Title Air Spring Field of the Invention The invention relates to an air spring and more particularly to an air spring sleeve wherein a sleeve end crimp region is folded back on itself to prevent an air pressure loss through a reinforcing cord.

Background of the Invention An air spring generally comprises a flexible sleeve connected to a piston at each end, or, to a piston at one end and an end cap at the other. A compressible gas, usually air, is contained in the air spring in a pressurized state. The pressure in the air spring directly affects the spring rate of the air spring. The air spring flexible sleeve, or simply sleeve, is connected to each piston and or end cap by means of a bead or crimp. The bead comprises a metal strap contained within the material of the sleeve.

The air spring flexible sleeve is capable of compressing and expanding in order to absorb movement in a vehicle suspension. In operation the sleeve rolls on the surface of each piston. The shape of the piston surface affects the operational characteristics of the air spring. More particularly, during the compression stroke a rolling lobe is formed in the sleeve on one or both piston surfaces. Hence, in such instance air springs may also be referred to as rolling lobe air springs.

The performance of a rolling lobe air spring is enhanced by reducing the thickness of the sleeve wall and by reducing the modulus of the elastomer with which the

sleeve is built. A disadvantage however, is that achieving correct compression of the sleeve wall so that the crimp connection integrity is maintained is difficult, particularly on rigid hardware. Typically, crimping a thin wall sleeve to rigid hardware will produce a crimp cut resulting in gas leakage, thus rendering the spring assembly unusable.

Representative of the art is U. S. patent no.

5,253, 850 to Burkley et al. (1993) which discloses a sleeve having an end portion which is wrapped about a bead ring and crimped within an annular rolled portion of at least one end member.

What is needed is an air spring having a flexible sleeve with a thin wall in a rolling lobe region and having a roll in an end crimp region to prevent an air pressure loss through a reinforcing cord. The present invention meets this need.

Summary of the Invention The primary aspect of the invention is to provide an air spring having a flexible sleeve with a thin wall in a rolling lobe region and having a roll in an end crimp region to prevent an air pressure loss through a reinforcing cord.

Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.

The invention comprises an air spring and more particularly, an air spring having a flexible sleeve with a thin wall in a rolling lobe region and having a roll in an end crimp region to prevent damage during crimping.

Brief Description of the Drawings The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.

Fig. 1 shows a cross-section of a prior art thin wall air spring sleeve.

Fig. 2 shows a cross-section of a prior art thin wall air spring sleeve crimped to an end cap.

Fig. 3 shows a cross-section of a sleeve with a roll on each end.

Fig. 4 shows a partial cross-section of a sleeve and reinforcing cords at 4-4 in Fig. 1.

Fig. 5 shows a cross-section of an air spring with the inventive sleeve.

Fig. 6 shows a cross-section of a crimp member.

Fig. 7 shows a cross-section of a crimp member.

Fig. 8 shows a cross-section of a crimp member.

Fig. 9 shows a cross-section of a crimp member.

Fig. 10 shows a cross-section of a crimp member.

Detailed Description of the Preferred Embodiment Fig. 1 shows a prior art thin wall air spring sleeve. An air spring generally comprises a tubular flexible sleeve connected to piston (end member) at each end or to a piston at one end and to an end cap (end member) on the other (not shown). A compressible gas, usually air, is contained in the air spring in a pressurized state. The pressure in the air spring directly affects the spring rate of the air spring.

The air spring flexible sleeve, or simply sleeve, is attached or connected to each piston and/or end cap by

means of a bead or crimp. The bead comprises a metal strap contained within the material of the sleeve. The crimp is a means of connection that uses a metal band that is formed in a radially compressive manner to capture the sleeve between a metal band and an end cap or piston.

The air spring flexible sleeve is capable of axially compressing and expanding in order to absorb movement in a vehicle suspension, for example, to which the air spring is connected. In operation a portion of the sleeve rolls on a surface of the piston. The shape of the piston surface affects the operational characteristics of the air spring. More particularly, during the compression stroke a rolling lobe is formed in the sleeve on the piston surface. Hence, such an air spring may also be referred to as rolling lobe air spring.

The performance of a rolling lobe air spring is enhanced by reducing the thickness of the sleeve wall and by reducing the modulus of the elastomer with which the sleeve is built. A disadvantage however, is that achieving correct compression of the sleeve wall under a crimp member so that the crimp connection integrity is maintained is difficult, particularly on a rigid piston or cap. Typically, crimping a thin wall sleeve to a rigid piston or cap will likely produce a crimp cut, thus making the air spring assembly unusable.

In Fig. 1 sleeve 100 comprises ends, namely, end cap crimp area 101 and a piston end crimp area 103. Rolling lobe region 102, disposed between ends 101 and 103, comprises a tapered form as shown, or may also describe a cylindrical form. The sleeve has a substantially uniform thickness T1. T1 is in the range of approximately 1. 2mm

to approximately 2mm. The elastomeric body 106 of the sleeve may comprise polychloroprene, polybutadiene, bromobutyl, natural rubber, chlorobutyl, EPDM, epichlorohydrin, nitrile, or SBR, or any combination of two or more of the foregoing.

The sleeve further comprises an internal reinforcing cord 104 which is wound helically within the sleeve body along a sleeve length L, see Fig. 1. Reinforcing cord 104 may comprise nylon, polyester, aramid, steel wire, fiberglass, polyethylene, or polypropylene, or any combination of two or more of the foregoing.

In the case of the inventive sleeve and airspring, the crimp ends of sleeve 100 are thickened by folding or rolling them while maintaining a sleeve thickness T1 in the rolling lobe region 102. Therefore, standard crimp compression parameters known in the art can be used while preventing crimp cuts in the sleeve. Namely, by folding or rolling each end of the sleeve outwardly back over itself, a double thickness at each end can be produced while maintaining a thin wall sleeve in the rolling lobe region 102, see Fig. 3.

Another improvement realized by the inventive sleeve applies to air spring arrangements wherein one end of the sleeve is disposed inside the pressure chamber of the spring, perhaps for clearance reasons. For such arrangements, where one end is disposed inside the pressure chamber of the spring, a prior art sleeve end must be sealed in a separate step to prevent air or gas pressure loss through the reinforcement cord caused by the compressed air or gas"wicking"along the reinforcement cord. By inverting an air sleeve with the end folded or rolled back over itself, and then crimping normally with a crimp member, reinforcement cord ends are not exposed to the pressure chamber 105, thereby

eliminating the need for a secondary seal over the reinforcing cord ends, see Fig. 5.

Fig. 2 shows a cross-section of a prior art thin wall air spring sleeve crimped to an end cap. Crimp area 101 of sleeve 100 is connected to end cap 201 by crimp member 202. Crimp member 202 is crimped using tools and methods known in the art. Crimp member 202 comprises a metal band.

Fig. 3 shows a cross-section of a sleeve with a roll on each end. Roll 300 and roll 310 are made in each end of the sleeve 100 such that ends 302 and 303 are disposed radially outwardly from a sleeve longitudinal axis A-A.

Reinforcing cord ends are exposed at ends 302 and 303.

Fig. 4 shows a partial cross-section of a sleeve and reinforcing cords at 4-4 in Fig. 1. Cords 104 are helically disposed adjacent to each other within the elastomeric body 106. The helical arrangement of the reinforcing cords is known in the art and is disclosed, for example, in U. S. patent number 4,763, 883 to Crabtree (1988) which discloses a sleeve wherein the cord is wound at various helical angles to a sleeve centerline.

Reinforcing cords 104 extend to each end of sleeve 100.

Fig. 5 shows a cross-section of an air spring with the inventive sleeve. Rolled end 300 is disposed between crimp member 206 and end cap 205. Rolled end 301 is disposed between crimp member 208 and piston 207. One can see that ends 302 and 303 do not communicate with pressure chamber 105, thereby eliminating any leakage of pressurized gas from the pressure chamber by wicking along the reinforcing cords to the outside. Rolling lobe region 102 is shown in a rolled configuration on piston surface 215 as well.

Crimp member 206 and 208 can have any cross-section compatible with the intended use. Figs. 6 through 10 are

examples of such cross-sections. Figs. 6-10 are not offered to limit the cross-sections to only those depicted.

Fig. 6 shows a cross-section of a crimp member.

Crimp member 400 is circular in form and has a flat cross-section.

Fig. 7 shows a cross-section of a crimp member.

Crimp member 206 is circular in form and has a single groove 210 disposed about an inner circumference. Crimp member 206 and crimp member 208, see Fig. 5, have substantially the same cross-section.

Fig. 8 shows a cross-section of a crimp member.

Crimp member 500 is circular in form and has two grooves 501 and 502 disposed about an inner circumference.

Fig. 9 shows a cross-section of a crimp member.

Crimp member 600 is circular in form and has four grooves 601,602, 603 and 604 disposed about an inner circumference.

Fig. 10 shows a cross-section of a crimp member.

Crimp member 700 is tubular in cross-section and circular in form.

Although a single embodiment of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.

Further, the description contained herein is exemplary only and the scope of the invention is to be limited only to the claims as interpreted in view of the prior art.