Patent Publication Number: US-2015061232-A1

Title: Sealing arrangement for follower-shaft assembly

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a follower-shaft assembly. More specifically, the present disclosure relates to a sealing arrangement for the follower-shaft assembly. 
     BACKGROUND 
     Follower-shaft assemblies are commonly known to measure rotational movement of a base shaft which may be part of a machine. A follower-shaft assembly generally includes a follower shaft attached to the base shaft and a rotation of the base shaft is determined by measurement of the rotation of the follower shaft. The follower shaft is typically positioned to extend into a housing of the machine to engage with the base shaft. Since the housing encases the rotating base shaft and is likely sealed to retain lubrication within the housing, the follower shaft may breach the sealed housing to engage with the base shaft. While being positioned in the housing, a portion of the follower shaft extends through the housing and therefore the clearance between the housing and the follower shaft may allow lubrication to leak from the housing. Therefore, a sealing arrangement is generally required to seal a gap between the follower shaft and the housing. 
     Conventional sealing arrangements may include a single lip-type seal, a double lip-type seal, an annular seal, a labyrinth seal, and/or the like. However, under high-speed rotation, the follower shaft also may experience a radial movement which causes the follower to “orbit” rather than rotate. The conventional sealing arrangements are generally designed to seal under rotation however when the follower shaft orbits these seals are less effective and often leakage around the seal at the shaft is common. This may also result in premature wear and failure of the sealing arrangement as the orbiting motion exceeds the radial capacity of these conventional sealing arrangements. 
     U.S. Pat. No. 7,997,858 discloses a sealing arrangement to seal a gap between a first component (rotating shaft) and a second component (housing). The sealing arrangement includes a sealing element and a sealing element displacement device. The sealing element displacement device includes a movable pressure element that adjusts the sealing element upon a displacement due to thermal expansion of the second component. The movable pressure element includes a first face bearing against a second inclined face of the sealing component and is attached to the second component via a screw and spring arrangement. The specific arrangement leads to displacement of the seal element upon displacement of the pressure element. However, the sealing arrangement may still fail under high speed orbiting conditions of the follower shaft. 
     SUMMARY OF THE INVENTION 
     Various aspects of the present disclosure are directed to a sealing arrangement for a follower shaft. The follower shaft extends within a housing to interface with, and to sense rotational movement of, a base shaft. The sealing arrangement includes a mount member and a seal member. The mount member has a first end, a second end, and an opening therethrough. The first end of the mount member is attached to the housing. The second end of the mount member defines a seal receiving portion. The follower shaft is extendable through the opening in the mount member. The seal member has an outer perimeter portion and a resilient inner portion. The outer perimeter portion is adapted to engage with the seal receiving portion of the second end of the mount member. The resilient inner portion being adapted to seal a perimeter of the follower shaft. Further, the second end of the mount member is structured and arranged to resiliently deflect in correspondence with the orbiting motion of the follower shaft to preserve the seal between the resilient inner portion of the seal member and the follower shaft. Therefore, the second end of the mount member limits the deflection of the resilient inner portion of the seal member in response to radial movement of the follower shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional side view of a first embodiment of a follower-shaft assembly that illustrates a sealing arrangement, employing a resilient mount member and a sealed roller bearing disposed therein to seal a gap between a follower shaft and a housing according to the present disclosure; and 
         FIG. 2  is a cross-sectional side view of a second embodiment of a follower-shaft assembly that illustrates the sealing arrangement, employing a resilient mount member and a lip type seal disposed therein to seal the gap between the follower shaft and the housing, according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts. 
     Referring to  FIG. 1 , there is shown a follower-shaft assembly  100  which includes a base shaft  102 , a follower shaft  104 , a housing  106 , and a sealing arrangement  108 . 
     The base shaft  102  which may be a rotating shaft that is a primary component of a machine (not shown) for example, is enclosed within the housing  106 . The housing  106  may include lubricant for lubricating rotating components such as the base shaft  102 . The follower-shaft assembly  100  is attached to the housing  106  and includes the follower shaft  104  which extends through a hole  110  in the housing  106  to engage with the base shaft  102 . The follower-shaft assembly  100  may extend into the housing  106  of any machine, such as, but not limited to an internal combustion engine, a transmission, a turbine, a compressor or any other device which incorporates rotating shaft machinery within a lubrication or otherwise sealed compartment. In an exemplary embodiment, the base shaft  102  may be an axle shaft of an electrically driven construction machine for example and the follower shaft rotational speed may be used for velocity input into the machine&#39;s ECM as an input indicative of machine speed. It may be required to continuously monitor rotation associated with the base shaft  102  in certain machines, however cumbersome to directly measure base shaft rotation. 
     In an exemplary embodiment of the present disclosure, the follower shaft  104  includes an end  109 , which may include a notched portion  111  that is coupled to an end  113  of the base shaft  102 , having a keyway slot  115 , for example, to receive the notched portion  111  of the follower shaft  104 . It will be understood that the follower shaft  104  may be coupled to the base shaft  102  or alternatively, may be fixed to the base shaft  102  though a threaded engagement. The follower shaft  104  tracks the rotation of the base shaft  102 . Therefore, the rotation associated with the base shaft  102  may be monitored by measuring the rotation associated with the follower shaft  104 . It is envisioned that the present disclosure contemplates alternative attachments between the end  109  of the follower shaft  104  and the end  113  of the base shaft  102 , such as for example, press fit, welding, or any other shaft attachment known to those with ordinary skill in the art. 
     The base shaft  102  and the follower shaft  104  are positioned such that a portion of the follower shaft  104  extends into the housing  106 , however a substantial amount of the follower shaft  104  is external to the housing  106 . The portion of the follower shaft  104  extend out via the hole  110  in the housing  106 . The hole  110  is generally larger in diameter than the follower shaft  104  and therefore defines a gap  112  between the follower shaft  104  and the housing  106 , when measured radially. It may be seen that a portion  117  of the follower shaft  104  may be connected to a rotational sensor (not shown) as is customary. 
     The sealing arrangement  108  is provided to prevent lubrication originating from the gap  112  (between the follower shaft  104  and the housing  106 ) from exiting the follower-shaft assembly  100 . The sealing arrangement  108  is positioned about a perimeter  114  of the follower shaft  104  however spaced from the housing  106 . The sealing arrangement  108  prevents lubricant from leaking from the housing  106  and spilling in the vicinity of the housing  106 . The sealing arrangement  108  includes a mount member  116  and a seal member  118 . 
     The mount member  116  may be frusto-conical in shape and is comprised of a resilient material. The mount member  116  is axially aligned with the follower shaft  104  and includes a first end  120 , a second end  122 , and an opening  124  between the first end  120  and the second end  122 . The first end  120  of the mount member  116  is attached to the housing  106 , while the follower shaft  104  extends through the opening  124  of the mount member  116 , and the second end  122  defines a seal receiving portion  126 . 
     The seal member  118  may include a sealed roller bearing  128  disposed in the seal receiving portion  126  of the mount member  116 . The seal member  118  includes an outer perimeter portion  130  and a resilient inner portion  132 . The outer perimeter portion  130  of the seal member  118  engages with the seal receiving portion  126  of the mount member  116 . The resilient inner portion  132  is adapted to seal the perimeter  114  of the follower shaft  104 . A rubber tube  134  is inserted between the resilient inner portion  132  and the perimeter  114  of the follower shaft  104 , to seal the resilient inner portion  132  with the perimeter  114  of the follower shaft  104 . More particularly, the sealed roller bearing  128  includes an outer ring member  136 , an inner ring member  138  and uniformly spaced ball bearings  140 . The inner ring member  138  seals and rotates with the rubber tube  134  and the outer ring member  136  is stationary and forms a seal with the second end  122  of the mount member  116 . 
     In assembly, the seal member  118  is mounted in the second end  122  of the mount member  116 . The second end  122  being made of a resilient material, is designed to resiliently deflect in correspondence with the follower shaft  104  as it orbits, which isolates the resilient inner portion  132  of the seal member  118  relative to the orbiting follower shaft  104 . In other words, the sealed roller bearing  128  orbits with the second end  122  (deflecting end) of the mount member  116  (resilient member), however the seal between the resilient inner portion  132  and the perimeter  114  of the follower shaft  104  does not deflect relative to the follower shaft  104 . Therefore, this construction allows the second end  122  of the mount member  116  to deflect with the follower shaft  104  which has the effect of limiting the deflection of the resilient inner portion  132  of the seal member  118 , in response to radial movement of the follower shaft  104 . 
     Referring to  FIG. 2 , there is shown a follower-shaft assembly  100 ′ that includes an alternative embodiment of a sealing arrangement  108 ′. In the alternate embodiment, the sealing arrangement  108 ′ employs a seal member  118 ′ to seal the gap  112 . The seal member  118 ′ is a standard lip-type seal  202  mounted in the seal receiving portion  126  of the mount member  116 . The seal member  118 ′ also includes an outer perimeter portion  130 ′ and a resilient inner portion  132 ′. The outer perimeter portion  130 ′ of the seal member  118 ′ is in engagement with the seal receiving portion  126  of the mount member  116 . The resilient inner portion  132 ′ of the seal member  118 ′ is directly attached to the perimeter  114  of the follower shaft  104  to seal the perimeter  114 . More particularly, the lip-type seal  202  include an outer casing  204 , an inner lip portion  206 , and a spring  208  disposed around the inner lip portion  206 . The outer casing  204  is fixedly attached to the second end  122  of the mount member  116  and is stationary. The inner lip portion  206  is in continuous sliding contact with the perimeter  114  and the spring  208  pushes the inner lip portion  206  to seal the perimeter  114  of the follower shaft  104 . 
     In assembly, the seal member  118 ′ is mounted in the second end  122  of the mount member  116 . The second end  122  being made of a resilient material is designed to resiliently deflect in correspondence with the follower shaft  104  as it orbits which isolates the resilient inner portion  132 ′ of the seal member  118 ′ relative to the orbiting follower shaft  104 . In other words, the lip-type seal  202  orbits with the second end  122  (deflecting end) of the mount member  116  (resilient member), however the seal between the resilient inner portion  132 ′ and the perimeter  114  of the follower shaft  104  does not deflect relative to the follower shaft  104 . Therefore, this construction allows the second end  122  of the mount member  116  to deflect with the follower shaft  104  which has the effect of limiting the deflection of the resilient inner portion  132 ′ of the seal member  118 ′, in response to radial movement of the follower shaft  104 . 
     INDUSTRIAL APPLICABILITY 
     In operation, the follower shaft  104  may be positioned to abut or in a keyway relationship (as shown) with the base shaft  102  to suitably engage therewith and replicate the rotation of the base shaft  102 . Therefore, the rotation of the base shaft  102  is determined by measuring the rotation of the follower shaft  104 . The rotation of the follower shaft  104  may be determined via a rotational sensor (not shown) which may be mounted to engage the portion  117  of the follower shaft  104  and may be mounted on the housing  106 , as is customary. 
     Referring to  FIGS. 1 and 2 , the sealing arrangement  108 ,  108 ′ is installed to prevent lubricant leaking past the follower-shaft assembly  100 ,  100 ′. During operation, the follower shaft  104  may displace radially and it may manifest an orbiting motion. The radial displacement and orbiting of the follower shaft  104  applies a radial and outward directed force on the resilient inner portions  132 ,  132 ′ of the seal members  118 ,  118 ′. However, since the mount member  116 ,  116 ′ is made from resilient material and the second end  122  of the mount member  116 ,  116 ′ is of smaller cross section, the second end  122  of the mount member  116  is allowed to deflect and any substantial force between the follower shaft  104  and the resilient inner portions  132 ,  132 ′ of the seal members  118 ,  118 ′ is neutralized. This limits the deflection of the resilient inner portions  132 ,  132 ′ of the seal members  118 , 118 , in response to radial movement of the follower shaft  104 . Therefore, the sealing arrangement  108 ,  108 ′ generates a much lower amount of stress on the seal members  118 ,  118 ′ due to the deflecting mount member  116 ,  116 ′ which results in a more efficient seal about the follower shaft  104  and lower stress on the seal which helps preserve the seal. 
     It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Those skilled in the art will appreciate that other aspects of the disclosure may be obtained from a study of the drawings, the disclosure, and the appended claim.