US2329145A - Lift truck - Google Patents

Description

Sept '7, 1943 l w. .sTul-:BINQ J R n 2,329,145

LIFT TRUCK Filed Aug. 20, 1941 "5 Sheets-Sheet l ATTORNEYS Sept 7, 1943. w. sTUEBlNG, JR 2,329,145

LIFT TRUCK Filed Aug.. 20,'1941 s sheets-sheet 2 Sept. 7, 1943. w. sTuEBlNG, .JR

LIFT TRUCK Filed Aug. 20, 1941 3 Sheets-Sheet 3 .om Nmv wn @L am.

'Q'HWM ATTRNEYS released, the check is not effective and the load falls to the floor causing damage to the equipment or the load, and in fact, even causing injury to the workman., It is an object of this invention to provide a lift truck which is efficient in operation and which is free of difficulties of the above character.

Referring to Figure 1 of the drawings, a lower frame is provided with a pair of front wheels I having anaxle IU and a pair of rear wheels 2 having an axle 3, and a pair of lower rails I and 1 (see alsoFigure 4). The front ends of lower rails G and 1 are joined together by a head-84Y aseaifis portion 32 of the lifting hook 24. With the elements positioned as shown, tooth 3I lies to the left of the segment portion 32, and when the handle is swung downwardly (clockwise), the lifting hook 24 is swung about the pivot pin 25 with the. result that the lifting frame 'is elevated upon the links I2and I8. However, when the handle 21 is slid upwardly or forwardly within the sleeve 28 so that pin 29 is positioned at the other extreme end of slots 30, the extreme end of tooth 3I rides upon the arcuate surface of segment 32. In this way, the steeering handle is disconnected from the lifting mechanism, and it which carries a swiveled fork 9 in which axle Il is mounted. Lower rails 6 and 1 providela mounting means for four links, there beingat the front a pair of links I2 carried attheir lower ends by a pair of pins II, and at the rear,V a pair of links I8 carried at theirlower ends by a shaft 5. V

.of each of links I2 and I8 is pivotally connected to the lifting frame I3 which is elevatedl to engage and lift the load. Lifting frame I3 is formed by two upper rails I4 and I5, a rear tie-bar I6,

and a forward saddle I9. Tie-bar IG supportsv a f shaft I1 (see Figure 1) 'similar to shaft 5 and upon which links I8 are pivoted. Links I2 are connected to the lifting frame by a pair of pivot pins 96.A Referring again toFigure 4, head 8 is attached to lower rails 6 and 1 by four rigid pins, each pin carrying'a' spacing collar II3.providing space for links I2 between thersides ofthelower rails and the head. l

When it is desiredL to lift a load, the lifting frame is pulled forwardly and upwardly,`and lit swings through an arcuate path from the position shown in Figure 1 toward the position of FigureZ, with the four links I2 and I8cooperating to provide a rigid support forithe lifting frame. The lifting frame is also connected to the lower frame by a latch-check unit 36.to be described in detail below,` whichy is expansible `longitudinally and which is effective as awlatch to hold thel lifting frame in any elevated position and which is also effectivel as a check'tolimit the speed of descent ofthe lifting frame. K 1 y The mechanismr for `performing the lifting operation is of the character'shown in my patent referred to above though'the operation kvand the leverage arrangement aredifferent. Accordingly, onfthe under side of the cle'ntralpo'rtion of saddle I9 `is a swinging double-'eyel link 20 which'is pivoted on a pin I20fcarried bya pairlof" ears 122 integral with saddle I9. Extending through the forward eye of linkZ` is a hairpin loop 2l which is rigidly attached at its upper end to a doughnut link 22 having an eye portion 23.. Extending through eye portion 23 is y'a lifting hook zawni'ch, is reckabiymounted on a. `pivot pin 25 is held in extended position by the engagement l between the arcuate end of tooth 3I and the arcuate surface of segment 32. A balancing spring 33 balances the weight of the handle and isy mounted on-a rod 34 which is pivoted at its lower end on a pin'35 and which extends through l 70 from the horizontal.

carried by the upper bifurcateaend 2s of fork e.

Lifting hook 24 is provided with a segment portion`32, and extending upon opposite sides of this segment portion-and pivoted on pin 25 are two downwardly extending ears of a steering handle A Sleeve 28 carries the steering handle 21, and limited longitudinal movement is provided by virtue of a pin 29 which is rigidly mounted in the extreme end of handlel 21 vand the opposite ends of which extend through a pair of elongated slots 30 in sleeve 28. Rigidly mounted in'the lower end of handle 21. is a plughaving a downwardly extending tooth 3I which engages; the segmenti a bracket at 'the upper end of sleeve 28.

. VThe lifting frame is moved fro-m the position` shown ,in Figure 1 to the position shown in Figure 2, and the linksv I2 and I8 swing through an arcof substantially, This arc is `from the position .of Figurel, where the links extend. substantially 30 from the horizontal,- to the position of Figure 2, where the links extend substantially The' mean lifting force applied through link 20 in raising the lifting frame is substantially atrightangles to a line bisecting the are through which the links swing. In this way the-lifting effort exertedupon the steering handle is utilized efficiently', and `the leverage is so adjusted that the load may be lifted without diiculty. In this/embodiment the movement of thesteering handle is substantially 100, andthe lifting effort exerted by the operator in lifting va load does not vary materially throughout the'swingingof the steering handle. j

During use the lifting frame is elevated until it. engages and supports the load; the vlifting frame may be'fully elevatedv as shown inFigure 2,jbut in practice it lis generally necessary to lift the` load only sufficiently to free the load from the floor. After rbeing elevated any desired amount, the latching or holding mechanism is automatically operative, and the lifting frame is held from descending. After the load is moved-to the newlocation, the latching` mechanism isy re- 'right the latch-check is connected to -saddle I9 by a bracket 42 pivoted to the saddle (see Figure 6). Extending from saddle 'I9 is an ear 14, and

apivot pin 12 extends through` this ear and a pair of similar earsf and 69 integral with bracket 42'. Similarly, a pin 13 extends through an ear 15 extending from saddle y,I9 'anda pair of ears 10 and 1I integralwith bracket 42.

Referring to Figure 5, latch-check 36 is pro- .vided with a cylinder |36, the left-hand end of which is closed by a threaded plug 38' and the right-hand end of which is closed4 by a threaded plugf31. yCylinder |36 is filled withl a suitable oil, and a piston 4U is slideably mounted in the cylinder with a leather cup and a backing washer 5I providinga seal at the piston so that the fcylinder is divided into a left-hand chamber 9| and a right-hand chamber. YA .hollow piston aeeeil'fs y l y lifting' iframe. Foot lever 6H. is provided Withf an rod M isthreaded to the piston and 'extends lae yon@ the ngntfhandend ofuleenmaer through plug 31 Where the pistony rod :isioonnected to bracket-A2; a vsuitable packing. gland- 131,. pre-y vents oil leakage from .the cylinder aldngl the piston rod. 'Afcompression .spring 92 is coiled about piston rod .4l 'Withlone end bearingagainst plug .31 and with the other '.endbearing against piston l so there is a tendency for the piston. to mov-e leftwardstoward Ythe position shown. 'f y UClzaarnhers il@ and y twovalved passageways through tnepistomemd oil `is permitted to iiow through thesepassagef' 'Ways in a controlled manner te limitfztne move# ment .of thepiston lalong the cylinder! or these.=passageways is an yoil inlet passageway and is formed by passagesl, M', anddvvith acne- Way'ball valve-41 normallyA closing the left-hand x end of passage 45. Bally-abre 81 is held seatedby a spring 48, thelet-hand end ofy whicnbears against apin 49 rigidly inountedinl the valve nip*- pie dll. Ball valvefll is readily unseated by oil pressure fat the right of the valve toperrnit the oil to move to the left throughtlie passageway Afrom chamber- 98 to` chamber 91,- but' oil cannotflow -to the right tlfiroughI the valve yfrom Achamber @tare connected byvmeans of upwardly extending-mmm atthe upper end of.

.which is .a treadleportion. 82. j Referring to'Fig n ure.A 6, thev foot lev'er'isv provided alknuckle l8.positioned between thebotto'rn edgesiofears erating. amil IMQ-supports' a1 transversely .extending pin GSF-(shown in dross-section in Figure Eli through which` is threaded the enelnf vait/.elmo t5, anar-the operating arm has a minderen-lopen ing "402-l therethrough to` permit flreeroking movement between? theo-perating arm and# fr valverod; -m l When r'foot lever 6l (see Figure' 2) isf depressed, 'it swings'about pin l1 carrying pin 66 and valve'rod 65-lfto `the right and opening'vthe K needle valve. The `rocking movement yoaf theffoot lever El' islirnited'lby a stopf 104' extending' upwardly iron; knuckle7 18--(seefalsol=igure 6);

" Feet lever' Ncarries a bell crank: Silwhic-h' is 9'! to Ichamber 9&1 Near theta-plof #the piston 1 an Voutlet passageway is-provided by the epening through ar nipple wand passages S35i-@hand f5@ to` an escapement Y chamber 63.. and the vesca-nefment chamber is connected through a radial-re-4 strioted opening 64 to chamber im.'Y

Chamber @3 -is formed by the enlarged open-y ing in tne'end olfpistonrod 4H and rat the-right tine chamber is sea-led by a leather :cup 51 land a .connectedto piston 69 and extends to the right beyond the end of piston rod 4l so thatl the` nee- A dle valve'may be opened by drawing-the "valve rodtotheright.

When-.the lifting iframe is' being envenena foree is exerted tending to movepiston 41! ,to the right and to extend pistonjrod `"41j fromfj the cylinder, and theoijl-rornchamber 90 A'linseats I ball valve l? rand-flows through passagesdtf; `1111,

and Q5 into chamber 9|.V However, when the lifting frame starts toidescerida force is exerted in the opposite'direction, and balllvalvel'l lis held closed so that the pistoncannot be -rnoved unless oil is permitted toes'cape fromhaniber y9| through'the outlet passageway. *When the needle valve i5@L isopenedL oil ovvs vto the 'right through'passages t3; 54, and 55 intochainber 63 'and escapes through thefrestriotedbpenng 64, and the size of this opening limits the ls115341:y yof descent.

. As indicated above, needle valve. 56de nor mally heldolosed'by spring 62,*.and`vthre needle valve is opened by depressing a footlever .5 1v t(see Figure 2). This foot lever isvfrolrably mounted on aj pivot. pin Il which` inlsturn, is carried hy' threepivot extension portions of bracket .42

which extend downwardly from'ears 59.19; and

Bracket 42 is in turnmomitedzupon saddle y rockab'ly vnliounted Vupon afstud pin 183 and has an?upwardlyextending-arml 84 and av horizon# tally extending arrni. Arm B vcarries an ad# justable'set se'revv` 86 Whiohis looked inposition by `a vlocking nut,V and a spring Hill' holdsjarrnd against. a lug lezrtendlng downwardly froinfsadff dle I9, the otherend ofthe spring beingattached to Afoutiever 6l; Bell crank 83 is foitiiefpurpose tion shownin Figure so that needle vaivej is .held openA until'f the lifting' 'framefhas completely returnedfromits elevatedposition. ,jncordinglm when-foot lever." 6l? isdepressedfto theiposition shown in Figure 3, springV` I9tl1swings 'thefbell crank clockwise With arm 84 engagingY beneath lug- `8l, andthis engagement holds thefootlever depressed. Rigidly mounted l'ipon kthe lower yside frame 'l `is a horizontally "extending bracketA @t which is' positior'ied sothat it 'is' engagedbyfset screv/'Sasthelifting frame vrneves'frorn the'ele'l -.vater-lposition.y As set screw' B6 engages braok'et 881,*-the bell orankis swung csunteroloolrwise vabout its pivot 133,"and-larm 84 isrnoved vto theleft of j Asipointed out thro'uglfi'an are4 from about-B09" to` 703 frozngthe honzontn, and the liftingl ffrce isappneafamng the line whichl is substantially atV right angles to a .lineubiseoting' this arc.-`Byf using'` the latchcheck unit-it is not necessary: to raise` the"-i links to averticalg-pos'ition, andin' fact;v the lifting'frarne is supported by the links and the latch-*cheek I9 which spar'tfoi the lifting frame'so that foot v leverV 6'! is actualiy carried byand moves'withthef unit, rvvith the latch-"check unity exerting asup porting force 'substantially at right anglesv to the links (seeL Figure' 2)". l Adrialin-th@ 'force wenn thebperator must exert upon the liftingghandle varies. depending upong the angleor 1 ar'cbetv/een `links .Hand 18 `and the-.horizontal@andf'upon Whether or'not the force is beingapplied to the linksv along lines at right anglesl tor they'links.A

This variation, depending upon the are', or angle, is a trigometric function o-this-ac'yor angleit being the tangent thereof.. In the presentern bodim'ent.- duringthe'liiting of the load'thisgarc or" angle startsv at approximately -3G-,*Wh` ere""the tangent is 5.71am as they-linksareUsvvu'ng"un- Wardly increasingr this angle, thev tangent ohanges at. a. relativ'ely-slivtrv rate. v To thev coinj plete'lifting -operatiomtne lifting handlers svn-ingV from a verticallposition to below the'hnrijzontal y position, andfthslthroughf v"an: are of if substan.,

above, the links i and i8 v and 70".`

tially 100, while the linksrsw'ing between'BO? l With this arrangement, and `with the releasable direct mechanical connection between the lifting handleand the lifting" frame, thevariationk during the lifting operation in the4 force necessary to lift a loadisat a minimum, and the lifting .ability Aof the operator and theA mechanical elements are used efficientlyn at all'r times.

,Theoperator may lift the load in a singlelifting operation, or he may stop at'` any vpointvto change his ,position with respect to the steering handle.` In any event, the latch-check holdsthe lifting frame at whatever height the load has reached until the lifting frame is released. VIf the latch-check unit should be rendered ineffective, as for example, if `the oil should Ibe lost, the latchcheck will not` hold, and the Aoperator will be immediately aware of this defect. Thus, the operting a lifting force whichy is substantially at i y right angles to said links during at least, a por- CII erator kwill not lift a load and thenrelease it to find that the descent is no1; checked. v,When the operator has moved a loadv to a new location and desires to release the load, he merely depressesv` thefoot leven-and the bell crank holds Vthe foot lever depressed until the lifting frame fully4 de@ sce/nds. In this manner the operatorisvrelieved of the responsibility of holding the lfoot `lever down, and he may give his entire attention to st'eadying and guiding the load as the load descends.

As` many possible embodimentsmaybe made f of the above invention and as many kchanges might be made in the4 embodiment aboveset forth, it is to ber understood that all matter here-, inbefore set forth, or shown in the accompanying drawings, is to be interpretedas illustrative and not in a limiting sense.

I claim: v

l. In a'manually operated lift-truck, the cornbination of: a chassis' comprising a supporting frame having mounted thereon a set of wheels and a steering handle; a lifting frame meu-ated and from an elevated position where it engages and lifts a load; meanstoelevate said lifting frame by swingingsaid steering handle compris-A ing linkage means forming a releasabledirect mechanical connection between said steering liandle and said lifting frame; means to hold-said lifting frame in its elevated position so that the load may' be moved to a new location bymoving the truck comprising a unitary mechanism which is effective to hold the lifting frame atsubstantially any point in its upward movement; and releasing meansmounted upon saidlifting frame and adapted to be operatedto render said unithrough'parallel vertical arcs whichy arcs extend substantially between 30 and lffromthe horizontal; aflifting frame mountedy upon the upper ends of said links so that as said links are swung through their arcs the lifting frameiselevated` and elevating mechanism comprising a releasable linkage assembly forming a ,direct mechanical connection between said lifting frameand said steering handle sothat the lifting framemaybe elevated by swinging said steering handle through an4 extended arc, saiduelevatingmechamsm ex,-

operated lift truck,the corn-1` tion of the elevating operation.

y 3.` In lifttruck apparatus, the combinationof: a chassis; a lifting frame mounted upon said chassis. and adapted to moveupwardly and longitudinally of the truck to thereby engage and liftthe loadga checking and latching mechanism` operatively` connectedbetween said base frame and said lifting frameto thereby regulate the movement of the lifting frame downwardly, said mechanism being automatically operative as a latching means to prevent the descent of the lifting frame and releasable so asztobe ineffectiye as a latching means to thereby permit the controlled descent of the lifting frame; a treadle rockably mounted on said lifting frame and having an operating arm which is effective when depressed to release said mechanism as a latching means; a latch pivotally mounted on said treadle and adapted to hold said treadle in its depressed position; spring means to move said latch toward its latching position; and releasing means to release said latch when the lifting frame hasreturned from its elevated position. f

In a manually operated lift truck; thecombination of a chassis; a lifting structure mountedon said chassis tobe moved to and fro-man elevated positionuto tlierebyli'ft a load; and a latch-check unit operatively connected between said chassis and said lifting structure and eective selectively to prevent or control the descent lupon said chassis and adapted to be lmoved vto;

of said lifting structure comprising, a cylinder, aripiston mountedto movelongitudinaliy along said'cylinder and having apiston rod extending from vthe end of said cylinder, means constituting-a passageway through said piston and including a valve` mechanism,l a bracket means mounted on the endof said piston rod and pivoted tosaid lifting structure to provide the mechani'calV connection .betweenl said lifting structure and ,thelatcli-check unit, and a valve releasing mechanism to` open said valve mechanism including "alY foot lever rockably -mounted on said bracket. i

,r5.,ii'pparatus as described in claim Li wherein said piston is provided with av ball valve through which fluid may pass from one endof said cylinder to the other during the elevatingof said lifting structure and said valve mechanism is in the form of .a needle valve which is openedby a `valve-operating rod extending through the center"of said lever.

' 6. In a manually operatedlift truck', the combination of: a chassis; a lifting structure mounted on saidchassis to be moved to" and from an piston rod and attached to said fcot `elevated position to thereby lift a load; and a latch-'check unit" operatively connected between said chassis and said lifting structure and effective7 selectively toY prevent or control Ythe descent of 'said lifting structure comprising, a casing, an operating member mounted to 'move within said casing and constituting with said casing the effective impediment means of the latch-check unit, an operating rod extending from said casing and having mounted on the extreme end thereof a bracket pivoted to said lifting structure to provide the mechanical connection between saidlifting structure and the latchcheck unit, andreleasing `mechanism to control the releasing of said latch-checkunit including a lever rockably mounted on'said bracket means.` *A

m7: Apparatusas describedvin claim `wherein saidfreleasingfgmeansiincludesa latch which is rendered effective upon the actuating oi said lever to hold said lever in actuated position, and latchreleasing means which is effective when said lifting structure returns from its elevated position to render said latching means ineffective.

8. In a Vmanually operated lift truck, the coinbination of a chassis having mounted thereon a steering handle; a' lifting structure mountedfon said chassis to be moved to and from an elevated position to thereby lift a load, means to elevate said lifting structure by swinging said steering handle comprising, an idler link having two eyes one of which is attached to said lifting structure, an intermediate linkage member having a lower U-shaped portion which is loopedinto the other of said eyes of said idler link and having an upper eye, and a segment hook member having a hook portion extending through the last-named of said eyes and a segment portion having a releasable latching connection with said steering handle; means to hold said lifting strucing means mounted upon said lifting structurer and adapted to be operated to render said unitary mechanism ineffective to hold the lifting structure.

WILLAM STUEBING, J R.

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