Note: Descriptions are shown in the official language in which they were submitted.
CA 02324190 2000-10-25
Crawler Link
Field Of Invention
This present invention relates to crawler belts, and more particularly to the
lug
face profile of a crawler belt link
Background of the Invention
Large excavating equipment, such as a mining shovel, drag line, and the like,
are movable on crawler belts Each belt engages rotatable drive tumbler which
drive
the belt The drive tumbler has teeth which engage the belt, and transfer
torque from
the tumbler to the belt The belt is formed from a plurality of crawler links
joined
= _ t~eether
Conventional links have lugs, such as shown in Fig. 1, incorporate a single
curved surface for engaging the tumbler and driving the link. These single
surface
lugs have a tendency to climb up on the tumbler when the torque on the belt is
opposite the torque on the drive tumbler. This condition occurs when the
excavating
2 0 equipment is traveling forward down a slope when the machine weight is
forcing the
belt around the tumbler .
CA 02324190 2000-10-25
Brief Summary Of The Invention
The present invention provides a crawler belt link including a link body
having an upper surface, and a lug extending upwardly from the upper surface
to a lug
top. The lug has a first face which is engageable with a drive tumbler. A
first surface
defining a first portion of the face extends at an angle from the lug top to a
first
surface edge. A second surface defining a second portion of the face extends
toward
the body upper surface from the first surface edge at an angle different from
the first
surface angle. In one aspect of the invention, the crawler belt link lug has a
second
face facing away from said first face. In another aspect of the invention the
crawler
1 o belt link first surface provides a mechanical advantage which is greater
than 1Ø
A general objective of the present invention is to provide a tumbler driven
crawler link having a lug which does not have a tendency to climb up on the
tumbler
when the torque on the belt is opposite the torque on the drive tumbler. This
objective
is accomplished by providing a multi-surface lug face profile which is guided
into
_ eneaeement with the tumbler
The foregoing and other objects and advantages of the invention will appear
from the following description In the description, reference is made to the
accompanying drawings which form a part hereof, and in which there is shown by
way of illustration a preferred embodiment of the invention.
Brief Description of the Drawings,
Figs. 1 a-d show prior art link drive lug profiles;
Fig. ? is a two stage drive lug profile incorporating the present invention;
Fig. 3 is the link of Fig. 2 engaging a tumbler;
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CA 02324190 2000-10-25
Fig. 4 is prior art lug profile superimposed over the lug profile of Fig. 2
showing the engagement of the two profiles with a tumbler.
Detailed Descr~tion of the Preferred Embodiment
As shown in Fig. 2 and 3, a crawler link 10 for use in an endless crawler belt
11 has a base 12 with pair of lugs 14 (one shown) which engage the rotatably
driven
drive tumbler 16 to drive the link 10, and thus the belt 11. The link base 12
includes a
plurality of forwardly and rearwardly facing fingers 15. A hole 17 is fomned
in each
finger 15, and is aligned with the holes 17 in the adjacent fingers 15. The
endless belt
11 is formed by interdigitating the fingers 15 of adjacent links 10, such that
the holes
17 in the interdigitated fingers 15 are aligned, and a pin 19 is inserted
through the
holes 17 to couple the links 10 together.
Each lug 14 on a link 10 extends from the base 12 and terminates at a lug top
'_'3, and has a leading face and a trailing face. Each face of the lug 14 has
a profile
_ which defined by two surfaces ?0. ?2 for engaging the tumbler 16 and then
transferring a force from the tumbler 16 to the link 10 to drive the belt 1 1.
The first
surface ?0 is an engagement surface which initially engages the tumbler 16,
and
guides the lug 14 into full engagement with tumbler 16. The second surface 22
is a
main driving surface, and transfers the loads between the link 10 and the
tumbler 16
In one embodiment shown in Fig. 2, the lug profile on each face 18, 24 is
defined by a pair of joined nonparallel sides of stacked upper and lower
symmetrical
trapezoids 26, 24.The lower trapezoid is defined by lower parallel sides 28,
30 and
nonparallel sides 36, 42 joining the lower parallel sides 28, 30. The upper
trapezoid is
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CA 02324190 2000-10-25
defined by upper parallel sides 32, 34 and nonparallel sides 38, 40 joining
upper the
parallel sides 32, 34.
The lower side 28 of the lower trapezoid 24 is adjacent to the link base 12,
and
is longer than the upper side 30 of the lower trapezoid 24 to define the
second surface
of the lug along the nonparallel side 36 having an angle A. The length of the
upper
side 30 of the lower trapezoid 24 is equal to the length of the lower side 32
of the
upper trapezoid 26, and the length of the upper side 34 of the upper trapezoid
26 is
shorter than the lower side 32 of the upper trapezoid 26 to define the first
surface 20
of the lug 14 along the nonparallel side 38 of the upper trapezoid 26 having
an angle
B Angle B is less than angle A to provide the two distinct surfaces 20, 22.
The profile of the lug trailing face 18 is defined by the joined, forivard
facing
nonparallel sides 36, 38 of each trapezoid 24, 26, and the profile of the lug
trailing
face is defined by the joined, rearward facing nonparallel sides 40, 42 of
each
trapezoid 24, 26. Each nonparallel side defines a distinct surface 20, 22, and
each pair
of the two joined distinct surfaces 20, 22 defines the profile of the
particular lug face
Substantially identical lug face profiles are defined on each lug face 18, 21
to
provide a bidirectional crawler belt which can reverse direction by reversing
the
rotational direction of the tumbler. Although substantially identical lug face
profiles
are disclosed, it should also be understood that the lug profile on each face
can be
'' o different, and one lug face profile can have a single surface without
departing from the
scope of the present invention. Preferably, the surfaces of the lug profile on
each face
are substantially straight to simplify manufacturing. However, two or more
curved or
straight surfaces can be provided depending upon the tumbler profile . The lug
corners
can be rounded, and filets added to simplify manufacturing.
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CA 02324190 2000-10-25
The lug face multiple surface profile provides a distinct advantage over prior
art lugs, such as shown in Fig. 1. Prior art lugs having a single surface have
a
tendency to climb up on the drive tumbler, and require a greater force to
engage the
tumbler. As shown in Fig. 4, an interference 25, 27 exists between the single
curved
drive surface of the prior art lugs 5, 7 and the tumbler 16. The interference
can cause
the lug 5 to climb up on the tumbler 16, or require additional force to
overcome the
interference to urge the lug 5, 7 into engagement with the tumbler 16. This
additional
force reduces the force available for driving the belt. By providing a multi-
surface lug
face profile having an engagement surface 22, as disclosed herein, the lug 14
smoothly engages the tumbler 16, thus reducing the tendency to climb on the
tumbler
16, and reducing the force required to engage the tumbler 16.
The engagement surface 20 of the present invention provides a mechanical
advantage to ensure proper engagement of the tumbler 16 with the lug 14. As
shown
in Fig 3, the mechanical advantage (M.A.) is determined by calculating the
ratio of
moments acting on particular points of the lug using the following equation:
M. A. _ (Lever Arm # 1 x Load at WP D)/(Lever Arm #2 x Load at WP A)
Lever Arm # I = distance between WP D and WP B.
WP D = work point D (pivoting connection between adjacent links).
WP B = arbitrary work point chosen at base of lug.
Lever Arm #2 = distance between WP A and WP B.
WP A = work point at point of contact between lug and tumbler.
Load at WP D= weight of the link.
Load at WP A= force exerted by the tumbler on the lug at WP A.
A mechanical advantage which is greater than 1.0 ensures that the lug engages
the
tumbler without climbing. As can be seen, the mechanical advantage will change
when the tumbler engagement changes from the engagement surface 20 to the
drive
surface 22.
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CA 02324190 2000-10-25
While there has been shown and described what are at present considered the
preferred embodiments of the invention, it will be obvious to those skilled in
the art
that various changes and modifications can be made therein without departing
from
the scope of the invention defined by the appended claims.
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