US2661249A - Endless track composed of rubber bonded to flexible metal bands - Google Patents

Description

Patented Dec. 1, 1953 UNITED I STATES FATENT OFFICE ENDLESS TRACK COMPOSED OF RUBBER BONDED T FLEXEBLE METAL BANDS Giovanni Bonmartini, Rome, Italy, assignor to E S T Etablissement Sciences Techniques, Vaduz, Principality of Liechtenstein, a company of Liechtenstein 6 Claims.

The object of the present invention is to render possible the application of continuous metal bands of curved or mixed polygonal cross-section as an element of support on the ground in tracks applied to vehicles in general and to aircraft in particular.

The use of continuous metal bands of curved or mixed polygonal cross-section in contra-distinction to any other system is convenient for many reasons, prominent among which are the following: (1) their slidability; (2) their absolute homogeneity and the consequent absence of vibration in service, even at high speeds; (3) the greater strength of the material used by comparison with rubber; (4) the possibility of easy and rapid inspection of the condition of the material constituting the band; (5) the greater bending strength possessed by the zone of the band interposed between one support and the next, due to the moment of inertia of a support of curved cross-section. This strength enables the band to support a much greater load, and hence permits the distribution of the weight applied to the track over a far greater surface whereas otherwise (in the case of fiat bands) the weight would have to be concentrated solely on the supporting wheels. This band nevertheless has the disadvantage of having a profile that is unstable under bending stresses, because under the action of the load applied to the convex face ertia of the section. This lowering of the moment of inertia reaches a critical point, beyond which the band is flattened abruptly and damaged; beyond this point, in consequence of this phenomenon, the moment of inertia of the section is suddenly reduced to that of the fiat band, which is infinitely lower than the original moment of inertia. This disadvantage, besides bringing about a sudden lowering of the strength of the support inherent in the band, sets up a violent mechanical stress in the material of which the latter is made and in the whole structure constituting the supporting frame assembly, thereby giving rise to the occurrence of undesirable strains and friction. It follows that, to

enable the system to be employed, it is necessary 2 tain the indispensable strength of the band in question, the dimensions of the latter, particularly for increasingly high loads, must be made such that practical application is not possible, either for constructional reasons or because of the dead weight of the band.

Previous proposals for practical application have all failed in view of this obstacle, because those who have concerned themselves with the problem heretofore have confined themselves solely to the positive factors of the continuous band of convex cross-section, without finding a practical solution for the negative elements which render the application thereof almost impossible. It has heretofore been considered possible to permit the application of the loads along the middle generatrix of the back of the band, that is to say in the zone most liable to provoke the damaging of the band, without paying further attention to the results of excessive stressing of the edges of said band.

The object of the present invention is to obviate these disadvantages. This is achieved by an arrangement whereby the reaction of the ground is always distributed uniformly over the whole cross-section of the band, and better still by distributing the load so the load diagram has two maxima towards the lateral edges of said band, while avoiding a maximum towards the central generatrice of the band. The result of this arrangement is that the loads, instead of being concentrated and causing damage, are distributed over the two lateral zones of the band. With this arrangement, the section no longer tends to be flattened, but is biased in the direction of a reduction of the mean radius of curvature, with a consequent automatic increase of the moment of inertia to bending, as a function of the increase of load. As a result of profound mathematical and experimental research, it has been found that in the application of these arrangements which modify the load diagram, it is then possible and convenient to adopt bands which, while retaining all the useful characteristics mentioned above, have far smaller weights. In this manner a high safety factor against damage is attained, not through the dimensions of the band but through a diiferent distribution of the loads.

In addition, the invention provides for safety devices which are capable of avoiding damage of the band when some accidental and exceptional cause arises which brings about an unforeseen concentration of the reaction of the ground in any zone of the band. There will further be illustrated in the text of the following description, a few aspects of the application of the system presenting the peculiarity of solving a number of heretofore unsolved problems, such as the floating craft, be it of the hydromobile or hydroplane type, or even amphibious; the rotating aerofoils and lastly the possibility of making use of the bearing band when undergoing accelerations of a particular apparatus and even when bringing about a clear alteration of the sense of the motion.

Some embodiments of the concept of the invention are illustrated by way of example in the attached drawing, in which:

Fig. 1 shows a band of curved cross-section with a layer of flat elastic material.

Fig. 2 shows the latter with a concave surface.

Fig. 3 shows the layer of elastic material with grooves.

Fig. 4 shows the curved band provided with two continuous projecting longitudinal zones of elastic material.

Fig. 5 shows the curved band witha layer of flat elastic material with transverse and longitudinal cavities.

Fig. 6 shows the curved band provided with two continuous longitudinals of elastic material having transverse and longitudinal cavities.

Fig. '7 shows intermediate guide rollers.

Fig. 7A shows the curved band provided with two projecting longitudinal zones of elastic material, in their turn provided with metallic band.

Fig. 7B shows the curved band provided with two projecting longitudinal zones of resilient matter, provided with incorporated band.

Fig. 8 shows intermediate rollers which are narrow in relation to the width of the band.

Fig. 9shows intermediate rollers equal in width to the band.

Fig. 10 shows lateral stops beneath the edges of the band.

Fig. 11 shows grooved rollers to prevent the transverse yielding of the band.

Fig. 12 shows the main rollers provided with guide flanges.

Fig. 13 shows the main rollers provided with rotating and eccentric lateral retaining discs.

Fig. 14 shows lateral rollers having their axis directed towards the center of the drum, for the lateral guiding of the band.

Fig. 15 shows a clearing blade.

Fig. 16 shows a supporting wheel provided with a pneumatic tire and grooving.

Fig. 17 shows a'schematical example illustrating the set up of a system for the acceleration of the band.

Fig. 18 shows a schematical example illustrating the application of the band in the keel of floating crafts.

Fig. 19 shows in cross sectional view a wing with rotating members.

Fig. 20 shows in longitudinal section a wing with rotating members.

According to the present invention, one method of achieving the desired purpose is that of covering the outer surface of the band i with an appropriate layer of elastic material 2 of variable thickness, so that the surface which bears on the ground is either flat (see Fig. 1) or concave (see Fig. 2).

In this manner the reaction of the ground is spread along the whole width of the track, and immediately concentrated towards the edges, which prevents the flattening of the band.

The material must naturally be such that it can be easily and firmly attached to the track,

and must be suitably elastic in order to be able to be deformed as necessary when the straight band becomes curved or vice versa, without increasing the strains. This elasticity is naturally also useful for absorbing slight roughness of the ground and for eliminating noise.

However, in order to reduce the alternate distension of the material, it is possible according to the invention to cut in the layer 3 (see Fig. 3) transverse grooves 4 of suitable depth and width, which substantially reduce the deformation of the surface layers, which would otherwise be the most severely strained.

According to a modification of the present invention, the layer of material may be thickened in two continuous longitudinal zones 5 (see Fig. 4) located near and along the edges, in order to attain still more efiiciently the desired effect.

In this case also the two strips 5 may be grooved transversely in order to reduce the maximum deformation of the material.

Finally, with the object of improving ability to absorb obstacles; the deformability of the material may be increased by providing inside the layer 2 (Fig. 5) or inside the strips 5 (Fig. 6) suitable cavities H3 or I9 full of air or of very soft spongy material, so that the layer 2 or the strips Ebehave like semi-pneumatic cushions.

In order to increase the effectiveness of strips 5, the outer, i. e., ground engaging, edges of said strips may be provided with band 24, similar to but narrower than the main band I (Fig. 7A). In a similar way (Fig. 713) band 25 instead of being fitted at the end of the expansions made of an elastic material is may also be incorporated in the said material itself.

The foregoing .constitutes an indispensable structural element of the continuous metal band of curved or equivalent transverse section, and also against the oxidisability of the resistant element.

With this application, it is also possible to transmit a driving thrust to the ground. For this purpose provision is made to equip the band with'teeth corresponding to the edges, which en-- gage with one or more of the guide drums, or with suitable means for transmitting the desired driving thrust.

This, however, overlooks the hypothesis that some accidental and exceptional cause might arise which would give rise to an unforeseen concentration of the reaction of the ground in a limited and even central zone of the band. In this case, the above described arrangement suitable for distributing the load might be found to be insufficient.

The following safety arrangements, which resist damage to the band in two difierent ways, also form objects of the present invention.

According to the present invention, a first method of increasing the carrying capacity of tracks is to interpose between the end guide drums 6 (see Fig. '7) wheels I of suitable shape and dimensions, which support the zone of the band 8 that is in contact with the ground, thereby relieving it of a part of the load to which it is subjected. Such wheels may have an axial development smaller than the width of the band, as illustrated at 9 in Fig. 8, or substantially equal thereto, as indicated at In in Fig. 9.

In this second case, however, the peripheral velocity of the rollers is different from point to point of the generatrices, and slipping in relation to the band, which moves at constant speed, inevitably results therefrom. According to the present invention, in order practically to eliminate such slipping (which becomes important in proportion as the width of the band increases). each roller or wheel may be divided into a plurality of independent rollers or wheels disposed side by side, each of which automatically assumes a peripheral velocity equal to the velocity of translation of the band.

The surfaces of the rollers and of the end guide drums may be of metal or of rubber in order to permit the band to adjust itself by yielding slightly under load and to eliminate noise.

Said rubber surface, by increasing the coeflicient of friction between the band and the roller, improves the effectiveness of transmitting any driving or braking couple.

Similarly, the axles of the rollers and of the drums may be mounted on the supporting frame of the track by means of elastic means (for example of the resilient block type) in order to achieve similar results.

These intermediate wheels may be designed and constructed so as to support the band only in cases of exceptional and dangerous overloading of the band, and are so constructed as to come into contact with the latter only when the previously calculated deflection of longitudinal curvature exceeds a certain limit, thereby preventing it from being exceeded. In this case, it is borne in mind that the intermediate wheel does not normally support the band, and therefore the greater unsupported length of the band will require a greater weight of the supporting band, but the band will run more easily since it does not normally engage the intermediate rollers. When, on the other hand, the intermediate Wheels are designed and constructed in such manner that they are permanently in contact with the band, the latter will undoubtedly be lighter, but there will be more friction on said band, depending on the number, diameter, and width of the aforesaid intermediate wheels. Selection between the two types of application and also of a mixed system is left to the judgment of the designer, who will thus be enabled to obtain maximum lightness corresponding to maximum ease of running.

According to the present invention, another important means of increasing the load that can be imposed on the track is that of using suitable devices which prevent the zone, of the band in contact with the ground from being flattened transversely. As has been stated hereinbefore the track loses its resistance to bending as a result of the abrupt transverse flattening which occurs when a predetermined and accurately calculable limit bending moment is reached.

If, however, the band is obliged by suitable devices to retain its transverse arched shape,

the resistance to bending is retained even with bending moments greatly superior to the limit moment.

According to the present invention, a first efiicient method of avoiding the deformation of the zone of the band bearing on the ground is that of disposing, beneath the edges of the band I (see Fig. fixed longitudinal stops I I against which the band bears when it tends to be flattened. The fixed stops I I are suitably supported by the track supporting structure.

These stops, combined with the rollers 9 and I c already mentioned, obviously render the band incapable of deformation and consequently greatly increase resistance to bending.

The fixed stops II mentioned above have, it is true, the disadvantage of applying a rubbing friction to the band in translation; but the stresses which arise between the band and the stops are very small and are applied for a short time, so that the relative friction is very small.

A second method of avoiding the deformation of the band is that of disposing along the edges of the latter grooved rollers I2 (see Fig. 11) having an almost vertical axis, which obviously pro duce the same effect as the fixed supports II mentioned above.

With this system, the rubbing friction is practically eliminated.

The perfectly homogeneous track must be mounted in such manner that it is constantly guided by the end drums and by the intermediate systems of support which have been described, despite any transverse stresses to which it may be subjected.

According to the present invention, one method of'achieving this result is that of providing the drums and the supporting rollers with guide flanges I3 (see Fig. 12), which keep the band in the desired position. These flanges, however, since they necessarily project from the contour of the edges of the band, may come into contact with and cut into the ground, unless other means are applied. In order to avoid these disadvantages, according to a modification of the present invention, the band may be held in position by means of retaining discs (see Fig. 13) fastened to the two ends of the drum but mounted to rotate on annular supports I5 which are concentric in respect to the axis of rotation of said drums but eccentric in the upwards direction, 1. e. towards the generatrix of the drum opposite that which comes into contact with the ground. By this arrangement the band is guided on both sides over almost all the periphery of the drum by a rim which is free to slide with said band and therefore causes no friction, the projection of the rim at the point of contact with the ground being nil.

Finally, according to another modification of the present invention (see Fig. 14), the tracks can be guided and prevented from passing over the edge by means of one or more pairs of rollers it having axes directed towards the centre of the drum 6 and disposed at the edges of said drum and in register with the zone where the track during its turning, comes into contact with the front drum, or at any point'in the are assumed by the track in the rear drum.

According to another modification of the present invention (see Fig. 15), in order to prevent mud, sand, rubbish, and the like, which falls inside the arrangement on to the inner face of the lower portion of the band during the movement of the track on the ground, from being carried beneath the main wheel and beneath the intermediate wheels, each wheel carries in front of it one or more deflector blades I! in the shape of a double ploughshare, which by sweeping the inner surface of the band, frees the'latter from any foreign bodies before they get beneath the wheel. In order to ensure the fastening of the blr do, the latter is pivotably mounted on the supporting frame. The clearing blade may be held against the band by a resilient system which permits the oscillations of the band to be followed.

According to another modification of the present invention, the clearing blade may be made of elastic material suitably profiled in fin shape.

Finally, in order to prevent small amounts of liquid mud or sand, which may adhere to the band, from causing trouble when the band comes into rapid contact with the roller, according to another modification of the present invention grooves of suitable design and direction are provided on the outer surface of the end and intermediate rollers which maintain the surface clean.

According to another modification of the present invention, either the end drum wheels or the intermediate wheels may consist of a metal hub 20 on which is mounted a pneumatic ring 2! of suitable measurements and suitable profile, with the object of rendering contact with the ground softer (see Fig. 16).

Fig. 1'7 shows a form of the invention in which means is provided to attenuate or suppress the violent acceleration which is undergone by the band at the moment when it contacts the ground, if fitted upon an airplane landing gear. Accordingly, there is provided a motor 22 of a known type for example an electric one, or a power takeoff from the motors, in such a way as to bring into motion with a progressive speed, both the band and its actuating wheels 6. In this manner, within a period of time settled beforehand-a factor which obviously allows of a low power motor being used-the band will be set in motion at a speed nearly equal to the one which would be imparted thereto by a sudden contact with the ground, so much so that the contingent stress is oflset thereby. Such an accelerating device can obviously be employed also during the take off for the purpose of complementing at the start of the take-off run, the low output of the normal propelling means.

On the other hand, Fig. 18 shows an application of the system to the keel of a floating craft, be it the float of a hydroplane or the hull of a motor boat or of any hydromobile in the generic sense.

In this case one or more bands are suitably fitted up insuch a way so to be brought in connection with the hull of the floating craft.

If at the instant of the take off the band is brought into motion through a device analogous with the one in the previously illustrated example, and further, if the direction of the motion of the lower span of the band has the same direction of motion as floating craft; the relative speed of the band in respect to the water will be equal to the sum of the speed of the floating craft plus that of the band. This greater speed has the effect of tending to promote the take ofi of the craft at the very instant the craft leaves the water by lessening the adhesion of the water to the craft.

There being thus avoided the necessity of using steps. Alternatively the band can be actuated in a direction of motion contrary to the aforegoing one, for the purpose of increasing the speed of the craft in water, whereas the sense of its motion may be reversed at the appropriate moment just before leaving the water.

The application of the band to the keel of floating craft converts it to an amphibious craft, permitting it to move overland. with a motion accomplished in a way altogether similar to that of any land vehicle which makes use of the system.

To this end. it will be preferable to apply on the bottom of the craft, instead of a single band, two parallel ones which would allow not only of a better adherence to the ground, also improve the directionality and the balance of the vehicle.

Figs. 19 and 20 show lastly, an applicationof the system to the embodiment of a rotating wing.

Such a foil is made up of a plurality of bands set alongside one another.

In front and behind the band are fltted the members 26 and 21 which constitute the leading edge and the trailing edge of the wing.

There being no need whatever to illustrate the characteristic features of such wing which permits very high linear speeds of the wing unit and aflords greater ease of steering.

The present invention has been illustrated and described in some preferred forms of realization, but it is understood that structural modifications may in practice be made thereto without departing from the scope of the claims.

I claim:

1. A track for track-laying running gear, comprising an endless spring-metal band of inherently concavo-convex cross section and a continuous non-metallic tread formed of resilient rubber-like material and having side edge portions of greater thickness than the mid portion, said tread being adherently applied to the convex surface of said metal band and forming a permanent unitary structure therewith.

2. A track for track-laying running gear, comprising an endless spring-metal band of inherently concavo-convex cross section and a continuous tread formed of resilient rubber-like material, said tread being of channel cross section having flanges extending longitudinally along the side edges, the band of the channel being concave and the flanges constituting the groundengaging portion of the track, the concave base of said tread being adherently applied to the convex surface of said metal band. v

3. A track for track-laying running gear, comprising an endless spring-metal band of inherently concave-convex cross section, a continuous tread formed of resilient rubber-like material, said tread being of channel cross-section with a concave base portion and with spaced flanges ex tending longitudinally along the side edges of the base, and metal bands extending along said flanges, the concave base of said tread portion being adherently applied to the convex surface of said metal band.

4. A track for track-laying running gear, comprising an endless spring-metal band of concavoconvex cross section, a continuous tread portion formed of resilient rubber-like material, said tread portion being of channel cross section with a concave base portion and with spaced flanges extending longitudinally along the side edges of the base portion, and metal bands embedded in said flanges, the concave base of said tread being adherently applied to the convex surface of said metal band.

5. A track for track-laying running gear, comprising an endless spring-metal band of concaveconvex cross section, a continuous tread portion formed of resilient rubber-like material, said tread portion being of channel cross section with a concave base and with spaced flanges extending longitudinally along the side edges of the base, said flanges having a plurality of spaced cavities formed therein, the concave base of the tread portion being adherently applied to the convex surface of said metal band.

6. A track for a track-laying vehicle, comprising an endless spring-metal band of concavoconvex cross section and a continuous endless tread portion formed of resilient rubber-like material, said tread portion having a concave base and being thicker along the side edges than in the central portion, and the concave base of said tread portion being adherently applied to the COHVGX SU.

rface of said metal band.

GIOVANNI BONMARTINI. 5

References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Schlueter Apr. 4, 1922 10 Number

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