GB1572350A - Hydraulic pile drivers - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO HYDRAULIC PILE DRIVERS (71) We, BSP INTERNATIONAL FOUN DATIONS LIMITED, a British Company of Claydon, Ipswich, Suffolk, IP6 OJD do here by 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 hydraulic pile drivers in which a weight or tup is operated by a hydraulic pressure mechanism.

According to the invention, there is pro vided a hydraulic pile driver comprising a hy draulic cylinder for raising a tup or weight, the hydraulic cylinder having a plurality of apertures in its peripheral wall communicating with the interior thereof, a fluid supply line for passing a fluid under pressure to the interior of the cylinder, and a control sleeve for periodically connecting the cylinder interior to the fluid supply line and to a fluid-discharge line, said control sleeve having apertures therein and being mounted around part of the peripheral wall of the cylinder for movement from a position in which fluid under pressure is supplied to the cylinder interior to a position in which fluid under pressure is discharged from the cylinder interior, fluid being supplied to or discharged from the cylinder interior through the apertures in the sleeve and in the peripheral wall which are in registry with each other in each position of the sleeve, and further comprising a closed chamber provided around the cylinder, the volume of said chamber being considerably in excess of that of the interior of the cylinder, said fluid-discharge line being connected to said closed chamber, the total area of the apertures in the sleeve and in the peripheral wall of the cylinder which are in registry with each other when fluid under pressure is discharged from the cylinder interior to said closed chamber being at least equal to the cross-sectional area of the cylinder interior.

More particularly, said control sleeve can be mounted within the cylinder to extend around part of the inner surface of the cylinder peripheral wall.

It is desirable also to prevent throttling of the inflow of hydraulic fluid from the pressure source to the cylinder or ram, and in a preferred feature of the invention the fluid supply line is adjacent its connection to the cylinder connected to a fluid accumulator for storing the fluid under pressure during the periods in which the fluid supply line is disconnected from the cylinder interior.

The invention will be more particularly described by way of example with reference to the accompanying schematic drawings, wherein: Figure 1 is a side view of a pile driver according to the invention, Figure 2 is a side view of the hydraulic lifting cylinder of the pile driver in Fig. 1, with its fluid accumulators, Figure 2a is a detail view, in section, of the lower part of Fig. 2, Figure 3 is a detail cross-sectional view on the plane III-III in Fig. 2a, Figure 4 is a diagram of the hydraulic circuit for the cylinder, and Figure 5 illustrates an electrical control system that can be employed in the pile driver of the preceding figures.

The pile driver illustrated comprises a main frame 2 having at its lower end support pads 4, preferably incorporating springs, for mounting the driver on a pile cap (not shown). A weight or tup 6 slidably guided by the frame is reciprocated by a hydraulic ram or cylinder 8 mounted in the frame. The ram or cylinder comprises an outer casing 10 bolted to the upper end 12 of the frame by its top flange 14 and laterally located by intermediate plate 16 of the frame.

A cylindrical wall portion 18 is disposed in the casing contiguously with a further cylindrical wall portion provided in an end block 34 of the casing. A piston 20 in the cylinder has a depending piston rod 22 from which the weight 6 is suspended, through a preferably resilient coupling 24.

The region enclosed below the piston forms a first, lower chamber 26 that is normally sealed from a second chamber 28 comprising the volume within the cylindrical wall portion 18 above the piston. This upper chamber is in permanent and free communication with an outer annular closed chamber 28a between the wall portion 18 and the outer casing 10. As is apparent from the drawings, the volume of the chamber 28a is considerably in excess of that of the interior of the cylinder. At its lower end the cylinder or ram has a coaxial control valve for interconnecting the chambers 26, 28 in the form of a control sleeve 30 axially displaceable along bore 32 of the cylindrical wall portion of the end block 34 of the casing, in which a series of axial bores 36 provide free communication between the outer chamber 28a and an annular space or aperture 38 opening onto the valve sleeve 30.

In the lowermost position of the sleeve 30 shown in Fig. 2, an upper ring of apertures or ports 40 in the sleeve are registered with the aperture or chamber 38 to open the path thereto from the lowermost region 39 of the cylinder interior so that the upper and lower cylinder chambers 26, 28 are in communication through the sleeve and the annular chamber 28a. As will be apparent, in order to minimise any throttling effect the total area of the apertures in the sleeve and in the peripheral wall of the cylinder which are in registry with each other when fluid under pressure is discharged from the cylinder interior to the closed chamber 28a is at least equal to the cross-sectional area of the cylinder interior.

The sleeve is displaceable from said lowermost position to an upper end position, in which it abuts against shoulder 42 at the end of the bore 32, when a lower series of ports 44 in the sleeve are registered with a series of ports 46 in a sealing ring 48 to communicate with an inlet space 50 connected to pressure fluid supply line 66 (Fig. 4) through a coupling union (not shown). In this position the chambers 26, 28 are isolated from each other and hydraulic fluid is admitted to the chamber 26 to raise the piston and the weight with it. Should the position rise above ports 18a in the cylinder wall portion 18, connection between the two chambers 26, 28 is re-established through the annular chamber 28a independently of the position of the sleeve valve 30.

Between the bore 32 of the end block housing 34 and the control sleeve 30 there is formed a pilot pressure chamber 52 having alternative supply lines 54, 56 respectively, to upper and lower ends of the chamber 52 that are sealed from each other by land 58 of the sleeve. A pilot valve 60 (Fig. 4) communicating with the ports is externally controlled manually and/or by automatically operated electrical switching means, which may comprise trip switches operated with the movement of the weight and/ or impact switches operable by the impact of the weight on the pile cap, said switches acting on the valve 60 through an electronic control circuit.

As one possible arrangement, the pilot valve 60 is a solenoid-operated valve with a return spring biasing it to the illustrated position, in which pressure fluid from an auxiliary pump 62 is directed through line 54 to urge the sleeve 30 to the lower position shown in Fig. 2. Since the upper and lower cylinder chambers are then in communication, the weight is able to fall to impact the pile cap, the piston moving to its bottom position in the cylinder. To change the pilot valve over, the valve solenoid is actuated by an impact switch on the pile driver frame that is triggered by the impact of the falling weight. Pressure fluid is then admitted through the line 56 to switch the position of the control sleeve and the main pressure fluid supply from a pump 64 flows through the line 66 to the lower cylinder chamber.

The solenoid is held in by an adjustable delay timer that thereby controls the height to which the weight is raised and so determines the impact force. The flow from the pump 64 is augmented by a flow from a high-pressure accumulator 68 mounted on the driver frame that has received and stored the output of the pump 64 during the downstroke of the ram.

It is thus possible to direct a very large flow of fluid at pressure into the lower cylinder chamber through the large-bore conduit 68a and the large cross-section passages provided by the immediately adjacent control sleeve with a minimal throttling effect, even if the supply pump 64 is some distance from the cylinder or ram.

Also during the.upstroke, exhaust fluid will be expelled from the upper cylinder chamber through the closed chamber 28a to exhaust line 72 leading to reservoir 74. To limit the pressure rise in the line 72 that would otherwise increase resistance to the lifting of the weight, a low- pressure accumulator 76 is also mounted on the pile driver frame and is connected to the annular chamber 28a through large-bore conduil 76a, thereby being able to absorb the surge of exhaust fluid. In addition, the accumulator 76 functions during the downstroke to provide a ready return flow of fluid into the cylinder or ram when the volume of the internal fluid spaces is expanding because of the extension of the piston rod, so avoiding vacuum conditions that might lead to cavitation in the fluid and also cause some retardation of the falling tup or weight. The provision of the accumulators thus allows the hydraulic fluid supply system to be located at any convenient position and some distance from the pile driver itself.

At start-up it can be arranged that when power is made to the circuit of the impact switch and solenoid, an actuating pulse is received by the solenoid to lift the tup or weight from rest. Additionally or alternatively there can be a manual override.

Figure 4 also shows a valve 80 in the main hydraulic circuit in a line bypassing the hydraulic cylinder. This is a combined relief and unloader valve and for the latter purpose it may comprise an actuating solenoid with spring return. The unloading function will be under the control of the operator, and the valve may be arranged so that the hydraulic cylinder is bypassed either when the solenoid is actuated, or alternatively it may be preferred that the actuated solenoid closes the valve (but does not interfere with its overpressure relief function) and when the solenoid is de-energised the bias spring opens the valve.

Figure 5 shows schematically an electrical control arrangement for the pile driver of Figs.

1 to 3 using a number of different limit switch combinations, The electrical circuits control the pilot valve 60 and the relief/unloader valve 80 of the solenoid-operated spring-return from described with reference to Fig. 4. In Fig. 5, enclosure 102 represents the driver frame and indicating the limit switches provided there for controlling the operation of the pile driver.

These include a ferrite rod inductive switch 110 arranged as an impact detector, respective tripsperated switches 112, 114 for upper and lower limits of the tup movement and of the same ferrite rod inductive type as the switch 110, and electromechanical upper and lower limit switches 116, 118 in the form of bistables, set at positions on the driver frame corresponding to those of the switches 112, 114. A delay timer 120 operates as an adjustable upper limit switch, but this can be mounted remote from the driver frame, for example in a control console represented by the enclosure 104.

Figure 5 also indicates at 106 a control pen- dant that is connected by a flexible cable (not shown) to the console to allow the operator freedom of movement while the driver is at work so that he can more readily control the pile-driving process. On the control pendant are an on-off dump switch 122, a control potentiometer 124 for the timer 120, a three-position selector switch 126 with a "manual" contact 126.7 and "automatic operation" contact 1 26b and an "off" contact 126c, a changeover switch 128 operated when the switch 126 is in its "automatic operation" position to select an adjustable stroke (contact 128a) or a maximum stroke (contact 128b) for the reciprocation of the cylinder or ram, and a manual operation push-button switch 130.

In its "on" position the dump switch connects the power supply to the solenoid of the relief/unloader valve 80 so that the tup or weight cannot be raised. (It is alternatively possible, as already mentioned, to have an arrangement in which the valve 80 is opened by its spring bias with the solenoid de-energised). In either case, the switch 122 is arranged so that when the unloader valve is closed, the selector switch 126 is connected to the power supply and is thus brought into operation. If it is in the "manual' position 126a, the pile driver is operated by means of the push button switch 130 that is spring-biased to a normally open state.If the switch 126 is in its "automatic operation" position 126b, the operator can select, by means of the switch 128, operation of the cylinder at its maximum stroke (contact 128b made) or at a variable stroke (contact 1 28a made), the length of stroke in the latter case being determined by the setting of the potentiometer 124 which can be adjusted continuously during the operation of the pile driver.

Selecting the automatic operation mode with adjustable stroke renders the inductive switches 110, 112 and 114 active. With the tup or weight initially at its bottom position, the bottom limit switch 114 will be in a state that energises the operating solenoid of the pilot control valve 60 and pressure fluid is admitted to the underside of the piston to raise the tup or weight. The delay timer 120 may, dependent upon the setting of the potentiometer 124, determine the upper limit of the tup movement but a maximum limit is in any event provided by the upper limit switch 112 on the driver frame. The ports 1 8a provide a further override that switches the direction of the resultant hydraulic force on the piston if the piston rises past them.

When the tup has risen sufficiently to operate the trip of the switch 112, the resulting output through amplifier 11 2a causes the timer to discharge and so to de-energise the pilot valve solenoid. Thereupon the pilot valve is switched to lower the control sleeve 30, cutting the cylinder off from the pressure supply and bringing the chambers 26, 28 into communication.

The tup or weight is allowed to fall, therefore, fluid flowing into the upper chamber partly by direct transfer from the lower chamber and partly from the low-pressure accumulator on the driver frame.

As the tup approaches the anvil or other impact surface, it operates the trip of the bottom limit switch 114, and if switch 134 is closed this will re-energize the pilot valve solenoid through amplifier 114a. The pressure supply is then again switched to the underside of the piston and the delay timer 120 is set in operation. Alternatively, switch 136 in circuit with the impact detector switch 110 may be closed instead of the switch 134, so that the switching of the valve solenoid and the actuation of the timer via amplifier 1 10a begins at the instant of impact of the tup or weight.

Both switches can be closed so that one acts as a back-up for the other but there can alternatively be a changeover switch allowing one or other of the inductive switches 110, 114 to be put in circuit, in which case a single amplifier can replace respective amplifiers through which the bottom limit inductive switch signals operate.

The dial-form potentiometer 124 on the control pendant can be adjusted while the pile driver is operating and if it is at a setting that causes the timer to time out before the upper limit switch trip is reached the stroke of the driver will be correspondingly reduced.

While the adjustable control allows the driver to be operated at maximum stroke, there can be advantages in providing a separate circuit using more robust electromechanical switches for operation in this mode, and by moving the changeover switch to its alternative position 128b the trip-operated upper and lower limit switches 116 and 118 are rendered active.

With the cylinder at the bottom of its stroke, both the switches 116, 118 will be closed and the pilot valve solenoid will be energised to allow the tup or weight to be raised, the circuit to that solenoid including a relay 140 that will also be energised to close its switch 142. In the initial part of the rising movement the lower limit switch 118 is opened as its trip is displaced by the weight, but with no effect because its circuit is bypassed by the closed contact 142.

When the upper limit switch 116 is also opened by operation of its trip the circuit to both the pilot valve solenoid and the relay 140 is broken and the sleeve 30 is switched to allow the weight to fall. The upper limit switch 116 is closed again almost immediately as the descent begins but since the switch 140 has already opened, this now has no effect on the operating solenoid circuit. Only when the lower limit switch 118 is tripped to close again and bypass the switch 140 is the circuit made via both switches 116, 118 to reenergise the pilot valve solenoid and the relay 140, and the cycle recommences.

Using the manual push-button control, the stroke of the tup or weight is determined simply by the length of time for which the pushbutton switch 130 is depressed. The ports 18a limit the point at which the fluid pressure will act to drive the weight upwards, but it may be also desired for reasons of safety to provide also an upper limit switch. The circuit of the push button switch 130 can for example be connected to the circuit of the limit switches 116, 118, as by connecting the switch 130 to the pilot valve solenoid via the control 128b, so that the opening of the limit switch 116 deenergises the solenoid.

The drawings accompanying this specification also appear in our application No. 21195/76 (Serial No. 1 572 349) where there is claimed a drop hammer having a hydraulic ram for reciprocating a hammer weight, said ram comprising an upwardly extending cylinder and piston assembly with respective upper and lower internal chambers of the cylinder at opposite sides of the piston and a piston rod extending downwardly from said piston through the lower chamber to connect it to the weight, means for admitting pressure fluid to the ram and for interconnecting said chambers comprising a control valve disposed at one end of the cylinder coaxially with the cylinder and piston assembly, said valve being actuatable by externally operable control means to control the flow of fluid through the ram to reciprocate the hammer weight, said control means being adjustable to vary the reciprocating stroke of the weight.

WHAT WE CLAIM IS: 1. A hydraulic pile driver comprising a hydraulic cylinder for raising a tup or weight, the hydraulic cylinder having a plurality of apertures in its peripheral wall communicating with the interior thereof, a fluid supply line for passing a fluid under pressure to the interior of the cylinder, and a control sleeve for periodically connecting the cylinder interior to the fluid-supply line and to a fluid-discharge line, said control sleeve having apertures therein and being mounted around part of the peripheral wall of the cylinder for movement from a position in which fluid under pressure is supplied to the cylinder interior to a position in which fluid under pressure is discharged from the cylinder interior, fluid being supplied to or discharged from the cylinder interior through the apertures in the sleeve and in the peripheral wall which are in registry with each other in each position of the sleeve, and further com- prising a closed chamber provided around the cylinder, the volume of said chamber being considerably in excess of that of the interior of the cylinder, said fluid-discharge line being connected to said closed chamber, the total area of the apertures in the sleeve and in the peripheral wall of the cylinder which are in registry with each other when fluid under pressure is discharged from the cylinder interior to said closed chamber being at least equal to the cross-sectional area of the cylinder interior.

2. A hydraulic pile driver according to claim 1 wherein said control sleeve is mounted within the cylinder to extend around part of the inner surface of the cylinder peripheral wall.

3. A hydraulic pile driver according to claim 1 or claim 2 wherein the fluid supply line is adjacent its connection to the cylinder connected to a fluid accumulator for storing the fluid under pressure during the periods in which the fluid supply line is disconnected from the cylinder interior.

4. A hydraulic pile driver according to claim 1 wherein the features et out in claim 1 are constructed, arranged, and adapted to operate substantially as describedherein with reference to the accompanying drawings.

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. driver is operating and if it is at a setting that causes the timer to time out before the upper limit switch trip is reached the stroke of the driver will be correspondingly reduced. While the adjustable control allows the driver to be operated at maximum stroke, there can be advantages in providing a separate circuit using more robust electromechanical switches for operation in this mode, and by moving the changeover switch to its alternative position 128b the trip-operated upper and lower limit switches 116 and 118 are rendered active. With the cylinder at the bottom of its stroke, both the switches 116, 118 will be closed and the pilot valve solenoid will be energised to allow the tup or weight to be raised, the circuit to that solenoid including a relay 140 that will also be energised to close its switch 142. In the initial part of the rising movement the lower limit switch 118 is opened as its trip is displaced by the weight, but with no effect because its circuit is bypassed by the closed contact 142. When the upper limit switch 116 is also opened by operation of its trip the circuit to both the pilot valve solenoid and the relay 140 is broken and the sleeve 30 is switched to allow the weight to fall. The upper limit switch 116 is closed again almost immediately as the descent begins but since the switch 140 has already opened, this now has no effect on the operating solenoid circuit. Only when the lower limit switch 118 is tripped to close again and bypass the switch 140 is the circuit made via both switches 116, 118 to reenergise the pilot valve solenoid and the relay 140, and the cycle recommences. Using the manual push-button control, the stroke of the tup or weight is determined simply by the length of time for which the pushbutton switch 130 is depressed. The ports 18a limit the point at which the fluid pressure will act to drive the weight upwards, but it may be also desired for reasons of safety to provide also an upper limit switch. The circuit of the push button switch 130 can for example be connected to the circuit of the limit switches 116, 118, as by connecting the switch 130 to the pilot valve solenoid via the control 128b, so that the opening of the limit switch 116 deenergises the solenoid. The drawings accompanying this specification also appear in our application No. 21195/76 (Serial No. 1 572 349) where there is claimed a drop hammer having a hydraulic ram for reciprocating a hammer weight, said ram comprising an upwardly extending cylinder and piston assembly with respective upper and lower internal chambers of the cylinder at opposite sides of the piston and a piston rod extending downwardly from said piston through the lower chamber to connect it to the weight, means for admitting pressure fluid to the ram and for interconnecting said chambers comprising a control valve disposed at one end of the cylinder coaxially with the cylinder and piston assembly, said valve being actuatable by externally operable control means to control the flow of fluid through the ram to reciprocate the hammer weight, said control means being adjustable to vary the reciprocating stroke of the weight. WHAT WE CLAIM IS:

1. A hydraulic pile driver comprising a hydraulic cylinder for raising a tup or weight, the hydraulic cylinder having a plurality of apertures in its peripheral wall communicating with the interior thereof, a fluid supply line for passing a fluid under pressure to the interior of the cylinder, and a control sleeve for periodically connecting the cylinder interior to the fluid-supply line and to a fluid-discharge line, said control sleeve having apertures therein and being mounted around part of the peripheral wall of the cylinder for movement from a position in which fluid under pressure is supplied to the cylinder interior to a position in which fluid under pressure is discharged from the cylinder interior, fluid being supplied to or discharged from the cylinder interior through the apertures in the sleeve and in the peripheral wall which are in registry with each other in each position of the sleeve, and further com- prising a closed chamber provided around the cylinder, the volume of said chamber being considerably in excess of that of the interior of the cylinder, said fluid-discharge line being connected to said closed chamber, the total area of the apertures in the sleeve and in the peripheral wall of the cylinder which are in registry with each other when fluid under pressure is discharged from the cylinder interior to said closed chamber being at least equal to the cross-sectional area of the cylinder interior.

2. A hydraulic pile driver according to claim 1 wherein said control sleeve is mounted within the cylinder to extend around part of the inner surface of the cylinder peripheral wall.

3. A hydraulic pile driver according to claim 1 or claim 2 wherein the fluid supply line is adjacent its connection to the cylinder connected to a fluid accumulator for storing the fluid under pressure during the periods in which the fluid supply line is disconnected from the cylinder interior.

4. A hydraulic pile driver according to claim 1 wherein the features et out in claim 1 are constructed, arranged, and adapted to operate substantially as describedherein with reference to the accompanying drawings.