Electrosurgical apparatus

1. An electrosurgical forceps, comprising:

a first member including a first housing and a first shaft member depending from the first housing, the first shaft member having a first jaw member with a tissue contacting surface;

a second member including a second housing and a second shaft member depending from the second housing, the second shaft member having a second jaw member with a tissue contacting surface configured to communicate electrosurgical energy with the tissue contacting surface of the first jaw member, the second member configured for movement relative to the first member to cause movement of the first and second jaw members between open and closed positions;

a fluid receptacle at least partially disposed within the first housing, the fluid receptacle defining first and second receptacle sections, the first receptacle section defining a first internal dimension and the second receptacle section defining a second internal dimension less than the first internal dimension;

a fluid disposed within the fluid receptacle;

a trigger plunger mounted within the first receptacle section and having a same diameter as the first receptacle section, the trigger plunger configured to push the fluid from the first receptacle section to the second receptacle section;

a knife shaft at least partially disposed within the fluid receptacle distal of the trigger plunger and the fluid, and having a knife blade disposed adjacent the first and second jaw members;

a manually engageable trigger mounted to the first housing and coupled to the trigger plunger, the trigger configured for linear movement a first linear distance to cause the trigger plunger to displace the fluid from the first receptacle section to the second receptacle section to cause corresponding linear movement of the knife shaft a second linear distance greater than the first linear distance whereby the knife blade at least partially traverses the first and second jaw members to sever tissue disposed therebetween.

2. The electrosurgical forceps according to claim 1 wherein the fluid disposed within the fluid receptacle is an incompressible fluid.

3. The electrosurgical forceps according to claim 1 wherein the knife shaft is configured to move from a retracted position to an extended position upon movement of the trigger the first linear distance.

4. The electrosurgical forceps according to claim 3 wherein the knife shaft includes a shaft plunger disposed within the second receptacle section of the fluid receptacle, the shaft plunger configured to be displaced by the fluid during movement of the trigger through the first linear distance to move the knife shaft to the extended position.

5. The electrosurgical forceps according to claim 4 wherein the knife shaft is normally biased toward the retracted position whereby upon release of the trigger subsequent to movement through the first linear distance, the knife shaft returns toward the retracted position with the shaft plunger displacing the fluid from the second receptacle section to the first receptacle section to cause the trigger plunger and the trigger to return to an initial position.

6. The electrosurgical forceps according to claim 1 wherein the fluid receptacle is a step design where the first receptacle section defines a first inner diameter and the second receptacle section defines a second inner diameter.

7. The electrosurgical forceps according to claim 6 wherein the ratio of the first inner diameter to the second inner diameter is greater than 1.5:1.

8. The electrosurgical forceps according to claim 7 wherein the ratio of the first inner diameter to the second inner diameter is at least 2:1.

9. A surgical forceps, comprising:

a first member including a first housing and a first shaft member depending from the first housing, the first shaft member having a first jaw member;

a second member including a second housing and a second shaft member depending from the second housing, the second shaft member having a second jaw member, the second member configured for movement relative to the first member to cause movement of the first and second jaw members between open and closed positions;

a fluid receptacle at least partially disposed within the first housing, the fluid receptacle defining first and second receptacle sections, the first receptacle section defining a first internal dimension and the second receptacle section defining a second internal dimension less the first internal dimension;

a trigger plunger mounted within the first receptacle section of the fluid receptacle and having a same diameter as the first receptacle section;

a knife shaft at least partially disposed within the second receptacle section, the knife shaft including a shaft plunger and a knife blade;

an incompressible fluid disposed within the fluid receptacle between the trigger plunger and the shaft plunger, the trigger plunger configured to push the incompressible fluid from the first receptacle section to the second receptacle section;

a manually engageable trigger mounted to the first housing and coupled to the trigger plunger, the trigger configured for linear movement through a first linear distance from an initial position to an actuated position to cause the trigger plunger to displace the incompressible fluid from the first receptacle section to the second receptacle section to cause corresponding engagement with the shaft plunger and linear movement of the knife shaft a second linear distance greater than the first linear distance whereby the knife blade at least partially traverses the first and second jaw members to sever tissue disposed therebetween.

10. The surgical forceps according to claim 9 wherein the knife shaft is normally biased to a retracted position whereby upon release of the trigger subsequent to movement to the actuated position, the shaft plunger engages the incompressible fluid to displace the incompressible fluid from the second receptacle section to the first receptacle section to cause linear movement of the plunger and return of the trigger to the initial position.

11. The surgical forceps according to claim 10 including a spring mounted in the first housing and engageable with the knife shaft to normally bias the knife shaft toward the retracted position.

12. The surgical forceps according to claim 9 wherein the fluid receptacle is a step design where the first receptacle section defines a first inner diameter and the second receptacle section defines a second inner diameter.

13. The surgical forceps according to claim 12 wherein the ratio of the first inner diameter to the second inner diameter is greater than 1.5:1.

14. The surgical forceps according to claim 13 wherein the ratio of the first inner diameter to the second inner diameter is at least 2:1.

15. The surgical forceps according to claim 9 wherein the first and second jaw members each include tissue contacting surfaces, the tissue contacting surfaces configured to communicate electrical energy therebetween.

16. The surgical forceps according to claim 15 including an electrosurgical generator in electrical communication with at least one of the first and second jaw members.

17. The electrosurgical forceps according to claim 1 wherein the trigger plunger is configured to contact a distal surface of the first receptacle section.