Technical Field

The present invention relates to a method for moving loads using a sky line, and in particular to a method for moving loads using a sky line where the upper end of the sky line is anchored on land and the lower end of the sky line is anchored on water. The method of the present invention has been developed for logging difficult or inaccessible areas near water (for example hillsides near a lake or the sea) and will be described with especial reference to that application. However, it will be appreciated that the method of the present invention is equally useful for moving any heavy or awkward load over difficult terrain, onto a barge or ship.

Background Art

Any discussion of the prior art throughout the specification is not an admission that such prior art is widely known or forms part of the common general knowledge in the field.

As used here, the term "sky line" means a rope or wire along which a carriage supporting a load can travel. In general, a carriage and its load arranged to slide down the sky line under gravity, but the carriage may also be driven along or even up the line.

It is known to use a sky line to move loads in situations where it is necessary to move large and/or heavy loads over steep or difficult terrain, where there are no suitable roads or where the load is too large to be accommodated on a vehicle. The most common setup is to anchor the upper end of the sky line above the position at which the loads are secured to the carriage, and to anchor the lower end of the sky line at or near the position to which the loads are to be delivered; the upper and lower ends of the sky line are spaced apart both vertically and horizontally.

If a load is to be delivered to a vessel (e.g. a barge or ship), it has been the usual practice to anchor the lower end of the sky line to the vessel. However, this has two major drawbacks:- first, it places a great stress on the vessel and limits the load which can be transferred; second, it means that once the vessel is fully loaded, the lower end of the sky line must be released before the load can be transported.

It has also been proposed to anchor the lower end of the sky line on the shore of the body of water near the vessel. Obviously, this avoids placing an undue load on the vessel, but the system is relatively inflexible and of course can be used only if the shore provides a suitable place for anchoring the lower end of the wire.

Another proposal was to anchor the lower end of the sky line to a permanent fixture in the body of water, e.g. a pylon secured to the sea bed or a pier or similar structure. However, structures such as pylons or piers require a substantial investment of time and money to install, and when installed, are permanent, so that they provide a fixed position and substantially inflexible system.

Disclosure of Invention

An object of the present invention is the provision of a method for moving loads using a sky line where the lower end of the sky line is anchored under water, which overcomes the above described difficulties.

The present invention provides a method for moving loads using a sky line, said method including anchoring the upper end of the sky line to land at an upper anchorage point and anchoring the lower end of the sky line at a lower anchorage point, to a relocatable anchor located on the bed of a body of water.

Preferably, the method of the present invention uses an anchor which permits the anchorage point of the upper end of the sky line to be moved between two or more positions, without requiring relocation of said anchor. A suitable anchor is described in co-pending New Zealand patent application number 5851 12.

Preferably, the angle between a first line drawn from a first upper anchorage point to the lower anchorage point and a second line drawn from a second upper anchorage point to the lower anchorage point is at least 45°, and may be up to 90 °. Preferably also, said lower anchorage point is adjacent a vessel, most preferably further from the upper anchorage point than the vessel, such that in use a load supported upon the sky line travels above the vessel.

In one preferred form of the invention, the vessel is provided with an arch which extends vertically above the vessel, so as to prevent fouling of the sky line or any load supported on the sky line, by the vessel or the cargo of the vessel. Said arch may be fixed in height or adjustable in height.

In one embodiment of the invention, the load to be moved is felled timber and the method includes the steps of:

1 . - selecting a first upper anchorage point and anchoring the upper end of the sky line at said point;

2. - selecting a lower anchorage point and securing the lower end of the sky line to said lower anchorage point, to a relocatable anchor located on the bed of a body of water; said anchor permitting the upper anchorage point to be moved between two or more positions without requiring relocation of said anchor;

3. - securing felled timber in the vicinity of said upper anchorage point to a carriage engaged with a sky line;

4. - using said carriage to move said timber down the sky line to a point above said vessel;

5. - lowering said timber onto said vessel;

6. - returning said carriage to a point on the sky line adjacent said first upper anchorage point;

7. - if necessary, repeating steps 3-6 until the required amount of timber has been loaded onto said vessel;

8. - selecting one or more further upper anchorage points and repeating the above steps 3-7 to move felled timber from the vicinity of the or each further upper anchorage point in turn down the sky line and on to said vessel, until the location of said upper anchorage point has reached the limit permitted by the location of said anchor.

Brief Description of the Drawings By way of example only, preferred embodiments of the present invention are described in detail with reference to the accompanying drawings in which:-

Figure 1 is a diagram showing the general layout of a system in accordance with the present invention;

Figure 1 a is a view of part of Figure 1 on a larger scale;

Figure 2 is a diagram showing a plan view of a proposed harvesting method for a hillside area; and

Figure 3 is a diagram showing a plan view of another proposed harvesting method for a hillside area.

Best Modes for Carrying out the Invention

Figure 1 of the drawings shows the general principles of the system in accordance with the present invention. In this setup, the method of the present invention is used to assist the logging of a steep hillside 9, where the logs are to be moved down to a vessel such as a barge which is moored on the adjacent sea. A sky line 10 is anchored at its upper end 1 1 on land, using any suitable known anchoring system (indicated diagrammatically at 12), and at its lower end 13 by an underwater anchor 14 located on the bed of the body of water a short distance further away from the upper end 1 1 than a barge 15 to which the logs are to be carried.

A carriage 16 for transporting the logs 17 is mounted on the sky line 10 and is arranged, in known manner, to travel down the sky line from the upper end 1 1 to the lower end 13 under gravity and then to be winched back to the other end 1 1 by a winch 18 operating a retrieval line 19, once the logs 17 have been deposited on the barge 15.

The sky line 10 naturally deflects vertically downwards as the carriage 16 travels along it. To allow logs 17 to be lowered down to the barge 15 rapidly, the sky line 10 needs to be reasonably low, (i.e. close to the top of the barge) when it travels over the barge, but obviously the sky line 10 must not deflected downwards sufficiently, when the carriage 16 is actually over the barge, so that the sky line 10 is fouled by the load on the barge. To prevent this, the barge is fitted with a supporting arch 20 (see Figure 1 a) which may be located on the far end of the barge, as shown in Figure 1 , or at other positions along the barge, depending upon the planned orientation of the barge to the sky line and on the intended position of the lower sky line anchor 14.

The supporting arch 20 may be a simple static arch with legs 21 one of each side of the barge, supporting a crosspiece 22, which is reinforced to take the weight of the sky line and to provide a smooth, low friction surface on which the sky line can rest without fouling. Preferably, however, the legs 21 are formed from, or incorporate, hydraulic cylinders, so that the height of the crosspiece 22 from the deck of the barge can be adjusted as necessary.

Figure 2 is a diagram representing a plan view of a steep hillside area which is to be logged.

The general setup is as described with reference to Figure 1 . The anchor 14, which is positioned on the seabed further from the shore than the barge onto which the logs are to be loaded, is designed such that the upper, land, end 1 1 of the sky line 10 can be moved over an angle of at least 45 degrees; this is the angle between position A, and position X of the sky line 10 as shown in Figure 2. For some locations, this angle may be up to 90 degrees. The angle between position A and position X as shown in Figure 2 is of course dependent upon the geometry of the setup, and especially upon the depth of the water close to the shore:- if it is possible to anchor the barge in deep water close to shore, this makes it possible to use a relatively low angle between positions A and X - typically, about 45 degrees. At the other extreme, if the water close to shore is too shallow to anchor the barge, and it is necessary to anchor the barge further out, a greater angle between positions A and X (for example up to about 90 degrees) is needed for efficient operation.

Any anchor which permits this variation in the position of the land end 1 1 of the sky line 10 may be used; one suitable anchor is described in co-pending New Zealand patent application number 5851 12.

In this operation, the land end 1 1 of the sky line 10 initially is set up in a suitable starting position, e.g. as it indicated by reference 1 1 a, and the area of hillside within working distance of that position is logged. Trees which have been felled may be connected to the carriage 16 of the sky line using the extension cable of the carriage, if the carriage is of a type which provides a cable which can be drawn on way from the carriage and then winched back to the carriage. Alternatively, if the carriage is not of this type, felled trees are moved to the position 1 1 a using any suitable means such as cranes or winches. The felled trees may be partially processed where they are felled, or near position 1 1 a, or may, if the carriage has a sufficient lifting capacity, be transported as felled, and processed either on the barge or at the barge's destination.

"Processing" the felled trees means removing the branches from the main trunk, and either discarding the branches or, preferably, chipping the branches.

Once all of the trees to be logged within range of position 1 1 a have been logged, the upper end 1 1 of the sky line 10 is moved to another position, e.g. position 1 1 b, and the area adjacent position 1 1 b is logged in turn. Figure 2 shows the positions of the upper end 1 1 arranged in an orderly, more or less radial, plan, but this is for purposes of illustration only:- in practice, the positions selected for the upper end 1 1 of the sky line can if necessary be arranged in any random arrangement within the angle of movement permitted by the design of the anchor 14. Obviously, the nature of the terrain to be logged will dictate the positioning of the other end 1 1 of the sky line.

The method described with reference to Figure 2 is particularly well suited to very steep and difficult terrain where there are no roads or tracks through the areas to be logged.

Figure 3 is a diagram representing a plan view of a steep hillside area to be logged which, unlike the area are described with reference to Figure 2, is provided with a number of access tracks represented by lines 25. The presence of the tracks allows conventional logging equipment to be used to move the felled trees to one of two sites 26,27, and the upper end 1 1 of the sky line is secured first at site 26 and then, when logging has been completed around that area, the other end 1 1 of the sky line is moved to site 27. As described with reference to Figure 2, the anchor 14 must be designed to permit movement of the upper end 1 1 of the sky line between positions 26 and 27, without having to relocate the anchor.

As described with reference to Figure 2, the trees logged may be wholly or partially processed where felled, or at or near the site 26 or site 27, or may be transported unprocessed, and processed on the barge or at the barge's destination. It will be noted that in Figures 2 and 3, the barge 15 is at right angles to the position of the barge shown in Figure 1 . This is merely to illustrate an alternate barge position. If the barge is in the position shown in Figures 2 and 3, then the supporting arch 20 described with reference to Figure 1 a is of course placed along one of the longitudinal sides of the barge, so that it is positioned underneath the sky line 10, rather than across one of the ends of the barge as shown with reference to Figure 1 .