GB2069034A - Pile drivers - Google Patents

Abstract

An underwater pile driver comprising one or more hydraulic cylinders (6) is operated by the water in which it is submerged. A pump (20) at the surface produces a pressurised water supply and the driver exhausts the water directly into its surroundings. Only a single large-bore high-pressure line (24) is therefore required as there is no return line. By means of a remotely actuated pilot valve (28) the pressure water supply is also used to operate a valve (26) through which the water flows into and out of the cylinder. The valves (26, 28) are disposed on the submerged pile driver frame (2). <IMAGE>

Description

SPECIFICATION Pile drivers This invention relates to hydraulic pile drivers and to a method of operating such pile drivers.

In driving piles underwater, considerable difficulties occur as soon as the depth of the pile is so great that the driver must itself be totally submeryed. Diesel, steam, or air hammers, for example, must be enclosed in a completely watertight outer casing while there are problems in establishing a supply of large flow rates of compressible fluid, such as compressed air or steam, to any considerable depth underwater.

Hydraulic pile drivers can be used, but they have been found to offer an expensive alternative because oi the need to provide large bore supply and return ines between the driver and a hydraulic pump on the surface. The cost of large bore highpressure hydraulic hose is such that when working at great depths the capital cost of the supply and reiuir, lines and their associated equipment may be of (h same order as that of the driver itself.

Moreover, due to their vulnerability these hoses may require frequent replacement.

According to one aspect of the present invention, there is provided a method of operating a hydraulic pile driver underwater in which water is empioyed as the pressure fluid supply and is .rallsmitted from a pressurizing source at the surface to the driver underwater, and the fluid exhausted from the driver is evacuated directly into its surroundings.

By these means it is possible to halve the cost of the hydraulic hose required to operate a pile driver at any given depth underwater. There are also advantages in that return line friction losses are avoided angel that leakages that may occur from the pumping system, and especially the supply line, are non-polluting.

The invention also provides a hydraulic pile driver adapted for underwater operation and comprising at least one hydraulic cylinder in which a piston is reciprocabie by water under pressure to generate a series of driving impulses, valve means for transmitting the inflow and outflow of the water to and from said at least one cylinder communicating with a pressure inlet connection for said water, and an exhaust path from said cylinder being provided by outlet porting opening into the intermediate ambient region externally of the cylinder, Preferably, control means are provided for the remote control of the operation of said valve means.

Preferably said valve means controlling the flow into and out of the or each cylinder comprises a valve body disposed at or adjacent one end of the cylinder and operable by a pilot valve. In a preferred arrangement the pilot valve is operable electrically, whereby its action may be regulated from a control station on the surface using only electrical leads from the control station to the pile driver under-water. In a convenient form of this arrangelnent, the valve means is operable by a hydraulic pilot valve, itself mounted in or on the driver and actuated by adjacent electrically operated switching means for the remote control of the operation of the driver.

The control valve body may comprise a sleeve disposed within and closely surrounding a cylindrical wall portion of its hydraulic cylinder and displaceable relatively thereto for controlling communication between the cylinder interior and the pressure inlet connection and said interior and the outlet porting selectively.

The invention will be described in more detail with reference to the accompanying drawings, in which: Fig. 1 is a schematic illustration of a pile driver according to the invention in situ with its associated power supply, Fig. 2 is a more detaiied front elevation of the pile driver in position on a pile, Figs. 3 and 4 illustrate in further detail a singleacting hydraulic cylinder of the pile driver of Figs.

1 and 2, in axial section and in side elevation respectively, and Figs. 5 and 6 are similar views of a doubleacting hydraulic cylinder for a pile driver according to the invention, also utilisable in the pile driver of Figs. 1 and 2.

The pile driver shown in Figs. 1 and 2 comprises a carrier frame 2 having suspension means 4 to attach to some suitable support and acting as a guide for the pile P being driven.

Mounted on the frame in Fig. 2 are two similar hydraulic cylinders 6 held fixed on opposite sides of the carrier frame to which they are secured by pin joints 8 at the lower ends of their casings. A piston 10 is slidable in each casing and piston rods 12 are both connected at their upper ends through a cross-head 14 to a tup or hammer weight 16 guided on the carrier frame 2. By reciprocating the pistons together in their hydraulic cylinders, the hammer weight is caused to produce a series of impulses on a drive cap 1 8 sitting on top of the pile and guided by the frame 2 for driving the pile.

The frame, together with its hydraulic cylinder or cylinders, is shown in Fig. 1 positioned underwater and pressure fluid is supplied from a hydraulic pump 20 on the surface that draws its supply from the surrounding water, through a filter 22. The power supply line 24 from the pump leads to a control valve 26 in each cylinder 6 that is regulated by a solenoid-operated pilot valve 28, a tapping 30 from the main hydraulic supply line providing pressure fluid for the pilot valve. In this example the pilot valve is common to both control valves and it switches both control valves simultaneously but when multiple cylinders are thus operated together it may be necessary to employ the solenoid operated valve as a servo valve for a hydraulic pilot valve that in turn operates the control valves of the cylinders.

The control valves move between the position shown, in which the interior space 32 below the piston in each cylinder is connected directly to the free water around the cylinder, and the piston is therefore allowed to fall, and a position in which said space 32 is closed from the outside and receives pressure fluid to raise the piston again.

The pistons are thus reciprocated together to produce a series of impulses on the pile and by controlling the switching of the pilot valve 28 it is possible to bary the piston stroke, and hence the impulse force and/or frequency of impulse.

An accumulator 42, also on the carrier frame, is permanently connected to the hydraulic supply line 24 and serves to store pressure fluid when the control valves 26 are closed, so reducing fluctuations in demand on the pump. If desired a separate accumulator can be provided for each cylinder. A dump valve 44 is provided in the supply line, to be used to release pressure when operation of the driver has ended, and non-return valve 46 prevents a back flow from the accumulator.

In Figs. 3 and 4 there is shown a particular construction of hydraulic cylinder with a control valve that has a valve body 52 comprising a valve sleeve 54 cooperating with porting in the cylinder.

The piston reciprocates in a cylindrical casing 58, at the top of which there is a guide sleeve 60 for the piston rod 12 projecting from the casing. The lower end of the casing is sealingly received in an end block 62 where an annular chamber 64 surrounds the lower end wall 66 of the casing 58 and is open to the pressure inlet connection 68.

The connection comprises a T-piece 70, on the branch of which the accumulator 42 is connected.

The valve body 52 is formed with a central stem 72 the lower end of which carries a piston 74 fitting in a servo chamber 76 sealed from the cylinder interior. The upper end of the servo chamber communicates continuously with the pressure inlet through passage 78 while the lower end of the chamber has a connection 80 to the pilot valve 28 so that it can be supplied controllably with fluid at the same pressure as in the upper end of the chamber 76.

In the illustrated position, the pilot valve 28 directs pressure fluid to the lower end of the servo chamber and, because of the differential areas of the upper and lower faces of the piston 74, the valve body 52 has been moved to an uppermost position, in which a series of ports 82 in the sleeve 54 are in communication with a series of ports 84 in the casing wall that open directly into the annular chamber 64. At the same time, the upper end of the sleeve seals off a series of exhaust ports 86 in the casing wall above the end block opening directly into the ambient water. Pressure fluid is thus admitted to the cylinder interior space below the piston via the annular chamber 64, the ports 84 in the casing wall and the ports 82 in the valve sleeve, to raise the piston.A balancing port 88 in the valve body transmits the fluid pressure to below the head so preventing the valve being switched by the main flow of fluid into the cylinder. The fluid in the interior of the casing above the piston is able to escape through ports 89 near the top of the casing.

When the pilot valve is switched to release the pressure at the lower end of the servo chamber, the hydraulic pressure acts to return the valve body 52 to a lowermost position. The interior space below the piston is now cut off from the pressure supply and the exhaust ports 86 are opened to discharge water from the cylinder into its immediate surroundings, so that the piston can fall under gravity to produce an impulse by impact of the weight 1 6 on the drive cap 1 8. The switching of the pilot valve can be performed manually or automatically, e.g. in a timed manner or by means of switches operated by the movement of the piston or weight. Illustrated are a series of top limit switches 90 which may be brought into operation selectively from the surface by appropriate circuitry.Alternatively, the pressure flow for the upstroke may be maintained for a controllable period, in generally known manner, to regulate the stroke.

Figs. 5 and 6 illustrate a double-acting hydraulic cylinder for an alternative embodiment of the invention. The mounting of the cylinder and its pressure supply system may be of the form already described with reference to Figs. 1 and 2, while parts identical to those described with reference to Figs. 3 and 4 are given the same reference numbers.

The construction of the control valve and its servo system thus correspond generally to that already illustrated and described with reference to Figs. 3 and 4. There is now a communicating conduit 92 between the annular chamber 64 in the bottom block and a further annular chamber 94 in a top block at the head of the hydraulic cylinder, a series of ports 96 in the casing wall providing communication between this further annular chamber and the cylinder interior space above the pistons. In this instance, the top sleeve guiding the piston rod is required to make a fluid tight seal with the casing and the piston rod.

With the control valve in the illustrated position, pressure fluid is admitted both to the underside of the piston and, through the conduit 92, to the space above the piston but due to the differential area of the top and bottom piston faces the piston is driven upwards. When the valve is switched, the lower space is exhausted, as in the first example, but the upper space continues to be connected to inlet pressure by way of the lower annulus 64 and the conduit 92, so that the piston is subjected to a downwards pressure force in addition to the gravity force acting on it. When the control valve is switched again, fluid above the piston will be transferred to below the piston to supplement the inflow from the pressure connection 68 which makes up for the increase of volume due to the extension of the piston rod 1 2 from the casing.

It will be appreciated that the double acting arrangement does not require gravity forces to act to return the piston and the cylinder can therefore be operated in any desired orientation.

It will be noted that in both the examples of the invention described only a single high pressure hydraulic supply hose needs to be run from the surface to the pile driver because the exhausted fluid is simply discharged to the surrounding water. Since large or high pressure hose is extremely expensive, this arrangement is able to show considerable economies especially when the driver is required to work in large depths of water.

Because the working liquid is allowed to escape to the immediate surroundings instead of being led back to the pump, frictional losses from that source are eliminated and the pile driver can be operated more efficiently and at a lower exhaust pressure.

In the preferred forms shown, the action of the hydraulic control valves from the surface is regulated by electrical connections, the main supply hose being the only hydraulic connection to the surface. As an alternative to the electrical servo control, it is, however, possible to run hydraulic servo lines between the surface and the pile driver with a less severe cost penalty as the expense of small bore hose is very much less than that of the large bore sizes needed to supply power to a hydraulic cylinder.

The control of the operation of the driver of either example by electrical control means has been referred to above. Further details of preferred control and monitoring arrangements are described more fully in our co-pending application filed simultaneously herewith.

Claims (10)

1. A method of operating a hydraulic pile driver under water in which water is employed as the pressure fluid supply and is transmitted from a pressurising source at the surface to the pile driver under water, and the fluid exhausted from the driver is evacuated directly into its surroundings.

2. A method according to claim 1 wherein the pressurised water supply is also used to operate valve means for controlling the flow through the driver.

3. A method according to claim 2 wherein the valve means is actuated electrically through a connection from electrical control means at the surface.

4. A hydraulic pile driver adapted for underwater operation and comprising at least one hydraulic cylinder in which a piston is reciprocable by water under pressure to generate a series of driving impulses, valve means for transmitting the inflow and outflow of the water to and from said at least one cylinder communicating with a pressure inlet connection for said water, and an exhaust path from said cylinder being provided by outlet porting opening into the intermediate ambient region externally of the cylinder.

5. A pile driver according to claim 4 wherein said valve means are actuated by a remotely operable pilot valve arrangement disposed adjacent said at least one cylinder.

6. A pile driver according to claim 4 wherein said valve means are actuated by a hydraulic pilot valve arrangement operated by electrical switching means for remote control of the operation of the driver, said switching means being mounted in or on the driver.

7. A pile driver according to any one of claims 4 to 6 wherein said valve means comprises a valve body disposed at or adjacent one end of the or each said cylinder.

8. A pile driver according to any one of claims 4 to 7 wherein the valve means comprises a sleeve disposed within and closely surrounding a cylindrical wall portion of the or each respective hydraulic cylinder and displaceable relatively thereto for controlling communication between the cylinder interior and the pressure inlet connection and said interior and the outlet porting selectively.

9. A method of operating a hydraulic pile driver substantially as described herein with reference to the accompanying drawings.

10. A hydraulic pile driver constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.