GB2045208A - Fork-lift truck - Google Patents

Abstract

In a fork-lift truck having a fixed mast section (21, Figures 1-6, or 102, Figures 8-12), one or more telescopic mast sections (24, 106, 110), and a load carrier (30, 114) mounted on the or an inner mast section (24, 110), an asymmetric lift piston-and-cylinder assembly (54, 170) is located adjacent one side of the mast in a position which provides improved overall operator visibility through the mast. The piston-and- cylinder assembly (54, 170) is connected by a bracket (58, 180) at its upper end to the or the first telescopic mast section for raising the latter, (24, 106) and a lifting chain (64, 204) is reeved on spaced and rotationally aligned sprockets (66, 65, 206, 205) supported either from a telescopic mast section (24, 110) or, in a further embodiment (Figures 13-17), from the piston (56') of the piston-and-cylinder assembly (54'), one chain end (63, 202) being connected in the two stage mast substantially centrally of the lifting or fork carriage (30, 110) and the other chain end (70, 210) being fixedly secured outwardly of one side of the piston-and-cylinder assembly (54, 170). In the triple stage mast disclosed one chain end (63, 202) is connected substantially centrally of the inner telescopic upright section (110) and a cantilevered piston-and-cylinder assembly (150) is mounted in the inner upright section (110) for elevating the lifting carriage (114). <IMAGE>

Description

SPECIFICATION Upright for lift truck This invention relates to uprights for lift trucks or the like.

In lift trucks of the type contemplated it has been one of the most persistent problems encountered in the art over the years to provide an upright construction which both affords the operator of the truck good visibility through the upright and which is of relatively simple and low cost construction, particularly in triple and quadruple stage uprights. Heretofore various means have been devised for improving, or which may incidentally improve, operator visibility through telescropic uprights in lift trucks, including upright structures such as are disclosed in U.S. Patents Nos. 2,394,458,2,456,320, 2,855,071, 3,394,778, 3,830,342 and German Patent No.

1,807,169, but none have satisfied adequately the above criteria.

The present invention provides an upright struc turefora lift truck or the like, comprising one upright section including transversely spaced vertical rails, a telescopic upright section including transversely spaced vertical rails mounted for elevation relative to said one section, an elevatable load carrier means mounted for elevation relative to said telescopic section, a sole asymmetric lift piston-and-cylinder assembly mounted in the upright structure and operatively connected to said telescopic upright section, and elongated flexible lifting structure operatively connected to said lift piston-and-cylinder assembly, to said one upright section and to said load carrier means and having one end structure thereof secured substantially outwardly of one side only of the lift piston-and-cylinder assembly and having the other end structure thereof secured to said load carrier means, said lift piston-and-cylinder assembly together with said flexible lifting structure being adapted to elevate said load-carrier means relative to the telescopic upright section and the latter section relative to the one upright section, the lift piston-and-cylinder assembly being located substantially at one side of the upright structure such that, when the upright is in use on a lift truck or the like, it projects at least partially into the area of interference by an adjacent vertical rail with the visibility of the operator from his normal line of sight through said adjacent vertical rail.

The present invention enables improved operator visibility to be provided in upright structures for lift trucks or the like while providing an upright of relative simiplicity and low cost.

The invention will be more particularly described with reference to the accompanying drawings, in which Figure 1 is a front view of an industrial lift truck showing a load carriage lowered to the bottom of the telescopic mast section of a two-stage upright, and exemplifying the improved operator visibility which is provided through the upright; Figure 2 is an enlarged full rear view of the upright shown in Figure 1 with the upright dismounted from the truck; Figure 3 is an enlarged plan view of the upright shown in Figure 2; Figure 4 is a somewhat schematized rear view reduced in scale and shown extended to full elevation; Figure 5 is a plan view of the upright which shows a modification of the structure shown in Figure 3; Figure 6 is a plan view of the upright which shows another modification of the structure shown in Figure 3;; Figure 7 is a view similar to Figure 1 showing a triple stage upright construction; Figure 8 is an enlarged full rear view of the upright shown in Figure 7 with the upright dismounted from the truck; Figures is an enlarged plan view of the upright shown in Figure 8; Figure 10 is a somewhat schematized rear view in reduced scale of the upright shown in Figure 2 wherein the load carriage is elevated by a primary cylinder to a full free-lift position; Figure ii is a somewhat schematized rear view of the upright at partial elevation; and Figure 12 is a partially cut-away rear perspective view of the upright with the load carriage at floor level.

Figure 13 its a front view of a modification of the upright shown in Figure 2; Figure 14 is a plan view of the upright of Figure 13; Figure 75 is aview of the upright of Figure 13 showing the fork carriage in a free-lift position; Figure 16 is a somewhat schematized front view of the upright of Figure 13 reduced in scale and shown extended to full elevation; and Figure 17 is a detail view of a part of the piston rod construction of the lift cylinder.

Referring to the drawings, and first to Figures 1 to 4, a conventional industrial lift truck is shown at numeral 10 having- a frame and body construction 12 mounted on a pair of steering wheels, not shown, at the rear end thereof and a pair of traction wheels 14 forwardly thereof, and embodying suitable power components, which may be operated either by electricity or gasoline, for operating the truck from an operator's compartment 16. An operator is illustrated in Figure 1 at numeral 18 as he would appear when operating the truck to an observer in front of the truck.

The upright assembly of the present invention is illustrated generally at numeral 20, the assembly being mounted on the truck in known manner. A fixed mast section 21 includes a pair of transversely spaced opposed channel members 22 arranged to receive a single telescopic mast section 24 formed of two laterally spaced I-beams 26, mast section 24 being guide roller supported in mast section 21 and arranged for longitudinal movement relative thereto.

A load or fork carriage 30 having a pair of transverse support plates 31 and 32 is guide roller mounted in known manner for elevation in the telescopic mast section 24.

Mast section 21 is cross-braced for rigidity by means of upper and lower transverse brace members 36 and 38, and telescopic mast section 24 is cross-braced by upper and lower transverse mem bers 40 and 42.

The I-beam mast section 24 is nested within the outer section 21 in known manner such that the forward flanges of the I-beams 26 are disposed outside of and overlapping the forward flanges of channels 22, and the rear flanges of the I-beams are disposed inside the adjacent channel portions and forwardly of the rear flanges of channels 22, pairs of rollers being suitably mounted betweenssaid adja cent pairs of the I-beams and channels for support ing the I-beam telescopic section longitudinally and laterally for extensible movement relative to the fixed channel section. The support and guide rollers of each said pair are illustrated in Figure 3 at numerals 33 and 34, while the upper rollers mount ing the load carriage 30 in the inwardly facing channel portions of the I-beam section are illustrated at 37.Particulars of the nested offset I-beam upright structure, the mounting of the load carriage thereon, and the details of structure and mounting of guide and support roller pairs are explained in detail in United States Patent No. 3,213,967.

As illustrated, a cylinder support block 50 is secured on brace 38 near the right hand side thereof in the aspect of Figures 2,3 and 4 and adjacent and partially behind the one I-beam rail 26, a hydraulic fitting 52 being mounted on the block to communi cate fluid under pressure to and from a cylinder 54 of a lift piston-and-cylinder assembly which is mounted on the block for communication with a lift truck hydraulic system, not shown. An extensible piston rod 56 of the piston-and-cylinder assembly is con nected to mast section 24 at the upper end by a bracket 58 which is secured to the piston rod end.

Bracket 58 is connected, as by welding, to brace 40 and to a cantilevered support member 60, said member being secured to the rear flange of the adjacent I-beam rail. A chain anchor plate 62 is secured centrally of lower fork carrier plate 32 to which is secured at anchor 63 (Figure 2) one end of a lifting chain 64, or other flexible lifting means, which extends upwardly and over a pair of spaced sprock ets or sheaves 66 and 68, and then downwardly to a fixed anchor connection 70 located in a predeter mined position adjacent the outer end of a step down support and brace plate 72 of brace member 36, the horizontal end portions of brace 36 being connected by a vertical plate 74.

Sprocket 66 is mounted for rotation on a stub shaft 67 which is secured in a support block member 76 in turn secured to brace 40. Sprocket 68 is similarly mounted on a stub shaft 69 on support member 60, the lifting chain and sprockets being mounted on a bias to the upright assembly as is best shown in Figure 3.

Although there is shown but a single relatively heavy chain 64, it should be understood that in practice it may well be found preferable for safety reasons to use two or more smaller chains reeved in substantially the same manner as is single chain 64 on modified single sprockets or on multiple side-byside sprockets as desired. Recitations in the claims hereof of "soleflexible lifting means", and the like, include such multiple side-by-side lifting elements which will perform the same function as does the single lifting element 64 shown in the drawing.

In order to substantially balance the force mo ments acting in a transverse plane on the embodi ment of the upright assembly as disclosed, the connection of the chain to anchor block 62 should be located at or substantially at the transverse center of carriage 30, and the connection of piston rod 56 to bracket 58 in combination with the location of chain anchor 70 should be such that the piston rod is connected to the bracket at or near one-half the distance between the chain anchor locations as projected in the transverse plane of the upright Then, the forces passing through upright sections 21 and 24 create substantially no unbalanced moments or a calculated small unbalanced moment in the transverse plane of the upright, as viewed in Figures 2 and 3, for example, because the cylinder assembly is centered or approximately centered between the said projected locations of the chain anchors.

As will be understood by persons skilled in the art, in a free body force moment system, neglecting the weight of inner upright section 24, the vertically directed forces acting on the upright in the said projected transverse plane with the piston rod centered as aforesaid comprise a one unit force in an upward direction at each chain end, a one unit force in a downward direction in each vertical run of chain, a two unit force directed upwardly at the centre of the piston rod connection to plate 58, and a two unit force directed downwardly at the center of the cylinder on support 50. Thus, the upright functions in theoretical force moment balance.Of course, such theoretical conditions do not exist in practice, and side thrusts or torque loading on the upright such as result from unbalanced moments effected by offcentre loads on the fork, for example, may be resisted by upper and lower pairs of carriage side thrust rollers 80 operating on the outer flange edges of I-beams 26 in known manner.

It should be noted that the weight of the inner upright section 24 will impart a slight unbalanced moment in a counter-clockwise direction, as seen in Figure 2, on a centered asymmetric cylinder assembly, so that if desired the latter unbalanced momemt may be compensated by adjusting the location of the cylinder assembly slightly inwardly of its said central position between the projected chain anchor locations. On the other hand any such inward adjustment of the cylinder assembly location may tend to interfere with maximum visibility through that side of the uprights, depending upon the operator's normal location on the truck. Also, any such unbalanced force moments are relatively minor and should, in most upright designs, be readily acceptable in the overall design, which usually includes some provision for resisting side thrust such as by rollers 80.

The designer of uprights of various widths, depths, seat locations, and the like may choose any one of a number of viable combinations of such structure within the scope of the present invention. It should therefore be understood that recitations in the claims hereof relating to the substantial balance of force moments in the upright, or to the asymmetic position of the cylinder substantially centered be tween the projected chain anchor locations or the like, shall be interpreted to include a range of positions ofthe cylinder assembly between the sprockets which best effects the desired result of good operator visibility through the upright and adequately balanced force moments acting on the upright in operation.

The design is such that the location of the cylinder assembly at one side of the upright combines with the location of the operator, preferably offset a predetermined distance to the opposite side of the longitudinal axis of the truck, to provide an operator's line of sight through the upright on the side at which the cylinder assembly is located so that the cylinder assembly interferes a relatively small amount or not at all with the operator's visibility through that side of the upright. In other words, the cylinder assembly projects at least partially into the area of interference by the adjacent side of the upright when in a retracted or collapsed position with the visibility of the operator from his normal line of sight through that side of the upright.

The principles of the upright design as described hereinabove may be applied to many and various types and designs of multiple stage uprights, including, without limitation, free-lift and triple stage uprights as described later herein.

References made in the specification and claims hereof to the longitudinal and/or transverse planes of one side of the upright, or of the vertical rails of the upright, or terms of similar import, shall have the following meanings: The longitudinal plane of the one side of the upright shall means a vertical plane extending longitudinally of the upright assembly bounded by the outer and inner surfaces of the vertical rail assembly on one side of the upright, while the transverse plane of the upright or of the one side thereof shall mean a vertical plane extending transversely of the upright assembly bounded by the front and rear surfaces of the vertical rail assembly of the upright.

Referring now to the modification shown in Figures 5 and 6, there is shown exemplary modified structure wherein some of the parts are or may be the same as in Figure 3, and these parts have been numbered the same as in Figure 3. Exemplary similar but modified parts are identified by the same numeral as in Figure 3, but carry a single or double prime designation, as, for example, element 72, 72' and 72" as between Figures 3, 5 and 6, respectively.

Wholly new parts are identified by new numbers. For example, a long cantilevered new anchor block is identified by numeral 90 in Figure 5, but by numeral 62' in Figure 6 in which, in combination with support block 76' for mounting sprocket 66, the latter parts represent basically merely a difference in configuration when compared with the similar parts 62 and 76 in Figure 3.

Referring now in detail to Figure 5, the modified structure comprises mainly a relocation of sprockets 66 and 68 so that they are mounted in transverse relationship to the upright which effects incidentally a shortening of the chain as shown at 64'. In order to accomplish this mounting arrangement while maintaining the lift cylinder assembly 54,56 in a similar adjacent relationship to the right hand side of the upright, the cylinder assembly is located somewhat longitudinally rearwardly of the position shown in Figure 3 out of the transverse plane of the adjacent one side of the upright.The cylinder assembly is thus located by securing it between cylinder support block 50' and bracket 58', the latter being secured, as by welding, to the rear side of upper brace 40' of inner mast section 24 which is secured to the rear faces of the rear flanges of I-beams 26 and which extends outwardly of the right side of the upright as seen in Figure 5 for supporting thereon adjacent the outer end of the sprocket 68, as shown.Sprocket 66 is aligned for rotation with sprocket 68 transversely of the upright, it being mounted also from the rear surface of brace 40', lifting chain 64' being reeved on the sprockets and secured at its one end at anchor 70 to step-down support plate 72' of modified configuration and secured at its opposite end at anchor 63 to an elongated cantilevered chain anchor support 90 which is secured from the rear of lower fork carriage plate 32, the same as is anchor block 62 in Figures 1-4. Sprockets 66 and 68 are cantilever supported from brace 40' in this embodiment by the stub shafts 67 and 69. The lower brace member 42' secured between I-beams 26 is of a bowed configuration as shown in order that anchor support member 90 may clear brace 42' during movements of the fork carriage near the lower end of the I-beam mast section.The mounting relationship between support block 90 and a lower brace 38 of outer section 21, is, of course, such that there is no interference between the support block and brace when the fork carriage is at its lowermost position in the upright.

Referring to Figure 6, a modified construction is shown wherein provision is made for sprockets 66 and 68 to be mounted in aligned transverse relationship of the upright in a forward location relative to the location thereof shown in Figure 5. In this construction a location of the lift cylinder assembly in relation to the adjacent one side of the upright may be provided, as shown, which is approximately the same relative location as shown in Figures 1-4.

Thus, the transverse upright braces 36, 38, 40 and 42 may be the same as in Figures 1-4, as shown, except that the configuration of the step-down portion 72" of brace 36 is altered to provide a suitable location for anchor 70, the cylinder assembly being mounted from support block 50 and secured at the upper end to bracket 58".

As mentioned above sprocket 66 is supported from block member 76' and the chain is secured at anchor 63 to anchor block 62', similarly as in Figures 1-4 except as modified to provide for a transverse aligned relationship between the sprockets. Sprocket 68 is mounted from a cantilevered support plate 92 which is secured at its inner end to the outer surface of the forward flange of the one I-beam 26 and above the upper side thrust rollers 80.

In the operation of the various embodiments of Figures 1 to 6 fluid under pressure is conducted to or exhausted from the single-acting lift cylinder assembly 54, 56 which effects a simultaneous elevation or lowering, as the case may be, of fork carriage 30 in telescopic mast section 24, and of the latter mast section in fixed mast section 21 without free-lift of the load carriage in relation to mast section 24 during elevation. The load carriage is elevated at a 2:1 ratio in relation to mast section 24fromthe position shown in Figures 1 and 2 to that shown in Figure 4, section 24 being elevated with the piston rod in relation to mast section 21.

Referring now to Figures 7 to 12, similar parts of the truck chassis and body are numbered the same as in Figure 1.

The triple stage upright assembly shown at numeral 100 comprises a fixed mast section 102 which includes a pair of transversely spaced opposed channel members 104 arranged to receive an intermediate telescopic mast section 106 formed of two laterally spaced I-beams 108, mast section 106 being guide roller supported in mast section 102 and arranged for longitudinal movement relative thereto.

An inner mast section 110 formed of two laterally spaced I-beams 112 is similarly guide roller supported in mast section 106 and arranged for longitudinal movement relative thereto. A load or fork carriage 114 having a pair of transverse support plates 116 and 118 is guide roller mounted for elevation in the inner mast section 110, all in known manner.

Mast section 102 is cross-braced for rigidity by means of upper and lower transverse brace members 120 and 122, intermediate telescopic mast section 106 is cross-braced by upper and lower transverse members 124 and 126, and inner mast section 110 is cross-braced by upper, intermediate and lower transverse members 128, 130, 132, and 134, members 130 and 132 also serving to support the primary lift piston-and-cylinder assembly, as will be explained.

The I-beam mast section 106 is nested within the outer section 102 in known manner such that the forward flanges of the I-beams 108 are disposed outside of and overlapping the forward flanges of channels 104, and the rear flanges of the I-beams are disposed inside the adjacent channel portions and forwardly of the rear flanges of channels 104, pairs of rollers being suitably mounted between said adjacent pairs of the I-beams and channels for supporting the I-beam telescopic section longitudinally and laterally for extensible movement relative to the fixed channel section. In a similar manner, inner I-beam mast section 110 is nested within intermediate section 106 for extensible movement relative to the intermediate I-beam section.The support and guide rollers of each said pair are illustrated in Figure 9 at 140,142 and 144,146, while the upper rollers mounting the load carriage 114 in the inwardly facing channel portions of the inner I-beam section are illustrated in Figure 9 at 148. Certain particularities ofthetriple-stage nested offset I-beam upright structure, the mounting of the load carriage thereon, and the details of structure and mounting of guide and support roller pairs are explained in detail in United States Patent 3,213,967.

A primary cantilevered lift piston-and-cylinder assembly 150 is supported centrally of inner mast section 110 on brace members 130 and 132 by brackets 152 and 154 secured, as by welding, to the cylinder and secured by studs to the transverse braces 130 and 132 (Figure 12).A single sprocket 156 is mounted for rotation by a bracket 158 at the end of a piston rod 160, a lifting chain 162 being reeved on the sprocket and secured at one end to an anchor plate 164 located on the cylinder, and at the opposite end secured centrally of carriage plate 118 by an anchor block 166 (Figure 9).The hydraulic lift cylinder 150 is substantially one-half the length of the inner mast section and when extended actuates the fork carriage at a 2:1 ratio to a full free-lift position as shown in Figure 10 prior to the elevation of intermediate and inner mast sections 106 and 110 by a secondary asymmetric hydraulic lift piston-andcylinder assembly 170, shown in a position of partial extension in Figure 11.

The assembly 170 is supported near the bottom from brace member 122 by a collar 172 welded to the cylinder and to the top edge of the brace member, the piston rod 174 being secured by a pair of studs 178 to a block member 180 which is welded to the rear surface of brace member 124, thus supporting the cylinder assembly from the top and bottom portions. A junction block 182 is located at the bottom of the cylinder for conveying fluid under pressure to and from the cylinder from a hydraulic system, not shown, it being also connected to a junction block 184 of the primary cylinder by a fitting 186 in block 182, non-flexible conduits 188 and 190, and a flexible conduit 192 which connects conduits 188 and 190 and which is reeved on three sheaves 194 mounted for rotation in a bracket 196 which is supported from brace member 124 by a bracket 198.

The sheaves and conduit assembly are mounted in an inverted U-shaped position behind or adjacent certain upright rails so that interference thereof with visibility of the operator is minimized.

A chain anchor block 200 is secured centrally of inner mast section transverse brace member 132 at an anchor connection 202 of a secondary lifting chain 204 which extends upwardly and over a pair of spaced sprockets 206 and 208, and then downwardly to a fixed anchor connection 210 located in a predetermined position adjacent the outer end of a step-down support and brace plate 212 of brace member 120, the horizontal end portions of brace 120 being connected by a vertical bar 214. The sprockets are mounted for rotation as in the twostage upright on stub shafts which are cantilever mounted in and secured to transverse brace member 124.

The force moments acting on the upright assembly are, of course, balanced in respect of the operation of centered primary piston-and-cylinder assembly 150, and in respect of operation of asymmetric piston-and-cylinder assembly 170, 174 operating centrally or approximately centrally between the sprockets and having the inner end of chain 204 connected substantially centrally of the inner mast section. The forces passing through the respective mast sections create substantially no unbalanced moments, or create a calculated unbalanced moment in the transverse plane of the upright in a manner similar to that described in detail above in respect of the two-stage upright.

The structure and operation of the triple stage upright as disclosed will now be apparent, particularly when taken in conjunction with the more detailed description of the principles of the invention and of some of the available design variations thereof described above in connection with the two-stage upright. It has been found that in order to achieve most desirable results in terms of operator visibility, that assembly 170 should be located such that it projects a distance into the aforementioned area of interference by the adjacent side of the retracted upright which is equal to or greater than the radius of the cylinder.

In operation to elevate the upright from the position in Figure 8 to that in Figure 11, for example, fluid under pressure is delivered by the hydraulic system simultaneously to cylinder assemblies 150 and 170 and, as is known, the cylinders operate automatically in a sequence related to the loads supported thereby whereby cylinder 150 functions initially to elevate load carriage 114 in inner mast section 110 to the full free-lift position illustrated in Figure 10 at a 2:1 ratio for the movement of piston rod 160.At the termination of the initial stage of operation the fluid under pressure automatically sequences asymmetric cylinder assembly 170 to elevate the entire telescopic upright structure in outer section 102 while the load carriage is maintained by primary cylinder assembly 150 in the aforementioned full free-lift position; i.e., the direct connection of cylinder assembly 170 to intermediate section 106 effects an elevation thereof in section 102, as shown in partial elevation in Figure 11, and simultaneously effects through the reeving and connection of chain 204 to inner mast section 110 an elevation thereof at a 2:1 movement ratio relative to section 106 to the position shown in Figure 11, and thence to a position of maximum elevation if the operator maintains the supply of fluid under pressure from the hydraulic system.Lowering of the upright is effected by venting the cylinders to the fluid reservoir, whereby a reversal of the above mentioned sequencing occurs as cylinder assembly 170 first fully retracts to the position of Figure 10, subsequent to which cylinder assembly 150 retracts the load carrier to the Figure 8 position.

Referring now to the modified two-stage upright assembly of Figures 13 to 17, major similar parts have been numbered the same as in Figures 2,4 and 5, the upright shown being basically in accordance with the modification of Figure 5 in respect of the mounting of the sprockets in transverse relation to the upright, except that the sprockets are mounted not on upper brace 40' of inner mast section 24 but on the upper end of the piston rod of the cylinder assembly so as to provide standard free-lift capability of the fork carriage as shown in Figure 15, as is well known. Except for the design variation which provides such free-lift, the upright assembly of Figures 13-17 is similar to the design as shown in Figures 2, 4 and 5. It will be appreciated, of course, that reference to Figures 2 and 4 construction assumes a Figure 5 type modification thereto.The use of single or double prime designations follows the same usage as in Figures 5 and 6 as defined above.

The cylinder assembly 54', 56' is mounted rigidly from the base at 50 on brace 38 and is of a shorter length than in Figures 2, 4, and 5, as shown, so as to enable the load carriage 30 to be actuated in the upright to a free-lift position, as shown in Figure 15, as piston rod 56' extends from the position in Figure 13 to that in Figure 15. Mounted rigidly atop the piston rod is a block or plate member 220 (Figure 17) having a projection 222 which extends forwardly so as to make contact with brace 40', Figures 14 and 15, in order to actuate inner upright section 24 to the Figure 16 position as carriage 30 is elevated from the Figure 15 to the Figure 16 position by chain 64', as the piston is extended the Figure 15 to the Figure 16 position.Sprockets 66 and 68 are mounted on shafts at the opposite ends of a pair of longitudinally spaced support plate members 224 and 226 which extend transversely of the upright and are mounted rigidly, as by welding, on the top of plate 220, the projection 222 extending forwardly as shown in Figure 14. The piston rod is connected to the sprocket assembly at or near one-half the distance between the chain anchor locations 63 and 70 in this modified upright design wherein its sprockets are aligned for rotation transversely of the upright the same as in Figure 5. The upper brace 36 has a deeper step-down portion 72" connected by member 74' than is present in Figures 4 and 5 so that the free-lift structure may be effected; i.e., so that a shorter cylinder assembly with predetermined free-lift and lower maximum fork height in an equal length upright is made available.

It will be understood by persons skilled in the art that many other design variations in the upright designs than those identified and described previously may be found feasible without departing from the scope of the present invention.

For example, although the basic design of the upright disclosed in all embodiments herein as being of the offset I-beam roller mounted design is preferred because of the space provided behind the rear flange or flanges of the I-beam vertical rails for partial nesting of the asymmetric cylinder assembly therein, as seen best in Figures 3,6 and 9, it will be appreciated that the invention may be also used with many other well-known upright designs, including coplanar (not offset) roller mounted channels or I-beams, fully nested roller mounted I-beams inside of outer channels, non-roller mounted sliding inner channel in outer channel, a telescopic upright section mounted outwardly of an inner mounted fixed upright section, and the like.

The location of the fixed chain anchor 70 and 210 may, of course, be varied in different upright designs as desired, such as at different selected vertical locations on the outer rail, or located on a cantilevered anchor support which may be secured to the asymmetric cylinder assembly, or in the case of an upright mounted from certain type of lift trucks without provision for fore and aft tilting thereof, the anchor can be located on the truck frame. In the latter design it may be feasible, of course, to mount the bottom of the asymmetric cylinder assembly also from the truck frame instead of directly from the bottom of the fixed mast section.

It may be found advantageous in some designs to mount the asymmetric cylinder assembly so that the cylinder 54 or 170 elevates on a fixed piston rod 56 or 174, in known manner; i.e., by reversing the position of the assemblies as shown, and ultilizing the piston rod also as a conduit for fluid under pressure to the cylinder to be actuated.

Depending upon such things as the axial distance of the operator from the upright, the width of the upright, or the transverse position of the operator when seated or standing in a normal operating position on different lift truck types, the most desirable precise location of the asymmetric cylinder assembly based upon the various factors will be estabilished, many of the major ones of which are discussed above. As noted previously the most critical combination of factors affecting the selection of cylinder assembly location is operator visibility and force moment balance on the upright, both of which may be compromised from the ideal within the scope of the present invention as required to effect the most desirable combination.In this connection it will be understood that the asymmetic cylinder assembly may in different sizes and designs of uprights desirably projet partially into both the longitudinal and transverse planes of the one side of the upright, as best seen in Figures 3,6 and 9.

In a relatively wide upright, for example, and with the operator located relatively close to the upright in a forward direction and well off-centre to the left thereof, it may be found advantageous to locate the cylinder assembly further forwardly than is shown in Figure 3, for example, necessitating a relocation thereof leftwardly and out of the longitudinal plane of the right side of the upright, in which event the cylinder assembly wouid project partially into only the transverse plane of the upright without interfering unduly with operator visibility through the upright. On the other hand, it may be found under certain design conditions that the cylinder assembly may be located further rearwardly so as to project into the longitudinal plane only, partially or even wholly, of the one side of the upright, and not project at all into the transverse plane thereof, as in Figure 5.

Again, it may be found desirable that the cylinder assembly project into neither such plane, all within the scope of the present invention.

However, before the particulars of any given upright design are finialized, it is important to understand that in any multi-section upright using this invention, whether of two, three, or more stages, and regardless of other available numerous design variations such as are described herein, the asymmetric cylinder assembly should be located such that it projects at least partially, and preferably substantially, into the area of interference by the adjacent side of the upright when in a retracted or collapsed position with the visibility of the operator from his normal line of sight through that side of the upright. Preferably the distance of cylinder assembly projection into said area of interference should be equal at least to the radius of the cylinder, although this may not be achievable in certain standard or two-stage upright designs.

Claims (14)

1. An upright structure for a lift truck or the like, comprising one upright section including transversely spaced vertical rails, a telescopic upright section including transversely spaced vertical rails mounted for elevation relative to said one section, an elevatable load carrier means mounted for elevation relative to said telescopic section, a sole asymmetric lift piston-and-cylinder assembly mounted in the upright structure and operatively connected to said telescopic upright section, and elongated flexible lifting structure operatively connected to said lift piston-and-cylinder assembly, to said one upright section and to said load carrier means and having one end structure thereof secured substantially outwardly of one side only of the lift piston-andcylinder assembly and having the other end structure thereof secured to said load carrier means, said lift piston-and-cylinder assembly together with said flexible lifting structure being adapted to elevate said load carrier relative to the telescopic upright section and the latter section relative to the one upright section, the lift piston-and-cylinder assembly being located substantially at one side of the upright structure such that, when the upright is in use on a lift truck or the like, it projects at least partially into the area of interference by an adjacent vertical rail with the visibility of the operator from his normal line of sight through said adjacent vertical rail.

2. An upright structure according to claim 1, wherein said load carrier means comprises a second telescopic upright section having transversely spaced vertical rails and mounted for elevation relative to said first mentioned telescopic upright section and a load carrier mounted for elevation relative to said second telescopic upright section, said flexible lifting structure having its said other end structure secured to said second telescopic section and actuatable with said asymmetric lift piston-andcylinder assembly to elevate said first and second telescopic sections.

3. An upright structure according to claim 1 wherein said flexible lifting structure is reeved on first and second sprockets operatively connected to said lift piston-and-cylinder assembly, said first and second sprockets being mounted in substantial longitudinal rotating alignment and spaced relation one to the other, said first and second sprockets being mounted in such a manner that said other end structure of said flexible lifting structure is secured substantially centrally of said load carrier means.

4. An upright structure according to claim 3, wherein the load carrier means comprises a second telescopic upright section mounted for elevation relative to said first mentioned telescopic upright section and a load handling carrier mounted for elevation relative to said second telescopic upright section, said flexible lifting structure having its one end structure secured substantially centrally of said second telescopic section and actuatable with said asymmetric lift piston-and-cylinder assembly to elevate said first and second telescopic sections.

5. An upright structure according to any one of the preceding claims, wherein said lift piston-andcylinder assembly projects into at least a portion of the longitudinal plane of an adjacent vertical rail on the said one side of the upright structure.

6. An upright structure according to any one of the preceding claims, wherein the location of said asymmetric lift piston-and-cylinder assembly is such that, when the upright is in use on a lift truck, it projects substantially into said area of interference by an adjacent vertical rail.

7. An upright structure according to any one of the preceding claims, wherein said asymmetric lift piston-and-cylinder assembly is located intermediate said one and other end structures of said flexible lifting structure in such a manner that the lifting force of said lift piston-and-cylinder assembly is approximately midway between the central plane of the load carrier means and the effective location of securement of the said one end structure.

8. An upright structure according to any one of the preceding claims, wherein said flexible lifting structure is reeved on sprockets, and the operative connection of said asymmetric lift piston-andcylinder assembly to said telescopic section in relation to said one and other end structures is such that at least approximately balanced lifting force moments act on the upright structure in the transverse plane of the upright.

9. An upright structure according to claim 3 or 4, wherein the sole substantial interference with operator visibility through that portion of the upright structure which comprises said asymmetric lift piston-and-cylinder assembly and first telescopic section is a single run of said flexible lifting structure when the load carrier means is lowered.

10. An upright structure according to any one of the preceding claims, wherein said asymmetric lift piston-and-cylinder assembly is connected at least approximately centrally of the projected one and other end structures of said flexible lifting structure.

11. An upright structure according to claim 3, wherein the first sprocket is mounted intermediate the said spaced vertical rails and the second sprocket is mounted outwardly of the one side of the upright structure.

12. An upright structure according to claim 3 or 4, wherein a second lift piston-and-cylinder assembly is provided for elevating said load carrier means and wherein an inverted U-shaped conduit structure connects hydraulically the base ends of the cylinders of the asymmetric and second lift piston-andcylinder assemblies, said conduit structure being supported from the upper end portion of the first telescopic section.

13. An upright structure for a lift truck or the like, substantially as herein described with reference to Figures 1, to 4, FigureS, Figure 6, Figures 7 to 9, Figures 10 to 12 or Figures 13 to 17 of the accompanying drawings.

14. A lift truck or the like when provided with an upright structure as claimed in any one of the preceding claims.