Abstract:
The present invention is directed to a device for producing a shock wave to impact an object that includes a transfer member. The device has a voice coil assembly including a permanent magnet and a bobbin member, wherein the permanent magnet provides a first magnetic field. A hammer is attached with the bobbin member; and a coil is operatively attached to the bobbin member, wherein when a voltage is applied to the coil a second magnetic field is generated that opposes the first magnetic field and thereby propels the hammer to contact the transfer member to cause a shock wave to travel along the transfer member. The present invention is also directed to a method for producing a shock wave, that includes the steps of providing a transfer member; providing a voice coil assembly including a permanent magnet and a bobbin member; providing a first magnetic field providing a hammer attached with the bobbin member; providing a coil operatively attached to the bobbin member; and applying a voltage to the coil to generate a second magnetic field that opposes the first magnetic field thereby propelling the hammer to strike the transfer member.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of devices for producing shock waves to impact objects and, in particular, to a device and method for crushing stones by a shock wave in the body. 
     BACKGROUND OF THE INVENTION 
     Stones or calculi are sometimes formed in organs in the body and their presence can cause significant pain and discomfort to an individual. Such stones often form in the urinary system, in areas such as the kidneys, the urinary tracts and in the bladder. The stones may be removed by surgery or by a procedure that involves using a device to crush the stones into small enough pieces so that they may wash out of the urinary system. 
     One type of device used to break up stones is commonly referred to as a lithotriptor. A lithotriptor uses a transfer media, such as water, or transfer member, such as a probe, to transfer a shock wave to a stone, thereby crushing the stone. In conventional lithotriptors, a striking member, often referred to as a hammer, is used to impact the transfer member to produce the shock wave. A variety of different apparatuses have been used to propel this hammer against the transfer member. Examples of such devices are shown in U.S. Pat. Nos. 5,160,336, 5,540,702 and 4,727,875. 
     BRIEF SUMMARY OF THE INVENTION 
     In a first aspect, the present invention is a device for producing a shock wave to impact an object that includes a transfer member. The device has a voice coil assembly including a permanent magnet and a bobbin member, wherein the permanent magnet provides a first magnetic field. A coil is operatively attached to the bobbin member, wherein when a voltage is applied to the coil a second magnetic field is generated that opposes the first magnetic field and thereby propels the bobbin member to contact the transfer member to cause a shock wave to travel along the transfer member. 
     Further in this aspect of the invention there may be provided a bobbin member comprised of a non-magnetic material, a voice coil assembly that has a hammer comprised of a non-magnetic material to contact the transfer member, a cup positioned inbetween and operatively attached to the bobbin member and the hammer, an o-ring positioned between the hammer and the cup, a transfer member that is a probe, a biasing member to bias the bobbin member in a first position and, a power source operatively attached to the device, the power source being a battery. Also in this aspect, a portion of the bobbin member may be disposed around the permanent magnet when the bobbin member is in a first position. 
     In a second aspect, the present invention is a device for producing a shock wave to impact an object, that includes a housing having an exit end; a transfer member operatively attached to the exit end of the housing; a hammer movable from a rest position to a second position, wherein when the hammer is in the second position the hammer impacts the transfer member to produce a shock wave that travels along the transfer member; and a battery to power the device. 
     Further, in this aspect the hammer may be operatively attached to a bobbin member, the bobbin member may be comprised of a non-magnetic material, the hammer may be comprised of a non-magnetic material and the transfer member may be a probe. Also in this aspect there may be provided a cup positioned inbetween and operatively attached to the bobbin member and the hammer, an o-ring positioned between the hammer and the cup and a biasing member to bias the bobbin member in a first position. 
     In a third aspect, the present invention is a device for producing a shock wave to impact an object that includes a housing having an exit end; a transfer member operatively attached the exit end of the housing; a permanent magnet disposed within the housing proximate the magnet end to provide a first magnetic field; a magnetic field generating member spaced apart from the permanent magnet; and a hammer fixed with the magnetic field generating member, the magnetic field generating member operative to provide a second magnetic field that opposes the first magnetic field to propel the hammer to strike the transfer member thereby causing a shock wave to travel along the transfer member. 
     Further in this aspect, the magnetic field generating member may be comprised of a non-magnetic material, the hammer may be comprised of a non-magnetic material, the biasing apparatus may be an o-ring and the transfer member may be a probe. 
     Also in this aspect, there may be a cup positioned inbetween and operatively attached to the magnetic field generating member and the hammer, a biasing apparatus positioned between the hammer and the cup, a biasing member to bias the magnetic field generating member in a first position and a power source operatively attached to the device, the power source being a battery. In addition, the magnetic field generating member may be a bobbin. 
     In a fourth aspect, the present invention is a device for producing a shock wave to impact an object that includes a housing having a magnet end and an exit end, the exit end defining an opening; a probe attached to the housing and extending through the opening; a permanent magnet disposed within the housing proximate the magnet end; a bobbin member located intermediate the permanent magnet and the probe; the bobbin member movable between a first position and a second position; a coil operatively attached to a portion of the bobbin member; and a hammer positioned intermediate the bobbin and the probe, wherein passing an electrical current through the coil results in the bobbin member moving from a first position to a second position causing the hammer to strike the probe, thereby causing a shock wave to travel through the probe. 
     Further in this aspect, the bobbin member may be comprised of a nonmagnetic material and the hammer may be comprised of a non-magnetic material. Also in this aspect there may be provided a cup positioned inbetween and operatively attached to the bobbin member and the hammer, an o-ring positioned between the hammer and the cup, a biasing member to bias the bobbin member in a first position and a power source operatively attached to the device, the power source being a battery. 
     In a fifth aspect, the present invention is a device for producing a shock wave to impact an object that includes means for transferring a shock wave to an object; means for providing a first magnetic field; means for generating a second magnetic field to oppose the first magnetic field; and means for impacting the means for transferring, the means for impacting being operatively attached to the means for generating so that when the second magnetic field is generated the means for impacting strikes the means for transferring to produce a shock wave. 
     In a sixth aspect, the present invention is a method for producing a shock wave, that includes the steps of providing a transfer member; providing a voice coil assembly including a permanent magnet and a bobbin member; providing a first magnetic field providing a hammer attached with the bobbin member; providing a coil operatively attached to the bobbin member; and applying a voltage to the coil to generate a second magnetic field that opposes the first magnetic field thereby propelling the hammer to strike the transfer member. 
     In a seventh aspect, the present invention is a device for producing a shock wave to impact an object, including a housing having an exit end; and a transfer member operatively attached to the exit end of the housing. The device includes a hammer movable from a rest position to a second position, wherein when the hammer is in the second position the hammer impacts the transfer member to produce a shock wave that travels along the transfer member; and a power supply, supplying a voltage in the range of about 12-57 volts. 
     In an eighth aspect, the present invention is a device for producing a shock wave to impact an object, including a housing having an exit end; and a transfer member operatively attached to the exit end of the housing. The device includes a hammer movable from a rest position to a second position, wherein when the hammer is in the second position the hammer impacts the transfer member to produce a shock wave that travels along the transfer member; and a power supply, supplying a voltage of less than about 48 volts. 
     The invention provides the foregoing and other features, and the advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention and do not limit the scope of the invention, which is defined by the appended claims and equivalents thereof. 
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a cross sectional view of an embodiment of the present invention when a bobbin is in a first position. 
     FIGS. 2 &amp; 2A are views of the embodiment shown in FIG. 1, when a bobbin is in a second position. 
     FIG. 3 is a cross sectional view of an embodiment of the present invention. 
     FIG. 4 is an exploded view of a portion of the invention shown in FIG.  3 . 
     FIG. 5 is a cross sectional schematic view of an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 5 there is generally disclosed a device  1  for producing a shock wave to impact an object. Generally, the device  1  comprises an outer housing or shell  2 . Within the housing there is located a voice coil  3 , which comprises a permanent magnet  4 , a bobbin  32  and a coil  6  (not shown in detail). The bobbin also may have a striking surface or hammer  7 . The device further has a probe or wire  8 . The device may further comprise a return spring  9 . Generally, in operation an electric current is applied to the voice coil resulting in the coil moving toward the probe. The striking surface of the coil then strikes the probe, which is also in contact with the object to be crushed. The force from the voice coil striking the probe is transmitted though the probe to the object to be crushed. The return spring then forces the voice coil back away from the probe. 
     Several variation of this design are disclosed and described below. These are provided by way of example and are illustrative and not intended to be limiting. 
     Referring to FIG. 1, there is shown an embodiment of a device to produce a shock wave to impact an object, such devices may also be referred to as a lithotriptor  1 . The lithotriptor  1  includes a housing  10 . Disposed within the housing is a voice coil assembly  5  that includes a permanent magnet  30  and a bobbin member or bobbin  32 . A coil  19  is wrapped around a portion of the bobbin  32  and a hammer  40  is attached with part of the bobbin  32 . Extending out of the housing is a transfer member or probe  50  that can make contact with a stone to transfer a shock wave to the stone. 
     The housing  10  may be sized and shaped to accommodate the voice coil assembly  5  and the transfer member or probe  50 . Referring to FIGS. 1 and 2A, in a preferred embodiment, as shown in FIG. 1, the housing has an exit end  12  and a magnet end  14  formed opposite the exit end  12 . A retaining ring  15  is held in position in a groove  200  of the housing  10  to prevent a cup pole  24  from moving. A screw  16  passes through an o-ring  11  and screws into a threaded hole  96  disposed in the cup pole  24 . A longer screw (not shown) may be inserted into the threaded hole  96  in order to withdraw the magnet. An end o-ring  11  seals the permanent magnet  30  from the atmosphere. An adhesive is preferably used to align the permanent magnet  30  with the cup pole  24  and a disk pole  26  to form a concentric assembly. A rubber bumper  13  is bonded to the disk pole  26 . The rubber bumper  13  prevents the bobbin  32  from hammering the disk pole  26 . 
     Referring again to FIG. I inner walls  23  of the housing  10  extend inward adjacent a journal bearing  22 . The journal bearing  22  is disposed concentrically around a second portion  36  of the bobbin  32  to position and guide the bobbin  32 . A front plate  17  is preferably attached to the exit end  12  of the housing  10  using front screws  18 . An o-ring seal  92  is disposed between the inner walls  23  and the front plate  17  to prevent leakage. The housing may be made from any material that is strong enough to hold the component parts in place during use. For example it may be made of metals, such as steel or aluminum, plastic and or combinations of these materials. Alternatively, the housing could be formed in a variety of different shapes and be comprised of a number of various materials. For example the inside surface of the housing could be sized and shaped to accommodate the voice coil assembly  5  and probe  50  where as the outside surface could be shaped to mold to a persons hand. The housing could be elliptical shaped, barrel shaped, conical shaped or oblong shaped. Additionally, the outside of the housing, the part that is held by the user could be made from a different material than the inside of the housing. Thus, the outside material could be select for feel, grip and ease of cleaning, while the inside material could be selected for strength. 
     In a preferred embodiment, an inner sleeve  28  is formed in the front plate  17  and extends towards the magnet end  14 . The inner sleeve  28  is designed to hold a portion of the probe  50  in place. Also formed in the front plate  17  is a threaded member  20  that is sized to accommodate a cap  60 . 
     In a preferred embodiment, the permanent magnet  30  is positioned proximate the magnet end  14  of the housing. The permanent magnet  30  is preferably located and held inbetween the cup pole  24  and the disk pole  26 . In a preferred embodiment, the permanent magnet  30  is cylindrical shaped and is rectangular shaped in cross section (as viewed from FIG.  1 ). The permanent magnet  30  provides a first magnetic field that is oriented generally towards the exit end  12  of the housing  10 . Alternatively, the permanent magnet  30  could have a variety of cross sectional shapes, such as elliptical, circular, or trapezoidal. Further, instead of being a separate element, the permanent magnet  30  could be formed as part of the housing. Further, two or more permanent magnets could be used to provide a first magnetic field. Instead of using a permanent magnet, other sources of providing a first magnetic field could be used such as an electromagnet. 
     As shown in FIGS. 1 and 2 a bobbin  32  is located inbetween the exit end  12  and the magnet end  14  and is movable between a first position and a second position. The bobbin  32  is preferably comprised of a first portion  34  and a second portion  36 . 
     Referring to FIG. 1, the first portion  34  generally opens in the direction of the permanent magnet. The first portion  34  includes a grooved portion  33  that in part extends along the permanent magnet. The grooved portion  33  is sized and shaped to accommodate the coil  19 . A receiving surface  35  is formed on the first portion  34  of the bobbin  32  proximate the exit end  12 . The receiving surface  35  is sized and shaped to accommodate a top member  37  of the second portion  34 . 
     Referring to FIGS. 1 and 2A, in a preferred embodiment, the second portion  36  is attached to the first portion  34 . The two portions  34 , 36  are preferably attached by positioning the top member  37  into the receiving surface  35  formed on the first portion  34 . In a preferred embodiment the interface between the top member  37  and the receiving surface  35  forms a press fit. Alternatively, an adhesive may be applied in a space  94  located between the top member  37  and the receiving surface  35  to glue the top member  37  to the receiving surface  35 . Also, the first portion  34  and second portion  36  could simply be glued together using some type of adhesive and without using a top member  37 . In still another embodiment, the bobbin  32  could be formed as one piece instead of two portions  34 ,  36 . In another embodiment holes (not shown) may be formed in the top member  37  to allow air to pass through. 
     The second portion  36  of the bobbin  32  also is preferably generally “U” shaped, opens around the sleeve  28  and is disposed within and adjacent to the journal bearing  22 . In an alternative embodiment, the bobbin  32  could be formed as one piece instead of two portions  34 ,  36 . The first portion  34  and second portion  36  are preferably made of a non-magnetic material such as aluminum, brass, titanium, stainless steel, nickel, beryllium, magnesium or inconel. Alternatively, the bobbin  32  may be made of a nonconductive material or out of a conductive material that is insulated. In another alternative embodiment, a split or gap may be formed in the bobbin  32  to prevent a shorted turn. 
     Referring to FIGS. 1 and 2A, a cup  42  having a first wall  41  and a second wall  43  is attached inside the second portion  36  to an end  39  of the second portion  36 . In a preferred embodiment the cup is attached to the second portion  36  by being press fit into the end  39  of the second portion  36 . A space  94  may be disposed between the cup  42  and the end  39  and adhesive may be disposed in this space  94 . The cup is generally “U” shaped and is sized so that the first wall  41  and the second wall  43  are adjacent the interior of the second portion  36 . In an alternative embodiment, the cup  36  could be press fit to the second portion  36 . The cup  42  is preferably made of hard plastic. Alternatively, the cup could be made of any ceramic or composite fiber material. 
     The cup  42  acts in part as an insulator between the bobbin  32  and the hammer  40 . Alternatively, the cup  42  could be removed, for example where a ground fault interrupter circuit was used in conjunction with the device thereby preventing the need for such an insulator. 
     Referring again to FIGS. 1 and 2A, a hammer  40  having a first edge  46  and a second edge  48  is positioned against the cup  42 . In a preferred embodiment the hammer  40  is fixed to the cup using a press fit and glue. A space  94  may be disposed between the cup  42  and the hammer  40  and adhesive may be disposed in the space  94 . The hammer is generally cylindrical shaped and is rectangular shaped in cross section (as viewed from FIG. 1) and sized so that the first edge  46  is adjacent the first wall  41  of the cup and so that the second edge  48  is proximate the second wall  43 , thus forming a gap  49  between the second edge  46  and the second wall  43 . In a preferred embodiment the hammer is made of a hard metal such as steel, aluminum, brass, titanium, stainless steel or nickel. Alternatively, the voice coil assembly itself could be formed with, reinforced, or hardened to form a striking surface. In another alternative embodiment, the hammer  40  may be fixed directly to the second portion  36  without the use of an intervening cup  42 . Alternatively, the hammer may be free floating, such as a slug or ball bearing or partially free floating. 
     A biasing member or spring  62  is positioned to extend from the exit end  12  of the housing  10  to the cup  42 . The spring has an upper member  64 . The upper member  64  is disposed in the gap  49  and makes contact with the cup  42 . The spring  62  biases the bobbin  32  towards the magnet end  14  of the housing  10 . The spring is preferably made of spring steel. Alternatively, the spring could be made of an elastomeric type material such as rubber or silicone. In an alternative embodiment electromagnetic, pneumatic or mechanical means could be used to return the bobbin  32 . 
     The probe  50  includes a shock receiving portion  52  and a shock transferring portion  56 . The shock receiving portion  52  has a first end  51  and a flanged end  54 . A substantial portion of the shock receiving portion  56  is positioned inside the sleeve  28  formed in the housing  10 . The shock receiving portion  56  is positioned so that the first end  51  is proximate the hammer and the flanged end  54  is situated adjacent the threaded portion  20  of the housing  10 . 
     As shown in FIG. 1, the shock transferring portion  56  is generally fused within the shock receiving portion  52  and has a second end  53  that extends out of the housing  10 . A sleeve  58  is disposed over the flanged end  54  of the shock transferring portion and a cap  60  is disposed over the shock transferring portion  56  and screwed to the threaded portion  20  of the housing. The cap  60  and sleeve  58  cooperate to retain the probe  50  within the housing  10 . In an alternative embodiment, instead of a probe  50  a transfer member  50  such as a flat plate disposed against or formed in the exit end of the housing  10  could be used to transfer a shock wave. In a preferred embodiment the probe is made of stainless steel. 
     A power source  70  is attached to the lithotriptor  1  to supply energy to the coil  19 . In a preferred embodiment the power source  70  is a battery. Alternatively, the power source may be a transformer, rectifier and a capacitor storage circuit. In another alternative embodiment the power source may be an external power source such as a pulse generator. Although larger power supplies may clearly be used to operate the device. One of the advantages with the present device is that relatively low amounts of power are required to operate the device. Thus, by way of example and without limitation a power source that is capable of supplying 150-2000 volts may be used to operate the device. Further, as examples but not limited to power sources of about 12 volts may be used, power sources of about 12-57 volts may be used, power sources having about 59 volts may be used, power sources having about 40 volts may be used, power sources having about 20 volts may be used, power sources having about 15 volts may be used, power sources having 10 volts may be used and power sources having about 5 volts may be used. 
     An actuator  80  is attached to the lithotriptor. In a preferred embodiment, the actuator is a push button  80  that may be pressed by the operating physician to supply current to the coil  19  of the voice coil. Alternatively, the actuator  80  may be a foot pedal, or a panel switch. Alternatively, the actuator may have the ability to regulate or control the amount of force with which the hammer strikes the probe. Such a variable control actuator may be, by way of example, a potentiometer. 
     The operation of a preferred embodiment of the present invention will now be described with reference to FIGS. 1 and 2. First the probe  50  is placed against a stone  90  and the bobbin  32  is in the position shown in FIG.  1 . Next, a first magnetic field is provided by the presence of the permanent magnet  30 ; the first magnetic field is generally oriented towards the exit end  12  of the device. Energy is then supplied to the coil  19  of the voice coil to generate a second magnetic field that is generally oriented opposite to the first magnetic field. The resultant force created by the opposing forces of the first magnetic field and the second magnetic field propels the bobbin  32  and thereby the hammer  40 , from the right to the left (as viewed from FIGS.  1  and  2 ), to the position shown in FIG.  2 . In this position, the hammer strikes the probe  50  and the kinetic energy of the bobbin  32  is transferred to the cup  42 , then the kinetic energy is transferred from the cup  42  to the hammer  40  and finally the kinetic energy is transferred to the probe  50 , thus producing a shock wave in the probe  50 . The shock wave propagates along the probe  50  to the second end  53  where it is transferred to the stone  90  and thereby crushes the stone  90 . 
     The movement of the bobbin  32  from the first position to the second position causes the spring  62  to compress. After the bobbin reaches the second position shown in FIG.  2  and the energy to the coil is stopped, the compressed spring  62  creates a force that directs the bobbin  32  from left to right (as viewed from FIGS. 1 and 2) to the first position, shown in FIG.  1 . 
     In use, the physician positions the lithotriptor using a endoscope (not shown) such that the second end  53  of the probe  50  contacts a stone  90  or calculus within the body that the physician wishes to crush. The physician provides a current to the coil  19  of the voice coil by using an actuator  80  to actuate the power source  70 . This results in the operation described above that produces a shock wave that crushes the stone  90 . The bobbin  32  then returns to the first position and the physician can then repeat the foregoing steps to destroy multiple stones. 
     Referring to FIGS. 3-4, a second preferred embodiment of a lithotriptor  1  of the present invention is shown. The device is generally the same as the lithotriptor of FIGS. I and  2  and the similar elements have similar reference numbers. The primary difference between the preferred embodiment and the second preferred embodiment is that in the second embodiment, a biasing apparatus or o-ring  110  is positioned between the hammer  140  and the cup  142 . Grooved openings  141  are cut into the hammer  140  and are sized and shaped to accept the o-ring  110 . As a result of the positioning of the o-ring  110 , the hammer  140  is not touching the cup  142  and in fact a gap  112  is formed between the hammer  140  and the cup  142 . The o-ring  110  biases the hammer  140  away from the cup  142 . Alternatively, the biasing apparatus could be a spring or an elastomeric pad. 
     A retainer  116  is positioned against the first wall  146  of the cup  142 . The retainer  116  is preferably cylindrical shaped and is rectangular shaped in cross section (as viewed from FIGS.  3 - 4 ). The retainer is preferably a metal piece that is secured to the first wall  146  and holds the hammer  140  in position. 
     In operation, when energy is applied to the coil the bobbin  132  moves to the left (as viewed from FIG. 3) and the hammer  140  strikes the probe  150 . Upon impact, kinetic energy is transferred from the bobbin  132  to the cup  142 , then to the o-ring  110  and finally to the hammer  140 . The presence of the o-ring creates a time lag in the kinetic energy transfer. 
     In another alternative embodiment of the invention (not shown), the device is generally the same as the device shown in FIGS. 1 and 2, however, the bobbin does not include a top member. Instead a biasing member is inserted inbetween the first portion and the second portion of the bobbin. In operation, when energy is applied to the coil the bobbin moves to the left (as viewed from FIG. 3) and the hammer  140  strikes the probe  150 . Upon impact, kinetic energy is transferred from the first portion of the bobbin, to the biasing member, to the second portion of the bobbin and finally to the hammer. The presence of the biasing member creates time lag in the kinetic energy transfer. In a preferred embodiment the biasing member may be a belleville spring, a disc spring or a garter spring. 
     In another alternative embodiment of the invention (not shown), the device is generally the same as the device shown in FIGS. 1 and 2, however, the voice coil assembly does not include a hammer. Instead a biasing member is preferably attached to the bobbin member. Additionally a sleeve member substantially surrounds the transfer member. In operation, upon applying a current to the coil the bobbin member moves toward the probe and the biasing member contacts the sleeve and is compressed, thereby resulting in potential energy being stored within the biasing member. When the current is stopped, the biasing member releases and impacts against the transfer member thereby resulting in a shock wave being transmitted through the transfer member that may be used to crush a stone. In a preferred embodiment the biasing member is comprised of a pair of leaf springs operatively attached to the bobbin member. 
     An advantage of the present invention is that generally a lesser amount of energy is required to operate the device as compared to prior art devices. The fact that the present invention requires less energy to operate than prior art devices provides several advantages. 
     First, the lower energy requirement allows the present invention to utilize a portable power source, such as a battery. This eliminates the necessity of having a cord running from the device to an external power source. 
     In addition, an important advantage from the foregoing design is that modifying the speed at which the bobbin  32  impacts the probe  50  is easier to accomplish than in prior art designs. The speed and therefore the impact force of the hammer can be better controlled because the device does not require saturating an electromagnetic mass body to cause it to move but instead requires passing relatively small amounts of energy through the coil disposed around the bobbin. 
     Further producing a first magnetic field without a permanent magnet would require a significant amount of coil that would have to be insulated. The need for this additional insulation would increase the cost of the product. Thus, the present invention is generally more cost efficient to manufacture than the prior art. 
     While the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.