GB1566101A

GB1566101A - Release device

Info

Publication number: GB1566101A
Application number: GB3845175A
Authority: GB
Original assignee: CEMENTATION GROUND ENG Ltd
Current assignee: CEMENTATION GROUND ENG Ltd
Priority date: 1976-09-17
Filing date: 1976-09-17
Publication date: 1980-04-30

Description

(54) RELEASE DEVICE (71) CEMENTATION GROUND ENGINEERING LIMITED, a British Company, of Mitcham House, 681 Mitcham Road, Croydon, Surrey, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement.: This invention relates to apparatus for use in the dynamic consolidation technique for deep ground compaction and consolidation of soil.

In the technique of dynamic consolidation for compacting and consolidating soil a large weight, hereafter called a compacting weight or tamping block, is dropped from a height onto the soil to be compacted. The size and shape of the compacting weight and the height from which it is dropped are selected in accordance with ground conditions but, usually, the compacting weight is between 10 and 40 tonnes and it is dropped from a height between 10 and 30 metres. The operation of consolidation is carried out on large sites. Consequently, the crane used must be mobile and is normally a heavy crawler crane such as those used on large construction sites. The crane also requires a long boom, preferably at least 30 metres, in order that the required height can be achieved.

In the technique of dynamic consolidation the compacting weight may be dropped by means of a release system so that it falls freely or it may be dropped with the hoist rope of the crane still attached. It is preferred that the compacting weight should fall freely, in order to reduce unnecessary wear on the hoist rope, pulleys, winding mechanism and other crane parts.

Furthermore, the compacting process is more efficient if the weight falls freely. The sudden release of a large weight, however, causes a recoil of the crane and this recoil causes wear and tear of the crane.

It is an object of this invention to provide apparatus comprising a weight and a device embodiments of which will release the weight in a controlled manner so that the weight falls freely and the recoil of the crane is reduced.

According to one aspect of the present invention there is provided apparatus for use in the dynamic consolidation technique for deep ground compaction and consolidation of soil, which comprises (a) a massive weight one surface of which is provided with an extension in the form of a pillar; (b) a device adapted to be suspended from or forming part of a crane or hoist, said device comprising at least one member which, in a first operative position, co operates with the pillar of, and supports, the weight and which, in a second operative position, disengages the weight; and (c) means for controlling the movement of the or each member from the first operative position to the second operative position so as to effect controlled downward acceleration of the weight prior to its separation from the crane or hoist when the or each member is at the second operative position, and to reduce the recoil of the crane or hoist resulting from the release of the weight.

Preferably the means for controlling the movement of the or each member of said device is a hydraulic control system. Such a system may involve passage of hydraulic fluid through an orifice or a restricted channel; in some embodiments of the invention the orifice or channel remains constant in size as the or each member moves from the first operative position to the second operative position, whereas in other embodiments the orifice or channel is modified during such movement (and in some cases the modification of the channel or orifice is brought about by such movement).

The or each suspension member is conveniently in the form of a suspension arm.

In a first type of embodiment of the invention, there are a plurality of suspension arms each of which pivots about a point intermediate its ends when moving from the first operative position to the second operative position. In this embodiment, control of the movement of the suspension arms is advantageously effected by having the upper ends of the suspension arms connected to pistons which are slidably mounted in respective arms of a chamber which in use contains hydraulic fluid; there is an orifice in the chamber through which hydraulic fluid can be forced under pressure when the suspension arms move from the first operative position to the second operative position. The connection between each suspension arm and its respective piston may be direct or via linkages.The hydraulic control system preferably includes a valve for controlling the flow of fluid from the chamber through the orifice. When the valve is closed no fluid can flow from the chamber so that the pistons cannot move to permit the suspension arms to move about their pivots to release the weight. When the valve is opened, fluid can flow from the chamber and through the orifice, thereby permitting the pistons to move and allowing the suspension arms to move about their pivots to release the weight. As the rate of flow of fluid is limited by the size of the orifice the rate at which the pistons can move and hence the rate at which the suspension arms can pivot are also limited.

Hence there is controlled downward acceleration of the weight prior to its separation from the crane or hoist.

The release device preferably has three or four suspension arms, although it is possible for it to function with a single arm of suitable construction. In one embodiment, each suspension arm is connected directly to a fluid-actuated piston in a radially outwardly extending arm of a central chamber containing hydraulic fluid. One surface bounding the centre chamber is provided by a plate containing the orifice.

Hence when the orifice is opened all the pistons can move simultaneously to permit release of the weight.

In embodiments of the first type just described, the lower ends of the suspension arms can be shaped to correspond with the pillar provided on the weight.

In embodiments of a second type, the suspension arms move downwards, in engagement with the weight, from the first operative position to the second operative position, whereat the weight is disengaged.

In these embodiments, the lower ends of the suspension arms can be adapted to engage a collar or to engage in slots provided on or in the pillar of the weight. Disengagement of the weight can be effected by provision of means whereby the suspension arms are caused to pivot about their upper ends, this resulting in their lower ends moving away from, and thus disengaging, the weight. In one embodiment of this second type, the device comprises (a) a rod whose upper end is connected to, or is adapted to be suspended from, the crane or hoist; (b) a collar slidably mounted on said rod and from which a plurality of suspension arms are pivotally suspended; and (c) one or more cams fixed to said rod and located so as to cause radially outward movement of the lower portions of the suspension arms when they reach the second operative position.Preferably, the downward movement of the suspension arms is controlled by means of an arrangement in which a plurality of annular cylindrical walls are located coaxially about said rod and are shaped and located so as to cooperate with one another to provide a restrictive channel through which hydraulic fluid may be forced in response to the mass of the weight when the collar and the suspension arms move downwardly from the first operative position of the suspension arms towards the second operative position.

The restrictive channel advantageously provides progressively less resistance to the passage of hydraulic fluid as the suspension arms move towards the second operative position. Conveniently, the plurality of annular walls can form an acceleration control chamber whose volume is variable.

The volume of the chamber is altered by supplying hydraulic fluid or withdrawing hydraulic fluid from the chamber, thereby causing end walls of the chamber to move towards or apart from each other. By this means the slidably mounted collar can be slid up or down the rod, which extends through the acceleration control chamber.

In the technique of dynamic consolidation the release of the compacting weight or tamping block tends to cause recoil of the entire crane. By suitably shaping the passages through which hydraulic fluid flows in the release devices of apparatus of this invention it is possible to control the rate of gain of acceleration of the compacting weight until it is released, so that the downward force on the crane hook is progressively reduced until the instant at which the weight is released. Hence the effects of recoil on the crane or hoist are reduced.

In one embodiment of the second type, each arm has a box shaped cross-section, made for example of strips of steel, and a roller is situated between the side plates of the box section at about the mid-point of the arm, so that the roller can contact a cam fixed to the rod. A further roller is provided at the lower end of each arm to engage the weight. The cams may be fixed so that they permanently project or they may be retractable and caused to project only when the hydraulic control system is actuated to cause the release device to release the weight. The latter arrangement is preferred for reasons of safety. In this embodiment, the release device is preferably provided with three suspension arms and three cams, although four or more suspension arms and a corresponding number of cams can be used if desired.

In embodiments of a third type, the lower ends of the suspension arms are connected to pistons which are slidably mounted in arms communicating with a chamber containing hydraulic fluid.

The compacting weight which is to be released from the crane or hoist is adapted for use with the releasing device. Attached to the upper surface of the compacting weight there may be a generally upright pillar. In one form of pillar suited for use with release devices of the first type a waist is provided in the pillar and the lower ends of the suspension arms engage the outer surface of the pillar in this waist when raising the compacting weight. The pillar may have a closed upper end and it is preferred that the upper end of the pillar is rounded because this assists in locating the release device on the pillar when picking up the weight. In other forms suited for use with release devices of the first type the pillar is hollow and open at its upper end.

The suspension arms of the release device enter the pillar and contact the inner surface of the pillar. Preferably the suspension arms have rollers at their lower ends which contact the surface (whether inner or outer) of the pillar. In one form of the pillar suited for use with release devices of the second type, the pillar is generally cylindneal and has on its outer surface an annular projection or collar which can be engaged by the arms of the release device which arms are turned inwards at their lower ends.

To assist in locating the device on the compacting weight when the weight is on the ground, the device can include a cylinder having a conical-shaped lower end.

If the upper end of the pillar on the compacting weight is rounded, when the device is lowered onto it the upper end of the pillar and the conical-shaped lower end of the cylinder cooperate to locate the device on the compacting weight. With such an arrangement the lower ends of the suspension arms are situated outside the cylinder (the suspension arms may be in the second operative position to achieve this result) during the location step and, when the device is correctly located on the compacting weight, the hydraulic means is actuated to pivot the suspension arms so that their lower ends engage the pillar, the lower ends passing through apertures provided in the wall of the cylinder in order so to do.

When the compacting weight is held by the device, the device and compacting weight can be raised by means of the crane or hoist. In preferred release devices of the first and third types, the compacting weight exerts a force tending to urge the lower ends of the suspension arms horizontally, either outwards or inwards, to release the weight.

Outward or inward movement of the lower ends of the suspension arms would result in movement of the piston or pistons to which the suspension arms are connected, and movement of the piston or pistons is prevented by the reacting pressure of hydraulic fluid due to the closed valve. The compacting weight is raised to the desired height, and then the hydraulic fluid is gradually released through the orifice when the valve is opened. This permits the suspension arms gradually to move outwards or inwards to release the compacting weight. As the suspension arms move the rollers at the lower ends of the suspension arms run over the surface of the pillar on the compacting weight.It is desirable that during the release of the compacting weight the rate of increase of acceleration with respect to time of the compacting weight shall be gradual, preferably linear, until when the weight is released its acceleration is that due to gravity. From a knowledge of the mass of the weight the size of orifice, piston area, density of hydraulic fluid and other factors it is possible to derive an equation which defines the shape of the pillar over which the suspension arms should run to achieve this condition. This matter is explained further below.

As the downward acceleration of the weight increases gradually in a controlled manner, the recoil effect of the crane or hoist is substantially reduced in comparison with what it would otherwise be.

To reduce further the effect of recoil on the crane, the crane can be stabilised as described in our British Patent Specification No. 1511249.

The invention will be further illustrated with reference to the accompanying drawings showing, by way of example, embodiments of the invention, in which: Figure 1 is an elevation of a preferred embodiment of a release device of the first type described above; Figure 2 is a sectional elevation of the release device of Figure 1, with some parts omitted for clarity; Figure 3 is a plan view of the device in the direction of arrow A of Figure 2; Figure 4 is a plan view of the device on the line B-B of Figure 2; Figures 5 and 6 are elevations of a second embodiment of a release device of the first type; Figures 7 and 8 are diagrammatic sections showing details of release devices of the third type described above;; Figures 9 and 10 show details of other release devices of the first type Figure 11 is a section of a release device of the second type described above, engaged with a compacting weight; Figure 12 is a section of the device shown in Figure 11 in the configuration the device adopts when the weight has been released; and Figure 13 is a plan view of the device shown in Figures 11 and 12.

Referring to Figures 1 to 4, the device includes a frame 1 which is square in plan view and is provided at each corner with shackles 2 for use in suspending the device from a crane. The frame includes four members 3, one depending from each corner of the frame. Attached to the lower end of each depending member 3 is a bracket 4. The inner end of each bracket 4 is connected to the outer surface of a cylinder 5. The cylinder 5 has a cone-shaped lower end 6 and has four apertures 7 in its wall, as shown.

The device has four suspension arms 8, each one pivotally mounted intermediate its ends on a pivot pin 9 located at the lower end of each member 3. The suspension arms 8 are shaped as shown and the lower end of each suspension arm 8 is turned inwards and has a roller 10 in suitable bearings at its lower end. At the upper end of each suspension arm 8 is a pin 11 on which is pivotally mounted a rod 12 connected to a piston 13 slidably located in an arm or "barrel" 14. The four barrels 14 all converge to provide a common chamber on the upper surface of which is an orifice plate 17 in which there is an orifice 18. A ball valve 19 is provided to close the orifice 18. The ball valve can be operated in any convenient manner, for example, electrically, hydraulically or pneumatically. Above the orifice plate 17 is a reservoir 20 for hydraulic fluid.Above the reservoir are mounted a motor 21 and a pump 22 for the hydraulic fluid. The pump 22 supplies hydraulic fluid to the barrels 14 via an inlet valve 23 which can be operated electrically, hydraulically or pneumatically. A relief valve (not shown) is provided beside the inlet 23 to protect the hydraulic system against overloading. The relief valve exhausts to the reservoir 20.

The device issued to raise and release a compacting weight 24, which may be of 20 tons mass. The compacting weight has fixed to its upper surface a pillar 25, having a waist 26 where the rollers 10 at the lower ends of the suspension arms 8 can engage the pillar. Also fixed to the top of the compacting weight 24 is a ring 27 which is contacted by the inside of the cone-shaped lower end 6 of the cylinder 5 when the release device is lowered over the pillar 25, this serving to ensure correct registration of the release device with the pillar. A compressible pad (not shown) may be provided at the head of the cylinder 5 to cushion any contact between the top of the cylinder 5 and the top of the pillar 25.

In operation, the compacting weight rests on the ground and the release device is lowered onto it so that the cylinder 5 encloses the pillar 25. The rounded upper end 28 of the pillar 25 and the cone-shaped lower end 6 of the cylinder 5 cooperate to locate the release device on the pillar 25.

The cylinder 5 slides over the pillar 25 until the lower end 6 rests on the ring 27. During this operation the suspension arms 8 are in the second operative position, shown in chain dotted lines in Figure 1, with the rollers 10 outside the cylinder 5. The inlet valve 23 and ball valve 19 are both closed.

When the lower end of the cylinder 6 comes to rest on the ring 27 the inlet valve is opened and hydraulic fluid is pumped from the reservoir 20 into the barrels 14. The fluid pressure moves the pistons 13 outwards, thus causing the suspension arms 8 to pivot about pivot pins 9. Consequently the lower ends of the suspension arms pass through the apertures 7 in the wall of the cylinder 6 and the rollers 10 enter the waist 26 of the pillar 25. In this condition, the suspension arms are in the first operative position. The inlet valve 23 is then closed and the compacting weight can be raised.

When the compacting weight is to be released the ball valve 19 is opened, so that hydraulic fluid can flow from the barrels 14 via the orifice 18 into the reservoir 20. The pistons 13 can therefore move inwards in the barrels 14, permitting suspension arms 8 to pivot about pins 9 from the first operative position to the second operative position.

The mass of the compacting weight and the shape of the pillar are such that there is a component of force urging the lower ends oi the suspension arms outwards to release the compacting weight. The rate at which the suspension arms move from the first operative position to the second operative position depends upon the mass of the compacting weight, the shape of the pillar, the dimensions of the arms, the area of the pistons 13 and the area of the orifice 18. The rate at which the lower ends of the suspension arms move outwards of course controls the rate of gain of acceleration of the compacting weight as it moves downwardly prior to its separation from the release device. Ideally the acceleration of the compacting weight increases linearly from zero to natural gravitational acceleration over the vertical height of the pillar 25 above the waist 26.The rollers 10 hug the pillar as the compacting weight descends, forcing the pistons 13 in towards the centre of the hydraulic chamber as hydraulic fluid escapes through orifice 18 to resevoir 20. Compacting weight 24 thus escapes and falls free of the crane rope and the recoil of the crane is also reduced by the controlled release of the weight.

The device preferably incorporates a fail safe mechanism. In one form this comprises a four arm spider, one arm of which locates with each suspension arm to prevent the suspension arm from pivoting to release the compacting weight. When the compacting weight is to be released, the spider is rotated about a vertical axis through an angle which is sufficient to allow the suspension arms to pass clear of the arms of the spider when pivoting to release the compacting weight.

Referring to Figures 5 and 6 there is shown a release device which is broadly similar to the device shown in Figures 1 to 4.

Parts which are the same as in Figures I to 4 are given the same reference numbers. In this embodiment the suspension arms 8 differ from those in Figures 1 to 4 in that they are each pivotally connected to one end of a horizontal arm 39 whose other end has a roller 10 in contact with pillar 25. An additional arm 8' is connected between bracket 4 and a point intermediate the ends of horizontal arm 39. The release device may have four suspension arms spaced at 900 from each other or may have three suspension arms at 1200 from each other.

The release device operates in the same manner as the device described with reference to Figures 1 to 4.

Figure 7 shows a release device of the third type in engagement with a compacting weight 24 having a pillar 25 which is hollow and open at the top. Inside the pillar are two or more suspension arms 8 which are pivotally mounted on a plate 29 suspended from a crane hook 30. A barrel 14 contains two pistons 13, each of which is connected to the lower end of a respective suspension arm 8 by a link 31. An orifice 18 is present in the upper surface of the barrel 14. Other parts of the hydraulic system are generally similar to the system described with reference to Figures 1 to 4. It will be appreciated that when a valve is opened to permit hydraulic fluid to flow out of barrel 14 via orifice 18, pistons 13 will move inwards under the influence of the mass of the compacting weight transmitted via links 31.Rollers 10 will run over the inner surface of the pillar 25 as the compacting weight undergoes controlled downward acceleration.

Figure 8 shows another release device of the third type, this device having three suspension arms 8, two of which appear in the drawing. The upper ends of the suspension arms 8 are again pivotally attached to a plate 29 by means of which the release device can be suspended. Also attached to the plate 29 is one end of a rod 32 connected to a piston 13 in a vertically oriented barrel 14. Pivotally attached to the lower ends of each suspension arm 8 and to the lower end of the barrel are arms 33. In a wall of the barrel 14 is an orifice 18: the remainder of the hydraulic system is similar to that of other embodiments and is not illustrated. It will be appreciated that when the release device raises the compacting weight the piston 13 is at the bottom of its stroke as shown and the barrel 14 above the piston is filled with hydraulic fluid.Since the piston in the barrel cannot move, the rollers 10 at the ends of the suspension arms are prevented from moving horizontally inwards, so that the compacting weight can be raised. When hydraulic fluid is permitted to flow out of barrel 14 via orifice 18 the rollers 10 can move horizontally inwards and run over the inside surface of pillar 25 to control gradually the downward acceleration of the compacting weight 24.

Figure 9 shows a further embodiment of the first type, for use with a closed ended pillar 25. The device has four suspension arms 8 each mounted on a pivot pin 9 in a bracket 4. The upper end of each arm is fixed to a plate 34 to which are attached link members 35. Between each pair of mutually opposed plates is a variable length horizontal member 36 including a barrel 14 and piston 13. When hydraulic fluid is released from the barrels, the plates 34 can move inwards permitting the suspension arms to pivot so that their lower ends move outwards to release the compacting weight.

As the rate of flow of fluid from the barrels is limited by the orifice through which the fluid flows, downward acceleration of the compacting weight is controlled and gradual.

Figure 10 shows in simplified diagrammatic form part of yet another release device in accordance with the invention, for use with a closed ended pillar 25. The upper ends of the suspension arms 8 are in contact, via rollers 37, with a cone 38 which is connected by rod 39 to piston 13 in barrel 14. An orifice 18 is provided in the upper end surface of the barrel 14. When fluid can flow out of orifice 18 the piston 13 will be urged upwards by the force exerted by the rollers 37 acting on the cone 38 as the suspension arms 8 pivot about pivot pins 9 to permit controlled release of the compacting weight.

It is possible to derive an equation in terms y=f(x) to describe the curve of the pillar 25 over which the rollers 10 run to give a desired rate of increase of acceleration of the compacting weight with respect to time.

In the general case, and if the horizontal thrust of the pistons due to the reaction of the suspension arms 8 to the mass of the weight 24 is independent of the velocity of horizontal movement of the pistons, the equation

can be derived, where TH is the horizontal thrust provided by the pistons, Aav is the average acceleration over time t, t is the time, M is the mass of the compacting weight and g is the acceleration due to gravity.

If the rate of increase of acceleration with respect to time is linear, the distance travelled in the vertical direction by the compacting weight can be expressed by the equation

Equations (1) and (2) can be rewritten in terms of x and y and this equation describes the curve which the surface of pillar 25 should follow.

If the rate of release of the compacting weight is controlled by the flow of hydraulic fluid through an orifice then TH will not be independent of the velocity of the horizontal movement of the pistons. In this case it is necessary to use the Bernoulli equation and the following equation can be derived

where Vx is the horizontal velocity of the pistons, p is the density of the hydraulic fluid, A1 is the cross-sectional area of the pistons and A2 is the area of the orifice.

Equations (1), (2) and (3) can be rewritten in terms of x and y and the equation so obtained describes the curve which the surface of pillar 25 should follow.

Referring next to Figures 11 to 13, the release device of the second type is suspended from a crane hook 1 by means of a shackle 2 attached to an end fitting 3 screwed on to a rod 4. The rod 4 carries the mass of a compacting weight 5 and the release device by means of a nut 6 at the lower end of the rod 4.

Above the nut 6 there is a steel disc 7 to which cams 8 are attached. The cams 8 are preferably retractable, as shown in Figure I I, although they can be fixed, as shown in Figure 12.

The steel disc 7 supports a flange 11 and two concentric tubes 9 and 10 connected to the flange 11 to form the lower part of an acceleration control chamber 24. The space between the walls 9 and 10 is open-ended at the top. The inner wall of the outer tube 9 is provided with two bulges, an upper one 12 and a lower one 13. The top portion of the acceleration control chamber 24 comprises three concentric tubes 14, 15 and 16. The inner and outer tubes 14 and 15 are connected at their top ends by a membrane 17. The lower end of the intermediate tube 16 is joined by a membrane 18 to the outer tube 15. The lower end of the inner tube 14 is provided with a bulge 19 on its inner face.

In operation the bulge 19 co-operates with bulge 12 on the inner wall of tube 9, the two bulges being suitably profiled to cause streamlined flow of hydraulic fluid in the gap between the bulges when the lower and top portions of the acceleration control chamber move relative to each other.

The space between the outer tube 15 and the intermediate tube 16 serves as a reservoir 23 for hydraulic fluid from chamber 24. Hydraulic fluid is supplied to chamber 24 via a port 43, which contains a non-return valve, and a conduit 47. The reservoir 23 is provided with an air vent 20.

A shield 45 is provided to prevent hydraulic fluid entering the reservoir 23 from above from entering the air vent 20.

The device further comprises a shaped collar 21 which sits in a compartment 22 between the inside face of the outer tube 15 and an upward extension 46 of the shield 45.

The shaped collar can be raised in the compartment 22 by passing hydraulic fluid under pressure into compartment 22 via a port 44. When the shaped collar 21 is raised hydraulic fluid can flow from the acceleration control chamber 24 to the reservoir 23. When the shaped collar 21 is not raised by hydraulic pressure the collar is maintained in its lowermost position by means of a spring 25. When the shaped collar 21 is in this lowermost position flow of hydraulic fluid between acceleration control chamber 24 and reservoir 23 is prevented.

At the top of the release device is a disc 26 which carries three lugs 27 spaced 1200 apart from each other around the disc.

Suspended from each lug 27 by a pin 28 is a hinged suspension arm 29. The lower end of each arm 29 is turned inwards at 30 and is fitted with a roller 31. At about the midpoint of each arm is another roller 32. Each arm consists of two side plates joined by flanges and the rollers 31 and 32 are situated between the side plates carried by pins whch span the plates. In Figure 11, the suspension arms are depicted in the first operative position, while in Figure 12 they are in the second operative position.

Welded to the top of the compacting weight 5 is a pillar 33 with a domed top 34 and an annular ring 35 fitted below the top.

The ring 35 has an upper sloping face 36 and a horizontal lower face 37.

Fixed to the lower end of the outer tube 15, for example by welding, is a downwardly extending cylinder 39 including a locating cone 38. The cone 38 is provided with apertures 40 to admit the lower ends 30 of the suspension arms 29.

As shown in Figure 13, tension springs 41 are provided between the suspension arms 29 to urge the arms inwards towards the central axis of the device.

When the compacting weight is held suspended by the crane, the release device is in the configuration shown in Figure 11.

To release the weight 5, hydraulic fluid is passed under pressure into compartment 22.

A valve to control the supply of hydraulic fluid to compartment 22 is suitably located in the operator's cab of the crane. The hydraulic fluid raises the shaped collar 21 so that hydraulic fluid present in acceleration control chamber 24 can flow into reservoir 23 and then out of reservoir 23 via port 42.

The air vent 20 is provided to enable the reservoir to accommodate the large flow of hydraulic fluid which passes from chamber 24 to reservoir 23. When flow of fluid takes place from chamber 24 into reservoir 23, the volume of the acceleration control chamber contracts due to the mass of the weight and other parts urging the disc 26 and upper portion of the acceleration control chamber downwards. The suspension arms 29 move from the first operative position as shown in Figure 11 towards the second operative position as shown in Figure 12. As the disc 26 and suspension arms 29 move downwards the rollers 32 will contact the cams 8 and the cams 8 will urge the arms 29 outwards, so that the rollers 31 at the lower ends 30 of the arms will disengage from the lower face 37 of the ring 35 on the pillar 33 of the weight.

The weight is thus released and falls freely.

The release device assumes the configuration shown in Figure 12, the suspension arms being in the second operative position. The hydraulic fluid in chamber 22 can then be released via port 44, so that shaped collar 21 returns to its lowermost position under the urging of spring 25, while the suspension arms 29 return to the first operative position.

To raise the weight 5 from the ground, the release device is lowered over the pillar 33 of the weight. The domed top 34 of the pillar 33 and the locating cone 38 assist in locating the release device on the weight so that the rollers 31 at the lower ends 30 of the suspension arms 29 will engage with the horizontal lower face 37 of the ring 35.

Hydraulic fluid under pressure is then supplied via port 43 and conduit 47 to acceleration control chamber 24. The pressurised hydraulic fluid raises the upper portion of the acceleration control chamber 24 until the release device has assumed again the configuration shown in Figure 11.

As the upper portion of chamber 24 rises the rollers 32 pass cams 8 and arms 29 are then urged inwards under pressure from springs 41. The weight can then be raised and released again as described above.

It will be observed that when the release device is in the configuration shown in Figure 11 the space between bulge 19 on the outer wall of tube 14 and bulge 12 on the inner wall of tube 9 is small. Furthermore the bulges are shaped so that flow of any fluid through the space between them will be streamlined. When shaped collar 21 is raised to permit flow of fluid from acceleration control chamber 24 to reservoir 23, the initial rate of flow of hydraulic fluid between bulges 19 and 12 is small, owing to the small gap between the bulges. As the bulges pass each other the space between them increases gradually, so that the rate of flow of hydraulic fluid also increases gradually. When the bulges have completely passed each other the space available for flow of hydraulic fluid is constant and hence the rate of flow is constant.Thus by means of the bulges the rate of flow of fluid from chamber 24 to reservoir 23 and consequently the rate of gain of acceleration of the weight 5 and its speed over the stroke of the acceleration control chamber 24 can be controlled.

As the upper and lower portions of the acceleration control chamber 24 reach the end of their stroke, i.e. approach the configuration shown in Figure 12, bulge 19 approaches bulge 13 on the inside face of wall 9. As the bulges near each other the space between them reduces so that the rate of flow of hydraulic fluid through the space is reduced. This reduces the speed with which the upper portion approaches the lower portion of the acceleration control chamber 24 so that there is a cushioning effect after the weight 5 has been released.

A seal 48 is provided in the upper end of intermediate tube 16 of the upper portion of the acceleration control chamber 24. This seal cooperates with shaped collar 21 when the rlease device is in the configuration shown in Figure 11 to prevent flow of hydraulic fluid from chamber 24 to reservoir 23. Should the seal 48 leak, hydraulic fluid would flow from chamber 24 to 23, so that the upper portion of the chamber 24 could approach the lower portion thereof. As it did so the rollers 32 in arms 29 would approach cams 8 and, if the cams 8 were fixed as shown in Figure 2, the rollers would contact the cams so that the arms 29 would be urged outwards to release the weight. To avoid unintentional release of the weight in this manner it is preferred to use retractable cams, as shown in Figure 11. With this arrangement the cams 8 normally hang from pivots 49 so that they do not project.Hence if leakage does occur at seal 48 the rollers 32 will pass by without contacting cams 8, so that arms 29 are not urged outwards to release the weight. Behind each cam 8 is a hydraulically operated piston 50 which is actuated to cause cams 8 to project by the same means which supplies hydraulic fluid under pressure to chamber 22. Thus cams 8 will project and the weight will be released only when the said means is actuated.

It may be desired to manoeuvre the weight and release device when the necessary hydraulic system on a crane is not available, for example when first arriving at a site or when departing. To permit movement of the release device and the weight, holes can be provided in the cylinder 39 of the release device and in the pillar 33 of the weight, the holes being situated so that they are aligned when the release device is properly located over the weight. A steel bar can then be inserted through the aligned holes to provide a mechanical connection between the release device and the weight.

WHAT WE CLAIM IS: 1. Apparatus for use in the dynamic consolidation technique for deep ground compaction and consolidation of soil, which comprises (a) a massive weight one surface of which is provided with an extension in the form of a pillar; (b) a device adapted to be suspended from or forming part of a crane or hoist, said device comprising at least one member which, in a first operative position, co-operates with the pillar of, and supports, the weight and which, in a second operative position, disengages the weight; and (c) means for controlling the movement of the or each member from the first operative position to the second operative position so as to effect controlled downward acceleration of the weight prior to its separation from the crane or hoist when the or each member is at the second operative position, and to reduce the recoil of the crane or hoist resulting from the release of the weight.

2. Apparatus as claimed in claim 1, wherein the means for controlling the movement of the or each member from the first operative position to the second operative position is a hydraulic control system.

3. Apparatus as claimed in claim 1 or 2, wherein the means for controlling the movement of the or each meinber reacts in response to the mass of the weight.

4. Apparatus as claimed in claim 1, 2 or 3.

wherein the device comprises a plurality of said members each of which is in the form of a suspension arm.

5. Apparatus as claimed in claim 4, wherein each of the suspension arms pivots about a point intermediate its ends when moving from the first operative position to the second operative position.

6. Apparatus as claimed in claim 5, wherein the upper ends of the suspension arms are connected to pistons which are slidably mounted in respective arms of a chamber which is adapted to receive hydraulic fluid and which includes an orifice through which the hydraulic fluid can be forced under pressure, the arrangement being such that the pivotal movement of the suspension arms from the first operative position to the second operative position forces the piston against the hydraulic fluid in the chamber, thereby causing the fluid to flow through the orifice into a reservoir, the resistance of the hydraulic fluid to flow through the orifice serving to control the rate of movement of the suspension arms from the first operative position to the second operative position.

7. Apparatus as claimed in claim 4, wherein the suspension arms move downwards with the weight in moving from the first operative position to the second operative position.

8. Apparatus as claimed in claim 7, wherein the suspension arms are substantially vertically disposed when in the first operative position and, when they reach the second operative position, they are caused to pivot about their upper ends thereby causing their lower ends to disengage and release the weight.

9. Apparatus as claimed in claim 7 or 8, wherein the device comprises (a) a rod whose upper end is connected to, or is adapted to be suspended from, the crane or hoist, (b) a collar slidably mounted on said rod and from which a plurality of suspension arms are pivotally suspended; and (c) one or more cams fixed to said rod and located so as to cause radially outward movement of the lower portions of the suspension arms as they approach the second operative position.

10. Apparatus as claimed in claim 9, wherein a plurality of annular cylindrical walls are located coaxially about said rod and are shaped and located so as to cooperate with one another to provide a restrictive channel through which hydraulic fluid may be forced in response to the mass of the weight when the collar and the suspension arms move downwardly from the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. approach cams 8 and, if the cams 8 were fixed as shown in Figure 2, the rollers would contact the cams so that the arms 29 would be urged outwards to release the weight. To avoid unintentional release of the weight in this manner it is preferred to use retractable cams, as shown in Figure 11. With this arrangement the cams 8 normally hang from pivots 49 so that they do not project. Hence if leakage does occur at seal 48 the rollers 32 will pass by without contacting cams 8, so that arms 29 are not urged outwards to release the weight. Behind each cam 8 is a hydraulically operated piston 50 which is actuated to cause cams 8 to project by the same means which supplies hydraulic fluid under pressure to chamber 22.Thus cams 8 will project and the weight will be released only when the said means is actuated. It may be desired to manoeuvre the weight and release device when the necessary hydraulic system on a crane is not available, for example when first arriving at a site or when departing. To permit movement of the release device and the weight, holes can be provided in the cylinder 39 of the release device and in the pillar 33 of the weight, the holes being situated so that they are aligned when the release device is properly located over the weight. A steel bar can then be inserted through the aligned holes to provide a mechanical connection between the release device and the weight. WHAT WE CLAIM IS:

1. Apparatus for use in the dynamic consolidation technique for deep ground compaction and consolidation of soil, which comprises (a) a massive weight one surface of which is provided with an extension in the form of a pillar; (b) a device adapted to be suspended from or forming part of a crane or hoist, said device comprising at least one member which, in a first operative position, co-operates with the pillar of, and supports, the weight and which, in a second operative position, disengages the weight; and (c) means for controlling the movement of the or each member from the first operative position to the second operative position so as to effect controlled downward acceleration of the weight prior to its separation from the crane or hoist when the or each member is at the second operative position, and to reduce the recoil of the crane or hoist resulting from the release of the weight.

4. Apparatus as claimed in claim 1, 2 or 3.

first operative position of the suspension arms towards the second operative position.

11. Apparatus as claimed in claim 10, wherein said restrictive channel provides progressively less resistance to the passage of hydraulic fluid as the suspension arms move towards the second operative position.

12. Apparatus as claimed in any preceding claim, the device of which further comprises at its lower end a cylinder the lower end of which is provided with a conical hood.

13. Apparatus for use in the dynamic consolidation technique, substantially as hereinbefore described with reference to, and as illustrated in, Figures 1 to 4 of the accompanying drawings.

14. Apparatus for use in the dynamic consolidation technique, substantially as hereinbefore described with reference to, and as illustrated in, Figures 5 and 6 of the accompanying drawings.

15. Apparatus for use in the dynamic consolidation technique, substantially as hereinbefore described with reference to, and as illustrated in, Figure 7 or 8 of the accompanying drawings.

16. Apparatus for use in the dynamic consolidation technique, substantially as hereinbefore described with reference to, and as illustrated in, Figure 9 or 10 of the accompanying drawings.

17. Apparatus for use in the dynamic consolidation technique, substantially as hereinbefore described with reference to, and as illustrated in, Figures 11 to 13 of the accompanying drawings.

18. A crane or hoist provided with an apparatus as claimed in any preceding claim.