Patent Publication Number: US-2012042542-A1

Title: Coupling element for a ski boot and ski boot

Description:
The present invention relates to a coupling element for a ski boot, comprising fastening means for fastening the coupling element to a heel region of a ski boot, two contact portions arranged either side of a vertical boot center plane extending in the longitudinal direction of the boot, against which contact portions pins projecting forwards from an automatic heel mechanism of a ski binding bear in a downhill position of the ski binding, and off which the pins slide in the event of a fall release of the ski binding once a release force acting on the ski boot has been overcome, the fastening means comprising a central fastening point, which lies between the two contact portions. The present invention relates further to a ski boot, to the heel portion of which a coupling element of the above described type is fastened. 
     A common type of ski binding uses two parallel pins projecting forwards from an automatic heel mechanism for coupling together the automatic heel mechanism and a heel portion of a ski boot, which pins enter into engagement with a coupling element fastened to the ski boot in order to fix the ski boot to the ski in its heel region. An example of a coupling system of this type is known from EP 0 199 098 A2, which describes as coupling element a metal plate to be fastened to the heel region of a sole of a ski boot. The metal plate is fastened to the ski boot by means of two central screws, which extend along a vertical ski center plane. The vertical boot center plane extends orthogonally to the metal plate and divides the metal plate into two mirror-symmetrical halves. The side edges of the metal plate lying on different sides of the boot center plane each comprise a groove as contact portion for the pins projecting from the automatic heel mechanism. The pins are pretensioned into engagement with the grooves by a resilient force, such that they hold the ski boot fixed securely to the ski binding and thus to the ski in the downhill position, the resilient force of the pins being overcome if a fall release force is exceeded, and the ski boot being released from engagement with the pins in order to release the ski boot. 
     The ski binding described in EP 0 199 098 A2 is designed as a touring ski binding and additionally allows adjustment from the downhill position to a walking position, in which the automatic heel mechanism being adjusted such that it allows the heel region of the ski boot to be lifted off the ski. It should however be pointed out at this point that the present invention is not limited to ski bindings of this type, but rather extends equally to other bindings for downhill skis and cross-country skis or indeed snowboards or splitboards, provided that the binding works with an automatic heel mechanism which has two forwardly projecting pins. Moreover, the term “ski binding” or “ski boot” should also be understood in the context of the present disclosure to mean snowboarding equipment and splitboarding equipment, such that a snowboarding boot is also understood as a ski boot for the purposes of the present disclosure and a snowboard binding is also understood as a ski binding for the purposes of the present disclosure. 
     Conventional coupling elements, for example of the above described type, are increasingly reaching their limits as the sport of skiing develops further. The reason for this is in particular the relatively high release thresholds for the automatic heel mechanism increasingly required above all in racing, which need to reliably prevent undesired ski binding release even under heavy peak loads during downhill skiing. These loads have in practice led to increased wear of the ski boots in the region of the coupling elements and sometimes to loosening or even breaking away of the coupling elements. Although the strength of the coupling elements could be improved somewhat by using larger screws, the possibilities for that are however limited as a result of the structural space defined by the pins. 
     Against this background it is the object of the present invention to provide a coupling element for a ski boot as well as a ski boot with such a coupling element, which exhibit greater fatigue strength and lower wear and also reliably withstand relatively high loads. 
     According to a first aspect of the present invention the object of the invention is achieved by a coupling element of the above-mentioned type, in which the fastening means further comprise two outer fastening points, which are arranged laterally outside the contact portions with regard to the boot center plane, and the coupling element comprises two arm portions extending laterally outwards with regard to the boot center plane, which arm portions each extend towards the outer fastening points. 
     According to the invention, enhanced robustness and wear resistance of the coupling element is not thus based on the use of larger and more robust screw fastenings or the use of a stronger material for the coupling element but rather on a fundamentally different shaping of the coupling element and on the use of a novel fastening structure with regard to the arrangement of the fastening points and with regard to the distribution and directions of the forces introduced into the ski boot. The arm portions extending laterally outwards allow the provision of two additional fastening points, which do not lie in the central region in the vicinity of the boot center plane but rather laterally to the outside and allow the forces introduced to be distributed advantageously over a larger area of the ski boot. 
     In particular, the outer fastening points according to the invention are arranged outside the contact portions of the coupling element, such that the fastening structure created in this way is no longer subject to the structural space limitations determined by the spacing of the pins. The arm portions lead out from this region, and use rear lateral portions of the heel region of the ski boot for additional fastening of the coupling element. In this way the coupling element may be fastened very robustly to the ski boot, such that it remains securely on the ski boot even in the event of long, demanding use and wear is reduced. In addition, loosening or even breaking away of the coupling element is reliably prevented even in the case of very high release threshold values. 
     The coupling element preferably comprises a central portion, on which the central fastening point is arranged, the arm portions extending out from the central portion substantially in mutually opposing directions. Such a coupling element is simple in shape and may be of cheap and robust manufacture, being made for example from a suitable sheet metal. 
     If the coupling element comprises a central portion, on which the central fastening point is arranged, the contact portions may be arranged on opposing lateral edge portions of the central portion and each comprise a groove for accommodating a pin of the automatic heel mechanism. With such a groove it is possible with simple means to create a form-fitting desired position for bearing contact of the pins in the downhill position, wherein the release properties of the coupling element may be influenced by appropriate dimensioning of the grooves. 
     Load tests and simulations performed by the inventors, together with calculations relating to release behavior have shown that the conventional coupling element, for example a coupling element according to EP 0 199 098 A2, is pulled downwards relative to the ski boot on exposure of the ski boot to a very high My torque (a torque about a transverse axis extending orthogonally to the longitudinal axis of the ski and orthogonally to the vertical axis), and at the same time is tilted away from the boot. The forces introduced into the coupling element thus act in part away from the boot and in part downwards. In a particularly preferred embodiment of the coupling element, the fastening points and the shape of the coupling element are optimally adapted to these force directions, in that the arm portions extend outwards in the manner of wings above the contact portions. This configuration in particular counteracts the tilting away of the coupling element observed during load testing. 
     In a further embodiment it is proposed that the outer fastening points should be arranged in widened end portions of the arm portions, such that it is possible to provide sufficient material in the end portions to form the fastening points, for example to arrange a fastening hole, while the thickness of the arm portions may be smaller to save weight while retaining the same overall coupling element strength. Preferably the widened end portions are downwardly widened end portions, so achieving the additional advantage that the position of the fastening points may be shifted closer vertically to the contact portions of the coupling element and the region in the heel region of the ski boot for fitting the coupling element may be put to optimum use. 
     It is further conceivable for the coupling element to have a substantially arcuate shape conformed to a heel region of a ski boot. The coupling element is then optimally conformed to the contour of a ski boot in the heel region, in order to be reliably fastened thereto. 
     At least one of the fastening points the fastening means may comprise a through opening. The coupling element may thus be fastened to the boot at the at least one fastening point by means of a screw passed through the through opening. Alternatively, the provision of a peg projecting towards the boot at least one of the fastening points would also be feasible, said peg sitting by interference fit in a corresponding opening in the ski boot. 
     According to the invention the outer fastening points of the coupling element are arranged laterally outside the contact portions of the coupling element. In a common type of ski binding the distance between the contact surfaces of the pins is around 20 mm, such that the improvement according to the invention of the fastening structure is achieved if a distance between the outer fastening points is greater than roughly 20 mm. A marked further increase in the robustness of the coupling element fastening may be achieved if the distance between the outer fastening points is greater than roughly 40 mm, since then the lever action of the lengthened arm portions may be put to good use. The best load tests were performed with coupling elements in which the distance between the outer fastening points is greater than roughly 60 mm. 
     In a further preferred embodiment of the invention the coupling element may comprise at least one peg projecting on the boot side, which peg is inserted or insertable into a hole in the heel region of the ski boot on fastening of the coupling element to the ski boot. The projecting peg may assist in fitting the coupling element to the ski boot, by holding the coupling element temporarily in the correct position on the ski boot. In addition, the form-fitting engagement between peg and associated hole may further improve the stability of the coupling element against tilting under load. 
     The arm portions according to the invention may provide additional fastening points on the coupling element, in order to increase coupling element fastening robustness, as has already been described above. To achieve this effect, it is not absolutely necessary for the coupling element to be fastened at all fastening points with the same mechanical effort, and the same load carrying capacity. It is thus for example proposed in variants of the invention that the coupling element be held at the central fastening point by means of a screw fastening and be held at the outer two fastening points only by in each case at least one projecting peg, which is inserted into a hole in the ski boot, or that the coupling element be held at the central fastening point only by at least one peg projecting on the boot side, which is inserted into a hole in the ski boot, and be held at the outer two fastening points by means of a screw fastening. It is accordingly feasible for one and the same coupling element to use a mixture of different fastening principles, so making fitting of the coupling element easier (in particular at the fastening points at which a projecting peg has merely to be inserted into a hole in the ski boot), while improved or constant stability of the connection between coupling element and ski boot is ensured compared with conventional coupling elements. 
     The coupling element is preferably made from a metal casting and has a thickness which is greater than roughly 2.5 mm at least in the region of its contact portions and/or above the contact portions. Such a coupling element has sufficient inner stability to be able to withstand the forces exerted by the pins when loaded. 
     If the thickness of the coupling element is between roughly 3.5 mm and roughly 4.5 mm, the peripheral area of the coupling element offers a larger contact surface than conventional coupling elements, such that frictional forces between the pins and the coupling element are reduced. This is particularly advantageous when the user shifts his weight onto the heel portion of the ski boot, by leaning back for example, and the ski binding is stressed in this state in the direction of lateral release (if a release torque acting around a vertical axis of rotation acts on the ski boot). The release behavior depends in this case also on the frictional force between the pins and the contact portions of the coupling element and a reduction in this frictional force allows a better defined, more predictable release threshold, such that release safety may be increased in comparison with coupling elements of lower material thickness. 
     According to a second aspect of the present invention the object of the invention is achieved by a ski boot which comprises an upper portion and a sole portion, wherein a coupling element of the above-described type according to the invention is fastened to the sole portion in a heel region of the sole portion. In conjunction with the various embodiments of the coupling element according to the invention described above, such a ski boot may achieve the advantages and effects in each case described above. 
     In addition, with a ski boot of the type according to the invention coupling holes may be provided in the heel region of the ski boot, in alignment with the two contact portions of the coupling element, in which holes there engage pins projecting forwards from an automatic heel mechanism of a ski binding and bearing on the contact portions. This enables the pins to be sufficiently long to pass completely through the thickness of the coupling element and project somewhat into the ski boot, such that the pins may be prevented from slipping off the contact portions as a result of slightly imprecise positioning of the ski boot relative to the automatic heel mechanism. 
     According to a third aspect of the present invention the object of the invention is achieved by ski equipment comprising a ski boot, which comprises an upper portion and a sole portion, in particular a ski boot of the above-mentioned type, a coupling element of the above-described type according to the invention being fastened to the sole portion in a heel region of the sole portion, and the equipment further comprising a ski binding, in particular a touring ski binding, with an automatic heel mechanism, which comprises forwardly projecting pins which in a downhill position of the ski binding bear on the contact portions of the coupling element and which slide off the contact portions of the coupling element in the event of fall release of the ski binding once a release force acting on the ski boot has been overcome. 
    
    
     
       The invention is explained in greater detail below on the basis of a preferred exemplary embodiment and with reference to the attached drawings, in which: 
         FIGS. 1 and 2  are perspective views from above and below respectively of a heel region of a ski boot with a coupling element fastened thereto according to one exemplary embodiment of the present invention; 
         FIG. 3  is a side view of the heel region shown in  FIGS. 1 and 2  with coupling element; 
         FIG. 4  is a rear view of the heel region shown in  FIGS. 1 and 2  with coupling element; 
         FIG. 5  is a side view of the coupling element shown in  FIGS. 1 and 2 , in a non-mounted state; 
         FIG. 6  is a rear view of the coupling element shown in  FIG. 5 ; 
         FIG. 7  is a plan view of the coupling element shown in  FIG. 5 ; and 
         FIGS. 8 and 9  are perspective views from above and below respectively of the coupling element shown in  FIGS. 1 and 2 , in each case in a non-mounted state. 
     
    
    
       FIGS. 1 to 4  are each perspective, side or rear views respectively of a heel region of a ski boot  10 , which comprises an upper portion  12  and a sole portion  14 . The ski boot  10  defines a boot centre line M, which passes through the ski boot  10  in the direction of a longitudinal boot axis, and defines a vertical boot center plane E, which contains the boot center line M. 
     At this point it should be pointed out that in the present disclosure, including the claims, all statements of direction such as “top”, “bottom”, “lateral”, “front”, “back” etc. relate to a ski boot which is standing with its sole portion on a horizontal surface, such that the toe of the ski boot is pointing forwards in the direction of the boot center line M, the sole portion  14  is arranged below the upper portion  12  and the upper portion  12  is open at the top. 
     A coupling element  16  is fastened in a manner to be described in greater detail below via three fastening points  18   l ,  18   r ,  20  to a rear portion of the sole portion  14 . The coupling element  16  comprises a central portion  24 , through which pass the boot center line M and the boot center plane E when the coupling element  16  is in the fastened state, and a left-hand arm portion  26   l  and a right-hand arm portion  26   r , which extend out from an upper portion of the central portion  24  in mutually opposing lateral directions. On the central portion  24  there is provided a central fastening point  20 , which is formed in the exemplary embodiment by a central hole arranged concentrically to the boot center plane E, which hole is provided to accommodate a central fastening screw  28  (cf.  FIG. 4 ). 
     On either side of the boot center plane E contact portions are in each case provided in the form of grooves  30   l ,  30   r  at the lateral edges of the central portion  24 , the contour of which grooves is conformed to the outer contour of pins  31   l ,  31   r  (cf.  FIGS. 6 and 7 ) of an automatic heel mechanism, not represented further, of a touring ski binding (for example an automatic heel mechanism known from EP 0 199 098 A2). In the exemplary embodiment the grooves  30   l ,  30   r  accordingly comprise a contour in the form of a segment of a circle. The grooves  30   l ,  30   r  preferably develop at their upper ends in each case into the arm portions  26   l  or  26   r , while at their lower ends they may each develop into release projections  32   l ,  32   r  extending laterally outwards. Further down from the release projections  32   l ,  32   r  the side edges of the central portion  24  preferably each form guide bevels  34   l ,  34   r , which extend downwards towards one another, such that the central portion  24  tapers downwards. 
     Two pegs  36   l ,  36   r  projecting towards the boot may additionally be provided on the central portion  24  (in the figures on either side of the boot center plane E), which pegs are designed for form-fitting engagement in corresponding holes in the sole portion  14 . 
     The arm portions  26   l ,  26   r  preferably extend laterally to the left and right respectively substantially in a T-shape from the central portion  24 . They start at the central portion  24  above the grooves  30   l ,  30   r , such that they extend above the pins  31   l ,  31   r  engaged in the grooves  30   l ,  30   r . In the exemplary embodiment the grooves  30   l ,  30   r  lead directly into the arm portions  26   l ,  26   r , and the arm portions  26   l ,  26   r  may bear with their lower edge portions  38   l ,  38   r  on the top of the pins  31   l ,  31   r , such that weight may be introduced from the ski boot  10  into the pins  31   l ,  31   r.    
     In the lateral directions (to the left or right from the boot center plane E) the arm portions  26   l ,  26   r  extend outwards beyond the grooves  30   l ,  30   r  and thus beyond the pins  31   l ,  31   r  engaged therein. At the same time, they extend, in a plan view according to  FIG. 7 , forwards in an arc, which is conformed to the contour of the heel region of the sole portion  14  of the ski boot  10 . 
     At the ends remote from the central portion  24  of the arm portions  26   l ,  26   r  the outer fastening points  18   l ,  18   r  are in each case provided for fastening the coupling element  16  to the ski boot  10 . In the exemplary embodiment the outer fastening points  18   l ,  18   r  are also formed as through holes, through which fastening screws  40   l ,  40   r  (shown only in  FIG. 4 ) may be introduced and screwed into the sole portion  14  of the ski boot  10 . Both the through holes of the outer fastening points  18   l ,  18   r  and the through hole of the central fastening point  20  may be provided with a conical bevel, to prepare the coupling element  16  for fastening by means of countersunk head screws  40   l ,  40   r ,  28 , which substantially do not project beyond the outer contour of the coupling element  16 . 
     In the exemplary embodiment the arm portions  26   l ,  26   r  are widened at their ends comprising the outer fastening points  18   l ,  18   r  and each in particular comprise a downwardly projecting widened portion  42   l ,  42   r . The widened portions  42   l ,  42   r  may provide sufficient space on the coupling element  16  for provision of the outer fastening points  18   l ,  18   r , so as in particular to be able to provide through holes of sufficient size for a stable screw fastening. Because the widened portions  42   l ,  42   r  are extended downwards, the height of the outer fastening points  18   l ,  18   r  may additionally be lowered, such that the overall structural height of the coupling element  16  may be reduced and the structural space available at the rear sole portion  14  may be put to good use. It is in particular clear for example from  FIGS. 4 and 6  that the arm portions  26   l ,  26   r  straddle the pins  31   l ,  31   r  like a bridge, such that the coupling element  16  is fastened on either side of each pin by the central fastening point  20  on the one hand and by one of the two outer fastening points  18   l ,  18   r  on the other hand. In this a way very stable fastening of the coupling element  16  is achieved with regard to the force introduction point (between the pins  31   l ,  31   r  and the grooves  30   l ,  30   r ). 
     In the exemplary embodiment illustrated the coupling element  16  is formed in one piece from a metal casting, for example a steel casting. The coupling element is preferably of sufficient material thickness, at least in the region of the grooves  30   l ,  30   r  and/or in the region of the bottom edge portions  38   l ,  38   r  of the arm portions  26   l ,  26   r , to enlarge the contact surface between the pins  31   l ,  31   r  and the grooves  30   l ,  30   r  such that the frictional forces between these elements are reduced, as is wear. Accordingly the coupling element  16  may comprise a reinforcing portion  43  in the region of the grooves  30   l ,  30   r  or the edge portions  38   l ,  38   r , which reinforcing portion is correspondingly thicker, for example with a thickness ranging from roughly 3 mm to roughly 5 mm, while in the other portions, e.g. in the more distal regions of the arm portions  26   l ,  26   r  and the remaining central portion  24 , the coupling element  16  has a plate thickness of only roughly 2 mm, such that the necessary stability is still ensured. 
     Alternatively, the coupling element  16  could be made from a metal plate of constant thickness ranging from roughly 3 mm to roughly 5 mm. If weight reduction is given priority over frictional properties, a stable coupling element may however also be provided with a continuous plate thickness of roughly 2 mm. 
     It should further be noted that a distance y between the outer fastening points  18   l ,  18   r  in the exemplary embodiment amounts to roughly 60 mm, while the distance between the pins  31   l ,  31   r  or the associated grooves  30   l ,  30   r  is roughly 20 mm. The outer fastening points  18   l ,  18   r  are thus markedly further away from the boot center line M than the pins  31   l ,  31   r  and, for fastening the coupling element  16 , may thus use significantly longer levers than the pins  31   l ,  31   r  to introduce the forces. This thus markedly reduces the retention force to be absorbed by the outer fastening points  18   l ,  18   r  when a force is exerted by the pins  31   l ,  31   r  on the coupling element  16 , such that loosening or even breaking away of the coupling element  16  from the sole portion  14  is barely possible even under severe stress. 
     The mode of operation of the boot  10  with the coupling element  16  according to the exemplary embodiment of the invention will be explained below. To get into the binding the ski boot  10  is positioned above the pins  31   l ,  31   r  of the binding and lowered in a roughly vertical direction, the pins  31   l ,  31   r  passing through corresponding slot-shaped recesses  44   l ,  44   r  in the sole portion  14 , which open at the bottom towards the sole  46  of the ski boot  10 . As the heel region of the ski boot  10  is moved further downwards the pins  31   l ,  31   r  then come into bearing contact with the guide bevels  34   l ,  34   r  and are forced apart thereby. The pins  31   l ,  31   r  are spread apart against the resistance of a resilient device of the automatic heel mechanism (not shown), which tensions the pins  31   l ,  31   r  towards one another with a spring force corresponding to the release force. Once the pins  31   l ,  31   r  have got past the release projections  32   l ,  32   r , they snap into the grooves  30   l ,  30   r , such that engagement between ski boot  10  and automatic heel mechanism is then complete. The front ends of the pins  31   l ,  31   r  are then located in coupling holes  48   l ,  48   r , which are formed in the rear heel region of the sole portion  14  of the ski boot  10  in alignment with the grooves  30   l ,  30   r  and widen in a downward direction, so as to develop into the guide slots  44   l ,  44   r . Ski boot  10  and ski binding are then in the downhill position. 
     When the ski boot  10  and the binding are exposed to functional stress, in particular during downhill skiing, the ski binding holds the ski boot  10  firmly on the ski by way of the pins  31   l ,  31   r , corresponding forces being introduced into the ski boot  10  via the pins  31   l ,  31   r  and the coupling element  16 . As a result of the fastening structure according to the exemplary embodiment of the invention, these forces are introduced optimally into the heel region of the ski boot  10  making use of lever effects and the distributed force introduction points, such that the coupling element  16  may be held stable on the ski boot  10 . 
     If a force acting between ski boot  10  and automatic heel mechanism exceeds a predetermined release threshold (depending on the magnitude of the resilient force acting between the pins  31   l ,  31   r ), for example during a fall, the pins  31   l ,  31   r  slide out of the grooves  30   l ,  30   r  over the release projections  32   l ,  32   r , such that the coupling element  16  is pulled upwards off the pins  31   l ,  31   r  and the heel region of the ski boot  10  is released. 
     The present invention is not restricted to the above-mentioned exemplary embodiment. It is thus also feasible, in particular instead of the screw fastening of the outer fastening points and of the central fastening point, to use different fastening principles. For example, a pin projecting from the coupling element towards the boot could be provided, at least one of the fastening points, which pin is anchored by interference fit in a corresponding opening in the boot. Due to the lever action of the lengthened arm portions, such a fastening may be feasible in particular for the outer fastening points, in order to reduce weight and fitting effort while ensuring a sufficiently robust connection between coupling element and boot. Alternatively, a fastening by means of interference fit could of course be provided at the central fastening point. Further per se known fastening principles, such as for instance adhesive fastening or clip fastening, are likewise conceivable.