| 摘要 |
<p>An improved rotatable joint of the kind disclosed in U:S: Pat. 5,381,570 for foldable tubular playpen frames having a step in the tooth of a recessed sprocket portion in which a connecting gear rests. In order to unlock the joint one must move the gear axially inwardly a pushbutton as well as relieve the stresses on the joint by lifting up the tubular bars connected to the joint so that the gear may slip off the step. In this way an additional factor of safety is built-in in order to unlock the joint, and accidental release is reduced.</p> |
