Increment borers are simple tools used to cut cylindrical cores from objects such as trees, telegraph poles and the like. These cores may be used, for example, to determine the age of a tree without cutting the tree down, or to investigate whether or not a pole is rotten in the centre.

A typical increment borer, as shown in Figure 1, consists of a hollow, cylindrical, metal shaft 1, one end having a sharp cutting rim 5 and a short section 7 of external screw thread, the opposite end having a removable handle 3. The. shaft is bored into or through the object to be cored by clockwise rotation of the handle, the screw thread pulling the shaft into the object and the hollow shaft receiving a core of material cut out by the cutting rim. In normal use the core is removed from the borer, which is then withdrawn from the object by anticlockwise rotation.

However, if the threaded portion of the shaft penetrates a rotten or hollow portion of the object, the thread may lose contact with sound material and lose its purchase. The borer cannot then be easily withdrawn. Thus there is a need for a tool to facilitate extraction of an increment borer (or a device having a similar rotational or axial sampling mode) from an object to be cored.

Accordingly, a first aspect of the present invention provides

an extractor device for extracting an increment borer from an object, the device comprising: a first body which has immobilising means for rotatably immobilising the first body relative to the object, and a second body which is threadingly engaged to the first body and has securing means for releasably securing the second body to the increment borer; whereby, in use, rotation of the second body on the first body causes the second body to move away from the object in the axial direction of the borer thereby extracting the borer from, the object. Thus the borer may be extracted even when the borer does not purchase on the object.

By"threadingly engaged"is meant any suitable construction by which rotational motion is converted into translational motion. Typically the first body is threadingly engaged to the second body by means of complementary screw formations on the first and second bodies.

In one embodiment, the first and second bodies comprise coaxial sleeve portions at which the bodies threadingly engage and which, in use, surround a portion of the borer projecting from the object. With this embodiment, the handle of the borer may need to be removed in order to slide the sleeve portions onto the shaft of the borer.

The immobilising means may comprise projections extending from the first body such as spikes or claws for gripping the object. In a preferred embodiment the projections are radially spaced from the longitudinal axis of the borer, which better prevents rotation of the first object relative to the object.

Alternative immobilising means may include (i) nails passing through respective holes in the first body, the nails then being driven into the object, or (ii) a belt attached to the first body which can then be tightened around the object.

The securing means may comprise one or more retaining screws which can be tightened onto the shaft of an increment borer.

The securing means may be of relatively soft material (such as plastics material) where it engages with the borer to avoid damaging the borer.

Alternatively the securing means may comprise a chuck having a number of adjustable jaws.

In a further embodiment, the second body has a handle or handles which can be used to turn the second body. Thus if for any reason the end portion of the borer is broken off so that the borer handles cannot be used, the handles or handles of the second body can rotate the second body and pull the borer from the object. Preferably the or each handle is detachably mounted to the second body (e. g. by threadingly engaging a corresponding hole in the second body) so that the handle can be dismounted from the second body when it is not needed.

It will be appreciated that the device comprises a number of component parts. Accordingly a further aspect of the present invention provides a kit of component parts for assembly into an extractor device according to the previous aspect.

The present invention further provides a method of extracting an increment borer from an object, comprising the steps of (i) providing an extractor device according to the first aspect of

the present invention, (ii) rotatably immobilising the first body with respect to the object and securing the second body to the borer, and (iii) rotating the second body, whereby the second body moves away from the object in the axial direction of the borer, thereby extracting the borer from the object.

A specific embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which : Figure 1 shows an increment borer, Figure 2 is a side view of an extractor device embodying the present invention, Figure 3 is a top view of the device shown in Figure 2, Figure 4 is a further side view of the device shown in Figure 2, and Figure 5 illustrates the operation of an extractor device according to the present invention.

Referring to Figures 2 to 4, an extractor device has a rectangular base plate 9 with claws 93 extending forwardly from the corners thereof. A hollow, cylindrical, inner sleeve 11 extends rearwardly from the base plate and has an external screw thread 111. An outer sleeve 13 is screwed over the end of the inner sleeve by means of a complementary internal thread 131. Thus the outer sleeve moves axially along the inner sleeve when the two sleeves are rotated relative to one another.

At the end of outer sleeve 13 furthest from base plate 9 are three retaining screws 15, which extend into the bore of the outer sleeve through threaded apertures 133. The screws have hollow tips containing nylon plugs 151 to ensure secure

contact between the screws and the shaft of an increment borer (which, as described below, in use extends through the sleeves) without causing damage to the borer. The outer sleeve is longer than inner sleeve 11 so that when the outer sleeve is screwed fully along the inner sleeve up to the base plate, the retaining screws do not collide with the inner sleeve.

Figure 5 illustrates the mode of operation of the extractor device. When a borer (such as that shown in Figure 1) is bored into a tree 200 and threaded portion 7 of the borer penetrates a rotten portion (indicated by shading in Fig. 5) of the tree, the threaded portion may lose purchase on the tree so that the borer cannot be extracted (or indeed further penetrated into the tree). To extract the borer using the extractor device, handle 3 of the borer is first removed from shaft 1, inner sleeve 11 and then outer sleeve 13 of the extractor device are slipped along the shaft, and the handle is replaced.

The device is slipped along shaft 1 until claws 93 engage the bark of the tree. Outer sleeve 13 is screwed along inner sleeve ll, up to base plate 9, and retaining screws 15 are then tightened to clamp the outer sleeve onto the shaft of the borer.

Handle 3 of the borer is then rotated anticlockwise, i. e. in the direction which would ordinarily achieve withdrawal from the tree. This causes outer sleeve 13 to rotate with respect to inner sleeve 11. The inner sleeve cannot itself rotate, because claws 93 of base plate 9 are engaged with the bark of the tree. Thus the rotation causes the outer sleeve to be drawn along the inner sleeve away from the base plate, pulling

the borer with it.

When thread 7 on the borer shaft re-engages with sound wood, the borer continues to withdraw from the tree by virtue of its own screw thread, and base plate 9 then disengages from the trunk. Once the borer is completely withdrawn from the tree, the extractor device can be slipped off the threaded end of the borer shaft simply by loosening clamping screws 15.