MECHANICAL SEAL

Abstract

A mechanical seal assembly has rotational and stationary sealing members) and a drive unit, which is axially adjacent one of the sealing members. An energizing member urges the drive unit towards the sealing members. A retainer axially and radially retains one of the sealing members. The drive unit is in contact with one of the rotational and stationary members by way of contacting surfaces which are in the range of 1 and 20 light bands of flatness, inclusive.

Claims

1-18. (canceled)

19. A mechanical seal assembly for sealing a rotatable shaft to a fixed housing, comprising: a rotary component comprising a rotational sealing member; a stationary component comprising a stationary sealing member, said rotational sealing member and said stationary sealing member having first contacting surfaces for providing a primary seal; a drive unit axially adjacent one of said rotational sealing member and said stationary sealing member, said drive unit being in contact with one of said rotational sealing member and said stationary sealing member via second contacting surfaces for providing a secondary seal, said second contacting surfaces being in a range of 1 and 20 light bands of flatness, inclusive; an energizing member in contact with, and urging, said drive unit toward said rotational sealing member and said stationary sealing member; and, a retainer located on said drive unit and said one of said rotational sealing member and said stationary sealing member for axially and radially retaining one of said rotational sealing member and said stationary sealing member, wherein an inner diameter of said retainer is radially offset from an outer diameter of one of said rotational sealing member and said stationary sealing member, said retainer being radially offset allowing for thermal expansion of said primary seal, said secondary seal being movable when the thermal expansion occurs for inhibiting distortion of one of said rotational sealing members and said stationary sealing member.

20. The mechanical seal assembly according to claim 19, wherein said contacting surfaces have a concave shape, a convex shape or a concave/convex shape.

21. The mechanical seal assembly according to claim 19, wherein said retainer has an annular shape.

22. The mechanical seal assembly according to claim 19, wherein said retainer is split into a plurality of sections.

23. The mechanical seal assembly according to claim 19, wherein said retainer being radially offset allows for radial thermal expansion of said primary seal.

24. The mechanical seal assembly according to claim 19, wherein said retainer being radially offset allows for axial thermal expansion of said primary seal.

25. The mechanical seal assembly according to claim 19, wherein said retainer is adjoined to said drive unit.

26. The mechanical seal assembly according to claim 25, wherein said retainer is an interference fit with said drive unit.

27. The mechanical seal assembly according to claim 25, wherein said retainer is connected to said drive unit via a shrink fit.

28. The mechanical seal assembly according to claim 25, wherein said retainer is connected to said drive unit via a thread.

29. The mechanical seal assembly according to claim 25, wherein said retainer is connected to said drive unit via an adhesive.

30. The mechanical seal assembly according to claim 25, wherein said retainer is connected to said drive unit via a weld.

31. The mechanical seal assembly according to claim 19, wherein said second contacting surfaces through both primary and secondary seal faces are lapped.

32. The mechanical seal assembly according to claim 19, wherein said first contacting surfaces and second contacting surfaces are harden-coated.

33. The mechanical seal assembly according to claim 19, wherein said first contacting surfaces and second contacting surfaces allow for sliding movement therebetween at varying temperatures.

34. The mechanical seal assembly according to claim 34, wherein said sliding movement allows for controlling seal face distortion.

35. The mechanical seal assembly according to claim 19, wherein said second contacting surfaces are lapped in a range of 1-2 light bands, inclusive.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0031] In the drawing, wherein similar reference numerals and symbols denote similar features throughout the several views:

[0032] FIG. 1 is a cross-sectional view of the prior art apparatus;

[0033] FIG. 2 is a cross-sectional view of an embodiment of a mechanical seal in accordance with the present invention;

[0034] FIG. 3 is a detailed view from of the mechanical seal of FIG. 2;

[0035] FIG. 4 is a detailed view of the mechanical seal of FIG. 2 showing an alternative design with a hard coating; and,

[0036] FIG. 5 is a detailed view of mechanical seal of FIG. 2 showing an alternative design incorporating drive lugs within the face retainer.

DETAILED DESCRIPTION OF THE DRAWING FIGURES AND PREFERRED EMBODIMENTS

[0037] The invention will now be described, by way of example only, with reference to the accompanying drawings:

[0038] Turning now, in detail, to the accompany drawing figures, with respect to FIG. 1, there is shown the prior art. The primary sealing member 1 is held within its holder 2 via an interference fit. The holder 2 is constructed from a material which has a similar coefficient of thermal expansion to the primary sealing member 1. However, there is still a minor difference in the coefficient of thermal expansion of the face of the primary sealing member 1 and the holder 2, which leads to loss of seal integrity at varying temperatures. The material which is commonly selected for the holder 2 is also not corrosive-resistant against substances being pumped.

[0039] Referring to FIG. 2, there is shown the sleeve 3 which is detachably attached to the shaft 4 by means of a plurality of grub screws 5. The grub screws are housed within a clamp ring 6 and provide rotational drive to the sleeve 3 and rotational sealing members 7a, 7b. A seal is created via the stationary sealing members 8a, 8b being in contact with the rotational sealing members 7a, 7b. The inboard rotational sealing member 7a is provided with a driving force by a drive pin 9. The outboard rotational sealing member 7b is provided with drive by a plurality of bolts 10, which are fastened to the shaft 3. All the aforementioned parts are housed within the one or more glands 11. Within the one or more glands 11 there are housed barrier/buffer ports 12, 13, which allow both the inboard and outboard sealing members 7a, 7b, 8a, 8b to be cooled via a seal support system. The one or more glands 11 are then fastened to a housing 14 via another (or second) plurality of bolts 15.

[0040] Now referring to FIG. 3 of the accompanying drawings, there is shown a detailed view of the rotary sealing members 7a, 7b. The primary rotary sealing member 16 is axially adjacent to the face aligning drive unit 17. The face aligning drive unit 17 is in contact with the primary rotary sealing member 16 via a lapped surface 18. The lapped surface 18 is designed so that it is in line with the sealing width 19 of the primary rotary sealing member 16 in order to maintain seal balance. The position of alignment 19 can be altered to varying positions (X) to change the face loading or balance of the primary rotary sealing member 16. The lapped surface 18 is allowed to move when thermal expansion occurs, which inhibits any distortion of the primary rotary sealing member 16. An annular retainer 20, both axially and radially, retains the primary rotary sealing member 16 via its wrap-around profile. The annular retainer is an interference fit onto the face aligning drive unit 17 and offset () from the outer diameter of the primary rotary sealing member 16. The offset () is created to allow for thermal expansion of the primary rotary sealing member 16. The annular retainer 20 and the face aligning drive unit 17 are created from like materials with identical coefficients of thermal expansion to ensure that they expand at the same rates to maintain contact at their interference. The face aligning drive unit 17 drives the primary rotary sealing member through a series of drive pins 21. All of the aforementioned parts are energized commonly via a bellow arrangement 22 to create a positive seal against the stationary sealing members 8a, 8b.

[0041] Referring to FIG. 4 of the accompanying drawings, there is shown an alternate iteration, or alternatively preferred embodiment of the present invention. The lapped section 18 is coated 23 to enhance seal performance between the face aligning drive unit 17 and the primary rotary sealing member 16. Commonly, the coating 23 is made from a hardened material.

[0042] Finally, with reference to FIG. 5 of the accompanying drawings, there is shown an alternate iteration, or alternatively preferred embodiment of the present invention. The drive pins 21 can be replaced with an internal driving lug 31 in order to drive the primary rotary sealing member 16.

[0043] While only several embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that many modifications may be made to the present invention without departing from the spirit and scope thereof.