Abstract:
An internal mechanism for a musical instrument snare drum that supports the snares and allows adjustment of the snare strands in tension as well as relative position to the vibrating member or head of the drum is provided. The mechanism has a support beam that gives a stiffer and more stable base for increased accuracy of all adjustment. The support beam also provides increased guiding for the snare holders during the tension adjustment of the snares. The adjustment of the position of the snares in relation to the vibrating member or drum head is accomplished by deflecting the strands with a bridge like arrangement providing precise placement of the strands for optimum performance.

Description:
CROSS RELATED APPLICATION 
     The present specification claims priority from U.S. Provisional Patent Application 61/048,921 filed Apr. 29, 2008, the contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present specification relates generally to percussion instruments and More particularly relates to snare drums. 
     BACKGROUND 
     Snare drums when played produce a particular crisp buzzing sound that is unique to the snare drum. This complex rattle sound is created when strands of wire or some other like material is held just touching the vibrating head of the drum. Precise placement of these snare strands at the right tightness is crucial in attaining and maintaining the desired sound of the drum. The tension of the strands has an effect on their frequency response and reactionary amplitude. The proximity to the head regulates ability of the strands to react to stimulus from the head. 
     Typical mechanisms have two adjustments, one to stretch or tension the strands and one to place the strands at point that they receive maximum stimulation from the vibrating head. The tension adjustments tend to be an arrangement where there exists some form of screw jack mechanism located and attached to two towers that have the snare strands attached through an intermediary bracket. 
     In the snare drums used for marching bands where the snare mechanism is located internal to the drum body under the batter head the snare strands can be metal wire. These metal wire strands can take up to ten pounds of force each to yield and the accumulative force on the mechanism can be quite high especially when there are forty wire snares available in the aftermarket. This high force can place a deflection force on the connecting beam that supports the snare carriers in relationship to each other that is sufficient to deform this connecting beam. 
     Deformation of the beam has a negative effect on the parallel relationship of the two carriers where the snares are attached. Any reinforcement of current designs also becomes an issue as the instrument is carried by the player sometimes for extended periods of time and therefore weight and certainly any addition of weight would be of major concern. 
     The height or proximity adjustment of the snare strands in relationship to the head is mechanisms that typically move the entire end of the snare attachment point vertically in relationship to the head. In order for these height adjustments to move there is a requirement for a certain amount of clearance between the components in order to allow free movement. This clearance manifests itself as another negative effect on the parallel of the snare carrier towers as the tension on the strands pulls the towers toward each other at their highest point of leverage. 
     The problem is that any lack of parallel of the snare towers or carriers has an effect on the precision of the tuning of the drum as the ends of the snare strands are where the adjustments are applied and any lean on the towers tends to allow the center of the stands to sag. To combat the sag in the snare strands a higher tension in the strands is required, which then has an effect on the flexibility of the strands. 
     Any bowing of the mechanism will not allow consistent contact of the snare strands to the head. There can be cases where the solder (or equivalent) used to fasten the strands to the holding bracket can be slightly protruding above the level of the strands and if the strands are bowing away from the head the solder contacts the head at a level below where the strands do and therefore full even contact of the snares to the head is not possible. Another circumstance of effect can be if the snare bracket relies on its shape and dimensions to provide retention to the carriers any bowing in the system can then be applied directly to the strands of the snare. 
     The foregoing phenomena is illustrated in  FIG. 1 , which shows a prior art snare drum mechanism. 
     SUMMARY 
     In accordance with the principles of the present specification the stiff platform with which to stabilize the desired adjustments is accomplished by the use of a larger section support beam which can be tubular in nature. The larger diameter (in comparison to any tubular or extruded beam currently in use in the market, for said purpose) provides a firm base and also guiding for the movable carriers that the snare strands are fasted to through the intermediate bracket. In the present embodiment of the invention the tube is formed from the lightest, strongest per unit weight material as overall weight reduction of the instrument is desirable. However, as will be apparent to those with skill in the art that beams or tubes or bars formed from other materials can be employed. The advantage of some composite materials is that the nature of the base material can provide an inherent lubricious surface for the components that must interface or slide in adjustment over the tube shape. For non-composite materials a reduced friction bearing material as a bushing may be employed. 
     In accordance with another aspect of the specification a movable or adjustable stable bridge like surface is used to deflect the snares towards the vibrating head that stimulates these snares. 
     The adjustable bridge is stabilized by not having the entire mechanism move vertically in relation to the head. The carriage that provides the mounting for the snares is designed as a solid entity to eliminate the “lean” of the mechanisms described above. The adjustable bridge then sits on or hinges on the solid mounting structure for the snare intermediate bracket. These “solid structure” carriages then move in relation to each other on the tubular beam in order to apply overall tension to the snare strands acting through the intermediary snare bracket which hooks on to the provided area of the carriage. Inclusive in the positive mounting area or nest of the carriage provided for the snare intermediate bracket is a shape to the nest area which allows a vertical articulation of the intermediate bracket. This articulation is to provide free movement without damage or strain being placed on the snare strands when the bridge is employed to deflect the strands toward the vibrating head. 
     As stated above the tendency of adjustment for maximum “snare” activity is for the snares to be as loosely suspended yet positively placed as possible. This adjustment regime often places the snare intermediate bracket in danger of disengagement from the nest provided on the carriage for such purpose. Another aspect is to provide a positive retainer such as a clip or equivalent in order to contain the intermediate bracket in place on the provided nest of the carriage. 
     An aspect of the specification also provides a larger cross section mounting beam than typically used designed specifically to take high loads and that represent a stiffer more stable platform for mounting the snare mechanism inside a snare drum. 
     An aspect of the specification also provides an adjustable bridge like device used to control the proximity of snare strands for a snare drum by deflecting the strands toward the membrane or the stimulation source. 
     An aspect of the specification also provides a mounting nest for the snare intermediate bracket which allows articulation of said bracket. 
     An aspect of the specification also provides a means of positive retention of the snare intermediate mounting bracket in its nest. An aspect of the specification also provides a positive retention device that allows the articulation as previously mentioned. 
     An aspect of the specification also provides a friction or ratchet or moveable lock on the various adjustments on the snare mechanism of a snare drum to help retain the desired settings. 
     An aspect of the specification also provides a changeable ramp or snare intermediate bracket nest to accommodate different snare intermediate brackets. The snare strand tension adjustment device can be located inside the main support beam of the snare mechanism. 
     An aspect of the specification also provides a return spring on the adjustment devices of the snare mechanism to give artificial feel to the adjustment and to reduce “backlash” in the mechanism for more precise adjustments. 
     An aspect of the specification provides a snare mechanism for a musical percussion instrument; the musical percussion instrument having a batter head and a percussion chamber having walls and supporting the member; the snare mechanism comprising: 
     attachment members mountable to the walls within the chamber; 
     a snare connected to the attachment members and responsive to vibrations to the batter head when the snare is proximal to the batter head; 
     a snare tensioning mechanism connected to the attachment members and the snare; the snare tensioning mechanism associated with a first actuator such that adjustment of the first actuator selectively causes an increase or decrease in tension of the snare; 
     a snare positioning mechanism connected to the attachment members and the snare; the snare positioning mechanism associated with a second actuator such that adjustment of the second actuator causes movement of the snare towards or away from the batter head. 
     The attachment members can be disposed at opposite sides of the chamber. 
     The snare mechanism can further comprise a first assembly member respective one of the attachment members and a second assembly member respective to an opposite one of the attachment members. 
     The snare tensioning mechanism can comprise a support beam disposed between the attachment members. 
     The first assembly member can be a carriage movable in relation to the support beam and the second assembly member is a fixture affixed in relation to the support beam. 
     The carriage can additionally support a first end of the snare and the fixture supports a second end of the snare. 
     The first actuator can be a tensioning knob connected to the carriage, such that rotation of the tensioning knob in a first direction urges the carriage away from fixture and increases tension of the snare and rotation of the tensioning knob in a second direction urges the carriage towards the fixture and decreases tension of the snare. 
     The snare mechanism can further comprise a biasing member joining the carriage and the fixture and urging the carriage towards the fixture. 
     The snare mechanism can further comprise a threaded element rotatable within a set of interior threads on the tensioning knob; the threaded element terminating in a nut element respective to the carriage, such that rotation of the knob corresponding linearly moves the carriage. 
     The snare positioning mechanism can comprise a first support ramp respective to the first assembly member and a second support ramp respective to the second assembly member. 
     The snare positioning mechanism can comprise a transfer shaft connected at a first end to the first assembly member and an opposite end to the second assembly member; the transfer shaft further connected to the second actuator such that rotation of the second actuator causes rotation of the transfer shaft. 
     The snare mechanism can further comprise a connecting rod movably connected along the transfer shaft and an adjusting bridge connected to a distal end of each connecting rod; each adjusting bridge resting along each respective support ramp; wherein rotation of the second actuator moves each the adjusting bridge along each the ramp. 
     A clevis can adjoin each connecting rod to the transfer shaft. 
     Each the connecting rod can be resiliently bendable and a nut can connects each the connecting rod to the transfer shaft. 
     The transfer shaft can have a first threaded section respective to the first assembly member, and a second threaded section respective to a second assembly member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exaggerated illustration of the type of “leaning” that can occur in traditional, prior art, mechanisms, where there is a stack up of clearances and bending of the support beam and related components under the tension of the snare strands. 
         FIG. 2  represents the build up of components of the snare mechanism and support beam in an embodiment. 
         FIG. 3  is a cross section of the snare mechanism showing both the tension and bridge adjusting components. 
         FIG. 4  is a perspective view of one configuration of the bridge adjustor with a support ramp and a round roller shaped bridge. 
         FIG. 5   a , b, shows two hinge type configurations of the bridge type adjustor 
         FIG. 6  is a side view of a roller/support ramp configuration with a dimensionally locked shape on the snare strand interfacing bracket nest. 
         FIG. 7  is a side view of a relieved edge ramp and roller configuration that accommodates articulation of the snare interface bracket. 
         FIG. 8  is a cross section of an alternate configuration that uses a round axle or pin to accommodate snare interface bracket articulation. 
         FIG. 9  is a perspective view of one type of snare carriage to accommodate a round support beam, and an elastomer retainer for the snare interface bracket retention 
         FIG. 10  is a perspective view of a round support beam type snare carriage that uses an axle pin style articulation and a wire clip for retention of the snare interface bracket. 
         FIG. 11   a, b, c, d  are perspective views of other types of large section/diameter support beam accommodating snare carts with both a ramp and pin style articulation allowance for the snare interface bracket. 
         FIG. 12  is a cross sectional view of the snare nesting system, showing the snare strand attachment bracket being held in place against the landing plate by a retaining clip. 
         FIG. 12   a  is a perspective view of the retaining clip shown of  FIG. 12 . 
         FIG. 13  is a perspective, exploded view of a snare mechanism showing both the tension and bridge adjusting components in another embodiment. 
         FIG. 14  is a sectional side view of the snare mechanism of  FIG. 13 . 
         FIG. 15  is another side view of the snare mechanism of  FIG. 14  showing movement of the tensioning mechanism. 
         FIG. 16  is another side view of the snare mechanism of  FIG. 14  showing movement of the positioning mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     The mechanism of a “Snare Drum” that produces the “Snare Sound” of a drum, provides means to tension the snare strands that vibrate when stimulated by the vibrating membrane of the drum, and provide a method to support the snare strands in the optimum position in relation to the batter head, vibrating head or membrane in order that they receive the amount of stimulation necessary to react to the membrane and in turn create the desired buzzing “snare” sound considered characteristic of the “Snare Drum.” 
     In order to accurately adjust these snare strands for tension and position the mechanism is structured to be stiff enough to provide consistent settings and robust enough to not yield to the forces placed on it. There can also be a consideration for weight, as in the case of a marching band snare drum which is carried by the player, reducing or at least not adding to the overall weight of the instrument is desirable. 
     Snare mechanisms traditionally can be located in two locations on the structure of the drum. The first location is on the external surface of the lower head or resonating membrane of the drum. The second location traditionally is internal to the drum shell placed below the surface of the batter head or top membrane of the drum. 
     This mechanism is intended to be located internal to the drum shell placing the snare strands against the bottom of the batter head, however this mechanism can also be located internal to the drum shell against or above the lower resonating head of the drum. 
     Accordingly, with reference to  FIG. 2   a  snare mechanism, provided in accordance with an embodiment is shown generally at reference  100 . The support beam indicated at  4  provides a stiff stable support for the mechanism. The larger the “diameter” section provides higher the resistance to the bending forces placed on the mechanism and the beam itself. These forces are generated by the tensioning of the snare strands plus the load created by the mechanism being pushed against the taught batter head of the drum, and the impact loads from the players sticks. The carriage  5  is the main component of the snare mechanism that interfaces with the support beam. The carriage acts as the chassis that all other components of the mechanism fasten to. The carriage transfers the loads of the snare mechanism to the support beam and intern to the structure of the drum. In  FIG. 11   a ,  FIG. 11   b ,  FIG. 11   c  &amp;  FIG. 11   d  are shown different example configurations that could be used as large cross section support beams. 
     Accordingly, with reference to  FIG. 3  the “tension” adjustment actuated by the tension knob  2  acts directly on the chassis moving it along the beam  4 . The actuation of the tension is through a threaded element  25  acting on a nut element  21  that transfers the tension load to the chassis through pin  20 . It is desirable for the adjustments to not back off or move once the desired settings are achieved so at position  29  is represented a “nylon” locking button, held in place by cover/cap  30  or a positive lock that is engaged by the “tuner” of the instrument once the desired settings are achieved. In this illustration the head of the threaded element  22  acts as a hard stop to one of the slack adjustment extreme. The loads passed through the beam  4  are transferred to the shell structure through mounting bracket  3 . Mounting bracket  3  also acts as the receptor for the hard stop bushing for the high tension setting. To reduce the “backlash” in the tension adjustment a spring  33  is engaged to the pin  20  in each of the snare carriers to provide a positive position return to the carriers. 
     The snare strand proximity to the membrane adjustment is moved by the rotary action of adjustment knob  1 . The knob is connected to the threaded element  26  that in turn acts on clevis nut  19 , as this clevis moves along the threaded element the actuating connecting rod  17  being connected to the adjusting bridge  7  moves the bridge up and down the support ramp  9 . As adjustable bridge  7  climbs and descends the ramp  9  the bridge deflects the snare strands  6  toward the membrane  27 , the proximity adjusting the direct stimulation by the membrane of the snare strands  6 . The spring  34  is shown as a positive return for the proximity adjustment and to give more dynamic “feel” to the adjustment. Spring  35  is shown as a torsional spring around the pin in clevis  19  and serves the function of maintaining positive pressure on ramp  9  through applying force on roller bridge  7  transferred to the bridge by connecting rod  17 . In order that the two ends of the snare strands are coincidentally adjusted the transfer shaft  24  is directly connected to the adjustment knob  1  through the threaded element  26 . Bearing elements  18   a  and  18   b  provide precise guiding of the rotating adjustment elements and smooth movement under load. Position component  31  and cap  31  represent a “nylon” button and cap respectively to maintain the desired settings once chosen. This “lock” device could also be a positive lock in this or in a similarly effective location of the mechanism that is disengaged and engaged respectively by the tuner before and after the desired settings are chosen. Boss  15  provides alignment for the rotating elements. The support ramp  9  is located and held in position by fasteners  34 . Various manufacturers of snare strands produce different interface brackets to support the various different numbers and types of snare strand sets that are required, therefore it is desirable that the support or nest be interchangeable to support the various options available for snares. 
       FIG. 5   a  and  FIG. 5   b  show in cross section an alternate version of the adjustable bridge, as those skilled in the art will recognize that there are many mechanisms that can provide this type of moving support bridge function to deflect the snare strands. Here  12  represents a pivot or hinge point that can allow bridge  7  movement towards the strands  6  in relation to the static interface bracket  8  through interface bracket nest position, that is a component of support platform  9  when adjustment knob  1  places or removes actuating force 
       FIG. 4  shows a perspective of a consistent section support ramp  9 . 
       FIG. 6  shows a cross section of element in  FIG. 4 . The consistent section presents a problem as the bridge  7  progresses under the snare strands  6   a  bending force is created at position  28  as the consistent section  9  constrains the interface bracket  8 . 
     Accordingly with reference to  FIG. 7   a  relief  10  is machined into the consistent section of component  9  and is provided in order to accommodate articulation of snare strand interface bracket  8  as the bridge  7  moves under the snare strands  6 . 
     In  FIG. 8  axle pin  11  is an alternate means of providing articulation, as alternate shape adjustable bridge  7  is shown supporting snare strands  6 . Those skilled in the art will know that these are only two examples of applying clearance for articulation of the snare interface bracket  8  and also alternative snare strand interface brackets which would demand different configurations based on specific design and dimensional differences. 
     In order to maintain installation position of the snare strand intermediate bracket in its nest position a positive retainer is necessary. Two examples of positive retention  13   a  and  13   b  are shown in  FIG. 9  and  FIG. 10 ; the differences are relative to the mechanical configuration of each style of guide ramp for the adjustable bridge. The configuration  13   b  represents an elastomeric element, where as  13   a  represents a metal wire configuration. Another example of a clip retainer  28  is shown in  FIG. 12  and in  FIG. 12   a  where  28  represents a formed flat spring clip. Those skilled in the art will recognize that there are appropriate clip/retainer configurations to match the snare interface bracket nests of the various possible configurations of the snare carrier. 
     Referring now to  FIGS. 13 ,  14 ,  15  and  16 , a snare mechanism in accordance with another embodiment is indicated generally at  100 . Snare mechanism  100  is a variant on the snare mechanism of the snare mechanism of the snare mechanism of  FIG. 2 . Therefore further understanding about the principles and structure of snare mechanism  100  can be gleaned from studying the snare mechanism in  FIG. 2 , and vice versa. 
     Snare mechanism  100  comprises a snare tensioning mechanism  104  and a snare positioning mechanism  108 . In a present embodiment, snare tensioning mechanism  104  and snare positioning mechanism  108  are integrated structurally into a single assembly that can be affixed, directly or indirectly, to an interior wall  109  of a drum  110  or percussion chamber via a first attachment plate  112  and a second attachment plate  116 , each of which are disposed at opposite ends of snare mechanism  100 . 
     As best seen in  FIG. 15 , tensioning mechanism  104  is adjustable via a first actuator implemented in the present embodiment as a tensioning knob  120 . When tensioning knob  120  is rotated, the end of snare  128  closest to attachment plate  116  is urged in the direction of arrows A, and away from the opposite end of snare  128  that is closest to attachment plate  112 , thereby increasing the tension of snare  128 . Rotation of knob  120  in the opposite direction has an opposite effect, thereby decreasing the tension of snare  128 . 
     As best seen in  FIG. 16 , positioning mechanism  104  is adjustable via a second actuator implemented in the present embodiment as a positioning knob  124 . When tensioning knob  120  is rotated, the length of snare  128  is urged in the direction of arrow B, and towards the batter head  132  of drum  110 , thereby substantially evenly decreasing the gap between batter head  132  and snare  128 . Rotation of knob  124  in the opposite direction has an opposite effect, thereby increasing the gap between batter head  132  and snare  128 . 
     Referring generally again to  FIGS. 13 ,  14 ,  15  and  16 , snare mechanism  100  comprises a carriage assembly that itself comprises a movable carriage  136  and a fixture  140 . Structurally, carriage  136  and fixture  140  are substantially mirror images of each other. As best seen in  FIGS. 15 and 16 , carriage  136  is movable along a support beam  144 , while fixture  140  remains fixed in relation to support beam  144 . 
     Snare  128  is affixable to carriage  136  and fixture  140 . Various structures for effecting such affixing are contemplated, but  FIG. 13  shows a presently preferred structure for removably affixing snare  128  to carriage  136  and fixture  140 . Each of carriage  136  and fixture  140  comprise notches  148  which can receive the ends of respective interface brackets  152 . Interface brackets  152  themselves are part of snare  128 , and support one or more snare members  156  therebetween. A pair of retaining clips  160 , each of which is affixable to carriage  136  and fixture  140  via nuts  164  or other fasteners, are ultimately used to secure brackets  152  within notches  148 . As can be best seen in  FIG. 16 , notches  148 , interface brackets  152  and retaining clips  160  are configured to cooperate so that snare  128  remains affixed to carriage  136  and fixture  140  even during upward travel of snare  128  in relation to snare mechanism  100 . 
     Turning now to a more detailed discussion of the present embodiment of structure of tensioning mechanism  104 , as best seen in  FIG. 14 , support beam  144  is hollow and houses a spring  168  or other biasing means which urges carriage  136  towards fixture  140 , but which can be tensioned outwardly as explained in greater detail below. Support beam  144  is itself affixed at one end to first attachment plate  112  and at the opposite end to second attachment plate  116 . 
     A first support pin  172  affixes support beam  144  to fixture  140 , and also provides a first attachment point for spring  168 . A second support pin  176  is attached to carriage  136  and provides a second attachment point for spring  168 . However, second support pin  176  is not affixed to support beam  144 . Instead, support pin  176  can travel within a channel  180  which is provided along a portion of support beam  144  best shown in  FIG. 14 . The length of channel  180  defines the length of travel of carriage  136  along support beam  144 , and generally corresponds to the movement represented by arrow A in  FIG. 15 . 
     Also as shown in  FIG. 14   a  threaded element  184  acts on a nut element  188  that transfers the tension load through to pin  176  via a donut shaped load transfer plate  192  through which the shaft of threaded element  184  passes. The central axis of knob  120  is hollow and is threaded in order to complementarily receive threaded element  184 , such that rotation of knob  120  causes linear movement threaded element  184 , thereby acting on carriage  136  and causing carriage  136  to likewise move. 
     Also as shown in  FIG. 14 , the distal tip of knob  120  passes through the center of attachment plate  116  and is rotatable therein. 
     Turning now to a more detailed discussion of the present embodiment of positioning mechanism  108 , carriage  136  and fixture  140  each comprise a support ramp  190  and a boss  194  which are pierced for a transfer shaft  198  to pass through. The base of each support ramp  190  also include a bearing  202  which are coaxial with each boss  194 . The bearing  202  respective to fixture  140  supports a terminating end of transfer shaft  198 , while the bearing  202  respective to carriage  136  supports the opposite end of transfer shaft  198 , but this end of transfer shaft  198  merges with knob  124 . As best seen in  FIGS. 14 and 16 , transfer shaft  198  also comprises a fixture threaded portion  206  and a carriage threaded portion  210 . Fixture threaded portion  206  resides between the boss  194  and bearing  202  respective to fixture  140 , while carriage threaded portion  210  resides between the boss  194  and bearing  202  respective to carriage  136 . 
     Positioning mechanism  108  also comprises a first nut  214  respective to carriage  136 , and a second nut  218  respective to fixture  140 . Each nut  214 ,  218  has internal threads complementary to its respective threaded portion  210  and  206 . Note that the threads of threaded portion  206  are oriented in the opposite direction to the threads of threaded portion  210 , such that rotation of knob  124  in a first direction simultaneously urges nut  214  and nut  218  outwardly, along the directions of arrows C in  FIG. 16 , while rotation of knob  124  in the opposite direction simultaneously urges nut  214  and nut  218  inwardly, opposite to the direction of arrows C in  FIG. 16 . 
     Each nut  214 ,  218  is pivotally attached to a respective connecting rod  222 ,  226 , and in turn each connecting rod  222 ,  226  terminates in a respective adjusting bridge  230 ,  234 . Each connective rod  222 ,  226  is a resiliently bendable, having a normal linear position, but are also bendable into curves of differing diameters. In a present embodiment, each rod  222 ,  226  is a helical spring with each coil in contact with the next. As best seen in  FIG. 16 , rotation of knob  124  in a first direction simultaneously urges nut  214  and nut  218  outwardly, along the directions of arrows C in  FIG. 16 , and at the same time urges adjusting bridges  230 ,  234  along ramps  190  along the direction of arrow D in  FIG. 16 . As previously indicated, such movements along arrows C and D, also urges snare  128  along the direction of arrow B, towards batter head  132 . Rotation of knob  124  in the opposite direction simultaneously urges clevis  214  and clevis  218  inwardly, opposite to the direction of arrows C in  FIG. 16 , and at the same time urges adjusting bridges  230 ,  234  along ramps  190  opposite the direction of arrow D in  FIG. 16 . As previously indicated, such movements opposite the directions of arrows C and D, also urges snare  128  in the direction opposite of arrow B, away from batter head  132 . 
     Positioning mechanism  108  also comprises a self-leveling feature such that when positioning mechanism  108  is assembled bridges  230  and  234  are substantially co-planar with each other (i.e. level) so that they remain substantially parallel with batter head  132  regardless of the distance between bridges  230  and  234  as adjusted via knob  124 . In a present embodiment, the self-leveling feature is effected by implementing transfer shaft  198  in two portions, best seen in  FIG. 14 . Transfer shaft  198  thus comprises a hollow exterior shaft portion  240  that connects to fixture  140  and threaded portion  206  and a solid interior shaft portion  244  that connects to carriage  136  and threaded portion  210 . The junction of solid interior shaft portion  244  and hollow exterior shaft portion  240  are keyed in relation to each other, such that shaft portion  244  and shaft portion  240  rotate together when a rotational force is applied to shaft portion  244  via knob  124 . The keying is effected in a present embodiment by configuring shaft portion  244  with a solid hexagonal shape as viewed from its end, and configuring shaft portion  240  with a hollow hexagonal shape as viewed from its end. The hexagonal shape of shaft portion  244  is dimensioned to be slidably received within the hollow hexagonal shape of shaft portion  240 . However, the keying of each shaft portion  244  and  240  is also configured such that shaft portion  244  can slide linearly within shaft portion  240 . As a result of this configuration, when nut  214  is threaded onto threaded portion  206 , and nut  218  is threaded onto threaded portion  210 , it is not necessary that each nut  214  and nut  218  be threaded onto the exact same location on its respective threaded portion  206 ,  210 . Rather, each nut  214  and  218  can be threaded onto the same general location of its respective threaded portion  206 ,  210 , and the linear play provided by shaft portion  244  and  240  compensate for any difference in location such that bridges  230  and  234  will self-level. 
     Variations of the foregoing are contemplated. For example, in a variation either the positioning mechanism or the tensioning mechanism can be omitted. Furthermore, combinations are contemplated, wherein the features of the snare mechanism  100  can be combined with various features of the snare mechanism in  FIG. 2 , and vice versa. 
     The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore this invention includes all modifications encompassed within the spirit of the following claims.