Safety binding for snowboards

A safety binding for snowboards has a base plate (1) on which the snowboarder's boot is fastened. This base plate (1) is fixed in its turning position by a spring plunger (8) and a stop pin (7), but can be turned out of this position when the torque acting on it exceeds a value preset by the initial tension of the spring (10) of the spring plunger (8). The base plate (1) is rigidly connected with the snowboard by means of a turning plate (2) and is not detached from the snowboard even in the case of a "turning release".

FIELD OF THE INVENTION 
The invention relates to a safety binding for snowboards. 
BACKGROUND OF THE INVENTION 
A safety binding of this kind is disclosed in U.S. Pat. No. 5,044,654. This 
safety binding has an elongated binding plate that is broadened in its 
center where it has a circular opening going through the plate. This 
binding plate is secured to the snowboard boot by means of retaining clips 
(front and heel clips). A central bolt fastened to the snowboard projects 
through the central opening during normal use and centers the binding 
plate. The binding plate is provided with two spring-loaded locking bolts, 
which are pushed into the opening of the binding plate where they engage 
recesses of the central bolt, thereby fixing the binding plate in position 
relative to the central bolt and thus relative to the snowboard. The 
pressure of the spring-loaded bolts is adjustable. "Excessive" forces, the 
limiting value of which is adjustable through the spring force, arising 
between the binding plate and the central fastening bolt will cause the 
locking bolts to be forced out of the central opening of the binding plate 
so that the entire binding plate will detach itself from the snowboard. 
Other safety bindings for snowboards are disclosed in the following patent 
publications (GM=Gebrauchsmuster=utility model patent): 
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US 4,728,116 FR 2 233 081 EP 0 397 969 B1 
EP 0 432 588 A2 
EP 0 373 548 A2 
EP 0 42 588 A2 
EP 0 373 548 A2 
EP 0 350 411 A2 
DE-GM 92 16 831 
DE-GM 92 15 933 
DE-GM 92 00 088 
DE-GM 92 02 987 
DE-GM 90 14 833 
DE-GM 89 08 061 
DE-GM 89 02 125 
DE-GM 88 15 236 
DE-GM 87 16 654 
DE 39 25 164 C2 
DE 38 41 912 C2 
DE 40 34 099 A1 
DE 40 18 276 A1 
DE 39 16 233 A1 
DE 39 10 156 A1 
DE 38 38 324 A1 
DE 38 09 194 A1 
______________________________________ 
The common thing about all snowboard bindings known up to now is that the 
snowboarder's foot under excessive stress is completely separated from the 
snowboard if the binding is released. This concept derived from skiing 
causes some problems with snowboards, however. Since the snowboarder's 
feet are fastened to a single board, it is not sufficient to separate only 
the overstressed foot from the board due to the risk that the other foot 
will be overstressed because of the longer lever arm of the board then in 
action, and it is not guaranteed that the second binding will also be 
released in due time. There is thus a serious risk of injury for the 
snowboarder when only one of the two binding components is released. To 
solve this problem, the aforementioned documents, 
______________________________________ 
DE 39 10 156 A1, 
DE 39 16 233 A1, 
DE 40 34 099 A1, 
DE 38 41 912 C2, 
DE 39 25 164 C2, 
DE-GM 90 14 833, 
DE-GM 92 02 987, 
DE-GM 92 00 088, 
DE-GM 92 15 933, 
______________________________________ 
EP 0 350 411 A2 and EP 0 97969 B1, have already suggested coupling the two 
release bindings with each other by means of cables, hydraulic lines or 
rods so that a release of one of the bindings will automatically lead to a 
release of the other, even if the connection forces between boot and board 
at the latter binding have not yet reached the pre-set release value. The 
consequential problem here, however, is how to prevent the board, when 
separated from its user, from injuring its user or other people on the 
slope. There is the risk with the check strap used earlier in skiing that 
the board will injure its user in a fall, the injury risk being greater 
with the snowboard than with skis because the snowboard is heavier. A 
transition was thus also made in skiing to the so-called ski stoppers, 
that is, braking claws that automatically go into action to hinder the ski 
from moving off by itself over considerable distances. Applying this 
principle of the ski stoppers to snowboards was suggested in DE 40 18 276, 
but it did not prove to be satisfactory in practice. Because of its 
greater sliding surface (compared to that of a ski), the snowboard is not 
reliably stopped thereby, particularly on hard or icy ski runs. In this 
case, other people on the ski runs are subject to a considerable risk of 
injury from uncontrolled snowboards racing down the slope. It is 
unacceptable for a snowboarder to be protected from injury in an accident 
caused by a safety binding while the system allows others "not involved" 
to be seriously injured or even killed. 
A further problem with all of the aforementioned safety bindings for 
snowboards is that the release forces for all release devices, as in 
twisting of the foot around the longitudinal axis of the shin bone 
(turning falls) and tipping of the foot and/or the shin bone in relation 
to an axis perpendicular to the surface of the snowboard (frontal or 
transverse falls), are equally great. If the release force is set at the 
lowest value that will safely avoid injury to the snowboarder in any fall 
possible, there can be an unwanted release with a load applied in other 
directions and thus a greater risk of injury. 
OBJECTS OF THE INVENTION 
These problems are solved or at least alleviated with the present 
invention. The object of the invention is thus to improve the snowboard 
binding of the type mentioned in the beginning so as to avoid injuries to 
its user because the board is secured to the user's feet through a 
"release" of the binding without causing any additional risk of injury to 
the users or to uninvolved persons nearby. 
SUMMARY OF THE INVENTION 
The invention is based on the knowledge that more than 90% of all foot and 
leg injuries in snowboarding occur in so-called twisting falls in which a 
torsional force arises from the boot, over the ankle joint and shin bone, 
and up to the knee joint, the concept of torsion relating here to the 
longitudinal axis of the shin bone. Falls in which the shin bone is tipped 
relative to an axis that is vertical to the surface of the snowboard, on 
the other hand, are not critical for the most part. If the shin bone is 
tipped transverse to the direction of travel, forces arising are only 
minimal because the board is set on edge. Likewise, if the shin bone is 
tipped forward or backward in the longitudinal direction of the snowboard, 
the critical limiting value of the loading force is reached only in 
extremely rare cases for three reasons. Firstly, the human ankle bone can 
be bent to a relatively high degree without a risk of injury; secondly, 
ordinary snowboard boots and the currently used bindings are quite 
flexible in this tipping direction; thirdly, the board can be set on edge 
because of the relatively short lever arm between the tip or the end of 
the snowboard and the binding nearest thereto, the forces are thus 
absorbed. Consideration should also be given in this respect to the fact 
that in the case of a frontal fall (relative to the direction of travel), 
for example, if the tip of the snowboard runs into an obstacle, for 
example, the forward leg of the snowboarder is put under stress in this 
tipping direction, while the rearward leg exercises a tensile force on the 
rear end of the board, so that as a whole, the board "gives" and it is set 
on edge toward the front, which causes a decrease in the forces acting on 
the forward leg. Based on this knowledge, the invention suggests in 
principle that only a twisting release be provided, maintaining rigid 
fixing in position of the boot in all other directions a force acts, the 
boot remaining fixed on the board even when there is a twisting release at 
the binding. The boot can thus be turned only relative to the board.

DETAILED DESCRIPTION 
In the example embodiment illustrated in FIGS. 1 and 2, the safety binding 
has a base plate 1 having the approximate configuration of a rhombus with 
rounded corners in the plan view and a central round opening engaged by a 
turning plate 2, which overlaps the base plate with a projecting 
circumferential edge 3. The turning plate 2 has a plurality of oblong 
holes 4, which are in a spaced arrangement and through which fastening 
screws 17 (FIG. 2) pass for fastening the binding to the snowboard. Fixed 
in place with fastening screws 6 at both ends of the base plate are 
mounting blocks 5 on which are fastened the usual front and heel clips 20 
that overlap the sole of the snowboard boot (not shown) and thus fix the 
boot in place relative to the binding, the boot lying against the mounting 
blocks 5 in the front and heel areas. To this extent, the binding 
described thus far corresponds to the snowboard binding described in DE 42 
19 036 A1. This binding now becomes a safety binding in that the base 
plate 1 can be turned relative to the snowboard and relative to the 
turning plate 2 when a preset torque is exceeded. At least one of the 
mounting blocks 5 is provided for this purpose with a stop pin 7, which 
projects from the associated mounting block 5 in the direction of the 
center of circle of the turning plate 2 and has a rounded tip. This stop 
pin 7 cooperates with a spring plunger 8 with a moving head 9 that is 
forced in the direction of stop pin 7 by a compression spring 10 arranged 
inside the spring plunger 8. The head 9 has a stop recess 11 which is 
engaged by the stop pin 7. In the plan view of FIG. 1, this stop recess 
has an approximately parabolic or hyperbolic curvature. However, it can 
also have another shape, such as a v-shaped groove, or have the shape of a 
circular arc or the like; it is only necessary to ensure that the shapes 
of the stop pin and the stop recess are matched to each other so that the 
head 9 is displaced against the force of the spring 10 when forces 
exceeding a value preset by the force of the spring 10 come into play 
between the stop pin 7 and the head 9. 
The force of the spring 10 can be changed by an adjusting screw 12 arranged 
on the end of the spring plunger 8 opposite the head 9 whereby the initial 
tension of the spring 10 is changed. 
In the normal assembly position, the spring plunger 8 is rigidly fixed in 
place on the turning plate 2, which is in turn rigidly fixed in place on 
the snowboard. With snowboard bindings, however, it is desirable to be 
able to adjust the binding angle, that is, the angle between the 
longitudinal axis of the binding and the longitudinal axis of the 
snowboard, which means that the angle between the longitudinal axis of the 
spring plunger 8 and the longitudinal axis of the snowboard must be 
adjusted relative to the non-twisting turning plate 2 so that the spring 
plunger, as shown in FIG. 1, is oriented on the longitudinal axis of the 
binding. 
A turning disc 13 lying between the top side of the turning plate 2 and the 
spring plunger 8 is provided for this purpose, this disc having a central 
opening that is in alignment with a central opening of the turning plate 
2. These two openings are tapered outwardly so that the turning disc 13 
can be connected to the turning plate 2 by a countersunk anchor 15 and a 
countersunk screw 16. The opposing surfaces of the aforementioned openings 
and of the heads of the anchors 15 and screws 16 can be roughened or 
knurled to provide improved slip protection with respect to torques. The 
bottom side of the turning disc 13 and/or the opposing top side of the 
turning plate 2 can also be roughened or provided with any other friction 
surface (not shown) to provide the aforementioned slip protection. 
The spring plunger 8 is provided on the side opposing the turning disc 13 
with an assembly disc 13' having screw holes 14 (FIG. 1). The turning disc 
13 has threaded holes associated with these screw holes 14 so that the 
assembly disc 13' and the turning disc 13 can be rigidly connected with 
one another. 
On its bottom side opposite the snowboard, the turning plate 2 has a 
friction-hindering surface 18. In the area where it cooperates with the 
turning plate 2 and its projecting edge 3, the central opening of the 
plate 1 is provided with a slip surface 19 that is designed here as a slip 
ring with a u-shaped cross-section made of a highly slippery plastic or 
polytetrafluorethylene (PTFE). It is also to be emphasized that the bottom 
side of the turning plate or its friction surface 18 is rigidly pressed 
against the surface of the snowboard by the screws 17, while the base 
plate 1 is held at a slight interval over the surface of the snowboard by 
the slip ring 19 and its dimensions so that the base plate 1 can turn 
relative to the surface of the snowboard when the binding is released, the 
slip ring 19, in cooperation with the outer edge of the turning plate 2, 
its projecting edge 3, and the inwardly pointing surface of the base plate 
1, serving as the "pivot bearing". 
The assembly of the safety binding and the adjustment of the "binding 
angle" are carried out as follows. 
First, the slip ring 19 is set over the central opening of the base plate 
1. The countersunk anchor 15 is then inserted and the unit, which is 
formed by the base plate 1, slip ring 19, turning plate 2 and the 
countersunk anchor 15, is screwed on the snowboard, an adjustment being 
made of the stepping distance, that is, the distance between the two 
bindings over the oblong holes 4. The turning disc 13 is then fastened to 
the turning plate 2 with the screw 16, the turning disc with its threaded 
holes being aligned so that the spring plunger 8 later lies in the 
longitudinal direction of the binding. In other words, the binding angle 
is already established here. The last action is to screw the spring 
plunger with its assembly disc 13' to the turning disc. This completes the 
assembly of the binding and the base plate can then assume any turning 
position. Finally, the base plate is turned so that its stop pin 7 engages 
the stop recess 11 of the head 9, thus the turning position of the base 
plate is also fixed. 
In order to facilitate movement into this "operating position", the head 9 
has leading surfaces at the side next to the stop recess 11, which cause 
the head to be forced inward by the stop pin 7. 
Briefly stated, the function of this binding, in the case of torsional 
forces acting on the base plate 1, that is, with torque action relative to 
an axis perpendicular to the snowboard surface, is to force the head 9 
back against the force of the spring 10 until the stop pin 7 comes free of 
the stop recess 11. The base plate can then become free of the snowboard 
and can be turned without any force to speak of. In spite of this, the 
snowboarder's boot remains solidly connected with the binding. Following 
such a "release", the snowboarder simply turns his foot and hence the base 
plate back into the pre-set running position in which the stop pin 7 has 
engaged the stop recess 11. 
The mounting of the head 9 relative to the spring plunger 8 can be carried 
out in different ways. As can be seen in FIG. 2, the head is cylindrical 
with a circumferential projecting edge 22, which comes to a stop against a 
step 23 inside the spring plunger 8. As FIG. 1 shows, the head can also be 
pushed from the outside over the spring plunger 8, in which case it has 
lateral recesses 24, which are engaged by claws (not shown) connected with 
the assembly disc 13' or the spring plunger 8, these claws limiting the 
travel path of the head 9 in both directions. 
ALTERNATIVE EMBODIMENTS 
The essential difference of the example embodiment of FIGS. 3 and 4 from 
that in FIGS. 1 and 2 is that spring plunger is mounted in one of the 
mounting blocks 5 on the base plate 1 and also contains the stop pin 7, 
while the opposite stop element is fixed in place with the stop recess, on 
the turning plate. The spring plunger is integrated here in one of the 
mounting blocks 5. The mounting block 5 at the right in FIG. 3 has a 
cavity 25 into which the movable head 9 is inserted, this head having a 
cylindrical extension 28, which projects out of the cavity 25 and supports 
the stop pin 7 on its free end. The head 9 also has a cylindrical 
projecting edge 22, which is forced by the spring 10 against a stop 23 
inside the cavity 25. Here, too, the initial tension for the head 9 can be 
adjusted by an adjusting screw 12 that can be screwed into the cavity 25. 
The opposite stop element consists here of an essentially cylindrical bolt 
26, rising vertically through a central opening of the turning plate 2 and 
having the stop recess 11 engaged by the stop pin 7. The bolt 26 must be 
rotatable for adjustment of the binding angle relative to the turning 
plate 2; however, it must be held in the assembled position so that it 
cannot turn on the turning plate 2. As in the case with the countersunk 
anchor 15 in FIG. 2, this requires that the bolt 26 be threaded at the end 
directed toward the snowboard surface or, in a variant of the invention, 
that the bolt have a radially projecting ring integrally formed with the 
bolt and have a shape similar to that of the countersunk anchor 15. On its 
side pointing upward, that is, toward the turning plate 2, this ring 27 
has knurling or teeth, the opposing surface in the turning plate having 
corresponding teeth. When the turning plate 2 is solidly screwed to the 
snowboard, the latter presses against the ring 27 and thus fixes the bolt 
26 so that it cannot turn relative to the turning plate. 
The difference of the embodiment of FIG. 5 from the embodiments of FIGS. 3 
and 4 is only that the spring plunger is not integrated with one of the 
mounting blocks 5 but rather is screwed as a separate component to the 
base plate 1. For this purpose, the spring plunger 8 has two side flanges 
29 with screw holes 30. The function of the binding in FIG. 5 is otherwise 
completely the same as that of FIGS. 3 and 4.