Abstract:
The boot has a cuff ( 4 ) articulated to a shell ( 1 ) and means for retaining the cuff which counteract the rearward tilting of the cuff but give way when the force tilting the cuff exceeds a specific value. These means consist essentially of a ramp ( 12 ) which is integral with the shell or the other component of the boot and against which a bearing element ( 8 ) integral with the cuff bears. The ramp and the bearing element can push one another against the action of a spring ( 9 ). An escape position allows the cuff to tilt. Such a boot is intended to prevent tearing of the anterior cruciate ligament of the knee.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a ski boot comprising a first component, consisting essentially of a sole and an upper which encloses the foot and the malleolar region, and a second component consisting of a cuff which is articulated with respect to the upper so as to allow the cuff to move from front to rear and vice versa, and means for retaining the cuff which counteract the rearward tilting of the cuff but give way when the force tending to tilt the cuff exceeds a specific value. 
     The purpose of such a design is to protect the skier&#39;s knee, and more precisely the anterior cruciate ligament, when an excessive forward force is exerted on the tibia relative to the femur. It has been observed that tears of the anterior cruciate ligament due to an excessive force of this type have become much more widespread while other types of injury, in particular broken legs and ankles have become much less frequent because of the progress made with safety bindings. Excessive force on the anterior cruciate ligament occurs, in particular, when going over a bump, either when jumping, on landing, or when going down the bump again quickly. 
     U.S. Pat. No 5,107,608, the content of which is incorporated by reference, has already disclosed a boot equipped with a releasable retaining device intended to protect the anterior cruciate ligament in case of excessive force. This device comprises a latch in the form of a bent lever of the first class which is retained by a spring. In case of excessive force on the cuff, the spring will no longer be capable of retaining the latch, which will tilt and free the cuff. Such a device has the drawback that the skier cannot put it back into its initial position. It is also relatively bulky. 
     International Patent Application WO 97/22 271, the content of which is incorporated by reference, moreover discloses a ski boot which is also equipped with a retaining device which releases in case of excessive force on the cuff, rearward. This device consists of a sprung linkage, the articulation of which has enough play to allow the articulation pin some degree of longitudinal movement in the lower element of the linkage, and the elements of which abut, at a point lying some distance from the articulation pin, at the end of a travel smaller than the possible displacement of the pin. Once the elements of the linkage have come to abut and the spring of the linkage has already undergone some degree of compression, if the force on the cuff continues to increase then the elements of the linkage will pivot about their bearing point and the linkage will release if its articulation moves beyond alignment of the points of articulation of the linkage to the upper and to the cuff. This device has the advantage that the skier can put it back into its initial position, but it is relatively complex and bulky. 
     With the aim of protecting the anterior cruciate ligament of the knee, it has also been proposed to introduce a simple spring into a ski boot closure device, joining the rear cuff to the shell of a rear entry boot (European Patent No 0,410,136, the content of which is incorporated by reference). The corresponding published patent application deals with a safety device which opens the closure device of the boot, but the document does not give any examples of embodiments. 
     Also for a rear entry boot, European Patent Application No 0,514,762, the content of which is incorporated by reference, describes releasable protective devices which are mounted on the front cuff or on the shell and which free a strap or a closure cable of this cuff when pressure on the rear cuff exceeds a specific value. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to produce retaining means based on a different principle which can be implemented by simple and compact means. 
     The boot according to the invention is one wherein the retaining means consist essentially of a ramp which is integral with one of the components of the boot and against which a bearing element integral with the other component of the boot bears, the ramp and the bearing element being capable of pushing one another against the action of an elastic means so as to allow the cuff to tilt, said retaining means having an escape position allowing the cuff to tilt freely rearward. 
     In the case of a boot whose cuff is articulated to the upper in the malleolar region, the ramp may for example be formed on the back of the upper and interact with a retractable finger mounted on the cuff. 
     According to another embodiment, in which the boot is equipped with a stirrup which surrounds the heel and is articulated in the malleolar region above the cuff, the ramp may be formed at the upper end of a catch for retaining the stirrup and the bearing element may consist of the lower edge of the cuff, tilting the catch allowing it to escape from its stop and the stirrup and the cuff to tilt. 
     According to another embodiment, the ramp consists of the rounded end of a finger integral with the cuff, at the rear of this cuff and directed downward, and the bearing element consists of at least two balls which are retained laterally by opposing ramps that diverge upward and are held at the top of the latter by the thrust of a spring so as to oppose passage of the finger, as long as the spring has not been compressed so as to allow the balls to move apart and the finger to pass through. 
     The invention is also applicable to a boot whose cuff is articulated by its lower rear end to the upper. In this case, the ramp may be formed on a hook-shaped end of at least one lever mounted so as to pivot on at least one side of the upper, the bearing element consisting of a pin or the like which is integral with the cuff and whose pressure exerted on the ramp tends to make the lever pivot rearward until escaping from its hook. 
     In all cases, the safety retaining device can be reset by the user. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The appended drawing represents a few embodiments of the invention by way of example. 
     FIG. 1 is a cutaway of the rear part of a ski boot represented partially, according to a first embodiment. 
     FIG. 2 is a partial view of a second embodiment. 
     FIG. 3 is a cutaway of the rear part of a ski boot according to a third embodiment, in the resting position. 
     FIG. 4 represents the same boot in the rear release position. 
     FIG. 5 is a cutaway of the rear part of a boot according to a fourth embodiment. 
     FIGS. 6 and 7 represent, in axial section, the device for retaining the boot represented in FIG. 5, respectively in the retaining position and in the release position. 
     FIG. 8 represents the retaining device put in the inactive position for resting or walking. 
     FIG. 9 is a view in section on IX—IX FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The ski boot whose rear part is represented in FIG. 1 consists essentially of a shell  1  forming the upper  2  and the sole  3  of the boot, the upper  2  extending substantially over the malleolar region, and a cuff  4  articulated to the upper  2  at two opposite points  5  in the malleolar region. The rest of the boot can be produced in any known way, the upper and the cuff being generally provided with buckles for closure and tightening. The posterior lower edge of the cuff  4  has an extra thickness  6  in which a hole  7  is formed, the axis of which is directed substantially perpendicular to the surface of the upper  2 , in the longitudinal mid-plane of the boot. A retractable finger  8 , subjected to a thrust by a spring  9  bearing on a screw-threaded plug  10 , that is to say a screw allowing the precompression of the spring  9  to be modified, is mounted in this hole  7 . The retractable finger  8  bears against the bottom of a recess  11  formed in the thickness of the upper  2 . The recess  11  is bounded at the bottom by a first ramp  12  and at the top by a second ramp  13 . In the position represented in the drawing, the cuff is slightly inclined forward. When the cuff tries to straighten up, the finger  8  comes to bear against the bottom of the ramp  12 . When a force on the leg tends to tilt the cuff  4  rearward, that is to say in the clockwise direction in the drawing, the retractable finger  8  slides along the ramp  12  and compresses the spring  9 . When the force is sufficient, the retractable finger  8  reaches the end of the ramp  12 , where it escapes from the housing  11  by sliding along an escape ramp  14  formed on the upper  2 . This ramp  14  further makes it possible to return the cuff  4  to the position represented in the drawing. 
     The upper ramp  13  makes it possible to control a forward tilting force. 
     For the sake of simplicity, the shell, the upper and the cuff of the boot will be denoted by the same references in the embodiments below. 
     In the embodiment represented in FIG. 2, the cuff  14  is articulated by the rear, at its lowermost point, to the upper  2  about an axle  15 . On at least one side of the boot, the cuff  4  is provided with a stud or pin  16  on which a lever  17  comes to bear which is mounted so as to pivot on the upper  2  about an axle  18  and which is urged to rotate forward, that is to say in the counterclockwise direction, by a spring  19  schematically represented by a spiral spring. The end  20  of the lever  17  is in the form of a hook which bears on the pin  16  via an oblique ramp  21  rising in the direction of the lower anterior edge of the cuff  4 . In other words, the slope of this ramp is such that when the cuff  4  is urged to rotate rearward, the force exerted by the pin  16  on the ramp is substantially perpendicular to this ramp. It can be resolved into two forces, one of which tends to pivot the lever  17  rearward against the action of the spring  19 . The pin  16  slides over the ramp  21  and, when the force is sufficient, it escapes from the hook  20  and the cuff  4  can tilt rearward following the movement of the leg. 
     The boot according to the embodiment represented in FIGS. 3 and 4 comprises, in addition to the cuff  4  articulated at a point  5  lying in the lower malleolar region, a stirrup  22  which encloses the heel and is articulated at two opposite points  23  below the articulation  5 . Such a stirrup is known in particular from the boot described in U.S. Pat. No. 4 839 973, the content of which is incorporated by reference. A catch  24  is articulated to this stirrup  22  about a horizontal axle  25 . This catch  24  bears by its tip  26  on a support surface  27  of the upper  2  forming a stop. The catch  24  is held in this position by a spring  28 . The end of the upper arm of the catch  24  has a ramp  29  descending rearward relative to the boot. At the rear, the cuff  4  has a continuation  30  extended downward in the direction of the ramp  29 . The cuff  4  is held away from the stirrup  22  by at least one spring  31  working in compression between the cuff  4  and the stirrup  22 . 
     When the cuff  4  is urged to tilt rearward, its part  30  abuts on the ramp  29 . This pressure tends to tilt the catch  24  so as to move its tip away from the upper  2 . When the pressure exerted by the cuff  4  reaches a certain value, the catch  24  escapes from its stop  27  (FIG.  4 ), thus allowing the stirrup  22  and the cuff  4  to tilt rearward. 
     It should be emphasized that the main spring is the spring  31 , the spring  28  being no more than a return spring for the catch. The force of this spring  28  is such that the catch  24  can be easily pressed down by hand so as to make it possible to free the cuff  4  and return it to the resting or walking position. 
     As in the first embodiment, the precompression of the spring  31  could be adjusted using a screw-threaded plug. 
     The boot retaining device represented in FIGS. 5 to  9  also uses the ramp principle. The boot is once more a boot with a cuff  4  articulated at  5  in the malleolar region. The ramp of the retaining device is formed by the rounded end  32 , for example in the form of a portion of a sphere, of a finger  33  with at least approximately rectangular cross section which is retained axially in an extra thickness  34  of the rear lower edge of the cuff  4  and whose axis is oriented approximately vertically. This finger  33  is engaged in a hole  35  of an extra thickness  36  of the upper  2  in which a recess  37  containing a spring  38  is formed. The upper part of this recess  37  has a frustoconically shaped taper  39 . This recess contains two diametrically opposite balls  40  rotationally retained about an axis of the recess by grooves (not shown). These balls  40  bear on a metal washer  41 , itself bearing on the precompressed spring  38 . In the resting position (FIG.  6 ), the balls  40  are in abutment against the upper front of the recess  37  and prevent the finger  33  from passing freely between the balls, when the finger is oriented as represented in FIG.  6 . 
     In this position of the finger  33 , when the cuff  4  is strongly urged to tilt rearward, the finger  33  pushes the balls  40  downward and compresses the spring  38 . As they move down, the balls  40  move away from one another because of the conicity of the part  39 . At a given moment, the balls will be far enough away from one another to allow the finger  33  to pass through and correspondingly allow the cuff  4  to tilt. 
     If the finger  33  is rotated about its axis, for example through 90°, as represented in FIG. 8, the finger  33  can pass freely and effortlessly between the balls  40 . A relaxation or walking position is thus obtained. In order for it to be rotated, the finger  33  is quite simply provided with a knurled head  42  having two positioning markers. 
     The bottom of the recess  37  could be provided with a screw-threaded plug for adjusting the precompression of the spring  38 . 
     Although illustrative embodiments of the invention have been shown and described, a wide range of modification, change and substitution is contemplated in the foregoing disclosure and in some instances, some features of the present invention may be employed without a corresponding use of the other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.