Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Background of the Invention
This is a division of Serial Number 310,139
filed August 28, 1978.
This invention generally relates to sleeve type,
rolling lobe airsprings as distinguished from bellows type
airsprlngs and more particularly to a high ratio L/D sleeve
type rolling lobe airspring that exhibits full recovery upon
pressurization from a full jounce position and column stabi-
lization under load in a pressurized condition.
; ~ A rolling lobe airspring is defined as a pneumatic -
device that has a piston aktached to an inner bead at one
end of an enclosed reversible flexible member and upon the
appllcation of load forces to the device, the flexible mem-
ber is caused to roll down over the piston. I~hile various
types and configurations of rolling lobe airsprings are
known and used in the art, the purpose of this invention
-is to provide an economically produced sleeve type rolling
lobe airspring that has a higher L/D ratio than heretofore
produced and which is column stabilized against lateral de-
flections that have tended to limit the working height and
thus the L/D ratio of the flexible membrane that could be
tolerated in some applications. ~-
An aspect of thi~ invention is as follows:
A high ratio L/D rolling lobe airspring for mount-
ing between two members capable of relative motion between
them comprising in combination: a piston mounted to one of
the members; a plug mounted to the o~her of the members;
- a tubular-walled sleeve-type flexible membrane of substan-
tially constant diameter in its undeformed state mounted
at one of its ends to the piston and at the opposite end to
the plug by means of ring fittings to form an airtight
chaTnber between them~ the mounting being such that the
piston moves axially into the tubular membrane and the .
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membrane walls form lobes éncasing the piston; means to
pressurize the chamber; and means mounted within the
chamber to limit the lateral de~lection of the membrane
when in its full jounce position such that upon being
inflated khe membrane returns to an axially symmetric con-
~iguration.
Description o~ the Dr w__~s
These advantages and other advantages and improve-
ments in the art will be better understood from the
: 10 ~ollowing description when considered in conjunction with
the accompanying drawings in the several figures of
which like reference numerals identify like elements,
and in which:
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Figure 1 is an elevational view of a typical sleeve-
type rolling lobe airspring showing i-t in an unpressurizedJ
unloaded and fully extended oQndition;
Figure 2 is an elevational view, partially in section,
showing the airspring of Figure 1 in a pressurized, loaded,
and wor~ing or design height condition;
: Figure 3 is an elevational view, partially in section,
illustrating a lateral deflection or "weinering" effect
experienced by an unmodified high-ratio LlD airspring of
Figure 2;
Figure 4 is an elevational view of an unmodified
sleeve type rolling lobe airspring showing it at full jounce
and illustrating a la-teral kinking, and the problem exper-
ienced upon re-pressurizing the spring;
.
Figure 5 is an elevational view, partially in section,
,. . of an improved high ratio L/D sleeve type rolling lobe air-
spring mod1fied in accordance with the teaching of this in-
vention;
Figure 6 is an elevational view, partially in section,
of a further modified high ration L/D, sleeve type rolling
lobe airspring; and
Figure 7 is an eleva-tional view, partially in section,
of another embodiment of a high ratio L/D, sleeve type rolling
lobe airspring that is also modified 1n accordance with this
invention.
Brief Descri~tion of the Inven-tion
Referring to the drawings, Figure 1 shows an unmounted,
unloaded and unpressurized rolling lobe t~pe airspring which
cornprises a flexible membrane 10 in a substantially cylindrical
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sleeve configura-tion, an end-plug 12 -that is mounted into
one end of the sleeve at lOa, and a piston 14 that is
mo~ted into -the other end of the sleeve a-t lOb. The sleeve
ends lOa and lOb are re-tained on -the plug 12 and piston 14
respectively by swaged-on rings 16 that effect a sealed air-
tight chamber bet~een the plug 12, piston 14 and sleeve lO.
The plug 12 is adapted for mounting by reason of bolt studs
18 and accepts air pressure 20 into the sleeve chamber by
way of a hollow stud 18 or else by way o~ a separate fitting
22 connected through the plug. Alternate arrangements of
mounting and connecting the air supply into the chamber may
be made, as for example, the air supply may be connected
through the piston. 0~ course, the manner of mounting will
depend on the particular application.
:
It should be clearly apparent ~rom the drawing that
the airspring of -this invention may be distinguished from
other type airsprings by reason of its length i.e., a high
L/D ratio where L is the overall length of the flexible
- . . . . . .
member and D is its diameter. Further, the rolling lobe
airspri-ng of this inven-tion may be distinguished by a
substantially tubular or sleeve configured membrane as
opposed to a bellows type membrarle. m e airspring may fur-
ther be distinguished by the fac-t that the membra~e is a
mandrel formed open-ended fle~lble sleeve whereas the other
types are fully molded sections characterized by molded in
beads at their open ends. ~hus, the sleeve type rolling lobe
airspring may be distinguished from alliothers by its basic
con~iguration, its manner o~ manufacture and its mode of
operation.
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;
Turning now -to Figure 2, -the airspring of Figure 1
is shown in its mounted, loaded and pressurized working
position. In this condition, the end plug 12 is mounted
to an upper plate 24 while the piston 14 is moun-ted -to a
lower pla-te 26, both plates capahle o~ relative motion
between them, either along the airspring axis 28 or along
an of~-axis arc 28' dependent,~o~ course, on the -type of
installation. I-t should be understood that Figure 2 illus-
trates an idealized working con~iguration ~or the airspring
at its design height H wherein the design heigh-t is defined
as that selected position o~ the spring which satisfies the
spring travel requirements between full rebound and ~ull
jounce an,d is usually speci~ied by a dimension H between
- reference points on the upper and lower extreme parts of the
spring as mounted and commonly identi~ied as a plate-to-plate
dimension. In practice, high ratio L/D sleeve type rolling
lobe airsprings have not been able to attain this ldealized
configuration and the reasons for this wlll be more fully
; - ~appreciated as the description continues with reference to
Figures 3 and 4.
Figure 3 illustrates a lateral deflectlon problem
experienced by a high ratio L/D sleeve type rolling lobe
airspring. Firstly, and because the flexible membrane is in
a sleeve or substantially tubular configuration as opposed
to a fully molded section, its diameter expands laterally
upon being inflated to its working pressure. Secondly,
and further because of its sleeve con~iguration, the ends
are mounted to the plug 12 and piston 14 by way o~ swaged-
on rings 16 as opposed to a bead type mounting characteristic
. . ,
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of the other types of airsprings. In this circumstance and
because of the high ratio L/D of the cylindrical sleeve,
the membrane -tends to deflect la-terally and roll upwardly
such as at lOc while also rolling downwardly on the opposite
side such as at lOd. The airspring thus exhibits an insta-
bility called "weinering" which is detrimental in its intended
applica-tion.
Flgure 4 illustrates a kinking effect experienced by
high ratio L/D sleeve type alrsprings when unpressurized and
in a full jounce position. In this unpressurized condition,
the cylindrical sleeve membrane 10 tends to kink such as at
lOe, and upon being repressurized, while restrained under
load the kink becomes accentua-ted laterally as shown by 10'
rather than recovering to its in-tended column configuration as
illustrated by Figure 2.
- Figure 5 illustrates a high ratio L/D slee~e type
rolling lobe airspring modified in accordance with this in-
vention to correct the instabili-ty problem shown in Figure 3.
In the drawing, a collar 30 is mounted on the airspring at
the end plug 12 such that upon mounting -the airspring to a
member 24 the collar fills in the space created by the end
plug to a thick~ess "h" at leas-t -that of the plug 12. The
diameter "d" of the collar is at leas-t to the point o~ tan-
gency "t" of the fle~ible membrane having an infla-ted diameter
D t . Upon being loaded the membrane 10 maintains its column
stability by reason of the collar preventing the membrane
from rolling upwardly over the ring 16. As shown in the
drawing, the collar 30 may be a separate item or in some
applications it may be designed into the configuration of the
mounting pla-te 24.
-- 5 --
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In ei-ther case -the collar 30 must have -the minimum thickness
'lhlla~hd diame-ter lld'1 as herebefore sta-ted.
Figure 6 illustrates a further modification -that is
made -to the airspring of Figure 2 to limi-t -the kink-ePfect
at full jounce. In this circumstance, a -thin-walled tubular
member 32 is positioned in the airspring chamber such that -the
flexible membrane 10 is limited in its lateral excursion due
to kink as illustrated by the dashed line showing 10". The
member 32 is thin-walled to retain the re~uired spring rate
by virture of a pre-es-tablished air volume within the chamber
and its length "1" is established by -the minimum of the design
height H selected for the particular airspring application. Of
course, the tubular member 32 may as well be mounted at the top
- of the airspring to the end plug 12 to obtain the same benefit as
described w1th respect to its mounting to -the piston. Furthermore,
' it-is anticipated that the member 32 may be made of metal, plas-
tic or any other material -that results in a rigid structure and
may be mounted within the airspring chamber by any means so long
as the configuration and type mounting results in a maintenance
of the required spring rate established for the airspring. Upon
repressurizing~ the airspring flexible membrane is restrained
from excessive lateral movement and therefore full axial symmetry
under load is accomplished.
Figure 7 illustrates an embodiment wherein the preselected
spring rate of a high L/D ratio airspring is preser~ed by mounting
a rod 34 within the airsprlng chamber such as to limit the lateral
excursion of the membrane as at lOf. In this circumstance, when
the airspring is not pressurized and may be in the dashed line
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position indicated by 10", the limi-t provided by the rod 34
allows for full recovery of -the airspring upon its pressur-
ization. Of course i-t will be recognized that the member
32 of Figure 6 or -the member 34 of Figure 7~may be of any
rigid configura-tion so long as -the pre-es-tablished spring rate
of the airspring is maintained.
While certain representative embodiments and details
have been shown for the purpose of illustrating -the invention,
it will be apparent to those s~illed in this art that various
changes and modifica-tions may be made therein without departing
from the spirit or scope of -the invention.
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