US2726065A

US2726065A - Rock drill supporting and feeding mechanism

Info

Publication number: US2726065A
Application number: US481751A
Authority: US
Inventors: Jacob E Feucht
Original assignee: CLEVELAND ROCK DRILL DIVISION
Current assignee: CLEVELAND ROCK DRILL DIVISION
Priority date: 1955-01-14
Filing date: 1955-01-14
Publication date: 1955-12-06
Anticipated expiration: 1972-12-06

Description

will 1955 .1. E. FEUCHT ROCK DRILL SUPPORTING AND FEEDING MECHANISM 3 Sheets-Sheet l Mled Jan.

INVENTOR. FEUCHT JACOB E.

ATTORNEY mm mm Hm fi Wu. K12. mum? ROCK DRILL. SUPPORTING AND FEEDING MECHANISM Filed. Jan. .14, 1955 3 Sheets-Sheet 2 .IN V EN TOR.

JACOB E. FEUCHT ATTORNEY M E51. FEUQM EP SUPPORTING AND FEEDING MECHANISM ROCK DRILL 3 Sheets-Sheet 3 JNVENTOR. JACOB E. FEUCHT ATTORNEY Filed Jan. M, .1955

United States Patent ROCK DRILL SUPPORTING AND FEEDING MECHANISM Jacob E. Feucht, Garfield Heights, Ohio, assignor to Cleveland Rock Drill Division, Westinghouse Air Brake Company, Pittsburgh, Pa., a corporation of Pennsyl= vama Application January 14, 1955, Serial No. 481,751 8 Claims. (Cl. 255-45) This invention relates broadly to rock drills, but more particularly to a support and feed mechanism for rock drills of the percussive type.

One object of this invention is to provide a movable support coupled with a feeding device through which a rock drill, preferably of the drifter type, may be fed to and from the work.

Another object of this invention is to produce such support and feeding mechanism affording possible feed length greater than heretofore possible with supports of equal retracted or minimum length.

Another object of this invention is to produce a rock drill support and feed mechanism of relatively short retracted overall length but capable of long feed, the improved mechanism being characterized by the use of a power feeding element moving at the same rate of speed as that of the rock drill driven thereby, thus resulting in a lower power requirement than needed in mechanisms where the drill moves at a greater rate of speed than its power driven feeding element.

These objects are accomplished by a construction free of complication, and by an arrangement of parts resulting in a compact unit which is strong, durable and efficient.

In the drawings:

Fig. l is a side elevational view of a support and feed mechanism embodying the invention. In this view the support is shown fully extended rearwardly with the drill in its rearmost position.

Fig. 2 is a view partly in longitudinal section of the support and feed mechanism shown in Fig. 1. In this view the drill is shown in its foremost position on the upper member of the support.

Fig. 3 is a side elevational view of the mechanism shown in a fully retracted position with the drill in its foremost position on the support.

Fig 4 is an enlarged cross sectional view taken on line 4-4 in Fig. 3, looking in the direction of the arrows and with the feeding motor omitted.

Fig. 5 is an enlarged cross sectional view taken on line 55 in Fig. 3 and looking in the direction of the arrows.

Fig. 6 is an enlarged cross sectional view taken on line 6-6 in Fig. 6.

Fig. 7 is an enlarged cross sectional view taken on line 7--7 in Fig. 1.

Fig. 8 is a side elevational view of a modified construction. In this view the support is fully extended forwardly and the drill is in its foremost position.

Fig. 9 is a view partly in longitudinal section of the support shown in Fig. 8, with the support shown fully retracted and the drill in its foremost position on the support.

Fig. 10 is a side elevational view corresponding to Fig. 9, but with the drill in its rearmost position.

Fig. 11 is an enlarged partial sectional view taken on line 11-11 in Fig. 2.

1 Referring to the drawings, thegdn'll support may be "ice broadly described as comprising a lower and stationary elongated frame 20 having slidably guided thereon a similar but slidable upper frame 22 on which is also slidably guided a rock drill 24. More particularly, the stationary or supporting frame 20 is formed of a pair of parallel channel bars 25 mounted back to back with a relatively large space between them. The bars 25 are fixed to each other by spacing cross bolts 26 having annular shoulders 27 engaging the inner sides of the channel bars and reduced threaded stems 28 extending through the channel bars to receive nuts 29. Both ends of the channel bars are thus secured together by such cross bolts. Near the front or right ends of the bars as viewed in the drawings, there is fixed to their lower flanges 30 by bolts 31 a depending cone member 32 through which the lower frame 20 may be secured to any supporting device such as a tripod or the like well known in this art. The upper flanges .33 of the channel bars 25 are made special to provide two parallel guideways 34 extending the full length of the bars.

The upper frame 22 is also made of two parallel channel bars 35 with the same space between them as between the channel bars 25, and also secured rigidly to each other by cross bolts 36 each having a sleeve 19 mounted thereon with its ends abutting the inner walls of the channel bars 35 while the head and nut of the bolt hold the bars tightly against the ends of the sleeve. Frame 22 is somewhat shorter than frame 20 and has the lower flanges 37 of its channel bars forming guides fitted within the guideways 34 for slidable guide movement of the upper frame longitudinally on the lower frame. The upper flanges 38 of the bars 35 form parallel guides having fitted over them guideways 39 provided within a saddle 40, thereby enabling slidable guided movement of the saddle longitudinally on the upper side of upper frame 22. To the saddle 40 is fixed by bolts 41 and changing plates 42 the rock drill 24, here shown to be of the drifter type. This rock drill is of the usual type well known in this art, and may briefly be described as including a cylinder 43 closed at one end by a back head 44 and at the other by a chuck housing 45. Within the cylinder is reciprocable a piston, not shown, adapted to deliver impacts in rapid succession on a drill steel 46 which extends forwardly from chuck housing 45.

From the foregoing description, it will be understood that the drill support comprises an elongated stationary supporting frame 20 in the upper side of which is slidably guided for longitudinal movement thereon an upper elongated frame 22. On the upper side of frame 22 is slidably guided, for longitudinal motion thereon, the rock drill 24.

Referring now to the feeding mechanism, that is the power actuated mechanism susceptible of imparting slidable movement to the upper frame and the drill relative to the lower frame. Preferably this mechanism includes a pressure fluid actuated reversible rotary motor of any suitable type, well known in this art, having pressure fluid admitted thereinto through a conduit such as 48 and controlled by any suitable throttle valve, not shown. The motor housing is made with an integral bracket 49 extending laterally therefrom, through which the motor is fixed to one side near one end of the supporting frame 20. More particularly, as shown in Fig. 6, bracket 49 is fixed by bolts 47 to the lower flange 3d of one of the channel bars 25, with the motor located alongside of the frame 20 and adjacent one end thereof. Motor 50 has a motor shaft 51 extending therefrom through a hole 52 provided through the side wall of the channel bar 25 to which the motor is attached, while the other bar is provided with a similar hole 53. Between the two channel bars, 25, the motor shaft 51 is reduced to form an annular a sprocket wheel 63 operatively mounted on frame 22'- adia'cent-therearend thereof: between the channel bars 35; Froin sprocket'wheel63', chain 60:extends' forwardly over a roller 64 operatively'mounted onframe 22 adjacent the front end thereof. Asshown in Fig. 4, roller- 64' is rotatably'mounted on'the' sleeve. on spacer 1'9 fitted on the bolt 36 and cl'ampedbetweentheinner walls of the channel b'ars 35 by the headof thebolt and itsnut. This Construction gives-rigidity to -the'upp'er frame while pro vidingan adequate shaft on: which roller 6'4 is free to rotate. From roller'64, chain Gile'xtendsrearwardly and downwardly over the motor sprocket 55 and into the lower frame 20', from where it extends forwardly over a -roller 65 operatively mounted within the front end of the frame 20'. This last roller is a replica of roller 64 and ismounted in the same manner. From front roller 65, chain 60 extends rearwardly andupwardly into upper frame 22 overa third roller-66mountedwithin the upper frame 22 adjacent rollers 64 and the front end of the frame. From this last rollerthechain' againex-tends forwardly overa-sprocket wheel 67 m'ounted within the front end of upper frame 22, from where it extends again rearwardly to the rock drill 24 where it is fastened. For the sake of better identification, the rollers Ka -and 66 may be referredto as adjacent idlers or intermediatewheels mounted within the front end'portion of upper frame 22, while the

sprockets

67 and 63 may be called endwheels mounted ontheupper frame and the'sprockets 65and '55 end wheels mounted on the lower frame, witht-he sprocket 55. alsorefer'red to as the-motor sprocketor wheel;

In order to limit-travel of therock drill on the upper frame 22; the. upper frame-is provided with the cross belts -70located"immediately bel'ow theupper flanges 33 asclearly shown in'Figi 7,each having its head and nut engaging especially shaped shortsleeves- 71 nestedunder the fianges=38 andabuttingagainstthe' side walls of the channel liars 3'5. These-boltsa're located within the path of thesaddle 40' and are thefefore adapted to b'e' engaged thereby to-limit movementrof the drill'on fi'ame'22i' Gne bolt is located near'tlie rearendofthe" frame'while the other is=loeated adjacent the front end thereof.

To also limit-slidable movement of'the upper frame'22 on the lower one 20, on the inside wall ofeacli of the channel bars 35 of the upper frame'22, is fixed by screws a flat plate or stop '68 (Fig. 2) depending into the lower frame 20 and engageable with stop screws 69 screwed into the channel bars 25 and protruding'interiorly thereof. Two stop screws 69 are carried'by each side of frame 20, one located near the rear end thereof and the'otherwithin its forward portion.

Also mounted on the front end ofthe upper frame 22, is a drill steel centralizer 72 of any suitable type, many of which. are well known in this art. Briefly it generally includes two arms, one which is shown in the drawings, each slideably and pivotably mountedvon opposite. sides of the frame on a shaft 73 fixed thereonby end fasteners 74. The two arms of'the centrallizer are generally biased by a' spring 75 into locked operative position to provide a guiding bearing for the drill steel 46. When desired the arms can be unlocked byaxial movement on shafts 73 against springs 75. Another similar centrallizer 76 is operatively mounted. on the front end of they stationary frame'20. This last centrallizer is taller than the other one withits drill steel bearing coaxially with that of centrallizer 72.

Except for the centrallizers 72 and 76, the modified construction shown in Figs. 8 to 10 include all the same parts as the construction above referred to. The main difference between the two constructions resides in the location of the 'idlers- 164 and 166,-Which in this construction is still adjacent to each other but located within the rear end portion of the upper frame 122. With this change in the locationof the idlers, the assenibly'is movable from the fully retracted'positionshown in Fig. 19 with the drill 124' in a rearmost position on the upper frame 122 to the full forward extension shown in Fig. 8 with the drill in aforemost position:onthe: upper'frame. In the construction. shown in Figs. 1 to 3, the assembly is movable from the full rearward extension shown in Fig. l with the drill in a rearmost position on the upper frame 22, to the fully retracted positionshown in Fig. 3 with the-drill= in a foremost position: on theupper frame.

In the operation of the-mechanism shown in Figs. 1' to 7 ,.assuming thevdrill 24ztorbexin-its rearmost position as shown'in Fig: 1, it canbe operated'toideliver impact and rotationzin theusual manner: to the'relatively long: drill steel 46 for starting the hole intended to'be drilled. In this. instance, the drill steel .is well supported or guided by the two "drills steel 'ceritralizers 72.:and' 7 6 which maintain the drill steel inaxial: alignment with the rockxdrill 24. Concurrently with the start of the rock drill, motor may also be started to impart rotationtor motor sprocket inxavclockwise' direction in Fig; 2;

An important feature of' thisinvention is. to provide means whereby the relative: short sliding hearings. between the lower and upper frame when fully extended rearwardly, .will gradually becomelonger and therefore become more efiicient immediately. after the" start of the drill hole.: This feature is accomplished? by virtue of differential resistance: to" travel. of sections: of chain 60. Itwillibe' notedxthat the-section of. the chain. extending from the: motor sprocket 3'5? overcroller 651to-roller 66,

which: is: hereinafter referred to as. first seotion,.having. only one sharp turn over roller 65, has less resistance to travel than when combined with the second sectionwhich extends-fromroller 66, over sprocket 67'xtorrocli dri1l524. As theffirst'section.is1.put='unden tensionrby rotation of the motor-sprocket 55, .roller.66%'together with: the secondsection of the chain will remain stationary relative to the upper frame. 22 and move-therewith relative. to the lower frame while the first section. er the. chain'f moves. over roller. 'Thus it willvbe understood that original feeding motion is imparted to the drill steel. 46 by sliding movement of. the upper: frame :22=on: the lower frame. 20,

while the drill 24 remains stationary on the upper frame This condition remains untilthe upper' frame stops 68 engage the'frontstop: member 69,.which limits further forwardwmovementof: the upper frame relative to the lower one. Thereaften'the entire driven-section of the chain, that is. the: first sectionicombinediwith the second one, will move for imparting :forward feedingmotion to.

the rock drill 24:-until its saddleAO: contacts the forward stop 71.

It willzalsobe notedz'thatkby. virtueof.the'disposition of the chain as above described, for a given rotary speed of.

motor 50,-. the drill moves at' a unifornrv rate of speed when fed with or" independently ofithe'upper frame 60. Since no speedmultiplyingv mechanism is incorporated in this structure, itcan operateetfectively. for feeding the drill: steel. to andfrom work With. a minimum power requirement;

As shown in Fig. 3, the two centralizers 72 and;7-6.;are.

located so :thatwhen the:drill .24 reaches theend ofits forward feeding travel, it remains. :short of 1 the centraliZers, which thereforeneed. not beremovedor swung open to allow complete forward movement; ofthe rock When it is.desireito-removethe drill steel 46:- from the drilled hole, that is feedthc rock drill rearwardly,

motor 50 is caused to rotate in the oppositedirection. In this instance the first driven section of chain 60, from motor sprocket 55 to sprocket 63, having only one sharp turn over roller 64, has less resistance to travel than when combined with the second section from sprocket 63 to rock drill 25. As this first driven section is put under tension by rotation of the motor sprocket 55, sprocket 63 together with the second section of the chain will remain stationary relative to the upper frame 22 and move therewith relative to the lower frame while the first section of the chain moves over roller 64. This condition will remain until the upper frame stops 68 engage the rear stop member 69, which limits further rearward movement of the upper frame relative to the lower. one and the chain and motor assume the position shown in Fig. 2. Thereafter the entire driven section of the chain, that is the first and second ones will move for imparting rearward feeding motion to the rock drill 24 until its saddle 40 contacts the rear stop 71.

From the foregoing description, it will be understood that during forward feeding motion, only the portion of the chain from motor sprocket 55 to rock drill 24 passing over

rollers

65, 66 and sprocket 67 is effective, and can therefore be referred to as the chain driven front portion, while the other portion of the chain is nothing more than a trailing position. Similarly when feeding rearwardly, the chain driven rear portion extends from motor sprocket 69 over roller 64 and sprocket 63 to the rock drill, while the other portion is nothing more than a trailing portion.

Since the operation of the modified construction shown in Figs. 8 to 10 is substantially the same as the one above referred to, no detailed description of it is thought necessary. Because the rollers 164 and 166 are located adjacent the rear end of the upper frame 122, upon rotation of motor 50 in a clockwise direction, the upper frame 122 with the drill located on the rear end thereof is first moved forwardly, and after it has reached its front stop, not shown, corresponding to 69 in Fig. 2, the drill 124 will move forwardly relative to the upper frame until it reaches its front stop 171.

Upon rotation of the motor 50 in the other direction, the upper frame 122 from its forward extended position will first be moved backward with the drill 124 stationary on its front end until the upper frame engages its rear stop, not shown, and assumes the position shown in Fig. 9. Thereafter the rock drill 124 will move rearwardly until its saddle contacts the rear stop 171.

In this modified construction, because the upper frame 152 is made to extend forward of the lower frame 120, and the rock drill 124 forward of the upper frame, it is not possible to equip this support with centralizers equivalent to 72 and 76.

The details of structure and arrangement of parts shown and described may be variously changed and modified without departing from the spirit and scope of the invention.

I claim:

1. A rock drill supporting and feeding mechanism comprising an elongated stationary lower frame, an upper frame slidably guided longitudinally on the lower frame, a rock drill slidably guided longitudinally on the upper frame, said mechanism being retractable into a position of said upper frame within the length of the lower frame and the rock drill near one end of the upper frame and extensible into a position of the major portion of the upper frame beyond one end of the lower frame with the rock drill near the other end of the upper frame,

means for effecting said retraction and extension including a power driven sprocket wheel mounted within one end of said lower frame, an endless chain in mesh with said sprocket wheel and fixed to said rock drill, end wheels having said chain passing over them operatively mounted one within the other end of said lo er frame and one within each end of said upper frame, and adjacent idlers operatively carried by said upper frame 'neaf one end thereof being engaged and passed over by portions of said chain, one idler by the portion of the chain between the wheels carried by the rear ends of said frames and the other idler by the portion of the chain between the wheels carried by the front ends of said frames.

2. A rock drill supporting and feeding mechanism comprising an elongated stationary lower frame, an upper frame slidably guided longitudinally on the lower frame, a rock driil slidably guided longitudinally on the upper frame, said mechanism being retractable into a position of said upper frame within the length of the lower frame and the rock drill near one end of the upper frame and extensible into a position of the major portion of the upper frame beyond one end of the lower frame with the rock drill near the other end of the upper frame, means for effecting said retraction and extension including a power driven sprocket wheel mounted within one end of said lower frame, an endless chain in mesh with said sprocket wheel and fixed to said rock drill, said chain extending rearwardly from the rock drill over an end wheel mounted within the rear end of the upper frame, then forwardly over a first intermediate wheel carried by said upper frame near one end thereof, then rearwardly and downwardly over said sprocket wheel, then forwardly over one end wheel mounted within the front end of said lower frame, then rearwardly and upwardly over a second intermediate wheel carried by said upper frame adjacent the first intermediate wheel, then forwardly over one end wheel carried within the front end of the upper frame, then rearwardly to said rock drill.

3. A rock drill supporting and feeding mechanism comprising an elongated stationary lower frame, an upper frame slidably guided longitudinally on the lower frame, a rock drill slidably guided longitudinally on the upper frame, said mechanism being retractable into a position of said upper frame within the length of the lower frame and the rock drill near one end of the upper frame and extensible into a position of the major portion of the upper frame beyond one end of the lower frame with the rock drill near the other end of the upper frame, means for effecting said retraction and extension including a power driven sprocket wheel mounted within one end of said lower frame, an endless chain in mesh with said sprocket wheel and fixed to said rock drill, and directional wheels operatively carried by said frames each engaged by said chain for changing its direction longitudinally of said frames, said wheels including one within the other end of said lower frame, one within each end of said upper frame, and two more carried by said upper frame between the end wheels thereof.

4. A rock drill supporting and feeding mechanism comprising an elongated stationary lower frame, an upper frame slidably guided longitudinally on the: lower frame, a rock drill slidably guided longitudinally on the upper frame, said mechanism being extensible into a position with more than one half the length of the: upper frame extending rearwardly beyond the rear end of the lower frame and with the rock drill near the rear end of the upper frame, and retractable into a position of said upper frame within the length of the lower frame with the rock drill near the front end of the upper frame, means effecting extension and retraction of said mechanism including a power driven sprocket wheel operatively mounted within one end of said lower frame, an endless chain in mesh with said sprocket wheel and fixed to said rock drill, and wheels having said chain passing over them operatively mounted one within the other end of said lower frame and one within each end of said upper frame, and front and rear adjacent idlers operatively carried by said upper frame near the front end thereof being engaged and passed over by portions of said chain extending respectively between the wheels carried by the front and rear ends of said frames.

5. A rock drill supporting and feeding mechanism erre -ow:-

comprisin'gan elongatedstationary lower frame; an upperframe: slidably guided: longitudinally on the lower frame;

a rock 'drill slidably guided. 'longitudinall on the uppcr frame, said-*mech'atnism bing -extensible -into aposit ion with' -'m0re *than' one half -the length of the upper frame extending rearwardly beyond the wear "endofth'e lower frame and with the rock drill near the rear end of 'theupper-frame; and retractabletinto apositionof-said upper frame withinthe length of" the-dowerw frame with th'e rock dr'ill'near the front end' 0f:theupper;frame, means:

enacting extension and retraction of; said mechanism including areversible rotary: motor fixed to the low-er frame; a sprocket wheelioperatively mounted within-one end of"the lower frame= driven by'said motor; and achain in mesh -wit-h- -said' sprockeewheel and: fixed to said-'- rock drill; said 'chain extending rearwardly from the rock earn-1 over: anend wheeloperatively' mounted withi'n the rear -*endo-f the upper frame, then forwardly over a-fi'rst intermediate-' wheel carried by said upperframe near 'the front end thereof,- then rearwardly and downwardly over said-'- sprocket-wheelythenforwardly over an end wheelmounted within the other end 1 .of said lower frame; then rearwardly andupWardlyover-a second' intermedi'ate wheel carried'by said upper frame adjacent thefifSt intermediate wheel, then forwardly over an end wheel carriedwithin the front end ofthe upper frame; then rearwardly-to' said rockdrill.

6i A" rock drill supporting and' feeding mechanism comprising-an elongated stationary lowerframe, an upper frame slidably guided longitudinallyonsaid lower frame,

a rock' drill slidably guided longitudinally on the upper frame, a drill steel extending longitudinally fromsaid rock drill,"a drill steel retainer mountedon said frame near the front 1 ends 'th'ereof -coaxially aligned with the centeraxis of saidrock drill and adapted to guide and support said idrill steel; said mechanism heing extensibleinto a position with more=than one half the length ofsaid upper frame extending rearwardly beyond the rear endv of said-- lower frame and iwith said -r0ckdrill near-the rear end of said upper frame, and-retractable'into a position of said upper frame-within the length-of saidlower frame with the front endt'ofthe uppen'fr'ame short-of the centralize!- of the'lower-fr'ame and with the rock' drill near the front end of-hut short-of the centralizer carried by said upperfr'ame, means for effectingextension and retraction of said mechanism including 3 a reversible rotary motor carried by; said lower;- frame, a sprocket wheel operativelymountedwit-hin one end of said lower-frame driven by said motor, an endless chain in mesh with said sprocket wheel and fixed to said rock drill; anddirectional wheelsoperatively carried-by said frames each 'engagedby said chain for changing its-direction longitudinally of, said" frames,--said wheels including; one within-the other end of said lowerframe, one-within each end of-saidupper frame-and two more carried bysaid upper frame-near the front end thereof betweenitstwo end wheels.

7. -A" rock-drill supporting and feeding mechanism comprising: an elongated stationary lower-frame, an upper frame: slrdably-ecgnidedfilongitudinallyxon' therlowenframee;. a rock drillIslidablyzaguidedrtlongitudinally onzathenuppen. frameg saidmeehanismebein g: extensiblei intoraposition'of: more than :one' half :tlre-lengtlr-of the upperrframex extends ingeforwardly;beyondtthe: front:ofvthenlowernframe and;

Witlith'fl *roclddrillhnean:thjerfront end ofitheeuppen:frarne,

andretractabletinto. anpositionsof saidnppensframeswithinri: the-.lengtlu of rther lowersiramer.with.. the rocky. drill: near." a

the? .rearrend (of i-thesupper'. frame; means :effiecting =r extenl frontvandu'earzendsfiof saidframes;

8: 2A rock adri-l-l v supporting; and feeding: mechanism comprisingsannelongatedstationaryn lower frames an-upper framerslidabliy guidedflongitudinallya on'zther lower frame; atrockz'dri-ll slidably guided longitudinallyson the upper-1 frame; saidemechanisrntbeing?extensiblesinto; a position of" moreithanszone halfi thesslengthu of the'euppen frame exe tending: forwardlyrbeyond ith'e-zfrontof 'therlo'wer frame: EILdIiWlth'fthflfIOCkldI'lil near the :frontend ofn'th'e: upperla'frame, and retractable into a position of saidupper frame withimtheslengthrof the a lowerrframezswitlr :the rockLdrill near;theirearaendiofiz-th'e uppersframqmeans effecting ex tension: andrretraction .ofr zsaidzamechanism"including: a

reversiblezrotarya motor fixedrl to... the .lowerx frame,- a- .--.sprocket-wheel pperativelyimounted wvithinone end" of the lower-frammdrivenby: saidimotonnand .a chain inhrnesh withi-gsaid;sprocketzwheel: and driven'thereb'y fixed :to said roclezdrilh: said--chainziextendingsrearwardly :from :the: rock dri1-1:over.;am end wheeltoperativelyzmounted withinz the reartend of:said upper frame, .;thene:fonwardly over a first intermediate wheel carried by saidlupper frame=overzthe rear: endr thereof', thenirearwardly and sdownwardly' over sadisprocket, wheel then forwardly over: anrend wheel) mounted within the: otherrendsof l'said lower-frame; then i rearwardlyr. and: 'upwarrdlyz overz .a second: intermediate.

wheel carried-by'-said:upper framegadjacent thedirst intermediate-wheel; thenyforwardly ovenan end wheel zcarried' within the front end of;said-;uppen frame; then rearwardly References (Cited: vinit-he :fileof this patent UNITED STATES' 'PATENTS 2,055,520 Curtis Spt.r29', 1936' 2,143,105 Curtis Ian. 10, 1939 2268573 Osgoodf Jan.. 6, 1942 2,704,203 Fucht" Mar -15, 1955-