Air spring bumper utilizing a combination of materials

An air spring has a pair of spaced end members for mounting the spring at spaced locations on a structure. A flexible sleeve of elastomeric material is sealingly engaged with the end members and forms a pressurized fluid chamber therebetween. A post is mounted on one of the end members and extends into the fluid chamber. A shock absorbing bumper having an outer shell formed of a high strength first plastic material is mounted on the post. The shock absorbing bumper shell is formed with a plurality of internal compartments containing one or more blocks formed of a second plastic material. The second plastic material preferably is a thermoplastic and is stronger in compression than the first plastic material of the outer shell. The relatively stronger but stiffer blocks are surrounded by the relatively softer plastic material of the outer shell and provides a bumper having extremely high compressive strength and a high resistance to breakage or fracture.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The invention relates generally to air springs and, in particular, to air 
springs having an internal bumper which acts as a back-up in case of air 
spring failure or to absorb sudden large deflections or shocks imparted on 
the air springs. Specifically, the invention relates to a block of an 
elastomeric material, such as a thermoplastic, that can be installed into 
the compartments of a bumper in various numbers and configurations to 
control the compressive elastic characteristics of the bumper. 
2. Background Information 
Pneumatic springs, commonly referred to as air springs, have been used for 
motor vehicles and various machines and other equipment for a number of 
years to provide cushioning between movable parts, primarily, to absorb 
shock loads and vibration damping imparted thereon. The air spring usually 
consists of a flexible rubber sleeve which extends between a pair of end 
members and which contains a supply of compressed air and may have one or 
more pistons located at ends of the flexible sleeve. The end members mount 
the air spring on spaced components or parts of the vehicle or equipment 
on which the air spring is mounted. 
The internal pressurized fluid, which is generally air, absorbs most of the 
shock impressed upon or experienced by one of the spaced end members on 
which the air spring is mounted, with the ends members moving axially 
toward and away from each other upon absorbing the imparted shock. 
Examples of such air springs are shown in U.S. Pat. Nos. 4,787,606, 
4,852,861, 4,946,144 and 5,201,500. 
Certain of these prior art air springs have internal bumpers mounted on one 
of the end members which extends into the interior of the pressurized 
chamber. The bumper prevents total collapse or deflection of the air 
spring member in the event of air spring failure. The bumper also absorbs 
shock whenever the spring experiences severe shocks and deflections which 
result in actual or near "bottoming out " of the air spring member. 
While these prior art bumpers are satisfactory for most applications, such 
bumpers still have a number of shortcomings related to their use. 
Particularly, the use of such bumpers has not been well suited to 
applications wherein the bumper is expected to experience a high number at 
a fast rate of extreme shocks inasmuch as such extreme shocks have 
resulted in complete deflection of the bumper without sufficient isolation 
of the extreme shocks from the structures mounted on the air spring. 
Another problem that occurs in the use of air springs is that when a 
vehicle such as a truck is at rest, the air is released from within the 
air spring and the internal bumper supports the weight without any fluid 
pressure assistance. Occasionally, the driver will then start and drive 
the vehicle before the air spring is fully inflated and severe shock can 
be impressed upon the partially inflated bumper causing severe damage 
thereto. 
Most prior art air springs are formed of a single elastomeric material 
which provides a compromise in order to absorb most of the shocks which 
are exerted thereon yet which is sufficiently pliable to prevent permanent 
damage or breaking of the bumper should a severe shock be applied thereto. 
A need thus exists for an improved air spring bumper that can withstand the 
extreme shocks that are experienced in certain applications and which can 
have multiple configurations suited to different loading applications. 
Examples of other devices including shock-absorbing components are set 
forth in the following patents. 
U.S. Pat. No. 3,658,314 discloses a fluid shock absorber having an 
elastomeric member mounted between two concentrically movable tubes with 
an elastomeric bumper mounted beneath the inner tube to absorb impact from 
the tube. 
U.S. Pat. No. 4,218,599 discloses a polymer spring for use in a drawer of a 
cabinet to ensure that when the drawer is closed, it does not rebound to a 
partially open position. 
U.S. Pat. No. 4,342,264 shows another type of air spring using an 
elastomeric bumper mounted on one of the end members. 
U.S. Pat. No. 4,478,396 discloses an elastomeric bumper which is mounted on 
the top of a vehicle strut. 
U.S. Pat. No. 4,506,910 discloses a bumper mounted on the inner surface of 
a mounting plate of the air spring, whereby the bumper provides a limit to 
any extreme swinging of the beam attached to the piston opposed to the 
mounting plate. 
U.S. Pat. No. 4,787,606 shows a rubber bumper attached to the inner surface 
of one of the end plates by a pin where the rubber bumper serves to 
prevent total collapse or deflection of the spring assembly. 
U.S. Pat. No. 4,925,224 discloses an energy-absorbing bumper with an 
elastomeric bumper module. The energy-absorbing bumper is attachable to a 
vehicle where it serves to absorb the energy of an impact of that vehicle 
with another object. 
U.S. Pat. No. 5,201,500 shows an air spring in which a post is mounted on 
one of the end members and extends into the fluid chamber where a 
shock-absorbing bumper is formed and snap-fitted on the enlarged top of 
the post. 
However, no known device, including those discussed above, disclose an air 
spring having an internal bumper that receives one or more elastomeric 
blocks of material into cavities formed in the bumper to allow the bumper 
to withstand extreme shock loading, the bumper having a number of 
different configurations suited to different loading applications. 
SUMMARY OF THE INVENTION 
An objective of the invention includes providing an improved air spring 
construction for motor vehicles and other types of equipment having spaced 
movable end members separated by a pressurized chamber extending between 
the end members for absorbing excessive shock imparted on the end members. 
A further objective of the invention is to provide such an improved air 
spring in which a plastic bumper is mounted within the pressurized 
chamber. 
Another objective of the invention is to provide such an improved air 
spring in which the shock-absorbing bumper is formed of a high-strength 
plastic material and one or more blocks of an elastomeric material, such 
as a thermoplastic, to absorb sudden large deflections and to act as a 
back-up device in case of air spring failure. 
Still another objective of the invention is to provide such an improved air 
spring in which the shock-absorbing bumper can have several configurations 
depending upon the number and positioning of elastomeric blocks received 
therein. 
A further objective of the invention is to provide an improved air spring 
that surrounds a relatively harder, stiffer block with a relatively softer 
outer shell material to provide a composite that provides the strength and 
stiffness while reducing the likelihood that the internal block might 
break or otherwise fracture during use. 
Another objective of the invention is to provide an improved air spring 
having a shock-absorbing bumper that utilizes a strong, relatively stiff 
block to withstand extreme shock loading and that obviates the risk that 
the relatively stiff block will break or otherwise fracture during use. 
A further objective of the invention is to provide such an improved air 
spring which provides both increased vertical and lateral load capability. 
A further objective of the invention is to provide such an improved air 
spring bumper which provides increased life in terms of cycles and impact 
loading. 
Another objective of the invention is to provide such an improved air 
spring which is light in weight, easy to assemble, which can carry greater 
loads than the heretofore-used softer elastomeric bumpers, and which has 
overall bumper height flexibility. 
These objectives and advantages are obtained by the improved air spring 
construction of the invention, the general nature of which may be stated 
as being an air spring of the type having a pair of spaced end members 
adapted to be mounted at spaced locations and a flexible sleeve formed of 
an elastomeric material sealingly engaged with the end members and forming 
a pressurized fluid chamber therebetween, a shock-absorbing bumper mounted 
on one of the end member and extending into the fluid chamber for possible 
impact engagement with the other said end members, said bumper being 
formed of an outer shell of a first plastic material and having at least 
one inner member formed of a second plastic material mounted within said 
outer shell, wherein said second plastic material is stronger in 
compression than said first plastic material.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The improved air spring of the invention is indicated generally at 1, and 
is shown in an unmounted, at-rest position in FIGS. 1 and 2. Air spring 1 
includes an upper end cap member and an opposed axially spaced piston 
member, indicated generally at 2 and 3, respectively (FIGS. 1 and 2). 
Piston 3 is of a usual construction, preferably having an inverted 
generally bowl-shaped configuration formed of a suitable material such as 
aluminum, steel, high strength plastic or the like. Piston 3 includes a 
base 4 and an annular wall 5 extending downwardly from base 4 and 
terminating in a peripheral edge 6. A central supporting structure 7 is 
joined with and extends downwardly from base 4. 
One end of a flexible sleeve which is indicated generally at 10, terminates 
in a lower bead 11 which is clamped on base 4 of piston 3 by a clamping 
plate 12 in an airtight sealing relationship with piston 3. The other end 
of sleeve 10 has an end bead (not shown) which is secured in a curled 
marginal edge (not shown) of mounting end cap 2 in an airtight sealing 
relationship therewith, providing a fluid tight chamber 15 within 
elastomeric sleeve 10. Other types of end sealing arrangements may be 
utilized without effecting the concept of the invention, such as shown in 
U.S. Pat. Nos. 4,852,861, 4,787,606 and 4,946,144, which are assigned to 
the same entity as is the present invention, and which do not require a 
beaded end seal. 
A source of pressurized air or other fluid communicates with an internal 
fluid chamber 15 formed within sleeve 10 through a hollow bore (not shown) 
of a mounting stud 18 extending outwardly from end plate 2. One or more 
additional mounting studs 19 are mounted on end cap 2 and extend upwardly 
therefrom for mounting air spring 1 on a vehicle, machine tool or other 
application in which it is to be used. 
The particular air spring construction described above and shown in the 
drawings and particularly in FIGS. 1 and 2 may vary without affecting the 
concept of the invention. 
A snap-on bumper, indicated generally at 20 (FIG. 3), is mounted on clamp 
plate 12 of base 4 and extends upwardly therefrom into chamber 15. Bumper 
20 engages end cap 2 upon the loss of the pressurized fluid within chamber 
15 and assists in absorbing excessive shock forces exerted on end member 2 
or piston 3. Bumper 20 is similar to the bumper shown and described in 
U.S. Pat. No. 5,201,500, the contents of which are incorporated herein by 
reference. 
Bumper 20 includes inner and outer generally cylindrical walls 23 and 24, 
respectively, concentrically arranged with each other and which both 
terminate in an integral dome-shaped connecting top wall 25. A plurality 
of radially extending reinforcing ribs 26 are formed integrally with inner 
and outer walls 23 and 24 and extend therebetween to provide a rigid 
integrally formed one-piece bumper member. Reinforcing ribs 26 define a 
plurality of compartments 27 between inner and outer walls 23 and 24. 
Inner wall 23 terminates in an annular base 29 which lies in the same 
plane as does the annular peripheral edge 30 of outer wall 24 as shown 
particularly in FIG. 3. 
In accordance with one of the features of the present invention, bumper 20 
additionally includes one or more blocks 28 of an elastomeric material. As 
is best shown in FIG. 5, blocks 28 are of a size and shape to be slidingly 
received in compartments 27, although blocks 28 could be received in 
compartments 27 in other fashions without departing from the spirit of the 
present invention. Blocks 28 are formed of an appropriate elastomeric 
material, as will be set forth more fully below. 
Plate 12 is secured in a fluid tight clamping relationship with sleeve bead 
11 by a threaded clamping stud 32 which extends through an opening 33 
formed in base 4 in cooperation with a bumper stud, indicated generally at 
34. Bumper stud 34 preferably is formed of a mild steel and may be secured 
to plate 12 by brazing at 35. The interior of stud 34 has a threaded bore 
37 for threaded connection with threaded shaft 38 of clamping stud 32, and 
together form a central bumper attachment post 36. Other types of 
attachment posts 36 may be utilized than that shown in the drawings, 
without effecting the concept of the invention. For example, post 36 could 
be molded of a high strength plastic integral with a plastic piston member 
3, or could be welded or brazed to an inside surface of a metal piston 
member. Both of these constructions would eliminate an opening being 
required through the base of piston 3. 
Bumper stud 34 is formed with an enlarged outer end 39 which forms an 
annular undercut 40 adjacent the outwardly tapering annular side wall 41 
of post 36. Bumper 20 is formed with a plurality of flexible angled 
fingers 43 (FIGS. 2 and 3) which extend upwardly inwardly into a hollow 
interior 44 formed by inner wall 23. 
Four flexible fingers 43 that are spaced circumferentially apart by 
intervening areas terminate in an outer arcuate edge 46 which snaps into 
and seats in undercut 40. Arcuate edges 46 preferably have arcuate lengths 
or angles of approximately 75 degrees each, and are inclined inwardly and 
form an included angle of approximately 20 degrees with inner wall 23. In 
alternate embodiments (not shown), only one finger 43 exists where such 
finger is annular. 
Post 36 forms a vertically extending member located within the interior 44 
of bumper 20 with flexible fingers 43 enabling bumper 20 to be snap-fitted 
on bumper stud 34 of post 36 by flexing outwardly as it is forced 
downwardly on post 36. Immediately upon the movement of edges 46 of finger 
43 beyond cylindrical side wall portion 47 of enlarged post end 39, the 
flexibility of fingers 43 enables them to snap into position in undercut 
40. When bumper 20 is in position on post 36, annular base 29 will seat 
upon plate 12, firmly mounting bumper 20 in position within pressure 
chamber 15. Thus, fingers 43 are secured between undercut 40 and clamp 
plate 12 and the flexibility of fingers 43 retain the arcuate edges 
thereof in undercut 40, with the slope surfaces of fingers 43 lying along 
tapered side wall 41 of end cap 34. 
In the preferred embodiment, bumper 20 provides an outer shell formed of a 
high strength elastomer or plastic such as sold under the trademark 
CRASTIN, by E.I. Du Pont de Nemours & Company of Wilmington, Del. which is 
a super tough thermoplastic polyester resin, such as an unreinforced 
polybutylene terephthalate. The grade of CRASTIN found most suitable has a 
hardness (Rockwell) of approximately 98 to 120 with a preferred value of 
98, a tensile strength in the approximate range of 5,500 to 8,400 psi with 
a preferred strength of 5,500 psi, and an elongation at break of 
approximately 50% to 300% with a preferred value of approximately 145%. 
Bumper 20 is preferably injection molded out of this material and may be 
configured square, cloverleaf etc., and may be of non-cylindrical shapes 
without affecting the concept of the invention. 
In the preferred embodiment, blocks 28 are formed of a high strength 
polyester elastomeric or plastic such as sold under the trademark ZYTEL by 
Du Pont de Nemours & Company which is stronger in compression than bumper 
20. The type of ZYTEL found most suitable is formed of a glass reinforced 
nylon 66 resin having a hardness (Rockwell) in the range of approximately 
110 to 122, a tensile strength in the range of approximately 15,000 to 
30,000 psi with the preferred value of approximately 27,000 psi, and an 
elongation at break being in the range of 2% to 4with the preferred value 
of approximately 3%. Other materials, both reinforced and non-reinforced, 
may be used without departing from the spirit of the present invention. 
Thus, the inner members or blocks 28 have a hardness of approximately 
three times that of bumper 20, with bumper 20 having an elongation of at 
least twenty-five times that of blocks 28. 
As is understood in the relevant art, reinforced glass-filled nylon is 
stronger than the thermoplastic materials of which bumper 20 is 
constructed and is able to withstand greater compressive forces than 
bumper 20. However, such reinforced glass-filled nylon is more brittle 
than the thermoplastic materials used to construct bumper 20 and has a 
tendency to crack or otherwise fracture in response to extreme shock 
loading thereof. In accordance with the features of the present invention, 
the insertion of blocks 28 into compartments 27 of bumper 20 result in 
blocks 28 being surrounded by the relatively softer material used to 
construct bumper 20. The relatively softer material of bumper 20 surrounds 
and reinforces blocks 28, thus reducing the tendency of blocks 28 to 
fracture under extreme shock loading. Further in accordance with the 
features of the present invention, the combination of the relatively 
stronger but more brittle block 28 and the relatively softer bumper 20 
provides the bumper with the characteristics of being able to withstand 
extreme shock loading without the risk that blocks 28 may crack or 
otherwise fracture with use. 
In the preferred embodiment, four blocks 28 are received within four 
equally spaced compartments 27 formed in bumper 20. However, bumper 20 can 
contain between one and eight blocks 28 inside compartments 27, thus 
providing at least eight different configurations for bumper 20 that can 
be adapted to suit different loading conditions for air spring 1. It is 
understood that bumper 20 could contain a greater or fewer number of 
compartments 27 without departing from the spirit of the present 
invention, thus providing additional configurations that are available as 
needed for bumper 20. Further in accordance with the present invention, 
the shock-absorbing characteristics of bumper 20 also vary with the 
specific positioning of blocks 28 within compartments 27 such that 
different shock-absorbing characteristics are achieved if the four blocks 
depicted in FIG. 4 are all positioned on one side of bumper 20 adjacent 
one another, with four empty compartments 27 disposed on the other side of 
bumper 20, which characteristics may be desirable for a specific loading 
application. 
The inclusion of the stiffer blocks 28 in compartments 27 of bumper 20 thus 
provides a number of different bumper configurations that permit the 
compressive characteristics of bumper 20 to be specifically tailored to 
suit a particular loading application for air spring 1. The combined 
strength and resilience of the different configurations of bumper 20 
permit air spring 1 to be used in applications that heretofore were not 
well suited to the use of existing bumpers in an air spring. The inclusion 
of blocks 28 in bumper 20 thus provides significant benefits in 
versatility and utility that were previously unknown in the relevant art. 
Accordingly, the improved bumper provides an effective, safe, inexpensive, 
and efficient device which achieves all the enumerated objectives, 
provides for eliminating difficulties encountered with prior devices, and 
solves problems and obtains new results in the art. 
In the foregoing description, certain terms have been used for brevity, 
clearness and understanding; but no unnecessary limitations are to be 
implied therefrom beyond the requirement of the prior art, because such 
terms are used for descriptive purposes and are intended to be broadly 
construed. 
Moreover, the description and illustration of the invention is by way of 
example, and the scope of the invention is not limited to the exact 
details shown or described. 
Having now described the features, discoveries and principles of the 
invention, the manner in which the improved air spring is constructed and 
used, the characteristics of the construction, and the advantageous, new 
and useful results obtained; the new and useful structures, devices, 
elements, arrangements, parts and combinations, are set forth in the 
appended claims.