Patent Publication Number: US-2020300368-A1

Title: Mechanical seal

Description:
BACKGROUND OF THE INVENTION 
     Technical Field of the Invention 
     The present invention relates, generally, to a mechanical seal which acts to retain effective sealing in varying temperature applications by maintaining the integrity of the mechanical seal between the face and its holder. 
     Description of the Prior Art 
     Mechanical seals are of common place in a multitude of industries for providing a seal between rotating and stationary components. The seal is created by one sealing face rotating against a stationary sealing face. It is a known issue that inserted faces are limited to a certain temperatures before thermal expansion causes the inserted face to become loose within its holder. This problem leads to ineffective sealing between the seal face and its holder which can result in catastrophic seal failure. 
     From prior art, this problem has been attempted to be rectified through the use of a holder constructed of specific materials of a very similar coefficient of thermal expansion to the seal face material. These materials, in which the seal face is held, are often not resistant to corrosion and/or still expand at slightly different rates in comparison to the seal member material. This limits the applications in which the seal can be installed. In addition, an effective secondary seal can be achieved through the use of an elastomeric or compressive member. However their performance is limited to certain temperatures. These factors limit the applications in which the seal can be installed. This problem can be solved by creating a more effective seal using alternative means. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed, but not solely limited, to a mechanical seal assembly for sealing a rotatable shaft to a fixed housing, the mechanical seal comprising rotational components fixed relative to the shaft and stationary components fixed relative to the housing; the one or more rotational components comprise of one or two rotational primary sealing members, each contacting different multiples of springs or one or more energizing elements to provide seal face pressure, The rotational components further comprise means for axially and radially retaining the one or more primary sealing members. The primary sealing members are also driven by the rotational or stationary components. The one or more primary sealing members comprise a secondary seal, which is between (and including) 1 and 20 light bands of flatness concave, convex or concave/convex. All aforementioned parts are housed within a gland to enable easy installation. 
     Preferably, the axial and radial retaining is achieved by an additional member. 
     More preferably, the additional member is of annular shape. 
     More preferably, the additional member may be split into a plurality of sections. 
     Preferably, the annular-shaped additional member is shaped so that it radially retains the primary sealing member. 
     Preferably, the inner diameter of the annular additional member is radially offset from the outer diameter of the primary sealing member. 
     More preferably, the offset allows for thermal expansion of the primary sealing members. 
     More preferably, the offset can be calculated such that it is optimized. 
     Preferably, the annular additional member is shaped so that it axially retains the primary sealing member. 
     More preferably, the axial retention is offset from the primary sealing member. 
     More preferably, the offset allows for thermal expansion of the primary sealing members. 
     More preferably, the offset is calculated such that it is optimized. 
     Preferably, the additional member is adjoined to one or more of the rotating or stationary parts through a fixing method. 
     More preferably, the fixing method is an interference fit. 
     More preferably, and alternatively, the fixing method is a shrink fit. 
     More preferably, and alternatively, the fixing method is a thread. 
     More preferably, and alternatively, the fixing method is an adhesive. 
     More preferably, and alternatively, the fixing method is a weld. 
     More preferably, more than one fixing method may be utilized. 
     Preferably, the annular member is retained axially located and/or retained by one or more of the rotating or stationary part or parts. 
     Preferably, the effective secondary seal is achieved at the interface between the adjacent parts to the primary sealing member. 
     More preferably, the interface is lapped. 
     More preferably, the interface is harden-coated. 
     More preferably, the interface allows for radial sliding movement between the faces at varying temperatures 
     More preferably, the sliding motion allows the seal face distortion to be controlled. 
     Preferably, the effective secondary seal is preferably lapped between (or including) 1-2 light bands. 
     Other objects and features of the present invention will become apparent when considered in combination with the accompanying drawing figures, which illustrate certain preferred embodiments of the present invention. It should, however, be noted that the accompanying drawing figures are intended to illustrate only select preferred embodiments of the claimed invention and are not intended as a means for defining the limits and scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       In the drawing, wherein similar reference numerals and symbols denote similar features throughout the several views: 
         FIG. 1  is a cross-sectional view of the prior art apparatus; 
         FIG. 2  is a cross-sectional view of an embodiment of a mechanical seal in accordance with the present invention; 
         FIG. 3  is a detailed view from of the mechanical seal of  FIG. 2 ; 
         FIG. 4  is a detailed view of the mechanical seal of  FIG. 2  showing an alternative design with a hard coating; and, 
         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 
     The invention will now be described, by way of example only, with reference to the accompanying drawings: 
     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. 
     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  7   a,    7   b.  A seal is created via the stationary sealing members  8   a,    8   b  being in contact with the rotational sealing members  7   a,    7   b.  The inboard rotational sealing member  7   a  is provided with a driving force by a drive pin  9 . The outboard rotational sealing member  7   b  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  7   a,    7   b,    8   a,    8   b  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 . 
     Now referring to  FIG. 3  of the accompanying drawings, there is shown a detailed view of the rotary sealing members  7   a,    7   b.  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 (α) from the outer diameter of the primary rotary sealing member  16 . The offset (α) 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  8   a,    8   b.    
     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. 
     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 . 
     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.