Abstract:
A snowmobile has an engine mounted with an exhaust port facing forwardly. A steering post extends substantially along a longitudinal centerline of the vehicle and over a top of the engine. An exhaust outlet is coupled to exhaust port and projects vertically upwardly to a position higher than the engine, and projecting rearwardly between the steering post and frame members. The rider position is re-defined relative to the snowmobile center of gravity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/597,104, filed on Feb. 9, 2012, the subject matter of which is expressly incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    The present application relates to a snowmobile. 
         [0003]    The present invention relates to snowmobiles, and more particularly, the present invention relates generally to a frame assembly and suspension assembly for snowmobiles. The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/597,104, filed on Feb. 9, 2012, the subject matter of which is expressly incorporated by reference herein. 
         [0004]    Performance characteristics of snowmobiles, including the comfort of the ride, depend on a variety of systems and components, including the snowmobile suspension. Typically, a snowmobile suspension includes two systems, a front suspension system for a pair of skis and a rear suspension system for the track. 
         [0005]    The rear suspension of a snowmobile supports an endless track driven by the snowmobile engine to propel the machine. The track is supported beneath a vehicle chassis by a suspension that is designed to provide a comfortable ride and to help absorb the shock of the snowmobile crossing uneven terrain. Most modern snowmobiles use a slide rail suspension which incorporates a pair of slide rails along with several idler wheels to support the track in its configuration. The slide rails are typically suspended beneath the chassis by a pair of suspension arms, with each arm being attached at its upper end to the chassis of the snowmobile, and at its lower end to the slide rails. The mechanical linkage of the slide rails to the suspension arms and to the snowmobile chassis typically is provided by springs and at least one element acting along a linear path, such as a shock absorber, damper, air shock, shock and spring combination, or other linear force element (LFE). The springs are loaded to bias the slide rails downwardly away from the snowmobile chassis and the shock absorbers; dampers or LFEs provide damping forces for ride comfort. 
       SUMMARY 
       [0006]    In one aspect, a snowmobile comprises a chassis having a front chassis portion and a rear chassis portion. The front chassis portion includes a bulkhead and a steering mount positioned above the bulkhead by way of frame members. An engine has at least one intake and at least one exhaust port, and the engine is mounted with the at least one exhaust port facing forwardly. A steering post is coupled to the steering mount and extends substantially along a longitudinal centerline of the vehicle and over a top of the engine. An exhaust outlet is coupled to the at least one exhaust port, the exhaust outlet projecting vertically upwardly to a position higher than the engine, and projecting rearwardly between the steering post and one of the frame members. 
         [0007]    In another aspect, a snowmobile comprises a chassis having a front chassis portion and a rear chassis portion, the front chassis portion includes a bulkhead. An engine is supported by the chassis. A steering post extends substantially along a longitudinal centerline of the vehicle and extends over a top of the engine and is coupled to the bulkhead. The snowmobile includes front steerable skis; spindles coupled to the skis; steering arms coupled to the spindles; and a first coupling link interconnecting the steering arms and the steering post, the first coupling link being an extruded member forming plural pivot points. 
         [0008]    In another aspect, a snowmobile comprises a chassis extending along a longitudinal axis; and an engine supported by the bulkhead. The engine has a crankshaft having a crankshaft axis transverse to the longitudinal axis. The engine has a piston coupled to the crankshaft and reciprocates along a piston reciprocation axis, the piston reciprocation axis extending upwardly and forwardly. A continuously variable clutch has a drive clutch coupled coaxially to the crankshaft and a driven clutch mounted rearwardly of the drive clutch, wherein a line between a rotational axis of the drive clutch and a rotational axis of the driven clutch define a clutch axis, and wherein an angle formed between the piston reciprocation axis and the clutch axis is approximately 90°. 
         [0009]    In yet another aspect, a snowmobile comprises a chassis including a bulkhead and a tunnel, an engine supported by the chassis, a front suspension coupled to the bulkhead, a rear suspension coupled to the tunnel, a fuel tank supported by a tunnel top surface, and a frame comprising frame tubes extending downwardly and rearwardly and coupled to rear corners of the tunnel, with the frame tubes flanking the fuel tank. 
         [0010]    In a further embodiment, a snowmobile comprises a chassis having a bulkhead and a tunnel. An engine is supported by the chassis and a front suspension is coupled to bulkhead. A rear suspension is coupled to the tunnel and slide rails are coupled to the rear suspension. The rear suspension comprises a toggle link pivotally coupled to the tunnel, and a rear control arm coupled between the slide rails and the toggle link. A front control arm is coupled between the slide rails and the tunnel; wherein the snowmobile has a snowmobile center of gravity, and the front control arm is mounted at a position in a range of 300-310 mm relative to the snowmobile center of gravity. 
         [0011]    In yet another embodiment, a snowmobile, comprises a chassis, having a bulkhead and a tunnel. An engine is supported by the chassis, and a front suspension is coupled to bulkhead. A rear suspension is coupled to the tunnel. Slide rails are coupled to the rear suspension, where the rear suspension is comprised of a toggle link pivotally coupled to the tunnel, and a rear control arm coupled between the slide rails and the toggle link; a carrier roller coupled to the toggle link, the toggle link being movable to a plurality of positions relative to the toggle link to vary the dynamics of the vehicle propulsion; and a front control arm coupled between the slide rails and the tunnel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a front perspective view of a snowmobile according to the present embodiment, shown without the body member and driver&#39;s seat; 
           [0013]      FIG. 2  is a front view of the snowmobile of  FIG. 1  with the exhaust system removed; 
           [0014]      FIG. 3  is a side view of the snowmobile of  FIG. 1 ; 
           [0015]      FIG. 4  is a rear perspective view of the steering system of the present embodiment; 
           [0016]      FIG. 5  is a view similar to that of  FIG. 4  showing the suspension system removed; 
           [0017]      FIG. 6  is an enlarged view of the steering coupler; 
           [0018]      FIG. 7  is a view similar to that of  FIG. 2 , including the exhaust system; 
           [0019]      FIG. 8  is a top view of the embodiment shown in  FIG. 7 ; 
           [0020]      FIG. 9  is a side view of the embodiment in  FIG. 8 ; 
           [0021]      FIG. 10  is an enlarged front view of the snowmobile of  FIG. 7 ; 
           [0022]      FIG. 11  is a side view of the engine and CVT configuration. 
           [0023]      FIG. 12  shows a rear perspective view of the snowmobile of  FIG. 1 ; 
           [0024]      FIG. 13  shows a top view of the snowmobile of  FIG. 12 ; 
           [0025]      FIG. 14  shows an enlarged view of the tunnel couplings; 
           [0026]      FIG. 15  shows a view similar to that of  FIG. 12  less the drive mechanism; 
           [0027]      FIG. 16  shows a top view of the snowmobile frame of  FIG. 15 ; 
           [0028]      FIG. 17  shows a bottom view of the snowmobile of  FIG. 16 ; 
           [0029]      FIG. 18  shows an underside perspective view of the rear suspension; 
           [0030]      FIG. 19  shows a rear perspective view of the rear suspension; 
           [0031]      FIG. 20  shows a rear perspective view of the snowmobile fuel tank; 
           [0032]      FIG. 21  shows a side view of the toggle link; and 
           [0033]      FIG. 22  shows an alternative embodiment of the toggle link. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    For the purposes of promoting an understanding of the principals of the invention, reference will now be made to the embodiments illustrated in the drawings, which are described below. The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings. It will be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrative devices and described methods and further applications of the principles of the invention which would normally occur to one skilled in the art to which the invention relates. 
         [0035]    With reference first to  FIG. 1 , a snowmobile is generally shown at  2  to include a frame  4 , a propulsion system  6  coupled to the frame, an exhaust system  8  coupled to an engine  10  of the propulsion system  6 , a steering system  12  coupled to steerable skis  14 , and front  16  and rear  18  suspensions. 
         [0036]    With respect to  FIG. 2 , frame  4  will be described in greater detail. It should be understood that frame  4  is similar in nature to that described in Applicant&#39;s patent application Ser. No. 13/027,116, the subject matter of which is incorporated herein in its entirety. Frame  4  includes lower cast members  20 ,  22  which are fastened together in a clam shell type arrangement. Cast members  20  and  22  include integrated upper and lower pivot members  24 ,  26  ( FIG. 3 ) and upper pedestals  28 . A coupler  30  is provided which couples frame tubes  32  between coupler  30  and pedestal  28  of cast member  20 . Cross tube  34  extends between the cast members  20  and  22 . Frame tubes  32  could be fastened by any mechanical means such as by fasteners, welding, adhesives and the like. 
         [0037]    With respect now to  FIG. 3 , frame  4  further includes engine cradle  40 , drive housing  42 , tunnel  44  and brace tubes  46  extending between coupler  30  and cast couplings  50  ( FIG. 1 ) attached to tunnel  44 . 
         [0038]    With reference now to  FIG. 4 , suspension system  16  will be described in greater detail. Suspension  16  includes upper  60  and lower  62  alignment arms having pivot mounts  64  and  66  attachable to pivot members  24  ( FIGS. 2) and 26  ( FIG. 3 ) where each of the alignment arms  60 ,  62  are attached to spindle  68  by way of ball joints  69  ( FIGS. 3 and 4 ) as is known in the art. A shock absorber  70  is attached at  72  to lower alignment arm  62  and extends upwardly through upper alignment arm  60  and is attached at  74  to pedestal  28  ( FIGS. 2 and 4 ). 
         [0039]    With reference now to  FIGS. 4-6 , steering system  12  will be described in greater detail. As shown, steering system  12  includes handlebars  80  attached to a steering post  82  which is rotatably fixed at a lower end thereof and rotates relative to a mounting block  84 . As shown, steering post  82  defines single post, center pivot steering, which extends over the engine  10  as shown best in  FIG. 3 . As shown in  FIG. 1 , steering post  82  includes an outward bend at  83  for clearance of engine  10 . Mounting block  84  is attached to a front inner surface of the cast members  20 ,  22  by way of fasteners at  86  ( FIGS. 2 and 4 ). Steering post  82  includes a pitman arm  87  having a ball joint  88  attached thereto. Ball joint  88  is coupled to a ball joint  90  by way of a link  91 . Ball joint  90  is attached to a coupling link  92  having four pivot points. 
         [0040]    As best shown in  FIG. 6 , coupling link  92  is a top extruded member having a pivot cylinder  94  with three radially extending webs or walls  96 ,  98  and  100  extending integrally from cylinder  94 , and terminating in respective pivot bosses  102 ,  104  and  106 . Bosses  102  and  104  are integrally connected by way of an integral link  108  whereas bosses  104  and  106  are interconnected by an integrated link  110 . 
         [0041]    With respect to  FIGS. 5 and 6 , coupling link  92  may be easily attached to the inside of cast member  20  by way of bracket  120  and pivotably mounted relative thereto by way of fastener  122 . As also shown, ball joint  90  is attached to first boss  106  by way of fastener  126 . Meanwhile, coupling link  92  is interconnected to tie rod  130  at boss  102  by way of fastener  132 . Furthermore, tie rod  130  is attached to spindle by way of ball joint  136  ( FIG. 5 ). As shown best in  FIG. 5 , coupling link  92  is interconnected in parallel to a second coupling link  142  by way of a drag link  144 . Coupling link  142  is similar to coupling link  92 , however, only includes two radial walls  146  and  150  attached to a pivot cylinder  152 . In a similar manner, coupling link  142  is attached to tie rod  160  by ball joint  162 , which in turn is coupled to spindle  168  by way of ball joint  170 . 
         [0042]    With respect now to  FIGS. 7-10 , the exhaust system  8  will be described in greater detail. As shown, exhaust system  8  includes an exhaust manifold  200  extending forwardly and downwardly from engine  10 , as best shown in  FIGS. 8 and 9 . Exhaust system  8  includes a first tube portion  202  extending generally longitudinally and forwardly past cast members  20 ,  22  and extending under cross tube  34  ( FIGS. 7 and 8 ). As shown in  FIG. 8 , tube portion  202  extends on the vehicle left hand side of steering post  82 . Exhaust system  8  further includes a vertically projecting radiused section  204  which turns the exhaust system  8  vertically upwardly and includes a reversely bent tube section  206  ( FIG. 8 ) which extends generally longitudinally and rearwardly and extends on the opposite and vehicle right hand side of steering post  82 . Tube portion  206  also extends above cross tube  34  and on the inside of frame tube  32 . Thus the exhaust system  8  at the front of the snowmobile  2  is defined between the envelope of frame tubes  32  on either side. 
         [0043]    With respect now to  FIG. 11 , engine  10  is shown mounted in engine cradle  40  and tipped forward. As shown, a CVT (continuous variable transmission) drive clutch  210  is mounted coaxially with a crank shaft rotational axis  212 . As shown, axis  212  is transverse to a longitudinal direction of snowmobile  2 . As shown, engine  10  is a reciprocating type engine having a piston (not shown) reciprocating within an engine head of engine  10 . Engine  10  includes a piston reciprocation axis  214  where axis  214  is rotated forward relative to vertical by an angle β. As shown, β equals 12°. As also shown, a CVT driven clutch  215  is mounted to drive housing  42  along a rotational axis  216 . As is known in the art, a CVT belt (not shown) would entrain the drive clutch  210  and the driven clutch  215  to transmit power between the engine  10  and the driven clutch  215 . A line drawn between axis  212  and axis  216  is known as the belt center axis, and is shown at  218 . As an angle α is defined between lines  214  and  218  where α is in the range of approximately 70-100°. As shown, α equals 78°. This prevents any reciprocation vibration from being transmitted to the driven clutch  215 . 
         [0044]    With reference now to  FIGS. 12-14 , the frame  4  will be further described. Frame tubes  46  include longitudinally extending sections  220 , inwardly directed sections  222  and outwardly directed sections  224 . Frame tubes  46  flank fuel tank  230  as described further herein. As also shown, tunnel  44  includes a top wall  240  and side walls  242  defining an internal enclosure for receiving the snowmobile track as is known in the art. Couplings  50  are mounted at the rear corners of tunnel  44  at the juncture of the top wall  240  and side walls  242 . As shown best in  FIG. 14 , couplings  50  include apertures  250  receiving frame tube portions  224 , a trunnion portion  252 , and a mounting portion  254 . 
         [0045]    With reference now to  FIGS. 15-19 , rear suspension  18  will be described in greater detail. It should be appreciated that rear suspension  18  is similar to that described in U.S. patent application Ser. Nos. 11/623,879 and 12/627,642, the subject matter of which are incorporated herein by reference. 
         [0046]    As shown, rear suspension  18  includes a front control arm  260 , rear control arm  262 , toggle link  264  and a pair (only one of which is shown) of slide rails  266 . As shown best in  FIGS. 17 and 18 , front control arm  260  includes upper couplers  270  coupled to an inner surface of tunnel sidewall  242 , arm portions  272  and a coupling tube  274 . Coupling tube  274  is interconnected to inside surfaces of slide rail  266  as shown best in  FIG. 15 . 
         [0047]    As shown best in  FIG. 15 , rear control arm  262  includes couplers  280  coupled to slide rail  266  and arms  282  coupled to toggle link  264 . Toggle link  264  is generally comprised of arms  290  including front couplers  292  pivotally mounted within trunnion portions  252  of couplers  50 . Toggle link  264  further includes rear coupling portions  294  which couple to an upper portion of arms  282 . A cross bar  296  locates a shock mount  298  ( FIG. 19 ) as described herein. Arms  290  include triangular link portions  300  including couplers  302  for carrying a carrier roller (not shown) which is similar in design to that shown in U.S. patent application Ser. No. 12/627,642, the subject matter of which is incorporated herein by reference. Brackets  310  ( FIG. 18 ) may also be provided to hold a rear heat exchanger as shown in U.S. patent application Ser. No. 13/018,824, the subject matter of which is incorporated herein by reference. 
         [0048]    Finally, a bracket  320  ( FIG. 19 ) is attached to top surface  240  of tunnel  44  where a shock absorber is mounted between shock mounts  298  and  322 . Thus with reference to  FIG. 15 , slide rails  266  move upwardly and downwardly relative to tunnel  44  by way of rear suspension  18 . More particularly, as slide rail  266  moves relative to tunnel  44  (or tunnel  44  moves relative to slide rail  266 ), slide rails  266  move by way of front control arms  260  which are interconnected between tunnel  44  and slide rails  266 . Moreover, as slide rails  266  move relative to tunnel  44 , toggle link  264  is moved about couplings  292  towards and away from tunnel  44  under compression from a shock absorber mounted between shock mounts  298  and  322  ( FIG. 19 ). 
         [0049]    With reference now to  FIG. 20 , fuel tank  230  is shown in great detail. Fuel tank  230  is shown having a base portion  340  which conforms to the top surface  240  of tunnel  44 , side walls  342 , front wall  344 , and a center narrow portion  346  defining shoulders  348  for receiving frame tubes  46 . Fuel tank  230  further includes a rear opening  350  including a rear wall  352  to receive shock mounting bracket  320 , shoulders  354  for receiving tube portions  224  and a rear opening  356  to receive shock absorber connected to shock mount  322 . 
         [0050]    With the rear suspension  18  described as mentioned above, the position of the operator and the operation of rear suspension  18  will now be described. With reference to  FIG. 1 , front ski  14  is attached to spindle  68  at position  400  which extends along a transverse axis  402 . The present embodiment differs from the embodiments shown in U.S. patent application Ser. Nos. 11/623,879 and 12/627,642. First, the embodiment differs in that the operator has been positioned closer to the vehicle center of gravity from the previous embodiment, such that the rider is positioned substantially at the vehicle center of gravity, including the fuel and driver (CG f-d ). It should also be noted that the CG f-d  may be changed plus or minus 2 inches based on the rider and the respective position on the snowmobile  2 . Secondly, the front control arm  260  of the rear suspension assembly  18  has been moved rearwardly, which has modified the pitch of the vehicle. Finally, the tunnel  44  of the present embodiment has been elongated, which has provided several inherent improvements. 
         [0051]    With reference to  FIG. 3 , a longitudinal position from ski bolt position  400  to a position of operator&#39;s hands on hand grip  404  is shown at X 1 , where X 1  is in a range of 750-770 mm, and in the embodiment shown X 1  equals 29.93 inches (760.24 mm). This is approximately 2.5-4.0 inches forward of the position of the embodiments shown in U.S. patent application Ser. Nos. 11/623,879 and 12/627,642. In a similar manner, the position of the operator&#39;s hands on hand grip  404  is forward of a belt drive axis  406  by a distance of X 2 , where X 2  is in a range of 100-120 mm, and in the embodiment shown X 2  equals 4.385 inches (111.39 mm). Snowmobile  2  also includes an operator&#39;s foot rest  408 , and a forward most position of foot rest  408  is forward of drive axis  406  by a dimension of X 3 , where X 3  is in a range of 30-50 mm, and in the embodiment shown X 3  equals 1.54 inches (39.1 mm). As also shown in  FIG. 3 , the center of gravity of the vehicle dry with the suspension in the fully extended position (CG d ) is shown at  410  which is rearward of drive axis  406  by a dimension of X 4 , where X 4  is in a range of 65-75 mm, and in the embodiment shown equals 2.699 inches (68.57 mm). 
         [0052]    Position  412  in  FIG. 3  represents the pivot axis of front control arm  260  and in particular the position for connection of couplings  270  ( FIG. 17 ) inside the tunnel  44 . This is approximately 5.5 inches rearward of the position shown in the embodiments shown in U.S. patent application Ser. Nos. 11/623,879 and 12/627,642. The longitudinal distance for pivot point  412  is positioned a distance of X 5  from drive axis  406 , where X 5  is in a range of 210-260 mm, and in the embodiment shown equals 236.33 mm. Position  414  shows a seating position for operator on snowmobile  2 . The seating position is rearward of drive axis  406  by a dimension of X 6 , where X 6  is in a range of 405-505 mm, and in the embodiment shown equals 18.00 inches (457.20 mm). Thus the positions  404 ,  408  and  414  define the operator coordinates relative to the CG d . Furthermore, the pivot point  360  for toggle link  264  ( FIG. 15 ) is at the center of coupler  292 . The distance between the drive axis  406  and pivot point  360  is X 7 , where X 7  is in a range of 700-800 mm, and in the embodiment shown equals 29.766 inches (756.055 mm). As also shown in  FIG. 3 , a distance from the ski bolt position  400  and spindle pivot axis  402  to the front control arm mounting  412  is in the range of 1000-1200, and is approximately 1100 mm. In the embodiment distance from the ski bolt position  400  to the front control arm mounting  412  is 1107.96 mm (X 1 +X 2 +X 5 ). 
         [0053]    As also shown in  FIG. 3 , the vertical position of pivot point  412  is Y 1  from a ground position and the vertical position of CG d    410  is in a range of 320-360 mm, and in the embodiment shown is equal to 345.10 mm or an incremental Y 2 , where Y 2  equals 92.22 mm. 
         [0054]    In this position, the pivot point  412  of front control arm  260  is rearward of the CG d , whereas in the version shown in U.S. patent application Ser. Nos. 11/623,879 and 12/627,642, the pivot point of front control arm  260  is forward of the CG d . Thus, the positioning of the front control arm  260 , and particularly the mounting of couplers  270 , can vary the amount of the vehicle pitch. The steeper the angle of control arm  260 , the greater the vehicle pitches; whereas the flatter the angle of control arm  260 , the lesser the vehicle pitches. This is due to the vertical force component of front control arm  260  acting on and through the coupler  270 . 
         [0055]    With reference still to  FIG. 3 , the pivot point for toggle link  264  is at coupler  292 , which is 54.6 mm further back from the position shown in U.S. patent application Ser. Nos. 11/623,879 and 12/627,642. This improves carrier wheel engagement, improves transfer control, reduces sensitivity, increases running-board length, provides room for fuel capacity and provides a more rearward position for the shock mounting. 
         [0056]    With reference now to  FIG. 21 , toggle link  264  is shown in side view. As mentioned above, toggle link  264  rotates relative to tunnel  44  via pivot couplings  292  and rotates relative to rear control arm  262  by way of pivot coupling  294 . As shown in the  FIG. 21  embodiment, legs  300 A,  300 B, which make up link  300 , are substantially the same length. A carrier roller (not shown) is rotatably mounted to coupling  302 . As toggle link  264  is rotatably coupled to tunnel  44  at pivot point  292 , during compression of rear suspension  18 , toggle link  264  rotates counterclockwise. As toggle link  264  rotates, a carrier roller attached at  302  has some slight vertical downward movement before it swings vertically upward. However, the carrier roller may be moved to other positions relative to the toggle link  264  to change the position of the carrier roller, and resultantly, can the dynamic attributes of the snowmobile  2 , as discussed below. 
         [0057]    For example, and with reference to  FIG. 21 , a carrier roller mounted further rearward along arm  300 B (for example to a point  302 ′), would have immediately upward movement upon counter clockwise rotation of toggle link  264  and would provide more aggressive propulsion of the drive belt. This is due to the increase in bias of the carrier roller, which upon acceleration of snowmobile  2 , causes more load to go down to the rear control arm  262 , then to the slide rail  266  and into the ground. Conversely, if a carrier roller were moved upward to a position  302 ″ along arm  300 A, upon acceleration, the chassis is pulled down resulting in more vertical lift of the snowmobile during acceleration. It should also be noted that movement rearward, for example to position  302 ′ also increases the cornering ability of the snowmobile  2 . 
         [0058]    Thus, and with reference to  FIG. 22 , a toggle link  324 ′ could be provided having front and rear pivot points  326  and  328 . Arms  300 A and  300 B of the  FIG. 21  embodiment are replaced by a trapezoidal plate  370  with a roller  372  mounted thereto. Roller  372  is mounted about a center of rotation  374 . Carrier roller  372  could be positioned within a zone defined within hypothetical box  380  where the desirability of the drive characteristics could be “tuned” by positioned roller on any one of the mounting apertures  382 . Hypothetical box  380  is defined relative to a reference line R drawn through the centers of pivot points  326  and  328 , and relative to a tangent line T, tangent to reference line R and through pivot point  326 . With reference to  FIG. 22 , hypothetical box  340  is approximately positioned between A 1  (80 mm) and A 2  (225 mm) from reference line R, and B 1  (60 mm) and B 2  (225 mm) from reference line T. In the embodiment shown, hypothetical box  340  is positioned between A 1  (80 mm) and A 2  (226.68 mm) from reference line R, and B 1  (59.35 mm) and B 2  (225.23 mm). 
         [0059]    While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practices in the art to which this invention pertains.