Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
11~45~36
1 ~his invention relates to a hydrostatic bearing
comprising at least one bearing shoe comprising a lower
part and an upper part which is tiltably and rotatably
supported thereon and which is fed with a hydraulic
pressure medium in the vicinity of its uppe~ side forming
the bearil-g surface, being provided with a connecting bore
which connects the upper side to the lower side and which
is designed to relieve the mechanical support of hydraulic
pressure.
In one known hydrostatic bearing construction (cf. DE-AS
20 49 402), the lower end of the upper part of the bearing
shoe with its hemi-spherical outer periphery projects into
a cylindrical recess in the lower part of the bearing shoe
and, at the same time, is supported by a centrally arranged
ball which is in engagement with hemi-spherical recesses
in the upper part of the bearing shoe on the one hand and
in the lower part of the bearing shoe on the other hand.
In addition, this ball is supported by the upwardly directed
end of a piston rod belonging to an adjusting piston
mounted for displacement in the lower end of the lower part
of the bearing shoe. The connecting bore which, in this
ca~e, is present between the upper side (bearing surface)
and the lower side of the upper part of the bearing shoe
opens in the vicinity of theouter edge of the bearing surface
and, in addition, mainly establishes the connection between
the bearing surface and the pressure medium supply line.
One major disadvantage of this known construction lies in the
particularly high structural outlay involved in obtaining
the movable, mechanical support with hydraulic pressure
release.
4586
1 Accordingly, the object of the present invention is to
provide a hydrostatic bearing of the type referred to at the
beginning which is distinguished by its particularly simple
construction and by its reliable hydraulic pressure relief
S for each bearing shoe.
According to the invention, this object i9 achieved in
that the bearing surface contains several pressure pockets
in known manner and the upper opening of the connecting bore
ls arranged symmetrically to these pressure pockets,
preferably at the centre of the bearing surface.
By virtue of the symmetrical arrangement of the upper
opening of the connecting bore to the pressure pockets of
the bearing surface, this open~ng is situated at a point at
which an averaged pressure of the hydraulic pressure medium
is present so that this averaged pressure may be optimally
used as a control pressure for the hydraulic pressure relief
of the mechanical support. This arrangement of the connecting
bore is preferably situated at the centre of the bearing
surface where the narrowest pressure medium gap between the
bearing surface and the rotary element to be supported is
also situ~ted. At this point of the bearing surface,
no mi8interpretation of the necessary control pressure will
occur, even in the event of pressure fluctuations in the
individual pressure pockets (attributable to the defonnations
encountered). By virtue of this arrangement, it is also
possible to make at least the upper part of each bearing
shoe lighter in construction by comparison with known
~rrangements (because there is no longer any need for a
dimensionally stable upper part of the bearing shoe so far
as the control of the hydraulic pressure relief is concerne~).
With the bearing construction according to the invention,
it has also been found that, by virtue of the previously
1~ ~4S86
-- 4 --
1 explained removal of the averaged pressure medium pressure
at the narrowest point where the highest pressure always
prevails, it is possible to obtain particularly high damping
of the bearing system as a whole.
According to the invention, the connecting bore best
opens into a relief chamber which is machined into the upper
side of the lower part of the bearing shoe ~nd which is
covered by the lower side of the upper part of the bearing
shoe.
In one particularly favourable embodiment of the
invention, the relief chamber is surrounded by a hemi-spherical
annular supporting surface with which a similarly hemi-
spherical counter supporting surface matchingly formed on
the underneath of the upper part of the bearing shoe is
in engagement, the annular supporting surface of the low~r
part of the bearing shoe and the counter supporting surface
of the upper part of the bearing shoe forming th~ mccn~nic~J
support of the bearing shoe. ~ bearing shoe constructed in
this way provides for extremely inexpensive manufacture and
offers a sufficiently large spherical supporting surface so
that, when the rotary element to be supported is stationary,
the supporting surface is subjected to an acceptable load
per unit area, even in the absence of special hydraulic
relief. In operation, the friction in the spherical
supporting surface is reduced to an acceptable minimum by
the hydraulic relief of pressure.
With the bearing construction according to the invention,
it is generally preferred for the annular supporting surface
to be machined in concave form into the upper side of
the lower part of the bearing shoe, whilst the annular
counter supporting surface is produced in convex form on
the underneath of a central part of the upper part of the
~1~4586
-- 5 --
1 bearing shoe which projects downwards in the shape of a
journal.
The construction described above may of course also be
inverted, i.e. the annular supporting surface of the lower
S part of the bearing shoe may be convex and the counter
supporting surface of the upper part of the bearing shoe
may be concave.
Where at least three bearing shoes are used in the
hydrostatic bearing, it is regarded as particula,rly favourable
in accordance with the invention for two bearing shoes to
have a substantially integral, fixed lower part whilst the
third bearing shoe and - if present - any further bearing
shoe is provided in its lower part with a radially adjustable
(relative to the rotary element to be supported) hydraulic
piston which is guided in this lower part and which carries
the relief chamber and the annular supporting surfsce for the
mechanical support on its upper side whilst its lower side
is connected through a hydraulic pressure cha~ber present
in the lower part and through a pressure line to the
connecting bore of one of the two bearing shoes with a fixed
lower part. In this way, the hydraulic piston of the
thlrd bearing shoe (and any further bearing shoe) may be
controlled in the sense of a uniform load distrlbution
through the bearing shoe comprising the fixed lower part.
Z5 Particularly reliable control of the hydraulic pressure
relief for the mechanical support is o~tained where the
bearing surface comprises four pressure pockets which are
separated from one another by webs, which are arranged
symmetrically to one another and to the centre of the bearing
surface and of which two pressure pockets diagonally opposite
one another relative to the centre are connected to a group
of pumps driven together ~ to a common multiple pump.
11f~4586
-- 6 --
1 Examples of embodiment of the invention are described
in the following with reference to the accompanying, largely
diagrammatic drawings, wherein:
Figure 1 is a vertical section through a bearing shoe
S comprising a one-piece lower part.
Figure 2 is a plan view of the bearing shoe shown in
Figure 1.
Figure 3 showsthe association of three bearing shoes
belonging to a hydrostatic bearing (bearing shoes shown in
vertical section).
Figure 4 is a plan view of the three bearing shoes
shown in Figure 3, including the purely schematised hydraulic
line system.
Figure 5 is a vertical section through a bearing shoe
which, in addition to the bearing shoes shown in Figures
1 and 2, i8 used in the association shown in Figures 3
and 4 and which comprises a hydraulic piston in its lower
part.
One embodiment of a bearing shoe which may be used in
a hydrostatic bearing according to the invention will first
be described with reference to Figures 1 and 2.
The bearing shoe 1 shown in Figures 1 and 2 comprises
~n upper part 2 which is tiltably and rotatably supported
on a lower part 3.
The upper surface of the upper part 2 fonms a bearing
surface 4 which is divided up into several pressure pockets
5, 6, 7, 8 (also known as oil pockets). As shown in
Figure 2, there are preferably four pressure pockets S to 8
which are separated from one another by webs 9, 10 and
which are arranged symmetrically to one another and to the
centre of the bearing surface.
Each pressure pocket 5 to 8 is supplied with hydraulic
li~4586
1 pressure medium, preferably oil, through separate connections
12, 13, 14 and 15, as will be explained hereinafter.
A connecting bore 16 is provided in the upper part 2,
connecting its upper side, i.e. the bearing surface 4, to
its lower side 17. This connecting bore ls preferably
arranged centrally in the upper part 2 (cf. in particular
Figure 2), its geometric axis being situated on the vertical
cent~al axis lla of the bearing shoe which passes through
the centre 11 of the bearing surface 4. In this way,
the upper opening 16a of the connecting bore 16 is also
situated symmetrically to the four pressure pockets 5 to 8,
i.e. lies at the point of intersection of the two webs 9
and 10 separating the pressure pockets 5 to 8 from one
another (cf Figure 2).
Figure ~ shows that the upper part 2 and the lower
part 3 of the bearing shoe 1 are in hemi-spherical
engagement with one another. To this end, the upper part
2 comprises a central part 18 wh~ch projects downwards
like a journal and of which the underneath 18a is convex
in shape towards the lower part 3 of the bearing shoe,
forming a hemi-spherical, annular (counter) supporting
8urface. By contrast, a similarly hemi-spherical annular
supporting surface l9a matching the underneath 18a of the
upper part 2 is machined into the upper side 19 of the
lower part 3 of the bearing shoe and thus forms a concave
recess. This annular supporting surface l9a together
with the counter supporting surface 18a essentially forms the
mechanical support of the upper part 2 on the lower part 3
of the bearing shoe 1.
In addition, a central relief chamber 20 (for example
in the form of a circular recess) is centrally machined
into the upper side 19 of the lower part 3 of the bearing
586
-
- 8 -
1 shoe, being surrounded by the annular supporting surface l9a
of this lower part 3 and being covered over its upper side
by the lower side 17 of the upper part 2, i.e. in this case
by the lower side 17 of the journal-like part 18. The
S lower end of the connecting bore 16 opens into this relief
ch~mber 20.
In oper~tion, i.e. when a machine part (not sho~) is
rotatingly supported by the bearing surface 4 of the upper
part 2, the pressure pockets 5 to 8 receive through their
connections 12 to lS an amount of oil sufficient to ensure
that, depending on the load, a more or less wide oil gap
is formed and can be maintained between the machine part
to be supported and the bearing surface 4. To ensure
that the upper part 2 of the bearlng shoe is able to follow
any shifting Movements of the machine part to be supported
(which is particularly important in the case of large-
diameter machine parts, such as rotary drums), it is
tiltably and rotatably supported on the lower part 3 of
the bearing shoe in the manner illustrated. The mechanical
support is then hydraulically relieved of pressure through
the relief chamber 20 by means of the connecting bore 16,
so that minimal friction occurs between the hemi-spherical
annular supporting surface 18a of the upper part 2 and the
similarly hemi-spherical annular coun~er supporting surface
19~ of the lower part 3, the hydraulic pressure relief
being controlled extremely favourably by ~he averaged oil
pressure of the bearing surface 4. In addition, it has
proved to be particularly favourable in this respect for
two of the four pressure pockets 5 to 8 which are situated
diagonally opposite one another relative to the centre 11 of
the bearing surface (i.e. 5 and 7 or 6 and 8) to be connected
to a group of pumps driven together or to a common multiple
S~36
p~op .
In connection with Figures 1 and 2~ it is further
pointed out that, as shown in Figure 1 in particular, the
lower part 3 of the bearing shoe 1 is largely in one piece
S and fixedly mounted (screwed).
Whilst it is generally possible to provide the hydrostatic
bearing with one or two of the bearing shoes illustrated in
Figures 1 and 2, it is preferred in the case of larger
rotating elements or machine parts to be supported to
provide at least three bearing shoes in the hydrostatic
bearing. One such embodiment is described in detail with
reference to Figures3, 4 and 5, Figures 3 and 4 showing
the purely schematic association of three bearing shoes.
In an association of three bearing shoes such as this,
two bearing shoes 1', 1" have a substantially one-piece,
fixed lower part 3', 3" on which an upper part 2', 2" is
supported. These two bearing shoes 1' and 1" with their
fixed lower parts 3', 3" have the same construction as the
bearing shoe 1 shown in Figures 1 and 2, so that there is
no need for further explanation.
The third bearing shoe 21 used in Figures 3 and 4
which, as shown in Figures 3 and 4, may be arranged
8ymmetrlcally between the two previously mentioned bearing
shoes 1' and 1" has an upper part 22 which may have exactly
the same construction as the upper parts 2' and 2" of the
bearing shoes 1' and 1". By contrast, the lower part 23
of this bearing shoe 21 is slightly modified in that it
comprises a hydraulic piston 24 mounted for radial adjustment
in this lower part in relation to the bearing element to
be supported (not shown).
As can be seen in particular from the detailed illustrat~on
of this bearing shoe 21 in Figure 5, the pressure relief
586
- 10 -
1 chamber 26 and the annular supporting surface for the
mech2nical support already known from the embodiment shown
in Figures 1 and 2 are in this case machined into the upper
side 25 of the hydraulic piston in exactly the same way and
S fonm as the annular supporting surface l9a and the relief
chamber 20 of the lower part 3 shown in Figures 1 and 2.
Since, as already mentioned, the upper part 22 of the bearing
shoe corresponds in its shape and configuration to the
upper part shown in Figures 1 ~nd 2, there is no need for
its construction to be discussed. Reference is merely made
once again to the connecting bore 28 arranged symmetrically
to the vertical central axis 27.
A hydraulic pressure chamber 29 is present in the
lower part 23 on the lower side of the hydraulic piston 24,
prefera~ly assuming the form of an outer annular chamber
(cf. for Figure 5) and comprising a pressure connection 30.
~he outer periphery of the piston 24 is sealed off by known
ring seals 31 from the fixed cylindrical peripheral wall 23a
of the lower part 23.
As shown in Figures 3 and 4, this third bearing shoe 21
is connected to one of the two bearing shoes comprising a
fixed lower part, in this case to the bearing shoe 1'.
This connection is established by connecting the lower side
of the hydraulic piston 24 through the hydraulic pressure
chamber 29, its pressure connection 30 and a pressure line
32 (shown only in chain lines) to the connecting bore 16'
of the bearing shoe 1', the pressure line 32 being connected
to a branch 16'b of the connecting bore 16'. In this way,
the pressure prevailing in the connecting bore 16' of the
bearing shoe 1' (i.e. the averaged ~l pressure of the bearing
surface 4') may be used to control the hydraulic piston 24
of the third bearing shoe 21, so that the upper part 22 of
1144586
1 the bearing shoe with its bearing surface 34 may be applied
radially to the rotating part (not shown in detail) by
correspondingly moving the piston 24 in the direction of
the double arrow 33 which in turn leads to an extremely
S uniform distribution of load between the bearing shoes of
the entire hydrostatic bearing.
A8 explained earlier on, two of the four pressure pockets
of e~ch bearing shoe which are arranged diagonally opposite
one another relative to the centre of the bearing surface
are best connected to a group of pumps driven together or
to a common multiple pump. This supply of pressure
medium to the pressure pockets for the three bearing shoes
1', 1" and 21 of the hydrostatic bearing shown in Figures
3 and 4 is diagrammatically illustrated in Figure 4. In
thls case, three multiple pumps 39, 40, 41 are provided,
being in the form of quadruple pumps and each being driven
by a separate drive motor 42, 43, 44.
Referring for example to the multiple pump 39 arranged
in the vicinity of the bearing shoe 1', two pump compartments
supply the two diagonally opposite pressure pockets 5' and
7~ of the bearing shoe 1' with oil , whilst the other two
pump comp~rtments supply the diagonally opposite pressure
pockets 36 and 38 of the bearing shoe 21 with oil. By
contrast, through two of its pump compartments, the
multiple pump 40 arranged in the vicinity of the middle
bearing shoe 21 supplies the other two diagonally opposite
pressure pockets 6', 8' of the bearing shoe 1' and the
two diagonally opposite pressure poc~ets 6" and 8" of the
bearing shoe 1". The other pressure pockets 35 ~nd 37 of
the bearing shoe 21 and the pressure pockets S" and 7" of
the bearing shoe 1" are then supplied with oil by the
corresponding pump compartments of the third multiple pump 41.
11~4S~
12 -
1 If in this case a motor, for example the motor 42, should
fail, the supply of oil from the associated multiple pump,
i.e. the multiple p~np 39, is interrupted, so that in the
case of the bearing shoe 1' the pressure pockets 5' and 7'
drop out, whilst in the case of the bearing shoe 21 the
pressure pockets 36 ~nd 38 drop out. Since the other
diagonally opposite pressure pockets of the two bearing
shoes 1', 21 continue to be supplied with oil through a
separate hydraulic circuit, a minimum lubricating function
can be maintained.
As can further be seen from Figure 4, a pressure monitor
46, 47, 48 may be associated with each connecting bore 16',
16", 45 of the bearing shoes 1', 1" and 21, being connected
control-wise to the oil supply of the associated bearing
shoes 1', 1" and 21.
Generally, it is pointed out that the bearing surfaces
of the bearing shoes may of course be adapted to the peripheral
form of the rotating element to be supported. The bearing
shoes of a hydrostatic bearing are not of course arranged
ln one plane (as shown in Figure 3 in the interests of
simpliclty), but instead are arranged at intervals on an
arc whlch is adapted to the peripheral form of the rotating
element to be supported. In contrast to the illustrated
embodiments, it is of course possible to select any other
suhable number of pressure pockets in the bearing surface
wlth a corresponding arrangement of the connecting bore.
~0
