Valve assembly prohibiting re-expansion of residual fluid

Details Valve assembly prohibiting re-expansion of residual fluid Valve assembly prohibiting re-expansion of residual fluid

2002-05-07

2004-03-09

Freay, Charles G. (Department: 3746)

Pumps

Expansible chamber type

Having pumping chamber pressure responsive distributor

C417S520000, C417S501000

Reexamination Certificate

active

06702557

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a fluid compressing apparatus, and more particularly, to a fluid compressing apparatus for discharging the fluid by a compressing or pumping action utilizing a linear reciprocating movement of a piston.
2. Description of the Related Art
A typical example of a conventional fluid compressing apparatus is shown in
FIGS. 1 and 2
, which will be described briefly below.
FIGS. 1 and 2
are sectional views that schematically show the structure and operation of the conventional fluid compressing apparatus. The reference numeral
10
indicates a cylinder block,
20
a piston,
30
a valve plate and
40
a cylinder head.
As shown in
FIGS. 1 and 2
, the cylinder block
10
has a cylinder bore
11
of a predetermined diameter that penetrates through the cylinder block
10
in a lengthwise or longitudinal direction. The piston
20
is movably mounted in the cylinder bore
11
of the cylinder block
10
so as to be capable of reciprocal action, and the valve plate
30
is disposed in the cylinder block
10
. The valve plate
30
has fluid suction/discharge ports
31
and
32
formed therein, and suction/discharge valves
33
and
34
(shown in phantom), that can open and cover the fluid suction/discharge ports
31
and
32
. The cylinder head
40
is disposed in the cylinder block
10
toward the longitudinal side adjacent the valve plate
30
, and the cylinder head
40
has fluid suction/discharge chambers
41
and
42
respectively interconnecting with the fluid suction/discharge ports
31
and
32
of the valve plate
30
. The cylinder head
40
is connected to fluid suction/discharge manifolds
43
and
44
that are respectively interconnected with the fluid suction/discharge chambers
41
and
42
of the cylinder head
40
.
In the conventional fluid compressing apparatus constructed as described above, and illustrated in
FIGS. 1 and 2
, a driving force transmitted from a piston driving source (not shown), causes the piston
20
to reciprocate within the cylinder bore
11
of the cylinder block
10
, thereby causing the fluid to be drawn in, compressed and discharged.
Additionally, as the piston
20
moves from the top dead end point T (
FIG. 1
) to the bottom dead end point B (
FIG. 2
) of the cylinder bore
11
, due to the different pressures in and out of the cylinder bore
11
, the suction valve
33
opens the suction port
31
of the valve plate
30
(as shown in phantom in FIG.
2
), and accordingly, the fluid is drawn into the cylinder bore of the cylinder block
10
sequentially through the suction manifold
43
, the suction chamber
41
of the cylinder head
40
and the suction port
31
of the valve plate
30
. At this time, the pressure in the discharge chamber
42
of the cylinder head
40
is higher than the pressure in the cylinder bore
11
so that the discharge valve
34
maintains the discharge port
32
closed.
Meanwhile, as the piston
20
is returned from the bottom dead end point B (
FIG. 2
) to the top dead end point T (FIG.
1
), the fluid in the cylinder bore
11
is gradually compressed. Finally, when the piston
20
reaches the top dead end point T, as shown in
FIG. 1
, the pressure in the cylinder bore
11
becomes higher than the pressure in the discharge chamber
42
of the cylinder head
40
, and accordingly, as shown in phantom in
FIG. 1
, the discharge valve
34
opens the discharge port
32
of the valve plate
30
, and the compressed fluid is discharged through the discharge port
32
of the valve plate
30
, the discharge chamber
42
of the cylinder head
40
and the discharge manifold
44
. At this time, the pressure in the suction chamber
41
is lower than the pressure in the cylinder bore
11
, and thus, the suction valve
33
maintains the suction port
31
closed.
Then, when the piston
20
moves back to the bottom dead end point B, the suction port
31
is opened by the suction valve
33
, whereas the discharge port
32
is closed by the discharge valve
34
. As a result, the fluid is drawn into the bore
11
. Then as the piston
20
is moved to the top dead end point T, the drawn air is compressed and then discharged through the discharge port
32
. As this reciprocating movement of the piston
20
repeats, the compression and discharge of the fluid also repeats the cycle described above.
In the conventional fluid compressing apparatus described above, however, the compressed fluid is often incompletely discharged, which retains some residual fluid at the discharge port
32
of the valve plate
30
. Such residual fluid re-expands during the fluid suctioning process in which the piston
20
is moved from the top dead end point T to the bottom dead end point B. The problem arises in the initial fluid suctioning process where the piston
20
is moved toward the bottom dead end point B. That is, due to the presence of re-expanding residual fluid, the pressure in the cylinder bore
11
is initially higher than the pressure in the suction chamber
41
, although the pressure in the cylinder bore
11
is lower than the pressure in the discharge chamber
42
of the cylinder head
40
. Accordingly, the suctioning does not occur at the beginning of the stroke of the piston
20
toward the bottom dead end point B. Then the suction valve
33
is opened to draw in the fresh fluid when the pressure in the cylinder bore
11
becomes lower than the pressure in the suction chamber
41
, which is obtained only when the piston
20
moves toward the bottom dead end point B for a sufficient period of time. In other words, the residual fluid from the fluid compression and discharge in the conventional fluid compressing apparatus causes a clearance volume in the cylinder bore
11
that makes a certain space in the cylinder bore
11
unavailable. Accordingly, the amount of drawn fluid decreases, and pumping efficiency deteriorates considerably.
Further, due to the complicated structure that is used for the suction valve
33
and the discharge valve
34
for opening/closing the fluid suction port
31
and discharge port
32
, the conventional apparatus is difficult to assemble and productivity thus deteriorates, and manufacturing costs increase considerably.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the above-mentioned problems of the related art, and accordingly, it is an object of the present invention to provide a fluid compressing apparatus for increasing pumping efficiency by discharging compressed fluid completely out of the bore and thus minimizing clearance volume in the cylinder bore.
Another object is to provide a fluid compressing apparatus having a simple structure and being easy to assemble and thereby increasing productivity and reducing manufacturing costs, by using a piston to open and close a fluid suction port, thereby omitting a need to use a separate suction valve device, and providing a discharge valve device having a simple structure.
The above objects are accomplished by providing a fluid compressing apparatus according to the present invention, including a cylinder block having a cylinder bore of a predetermined diameter penetrating through the cylinder block in a lengthwise direction, a discharge chamber having a diameter larger than the diameter of the cylinder bore, and at least one fluid suction port penetrating in the cylinder block in a substantially perpendicular direction with respect to the cylinder bore, the cylinder block using a certain space thereof that is interconnected with the discharge chamber of the cylinder borer as a fluid discharge port; a piston movably disposed in the cylinder bore of the cylinder block to be linearly reciprocated; a discharge valve assembly having a valve plate disposed to be resiliently biased from the discharge chamber toward the fluid discharge port so as to selectively open or close the fluid discharge port of the cylinder block; and a cylinder head disposed at an end of the discharge chamber of the cylinder block, and having a fluid discharge channel interconnected wi

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