US2520857A - Lift truck - Google Patents

Description

L F. SCHRECK LIFT TRUCK 3 Sheets-Sheet 1 Filed Nov. 19, 1946 YmFH 1m M/s n R La mh# m /lll J E S wl m Ri- ME M m n w1 i v .NN\ 1 MP wf b Y N -JNQ m B Il.| QN n M .MFN E FIL QN &- NN E E. S 9 P Www N o o ./R l o N N n k o n @S HY Sv mw S, 54-12A T .wm S s QN, NN ........r ,\........u S mw.- .I. v if.. v@ ww ,/M. EN@ N -L fw.

Aug. 29, 1950 l. F. scHREcK 2,520,857

LIFT TRUCK Filed Nov. 19, 194e s sheets-sheet 2 INVENTOR Irvin F. Sciare ek ATTORNEY Aug. 29, 1950 i. F. scHREcK 2,520,857

LIFT TRUCK FIed Nov. 19, 1946 5 Sheets-Sheet 3 }NVENTOR Irvin 17'. Schreck BY www f Q47 ATTORNEYS Patented Aug. 29, 1950 ifi PATENT FflfCE 4 Claims.

AThis'inv'en`.ton relatesto lift trucksandimore particularly' to trucksof y'the 'type disclosed inmy Patent No. 23955345 grante'diFebruary 19, "1946, which -are 'supported ^at vtheir front ends by "a swiveledpropelling and steering wheelfand guided by means of .av draft tongue.

An 'important `objet 'of the "present invention is to provide `an 'improved control for 4*the `rloa'd liftngmechanism. y

It'isalsoan object of the'invention to `so dispose uthe operating mechanism with respect 4to theelevator standard of the-truck as'toprovide 'a truck-With'a lowfcenter of gravity toi provide stability and of minimum `'overall length Cso f that the tru-ck "can be 'conveniently .-'manipulated fin restricted spaces in warehouses, 'faotoriesand the like.

.A further object ofthe inventionistoprovide a -truck' with an? improvedk hydraulic zlif t' in :which .danger f liquid leakage' is 'minimized W ith the iabove' 'and other Objects 1 inA View, the invention may be said to comprise the lift truck :as lillustrated in the accompanying ndrawings, hereinafter Ydescribed .and particularly set forth inthe appended claims, togetherwithsuch'varia'- .tions and modifications thereof Nas willbe ap- `parent fto lone :skilled iin 'the art -to which -the invention pertains.

.-Reference"should be'hadfto the accompanying drawings f forming a .part of thisffspecieation, :in which:

Figure lis aside elevation of a truek--embody ing thelinvention;

nFigi-gis :a horizontal :section tak-enlon theflin-e indicated at 2-2 invFignl;

`3y isa vViewpartiallyin section of .the outer -end of the draft tongue -v-ewedasindicatedat f3-3 r in Fig. 1;

"Figs-4 isaa front elevation of ythe-truck;

Fig.l 5'i's a fragmentary-Vertical section ,through Jthe upper'7 portionofvthe liquid reservoir,A showing the motor and pumpin side elevation;

-Fig. 6 y.is a -fragmentary .side .eleva-tion of lthe :truck `frame with the operating vmechanism removed;

Fig. 7 is a v-top rplan View of the imotor and liquidre'servoir shown `in fFigs. 4-.and 5;

.-.Fig r"8 isa ldiagrammatic vView showing -the hydraulic hoist mechanism .and

Fig.9 is azwiring diagramshowing.theieontrol .for thelload 'carriage raising .and loweringmechanism.

Referring `to the accompanyingdrawings, the truck1 of .ther present inventionhas a frame `which includes an elevator A:standard Iformedof `two vertical .side posts J2 each provided with a web 3 projecting :from `:its inner face, :a rtop :cross bar 4 and abiottomseross banor'basemember-5 "conneoting l thelower endsiof :the pos-ts. The frame aisodncludes-rearwardlyrprojeeting side members Ii rrigidlyfattachedto the-base yof the standard I. .and-ea.l forwardly proiecting framefmember f1 connected--torthe'base member-l5 intermediate-the .posts 2. rRear supporting wheels -.8 .are earried by -the -1arms-6 and a 'front .steering .and driving wheelfllrismountedinaiframe III swiveled in= the forwardly `extending frame member 'L The wheel 9 is \driven-.byv means of an electric,..motor yH mountedhon the frame L0 and -gearedto `the wheel 9 through a :sprocket .chain Il2.

.A--drafttongue I 3 is-eonnected ebyahorizontal .pivot I4 lto .theframe J0 and `may `be .used .to steerithetruok While vitis being .propelled bythe motor I-Ifor -to manually move -the truck -for- -wardly orf-rearwardly whenthefmotor H `-is idle. The .forwardly extending frame member lis .preferably `pivoted to .the base member .5 of Lthe standard .and as `hereinfshovvnI is `eonnectedlby horizontal .pivots I 4 Ito `brackets I5 .which may be .formed integrally with :the Y base member `5. In order to.. insure adequate traction, .means is prolvidedor .maintaining asubstantial proportion .of .thelload .upon .the '.frontsupporting wheel .9.

.-Assshowninlig-s. 1, .4.and 6,leaf .springs I6 .are rigidlytattaehedat their .rear .end by means of bolts yI'l f-to wflanges .I8 formed .integrally `With .the brackets=l5 on the outer .sidesthereof '.The springs I.6.extend forwardly ata slight inclination-land engage lthe .upper sides of flanges I9 formed integrally with the frame member 'I on .opposite sides of the swiveled .frame II). lThe springs vI6 tend to 'lift the standard AI so as to dispose .the forwardly projecting rframe member .'Ietaslight inclination to the arm 6 of the'frame ,so that the .load imposedon .the standard I de- .fleets .the springs I6 and maintains-a downward .thrust upon the wheel '9.

In or'der'to increase lthe stability of the truck, brackets `2Il are-carried by the opposite ends `of .the base member 5 andprojectlforwardly therefrom, 'the tops `of the .brackets being preferably below .the topo'f the forwardlyprojecting'frame member 11. Thebrackets ZILcarry castor wheels l2 I .which `engage lthe floor .when the truck 'is loaded,'to"limit the downward'movement-of the standard I with respect .tolthe supportingwheels and tovprevent Vtipping ofthe truck. The .castor Wheels "2l being swiveled to -turn about vertical axes, do Anot interfere with the steering ofthe truck by turning the front supporting `vvheelll.

A load supporting carriage 22 in the form of a forwardly projecting platform is mounted for vertical travel on the standard I and is provided at its forward end with a vertically disposed plate 23 that is positioned between the posts 2 and provided with forwardly projecting side flanges 24 which carry vertically spaced rollers 25 and 26 which engage with the front and rear faces of the webs 3 of the posts 2. The carriage 22 is raised and lowered by means of an hydraulic cylinder 2l mounted in vertical position upon the base member 5 midway between the side posts 2 of the standard I. The cylinder 27 has a vertically movable plunger 28 that carries a sprocket wheel 29 at its upper end. A sprocket chain 30 is attached at one end to the upper end of the carriage plate 23, extends over the sprocket 29 and is attached at its opposite end to the upper end of a guard plate 3I which is attached to the posts 2 and extends across the space between the posts 2 at the front side of the standard.

Immediately to the front of the standard I a platform 32 is attached-to the top of the frame member 'I and this platform extends the full width of the standard, vhaving its opposite ends overlying the brackets 20 and castor wheels 2|. The platform 32 provides Ya support for a liquid reservoir inthe form of a tank 33 mounted at one end thereof and a'battery 34 mounted alongside the liquid reservoir. Liquid from the tank 33 is delivered under pressure to the cylinder 21 to elevate the load carriage by means including a pump 35 that is mounted within the tank 33. The pump 35 has an inlet pipe 36 that extends downwardly to near the bottom of the tank 33 and is operated by a driving motor 31 mounted upon the top of the tank. A The pump 35 delivers liduid under pressure through an outlet pipe 38 within the tank 33 and the check valve 39 mounted in the top of the tank, to a pipe 40 that leads from the tank toV the cylinder 2,1. A return pipe 4I connects the pipev 4Dvto the'upper portion of the tank 33 and anormally closed valve 42 is provided in the return pipe 4I. When the valve 42 is closed liquid may be delivered under pressure'into the cylinder 2 1 by operating the pump 35,v and when the valve 42 is, opened the liquid may iiow from the cylinder l2l back into the tank 33. the Valve 42 preferably providing a passage of a size suitable to provide the desired rate of ow of liouid from the cylinder to the tank and thedesired lowering speed for the carriage. The valve 42 is controlled by suitable means such as a solenoid 43 which acts to open the valve when it is energized. Y

The battery 34 provides current for operating the propelling motor II, the pump motor 3l' and the solenoid 43. The battery is connected to .the motor II through a cable 44 and a normally closed'safety switch 45 which is controlled by an abutment 46 that is engaged by the tgngue I3 to open the switch 45 when the tongue is swung to vertical position. Suitable conductor cables 41 carry wires leading from the battery 34 to the swiveled frame I and the motor control wires extend at 49 from the frameIU to the draft tongue I3 so that the operation 4of the motor II and the raising and lowering mechanism for the load carriage may be controlled by the operator from the draft tongue.

At the outer end of the draft tongue there is mounted a controller 59 which is movable endwise and connected to sleeves I that are rotatable on tubular hand grip members rigidly attached to the outer end of the draft tongue I3 4 and projecting from opposite sides thereof. The controller 50 operates suitable switches, so that when shifted in one direction it causes the motor I I to be driven in a direction to propel the truck forwardly and when moved in the opposite direction it causes the truck to be propelled in a rearward direction. The controller 50 may be the same as that shown in my copending application Serial No. 547,930, filed August 3, 1944, now Patent No. 2,478,327, dated August 9, 1949. Sleeves 5I are retained on the tubular hand grip members 52 by means of collars 53 attached to the outer ends of the members 52.

In order to provide a control for the load lifting and lowering mechanism that is at all times conveniently positioned with respect to the operator, normally open push button switches 54 and 55 are mounted in the outer ends of the tubular hand grip members 52. The switch 54 serves to energize theV electric motor 31 to operate the pump to elevate the carriage and the switch 55 serves to energize the solenoid 43 to open the valve 42 and lower the carriage. As shown in Fig. 9, the switch 54 is connected by a wire 56 to one terminal of a solenoid 51, the other terminal of which is connected to the battery 34 by a wire 58. The solenoid 5l operates a switch 59 which when closed connects the wire 58 to a wire Ell leading to the motor'3'I to energize the same. While the switch 54 is held closed by the operator the solenoid 51 is energized and the switch 59` is held closed to operate the motor 3l. When the switch 54 is released and allowed to open, the motor 3l is stopped and the carriage 22 will be held in adjusted position by the liquid which is trapped in the cylinder 21 and the pipe 40 by the check valve 39. Y

One terminal of the switch 55 is connected by a wire 5I to one terminal of the solenoid 43, the other terminal of which is grounded and the other terminal of the switch is connected to the battery 34 by a wire 62. While the switch 55 is held closed by the operator, the solenoid 43 is energized to hold the Valve 42 in open position. Whenever the switch'55 is released and allowed to open, the valve 42 will again close and the `carriage 22 will be held in adjusted position by liquid trapped in the cylinder 21 and pipe 40 by the check valve 39. By providing a control for the load raising and lowering mechanism on the draft tongue, desired adjustments of the load may be effected while the truck is in motion or while the truck is being stopped by swinging the tongue I3 to vertical position and while the operator still holds the tongue.

By mounting the liquid supply tank 33 and battery 34 side by side immediately to the rear of the elevator standard, the frame member I may be made shorter and the center of gravity lowered. shortening the truck is advantageous in that it enables the truck to be more easily manipulated in restricted spaces in warehouses, factories and the like, and the lowering of the center of gravity is advantageous because it reduces the tendency of the truck to tip. Y

A difliculty that is commonly experienced with trucks provided with hydraulic lifts is the leakage of oil past the pump packing onto the iioor of the building in which the truck is used, which necessitates frequent replacement of the oil sealing rings of the pun-ip.v By placing the oil pump within the oil tank 33 slight leakage of oil past the pump packing does no harm, since the oil simply drips into the tank and frequent replacement Qf. oil seals is unnecessary.

It is to be understood that variations and modifications of the specific devices herein shown and described for purposes of illustration, may be made without departing from the spirit of the inn vention.

What I claim is:

l. A lift truck having a Wheel carrying frame adjacent its front end swiveled to turn about a vertical axis, a draft tongue pivoted to said sWiv eled frame, said draft tongue having hand grip portions at its outer end that project laterally from opposite sides thereof, a load supporting member mounted for vertical movement on said truck, means for raising said load carrying member, means for' lowering said load carrying member, means for controlling the operation of said raising means including a normally open push button switch in the outer end of one hand grip portion of said draft tongue, and means for con-- trolling the operation of said lowering means including a normally open push button switch in the outer end of the other hand grip portion of said draft tongue.

2. A lift truck having a wheel carrying frame adjacent its front end swiveled to turn about a vertical axis, a draft tongue pivcted to said swiveled frame, said tongue having hand grip portions projecting laterally from opposite sides thereof at its outer end, a motor for propelling said truck, a vertically movable load supporting member on the truck, means for raising said load supporting member, means for lowering said load supporting member, means for controlling the operation of said raising means including an electric push button switch in the outer end of one hand grip portion, means for controlling the operation of said lowering means including a push button switch in the outer end of the other hand grip portion, and a controller for said motor including a sleeve rotatable on a hand grip portion of said tongue.

3. A lift truck having a frame comprising a vertically disposed guide standard, members projecting forwardly and rearwardly from the base of said standard, the forwardly projecting member being centrally disposed and connected at its rear end to the stan/:lard by a horizontal pivot and the rearwardly extending members being rigidly connected to the standard, supporting wheels carried by the rearwardly extending members, a steering and driving unit mounted in the forwardly extending member and including a swiveled frame, a supporting wheel and a driving motor, a platform on said forwardly projecting member immediately in front of said standard adjacent its base and between said standard and said steering unit, said platform projecting past opposite sides of said forwardly projecting member, a load carrying member mounted for vertical movement on said standard, means including a motor for raising and lowering said load carrying member, a battery mounted on said platform, means connecting said battery to said motors, means for controlling said motors, and a leaf spring extending longitudinally of the truck frame and beneath said platform, said spring being interposed between the standard and said forwardly extending member and arranged to exert a downward thrust on the latter, brackets attached to the base of said standard and projecting forwardly on opposite sides of said forwardly projecting member beneath said platform to limit the downward movement of said forwardly projecting member about its horizontal pivot, and castor wheels carried by said brackets:

4. A lift truck having an elevator standard, a carriage mounted for Vertical movement on the standard, a hydraulic cylinder for operating said carriage, a reservoir for liquid comprising a storage chember, and means including a motor driven pump within said storage chamber for delivering liquid under pressure to said cylinder.

IRVIN F. SCHRECK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,359,493 Schreck Oct. 3, 1944 2,369,838 Minnis Feb. 20, 1945 2,395,345 Schreck Feb. 19, 1946 2,417,018 Schroeder Mar. 4, 1947

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