EP2134903A1

EP2134903A1 - Improvements in and relating to pile driving

Info

Publication number: EP2134903A1
Application number: EP08718846A
Authority: EP
Inventors: David Thomson; Paul R. Demarest
Original assignee: Demarest Vincent Michael
Current assignee: Demarest Vincent Michael
Priority date: 2007-03-21
Filing date: 2008-03-20
Publication date: 2009-12-23
Also published as: WO2008114031A1; GB2447785A; GB0805262D0

Abstract

A pile driving device comprising: a yoke selectively clampable at any position along the length of an elongate rigid pile, post or the like to be driven into the ground; a vibrator or percussion device in contact with or forming part of the yoke and a support, supporting the yoke in use and operable in use to adjust the initial position of the pile, post or the like.

Description

Improvements in and relating to pile driving

This invention relates to pile driving, which expression includes the driving of posts, such as 'H' section steel posts of the kind used to support fencing panels. A problem with pile driving steel posts into the ground is that because the post has to be hit at the end remote from the part being driven into the ground, usually by a hydraulically operated hammer mounted on a support mast of a pile driving machine, there is a practical limit to the length of posts that can be driven into the ground unless the pile driving apparatus itself is very tall. For example, a pile driver capable of driving a 3 metre post must itself be capable of moving the hammer head region of the pile driver by at least this amount, such that the fully extended height of the pile driver including the hammer head could be over 4 metres. This therefore brings into question health and safety issues, particularly where the pile driving machine is moveable, such as being mounted on a tractor vehicle. Where long fence posts need to be driven in so that they rest with 3 metres above ground, such as 4.5 metre long posts, the total range of movement for the hammer head portion of the pile driver would be about 6 metres where, again, stability becomes an issue unless the pile driver is mounted on a correspondingly large vehicle stable enough to operate safely. A solution to the foregoing problem is to use segmented posts where, after each segment is driven into the ground, another segment is bolted or screwed to it, to be either driven further into the ground or form part of the exposed post. However, it will be appreciated that this solution may not be as mechanically strong as with a single post, it can be time consuming and presents the opportunity for vandals or thieves to damage, destroy or even remove that part of the segmented post remaining above ground after the base has been driven in to the required extent.

The present invention is derived from the realisation that there is a need for the ability to drive in posts of any length wherein the size of the apparatus used is not necessarily related to the length of the pile to be driven.

According to a first aspect there is provided a pile driving device comprising or including: a yoke selectively clampable at positions along the length of an elongate rigid pile, post or the like, to be driven into the ground; a vibrator or percussion device contactable with or forming part of the yoke, and a support member for supporting the yoke in use and operable to adjust or maintain the position of the pile, post or the like as it is being driven.

In one embodiment the yoke comprises a pile clamp and the pile driving device further comprises at least one pile guide member spaced from the clamp for guiding the pile in use.

Conveniently said yoke and said at least one guide member are moveable together relative to the support member.

Preferably said at least one pile guide member comprises a pair of guide members spaced from the clamp each one of the pair being disposed on opposing sides of the clamp.

Conveniently the support member includes an alignment hinge having a first pivot axis substantially parallel with the longitudinal extent of the pile, for said positional adjustment the pile, about said first axis, relative to a ground surface . Conveniently the support member further includes two levelling hinges having second and third mutually orthogonal pivot axes each being substantially transverse or oblique to the longitudinal extent of the pile, for positional adjustment of the pile about said second and third axes, for vertical levelling of the post into a generally upright position or otherwise to a specified inclination.

The support member may include: a mounting frame for attaching to a tractor vehicle such as an excavator; a first intermediate portion pivotally connected to the mounting frame for movement about one of the first, second or third axes; a second intermediate portion pivotally connected to the first intermediate portion for movement about another one of the first second or third axes, the yoke being pivotally connected to the second intermediate portion for movement about a last one of said first, second or third axes

Preferably the second intermediate portion includes a bar for allowing sliding movement of the yoke as well as said movement about the last of the axes, relative to the second intermediate portion.

The or each guide may be fixed to the yoke such that the yoke when clamped to the pile by the clamp is slideable with the pile and the guide(s) move with the yoke.

According to a second aspect there is provided a method of pile driving including the steps of providing a releasable yoke, for securing the yoke on a pile at a position along its length indicative of an amount by which the pile is to be driven into the ground, providing pile driving apparatus including a vibrating or percussion device in contact with, or forming part of the yoke, providing a moveable support member which supports the vibrating or percussion device to follow movement of the pile as it is driven into the ground by the yoke, driving the pile with the use of the vibrating or percussion device and thereafter disengaging the yoke from the pile, leaving it driven into the ground, or repeating the sequence to drive the pile to a required depth. In this way, a yoke is secured to the pile, for example the yoke can be clamped around a pile, and the yoke is driven into the ground by use of a vibrating device or a percussion device such as a hammer device in contact with the yoke. The overall height of the machinery necessary for inserting the post can be minimised because the yoke can be clamped to the pile well below its full height when upright.

In an embodiment the yoke is formed from a pair of jaws. The jaws may be shaped to fit the pile, for example, where a ¹H' section pile is used, the jaws may have generally concave formations for accepting the outer edges of the flanges of the Η'. Preferably the yoke is rotatable relative to the moveable support about a first axis parallel to the axis of the pile. More preferably the yoke is rotatable about second and third axes both perpendicular to the first axis.

According to another aspect the invention extends to a pile driving device including a releasable yoke, securable along the length of a pile to be driven into the ground, the yoke including means to grip the pile at positions along its length and a vibrating or percussion device in contact with, or forming part of the yoke, the pile driving device including also a support which supports the yoke to generally follow movement of the pile as it is driven into the ground.

According to another aspect of the invention there is provided a method of pile driving which includes the steps of providing at least one anvil on a pile to be driven at a position along its length indicative of an amount by which the pile is to be driven into the ground, providing pile driving apparatus including a yoke for at least partially surrounding percussion means for simultaneously hitting the at least one anvil, and drive means for driving the yoke to follow movement of the pile as it is driven into the ground by the percussion means to a required extent, thereafter disengaging the yoke from the pile, leaving it driven into the ground, and thereafter removing the at least one anvil to leave a substantially contiguous pile. Conveniently, the pile driving apparatus used in the method comprises a moveable, such as tracked, hydraulically operated pile driver wherein, instead of having a hammer adapted to engage with the free end of a pile to be driven it has instead a yoke engageable with the pile and the or each anvil secured thereto such that the height of the pile driving apparatus is dictated solely by the required depth of penetration of the pile as dictated by the position of the or each anvil as opposed to being dictated by the more conventional overall length of the pile.

Alternatively, the apparatus used may be purely mechanical in which one or more anvils are attached to a pile at a position indicative of the required depth of penetration of the pile and the or each anvil is hit by a hammer dropped from a height, whereafter the hammer is lifted back to its original position to be dropped again until the pile driving operation is complete.

The yoke is preferably openable and adapted to, when closed, embrace, whether wholly or partially, the pile to be driven, at which closed position the or each hammer is in alignment with the or each anvil on the pile.

Preferably, especially for use with ¹H' section post the yoke is box shaped and formed from a pair of generally 'L' shaped members joined together at respective ends by a pivot pin such that one part is openable with respect to the other by means of a swivel movement, the free ends of the 'L' shaped members being releasably lockable with respect to each other so that when so locked the yoke completely surrounds the pile to be driven and, by the use of spacer shims the or each hammer may be aligned vertically with the or each anvil irrespective of the size or shape of the pile to be driven. This is a particularly convenient arrangement where the yoke is for use with ¹H' section steel posts which, because of their shape, which includes a generally flat central web, a pair of oppositely disposed hammers can be positioned symmetrically on either side of the web immediately above, preferably, a pair of anvils attached to the web, such that the yoke, by use of shims of required thicknesses can be used for a wide range of post thicknesses.

Conveniently, the yoke is integral with a foot by which it may be attached to a moveable carriage forming part of a vertically disposable support mast, which mast itself need only be little more than the height of the required maximum depth of penetration of pile to be driven since, as will be appreciated, with the method and apparatus of the invention the height of the mast is not dictated by the maximum length of the pile and may instead be considerably shorter than corresponding masts on apparatus used for pile driving by the traditional method of hammering one end of the pile to drive the other end into the ground. The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figures 1 to 13 show views and details of a first embodiment of a pile driving device according to the invention; Figures 13 to 18 show views and details of a second embodiment of a pile driving device according to the invention;

Figure 19 is a plan view of a pile driving device according to a third embodiment of the invention;

Figures 20 and 21 show plan views of a pile driving device according to a fourth embodiment of the invention;

Figure 22 shows a schematic view of a pair of piles in the form of steel posts, one of which has been driven into the ground and the other of which is awaiting pile driving in accordance with a method of the invention using the pile driving device shown in Figures 20 and 21 ; and Figures 23 and 24 shows end details of a pile, in the form of a steel post, for driving into the ground using the pile driving apparatus of the first, second or third embodiments of the invention.

Referring firstly to Figures 1 , 2, 3 and 4 there is shown four different perspective views of a first pile driving device 5 according to the invention. The pile driving device 5 is connectable to the arm of an excavator or mechanical digger (not shown) by a mounting frame 10. As will be described in more detail below, the frame 10 and interconnected parts 20, and 30 together form a support member for supporting a yoke 40.

The frame 10 includes two spaced parallel pins 12 and 14 which will fit to the end of an articulatable arm of an excavator. A first intermediate portion of the device 5, in the form of a roll control bracket 20, is pivotably connected to the mounting frame 10 by means of the pivot pin 18 which forms a hinge. Relative pivoting between the mounting frame 10 and the roll bracket 20 takes place about axis "x" and is controlled by a hydraulic ram 16 which at one end is pivotably mounted to the mounting frame 10 and at the other end is pivotably mounted to the roll bracket 20.

A second intermediate portion of the device 5 is in the form of a yoke support frame 30. The yoke support frame 30 is pivotably mounted to the roll control bracket 20 at pivot point 28 (shown in Figures 2 and 3), which also forms a hinge for rotation about axis "y". Pivoting of the yoke support frame 30 with respect to the roll control bracket 20 is effected and controlled by a hydraulic ram 26 pivotably connected at each of its ends to the bracket 20 and frame 30. Yoke support frame 30 includes an upright beam 32 having brackets 34 for supporting each end 36 of a connecting rod 38 of a double acting hydraulic ram

42 which is described further below.

Attached to the double acting ram 42 is yoke 40. Yoke 40 is capable of moving up and down with the ram 42 on the connecting bar 38 which is in turn secured at its ends 36 to the beam 30. In addition the yoke 40 can rotate on the connecting bar 38, about axis "z", to form another hinge. The yoke 40 includes a journal block 44 which rides up and down on the double acting ram 42 but, the ram 42 is rotatable relative to the journal block 44. Journal block 44 includes rollers 46 which prevent its rotation with the ram 42 but allow its movement up and down the beam 32 together with the ram 42. A further hydraulic ram 48 connecting the journal block 44 to the remainder of the yoke 40 effects rotation of the yoke 40 about the connecting rod 38 and axis "z" as the length of the hydraulic ram 48 is altered.

The yoke also includes a pair of spaced rests 50 and a clamp mechanism 60 between the two rests 50. The rests 50 each include a replaceable roller 52 which are used to guide a pile in the form of an 'H' section steel post 1. The post can be guided by the rollers 52 either with its outer flanges parallel to the axis of the roller or with its outer flanges perpendicular thereto. In Figures 1 to 4 the post 1 has been illustrated in both the orientations mentioned immediately above.

Clamp 60 includes a pair of clamping rams 62 and a pair of jaws 64, which again can clamp the post 1 in the two orientations illustrated.

The yoke 40 further includes a vibration unit 70 driven by a hydraulic motor 72. Figure 4 shows a plan view of the pile driving device 5 shown in Figures 1 to 3.

Figure 5 shows an enlarged view of the items within circle V in Figure 4.

Figure 6 shows how the post 1' in a first orientation can be clamped by the jaw pair 64 by holding its central flange 3'. Figure 7 shows how the same jaw pair 64 can be used to clamp a post 1" in a different orientation by clamping the post's outer flanges.

Figure 8 shows how roller 52 can be used to guide the post V by means of contact with one of its outer flanges.

Figure 9 shows how the roller 52 can be used to guide post 1" by means of contact with an edge of each of its two outer flanges.

Figures 10 to 13 show various further pictorial views of the pile driving device 5 to provide a better understanding of the invention. In Figures 12 and 13 annular rubber bushes 74 are visible. These bushes provide a resilient mount for the yoke 40 on the double acting ram 42 and thereby reduce the amount of vibration transmitted from the vibration unit 70 to the ram 42 and the remainder of the device 5.

In use, the pile driving device 5 is attached to an excavator arm at mounting frame 10. A post 1 is positioned for clamping by means of the clamp 60. Alternatively, the device can be offered up to a post and used to pick up the post 1. The excavator is used to position the post approximately in place. The length of hydraulic ram 16 is increased or decreased to adjust the pitch P of the post in the direction of arrow P as shown in Figure 1 i.e. hinged rotation in the x axis. The length of hydraulic ram 26 is increased or decreased to adjust the roll position R of the post in the direction of arrow R as shown in Figure 1 i.e. hinged rotation in the y axis. Though not necessarily so, usually it is desirable to have the post 1 upright and so the adjustments in the direction of arrow R and P are used to obtain a level upright post, or whatever lean in the post that is desired. Further adjustment of the location of the post 1 can be obtained by increasing or decreasing the length of hydraulic ram 48 which in turn rotates the post 1 about the axis z, and aligns the post in the correct position for driving. Once correctly positioned the post is lowered by means of lowering yoke 40. Yoke 40 is lowered by means of movement of the hydraulic ram 42 on connecting rod 38.

Hydraulic motor 72 is operated to power the vibration unit 70 which imparts vibrations into the yoke 40 and in turn into the post 1 via clamp 60. The post is driven into the ground in the direction of arrow D by means of the action of ram 42. The driving is assisted by the vibration from the vibration unit 70. If the post 1 is required to be driven into the ground to a depth greater than the stroke distance of the double acting ram 42 then the clamp 60 can be slackened, but need not be removed, and the yoke can be raised and reclamped to the post 1 at a higher position. The clamp 1 can then be driven further into the ground by repeating the driving process mentioned above. This driving technique can be repeated until post 1 is driven into the ground to the desired depth. Referring to Figures 14 and 15 there is shown two different views of a second embodiment of the invention. Pile driving device 6 is shown which is a modified version of the device shown in Figures 1 to 13. As will be described below in more detail, the pile driving device 6 has a mounting frame 70, and further parts 80 and 82, which provide a support member for a yoke 90. The pile driving device 6 is again attached to an excavator arm by means of a mounting frame 70 which includes two spaced parallel pins 72 and 74 which engage with complimentary parts of the excavator arm. Pivotably attached to the mounting frame 70 is a first intermediate portion of the device in the form of a bracket 80. A hydraulic ram 76 controls the pivoting motion of the bracket 80 relative to the mounting support 70.

Pivotably mounted to the bracket 80 is a swash plate 82 which forms a second intermediate portion of the device. A yoke 90 is illustrated which is rotatable on swash plate 82 to provide rotation in the direction of arrow R. The rotation in the direction of arrow R is achieved by adjusting the elements of the yoke 90 which engage with the swash plate 82. The yoke 90 has a saddle portion 92 which is slideably supported on a rod 94, which is in turn rigidly supported to a beam 96. The slideable saddle 92 includes two opposed clamping wedges 98 which can be engaged with or disengaged from post 1 by movement in the direction of arrow C resulting from the movement of hydraulic rams 99. The wedges 98 are attached to percussion devices in the form of hydraulic hammer units 91. As hydraulic rams 99 move the wedges 98 closer together the wedges are forced into engagement with the post 1 because they abut also opposing slide plates 93. Rests 130 are illustrated also and are disposed on each side of the saddle 92. The operation of the rests is described below. Referring additionally to Figure 16, whereat an enlarged view of the items within circle XVI in Figure 14 is shown, the rests 130 include a pair of rollers 131 have static rotational axes and a further pair of rollers 132 which are each mounted for total movement on the frame 96. Extension of the hydraulic rams 133 causes engagement of the rollers 132 with the flanges of the post 1. The rollers 131 and 132 allow movement of the post in the direction of arrow D as it is driven into the ground.

Figure 17 is a plan view of the pile driving device 6 illustrated in Figures 14 and 15, wherein some of the parts mentioned immediately above are more clearly visible. Shown also in this view are a pair of hydraulic rams 81 which are used to rotate the swash plate 82 about an axis generally parallel with the post 1 to provide adjustment of the position of the post 1 relative to the ground surface. Figure 18 shows the items of the pile driving apparatus 6 within the circle XVIII shown in Figure 17. More clearly visible in Figure 18 are the pair of rollers 131 and the opposing rollers 132 which slideably clamp a flange of the post 1 in position.

In use pile driving device 6 is used in much the same manner as the pile driving device 5. Post 1 can be positioned ready for clamping by rests 130 and the posts can be held to the machine by operation of the hydraulic rams 133.

Thereafter the posts can be levelled by movement in the R and P directions and positioned all by means of operation of the hydraulic rams 76 and 81 and adjustment to the swash plate 82. Saddle 92 is lifted by a hydraulic ram (not shown) and the wedges 98 are brought into engagement with the post 1. Following this operation the hydraulic hammers 91 are operated to drive the wedges 98 further into engagement with the post 1 and to cause vibrations in the post as the post is driven into the ground by the downward movement of saddle 92 on bar 94. Engagement of the wedges 98 can be released by extending hydraulic rams 99. The saddle can be lifted and the driving process can be repeated. This operation can be repeated until the desired depth of driving has been achieved.

Figure 19 shows a plan view of a third embodiment of the invention which is a simplified version of the first and second embodiments. In this embodiment the pile driving apparatus is in the form of a hydraulic vibration device 140 comprising a frame 141 which has two removeable pins 142 and 144 which attach to the bucket receiving end of a conventional excavator or digger arm 143, or other moveable support. The device 140 includes a hydraulically powered vibration unit 146 which is mounted to the frame 141 via resilient elastomeric blocks 148. The blocks 148 allow the vibration unit 146 to vibrate on the frame 141 without transmitting those vibrations into the arm 1143.

Rigidly coupled to the vibration unit is a plate 150. The plate provides a pivotable mounting 159 for a pair of jaws 152 and 154 which together form a yoke 151. The jaws can be brought together to clamp around a pile, in this case a further Η' section post 1, by means of tightening screw clamp 156. The jaws have concave recesses 162 which fit around the ends of the flanged sections of the post 1.

In use, the yoke 151 is secured around the post 1 at a position along its length indicative of an amount by which the post is to be driven into the ground. The excavator arm can be positioned such that the post is in the correct position and the vibration unit 146 can be powered. Moving the digger arm down as the post is sunk, provides continual downwardly directed vibration of the post. The yoke is disengaged from the pile after it has been driven to the correct depth. Thus there is no need to use an anvil. Use of a pivot pin 158 allows the jaws 152 and 154 to rotate about the axis of the pivot pin, even when they are clamped to the post 1. This in turn allows an operator to position the post rotationally about an axis parallel to the post axis prior to sinking the post.

In the embodiment shown in Figure 19 various modifications, alternatives and improvements will be apparent to the skilled addressee. For example the clamping of the jaws 152 and 154 could be done hydraulically or using another power source to avoid an operator having to leave the cab of digger. Likewise the pivoting of jaws 152 and 154 about pivot pin 158 could be powered, for example using a known hydraulic ram acting between the yoke 151 and plate 150. The jaws 152 and 154 could be replaced by other clamping means such as cam locks or over-centring locking devices.

Pivoting of the post 1 about horizontal axes X and Y, so that the post is vertical or inclined correctly, can be accomplished, in the X axis by moving the bucket controls of the digger, and in the Y axis by slackening nut 160, adjusting the position of the pivot pin support 159 about the Y axis, and retightening the nut 160. It will be apparent that adjustments in the Y axis too can be powered such that an operator need not have to manually adjust the position of the post. Such powered adjustments could be accomplished using a further hydraulic ram acting between the appropriate portion of a yoke 151 and the plate 150.

In the embodiments shown in Figures 1 to 19 it is envisaged that a source of hydraulic power will be provided by an excavator to which the pile driving devices are attached. It would be possible for the driver of the excavator to control the driving process however, it is preferred that control of the various hydraulic rams mentioned and the vibration unit or percussive hammer units are controlled by a control unit (not shown) close to the pile driving device for example a hand held unit could be provided having buttons or levers being connected to the pile driving device by an umbilical cord. Other control methods are possible for example a wireless connection could be used. Referring to Figure 20, a plan view of a fourth embodiment of the invention is illustrated which is even more simplified, and in which a pile in the form of an 'H' section steel post 1 (shown in section) has a central web 2 onto which have been releasably secured thereto oppositely disposed flat-faced anvils 103, 104, each secured to the web 2 and each other by a pair of bolts 105, 106 which extend through correspondingly shaped smooth bores (not shown) through anvil 103 and web 2 and into threaded bores (not shown) in anvil 104. A yoke shown generally at 107 comprises a foot 108 by which it may be bolted to a moveable carriage on the mast of an hydraulically driven pile driver (not shown), the foot 108 being connected by a leg portion 109 to one of a pair of 'L' shaped yoke arms 110, 111 , arm 110 being integral with the leg 109 and foot 108 and arm 111 being secured for swivelling movement to yoke arm 110 by means of a pivot pin 112 extending through associated smooth bores within that part of the yoke arm 110, 111. Each yoke arm 110, 111 has respective hydraulically operable hammer heads 113, 114 each secured on thickened neck portions 115, 116 which also act as spacers to position the hammers 113, 114 precisely over the anvils 103, 104 in a manner described with reference to Figure 2.

In Figure 21 it will be seen that the swivellable open arm 111 has been moved to its closed position and releasably secured thereto by means of a bolt

117 extending through the arms of a capture yoke 118 which thereby embraces and releasably holds the otherwise free end 119 of the yoke arm 110. Prior to this happening, sizing shims 120, 121 , which may be made of any suitable material, such as wood, rubber etc, are placed to ensure that hammer heads 113, 114 are each correctly aligned immediately above the anvils 103, 104 and remain in that position throughout the subsequent operation of pile driving.

As will be apparent, in operation, the anvils 103, 104 are secured to the central web 2 of the steel pile 1 which is then inserted within the yoke 107 whereafter, following precise alignment of the hammer 113 with respect to anvil 104 through the use of sizing shims 120, 121 the openable yoke arm 111 is then closed to the position shown in Figure 21 and releasably secured in place. Thereafter, repetitive hammering of the hammers 113, 114 against the anvils 103, 104 causes the steel pile 1 to be driven into the ground over which it has previously been positioned, such as by being mounted on a tracked vehicle used to progressively pile drive a line of such steel posts. When the steel pile 1 has been driven into the ground to a required depth the pile driving operation then ends and the yoke 107 and the pile driving apparatus to which it is affixed is then released from its attachment to the steel pile 1 and moved to another location where further pile driving is required.

The steel pile 1 is then left with the anvils 103, 104 and the fixing bolts 105, 106 exposed, in the manner as shown in Figure 23, whereafter they can be removed for re-use elsewhere, leaving the steel pile 1 in the required position and substantially contiguous other than in respect of the smooth bore holes which are used for receiving the fixing bolts 105, 106. Figure 23 also shows the relative differences in the height clearance required of the hammers 113, 114 to begin pile driving, marked as height 'A' in accordance with the method of the invention, and the conventional height required, marked 'B', required to begin pile driving in accordance with conventional techniques which, for a 4 metre high post required to be driven into the ground 1.5 metres represents an effective advantage with the method of the invention of some 266% for this particular example.

The invention therefore provides an elegantly simple method and apparatus for solving and resolving an otherwise difficult problem of pile driving in the conventional manner, which thereby permits the use of relatively short or low-level equipment for driving effectively any length of pile in a safe manner.

Although the method has been described primarily for use with hydraulic hammers it will be understood that it may be used with mechanical drop hammers where the hammer is repeatedly lifted and dropped onto one or more of the anvils 103, 104 until the required depth of penetration has been achieved. Similarly, although the preferred embodiment utilises a pair of oppositely disposed hammers 113, 114 it will be understood that a single hammer operating on a single anvil is also possible, although in that instance the pile could require a separate guide to ensure that it remains upright as the anvil is repeatedly hit by the hammer.

Although the anvils 103, 104 are shown bolted to each other through the web 2, it will be understood that other forms of attachment may be used, such as by opposing pairs of anvils having stepped projections insertable within correspondingly shaped recesses or apertures in the pile, such as in the central web 2 of the pile 1 shown in the drawings, the arrangement being such that one such projection, which may generally be slotted, is inserted within a correspondingly shaped aperture in the web 2 and the other such projection is inserted into a correspondingly shaped other aperture in the web 2 which, by virtue of the projections being stepped permits the upper surfaces of the anvils to occupy a common plane with respect to the hammers 113, 114. Alternatively, the hammers themselves may be stepped with respect to each other and the anvils themselves also being stepped with respect to each other such that a common pair or sets of pairs of apertures may be formed in the web 2 of the steel pile 1 permitting identically shaped anvils to be slotted into place on opposite sides of the web 2 so that they adopt a stepped configuration corresponding to the stepped configuration of the hammers.

The invention extends to hydraulic pile driving apparatus comprising a support mast for a hammer head portion itself mountable on a slideable carriage for movement up and down the mast wherein the length of sliding movement substantially corresponds to the maximum required depth of penetration during pile driving and not the maximum length of a pile to be driven. Conveniently, the mast is mounted or mountable on a vehicle, such as a tracked vehicle. The invention also extends to a method which includes the steps of, where required, after initial pile driving and removing of the at least one anvil to leave a substantially contiguous pile, the or each anvil is again attached to the pile at a position further up it and the process of pile driving is recommenced, to drive the pile further into the ground, and so on until a required depth of penetration has been reached. This is particularly advantageous where the pile is intended to stabilise the ground or provide a stable structure in the ground to which a structure to be built above it, such as a building, may subsequently be anchored.

The post 1 shown in Figure 23 has slots 200a, 200b, 200c and 20Od, into which any combination of plates 202a, 202b and 202d can be fitted. The plates

202 act to inhibit rocking of the post after it is driven into the ground and they can be fitted into any of the slots 200 in the web 3 to suit the soil or ground conditions, and to suit the depth of driving of the post 1.

Figure 24 shows the items within circle XXIV in Figure 23. The plates 202 have a central slot 204, e.g. 204a in plate 202a and two holes 206, e.g. 206a in plate 202a. The slot engages with the sides of the web 3 immediately above the slot 200 and dowels 208 fit into the holes 206 to hold the plate in place before it is driven into the ground with the post. Having separate plates 202 and posts 1 saves space during transportation and provides a post system which is adaptable to suit ground conditions.

Although the invention has been outlined above in its various embodiments it will be understood that it includes any novel combination of the features set out or any obvious equivalent thereto.

Claims

1. A pile driving device comprising or including: a yoke selectively clampable at positions along the length of an elongate rigid pile, post or the like, to be driven into the ground; a vibrator or percussion device contactable with or forming part of the yoke, and a support member for supporting the yoke in use and operable to adjust or maintain the position of the pile, post or the like as it is being driven.

2. A pile driving device as claimed in claim 1 wherein, the yoke comprises a pile clamp and the pile driving device further comprises at least one pile guide member spaced from the clamp for guiding the pile in use.

3. A pile driving device as claimed in claim 2 wherein, said yoke and said at least one guide member are moveable together relative to the support member.

4. A pile driving device as claimed in claim 2 or 3 wherein, said at least one pile guide member comprises a pair of guide members spaced from the clamp each one of the pair being disposed on opposing sides of the clamp.

5. A pile driving device as claimed in any one of the preceding claims wherein, the support member includes an alignment hinge having a first pivot axis substantially parallel with the longitudinal extent of the pile, for said positional adjustment the pile, about said first axis, relative to a ground surface.

6. A pile driving device as claimed in claim 5 wherein, the support member further includes two levelling hinges having second and third mutually orthogonal pivot axes each being substantially transverse or oblique to the longitudinal extent of the pile, for positional adjustment of the pile about said second and third axes, for vertical levelling of the post into a generally upright position or otherwise to a specified inclination.

7. A pile driving device as claimed in any one of the preceding claims wherein, the support member includes: a mounting frame for attaching to a tractor vehicle such as an excavator; a first intermediate portion pivotally connected to the mounting frame for movement about one of the first, second or third axes; a second intermediate portion pivotally connected to the first intermediate portion for movement about another one of the first second or third axes, the yoke being pivotally connected to the second intermediate portion for movement about a last one of said first, second or third axes.

8. A pile driving device as claimed in claim 7 wherein, the second intermediate portion includes a bar for allowing sliding movement of the yoke as well as said movement about the last one of the axes, relative to the second intermediate portion.

9. A pile driving device as claimed in any one of the preceding claims wherein, the or each guide is fixed to the yoke such that the yoke when clamped to the pile by the clamp is slideable with the pile and the guide(s) move with the yoke.

10. A method of pile driving including the steps of providing a releasable yoke, for securing the yoke on a pile at a position along its length indicative of an amount by which the pile is to be driven into the ground, providing pile driving apparatus including a vibrating or percussion device in contact with, or forming part of the yoke, providing a moveable support member which supports the vibrating or percussion device to follow movement of the pile as it is driven into the ground by the yoke, driving the pile with the use of the vibrating or percussion device and thereafter disengaging the yoke from the pile, leaving it driven into the ground, or repeating the step above to drive the pile to a required depth.

11. A pile driving device including a releasable yoke, securable along the length of a pile to be driven into the ground, the yoke including means to grip the pile at positions along its length and a vibrating or percussion device in contact with, or forming part of the yoke, the pile driving device including also a support which supports the yoke to generally follow movement of the pile as it is driven into the ground.

12. A method of pile driving which includes the steps of providing at least one anvil on a pile to be driven at a position along its length indicative of an amount by which the pile is to be driven into the ground, providing pile driving apparatus including a yoke for at least partially surrounding percussion means for simultaneously hitting the at least one anvil, and drive means for driving the yoke to follow movement of the pile as it is driven into the ground by the percussion means to a required extent, thereafter disengaging the yoke from the pile, leaving it driven into the ground, and thereafter removing the at least one anvil to leave a substantially contiguous pile.