Patent Application
20090159155
The present invention relates to tree stump grinding machines, and in particular to the configuration of the teeth and/or the retention thereof in a grinding rotor or wheel of such a machine.
It is known in the prior art to provide a tree stump grinding machine with a cutting wheel (or “rotor”) driven by a belt, a chain, shafts, or hydraulic motors. Typically, the cutting wheel is circular with a number of receiving brackets positioned around the rim. The receiving brackets have channels into which are fitted individual cutting teeth. Each tooth is individually mounted and a gauge is often required to set each tooth at the correct distance from the center of the wheel. Each tooth is held in place by retaining bolts that are tightened to a very high degree in order to properly hold the teeth. The bolts and retaining brackets are required to take the full rotational force of the grinding action. The wheel is provided with a plurality of teeth, some of which are fitted to cut vertically while others are fitted to cut horizontally, as the wheel moves along a horizontal and vertical axis. An example of such a grinding wheel is found in U.S. Pat No. 6,484,766.
The teeth and receiving brackets described above have to be changed regularly as a result of the considerable wear that they encounter in use. Changing the teeth and receiving brackets is time consuming because of the set up accuracy required. Each tooth is generally held in place using two bolts to secure the receiving bracket and the tooth. The task of changing the teeth is invariably complicated by the earth and mud that clogs the teeth, brackets, and bolt threads which then require cleaning prior to fitting of a new tooth. Further, the receiving thread in the cutting wheel and the bolt or bolts may become cross-threaded as a result of the earth and mud, and require repair before a new tooth can be fitted. In addition to the expense incurred in a long down-time to change the teeth, the teeth and receiving brackets themselves are expensive because of the number of heavy duty components.
Currently co-pending U.S. patent application Ser. No. 10/588,348 (filed as a U.S. national phase on Aug. 3, 2006), which is incorporated herein by reference in its entirety, describes a tooth for use in a tree stump grinding wheel. In some embodiments, a keeper plate is used to retain the tooth in the grinding wheel. While the '348 application describes one or more embodiments of a keeper plate and/or tooth, there remains a need for alternative designs.
In one embodiment, the present invention provides a novel tree stump grinding machine that includes a rotor having at least one peripheral slot therein; a cutting tooth removably disposed in the slot and having a primary cutting face; a fastener operatively securing the tooth to the rotor; and a secondary cutting face disposed circumferentially offset with respect to the primary cutting face and nearer a rotational center of the rotor than the primary cutting face. In some embodiments, the tooth may comprise a cutting tip disposed radially inward from the primary cutting face and forming the secondary cutting face. In some embodiments, the device may include a keeper plate disposed circumferentially adjacent the tooth in the slot and secured to the rotor, the keeper plate comprising a cutting tip that forms the secondary cutting face.
In another embodiment, the present invention provides a tree stump grinding machine that includes a novel keeper plate configuration. The tree stump grinding machine includes a rotor having at least one peripheral slot therein and defining a rotor plane; a tooth removably disposed in the slot and having a primary cutting face; a keeper plate distinct from the tooth and disposed circumferentially adjacent the tooth in the slot; means for coupling the keeper plate to the tooth; a fastener removably securing the keeper plate to the rotor; and a secondary cutting face formed by a second protrusion on the keeper plate oriented perpendicular to the rotor plane. The secondary cutting face may be disposed circumferentially and/or radially offset with respect to the primary cutting face. For example, the second protrusion may be disposed nearer a rotational center of the rotor than the primary cutting face. In some embodiments, the slot may be enlarged toward a rotational center of the rotor to form an aperture, with an insert disposed in the aperture. The fastener may engage the insert to couple the insert and the keeper plate to the rotor. In some embodiments, the keeper plate may be formed of a softer material than the rotor.
The present invention improves the grinding efficiency by reducing the amount of time it takes to remove a tree stump.
As can be seen, tooth 30 may be provided with a tapered surface 87. The taper is advantageously radial and provides a broader tooth cross-section closer to the tip of the tooth 30 and a narrower tooth cross-section closer to the center of the rotor 20 when the tooth 30 is positioned for use on the rotor 20. Just by way of example, the taper may be at approximately 11°. The slot 24 in the rotor 20 may also be provided with a corresponding taper.
When the tooth 30 is initially fitted into the rotor 20, bolt 86 is screwed into the keeper plate 80 so that the tooth 30 is held securely. After the tooth 30 has been used for some time, the tooth 30 may work loose and begin to move slightly relative to the rotor 20. When this occurs, bolt 86 may be tightened so that keeper plate 80 and tooth 30 move together radially inwardly toward the center of rotor 20. As a result of the tapered surface 87 on the lower part of the tooth 30 and matching taper on the slot 24, the tooth 30 will be tightened into position on the rotor 20 by the action of the bolt 86 being tightened.
The keeper plate 80 and the tooth 30 may be made from a metal that is soft in comparison with the metal of rotor 20 so that keeper plate 80 will wear more quickly than rotor 20 and can be replaced more conveniently. The use of a keeper plate 80 therefore increases the useful life of rotor 20. In this example, the rotor 20 is manufactured from hardened steel, such as HARDOX 400, while the keeper plate 80 may be manufactured from drop forged steel, or the like.
The cutting tip 102 allows the grinding machine 100 to cut deeper into a tree stump in comparison with a conventional grinding machine. The support arm 10 of the grinding machine 1 is swept back and forth such that the rotor 20 is swept back and forth across the tree stump, with each sweep allowing a slightly deeper cut into the tree stump. The cutting tip 102 acts to increase the depth of the cut into the tree stump because it provides an additional cutting face.
The cutting tip 102 is located circumferentially away from the tooth cutting tips 33-36 so that the impact of each of the cutting tips 102 and 33-36 on the tree stump are staggered. In other words, during operation of the grinding machine 1, the cutting tip 102 will hit the tree stump after the cutting tips 33-36 have hit the tree stump. During operation of the grinding machine 100, the rotor 20 is required to rotate at a high speed, and the staggering of each impact of the cutting tips allows the rotor to maintain the torque needed to keep rotating.
By locating cutting tip 102 on keeper plate 100, the load that acts on the cutting tips 102, 33-36 is dispersed. If the cutting tip 102 was to be provided at a similar radial location, but on tooth 30, the pressure acting on the various cutting tips of tooth 30 would be much greater than when the cutting tip 102 is disposed on the keeper plate 100. This increased loading may lead to damage of the tooth 30 when the tooth 30 impacts the tree stump.
It is preferable to position the cutting tip 102 closer to the center of the rotor 20 than the cutting tips 33-36 because this results in less wear on the cutting tip 102. There is less wear on the cutting tip 102 because of the distance that the cutting tip 102 is located from the outer edge of the rotor 20. When the rotor 20 rotates, the outer edge will run in detritus, such as soil, stones and the wood removed from the tree stump. The inwardly positioned cutting tip 102 will be subjected to less detritus than the cutting tips 33 to 36. Furthermore, the operator of the grinding machine 1 will not always make a deep enough cut in the tree stump to engage the cutting tip 102.
The provision of the cutting tip 102 is advantageous because if it allows the grinding machine 1 to cut deeper in a tree stump for a given amount of power. The provision of the cutting tip 102 on the keeper plate 100 is also advantageous for economic reasons. This is because when the cuttings tips 33-36 on the tooth 30 are worn, so that the tooth 30 needs to be replaced, it is not always necessary to replace the cutting tip 102 provided on the keeper plate 100 since the cutting tips 33-36 wear at a faster rate than the cutting tip 102.
While it is believed advantageous if the keeper plate 100 and tooth 30 are readily separable when removed from rotor 20, the keeper plate 100 may be relatively permanently attached to the tooth 30 in some embodiments. For example, the keeper plate 100 of
In another embodiment, the tooth 30 itself is modified to provide the secondary cutting face at a location that is both circumferentially and radially offset from the primary cutting face. For example,
The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein
