ELEMENT OF A CRAWLER-TRACK MOVEMENT ASSEMBLY FOR WORKS VEHICLES

The present invention relates to an element of a crawler-track movement assembly for works vehicles.

Machines provided with crawler tracks for transmitting motion from the engine to the ground have widespread use. The use of machines equipped with crawler tracks is to be preferred in environments in which traction is problematic. These machines can be used to perform various kinds of work, for example at building sites, demolition sites, landfills and mines. In summary, the expression“truck components” is used to reference all the components that are necessary for and support transmission of the motion between the reduction unit and the ground. In particular, chains, driving wheels, track tensioning wheels, lower rollers and upper rollers belong to this category.

During setup, the chain is assembled on the machine, forming a continuous structure which is closed on itself and wound between two or more wheels, arranged at a given operating center distance, and guided by means of a variable number of rollers. The wheel that transmits the motion from the engine to the chain is termed sprocket or tumbler. This component can be constituted monolithically or by a plurality of segments. There is also at least one free guiding wheel for closing the winding of the chain. The chain, in its upper portion, is supported by one or more upper rollers. The lower rollers are accommodated in the lower portion. The vertical loads that are the result of chain-machine interaction are transmitted to the frame of the machine itself by means of these last components. Furthermore, the rollers are indispensable in order to obtain the relative motion between the ground and the machine both in a longitudinal direction and during steering.

The definition "element of a crawler-track movement assembly for works vehicles" used in the present description is understood to reference any component chosen among the wheel that transmits motion from the engine to the chain, the idle guiding wheel and a roller (equally an upper or lower one).

By way of example, some problems that occur with rollers are mentioned hereinafter, although it is specified that these problems can also be observed in the driving wheel, in the driven wheel, and in general in any rotating element of a crawler-track movement assembly for works vehicles.

A roller, during its operation within a machine provided with crawler tracks, is subjected to mechanical stresses caused by axial and radial loads. Various constructive solutions are used currently in order to absorb these loads and avoid misalignments which might compromise the correct movement of the chain.

A first constructive version provides for the use of bearings (generally of the roller type with radial and axial sealing).

In this case, the main body of the roller accommodates the outer rings of the bearings, while the inner rings are mounted on the fixed shaft, which is coupled by means of appropriate supports to the chassis of the machine. In this embodiment, the bearings require a specific adjustment/setting and a mechanical preloading in order to perform their function optimally. For this reason, auxiliary components are also provided, such as springs the action of which can be adjusted by means of at least one respective adjustment ring.

The constructive versions that provide for the use of bearings, while yielding good responses from the functional standpoint, on the other hand have high costs (due to the use of onerous components, the assembly and preliminary machining of which are complex).

A more economical alternative constructive solution is to utilize bushings which make contact with the fixed shaft coupled to the chassis: the roller is thus mounted on them.

In any case, in order to reduce the friction coefficient, bear loads better and dissipate heat, generally there is, in both of the previously described constructive solutions, a lubrication. The lubrication system is of the oil bath type. Lubricant circulation therefore occurs by sloshing during the rolling motion of the roller with respect to the shaft. During this motion, the lubricant passes through the gap created between the shaft and the roller.

In order to then avoid the escape of the lubricant, sealing components are used which form a hermetic containment chamber (between the roller and the shaft) which is closed toward the outside.

The sealing components, in addition to performing the task of avoiding the loss of lubricant, must be able to withstand more or less intense axial plays, vibrations, impacts, and protect from the presence of abrasive and corrosive materials even in case of use in environments with extreme temperatures.

Generally speaking, the sealing components comprise a ring which is integral with the roller body and a collar which is keyed onto the shaft. However, these couplings are not sufficiently stable over time and leaks can occur due to mechanical stresses that occur with use. Therefore, the use of an external flange which, fastened onto the roller by means of screws, compacts the assembly can be provided.

The body of the roller is normally provided by joining two parts, commonly tenned roller halves: joining is obtained, in most cases, by welding (with the addition of material or by friction). However, the welding process causes a localized modification of the mechanical and crystalline properties of the metal, with possible consequent deterioration of the performance of the welded materials, as well as possible geometric deformations.

The aim of the present invention is to solve the problems described above, by proposing an element of a crawler-track movement assembly for works vehicles that is not subject to geometric deformations caused by the mutual welding of the element halves, such as wheel halves and roller halves. Within this aim, an object of the invention is to propose an element of a crawler-track movement assembly for works vehicles that is not subject to deterioration of the local mechanical performance due to the mutual welding of the element halves, such as wheel halves and roller halves.

Another object of the invention is to propose an element of a crawler- track movement assembly for works vehicles that is not subject to variations of the micrographic and crystalline properties caused by the mutual welding of the element halves, such as wheel halves and roller halves.

Another object of the invention is to propose an element of a crawler- track movement assembly for works vehicles that avoids leaks of lubricant.

Another object of the invention is to propose an element of a crawler- track movement assembly for works vehicles that is constituted by a minimal number of components.

Another object of the invention is to propose an element of a crawler- track movement assembly for works vehicles that is simple and quick to assemble.

A further object of the present invention is to provide an element of a crawler-track movement assembly for works vehicles that has modest costs, is relatively simple to provide in practice and safe in application.

This aim and these objects, as well as others which will become better apparent hereinafter, are achieved by an element of a crawler-track movement assembly for works vehicles of the type comprising a rotatable tubular body and a shaft which is fixed with respect to the chassis of the works vehicle, at least one bushing for reducing friction being interposed between said cylindrical body and said shaft, characterized in that said tubular body comprises

- two body halves which are mutually mated at corresponding internal ends, which have substantially complementary shapes and dimensions,

- external ends provided with a respective contoured shoulder which constitutes the movable ring for a sealing element, said sealing element abutting against a fixed annular element which is coupled to said shaft.

Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of the element of a crawler-track movement assembly for works vehicles according to the invention, illustrated by way of nonlimiting example in the accompanying drawings, wherein:

Figure 1 is a partially sectional perspective view, taken from a first angle, of an element of a crawler-track movement assembly for works vehicles according to the invention;

Figure 2 is a view of the element of Figure 1 from a different angle;

Figure 3 is an enlarged-scale perspective view of a detail of Figure 2;

Figure 4 is a partially sectional perspective view, taken from a first angle, of a different embodiment of an element of a crawler-track movement assembly for works vehicles according to the invention;

Figure 5 is a partially sectional perspective view, taken from a first angle, of a different embodiment of an element of a crawler-track movement assembly for works vehicles according to the invention.

With reference to the figures, the reference numeral 1 generally designates an element of a crawler-track movement assembly for works vehicles.

The element according to the invention comprises a rotatable tubular body 2 and a shaft 3 which is fixed with respect to the chassis of the works vehicle (which is not shown in the accompanying figures).

At least one bushing 4 is interposed between the cylindrical body 2 and the shaft 3 in order to reduce the friction between these components.

According to the invention, the tubular body 2 comprises two body halves 2a and 2b which are mutually mated at corresponding internal ends 5a and 5b, the shape and dimensions of which are substantially complementary. The internal ends 5a and 5b, in the assembly configuration, can be arranged at the centerline of the tubular body 2, although it is not excluded to arrange them in a different position.

The external ends 6a and 6b of the tubular body 2 are conveniently provided with a respective contoured shoulder 7a and 7b, which constitutes the movable (rotatable) ring for a sealing element 8.

The sealing element 8 abuts against a fixed annular element 9 which is coupled to the shaft 3.

With particular reference to a first constructive solution of unquestionable interest in practice and in application, illustrated by way of nonlimiting example in the accompanying Figures 1 and 2, the internal ends 5 a and 5b of the tubular body halves 2a and 2b interfere with each other.

The mutual mating of the ends 5 a and 5 b can therefore be obtained validly by mechanical driving with interference of one internal end 5a (or 5b) in the other one 5b (or 5a) after optional thermal conditioning of at least one of them.

With particular reference to the enlarged-scale view provided by way of nonlimiting example with Figure 3, the outside diameter ⁽ Fa of the internal end 5a is greater than the inside diameter b of the internal end 5b: mutual driving, in this case, can be performed by thermal conditioning of the ends 5a and 5b (i.e., by heating the hollow end 5b, causing its expansion, and cooling the end 5a, causing a contraction thereof) until inserting one in the other becomes possible.

The term "hot driving", also known as hot keying, is understood to reference a method that is adopted for operations for the assembly or disassembly of mechanical components and transmission elements.

This method provides for the use of heat and of the phenomenon of thermal expansion to overcome the dimensional interference of two components and create an extremely strong mechanical mating between two parts. The most common applications are the mechanical mating of components with given inside/outside diameters which interfere with each other. When the two parts are at the same temperature (ambient temperature), interference prevents their correct mechanical assembly; if instead the part into which driving is to be performed is first heated (in general to temperatures between 90 and 250°C) it is possible to expand considerably the size of the hole (thermal expansion), thus allowing the insertion or removal of the component which, once it has cooled, returns to its original size.

It is specified that excellent results can be obtained by driving by mechanical interference without the use of any thermal conditioning: moreover, this method is also particularly advantageous in economic terms, since it does not require any device and apparatus designed for thermal conditioning of the parts to be mated.

With particular reference to an alternative constructive solution, the internal ends 5a and 5b of the tubular body halves 2a and 2b can advantageously have a shape chosen preferably among cylindrical, frustum like, prismatic with a substantially polygonal profile, and combinations thereof.

Frustum-like matings and prismatic matings ensure the elimination of some degrees of freedom even without the need to resort to mechanical driving and/or other methods for rigid mating of the two body halves 2a and 2b.

In one possible constructive variation of unquestionable interest in practice and in application, the internal ends 5a and 5b of the distinct tubular body halves 2a and 2b can be conveniently mutually mated by means of a localized welding process such as laser welding, electron beam welding, and the like.

Laser welding is a welding method that is used to join multiple pieces of metal by using a laser: the beam provides a concentrated source of heat, which allows thin and deep welding, and a high welding rate. It should be noted that this type of welding has a high power density (on the order of 1 MW/cm ² ), which allows to localize the energy in small areas, which are heated (and then cooled) at high speed.

Electron beam welding is instead designated by the acronym EBW. This is a process for welding metal by melting, by virtue of the application of a beam of electrons which strikes at high speed the flaps to be joined. The electrons have great kinetic energy and, by striking the flaps to be mated, produce the heat necessary to cause melting.

With reference instead to a further possible constructive variation, it is specified that the internal ends 5a and 5b of the distinct tubular body halves 2a and 2b can be validly mutually mated by means of a structural adhesive bonding process, i.e., by using specific structural adhesives.

Structural adhesives are those adhesives, based on modified acrylic resins, polyurethane resins, epoxy resins or silicone resins, which are capable of withstanding great mechanical stresses and of replacing traditional joining methods. They allow to have a continuous distribution of stresses in the joining points and also a greater resistance to vibrations. They are termed structural because they can bear loads beyond 100 kg/cm ² .

Furthermore, it is specified that a constructive version of assured industrial interest is in any case also provided in which the internal ends 5 a and 5b of the tubular body halves 2a and 2b can be advantageously mutually mated by interposition of a component such as a tab, a key, a pin, a screw and the like.

Additional constructive variations are in any case provided in order to ensure the mating of the two tubular body halves 2a and 2b.

In particular, it is noted that the internal ends 5a and 5b of the mutually distinct tubular body halves 2a and 2b comprise respective threads which are complementary for mutual screw coupling. The two threads are respectively a female thread and a screw, allowing easy and stable mating of the two body halves 2a and 2b: any stable coupling of the two body halves 2a and 2b can be obtained by interposing a thread braking substance or a generic adhesive between the two threads before mutual fastening.

Finally, a further constructive solution which also allows to provide bodies 2 of any length (and therefore suitable for multiple different applications) can provide for interposing, between the internal ends 5 a and 5b of the distinct tubular body halves 2a and 2b, at least one joining spacer sleeve (which is coupled at said ends with any one of the known methods, including the ones described previously).

It is specified furthermore that a gap is formed between the shaft 3 and the tubular body 2 for the containment of a predefined quantity of lubricating fluid.

In order to lower the friction coefficient, bear the loads and dissipate heat, lubrication is adopted and is of the oil bath type. Lubricant circulation thus occurs by sloshing during the rolling motion of the tubular body 2 with respect to the shaft 3. During this motion, the lubricant passes through the gap created between the shaft and the roller (striking and coating also the bushings 4 on at least one of their surfaces).

In order to avoid the escape of the lubricant with respect to the assembly defined previously, which would cause the leakage of said lubricant and the almost immediate deterioration of performance, the sealing elements 8 are used, thus creating a containment chamber which is hermetic and closed toward the outside.

The sealing elements 8 comprise, according to a particularly effective and functional embodiment, a sealing ring of the type with a double taper, which is interposed between each contoured shoulder 7a and 7b of a respective external end 6a and 6b of the tubular body 2 and a corresponding fixed annular element 9 which is coupled to the shaft 3.

The sealing elements 8 can be made of polymeric material, metallic material, sintered material, elastomeric material and/or of a combination thereof.

With particular reference to the constructive solution shown by way of nonlimiting example in Figures 1 and 2, at least one tubular half body 5b can efficiently comprise a hole 10 for the supply of lubricating fluid.

In turn, the hole 10 can be provided with a respective removable plug 11 for hermetic closure.

Advantageously, the present invention solves the problems described above, proposing an element 1 of a crawler-track movement assembly for works vehicles that is not subject to geometric deformations caused by the mutual welding of the element halves (the body halves 2a and 2b), such as wheel halves and roller halves.

Positively, the element 1 according to the invention is not subject to deterioration of local mechanical performance caused by the mutual welding of the element halves (the body halves 2and 2b), such as wheel halves and roller halves.

Favorably, the element 1 according to the invention is not subject to variations of the micrographic and crystalline properties caused by the mutual welding of the element halves (the body halves 2a and 2b), such as wheel halves and roller halves. This occurs by virtue of the fact that the welding process is avoided or, when it is used, is of an extremely localized type.

Usefully, the element 1 according to the invention avoids the losses of lubricant by virtue of the use of sealing elements 8 which are blocked directly between the shoulders 7a and 7b (provided on the ends 6a and 6b of the body halves 2a and 2b) and the fixed annular element 9 which is coupled to the shaft 3.

Efficiently, the element 1 according to the invention is constituted by a minimal number of components: this produces a clear containment of production and setup costs with respect to the background art.

Conveniently, the element 1 according to the invention is simple and quick to assemble.

Validly, the element 1 of a crawler-track movement assembly for works vehicles according to the invention is relatively simple to provide in practice and modest in costs: these characteristics render the element 1 according to the invention an innovation of assured application.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may furthermore be replaced with other technically equivalent elements.

In the exemplary embodiments shown, individual characteristics, given in relation to specific examples, may actually be interchanged with other different characteristics that exist in other exemplary embodiments.

In practice, the materials used, as well as the dimensions, may be any according to the requirements and the state of the art.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.