Pumps – Expansible chamber type – Having pulsation dampening fluid receiving space
Reexamination Certificate
2001-05-04
2002-12-03
Freay, Charles G. (Department: 3746)
Pumps
Expansible chamber type
Having pulsation dampening fluid receiving space
C417S542000, C417S394000, C138S030000
Reexamination Certificate
active
06488487
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device that is interposingly used in a liquid transporting pipe through which transported liquid such as liquid for processing a semi-conductor device is transported to various portions by a reciprocal pump, to damp pulsations generated by variations in flow quantity and pressure due to the reciprocal operation of the reciprocal pump.
2. Description of the Prior Art
A pulsation damping device of this kind is disclosed in, for example, Japanese Patent Application Laying-Open Nos. 617752 and 8-159016.
Among such disclosed devices, the pulsation damping device for a pump which is disclosed in Japanese Patent Application Laying-Open No. 6-17752 is shown in FIG.
11
. The device comprises: a sealed device body casing
60
; a liquid chamber
61
a
which is disposed in the device body casing
60
, which temporarily stores liquid transported by a reciprocal pump to exert a liquid storage function, and which then allows the liquid to flow out; and an air chamber
61
b
which is disposed in the device body casing
60
and separated from the liquid chamber
61
a
via a pulsation suppression diaphragm
62
that is configured by an extendable and contractible bellows, and which is filled with compressed air. The device is configured so that the pulsation suppression diaphragm
62
is extended and contracted by pulsations due to the discharge pressure of the pump, and the pulsations are damped by the capacity change of the liquid chamber
61
a.
In the case where the discharge pressure of the reciprocal pump is varied, the extension and contraction amount of the pulsation suppression diaphragm
62
must be restricted to a predetermined range in order to balance the liquid pressure in the liquid chamber
61
a
with the air pressure in the air chamber
61
b.
To comply with this, the following configuration is employed in the device shown in FIG.
11
. An automatic air supply valve mechanism
63
and an automatic air discharge valve mechanism
64
are disposed in the device body casing
60
. In the case where the pulsation suppression diaphragm
62
is extended from a reference value S in the direction of increasing the capacity of the liquid chamber by the liquid pressure variation in the liquid chamber
61
a,
when the diaphragm exceeds a predetermined range A, an air supply port
66
is opened by the pulsation suppression diaphragm
62
via a valve push rod
65
of the automatic air supply valve mechanism
63
, to adjust the air filling pressure of the air chamber
61
b
so as to raise the pressure. In the case where the pulsation suppression diaphragm
62
is contracted from the reference value S in the direction of decreasing the capacity of the liquid chamber, when the diaphragm exceeds a predetermined range B, an air discharge port
68
is opened by the automatic air discharge valve mechanism
64
by means of a slider
67
which abuts against a closed end face
62
a
of the pulsation suppression diaphragm
62
, to discharge the air in the air chamber
61
b
so as to lower the air filling pressure.
By contrast,
FIG. 12A
shows the pulsation damping device for a pump which is disclosed in Japanese Patent Application Laying-Open No. 8-159016, and
FIG. 12B
shows an air supply/discharge switch valve mechanism for the pump. The device uses an air chamber internal pressure adjust valve mechanism which restricts the capacity change of a liquid chamber
61
a
that is disposed in a similar manner as the liquid chamber
61
a
disclosed in Japanese Patent Application Laying-Open No. 6-17752, within a predetermined range. In the mechanism, the air supply/discharge switch valve mechanism comprising: an operating rod
69
which operates in accordance with the displacement of the closed end face
62
a
of the pulsation suppression diaphragm
62
; and a slide valve element
71
which is operated by the operating rod
69
to cause an air supply and discharge passage
70
connected to the air chamber
61
b
to selectively communicate with the air supply port
66
and the air discharge port
68
is protrudingly attached to the outside of the device body casing
60
. The valve mechanism is configured so that, when the capacity of the liquid chamber
61
a
is increased to exceed a predetermined range, the air supply port
66
communicates with the air supply and discharge passage
70
, and, when the capacity of the liquid chamber
61
a
is decreased to exceed the predetermined range, the air discharge port
68
communicates with the air supply and discharge passage
70
. The valve mechanism comprises: a cylindrical casing
72
in which the air supply port
66
, the air discharge port
68
, and the air supply and discharge passage
70
communicating with the air chamber
61
b
are formed; and the slide valve element
71
which is coaxially connected to the operating rod
69
, and which is slidably fitted into a cylinder
73
housed in the cylindrical casing
72
.
Among the above-mentioned two conventional art examples, in the former pulsation damping device disclosed in Japanese Patent Application Laying-Open No. 6-17752, as shown in
FIG. 11
, the automatic air supply valve mechanism
63
and the automatic air discharge valve mechanism
64
are disposed integrally with a lower end member
60
a
constituting a part of the device body casing
60
. When one of the valve mechanisms
63
and
64
is broken or becomes faulty, therefore, the whole device must be disassembled and repaired, or replaced with another one. In any case, the work requires much labor. Therefore, the configuration is disadvantageous in maintenance and cost. Furthermore, the device has a structure in which the air discharge port
68
of the automatic air discharge valve mechanism
64
is closed by a gravitational drop of a discharge valve element
75
. Therefore, the closing operation is unstable, and the device must be always placed so that the discharge valve element
75
in a vertical posture and the air discharge port
68
maintain their vertical positional relationship. For example, the device cannot be applied to a use in which the discharge valve element
75
has a horizontal posture, and hence the kinds of devices are restricted. Moreover, the valve push rod
65
of the automatic air supply valve mechanism
63
, and the slider
67
of the automatic air discharge valve mechanism
64
which are independently juxtaposed are in direct contact at two points with the closed end face
62
a
of the pulsation suppression diaphragm
62
configured by the bellows. One of the members, or the valve push rod
65
is in direct contact with a position which is deviated from the center portion of the closed end face
62
a.
When the pulsation suppression diaphragm
62
is extended and contracted, therefore, an offset load is applied to the diaphragm, thereby hindering the extendable and contractible portion of the pulsation suppression diaphragm
62
from being straightly deformed extendingly and contractingly in the axial direction X—X of the device body casing
60
. This impairs the response property of the automatic air supply and discharge valve mechanisms
63
and
64
, thereby causing the pulsation suppressing performance to be lowered.
In the air supply/discharge switch valve mechanism disclosed in the latter publication or Japanese Patent Application Laying-Open No. 8-159016, the configuration in which suction and discharge of air are concentrated into the single valve mechanism as shown in
FIGS. 12A and 12B
is employed. Even when the valve mechanism is broken or becomes faulty, therefore, it is not required to disassemble the whole device, and repair and replacement can be performed by detaching only the single air supply/discharge switch valve mechanism. Unlike the former device, the closing of the air supply and discharge ports
66
and
68
is not performed by the weight of the discharge valve element
75
. Therefore, the problem of the former device can be solved. By contrast, however, the device has drawbacks that the air supply/discharge swi
Freay Charles G.
Gray Michael K.
Griffin & Szipl, P.C.
Nippon Pillar Packing Co. Ltd.
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