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Патент USA US3032332

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May 1, 1962
F. L. LAWRENCE
PORTABLE SPAR WITH COUNTER-BALANCE MECHANISM
FOR BIAS-MOUNTED HEAD BLOCK
Filed Nov. 17, 1960
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INVENTOR.
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BY
FIG. I
ATTORNEYS
May 1, 1962
F. L. LAWRENCE
3,032,322
PORTABLE SPAR WITH COUNTER-BALANCE MECHANISM
FOR BIAS-MOUNTED HEAD BLOCK
2 Sheets-Sheet 2
Filed Nov. 17, 1960
FIG.2
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ATTORNEYS
ire States
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Patented May 1, '1962
2
1
driven spooling drums to respective sheaves 11 and 12.
A self-aligning block 13 which carries the main sheave 11
is mounted at the head end of the spar for swivel move~
ment about a generally vertical axis, and a self-aligning
3,032,322
PORTABLE SPAR WlTH C(lUNTER-BALANCE
MECHANISM FOR BIAS-MOUNTED HEAD
BLOCK
Frank L. Lawrence, Surrey, British Columbia, Canada,
assignor to Aerialmatic Co. Ltd, a corporation of Can
ada
3,032,322
r.
Filed Nov. 17, 1960, Ser. No. 69,882
10 Claims. (Cl. 254-—190)
block 14 for the haulback sheave 12 is in turn mounted
at the head end of the block 13‘ for swivel movement
about a coinciding axis. The swivelled hubs of said
blocks are made hollow to accommodate the cables, and
the axis about which the hubs swivel is set at a moderate
10 angle from the center line of the spar in order that the
cables will pass, rub-free, through the wall opening ill.
This angularity is shown as 8°. The swivel mounting
for the main block 13 is provided by welding an adapter
pipe 15 in the head end of the spar section and ?tting this
head block having its hub journaled for swivel movement
15 pipe with a journal bushing 16 at the bottom and a thrust
about a generally vertical axis.
and-journal bushing 17 at the top.
The spar of the present invention is one in which the
' Such main block projects by its lower end moderately
swivelled hub of said ‘block is hollow and the main and
below the adapter‘ pipe. An open annular crown cam 18
haulback cables lead downwardly from the respective
is bolted or otherwise rigidlyv secured to said projecting
sheaves through the hollow center of the hub and thence
through an opening in the wall of the spar to the spooling 20 lower end with its camming surface facing downwardly.
Said camming surface is “regular,” being developed with.
drums of a yarder. The erected spar occupies substan-‘
substantially a'uniform rise in both directions between;
tially a vertical position. The spooling drums are spaced
high and low points ‘which are at 180° ‘from one another.
horizontally from the base‘of the spar and this, perforce
. This invention relates to portable spars of the type in
which the main or haulback sheaves, or both, are located
at the head end of the spar, receiving support from a
' A roller 21, journaled between the fork-arms 22 of a.
dictates for the cables a path angular to the vertical if
25 yoke for rotation about an axis radial to the cam, rides
the cables are to run rub-free between the spooling drums
on the cam and is yieldingly pressed against the latter by
and the'sheaves. To insure this rub-free path the head
a spring 23. The spring used is an open spiral spring
block’s swivel axis is biased from the vertical to bring the
opposing compression, and exerts its thrustload through
hollow center into line with the wall opening. Since
the overhang of the fairleader head block and its sheave 30 a ball-joint connection 24 to a vertical slide 25 presenting
at its upper end the yoke which supports the roller. A
establishes for such head block a weight center which is
guide 26, for vertical reciprocation of the slide along an
offset from the swivel center, the main sheave carried by
axis paralleling the swivel aXis of the block 13, is made
the head block normally tends to gravitate into an estab
an integral part of the spar section.
lished position. This is perforce undesirable when the
direction in which the main cable runs out from the spar 35 ' Considering “low” and “high” as the cam. surface which
is remote or proximate, relatively speaking, to the level
is angular to the direction in which the sheave points by
force of gravity. A con?ict arises between the pull force
exerted on the head block by the main cable, to align the
head block with the vertical plane in which the cable is
working, and the countering force of gravity. This
causes the cable to drag against a ?ange of the sheave,
developing frictional losses and increasing wear on the
occupied by a stationary bottoming disk 27 from which
the spring 23 takes its purchase, the roller is so located
that it rides upon the high point 28 of the cam when the
main sheave 11 hangs in a position dictated by gravity.
This is the position in which the sheave is shown in the
drawing. As the vertical plane of the sheave shifts to
upon a head block swivelled to turn about a biased axis.
' line runs out from the spar at 180° to the initial position.
one side‘or the other in consequence of running the
cable, the sheave, and the journals.
main line on a course angular to said gravity-dictated
The present invention has for its general object to
provide a portable spar of the nature described embodying 45 plane, the roller responsively works toward the cam’s low
point 29, ultimately occupying the latter when the main
a mechanism counterbalancing force of gravity imposed
This and other more particular objects and advantages
will appear and be understood in the course of’ the fol
lowing description and claims,‘ the invention consisting so
in the novel construction and in the adaptation and com
bination of parts hereinafter described and claimed.
In the accompanying drawings:
body the preferred teachings of the present‘ invention.
- FIG. 2 is a fragmentary elevational view thereofrinclud
ing an illustration of the main and haulback sheaves which
surmount the spar, the scale being reduced from that of
FXG. l; and
FIG. 3 is a fragmentary vertical sectional view em
ploying the same scale as that of FIG. 1 and detailing
The maximum turning moment which the roller exerts
obtains when the cam has moved 90°, the slope of the
cam then being at its maximum. The directional in?uence
’
FIGURE 1 is a fragmetary vertical sectional view illus
trating the head end of a portable spar engineered to em
The turning moment exerted upon the cam by the spring
loaded roller is perforce zero at either of these points in
that the roller is occupying a level surface, so to speak.’
of this turning moment is perforce toward the low point
55
29 and the design of the cam is such that this moment
equals the oppositely directed turning moment due to the
o?-center mounting of the main sheave block.
The load exerted by the spring upon the cam is ap
proximately equal to the total weight of the main and
the haulback sheave assemblies plus an allowance for
the weight of the cable carried by each sheave. The cam
is designed so that, as the main sheave block shifts to any
the thrust-and-journal mounting ‘for the upper end of the
head block’s swivelled hub.
Referring to said drawings, the numeral 5 designates
position, the spring-loaded roller 21 exerts upon the
dation of main and haulback cables running from power
tion at right angles thereto.
cam a turning moment equal to the turning moment which
re?ects the degree to which the weight center of the sheave
assembly is laterally removed from a plane radial to
the hollow upper section of a portable spar. Stabilizing
the swivel axis of the sheave block into which said weight
guy lines (not shown) run from stumps or other suitable
center normally tends to move by the in?uence of gravity.
ground anchors to connectors 6 hung from an anchoring
This turning moment, to reiterate, varies from zero when
ring 7 which surrounds the spar section and bears upon a
thrust ring 8 welded or otherwise ?xedly secured to the 70 the main sheave block occupies either the position in
which it is shown or lies diametrically opposite there
spar section. Below said thrust ring an elongated open
from,
and increases to maximum when moved to a posi
ing it} is provided in said spar section for the accommo
3,032,322
3
It is believed that the invention and the manner of its ‘
working will have been clearly understood from the fore
going detailed description of my now-preferred illustrated
embodiment. Changes within the spirit of the invention
from the spar upon the block a force component work
ing counter to said force of gravity.
6. In a spar, in combination with a head block carried
for swivel movement by the spar with its swivel axis so
placed as to be biased from the vertical upon erecting
the spar to have the same occupy a predetermined posi
tion and having mounted upon said block a self-aligning
will suggest themselves. It is my intention that no limita
tions be implied and that the hereto annexed claims be
given the broadest interpretation to which the employed
language fairly admits.
sheave characterized in that its weight distribution in said
What I claim is:
erected condition of the spar is oil-center in relation to
1. In combination with a portable spar having a hol 10 the swivel axis and hence imposes upon the sheave a
low top section provided with an opening in the wall,
gravitational force tending to swing the sheave in one di
a block having a hollow hub journal-mounted in the head
rection, co-acting spring-loaded means carried by the spar
end of said top section above the wall opening for swivel
and the block exerting from the spar upon the block a
movement about an axis so biased from the vertical center
force component approximately counter-balancing said
of the erected spar that a cable will pass rub-free from 15 force of gravity.
the hollow center of the hub through said wall opening
7. In a spar, in combination with a head block carried _.
to the spooling drum of a yarder occupying a ground
‘for swivel movement by the spar with its swivel axis so ':
position adjacent the base of the spar, a self-aligning
placed as to be biased from the vertical upon erecting '
sheave over which said cable is fed to said hollow center of
the spar to have the same occupy a predetermined posi
the hub carried by the block ‘and in?uencing the latter 20 tion and having mounted upon said block a self-aligning
when the spar is approximately vertical to gravitate in
one direction by oft-center distribution of weight, and
means operatively connected with the block exerting there
sheave characterized in that its weight distribution in said
erected condition of the spar is oft-center in relation to
the swivel axis and hence imposes upon the sheave a
on a force counter-balancing said force of gravity.
gravitational force tending to swing the sheave in one
2. Structure according to claim 1 in which said block 25 direction, co-acting means one carried by the block and
is given a journal mounting at its lower end and a thrust
the other by the spar exerting upon the block a turning
and-journal mounting at its upper end.
'
moment working counter to said force of gravity, one
3. In combination with a portable spar having. a hol
of said means comprising a crown cam ?xed to said mem
low top section provided with an opening in the wall, a
ber by which it is carried in a position concentric to said
block having a hollow hub journal-mounted in the head
swivel axis of the block.
end of. said top section above the wall opening for swivel
8. A spar according to claim 7, said means which co
movement about an axis so biased from the vertical center
acts with the cam comprising a roller riding on said cam
guided for reciprocal movement in. a direction paralleling
of the erected spar that a cable will pass rub-free from
the hollow center of the hub through said wall opening
the swivel axis of the ‘block, and a spring under compres
to the spooling drum of a yarder occupying a ground
sion-loading pressing said roller against the cam.
9. Structure according to claim 7, said cam being a
position adjacent the base of the spar, a self-aligning
sheave over which said cable is fed to said hollow center
regular cam developed so that the counter force exerted
is a turning moment approximately equaling the turning
of the hub carried by the block and in?uencing the latter
when the spar is approximately vertical to gravitate in one.
moment due to said oft-center distribution of weight.
10. In a spar, in combination with a head block car
direction by o?f-center distribution of weight, a crown cam 40
ried for swivel movement by the spar with its swivel axis
?xed to said block concentric to the swivel axis, the de
velopment of said cam being regular with a single high
so placed as to be biased from the vertical upon erecting
and low point placed diametrically opposite to one an
the spar to have the same occupy a predetermined posi
tion and having mounted upon said block a self-aligning
other, and a spring-loaded roller bearing against said
cam and so placed as to occupy the high point of the cam 45 sheave characterized in that its Weight distribution in
said erected condition of the spar is off-center in relation
when the sheave is pointed in said direction in which
it is gravitationally in?uenced.
to the swivel axis and hence imposes upon the sheave a
gravitational force tending to swing the sheave in one
4. Structure according to claim 3, said roller being
guided for reciprocal motion along an axis paralleling the
direction, a crown cam ?xed to said block concentric to
swivel axis of the block, the spring load being imposed 50 the swivel axis, the development of said cam being regu
through a ball-and-socket joint.
lar with a single high and a single low point placed
diametrically opposite one another, and a spring-loaded
roller carried by the spar bearing against said cam and
5. In a spar, in combination. with a head block carried
for swivel movement by the spar with its, swivel axis so
placed as to be biased from the vertical upon erecting
the spar to have the same occupy a predetermined posi
so placed as to occupy the high point of the cam when
55 the sheave is pointed in said ‘direction in which it is gravi
tion and having mounted upon said block a self-aligning
sheave characterized in that ‘its weight distribution in said
erected condition of the spar is off-center in relation to the
swivel axis and hence imposes upon the sheave a gravita
tional force tending to swing the sheave in one direction, 60
co-acting means carried by the spar and the block exerting
tationally influenced.
References Cited in the ?le of this patent
UNITED. STATES PATENTS
964,035‘
Lombard ____________ .._ July 12, 1910
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