the present invention overcomes the disadvantages of prior art ski boots , and provides a ski boot whose flexional properties of the calf with respect to the shell base include an elastic - return or spring - back property . additionally , in order to accomplish a principal aim of the invention , which is to provide a ski boot in a simple and efficient manner by utilizing modern plastic materials as the means for controlling the angular flexion of the calf , as well as its return and / or spring - back elastic means , additional adjustment means for adjusting these elastic - return characteristics may be provided . the ski boot , according to one preferred embodiment of the invention , has a rear insertion capability which comprises a rigid shell base essentially surrounding the foot provided with a sole . the upper portion of the zone surrounding the heel and the malleoli is provided with at least one pivot axis on which a relatively rigid calf surrounding the bottom of the leg of the skier is journalled . in this embodiment , the calf itself is composed of at least one rear portion or spoiler serving as a support for the bottom of the leg , and at least one front portion or cuff assuring the closure of the boot . the boot is characterized in that the shell base comprises , respectively , on each side of the malleoli , a vertical extension in the form of a deformable elastic blade extending approximately parallel to the axis of the calf from the zone surrounding the heel . the calf contains a second pivot axis with the shell base provided at one point , situtated above the first pivot axis , along the length of the extension . nevertheless , the invention is not limited to boots in which insertion of the foot occurs from the rear , and it is possible to apply the invention to ski boots of the front - insertion type . another aim of the invention is to obtain flexional characteristics of the calf to provide a good shock - absorption capacity of the flexional forces sustained with a sufficient elastic return for small forces while providing a good lateral security to the leg . these aims are achieved with the boot according to the invention by virtue of its particular structure . in effect , it is the vertically extending lateral extensions extending upwardly from the rigid shell base which assure flexional control , as well as the elastic return , while the calf , and more particularly the spoiler journalled on the shell , which , by virtue of its shape , envelopes the leg in a tubular fashion , and assures the necessary lateral rigidity and security for the bottom of the leg of the skier . finally , another aim of the invention is to provide &# 34 ; rear insertion &# 34 ; boots whose cuff cooperates with the top of the shell base in the approximate zone of the instep to resist permanent deformation which occurs at the lower edge of the front portion of the calf after repeated periods of use . furthermore , this cooperation zone between the shell base and the lower edge of the calf is determinative in establishing of the rigidity of the calf , whose curve of values increases sharply . it is with a view towards modifying the characteristics of the rigidity curve of the calf that the construction according to the invention has also been developed . additionally , the great advantage of this type of construction resides in the fact that the lateral extensions are formed directly during the same molding step as the shell base , whose unique material assures both lightness and good mechanical characteristics linked with simplicity of production . various embodiments of the boot according to the invention can be provided . thus , depending on the possibilities of adjustment that one wishes to obtain for a finer modulation of the flexional characteristics and elastic - return qualities , the lateral extensions in the form of elastic blades will be connected to the front portion of the calf , called the cuff , at a distance which is more or less raised above the journal axis of the calf on the shell base . it is likewise possible , according to this concept , to provide an attachment apparatus for attaching the calf to the extensions which varies the distance of the upper pivot axis from the lower first pivot axis along the height of the calf such that , depending upon the level of the skier &# 39 ; s abilities , the flexional conditions of the boot can be adjusted to suit the skier &# 39 ; s needs . according to another embodiment , a different manner of varying the flexional and elastic - return characteristics is provided by providing at least one of the lateral elastic blades with an oblong slot which serves effectively to diminish the cross - section of the beam constituted by the elastic blade . in another embodiment , the boot according to the invention is provided with a latching means between the elastic blades and the cuff which is removable or retractable to allow for the possibility of totally eliminating the return and / or flexion of the calf provided by the blades . as a result of this , the calf is connected to the shell base only at its lower first pivot axis . one thus obtains good angular deflection in the longitudinal perpendicular plane of the boot , which facilitates walking . it is also possible to provide an alternative embodiment for a ski boot having insertion through the front . in this case , the lateral extensions still originate at the shell base and extend upwardly substantially the length of the calf , but the calf in this embodiment comprises a single , relatively rigid element surrounding the bottom of the leg of the skier . the calf is connected at its upper portion to the lateral elastic blades by known assembly means , while the calf can be opened to the foot when the boot is to be put on . referring to the embodiment illustrated in fig1 and 2 , ski boot 1 comprises a shell base 2 made of rigid plastic material on which a calf 3 surrounding the bottom of the leg of the skier is journalled . this calf itself comprises a front calf portion 3 &# 39 ;, called a cuff , and a rear portion 3 &# 34 ;, called a spoiler . in the case of the embodiment described , the cuff and spoiler 3 &# 39 ;, 3 &# 34 ; are simultaneously journalled on the same pivot axis 5 , situated approximately in the zone of the shell base adjacent to the malleoli of the skier . furthermore , shell base 2 entirely encases the front of the foot up to the zone of the instep , as well as in the zone of the heel . the base is generally slipper - shaped , which advantageously facilitates putting on the boot through the rear . quite obviously , tightening and locking means of the cuff and of the spoiler may be provided on the calf ; these means not being shown for purposes of clarity . according to one of the principal characteristics of the boot according to the invention , the shell base 2 comprises , on both sides of the malleole zone and above the pivot axis 5 , an extension originating from the shell base , which extends above the zone of the malleoli , in the form of two lateral blades 4 and 4 &# 39 ; positioned substantially parallel to the longitudinal median plane of the boot . the two lateral blades 4 and 4 &# 39 ; are substantially of the same thickness as the walls of the shell base , and extend upwardly along the general axis of the calf 3 of the boot 1 . the lateral elastic blades 4 and 4 &# 39 ;, which extend up to a height which is approximately equal to that of the calf , are equivalent to beams anchored at one of their ends , i . e ., at their bases 41 , 41 &# 39 ;. these blades can be provided at their bottom or base 41 , 41 &# 39 ;, with a width which is greater than along the rest of the blade , which leads to a modification of the original flexional characteristics . in the case of fig1 and 2 , a ski boot according to the invention has been shown which is provided with lateral elastic blades 4 , 4 &# 39 ; whose edges are each parallel . at the upper portion or top 42 , 42 &# 39 ; of the lateral blades 4 , 4 &# 39 ;, second attachment points 6 , 6 &# 39 ; of the shell base 2 with the calf 3 are provided . these attachment points 6 , 6 &# 39 ; are provided by known assembly means such as rivets , clips , screws , etc . this second attachment point , which is an essential aspect according to the invention , assures the cooperation of the calf with the lateral blades during the various phases of active use of the boot . as shown in fig2 when the skier exerts a frontwardly - directed flexion in the direction shown by arrow 7 in dashed lines , cuff 3 &# 39 ; flexes frontwardly ( along the position shown in dotted lines 31 &# 39 ;), and causes the same frontward force to be exerted on lateral blades 4 , 4 &# 39 ;. the blades flex as shown in the advanced position in dashed lines 43 at their upper ends 42 , 42 &# 39 ;. the flexional force shown by arrow 8 to which the blades 4 , 4 &# 39 ; are subjected is applied to the linkage points 6 , 6 &# 39 ;, and acts , as a result , on the blades , as a force applied to the end of a cantilevered beam . however , as soon as the flexional force stops being applied to cuff 3 &# 39 ;, force is no longer applied to the lateral extension blades 4 , 4 &# 39 ;. by virtue of the elasticity of the plastic material itself of which the blades are made , as well as by virtue of their connection with respect to the direction of the flexional forces , the forces are approximately contained in the same plane as the blades . the blades thus act as beams of rectangular cross - section positioned such that one thus obtains a quadratic moment of inertia which is relatively substantial for the mass which the beams represent , and consequently , one thus obtains a very low deformation under flexion , and thus better elastic resistance ( greater rigidity ). it follows likewise that one achieves an excellent elastic return of the lateral blades 4 , 4 &# 39 ;, and consequently of the calf assembly 3 . another advantage of this type of construction according to the convention is obtained by virtue of the fact that the inventive apparatus makes it possible to compensate for the eventual permanent deformation of the bottom 32 &# 39 ; of the cuff 3 &# 39 ; which occurs when the cuff slides and rests against the top of the shell base 2 during repeated flexions . this ablility to compensate is made possible by virtue of the fact that the shell base 2 has an upper edge running along the top of the zone of the instep , which forms on each side of the foot a sort of cut - out 21 , 21 &# 39 ; having a &# 34 ; v &# 34 ; shape . this cut - out 21 allows , within acceptable human physiological limits , for the frontward angular deflection of the lateral elastic blades 4 , 4 &# 39 ; during flexional movements of the leg of the skier . fig3 illustrates an alternative ski boot 10 according to the invention , where only the shell base 2 and calf 3 have been shown , so as to not complicate the drawing . in this embodiment , lateral elastic blades 14 , 14 &# 39 ; ( only blade 14 will be mentioned , since the boot is shown in side view ) beginning at shell base 2 are cut by an oblong slot 142 defining , as a result , two tie beams 141 and 143 . the principle of operation is similar to that which has been previously described for fig1 and 2 . in this embodiment , blade 14 , which is still connected to cuff 3 &# 39 ; by attachment means 6 , which are known in themselves , differs from that which has been previously described by the structure of the blade 14 , whose flexional characteristics are fundamentally modified . the quadratic moment of inertia of the two tie beams 141 and 143 becomes less substantial , which allows for greater deformation . this makes it possible to employ materials having greater natural rigidity for the shell base 2 ( and consequently the vertical extensions ), while making it possible to preserve good elastic - return properties . fig4 illustrates a variant of the boot shown in fig3 . in this embodiment , the lateral elastic blade 24 of boot 20 comprises , between the non - parallel edges , on oblong slot 245 having the general shape of a parallelogram . furthermore , the lateral elastic blade comprises a base 241 of greater width than its head 242 , situated at a height substantially equal to that of the calf 3 of the boot 20 , while the slot 245 extends from the base 241 until the zone of the attachment point or pivot axis 6 . according to a complementary aspect of the invention , it is possible to vary the flexional characteristics of the lateral blade 24 , whose interior edges are spaced by virtue of a cursor 9 , which can be moved along the length of the slot 245 , as indicated by double arrow 11 . the operation of boot 20 remains similar to that of the boots previously described , besides having the supplemental possibility of modulating the flexion of the calf , depending upon the position occupied by cursor 9 in slot 245 . so as to maintain the selected position of the cursor , even when the boot is subjected to strong mechanical forces due to the irregularities of the terrain , the cursor may be provided with stop means or a rack in the slot itself provided with corresponding means such as teeth , serrated or embossed rollers , etc ., known in themselves , which have not been shown so as not to detract from the clarity of fig4 . fig5 and 6 illustrate another embodiment of a boot 30 according to the invention where the lateral elastic blade 34 is connected to cuff 3 &# 39 ; at its upper portion 342 by a releasable latching apparatus . by way of example , this apparatus can comprise a latch 12 journalled on an axis 13 positioned at the upper portion of the cuff 3 &# 39 ; at the height of the upper linkage point 16 . the latch is adapted to be secured to an attachment nipple attached to the lateral extension blade 34 . this attachment nipple 16 is constituted , in the case shown in the figure , by a flat - head rivet 17 , and extends to the exterior of the wall of cuff 3 &# 39 ; across an arcuate slot 15 , having its center of rotation on journal axis 5 of calf 3 . slot 15 has a length such that it allows for the angular deflection of the calf 3 , as a result of the walking gait when latch 12 is unhooked from the attachment nipple 16 , as shown by fine dashed lines 18 . boot 30 is thus provided with a first position of use , known as the &# 34 ; ski position &# 34 ;, with calf 3 having good flexional properties and good elastic - return properties , and a second use position , known as the &# 34 ; walking position &# 34 ;, with calf 3 being free to pivot around journal axis 5 . of course , it is possible to adapt this type of construction to the slotted lateral blade structure disclosed above , with or without a flexion - control cursor . fig7 , and 9 shown an embodiment of boot 40 according to the invention in which lateral elastic blade 33 extends substantially over the length of the calf , and comprises a slot provided substantially over its entire height . however , contrary to the embodiments described above , the upper point of linkage between the blade 44 and cuff 3 &# 39 ; is no longer at a fixed , predetermined position , but can , by virtue of an adjustable linkage apparatus 26 , assure attachment at different points between the lower or first pivot axis 5 and the uppermost pivot axis . it is adapted such that , from a purely mechanical point of view , it is possible to vary the position of the point of application of the force on the cantilevered beam at one of its ends . consequently , a variation of the flexional properties occurs , depending upon the position of the adjustable attachment apparatus 26 along the slot 441 of the blade 44 . depending upon the degree of flexion of the calf sought by the skier , the position of the adjustable attachment apparatus 26 along the calf 3 can be varied by means of plugs 19 . the plugs are adapted to have protrusions be embedded in recesses 22 provided for this purpose on the internal surface of the wall of cuff 3 &# 39 ; ( fig8 and 9 ). plugs 19 extend beyond the guide surface 23 which functions as a slide for the attachment apparatus . slide 23 has the shape of a rounded tail ( fig8 ) fitting within the hollow space within slot 441 having a corresponding cross - section , such that the device cannot leave the slot . to change the position of the attachment device 26 , the skier spaces the lateral elastic blades 44 from the wall of cuff 3 &# 39 ;, which makes plugs 19 leave their recesses 22 , and the skier slides the apparatus 26 ( along the direction of the double arrow 25 of fig9 ) to the height selected along blades 44 to make plugs 19 face the new recesses 22 situated higher or lower than the original position occupied by the attachment apparatus . the release of the lateral blades 44 towards the wall of the cuff 3 &# 39 ;, makes the plugs 19 penetrate the recesses 22 selected , thereby providing a new degree of flexibility to the calf . the invention is not limited only to the embodiments described above . thus , without going beyond the scope of the invention , it is possible to adapt the structural principles of the lateral elastic blades to ski boots having calves which are higher or lower , depending upon the tendencies and the requirements , as well as the skiing technique of the market in which it is to be used . fig1 illustrates another possible embodiment of a ski boot according to the invention . in this case , boot 50 is of the front - insertion type , wherein the lateral elastic blades 54 , 54 &# 39 ; likewise beginning at shell base 27 allow for the boot to be put on from the front , by virtue of an opening between the two convering portions 27 and 27 &# 39 ; at the top of the foot . the rear of the shell base is cut away around the zone at the front of the malleoli and the heel . in this zone , lateral blades 54 and 54 &# 39 ; extend upwardly along the general axis of calf 28 of the boot . calf 28 is made of a single element surrounding the bottom of the leg , and is connected to the shell base 27 by pivot axis 29 and to the upper portion 542 of the lateral elastic blades 54 and 54 &# 39 ;, forming an integral portion of the shell base by virtue of attachment means 33 and 33 &# 39 ;. the operation of such boot remains similar to that of the rear - insertion boot previously described . in effect , when calf 28 is closed in the position of use by virtue of locking means 31 schematically illustrated in the figure , the compact shell - calf assembly thus formed exhibits the functional properties previously described . furthermore , it is likewise possible to vary certain functional characteristics by the intercombination of various aspects of the embodiments described above . it is , furthermore , possible to provide slots and lateral elastic cams having edges which may or may not be parallel , and by using shell base materials , and cursors which are very different , depending upon the needs and / or industrial technological necessities .
a ski boot including a shell base with a sole on its bottom , and a calf , the calf being adapted to accommodate the leg of a skier and being pivotably mounted to the shell base along a first pivot axis . the shoe further includes at least one vertical extension extending from the shell base , the calf being pivotably secured along a second pivot axis on the extension .