Excavating equipment typically includes various wear parts to protect underlying products from premature wear. The wear part may simply function as a protector (e.g., a wear cap) or may have additional functions (e.g., an excavating tooth, which functions to break up the ground ahead of the bucket as well as protecting the underlying digging edge). In either case, it is desirable for the wear part to be securely held to the excavating equipment to prevent loss during use, and yet be capable of being removed and replaced when worn. In order to minimize equipment downtime, it is desirable for the worn wear part to be capable of being easily and quickly replaced in the field. Wear parts are usually formed of three (or more) components in an effort to minimize the amount of material that must be replaced on account of wearing. As a result, the wear part generally includes a support structure that is fixed to the excavating equipment, a wear member that mounts to the support structure, and a lock to hold the wear member to the support structure.
As one example, an excavating tooth includes an adapter as the support structure, a tooth point or tip as the wear member, and a lock or retainer to hold the point to the adapter. The adapter is fixed to the front digging edge of an excavating bucket and includes a nose that projects forward to define a mount for the point. The adapter may be a single unitary member or may be composed of a plurality of components assembled together. The point includes a front digging end and a rearwardly opening socket that receives the adapter nose. The lock is inserted into the assembly to releasably hold the point to the adapter.
The lock for an excavating tooth is typically an elongate pin member that is fit into an opening defined cooperatively by both the adapter and the point. The opening may be defined along the side of the adapter nose, as in U.S. Pat. No. 5,469,648, or through the nose, as in U.S. Pat. No. 5,068,986. In either case, the lock is inserted and removed by the use of a hammer. Such hammering of the lock can be an arduous task and impose a risk of harm to the operator.
The lock is usually tightly received in the passage in an effort to prevent ejection of the lock and the concomitant loss of the point during use. The tight fit may be effected by partially unaligned holes in the point and adapter that define the opening for the lock, the inclusion of a rubber member in the opening or in the pin, and/or close dimensioning between the lock and the opening. However, as can be appreciated, an increase in the tightness in which the lock is received in the opening exacerbates the difficulty and risk attendant with hammering the locks into and out of the assemblies.
The lock additionally often lacks the ability to provide substantial tightening of the point onto the adapter. While rubber members have been provided in prior locking systems to provide some tightening of the wear member on the support structure, it has tended to provide only limited benefit as the rubber lacks the strength needed to ensure a tight fit when the teeth are under load during use. Most locks also fail to provide any ability to be retightened as the parts become worn. As a result, many locks used in teeth are susceptible to being lost as the parts wear and the tightness decreases. Prior locks that provide take up or the ability to be retightened tend to rely upon threads or wedges, which commonly suffer from removal difficulties and/or safety issues.
Shortcomings in the locking arrangements are not limited strictly to the mounting of points on adapters. In another example, an adapter is a wear member that is fit onto a lip of an excavating bucket, which defines the support structure for the adapter. While the point experiences the most wear in the system, the adapter will also wear and in time need to be replaced. It is common for adapters to be mechanically attached to a bucket lip so as to permit the use of harder steel and to accommodate replacement in the field. One common approach is to use a Whisler style adapter, such as disclosed in U.S. Pat. No. 3,121,289 (see FIG. 8). In a traditional Whisler system, the adapter is formed with bifurcated legs that straddle the bucket lip. The adapter legs and the bucket lip are formed with openings that are aligned for receiving the lock. The lock in this environment comprises a generally C-shaped spool and a wedge. The arms of the spool overlie ramps on the rear end of the adapter legs. The ramps on the legs and the inner surfaces of the arms are each inclined rearward and away from the lip. The wedge is then hammered into the aligned openings to force the spool rearward. This rearward movement of the spool causes the arms to tightly pinch the adapter legs against the lip to prevent movement or release of the adapter during use.
However, the hammering of the wedge into and out of the openings in a Whisler-style lock tends to be difficult and potentially hazardous. Removal can be particularly difficult as the bucket must generally be turned up to provide access for driving the wedges out of the assembly. In this orientation of the bucket the worker must access the opening from beneath the bucket and drive the wedge upward with a large hammer. The risk is particularly evident in connection with large buckets. Also, because wedges can eject during service, it is common for the wedges to be tack-welded to its accompanying spool, which eliminates any retightening and makes wedge removal more difficult.
In many assemblies, other factors can further increase the difficulty of removing and inserting the lock when replacement of the wear member is needed. For example, the closeness of adjacent components, such as in laterally inserted locks (see, e.g., U.S. Pat. No. 4,326,348), can create difficulties in hammering the lock into and out of the assembly. Fines can also become impacted in the openings receiving the locks making access to and removal of the locks difficult.
There have been some efforts to produce non-hammered locks for use in excavating equipment. For instance, U.S. Pat. Nos. 5,784,813 and 5,868,518 disclose screw driven wedge-type locks for securing points to adapters, and U.S. Pat. Nos. 4,433,496 and 5,964,547 disclose screw-driven wedges for securing adapters to buckets. While these devices eliminate the need for hammering, they each require a number of parts, thus, increasing the complexity and cost of the locks. The ingress of fines can also make removal difficult as the fines increase friction and interfere with the threaded connections. Moreover, with the use of standard threads, the fines can build up and become “cemented” around the threads to make turning of the bolt and release of the parts extremely difficult as can corrosion and damage to the threads.
U.S. Pat. Nos. 6,986,216, 7,174,661 and 7,730,652 disclose locking arrangements for wear assemblies that rely upon a threaded wedge that engages a thread formation on the spool or wear member, and is rotated to drive the wedge into and out of the opening. These systems require minimal components, eliminate hammering, and alleviate the removal problems associated with prior systems. However, they lack the ability to provide substantial take up to ensure a tight fit with the lip or other supporting structure, or effective retightening after wear occurs.
Typically, in a mining operation, a major earthmoving machine like a large cable shovel or dragline machine may have as many as three buckets dedicated to the machine. These buckets will include one bucket that is actively in use on the machine, one bucket that has been taken off the machine and is in the rebuild shop (e.g., to have various wear members removed and replaced with new wear members and to rebuild the lip for the tooth base and shroud fit areas), and one “ready line” bucket. The ready line bucket is a bucket that is new or has been through the re-build process and is ready to go back to work. The ready line bucket is needed because a bucket rebuild can take months to complete. It can be used on a scheduled maintenance cycle or, as can happen, when a major failure occurs with the bucket on the machine. Because the rebuild process takes so long, a mine cannot afford to not have a bucket available to put on a machine in case of emergency. The downtime and associated economic loss would be too great.
While larger mining operations (e.g., operations involving multiple cable shovels and/or dragline machines) may not have three buckets dedicated to each machine, the operation will still typically have a sufficient number of ready line buckets available, if needed, to prevent excessive downtime (i.e., to avoid having a machine inoperable while waiting for a bucket rebuild job to be completed). The need for numerous ready line buckets represents a significant cost for the mining operation.
Because the lip rebuild tends to be the most time consuming part of the bucket rebuild process, reducing the number of rebuilds by lengthening the time between rebuilds would be a huge savings. Such a reduction in the number or frequency of rebuilds to the lip or other parts of the bucket would save the end user the money and time needed to perform these rebuilds as well as avoid the downtime associated with having the excavating bucket detached from the machine or unavailable for use in moving material. Reducing the number of lip rebuilds could constitute a huge savings in terms of less inventory of replacement buckets, fewer welders required to do these rebuilds, and a more forgiving system that is easier to operate and can be changed when it is more convenient for the operation.
Since the bucket lip takes substantial abuse and is under considerable load during use, it needs to retain its strength and integrity to avoid failure. While welding on a lip rebuilds the leading edge of the lip to its original form, it also poses a risk to the lip if not done correctly. The lip must be preheated and welding procedures must be followed very carefully in order to avoid developing cracks. A cracked lip will necessitate the bucket being removed from the machine and repaired. However, if one does not need to weld repair the lip as often, then one possible failure mode is reduced or limited, thus minimizing the chances for a lip crack or failure.
One factor that may influence the need to repair or rebuild the lip on a bucket relates to whether the system for coupling the wear member to the lip is capable of securely engaging the parts together. The coupling system must be able to move the wear member a sufficient distance with respect to the lip to seat the wear member onto the lip. This amount of movement is referred to as “take up” (e.g., the coupling system must move the wear member a sufficient distance with respect to the lip to “take up” any gap or distance between the wear member and the lip). If a coupling system can only move a wear member a small distance with respect to the lip, the coupling system has a small take up capability, and in such systems, the mine operator may be forced to rebuild the lips more frequently (to assure that the coupling system will have sufficient take up to move the wear member and securely hold it against the lip). For coupling systems with a small amount of available take up, the lip rebuild also must be relatively precise to assure that the coupling system will be able to move the wear member and hold it onto the lip. Systems with wear members that are not tightly held to the supporting structure will tend to suffer more wear and tend to be more susceptible to wear member loss. While premature wearing of the lip may be of primary concern, premature wearing of other support structures, such as adapters, can also increase downtime and costs due to more frequent replacement.
Accordingly, improvements in releasable coupling systems for securing wear members to the digging edge of a bucket would be welcome in the mining and construction industries. There remains a need for coupling systems that are easy and safe to install and remove, are reliable in use, enable substantial take up, allow longer time periods between bucket rebuilds, permit a wider range of dimensional variation in the manufacturing processes for the various parts, and lead to less machine downtime. Such improvements would result in reduced costs by decreasing the need for ready line buckets and the expense associated with rebuilding the digging edge of the buckets.