US2571550A

US2571550A - Material handling device for industrial trucks

Info

Publication number: US2571550A
Application number: US32429A
Authority: US
Inventors: Leslie G Ehmann
Original assignee: Hyster Co
Current assignee: Hyster Co
Priority date: 1948-06-11
Filing date: 1948-06-11
Publication date: 1951-10-16
Anticipated expiration: 1968-10-16

Description

Oct. 16, 1951 G. EHMANN MATERIAL HANDLING DEVICE FOR INDUSTRIAL TRUCKS 4 Sheets-Sheet 1 Filed June 11, 1948 INVENTOR LESL/E EHMAN/V M ATTORNEYS Oct. 16, 1951 1.. ca. EHMANN MATERIAL HANDLING DEVICE FOR INDUSTRIAL TRUCKS 4 Sheets-Sheet 2 Filed June 11 1948 IN VEN TOR. LESL/E 6'. [HMANN A T TORNE Y5 Oct; 16, 1951 EHMANN 2,571,550

MATERIAL HANDLING DEVICE FOR INDUSTRIAL TRUCKS Filed June 11, 1948 4 sheet -s eets INVENTOR. vLESLIE 6. EHMANN ATTORNEYS Oct. 16,1951 L. G. EHMANN MATERIAL HANDLING DEVICE FOR INDUSTRIAL TRUCKS Fi-led June '11, 1948 4' Sheets-Sheet 4 INVENTOR LESLIE G EH/VA/V/V A TTOR/VEYS Patented Oct. 16 1951 MATERIAL HANDLING DEVICE FOR 1 INDUSTRIAL TRUCKS Leslie G. Ehmann, Portland, reg., assignor to Hysteiacompany, Portland, 0reg., a corporation of Oregon Application June 11, 1948, Serial No. 32,429

7 7 Claims.

This invention relates to material handling devices of the type having power operated means for picking up and carrying a load. 7

.This type of material and load handling mechanism is utilized to especial advantage on a class of vehicles known as industrial lift trucks, although it is not necessarily limited to the'conventional forms ofsuch trucks. Conventional lift trucks are extensively used for handling and moving different kinds of materials and objects in industrial plants and warehouses and the like. Such lift trucks are usually provided with a pair of forwardly extending forks or arms for lifting a load and carrying it in front of the vehicle. To avoid manual handling as much as possible, the materials or packages ordinarily must be piled on low platforms called pallets having space for the arms of the lift truck to. extend? therebeneath to lift the .load. Conventional lift trucks cannot pick up a load which is resting fiat on the floor, nor can they pick up thetop part of a stack of articles such as boxes,'cartons of barrels without the use of pallets or their equivalents in the stacks j to allow space for entrance of the lift truck-arms. Thus a very large number of pallets have heretofore been required for the handling of material by lift truck, whichentails a considerable expense. The use of pallets is also wasteful of space, and, furthermore, articles such as, bales and packages'with roundedor bulging ends. and sides will not rest securely either individually or in tiers to be carried on pallets. Another shortcoming of conventional lift trucks is that they merely lift, and therefore cannot pull a selected object such as a bale of cotton previous equipment for this purpose is that the travel of the load engaging arms has been so limited that the equipment could be used for only a limited range of sizes of packages or arti-- The adjustments necessary to grip loads of cles. different width have heretofore required the services of a mechanic and have necessitated taking the equipment out of service temporarily. Moreover, the movement of the linkage and pistons has been of such nature that-the equipment here- 2 tofore proposed has not had satisfactory rigidity and load capacity when spread apart to extreme limits where the equipment was also capable of handling narrow loads.

The front overhang of the arm clamping mechanism has also been a serious handicap in 7 prior devices. Such objectionable overhang has been largely unavoidable heretofore because of the inherent nature 'of the apparatus employed with the result that the pay load of the vehicle is reduced. For example, a lift truck which is rated as a one-ton truck is supposed to be able to carry two thousand pounds fifteen inches in front of its upright lifting frame. If the mechanism for operating the clamping-arms takes up a part of this fifteen inch space, the center of gravity of the load is thereby necessarily moved forward which has the practical result of reducing the load ratingof the truck.

The use of pivotally mounted load clamping arms in prior devices has also been found to be of disadvantage. When the arms are arranged to reach outto a widespread and also to retract to engage a-narrow loadthey have considerable vertical movement in addition to their lateral movements. Such arms may be brought near the ground for a low grip on a narrow load but they are ordinarily'well above the ground when they are spread out, making it necessary to obtain a highgrip on a wide load. Angular movement of the arms is further objectionable because of the varying angular positions of the hydraulic cylinders and operating pistons which reduce the effective clamping effort which may be exerted on a load in certain positions of the arms. In constructions of this type heretofore proposed, the least clamping force is obtainable when the arms are spread thewidest as they are likely to be in carrying an unusually large and heavy load.

Another objection to previous load clamping mechanisms is that they have been of too great vertical height. When loading to the ceiling in a box car or other low ceiling place, themechanism frequently strikes the ceiling before the load is lifted into place. I

'Objects of the present invention are to provide an improved load handling mechanism to dispense'with the use of pallets, toprovide a handling mechanism for stacking heavy and bulky objects compactly and for removing compactly Stacked objects without manual assistance, to provide'an improved load lifting mechanism having a pair of arms adapted to grasp an object by its sides without furnishing bottom support under the object, to provide novel means for clamping the lifting arms together with suflicient force to grip and lift a heavy object, or to lift and transport a tier of objects by merely embracing the sides of the lowermost object by the lifting arms, and to provide novel forms of detachable and interchangeable lifting arms for handling and manipulating different kinds of materials.

Still other objects are to provide a mechanism of the type described which may be manufactured as an attachment for lift trucks which will overcome the above mentioned shortcomings 'of prior devices of this type, to provide a very compact mechanism projecting out rnot;more than-.a few inches in front of the uprights of athe .lift :truck and having a low over-all height so that loads may be lifted up close to a ceiling at any height, and to provide a wide range of movement in the mechanism from a very narrow grip to .ansexceedingly wide grip without loss of rigidity and clamping force in :any position of :the .arms .and without having a base unit for the attachment widerrthan the-truck. .Otherobjects areto eliminate pivot points and pivoted arms, to 1 provide a mechanism capable of movement torits extreme minimum or maximum width positions,bymerely operating a valve control and :without making any mechanical adjustment of the parts-and .to provide a mechanism having a load arm movement parallelto the ground throughout its range of movement.

The illustrated embodiment ,of :thepresent device constitutesia novel and improved form of load. carriage, or attachment fora load carriage, for .an industrial :lift truck or other apparatus having some'form of elevating-and :transporting means. Instead of carrying the load on fixed arms extending under a "pallet, --the present load carriage is provided with vforwardly :extending arms which may 'be :drawn together laterally in horizontal movement parallel withthe groundto grip or clampthe sides of :the article to be lifted or thesides 10f thebottomarticle of atier-where the whole itierzisato bemoved atonce. lhe arms are thus drawn together with suflicient force for the purpose by a pair of hydraulic cylinders mounted on the carriage. 'VlZhen .the vpresent mechanism is used on =a .lift truck or similar vehicle, the movements of the armsare controlled by a simple valve :lever accessible :torthe .driver and adjacent the .othercontrol levers for raising and lowering'the load .carriage'and operating the vehicle. As the description proceeds, it will be apparent that .the'present mechanism eliminates the need for :pallets:and-enables .objects to --be handledindividuallyand in-stacks with greater facility than the-conventional lift truck.

with the :foregoingand :other objects .-in view. the invention furtheriresides in the details 'of constructionandzarrangement'of. parts illustrated in the preferred embodiments shown-on -the accompanying drawings. It is to be understood, however, that the presentembodiment is shown for purposes of illustration'only and notfor-the purpose of limiting the invention, -:as :varions changes will occur to'persons skilled'in the art, and all such modifications within thescope of the appended claims are included in the invention.

In the drawings:

Figure 1 is a perspective .view of .a lifttruck showing the .present materialhandling .device installed thereon;

.Figure .2 is a front elevation view of the load view of the load .ingaxnetering orifice in one of the horizontal cylinders :on the load carriage;

Figures"? to 9, inclusive, are perspective views of different forms of load carrying arms for the load carriage;

Figure 10 is a side elevation view of a modificationhavingarms adapted to grasp an object close to the floor;

Figuredl is a schematic view of the hydraulic system for extending and retracting the load carrying arms;

.Figure .12 :is a front elevation view :of gaimodification wherein .the :clamping (arms and itheir actuating :mechanism are .mounted .on a rotatablezmember nnathe-lift carriage, the parts being shown rin -.diflerent 'positiom in :full and broken lines;

Figure 1311s aside-elevation iview of thestructure of Figure l2; and

Figure 14 is .ia Lfragmentany view showing anothergform of horizontal guide and supports'tructure for Ithe clamping arms.

:InFigure. 1 :the rinventionzis illustrated in :connection with :aiiift truck All having .a pair .of eng ine driven rfront .wheels 1:! and a single :rear wheel,motshown,'whichissteerablebytheusual hand :wheel l2. .The numeral .[3 designatm the driversseat which ;is :accessible to the necessary controls for driving the .vehicle,.and .also-to levers l4, :[5 :and 16 for controlling the load handling mechanism. In "this type of truck, the .loadis carried entirely in front :of front *wheels 1 I, and so themeanend 1:1 -:of the -:vehicle .is usually equipped with :-a [heavy "counterweight in addition to;thewveightnf";theengine to hold the rear end of .-:the'v ehi'cle down.

iSuch lift:trnclm are fnrtherlequipped-xvith an upright frame '20 on the :front/o'f the truck to guide a; ilift .cframe :22. :The lift :frame 22 has a top horizontal isms :member 23 and .a pair of vertical .membersall mounted .for vertical sliding movement in :the :upright sframe 20. The lift frame'22 :mayrbe raised by various -means,-such asra yertical :hydraulic cylinderrhaving a piston with .apiston :rod artending upwardly to support the :top cross,- member .23. 1Llft trucks of this type are equippedwith a :-hydraulic pump 25 (Figure 11 for operating various hydraulic instrumentalities much as time vertical cylinder for the lift "frame 122 and :a cylinder :;for tilting the upright frame lfl. fihelift cylinder iscontrollediby anvalve leversuch asathe'lever'l'l inFlgure 1. 'The mechanism of the. present invention includes additional :hydraulic :cylinders which are intended tether-supplied from :thelhydraulic pressure. system of-thevhicle. :The general. arrangement of: parts thus :far described comprises one form .of lift truck :to which the present Iload handling mechanism 'may ,be'applied, 'butit is .to "be understood thatthe; mechanismnf .the invention may .also the applied "to :other types ;of :trucks .and :apparatus not-possessing :these specificrfeatures.

The principal features of the .presentiinvention are embodied in thealoadzearriagefifl. shown in Figures .2 1305, having .a ,pair of iforwardly extending load engaging arms 3| which may be drawn together with a powerful force to grip thesides of an object for the purpose of lifting it oif the floor without bottom support. The carriage 39 is provided with pairs of

rollers

32, 33 and 34 to guide it for smooth vertical movement with a minimum of friction. These various rollers are mounted on a pair of vertical side plates 35 which comprise parts of the frame of carriage 30. The carriage frame also includes afront bumper guard plate 36 and cross member 31 extending between the side plates 35.

The carriage is supported by a link chain 36 which has one end secured to the cross member 31, and is trained over a sheave 39 in a sheave mounting on the upper cross member 23 of the lift frame 22, the chain having its other end anchored at the bottom of the'upright frame 20. The above described arrangement is such that when hydraulic pressure is admitted to the lower end of the vertical lift cylinder (not shown), its piston is forced upwardly to elevate the lift frame 22 and sheave 39 to raise the carriage 30. The arrangement of the vertical cylinder for raising the lift frame 22 is not important to an understanding of the present invention, the only important requirement being that the carriage 30 is raised and lowered by some suitable power operated means.

Each arm 3| is detachably secured by bolts 43- (Figure 4) on a vertical cross head member 44 integrally interconnecting the outer ends of a pair of horizontal tubular slides 45. The slides 45 are supported for lateral sliding movement in a series of parallel horizontal tubular guides 46 whereby the integral parts 44 and .45 may be considered to constitute a slide for an arm 3|. Each cross head member 44 stands out forwardly from the slides 45 on horizontal end portions 4? which are adapted to travel in slots 48 in the guide tubes 46 when the arms are retracted toward a central position. The guide tubes 46 may thus be made long enough to provide a wide support base-for the load carrying arms in their widest extended position while still permitting the cross head and arms to be retracted close together to clamp small objects. Each guide tube 46 extends through aligned holes in the side plates 35 where it is welded to each of these plates and the outer ends of each pair of guides 46 are interconnected by a spacing member or plate 49 which is welded to the guides to make the members 49 integral parts of the carriage 3D. The ends of the'guide tubes are left open for the ends of the slides to project therethrough when the arms are retracted. The minimum spacing of the arms 3| to grip small objects is thereby not limited "by the outside length of the guide tubes, which length is critical only to determine the minimum width of the apparatus for traveling down'a narrow aisle without a load, as will be seen from Figure 3 where the parts are shown at minimum width and in almost the minimum gripping position. it'will be observed that the arms 3| may be retracted still further without changing the outside width of the apparatus. It will further be observed that the minimum spacing of theload carrying arms is not limited by the length of the slides since the opposed slides may freely pass each other in their individual guides.

The arms 3| are extended and retracted by hydraulic pressure in a pair of horizontal cylinders 56 extending in opposite directions. One end-of each cylinder 50 is pivotally mounted on a In the present embodiment pin 5| extending through ears 52 on one of the plates 49. Within each cylinder 56 is a piston 53 on a piston rod 54 whose outer end is pivotally connected with a pin 55 in a pair of ears 56 on one of the connecting members 44 carrying an arm 3|. The piston rod 54 slides in a guide hearing 57 in the end of the cylinder in addition to the usual packing gland 58 to hold the piston rod in axial alignment within the cylinder without undue wear on the packing. Each cylinder and piston rod unit is thereby supported solely by the two pin connectors 5| and 55 to maintain true alignment and free movement of the piston and piston rod within the cylinder without the possibility of'binding in any position of the parts. Any deflection of the structure under a heavy load will thereby not interfere with the free action of the pistons or produce excessive wear and friction in the moving parts. For this reason also, the vertical side plates 35 of the frame are provided with large holes 59 for the cylinders so that the cylinders will not engage these members. In retracted position the cross heads 44 clear and pass the outer ends of the cylinders 50 as shown in Figures 3 and 4.

The piston rods and load carrying arms 3| are extended by pumping hydraulic fluid into the inner ends of the two cylinders 50 through'a flexible tube or conduit 60. The conduit 6|] terminates in a T fitting 6| connected with branch pipes '62 and flexible conduits 63 leading to the inner ends of the cylinders adjacent their pin connectors 5|. The piston rods and arms 3| are retracted by pumping hydraulic fluid through a flexible tube or conduit 65 into the outer ends of the two cylinders. The conduit 65 terminates in a T fitting 66 connected with a pair of branch pipes 6'! and flexible conduits 68 leading to the outer ends of the cylinders adjacent the previously mentioned bearings 51 and packings 58. It is understood that when hydraulic fluid is pumped through one of the

conduits

60 or 65 to extend or retract the arms 3|, the movement of the pistons in the cylinders causes an. equal return flow of hydraulic fluid through the other one of the conduits.

Fluid flow through the

conduits

69 and 65 is controlled by the previously mentioned lever |5 connected with a three-position valve 46 in pressure line 4| of the oil pressure system used for raising and tilting the lift. The arrangement, as shown schematically in Figure 12, is such that when the lever I5 is moved in one direction bydraulic fluid is pumped under high pressure through the conduit 69 to the inner ends of the cylinders 56, while another portion of the hydraulic fluid in the system is returned from the outer ends of the cylinders through the conduit 65. When the lever |5 is moved in the opposite direction, the conduit 65 becomes the pressure line and the conduit 66 becomes the return line. The lever |5 has a rest position between the two extreme positions just mentioned, in which rest position the valve 40 closes both

conduits

60 and 65 to hold the pistons rigidly in any desired positions in their cylinders. The hydraulic pump and pressure system are of course a part of the usual equipment of any lift truck having a hydraulic lift and the present invention is intended to be operated from such a system, although it maybe adapted for operation by compressed air.

The

flexible conduits

60 and 65 are trained over a pair of sheaves 69 on the shaft of the chain sheave 39 at the top of the lift frame 22 to accommodate vertical movements of the carriage 30 without producing-slackin-the conduits. The

conduits thereby move with thechain "38.

It is desired to provide some means "for metering the flow of hydraulic fluid into-the two cylinders =50 to control the relative movements of the two pistons. In the present embodiment the fluid flow is metered into-the two cylinders totend to produce equal and opposite movement of the two arms 3| atalltimes. Figure 6 shows-anovel and very simple form of metering device which causes the two pistons 53 to move "substantially at the same rate, so that-an object engaged between the arms 3| may be centered in front 'of the lift truck. "It is possible with the present metering device to center rather large and heavy objects such as steel drums of oil by engaging such an object with only one of the arms 3| to slide it sidewise on'the-fioor without substantially disturbing the symmetrical position of the two arms 3| with respect to the lift truck. The present metering device comprises -a relatively small orifice 10 through the wall of the cylinder '50 to restrict the 'fluid flow into andout of the-cylinder. The orifice -10 opens into the interior of a collar H welded to the outside of the cylinder and threaded to receive a fitting! 2 on the end of one of the flexible conduits 63 or '68. It is understood that-each end of each of the cylinders 50 is provided with an orifice 70 of the type described to meter the fluid flow to or from each of the four

conduits

63 and 68. It is desirable to have the orifices 10 very small in comparison with the volumetric capacity of the oil pump 'in the oil pressure system of the lift truck, so that the desired working pressure will be maintained in the pressure lines at all times, regardless of the movement of the pistons. It will thus be apparent that if one of the arms 3| is engaged against a heavy object on the floor to move it sidewise while theother arm 3| encounters no resistance, the two arms will nevertheless move together substantially at the same rate because the maximum operating pressure is maintained on the working piston regardless of the movement of the idling piston.

The function of the orifices ill may be explained more clearly by pointing what would happen if these orifices were enlarged to form ports of conventional size to handle the flow of the conduits and pipe lines without substantial restriction. With conventional ports substituted for the orifices 69, the two arms 3! would not remain centered with respect to the load carriage 30 if only one of the arms were engaged with the load. In such case, the freely movable arm would move quickly because substantially the entire output of the hydraulic pump would be directed into that cylinder having the relatively free piston. During this interval, the hydraulic pressure would drop to a very low value and very little force could be exerted by the other arm which was endeavoring to move the load. The result would be that the arm engaging the load would not move until the originally free arm had ceased to move and would then be either .at its limit of movement or engaging the other side of the load, so that the load could not be centered without the use of valves in the fourpipes 62 and 62'. In the present system the orifices '10 pro-- duce a slow approximately uniform motion of the arms 3| at a rate which is substantially constant regardless of the resistance to such motion, within the limits of the fluid pressure system. It is not necessary that the orifices 19 be so fine that they slow up the movements of the arms to an extent which would be detrimental to the expeditious handling of materials, "but merely to prevent the arms, or one of them, when free, from moving'at 'a'speed which would materially reduce the working pressure in the hydraulic system. If one of the arms 3| becomes extended orretracted more than the other, itis only'necessary to extend or retract the arms 'momentarily to their limits of 'movementto place both arms in similar position.

Different types of load carrying farms are shown for use with different kinds of materials and'containers. The arms '31 shown-in Figures 1 to 5,'inclusive, comprise channel membershav'ing vertical web portions '15 with inwardly'dlrected top and bottom horizontal flanges 16 extending from the web portions sufii'ciently to in-dent themselves into materials or containers to be lifted. The arms'are'preferably not exactly parallel but slightly convergent toward "their 'outer ends to compensate for a certain unavoidable amount of elastic deformation of the apparatus under maximum possible pressure which may be developed by the pistons.

Figures 7 to 9, inclusive, show other forms '01 load carrying arms. The arm 31a shown-in Figure 7 is provided with-a perforated rubber pad'l'l in its channel to prevent damage to the object being lifted. In this case the compression necessary to exert a firm. grip omthe'objecbta'kes place in the rubber cushion 11 rather than in thezobject itself. The rubber cushion 11 may be mounted on .a plate which is securedin the channel of the arm .3la by .means of machine .screws 18,-or1the like, in the flanges. In Figure .8 a steel plate equipped with spikes 8| is.secured in .theorm 3H: for use on materials that will .not'bedamaged by the spikes.

The arm 31d in Figure .9 .is designed for handling heavy, cylindricalo'bjects such asoil drums and .the like. The :top and bottom flanges .16 are recessed in circular arcs .90 to fit .the cylindrical shape of the object, the am being located near the end of the arm to leave a-relatively'thin nose 9| at the end of the arm. The purpose of the thin nose 9| is to permit the .arms to .be driven forward between tightly packed-oil drums and the .like to remove any particular drum, or to place such oil drums closely together on the Cylindrical containers such as oil drums are usually provided with one or more circumferential ridges or beads in the mid portion which serve to maintain a slight lateral spacing .between the cylindrical parts of the drums when they are standing on end and which provide a ledge or shoulder to engage over one of the flanges 16 of the load carrying arm to reduce the compressive force required :to be exerted by the arms to lift the drum. The present mechanism, using the arms 31d, is capable of picking up .two full 55-gallon oil drums in side by side position without damaging the drums. The cylindergripping device shown in Figure .9 may also be made as an attachment for the .arms 3|, but it is usually preferred to make the arms considerably shorter for this purpose. With some modification the arms of Figure -9 may be adapted to grip rolls of paper and other cylindrical objects.

Still other types of load carrying arms may be devised by persons skilled .in theart'for handling other kinds of materials, the various modifications illustrated in the drawings being sufllcient to teach persons skilled .in the .art how to apply the principles of the invention to a wide variety of purposes. .Also, conventional lifting forksmay be bolted to the cross heads 44 if desired.

It will be observed in Figures 1 and 2 that one of the arms 3| must be mounted lower on its plate 44 than the other arm because of the offset relation of the two pairs of guide tubes 46. With the arms 3| mounted as shown in Figures 1 and 2, they cannot be lowered quite to the floor level because of the thickness of the lowermost guide tube 45. Figure 10 shows a mounting arrangement for the arms 3| on extension brackets 93 to place them in a lower position so that they may be dropped down on the floor when necessary. Where this is not an essential requirement, the construction of Figure 2 is preferred so that the two arms will be disposed about equally above and below the two piston rods 54.

For handling fragile packages, the pressure in conduit 65 may be controlled by an auxiliary valve to positively limit the crushing force which may be exerted by the load-carrying arms. In Figure 11 this pressure regulating valve is indicated at 95 as a relief valve connected across the

lines

60 and 65 in addition to the usual relief valve 96 ordinarily connected across the gear pump 25. A pressure gauge 91 in lieu of, or in addition to, the pressure regulating valve 95 may be used to indicate to the operator when the maximum safe force has been applied to the arms.

The low pressure relief valve 95 does not interfere with the action of the lift cylinder and other hydraulic devices which may require a high pressure, because when any of such devices are functioning the valve 40 is in its closed position to isolate the relief valve 95. When the valve 40 is in the position shown to clamp the arms 3|, the valves for the lift cylinder and other hydraulic apparatus are then in closed position to isolate all such apparatus from the system so that it will not be affected by the reduction in pressure in the line 65. Ordinarily, the valve 40 would not be moved to either of its open positions while other hydraulic apparatus in the system was operating. In lieu of the relief valve 95, a pressure reducing valve may also be used for the same purpose, and still other refinements may be added to the system as will readily occur to persons skilled in the art. Figure 11 is a schematic representation of a part of the hydraulic system and is not intended to portray the true physical arrangement of the different elements.

Figures 12 and 13 illustrate a modified form of construction where the load clamping mechanism is mounted for rotation on the lift carriage. In this embodiment the guides 46 form an integral part of a frame having a back plate I mounted for rotation on the lift carriage IOI. Th plate I00 is supported on the carriage on a hollow bearing I02 having a central opening for the flexible

hydraulic conduits

60 and 65. Suitable means forming no part of the present invention may be connected between the plate I00 and carriage IOI to rotate the plate and its clamping arms through an angle of substantially 180 in either direction from its normal upright position.

With the apparatus just described, a heavy object may be easily turned over, or an open barrel or box may be lifted and inverted to dump the contents therefrom. In Figure 12 the mechanism is shown erect in its lowermost position in full lines as it would be, for instance, in picking up a barrel of loose material. Then, by lifting the carriage IOI and rotating the plate I00, as indicated in broken-lines, the barrel would be inverted and its contents dumped. In such construction the centering of the load by the metering action of the orifices I0 is important to obtain the nec'essary balance for easy rotation on the bearing I 02.

Figure 14 shows a modified form of construction for the guides and slides for the clamping arms 3|. The guides 46a are of tubular construction, having a rectangular cross section and provided at their outer ends with longitudinal slots 48 for the horizontal end portions 41 of the cross head members 44. The slides 45a in this case are also of rectangular cross section to have a smooth sliding fit in the guides 46a. Other equivalent and suitable forms of slides and guides will occur to persons skilled in the art.

In the various modifications and embodiments hereinabove described, a salient feature of the invention resides in the compact construction and arrangement of the guides and hydraulic cylinders for supporting and moving the load carrying arms in opposed reciprocating travel on the lift carriage. The parallel overlapping disposition of the guides and cylinders in a common vertical plane accomplishes the objects of the invention in a novel and efiicient manner and successfully overcomes the numerous Shortcomings and limitations of prior apparatus for the same purpose. The parallel guides and cylinders form a fiat as-- sembly which does not project above or below a conventional lift truck load carriage and which has a thickness of only a few inches to be accommodated between the upright frame of the lift truck and the load. All pivotal connections are eliminated in the mounting of the load carrying arms which have rectilinear horizontal movement parallel with the floor. This arrangement of the operating parts greatly extends the range of movement of the arms, so that they are extendible from closely spaced positions to very widely spaced positions in continuous movement without any mechanical adjustments and with a uniform clamping force on the arms in all positions. When the parts are proportioned as best illustrated in Fig. 2, it will be observed that the cylinders 50 each have a length approximately equal to three quarters of the width of the lift carriage, measured between the end plates 49, whereby each cylinder extends beyond the middle of the carriag and the two cylinders overlap for a considerable distance. Thus the load carrying arms 3| may be retracted to a minimum spacing of approximately half the width of the carriage;

on lift trucks or attachments for lift trucks, butthat they may also be applied to other types of material handling apparatus within the scope of the appended claims.

Having now described my invention and in what' manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

1. In a lift truck, a lift carriage, a pair of load armson opposite sides of the carriage rigidly mounted on the outer ends of oppositely directed elongated slides, horizontal guides on said lift carriage supporting said slides for extension and retraction of aid arms laterally of the truck, and a pair of horizontal fluid pressure cylinder and piston rod units disposed one above the other in overlapping relation, each of said units being connected between one of said load arms and the opposite side of the carriage, said cylinders each having a length approximately equal to three quarters of the width of the carriage to draw said arms together to a minimum spacing approximately equal to half the carriage width and to It will 11 extend said arms to a maximum spacing approximatelyequal to twice the carriage width.

2. In a lift truck, a lift carriage having two pairs of horizontal guides disposed in intergacent relation one above the other, a pair of load arms mounted on opposite sides of the carriage for sliding movement on the respective pairs of guidesbetween a retracted position within the width of the carriage and an extended position beyond the width of the carriage, and a pair of horizontal fluid pressure cylinder and piston rod units. disposed one above the other for moving the respective load arms between said retracted and extended positions, each of said units being connected between one of said load arms and the opposite side of the carriage.

3. In a lift truck, a lift carriage having two pairs of horizontal guides, each pair comprising upper and lower guides wherein the lower guide 0! one pair is disposed between the guides of the other pair and the upper guide of said other pair i disposed between the guides of said one pair, a pair of load arms mounted on opposite sides of the carriage for sliding movement on the respective pairs of guides between a retracted position within the width of the carriage and an extended position beyond the width of the carriage, and

a pair of horizontal fluid pressure cylinder and piston rod units disposed one above the other for moving the respective load arms between said retracted and extended positions, each of said units being connected between one of said load arms an'd the opposite side of the carriage.

4'. In a lift truck, a lift carriage having two pairs of horizontal guides disposed in interj acent relation one above the other, a pair of load arms mounted on opposite sides of the carriage for sliding movement on the respective pairs of guides between a retracted position within the width of the carriage and an extended position beyond tlie-width of the carriage, and a pair of of the carriage and a piston rod in its other end connected with the load arm on the opposite side of the carriage, and. each cylinder having a length exceeding half the width of the carriage to impart a corresponding length of travel to each load arm.

5. In a lift truck, a lift carriage having two pairs of horizontal guides disposed in interjacent relation in a common vertical plane, a pair of load arm mounted on opposite sides of the carriage. for sliding movement on said guides, a pair of oppositely directed horizontal fluid pressure cylinders disposed one above the other between said guides, each cylinder having one end connected to one side of the carriage and a piston rod in its other end connected. with the load. arm on the opposite side of the carriage, said cylinders extending more than half way across the carriage so that said other ends overlap eachother in the center of the carriage, said load arms having an extended position beyond the opposite sides of the carriage and a. retracted position intermediate the lengths of said cylinders near the center of the carriagla. and a bumper guard. plate covering said guides. and cylinders in the center portion. of the carriage.

6; In a liftv truck, a lift carriage having. two pairs of horizontal tubular guides disposed in a common vertical plane, longitudinal slots in said guides, a pair of slide in eachv pair of. guides. offset. cross heads on. the respective pairs. of slides arranged to travel in. said slots. on opposite side of the carriage, load arms on.said cross heads movable between a. retracted position intermediate, the lengths. of the respective guides and an extended positionbeyond the ends of the guides on opposite sides. of the carriage, a. pair of horizontal fluid pressure cylinders disposed betweensaid guidesinsaid common plane, each cylinder being connected atone end to one side of-v the carriage and extendingtoward the opposite side of the. carriage, each cylinder having alength. greater than half the width oi said carriage and less. than the full width of the carriage, and piston rods extending from the other. ends of said. cylinders and connected. with said cross heads.

7. In a lift. truck, a lift. carriage having two pairs of horizontal guides disposed in a common verticalplane, a pair of. load arms mounted. on opposite sides of the carriage for sliding movement on. the. respective, pairs of guides between.

a retracted positionwithin the width of the car'- riage and an extended position beyondthe width.

of the carriage, a pair of fluid pressure cylinder and piston. rod units disposed one above the:

other for moving the respective load arms be.-

tween said retracted: and extended positions, each of. said. units being; connected between one.

of said load arms-and the: opposite side: of the carriage,,means,to deliver. fluid to said cylinders. under pressure, andmeans to meter the; fluid flow to each cylinder individuallyto tend to pro duce equal movementsof the two load'arms whenv said arm encounterunequalresistance to. movement.

LESLIE. G. EHMANN;

REFERENCES CITED The following references are of record in the