Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Tlli~ applicatioIl is divided out of copending Canadian application
No. 324~482J filed Marc}l 2~, 1979.
BACK~ROUND OF TIIE INVENTION
Tllis invention relates to log skidders or the like for dragging
heavy loads such as logs through rough terrain.
In many operations, such as timber harvesting operations, it is
often necessary to move, by dragging, loads such as logs over rough terrain.
In a timber harvesting operation, for example, the point at which trees are
felled may be quite remote from a loading point or the like. Consequently,
skidding vehicles, such as log skidders, have been utilized to drag such loads
across rough terrain from one point to another.
Many conventional log skidders in use today have fixed arch assem-
blies, that is, the boom-like assembly on the vehicle frame to which one end
of the log to be skidded is attached as, for example, by a grapple or a fair-
lead and choker assembly. Because the end of the logs to be secured to the
vehicle must be elevated to facilitate skidding, the arch assemblies extend a
fair distance above the underlying terrain and, because the logs are to be
dragged, the arch assembly is typically located near the rear of the vehicle.
As a consequence, abrupt forces caused by the logs dragging over uneven
terrain are directed to the vehicle at a relatively high location which pro-
duces rearward pitching of the vehicle and poor ground pressure distribution
of the ground engaging means of the vehicle which produces ground disturbance
and reduces traction. Obviously, rearward pitching is undesirable as an
impediment to good handling qualities of the vehicle. Poor traction is
undesirable due to its deleterious effect on vehicle handling qualities as
well as promoting the possibility that the vehicle may become mired in a par-
ticular location. A high degree of ground disturbance is likewise undesir-
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able, particularly where a ~ehicle must traverse substantially the same path
several times since, as the ground progressivcly becomes more and more dis-
turbed with each passing vehicle, traversing the path becomes increasingly
difficult.
In an attempt to at least partially overcome one or more of the
above difficulties, the prior art has resorted to pivoted arch assemblies and
at least one log skidder having a pivoted arch assembly is commercially avail-
able today. In that vehicle, the arch extends rearwardly of the vehicle when
logs are to be loaded and is pivoted forwardly on the vehicle to hoist the
logs into a skidding condition. A choker type load carrying device is
utilized and, as a consequence, the point of attachment of the fairlead when
the arch is in a skidding position is relatively high on the vehicle and
intermediate the ends of the vehicle frame. The latter factor improves weight
distribution on the vehicle which includes traction and tends to reduce ground
disturbance However, because of the high location of the point of attachment
of the fairlead, forces conveyed to the vehicle are applied thereto well above
its center of gravity so that rearward pitching movemsnts and any ground dis-
turbances caused by such movement remain as problems accompanying the use of
such vehicles.
SUMMARY OF THE INVENTION
The present invention is directed to o~/ercoming one or more of the
above problems.
According to the present invention there is provided a log skidder
or the like, comprising:
a vehicle including a frame having front and rear ends~
ground engaging means on said frame whereby said vehicle may tra-
verse the underlying terrain~
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an elollgated boom on said frame and mounted thereto for pivotal
movement about a gellerally horizolltal axis between an extended position
adjacent said rear end and a retracted position intermediate said ends;
load engaging mea]ls;
lever means mounting at one end said load engaging means and hori-
zontally pivoted at a location remote from said lever means one end to said
boom at a location spaced from said horizontal axis, said lever means one end
extending rearwardly with relation to said frame;
means on said frame for moving said boom between said position; and
means for maintaining said lever means one end directed generally
rearwardly through all positions of said boom on said frame.
Other objects and advantages will become apparent from the following
specification taken in connection wit11 the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevation of a log skidding vehicle made accord-
ing to the invention with parts broken away for clarity;
Figure 2 is an enlarged, side elevation of a boom and related struc-
ture employed on the vehicle;
Figure 3 is a rear view of the vehicle;
Figure 4 is a schematic illustrating the position of various compon-
ents of the embodiments shown in Figure 1 at various points in boom travel;
Figure 5 is a fragmentary, side elevation of a modified embodiment
of the invention; and
Figure 6 is a fragmentary, side elevation of still another modified
embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An exemplary embodiment of a log skidding vehicle or the like made
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according to the invention is illustrated in Figure 1 and is seen to include
an articulated vehicle includillg a forward frame 10 and a rearward frame 12
suitably pivotally interconnected at 14 by means well known in the art. Both
frames 10 and 12 mount ground engaging means in the form of wheels 16 so that
the vehicle can traverse the underlying terrain.
The forward frame 10 additionally mounts an engine housed in a com-
partment 18 and an operator cab 20 including suitable vehicle controls. The
rear frame 12 mounts a folding arch, generally designated 22, made according
to the invention.
10Referring to Figures 2 and 3, the folding arch 22 includes a boom
24 formed of elongated, spaced supports 26. The boom 24 is pivoted to the
rear of the frame 12 by two sets of tag links 28 and 30. The tag links 30
have their lower ends pivoted by shafts 32 to rearwardly extending plates 34
projecting rearwardly from the frame 12 and their upper ends directed for-
wardly and pivotally connected by a shaft 36 to respective lower ends of the
supports 26.
The tag links 28 have their rearwardmost ends pivoted by shafts 38
to the supports 26 intermediate the ends of the same. The opposite ends of
the tag links 28 are pivotally connected as by a shaft 40 to the plates 34.
The ~ag links 28 and 30, along with the various shafts which are all disposed
on a horizontal axis, constitute a means for pivoting the boom 24 to the
vehicle frame 12.
The opposite end of the boom 24 horizontally pivotally mounts by
means of a shaft 42, a bellcrank 44. One arm 46 of the bellcrank 44 extends
rearwardly with relation to the vehicle from the shaft 42 while another arm
48 extends forwardly in relation to the shaft 42. The rearward end of the arm
46 pivotally mounts a conventional fairlead 50. As seen in Figure 3, two of
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the bellcranks 44 are utilized, one associated with each support 26 and the
fairlead 50 extends betweell the two.
Links 52 pivotally interconnect the forwardmost ends of the bell-
cranks 44 and the fran~e 12. Specifically, each of the links 52 has one end
pivoted to the frame 12 by means of the shaft 40 and its opposite end pivoted
to the forwardmost end of the arm 48 of the bellcrank 44 by a pivot 54.
A pair of hydraulic cylinders 56, one for each of the links 52, has
its cylinder end pivoted by a pin 58 to an upstanding tongue 60 mounted on
the frame 12 and its rod 62 pivoted by a pin 64 to an associated one of the
links 52 intermediate the ends of the latter.
The forward part of the rear frame 12 mounts a conventional cable
winch 66 and a cable 68 extends therefrom through the path illustrated and
through the fairlead 50 to terminate in a choker 69 (Figure 1) which serves as
a load engaging means for, for example, logs 70. Sheaves are provided to
guide the cable through the path illustrated~ two such sheaves 72 and 74 being
clearly illustrated in Figure 3. The sheave 72 is disposed on a shaft 76 by
which the fairlead 50 is secured to the bellcrank arms 46 while the sheave 74
is mounted on the shaft 42. A similar sheave 78 is disposed on the shaft 38
and finally, a sheave 79 is located on the shaft 40.
Because the sheaves 72, 74, 78 ~ 79 are all rotatable about respec-
tive axes of the pivotal connections of the levers, links, booms and frame to
each other, regardless of the angular relation of, for example, the link 28 to
the boom 24, the length of the cable 68 between the various sheaves will re-
main constant as will the length of the cable from the winch 66 to the fair-
lead 50; and this wlll be true for all positions of the boom. Thus, once the
choker 69 is in desired proximity to the fairlead 50, subsequent movement of
the boom 24 will neither allow the choker 69 to move away from the fairlead 50
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nor l-ull the chokel (9 in~o the fairlead 50.
I`he embodiment of Figure 1 is completed by a plurality of angle
irons 80 which e~tend between and are mounted on the supports 26 over a
majority of the length of tlle latter. The angle irons 80 define a cradle, as
will be seen. Figure 1, in solid lines, illustrates the position of the arch
22 in a loading position. The choker 69 is secured to logs 70. The winch 66
may then be operated to draw the choker 69 close to the fairleads 50 so that
the log 70 will assume the dotted line position illustrated at 70'.
Thereafter, the cylinders 56 may be retracted to move the arch into
the dotted line position shown at 22' so that the logs will assume the dotted
line position illustrated at 70". In the latter position, the folding arch is
in a vehicle and the attachment of the arch to the logs is at a lowered posi-
tion disposed between the front and rear end of the vehicle and the attachment
of the arch to the logs is at a relatively low level which is much lower than
the level of attachment for an identically sized vehicle employing a prior art
arch construction. The logs will also be partially supported by the cradle
80. As a consequence, weight distribution on the vehicle tends to be more
equalized than for various prior art constructions, providing for good trac-
tion. In addition, because the point of attachment of the arch to the log is
relatively low, the center of gravity of the vehicle and its load will be
lower than that heretofore obtainable, with the result that vehicle stability
and thus handling qualities are significantly improved while ground distur-
bance is minimized.
Figure 4 illustrates, in schematic form the path of travel of vari-
ous identified points in the system. It will be appreciated that at all times.
the arm 46 of the bellcrank 44 is directed rearwardly so that the fairlead 50
is always interposed between the load and the arch 22. At the same time, as
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the arch llloves tow~rds its lowered pOsitioll forwardly on the vehicle, the
fairlead moves in a relatively higll arc to sufficiently lift the ends of the
log 70 well above the cradle surfaces 80 to prevent their snagging there-
against before the final lowered position is achieved. It will also be appre-
ciated from Figure 4 that once the apex of the path of movement of the fair-
lead 50 is reached during holding movement to the lowered position, the fair-
lead lowers relatively abruptly with minimal rear to forward movement that
could cause undesirable snagging of the logs 70 on the cradle surfaces 80 and
yet deposits the log ends on the cradle surfaces 80 to support the log ends
and provide the desired weight distribution mentioned previously.
A further embodiment is illustrated in Figure 5 and is seen to in-
clude a boom 100 formed of two elongated supports 102, only one of which is
shown. The lower end of the supports 102 are pivoted by a shaft 104 to side
plates 106 extending rearwardly from the frame 12. The upper end of the
supports 102 journal, by a shaft 108, bellcranks 110 having a rearwardly
directed arm 112 and a forwardly directed arm 114. The rearward end of each
arm 112, by means of a pivot 116, pivotally mounts a link 118 intermediate its
ends. The rearwardmost end of each link 118 pivots, by a shaft 120, the fair-
lead 50. Angle irons 124 extend between the supports 102 to form a cradle in
the same manner as mentioned previously and hydraulic cylinders 56 are pivoted
to the frame 12 and have their rods 62 pivoted by a shaft 126 to the supports
102.
A pair of links 128 pivotally interconnect the bellcranks 110 and
the frame 12. The links 128 are S-shaped and have their lower ends pivoted by
pins 130 to the plates 106 below the shaft 104 and their upper ends pivoted by
pins 132 to the ends of the arms 114 of corresponding ones of the bellcranks
110. Links 136 are pivoted by pins 138 to the links 128 intermediate the ends
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ot` the lattcr but ne.lr the upl~er ends thereof and to the forwardmost ends of
corresponling ones of tlle links 118.
Tlle cable win~ h 66 is employed as before and includes the cable 68
WlliC]I extends through the yath shown to a load engaging means in the form of
the choker 69 (not shown). Sheaves 142 at the locations illustrated assure
that when the winch 66 is not being operated, the length of cable 68 between
the winch 66 and the load engaging means will remain constant irrespective of
the position of the boom 100 with respect to the vehicle, as will be appreci-
ated by those skilled in the art. This feature provides the advantage men-
tioned previously in connection with the description of the embodiment shown
in Figures 1-4, inclusive.
As shown in Figure 5, the arch is in its loading, or uppermost posi-
tion and can be folded to a lower position located principally between the
ends of the vehicle frame. During such movement, the nature of the linkage is
such that the point defined by the pivot 120 will move slightly upwardly and
forwardly while the point defined by the pins 140 will initially move upwardly
and then forwardly and downwardly. Similarly, initially, the shaft 132 will
move upwardly with some forward movement and eventually begin to move down-
wardly. The point 138 will always move forwardly, initially with a slight up-
20 ward component and finally moving downwardly. Thus, it will be appreciatedthat the embodiment illustrated in Figure 5 provides the same advantages
enumerated previously in connection with the embodiment illustrated in Figures
1-4, ir.clusive.
Figure 6 illustrates still a further embodiment of the invention.
There is provided a boom 200 defined by two S-shaped, elongated supports 202
which are spaced. Cradle defining angle irons 204 extend between the supports
202 and the lower ends of the supports 202 are pivoted by pins 206 to rear-
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wardly extelldillg platcs 208 secured to the rear of the frame 12. Tlle plates208 also mount a cable wincll 2lO.
The upper ends of the supports 202 mount a shaft 212 which, in turn,
mounts, intermediate its ends, bellcranks 214. The bellcranks 214 each in-
clude a rearwardly extending arm 216 and the rearwardmost end thereof pivot-
ally mounts, at 218, the fairlead 50. Each of the bellcranks 214 includes a
forwardly extending arm 220 and the forwardmost and thereof mounts a shaft 222
which is pivoted to a pair of spaced links 224. The lower end of the links
224 are pivoted by pins 226 to upstanding tongues 227 adjacent the rear of the
rear frame 12.
A cable 68 extends from the winch 210 about an idler sheave 228
intermediate the ends of the supports 202, a sheave 229 supported by the shaft
212 and a sheave 230 supported by the shaft 218. Preferably, the winch 210 is
located very closely to the pivot point 206 for the lower ends of the arms 202
so that, for the reasons mentioned previously, when the winch 210 is inactive,
the length of cable 68 between the winch and the load engaging means (not
shown) will not appreciably change irrespective of the position of the boom
200 with respect to the vehicle.
Cylinders 56 are employed and are pivotally connected at 232 to the
supports 202. Figure 6 illustrates the configuration of the components when
logs are about to be loaded with the arch in its upright position. ~hen it is
desired to move the arch to its lowered position, the cylinders 56 are
retracted with the consequence that supports 202 will be pivoted forwardly
about the pivot point 206. At the same time, ~he links 224 will cause the
pivot point 222 to move upwardly and forwardly and finally forwardly and down-
wardly. At this time, the pivotal connection 218 of the bellcranks 214 to the
fairlead 50 will move downwardly and forwardly to lower the logs onto the
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cradle defilled by the ~Ingle irons 204. Again, it will be appreciated that at
all times, the arms 216 of the bellcranks 21~ will be directed substantially
entirely rearwardly to avoid undesirable, premature interference of the load
with the cradle surfaces.
With respect to all embodiments, the illustrated routing of the
cable 68 represents a preferred routing. However, those skilled in the art
will appreciate that other routes, including direct routes to the fairleads,
can be used where desired.
From the foregoing, those skilled in the art will readily appreciate
that a log skidder or similar vehicle made according to the invention mini-
mizes or eliminates problems heretofore present in terms of improving vehicle
handling capability, improving traction and load distribution, and minimizing
or eliminating ground disturbance.
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