JPS6256370B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to compressive load bearings, and more particularly to such laminated bearings comprising alternating adhesive layers of elastic materials such as elastomers and non-stretchable materials such as metals.

It is widely known that the compressive load carrying capacity of an elastomeric material of a given thickness can be increased many times by dividing it into layers and separating the layers by intermediate layers of non-stretchable material. At the same time, however, the ability of the elastic material to shear or twist in a direction parallel to this layer is substantially unaffected. This concept has been adopted or utilized in various laminated bearing designs as shown in the following US patents: That is, Schmidt's U.S. Patent No.
3679197, Botsugus Patent No. 3377110, Olein Patent No. 2995907, Hinx Patent No. 2900182
No. 2,752,766, and Wildheiba Patent No. 2,752,766. Various types of laminated bearings are typically used in industrial applications where they are required to support large compressive loads in one direction and also accommodate limited relative movement in the other direction. This bearing is designed so that large compressive loads are supported generally perpendicular to the elastic layer. A significant industrial difference in bearings is characterized by alternating adhesive layers arranged concentrically around a common center. That is, alternating layers of elastic and non-stretchable materials are disposed at increasing radial distances from a common center. This type of bearing includes many different shapes, in particular cylindrical, conical or generally spherical or fan-shaped bearings which are necessarily cylindrical, conical and spherical in shape. Such bearings are typically used in aviation, particularly for supporting rotor shafts in helicopters. As pointed out by Schmidt supra, this type of bearing can be required to accommodate synchronous twisting movements about a given axis, while at the same time supporting large compressive loads along that axis. many,
As a result, large compressive and shear stresses and strains occur in the elastic layers closest to the common center, and fatigue failures are likely to occur in the innermost elastic layers to accommodate the twisting motion. Schmitt proposed to improve the fatigue life of such bearings by increasing the thickness of successive layers of elastic material with increasing radius and at the same time decreasing the elastic modulus of the same layers successively with increasing radius. did. However, Schmidt's method is expensive because each elastomer layer must be made of a different material. That is, an elastomer bearing consisting of 15 elastic layers must be prepared from 15 different elastomer materials. Even though this could commonly be accomplished by dividing the basic feed of elastomer into 15 lots and varying each lot with different amounts or types of additives, it is expensive, time-expensive, and It is inconvenient to provide different materials for each elastic layer.
Additionally, care must be taken to properly align the material so that it can be properly positioned with a modulus of elasticity that decreases with increasing radius, as directed by Schmidt.

The main object of the invention is therefore to provide a laminated bearing as described above, in which only two different elastic materials are used to obtain a relatively large number of elastic layers, each exhibiting a different effective elastic modulus.

Another object of the invention is to provide a laminated bearing of an elastomer which has a high compressive modulus of elasticity and yet has a low, or at least no increased, shear modulus of the same part.

Yet another object of the invention is to improve the fatigue life of laminated bearings and to provide flexible bearings which not only have a particularly high shear to permissible compressive load ratio but also have a low strain energy in areas prone to high strain in the elastic layer. The object of the present invention is to provide an elastomeric bearing with improved fatigue life by using a resilient material.

Yet another object of the present invention is to provide a laminated bearing capable of varying the shear stiffness in different directions of motion in the same part of the bearing, in order to adapt to the special strain distributions occurring in different applications; It is an object of the present invention to provide a bearing having a resilient material selected and arranged to limit expansion of the side ends for the purpose of maintaining stiffness.

The foregoing objects and the objects and advantages described or specified below are achieved by each of at least some of the elastic layers of the laminated bearing being comprised of at least two portions of material having different moduli of elasticity. achieved. The elastic layer is formed of three parts arranged from one end to the other in the longitudinal direction of the bearing, the two end parts having greater compression stiffness than the central part, and the expansion restriction of the side ends relative to the softer central part. It is desirable to have it act as a barrier or barrier.

Other features, variations, and advantages will be indicated or become apparent in the following detailed description, which should be considered in conjunction with the drawings.

As is known to those skilled in the art, a primary consideration in the design of elastomeric bearings and other elastomeric fittings that primarily accommodate compressive loads is the so-called form factor. In the case of an elastomeric compression pad, the more restrictions there are on freedom of deformation, the stiffer it becomes. This parameter, which often depends on the bulge area or compression free area, can be used to adjust the stiffness of the adhesive rubber pad under compressive loads.
Since the stiffness of a given compression pad is a direct function of its shape factor, the higher the shape factor, the
The permissible compressive load of the pad is large. The shape factor is the ratio of the load area and bulge area of the same pad. For example, consider a bearing or other attachment consisting of an elastomer pad sandwiched between and bonded to two rigid metal plates, each of which has the same length L and the same width W, and When the thickness of the pad is t, the load area LA and bulge area BA are as follows.

LA=L×W BA=2t(L+W) Therefore, the shape factor SF can be expressed as follows, SF=LW/2t(L+W) If the bulge area is reduced without reducing the load area, the shape factor increases. It is clear that this has the effect of increasing the allowable compressive load. Also, if the shape factor is increased by limiting or reducing the bulge area, the bearing structure becomes more anisotropic in the sense that the shear stiffness is unaffected or changes only slightly at the same time as the allowable compressive strain increases. It will become sexual.

Laminated construction with bearings and other attachments, such as those mentioned above, means that if the overall thickness of the elastomeric pad profile remains unchanged, the shape factor and therefore stiffness will greatly increase due to the reduction in free bulge area. There is profit. At the same time, however, because the thickness of the metal plate or clasp that separates the layers of elastomer is relatively small compared to the overall thickness of the laminate pad, essentially the sole effect of the intermediate clasp is the freedom of expansion of the elastomer layer. will begin to decrease. This expansion limitation has no substantial effect on shear stiffness. Therefore, an important aspect of the present invention is to increase the expansion limit of elastic layers in laminated bearings and other attachments for the purpose of increasing compressive modulus, while simultaneously reducing the relatively small shear stiffness of these same layers. The objective is to provide a laminated bearing that obtains the following. In an embodiment of the invention, each layer consists essentially of two expansion limits or barriers formed of a relatively stiff elastic material and an intermediate portion formed of a flexible material sandwiched between the two expansion restrictions. This is achieved by making each elastic layer such that The expansion limiter is adhered to the intermediate portion to form a single elastic layer characterized by relatively stiff end portions and a relatively flexible intermediate portion.

The stiff end portions prevent expansion and cooperate with the middle portion to exhibit a predetermined value of the resultant or net modulus, and at the same time the middle portion acts to maintain the shear stiffness of the single layer at a low value. . This use of a relatively stiff and relatively flexible elastomer to form an elastic layer is an effective method of maintaining low twisting stiffness and increasing stiffness against compressive loads.

Referring now to FIGS. 1 and 2, a conical laminated bearing made in accordance with the invention comprises two annular metal end members 2, 4 having frustoconically shaped inner and outer surfaces 6, 8. Each is equipped with one. Second
As shown in the figure, in the completed bearing,
Alternating adhesive layers of elastic material 10 and non-stretchable material 12 are disposed between the end members 2, 4, the surfaces 6, 8 of which are adhered to the layers of elastic material. The elastic material is preferably an elastomer such as natural or synthetic rubber, but may also be a suitable metal such as stainless steel. As can be seen in FIG. 2, the layers 10, 12 are frustoconical in shape and are arranged generally parallel and coaxially to the surfaces 6, 8 of the two rigid metal end members.

In this case, layers 10, 12 are of uniform thickness, but the non-stretchable layer 12 (which is commonly referred to as a shim) is thinner than the elastic layer. Moreover, the elastic layer is made such that its ends have greater stiffness than the center, and therefore the effective modulus of each layer decreases with increasing radius. This arrangement of elastic layers is accomplished by making each elastic layer 10 from two different elastic materials arranged side by side as shown in FIG.

Referring to FIG. 1, each elastic layer 10 is placed over one of the end members, member 4, to create a composite layer which includes two frusto-conical side ends 10A. , 10B and the frustoconical central portion 10
C, the side end portions 10A, 10B are made of the same elastic material with a predetermined stiffness, and the central portion 10C is made of another flexible elastic material, namely the side end portion 1
It is made of a material that is less hard than 0A and 10B. The above-mentioned parts are provided so as to be in contact with each other as shown in the figure. A shim 12 is then placed on top of this composite layer, and a second composite layer is provided on top of this shim. This second composite layer has its side end portion 10
It is similar to the first layer except that A, 10B has a narrower width than the corresponding end portion of the first layer. As used herein, the term "width" refers to a dimension extending parallel to layer 12 as shown in FIG. This second
A second clamp is placed on top of the composite layer elastic layer, and then a third composite layer is placed over it. This third composite layer is similar to the second composite layer except that its side edge portions 10A, 10B are narrower than the side edge portions of the second layer. This process of alternating elastic and non-stretchable layers is repeated such that the side edge portions 10A, 10B of each elastic layer have a narrower width than the corresponding portions of the previous inner layer. After arranging a predetermined number of elastic layers, another end member is superimposed on the last elastic layer, and then this assembled product is integrally molded under appropriate temperature and pressure to form elastic parts 10A, 10B, 10C are bonded to each other and adjacent clamps 12 or end members 2
Or glue both 4 together. As a result, each group of elastic portions 10A, 10B, 10C together form a single elastic layer 10, which has greater stiffness at both ends and which, starting from end member 4, extends outwardly from end member 4. Successive elastic layers following 2 have successively wider flexible central portions and successively narrower stiffer side end portions. Thus, as already mentioned, each successive elastic layer outwardly from the end member 4 has a successively smaller elastic modulus. By appropriately changing the dimensions of the side end portions 10A and 10B with respect to the central portion 10C, it is possible to make the strain distribution uniform, as Schmidt did, in order to improve the fatigue life of the laminated structure. It is possible. At the same time, the relatively stiff side end portions of the elastic layer have the effect of limiting expansion of the flexible central portion, thereby increasing the allowable compressive load. If necessary, the thickness of the layer 10 also increases with increasing radius, as in the bearing disclosed by Schmidt;
Or, conversely, it can be constructed such that its thickness decreases with increasing radius.

The above method of making a bearing such as that shown in FIG. 2 is particularly suitable when the elastic material is an elastomer that can be melted and molded under heat and pressure. If the elastic material is rubber, the bonding process includes sulfurization. Other aspects of the assembly and gluing procedures for the stacking of elastic layers, shims and bearing members 2, 4 are known to those skilled in the art of laminated elastomeric bearings and are conventional and form part of the present invention. Because it is not a thing,
I will not elaborate here. However, it is sufficient to indicate that the clamping and bearing parts need to be cleaned to be suitable for bonding and that bonding of the elastic layer to these parts usually involves the use of adhesives or adhesive cements. . Further, the mounting of the clamps and the elastic layer components may be carried out using a suitable jig, or may be carried out during the molding process at the bonding stage.

FIG. 3 shows how the invention is applied to the manufacture of cylindrical laminated bearings. In this case, the assembled parts are the inner and outer bearing members 2
2, 24 and a plurality of intermediate cylindrical clamps 26, which are separated from each other by a three-part elastic layer consisting of side portions 28A, 28B and a central portion 28C. . Although the clamp is of uniform thickness, we will not discuss it here, although it is already easy to understand that the elastic layer may have a uniform thickness as shown in Figures 1 and 2. It is not shown. The thickness of the elastic layer increases with increasing diameter, as shown in FIG. 3, although it is clear that it may decrease with increasing diameter. For each layer, component parts 28A, 28B,
28C has the same thickness, but the side end portion 2
8A, 28B are constructed of the same relatively stiff resilient material, and differ in that the central portion 28C is constructed of a different, relatively soft resilient material. However, the side end portions 28A, 28B of each elastic layer may be made of the same material as the side end portions of other elastic layers,
All central portions 28C may also be made of the same material. In contrast to the bearing shown in FIG. 1, the side end portions 28A, 28B are identical in width, ie, dimension measured parallel to the bearing axis. Although not shown in the figure, since the structure of Figure 3 is compressed under heat and pressure, the three sections of each elastic layer adhere to each other and to the adjacent shims and bearing members. are also bonded to form a uniform laminated bearing structure. Of course, in this case the barrier or side end portion 28
A, 28B serve primarily as expansion limiters, and the elastic modulus of each elastic layer is the same as all others. However, if necessary, the width of the barrier section can be reduced or increased with increasing radius, such that the net elastic modulus of each elastic layer decreases or increases with increasing radius, as described with respect to FIGS. 1 and 2. May be increased. It is also contemplated to construct the bearing in such a way that the thickness and/or elastic modulus of the elastic layer varies according to a step function. That is,
For example, in a cylindrical or conical bearing consisting of 15 elastic layers, the first three layers starting closest to the central axis have a different net elastic modulus and/or thickness than the next three layers; Each of the next three layer groups also differs from the others in modulus of elasticity and/or thickness.

The present invention can be implemented in other ways than those shown and described above. That is, it is possible to manufacture a bearing in which the use of an expansion limiter or barrier, for example made of a relatively stiff elastic member, is limited to one side of the bearing. In other words, regarding the embodiment of FIG. 1, the elastic portion 10B is removed and the portion 10C is
It is possible to build a bearing by increasing the length of. It has also been considered to eliminate the use of expansion limits or barriers altogether in certain elastic layers. That is, for example, according to the present invention,
Conical bearings have been constructed that limit the use of rigid member expansion limitations to a predetermined number of elastic layers closest to the outside of the bearing. In certain applications, expansion limits or barriers were used in only the outer seven layers.
A conical bearing similar to that shown in FIGS. 1 and 2 has been fabricated, consisting of 15 elastic layers.

A further possible variant of the invention consists in reversing the arrangement of the elastic layers so that the central part is made of a stiffer member than the end parts. This particular arrangement is suitable for certain bearing structures where the stiff member portion is loaded when the movement is relatively slow, and the flexible member portion is loaded when the movement is fast. Another example where such an arrangement may be used is a circular laminate bearing pad consisting of upper and lower disc-shaped end retention members bonded to an array of alternating discs of elastic and non-stretchable material; is mounted to support compressive loads applied perpendicular to the alternating layers and also to meet the requirements of withstanding twisting movements about its central axis. In such cases, the elastic layer experiences greater deflection and therefore greater strain at its periphery under twisting loads. Accordingly, in accordance with the present invention, each elastic layer is constructed as at least two parts: a relatively stiff circular central part and a relatively flexible annular outer part. Of course, each elastic layer can be made up of several annular sections concentrically surrounding a central section, with the annular sections becoming progressively more flexible with increasing radius. In this case, as in other embodiments of the invention, the outer end portion of the synthetic elastic layer may be made to have greater environmental resistance than the inner portion. Of course, the relative length of central portion 28C may be progressively smaller to obtain a tapered flat bearing.

As already mentioned, the present invention has many benefits, but its main advantage is that it can be made as small as possible.
Two different elastic members can be used to selectively construct bearings of compression type and twist type characteristics. At the same time, however, it is possible to assemble the elastic layer to include two or more different elastic members. For example, for special applications requiring conical bearings as shown in Figures 1 and 2, the side end portion 10B is made of a harder material than 10A, and the side end portion 10A is glued to the intermediate portion. Stiffer than 10C may be desirable. A further important advantage of the present invention is that the use of relatively stiff side end portions eliminates the extrusion and delamination erosion that is likely to occur on the exposed end faces of the elastic layer when the bearing is subjected to repeated twisting and compressive loads. This is to help reduce bearing failure. Additional advantages and modifications will readily appear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a part of a conical bearing structure made in accordance with the present invention, in the state of the part before the elastic material is molded and bonded to the associated metal parts, and FIG. 2 is after molding and bonding. FIG. 3 shows the conical bearing structure as shown in FIG.
It is a longitudinal cross-sectional view similar to the figure. In the figure, 2, 4...end face member, 10A, 10B,
10C...Elastic layer, 12...Non-stretchable layer, 22,
24...Bearing member.

Claims (1)

Claims: 1. A laminated bearing for supporting compressive loads, consisting of a number of elastic and inextensible layers generally arranged concentrically around a common center;
At least some of the elastic layers have at least a first side end portion and a second side end portion and a third portion between the first and second side end portions, respectively, at opposite ends of the bearing. the first and second side end portions have a modulus of elasticity different from the modulus of elasticity of the third portion, and at least some of the third portion comprises:
having different widths as a function of distance from the common center, such that the effective elastic modulus of the at least some layers is greater than or equal to the width between the at least some layers and the common center. A laminated bearing characterized in that it differs as a function of distance. 2. A laminated bearing according to claim 1, wherein the successive layers are arranged on successively increasing radii around the common center and the thicknesses of at least two of the elastic layers differ from each other. 3. The laminated bearing according to claim 1, wherein each elastic layer has substantially the same thickness. 4. The laminated bearing according to claim 1, wherein the first and second side end portions have the same elastic modulus. 5. The laminated bearing of claim 1, wherein at least one of the elastic layers has first and second side end portions with a greater elastic modulus than the third portion. 6. The laminated bearing of claim 1, wherein at least one of the elastic layers has first and second side end portions having a smaller elastic modulus than the third portion. 7. The laminated bearing according to claim 1, wherein all the elastic layers of the laminated bearing have a first side end portion, a second side end portion and a third side portion. 8 the first and second side edge portions of the at least one elastic layer have larger dimensions in the lateral direction of the laminated bearing than the first and second side edge portions of the at least one other elastic layer; A laminated bearing according to claim 1. 9 The first and second side end portions are comprised of a first material and the third portion is comprised of a second material, and at least some of the third portions are at a distance from a common center. 2. Laminated bearing according to claim 1, having different widths as a function of .