US2752058A

US2752058A - Material handling lift truck

Info

Publication number: US2752058A
Application number: US369559A
Authority: US
Inventors: Christian D Gibson
Original assignee: Raymond Corp
Current assignee: Raymond Corp
Priority date: 1953-07-22
Filing date: 1953-07-22
Publication date: 1956-06-26
Anticipated expiration: 1973-06-26

Description

J1me 1956 c. D. GIBSON MATERIAL HANDLING LIFT TRUCK 5 Sheets-Sheet 1 Filed July 22, 1953 654 0 2M 1/, p i w 4 In m 7 2 m 6 M Z 0 9 0 M2 0 5 4 0 0% n M G H II 6 F a 4 FIG. I2. g

FIG. ll.

INVENTOR Cflk/SNAN 0.

ATT NEY 5 Sheets-Sheet 2 June 26, 1956 c. D. GIBSON MATERIAL HANDLING LIFT TRUCK Filed July 22, 1953 June 26, 1956 c. 'D. GIBSON 2,752,053

MATERIAL HANDLING LIFT TRUCK Filed July 22, 1955 5 Sheets-Sheet 5 FIG. 3.

RNEY

June 26, 1956 c. D. GIBSON MATERIAL HANDLING LIFT TRUCK 5 Sheets-Sheet 4 Filed July 22, 1955 INVENTOR (MP/SWAN 0 6/B50/V RNEY June 26, 1956 c. D. GIBSON MATERIAL. HANDLING LIFT TRUCK 5 Sheets-Sheet 5 Filed July 22 INVENTOR (MP/SWAN 0.

United States Patent MATERIAL HANDLING LIFT TRUCK Christian D. Gibson, Greene, N. Y., assignor to The Raymond Corporation, Greene, N. Y., a corporation of New York Application July 22, 1953, Serial No. 369,559

12 Claims. (Cl. 214-730) This invention relates to material handling trucks of the class in which a mast, mounted upon a wheel-supported base, has a load carrier arranged to travel vertically thereon between load pick-up and load discharge positions. Of this class of trucks there are two specific types in commercial use, namely, the counterbalanced type and the type in which a substantial part of the wheel-supported base is located in front of the mast and, in the operation of the truck to pick up or deposit a load, either enters beneath a skid or pallet which is to be picked up by the load carrier or straddles the skid or pallet. Each type has certain advantages for certain uses.

In the counterbalanced type of truck the mast is located substantially at the front of the wheel-supported base so that the center of gravity of the load on the fork or other load carrier which projects in front of the mast is at all times in front of the front wheels. This location of the mast and load carrier obviously requires considerable counterbalancing weight behind the front wheels, especially when the loaded truck is in motion. However, since these front wheels do not have to go under or straddle anything in the pick-up and discharge operation they may be quite large in diameter, thus facilitating the travel of the loaded truck over storage room and other floors.

In the straddle-base truck, a forked base extends in front of the mast and has supporting wheels near the front ends of the fork members, the forked base being of such dimensions that it will straddle the skid or pallet which is to be picked up by the load carrier, the skid or pallet being usually of such length that when the load is picked up its verticaally projected center of gravity will be within, or not substantially outside, the wheel base. Since with this type of truck it is necessary for the base to straddle the skid or pallet to be picked up in order to bring the pick-up fork or other means into pick up relation to the skid or pallet it is usually desirable, especially with Wing-type pallets or skids or in cases where the loads overhang the sides of the pallets or skids, that the front wheels of the straddle base be of a diameter somewhat less than the height of the pallet or skid above the floor. This afiects the ease of travel of the loaded truck, especially on rough or uneven floors.

The straddle base design has more lateral stability than other material handling trucks and is therefore particularly useful for tiering and other high-lift trucks. However, in low-lift trucks a narrow base extension in front of the mast may be used which enters between the skid or pallet supports instead of straddling them. The present invention may advantageously be incorporated in either or both of the last mentioned two truck constructions.

A general object of the present invention is to combine in one truck the advantages of the two types of mast trucks above described by so arranging the skid or pallet pick-up fork or other load carrier that, in a truck in which a substantial part of the wheel-supported base is located in front of the mast and has its front supporting wheels substantially at its front end, the load pick-up and carrying fork 2,752,058 Patented June 26, 1956 ice or other pick-up means may, without disturbing the position of the mast, be projected in front of said front wheels to enter into pick-up relation to the load-carrying skid or pallet, lift it and then retract it until the vertically projected center of gravity of the loaded skid or pallet lies within, or not substantially outside, the wheel base of the truck, thus making unnecessary any substantial dynamic counterbalancing of the kind required in the ordinary counterbalanced truck.

More particularly the invention aims to provide a truck of the type which has a mast mounted on a Wheel-supported base at a substantial distance behind the front supporting wheels of said base and which is provided with a load carrier movable up and down said mast and normally positioned to carry its load with its vertically projected center of gravity within or not substantially outside the wheel base, which truck has, as an improvement interposed between the load carrier and the mast, means by which the load carrier, at any point of elevation on said mast, may be projected to pick up or deposit a load located in front of the wheel supported mast-carrying base and again retracted to its normal position, all without disturbing the position of the mast.

The invention further aims to provide a material handling truck operable in the manner just described which is of such compact construction and so maneuverable that it can be used in very narrow aisles and other narrow spaces to perform its functions, thus making possible a more economical use of storage space resulting from the above described increased reach without reduction of maneuverability. In this connection it will be noted that the invention, when the straddle base is c0nstructed and designed to straddle the load to be lifted, as in the ordinary straddle base truck, makes possible the tiering of goods on skids or pallets in tiers which are two skids or pallets deep, measured from the aisles, thus at least halving the number of aisles which would be required for tiers which are one skid or pallet deep.

An important feature of the invention is the novel means for projecting and retracting the fork or other means for picking up or depositing the pallet or skid and particularly the novel construction and arrangement of the parts of the projecting and retracting means to permit their subs'tantially complete collapse into the mast or, more accurately stated, into the carriage on the mast through Which the lifting and lowering movements of the load carrier are effected.

Another important feature of the invention is to be found in the simple and compact hydraulically operated mechanism through which the projecting and retracting movements are brought about.

' Other objects, important features and advantages of the invention, to which attention has not specifically been directed hereinabove, will be obvious when the following specification and claims are considered in connection with the accompanying drawings, in which Figure 1 is a perspective view of the material handling truck embodying the present invention, this view showing the load support in its projected position;

Figure 2 is a side elevation on a somewhat larger scale of the truck shown in Figure 1 but with the load support shown in full lines in its retracted position and in dotted lines in its projected position, parts of the structure being broken away to permit inclusion within the confines of the drawing sheet;

Figure 3 is a rear elevation of the load lifting part of the truck with the automotive part of the truck removed and with parts broken away to show other parts which otherwise would be concealed thereby;

Figure 4 is a perspective detail showing the carriage upon which the projectable and retractable load support r a a V 3 is mounted, and the projecting and retracting means including the hydraulic jack used for furnishing projecting and retracting power, parts being broken away to show P r h r i e a ed ere y; a V

Figure 5 is an exploded view of the inner scissors link co s i g a p r of t e i a e fo P TQiQC lDg; and re.- tracting the load support, this view illustrating the manner in which this link may be. disassembled preparatory to its insertion within or removal from the outer scissors link during the assembly or disassembly, of the scissors. l ag s, Y

Figure 6 is a detailed view showing the larger front e l used on the b s o ks hen, hese-base forks a not required to straddle the load to be lifted or when other conditions permit the use of the larger wheels;

Figures 7. and Saredi'agrammatic views illustrating the means for tilting the load support into load cradling position, Figure 7 showing the parts in the retracted position ith t e o d if m a s n r dl ng p t n, and. Fi ure 8 showing the load lifting means in its projected .position with its upper load-engaging surface horizontal;

Figures 9 and 10 are diagrammatic views illustrating an alternative method of obtaining the sameresult as is, obtained by the structure: shown in Figures 7 and 8, Figure 9 showing; the load-lifting means in cradling position. and Figure 10 showing it in projectedposition; 7

. Figures 11 and 12 are diagrammatic views similar to Figures 7 and. 8, the purpose of these two views being to: show the greater tilt required to Qbtain the same cradling action when what is known in the industry as; a chisel skid or pallet.

, The intention is herein shown as embodied, in a tiering truck of the straddle-base type which is power-driyen and ters Patent above identified, has a combined dril i g andv steering wheel 2, offset to one side of the axis. of symrnetry of the truck, and a stabilizing caster on the, other side of the axis of symmetry and preferably under an operators platform located at one side of the motor containing turret. This arrangement reduces much the over-.

all length of a stable, operator-riding,power-driven, sharply steerable truck andmakespossibleits manipulation in much narrower aisles than those in which trucks of con-. ventional design can operate. The supporting frame of r the automotive part of the truck ispreferably rigidly connected, as by bolts or machine screws 8, tothe. frame plate 6 of the load-lifting part of the truck. Although they rigid connection between the automotive and load-lifting parts of the truck structure, such as herein shown, has many practical advantages it will. be understood that the inventionis not limited to use in trucks having such rigid fork is used, that is, one intended to go under material to be picked up that has not already been placedon, a.

1 shown in Figure 6 connection between the automotive and load-lifting parts.

thereof.

The mast of the truck herein shown isof the telescoping type and comprises a stationary mast part made up of upright side channels 10 connectednear their topsby an angle cross-piece 12 welded tothe rear sides of the channels 16; At their bases the uprights 1,4} are connected both. to a plate 1'4, which is welded to theframe plate 6, and to a bottom cross plate 16' which extends across the entire frame of the elevating part of the truck and'is connected,

'asby welding, to'the forkmembers 18 of the truck base. 'These fork members 18 in the ordinary truck of the straddle base type are permanently spaced; far enough apart, when not adjustably mountedas shown in my copendingapplication Ser. No. 195526; filedNovember 14',

handled by: the truck. T he beveledrear endof each base Patent Noi 2 ,678,746; so that they'will fork member 18 is also welded to a beveled end of the plate 14, as shown in Figure 3. A brace plate 20, welded at its rear end to the plate 14 and at its lower edge to the fork member 18, serves to increase the resistance of each fork member 18 to deflection from its normal perpendicular relation to the

plates

14 and 6. The plate 20 at its upper edge is also welded to a plate 21 that enters the channel. 10. and is welded thereto,

At their forward ends the base fork members 18 have welded to their sides outerand inner plates 22. and 24. connected by. an end plate: 26. Bearings for tandem base-supporting

wheels

28 and 30 are provided in the plates 22, and: 24. As shown in- Figuresl and 2, the

wheels

28 and 30 are of small diameter, say 4", so that the truck shown in these-figures may: be used not only to straddle, pick up and deposit skids or pallets to form or remove goods from tiers one skid or pallet deep but it may also. be used in aisles as narrow as those now provided between tiers one. skid. or pallet deep totier loaded skids or, pallets and to remove the loaded. skids or pallets, from tiersor racks on which they are to lie or do lie two, deep, measured from the aisle. It will be seen that with the lifting fork 32, shown in these figures and with base forks dimensioned to straddle the pallet supports and to go under any load or pallet, overhangs of slightly over 4 clearance the forked base may enter between the pallets or skids of the first tier to-per-mit the projected fork to deposita loaded skid onpallet on or remove it from a tier behind the first tier.

When it is not intended for use in places where the straddle base needsto enter beneath. a possible load over: hang or awing on a skid or pallet, front wheels of considerably greater diameter, say 10", may besubstituted for the wheels 28 and. 3t}, asingle. large wheel 34 for each pair of tandem wheels, thus facilitating the travel. of the truck between'load pick-up, and load depositing positions. Such front wheels 34 of greater diameter are It. will be understood, however, that if the transverse dimensions of a load to be handled is greater, than the width between the fork members 18. of. the forked truck base it will. be necessary to lift. the load far enough to clear the large front wheels 34 before retracting; the load-carrying fork 32. Such situations will not often arise, however, when the skids or pallets, have. been constructed and; loaded for. use with a truck having a given straddle span. 7

It will be noted that the present invention. has the advantage over the type of truck in which the mast, to,-. getheri with the loadt carrier, is retracted after the load, is lifted inv that the mast, hydraulic cylinders etc. make up av good. part of the truck weight and. therefore when, they are in their projected position this, weight provides no. part of the counter balance. Since in the truck of the present invention the mast, hydraulic cylinders etc. are alwayslocated behind the base forks and at a distance from the front wheels of the truck, these parts provide, a.

upright sidernembers 36, cross-connected near their tops by a rearwardlyotfset cross piece 38; to which is attach.- ed, the closed end of the cylinder 40 of a hydraulic ram. The side members 36 are cross-connected near their lower ends. by a cross-plate 42 to which are attached the; closed ends of cylinders. 44, and 46 of two hydraulic rams located on opposite sides of the cylinder and in symmetrical. relation thereto and to the axis of symmetry of the telescopable part of the mast. Guide grooves 48 in thegoutcr faces. of theside members 36cooperate with guide rollers 50 and thrustrollers 521111 the innerfaces of the channels 10 to insure'straightline extension and telescoping movements of the telescopable partof the mast m1 respect to thestationary part thereof.

i The load carrier of the present invention difiers from conventional constructions in that the pallet or skid engaging fork 32, instead of being mounted directly upon a carriage slidable up and down the telescopable part of the truck mast, is mounted upon a frame which in turn is so connected by a lazy tongs or scissors type of linkage to a carriage on the telescopable part of the mast that the fork 32, with any load thereon, may be projected away from or retracted toward the mast in any elevated or lowered position of the carriage on the mask.

The carriage which travels up and down the telescopable part of the truck mast and on which the mechanism is mounted which effects the projection and retraction of the fork 32 comprises edgewise rearwardly extending plates or bars 54 located between the side members 36 of the telescopable part of the mast, the plates or bars 54 having thereon spaced guide rollers 56 and thrust rollers 58 which travel in guide grooves 60 in the adjacent faces of the telescopable mast side members 36. A cross-bar 62 extending between and connected to the plates or bars 54 has holes therein for connection to chains 64 and 66 which pass over

pulleys

68 and 70 on the upper ends of plungers 72 and 74 operating respectively in the hydraulic cylinders 44 and 46. The other ends of the chains 64 and 66 are connected to a crossbar 76 welded to the side members 36.

The frame in which the fork projecting and retracting linkage is mounted is attached to the front of the mast engaging part of the carriage just described and is shown as considerably wider than the mast engaging part. As shown, this frame comprises outwardly open side channel bars 78 and 80 connected at their bottoms by a fiat cross-bar 32 and connected at their tops by angle bars, assembled to form a cross-piece 84 of substantially hollow rectangular section. Upon the lower parts of the inner faces of the side bars 78 and 80 are welded bars having narrow vertical slots milled therein to form vertical guide grooves 86 for guide rollers 90 on one of the links of the lazy tongs or scissors type linkage, now to be described.

The scissors link just referred to, which will sometimes hereinafter be designated as the outer scissors link, comprises rigidly and permanently cross-connected scissors arms 92. The upper cross-connection consists of a tubular member 94 welded at its ends to the arms 92 and having, inside its ends and extending through the arms, bearing bushings 95 which may be of the permanently lubricated type.

The lower cross-connection shown comprises an angle bar 96 overlapping the lower ends of the arms 92 and welded thereto. Attached to the arms 92 near their lower ends and projecting from their outer faces are stud shafts 100 for the guide rollers 90. Hub-like rings 102, surrounding openings 104 approximately at the middle of the scissors arms 92 provide thrust edges for washers 106 bearing against the ends of stud shafts 108 on the inner scissors link, which, with the reduced threaded extensions 110 of the stud shafts 108 and the nuts 112, make up the pivotal interconnection between the outer and inner scissors links.

The inner scissors link comprises scissors arms 114 rigidly but not permanently cross-connected. As shown, the lower rigid cross-connection comprises a plate 116 secured by cap screws 118 to the rear edges of the arms 114. The upper ends of the arms 114 are approximately T- shaped, the forwardly projecting part of the T end of each arm carrying the bearing for the arm somewhat in front of the arm for a purpose hereinafter set forth and the rearwardly projecting part of the T end constituting a bell-crank arm to which hydraulic means are connected for effecting the fork projecting and retracting movements of the linkage. Permanently attached to the outer face of each arm 114 near its upper end, so that its bearing opening 120 registers with a bearing opening 122 of like diameter in the arm 114, is a hub-like part 124 having fixed thereon a rearwardly extending arm 126. The arm 126 is parallel to but spaced from the rearwardly extending part of the T end of the arm 114 and has an opening 128 registering with a like opening 130 in the T end of arm 114 to receive a bearing pin 132 for pivotal connection to the piston rod 134 of a hydraulic ram having its cylinder 136 mounted upon the vertically movable linkage-carrying frame, as more fully hereinafter set forth. A set screw 137 in the rearwardly extending part of the T end of arm 114 holds the bearing pin 132 in the bell-crank.

Extending between the arms 114, near the forward ends of their T s, is a tubular cross-bar 138 having its tubular opening concentric with the bearing openings 120 and 122 but of somewhat larger diameter. An arm 140 at each end of the tube 138 and fixed thereto flush with the tube end is provided with openings registering with threaded openings in the T end of the adjacent T arm 114 to receive cap screws 142 by which a rigid crossconnection between the arms 114 by means of the tube 138 and arms 140 may be obtained. It will be seen that this construction of the inner scissors link, which permits ready disassembling of the link itself, facilitates the assembling and disassembling of the linkage as a whole.

At its upper end the inner scissors link is supported to swing on a shaft 143 that extends through the bearing openings 120 and 122, through the tube 138, through openings 144 in the webs of the channel bars 78 and 30 and through registering openings in reinforcing plates 146 in the bar channels. The ends of the shaft 143 are threaded and are secured in position by nuts 148. The lower end of the inner scissors link is provided with inwardly projecting stud shafts 159 for rollers 152 which are guided in outwardly opening vertical grooves 154 in the side frame members 156 of the load fork supporting frame.

As shown in the drawings the fork supporting frame comprises the vertical side bars 156, having the guide grooves 154 machined in their outer faces. These side bars 156 are connected at their bottoms by an angle plate having a rearwardly extending horizontal part and having its upright wider part 158 provided with holes 160 for fork tine spacing adjustment as set forth hereinafter. At their tops the side bars 156 are connected by a top plate 162 which projects a short distance beyond the outer face of each side bar. At each end of the plate 162 a shaft supporting bracket 16 having near its upper end a shaft receiving opening 166 into which is tapped an opening 168 for a set screw 170, is welded to the associated end of the plate 162 and is bent into contact with the side bar 156 and also welded thereto. The brackets 164 are adapted to embrace the upper end of the outer scissors link and to support a shaft 172 extending through the bearings 96 and tubular cross-connection 94 of this outer scissors link.

It will further be seen that the fork supporting frame has a central vertical reinforcing bar 174 and that this, as well as each of the side bars 156, is provided with an opening 176 to receive a fork supporting shaft 178.

From the foregoing description it will be seen that, of the interconnected scissors links, the inner one has a fixedly located pivotal connection at its upper end with the vertically slidable linkage supporting frame and a sliding connection at its lower end with the fork supporting frame and that the outer scissors link has a fixedly located pivotal connection at its upper end with the fork supporting frame and a sliding connection at its lower end with the vertically slidable linkage supporting frame or carriage. It will further be noted that the forwardly offset cross-bar 94 of the outer scissors link is located at a distance from the pivotal interconnection of the links suificiently less than the distance from said interconnection of the forwardly offset cross-bar 138 of the inner link so that the side arms of the scissors links may be brought into substantially complete overlapping or porting frame part of the carriage when in collapsed or retracted condition.

Each of the fork members of the pallet or skid en.- gagingfork is of substantially the, same construction; as,

the fork membersv shown and claimed in my: copending application abovev identified; From. an inspection. of? Figure. 1-, it will be seen that horizontallyproiectingfork prongs 32 have upright. portions. 33: which are pi otally hung on the fork supporting shaft 17.8; which so located in the fork Supporting frame. that the rear faces of the; uprights 33; are forced by gravity against; the plate. 158a. Pins 18% projecting from. the rear facesof the. uprights. 33 enter selected holes. 161 in the plate 553'. and. hold the prongs. 32' in the desired spaced; relation to each other, thus. providing a quick, easy adjustment of: the. prong spread.

. The projection and retraction of the fork carrying frame by. means of the lazy tongs or scissors. type linkage. hereinabove described is effected, as; above suggested, by; hydraulic jacksv or rams mounted on-the load elevating; and lowering carriage and traveling therewith- As above; pointed out each jack or ram comprises. a piston rod'134 pivotally connected at its outer end to the bearing pin; 132- in the forked bell-crank rearwardv extension. of the T end of the scissors arm 114'- of the inner scissors. link, and a cylinder 136. having a downwardly extending car 182 through which extends a pivot pin 18.4: held: by. a. set screw or other suitable means. in a bracket 186. con.- nected to the rear face of one of the side channel bars: 78 and 81), there being a jack or ram connected to. thebell-crank extension of each scissors arm 1E4 of the inner scissors link. It will be seen that projection of the piston rods 134 from the cylinders 136 will cause retraction. of the fork carrying frame by. the scissors linkage and that withdrawal of the piston rods. 134: into the cylinders 136 will cause projection. of the. fork can.

rying' frame.

To permit travel of the packs with the carriage flexible;

tubes. 158 and 1%; connect each of the jacks with the pressure into the hollow piston. rod. 196- of the piston whichv operates in the hydraulic cylinder 40. such in-. troduction of hydraulic fluid. under pressure intoipi'ston rod 1% serves first to effect the lifting. off the. linkage supporting carriage on the telescopable part of the truck: mast. and. then. the lifting of the telescopable-part of the mast together with said carriage on: the stationary part: of the mast. The hydraulic connections between the cylinders 44 and 46 and the cylinder 40 through which: such operations. are caused toproceedin. a pred'etermined 'sequence'may be the same as thosedisclosed in my co t truckdisclosed in U; s. Letters: p aten No; 7'5

2 ,564,002; granted August 14, 1951:, has made possible a. marked; reduction. in aisle widthsin storage warehouses and other placeswhere operation'in narrow spaces is necessary or: desirable and; the present invention has been soincorpora-ted in. a truck having the space making features of the. truck" of said Letters Patent that it can operate in. substantially'equally narrow spaces. Thishas been made. possiblein: the-truck of. the present invention by the noveldesignv and; arrangement. of. the elements making up the linkage supporting carriage slidable on the mast, the fork carryingframe and thelirikage itself, whereby these. elements, wherrthe; fork is retracted. are. so nested that they add; substantially nothing, possibly two inches or so, to. the. overall length. of the truck and thus do. not materiallyreduce; its maneuverability in narrow spaces. This is. an

time the load; is to be pickedup, and that the underside of the fork is taperedzsomewhat upwardly toward the end. a When the truck,however.,,is.to be.used to pick up package O ales which have. not been loaded upon skids or pallets, atloadsengaging fork 32a such asshown in Figures.

. L1; and 12 is.used, sometimes. called in. the trade a chiseL forkf since its upper face tapers down to a sharp end while, its lower; face. in. the. pick-up. position is horizontal: so,- that; the fork, can be slid along thefioor and; broughtunder a. bale orpackage resting on the floor.

There is anadyantagein usingeither typeof fork, espe-. ially. one. carrying a lead: over rough. floors, to. have the LQrkin a,loa.d;-cr.adling position. Since theupper face of he chisel; fork slopes downwardly from. its. rear. end, it willbe apparent that a greater cradling tilt; will. be necessary to produce the same cradling-action as with the fork different: positions. of adjustment in. respect to each other must belong enough2 sothat-the cradling action will not: push these pins outofi their retainingholes.

Ashereinabove; suggested, since. the chisel fork 32a.

has an, upper surfacethatslopes: downwardly toward the. floor the tilting action necessary to bring. this into a: suit-. ahle-loadg-cradling position reqniresa. stop member or stop members :93 projectingsoniewhat further. from. theframe that moyesupandidown the. mast and the pinson the fork members 3.2a entering the holes. lfitlgwould: also hayetobe somewhat longer.

In Eigures 9; and; 1,0; is. shown. a modification. of the means. forobtaining; thecradling tilt of. the; loadrsup'p'ortns for s;. h bi 'g' f.QughI about; by so 'proportioning. the arms of;the;sciss qrs 1inkage thatwhen extended they will hold; thefcrhmembers 3 2; in their; normal horizontal load pick-up,- position; but when retracted the; differenceing arm; lengths of the scissors links. in respect to theircorrunon piyotwillbring; ahoutythe tiltinga action. as shown nEiallr 9.

Erom the foregoing; deseription. it willbe seen thatthe novel; tru k; of the present invention. has: wideutility in:

ma e al; handling. field. Not. only hasthe truck all of theaadyantagesof. the counterbalanced truck so far as handlirigtlqadslocatedi front of it is concerned but it also has the advantage of the straddle base typeof truck so far as lateral stability is concerned when transporting loads. This truck has a further advantage over the ordinary counterbalanced truck by reason of its carrying the load with its vertically projected center of gravity either Within or not substantially outside the wheel base, and by reason of its counterbalancing the load, when it is being picked up or deposited, about the front wheels as a fulcrum by means of a mast, battery, etc. located at such a distance from the front wheels as to give a favorable counterbalance moment. By reason of the foregoing important design advantages the truck can be made much shorter and lighter than the ordinary counterbalanced truck. This facilitates manipulation of the truck in narrow aisles, elevators etc. and permits its use in buildings where the heavy counterbalanced trucks have proved impracticable.

An example of a practical truck embodying the present invention is the following: Assuming that the base fork members 18 are provided with the large front wheels 34 shown in Figure 6 and that the distance from the vertical arm of either of the load-lifting fork members 32 to a line through the extreme front edges of the wheels 34 is 24 inches and that the scissors linkage provides a projecting movement of the fork members 32 of 24 inches, then the front face of the vertical arm of each fork 32 will be flush with the extreme front edge of the wheel 34, when the forks 32 are in their projected position. This will permit picking up of any load located in front of the wheels 34 and against which these wheels may have been moved.

' Let us assume that the load is 48 inches long, that is, in the direction of the length of the truck, and that the fork members 32 normally project in front of the extreme front edges of the wheels 34 a short distance, say from 6 to 12 to 16 inches, a projection in either case which will not interfere with the ordinary manipulation of the truck in a narrow aisle, especially if the load is located on a pallet or skid. It will be seen that a 40 inch fork 32 extends fivesixths of the length of the load.

If the load be wider than the space between the fork members 18 it will need to be lifted over the wheels 34 before being retracted. When, however, it has been retracted it will be seen that, of the 48 inch load length, 24 inches will practically be over the wheel base of the truck, a vertical plane through the middle of the 48 inch load touching the front edges of the wheels 34.

Assuming that the center of gravity of the 48 inch load to be picked up is near the middle thereof then the vertically projected center of gravity of the load will, in the construction cited as an example of a practical truck design embodying the present invention, be in a plane that includes the front edges of the two wheels 34. If the load be less than 48 inches long the center of gravity would usually be within the wheel base, that is, behind V the front edges of the wheels 34.

What I claim as new is:

1. In a material handling truck, the combination with a mast, a carriage slidable up and down said mast and means for effecting the sliding movements of said carriage, of a rectilinearly projectable and retractable load support so mounted on said carriage as to support its load in front of said carriage and unconfined in any way thereby in all positions of projection or retraction, a wheelsupported base upon which said mast is fixedly mounted, said base having a low stabilizing extension in front of said mast, with supporting wheels near its front end, which base extension is forked to embrace the load support in its lowered retracted position and has free clearance thereabove for any retractable load, and projecting and retracting linkage between said carriage and said load support, operable, in any position of said carriage on said mast, to carry said load support substantially rectilinearly between a retracted position in which it may support a load with the vertically projected center of gravity of the load within or not substantially outside the truck wheel base and a projected position in which it may pick up or deposit a load which is, or is to be, located in front of said wheel base, the carriage including an upright rectangular frame and the projectable and retractable load support including a second frame adapted to nest within 1 the carriage frame and on which the load engaging means are mounted, the projecting and retracting linkage connecting said frames in such overlapping relation thereto as also to nest within said carriage frame when in retracted condition.

2. A material handling truck according to claim 1 in which the projecting and retracting linkage comprises pivotally interconnected scissors links between said frames, each link having a fixedly located pivotal connection to one of said frames and a slidable pivotal connection to the other, and a hydraulic ram mounted on the carriage frame and connected to the scissors linkage serves to effeet the opening and closing movements thereof and, consequently, substantially rectilinear movement of the load engaging and supporting elements away from and toward said mast.

3. A material handling truck according to claim 2 in which the scissors linkage is of such dimensions in respect to the mast to base-front length that, when opened to the limit, the load engaging and supporting elements of the load support are projected in front of the front end of the truck base and that, when collapsed, the said elements support the load with its vertically projected center of gravity within or not substantially outside the wheel base.

4. A material handling truck according to claim 2 in which the fixedly located pivotal connection of one scissors link to the carriage frame and the fixedly located pivotal connection of the other scissors link to the other frame are both at the upper ends of the respective links.

5. A material handling truck according to claim 2, in which the sliding pivotal connections of the respective links are at the lower ends of said links.

6. A material handling truck according to claim 2 in which the linkage comprises two pairs of rigidly crossconnected scissors arms so pivotally interconnected that one pair swings between the other pair into and out of substantially nested relation thereto, the outer pair having at one end outwardly extending sliding pivotal connections with inwardly opening guides in the sides of the carriage frame and having at its other end fixedly located pivotal connections with the frame carrying the load engaging and supporting elements, the inner pair having at one end inwardly extending sliding pivotal connections with outwardly opening guides in said last-mentioned frame and having at its other end fixedly located pivotal connections with the first-mentioned frame, the outer and inner scissors arms being so proportioned and so offset at their fixedly located pivotal connections that the secondmentioned frame, as well as the scissors links, may nest substantially within the carriage frame when the scissors linkage is in its collapsed condition.

7. A material handling truck according to claim 6 in which the inner scissors arms are provided with bellcrank ofisets, and hydraulic rams, mounted on the carriage frame, act on said bell-cranks to rock said arms about their fixedly located pivots to effect the opening and closing operations of the scissors linkage.

8. In a material handling truck, the combination with a mast, a carriage slidable up and down said mast and means for effecting the sliding movements of said carriage, of a projectable and retractable load support on said carriage, a wheel-supported base upon which said mast is mounted, said base having a low stabilizing extension in front of said mast with supporting wheels near its front end, which base extension is shaped to be brought into such relation to a load to be picked up that the load support wil be brought into pick-up relation thereto in its lowered retracted position, and projecting and retracting means operable in any position of said carriage on said mast, to move said load support between a retracted position in which it may pick up, carry or deposit a load with the vertically projected center of gravity of the load and a projected position in which it may pick up or deposit a load which is, or is torbe, located in front of said wheelbase.

9. A material handling truck having, in combination, a mast, a wheel-supported base on which said'rnast is fixedly. mounted at a substantialdistance behind the front wheels of said base, a carriage slidable up and down said mast, aload support on saidcarriage so connected thereto as to-support its load at all times in front of said carriageand unconfined in any way thereby and to be projectable from a position immediately adjacent to said mast to a position in which it may pick up or deposit a load located or to-be located in front of said front wheels, means for effecting the sliding-rnovements of 'said carriage on said mast and means for effecting the projecting and retracting: movements of said load support comprising load support carrying linkage constructed to provide substantially rectilinear projection and retraction of said load support, the loadsupport being L-shaped and being carried on a projectible frame on which it is suspended so that the angle of the L, normally abutting said frame, is free to swing away therefrom andstop means on saidcarriage' limiting the retracting movement of said load support and: effecting a swinging of said load support into load cradling position.

10. A material handling truck having, in combination, a mast, a wheel-supported base on which said mast is fixedly mounted at a substantial distance behind the front wheels of said base, a carriage slidable up and down said mast, a load support on saidcarriage so connected thereto as to support its lead at-all times in front of said carriage and unconfined in any-waythereby and to be projectable from a position immediately adjacent to said mast to a position in which it may pick up or deposit a load located or to be located in front of said front wheels,

means for effecting the sliding movements of said car-' 'riage on said mast and; means for effecting the projecting and retracting movements of said load support comprising load support carrying linkage constructed to provide projection and retraction comprise scissors arms of vary:

ing lengths from their common pivot to their end pivots. 1.1. A material handling truckhaving, incombination, a. mast, a wheel-supported base upon which said mast is fixedly mounted, a carriage slidable up and down said mast, said wheel-supported basehaving a low stabilizing extension: in front ofsai'd mast, withthe front'base-supporting wheels near the front end and free clearance thereabove, a load support on said carriage so connected thereto. as to. support its load at all times in front of" said carriage and unconfined in anyway thereby and to be projectablefrom a position immediately in front of said carriage and. saidmast to-a position in which it may pick up or deposit a load located or-tobe located in front of 43 V 7 n5 r said front wheels, means for effecting themovements of said. carriage up and down said'mast and meansifor effect; ing the projecting and retracting movements of said load support, comprising loadsupport carrying linkage ar-- ranged to: provide substantially rectilinear projecting and retracting movements of said load support, the linkage comprising two pairs of rigidly cross-connected scissors arms so pivotally interconnected that one pair swings. between the other pair into and out of substantially nested relation thereto, one'pair having fixedly located. pivotal connections at its carriage-supported end and having transversely extending portions vertically slidable. in: respect to the load support at its other end and the other pain having fixedly located pivotal connections to the load" support at one end and. transversely extending portions vertically slidable in respect to said carriage" at its other end, the scissors arms of the pair having the fixedly located pivotal connections to. the carriage being pro vided. with bell-crank offsets, and: hydraulic rams, mount ed, on, the. carriage, acting on said bell-cranks to rock said scissors armsv about their fixedly located pivots to eflect' load support projecting andi retracting operations of the scissors linkage. V a

12. A material handling. truck having, in. combination,. a; mast, a: wheel-supported base upon; which said mast isv fixedly mounted, a carriage slidable up and down said.

mast, said wheel supported basehaving a. low stabilizing.

extension in front'of. said mast, with the front base-sup.-

porting wheels. near the, front end and: free. clearance:

thereabove, a load, support on said; carriage: so connected thereto asto support; its. lead, at all times in. front of said carriage and unconfined in any way thereby and to be projectable from. a. position immediately: in front of said: carriage and said-mast; to a: position: ingwhich it may pick up or deposit a load located on toibe. located front of said front wheels, means for effecting the; movements of said1carriageupv and'down said mast andmeans for effect: ing the projecting and retracting; movements of said lead support, comprising leadsupport'. carrying. linkage arranged. to provide substantially rectilinear. projecting: andt retracting movements of said load suppornthe base extension-in front of the mast beingforked to embrace the load.

support inits lowermost-position and to permit load pick.

up and depositing; operations'of the load support between. said fork members;

ReferencesCited in the file ofthispatent;

ED STATES PATENTS- Ulinski May 24', 1955.