Abstract:
An improved mechanical seal for a pump includes a seal cartridge slidably received inside an end plate. The cartridge includes an outer cylindrical stator member which is slidably received in the end plate and an inner cylindrical rotor which is rotatable within the stator member. The stator member is prevented from rotation in the end plate. The stator member includes a shoulder which extends outwardly over the end plate and is captured between the end plate and the housing of the pump. A clinching collar is fixed to the rotor member and retains the rotor member of the cartridge to the pump shaft. The clinching collar may pass through the end plate while attached to the rotor member and pump shaft. Lubricating passageways in the end plate allow lubricants to circulate past the seal cartridge bearing surfaces.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) and 37 C.F.R. §1.78 of copending U.S. provisional patent application serial No. 60/181,805 filed Feb. 11, 2000. The contents of serial No. 60/181,805 are incorporated in this application. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    In the use of pumps or other rotating shaft machinery in which liquids or emulsions are present, it is necessary to prevent leakage of the liquids or emulsions from the machine. In early applications, rope or cordage was stuffed around the drive shaft to create a seal. Later, mechanical seals were developed which include a member locked to the rotating shaft and rotatable within a stationary mounting flange mounted to the body of the machine. The seal is achieved by attaching a bearing face to the shaft and another bearing face to the housing of the equipment with each face mechanically loaded against the other to form a seal between the rotating member and the mounting flange. A fluid is used to lubricate and cool the faces to avoid destruction due to friction between the two parts.  
           [0004]    Conventional seals are longitudinally compressed and longitudinally fixed within the mounting flange which is mounted to the pump body. A collar having multiple radially disposed screws is typically used to attach the rotating parts of the seal to the driven shaft. When the bearing surfaces of such mechanical seals become worn, it is necessary to remove the entire seal and mounting flange assembly and either discard the assembly or return the entire assembly to a repair facility for refurbishing. That is, prior art seals are not typically amenable to disassembly in the field of the bearing components from the mounting end plate. Because of this, users of such mechanical seals must inventory bulky and expensive spare parts which include mounting flanges.  
           [0005]    Conventional mechanical seals are also provided with spacers to maintain axial alignment of the rotating element within the mounting flange, such spacers requiring removal during installation. Frequently, seal members are located in inaccessible and tight spaces, making them difficult to remove and replace while maintaining proper axial alignment and while accessing radial set screws to retain the rotatable element of the seal to the rotatable shaft. Additionally, existing seal assemblies are provided with lubrication passageways which are dead ended at the component to be lubricated, leading to heat damage to the lubricants. There is a need for an improved mechanical seal which may be easily disassembled at the installed location and quickly repaired. A need also exists for a mechanical seal which may be more easily installed on the pump or other rotating machinery and which allows better lubrication and cooling of bearing components.  
         SUMMARY OF THE INVENTION  
         [0006]    This disclosure concerns a cartridge mechanical seal which may be used with pumps or any rotating shaft equipment requiring a liquid to be sealed in the equipment where a drive shaft enters the equipment housing from the outside through a shaft opening that would allow the liquid to leak or drain from the housing. Though pumps are a primary use for such seals, the seals may also be used in a compressor, mixer, fan, reactor, agitator, conveyor or any other rotating shaft equipment.  
           [0007]    The improved mechanical seal includes an end plate which receives a seal cartridge, the cartridge including a closely fitting cylindrical stator assembly having an axial opening through it. The stator assembly is received in a central opening in the end plate which is mounted to the housing of the pump or other rotating shaft machinery to be sealed. A rotor assembly is axially received within the cylindrical opening of the stator assembly. Opposing annular faces on the rotor assembly and the stator assembly provide bearing surfaces between the stator assembly and the rotor assembly, those bearing faces being internal to the cartridge. A clamp having a radial gap may be fixed to the rotor assembly after the cartridge has been installed in the end plate and the rotor assembly has been received on the pump drive shaft. The clamp is retained to the rotor assembly by a radial pin and the clamp is clinched around the drive shaft of the pump by a tightening screw which reduces the gap of the clamp. An annular groove in an end face of the stator assembly receives multiple locator pins which are retained in the opposing end face of the clamp. The locator pins space the clamp away from the stator assembly. The end plate and stator assembly have intake and exit openings in registry such that lubricants may flow past the bearing surfaces of the stator assembly and the rotor assembly. Because the clamp has a smaller diameter than the axial opening of the end plate, the end plate may be removed without first removing the clamp and cartridge from the drive shaft thereby facilitating removal of the seal doing during repair.  
           [0008]    It is an object of the invention to provide a field repairable mechanical seal for a pump or other rotating shaft machinery.  
           [0009]    It is also an object of the invention to provide a mechanical seal which allows disassembly of disposable bearing elements from the mounting flange of the seal.  
           [0010]    It is a further object of the invention to provide a mechanical seal which reduces the cost of and space required for inventory of spare seals and eliminates the need to keep mounting flanges as part of seal inventory.  
           [0011]    It is yet another object of the invention to provide an improved seal cartridge which may be used on multiple shapes of end plate.  
           [0012]    It is also an object of the invention to provide an improved mechanical seal which allows use of a single screw to clamp the seal rotating parts to the pump drive shaft.  
           [0013]    It is further an object of the invention to provide a mechanical seal with improved concentricity of the moving and stationary components of the seal.  
           [0014]    It is still another object of the invention to provide a seal which allows greater ease and speed of installation along with easier shaft adjustment.  
           [0015]    It is a further object to provide a mechanical pump seal which allows removal of the mounting flange without releasing the seal cartridge from the drive shaft.  
           [0016]    These and other objects of the invention will become apparent from examination of the description and claims which follow.  
       
    
    
     DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is an exploded view in perspective of the preferred embodiment of a single seal version of the invention.  
         [0018]    [0018]FIG. 2 is a cross section of the preferred embodiment single seal invention of FIG. 1 shown mounted to a pump body.  
         [0019]    [0019]FIG. 3 is an exploded view in perspective of the preferred embodiment of a double seal version of the invention.  
         [0020]    [0020]FIG. 4 is a cross section of the preferred embodiment double seal invention of FIG. 3 shown mounted to a pump body. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    Referring to FIGS. 1 and 2, the components of the preferred embodiment invention seal  40  may be observed. Seal  40  comprises an end plate  14  and a seal cartridge  42  which is slidably receivable within opening  54  of end plate  14 . Seal cartridge  42  includes a rotor assembly  44  which is axially receivable within stator assembly  46  and is coaxial therewith. Pump drive shaft  70  is received within the axial passageway  52  of rotor assembly  44  and is retained to rotor assembly  44  by drive clamp  5  which is accessible from the outside of the pump during installation.  
         [0022]    Rotor assembly  44  comprises sleeve  2  which includes a barrel  62  having a radially extending collar  64  fixed annularly thereto, collar  64  having a recess  66  therewithin. Second O-ring  3  is slidably received on barrel  62 , in recess  66 . Seat member  1  is slidably received on barrel  62  and the extension  68  thereof is received in recess  66  compressing second O-ring  3 . First O-ring  4  is received within the enlarged first end  61  of sleeve  2  and will touchingly engage the drive shaft  70  when it is received in passageway  52  thereby sealing drive shaft  70  to sleeve  2 . Seat member  1  includes an enlarged shoulder  58  on which is located first bearing face  60 .  
         [0023]    Stator assembly  46  comprises a housing  9  which receives washer  8  in first end  90  thereof such that cylindrical body  80  of washer  8  may be slidably received within housing  9 . Washer  8  is provided with bearing surface  84  which touchingly engages first bearing face  60  of seat member  1  when the cartridge  42  is assembled. At least one lock pin  12  is pressed into a hole in housing  9  and extends therefrom to be receivable by slip fit in slot  86  of cylindrical body  80  to prevent rotation of washer  8  on housing  9 . Third O-ring  10  is slidably receivable on cylindrical body  80  and provides sealing contact between cylindrical body  80  and the interior axial cylindrical passageway  56  of housing  9 . Springs  11  bias washer  8  toward seat  1  of rotor assembly  44  to providing loading of bearing surface  84  of washer  8  upon first bearing face  60  of seat member  1 . In addition to loading bearing surface  84  and bearing face  60 , springs  11  help to compensate for variations in dimension in the parts of cartridge  42 . Fourth O-ring  13  is received in an annular groove  94  on first end face  96  of housing  9 . Fourth O-ring  13  is compressed between housing  9  and the pump body  99  to which end plate  14  is mounted. When barrel  62  of sleeve  2  is fitted in interior axial passageway  56  of housing  9 , barrel  62  extends from second end  92  of housing  9  and past outboard side  59  of end plate  14 .  
         [0024]    Housing  9  comprises a radially extending annular flange  98  at or near first end  90  thereof. Flange  98  abuts counterbore  89  in inboard face  74  of end plate  14  when cartridge  42  is installed in end plate  14 . O-ring grooves  95  and  97  along housing  9  receive paired O-rings  16  therein. When pump drive shaft  70  is received in cartridge  42  and cartridge  42  is installed in end plate  14  as shown in FIG. 2, pump shaft  70  extends from opening  54  of end plate  14 . Drive clamp  5  may be placed around drive shaft  70  and one or more pins  6  may be pressed through one or more radial openings  76  and into slip fit in one or more holes  78  of barrel  62  of sleeve  2 , thereby locking drive clamp  5  to rotor assembly  44 .  
         [0025]    Drive clamp  5  includes a radially disposed gap  51  which is narrowed by tightening of cap screw  7  in threaded opening  53  which bridges gap  51  perpendicularly. As gap  51  is narrowed, drive clamp  5  is compressed to clinch drive shaft  70 . One or more relief slots  63  may extend radially part way into drive clamp  5  from the outer circumference thereof to facilitate narrowing of gap  51 . Preferably relief slots  63  are spaced apart evenly from gap  51 , e.g. if two relief slots  63  are used, each will be one hundred twenty degrees away from gap  51 . Gap  51  and relief slots are preferably one-half to two millimeters in width.  
         [0026]    Multiple locator pins  17  are pressed into holes  57  in inboard face  55  of drive clamp  5 . Locator pins  17  extend from inboard face  55  of drive clamp  5  and are received in annular groove  91  of end face  93  of second end  92  of housing  9 . The centers of holes  57  are concentric to the annular groove  91 . The use of multiple locator pins  17 , preferably three locator pins  17 , facilitates coaxial attachment of stator assembly  46  and rotor assembly  44  to drive shaft  70  to assure concentricity of the seal  40  to drive shaft  70 . Each of locator pins  17  is longer than the depth of holes  57  and groove  91  such that drive clamp  5  remains spaced apart from stator assembly  46 . Locator pins  17  are preferable of polymeric material such as nylon and may remain in place after assembly.  
         [0027]    End plate  14  is provided with lubrication passageway  41  which is maintained in registry with radial lubrication opening  43  of housing  9  due to the action of pin  15  which extends from housing  9  and is received in notch  88  in rear face  74  of end plate  14 . The seal  40  may be retained to the pump body  99  by bolts received in mounting openings  39  of end plate  14 .  
         [0028]    The multiple seal design of FIGS. 3 and 4 contains two sets of faces as will be described below but may contain more sets of faces. In a multiple seal arrangement the term “inboard” refers to the seal nearest the pumped fluid and “outboard” refers to the seal nearest the exterior of the pump. “Buffer fluid” refers to an external fluid being introduced between the inboard and outboard sets of seals.  
         [0029]    In the double seal embodiment of FIGS. 3 and 4, the inboard set of faces (on washer  18  and inboard seat  22 ) is used to keep a buffer fluid from entering the fluid being pumped. The outboard set of faces (on washer  18 ′ and outboard seat  23 ) is used to seal the buffer fluid from leaking into the atmosphere. In this case, the buffer fluid would be at higher pressure than the pumped fluid. This double seal embodiment allows the buffer fluid to be used to lubricate and cool the sliding surfaces of washer  18  and inboard seat  22  and to keep the pumped fluid completely isolated from escaping from the pump due to its lower pressure. The seal of FIGS. 3, 4 may be used in application where the pumped fluid is either a poor lubricant for the seal faces or is too hazardous to be allowed to escape to the environment.  
         [0030]    The double seal embodiment of FIGS. 3 and 4 may be used in tandem where the inboard set of faces is used to seal the fluid being pumped. The outboard set of faces is used to seal the buffer fluid from leaking into the atmosphere as in the double seal arrangement. The tandem arrangement is used for several reasons: (a) to wash away the pumped fluid from the inboard faces as they leak to prevent damage to the atmospheric side of the seal; (b) to keep the leaking pumped fluid contained preventing it from entering the atmosphere; (c) To provide additional cooling to the inboard faces; and (d) to reduce the pressure in stages from the pumped fluid pressure reducing down to atmospheric pressure.  
         [0031]    The structure of the double seal arrangement is described below, reference being made to FIGS. 3 and 4 wherein identical parts are referenced identically. Washers  18 ,  18 ′ are mounted onto sleeve  19  with a slip fit using O-rings  20  to seal the inboard washer  18  and outboard washer  18 ′ to the sleeve  19 . The washers  18  and  18 ′ also float on the sleeve  19  on a spring or springs  21 . The springs  21  serve two purposes. First, they are used to mechanically load the washers  18 ,  18 ′ against the seats  22  and  23  respectively to form the primary seals. Second, they allow the washers  18 ,  18 ′ to align themselves to the seats  22 ,  23  to compensate for variations in the dimensions in the seal parts and the equipment to which the seal is mounted. A pin or pins  24  are pressed into the sleeve  19  and engage with a slip fit into matching slots  118  in the washers  18 ,  18 ′ to cause the washers  18 ,  18 ′ to turn with the sleeve  19 . The sleeve  19  is mounted on the shaft  170  with a slip fit using an O-ring  25  to seal the sleeve  19  to the shaft  170 .  
         [0032]    The sleeve  19  extends through the stationary portion of the mechanical seal (stationary housing  31  and end plate  34 ) and is then attached to a drive clamp  26  that is accessible from the outside of the pump during installation. The drive clamp  26  and sleeve  19  slip fit together and have matching radial holes  126 ,  116  respectively that are secured together using tension pin or pins  27  that are press fit into the hole  126  in the drive clamp  26  and slip fit into the hole  116  in the sleeve  19 .  
         [0033]    The drive clamp  26  is the final means of attaching the rotating faces of the mechanical seal to the drive shaft  170 . A cap screw  28  compresses the drive clamp  26  radially to the shaft  170 . A narrow radial void  122  in the drive clamp  26  and relief slots  124  in the circumference thereof allow the drive clamp  26  to be compressed to conform to the shaft  170  creating a friction drive. Relief slots  124  extend from the outer circumference wall of drive clamp  26  part way into drive clamp  26 . Drive clamp  26  locates the washers/sleeve assembly  112  axially in relation to the seats  22 ,  23  and drives the washers/sleeve assembly  112  with the shaft rotation.  
         [0034]    The inboard seat  22  and outboard seat  23  are mounted to the equipment housing  109  as follows: The inboard seat  22  is mounted into a housing adapter  29  using an O-ring  30  to seal the parts together. The outboard seat  23  is mounted into the stationary housing  31  using an O-ring or gasket  32  to seal the parts together. The housing adapter  29  and stationary housing  31  are press fit together with the washer/sleeve assembly  112  and drive clamp  26  sandwiched in between them so the washers  18 ,  18 ′ and seats  23 ,  23  are mechanically loaded in contact with each other to form the inboard and outboard sets of primary seal faces. The housing adapter  29  and stationary housing  31  are clamped to equipment housing  109  using an O-ring or gasket  33  to seal the parts together.  
         [0035]    The end plate  34  is used to clamp the stationary housing  31  to the equipment housing  109  utilizing bolts or studs on the equipment housing  109  thus keeping the stationary housing  31  and end plate  34  stationary in relation to each other. The end plate  34  also serves as the means to connect piping (not shown) to the seal  102  to permit buffer fluid to pass through ports  104 ,  106  through the end plate  34  to aligned ports  108 ,  110  in the stationary housing  31 . A pin  35  is press fit into the stationary housing  31  and slip fits into a matching notch  114  in the end plate  34  to locate the ports  108 ,  110  in the stationary housing  31  in registry with the ports  104 ,  106  in end plate  34 . The stationary housing  31  is a slip fit into the end plate  34  and is sealed to the end plate  34  to isolate each port by means of three O-rings  36 .  
         [0036]    Finally, the assembled rotating unit containing the washers  18 ,  18 ′, sleeve  19 , and drive clamp  26 ; and the assembled stationary unit containing the seats  22 ,  23 , housing adapter  29 , stationary housing  31 , and end plate  34  are aligned to each other by means of spacer pins  37 . The spacer pins  37  are elongate pins, preferably plastic. The spacer pins  37  are press fitted into holes in the inboard face  128  of the drive clamp  26  and fit snugly into a corresponding groove  130  in the outboard face  132  of the stationary housing  31 . The holes in inboard face  128  and groove  130  in outboard face  132  are machined so the centerline of the holes is concentric to the diameter of the groove  130 . When the mechanical seal is mounted on the shaft  170 , the drive clamp  26  is centered to the shaft  170  and the spacer pins  37  keep the stationary housing  31  centered to the drive clamp  26  and thus to the shaft  170 . The spacer pins  37  are longer than the collective depth of the holes on inboard face  128  of drive clamp  26  and the depth of groove  130 , thereby serving to space drive clamp  26  from stationary housing  31  during operation. Spacer pins  37  need not be removed during operation.  
         [0037]    Preferably a radial enlargement  71  is formed in drive clamp  5  to receive second end  65  of sleeve  2 .  
         [0038]    Although the present invention has been illustrated and described in connection with the example embodiments it should be understood that this is illustrative of the invention and by no means restrictive thereof. It is to be expected that those skilled in this art can make numerous revisions and adaptations of the invention and it is intended that such revisions and adaptations will be included in the scope of the following claims.