CA2280624C - Log grapple - Google Patents

Abstract

A grapple suitable for standing-stem log harvesting includes a vertical elongate backplate located between a pair of horizontally extending gripping jaws pivotally mounted relative to the backplate for gripping and releasing the trunk of a tree.
The grapple hangs in vertical operating position when suspended, and may include a plurality of vertically spaced and mutually vertically offset fingers associated with the jaws to distribute the gripping force.

Description

Y:\HS101 vic\60480 CAlspec 990818 final.wpd LOG GRAPPLE
FIELD OF THE OF INVENTION
This invention relates to a grapple suitable for use in a standing-stem timber harvesting system for harvesting topped tree trunks, making use of a helicopter.
BACKGROUND OF THE OF INVENTION
For selective harvesting of individual tree trunks, trees are conventionally individually felled and de-branched.
Felling trees often causes damage to the felled tree trunk and invariably causes damage to undergrowth. Removal of the felled tree trunks (i.e., logs) is often difficult, particularly in rugged terrain. Helicopters may be used to pick up felled and trimmed logs and to carry them to a stacking area, to a watercourse, or even directly to a logging truck. One system of lifting and transporting felled timber is disclosed in Jarman United States Patent No. 4,152,019 granted on 1 May 1979.
An improved logging technique is described generally in Jarman International Patent Application No. PCT/CA99/00146 filed on 18 February 1999. Specifically, a method of standing-stem log harvesting has been devised that allows a tree trunk to be harvested without felling. According to the method, a selected tree is first topped. After topping, a first saw cut is then made through the trunk of the tree near ground level. Then, a second cut through the trunk from the opposite side is made, terminating at a cut edge generally aligned with and parallel to the cut edge of the first cut and separated from it by holding wood. By "holding wood" is meant a relatively narrow portion of uncut wood extending substantially from one side of the trunk to the other, and sufficiently strong, with auxiliary support, to impede breaking by wind forces, etc. of the topped trunk away from what will become the stump. The auxiliary support conveniently is provided by support wedges driven into both cuts to stabilize the trunk, so that the wedges and the holding wood maintain the trunk stable and upright until it is harvested.
The holding wood is readily frangible in response to generally horizontal pivoting force applied to the trunk near the top in a direction generally perpendicular to the cut edges (and therefore also generally perpendicular to the long dimension of the holding wood), thereby to cause the trunk to pivot about the holding wood, and to permit the trunk to be broken away from the stump for removal. The horizontal holding wood breaking force is preferably applied by a grapple supported by a helicopter.
When the log is ready to be harvested, a helicopter provided with a suitable grapple suspended underneath the helicopter manoeuvres into position over the tree trunk so that the grapple can engage and grip the top of the trunk.
Once the grapple grips the top of the trunk, then by moving the helicopter in a direction generally horizontally and generally perpendicular to the cut edges (and thus the long dimension) of the holding wood, the helicopter is able to apply sufficient force to the trunk to break the holding wood, dislodging the wedges. It may be necessary to apply the horizontal pivoting force alternately in both directions perpendicular to the cut edges until the holding wood breaks.
The helicopter then removes the severed log to a selected drop site.
SUMMARY OF THE INVENTION
The present invention is an improved grapple particularly suitable for implementing the standing-stem log harvesting method described above. The improved grapple has opposed gripping jaws for engaging the tree trunk top. The jaws are pivotally mounted relative to a backplate of the grapple about pivot axes that are generally vertically oriented when the grapple is in operating orientation. For convenience in this description, that operating orientation will be assumed when the terms "vertical" and "horizontal" are used. The grapple is suitably provided with connection means, such as an eye, located in a preferred position relative to the grapple structure such that the grapple tends to hang vertically from its support cable. Means may be further provided to enable counterweights to be attached to the grapple to reinforce the tendency of the grapple to hang vertically.
The grapple's backplate is generally vertically elongate and generally vertically oriented. The backplate is preferably approximately arcuate in horizontal section so as to form a concave bearing surface roughly corresponding to the curvature of the log to be harvested, thereby distributing the gripping force applied to the log by the backplate.
The gripping jaws of the grapple are preferably opened and closed by means of a suitable conventional hydraulic cylinder/piston device linked thereto; the jaws are preferably provided with separate crank arms for this purpose. The jaws extend outwardly preferably as vertically spaced fingers offset from one another so as to distribute (when the grapple is operating) gripping force vertically over the vertical extension of the fingers of the grapple. The jaws and fingers are generally symmetrically disposed about the vertical center line of the backplate, but fingers on one jaw preferably alternate vertically with those on the the other jaw - in other words , the two sets of f fingers are vertically of f set from one another. Such grapple design tends to minimize the gripping force required (both per finger and per surface area of contact between the grapple and the log) to grip and remove the log, and thereby to minimize the damage caused to the log by the grapple; further, the offset fingers permit the grapple jaws to close completely without interference.
Because of the liberal distribution of gripping force throughout the bearing surfaces of the grapple, such grapple may be used to remove logs that are to be used intact as poles. Since the tree has not been felled and the pole undergoes minimal damage during removal, a pole thus harvested is preferred for a number of applications, including for use to support telephone or electric power cables.

The grapple may optionally be provided with wands extending generally horizontally outwardly from the opposed jaws of the grapple to facilitate the visibility of the grapple to the helicopter pilot and to facilitate the S engagement of the grapple with the tree top. Such wands should be strong enough to withstand abuse but resilient to tolerate deflection as the grapple moves into engagement with the tree top.
For harvesting logs of widely different diameters, grapples of different dimensions may be used.
Since the grapple may be subjected to blows when in use, its structure should be such as to withstand such blows.
In particular, the hydraulic hoses and couplings for the hydraulic piston/cylinder device should preferably be shielded at least to some extent by the grapple structure.
Advantageously, jaw crank arms linked to the ends of the hydraulic piston/cylinder device extend to the rear of the grapple (the "rear" meaning in a direction generally opposite the direction in which the open jaws extend, behind the bearing surface of the backplate) so that the hydraulic piston/cylinder device may be located behind the backplate.
Preferably a flange extending generally vertically centrally of the backplate from the rear surface of the backplate strengthens the grapple structure and is provided with an aperture through which the hydraulic piston/cylinder device passes. This flange affords further protection of the hydraulic piston/cylinder device.
SUMMARY OF THE DRA4~lINGS

Figure 1 is a schematic elevation view of a helicopter about to engage a topped and partially severed tree trunk with a grapple constructed according to an embodiment of the invention.
Figure 2 is a schematic elevation view of a helicopter engaging a topped and partially severed tree trunk with a grapple conforming with an embodiment of the invention.
Figure 3 is a schematic elevation view of a portion of a tree trunk showing the two cuts of the trunk required by the standing-stem logging technique for which a grapple according to the invention is useful.
Figure 4 is a schematic front perspective view of a grapple according to an embodiment of the invention, illustrated without hydraulic lines and with the grapple jaws in an open position, and including an auxiliary guide line connector.
Figure 5 is a schematic front perspective view of the grapple of Figure 4, illustrating the grapple jaws in a closed position.
Figure 6 is a rear elevation view of the grapple of Figure 4.
Figure 7 is a schematic rear perspective view of the grapple of Figure 4, with the grapple jaws in a closed position.

Figure 8 is a section view taken along line A-A of Figure 6, with the grapple jaws in a closed position.
DETAILED DESCRIPTION
Referring to Figure 1, a tree 10 has been selected for logging. Tree 10 has been topped and de-branched to the extent considered desirable, and what is left standing is a tree trunk 80 having a top portion 82 and a stump portion 84, the latter being close to the ground.
The tree trunk 80 is shown having been partially cut through by two generally horizontal sawcuts 86 and 88 on opposite sides of the trunk above what will be a residual stump 84 once the trunk 80 is harvested as a log. Once the tree 10 has been topped and de-branched, an initial cut 88 is made in the trunk extending into the trunk approximately two-thirds the diameter of the trunk. This cut 88 is preferably made against the lean of the tree . Wedges may be inserted into the cut 88 progressively as the cut proceeds. When the cut 88 is complete, the chainsaw bar is removed, and final support wedges 94 are positioned and driven to stabilize the trunk 80 at the outer peripheral portions of the cut 88.
The second cut 86 is then made preferably generally in the same horizontal plane as the first cut 88, but stopping short of the first cut so as to leave holding wood 90 between the first cut 88 and the second cut 86. Again, suitable wedges 92 are driven into the second cut 86 so as to support and stabilize the trunk 80 at the outer peripheral portions of the cut 86. The wedges 92, 94 are preferably taped in place with high-visibility tape to make them conspicuous and to help keep them in place if the tree trunk 80 rocks in the wind.
As seen more clearly in Figure 3, guide bars 96, 98 preferably constructed of plastic, aluminum, or some other material softer than the teeth of the chainsaw but providing resistance to cutting by the chainsaw, may be positioned on the tree trunk 80 to facilitate the accurate completion of cuts 88 and 86. As illustrated in Figure 3, cut 88 has been completed, but cut 86 is in progress. When cut 86 has been completed, holding wood 90 will remain, identified in Figure 3 by its section; the width of the holding wood 90 is slightly exaggerated relative to the phantom view of spacer bar (guide bar) 98 for clarity of the schematic illustration.
As mentioned above, the selection of the thickness of the holding wood 90 remaining after cuts 88, 86 are made will depend upon a number of factors, including the length and diameter of the tree trunk to be harvested, the species of tree, prevailing conditions (especially susceptibility to strong winds), moisture content, and possibly other factors, and is best empirically determined. In most cases, the thickness of the holding wood (i.e. the distance between the cut edges of sawcuts 86, 88) is between about 1/4" and about 2". Note that since most of the stabilization force is provided by the wedges 92, 94, the holding wood 90 does not itself have to offer appreciable resistance to torque applied to the trunk 80 by wind loading.
When the trunk 80 is ready for harvesting, a helicopter 12 carrying a suitable grapple 14 approaches the _g_ trunk 80. The grapple 14 is preferably suspended on a fixed-length support cable 18 (preferably made of wire rope) from attachment point 24 mounted on the underside of the helicopter 12 beneath the center of gravity 26 of the helicopter 12 (and beneath its rotor shaft). The fixed length of cable 18 is fixed only for a given harvesting situation; the cable 18 may be made longer or shorter as circumstances require. For example, if the forest canopy is relatively shallow, a shorter cable 18 may be used; if the canopy is relatively deep, a longer cable 18 can be used.
In Figures 1 and 2, the various elements are not depicted to a consistent scale. The grapple 14 is oversize relative to the helicopter 12, and the tree trunk 80 is overly short. These drawings are schematic only.
Optionally, a guide line 16 may be suspended underneath the nose 20 of the helicopter 12 on a recoilable drum or winch 74 or the like. The recoilable drum 74 maintains enough tension on the guide line 16 to maintain the unloaded grapple 14 generally vertically suspended below the nose 20 so that the pilot may more easily view the grapple 14 and bring the grapple 14 into engagement with the trunk 80.
The pilot's vision may be further facilitated by locating the drum 74 below and to one side of the pilot's seating position within the helicopter 12. Once the grapple 14 has engaged the top portion 82 of the trunk 80, the pilot closes the grapple 14 to grip the trunk 80, as illustrated in Figure 2.
Figures 4 to 8 illustrate a preferred embodiment of grapple 14 according to the invention, preferably made of steel. The grapple 14 includes a vertical backplate 106 welded to an upper horizontal cross-beam 101 and a lower horizontal cross-beam 103. A vertical flange 99 is welded to the spine of the rear surface of the backplate 106, extending generally rearwardly from the backplate 106. The flange 99 is provided with an aperture 107 whose upper limit is coincident with the upper horizontal cross-beam 101 and whose lower limit is coincident with lower horizontal cross-beam 103. For greater strength, the flange 99 may be welded to the cross-beams 101 and 103 along the surfaces of contact between the two. Additional reinforcing plates such as plates 91, 93 may be welded to two or more of the principal structural elements 99, 106, 101 and 103. (Recall that the terms "vertical" and "horizontal" are used in a relative, not an absolute, sense.
The normal operating orientation of the grapple 14 is assumed.) Between the upper horizontal cross-beam 101 and the lower horizontal cross-beam 103 are mounted vertical axles 108, 110 on which openable and closeable jaws 100, 102 are pivotally mounted. Each jaw 100, 102 is a welded composite of vertical and horizontal plates, the vertical plates being bent to the preferred configuration illustrated. The spaced upper and lower horizontal plates comprising structural portions of the composite structure of each of jaws 100, 102 extend generally rearwardly as crank arms 95, 97 respectively, each crank arin pair therefore comprising an upper and a lower horizontal component plate spaced from one another. Vertical pivot axles 120, 122 respectively pivotally connect the distal ends of crank arms 95, 97 with end bushings 85, 87 respectively at the distal ends of cylinder 104 and piston 105 respectively. The piston/cylinder hydraulic device 104, 105 is operated in conventional manner by a hydraulic pump and controls (not shown) in the helicopter 12 to which the grapple jaws operating cylinder 104 is operatively connected by means of hydraulic supply lines (not shown). Apart from the location of the cylinder 104 and its associated piston 105, and the manner of linking of the jaws 100, 102 to cylinder 104 and piston 105, the entire hydraulic arrangement can be conventional. Note that cylinder 104 is pivotally connected to jaws 100,102 at pivot axes 120, 122, but is otherwise not fixed to grapple 14; this arrangement prevents binding of operating cylinder 104 when jaws 100, 102 are opened and closed and allows asymmetrical closing of the jaws 100, 102.
Note that the aperture 107 in flange 99 accordingly extends rearwardly sufficiently to enable cylinder 104 to move rearwardly without bearing against the adjacent aperture surface of flange 99.
In use, grapple 14 is suspended from support cable 18 at attachment point 124, and may optionally also be connected to guide line 16 at attachment point 126 on bracket 128, itself removably attached by bolts and nuts to the top of flange 99. (Bracket 128 is illustrated only in Figure 4. ) Alternatively, if no guideline is required, the support line could be connected to eye 140, in which case bracket 128 would not be present. Attachment point 124 is positioned on body 99 such that the combined weight of grapple 14 and a tree trunk being carried in the grapple 14 will result in the grapple 14 hanging substantially vertically. The location and spacing of connection points 124 and 140 are selected to optimize vertical orientation of the unloaded grapple 14 with and without a guideline present. An optional counterweight 130 (Figure 4 only) may be provided to reinforce the tendency of the unloaded grapple 14 to hang substantially vertically.
Further weights may be attached if desired to grapple 14 by means of eye 83 located near the bottom of flange 99.
Optionally, a guard plate 132 (Figure 4) may be attached to the cross-beams 101, 103 to provide additional protective cover for cylinder 104 to reduce the likelihood of damage to cylinder 104.
The backplate 106 is generally vertically elongate and generally vertically oriented. It may be made of a single plate of steel suitably bent about vertical bend lines to form a generally concave bearing surface for bearing against the tree trunk (log) 80 to be gripped, the concave bearing surf ace following in a general way the curvature of the generally cylindrical trunk 80. Of course, the degree of concavity chosen for the bearing surface of the backplate 106 is necessarily a compromise, as the grapple 14 must cope with a range of log diameters. For gripping logs of widely disparate diameters, grapples 14 of different dimensions may be used.
The jaws 100, 102 are generally symmetrically disposed about the vertical center line of the backplate 106.
The jaw 100 is preferably provided with vertically spaced fingers 112, 114 offset from finger 116 of jaw 102 so as to distribute (when the grapple 14 is operating) gripping force over the vertical extension of the fingers of the grapple, and so that the fingers do not interfere with one another when the jaws 100, 102 are closed. Although three fingers 112, 114, 116 are shown by way of illustration, a greater number of fingers (or wider fingers in the vertical sense) may also be used to advantage. The grapple design including the vertically elongate configuration of back plate 106, its concavity, and the provision of vertically spaced offset fingers 112, 114, 116 on jaws 100, 102 tends to distribute advantageously the gripping force required per contact surface area to grip and hoist the log 80, and thereby to minimize the damage caused to the log 80 by the grapple 14. As a result, such grapple 14 may be used to remove logs that are to be used intact as poles. Since the tree has not been felled and the log 80 undergoes minimal damage during harvesting, a log 80 thus harvested is sound, with minimal surface damage, and preferred for a number of applications, including for use as poles to support telephone or electric power cables.
The grapple 14 may be provided with wands 118 (made of steel rod or fiberglass or the like; fiberglass provides a good combination of strength and flexibility) whose proximate ends are fixed in sockets welded or otherwise attached to fingers 112, 114, 116 as illustrated. The wands 118 extend generally horizontally outwardly from the opposed jaws 100, 102 of the grapple 14 to facilitate the visibility of the grapple 14 to the helicopter pilot and to facilitate the engagement of the grapple 14 with the tree top 82. Such wands should be strong enough to withstand abuse but resilient to tolerate deflection as the grapple moves into engagement with the tree top.
It will be appreciated by someone skilled in the art that many of the details provided above are by way of example only and are not intended to limit the scope of the invention, which is to be interpreted with reference to the following claims.

Claims (9)

1. A grapple suitable for standing-stem log harvesting comprising a) a generally vertically elongate backplate located between a pair of generally horizontally extending gripping jaws pivotally mounted generally vertically on the grapple relative to the backplate for gripping and releasing the trunk of a tree; and b) attachment means for connecting the grapple to means for suspending the grapple so that the grapple hangs in vertical operating position when suspended.

2. A grapple as defined in claim 1, wherein each of the jaws of the grapple is provided with a plurality of vertically spaced and mutually vertically offset fingers for gripping the trunk, the vertical spacing distributing the gripping force over a vertical distance so as to limit the amount of force applied to the trunk by each said finger.

3. A grapple as defined in claim 1 or 2, wherein the bearing surface of the backplate in contact with a log to be harvested is generally concave and generally arcuate in horizontal section.

4. A grapple as defined in any one of claims 1, 2 or 3, additionally including wands extending generally horizontally outwardly from the jaws, for facilitating the visibility of the grapple to the operator thereof, and for facilitating engagement of the grapple with a tree trunk.

5. A grapple as defined in any one of claims 1, 2, 3 or 4, wherein the center of gravity of the grapple is generally below the attachment means.

6. A grapple as defined in any one of claims 1, 2, 3, 4 or 5, wherein crank arms for the jaws extend generally rearward and are operated by hydraulic means located behind the backplate.

7. A grapple as defined in claim 6, further comprising a shield to protect pistons, couplings, and hoses of the hydraulic means and the crank arms from damage during use.

8. A grapple as defined in any one of claims 1, 2, 3, 4, 5, 6 or 7 additionally comprising a vertically extending flange attached to and extending generally vertically centrally along the rear surface of the backplate.

9. A grapple as defined in claim 8, wherein the flange is provided with an aperture for receiving a hydraulic piston and cylinder free from bearing contact of the flange with the piston and cylinder.