Abstract:
A split mechanical face seal having a rotating seal assembly comprising a rigid seal ring of split ring segments and a pair of attachable body ring segments holding the rotating seal ring segments together when the body ring segments are attached, a stationary seal ring assembly comprising a rigid seal ring of split ring segments and a pair of attachable housing segments holding the stationary seal ring segments together when the housing segments are attached, a single segment retainer ring having a split forming first and second opposing end faces, the retainer ring being made of a flexible material, the retainer ring being operatively engaged with the stationary seal ring segments and resilient members carried by the retainer ring and operatively engageable with axially facing abutments formed in the housing segments when the housing segments are attached such that the retainer ring exerts a biasing force against the stationary seal ring segments in a direction toward the rotating seal ring segments.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to mechanical seals for pumps and other machinery having rotating shafts and, more particularly, to a split mechanical face seal. 
     2. Description of the Prior Art 
     Mechanical seals are used in a wide variety of machines, e.g., pumps, having rotating shafts that pass through housings in order to prevent leakage of pressurized fluids. In one type of mechanical seal, the rotary face seal, sealing is achieved by arranging at least two rigid, durable sealing rings having flat, radially extending sealing surfaces axially adjacent each other and concentrically about the shaft so that the faces are in sealing contact. One seal ring is held stationary in the seal housing or gland while the other rotates with the shaft. 
     Repair or replacement of parts of such seals is difficult whenever inaccessibility of the outboard end of the shaft or the location of this machine makes it impossible to take the seal off the end of the shaft. In such situations, the machines themselves must be disassembled. 
     One solution to this problem has been to split the sealing rings and other seal parts radially into two or more segments so that each ring may be removed from the seal and new rings reassembled within the seal and about the shaft as disclosed, for example, in U.S. Pat. Nos. 4,576,384 and 5,961,122, both of which are incorporated herein by reference for all purposes. 
     Split mechanical face seals of the prior art typically have numerous parts. For example, it is common in split face seals to bias the stationary face seal against the rotating face seal by means of a plurality of springs carried in the gland or housing of the mechanical seal. In assembling split seals employing multiple springs for biasing purposes, it is not uncommon for the springs to fall out of the gland or other spring retainer during assembly, making the assembly job tedious and time-consuming. Furthermore, it is difficult to hold various parts of the split seal assembly in concentric relationship with the shaft on which they are mounted during assembly. 
     SUMMARY OF THE INVENTION 
     It is therefore an object ofthe present invention to provide a split mechanical face seal that is easy to assemble and disassemble. 
     Another objects of the present invention is to provide a split mechanical face seal wherein the biasing members are carried on a single piece spring retainer. 
     Yet another object of the present invention is to provide a split mechanical face seal having a removable alignment sleeve for ease of assembly. 
     The above and other objects of the present invention will become apparent from the drawings, the description given herein and the appended claims. 
     In one embodiment, the split mechanical face seal of the present invention includes a rotating seal ring assembly having a rigid seal ring of split ring segments forming rotating seal ring faces and a pair of attachable body ring segments holding the rotating seal rings segments together when the body ring segments are attached. There is also a stationary seal ring assembly comprising a rigid seal ring of split ring segments forming stationary seal ring faces and a pair of attachable housing segments holding the stationary seal ring segments together when the housing segments are attached. A single segment retainer ring has a split forming first and second opposing end faces. The retainer ring is made of a material that has sufficient flexibility such that the first and second end faces can be spread apart by a distance at least equal to the diameter of the circle formed when the first and second faces are in engagement. The retainer ring has first and second axially facing surfaces, the retainer ring being operatively engaged with the stationary seal ring segments to apply a biasing force thereto by means of resilient members carried by the retainer ring and that engage axially facing abutments formed by the housing segments when the housing segments are attached. 
     In another embodiment of the present invention, there is provided a split mechanical face seal with a positioning collar or sleeve that holds the stationary seal ring assembly in a generally concentric relationship with respect to a shaft upon which the face seal is mounted, the positioning collar being removable when assembly of the split mechanical face seal is completed. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     FIG. 1 is an end, elevational view, partly in section, of the split mechanical face seal of the present invention; 
     FIG. 2 is a cross-sectional view taken along the lines  2 — 2  of FIG. 1; 
     FIG. 3 is a view similar to FIG. 2 but showing the positioning collar; 
     FIG. 3 is a cross-sectional view taken along the lines  3 — 3  of FIG. 1; 
     FIG. 4 is a cross-sectional view taken along the lines  4 — 4  of FIG. 3; 
     FIG. 5 is a cross-sectional view taken along the lines  5 — 5  of FIG. 3; 
     FIG. 6 is a cross-sectional view taken along the lines  6 — 6  of FIG. 3; 
     FIG. 7 is a fragmentary, elevational view, partly in section, of an O-ring used in a split mechanical face seal of the present invention; 
     FIG. 8 is a planar view of an installer ring for use in installing the rotating seal segments of the mechanical seal of the present invention; and 
     FIG. 9 is a view taken along the lines  9 — 9  of FIG.  8 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference now to the drawings, FIG. 1 shows the mechanical seal, shown generally as  10 , affixed to a rotating shaft, e.g., a pump shaft,  12 . As can be seen, mechanical seal  10  comprises gland or housing segments  14  and  16  that are attachable to one another by means of bolts  18  and  20 . Gland segment  14  is provided with a lubricant port  22  that communicates with a passageway  24  by means of which a lubricant fluid can be introduced internally of mechanical seal  10 , port  22  being selectively closed with a removable plug  26 . In like fashion, gland half  16  is provided with a lubrication system and plug  28 . Mechanical seal  10  is secured to the stuffing box  31  of a pump or the like, gland or housing segment  14  being secured by means of a threaded bolt  30  in a slot  33 , gland segment  16  being secured by means of a threaded bolt  32  received in a slot  34 . As best seen in FIG. 2, gland segments  14 ,  16  are sealed to stuffing box  31  by means of semicircular gaskets  31   a  and  31   b.    
     It will be understood that gland segments  14  and  16  are identical to one another to the extent that if gland section  14  is rotated 180° around shaft  12 , it will be identical to gland segment  16 . Accordingly, with reference to FIG. 3, the mechanical seal of the present invention will be described with respect to gland  16 . Gland  16  has a gland face  16   a . Formed in gland face  16   a  is a generally G-shaped groove  16   b  (see FIG. 4) in which is positioned complementary-shaped gasket  16   c . An aligning pin  16   d  protruding from gland face  16   a is received in a registering bore in the mating face of gland  14 , while an aligning pin  14   d  is likewise received in a registering bore in gland face  16   a . When the gland segments  14  and  16  are attached, the gaskets  16   c  will be received in the registering grooves, as seen in FIG.  4 . 
     As seen in FIG. 2, gland segment  14  is provided with generally semicircular, internally formed recesses  36 ,  38 ,  40 , and  42 , while gland segment  14  is provided with registering semicircular, internally formed recesses  44 ,  46 ,  48 , and  50 . It will be appreciated that when the gland halves  14  and  16  are connected, as shown, recesses  36  and  44  cooperate to form an annular recess, as is the case with recesses  38 ,  46 ;  40 ,  48 ; and  42 ,  50 . Recess  36  in gland segment  14  is partially defined by an end wall  52 , while recess  44  in gland segment  16  is partially defined by an end wall  54 , end walls  52  and  54  cooperating to define an annularly extending, axially facing coplanar engagement surface when gland segments  14  and  16  are connected, as shown. Recess  42  is partially defined by an end wall  56 , opposite end wall  52 , while recess  50  is partially defined by an end wall  58 , opposite end wall  54 . When gland segments  14  and  16  are attached, end walls  56  and  58  cooperate to define an axially facing, annularly extending coplanar abutment. 
     Received in recess  36 ,  44  is a rotating seal ring assembly, shown generally as  60 . Seal assembly  60  comprises a first body segment  62  and a second body segment  64  (see FIG. 2) that are identical and that are generally semicircular and attachable by means of bolts, one of which is shown in FIG. 5 as  66 , the other of which is shown in FIG. 3 as  68 . Body segments  62  and  64  are provided with registering O-ring grooves  70  and  72 , respectively, that receive a split O-ring  74  to effect a seal between body segments  62  and  64  and shaft  12 . As disclosed more fully in U.S. patent application Ser. No. 09/656,190, entitled “Method and Apparatus for Applying a Split Mechanical Seal to a Rotatable Shaft,” filed contemporaneously herewith, naming Michael A. London as inventor, and incorporated herein by reference for all purposes, it will be appreciated that when bolts  66  and  68  are tightened to attach body segments  62  and  64  together, body segments  62 ,  64  essentially form a unitary body that is tightly clamped onto, and rotates with, shaft  12 . For ease of assembly, an aligning pin  76  is received snugly in a bore  78  in body segment  64  and loosely received in a registering bore  80  in body segment  62 . Conversely, a second aligning pin is received snugly in a bore in body segment  62  and loosely received in a registering bore, such as bore  80  in body segment  64 . As more fully disclosed in U.S. patent application Ser. No. 09/656,190, the aligning pins, e.g. pin  76 , serve to prevent relative axial movement between body segments  62  and  64  but permit limited radial, flexing movement between body segments  62  and  64 , ensuring tight engagement of body segments  62  and  64  with shaft  12 . The mating end faces of body segments  62  and  64  are identical and, as shown with respect to body segment  62 , are provided with Z-shaped channels in which are received Z-shaped gaskets, e.g. gasket  88 , Z-shaped gasket  88  having a portion received in Z-shaped grooves  62   b  in body segment  62  and a portion received in Z-shaped grooves  64   b  in body segment  64 . It will thus be seen that when bolts  66  and  68  are tightened, body segments  62  and  64  will be securely affixed to shaft  12  and will be in fluid-tight engagement with one another by virtue of Z-shaped gaskets  88 . 
     Body segment  62  is provided with an axially extending lip  100 , while body segment  64  is provided with an axially extending lip  102 . Lips  100  and  102  in turn have radially outwardly opening registering grooves  104  and  106 , respectively. In effect, lips  100  and  102 , when body segments  62  and  64  are attached, form a radially outwardly extending annular recess having recess portions  108  and  110 . Received in recess portion  108  is a rotating seal ring segment  112 , while a rotating seal ring segment  114  is received in recess  110 . A split O-ring  116  connected by a ball and socket arrangement (see FIG. 7) provides sealing between seal ring segments  112  and  114  and the lip portions  100  and  102  of body segments  62  and  64 , respectively. A drive pin  105  received in a ball in body segment  62  and a registering recess  107  in seal segment  112  ensures that the seal segments  112 ,  114  rotate with the body segments  62 ,  64 . 
     The stationary seal assembly, shown generally as  120 , includes stationary seal ring segments  122  and  124 . Stationary seal ring segments  122  and  124  have lapped seal faces that engage lapped seal faces on rotating seal ring segments  112  and  114 , as shown at  126 . Seal ring segment  122  is generally L-shaped when viewed in transverse cross-section and has an axially extending portion  128  that is received in recess  42 , while rotating seal ring segment  124  has an axially extending portion  130  that is received in recess  50 . It will be seen that when the mechanical seal  10  is assembled, seal segments  122  and  124  form a counterbore  134 . 
     A retainer ring  132  has an axially extending lip  136  that is received in counterbore  134 . Unlike the components heretofore described, which are basically segmented into two pieces with the exception of the O-rings, retainer ring  132  is a single segment having one butt cut, as shown in FIG. 3, thereby forming opposed end faces, one end face being shown as  137 . Retainer ring  132  has a first axially facing surface  140  that abuts seal ring segments  122  and  124  and a second axially facing surface  142  in which are formed a plurality of circumferentially disposed cylindrical bores  144 , a series of compression coil springs  146  being positioned in bores  144 . As can be seen, springs  146  engage end wall  56  and  58  of housing segments  14  and  16  and accordingly serve to bias retainer ring  132  against stationary seal ring segments  122  and  124 , with the concomitant result that the seal faces on the stationary seal segments  122 ,  124  are forced into sealing engagement with the seal faces on rotating seal segments  112  and  114 . Further, since body segments  62  and  64  are in engagement with end wall  52  and  54  of gland segments  14  and  16 , the stationary seal faces formed on stationary seal ring segments  122  and  124  remain in engagement with the seal faces on rotating seal ring segments  112  and  114 . Radial sealing between seal ring segments  122 ,  124  and gland segments  14 ,  16  is accomplished by a split O-ring  125 . 
     To prevent stationary seal ring segments  122 ,  124  and retainer ring  132  from rotating, an anti-rotation pin  150  is received axially through a bore in retainer ring  132 , one end of anti-rotation pin  150  being received in a recess  152  and stationary seal segment  124 , the other end of pin  150  being received in a slot  154  of housing segment  16 . 
     As noted, retainer ring  132  is of a single segment having a butt cut or single slice forming opposed end faces, the opposed faces when in engagement forming a circular ring. Retainer ring  132  is made of a material that has sufficient flexibility that the opposed end faces, as described above, can be separated by a distance equal to the diameter of the circular ring formed when the end faces are in engagement. Although a split retainer could be made of certain metals that have the requisite flexibility, more generally retainer ring  132  would be made of a plastic or polymeric material or a composite, materials such as polytetrafluorethylene, certain polyolefins, nylon, certain polyurethanes, fiberglass composites, and the like being preferred. It will be apparent that the material from which retainer ring  132  is made must be sufficiently hard so as to not be deformed to the point that the biasing effect of the springs is lost or greatly minimized. An advantage of using a polymeric material such as polytetrafluoroethylene is that when bores are used to retain the individual springs, the bores can be made slightly undersized so as to hold the springs in place while the retainer ring is being manipulated during installation. 
     While coil springs are shown as the biasing means, it would be possible to use other resilient means carried by the retainer ring. For example, individual leaf springs could be mounted on the retainer ring as long as such rings did not interfere with the ability to spread the end faces of the retainer ring sufficiently to place it over the shaft on which the mechanical seal is to be mounted, with the retainer ring then assuming its relaxed position—i.e., with the end faces abutting or at least adjacent one another. Also, a resilient member that could be opened—i.e., spread like retainer ring  132 —could be employed. 
     As noted above, normally the installation of split mechanical face seals of the type under consideration poses a problem because of the fact that inherently there are numerous parts, e.g., the gland segments, the stationary seal segments, and, if carried by a retainer ring according to the present invention, the biasing springs, that need to be maintained substantially coaxial with the shaft on which they are being mounted. To alleviate this problem, as shown in FIG. 2 a , the present invention provides a positioning collar or spacer, shown generally as  200 . Collar  200  is again of a single segment having a single split or butt cut forming opposed end faces, one of which is shown as  202 . Collar  200  has an enlarged head portion  204  that has an outer diameter greater than the diameter formed by the bore of the gland segments  14 ,  16  when the gland segment are attached. Accordingly, the positioning collar or sleeve is prevented from being pushed inside of the gland segments  14 ,  16 . The collar  200  can be made of polymeric materials, such as those name above with respect to retainer ring  132 . While the positioning collar is particularly useful where there are stationary seal ring segments and a retainer ring or other supports, separate from the gland segments, for holding biasing springs, the collar can also be used with advantage where there are only gland segments and stationary seal ring segments, e.g., where the biasing springs are carried by the gland segments. 
     In installing the mechanical seal of the present invention on a shaft such as a pump shaft, the rotary seal assembly is first positioned on the shaft. In this regard, the body segments are first positioned around the shaft, the body segments being tightened together sufficiently to hold together but still allow the rotary seal ring segments to be positioned into the body segments. The stationary seal assembly can then be installed, the retaining ring being engaged with one of the stationary seal ring segments such that the anti-rotation pin is engaged. The positioning collar is then spread and positioned on the shaft to hold the stationary seal ring segments and retainer ring in a concentric relationship around the shaft, the stationary seal assembly being moved up against the rotary seal assembly. Lastly, the gland segments are positioned over the rotary and stationary seal assemblies and the positioning collar, care being taken to ensure that the anti-rotation pin is received in a gland slot. Once the gland segments have been tightened together, the now unitary gland can be securely tightened to the stuffing box. At this point, the positioning collar can be removed (see that collar  200  is shown in phantom in FIG.  2 ), and the mechanical seal is ready for operation. 
     To facilitate installation of the rotary seal segments, it is desirable to use an installer ring, shown generally as  300  in FIG.  8 . Installer ring  300  is a single segment piece having one butt cut to provide opposed end faces that can be brought into engagement to essentially form a complete annular body. Installer ring  300  can be made of the same material as described above with respect to the positioning collar and the retainer ring. Installer ring  300  includes a ring-shaped, generally flat member  302  that, prior to being butt cut, would form an annular ring from which projects a peripheral lip portion  304 . As best seen in FIG. 9, member  302  and lip  304  cooperate to form, when butt cut, end faces that are generally L-shaped when viewed in transverse cross-section. To use installer ring  300 , the rotating seal ring segments  112  and  114  are positioned such that the portions thereof that form the seal faces are placed against the surface  306  of member  302 . In this regard, it should be observed that installer ring  300  has the same flexibility as that described above with respect to the positioning collar. It will be appreciated that once the seal faces of the rotating seal ring segments are pressed against surface  306 , the peripheral lip  304  will engage the radially outermost portions  112   a  and  114   a  (see FIG. 2A) of rotating seal segments  112  and  114 . Accordingly, rotating seal rings segments  112  and  114  are now held with their seal faces coplanar because they are in engagement with the surface  306  of member  302 . Additionally, lip  304  holds the seal ring segments in a generally concentric relationship with respect to shaft  12 . Accordingly, in installing the rotating seal ring segments, an installer ring would be placed around the shaft  12 , following which the rotating seal ring segments would be placed into the installer ring as described above whereupon the assembly comprised of the installer ring and the rotating seal ring segments could be held in place and moved axially into body segments  62  and  64 , at which point installer ring  300  can be removed and the assembly of the mechanical seal completed. 
     The foregoing description and examples illustrate selected embodiments of the present invention. In light thereof, variations and modifications will be suggested to one skilled in the art, all of which are in the spirit and purview of this invention.