Fluid handling – Convertible
Utility Patent
1997-10-08
2001-01-02
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Convertible
C137S625640, C137S854000, C251S026000
Utility Patent
active
06167901
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a pilot 3-port transfer valve that switches a 3-port main valve using a pilot valve.
PRIOR ART
FIG. 3
shows a publicly known single pilot 3-port transfer valve wherein a transfer valve
1
comprises a 3-port main valve
2
and a solenoid-driven pilot valve
3
. The main valve
2
includes a supply port P that is connected to a supply source of pressurized fluid such as compressed air; an output port A that is connected to an actuator; an ejection port R that is externally open; and a main valve member (not shown) that is operated by a pilot fluid pressure to connect the output port A to the supply port P or the ejection port R. In addition, the pilot valve
3
includes a pilot supply port (p); a pilot output port (a); a pilot ejection port (r); and a pilot valve member (not shown) that is driven by a solenoid
4
to connect the pilot output port (a) to the pilot supply port (p) or the pilot ejection port (r).
When the solenoid
4
of the pilot valve
3
is energized, the transfer valve
1
switches the pilot valve
3
to a position opposed to that shown in the figure to allow a pilot fluid to be output to the main valve
2
from the pilot output port (a), thereby switching the valve member of the main valve
2
to allow the supply port P to communicate with the output port A. As a result, a pressurized fluid is output from the output port A. When the solenoid
4
is de-energized, the pilot valve
3
returns to the switching position shown in the figure to externally eject the pilot fluid supplied to the main valve
2
, from the pilot ejection port (r). Thus, the force of a return spring
5
causes the valve member of the main valve
2
to return to shut the output port A off from the supply port P while allowing the port A to communicate with the output port R. As a result, a pressurized fluid is output from the output port R.
The pilot 3-port transfer valve
1
is classified into an internal and external pilot types based on the method for supplying a pilot fluid to the pilot valve
3
. In the internal pilot transfer valve, pilot fluid is supplied from the supply port P of the main body
2
through a channel provided in the valve body to the pilot supply port (p) of the pilot valve
3
, whereas in the external pilot transfer valve, pilot fluid is supplied to the pilot supply port (p) through external piping connected to the pilot valve.
The pilot 3-port transfer valve
1
is also classified into a constantly closed type, such as that shown in the figure, in which the supply port P and the output port A are shut off during non-operating states in which a pilot fluid is not being supplied to the main valve
2
; and a constantly open type in which the supply port P is in communication with the output port A.
The pilot 3-port transfer valve thus involves various types, and these different types of valves are used for different applications. Since, however, most of these valves are mutually incompatible, these various types have had to be individually provided and used, resulting in very cumbersome manufacturing and product control processes.
In particular, if the transfer valve is an external pilot transfer valve, a pilot fluid is supplied to the pilot valve
3
through external piping. Thus, the transfer valve can be changed between the constantly closed and the constantly open types by connecting either the port P or R of the main valve
2
to a supply source for pressurized fluid. In the internal pilot transfer valve, even when the port R is connected to such a supply source, the transfer valve cannot be changed between the constantly closed and constantly open types because a pilot fluid is not supplied to the pilot valve from the port R.
DISCLOSURE OF THE INVENTION
It is a main object of this invention to provide a pilot 3-port transfer valve that can be changed between a constantly closed type and a constantly open type even if it is of an internal pilot type.
It is another object of this invention to provide a pilot 3-port transfer valve that can be used as either an internal pilot or external pilot type.
To achieve these objects, this invention provides a pilot transfer valve comprising a first, second, and third ports for supplying, outputting, and ejecting a pressurized fluid characterized in that a pilot valve includes a pilot supply channel for supplying a pilot fluid to the pilot valve and in that the pilot supply channel and each of the first and the third ports are connected together via a check valve that allows a pressurized fluid to flow into the pilot supply channel from each port while checking the flow of pressurized fluid in the opposite direction.
Due to its ability to supply a pilot fluid from either of the first and the third ports through the check valve to the pilot valve, the transfer valve of the above configuration can be operated by connecting any of the ports to a supply source for a pressurized fluid. The transfer valve operates as the constantly closed type if the first port, which is shut off during an idle state, is connected to the supply source for pressurized fluid, and operates as the constantly open type if the third port, which communicates with the second port during an idle state, is connected to the supply source.
According to a specific embodiment, each check valve comprises a cylindrical valve body inserted into a circular valve chamber with a gap maintained for fluid communication; and an annular lip seal fitted around the outer circumference of the valve body to seal between the valve body and the inner wall of the valve chamber.
According to another specific embodiment, part of the pilot supply channel is defined and formed between the valve body of the transfer valve and a cover mounted on the valve body, the check valves corresponding to the first and the third ports are installed in the part beneath the cover, and the cover includes a protrusion that contacts the check valve to prevent it from slipping out from the valve chamber.
According to a preferred embodiment of this invention, the transfer valve includes an external pilot port for externally introducing a pilot fluid; a check valve that allows pressurized fluid to flow into the pilot fluid channel from the pilot port while checking the flow of pressurized fluid in the opposite direction is installed between the external pilot port and the pilot supply channel.
This configurations enables the transfer valve to be used as the external pilot type. If external piping is connected to the external pilot port and a pilot fluid with a higher pressure than a main fluid is supplied, the transfer valve is used as the external pilot type because the pilot fluid pushes the check valve open and is supplied to the pilot valve. In this case, the check valves corresponding to the first and the third ports prevent the highly pressurized pilot fluid from flowing back to these ports.
REFERENCES:
patent: 4966196 (1990-10-01), Meyer
patent: 5400821 (1995-03-01), Ott
patent: 0 590 339 A1 (1994-04-01), None
patent: 2 315 653 (1977-01-01), None
Patent Abstracts of Japan: vol. 010, No. 218 (M-503), Jul. 30, 1986.
Michalsky Gerald A.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
SMC Corporation
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