Electrically powered drive system for medical device

1. An electrically powered drive system for a medical device, comprising:

a motor;

a gear box driven by the motor and comprising an output member;

a driving member configured to move a movable part of the medical device;

a crank mechanism comprising:

a first crank arm having a connection end and a distal end, the distal end of the first crank arm being pivotally connected to the driving member; and

a second crank arm having a connection end and a distal end, the connection end of the second crank arm being pivotally connected to the connection end of the first crank arm, and the distal end of the second crank arm being pivotally connected to a stationary member; and

a push-pull mechanism connected between the gear box and the crank mechanism, the push-pull mechanism being connected to the output member of the gear box, the push-pull mechanism being configured to drive the crank mechanism to move the driving member between a retracted position and an extended position under the drive of the output member;

wherein when the driving member is at the extended position, the angle between the first crank arm and the second crank arm is less than 180 degrees.

2. The drive system of claim 1 , wherein the push-pull mechanism comprises a cam connected to the output member of the gear box, and the movement of the driving member between the retracted position and the extended position results from a movement of the cam between a first position and a second position.

3. The drive system of claim 2 , wherein the push-pull mechanism further comprises a push-pull arm having one end connected to the crank mechanism and the other end connected to and drivable by the cam.

4. The drive system of claim 3 , wherein the one end of the push-pull arm is connected to a joint between the first crank arm and the second crank arm.

5. The drive system of claim 3 , wherein the other end of the push-pull arm defines an opening in which the cam is received.

6. The drive system of claim 2 , wherein the cam is located outside an angle formed between the first crank arm and the second crank arm of the crank mechanism and abuts against one of the first crank arm and the second crank arm, and the push-pull mechanism further comprises a resilient element for returning the crank mechanism.

7. The drive system of claim 2 , wherein when the driving member is at the retracted position, a joint between the first and second crank arms of the crank mechanism sinks below the distal ends of the first and second crank arms so that an angle is formed between the first and second crank arms, and the cam is located outside the angle.

8. The drive system of claim 1 , wherein the push-pull mechanism comprises a wheel connected to the output member of the gear box and a cable, one end of the cable is fixed to the wheel, and the other end of the cable is connected to the crank mechanism.

9. The drive system of claim 8 , wherein the push-pull mechanism further comprises a resilient element for returning the crank mechanism.

10. The drive system of claim 1 , wherein the stationary member is a housing of the gear box.

11. The drive system of claim 1 , wherein the first crank arm has a greater length than the second crank arm.

12. The drive system of claim 1 , wherein the cam is an off-center pin on the output member.

13. The drive system of claim 1 , wherein the medical device is a surgical stapler or a surgical cutter.