in the first embodiment , the body of the binding consists of a plate 1 having a thickness of about 2 cm , but in any event sufficient to make it possible for two recesses 2 and 3 of rectangular parallelepipedal shape , extending longitudinally one after the other over the majority of the length of the plate 1 and separated by a cut - out wall 4 , to be formed in it . a thin plate 5 , having a rectangular cut - out 6 whose width is slightly less than the width of the recesses 2 and 3 , is fixed on the plate 1 so as to form a rail with a t - shaped profile . such a rail could , of course , have been machined in the plate 1 , but in this case it would have had to have opened at least at one of the ends of the plate 1 . the plate 1 is provided with four holes 7 for fastening it to a ski . the plate 1 also has , at one of its ends , a cylindrical axial hole 8 opening into the part 2 of the rail ( fig2 ). two sliding pieces of rectangular shape 9 and 10 are mounted in the part 2 of the rail . the piece 10 consists of a first retaining piece fitted with a jaw 11 rising above the plate 1 . the piece 10 is set back in its horizontal part so as to form a hollow 12 in which a piston 13 , having two parallel cylindrical indentations such as the indentation 14 ( fig3 ), is mounted so as to slide , which indentations respectively accommodate two identical parallel springs 15 and 16 working in compression between the bottom of the hollow of the piece 12 and the piston 13 . the piece 9 has a threaded axial hole 17 whose axis lies in the vertical plane of symmetry of the plate 1 . this hole 17 engages on a screw 18 which is accessible through the hole 8 in the plate and bears on the piston 13 . a second piece 19 , also sliding in the rail and of rectangular shape , from which a pair of parallel supports 20 and 21 facing the jaw 11 rise , is mounted in the other part 3 of the rail . the piece 19 also has two threaded holes parallel to the axis of the rail , such as the hole 22 ( fig3 ). the threaded ends of two rods 23 and 24 , provided with a head 25 by which these rods bear on the piece 9 , are respectively screwed into these holes . it can be seen that the sliding piece 9 , which tends to be pushed back by the piston 13 under the thrust of the springs 15 and 16 , is actually retained by the rods 23 and 24 , which are themselves retained by the sliding piece 19 butting against the intermediate wall 4 of the rail . for the same reason , the sliding piece 10 is held bearing against the other side of th is wall 4 . between them , the jaw 11 and the supports 20 and 21 define a transverse recess 26 having a notch - shaped profile ( fig2 and 3 ) widening in its upper part . on the side next to the jaw 11 , this profile has an oblique side 27 inclined in the direction of the supports 20 and 21 , while the opposite side 28 of the notch is rounded . a heart - shaped cam 29 , suspended in its upper part about a transverse pin 30 carried by the supports 20 and 2 1 , is mounted between the supports 20 and 21 . when the notch 26 is free , the cam 29 occupies , under the effect of its own weight and optionally an auxiliary spring , the position 29 ′ represented by dots and dashes , that is to say it penetrates into the notch 26 . the cam 29 penetrates into the notch 26 by a cylindrical convex face 31 . the plate 1 is also provided at one of its ends with a lever 32 which is articulated , about a pin 33 transverse to the plate , in a notch 34 of the plate . a tie 36 whose bent end 37 is located , at rest , slightly in front of the cam 29 , at the border of the notch 26 , is attached to this lever 32 at a point 35 . in this position , the lever 32 is held butting against the top of the plate 1 by a spring ( not shown ), for example a torsion spring mounted about the pin 33 . this binding is intended to hold a boot whose sole 42 is fitted with a cylindrical transverse metal bar 38 in a central hollow 39 of the sole by means of a metal stirrup . the diameter of the bar 38 is such that the lower part of the profile of the recess 26 has a width substantially equal to the diameter of the bar 38 . this width is substantially constant in the lower part of the notch 26 and increases in the upper part . before the boot is fitted in the binding , the cam 29 occupies the position 29 ′. when the boot is being fitted in the binding , the bar 38 encounters the cam 29 and pushes it away without effort . the cam 29 then returns to bear against the bar 38 , as shown . in this position , a wrenching force directed upward exerted on the bar 38 tends to move the cam 29 with it by friction and consequently reduce the width of the notch 26 owing to the eccentricity of the working face 31 of the cam . the bar 38 is consequently retained in the notch 26 . the slope at the point of contact between the cam 29 and the bar 38 is great enough to lock the cam , but nevertheless not strong enough for this locking to prevent the cam 29 from being moved away from the bar 38 with ease by the tie 36 by means of an action on the lever 32 , as indicated by the arrow , fig2 . this boot - removal action takes place without stressing the springs 15 and 16 . in the event of falling , that is to say a force on the bar 38 exceeding a certain value , the bar moves the jaw 11 and the cam 29 apart from one another by compressing the springs 15 and 16 , and disengages from the notch 26 . this can occur both owing to pulling forces lying in a plane passing through the axis of the bar and owing to a torque tending to rotate the bar in a horizontal plane . since the system is in principle balanced , the two sliding pieces 10 and 19 are both moved away from the rib 4 and the piece 19 moves the piece 9 along with it . the precompression of the springs 15 and 16 , that is to say the hardness upon release of the binding , can be adjusted by means of the screw 18 . the setting is displayed by an index 40 which , in the example represented , consists of a notch in the piston 13 , this notch being visible through a slot 41 in the piece 10 . according to an alternative embodiment , the pieces 9 and 19 could be fixed to the plate 1 , only the jaw 11 being mobile in this case . as represented , the boot - release lever 32 is located to the rear of the plate , that is to say behind the heel of the boot . nevertheless , all this could be reversed of course , with the boot - release lever lying in front of the plate , and the position of the jaw 11 and of the cam 29 being altered accordingly . the second embodiment , represented in fig5 can be regarded as a variant of the first embodiment . in this case , the transverse recess consists of two notches 50 and 51 formed by the bent lateral parts 52 , 53 and 54 , 55 of two plates 56 and 57 equivalent to the pieces 10 and 19 of the first embodiment . two cams 58 and 59 , similar to the cam 29 of the first embodiment , are mounted on the bent parts 52 and 53 . the cams are articulated about an axis a and are connected to one another by a link 60 crossing the bent parts 52 and 53 through holes located at the bottom of the bent parts 52 and 53 . this link 60 is also used as the rotation pin of a boot - release lever 61 acted on by a torsion spring tending to hold the boot - release lever in the lowered position as represented . on the side next to the bent part 53 , the link 60 is bent two times and its end is engaged in a slit 62 of the cam 59 . the spring of the boot - release lever 61 hence tends to hold the cam 59 lowered , as represented . the other cam 58 has a slit similar to the slit 62 , and a finger which is secured to the lever 61 and fulfils the same role as the bent end of the link 60 , is engaged in this slit . the cams are thus mechanically connected . in order to remove the boot from the binding , the lever 61 is lifted , the effect of which is to pivot the cams downward and open the notches 50 and 51 , releasing the bar 38 which , in this case , is retained at two locations close to its ends . 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 .
the assembly consists of a boot whose sole is fitted with a transverse bar which engages between a bearing piece and a self - locking cam . the bearing piece is secured to a sliding piece and the cam is mounted on a piece which preferably slides . these two pieces are mounted in a rail while being drawn toward one another by springs . the bar can be disengaged by means of a lever . this binding releases both in the event of falling forward or backward and in response to twisting .