Abstract:
A surgical instrument for grasping and controlling a guide wire includes a male member having a longitudinal slit in communication with an inner hollow bore and a female member having a longitudinal slit in communication with an inner chamber. The male member is rotatably engageable within at least a portion of the female member. A method of threading a guide wire into a surgical instrument includes engaging a male member within a female member, rotating the male member relative to the female member until a longitudinal slit of the male member is aligned with a longitudinal slit of the female member; inserting a guide wire through the slits and into an interior of the male member and female member; and rotating the male member relative to the female member until the slits of the male member and female member are not aligned, trapping the guide wire within the surgical instrument.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a non-provisional of: 
         [0002]    pending U.S. Provisional Patent Application No. 61/548,794, filed Oct. 19, 2011, which carries Applicant&#39;s docket No. MLI-101 PROV, and is entitled SIDE-LOADING TORQUE DEVICE. 
         [0003]    The above-identified document is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0004]    This invention relates to guidewires used in diagnostic and interventional medical procedures and, more particularly, to a torque device including a body disposed on a guidewire used to position the guidewire within a body for an endovascular procedure. 
       BACKGROUND OF THE INVENTION 
       [0005]    Guidewires (also known as wire guides) have been used in percutaneous entry procedures for diagnostic X-Ray studies and interventional procedures since the 1950&#39;s when the idea of percutaneous, guidewired entry into the vasculature was conceived. Typically, guidewires are inserted percutaneously into a body vessel, such as a vein or artery, and advanced or manipulated within the body vessel until reaching a desired location. A catheter (or other insertable device) is then positioned over the guidewire, inserted percutaneously into the body vessel, and advanced along the guidewire to a desired location to perform a desired treatment, diagnosis, investigation, or medical intervention. 
         [0006]    Therefore, guidewires typically have particular characteristics to improve the pushability of the guidewire within the body vessel. For example, the guidewire is preferably generally radially flexible to negotiate the potentially-winding path of the body vessel and to reduce potential damage to the body vessel walls while the guidewire is being advanced. More specifically, the guidewire preferably has a relatively high axial stiffness to improve the pushability and control of the guidewire along the body vessel. The relatively high axial stiffness reduces kinking and bending so that the guidewire will not become stuck or obstructed during the advancement thereof along the body vessel. The axial stiffness of the guidewire is preferably sufficient to prevent the guidewire from folding over itself and becoming obstructed within the body vessel when the distal tip encounters a bend or curve in the body vessel. 
         [0007]    However, during positioning of the guidewire and advancement through the body vessel, it may be required to adjust the guidewire to advance through a desired branch of the body vessel. To advance the guidewire through the desired branch, the guidewire may need to be moved laterally or rotated. Given a distance between a distal end of the guidewire and a portion of the guidewire outside the body that may be manipulated by a doctor, the distal end of the guidewire may be difficult to advance through the desired branch. Furthermore, a length of guidewire outside of the body of the patient is as long as or longer than a length of guidewire within the patient. Therefore, guiding and/or rotating the distal end of the guidewire may be difficult. Also, once a guidewire is positioned within the body vessel in a desired location, the guidewire may be accidentally advanced or pulled from the body vessel requiring a doctor to reposition the guidewire. 
         [0008]    It would be desirable to provide a torque device adapted to facilitate advancement and/or rotation of the guidewire through a body vessel that is able to maintain a position of the guidewire at a desired location and that may be easily removed from the guidewire. 
       SUMMARY OF THE INVENTION 
       [0009]    Concordant and congruous with the present invention, a torque device adapted to facilitate advancement and/or rotation of the guidewire through a body vessel that is able to maintain a position of the guidewire at a desired location and that may be easily removed from the guidewire has surprisingly been discovered. 
         [0010]    According to an embodiment of the invention, a torque device comprises a cap having a first end and a second end and forming a hollow passage therethrough and a first channel extending along a longitudinal axis thereof; a body having a first end and a second end and forming a hollow passage therethrough and a second channel extending along a longitudinal axis thereof, the first end of the body received within the hollow passage of the cap; and an annular array of spaced apart protuberances formed on the first end of the body, the protuberances adapted to selectively compress when the first end of the body is selectively advanced through the hollow passage of the cap toward the first end thereof. 
         [0011]    According to another embodiment of the invention, a surgical instrument for grasping and controlling a guide wire, comprises a male member having a longitudinal slit in communication with an inner hollow bore; and a female member having a longitudinal slit in communication with an inner chamber of the female member, wherein the male member is rotatably engageable within at least a portion of the female member. 
         [0012]    According to another embodiment of the invention, a method of threading a guide wire into a surgical instrument comprises engaging a male member within a female member, wherein the male member comprises a longitudinal slit and wherein the female member comprises a longitudinal slit; rotating the male member counterclockwise relative to the female member until the longitudinal slit of the male member is substantially aligned with the longitudinal slit of the female member; inserting a guide wire through the substantially aligned longitudinal slits and into an interior of the male member and female member; and rotating the male member clockwise relative to the female member until the longitudinal slits of the male member and female member are not substantially aligned, thereby trapping the guide wire within the surgical instrument. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The above, as well as other objects and advantages of the invention, will become readily manifest to those skilled in the art from reading the following detailed description when considered in light of the attached drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. 
           [0014]      FIG. 1  is a side view of a back loading torque device known in the prior art with male and female members disconnected and a wire guide threaded through both of the female and male members; 
           [0015]      FIG. 2  is a side view of the back loading torque device of  FIG. 1  with the male and female members connected to each other; 
           [0016]      FIG. 3  is a side view of a different embodiment of a back loading torque device known in the prior art with the male and female members translated distal from each other; 
           [0017]      FIG. 4  is a side view of the back loading torque device of  FIG. 3  with the male and female members in closer proximity to each other; 
           [0018]      FIG. 5  is a side view of a side loading torque device according to an embodiment of the invention with the male and female members disconnected and a guide wire disposed there through; 
           [0019]      FIG. 6  is a side view of the torque device of  FIG. 5  with the male and female members connected to each other and their longitudinal slits in alignment with a guide wire disposed therein; 
           [0020]      FIG. 7  is a side view of the torque device of  FIG. 6  with the male and female members connected to each other with their respective longitudinal slits not in alignment with each other and a guide wire disposed there through; 
           [0021]      FIG. 8  is a cross-sectional view of the torque device of  FIG. 7 ; 
           [0022]      FIG. 9  is an end elevational view of the torque device of  FIG. 7  illustrating a longitudinal slit with opposing parallel sides; 
           [0023]      FIG. 10  is an end elevational view of a torque device according to another embodiment of the invention illustrating a longitudinal slit with opposing sides which converge towards each other from the inside of the torque device toward the outside the torque device; 
           [0024]      FIG. 11  is an end elevation view of a torque device according to another embodiment of the invention illustrating a longitudinal slit with opposing sides which diverge towards each other from the inside of the torque device toward the outside of the torque device; 
           [0025]      FIG. 12  is an end elevation view of a torque device according to another embodiment of the invention illustrating a longitudinal slit which is offset from the center longitudinal axis and has a divergent portion closer to the outer edge of the torque device; 
           [0026]      FIG. 13  is an isometric view of a side loading torque device with male and female members connected to each other having their longitudinal slits in alignment with their stop members engaged; 
           [0027]      FIG. 14  is an isometric view of the side loading torque device of  FIG. 13  with a guide wire about to be threaded into the longitudinal slits of the torque device; 
           [0028]      FIG. 15  is an isometric view of the side loading torque device of  FIG. 14  with the guide wire threaded into the longitudinal slits of the torque device; 
           [0029]      FIG. 16  is an isometric view of the side loading torque device of  FIG. 15  with the guide wire threaded inside the torque device and the male member rotated clockwise such that the longitudinal slits no longer are in alignment, thereby locking the guide wire within the torque device; 
           [0030]      FIG. 17  is a top view of the torque device of  FIG. 16  showing a cross-sectional line  18 A- 18 B; 
           [0031]      FIG. 18  is a cross-sectional side view of the torque device of  FIG. 17  taken along the line  18 A- 18 B in  FIG. 17 ; 
           [0032]      FIG. 19  is an isometric view of the torque device of  FIG. 18  with stop members connected to the male and female members and engaged with each other aligning the longitudinal slits; 
           [0033]      FIG. 20  is an isometric view of the torque device of  FIG. 19  with the stop members disengaged with each other and the longitudinal slits out of alignment; 
           [0034]      FIG. 21  is an isometric view of the male member of  FIG. 20  showing the collet locking mechanism and male stop member; and 
           [0035]      FIG. 22  is an isometric view of the female member of  FIG. 21  showing the inside threaded portion of the female member, the longitudinal slit, and the female stop member. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical. 
         [0037]    In this specification, standard medical directional terms are employed with their ordinary and customary meanings. Superior means toward the head. Inferior means away from the head. Anterior means toward the front. Posterior means toward the back. Medial means toward the midline, or plane of bilateral symmetry, of the body. Lateral means away from the midline of the body. Proximal means toward the trunk of the body. Distal means away from the trunk. 
         [0038]    In this specification, a standard system of three mutually perpendicular reference planes is employed. A sagittal plane divides a body into bilaterally symmetric right and left portions. A coronal plane divides a body into anterior and posterior portions. A transverse plane divides a body into superior and inferior portions. 
         [0039]    Guide wires are used in most catheter-based procedures. The distal end of a guide wire typically has an angled tip, which can be oriented to help steer the guide wire through curves and junctions of the vasculature or vessels of a patient. The orientation of the angled tip is achieved by torqueing the guide wire so that it rotates about its axis. However, since the guide wire has a small diameter and typically a smooth surface, it is difficult to torque with an operator&#39;s fingers. Torqueing requires the aid of a larger diameter torque device, which is attached to the guide wire. A torque device is used to provide a “handle” whereby the surgeon can have maximum control over the positioning and orientation of the guide wire. 
         [0040]    One of the disadvantages of guide wire torque devices known in the art, such as those shown in  FIGS. 1-4 , is that they must generally be “back loaded” over the proximal end of a guide wire, costing the surgeon precious time and attention in order to thread the torque device over the guide wire. In addition, to remove these types of devices to dispose tools or implements required to perform a procedure, such as catheters, and the like, the device must be slidingly removed from the guidewire which may have a great length. During removal of this device, the guidewire may be moved or accidentally pulled out of the patient, thereby requiring the guidewire positioning procedure to be repeated. 
         [0041]    One way to alleviate this problem is to create a slit or longitudinal aperture in both the male  532  and female  530  parts of the torque device as shown in  FIGS. 5-12 . This allows a surgeon to “side load” the guide wire into the torque device, obviating the need to load the torque device from the proximal end of the guide wire. 
         [0042]      FIGS. 5-12  illustrate a torque device  510  according to an embodiment of the invention. The torque device  510  is disposed on a guidewire  512  for advancement within a body vessel (not shown), such as a vein or an artery, for example. The torque device  510  includes a cap  514  and a cooperating body  516 . As shown, the cap  514  and the body  516  are formed from a plastic, but the cap  514  and the body  516  may be formed from a metal, such as a stainless steel, for example, as desired. 
         [0043]    The cap  514  includes a first end  518  and a second end  520 . A hollow passage extends between the first end  518  and the second end  520 . A channel  530  providing communication with the passage is formed along a longitudinal axis of the cap  514 . The channel  530  may form a substantially linear aperture, as shown in  FIG. 9 ; an aperture tapering away from the guidewire  512  to facilitate removal of the guidewire  512  therefrom, as shown in  FIG. 10 ; an aperture tapering toward guidewire  512  to militate against removal of the guidewire  512  therefrom, as shown in  FIG. 11 ; or the aperture may formed at an angle with respect to plane tangential to the cap  514  to militate against removal of the guidewire  512  therefrom, as shown in  FIG. 12 . An aperture formed in the first end  518  and an aperture formed in the second end  520  provide access to the passage and facilitate advancement of the guidewire  512  through the cap  514 . The first end  518  has a conical shape, and a portion of the passage formed in the first end  518  is narrower than a portion of the passage formed through the second end  520 . As shown in  FIG. 8 , threads  523  formed adjacent the second end  520  on an interior of the cap  514  cooperate with threads  522  on a first end  524  of the body  516 . 
         [0044]    The body  516  includes the first end  524  and a second end  526 . A hollow passage extends between the first end  524  and the second end  526 . A channel  532  providing communication with the passage is formed along a longitudinal axis of the body  516 . The channel  532  may form a substantially linear aperture, as shown in  FIG. 9 ; an aperture tapering away from the guidewire  512  to facilitate removal of the guidewire  512  therefrom, as shown in  FIG. 10 ; an aperture tapering toward guidewire  512  to militate against removal of the guidewire  512  therefrom, as shown in  FIG. 11 ; or the aperture may formed at an angle with respect to plane tangential to the body  516  to militate against removal of the guidewire  512  therefrom, as shown in  FIG. 12 . An aperture formed in the first end  524  and an aperture formed in the second end  526  provide access to the passage and facilitate advancement of the guidewire  512  through body  516 . The first end  524  includes an annular array of spaced apart protuberances  528  cooperating to form a portion of the passage through the first end  524 . The protuberances  528  are flexible and adapted to be selectively compressed around the guidewire  512  to militate against advancement thereof through the body  516 . The threads  522  of the body  516  are formed intermediate the protuberances  528  and the second end  526 . It is understood that an annular channel (not shown) adapted to receive and cooperate with a detent (not shown) formed on an interior of the cap  514  may be formed between the protuberances  528  and the threads  522 . The annular channel and the detent cooperate to militate against removal of the first end  524  of the body  516  from the cap  514  once the torque device  510  is assembled. 
         [0045]    In use, the cap  514  and the body  516  are assembled to form the torque device  510  with the first end  524  of the cap  514  disposed within the passage of the cap  514  adjacent the second end  520  thereof. The cap  514  and the body  516  may be assembled by clicking the detent into the annular channel, or by rotating the body  516  to engage the threads  522  thereof with the threads  523  formed on the interior of the cap  514 . The passages of the cap  514  and the body  516  cooperate to form a unitary passage through which the guidewire  512  is fed when the torque device  510  is assembled. It is understood that the cap  514  and the body  516  may include indicia thereon to indicate when the channels  530 ,  532  are properly aligned for insertion of the guidewire as in  FIG. 6 , and when the channels  530 ,  532  are appropriately misaligned for use of the torque device  510 , as in  FIG. 7 . 
         [0046]    The guidewire  512  is disposed through the aperture formed in the second end  526  of the body  516 , through the passage formed in the body  516 , through the passage formed in the cap  514 , and through the aperture formed in the first end  518  of the cap  514 . Alternatively, the grooves  530 ,  532  of the assembled torque device  510  may be aligned, as shown in  FIG. 5  so that the guidewire  512  may be disposed therethrough. An end of the guidewire  512  is then disposed through a puncture in the skin of a patient and into a body vessel (not shown). Using x-ray pictures as a guide, the guidewire  512  is advanced through the body vessel. When a branch or bend in the body vessel is reached, the body  516  is rotated and threaded into the cap  514  to advance the first end  524  toward the first end  518  of the cap  514 . As the first ends  524 ,  518  converge, the protuberances  528  advance into the narrowing passage of the conical portion of the cap  514  causing the protuberances  528  to compress around the guidewire  512 . Once the protuberances  528  are compressed around the guidewire  512 , the torque device  510  is in a closed position and advancement of the guidewire  512  through the torque device  510  is militated against. In the closed position, the groove  530  is offset from the groove  532 , as shown in  FIG. 7 , to militate against removal of the guidewire  512  therefrom. The torque device  510  may be gripped by the doctor to rotate and/or laterally move the guidewire  512  disposed within the body vessel of the patient, or the guidewire  512  disposed between the puncture and the torque device  510  may be gripped by the doctor to rotate and/or laterally move the guidewire  512  disposed within the body vessel of the patient. 
         [0047]    The body  516  may then be unscrewed from the cap  514  to allow the guidewire  512  to be fed therethrough. Once the end of the guidewire  512  is in a desired location within the body vessel, the torque device  510  is returned to the closed position with the torque device  510  adjacent the puncture in the patient. If the guidewire  512  is inadvertently withdrawn from the patient, the guidewire  512  and the torque device  510  may be re-advanced until the torque device  510  is again adjacent the puncture. Once the guidewire  512  is in the desired location and advancement through the body vessel is complete, the torque device  510  may be opened and slidably removed from the guidewire  512 . Once the guidewire  512  is in place, the doctor can proceed with the endovascular procedure. To remove the torque device  510  to dispose tools or implements required to perform the procedure, such as catheters, and the like on the guide wire  512 , the cap  514  and the body  516  are positioned to align the channels  530 ,  532  to form a unitary channel that extends the length of the torque device  510  and the torque device  510  may be removed laterally from the guidewire  512  without having to slidably remove the torque device  510  longitudinally from the guidewire  512  which may be very long. 
         [0048]      FIGS. 9-12  show end elevational views of the torque devices of  FIGS. 5-8  and illustrate how the longitudinal slits in the male and female members create an opening through which a guide wire may be inserted in a side loading fashion into the interior of the torque device. The surgeon can use one or both hands to grasp the side-loading endovascular torque device and rotate the male member in relation to the female member such that the slits of both the male member and the female member align. The surgeon may then insert the guide wire through the side slits, and rotate the male and female members relative to each other such that the side slits no longer align causing the guide wire to be retained within the torque device. This reduces the time needed for the surgeon to thread the guide wire into the torque device. However, the surgeon still needs to look at the orientation of the slits in both the male and female members in order to verify that both slits are in alignment before inserting the guide wire into the torque device. 
         [0049]    Another embodiment to further reduce the time and effort required by the surgeon to thread the guide wire into the side loading torque device is seen in  FIGS. 13-22 .  FIG. 13  shows a perspective view of a side loading torque device having male member  104  engaged within female member  102 . Male member  104  may have threads  114  to threadably engage within female member  102  which may also have complementary threads disposed with in female member  102  and configured to receive male member  104 . Male member  104  has a male longitudinal slit or aperture  108  which spans the length of male member  104  Likewise, female member  102  has a female longitudinal slit or aperture  106  which spans the length of female member  102 . Male longitudinal slit  108  and female longitudinal slit  106  can be better seen in  FIGS. 21 and 22 , wherein the male member  104  is disconnected from the female member  102 . 
         [0050]    Referring back to  FIG. 13 , male member  104  may also have a hollow inner bore  116  spanning the length of male member  104  which may be configured to receive a guide wire within the hollow inner bore  116 . Male longitudinal slit  108  may be in communication with, or configured to allow access to, the hollow inner bore  116  such that a guide wire (not shown) can pass through male longitudinal slit  108  and into hollow inner bore  116  in a “side loading” fashion. Male member  104  may also have a male stop member  110  protruding from a surface of male member  104  Likewise, female member  106  may also include a female stop member  112  protruding from a surface of female member  102 . Male stop member  110  and female stop member  112  may be shaped so as to engage each other in such a fashion as to prevent rotation of male member  104  within female member  102  when male longitudinal slit  108  is aligned with female longitudinal slit  106 . 
         [0051]      FIGS. 14-16  illustrate how a guide wire  118  is side-loaded it into a torque device  100  according to the present disclosure. In operation, a surgeon can rotate male member  104  counterclockwise until male stop member  110  engages with female stop member  112  preventing the surgeon from further rotation in the counterclockwise direction. At the point which male stop member  110  engages with female stop number  112 , male longitudinal slit  108  is substantially in alignment with female longitudinal slit  106  and ready to receive the guide wire  118 , as can be seen in  FIG. 14 . In this orientation, the slits of the collet style locking mechanism  128  (see  FIG. 21 ) at the distal end of male member  104  may also be substantially aligned with the longitudinal slits of the male and female members. Furthermore, the collet style locking mechanism  128  may also be substantially uncompressed, thereby not exerting a substantial amount of frictional force upon a guide wire to be inserted therein. The surgeon can then side-load guide wire  118  into the torque device  104 , as is shown in  FIG. 15 . The surgeon then may rotate male member  104  in the clockwise direction such that male longitudinal slit  108  and female longitudinal slit  106  are no longer in alignment, thereby retaining guide wire  118  disposed within torque device  100  as can be seen in  FIG. 16 . Furthermore, with sufficient clockwise rotation the surgeon can actuate the collet locking mechanism  128  (shown in more detail in  FIGS. 18 and 21  and discussed in more detail below) to produce sufficient frictional force to grasp the guide wire  118  thereby locking the guide wire  118  relative to the torque device  100 .  FIGS. 19 and 20  illustrate another isometric view of the torque device  100  according to the present disclosure with the stop members engaged in  FIG. 19  and disengaged in  FIG. 20 . 
         [0052]      FIGS. 17 and 18  illustrate a cross-sectional view of torque device  100  with  FIG. 18  showing the cross-sectional view of the torque device of  FIG. 17  taken along the line  18 A- 18 B in  FIG. 17 .  FIG. 18  shows the distal end  120  of male member  104  disposed with in female member  102 . The distal end  120  of the male member  104  may comprise a compression device such as a collet locking mechanism  128  (shown in more detail in  FIG. 21 ). The interior within female member  102 , intermediate the tip  124  of female member  102  and the threaded portion  126  of female member  102 , may comprise a chamber  122  configured to receive the distal end  120  of male member  104 . The chamber  122  may have a conical shape with a larger interior space volume at the end of chamber  122 , closest to the threaded portion  126 , and a smaller interior space volume at the end of chamber  122 , closest to the tip  124  of female member  102 . As the surgeon rotates male member  104  clockwise, male member  104  enters further and further into female member  102 . As the collet locking mechanism  128  enters further and further into chamber  122 , the collet  128  is compressed into a smaller and smaller space causing the flanges  130  (see  FIG. 21 ) to compress together and frictionally engage the guide wire  118 . With enough compression, the collet locking mechanism  128  exerts sufficient frictional force upon the guide wire  118  such that the guide wire  118  is “locked” relative to torque device  100 , preventing the guide wire  118  from sliding freely within the hollow inner bore  116  of torque device  100 . 
         [0053]    Either or both of the stop members  110 ,  112  may be deflectable to permit the stop members to rotate past each other upon initial assembly of the torque device  100 . Either or both of the stop members  110 ,  112  may be attachable to the corresponding member  102 ,  104  after initial assembly of the members  102  and  104 . 
         [0054]    It should be understood that the present system, kits, apparatuses, and methods are not intended to be limited to the particular forms disclosed. Rather, they are to cover all modifications, equivalents, and alternatives falling within the scope of the claims. 
         [0055]    The claims are not to be interpreted as including means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for,” respectively. 
         [0056]    The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more” or “at least one.” The term “about” means, in general, the stated value plus or minus  5 %. The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.” 
         [0057]    The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a method or device that “comprises,” “has,” “includes” or “contains” one or more steps or elements, possesses those one or more steps or elements, but is not limited to possessing only those one or more elements. Likewise, a step of a method or an element of a device that “comprises,” “has,” “includes” or “contains” one or more features, possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed. 
         [0058]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. It is appreciated that various features of the above-described examples can be mixed and matched to form a variety of other alternatives. For example, indicia and/or stop members may be included on any of the embodiments. As such, the described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.