Patent Application
20050242528
The present invention relates to a fluid seal for use in sealing a rotating member and more particularly, to a mechanical face seal assembly.
Mechanical face seal assemblies are often used to provide a fluid seal between a housing member and a shaft, one of which is rotating with respect to the other. Typically, the housing is stationary and the shaft is rotating. The mechanical face seal prevents fluid loss for between the shaft and the housing.
A mechanical face seal assembly normally includes a seal ring or washer and a mating seal seat. The seal seat is mounted such that it rotates with the shaft while the seal washer remains stationary. The seal washer is axially loaded; i.e., a spring or other force transmitting member urges the seal washer in the axial direction of the shaft. The axially transmitted force urges the seal washer into engagement with the seal seat to provide the fluid seal. Seal assemblies of this type are known as dynamic seals in that one of the seal elements, in this case the seal washer, moves axially with respect to a corresponding seal seat. In typical mechanical face seals, the seal seat member is in a form of an annular ring and does not serve any other purposes other than to act as the mating surface against the seal washer.
According to the present invention, the seal seat is provided with an additional hub portion to which other components can be mounted for rotation with the shaft. For example, for mechanical face seals used in a dishwasher, other rotatably driven members such as particle cutters, pump impellers, or other rotatable members as is known in the art can be mounted to the hub portion. The seal seat member is made from powder metal with different densities in the hub portion and seal seat portion. The hub portion is provided with a higher density than the seal seat portion in order to provide the hub portion with better structural characteristics, such as hardness, impact strength, improved yield stress and crush strength. The lower density in the seal seat region allows for higher levels of lubrication to be impregnated in the seal seat portion while allowing minimal lubrication impregnation in the hub portion. The higher density hub portion also has a higher coefficient of thermal conductivity than the seat. The higher density hub portion takes heat away from the seal seat portion to prevent the seal seat portion from wearing prematurely.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
a is a perspective view of an exemplary face seal seat according to the principles of the present invention;
b is a top plan view of the seal seat shown in
c is a bottom plan view of the seal seat shown in
d is a cross-sectional view taken along line D-D of
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
With reference to
The hub portion 22b includes a centrally disposed aperture 24 having a pair of flats 26 which non-rotatably engage a shaft inserted therethrough (not shown). The hub portion 22a is also provided with external mounting features 28 (best shown in
The seal seat member 22 is formed of powder metal with the hub portion 22b being formed integrally with the seal seat portion 22a as a unitary piece. The density of the powder metal in the hub portion is higher than the density of the powder metal in the seat portion 22a as illustrated by the cross-hatched portion in the hub portion 22b. The greater density in the hub portion 22b allows for better structural characteristics, such as hardness, impact strength, improved yield stress, and crushed strength. The better structural characteristics in the hub portion 22b is desirable since it connects the mechanical face seal seat to the shaft, and must have different characteristics than the seal seat portion 22a. The higher density hub portion 22b also has a higher coefficient of thermal conductivity than the seat portion 22a. Thus, the hub portion 22b takes heat away from the seal seat 22a to prevent the seal seat 22a from heating up and wearing prematurely.
The design of the present invention allows for various levels of impregnation within the seal seat member 22 so that presently used vacuum impregnation systems can be used without the need to mask certain portions of the mechanical face seal seat. This allows the impregnation of lubrication to be maximum on the mechanical face seal seat contact area and minimal in the hub area 22b where it is not needed. The various levels of impregnation that are obtainable reduces the amount of impregnation that slings off of the part since less impregnation is needed and the higher density hub portion has smaller pores. The smaller pores create a capillary effect, and when the mechanical face seal seat and hub is not spinning, and no heat is being generated, the impregnation is sucked back into the hub portion 22b and the seal seat portion 22a and off of the contact area surface through the capillary action such that there is less impregnation material left on the mechanical face seal seat to be slung off. This may also decrease the amount of torque required at initial start-up since less impregnation material on the mechanical face seal seat will reduce the amount of bond between the mechanical seal seat face and the mechanical seal washer face 20.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
