MXPA01005447A - Improvements to anchoring and retention elements intended to machines used in public works and similar - Google Patents

Abstract

The improvements are applied to anchoring and retaining elements intended to machines used in public works and similar of the type comprising a combination of one or a plurality of metal elements with one or a plurality of elastomer blocks which are connected or not to the former. The elastomer block is comprised of an elastic structural material which has multiple internal cavities configured like closedells which, for the majority, are separated between each other and contain a gas. Through the compression exerted by the metal parts to the elastomer block, the latter is compressed thereby reducing its volume and forming minimal transversal expansions.

Description

IMPROVEMENTS IN THE ELEMENTS OF ANCHORAGE AND RETENTION INTENDED FOR WORKS MACHINERY PUBLIC AND SIMILAR DESCRIPTIVE MEMORY The present invention is intended to disclose improvements in anchoring and retaining elements intended for public works, mining and similar machinery, < that provide interesting characteristics of novelty and inventive activity on what is known so far. The machines of public works, mining and other similar, have the function of plucking and loading masses of earth and stones. They are equipped with an active edge, called a blade, in which assemblies designed to penetrate the ground are mounted. These assemblies are usually a series of adapters or adapters (welded, screwed or mechanically fastened to the blade) that are coupled parts, called spikes or teeth, which perform the function of entering the ground. There are several coupling systems between teeth and adapters, and all of them have a different fastening or anchoring system. The anchoring system must keep the tooth perfectly mounted in the nose of the adapter, resisting all the efforts to which the assembly (tooth-anchor-adapter) is exposed. The anchoring system can be forged by a single body (all integrated) or by several bodies (pin incorporating washers, retainers or tensioners). The pins have different forms and constitutions. There are pins made only of metal, although the most usual are those that present a combination of metal and rubber type material. The anchoring elements constituted by a combination of metal and rubber-like material, comparing them with the anchoring elements made only of metal, entail a greater ease of assembly and disassembly, a greater possibility of giving tension to the assembly and a good absorption of the efforts media. But they also have considerable drawbacks that cause the breakage and loss of these elements. These drawbacks are the influence of temperature on the mechanical characteristics of the rubber-like material and the possible deterioration of it due to the absorption of oils and greases, although the main drawback is the high transverse expansion suffered by the rubber-like material when compressed, tending to tear This supposes the imminent loss of the pin. So far, in anchoring systems formed by a combination of metal and rubber-like material, compact (or solid) elastomers have been used. A compact (or solid) elastomer is one that is constituted by a single phase.

Normally, natural rubbers are used. These have good resistance to traction, abrasion, tearing and fatigue, as well as high resilience. Its limitations include a moderate maximum service temperature (between 70 ° C and 90 ° C) and its sensitivity to oxidation and attack by ozone. Likewise, like all non-polar rubbers, it swells appreciably when it comes into contact with hydrocarbon solvents. When it is swollen, its mechanical strength is considerably reduced and its susceptibility to degradation increases. The property that characterizes rubber is its high elasticity, that is, its capacity to undergo considerable deformations under relatively weak stresses and to quickly recover the original shape and dimensions when the deformation force ceases to act, restoring the energy stored during deformation. The disadvantage of presenting a high transverse expansion when compressed is common to all the compact elastomers used hitherto in anchoring or retaining elements. Due to this high capacity of transversal expansion, the compact elastomer implemented in pins is easily deteriorated by friction or pinching when making the pin assembly and also while the assembly is working. As shown in figure 18, by applying a force Fx on a block of compact elastomer, it responds by compressing and presenting a transverse expansion (bulging of the sheet). This happens because the compact elastomer keeps its volume constant although it is subjected to forces. If a force F2, greater than Fx, is applied, the transverse expansion increases. If larger forces (F3) continue to be applied, the compact elastomer will continue to expand to a point where it will eventually break. The volume remains constant in the four represented states, increasing more and more the transversal expansion suffered. The main problem of the transverse expansions caused by the maintenance of the same volume when applying a force entails that the compact elastomer interferes with other bodies (inner walls of the housing of the pin, internal walls of the tooth and the nose of the adapter) and ends up suffering frictions , pinching, shearing and bending that inevitably cause breakage. The breakage of the compact elastomer involves the loss of the pin and, consequently, the loss of the tooth. That is why it is very important that the anchoring system is tightly fastened and is resistant to the efforts suffered by the assembly.

Description of the Invention Figure 11 shows a set consisting of a tooth, a tooth holder and a "sandwich" pin with lateral introduction, metal-rubber-metal type. In figures 12, 12bis and 13 you can see the evolution of the assembly of this pin. In Figure 12 one end of the pin is inserted into its housing and struck with a hammer. The pin penetrates the housing compressing the rubber that joins the metal parts; the metal end parts are separated by forcing the elastomer, which often tends to disengage and tear (Figure 12a). By continuing to introduce the pin, the rubber continues to compress, already presenting a considerable lower and upper transverse expansion that interferes with the external wall of the tooth, inevitably causing the rubber to deteriorate (Figure 13). Once assembled (figure 14), the rubber remains deformed, interfering with the internal wall of the nose of the adapter and the internal wall of the tooth. When the whole is subjected to stress, the rubber deteriorates more and more until it breaks. To try to minimize the inconvenience of the transverse expansions that interfere with other bodies, slight modifications have been made in the design of the elastomeric elements; but these have not managed to solve the problem.

The modifications made to try to minimize the transverse expansions are based on the extraction of part of the elastomeric material. These include the perforation of the material and the concave shapes of the sheets. Figure 23 shows a retainer / tensioner with three holes arranged vertically. In figure 24 the holes, through, are arranged laterally on a "sandwich" type pin. In Figure 25 the retainer / tensioner is vertically bored and in Figure 26 a "sandwich" type pin has a concave elastomeric sheet. The main problem with perforated elastomers is the introduction of ferrous materials called fines into the holes. These fines are compacted and prevent the deformation caused by the compression from being absorbed by the holes, causing it to be transmitted again to the ends, expanding transversely, as an unperforated elastomer would respond. It also weakens the pin. The solution of presenting the concave shaped elastomers also does not solve the problem of transverse expansion. For large compressions, such as those caused during the assembly of the pin, the elastomers deform and end up interfering with other bodies. In addition, the fact of presenting a concavity means that the pin is weaker and, having less amount of elastomeric material, its elastic response is lower than that of a pin with the elastomer without concavity. Patent US 5 731 359 refers to elements for the absorption of vibrations comprising a thermoplastic elastomer, spongy polyamide, consisting of a block intended to support conduction pipes, mainly for the braking system in automobiles, having a plate carrier with a threaded bolt housed in a hole in the vibration absorber block, which has pore dimensions that gradually decrease from the inside to the external surface, ending in a smooth and closed surface. The patent application UK 2 150 667 relates to a device for absorbing shocks, made of plastic material, having a plastic casing that supports a spongy plastic material provided with closed cells and which has a piston acting on said spongy mass . US Pat. No. 4,678,707 discloses a composite laminate for vibration damping comprising two layers of a metal and a layer of a viscoelastic polymer, said cushioning compound having the capacity for electric welding to a metal structure. The inventors have carried out multiple investigations to try to solve the aforementioned drawbacks, having achieved an effective technical solution by introducing the use of compressible (cellular) elastomers preferably of cellular polyurethane as the basis for the bodies to be introduced in the retaining and anchoring elements used in public works, mining and other machinery. In the experiments carried out it has been discovered that for this application, the indicated elastomers combine a large reversible deformation with a very low transverse expansion, making them ideal for applications where the space surrounding the material is reduced. Thanks to these characteristics an unbeatable behavior of the anchoring elements is achieved during the assembly and during the operation time. In addition, the implementation of compressible (cellular) elastomers prevents design modifications, such as special shapes or perforations, thus simplifying manufacturing. The application of the compressible (cellular) elastomers, preferably of cellular polyurethane, will usually take place in the form of blocks of said material, of the appropriate dimensions, associated with metal receiving parts, integrating together a retention device. The blocks of elastomer material will give the elastic properties to the anchoring and retaining elements. The application of the blocks may take place both by adhesion of the previously formed material, and by molding and polymerization of the components of the polyurethane together with the metal parts that together make up the retention element. For better understanding, a series of drawings relating to the construction of the improved anchoring and retaining elements according to the present invention are attached as explanatory but not limiting examples. Figures 1, 2, 3, 4 and 5 represent views of a key-type retention device to which the present improvements can be applied. Figures 6, 1, 8, 9 and 10 represent views of another embodiment of a key to which the present improvements can be applied. Figure 11 shows a representative perspective view of the manner of insertion of horizontally disposed "sandwich" type keys. Figures 12, 13 and 14 show respective views of the introduction of a key in its housing and a cross section thereof, corresponding to an embodiment according to the current state of the art. Figure 12 bis shows a phase, intermediate, of widening of the ends during the introduction. Figures 15, 16 and 17 represent views of the placement and a perspective with partial section of a key incorporating the present improvements. Figure 18 schematically shows the successive phases of compression of a block of rubber-like material used according to the state of the art. Figure 19 schematically shows the behavior of a block of rubber-like material (compact elastomer) and the behavior of a compressible (or cellular) elastomer block within a closed space. Figure 20 shows schematically the constitution of a compressible (cellular) elastomer block. Figure 21 shows a 37-fold view of an elastomer block of the type used in the present invention. Figure 22 shows a section of an elastomer block according to the invention shown at approximately 90 magnifications. Figures 23, 24, 25 and 26 represent different versions of anchoring elements according to the state of the art in which modifications have been made to reduce the effect of transverse expansions. The improvements of the present invention could be applied to these elements avoiding the performance of perforations or any other type of modification that affects the mechanical response of these elements.

Figure 27 shows the behavior of an incompressible elastomer and a compressible elastomer. Figure 28 schematically shows the arrangement of a tooth and its tooth holder, with the relative position of the holes of both intended for the pin. Figure 29 shows schematically a pin, referencing its width. As seen in FIGS. 1 to 5, an anchoring element according to the state of the art, to which the present invention is applied, can be constituted in the form of a key with metal parts -1- and -2-, between that a block -3- of an elastomer is disposed which will usually be adapted by vulcanizing or by gluing on the internal faces -4- and -5- of the metal parts respectively -1- and -2-. In another embodiment shown in figures 6 to 10, the anchoring part also in the form of a key comprises two metal parts -6- and -7- which in this case are symmetrical and which are provided with intermediate projections on their external faces -8- and -9-, internally receiving, in opposition between the internal faces -10- and -11- of the pieces -8- and -9-, a block -12- of an elastomer. Figure 23 shows a version of a retention element according to the state of the art, formed by a metal base -50- * and a block of rubber-like elastomer -51-, in which various holes have been made as -52- to allow the compensation of the transverse deformation produced by said material of the currently known type. Figure 24 shows another version based on two metal parts -53- and -54- with an intermediate block of elastomer -55-, with through holes -56- with the same purpose. Likewise, in figure 25 there is represented a variant similar to that of figure 23, in which a metal part -57- receives the action of an elastomer block -58- provided with a longitudinal hole -59- with the same purpose than the one explained above. Also shown in figure 26 is a retaining element formed by the two metal pieces facing each other -60- and -61- in which the block of elastomeric material -62- has concave side faces such as -63- and -64- intended also to allow transverse deformation of the elastomer. All these technical measures to avoid transverse deformation, corresponding to the state of the art, are overcome by the application of the present invention. The use of these anchoring elements takes place as shown in FIG. 11, so that the key assembly 13, for example, of the type shown in FIGS. 6 to 10, is inserted between the tooth 14. - and the adapter -15- when introduced in the through holes made for this purpose, of which only the orifice -16- has been represented. As can be seen in figures 12, 12bis, 13 and 14, the introduction of the key -13- into the holes intended to receive it produces a compression of the metal parts -17- and -18- integrating the key, which act compressing the rubber type material block -19-, whereby it expands laterally giving rise to the laterally projecting areas -20- and -20'-. Said protruding areas create problems due to their interference with the external wall of the tooth and with the opposite faces -21- and -22- of the housing in which the key is coupled, which translates into abrasions and cracks in the elastomeric material, as well as shearing stresses that can compromise the integrity of the elastomer block and, therefore, the correct functioning of the key. Figures 15, 16 and 17 show the behavior of a retention element that incorporates the present improvements. A key -43- is inserted in the hole -44-, exerting a compression on the elastomer -45-, whose lateral faces -46- and -47- do not suffer practically any deformation. For a better explanation of the deformation suffered by an elastomer block of rubber-like material, a schematic section of a block -23- on which a compression force is applied according to the vector -24- is shown in FIG., which produces the compression of said block, causing lateral expansions such as those indicated expi that will be a function of the Fi effort. In case the compression effort increases, which is represented by the vector -25-, the deformations on both sides will be represented by exp2, being also equal in both cases. In the continuation of the compressive stress on the elastomer block -23-, a situation is reached in which said stress, represented by the vector -26-, produces exp3 expansions on both sides that result in the breaking of the zones extreme or distal -27- and -28- of the block -23-. In this case, in which the block of rubber material is applied, the volumes in the four represented states indicated by V0, Vi, V2 and V3, are equal, that is, that V0 = Vi = V2 = V3 is fulfilled. can be seen in figure 28, when mounting a tooth in a tooth holder there is a space determined by the back wall of the tooth hole and the anterior wall of the housing in the nose of the tooth holder. In this space (A) the pin must be inserted. This space has a casting tolerance. By dimensioning the posterior wall of the tooth hole and the anterior wall of the housing in the nose of the tooth holder with respect to the vertex of the triangle that determines the conicity of the tooth and the nose of the tooth holder (C), the dimensions are determined with tolerance. For example: X = 180 mm (0; -1.5) Y = 200 mm (+1.5; 0) Knowing that Y-X = A, then A = 20 mm (+3; 0). In this way, the space where the pin must be inserted can vary from 20 to 23 mm. The graph of figure 27 shows the behavior of an incompressible elastomer -70- (rubber type) and a compressible elastomer -71- within a closed space, representing the force in ordinates and the deformations in abscissas. The pin, once mounted in the housing of 23mm, must make a force to stay anchored in its housing fixing the tooth (F). This force, when the tolerance is applied (compression of 3 mm), is considerably increased in the case of a pin implemented with rubber type material (Fmc) implying a great transversal expansion. In contrast, for a pin implemented with compressible elastomer, the force that must be made to absorb the compression is much lower (Fmp). In addition, the pin implemented with compressible elastomer has a greater range of compression than the pin impregnated with rubber-like material, and can thus absorb the wear suffered by the nose of the adapter (Rcp> Rcc) • This wear causes more and more play between tooth and tooth holder and, consequently, that the pin has to absorb this set to avoid the tooth falling. If the width of the pin is B, it must be compressed to A when it is inserted in its housing. This causes the pin to be designed so that it can, deforming, enter its housing and, once introduced, have sufficient capacity to provide the necessary tension to anchor the tooth. Implementing rubber type material in the pins, the range of freedom is minimal, forcing to sacrifice one of the two facets. That is, hindering the assembly of the pin or worsening the fastening and tension of the pin once assembled. On the other hand, by implementing compressible elastomers in the pins it is possible to work with greater casting tolerances, allowing a lower dimensional accuracy than in the case of a pin implemented with rubber type material and achieving a much easier assembly with a good fixation. This supposes a saving in costs of manufacture, avoiding possible zones to mechanise and extending the tolerances of manufacture. Figure 19 shows the comparison between the behavior of a rubber-like elastomer -29- and the behavior of a compressible (or cellular) elastomer -311"- within a closed space -31-. In the absence of space for lateral expansion because the enclosure -31- is closed type, the rubber block is not deformed, so that its surface -31'- is not altered by the application of a force -30- represented by the vector Fi. In contrast with the compressible elastomer block -31 '' '-, this can be deformed because the material is compressible, not requiring transverse expansion. Therefore, the upper surface, which initially was at the same level as that of the block 29, is at the level represented by the numeral 31, after the application of a force 32 represented by the vector F2. By way of example, it can be indicated that by experiments carried out in the laboratory with a cellular polyurethane elastomer with a density of 350 kg / m3, a compression of 80% with respect to the original dimensions of the component is obtained, within a closed space such as that represented In Figure 19, the cellular polyurethane elastomer with a density of 350 kg / m3 reaches 63% of its volume, a rubber with a hardness of 45 Shore A with a density of 1.18 g / cm3 can not be compressed. better understanding of this characteristic behavior phenomenon of the compressible (or cellular) elastomers, it will be seen in figure 20 a block -33- of compressible (or cellular) elastomer schematically represented, in which it is appreciated in the area represented on a larger scale -34- the existence of multiple cavities -35-, -35'-, -35"-, which form closed type chambers filled with gas, in the most usual case, carbon dioxide. It will be understood, however, that an equally satisfactory operation could be achieved with other types of synthetic resins endowed with a certain degree of elasticity, which contained a gas other than C02 in the closed cells that said gas constitutes in the mass of the elastomer. In this regard, it will be understood that since these are cavities filled with a gas generated in the actual manufacture or treatment of the material, the shape thereof will be substantially spherical. In the figure 20 itself, another area -36- of the same block -33- is shown, on a larger scale, in which the structural material -37- is seen, preferably formed by a synthetic elastomer and the cavities -38-, -38 '-, -38' - of gas enclosed therein, so that the structural material completely surrounds and separates said cavities occupied by the gas In Figures 21 and 22, respective sectional views of real blocks of gas have been represented. cellular elastomers at approximately 37 and 90. In said photographic views, the cavities are represented by the different somewhat lighter contour areas, such as those indicated respectively with the numerals -39- and -40- in said figures. darker, such as -41- and -42-, respectively, correspond to cavities that have been cut above their median plane, leaving the background dark.From the point of view of the present invention, the elastomers of Cellular polyurethane is preferably having densities comprised between about 200 and 1000 kg / m 3. Likewise, the percentage of the volume occupied by the cavities with respect to the total volume of the cellular polyurethane block, will be comprised between approximately 30% and 90%, that is to say, that the volume occupied by the sum of the different cavities with respect to the total volume of the block will oscillate between 30% and 90%. Another additional advantage of the present invention is that by using a cellular polyurethane elastomer, a material is obtained which, unlike the rubbers currently used, is resistant to oil, fats and aliphatic hydrocarbons, also having a better resistance to aging. Likewise, the new materials applied to the retaining elements of the type envisaged in the present invention show a better behavior in terms of the remaining deformation after compression. Thus, for example, subjected to the same deformation force for 22 hours at a temperature of 70 ° C, the cellular polyurethane elastomers have a remaining deformation comprised between approximately 4% and 7%, while under the same conditions, an elastomer type rubber has a remaining deformation comprised between approximately 30% and 40%. The structural material of a compressible elastomer (cellular) can be ethylene-propylene-diene terpolymer (EPDM), polychloroprene, butadiene-styrene rubber (SBR), polyvinyl chloride (PVC), polyolefins ... Although the structural material that currently has the best mechanical properties for the related application in this invention is polyurethane. It is understood, by all the foregoing, that the essentiality of the invention will consist in arranging, between the metal part (s) of a retaining part or tension, one or more blocks of elastomeric material, whether or not joined thereto, comprising a structural material. or matrix of elastic type material, preferably synthetic, which contains in its mass a large number of small cavities or closed cells, mostly separated from each other, filled with a gas capable of being compressed when a compression action of the elastomer block is carried out, presenting a minimum deformation in directions transverse to the stress exerted on the elastomer. The present invention, by introducing blocks of cellular material with a matrix or structural material of synthetic and elastic type and multiple chambers filled with a gas, eliminates the disadvantages of the conventional rubber-type compact elastomers and retains the main advantages of these. The application of the present invention in anchoring systems in the form of a block between two sandwich-type metal support pieces or as a tensioner or retainer, allows these elements to absorb great stresses, having a very reduced transverse expansion and a greater resistance to bending. / torsion, practically eliminating the possibility of breakage or loss of the anchor element. Also, a greater resistance to aging and a better response to deformation efforts is achieved. At the same time, assembly is facilitated, since the anchoring elements, for example, pins or cotters, have a better elastic behavior with respect to those currently implementing compact elastomers and the deteriorations suffered by the elastomeric material are eliminated. Likewise, among the advantages of the application of the present invention should be included the possibility of varying between broad limits the characteristics of the material to adapt it to specific applications, acting by additives to achieve greater mechanical resistance, abrasion or oils and environmental agents or by varying the density and / or the volume occupied by the gas carrying cavities for the adaptation of the anchoring element to specific working characteristics. Everything that does not affect alter, change or modify the essence of the described improvements, will be variable for the purposes of the present invention, within the scope of the appended claims.

Claims (11)

Claims

1. Anchoring and retaining element, intended for fixing a tooth to the blade of an excavator or the like, whose anchoring element retains a combination of at least one metallic element and at least one block of elastomeric material, characterized in that: said block of elastomeric material (3) is made by an elastic structure containing multiple internal cavities in the form of closed cells filled with gas, so that when said metallic element (1, 2) exerts a compressive force on said block of elastomeric material (3) the resulting expansion of each elastomeric material is minimized in a direction transverse to each metallic element (1, 2).

2. Anchoring and retaining element, according to claim 1, characterized in that the structural material is constituted by a polyurethane resin.

3. Anchoring and retaining element, according to claim 1, characterized in that the gas that is comprised in the cells, which are generally separated from each other, is carbon dioxide.

4. Anchoring and retaining element, according to claim 1, characterized in that the elastomer is constituted by a cellular polyurethane with a density comprised between 200 and 1000 kg / m3.

5. Anchoring and retaining element, according to claim 1, characterized in that the elastomer is constituted by cellular polyurethane in which the volume of the cells is comprised between 30% and 90% with respect to the total volume of the elastomer.

6. Anchoring and retaining element, according to claim 1, characterized in that the elastomeric material is constituted by cellular polyurethane that shows a residual deformation at a compression comprised between 2% and 10% at a temperature of 70 ° C.

7. Anchoring and retaining element according to claim 1, characterized in that the structural element is constituted by EPDM (ethylene-propylene-diene terpolymer).

8. Anchoring and retaining element according to claim 1, characterized in that the structural element is constituted by polychloroprene.

9. Anchoring and retaining element, according to claim 1, characterized in that the structural element is constituted by SBR (styrene-butadiene rubber).

10. Anchoring and retention element, according to claim 1, characterized in that the structural element is constituted by PVC (polyvinyl chloride).

11. Anchoring and retaining element, according to claim 1, characterized in that the structural element is constituted by polyolefins.