Interface joint for an electrosurgical apparatus
The present invention relates to an interface joint for interconnecting an electrosurgical generator and an electrosurgical instrument. In particular, the invention relates to an interface joint comprising a coaxial cable assembly for connecting the interface joint to an electrosurgical instrument. The interface joint comprises a housing made of electrically insulating material, the housing having: an inlet for receiving radiofrequency (RF) electromagnetic (EM) energy and/or microwave frequency EM energy from the electrosurgical generator, and an outlet; and a coaxial cable assembly for connecting the outlet to the electrosurgical instrument, the coaxial cable assembly comprising a first cable section and a second cable section, wherein the first cable section has a lower loss per unit length than the second cable section.
1 . An interface joint for interconnecting an electrosurgical generator and an electrosurgical instrument, the interface joint comprising:
a housing made of electrically insulating material, the housing having:
an inlet for receiving radiofrequency (RF) electromagnetic (EM) energy or microwave frequency EM energy from the electrosurgical generator, and
an outlet; and
a coaxial cable assembly for connecting the outlet to the electrosurgical instrument, the coaxial cable assembly comprising a first cable section and a second cable section, wherein the first cable section has a lower loss per unit length than the second cable section;
wherein the first cable section and the second cable section are coupled together by a transition portion, wherein the transition portion comprises a tapering section of coaxial cable in which at least one of applies:
an inner conductor of the tapering section of coaxial cable tapers;
an outer conductor of the tapering section of coaxial cable tapers; or
a dielectric material of the tapering section of coaxial cable tapers; and
wherein a ratio of an inner diameter of the outer conductor to an outer diameter of the inner conductor is constant through the tapering section.
2 . The interface joint according to claim 1 , wherein the first cable section has a larger diameter than the second cable section.
3 . The interface joint according to claim 2 , wherein the first cable section has a diameter of at least 2 mm.
4 . The interface joint according to claim 2 , wherein the second cable section has a diameter of less than 5 mm.
5 . The interface joint according to claim 1 , wherein the ratio is 3.45:1.
6 . The interface joint according to claim 1 , wherein a length of the tapering section is no more than one eighth of a wavelength of the EM energy received from the electrosurgical generator at the inlet.
7 . An interface joint for interconnecting an electrosurgical generator and an electrosurgical instrument, the interface joint comprising:
a housing made of electrically insulating material, the housing having:
an inlet for receiving radiofrequency (RF) electromagnetic (EM) energy or microwave frequency EM energy from the electrosurgical generator, and
an outlet; and
a coaxial cable assembly for connecting the outlet to the electrosurgical instrument, the coaxial cable assembly comprising a first cable section and a second cable section, wherein the first cable section has a lower loss per unit length than the second cable section;
wherein the first cable section and the second cable section are coupled together by a microstrip transmission line.
8 . The interface joint according to claim 7 , wherein the microstrip transmission line is configured to match an impedance of the first cable section and the second cable section.
9 . The interface joint according to claim 1 , further comprising an outer shaft about the coaxial cable assembly and defining a passageway therebetween.
10 . An electrosurgical apparatus comprising:
an electrosurgical generator configured to generate radiofrequency (RF) electromagnetic (EM) energy or microwave frequency EM energy;
an electrosurgical instrument configured to deliver RF or microwave frequency EM energy to tissue;
an interface joint according to claim 1 ; and
an interface cable configured to deliver RF or microwave frequency EM energy from the electrosurgical generator to the interface joint.
11 . The electrosurgical apparatus according to claim 10 , further comprising a surgical scoping device having an instrument channel for receiving at least a portion of the coaxial cable assembly.
12 . The electrosurgical apparatus according to claim 11 , wherein only the second cable section of the coaxial cable assembly is configured to be received within the instrument channel.
13 . The electrosurgical apparatus according to claim 12 , wherein an outer diameter of the first cable section is greater than a diameter of the instrument channel of the surgical scoping device.
14 . The electrosurgical apparatus according to claim 11 , wherein a length of the second cable section is at least a same as the length of the instrument channel of the surgical scoping device.
15 . The interface joint according to claim 7 , wherein the microstrip transmission line comprises a ground plane, and wherein an outer conductor of the first cable section is connected to the ground plane
by a first ground plane conductor, wherein the first ground plane conductor comprises a portion of the outer conductor of the first cable section that extends beyond a distal end of a dielectric of the first cable section and is electrically and mechanically connected to the ground plane.
16 . The interface joint according to claim 15 , wherein an outer conductor of the second cable section is connected to the ground plane by a second ground plane conductor, wherein the second ground plane conductor comprises a portion of the outer conductor of the second cable section that extends beyond a proximal end of a dielectric of the second cable section and is electrically and mechanically connected to the ground plane.
17 . The interface joint according to claim 7 , wherein the microstrip transmission line, the first cable section and the second cable section each have an impedance of 50 Ω.