Electrosurgical instrument
An embodiment of the invention includes an electrosurgical jaw structure that carries cooperating PTC bodies in both series and parallel circuit components for controlled RF energy application to engaged tissue to effectively weld tissue.
1. An electrosurgical instrument for applying energy to a body structure, the instrument comprising first and second jaws carrying respective first and second energy-delivery elements coupled to an RF source by a first circuit component, the first energy-delivery element coupled to a resistive body in the first jaw, wherein the first energy-delivery element and the resistive body are coupled the RF source by a second circuit component, and wherein the second energy-delivery element is a positive temperature coefficient (PTC) composition and the resistive body is a PTC composition and the second energy-delivery element PTC composition and the resistive body PTC composition define different temperature-impedance curves.
2. An electrosurgical instrument as in claim 1 , wherein the first circuit component comprises a series circuit when engaging body structure.
3. An electrosurgical instrument as in claim 1 , wherein the second circuit component comprises a parallel circuit.
4. An electrosurgical instrument as in claim 1 , wherein the second energy-delivery element PTC composition defines a substantially low impedance in a 40° C. to 60° C. range.
5. An electrosurgical instrument as in claim 1 , wherein the second energy-delivery element PTC composition defines a substantially lower impedance in a 40° C. to 60° C. range than the resistive body PTC composition in a similar temperature range.
6. An electrosurgical instrument comprising first and second jaws coupled to an RF source and actuatable between a first open position and a second closed position, the jaws in a closed position define an engagement gap, wherein the first jaw carries a first energy-delivery element and the second jaw carries a second energy-delivery element of PTC composition, the first energy-delivery element coupled to a resistive body PTC composition in the first jaw, and the second energy-delivery element PTC composition and the resistive body PTC composition define different temperature-impedance curves.
7. An electrosurgical instrument as in claim 6 , wherein the engagement gap ranges from about 0.0005 inches to about 0.050 inches.
8. An electrosurgical instrument as in claim 6 , wherein the engagement gap ranges from about 0.001 inches to about 0.005 inches.
9. An electrosurgical instrument as in claim 6 , wherein the first and second energy-delivery elements are coupled to the RF source by a first circuit configuration.
10. An electrosurgical instrument as in claim 6 , wherein the first energy-delivery element and the resistive body PTC composition are coupled to the RF source by a second circuit configuration.
11. An electrosurgical instrument as in claim 6 , wherein the first circuit configuration comprises a series circuit when engaging a body structure.
12. An electrosurgical instrument as in claim 10 , wherein the second circuit configuration comprises a parallel circuit.
13. An electrosurgical instrument as in claim 6 , further comprising a axially-extending member that is actuatable from a first retracted position to a second extended position, wherein actuation of the axially-extending member toward the second extended position actuates the first and second jaws toward the second closed position.
14. An electrosurgical instrument as in claim 13 , wherein the axially-extending member carries a blade member for transecting tissue.
15. An electrosurgical instrument as in claim 13 , wherein the axially-extending member is connected to the RF source.
16. An electrosurgical instrument as in claim 6 , wherein the second energy-delivery element PTC composition defines a substantially low impedance in a 40° C. to 60° C. range.
17. An electrosurgical instrument as in claim 6 , wherein the second energy-delivery element PTC composition defines a substantially lower impedance in a 40° C. to 60° C. range than the resistive body PTC composition in a similar temperature range.