US2488521A - Lift truck - Google Patents

Description

A. M. BARRETT LIFT TRUCK Nov. 22, 1949 Filed April 18, 1945 4 Sheets-Sheet l Nov. 22, 1949 A.. M. BARRETT LIFT TRUCK Fil'ed April 18, 1945 4 Sheets-Sheet 2 4 I N V EN TOR.

rwrfffre wila/@Mu Nov. 22, 1949 A. M. BARRETT LIFT TRUCK Filed April 18, 1945 4 Sheets-Sheet 3 auw A. M. BARRETT Nov. 22, 1949 LIFT TRUCK' 4 Sheets-Sheet 4 Filed April 18, 1945 Y INVENTOR. @rur/rrez BY l M al/m, am www Patented Nov. 2.2, 1949 Arthur' M. rrett; Winnetkaylll, assigner` tof BarrettlCx-avense Gcmpany; at corporatiom off ApplicaticnApriIlS, 1945,' Serlal-N. 538325' (Cl: 28o-471) zoclaimsa .The present invention'. relates; to lift" trucks; and more particularly Vto', those of" the`v hydraulic type in' which the loadv is liftedthrough'tlie a'ction of. a hydraulicjack or ram.

One ofthe .principali features' of the'. invention resides in an improved operatingrelaton between the hydraulic uniti. andftl'ie frame; which lifts the load. The hydraulic` unit'is mountedonth'e lifting frameto moveup anddown bodily there# with. The lifting force f of. the; hydraulic ram is applied in an upward directionlto the inner end of a rocker member.A which has pivotalv support intermediate its ends on the lifting frame; The outer end of thisrocker member is arranged to exert downward reaction on the iron-t Wheelsof the truck or-other groundengaging'isupport.

Another: feature ofthe invention Vresides in an improved. motion transmitting. arrangement wherein the above motion of "the rockerimemb'er is also made eective to raise' the; rear portion of the frame relative tothe reark wheels.

Another feature ofthe invention is to. provide a. low level truck of` the single. frame.or'pal1et type embodying the aforementioned improved hydraulic mechanism and" improved motion transmittingv arrangement; Another featureofthe'invention residesdn 7an improved mounting.; ofjtlie. lifting.fame Ion the front truck whereby the lifting, f'ame. has guided sliding .cmovement'up and dow-n alngitle vertical king', pin ofthe front"tru`clii Another featureof the.iiiventiontresidslii'co structingl the hydraulicjpump, tthe, ram,jtl:iere.- lease valve, thegoverningevalve andthe hydraulic reservoir all"as onecomplete unitlwlih .can be readilyremoved as a unitfromth-e lift. truck for the purposes of'repair', adjustmentlpire.; placement ofthe hydraulic mechanism; Itfisonly necessary to release two mountingjor, operating connections, whereupon .the entirethy'draulie-.unit

can be removedin its entirety.. from the bottom of the truck. By havingall'ofithehydraulic parts constructed or assembled inunitl form, thereeis avoided all necessity of flexible hose connections, moving joints, etc., in the .hydraulic conduits, .and hence leakage problems are minimized.

Another feature of'the invention. residesin. an improved automatic cut-off ofthe hydraulic.. lift mechanism which prevents .further liquidlbeing forced into the hydraulic ram after-.theJif-ting frame has been raised to.' a. predetermined maxi-- mum height.

Another feature ofthe invention residessinan improved pedal type of. actuating, arrangement in use it'o'ccu'piesfa substantially-vertical position' Whereitiis outofitheway': Wh'enzthe pedal fis to be putVl into use'v itV is` swung.- into-a lower" position Where' it is. very convenient-fof foot actuation'.` Such pedal carrbe actuated. in` cramped quarters Wherethere wouldnot be room' toimpar't load lifting movement to the conventional draft and steering handle. However; theinventionis not limited to pedal actuation 'of "th'ehydraulic pump, butL also includes modied arrangements wherein the steerin'gand drafthandle isjusedtoactuate the. hydraulic pump, Where'that is desired;

Other features, objects' and" advantagesV of the invention' will appear" from the following detail description of oncpreferred embodiment ofthe invention.' In the accompanying. drawings illustrating such embodiment'z' Figure 1 is a fragmentary side elevational -view of` my improved truck showing' the frame, inits lowered position;

Figure2is atfragmentary horizontals'ection of the. front end' ofthe truck;` taken approximately on the plane ofthe line`2-2 of Figurer;

Figure 3-is a fragmentary sid'view 'ofthelfont portion of 'the truckon' a larger sca1e,.showing the truck vin its raised position;

Figure 4 is. atransv'er'se .sectinalfvi'evv' 'through the`liydrauli'c unit; corresponding" to a section taken` on." the, planel of the line. 4-4 ofi Figure. 2; 8nd

F'i'g11re5is,l a fragmentary sectional. view show. ing.. the releaset mechanism, both. manual and automatic, for releasing. the hydraulic. lifting mechanism.. Y

In. itsA preferred. embodiment; .my invention is constructedflthe form of"a-single frame or pallet` type of. lifting truck comprising.. aasingle frame I i 'Whichserves to connect the frontwh'eels l'2with. therear. wheels.. I 3' and whic'halso serves as a.li'ftinge1ement. pallet type of lift truck is particularly. adaptedlfr uscwithlthe relatively` low pallet ytypefof load carrying. platforms. f While this is. the. preferred.` embodiment ofmy invention,v .nevertheless I"wish`. it toibe understoodthat the.invention,.or certain.. features thereof, can be yernbodiedin. other types oflift'trucks as well. There. are-two front Awheels I 2.1 mounted on7 the outer.. ends zoffan. axle. pinoraxle studs I 4.. carried by the main frame membenA or casting `of a fron-t for the hydraulicfspump.- When the. pecl-ellis:4 not 55 truck i5... Rising..-substantially. vertically on-this main casting..- l 5; .between the-front wheels I2v,^ is afkingfb'olt .l lformed with a.long cylindrical 'guide surface y |65. Sliding upfand .down-along .,thisncylindrioalf guide surface is` a cylindrical sleeve IJ- which-.Visy rigidly Secured-textile forward portion tween a pair of laterally diverging yoke bars 2I.

which are pivotally mounted on pivot pins 22 projecting outwardly from a front portion 23 of The handle I8 is biased the truck casting I5. toward its upright position byV a tension spring 25 which has its upper end secured to a lug 2B projecting from the upper or back edge of theY handle and which has its lower end hooked to a clevis 21 extending upwardly from the front portion of the front wheel truck. It will be evident that the front end of the frame Il can be raised or lowered by merely causing the guide sleeve I1 to slide up and down along the cylindrical guide surface of the king bolt I8, and it will also be seen that in any one of the raised or lowered .positions of the frame the front wheel truck is free to be swiveled to right or left in pulling, steering and maneuvering the truck.

The two rear wheels I3 are mounted on a swinging crank assembly 3I for fore and aft swinging motion under the rear portion of the frame II.

When this crank assembly 3l together with the rear wheels I3 is swung in a forward direction relatively to the frame the frame is lifted bodily at its rear end, and when the crank assembly and wheels are swung rearwardly the rear portion of the frame is lowered. The swinging crank assembly comprises two pairs of laterally spaced crank arms 32 which have their upper or forward ends pivotally connected with the frame II on a transverse pivot shaft or shafts 33 carried between the side bars of the frame II. The wheels I3 are journaled upon a transverse axle or axles 34 extending through the rear portions of the crank arms 32. The swinging crank assembly and rear wheels are swung forwardly and rearwardly in the lifting and lowering of the frame through the instrumentality of two tie or pull rods 36 which extend from the front portion of the truck back to the rear portion, near each side bar of the frame. The rear ends of these tie rods have adjustable threaded fastening in T- shaped bearing members 38 whichare disposed between each pair of crank arms 32, where they are journaled on pivot pins 39 extending between these pairs of crank arms. The pivot pins 39 are so spaced from the pivotal axis 33 of the crank arms that when forward pulling force is exerted through the pull rods 36 the wheels I3 are swung forwardly to raise the rear end of the truck substantially to the position illustrated in Figure 3, and when the rods are moved rearwardly, or allowed to move rearwardly, the wheels I3 swing back to their rearward position and thereby allow the frame II to move down to its lower position as illustrated in Figure 1. The operative connection of the rods 38 with the hydraulic lifting mechanism at the front end of the truck will be described after the details of the hydraulic lifting unit have been described.

Referring to Figure 4, the hydraulic unit is indicated in its entirety at and comprises a hydraulic pump 46 for generating the hydraulic pressure, a hydraulic ram 41 for raising the truck in response to this pressure, and a release valve 48 for releasing the hydraulic pressure from the ram 41 for lowering the truck. These three parts 45, 41 and 48 all have their base portions welded or otherwise rigidly secured to a base plate 49 so that the pump, ram and release valve are all rigidly joined together as a single hydraulic unit 45. Surrounding the lower portions of the pump, ram and release valve is an oil reservoir 5I which stores the necessary amount of oil for the operation of the hydraulic unit. This hydraulic unit assembly is removably mounted within a box-like compartment 53 (Figure 2) which is formed between the forward frame plates I8 directly back of the king bolt guide sleeve I1. The front wall of this compartment 53 is dened by a transversely extending vertical plate 54 which has its ends welded to the inner side surfaces of the forwardly converging frame plates I8. The rear wall of the compartment is dened by the upstanding flange of a heavy angle bar 5B and extension plate 51 which extend transversely of the frame and have their ends welded to the frame side bars II. The load cariying area of the frame extends forwardly up to this angle bar 56.. The side walls of the compartment 53 are defined by two spaced side plates 58 which have their front edges welded to the transverse front plate 54 and which have their rear edges welded to the transverse rear plate 51. The hydraulic unit assembly is mounted for slight fore and aft tilting movement within this box-like compartment 53, this tilting motion occurring around a transverse mounting shaft 6I which is removably mounted in the lower portion of the compartment 53. The ends of this mounting shaft 6| are slidably seated in holes formed in the lower portions of the spaced side plates 58, being releasably held in these holes by a set screw or other suitable fastening means. Upon the release of this fastening means, the shaft can be slid endwise out of its supporting position in the plates 58. As shown in Figure 5, the base plate 49 of the hydraulic unit is formed with an arcuate groove 63 extending transversely across its bottom surface, and this arcuate groove sets down over the upper surface of the mounting shaft 6I, affording a rockable bearing support which enables the hydraulic unit to tilt fore and aft around the axis of the mounting shaft 5I. Upon the aforementioned removal of the mounting shaft 6I, the entire hydraulic unit can be dropped straight down through the open bottom of the compartment 53, whereby the unit can be readily removed for repairs, adjustments, or for the substitution of another hydraulic unit.

Referring now t0 the manner in which the hydraulic unit transmits lifting force to the lifting frame, it will be seen from Figure 4 that the hydraulic ram 41 comprises a cylinder G5 in which a piston 65 is adapted to be forced upwardly by the admission of oil under pressure into the lower end of the cylinder 65. The piston comprises a, slightly reduced shank portion 61 which has a tight pressure t within an upper gland packing B8 carried in the head end of the cylinder 65. This gland packing comprises a plurality of packing rings 69 which are maintained under pressure by a compression spring 1| and pressure ring 12, the rings 69 preferably being composed of neoprene or other like material capable of effecting a tight seal. The upper end of the piston shank 61 is formed or provided with a yoke or saddle 11 which bears against the underside of a horizontally extending thrust pin 18. If desired, the yoke 11 may be held up against the underside of the thrust pin 1S by a the rear end. ofJ

'which extends through. the, two'A rocker |6- being freely rota-table* aeree-1 estable' Gatter. el ver, retainer; straaaianot essential the-,yolzeA 'Maand and may beomitted because,

Weight of. thev truck. and; the. weightlogf,t the load on the4 truck. The.. yokel TL thushasiaVS one-way pushing connection againstitl;e -'thrust.pinY 1.8, which pushing coifineetiun ma! be, readilyT separated when the hydraulicunit 45de toabejremoved by dropping down through, the` hQtfOm.' of.4 compartment 5.3.

The. thrust pin. 18,y is,A mountedtransversely. in a rocker^ arm Bawhich. is.. made up of twospaced.' side plates,n 8&7, ,the pin '18.hav-

ingvits endsmounted. in holesinthesefside plates.

Said' rocker mounting on armE has, intermediatev fulcrum va .heavyAT transverse, l5caringI pin, 8,5 .plates 83' andwhi'ch hasits ends mounted ingholes formed in upward; extensionsv of4 the side plates 5.8' of box-like'. compartment 53.'` Thus this. in,- termediate, mounting pl/QtLSB'oFthe rocker arm 83l always remainsin fixed relation` to` the lifting frame for exerting, li,ftingforcet on the frame. The frontend of the rocker, member 83' extends forwardly cut'over the top ofthe king, bolt |6 whereit is provided with atransverse pin flon which" a pressure'rolleris journaled between the side plates; 83"' of the- ,rocker member, This pressure Vroller'is adaptedj tojexert downward reaction force against thefupper end; of" the king bolt |6. Theu upper 'end of" the;v king boltcarries an antifrictiondisc' 89"'against'which the4 roller 88 is adapted toexertits pressure-the king bolt relatively to the disc ilso that steering rotationof the king'bolt' is not' materially resi-s-ted by' the downward* pressure which the rollerfjexerts against the disc 89. As shown inFigure 3', the disc--89`hasan anti-friction turntablemountingj in the upper end of the kingbolt |76i through;- the mediumI of an antifriction bearing 9| which-isfseated irra counterbored recess 92 in theuppe-rend of the kling bolt.

It will be seen fromtheforegoingthat'when oil underpressure isfforrced :intothe lifting 'ram fi'lfthe upward motion'of'fthe piston '66 jwill thrust upwardly onlthe'rear' pin118 ofthe rocker member |23.`v The action of"v this' upwardn thrusting force -against'fthe` rear endof# the( rock-ing member is-tocause thermember.y toswing around the intermediate pivot 851; whereby to.` cause the rocker member to assumediiferentrangular posi-A tions aroundr this 1 intermediate pivotr relatively to the. frame plates-53; Inassum-ing-these dife ferent angular positionsaroundffthe axis of ythe intermediate pi-voti',` the-'- outer-roller endr` 81; 88 of the yrocker memberissprevented from -moving. downwardlybyvirtue-of the fact that itis reacting downwardly against-'a1 stationary point or reaction whichy bear-s directly on the'floor through the king:- bolt= |-6-i and fronvtwheels |21 Hence, while the rockerlmembera'is changing its angular positionrelativelyl to the frame vplates 58,. with the outerv endl 81;' .88` held 'againstI downward movement;` ity necessarily follows that the intermediate pivot 85 mustrise.- Thus, theV front end 'of the lifting frameI I *l is carried`l upwardly, notwithstanding the fact'tha-tf'the hydraulic-'cram 47 is carried I by; thissame lifting-frameand-is exerting a. downward-inaction: force `against the frame through the oils pressure acti-rigm against thelower end: orf-.theeV CylinderA 65.5 With-'conhln-ucdy intredecivieley of "emittente cylinder @iof.. closely spaced arms the rocker: member 83 will; Contnua. te- Swing around, the axis of' the-intermediata pivot. 8,5 until theframe` is Ain-,-r its 1 fully, raised position* as illustratedin Figure..

Referring new to. the motion transmitting mechanism which transmits. this lifting: mation to the rear wheelsV |3Yfor causingtherearend of the truck, to.; lift relatively tothe rear wheels, this mechanism comprises a. pair, of vertically extending pull links 94whicli( have their upper ends pivotally7 mountedL over the.y projecting. ends ofthe pin..'|8.extendingthrough the rearV en'dof the rocker membery 8.3.' ,The lower end of leach pulling link or liftingilinkll haspivotalj mounting on a pivot pinext'ending between a pair 95., 95A` which. extend .frwardly from a. rocker 'sleeve 98I This rocker sleeveis pivotally mounted'jto turn ,about a trans;` verse pivot shaft. 99 whichy has its endsV mounted in the side railsl Ijlofl theliftingirame. This rocker' sleeve 98" extends across substalltfilly.` the full width of the rframe toL carry pairs of 'fjorwardly extending arms 9'6" for effecting pivotal attachment to the lifting links @dat eacliside of the hydraulic unite. The linksllfextendd'ownwardly on the outerA sides ofthe side plates 5 8 which dene the compartment' forhousingAv the hydraulic unit. Projecting rearwardly from the rocker sleeve 981 adjacentV itsv en-dsfare" pairs of arms lul which carry pivot pins-- |02 Pivotally mounted on the pins |-02i between the-pairs of arms lili are 'reshaped coupling membersV |03 into Vwhichare threaded'the' forward endsof fthe previously' describedA pull rods 3S? whichv exten-d back to the swinging vcranlrassembly 3| 'onwliich are mounted-the rea-r wheelsV |13? It willbeseen from the foregoing that-when they hydraulic uni-t is actuated to Itransmitliftingjmotion -to the -front rocker member 8'3"; the upward motiony ofthe, rear pi-n- 18 relatively-to the frame--ofitheftrucktransmits an upward* pull* through links 911.@ which causes the rocker-sleeve98*to rotatein alclockwise direction around its n'iountingfshafti |39'M for transmittingA aforward pull throughl theJ pull rods 36; This forwardy pull one thespulli rods causes` the crank arms 32- of theeswingingw crank assembly -3|\VA to swing ina' forward direction-rela` tively to the frame for causing the rear wheels |3- tov be moved in a forward and-downward-die rection relatively to the frame.4 Suc-lr relative forward 'and ldownward Imovement rofftfhe wheels causes the rearendofftheirame-toswing-up wardly, this occurringboncurrently with the-upa ward vmotion of 'the fr'ontendlofV the frame: The parts are so proportioned1thatV the rear-endof theframe rises.4` at substantially; thesan-1eL rate as the front endl of' the framesovthat theload is liftedfand lowered substantiallyuniformlylfore and aft;

Referring now to the manually; actuated meche anism for operating thehydraulie pump iin-'the lifting operation, I' have shownS a pedali typef of actuating mechanism in* the exemplaryr embodiment of truckA herein shown, butrit willbe under-A stood that the. pump canbe actuatedin other ways if desired. In some-instances; truck "operators prefer :pedalactuationand `lmother instances theyprefer handle actuation; In -theTpedaPem-e b'odiment shown; the i pumpingfpedal is'y indicated at |05, beinge-pivoted `atfit'srear-fendwm ra-pivot pin |06 'which extends through the framey` plates@ I8 and- 58-and which has'its'eouterend supported 'in a reinforcing strap U-'|. The `'pedal' is-formed-lwith a relatively wide-hu-kr-I|l8frem1the inneriportion offwhicli-proj ects af forwardlyxtending; farmi' H23 carrying a pivot pin I I.

plate 58 (Figure 3). 'ing lever H4 has bearing mounting on a trans- `plate 51 (Figure 2).

operating linkage A link H2 extends upwardly from the pivot pin I I, on the outer side of the adjacent side plate 58 of compartment 53, and

the upper end of this link has a long vertical slot 'H0 therein which engages over a pivot pin H3 which actuates pumping lever I4. The front end of this lever is formed with a laterally projecting portion H4 (Figure 2) for carrying the pin H3, and this laterally projecting portion extends outwardly through a slot |29 in the adjacent side The rear endof the pumpverse pivot pin H6 which is supported at one end 'in the adjacent frame plate 58 and at the other end in a bracket |I1 projecting forwardly from Pivotally mounted in a yoke portion of the pumping lever H4 is a roller H8 which is adapted to transmit downward strokes to the fiat upper surface of a plunger head ||9 secured to the upper end of the pump plunger |2|. The plunger is thrust in an upward direction by a compression spring |22 which is confined between the plunger head I I9 and a gland body |39 closing the upper end of the pump cylinder. By reason of the fact that the pumping lever I4 merely has a one-way pushing connection with the pump plunger through the medium of the roller I I8, it is not necessary to disconnect any of the pump when the hydraulic unit is removed down through the bottom of compartment 53, the plunger head H9 merely separating from the roller H8. While the truck is being maneuvered into position for picking up a load, or while it is transporting a load from one point to another, the foot treadle |65 is held in a substantially vertical position where it is entirely out of the way, this position being illustrated in full lines in Figure 1. The treadle is held in this upright position by a tension spring |23 which is pivotally connected at its lower end to the treadle in any suitable manner, such as by attachment to the link H2, and which has its upper end connected to the adjacent frame plate 58. This spring is of just suicient tension to overcome the weight of the treadle. The provision of the lost motion slot I in link H2 permits the treadle to swing to this upright position, while the pumping lever I4 still remains in its substantial horizontal position. When the treadle is to be actuated for raising the truck, it is first swung down to the upper diagonal position indicated in dotted lines in Figure 1, from whence it is stroked upwardly and downwardly by the operators foot, and the action of the spring |23, one of the lower positions being fragmentarily indicated by the dash and dot lines in Figure l. As the truck frame moves upwardly in the lifting operation, the treadle is permitted to have a greater range of oscillatory movement, before striking the ground.

Referring again to the hydraulic pump 46, it will be seen from Figure 4 that as the pump piston |23 is moved upwardly in the pump cylinder |21, oil will be conducted from the reservoir into the pump cylinder |21 through a suitable inlet valve |28 and associated passages, the details of which arrangement will be well understood by those skilled in the art. On the downstroke of the piston |26, oil will be forced from the cylinder |21 through suitable passageways and past the check valve |3| leading into the ram cylinder 65. The successive actuations of the hydraulic pump force the ram piston 66 upwardly to effect the lifting operation previously described.

Referring now to the release valve mechanism 48. it will be seen. from Figure l that this, mechanism comprises a 'stationary valve housing |34 having an axial bore in which a ball type of release valve |36 is mounted. This valve is normally pressed upwardly into closing position against a tapered Valve seat |31 by the action of a compression spring |38. The axial bore |35 has communication with the lower end of the ram cylinder area, and the valve port |31 has communication with radial ports |39 leading back into the reservoir 5|. When the release valve |36 is forced downwardly off its seat |31, oil is free to flow from the lower end of the ram cylinder back into the reservoir through ports |39, whereby the piston of the ram is permitted to descend. The valve |36 is adapted to be forced downwardly oi its seat |31 through downward thrusting motion imparted thereto by release plunger I4 I. This release plunger extends out through a gland packing |42 extending upwardly from the valve housing |34, and the upper end of the plunger carries a head |44 which is adapted to be forced downwardly by a release lever which I shall presently describe. A compression spring |45 normally holds the release plunger |4| in its raised position. When the release valve |36 is opened the rate of return ow from the ram to the reservoir is automatically governed by a velocity responsive control valve |41. These automatic regulating valves are well known to those skilled in the art and hence a detailed description is not necessary. It will suice to say that the valve element |41 is balanced between two springs |49 and |5| in such manner that if the rate of release flow exceeds a predetermined velocity the valve shifts in an upward direction so as to exert a throttling action on laterally directed governing ports |52 formed in the stem |53. The oil issuing from the ports |52 flows upwardly to release valve |36 and its port |31. The lower end of the stem |53 connects with ports |55 which communicate with a passageway |56 extending from the lower end of the ram cylinder 65.

Two mechanisms are operative to open the release valve |36 for venting oil back into the 45 reservoir, one mechanism being manually actuated for the purpose of lowering the lifting truck when it is desired to deposit the load, and the other mechanism being automatic and being brought into action when the lifting frame has reached a predetermined maximum height so as to prevent the possibility of the hydraulic mechanism being further actuated and causing damage to the parts after the lifting frame has been raised to its maximum position. Referring 55 to Figure 5, the release plunger |4| is adapted to be forced downwardly by the rocking action of a release lever |58 carrying an adjustable screw |59 at its outer end adapted to bear on the plunger head |44. The lever |58 is secured to a 60 rock shaft |6| which is journaled between the adjacent side plate 58 and frame plate I8. An arm |62 extends downwardly from the shaft |6| in position to be engaged by the front edge of a rocker arm |63 extending upwardly from a lower 65 pedal shaft |64. The pedal shaft is journaled in the frame plate I8 and carries a release pedal |66 which is normally held in a substantially upright position by a tension spring |61. When the Y lift truck is to be lowered by manipulation of the 70 pedal |66, the latter is swung forwardly and downwardly from its raised position so as to bring the arm |63 into engagement with the arm |62, whereupon further downward movement of the pedal is operative to rock the release lever |58 for opening the release valve |36. The automatic vactuation of the release valve-isfeifected through an upwardly "extending narm ITI vwhich is `'also secured `to 4-therock shaft itl. The upper endiof'the arm FH isdisposedfin thepath o'f a release lug or arm l1-2wh`ich projectsv downwardly from the rocker lmember 813 or from 'the vrocker shaft85 in ysuch position Athat the v'lug l i2 engages the lforwardredge Vofthe Ill I and sta-rtsswin-ging the latter varm when 'the lifting irai-'ne has been raised approximately toits predetermined maximum position. This `operates througlrr-"the release lever-'|58 to-open the release v1valve [36, thereby 4holding 'the ilifting frame at --thispredetermined maximum position and preventing further upward movement of the frame.

AWhile I have illustrated and described what v-I regard to vbe the preferred embodiment of lmy invention nevertheless it will be understood vthat su'ch is merely temporary and that numerous modifica-tions and rearrangements may be lmade therein without Vdeparting -from the essence of the invention.

-1. In a lifttruck Vfor lifting pallets or skids, the 'combination'of a frame, dirigible front 'wheel means'supporti-ng *the iront end 'of --said frame, a swivel-ing king 'pin connecting said iront wheel means withsaid iframe, lrear wheels Vv'for supporting therearpndof said frame, a'hand-le arranged for pullingfthe vtruck and steering said front wheels, arocker member pivotally mounted at a point intermediate its ends on lthe 'fronttend "of said "frame to iextend substantially fore Vand `"aft thereof, hydraulic mechanism mounted -onjsafd framean'd operatively connected to transmit iup- Ward `thrust-ing:motion against 'the rear end df said vrocker member, 'means for transmitting downward thrusting force from Vthe front end of said rocker member tosaid'swivelingkingpin whereby to lift Vthe 'front portion of said frame, and 'means respon-sive to pivotal motion of 'said rocker 'member for. causing lifting movement of the rear portion ofsaid frame relatively torsaid reai wheels. Y Y f "2. lIn alift truck forlifting palletsor skids, the combination of a frame, dirigible front wheels supporting Athe front end of said frame, rear wheels for supporting'the rear end of said `frame, a handle for manually pulling the truck and s'teeringfsai'd front twheels, a king bolt `rising from said lfront wheels, a guide sleeve secured to said frame and movablefvertically along said king bolt, a :rocker member pivotally ymounted on the 'iront en'dof said irame to extend substantially longitudinally thereof and arranged to have its forward end lexert downward thrust reaction on 'said .king bolt, and a substantially vertical hydraulic lifting ram connected with the rear portion ofV said 'rocker member for causing rocking movement'of said rocker member whereby to liftsaid frame.

-3. In a lift truck for lifting pallets, skids or the like, the lcombination of la frame, dirigible front wheels supporting the frontend of said frame, rear wheels for supporting the rear end lof said frame, a handle connected for manually pulling the truck and steering said front wheels a king bolt'ri'sing vfrom said front wheels, aguide sleeve secured to said frame and movable vertically along said 'king bolt, a rocker member pivotally mounted on the :front end of said frame to extend substantially fore and aft of the frame and 'ar-- ranged to have its front end exert downward thrust reaction l'on said kngbolt, a substantially vertical hydraulic `ram connected between' said A andlhaving its iront'end arranged to exert downthrustrea'ction on said'kin'g bolt, and hydraulic lifting mechanism comprising a hydraulic 11am pivotally "mounte'dbetween said frame and the "ear end 'of said vrockermember for transmitnnfgmotion'to said frame.

55. En a lift truck, the combination of-affra'me, dir'igible front wheels for supporting-the -iront'e'nfd of Y"said frame, rearwheels supporting the rear end of said frame, ra king bolt rising fromsa'id front wheels, a guide sleeve secured to said frame and fmovable vertically alongr said Aking bolt, "a rocker member pivotally 'supported intermediate its fends on said frame to extend substanti'allryifore andaft of said truck `and having-lits "frontend arranged to exert downward thrust reaction on said king bolt, a hydraulic ram having its lower end -pivotally supported onsaid frame and having its upper end pivotally connected "with'the rear endof said rocker-member for rocking saidmember relatively to Asaid frame whereby to lift 'the front-'end of said iram'errelatively to said front wheels, and motion transmitting mechanism pivotally connected with the rear end of Vsaid rocker :mem-ber for lifting vrthe rear end of -'saiil frame `relatively 'tosai'd rearwheel's.

56, `In aflift truck, Vthe combination 'of a 'irame, front supporting wheels for said trame, liftin'g mechanism for raising A`said frame Vrelatively to said front wheels comprising a rocker fme'rnber adapted to transmit downward reaction p'ressire to said front 'vv-heels, hydraulic mechanism 'fr actuating said rocker member, `'said hydraulic mechanism comprising a ram 'anda pump, andra readily releasable mounting shaft for mounting said hydraulic mechanism on said truck whereby said lram and said Ypump can b' removed as a tromthe 'truck by the release fof said mountingfs'haft.

"7. In a lift truck, the combination 'of "a frame, supporting wheels for said frame, lifting mech-y anis'm for raising said frame relatively to 'said wheels, hydraulic mechanism for actuating said lifting mechanism, said 'hydraulic mechanism comprising a ram, 'a pump and a release valve,

and readily releasable mounting means .for mounting said hydraulic mechanism on said truck, said mounting means comprising a shaft on which said ram, pump, 'and release valve 'have tiltable support, and arranged whereby upon the release 'of Said shaft said ram, pump and release valve can be removed as a unit from 'the trunk without disassembling either said ram, pump or release valve.

f8; "In a Alift truck, the combination of a trahie, supperting wheels lior said frame, lifting Vmecl'rfanish'a tor raising said frame relatively to said wheels, hydraulic `mechanism for actuating 'said lifting mechanism, said hydraulic m'echa ctniirising a ram and. a pump, releasabie pivotv means pivotally connecting one end of said ram with said lifting mechanism, and releasable pivot means pivotally supporting the other end of said ram on said frame, said ram and said pump pivoting as a unit between said two pivot means, both of said releasable pivot means being adapted to be released for permitting said ram and said pump to be removed as a unit from the truck.

9. In a lift truck, the combination of a frame, front and rear wheels supporting said frame, a rocker member pivotally mounted on said frame, means responsive to rocking movement of said rocker member relatively to said frame for transmitting downward reaction force to said front wheels and thereby raising said frame relatively to said wheels, hydraulic mechanism for actuating said rocker member, said hydraulic mechanism comprising a ram, pump and release valve, upper pivot means pivotally -connecting said ram with said rocker member, lower pivot means pivotally supporting said ram, pump and release valve on said frame, and means permitting ready removal of said lower pivot means whereby said ram, pump and release valve can be readily removed as a unit from the truck.

Y 10. In a lift truck, the combination of a frame, supporting wheels for said frame, a rocker member pivotally mounted on said frame, a lifting mechanism responsive to rocking motion of said rocker member for raising said frame relatively to said wheels, hydraulic mechanism for actuating said rocker member, said hydraulic mechanism comprising a ram and a pump, manual actuating means for actuating said pump, a one-way pushing connection between said ram and said rocker member, a one-way pushing connection between said manual actuating means and said pump, and readily releasable mounting means for said hydraulic mechanism enabling said ram and said pump to be removed as a unit from the truck, said one-way pushing connections facilitating the separation of said ram and pump from said rocker member and said manual actuating means in the removal of the hydraulic mechanism from the truck.

11. In a lift truck, the combination of a frame, supporting wheels for said frame, a rocker member pivotally mounted on said frame, lifting mechanism responsive to rocking movement of said rocker member for lifting said frame relatively to said wheels, hydraulic mechanism for actuating said rocker member, said hydraulic mechanism comprising a ram, a pump and a release valve, readily releasable mounting means for said hydraulic mechanism enabling said ram, pump and release valve to be removed from the truck as a unit, manual pumping means for actuating said pump, manual release means for actuating said release valve, a one-way pushing connection between said ram and said rocker member, a one-way pushing connection between said manual pumping means and said pump, and a one-way pushing connection between said manual release means and said release valve, saidroneway pushing connections facilitating the ready removal of said hydraulic mechanism from the truck.

12. In a lift truck, the combination of a frame, supporting wheels for said frame, hydraulic lifting mechanism for causing lifting motion of said frame relatively to said wheels, said hydraulic lifting mechanism -comprising a pump, a treadle for actuating said pump, spring means normally tending to hold said treadle in an upwardly extending non-operating position, and motion 12 transmitting means including a lost motion connection which is operative to transmit motion from said treadle to said pump only after said treadle has been swung down to a lower operating position below said non-operating position.

13. In a lift truck, the combination of a frame, supporting wheels for said frame, a rocker member rockably mounted on said frame, hydraulic mechanism mounted on said frame for rocking said rocker member, means actuated by said rocker member for transmitting downward reaction forces against said supporting wheels for lifting said frame, said hydraulic mechanism comprising a pump, a treadle for actuating said pump, spring means normally tending to hold said treadle in an upwardly extending non-operating position, and motion transmitting means including a lost motion connection which is only operative to transmit motion from said treadle to said pump after said treadle has been swung down to a lower operating position below said non-operating position.

14. In a lift truck, the combination of a frame, supporting wheels for said frame, a rocker member rockably mounted on said frame, hydraulic mechanism mounted on said frame and operatively connected to rock said rocker member, means actuated by said rocker member for transmitting downward reaction forces against said supporting wheels for lifting said frame, said hydraulic mechanism comprising a release valve, manually actuated means operative to open said release valve for lowering the frame, and automatically actuated means operative to open said release valve in response to rocking movement of said rocker member for preventing continued operation of said hydraulic lifting mechanism after said frame has been raised to a predetermined maximum height.

15. In a lift truck, the combination of a frame, supporting wheels for said frame, a rocker member rockably mounted on said frame, hydraulic mechanism mounted on said frame and operatively connected to rock said rocker member, means actuated by said rocker member for transmitting downward reaction forces against said supporting wheels for lifting said frame, said hydraulic mechanism comprising a release valve, a release pedal operative to open said release valve for lowering the frame, spring means normally holding said release pedal in an upwardly extending, nonoperating position, and automatically actuated means operative to open said release valve in response to rocking movement of said rocker member, .whereby said hydraulic mechanism is prevented from exerting continued lifting force after said frame has been raised to a predetermined maximum position.

16. In a lift truck for lifting pallets, skids and the like, the combination of a frame, dirigible front wheels for supporting the front end of said frame, rear wheels supporting the rear end of said frame, a swiveling king bolt rising from said front wheels, means supporting the front end of said frame on said king bolt for vertical movement thereon, a hydraulic ram mounted on said frame in rear of said king bolt, a supporting structure extending upwardly from said frame between said king bolt and said hydraulic ram, a walking-beam type of rocker having pivotal support intermediate its ends on said supporting structure, and having its front end extending forwardly across the top of said king bolt and having its rear end extending rearwardly across the top Of .Said hydaflll ram, means for trans- 13 mitting upward thrusting force from said hydraulic ram to the rear end of said rocker beam, and means for transmitting downward thrusting force from the front end of said rocker beam to said king bolt.

17. In a lift truck for lifting pallets, skids and the like, the combination of a frame, dirigible front wheels for supporting the front end of said frame, rear wheels supporting the rear end of said frame, a swiveling king bolt rising from said front wheels, means supporting the front end of said frame on said king bolt for vertical movement thereon, a hydraulic ram mounted on said frame in rear of said king bolt, a supporting structure extending upwardly from said frame between said king bolt and said hydraulic ram, a walking-beam type of rocker having pivotal support intermediate its ends on said supporting structure, and having its front end extending forwardly across the top of said king bolt and having its rear end extending rearwardly across the top of said hydraulic ram, means connecting said hydraulic ram to the rear end of said rocker beam, anti-friction pressure transmitting means effective between the front end of said rocker beam and the top end of said king bolt for transmitting downward pressure to said king bolt, bell crank lever means pivotally mounted on said frame, link means pivotally connected between the rear end of said rocker beam and one arm of said bell crank lever means for transmitting oscillatory movement to said lever means when said rocker beam is rocked to raise the frame, and motion transmitting link means extending from the other arm of said bell crank means to said rear wheels for lifting the rear end of said frame relatively to said rear wheels.

18. In a lift truck for lifting pallets or skids, the combination of a frame, front and rear wheels for said frame, a handle arranged for pulling the truck and steering said front wheels, a rocker member pivotally mounted at a point intermediate its ends on the front end of said frame to extend substantially fore and aft thereof, hydraulic mechanism mounted on said frame and operatively connected to transmit upward thrusting motion against the rear end of said rocker member, means for transmitting downward thrusting force from the front end of said rocker member to said front wheels whereby to lift the front portion of said frame, and means responsive topivotal motion of said rocker member for causing lifting movement of the rear portion of said frame relatively to said rear wheels.

19. In a lift truck for lifting pallets, skids or the like, the combination of a frame, front and rear wheels for said frame, a handle connected for pulling the truck and steeringv said front wheels, a rocker member pivotally mounted on said frame to extend substantially longitudinally thereof and having its front end arranged to exert downward thrust reaction on said front wheels, hydraulic mechanism for causing pivotal motion of said rocker member, and means connected with the rear end of said rocker member for causing lifting movement of the rear portion of said frame relatively to said rear wheels.

20. In a lift truck for lifting pallets, skids or the like, the combination of a frame, front and rear wheels for said frame, a handle connected for pulling the truck and steering said front wheels, a rocker member pivotally mounted at a point intermediate its ends on the front portion of said frame and extending substantially fore and aft of said frame, lifting mechanism mounted on said frame and operatively conected to transmit upward thrusting motion against the rear end of said rocker member, means for transmitting downward thrusting force from the front end of said rocker member to said front wheels whereby lto lift the front portion of said frame, and

` means responsive to upward pivotal motion of the rear end of said rocker member for causing lifting movement of the rear portion of said frame relatively to said rear wheels.

ARTHUR M. BARRETT.

REFERENCES CITED The following references are of record in the

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