DOUBLE-SHOE SKI WITH INTERMEDIATE LINKING MEMBER

Abstract: A double-shoe ski comprising a front shoe (11) and a rear shoe (10) aligned according to their longitudinal axis; and intermediate floating arm (12) linking together the two shoes. Compression spring members (20, 21) are dis­ posed between said linking arm (12) and the shoes (10, 11) of the ski.

Description: As is known, conventional skis are suitably arched and have a downward facing convex sur­ face whose camber is referred to as "rise", in order to give the ski sufficient grip, that is, to ensure that it slides evenly and conti­ nuously over the ground without side-slipping or pendular oscillations, both on the straight and on relatively wide-radius curves. If, in fact, a ski has a high "rise" and, si­ multaneously, a high degree of flexural rigid­ ity, the reaction load, due to the ground on which it is pressed and "flattened" by the weight of the skier, has a distribution which is highly concentrated at the ends, with sepa­ rate relative maximum loads spaced considerably far apart. This distribution, in fact, permits greater incision of the edges at the ends and, there­ fore, ensures greater stability. It is also known, moreover, that when curving with parallel skis, each ski, and especially the outside one, must be able to bend in the reverse direction, especially in the front area towards the shovel. In fact, since it is also placed "edgewise", or slanting towards the in­ side of the curve (as a result of the anala­ gous centripetal displacement of the barycentre of the skier and, earlier still, as a result of the "angulation" that he assumes by bend­ ing his legs and the top half of his body side­ ways), its "reverse bending", together with the natural lateral concavity of its plan pro­ file enables the inside edge provided with a metal strip, to assume a deformed attitude identical to the curve. But, in order to enable the skier to carry out this manoeuvre easily (especially at the ini­ tial stage, during the "reversing of the edge", the ski should, on the contrary, have a low "rise" and a very limited flexural rigidity. It should be made in such a way as to submit to the reaction ground with the load concen­ trated to a great extent at the centre. For the conventional ski therefore, the situa­ tion is intrinsically contradictory, as far as its elastic properties are concerned. And so, the general tendency is to seek the compro­ mise solution by shifting slightly in one di­ rection or the other according to use and to the user for whom the ski is presumably des­ tined and, moreover, according to the most up-­ to-date trends, tending mainly towards flexi­ bility with sufficient flexural deformation as to give rise to a rather uniform distribu­ tion of the reaction load but with a single peak close to the centre of the ski. In this respect, manufacturers have perfected relatively sophisticated techniques, with multi-­ composite sandwich structures, in order to de­ velop elasic properties aimed at achieving solutions capable of encouraging such compro­ mise, by resorting to skis having a very high degree of rigidity over quite a wide area around the centre line while having a considerably high degree of flexi­ bility at the ends, especially towards the shovel; skis having a very high degree of torsional rigidity in relation to flexural rigidity, that is to say, skis having a high ratio between said rigidities, especially towards the shovel. Both these properties, in fact, give the ski quite good stability, both on the straight and in wide radius curves, with reasonably satis­ factory resistance to side-slipping and pro­ gressive driving, while at the same time per­ mitting a certain amount of ease of movement in "reversing the edge" when approaching each subsequent curve. This structural tendency, however, involves complex and costly technologies (sandwiches with numerous differentiated layers, including two preferably fine metal layers reinforced by adjacent layers in fibre or plastic), and it is nevertheless a compromise solution with which it is not possible to radically over­ come the contradiction mentioned previously, which remains an intrinsic and physiological characteristic of the conventional "single con­ tinuous" bar structure of the ski. This invention constitutes the logical out­ come of this analysis and aims to radically overcome the aforesaid contradiction by pro­ viding a new ski structure capable of auto­ matically adapting to the load conditions and in which the distribution of the reaction load can vary with variations in the conditions of use of the ski itself. A further scope of this invention is to pro­ vide a ski of the aforementioned type, which can be inexpensively mass-produced, while at the same time keeping very high standards of quality. The scopes of this invention are achieved by means of a double-shoe ski as claimed in claim 1; further features of the ski are specified in the dependent claims. The structural and operating characteristics of the ski according to the invention, compared to a conventional ski, are described in greater detail hereunder, with reference to the accom­ panying drawings, in which: Fig. 1 shows the profile of a conventional ski, in the non-loaded condition; Fig. 2 shows the same ski of figure 1 in a highly deformed counterflexed condition; Fig. 3 shows the same ski of figure 1, in a flattened condition; Fig. 4 shows the distribution of the reaction load of a conventional rigid ski with a high rise; Fig. 5 shows the distribution of the reaction load of a conventional flexible ski with limit­ ed rise; Fig. 6 shows the distribution of the reaction load in a conventional "compromise" ski; Fig. 7 shows a side view of a first embodiment of a ski according to the invention; Fig. 8 shows a side view of a second embodi­ ment of a ski according to the invention; Fig. 9 shows a top view of the skis of figures 8 and 9; Fig. 10 shows the natural profile in an un­ loaded condition, of the ski of figure 7; Fig. 11 shows the flattened profile of the ski of figure 10, loaded by the weight of the skier; Fig. 12 shows the two reaction load distribu­ tion situations for the ski according to the invention. Figures 1 to 6 show different situations for a conventional ski, the characteristics of which are compared further on with the ski ac­ cording to this invention. In particular, figure 1 shows tha natural pro­ file of a conventional ski, in the non-loaded condition, in which reference p has been used to indicate the "rise" or maximum camber at the centre line of the ski. Figure 2, on the contrary, shows the profile of the same ski highly deformed in the opposite direction, especially at the front part of the ski when curving with the skis parallel, as mentioned previously, while figure 3 shows the same ski loaded by the weight of the skier and flattened against the ground. In this latter condition, in the case of skis having a high rise and high flexural rigidity, the ground reaction load is schematically represented by the graph of figure 4, in which reference I has been used to indicate the considerable distance between the two reaction load peaks. The remaining figures 5 and 6 show the reaction load situa­ tion in two conventional skis, the first with limited rise and a high degree of flexibility, and the second with characteristics ranging between those of the first. As shown in figure 7, unlike the conventional ski of figure 1, the ski according to this in­ vention comprises two separate shoes 10, 11 of different lengths aligned according to their longitudinal axis. The two shoes 10 and 11 are connected by a mechanical arm 12, movable on a plane perpendicular to the base surface of the shoes; said arm or link member 12 hav­ ing the function of providing most of the flexu­ ral elasticity of the ski, as well as the task of ensuring the utmost torsional rigidity. In particular, as shown in figure 7, the ski com­ prises a main shoe 10, or rear shoe, which extends from the tail to a sufficient portion (100 - 200 mm) ahead of the area designed to house the toe binding 13, with the front end 10a of the main shoe 10 slightly curved up­ wards. The ski comprises a second shoe 11, or front shoe, comparable to the shovel of a conventional ski, having an upward curved tip 11a. As shown in the top view of figure 9, the profile of the side edges 14 of the rear shoe 10 is preferably slightly convex from one end of the shoe to the other; likewise, the profile of the side edges 15 of the front shoe 11 is fully convex, or "drop-shaped" with a truncated tail, whose point of maximum width 16 is located over half way and in the front portion of the shoe itself. The two shoes 10 and 11 are connected by means of a rigid or semi-rigid floating arm or link member 12, which is pivoted on transversal axes to the ski, by 17 to the front end of the rear shoe 10, and by 18 to the front shoe 11, in a position to the rear of the point of maxi­ mum width of the front shoe. A first elastic or compression member 20, (spring, rubber element, etc.) which suitably restricts the mobility of the front shoe 11 on said hinge 18 is disposed between the arm 12 and the front shoe 11. A second elastic or compression member 21, (spring, rubber element, etc.) is disposed be­ tween a rear extension of the arm 12 and the rear shoe so as to suitably control the mobi­ lity of the arm 12 on the main hinge 17 and, therefore, the rotational traversing movement of the front shoe 11 with respect to the rear or main shoe 10, thereby constituting the elas­ tic deformation of the overall assembly of the two shoes linked together to form a ski. The compression members 20 and 21 can easily be provided with means to adjust the volume of their load, as well as stop means to de­ fine the position of the start and end of the stroke itself, thereby offering the possibility of producing skis with "rise" and flexural rigidity which can be adjusted according to need (figs. 7 and 10). According to the embodiment of figure 8, the rear compression member 21 could, if required, be eliminated, and with it, the hinge 17, so that the connection between the arm 12 and the rear shoe 10 would become rigid and the elastic fnction would be entrusted exclusive­ ly to the flexibility (suitably provided) of the rear shoe itself, in its projecting por­ tion 23 which extends forward beyond the posi­ tion of the foot binding 13 (fig. 8). Intermediate solutions are obviously possible, so that the flexural elasticity of the ski can be entrusted partly to the flexible projection of the rear shoe 10, as described above, and partly to an independent elastic system (springs or the like) functioning as a "limiter" of the degree of freedom of a hinge, such as the hinge 17 originally provided for the rear shoe. In any case, the load with which it must be assumed that the ground reacts, when a ski ac­ cording to the invention is pressed onto it and "flattened" by the weight of the user (fig. 11) can only be distributed in such a way as to show two distinct areas of maximum concen­ tration : (fig. 12) one between the heel bind­ ing 22 and tail of the rear shoe, in an area which depends upon the intensity of the main spring system 21 and the height of the rise P (the greater the intensity and the height, the further back the area), that is to say, the angle of balance α p formed by the lower face of the rear shoe 10 with the ground, in the "non-loaded" condition, and the other in correspondence with the front pivot 18, when­ ever (figs. 10, 11, 12) the load of the spring system 20 and the angle α a of balance of the front shoe in the "non-loaded" condition are negligible, or immediately behind said hinge whenever such loads are not at all negligible, the moving back obviously being proportional to their intensity. The distance I1 or I2 between these areas of maximum concentration must therefore be con­ sidered as variable and easily adjustable to a considerable degree. As we have seen, in fact, it is considerable whenever the load of the main spring system 21 and the angle of balance α p of the rear shoe in the "non-loaded" condition (or the rise) are considerable, but at the same time the load of the secondary spring system 20 and the angle of balance α a of the front shoe in the "non-loaded" condition are limited (figs. 10, 11, 12), whereas it can be reduced con­ siderably by reducing the load of the main spring system 21 and the angle of balance α p of the rear shoe in the "non-loaded" condi­ tion (or the rise), while at the same time in­ tensifying the load of the secondary spring system 20 and the angle of balance α a of the front shoe in the "non-loaded" condition. These two conditions are represented by the curves A1, A2 and B1, B2 of the graph of fig. 12. Attention should however be drawn, in this con­ nection, to the undoubtedly considerable pro­ portion (at least half the overall length) that can be reached by the center distance "I" be­ tween said points of maximum concentration, similarly to the ski exemplified in fig. 4, and in correspondence with a substantial ab­ sence of the points of maximum concentration (figs. 5 and 6) in the hypothetical conven­ tional ski of equal flexural elasticity which can be used as a comparison. This latter aspect is extremely important in terms of stability of the ski, not only on the straight, but also on curves, especially along wide-radius curves, covered at high speed, on frozen or, in any case, hard snow. In this case, in fact, the ground reacts ac­ cording to the stress, which is not only re­ lated to the static weight of the skier but also to the centrifugal force, which is sub­ ject to the possibility of rather sudden os­ cillations of various origin (unevenness of the ground, variations in the slant and speed of the skier, variations in the radius of the curve itself), while the very nature of the ground itself is such as to give rise to con­ tinuous and even sudden variations in the con­ ditions and intensity of the grip on the blades. In the conventional ski, this gives rise to a situation of continuous and unexpected chan­ ges in the distribution of the reaction load along the inside edge (which should adhere to the line of the curve) and of its own "counter­ flexed" deformation (fig. 2) and, therefore, a condition of substantial precariousness and "microinstability" which, on the contrary, does not exist in the case of the ski referred to in this invention, where it must be consider­ ed that there are, both on the curve (with the skis "edgewise"), and on the straight (with the skis flat), well defined and spaced apart points of concentration of the load; one around the front hinge 18 and the other on the rear portion of the main shoe 10, with center dis­ tance "I" substantially unchanged (in any case, not subject to sudden and recurring variations during the course of the same curve). Having stated all this with regard to the sta­ bility of the ski presented herein, emphasis should likewise be place on its features of ease of use on curves, or rather, when "revers­ ing the edge" during the transition from one curve to the other, so that it will be clear that the ski of this invention constitutes a valid solution in order to overcome the im­ plicit contradiction of the conventional ski. And, in fact, it is easy to see how a ski thus designed can, when place "edgewise", or slant­ ed sideways, towards the inside of the pro­ grammed curve, spontaneously tend to conform with it as a result of the rotation of the front shoe 11 on its hinge 18, biased by the relative compression member 20 and, above all, in relation to its lateral conformation, where this is the outcome of careful and specific design, having the form of a "truncated drop", with totally convex sides, although, obviously only slightly curved), consequently lacking in point of contrary flexure (which is always present in the shovel of a conventional ski, for obvious conjunction requirements), and sec­ tion of maximum width located sufficiently close to the axis of the hinge 18, which is in turn conveniently situated close to the cen­ ter line of the portion of the shoe in contact with the ground. However, in addition to what has been described hereinbefore with regard to the functional features of the invention, stress should also be placed on the industrial aspect, which proves to be of even greater interest. In fact, in a ski of this type, the flexural elastic characteristics depend for the most part upon the mechanical system comprising the arm 12 and the relative compression springs 18, 21. Consequently, the shoes 10 and 11 are no longer required to be flexible, except, partly on the tail portion of the rear shoe 10. This means that each shoe 10, 11 no longer re­ quires a sandwich structure and can be very inexpensively made in one piece, or by fitting together longitudinal shells, according to in­ jection molding techniques using suitable plas­ tic materials. This is an extremely important aspect which can revolutionize the production and economic problems of this industrial sector which, to date, encounters intrinsic and unsurmountable obstacles in the way of reducing costs and mass-producing conventional skis while main­ taining high standards of quality.

Claims: 1. Double-shoe ski characterized by the fact of comprising a rear shoe (10) and a front shoe (11) aligned according to their longitudinal axis, an intermediate link member (12) between the two shoes (10, 11), said link member (12) being hinged to at least one of the aforesaid shoes (10, 11); and an elastic member (20, 21) between said link member (12) and the afore­ said at least one shoe (10, 11). 2. Ski as claimed in claim 1, characterized by the fact that said link member (12) is hing­ ed to an intermediate point of the front shoe (11), respectively to the front end of the rear shoe (10), and by the fact that the elas­ tic members (20, 21) are disposed near to the hinge connections (17, 18) between the link member (12) and the front shoe (11), respec­ tively between the link member (12) and the rear shoe (10). 3. Ski as claimed in claim 2, characterized by the fact that the elastic member (21) is disposed between the rear shoe (10) and a rear extension of said link member (12). 4. Ski as claimed in claim 1, characterized by the fact that the link member (12) is hinged in an intermediate position to the front shoe (11), and is rigidly secured to the rear shoe (10). 5. Ski as claimed in claim 2 or 4, charac­ terized by the fact that the link member (12) between the shoes (10, 11) is hinged to the front shoe (11) close to the center zone of the portion of the shoe designed to come into contact with the ground. 6. Ski as claimed in claim 1, characterized by the fact that said elastic members (20, 21) are in the form of adjustable spring members. 7. Ski as claimed in claim 6, further cha­ racterized by the fact that adjustable stop means are provided at the start and end of the stroke of the spring member (20, 21). 8. Ski as claimed in claim 1, characterized by the fact that said link member (12) is in the form of a rigid or semi-rigid arm. 9. Ski as claimed in claim 1, characterized by the fact that each shoe (10, 11) is in the form of a flat shoe, ending with an upwardly curved front end. 10. Ski as claimed in claim 9, characterized by the fact that each shoe (10, 11) has out­ wardly curved lateral edges. 11. Ski as claimed in claim 10, character­ ized by the fact that the point of maximum width of the front shoe (11) is positioned forward to and in an area close to the hinge connection (18) to the linking member. 12. Ski as claimed in claim 10, character­ ized by the fact that the front shoe (11) has a shape similar to a drop having a truncated tail.

Inventors: QUAGGIOTTI, VITTORIO
Applicants: S.B.P. S.R.L.
Application year: 1987
Main classification: A63C5
IPC codes: A63C5