Boring or penetrating the earth – With above-ground means for handling drilling fluid or cutting – Fluid or cuttings directing or receiving means engaging bore...
Reexamination Certificate
1999-04-27
2001-03-06
Bagnell, David (Department: 3672)
Boring or penetrating the earth
With above-ground means for handling drilling fluid or cutting
Fluid or cuttings directing or receiving means engaging bore...
C175S067000
Reexamination Certificate
active
06196337
ABSTRACT:
BACKGROUND OF THE INVENTION
a. Field of the Invention
The present invention relates generally to apparatus for digging postholes and other small-diameter holes in the earth, and more particularly, to a hand-held posthole digger which forms bores in the earth by application of water pressure.
b. Related Art
Posthole diggers are used to bore comparatively small diameter holes in the earth, for installation of fence posts, and other posts and supports of various kinds. For purposes of convenience, the term “fence post”, as used in this description will be understood to include all such supports and similar members, which are installed or otherwise placed so as to extend a few feet into the earth.
Although fence posts are, of course, widely used, they are particularly prevalent in the agricultural industries. For example, a typical livestock operation or orchard will have many hundreds or even thousands of fence posts, used for fences, to support trees or vines, and so on. Since the posts must be replaced or moved from time-to-time, the time and labor involved in installing fence posts becomes a major concern for many farmers, ranchers, orchardists, and so on.
Prior art posthole digging tools, however, have remained notoriously slow, labor-intensive, and inefficient in use. Manual posthole diggers have generally taken one of two forms: The most common comprises a pair of shovel-shaped blades which are joined together by a hinge, at the end of a pair of long poles; the operator thrusts the tool downwardly into the ground and then brings the blades together to withdraw a scoop of dirt. These tools are slow and tiring to use, and all the more inefficient due to their tendency to let dirt fall back into the hole as it is being withdrawn.
A second form of manual posthole digger uses a pair of auger like blades which define a bucket-like structure at the lower end of the tool, into which the dirt is scooped as the tool is rotated by the operator; after a few turns, the tool is lifted from the ground, dumped and the process is repeated. While superior in some respects to the type of tool described above, this latter form does not work well in rocky earth, and in any event remains an highly labor-intensive device.
Powered posthole diggers generally take the form of a long, screw-like auger mounted to a power head. Portable types are usually powered by a gasoline engine, and are comparatively fast in action. However, they are expensive, complicated, unreliable, and generally require two men in order to hold the power head against the torque which is generated by the bit during operation. These problems, especially the additional labor costs, represent serious drawbacks in commercial use.
Other types of posthole diggers are available which are designed to be mounted to a vehicle, such as a tractor or BOBCAT™ loader or similar vehicle for example. These devices are commonly driven using the vehicle's hydraulic system, and have the advantage of requiring only one operator. Again, however, they tend to be very expensive. Moreover, because they are mounted to the vehicle, this means that the vehicle must be maneuvered each time another hole is to be made, and in many instances there will not be enough room in which to maneuver the vehicle, as around trees or other obstacles. Once again, these drawbacks can present serious problems in a commercial operation, especially in the case of an orchard or a vineyard where many posts and other supports need to be placed in and amongst the plants themselves.
Accordingly, there exists a need for a posthole digger which is fast and efficient in operation, and which requires only a single operator, but which is also easily portable and convenient to use. Moreover, there exists a need for such a posthole digger which is simple and inexpensive in construction, and highly durable and reliable for extended use in a commercial operation.
SUMMARY OF THE INVENTION
The present invention has solved the problems cited above, and is a portable tool for formation of postholes and other bores by application of water pressure.
The tool includes a vertically elongate conduit having an enlarged mandrel member mounted on its lower end, and means for connecting the upper end of the conduit to a source of water pressure. The water pressure is discharged through an open end of the conduit at the bottom of the mandrel member, so that soil is dislodged and carried in the flow upwardly along the sides of the mandrel member, and then discharged out of the bore at the surface of the ground.
The mandrel member may be a vertically elongate, three-dimensional member which is generally circular in horizontal cross-section. The lower tip of the mandrel member may have a conical downward taper for penetrating into the ground, and for distributing the flow outwardly and upwardly over the body of the member. The body of the mandrel member may be generally cylindrical in form, and may have a diameter approximately equal to the diameter of the bore to be formed. The upper tip of the mandrel member may have an upward conical taper, over which the flow passes into the bore and to the surface.
The mandrel member may have a central bore through which the vertical pipe extends axially. The mandrel member may be detachably mounted to the pipe member so as to permit the mandrel member to be interchangeably removed and replaced with mandrel members of different sizes or shapes.
The tool may also include a valve for controlling the flow of water to the lower end thereof, and the control valve may be a manually operated ball valve. The tool may also include at least one transversely extending handle member for enabling the operator to exert a downward pressure on the tool.
The means for connecting the upper end of the vertical conduit to the source of water pressure may be a flexible hose for permitting the operator to manually maneuver and position the tool. The flexible hose may include a reinforced section where this is attached to the conduit.
The conduit may suitably be formed of pipe, such as galvanized steel pipe. The mandrel member may suitably be formed of dense plastic material.
REFERENCES:
patent: 3638741 (1972-02-01), Zizak
patent: 3887021 (1975-06-01), Elbert
patent: 4919204 (1990-04-01), Baker et al.
patent: 4921375 (1990-05-01), Famulari
patent: 4986373 (1991-01-01), Charland et al.
patent: 5029651 (1991-07-01), Ubbink
patent: 5361885 (1994-11-01), Schuermann et al.
patent: 2406699 (1977-10-01), None
Bagnell David
Hathaway Todd N.
Hawkins Jennifer M
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