Pumps – Motor driven – Fluid motor
Reexamination Certificate
1999-10-08
2001-10-09
Walberg, Teresa (Department: 3742)
Pumps
Motor driven
Fluid motor
C417S342000
Reexamination Certificate
active
06299416
ABSTRACT:
FIELD OF THE INVENTION
The instant invention pertains generally to a hydraulically operated bulk material pump device and, more specifically, to a hydraulic pump device built in a typical concrete pump truck such that, when operated, it can forcedly feed fluidized concrete through an elongated transportation conduit up to a remote pouring location within a construction site.
BACKGROUND OF THE INVENTION
There are two kinds of generally known methods of pumping bulk material through a pipeline which leads to a remote pouring position. One is a screw pumping method whereby bulk material can be pumped into a transportation conduit by means of a motor-driven feeder screw or auger. This method has been extensively used in pumping a uniform amount of low viscosity bulk material with reduced pulsation but has a drawback in that it is unsuitable for use in high-pressure, long-distance pumping of the bulk material because the drive motor cannot endure severe overload condition encountered.
The other method of pumping bulk material is to use a pair of hydraulic drive cylinders which are designed to cause alternate reciprocating movement of dual pump cylinders to thereby force the bulk material into a transportation pipeline. The drive cylinder type pumping method can be advantageously utilized in high-pressure, long-distance transportation of high density and high viscosity bulk material such as concrete, mortar and industrial wastes, although it tends to produce a great deal of vibration and pulsation in the pumping process.
With reference to
FIGS. 1 through 3
, there is illustrated a prior art drive cylinder type concrete pump device widely employed in a typical concrete pump truck. The concrete pump device has a reversible oil pump
10
which can discharge a variable volume of pressurized oil, and first and second hydraulic drive cylinders
12
,
14
each of which remains in fluid communication with the oil pump
10
. The first drive cylinder
12
consists of a cylinder housing
16
with an axial bore
18
and a drive piston
20
with a piston rod
22
slidably fitted into the cylinder housing
16
to divide the axial bore
18
of the cylinder housing
16
into a base chamber
24
and a head chamber
26
. The volume of the base and head chambers
24
,
26
varies with the position of the drive piston
20
in such a manner that, if the volume of the base chamber
24
becomes greater, that of the head chamber
26
gets smaller in proportion thereto and vice versa. The base chamber
24
is connected to the oil pump
10
via a first fluid line
28
which serves both as a supply line and a return line depending on the direction of rotation of the oil pump
10
.
The second drive cylinder
14
consists of a cylinder housing
30
with an axial bore
32
and a drive piston
34
with a piston rod
36
slidably received in the cylinder housing
30
to divide the axial bore
32
of the cylinder housing
30
into a base chamber
38
and a head chamber
40
. As with the first drive cylinder
12
set forth above, the volume of the base and head chambers
38
,
40
in the second drive cylinder
14
varies with the position of the drive piston
34
in such a manner that the volume of the head chamber
40
becomes smaller in proportion to the increase of the volume of the base chamber
38
and vice versa. The base chamber
38
is coupled to the oil pump
10
by way of a second fluid line
42
which functions both as a supply line and a return line. The head chamber
40
of the cylinder housing
30
of the second drive cylinder
14
is in fluid communication with the head chamber
26
of the cylinder housing
16
of the first drive cylinder
12
via an intermediate fluid line
44
.
The concrete pump device further includes first and second pump cylinders
46
,
48
operatively connected to the first and second hydraulic drive cylinders
12
,
14
. The first pump cylinder
46
has a pumping barrel
50
with an open front end and a pumping piston
52
slidably received in the pumping barrel
50
. The pumping piston
52
is affixed to the piston rod
22
of the first drive cylinder
12
so that it can be subjected to reciprocating movement together with the drive piston
20
of the first drive cylinder
12
, thus pumping the concrete contained in a hopper
54
. The second pump cylinder
48
has a pumping barrel
56
with an open front end and a pumping piston
58
slidably fitted through the pumping barrel
56
. The pumping piston
58
of the second pump cylinder
48
is secured to the piston rod
36
of the second drive cylinder
14
, meaning that the pumping piston
58
can move together with the drive piston
34
of the second drive cylinder
14
to thereby pump the concrete contained in the hopper
54
. A transportation conduit
60
is alternately coupled to the respective one of the pumping barrels
50
,
56
just prior to the extending movement of the pumping pistons
52
,
58
, thus receiving the concrete pumped by the first and second pump cylinders
46
,
48
. Alternate coupling of the transportation conduit
60
to the first and second pump cylinders
46
,
48
is performed by a hydraulic switching actuator not shown in the drawings.
It will be noted that a head bypass line
62
is provided at the head portion of the cylinder housing
16
to allow fluid introduction from the base chamber
24
into the head chamber
26
when the drive piston
20
of the first drive cylinder
12
is at the end of retracting movement as indicated in a phantom line in FIG.
1
. Such fluid introduction through the head bypass line
62
helps increase the pressure in the head chamber, thus swiftly reducing the retracting speed of the drive piston
20
and hence avoiding any crash of the piston
20
against the head cover of the cylinder housing
16
. Backflow of fluid through the head bypass line
62
is inhibited by a check valve
64
even though the pressure in the head chamber
26
becomes higher than the pressure in the base chamber
24
at the beginning of extending movement of the drive piston
20
.
Provided at the base portion of the cylinder housing
16
of the first drive cylinder
12
is a base bypass line
66
which permits fluid introduction from the head chamber
26
into the base chamber
24
when the drive piston
20
of the first drive cylinder
12
is at the end of extending movement as illustrated in a solid line in FIG.
1
. Such fluid introduction into the base chamber
24
through the base bypass line
66
helps increase the pressure in the base chamber
24
, thereby quickly decreasing the extending speed of the drive piston
20
and hence avoiding any crash of the piston
20
against the base cover of the cylinder housing
16
. Backflow of fluid through the base bypass line
66
is prohibited by a check valve
68
even though the pressure in the base chamber
24
grows higher than the pressure in the head chamber
26
at the beginning of retracting movement of the drive piston
20
.
Likewise, a base bypass line
70
is provided at the base portion of the cylinder housing
30
of the second drive cylinder
14
. The base bypass line
70
allows fluid introduction from the head chamber
40
into the base chamber
38
when the drive piston
34
of the second drive cylinder
14
is at the end of extending movement as shown in a phantom line in FIG.
1
. Such fluid introduction through the base bypass line
70
helps increase the pressure in the base chamber
38
to thereby reduce the extending speed of the drive piston
34
for avoidance of its crash against the base cover of the cylinder housing
30
. Backflow of fluid through the base bypass line
70
is prevented by a check valve
72
even though the pressure in the base chamber
38
becomes greater than the pressure in the head chamber
40
at the beginning of retracting movement of the drive piston
34
of the second drive cylinder
14
.
A retraction sensor
74
and an extension sensor
76
are placed respectively at the head portion and the base portion of the cylinder housing
30
of the second drive cylinder
14
. The retraction sensor
74
i
Daewoo Heavy Industries Ltd.
Fastovsky Leonid M
Staas & Halsey , LLP
Walberg Teresa
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