Sheath type disposable safety scalpel

1. A sheath type disposable safety scalpel, comprising:

a blade;

a handle; and

a sheath,

wherein:

the blade is fixed a front end of the handle, and the sheath covers the front end of the handle and is connected with the handle through a sliding mechanism and a positioning mechanism;

the positioning mechanism is formed by the matching of a button provided on a top of the sheath and a blade protection locking notch and a blade exposure locking notch at one side of the handle;

the button is a flexible arm extending from the sheath and the flexible arm is provided with a pressing portion, the flexible arm is transformed flexibly in a width direction of the handle when pressing the button, and a locking head is provided at the end of the flexible arm facing the side of the handle;

the blade protection locking notch is located in a blade protection position at a lateral face at a front of the handle, and the blade exposure locking notch is located in a blade exposure position at a lateral face in a middle of the handle;

the blade protection locking notch is a first concave notch, and a first blocking face is provided at a right side of the first concave notch from a front face of the blade protection locking notch, and a first unlocking inclined face is provided at a lower portion of the first concave notch;

the blade exposure locking notch is a second concave notch, and a second blocking face is provided at a left side of the second concave notch, and a second unlocking inclined face is provided at a lower portion of the second concave notch;

under the assembly state, when the sheath presents a blade protection state in relation to the handle, the locking head is inserted into the blade protection locking notch to form a positioning and locking of blade protection and when the sheath presents a blade exposure state in relation to the handle, the locking head is inserted into the blade exposure locking notch to form a positioning and locking of blade exposure;

under the blade protection state, when the button is pressed and pulled backward, the locking head climbs out of the blade protection locking notch along the first unlocking inclined face to unlock and slides backward along with the sheath until the locking head drops in the blade exposure locking notch;

under the blade exposure state, when the button is pressed and pushed forward, the locking head climbs out of the blade exposure locking notch along the second unlocking inclined face to unlock and slides forward along with the sheath until the locking head drops in the blade protection locking notch, so that the sheath slides between the blade protection locking notch and the blade exposure locking notch in relation to the handle.

2. The sheath type disposable safety scalpel according to claim 1 wherein the locking head is a convex or lug structure perpendicular to a lateral face of the handle.

3. The sheath type disposable safety scalpel according to claim 1 wherein the locking head is a convex or lug structure parallel to a lateral face of the handle.

4. The sheath type disposable safety scalpel according to claim 1 wherein the first unlocking inclined face is provided below the blade protection locking notch, when the button is pressed, a slant of the first unlocking inclined face makes the locking head climb out of the blade protection locking notch from below the first concave notch; the second unlocking inclined face is provided below the blade exposure locking notch, and when the button is pressed, a slant of the second unlocking inclined face makes the locking head climb out of the blade exposure locking notch from below the second concave notch.

5. The sheath type disposable safety scalpel according to claim 4 wherein the first unlocking inclined face and the second unlocking inclined face are connected by a transition inclined face.

6. The sheath type disposable safety scalpel according to claim 1 wherein the first unlocking inclined face is provided at a lower right side of the blade protection locking notch, and when the button is pressed, the locking head moves to a lower position of the blade protection locking notch, and when the button is pulled backward, a slant of the first unlocking inclined face makes the locking head climb out of the blade protection locking notch from a lower right side of the first concave notch; the second unlocking inclined face is provided at a lower left side of the blade exposure locking notch, and when the button is pressed, the locking head moves to a lower position of the blade exposure locking notch, and when the button is pushed forward, a slant of the second unlocking inclined face makes the locking head climb out of the blade exposure locking notch from a lower left side of the second concave notch.

7. The sheath type disposable safety scalpel according to claim 1 wherein the blade protection locking notch and the blade exposure locking notch are provided at a front side and/or a back side of the handle and the locking head is provided on the button according to the quantity and position of the blade protection locking notch and the blade exposure locking notch.

8. The sheath type disposable safety scalpel according to claim 1 wherein the blade protection locking notch and the blade exposure locking notch on the handle are connected by a concave cambered surface, and a concave shape makes the handle thin in the middle and thick at the ends thereof.

9. The sheath type disposable safety scalpel according to claim 1 wherein the blade protection locking notch includes a lock notch, which is a third concave notch, and a third blocking faces are provided at positions at a left, a right, and below, front face of the lock notch, and a cambered surface or slope is provided between the lock notch and the blade protection locking notch, the cambered surface or slope configured to make the locking head slide from the blade protection locking notch into the lock notch under a forward driving force.

10. The sheath type disposable safety scalpel according to claim 9 wherein an assembly inclined surface is provided under the lock notch and the assembly inclined surface is connected with or adjacent to the first unlocking inclined face on a rear end and the assembly inclined surface leads to an installation base direction of the blade on the front end, of the handle and when the sheath covers the handle, press the button and push the sheath backward, then the locking head slides from the assembly inclined surface to the blade protection locking notch.