Insulin needle tip protection mechanism and insulin injection device

An insulin needle tip protection mechanism, comprising:

• a needle holder, a spring, and a tail seal member;
• the needle holder has a cylinder, and the tail seal member is installed inside the cylinder equipped with the spring;
• the head of the tail seal member has a pin head, and its side wall has a flexible wall;
• the flexible wall protrudes outward from the main body of the tail seal member which can be pressed inward towards the interior of the tail seal member;
• the side wall of the cylinder of the needle holder has a U-shaped reciprocating slot;
• the pin head of the tail seal member is located within the U-shaped reciprocating slot and can move up and down within it;
• at the bottom of the cylinder of the tail seal member, there is an oblique keyhole slot, when the flexible wall of the tail seal member aligns with the oblique keyhole slot in a circumferential direction, then pushing the tail seal member, the flexible wall can be pressed into the tail seal member through the oblique keyhole slot;
• when the flexible wall of the tail seal member is misaligned with the oblique keyhole slot in a circumferential direction, it cannot be pushed into the cylinder due to the obstruction by the flexible wall;
• there is a beveled edge set at the bend of the U-shaped reciprocating slot, making one groove of the U-shaped reciprocating slot longer and the other shorter;
• the insulin needle tip protection mechanism is assembled in such a way that before injection, the pin head of the tail seal member is located at the bottom of the short groove of the U-shaped reciprocating slot, and at this time, the flexible wall of the tail seal member is aligned with the oblique keyhole slot in a circumferential direction;
• when the insulin pen is screwed or the insulin needle is pushed, the tail seal member can compress the spring and advance towards the inside of the cylinder, and the pin head also moves upward within the short slot, when it reaches the bend of the U-shaped reciprocating slot, it diagonally moves under the action of the beveled edge to the top of the long groove of the U-shaped reciprocating slot;
• when the injection is completed and the external force is removed, the tail seal member and its pin head retract backward under the restoring force of the spring, until the pin head moves downward to the bottom of the long groove of the U-shaped reciprocating slot, at the same time, the flexible wall of the tail seal member exits the oblique keyhole slot and returns to its protruding state, and because the tail seal member as a whole has rotated during the advancement process, at this time, the flexible wall of the tail seal member is misaligned with the oblique keyhole slot in a circumferential direction, so even if the tail seal member is pushed again, it cannot advance to the injection position and exposing the needle tip again.