Patent ID: 7993091
Filing Date: 2011-08-09
Classification: B66F,E02F

Abstract:
1. A working machine comprising: a boom having a first end attached to a structural body; an attachment attached to a second end of the boom; a bell crank attached to a middle position of the boom in a longitudinal direction thereof; a tilt cylinder having a first end pivotally supported on the structural body and a second end pivotally supported on an upper end of the bell crank when the attachment is horizontally at a ground position; a boom cylinder having a first end pivotally supported on the structural body and a second end pivotally supported on the boom; and a connecting link for connecting a lower end of the bell crank and the attachment when the attachment is horizontally at a ground position, wherein: an angle between a first line segment connecting a pivot position on the boom and a pivot position on the connecting link of the bell crank and a second line segment connecting the pivot position on the boom and a pivot position on the tilt cylinder of the bell crank is set in a range from 0 degrees to 180 degrees on the attachment side; the attachment is one of a plurality of attachments; each of the attachments is pivotally supportable at a different position by the connecting link with reference to a pivot position on the boom, the attachments include a bucket, the bucket being attached to the boom and the connecting link such that the bucket has different postures at the ground position including a horizontally supported posture and a tilted posture in which the bucket is tilted by the tilt cylinder, a pivot position of the tilt cylinder to the structural body is below a pivot position of the boom to the structural body, and a pivot position of the boom cylinder to the structural body is above a pivot position of the boom to the bell crank when the attachment is horizontally at a ground position, the bell crank is constructed and connected to the tilt cylinder and the boom, the tilt cylinder is constructed and connected to the bell crank and the structural body, and the boom is constructed and connected to the bell crank and the structural body to provide the attachment with the ground position, a top position and at least one intermediate position between the ground position and the top position in which the attachment, including the bucket with the different postures at the ground position, has the same posture in all of the ground position, the at least one intermediate position and the top position, the angle between the first line segment and the second line segment is set at an angle at which a sum of the attachment angle of the attachment at the at least one intermediate position and at the top position becomes substantially zero, and the bell crank is constructed and connected to the tilt cylinder and the boom, the tilt cylinder is constructed and connected to the bell crank and the structural body, and the boom is constructed and connected to the bell crank and the structural body such that the pivot position of the tilt cylinder to the bell crank is maintained radially outward of the pivot position of the boom to the bell crank at all of the ground position, the at least one intermediate position and the top position while the attachment has the same posture.