Control device for a power shovel

Material or article handling – Vertically swinging load support – Shovel or fork type

Patent

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Details

414699, 172 45, E02F 332

Patent

active

048894664

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a device for controlling a power shovel having a first boom, a second boom and an arm rotatable around a longitudinal axis of the arm.
2. Background Art
A power shovel of this type has a first boom, a second boom and an arm which is rotatable around the longitudinal axis thereof. Accordingly, it can perform more sorts of operations than a conventional type. For example, it can carry out corner digging by raising a bucket thereof in the vertical direction. And so-called transversal digging by rotating an upper revolving superstructure while the cutting edge of the bucket is kept to be directed toward the transversal direction by rotating the arm.
However, in the corner digging, the first boom and the second boom is operated such that the connection point between the second boom and the arm is moved in the vertical direction, which consequently varies the angle of the arm with respect to the horizontal plane. As a result, the connection point between the arm and the bucket does not move along the vertical line due to the variation of the arm's angle with respect to the horizontal plane. Accordingly, when corner digging is performed, the arm must be operated so that the angle of the arm to the horizontal plane may be held constant.
However, it will impose a heavy burden on an operator to operate the arm while operating the first and second booms concurrently. Moreover, it requires a great deal of skill to carry out appropriately this operation.
In the transversal digging, when the upper revolving superstructure is rotated, the direction of the edge of the bucket varies as the upper revolving superstructure rotates. Accordingly, when forming a straight ditch, the direction of the cutting edge of the bucket should be corrected corresponding to the rotation of the upper revolving superstructure so that the cutting edge of the bucket is directed toward a fixed direction.
In order to correct the direction of the cutting edge of the bucket, the arm should be revolved around the longitudinal axis thereof. However, when forming the straight ditch, the first and second booms and the upper revolving superstructure should be operated, and therefore it will be a heavy burden for an operator to perform a further operation for revolving the arm in addition to the above-mentioned operations.
As described above, when performing the corner digging, the connection point between the second boom and the arm should be moved in the vertical direction. However, it is not easy even for a skillful operator to move the connection point in the vertical direction by operating the first and second booms concurrently. Consequently, in reality, the connection point often deviates from the vertical direction back and forth. This back-and-forth deviation causes the edge of the bucket to move back and forth, so that accurate corner digging cannot be performed.
Furthermore, to form the straight ditch in the transversal digging, the first and second booms are operated so that the connection point is moved along a straight line. However, the bottom of the ditch will be irregular because the height of the connection point is likely to change.
This invention is made to solve the above-described problems in the conventional technology.


DISCLOSURE OF INVENTION

This invention relates to a control device for use in a power shovel having a first boom, a second boom and an arm rotatable around the longitudinal axis of the arm.
The first aspect of this invention comprises: angle detecting means for detecting the posture angles of a first boom, a second boom and an arm; posture angle calculating means for calculating the angle of the arm with respect to the horizontal plane based on the output from the angle detecting means; means for setting a target angle of the arm with respect to the horizontal plane; and control means for controlling an arm cylinder so that the angle of the arm with respect to the horizontal plane may be set to the target angle.
The second aspect of this invention co

REFERENCES:
patent: 3463336 (1969-08-01), Mark
patent: 3717269 (1973-02-01), Schaeff
patent: 4129224 (1978-12-01), Teach
patent: 4140144 (1979-02-01), Dowd et al.
patent: 4221266 (1980-09-01), Fardal
patent: 4288196 (1981-09-01), Sutton II
patent: 4685861 (1987-08-01), Huetsch
patent: 4699239 (1987-10-01), Ishino et al.
International Publication WO/81/02904, 10/15/81, Bachmann.

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