet 5 T' If EZ ZZZ Inventor FRODE HA NSEN By ,46 Attorneys F. HANSEN July 26, 1966 DRIVING AND EXTRACTION OF FILES AND/OR ENCASING STRUCTURES 5 Sheets-Sheet 4 Filed Oct. 14, 1963 Inventor FRODE HANSEN Y-M Attorneys July 26, 1966 F. HANSEN 3,262,507

DRIVING AND EXTRACTION OF FILES AND/OR ENCASING STRUCTURES Filed Oct. 14, 1963 5 Sheets-Sheet 5 Inventor FRODE HANSEN By M A ttorney;

United States Patent 3,262,507 DRIVING AND EXTRACTION 0F PILES AND/ OR ENCASING STRUCTURES Frode Hansen, Westminster, London, England, assignor to Christiani and Nielsen Limited, London, England, a company of Great Britain Filed Oct. 14, 1963, Ser. No. 315,850 Claims priority, application Great Britain, Oct. 17, 1962, 39,359/ 62 12 Claims. (Cl. 175-56) This invention relates to methods of and apparatus for driving piles into the earth such as piles used in erecting bridges, tall buildings and like structures, but it could be used to drive any elongated object into earth or like compacted material, e.g. soft rock, and in any direction including driving upwardly.

Such piles, which may be of reinforced concrete, prestressed concrete or steel for example, are of considerable length, e.g. 50 to 150 feet, may have a pointed end preferably steel protected or, in the case of steel tube or box pile may be open ended, and in certain circumstances may be driven their full length into the ground.

Existing pile drivers, e.g. steam pile drivers, require considerable effort in erecting them on the site and they have to be mounted for movement from, one pile to another so that the operation becomes highly expensive. Moreover they operate on the principle of hammering them to force them into the earth which can be a slow process and in some cases damage the piles since very high stresses can occur during driving and such stresses can occur in parts of the piles which later under permanent conditions are only moderately stressed.

More recently it has been realised that it would be possible to drive the piles into the earth by means of applying longitudinal vibrations to them at very high frequency, e.g., to 150 vibrations at second, whereby the cohesion and/or friction of the soil in contact with the pile is reduced considerably, enabling the pile, if suitably loaded with a heavy weight, to move into the earth as through a viscous medium. The direction of the piles movement is dependent upon the static load applied to the pile which may be the weight of the pile itself, but may also include a very heavy weight of several tons, depending on thesite conditions, mounted on the top of the pile causing it to sink into the soil as it is vibrated. By exerting a pull on the vibrating pile it can be withdrawn from the earth also.

It has been proposed to obtain such vibrations by mounting on the pile a pair of heavy eccentrically mounted Weights rotating about parallel horizontal axes disposed on either side of the vertical axis of the pile, the two weights rotating in opposite directions and thereby eliminate any sideways vibration of the piles, while in the direction of drive, normally vertical, the eccentric weights augment each other. Two main difiiculties are encountered in such machines. Firstly, all forces acting have to be transmitted through high speed bearings which become heavy and/or vulnerable. Secondly, a consid erable amount of dead weight, as opposed to reactive mass, in the form of bearings, shafts, casings, etc., must be clamped rigidly to the pile, taking part in the vibration and thereby increasing the internal forces in the vibrator or reducing the active forces acting on the pile.

The main object of the present invention is to provide a method of and apparatus for driving piles or like structures into a compacted medium such as the earth and for withdrawing them from the medium by means of high frequency vibrations thereon, which overcomes the aforesaid disadvantages, e.g., eliminates the load carrying high speed bearings by avoiding heavy rotating parts and improves the reactive mass/deadweight ratio. r

According to the present invention a means is provided of moving an elongated member, e.g. a pile, through a compacted medium, e.g. earth, in contact with which one end thereof is supported, said means comprising mounting on the free end of the member an oscillating device oscillated by alternating high frequency liquid pressure on opposing faces of a mass of substantial inertia or of a piston or pistons associated with such a mass to impart vibrations axially onto the elongated member, sensing the vibrations in the elongated member and the medium surrounding it, and feeding the sensed conditions of vibration to means governing the flow in the liquid cycle, whereby the frequency and amplitude of the vibrations imparted to the elongated member are continuously adjusted by regulating the governing means to the optimum operating conditions for driving the elongated member into or withdrawing it from the compacted medium.

In order that the invention may be more clearly understood some embodiments in accordance therewith will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a cross section of a pile driving apparatus;

FIG. 1A is a block diagram of electrical apparatus for obtaining an optimum frequency;

FIG. 2 is a cross section looking downwardly taken on the line II II of FIG. 1;

FIG. 3 is a similar view to FIG. 1 of an alternative v construction; and

FIG. 4 is a cross section on the line IV-IV of FIG. 3;

FIGS. 5 and 5A are cross sections of right and left halves of further pile driving apparatus showing modifications to suit different sized piles;

FIGS. 6 and 6A are cross sections on the line VIVI of FIGS. 5 and 5A looking in the direction of the arrows; and,

FIGS. 7 and 7A are cross sections similar to FIGS. 5 and 5A, also showing two forms to suit diiferent sized piles.

In the drawings the same references are used to designate the same or similar parts.

Referring to FIGS. 1 and 2 the top of an elongated member in the form of a pile 1 is shown (or this may be connected to or mounted on the pile), this pile being supported by conventional means such as guy ropes with its other end in contact with a compacted material, e.g., earth. The top of the pile 1 or the member 1 mounted on the pile has an upstanding annular wall on which is fixed an element shown as a helmet 2 carrying within it a cylinder 3 in which slides a cylindrical portion 4 which may be chosen of different diameter; the portion 4 supports an annular piston 7 and passes through glands 5 at the ends of the cylinder and is connected to a mass of substantial inertia shown as a heavy weighted member 6 or mass of say 3 to 10 tons dead weight.

The piston 7 is in sliding contact with the cylinder walls and forms a divided chamber having portions 8 and 9 on opposite faces of the piston 7 and is connected to an inlet 16 and outlet 17 in a liquid supply flow of a liquid under pressure provided as by a pump situated at a suitable location, e.g., on the ground beside the pile. In the cavity 13 an electro-hydraulic servo valve 13a is mounted on shock absorbing means (not shown) such as rubber blocks. The servo-pump 13a forms no part of the present invention and requires no further description here, but it may be a conventional solenoid operated valve. Two ducts 12 lead through the mass and the portion 4 to outlets 10, 11, facing into the two portions 8, 9 of the cylinder 3 thereby providing a source for the supply and withdrawal of operating fluid above and below the piston, i.e., into chamber portions 8 and 9. The cavity 13 for the valve 13a is formed in the top of the member 6 and is preferably covered as shown by a lid 3 17a which is also heavily weighted to increase the interia of the mass.

The weight of the member 6 can be augmented if desired by adding weighted members on to the cap 17a or fixing them around the outside of the member 6 which may be provided with brackets 18 or like means to support these extra weights.

In operation the apparatus is mounted on the pile by a crane or like hoist on the site and the ducts 16 and 17 are connected thereon. An electric current supply line (not shown) is also connected to the valve 13a to supply a solenoid therein which elI'ects the operation of the pump. The pump and electric current are switched on and liquid, e.g., oil is supplied under pressure, e.g., 3000 lbs./ sq. in. or higher through the duct 16 to the valve 13a which is operated to provide alternate pulsations of oil into the ducts 12 at high speed, e.g., 25-150 pulsations per second. The oil in one pulsation flows down one duct 12 and into one part of the cylinder 3 and then on the next pulsation flows down the other duct 12 and into the other part of the cylinder 3 thereby giving rapid short reciprocatory movement axially of the pile between the cylinder 3 and the member 6. When one duct 12 is supplying liquid to the portion 8 or 9, the other duct 12 acts as a return line for the liquid from 9, 8 respectively; or additional ducts 12 may be provided to each of the portions 8, 9 to act as liquid return lines to the pump. These pulsations necessitate relative movement between the pile 1 and the member 6 and due to the great weight of the member 6 that acts as a reactive mass and does not move any appreciable amount, but the forces of reaction causes longitudinal vibrations in the pile itself. The pile thus vibrating in the earth fluidises the earth around the pile reducing its cohesion and internal friction to such a degree that the weight of the pile together with the weight of the said apparatus causes the pile to sink through the viscous earth. At the same time the vibrations also cause the earth to be compacted around the pile as it moves into the earth so that when the vibrations are stopped and the cohesion and internal friction have been re-established the overall carrying capacity of the surrounding earth may have been increased.

Referring to FIGS. 3 and 4 the construction is basically similar to that shown in FIGS. 1 and 2 and the weighted member 6 carries flexible sacks 20 and 21 on its upper and lower faces respectively which are contained between the end faces of the member 6 and transverse plates 23 slidably interconnected with the member 6 and with eachother by rods 24, the lower plate forming or being mounted on the pile helmet 2a. The inlet and outlet for the liquid are disposed centrally of the length of the member 6 and are connected in the centre thereof with a rotary valve 25 rotated by any suitable means at the required frequency whereby the liquid flows into and out of, in succession and alternatively, each of the sacks 20, 21. Thus as one sack fills and the other empties the member 6 will move axially and these longitudinal pulsations will cause the vibration. The valve can be rotated by any suitable means such as an electric motor mounted on the member 6.

Referring to FIGS. 5 and 5A and 6 and 6A these show half sections of construction similar to FIGS. 1 and 2 but the portion 4 is integral with the mass 6, and is threaded to receive an alternative cylinder-piston arrangement. In FIGS. 5A and 6A an annular member 22 is screwed onto this portion 4 and has a central annular cavity 2211 while the end portions form stulfing boxes 5. Sliding on the member 22 is an annular piston 4a mounted on the helmet 2 and sliding over the boxes 5 in liquidtight relationship, while a central part 4b slides over the surface of the cavity 22a dividing it into the two portions 8, 9. Four ducts 12 are provided in the mass 6 two for each portion 8, 9 thereby forming alternatively flow and return liquid paths, i.e., being alternatively at high and low pressure under the pulsating action of the pump.

In FIGS. 5 and 6, the member 22 is of larger diameter to fit a larger pile helmet 2 and the boxes 5, or one of them, e.g., the lower one as shown, are screwed onto the threaded exterior of the member 22.

FIGS. 7 and 7A also show halves of two constructions, both of which employ a number of cylinder-piston assemblies (one of which is shown in each half of FIGS. 7 and 7A) disposed round the mass 6 in dynamic balance about the central vertical axis of the mass 6. In each case the cylinder 26 is mounted on the mass 6 and the two ducts 12 lead to each of the portions 8, 9 while the piston 27 on guide rods 28 moving through stuffing boxes 29 slides in the cylinder to form the portions 8, 9.

The FIG. 7 construction is similar to the FIG. 7A construction but the cylinders 26 are supported on members 30 fixed to the mass 6 and the ducts 12 may be flexible to span the members 30 which may be hollow. A helmet (not shown) may be interposed between the rods 28 and the pile 1 or a member on the pile, or may be connected as shown onto the pile 1.

The operation of the constructions of FIGS. 5, 5A, 6, 6A, 7 and 7A is the same as described with reference to FIGS. 1 and 2 except that in FIGS. 7 and 7A a greater reactionary mass 6 is provided and smaller parts of dead weight, i.e., pistons and cylinders, are used.

In all the constructions shown the units that comprise the motive power and pressure in the oil feed lines are divided into four basic mechanisms, namely a motor, a pump, main valve, and electro-hydraulic or pilot valve.

The motor is a high horse-power unit, either electrically or mechanically driven and is coupled to the pump capable of delivering a quantity of oil at a high pressure, say 3,000 p.s.i., or higher, and circulating it through a high pressure line. The purpose of the main valve is to control the oil feed from the pump to the divided chamber. The regulation of the oil feed from the pump to the chamber is obtained by means of an electro-hydraulic valve, called the pilot valve. This pilot valve may have its own motor and pump as a separate self contained unit, controlled and governed externally. The purpose of this variation is to contain a dustfree circuit of oil powering the pilot valve. If this variation is not used the oil from the main pump could be used to power the pilot valve.

There are three ways of arranging the components of the system together, all producing the same effect on the mass 6.

First, the motor, pump, valve, and pilot valve are attacked to the mass 6 or incorporated inside, but supported, e.g., on springs to minimize vibration effects on the moving parts of the motors, pumps, and valves. The control system would necessarily be placed on the ground and electrical leads supplied to the power units.

Secondly, the motor, pump, and control units are housed on the ground or in a suitable vehicle and the electrical leads and high pressure oil lines pass to the main and pilot valves placed on springs externally or internally with the mass.

Thirdly, the motor, pump and control units are housed on the ground or suitable vehicle and the electrical leads and high pressure oil lines pass to the main valve, placed externally or internally with the mass. The pilot valve has its own oil circulation derived from a motor and pump housed externally or internally with the mass. The pilot valve then has a separate electrical feed for running the motor and its control system.

It is assumed that for a given size vibrator and power unit, there must be an optimum frequency and perhaps wave form giving maximum penetration or minimum power consumption at constant penetration. This optimum frequency must be a function of the physical properties of the vibrator, the pile and the surrounding ground. Also the conditions change as the pile penetrates into the ground, for example, the damping effect of the ground on the pile changes considerably and the optimum frequency at the beginning of the penetration may be vastly different from that when the pile is fully embedded in the ground. It is therefore desirable to have means of varying the frequency of the vibrations during the driving and preferably to be able to do it automatically.

Accordingly, as illustrated in FIG. 1A, a pick-up device is associated with the vibrating system as a whole including the damping effect of the surrounding earth through which the pile is being driven. Any pick-up device of an electronic, ultrasonic or electro-magnetic nature may be employed such, for example, as the pick-up head of an electrical record player or tape recorder. The construction of the pick-up device forms no part of the present invention and does not need further explanation.

Sensing or pick-up devices of known construction are provided in contact with the earth and/ or the pile and signals emanating therefrom are fed back to a device such as a pilot valve which controls regulation of the main valve, i.e. the valve 13a, so. that the apparatus will be responsive to the vibrations in the compacted medium and the elongated member therein and these may .be compared with a standard vibration as by means of a Wheatstone bridge for example, or may be compared in any conventional comparator with the amplitude of the pile head, the stresses at the'pile toe, or whatever feature experiments show is most significant at optimum conditions, and if they differ from the optimum then the pilot valve will be actuated in a conventional manner to cause the speed of alternations in the ducts 12 to be adjusted so as to oscillate the piston in FIGS. 1 and 2, and to control the speed of the valve in FIGS. 3 and 4 so as to vibrate the pile at the optimum driving frequency.

The vibration pick-ups are preferably rigidly attached to the pile being driven and leads from these pick-ups are carried'to a control device associated with the pilot valve.

It will therefore be seen that a minimum amount of machinery is necessary on site which will be operated automatically under optimum conditions of vibration to expedite the driving of the pile into the earth. At the end of the driving operation the pick-up device may remain in situ with the pile or may be removed. The earth which has been vibrated and through which the pile has been passed will by virtue of the high vibrations be consolidated round the pile and thereby pack it tightly into its driven position.

Not only is the apparatus and method of the invention very simple in construction particularly compared with the aforesaid known apparatus, but it has a long life because it has a minimum-of moving or rotating parts and many obligatory elements such as appear in rotating vibrators are dispensed with. The only delicate part of machinery which must form part of the vibrator is the valve unit but this can be made easily detachable so that a stand-by unit can be fitted in if necessary while the other one is being serviced. The vibrator is entirely unilinear in its action and therefore acts along the longitudinal axis of the pile.

Although the invention has been described with reference to piles being driven vertically downwards it is equally applicable to any element being driven into earth at any angle.

I claim:

1. A methodof moving an elongated member, e.g., a pile, through a compacted medium, e.g., earth, in contact with which one end of said member is held, said method comprising mounting on the free end of said memher an assembly of a vertically reciprocalble heavy reactant, non rotatable mass of substantial inertia, a high frequency liquid pressure oscillating device and at least one piston slidable in a cylinder connected by ducts to said oscillating device, actuating said oscillating device to provide rapid increases and decreases in liquid pressure in the range of 25 to 150 pulses per second on opposite sides of each piston in its cylinder thereby imparting high frequency vibrations axially of said elongated member, sensing said vibrations in said elongated member and the surrounding medium as said member moves therethrough, comparing the sensed vibrations to a standard vibration of optimum frequency feeding the difference between the sensed and standard vibrations to means operable to control the liquid flow through said oscillating device to create a desired vibration frequency in the elongated member and to adjust the frequency and amplitude of said desired vibration to theoptimum operating conditions for moving said elongated member through said medium.

2. An apparatus for moving an elongated member, e.g. a pile, through a compacted medium, e.g. earth, in contact with which said member is held, said apparatus comprising a heavy reactant mass of substantial inertia, at least one cylinder element and piston element sliding therein one of whichelements is secured to said mass while the other of said elements is secured to said elongated member, at least one valve having a liquid inlet and outlet for connection to a pressure liquid cycling supply, twin liquid ducts both connected between each said valve and opposing sides of each said piston element in its cylinder element, and means for actuating said valve to effect rapid changes of liquid pressure on opposite sides of each said piston thereby imparting to said elongated member vibrations in the longitudinal axis thereof of selected frequency and amplitude to move said member through said medium.

3. An apparatus according to claim 2 wherein each valve is a rotatable valve and means is provided to actuate said rotatable valve.

4. An apparatus according to claim 2 wherein an electrically operated solenoid device is connected to each valve for operation thereof.

5. An apparatus according to claim 2 wherein each valve is mounted in a cavity in the mass.

6. An apparatus for moving an elongated member, e.g. a pile, through a compacted medium, e.g. earth, in contact with which said member is held, said apparatus comprising a heavy reactant mass of substantial inertia, a liquid chamber divided by the mass, an electro-hydraulic servo valve, a liquid inlet and outlet to said valve for connection to a pressure liquid cycling supply system, twin liquid ducts between said valve outlet and said chamber on each side of said mass, an element for mounting said mass on the free end of said elongated member, and

means for actuating said valve at a predetermined frequency to cause said liquid to apply pressure alternately to opposite sides of said mass in said chamber to impart to said elongated member in the longitudinal axis thereof vibrations of a predetermined frequency and amplitude to cause said member to move through said medium.

7. An apparatus for moving an elongated member, e.g. a pile, through a compacted medium, e.g. earth, in contact with which said member is held, said apparatus comprising a heavy reactant mass of substantial inertia, at least one cylinder and a piston slidable therein one of which is connected to' said mass, an electro-hydraulic servo valve supported by said mass, a liquid inlet to said valve for connection to a source of liquid under pressure, a liquid outlet from said valve, twin ducts between said valve and both sides of each said piston in each said cylinder, an element for mounting said mass on said elongated member with the sliding axis of each said piston parallel to the longitudinal axis of said elongated member, and means to actuate said valve to cause rapid increases and decreases of liquid pressure successively and alternately on the opposing faces of each said piston to impart to said elongated member vibrations of predetermined frequency and amplitude to move said member through said compacted medium.

8. An apparatus according to claim 7 wherein the mass is provided with at least one cylindrical portion round each of which said piston is provided in the form of an annulus, the cylindrical portion being slidably disposed through said cylinder so that the piston is disposed with- 1 in the cylinder, at least an additional pair of twin ducts to form tour ducts leading through the mass to the cylinder on opposite sides of the axis of the piston, and said valve alternately connects the ducts to said liquid inlet and outlet of the valve, whereby the two parts of the cylinder on opposite sides of the axis of the piston are alternately filled and emptied of liquid in rapid succession thereby imparting rapid vibrations to the elongated member.

9. An apparatus for moving an elongated member, e.g. a pile, through a compacted medium, e.g. earth, in contact with which said member is held, said apparatus comprising a heavy reactant mass of substantial inertia, a number of cylinders each with a piston slideable therein to form assemblies, said assemblies being supported by said mass, means for mounting said assemblies on said member, an electro-hydraulic servo valve supported by said mass, a liquid inlet and a liquid outlet to said valve for connection to a pressure liquid cycling source, twin liquid ducts from said valve to both sides of each piston in its cylinder, means to actuate said valve to cause liquid to flow through said ducts alternately and rapidly to increase and decrease the liquid pressure on opposite sides of each said piston to impart axially to said elongated member vibrations of predetermined frequency and amplitude to move said member through said mediurn.

10. An apparatus according'to claim 9 wherein a number of valves are provided and twin ducts connect each of said valves to one of said cylinders on both sides of the piston therein.

11. An apparatus according to claim 9 wherein the free end of the elongated member to which the vibrations are imparted is-provided with a helmet and each piston is secured to the helmet and the reactive mass is secured to each cylinder and each valve is mounted on said reactive mass. i

12. A method of moving an elongated member,. e.g. a pile, through a compacted medium, e.g. earth, in contact with which one end of said member is held, said method comprising mounting on the free end of said member an assembly of a vertically reciprocable, heavy reactant, non rotatable mass of substantial inertia, a high frequency liquid pressure oscillating device and at least one piston slidable in a cylinder connected by ducts to said oscillating device, and actuating said oscillating device to provide rapid increases and decreases in liquid pressure in the range of 25 to 150 pulses per second on opposite sides 'of each piston in its cylinder thereby imparting high frequency vibrations axially of said elongated member.

References Cited by the Examiner Bodine 166-46 CHARLES E. OCONNELL, Primary Examiner.

- R. E. FAVREAU, Assistant Examiner.

Patent Citations
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US2743083 *Feb 3, 1954Apr 24, 1956Zublin John AApparatus to impart vibrating motion to a rotary drill bit
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3371726 *May 24, 1965Mar 5, 1968Gen Dynamics CorpAcoustic apparatus
US3452830 *Dec 5, 1966Jul 1, 1969Raymond Int IncDriving systems
US3463251 *May 23, 1967Aug 26, 1969Shell Oil CoPneumatic transformer coupling for sonic pile driver
US3477237 *Oct 1, 1968Nov 11, 1969Orkney John CMethod of vibrating a member to drive it in a resistive medium
US3650335 *Oct 8, 1969Mar 21, 1972Keelavite Hydraulics LtdApparatus for driving and/or extracting piles
US3990522 *Jun 24, 1975Nov 9, 1976Mining Equipment DivisionRotary percussion drill
US4026370 *Apr 2, 1975May 31, 1977Secretary Of State For Industry In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain & Northern IrelandDriving tools
US4574888 *Aug 2, 1984Mar 11, 1986Urs CorporationMethod and apparatus for removing stuck portions of a drill string
US4650008 *Sep 19, 1984Mar 17, 1987Simson and PartnerPile driver and extractor
US4674571 *Oct 16, 1985Jun 23, 1987Urs CorporationMethod and apparatus for improving oil production in oil wells
US4890682 *May 5, 1989Jan 2, 1990Shell Oil CompanyApparatus for vibrating a pipe string in a borehole
DE1608411B1 *Feb 5, 1968Dec 17, 1970Electronic Assistance CorpSchwingsystem mit einem Koerper veraenderlicher Masse
EP0135479A1 *Sep 14, 1984Mar 27, 1985Simson und PartnerDevice for driving and extracting
WO2010059036A1Nov 19, 2009May 27, 2010Magali HadarRebound-effector
Classifications
U.S. Classification175/56
International ClassificationE02D11/00, E02D7/18, E02D7/00
Cooperative ClassificationE02D7/18, E02D11/00
European ClassificationE02D7/18, E02D11/00