Wood corer device

Details Wood corer device Wood corer device

1998-09-01

2000-01-18

Bishop, Steven C.

Cutting by use of rotating axially moving tool

Tool or tool with support

Having axial, core-receiving central portion

7386444, 408206, 408703, G01N 108, B23B 5104

Patent

active

060152486

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention concerns wood corers. More particularly, it concerns a drill bit for coring wood which comprises a hollow drill bit with helical bodies and flutes which can be adapted for use with a power drill to obtain core samples of wood (for example, trees or telegraph poles).


BACKGROUND TO THE INVENTION

There are many instances in which it is desirable to be able to take a core sample of a timber structure. Forestry workers use such wood cores to evaluate the properties of selected trees--particularly for an analysis of the fibre structure of the tree wood. Electrical power companies and telephone companies use wood cores to test the soundness of the poles on which power and telephone cable are mounted. Structural engineers use core samples of wooden beams, poles and the like to assess the soundness of wooden structures.
A number of devices have previously been used to obtain wood cores. Probably the most popular corer for green wood sampling is a hand-operated tree corer (from Scandinavia) which consists of a hollow steel tube with a tapered spiral external thread on the head. The rotating action cuts the wood fibres on scribes and the cut core slips inside the tube during extraction. The device is operated by quite extreme physical exertion in applying force to a pair of transverse arms extending outwardly from the rear of the T-shaped device. As the corer moves into the tree it compresses the wood tissue around the shaft, rather than removing it, making rotation more difficult the further the corer moves into the tree, particularly when coring wood such as eucalypt which does not compress readily. Risk of muscular injury is therefore quite high. Although this device has the advantages of simple construction and an ability to provide wood cores on soft conifers, it is physically exhausting to use constantly, and extremely difficult to use on hardwood species such as eucalypts.
Another wood corer that has been used in Australia comprises a trepanning head at the end of a long hollow shaft attached to a power drill. This equipment requires a heavy frame, which is clamped to the tree, beam or pole that is being sampled before drilling can commence. In addition to being difficult to transport, it cuts a core with a 25 mm diameter and leaves a hole which has a diameter of 40 mm--which is generally unacceptable from a tree husbandry viewpoint.
There has long been a need for a wood corer which is easy to use and easily transportable, and which cuts a suitable size core quickly, through all species of wood, both green and dry.


SUMMARY OF THE INVENTION

According to the present invention there is provided a wood coring drill bit comprising a hollow tube having a internal bore and an exterior with equally spaced bodies of substantially uniform width extending in a helical manner from a cutting end of said drill bit, said bodies defining equally spaced flutes between the edges of adjacent bodies, each body comprising a land upstanding from a relief at the leading edge of the body, a respective cutting face and associated lip being formed at the end of each body at said cutting end. The tube of the coring drill bit has three equally spaced bodies and flutes, said cutting face has an included angle which is within the range of 106.degree. to 131.degree., the lip has a lip clearance angle that is about 6.degree..+-.1.degree., the lands on the bodies extend for an axial distance of about 65 mm.+-.5 mm from said cutting end and the internal bore of the hollow tube is tapered outwardly from or adjacent the cutting end.
Preferably the outside diameters of the bodies are stepped down by about 0.5.+-.0.1 mm at a distance of about 65 mm.+-.10 mm from said cutting end.
When used on hardwood the included cutting angle is within the range 118.degree. to 131.degree. preferably 125.degree..
When used on softwood the included cutting angle is within the range 106.degree. to 118.degree. preferably 112.degree..
When used on drywood the included cutting angle is within the range 118.degree. to 131.degree. b

REFERENCES:
patent: 715631 (1902-12-01), Ayres
patent: 1162901 (1915-12-01), Cantey
patent: 3110184 (1963-11-01), Gruetzman
patent: 4696308 (1987-09-01), Meller et al.
patent: 5433560 (1995-07-01), Duncan

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