Laparoscopic bipolar electrosurgical instrument

1. A laparoscopic bipolar electrosurgical instrument comprising:

a first jaw having a first flange with a first slot, and a second jaw having a second flange with a second slot, wherein the first and second jaws are located at a distal end of the instrument and comprise an electrically conductive material for conducting bipolar electrosurgical current therebetween;

an electrically conductive pushrod for connecting the first jaw to a source of electrosurgical energy;

an electrically conductive tube for connecting the second jaw to a source of electrosurgical energy;

a yoke attached to the pushrod and positioned to electrically insulate the first flange from the second flange, the yoke having a first side facing the first flange and a second side facing the second flange, the yoke further comprising a first shoulder and a second shoulder;

a first pin located on the first side and movably engaged with the first slot;

a second pin located on the second side and movably engaged with the second slot;

the first slot and the second slot shaped such that an angle, subtended by the first and second jaws, decreases with distal motion of the pushrod;

first and second cul-de-sacs positioned respectively in the first and second slots to relieve shear stresses on the first and second pins approximately when the first and second shoulders respectively engage the first and second flanges to provide a closure force between the first and second jaws; and

a handle attached to the pushrod for imparting movement to the yoke.

2. The laparoscopic bipolar electrosurgical instrument of claim 1 wherein:

the electrically conductive tube surrounds at least a portion of the pushrod, and

an electrically insulative layer is disposed between the tube and the pushrod capable of supporting an electrosurgical alternating potential across the tube and the pushrod.

3. The laparoscopic bipolar electrosurgical instrument of claim 2 further comprising:

an inner nose piece electrically connected to the pushrod, and

an outer nose piece electrically connected to the tube, wherein the inner nose piece and the outer nose piece capture the yoke, along with the first and second flanges, to conduct bipolar electrosurgical current to the first and second jaws.

4. The laparoscopic bipolar electrosurgical instrument of claim 3 further comprising an electrical spring contact between the pushrod and the inner nose piece to provide electrical continuity therebetween.

5. The laparoscopic bipolar electrosurgical instrument of claim 1 further comprising ridges in each of the first and second jaws.

6. The laparoscopic bipolar electrosurgical instrument of claim 1 wherein each of the first and second jaws has a seal surface with width and a length, and wherein at least one location along the length has a width such that the closure force in grams divided by the width in millimeters is in the range of 400 to 650.

7. The laparoscopic bipolar electrosurgical instrument of claim 6, wherein the width of each seal surface is tapered along its respective length.

8. The bipolar electrosurgical instrument according to claim 7, wherein the closure force divided by the width is approximately constant along the length for each of the first and second jaws.

9. A laparoscopic bipolar electrosurgical instrument comprising:

a first jaw having a first flange with a first slot, and a second jaw having a second flange with a second slot, wherein the first and second jaws are located at a distal end of the instrument and comprise an electrically conductive material for conducting bipolar electrosurgical current therebetween;

an electrically conductive pushrod for connecting the first jaw to a source of electrosurgical energy;

an electrically conductive tube for connecting the second jaw to a source of electrosurgical energy;

a yoke attached to the pushrod and electrically insulating the first flange from the second flange, the yoke having a first side facing the first flange and a second side facing the second flange, the yoke further comprising a first shoulder and a second shoulder;

a first pin located on the first side and movably engaged with the first slot;

a second pin located on the second side and movably engaged with the second slot;

the first slot and the second slot shaped such that a subtended angle between the first and second jaws decreases with distal motion of the pushrod;

first and second cul-de-sacs positioned respectively in the first and second slots to relieve shear stresses on the first and second pins at the subtended angle approximately when the first and second shoulders engage the first and second flanges,

the electrically conductive tube having an outer surface and a length, wherein the tube surrounds at least a portion of the pushrod; an electrically insulative layer between the tube and the pushrod capable of supporting an electrosurgical alternating potential across the tube and the pushrod;

an inner nose piece electrically connected to the pushrod;

an outer nose piece electrically connected to the tube, wherein the inner nose piece and the outer nose piece capture the yoke along with the first and second flanges to conduct bipolar electrosurgical current to the first and second jaws;

an electrical spring contact between the pushrod and the inner nose piece to provide electrical continuity therebetween; and

a handle attached to the pushrod for imparting movement to the yoke.

10. A method of making a laparoscopic bipolar instrument comprising the following steps:

forming a first jaw having a first flange with a first slot, and a second jaw having a second flange with a second slot, wherein the first and second jaws are located at a distal end of the instrument and comprise an electrically conductive material for conducting bipolar electrosurgical current therebetween;

providing an electrically conductive pushrod for connecting the first jaw to a source of electrosurgical energy;

providing an electrically conductive tube for connecting the second jaw to a source of electrosurgical energy;

attaching a yoke to the pushrod;

electrically insulating the first flange from the second flange with the yoke, the yoke having a first side facing the first flange and a second side facing the second flange, the yoke further comprising a first shoulder and a second shoulder;

engaging a first pin located on the first side with the first slot;

engaging a second pin located on the second side with the second slot;

shaping the first slot and the second slot such that a subtended angle between the first and second jaws decreases with the distal motion of the pushrod;

positioning first and second cul-de-sacs respectively in the first and second slots to relieve shear stresses on the first and second pins at the subtended angle approximately wherein the first and second shoulders engage the first and second flanges; and

providing a handle for imparting movement of the yoke.

11. The method of making a laparoscopic bipolar electrosurgical instrument of claim 10 further comprising the steps of:

surrounding at least a portion of the pushrod with the electrically conductive tube having an outer surface and a length, and

electrically insulating the tube from the pushrod.

12. The method of making a laparoscopic bipolar electrosurgical instrument of claim 11 further comprising the steps of:

electrically connecting an inner nose piece to the pushrod, and

electrically connecting an outer nose piece to the tube, wherein the inner nose piece and the outer nose piece capture the yoke along with the first and second flanges to conduct bipolar electrosurgical current to the first and second jaws.

13. The method of making a laparoscopic bipolar electrosurgical instrument of claim 12 further comprising the step of electrically connecting the pushrod and the inner nose piece with a spring contact.

14. The method of making a laparoscopic bipolar electrosurgical instrument of claim 10, wherein the first and second jaws each has a length and a width and oppose each other with a closure force, the method further comprising the step of tapering the width along the length of each of the first and second jaws.

15. The method of making a laparoscopic bipolar electrosurgical instrument of claim 14 further comprising the step of wherein the closure force in grams divided by the width in millimeters is in the range of 400 to 650.

16. The method of making a laparoscopic bipolar electrosurgical instrument of claim 14 further comprising the step of, wherein the width of the first and second jaws is tapered along its respective length.

17. The method of making a laparoscopic bipolar electrosurgical instrument of claim 16 further comprising the step of, wherein the closure force divided by the width is approximately constant along the length for each of the first and second jaws.

18. A laparoscopic bipolar endoscopic instrument, comprising:

first and second jaw members pivotally attached in opposing relation relative to one another, each of the jaw members including a flange which extends therefrom and the jaw members being relatively movable from a first open position wherein the jaw members are disposed in spaced relation relative to one another to a second clamping position wherein the jaw members cooperate to grasp tissue therebetween,

an electrically conductive push rod for connecting the first jaw member to a first pole and an electrically conductive tube for connecting the second jaw member to a second pole such that the jaw members are capable of conducting bipolar energy through the tissue held therebetween;

a yoke attached to a distal end of the push rod and attached between the jaw members, the yoke includes a pair of pins which cooperate with a corresponding pair of slots in a cam-follower-like manner to impart movement of the jaw members from the first and second positions;

a pair of shoulder portions attached to the yoke which are dimensioned to abut the flanges of the jaw members when the jaw members are moved into the second position to relieve shear stresses on the pins during clamping and sealing of the tissue; and

a handle attached to the push rod for imparting movement to the yoke.