Patent Publication Number: US-2020275947-A1

Title: Transducer for ultrasonic scalpel

Description:
BACKGROUND 
     Technical Field 
     This invention relates to the field of medical devices, in particular to an ultrasonic scalpel transducer. 
     Description of the Related Art 
     Ultrasonic scalpel large-scale applications have had more than 20 years of history. Comparing to other surgical methods, ultrasonic scalpel has advantages of producing less smoke, clearer surgical view field, smaller thermal damage; it combines multiple functions of tissue cutting, coagulation and dissection in one instrument, and is able to precisely control the cutting and coagulation area; no electrical damage; rapid ultrasonic oscillation has a self-cleaning effect, which reduces the sticking of blade with tissue. 
     Ultrasonic scalpel can be used for laparoscopic and endoscopic surgery, and for open surgery as well; can be used in combination with other surgical instruments, such as traditional mechanical scalpels and electric knifes, and can be used alone as well, because it combines multifunction of grasping, cutting, dissection and coagulation in one instrument. For different operations, suitable hand pieces are needed for easy operation and more stable performance. 
     For the safety purpose, the doctor&#39;s hand-held ultrasonic scalpel device cannot overheat during the working process, so it is necessary to improve the efficiency of the ultrasonic scalpel, to make itself consume very little energy. In order to achieve the above, it is necessary to increase the gain of the ultrasonic scalpel system. However, too much high gain will reduce the stability of the system. 
     BRIEF SUMMARY 
     Provided is a transducer that improves the gain of the ultrasonic scalpel system but without sacrificing the stability. 
     In order to solve technical problems, provided is a transducer for an ultrasonic scalpel, which from distal end to proximal end comprises a connecting feature, a fixing feature, a horn, a piezoelectric converting body, a rear-end ring and a connecting member. The total length Ld of the piezoelectric converting body satisfies the following formula: the wavelength in the piezoelectric converting body corresponding to the operating frequency of the transducer is λ; the horn is provided with two sections for amplitude amplification; the diameters of the front and back ends at the two sections are Df 1 , Db 1  and Df 2 , Db 2 ; the following conditions are satisfied between Ld, λ, Df 1 , Db 1 , Df 2 , and Db 2 : 
     
       
         
           
             
               
                 
                   
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     When Df 2  and Db 1  are chosen based on a practical application needs, Df 1  and Db 2  are calculated according to formula (2), and then Ld is obtained according to formula (1) and λ; the calculated result of Ld is adjustable within a range of 10%. 
     Preferably, the piezoelectric converting body includes 4-8 piezoelectric elements. 
     Preferably, the piezoelectric converting body is within the proximal half wavelength region. 
     Preferably, the rear-end ring and the connecting member at the proximal end are made of steel or titanium alloy, and the horn at the distal end is made of aluminum or titanium alloy. 
     In a preferred solution, the horn includes: 
     A tapered cone and a stepped portion at the proximal end; the cone includes a front end and a back end, and the front end is connected to the stepped portion; the front end diameter is Df 1 , and the back end diameter is Db 1 ; 
     An enlarged portion in the middle section and the diameter of the enlarged portion is Db 2 ; 
     In the distal section, a tapered arc portion is formed. The arc portion extends to the distal end with a distal rod, and the diameter of the distal rod is Df 2 . 
     Preferably, the cone body and the stepped portion form a first amplification portion; the enlarged portion and the distal rod form a second amplification portion. 
     Or another preferred solution, the horn includes: 
     A tapered cone and a stepped portion at the proximal end; the cone includes a front end and a back end; the front end diameter is Df 1 , and the back end diameter is Db 1 ; 
     An enlarged portion is provided in the middle section, a flange structure is provided on the enlarged portion, and a step connected to the flange structure is provided. An arc is provided at the connection between the enlarged portion and the distal rod. The diameter of the enlarged part connected to the arc part is Db 2 ; and the diameter of the distal rod is Df 2 . 
     Preferably, the cone body and the stepped portion form a first amplification portion; the enlarged portion and the distal rod form a second amplification portion. 
     Preferably, the core length of the horn is 64-72 mm from the front end surface to the back end surface. 
     Preferably, the ultrasonic scalpel transducer is a wavelength transducer, specifically the transducer is provided with two longitudinal vibration nodes. 
     The transducer provided here considers the mechanical and electrical gains of the transducer together, so that the total gain of the hand piece and the stability of the system can be improved at the same time. For the mechanical load to the ultrasonic scalpel, that is, the mechanical impedance generated by clamping the soft tissue, if the mechanical gain, that is, the amplitude amplification calculated by formula (2) is too small, the transducer will become hot due to the large mechanical oscillations in the body. However, if the amplitude amplification from the first amplification portion is too large, the amplitude at the distal end may be suppressed and the output may be unstable. By using two amplification portions and the amplification range limited by formula (2), one can make a transducer suitable for such soft tissue surgical load conditions. According to the mechanical gain, the electrical gain must also be adjusted. Otherwise, the electrical input impedance of the transducer may be very high and sensitive to the load and frequency. Therefore, the size and position of the piezoelectric converting body need to be adjusted accordingly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a transducer provided by Embodiment 1 of the present invention; 
         FIG. 2  is a schematic diagram of a horn corresponding to a transducer provided in Embodiment 1 of the present invention; 
         FIG. 3  is a schematic diagram of a hand piece and an instrument used for laparoscopic or open surgery provided in Embodiment 1 of the present invention; 
         FIG. 4  is a schematic diagram of a transducer provided by Embodiment 2 of the present invention; 
         FIG. 5  is a schematic diagram of a horn corresponding to a transducer provided in Embodiment 2 of the present invention; 
         FIG. 6  is a schematic diagram of a hand piece and an instrument used in open surgery provided in Embodiment 2 of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In order to enable those skilled in the art to better understand the technical schemes of the present invention, the present invention will be further described in detail below with reference to specific embodiments. 
     In order to meet the appropriate gain, dielectric performance, enough ability to drive tissue cutting and coagulating, and the requirements from circuit drive, the present invention proposes the following design scheme: 
     A transducer used for an ultrasonic scalpel, which from distal end to proximal end comprises a connecting feature, a fixing feature, a horn, a piezoelectric converting body, a rear-end ring and a connecting member. The total length of the converting body is Ld, and its wavelength corresponding to the operating frequency of the transducer is λ. The horn is provided with two sections for amplitude amplification; the diameters of the front and back ends at the two sections are Df 1 , Db 1  and Df 2 , Db 2 ; the following conditions are satisfied between Ld, λ, Df 1 , Db 1 , Df 2 , and Db 2 : 
     
       
         
           
             
               
                 
                   
                     Ld 
                     λ 
                   
                   = 
                   
                     
                       
                         1 
                         25 
                       
                       × 
                       
                         
                           ( 
                           
                             
                               
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     When Df 2  and Db 1  are chosen based on practical application requirements, Df 1  and Db 2  are calculated according to formula (2), and then Ld is obtained according to formula (1) and λ; the calculated result of Ld is adjustable within a range of 10%. 
     As we know, the ultrasonic scalpel system usually consists of three parts, the ultrasonic generator, the hand piece and the instrument aka tool. The connected hand piece and instrument are called hand-held device here. According to the convenience of operation, there are two types of hand-held devices that are more suitable for laparoscopic and open surgery, respectively. The ultrasonic electric generator generates ultrasonic frequency electric signal, to drive the hand piece to vibrate through the connecting cable. The hand piece transmits the ultrasonic vibration to the cutting blade through the waveguide inside the instrument. The blade contacts the tissue to produce cutting and coagulating effects. 
     The gain of the hand-held device is determined by both the hand piece and the instrument. The transducer is the key ultrasonically functional component of the hand piece, so the gain of the transducer constitutes a part of the system gain. In order to achieve the beneficial effect of optimizing gain and increasing stability, with reference to the drawings, the technical scheme and characteristics of this transducer design are described in detail below. 
     According to the calculation from the above formulas, the structure of the transducer is obtained.  FIG. 1  is a schematic diagram of a transducer usually used in laparoscopic or endoscopic surgery, including: horn  31 , piezoelectric converting body  32 , rear-end ring  33 , and connecting member  34 . On the horn, at the node usually has a protrusion  36 , which is similar to the flange design, and is used to fix the hand piece housing. At the distal end is a connecting feature  35 , which is used to connect the instrument. 
     Based on the above design scheme, in order to meet the reasonable design of different variables in the transducer, provided is a specific structure design of the horn as shown in  FIG. 2 , which is the horn included in the transducer shown in  FIG. 1 . 
     A tapered cone  54  and a stepped portion  53  are provided at the proximal end; the cone  54  includes a front end and a back end, the front end is connected to the stepped portion. The front end diameter is Df 1 , and the back end diameter is Db 1 , range 12-19 mm. Preferably, the diameter Df 1  of the front end of the cone  54  is 7-14 mm, more preferably 10-11 mm, and most preferably 10 mm. The length of the step  53  is preferably 7-14 mm, more preferably 10 mm. The cone  54  has a length of 7-14 mm. An enlarged portion  52  is provided in the middle section, and the diameter of the enlarged portion  52  is Db 2 ; the diameter of the Db 2  is preferably 12-16 mm, and more preferably 14 mm. At the distal end, there is a tapered arc portion  51 . The arc portion  51  extends to the distal end with a distal rod. The diameter of the distal rod is Df 2 , which is 5-10 mm. The arc radius is preferably 10-16 mm, and more preferably 12 mm. 
       FIG. 3  is a schematic view of a hand piece and an instrument for laparoscopic surgery, including a driving hand piece  11 , a transducer disposed inside the housing of the hand piece, an instrument housing  12 , a sheath  13 , a blade  14  and a connecting cable  15 . Through the connecting cable  15  the hand piece  11  is driven by the generator. The hand piece transmits ultrasonic frequency vibration to the blade  14  through the waveguide inside the sheath  13 , and the blade  14  contacts the tissue to produce cutting and coagulating effects. 
     In this embodiment, the operating frequency of the transducer is 53-57 kHz, the corresponding wavelength λ, in the piezoelectric converting body is 88-94 mm, and Ld is 8-15 mm. 
       FIG. 4  is a schematic diagram of an open surgical transducer, including: a horn  41 , a piezoelectric converting body  42 , a rear-end ring  43 , and a connecting member  44 ; The protrusion  46 , at the vibration node on the horn, has a flange-like design for fixing the hand piece housing; and a connecting feature  45  is provided at the distal end for connecting an instrument. 
     The diameter of the piezoelectric converting body  42  in the transducer of  FIG. 4  is preferably 8.5-11 mm, more preferably 9.5 mm; the total length Ld of the piezoelectric converting body  42  is preferably 12-20 mm, and more preferably 16 mm, and the piezoelectric converting body part is composed of 6-12 pieces of piezoelectric elements, preferably 8 pieces. 
     As shown in  FIG. 5 , the horn used in the transducer shown in  FIG. 4  includes a tapered cone  64  and a stepped portion  63  at the proximal end. The cone  64  includes a front end and a back end. The diameter Db 1  of the back end is preferably 8.5-11 mm, more preferably 9.5 mm; and the diameter Df 1  of the front end of the cone  64  is preferably 7-9 mm, more preferably 8 mm; the length of the cone  64  is preferably 1-4 mm, more preferably 2 mm; the change in the length of the step  63  will affect the amplification of the first amplitude gain, so in order to better obtain the amplitude of the first amplitude gain, the length of the step  63  in this embodiment is preferably 5-9 mm, more preferably 7 mm. 
     An enlarged portion  62  is provided in the middle section, a flange structure is provided on the enlarged portion  62 , and a step connected to the flange structure is provided. There is an arc portion connecting the enlarged portion and the distal rod, the enlarge portion diameter close to the arc is Db 2 , preferably 9-12 mm. 
     The diameter Df 2  of the distal rod  61  is preferably 2.6-3.6 mm, more preferably 3.1 mm, and the core length of the horn from the end face  65  to the end face  66  is preferably 64-72 mm, more preferably 68 mm. 
     Preferably the transducer is a wavelength transducer, specifically, the transducer is provided with two longitudinal vibration nodes. 
     The piezoelectric converting body is within the proximal end half-wavelength region. If the piezoelectric converting body is outside this region, the electrical gain of the transducer will be reduced, the electrical input impedance will be high, and it will be sensitive to the load and frequency. Therefore, the position of the piezoelectric converting body needs to be maintained. The position of the piezoelectric converting body in the transducer affects the characteristics of the latter. 
       FIG. 6  is a schematic diagram of a hand piece and an instrument used in open surgery provided in Embodiment 2 of the present invention. Provided is a hand piece  21 , a housing  22 , a cable  25 , and a blade  24 . 
     In order to further improve the service life and electrical performance of the transducer. Preferably, the rear-end ring and the connecting member at the proximal end of the transducer are made of steel or titanium alloy, and the distal end horn is made of aluminum or titanium alloy. 
     The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as a limitation on the present invention, and the protection scope of the present invention shall be subject to the scope defined by the claims. For those of ordinary skill in the art, without departing from the spirit and scope of the present invention, a number of improvements and modifications can be made, and these improvements and modifications should also be regarded as within the protection scope of the present invention.