Patent Application
20120246980
The present disclosure relates to tractor scrapers and, more particularly, to drives for raising and lowering aprons on tractor scrapers.
Tractor scrapers typically include a tractor portion connected to a scraper portion for scraping and transporting material (e.g., soil) from a terrain surface. The scraper portion of a tractor scraper generally includes a bowl with a floor and sides, as well as a blade adjacent a forward end of the floor of the bowl. Such a tractor scraper typically scrapes and gathers material from the terrain surface by driving forward with the blade engaged to the terrain surface and a forward portion of the bowl at least partially open, such that material scraped from the terrain surface by the blade travels across the top of the blade, through the opening in the front of the bowl, onto the floor of the bowl.
To control intake and discharge of material through the front of the bowl, a tractor scraper typically also includes an apron disposed between the sides of the bowl at a forward portion of the bowl, as well as a drive for raising and lowering the apron to either close or open the forward portion of the bowl. For example, U.S. Pat. No. 3,016,633 to Le Tourneau (“the '633 patent”) discloses a tractor scraper with such an apron and drive system disposed adjacent a forward end of the bowl. The apron disclosed in the '633 patent has its sides pivotally engaged to the sides of the bowl, and the drive for the apron pivots the apron upward or downwardly to open or close the front of the bowl.
The drive for the apron in the '633 patent has a rack-and-pinion design. The rack of the system is a semicircular gear fixed on the front face of the apron in a position concentric with the pivot joints connecting the apron to the bowl. The pinion sits adjacent the front face of the apron in a position where teeth of the pinion engage teeth of the rack. As a motor rotates the pinion, the pinion drives the rack upward or downward, thereby pivoting the rack and the apron upward or downward about the pivot joints connecting the apron to the bowl. Because the rack is positioned concentric to the pivot joints, each portion of the rack passes through the same point adjacent the pinion as the apron and rack move upward or downward. This maintains the teeth of the rack engaged to the teeth of the pinion while the apron and rack move upward and downward.
While the '633 patent discloses a drive for moving the apron of a tractor scraper up and down, the configuration of the system shown in the '633 patent may have certain disadvantages. For example, with the apron pivotally mounted to the bowl and the rack fixedly attached to the front face of the apron, proper functioning of the drive may require the disclosed semicircular shape and concentric mounting of the rack to keep the rack properly engaged to the pinion over the full range of motion of the apron. These restrictions may have some drawbacks. For example, a semicircular shape of the rack may drive more cost and complexity in the processes of manufacturing the rack. Additionally, the configuration of the rack and pinion disclosed by the '633 patent may require tight tolerances in the manufacturing of the apron and the components for mounting it, so that the front face of the apron moves through a precise path to also ensure that the rack remains properly engaged to the pinion through the full range of motion of the rack. These requirements may also increase the cost and complexity of manufacturing the apron and the tractor scraper.
The system and methods of the present disclosure may help address these disadvantages.
One disclosed embodiment relates to a tractor scraper. The tractor scraper may include a tractor portion and a scraper portion. The scraper portion may include a bowl and an apron disposed adjacent a forward end of the bowl. The tractor scraper may also include a drive configured to raise the apron. The drive may include an actuator drivingly connected to a pinion. The drive may also include a rack connected to the apron and the pinion in a manner allowing the actuator to raise the apron by driving the rack with the pinion. The rack may be connected to the apron in a manner allowing relative movement between the rack and the apron.
Another embodiment relates to a method of operating a tractor scraper. The tractor scraper may have a tractor portion and a scraper portion. The scraper portion may include a bowl and an apron disposed adjacent a forward portion of the bowl. The method may include raising the apron to open the forward portion of the bowl, which may include driving a pinion with an actuator, driving a rack with the pinion, and raising the apron with the rack while allowing relative movement between the rack and the apron.
A further disclosed embodiment relates to a tractor scraper, which may include a tractor portion and a scraper portion. The scraper portion may include a bowl and an apron with a forward face disposed adjacent a forward end of the bowl. The tractor scraper may also include a drive configured to raise the apron to open the forward end of the bowl. The drive may include an actuator drivingly connected to the pinion. The drive may also include a rack connected to the apron and the pinion in a manner allowing the actuator to raise the apron by driving the rack with the pinion. A shape of the rack may differ from a shape of a vertical cross-section of the forward face of the apron.
Scraper portion 14 may be connected to tractor portion 12 in such a manner that scraper portion 14 moves across terrain surface 15 in concert with tractor portion 12. For example, scraper portion 14 may connect to tractor portion 12 via an articulating hitch 16. Tractor scraper 10 may have various provisions for suspending a rear portion of scraper portion 14 from terrain surface 15. For example, scraper portion 14 may include wheels 32 for supporting a rear portion of scraper portion 14 from terrain surface 15. Alternatively, scraper portion 14 may include one or more track units, skids, or similar components for supporting the rear portion of scraper portion 14 from terrain surface 15.
To suspend the forward portion of scraper portion 14, tractor scraper 10 may include arms 17 (one shown). A forward end of each arm 17 may connect to hitch 16, and a rearward end of each arm 17 may pivotally connect to scraper portion 14 ahead of wheels 32.
In some embodiments, scraper portion 14 may also include provisions for assisting tractor portion 12 in propelling tractor scraper 10. For example, in some embodiments, scraper portion 14 may include one or more power sources driving wheels 32 to assist in propelling tractor scraper 10.
Scraper portion 14 may be configured to gather and haul matter (e.g., soil) from terrain surface 15. Scraper portion 14 may include a bowl 22 for receiving and hauling the gathered matter.
Between forward ends of right side 24 and left side 26 of bowl 22, scraper portion 14 may include an apron 34. As shown in
As shown in
Tractor scraper 10 may include a drive 46 for raising and lowering apron 34 to either open or close a forward portion of bowl 22 above blade 30. Drive 46 may be a rack-and-pinion type drive having a rack 48, a pinion 50, and an actuator 52 for driving the pinion 50. The components of drive 46 may be mounted to various parts of tractor scraper 10. In some embodiments, rack 48, pinion 50, and actuator 52 may all be fully mounted to scraper portion 14. For example, as shown in
To allow drive 46 to move apron 34 by driving rack 48, apron 34 may be connected to rack 48. In some embodiments, rack 48 may connect to apron 34 in a manner allowing relative movement between apron 34 and rack 48 when drive 46 moves apron 34 up and down. For example, a lower end of rack 48 may be pivotally connected to a bracket 58 attached to forward face 36 of apron 34, such that pivotal relative movement may occur between apron 34 and rack 48 as drive 46 moves rack 48 to raise and lower apron 34. In some embodiments, such a pivotal connection may be effected via a pin 61 connecting the lower portion of rack 48 to bracket 58.
With rack 48 connected to apron 34 in a manner allowing relative movement between the two components, tractor scraper 10 may include additional provisions for restraining the motion of rack 48 to maintain its teeth 54 engaged to the teeth 56 on pinion 50. For example, as best shown in
In addition to preventing rack 48 from moving away from pinion 50 in directions perpendicular to the axis of pinion 50, retainer 65 may also limit movement of rack in directions parallel to the axis of pinion 50. For example, retainer 65 may include a shoulder 68 that abuts one side of rack 48, as well as a similar shoulder abutting the opposite side of rack 48. Additionally, pinion 50 may include annular rings 70, 72 abutting opposite sides of rack 48 to help restrain rack 48 in directions parallel to the axis of pinion 50. Retainer 65 may have different configurations than that shown in
Rack 48 may have various shapes and may be oriented in various manners. In some embodiments, the shape of rack 48 may differ from the shape of the vertical cross-section of forward face 36 of apron 34. For example, as shown in
A tractor scraper 10 according to the present disclosure is not limited to the exemplary configuration shown in
Furthermore, in addition to rack 48, pinion 50, and actuator 52, tractor scraper 10 may include one or more additional components for assisting movement of apron 34. For example, tractor scraper 10 may include one or more additional rack and pinion assemblies for assisting movement of apron 34. Furthermore, apron 34 may have a different configuration than shown in the figures and/or apron 34 may be connected to tractor scraper 10 in manners other than through pivot joints 40 connecting apron 34 to sides 24, 26 of bowl 22. Similarly, bowl 22 may have a different configuration than shown in the figures. Additionally, tractor scraper 10 may have different configurations of components for raising and lower the front portion of bowl 22, for connecting scraper portion 14 to tractor portion 12, for suspending the rear of scraper portion 14, and/or for propelling tractor scraper 10.
Tractor scraper 10 may have use in any situation where it may prove useful to scrape material from a terrain surface and collect the material in bowl 22. Apron 34 and drive 46 for moving it may have use in any situation where it may prove helpful to use apron 34 to control intake and discharge of material from the forward end of bowl 22 by closing or opening the forward portion of bowl 22. In many circumstances, an operator of tractor scraper 10 may initially activate drive 46 to raise apron 34 as high as it will go to create an opening in the forward portion of bowl 22 between a lower edge of apron 34 and blade 30 of bowl 22. Subsequently, the operator may lower blade 30 to engage terrain surface 15 and drive tractor scraper 10 forward, so that blade 30 scrapes material from terrain surface 15 and the material scraped from terrain surface 15 accumulates on floor 28 of bowl 22. After at least some material has accumulated in bowl 22, the operator may activate drive 46 to lower apron 34 to reduce or close the opening in the forward portion of bowl 22 to retain the accumulated material in bowl 22 with apron 34. The operator may also raise blade 30 to disengage it from terrain surface 15. Subsequently, the operator may drive tractor scraper 10 to another location, activate drive 46 to raise apron 34 to at least partially open the forward portion of bowl 22. With the apron 34 leaving the forward portion of bowl 22 at least partially open, the operator may then discharge material from bowl 22 through the opening at the forward portion of bowl 22.
The operator may command upward or downward movement of apron 34 with operator input device 80. If the operator manipulates operator input device 80 to request upward movement of apron 34, controller 82 may receive this command and adjust the operation of reversible, variable-displacement hydraulic pump 74 and/or hydraulic valve 78 to power actuator 52 to rotate pinion 50 to drive rack 48 upward. For example, in the configuration shown in
As pinion 50 drives rack 48 generally upward and apron 34 rotates upward around axis 41, rack 48 may move upward between pinion 50 and retainer 65. At the same time, the angular orientation of rack 48 relative to vertical and relative to apron 34 may change. As apron 34 rotates upward around axis 41, bracket 58 and pin 61 may move both horizontally and vertically, changing the angular relationship between the position of pin 61 and pinion 50, thereby changing the angular relationship between the lower end of rack 48 and the portion of rack 48 engaged to pinion 50. As this occurs, retainer 65 may automatically respond by sliding within slot 66 to accommodate the changing angular orientation of rack 48 while retaining rack 48 sandwiched between retainer 65 and pinion 50, so that teeth 54 of rack 48 remain properly engaged to teeth 56 of pinion 50. Alternatively, in some such embodiments, rack 48 may be curved in a manner such that, when the pinion 50 drives the rack 48 upward and downward and the position of pin 61 moves relative to pinion 50, the portion of the rack 48 engaged to the pinion 50 always maintains the same angular relationship relative to the pinion 50. This may allow omitting slot 66 and fixing retainer 65 in one position. During lowering of apron 34 by driving rack 48 generally downward, pivot pin 61, pinion 50, and retainer 65 may similarly function to allow rack 48 to slide and rotate in directions opposite which rack 48 did on the ascent.
Thus, the disclosed embodiments allow considerable movement of rack 48 relative to apron 34 while maintaining rack 48 engaged between apron 34 and pinion 50 in a manner allowing rack 48 to transmit lifting or lowering force to apron 34. This may allow maintaining pinion 50 drivingly connected to apron 34 via rack 48 through a wide range of upward and downward movement of apron 34, regardless of the positional relationship between forward face 36 of apron 34 and pinion 50. This may provide significant freedom in the design of the shape of apron 34 and the manner in which it attaches to and moves relative to tractor scraper 10. It may also accommodate substantial variation in the position of the apron 34 at various points during the lifting cycle, which may help suppress manufacturing cost and complexity by allowing use of relatively looser tolerances in the manufacture and assembly of apron 34 and pivot joints 40. This may also facilitate retrofitting a drive 46 according to the present disclosure to a tractor scraper 10 that originally included a different apron drive, as the drive 46 of the present disclosure may be able to accommodate relatively loose tolerances that may have been used in manufacturing and mounting the apron 34 of such an existing tractor scraper.
The disclosed configurations of drive 46 may also afford substantial freedom in designing the shape of rack 48. This may allow the designer to select a configuration of rack 48 that provides low manufacturing cost and complexity, as well as durability. For example, a rack 48 that has a substantially straight longitudinal axis like that shown in
The disclosed configurations may also help avoid plugging of teeth 54 on rack 48 with material (e.g., soil) scraped from terrain surface 15. Facing teeth 54 of rack 48 rearwardly may help shield them from any material collecting in front of rack 48 as tractor scraper 10 moves forward. By helping to keep teeth 54 clean, this configuration may promote reliable operation and durability of drive 46.
The disclosed embodiments also have other advantageous features. For example, mounting actuator 52, pinions 50 and rack 48 all on the scraper portion 14 of tractor scraper 10 may provide certain benefits. In particular, placing these components of drive 46 all on scraper portion 14 may ensure that relative movement between scraper portion 14 and tractor portion 12 does not create unintended movement of apron 34 relative to bowl 22. This may help keep the task of controlling the position of apron 34 simple.
Operation of the tractor scraper 10, apron 34, and drive 46 is not limited to the examples discussed above. For instance, rack 48 may move in different manners relative to apron 34 and/or pinion 50. For example, rather than only pivoting about pin 61 relative to apron 34, in some embodiments, rack 48 may also translate in one or more directions relative to apron 34. Similarly, apron 34 may move in different manners than discussed. Additionally, tractor scraper 10 may provide hydraulic fluid to actuator 52 with different components than those shown in
It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed system and methods without departing from the scope of the disclosure. Other embodiments of the disclosed system and methods will be apparent to those skilled in the art from consideration of the specification and practice of the system and methods disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
