Abstract:
A handpiece having a set of longitudinally vibrating piezoelectric elements and which may additionally have an electric motor to provide rotational or oscillatory movement to the ultrasound horn. The piezoelectric elements are surrounded by a high temperature plastic sleeve, and the sleeve is filled with high temperature potting material. The potting material seal the piezoelectric elements against moisture without affecting the performance of the piezoelectric elements.

Description:
[0001]    This invention relates to ultrasonic devices and more particularly to an ophthalmic phacoemulsification handpiece.  
         BACKGROUND OF THE INVENTION  
         [0002]    A typical ultrasonic surgical device suitable for ophthalmic procedures consists of an ultrasonically driven handpiece, an attached hollow cutting tip, an irrigating sleeve and an electronic control console. The handpiece assembly is attached to the control console by an electric cable and flexible tubings. Through the electric cable, the console varies the power level transmitted by the handpiece to the attached cutting tip and the flexible tubings supply irrigation fluid to and draw aspiration fluid from the eye through the handpiece assembly.  
           [0003]    The operative part of the handpiece is a centrally located, hollow resonating bar or horn directly attached to a set of piezoelectric crystals. The crystals supply the required ultrasonic vibration needed to drive both the horn and the attached cutting tip during phacoemulsification and are controlled by the console. The crystal/horn assembly is suspended within the hollow body or shell of the handpiece at its nodal points by relatively inflexible mountings. The handpiece body terminates in a reduced diameter portion or nosecone at the body&#39;s distal end. The nosecone is externally threaded to accept the irrigation sleeve. Likewise, the horn bore is internally threaded at its distal end to receive the external threads of the cutting tip. The irrigation sleeve also has an internally threaded bore that is screwed onto the external threads of the nosecone. The cutting tip is adjusted so that the tip projects only a predetermined amount past the open end of the irrigating sleeve.  
           [0004]    When used to perform phacoemulsification, the ends of the cutting tip and irrigating sleeve are inserted into a small incision of predetermined width in the cornea, sclera, or other location in the eye tissue in order to gain access to the anterior chamber of the eye. The cutting tip is ultrasonically vibrated along its longitudinal axis within the irrigating sleeve by the crystal-driven ultrasonic horn, thereby emulsifying upon contact the selected tissue in situ. The hollow bore of the cutting tip communicates with the bore in the horn that in turn communicates with the aspiration line from the handpiece to the console. A reduced pressure or vacuum source in the console draws or aspirates the emulsified tissue from the eye through the open end of the cutting tip, the bore of the cutting tip, the horn bore, and the aspiration line and into a collection device. The aspiration of emulsified tissue is aided by a saline flushing solution or irrigant that is injected into the surgical site through the small annular gap between the inside surface of the irrigating sleeve and the outside surface of the cutting tip.  
           [0005]    Ultrasound handpieces are subjected to the extreme heat and pressure of autoclave sterilization, which can shorten the life of the piezoelectric elements. Prior attempts to increase the longevity of the electronic components of piezoelectric handpieces have been directed primarily to preventing moisture from entering the handpiece by better sealing of the outer shell and/or electric cabling. While these attempts have increased significantly the useful life of ultrasound handpieces, further improvements are needed.  
           [0006]    Accordingly, a need continues to exist for an ultrasound handpiece having increased reliability.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The present invention improves upon prior art ultrasonic devices by providing a handpiece having a set of longitudinally vibrating piezoelectric elements and which may additionally have an electric motor to provide rotational or oscillatory movement to the ultrasound horn. The piezoelectric elements are surrounded by a high temperature plastic sleeve, and the sleeve is filled with high temperature potting material. The potting material seal the piezoelectric elements against moisture without affecting the performance of the piezoelectric elements.  
           [0008]    It is accordingly an object of the present invention to provide an ultrasound handpiece having both longitudinal and torsional motion.  
           [0009]    It is a further object of the present invention to provide an ultrasound handpiece having piezoelectric elements sealed against moisture.  
           [0010]    Another objective of the present invention is to provide a more reliable ultrasound handpiece.  
           [0011]    Other objects, features and advantages of the present invention will become apparent with reference to the drawings, and the following description of the drawings and claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a perspective view of one embodiment of the ultrasonic handpiece of the present invention.  
         [0013]    [0013]FIG. 2 is a cross-section view of one embodiment of the ultrasonic handpiece of the present invention.  
         [0014]    [0014]FIGS. 3A &amp; 3B are perspective views of one embodiment of the ultrasonic handpiece of the present invention having the inner and outer handpiece shells removed. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    As best seen in FIG. 1, handpiece  100  of the present invention generally consists of handpiece body  110 , electric cable  112  and electric connector  20 . Handpiece  100  combines both longitudinal motion and rotary or oscillatory motion, such handpieces being more fully described in U.S. Pat. Nos. 5,222,959, 5,492,528, 5,827,292 (Anis), 5,722,945, 5,730,718, 5,911,699(Anis, et al.) and 4,504,264 (Kelman), the entire contents of which are incorporated herein by reference. One skilled in the art will recognize that the present invention is suitable for use on ultrasonic handpieces having only longitudinal motion.  
         [0016]    As best seen in FIG. 2, handpiece body  110  of the present invention generally includes nosecone shell  5 , handpiece inner shell  7 , handpiece outer shell  8  and handpiece end piece  17 . Motor  114  is mounted within inner shell  7  by motor mount  3  and seal  116  and may contain devices, such as torsioner ring  2  and torsioner wire  4 , for limiting the rotary movement of motor  114 . Attached to distal end of shaft  118  of motor  114  is driveshaft  120  portion of horn  13 . Piezoelectric stack  21  is received over driveshaft  120  portion of horn  13  and held in place against end plate  122  on driveshaft  120  by split nuts  22  and  23 . Front bulkhead  1  is threaded onto driveshaft  120  behind nut  23  to de-couple the ultrasonic energy generated by piezoelectric stack  21  from motor  114 . Power is supplied to piezoelectric stack by electrodes  18  and  19 , and the entire assembly may be surrounded by insulating sleeve  39 . Ultrasound horn  13  is threaded into endplate  122  on driveshaft  120 . Horn  13  is held within inner shell  7  by spring-loaded seal  35  and by bearing  37  contacting hub  124  of horn  13 . Piezoelectric stack  21  is supported by bearings  6  and  41 . Inner shell  7  is held within outer shell  8  by silicone rubber or elastomeric O-rings  30 ,  31 ,  41  and  42 . Nosecone shell  5  is received in the distal end of outer shell  8  and sealed fluid tight by silicone rubber or elastomeric O-rings  24  and  29 . End piece  17  is received on the proximal end of outer shell  8  and sealed fluid tight by silicone rubber or elastomeric O-rings  25  and  32 . Proximal end  119  of motor shaft  118  is held within end piece  17  by spring-loaded seal  36  and by spanner ring  33 .  
         [0017]    In use, motor  114  is energized and causes motor shaft  118  to rotate. Rotation of shaft  118  causes rotation of driveshaft  120 , piezoelectric stack  21  and horn  13 . Rotation of horn  13  and motor shaft  118  causes friction and wear at the interface between hub  124  and seal  35  and distal end  119  of shaft  118  and seal  36 . This friction can cause excessive wear on hub  124  and shaft  118 , which preferably are made from titanium, by seals  35  and  36 , which are preferably carbon/graphite filled, a very abrasive material. When such wear occurs, handpiece body  110  may no longer be sealed fluid tight, particularly in a steam autoclave. To prevent excessive wear on hub  124  and shaft  118 , hub  124  and proximal end  119  of shaft  118  may be plated or coated with any hard coating such as titanium nitride, zirconium nitride, chromium nitride or boron carbide (also know as black diamond), but titanium nitride is preferred. While titanium nitride coatings may be applied as thin as 2-4 microns, the inventors have found that such a thin coating is easily cracked when applied over a relatively soft material such as titanium. Therefore, it has been discovered that a titanium nitride coating greater than 4 microns, and preferably between 9-12 microns gives the best results. Coatings greater than 4 microns, however, may change the surface morphology of the coating, resulting in a sandpaper-like finish undesirable for a sealing surface. The inventors have discovered that is such situations, polishing of the surface, for example, with a diamond powdered paste, removing approximately 1 micron of material or less, results in a satisfactory surface.  
         [0018]    [0018]FIGS. 3A and 3B illustrate the operative parts of handpiece  110  with nosecone  5 , inner shell  7  and outer shell  8  removed. As seen in FIG. 3A, endplate  122 , piezoelectric stack  21 , split nuts  22  and  23  and electrodes  18  and  19  are exposed to the atmosphere internal to handpiece  110 . As been seen in FIG. 3B, piezoelectric stack  21 , endplate  122  split nuts  22  and  23  and electrodes  18  and  19  may be covered by protective sleeve  39 . Sleeve  39  preferably is made from a high temperature plastic such as polyetheretherketone (PEEK) and is slip-fitted around endplate  122 , piezoelectric stack  21 , split nuts  22  and  23  and electrodes  18  and  19 . The interior of sleeve  39  may be filled with high temperature potting material  141 , such as a primerless silicone adhesive (Dow Coming Q3-6611). The filling operation generally may include raising the temperature of potting material  141  and sleeve/piezoelectric stack assembly  139  to, for example, around 120° C. and injecting potting material  141  into sleeve/piezoelectric stack assembly  139  with a syringe. The elevated temperature is held for a short time, approximately 5 minutes, for example, to degas any air bubbles from potting material  141 . Additional potting material  141  is injected into sleeve/piezoelectric stack assembly  139  to replace any volume lost by the escaping gases. The entire potting material  141  filled sleeve/piezoelectric stack assembly  139  is then cured, for example, at around 120° C. for 2 hours. Such a potting process does not affect the ultrasonic performance of handpiece  110 , but helps to increase the reliability and longevity of handpiece  110  be sealing piezoelectric stack  21  and electrodes  18  and  19  from moisture.  
         [0019]    While certain embodiments of the present invention have been described above, these descriptions are given for purposes of illustration and explanation. Variations, changes, modifications and departures from the systems and methods disclosed above may be adopted without departure from the scope or spirit of the present invention.