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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to hydraulic anti-vibratory support sleeves including
two rigid tubular frames, one surrounding the other, preferably of
revolution at least partially, coaxial and concentric at least under load,
which frames are joined together by a elastomer body adhering thereto and
shaped so as to form therewith at least two diametrically opposite sealed
pockets communicating therebetween through a narrow channel, the assembly
of said pockets and said channel being filled with a shock absorbing
liquid.
Such sleeves are intended to be mounted between two rigid pieces fixable
respectively to the two frames and adapted to undergo, with respect to
each other, oscillation oriented in a diametrical direciton D with respect
to the axis common to the two frames, the assembly being arranged so that,
for some at least of these oscillations, the liquid is driven alternately
from one of the pockets towards the other and conversely through the
narrow channel, which creates in this liquid, for certain oscillation
frequencies, a resonance phenomenon capable of damping the transmission of
these oscillation from one of the frames to the other.
The sleeves of the kind in question are for example intended to be inserted
between a vehicle chassis and the internal combustion engine or the front
or rear undercarriage.
2. Description of the Prior Art
The invention relates more particulary, among the above support sleeves, to
those in which the portion of the elastomer body which defines one at
least of the pockets has in axial section the general shape of a radially
outwardly open V, such as described in patent U.S. Pat. No 3,698,703:
these sleeves lend themselves to relatively large resilient deformations
representing relatively high mutual tilting of the axes of the two frames.
In presently known embodiments of these sleeves, the narrow channel which
connects the two pockets together is generally formed by a channel in the
form of an arc of a circle extending in the median transverse plane of the
sleeve, along the internal frame or, more rarely, along the external
frame.
These embodiments have the following drawback: the narrow channel is
relatively far removed from the endmost axial faces of the sleeve, which
raises problems for filling this sleeve with liquid and for providing
sealing, such filling having to be carried out before the external frame
is positioned about the elastomer body.
Furthermore, it is not possible to modify the dimensions of the narrow
channel, and so the damping characteristics fo the sleeve, after
manufacture thereof.
The aim of the invention is, especially, to overcome these drawbacks.
SUMMARY OF THE INVENTION
For this, in the support sleeves of the kind in question in accordance with
the inventin, the channel extends in a way known per se along a transverse
arc of a circle having as axis the axis of the external tubular frame and
this arc is situated axially and radially at the level of the end of one
of the arms of the above V.
In advantageous embodiments, recourse is further had to one and/or the
other of the following arrangements:
the channel is defined by a metal shroud having a U section opening
outwardly of the sleeve in the direction of the axis of this sleeve and
disposed inside the external tubular frame, in the vicinity thereof, and
by a rigid annular packing introduced axially into this shroud,
in a sleeve according to the previous paragraph, the bottom of the shroud
communicates with at least one of the pockets through a circumferentially
elongate aperture and the length of the channel may be adjusted by
modifying the angular position of the annular packing in the shroud,
communication is provided between the channel and the outside for filling
the sleeve with liquid, the sleeve has two channels disposed respectively
in the vicinity of its two axial ends, symmetrically with respect to its
transverse median plane,
in a sleeve according to the preceding paragraph, one of the two channels
is provided with a resiliently compressible cushion formed more
particularly of a cellular material with closed cells and placed in
communication with at least one of the two packets,
the outwardly divergent walls forming the elastomer body are adhered to two
truncated cone shaped faces which define a central annular V shaped rib
forming part of the internal frame, each of these two truncated cone
shaped faces being substantially normal to the generatrices of the
truncated cone shaped wall adhering thereto,
a dividing wall extending along the transverse median plane of the sleeve
extends the internal frame radially outwardly as far as a short distance
from the external frame so as to divide the corresponding pocket into two
compartments communicating together through the channel defined radially
between this wall and said external frame, a rigid cylindrical ring is
fixed along the inner face of the external frame, between two pads which
define the elastomer body outwardly,
the elastomer body is prestressed axially during fitting thereof inside the
external frame,
the number of sealed pockets is equal to four, diametrically opposite in
pairs, and each of these pockets communicates with the diametrically
opposite pocket through a channel, one of the pockets is defined by the
external tubular frame and by a flexible membrane sealingly fixed to this
frame.
The invention includes, apart from these main arrangements, certain other
arrangements which are preferably used at the same time and which will be
more explicitly discussed hereafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In what follows, several preferred embodiments of the invention will be
described with reference to the accompanying drawings in a way which is of
course in no wise limitative.
FIGS. 1 and 2 of these drawings show a hydraulic anti-vibratory sleeve
constructed in accordance with the invention, respectively in axial
section through I--I of FIG. 2 and in cross section on a smaller scale
through II--II of FIG. 1.
FIGS. 3 and 4 show a variant of such a sleeve also in accordance with the
invention, respectively in axial section in the offload condition through
III--III of FIG. 4 and in cross section under load through IV--IV of FIG.
3.
FIGS. 5 and 6 show yet another variant of such a sleeve in accordance with
the invention, respectively in axial section through V--V of FIG. 6 and in
simplified cross section through VI--VI of FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a way known per se, the sleeve illustrated in FIGS. 1 and 2 includes:
an internal metal tubular frame of revolution 1,
an external metal tubular frame of revolution 2, coaxial with frame 1 at
least in the mounted and loaded condition of the sleeve and surrounding
this frame 1,
and an elastomer body 3 connecting the two frames 1 and 2 together while
forming therebetween two sealed pockets 4, 4' which are disposed
diametrically opposite in the direction D.
The internal frame 1 is intended to be fixed to a pin (not shown) which
passes jointingly therethrough whereas the external frame 2 is intended to
be fixed to a bearing (not shown), this pin and this bearing being fixed
respectively to two rigid elements between which it is desired to mount an
inti-vibratory support, elements such as a vehicle engine and the chassis
of the vehicle.
The two pockets 4 and 4' communicate together through a narrow channel 5.
These two pockets and the narrow channel are filled with a liquid L.
In the embodiment shown in FIGS. 1 and 2, the essential portion of body 3
has, under load, a form of revolution with an axial section in the form of
an X: two grooves 19 opening axially outwardly of the sleeve are then
disposed between the inner tubular frame 1 and the thick walls 3.sub.1,
3.sub.2 of a general conical shape corresponding to this X.
Two diametrically opposite radial arms 3.sub.3 complete these walls
3.sub.1, 3.sub.2 so as to form body 3 therewith.
When an oscillation of a relatively low frequency (for example of the order
of 10 to 50Hz) and of a relatively large amplitude (greater than 1mm) is
imposed in the diametrical direction D on one of the frames 1, 2 with
respect to the other, liquid L is driven alternately at said frequency
through channel 5 from one of the pockets 4, 4' to the other and
conversely and the dimensions of said channel, in particular its length
and it section, are determined so that excellent damping of said
oscillation is obtained for a given value of said frequency by the
creation of a resonance effect in the liquid column then present in the
channel.
This channel extends, again in a way known per se, along an arc of a circle
havng an axis that of the sleeve, but it is here located, not in the
median transverse zone of this sleeve, but in the vicinity of one of the
axial ends of the elastomer material body 3 and in the vicinity of the
external tubular frame 2, that is to say axially and radially at the level
of the ends of the arms of the above defined X.
In the embodiment shown in FIG. 1 and 2, the external contour of body 3 is
defined axially and radially by two annular "sausages" and it is in at
least one of these sausages that channel 5 is housed.
The channel could, at least partically, be directly formed in the sausage
concerned.
In the embodiment considered, a metal shroud 6 having a U shaped profile
opening axially outward of the sleeve is disposed in each sausage and one
at least of the two shrouds 6 is closed by an annular packing 7 formed
more particularly by a rigid plastic material.
The profile of packing 7 is such that it is force fitted into shroud 6 and,
once fitted, channel 5 is formed between the packing and the shroud.
The bottom of shroud 6 as well as the elastomer mass which covers this
bottom are formed with two apertures 8, 8' causing channel 5 to
communicate with respectively the two pockets 4 and 4'.
In an interesting embodiment, the section of each aperture 8, 8' is
elongated circumferentially, as can be seen in FIG. 2.
The length of channel 5 may then be adjusted by simply modifiying the
angular positon of packing 7 in shroud 6, the shape of this packing being
provided accordingly.
Channel 5, disposed in a lateral sausage of body 3, may be the only one and
then extend over an arc generally between 90.degree. and 270.degree., for
example of the order of 180.degree..
It may also be double, being in this case formed more particularly of two
semicircular sections symmetrical with each other with respect to an axial
plane passing through the middles of the two apertures 8 and 8'.
Such a single or double channel 5 may be provided in each of the two
lateral sausages of body 3.
Because channel 5 is adjacent an axial end of the sleeve, it may be readily
placed in communication with the outside of this sleeve throght a very
short duct 9 formed in the packing 7.
This duct may be used for filling the sleeve with liquid L.
Said duct may be a single one, and in this case filling of the sleeve with
liquid may involve a previous phase of evacuating the volume to be filled;
but it may also be divided into two ducts of the same kind sufficiently
distant from each other to facilitate removal of the air inside the sleeve
during filling.
At 10 is shown a plug closing the duct 9 at the end of filling.
To make the sleeve capable of damping not only oscillation of a relatively
low frequency and a relatively large amplitude, but also certain
vibrations of higher frequency and smaller amplitude, in one of the two
above described shrouds 6 there is advantageously provided a compressible
resilient cushion placed in permanent communication with one at least of
the two pockets through apertures of the same kind as those designated
above by the references 8 and 8'.
Such a cushion may be formed by a cellular body with closed cells or else
by an air chamber defined by a sealed resilient material pipe containing a
slightly compressed gas such as air.
Considering the deformability of cushion 11, it is advisable to complete an
annular cage containing this cushion by means of a rigid L shaped washer
12.
Transverse flanges 13 may be provided at the axial ends of the external
frame 2 for maintaining not only packing 7 but also washers 12 in
position.
The sleeve which has just been described is essentially intended to receive
and damp the alternate forces exerted between the two frames 1 and 2 in
the diametrical direction D.
It may be advantageous to adapt it so as to receive, possibly with damping,
forces exerted between these two frames in the axial direction of the
sleeve or in a direction slightly slanted with respect thereto.
The above described construction of the elastomer body 3 by means of two
thick truncated cone shaped walls 3.sub.1, 3.sub.2 is adavantageous to
this end.
These two truncated cone shaped walls are juxtaposed by their small bases
or, more precisely, the small bases are adhered respectively to two
truncated cone shaped areas 14 which define a thick annular rib 15
projecting outwardly from the internal frame 1, each area 14 being
substantially normal to the generatrices of the truncated cone shaped wall
which is adhered thereto.
The presence of the thick rib 15 is made possible by the fact that the
narrow channel is no longer provided about the central region of the
internal frame 1.
By modifying the obliqueness of areas 14, the resistance of the sleeve to
axial forces and resistance thereof to radial forces may be modified at
will, the first being all the higher and the second all the lower the
higher the slant of areas 14 with respect to the axial direction.
To increase resistance to axial forces, it may be advantageous to provide
along the internal face of the external frame 2 a rigid cylindrical ring
extending axially and jointingly between the two sausages or pads of body
3: such a ring has been shown with a dash dot line at 16.
Similarly, to increase the resistance of the sleeve not only to axial but
also radial forces, an axial prestress is exerted on body 3, particularly
during mounting of this body inside the external frame 2.
Because of the obliqueness of walls 3.sub.1 and 3.sub.2, this axial
prestress is automatically accompanied by a certain raidal prestress.
The length of ring 16 is advantageously chosen so as to adjust to the
desired value the amount of said prestress, the elastomer pads after
mounting coming into abutment against the axial edges of this ring.
As mentioned above, the sausages in which the channels 5 or cushions 11 are
housed are disposed radially about and opposite the endmost outer zones of
the internal frame 1, being separated from these zones by grooves 19.
The small radial distance which separates these sausages from these zones
may be cancelled out when high radial forces are exerted between the two
annular frames 1 and 2; said sausages then come into abutment against said
zones, which are advantageously coated with an elastomer layer 17 integral
with body 3 - and thus a very efficient means is obtained for limiting the
radial deformations of the sleeve.
To make the above described sleeve capable of damping, by a liquid
throttling effect, certain relative oscillations exerted axially between
the two frames 1 and 2, one at least of the two pockets 4 and 4' may be
divided into two compartments communicating with each other through a
narrow channel.
For this it is sufficient to fix to the rib 15 a rigid dividing wall in the
form of a circular sector extending radially from said rib up to a small
distance from the external frame 2: such a dividing wall has been shown
with a dot dash line at 18 in FIGS. 1 and 2.
When an axial oscillation is exerted on frame 1 with respect to frame 2, or
conversely, the liquid contained in one of the two compartments thus
defined is driven alternately from this compartment into the other through
the narrow channel defined radially between dividing wall 18 and the
external frame 2 and the dimensions of this channel are chosen so that the
maximum damping is then obtained for a given desired value of the
frequency of said oscillations.
The embodiment shown schematically in FIGS. 3 and 4 differs essentially
from the preceding one by the construction of pocket 4'.
Here, the portion of the elastomer body 3 which partially defines this
pocket 4' is no longer formed by truncated cone shaped wall sections
forming an X in axial section, but by a thin flexible membrane 20. This
membrane is here in the form of a band curved in a semicircle and bulging
slightly towards the axis. This band has two semicircular edges connected
sealingly to the external frame 2 along the shrouds 6 and its two ends in
the circumferential direction are connected to the arms 3.sub.3.
In this construction, rib 15 is not provided on the membrane 20 side.
Thus, only pocket 4 is defined by a portion of the elastomer body 3 having
an axial section in the form of a radially outwardly open V and extending
about the axis of the sleeve along only a half of the circumference.
This disymmetrical construction has the advantage of great radial
flexibility.
Finally, the embodiment shown schematically in FIGS. 5 and 6 differs from
that illustrated in FIGS. 1 and 2, in that it has no longer only two
sealed pockets 4 and 4', but four such pockets 21, 21', 21", 21'" disposed
oppositely in pairs.
Each of these pockets is connnected to the diametrically opposite pocket by
a narrow channel 22 or 22'.
Such a construction has the advantage of providing excellent damping of
oscillations exerted on the support in two radial directions perpendicular
to each other.
Following which, and whatever the embodiment adopted, a hydraulic
anti-vibratory support sleeve is finally obtained whose construction,
operation and advantages follow sufficiently from the foregoing.
As is evident, and as it follows moreover already from what has gone
before, the invention is no no wise limited to those of its modes of
application and embodiments which have been more especially considered; it
embraces, on the contrary, all variants thereof.
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