GB2104187A - Vibrator unit - Google Patents

Abstract

In a vibrator unit for driving a penetrating element (16), such as a pile tube, two weights (10A, 10B) of equal sizes are put in synchronous motion in opposite directions each along one of two uniform and mutually parallel or bits located on opposite sides of and at equal distances from an axis (2) coinciding with the longitudinal axis of the element (16) in such manner that the weights (10A, 10B) always simultaneously cross a plane of symmetry of the two orbits coinciding with said axis (2) and between these crossings are on opposite sides of said plane of symmetry. The speed of weights (10A, 10B) cyclically varies during each revolution and reaches a maximum at one crossing of the weights through said plane of symmetry, whereby the penetrating element (16) will be subjected to unidirectional axial thrusts and at the same time to momentarily increased torques causing the element to rotate stepwise in a predetermined direction. Each weight (10) is pivoted to a fixed crankshaft (9) and is longitudinally slidable in a bearing (11) mounted by trunnions (12) in a flywheel (3). <IMAGE>

Description

SPECIFICATION Vibrator unit This invention relates to a vibrator unit for driving a penetrating element, such as a pile tube, a rock drill or the like, having a longitudinal axis by imparting thereto longitudinal forces as well as torques about the longitudinal axis thereof.

More specifically the invention is concerned with a vibrator unit of the kind comprising a supporting structure having a geometric axis and being adapted to be rigidly connected to the penetrating element to be driven in a manner to make its geometric axis coincide with the longitudinal axis of the element, two separate, equal masses movably mounted in the supporting structure in a manner to move with their respective centres of gravity along uniform and parallel orbits lying on opposite sides of and at equal distances from the geometric axis of the supporting structure and being symmetrical in relation to and forming an angle with a common plane of symmetry coinciding with said geometric axis, and driving means for synchronously moving the two masses in opposite directions along their respective orbits in such a manner that the two masses always simultaneously cross said plane of symmetry. It is to be noted that there are two such crossings during each revolution, and that the masses between these crossings will be on opposite sides of the plane of symmetry referred to.

For driving down generally cylindrical elements, especially tubes, into the ground, e.g. in connection with piling works, and in certain cases also for pulling them up, vibrator units of this kind have been used for decades. However, the longitudinal forces as well as the torques generated by these known vibrator units vary mainly according to a sine curve and, thus, give rise only to a reciprocatory longitudinal movement and a simultaneous oscillating turning movement of the actuated element, of which neither one nor the other is capable of driving the element in a desired direction. Thus, the positive driving force required for the last-mentioned purpose must be provided in some other way, for example, by the action of gravity, if the element is to be moved downwards, or by the application of a lifting force, if the element is to be moved upwards.

This is a considerable inconvenience because, for example, in driving down pile tubes into the ground, the combined weight of the element itself and of the vibrator unit connected thereto frequently is insufficientfor attaining an optimum driving speed, and, hence, the load on the element must somehow be increased, which makes the work more complicated and requires undesirable additional equipment for carrying out the same.

The aim of the present invention is to provide a vibrator unit of the kind defined hereinbefore which is capable not only of exerting a unidirected positive longitudinal driving force or trust on a connected penetrating element but also of imparting thereto a stepwise rotating movement in a predetermined direction, whereby the penetrating capacity of the actuated element will be considerably increased.

According to the invention there is provided a vibrator unit for driving a penetrating element having a longitudinal axis by imparting thereto longitudinal forces as well as torques about the longitudinal axis thereof and of the kind comprising a supporting structure having a geometric axis and being adapted to be rigidly connected to the penetrating element to be driven in a manner to make its geometric axis coincide with the longitudinal axis of the element, two separate, equal masses movably mounted in the supporting structure in a manner to move with their respective centres of gravity along uniform and parallel orbits lying on opposite sides of and at equal distances from said geometric axis of the supporting structure and being symmetrical in relation to and forming an angle with a common plane of symmetry coinciding with said geometric axis, and driving means for synchronously moving said two masses in opposite directions along their respective orbits in such manner that the two masses always simultaneously cross said plane of symmetry, wherein the driving means are adapted to move the two masses along their respective orbits at a speed which cyclically varies during each revolution and reaches a maximum at one crossing of the masses through said plane of symmetry.

In this connection it should be mentioned that e.g.

for sheet file driving, so called hammering vibrator units have also been suggested which are capable of exerting a unidirected longitudinal driving force on an element connected thereto by the fact that two unbalanced masses of equal size are put in motion in opposite directions along uniform orbits at a speed that cyclically varies during each revolution. However, these known vibrator units are not capable of imparting to the actuated element any rotary motion and particularly not a rotary motion in a predeterminable direction, because the orbits of the two moving masses lie in one and the same plane.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure lisa sectional elevation of a vibrator unit as viewed generally from the line I-I in Figure 2, Figure 2 is a sectional elevation taken at a right angle to the one in Figure 1, and Figure 3 is a curve diagram illustrating the forces occurring in a vibrator unit according to the invention.

The vibrator unit illustrated in Figures 1 and 2 comprises an outer casing 1 having a central geometric axis 2. Within this casing on opposite sides of and at equal distances from the geometric axis 2 are journalled two identical but mirror-reversed flywheel units 3A and 3B. These two flywheel units are individually rotatable about a common axis 4 intersecting the geometric axis 2 at a right angle, and they are driven in opposite directions at equal speeds by a common motor 5 through a toothed wheel transmission 6.

The two flywheel units 3A and 3B are hollow, and inside each one of them there is provided a yoke 7 which in appearance resembles a crankshaft but which is rigidly connected to the casing 1. Each yoke 7 comprises a pair of arms 8 supporting between them a pin 9, which in relation to the axis of rotation 4 ofthefiywheel units is fj offset in the direction of the geometric axis 2 in such a mannerthatthe pins 9 of the two yokes will be coaxial. Inside each flywheel units 3A and 3B, respectively, there is a swingably journelled about the pin 9 an unbalanced mass or swing weight in the shape of an arm or lever 1 OA and 10B, respectively, one end of which surrounds the pin 9 and the other, free end of which suitably is tubular and filled with a heavy materiai such as lead.

Each of the two arms 10A and 10B is surrounded by a driver 11 movable with a sliding fit in the lon gitudinai direction of the arm, which driver by means of coaxial studs 12 is rotatablyjournalled in the related flywheel unit 3A and 38, respectively, in such manner that the driver 11 will partake in the rotation of the flywheel unit about the axis 4 and in doing so will move along a circular path as indicated in Figure 1.Thanks to this coupling between each flywheel unit 3A and 38, respectively, and its related arm or lever 10A and 10B, respectivley, the two arms will be continuousy swung about their related pins 9 at a speed, which varies cyclically during each revolution, although the related flywheel unit rotates at a constant speed. More specifically, in the example shown each arm 10A and 10B, respectively will accelerate when moving downwards from an upper position indicated at 13 in Figure 1 to a lower postion indicated at 14 and decelerate when moving upwards.

As upwards from Figure 1, the drivers 11 are now arranged in such manner in their respective flywheel units 3A and 38 thatthe two arms 10and 10B swinging in opposite directions will always simultaneously reach their upper positions 13 as well as their lower positions 14 but between these positions will always be on opposite sides of a plane of symmetry coinciding with the geometric axis 2 of the vibrator unit and with the axis of rotation 4 of the flywheel units. At the same time as appears from Figure 2, the two arms 10A and 108 move in orbits which are mutually parallel but located on opposite sides ofthe geometric axis 2 and at mutually equal distances therefrom.

In the example shown the two arms or levers 10A and 1 OB have a fairly great free length and, there- fore, each flywheel unit 3A and 38, respectively, has been provided with a radial opening 15 in its periphery, through which the related arm is allowed to extend during a part of its orbit. However, such an opening may be dispensed with, if the arms 10A and 10B are instead made shorter ortheflywheel units are given a larger internal diameter.

When the flywheel units 3A and 3B are driven by the motor 5 via the toothed wheel transmission 6, the two unbalanced masses represented by the arms 10A and 10B will together generate forces in the direction of the geometric axis 2 and at the same time also torques about this axis. These forces and torques are transmitted to e.g. a pile tube 16 by one end of thins tube being rigidly connected to the outer casing 1 of the vibrator unit in such manner that the geometric axis 2 of the unit coincides with the longitudinal axis of the tube 16. The connection may be accomplished in any suitable known manner.

The forces generated by a vibrator unit of the kind hereinbefore described are, of course, dependent on several variable factors, such as the magnitudes and positions of the points of gravity of the unbalanced masses 10Aand 10B relative to the pins 9, the dis- tances between these pins and the axis of rotation 4 of the flywheel units 3A, 38, and the distances between the orbits of the unbalanced masses and the geometric axis 2 of the unit (in Figure 2), but they are always distributed in time in the manner basically illustrated by the coordinated curves 17 and 18 in Figure 3, wherein curve 17 shows the variations of the longitudinal force with time, whereas curve 18 shows the variations of the torque during the same period of time.

From curve 17 it clearly appears that the longitudinal driving force orthrust in one direction, namely in the downward direction in Figures 1 and 2, reaches a considerably higher value than in the opposite direction, and that is does so very quickly, i.e. during only a small fraction of the complete operating cycle.

Thereby a very strong impact or trust effect is achieved in the downward direction in the case illustrated. From the curve 18 it further appears that the torque, although it has the same amplitude in both directions, changes more rapidly in one direction than in the other, which means that the vibrator unit and, hence, also the element actuated by the same will be set in stepwise rotation in said one direction, which very favourably promotes the penetrating capacity of the element. The direction in which the stepwise rotation takes place depends, of course, on the direction of rotation of the unbalanced masses along their orbits.

It should be clearthatthe desired favourable effect may be achieved also with other designs of the vibrator unit than the one here shown and described.

Thus, the unbalanced masses may in other ways be imparted the required, cyclically varying speed during each revolution, and the orbits of the masses need not necessarily be circular.

As will be readily understood, the penetrating element to be driven by the vibrator unit may not only be a generally cylindrical, hollow or solid body to be driven wholly or partially into the ground for piling, water-finding of soil-exploration purposes, or for supporting fences, railings or the like, but also a rock bit or any other percussion tool, the penetrating ability of which may be improved by stepwise rotation.

Claims (5)

1. A vibrator unit for driving a penetrating element having a longitudinal axis by imparting thereto longitudinal forces as well as torques aboutthe longitudinal axis thereof and of the kind comprising a supporting structure having a geometric axis and being adapted to be rigidly connected to the penetrating element to be driven in a manner to make its geometric axis coincide with the longitudinal axis of the element, two separate, equal masses movably mounted in the supporting structure in a manner to move with their respective centres of gravity along uniform and parallel orbits lying on opposite sides of and at equal distances from said geometric axis of the supporting structure and being symmetrical in relation to and forming an angle with a common plane of symmetry coinciding with said geometric axis, and driving means for synchronously moving said two masses in opposite directions along their respective orbits in such manner that the two masses always simultaneously cross said plane of symmetry, wherein the driving means are adapted to move the two masses along their respective orbits at a speed which cyclically varies during each revolution and reaches a maximum at one crossing of the masses through said plane of symmetry.

2. A vibrator unit according to Claim 1, wherein the two separate masses comprise swing weights pivotally mounted in the supporting structure to swing about spaced pivots having a common axis which intersects the geometric axis of the supporting structure at a right angle in said plane of symmetry, the driving means comprise two separate flywheel units, one for each swing weight, mounted in the supporting structure for rotation about a common axis also intersecting the geometric axis of the supporting structure at a right angle in said plane of symmetry but being displaced in said plane rela tire to said common axis of said swing weight pivots, means are provided for synchronously rotating said two flywheel units in opposite directions at equal speeds, and each of said flywheel units is drivingly connected to its related swing weight in a manner to impart thereto a cyclically varying speed during each revolution thereof.

3. A vibrator unit according to Claim 2, wherein each swing weight comprises a lever swingabiy mounted on its related pivot, eacn of said flywheel units has a sleeve-like driver pivotally connected thereto in a manner to oscillate about an axis which is eccentric to the axis of rotation of the flywheel unit itself, and this driver embraces the related swing weight lever in a manner to be slidable longitudinally thereof.

4. A vibrator unit according to Claim 2, wherein each flywheel unit is hollow, and its related swing weight is pivotally mounted within said hol low flywheel unit.

5. A vibrator unit substantially as herein described with reference to the accompanying drawings.