BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a joint and, more particularly, to a rotation joint structure.

2. Description of the Related Art

A conventional joint structure comprises a fixed joint and a movable joint pivotally connected with the fixed joint. The conventional joint structure is available for a household implement or utensil, such as a baby bed, a play pen, a baby stroller, a coat rack or the like. Thus, the movable joint is rotated relative to the fixed joint to expand or fold the conventional joint structure and the household implement. The conventional joint structure also comprises a locking mechanism to lock the movable joint so as to prevent the movable joint from being pivoted freely. However, the conventional joint structure only has a single locking mechanism so that the locking mechanism is easily unlocked and released due to an inadvertent touch. Thus, the conventional joint structure cannot be used safely.

BRIEF SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a rotation joint structure that provides a two-stage locking mechanism to ensure a safe usage.

In accordance with the present invention, there is provided a rotation joint structure comprising a fixed joint, a movable joint, at least one primary spring, a slide knob, a first limit member, a second limit member, a secondary spring, and a movable rod. The fixed joint has a fixed base. The fixed base has a face provided with at least one primary receiving slot. The fixed base has an outside provided with a locking groove. The movable joint has a movable seat. The movable seat has a face formed with at least one resting portion, a first slideway, and a second slideway. The at least one resting portion protrudes from the movable seat. The first slideway is connected to the second slideway. The second slideway has an interior formed with a protruding block. The movable seat has an outside formed with an opening and a mounting portion. The opening is connected to the first slideway. The mounting portion extends outward from the outside of the movable seat and defines a mounting recess. The mounting recess linearly aligns with the second slideway and is connected to the second slideway. The movable seat is pivotally connected with the fixed base. The at least one resting portion extends into the at least one primary receiving slot. The at least one primary spring is mounted in the at least one primary receiving slot and has a first end pressing one end of the at least one primary receiving slot and a second end pressing the at least one resting portion. The slide knob has a knob body. The knob body has a side formed with an insert. The slide knob is mounted in the opening such that the knob body is exposed outward from the movable seat. The insert extends through the opening into the first slideway. The first limit member has a first limit body. The first limit body has a side formed with an insert slot. The first limit body has an end formed with a stop block. The first limit member is mounted in the first slideway. The insert is inserted into the insert slot. The second limit member has a second limit body. The second limit body has a first side formed with a locking block and a second side formed with a protruding wall. The protruding wall defines a secondary receiving slot. The second limit member is mounted in the second slideway. The locking block is located outside of the second slideway. The protruding wall is received in the second slideway. The secondary spring is mounted in the secondary receiving slot. The secondary spring has a first end pressing the protruding block and a second end pressing one end of the secondary receiving slot. The movable rod is mounted in the mounting recess. The movable rod has an end secured to the second limit body of the second limit member.

When the rotation joint structure is disposed at a locked state, the at least one primary spring is extended normally, and the movable joint is pressed by the at least one primary spring such that the second slideway corresponds to the locking groove. At this time, the secondary spring is also extended normally to push the second limit member such that the locking block is locked in the locking groove. Thus, the movable joint is locked and cannot be rotated. In addition, the slide knob is located at a position where the stop block of the first limit member extends into the second slideway and rests on the protruding wall of the second limit member to stop movement of the second limit member, such that the second limit member is locked, and the movable rod cannot be pulled outward, to prevent the locking block from being detached from the locking groove. Thus, the rotation joint structure provides a two-stage locking mechanism.

According to the primary advantage of the present invention, the first limit member and the second limit member construct a two-stage locking mechanism, such that the movable joint is locked solidly and steadily and cannot be rotated, to ensure the safety of usage of the rotation joint structure.

Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.

