Pumps – Three or more cylinders arranged in parallel – radial – or... – Radial cylinders
Reexamination Certificate
1998-05-07
2001-01-09
Freay, Charles G. (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
Radial cylinders
C123S04500R, C417S063000, C417S454000, C417S552000, C417S254000, C417S490000, C417S003000, C092S128000, C134S010000, C415S168200, C403S013000, C277S377000, C277S377000, C206S318000
Reexamination Certificate
active
06171070
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to high-pressure reciprocating pumps for producing high pressure or superhigh pressure in a liquid phase and, more particularly, pertains to high-pressure reciprocating pumps suited for pressurizing a slurry and transferring it under pressure.
A conventional high-pressure reciprocating pump is constructed such that a plunger is made to move back and forth inside a cylinder, a channel connected to an inlet pipe or a discharge pipe is opened and closed by a valve in synchronism with movements of the plunger to vary the volume of a fluid within a pumping chamber, and the fluid is thereby transferred to a high-pressure side.
This type of high-pressure reciprocating pumps is used for cleaning wastewater gutters in chemical plants, food processing plants and buildings, for cleaning ships, and for maintaining and cleaning civil engineering and construction machines. Also, these pumps are incorporated in such equipment as water-jet cutting machines or electronic parts cleaning systems.
FIGS. 8A and 8B
illustrate a general construction of a high-pressure reciprocating pump mainly comprising a crankshaft
61
provided inside a crankshaft case
60
, a connecting rod
62
whose one end is connected to the crankshaft
61
, a plunger
64
which is connected to the other end of the connecting rod
62
and moves back and forth inside a cylinder
63
, and a valve case
65
which is affixed to a foremost end of the crankshaft case
60
, closing its opening.
The plunger
64
moves to the left in each intake stroke of the pump as shown in FIG.
8
A. As the inner volume of the valve case
65
increases corresponding to the amount of leftward movement of the plunger
64
, the internal pressure of the valve case
65
is reduced. Forced by atmospheric pressure, a fluid is drawn in through an intake port
66
and introduced into the valve case
65
through an inlet valve
67
. In each output stroke, the plunger
64
moves to the right as shown in FIG.
8
B and the fluid in a forward part of the plunger
64
pushes an outlet valve
68
to its open position and is discharged through a delivery port
69
.
Pressure in a fluid outflow and flow rate vary in the aforementioned construction in which the plunger
64
is made to move back and forth. Generally, this type of construction employs an accumulator to absorb and reduce pressure pulsation which occurs in outflow tubing, or an increased number of cylinders, forming a multi-cylinder structure, in order to increase the number of output strokes per rotation of the crankshaft and thereby produce a more uniform flow.
In the above construction, the plunger
64
is joined to a piston
64
a
to form a single structure by tightening their externally and internally threaded portions together.
The valve case
65
of such conventional high-pressure reciprocating pump is usually a blocklike heavy object which is one-piece formed by metal casting or forging, with a pressurizing chamber
65
a,
an intake channel
65
b
and a discharge channel
65
c
formed in the valve case
65
in a complex configuration by carrying out precision cutting operation using a machine tool. This makes it difficult to create each pressurizing chamber and valve section. Especially when assembling a multi-cylinder type reciprocating pump or disassembling it for servicing, no matter whether it is relatively small, more than one worker and a crane are required to handle the pump and great care must be taken not to break or otherwise damage any plungers or packing, because its valve case is a heavy object incorporating multiple pressurizing chambers and valve sections. Thus, one problem of the conventional construction is poor labor efficiency. Another problem is that the whole valve case must be removed from the crankshaft case.
Furthermore, in the conventional valve case
65
in which the pressurizing chamber
65
a,
the intake channel
65
b
and the discharge channel
65
c
are formed by cutting operation, the intake channel
65
b
or the discharge channel
65
c
is made perpendicular to the pressurizing chamber
65
a
and, therefore, edges are formed where the pressurizing chamber
65
a
and the intake channel
65
b
or the discharge channel
65
c
adjoin. If such edges are exposed to high-pressure or superhigh-pressure pulsating fluid flows when the high-pressure reciprocating pump is in operation, low-cycle fatigue fracture is likely to occur from the edges, eventually causing a breakdown of the valve case
65
.
It might be possible to employ a more expensive high-strength material or a rigid material which has been treated by a quench hardening process, for example, to avoid such breakdown. This would, however, make it infeasible to reduce the weight of the valve case
65
and its machining and handling would become more difficult.
The driving piston
64
a
and the plunger
64
are joined together to form a single structure as stated above. For this reason, extremely high accuracy is required to provide good sealing for the plunger
64
when the pressurizing chamber
65
a
is formed by assembling the crankshaft case
60
and the valve case
65
.
To achieve such high accuracy in assembling the heavy high-pressure reciprocating pump, however, an extremely high level of skill has been required. Although this does not cause any serious problem if the plunger
64
is made of metal, there arises a problem that the plunger
64
could easily break if it is of a type coated with such fragile material as ceramics and is not properly centered with respect to the piston
64
a
due to poor positioning accuracy. Furthermore, low-accuracy centering of the plunger
64
could cause eccentric wear of its sealing device, resulting in a shortened useful life of sealing and deterioration of the reliability of the high-pressure reciprocating pump.
Another problem potentially encountered with this type of high-pressure reciprocating pump is that leakage could occur at sealing of sliding parts of the pump when transferring a pressurized slurry, especially a slurry containing an inorganic substance.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a high-pressure reciprocating pump which has overcome the problems residing in the conventional high-pressure reciprocating pumps.
According to an aspect of the invention, a high-pressure reciprocating pump is such that a plunger connected to a driver is made to move back and forth and an intake channel or a discharge channel is opened and closed by a valve in synchronism with movements of the plunger for transferring a fluid under high pressure. This high-pressure reciprocating pump comprises a pressurizing case having in its internal space a pumping chamber and accommodating the plunger, and a directional control valve detachably fitted to the pressurizing case to control fluid intake and discharge operations.
According to another aspect of the invention, a high-pressure reciprocating pump is such that a plurality of plungers connected to a driver are made to move back and forth and intake channels or discharge channels are opened and closed by valves in synchronism with movements of the plungers for transferring a fluid under high pressure. This pressure reciprocating pump comprises a plurality of plunger cases in which the plungers are individually inserted, sealing devices for sealing gaps formed between inside surfaces of the plunger cases and the plungers, a supporting frame removably supporting the plunger cases which are arranged parallel to each other, a head plate portion detachably closing foremost ends of the individual plunger cases, thereby forming pumping chambers in which the plungers move back and forth, the head plate portion having internal passages whose openings on one side open into the head plate portion, the directional control valves being individually connected to openings on the other side of the passages.
These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description in conjunct
Brown Steven
Freay Charles G.
Hakusu Tech Co., Ltd.
Jordan and Hamburg LLP
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