Abstract:
A power train assembly is driveably engaged with an input source and includes a transmission module having a casing and a drive member. The transmission module is driveably connected to the input source and a creeper module is driveably engaged with the drive member of the transmission module. The creeper module is detachably mounted to the casing of the transmission module. An output assembly is in driving engagement with the creeper module and a control interface is configured to selectively engage the creeper module to transform the speed of the drive member to a reduced speed of the output member.

Description:
This application claims the benefit of prior provisional patent application Ser. No. 60/312,588 filed Aug. 15, 2001. 

   TECHNICAL FIELD 
   The present invention relates to a power train system having a gear reducing creeper assembly. More particularly, the invention pertains to a power train including a selectively activated creeper module. 
   BACKGROUND 
   In known power train systems having creeper capabilities the operator may select a low gear which is typically desirable when accurate and precise machine positioning is warranted. The power train system generally includes a transmission having a creeper gear assembly integrated into the transmission gearing within a transmission casing. Consequently, manufacturers are required to manufacture and stock several types of transmissions including transmissions having creeper capabilities and transmission without. Moreover, designers of creeper mechanisms are generally allowed little if any extra space within the transmission casing and are forced to maintain the creeper assembly within a compact space within the transmission casing. 
   For example, U.S. Pat. No. 4,706,519, issued to Beim and having an issue date of Nov. 17, 1987, discloses a transmission assembly including a creeper mechanism integrated into the transmission assembly. The creeper portion of the transmission, in addition to the transmission gearing are enclosed within a transmission casing. More specifically, a bulkhead is anchored to an interior of the casing and supports the creeper mechanism. 
   It is desirable to provide a power train system of simple construct which includes a creeper mechanism without a significant increase in cost of manufacture, processing and storage of additional components associated with this system. Further, a power train system which is easy to engage, disengage and disable without premature creeper component failure and wear is desirable. 
   The present invention is directed to overcoming one or more of the problems as set forth above. 
   SUMMARY OF THE INVENTION 
   In one aspect of the present invention a power train assembly is driveably engaged with an input source and includes a transmission module having a casing and a drive member. The transmission module is driveably connected to the input source and a creeper module is driveably engaged with the drive member of the transmission module. The creeper module is detachably mounted to the casing of the transmission. An output assembly is in driving engagement with the creeper module and a control interface is configured to selectively engage the creeper module to transform the speed of the drive member to a reduced speed of the output member. 
   In another aspect of the present invention a creeper module for receiving a drive member of a transmission rotating at a drive speed and being selectively engageable with an output assembly includes a housing disposed between the transmission module and the output assembly. A sun gear is in driving engagement with a ring gear through a plurality of planetary gears and said plurality of planetary gears are supported by a carrier member. A clutch assembly is rotatably supported by the housing and is configured to directly and driveably couple the output assembly with the drive member in a direct drive arrangement and is configured to directly and driveably couple the output shaft with the carrier member in a creeper drive arrangement. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic representation of a power train system according to the present invention; 
       FIG. 2  is a perspective view of the creeper module and transmission of the power train system of  FIG. 1 , showing the creeper module attached to the transmission casing; and 
       FIG. 3  is sectional view of the creeper module of  FIG. 2  taken along line  2 - 2  of  FIG. 2 ; and 
       FIG. 4 . is a chart showing the gear and respective speed of the power train system of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , a power train system is driven by an input source  12 , such as an internal combustion engine, for example. A transmission module  14  is mounted directly to the input source  12  through a drive engagement  15  such as a spline engagement or as is customary. The transmission module  14  includes a drive member  16  which connects with the creeper module  18 . Creeper module  18  is coupled to an output assembly  20  through an output member  22 . 
   Creeper module  18  includes a clutch assembly  24  which is effective to reduce the speed of drive member  16  and deliver the reduced speed output to output member  22 . Alternatively, and as will be explained in detail hereinbelow, the creeper module  18  also includes a mode in which the speed of output member  22  substantially tracks the speed of drive member  16 . 
   Creeper module  18  is selectively engaged by user manipulation of activation member  26  which transmits a signal to solenoid  42  through instrument line  28 . In turn, solenoid positions operator  36  such that creeper module  18  is engaged, disengaged (to provide a 1:1 speed ratio between the drive and output member  16 ,  22 ), or placed in neutral. 
   Clutch assembly  18  is engaged when fluid is supplied to either hydraulic line  30  or  32  by pump  34  through supply line  44  and operator  36 . Fluid pressure within clutch assembly  24  is relieved to tank  40  through operator  36  and return line  38 . Although, operator  36  is illustrated as a three-position valve arrangement, it is envisioned that the operator  36  may include a two-position valve which eliminates the neutral mode. 
   Referring to  FIG. 2 , the creeper module  18  is shown, and notably, creeper module  18  is mounted to an external portion  46  of a casing  48  of the transmission module  14  by bolts  50 . Hence, power train system  10  may be constructed using a common transmission mechanism and by adding on the creeper module which eliminates the significant costs associated with designing, manufacturing and stocking multiple transmission types. 
   Referring again to  FIG. 2 , clutch assembly  24  of creeper module  18  is hydraulically connected to operator  36  through hydraulic lines  30 ,  32 . Hydraulic line  30  is directly connected to a first clutch mechanism or a direct drive clutch  52  ( FIG. 3 ) and hydraulic line  32  is connected to a second clutch mechanism or a creeper clutch  54  ( FIG. 3 ). As best shown in  FIG. 2 , a lubrication line  56  supplies oil to creeper gear assembly  58 . 
   Referring to  FIG. 3 , creeper module  18  includes a housing  60  having a collar portion  62  supporting a bearing assembly  64 . Housing  60  abuts external portion  46  of transmission module  14  as is best shown in  FIG. 2 . A piston housing  66  is mounted on bearing assembly  64  such that piston housing  66  is rotatable relative to collar position  62  of creeper housing  60 . A carrier ring  68  is attached to collar portion  62  and includes a pair of seals  74  which straddle through ports  72 . Seals  74  provide a fluid seal between stationary housing  60  and rotatable piston housing  60 . It may be seen that a fluid piston chamber  70  for the direct drive clutch  52  is formed between the piston housing  66  and axial moveable piston  71 . Piston  71  is biased toward piston housing  66  by spring  78  which encircles rim  75  of piston housing  66 . A retaining ring  76  retains both spring  78  and piston  71  on piston housing  66 . 
   Inner clutch assembly or direct drive clutch  52  includes a plurality of axially spaced clutch plates  82  fixed to hub  80  through a spline engagement, for example. Hub  80  is splined to sun gear  83  and sun gear  83  is splined to drive member  16 . Each clutch plate  82  is separated by an associated clutch plate  84  and each clutch plate  84  is fixed to ring gear  86  on an outer diameter thereof. Hence, clutch plates  82  inter-engage within clutch plates  84  and the inter-engage arrangement abuts piston  71  to form the direct drive clutch  52 . 
   Outer clutch assembly or creeper clutch  54  is formed of a plurality of axially spaced clutch plates  92  which are attached, at an inner diameter thereof, to an outer portion  90  of ring gear  86  through a spline engagement, for example. Clutch plates  92  are separated by associated clutch plates  94  and clutch plates  94  are attached to an inner portion  96  of creeper housing  60 . 
   A piston  98  abuts an axial end  99  of creeper clutch  54 . Piston  98  is axially moveable within piston housing  100  and a piston chamber  104  is formed between piston  90  and housing  100 . Chamber  104  is fluidly sealed through seal  102 , captured within piston  90 , and in sealing contact with the walls forming piston housing  100 . 
   Ring gear  86  includes a projecting ring portion  108  which has an inner wall  110  defining a plurality of gear teeth  112  which mesh with planet gears  114  of creeper gear assembly  58 . Creeper gear assembly includes sun gear  83 , planet gears  114  and carrier member  116 . Carrier member  116  includes gear support posts  118  which respectfully rotateably support planet gear  114 . Retaining ring  120  retains carrier member  116  within ring gear  86 . Carrier member  116  includes a splined portion  122  which is engaged by splined portion  124  of output member  22 . Noteably, output member  22  includes a butt end  126  facing a butt end  128  of drive member  16 . It may be seen that carrier member  116 , fixed to output member  22 , is independently rotatable relative to hub  80  and sun gear  83  which are fixed relation to drive member  16 . 
   INDUSTRIAL APPLICABILITY 
   Referring now to  FIG. 3 , in operation, activation member  26  ( FIG. 1 ) is manipulated by a user when creeper mode is desired and the operator  36  is shifted toward position  130  ( FIG. 1 ). Pump  34  ( FIG. 1 ) pressurized fluid toward creeper clutch mechanism  54  of creeper module  18  and power flow is directed from the drive member  16  of the transmission module  14  to the sun gear  83 . Engagement of the creeper clutch “grounds” the ring gear  86  and power flows out of the creeper planetary assembly  58  through the carrier member  116  to the output assembly  20 . The output assembly  20  may be a pinion shaft in mesh with a bevel gear to provide movement to ground engaging wheels of an earthmoving machine, for example. The speed of the output member at this point is now as low as one-fourth the speed of the drive member of the transmission module. 
   When direct drive and disengagement of the creeper module is desired, the activation member  26  ( FIG. 1 ) is accordingly positioned and operator  36  ( FIG. 1 ) is placed in position  132 . Correspondingly, the direct drive clutch is engaged and the creeper clutch is disengaged. With the direct drive clutch engaged, power flows from the drive member of the transmission module to the sun gear, and the sun gear, the ring gear, and the carrier member, all rotate at the same speed. Power flows from the output member to the output assembly, however, now the speed ratio between the drive member speed and output member speed is 1:1. 
   In a third position indicated as  134  ( FIG. 1 ), operator  36  blocks all pump flow to the clutch assembly which disables the creeper module. Accordingly, the drive member rotates, however the output member includes little if any movement and the creeper module is in a neutral mode. 
   Referring to  FIG. 4 , listed an exemplary transmission gears of a  16  forward,  4  reverse transmission attached to the present invention creeper module and associated speed relative to each gear. It may be seen that the creeper module provides a forward speed range of 0.4 mph to 6.2 mph and a reverse speed range of 0.3 mph to 2.2 mph.