Sliding rail positioning device

1. A sliding rail positioning device comprising:

a first rail;

a second rail, the first rail slidably coupled to the second rail; and

a third rail, the second rail slidably coupled to the third rail, wherein:

the second rail comprises a second body and a second holding member, the second body defining a first receiving hole;

the third rail comprises a third body and a third holding member;

when the second body is driven by the first rail to slide out, the third holding member is biased toward the second body to be received in the first receiving hole, so that the second body cannot be retracted back; and

when the first rail is retracted, the first rail presses the second holding member to press the third holding member out of the first receiving hole so that the second body can be retracted;

wherein the first rail comprises a first body and a first holding member, the second body defines a latching hole, the first holding member is biased toward the second body to be accommodated in the latching hole so that the first body drives the second body to slide out.

2. The sliding rail positioning device of claim 1 , wherein:

the second holding member is biased toward the first body; and

the second holding member can be pressed by the first body to be received in the first receiving hole.

3. The sliding rail positioning device of claim 1 , wherein:

the first holding member comprises a first fixing portion and a first latching portion;

the first fixing portion is fixedly coupled to the first body;

the first latching portion is biased toward the second body, and a surface of the first latching portion facing the second body is provided with a latching protrusion; and

the latching protrusion is configured to be accommodated in the latching hole.

4. The sliding rail positioning device of claim 3 , wherein:

a side of the first latching portion facing the second body is provided with a pressing protrusion located on a side of the latching protrusion adjacent to the first fixing portion;

the second body further defines a pressing hole at a position adjacent to the latching hole; and

the pressing protrusion is configured to be received in the pressing hole.

5. The sliding rail positioning device of claim 3 , wherein:

the first body further defines a clearance hole;

the first body comprises a hook protruding into the clearance hole;

the first holding member further comprises a first limiting portion extending into the clearance hole; and

an end of the first limiting portion away from the first fixing portion abuts on the hook.

6. The sliding rail positioning device of claim 1 , wherein:

the second holding member comprises a second fixing portion, a second latching portion, and a pressing portion;

the second fixing portion is fixedly coupled to the second body;

an end of the second holding member away from the second fixing portion is biased toward the first rail;

the second latching portion is arranged toward the third body, and the pressing portion is arranged toward the first body; and

the pressing portion is configured to be pressed by the first rail so that the second latching portion is received in the first receiving hole.

7. The sliding rail positioning device of claim 1 , wherein:

the third holding member comprises a third fixing portion and a third latching portion;

the third fixing portion is fixedly coupled to the third body;

the third latching portion is biased toward the second body, and a side of the third latching portion facing the second body is provided with a limiting protrusion;

the limiting protrusion is configured to be accommodated in the first receiving hole and latched with the first receiving hole.

8. The sliding rail positioning device of claim 1 , wherein:

the second body further defines a limiting hole; and

when the second body is slidably retracted back to the third body, the limiting hole is configured to accommodate the third holding member and limit a sliding distance of the second body.

9. The sliding rail positioning device of claim 1 , wherein:

the third body defines a second receiving hole; and

the third holding member is configured to be held by the second body to be received in the second receiving hole.

10. A sliding rail positioning device comprising:

a first rail comprising a first body and a first holding member;

a second rail comprising a second body and slidably coupled to the first rail; and

a third rail comprising a third body and slidably coupled to the second rail; wherein:

the second rail comprises second holding member, and the second body defines a first receiving hole and a latching hole, wherein the first holding member is biased toward the second body to be accommodated in the latching hole so that the first body drives the second body to slide out;

the third rail comprises a third holding member;

the first rail is configured to drive the second rail to move relative to the third rail through the cooperation of the first holding member and the latching hole to slide out to a designated position and length of the sliding rail positioning device;

when the second body is driven by the first rail to slide out, the third holding member is biased toward the second body to be received in the first receiving hole, so that the second body cannot be retracted back; and

when the first rail is retracted, the first rail presses the second holding member to press the third holding member out of the first receiving hole so that the second body can be retracted.