In constructing a space truss structure, using a multiplicity of structure members, e.g. lengths of steel pipe, each end of the structure members is joined to the spherical node. In order to radially join the structure members to nodes provided with several fastening portions, joint devices equipped with fastening bolts are commonly used. In that case, however, it may frequently be impossible to firmly screw the fastening bolt into a screw hole of the node.
Upon assembling all but one of the portions of the truss, the positions of the two nodes between which the final structure member is to be joined are established. Under this circumstance, if the end of the fastening bolt projects too far from the joint device, the last structure member cannot be fitted into the space between the two nodes whose separation has been already defined by assembly of the other members.
In order to solve the afore-mentioned problems, the applicant proposed in U.S. Pat. No. 4,872,779 a joint device wherein the fastening bolt can be led back into the side of the structure member. Such a joint device 41 is equipped with a spring 29 generating an elastic force, as best seen in FIG. 11 hereof. When the end of a threaded part 26a of the fastening bolt 6 comes into contact with the node (not shown), the spring 29 is automatically compressed. As shown by the two-dot chain line in FIG. 11, the threaded part 26a is then retracted into a sleeve 21. For this reason, the structure member 31 which is exactly sized to match with a designed length and the joint device 41 can be easily fitted into the space between the two nodes whose separation has been already defined.
In the joint device 41 described above, the spring 29 urges the fastening bolt 6 into a screw hole of the node. When the structure member 31 is directed to be in a vertical state as shown in FIG. 11, only the relatively weak elastic force of the spring 29 cannot lift the fastening bolt 6 up to the node enough to commence to be engaged with the screw hole of the node. For this reason, even a rotation of the sleeve 21 will not be able to facilitate an advance of the threaded part 26a toward the screw hole of the node. This is because initial engagement between the fastening bolt 6 and the screw hole of the node cannot be accurately assured.