FIELD OF THE DISCLOSURE

The present invention relates to a timber-working device and a timing link for same.

BACKGROUND

It is well-known to mount timber-working devices, commonly referred to as forestry or harvester heads, to a carrier vehicle in order to perform a number of operations in connection with timber processing. These operations may include one, or a combination of, grappling and felling a standing tree, delimbing a felled stem, debarking the stem, and cutting the stem into logs (known as bucking) - commonly using at least one chainsaw.

Feeding the stem along its length relative to the head is typically achieved using arm mounted rotary drives having a feed wheel at the end of opposing drive arms configured to grasp the stem, together with at least one frame mounted feed wheel. It is generally desirable to have the drive arms close at the same rate in order to centre them (and the stem or stems they are acting against) in the head. It is known to provide a timing link between the drive arms in order to achieve this.

However, where there is variance in the size or linearity of the stem this synchronization can lead to one of the wheels having a lesser degree of contact with the stem than the other, creating inefficiencies.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

Throughout this specification, the words "comprise" or "include", or variations thereof such as "comprises", "includes", "comprising" or "including", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

SUMMARY

According to one aspect of the present invention there is provided a timing link for connecting a first pivoting drive arm and a second pivoting drive arm of a timber-working device, including: an elongate member having a first end and a second end, and a first aperture at the first end and a second aperture at the second end, wherein at least one of the first aperture and the second aperture is elongate along the length of the member. According to another aspect of the invention there is provided a timber-working device, including: a frame; a first drive arm and a second drive arm, the first arm and second arm pivotally attached to the frame; and a timing link including an elongate member having a first end and a second end, and a first aperture at the first end and a second aperture at the second end, wherein at least one of the first aperture and the second aperture is elongate along the length of the member, wherein the timing link is connected to the first and second arms via the first and second apertures. The timber-working device may be a forestry or harvester head, and may be referred to as such throughout the specification. Forestry heads typically have the capacity to grapple and fell a standing tree, delimb and/or debark a felled stem, and cut the stem into logs. However, a person skilled in the art should appreciate that the present invention may be used with other timber-working devices, and that reference to the timber-working device being a forestry head is not intended to be limiting.

One well known system for forestry heads uses opposing drive arms, one on each side of the feed axis. Each drive arm may include a feed wheel configured to be brought in contact with stem. The arms may be driven, for example by hydraulic cylinders, to pivot relative to the frame of the device in order to grapple the stem with the feed wheels. The feed wheels may each be connected to a rotary drive and used to drive or feed the stems along the feed axis of the head. The timber-working device may further include a single feed wheel driven by a rotary drive and mounted to the frame. This frame mounted feed wheel may be used together with the arm mounted feed wheels to drive the stem(s). The frame mounted feed wheel may be aligned with the arm mounted feed wheels relative to the feed axis. It should be appreciated that the device may include more than one frame mounted feed wheel.

Each drive arm may include an engagement member configured to be inserted into one of the apertures.

The engagement member may be any suitable means known in the art for connecting via an aperture and permitting pivotal movement therebetween. For example, the engagement member may be a pin connected to the drive arm and configured to extend into the aperture. It should be appreciated that the engagement member may include more than one component - for example a pin together with a bush.

The fit of the engagement member of the drive arm with the elongate aperture may be looser than that of the engagement member of the other drive arm with the other aperture. This may allow for sliding of the engagement member along the elongate aperture without undesirable friction causing wear.

The longitudinal axis of each aperture, with which the respective engagement members may be aligned, may be parallel to each other.

In an embodiment, the travel of the engagement member along the at least one elongate aperture may be within the range of substantially 40 millimetres to 60 millimetres. More particularly, the travel may be substantially 50 millimetres. Limiting the range of travel may be useful

The elongate member may have a reverse curvature along its length. Reference to a reverse curvature should be understood to mean a shape in which a curve transitions to another curve in the opposite direction - occasionally referred to as an "S" curve.

The elongate member may have a long section at a first end of the reverse curvature, and a short section at the other end of the reverse curvature.

The elongate aperture may be located in the long section. It is envisaged that locating the elongate aperture in the long section may allow the elongate aperture to be substantially linear along its length.

The length of the at least one elongate aperture may be at least substantially twice the diameter of the other aperture. The timber-working device may include delimb arms. Such delimb arms are known in the art, being configured to be closed about the stem(s), and including sharpened edges to cut limbs from the stem as it is driven by the feed wheels.

The timber-working device may include a cutting device - for example at least one saw. It is known for forestry heads to include a main chainsaw which is primarily used for the felling and cross cutting of stems. Further, some forestry heads may include a secondary or topping chainsaw. The topping saw is typically of a lower specification than the main saw, and used primarily during processing once a tree is felled.

Reference to the cutting device being a chainsaw is not intended to be limiting, as the saw may take other forms - for example a disc saw. Further, the cutting device may take other forms known in the art, for example a shear.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

FIG. 1 is a side view of an exemplary timber-working system including, for example, a forestry head according to one aspect of the present invention;

FIG. 2 is a perspective view of the forestry head;

FIG. 3 is face on view of an exemplary timing link for use in the forestry head;

FIG. 4A is an exploded perspective view of an exemplary drive system including the

timing link, and

FIG. 4B is a face on view of the exemplary drive system.

DETAILED DESCRIPTION

FIG. 1 illustrates a timber-working system including a carrier 1 for use in forest harvesting. The carrier 1 includes an operator cab 2 from which an operator (not shown) controls the carrier 1. The carrier 1 further includes a boom assembly 3, to which a timber-working device in the form of a forestry head 4 is connected. Connection of the head 4 to the arm 3 includes a rotator 5, configured to rotate the head 4 about the generally vertical axis of rotation marked by dashed line 6. A tilt bracket 7 further allows rotation of the head 4 between a prone position (as illustrated) and a standing position.

Referring to FIG. 2, the head 4 includes a frame 8 to which the tilt bracket 7 of FIG. 1 is pivotally attached. Left hand (LH) and right hand (RH) delimb arms 9a and 9b are pivotally attached to the frame 8, as are opposing LH and RH drive arms 10a and 10b. LH and RH feed wheels 11a and 11 b are attached to LH and RH drive arms 10a and 10b respectively, which together with a central frame-mounted feed wheel 12 may be controlled to feed one or more stems (not illustrated) along a feed axis of the head 4. Feed wheels 1 1a, 11 b, and 12 may collectively be referred to as the 'feed mechanism.'

A main chainsaw 13, and a topping chainsaw 14, are attached to the frame 8. The main saw 13 is typically used to fell a tree when the head 4 is in a harvesting position, and to buck stems into logs in the processing position of the head 4 (as seen in FIG. 1). The topping saw 14 may be used to cut off a small-diameter top portion of the stem(s) to maximize the value recovery of the trees.

The LH and RH drive arms 10a and 10b are interconnected by timing link 15, which is described in more detail below with reference to FIG. 3.

The timing link 15 includes an elongate body 30 made of flat steel. The elongate body includes a long section 31 having a shallow curvature which transitions into a reverse curvature section 32 and ends in a short section 33.

The timing link includes a circular aperture 34 at the end of the short section 33, and an elongate aperture 35 at the distal end of the long section 31.

In this exemplary embodiment the length 36 of the elongate aperture 35 is substantially 50 millimetres along the centreline 37 between its centre marks 38a and 38b at its respective ends. The overall length of the elongate aperture 35 is at least substantially 90 millimetres.

The angle 39 between the centre line 37 of the elongate aperture 35 and line 40 drawn between the first centre mark 38a of the elongate aperture 35, and the centre mark 41 of the circular aperture 34, is substantially 30 degrees.

The width 42 of the elongate aperture 35 is greater than the diameter of the circular aperture 34, in order to achieve a comparatively looser fit when bushes having the same dimensions are inserted into the respective apertures. FIG. 4A and 4B show the timing link relative to the feed mechanism of the head 4 (although central frame-mounted feed wheel 12 is not illustrated). Reference may be made to the frame 8 and central frame-mounted feed wheel 12 of FIG. 2.

LH and RH drive arm pins 50a and 50b are used to pivotally couple the LH and RH drive arms 10a and 10b to the frame 8. LH and RH hydraulic cylinders 51a and 51 b are coupled to the frame 8 and LH and RH drive arms 10a and 10b.

The drive arms 10a and 10b include wing plates 52a and 52b respectively, to which the link 15 is connected. Wing plate 52a is positioned on the other side of the LH drive arm pin 50a relative to the feed wheel 11a, while wing plate 52b is positioned on the same side of the RH drive arm pin 50b.

The timing link 15 is connected to the wing plate 52a way of LH link pin 53a and bush 54a through the elongate aperture 35, the LH link pin 53a located in position by retainer clip 55a. Similarly, the other end of the timing link 15 is connected to the wing plate 52b way of RH link pin 53b and bush 54b through the circular aperture 34, the RH link pin 53b located in position by retainer clip 55b.

The longitudinal axes of apertures 45 and 35, which align with those of the LH and RH link pins 53a and 53b respectively, are parallel to each other.

Operation of the feed mechanism will be described with reference to FIG. 3 as well as FIG. 4A and FIG. 4B.

Extension of the LH and RH cylinders 51a and 51 b causes LH and RH drive arms 10a and 10b to pivot inwardly - causing the feed wheels 11 a and 11 b to bear against any stems therebetween and hold them against central frame-mounted feed wheel 12.

When closing the arms 10a and 10b, it may be desirable to ensure that the arms close at essentially the same rate to assist in picking up the stem(s) and centring it in the head 4.

If the LH drive arm 10a leads the RH drive arm 10b, the LH link pin 53a and bush 54a travel along the elongate aperture 35 to centre mark 38a, at which point the timing link 15 begins to pull RH drive arm 10b, or at least restrict movement of the LH drive arm 10a until the RH drive arm 10b has caught up. The same logic applies in reverse. Once the drive arms 10a and 10b have closed on the stem(s), the length 36 of the elongate aperture permits a degree of "float" between the respective angular positions of the drive arms 10a and 10b to accommodate for variance in the size and position of the stem as it is fed through the head 4 by the feed wheels 11 a, 11 b, and 12. This float may allow more consistent contact between the feed wheels 11a and 11 b, which influences the effectiveness of debarking and feeding using the wheels 11 a and 11 b.

The exemplary 50 millimetres of travel may allow for this, while still maintaining a degree of synchronisation - particularly when opening and closing the drive arms 10a and 10b.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.