Note: Descriptions are shown in the official language in which they were submitted.
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MEANS FOR DRIVING THE BACK WALLS OP A BUCKET EXCAVATOR
Background of the Invention
1. Field of the Invention
This invention relates to a means for driving the back walls of a
bucket excavator. More particularly, this invention relates to a
S means for driving the back wall of a bucket excavator which utilizes
a constrained chain which is engaged with two sprockets, and a
plurality o~ push rods which are pivotelly attached to the chain and to
the back walls.
` 2. Description of the Prior Art
References made to the following U.S. Patent: Satterwhite,
3,896,571, "Multi-Wheeled Excavator and Conveying System," issued
on July 29, 1975; Satterwhite, 3,897,109, "Multi-Wheeled Excavation
and Loading System," issued on July 29, 19~5.
The two Satterwhite patents show and describe an excavation
7' 15 system which incorporates several rotatable excavation wheels pr~
vided with a plurality of digging buckets disposed between each of
the wheels. Each digging bucket is provided with a cutting edge
extending slightly beyond the rim of the excavation wheel. The
cutting edge extends inward to form a stationary front wall. The
20 back wall of the digging bucket is pivotally mounted on the
excavation wheel near the surface of the front wall of the next
buclcet along the circumference of the excavation wheel. The back
wQll pivots so that its free, opposite end is adiacent its associated
front w~ll. As the excavation wheel is rotated against the material
25 to be excavated, the cutting edge collects material which is forced
inward elong the front wall and against the back wall by the later
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collected material. It is desirable to dump the collected material on
to a conveyor to remove it from the operational site. As the
excavation wheel is rotated, each digging bucket, which is now filled,
passes adjacent to a conveyor belt. While the digging bucket is
5 adjacent to the conveyor belt, it is desirable to pivot the back wall
outwardly because the movement Gf the back wall will result in the
dumping of the material from the digging bucket.
The Satterwhite patents describe several different means for
driving the back wall. One means disclosed is an unconstrained chain
10 with push rods attached at one end to the links o the chain. The
push rods are pivotally attached at an opposite end to the back wall.
The chain passes over a roller which urges the push rods outward and,
in turn, the back wall pivots outwardly along the front walls dumping
the excavated material. The chain is unconstrained and is subject to
15 all the stresses, instabilities, and breakdowns known in the art to
occur with such unconstrained systems. For example, the pivotal
connecting links are not rotatably connected to the links of the chain
and a torque will be present at the connections between the chain
links and the pivotal connecting links. Therefore, the pivotal
20 connecting links will not be aligned but rather will be twisted relative
to the direction of movement of the chains. Any jerks which occur
will not be evenly distributed down the links of the chain because of
the twisting movement.
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Summary of the Invention
The present invention involves a means for driving the back
walls of the buckets of an excavating wheel which is rotatably
mounted on a central shaft and which is provided with a plurality of
5 digging buckets arranged circumferentially around the wheel. Each
' digging bucket has a cutting edge extending beyond the rim of the
wheel. The cutting edge extends inward relative to the central shaft
to connect with a stationary front wall of the digging bucket. The
remainder of the digging bucket consists of a movable back wall.
, 10 Each back wall extends from its pivotal attachment towards the front
wall of its digging bucket. The free, opposite end of the back wall
moves along the surface of the front wall ~vhen the back wall pivots.
A central sprocket is freely rotatably mounted on a bucket
wheel hub which is mounted on the central shaft with its axis of
15 rotation being the longitudinal axis of the central shaft. A smaller
offæt sprocke~ is attached to a mounting bracket which is attached
to the main frame of the vehicle. The axis of rotation of the smaller
- offset sprocket is parallel to the longitudinal axis of the central
shaft. ~. eontinuous chain composed of links passes around the
a~ sprockets with a controlled amount of slack. Thus, the chain is
constrained to move in a predetermined path. A plurality of push
rods is provided. Each push rod is pivotally attached to a pivotal
connecting link of the chain at one end and at the opposite end to one
of the back wal~s.
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As the excavation wheel is rotated, some of the push rods
connected to the back walls pull on the chain and some will push on
the chain. This causes the chain to move which, in turn, rotates both
of the sprockets. As each push rod approaches and passes around the
S offset sprocket, the push rod will urge its associated back wall to
pivot outwardly relative to the central shaft to a material dumping
position. After each push rod has passed around the offset sprocket,
the push rod will urge its associated back wall to pivot inwardly
relative to the central shaft to a material receiving position. As the
10 excavation wheel continues to rotate each push rod will continue to
push or pul~ the chain in a cyclical pattern and will repeat the above
described operation.
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Brief Description of the Drawings
Figure la is a side view showing the left side of an excavating
t wheel with means for driving the back walls constructed according to
the present invention with portions broken away to reveal internal
details;
Figure lb is a side view showing the right side of an excavating
wheel with means for driving the back walls constructed according to
the present invention with portions broken away to reveal internal
details;
Figure 2 is a perspective view of the offset sprocket and the
mounting bracket of the bucket excavQtor shown in Figures la and
1~;
Figure 3 shows the offset sprocket's positioning on the mounting
f bracket of the bucket excavator shown in Figures la and lb;
Figure 4 shows a front view of the bucket excavator shown in
Figures la and lb with portions cut-away for clarity; and
Figure 5 is a mirror-im~ge of the excavating wheel shown in
Figures la and lb illustrating the whip-like effect imparted to the
bucket back walls by maintaining a controlled amount of slack in the
chain.
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Detailed Description of the Preferred Embodiments
As shown in Figures la and lb, an excavating wheel 10 is
rotatably mounted on a central axle or shaft 15 which would normally
extend across the front end of a vehicle (not shown) of the type
illustrated in Satterwhite Patents 3,896,571 and 3,897,109. In a
typical application of the invention there would be four excavating
wheels lO mounted on the central shaft 15 of the vehicle. The
central shaft 15 may be stationary with each wheel mounted on the
shaft bearings, that is, the shaft would not rotate with respect to the
main frame of the vehicle (as shown in the Satterwhite Patents
3,896,571 and 3,897,109). Alternatively, the shaft may rotate on
bearings in the frame and the shaft and wheel rotate at the same
speed. The excavating wheel 1~ is broadly sirnilar to any one of the
three excavating wheels disclosed in the aforementioned Satterwhite
patents. Excavating wheel 10 is provided with a plurality of
circumferentially sp~ced stationary walls 20' through 31t (hereinafter
sometimes referred to as stationary front walls). All of the digging
buckets 20 through 31 are similar in construction.
Freely rotatably mounted on the hub 12 oî the excavating wheel
ao lo is a central sprocket or sprocket wheel 34~ The hub 12 rotates on
the central shaft 15. An offset sprocket 36 is freely rotatsbly
mounted on shaft 38 (not shown in Figures la or lb) so that its axis of
rotation is parallel to the longitudinal axis of central shaft 15
although offset therefrom. A m ounting bracket 39 is attached
directly to the main frame of the vehicle by some standard method,
for example, by being bolted. The bracket 39 is best seen in Figure 2.
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Offset sprocket 36 and central sprocket 34 are aligned so that a
continuous chain 40 may pass between and around portions of the
sprocket with a controlled amount of slack in the chain. The chain is
composed of links. Certain of the links 42 through 53 (which are
spaced from each other) have push rods 54 through 65, respectively,
pivotally attached thereto. These pivotal connecting links 42 through
53 are replaceable with pivotal connecting links of a different height,
the longer the links, the faster the velocity of the back walls~
The push rods 54 through 65 extend generally outwardly relative
to the central shaft 15 and are at their outer ends pivotally ~ttached
to the pivotal back walls of digging bucke~s 20 through 31,
respectively.
As shown in Figure 2, digging bucket 25 has a cutting edge 80
which extends beyond a rim 82 of excavating wheel 10. Cutting edge
80 extends from ~nd connects with stationary front wall 25' of
digging bucket 25. L)igging bucket 25 is also provided with a pivotal
back wall 71 which is pivotally at~ached to the rear of the front wall
24' of the next digging bucket 24. The pivotal attachment of the
back wall 71 is by some standard method, for example, by providing
ears 84 on back wall 71 and on front wall 24' and providing ears 84
with holes and passing rods or bolts 86 therethrough. Back wall 71
has a dogleg shape with two straight portions 8~ and 90. Push rod 58
is pivotally attached to the back wall ~1 alor~ the straight portion
88. The pivotal attachment of push rod 58 lo straight portion 88 is by
some standard method, for example, by providing an ear 92 on
straight portion 88 and passing a threaded bolt 94 through holes (not
shown) in ear 92 and push rod 58 and placing a suitable nut on the
threaded end of the bolt 94 for connecting push rod 58 to ear 92. The
~ttachment of the pivotal back walls o~ all of the other digging
buckets, 21 through 31, to their push rods 54 through 85, respectively,
is similar to the attachment of push rod 58 to the back wall 71 of
digging bucket 25.
As best seen in Figure 4, the back wall 71 extends la terally
from one side wa~ to the other side wall, bl~t is sufficiently spaced
therefrom to allow the back wall to be freely pi~otedO The front
walls 20' to 31' of digging buclcets 20 ~hrough 31 extend from ssde
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wall 95 to the other side w~ll 95' and are ~t~ached thereto. The front
waLls also extend in a generally radial direction towards the periphery
of the wheel 10. The construction of the other digging buckets is
similar to the construction of digging bucket 25.
Returning to a consideration of Figures la ~nd lb, the exca-
vating wheel 10 is rotated by a power means (not shown) which turns
drive sprocket 9ô in a clockwise direction. The drive sprocket
engages with teeth 99 on the wheel 10, turning the wheel and the
attached buckets. The protruding cutting edges of digging buckets 20
through 31 (which are all similar to cutting edge 80 of bucket 25) will
contact and dislodge material to be excavated. This material is
forced toward the back wall of the digging bucket. This part of the
operation would ordinarily occur when the bucket wheel reached
approximately the position shown in Figure 1 for digging buckets 21,
20, 31 and 30. As the excavating wheel 10 continues to rotate, each
digging bucket will pass adjacent to a conveyor belt (not shown); at
that time it is desired to pivot the back wall to force the material
out cf the bucket so that the material can drop onto the conveyor
belt. This condition is represented by $he positions occupied by
buckets 26 and 25 in Figures 1~ and lb.
As the excavatirlg wheel is rotated, the back walls of the
buckets 20 through 31 will exert forces on the push rods 54 through
65. For example, back wall 74 will be pushing on push rod 61 while
back wall 69 will be pulling on push rod 56. These forces will, in turn,
cause chain 4û to move in ~ clockwise direction and in a predeter-
mined path around sprockets 34 and 36 causing the latter to rotate in
a clockwise direction also. The mounting bracket 39 will not move
during the operation of the excavating wheel 10 because of the fixed
attachment of the bracket to the main frame.
The back wall 71 has two extreme positions of pivotal
movement. One is its ~urthest inward point relative to shaft 15
which is shown in digging buckets 23 and 27. As the link associated
with each push rod approaches the offset sprocket 36, the back wall
of the associated digging bucket~ as shown by the back wall of bucket
25, is urged to pivot outwardly.
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The extreme outward pivotsl position of the back wall is the
material dumping position. The back wall of digging bucket 25 is
shown in the material dumping position. The material ~not shown)
which was collected while the digging bucket was in the positions
shown by buckets 21, 20 31, and 30 is dumped while the digging
bucket is in the position shown by buckets 26 and 25.
As the excavating wheel 10 continues to rotate and the link of
each push rod has, in turn, passed by offset sprocket 36 the back wall
of the digging bucket is urged to pivot inward relative to central axle
or shaft 15 towards the inward position. This is the material
receiving position of the digging bucket and the digging bucket will
remain in this position as the link of the associated push rod passes
around central sprocket 34.
The chain 40, as shown in Figures la and lb, is composed of
links which engage the teeth of sprockets 34 and 36. Thus, the chain
is constrained to follow a predetermined path of movement. Certain
of the links 42 through 53 (which are spaced from each other) have
push rods 54 through 65 respectively, pivotally attached thereto. The
slack in the chain may be increased up to a point. As the slaclc in the
chain is increased, the wrist-like or whip-like snap action of the links
42-53 increases and acceleration of the bucket back walls 66-77 is
increased. A fast acceleration of the bucket back walls 66-77 is
desirable to ensure that all of the extracted material in each bucket
is dumped. This whip-like effect can best be seen in Figure 5, which
illustrates the movernent of the pivotal links and the chain around the
sprockets. It should be noted that Figure 5 is a mirror-image of the
excavating wheel shown in Figures la and lb. The chain 40 sags
slightly as it passes between the central sprocket 34 and the offset
sprocket 36. As each pivotally connecting link 42-53 pa.sses through
this area, and in particular the upper end of each link furthest fro~n
the sprockets, its velocity is slowed slightly until just prior to
reaching the offset sprocket, each link is nearly stagnant. When each
pivotal connecting link reaches the of~set sprocket, the whip-like
effect is transmitted tD each pivotal back wall. This whip-like effect
can be seen by the series of positions back wall 71 takes prior to
reachiry~ the vertical dumping position in Figure 5~
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The amount of slack in the chain 4Q can, of course, be adjusted
by adjusting the center to center distance of the sprockets 34 and 36.
The timing of the dumping action can be advanced or retarded by
changing the circumferential position of the offset sprocket on the
5 mounting bracket 39. Increasing the length of the connecting links
42-53 will also make the action more violent.
Figure 3 shows, in isolation, the offset sprocket 36, the
~ccompanying shaft 38 and the mounting bracket 39. The offset
sproclcet is freely rotatably on the shaft 38. This assembly can be
10 secured to the mounting bracket 39 by any standard method, for
example, by bolts 98. A series of holes is provided in the mounting
bracket 39 so that the position of the offset sprocket is adjustable.
Figure 4 shows the offset sprocket 39 and the mounting bracket
39 in their positions relative to the excavating whee] 10. The
15 mounting bracket 39, the pipe lOU and the circular plate 102 are
shown in front of the central shaft 15 and the central sprocket 34 but
they are not connected.
The sprockets 34 and 36 may be of various sizes although the
diameter of sprocket 34 is preferably several times that of sprocket
2û 36; thus, the relationship between the sprockets, as shown in Figures
la and lb, can be varied. It should be noted that the teeth on offset
sprocket 36 and central sprocket 34 act as guides for the chain 40
rather than as a means of transmitting power. Therefore, other types
of guide wheels could be used.
The push rods 54 through 65 are designed so that their lengths
could be adjusted. Although Figures la and ~b show twelve digging
buckets and associated push rods, the number of digging buckets and
push rods could be more or less than twelve.
W.hereas the present invention has been descri.bed in
particular relation with the drawings attached hereto, it should
be understood that other and further m~difications, apart from
those shown or suggested herein, may be made within the spirit
an~ scope of this invention.
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