GB2424024A

GB2424024A - Adjustable pile cap assembly

Info

Publication number: GB2424024A
Application number: GB0505127A
Authority: GB
Inventors: Duncan Clift Mcgregor
Original assignee: Screwfast Foundations Ltd
Current assignee: Screwfast Foundations Ltd
Priority date: 2005-03-12
Filing date: 2005-03-12
Publication date: 2006-09-13
Also published as: GB0505127D0

Abstract

In order to adjust the height of a base plate (10) which is mounted at the top of a pile (20) to make it level with one or more other base plates atop adjacent piles, the base plate (10) has a generally central aperture (13) whereby it is secured to a drive plate (22) at the top of the pile (20) by a primary bolt (14). A plurality of threadedly adjustable spacers, such as bolts (16) and corresponding nuts (18) which are threadedly engageable thereon, then enable adjustment and setting of the spacing between the drive plate (22) and the base plate (10). The head of the primary bolt (14) may be countersunk in a central well or recess in the base plate (10).

Description

1 2424024

MJUSTABLE PILE CAP ASSEMBLY

This invention concerns a cap assembly for attachment to an individual pile.

Screw piles are commonly used to support and anchor structures such as masts, towers and pylons. Typically four piles are driven into the ground at appropriate positions at corners of a square or rectangle corresponding to the lower ends of the legs of the mast or tower. Typically each pile has a large steel disc, known as either a pile head plate or a drive plate, welded to its upper end. This disc is for attachment of a piledriving tool during installation of the pile. For this purpose it has either a threaded stud projecting centrally or else a tapped bore through the centre as well as several, typically four, spaced bores, all of these enabling bolting on of the driving tool. As the installation of screw piles is now more readily achievable, they are now contemplated for use for support of prefabricated buildings, for example below the corners of prefabricated cabins.

An object of the invention is to provide a simple pile cap assembly, including a base plate for support of a structure, which plate can readily be adjusted so as to be made level with one or more other base plates atop adjacent piles.

A further object is to enable vertical alignment of the base plates of numerous similar pile cap assemblies on a particular site, not just those used for mounting a single specific structure.

According to the invention an adjustable pile cap assembly comprises a base plate having a generally central aperture, attachment means which will serve, by way of said aperture, to secure the base plate to the pile, and a plurality of threadedly adjustable spacers which will enable adjustment of the spacing between the drive plate and the base plate.

Preferably, the drive plate is provided with a plurality of spaced apertures and the threadedly adjustable spacers are adapted to extend through these apertures in order, adjustably, to set the spacing between the drive plate and the base plate.

Thus, spacer adjustment is preferably achieved from below the base plate, which does not then require any extra apertures therein, and which can then provide a substantially planar support surface without upstanding projections. This may be particularly desirable when used for supporting a corner of a prefabricated building, or adjacent corners of two or more such buildings which are positioned close to each other.

The threadedly adjustable spacers may consist solely of bolts in cases where the apertures in the drive plate are tapped (ie, internally threaded) and the bolts are of a diameter to threadedly engage in these apertures. However, the spacers preferably comprise bolts together with corresponding nuts which threadedly engage thereon so as to cater for the more usual form of drive plate having untapped apertures as well as providing greater reliability in any instances where tapped apertures are provided in the drive plate.

The invention also provides a method of adjustably fitting a base plate to a drive plate mounted atop a pile comprising the steps of: providing a generally central aperture in the base plate; attaching the base plate to the drive plate by a primary bolt through said generally central aperture; adjusting the height of the primary bolt to a predetermined level; providing a plurality of threadedly adjustable spacers and adjusting the extent to which these project between the drive plate and the drive base plate until the base plate reaches a height determined and limited by that of the primary bolt and is also substantially level.

The assembly of the invention and the method of its fitting are exemplified below with reference to the accompanying drawings, in which: Fig. 1 is a fragmentary, part sectional side view showing a preferred embodiment of a pile cap assembly of the invention installed at the top of a pile; Fig. 2 is a reduced scale plan view of the upper plate of the assembly shown in Fig. 2; Fig. 3 is a reduced scale plan view of the retaining plate which is welded below the upper plate of the assembly shown in Fig 1; and Fig. 4 is a reduced scale plan view of the drive plate which is mounted atop the pile shown in Fig. 1 With reference to the drawings, this practical embodiment of the assembly comprises a base plate 10, attachment means in the form of a primary bolt 14 and four threadedly adjustable spacers in the form of respective bolts 16 and their corresponding nuts 18. The base plate 10 itself takes the form of a substantially square upper plate 12 having a large central aperture 13 (Fig. 2) and a small circular retaining plate 11 having a relatively smaller central aperture 15 (Fig. 3) which is welded concentrically to the underside of the upper plate 12, as evident in Fig. 1 so that the aperture 13 provides a well or recess to accommodate the head of the bolt 14 in use.

In use, and with reference to Fig. 1, the assembly is attached to the top of a pile 20, which is at or near ground level, after the pile 20 has been driven into the ground. A drive plate 22 (Fig. 4) is already mounted onto the top of the pile 20 by means of a concentric dependent bush 24 which is welded to the drive plate 22 and the pile 20.

The drive plate 22 has a central tapped hole 26 and the primary bolt 14 is of an appropriate dimension to threadedly engage in and through this hole 26. The drive plate 22 also has four additional apertures 28 which are spaced an equal distance apart around an imaginary circle concentric with the plate 22.

In practice there will generally be several piles driven into the ground at spaced apart locations, for example at locations to support the corners of a prefabricated structure.

The piles are installed as accurately as possible and earth is rammed around each to stabilise them. A cap assembly is then fitted to each as shown in Fig. 1 with the primary bolt 12 projecting through the base plate 10 and engaging into the central hole 26 of the drive plate. The base plate 10 is orientated so that the retaining plate 11 is to the underside so the head of the primary bolt 12 is countersunk in the aperture 13. The spacer bolts 16 are applied from below through each of the apertures 28 in the drive plate 22 and are held by engagement with their associated nuts 18 which are positioned above the drive plate 22, between it and the base plate 10.

At this stage it is only a matter of a relatively loose intercoimection of the parts.

The retaining plate 11 is suitably allowed to rest upon the drive plate 22, the spacer bolts 16 being sufficiently unscrewed to enable this.

The primary bolt 14 of each assembly is then screwed up or down to a desired common level which will be ascertained using an optic level or laser level or similar.

Once these bolts 14 are set level and aligned with each other care should be exercised not to disturb them until the stage of final tightening.

Then, by screwing the spacer bolts 16 upwards through their nuts 18, the base plates of each of the assemblies are moved upwards to abut the heads of the respective primary bolts 14. Precise levelling of each of the upper plates 12 can be achieved by use of a small levelling tool upon each and appropriate adjustment of the spacer bolts 16.

When all the upper plates 12 are level and each base plate 10, as a whole, firmly retained against its primary bolt head, these primary bolts 14 can be tightened down and the space between each drive plate 22 and its base plate 10 can be filled with a stiff grout.

After a final checking of the level of the plates 12 and any final adjustments, the structure to be supported may be lowered into position so that its corner regions are resting upon the cap assemblies, specifically the level plates 12.

The foregoing is illustrative and not limitative of the scope of the invention and many variations in detail are possible. For example, in other embodiments the base plate may be a unitary item. Also, in other embodiments, the head of the primary bolt may not be countersunk or not fully countersunk (although that is preferable for a planar support surface). Indeed, the attachment means could possibly be a nut mounted onto an upstanding stud instead of a bolt, although the latter is preferred for the reasons just given to avoid upward protrusions of any sort. Another possible variation is that the holes in the drive plate, through which the spacer bolts engage, may be tapped such that the nuts are not essential. Also the spacer bolts could be mounted from above and engage or project through holes in the base plate instead of through holes in the drive plate, although such an arrangement is less likely to be favourable as it would result in upward protrusions from a planar support surface unless there is careful countersunk provision, which adds to complexity and detracts from the simplicity of the above described installation method.

Claims

1. An adjustable pile cap assembly comprising a base plate having a generally central aperture, attachment means which will serve by way of said aperture to secure the base plate to a drive plate at the top of a pile and a plurality of threadedly adjustable spacers which will enable adjustment of the spacing between the drive plate and the base plate.

2. An assembly as claimed in claim 1 wherein the drive plate is provided with a plurality of spaced apertures and the threadedly adjustable spacers are adapted to extend through these apertures in order, adjustably, to set the spacing between the drive plate and the base plate.

3. An assembly as claimed in claim 1 or claim 2 wherein the threadedly adjustable spacers comprise bolts and corresponding nuts which are threadedly engageable thereon.

4. An assembly as claimed in any preceding claim wherein the attachment means comprises a primary bolt and the base plate includes a entraI well or recess in which the head of the primary bolt may be countersunk.

5. A method of fitting a base plate to a drive plate which is mounted at the top of a pile comprising the steps of: providing a generally central aperture in the base plate, attaching the base plate to the drive plate by a primary bolt through said generally central aperture; adjusting the height of the primary bolt to a predetermined level; providing a plurality of threadedly adjustable spacers and adjusting the extent to which these project between the drive plate and the base plate until the base plate reaches a height determined and limited by that of the primary bolt and is also substantially level.