Abstract:
The cartridge assembly being lubricated and includes a bushing rotatably mounted on a pin with a passageway to receive lubrication oil in the pin. The end portion of the pin includes first and second collars having a groove to receive a sealing arrangement. The collars are press fitted onto the shaft.

Description:
TECHNICAL FIELD 
     This invention relates generally to track type work machines, and more particularly to a drive sprocket for a track type work machine. 
     BACKGROUND 
     Work machines which utilize a track type drive mechanism have several advantages over wheel type work machines. The tracks give the work machine excellent traction while spreading the weight of the machine over a large area. Thus, the track type work machine has enhanced off road capabilities. 
     A typical undercarriage of a track type drive mechanism consists of a track made of a number of shoes linked together, a drive sprocket which drives the track, and a number of rollers which distribute the weight of the work machine along the track. 
     In a conventional track type drive, a tooth of the drive sprocket engages a stationary bushing in the shoe of the track. This type of engagement causes considerable wear as the teeth of the drive sprocket advance the track around the drive sprocket. A disadvantage to this type of track drive is that the bushings of the track must be replaced as they wear out. Replacing the shoes of the track and the teeth of the sprocket is costly and time consuming. 
     One method of reducing track wear is to mount a rotating bushing on the shoes of the track of the work machine. The rotating bushing eliminates much of the friction between the shoes and the teeth of the drive sprocket as the drive sprocket engages and disengages the track as the track is advanced around the drive sprocket. Mounting a rotating bushing on the shoe greatly reduces wear on the track. However, a disadvantage of mounting a rotating bushing on each shoe is the cost of the large number (typically 30 to 50) of bushings needed in order to place a bushing on each shoe of the track assembly. 
     Another method of reducing track wear is to mount rotating members on the drive sprocket. These rotating members engage drive lugs attached to each shoe of the track. This arrangement also reduces wear on the track. However, this approach also suffers from disadvantages. For example, one disadvantage this approach suffers from is the difficulty of replacing the rotating members on the drive sprocket as they wear out. In particular, replacing the rotating members on the drive sprocket can be costly and time consuming, which in turn increases the cost of operating the work machine. 
     The present invention is directed to overcoming one or more of the problems or disadvantages associated with the prior art. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the present invention, there is provided a drive sprocket for a track type work machine. The drive sprocket includes a hub and a support secured to the hub. The drive sprocket also includes a cartridge assembly secured to the support. The cartridge assembly has (i) a bushing having a passageway defined therethrough, (ii) a pin having a longitudinal axis, the pin being located within the passageway so that a first end portion and a second end portion of the pin extend outwardly from the passageway of the bushing, (iii) a first collar having a first hole defined therein, the first collar being positioned relative to the pin so that the first end portion of the pin is disposed within the first hole, (iv) a second collar having a second hole defined therein, the second collar being positioned relative to the pin so that the second end portion of the pin is disposed within the second hole, (v) a first seal arrangement interposed the first collar and the bushing such that the first seal arrangement contacts the first collar and the bushing, and (vi) a second seal arrangement interposed the second collar and the bushing such that the second seal arrangement contacts the second collar and the bushing. The first collar is fixed in relation to the pin so that the first collar is unable to rotate relative to the pin. The second collar is fixed in relation to the pin so that the second collar is unable to rotate relative to the pin. The bushing is able to rotate relative to the pin around the longitudinal axis. 
     In accordance with another embodiment of the present invention, there is provided a track type work machine. The track type work machine includes a track shoe and a drive lug secured to the track shoe. The work machine also includes a drive sprocket having (i) hub, (ii) a support secured to the hub, and (iii) a cartridge assembly secured to the support, the drive sprocket being positioned relative to the drive lug such that the cartridge assembly is in contact with the drive lug. The cartridge assembly includes (i) a bushing having a passageway defined therethrough, (ii) a pin having a longitudinal axis, the pin being located within the passageway so that a first end portion and a second end portion of the pin extend outwardly from the passageway of the bushing, (iii) a first collar having a first hole defined therein, the first collar being positioned relative to the pin so that the first end portion of the pin is disposed within the first hole, (iv) a second collar having a second hole defined therein, the second collar being positioned relative to the pin so that the second end portion of the pin is disposed within the second hole, (v) a first seal arrangement interposed the first collar and the bushing such that the first seal arrangement contacts the first collar and the bushing, and (vi) a second seal arrangement interposed the second collar and the bushing such that the second seal arrangement contacts the second collar and the bushing. The first collar is fixed in relation to the pin so that the first collar is unable to rotate relative to the pin. The second collar is fixed in relation to the pin so that the second collar is unable to rotate relative to the pin. The bushing is able to rotate relative to the pin around the longitudinal axis. 
     In accordance with still another embodiment of the present invention, there is provided a method of servicing a drive sprocket having (i) a hub and (ii) a support secured to the hub. The method includes securing a cartridge assembly to the support. The cartridge assembly has (i) a bushing having a passageway defined therethrough, (ii) a pin having a longitudinal axis, the pin being located within the passageway so that a first end portion and a second end portion of the pin extend outwardly from the passageway of the bushing, (iii) a first collar having a first hole defined therein, the first collar being positioned relative to the pin so that the first end portion of the pin is disposed within the first hole, (iv) a second collar having a second hole defined therein, the second collar being positioned relative to the pin so that the second end portion of the pin is disposed within the second hole, (v) a first seal arrangement interposed the first collar and the bushing such that the first seal arrangement contacts the first collar and the bushing, and (vi) a second seal arrangement interposed the second collar and the bushing such that the second seal arrangement contacts the second collar and the bushing. The first collar is fixed in relation to the pin so that the first collar is unable to rotate relative to the pin. The second collar is fixed in relation to the pin so that the second collar is unable to rotate relative to the pin. The bushing is able to rotate relative to the pin around the longitudinal axis. The bushing, the pin, the first collar, the first seal arrangement, the second collar, and the second seal arrangement define a substantially sealed chamber between an interior surface of the bushing and an exterior surface of the pin. 
     In accordance with yet another embodiment of the present invention, there is provided a drive sprocket arrangement having (i) a hub and (ii) a support secured to the hub. The support has a first aperture and a second aperture defined therein. The arrangement includes a cartridge assembly configured to be press fit into the first aperture and the second aperture. The cartridge assembly has a bushing having a passageway defined therethrough and a pin having a longitudinal axis. The pin is located within the passageway so that a first end portion and a second end portion of the pin extend outwardly from the passageway of the bushing. The arrangement also includes a first collar having a first hole defined therein. The first collar is positioned relative to the pin so that the first end portion of the pin is disposed within the first hole. The arrangement also includes a second collar having a second hole defined therein. The second collar is positioned relative to the pin so that the second end portion of the pin is disposed within the second hole. The arrangement further includes a first seal arrangement interposed the first collar and the bushing such that the first seal arrangement contacts the first collar and the bushing. The arrangement also includes a second seal arrangement interposed the second collar and the bushing such that the second seal arrangement contacts the second collar and the bushing. The first collar is fixed in relation to the pin so that the first collar is unable to rotate relative to the pin. The second collar is fixed in relation to the pin so that the second collar is unable to rotate relative to the pin. The bushing is able to rotate relative to the pin around the longitudinal axis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic representation of a work machine showing a fragmentary perspective view of an undercarriage assembly thereof; and 
     FIG. 2 is a cross sectional view of a cartridge assembly taken along line  2 — 2  of FIG. 1 (note that the support is not shown for clarity of description). 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1 there is shown a schematic representation of a work machine  10  which incorporates the features of the present invention therein. Work machine  10  includes an undercarriage assembly  12  having a drive sprocket  16 , a track chain  14 , and a drive shaft  82 . Drive shaft  82  is operatively coupled to drive sprocket  16 . In particular, drive shaft  82  is mechanically coupled to hub  22  such that an engine (not shown) operatively coupled to drive shaft  82  can rotate drive shaft  82  and drive sprocket  16  in the directions indicated by arrows  86  and  88 . 
     Drive sprocket  16  includes a hub  22  and a support  24  secured to hub  22 . Support  24  includes a flange  26  and a flange  28 . Each flange  26  and  28  extends outwardly from hub  22  and has a number of apertures defined therein. In particular, flange  26  has apertures  30  defined therein and flange  28  has apertures  32  defined therein. It should be understood that flange  26  is positioned relative to flange  28  so that each aperture  30  is linearly aligned with an aperture  32 . As discussed in greater detail below, drive sprocket  16  also has a number of cartridge assemblies  34  secured to support  24 . In particular, each pair of aligned apertures  30  and  32  has a cartridge assembly  34  disposed therein, for example press fit therein, so that collars  48  and  52  of cartridge assembly  34  are respectively located with in apertures  30  and  32 . 
     Track chain  14  includes a number of track shoes  18  entrained by a plurality of track links (not shown for clarity of description) which are secured to track links  18 . Track chain  14  also includes a drive lug  20  secured to each track shoe  18 . It should be appreciated that track chain  14  defines a closed loop which is operatively coupled to the above described drive sprocket  16 . 
     As previously mentioned, drive sprocket  16  has a number of cartridge assemblies  34  secured to support  24 . Note that all of the cartridge assemblies  34  secured to support  24  are substantially identical, therefore only one cartridge assembly  34  will be discussed herein. Now referring to FIG. 2, cartridge assembly  34  includes a bushing  36  having a passageway  38  defined therethrough and a pin  40  having a longitudinal axis  42 . Pin  40  is located within passageway  38  so that an end portion  44  and an end portion  46  of pin  40  extend outwardly from passageway  38  of bushing  36 . Furthermore, pin  40  has a reservoir  70  and a channel  72  defined therein. Channel  72  is in fluid communication with both reservoir  70  and an exterior surface  64  of pin  40  so that a fluid (e.g. oil) contained within reservoir  70  is advanced from reservoir  70  onto exterior surface  64  of pin  40  during use of drive sprocket  16 . 
     As previously mentioned, cartridge assembly  34  also includes collar  48 . Collar  48  has a hole  50  and a seal groove  66  defined therein. Collar  48  is positioned relative to pin  40  so that end portion  44  of pin  40  is disposed within hole  50  and seal groove  66  is in an opposing relationship with bushing  36 . As mentioned above, cartridge assembly  34  further includes collar  52 . Collar  52  has a hole  54  and a seal groove  68  defined therein. Collar  52  is positioned relative to pin  40  so that end portion  46  of pin  40  is disposed within hole  54  and seal groove  68  is in an opposing relationship with bushing  36 . Cartridge assembly  34  also has a seal arrangement  56  interposed collar  48  and bushing  36  such that seal arrangement  56  contacts collar  48  and bushing  36 . In particular, seal arrangement  56  includes a thrust member  76  and a seal member  78  which are located in seal groove  66  so that seal member  78  is interposed thrust member  76  and bushing  36  such that seal member  78  is urged into contact with an end face  80  of bushing  36 . Cartridge assembly  34  further includes a seal arrangement  58  interposed collar  52  and bushing  36  such that seal arrangement  58  contacts collar  52  and bushing  36 . In a similar manner as that discussed above, seal arrangement  58  includes a thrust member  90  and a seal member  92  which are located in seal groove  68  so that seal member  92  is interposed thrust member  90  and bushing  36  such that seal member  92  is urged into contact with an end face  94  of bushing  36 . 
     Collar  48  is fixed in relation to pin  40  so that collar  48  is unable to rotate relative to pin  40 . Collar  52  is also fixed in relation to pin  40  so that collar  52  is unable to rotate relative to pin  40 . Bushing  36  is able to rotate relative to pin  40  around longitudinal axis  42 . 
     It should be appreciated that bushing  36 , pin  40 , collar  48 , seal arrangement  56 , collar  52 , and seal arrangement  58  define a substantially sealed chamber  60  between an interior surface  62  of bushing  36  and an exterior surface  64  of pin  40 . Substantially sealed chamber  60  contains a lubricant, such as oil, therein which facilitates the functioning of cartridge assembly  34 . 
     Now referring back to FIG. 1, track chain  14  is positioned relative to drive sprocket  16  so that as drive shaft  82  rotates drive sprocket  16  in the directions indicated by arrows  86  and  88 , cartridge assemblies  34  come into contact with drive lugs  20  secured to track shoes  18 . Contacting cartridge assemblies  34  with drive lugs  20  in the above described manner results in track chain  14  being rotated around a path defined by drive sprocket  16  and one or more idler wheels (not shown). Rotating track chain  14  in the above described manner advances work machine  10  over the ground (not shown) to perform various work functions. 
     After a time period of operating work machine  10  in the above described manner one or more cartridge assemblies  34  may need replacing due to the wear and tear the cartridge assemblies  34  are subjected to during their use. For example, as shown in FIG. 1, once a worn cartridge assembly  34  that needs replacing is identified, it is removed from support  24  by any a well known manner. Once the worn cartridge assembly  34  is removed from support  24 , a pre-assembled replacement cartridge assembly  84  is secured to support  24  so as to replace the worn cartridge assembly  34 . In particular, pre-assembled replacement cartridge assembly  84  is press fit into the appropriate apertures  30  and  32  so as to replace the worn cartridge assembly  34 . It should be appreciated that replacement cartridge assemblies  84  are substantially identical to the above described cartridge assemblies  34  and therefore a detailed description of replacement cartridge assemblies  84  will not be given herein. 
     The above described method of replacing worn cartridge assemblies  34  with replacement cartridge assemblies  84  can be repeated as many times as required. Once the worn cartridge assemblies  34  are replaced in the above described manner, track chain  14  is rotated again as previously described so as to advance work machine  10  over the ground (not shown) to perform various work functions. 
     INDUSTRIAL APPLICABILITY 
     It should be appreciated that each cartridge assembly  34  (and therefore any replacement cartridge assembly  84 ) has many advantages which facilitate the functioning of drive sprocket  16  and therefore work machine  10 . For example, each cartridge assembly  34  enhances the life of drive sprocket  16  by improving the retention of a lubricant contained within cartridge assembly  34 . Moreover, since each cartridge assembly  34  is self-contained and provides essentially all of the sealing and bearing functions required by drive sprocket  16 , drive sprocket  16  can be easily serviced by removing old worn cartridge assemblies  34  and replacing them with new replacement cartridge assemblies  84 . Removing and replacing the entire worn cartridge assembly  34  to service drive sprocket  16  is more cost effective and efficient as compared to other drive sprocket designs which require servicing in a piece part manner. 
     Other aspects and features of the present invention can be obtained from a study of the drawings, the disclosures, and the appended claims.