Patent Application
20090278290
This application generally relates to shock-absorbing components, and more specifically to air springs used in vehicles or machines.
Pneumatic springs, commonly referred to as air springs, are used in motor vehicles to provide cushioning between movable parts. Air springs thus play an important role in the suspension systems of motor vehicles, especially tractor-trailer trucks. These air springs are designed to dampen vibrations and/or absorb shock loads impressed on the vehicle axles when the wheels of the vehicle strike an object in the road, such as a bump, depression, or other obstruction.
Conventional air springs typically include a flexible elastomeric sleeve or bag-like element that extends between a pair of end closures. At least one of the end closures is typically in the form of a rigid support plate or retainer. The sleeve is attached to the retainer in a seal-tight manner by clamping (e.g., with a clamp ring), swaging, or similar techniques. In rolling lobe air springs, the other end closure is in the form of a piston. The sleeve is also attached to the piston in a seal-tight manner, but forms a lobe configured to bear against the outer surface of the piston.
The end closures are mounted to spaced-apart components of the vehicle, and the sleeve forms a chamber between the end closures. Pressurized gas (e.g., air) within a chamber helps absorb the loads impressed on the spaced-apart components. For example, when the vehicle experiences a shock load that urges the components to move towards each other, most of the motion is absorbed by the pressurized chamber. In rolling lobe air springs, the lobe of the elastomeric sleeve rolls along the outer surface of the piston to absorb such loads.
One aspect of current air springs that can be improved is the mounting of the end closures to the vehicle components. Many air springs are bolted to the vehicle components. For example, one or both of the end closures may include a tapped hole configured to be aligned with a through hole in the vehicle component. A bolt is inserted through the vehicle component to engage the threads of the tapped hole, thereby securing the end closure to the vehicle component. Alternatively, one or both of the end closures may include a threaded projecting portion that serves as a bolt itself. The projecting portion is configured to extend through a hole in the vehicle component so that a nut may be secured onto the threads.
Using nuts and bolts to install an air spring to a vehicle requires the use of additional tools, such as a wrench. This can be cumbersome in areas of the vehicle where there is limited access to the intended location of the air spring. Furthermore, the difficulties associated with installing such air springs are also present when removing the air springs for repair or replacement. Although some attempts have been made to provide air springs having a snap-mounting feature, there remains room for improvement.
Therefore, an air spring with improved installation capabilities would be highly desirable.
An air spring generally comprises a first end closure, a flexible member coupled to the first end closure and defining a pressurizable chamber, and a first mounting member projecting from the first end closure in a first direction. The first mounting member has an outer surface with a plurality of barbs projecting radially outward from the outer surface. The barbs have a spaced arrangement along the first direction. When the member is inserted into a through-hole provided in a component to which the air spring is mounted, such as a suspension component of a vehicle, the barbs create a ratcheting-like effect to secure the air spring to the vehicle.
The plurality of barbs may comprise first and second sets of barbs located on diametrically opposite sides of the outer surface. For example, the first mounting member may be substantially cylindrical with first and second flat portions on opposite sides of the outer surface. The first set of barbs may be arranged along the first flat portion, while the second set of barbs may be arranged along the second flat portion.
In one aspect or embodiment, each barb has a triangular cross-section defined by the outer surface of the first mounting member, a leading surface extending outwardly from the outer surface and toward the first end closure at a first angle, and a trailing surface extending outwardly from the outer surface at a second angle. The leading and trailing surfaces converge at a corner or peripheral edge of the barb, and the first angle is less than the second angle. For example, the first angle may be approximately 30° and the second angle may be approximately 90°.
In another aspect or embodiment, the air spring further comprises a second end closure coupled to the flexible member opposite the first end closure. A second mounting member projects from the second end closure in a second direction and also includes a plurality of barbs. Either or both of the first and second mounting members may be integrally formed with the associated end closure. When the components are integrally molded, the first end closure may be molded from a first material and the first mounting member may be molded from a second material having a lower stiffness than the first material.
A method of forming an air spring is also provided. The method generally comprises constructing an end closure, constructing a mounting member having an outer surface with a plurality of barbs projecting radially outward, coupling the mounting member to the end closure so that the mounting member projects from the end closure in a first direction, and coupling the end closure to a flexible member. The plurality of barbs are arranged along the first direction, and the flexible member defines a pressurizable chamber.
In one embodiment of the method, the mounting member is integrally formed with the end closure. For example, constructing the end closure may comprise molding the end closure from a first material, constructing the mounting member may comprise molding the mounting member from a second material having a lower stiffness than the first material, and coupling the mounting member to the end closure may comprise integrally molding the mounting member with the end closure.
For example,
The air spring 10 further includes a first mounting member or stud 36 projecting from the first end closure 20 in a first direction. The first mounting member 36 may be a separate component secured to the first end closure 20 or a component integrally formed with the first end closure 20. Indeed, as will be described in greater detail below, the first end closure 20 and first mounting member 36 may be integrally formed together as a unitary structure.
Barbs 40 are provided on an outer surface 42 of the first mounting member 36. The barbs 40 project radially outward from the outer surface 42 and have a spaced arrangement along the first direction. Each barb 40 may extend completely or partially around the outer surface 42. In the embodiment shown, a first set 46 of barbs 40 and a second set 48 of barbs 40 are provided on diametrically opposite sides of the first mounting member 36. The first mounting member 36 may be substantially cylindrical with the barbs 40 projecting radially outward across arcuate sections (not shown) of the outer surface 42. Alternatively, as shown, the first mounting member 36 may include a first flat portion 50 and a second flat portion 52 on diametrically opposite sides of the outer surface 42 so as to define a truncated cylinder. The first set 46 of barbs 40 is provided on the first flat portion 50, and the second set 48 of barbs 40 is provided on the second flat portion 52.
The first angle 62 and second angle 66 are selected so that the first mounting member 36 is easy to install in a hole 74 (
The trailing surface 64 serves to retain the first mounting member 36 against a surface 80 (
Still referring to
The barb 40 shown in
Indeed, it will be appreciated that the barbs 40 may be designed to have a larger or smaller area of interference 76 based on material properties. If a relatively soft material is used to form the barbs 40, the barbs 40 can be designed to provide a greater amount of interference without compromising the ease of installation of the first mounting member 36. Conversely, if a relatively stiff or rigid material is used to form the barbs 40, the barbs 40 may be designed to provide less interference with the hole 74.
The barbs 40 and first mounting member 36 may be integrally formed together. For example, the barbs 40 and the first mounting member 36 may be constructed from the same material during a single molding operation to form a unitary structure. Alternatively, the first mounting member 36 may be molded or otherwise constructed from a first material and then over-molded with a second material to form the barbs 40. The barbs 40 may be formed from any type of thermoplastic or other material having sufficient elastic deformation properties. One such material is Zytel® nylon, available from DuPont.
The first mounting member 36 may be secured to the first end closure 20 using conventional fastening techniques. In one embodiment, the first mounting member 36 is constructed with a threaded portion (not shown) configured to engage a tapped hole (not shown) formed in the first end closure 20. Alternatively, the first mounting member 36 and first end closure 20 may be integrally formed together. This may be achieved by molding the first mounting member 36 and first end closure 20 from the same material to form a unitary structure. In some embodiments, it may be desirable for the first mounting member 36—particularly the barbs 40 thereof—to be constructed from a softer material than the first end closure 20. The components may be integrally molded together in such embodiments by molding the first end closure 20 from a first material and then molding the first mounting member 36 and barbs 40 from a second material having a stiffness less than the first material. One example of a suitable first material is Hytrel® (available from DuPont), and one example of a suitable second material is Zytel®.
To install the air spring 10, the first mounting member 36 is inserted into the hole 74 provided in the first component 12. As the first mounting member 36 is pressed into the hole 74, the leading surface 60 of the barbs 40 acts as a ramp until the area of interference 76 contacts the inside surface 78. The area of interference 76 is deformed until the barb 40 is pushed through the hole 74, at which point the area of interference 76 springs back toward its normal shape. The trailing surface 64 at the area of interference 76 then confronts the surface 80 on the first component 12 surrounding the hole 74. This overlap helps prevent the first mounting member 36 from being pulled back through the hole 74 during operation of the vehicle 18.
By providing a plurality of barbs 40, a ratcheting-like effect is created as the first mounting member 36 is pushed into the hole 74. Thus, although the first barb 40 to exit the hole 74 may help retain the first mounting member 36 in the manner described above, the first end closure 20 may still be spaced from the first component 12. An individual may continue to push the first mounting member 36 into the hole 74 to move the first end closure 20 closer toward the first component 12. This results in successive barbs 40 exiting the hole 74, with each barb 40 serving to retain the first mounting member 36 until the next barb 40 exits the hole 74. Accordingly, when the first end closure 20 contacts the first component 12, the last barb 40 to exit the hole 74 helps maintain this contact.
Although only the first mounting member 36 and first end closure 20 are described above, those skilled in the art will appreciate that description may equally apply to the second end closure 24 (
Regardless of their construction, the first mounting member 36 and second mounting member 92 may be used to install the air spring 10 to holes of different thicknesses due to the ratcheting-like effect described above. An individual need not worry about whether the thickness of the component to which the air spring 10 is mounted corresponds to the length of the first mounting member 36 or second mounting member 92. The plurality of barbs 40 helps ensure that the first end closure 20 and second end closure 24 can be retained against the first component 12 and second component 14, respectively, regardless of the thickness of the first component 12 and second component 14. This represents an advantage over other air springs that are snap-mounted.
Furthermore, unlike conventional air springs installed using nuts and bolts, the air spring 10 does not require additional tools (e.g., wrenches) for installation. This reduces the amount of time and effort to install the air springs. The barbs 40 also eliminate the need for additional fasteners, although such fasteners may still be used if desired. The savings in installation time and elimination of additional tools and/or parts reduces the overall cost associated with the use of the air spring 10.
To remove the air spring 10 from the vehicle 18, an individual pulls the first end closure 20 away from the first component 12. The force applied must be sufficient to overcome the resistance created by contact between the trailing surface 64 of the barb 40 and the surface 80. To this end, the barbs 40 may be designed to retain the first mounting member 36 within the hole 74 under the loads experienced during operation of the vehicle 18, but not under the forces applied by an individual. The second end closure 24 may be pulled in a similar manner to complete the removal process. Thus, as with its installation, the removal of the air spring 10 may not require additional tools and can be completed in a time-efficient manner.
While the invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. For example, those skilled in the art will appreciate that although the first component 12 and second component 14 are shown as being located in the suspension system 16 of a vehicle 18, the air spring 10 may be installed elsewhere on the vehicle 18 or in a different article of manufacture (e.g., a machine). The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of the general inventive concept.
