Abstract:
There is disclosed suture manipulating instrumentation having measuring structure to determine the length of suture during a given point in a surgery. The instrument is preferably a surgical suturing instrument capable of manipulating a suture carrying needle at the distal end. The measuring structure in the form of a scale is provided on the suturing instrument at a location remote from the distal end. The length of suture can easily be determined with the use of the scale at any point during a surgery. There is also disclosed a kit for providing the suture measuring structure on other suture manipulating instruments, as well as, methods of using suture manipulating instrumentation haying the disclosed measuring structure.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This is a Divisional Application of U.S. patent application Ser. No. 10/529,567, filed Mar. 28, 2005, which is a National Stage Application of PCT/US03/31640, filed Oct. 6, 2003, under 35. U.S.C. §371(a), which claims priority to, and the benefit of, U.S. Provisional Patent Application Ser. No. 60/416,058, filed Oct. 4, 2002, entitled “Surgical Suturing Apparatus With Measurement Structure”, now abandoned, the disclosures of which are hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates generally to surgical instrumentation and, more particularly, to surgical instrumentation having measuring apparatus for use in endoscopic or laparoscopic surgical procedures. 
         [0004]    2. Description of Related Art 
         [0005]    Endoscopic procedures are typically performed through an elongated cannula structure having a relatively small diameter with a proximal and distal end. In laparoscopic surgery an incision is made in the abdominal wall and the distal end of the cannula is passed through the tissue into the body cavity wherein the surgical procedure or examination is to be effected, thus providing a conduit for the insertion of surgical instrumentation. A plurality of cannula structures may be used to allow operation of a variety of instruments simultaneously during a given procedure. For example, one cannula may provide a conduit for an endoscope for vision and illumination within the operative cavity while the other cannulas may provide conduits for control of specialized surgical instruments designed for performing specific procedural functions. 
         [0006]    Many surgical procedures call for suturing tissue, a procedure traditionally accomplished by hand, or by passing a needle between forceps. Laparoscopic suturing presents a particularly challenging task, because it must be accomplished using instrumentation extended through a port that typically has an internal diameter that averages between five and twelve millimeters. Instruments for facilitating laparoscopic suturing are disclosed in U.S. Pat. No. 5,478,344, issued Dec. 26, 1995, to Stone et al., which is incorporated herein in its entirety by reference. The Stone et al. patent discloses in certain embodiments, a surgical suturing apparatus capable of passing control of a surgical needle, having a length of suture attached thereto, back and forth between its jaws to repeatedly pass the surgical needle and suture through tissue to suture tissue. In addition, it discloses methods of using the apparatus to suture tissue. 
         [0007]    Other laparoscopic suturing instruments are also available in the marketplace. For example, U.S. Pat. No. 5,690,653, issued Nov. 25, 1997, to Richardson et al. discloses in certain embodiments a suturing device that includes an elongated tubular shaft having a needle disposed at the distal end. The needle is attached to a suture and is passed between one or more relatively movable jaws, as well as a method of using the device. 
         [0008]    However, while the above-mentioned devices are valuable for laparoscopic suturing, none of the above-mentioned devices includes structure or discloses a method that facilitates measurement of the length of suture material while the device is in the body cavity. Therefore, a need exists for a suturing apparatus that maintains the advantages of laparoscopic suturing and incorporates a suture material measurement structure. 
       SUMMARY 
       [0009]    Various measuring structures are provided for use with a number of different laparoscopic surgical instruments. The measuring structures are disposed on the apparatus for determining the length of a suture or determining the amount of suture material remaining when using the apparatus. Preferably, the measuring structure is an integral part of the laparoscopic instrument and is disposed at the distal end of the instrument for accurate measurement of the suture. Alternatively, the measuring structure is included in a kit that can be used with a number of different laparoscopic instruments. In either embodiment, the measuring structure has a number of graduations showing the selected units of measure. Further still, the measuring structure can be positioned such that the graduations are only visible from one vantage point. However, in a preferred embodiment, the measuring structure will be disposed so that it covers the outer perimeter of the surgical instrument substantially in its entirety. In this embodiment, the graduations of the measuring structure will be visible to the surgeon from most any vantage point enabling the surgeon to obtain a measurement without undue manipulation of the laparoscopic instrument. 
         [0010]    Specifically a surgical instrument for manipulating a suture is disclosed including an elongate member having a distal end configured to manipulate a suture and a scale on at least a part of the elongate member and adjacent the distal end. The scale has at least one graduation and preferably a plurality of graduations to measure suture lengths. A predetermined point is identified on the elongate member such that the scale indicates the distance from the predetermined point to the at least one graduation. Preferably, the elongate member includes at least one jaw and the predetermined point is disposed on the the jaw. The jaw is configured to retain a needle carrying a suture and, alternatively, the predetermined point is located on the needle. 
         [0011]    The surgical instrument is preferably a suturing apparatus and, predetermined point is located at the point of connection between the suture and the needle. The point of connection can be at one end of the needle, but preferably is located between the ends of the needle, especially with a double pointed needle. 
         [0012]    The surgical instrument has at least one jaw is movable relative to the elongate member such that the distance from the predetermined point and the scale is calibrated with the at least movable jaw in a predetermined position. In a preferred embodiment of the surgical instrument the elongate member includes two movable jaws which are configured to repeatedly pass control of a needle carrying a suture therebetween and through tissue to form stitches. 
         [0013]    The scale is provided to measure the remaining amount of suture after suturing and includes a plurality of graduations. Preferably, the scale is provided on a material affixed to the elongate member such as a shrink wrap affixed to the elongate member. Alternatively, the scale can be located on at least one longitudinally extending strip of material or etched into the elongate member. Preferably, the graduations indicate the distance in centimeters. 
         [0014]    There is also disclosed a kit to assist manipulation of a suture with an elongate instrument including a scale configured to be attached to the distal end of a suture manipulating instrument and a template to calibrate the position of the scale relative the predetermined point on the distal end of the instrument. Preferably, the scale is provided on a shrink wrap material. 
         [0015]    There is further disclosed a method of manipulating a suture by providing an elongate suture manipulating instrument configured to hold a first end of a suture at a predetermined point on a distal end of the instrument and a scale having at least one graduation provided on the instrument at a location remote from the distal end. During surgery a second end of the suture is grasped with a separate device and drawn along the instrument adjacent the scale so that a second end of the suture is adjacent the graduations on the scale to measure the length of suture. The drawing of the suture can be performed while the suture is being passed through tissue or after the suture is passed through tissue. 
         [0016]    These together with other advantages will become apparent from the details of construction and operation as more fully hereinafter described. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0017]    Various embodiments are disclosed herein with reference to the drawings wherein; 
           [0018]    PIG.  1  is a perspective view of the distal end of a surgical suturing apparatus in accordance with an embodiment of the present disclosure, showing a measuring structure; 
           [0019]      FIG. 2  is a side plan view, partially shown in section, of the suturing apparatus in accordance with the embodiment of  FIG. 1 ; 
           [0020]      FIG. 3  is a exploded perspective view of the distal end of a surgical suturing apparatus in accordance with the embodiments of  FIGS. 1 and 2 ; 
           [0021]      FIG. 4  is a side view of the distal end of the suturing apparatus in accordance with the embodiment of  FIGS. 1-3 , showing a grasping instrument holding the suture along the measuring structure; 
           [0022]      FIG. 5  is a plan view of a measuring structure in accordance with the embodiment of  FIGS. 1-4 ; 
           [0023]      FIG. 6  is a side view of the distal end of the suturing apparatus in accordance with the embodiment of  FIGS. 1-5 , illustrating the measuring structure measuring a length of suture material; 
           [0024]      FIG. 7  is a side view of the distal end of the tubular housing in accordance with the embodiment of  FIG. 1-6 , illustrating the measuring structure measuring a different length of suture material; 
           [0025]      FIG. 8  is a perspective view of the distal end of a surgical suturing apparatus in accordance with a further embodiment of the present disclosure; 
           [0026]      FIG. 9  is a perspective view of the distal end of a surgical apparatus in accordance with another embodiment of the present disclosure; and 
           [0027]      FIG. 10  is a perspective view of a surgical grasping instrument in accordance with another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]    The embodiments disclosed herein below relate to surgical instruments for manipulating a suture and having measuring structure to measure a length of suture at any time during a surgery. 
         [0029]      FIGS. 1-7 , show an embodiment of a suturing apparatus in accordance with an embodiment of the present disclosure. Suturing apparatus, generally indicated by reference numeral  10 , has an elongated tubular housing or body portion  12 , and two movable jaws (or jaw elements)  14  and  16 . A needle  18  is releasably retained in one of jaws  14  and  16  at the distal end of suturing apparatus  10 . Suturing apparatus  10  is configured to pass needle  18  back and forth between jaws  14  and  16 . A length of suture  20  is connected to needle  18  such that passing needle  18  back and forth between tissue passes suture  20  through the tissue to form stitches. A measuring structure  90  is disposed on the distal portion of tubular housing  12  to measure the length of suture  20 . As is conventional, the term “distal” refers to that direction further from the user while the term “proximal” refers to that direction closer to the user. 
         [0030]    Referring to  FIGS. 2 and 3 , there is shown suturing apparatus  10  in greater detail. Suturing apparatus  10  is described in certain embodiments of U.S. Pat. No. 5,690.653, the disclosure of which is hereby incorporated by reference herein. Suturing apparatus  10  has a handle housing  30  with a two-armed handle  2 , elongated tubular housing  12 , and two jaws  14  and  16 . Handle  2  is used to control the opening and closing of jaws  14  and  16 . Handles  2  are connected to a rod  7  by a pair of links  33  and  34  and pins  49 , 50  and  51 . Center rod  7  is spring biased distally by spring  6 . Spring  6  fits around center rod  7  and rests in a channel of housing  30 . When the handles  2  are squeezed, center rod  7  moves backward (proximally), causing spring  6  to be compressed. Referring to FIG  3 ., the distal end of center rod  7  has a pin  8  which rides in a cam slots  9  and  41  in each of the jaws  14  and  16 . Jaws  14  and  16  are pivotally connected to each other by pin  11  extending through holes  43  and  13  and through holes  53  and  54  of support  52 . When center rod  7  is pulled proximally through actuation of the handles  2 , pin  8  is also pulled proximally in cam slots  9  and  41 , camming jaws  14  and  16  closed. 
         [0031]    Each jaw  14  and  16  is adapted to receive needle  18  in recess  15 . When jaws  14  and  16  are closed needle  18  sits in recesses  15  in both jaws  14  and  16 . When jaws  14  and  16  are opened, needle  18  is retained in one or the other recesses  15  depending on which blade  31  or  29  intersects needle  18  through recess  15 . Blade  31  cooperating with upper jaw  14  extends into recess  15  to secure needle  18 . Alternatively, blade  29  may intersect needle  18  through recess  15 , securing needle  18  in jaw  16 . The movement of blades  31  and  29  to engage needle  18  will now be described. 
         [0032]    On either side of center rod  7  are side rods  21  and  22  which sit inside tubular housing  12  and are connected at their proximal ends to a wheel  23  movably housed inside handle housing  30 . Wheel  23  has two arms  24  and  25  projecting from either side that allow the operator of the apparatus to turn wheel  23 . To transfer needle  18  from jaw  14  to jaw  16 , the jaws are closed and wheel  23  is rotated by turning side arm  25  clockwise so that side rod  21  is pulled proximally and side rod  22  is pushed distally. Side rods  21  and  22  are connected to blades  31  and  29 , respectively. Therefore, when side rod  22  is pushed distally, blade  29  is pushed distallly and engages needle  18  by extending into recess  15  to secure needle  18  in jaw  16 . While blade  29  is in a distal position, blade  31  is in a retracted or proximal position, as each blade is connected to wheel  23  through a respective rod. Thus blade  31  docs not contact needle  18 , thereby allowing release of the needle  18  from jaw  14 . Similarly, side arm  24  may be turned counterclockwise, sliding side rod  21  and blade  31  distally and side arm  25  and blade  29  proximally, thereby securing needle in jaw  14  and allowing release of needle  18  from jaw  16 . 
         [0033]    Referring to FIGS.  1  and  4 - 7  measuring structure  90  has a scale  100  preferably disposed along a portion of tubular housing  12  such that scale  100  is adjacent to the distal end and extends longitudinally along tubular housing  12 . Scale  100  has a longitudinal axis  101  that extends in the same direction as the longitudinal axis of body portion  120 . A plurality of graduations  110  are disposed on scale  100  and are uniformly spaced apart along longitudinal axis  101  of scale  100 . Graduations  110  indicate the distance from a predetermined point on the distal end of suturing apparatus  10 . Preferably, the predetermined point is the point of connection between suture  20  and needle  18  to give an accurate measurement of the remaining usable length of suture  20 . Since at least one of jaws  14  and  16  are movable, scale  100  must be calibrated with the jaw holding needle  18  in a predetermined position. This predetermined position may be fully open, fully closed or some predetermined position in between. Otherwise, movement of the jaw holding needle  18  will affect the measurement reading. 
         [0034]    Graduations  110  may be marked with Arabic numerals, Roman numerals, Greek letters, or other suitable symbols of indicia. Preferably, graduations  110  are marked with Arabic numerals so that the units of measure are readily ascertainable. Although graduations  110  are shown in centimeters, the actual units of measure may be changed to suit the user&#39;s needs without departing from the scope of the disclosure (e.g. inches, millimeters, decimeters, etc.). 
         [0035]    As shown in  FIGS. 1 and 4 , graduations  110  on scale  100  are generally in the same viewing plane as needle  18 . Placing needle  18  and graduations  110  in the same viewing plane allows the surgeon using suturing apparatus  10  to observe scale  100 , needle  18  and a suture  20  simultaneously. However, during endoscopic surgery, the surgeon&#39;s field of view is limited by the endoscope, and suture  20  may not lie in the field of view of the endoscope. It is preferred that graduations  110  be visible to the surgeon regardless of the physical orientation of the surgical instrument. Therefore, the lateral dimensions of scale  100  and graduations  110  are such that graduations  110  cover a large enough area on tubular housing  12  so that graduations  110  are visible to the surgeon regardless of the orientation of the surgical instrument. Scale  100  and graduations  110  may cover the full perimeter of body portion  12  or only a part thereof. 
         [0036]    Extending scale  100  and graduations  110  along a greater portion of the surface of regular housing  12  does not alter the accuracy of the instrument since graduations  110  are still uniformly spaced apart, but allows graduations  110  to be visible in more than one plane of view. For example, graduations  110  may encompass approximately up to 90 degrees of the surface of tubular housing  12  as shown in  FIG. 1 . In addition, more than one scale may be disposed on a surgical instrument such as disposing a number of scales around the surface of tubular housing  12 . When a number of scales are disposed in this fashion, the scales may be contiguous or may be transversely spaced apart. Preferably, graduations  110  will extend circumferentially about tubular housing  12  up to and including 360 degrees of the surface. 
         [0037]    Scale  100  and graduations  110  are shown in the figures as being disposed on tubular surgical instruments for illustrative purposes only. It is within the scope of this disclosure for scale  100  and graduations  110  to be disposed on instruments that have regular or irregular polygonal shapes. With instruments that have regular or irregular polygonal shapes, graduations  110  may be disposed on one or more surfaces of the polygon, alternating surfaces of the polygon or all surfaces of the polygon depending on the particular instrument and its application. 
         [0038]    A more detailed view of scale  100  with graduations  110  is shown in  FIG. 5 . Although scale  100  is shown having a range of 5-20 units, preferably centimeters, other units and ranges are entirely within the scope of the present disclosure. The selected range of scale  100  and units of graduations  110  are determined by the user&#39;s requirements. In the present example of 5-20 centimeters, scale  100  has an accuracy of +/−0.6 centimeters. In this figure, the scale  100  uses one (1) unit graduations commencing with the numeral five (5). It is within the scope of the disclosure that scale  100  could be designed to include graduations  110  representing less than one (1) unit (i.e. ½ unit) or units greater than one (1) unit (e.g. 1½, 2, or 5). The number of units represented by each graduation  110  is not limited to what is disclosed here, but is to be determined by the ultimate application of the scale  100 . In addition, graduations  110  are illustrated in centimeters, the actual units of measure may be changed to suit the user&#39;s needs without departing from the scope of the disclosure (e.g. inches, millimeters, decimeters, etc.). 
         [0039]      FIGS. 6 and 7  depict the distal end of tubular housing  12  of suturing apparatus  10 . Scale  100  is disposed adjacent and posterior to the jaw support  52 . In  FIG. 6 , scale  100  shows that approximately twenty (20) centimeters of suture  20  are attached to needle  18 . It should be noted that the figure is not to scale as it appears that the distance from the predetermined point to the first graduation is greater than 5 cm and that while suture  20  appears loose in  FIGS. 6 and 7 , in actuality suture  20  would be slightly tensioned or straightened as shown in  FIG. 2  to give an accurate reading. Furthermore, it is necessary that suture  20  be drawn along a direct line from its point of connection with needle  18  to give an accurate measurement. Care should be taken that suture  20  not get caught on, or bend around the distal most ends  15  and  17  of jaws  14  and  16 , respectively, as this would give an incorrect measurement indicating a smaller amount of suture  20  left than is actually the case. 
         [0040]      FIG. 7  illustrates the situation in which one or more stitches have been sewn leaving approximately ten (10) centimeters of suture  20  available for use. The accuracy of scale  100  is +/−0.6 graduations, or in the present example +/−0.6 centimeters. The ability of the surgeon to discern the remaining length of suture  20  easily and readily enables the surgeon to predict the number of sutures that can be safely sewn before it is necessary to remove suturing apparatus  10  for reloading. 
         [0041]    Although suturing apparatus  10  will be periodically removed for reloading, the addition of attached scale  100  permits the surgeon to minimize the number of reloading operations that must be performed clue to guess work involved in determining the amount of suture  20  remaining. This enables the surgeon to minimize the time of the procedure and optimize the quantity of suture material used. Scale  100  is envisioned to be incorporated into the structure of tubular housing  12  during the manufacturing process wherein graduations  110  would be etched, embossed or otherwise permanently part of tubular housing  12 . 
         [0042]    Alternately, scale  100  and graduations  110  could be supplied as part of a kit to allow the surgeon to select the units of measurement and the length of scale  100 . Furthermore, supplying scale  100  in kit form allows existing owners of suturing apparatus  10  to take full advantage of this disclosure without the need to purchase new suturing apparatus  10 . For example, the kit could include several scales  100  having different ranges of graduations, different units of measurement, or numerous combinations of the preceding depending on the demands of the marketplace. In one embodiment, each scale  100  that is supplied as part of a kit would has an adhesive backing for attachment to tubular housing  12  and that this adhesive backing would securely attach scale  100  to tubular housing  12  to alleviate any concerns about scale  100  becoming dislodged in the cavity during the endoscopic procedure. 
         [0043]    The preferred method for attaching scale  100  is to place scale  100  on heat shrinkable tubing. During preparation for surgery, the heat shrinkable tubing would be placed over the distal end of the surgical instrument and moved towards the proximal end along the longitudinal axis of the instrument. Once the heat shrinkable tubing is properly positioned, a flameless heat source is applied uniformly to the heat shrinkable tubing. Once the heat shrinkable tubing has shrunk to its designed size, and conformed to the shape of the surgical instrument, the heat source is removed leaving the surgical instrument with a measuring apparatus properly positioned for use. Further still, the kit may include an assembly template or other calibration device to ensure that scale  100  is disposed along tubular housing  12  with the proper orientation and proper longitudinal positioning from the predetermined point. The tubular housing  12  and heat shrinkable tubing may include reference marks that are aligned by placing the heat shrinkable tubing on tubular housing  12 . This is essential so that each suturing apparatus  10  will produce the same accurate measurements and ensure highly repeatable results for the surgeon. 
         [0044]    Referring now to  FIG. 4 , the use of suturing apparatus  10  including scale  100  to suture tissue and measure the remaining amount of suture  20  will now be described. As noted above, scale  100  is disposed along the longitudinal axis of tubular housing  12  and posterior to jaws  14 ,  16  with suture  20  extending from a predetermined point which is preferably the connection point with needle  18 . During laparoscopic suturing, the surgeon closes jaws  14 ,  16  about the tissue, forcing needle  18  and suture  20  to pierce the tissue and passes control of the needle  20  between jaws  14  and  16 . Next, the surgeon then takes a grasping tool  150  and grabs the distal end of suture  20  with grasping tool  150 . Using grasping tool  150 , the surgeon holds suture  20  taut against the surface of scale  100  thereby allowing the surgeon to measure the length of suture  20 . By holding suture  20  taut against scale  100 . the surgeon is able to read the remaining length of suture  20  accurately. Again, care should be taken to ensure that suture  20  extends in a generally straight line from the predetermined point to scale  100  and does not become wrapped around the distal most ends of the jaws which would cause an inaccurate reading. 
         [0045]    It should be noted that by measuring the remaining usable length of suture after a stitch, the surgeon can estimate the number of stitches that can be performed before having to reload a new needle and suture to a fairly certain degree of accuracy. This asset is not limited to endoscopic uses of measuring structure on suture manipulating instruments, but rather, may also find useful application in open surgery. 
         [0046]    Alternatively, the surgeon may pass needle  18  through the tissue and move suturing apparatus  10  adjacent the tissue and then take the measurement. As noted above, the measurement is taken with suture  20  extending from a predetermined point and with at least one of jaws  14  and  16  in a predetermined position corresponding to the calibration of scale  100  on suturing apparatus  10 . 
         [0047]    Turning to  FIG. 8 , the distal end of a surgical suturing apparatus in accordance with a further embodiment is illustrated. This particular surgical instrument  210  includes a tubular housing  212  with only one movable or pivotably hinged jaw  216  disposed at the distal end of tubular housing  212 . A needle  218  is removably receivable by an aperture in jaw  216 . A suture  220  is attached to the end of needle  218 , which establishes the predetermined point for the measuring structure of this apparatus, and the remaining length of suture  220  is disposed along the longitudinal axis of tubular housing  212 . Scale  100  is disposed near the distal end of tubular housing  212  and preferably covers the entire outer perimeter of tubular housing  212  so that graduations  110  are visible to the surgeon regardless of the orientation of surgical suturing apparatus  210 . Scale  100  is calibrated to read accurately with jaw  216  in the predetermined position, i.e., fully open, fully closed or some predetermined position in between. 
         [0048]    In  FIG. 9 , a surgical suturing apparatus in accordance with yet another embodiment is illustrated. As in previous embodiments, the surgical suturing apparatus  310  has a scale  100  disposed near the distal end of a tubular housing  312 . A suture  320  extends from the most distal end of tubular housing  312  with a needle  318  at the distal end of suture  320 . Needle  318  and suture  320  are attached to a cartridge carrier  322  that is removably attached to tubular housing  312 . It is preferred that scale  100  and graduations  110  are disposed such that graduations  110  encompass the entire outer perimeter of tubular housing  312  of surgical suturing apparatus  310 . 
         [0049]    Referring to  FIG. 10 , a surgical instrument in accordance with a further embodiment is shown. Similar to previous instruments, surgical instrument  510  is particularly arranged for laparoscopic or other minimally invasive surgery and it includes an elongate tubular housing  512 . Surgical instrument  510  has a grasping tool  514  at the distal end of tubular housing  512 . This instrument permits the surgeon to grasp a suture  520  and determine the length of the unused portion. Once again, scale  100  is disposed along the distal end of tubular housing  512  just posterior to grasping tool  514 . Having scale  100  disposed in this location permits the surgeon to determine the length of suture  520  accurately by moving suture  520  with grasping tool  514  along the side of tubular housing  512  to measure the length of suture  520 . It is preferred that scale  100  and graduations  110  cover the outer perimeter of tubular housing  512  so that the surgeon can view graduations  110  without having to reposition surgical instrument  510 . The surgical instrument  510  may be used to manipulate a needle and suture or may be used in conjunction with a suturing apparatus. 
         [0050]    It will be understood that various modifications may be made to the embodiments disclosed herein. For example, the unit may be color coded to indicate the range and units of measurement. When supplied as part of a kit, it is fully compatible with other laparoscopic surgical instruments such as scissors, knot-tying tools, and other tools. Further still, other methods for disposing measuring structures on surgical instruments such as shrink-wrapping may be employed. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto. 
         [0051]    The foregoing is considered illustrative only of the principles of the measuring apparatus. Further, this is not intended to be limited to the exact structure, construction and operation shown and described.