Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
HYDRAULIC OIL CYLINDER, CORRELATIVE DEVICE THEREOF, HYDRAULIC
CUSHION SYSTEM, EXCAVATOR AND CONCRETE PUMP TRUCK
[0001]
FIELD OF THE INVENTION
[0002] The present application relates to the field of hydraulic technology,
and particularly to a
hydraulic oil cylinder. The present application also provides related devices
for the hydraulic oil
cylinder, such as a rod cavity end cover, and a hydraulic buffer system having
the hydraulic oil
cylinder, an excavator and a concrete pump truck both having the hydraulic oil
cylinder.
BACKGROUND OF THE INVENTION
[0003] The hydraulic oil cylinder is a component widely used in the
construction machinery,
and during the working process of the hydraulic oil cylinder a piston needs to
reciprocate
continuously. When a piston rod extends to a limiting position, an end cover
may be impacted
strongly by a piston end surface, which may cause damage to the hydraulic oil
cylinder.
Therefore, a buffer device needs to be provided at that position to avoid the
damage to the
hydraulic oil cylinder caused by the above impact.
[0004] There are great differences among the existing buffer devices according
to different
applications and different sizes of the hydraulic oil cylinders. A compression
spring can be used
directly as a buffer device in a small-sized oil cylinder, however, in the
hydraulic oil cylinder
with a large cylinder diameter and a long stroke, if the compression spring is
used as the buffer
device, it is hard to obtain a spring having sufficient elasticity, and
because that the pressure in
the hydraulic oil cylinder is great, the spring will be damaged soon because
of being repeatedly
compressed. Therefore, the hydraulic oil cylinder with a large cylinder
diameter and a long
stroke generally use a hydraulic buffer mechanism shown in Figure 1.
[0005] Referring to Figure 1, the buffer device includes a big buffer ring 06,
being mounted in
an intermediate annular groove arranged on a buffer position of a piston rod,
and a big
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buffer sleeve 04, being sleeved on the buffer position. Corresponding to the
big buffer sleeve
04, a buffer inner hole 07, having an inner diameter cooperating with an outer
diameter of the
big buffer sleeve 04, is provided at a cover opening portion of a rod cavity
end cover 01 of the
oil cylinder. When the piston rod is extended, the big buffer sleeve 04 is
firstly inserted into
the buffer inner hole 07 to block an oil-returning oil passage of the rod
cavity in a cylinder
barrel 02, and at the same time, a throttling oil channel is formed by a gap
between the big
buffer sleeve 04 and the buffer inner hole 07; so that, a piston 05 can
continue to move in an
extending direction, however due to a buffer effect of the throttling oil
channel, the movement
speed of the piston 05 is slowed down. And when the piston 05 gradually
approaches an end
position of the extending process of the piston rod 03, the length of the
throttling oil channel
between the big buffer sleeve 04 and the buffer inner hole 07 is gradually
increased, which
gradually increases the damping effect of the throttling oil channel, thus the
movement of the
piston 05 is gradually slowed down until the piston eventually reaches the end
position of the
extending process of the piston rod 03 smoothly.
[0006] Currently, the above buffer mechanism is widely used in the hydraulic
oil cylinder
with a large cylinder diameter and a long stroke to provide a better buffer
protection for the
hydraulic oil cylinder.
[0007] However, the above buffer mechanism also has some obvious
disadvantages. Firstly,
for the hydraulic oil cylinder with a large cylinder diameter and a long
stroke, such as a
driving cylinder used for driving a digging arm of an excavator, the hydraulic
oil cylinder is
generally working in a working condition of huge load and high frequency. In
such a case, the
big buffer sleeve 04 in the above buffer mechanism needs to repeatedly insert
into the above
buffer inner hole 07 at a high speed, and because that the fitting interspace
between the big
buffer sleeve 04 and the buffer inner hole 07 is very small and the piston rod
03 is very heavy,
the piston rod 03 is easy to be tilted to one side under the action of
gravity. Therefore in the
above hydraulic oil cylinder, failures of the buffer mechanism that the buffer
sleeve 04 fails to
insert into the buffer inner hole 07 are very easy to happen, which may cause
the entire
hydraulic oil cylinder being not able to operate normally.
[0008] Another key problem of the above buffer mechanism is that, the outer
diameter of
the big buffer sleeve 04 must fit with the inner diameter of the buffer inner
hole 07 precisely,
otherwise the buffer effect may not be achieved, thus the buffer mechanism has
an extremely
high manufacturing precision requirement which is hard to meet for
manufacturers with
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ordinary manufacturing level. Due to the excessive high manufacturing
precision
requirements, the hydraulic oil cylinder with a large cylinder diameter and a
long stroke has
become a bottleneck problem for producing construction machineries such as
excavators,
which severely restricts the production capacity of the manufacturers in
downstream
production chain.
SUMMARY OF THE INVENTION
[0009] The present application provides a hydraulic oil cylinder, and a buffer
system of the
hydraulic oil cylinder may realize a buffer effect reliably in an operating
condition of large
load and high frequency and has a longer service life. The manufacturing
precision
requirement for the hydraulic oil cylinder is low, thereby facilitating the
production of the
hydraulic oil cylinder. The hydraulic oil cylinder particularly facilitates
the manufacturing of
the hydraulic oil cylinder having a large cylinder diameter and a long stroke.
[0010] The present application further provides related devices used in the
above hydraulic
oil cylinder, including a piston rod, a rod cavity end cover and a buffer
sleeve.
100111 The present application further provides a hydraulic buffer system
having the above
hydraulic oil cylinder.
[0012] The present application further provides an excavator having the above
hydraulic oil
cylinder.
[0013] The present application further provides a concrete pump truck having
the above
hydraulic oil cylinder.
[0014] The present application provides a hydraulic oil cylinder, wherein a
buffer sleeve
being able to axially slide along a piston rod is sleeved on a buffer
position, located in a rod
cavity, of the piston rod; and an end surface of the buffer sleeve away from a
piston is a first
end surface of the buffer sleeve; a rod cavity sealing end surface is provided
in an oil cylinder
cavity between a rod cavity oil-passing hole and an end position of a rod
cavity end surface of
the piston in an extending movement of the piston rod, and is configured to
block the buffer
sleeve and to abut against the first end surface of the buffer sleeve so as to
form a sealing
surface; and at least one throttling oil channel is further provided, such
that during the
extending movement process of the piston rod, the hydraulic oil at a side of
the sealing
surface close to the piston can flow towards the rod cavity oil-passing hole
through the
throttling oil channel in a period from a time when the first end surface of
the buffer sleeve
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abuts against the rod cavity sealing end surface to form the sealing surface
to a time when the
piston rcaches an end position of the extending movement.
[0015] Preferably, the throttling oil channel is provided axially and linearly
between the
piston rod and the buffer sleeve.
[0016] Preferably, an end of the throttling oil channel close to the piston is
named a first end,
the other end of the throttling oil channel close to the rod cavity oil-
passing hole is named a
second end, and a cross-sectional area of the throttling oil channel is
increased gradually from
the first end to the second end.
[0017] Preferably, in the case that the piston rod is extended to a stroke end
position, there
is a distance between the buffer sleeve and an end point of the sliding
movement of the buffer
sleeve towards the piston.
[0018] Preferably, in the case that the first end surface of the buffer sleeve
contacts the rod
cavity sealing end surface to form the sealing surface, an area of an axial
action, applied on
the buffer sleeve by the hydraulic oil at a side of the sealing surface close
to the piston, is
greater than an area of an axial action, applied on the buffer sleeve by the
hydraulic oil at the
other side of the sealing surface close to the rod cavity oil-passing hole.
[0019] Preferably, the piston rod is provided with a buffer position stop
shoulder, and in the
case that the buffer sleeve is not blocked by the rod cavity sealing end
surface, the first end
surface of the buffer sleeve is pressed against the buffer position stop
shoulder under the
action of an elastic member having elasticity.
[0020] Preferably, a piston stop shoulder is provided at the end position of
the extending
movement of the piston rod, for allowing the buffer sleeve to pass through and
stopping the
piston at the end position.
100211 Preferably, the first end surface of the buffer sleeve abuts against
the rod cavity
sealing end surface to form a surface sealing or a linear sealing.
[0022] Preferably, a main body of the throttling oil channel is a throttling
groove arranged
axially and linearly on a surface of the piston rod.
[0023] Preferably, in the case that the buffer sleeve is blocked by the rod
cavity sealing end
surface and slides relatively towards the piston, a flow sectional area of the
throttling groove
is reduced accordingly.
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[0024] Preferably, an oil-passing groove is arranged on the buffer position
stop shoulder at
a position corresponding to an end point of the throttling groove.
[0025[ Preferably, one or a plurality of annular grooves functioning as
balancing grooves
are provided on an outer surface of the buffer position of the piston rod, or
on an inner
diameter surface of the buffer sleeve, and a cross section of the annular
groove is V-shaped,
U-shaped, square or other forms.
[0026] Preferably, the throttling oil channel includes two sections, that is,
a front section
close to the piston and a rear section close to the rod cavity oil-passing
hole; a main body of
the front section is a throttling groove axially provided on a surface of the
piston rod, and a
main body of the rear section is a hidden oil channel extending axially in the
piston rod.
[0027] Preferably, the throttling oil channel includes a hidden oil channel
extending axially
in the piston rod and a plurality of throttling oil holes communicating a
surface of the piston
rod with the hidden oil channel, the throttling oil holes are axially
distributed on the surface of
the piston rod, and the closer the throttling oil hole is to an outlet of the
hidden oil channel,
the larger the hole diameter of the throttling oil hole is; and the outlet of
the hidden oil
channel is a second end of the throttling oil channel, and the throttling oil
holes are a first end
of the throttling oil channel.
[0028] Preferably, a main body of the throttling oil channel is a chamfered
surface axially
arranged on the surface of the piston rod.
[0029] Preferably, a transition sleeve cooperating with the piston rod is
sleeved on the
buffer position, and the throttling oil channel is arranged on the transition
sleeve.
[0030] Preferably, one or a plurality of annular grooves functioning as
balancing grooves
are provided on the transition sleeve, and a cross section of the annular
groove is V-shaped,
U-shaped, square or other forms.
[0031] Preferably, the rod cavity sealing end surface is provided on the rod
cavity end
cover.
[0032] Preferably, the piston stop shoulder is an end surface of a cover
opening of the rod
cavity end cover.
[0033] The present application also provides a hydraulic oil cylinder related
device, in
particular a piston rod, wherein the piston rod is provided with a buffer
position stop shoulder
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located at a starting point of the buffer position and at least one throttling
oil channel
extending axially on a surface of the piston rod, a first end of the
throttling oil channel is an
end close to a position where a rod cavity end surface of a piston is located
after the piston is
mounted, and a second end of the throttling oil channel is the other end
located on a side wall
of an undercut of the buffer position stop shoulder.
[0034] Preferably, a cross-sectional area of the throttling oil channel is
increased gradually
from the first end to the second end.
[0035] Preferably, a main body of the throttling oil channel is a throttling
groove extending
axially on the surface of the piston rod, and the cross-sectional area of the
throttling groove is
gradually increased from the first end to the second end by gradually
increasing a depth of the
throttling groove.
[0036] Preferably, the buffer position of the piston rod is provided with a
plurality of
annular grooves functioning as balancing oil grooves.
[0037] The present application further provides another hydraulic oil cylinder
related device,
in particular a rod cavity end cover, from a top end to a cover opening of the
rod cavity end
cover, a rod cavity oil-passing hole and a rod cavity sealing end surface are
sequentially
provided, and the rod cavity sealing end surface is a stepped surface having
an integral
annular shape provided in an inner cavity of the rod cavity end cover.
[0038] Preferably, the cover opening of the rod cavity end cover functions as
the piston stop
shoulder.
[0039] The present application further provides a hydraulic oil cylinder
related device, in
particular a buffer sleeve, the buffer sleeve has an outer diameter smaller
than an inner
diameter of a cylinder barrel of a hydraulic oil cylinder in which the buffer
sleeve works, an
inner diameter of the buffer sleeve is configured to enable the buffer sleeve
to be sleeved on a
piston rod buffer position and to slide freely in an axial direction; upon
assembling, a first end
surface, away from the piston, of the buffer sleeve is configured to abut
against a sealing end
surface, located in an oil cylinder cavity between a rod cavity oil-passing
hole and an end
position of an extending movement of the piston rod, so as to form a sealing
surface.
[0040] Preferably, an end surface of the buffer sleeve opposite to the first
end surface is
provided with a central protruding portion cooperating with a compression
spring.
[0041] The present application provides a hydraulic buffer system including
the hydraulic
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oil cylinder described in any one of the above technical solutions.
[0042] The present application also provides an excavator including at least
one hydraulic
oil cylinder described in any one of the above technical solutions.
[0043] The present application also provides a concrete pump truck including
at least one
hydraulic oil cylinder described in any one of the above technical solutions.
[0044] In the hydraulic oil cylinder provided by the present application, when
the piston rod
is extended to the buffer position, the first end surface of the buffer sleeve
cooperates with the
rod cavity sealing end surface arranged in the oil cylinder cavity at a rod
cavity side to form a
sealing surface so as to block the oil passage. The rod cavity is divided into
two cavity bodies
by the sealing surface, a cavity body located at a side of the sealing surface
close to the piston
is referred to as a buffer oil cavity, and the other cavity body is located at
a side of the sealing
surface close to the rod cavity oil-passing hole. The hydraulic oil in the
buffer oil cavity being
pushed by the piston has a higher oil pressure and may press the first end
surface of the buffer
sleeve against the rod cavity sealing end surface tightly, such that the
sealing effect of the
sealing surface, formed by the first end surface of the buffer sleeve and the
rod cavity sealing
end surface abutted together, is more reliable. The oil cylinder is further
provided with a
throttling oil channel, and the throttling oil channel may provide an oil
passage for the
hydraulic oil in the buffer oil cavity to flow to a side of the rod cavity oil-
passing hole in a
period from the sealing surface is formed to the piston reaches the end
position of the
extending movement. Due to the formed sealing surface, which blocks the oil
passage, the
hydraulic oil can flow, only through the throttling oil channel, towards the
rod cavity
oil-passing hole, and the oil passage of the throttling oil channel is very
narrow, thus a passing
capability of the hydraulic oil is restricted, such that the movement of the
piston is subjected
to a great resistance, thereby realizing the buffer effect.
[0045] In a preferred embodiment of the present application, the above
throttling oil
channels may be arranged axially and linearly between the piston rod and the
buffer sleeve,
such that the hydraulic oil in the buffer oil cavity may be discharged
smoothly and directly to
the side of the rod cavity oil-passing hole, and an axial range of the
throttling oil channel is
easy to determine, which ensures that the throttling oil channel can be formed
after the sealing
surface is formed so as to avoid blocking during the buffer process. Further,
the
cross-sectional area of the throttling oil channel can be changed according to
the requirements,
specifically, an end of the throttling oil channel close to the piston has a
smaller
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cross-sectional area and the other end of the throttling oil channel close to
rod cavity
oil-passing hole has a larger cross-sectional area.
[0046] In a further preferred embodiment, a main body of the throttling oil
channel is a
throttling groove arranged axially on the surface of the piston rod, and a
cross-sectional area
of the throttling groove is gradually increased from the first end to the
second end. In this way,
as the piston rod moves to the end position, the buffer sleeve slides
relatively on the piston
rod to gradually approach the first end of the throttling oil channel, thus
the discharging
capacity from a side of the sealing surface close to the buffer oil cavity to
the other side of the
sealing surface close to the rod cavity oil-passing hole is gradually reduced,
the resistance for
the extending movement of the piston is gradually increased, and the movement
speed of the
piston is gradually reduced, thereby achieving a good buffer effect. Due to
the throttling
grooves arranged axially and linearly, in the case of a constant width, the
throttling effect can
be well controlled by controlling the depth variation of the throttling
groove, thereby realizing
a smooth buffer process. The depth of the throttling groove is easy to control
during the
machining process, thus the throttling groove has a good manufacturability.
[0047] In a further preferred embodiment of the present application, in the
case that the
throttling groove is provided, a plurality of annular grooves functioning as
balancing oil
grooves are provided on the outer diameter surface of the piston rod or the
inner diameter
surface of the buffer sleeve, and the balancing oil grooves can cooperate with
the throttling
groove, such that the hydraulic oil may distributed evenly on the inner
diameter surface of the
buffer sleeve, which ensures that the first end surface of the buffer sleeve
will not be inclined
when abutting against the rod cavity sealing end surface, thereby ensuring the
tightness of the
sealing surface.
[0048] In another preferred embodiment of the present application, the
following condition
has to be satisfied: when the first end surface of the buffer sleeve contacts
with the rod cavity
sealing end surface to form the sealing surface, an area of an axial action,
applied on the
buffer sleeve by the hydraulic oil at a side of the sealing surface close to
the piston, is greater
than an area of an axial action, applied on the buffer sleeve by the hydraulic
oil at the other
side of the sealing surface close to the rod cavity oil-passing hole. The
above condition is easy
to be satisfied by designing the two end surfaces of the buffer sleeve. If the
above condition is
not satisfied, the oil pressure at two sides of the sealing surface are
substantially same at the
moment when the sealing surface is formed, and when the first end surface of
the buffer
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sleeve is pressed towards the rod cavity sealing end surface at a certain
speed, the first end
surface of the buffer sleeve may not be pressed tightly against the rod cavity
sealing end
surface at the above moment, which may affect the smoothness of the buffer
process at that
time point. If the above condition is satisfied, a total pressure V1 is
obtained by multiplying
the oil pressure at the side of the sealing surface close to the piston by the
area of the axial
action applied on the buffer sleeve at the same side, and a total pressure V2
is obtained by
multiplying the oil pressure at the other side of the sealing surface close to
the rod cavity
oil-passing hole by the area of the buffer sleeve at the other side. Because
the oil pressure at
two sides of the sealing surface are substantially same at the moment when the
sealing surface
is formed, a total pressure at a side having a larger area is relatively
large, i.e. V1>V2, thus in
this way, the buffer sleeve can be tightly pressed against the rod cavity
sealing end surface,
thereby ensuring the smoothness of the buffer process.
[0049] Other preferred embodiments of the present application also provide
throttling oil
channels in other forms, which also can achieve a good discharging effect.
[0050] The present application also provides a plurality of parts for the
hydraulic oil
cylinder, for example a piston rod, a rod cavity end cover and a big buffer
sleeve, and these
parts are all designed specifically to realize the above buffer mechanism.
[0051] The present application also provides a hydraulic buffer system having
the above
hydraulic oil cylinder, and the hydraulic buffer system having the above
hydraulic oil cylinder
can achieve a good and stable buffer effect.
[0052] The present application also provides an excavator and a concrete pump
truck both
having the above hydraulic oil cylinder, and by using the above hydraulic oil
cylinder, the
excavator and the concrete pump truck can obtain a longer trouble-free service
time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] Figure 1 is the hydraulic oil cylinder described in the background art
having a buffer
mechanism in which a buffer sleeve is inserted into a buffer inner hole;
[0054] Figure 2 is a mechanical structural view of a hydraulic oil cylinder
according to a
first embodiment of the present application:
[0055] Figure 3 is a part drawing of a piston rod in the first embodiment of
the present
application;
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[0056] Figure 4 is a view of the piston rod 3 taken along the line A-A;
[0057] Figure 5 is a sectional view of the piston rod 3 taken along the line C-
C;
[0058] Figure 6 shows the hydraulic oil cylinder, in a state when a sealing
surface starts to
form, according to the first embodiment of the present application;
[0059] Figure 7 shows the hydraulic oil cylinder, in a state when the piston
moves to an end
position, according to the first embodiment of the present application;
[0060] Figure 8 is a mechanical structural view of a hydraulic oil cylinder
according to a
second embodiment of the present application;
[0061] Figure 9 is a part drawing of a transition sleeve in the second
embodiment of the
present application;
[0062] Figure 10 is a part drawing of a buffer sleeve in the second embodiment
of the
present application, wherein a balancing oil groove is provided on an inner
diameter surface
of the buffer sleeve;
[0063] Figure 11 is a schematic view of a throttling oil channel suitable for
using in a buffer
mechanism having a transition sleeve;
[0064] Figure 12 is schematic view of another throttling oil channel suitable
for using in the
buffer mechanism having the transition sleeve; and
[0065] Figure 13 is a schematic view of a throttling oil channel suitable for
using in a buffer
mechanism having no transition sleeve.
DETAILED DESCRIPTION OF THE INVENTION
[0066] The first embodiment of the present application provides a hydraulic
oil cylinder
with a buffer device provided in a rod cavity side of the hydraulic oil
cylinder.
[0067] Referring to Figure 2, Figure 2 is a mechanical structural view of the
hydraulic oil
cylinder according to the first embodiment of the present application.
[0068] As shown in Figure 2, the hydraulic oil cylinder includes a rod cavity
end cover 1, a
cylinder barrel 2, a piston rod 3, a butler sleeve 4, a spring 5 and a piston
6.
[0069] The cylinder barrel 2 provides a space to seal the hydraulic oil for
the hydraulic oil
cylinder, an inner cavity of the cylinder barrel 2 is divided into a rod
cavity 2-1 and a rodless
cavity 2-2 by the piston 6 which is movable axially along a cavity body of the
inner cavity,
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and a cavity body at which the piston rod 3 is located is the rod cavity 2-1.
An outer diameter
surface of the piston 6 cooperates with an inner diameter surface of the
cylinder barrel 2 and
multiple sealing rings are provided on the outer diameter surface so as to
completely isolate
the hydraulic oil in the rod cavity 2-1 from the hydraulic oil in the rodless
cavity 2-2.
[0070] The cylinder barrel 2 is sealed by an end head, located at a side of
the rod cavity 2-1
of the cylinder barrel 2, of the rod cavity end cover 1, and a rod cavity oil-
passing hole 1-1 is
provided on the rod cavity end cover 1 and is connected to an oil tube so as
to provide a
passage for the hydraulic oil in the whole inner cavity of the cylinder barrel
2 to flow into or
out of the rod cavity 2-1. A passage for the hydraulic oil to flow into or out
of the rodless
cavity 2-2 is provided by a rodless cavity oil-passing hole provided on a
rodless cavity end
cover of the cylinder barrel 2. This embodiment only describes the buffer
device at the rod
cavity side and does not involve the situation at a side of the rodless cavity
2-2.
[0071] A buffer mechanism of the hydraulic oil cylinder includes the buffer
sleeve 4, the
spring 5, and structures provided on the piston 6, the piston rod 3 and the
rod cavity end cover
1 for forming the buffer mechanism.
[0072] The buffer sleeve 4 is sleeved on a buffer position, located in the rod
cavity 2-1, of
the piston rod 3. The buffer position is a piston rod section with a certain
length on the piston
rod 3 starting from an end surface of the piston 6 at the side of the rod
cavity 2-1, and at this
rod section the buffer process must be performed to avoid the damage to the
rod cavity end
cover 1 caused by direct impacting of the piston 6. The piston rod 3 is
provided with a buffer
position stop shoulder 3-4 at a position having a certain distance from the
end surface of the
piston 6, and the buffer position is a piston rod section starting from the
buffer position stop
shoulder 3-4 to a position at which a second end surface 4-2 of the buffer
sleeve 4 is located
when the piston 6 reaches an end position of the extending movement. The
buffer sleeve 4
may slide on the piston rod 3 within the above position range of the buffer
position. An inner
diameter of the buffer sleeve 4 is configured in a way which enables the
buffer sleeve 4 to
slide axially along the piston rod 3 and meanwhile keeps a small gap between
the buffer
sleeve 4 and the piston rod 3; an outer diameter of the buffer sleeve 4 is
significantly smaller
than an inner diameter of the cylinder barrel 2, and a length of the buffer
sleeve 4 accounts for
a part of the length of the buffer position. An end surface of the buffer
sleeve 4. facing a top
end of the oil cylinder, i.e. an end surface at a side of the rod cavity end
cover 1, is a plane
having a chamfered outer edge, and the plane is referred to as a first end
surface 4-1 of the
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buffer sleeve 4. The other end of the buffer sleeve 4 is referred to as a
second end surface 4-2
of the buffer sleeve 4, and a protruding portion 4-3 for fixing the spring 5
is further provided
on the buffer sleeve 4. The design of the buffer sleeve needs to preferably
ensure the
establishment of the following conditions, when the first end surface of the
buffer sleeve
contacts with a rod cavity sealing end surface to form the sealing surface, an
area of an axial
action, applied on the buffer sleeve by the hydraulic oil at a side of the
sealing surface close to
the piston, is greater than an area of an axial action, applied on the buffer
sleeve by the
hydraulic oil at the other side of the sealing surface close to the rod cavity
oil-passing hole.
For example, in the first embodiment, a part of the first end surface of the
buffer sleeve is
shielded by the rod cavity sealing end surface 1-2 such that the area of the
axial action applied
on the first end surface of the buffer sleeve by the hydraulic oil is
obviously smaller than that
on the other end surface.
[0073] The spring 5 is a compression spring having compression tension and is
surroundingly provided on the piston rod 3, a bottom end of the spring 5 abuts
against an end
surface, at the side of the rod cavity 2-1, of the piston 6, and a spring
protruding portion for
fixing the spring is provided on the above end surface of the piston 6. A rear
end of the spring
5 abuts against the protruding portion 4-3 of the buffer sleeve 4. By resting
against the end
surface of the piston 6, the spring 5 may abut against the buffer sleeve 4
with its elastic force,
such that the first end surface 4-1 of the buffer sleeve 4 may abut against
the buffer position
stop shoulder 3-4 of the piston rod 3 when the piston 6 is not moved to the
buffer position.
The elastic force of the spring 5 is configured in a way, as long as it is
enough for making the
buffer sleeve 4 abut against the buffer position stop shoulder 3-4 when the
buffer sleeve 4 is
not blocked, i.e., the spring 5 provides a reset function.
[0074] The rod cavity oil-passing hole 1-1 and the rod cavity sealing end
surface 1-2 are
sequentially provided on the rod cavity end cover 1 from a cover top to a
cover opening. The
rod cavity sealing end surface 1-2 is a stepped surface having an integral
annular shape
provided in an inner cavity of the rod cavity end cover 1, and the stepped
surface is facing the
piston 6. When the buffer process starts, the rod cavity sealing end surface 1-
2 can cooperate
with the first end surface 4-1 of the buffer sleeve so as to form a sealing
surface for separating
the hydraulic oil in the rod cavity 2-1. The rod cavity end cover 1 also has a
buffer sleeve
passing section 1-3 extending from the rod cavity sealing end surface 1-2
towards the piston 6,
an inner diameter of a cavity body at where the buffer sleeve passing section
1-3 is located is
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larger than an inner diameter of the cavity body at where the rod cavity
sealing end surface
1-2 is located, is smaller than an inner diameter of the cylinder barrel 2 at
where the piston 6
is located, and is also larger than an outer diameter of the buffer sleeve 4
such that the buffer
sleeve 4 can enter this section smoothly. An end surface of the cover opening
of the rod cavity
end cover 1 abuts against an inner wall surface of the cylinder barrel to form
a piston stop
shoulder 1-4 for locating an end point of the movement of the piston 6.
[0075] The piston rod 3 is provided with a plurality of structures related to
the buffer
mechanism, and except for the buffer position, related to the mounting of the
buffer sleeve 4,
and the buffer position stop shoulder 3-4, other structures are further
provided, such as
throttling grooves, balancing oil grooves and oil-passing grooves, which will
be described in
detail hereinafter. Referring to Figure 3, Figure 3 is a part drawing of the
piston rod 3;
referring to Figure 4, Figure 4 is a view of the piston rod 3 taken along the
line A-A; and
referring to Figure 5, Figure 5 is a sectional view of the piston rod 3 taken
along the line C-C.
[0076] The piston rod 3 is provided with at least one throttling oil channel,
and a main body
of the throttling oil channel is a throttling groove 3-1 located on an outer
diameter surface of
the piston rod 3 and extending axially. The throttling groove 3-1 is provided
on the piston rod,
a starting point (or referred to as a first end) of the throttling groove 3-1
is located at a
position close to a rod cavity end surface of the piston, and an end point (or
referred to as a
second end) of the throttling groove 3-1 reaches a sidewall of an undercut of
the buffer
position stop shoulder 3-4 of the piston rod 3. Relative to the end point, the
first end is located
at the position close to the rod cavity end surface of the piston; and in
fact, the position of the
starting point of the throttling groove 3-1 needs to cooperate with an end
position of the
extending movement of the piston 6, such that there is an appropriate
hydraulic buffer
capability before the piston 6 reaches the end position. In the present
embodiment, the first
end has been shielded completely by the buffer sleeve 4 before the piston 6
reaches the end
position.
[0077] The buffer position stop shoulder 3-4 is provided with oil-passing
grooves 3-3
corresponding to outlets of the throttling grooves 3-1, as can be seen from
Figure 4, the
position of the oil-passing grooves 3-3 are precisely aligned to the outlets
of the throttling
grooves 3-1, and there are four oil-passing grooves 3-3 corresponding to four
throttling
grooves 3-1. These oil-passing grooves 3-3 provides an outflowing passage for
the hydraulic
oil flowing out of the outlets of the throttling groove 3-1, such that the
flow direction of the
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CA 02905789 2013-01-17
hydraulic oil flowing out of the throttling grooves 3-1 during the buffer
process is more stable,
and these oil-passing grooves 3-3 also provides an outlet for the hydraulic
oil at the moment
when the first end surface 4-1 of the buffer sleeve 4 abuts against the rod
cavity sealing end
surface, thereby avoiding the situation that a hydraulic damping is suddenly
increased and
ensuring the smooth operation.
[0078] A plurality of annular grooves, which are referred to as balancing oil
grooves 3-2,
are uniformly distributed on the circumferential surface of the buffer
position of the piston rod
3. The cross sections of the balancing oil grooves 3-2 may be U-shaped, V-
shaped or square
or other forms, which are determined according to the requirements, and a
depth of the
balancing oil grooves 3-3 may also be determined by experiments according to
the
requirements. The balancing oil grooves 3-2 are provided to realize an oil-
pressure balance
when the hydraulic oil flows through the throttling grooves 3-1, thereby
avoiding an untighten
sealing of the sealing surface during the buffer process caused by the buffer
sleeve 4 being
tilted under an unbalanced oil pressure.
[0079] The operation process of the buffer mechanism of the hydraulic oil
cylinder
according to the present embodiment will be illustrated hereinafter. Figure 2
shows a state
when the piston 6 has not yet reached to the buffer position; referring to
Figure 6, a state when
the buffer process is beginning is showed; and referring to Figure 7, a state
when the buffer
process is finished is showed.
[0080] At the position shown in Figure 2, the piston rod 3 has just begun the
extending
movement and not yet reached the position where the buffer process needs to
start. At this
time, under the action of the elastic force of the spring 5, the first end
surface 4-1 of the buffer
sleeve 4 abuts against the buffer position stop shoulder 3-4 of the piston rod
3. And the buffer
sleeve 4 is pressed against the buffer position stop shoulder 3-4 during the
period before the
piston 6 moves to the buffer position, and the period after the first end
surface 4-1 of the
buffer sleeve 4 is separated from the rod cavity sealing end surface 1-2 by
the retracting
movement of the piston rod 3, therefore, the spring 5 provides a reset
function. Along with the
extending movement of the piston rod 3, the hydraulic oil in the rod cavity 2-
1 is pushed by
the piston to flow towards the rod cavity oil-passing hole 1-1 and flow out
from the rod cavity
oil-passing hole 1-1. The buffer sleeve 4 moves along with the piston 6 and
the piston rod 3
and after moving a certain distance may pass through the buffer sleeve passing
section 1-3 of
the rod cavity end cover 1, and because the outer diameter of the buffer
sleeve 4 is smaller
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CA 02905789 2013-01-17
than the buffer sleeve passing section 1-3, the buffer sleeve 4 will not be
blocked and may
continue to move along with the piston rod 3. As the buffer sleeve 4 enters
the buffer sleeve
passing section 1-3, the oil passage of the hydraulic oil in the rod cavity 2-
1 is partially
blocked, the hydraulic oil can flow, only through the gap between the buffer
sleeve 4 and the
buffer sleeve passing section 1-3, towards the rod cavity oil-passing hole 1-
1, thus the
damping action from the oil passage applied on the piston 6 is significantly
increased; as the
buffer sleeve 4 enters further in the buffer sleeve passing section 1-3
gradually, the blocking
extent of the oil passage of the hydraulic oil is gradually increased, and the
hydraulic damping
applied on the piston 6 is gradually increased, and then the damping action of
the oil passage
reaches a substantially constant stable period until the buffer sleeve 4 is
completely into the
buffer sleeve passing section 1-3.
00811 After the buffer sleeve 4 is moved in the buffer sleeve passing section
1-3 for a
certain time, the first end surface 4-1 of the buffer sleeve 4 gradually
approaches the rod
cavity sealing end surface 1-2 on the rod cavity end cover 1. When moving to
the position
shown in Figure 6, the first end surface 4-1 of the buffer sleeve 4 abuts
against the rod cavity
sealing end surface 1-2 on the rod cavity end cover 1 so as to form an
integral sealing surface,
such that the oil passage of the hydraulic oil, pushed by the piston 6, in the
rod cavity 2-1
flowing towards the rod cavity oil-passing hole 1-1 through the gap between
the buffer sleeve
4 and the buffer sleeve passing section 1-3 of the rod cavity end cover 1 is
completely blocked,
and being blocked by the sealing end surface 1-2, the buffer sleeve 4 stops
moving forward
along with the piston rod 3.
[0082] The oil pressure at two sides of the sealing surface are substantially
same at the
moment when the sealing surface is formed, and when the first end surface 4-1
of the buffer
sleeve 4 is pressed towards the rod cavity sealing end surface 1-2 at a
certain speed, the first
end surface 4-1 of the buffer sleeve 4 may not be pressed tightly against the
rod cavity sealing
end surface 1-2 at the above moment, which may affect the smoothness of the
buffer process
at that time point. For solving the above problem, the following condition is
satisfied in
design: when the first end surface 4-1 of the buffer sleeve 4 contacts with
the rod cavity
sealing end surface 1-2 to form the sealing surface, an area of an axial
action, applied on the
buffer sleeve by the hydraulic oil at a side of the sealing surface close to
the piston, is greater
than an area of an axial action, applied on the buffer sleeve by the hydraulic
oil at the other
side of the sealing surface close to the rod cavity oil-passing hole. In this
embodiment, areas
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CA 02905789 2013-01-17
of two end surfaces of the buffer sleeve 4 are same, however, after the
sealing surface is
formed, the first end surface 4-1 is partially shielded, thereby satisfying
the above condition.
After the above condition is satisfied, a total pressure VI is obtained by
multiplying the oil
pressure at the side of the sealing surface close to the piston by the area of
the axial action
applied on the buffer sleeve at the same side, and a total pressure V2 is
obtained by
multiplying the oil pressure at the other side of the sealing surface close to
the rod cavity
oil-passing hole by the area of the buffer sleeve at the other side. Because
the oil pressure at
two sides of the sealing surface are substantially same at the moment when the
sealing surface
is formed, a total pressure at a side having a larger area is relatively
large, i.e. V1>V2, thus in
this way, the buffer sleeve can be tightly pressed against the rod cavity
sealing end surface 1-2,
thereby ensuring the smoothness of the process of forming the sealing surface.
100831 After the sealing surface is formed, the buffer sleeve 4 and the rod
cavity end cover
1 form a one-way valve, thereby blocking the oil passage. At this point, the
hydraulic oil in
the rod cavity is divided into two cavity bodies, and one cavity body at a
side close to the
piston 6 is referred to as a buffer oil cavity T. The hydraulic oil in the
buffer oil cavity T is
pushed by the piston 6, and a main passage of the hydraulic oil flowing
towards the rod cavity
oil-passing hole 1-1 is restricted by the formed sealing surface, thus the
pressure of the buffer
oil cavity T is further increased, and the increased oil pressure is enough to
press the buffer
sleeve 4 against the rod cavity sealing end surface 1-2 tightly, which makes
the sealing
surface more reliable. At this time, the hydraulic oil can flow, only through
the throttling
groove 3-1, towards the side of the sealing surface having the rod cavity oil-
passing hole 1-1.
During an initial stage of the formation of the sealing surface, a depth of
the throttling groove
3-1 at the second end side is relatively larger, such that the flow capability
of the throttling
groove 3-1 is relatively higher and more hydraulic oil may flow through the
throttling groove
3-1. As the piston rod 3 continues to move, the sealing surface moves backward
relative to the
piston rod 3, such that the depth of the throttling groove 3 communicating two
sides of the
sealing surface with each other is gradually reduced, which gradually reduces
the flow
capability of the throttling groove 3. During the above process, when flowing
through the
throttling groove 3-1, the hydraulic oil flows through the balancing oil
grooves 3-2 and fills a
rod section at where the buffer sleeve is located, such that the oil pressure
on the buffer sleeve
at various positions in the circumferential direction are balanced which
ensures that the buffer
sleeve 4 will not be tilted, thereby ensuring the sealing effect of the
sealing surface.
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CA 02905789 2013-01-17
[0084] After reaching the position shown in Figure 7, the piston 6 is blocked
by the piston
stop shoulder 1-4 formed at the end surface of the cover opening of the rod
cavity end cover 1,
thus cannot move forward; and the piston rod 3 reaches the end position of the
extending
process, and at this time, the first end of the throttling groove 3-1 has
already entered into the
buffer sleeve 4, thus the throttling oil channel is substantially blocked and
the buffer process
is finished. It should be noted that when the piston 6 moves to the end
position, there is still a
distance L between the second end surface of the buffer sleeve 4 and the rod
cavity end
surface of the piston 6, which ensures that the normal movement of the piston
6 will not be
blocked by the buffer sleeve 4. The distance L is a distance between the
buffer sleeve and an
end point of the sliding movement of the buffer sleeve towards the piston,
when the piston rod
is extended to the end position of the stroke.
[0085] When the piston rod 3 starts to retract, i.e., when the piston 6 starts
to move
rightwards, the piston rod 3 is at the end position of the extending stroke,
and the buffer
sleeve 4 and the rod cavity end cover 1 are in a contact sealing state. For
making the oil flow
into the rod cavity quickly so as to push the piston rod 3 to retract, there
is the distance L
between the buffer sleeve 4 and the end point of the sliding movement of the
buffer sleeve 4
towards the piston 6. Under the action of the hydraulic oil, the buffer sleeve
4 compresses the
spring 5 and slides towards the piston 6, thus the first end surface 4-1 of
the buffer sleeve 4 is
separated from the rod cavity sealing end surface 1-2 of the rod cavity end
cover 1. During the
retraction process of the piston rod 3, the buffer sleeve 4 and the rod cavity
end cover 1
cooperate with each other to function as a one-way valve.
[0086] The greater the distance L, the larger the separation distance between
the first end
surface 4-1 of the buffer sleeve 4 and the rod cavity sealing end surface 1-2
of the rod cavity
end cover 1, and the more the flow quantity of the hydraulic oil flowing into
the rod cavity.
The smaller the distance L, the smaller the separation distance between the
first end surface
4-1 of the buffer sleeve 4 and the rod cavity sealing end surface 1-2 of the
rod cavity end
cover 1, and the fewer the flow quantity of the hydraulic oil flowing into the
rod cavity.
[0087] In fact, due to a gap provided between the buffer sleeve 4 and the
piston rod 3, a few
amount of hydraulic oil can also enter into the throttling groove 3-1 through
the above gap to
be discharged. Thus in this way, when the first end of the throttling groove 3-
1 is shielded
completely by the buffer sleeve 4, the piston 6 will not be stuck due to
excessive hydraulic oil
stored in the buffer oil cavity. Of course, the first end of the throttling
groove 3-1 can also be
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CA 02905789 2013-01-17
exposed out of the buffer sleeve 4 when the piston rod 3 reaches the end
position of the
extending process. The position of the first end of the throttling groove 3-1
and the positional
relationship thereof with the buffer sleeve 4 can be designed according to the
buffer damping
needs.
[0088] During the buffer process, the damping effect of the hydraulic oil is
gradually
increased from the time when the buffer sleeve 4 enters the buffer sleeve
passing section 1-3
of the rod cavity end cover 1; specifically, along with the changing of the
depth of the
throttling groove 3-1, the throttling capability is gradually increased and
the hydraulic
damping is gradually increased, such that the speed of the piston 6, before
reaching the end
position, is gradually reduced. At the final short distance, an oil channel
can be formed only
by the gap between the buffer sleeve 4 and the piston rod 3. During the whole
buffer process,
the hydraulic damping is gradually increased, thereby avoiding the impact on
the rod cavity
end cover 1 and the cylinder barrel 2.
[0089] In the above buffer mechanism, under the premise that a width of the
throttling
groove 3-1 is not changed, a changing curve of the throttling capability of
the throttling
groove 3-1 can be controlled by controlling the changing of the depth of the
throttling groove
3-1, thereby ensuring the piston 6 having a very smooth buffer process.
[0090] In fact, instead of being provided on the piton rod 3, the balancing
oil grooves may
also be provided on an inner diameter surface of the buffer sleeve 4, which
may have the
same effect as being provided on the piston rod 3. Figure 10 shows a buffer
sleeve 4 with
balancing oil grooves 4-4 provided on its inner diameter surface. In addition,
instead of being
annular groove, the balancing oil grooves 3-3 can also be thread groove,
however, the annular
groove used in the present embodiment is preferable, because it is easy to
process and has a
better balancing effect.
[0091] In the above embodiments, the passages, communicating the cavity bodies
at two
sides of the sealing surface with each other after the sealing surface is
formed, are all referred
to as the throttling oil channel, and in the above embodiments, the main body
of the throttling
oil channel is the throttling groove, however, the composition of the
throttling oil channel is
different at different times. At the moment when the sealing surface is
formed, the oil-passing
groove 3-3, provided on the buffer position stop shoulder and corresponding to
the throttling
groove, functions as an opening of the second end of the throttling passage
and has an
important effect for realizing the smoothness of the buffer process. If the
throttling groove is
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CA 02905789 2013-01-17
shielded completely by the buffer sleeve when the buffer sleeve 4 slides to
the end position of
the buffer position, the gap between the buffer sleeve 4 and the piston rod 3
also constitutes a
part of the throttling oil channel.
[0092] In the above embodiments, the second end of the throttling oil channel
is provided
on the side wall of the buffer position stop shoulder. In fact, the second end
of the throttling
oil channel may be provided at other positions, as long as the second end of
the throttling oil
channel is still in the inner cavity of the hydraulic oil cylinder when the
piston reaches the end
position.
[0093] In the above embodiments, the planar sealing surface, formed by the rod
cavity
sealing end surface abutting against the first end surface of the buffer
sleeve, is a surface
contacting sealing surface, and actually, a corresponding design can be
performed to the rod
cavity sealing end surface and the first end surface of the buffer sleeve,
such that the formed
sealing surface may be a planar sealing structure, a conical sealing
structure, a curved surface
sealing structure, or other surface sealing structures, or a linear sealing
structures.
[0094] The second embodiment of the present application provides a hydraulic
oil cylinder,
a rod cavity side of which is provided with a buffer device. The second
embodiment is
substantially identical with the first embodiment, except that a transition
sleeve 12 is sleeved
on the buffer position of the piston rod 3.
[0095] Referring to Figure 8, Figure 8 is the hydraulic oil cylinder provided
by the second
embodiment of the present application. The second embodiment is derived by
modifying the
first embodiment, and in the following description, parts that are identical
with the first
embodiment are indicated by the same reference numerals.
[0096] Differing from the first embodiment, the transition sleeve 12 is
sleeved on the buffer
position of the piston rod 3 of the hydraulic oil cylinder, a radial length of
the transition sleeve
12 is enough to take up most of the length of the buffer position, and an
inner diameter of the
transition sleeve 12 cooperates with the outer diameter of the buffer position
of the piston rod
3, such that the transition sleeve 12 may be tightly sleeved on the buffer
position of the piston
rod 3.
[0097] Figure 9 is a part drawing of the transition sleeve 12. As can be seen
from Figure 9,
an outer diameter surface of the transition sleeve 12 is provided with a
throttling groove 12-1
extending axially, and a depth of the throttling groove 12-1 is gradually
increased from a rear
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CA 02905789 2013-01-17
=
end of the transition sleeve 12, close to the piston, to a front end of the
transition sleeve 12,
close to the rod cavity oil-passing hole. The throttling groove 12-1 has a
first end located at a
position close to a rear end surface of the transition sleeve 12, and a second
end located at a
front end surface of the transition sleeve 12. Four throttling grooves 12-1
are evenly
distributed on the outer diameter surface of the transition sleeve 12 to form
the throttling oil
channel together. Meanwhile, the outer diameter surface of the transition
sleeve 12 is further
provided with a plurality of annular grooves functioning as the compensating
oil grooves
12-4.
[0098] In fact, instead of being provided on the transition sleeve 12, the
compensating oil
groove may also be provided on the inner diameter surface of the buffer sleeve
4, which may
have the same effect as being provided on the transition sleeve 12. Figure 10
shows a buffer
sleeve 4 with compensating oil grooves provided on its inner diameter surface.
[0099] The working process of the above hydraulic oil cylinder is identical
with that of the
first embodiment, which will not be described in detail herein.
[00100] The second embodiment has the following advantages. By using the above
technical
solution, there is no need to machine throttling grooves extending axially on
the buffer
position of the piston rod 3. Due to the piston rod 3 having a relatively long
length, it is
difficult to machine throttling grooves, having relatively high precision
requirement, on the
surface of the piston rod 3. It is relatively simple and convenient to machine
throttling
grooves 12-1 on the transition sleeve 12 having a shorter length.
[00101] Further, there are a variety of options for the structure and size of
the throttling
groove, in the above technical solution, the throttling grooves with different
size and structure
can be obtained by changing a piston shaft sleeve, which may meet the buffer
requirement
flexibly.
[00102] In the above two embodiments, the main bodies of the throttling oil
channels are
both throttling grooves. In fact, the throttling oil channel may use other
structural forms,
which are shown in Figures 11 to 13.
[00103] Figure 11 shows a throttling oil channel suitable for using in a
buffer mechanism
having a transition sleeve. The throttling oil channel can include two
sections, a front section
close to the first end is a throttling groove 12-1 axially provided on the
surface of the
transition sleeve 12, a rear section close to the second end is a hidden oil
channel 12-2
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CA 02905789 2013-01-17
extending axially in the transition sleeve, and the above way can also have
the throttling effect.
The section of the throttling groove 12-1 can also be designed in this way
that the depth
thereof is gradually increased from the first end to the second end so as to
achieve the smooth
buffer effect.
[00104] Figure 12 shows another throttling oil channel suitable for using in a
buffer
mechanism having a transition sleeve. As shown, the throttling oil channel
includes a hidden
oil channel 12-2 extending axially in the transition sleeve 12 and a plurality
of throttling oil
holes 12-3 communicating the surface of the piston rod with the hidden oil
channel The
throttling oil holes are axially distributed on the surface of the piston rod,
and the closer the
throttling oil hole is to the front end surface of the transition sleeve 12,
the larger the hole
diameter of the throttling oil hole is. In this way, as the buffer sleeve
slides on the piston rod,
the piston rod 3 gradually approaches the end position of the extending
process, thus the
discharging capacity is gradually reduced and the hydraulic damping effect is
gradually
increased, which gradually slows down the speed of the piston, thereby
achieving a relatively
smooth buffer process.
[00105] Figure 13 shows another throttling oil channel. The throttling oil
channel is a
chamfered surface 3-5 axially arranged on the surface of the piston rod 3. The
chamfered
surface 3-5 is inclined from a portion close to the piston to the buffer
position stop shoulder
3-4, and one or more chamfered surfaces can be arranged. In this way, the
hydraulic oil can
flows out through the chamfered surface 3-5 after the sealing surface is
formed by the first
end surface 4-1 of the buffer sleeve 4 and the sealing end surface 1-2 on the
rod cavity end
cover 1, thereby forming the throttling oil channel. By using the chamfered
surface 3-5 to
form the throttling oil channel, it can also ensure that when the piston rod 3
gradually
approaches the end position of the extending process, the discharging
capability is gradually
reduced and the hydraulic damping effect is gradually increased, which
gradually slows down
the speed of the piston 6, thereby achieving a relatively smooth buffer
process.
[00106] An embodiment of a hydraulic buffer system of the present application
may be
achieved by using the hydraulic oil cylinder according to the present
application to replace the
existing oil cylinder in a hydraulic buffer system.
[00107] An embodiment of an excavator of the present application may be
achieved by using
the hydraulic oil cylinder according to the present application in an
excavator.
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CA 02905789 2013-01-17
[00108] An embodiment of the concrete pump truck of the present application
may be
achieved by using the hydraulic oil cylinder according to the present
application in a concrete
pump truck. The hydraulic oil cylinder according to the present application
may also be used
in other types of construction machinery.
[00109] The present application is illustrated by the above disclosed
preferred embodiments;
however, the preferred embodiments are not intended to limit the present
application. For the
person skilled in the art, many variations and modifications may be made to
the present
application without departing from the spirit or scope of the present
application, and the
protection scope of the present application is defined by the claims.
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