Fluid handling – Systems – Flow path with serial valves and/or closures
Reexamination Certificate
2001-08-28
2003-02-18
Lee, Kevin (Department: 3753)
Fluid handling
Systems
Flow path with serial valves and/or closures
C137S613000, C137S614110
Reexamination Certificate
active
06520206
ABSTRACT:
TECHNICAL FIELD
The present invention relates to two-way or bi-directional pilot type electromagnetic flow valves and bi-directional piping that utilizes such bi-directional pilot type electromagnetic flow valves. In this specification, “two-way” or “bi-directional” is intended to mean a structure having ports A and B, in which a fluid may flow from port A to port B, or conversely, the fluid may flow from port B to port A.
DESCRIPTION OF THE RELATED ART
A known pilot type electromagnetic flow valve is described in Japanese Utility Model Publication No. 59-83262 (1984) and is shown herein in
FIG. 1. A
body
1
includes a flow inlet port
2
and a flow outlet port
3
that are connected by a passage
4
. A valve seat
5
is formed at the upper end of the passage
4
. A cup-shaped main valve
6
reciprocates up and down within the body
1
. A pilot space
7
is formed inside the main valve
6
. A pilot hole
8
is defined at a bottom center of the main valve
6
and a ring shaped protrusion
9
surrounds the pilot hole
8
on the outside bottom surface of the main valve
6
. The ring shaped protrusion
9
is free to contact or separate from the valve seat
5
. A solenoid coil
10
is provided at the upper end of the body
1
and a plunger
11
and a spring
13
are provided inside the solenoid coil
10
. A spherical pilot valve
12
is attached to the tip of the plunger
11
. A narrow gap
14
is provided between the outer peripheral surface of the main value
6
and the inside surface of the body
1
.
When the solenoid coil
10
is not energized, the pilot valve
12
closes the pilot hole
8
due to the biasing force of the spring
13
. When the solenoid coil
10
is energized, the pilot valve
12
is pulled away from the pilot hole
8
due to the magnetic pulling or attracting force of the solenoid coil
10
.
Normally, the fluid pressure at the flow inlet port
2
is greater than the fluid pressure at the flow outlet port
3
. While the solenoid coil
10
is not energized and the pilot valve
12
closes the pilot hole
8
, the pressure difference between the pilot space
7
and the flow outlet port
3
, which works on the main valve
6
, maintains the main valve
6
at the closed position. It is not required to energize the solenoid coil
12
to maintain the main valve
6
at the closed position. When the solenoid coil
10
is energized and the pilot valve
12
is pulled away from the pilot hole
8
, fluid can communicate between the pilot space
7
and the flow outlet port
3
, thereby eliminating the pressure difference between the pilot space
7
and the flow outlet port
3
. In this condition, greater fluid pressure at the flow inlet port
2
than the pilot space
7
lifts the main valve
6
upwardly, and the ring shaped protrusion
9
will separate from the valve seat
5
. Because the fluid pressure supplied to the flow inlet port
2
is greater than the fluid pressure at the flow outlet port
3
, fluid will flow from the flow inlet port
2
toward the flow outlet port
3
.
The required force for pulling away the pilot valve
12
from the pilot hole
8
by the solenoid coil
10
is much less than a force required for pulling away the main valve
6
. A small solenoid coil
10
may be used for opening the pilot type electromagnetic valve that has the pilot valve
12
, pilot hole
8
and pilot space
7
. If the pilot valve
12
, pilot hole
8
and pilot space
7
are not provided, and the main valve
6
is directly connected to the solenoid coil
10
, a big solenoid coil
10
is required to pull away the main valve
6
from the valve seat
5
, because the great pressure difference between the flow inlet port
2
and the flow outlet port
3
works on the main valve
6
to maintain the main valve
6
at the closed position.
When the main valve
6
should be closed again, the electric current to the solenoid coil
10
is stopped. As a result, the spring
13
causes the pilot valve
12
to contact and close the pilot hole
8
. Thus, the high pressure fluid supplied from the flow inlet port
2
passes through the gap
14
into the pilot space
7
, thereby pushing the main valve
6
downward as shown in FIG.
1
. When the main valve
6
moves downward, the ring shaped protrusion
9
again comes into contact with the valve seat
5
and fluid communication between the flow inlet port
2
and flow outlet port
3
is stopped.
The cross sectional area of the main valve
6
is much bigger than the cross sectional area of the pilot valve
12
and the plunger
11
. Therefore the force applied to the main valve
6
due to the pressure difference between the flow inlet port
2
and flow outlet port
3
is much higher than the force applied to the pilot valve
12
due to the pressure difference. If the pilot valve
12
is not provided, a relatively strong force would be required to move the main valve
6
upwardly against the large force due to the pressure difference between the flow inlet port
2
and flow outlet port
3
, in order to open the main valve
6
. Thus, if the pilot valve
12
is not provided, a solenoid coil
10
capable of generating a relatively strong pulling force is necessary to pull the main valve
6
upward.
However, the pilot valve
12
of the known pilot type electromagnetic flow valve can be easily opened by applying a small pulling force to the pilot valve
12
, even if a large pressure difference exists between the flow inlet port
2
and flow outlet port
3
. As a result, a relatively small solenoid coil
10
is sufficient to operate the known pilot type electromagnetic flow valve.
Consequently, the known pilot type electromagnetic flow valve, has the advantage of being able to use a small solenoid coil
10
to open the flow path, even when a large pressure difference exists between the flow inlet port
2
and the flow outlet port
3
. In order to realize this advantage, the spring
13
must have a relatively small or weak biasing force.
In a typical piping system, the direction of the fluid flow is designed to flow in from the flow inlet port
2
and flow out from the flow outlet port
3
while passing though the pilot type electromagnetic flow valve in an opened state. Thus, the known pilot type electromagnetic flow valve can be utilized in typical piping systems, as long as the fluid pressure at flow inlet port
2
is greater than the flow outlet port
3
.
However, if the fluid pressure at the flow outlet port
3
becomes higher than the fluid pressure at the flow inlet port
2
, the known pilot type electromagnetic flow valve has little capability to reliably prevent fluid flow in the reverse direction. When relatively high pressure fluid is supplied to the flow outlet port
3
, the main valve
6
will easily open, if the biasing force of the spring
13
is relatively small. In the known art, this reverse flow problem can be overcome by substantially increasing the biasing strength of the spring
13
. If the spring
13
pushes the valves
6
and
12
downwardly with a greater force, the spring
13
will prevent high pressure fluid supplied to the flow outlet port
3
from opening the main valve
6
. However, in this case, a relatively strong force will be required to pull away the pilot valve
12
against the strong biasing force of the spring
13
to open the pilot hole
8
, and the advantage of pilot type electromagnetic flow valve will be lost.
Thus, in normal operation (i.e. a relatively high pressure fluid is supplied to the flow inlet port
2
), a relatively strong electromagnetic force will be required to open the pilot valve
12
in order to overcome the increased biasing strength of spring
13
. Consequently, in order to overcome the reverse flow problem, the advantage of using a pilot type electromagnetic valve will be eliminated, because it will be necessary to use a relatively large solenoid coil in order to supply a sufficient pulling force in order to open the flow path. Thus, the knowing pilot type electromagnetic valve is typically not used in two-way or bi-directional piping, because reverse flow can not be reliably prevented without losing
Hotta Akihisa
Suda Koichi
Yamamoto Takeshi
Aisan Kogyo Kabushiki Kaisha
Dennison, Schultz & Dougherty
Lee Kevin
LandOfFree
Bi-directional pilot type electromagnetic valves does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bi-directional pilot type electromagnetic valves, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bi-directional pilot type electromagnetic valves will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3181698