Material or article handling – Vertically swinging load support – Shovel or fork type
Patent
1997-09-29
1999-11-02
Underwood, Donald W.
Material or article handling
Vertically swinging load support
Shovel or fork type
212232, 212300, E02F 500
Patent
active
059758333
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a hydraulic excavator comprising a traveling carriage and a turning structure turnably mounted on the traveling carriage, and more particularly to a swing type hydraulic excavator with a boom capable of swinging to the left and right in a position on the front end side of the turning structure to carry out excavating, e.g., digging of a side trench.
BACKGROUND ART
Recently, an attention has been focused on small-turn type hydraulic excavators wherein a work front is designed to be able to turn with a small radius so that the excavator can work in a narrow place. It is essential for these small-turn type hydraulic excavators to have a function of enabling a side trench to be dug in a position near and transversely of an excavator body without changing the body position. To this end, hydraulic excavators of the offset and swing types have been proposed. There are known the following examples (1) an example of the offset type and (2), (3) examples of the swing type.
(1) JP, A, 3-255241
According to this known art, an arm is made up of an offset arm coupled to a front end of a boom in such a manner as to be able to be offset to the left and right, and a bucket arm capable of pivotally moving up and down with respect to the offset arm while being kept parallel to the boom. This known art also discloses a structure in which a longitudinal groove is formed in an upper cover, which covers most of an area over a turning frame except for the cab, to prevent interference between the boom and the upper cover when the boom is maximally lifted upward.
(2) JP, A, 5-125743
This known art discloses a swing type hydraulic excavator wherein a boom is swingable to the left and right about a swing post in a position on the front end side of a turning structure.
(3) JP, A, 7-243223
This known art discloses a structure that, in a swing type hydraulic excavator similar to that of the above (2), includes a boom having a two-piece boom made up of a lower boom capable of pivotally moving up and down with respect to a swing post and an upper boom capable of pivotally moving up and down with respect to the lower boom, and an opening angle adjusting means for changing an angle between the lower boom and the upper boom depending on the angle of pivotal movement of the lower boom.
DISCLOSURE OF THE INVENTION
Meanwhile, in general, the area over a turning frame of a hydraulic excavator except for the cab is covered by an upper cover, and various equipment such as a prime mover, a hydraulic pump and a tank are installed inside the upper cover. Therefore, the upper cover is required to have a necessary minimum volume sufficient to install the equipment.
In the offset type hydraulic excavator of the above known art (1), the longitudinal groove into which a back portion of the boom comes into contact when the boom is lifted rearwardly upward, is formed in the upper cover. But, because the boom of the offset type hydraulic excavator is just lifted up and down, the presence of the longitudinal groove brings about a so small reduction in the volume defined by the upper cover that the necessary equipment can be installed inside the upper cover. Also, because the boom can be inclined rearward to a large extent, it is possible to reduce the radius of turn of the work front in its minimum-turn posture.
In the offset type hydraulic excavator, however, a complex parallel link mechanism and a cylinder for driving the parallel link mechanism are provided on an upper portion (upper boom) of the work mechanism or front. Accordingly, the weight of the work front mechanism is increased, resulting in the problems below.
(1) Because of a substantial increase in weight of the work front, the position of the center of gravity is displaced toward the distal end of the work front depending on the posture of the work front, and therefore stability of the excavator tends to become worse.
(2) Because of the increased weight of the work front, the weight of a counterweight is also required to be increased. Hence
REFERENCES:
patent: 4728251 (1988-03-01), Takashima et al.
patent: 4797060 (1989-01-01), Kishi et al.
Kobori Masashi
Nishimura Takaharu
Yamada Kazuyoshi
Hitachi Construction Machinery Co. Ltd.
Underwood Donald W.
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