Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a seal assembly for providing sealing engagement between a vessel and a rotatable shaft extending through a wall of the vessel. 
     2. Description of Prior Art 
     In material processing equipment it is common that a rotatable shaft is positioned through a wall of a vessel containing material. The interface between the rotatable shaft and the vessel is often the source of leaks of the material as the rotatable shaft rotates. Mechanical, safety and efficiency problems may occur if the material contaminates the processing equipment, the material is hazardous or the material is expensive. 
     Stuffing boxes were often used in the prior art in an attempt to seal the area between the rotatable shaft and the vessel. A stuffing box comprises a box that is filled with dense packing or stuffing attached to the vessel around the interface between the vessel and the rotatable shaft. Such stuffing boxes are often ineffective after extended periods because the packing or stuffing begins to wear away around the rotatable shaft. 
     Other prior art sealing apparatuses, such as Escue, U.S. Pat. No. 4,575,098, use a series of rotatable components attached with respect to the shaft and the vessel. The Escue patent teaches an undersized collar attached to the shaft which rotates around an insert and a faceplate. The seal apparatus taught by the Escue patent involves many rotating components which may result in wear of several different components. Such wear results in frequent replacement of various components. 
     SUMMARY OF THE INVENTION 
     It is one object of this invention to provide a seal apparatus that eliminates leakage between a vessel and a rotatable shaft extending through a wall of the vessel. 
     It is another object of this invention to provide a seal apparatus that does not require frequent replacement of sealing members. 
     It is still another object of this invention to provide a seal apparatus that does not lose its seal when the rotatable shaft expands or contracts. 
     It is yet another object of this invention to provide a seal apparatus that occupies less space than prior art seal apparatuses. 
     It is another object of this invention to provide a seal apparatus having a minimum of rotating components. 
     It is yet another object of this invention to provide a seal apparatus wherein replacement components are easy to replace. 
     A seal apparatus according to this invention for providing sealing engagement between a vessel and a rotatable shaft extending through a wall of the vessel achieves the above objects and is described in more detail below. 
     The seal apparatus includes an insert retainer mounted to the vessel. The insert retainer preferably includes an inner diameter formed around the rotatable shaft. The inner diameter of the insert retainer is preferably substantially larger than an outer diameter of the rotatable shaft. 
     A shaft ring, having an inner diameter approximately equal to an outer diameter of the rotatable shaft, is mounted to the rotatable shaft and rotatably positioned within the insert retainer. The shaft ring is preferably the only rotating component in the entire seal apparatus. 
     An insert, having an inner face and an outer face, is positioned against the shaft ring and within the insert retainer. The insert is constructed of Teflon® or similar material and is preferably the only component in the seal apparatus requiring occasional planned replacement. The insert preferably fits snugly within the insert retainer and includes a sealing member, such as an O-ring cord, positioned between the insert and the insert retainer. 
     A retainer assembly biases the insert against the shaft ring to complete the seal apparatus. The retainer assembly preferably includes a bias plate positioned against the insert and a retainer plate positioned opposite the insert and adjacent the bias plate. The retainer plate is preferably connected with respect to the insert retainer and includes bias members for biasing the bias plate against the insert. 
     As a result of the seal assembly described herein, the vessel does not leak material through the interface between the rotatable shaft and the vessel. The seal assembly includes only one rotating component, the shaft ring, and only one component that must occasionally be replaced, the insert. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and objects of this invention will be better understood from the following detailed description taken in conjunction with the drawings wherein: 
     FIG. 1 is an exploded perspective view of a seal assembly according to one preferred embodiment of this invention. 
     FIG. 2 is a front view of a seal assembly according to the preferred embodiment of this invention shown in FIG.  1 . 
     FIG. 3 is a front view of an insert retainer according to one preferred embodiment of this invention; 
     FIG. 4 is a front view of a shaft ring according to one preferred embodiment of this invention; 
     FIG. 5 is a front view of an insert according to one preferred embodiment of this invention; 
     FIG. 6 is a side view of the insert shown in FIG. 5; and 
     FIG. 7 is a front view of one half of a retainer plate according to one preferred embodiment of this invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows an exploded view of seal assembly  1  according to one preferred embodiment of this invention. As shown, seal assembly  1  is positioned around rotatable shaft  10  and adjacent vessel  8 . Rotatable shaft  10  extends through wall  9  of vessel  8 . Vessel  8  may be a mixer or other enclosure for holding and processing material that requires a rotatable shaft  10  extending through wall  9  thereof. 
     Without a sealing engagement between rotatable shaft  10  and vessel  8 , the material within vessel  8  may gradually escape through a gap between rotatable shaft  10  and vessel  8 . Such escaping material may contaminate material processing equipment or, in the case of hazardous material processing, result in a dangerous condition for workers exposed to such material processing equipment. 
     Accordingly, sealing assembly provides a sealing engagement between vessel  8  and rotatable shaft  10  extending through wall  9  of vessel  8 . As shown in FIG. 1, seal apparatus  1  preferably includes insert retainer  20 , shaft ring  30  and insert  40 . 
     Insert retainer  20  is mounted or connected with respect to vessel  8  and around rotatable shaft  10 . Insert retainer  20  is preferably machined from stainless steel or similar material known to those having ordinary skill in the art. As shown in FIGS. 1 and 3, insert retainer  20  is preferably separable into two insert retainer halves  20 ′,  20 ″. Such a configuration permits insert retainer  20  to be mounted with respect to vessel  8  without removal of rotatable shaft  10  from vessel  8 . Further, seal assembly  1  according to a preferred embodiment of this invention is entirely separable to permit installation and maintenance with respect to vessel  8  without removal of rotatable shaft  10 . 
     Insert retainer  20  is positioned with respect to vessel  8  so that outer diameter  12  of rotatable shaft  10  is freely rotatable with respect to inner diameter  23  of insert retainer  20 . As shown in FIG. 3, insert retainer  20  is preferably assembled by joining two insert retainer halves  20 ′,  20 ″ with insert retainer screws  25  and aligning such insert retainer halves  20 ′,  20 ″ with alignment pins  22 . Insert retainer  20  is then preferably connected with respect to vessel with fasteners and insert retainer mounting bores  21  to create a sealed engagement between insert retainer mounting bores  21  and vessel  8 . In one preferred embodiment of this invention, end portions  29  of insert retainer halves  20 ′,  20 ″ may be removed to facilitate machining and assembly. 
     In addition, jack screws  27  are positioned around insert retainer  20  to facilitate squaring of insert retainer  20  with respect to vessel  8  and rotatable shaft  10 . Insert retainer  20  additionally comprises retainer plate mounting bores  28  positioned around an inner perimeter of insert retainer  20 . 
     Seal assembly further includes shaft ring  30  positioned on rotatable shaft  10 . Shaft ring  30 , shown in FIGS. 1 and 4, has inner diameter  32  approximately equal to or slightly greater than outer diameter  12  of rotatable shaft  10 . Like insert retainer  20 , shaft ring  30  is constructed from stainless steel or similar material and preferably comprises two shaft ring halves  30 ′,  30 ″ that are connected with respect to each other with shaft ring screws  34  through shaft ring bores  33 , as shown in FIG.  4 . 
     Shaft ring  30  is connected to rotatable shaft  10  so that shaft ring  30  is rotatable with rotatable shaft  10 . Shaft ring  30  is preferably connected to rotatable shaft  10  directly adjacent the wall of vessel  8 . Shaft ring  30  is preferably rotatably positioned entirely within insert retainer  20 . Shaft ring  30  does not directly contact insert retainer  20  within seal assembly  1 . 
     In one preferred embodiment of this invention, shaft ring  30  further comprises shaft ring groove  37  positioned circumferentially around inner diameter  32  of shaft ring  30 . Shaft ring groove  37  is preferably a shallow channel positioned toward one end of shaft ring  30 . Shaft ring groove  37  preferably accommodates shaft ring seal  35  positioned around inner diameter  32  of shaft ring  30 . Shaft ring seal  35  may comprise an O-ring cord that is laid around shaft ring groove  37 . O-ring cord is constructed from a fluorinated rubber such as Viton®, or other temperature and chemical resistant sealing material known to those having ordinary skill in the art. 
     Shaft ring seal  35  preferably creates a sealing engagement between inner diameter  32  of shaft ring  30  and outer diameter of rotatable shaft  10 . Alternatively, depending upon the application, shaft ring  30  may not include shaft ring seal  35 . 
     As shown in FIGS. 1,  5  and  6 , seal assembly  1  further includes insert  40 . Insert  40  is preferably constructed from Teflon® (polytetrafluoroethylene) or other similar material known to those having ordinary skill in the art. Like the other components discussed above, insert  40  preferably comprises two separable insert halves  40 ′,  40 ″. Insert  40  further includes inner face  42  that in an assembled seal assembly faces toward vessel  8  and outer face  43  that in an assembled seal assembly  1  faces away from vessel  8 . Outer diameter  41  of insert  40  is approximately equal or slightly less than inner diameter  23  of insert retainer  20 . 
     In one preferred embodiment of this invention, shown in FIGS. 5 and 6, insert  40  further includes insert groove  47  positioned circumferentially around insert  40 . Insert groove  47  preferably accommodates sealing member  45 . Sealing member  45  may comprise an O-ring cord, similar to shaft ring seal  35 , laid around insert groove  47 . Alternatively, insert  40  may not include insert groove  47  and/or sealing member  45 . 
     In one preferred embodiment of this invention, shown in FIG. 5, two separable insert halves  40 ′,  40 ″ are joined through axial notch  48  and axial groove  49  positioned at an interface between two separable insert halves  40 ′,  40 ″. Axial notch  48  and axial groove  49  maintain a fixed radial position of separable insert halves  40 ′,  40 ″ with respect to each other. In addition, the axial arrangement of axial notch  48  and axial groove  49  in combination with sealing member  45  around insert  40 , help maintain an effective seal in seal assembly  1 . 
     Insert  40 , and specifically inner face  42  is biased against shaft ring  30  and seated at least partially within insert retainer  20 . In one preferred embodiment of this invention, insert  40  is positioned entirely within insert retainer  20 . Sealing member  45  in insert  40  creates a sealed relationship between insert  40  and insert retainer  20 . Retainer assembly  80  is preferably positioned adjacent insert  40  and maintains a fixed position of insert  40  with respect to shaft ring  30 . 
     According to one preferred embodiment of this invention and as shown in FIG. 1, retainer assembly  80  includes bias plate  50 , retainer plate  60  and bias members  70 . Retainer assembly  80  is preferably designed to maintain a fixed position of insert  40  with respect to shaft ring  30  and in addition minimize wear of insert  40  and other components within seal assembly  1 . 
     As shown in FIG. 1, bias plate  50  has insert surface  53  and retainer surface  55  opposite insert surface  53 . Bias plate  50  is divided into separable bias plate halves  50 ′,  50 ″ that are preferably connected with hinge  52 . Bias plate  50  is preferably constructed from a thin piece of material having inner and outer diameters that approximately coincide with inner and outer diameters of insert  40 . Insert surface  53  of bias plate  50  is preferably positioned against insert  40 . Preferably, bias plate  50  is biased against insert  40 . 
     Retainer assembly  80  further comprises retainer plate  60 . As shown in FIGS. 1 and 7, retainer plate  60  is separable into two separable retainer plate halves  60 ′,  60 ″. In one preferred embodiment of this invention, retainer plate  60  includes a plurality of bias member apertures  62  spaced around an inner perimeter of retainer plate  60 . Retainer plate  60  preferably further includes a plurality of retainer apertures  63  spaced around an outer perimeter of retainer plate  60 . Retainer plate  60  is preferably attached to insert retainer  20  with a plurality of retainer screws  65  positioned through retainer apertures  63  and threadedly mounted with respect to retainer plate mounting bores  28 . Spacers  75  are preferably positioned around retainer screws  65  between retainer plate  60  and insert retainer  20 . 
     According to one preferred embodiment of this invention, a plurality of bias members  70  are positioned through retainer plate  60  and biased against the bias plate  50 . Specifically, bias members  70  are preferably positioned through bias member apertures  62  in retainer plate  60  and biased against retainer surface  55  of bias plate  50 . Bias members  70  may comprise spring loaded screws that exert a bias force against bias plate  50 , which bias force is then translated from bias plate  50  to insert  40 . Therefore, as a result of the bias force exerted on bias plate  50 , insert  40  is biased against shaft ring  30 . 
     Vessels  8  such as mixers, specifically horizontal vacuum mixers, may generate internal vacuums of up to approximately 30″. Additionally, rotatable shaft  10  may rotate in excess of 3600 revolutions per minute. Seal apparatus  1  according to this invention is effective for either of the above described conditions. As a result of the described rotation of rotatable shaft, shaft ring  30  rotates correspondingly in contact with insert  40 . Therefore, inner face  42  of insert  40  may wear along contact surfaces with shaft ring  30 . As such wear occurs, insert  40  remains in contact with shaft ring  30  because of the bias force exerted by bias members  70  indirectly upon insert  40 . Bias plate  50  functions as a buffer between such bias force and insert  40 . 
     While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that this invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

Technology Category: 2