Vibrator Device For Earth Boring Or Compacting

Abstract

A vibrator is mounted on a universal joint at the bottom of a hollow shaft which is lowered into the earth for boring or compacting. The vibrator is horizontally vibrated by an electric or pneumatic drive mounted in the vibrator body. For boring service the bottom of the vibrator body comes to a point. To avoid dissipation of vibratory energy communicated to the shaft by the universal joint, the latter is placed at a vibration node and a narrower extension of the vibrator body bearing counterweights extends upward of the universal joint coupling into the hollow shaft.

Description

This invention concerns a vibrator for compacting soil and other solids and for boring into the earth. The vibrator, like other such devices already known, comprises a vibrator body with a vibration generator and its drive and also a coupling for hanging the vibrator body on a shaft.

Devices are known for compacting soil or for boring holes that utilize a vibrator body containing a vibration generator adapted to drive the vibrator body in horizontal vibrations which then impinge on the surrounding soil or other solids to be compacted or bored.

When such a vibration body is hung on a rigid shaft, usually a hollow shaft, and lowered into the material to be compacted, the shaft above the coupling usually vibrates also. Thus, part of the vibration energy, which particularly in the drilling of well bores should be concentrated in the vibrator, is lost to the boring process. Apart from this undesired energy loss such an arrangement has the further disadvantage that under certain conditions the coupling between the vibrator and the shaft, or the shaft itself, breaks.

To counteract this disadvantage it has heretofore been proposed, for example in German Pat. No. 1,021,264, to provide an elastic coupling between the shaft and the vibrator body in order to reduce or avoid the transmission of vibrations to the shaft. Such elastic couplings have the disadvantage, however, that they are not suited for the mechanical connection between the vibrator and the shaft. On account of the high horizontal vibration load of the coupling, it is impossible to prevent a coupling of elastic construction from soon being damaged and ultimately breaking or tearing.

The object of the invention is to devise a vibrator equipment in which the coupling, so far as possible, is not subject to any horizontal vibration and hence does not need to be made elastic. The solution of this problem is found by the present invention in a vibrator with a body relatively long in vertical dimension in which the vibration generator is arranged in the region of one end of the vibrator body and in which the coupling to the shaft is located at a vibration node of the vibrator body. On the upper end of the body, which may generally take the form of a tapered extension penetrating the interior of the shaft, weights serve to place the node at a convenient point for coupling, which is to say they make possible the use of a relatively short upper extension.

When an elongated body is vibrated, there is generally a location where the imposed vibrations may be regarded as concentrated, and then there is generally also a mathematically calculable point inside or outside the body where vibrations in the opposite sense may be regarded as concentrated. Between those two vibration centers there is a point of the body which is not brought into any vibrational motion whatever. In the case of an elongated body with uniform distribution of mass and uniform density, for example a rod or a tube, when the application of vibratory force is made at right angles to the longitudinal axis of the body at one of its ends, the vibration node lies in the other half of the body. If on the other hand the application of vibratory force occurs in the middle of the body, the node for the vibration lies at infinity. In order to avoid setting the coupling between a vibrator body and a supporting vertical shaft into horizontal vibrations and transmitting such horizontal vibrations to the shaft when the vibrator is horizontally excited, it is accordingly necessary to place the vibration generator near one end of an elongated vibrator body, so that a vibration node will appear at some level of that body and to provide the coupling to the supporting shaft in the neighborhood of the vibration node.

When a vibrator is used for downward boring operation, there is advantage in placing the point of greatest horizontal vibration as far down as possible in the vibrator body and it is accordingly advantageous to locate the vibration generator in the lowest portion of the vibrator body as directly as possible over its working extremity which, at least in the case of boring equipment, is usually pointed and hard.

A general angular rotation linkage, for example a universal joint or a ball and socket joint, is preferably used for the coupling. Besides, other known linkages that can transfer compression and tension forces can be used, however.

For the compacting of soil down to relatively great depths and for the boring of deep holes with a vibrator, it is effective to use a hollow mounting shaft with the same external diameter as the vibrator body or a diameter only a little smaller than that of the vibrator body. In order to prevent the upper end of the vibrator body from hitting against the inner wall of the hollow shaft above the location of the coupling during horizontal vibration, it is desirable to taper the upper portion of the vibrator body above the vibration node. The universal joint indeed is not subject to horizontal vibration, but the upper part of the body, which may have the form of an extension of reduced diameter, executes horizontal vibrations of an amplitude that increases proportionally with the distance from the vibration node.

It appears that the location of the vibration node of a body, when the effective center of vibrations is in the neighborhood of one end of it, depends not only on the length of the body but importantly on the distribution of mass along the length. It is therefore advantageous to reduce the length of the portion of the vibrator body extending into the hollow shaft by the provision of counterweights which increase the vibrating mass in this part of the vibrator body compared with that in the remaining portion, producing the desired angular moment with a smaller distance from node to end.

For the further explanation of the invention reference is made to the illustrative embodiment of the invention shown in the annexed drawing, in which:

FIG. 1 is a partial longitudinal section through the vibrator body which is suspended on a hollow shaft, and

FIG. 2 is a cross-section of the coupling.

The vibrator body 1 is a hollow structure having a pointed bit 2 at one end and at the other end an extension 3 of smaller diameter than that of the hollow body 1.

In the bottom portion of vibrator body 1 immediately above the bit 2 a vibration generator 4 of known type is provided which is driven by a drive motor 5 located above the vibrating element 4. For the drive an electric or hydraulic motor can be used in a known way.

The extension 3 of the vibrator body 1 projects into the end of the hollow shaft 6 the outer diameter of which is about the same as that of the vibrator body 1 or only slightly smaller. The shaft 6 may be the end of a string of pipe to which addition is made at the top in the usual way as boring progresses. The vibrator body is connected to the end of the hollow shaft 6 by a universal joint 7 surrounding the extension 3. The universal joint 7 is located at the vibration node of the vibrator body 1. Above the universal joint 7 counterweights 8 are provided on the periphery of the extension 3. The position of the node can be approximated by calculation or experiment and if coupling at the position first determined is found still to transmit some vibration when the vibrator is loaded by its work, a small shift of the axial position of the counterweights will shift the node to the coupling location.

Claims

What is claimed is:

1. A vibrator adapted for mounting on a hollow shaft for boring into the earth or for vibratory earth compacting comprising, in combination,

a. an elongated body having a cavity therein, having a work surface at one extremity adapted to be lowered on to the work and having an extension of reduced girth at the other extremity;

b. a vibration generator in said cavity near one extremity of said body adapted to excite said body into transverse vibrations;

c. driving means for actuating said vibration generation;

d. a non-elastic, mechanical coupling adapted to hang said elongated body on a hollow shaft in such a way that said extension projects into said shaft and that the attachment of said coupling to said body is in a location where a vibration node is found when said body is excited into transverse vibrations by said generator; and

e. counterweight means mounted on said reduced girth extension of the elongated body to shift the vibration node to the coupling location.

2. A vibrator as defined in claim 1 in which said vibration generator is positioned with its actuating elements near said lower extremity of said elongated body.

3. A vibrator as defined in claim 1 in which said coupling is a universal joint.

4. A vibrator as defined in claim 1 in which said driving means in an electric motor.

5. A vibrator as defined in claim 1 in which said body is essentially cylindrical in shape, said work surface is the surface of a tough conical point and said generator is adapted to excite said vibrations at a location near said work surface.

6. A device for vibratory boring into the earth or vibratory earth compacting which comprises, in combination:

a. an elongated body having an elongated cavity therein, having a work surface at its lower extremity and having an extension of reduced girth providing its other extremity;

b. a vibration generator in said cavity near one extremity of said body adapted to excite said body into vibration such that said work surface is caused to move transversely with respect to the longitudinal axis of said body;

c. driving means in said body for said vibration generator;

d. a supporting shaft for said body which shaft is hollow at least at and near its lower end, said shaft having a girth approximately equal to or slightly smaller than that of said elongated body and having hollow space sufficiently larger than said extension of said body to permit said extension to vibrate without impinging on said shaft;

e. a non-elastic, mechanical coupling connecting a node of said vibrations of said body to the lower end of said shaft, so that said extension protrudes into the hollow of said shaft and so that said body is securely mounted on said shaft with little or no restraint of said vibrations; and

f. counterweight means mounted on said reduced girth extension of the elongated body to shift the node of said vibrations to the coupling location.

7. A device as defined in claim 6 in which said vibration generator is positioned close to said lower extremity of said body.

8. A device as defined in claim 6 in which said coupling is a universal joint.

9. A device as defined in claim 8 in which said driving means is an electric motor, said body and said shaft are essentially cylindrical in shape and said work surface is the surface of a tough conical point.