Hydraulic cylinder having rod safety device

Abstract

A hydraulic cylinder having a rod safety device is provided, which can prevent a free falling of an arm and a bucket by fastening members when a welding part is broken to protect a cab and an operator. The hydraulic cylinder having a rod safety device which includes a cylinder rod sliding within a set stroke range in a tube and composed of a rod head and a rod body joint-connected to the rod head; a cover connected by weld joint to one end part of the tube; an end cover connected by weld joint to the other end part of the tube; a piston fastened to one end part of the cylinder rod to reciprocate along an inner periphery of the tube; and a connection means composed of a screw engagement part formed in center parts of mutual contact surfaces of the rod head and the rod body in a shaft direction to joint-connect the rod head and the rod body by screw-engaging the rod head and the rod body, and a weld joint part joint-connecting the rod head and the rod body by welding outer peripheries of the contact surfaces of the rod head and the rod body.

1 . A hydraulic cylinder having a rod safety device, comprising:
 a cylinder rod sliding within a set stroke range in a tube and composed of a rod head and a rod body joint-connected to the rod head;   a cover connected by weld joint to one end part of the tube;   an end cover connected by weld joint to the other end part of the tube;   a piston fastened to one end part of the cylinder rod to reciprocate along an inner periphery of the tube; and   a connection means composed of a screw engagement part formed in center parts of mutual contact surfaces of the rod head and the rod body in a shaft direction to joint-connect the rod head and the rod body by screw-engaging the rod head and the rod body, and a weld joint part joint-connecting the rod head and the rod body by welding outer peripheries of the contact surfaces of the rod head and the rod body.   
   
   
       2 . The hydraulic cylinder of  claim 1 , wherein the screw engagement part comprises screw holes respectively formed in the center parts of the mutual contact surfaces of the rod head and the rod body in the shaft direction, and a connection bolt engaged into the screw holes to screw-engage the rod head and the rod body. 
   
   
       3 . The hydraulic cylinder of  claim 1 , wherein the screw engagement comprises a screw hole formed in one of the center parts of the contact surfaces of the rod head and the rod body, and a connection bolt fixed by welding to the other of the center parts of the contact surfaces of the rod head and the rod body to correspond to the screw hole.