Abstract:
A locking collar to be inserted into a cylindrical cavity or lumen of a device for securing mechanical elements from moving axially within the cavity. The collar includes two semi-circular cylindrical segments hinged together with an opposed single slit to allow easy installation within the cavity and pushed into position against the installed elements without the need to disassemble a device. The collar is a substantially cylindrical rigid member with an outer diameter closely matching the inner bore diameter of the cavity and includes an opening at the slit to receive a securing screw member to urge the two segments apart to engage the inner bore surface of the cavity and fix the collar in place thereby locking the elements in place.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a locking collar for installation in a cylindrical cavity or a stuffing box of a rotary mechanical device, and more particularly to a two-piece collar to be placed in a cylindrical cavity, and to a method for installing the collar. 
     Rotary mechanical devices, such as mixers and centrifugal pumps, include an impeller mounted on a shaft which is driven by an electric motor. The shaft passes through a seal cavity or a stuffing box defined by a cylindrical cavity in the device housing. Typically, the shaft is supported by bearings at the motor end and seals are placed in the stuffing box to engage the shaft to prevent fluid from passing through the seal cavity and reaching the bearing and the motor to avoid causing damage to both. 
     In mechanical pumps, the seal cavity passes chemical fluids, solids, or solvents being pumped, many of which are corrosive or erosive. Accordingly, it is important that appropriate packing material is placed within the seal cavity. The end of the seal cavity is closed by a gland follower which can be adjusted axially to fix the position of mechanical seal elements. 
     Typically seal water is pumped into the seal cavity through a flush port (1) to prevent the fluid being pumped or mixed from traveling along the shaft to the bearings and motor and (2) to provide lubricant to the packing. It is desirable to prevent movement of seals or other mechanical elements about the shaft. Thus, it is highly desirable to provide a locking collar that prevents axial movement of these mechanical elements. 
     A suitable stuffing box with a bearing sealing element and system is described and claimed in U.S. Pat. No. 6,834,862 to Mark R. Wilkinson, the contents of which are incorporated by reference in their entirety. This patent describes a seal system including a bearing element with a bearing surface. This shaft sealing system works well, particularly when an additional bearing surface for the shaft is required. A rigid locking collar is desirable to fix the axial portion of the sealing elements. 
     While there are a wide variety of devices available for locking mechanical elements in place in rotary mechanical devices, it is desirable to provide an improved locking collar that can easily be installed in a seal cavity or stuffing box of such a device without the need to disassemble the device. 
     SUMMARY OF THE INVENTION 
     Generally speaking, in accordance with the invention, a substantially rigid locking collar for installation in a cylindrical cavity or lumen, such as a seal cavity or stuffing box of a rotary mechanical device with a shaft driven by a motor, is provided. The locking collar includes two semi-circular cylindrical segments hinged together at one end with an opposed single slit formed at the other end to allow easy installation in the cavity over the shaft of the device. The locking collar has an outer diameter comparable to the bore of the inner bore of the cavity and an inner diameter greater than the diameter of the pump shaft. When fixed in position, the locking collar prevents axial movement of mechanical elements in the cavity. The annular space between the outer surface of the shaft and the inner surface of the locking collar in a pump cavity allows for pump flush fluids to flow within the cavity. 
     The two semi-circular segments of the locking collar are hinged with an opposed mating slit to facilitate placing the locking collar around the shaft adjacent to the mechanical element. A locking member, such as a threaded screw, is installed at the slit to fix the position of the locking collar. The locking member is aligned axially and is threaded into one or both edges of the slit opposite the hinge. Tightening the locking member forces the two annular pieces away from each other so that the locking collar is urged against the inner wall of the cavity and sits securely in position within the cavity. Once the locking collar is locked in place, the axial position of the mechanical element adjacent the locking collar is fixed. 
     Accordingly, it is an object of the invention to provide an improved locking collar for a cylindrical cavity. 
     A seal system including seal elements and the locking collar is also provided. 
     It is another object of the invention to provide an improved two-piece locking collar for a rotary mechanical device with a hinge to facilitate installation. 
     It is a further object of the invention to provide an improved two-piece hinged locking collar with an opposed mating slit. 
     It is yet another object of the invention to provide an improved two-piece hinged locking collar with an opposed slit having a semi-circular opening for receiving a locking screw. 
     It is yet a further object of the invention to provide an improved two-piece hinged locking collar with an opposed notched slit. 
     It is still another object of the invention to provide an improved two-piece hinged locking collar for a rotary mechanical device having an opposed slit with an angled screw receiving opening for locking the collar in place. 
     It is still a further object of the invention to provide an improved seal system for a rotary mechanical device including a locking collar to prevent axial movement of mechanical elements in the cavity. 
     Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification. 
     The invention comprises a product possessing the features, properties, and the relation of components which will be exemplified in the product hereinafter described and the scope of the invention will be indicated in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a partial cross-sectional view of a typical centrifugal fluid pump; 
         FIG. 2  is an enlarged cross-sectional view of the seal cavity of the pump of  FIG. 1  showing a shaft sealing system with a sealing element and a locking collar in place in the seal cavity in accordance with the invention; 
         FIG. 3  is a perspective view of a two-piece hinged locking collar with a slit with semi-circular receiving openings constructed and arranged in accordance with an embodiment of the invention; 
         FIGS. 4A and 4B  are each a side elevational view of a segment of the locking collar of  FIG. 3 ; 
         FIGS. 5A and 5B  are each a top plan view of a segment of the locking collar of  FIGS. 4A and 4B , respectively; 
         FIG. 6  is a perspective view of a two-piece hinged locking collar formed with a longitudinal notched slit and receiving opening in accordance with another embodiment of the invention; 
         FIGS. 7A and 7B  are each a perspective view of a segment of the locking collar of  FIG. 6 ; 
         FIGS. 8A and 8B  are each a side elevational view of a segment of the locking collar of  FIG. 6 ; 
         FIGS. 9A and 9B  are each a plan view of a segment of the locking collar of  FIGS. 8A and 8B , respectively; 
         FIG. 10  is a perspective view of a two-piece hinged locking collar with an angled screw locking element receiving opening constructed and arranged in accordance with another embodiment of the invention; 
         FIGS. 11A and 11B  are each a perspective view of a segment of the locking collar of  FIG. 10 ; 
         FIGS. 12A and 12B  are each an elevational view of a segment of the locking collar of  FIG. 10 ; 
         FIGS. 13A and 13B  are each a perspective view of a segment of the locking collar of  FIGS. 12A and 12B , respectively; and 
         FIG. 14  is a perspective view of the collar segment of  FIG. 7A  modified to include flush grooves. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a generic form of a centrifugal pump  11  in cross-section mounted on a frame  10 . Pump  11  includes a centrifugal impeller  12  driven by an electric motor  13  that drives a rotary shaft  14  coupled to impeller  12 . Shaft  14  is supported by a bearing housing  16  and rotates to draw fluid in through an impeller inlet  17  and expel the fluid out through a radial impeller outlet  18 . Pump  11  includes a housing  19  having an internal bore  21  that defines a seal cavity or stuffing box  22  with shaft  14  passing therethrough as shown in detail in  FIG. 2 . Housing  19  includes an opening  23  through which shaft  14  passes to engage impeller  12  secured to shaft  14  by a nut or fastener  24 . Housing  19  also includes a flush port  26  for introduction of a seal fluid, such as water, into seal cavity  22 . 
     Pump  11  operates by drawing a fluid to be pumped into inlet  17  and forced to exit at outlet  18 . During pumping, fluid tends to migrate and be forced into seal cavity  22  through opening  23 . A wide variety of seals and packing configurations are available to be placed in seal cavity  22  abutting opening  23  in order to restrict and limit entry of pumped fluid into seal cavity  22 . If fluid enters seal cavity  22  and migrates to bearings at the motor end, the bearings may be subject to substantial degradation due to the corrosive action of the pumped fluid. 
       FIG. 2  is an enlarged view of seal cavity  22  with a sealing element such as a bearing seal element  27 . A locking collar  31  is positioned against seal element  27  to hold it in place in accordance with the invention. The motor end of seal cavity  22  is defined by a gland follower or mechanical seal  34  about shaft  14  and secured to housing  19  by gland bolts  36  and gland nuts  37 . 
     As shown in  FIG. 2 , shaft seal element  27  is installed in seal cavity  22  at the impeller end of seal cavity  22  and is secured in position by locking collar  31  positioned against seal element  27  on the motor side thereof. Seal element  27  may be a rigid sealing bearing member of stainless steel, a non-ferrous carbon or glass filled thermoplastic material, such as polytetrafluoroethylene (PTFE), or another suitable material as described in U.S. Pat. No. 6,834,862. Seal element  27  may be a semi-rigid bushing as described in co-pending U.S. patent application Ser. No. 11/432,679, filed May 11, 2006. The contents of the patent and the patent application are incorporated herein by reference in their entirety. 
     In the embodiment illustrated, an integral lantern ring  28  is formed in seal element  27  aligned with flush port  26 . A pair of O-rings  29  are placed in grooves on the inner diameter of seal element  27  against shaft  14 . 
     In  FIG. 3 , a two-piece locking collar  41  constructed and arranged in accordance with the invention is shown in perspective. Locking collar  41  is custom made for the bore of a particular rotary device. Dimensions vary depending on the size of the inner bore of the device, as will be described in detail in connection with the examples. Locking collar  41  comprises a first semi-circular segment  42  and a mating second semi-circular segment  43 , joined together at a hinge  44  by a hinge rivet  46 . A slit  47  formed opposite hinge  44  includes a portion of a threaded receiving opening  48  on first segment  42  and a threaded receiving opening portion  49  on second segment  43 . 
     When locking collar  41  is positioned against a mechanical element in a device cavity, such as seal element  27 , a threaded locking member  51  having an external thread  52  is threaded into the opening formed by receiving opening portions  48  and  49  to force segment  42  and  43  apart and thereby locked against internal bore  21  of seal cavity  22 . This prevents axial movement in the direction of shaft  14  of seal element  27  placed at the impeller end of seal cavity  22 . 
     The use of locking collar  41  and a mechanical seal as the sealing device avoids the need to utilize flexible packing rings at the motor end of seal cavity  22 , as is customary in the art. Locking collar  41  prevents movement of seal element  27  and avoids the need to use and replace packing. This advantageously extends the intervals between required seal cavity maintenance. 
       FIGS. 4A and 4B  show elevational views of segments  42  and  43 , respectively.  FIGS. 5A and 5B  are each a plan view showing opening portions  48  and  49  in segments  42  and  43 , respectively. 
     In the embodiment illustrated in  FIG. 2 , an inner seal fluid groove  33  is formed in seal element  27  at a position corresponding to the location of an outer seal fluid groove  34  to create lantern ring  28  at the gland end of seal element  27 . A plurality of seal fluid holes are formed between outer seal water groove  34  and an inner seal water groove as described in detail in U.S. Pat. No. 6,834,862. Here, seal element  27  includes two O-rings  29  on its inner surface adjacent shaft  14 . 
     To be able to lock locking collar  31  in position in seal cavity  22 , first segment  42  and second segment  43  are pivoted open about hinge  44  and placed around shaft  14 . Once around shaft  14 , locking collar  31  is positioned against seal element  27  and a threaded locking member  51  is threaded into a threaded receiving opening formed by opening segments  48  and  49  in slit  47 . As locking member  51  moves into the threaded receiving opening, segments  42  and  43  move in a substantially radial direction to seal seal cavity  22 . 
       FIG. 6  represents a two-piece locking collar  56  with a notched slit constructed and arranged in accordance with the invention as shown in perspective. As with locking collar  41  in  FIG. 3 , locking collar  56  is custom made for the bore of a particular rotary device. Locking collar  56  includes a first semi-circular segment  57  and a mating second semi-circular segment  58  joined together at a hinge  59  with a hinge rivet  61 . 
     A slit  62  formed opposite hinge  59  includes a notch projection  63  formed on the edge of second segment  58  and a receiving notch slot  64  formed on the mating edge of first segment  57 . This projection  63  and notch  64  ensure proper alignment of locking collar  56  against inner bore  21  of device cavity  22 . A threaded receiving opening  66  is formed on first segment  57  through at least a portion of receiving notch opening  66 . When locking collar  56  is positioned about a shaft and against a mechanical element, such as seal element  27  in  FIG. 2 , a locking member  67  having an external thread  68  is threaded into receiving opening  66  to force segments  57  and  58  apart. This moves segments  57  and  58  of locking collar  56  in a substantially radial direction to lock segments  57  and  58  against internal bore  21  of seal cavity  22 . 
     Once locking collar  56  is locked in place, this prevents axial movement of seal element  27  placed at the impeller end of seal cavity  22 . Use of locking collar  56  as in the case of locking collars  31  and  41  avoids the need to utilize flexible packing rings at the motor end of seal cavity  22  and extends the interval between required seal cavity maintenance. 
       FIGS. 7A and 7B  are each a perspective view of locking collar segments  57  and  58 , respectively.  FIGS. 8A and 8B  are each an elevational view of segments  57  and  58 , respectively, and  FIGS. 9A and 9B  are each a plan view showing the inner side of segments  57  and  58 , respectively. 
     With reference to  FIG. 10 , a two-piece locking collar  71  with an angled screw receiving opening  72  at a slit  73  constructed and arranged in accordance with the invention is shown in perspective. As with locking collar  41  in  FIG. 3 , locking collar  71  is custom made for the bore of a particular rotary device. Locking collar  71  includes a first semi-circular segment  74  and a mating second semi-circular segment  76  joined together at a hinge  77  with a hinge rivet  78 . 
     Slit  73  formed opposite hinge  77  includes a flat mating edge  80  formed on the mating edge of first segment  74  and a flat mating edge  83  formed on second segment  76 . Angled receiving opening  72  includes and internal thread  79  is formed in first segment  67  through at least a portion of edge  74   a  of first segment  74 . When locking collar  71  is positioned about a shaft and against a mechanical element, such as seal element  27  in  FIG. 2 , a threaded locking member  81  having an external thread  82  is threaded into angled receiving opening  72  to force segments  74  and  76  apart and thereby locked at the internal bore of a cylindrical cavity. 
     Once locking collar  71  is locked in place, this prevents axial movement of, for example, seal element  27  placed at the impeller end of seal cavity  22 . Use of locking collar  71  as in the case of locking collar  31 ,  41  and  56  avoids the need to utilize flexible packing rings at the motor end of seal cavity  22  as is customary in the art. Locking collar  71  prevents movement of elements, such as seal element  27 , and avoids the need to use and replace packing and extends the interval between required seal cavity maintenance. 
       FIGS. 11A and 11B  are each a perspective view of segments  74  and  76 , respectively.  FIGS. 12A and 12B  are each an elevational view of segments  74  and  76 , respectively, and  FIGS. 13A and 13B  are each a plan view showing the inner side of segments  74  and  76 , respectively. 
     Locking collars in accordance with the invention are generally made with an outside diameter smaller than the diameter of the inner bore of a receiving cylindrical cavity. Preferably the outside diameter is from about 0.005 to about 0.015 inch, preferably about 0.010 inch, smaller. The outside diameter may vary, that is, it may not be uniform. The inside diameter of the locking collar is generally about 0.750 inch smaller than its outside diameter. This will provide a standard 0.375 inch square cross-section for a locking collar having a length of 0.375 inch. This 0.375 inch square may vary from about 0.312 to about 0.437 inch. 
     For use in a rotary device seal cavity where the distance between the shaft and the inner bore is less than 0.375 inch, the bore clearance should be maintained from about 0.050 to about 0.150 inch, but the inner diameter of the locking collar will be from about 0.020 inch to about 0.040 inch, preferably about 0.030 inch, greater than the diameter of the shaft. In a case where more flush is needed to cool the device, axial grooves may be formed in the inner diameter of the locking collar.  FIG. 14  shows one segment  86  of such a locking collar as collar segment  58  of  FIG. 7A  having a plurality of axial grooves  87  to provide more cavity volume. 
     When a cylindrical cavity has an inner bore of 5.00 inches or greater, the length of the locking collar is increased by a factor of from about 1.15 to about 1.35 times per inch over 5.00 inches, preferably about 1.25 times per inch. For example: 
     
       
         
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Square 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Standard (bore less than 5.00″) 
                 0.375 inch 
               
               
                   
                 Bores over 5.00″ (1.25 × .375 
                 0.469 inch 
               
               
                   
                 Bores over 6.00″ (1.25 × .469) 
                 0.586 inch 
               
               
                   
                 Bores over 7.00″ (1.25 × .586) 
                 0.733 inch 
               
               
                   
                   
               
             
          
         
       
     
     For use in devices where the operating pressures are over 1,000 psi, the standard length of the locking collar is 0.5000 inch. This is increased by a factor of from about 1.15 to about 1.35 times per inch, preferably about 1.25 times per inch, over 5.00 inches. For example: 
     
       
         
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Length 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Standard (bores &lt;5.00 inch) 
                 0.500 inch 
               
               
                   
                 Bores over 5.00″ (1.25 × 0.500) 
                 0.625 inch 
               
               
                   
                 Bores over 6.00″ (1.25 × 0.629) 
                 0.781 inch 
               
               
                   
                 Bores over 7.00″ (1.25 × 7.81) 
                 0.977 inch 
               
               
                   
                   
               
             
          
         
       
     
     Locking collars  31 ,  41 ,  56  and  71  are substantially rigid and formed of materials which will not be attacked or destroyed by corrosive fluids being transported by pump  11 . The material of construction includes a wide variety of material. These include non-ferrous metals, silica-based materials, carbonaceous materials, and polymeric materials, such as nylon, polyacetals, polyvinylchloride, polyethylene, polypropylene and fluorine containing polymers, such as polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), or other suitable plastic material. The polymeric materials may be filled or unfilled. Filled materials may include a molybdenum/carbon or glass filled thermoplastic material, such as a PTFE, PFA and nylon. 
     EXAMPLES 
     Example 1 
     The dimensions of locking collar  22  in accordance with the invention made of filled PTFE where the inner bore of the cavity is 3.50 inches in diameter are as follows: 
     (1) Outer diameter of the collar is 3.49 inches; 
     (1) Inner diameter of the collar is 2.74 inches; 
     (2) Length of the collar is 0.5 inch; and 
     (2) Diameter of the threaded receiving opening is 0.17 inch. 
     Example 2 
     The dimensions of notched locking collar  41  in accordance with the invention made of filled PTFE bearing material where the inner bore of the cavity is 2.5 inches in diameter are as follows: 
     (1) Outer diameter of the collar is 2.49 inches; 
     (2) Inner diameter of the collar is 1.78 inches; 
     (3) Length of the collar is 0.375 inch; 
     (4) Height of projecting notch  58  and length each is 0.10 inch; and 
     (5) Diameter of the threaded receiving opening is 0.17 inch. 
     Example 3 
     The dimensions of angled receiving opening locking collar  71  in accordance with the invention made of filled PTFE bearing material where the inner bore of the cavity is 2.5 inches in diameter is as set forth in Example 2, except that faces  80  and  82  are flat except where receiving opening  72  intersects face  80 . The outer diameter of locking collar  71  matches the bore of the device cavity and the inner diameter is about 0.750 less. 
     It can readily be seen that a locking collar to fix the axial position of a cylindrical seal element in a seal system constructed in accordance with the invention can be easily installed in a cylindrical cavity or lumen, such as a conventional rotary impeller pump without the need to use pins necessary to guarantee alignment due to the one-piece bushing construction of the seal upon installation. When in place, a bearing seal element can support the impeller end of the pump shaft, providing an additional bearing surface to aid in eliminating the whip commonly found in pump shafts. Since there is clearance between the pump shaft and the locking collar seal fluid or water entering the lantern ring groove would be at the motor end of the cavity, thereby minimizing the quantity of the product being pumped at the motor end of the cavity. 
     The various modification to the locking collar in accordance with the invention allow for a quick and easy installation. The need for flexible packing rings and the cutting to properly fit them is avoided and the axial position of the sealing element is secured. 
     It will thus be seen that the object set forth above, among those made apparent from the preceding description are efficiently attained and, since certain changes may be made in the device set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention, which, as a matter of language, may be said to fall there between.