Patent Application
20090039574
This application claims the benefit of priority under 35 U.S.C. §119(e) from U.S. Provisional Patent Application No. 60/035,396, filed on Aug. 10, 2007, in the U.S. Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference.
Spring assemblies designed to withstand compression loads are used in a wide range of applications, such as railway carriages, heavy duty vehicles and other applications where damping or shock absorbing is essential. In general, such spring assemblies include an elastomeric body positioned between a pair of rigid end plates. The elastomeric body is made of rubber and is compressed by the load applied to the spring assembly. In many cases, these spring assemblies are used in combination with an air bellow/diaphragm, to achieve the desired characteristics needed for the application in question.
A problem with prior-art elastomeric spring assemblies of this kind is that they are hard to realize because the space available at the top of the spring assembly is often limited by an air bellow to approximately halfway down the elastomeric body, when the spring assembly is used in combination with an air bellow. To achieve a reduced diameter at the top half, an interleaving element are necessary to prevent overloading of the rubber and to maintain the vertical non-linear stiffness characteristic.
The space envelope available, when the spring assembly is used in combination with an air bellow, makes it difficult to control the compression of the elastomeric spring without having to adapt the surrounding parts. The space envelope of the top part of the spring assembly is essentially restricted by the air bellow. Also the design of the surrounding parts may restrict the space envelope significantly.
Previous designs of non-linear springs having approximately constant natural frequency can not be designed to achieve the space envelope restrictions when used in combination with an air bellow. This means that a larger air bellow/diaphragm would be needed in order to avoid contact between the spring assembly and the air bellow during horizontal and transversal loads. Furthermore the horizontal stiffness can only be controlled by adjusting the aspect ratio between the inner and outer profiles of the elastomeric body or by altering the number of elastomeric layers.
In view of the above, example embodiments provide a new spring assembly which is improved over prior-art spring assemblies and which solves or at least reduces the problems discussed above.
Example embodiments may provide a spring assembly which comprises:
A specific problem to be solved may be to provide an improved spring assembly for a secondary rail suspension air spring. A stopping element or means may be useful in order to keep a rail-mounted vehicle within its kinematic envelope. Therefore, an external stopping element or means were needed in previous designs. In example embodiments, a stopping element or means is provided integral to the design.
The required vertical stiffness is very low with a high load capacity. The use of interleaving elements restricts the elastomeric body to maintain a smaller diameter, whilst maintaining the near constant natural frequency requirement for vertical stiffness. This is advantageous in that a smaller air bellow/diaphragm can be used when the spring assembly is used with air bellow element or means. The improved design in general allows a lower horizontal to vertical stiffness ratio whilst maintaining the progressive nature of the vertical stiffness curve.
In example embodiments, the stopping element or means of the spring assembly comprises a protuberance which projects from said first end member and is located within said elastomeric body, which is advantageous in that integral stopping element or means can be realized without altering the external dimensions of the spring assembly.
In example embodiments, the stopping element or means comprises a protuberance which projects from said second end member and is located within the internal cavity of the elastomeric body.
In example embodiments, the stopping element or means comprises a first protuberance which projects from the first end member and is located within the elastomeric body, and a second protuberance which projects from the second end member and is located within the internal cavity.
In example embodiments, the stopping element or means is at least partly enclosed by elastomeric material of said elastomeric body, which is advantageous in that it provides the ability to tune the horizontal stiffness characteristics by providing a second higher rate stiffness after the initial deflection.
In example embodiments, the interleaving element or means comprises at least two annular interleaving elements which concentrically arranged about the centre axis in axially spaced positions. This provides favourable reinforcing effects, and provides the spring assembly with symmetric characteristics.
In example embodiments, the interleaving elements are made of substantially rigid material, for instance metal such as steel, which is favourable in that the elements are easily manufactured by casting, turning, milling, pressing, spinning or laser cutting.
In example embodiments, at least one of said interleaving elements has a conical cross-section. This results in lower material stress and that the fatigue endurance of the interleaving elements and the elastomeric body, the vertical stiffness is improved simultaneously.
The interleaving elements may be at least partially or predominantly embedded in the elastomeric body. This means that the interleaving elements are exposed to lower material stresses and that the vertical to horizontal stiffness ratio is lowered.
In example embodiments, the elastomeric body has a cross-section which is symmetric about the centre axis, which is advantageous in that it is easily manufactured and shows uniform stiffness characteristics in different directions.
In example embodiments, the elastomeric body has a general frustoconical cross-section, which is advantageous in that the spring assembly can be easily fitted to air bellow element or means with a small diameter air bellow/diaphragm, without having to adapt the air bellow or the air spring.
The elastomeric body may consist of rubber, for instance polyisoprene, which means that low dynamic stiffness together with low creep is achieved in the elastomeric body.
In example embodiments, the internal cavity of the elastomeric body opens towards the second end member, which is favourable in that the vertical and horizontal characteristics can be tuned by adjusting the shape of the internal cavity.
In example embodiments, the elastomeric body is bonded to the end members.
In example embodiments, the elastomeric body is bonded to the end members by vulcanization, which is favourable in that a strong and durable bond is established between the elastomeric body and the end members.
Alternatively, the elastomeric body is cold-bonded to the end members by means of an adhesive, which is advantageous in that the bonding can take place without heating the spring assembly.
In example embodiments, the spring assembly further comprises air bellow element or means configured to be compressed in at least the main load direction.
The air bellow element or means may be attached to one of the end members, which means that the air bellow element or means can take up different frequencies and therefore enhances the damping characteristics of the spring assembly.
In example embodiments of the spring assembly, one of the end members supporting the air bellow element or means is provided with a circumferential sealing area for an annular bellow of said air bellow element or means. This means that the air bellow can be fitted to the spring assembly without having to modify the spring assembly.
In example embodiments, one of the end members is provided with an air through passage. This means that air can be fed through the spring assembly to, for example, an air bellow.
Example embodiments provide a spring arrangement, a suspension system, a vibration anti-shock mounting system and a vehicle as defined in the appended claims.
In the following, example embodiments will be further described with reference to the appended drawings which illustrate embodiments, given as non-limiting examples, and in which:
Example embodiments described below are particularly applicable to a railway carriage or other types of vehicles, but may also be used as a low frequency mount for marine or industrial equipment (for instance suspension of machinery).
With reference to
The central protuberance 2 can also be used in combination with a second central protuberance 22 (shown in phantom) which then also limits compression of the elastomeric body 6. The second central protuberance 22 can also be used solitarily without the central protuberance 2 to limit the compression.
The elastomeric body 6 is shaped in such a way that it provides a non-linear vertical stiffness, and it can be made of various elastomeric materials, such as a synthetic version of natural rubber, natural rubber or another elastomeric material, like polyisoprene. In example embodiments, the elastomeric body 6 is bonded to the first and the second end members 1, 3. In example embodiments, the entire interface between the upper end member 1 and the elastomeric body 6 is bonded. At its bottom the elastomeric body 6 is bonded to an annular element 3′ mounted to the lower end member 3. The bonding may be accomplished by vulcanization, but alternatively cold-bonding can be applied using an adhesive.
The elastomeric body 6 comprises a lower internal cavity 17 which opens towards the second end member 3. Further, the elastomeric body 6 comprises an upper internal cavity 20 in which the central protuberance 2 is located and bonded.
In order to achieve the aimed-at spring effect, the two interleaving elements 4, 5 are substantially rigid and embedded into the elastomeric body 6. It should be noted that embodiments with a number of interleaving elements 4, 5 are feasible within the scope of example embodiments. The interleaving elements 4, 5 are annular and continuous and they reinforce the elastomeric body 6 during compression and restrict the diameter of the elastomeric body 6 to increase during compression.
The lower end member 3 has a shaped profile defining vertical and horizontal characteristics, and it also has a boss or spigot 7 to provide a solid horizontal location where the spring assembly is installed.
As can be seen from the drawings, the spring assembly is symmetric about a centre axis CA.
In example embodiments (see
In the embodiment shown in
The stopping element or means 2 of the upper end member 1 connects to an annular projection 10 of the elastomeric body 6 in order to alter the characteristics of the stopping element or means 2. By adding different thicknesses and shapes of the projection 10, the compression limitation can be tuned accurately to fit the application. In addition, the shape of the elastomeric body 6 is also altered relative to that of
With reference to
In
As shown in
Finally it should be mentioned that example embodiments are not restricted to those described herein, and several modifications are feasible within the scope of the appended claims. For instance, various structures of the interleaving element or means can be used. Furthermore, different types of air bellows can be used in combination with the spring assembly.
| Number | Date | Country | |
|---|---|---|---|
| 60935396 | Aug 2007 | US |
