Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1999-06-07
2001-05-15
Melius, Terry Lee (Department: 3628)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C277S511000, C277S371000, C277S370000
Reexamination Certificate
active
06231048
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a mechanical seal incorporating a pusher ring to hold the integral parts of the seal together, in lieu of a snap ring. Socket head cap screws are inserted through the plate and threaded into the gland face, allowing for ease of repair and assemblage without the danger of possible injury from any part of the seal.
DESCRIPTION OF THE PRIOR ART
A mechanical seal provides a hydraulic seal between a rotatable element, typically, a shaft and a stationary housing of the apparatus. Such seals are associated with a fluid pump having a shaft extending through a pump housing wall, handling fluids of varying viscosity. The lower the viscosity of the fluid being handled, the tighter the seal required within the pump design.
Although these seals are most commonly employed on pump equipment, other fluid handling equipment also utilize mechanical seals. So, although the present invention is addressed in terms of pump applications, the invention is not restricted therein, but may be employed on all such equipment having mechanical seals.
The pump shaft is typically coupled to a motor through a motor shaft. The mechanical seal forms a seal between the pump shaft and the outer surface of the pump housing. Mechanical seals for such applications are commercially available and have been available for more than 25 years.
Seals, Generally
Seals, in their most common and most basic form, are known in the art and comprise rotatable components and stationary components which contact to form a seal at opposing sealing surfaces. The rotatable components include a shaft attachment means. Such a means is typically a sleeve having an inner perimeter surface which sealingly fits over the outer perimeter surface of the shaft and is connected to the shaft, by connecting means such as set screws. An “O” ring typically provides a seal between the shaft and the sleeve. There is a rotatable circumferential seal element interconnected to the sleeve so as to rotate when the shaft and sleeve rotate. The sleeve extends axially along the shaft.
The stationary components comprise a gland which extends circumferentially around the shaft. The gland abuts against the outer housing surface around the shaft. There is typically a sealing gasket interconnected to the gland and located between the gland and the housing. The gland functions as a base by which the seal is attached to the housing. The connection is typically accomplished by bolts extending from the outer housing wall. The bolts pass through slots or connecting extensions extending radially from the gland through the connecting slots or connecting extensions and secured with nuts. A stationary seal element is located between the inner circumferential surface of the gland facing the shaft (i.e. the gland inner surface) and the shaft. The stationary seal is directly or indirectly connected to the stationary gland. There are suitable means such as described in U.S. Pat. Nos. 4,832,351 and 4,989,882 to axially center the various stationary elements on the shaft. A circumferential spacing is maintained between the stationary elements, and the shaft and various of the rotating elements.
Mechanical Seals, Specifically
The mechanical seal also comprises rotatable components and stationary components. The rotatable components are interconnected to the shaft and rotate with the shaft. The stationary components are interconnected to the housing and do not rotate. The rotatable components and stationary components are positioned relative to each other so that a rotatable seal surface sealingly engages a stationary seal surface. Such a mechanical seal is particularly useful to form seals on machines which have rotatable shafts extending therefrom and fluid inside such as fluid pumps, i.e., water pumps, which have close tolerances, particularly in applications requiring the handling of caustic chemicals or flammable liquids. They are also widely used in nuclear reactor cooling systems to contain radioactive liquids. Typical mechanical seals are designed for leakage of less than one one-thousandth of one percent of the volume of the liquid pumped, per unit time.
The prior art mechanical seals date back to the early 1980's. They have existed for many years, as relative to this art. There has existed, however, safety concerns over a number of the seals because they generally employ snap rings on the seal which, while being installed or removed, can become projectiles which pose a threat to the mechanics.
Original designs used a heavy duty snap ring just inside the gland to hold the integral parts of the seal together. This snap ring was rated at upwards of 80,000 ft. lbs. of axial thrust load. This is more axial thrust load than any pump would ever experience with these seals, and was extreme for a snap ring as applied to these seals. Therefore, when the snap ring was removed, special pliers had to be employed, and risk of severe injury was possible because of the loaded spring causing the threat of projectiles.
Mechanical seals known in the art have at least one “O” ring associated with the sealing element being acted on, and in most instances, acted on by the spring. The spring forces this element toward the opposing element to form a seal. The “O” ring must form a seal not withstanding the axial movement and is known as a “dynamic-O” ring. Additionally, the dynamic “O” ring is located in an “O” ring slot which can clog. The spring must, therefore, provide force to cause the sealing elements to come together under sufficient pressure to form a seal while overcoming the resistance of the dynamic-O ring.
It would be desirable to eliminate the metal spring installed in concert with the dynamic “O” ring, and that is the present sense of the invention disclosed and claimed herein. The present invention retains all the favorable characteristics of the “O” ring, but without the disadvantages of snap ring and retaining rings, the mechanisms which create the dangerous tendency of the spring mechanisms in current art.
Additionally, the means to connect the mechanical seal to the housing is integrated into the structure of the stationary components. The mechanical seal is often set in place and removed in the small space between the pump and motor. The means to attach the seal takes up space and make access to the mechanical seal difficult for both installation and removal. A design with easier access to the seal elements at the location where the shaft extends from the housing is desirable, also an attribute of the present invention.
The present invention retains all the favorable characteristics of the “O” ring, but without the disadvantages of snap ring and retaining rings, the mechanisms which create the dangerous tendency of the spring mechanisms in current art.
PRIOR ART
U.S. Pat. No. 4,342,461, Lindsay, (Aug. 3, 1982) shows a seal assembly for sealing a rotary shaft including a rotary sealing cartridge and a stationary sealing cartridge and a flexible metal diaphragm secured to the face of the stuffing box. The use of the diaphragm eliminates the need for O-rings or springs for the purpose of self-alignment, and permits the seal assembly to accommodate caustic and high temperature fluids.
U.S. Pat. No. 4,410,190, Potter, (Oct. 18, 1983) demonstrates a sealing arrangement developed to reduce fluid pressure in the lip region wherein the annular gap between a shaft and a housing is sealed at an angle of 15°-30°.
U.S. Pat. No. 4,438,936, Schlegel, (Mar. 27, 1984) shows a secondary sealing element having a lip seal with a double contact ring to allow further dissipation of heat and low susceptibility to pressure in comparison to an O-ring.
U.S. Pat. No. 4,502,695, Choi, (Mar. 5, 1985) demonstrates a mechanical seal that prohibits leakage by providing reverse flow from an impeller secured to the shaft as the shaft rotates. O-rings are provided to prevent leakage during non-rotation. A seal cartridge is attached to a rear stuffing box by a locking bolt.
U.S. Pat. No. 4,538,821, Wallace, (Sep. 3, 1985) teaches a mechanical seal for
Law Offices of K. Patrick McKay
Melius Terry Lee
Santos Robert G.
LandOfFree
Mechanical seal incorporating a pusher ring for safe and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mechanical seal incorporating a pusher ring for safe and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mechanical seal incorporating a pusher ring for safe and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2556960