WO2006037096A2

WO2006037096A2 - One-piece outer split shell pre-compressed cradle/sub-frame mount

Info

Publication number: WO2006037096A2
Application number: PCT/US2005/034994
Authority: WO
Inventors: John G. Lew
Original assignee: Cooper-Standard Automotive Inc.
Priority date: 2004-09-28
Filing date: 2005-09-28
Publication date: 2006-04-06
Also published as: WO2006037096A3

Abstract

An isolator member includes an inner member, an outer member having first and second outer shell portions, a first rate plate secured to the outer member, and an elastomer interconnecting the inner and outer members. The one-piece outer shell and rate plate insert is preferably formed of a non-metallic, composite material. The outer member and rate plate can be formed of the same material and in the same operation. A method of assembling the isolator assembly includes providing an outer member having first and second shell portions secured by an interconnecting member, positioning an inner member within the outer member, interconnecting the inner and outer members with an elastomer, and removing the interconnecting member joining the first and second shell portions.

Description

ONE-PIECE OUTER SPLIT SHELL PRE-COMPRESSED CRADLE/SUB-FRAME MOUNT

Background of the Invention

[0001] The present application relates to an isolator assembly, such as a cradle or sub-frame mount assembly, that secures a body, such as a vehicle body, to an associated support, such as a vehicle frame or cradle. An elastomeric material is incorporated into the assembly to absorb vibration and shock between the two components, namely the body and support. These types of body or cradle mount assemblies, which are generally referred to as an isolator assembly, are particularly used in the automotive industry. Commonly owned application in the same general field, namely, International Published Application WO2004/011299, is incorporated herein by reference and generally representative of these type of isolator assemblies.

[0002] FIGURE 1 illustrates a pre-compressed cradle mount assembly as is conventionally used in the industry. This assembly includes multiple components that are typically loaded into a press having multiple cavities. In other words, the multi-cavity press simultaneously forms a number of isolator assemblies during a single cycle. If each isolator assembly includes multiple components, a large amount of operator time is taken to load each component into the press. Moreover, it is common to provide adhesive on the inserts to improve the mold bonding with an elastomer introduced into the mold cavity and the potential exists for problems arising where, for example, the adhesive begins to cure while the individual components sit in the press during loading of the components into the multiple cavities. As a result, adhesive curing may begin prematurely and is undesirable since the resultant bonding may be less than ideal in the final manufactured assembly.

[0003] In FIGURE 1 the multiple components of a typical pre-compressed cradle mount assembly 10 are shown in exploded form. The assembly 10 includes an inner insert 12, a mold bonded elastomer 14, rate plate inserts 16, and an outer insert shown here as a split shell insert 18. The inner insert 12 is typically a metal structure, may adopt a wide variety of cross-sectional configurations, and usually includes an elongated opening that receives a fastener (not shown), the shank of which is received therethrough for securing the assembly between the vehicle body and frame. The outer split shell insert 18 is comprised of two separate components 18a, 18b sometimes referred to as can halves or shells and are typically a steel or similar metal. The rate inserts 16, two of which are shown in FIGURE 1 , are also typically of metal construction and may include openings extending through the wall of each insert so that when placed in a mold cavity, the elastomer 14 (illustrated separately in FIGURE 1) can flow therethrough and encapsulate the inserts into the mold-bonded elastomer. Thus, the individual components -namely, the insert 12, rate plate inserts 16, and split shell components 18a, 18b are inserted into a mold cavity and once the press is closed, an elastomer is introduced into the cavity and the components mold bonded together. As will be appreciated, during the molding process, some of the elastomer or rubber may bleed onto an outer surface of the shell. Any elastomer on the outer surface is undesirable and typically a machining or buffing process removes any flash or rubber from the outer surface of the shell. [0004] These metal components are conventionally or traditionally stamped components. As such, the metal components are inexpensive to manufacture. On the other hand, components that are stamped are limited to shapes or conformations that are conducive to this manufacturing process. Thus, attempts to remove cost from the components and manufacturing steps have heretofore deemed to be limited.

[0005] While a pre-corn pressed style mount assembly with split shell inserts made from steel increases the spring rate beyond what an uncompressed mount would offer, the pre-compressed style mount assembly still contains up to five components. This style mount uses a bulging effect on the elastomer, created by the compression, to increase spring rate. Consequently, to further increase the spring rate, the industry incorporates rate plates into the mount. The mount assembly may include an inner insert, rate plate inserts (two), and two outer split shell inserts for a total of five components that are mounted in a press cavity. In addition, inserts typically require cleaning, coating, applying adhesive, as well as a loading or inserting the inserts into the rubber mold. The outer steel inserts require corrosion-resistant coating and some separate means to mount the assembly to the frame. [0006] Ultimately, there is a need to reduce the total number of components, reduce manufacturing complexity, reduce costs, and reduce the weight of a traditional pre-compressed style cradle mount assembly. A need exists, therefore, that overcomes the above-noted problems, in a manner that is both efficient and cost-effective, while providing greater variability in the design.

Summary of the Invention

[0007] A preferred isolator assembly includes an inner member, an outer member having first and second shell portions, a rate plate secured to the outer member, and an elastomer interconnecting the inner and outer members.

[0008] The outer member is preferably a composite material.

[0009] The outer member may further include a locking tab adapted to secure the isolator assembly to an associated frame or vehicle body.

[0010] The outer member and rate plate are formed of the same material in an exemplary embodiment.

[0011] A preferred method of assembling an isolator assembly includes providing an outer member having first and second shell portions secured together by an interconnecting member, positioning an inner member within the outer member, interconnecting the inner and outer members with an elastomer; and removing the interconnecting member joining the first and second shell portions.

[0012] The providing step includes forming the shell portions and rate plates as a one-piece member, preferably from a composite material.

Brief Description of the Drawings

[0013] FIGURE 1 is an exploded view of a conventional pre-compressed cradle mount typically used in the industry.

[0014] FIGURE 2 is an exploded view of a preferred embodiment of a one- piece outer insert cradle mount assembly.

Detailed Description of the Preferred Embodiment

[0015] For purposes of brevity and clarity, similar components will be referred to by similar numerals increased by a factor of one hundred (100), e.g., insert 12 of the prior art arrangement of FIGURE 1 is identified as insert 112 in the preferred ^• - A -

embodiment of FIGURE 2. As is evident in FIGURE 2, the cradle mount assembly 110 has some similarities to the prior art assembly shown in FIGURE 1 , and some distinct differences. For example, the inner insert 1 "12 is typically a metal component having an opening 120 extending longitudinally therethrough. The inner member or inner insert may adopt a wide variety of configurations in order to comply with the form, fit, and function required in the end use. Likewise, the inner insert can be more than one component as shown and described in cornmonly-owned international application WO2004/011299. In order to reduce cost, the inner insert is typically formed of a material that can be extruded or easily formed in a cost effective manufacturing operation. For example, an extruded aluminum component meets this goal and is desirable because of it is light weight. The central opening 120 is dimensioned to receive a shank of a mounting bolt (not shown) that extends therethrough and secures the cradle mount assembly to the vehicle frame and body. [0016] The mold bonded elastomer 114 of FIGURE 2 is also substantially identical to that shown in FIGURE 1. As will be appreciated, the elastomer can be any suitable material that dampens vibration, such as natural rubber, and that can be easily molded and conform to the shape and config uration of adjacent components. As is well known in the art, the elastomer is introduced into the mold cavity after the other components have been mounted therein and the press closed. The elastomer fills the cavity between the inner insert 112 and the outer split shell insert 118. Thus, where there are minor differences in the configuration or shape of the inner insert or outer insert, including the rate plate insert, then the elastomer may adopt a slightly different configuration in the final assembly. In the end, the elastomer serves the same function of damping the vibrations between the inner insert and the outer insert. Typically, the elastomer is mold bonded to ah external or outer surface 122 of the inner insert and also mold bonded to an inner surface 124 of the one-piece outer insert 118. It is received around both the inner and outer surfaces of the integrated rate plate inserts 116a, 116b that are incorporated into the one-piece outer insert design as will be described further below. As previously noted in the Background, any elastomeric material that inadvertently reaches the outer surface of the outer shell insert 118 is typically removed during a subsequent machining operation. [0017] The one-piece outer and rate plate insert 118 shown in FIGURE 2 has substantial differences and advantages over prior arrangements. Here, the one- piece insert 118 is preferably formed of a composite material. The insert need not be limited to steel, which is a typical material used in forming stamped components. Using a composite allows development of non-traditional shapes and configurations that are otherwise unavailable with conventional or traditional stamped components. The composite component is preferably a non-metallic one-piece insert. Preferred composite materials are preferably those that are sufficiently flexib Ie so as not to crack when compressed or pushed into a surrounding sleeve, which is typical with a compression-style mount. If a material is too stiff, cracking results and impairs the function of the cradle mount assembly. Thus, preferred composite materials include a polypropylene such as nylon, and more preferably a nylon impact modified material that is sufficiently flexible so as not to crack when finally assembled. Although nylon with glass fill was considered, it was found that the nylon impact modified material better serves the needs for a flexible material. Similarly, an unfilled polyamide, such as may be available under the trademark Amodel®, also has sufficient flexibility like the nylon described above. By using unfilled polyamide, sufficient flexibility is maintained to allow the one-piece insert to be pushed into a sleeve without cracking. Other composite materials can be used, although these are presently preferred for the reasons noted above and any alternatives would be required to meet these same needs.

[0018] As briefly alluded to above, the rate plates 116a, 116b are preferably joined to respective first and second portions 118a, 118b of the composite one-piece outer insert. Preferably, the rate plates are formed from the same composite material as the remainder of the one-piece outer insert, namely the rate plates are preferably formed in the same forming operation with the outer shell portions 118a, 118b.

[0019] The composite outer insert is deemed to be one-piece through incorporation of an interconnecting member or joining tab 130, which in the preferred arrangement includes a pair of joining tabs 130a, 130b (hidden from view in FIGURE 2). Thus, by integrally forming the rate plates with the outer shell portions, and joining the shell portions via the interconnecting members 130, a one-piece outer and rate plate insert formed of a composite material is achieved. During manufacture of the assembly, only an inner insert and the one-piece outer plate insert are initially inserted into the mold cavity. This results in substantial time and resultant cost savings, as well as overcoming the other noted problems in the Background. The one-piece rate plates and outer shell portions are held in fixed position which assures that each manufactured cradle mount assembly is identical to another cradle mount assembly.

[0020] Further, use of the composite materials allow advanced engineering designs to be incorporated into the cradle mount assembly, heretofore unavailable through use of stamped components. Thus, not only is cost and weight reduced, but there is a significant improvement in engineering design options. [0021] The same tooling used in the prior art arrangement to remove flash or any other elastomer that made its way to the outer surface of the shell portions during the molding process can be used to remove the joining tabs 130 once the molded component is removed from the press. In other words, in the final assembly, the cradle mount assembly does not include the joining tabs, although the elastomer will be mold bonded to the outer shell portions and the integrated rate plate inserts. [0022] Still another feature incorporated into the preferred embodiment is at least one molded-in or integrated snap-on tab 140. As shown, plural snap-on or locking tabs 140 are provided and cooperate with similarly configured recesses or openings in the frame so that the cradle mount assembly may be snap-fit or locked to the frame. Again, by forming the one-piece outer insert from a composite material, the locking tabs or snap-fit feature can be easily incorporated therein. [0023] As a result, there is a substantial reduction in the number of components. This is achieved by combining the rate plate inserts and the outer split inserts into a one-piece composite component.

[0024] There is a similar reduction in the number of manufacturing operations.

Fewer components need to be processed. Likewise, typical operations for processing inserts, such as cleaning, coating, applying adhesive, and loadi ng or inserting the inserts into the rubber mold are either eliminated or reduced. [0025] There is also a reduction in weight. Typically, composites have a 1:7 density ratio compared to corresponding steel material that is used to manufacture conventional plates and split shell inserts.

[0026] Further reduction in cost is also associated with the need for less tooling due to the overall reduction in components. For example, the outer steel inserts of the prior arrangement require corrosion-resistant coating, while the composite material of the preferred embodiment will not require such coating. Throughput will ultimately increase due to less processing operations in the plant. [0027] Use of a snap-on or locking tab feature molded into the outer shell also reduces costs. This feature assists in assembly of the mount to the frame and assists in retaining the mount to the frame in a simple, easy manner. It will also be appreciated that the method of assembly is similarly improved since the outer member is now one-piece where the first and second shell portions are secured together by an interconnecting member. The inner member is positioned within the outer member, and placed in the mold cavity. Subsequently, an elastomer interconnects the inner and outer members by introducing the elastomer into the mold cavity and mold-bonding the components together. The interconnecting member is subsequently removed from the shell portions, thus using existing equipment to remove the interconnecting member, but increasing the processing and manufacturing costs as noted above. Moreover, by providing first and second rate plates in first and second shell portions, only a single component need be handled by the press operator. Likewise, supplying non-metallic shell portions and rate plates allows for reduced weight in the final assembly, while also broadening the design that may be used. Thus, forming the shell portions and rate plates as a one- piece member, particularly a one-piece composite member, results in substantial improvements over known arrangements and methods of assembly. Further, supplying a locking tab on the outer shell reduces costs associated with subsequent assembly of the cradle mount assembly to the vehicle.

[0028] It will be appreciated that although the outer shell is shown as two components, a greater number may be used, and likewise the rate plate inserts may be eliminated, or a greater or lesser number of rate plate inserts incorporated into the assembly to provide the desired spring rate and vibration damping characteristics. Similarly, the inner insert may adopt a wide variety of configurations or be formed from multiple components, for example as taught in commonly-owned application WO2004/011299.

[0029] The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the preferred embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

Having thus described the invention, it is now claimed:

1. An isolator assembly comprising: an inner member; an outer member including first and second outer shell portions; a first rate plate secured to the outer member; and an elastomer interconnecting the inner and outer members.

2. The isolator assembly of claim 1 wherein the outer member is formed of a non-metallic material.

3. The isolator assembly of claim 2 wherein the outer member is a composite material.

4. The isolator assembly of claim 3 wherein the outer member is a nylon impact modified material.

5. The isolator assembly of claim 3 wherein the outer member is an unfilled polyamide.

6. The isolator assembly of claim 1 wherein the outer member further includes a locking tab adapted to secure the isolator assembly to an associated frame or vehicle body.

7. The isolator assembly of claim 1 wherein the outer member has a density ratio on the order of 1:7 relative to steel.

8. The isolator assembly of claim 1 wherein the outer member and rate plate are formed of the same material.

9. The isolator assembly of claim 1 further comprising a second rate plate, the first and second rate plates secured to the first and second outer shell portions, respectively.

10. The isolator assembly of claim 1 wherein the outer member and rate plate are molded together.

11. A method of assembling an isolator assembly comprising: providing an outer member having first and second shell portions secured together by an interconnecting member; positioning an inner member within the outer member; interconnecting the inner and outer members with an elastomer; and removing the interconnecting member joining the first and second shell portions.

12. The method of claim 11 wherein the interconnecting step includes molding the elastomer to the inner and outer members.

13. The method of claim 11 further comprising providing first and second rate plates in the first and second shell portions, respectively.

14. The method of claim 13 wherein the providing steps include supplying non-metallic shell portions and rate plates.

15. The method of claim 13 wherein the providing steps include forming the shell portions and rate plates as a one-piece member.

16. The method of claim 13 wherein the providing steps include forming the shell portions and rate plates as a one-piece composite member.

17. The method of claim 1 wherein the providing steps include forming the shell portions and rate plates as a one-piece, non-metallic member.

18. The method of claim 11 includes supplying a locking tab on the outer member.

19. The method of claim 11 wherein the providing step includes forming the outer member from a nylon impact modified material.

20. The method of claim 11 wherein the providing step includes forming the outer member from an unfilled polyamide.