US1899345A - Excavator - Google Patents

Description

vP31323, 1933. KMSSICK. 1,899,345

EXCAVATOR K. MESSICK Feb. 28, 1933.

EXCAVAT'OR Filed Aug. 26, 1931 4 Sheets-Sheet 2 Feb. 28, 1933. `K MESSlgK `1,899,345

EXCAVATOR Filed Aug. 2S,` 1931 4 Sheets-Sheet 3 mu fag L I j 45 K ////l l Y ,///W Q 4,0 60

Feb. 28, 1933. K MESSlCK 1,899,345

EXCAVATOR Filed Aug. 25, 95l 4 Sheets-Sheet 4 IH INI www"WIWMW/W fin l Patented Feb; 28,1933 y v i i `f F IC .i

c KIRWAN MEssIex, or CLARENDON, VIRGINIA Application-mea- August zaisai. serial Nassasaf The present'invention relates toexcavating ,f

machinery of the type now commonlyused, employingatruckhaving a power plant arranged thereupon, which is utilized not only for Vdriving the tractor mechanism of the truck, but also for driving `andheisting the excavating implementthereof, having among its principal desiderata. the provision of such. an excavator capable ofbeing selectivelyconel vertedinto any of the prevailing types suchy as clipper shovel, clamshell, skimmer-scoop, drag line excavator, or which may be convert- Ved into a pile driver, derrick or craneby sim-k ply attaching to the truck the required.,v Y

Another and equallyl important object of the present invention'is to provide amechanically operable drive capable of being permanent-ly mounted upon a boom of an :excavator type of boom so that uponattaching the boom to the exea-1 f vators tractor truck, the `power plant arranged uponthe latter may be 'utilizedfor driving such mechanically operable drive, thereby keeping the cab of the truck clear of Y the usualI reversible drive mechanism iwhich not only reduces the amount of space required inthe cab of the tractor truck, `but also mate# rially reduces the cost of building such tractor trucks.

A still further object of the present invention is to provide a reversible crowd or thrust mechanism capable of being permanently attachedy to the boom of ran excavator, thereby not only eliminating the complicated and ex- F pensive reversing mechanism usually required within the cab of such tractor trucks for driving the shipper shaft, but permitting apower plant of reduced horsepower to be utilized,

materially rreducingr vthe cost of maintenance.

A still further object of they presentinvention is to provide a reversible planetary mech` anism capable of being permanently attached ,and carried by the boom of an excavator and allowing a speed reduction in orderxthat greater force may be obtained from a small power vplant when a crowdingor thrusting voperation is desired, and one which is capable of being 'speeded' up when retracting or lifting the excavating implement from its work, and further, such aplanetary reversible drive in which'even distribution of stresses to the gearingthe'reo'f'may be effectedv during 'thevfcrowding operation, thereby increasing its durability, stability and'fa more even and uniformi transmission of drive power.

Astill further object of the present invent tionis to provide a power plantfor excavators .havingy a three speed drum drive for the` drag lines and hoisting Acables of such Ina-V chines whereby not only ka yreduced amount ofk u speed to obtain the maximumvpower and opf f erated at a faster rate of speed when only the minimum amou-ntofv power is required. Y r

yThe excavating vmachine embodying the present invention and as herein shown comprises a tractor truck. with a power Lplant mounted ,inthe cab thereof and a boom to which is connected the usual 'dipper shovel excavator.l vThis boom .may be readily replaced with other booms when a diierent type of excavating-implement is required, or the machine may be converted into a crane, piledriver, or derrickf by substituting fthe required boonrfor the one as herein shown; This power plant arranged upon the'tractor` truck not onlyy requires two power driven shafts, one of Vwhich has operatively conf nected thereto the cable of the boom hoist, whereas the other drive shaft has connectedV thereto not only the cable ofthe shovel yor other implement hoist, but has suitable connections for driving the reversible' crowd orl thrust mechanism of' thev shovel or otherex- *cavatingv implement employed. `From this arrangemennit' is quite'obvious that but :few

"cable is requiredbut establishing a drive for working parts are required within the cab of the tractor truck, thereby not only keeping the cab clear of machinery which is not at all times needed, but materially reduces the cost of manufacture of such tractor trucks.

The reversible crowd or thrusting mechanism usually required for excavating machines is herein mounted upon the boom of the excavator and arranged about the shipper shaft thereof, whereby this shipper shaft may be driven in opposite directions only and by mechanically centrollingthis reversible drive mechanism, the clipper stick and its shovel may be caused to travel in reverse directions as is needed when crowding the dipper within the work or withdrawing the sameV from the work. TWhereas itis quite common in this particular art to arrange reversible motors upon the booms or excavators or to drivethe shipper shaft arranged upon the boom from a reversible drive mechanism arranged in the cab of the excavator, I believe that I am the first to'provide a mechanical reversing mechanism upon the booms of eXcavators'and which can be driven from a power'plant arranged within the tractor truck thereof and capable of being manually controlled by the operator seated within the cab of such tractor truck. It is also quite common in this .particular art to arrange a reversible crowd mechanism of the planetary type Within the cab of a tractor truck and drive the shipper shaft arranged upon the boom in opposite directions, but by arranging such reversible crowd mechanism of the planetary type upon the boom of an excavator permits the power plant and tractor truck thereof to be converted into other types of excavating machines than of the dipper shovel type as herein shown, by simply disconnecting the drive to the reversiblecrowd mechanism arranged upon the boom and also substituting the boom of the required excavator for the one herein shown.

InY order that the invention and its mode of operation may be readily understood by persons skilled in the art, I have in the accompanying illustrative drawings and in the detailed following description basedthereon, set out several possible embodiments of the same.

In these drawings:

-Figure l is aside elevation of a power driven excavator employing the outsidedipper stick and having one form of my invention applied thereto; i

Figure 2 is a plan view of the same;

Figure 3 is a side elevation of an excavator employing the inside dipper stick and also having another form of the invention applied thereto; i

Figure 4 is a detail side elevation of a boom with the inside clipper stick applied thereto and showing the shipper shaft of the crowd mechanismjournaled within the boom;

Figure 5. is another detail side elevation of the boom showing an electric motor mounted upon the boom for driving the crowd reversing mechanism;

Figure 6 is a detail transverse sectional view taken through the boom as is illustrated in Figure 3 ofthe drawings, and showing my improved crowd reversing mechanism mounted upon the boom;

Figure 7 is a detail sectional view through my crowd reversing mechanism as applied to the boom;

Figure 8 is a detail side elevation of the boom with my crowd reversing mechanism I mounted thereon;

Figure 9 isa detail sectional view taken through the crowd reversing mechanism, as is shown in Figure l of the drawings, whereinv an outside dipper stick is employed, and

Figure 10 is a detail perspective view of one of the idler gears and its mounting.

Referring Vnow more particularly to the accompanying drawings wherein like corresponding parts are designated by similar reference characters throughout the several views, I have herein shown a truck l which is preferably propelled over the ground by means of a tractor mechanism, a conventional form of whichis herein shown and indicated by the numeral 2. Mounted upon and adapted to revolve upon the truck l is a cab comprising a platform 3 and hingedly connected to the forward end of this plat form is a boom 4. The hinge connection 24 between the boom 4 and the platform 3 of the cab is preferably of a detachableconstruction wherein the shovel boom as herein shown may be easily and readily removed in order that other types of booms may be connected thereto and the machine selectively converted into other types of excavators such as skimmer-scoops, trench hoes, clamshells, and thelike, or the machine may be employed as a crane, derrick or pile driver.

In Figures 1,2 and 9 of the drawings, I have illustrated an outside clipper stick carried by the boom 4 in that this clipper stick is forked so as to straddle the boom 4. Connected to the lower end ofthe dipper stick in any preferred or well known manner is a dipper shovel 7 carrying a sheave 8 over which passes the shovel hoisting cable 9.

VThe reversible crowd mechanism herein generally indicated by the numeral 10 is mounted upon the boom Il and is employed for directing the shovel 7 to and from the work.

Mountedupon the platform 3 of the cab is a prime mover preferably of the internal combustion engine type and herein indicated by the numeral 11, which, through the gearing 12, drives a shaft 13. `This shaft 13 has suitably connected thereto a drum (not shown) to which is connected the cable la of the boom hoist. This cable le has one end connected to the outer end of the boom and after extending over a pulleyl carried by i' Wise connected thereto, a sprocket wheel Vover which passes` a sprocket chain 24 andthis lat-fy ter passes over another sprocketwheel securedV to the shaft "25 which` latter is preferably jour- 1,899,845 f y Y the framework arrangedr upon the platform 3 of the cab passes .over the f pulley 16 and attached to the drum mounted upon. the shaft 13, whereby when this shaft is setIin motion the boom 6 may be raised or lowered to-the desired position.` Another shaft 17 is journaled in suitable bearings upon theplat-y form l3 `of the cab and isalso driven through the gearing 12 by the motor 1l in orderthat thisy shaft .17 may revolve .in one direction. Loosely mounted `upon this shaft 17 is a smalldruni 183s Well as `a `larger' drum 19 and the opposite ends of the cablei9 are con` nected tothese drums.` Suitable clutches 20 are employed for` establishing *a means whereby these drums 18 and 19 may-be selectively connected to the shaft 17 in order that they will be caused to rotate with y,thisshaft 17 and these clutches 20 are controlled by the foot pedals 21 arrangedadjacent the op# erators seat 22. As the ends of the cable 9 of the dipper shovel hoist are` connected to these drums l18 and 19, the medialportion of the cable passes over the sheaves 23 arranged atthe fair-lead end of thebooni 4,*and the sheaves 8 ofthe shovel. When the drumlS is operatively connected-to the drivenshaft 17 the cable 9 will be caused to wind thereupon and as the opposite endof thisfcable is fixed- Then it is desired to raise this dipper shovel ata greater rate of speed,kfor instance, where it has been released from the earth in which it has been digging, the drums 18 and 19 may be jointly ,connected tothe shaft; 17 through their respectiveV clutch mechanisms 20whereupon both ends .of the cable 9V will -be wound thereupon andthe shovel 7 raised at a much increased rate of speed. p Thisdriven shaft 17 hasl also keyed or othernaled in bearings arranged at the pivotpoint of connection between the boom 4.and the platform 3. This driven shaftf25 is provided withl another sprocket wheel over lwhich 3 travels a sprocket chain25 and the latter passing over a sprocket wheel carried by the shipper shaft of the crowdreversing mechanism 10 arranged upon the boom 4 in order that with rotation ofthe driven shaft V17 the sprocket chain 25 which is connectedto the shipper shaft of thefcrowd mechanism arranged upon thezboom will travel in one` direc- 16 and the. opposite end of the lcable 14 is tion only.V s s e Whenemploying the outside dipper Stick as is illustrated in'Figures 1, 2 and 9 of the drawings, the drive connection 'between the drive shaft 17- andthe crowd reversing mechanism is arranged within the boom 4 but when employing -inside dipper stick as shown in Figures 3 and 6 ofthe drawings, the sprocket wheel 26 is connected to one side of this drive shaft'z17 and a double sprocket wheel 271 is reversible crowd mechanism 10 isshown as f being arranged ,uponthe boo1n4V but it may kbe preferableto arrange this reversible crowd mechanism within the boom 4 so that its shipper vshaft will be journaled withinthe side members of the boom'in the manner asis -illustrated in 'Figure 4 ofthe drawings.

Referring now to Figures 6, 7 andf8 of the drawings wherein I havefshown in detail `a reversible crowd mechanism as mounted upon f a boom eniployngvfanfinside ldipper stick. Seated upon the faces of the spaced 'and parallelly arranged'bars 28 of the boom and t connectedthereto by means ofthe bolts 29, are bearingfbrackets 30 and journaled within` thebearings 31 of these brackets30 is a sleeveV 32.'. Formed with this sleeve 32 are ,the gears 33 which latter are adapted to mesh with the rack bars 34formed withl orcarried by oneA face ofthe dipper stick 6 ywhereby with rotation of this sleeve the dipper stick may be raised or lowered. Loosely mountedl upon this sleeve 32 andy arrangedbetweenthe gears 33 is a bearing sleeve 35 having formed therewith a projecting block 36 which 4.latter `is arranged betweenthe side bars of the dipper stick 6 yandvconnected to the-outer end of this 'block 36 bymeansfof a bolt 37 isa cross plate 38 which latter holds the yrack teeth 34 of this dipper stick in mesh withthegears 33. Jourynaled within and :extending through this sleeve 32 is a'shipper shaft39 and alsokeyed to .one proJecting end* ofthis shippershaft 39is Aaisprocket wheel'40 over thelatter of rwhich vpasses a sprocket chain 25l`in order that with rotation ofthe 'drivenshaft 17 arranged within the cabof this machine, this shipper shaft 39 willbe caused to revolve 'in one direction only. Formedwith one end of the sleeve 32;is a drum 41 and adapted to be kbrought into engagement with this drum 41 is an yinner brake band 42 and an outer brake. band 43. LThis inner brake band 42 is sup-y ported and carried by the sprocket wheel 40` so as to rotate therewith and when this brakey band 42 is expanded as to engage the drum 41,

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this drum, together with the sleeve 32 will be caused to revolve with the sprocket wheel 40. The other brakeband 43 is carried and fixedly secured to, as at 44, one of the side members 28 of the boom 4 in order that when this brake band 43 is forced into engagement with the drum-4l, the sleeve 32 will be held stationary.

The opposite end of this sleeve 32 isf provided with another drum 45 having internally arrangedV gear teeth 46 and meshing with this internal gear 46 are a: pair of idler gears 47, the latter meshing with a larger gear 48 keyed. to the shipper shaft 39. The gear wheels 47 are carried by a drum 49 which extends over the drum 45 andgthis drum 49 is provided with a hub 50 which latter is loosely mounted upon one of the projectingends of the shaft 39. Supported by and connected to the other side member 28 of the boom `4 is a brake band 5l which latter is adapted to engage the drum 49 in order that the gears 47 may, at times, be' retained against rotation around the gear 48, and in this manner effect a reverse drive between the gear 48 keyed to the shaft 39 and theinternal gear 46 which is carriedby the sleeve 32. Theconnection between the brake bands 43 and 5l consists of the levers 52 pivotally supported upon the bearing block and are provided with the usual eccentric connections between the opposite The gears 47 are each mounted upon a shaftk 54 which latter is arranged within a suitable bearing block 56, as is better illustrated in Figure 10 'of the drawings. This bearin block 56 has formed therewith, a plate 55an the bearing block fits within an opening formed yin the plate 49, whereas the plates are secured by means of bolts 57 to this plate 49.`

\ From the construction herein setV forth, it is quite obvious that I have provided a -reversible crowd mechanism which is arranged solely upon the boom 4 of the machine and is driven by the power plant within the cab .of the machine whereupon with `rotation of the shipper shaft 39 of this reversible drive mechanism in'one direction, a shovel 7 may be thrust or crowded within the works byV simply operating the brake band Y51. rlhe gear connection between the shaft 39`and sleeve 32 is such as will'provide a two to one ratio between the driven lshaft 39 and this sleeve 32, whereby with a small amount of power an increased thrust may be givento the shovel 7 than where a direct driveis ef-V fectedbetween such a shipper shaft 39 and the dipper shovel 6. When withdrawing this dipper stick 7 from the work, it is preferable that the withdrawing operation be done at a' greater rateof s `eed and the operator, bycausing the brake and 42 to be brought into engagement with the drum 4l of the sleeve 32, a direct drive is established between the prime mover and the dipper stick, whereupon the latter will `be caused to be withdrawn from the work in a rapid manner; When it is desired to hold the 'dipper stick 6 stationary at any desired position, the operator positioned within the cab may actuate the brake band 43 thereby locking the drum 4l and the sleeve 32 to the boom 4.

' Whereas I have herein shown the brake bands 43 and 51 las being capable of manual operation by the operator within the cab of the machine it is, of course, to be understood that other means well known in the art may be so employed. Instead of showing a manually operative means for controlling the brake band 42, I have herein Villustrated how this brake band may be operated under `fluid pressure. Within the cylinder 58 carried by the sprocket wheel 40 is a piston, which is connected to the brake band 42 through the link connection 59. The shipper shaft 39 is provided with a passageway 60 having communicatin with one end thereof the interior of the cylinder 58 whereas Vthe opposite end of this passageway 60 is connected with a fluid supply pipe 6l. This Huid supply pipe 6l should extend within the cab of the machine and have a` suitable valve arranged therein, whereby the operator upon opening such valve would permit the fluid vto pass through this pipe 61 into the cylinder 58 whereby the barke band 42 may be expanded and caused to engage the drum 41.

In Figure 9 of the drawings, I have illustrated my reversible crowd mechanism as carried upon the boom 4 of an excavator wherein an outside dipper stick is employed. In this form of the invention, the drive chain 25 which moves in one direction passes over afsprocket wheel 62 `and the latter is journaled upon the shipper shaft63. This shaft 63 is mounted within suitable bearings 64 carried by the side members 65 of the boom 4 and gear wheels 66 are secured to this shaft 63, which mesh with the rack bars 67 Vcarried by the opposite side members of the dipper stick6. These rack bars 67 of the dipper stick are retained in` mesh with the gears 66 by means of the bracket arms 68 mounted upon the oppositev end of the shaft- 63. The h'ub of the sprocket 62 has formed therewith a large gear 69 and ixedly secured to the shaft 63 is a plate 70"formed with internal lgear teeth whichmesh with the intermediate gears 7l and the latter alsomesh with the llarger gear wheel 69. The intermediate the cab, requiring `expensive machinery andl Sii recaen caused to revolve ina direction opposite to a sprocket wheel 62at a reduced rate of speed,

whereby the dipper stick of the shovel will be forced outwardly or f towards the work.

`When withdrawing the dipper 7 fromy the work, the brake band 74 is brought` into operation whereby the drum 75 carried by the shaft 63' will' be directly connected to the sprocket wheel 62`-due to the fact that this brakeband 74 is attached to a plate76 car-r ried by the sprocket` wheel 62. Another brake band 77 carried by one iof the side members 65 of the boomk may also' be brought into engagement with the drum 7 5 whereupon the, shafted may remain stationary and the dipper held at the desiredposition.`

c When it is desired to mo'nt a motor upon the boom 4 and employ `my reversible crowd mechanism it'may be done in the manner as illustrated in FigureV whereinI have shown an electric motor 78 'havingaysmallf gear wheel 7 Q'carried by the armatureshaft there-4 of which latter is adapted to engagea large gear wheel 80 of the shipper shafts V39 or 6.3

of the reversible crowd mechanism." VFrom this construction, it isobvious that upon setting the motor 78 intomotion', the gear 8O will` be caused to revolve in'one` direction wherenl upon the operator seated within the cab of the machine may control they brake kband of? this reversible crowd mechanism `as herein before described, in order that the dipper and its dipper stick may be caused lto travel in opposite directions or be retained inthe de# sired stationary position upon the boom. L An excavator made in accorda-nce withmy invention can be driven from a power plant arranged within the cab of a propelled car or truckhay'ing a suitable motor such asa gas enL y gine, and ltwo driven shafts therein, similar to the shafts 13 and 17 ,thereby greatly reducing. the amount of space necessary for the instal lation ofsuch drive mechanismk within the cab as well as reducing the costj thereof, due to vthe elimination of expensive drums and connections k with the motor for loperating the reversible crowd ,mechanism of the excavator. I am aware` of the fact that reversiblecrowd mechanism of the planetary" gear `type V.has been heretofore used on excavators, which reversing crowd mechanism is installed within taking up considerable space therein. I am also aware of the fact thatvarious forms of motors, steam and fluid, have been arranged upon the boom ofex'cavators for giving va r'e-KV verse motion 'to t-liedipperA `s`tick,1and alsoV chain .drive mechanismsr yconnecting the' dip perv stick'wi-th the motor arrangedwithinthe cab.` IIowever,I believe that-I am the first to adopt a, mechanical reversing mechanism upon the boom cfa-n excavator, whereupon a dipper stickcan'be moved in opposite directions.` yThe vchain drive lbetween thegmotor driven mechanism arranged wthinvthefcab and the reversible crowd mechanism is such that the chain 25 will-at all times, travel in one direction and the mechanical reversing mechanism will cause the dippery sticky to c travel'in opposite directions thereby materially reducing the size of chain drives necessary, over those heretofore used wherein the `chain moves in opposite directions.y p'

Also, this mechanical crowd connection be= tween the dipper stickand the drive chain permits the latterto accomplish greater work due to the reduced gear ratio between the shipper shaft of the reversible crowdf'mecha# .nism and the dipper stick'when the latter is being thrust into 4the work. When with;l

drawing the dipper from the work, less power is needed, and,`therefore, my reversible crowd mechanism may establish a direction'between therdrive mechanism and the dipper stick for withdrawing the latter from tliework rapid# ly,V and with a minimum amount ofpower.

Wherein I have Vherein shown .a .shovel type of excavator as being connected vtoa p kportable power plant,other types: ofexcavators. suoli asa trench hoe, skimmerescoop,

clamshell, may; be readily connected to this traveling power plant'by simplyfremoving l the boom 4tr and substituting therefor the boom ofthe typev of excavator desired. By v arranging the reversible crowd mechanism upon kthis boom, considerable amount] ,of space \may be saved within the cab of the power plant whereby van ordinar'ypowerf plant may be'employed'having drums; ar-

ranged within thecab for connecting f. the

drag line or cable to the other types of excaf similar toV those indicated by thenumerals 18 and 19, `hoisting cables maybe connected theretoffor "lifting objectsat three different rates of speed, one of which is needed when used when it isdesired to quickly raisean article such as the Vdipper `7 connected tothe cable. which windsupon the drums 18' and y19.

Inmountinglthe two drums 18 and19 upon k120 f a single drive shaft and permitting the saine*A y.

to be jointly or selectively connected to such drive shaft, a three speed hoist may be estabi lished,not only lfor shovel 'excavators as herein shown, but Vfor other excavating machinesV whenconvert= c.

or hoists which are employed ing `the machine.I

'Manifest1y, the construction herein shown is 'capable of considerable modification 'and such modifications as come within the scope heavy-work is beingy done, the secondbeing employed when lighterworkisbeing done'- and thethirdor'ffaster rate of speed, being 1 iso l of my claims, I consider within the spirit of Y my invention.

site ends of said sleeve, means for connecting Y one of said drums nto said shipper shaft whereby said dipper stick will be caused to travel inV one direction, and means for connecting the other. of said drums to said shippershaft whereby said dipper stick will be caused to travel in a reverse direction.

2. A reversible crowd mechanism for power driven excavators comprising in combination a boom, a dipper stick mounted for reciprocation within said boom, rack bars secured to said dipper stick, a shipper shaft journaled upon said boom, a sprocket wheel keyed to said shipper shaft whereby the latter may be driven in one direction only, a

sleeve loosely mounted upond said shipper` shaft, gears formed with said sleeve 4and adapted to mesh with said rack bars secured `to said dipper stick, drums secured to the oppositeends of said sleeve, means for operatively connecting one of said drums to sald sprocket wheel whereby said dipper stick will be caused to travel in one direction, kand a planetary gearing connecting the other of said drums with said shipper shaft whereby said dipper stick Vwill be caused to travel in a reverse direction.

3. A reversible crowd mechanism for power driven excavators comprising in combination a boom, a dipper stick mounted for reciprocation within said boom, rack bars secured to said dipper stick, a shipper shaft journaled upon said boom and having its opposite ends projecting beyond the opposite sides ofthe boom, a sprocket wheel keyed to one of the extended endsv of said shaft for driving the latter in one direction only, a sleeve journaled upon said shipper shaft, gear wheels Vformed with said Asleeve and adapted to mesh with said rack bars of the dipper stick, drums formed with the opposite endsV ofisaid sleeve and arranged on the opposite side of said boom, means whereby one of said drums may at times be connected to said sprocket wheel for causing said sleeve to rotate in one direction, aY planetary gear- Y ing `connectingthe other Vof said drums to 4. A reversible crowd mechanism for power driven excavators comprising in combination a boom, said boom consisting of a pair of spaced and parallelly extending bars, a bearing block secured to each of said bars, a dipper stick mounted for reciprocation within the bars of said boom, rack bars secured to said dipper stick, a sleeve journaled within said bearing blocks carried by the bars of said boom, ears formed with said sleeve and adapte to mesh with said rack bars of the dipper stick, a drum formed with each end of said sleeve and said drums extending from the outer side of the bars of said boom, a shipper shaft, and means whereby said shipper shaft may be operative-ly connected to the drums` of said sleeve, substantially as and for the purpose specified.

5. A reversible crowd mechanism for power driven excavators comprising in combination a boom, a pair of bearing blocks secured to said boom, a dipper stick mounted for reciprocation Within said boom, rack bars secured to said dipper stick, gears formed with said sleeve and adapted to mesh with said rack bars, a shipper shaft extending through said sleeve and mounted for rotation therein, a drum formed with each end of said sleeve, a sprocket wheel keyed to said shipper shaft and adapted to be driven in one direction only, means for connecting at times one of said drums with said sprocket wheel whereby said dipper stick will be caused to travel in one direction, a drum loosely mounted upon said shipper shaft, planetary gearing for connecting said shipper shaft with the other of said drums formed with said sleeve, and means for holding said drum which is loosely mountedV upon said shipper shaft against rotation whereby through said planetary gearing said dipperstick will be caused to move in a reverse direction. Y

6. A reversible crowd mechanism for power driven excavators comprising in combination arboom, said boom consisting of a pair of spaced and parallelly extending bars, a dipper stick mounted for reciprocation within the bars of said boom, rack bars secured to said dipper stick, bearing blocks secured to the bars of said boom, a sleeve journaled within said bearing blocks, gears formed with said sleeve and adapted to mesh with said Vrack bars carried by said boom, means supported by said sleeve for holding said rack bars carried by said dipper stick in mesh with the gears formed with said sleeve, a'shipper shaft extending through and journaled within said sleeve, a sprocket wheel keyed'to said shipper shaft and adapted to rotate in one direction only, 'a drum formed with said sleeve,rmeans for connecting at times said drum with said sprocket wheel, `a brake adapted to engage said drum for holding said sleeve vagainst rotation, an internally arranged gear formed with said sleeve, a gear Wheel keyed to said shippershavft, ka drum loosely mounted uponsaid shipper shaft, idler gears carried by said drum which is loosely mounted upon said shipper shaftand meshing With the gear Wheel keyed to said shipper shaft and the internally arranged gear formed Vvvith said sleeve, and ineens whereby at times said drum having the idlergears supported therein may be held againstrotation and said sleeve caused to be rotated in a direction opposite to that of said shipper shaft.

In Witness whereof I have hereunto set my hand. n

KIRWAN MESSICK,

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