FR2827564A1 - Rubber caterpillar for tracked vehicle comprises several guide and driving force transmission teeth on inner surface, each tooth consisting of two transverse faces and two lateral faces - Google Patents

Abstract

The rubber caterpillar comprises several guide and driving force transmission teeth on its inner surface. Each tooth (20) consists of two transverse faces directed transversely to the caterpillar and two lateral faces directed in the longitudinal forward movement of the caterpillar. A plane perpendicular to the caterpillar longitudinal direction cuts a transverse face in three lines. The tooth comprises a front face (21), comprising a cavity (23), and a rear face (22). The front face is composed of two curves (24,25) secant in an intersection point (26). The tangent (27) in this point which cuts the caterpillar internal face, represented by line (28), delimits the front face cavity. The line (29) which represents a plane perpendicular to the caterpillar longitudinal direction cuts the front face in three points (30,31,32).

Description

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 The invention relates to rubber tracks for vehicles and more particularly tracks for agricultural or civil engineering machines. The conditions of mixed driving, that is to say both on soft ground and on the road, of this type of machine lead to a development of the use of rubber tracks.

 By rubber or rubbery material or mixture of gum is meant any elastomeric material comprising at least one elastomer which can be reinforced with at least one reinforcing filler such as, for example, carbon black.

 A rubber track for a vehicle comprises in particular: a strip forming a closed loop in a longitudinal direction of given width (in a transverse direction) having an internal surface and an external surface, said strip being mainly composed of rubber, on the external surface, a plurality of elements in relief intended to come into contact with the ground to ensure good traction in the vehicle equipped with this track, - on the interior surface, a plurality of teeth comprising lateral faces and front faces and rear (the latter being spaced in the longitudinal direction), these teeth being intended at least for guiding this track, in order to ensure good coupling between the track and the vehicle equipped with this track.

 The concepts of front face and rear face of said teeth are usually defined by the direction of rotation of the track which is itself defined by the orientation of the elements in relief present on the external face; indeed, these generally have V-shaped figures in particular to improve certain performances such as the self-cleaning of the spaces between these elements in relief. The track thus automatically has a direction of rotation and it is possible to define front and rear faces for all internal or external protuberances.

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 In addition, taking into account the forces supported by a track mounted on a vehicle, it is known to provide inside the strip at least one reinforcing reinforcement ensuring the dimensional stability of the track in the longitudinal direction corresponding to the direction of the loop formed by said track. This reinforcing reinforcement is generally composed of a plurality of cables arranged in the longitudinal direction or else of a cable wound at a relatively small angle with said direction so as to give the strip an appropriate extension rigidity in the direction longitudinal to withstand the stresses in use.

 It is also usual to provide for adding an additional reinforcing reinforcement comprising a stack of plies each formed from a plurality of cables or reinforcing wires arranged parallel to one another and capable of crossing from one layer to another.

 Among the vehicles fitted with rubber tracks, there are two families according to the function fulfilled by the teeth of said tracks.

 In a first family, the teeth have only a guiding role, the teeth being housed between the sides of two wheels of the vehicle, which ensures good solidarity between the track and the vehicle.

 In a second family of tracked vehicles which are more particularly the subject of the present invention, the teeth play both a guiding role and a role of transmitting the drive forces of the track. The drive is carried out by drive means such as at least one wheel disposed inside the track and comprising a plurality of bars oriented transversely to form a sort of squirrel cage; each guide and drive tooth of the track is inserted between two bars of said wheel. The teeth regularly spaced from each other, are separated by crossbeams in which mesh the bars of the drive wheel. In general, at least three bars are permanently engaged in cross beams and transmit either engine or braking torque from the tractor to the track.

 The trajectory followed by the bars will therefore consist in following a passage through the gangways; these passages are defined to be identical and produced with the least amount of

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 possible friction against the track. In this way, it is possible to preserve the integrity of the caterpillar teeth and avoid their deterioration. To do this, the teeth of the track are made uniformly and the pitch of the teeth of the track is related to that of the bars of the squirrel cage. The operation thus obtained of the caterpillar on the squirrel cage (s) makes it possible to obtain a good meshing of the bars between the teeth.

 However, this good meshing is obtained in a situation of normal motor skills but may present weaknesses in certain cases leading to an alteration either of the caterpillar or of the motor system. In fact, users may have to in some cases have to perform heavy braking, that is to say sudden braking while the machine is launched at full speed. These brakes, in particular due to the great inertia of the machine, lead to a violent jolt which can cause the track to slide on the bars. This shift leads to the jump between the beams from one training bar to the next. Such a reaction leads on the one hand to poor braking and makes the machine insecure and on the other hand, can damage the track so that it is no longer operational.

 The Applicant has thus given itself the mission of producing a rubber track which does not have these drawbacks and more precisely authorizing emergency braking without the risk of seeing the track slide on the drive bars.

 This object is achieved according to the invention by a rubber track comprising on its inner surface a plurality of guide teeth and transmission of drive forces, each tooth consisting of two transverse faces, oriented in the transverse direction of the track , and from two lateral faces oriented in the longitudinal direction of advancement of the track, the four surfaces rising from a base in coincidence with the inner surface of the track, at least one plane perpendicular to the longitudinal direction of the cutting track a transverse face in at least three lines.

 According to an advantageous embodiment of the invention, in a longitudinal section, the profile of at least said transverse face, cut by the plane in at least three lines, consists of at least two intersecting curves.

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 When the caterpillar has an imposed direction of rotation which defines the two transverse faces of each of its teeth as being a front face and a rear face, the front face preceding the rear face during rotation, the profile of at least the face front, seen in a longitudinal section, advantageously consists of at least two intersecting curves. The two intersecting curves create a point of intersection.

 In a preferred embodiment of the invention, in a longitudinal section, the tangent to the point of intersection of the two curves which intersects the inner surface of the track between said front face and the rear face of the neighboring tooth delimits an area of the surface front of the tooth forming a cavity on said surface.

 The track thus defined according to the invention consists of a strip forming a closed loop in a longitudinal direction and of given width (in a transverse direction) having an inner surface and an outer surface, said strip being mainly composed of rubber; on the outer surface of said strip, there are a plurality of elements in relief intended to come into contact with the ground to ensure good traction in the vehicle equipped with this track; on the inner surface, there are a plurality of teeth having lateral faces and front and rear faces (the latter being spaced apart in the longitudinal direction). These teeth are intended for guiding and driving the track, in order to ensure good coupling between the track and the vehicle equipped with this track. More specifically, the teeth of the track according to the invention has a front face comprising a cavity delimited by the point of intersection. This cavity will make it possible, in particular in the event of sudden braking, to avoid sliding of the strip and more precisely of the teeth on the drive means such as the bars of a squirrel cage. It has indeed appeared that such a profile of the front face of the teeth of the track makes it possible to avoid the previously mentioned sliding of the track on the drive means.

 The Applicant has been able to demonstrate that the profile according to the invention allows braking over a shorter distance without risk of damaging the equipment, the profile of the front face according to the invention ensuring a non-return function of the track when the drive means are braked suddenly.

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 In the case of bars with a circular section, the cavity, seen in a longitudinal section, advantageously presents itself with a circular profile so as to best match the shape of the bars. In the same way, in the case of bars of non-circular sections, the skilled person will be able to adapt the profile of the cavity to obtain a similar result. In particular in the case of drive bars with oval section, the cavity will have an oval profile.

 Advantageously, the cavity is located at the base of the entrance and is contiguous to said base.

 According to this advantageous embodiment of the invention, the cavity prevents the track from returning to the drive means by creating a retaining zone for said drive means from the first contact of the latter with the front face of a tooth. during braking. Such an embodiment of the invention also allows an embodiment of the front face of a tooth which does not disturb the path of the motor tool in operation, that is to say that the path followed by the means of training according to the profile of the teeth or more precisely of the teeth is not disturbed by this advantageous embodiment of the invention. Furthermore, the strength and rigidity of each tooth are not disturbed, this cavity being produced at the base of each tooth, that is to say in the region of their greatest thickness.

 According to a preferred embodiment of the invention, the teeth have, in a longitudinal section, an asymmetrical profile with respect to a median plane perpendicular to the longitudinal direction of the track.

 This preferred embodiment of the invention allows a rear face adapted to the profile to be followed by the drive means to ensure the best possible drive of the track. Indeed, the rear face thus does not constitute an obstacle to the evacuation of the drive means which leave the entry.

 According to a variant of the invention where the caterpillar collaborates with drive bars such as those of a squirrel cage, the distance between the base of the tooth and the point of intersection in a direction perpendicular to the longitudinal directions and

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 transverse of the track is greater than at least seventy percent of the largest dimension of the cross-section of the bars.

 According to a preferred embodiment of the invention, when the track collaborates with drive means, the point on the front face on which the motor tool comes into contact during braking, is located between the base of the tooth and the point of intersection.

 According to a preferred embodiment of the invention, in a longitudinal section, the distance between the straight line perpendicular to the longitudinal direction of the track and passing through the point of intersection, and the point of the transverse face, comprised between the base of the tooth and the point of intersection, said point being the furthest from said straight line, is at least 0.05 mm. The inventors have been able to demonstrate that a recess or recess area having a depth of 0.05 mm makes it possible to avoid sliding of the track on the drive means during sudden braking.

 Advantageously also, this distance is greater than 0.5 mm and less than 2 mm, in particular so that the shape of the front face according to the invention does not disturb the proper functioning of the track when the latter is driven by a movement of reverse rotation to perform for example a reverse maneuver.

 According to an advantageous embodiment of the invention, the cavity is such that, in a longitudinal section, the distance between the tangent to the point of intersection of the two curves, which cuts the interior surface of the track between said front face and the rear face of the neighboring tooth, and the point of the transverse face, between the base of the tooth and the point of intersection, said point being the furthest from said tangent in a direction perpendicular to said tangent is greater than 1 mm.

 An alternative embodiment of the invention also provides that at least the zone of the transverse face, consisting of at least two intersecting curves, lying between the base of the tooth and the point of intersection comprises a surface coating increasing the friction.

Such a coating can help prevent the track from sliding on the drive means.

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figure 1, un schéma d'une vue en perspective d'une chenille en caoutchouc, figure 2, un schéma d'une vue partielle montrant les dents de guidage de ladite chenille, - figure 3, un schéma d'une vue en perspective d'une roue d'entraînement de type cage d'écureuil , figure 4, un schéma du profil, selon une coupe longitudinale, d'un entredent d'une chenille selon l'invention associé à un barreau d'entraînement,

- figure 5, un schéma du profil, selon une coupe longitudinale, du même entredent lors d'un freinage, associé au même barreau d'entraînement, figure 6, un schéma du profil d'une dent selon l'invention, vu en coupe longitudinale. Other details and advantageous characteristics of the invention will emerge below from the embodiments of the invention and from the description of FIGS. 1 to 6 which represent:

Figure 1, a diagram of a perspective view of a rubber track, Figure 2, a diagram of a partial view showing the guide teeth of said track, - Figure 3, a diagram of a perspective view of a squirrel cage type drive wheel, FIG. 4, a diagram of the profile, in a longitudinal section, of an entry of a track according to the invention associated with a drive bar,

- Figure 5, a diagram of the profile, in a longitudinal section, of the same entry during braking, associated with the same drive rod, Figure 6, a diagram of the profile of a tooth according to the invention, seen in section longitudinal.

 The figures are not shown to scale to simplify understanding.

 FIG. 1 represents a track 1 made up of a continuous strip 2 delimited by exterior 3 and interior surfaces 4. FIG. 2 represents an enlarged area of this strip 2. The longitudinal direction of the track or strip is defined as being the direction of its greatest length, the transverse direction as being the direction perpendicular to the longitudinal direction and to the thickness of the strip (the thickness corresponding to the distance between the exterior 3 and interior 4 surfaces). The strip 2 is provided on its outer surface 3 with a plurality of protrusions 5 intended to come into contact with the ground during the running of the track 1. For convenience, only two protrusions 5 are shown in FIG. 1. The strip 2 is provided on its inner surface 4 with a plurality of guide and drive teeth 6 intended to cooperate with means for guiding the vehicle on which the track 1 is installed.

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dents de guidage et d'entraînement 6 sont destinées à coopérer avec des flasques et des t : l barreaux 12 d'une roue de guidage et d'entraînement 13 de type cage d'écureuil comme représentée sur la figure 3. La fonction de guidage est assurée par un contact entre les flasques de la roue 13 et les faces latérales 10, 11 des dents 6. La fonction d'entraînement est assurée par un appui des barreaux 12 sur les faces arrières 8 des dents 6. Each guide and drive tooth 6 has a front face 7, a rear face 8, an upper face 9 and two lateral faces 10 and 11, visible in FIG. 2. These

guide and drive teeth 6 are intended to cooperate with flanges and t: l bars 12 of a guide and drive wheel 13 of squirrel cage type as shown in FIG. 3. The guide function is ensured by contact between the flanges of the wheel 13 and the lateral faces 10, 11 of the teeth 6. The drive function is ensured by pressing the bars 12 on the rear faces 8 of the teeth 6.

 FIG. 4 represents a diagram of the profile of an intermedent 14, that is to say of the zone comprised between two teeth, seen in a longitudinal direction. Figure 4 to illustrate this entry 14 shows the rear face 8 of a tooth 6 and the front face 7 'of a tooth 6'. FIG. 4 also shows a rod 12 of a drive wheel 13 and the path 15 followed by this rod 12 relative to the inlet 14 during the forward operation of the machine on which the track is installed. It appears that the bar for transmitting its motor force comes to bear on the rear face 8 of a tooth 6 at point 16.

 The path 15 shown in Figure 4 is largely defined by the combination of the pitch of the bars of the squirrel cage and the pitch of the teeth 6 on the inner surface 4 of the strip 2. This trajectory is advantageously provided so that the bar has no contact with the front face of the tooth 6 ′ when it enters the intermediate 14; this penetration phase in the entry corresponds to part 17 of the curve 15. This absence of contact makes it possible to avoid any risk of friction and overheating which could lead to damage to the teeth. In addition, the absence of contact prevents energy losses.

 The bar 12 then comes into contact with the rear face 8 of the tooth 6 at the point 16 to transmit traction to the track 1.

 The bar 12 then leaves the entry 14 along the path 15 illustrated more precisely by the part 18 of this path. Contacts when the bar 12 leaves the entrance 14 are also non-existent.

 Obtaining such a trajectory 15 is, as mentioned above, largely linked to the respective pitches of the teeth on the track and of the bars of the cage.

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 squirrel. US Pat. No. 6,139,121 thus recalls the principle of the kinematic study of the trajectory and describes an exemplary embodiment of a tooth.

 FIG. 5 illustrates the position of the bar 12 relative to the entry 14 during braking. It appears that during braking, the bar bears on the front face 7 ′ of the tooth 6 ′. In the case of the profile of a usual tooth, the inertia of the machine is such that it is possible to observe a sliding of the bar on the front face of the tooth and it follows that the bar makes a jump until the previous entry; on the one hand, this increases the braking distance; on the other hand, this phenomenon leads to a stretching of the caterpillar which can deteriorate it.

 In the case of the invention as shown in FIG. 5, the position of the bar 12 relative to the inlet 14 during braking is in the cavity 19 and remains in this zone, the bar appearing to be held in this position during braking. It turns out that the situation is the same, whatever the importance in terms of intensity, of braking and in particular during a sudden braking the machine being launched at full speed, that is to say, in the case of a high power agricultural tractor, at a speed of the order of 40 krn / h.

 FIG. 6 represents a caterpillar tooth 20 according to the invention, seen in longitudinal section. The tooth 20 has a front face 21 and a rear face 22, the front face comprising the cavity 23. The front face 21 is constituted as defined by the invention by two curves 24,25 intersecting at a point of intersection 26 The tangent 27 at this point 26 and which intersects the inner face of the track represented by the line 28 delimits the cavity 23 of the front face 21. Furthermore, as defined by the invention, the line 29, which represents a plane perpendicular to the longitudinal direction of the track, cuts the front face 21 at three points 30, 31, 32.

 Further details will appear on reading the following results measured during tests which have been carried out.

 The tests were carried out on a track for agricultural machinery having the following characteristics: - circumference: 6400 mm

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- number of teeth: 42 - height of teeth: 63 mm - radius of curvature of the entrance: 25.8 mm - position of the point of intersection above the inside of the track:
27.5 mm - distance between the line perpendicular to the longitudinal direction of the track and passing through the point of intersection, and the point of the cavity furthest from said line: 0.05 mm. distance between the tangent to the point of intersection of the two curves, which intersects the inner surface of the track between said front face and the rear face of the neighboring tooth, and the point of the cavity furthest from said tangent in a perpendicular direction at said tangent: 1.2 mm.

 The transmission devices are squirrel cage type wheels, the bars of which have a circular section with a diameter of 38.1 mm.

 The tests were carried out several times; the machine, with a mass of twenty tonnes, is brought to a speed close to 40 km / h and brakes are abrupt. There is a significant jolt of the machine due to its inertia but during none of the tests it was observed a sliding of the track on the drive bars.

Claims (12)

CLAIMS 1-Rubber track having on its inner surface a plurality of guide teeth and transmission of drive forces, each tooth consisting of two transverse faces, oriented in the transverse direction of the track, and two oriented lateral faces in the longitudinal direction of advancement of the track, the four surfaces rising from a base in coincidence with the inner surface of the track characterized in that at least one plane perpendicular to the longitudinal direction of the track cuts a transverse face in at least three lines. 2-track according to claim 1 characterized in that in a longitudinal section, the profile of at least one of the transverse faces consists of at least two intersecting curves. 3-track according to claim 1 or 2, having an imposed direction of rotation which defines the two transverse faces as being a front face and a rear face, the front face preceding the rear face during rotation, characterized in that the profile at least the front face, seen in a longitudinal section, consists of at least two intersecting curves. 4-track according to claim 3 characterized in that, in a longitudinal section, the tangent to the point of intersection of the two curves which intersects the inner surface of the track between said front face and the rear face of the neighboring tooth delimits an area of the front surface of the tooth forming a cavity on said surface. 5-caterpillar according to claim 4 characterized in that the cavity extends over the entire width of the tooth in the transverse direction, in that it is located at the base of the tooth and in that it is contiguous to said base. 6-track according to claim 1 to 5 characterized in that the teeth have an asymmetrical profile relative to a median plane perpendicular to the longitudinal direction of the track. <Desc / Clms Page number 12> 7-track according to one of claims 2 to 6, intended to collaborate with drive bars, characterized in that the distance between the base of the tooth and the point of intersection in a direction perpendicular to the longitudinal and transverse directions of the track is greater than at least seventy percent of the largest dimension of the cross-section of the bars. 8-track according to one of claims 3 to 7, intended to collaborate with a power tool, characterized in that the point of the front face on which the power tool comes into contact during braking, is located between the base of the tooth and the point of intersection. 9-track according to one of claims 2 to 8 characterized in that, in a longitudinal section, the distance between the line perpendicular to the longitudinal direction of the track and passing through the point of intersection, and the point of the face transverse, between the base of the tooth and the point of intersection, said point being the furthest from said straight line, is at least 0.05 mm. 10-track according to one of claims 2 to 9 characterized in that, in a longitudinal section, the distance between the tangent to the point of intersection of the two curves, which cuts the inner surface of the track between said front face and the rear face of the neighboring tooth, and the point of the transverse face, between the base of the tooth and the point of intersection, said point being the furthest from said tangent in a direction perpendicular to said tangent is greater than 1 mm . 11-caterpillar according to one of claims 2 to 10 characterized in that at least the area of the transverse face, consisting of at least two intersecting curves, between the base of the tooth and the point of intersection comprises a surface coating increasing friction. 12-Use of a track according to one of claims 1 to 11 on an agricultural machine or a civil engineering machine.