Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
`` ` 1166t70
~lethod and device for feeding lubricant to a ~ylinder-piston
arrangement
The invention refers to a method of feeding lubricant to a
cylinder-piston arrangement having at least one working space
lying under a pulsating working pressure as well as having at
least one easily deformable bellows-like, in particular
tubular, sealing element which bears at its surface against
a lubricant space, the lubricant flowing through this space
under a continuous feed. The invention further refers to a
device for the lubricant feed to a cylinder-piston arrangement
having at least two working members which define a pulsating
working space as well as having at least one easily deformable
bellows-like, in particular tubular, sealing element which
via a lubricant space connected to a lubricant feed machanism
bears during its periodic deformation corresponding with the
pulsation of the working space, against a bearing surface
formed by a first working member.
A method and a device of the aforesaid kind are known from the
West German O/S 25 54 733. The bearing here described in
particular, of a tubular sealing element via a lubricant
against a cylindrical bearing surface is effected with lubricant
feed even during the pressure working stroke, i.e., the stroke
with decreasing volume of the working space in the case of
pump service or respectively with increasing volume of the
working space in the case of motor service. The feed is
effected, for example, by forcing in a quantity flow which is
more or less independent of the counterpr~essure and subsequently
leaves the lubricant space via a throttle point into a low- ~
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pressure chamber. In this way independently of the oscillations
of the pressure in the working space ~called below for short
"wor~ing pressure") an e~uilibrium between the latter and
pressure in the lubricant space can be achieved and thereby
direct contact or mixed friction between the sealing element
and the bearing surface can be avoided. Such a lubricant feed,
however, demands a pump pressure which in any case lies above
the maximum value of the working pressure, as well as a
suitable control or regulation of the ~uantity ~low in the
feed. This is connected with comparatively high outlay.
The object of the invention is therefore the creation of a
method and respectively a device for the feeding of lubricant
to a cylinder-piston arrangement having a resilient sealing
element of the kind mentioned initially, which fundamentally
manages with a lubricant feed pressure which is lower with
respect to the working pressure and does not need any control
or regulation for a constant quantity flow in the case of the
lubricant feed. The solution of this problem is iil accordance
iS
with the invention/characterized as regards the method and
the device respectively by the features specified in Claim 1
and Claim 4.
Because of this solution, at intervals of time at comparatively
low working pressure there may be introduced at comparatively
low feed pressure into the lubricant space between the sealing
element and the bearing surface an amount of lubricant which
taking into consideration the throttl~ discharge is adequate
for safe bearing of the sealing element without contact or
mixed friction against the bearing surface. In that case a
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1 166170
reverse flow into the l~ricant feed mechanism working at
lower pressure is advantageously prevented by a non-return
v~lve arrangement so that the necessary equilibrium between
the lubricant pressure and the working pressure against the
sealing element- may rapidly establish itself. But if the
oc:casion arises a definite reverse flow blocking or respectively
a non-return valve arrangement may also be waived if the
reverse flow resistance in the feed system allows the build-
up of an adequate bearing pressure in the lubricant space.
In accordance with a fùrther development of the invention,
with the advantage of particular simplicity a variation in
time of the lubricant feed pressure which is independent of
the working stroke of the cylinder-piston arrangement and
is preferably at least approximately constant, may be provided.
This in particular enables in a simple way a common lubricant
feed for a multi-cylinder-piston arrangement with a
corresponding plurality of sealing elements.
On the contrary another further development of the invention
provides that the lubricant feed pressure exhibits a variation
in time which is synchronous with respect to the periodic
alteration in the working space of the cylinder-piston
arrangement, with maximum values in the regions of the working
stroke between the maximum values of the working pressure,
i.e., at low working pressures. Such an execution presents
itself above all forarrangements having only one sealing
element or a small number of such elements, where in each
case a lubricant pump may be coupled with the drive of the
cylinder-piston pair in question.
136~370
An important further development of the device in accordance
with the invention is characterized in that the non-return
valve arrangement exhibits at least one valve member arranged
in the region of the mouth from the lubricant feed into the
lubricant space. By this arrangement of the valve member of
the non-return valve arrangement there results a particularly
low-inertia blocking of the lubricant feed channel at the start
of the increase in the working pressure. Above all at very high
working pressures which would make necessary the taking into
consideration of the compressibility of the lubricant and of the
elastic resilience of the feed pipes and other feed members, this
signifies a considerable relief from loading of the whole feed
mechanism and avoids a reduction in the volume of lubricant
effective for the bearing and thus secures the sealing element
against contact with the unevennesses at the mouth of the lubricant
feed and thereby against damage.
More particularly, the present invention relates to a method of
feeding lubricant to a cylinder-piston arrangement operating with
a working pressure varying periodically between maximum and
minimum values and having at least one deformable, particularly
tubular, sealing element defining a working space in which said
working pressure prevails, said sealing element bearing at its
surface located oppositely to said working space against a lubricant
space, the lubricant flowing through this space under a current feed,
characterized in that the lubricant is fed into said lubricant
space with a periodically varying flow rate as well as predominantly
within sections of the working pressure periods extending between
the maximum values of the working pressure.
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~ 1 ~6~ 70
The present in~ention also relates to a device for the
lubricant feed to a cylinder-piston arrangemellt having at least
two working members which define a pulsating working space and
having at least one easily deformable bellows-like, in particular
tubular, sealing element which, via a lubricant space connected
to a lubricant feed mechanism, bears during its periodic
deformation corresponding with the pulsation of he working
space against a bearing surface formed by a first working member,
characterized in that the lubricant feed mechanism (8) exhibits
a low maximum value of pressure with respect to the maximum
values of the periodic working pressure and is preferably provided
with a non-return valve arrangement.
The invention is further explained with the aid of the
embodiments illustrated in the drawings. In these there is
shown in:
Figure 1 - a cylinder-piston arrangement having a tubular sealing
element and a driving and lubricant feed mechanism
indicated diagrammatically;
Figure 2 - in three graphs (a), (b) and (c) the variation in time
of various operating quantities of the cylinder-piston
arrangement, essential for the lubricant feed;
Figures 3a and 3b - on a larger scale an axial section and
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l l B6 .t 7 0
a section transversely to the axis respectively
through the connection region of a sealing tube to a working
cylinder with a non-return valve arrangement; ana
Figures 4 and 5 - each an axial section through the connection
region of a sealing tube with two modified
executions of non-return valve arrangements.
~`
In the case of the arrangement as in Figure 1 a cylinder 1
as a first working member and a piston 2 as a second working
member are connected together via a tubular sealing element
3 which beàrs against a cylindrical bearing surface 4 on the
first working member. In the radially thickened connection
region 3a of the sealing element 3 to the cylinder 1 the
bearing surface 4 formsa transitionsection 4aof thesurface curved
toroidally outwards. The connection region 3a has a
connection of the substance Qf the material, for example,
by vulcanization to an intermediate ring la of the cylinder 1.
In this connection region lies the mouth of the lubricant feed
which is still to be explained. At the oppostie end the sealing
element likewise has a connection of the substance of the
material to a conical face on the piston 2. A spiral
compression spring 2a forces downwards the shank 2b which is
guided to be able to be displaced in the cylinder 1, against
an oscillating driving member so that the working space 5
formed`inside the sealing element is reduced in the case of
a movement in accordance with the arrow X. In the illustration
the piston 2 adopts its bottom position with maximum volume
of the working space. At the top the working space is
connected by a cover 6 to the feed and discharge pipe 6a to
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1 166170
a valve arrangement (not shown) for a way of working of
the device as a pump. Between the sealing ele~ent 3 and
the bearing wall ~ there is a lubricant space 3b in the
form of a crevice of small radial thickness, the lubricant
filling in which excludes contact between the sealing element
and the bearing surface upon the oscillating longitudinal
stretching of the sealing element corresponding with the
piston motion. A motor unit 7 with a driving shaft 7a and
cam 7b is provided as the`drive for the piston motion, the
shank 2b of the piston being pressed against the latter by
the compression spring 2a. A lubricant feed mechanism with
a pump 8 is further coupled to the motor unit 7 via a
diagrammatically indicated shaft 8a and a cam 8b. A non-return
valve 8d, for example, may be inserted in the lubricant feed
pipe 8c but preferably the mouth 9 from the lubricant feed is
provided with a non-return valve member 15 having a low-inertia
action. The mouth 9 from the lubricant feed lies at the
underside of an annular body lO, provided with
corresponding outlet groov~ and forming on its upper side
the section 4a of the transition surface. During the
oscillating str~ching of the sealing element the tensile forces
inside the sealing material are deflected towards the outside
by the curvature of this surface section and distributed
over the connection of the substance of the material to the
intermediate ring la.
The graphs in Figure 2 referred to service of the cylinder-
- piston arrangement as a pump, i.e., with high working pressure
in the case of decreasing volume of the working space. In
the graph (a) the variation of the stroke hA of the working
piston 2 and of the pump stroke hz of the lubricant feed pump
1 ~ ~6~70
with respect to the time t is indicated. This way of working
corresponds with a lubricant feed synchroniz~ with the
working stroke at increasing volume of the working space.
in ~ime
Th~e associated variation/of the lubricant feed pressure pz is
indicated in the curve B of the graph (b). This feed allows
of a comparatively low maximum feed pressure Pzl~ The
variation in time of the lubricant quantity flow vz is
indicated in the graph (c) by the curve B. On the other hand
with the advantages mentioned in the introduction an asynchronous
lubricant feed may be applied, for example, at an essentially
constant feed pressure pZO in accordance with the line A in
the graph (b). Here too a penetration of lubricant into the
space 3b of the arrangement as in Figure 1 results in the
region of the working stroke with increasing volumè of the
working space, i.e., at low working pressure, with a quantity
flow vz in accordance with curve A in the graph (c).
In Figures 3a and 3b the form of the mouth from the lubricant
feed with a non-return valve against the end face lOa of the
annular body lO is shown in detail. A radial channel 11 in
the cylinder 1 is connected to the feedpipe 8c as well as
a circumEerential distributor groove 12 on the annular body
lO and further a plurality of radial feed grooves 13 inside
the end face lOa. The radial feed grooves 13 open into an
inner circumferential groove 14 between the annular body lO
and the cylinder 1, which acts as the terminal distributor
for the lubricant feed into the clearance space 3b. The mouth
9 itself is formed by a circumferential groove which in
cross-section is of a flat triangular shape, into which is
inserted an annular radially deformable valve member 15.
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The base 15a of the annular cross-sec~ion facing the sealing
element 3 exhibits a width b which is dimensioned to be
considerably larger than the radial height d of the cross-
section, so thàt faces 15b result on the rear of the ring
which are inclined at an acut~ angle with respect to the
cylindrical part of the bearing surface 4. As soon as the
lubricant feed pressure adequately exceeds the working
pressure acting on the in~ide of the sealing element, the
annular valve member 15 is deformed radially inwards as i~
indicated in Figure 3a in dotted line. At the rear faces 15b
o~ the ring outlet channels thereby result which open out at
an acute angle into the lubricant space 3b and upon the working
pressure being exceeded they are closed again automatically
with radial outwar~ stretching of the ring. The annular valve
me~ber may if necessary consist of a material which is stiff
against deformation but comparatively resilient, in particular
of a plastics which slides readily, so that low differences
in pressure are adequate for rapid valve actuation and further-
more only low loading of the surface of the sealing element
occurs by contact with the valve member. The low mass of the
annular valve member also contributes to low-inertia operation.
On the outside of the annular valve member 15 an annular
extension 15c running in the circumferential direction is
provided, which engages snugly in the circumferential groove
14 and`secures the valve member against axial shifting. As
may be seen from Figures 3b notches 15d are provided in the
annular extention 15c and engage radially inwards in the
region of the rear faces 15b. Consequently the lubricant can
- - ~ g~ out of the circumferential groove 14 into the outlet
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1 16&~70
channels formed on the rear faces 15b upon radial inwards
deformation if the radial inwards deformation has only come
to a small amount. This contributes too to low-aelay
operation of the non-return valve.
In the case of the execution of ~he non-return valve a`s in
Figure 4 there are connected to the feed pipe 8c and the
radial channel 11 a circumferential distributor groove 22
as well as radial channels 23 and a terminal distributor
~roove 24 inside the righthand end face of an annular body
2~. The transistion section4a ofthe surfaceis.ormedby an
annular valve member 25 separate from the annular body 20 and
axially displaceable because of the deformability of the
connection region 3a of the sealing element, this valve body
25 closing by its rear face 25a the mouth of the lubricant
feed when the working pressure exceeds the lubricant feed
pressure. Upon axial shifting of the valve member 25 towards
the left in the sense of Figure 4 the bottom section of the
rear face 25a releases the passage into the lubricant 3b.
Here too a discharge of the flow of lubricant results again
at an acute angle with respect to the cylindrical part of the
bearing surface 4,which contributes to a uniform and rapid
distribution of the lubricant.
The annular valve member 25 may for the rest instead of or if
necessary in addition to its axial displaceability exhibit
a radial deformability~which may readily be achieved by the
` choice of appropriate material. In the case of the inwards
deformation the cross-section of the annular body in the
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l 3fi6170
case of the execution as in Figure 4 may easily be twisted
so that the inner edge region of the rear face 25a lifts from
the cylinder whilst the outer region of the ring still bears,
In this way a slight deformation of the annular body is
5 sufficient for the valve action.
In the case of the execution as in Figure 5 an axially
displaceable annular valv;e member 35 is provided, which in
the flow state res~ by its right hand end_face 35a against
a corresponding flat endface of the cylinder 1 and under
the action of the lubricant feed pressure is shifted towards
the left to open. For that purpose the valve member is
fitted radially into a spacer ring 36 which exhibits at its
righthand endface circumferential distributor grooves 32a
and 32b as well as radial channels 33 for the outlet of the
lubricant to the righthand endface of the valve member 35.
Such an execution comes into consideration particularly also
for the employment of non-deformable materials capable of
wear for the valve member 35.
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