Excavating – Digging edge – Tooth or adaptor
Reexamination Certificate
2001-11-09
2004-05-04
Batson, Victor (Department: 3671)
Excavating
Digging edge
Tooth or adaptor
C403S374400
Reexamination Certificate
active
06729052
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to an assembly for securing an excavating tooth to excavating equipment, and in particular, for mechanically attaching an adapter to a dredge cutterhead.
BACKGROUND AND SUMMARY OF THE INVENTION
Dredge cutterheads are used for excavating earthen material that is underwater, such as a riverbed. One example of a dredge cutterhead is illustrated in FIG.
17
. In general, a dredge cutterhead include several arms
11
that extend forward from a base ring
16
to a hub
23
. The arms are equally spaced about the base ring and formed with a broad spiral about the central axis of the cutterhead. Each arm is provided with a series of spaced apart teeth
12
to dig into the ground.
In use, the cutterhead is rotated about its central axis to excavate the earthen material. To excavate the desired swath of ground the cutterhead is moved side-to-side as well as forward. On account of swells and other movement of the water, the cutterhead will also tend to move up and down, and periodically impact the bottom surface. As a result of this unique cutting action, the teeth of a dredge cutterhead experience heavy transverse as well as axial loading and heavy impact jacking loads that thrust the tooth up, down and sideways. The heavy transverse loading of the tooth is further engendered by the operator's inability to see the ground that is being excavated underneath the water. Unlike other excavators (e.g., a front end loader), the operator of a dredge cutterhead cannot effectively guide the cutterhead along a path to best suit the terrain to be excavated.
Due to the rotative digging action of the cutterhead, each tooth penetrates the ground on the order of 30 times a minute as compared to about 1 time a minute for mining teeth. As a result, the teeth experience a great amount of wear during use. It is desirable therefore for the teeth to be easily removed and installed to minimize downtime for the cutterhead. As is common with wear assemblies for excavating equipment, dredge teeth comprise a plurality of integrally connected parts so as to minimize the amount of material needing replacement, i.e., only the worn components need to be replaced.
In the example of
FIG. 17
, each tooth includes a base
18
, an adapter
13
, a point or tip
17
, and a lock
29
. The base
18
is cast on the arm
11
at a particular location and orientation to maximize digging. Adapter
13
includes a rear end
22
that is received in a socket
14
defined in the base, and a forwardly projecting nose
15
to hold the point
17
. A removable lock
29
is provided to facilitate the required frequent replacement of the tooth points
17
. The adapter is held in the socket by a large fillet weld about the circumference of the rear end
22
. In other known dredge cutterheads
1
, the adapter
2
is bifurcated to define a pair of legs that are configured to wrap about the arm
3
(FIG.
18
). These adapters are welded directly to the arm without a base member.
Although the tooth points require the most frequent replacement in a dredge cutterhead, the adapters still wear and need periodic replacement. However, replacing even a single adapter on a dredge cutterhead is a long process. The welded adapter must first be cut off with a torch. Then, portions of the arm and base that were damaged by the removal of the adapter must be repaired and rebuilt. Finally, a new adapter is welded into place. This process typically entails 10-12 man-hours per adapter. Hence, a lengthy delay in a dredging operation is unavoidable even when replacing only a single adapter. Moreover, in view of this lengthy delay, an operator will often wait until several adapters need replacement to take the cutterhead out of operation. As a result, the actual delay in operation that usually results is longer. Indeed, with a typical cutterhead having 50-60 teeth a rebuilding process of the entire cutterhead could require more than 600 man-hours. In an effort to avoid substantial loss of dredging time, most dredging operations maintain three or four cutterheads so that the entire cutterhead can be exchanged when one or more adapter needs to be replaced, the cutterhead needs to be rebuilt, or if the cutterhead breaks. However, a cutterhead is expensive. The maintaining of extra cutterheads that are not used, but held only when the one in use is serviced is an undesirable use of resources.
In one aspect of the present invention, the adapter is mechanically attached to the arm for easy installation and removal. The adapter is held to a base on the arm solely by a mechanical construction without the need for welding the adapter. In the preferred construction, the base and adapter are formed with complementary coupling configurations to prevent release of the adapter from the base except in a release direction. A removable lock is used to prevent undesired release of the adapter from the base in the release direction. With a mechanical attachment, the adapter can be easily replaced by simply removing the lock and moving the adapter in the release direction. There is no weld to be cut, no need to repair the base and arm, and no re-application of a weld. As opposed to 10-12 man-hours for replacing a welded adapter, a mechanically attached adapter in accordance with the present invention can be changed in as little as 10 minutes. This is a dramatic improvement which not only substantially reduces downtime for the cutterhead, but can also make the elimination of an entire spare cutterhead at the dredging site possible. As a result, instead of typically needing three or four cutterheads at a dredge site, only two or three may be needed.
In the preferred construction of the present invention, the adapter includes a T-shaped slot that receives a T-shaped tongue on the base, and an opening for receiving a lock. The lock, when inserted into the opening, opposes a wall of the base and a wall of the opening to prevent release of the T-shaped tongue and slot, and thereby hold the adapter to the base.
It is common for adapters of various excavators, such as a front end loader, to be mechanically attached to the excavating bucket. For example, U.S. Pat. No. 5,653,048 discloses an adapter with a T-shaped slot that receives a T-shaped boss welded to the lip of an excavating bucket. A lock is fit within an opening in the top of the adapter to prevent loss of the adapter from the lip. A bearing surface is formed at the front end of the boss to provide axial support for the adapter. While this construction well supports an adapter on an excavating bucket, it is not well suited for use on a dredge cutterhead.
In an excavating bucket, the teeth are primarily subjected to axial loading as the bucket is driven forward through the ground. However, as discussed above, the teeth on a dredge cutterhead are subjected to heavy and frequent transverse loads due to the manner in which the cutterhead is operated. In the noted '048 patent, the adapter 4 is slid onto the boss 5 with a slight side clearance for ease of assembly. The application of a large side load L applied against the tooth point 6 tends to rotate the adapter about the received boss to the extent of the defined clearance between the parts (FIG.
16
). This rotation of the adapter results in the generation of resistant forces R1-R4 and high stresses being generated through essentially “point” contacts in the corners of the assembly. Although true point contact is impossible, the term is used to identify large applications of force over a relatively small area. In particular, the application of large forces R2, R3 at “points” on the front of the base and the lock
7
place exceptionally high levels of stress on the components. Such high stress levels, in turn, cause greater wearing of the parts at these locations and a shortened usable life of the parts. The increased wearing also enlarges the clearance space, which can lead to rattling of the components during use. Such rattling of the parts further quickens wearing of the parts.
In ordinary digging, such as with a front e
Cowgill Noah David
Ollinger, IV Charles G.
Batson Victor
ESCO Corporation
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