Note: Descriptions are shown in the official language in which they were submitted.
~ 9208
SURFACE MINING SHOVEL
This application is a continuation-in-part of co-pending
application serial no. 08/237,955, filed May 3, 1994, which is
incorporated herein by reference and which is a continuation-in-
part of application serial no. 07/803,839, filed December 9,
1991, now abandoned.
BA~KGROUND OF THE INVENTIQN
Field of the Invention
The invention relates to surface mining shovels.
Discussion of Prior Art
The most common type of surface mining shovel, usually
referred to as an "electric" shovel, is typified by the P&H Model
4100 (P&H Mining Equipment; Milwaukee, Wisconsin). An electric
shovel includes a frame which is supported on a set of crawler
tracks for movement across the ground. A machinery house is
mounted on the frame and houses electric swing motors and gear
drives for revolving the frame on the crawler tracks. The
machinery house also houses a hoist drum and an associated
electric motor and drive gears for rotating the hoist drum. An
operator's cab is mounted on the machinery house. A gantry
support extends upwardly from the frame. The lower end of a long
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fixed boom is mounted on the frame, and boom supports extend from
the gantry support to the outer end of the boom for supporting
the boom in a fixed position relative to the frame. A sheave is
mounted on the outer end of the boom. A rack and pinion crowd
mechanism is supported on the boom at a position intermediate the
ends of the boom. The crowd mechanism supports the inner portion
of an elongated dipper handle for translational movement relative
to the boom. The crowd mechanism is driven by electric motors
and is operable for translating or crowding the dipper handle
relative to the boom in the direction along the longitudinal axis
of the dipper handle. A two-part dipper, including a body and a
door, is rigidly mounted on the outer end of the dipper handle.
A hoist rope is connected to the dipper, is reeved over the
sheave and is wound around the hoist drum for raising and
lowering the dipper. A control mechanism such as a pull rope is
connected from the operator~s cab to the dipper for opening a
catch to permit the door o~ the dipper to swing open by gravity
for emptying earth material from the dipper.
A variation of an electric shovel is disclosed in U.S.
Patent 3,465,903 to Wilson. The shovel disclosed therein
includes a relatively short boom. An elongated triangular handle
is mounted intermediate the ends thereof for pivotal movèment
about a toggle joint at the outer end of the boom. A front dump
bucket is mounted on the lower end of the handle and a sheave is
mounted on the upper,end of the handle. One end of a hoist rope
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is fixed to the gantry, and the hoist rope is reeved'around the
sheave on the handle and another sheave mounted on the gantry,
and the other end of the hoist rope is wound around a hoist drum
for pivoting the handle relative to the boom. An electrically
powered rope crowd mechanism is connected to the toggle joint at
the handle pivot point for imparting a horizontal crowd component
in the motion of the bucket. A tilt mechanism is mounted on the
handle for tilting the bucket relative to the handle. The tilt
mechanism includes a primary link which is pivotally mounted on
the handle intermediate the ends of the primary link, a hydraulic
assembly which is connected between the posterior end of the
primary link and a pin in the outer end of the boom, and a link
which is connected between the anterior end of the primary link
and the top of the bucket.
A second type of surface mining shovel, commonly referred to
as a "hydraulic~ shovel, is typified by the P&H Model 2250
Series A (P&H Mining Equipment; Milwaukee, wisconsin). A
hydraulic shovel includes a frame which is supported on a set of
crawler tracks. A machinery house is mounted on the frame and
houses hydraulic swing motors and gear drives for revolving the
frame on the crawler tracks. The lower end of a short boom is
mounted on the frame for pivotal movement about a first
horizontal axis. A first set of hydraulic assemblies extends
from the frame to the boom for supporting and pivoting the boom
relative to the frame. The inner end of a short arm is connected
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to the outer end of the boom for pivotal movement about a second
horizontal axis. A second set of hydraulic assemblies extends
from the boom to the arm for supporting and pivoting the arm
relative to the boom. A two-part bucket having a door and a body
is mounted on the outer end of the arm for pivotal movement about
a third horizontal axis. A third set of hydraulic assemblies
extends from the arm to the bucket for tilting the bucket
relative to the arm. A suitable bucket opening mechanism, such
as a set of hydraulic assemblies, is connected between the door
and body of the bucket for opening the bucket to empty material
therefrom.
SUMMARY OF THE INVENTION
A disadvantage of some electric shovels is that the rack and
pinion crowd mechanism is heavy and is relatively expensive to
construct and maintain. In particular, maintenance of a rack and
pinion crowd mechanism requires considerable specialized training
of the maintenance personnel.
An additional disadvantage of electric shovels which have a
rack and pinion crowd mechanism is that when crowd force is
applied to move the dipper into the earth material, an opposing
force is transmitted back to the boom and can cause the boom to
pivot back or ~jack~ relative to the frame. Boom jacking can
lessen the effectiveness of the hoist mechanism. Boom jacking
also creates high stresses on the boom supports, which absorb the
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}IA}W9095 .CIP
force transmitted back through the boom, and on the hoist rope.
Boom jacking can also limit the amount of crowd force which is
actually applied to the dipper.
Another disadvantage of electric shovels which have a rack
and pinion crowd mechanism is that the location and manner of
operation of the crowd mechanism prevents the extension of
hydraulic fluid lines from the frame to the dipper to provide
hydraulic fluid to hydraulic apparatus which articulates the
dipper relative to the dipper handle.
A disadvantage of other electric shovels is that the rope
crowd mechanism is relatively complex to construct and expensive
to maintain. This is an especial problem when the rope crowd
mechanism is designed to apply force in opposite directions.
Another disadvantage of electric shovels is that the boom is
supported in a fixed position and cannot be pivoted relative to
the frame.
A further disadvantage of electric shovels is that the
dipper is rigidly fixed on the dipper handle and cannot be
articulated relative to the dipper handle in order to control the
attitude of the dipper relative to a bank or the ground for
scooping material therefrom. The fixed position of the dipper
relative to the handle is a particular problem which causes low
fill factors when digging from a low bank or from the low portion
of a bank. A related disadvantage of electric shovels is that a
relatively long digging stroke is required to fill the dipper, so
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the dipper must be supported by a long handle and boom. The
fixed position of the dipper relative to the handle also prevents
effective use of the dipper for ground level cleanup, because the
dipper cannot be moved in a long horizontal path along the ground
for scooping material therefrom without also digging down into
the ground. Because of this limitation, an auxiliary piece of
equipment, such as a front end loader, is often used for ground
level cleanup around an electric shovel. Another disadvantage of
the fixed position of the dipper relative to the handle is that
the dipper cannot be used to pry or loosen packed material from a
bank.
Another disadvantage of electric shovels is that the dipper
is very heavy and complex and is expensive to construct and
maintain. A related disadvantage is that because the dipper is
very heavy, consequently, the shovel as a whole is very heavy.
In particular, the handle and boom must be very large in order to
support the dipper. As a result, the shovel requires relatively
large counterweights and when swinging is subject to large
inertial forces. Accordingly, the components of the swing and
drive systems must be very large in order to bear the inertial
forces. Another related disadvantage is that the center of mass
of the lifting attachment of an electric shovel is far from the
centerline of rotation of the frame, so the payload or capacity
of the dipper is relatively small in proportion to the weight of
the lifting attachment.
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Another disadvantage of electric shovels is that the dipper
handle must be supported at a relatively high position on the
boom in order to accommodate the long handle and to permit the
dipper to clear the side of a waiting truck for emptying the
load. A related disadvantage is that the material to be dumped
will hang up or remain in the dipper when the dipper is pivoted
too low above the truck. Also, it is easy to raise the dipper
too high and to dump the material from too far above the truck,
and thus to cause significant shock or damage to the truck.
A disadvantage of hydraulic shovels is that the lifting
attachment, including the boom, arm, bucket and associated
hydraulic components, is very heavy, and the weight of the
lifting attachment decreases the lifting capacity, upward digging
force and/or digging radius of the shovel. The combination of
hydraulic components supporting the boom, arm and bucket do not
provide dead weight lifting capacity comparable to that provided
by the rope hoist of an electric shovel.
Another disadvantage of hydraulic shovels is that
sufficiently large hydraulic components operating at high
pressures have been perceived as being unreliable for high duty
cycle applications, such as mining.
Another disadvantage of hydraulic shovels is that the front
end of the frame can be lifted off the ground when digging by
forces transmitted through the arm and boom. The arm and boom
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and associated hydraulic components are rigidly interconnected
and transmit shock back to the frame.
An additional disadvantage of hydraulic shovels is that the
combination of hydraulic components supporting the boom, arm and
bucket is relatively complex to operate when digging. The
lifting attachment of a hydraulic shovel has three degrees of
motion which must be controlled, whereas the lifting attachment
of an electric shovel has only two degrees of motion, and
accordingly hydraulic shovels are more complex to operate than
electric shovels. Further, simultaneous movement of all the
hydraulic components is frequently necessary for digging with a
hydraulic shovel.
The invention provides a power shovel that does not suffer
from the foregoing disadvantages. The power shovel includes a
frame and a gantry support which extends upwardly from the frame.
A first rotatable sheave is mounted on the upper end of the
gantry support. A short boom extends upwardly from the frame and
is mounted for pivotal movement relative thereto. A banana-
shaped handle or arm is mounted on the upper end of the boom for
pivotal movement relative thereto about an arm pivot axis. A
hydraulic crowd mechanism is connected between the gantry support
and the boom and is operable for pivoting the boom relative to
the frame. The hydraulic crowd mechanism is connected to the
boom at a point which is spaced from the arm pivo~ axis about 1/3
of the distance along the boom. The arm pivot axis is
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intermediate the upper and lower ends of the handle. A second
sheave is mounted on the upper end of the arm. A large front
dump bucket is mounted adjacent the lower end of the arm for
tilting movement relative thereto. A bucket tilting mechanism is
connected to the bucket and is operable for tilting the bucket
relative to the arm. The bucket tilting mechanism includes a Z-
type linkage having an elongated primary link which is pivotally
mounted on the arm, a hydraulic assembly which is connected
between the first end of the primary link and the arm pivot
point, and a secondary link which is connected between the second
end of the primary link and the bucket. A hoist mechanism is
operable for pivoting the arm relative to the boom about the arm
pivot axis. The hoist mechanism includes a rope which is wound
around a hoist drum and which is reeved over the first and second
sheaves and fixed to the gantry support.
In operation of the shovel, the operator has the option of
penetrating the material with the bucket by operating the hoist
mechanism to pivot the arm relative to the boom and move the
bucket along a constant radius arcuate path, by operating the
hydraulic crowd mechanism to pivot the boom relative to the frame
and move the bucket along a substantially linear path, or by
operating both the hoist and the hydraulic crowd mechanism in
order to move the bucket along an optimal path. After the bucket
has penetrated the material, most of the digging and lifting
force is provided by operation of the hoist to pivot the arm
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2~ 992~8
relative to the boom. The hydraulic crowd mechanism can be
operated simultaneously with the hoist in order to move the
bucket in the horizontal direction, especially when digging at
ground level near the frame. The bucket can be articulated
relative to the arm for efficiently and quickly filling the
bucket and for emptying the bucket.
The inventors have recognized that it is sufficient for the
hydraulic crowd mechanism and boom to provide a relatively small
crowding moment to the arm pivot point in order to cause the
bucket to penetrate into the earth material and, accordingly, the
boom is very short. Operation of the hoist to pivot the arm
relative to the boom provides a large moment to the bucket for
penetrating the material. The mass of the boom and arm also
contribute to generating crowd force. The hydraulic crowd
mechanism serves primarily to pivot the boom and thus to adjust
the position of the arm pivot point relative to the frame (i.e.,
to adjust the digging radius), and to support the boom in a
static position relative to the frame during operation of the
hoist to pivot the arm for digging.
The power shovel has a hydraulic crowd mechanism and thus
does not suffer the disadvantages of constructing and maintaining
either a rack and pinion crowd mechanism or a rope crowd
mechanism. The hydraulic crowd mechanism is relatively simple
light and inexpensive to construct. The hydraulic crowd
mechanism also is simple and inexpensive to maintain,
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particularly because the crowd mechanism will be used primarily
only for positioning the arm pivot point to adjust the digging
radius. The hydraulic crowd mechanism supports the boom relative
to the frame and prevents boom jacking. The hydraulic crowd
mechanism is connected at a point spaced from the outer end of
the boom, and the gantry support which braces the hydraulic crowd
mechanism is mounted near the boom, in order to utilize a
relatively short hydraulic crowd mechanism and to thus provide
adequate operational speed.
The front dump bucket can be articulated relative to the arm
for efficiently digging and for quickly filling the bucket with a
short digging stroke, for versatility in digging, and for
clearing the side of a waiting truck. Accordingly, the arm and
boom are not excessively long. The front dump bucket is
relatively lightweight, and the arm is mounted or balanced on the
boom intermediate the ends thereof, so a large boom is not
required for supporting the arm and bucket. The center of mass
of the lifting attachment is relatively close to the frame, so
the shovel is lighter than an electric shovel having a comparable
digging capacity. The shovel requires less counterweight and
generates lower inertial forces when swinging than an electric
shovel, and also has a lower moment on the boom when the arm is
pivoted in the vertical direction, so the drive and swing
components can be lighter and less expensive. The lightweight
front dump bucket is relatively large. The lightweight front
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2 t q9208
dump bucket also is inexpensive to construct and maintain, and
the lightweight boom also is relatively inexpensive to construct.
The power shovel includes a hoist mechanism for pivoting the
arm, so the weight of the hydraulic components does not
substantially decrease the lifting capacity, upward digging force
or digging radius of the shovel. The hoist mechanism is reliable
and provides a lifting capacity which is comparable to an
electric shovel. The hoist mechanism also absorbs shock which is
transmitted through the arm.
Operation of the power shovel for digging is relatively
simple, because the hydraulic crowd mechanism can be operated to
position the empty bucket in or near the digging position, and
then can be maintained in a static position to support the boom
during operation of the hoist mechanism to move and lift the
bucket. The operator has the option of operating the hoist
mechanism, the hydraulic crowd mechanism or the bucket tilting
mechanism, or all simultaneously, in order to penetrate the
material. The arm is pivotable through a very wide range of
motion for digging at ground level close to the frame or at a
position high up a bank and far away from the frame.
objects and advantages other than those set forth above will
become apparent to those skilled in the art upon review of the
following detailed description, drawings and claims.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side view showing a power shovel in an initial
position with the boom in an upper position and the arm pivoted
down.
Fig. 2 is a side view showing the power shovel in a digging
position with the bucket moved horizontally into a bank of
material.
Fig. 3 is a side view showing the power shovel in a filled
position with the bucket lifted and in phantom lines showing a
carrying position.
Fig. 4 is a side view showing the power shovel in a dumping
position and in phantom lines showing a carrying position.
Fig. 5 is a partial side view showing the power shovel in
the initial position shown in Fig. 1.
Before one embodiment of the invention is explained in
detail, it is to be understood that the invention is not limited
in its application to the details of the construction and the
arrangements of components set forth in the following description
or illustrated in the drawings. The invention is capable of
other embodiments and of being practiced or being carried out in
various ways. Also, it is to be understood that the phraseology
and terminology used herein is for the purpose of description and
should not be regarded as limiting.
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DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Illustrated in the drawings is a power shovel 10 including
various features of the invention. The power shovel 10 is
adapted for digging into and moving earth material in a surface
mining operation.
The power shovel 10 includes a frame 12 which is supported
on a set of crawler tracks 14 for movement across the ground
between different digging positions. The frame 12 is revolvable
on the crawler tracks 14 about a vertical axis. A machinery
house 16 is mounted on the frame 12. The machinery house 16
houses electric swing motors (not shown) and gear drives (not
shown) for revolving the frame 12 on the crawler tracks 14. The
machinery house 16 also houses a hoist drum 18 and an electric
motor (not shown) and associated drive gears (not shown) for
rotating the hoist drum 18. The machinery house 16 also includes
an operator's cab 20. A gantry support 22 extends upwardly from
the base of the frame 12.
The power shovel 10 includes a short boom 30 which extends
upwardly from the frame 12. The boom 30 has a lower end 32 which
is mounted on the frame 12 for pivotal movement relative thereto
about a horizontal boom pivot axis 34. The boom 30 also has an
upper end 36. A horizontal arm pivot axis 38 is located adjacent
the upper end 36.
The power shovel 10 includes a hydraulic crowd mechanism 40
which is operable for pivoting the boom 30 relative to the frame
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12. In a static position, the hydraulic crowd mechanism 40
resists pivotal movement of the boom 30 relative to the frame 12.
The hydraulic crowd mechanism 40 thus is operable to support and
move the boom 30 relative to the frame 12. The hydraulic crowd
mechanism 40 includes a pair of extendible and contractible
hydraulic apparatus 41 (one shown). The hydraulic apparatus 41
are identical, and only one will be further described. In the
illustrated embodiment, the hydraulic apparatus 41 is a hydraulic
cylinder/piston assembly (hereinafter "hydraulic assembly")
having opposite ends. One end of the hydraulic assembly 41 is
pivotally connected to the gantry support 22 at a first crowd
mounting point 42. The gantry support 22 is mounted on the base
of the frame 12 near the boom 30 in order to decrease the length
of the hydraulic assembly 41. The piston or other end of the
hydraulic assembly 41 is pivotally connected to the boom 30 at a
second crowd mounting point 43. The second crowd mounting point
43 is spaced from a line extending through the boom pivot axis 34
and the arm pivot axis 38, such that the boom 30 has a triangular
profile (Fig. 1). In the illustrated embodiment, the second
crowd mounting point 43 is spaced from the arm pivot axis 38
about 1/3 of the distance between the arm pivot axis 38 and the
boom pivot axis 34. The location of the second crowd mounting
point 43 along the boom 30 establishes that a preselected
crowding force is applied to the boom 30 and also provides for a
predetermined range of motion.and operational speed of the
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hydraulic assembly 41. When the power shovel 10 rests on level
ground and the hydraulic assembly 41 is fully contracted, the
first and second crowd mounting points 42 and 43 are located at
substantially the same vertical height. Accordingly, for
providing a predetermined crowd force, the length of the
hydraulic assembly 41 is m;n;m; zed and the operational speed of
the hydraulic assembly 41 is relatively fast. The hydraulic
crowd mechanism 40 also includes a large hydraulic fluid supply
system (not shown~ which has a pump, filters and a fluid
reservoir mounted on the frame 12 and connected to the hydraulic
assembly 41 via piping and hoses to supply hydraulic fluid
thereto.
In another embodiment (not shown), the second crowd mounting
point 43 can be located at another suitable point along the boom
30 in order to provide a different crowding force to the boom 30
or a different operational speed of the hydraulic assembly 41.
The boom 30 is pivotable relative to the frame 12 about the
boom pivot axis 34 between an upper position (Fig. 1) and a lower
position (Fig. 5) respectively corresponding to fully contracted
and fully extended conditions of the hydraulic assembly 41. When
the power shovel 10 rests on level ground and the boom 30 is in
the upper position (Fig. 1), a line extending through the boom
pivot axis 34 and the arm pivot axis 38 defines an angle of about
10~ relative to vertical. When the boom 30 is in the lower
position (Fig. 5), a line extending through the boom pivot axis
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34 and the arm pivot axis 38 defines an angle of about 50~
relative to vertical. In the illustrated embodiment, extension
of the hydraulic assembly 41 forces the second crowd mounting
point 43 on the boom 30 away from the first crowd mounting point
42 on the gantry support 22, so as to pivot the boom 30 in the
downward direction (clockwise as shown in the drawings).
Contraction of the hydraulic assembly 41 draws the second crowd
mounting point 43 toward the first crowd mounting point 42, so as
to pivot the boom 30 in the upward direction (counterclockwise as
shown in the drawings).
The power shovel 10 includes a generally banana-shaped
handle or arm 44. The arm 44 is an elongated member having
spaced upper and lower ends 46 and 48. The arm 44 is mounted on
the upper end 36 of the boom 30 for pivotal movement relative
thereto about the arm pivot axis 38 between a pivoted up position
(Fig. 3) and a pivoted down position (Fig. 1). As further
described below, the arm 44 is pivotable such that the lower end
48 is highest when the arm 44 is pivoted up and is lowest when
the arm 44 is pivoted down. The arm pivot axis 38 is
intermediate the upper and lower ends 46 and 48 and is spaced in
the direction of the frame 12 from a line extending through the
upper and lower ends 46 and 48. More particularly, when the
power shovel rests on level ground and the crowd mechanism 40 is
fully contracted such that the boom 30 is in the corresponding
upper position, the arm pivot axis 38 is located in a vertical
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plane which extends through the crawler tracks 14. In the
illustrated embodiment, the arm 44 is a fabricated structure
having a box-type cross sectional configuration.
The power shovel 10 includes a digging tool 52 mounted on
the arm 44 adjacent the lower end 48. In the illustrated
embodiment, the digging tool 52 is a front dump bucket 52. In
another embodiment (not shown), the power shovel may include
another suitable digging tool such as, for example, a dipper.
The front dump bucket 52 is mounted on the arm 44 adjacent the
lower end 48 for pivotal movement relative thereto about a bucket
pivot axis 54. The bucket 52 has (see Fig. 1) a lower wall 56,
an upper wall 58 which is spaced from the lower wall 56, and a
back wall 60 joining the lower and upper walls 56 and 58. The
bucket 52 also includes a pair of side walls 62 (one shown) which
are perpendicular to and which connect with the lower, upper and
back walls 56, 58 and 60. Forward edges of the lower wall 56,
upper wall 58, and side walls 62 cooperate to define an open
mouth 64. A set of digging teeth 65 extend outwardly from the
lower wall 56 along the lower portion of the mouth 64. The mouth
64 is spaced from the back wall 60 for scooping earth material
into and for emptying earth material from the bucket.
The power shovel 10 includes a bucket tilting mechanism 66
which is connected to the bucket 52 for tilting the bucket 52
relative to the arm 44 about the bucket pivot axis 54. More
particularly, the bucket tilting mechanism 66 includes (see
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Fig. 1) a pair of Z-type linkages 68 (one shown) mounted on
opposite sides of the arm 44. The Z-type linkages 68 are
identical, and only one will be further described. The Z-type
linkage 68 includes an elongated primary link 70 having opposite
first and second ends 72 and 74. More particularly, when the arm
44 is pivoted down, as shown in Fig. 1, the first end 72 is above
the second end 74. The primary link 70 is mounted on the arm 44
for pivotal movement relative thereto about a pivot point 76
which is located between the first and second ends 72 and 74.
The pivot point 76 is located on the forward edge of the arm 44
(the right edge in Fig. 1) at a location intermediate the arm
pivot axis 38 and lower end 48. The primary link 70 is
sufficiently short that when pivoted about the pivot point 76,
the ends 72 and 74 never extend below or inside the rear edge of
the arm 44 (the left edge in Fig. 1). The Z-type linkage 68 also
includes an elongated secondary link 78. The secondary link 78
has a first end 80 which is pivotally connected to the second end
74 of the primary link 70. The secondary link 78 has a second
end 82 which is pivotally connected to the bucket 52 at a point
84 spaced from the bucket pivot axis 54. The Z-type linkage 68
also includes an extendible and contractible hydraulic apparatus
86. In the illustrated embodiment, the hydraulic apparatus 86 is
a hydraulic cylinder/piston assembly (hereinafter "hydraulic
assembly") having opposite ends. One end of the hydraulic
assembly 86 is pivotally connected to the first end 72 of the
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primary link 70. The piston or other end of the hydraulic
assembly 86 is pivotally connected to the arm pivot axis 38.
The hydraulic assembly 86 is operable to pivot the primary
link 70 so as to tilt the bucket 52 relative to the arm 44
between an upwardly tilted position (Fig. 1) and a downwardly
tilted position (Fig. 5). More particularly, when the hydraulic
assembly 86 is extended (Fig. 1), the Z-type linkage 68 is
operable to tilt the bucket 52 to the upwardly tilted position
for scooping and retaining earth material in the bucket 52. When
the hydraulic assembly 86 is contracted (Fig. 5), the Z-type
linkage 68 is operable to tilt the bucket 52 to the downwardly
tilted position for dumping earth material from the bucket 52.
When the bucket 52 is tilted to the downwardly tilted position
(Fig. 5), the bucket 52 engages a stop 89 on the lower end 48 of
the arm 44 so as to decrease the load on the tilting mechanism
66.
The power shovel 10 includes a hoist mechanism 90 which is
operable for pivoting the arm 44 relative to the boom 30 about
the arm pivot axis 38 for moving and lifting the bucket 52. More
particularly, the hoist mechanism 90 includes the hoist drum 18
and a rope 92 which is windable on to and off of the hoist drum
18. The hoist mechanism 90 also includes a first sheave 94
rotatably mounted on the upper end of the gantry support 22, and
a second sheave 96 rotatably mounted on the upper end 48 of the
arm 44 at a mounting point 98. The rope 92 is reeved over the
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sheaves 94 and 96 and is fixed to the gantry support 22 at the
end opposite the hoist drum 18. The hoist drum 18 is rotatable
in one direction for winding the rope 92 on to the drum to pivot
the arm 44 upwardly (counterclockwise in Fig. 1) for lifting the
bucket 52. The hoist drum 18 is rotatable in the opposite
direction for unwinding the rope 92 off the drum to pivot the arm
44 downwardly (clockwise in Fig. 1) for lowering the bucket 52.
In particular, when the rope 92 is unwound off the hoist drum 18,
the weight of the arm 44 causes the arm 44 to pivot downwardly
about the arm pivot point 38. The size of the arm 44, and
particularly the distance between the second sheave 96 and the
boom pivot axis 38, is predetermined so that operation of the
hoist mechanism 90 to pivot the arm 44 upwardly provides a pre-
selected digging force to move the bucket 52 into the earth
material. The hoist mechanism 90 can àlso be operated
simultaneously with the hydraulic crowd mechanism 40 to provide a
greater digging force to the bucket 52 than provided solely by
operation of the hoist mechanism 90.
The arm pivot axis 38, the sheave mounting point 98 and the
bucket pivot axis 54 define a triangle. More particularly, a
line segment A (Fig. 6) extending between the arm pivot axis 38
and the sheave mounting point 98 and a line segment B extending
between the sheave mounting point 98 and the bucket pivot axis 54
define an angle of about 40~. The line segment B and a line
segment C extending between the bucket pivot axis 54 and the arm
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~ARN9095 . CIP
pivot axis 38 define an angle of about 30~. The line segments A
and C define an angle of about 110~.
When the boom 30 is in the upper position and the arm 44 is
in the pivoted down position (Figs. 1 and 6), the line segment C
defines an angle D (Fig. 6) of about 15~ relative to vertical.
Accordingly, the bucket 52 can be positioned to dig very near the
frame 12 near ground level. When the arm 44 is in the pivoted
down position as shown in Fig. 1, the upper end 46 is spaced from
the arm pivot axis 38 in the direction away from the frame 12.
The shape of the upper end 46 permits the arm 44 to be pivoted
upwardly from the pivoted down position through a range of motion
of at least about 100~, to the pivoted up position (Fig. 5) in
which the line segment C (not shown in Fig. 5) defines an angle
of at least about 115~ relative to vertical. Further, when the
arm 44 is in the pivoted down position, the lower end 48 is
spaced from the arm pivot axis 38 in the direction away from the
frame 12. The shape of the lower end 48 of the arm 44, and
particularly the location of the bucket pivot axis 54 in relation
to the arm pivot axis 38, ensures that the bucket 52 can dig at
positions which are high up a bank by pivoting the arm 44. The
shape of the arm 44 thus provides a very large digging area,
especially in the vertical direction.
The shape of the arm 44 also causes the center of gravity of
the arm 44 to be located near the arm pivot axis 38 and thus near
the frame 12. Accordingly, the hoist mechanism 90 is required to
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IIARN9095 .CIP
do relatively little work for pivoting the arm 44 upwardly. The
shape of the upper end 46 of the arm 44, and particularly the
location of the sheave mounting axis 98 in relation to the arm
pivot axis 38, ensures effectiveness of the hoist mechanism 90
for pivoting the arm 44, because appropriate moments are obtained
in all positions of the arm 44. The location of the bucket pivot
axis 54 in relation to the arm pivot axis 38 also establishes an
appropriate orientation of the bucket 52 when raised for emptying
material therefrom. The shape of the lower end 46 of the arm 44
also ensures that the Z-type linkage 68 will not extend rearward
or below the arm 44 and thus will not be damaged when digging or
emptying material from the bucket 52.
Although the shovel 10 can be operated in any suitable
manner, an exemplary mode of operation will now be described.
The power shovel 10 is initially moved by operation of the
crawler tracks 14 to a desired stationary digging location on
level ground adjacent an upwardly extending bank of earth
material. The power shovel 10 typically will remain in the same
digging location for a period of about an hour or more, digging
from the bank in a wedge-shaped digging region (as viewed from
above), before again being moved on the crawler tracks 14 to an
adjacent digging location. As shown in Fig. 1, digging
ordinarily will commence at ground level from the lower portion
of the bank. In an initial position of the bucket 52 (Fig. 1),
the crowd mechanism 40 is contracted and the boom 30 is in the
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upper position, the arm 44 is pivoted down, and the bucket 52 is
in the upwardly tilted position with the digging teeth 65
extending horizontally. From the initial position (Fig. 1), the
bucket 52 is moved in the horizontal direction to a second or
digging position (Fig. 2) in the earth material by extending the
crowd mechanism 40 to pivot the boom 30 downwardly about the boom
pivot point 34 from the upper position to an intermediate
position, and by slightly contracting the hydraulic apparatus 86
to maintain the bucket 52 in a relatively constant attitude with
the digging teeth 65 extending horizontally for cutting through
the earth material. secause the hoist mechanism 90 is maintained
in t~e same condition from the initial position (Fig. 1) to the
digging position (Fig. 2), the angle or position of the arm 44
relative to the boom 30 changes from the initial position (Fig.
1) to the digging position (Fig. 2). Accordingly, the hydraulic
apparatus 86 must be slightly contracted in order to maintain the
bucket 52 in a relatively constant attitude with the digging
teeth 65 extending horizontally.
From the digging position (Fig. 2) the bucket 52 is moved
through the earth material to a third or filled position (solid
lines in Fig. 3) by operating the hoist mechanism 92 to pivot the
arm 44 upwardly about the arm pivot axis 38. Because the bucket
tilting mechanism 66 is connected to the arm pivot axis 38, the
bucket 52 r~m~; ns in a fixed tilt position in relation to the arm
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44 while the arm 44 is pivoted upwardly without operating the
bucket tilting mechanism 66.
From the filled position (solid lines in Fig. 3) the bucket
52 is tilted up relative to the arm 44 to a fourth or carrying
position (phantom lines in Fig. 3) in which the earth material is
retained in the bucket 52. In order to move the bucket 52 from
the filled position (solid lines in Fig. 3) to the carrying
position (phantom lines in Fig. 3), the bucket tilting mechanism
66 is operated to tilt the bucket 52 upwardly about the bucket
pivot axis 54. With the bucket 52 in the carrying position, the
frame 12 is pivoted relative to the crawler tracks 14 to swing
the bucket 52 from a position above the digging area to a
position above a truck (Fig. 4). In order to provide a desirable
orientation of the bucket 52 for readily dumping the material
into the truck, the crowd mechanism 40 is contracted to pivot the
boom 30 to the upper position, with the bucket 52 r~m~;n;ng
generally in the carrying position (phantom lines in Fig. 4).
With the bucket 52 positioned over the truck in the carrying
position, the bucket tilting mechanism 66 is operated to tilt the
bucket 52 downwardly relative to the arm 44 to a dumping position
(solid lines in Fig. 4) wherein the mouth 64 opens downwardly for
emptying the earth material from the bucket 52 and into the
truck. As shown in Fig. 4, the location and orientation of the
Z-type linkage 68 on the arm 44 prevents the Z-type linkage 68
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from extending below the arm 44 and contacting the side wall of
the truck and from being damaged thereby.
The power shovel 10 weighs much less than an electric shovel
having a comparable dipper capacity and digging radius. For
example, a power shovel 10 weighing about 1,600,000 lbs. can have
a bucket capacity (about 46 cubic yards) and digging radius
(about feet) comparable to an electric shovel weighing about
1,900,000 lbs.
The arm 44 can be pivoted relative to the boom 30, and the
boom 30 also can be pivoted relative to the frame 12, for the
bucket 52 to reach a large digging area. The bucket 52 can be
articulated relative to the arm 44 for efficiently digging and
for quickly filling the bucket 52 with a short digging stroke.
The bucket 52 also can be articulated for digging in the lower
portion of a bank with a high fill factor. The bucket 52 can be
moved in the horizontal direction along the ground and
articulated relative to the arm 44 for scooping material from the
ground, without also digging down into the ground. This
eliminates the need for an additional piece of equipment, such as
a front end loader, for ground cleanup around the power shovel
10. The bucket 52 is lightweight and of relatively simple
design, and accordingly is inexpensive to construct and maintain.
The boom 30 is short and lightweight. In the illustrated
embodiment, the length of the boom 30 between the arm pivot axis
38 and the boom pivot axis 34 is less than the length of the line
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segment C (Fig. 6) extending between the arm pivot axis 38 and
the bucket pivot axis 54, and also is less than about half the
length of the line segment A extending between the upper and
lower ends 46 and 48 of the arm 44. The lightweight boom 30 is
simple and inexpensive to construct and maintain.
The lifting attachment is relatively lightweight, and the
center of mass of the lifting attachment is relatively close to
the centerline of rotation of the frame 12. This is because, in
addition to the bucket 52 being lightweight and the boom 30 being
short and lightweight, the arm pivot axis 38 is located
intermediate the ends of the arm 44, so the center of mass of the
arm is near the arm pivot axis 38. The inertial force generated
by rotating the frame 12 relative to the crawler tracks 14 to
swing the bucket 52 over a truck is relatively low, and the
moment on the boom 30 when pivoting the arm 44 in the vertical
direction also is relatively low. Accordingly, swing and drive
components are relatively lightweight.
The hydraulic crowd mechanism 40 is relatively simple to
construct and is simple and inexpensive to maintain. The
hydraulic crowd mechanism 40 is short and is capable of
relatively fast operation.
The power shovel 10 has a greater lifting capacity than a
comparable hydraulic shovel. The bucket 52 is lifted primarily
by operating the hoist mechanism 90 to pivot the arm 44. By
operating the hoist mechanism 90 to pivot the arm 44, the bucket
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52 can be moved along a long horizontal path for scooping
material near ground level, or along an upward path for scooping
material from a bank or emptying material into a truck. The
hoist mechanism 90 is a relatively reliable means of moving and
lifting the bucket 52. The hoist mechanism 90 also absorbs shock
which is transmitted through the arm 44. The hydraulic crowd
mechanism 40 ordinarily can be operated to position the empty
bucket 52 in or near the digging position, and then maintained in
a static position to support the boom 30 during operation of the
hoist mechanism 90 to move and lift the bucket 52.
Various features of the invention are set forth in the
following claims.
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