Information
-
Patent Grant
-
6267571
-
Patent Number
6,267,571
-
Date Filed
Tuesday, August 17, 199924 years ago
-
Date Issued
Tuesday, July 31, 200122 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Freay; Charles G.
- Gray; Michael K.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 417 539
- 417 403
- 417 399
- 417 900
- 091 189 R
- 091 191
- 091 193
- 091 278
-
International Classifications
- F04B1100
- F04B1700
- F04B1502
- F01L1500
-
Abstract
A pump having both a short stroke pumping mode and a long stroke pumping mode. The pump has two material cylinders, each with an attached hydraulic cylinder for operating a piston rod extending through both the material and hydraulic cylinders. The piston rods are driven by hydraulic fluid supplied to the hydraulic cylinders and are synchronized so that as one piston rod extends, the other piston rod retracts. The piston rods draw material into the material cylinders when retracting, and pump material out of the material cylinders when extending. To pump in a short stroke mode, a diverter valve is placed between the hydraulic pump and the hydraulic cylinders which diverts an amount of hydraulic fluid to the cylinders, causing the hydraulic pistons to only be extended about half the length of the hydraulic cylinder.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
None.
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulically driven viscous material pump. More particularly, the present invention relates to a hydraulic system which allows a concrete pump to pump in both a long stroke and short stroke mode.
Concrete pumps are used in a variety of applications in the construction field. Particularly, concrete pumps are used when the concrete must be placed in an area that is physically difficult to approach with a ready mix truck. Due to the nature of concrete, the pump must be rugged and wear resistant, and the flow of concrete must be as continuous as possible. Often, concrete pumps attempt to move the concrete at least every ten minutes and with clearing of the lines being required for stops over thirty minutes to an hour depending on the temperature and the concrete admixture.
Certain types of concrete, such as shotcrete and gunite, are shot at a high velocity under pressure, most often by using air, onto a form or other surface. Shotcreting has been used where a relatively thin section of concrete is needed, such as in shell roofs, walls, tanks, chimneys, swimming pools, jacuzzis, and cover and repair applications for all types of structures. Shotcrete is applied in layers of an inch to an inch and half thick, with the total thickness of up to four inches being obtained by successive placements. With advances in equipment, admixtures and mix designs, many jobs that have traditionally been form and pour are now being shotcreted.
Normally applying standard types of concrete and applying shotcrete require two entirely different types of concrete pumps to apply the material. As a result, contractors are forced to have two kinds of pumps if they wish to apply shotcrete and also work with standard concrete. Requiring two pumps greatly increases the cost to the construction company.
BRIEF SUMMARY OF THE INVENTION
The present invention is an improved dual cylinder material pump for pumping relatively viscous materials such as sludge or concrete. The invention can be operated in two modes, a long stroke mode and a short stroke mode. The concrete pump comprises two material cylinders having movable material pistons on piston rods inside. Connected to each material cylinder is a hydraulic cylinder which drives the hydraulic pistons located on the end of the piston rods opposite the material pistons. The pump operates using reciprocating piston rods so that as the piston rod in one material cylinder is retracting, material is drawn into the material cylinder. At the same time, the other piston rod is extending and material is extruded from the material cylinder. An output valve mechanism is used in conjunction with the synchronized piston rods to ensure a constant outflow of concrete.
The long stroke mode involves extending the hydraulic pistons in the hydraulic cylinder almost the entire length of the hydraulic cylinder. The second mode has a short length stroke which is approximately half the length of long stroke. The selection of the stroke length can be done manually by the pump operator. The benefit of the pump having two stroke lengths is that it allows the pump to operate at maximum efficiency under different operating conditions. The short stroke mode is used in shotcreting applications and has a better cylinder fill efficiency rate. The long stroke mode is used in regular concrete applications, where cylinder fill efficiency can be lower.
The change to the short stroke mode is effected by a valve which changes the volume of flow of hydraulic fluid to the hydraulic cylinders driving the pistons. In addition, two logic signal hydraulic valves monitor the position of the piston in the cylinder. When the piston reaches the short stroke valve, the short stroke valve signals a reciprocating cylinder valve to switch the flow of hydraulic fluid from one cylinder to the other. The short stroke valve also signals the output valve mechanism to change states.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view of a concrete pump capable of pumping in both a short and long stroke mode.
FIG. 2A
is a concrete pump showing the hydraulic system as it operates in the first half of the pumping cycle in the long stroke mode.
FIG. 2B
is a concrete pump showing the hydraulic system as it operates in the second half of a pumping cycle in the long stroke mode.
FIG. 3A
is a hydraulic schematic of the concrete pump as it operates in the first half of a pumping cycle in the short stroke mode.
FIG. 3B
is a hydraulic schematic of the concrete pump as it operates in the second half of a pumping cycle in the short stroke mode.
DETAILED DESCRIPTION
FIG. 1
is a perspective view of a dual stroke hydraulic pump
10
. The pump
10
can be divided into three areas; a hydraulic cylinder area
12
, a material cylinder area
14
, and a material output valve unit
16
. The hydraulic cylinder area
12
includes differential cylinders
18
A,
18
B, differential cylinder hydraulic valves
20
, an oil flow connecter
22
, and a water box
24
. The hydraulic valves
20
is connected to the differential cylinders
18
A,
18
B are part a hydraulic system described more fully below which allows the differential cylinders
18
A,
18
B to operate in either a short or long stroke mode. The oil flow connector
22
connects the two differential cylinders
18
A,
18
B and allows hydraulic fluid to flow across the connector
22
between the two cylinders
18
A,
18
B.
In the material cylinder area
14
are two material cylinders
26
A,
26
B, two piston rods
28
A,
28
B, and two material pistons
30
A,
30
B. The pistons
30
A,
30
B are located on the piston rods
28
A,
28
B, which are located inside the material cylinders
26
A,
26
B. The two sets of cylinders
18
A,
18
B,
26
A,
26
B are axially aligned so that the piston rods
28
A,
28
B extend through the material cylinders
26
A,
26
B and into the differential cylinders
18
A,
18
B. The piston rods
28
A,
28
B are caused to alternately extend or retract by hydraulic fluid forced into the differential cylinders
18
A,
18
B. When fully retracted, the piston rods
28
A,
28
B are located almost entirely within differential cylinders
18
A,
18
B. Conversely, when fully extended, the piston rods
28
A
28
B are located almost completely within the material cylinders
26
A,
26
B. As the piston rods
28
A,
28
B move forward or backward, they either draw material into the material cylinders
26
A,
26
B or force material out of the material cylinders
26
A,
26
B.
The material pistons
30
A,
30
B create a seal at the surface of the material cylinder
26
A,
26
B wall so that material cannot get behind the pistons
30
A,
30
B and into the piston hydraulics system
20
or the water box
24
. The seal created by the pistons
30
A,
30
B also allows for material to be drawn into the material cylinders
26
A,
26
B. The water box
24
contains water with which to lubricate the cylinders
26
A,
26
B to both minimize friction in the cylinders
26
A,
26
B caused by the concrete being pumped through them, and prevent overheating. The water box
24
is also a final barrier for any material which may get behind the pistons
30
A,
30
B so that the material does not work its way back into the hydraulic system
20
or differential cylinders
18
A,
18
B. To further reduce friction, the inside of the material cylinders
26
A,
26
B is coated with a layer of chrome.
At the end of the material cylinder area
14
and next to the output valve unit
16
is control block
32
. The control block
32
controls the hydraulic flow of fluid which operates the piston rods
28
A,
28
B and the material output valve unit
16
. The material output valve unit
16
includes an output valve
34
, material delivery holes
36
, material hopper
38
, slewing cylinder
40
, and a material outlet
42
. A material delivery hole
36
is located in the material hopper
38
directly in front of each material cylinder
26
A,
26
B. The delivery holes
36
allow material held in the hopper
38
to enter the material cylinders
26
A,
26
B as the piston rods
28
A,
28
B are retracted. The slewing cylinder
40
is connected to the output valve
34
and moves the output valve
34
back and forth so that it alternately covers one or the other material delivery holes
36
. The output valve
34
is configured to redirect the flow of concrete from the material cylinders
26
A,
26
B through the hopper
38
to the outlet
42
. Thus, as the piston rods
28
A,
28
B are extended, the material in the corresponding material cylinder
26
A,
26
B is forced out via the output valve
34
to the outlet
42
.
In operation, the pump
10
is driven by hydraulic fluid moved by a hydraulic pump (not shown in FIG.
1
). The pump supplies hydraulic fluid to the differential cylinders
18
A,
18
B via. As the differential cylinder
18
A fills with fluid, the corresponding piston rod
28
A is moved. The piston rods
28
A,
28
B are synchronized so that as one piston
28
A is retracted, the other piston
28
B is extended. To cause this synchronized movement, the oil flow connection
22
at the top of the differential cylinders
18
A,
18
B is a closed loop system of hydraulic fluid that allows fluid to pass between the differential cylinders
18
A,
18
B. Thus, as one piston rod
28
A is extended due to hydraulic pressure in its associated differential cylinder
18
A, the other piston rod
28
B is forced to retract by the hydraulic fluid forced across the oil flow connection
22
. On the intake stroke, the piston
28
B draws in material and on the out take stroke, the piston
28
A pushes the material out of the cylinders
26
A,
26
B. In this manner, the pump
10
continuously pushes material through the outlet
42
.
To allow for material to be pushed through the outlet
42
at the same time material is being drawn in by a piston
28
B, the output valve
34
pivots back and forth alternately closing off or opening a material delivery hole
36
. More specifically, as the first piston
28
A is being retracted, it draws concrete into the first material cylinder
26
A. At the same time, the output valve
34
is positioned over the material delivery hole
36
at the second material cylinder
26
B. As the piston rod
28
B in the second material cylinder
26
B is being extended, material in the material cylinder
26
B is forced to the output valve
34
. The output valve
34
connects the material delivery hole
36
to the outlet
42
so that the material in the second cylinder
26
B is moved through the hopper
38
and to the outlet
42
. When the next pump cycle begins, the output valve
34
changes position so that it now covers the material delivery hole
36
in front of the first material cylinder
26
A, allowing the material in that cylinder
26
A to be extruded through the output valve
34
to the outlet
42
. At the same time, the delivery hole
36
in front of the second material cylinder
26
B is unobstructed so that as the piston rod
28
B retracts, the cylinder
26
B fills with the concrete held in the hopper
38
.
The pump
10
operates in both a long stroke and a short stroke mode. The long stroke mode refers to the pumping mode where the pistons
28
A,
28
B are fully retracted so that almost the entire material cylinder
26
A,
26
B is filled with concrete. The short stroke mode refers to the pumping mode wherein the pistons
28
A,
28
B are retracted only about half of the way so that only about half of the material cylinder
26
A,
26
B is filled with concrete. Pumping in the long stroke mode is used in standard concrete pumping applications, whereas short stroke pumping is used in shotcreting applications. The stroke length is controlled by the amount of hydraulic fluid supplied to the differential cylinders
18
A,
18
B. The main difference between long stroke and short stroke pumping is that short stroke pumping provides for better cylinder fill efficiency. Long stroke pumping results in about 80% cylinder fill efficiency due to more air being drawn into the cylinders along with the concrete. In the short stroke mode, the cylinder fill efficiency is raised to about
95
%. The shorter distance traveled by the pistons
28
A,
28
B in the short stroke mode ensures more material and less air is drawn into the cylinders.
FIGS. 2A and 2B
are hydraulic schematics showing the operation of the concrete pump in the long stroke mode, while
FIGS. 3A and 31B
show the operation of the concrete pump in the short stroke mode. In
FIGS. 2A-3B
, the solid lines indicate high pressure hydraulic fluid flow, while the dashed lines indicate a lower pressure fluid flow for signaling valves.
FIG. 2A
is a schematic view of the concrete pump when the pump is operating the first half of a pumping cycle in the long stroke mode. Beginning at the left of
FIG. 2A
, the components of the concrete pump are output valve
34
, slewing cylinders
40
, slewing piston rod
44
, material pistons
30
A,
30
B, piston rods
28
A,
28
B, hydraulic pistons
50
A,
50
B, and material cylinders
26
A,
26
B. Located below (as viewed in
FIG. 2A
) the material cylinders
26
A,
26
B are the first and second differential cylinders
18
A,
18
B. Between the first and second differential cylinders
18
A,
18
B there is the oil flow connection
22
. Located on the second differential cylinder
18
B is a logic switching valve
52
, a short stroke logic switching valve
54
(short stroke valve), and a long stroke logic switching valve
56
(long stroke valve). Connected to the short stroke valve
54
is a directional valve
58
. The directional valve
58
is connected to a double check valve
60
, a globe valve
62
, a soft switch
64
, and relief valve
66
.
FIG. 2A
also shows a directional control valve
70
, a pilot valve
72
, a reciprocating cylinder valve
74
, and directional valve
76
with a mechanical handle. In addition, there is a main directional valve
78
to select the long or short stroke mode, a diverter valve
80
, a main hydraulic pump
82
, and the hydraulic fluid tank
84
. A pilot signal
86
runs from the main directional valve
78
to the directional valve
58
. A long stroke pilot signal
88
runs from the long stroke valve
56
to the directional control valve
70
(via the pilot valve
72
), and a return stroke pilot signal
90
runs from the logic switching, valve
52
to the directional control valve
70
(via the pilot valve
72
) as well. The directional control valve
70
conveys a reversing signal
92
,
92
A to the reciprocating cylinder valve
74
. The reversing signal
92
,
92
A synchronizes the directional control valve
70
and the reciprocating cylinder valve
74
.
At the far right of
FIG. 2A
are the agitator
98
and the accumulator manifold
100
. The accumulator manifold
100
acts to store energy and maintains the pressure of the hydraulic fluid at a desired level. The agitator
98
is an optional feature which can be added to the input hopper and is a device to keep the concrete stored in the hopper
38
moving to prevent premature setting. Connected to the accumulator manifold
100
is a bladder accumulator
102
. The bladder accumulator
102
comprises a bladder with nitrogen which serves to maintain pressure in the hydraulic valves and the stewing cylinder
40
. Also connected to the accumulator
100
is an associated fixed displacement pump
104
to supply hydraulic fluid to the accumulator system. Similarly, a gear pump
106
is used to operate the agitator
98
. All the pumps
82
,
104
,
106
are powered by a prime mover
114
, often a diesel engine.
In the lower middle area of
FIG. 2A
are an on/off switch
108
, a filter
110
, and a pressure gauge
112
. The on/off switch
108
is used to turn the concrete pump on and off, and is typically an electric switch. The hydraulic fluid filter
110
is located near the tank
84
and is used to clean the fluid as it is returned to the tank
84
. Finally, the pressure gauge
112
shows the pressure of the hydraulic fluid in the system.
The inventive aspect of the pump, however, centers about the ability of the pump to pump in both a long stroke and a short stroke mode. The main directional valve
78
allows the operator to choose between a long stroke or a short stroke mode. The main directional valve
78
is connected to the diverter valve
80
. The diverter valve
80
is a two position, two way valve; one position allows a full flow of hydraulic fluid through the valve, and the other position restricts the flow of hydraulic fluid through the valve to about half of the full flow. When a long stroke is selected at the main directional valve
78
, full flow past the diverter valve
80
occurs. When a short stroke is selected, only about 50% of the full flow amount is allowed to pass through the diverter valve
80
. The diverter valve
80
can be any commercially available valve which will restrict the flow of hydraulic fluid to the desired amount via an orifice.
The diverter valve
80
is connected to the reciprocating cylinder valve
74
so that the hydraulic fluid that passes the diverter valve
80
is sent to the reciprocating cylinder valve
74
. The reciprocating cylinder valve
74
is a four way directional valve, and thus allows for hydraulic fluid to flow through the valve in four directions. In the first half of the pumping cycle, the reciprocating cylinder valve
74
supplies the first differential cylinder
18
A with hydraulic fluid while allowing the hydraulic fluid in the second cylinder
18
B to be returned to the tank
84
. Similarly, in the second half of the pumping cycle, the reciprocating cylinder valve
74
supplies the second differential cylinder
18
B with hydraulic fluid while allowing the hydraulic fluid in the first cylinder
18
A to be returned to tank
84
.
The main directional valve
78
also sends a pilot signal
86
to the directional valve
58
. In addition to being connected to a double check valve
60
, the directional hydraulic valve
58
is also connected to the reciprocating cylinder valve
74
via the directional control valve
70
. The pilot signal
86
from the main directional valve
78
causes the directional valve
58
to either allow or suppress a signal from the short stroke valve
54
to the reciprocating cylinder valve
74
via the directional control valve
70
. The short stroke valve
54
is located on the second differential cylinder
18
B midway between the logic signal valve
52
and the long stroke valve
56
(as viewed in FIG.
2
A). When operating in the long stroke mode, the pilot signal
86
places the directional valve
58
in the closed position, which suppresses any signal from the short stroke valve
54
. With directional valve
58
in the closed position, the long stroke valve
56
is left operational and sends a long stroke pilot signal
88
to the directional control valve
70
, via the pilot valve
72
.
The pilot valve
72
only operates when the pump must be reversed, such as when necessary to clear a blockage. The directional valve
76
is activated by the handle located on valve
76
and reverses the pumping action of the pump. The double check valve
60
, and relief valve
62
, soft switch
64
, and relief valve
66
all operate to alleviate the pressure spike caused when the piston
50
B reaches the bottom of its stroke. Also shown are several check valves
96
. The check valves
96
prevent fluid from bleeding back into the other valves. In addition, because the concrete pump's hydraulic system may loose pressure, the check valves
96
allow for more hydraulic fluid to be added to certain areas of the hydraulic system as necessary.
The long stroke pilot signal
88
is used by the directional control valve
70
to change position of the output valve
34
by causing hydraulic fluid to flow to the slewing cylinder
40
. The directional control valve
70
sends a reversing signal
92
to the reciprocating cylinder valve
74
which changes position of the reciprocating cylinder valve
74
so that the other half of the pumping cycle can begin by the opposite differential cylinder being filled with hydraulic fluid.
The material cylinders
26
A,
26
B are located above the differential cylinders
18
A,
18
B so that all cylinders
26
A,
26
B,
18
A,
18
B are axially aligned (as viewed in FIG.
2
A). The piston rods
28
A,
28
B arc located inside the material and differential cylinders
26
A,
26
B,
18
A,
18
B. The material pistons
30
A,
30
B are on the top of the piston rods
28
A,
28
B, and the differential pistons
50
A,
50
B are on the bottom. Thus, as the piston rods
28
A,
28
B are moved back and forth through the cylinders
26
A,
26
B,
18
A,
18
B, the material pistons
30
A,
30
B are extended in the material cylinders
26
A,
26
B only, and on the other end of the piston rods
28
A,
28
B, the hydraulic pistons
50
A,
50
B are extended the length of the differential cylinders
18
A,
18
B only.
The hydraulic pistons
50
A,
50
B are driven by hydraulic fluid supplied by the hydraulic pump
82
. As described above, the reciprocating cylinder valve
74
located between the hydraulic pump
82
and the differential cylinders
18
A,
18
B alternately supplies the cylinders
18
A,
18
B with fluid. The differential cylinders
18
A,
18
B are connected by an oil flow connection
22
. Thus, as the valve
74
supplies one cylinder
18
A
18
B with hydraulic fluid, the piston
28
A,
28
B corresponding to that cylinder
18
A,
18
B is extended. Due to the oil flow connection
22
, the opposite piston
28
A,
28
B is retracted.
The oil flow connection
22
is a closed loop system of hydraulic fluid located in the differential cylinders
18
A,
18
B above the hydraulic pistons
50
A,
50
B (as viewed in FIG.
2
A). A set amount of hydraulic fluid is maintained above the hydraulic pistons
50
A,
50
B so that as the piston
50
A is extended by hydraulic fluid entering the first differential cylinder
18
A, the hydraulic fluid above the piston
50
A is forced from the first cylinder
18
A across the connection
22
and into the second differential cylinder
18
B. As hydraulic fluid enters the second differential cylinder
18
B above the hydraulic piston
50
B, that piston rod
28
B is forced downward.
As one piston rod
28
B retracts, it draws material into the corresponding material cylinder
26
B. As the other piston rod
28
A extends, it pushes the concrete out of its corresponding material cylinder
26
A, past the output valve
34
to an outlet. To complete the pumping cycle, the reciprocating cylinder valve
74
switches the flow of hydraulic fluid from the first differential cylinder
18
A to the second cylinder
18
B. At the same time, the directional control valve
70
reverses the position of the output valve
34
so that material in the other material cylinder
18
B can be forced out. The material used in connection with the present pump is most often a type of concrete.
Thus, as is shown in
FIG. 2A
, moving a handle on the main directional valve
78
to the long stroke position does two things. First, it sends a pilot signal
86
to the directional valve
58
, and second, it allows full flow of hydraulic fluid through the diverter hydraulic valve
80
. The full flow of hydraulic fluid through the diverter valve
80
goes to the reciprocating cylinder valve
74
. The reciprocating cylinder valve
74
is in a first position, so that fluid is directed to the first differential cylinder
18
A, forcing the hydraulic piston
50
A to extend upwards, as viewed in FIG.
2
A. As the piston
50
A is extended, the concrete in the material cylinder
26
A is pushed by the material piston
28
A toward the output valve
34
. The output valve
34
is positioned so that the material in the material cylinder
26
A can be pushed through the output valve
34
and to the concrete outlet.
While the first piston rod
28
A is extended by the flow of hydraulic fluid from the reciprocating valve
74
, the second piston rod
28
B is moved in the opposite direction due to the closed amount of hydraulic fluid existing above the hydraulic pistons
50
A,
50
B in each differential cylinder
18
A,
18
B. This portion of the cylinders
18
A,
18
B is connected by the oil flow connection
22
and as the first piston rod
28
A extends, the fluid above the hydraulic piston
50
A is forced across the oil flow connection
22
. The hydraulic fluid crossing the connection
22
forces the second hydraulic piston
50
B to be moved downward, or forces it to retract. As the second hydraulic piston
50
B retracts, concrete is drawn into the material cylinder
26
B by the material piston
30
B. The hydraulic fluid below the second hydraulic piston
50
B is forced out of the bottom of the differential cylinder
18
B, back through the valve
74
, and eventually to the hydraulic tank
84
.
When the second hydraulic piston
50
B reaches the bottom of the second differential cylinder
18
B, the long stroke logic valve
56
is activated. The long stroke valve
56
is a pressure differential valve that operates when one side of the valve
56
has less pressure than the other. When the hydraulic piston
50
B reaches the valve
56
, there is more hydraulic pressure above the valve
56
than below it, so as the top part of the valve
56
is closed off, fluid flows past the valve
56
to the directional control valve
70
in the form of long stroke control signal
88
. Any extra pressure created when the hydraulic piston
50
B reaches the bottom of the stroke is bled off the system through the double check valve
60
. The directional control valve
70
changes the position of the output valve
34
and sends a reversing signal
92
to the reciprocating cylinder valve
74
, which moves the reciprocating cylinder valve
74
to its second position.
FIG. 2B
is a schematic view of the concrete pump when the reciprocating valve
74
is in its second position. The main directional valve
78
remains in the long stroke position, and the diverter valve
80
continues to allow full flow of the hydraulic fluid to the reciprocating valve
74
. In addition, the pilot signal
86
from the main directional valve
78
continues to control the directional valve
58
so that the short stroke valve
54
is suppressed. However, as is shown in
FIG. 2B
, the reciprocating cylinder valve
74
has changed position so that the path of the hydraulic fluid is reversed. The directional control valve
70
also changes the position of the output valve
34
.
More specifically the reciprocating cylinder valve
74
now fills the second differential cylinder
18
B behind the hydraulic piston
50
B with hydraulic fluid. As the hydraulic fluid enters the second differential cylinder
18
B, the piston rod
28
B is forced upward, forcing the material in the material cylinder
26
B past the output valve
34
and to the concrete outlet. The hydraulic fluid above the hydraulic piston
50
B is forced through the oil flow connection
22
to the other differential cylinder
18
A, which forces the first hydraulic piston
50
A to be moved downward (as viewed in FIG.
2
B). When the first hydraulic piston
50
A moves downward, concrete is drawn into the material cylinder
26
A by the material piston
30
A. The hydraulic fluid on the other side of the first hydraulic piston
50
A is returned to the tank
84
via the reciprocating cylinder valve
74
.
As the second hydraulic piston
50
B approaches the top of the differential cylinder
18
B, the logic switching valve
52
is activated. The logic switching valve
52
is a pressure differential valve that functions similarly to the long stroke valve
56
. When the hydraulic piston
50
B reaches the logic switching valve
52
, the pressure on the top of the piston
50
B is less than the hydraulic pressure below the piston
50
B. Thus, hydraulic fluid flows through the logic switching valve
52
and to the directional control valve
70
in the form of return stroke pilot signal
90
. The directional control valve
70
changes the position of the output valve
34
and sends a reversing signal
92
A to the reciprocating cylinder valve
74
. The reciprocating cylinder valve
74
moves back to its first position, illustrated in
FIG. 2A
, and the pumping cycle can begin again.
FIGS. 3A and 3B
are schematic views of the concrete pump illustrating the concrete pump as it operates in the short stroke mode. The components of the pump remain the same, and as shown in
FIG. 3A
are the output valve
34
, slewing cylinders
40
, stewing piston rod
44
, material pistons
30
A,
30
B, piston rods
28
A,
28
B, hydraulic pistons
50
A,
50
B, and material cylinders
26
A,
26
B. Located below (as viewed in
FIG. 3A
) the material cylinders
26
A,
26
B are the first and second differential cylinders
18
A,
18
B. Between the first and second differential cylinders
18
A,
18
B is the oil flow connection
22
, and on the second differential cylinder
18
B is the logic switching valve
52
, the short stroke valve
54
, and the long stroke valve
56
. Connected to the short stroke valve
54
is the directional valve
58
.
Also shown in
FIG. 3A
are the directional control valve
70
, the pilot valve
72
, the reciprocating cylinder valve
74
, and the directional valve with a mechanical handle
76
. In addition, the main directional valve
78
, the diverter valve
80
, the pump
82
, and the hydraulic fluid tank
84
are shown. The pilot signal
86
once again runs from the main directional valve
78
to the directional valve
58
. A short stroke pilot signal
94
runs from the short stroke valve
54
to the directional control valve
70
via the pilot valve
72
, and a return stroke pilot signal
90
runs from the logic switching valve
52
to the directional control valve
70
via the pilot valve
72
as well. The directional control valve
70
conveys a reversing signal
92
to the reciprocating cylinder valve
74
. The reversing signal
92
synchronizes the directional control valve
70
and the reciprocating cylinder valve
74
.
To operate the concrete pump in the short stroke mode, the main directional valve
78
is placed in the short stroke position. This does two things, first it sends a pilot signal
86
the directional valve
58
, which activates the short stoke valve
54
. Secondly, placing the main directional valve
78
to the short stoke position signals the diverter valve
80
, which then decreases the flow of hydraulic fluid to the reciprocating cylinder valve
74
. The diverter valve
80
restricts the flow of hydraulic fluid to about half the flow allowed during long stroke operation. This restriction of the oil flow at the diverter valve
80
causes the concrete pump to pump at only a short stroke, about half of the long stroke.
More specifically, during the first half of the pumping cycle, the pump
82
pumps hydraulic fluid through the diverter valve
80
, which restricts the flow of hydraulic fluid to about half of the full flow. The reduced flow of hydraulic fluid is sent to reciprocating cylinder valve
74
. The reciprocating cylinder valve
74
directs the fluid to the first differential cylinder
18
A and the hydraulic fluid forces the piston
50
A upward (as viewed in FIG.
3
A), extruding the concrete in the material cylinder
26
A. At same time, hydraulic fluid is also forced through the oil flow connection
22
so that the other piston
50
B is moved downward or is retracted. The oil below the piston
50
B returns to the hydraulic oil tank
84
via the reciprocating cylinder valve
74
. As the second piston
50
B is retracted, concrete is drawn into the corresponding material cylinder
26
B. The piston
50
B continues to retract until the hydraulic piston
50
B reaches the short stroke signal valve
54
, about half way down the differential cylinder
18
B.
The directional valve
58
is connected to the short stroke valve
54
and is operational due to the pilot signal
86
from the main directional valve
78
. Once the piston
50
B reaches the short stroke valve
54
, the valve
54
operates to allow fluid flow through the short stroke valve
54
to the directional valve
58
. The short stroke valve
54
is a pressure differential valve that sends a short stroke signal
94
through the directional valve
58
when the pressure across the short stroke valve
54
is not in equilibrium. From the directional valve
58
, the short stroke signal
94
goes to the directional control valve
70
via the pilot valve
72
. Once the signal
94
reaches the directional control valve
70
, fluid is sent to the appropriate slewing cylinder
40
to change the position of the output valve
34
. At the same time, a reversing signal
92
is sent to the reciprocating cylinder valve
74
, which operates synchronously with the directional control valve
70
. The reversing signal
92
changes the position of the reciprocating cylinder valve
74
so that the flow of hydraulic fluid to the differential cylinders
18
A,
18
B is reversed. A check valve
96
prevents any fluid from entering the cylinder at the long stroke valve
56
.
Once the reciprocating cylinder valve
74
is moved to its second position, the other half of the short stroke pumping cycle begins as seen in FIG.
3
B. The main directional valve
78
remains at the short stroke setting so that the pilot signal
86
to the directional valve
58
keeps the directional valve
58
in the open position. In addition, the main directional valve
78
allows a reduced amount of fluid to go through diverter valve
80
. From the diverter valve
80
, fluid travels to the reciprocating cylinder valve
74
. The reciprocating cylinder valve
74
has been moved to its second position, which switches the flow path of the hydraulic fluid from the first differential cylinder
18
A to the second differential cylinder
18
B. As the second differential cylinder
18
B is filled with hydraulic fluid, the second piston
50
B is extended. As the second piston
50
B is extended, the hydraulic fluid located above the hydraulic piston
50
B is forced from the second differential cylinder
18
B to the first differential cylinder
18
A via the oil flow connection
22
. The concrete that was drawn into the material cylinder
26
B during the first half of the pumping cycle is thus extruded in the second half of the pumping cycle. Likewise, the first material cylinder
26
A fills with concrete as the first piston
50
A retracts due to the fluid coming across the oil flow connection
22
.
Once the second piston
50
B is fully extended, the hydraulic piston
50
B reaches the logic switching valve
52
. Just as in the long stroke mode, the logic switching valve
52
sends a return stroke pilot signal
90
to the directional control valve
70
. The directional control valve
70
sends a reversing signal
92
A to the reciprocating cylinder valve
74
and changes position of the output valve
34
by directing fluid to the appropriate slewing cylinder
40
. The reversing signal
92
causes the reciprocating cylinder valve
74
to move to its first position. With the reciprocating cylinder valve
74
in its first position, the pumping cycle starts all over again.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For instance, though discussed as differential pressure valves, the logic switching valve
52
, short stroke valve
54
, and long stroke valve
56
may be operated by other valve or sensing means, such as electronic or pneumatic sensors or valves. Similarly, the signals may be other than hydraulic, such as electrical. Though discussed generally as using an output valve, the present invention can be utilized with any pivoting valve such as the Rock Valveā¢ from Schwing, an S-tube valve, a C-tube valve, ball valves, or gate valves. The pump is typically horizontally oriented, though the schematic figures of the concrete pump show a vertical orientation.
Claims
- 1. A pump having a long stroke and a short stroke mode, the pump comprising:two material cylinders for moving material, each material cylinder including a hydraulic cylinder and a piston rod, wherein the piston rods are synchronized so that as one piston is extended, the other piston rod is retracted; a valve mechanism which connects one material cylinder to an outlet and the other material cylinder to a material hopper, wherein the valve mechanism changes position so that as material exits one material cylinder at the outlet, material can enter the other material cylinder at the material hopper; a pump supplying the hydraulic cylinders with hydraulic fluid; a diverter valve located between the pump and the hydraulic cylinders for diverting an amount of hydraulic fluid supplied to the hydraulic cylinders; a reciprocating cylinder valve between the pump and the hydraulic cylinders which alternately drives one piston rod by supplying hydraulic fluid to its corresponding hydraulic cylinder and allowing fluid to exit from the other hydraulic cylinder; a short stroke valve located on one hydraulic cylinder that signals the material output valve and the reciprocating cylinder valve to change position when the piston rod reaches the short stroke valve; and a switch having a first position for selecting a long stroke mode and a second position for selecting a short stroke mode, wherein the second position activates the diverter valve and the short stroke valve.
- 2. The pump of claim 1 wherein the short stroke valve is a pressure differential valve.
- 3. The pump of claim 1 wherein the short stroke valve is located about half way down a length of the hydraulic cylinder.
- 4. The pump of claim 1 wherein the diverter valve diverts about half a flow of hydraulic fluid to the hydraulic cylinders when the switch is in the second position.
- 5. The pump of claim 1 and further comprising a long stroke valve located on one hydraulic cylinder that signals the reciprocating cylinder valve to change position when the piston reaches the long stroke valve and operates when the switch is in the first position.
- 6. A pump having a short stroke pumping mode and a long stroke pumping modes, the pump comprising:first and second cylinders, wherein the first cylinder comprises a first piston driven by hydraulic fluid and the second cylinder comprises a second piston driven by hydraulic fluid; a hydraulic pump that supplies hydraulic fluid to the first and second cylinders; a diverter valve located between the pump and the first and second cylinders having a first and second position, wherein the first position allows a full flow of hydraulic fluid to the first and second cylinders and the second position allows a lesser flow of hydraulic fluid to the first and second cylinders than the first position; and a short stroke valve located near the middle of the second cylinder, wherein the short stroke valve is made operational when the diverter valve is in the second position and prevents the pistons from being driven a full length of the cylinders.
- 7. The pump of claim 6 and further comprising a long stroke valve located on the end of the cylinder wherein the long stroke valve is operational when the diverter valve is in the first position and allows the pistons to be driven a full length of the cylinders.
- 8. The pump of claim 6 wherein the short stroke valve is a pressure differential valve.
- 9. The pump of claim 6 wherein the second position of the diverter valve allows an amount of hydraulic fluid to flow to the first and second cylinders which is about half the full flow.
- 10. The pump of claim 6 wherein the diverter valve allows the pistons to be driven about half the length of the cylinders when in the second position.
- 11. A method of operating a dual cylinder displacement pump having both a long stroke mode and a short stroke mode in the short stroke mode, the method comprising:providing a flow of hydraulic fluid to a first and second pumping cylinder to actuate them; restricting the flow of hydraulic fluid to the first and second pumping cylinder so that about half the full amount of fluid is supplied to the pumping cylinders; sensing a position of a piston in the first pumping cylinder at a short stroke position; and switching the flow of hydraulic fluid from one pumping cylinder to the other pumping cylinder when the piston reaches the short stroke position to allow the pistons to pump at a short stroke mode.
- 12. A pump having a short stroke mode and a long stroke mode, the pump comprising:first and second material cylinders; first and second hydraulic drive cylinders axially aligned with and connected to the material cylinders; first and second piston rods comprising hydraulic pistons located in the hydraulic drive cylinders wherein the hydraulic pistons are driven by hydraulic fluid supplied to the hydraulic cylinders; and a hydraulic valve system for selectively operating the hydraulic pistons in a long stroke mode and a short stroke mode, the hydraulic valve system comprising a diverter valve and a short stroke valve on the first hydraulic cylinder, wherein the short stroke valve senses when the hydraulic piston reaches a short stroke position and the diverter valve diverts about half a flow of hydraulic fluid to the hydraulic drive cylinders so that a shorter stroke is made by the hydraulic piston in the hydraulic drive cylinder.
- 13. The pump of claim 5 wherein the short stroke position is at about a middle position of the first hydraulic cylinder.
- 14. A pump having a short stroke mode and a long stroke mode, the pump comprising:first and second material cylinders; first and second hydraulic drive cylinders connected to the material cylinders; and a hydraulic valve system comprising: a material output valve which connects one material cylinder to an outlet and the other material cylinder to a material hopper. wherein the material output valve changes position so that as material exits one material cylinder at the outlet, material can enter the other material cylinder at the material hopper; a pump supplying the hydraulic drive cylinders with the hydraulic fluid; a diverter valve located between the pump and the hydraulic drive cylinders for diverting an amount of hydraulic fluid supplied to the hydraulic drive cylinders; a reciprocating cylinder valve between the pump and the first and second hydraulic drive cylinders which alternately drives the first and second material cylinders by supplying hydralilic fluid to one of the hydraulic cylinders and allowing fluid to exit from the other of the hydraulic cylinders; a short stroke valve located on one hydraulic drive cylinder that signals the material output valve and the reciprocating cylinder valve to change position when the material cylinder reaches a short stroke position; and a switch having a first position for selecting a long stroke mode and a second position for selecting a short stroke mode, wherein the second position activates the diverter valve and the short stroke valve, so that an amount of fluid supplied to the hydraulic drive cylinders in the short stroke mode is about half an amount of hydraulic fluid supplied to the hydraulic drive cylinders in the long stroke mode.
US Referenced Citations (5)