Patent Document

FIELD OF THE INVENTION 
     The present invention generally relates to a shaft seal, and, more specifically, to a shaft seal that provides a high resistance to infiltration of contaminants from one side of the shaft seal to the other side of the shaft seal. 
     BACKGROUND OF THE INVENTION 
     Many mechanical devices have shafts that extend from a housing. Conventionally, the housing is filled with fluid or lubricant. The shafts which pass through the housing wall drive or may be driven by an external component. A gear set or other mechanical device that modifies the rotational energy, torque or speed supplied from one shaft to another shaft is located inside of the housing. These devices must be fluidly sealed from the external environment to ensure that contaminants do not enter the housing. Also, the housing is sealed from the inside so that fluid does not leak from the housing to the external environment. It is difficult to seal the housing with the rotating shaft since space is required between the shaft and housing to allow for rotation. Fluid seals are positioned between the shaft and the wall of the housing to aid in fluidly sealing this space. Typically, these seals are donut like with a through bore. The inner diameter surface of the seal presses against the seal area of the shaft. The outer diameter surface of the seal engages an aperture formed in the housing wall. As a result, the shaft rotates and slides against the fluid seal. The fluid seal presses against the seal area of the shaft and against the housing wall to form a barrier between the inside of the housing and the external environment. 
     While such devices serve well to seal one side of the seal area from the other, drawbacks exist by virtue of spacing between the seal and shaft. Specifically, the natural spacing that exists between the shaft and the seal area can allow a small amount of contaminants to pass from one side of the seal to the other. Although small in quantity, these contaminants can substantially increase the amount of wear between the seal and shaft. Also, the matter can damage internal components within the housing. In addition, the exterior side of the seal is typically exposed to the outside environment which often contains elements detrimental or damaging to the seal such as sunlight, moisture, dust, debris or other airborne materials. The present invention was developed in light of these and other drawbacks. 
     SUMMARY OF THE INVENTION 
     To address these and other drawbacks, the present invention provides a multiple shaft seal arrangement positioned between the shaft and the inside diameter of an aperture in the housing wall. The multiple shaft seal arrangement includes a disc mounted to the outside diameter of the shaft. The disc extends radially outward to a position spaced from the inside diameter of the aperture. One side of the disc faces the external environment. A face seal is mounted to an opposite side of the disc. A second disc extends from the inside diameter of the aperture to a position spaced from the outside diameter of the shaft. The face seal abuts the second disc to prohibit debris from passing from one side of the multiple shaft seal arrangement to the other side. A seal is attached to the second disc and abuts the outside diameter of the shaft. Accordingly, the multiple shaft seal arrangement prohibits particulate matter and other debris from passing from one side of the wall to the other side. 
     In another aspect, a speed reducer with a housing includes an aperture in a housing wall. A shaft passes through the aperture. A multiple shaft seal arrangement is positioned between the shaft and the wall defined by the aperture. The multiple shaft seal arrangement includes a disc mounted to the outside diameter of the shaft. The disc extends radially outward to a position spaced from the inside diameter of the aperture. One side of the disc faces an external environment of the housing. A face seal is mounted to an opposite side of the disc. A second disc extends from the inside diameter of the aperture in a direction radially toward the shaft. The face seal presses against the second disc. A seal is attached to the second disc and presses against the outside diameter of the shaft. 
     In another aspect, a method is disclosed to position a multiple shaft seal arrangement between the wall defined by an inside diameter of an aperture and the outside diameter surface of a shaft. The method utilizes the following steps. The shaft is positioned in the aperture. Next, a seal is mounted to the inside diameter of the aperture. A face seal is then attached to a side of a flinger and the flinger/face seal assembly is mounted to the shaft such that the assembly rotates with the shaft and the face seal presses against the seal. 
     Further areas of applicability of the present invention will become apparent from the below detailed description. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a cross sectional view of a multiple shaft seal arrangement according to the present invention; 
     FIG. 2 is a perspective view of a speed reducer including a multiple shaft seal arrangement according to the present invention; 
     FIG. 3 is an exploded perspective view of a multiple shaft seal arrangement according to the present invention; 
     FIG. 4 is a cross sectional schematic view of the application of a multiple shaft seal arrangement according to the present invention; and 
     FIG. 5 is a flow diagram for the assembly of a multiple shaft seal arrangement according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring now to FIG. 1, a multiple shaft seal arrangement according to the present invention is shown and designated with the reference numeral  10 . The multiple shaft seal arrangement  10  is positioned between a wall  26  and a shaft  20  to seal the internal environment  50  on one side of the wall  26  from the external environment  46  on a second side of the wall  26 . Multiple shaft seal arrangement  10  allows shaft  20  to rotate within wall  26  while minimizing the amount of matter  48  that passes from external environment  46  to internal environment  50 . 
     The multiple shaft seal arrangement  10  generally includes a flinger  12 , a face seal  14  and a seal  16 . The finger  12  includes a disc  18 , external cup area  22 , and a mounting area  28 . The disc  18  is mounted on and extends radially from the shaft  20 . The external cup area  22  is at a radially outward portion of disc  18  and is positioned in close proximity to the inside diameter of aperture  24 . The close proximity of external cup area  22  to the inside diameter of aperture  24  provides a minimal gap to enable rotation of the shaft while preventing material from passing through the gap. 
     External cup area  22  preferably extends away from disc area  18  in a direction along the inside diameter of aperture  24 . As a result, a large surface of external cup area  22  faces the inside diameter of aperture  24 . This, helps to reduce the amount of matter that passes between external cup area  22  and the inside diameter of aperture  24 . However, alternate designs and arrangements may be used other than the external cup disclosed in the present application. Or, no external cup may be used if so desired. 
     Shaft mounting flange  28  extends radially inward from the disc area  18 . Shaft mounting flange  28  preferably extends along shaft  20  to provide a surface for a press fit attachment between the flinger  12  and shaft  20 . Shaft mounting flange  28  supports face seal  14  on an interior surface. 
     Face seal  14  is preferably made of rubber and has a mounting portion  30  and a seal lip  32 . Mounting portion  30  is preferably elastic and is able to be stretched over the outer diameter of shaft mounting flange  28 . Accordingly, mounting portion  30  elastically presses against the shaft mounting flange  28  to create increased friction between the mounting portion  30  and shaft mounting flange  28  to maintain the face seal  14  as part of the flinger  12 . The mounting portion  30  may be attached to a back side of the disc area  18  and also to interior surface of shaft mounting flange  28 . Such attachment may be accomplished by adhesion, glue or any other known means. Moreover, mounting portion  30  may be attached to either the disc area  18  or the shaft mounting flange  28  and not attached to both. Furthermore, mounting portion  30  can be attached to flinger  12  by any other known means and is not limited to the description disclosed herein. 
     Seal lip  32  is conically shaped and extends away from the mounting portion  30 . Preferably, seal lip  32  and mounting portion  30  are formed as a one piece unit. As will be discussed in greater detail, seal lip  32  is pressed against seal  16  such that seal lip  32  exhibits an elastic force against seal  16 . 
     Seal  16  includes a bracket portion  34  (preferably made of metal), a seal area  36 , and a spring  42 . Bracket portion  34  has a cup area  38  and a support  40 . Cup area  38  has an outside diameter that press fits into the aperture  24 . This serves to mount the entire seal  16  in the wall  26 . Support  40  extends radially inward from the cup area  38 . 
     Seal area  36  is attached to support  40  by adhesion, glue or other known means of attachment. Spring  42  extends around an outer circumference of the seal area  36  to press the lip  52  against the outer surface of the shaft  20 . This provides a fluid barrier and sealing action from one side of the multiple shaft seal arrangement  10  to the other. It is noted that seal  16  can be any type of oil seal known in the art including a single lip or double lip oil seal. 
     Grease or another similar substance is positioned within the space  44 , defined by wall  26 , flinger  12 , face seal  14 , and seal  16 . As will be discussed, the grease or other substance within space  44  helps prohibit material from passing from one side of multiple shaft seal arrangement  10  to the other. 
     When assembled, flinger  12  is press fit onto an outer surface of shaft  20  and rotates with shaft  20 . As mounting portion  30  of face seal  14  is also attached to flinger  12 , it also rotates with the rotation of shaft  20  and flinger  12 . Seal  16  is press fit into aperture  24  of wall  26 . Therefore, seal  16  is rotationally fixed and does not rotate with shaft  20 . Instead, lip  52  slides against the outer surface of shaft  20 . 
     In operation, shaft  20  is rotated, causing rotation of flinger  12  and face seal  14 . The disc area  18  of flinger  12 , by centrifugal force, throws matter  48  away from the disc area  18  as shown in FIG.  4 . This removes matter from the general area of multiple shaft seal arrangement  10 . Additionally, the centrifugal force throws the grease to the outermost area of the flinger, thereby plugging up the gap between the cup portion  22  and wall surface  24 . This, again, helps minimize the amount of matter that passes through the gap. 
     Due to the rotation of shaft  20  with respect to wall  26 , some space must exist between shaft  20  and the wall  26 . Multiple shaft seal arrangement  10  serves to minimize this space and reduce the possibility of matter, such as matter  48 , from traveling from external environment  46  to internal environment  50 . However, a path still exists as illustrated by the arrows in areas  54 ,  56 ,  58  and  60 , which also represents the large number of areas that matter must pass through to get to internal environment  50 . This large number of areas is generally created by all the elements in the multiple shaft seal arrangement  10 . The large number of areas through which the matter  48  must pass makes it difficult for matter  48  to pass to internal environment  50 . 
     Specifically, matter must first pass through area  54 . Here, matter must pass between the small space provided between external cup area  22  and aperture  24 . As a further barrier at area  54 , the rotational energy of disc area  18  throws matter  48  away from the general area of disc area  18 . Also, space  44  is filled with grease or other material. Therefore, matter  48  must pass through the entire area of grease before even arriving at area  56 . Next, matter  48  must pass through area  56 . Here, the elastic force of seal lip  32  against support  40  creates an additional barrier which matter  48  must pass through. If matter  48  manages to pass through area  54 , the grease in space  44  and area  56 , it must next pass through areas  58  and  60 . At area  60 , the tightening force of spring  42  clamps lip  52  against the outer surface of shaft  20  to create a further barrier. Accordingly, multiple shaft seal arrangement  10  according to the present invention creates a substantial barrier to prevent matter  48  from passing from external environment  46  to internal environment  50 . 
     With respect to FIG. 2, a speed reducer  62  is shown having shafts  20   a  and  20   b  passing through housing  64 . The walls of housing  64  operate as wall  26  in FIG.  1  and the multiple shaft seal arrangement  10  serves to allow rotation of shafts  20   a  and  20   b  while maintaining matter external to the housing  64  from entering the speed reducer  62 . 
     Referring now to FIGS. 3 and 5, the assembly of the present invention is shown and described. In step  68  of FIG. 5, the face seal  14  is first attached to the flinger  12  by any of the methods described previously. Next, the shaft  20  is positioned in the housing bore in step  70 . However, it is noted that the order of steps  68  and  70  can be reversed or the operations can be performed simultaneously. The positioning of the shaft  20  in step  70  places the shaft  20  at the proper location in the aperture  24 . The seal  16  is then pressed into the aperture from the external environment as the internal environment is preferably sealed by this point by the wall  26 . The seal is preferably pressed into the aperture  24  to a predetermined recessed distance from the outer surface of the wall  26 . The amount of this recess is selected to distance the face seal  14  from the oil seal such that the seal lip  32  is pressed against the seal  16 , while at the same time, the recess is also selected to position the flinger close enough to the outside of the wall  26  to ensure that the minimal gap exists between the outer diameter of the flinger  12  and the inside diameter of the aperture. More specifically, the recess preferably positions the outside surface of the flinger  12  flush with the outside surface of the wall  26 . As a result, the flinger  12  does not stick out from the wall  26  and allow matter to pass therebetween. However, it is noted that variations in the dimensions of the recess can exist, and that the present application is not limited to that disclosed herein. 
     Accordingly, in step  74 , the flinger  12  and face seal  14 , as an assembled unit, is pressed onto shaft  20 . Preferably, between steps  72  and  74 , grease  44  is filled between flinger  12  and face seal  14 . However, it is noted that grease  44  is not a necessary element and it may be omitted. 
     Accordingly, in the above described invention, a sealing arrangement is provided that minimizes the amount of contaminants or dirt that may pass from one side of a wall to another where the wall contains a rotating shaft. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Technology Category: f