referring first to fig1 an in - line skate 1 has a boot 2 having a bottom plane ( not shown ) coming out of the page at the bottom of the boot , an open elliptical frame 3 , mounting blocks 4 and 5 , and a heel elevator 6 . the open elliptical frame 3 is symmetrical having a peak at p in the center of the ellipse and between the mounting blocks 4 and 5 . the one - piece elliptical frame 3 includes an upper continuous leaf spring portion 7 , a forward lower leaf spring portion 9 , and a rear lower leaf spring portion 8 . the line 10 passes along the center of the lower leaf spring portions 8 , 9 . the axles 11 , 12 , 13 , 14 are supported along line 10 in leaf spring portions 8 and 9 . the wheels 15 , 16 , 17 , 18 are supported by axles 11 , 12 , 13 , 14 respectively . overload protection posts 19 , 20 extend upward from the lower leaf spring portions 8 , 9 . the overload protection posts 19 , 20 hit either the upper continuous leaf spring portion 7 or the mounting blocks 4 , 5 , or both , under maximum load conditions . under load , the open elliptical frame 3 flexes as indicated by arrows l1 , l2 , l3 . the inner wheels 16 , 17 are supported in the most flexible portion of the open elliptical frame 3 at the inside ends 21 , 22 of the lower leaf spring portions 8 , 9 . this arrangement can provide a soft , comfortable ride for the skater . additionally , the inside ends 21 , 22 flex perpendicularly to the forward direction f of the skater . this flex can improve maneuverability by allowing an increased rocker distance d to be included when the skate is unloaded . the open elliptical frame 3 is thickest at ends 23 , 24 to provide the necessary overall structural strength to support the load of the skater . the open elliptical frame 3 thins out at points 25 , 26 to provide a more even distribution of stress . thus , the open elliptical frame 3 is stiffer at the outside wheels 15 , 18 than the inside wheels 16 , 17 . as the load increases , more of the load is transferred to the outer wheels , and the frame becomes stiffer . also , since the inner wheels deflect more than the outer wheels , the rocker radius increases ( i . e ., the skate &# 34 ; flattens out &# 34 ;) as the load increases . these are important characteristics for advanced skaters . the amount of rocker can be represented by distance d . the skate geometry and stiffness can be designed so that the skate flattens out ( d = 0 ) at a typical skater &# 39 ; s push - off load . in this way , all the wheels actively participate in the push - off , yet the skate has a rocker when initiating a turn for improved maneuverability . the mounting blocks 4 , 5 have extensions 40 , 50 which provide lateral and torsional support for the lower leaf spring portions 8 , 9 via the overload protection posts 19 , 20 . moving the mounting blocks 4 , 5 toward or away from each other along the frame 3 provides an adjustable stiffness to the in - line skate 1 . the closer the mounting blocks 4 , 5 are to each other , the softer the frame . it can been seen that the open elliptical frame 3 can be constructed from one piece bars that can be economically produced by stamping , fineblanking , or molding . it can also be seen that a variety of different stiffness frames can be readily adapted to the same boot . it can be seen that each wheel 15 , 16 , 17 , 18 can be lifted individually by a bump in the road while leaving the remaining wheels in contact with the road ( i . e ., the wheels have independent suspension ). it can be seen that the mounting blocks 4 , 5 remove any necessity to drill holes into the open loop elliptical frame 3 . it can be seen that the cross - sectional shape of each bar can be varied along its length in such a way that the stress is evenly distributed along the length of the bar based on a given design load . this can maximize the amount of flex achievable while keeping the maximum stress below a given level . for a rectangular cross section bar , this bar , this includes varying the height and depth of the bar both independently and in concert . the primary function of the overload protection posts 19 , 20 is to limit the frame &# 39 ; s flex to a certain amount of travel , thus making it nearly impossible to break the frame under normal use . the longer the columns are , the shorter the maximum travel is . a secondary function is to work in conjunction with the &# 34 ; walls &# 34 ; of the mounting blocks in order to increase the lateral and torsional stiffness of the frame . yet another potential function is to accommodate springs or other shock absorbing devices as shown in fig1 - 22 . the primary function of mounting blocks 4 and 5 is to affix the frame to the boot in such a way that holes or other stress concentrators in the frame are not necessary . a secondary function is to provide walls ( for columns ) which play an important role in increasing the lateral / torsional stiffness . thirdly , the flex properties of the frame can be varied by varying the length and / or position of the mounting blocks . the mounting blocks can also accommodate a &# 34 ; bed &# 34 ; of rubber - like material to add more stiffness , rebound , and / or damping and thus reduce vibration even more . this can make the frame flex properties readily adjustable by the user . slightly increasing the depth of the slots which accommodate the frame will make the clamping force of the mounting block entirely between the block and boot -- no clamping pressure on the frame itself . in this way , the rear ( preferable ) or front mount can be made free to slide in the front to back direction . this will allow the frame to flex without flexing the boot , or reducing the flex of the boot . adding a thin plate of low friction material such as teflon between the boot and the mounting block / top of frame will reduce the sliding friction at the top surface of the frame when the frame slides relative to the boot . additionally , the mounting block can be made of , or coated with a low friction material ( teflon - impregnated hard coat anodizing , if made of aluminum ) to further reduce the sliding friction between the frame and the mounting block . the stiffness / flex properties of the frame are adjustable in the following ways : 1 . mounting block positioning -- changing the boot mount location affects the stiffness of the frame . moving the mounts in towards the center reduces the frame stiffness while moving the mounts outward towards the front and back increases the frame stiffness . 2 . the length of the mounting block ( s ) can be increased or decreased to allow the frame to flex less or more . in the extreme , a single one - piece mounting block can be used . the stiffness of the mounting block itself can also be varied . 3 . springs can be used between the top of the frame and the overload protection posts . springs of different stiffnesses can be readily interchanged to vary the frame stiffness . these springs could also simply be a piece of resilient material such as rubber , or shock absorbers such as oil or compressed air type shocks . these shocks are common on automobiles , and now on mountain bikes as well . 4 . stiffeners such as posts or strips of material can be fixed to the frame , preventing or reducing flex in certain parts of the frame , and thus stiffening the frame . the frame has a different stiffness with respect to a load on the inside wheels versus the outside ( front and rear ) wheels . the frame is stiffer with respect to a load on the outside wheels than with respect to a load on the inside wheels . varying the cross sectional shape of the bars affects these two stiffnesses . there are two important ramifications of these two different stiffnesses : the inner wheels deflect more than the outer wheels , so the rocker of the skate decreases ( frame flattens out ) with increasing load as the load increases and the frame flattens out , more load is put on the outside wheels , and thus , the frame becomes stiffer as the load increases . while the elliptical frame 3 is shown as a bar with a rectangular cross section , any cross sectional shape may be used , such as circular , oval , tubular , hollow , rectangular and non - symmetrical shapes . non - symmetrical shapes in which the left and right bars are mirror images may be useful . for example , a trapezoidal shape in which the bar height is greater on the inside than on the outside . a laminated construction , such as with skis , may also be attractive . while the frame construction shown is basically elliptical in shape , this shape may be generalized . for example , the top half of the frame could follow the contour of the boot . fig1 provides one example . the shape of the inside and outside bars of a single skate can be different as well . it may be useful to make the inside bar slightly stiffer than the outside bar , as the skater &# 39 ; s push - off tends to be stronger here . referring next to fig2 it can be seen that the open elliptical frame 3 is further comprised of a left frame member 3 l and a right frame member 3 . members 3 l and 3 may be identical , or may be mirror images , or may be asymmetrical . for example , inside member 3 may be stiffer than outside member 3 l . mounting blocks 4 , 5 hold the members 3 l and 3 together in grooves g 1 , g 2 as shown in fig4 . the axles 11 , 12 , 13 , 14 provide the final support for the assembly 3 l , 3 , 4 , 5 . bolt ( s ) 51 mounts the mounting block 5 to the boot 2 . bolt ( s ) 54 mounts the mounting block 4 to the boot 2 . a unique aspect of this construction is that the frame itself is not self - supporting -- the axles and / or boot must be secured to support the frame . it would be obvious to one skilled in the art to manufacture members 3 l , 3 in a one piece construction having crosswise support members between them . referring next to fig3 the boot 2 has a liner 200 . extension 50 is mirrored in extension 50 l . optional inside extensions 500 offer extra lateral stability for the in - line skate 1 if desired . optional springs 201 offer extra shock absorption and adjustable stiffness if desired . optional dampening material 204 offers extra damping if desired . the thickness of axle spacers 205 can be increased to further separate frame members 3 l , 3 for various mounting blocks and / or wheel combinations . optional damping pad 207 offers extra damping if desired . referring next to fig4 holes 510 , 520 , 530 provide access for bolt ( s ) 51 of fig2 . planar top surface 531 distributes the skater &# 39 ; s load evenly and eliminates wear producing stress concentrations . the depth of slots g 1 , g 2 can be increased to permit a slight forward and backward movement of the frame members 3 l , 3 if desired . the mounting block allows variable boot mount locations . a combination of one fixed mount and one sliding mount can be used . referring next to fig5 , 7 the open elliptical frame 3 is seen in an undeflected state in fig5 . s 1 is maximal . also , the rocker offset d is maximal . fig6 shows s 2 at a smaller distance as the frame 3 flattens out and becomes stiffer by force ff . fig7 shows a maximal force fff forcing the overload posts 19 , 20 against the frame 3 . s 3 is minimal . the overload posts 19 , 20 protect the frame 3 from breaking . referring next to fig8 a closed loop elliptical frame 800 is shown . the same mounting block 4 is used . all functionality of the frame assembly 4 , 801 , 802 are identical to the embodiment of fig1 . this embodiment offers a stiffer ride than the preferred embodiment of fig1 with improved lateral and torsional stiffness , realized by closing the elliptical frame . the wheels are no longer suspended independently . referring next to fig9 , 11 , 12 , the fig1 embodiment has been modified to create a closed loop hybrid frame 900 . frame member 901 is open . connecting rods 902 , 903 pivot at points 904 , 905 which may be the axles . the adjusting nut 906 can bring the connecting rods together under tension to close the loop and to increase the frame stiffness . fig1 shows how this frame design offers independent wheel suspension as wheel 911 passes over rock 910 . it can be seen that connecting rods 902 , 903 add lateral support to the frame 900 while maintaining independent wheel suspension . referring next to fig1 a skate 1300 has a boot 1303 mounted on a frame 1301 . the frame 1301 is based on the open ellipse of fig1 but is non - symmetrical . the high point of the frame is at 1302 under the heel 1304 of the boot 1303 . this design eliminates the need for a separate heel lift . this modification may also provide more rebound energy during skating . referring next to fig1 a closed loop embodiment is shown as skate 1400 . frame member 1401 is supported by axles 1410 , 1411 , 1412 , and 1413 . mounting blocks 1404 , 1405 serve to stop overload protection posts 1402 , 1403 which are located between the axles rather than over the axles . an optional heel elevator 1415 is shown . referring next to fig1 a skate 1500 has a frame member 1501 that features a lower height for the top of the elliptically shaped frame at 1505 . the axles are mounted above the bottom half of the elliptical center line 1502 at a higher mounting line 1503 . this embodiment is useful for large ellipses which otherwise would tend to raise the skater too high off the ground . referring next to fig1 a double elliptical frame 1600 is shown . the inner frame 1601 shares a top leaf 1604 with the outer frame 1602 , 1603 . although inner frame 1601 is a closed loop , it could have a connecting rod design at 1607 as shown in fig8 - 12 , or an open loop design . while lower leaf springs 1602 , 1603 are open loop , they could be closed loop . thus , a wide variety of suspension characteristics can be designed from the above teachings . fig1 - 22 show various designs of overload protection assemblies which can also be used to make the frame stiffness / flex properties easily adjustable . overload protection ( op ) rod 1700 forces spring 1701 against frame 1702 . op rod 1800 forces spring 1801 against frame 1802 . op rod 1900 forces resilient pad 1901 against frame 1902 . op rod 2000 forces resilient pad 2001 against frame 2002 . op rod 2100 forces shock absorber piston 2111 up the shock 2101 which is mounted on frame 2102 . op rod 2200 forces spring 2201 into the frame 2203 and piston 2202 into the shock 2204 . these embodiments can dampen vibrations , change the force - deflection curve to make the frame stiffen with load , and increase the rebound . the teachings of a two wheel skate in the co - pending 08 / 126 , 695 application can be applied to and combined with the present application . although the present invention has been described with reference to preferred embodiments , numerous modifications and variations can be made and still the result will come within the scope of the invention . no limitation with respect to the specific embodiments disclosed herein is intended or should be inferred .
several embodiments of open and closed loop frames substantially elliptical in shape are disclosed for in - line skates . some embodiments include independent suspension for each wheel . the frame is flexible to provide shock absorption and rebound . the frame stiffness increases with the applied load . the rocker of the skate is made to vary with the applied load , so that the skate has high maneuverability yet is very stable when gliding . the frame includes a boot mounting system which adds no stress concentrations , thus assuring even flex properties over the entire frame , and high durability . overload protection is included to further enhance durability .