Double gas seal with coplanar pad faces

Details Double gas seal with coplanar pad faces Double gas seal with coplanar pad faces

1999-03-06

2001-04-10

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Relatively rotatable radially extending sealing face member

C277S387000, C277S400000, C277S401000, C277S408000

Reexamination Certificate

active

06213473

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to gas-lubricated non-contacting seals and, more particularly, to a gas lubricated seal with radial coplanar pad faces. The gas seal of the present invention has various applications, and is particularly well suited for sealing between a rotating drive shaft sleeve and a pump housing, so that the double gas seal reliably seals process fluid within the pump housing.
BACKGROUND OF THE INVENTION
Gas lubricated seals have been used for many years in compressors and, in some applications, have largely replaced more conventional seals, including liquid lubricated seals. Since the sealing faces of gas lubricated seals are not in dynamic contact, properly designed gas lubricated seals offer significant benefits of reduced frictional torque and reduced heat generation compared to conventional seals. Moreover, since the high pressure gas supplied to a gas lubricated seal may be selected for its inert qualities in view of the application, and since a properly designed gas lubricated seal offers a long life, these seals are ideal for applications requiring complete emission control and process purity. In more recent years, gas lubricated seals have been applied to pump technology to seal between the rotating shaft sleeve and the pump housing. Accordingly, pump manufacturers have desired improved gas seals for various pump sealing applications.
One type of gas seal uses circumferentially spaced grooves in one of the sealing faces. The spiral grooves each extend radially inward from an outer periphery of the respective sealing face. Pressurized gas is supplied to these grooves to block the escape of the fluid being sealed. One such gas lubricated seal which is embodied in a cartridge design is the Type 2800 seal manufactured by John Crane, Inc. Other types of gas lubricated seals with spiraling grooves are disclosed in U.S. Pat. Nos. 4,423,879; 5,246,295; 5,385,409; 5,498,007 and 5,713,576. Other variations of gas lubricated seals are disclosed in an article entitled “
Analysis of Spiral
-
Groove Face Seal for Liquid Oxygen
” by Shapiro et al., published in ASLE Transactions, Volume 27, 3, pp. 177-188. Another type of non-contact gas seal marketed by A.W. Chesterton Co. as the 4400 TwinHybrid Gas Seal utilizes radially inward and outward sealing faces with the pressurized gas being supplied through the stationary ring and to circumferentially spaced elongate grooves spaced radially between the sealing faces.
While various types of double gas seals have been devised, the prior art has failed to effectively benefit from double gas seal technology. Prior art coplanar double gas seals do not provide effective lift off of both the radially outer sealing face and the radially inner sealing face under various conditions. Also, much of the prior art relating to double gas seals provide seal designs which are too large for many applications since the seals have a long axial length or require a considerable diametral space.
The disadvantages of the prior art are overcome by the present invention. An improved double gas seal is hereinafter disclosed which provides effective lift off of the radially spaced sealing faces and reliably seals pressurized fluid while minimizing seal wear.
SUMMARY OF THE INVENTION
A double gas pressure seal is provided for sealing between a stationary housing and a rotary housing within the stationary housing. The gas pressure seal includes a stationary ring and a rotary ring which cooperate to seal fluid within the stationary housing. In an exemplary application of the invention, the stationary housing may be a pump housing and the rotary housing may be a sleeve which is rotatable with the pump shaft. The double gas seal is supplied with pressurized gas from an external source and at a pressure higher than the pressure of the process fluid in the pump housing to reliably seal the process fluid.
Each of the stationary ring and the rotary ring has an annular inner sealing face and an annular outer sealing face, such that the inner and outer sealing faces are in sealing engagement. The phrase “sealing engagement” as used herein with respect to the sealing faces does not mean that the pad sealing faces are touching, and instead the faces are separated by a stiff gas film, as discussed more fully below, to achieve long seal life. A spring or other biasing member axially biases one of the stationary ring and rotary ring toward the other ring, and in a preferred embodiment biases the stationary ring toward the rotary ring. An annular groove is provided in one of the stationary ring and the rotary ring, with the annular groove being radially spaced between the inner sealing faces in sealing engagement and the outer sealing faces in sealing engagement. A supply port in one of the rings supplies the pressurized gas from an external source to the annular groove. A plurality of circumferentially spaced inner recesses and a plurality of circumferentially spaced outer recesses are each provided in one of the stationary ring and in the rotary ring, and preferably in the rotary ring. Each inner recess is spaced between the annular groove and a radially innermost portion of the inner sealing faces in sealing engagement, and each outer recess is spaced between the annular groove and a radially outermost portion of the outer sealing face is in sealing engagement. The plurality of inner recesses and the plurality of outer recesses exert a gas lift-off force on the axial movable one of the stationary ring and the rotary ring while providing a stiff pressurized gas film between the sealing faces. Each of the plurality of inner recesses and each of the plurality of outer recesses has a rotary leading portion and a circumferentially spaced rotary trailing portion. A plurality of inner feed channels and a plurality of outer feed channels fluidly connect the annular groove with the rotary leading portion of each inner recess and outer recess, so that the rotary trailing portion of each of the inner recesses and outer recesses is circumferentially spaced from the respective feed channel. In a preferred embodiment, each of the sealing faces lies within a single plane which is perpendicular to an axis of the rotating shaft.
It is an object of the invention to provide an improved gas seal with coplanar pad faces for sealing between a stationary housing and a rotary housing. A supply port in one of the stationary ring and rotary ring supplies pressurized gas to an annular groove. The pressurized gas then passes radially inward from the annular groove through a plurality of inner feed channels to a plurality of inner recesses, and similarly passes radially outward from the annular groove through a plurality of outer feed channels to a plurality of outer recesses. The circumferentially spaced inner and outer recesses provide the desired pressurized gas lift-off force which separates the stationary ring from the rotary ring while allowing a relatively small quantity of pressurized gas to leak from the gas pressure seal.
It is a feature of the invention that the double gas pressure seal may occupy a small axial and radial space and thereby be used in a large number of applications. It is a related feature of this invention that the gas pressure seal may be used over a wide range of external gas pressures and a wide range of fluid pressures within the stationary housing.
A significant advantage of the present invention is that the double gas pressure seal is relatively inexpensive and has a long life. The double gas pressure seal may be reliably used at elevated temperatures, and may be used to seal various types of fluids in the stationary housing, including abrasive, sticky, and corrosive fluids. The gas pressure seal also has the ability to relatively contain fluids within the stationary housing in the event that pressurized gas from the external source is temporarily lost, and the seal has the ability to return to normal operation after pressurized gas from the external source is restored.
These and further objects, features, and advantages of the pres

Affiliated with

Also associated with

Rating

Double gas seal with coplanar pad faces does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Double gas seal with coplanar pad faces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Double gas seal with coplanar pad faces will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2525033