PISTON STROKE END ABUTMENT FOR SHOCK ABSORBER AND LIKE TELESCOPING APPARATUS

BUTOIR DE FIN DE COURSE DE TIGE DE PISTON POUR AMORTISSEUR TELESCOPIQUE

English Abstract

PISTON STROKE END ABUTMENT FOR SHOCK ABSORBER AND LIKE
TELESCOPING APPARATUS
Jacques Gabriel ALLINQUANT
Société J.G. ALLINQUANT
ABSTRACT OF THE DISCLOSURE: -
A shock absorber having a work cylinder and
piston is provided on the one hand with a stationary stop
made of elastomeric material fitted against the rod-guide
bottom of the work cylinder, and on the other hand with
a movable rigid stop integral with the piston rod and
leaving a substantial clearance between its periphery and
the cylinder wall. The latter has an inward deformation or
constriction located close to its rod-guide bottom, forming
an inner annular protrusion over such a radial depth as to
leave but a minimized clearance between it and the periphery
of the movable rigid stop when the piston rod is at the
end of its stroke.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Piston stroke end abutment system for a
shock absorber or like telescoping apparatus having a work
cylinder, a piston rod movable therein, a bottom closure
for said cylinder adapted to guide said piston rod there-
through, a stationary stop made of elastomeric material
fitted against said rod-guide bottom, and a rigid movable
stop integral with said piston rod and leaving a relatively
wide clearance between its periphery and the inner wall
of said cylinder, wherein the improvement comprises a loca-
lized constriction formed on said work cylinder adjacent
said rod guide bottom closure thereof and extending over a
radial depth such that said constriction leaves but a
relatively narrow clearance with the periphery of said rigid
movable stop, at the end of the stroke of said piston rod.
2. Abutment system as claimed in claim 1,
wherein said constriction is annular and extends all around
said work cylinder at a level with said flexible stationary
stop.
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Description

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BACKGROUND 0~ T~ INVENTION
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The ~hock absorbers which are currently used in
the automobile industry are most o:~-ten provided with an
extension stroke limiter composed of -two stops which are
respectively stationary and movable (as shown diagrammati-
cally on Figure 1) 7 namely : on the one hand, a stop 1 of
elastomeric material having a progresslve de~lection curve
and fit-ted agrainst the rod-guide 2 which constitutes one
of the bot-tom closures of the work cylinder 3 of the shock
absorber ; on the other hand~ a rigid stop 4 integral with
-the pis-ton rod 5 of the shock absorber and engaging the
formex stop 1 into compression thereof a-t the end of the
extension stroke of the pistonO
In use, the ~lexible stop 1 is crushed and in
its deformation, i-t occupies the whole availabl.e room which
includes the annular clearance 6 between the inner wall of
cylinder ~ and the periphery of rigid stop 40 The compressed
elastomeric material can then creep through this annular
clearance 60
Because of this~ there is a serious risk7
especially upon strong abu-tmen-t, that stop 1 gets damaged9
being torn or disintegratedS causing total deterioration
of the shock absorber due to slashed particles of elas-
tomeric ma-terial which are dragged by the inner liquid
flows Qf the shock absorber and get eventually caught in
a valve, impeding its operation. In general) the injury
is caused by the fact tha-t the rigid stop 4 integral
with -the pis-ton rod 5 cuts off -the heel of the flexible
stop 1~
In order to avoid such a cu-tting off~ it would
be necessary to give to the movable stop 4 an outer diameter
almost equal to the inner diameter of the work cylinder 30
But then -the movable ~top 4 would act as an effective spu-
rious pis-ton producing i-ts own hydraulic resistance which
would interfere with that of the genuine or basic piston and
render practically impossible any correct ad~ustement of the
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hydraulic damping sys-tem~ sinoe oil would be permanently
laminated be-tween the movable stop 4 and the cylinder 3O
SUMMARY OF THE I~VENTION
An object of -the present in~ention is to prevent
any damage to the flexible stop even if strongly stressed,
while in-troducing no secondary disturbance on the hydraulic
operation of the shock absorber.
A fur-ther object of thls invention is to provide a
simple and cheap adaptation, though highly e~fective, of the
shock absorber to preclude the above defectO
In accordance with the present inven-tion~ an
inward deformation or constriction is ~ormed on the cylin-
der wall adjacent its rod-guide bottom, over such a radial
depth that the inner diameter o.~ the cylinder at the level
of this constriction be just slightly greater than the outer
diameter o~ the sto~ which is integral with the piston rod
leaving but a minimized clearance between the periphery of
the latter s-top and the inner wall of this constriction,
at the end of the extension stroke of the rodO
BRIEF DESCRIPTI0N OF` THE DRAWINGS
_ ___ ,
Figure 1 is a fragmentary half axial section of
a prior art shock absorber.
Figures 2 and 3 are similar views showing a pre-
ferred embodiment of the present in~ention, in two different
positions of the piston rod ~ respectively, in an intermediate
position and in an extreme position corresponding to the end
of the extension strokeO
As apparent from Figures 2 and 3 7 the work tube
or cylinder 3 is deformed at its end portion close to the
rod-guide bottorn 2 and at a level with the elastomeric sta-
-tionary stop 17 SO as to constitute a localized armular
constriction Ro
In normal opexation (see Figure 2) 9 the rigid
movable stop 4 which is in-tegral with -the pis-ton rod 5 has
an external diameter substantially smaller than the internal
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diameter o~ -tube 3, leaving a relatively large a~nular
clearance 6 which does not upset the hydraulic acl~ustmen-t
of the shock absorberO When this movable stop 4, at the end
of the extension s-troke (see Figure 3), engages -the flexible
s-tationary s-top 1 ancl crushes the latter agains-t -the rod-guide
bottom 2, the annular clearance 6' is highly reduced owing -to
-the :localized constriction R and does not allow lnsertion
thereinto o~ the flexible stop 1. Hence it cannot be
slashecl, and no damage is to be feared in this respect~