Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Applicant: Dr. Michael Polus
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s Title: Damping Device for Shock Loaas
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Description
This invention relates to an energy-absorbing damping
device for shock loads wherein a core consists of
elastically deformable material, is ela~tically com-
pressible and bounds a fluid-filled cavity, wherein
valveless passages formed in the core extend from said
cavity, each forming an opening at the perimeter of the
core and providing a connection to means which elasti-
cally yield to fluid pressure, wherein hydraulic
throttling devices are provided between said cavity and
the elastically yielding means and wherein the core
forms a supporting surface and a load surface which are
on opposite sides, said passages extending substan-
tially in the direction of said surfaces. -
In a prior-art (German Patent 12 03 578) damping device
of this kind, the passages providing the connections
are of a wide configuration. With their outer open-
ings, the connecting passages communicate with a con-
duit to which are connected gas cushions which are
elastically compre~sed as a load is applied to the
core. The fluid entering the gas cushions via one-way ;~i
valves returns via throttling valves into the conduit. -~
The use of the conduit, the gas cushion and the valves
makes this damping device a complex one.
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It is an object of the present invention to provide a
, damping device of the type initially referred to which
is less complex. In achieving this object, the damping
device according to the invention is characterized in
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~ that the passages are of narrow construction to act as
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throttling passages, in that the elastically yielding
means is an elastically extensible diaphragm fixed and
sealed all round and covering the outer openings of the
throttling passages, in that the cavity is bounded by a
depression provided in the supporting surface or load
surface of the core, in that the throttling passages
formed in the load or supporting surface of the core
forming the depression are open at one side and roofed
over by cover means, and in that the throttling pas-
sages are bounded at their sides by ridges formed in
the core, the cross-section of said ridges decreasing
towards their tips.
Energy-absorption takes place in as much as the energy
of an impact or shock forces the fluid through the
narrow throttling passages and the elastic diaphragm i8
extended. The damping device requires little space and
is straightforward because there is only the extensible
diaphragm provided instead of a plurality of additional
parts, such as the ring conduit, gas cushions and
valves. Damping takes place under conditions of suc-
cessive energy dissipation and without any oscilla-
tions. The damping action is not sudden and forceful
initially, but increases gradually.
The throttling passages provided in the surface result
in improved energy dissipation in damping applications.
They afford greater freedom in designing the structured
surface to match desired damping conditions. Because
the throttling passages are provided in its surface, it
is possible to design the core with a lower Shore
hardness than in a configuration where the throttling
passages are completely bounded by the core, i.e. en-
closed by the core all round.
The damping device according to the invention in-
volves an elastic hydraulic energy-absorption system
where fluid is forced through throttling passages out
of the elastic cavity which is formed to suit th2 ~ ~ 7~~~
applied. The forced out fluid is collected in the dia-
phragm and is returned in the working cycle into the
cavity which was deformed by the shock or impact. The
parameters: elasticity, volume and throttling device~
produce an exactly defined damping performance. Any
peak forces as occurring in rigid systems due to iner-
tia are avoided. Under conditions of constant static
loading, the damping device can be used as a damped
oscillation system.
In the case of the damping device according to the in-
vention, the core is subject to less flexing under im-
pact and to less increase in diameter. The friction of
the diaphragm on the core as its shape changes due to
loading and unloading is reduced. It doe~ not matter
whether the surface which is provided with the cavity
and the ridges or ribs is the load surface or the sup-
porting surface and whether the ridges are directed
upwards and downwards. The material of the core may be
less soft and less compressible so that flexing and
instability are reduced and practically avoided. Under
conditions of shock or impact, the ridges are com-
pressed and through the dimensioning of the ridges the
extent and pattern of energy absorption can be more
conveniently calculated and controlled. Since, as a
rule, the core would be round or oval in plan, the
ridges would as a rule extend in a radial direction.
The diaphragm or foil may, for instance, consist of an
elastic plastic or synthetic rubber. The core, for in-
stance, may consist of closed-cell polyurethane, 9ili- ~-
cone rubber or cellular rubber. The diameter of the
throttling passages depends on the specific use of the
damping device and the desired damping characteristic.
The core would generally be in one piece. In plan, the
structure according to the invention would be circular,
oval or even rectangular.
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It is especially effective and advantageous if the
ridges whGse cross-section decreases towards their tips
have their one side rising at a flatter angle than the
other. On application of shock or impact, these ridges
will deflect to the side of their steeper flank whereby
improved control of the energy absorption i9 obtained.
The effect of lateral deflection can be influenced by
varying the angles of the steeper flank and the flatter
flank.
Furthermore, it is especially effective and advanta-
geous if the ridges are provided on a substantially
plane surface of the truncated core and the height of
the ridges rising from the truncation surface increases
in the direction towards the outer perimeter of the
truncation surface so as to form a depression. In this
case, the throttling passages will initially be closed
only in the area of the greater ridge height by the
cover means and produce their throttling action only in
said closed area. As compression due to the impact in-
creases, closure of the passages also extends to the
lower heights of the ridges whereby the length of the
throttling passages in which throttling action occurs
increases.
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Moreover, it is specially effective and advantageous if
the length of the ridges equals at least one third of
half the diameter of the supporting or load surface in
the direction of the ridges. Starting from this minimum
length of the ridges, the throttling passage~ will have
a length which provides useful results in a great num-
ber of applications.
It is also specially effective and advantageous if the
fluid is silicone oil. Silicone oil is non-toxic and ;
useful over a wide temperature range from minus 70 to
plus 200. Dimensioning the energy absorption action is
simplified where silicone oil is used. ;~
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If the damping device provided with the ridges accord-
ing to the invention is subjected to a sudden load
directed against it, what happens is as follows:
A pressure build-up occurs in the fluid whereby the
fluid is accelerated towards the outside and fluid flow
occurs through the ridge structure.
Simultaneously, due to the outer load applied, the -~
ridge structure is deformed, for instance, the outer
ridge tips will be deflected; as the load increases,
the flow passages continue to narrow, throttling action
is produced and there will be a pressure build-up with
energy consumption increasing exponentially. At the end
of load application, the major portion of the fluid
will have collected at the outer perimeter of the core,
causing dilation of the diaphragm.
During the subsequent unloading, the ridge structure
will rise again immediately; this and the force of the
dilated diaphragm will cause the fluid to return into
the cavity as unloading takes place.
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It is especially effective and advantageous if more
than two throttling passages are provided. A greater
number, for instance more than three throttling pas-
i` sages, will i~prove the effectiveness of the damping
device.
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`~ The damping device according to the invention is de-
signed to provide a gradually increasing damping pat-
tern and to avoid a high initial oscillation. It is
specially effective and advantageous if the core, the
throttling passages and the diaphragm are matched up to
give a paraboloidal damping characteristic. Such a
damping characteristic, i.e. the variation of such a
force plotted against time, is preferred for many ap-
plications where a sudden load is applied to the load
surface. ~ --
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Another specially effective and advantageous configura
tion provides for the cavity to be bounded by an area
of the diaphragm spanning the cavity and extending over
a raised part forming the cavity as far as over the
outer open-ings of the throttling passages. In this
configuration, the fluid will return very quickly at
the end of the impact from the dilated part of the di-
aphragm at the outer openings of the throttling pas-
sages via said raised part into the cavity.
The damping device according to the invention, espe-
cially if it is formed with the ridges is a special
asset when applied to the lower part, in particular the
heel area, of a shoe. The damping device will improve
the comfort of the shoe with simple means.
A preferred embodiment of the invention is illustrated
in the drawing in which:
Figs. 1 - 4 each shows a cross-section through a damp-
ing device for sudden loads in various
phases of loading and unloading,
Figs. 5 - 7 each shows a part of the damping device
according to Fig. 1 under different loading
conditions of the ridges and
Fig. 8 shows the time-force characteristic at a
supporting surface of the d~mping device
with a shock load applied to the load sur-
- face. ~ -~
The damping device according to Figs. 1 - 7 comprises a --
single-piece core 1 which has a circular perimeter and,
on one side, forms an uneven supporting surface 2 which -
bears upon a base which is not shown. In the area of ~-~
the supporting surface, the core 1 forms a broken cir-
cumferential raised part 4 which surrounds a dish-
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shaped cavity 5. The raised part g is formed by radi-
ally extending ridges 16 which, at the center, leave a
secondary space 17 clear and steadily increase in their
height from the inside to the outer perimeter of the
core 1 relative to a plane truncating core surface 18.
At the side of the core 1 opposite the supporting sur-
face 2 there is provided a plane load surface 6 onto
which a loading member which is not shown in detail is
capable of acting as shown by the arrows 13. In the
surface of the core 1 are provided a plurality of
straight radially extending elongated throttling pas-
sages which are open at one side and each of which is
formed at the outer rim of the core with an outer
opening 9 while its inner opening 10 is located in the
central area of the dish-shaped depression 5 at its
bottom [top] proximate to the secondary space 17. A
diaphragm 11 is provided which is attached to the load
surface 6 with a flat joint which seals in the fluid.
The diaphragm 11 extends over the outer rim of the core
1 and the outer openings 9 provided in the latter and
is undetatched to the core rim. As shown in Fig. 1, the
diaphragm 11 is so~ewhat slack and has some clearance
relative to the rim of the core while a clearance also
exists relative to the crest of the raised part 4.
The throttling passages 8 are each bounded at the side
by a ridge 16 whose cross-section is shown in Fig. 5.
Since the ridges 16 extend radially, the size of their
contour increases from the inside towards the outer rim
of the core 1. The cross-section of each ridge 16 de-
creases as shown in Fig. 1 towards its tip or crest.
~ccording to Fig. 1, this decrease is relatively pro- -~
nounced and acute. It is also possible to adopt a
rounded or trapezoidally decreasing cross-section. Each
ridge 16 is formed with a little inclined flank 19 and
a steeply inclined flank 20. ~
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At the rim face of the core, the diaphragm 11 extends
not only with a loose contact, but slack with a clear-
ance 21 to the crest of the raised part ~ and then,
with its portion 12, covers the cavity 5. The cavity 5,
the throttling passages 8 and the clearance space 21
are filled with a fluid, for instance, silicone oil.
When the loading member acts according to the arrows 13
suddenly or shock-like onto the damping device accord-
ing to Fig. 1, then the core l together with its ridges
16 is stressed in compression, with the ridges being
deformed as shown in Figs. 6 and 7. The volume of the
cavity 5 is decreased and the throttling passages 8 are
closed progressively starting on the outer rim of the
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core 1 towards the inside and their cross-section i9
narrowed. Liquid is emitted at the outer openings 9 so
that the diaphragm 11 is dilated in a radial direction
as shown in Fig. 3 to form a convolution 14 which ex-
tends all round. When, according to Fig. 4, unloading
takes place after the impact, fluid returns through the
throttling passages 8 which have their full, if only
narrow, cross-section restored very quickly, with the
ridges 16 rising into their upright position.
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According to Figs. 1 - 4, the diaphragm 11 is made up
of a disc-shaped portion and a cup~shaped portion which ;~
are tightly welded to each other along a peripheral
area 22. As shown in Figs. 1 - 4, cover means 23 ex-
tending over the passages 8 are formed by part of the
diaphragm. It is conceivable to have two or more cores
stacked in a common enclosing diaphragm in a manner -
that the ridges of the one core contact the plane load ~-
surface of the adjacent core when this load surface
acts as a cover means.
Plotted in Fig. 8 i5 the force applied by the sudden
load according to the arrows 13 and measured at the
supporting surface 2 as a function of time. Transmis-
sion of the sudden load is subject to damping action,
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i.e. the load will be transmitted without any initial
peaks to the supporting surface 2 and rise steadily to
its maximum value.
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