in the detailed description of the invention , like numerals are employed to designate like parts throughout . various items of equipment , such as fasteners , fittings , etc ., may be omitted to simplify the description . however , those skilled in the art will realize that such conventional equipment can be employed as desired . although the protection system of the current will be described in relation to a center pivot irrigation system , those skilled in the art will understand that the invention is also applicable to gear drive gearboxes or other drive train or power transmission systems used with other irrigation system uses , one such non - limiting example being linear or lateral irrigation systems , or other oil field or industrial , or agricultural application . with reference to fig1 a center pivot irrigation system 10 of the kind known in the art generally comprises an approximately one - quarter mile length of mechanized irrigation pipe 12 supported and propelled by motorized wheel towers 14 rotating on a center pivot point ( not shown ). typically , the pipe spans are approximately 120 to 180 feet in length and utilize 6 to 10 inch diameter steel pipe irrigating waters or other fluids . drive motors 16 are utilized to provide forward or reverse propel movement of the irrigation system . attached to the pipe 12 are sprinkler or other liquid emitters 18 . fig2 more specifically illustrates the drive train 20 for each support tower . specifically , the mechanized drive train 20 , which is supported on tower chassis 14 , includes an electric gearmotor 16 and primary gearbox 22 acting as the primary drive unit . extending from primary gearbox 22 to each wheel 24 is a drive shaft 26 . at wheel 24 , drive shaft 26 attaches to a wheel drive gearbox 28 which powers wheel hub 30 on which is mounted wheel 24 . typically drive shaft 26 will be attached to wheel drive gearbox 28 via a universal joint or coupler ( not shown ). with reference to fig3 and 4 , a wheel drive gearbox 28 of the present invention is shown . gearbox 28 is formed of an outer housing 32 in which is mounted an output bearing 34 used to rotatingly secure an output shaft 36 within housing 32 . output shaft 36 includes a first end 38 and a second end 40 , wherein said second end 40 extends from said outer housing 32 through a housing cap 42 having an output aperture 44 defined therein . mounted on the second end 40 of output shaft 36 is an output spindle 46 comprising a tubular member 48 attached to said output shaft 36 and a wheel hub 30 concentrically attached to said tubular member 48 . adjacent the first end 38 of output shaft 36 is mounted worm gear 50 . worm gear 50 includes a cylindrical collar 52 around which is disposed a circular flange 54 having teeth 56 mounted around the periphery of the flange 54 . rotation of worm gear 50 results in rotation of output spindle 46 and wheel hub 30 . an input shaft 58 having a first end 60 and a second end 62 is also rotatingly mounted within housing 32 . input shaft 58 is supported within housing 32 by input bearings 64 and is provided with worm threads 66 along its length . the second end 62 of input shaft 58 extends from housing 32 through a housing cap 68 having an input aperture 70 therein , and is disposed for engagement by drive shaft 26 ( fig2 ). input shaft 58 is mounted within housing 32 so that the axis of input shaft 58 is perpendicular to the axis of output shaft 36 and the worm threads 66 of input shaft 58 engage the teeth 56 of worm gear 50 . a ceramic face mechanical seal 72 is provided adjacent the input shaft 58 and output shaft 36 where each shaft extends from housing 32 . specifically , adjacent the output shaft 36 , seal 72 is fitted within housing cap 42 and adjacent the input shaft 58 , seal 72 is fitted within cap 68 . seal 72 is also mounted so that it is substantially flush with the adjacent bearing 34 , 64 , and in sealing contact with the shaft around which said seal 72 is mounted . as seen in the figures , adjacent both output aperture 44 and input aperture 70 , seal 72 is mounted within gearbox housing 32 , and specifically cap 42 , 68 , thereby protecting seal 72 from the exterior environment . those skilled in the art will understand that by mounting seal 72 between the cap , bearing and shaft , the seal 72 of the present invention is preloaded and does not require external spring elements for loading as do the general face seals of the prior art . it is this preloading that boosts the seal &# 39 ; s pressure capacity and results in the achieved benefits for the gearbox of the present invention . with reference to fig5 and turning more particularly to seal 72 , it is formed of a compressed and sintered silicon carbide and is comprised of a cap element 78 and a bearing element 80 . cap element 78 includes a cup portion 82 and a face portion 84 wherein cup portion 82 mounts within a journal 86 bored into cap 46 , 68 . bearing element 80 includes a boot portion 88 and a face portion 90 , wherein bearing element 80 is mounted around shaft 36 and said boot portion 88 is compressed against the adjacent bearing . as seen in fig3 and 4 , when mounted in this fashion , the face portion 84 of cap element 78 and the face portion 90 of bearing element 80 are urged into sealing contact with one another at a seal interface . the above described system will inhibit vegetation or other debris from damaging gearbox and gear motor seals or compromising the drive train of various agricultural and industrial equipment . furthermore , the system assures internal pressure of the gear drive of such equipment . while standard prior art seals will generally only hold internal gearbox pressures of 10 - 15 psi , internal gearbox pressures in excess of 60 psi have been experienced in irrigation drive line gearboxes of the present invention . those skilled in the art will understand that although the protection system has been specifically described for use with center pivot irrigation systems , the protection system is also suitable for other equipment . while certain features and embodiments of the invention have been described in detail herein , it will be readily understood that the invention encompasses all modifications and enhancements within the scope and spirit of the following claims .
a gearbox for a drive line irrigation system in which the input and output shafts of the gearbox are sealed with a compressed and sintered silicon and carbide face seal . the face seal is contained within the gearbox and compressed between a gearbox end cap and a shaft bearing , obviating the need for external loading by bellows or similar spring elements .