ZA200605818B - Housing for long travel high capacity friction draft gear assembly - Google Patents

Description

HOUSING FOR LONG "TRAVEL HIGH CAPACITY

FRICTION DRAFT GEAR ASSEMBLY

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims prior ity from U.S. Provisional Patent Application Serial No. 60/537, 294 filed on January 16, 2004. This application ig further closely related to co-pending U.S. Serial Number 10/927,910 entitled "Long Travel High Capacity Friction Draft Gear Assembly”, to co-pending U.S. Serial Number _10/928,843 entitled "Long Bwff

Short Draft Travel Draft Gear for Use in a 24.625 Imch

Pocket”, filed concurrently herewith. These applications are being assigned to the assignee of the present invention and the disclosures of these co-pending applications are hereby incorporated by reference thereto.

FIELD OF THE INVENTION

The present invention relates, in general, to friction-type draft gear assemblies for use in cushioning both buff and draft shocks normally encountered by railroad roll-ing stock during make-up and opexation of a train consist on. a track structure and, more part icularly, this invention relates to a friction-type draft gear assembly having a longer travel.

BACKGROUND OF THE INVENTION

Friction type draft gear assemblies are widely ussed in United States railroad industry to provide protection to a railway car. by absorbing shocks in both draft and buff conditions must meet various Association of American Railroads (AAR) requirements. In one aspect, draft gear must be capable of maintaining the minimum shock absorbing capacity during dts service life required by AAR standard M-901-G to be at least 36,000 foot pounds being measured during a drop hammer tesst.

In the other aspect, AAR mandates working action of such draft gear to be achieved without exceeding a 500,000 pound reaction pressure acting on the freightt car sills in order to prevent upsetting the coupler shank. In a further aspect, the draft gear must fit into a standard railway car pocket of 24.62 inches in length.

US Patents 5,152,409, 5,590,797 and 3,368,698, all owned by assignee of the present invention and hereby incorporated by reference thereto, relate to commonly used friction draft gears, which are installed in alignment with a railway car center sill havimg a pair of front stops and a pair of rear stops. Such draft gears include a housing fitting entirely between the front and rear stops and having an open front portion disposed adjacermt a pair of front stops and a closed rear portion which engages a pair of rear stops. A compressible cushioning element is positioned within the rear portion of the housing. A <Xriction cushioning element is adopted in the front portion of the housing. The draft gears further include a spring release mechanism for continuously urging the friction cushionimg element outwardly from the compressible cushioning elemment thereby releasing such friction cushioning element after compression of such draft gears. The compressible cushioriing element is typically either of an all spring configuration as taught in US Patents 5,152,409 and 5,590,797 or of a spring and hydraulic assembly combination as taught in US Pat_ent 3,368,698.

It is now known that certain railroads require a higher protection to the railway car by allowing an extended travel of about 4.75 inches in oxder to meet the requirements.

At the same time, the draft «gear with such extended travel must fit within the identical draft gear pocket length of 24.625 inches as the draft gears presently in use which are capable to travel only 3.25 inches.

SUMMARY OF THE INVENTION

The present inventiomm provides a friction draft gear assembly for railway car stock having a higher shock absorbing capacity while fitting into a standard 24.62 inch long draft gear pocket within the center sill. The friction draft gear assembly comprises a housing closed at one end and open at- the opposed end. The housing has a dual rear chamber adj acent the closed end and a front chamber adjacent the open end which is .in open communication with the dual rear chamber.

The dual rear chamber has a larger first rear portion and a smaller second rear portion disposed adjacent closed end a pair of ledge members disposed intermediate the first and second rear portions for enabling the second por-tion to fit between a pair of rear stops.

The first rear portion is adapted to receive a compressible cushioning element with a pair of spring elements which extend longitudinally from the second portion toward the open front portion.

The use of dual rear chamber enables employment of the longer spring elements, which in combination, enables a longer travel distance of 4.75 inches and, more importantly, enables the friction draft gear assembly to achieve a higher shock absorbing capac:ity while fitting into the standard d=xaft gear pocket being 24.625 inches in length.

Alternatively, the second rear pcrtion may be adapted to receive a compressible cushioning element being a hydraulic assembly or a well known elastomeric pad stack or any combination thereof.

Additionally, the open end may be provided with an extension portion incorporating standard yoke features for direct attachment to a coupler of such railway vehicle.

OBJECTS OF THE INVENTION

It is therefore one of the primary objects of the present invention is to provide a friction draft gear assembly which protects a railway car by absorbing shocks in both dr-aft and buff conditions.

A further object of the present invention is to provide a friction draft gear assembly having a higher shock abezorbing capacity then draft gear assemblies presently in uses.

Another object of the pmesent invention is to prosvide a friction draft gear assembly having a higher shock abs:orbing and having a longer travel d_istance.

Yet another object of the present invention is to provide a friction draft gear assembMy having a higher shock abs orbing capacity and having a longer travel distance while fitting into a 24.625 inches long pockeet.

Additional object of the present invention is to pro-vide a friction draft gear assembly having a higher shock absorbing capacity and having a longer— travel distance capable of direct attachment to a coupler of tke railway car.

These and various other ob—jects and advantages to the present invention will become rmore. apparent to those persons skilled in the relevant art from the following more detailed description, particularly, wken such description is takeen in conjunction with the. atta ched drawings and the appe=nded claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a friction draft gear- assembly of the present invention as installed into a 24.6 25 inch long railway car pocket, pa-xrtially illustrated.

FIG. 2 is a longitudinal cross-sectional view of a friction draft gear assembly of the pressent invention.

FIG. 3 is a perspective views of the friction draft gear assembly of the present inventio:n having an integrated yoke portion for direct attachment to a coupler of a railway car.

DETAILED DESCRIPTION OF THE PREFERRED AND ALTERNATIVE

EMBODIMENTS OF THE INVYENTION

: Prior to proceeding to the mozxre detailed description of tlze present invention, it should be moted that for the sake of c larity identical components, havimg identical functions have been identified with identical reference numerals throughout the several views, which have been illustrated in the drawing £igures.

Thee present invention enables -a higher shock 5 absorbing capacity of the friction draft gear— assembly having a longer travel distance of 4.75 inches anda fitting into a 24.625 inch long pocket by employing a novel housing construction having an extended rear portiora, which enables adaptation of a longer spring design result ing in a longer travel distamce and, wore importantly, in a higher shock absorbing capacity. .

Ref erring to the present invention, as shown in FIG. 1, a friction draft gear assembly, generally designated 10, of the present 4dnvention is disposed within a cavity 102 of a

I5 center sill, generally designated 100, of a r-ailway car which is not shown, but is well known in the art. #2 front stop 104 : and an axlallws opposed rear stop 106 are attached to each side member 103 of the center sill 100 and form a draft gear pocket 108 of a first predetermined length being 24.625 inches. A coupler arm 112 of a coupler 2199 extends from a typical coupler knuckle 110 into the pocket M02. The coupler 109 is genera lly disposed along the longitudinal axis 116 of the center si 11 100. The knuckle 110 of the c¢oupler arm 109 engages a sim-ilar member protruding from a second railway car _ 25 or locomotive to connect the railway cars Eeor travel along railway tracks. A front coupler follower 1.14 is disposed intermediate t-he coupler arm 112 and the fricction draft gear assembly 10 for evenly transmitting the shock »from the coupler knuckle 110.

The friction draft gear assembly 10 includes a housing, genercally designated 12, having a f-irst closed end which is oriented toward the rear stops 106 andl a second open end which is oriented toward the coupler 109. Whe first closed end comprises a first rear portion 13 heaving a first predetermined crosss-section and a second predetermined lencsih and a second rear portion 15 having a second predetermiraed cross-section and a third predetermined length and being axially aligned with the first rear portion 13. The second "rear portion 15 is disposed adjacent a bottom wall 16 whic=h, in combination, close the end of the housing 12. A pair of ledge members 14 having a predetermined width are disposed : intermediate the £ irst and second rear portions 13 and 15 respectively and abut a working surfaces 107 of the pair of the rear stops 106. Such pair of ledge members 14 enables t he second rear portion 15 of the first closed end to extend in to such sill 100 past the working surface 107 of the rear stops 106. It will be appreciated that such second rear portion 15 will be at least partially disposed intermediate such re ar stops 106.

A front portion 20 of the second open end of tlhe housing 12 having a third predetermined cross-section and a forth predetermined length is disposed adjacent the first rear portion 13. Such fr-ont portion 20 is axially opposed to the first closed end and is maintained in open communicaticon therewith. Preferably, such third predetermined cross-sectiecon is equal to the first predetermined cross-section of the firsst rear portion 13.

The second rear portion 15 is adapted for receiving "therein a compressimble cushioning means, generally designate=d 18, which has one e=nd thereof abutting at least a portion of an inner surface 22 of the bottom wall 16 of the housing 12.

A positiorming means 36 disposed adjacent the inner surface 22 of thes bottom wall 16 may be provided for maintaining that end of the compressible cushioning element 8 centrally located wwithin the second rear portion 15 of tlie housing 12 during compression and extension of such _ compressible cushion.ing element 18.

AS best shown in FIG. 2, the compressible cushioning element 18 £urther extends into the first rear port ion 13.

The compressible cushioning element 18 may comprises at least one cushioning spring and a hydraulic assembly as taught by U.S. Patent 3,368,698, or at least ‘one elastomeric pad stack as taught by U.S. Patent 6,488,162 and U.S. Patent 6,446,820, but preferably the compressible cushioming element 18 comprises at least one cushioning spring 28, amd, yet more preferably, the compressible cushioning element 18 comprises a pair of first and second resilient compression means, being a } pair of first and second spring elements =8 and 28a respectively. The pair of first and second spring elements 28 and 28a respectively having a fifth predetermined length and a first and second predetermined spring rates respectively to enable the higher shock absorbing capacity of tthe friction draft gear assembly 10 in combination with the housing 12 having a second rear portion 15.

A . seat means 24 abutting the pair of first and ~ second springs 28 and 28a respectively is adapteci within the housing 12 for longitudinal movement therein for respectively compressing and releasing the compressible cushioming element 18 during application and release of a force on thme draft gear assembly 10.

A friction cushioning means, generally dlesignated as 42, is disposed at least partially within the ‘fromt portion 20 of the housing 12. The friction cushioning means 42 absorbs energy during application of a force sufficient to cause a compression of the draft gear assembly 10.

Those skilled in the art will understand that a combination of the second predetermined length of the first rear portion 13, the forth predetermined length of the front portion 20, the exposed portion of the frictiom cushioning means 42 and the predetermined thickness of the coupler follower 114 will be alkdout equal or slightly smaller that the first predetermined length of the draft gear pocket 108.

The friction cushioning means 42 includes a pair of laterally spaced outer stationary plates 44 having an inner friction surface 48 ancl an opposed outer surface 46 engaging the housing 12.

A pair of 1 aterally spaced movable plates 50 of substantially uniform thickness having an outer friction surface 52 and an innex friction surface 54 and at least one substantially flat edgge 56 intermediate the outer friction surface 52 and an inner" friction surface 54. is disposed within the open end of the draft gear assembly 10. The inner friction surface 54 having an e<dge 56 thereof engaging the seat means 24. At least a portion of the outer friction surface 52 movably and frictionally engages the inner friction surface 48 of the outer stationary plate 44.

A pair of laterally spaced tapered plates 58 having an outer friction surface 60 and an opposed inner friction surface 62 are adapted adjacently such movable plates 50. The outer friction surface 6C movably and frictionally engages at least a portion of the inner friction surface 54 of the movable plate 50.

The friction cushioning means 42 further includes a pair of laterally spaced wedge shoes 64 which have at least a portion of an outer friction surface 66 movably and frictionally engaging at least a portion of the inner friction surface 62 of the tapexed stationary plate 58. Wedge shoes 64 have at least a portiora of one edge 68 engaging seat means 24 and a predetermined tapered portion 70 on an opposed edge thereof.

A center wedgge 72 having a pair of matching tapered portions 74 for engagirig the tapered portion 70 of the wedge shoe 64 is provided to initiate frictional engagement of the ’ friction cushioning meams 42.

The friction dwxaft gear assembly 10 additionally” includes a spring release means 76 engaging and extendincs longitudinally between the seat means 24 and the center wedges 72 for continuously urgimg the friction cushioning mean 42 outwardly from the compressible cushioning means 18 to releases the friction cushioning means 42 when an applied force compressing the friction draft gear assembly 10 is removed.

In operation upon impact into a coupler knuckle 110 the buffing shock is transmitted from the coupler arm 112 through the coupler follower 114 to the central wedge 72, causing it to act through the wedge shoes 64 and thereby compress all of the cushioning elements simultaneously. These parts will furnish sufficient cushioning for light buffing shocks. After a suitable travel, however, the coupler followex 114 will abut the outex ends of the movable plates 50 introducing energy-absorbing friction between the movable plates 50 and the stationary plates 58 and 44 which have been pressed together by the action of the wedge shoes 64. As this action continues, the pressure between the adjacent surfaces of the intercalated plates has been enormously increased due to the fact that the wedge shoes 64 are loaded against the cushioning mechanism 42. The energy absorption and dissipation through friction and compression of the cushioning mechanism continues until the friction draft gear assembly 10 is closed including ‘compression of cushioning element 18. Extension of such cushioning element 18 into the second rear portion 15 of the housing 12 enables a longer travel thereof and, more importantly, enables the friction ‘draft gear assembly 10 to absorb higher buffing shocks from the coupler 109.

During release of the friction draft gear assembly 10, the compressible cushioning element 18 is waintained in alignment by the seat means 24. . The housing, generally designated 200, for a friction draft gear assembly 10 containing an integral yoke portion, best shown in FIG. 3, has a pair of opposed first follower apertures 220 having a fifth predetermined length and a first predetermined height which axe disposed within the first front portion 210 of the second open end. A second front portion 216 extends outwardly from the first front portion 210 and contains a pair of oppositely disposed vertical side members 218. Each side member 218 is adapted with a second follower aperture 222 of a sixth predetermined length and a second predetermined height and a Xongitudinally disposed aperture 224 for attachment to coupler arm 112 with a standard coupler key (not shown).

Preferably, a pair of opposit-ely disposed horizontal surfaces 217 is provided intermediate the side members 218 forming a box like structure, best illwmistrated in FIG. 1, for reinforcing structural integrity of such vertical side members 218 during operation of the friction draft gear assembly 10.

Those skilled in the art will readily understand that a pair of opposed round apertures may be disposed within such horizontal surfaces 217 for attachment to a coupler 109 being of a standard F-shank coupler with a coupler pin (not shown)

A pair of front ledge membexxrs 211 having a second predetermined width are disposed intexmediate the first and second front portions 210 and 216 respectively and abut the working surface 105 of each of the front stops 104 with the friction draft gear assembly 10 being at the end of a full draft travel.

Although a presently preferred and various alternative embodiments of the presemt invention have been described in considerable detail above with particular reference to the drawing FIGURES, it slaould be understood that various additional modifications and/or adaptations of the present invention can be made and/osxr envisioned by those persons skilled in the relevant art without departing from either the spirit of the instant invention or the scope of the appended claims.

Claims (1)

1. We claim :

   1. A housing for a long travel higla capacity railway car friection-type draft gear assembly which enables the cushionirmg of buff and draft shocks that are usually '5 encountemed in such railway car rolling stock during a coupling operation of such railway car to a train consist and ~ during mmormal operation of such train consist on a track structure, such buff and draft shocks transmi tted by a coupler and a ce-oupler follower of such railway car, such coupler follower having a first predetermined thick=mess, such draft gear assembly disposed within a center sill of such railway car intermediate a pair of front stops and am axially opposed pair of rear stops, such front and rear stops forming a 24.625 inch drafft gear pocket, said housing comprisirng: (a) a first end having a first poertion of a first predetermined cross-section and a second predeetermined length, a second portion of a second predetermined creoss-section and a third predetermined length being axially aligned with said first portion, said second portion closed by an end wall, and a pair o£ ledge members having a predetermined width disposed intermediate said first and second portions and abutting a working swirface of each of such rear stops; (b) a second end having a forth predetermined length being disposed adjacent said first portion of said first end said second end being axially oppossed to said first end and further being in open communication with said first portion thereof; and {c) whereby said pair of ledge rmembers enabling extension of said second portion of said firsst end into such sill past said working surfaces of such pair oef rear stops for disposition intermediate such rear stops, said extension enabling longer travel of such draft gear assembly while retaining an ability of such draft gear toe fit into such

   24.625 inc=h pocket. :

   2. A housing for a long travel high capacity railway car friction-type draft gear assembly according to claim 1, wherein said end wall having an inner surface.

   3. A housing for a long travel high capacity railway car friction-type draft gear assembly according to claim 2, wherein said first end further includes a positioning means disposed adjacent said innex surface of said end wall for centrally maintaining one emd of a compressible cushioning element disposed in said second portion of said first end during compression and extension of said compressible cushioning element, said one end abutting at least a portion of said inner surface of said end wall closing said first end 1S of said housing, said compressible cushioning element extending longitudinally from said inner surface of said end wall into said first portion of said first end.

   4. A housing for a long travel high capacity railway car friction-type draft gear assembly according to claim 3, wherein said compressible cushioning element includes at least one resilient compression means of a fifth predetermined length.

   5. A housing for a long travel high capacity railway car friction-type draft gear assembly according to claim 4, wherein said at least one resilient compression means is at least one of spring element, hydraulic assembly, elastomeric pad stack, and combination thereof.

   6. A housing for a long travel high capacity railway" car friction-type draft gear assembly according to claim 5, wherein said at least one xesilient compression means is a pair of a first spring element having a first predetermined spring mMcate and a second spring element having a second predeterrmined spring rate.

   7. A housing for a long travel high ¢ apacity railway car fricetion-type draft gear asdembly accordimg to claim 3, wherein said first portion of said first end is adapted to receive «a seat means having at least a portion of one surface thereof abutting an axially-opposite end of said compressible cushionimg element and mounted to move longitwidinally within said housing for respectively compressing and releasing said compressible cushioning element during applicat._ion and release of a force exerted on such draft gear assembly.

   8. A housing for a long travel high c¢ apacity railway car fric:tion-type draft gear assembly accordirig to claim 1, wherein said second end 1s adapted for at least partially receiving a friction cushioning means for alosorbing energy during a compression of such draft gear assembly and a spring release means engaging and longitudinally ext—ending between said seat means and said friction cushicn=ng means for continuowisly urging said friction cushioning mmeans outwardly from said compressible cushioning means to release said friction cushioning element when an applied fomrce compressing such drafft gear assembly is removed.

   9. A housing for a long travel high capacity railway car fric tion-type draft gear assembly accordirmg to claim 3, wherein =a combination of said second predetermined length of said fir st portion, said forth predetermined length of said second erd, an exposed portion of said frictiorm cushion means and saicl first predetermined thickness of such coupler follower is being one of equal to and smaller than 24.625 inch long draft gear pocket.

   10. A housing for a long travel high capacity railway car friction-type draft gear assembly according to claim 1, wherein said second end further includes a pair of oppogitely disposed verti cal side members extending outwarcily therefrom.

   11. A housing for a long travel high capaczHity railway car friction-type draft gear assembly according to claim 10, wherein each of said pair of vertical side members includes a longitudinally” disposed aperture for attachment to such coupler arm with a standard coupler key.

   12. A housing for a long travel high capacity railway car friction-type draft gear assembly which enablés the cushioning of buff and draft shocks that are usually encountered in such railway car rolling stock during a coupling operation of such railway car to a train consist and during normal operation of such train consist on a track structure, such buff and draft shocks transmitted by a coupler of such railway car, such draft gear assembly disposed within a center sill of such railway car between a pair of front stops and an axially opposed pair of rear stops, such front and rear stops forming a 24.625 inch draft gear pocket, said housing comprising: (a) a first end having a first rear portion of a first predetermined cross-section and a second predetermimed length, a second rear portion of a second predetermined cro ss- section and a third predetermined length being axially aligmed with said first portion, said second portion closed by an end wall and a palr of rear ledge members having a £i rst predetermined width disposed intermediate said first and second rear portions and abutting a working surface of each of such .rear stops;

   (b) a second end having a first front portion of a third predetermined cross-section and a forth predetermined length being disposed adjacent- said first portion of said first end, said second end being axially opposed to said first end and further being in open communication with said first rear portion thereof, a second front portion extending outwardly from said first front portion for attachment to such coupler; (c) whereby a combination of said second predetermined length of said first rear portion and said forth predetermined length of said fi rst front portion is being one of equal to and smaller than such 24.625 inch long draft gear pocket; and (d) whereby said pair of rear ledge members enabling said second rear portion of sai d first end to extend into such sill intermediate such pair of rear stops past said working surfaces thereof.

   13. A housing for a long travel high capacity railway car friction-type draft gear assembly according to claim 12, wherein said second end includes a pair of front ledge members having a second predetermined width disposed intermediate said first and second front portions.

   14. A housing for a long travel high capacity railway car friction-type draft gear assembly according to claim 12, wherein said first f ront portion includes a pair of opposed first follower apertur<s having a fifth predetermined : length and a first predetermined height and abutting said pair of front ledge members.

   15. A housing for a long travel high capacity railway, car friction-type draft gear assembly according to claim 12, wherein said second front portion includes a pair. of oppositely ‘disposed vertical side members.

   16. A housing for a long travel high capacity’ railway car friction-type draft gear assembly . according to claim 15, wherein said second end includes a pair of opposed second follower apertures of a sixth predetermined length and a second predetermined height, each of said second followe=xs apertures disposed in one of said first front portion and said vertical side member of said second front portion of said second end.

   17. A housing for a long travel high capacits railway car f£riction-type draft gear assembly according to 1S claim 16, wherein said fifth predetermined length of said paim= of said first follower apertures is one of larger and equa-l than said sixth predetermined length of said pair of saici second follower apertures.

   18. A housing for a long travel high capacitwy railway car friction-type draft gear assembly according to claim 17, wherein said fifth predetermined length of said paix of said first follower apertures 1s larger than said sixtEk predetermined length of said pair of said second followex apertures. ‘

   19. A housing for a long travel high capacitw railway car friction-type draft gear assembly according to claim 15, wherein each of said vertical side members includes a longitudinally disposed aperture for attachment to a couplex arm with a standard couplex key.

   20. A housing for a long travel high capacity railway car friction-type draft gear assembly according to claim 12, wherein saie«d second front portion further include=s a pair of opposed horiz ontal surfaces disposed intermediate ssaid vertical side members forming a box like shaped structure.

   21. A housing for a long travel high capaczity railway car. frictiom-type draft gear assembly according to claim 20, wherein sa-id second end includes a pair of oppeosed apertures disposed wi thin said opposed horizontal surfaces for attachment to a coupl er arm with a standard coupler pin.

   22. A housing for a long travel high capa city railway car frictiom-type draft gear assembly accordincy to claim 12, wherein said third predetermined cross-sectior of said first front portion is equal to said first predetermined cross-section of saidl first rear portion.

   23. A howsing for a long travel high capa_city railway car frictiom-type draft gear assembly according to claim 12, wherein said second open end is adapted for completely receiving a friction cushioning means for absor—bing energy during a comp=xession of such draft gear assembly amd a spring release meanss engaging and longitudinally extemmding between said seat means and said friction cushioning means= for continuously urging said friction cushioning means outwamrdly from said compressible cushioning means to. release said friction cushioning eelement when an applied force compresssing such draft gear assembly is removed.

   24. A housing for a high capacity railway car friction-type draft cgear assembly which enables the cushioning of buff and draft shaocks that are usually encountered in such railway car rolling stock during a coupling operation of such railway car to a train consist and during normal operation of such train consist on a track structure, such buff and raft

   WE 2005/073047 PCT/US2005/001298 ghock-s transmitted by a coupler of such railway car, such draft gear assembly disposed within & center sill of such railway car between a pair of front stops and an axially oppossed pair of rear stops, such front and rear stops forming a 24_625 inch draft: gear pocket, said housing comprising: (a) a first end having a firsst predetermined cross- section and a second predetermined 1 ength, said first end closed by an end wall, said end wall abutting a working surface of each of such rear stops; (b) a second end having a first front portion of a third predetermined cross-section and a forth predetermined leng th being disposed adjacent said first end, said second end being axially opposed to said first erad and further being in open. communication therewith, a second front portion extending outwardly from said first front portiom for attachment to such coupler; and (c) a pair of opposed folloswer apertures having a predetermined length, said pair of opposed follower apertures disposed within said second end.

   25. A housing for a high capacity railway car friction-type draft gear assembly according to claim 24, wherein said predetermined length of said pair of said opposed foll ower apertures is equal to a travel distance of such high capacity railway car friction-type draf t gear. }

   26. A housing for a high. capacity railway car friction-type draft gear assembly according to claim 24, wherein said second end includes a paix of front ledge members having a second predetermined width diasposed intermediate said firsst and second front portions.