MXPA00001298A - Hybrid leaf spring and suspension system for supporting an axle on a vehicle - Google Patents

Abstract

In a hybrid leaf spring (10), an elongated primary leaf element (12) is provided having a first modulus of elasticity, a tension surface (14), and a compression surface (16). At least one layer of composite material (20) is substantially parallel to and bonded to the tension surface (14) of the primary leaf element (12) with at least a second layer of composite material (20) bonded to the compression surface (16) of the primary leaf (12). The primary leaf element (12) can also include mounting eyes (18) coupled to the ends of the primary leaf element (12) for mounting the hybrid leaf spring (10) to the frame of a vehicle. The hybrid leaf spring (10) can also include multiple layers of composite material (20) bonded to both the tension (14) and compression (16) surfaces of the primary leaf spring (12).

Description

SPRING OF HYBRID SHEET AND SUSPENSION SYSTEM TO SUPPORT AN AXLE ON A VEHICLE FIELD OF THE INVENTION The present invention relates generally to vehicle suspension systems and more particularly to leaf springs incorporating layers of mixed materials. BACKGROUND OF THE INVENTION The present invention relates to leaf spring suspension systems for both motorized and non-motorized vehicles and is described herein as being applied to such use. Known leaf springs are constructed of several elongated strips or metal sheets stacked one on top of the other and then joined together. Usually, these springs are used in suspension systems for vehicles in one of two different configurations of load transport, cantilever configuration, or bending at three points; the latter being the most common method of use.

A leaf spring of cantilevered configuration is one in which the leaf spring is fixed or supported at one end to a structure of a vehicle and coupled to an axle at its other end.

Alternatively, a leaf spring mounted in three-point flexure is supported or fixed at one end to a structure with the other end mounted such that it can float and the load is supported by the spring between its two ends. The use of springs Ita of sheet mounted in flexion of three points, is so widespread that the Society of Automotive Engineers (SIA) has developed a formal leaf spring design and procedure of use. Metal sheet springs constructed in the manner described above are incorporated in a variety of different vehicle suspensions including automobiles, light and heavy trucks, trailers, construction equipment, locomotives and rail cars. These are also used in recreational vehicles, such as bicycles, sledges and VTTs (all-terrain vehicles). The leaf springs mounted on the vehicles mentioned above, function to improve the uniformity of the trajectory of the vehicle and to absorb and store energy in order to release it in response to bends and / or impact loads imposed on the spring resulting from such events such as finding obstructions in a road during vehicle operation. The mechanical properties that define a suspension system for vehicles, particularly the spring and static deflection regime of the leaf springs, directly influence the uniformity of the vehicle's rail. Generally, a uniform path requires that leaf springs have large static deflections. The uniformity of the travel also influences the damping characteristics of the vibrations of the leaf springs. Damping is a parameter that quantifies the capacity of the leaf spring to dissipate the vibratory energy. Therefore, a high degree of damping is desired in the leaf springs used in automobiles to minimize the vibrational amplitudes transferred to the passenger area. The ability to accurately determine the mechanical properties and performance characteristics of the leaf spring is critical to the proper design of vehicle suspension systems. One of the problems that results from the construction of conventional leaf springs is that the variable lengths of individual sheet stacks create a stepped spring construction that only approximates constant fatigue, the steps tend to create localized areas of high fatigue known as fatigue concentrations which detrimentally affect the ability to carry the load and the life of the leaf spring. In addition, the fact that the springs are composed of metal lengths stacked one on top of the other, makes them very heavy, this additional weight causes a concomitant reduction in fuel economy. further, because it is impossible to predict the exact conditions and stresses to which a leaf spring will be subjected, the fatigue life of the spring is generally limited. This problem is further increased by the production of foreign material on and between the individual sheets. This not only causes corrosion, thus weakening the leaf spring and makes it more susceptible to fatigue failure, but also affects the stiffness of the leaf spring and, therefore, the uniformity of the vehicle's path in the which spring is used. Generally, the magnitude of the contribution made to the strength of a particular leaf spring due to the friction between the sheets is determined empirically. When the foreign material arrives between the sheets, it can dramatically increase, in the case of particulate matter, or decrease, in the case of oil, the friction between the sheets, thus altering the original mechanical properties of the spring. In addition, the shear conductivity between the sheets, which is a measurement of the amount of shear fatigue transferred from sheet to sheet, is usually low in conventional sheet springs because the individual sheets are only held in the sheets. extremes. Therefore, the fatigue transfer capacity along the length of the spring depends on the friction between the sheets mentioned above. In many applications, sheet springs are loaded not only by vertical forces, but also by horizontal forces and torques in the vertical longitudinal and vertical transverse planes. These forces are usually generated when the brakes on the vehicle are applied to the leaf spring. The horizontal forces and torques mentioned above cause the leaf spring to assume an "S" configuration, a phenomenon called "S-shape". Fatigue induced in the spring when this occurs can be very high. In order to minimize the shape of a leaf spring, the stiffness of the spring should be increased, however, this can detrimentally affect the uniformity of the travel of a vehicle. In order to address the problems described above, those skilled in the art have attempted to manufacture only sheet springs of mixed materials, wherein the individual sheets are formed of a mixed material of the type consisting of a plurality of fibers embedded in a polymer matrix. However, while these springs offered significant reductions in weight, as well as life of increased fatigue and damping, their cost was prohibitive. Springs of mixed material were also difficult to attach to the structure of a vehicle and the use of special adapters was required. Based on the foregoing, it is the general objective of the present invention to provide a lightweight, durable, cost-effective sheet spring. It is a more specific objective of the present invention to provide a leaf spring incorporating mixed materials that can be mounted to a vehicle structure without the need for special adapters. It is still another object of the present invention to provide a leaf spring having the capacity of not having an S-shape while not reducing the uniformity of a vehicle path.

It is still a further object of the present invention to provide a leaf spring having increased shear conductivity. SUMMARY OF THE INVENTION The present invention meets these and other objectives by providing, in one aspect, a hybrid sheet spring having an elongated primary sheet element with a first modulus of elasticity, a compression surface, and a surface of opposite tension . The primary sheet element also includes means for attaching it to the structure of a vehicle. At least one layer of mixed material having a second modulus of elasticity different from the first modulus of elasticity is attached to one of the surfaces of the primary sheet element. The aforementioned mixed material is preferably composed of a plurality of substantially parallel, elongated fibers embedded in a polymeric matrix. In a related aspect, a first layer of elastic material can be interposed between the primary layer and at least one layer of mixed material to provide the hybrid sheet spring with damping and impact resistance, as well as to absorb residual stresses at the interface between the primary sheet element and the layer of mixed material resulting from the shrinkage of the polymer matrix during the curing process. The first layer of the elastic material is attached to a surface of the primary sheet element by a first layer of adhesive and to at least one layer of the mixed material by a second layer of adhesive. Alternatively, the first layer of the elastic material can be interposed between the primary sheet element and at least one layer of the mixed material before curing the polymer matrix. As the polymer matrix cures and hardens, it will also act as its own adhesive bonding the first layer of the elastic material to at least one layer of the mixed material. The present invention can also employ a second layer of the mixed material bonded to the other surfaces of the primary sheet element, thereby adding to the stiffness and damping capacity of the sheet spring. A second layer of elastic material can also be placed between other surfaces of the primary sheet element and the second layer of the mixed material. The second layer of the elastic material can be joined to the other surface of the primary sheet element by a third layer of adhesive and to the second layer of the mixed material by a fourth layer of adhesive. Alternatively, and in the same manner as described above, the second layer of the mixed material can be joined to the second layer of the elastic material by the polymeric matrix material that is part of the mixed material. The hybrid sheet spring described above can also incorporate multiple layers of the mixed material placed one on top of the other and joined to either or both compression and tension surfaces of the primary sheet element.

These layers of mixed material can be defined by identical polymeric matrix materials and fibers, or can vary from layer to layer. In an alternative embodiment of the present invention, an encapsulated hybrid spring is provided, and is defined by a central metal sheet element, encapsulated by a sleeve of narrow coupled mixed material. A first layer of adhesive can be used to join the sleeve to one of the respective compression and tension surfaces of the primary sheet element and a second layer of adhesive can be used to join the sleeve to another surface, thereby joining the sleeve of mixed material to the surface. primary sheet element. The composite material sleeve is preferably made of a mixed material by a plurality of substantially elongate parallel fibers embedded in a polymeric matrix. Another embodiment of the present invention, useful with heavy vehicles, employs two or more hybrid leaf springs mounted to the structure of a vehicle, one on top of the other. In this way, you can increase the capacity to carry the load of a vehicle by simply adding more springs. The preferred and alternative embodiments described above of the present invention have several advantages over sheet springs that are all made of steel. One of the most important advantages is that a conventional metallic primary sheet element is used as the core of the hybrid sheet spring with layers of mixed material attached thereto. Therefore, the means by which the leaf spring can be mounted to the structure of a vehicle, can be incorporated into the metal primary sheet element, avoiding the need for special adapters as needed to mount the leaf springs of materials mixtures known from the prior art to the structures of the vehicles. A further advantage of the present invention is that the aforementioned layers have a significantly lower mixed material weight than that of the steel sheets, while still being able to withstand higher loads. This results in a lower total vehicle weight, which translates into higher fuel economy. As long as the weight of the spring is lower, the use of computers of lower weight to attach the spring to the structure of a vehicle will also be allowed. Another advantage of the present invention resides in the fact that a lower external surface fatigue is realized in the mixed material portion of the leaf spring because the modulus of elasticity of the mixed material is several orders of magnitude lower than that of the metallic primary sheet element. This results in a concomitant reduction in the stresses in the metallic primary sheet element to subsequently assess those found in springs that are steel, conventional, similar that have an equivalent spring rate. Because the mixed materials are bonded to the main steel sheet, resulting in increased conductivity of the compartment, the use of the mixed material layers results in a reduction in the thickness of the sheet spring. Since the external tension in a leaf spring is directly proportional to the distance of the outer edge in a leaf spring from the neutral or central axis of the spring, the thinner leaf springs result in less fatigue. This in turn results in increased fatigue life of sheet springs incorporating layers of mixed materials over conventional steel sheet springs. In addition, the use of mixed materials having a lower modulus of elasticity results in a lower external fiber tension. The "S-shape" resistance is a result of the upper section modulus (stiffness) of the hybrid spring compared to the stack of individual steel sheets that depend mainly on the stiffness of the steel main spring. Yet another advantage of the present invention arises from the fact that the formation of sheets of two or more treated materials having a different modulus of elasticity results in a spring system having a greater degree of damping than if the leaf spring were build a simple material. This is mainly due to the fact that the natural frequencies (eg, the frequency at which a given system will vibrate at their own pace) differ from those of the individual materials, thus resulting in energy quenching and dissipation more fast, at a given vibratory input. In addition, the incorporation of the layers of the elastic material between the primary sheet element and the mixed material layers also adds to the cushioning capacity of the hybrid sheet spring. A further advantage of the present invention is that the bonded structure of the hybrid sheet spring prevents the ingestion of foreign material between the spring sheets. Thus, the mechanical and performance properties of the leaf spring of the present invention, tend to deteriorate less with time than those of conventional steel springs. Still a further advantage of the present invention is that the shear conductivity between the primary sheet and the mixed material layers is increased because the layers of mixed materials are joined along their lengths to the primary sheet. BRIEF DESCRIPTION OF THE DRAWINGS These and other features, aspects, and advantages of the present invention understood will be better with respect to the following description, claims and accompanying drawings in which: FIG. 1 is a front elevation view of the leaf spring of the present invention, FIG. 2 is a cross-sectional side view of the leaf spring of FIG. 1; FIG. 3, is a front elevation view of an alternative embodiment of the leaf spring of the present invention; FIG. 4, is a planar top view of the leaf spring of FIG. 3; FIG. 5, is a sectional view taken through line 5-5 in FIG. 4, of the leaf spring of FIG. 4; FIG. 6, is a front elevation view of the leaf spring of a further embodiment used as a beam of cantilever configuration; FIG. 7, is a front elevation view of a further embodiment of the leaf spring of the present invention; FIG. 8, is a front elevation view of an additional embodiment of the leaf spring of the present invention; FIG. 9, is a front elevation view of a further embodiment of the leaf spring of the present invention; FIG. 10, is a planar top view of the leaf spring of FIG. 9; FIG. 11, is a partial transverse sectional view taken through line 11-11 in FIG. 10, of the leaf spring of FIG. 9; FIG. 12 is a cross-sectional side view of another embodiment of the leaf spring of FIG. 1; and FIG. 13, is a side elevation view of yet another embodiment of the leaf spring. Detailed Description of the Preferred Modalities Referring to FIG. 1, a preferred embodiment of a hybrid sheet spring generally designated 10, includes, an elongated primary sheet element 12, having a first modulus of elasticity, a tension surface 14, an opposing compression surface 16, and means of assembly 18, shown as, but not limited to, mounting clips formed integrally with the ends of the elongated primary sheet element, for coupling the sheet to a vehicle structure. The elongated primary sheet element 12 is also formed of a suitable material, such as, but not limited to, metal, preferably steel, having higher elastic moduli than the mixed materials described above. Alternatively, the primary sheet element 12, and at least one layer of mixed materials 20, can be fabricated from a mixed metal matrix material which consists of a plurality of fibers embedded in a metal matrix. At least one layer of mixed material 20 is placed substantially parallel to, and joined to, one of the surfaces, such as the compression surface 16, of the primary sheet element 12. The hybrid sheet spring 10 is preferably fabricated by joining the layer of the mixed material 20 to the primary sheet 12 and placing the assembled components in a press using a hot die having a shape conforming to the desired non-charged shape of the finished hybrid sheet spring. The components are then pressed together and by the combination of heat and pressure, the hybrid sheet springs in a repeatable manner can be formed consistently. In the illustrated embodiment, the mixed material layer 20 is profiled along the length of the primary sheet element 12, which is generally the thickest at the junction of the axis but is not limited to the center of the sheet element primary and tapering at each end. This tapered configuration provides a substantially constant tension to the spring by placing the greatest amount of mixed materials at the point of greatest tension and gradually reducing the thickness of the mixed material towards the point of least tension near the mounting means 18 on the primary sheet element 12 In addition, the retaining means 21, preferably in the form of a metal band, are joined around the primary sheet element 12 and the opposite ends of the mixed material layer 20 to prevent the layer of mixed materials from separating from the element. of primary sheet. The mixed material layer 20 is preferably formed of a plurality of substantially parallel fibers embedded in a polymeric matrix. The fibers that are part of the layer of mixed materials 20, can be made of inorganic glass "E" and high resistance glass "S" or organic carbon (synthetic), aramid, or some type of polyethylene, with a modulus of elasticity of approximately 0.738 - 3.866 million kg / cm2, and a permissible tension of approximately 21.090-42.180 kg / cm2; however, the invention is not limited in this respect, since other types of fibers known to those skilled in the art of formulating mixed materials, such as boron fibers, can be substituted without departing from the broad aspects of the invention. In addition to the above, the polymeric matrix in which the fibers mentioned above are embedded, preferably is thermofixed, or of the thermoplastic type, such as, but limited to, polyester, vinyl ester, epoxy, nylon or polyethylene with elastic moduli of about 14.060 to 140.600 kg / cm2 and a shear strength of about 140.6-632.7 kg / cm2. Referring to FIGS. 1 and 2, the fastening means 22 is used to engage the leaf spring 10 in a three-point bending configuration to a vehicle axle 24. In the illustrated embodiment, the fastening means 22 includes a pair of bolts 26 that extend around the axis 24 with the leaf spring 10 that is received between the U-bolts. A sealing plate 30 that defines 2 pairs of openings 32 for receiving the ends 28 of the U-shaped bolts 26 is positioned adjacent to the mixed material layer 20 and the fastening means 32 are threadably engaged with the ends of the U-shaped bolts to releasably hold the bolts in place. U-shaped and the leaf spring 10 on the axis 24. In addition, a loading sheet 34, to increase the capacity to support the load of the leaf spring in the area of the highest tension, is interposed between at least one layer of mixed material 20 and the sealing plate 30. The loading sheet 34 can be attached to the mixed material layer 20 or can be kept in contact with the mixed material layer by the fastening means 22. The loading sheet 34 can be both curca as flat and be constructed of a mixed or metallic material.

In order to properly position the leaf spring 10 along the axis 24, the positioning means 36 engages with the shaft, and in the illustrated embodiment extends through the leaf spring 10, the loading sheet 34, and the sealing plate 30 on the shaft 24 whereby the position of the leaf spring relative to the shaft is fixed. The positioning means 36 can have various shapes, and in the illustrated case is a fastener, however, a bolt can also be used without departing from the broad aspects of the present invention. As shown in Fig. 2, a first layer of elastic material 38 may be interposed between the primary sheet element 12 and the mixed material layer 20 to increase the damping, provide impact resistance, and compensate for any residual stress that may be present in the material. Somehow it could be induced in the spring at the interface between the primary sheet element and the layer of mixed material resulting from the shrinkage of the polymer matrix during curing. The first layer of elastic material 38 is made of a suitable material, such as, but not limited to, natural or synthetic rubber, thermosetting elastic, or thermoplastic elastomers. The first layer of elastic material 38 can be bonded on a surface to the compression surface 16 of the primary sheet element 12 via a first layer of adhesive 40 and on a surface opposite the mixed material layer 20 by a second layer of adhesive 41 Alternatively, the first layer of elastic material 38 can be attached to the primary sheet element 12 by the material constituting the layer of material 20. Prior to forming the composite material, the first layer of elastic material can be placed on the element primary sheet 12 so that the layer of the mixed material 20 can then be formed or molded into the primary sheet element 12 and the first layer of elastic material 38, with the polymeric matrix material constituting part of the mixed material encapsulating the elastic material and It acts as the adhesive to join the first layer of elastic material 38 to the primary sheet element 12. In order to ensure a strong adhesive ion between the first layer of the elastic material 38 and the layer of the mixed material 20, the layer of the mixed material is usually a surface treated, or prepared for bonding, grounding or mechanically roughening the surface of the layer of the mixed material that will be in contact with the adhesive and then uniformly cleaning the surface. In addition, and depending on the type of mixed material used, a flame treatment or corona discharge process may be used to prepare the surface for bonding. The first layer of the elastic material is also normally prepared to be joined by said processes such as sand application, flame treatments or corona discharge, plasma treatments in fio or etching and acid texturing. The corona discharge processes operate on the principle that an air space between an electrode and the surface of the product has a dielectric breakdown voltage lower than that of the product itself. As high voltage, high frequency electrode power is applied, and through the air gap to the substrate, the air in space is ionized and forms a gaseous conductor observed as a bluish corona. The space of ionized air is caused by the acceleration of electrons that move away from the surface of the electrode. As the electrons accelerate, they get enough energy to cause an avalanche of electrons, which in turn creates oxidative molecules tending to break the molecular bonds on the surface of most substrates causing the surface to oxidize. This oxidation increases the surface energy, which allows better wetting by liquids. In addition to the corona discharge process, cold plasma processes are used in the preparation of polymers and elastomers for the formation of bonds. The cold plasma treatments normally employed include activation plasmas, grafting processes and plasma polymerization. Activation plasmas use a gas that reacts with the chemistry of the product. These plasmas use oxygen, ammonia, air, halogens and other gases to etch and separate surface material. The grafting processes create free radicals on the surface by exposure to a noble gas plasma, followed by a wash of the surface in the vapor of an unsaturated monomer. The free radicals on the surface of the polymer initiate the grafting reactions with the monomers of the reaction. Plasma polymerization uses plasma energy to initiate gas phase polymerization and deposition on a substrate within the plasma chamber. After the surfaces described above for bonding have been prepared, the layers of adhesives mentioned above must provide sufficient bond strength, therefore, adhesives having shear strengths greater than 140.6 kg / cm2. Still referring to Fig. 2, a second layer of the elastic material 42 can be interposed between the loading sheet 34 and the mixed material layer 20 with a third layer of adhesive 44 joining the second layer of elastic material to the layer of the second layer. mixed material and a fourth layer of adhesive 46 joining the second layer of elastic material to the loading sheet 34. Alternatively, and in the same manner as described above, the polymer matrix material comprising part of the layer of the mixed material can used to encapsulate the second layer of the elastic material 42 and joins the layer of the mixed material and the second layer of the elastic material to the primary sheet 12, thus making obvious the need for the adhesive layers 44 and 46. Figures 3-5 illustrate another embodiment of the hybrid sheet spring, generally designated 47, in which the elements described above have the same reference numerals. In this embodiment, in addition to the first layer of mixed material 20 on the compression surface, a second layer of mixed material 48, also preferably formed of a plurality of substantially parallel fibers embedded in a polymeric matrix, is attached to the tension surface. 14 of the primary sheet element 12. Due to the fact that most mixed materials exhibit higher stress than the compressive strength, it is preferred in the embodiment of Figure 3 that the first layer of mixed material 30 bonded to the surface 16 of the primary sheet element 12 is thicker than the second layer of the mixed material 48 joined to the tension surface of the primary sheet element. The increased thickness of the layer of the mixed material 20 in relation to the layer of the mixed material 48 attached to the compression surface 16 of the primary sheet element 12, gives the layer of the mixed material 20 the ability to sustain compression fatigue in proportion with the stress fatigue imposed on the layer of the mixed material 20. Furthermore, the increased thickness of the layer of the mixed material 48 attached to the compression surface 16 causes the central or neutral axis of the hybrid sheet spring to change towards the surface of compression 14 of the spring, thus decreasing the compression fatigue of the external fiber. This results in a concomitant reduction in the compression stresses induced in the primary sheet 12 and the layer of the mixed material 20. As shown in Fig. 5, a third layer of the elastic material 50 can be interposed between the second layer of the material mixed 48 and the tension surface 14 of the primary sheet element 12 and a fifth layer of adhesive 52 join the third layer of the elastic material 50 to the second layer of the mixed material 48 with a sixth layer of the adhesive 54 joining the third layer of the material elastic to the tension surface 14 of the primary sheet element 12. Alternatively, as described above, the polymer matrix material forming part of the second layer of the mixed material 48, can be used to join the third layer of the elastic material 50 to the primary sheet element 12. Referring to Figure 6, while the embodiments of the present invention shown in Figures 1-5 illustrate a hybrid sheet spring mounted in three-point flexure, it is also possible to employ the invention in a cantilever configuration. Accordingly, FIG. 6 illustrates a hybrid leaf spring 55 having a first end 56 mounted to a structure, such as, but not limited to, the structure of an automobile. The opposite end 58 is coupled to a shaft 24 of the vehicle in the same manner as in the previously described modes, via the clamping means 22. A first layer of mixed material 60 is attached to the tension surface 62 of the primary sheet 64. , and a second layer of mixed material 66 is attached to the compression surface 68 of the primary sheet. A loading sheet 70 is also provided and can be attached to the second layer of mixed material 66, or it can simply couple the second layer of the mixed material. It is also possible to build a hybrid sheet spring using only the above mentioned second layer 48 of the mixed material 48 attached to the tension surface 14 of the primary sheet element 12. Said hybrid sheet spring is illustrated in Fig. 7 and is generally designated by the reference number 72 in whose elements described above have the same reference numbers. The third layer of the elastic material 50, Fig. 5 can be interposed between, and joined to. the second layer of mixed material 48 and the tension surface 14 of the primary sheet element 12. In the illustrated embodiment, the overburden sheet 34 is placed between, and is in communication with, the compression surface 16 of the primary sheet element 12 and the closure plate 30, with the fastening means 22 coupling the leaf spring to the axis of the vehicle 24. Referring to Fig. 8, the hybrid leaf spring of the present invention is shown, and are generally designated by the reference numeral 74, multiple layers of mixed material stacked one on top of the other and attached to both the tension surface 14 and the compression surface 16 of the primary sheet element 12 can also be used. As illustrated, a third layer of the mixed material 76 is attached to the second layer of the mixed material 48, with a fourth layer of the mixed material 78 attached to at least one layer of the mixed material 20. As with the previous embodiments of the This invention. The layers of the elastic material can be interposed between, and joined to, the second and third layers of the mixed material, 48 and 76 respectively, and at least at one end and the fourth layers of the mixed material 20 and 78, respectively.

Switching to Figs. 9-11, an alternative embodiment of the present invention wherein the primary sheet 12 is encapsulated by a mixed sleeve 79, is generally designated by the reference numeral 80, in which the elements described above have the same reference numerals. The mixed sleeve 79 defines an upper interior wall 82 and a lower interior wall 84. A first adhesive layer 86 connects the tension surface 14 of the primary sheet element 12 to the upper interior wall 82, and a second layer of adhesive 88. joins the compression surface 16 of the primary sheet element to the lower inner wall 84. The mixed sleeve is preferably formed of a material consisting of a plurality of substantially parallel fibers embedded in a polymeric hue. However, the invention is not limited in this respect, since other materials, such as mixed metal matrix materials, can be substituted without departing from the broad aspects of the invention. In addition, as best shown in Fig. 11, a first layer of elastic material 88 can be placed between, and joined to, the upper interior wall 82 and the tension surface 14 of the primary sheet element 12, and a second layer of the material elastic 90 can be placed between, and joined to, the lower inner wall 84 and the compression surface 16 of the primary sheet element. While it has been described that the leaf springs of the present invention are arched, the invention is not limited in this respect as other configurations, such as, but not limited to, that of Fig. 12 in which the spring is illustrated of sheet without having an initial curvature. As shown in Fig. 13, multiple sheet springs 100 can be mounted to the structure of a vehicle, one on top of the other, where a larger load having the ability to be achieved practically using a spring is desired. of a single sheet. In the illustrated embodiment, a leaf spring 110 having a primary sheet element 112 and at least one layer of mixed material 120 attached to the primary sheet element is mechanically co-molded by the fastening means 22 to a second sheet spring. 122 also having at least one layer of mixed material 124 attached to a second primary sheet element 126. In this way, the second leaf spring 122 assumes a portion of the load imposed on the first leaf spring. Although preferred embodiments have been shown and described, various modifications and substitutions can be made without departing from the spirit and scope of the invention. Accordingly, it should be understood that the present invention has been described by way of example and not limitation.

Claims (28)

1. CLAIMS 1. A hybrid sheet spring comprising: an elongated primary sheet element having a compression surface, an opposing tension surface, a first modulus of elasticity, and including means for joining the primary sheet to a structure of vehicle; and at least one layer of mixed materials having a second modulus of elasticity different from the first modulus of elasticity, substantially parallel and joined to a respective one of the tension or compression surfaces of the elongate primary sheet element.
2. 2. A hybrid sheet spring as defined in claim 1, wherein at least one layer of mixed materials is found along the length of the primary sheet.
3. 3. A hybrid sheet spring as defined in claim 1, further comprising a first layer of elastic material interposed between the primary sheet element and at least one layer of mixed materials.
4. A hybrid sheet spring as defined in claim 3, further comprising: a first layer of adhesive placed between, and joining, the first layer of the elastic material to one of the tension and compression surfaces of the primary sheet element; and a second layer of adhesive placed between, and joining, the first layer of the elastic material to at least one layer of mixed materials.
5. A hybrid sheet spring as defined in claim 1, wherein the modulus of elasticity of at least one layer of mixed materials is less than the modulus of elasticity of the primary sheet member.
6. A hybrid sheet spring as defined in claim 1, wherein: the primary sheet element is metal and at least one layer of mixed materials is defined by a plurality of substantially parallel fibers embedded in a polymer matrix material .
7. A hybrid sheet spring as defined in claim 1, wherein the primary sheet member and at least one layer of mixed materials are formed of a mixed material of mixed metal matrix materials defined by a plurality of fibers embedded in a metal matrix material.
8. 8. A hybrid sheet spring as defined in claim 1, wherein: at least one layer of mixed materials includes opposite ends; and the retaining means are placed at each of the opposite ends to prevent the mixed material layer from separating from the primary sheet member.
9. 9. A hybrid sheet spring as defined in claim 6, wherein the retaining means is a pair of bands fastened around the primary sheet member and at least one layer of mixed materials.
10. 10. A hybrid sheet spring as defined in claim 1, wherein the hybrid sheet spring is arcuate in the non-loaded condition.
11. 11. A hybrid sheet spring as defined in claim 1, wherein the hybrid sheet spring is straight in the non-loaded condition.
12. A hybrid sheet spring as defined in claim 1, further comprising: at least a second layer of mixed materials bonded to the other tension and compression surface of the elongated primary sheet element.
13. A hybrid sheet spring as defined in claim 12, wherein the layer of mixed materials attached to the compression surface is thicker than the layer of mixed materials attached to the tension surface.
14. A hybrid sheet spring as defined in claim 3, further comprising: a second layer of mixed materials bonded to the other tension and compression surfaces of the primary sheet member; a second layer of elastic material interposed between the primary sheet element and the second layer of mixed materials; A third layer of adhesive placed between, and joining, the second layer of the elastic material to the compression surface of the primary sheet element; and a fourth layer of adhesive placed between, and joining, the second layer of the elastic material to the second layer of mixed materials.
15. 15. A hybrid sheet spring as defined in claim 1, further comprising an overload sheet attached to at least one layer of mixed materials.
16. 16. A hybrid sheet spring as defined in claim 1, wherein: the primary sheet member includes opposite ends; and the means for mounting the leaf spring to a vehicle structure includes at least one mounting clip coupled to at least one of the opposite ends.
17. 17. A hybrid sheet spring comprising: a primary sheet element having a compression surface, a tension surface, and including means for attaching the primary sheet to a vehicle structure; and a sleeve of mixed materials that encapsulates the primary sheet.
18. 18. A hybrid sheet spring as defined in claim 17, wherein: the mixed material sleeve defines upper and lower interior walls; a first layer of adhesive is placed between, and joins, the compression surface to the upper inner wall; and a second layer of adhesive is placed between, and joins, the tension surface to the lower inner wall.
19. 19. A hybrid sheet spring as defined in claim 18, further comprising: a first layer of elastic material interposed between the compression surface and the upper internal wall, and joined to the compression surface by the first adhesive layer; a third layer of adhesive placed between, and joining, the first layer of elastic material to the compression surface, a second layer of elastic material interposed between the tension surface and the lower inner wall, the second layer of elastic material joining the surface of tension by a second layer of adhesive; and a fourth layer of adhesive placed between, and joining, the second layer of elastic material to the tension surface.
20. 20. A hybrid sheet spring as defined in claim 17, wherein: the primary sheet member includes opposite ends; and the means for attaching the primary sheet element to a vehicle structure includes at least one mounting clip coupled to at least one of the opposite ends of the primary sheet member and extending outwardly from one end of the tubular layer of the first layer. mixed material.
21. 21. A hybrid sheet spring as defined in claim 17, further comprising a loading sheet coupled to the composite material sleeve.
22. 22. A hybrid sheet spring as defined in claim 17, wherein: the mixed material is formed of a material defined by a plurality of substantially parallel fibers embedded in a polymeric matrix material.
23. 23. A hybrid sheet spring suspension system for supporting an axle of a vehicle structure, comprising: a primary sheet element having a compression surface, a tension surface, a first modulus of elasticity, and including means for joining the primary sheet to a vehicle structure; at least one layer of mixed material joined to a respective one of the tension or compression surfaces of the primary sheet element, at least one layer of mixed material having a second modulus of elasticity different from the first modulus of elasticity; and fastening means for coupling the leaf spring to the shaft.
24. 24. A hybrid sheet spring suspension system for supporting an axle on a vehicle structure as defined in claim 23, further comprising a loading sheet interposed between the fastening means and the leaf spring. MWlMrrr r - pti ?? ifip? Tl_a_i? _p? P
25. 25. A hybrid sheet suspension system for supporting an axle on a vehicle structure as defined in claim 23, wherein the securing means comprises a pair of U-shaped bolts, which extend around the axle and which have threaded ends, the leaf spring being received between the pair of U-bolts; a sealing plate defining two pairs of openings for receiving the threaded ends of the U-shaped bolts, the sealing plate which is placed on the upper part of the leaf spring; fastening means threadably engaged with the threaded ends of the U-shaped bolts, to freely grip the sealing plate on the leaf spring; and locating means extending through the sealing plate and the leaf spring and coupling the shaft, thereby releasably fixing the position of the leaf spring along the axis.
26. 26. A hybrid sheet spring suspension system as defined in claim 23, wherein at least one layer of mixed material is defined by a plurality of substantially parallel fibers embedded in a polymeric matrix.
27. 27. A hybrid sheet spring suspension system as defined in claim 23, wherein at least one of the primary sheet elements or at least one layer of mixed material is formed of a mixed metal matrix material.
28. 28. A hybrid sheet spring comprising: a first leaf spring for mounting to a vehicle structure, having a primary sheet element, at least one layer of mixed materials attached to the primary sheet member, and mounting means coupled to the primary sheet member and the structure of the vehicle; and at least a second leaf spring coupled to the first leaf spring and having a second primary sheet element and at least a second layer of mixed material attached to the second primary sheet element.