Construction machine

Abstract

A revolving frame is composed of a center frame and a tail frame. The center frame is composed of a front bottom plate and left and right front vertical plates erected on the front bottom plate and having front part sides being left and right bracket portions performing pin-connection between a lower boom of a working mechanism and a boom cylinder. The tail frame is composed of left and right I-section beams and a rear bottom plate connecting each I-section beam to each other. A height dimension (A) between boom pin through holes provided in the bracket portions is set smaller than a height dimension (B) of the front end of an upper flange portion of the I-section beam.

1 . A construction machine comprising:
 a lower traveling structure;   an upper revolving structure rotatably mounted on said lower traveling structure; and   a working mechanism liftably provided on a front part side of said upper revolving structure;   wherein a center frame of a revolving frame constituting said upper revolving structure is composed of a front bottom plate and left and right front vertical plates extending in the front and rear directions on said front bottom plate, erecting in the left and right directions with an interval, and having the front part side being a bracket portion for performing pin-connection of a boom of said working mechanism and a boom cylinder;   a tail frame connected to a rear part side of said center frame is composed of left and right I-section beams joined to a rear part of each of said front vertical plates and a rear bottom plate connecting each of said I-section beams to each other; and   said left and right I-section beams are formed of left and right rear vertical plates extending in the front and rear directions and having front ends joined to each of said front vertical plates, an upper flange portion provided on the upper side of each of said rear vertical plates, extending in the front and rear directions, and having a front end joined to each of said front vertical plates, and a lower flange portion provided on the lower side of each of said rear vertical plates, extending in the front and rear directions and having the front end joined to said front bottom plate; characterized in that:   a boom pin through hole performing pin-connection of a foot portion of said boom is provided on said bracket portion of said center frame; and   supposing that a height dimension from said front bottom plate to a hole center of said boom pin through hole is (A) and a height dimension from said front bottom plate to the front end of said upper flange portion, portion is (B), said height dimension (A) is set smaller than said height dimension (B).   
     
     
         2 . The construction machine according to  claim 1 , wherein a cylinder pin through hole performing pin-connection of said boom cylinder is provided in said bracket portion of said center frame on the front side of said boom pin through hole and at a position on the lower side; and
 supposing that a distance dimension between the hole center of said cylinder pin through hole and the hole center of said boom pin through hole is (C) and a distance in the horizontal direction is (D) when said height dimension (A) is set smaller than said height dimension (B), and   supposing that, as a comparison target, a distance dimension between the hole center of a cylinder pin through hole and the hole center of a boom pin through hole is (Cp) and a distance in the horizontal direction is (Dp) when a height dimension (Ap) from a front bottom plate to the hole center of said boom pin through hole is set larger than a height dimension (Bp) from said front bottom plate to the front end of an upper flange portion,   said distance (D) is set larger than said distance (Dp) in accordance with a portion by which said height dimension (A) is set smaller than said height dimension (Ap) so that said distance dimension (C) becomes substantially equal to said distance dimension (Cp).   
     
     
         3 . The construction machine according to  claim 1 , wherein supposing that a distance between a center line (S-S) in the front and rear directions passing through the middle of said left front vertical plate and said right front vertical plate of said center frame and a revolving center (O) of said center frame is (E) when said height dimension (A) is set smaller than said height dimension (B), and
 supposing that, as a comparison target, a distance between a center line (Sp-Sp) in the front and rear directions passing through the middle of a left front vertical plate and a right front vertical plate of a center frame and a revolving center (Op) of said center frame is (Ep) when said height dimension (Ap) from said front bottom plate to the hole center of said boom pin through hole is set larger than said height dimension (Bp) from said front bottom plate to the front end of said upper flange portion,   said distance (E) is set smaller than said distance (Ep).   
     
     
         4 . The construction machine according to  claim 1 , wherein a cylinder pin through hole performing pin-connection of said boom cylinder is provided in said bracket portion of said center frame on the front side of said boom pin through hole and at a position on the lower side; and
 supposing that a distance dimension between the hole center of said cylinder pin through hole and the hole center of said boom pin through hole is (C) and a distance in the horizontal direction is (D) when said height dimension (A) is set smaller than said height dimension (B), and that a distance between a center line (S-S) in the front and rear directions passing through the middle of said left front vertical plate and said right front vertical plate of said center frame and the revolving center (O) of said center frame is (E),   supposing that, as a comparison target, a distance dimension between a hole center of a cylinder pin through hole and a hole center of a boom pin through hole is (Cp) and a distance in the horizontal direction is (Dp) when a height dimension (Ap) from a front bottom plate to the hole center of said boom pin through hole is set larger than a height dimension (Bp) from said front bottom plate to a front end of an upper flange portion, and that a distance between a center line (Sp-Sp) in the front and rear directions passing through the middle of a left front vertical plate and a right front vertical plate of a center frame and a revolving center (Op) of said center frame is (Ep),   said distance (D) is set larger than said distance (Dp) and also, said distance (E) is set smaller than said distance (Ep) in accordance with a portion by which said height dimension (A) is set smaller than said height dimension (Ap) so that said distance dimension (C) becomes substantially equal to said distance dimension (Cp).   
     
     
         5 . The construction machine according to  claim 1 , wherein a front plate extending in the left and right directions and connecting said left and right front vertical plates is provided on the front part sides between said left and right front vertical plates; and
 a first bent portion and a second bent portion bent at two spots in the front and rear directions are provided in said front plate.