Aerospace housing and shaft assembly

Details Aerospace housing and shaft assembly Aerospace housing and shaft assembly

1999-06-08

2001-07-10

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Relatively rotatable radially extending sealing face member

C277S404000, C277S406000

Reexamination Certificate

active

06257589

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to the field of aerospace housing and shaft assemblies, and more specifically to seals for providing a barrier between a housing and a shaft in an aerospace application.
BACKGROUND OF THE INVENTION
Mechanical face seals are commonly used to provide a seal between a stationary housing and a rotating shaft. Such seals include a rotating ring mounted on the shaft and a stationary ring mounted on the housing. Either the stator or the rotor is biased toward the other to provide a biased seal therebetween.
A typical seal design for inhibiting process fluid, whether liquid or gas, from escaping from a housing along a rotating shaft includes two seals in fluid communication with an intermediate chamber containing a buffer fluid. One seal pumps the buffer fluid having a certain pressure across the seal between a stator and rotator into the housing containing the process fluid. The process fluid in the housing has a lower pressure than the buffer fluid in the intermediate chamber. The other seal pumps the buffer fluid to an environment external to the housing, such as ambient, which is at a pressure lower than the buffer fluid in the intermediate chamber.
To accomplish this pumping, each seal includes spiral grooves on either the face of the stator or rotor. The grooves are angled relative to the radius and circumference of the rotating shaft, and when the rotator is rotating, the grooves pump the buffer fluid across the seal. This pumping of the high-pressure buffer fluid toward the lower-pressure external environment or process fluid inhibits the loss of the process fluid from the housing. U.S. Pat. No. 5,375,853 discloses a seal design of this type.
In another design, grooved face seals are used in pumps to provide a seal between a high-pressure gas (e.g., a combustible gas) and the ambient atmosphere. In this situation, two seals are commonly used. A grooved inner seal pumps the high pressure gas to an intermediate chamber, and a grooved outer seal pumps from the intermediate chamber to the atmosphere. The intermediate chamber routes the high-pressure gas to a flare stack where the pumped gas is burned. The amount of high-pressure gas that is lost through the outer seal is thereby minimized. An example of this type of seal is disclosed in U.S. Pat. No. 5,217,233.
SUMMARY OF THE INVENTION
The present invention recognizes that grooved face seals are useful in applications other than in a fluid pump. For example, it has been discovered that grooved face seals provide significant benefits in terms of reduced heat generation and longer seal life when used in aerospace applications, such as on gear boxes, starters, constant speed drives and integrated drive generators. In fact, in some situations, significant benefits can be achieved by using grooved face seals to replace existing non-grooved seals. Surprisingly, this also has been found to work in situations where the seal is exposed to atmospheric pressures substantially less than 14.7 psia, such as when the seal is being used in an aerospace application (e.g., an aircraft) at altitude. In addition, the present invention has discovered a cost-effective method for forming the grooves on the seal rings, thereby making the grooved seals applicable to a larger number of applications where cost may be an issue. Furthermore, a unique and simple hydropad configuration has been developed.
In one aspect, the present invention provides an aerospace housing and shaft assembly comprising a housing, a shaft rotatably mounted within the housing, a seal assembly operatively positioned between the housing and the shaft, and low pressure air (e.g., atmospheric air) having a pressure substantially less than 14 psia and being positioned on one side of the seal assembly. The seal assembly includes a first seal ring mounted on the housing, and a second seal ring mounted on the shaft in facing relation to the first seal ring. One of the first seal ring and the second seal ring includes a hydropad. Preferably, the hydropad is positioned to pump from the inner diameter toward the outer diameter. For example, the low-pressure air can be positioned on the inner diameter of the seal assembly, in which case the hydropad would pump the low-pressure air. In a preferred embodiment, the low-pressure air has a pressure less than about 10 psia, and more preferably less than about 5 psia.
The present invention also provides a method of producing a seal assembly having a seal ring. The method comprises the steps of positioning the seal ring in alignment with a media blaster, placing a template between the seal ring and the media blaster, and forcing media from the media blaster, through the openings in the template, and into contact with the seal ring. The seal ring can then be mounted in a seal assembly. In one embodiment, ceramic beads are used as the blast media. The positioning step can include the step of mounting the seal ring on a holder. Preferably the holder is rotated while the media is being forced at the seal ring. To obtain better results, a timer can be used to insure that the blast time is consistent.
The present invention also recognizes that hydropads do not need to be spiral in shape. More specifically, the hydropads can include an inner edge oriented substantially circumferentially, an outer edge oriented substantially circumferentially and spaced radially outward from the inner edge, a leading edge interconnecting the inner edge with the outer edge, and a trailing edge interconnecting the inner edge with the outer edge. Both the leading edge and the trailing edge are substantially straight and oblique to a radial direction. Preferably, to simplify the design, the inner edge and the outer edge are also both substantially straight. In one embodiment, the leading edge is positioned at an angle relative to the radial direction passing through a mid-point of the leading edge, and the trailing edge is positioned at the same angle relative to the radial direction passing through a mid-point of the trailing edge.
A more detailed description of a specific embodiment of the present invention is illustrated and described below.


REFERENCES:
patent: Re. 34319 (1993-07-01), Boutin et al.
patent: 3499653 (1970-03-01), Gardner
patent: 3744805 (1973-07-01), Heinrich
patent: 3804424 (1974-04-01), Gardner
patent: 4212475 (1980-07-01), Sedy
patent: 4290611 (1981-09-01), Sedy
patent: 4407513 (1983-10-01), Takenaka et al.
patent: 4423879 (1984-01-01), Takenake et al.
patent: 4768790 (1988-09-01), Netzel et al.
patent: 4836561 (1989-06-01), Lebeck et al.
patent: 4884945 (1989-12-01), Boutin et al.
patent: 4887395 (1989-12-01), Lebeck et al.
patent: 4889348 (1989-12-01), Amundson et al.
patent: 5039113 (1991-08-01), Gardner
patent: 5054938 (1991-10-01), Ide
patent: 5071141 (1991-12-01), Lai et al.
patent: 5090712 (1992-02-01), Pecht et al.
patent: 5143384 (1992-09-01), Lipschitz
patent: 5169159 (1992-12-01), Pope et al.
patent: 5172918 (1992-12-01), Pecht et al.
patent: 5174584 (1992-12-01), Lahrman
patent: 5199172 (1993-04-01), Runowski
patent: 5201531 (1993-04-01), Lai
patent: 5215385 (1993-06-01), Ide
patent: 5217233 (1993-06-01), Pecht et al.
patent: 5222743 (1993-06-01), Goldswain et al.
patent: 5224714 (1993-07-01), Kimura et al.
patent: 5249812 (1993-10-01), Volden et al.
patent: 5253876 (1993-10-01), Gardner et al.
patent: 5281032 (1994-01-01), Slocum
patent: 5312117 (1994-05-01), Takenaka et al.
patent: 5375853 (1994-12-01), Wasser et al.
patent: 5375855 (1994-12-01), Goldswain et al.
patent: 5385409 (1995-01-01), Ide
patent: 5399024 (1995-03-01), Shapiro
patent: 5441283 (1995-08-01), Pecht et al.
patent: 5454572 (1995-10-01), Pospisil
patent: 5490679 (1996-02-01), Borrino et al.
patent: 5492341 (1996-02-01), Pecht et al.
patent: 5496047 (1996-03-01), Goldswain et al.
patent: 5529315 (1996-06-01), Borrino et al.
patent: 5538260 (1996-07-01), Takenaka et al.
patent: 5605339 (1997-02-01), Pecht et al.
patent: 5941532 (1999-08-01), Flaherty et al.
patent: 6142478 (2000-11-01), Pecht et al.
patent: 0369295

Affiliated with

Also associated with

Rating

Aerospace housing and shaft assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Aerospace housing and shaft assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aerospace housing and shaft assembly will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2492719