Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
In lumbering operations it becomes necessary, after trees are cut,
to move the felled logs from the area where they have fallen to a
location near a road where they can be loaded and carried away. One way
in which this has been done is to move into the area with a tractor-like
vehicle and simply drag the logs to the road. This is often an unaccept-
able method because of damage to the terrain and to young trees caused
by the vehicle and the dragging of the logs. In many areas the terrain
is too rough for such vehicles to operate successfully.
A more acceptable ~echnique and one which has been used in many
forms for years involves the use of logging systems with skylines
extending from a yarder machine over many hundreds of feet to a tail
block with a carriage movable back and forth on the skyline between the
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yarder and the tail block for transporting the logs to a road near the
yarder. The yarder itself is typically a large and heavy vehicle with
a prime mover of 300 to 500 horsepower or more, a tower with fairleader
sheaves, various drums with cable of-different sizes, and clutches and
brakes for controlling the reeling of the cable or wire rope off or on
the drums and through the various fairleader sheaves. A typical yarder
may be capable of being set up to operate with several kinds of rigging
arrangements. One such arrangement is called grapple yarding and is
described in detail in U. S. Patent No. Re. 27621 (common assignee).
In this system a '7running skyline" is rigged from a skyline drum through
a fairleader sheave at the top of the tower out to a tail stock and back
to a stationary terminal on the far side of the carriage from the
yarder, the carriage having one or two sheaves riding on the skyline.
A separate mainline has both ends connected to mainline drums on the
lS yarder and passes around a sheave on the carriage. A tag line attached
to one of the mainline halves passes over a load sheave on the carriage
and is connected to trip a grapple which is suspended from the carriage
to cause it to close to pick up a turn of logs or to open to drop the
logs. Normally, the skyline is slackened to cause the grapple to lower
toward the logs and is tightened to lift the load before the carriage
is caused to move toward the yarder.
A somewhat similar arrangement is described in U. S. Patent No.
3,531,000 (common assignee) but is used for operation with chokers. In
this system, a crew in the field attaches a choker cable to a turn of
logs, and the carriage is lowered by slackening the skyline so that the
choker cable may be attached tv the carriage or to a line suspended from
the carriage. In either of these arrangements, the yarder must include
the drums mentioned above, and such drums are sized differently because
the skyli~e and mainline cables are usually of different size. Some
rigging a~rangements require three different sizes of cable. The cables
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are typically wound twelve or more layers deèp on the drums which means
that the effective diameters of the drums vary as they are wound and
unwound with accompanying changes in forces and speeds connected wîth
cable movement. To deal with these changes the yarder operator is
required to operate various brakes and clutches which absorb substantial
energy and which also require considerable operator skill. The winding
of many layers of cable on the mainline drums also results in some wear
on the cables due to crushing and abrasion.
IN THE DRAWINGS
Figure 1 is a perspective view of a yarder rigged according to
our invention;
Figure 2 is a schematic diagram showing details of the rigging
arrangement of Figure l; and
Figure 3 is a plan view of a yarder according to our invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIME~T
Referring now to Figure l a yarder, shown generally at numeral
10, carries a tower 12 to which are attached a skyline fairleader 14,
an outhaul fairleader 16, and an inhaul fairleader 18. Additional
pulleys or sheaves 20 and 22 are attached to the tower. Attached to
an arm at the forward end of the yarder is a strawline sheave 24. The
tower 12 is supported by a plurality of guylines 25. Carried on the
frame of the yarder 10 is a storage and skyline drum 26J a separate
tram or drive drum 28 and an idler drum 3p. Drums 26, 28 and 30 are
driven by an engine carried on the yarder and controlled as discussed
below. The skyline cable 32 is anchored on the drum 26 and feeds from
this drum through fairleader 14 from which it extends outwardly to a
carriage 34 and back around drums 28 and 30 and outwardly to support
carriage 34 and from thence through a tail block 36, a tail hold 38,
back through a sheave 40 on carriage 34 to an anchor 42.
Details of this rigging arrangement may be more apparent from
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consideration of Figure 2. In this schematic drawing the skyline and
storage drum 26 has one end of the skyline cable.32 anchored thereto,
and from this drum the cable extends outwardly through the skyline
; fairleader 14, outwardly and around a sheave 44 on the yarder side of
the carriage 34, back around the inhaul fairleader 18, sheave 20, under
the idler drum 30 to wrap several times around tram drum 28 and idler
drum 30, passing around sheave 22, back up the tower to the outhaul
fairleader and outwardly through the carriage 34 where it passes under
a pair of sheaves 46 and 48, thereby support mg the carriage. Continuing
outwardly to tail block 36, it passes around this sheave, another sheave
in tail hold 38 and back toward the carriage where it passes around a
sheave 40 before bein~ dead-ended at an anchor 42.
Prom ~ollowing this arrangement, it is apparent that a single
cable extending between the storage drum 26 and anchor 42 provides the
skyline,haulback and mainline functions requiring three separate cables
of different sizes in conventional rigging arrangements. A plurality
of choker cables 50 are shown suspended from carriage 34, and when it
is desired to lower the carriage to pick up a log 52, the skyline and
storage drum 26, along with tram drum 28, is rotated to reel out cable
which causes slack in the skyline, thus lowering the carriage to permit
the choker cables to be attached to the log 52. A number of logs might
be attached to the choker cables, if located such as to be convenient.
The iog can then be lifted by tightening the skyline--a reversal of the
drum rotation previously described--and transported back to the vicinity
of the yarder 10 by holding the storage drum 26 and rotating tram drum
28 and idler drum 30 in such direction (clockwise as shown) as to pull
sheave 44 toward the yarder while at the same time cable is reeled off
the top of the drum 28 to feed more cable through the carriage and
sheaves 36 and 38 to allow sheave 40 to move to the left. The log can
be moved downwardly by slackening the skyline as described. When the
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skyline is again tightened, the carriage may be moved outwardly by
holding the storage drum 26 and rotating tram drum 28 and idler drum 30
counterclockwise, which reels in on that part of cable 32 upon which
the carriage rides, thus pulling sheave 40 to the right. At the same
S time that part of the cable passing over sheaves 20 and 18 is reeling
out, thus permitting sheave 44 to move toward the right.
It will be observed that the arrangement involving tram drum 28
and idler drum 30 is somewhat unconventional since line 32 is wound
around both drums together. Thus they are not operated differentially
as is customary with yarders. It is also conventional for the corres-
ponding drums (usually called mainline drums) to each have one end of
a mainline cable anchored thereon. In the arrangement described herein,
neither of drums 28 and 30 ever contacts either end of cable 32, which
ends are on drum 26 and at anchor 42. Since these drums 28 and 30 are
lS not storage drums, they carry only one layer of cable, and so there is
no problem with varying effective drum diameters with the resulting
different speeds and torques. Thus the operator is relieved of a sub-
stantial problem in operating brakes and clutches to compensate for
these different diameters. The energy dissipated in the conventional
clutching and braking operation is not lost, and the power requirements
of the system are, therefore, reduced. The size of the drums 28 and 30
is less than for the usual mainline drums because they only carry one
layer of cable, and the usual deep flanges are eiiminated. Applicants
have referred to the rigging system described above as an endless cable
system or a tram system because the drums 28 and 30 and the carriage 34
are always in an intermediate position along the same line. Drum 28,
referred to as the tram drum, might be considered as in the nature of a
capstan since it is driven, has only one layer of cable, and, in
combination with idler drum 30, primarily provides a frictional holding
means for cable 32.
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Figure 3 is a plan view showing the showing the arrangement of
drums and driving mechanism on the yarder 10. A prime mover 54, located
at the rear of the yarder twhich may be a diesel engine using a trans-
mission or hydrostatic drive) drives a sprocket 56 which, in turn,
drives a chaln 58 meshing with a sprocket 60. Sprocket 60 drives a
cross shaft 62 having a gear 64 at its opposite end which meshes with ,
a first gear 66 which drives the storage and skyline drum 26 through a
clutch 68 and a second gear 70 which drives tram drum 28 through a
clutch 72. Conventional band brakes 74 and 76, which are normally air-
io operated, are available for holding drums 26 and 28, respectively.Gear 70 meshes with a smaller gear 78 at the end of a cross shaft
which drives a straw drum 80 through a clutch 8l~. Straw drum 80 carries
a length of comparatively lightweight wire rope which can be handled
manually and which is used ~or rigging in a conventiona] manner familiar
to those skilled in the art. Idler drum 30 has an axle journaled in a
- frame of the yarder 10 carrying a number of grooved sheaves 82, all of
which float on the axle. This permits individual sheaves to rotate
slightly relative to others as needed to relieve stress in the cable
as it wraps around the drum.
With the clutches and brakes shown on the drums 26 and 28, the
operator may operate the skyline drum 26 and drum 28 to lower or raise the
carriage, or hold drum 26 while rotating drum 28 to move the carriage
along the skyline, as described above. Since there is no problem with
different effective diameters with drums 28 and 30, however, there is no
occasion to operate these drums differentially, and so no dealing with
separate clutches and brakes on each as is done with a conventional
mainline arrangement. Thus the losses in these brakes are eliminated,
the cooling water therefor is eliminated, one set of clutches and
brakes is eliminated entirely, and the drums become smaller because
they are ~ot storage drums. The effect of these differences is to
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significantly reduce the power required to drive the system, permitting
use of a smaller prime mover and a somewhat smaller yarder chassis than
required to do the same job with conventional equipment.
Those skilled in the art will recognize ~hat certain modifications
may be made to suit requirements. While use of both of blocks 36 and
38 helps to assure that the cable does not become fouled, operation with
a single tail block is quite possible.
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SUPPLEMENTARY D!SCLOSURE
Reference will now be made to two alternative embodiments of
yarders according to the invention, with reference to the following two
additional Figures:
Figure 4 is a plan view of a further embodiment of a yarder
according to the invention; and
Figure S is a plan view of a still further embodiment of a yarder
according to the invention.
The embodiment shown in Figure 4 is similar to that of Figure 3,
10 and identical numerals are used for corresponding parts. Operation is
similar to Figure 3 except that sheaves 82 do not float on the shaft of drum 30
but are keyed thereto and are driven by a gear 86 which is driven by gear 78.
Gear 86 drives drum 30 through a clutch 88. A conventional band brake 90 is
supplied for holding drum 30. With this arrangement the cable 32, which is
wrapped around both of drums 28 and 30, as described, is driven by both oF
sa7d drums. Since the amount of wrap of the cable subject to being driven is
thereby approximately doubled, somewhat fewer turns of the cable around
drums 28 and 30 are required to avoid slippage.
In Figure 5 an embodiment is shown in which drums 28 and 30 are
20 again driven directly and simultaneously as in Figure 4, but wherein a single
holding brake for drums 28 and 30 and a single clutch are carried on the drive
shaft. This provides an operation similar to that of Figure 4, but at some
saving In components. Again similar parts have been given the same numbers.
As previously described, the prime mover 54 drives an output shaft and gear S6
connected through a chain 58 to a gear 60 and one end of a cross-shaft 62. At
the other end of cross-shaft 62 is a gear 64 meshed with a gear 66. Drum 26
is driven when a clutch 68 is engaged.
Also carried on cross-shaft 62 is a third gear 92 driving a chain
94 engaged with a gear 96 on one end of a second cross-shaft 98. At the
30 opposite end of cross-shaft 98 is a gear 78 which is connected to drive both of
gears 70 and 86 and drums 28 and 30 when engaged by a clutch 100. Band
brakes 102 are associated with clutch 100 to hold drums 28 and 30 when desired.
`~ At the opposite end of cross-shaft 98 is positioned a straw line drum 80 which
is engaged through operation of a clutch 84.
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Those skilled in the art will recognize that certain modifications
may be made to suit requirements. While use of both of blocks 36 and 38
helps to assure that the cable does not become fouled~ operation with a single
tail block is quite possible.
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