Abstract:
An accessory drive system to provide engagement between a driving input source and a driven accessory unit includes a housing attachable to the input source. A fluid suction port and a discharge port are defined by the housing and the suction port is in fluid communication with a fluid reservoir of the input source. The fluid discharge port is in fluid communication with the suction port and a gear assembly is rotatably supported by the housing. The accessory unit is operably engaged by the input source through the gear assembly and the gear assembly is structured and arranged within the housing to urge fluid away from the housing in response to movement of the gear assembly.

Description:
TECHNICAL FIELD 
     The present invention relates to a combination drive assembly and particle trap for operatively engaging a plurality of accessory units and providing filtered fluid to the accessories under a positive head condition. 
     BACKGROUND 
     Pump drive assemblies for mechanically powering an accessory pump such as a steering pump and/or implement pump are well known. One type of known pump drive assembly includes a gear assembly support housing externally mounted to a transmission casing of a transmission with the input gear of the transmission utilized to drive the pump drive assembly. The accessory pump, as it is driven by the transmission, pumps transmission fluid through a dedicated line connected between the accessory pump and a flanged suction port provided on the transmission casing. The dedicated line may include a screen assembly spliced into the dedicated line to trap particles entrained in the transmission fluid before the fluid reaches the accessory pump. 
     The accessory drive assembly is typically mounted on the transmission casing at a position above the fluid level in the transmission so that the fluid does not unduly restrict rotation of the drive assembly in contact with the fluid. The gears of the accessory drive assembly are often pre-lubricated, during assembly, for example, with grease so that additional lubrication by the transmission fluid is not required. If fluid does enter the accessory drive assembly housing for any reason an amount of fluid may be trapped within the accessory drive housing and become significantly elevated in temperature which is known to cause gear failure or premature wear of the gears and bearings. To avoid compromising the accessory drive assembly, the accessory drive assembly is generally positioned away from the fluid to prevent problems caused by the interaction between the stagnant fluid and the gears. 
     The installation of the accessory drive assembly to the transmission generally includes, first, attaching the various drive assemblies so that the accessory pump is activated corresponding to rotation of the input shaft of the transmission. Second, at least one transmission fluid line must be installed between a flange on the transmission casing, below the level of fluid contained in the transmission casing, and the flange or connector on the accessory pump. Furthermore, a particle trap or filter screen is generally introduced within the transmission fluid to ensure that particles and debris entrained in the fluid are prevented from entering the accessory pump. Hence, installing an accessory pump and drive system requires multiple components and significant labor to equip a transmission with such a system. 
     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 an accessory drive system to provide engagement between a driving input source and a driven accessory unit is provided and includes a housing attachable to the input source. A fluid suction port and a discharge port are defined by the housing and the suction port is in fluid communication with a fluid reservoir of the input source. The fluid discharge port is in fluid communication with the suction port and a gear assembly is rotatably supported by the housing. The accessory unit is operably engaged by the input source through the gear assembly and the gear assembly is structured and arranged within the housing to urge fluid away from the housing in response to movement of the gear assembly. 
     In another aspect of the present invention a method for operably engaging a fluid circulating accessory unit to an input source is provided and the method includes driving a gear assembly attached to the input source through a housing; circulating fluid from a reservoir to the accessory unit through the housing; and removing substantially all of the fluid entering a gear chamber of the housing through movement of the gear assembly within the housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an accessory drive system according to the present invention; 
     FIG. 2 is an exploded view of the input source and the accessory drive assembly of FIG. 1; 
     FIG. 3 is a plan view of the accessory drive unit of FIG. 1; 
     FIG. 4 is a sectional view of the accessory drive unit of FIG. 1, taken along line  4 — 4  of FIG. 3; 
     FIG. 5 is a perspective view of the accessory drive unit of FIG. 1 illustrating the idler gear and suction port; 
     FIG. 6 is a sectional view of the accessory drive unit of FIG. 1, taken along line  6 — 6  of FIG. 3, showing the particle trap assembly contained therein; and 
     FIG. 7 is a sectional view of the accessory drive unit of FIG. 1, taken along line  7 — 7  of FIG. 4, showing the gear assembly within the housing. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, an accessory drive system  9  is shown which includes input source  10 , such as transmission, for example, in driving engagement with an accessory drive assembly  12 . Accessory drive assembly  12  includes housing  14  attached to casing  16  of input source  10 . Accessory drive assembly  12  supports a first accessory unit  18  and a second accessory unit  20  which may be steering and implement pumps, for example. 
     Referring to FIG. 2, housing  14  includes a flange portion  24  and a projecting portion  22  extended from the flange portion  24 . The projecting portion  22  includes an opening  23  from which an idler gear  42  extends therefrom. Flange portion  24  includes a flange face  26  which overlays face  28  of casing  16 . Projecting portion  22  extends into slot  32  within casing  16 . As best shown in FIG. 5, housing  14  includes a suction port  30  which overlays port  34  extended through casing  16  of input source  10 . Referring to FIG. 3, bolts  36  extend through flange portion  24  of housing  14  and engage threaded holes  38  (FIG. 2) in casing  16 . 
     Referring to FIG. 4, accessory drive assembly  12  includes a gear assembly  40  including the idler gear  42  and an output gear  44 . Idler gear  42  meshes with an input gear (not shown) enclosed within the casing  16  and is driven by the input source  10 . The output gear  44  is meshed with the idler gear  42  and both output and idler gears  44 ,  42  are rotatably supported by the housing  14 . In an exemplary embodiment, the idler gear includes thirty-six teeth and is respectively meshed with a transmission gear having thirty-five teeth and an output gear having thirty-nine teeth. As best shown in FIG. 4, output gear  44  includes a first spline portion  46  which accordingly engages with a splined shaft (not shown) of first accessory unit  18  (FIG.  1 ). Similarly, a second spline portion  48  is provided in output gear  44  and accordingly engages with a splined shaft (not shown) provided by second accessory unit  20  (FIG.  1 ). 
     Referring again to FIG. 4, housing  14  includes first housing portion  52  sealably attached with housing cover  54  by conventional bolting means. Output gear  44  is rotatably supported by first housing portion  52  and housing cover  54  through respective bearing assemblies  56 ,  58 . First bearing assembly  56  includes an outer surface  60  which is engaged by inner bore  62  of first housing portion  52 . Bearing assembly  56  includes an inner surface  64  engaged by collar portion  66  of output gear  44 . Similarly, second bearing assembly  58  includes an outer surface  68  engaged by inner bore surface  70  of housing cover  54 . Bearing assembly  58  includes an inner surface  72  engaged by collar portion  74  of output gear  44 . 
     Idler gear  42  is rotatably supported by housing  14  as hereinafter described. Pin  76  and bearing  77  extend through hole  78  in idler gear  42  to generally center gear  42  about outer surface  80  of pin  76 . Pin  76  is accordingly sized in relation to holes  82 ,  84  within housing  14  to hold pin  76  stationary as idler gear  42  rotates thereabout. 
     Referring to FIGS. 4 and 7, output gear  44  includes a periphery portion  86  which is closely arranged with an inner surface  88  of housing  14 , forming clearance  90  therebetween. Clearance  90 , which may also be referred to as a “draft”, uniformly extends along each lateral surface  91 ,  93  and along the periphery portion  86  of output gear  44  within a gear chamber  95  of housing  14 . In an exemplary embodiment, clearance or draft  90  may be 1.5 mm, for example. A discharge chute  92  is provided radially outside output gear  44  within the housing  14  which receives fluid purged from gear chamber  95  of housing  14  by output gear  44  as hereinafter described. An opening  97  is provided in flange  24  of housing  14  so that fluid directed through discharge chute  92  may exit the accessory drive assembly  12  (FIG.  7 ). 
     As best shown in FIG. 4, the accessory units  18 ,  20  (FIG. 1) respectively mount to faces  45 ,  47  of housing  14 . Housing  14  includes a pair of intake openings  49 ,  50  which respectively receive fluid from the accessory units  18 ,  20 . 
     Referring to FIG. 6, a particle trap assembly  96  is provided within suction chamber  94  of housing  14  to trap particles and debris entrained within the fluid entering the accessory drive assembly  12  from a fluid reservoir (not shown) formed within the casing  16 . The particle trap assembly  96  may include a cylindrical screen assembly  98  which is impregnated, circumferentially along portions of each end  100 ,  104  with a resilient elastomer or other screen-to-casting-seal structure known to those having ordinary skill in the art. Furthermore, it is envisioned that the screen assembly  98  may be made of an alternative material such as corrugated cellulose, for example, or any other alternative material known to those having ordinary skill in the art. 
     Screen assembly  98  includes end  100  projecting into, and circumferentially sealed within, counterbore  102  of housing  14 . Similarly, end  104  of screen assembly  98  engages circumferential rim portion  106  of housing  14 . End  104  of screen assembly  98  includes end wall  105  which encloses end  104  and is preferably constructed of either the filter material itself or by the seal extending over end  104  of the screen assembly  98 . In contrast, end  100  of screen assembly  98  includes opening  107  to allow the clean fluid, which has passed through the screen assembly, to pass through the discharge port  99  and be accordingly directed to the accessory units. A retaining member  108 , such as a wave spring or arched retaining ring, for example, is positioned between end wall  105  of screen assembly  98  and a service cover  110  to secure the screen assembly  98  such that it is sealed within suction chamber  94  of housing  14 . Cover  110  is sealed to housing  14  through an O-ring seal  114  and is secured to housing  14  by fasteners  112  (FIG.  3 ). 
     Referring to FIGS. 1 and 5, discharge port  99  includes an inner surface  116 , preferably machined, to sealably receive a tube end (not shown) fitted with an O-ring seal (not shown) to form a conventional pipe-to-port, or “slip-joint” type sealing arrangement. Alternatively, it is envisioned that the pipe may include an integral flange which may abuttingly interface with a complementary flange provided by the housing, such as a four-bolt flange for example. Accordingly, fluid passing through discharge port  99  is directed to respective charge pumps (not shown) fluidly connected to accessory units  18 ,  20  (FIG.  1 ). 
     Industrial Applicability 
     Referring to FIG. 2, in an exemplary embodiment accessory drive system  9  is driven by input source  10  which may be a transmission including a rotatable drive gear (not shown) meshed with idler gear  42  which urges rotation of output gear  44  (FIG.  7 ). The transmission includes a reservoir having a level of fluid contained within casing  16  which is generally above the port  34  within casing  16 . Since the port  34  is generally below the level of fluid within the casing, the fluid flows into, and is continuously present within, the suction chamber  94  of the housing  14 . Fluid enters the gear chamber  95  from the accessory units  18 ,  20  through intake openings  49 ,  50  within the housing  14  (FIG.  4 ). 
     Referring to FIG. 7, operation of the gear assembly  40  will now be described. Accessory units  18 ,  20  (FIG. 1) direct fluid to the gear assembly  40  through bearing assemblies  56 ,  58  (FIG.  4  and FIG. 7, however only bearing assembly  56  is shown in FIG. 7) rotatably supporting idler gear  42 . As the fluid travels through the bearings and across the idler gear, the fluid is urged from the idler gear to the output gear. The respective rotational motion of the idler and output gears is shown by arrows  118 ,  120 . Fluid may enter opening  23  in projecting portion  22  of housing  14 , possibly subjecting gear  42  to partial immersion in fluid, however it is envisioned that the gear assembly  40  would be effective to remove even significant amounts of fluid which may have entered into housing  14 . 
     Since the output gear  44  is closely fitted within the gear chamber  95  substantially all of the fluid entering the gear chamber  95  is urged out of the gear chamber  95  by the output gear  44 . Arrows  122 , which are in proximity to the periphery portion  86  of the output gear  44 , indicate the fluid path as fluid passes through the gear chamber  95 . It may be seen that the fluid moves through the discharge chute  92  and exits the accessory drive assembly  12  through discharge opening  97 . The output gear  44  urges fluid away from the accessory drive assembly and back into the transmission casing  16  through the discharge chute  92  and then through the opening  97  within projection portion  22  of housing  14 . As a result, an insignificant amount of fluid resides within the housing, and consequently, the input and idler gears experience little if any resistance due to fluid. 
     Since the suction port  30  (FIG. 5) of the housing  14  is submersed in fluid within the fluid reservoir and generally below a fluid level of the reservoir, a positive fluid pressure or “head” is established at the site of the input of the accessory unit (not shown). As a result, a positive head is experienced by accessory units which increase the performance, controllability and responsiveness of the accessory units. 
     Other aspects, objects and advantages of the invention can be obtained from a study of the drawings, the disclosure and the appended claims.