Folded ultrasonic end effectors with increased active length

1. An end effector for use with an ultrasonic surgical instrument, comprising:

a body extending along a longitudinal axis comprising a proximal end and a distal end, the body comprising an outer surface that defines an inner portion, the proximal end of the body is configured to couple to an ultrasonic transducer configured to produce vibrations at a predetermined frequency and a predetermined amplitude;

a folded element having a predetermined length, the folded element comprising a first end coupled to the distal end of the body and extending proximally along the longitudinal axis from the distal end of the body toward the proximal end of the body into the inner portion, the folded element comprising a second free acoustic end;

wherein the folded element and the outer surface of the body define a single substantially parallel acoustic path spanning the length of the folded element; and

a clamp arm operatively coupled to the body.

2. The end effector of claim 1 , wherein the distal end of the body substantially coincides with a node, wherein the node is a location of minimum amplitude displacement, wherein the second free acoustic end of the folded element substantially coincides with an antinode, wherein the antinode is a location of maximum amplitude displacement, and wherein when the end effector is energized by the ultrasonic transducer, the distal end of the body substantially coinciding with the node remains stable and the second free acoustic end vibrates at the predetermined frequency and amplitude.

3. The end effector of claim 1 , comprising a tissue pad coupled to the clamp arm.

4. The end effector of claim 1 , wherein the clamp arm is configured to apply a predetermined force profile against the body, wherein the force is inversely proportional to a displacement profile of the active length of the body.

5. The end effector of claim 4 , wherein the clamp arm is configured as a leaf-spring.

6. The end effector of claim 4 , wherein the clamp arm comprises a spring operatively coupled to first and second hinged clamp arm members.

7. The end effector of claim 1 , wherein the distal end of the body is located in proximity to a node; and

wherein the second free acoustic end of the folded element is located in proximity to an antinode.

8. The end effector of claim 1 , wherein the distal end of the body substantially coincides with a first displacement region located between a node and an antinode; and

wherein the second free acoustic end of the folded element substantially coincides with a second displacement region located between a node and an antinode.

9. The end effector of claim 1 , wherein the body is configured as a tubular member and the folded element is configured as a solid member.

10. The end effector of claim 1 , wherein the body comprises a solid portion at the proximal end and a hollow portion at the distal end, wherein the hollow portion defines a slot to receive the folded element therein.

11. The end effector of claim 1 , wherein the outer surface of the body defines an active length that is greater than one quarter wavelength, wherein the active length is defined as a region that begins at the distal end of the body where amplitude displacement is at a minimum and extend proximally to a location where the amplitude displacement is one-half of a maximum amplitude displacement that occurs along the active length.

12. The end effector of claim 1 , wherein the longitudinal cross-sectional area of the body is substantially equal to the longitudinal cross-sectional area of the folded element.

13. A surgical instrument, comprising:

a transducer configured to produce vibrations along a longitudinal axis at a predetermined frequency and a predetermined amplitude;

an end effector for use with an ultrasonic surgical instrument, comprising:

a body extending along a longitudinal axis comprising a proximal end and a distal end, the body comprising an outer surface that defines an inner portion, the proximal end of the body is configured to couple to an ultrasonic transducer configured to produce vibrations at a predetermined frequency and a predetermined amplitude;

a folded element having a predetermined length, the folded element comprising a first end coupled to the distal end of the body and extending proximally along the longitudinal axis from the distal end of the body toward the proximal end of the body into the inner portion, the folded element comprising a second free acoustic end;

wherein the folded element and the outer surface of the body define a single substantially parallel acoustic path spanning the length of the folded element; and

a clamp arm operatively coupled to the body.

14. The surgical instrument of claim 13 , wherein the folded element comprises sealing edges formed on lateral portions of the body.

15. The surgical instrument of claim 13 , wherein the body is configured as a tubular member and the folded element is configured as a solid member.

16. The surgical instrument of claim 13 , wherein the body comprises a solid portion at the proximal end and a hollow portion at the distal end, wherein the hollow portion defines a slot to receive the folded element therein.

17. The surgical instrument of claim 13 , wherein when the end effector is energized by the ultrasonic transducer, the outer surface of the body defines an active length that is greater than one quarter wavelength, wherein the active length is defined as a region that begins at the distal end of the body where amplitude displacement is at a minimum and extend proximally to a location where the amplitude displacement is one-half of a maximum amplitude displacement that occurs along the active length.

18. The surgical instrument of claim 13 , wherein the longitudinal cross-sectional area of the body is substantially equal to the longitudinal cross-sectional area of the folded element.

19. An end effector for use with an ultrasonic surgical instrument, comprising:

a body extending along a longitudinal axis comprising a proximal end and a distal end, the body comprising an outer surface that defines an inner portion, the proximal end of the body is configured to couple to an ultrasonic transducer configured to produce vibrations at a predetermined frequency and a predetermined amplitude;

a folded element having a predetermined length, the folded element comprising a first end coupled to the distal end of the body and extending proximally along the longitudinal axis folded element comprising a second free acoustic end;

wherein the folded element and the outer surface of the body define a single substantially parallel acoustic path spanning the length of the folded element, the folded element comprising sealing edges formed on lateral portions of the body; and

a clamp arm operatively coupled to the body.

20. The end effector of claim 19 , comprising a tissue pad coupled to the clamp arm.

21. The end effector of claim 20 , wherein the clamp arm is configured to apply a predetermined force between the tissue pad and the sealing edges.

22. The end effector of claim 19 , wherein the body is adapted to receive a knife between the first and second sealing edges.