Patent Application
20130071216
The present invention relates to a boom of a work vehicle, and in particular to an exoskeleton boom structure.
Work vehicles can be equipped with booms for doing excavation, harvesting, logging and other heavy-duty work. In
The work vehicle can also include a work attachment 110, such as a single grip harvesting head, for performing a working operation (e.g., logging). The work attachment 110 is pivotally mounted to one end of a dipper stick 112 which in turn is pivotally mounted to a boom 116. A first hydraulic cylinder (not shown) is used for pivoting the work attachment 110 relative to the dipper stick 112. Similarly, a second hydraulic cylinder 114 is provided for pivoting the dipper stick 112 relative to the boom 116 and a third hydraulic cylinder 118 is provided for pivoting the boom 116 relative to the supporting structure 106. The supporting structure 106 can be pivoted relative to the undercarriage 102 by a hydraulic motor (not shown). Although the work vehicle 100 is described for use as a tracked harvester, the embodiments of the present disclosure are not limited to the tracked harvester and may be incorporated in other work vehicles including a tracked feller buncher, wheeled feller buncher, etc.
The boom 116 is an elongated body that is loaded at both ends thereof during operation and is also heavily loaded at cylinder attachment points. Conventional booms are formed by materials having different thicknesses which are welded together. The boom structure is designed to achieve a desirable strength and service (fatigue) life, but also maintain a desirable weight that allows the hydraulic cylinder to operably control the boom. If a boom weighs too much, for example, the hydraulic cylinder can have difficulty controlling the boom during operation.
To achieve a desired strength and weight, a conventional boom will include side members having a thicker portion near each end and a thinner portion therebetween. One such example is illustrated in
There are several shortcomings found in the structural design of the conventional boom 200. First, the interfaces 216, 218 between the thicker bodies 210 and thinner body 208 can form significant stress risers which reduce the strength of the boom 200. The stress risers can eventually cause cracks near each interface 216, 218. In addition, the thinner body 208 is susceptible of being dented or damaged during boom operation and therefore weakening the boom structure, particularly since the thinner body 208 is welded directly to the top member 214, bottom member 220, and each thicker body 210.
Another shortcoming of the conventional boom structure is the required use of a weld support or backup bar. Referring to
A need therefore exists to provide a boom having a structural design that possesses an increased strength, without increasing the weight of the boom, and includes a continuous weld backup.
In an exemplary embodiment of the present disclosure, a boom structure including an elongated body having a first end and a second end, the first end configured to couple to a dipper and the second end configured to couple to a support structure. The boom structure further includes a top member, a bottom member, and a pair of sides members of the body coupled to the top member and bottom member. Each side member includes a first portion extending between the first end and second end of the body and forming an outer frame structure. Each side member also includes a second portion coupled to an inner surface of the first portion and being substantially enclosed by the first portion. The first portion can have a greater thickness than the second portion.
In one aspect of this embodiment, the boom structure includes a lug portion defined by the first portion. In another aspect, the boom structure includes a uniform and continuous weld backup. The second portion can form the weld backup. In an alternative aspect, the boom structure can include a top edge of the second portion welded to a bottom edge of the top member and a bottom edge of the second portion welded to a top edge of the bottom member.
In one embodiment, the boom structure can further include a penetration weld formed between the interfaces of the first portion and second portion, top member and second portion, and bottom member and second portion. In addition, a substantially H-shaped cross-section is defined at the interface of the top member, first portion and second portion. Also, the first portion defines an opening disposed within the outer frame structure and the second portion completely covers the defined opening in the first portion.
The first portion can extend past the top member to define a flange-like structure. Further, the boom structure can include a recess defined between the top member and first portion of the pair of side members. In addition, the relationship between the first portion and second portion can be such that the first portion is at least twice as thick as the second portion.
In another embodiment, a work vehicle includes an undercarriage and a ground engaging assembly for supporting and propelling the vehicle; a support structure disposed upon the undercarriage, the support structure being pivotally mounted to the undercarriage; a work attachment for performing a work operation; a dipper stick pivotally coupled to the work attachment; and a boom pivotally coupled to the dipper stick at a first end and to the support structure at an opposite end thereof. The boom comprises an elongated body having a top member and a bottom member of the body; and a pair of sides members coupled to the top member and bottom member, each side member including a first portion and a second portion, where the first portion extends between the first end and the second end of the body and forms an outer frame structure and the second portion couples to an inner surface of the first portion and is substantially enclosed by the first portion; wherein, the first portion can have a greater thickness than the second portion.
In one aspect, the second portion defines a uniform and continuous weld backup. Related thereto, a top edge of the second portion is welded to a bottom edge of the top member; and a bottom edge of the second portion is welded to a top edge of the bottom member. In another aspect, a penetration weld is formed between the interfaces of the first portion and second portion, top member and second portion, and bottom member and second portion. In a different aspect, a substantially H-shaped cross-section is defined at the interface of the top member, first portion and second portion.
In this embodiment, the first portion defines an opening disposed within the outer frame structure; and the second portion completely covers the defined opening. Alternatively, a recess is defined between the top member and first portion of the pair of side members. In this arrangement, the first portion extends past the top member to define a flange-like structure.
An advantage of the present disclosure is a reduction in stress risers at the interface or adjoining of the first and second portions of the side members. The first portion can provide an outer, frame-like structure that defines the side member, whereas the second portion has a reduced thickness encompassed within a window-like portion defined in the first portion. This new structural design reduces or eliminates the stress risers found in conventional boom structures and provides improved strength to the boom. In addition, the frame-like structure defined by the first portion provides support to the boom against objects and debris that impact the boom. In conventional booms, the thinner portion of the side members extends from the top to the bottom panels of the boom and can be dented or damaged when impacted by debris. The new design is better able to withstand debris. Also, the first portion can define the cylinder lug for coupling to a hydraulic cylinder. This eliminates the need for a separate lug portion to be welded to the boom and create additional stress risers.
The second portion also allows the boom to have a maintained weight so the hydraulic cylinder can operably control the functionality of the boom. The second portion has a thickness less than the first portion, and this reduced thickness allows the boom to have less weight than if the second member was completely formed by the first portion.
Another advantage of the present disclosure is the continuous and uniform weld backup defined by the second portion of each side member. The continuous weld backup allows for a complete penetration weld which adds strength and support to the boom. The improved weld backup also eliminates the need of weld backup bars. As previously noted, backup bars are commonly used in conventional booms to support the weld interface between various members. The backup bars, however, cannot form a continuous weld, and therefore interruptions or gaps between the bars give rise to stress risers and cracks. The continuous and uniform weld backup formed by the second portion of the embodiments of the present disclosure reduce or eliminate the stress risers and potential cracks.
A further advantage of the present disclosure is the H-shaped cross-section formed by the first portion, second portion, and top member of the boom. This cross-section defines a recess or trough between the first portion and top member such that hoses, wires, fittings, etc. can be disposed within the recess or trough to add shielded from potential debris and damage.
The above-mentioned aspects of the present invention and the manner of obtaining them will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention, taken in conjunction with the accompanying drawings, wherein:
Corresponding reference numerals are used to indicate corresponding parts throughout the several views.
The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present invention.
Referring to
The boom 400 further includes a lug 424 that is formed as a portion of each side member 410. The lug 424 protrudes or extends in a direction towards the bottom member 408 and includes a defined opening 428 therethrough. In a work vehicle, similar to the one depicted in
Each of the side members 410 is structured to include a first frame body 412 and a second frame body 414. The first frame body 412 and second frame body 414 can be coupled to one another by welding, fastening, or other known means to form each side member 410. For purposes of this disclosure, the first frame body 412 has a greater thickness than the second frame body 414. For example, the first frame body 412 can have a thickness of approximately 20 mm and the second frame body 414 can have a thickness of about 10 mm. These thicknesses are only exemplary and not intended to be limiting to the scope of this disclosure. In other embodiments, the first frame body 412 can have a greater thickness than 15 mm and the second frame body can have a thickness less than 20 mm. Regardless of the embodiment, however, the first frame body 412 has a greater thickness than the second frame body 414.
In the illustrated embodiments of
Thus, one advantage of the boom structure 400 is the uniform and continuous frame structure 412 that incorporates the lug 424. Similarly, the first end 402 and second end 404 of the boom 400 are substantially incorporated into the first frame body 412. This structure does not include the welding or other coupling means as required by the conventional boom structure 200 and therefore stress risers and the like are reduced or eliminated from the boom structure 400.
Similarly, the conventional boom 200 requires separate materials at each end 202, 204 and the lug area 212 to be welded to the side member 206. These additional materials or features increase the overall cost of the boom 200. In the structural design of the boom 400, however, these additional materials or features are incorporated into a uniform, all-in-one design that costs less, does not require the numerous welding processes to form the side member, and further strengthens each side member 410 by reducing or eliminating stress risers.
Another advantage of the boom 400 is its improved rigidity over conventional booms. In the conventional boom 200, a substantial portion of the length of the top member 214 interfaces with the thin portion 208. During operation, trees, debris, and other objects can dent the thin portion 208 of the side member 206 due to its lack of rigidity. In some instances, the thin portion 208 can crack or be severely damaged due to these objects. In the structural design of the boom 400, however, the first frame body 412 substantially supports the side member 408 by forming an outer boundary of the side member 410 and thereby adds rigidity that is lacking in conventional boom structures.
In addition to strength and rigidity, a further advantage of this design is the ability to maintain a desired weight of the overall boom structure 400. Referring to
In addition, the internal edges of the upper boundary 416, lower boundary 418, and side boundaries 420, 422 define an open or window-like area 604 therebetween which is free of the thicker material that forms the first frame body 412. As shown in
The arrangement of the first frame body 412 with respect to the top member 406 and bottom member 408 as shown in
As noted above, conventional booms require a weld backup in the form of a plurality of support bars 300 to add strength and stability to the boom. However, these support bars have been unable to provide sufficient support to the welds and discontinuity between each bar often cause cracks or fractures. Embodiments of the present disclosure are able to overcome these disadvantages by providing a uniform, continuous support structure along the length of the boom 400. In particular, the second frame body 414 provides a continuous weld backup to support the welds between the top member 406, bottom member 408 and each side member 410.
Referring to
Since the outer surface 802 and upper surface 804 of the second frame body 414 extend along a substantial portion of the length of the boom 400, without discontinuity or interruption, the second frame body 414 provides a uniform, continuous weld backup for the boom structure. In addition, the boom structure can be constructed with a penetration weld, which is generally much stronger than a fillet weld used in many conventional booms 200. The other advantage is the second frame body 414 replaces backer support bars 300, which as described above, are difficult to position inside the boom and often provide inadequate support to the formed welds.
An additional advantage of the H-shaped cross-sectional boom structure is the ability to reposition or relocation hoses, fittings, wires, etc. Referring to
As best shown in
While exemplary embodiments incorporating the principles of the present invention have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
