Toe iron

A safety toe clamp for a ski binding is disclosed wherein a ski boot sole holder is pivotally mounted for lateral movement on a body member provided with adjustable spring means urging said sole holder in a forward direction. Each of a pair of surfaces on said body member is each oppositely disposed outside of the central axis of the body member and adapted to cooperate with corresponding surfaces on the sole holder, the cooperating surfaces respectively being adapted to form a first swivel axis separated from the central axis of the toe clamp upon the application of an initial lateral force, and a second swivel axis upon application of further lateral movement of the sole holder.

BACKGROUND OF THE INVENTION 
The invention relates to a safety toe iron for a ski binding with a sole 
holder which can be laterally swung out about in each case one 
perpendicular swivel axis located to the right and left of the 
longitudinal central axis, whereby a spring tension acts on said sole 
holder in the forward direction between the swivel axes. 
With known safety toe irons of this type (DOS NO. 2,359,490, Austrian 
application No. 9991/72) the lateral swivel axes for the sole holder are 
arranged in such a way that in the case of lateral stressing up to a 
particular rotation angle of the sole holder about one of the pins the 
boot tip cannot be removed from the binding, whereby at the end of the 
lateral action of the springs the sole holder and therefore also the boot 
is returned to the axial position. If the swinging out of the sole holder, 
due to the action of the lateral forces is greater than the rotation 
angle, then the boot tip can be removed laterally from the binding, so 
that the connection with the ski is broken. 
In the case of the known safety toe irons the spring tension must be 
regulated in such a way that a lateral swinging out of the sole holder is 
only possible when a dangerous starting torque acts on the leg of the 
skier. However, if parts of the binding are frozen solid or if an 
excessive forwardly directed pressure exerted by the heel iron which 
cooperates with the toe iron acts on the latter, then the release 
characteristics of the toe iron are significantly changed and the leg can 
be broken, despite the correct presetting of the initial tension of the 
springs in the toe iron. 
BRIEF SUMMARY OF THE INVENTION 
The problem of the present invention is a safety toe iron of the type 
defined hereinbefore which provides a reliable release at the given 
lateral force value even if the binding is frozen solid, if an excessive 
pressure is exerted by the heel or if other criteria exist which have a 
negative influence on the release characteristics, but which nevertheless 
still has the typical high lateral elasticity of such toe irons. 
According to the invention this problem is solved in that the swivel axes 
are displaced outwards during the swinging out of the sole holder. This 
displacement should be 20 to 30%, but perferably 25% of the initial 
distance of the pivot axis from the longitudinal central axis. If the toe 
iron cooperates with a heel iron which exerts a pressure, according to the 
invention, as a function of the swivel angle the displacement is so large 
that the line of pressure application at least substantially runs through 
the outwardly displaced swivel axis when the sole holder reaches the 
angular position where the displaced swivel axis has just become 
effective. 
Due to the construction according to the invention the first lateral 
release phase takes place when the lateral force is still completely 
harmless for the leg of the skier. The available reserves of force can be 
used for any frozen parts of the binding or for overcoming pressures which 
act against the release. If a certain small swivel angle has only been 
covered about the inner swivel axes the influences which hinder release 
are substantially eliminated. In this phase the swivel axis located 
further outwards is effective which, in view of the spring tension, is 
positioned in such a way that the lateral release of the sole holder takes 
place at the lateral force which is just tolerable to the leg of the 
skier. Therefore the final release can now take place at a clearly defined 
release value and proceeds unimpeded by other factors. 
In practise the invention can be realized for example by the inner swivel 
axis being defined by a projection resting on a counter-surface, followed 
in the outwards direction by two rolling surfaces kept at a limited 
distance apart by the projection. 
The sole holder is forced against the swival axes by a spring-loaded tie 
rod fixed in articulated manner thereto, whereby the tie rod articulation 
is located substantially between the swivel axes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
According to FIGS. 1 and 2 the toe iron according to the invention is fixed 
in conventional manner to ski 18. A compression spring 21 is arranged in 
an axial recess 20 of casing 19, said spring acting on the end of the tie 
rod 16, which is to the left in the drawings. The abutment 22 of 
compression spring 21 is formed by a nut screwed onto tie rod 16, so that 
by screwing down abutment nut 22 to a greater or lesser extent onto tie 
rod 16 the initial tension of spring 21 can be present. 
The end of spring 21, to the right in the drawings, is supported on casing 
19. 
As can be gathered from FIG. 2 an adequate gap 23 (FIG. 2) is provided 
between abutment nut 22 and casing 19, making possible the slight 
deflections to the left and right of tie rod 16 which occur in conjunction 
with the operation of the binding. 
At the right end in the drawings at 17 pole holder 12 is pivotably 
connected about an axis which is perpendicular to the ski. The sole holder 
not only laterally retains the boot, but also holds down the sole thereof. 
A screw mechanism 24 permits a height adjustment of sole holder 12, so 
that the latter can be adapted to different boot sizes. 
An elastic member 25 is positioned between the parts of sole holder 12 
whose height relative to one another can be adjusted. 
According to the invention symmetrically and on either side of the 
longitudinal central axis 15 are provided forwardly directed projections 
13, constructed as vertical edges, which cooperate with an opposite 
surface of casing 19 in order to define a swivel axis 11 positioned 
perpendicularly on ski 18. An identical arrangement exists on the other 
side of the longitudinal central axis 15. 
Two cooperating, arcuate surfaces 14, 14' curved in the indicated manner to 
one another and having a limited spacing from one another extend outwards 
from projection 13. 
If a lateral force Q of predetermined size acts on sole holder 12 then the 
sole holder 12 initially rotates about the swivel axis 11 located on the 
relevant side of the lateral force Q, whereby spring 21 is compressed 
somewhat via connection 17 and abutment nut 22. Rotation continues until 
the two arcuate surfaces 14, 14' engage on one another, as is shown by 
dotted lines in FIG. 3. Further rotation now takes place round the swivel 
axis 11' positioned further outwards. The dimensioning of the individual 
parts and particularly projection 13 is such that on reaching the dotted 
position in FIG. 3 the pressure A produced by the heel iron runs 
substantially through the outer swivel axis 11', as is illustrated by a 
dotted arrow in FIG. 3. Whereas the pressure which acts in the normal 
position of FIG. 2 exerts a closing action on the toe iron, said closing 
moment substantially disappears in the swung out position of sole holder 
12, shown by dotted lines in FIG. 3. On swinging out further the pressure 
gives rise to an opening moment. 
In FIG. 4 the operation is shown graphically, the lateral force Q acting on 
the sole holder is plotted on the ordinate and the release path on the 
abscissa. 
The first leg of the release curve extends from the start to stage "1," 
corresponding to the swinging out about inner swivel axis 11. However, the 
actual release force is only encountered level with stage "2," which only 
occurs when the arcuate surfaces 14, 14' engage with one another. The boot 
is only released on passing beyond stage "2." If during the release 
process the sole holder does not reach state "2," the toe iron is returned 
to its normal position when the lateral force disappears. 
Thus, in the first part of the release path there is a relatively small 
lever arm between swivel axis 11 and pivotal connection 17, so that the 
first part of the release takes place relatively easily. On outwardly 
displacing the swivel axis the force which acts counter to the swinging 
out increases, in accordance with the diagram of FIG. 4. In the first 
stage of the release movement it is thus possible to break undesired 
connections of movable parts caused by icing, whilst simultaneously the 
overcoming of the closing moment resulting from the pressure action is 
facilitated. 
The invention can also be used in the case of two separately pivotably 
arranged side irons. In addition, the toe iron could fundamentally also be 
used as a heel iron, provided that it cooperates with a suitable front 
binding. 
FIG. 5 schematically shows that the invention can also be realized 
differently from the manner shown in FIGS. 2 and 3. In the embodiment 
shown above the longitudinal central axis 15 and projection 13 engages in 
a recess of a member 26 on casing 19. After a certain swinging path the 
further outwardly located arcuate surfaces 14, 14' engage with one 
another, whereby projection 13 is raised from the base of the recess. 
Another embodiment is shown below axis 15, whereby in normal operation the 
inner projection 13 of member 26 cooperates with a corresponding recess on 
sole holder 12. On reaching a certain swivel angle the further outwardly 
located arcuate surfaces 14, 14' engage with one another to continue the 
swinging process. 
The invention is not limited to the embodiments described and represented 
hereinbefore and various modifications can be made thereto without passing 
beyond the scope of the invention.