Bumper extension for use with a bumper on an air spring

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 formed of a high strength plastic is snap-fitted on an enlarged top of the post. One or more bumper extensions are stackable and matable on top of the bumper so as to allow for height adjustment without bumper removal.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The invention relates 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. More particularly, the invention relates to a bumper 
extension for use on an air spring having an already-existing bumper 
utilized in the air spring, where the bumper extensions are positioned 
over the existing bumper in either a single or a stacked configuration so 
as to allow the adjustment of the stop height of an air spring without 
requiring the replacement of the existing 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 imparted thereon. The air spring usually consists of a 
flexible rubber sleeve which extends between a pair of end members which 
contain a supply of compressed air and may have one or more pistons 
located within 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 by 
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 well known in the art and include U.S. 
Pat. Nos. 4,787,606, 4,852,861, 4,946,144 and 5,201,500. 
Certain of these prior art 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 spring 
member in the event of air spring failure. The bumper also absorbs shock 
upon the spring experiencing severe shocks and deflections which result in 
actual or near "bottoming out" of the spring member. Heretofore, these 
bumpers consisted of an elastomeric member which was mounted on a stud 
extending outwardly from one of the end members, such as is shown in U.S. 
Pat. Nos. 4,787,606 and 5,201,500. Although these elastomeric bumpers are 
satisfactory for most applications, it is found that several disadvantages 
or inconveniences result from their use, including the requirement of 
lubrication, special equipment to assemble the bumpers on the projecting 
studs, and the inability to alter the height of the bumper without 
complete removal and replacement thereof. 
Therefore, the need exists for an improved type of air spring bumper which 
eliminates the heretofore-used elastomeric bumpers, thereby overcoming any 
disadvantages of their use. 
Examples of other prior art inventions including shock-absorbing components 
are set forth in the following summaries. 
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 60 mounted on the inner surface 
of mounting plate 53 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 prior art, including those discussed above, disclose an 
air spring having an internal bumper that receives bumper extensions to 
provide height adjustability of the bumper. 
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. 
A further 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 to absorb sudden large deflections and to act as a 
back-up device in case of air spring failure. 
A further objective of the invention is to provide such an improved air 
spring in which the height of the shock-absorbing bumper may be adjusted 
without removal of the shock-absorbing bumper. 
A further objective of the invention is to provide such an improved air 
spring in which the shock-absorbing bumper may selectively receive bumper 
extensions so as to selectively adjust the height of the bumper without 
removal of said bumper mounted within the pressurized chamber. 
A further objective of the invention is to provide such an improved air 
spring which allows for interchangeable extension of the existing bumper. 
A further objective of the invention is to provide such an improved air 
spring which provides for bumper stop height flexibility. 
A further objective of the invention is to provide such an improved air 
spring which provides sufficient vertical load capability. 
A further objective of the invention is to provide such an improved air 
spring which provides sufficient lateral load capability. 
A further objective of the invention is to provide such an improved air 
spring which provides sufficient life in terms of cycles. 
A further objective of the invention is to provide such an improved air 
spring which is lighter in weight, easier and less expensive to assemble, 
which can carry greater loads at equivalent deflections than the 
heretofore-used 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, said improved air spring further 
including a shock-absorbing bumper mounted within the pressurized fluid 
chamber on one of the spaced end members for possible impact engagement 
with the other of said end members, said improvement including a bumper 
extension stackable on the bumper to add height to the shock-absorbing 
bumper.

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 7. 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 7). 
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 the base, 
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 air tight sealing relationship with piston 3. The other end 
of sleeve 10 has an end bead 13 which is secured in a curled marginal edge 
14 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, which do not require a beaded end seal. 
A source of pressurized air or other fluid, communicates with chamber 15 
through a hollow bore 17 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 7, may vary without affecting the 
concept of the invention. 
A snap-on bumper, indicated generally at 20 (FIG. 6), is mounted on base 4 
of piston 3 and extends upwardly therefrom into chamber 15. This bumper is 
described and shown in detail in U.S. Pat. No. 5,201,500, which is hereby 
incorporated by reference. Bumper 20 engages end cap 2 in the event of a 
failure of the pressurized fluid within air chamber 15, or assists in 
absorbing excessive shock forces exerted on either of the end members. 
Bumper 20 includes inner and outer generally cylindrical walls 23 and 24, 
respectively, concentrically arranged with each other which 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. A second plurality of reinforcing ribs 27 
are located between adjacent pairs of reinforcing ribs 26, and extend 
radially inwardly toward inner wall 23 from outer wall 24 only a short 
distance to provide increased strength for outer wall 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. 
6. 
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 an end cap, indicated generally at 
34. Cap 34 preferably is formed of a mild steel and is secured to clamp 
plate 12 by brazing at 35. The interior of end cap 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 the piston. 
End cap 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. 6 and 8) which extend upwardly inwardly into a hollow interior 44 
formed by inner wall 23. 
In one embodiment, there are four flexible fingers 43 spaced 
circumferentially apart by intervening areas 45, with each finger 
terminating in an outer arcuate edge 46 which snaps into and seats in 
undercut 40. Arcuate edges 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 another 
embodiment, 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 end cap 34 of the mounting post as shown in FIG. 8, by flexing 
outwardly as it is being forced downwardly on the mounting post. 
Immediately upon edges 46 of finger 43 moving beyond cylindrical side wall 
portion 47 of enlarged post end 39, the flexibility of the fingers will 
enable them to snap into position in undercut 40. When bumper 20 is in 
position on post 36, annular base 29 will seat upon clamp 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 the fingers lying along tapered side wall 41 of end cap 
34. 
In accordance with the invention, one or more bumper extensions 50 may be 
selectively mounted on snap-on bumper 20, as is shown in FIGS. 7-9. Bumper 
extensions 50 allow the use of existing bumpers 20 while serving to 
provide different stop heights without making and installing a new or 
replacement bumper. 
Each bumper extension 50 includes inner and outer generally cylindrical 
walls 51 and 52, respectively, concentrically arranged with each other 
which terminate in an integral dome-shaped connecting top wall 53. A 
plurality of radially extending reinforcing ribs 54 (FIG. 4) are formed 
integrally with inner and outer walls 51 and 52 and extend therebetween to 
provide a rigid integrally formed one-piece bumper member. A second 
plurality of reinforcing ribs 55 are located between adjacent pairs of 
reinforcing ribs 54 and extend radially inwardly toward inner wall 51 only 
a short distance to provide increased strength for outer wall 52. 
Inner wall 51 terminates in an alignment cylinder 58 (FIG. 3) having an 
offset extension 56 which includes an inwardly angled annular cylinder 57 
(FIG. 8). Alignment cylinder 58 extends downward in an offset manner from 
inner wall 51 further than the annular peripheral edge 59 of outer wall 
52. Alignment cylinder 58 also is of a smaller diameter than the annular 
area (interior 60) created by inner wall 51, where the outer diameter of 
the alignment cylinder 58 is substantially equivalent to the inner 
diameter of the annular area (interior 60) created by inner wall 51 such 
that the alignment cylinder snugly seats within interior 44 of bumper 20, 
as shown in FIG. 8, or within interior 60 of an adjacent bumper extension 
50, as shown in FIG. 9. 
After one or more bumper extensions 50 has been snugly seated within 
interior 44 of bumper 20, as shown in FIG. 8, or within interior 60 of an 
adjacent bumper extension 50, as shown in FIG. 9, the extension is either 
temporarily or permanently connected thereto. Specifically, a sonic or 
spin-weld or glue could be used to permanently affix the stacked bumper 
extensions 50 to each other and to bumper 20. The result would be an 
increase in the bump-stop height of the air spring. The lower extended 
part or alignment cylinder 58 provides for perfect alignment as well as 
lateral support and a larger area for attachment, using such attachment 
methods as spin welding, sonic welding, or adhesive attachment via glue. 
As is clearly shown in FIGS. 8 and 9, only one bumper extension 50 may be 
mated with bumper 20, or multiple bumper extensions 50 may be mated with 
each other and then mated with bumper 20. 
Bumper 20 and bumper extensions 50 are formed of a high strength polyester 
elastomer or plastic such as sold under the trademark HYTREL, by Du Pont 
de Nemours Company of Wilmington, Del. The type of HYTREL found most 
suitable is Dupont's grade 8238 which has a hardness Durometer D of 82, a 
tensile strength at break of 6800 psi and an elongation at break of 350%. 
Each of the bumpers 20 and bumper extensions 50 is preferably injection 
molded out of the same material. Bumper 20 and associated bumper 
extensions 50 also may be configured square, cloverleaf etc., and need not 
be cylindrical as described above and shown in the drawings, without 
effecting the concept of the invention. 
Thus, the improved air spring of the invention, and in particular snap-on 
bumper 20 and bumper extensions 50 thereof, enables the bumper to be 
installed easily on center post 36 by snap-fitting the bumper in a 
vertical downward direction over enlarged end 39 of the post, with 
flexible fingers 43 snapping into position into undercut 40 formed beneath 
enlarged end 39. This provides a bumper and resulting air spring, which is 
lighter in weight than prior art bumpers formed of an elastomeric material 
and, most importantly, enables the bumper to be snap-fitted into position 
without requiring lubricant and extra equipment heretofore required for 
installing the elastomeric bumper. Also, the high strength plastic of 
bumper 20 enables it to absorb greater load shocks at equivalent 
deflections than that absorbed by the prior elastomeric bumpers. 
Bumper extensions 50 provide for interchangeable extension of the existing 
bumper, bump-stop height flexibility, sufficient vertical load capability, 
sufficient lateral load capability, and sufficient life in terms of 
cycles. Basically, this invention allows the use of existing bumpers at 
different bump-stop heights without making a new bumper, removing the old 
bumper, and installing the new bumper. Currently, most bumpers or bump 
stops are fixed at one of only a few standard heights, such as 2.25 inches 
and 3.25 inches tall. This invention allows the attachment of extensions 
via a sonic or spin weld or adhesive, whereby one or more extensions could 
then be stacked upon each other and mated within each other to make the 
bump-stop height taller than these standard heights. 
The extensions are made via injection mold, using the same material and 
same manufacturing process as the original bumper 20. The extensions will 
be molded with a mating contour which would fit the existing bumper, as 
well as with a top contour identical to the existing bumper and/or other 
mating bumpers, so that more extensions could be stacked and mated on top 
thereof. 
Accordingly, the improved bumper extension is simplified, 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 containing the 
snap-on bumper and bumper extensions 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.