EP0951949A1

EP0951949A1 - Method and device for vibratory driving of an object

Info

Publication number: EP0951949A1
Application number: EP99201235A
Authority: EP
Inventors: Johan Bernard Van Randen
Original assignee: International Construction Equipment BV
Current assignee: International Construction Equipment BV
Priority date: 1998-04-22
Filing date: 1999-04-22
Publication date: 1999-10-27
Also published as: NL1008965C2

Abstract

Method for vibratory driving of an object, in particular a pile or sheet piling for introducing into or removing from the ground. The object is fixed to a vibrating device. In the device a first pair of eccentric rotatable weights (5,6) is driven by a first hydraulic motor (3) and a second pair of eccentric rotatable weights (7,8) is driven by a second hydraulic motor (4). A difference in phase between the alternating forces generated by the first pair (5,6) and the second pair (7,8) is changed by temporarily changing the ratio of the liquid flow to each of the motors (3,4).

Description

The invention relates to a method for vibratory driving of an object, in particular a pile, sheet piling or other object for introducing into or removing from the ground, wherein the object is fixed to a vibrating device, in which device a first pair of eccentric rotatable weights is driven by a first hydraulic motor and a second pair of eccentric rotatable weights is driven by a second hydraulic motor, wherein the weights of each pair are rotated at equal angular speed in mutually opposed directions and thereby generate an alternating force in substantially one direction, wherein the difference in phase between the alternating forces generated by the first pair and the second pair is changed in order to control the intensity of the resultant vibration, wherein both motors are displacement motors, the rotation speed of which is proportional to the liquid flow through the motor.
Liquid flow is here understood to mean the amount of liquid which passes through per time unit, which is also referred to as the concept of flow rate or the concept of flow volume.
In such a device, which is known from EP-A-0524056, the weights of each pair are arranged on two mutually meshing toothed wheels. Each pair of weights exerts on the device an alternating force acting in one direction and, because the alternating forces are generated by each of the pair of weights in the same direction, the alternating forces cause a vibration of the device in this same direction. When the frequency of the alternating forces of each of the pairs is the same, a continuous vibration will be caused, the intensity of which depends on the phase difference of the two alternating forces. This phase difference can be varied in order to control the intensity.
In a vibrating device as known from EP-A-0524056 the phase difference of the alternating forces exerted by the two pairs of rotating weights, referred to hereinbelow as the phase difference between the pairs of weights, is controlled by means of a phase shifter which can adjust the mutual rotation position of two coaxial toothed wheels. Because each of the two toothed wheels engages with a pair of weights, the phase difference of these pairs of weights can be adjusted.
Such a phase shifter is a complicated apparatus, the whole of which is in rotation and which is moreover subject to vibrations generated by the vibrating device. Such a phase shifter is therefore a component of the vibrating device which is susceptible to malfunction.
The invention has for its object to provide a method and a device for setting an object into vibration, wherein the intensity of the vibration can be controlled in efficient and reliable manner.
Present for this purpose are control means for changing the phase difference between the pairs of weights which can temporarily change the ratio of the liquid flow to each of the motors. When each of the pairs of weights is driven by means of a hydraulic motor of the type wherein the rotation speed depends on the liquid flow, the so-called displacement type, the rotation speed of each of the pairs of weights can individually be precisely controlled by varying the liquid flow to the relevant motor. This variation of the liquid flow can take place outside the vibrating device, wherein the desired liquid flow can be guided to each of the hydraulic motors by means of a flexible conduit.
Both hydraulic motors can herein be driven by one hydraulic pump, wherein a difference in the liquid flows to each of the motors is brought about by limiting the liquid flow to at least one of the hydraulic motors by means of an adjustable throttle valve.
In another preferred embodiment the liquid flow to each of the hydraulic motors is individually controlled. This can take place by dividing the liquid supply into two liquid flows by means of a hydraulic distributor, this in a determined ratio. The phase difference between the pairs of weights can herein be controlled by altering the ratio.
In another embodiment the liquid flow to each of the two hydraulic motors is effected by a separate liquid pump for each motor. The two liquid pumps can herein be separately adjusted in order to cause each to bring about a determined liquid flow. Herein the rotation speed of each pump can for instance be controlled.
In another embodiment the ratio of the liquid flows to the first and the second hydraulic motor is changed by an additional hydraulic pump which effects a liquid flow between the feed conduits to the first and second hydraulic motor. Such an additional hydraulic motor can carry liquid from the one feed conduit to the other feed conduit, whereby a phase shift of the one pair of weights relative to the other pair of weights can be brought about.
In a preferred embodiment the first pair of weights and the second pair of weights can be mechanically connected to and disconnected from each other such that the pairs of weights are fixed in different rotation positions relative to each other. An adjusted phase difference between the pairs of weights can hereby be retained, wherein both hydraulic motors can be utilized at full power. Such a mechanical clutch (coupling) can be a plate clutch wherein the plates are pressed against each other under spring pressure and the clutch can be released by moving the clutch plates apart counter to the spring pressure. Such a clutch is known.
A clutch is preferably applied wherein the two pairs of weights can be mutually coupled in a number of positions relative to each other, so that the intensity of the vibration of the device can be adjusted at a number of predetermined levels.
It is also possible herein to apply a clutch which allows a determined relative rotation each time the clutch is energized.
The intensity of the vibration of the device can be controlled by monitoring the vibrating device and/or the object set into vibration and, subject to this monitoring, adjusting the liquid flows to the two hydraulic motors. The vibrating device can herein be started in the situation where the alternating forces counteract each other so that there is no resultant vibration. A phase difference is then effected between the pairs of weights, this to a degree where the desired vibration effect is achieved.
In a preferred embodiment the liquid flows to hydraulic motors are controlled on the basis of the detection by detection means of the rotation position of at least one of the pairs of weights. It is herein possible for instance to detect at which moments in time each of the pairs of weights passes a determined rotation position, wherein the maximum intensity of the vibration is present when the same rotation position for both pairs of weights is detected simultaneously, while no resultant vibration is present when the moments in time at which the one pair of weights and the other pair of weights pass the same rotation position have equal intervals.
Further features which can be applied both individually and in combination will be described with reference to several embodiments and are stated in the claims.
For elucidation of the invention three embodiments of a vibrating device will be described with reference to the drawing.
Figures 1, 2 and 3 are schematic views of the three embodiments, wherein corresponding components are designated with the same reference numerals. For the sake of clarity parts which are of lesser importance for explanation of the invention are omitted.
Figure 1 shows a hydraulic pump 1 which pumps hydraulic fluid from a reservoir 2 to both a first hydraulic motor 3 and a second hydraulic motor 4. First hydraulic motor 3 is connected drivably to a pair of eccentric rotatable weights 5,6 and second hydraulic motor 4 is connected drivably to the pair of eccentric rotatable weights 7,8. Weights 5,6;7,8 of each pair of weights are mounted on toothed wheels, which toothed wheels are mutually meshed such that the weights rotate in the direction as indicated by arrows 9.
It will be apparent that when weights 5,6,7,8 are rotatably mounted in a device and rotate at equal angular speed in the direction indicated by arrows 9, the device in question is set into rotation. Figure 1 shows the situation in which the pairs of weights have the same phase. In figure 3 the pairs of weights 5,6;7,8 have an opposite phase and in figure 2 the pairs of weights have another mutual difference in phase. It will be apparent that in the situation shown in figure 1 there occurs a maximum vibration, in the situation shown in figure 3 there occurs no vibration and in the situation shown in figure 2 there occurs a vibration less than the maximum. By effecting a difference in phase between the two pairs of weights 5,6;7,8 a determined intensity of the vibration can therefore be adjusted as desired.
It is noted that in the figures the upper pair of weights 5,6 and the lower pair of weights 7,8 rotate in corresponding directions 9. It is however also possible that for instance both upper weights 5,6 each rotate in a direction opposed to directions indicated with arrows 9. The same effect is then achieved.
The difference in phase between the pairs of weights is adjusted by controlling the liquid flow to each of the motors 3,4. According to the embodiment shown in figure 1, this control takes place by means of two adjustable throttle valves 10,11. Throttle valve 10 can limit the liquid feed to motor 3 and throttle valve 11 can limit the liquid feed to motor 4. Throttle valves 10,11 are controlled by means of control unit 12, this on the basis of detection of the actual rotation position of the pairs of weights and the desired phase difference between the two pairs of weights. These information flows are indicated with dashed lines, wherein a detector 13 detects when weight 6 passes a determined rotation position and detector 14 detects when weight 8 passes a determined rotation position. Control unit 12 determines the phase difference of the pairs of weights on the basis of these detections and, subject to the desired phase difference which is made known to control unit 12 as information 15, control unit 12 drives one of the throttle valves 10,11 into a throttling position until the desired phase difference is obtained.
Throttle valve 10 can herein limit the liquid feed in conduit 16 to motor 3 and throttle valve 11 can limit the liquid feed via conduit 17 to motor 4. The liquid can flow back to reservoir 2 via conduit 18.
Figure 1 further shows schematically a mechanical clutch 19 which can couple the two pairs of weights 5,6;7,8 mechanically such that an adjusted phase difference remains constant. When this phase difference must be changed, clutch 19 can be disengaged for a short time, wherein a change in the phase difference can be effected by temporarily limiting a liquid flow with throttle valve 10 and/or throttle valve 11. when the desired phase difference is set, both throttle valves 10,11 can be placed in a non-throttling position, whereby the two motors 3,4 can rotate at maximum power. Clutch 19 can be used either in combination with control unit 12 or not.
Figure 2 shows an embodiment wherein motor 3 is driven by pump 25 and wherein hydraulic motor 4 is driven by pump 26. The liquid flows through conduits 16 and 17 to motors 3 and 4 can be controlled by regulating the rotation speed of pump 25 respectively pump 26, at least when the pumps as well as the motors are of the so-called displacement type, wherein the rotation speed is proportional to the liquid flow passing through. At least one of the pumps 25,26 can also be embodied as pump which can pump an adjustable volume at a constant rotation speed. Both pumps 25,26 can then be driven at the same rotation speed. Another alternative is that at least one of the motors 3,4 is embodied as a motor with a rotation speed which can be adjusted at a constant flow volume.
Figure 3 shows an embodiment wherein two pumps 25,26 are likewise present and wherein a pump 27 is moreover present which is placed between feed conduit 16 of pump 3 and feed conduit 17 of pump 4. Pump 27 can pump liquid in two directions so that the ratio of the liquid flow sent to hydraulic motors 3,4 can be changed as required. Pump 27 can also be embodied such that it can only pump liquid in one direction, and in that case the phase difference between the pairs of weights 5,6;7,8 can be adjusted by causing one of the two motors 3,4 to run faster than the other motor 4,3 for a short time.
In the embodiment of figure 3 pumps 25 and 26 can also be replaced by a single pump, wherein a flow distributor downstream of this pump divides the pumped liquid into two equal liquid flows to conduit 16 and conduit 17.
In the embodiment according to figure 3 a control unit 12 is also present for driving pump 27 subject to the detections by detectors 13,14 and the desired phase difference 15 required.
In the embodiments of figures 2 and 3 use can additionally be made of the clutch 19 shown in figure 1.

Claims

Method for vibratory driving of an object, in particular a pile or sheet piling for introducing into or removing from the ground, wherein the object is fixed to a vibrating device, in which device a first pair of eccentric rotatable weights (5,6) is driven by a first hydraulic motor (3) and a second pair of eccentric rotatable weights (7,8) is driven by a second hydraulic motor (4), wherein the weights (5,6;7,8) of each pair are rotated at equal angular speed in mutually opposed directions and thereby generate an alternating force in substantially one direction, wherein the difference in phase between the alternating forces generated by the first pair (5,6) and the second pair (7,8) is changed in order to control the intensity of the resultant vibration, wherein both motors (3,4) are displacement motors, the rotation speed of which is proportional to the liquid flow through the motor (3,4), characterized in that the phase difference between the two pairs of weights (5,6;7,8) is changed by temporarily changing the ratio of the liquid flow to each of the motors (3,4).
Method as claimed in claim 1, characterized in that the liquid flow to at least one of the hydraulic motors (3,4) is limited by means of an adjustable throttle valve (10,11).
Method as claimed in either of the foregoing claims, characterized in that the liquid flow to each of the hydraulic motors (3,4) is individually controlled.
Method as claimed in claim 3, characterized in that the liquid flow to each of the hydraulic motors (3,4) is effected by a separate liquid pump (25,26) for each motor (3,4).
Method as claimed in any of the foregoing claims, characterized in that the ratio of the liquid flows to the first and the second hydraulic motor (3,4) is changed by an additional hydraulic pump (27) which effects a liquid flow between the feed conduits (16,17) to the first and second hydraulic motor (3,4).
Method as claimed in any of the foregoing claims, characterized in that during rotation the rotation position of at least one of the pairs of weights (5,6;7,8) is detected, on the basis of which detection the liquid flows to the hydraulic motors (3,4) are controlled.
Method as claimed in claim 6, characterized in that the moments in time at which the first pair of weights (5,6) and the second pair of weights (7,8) pass a determined rotation position are detected.
Vibrating device for vibratory driving of an object, in particular a pile or sheet piling for introducing into or removing from the ground, which device can be fixed to the object, in which device a first pair of eccentric rotatable weights (5,6) is drivable by a first hydraulic motor (3) and a second pair of eccentric rotatable weights (7,8) is drivable by a second hydraulic motor (4), wherein the two weights (5,6;7,8) of each pair are rotatable at equal angular speed in mutually opposed directions and can thereby generate an alternating force in substantially one direction, wherein control means (10,11,12) are present for adjusting the difference in phase between the alternating force generated by the first pair (5,6) and the second pair (7,8) in order to control the intensity of the resultant vibration, wherein both motors (3,4) are displacement motors, the rotation speed of which is proportional to the liquid flow through the motor, characterized in that the control means (10,11,12) can change the phase difference between the two pairs of weights (5,6;7,8) by temporarily changing the ratio of the liquid flow to each of the motors (3,4).
Device as claimed in any of the claims 8, characterized by a mechanical clutch (19), preferably a plate clutch, which can fix the rotation position of the first pair of weights (5,6) relative to the rotation position of the second pair of weights (7,8), whereby preferably the clutch (19) is embodied such that a determined number of rotation positions are possible relative to each other.
Device as claimed in any of the claims 8 or 9, characterized by detection means (13,14) for detecting during rotation the rotation position of at least one of the weights (6,8), and by control means (10,11,12) which on the basis of the detection can control the mutual difference in rotation position of the first weight (6) relative to the second weight (8).