Motors: expansible chamber type – Working member position responsive motive fluid control – Working member carries part within working chamber which...
Reexamination Certificate
2000-01-27
2002-05-14
Lopez, F. Daniel (Department: 3745)
Motors: expansible chamber type
Working member position responsive motive fluid control
Working member carries part within working chamber which...
C091S396000, C091S405000
Reexamination Certificate
active
06386088
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a hydraulic cylinder used in hydraulic working machine such as a hydraulic construction machine, or the like, and in particular to a hydraulic cylinder in which a piston connecting structure is improved and a structure for mounting a bottom side cushioning device is simplified.
BACKGROUND ART
In a hydraulic working machine such as a hydraulic excavator which is a representative of the hydraulic construction machine, or the like, a hydraulic cylinder is used as an actuator for driving an operating member. As shown in
FIG. 27
, the hydraulic cylinder comprises a cylinder body
102
, a piston rod
103
moving in the cylinder body
102
, and a piston
104
provided at an end of the piston rod
103
and divide the inside of the cylinder body
102
into a rod-side chamber
107
a
and a bottom-side chamber
107
b.
Such a hydraulic cylinder generally has a piston connecting structure described in JP-Y-7-16888, JP-U-6-62207, etc., for example. That is, a piston insertion portion
103
f
is provided at an end portion of the piston rod
103
through a stepped portion
103
e
, and a male screw portion
103
g
is formed at an end portion of the piston insertion portion
103
f
. The piston
104
is inserted onto the piston insertion portion
103
f
, and a nut
112
is fastened to the male screw portion
103
g
to force the piston
104
to abut against the stepped portion
103
e
. As a result, the piston
104
is fixed and connected to the piston rod
103
.
Another piston connecting structure shown in
FIG. 28
has been proposed. This example is one described in JP-U57-203103. An annular groove
103
k
is further provided in a small-diameter piston insertion portion
103
j
, and the piston
104
is fitted until abutting against a stepped portion
103
m
, and under the condition, half-ring shaped flanges
160
formed by radially dividing a circular ring into two sections are fitted into the annular groove
103
k
, and therefore the flanges
160
are fastened to the piston
104
by bolts
170
. As a result, the piston
104
is fixed and connected to the piston rod
103
. The inside of the cylinder body
102
is divided by the piston
104
into the chambers
107
a
and
107
b
, and an O-ring
180
is provided between the piston insertion portion
103
j
and the piston
104
in order to seal the chambers
107
a
and
107
b
from each other.
On the other hand, as a cushioning device for reducing a shock at a stroke end of the piston rod, there is known such a device using a floating type cushion ring as described in JP-Y-7-16888 and JP-U-6-62207. That is, JP-Y
7
-1-6888 discloses a cushioning device using a floating type cushion ring as each of the rod side and bottom side cushioning devices and JP-U-6-62207 discloses a cushioning device using a floating type cushion ring used as a bottom side cushioning device.
FIG. 27
shows an example in JP-Y-7-16888. In
FIG. 27
, a rod-side ring insertion portion
103
a
is provided between the piston rod
103
and the piston insertion portion
103
f
, and a bottom-side ring insertion portion
103
h
is provided further in an end of the male screw portion
103
g
of the piston rod
103
, and the piston rod
103
, the rod-side ring insertion portion
103
a
, the piston insertion portion
103
f
and the bottom-side ring insertion portion
103
h
are reduced in diameter in this order. A rod-side cushion ring
130
is loosely fitted on the rod-side ring insertion portion
103
a
so as to be movable axially and radially, and a bottom-side cushion ring
140
is loosely fitted on the bottom-side ring insertion portion
103
h
so as to be movable axially and radially. A cushion stopper
150
such as a plug is attached in a threaded hole
103
i
formed in an end surface of the ring insertion portion
103
h
to retain the cushion ring
140
.
When a hydraulic fluid is supplied to the rod-side chamber
107
a
, the piston rod
103
is moved to the right in the figure to retract the hydraulic cylinder. At this time, in the vicinity of the stroke end, the bottom-side cushion ring
140
enters a cushion hole
105
c
formed in an inlet portion of a supply and discharge port
109
in a bottom-side cylinder head, and a corresponding portion of the cushion hole
105
c
is occupied by the cushion ring
140
so that a hydraulic fluid passage is restricted. As a result, a cushioning pressure is established in the chamber
107
b
to reduce a stroke speed thereby to reduce the shock at the stroke end. At this time, since the cushion ring
140
is movable axially and radially, the cushion ring
140
enters the cushion hole
105
c
following the shape of an the inner circumference of the cushion hole
105
c
(centering function). Accordingly, there is no fear of biting between the cushion ring
140
and a wall portion of the cushion hole. Further, the cushioning pressure is established in the bottom-side chamber
107
b
when the cushion ring
140
enters the cushion hole
105
c
, and a pressure difference is generated between the cushion hole side of the cushion ring
140
and the chamber
107
b
side thereof to urge the cushion ring
140
against the cushion stopper
150
so as to be brought into tight contact with the cushion stopper
150
. Accordingly, there is no fear of flowing of a hydraulic fluid from the bottom-side chamber
107
b
into the supply and discharge port
109
via a gap between the outer circumferential surface of the ring insertion portion
103
h
and the inner circumferential surface of the cushion ring
140
(undirectional flow function.
When a hydraulic fluid is supplied to the hydraulic cylinder through the port
109
after the hydraulic cylinder reaches the stroke end, the piston rod
103
begins to move to the left in the figure in an extending direction and the cushion ring
140
is withdrawn from the cushion hole
105
c
. At this time, the hydraulic fluid supplied to the hydraulic cylinder through the supply and discharge port
109
flows into the chamber
107
b
via the gap between the outer circumferential surface of the cushion ring
140
and the inner circumferential surface of the cushion hole
105
c
. Further, the cushion ring
140
is pressed against an end surface of the piston insertion portion
104
f by the hydraulic fluid given through the port
109
. At this time, however, since grooves
140
a
are provided at an end portion of the cushion ring
140
at the side of the piston insertion portion
103
f
, and therefore the hydraulic fluid flows into a gap between the outer circumferential surface of the ring insertion portion
103
h
and the inner circumferential surface of the cushion ring
140
and further flows into the chamber
107
b
through the grooves
140
a
(unidirectional flow function). Thus, the cushion ring
140
is satisfactorily withdrawn from the cushion hole
105
c.
Although the bottom-side cushion ring
140
has been described above, the rod-side cushion ring
130
functions in the same manner as in the bottom-side cushion ring
140
. That is, the rod-side cushion ring
130
is also movable axially and radially, and grooves
130
a
are provided in the piston-side end portion of the cushion ring
130
, while the end portion of the cushion ring
130
on the opposite side can be brought into tight contact with a stepped portion
103
b
which is a boundary between the piston rod
103
and the ring insertion portion
103
a
. When the hydraulic cylinder extends and enters the cushion hole upstream of the supply and discharge port in the vicinity of the stroke, the stroke speed is reduced so that the shock at the stroke end is reduced while the cushion ring fulfills the centering function and the unidirectional flow function with respect to the cushion hole. When the hydraulic cylinder contracts from the stroke end position, the cushion ring is satisfactorily withdrawn from the cushion hole by the unidirectional flow function.
Further, a bottom-side cushioning device using a cushion plunger instead of the cushion ring is known, and an example thereof is described in JP-U-1-166105. In
Ro Akinori
Yasuoka Tomohiko
Yoshimoto Mitsuhiro
Hitachi Construction Machinery Co. Ltd.
Kershteyn Igor
Lopez F. Daniel
Mattingly, Stanger & Malur
LandOfFree
Hydraulic cylinder does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic cylinder, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic cylinder will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2900190