in the following figures the same reference numerals denote respectively equal or corresponding parts so that a repeated description will be dispensed with and merely the variations of the embodiments illustrates in these figures from the previous embodiments will be explained . fig1 is a schematic cross - sectional view of one part of an inventive handpiece . this figure serves to explain specifically the switching function by remote operation . the reference numeral 1 denotes the rear case part and numeral 2 identifies the front case part . a reed relay 6 or a reed contact 6 , respectively are switched by means of a permanent magnet 3 which is connected to a slide 5 , in this case the actuator element , by displacement of the slide 5 and hence the magnet 3 . a spring 4 , which is inserted into an offset bore 32 , like the slide 5 , serves to push the slide again into its initial position . the slide 5 presents a milled tip so that it is protected from falling out by the front case part 2 . the double arrow indicates the movement of the slide 5 . only when the slide 5 is operated , for instance , the ultrasonic voltage is applied to the end of the handpiece . when the case is dismantled the slide can be removed for cleaning . fig1 moreover shows piezo elements 7 . fig2 to 5 roughly illustrate various possibilities of isolation between the ultrasonic section and the high frequency section . in operation it is necessary — particularly in the event of a defect and also in normal operation — to provide an electrical insulation of the high frequency from the ultra - sound . in accordance with the invention a bucking coil is used in this embodiment . for this reason , and on account of the capacitive coupling between high frequency and ultra - sound by the used cable accommodating all the lines , the voltage across the insulation in the handpiece amounts only to a fraction of the full high frequency voltage in normal cases . insulating provisions must be provided between the mains supply and the patient in a magnitude which is derived from the maximum voltage applied . the standards demand an air gap of 16 mm and a leak path of 23 mm for the isolation of 5000 vpp . this is difficult to implement in the generator so that the insulation provisions are shifted to the handpiece . on the condition that the insulation is implemented in the ultrasonic generator the isolator in the handpiece fulfils the function of additional safety measures . specific structures are provided to extend the leak paths between the high frequency and ultrasonic sections , without taking a substantial influence on the ultrasonic function . a tensioning screw 15 with an extension lip is provided on the rear end of the converter or transducer , which is outlined by the piezo section 8 and the electrode 9 in fig2 onto which lip an isolating tape 13 is wound . the tensioning screw 15 with its bolt 10 or the cylindrical edge of the bolt , respectively , are connected to high frequency . an additional isolation is achieved via a ceramic section 11 and a silicone mass 14 . to this end a silicone casting substance 14 is pressed along the extension of the arrow through a charging opening 12 a until it is discharged at the vent 12 b . the suspension is made , for instance , of an insulating ceramic material 17 ( cf . fig3 ). the space between the front part 2 and the case wall 19 is filled with silicone 14 to achieve a discontinuity of the leak path . this provision serves at the same time to attenuate transverse oscillations and to ensure protection from torsion . the bolt 10 and the piezo sections 8 are insulated by a silicone tube 16 . the ends of the tube 16 are cast together with the respective ceramic parts 11 or 17 , respectively . casting is performed through appropriate injection and venting openings 12 a and 12 b . the silicone casting substance 14 establishes a perfect vulcanisation - type connection with the tube 16 . the case wall 19 may be made of plastic material , for instance . another possibility of insulation on the suspension is illustrated in fig4 . there the leak path is extended by an isolation ring 20 . fig5 illustrates another possibility of isolation . there the front part 2 is wrapped with an insulating tape 13 . the site of joint on the ceramic suspension 17 is then sealed with the silicone mass 14 . fig6 is a schematic view of a multifunctional instrument for endoscopic surgery . the ultrasonic voltage generator 21 comprises a bucking coil 22 . the lines from the ultrasonic voltage generator 21 as well as the line from the high frequency generator 24 are passed through a common cable 23 to the handpiece 25 . the piezo converter , the reed relay and the sonotrode 27 are schematically indicated in the handpiece 25 . moreover , a neutral electrode 26 is shown in fig6 . the electrical connections ( switching lines , high frequency , ultra - sound ), which are integrated into a common cable 23 , are spliced at the proximal end , specifically into one segment with ultrasonic and switching lines for the ultrasonic voltage generator and one part with the high frequency line for the high frequency generator . the four lines ( here : 2 ultra - sound lines and 2 signal lines ) are wound about the core of the bucking coil 22 such that the coil will suppress the “ common - mode ” high frequency component and will not take an influence on the differential ultrasonic and signal currents . the inventive handpiece is particularly well suitable for application with trocars using sonotrodes having an extended length . this becomes evident from fig7 in particular which shows a sonotrode 27 . the reference numeral 28 in fig7 indicates a screw thread for fastening the sonotrode on the handpiece case so as to establish specifically the coupling with the piezo elements . the sonotrode as illustrated presents a length of four half - wave lengths . the weld sites are provided in the anti - nodal points 29 of the half - wave lengths . the sonotrode of fig7 presents an anti - nodal point at the end close to the patient . the welding sites are necessary because the titanium alloys used are not available in the form of the appropriate tube so that the probes must be deeply bored . extended probes such as those used in endoscopic applications , e . g . for insertion into trocars , are composed of various segments because deep boring is possible only up to 200 mm at a reasonable reject rate ( 20 %). it has been found according to the invention that the desired ultrasonic characteristics and the endurance can be achieved with little to no subsequent finishing by welding . moreover , the welding technique is inexpensive and reliable , which means that the number of rejects is low . in order to achieve an efficient tissue removal with certain surgical techniques ( resection of the prostate ) the invention provides for the arrangement of an annular envelope at the probe tip . fig8 shows a side view of a probe tip 30 with an annular envelope 31 for such applications . on the left side , a cylindrical design is illustrated which is shown again in a perspective view in fig9 . the right side of fig8 illustrates an annular envelope 31 having an increased rigidity due to an exponential curve of the shape . an increased rigidity is required in view of the very high acceleration and hence the high load on the material in ultrasonic applications .
a handpiece is disclosed for a multifunctional instrument for endoscopic surgery . the handpiece comprises a case ; a connector disposed on the case and adapted to be connected to connecting lines such as electrical lines , liquid supply and discharge lines , and the like ; at least one ultrasonic transducer arranged in the case ; an ultrasonic sonotrode transmitting the ultrasonic energy ; and at least one switch for controlling functions of the handpiece . the handpiece is characterized by , among other things , the provision that the sonotrode includes a long and thin probe section with a duct composed of several segments which are welded to each other .