Seal arrangement for a metering valve

A seal arrangement for a metering valve wherein a cylindrical member has a groove located on a face adjacent a seat which surrounds an opening connected to an inlet port. An elastomeric member has a base which is located in the groove with a projection that extends past the face on the cylindrical member. A ring is resiliently held against the elastomeric member by a sleeve to form a first static seal between the cylindrical member, retaining ring and sleeve. A piston located in the sleeve has a flange with first and second ribs thereon separated by a recess. An input member positions the piston such that the first rib engages the projection and compresses the elastomeric member before the second rib engages the seat to form a static seal between the piston and cylindrical member to assure that fluid flow between an inlet port and an exit port terminates when the piston is in a closure position. The recess on the piston provides a space for the elastomeric material to flow without damage to the projection when the first rib engages the ring and the second rib engages the seat.

This invention related to a seal arrangement for metering valve. The seal 
arrangement has a cylindrical member with a groove for locating an 
elastomeric member which has a projection that extends above a face on the 
cylindrical member. A retaining ring is resiliently urged against the 
elastomeric member by a ceramic sleeve which has a plurality of openings 
connected to an outlet port. A ceramic piston has a flange with first and 
second ribs separated by a recess. An actuator moves the piston to a 
closure position where the first rib engages the projection while a second 
rib engages the seat to prevent flow of fluid between an inlet port and 
the outlet port. The recess allows the elastomeric material to flow 
without damage when the piston is in the closure position. 
In fuel systems for use in supplying a turbine engine of an aircraft with 
fuel, it is important that the fuel supply is terminated when the turbine 
is inoperative or shut down. U.S. Pat. No. 4,876,857 discloses a shut 
off/pressure regulating valve for a turbine engine wherein a sealing 
arrangement allows for substantially friction free operation and 
terminates the flow of fuel when the turbine is in a shut off condition. 
In an effort to simplify a fuel control system it was decided to 
incorporate the shut off valve in the metering valve. Unfortunately, after 
incorporating the shut off valve in the metering valve it was observed 
that an elastomeric seal could be damaged by repeated engagement of an 
operational piston. 
The present invention provides a seal arrangement for a metering valve with 
an integral shut off wherein the possibility of damage to an elastomeric 
member has been reduced and essentially eliminated. In this seal 
arrangement, the metering valve housing has a bore with an inlet port 
connected to a source of fluid and an outlet port connected to a turbine. 
A cylindrical member is positioned against a shoulder in the bore by an 
end cap. The cylindrical member has a face with a first groove located 
adjacent adjacent a seat. An elastomeric member having a base with 
projection extending therefrom is located in the groove adjacent the seat. 
A projection on the elastomeric member extends past the face. A retaining 
ring is resiliently urged against the base of the elastomeric member by 
the end of a sleeve. A plurality of openings in the sleeve adjacent the 
end define a flow path between the seat and the outlet port. A piston 
located in said sleeve and connected to an actuation member has a flange 
with first and second ribs thereon separated by a recess. When the 
actuation member moves the piston toward a closure position, the first rib 
engages the projection to compress the elastomeric material prior to the 
second rib engaging the seat and the first rib engaging the ring to 
terminate fluid communication between the inlet port and outlet port. In 
the closure position, the elastomeric member flows into the recess in the 
flange of the piston to create a static seal between said piston and 
cylindrical member and thereby assure that fluid communication is 
completely terminated. 
It is an object of this invention to provide a metering valve having an 
integral shut off valve with a seal arrangement wherein an elastomeric 
member is protected from damage caused by repeated engagement with an 
operational piston. 
It is a further object of this invention to provide a metering valve with a 
piston having first and second sealing surfaces which engage a seat and 
elastomeric member, respectively to prevent the communication of fluid 
between an inlet and outlet port when the metering valve is in a closure 
position. 
An advantage of this invention occurs through the simplicity of the 
integration of a metering valve with an operational piston responsive to 
an input actuator to control the flow of fluid between an input port and 
an exit port through the sequential engagement of a resilient member and 
seat to completely terminate fluid communication from the inlet port to an 
outlet port.

The metering valve 10 shown in FIG. 1 is designed as part of a fuel system 
for a turbine engine for use in an aircraft. The metering valve 10 has an 
actuation solenoid 12 which is controlled by an input signal from an 
electronic control unit 15 to meter fuel to the combustion chamber in the 
turbine. 
The metering valve 10 has a housing 16 with a stepped bore 18 connected to 
a source of fuel 24 through an inlet port 20 and to the combustion chamber 
of the turbine through an outlet or exit port 22. A shoulder 26 in bore 18 
separates the inlet port 20 and the outlet port 22. An annular shield 28 
is located in bore 18 against shoulder 26 to guide or direct fluid into 
the outlet port 22 prior to the placement of a cylindrical body 30 in bore 
18. The cylindrical body 30 forms the closure seat for the metering valve 
and an entrance cone for guiding or directing the flow of fluid from the 
inlet port 20 to the outlet port 22. 
As best shown in FIGS. 2, 3 and 4, the cylindrical body 30 has a peripheral 
surface 36 which engages bore 18 and first and second faces 32 and 34 
which are located in planes perpendicular to bore 18. Face 32 has a groove 
38 and a rib or ledge 40 thereon. 
An elastomeric material 42 has a base that is located in groove 38 and a 
projection 44 that extends past face 32 on cylindrical member 30. A 
retainer ring 46 made of a hard plastic material such as Teflon, initially 
has a portion that is located in the groove 38 and a portion that extends 
past face 32 as shown in FIG. 3. An end cap 48 has a cylindrical body 50 
that extends into bore 18 and engages face 34 on cylindrical body 30 to 
hold annular shield 28 against shoulder 26. Cylindrical body 50 has a 
series of openings or slots 52, 52' . . . 52.sup.n through which fluid is 
communicated from inlet port 20 to the cone surface 31 on the interior of 
cylindrical body 30. Head 54 on end cap 48 is attached to housing 14 by 
the threads 56 and a seal 58 located in a groove in housing 16 assures 
that fluid from inlet port 20 is retained in bore 18. 
A ceramic sleeve 60 located in bore 18 has a first end 62 that extends into 
bore 18 and sets on ledge or rib 40 on face 32 of cylindrical member 30 
and a second end 64. A resilient member 66 in the form of a wave washer is 
located in bore 18 adjacent to the second end 64 of sleeve 60. A snap ring 
68 connected to housing 16 holds sleeve 60 in bore 18 while resilient 
member 66 provides sufficient force such that the first end 62 urges 
retainer ring 46 into groove 46 as shown in FIG. 4 and forms a static seal 
between ring 46, end 62 and the elastomeric member 42. Sleeve 60 has a 
plurality of openings 61 (only one is shown) that connect bore 18 to 
outlet or exit port 22. 
A shaft 70 that extends from actuation solenoid 12 has an end 76 located in 
bore 18. A nut 78 attached to end 76 acts on resilient member or wave 
washer 80 to position hub 86 on piston 72 against stop ring 74 on shaft 
70. 
Piston 72 which is also made from a ceramic material has a cylindrical body 
88 which is located in the ceramic sleeve 60. Cylindrical body 88 has a 
flange with a first rib 90 connected to or separated from a second rib 92 
by an annular recess or groove 94, as more clearly shown in FIG. 2. Hub 86 
has a plurality of openings 82 and 84 which allows fluid communication 
between the inlet port 20 and the interior of sleeve 60 to provide for a 
balance force across piston 72. Seal 94 retained in housing 14 of the 
actuation solenoid 12 surrounds shaft 70 to retain fluid or fuel presented 
to bore 18 on housing 16 after housing 14 is connected to housing 16 by 
threaded connection 11. 
The metering valve 10 shown in FIG. 1 is in the shut down condition with 
rib 92 on the flange of piston 72 seated on face 32 of cylindrical body 30 
while rib 90 on the flange compresses projection 44 on elastomeric member 
42 and ring 46 to statically seal bore 18 from the outlet port 22. 
When actuator solenoid 12 receives an input signal from ecu 15, shaft 70 
provides an actuation force which moves piston 72 to allow fluid or fuel 
to flow from the inlet port 20 to the outlet port 22. The input force from 
shaft 70 is communicated through wave washer or resilient member 80 to 
provide a smooth force which moves ribs 90 and 92 on piston 72 away from 
face 32 on cylindrical member 30 to allow fluid or fuel to flow from inlet 
port 20 to outlet port 22 by way of openings 52, 52' . . . 52.sup.n in end 
cap 48, annular opening 33 in cylindrical body 30, past seat on face 32 
and through openings 61 in sleeve 60 as shown in FIG. 4. Spherical surface 
on nut 78 and guide 28 aids in directing the flow of fuel through openings 
31 without the creation of turbulence. The pulling or cavitation force of 
the fuel or fluid as it flows through opening 33 which attempts to 
displace the elastomeric member 42 from groove 38 is overcome through the 
constant resilient engagement of retaining ring 46 by end 62 of sleeve 60. 
When ecu 15 supplies actuation solenoid 12 with a termination signal, a 
closure spring provides a force which moves shaft 70 and piston 72 toward 
seat or face 32 on cylindrical member 30 in bore 18. As piston 72 
approaches face 32, rib 90 on the flange moves past openings 31 in sleeve 
60 to initiate termination of fuel flow from inlet port 20 to the outlet 
port 22 through bore 18. Thereafter, rib 90 contacts projection 44 on the 
elastomeric member 42 to compress the elastomeric member 42 into groove 38 
prior to engagement with ring 46. Thereafter, rib 92 is seated on face 32 
to form a static seal that completely terminates communication of fuel 
from bore 18 to outlet port 22 through opening 33. During the closure, 
when a sufficient force has been applied to elastomeric member 42 through 
rib 90, a portion of the elastomeric member 42 flows into recess 94 to 
prevent damage to the elastomeric member 42 while at the same time forming 
the static seal which prevents fuel from flowing past the seat on face 32.