TECHNICAL FIELD

The present invention relates to an electrosurgical instrument, in particular for argon plasma coagulation.

BACKGROUND

Electrosurgical instruments of the type referred to at the outset are used for cutting tissue or for coagulation with high-frequency alternating current. Argon plasma coagulation is a special form of electrosurgery in which non-contact transmission of the HF current takes place via ionised argon gas.

The effect of the energy input takes place with the known instrument referred to at the outset in that the exposed length of the electrode is altered. Provided for this purpose is an axially movable shaft which surrounds the electrode with an insulating effect and can be moved along the electrode in order to expose it as required.

A key requirement for such instruments is the possibility of single-handed operation. At the same time, the position of the instrument in the OP area should not change if at all possible. This means that as far as possible the grip position should be retained when operating the instrument even when the shaft is moved. In the generic instrument, this is achieved by a rotary knob which is arranged centrally in the handpiece of the instrument and can be operated with the index finger. The rotary knob actuates the shaft which can be moved axially along the electrode as a result.

A further requirement for electrosurgical instruments arises from their use in connection with a trocar which is used for inserting the electrode. At the same time, friction forces may arise between the shaft and the trocar while moving the instrument within the trocar, such forces holding back the shaft and unintentionally exposing the electrode.

SUMMARY

The object of the invention is to improve the electrosurgical instrument referred to at the outset, to the effect that the risk of injury when using the instrument in connection with a trocar or also during preparation is reduced without compromising handling of the apparatus in the process. The object of the invention is also to specify an apparatus having such an instrument.

In particular, the object is achieved by an electrosurgical instrument, in particular for argon plasma coagulation, having a handpiece and having an electrode connected to the handpiece. A shaft surrounds the electrode which is held in the handpiece. The instrument comprises an operating mechanism which has at least one rotary knob arranged on the handpiece. The shaft is axially movable relative to the electrode and a shear force can be applied to it by operating the rotary knob. The handpiece has a brake device which exerts a braking force on the shaft. The operating mechanism forms a transmission gear which is connected to the shaft for transferring the shear force.

The invention has various advantages:

The brake device improves the safety of the instrument against unintentional exposure of the electrode, for example when used together with a trocar. The braking force exerted on the shaft by the brake device prevents the shaft from being moved proximally during an application, for example during insertion through a trocar. The braking force thus leads to self-locking of the shaft which secures it against being moved unintentionally.

By operating a rotary knob, an operating force can be exerted on the shaft to alter the exposed length of the electrode. This force is normally applied by the user's finger. So as not to obstruct the user when operating the instrument, the resistance of the rotary knob should remain within a range that is felt to be ergonomically pleasant. For this, the instrument according to the invention has a transmission gear which is formed by the operating mechanism and is connected to the shaft for transferring the shear force. The transmission gear compensates the braking force applied by the brake device such that the rotary knob or the operating mechanism in general is easy to operate.

It is understood that the rotary knob is rotatable in two directions (clockwise/anti-clockwise) such that the shaft can be moved distally and proximally.

In summary, the invention increases the safety of the instrument because the shaft is secured against being moved unintentionally by the brake device. At the same time, smooth operation of the instrument is retained as the operating mechanism forms a transmission gear which converts the finger force applied by the user into the shear force acting on the shaft. In this case, the transmission gear acts like a lever arrangement which increases the shear force compared to the finger force.

The rotary knob preferably comprises a drive gear and at least one driven gear connected torque-resistantly to said drive gear, said driven gear being connected to the shaft for transferring the shear force. The diameter of the driven gear is smaller than the diameter of the drive gear. In this way, the transmission ratio necessary for smooth operation of the shaft is easily achieved. A further advantage of this embodiment is the inexpensive and safe design offered by this embodiment.

The operating mechanism may comprise a slide that is axially movable in the shear direction, said slide being connected on one hand to the shaft and on the other hand to the transmission gear. This creates a robust and simple construction that safely transmits the drive force, which is applied by the user, to the shaft.

The slide may have at least one first toothed rack which is arranged parallel to the shear direction and meshes with the driven gear. This design enables the rotary motion of the rotary knob to be easily and safely converted into a linear motion of the shaft.

For improved transmission of the force, the slide may have a second toothed rack parallel to the first toothed rack, the drive gear being arranged between the two toothed racks and being torque-resistantly connected to a further driven gear. The further driven gear is meshed with the second toothed rack.

The handpiece preferably has a retaining plate with a linear guide in which the slide is arranged so as to be axially movable. The linear guide has at least one aperture, in particular two parallel apertures, for the slide. The retaining plate enables a compact structure which requires a smaller installation space for storage of the slide.

The brake mechanism may have a clamping element, in particular a clamping ring, the clamping element being held in the handpiece and applying braking force to the shaft. The clamping element forms a passive braking means that enables easy and inexpensive construction of the instrument.

In a preferred embodiment, the operating mechanism has a locking device with which the shaft can be fixed in at least one position, in particular in a fully extended position. The locking device is particularly suitable for trocars which produce an especially high resistance during insertion of the instrument, such as reusable trocars with valve flap. The locking device is used to fix the shaft in addition to the brake mechanism so that the shaft can transfer higher axial forces without it being moved relative to the electrode.

In this case, the locking device may comprise at least a first latching means which is arranged on the slide. A second latching means is arranged on the handpiece, in particular on the mounting plate, said latching means being combinable with the first latching means for fixing the shaft. The two latching means have the advantage that they are easy to manufacture, by means of an injection moulding process for example, and at the same time they enable secure fixing of the shaft.

In an especially preferred embodiment, the electrode and the shaft are each arranged rotatably about their longitudinal axis relative to the handpiece. The electrode is guided through a sliding sleeve which connects the shaft and the electrode so as to be torque-resistant and axially movable.

This embodiment is suitable for non-rotationally symmetrical electrodes, such as spatula electrodes for example. The electrode can therefore be aligned easily in the peripheral direction. This embodiment has the advantage that rotation of the electrode is even possible when the instrument is located in the trocar. In this embodiment, the rotary motion is introduced by the shaft which is connected torque-resistantly to the electrode via the sliding sleeve. The sliding sleeve additionally has the function of establishing relative mobility between the shaft and the electrode. To do this, the sliding sleeve forms a torque-resistant and axially movable connection between the shaft and the electrode. As the shaft protrudes out of the handpiece, no additional components are necessary in order to rotate the electrode. The user simply grips the shaft and rotates it together with the electrode.

At the same time, the sliding sleeve may have profiling, at least in sections, on the inner circumference, said profiles being engaged in a positive-locking manner with the correspondingly profiled electrode, at least in sections, for transferring a torque. This design is inexpensive and safe as it is easy to manufacture an appropriately profiled sliding sleeve and safe torque transmission is achieved by the positive fit.

A cheaper and simpler construction is preferably achieved in that the sliding sleeve and the slide are rotatably and firmly connected in the axial direction of the sliding sleeve for transferring the shear force. The slide has a retaining ring which surrounds the sliding sleeve at least partially around the circumference.

In another approach, the operating mechanism has a locking device with which the shaft can be fixed in at least one position. This embodiment is not limited to the transmission gear but also functions with a simple, non-transmission gear. The safety aspect in this instrument is fulfilled by the locking device which secures the shaft against moving unintentionally even in the case of strong resistance forces.

In an approach where the electrode and the shaft are each arranged rotatably about their longitudinal axis relative to the handpiece, the electrode is guided through a sliding sleeve which connects the shaft and the electrode in a torque-resistant and axially movable manner. This makes handling easier regardless of the transmission gear because the shaft protruding out of the handpiece is simply rotated manually to align the electrode.

The invention is described below in greater detail with further particulars and with reference to the associated schematic Figures.

