System comprising a cross country ski boot and a device to hold the front of the boot on a ski. The holding device (3) holds the front part (17a) of the sole (17) of the boot (1) flat on the upper part of the ski, in a holding zone extending between the front end of the sole and a rear limit (P, P1) thereof, located substantially under the metatarsal-phalangeal joint (A) of the skier's foot, and the boot (1) is shaped so that in the resting position the rear part (17b) of the sole is released obliquely from the upper part of the ski, i.e., the heel (17c) of the boot is normally raised.

FIELD OF THE INVENTION 
This invention pertains to a system comprised of a cross country ski boot 
and a device to retain the front of this boot on a ski. 
BACKGROUND OF THE INVENTION 
In cross country skiing, it has been noted that the thrust force of the leg 
on the foot is more intense when the heel is in a raised relative position 
above the ski, a position in which the foot applies pressure especially on 
the area where the metatarsal and the phalanges meet, which is called the 
metatarsal-phalangeal joint. 
PRIOR ART 
To facilitate the raising of the heel, conventional devices for holding the 
front of a boot on a cross country ski are most often designed to allow 
the highest possible degree of freedom for the flexion of the boot, and, 
for this purpose, they comprise, on the one hand, means allowing the boot 
to pivot around its front end and, on the other hand, elastic means 
intended to facilitate the raising of the heel. For example, Austrian 
Patent No. 346,743 and Finnish Patent No. FI 55 936 pertain to devices of 
this type. Moreover, independently of holding devices, ski boots are known 
which are pre-deformed in the forward movement direction, in which the 
front part of the sole is inclined with respect to its rear part, forming 
an obtuse angle opening upward, with the heel located in elevated 
position, when the front part of the sole extends horizontally (German 
Patent No. 2,752,491). However, in the case of both the aforementioned 
holding devices and pre-deformed boots, the foot is pressed forward 
successively from the metatarsal-phalangeal joint to the end of the toes 
at the end of the pressing and, as such, the transmission of the force of 
the leg is retarded appreciably. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide a boot-binding system comprising 
a holding device and a pre-deformed boot which, when combined, place the 
skier's foot on the ski in a position of active pressure repetition, a 
position in which the foot bears on the entire front surface of the 
plantar arch. 
For this purpose, this system comprised of a cross country ski and a device 
for holding the front of the boot on a ski is characterized in that the 
holding device keeps the front part of the sole of the boot flat on the 
upper part of the ski in a holding zone extending between the front end of 
the sole and a rear limit thereof located substantially under the 
metatarsal-phalangeal joint area of the skier's foot, and the boot is 
shaped so that, at rest, i.e., when the skier's foot is not engaged in the 
boot held on the ski, or when the skier is not applying his foot in at 
least the vertical direction, the rear part of the sole, extending from 
the rear limit of the holding zone of the front part, is disengaged 
obliquely from the top of the ski, i.e., it is inclined upwards and to the 
rear so that the heel of the boot is normally raised a certain distance 
above the ski.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The boot-binding system according to the invention which is shown in FIGS. 
1 and 2 is intended to hold a cross country ski boot 1 on a ski 2 by means 
of a holding device 3. 
In the embodiment illustrated in FIGS. 1 and 2, the holding device is of 
the elastic locking type and comprises two elements attached to the upper 
surface of the ski, namely, a front stop 4 and a rear fastening and 
holding block 5. The front stop 4 comprises a collet 6 having an internal 
longitudinal housing 7 in which a locking tappet 8 is slidably mounted, 
projecting towards the rear. This locking tappet 8 is biased towards the 
rear by a spring 9 placed in a longitudinal housing 7. The locking tapper 
8 can be pushed forward using a lever 11 articulated on the collet 6 about 
a horizontal and transverse axis 12 and coupled to the locking tappet 8 
through the intermediary of a transverse pin 13. 
The locking tappet 8 engages in a corresponding depression 14 in the front 
end of the boot 1. 
The rear fastening block 5 which is attached to the ski by screws 15 has, 
in its upper and front part, an edge 5a projecting forward, which engages 
in a corresponding groove 16 provided in the sole 17 of the boot 1. This 
sole 17 comprises a front holding part 17a, which is thicker than the rest 
of the sole comprises of a relatively thin intermediary part 17b located 
under the plantar arch and connected to the heel 17c. 
It will be understood from the above description that the front part 17a of 
the sole 17 is immobilized flat on the upper part of the ski 2 between the 
front stop 4 and the rear fastening block 5. Moreover, the boot 1 is 
shaped so that at rest, i.e., when the skier's foot is not engaged in the 
boot, as shown in FIGS. 1 and 2, the rear part of the sole, comprising the 
relatively thin intermediary part 17b located under the plantar arch and 
the heel 17c, is disengaged obliquely from the upper part of the ski, 
i.e., it is inclined upward and towards the rear. Consequently, at rest, 
the heel 17c of the boot 1 is normally raised a certain distance above the 
ski. 
The relatively thick front part 17a of the sole 17 of the boot 1 extends 
over a distance in the longitudinal direction so that its rear limit 
defined by the vertical and transverse plane P passing substantially 
through the end of the edge 5a of the rear fastening block 5 or the bottom 
of the groove, is substantially located under the zone where the phalanges 
and the metatarsals of the skier's foot engaged in the boot meet, with the 
foot being shown in mixed lines in FIG. 2. In other words, the front 
holding part 17a of the sole 17 extends towards the rear up to a rear 
limit located under the metatarsal-phalangeal joint area indicated by A in 
FIG. 2, and this rear limit is constituted by plane P which is 
perpendicular to the longitudinal axis of the ski. 
Because only the front part 17a of the sole 17 is held firmly, flat against 
the ski, all the rest of the sole and consequently the boot can bend 
freely, allowing the foot to be rolled back and forth during cross country 
skiing. 
The ski boot 1 can be pre-formed using any appropriate means or process, 
for example, by molding the sole 17, and it can comprise any stiffening 
element and/or reinforcement element which can elastically withstand the 
flexion of the foot. FIG. 3 illustrates a stiffening element 18 in the 
shape of a blade which is embedded in the sole 17 in the front holding 
part 17a as well as in the intermediary part 17b located under the plantar 
arch. 
FIG. 4 illustrates the manner in which the elastic locking front stop 4 
makes it possible to release the boot in case the skier falls forward or 
in the case of dangerous stress applied to the boot substantially in the 
same direction. In this embodiment, the fastening block 5 has an anterior 
frontal surface 5b which is inclined from bottom to top and back to front 
and with this inclined surface 5b cooperates a posterior frontal surface 
17d having the same slope and constituting the rear limit of the front 
holding part 17a of the sole 17. Consequently, when the skier falls 
forward, for example, the boot pivots in the clockwise direction around 
the end of the locking tappet 8, raising away from the rear fastening 
block 5, this raising being made possible by the relative sliding of the 
posterior frontal surface 17d of the sole on the anterior frontal surface 
5b of the fastening block 5 against the effects of the thrust of the 
holding device 3. After the front part 17a of the sole is raised 
sufficiently, the latter can escape completely from the holding device 3 
comprised of the front stop 4 and the rear fastening block 5. 
FIGS. 1 to 4 illustrate the application of the invention to a ski having a 
flat upper surface. FIGS. 5 to 7 illustrate an adaptation of the invention 
to a ski which has a longitudinal guiding and centering rib 19 on its 
upper surface 2a which can form a unit with the ski or can be comprised of 
an element mounted thereon. In this case, the front stop 4 ensuring the 
elastic locking can be mounted on an upper surface 19a of the rib 19, 
which preferably is of right trapezoidal section as shown in FIG. 6. To 
constitute the holding device 3, two rear fastening blocks 21 which are 
respectively attached to the upper surface 2a of the ski 2 on both sides 
of the central guide rib 19 cooperate with this front stop 4. These 
fastening blocks 21 can, in vertical cross section, have the shape of a 
parallelogram defining, for each one, a front transverse wall 21a inclined 
from bottom to top and back to front, for holding the front part 17a of 
the sole of the boot. In this embodiment, front part 17a has a 
longitudinal groove in its central part having substantially the same 
shape as the central guide rib 19 and fitting over the latter. 
The two fastening blocks 21 are attached to the ski by screws 22 so that 
their front inclined transverse surfaces 21a, which are in contact with 
the rear limit surface 17d of the front part 17a of the sole 17, are 
located approximately under the metatarsal-phalangeal joint A of the 
skier's foot. 
The upper horizontal surfaces of the two rear fastening blocks 21 can be 
flush with the upper horizontal surface 19a of the guide rib 19, as shown 
in FIG. 5, or they can be located at a higher or lower level. 
In all the embodiments described above, the zone of flexion of the boot 
extends in a direction perpendicular to the longitudinal axis of the ski. 
FIGS. 8 and 9 shown different embodiments in which the flexion zone of the 
boot is inclined with respect to the longitudinal axis of the ski and 
substantially follows the natural axis for the flexion of the 
metatarsal-phalangeal joint A of the skier's foot. In FIG. 8, which 
corresponds to the case of a ski 2 having a flat upper surface, the 
fastening block 5 ends towards the front with an upper front edge 5a which 
extends following a plane P1 inclined with respect to the longitudinal 
axis of the ski and which, in plan view, is located substantially under 
the axis of the metatarsal-phalangeal joint A. In other words, the plane 
P1 containing the edge 5a is inclined from the rear to the front and the 
outside to the inside of the ski. The front edge 5a of the rear fastening 
block 5 can be continuous or can have a depression 5c in this central 
part, which is open towards the front and in which a boss provided in the 
frontal surface 17d, forming the rear limit of the front holding part 17a 
of the sole 17, engages. 
In the embodiment shown in FIG. 9, the chosen device is adapted to a ski 
with a longitudinal guiding and centering rib 19 as illustrated in FIGS. 5 
to 7. The two rear fastening blocks 23, 24, which are attached to the 
upper surface 2a of the ski on both sides of the guide rib 19, end in 
anterior frontal surfaces 23a, 24a, inclined from bottom to top and from 
back to front, with these two surfaces being coplanar and defining a zone 
of flexion for the boot inclined with respect to the longitudinal axis of 
the ski and substantially corresponding to the metatarsal-phalangeal joint 
A of the foot. Because of this incline of the zone of flexion, the 
anterior frontal surface 23a of the rear fastening block 23 located on the 
inner side of the ski is located slightly in front of the anterior frontal 
surface 24a of the rear anchoring block 24 located on the outer side of 
the ski. 
In the embodiment of the invention shown in FIG. 10, the holding device 3 
is of the laterial release type to allow the boot to be released in case 
the skier falls or dangerous torsion stress is applied at the level of the 
boot. This holding device comprises a plate 25 constituting a seating, 
which is mounted on the ski. In its rear part, this seating 25 has two 
vertical wings 26 and 27 which extend upward from the edges of the seating 
and which overhang the edges of the ski 2. The front part 17a of the sole 
17 of the boot is held on the seating 25 of the holding device using a 
U-shaped spring 28 which is open towards the rear and whose ends 28a, 28b, 
cambered in an appropriate manner, are engaged in holes pierced 
respectively in the upper parts of the wings 26 and 27 in order to 
constitute pivoting axes for the spring 28. Wing 26 is the inside wing, 
i.e., that which faces the other ski (not shown), while the other wing 27 
is located on the outside of the ski. The highest point of the spring 28, 
i.e., its central front part, crosses a locking lever 29 mounted in a 
pivoting manner around a horizontal and transverse axis 31, on a cap 32 
extending the seating 25 forward. 
When the boot 1 is held on the ski 2, the two branches 28c and 28d of the 
spring 28 which extend towards the rear are held pressed on the upper 
surface of the sole 17, on both sides of the upper of the boot 1. 
Moreover, the wings 26, 27 and the branches 28c, 28d extend to the rear 
substantially up to plane P1 defined above, which contains the 
metatarsal-phalangeal joint. 
The seating 25 of the holding device 3 is mounted in a rotating manner on 
the ski 2, about an axis 33 perpendicular to the ski, and the front part 
of the seating 25 is held in locked position using an elastic locking 
device 34 of any known type, fastened to the ski. This device thus allows 
the lateral release of the binding in case of torsion exerted on the leg, 
as shown schematically by the arrows in FIG. 10. 
The invention is not limited to the embodiments described above. The 
holding zone for the front part 17a of the sole 17 up to a rear limit, the 
maximum of which can be located at the level of the metatarsal-phalangeal 
joint area A of the skier's foot as described above but also at a distance 
smaller than that between A and the front end of the sole.