Abstract:
In an apparatus that includes a head, spindle, and a handle, the handle is rotatably fastened to the head by the spindle. The handle and head mate at an interface. The apparatus further includes a head axial bore offset from the spindle and configured to occupy a portion of the head and a handle axial bore offset from the spindle and configured to occupy a portion of the handle, the handle axial bore being configured to receive a torque limiting insert, wherein in response to the head being at a first rotational conformation relative to the handle, the head axial bore and handle axial bore is disposed in cooperative alignment to allow the torque limiting insert to transect the interface and enter the head axial bore. The head and the handle are rotationally coupled via the torque limiting insert. The head and the handle are rotationally uncoupled in response to a shear force being applied across the interface that exceeds a shear limit for the torque limiting insert.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 60/831,953, filed on Jul. 20, 2006, titled “SEMI AUTOMATIC DISPOSABLE TORQUE LIMITING DEVICE AND METHOD,” the disclosure of which is incorporated herein by reference in its entirety. 
     
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to a torque limiting device and method. More particularly, the present invention pertains to a device and method for limiting an amount of torque applied by the device using a disposable insert. 
       BACKGROUND OF THE INVENTION 
       [0003]    In various manufacturing, construction, and medical industries, objects or fasteners are utilized that are positioned, threaded or screwed into place. These objects or fasteners may include a predetermined amount of torque that has been determined to be optimal for a given fastening or positioning situation. In addition, the fastener or object may include a predetermined amount of torque that has been determined to fatigue or break the fastener or object. Often, these predetermined torque values are determined by the manufacturer or by a testing facility. In use, a technician or user may employ a device such as a torque wrench to set the fastener or object according to the predetermined amount of torque. In a particular example, bone screws may be employed by surgeons to reconstruct bones or attach replacement components to bones of patients. In such circumstances, applying a proper amount of torque may be critically important. 
         [0004]    Conventional torque wrenches utilize forces from coil springs and spring washers along with friction to limit the amount of torque applied. Unfortunately, as components within these conventional torque wrenches slide by one another, wear may alter the torque setting of the conventional torque wrench. As such, conventional torque wrenches need to be re-calibrated to maintain their torque limit range. 
         [0005]    Conventional torque wrenches require lubricants for the proper operation of the mechanism. These lubricants break down during steam-sterilization and can oxidize components which may reduce the accuracy of the device. In addition, these conventional torque wrenches require re-lubrication during cleaning or re-calibration cycles. 
         [0006]    Conventional torque wrench mechanisms may also fail and bind or lock-up thereby eliminating the torque-limiting effect and essentially converting the tool to a rigid, non-limiting tool with torque limiting now regulated to the tool users ability to discern torque forces by hand. This could lead to over-torquing, an unsafe condition. 
         [0007]    Accordingly, it is desirable to provide a device and method capable of overcoming the disadvantages described herein at least to some extent. 
       SUMMARY OF THE INVENTION 
       [0008]    The foregoing needs are met, to a great extent, by the present invention, wherein in one respect a device and method of limiting an amount of torque applied is provided. 
         [0009]    An embodiment of the present invention pertains to a torque limiting apparatus. The torque limiting apparatus includes a head, handle, head axial bore, and handle axial bore. The head includes a central rotational axis. The handle is rotatably fastened to the head. The handle and head mate at an interface. The head axial bore is defined by the head and is offset from the central rotational axis. The handle axial bore is defined by the handle and offset from the central rotational axis. The handle axial bore is shaped to receive a torque limiting insert. In response to the head being at a first rotational position relative to the handle, the head axial bore and handle axial bore are disposed in cooperative alignment to allow the torque limiting insert to transect the interface and enter the head axial bore. The head and the handle are rotationally coupled via the torque limiting insert. The head and the handle are rotationally uncoupled in response to a shear force being applied across the interface that exceeds a shear limit for the torque limiting insert. 
         [0010]    Another embodiment of the present invention relates to an apparatus for applying a predetermined amount of torque to a fastener. The apparatus includes a head means, handle means, and torque limiting means. The head means transmits torque to the fastener. The handle means is coupled to the head means for applying an amount of torque to the fastener. The torque limiting means is interoperably disposed between the head means and the handle means to limit an applied torque from being transmitted from the handle means to the head means by shearing a torque limiting insert in response to the amount of torque being greater than the predetermined amount of torque. The handle means is rotationally decoupled from the fastener in response to the torque limiting insert being sheared. 
         [0011]    Yet another embodiment of the present invention pertains to a method of applying a predetermined amount of torque upon a fastener. In this method, a torque limiting device is coupled to the fastener. The torque limiting device includes a torque limiting insert. In addition, an amount of torque is applied upon the fastener by urging a handle of the torque limiting device to rotate. The torque limiting insert is subjected to a shear force in response to the amount of torque. The torque limiting insert is sheared in response to the amount of torque being greater than the predetermined amount of torque. The handle is rotationally decoupled from the fastener in response to the torque limiting insert being sheared. 
         [0012]    There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
         [0013]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
         [0014]    As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective view of the torque limiting device according to an embodiment of the invention. 
           [0016]      FIG. 2  is an exploded view of the torque limiting device of  FIG. 1 . 
           [0017]      FIG. 3A  is a side view of a disposable insert suitable for use with the torque limiting device of  FIG. 1 . 
           [0018]      FIG. 3B  is a side view of the disposable insert following a calibration procedure. 
           [0019]      FIG. 3C  is an exploded view illustrating insertion of the disposable insert into the torque limiting device of  FIG. 1 . 
           [0020]      FIG. 4A  is a top view of the torque limiting device in a loaded position. 
           [0021]      FIG. 4B  is a cross-sectional view A-A of the torque limiting device in the loaded position. 
           [0022]      FIG. 5A  is a top view of the torque limiting device in a shear position. 
           [0023]      FIG. 5B  is a cross-sectional view B-B of the torque limiting device in the shear position. 
           [0024]      FIG. 5C  is an end view of the torque limiting device in the shear position. 
           [0025]      FIG. 5D  is a cross-sectional view C-C of the torque limiting device in the shear position. 
           [0026]      FIG. 6A  is a top view of the torque limiting device in an eject position. 
           [0027]      FIG. 6B  is a cross-sectional view D-D of the torque limiting device in the eject position. 
           [0028]      FIG. 6C  is an end view of the torque limiting device in the eject position. 
           [0029]      FIG. 6D  is a cross-sectional view E-E of the torque limiting device in the eject position. 
           [0030]      FIG. 7A  is a top view of the torque limiting device in a second loaded position. 
           [0031]      FIG. 7B  is a cross-sectional view F-F of the torque limiting device in the second loaded position. 
           [0032]      FIG. 8A  is a top view of the torque limiting device in a second shear position. 
           [0033]      FIG. 8B  is a cross-sectional view G-G of the torque limiting device in the second shear position. 
           [0034]      FIG. 8C  is an end view of the torque limiting device in the second shear position. 
           [0035]      FIG. 8D  is a cross-sectional view H-H of the torque limiting device in the second shear position. 
           [0036]      FIG. 9A  is a top view of the torque limiting device in a second eject position. 
           [0037]      FIG. 9B  is a cross-sectional view I-I of the torque limiting device in the second eject position. 
           [0038]      FIG. 9C  is an end view of the torque limiting device in the second eject position. 
           [0039]      FIG. 9D  is a cross-sectional view J-J of the torque limiting device in the second eject position. 
           [0040]      FIG. 10A  is a cross-sectional view of the torque limiting device in a final eject position. 
           [0041]      FIG. 10B  is a cross-sectional view of the torque limiting device in the final eject position. 
           [0042]      FIG. 10C  is a cross-sectional view of the torque limiting device in the final eject position according to another embodiment. 
           [0043]      FIG. 11  is an exploded view illustrating removal of the used insert from the torque limiting device of  FIG. 1 . 
           [0044]      FIG. 12  is a flow diagram illustrating a method of installing a fastener according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0045]    The present invention provides a semi automatic torque limiting device and method. In one example of a preferred embodiment, the torque limiting device includes a disposable, torque limiting, insert. The disposable insert includes a predetermined number of segments. During use, a segment of the insert is sheared off in response to a predetermined amount of torque being applied to a handle of the torque limiting device. The sheared segment may be stored in the handle. 
         [0046]    In various embodiments, the torque limiting device may include any suitable material, such as, plastic, polymer, resin, metal, or the like. In a preferred example, the torque limiting device includes materials that may be sterilized for use in an operating theater. For example, autoclaveable polymers and corrosion resistant-type metals may be utilized to fabricated the torque limiting device and/or the insert. The insert may include a rod or bar with a number of annular grooves that correspond to the number of segments. Material characteristics of the insert and the cross sectional area at the groove may be utilized to determine a torque value for the torque limiting device. 
         [0047]    It is an advantage of embodiments of the invention that the torque limiting device substantially and/or continually maintains a pre-set torque limit that is governed by the insert. It is another advantage that this pre-set torque limit is essentially unaffected by frictional wear. As such, the need for testing and recalibration of the torque limiting device may be eliminated. 
         [0048]    Preferred embodiments of the invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. As shown in  FIG. 1 , a torque limiting device  10  may be utilized to install a fastener  12  in a substrate  14 . The torque limiting device  10  includes a handle  16  for the user, technician, or surgeon to grasp. The torque limiting device  10  further includes a shaft  18  connecting the handle  16  to a head  20 . The head  20  is configured to engage the fastener  12 . In various embodiments, the head  20  and shaft  18  may be essentially a single component or the head  20  may be releasably attached to the shaft  18  to facilitate exchanging the head  20  with another head  20 . 
         [0049]    In general, the torque limiting device  10  is configured such that in response to turning the handle  16  about an axis A (as shown in  FIG. 1 ), an applied torque will urge the shaft  18  to rotate in a similar fashion. The torque limiting device  10  is configured such that at a threshold or max torque, the shaft  18  ceases to rotate about the axis A in response to rotating the handle  16  about the axis A. In conventional devices, the limit at this threshold torque is affected by frictional forces of one member sliding against another. Unfortunately, this friction results in mechanical wear that may alter the characteristics of the torque applied through the device. It is an advantage of various embodiments that friction is a substantially negligible component of the applied torque. As such, the embodiments are essentially unaffected by frictional or mechanical wear. 
         [0050]    In addition, while not explicitly shown in  FIG. 1 , the torque limiting device  10  may include a display to display the amount of torque being applied to the fastener  12 . Furthermore, the torque limiting device  10  may include a ratcheting mechanism to provide unidirectional or selectable unidirectional rotation of the shaft  18 . This is an optional feature so that the operator does not have to change or reset the hand position on the tool. 
         [0051]      FIG. 2  is an exploded view of the torque limiting device of  FIG. 1 . On a driver-end of the device  10  there is the shear component  22 . On the proximal end of the shear component  22  there are two holes: a center hole  24  and a shearing hole  26 A. The center hole  24  receives a shoulder screw  28  that connects the rotating handle  16  to the driver-end  18 . The shearing hole  26 A carries a spring-loaded ejector pin  30  and a spring  32  whose travel is limited by the mating of an axial slot  34  in the ejector pin  30  and a limit pin  36 . 
         [0052]    The handle  16  includes a plurality of holes or bores that may be selectively aligned with the shearing hole  26 A. For example, as shown in  FIG. 2 , the handle  16  includes an insert loading bore  26 B and a segment collecting bore  26 C. The insert loading bore  26 B may further include a bushing  26 BB to facilitate shearing the torque limiting insert  40 . 
         [0053]    In addition, the torque limiting device  10  includes one or more torque limiting disposable inserts or inserts  40 , springs  42  to advance the inserts  40  and a cap  44  to retain the inserts  40  and a spring assembly  46 . 
         [0054]      FIG. 3A  is a side view of the disposable insert  40  suitable for use with the torque limiting device  10 . The inserts may be made from any suitable material. Suitable materials include plastic or polymers, metals, and the like. In a particular example, the inserts include a segmented plastic length of material. As shown in  FIG. 3A , the insert  40  includes segments  50 A to  50   n  that are delineated by annular grooves  52 A to  52   n . The annular grooves  52 A to  52   n  serve to concentrate shear stress between adjacent segments  50 A to  50   n . In this manner, the annular grooves  52 A to  52   n  facilitate a clean and/or repeatable shearing action. Because the shearing hole  26 A is rotationally offset from the central axis A, torque applied to the handle  16  generates a corresponding force at the shearing hole  26 A and a shearing force upon the torque limiting insert  40 . In particular, the depth of the shearing hole  26 A and length of the segments  50 A to  50   n  are matched such that the shearing force is exerted, each in its turn, upon the annular grooves  52 A to  52   n . The cross sectional area and material characteristics of the torque limiting insert  40  at the annular grooves  52 A to  52   n  is configure to shear in response to a predetermined amount of shear force. The amount of shear force each of the annular grooves  52 A to  52   n  can absorb before being sheared or severed is a “shear limit.” The shear limit is defined as the amount of shear stress or strain sufficient to result in the partial or complete fracture or breaking of the torque limiting insert  40 . One or more of the segments  52 A- 52   n  may be sheared in the torque limiting device  10  or reasonable facsimile thereof to test or calibrate the insert  40 . The insert  40  further includes a base or flanged insert portion such as a flange  54  shown in  FIG. 3A . 
         [0055]    In various embodiments, the shear limit of the torque limiting insert  40  may include any suitable value. For example, various standard fasteners may have a manufacturer&#39;s recommended installation torque of less than 1 Newton Meter (Nm) to greater than 10 Nm. Accordingly, the torque limiting insert  40  may include a shear limit of 1 Nm, 2 Nm, 4 Nm, 6 Nm, and the like. To differentiate the torque limiting insert  40  having one shear limit from another torque limiting insert  40  having another shear limit, the torque limiting insert  40  may include an indicator value, differentiating color, size, shape, or the like. In a particular example, the torque limiting insert  40  may include a particular shape for each shear limit. That is, while the torque limiting insert  40  shown in  FIG. 3A  is depicted as generally cylindrical, the torque limiting insert  40  having a different shear limit may be, for example, an elongated  3 ,  4 , or multi-sided prism. According to an embodiment, the insert loading hole  26 B and/or bushing  26 BB may be configured to accept only a certain shaped torque limiting insert  40 . 
         [0056]      FIG. 3B  is a side view of the disposable insert following a calibration procedure. Once the testing or calibration is performed a “working” length segmented insert  40  is left with three torque-limiting segments  50 C to  50   n  remaining. However, in other embodiments, more or less than three segments  50 A- 50   n  may be retained. 
         [0057]      FIG. 3C  is an exploded view illustrating insertion of the disposable insert  40  into the torque limiting device  10 . Loading the torque limiting device  10  is simple and a thrust bearing  56 , for example, may be included on the backside of the spring assembly  46  to reduce assembly friction. 
         [0058]      FIG. 4A  is a top view of the torque limiting device  10  in a loaded position. The handle  16  is rotated to a “Load” position. At this point an insert  40  will be aligned with the eject pin  30 . 
         [0059]      FIG. 4B  is a cross-sectional view A-A of the torque limiting device  10  in the loaded position. In the transparent view above, the loaded positions are shown. The handle  16  is turned till one of the insert  40 , hereafter referred to as the “first insert  40 ,” is loaded into the hole  26  in the shear component  22 . There are springs  42  and  32  behind the first insert  40  and the ejector pin  30 . The larger spring  42  behind the first insert  40  has a higher spring rate than the ejector pin spring  32 , thus over-powering the ejector spring  32  and the first insert  40  advances the ejector pin  30  until its movement is limited by the pin-slot combination. When the first insert  40  is fully advanced to the stop the insert  40  is correctly positioned for the “torque-limiting” step. 
         [0060]      FIG. 5A  is a top view of the torque limiting device  10  in a shear position. When the first insert  40  shears at the pre-determined torque value, the handle  16  will rotate relative to the shear component  22  to an in-between position between “Load” and “Eject”. 
         [0061]      FIG. 5B  is a cross-sectional view B-B of the torque limiting device  10  in the shear position. In the above view the front segment  50 C of the first insert  40  is shown sheared and retained inside the shearing hole  26 A of the shear component  22 . Because there is only the one shearing hole  26 A on the shear component  22  that is on the same bolt circle as the first insert  40 , the first insert  40  will not advance to the next position until the shearing hole  26 A is emptied. 
         [0062]      FIG. 5C  is an end view of the torque limiting device in the shear position. As shown in  FIG. 5C , the section line C-C is disposed at an angle to pass through the loading bores  26 B. 
         [0063]      FIG. 5D  is a cross-sectional view C-C of the torque limiting device  10  in the shear position. As shown in  FIG. 5D , the cross-sectional view C-C transects the loading bore  26 B and illustrates how both the first insert  40  and a second insert  40  are essentially prevented from advancing while the shear component  22  is positioned between “Load” and “Eject” position. 
         [0064]      FIG. 6A  is a top view of the torque limiting device  10  in an eject position. As shown in  FIG. 6A , the handle  16  is rotated into an “Eject” position. 
         [0065]      FIG. 6B  is a cross-sectional view C-C of the torque limiting device  10  in the eject position. As shown in the cross-sectional view, the segment  50 C of the first insert  40  that has been sheared off will now advance into ejection chamber of the handle  16 . Because of the limit slot in the ejector pin  30  it will not advance into the ejection chamber. A cleaning port or clearing port  58  is optionally included to augment ejection. For example, if included, a wire or pin may be inserted to augment the action of the spring  32 . 
         [0066]      FIG. 6C  is an end view of the torque limiting device  10  in the eject position. As shown in  FIG. 6C , the section line E-E is disposed at an angle to pass through the loading bores  26 B. 
         [0067]      FIG. 6D  is a cross-sectional view E-E of the torque limiting device  10  in the eject position. As shown in  FIG. 6D , the cross-sectional view E-E transects the loading bore  26 B and illustrates how both the first insert  40  and second insert  40  are essentially prevented from advancing while the shear component  22  is in the eject position. 
         [0068]      FIG. 7A  is a top view of the torque limiting device  10  in a second loaded position. The handle  16  is now rotated to the next “Load” position. 
         [0069]      FIG. 7B  is a cross-sectional view F-F of the torque limiting device  10  in the second loaded position. As can be seen in the cross-sectional view, the first segment  50 C of a second insert  40  advances into the shear component  22 , pushing the ejector pin  30  until it stops. Note that the first segment  50 C will not advance until it aligns with the hole  26 A in the shear component  22 . 
         [0070]      FIG. 8A  is a top view of the torque limiting device  10  in a second shear position. When the second insert  40  shears at the pre-determined torque value, the handle  16  will be in an in-between position of “Load” and “Eject”. 
         [0071]      FIG. 8B  is a cross-sectional view G-G of the torque limiting device  10  in the second shear position. In the above view the front segment  50 C of the second insert  40  is shown sheared and retained inside the hole  26 A of the shear component  22 . Because there is only the one hole on the shear component  22  that is on the same bolt circle as the second insert  40 , the second insert  40  will not advance to the next position. 
         [0072]      FIG. 8C  is an end view of the torque limiting device  10  in the eject position. As shown in  FIG. 8C , the section line H-H is disposed at an angle to pass through the loading bores  26 B. 
         [0073]      FIG. 8D  is a cross-sectional view H-H of the torque limiting device  10  in the eject position. As shown in  FIG. 8D , the cross-sectional view H-H transects the loading bore  26 B and illustrates how both the first insert  40  and second insert  40  are essentially prevented from advancing while the shear component  22  is between the load eject positions. 
         [0074]      FIG. 9A  is a top view of the torque limiting device  10  in a second eject position. In response to rotating the handle  16  the torque limiting device  10  advances to an “Eject” position. 
         [0075]      FIG. 9B  is a cross-sectional view I-I of the torque limiting device  10  in the second eject position. As shown in the transparent view above, the segment  50 C of the second insert  40  that has been sheared off will now advance into ejection chamber of the handle  16 . Because of the limit slot  34  in the ejector pin  30  it will not advance into the ejection chamber. Note that there are now two separate insert  40  (e.g., the first and second insert  40 ) segments in two separate ejection chambers. 
         [0076]      FIG. 9C  is an end view of the torque limiting device  10  in the second eject position. As shown in  FIG. 9C , the section line J-J is disposed at an angle to pass through the loading bores  26 B. 
         [0077]      FIG. 9D  is a cross-sectional view J-J of the torque limiting device  10  in the second eject position. As shown in  FIG. 9D , the cross-sectional view J-J transects the loading bore  26 B and illustrates how both the first insert  40  and second insert  40  are essentially prevented from advancing while the shear component  22  is in the eject position. 
         [0078]      FIG. 10A  is a cross-sectional view of the torque limiting device  10  in a final eject position. As shown in  FIG. 10A , the segments  50 C- 50 E are retained within the collecting bores  26 C 
         [0079]      FIG. 10B  is a cross-sectional top view of the torque limiting device  10  in the final eject position. As shown in  FIG. 10B , the flange  54  is configured to engage a lip or otherwise essentially prevent the insert  40  from progressing further than the final segment. 
         [0080]      FIG. 10C  is a cross-sectional top view of the torque limiting device  10  in the final eject position according to another embodiment. As you can see from the cross-sectional views above, the torque limiting device  10  according to this particular embodiment is capable of six torque-limiting uses. In other embodiments, the torque limiting device  10  and/or the insert  40  may be configured for more or fewer torque-limiting uses. Once the segments  50 C- 50   n  are all sheared off the flange  54  will prevent the insert  40  from advancing further. At this point the device  10  will only spin. The device  10  is also designed to hold all six segments  50 A- 50   n.    
         [0081]      FIG. 11  is an exploded view illustrating removal of the used insert  40  from the torque limiting device  10  of  FIG. 1 . 
         [0082]      FIG. 12  is a flow diagram illustrating a method  60  of installing a fastener according to an embodiment of the invention. As shown in  FIG. 12 , the method  60  may be initiated at step  62  in response to installing a torque limiting insert such as the insert  40  in the torque limiting device  10 . To initiate installation, loading sleeves or bores may be accessed. For example, the retaining cap  44  may be unscrewed or otherwise removed along with the spring  42  and spring assembly  46  to expose the loading bore  26 B and the collecting bore  26 C. Thereafter, the insert  40  may be positioned in the loading bore  26 B and the torque limiting device reassembled. Of note, the insert  40  installed in the torque limiting device  10  may be selected based upon a predetermined torque limit for a particular fastener that is to be installed. For example, a fastener such as a bone screw may have a recommended installation torque of 4 Newton Meters (Nm). The insert  40  selected for installation may include a predetermined shear strength that corresponds to 4 Nm of torque. 
         [0083]    At step  64 , the fastener  12  may be installed in the substrate  14 . For example, a bone screw may be screwed into the bone of a patient. More particularly, the fastener  12  may be coupled to the torque limiting device  10  by a bit and the handle  16  may be rotated until the insert  40  is sheared as shown in  FIGS. 5A and 5B . 
         [0084]    At step  66 , a severed segment may be ejected from the head  20 . For example, as shown in  FIGS. 6A and 6B , the shearing hole  26 A may be aligned with the collecting bore  26 C. In response, the segment  50 C, for example, may be urged by the spring loaded ejector pin  30  and spring  32  into the collecting bore  26 C. 
         [0085]    At step  68 , it may be determined if additional fasteners are to be installed. For example, if an ongoing operational procedure indicates addition fasteners may be utilized, it may be determined if the additional fasteners include essentially the same torque indication at step  70 . If no additional fastener installation is indicated, the torque limiting device  10  may be cleaned at step  78 . 
         [0086]    At step  70 , it may be determined if essentially the same torque limit is indicated. For example, essentially the same torque limit may be indicated in situations utilizing the same type of bone screw being installed into similar boney tissue. If it is determined that essentially the same torque limit is indicated, it may be determined if additional segments  50 C- 50   n  remain attached to the insert  40 . If it is determined that a different torque limit is indicated, the insert  40  may be exchanged at step  74 . 
         [0087]    At step  72 , it may be determined if more segments remain. For example, if upon rotating the handle  16  relative to the head  20  one full rotation, no segment  50 C- 50   n  is loaded into the shearing hole  26 A, then it may be determined that no segments remain and the insert  40  may be replaced at step  74 . If segments  50 C- 50   n  do remain, a next segment may be loaded if not already done so at step  76 . 
         [0088]    At step  74 , the insert  40  may be replaced. For example, the retaining cap  44  may be unscrewed or otherwise removed along with the spring  42  and spring assembly  46  to expose the loading bore  26 B and the collecting bore  26 C. As shown in  FIG. 11 , the insert  40  and any spent segments  50 C- 50   n  may be removed via the assistance of gravity by tilting the torque limiting  10 . Thereafter, the insert  40  having a torque limit corresponding to a next fastener to be installed in the loading bore  26 B as shown in  FIG. 3C  and the torque limiting device reassembled. 
         [0089]    At step  76 , a next segment  50 C- 50   n  may be loaded. For example, if a segment has not already been loaded, the head  20  may be rotated relative to the handle  16  until the load position is obtained as shown in  FIGS. 7A and 7B . Following loading, a fastener may be installed at step  64 . 
         [0090]    At step  78 , the torque limiting device  10  may be cleaned. For example, the torque limiting device  10  may be disassembled as shown in  FIG. 11  and the torque limiting device  10  may be washed. Once emptied of inserts  40 , the torque limiting device may be reassembled and/or sterilized. In a particular example, the torque limiting device  10  may be autoclaved. 
         [0091]    The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.