US3841442A

US3841442A - Lift truck upright

Info

Publication number: US3841442A
Application number: US00398055A
Authority: US
Inventors: D Erickson; H Harrington
Original assignee: Clark Equipment Co
Current assignee: Doosan Bobcat North America Inc
Priority date: 1972-02-15
Filing date: 1973-09-17
Publication date: 1974-10-15
Anticipated expiration: 1991-10-15

Abstract

A lift truck upright having outer, intermediate and inner telescoped mast sections with a load carriage elevatable in the inner mast section, and lift cylinders and lifting chains mounted in tandem and connected to the mast sections such that one lift cylinder and chain set is adapted to elevate above ground level the load carriage in the inner mast section and the inner mast section in the intermediate mast section, and the other lift cylinder and chain set is adapted to lower below ground level the load carriage and inner and intermediate mast sections together as a unit in the outer mast section.

Description

Unite States atent 1 Erickson et al.

1 1 Oct. 15,1974

[ LIFT TRUCK UPRIGHT [73] Assignee: Clark Equipment Company,

Buchanan, Mich.

221 Filed: Sept. 17, 1973 21 Appl. No.: 398,055

Related US. Application Data [63] Continuation of Ser. No. 226,636, Feb. 15, 1972,

banqeneqnu a, s

[52] US. Cl. 187/9, 214/1 A [51] lnt. C1 B66b 9/20 [58 Field of Search 187/9, 17, 95; 214/730, 214/1 A; 91/411 [56] References Cited UNITED STATES PATENTS 2,886,197 5/1959 Harris 91/411 3,029,959 4/1962 Crosby. 187/17 3,174,634 3/1965 Peck 214/75 3,433,324 3/1969 Mclntosh 187/95 8/1971 Wilson 214/730 OTHER PUBLICATIONS Put My Boat In Water, Hyster Product Application Report No. 136.

Primary ExaminerRichard E. Aegerter Assistant Examiner]effrey V. Nase Attorney, Agent, or FirmJohn C. Wiessler 5 7 ABSTRACT A lift truck upright having outer, intermediate and inner telescoped mast sections with a load carriage elevatable in the inner mast section, and lift cylinders and lifting chains mounted in tandem and connected to the mast sections such that one lift cylinder and chain set is adapted to elevate above ground level the load carriage in the inner mast section and the inner mast section in the intermediate mast section, and the other lift cylinder and chain set is adapted to lower below ground level the load carriage and inner and intermediate mast sections together as a unit in the outer mast section.

10 Claims, 5 Drawing Figures LIFT TRUCK UPRlGl-IT CROSS REFERENCE TO RELATED APPLICATION This is a continuation application of application Ser. No. 226,636, filed Feb. 15, 197 2, abandoned.

BACKGROUND OF THE INVENTION The field of art to which the invention pertains includes elevators, and more specifically portable elevators.

Certain applications of lift trucks require an upright construction which is capable of both positive and negative lift from a ground or support level position. For example, the pleasure boat population has increased enormously in recent years and the fork truck has become a particularly useful machine for handling such boats in and around marinas. This involves not only the handling of boats from ground or support level of the truck (herein sometimes referred to as zero lift) to elevated storage locations (herein sometimes referred to as positive lift), such as in boat storage buildings, but also the lowering and lifting of boats to and from locations well below the ground or support level (herein sometimes referred to as negative lift), such as commonly is required in handling a boat in the water from an elevated dock or the like.

Heretofore certain means have been devised for performing the functions of both negative and positive lift, l such as the use of fork tines mounted from a standard fork carriage and having long vertical sections varying between 3 and I feet, for example, for different marina operations, thereby enabling the horizontal tines of the fork to be lowered from the end of a dock, for example, an equivalent number of feet below the fully lowered position of the fork carriage in the upright. In the use of such specialized fork tines a serious disadvantage is introduced in that when the carriage is at its maximum elevated position the fork tines are located 3 to feet below the normal maximum elevation in the upright which would pertain to a standard design.

SUMMARY Our invention provides a compact triple-stage upright having independently operable lift cylinder and chain sets in tandem, one of which sets is connected to the intermediate and inner mast sections and to the fork carriage for elevating the inner section on the intermediate section and the fork carriage on the inner section, and the other of which sets is connected to the intermediate and outer mast sections for lowering to a negative lift position on the outer section the intermediate and inner sections and the fork carriage together as a unit. In a preferred embodiment, when the entire upright assembly is at a ground or truck support level position the lift cylinder of said one set is retracted and the lift cylinder of said other set is extended. In effect, a functional two-stage upright comprising three mast sections is operable in opposite directions from a ground level position.

A primary object of the invention is to provide a triple-stage lift truck upright functionally operable as a two-stage upright in positive lift and as a two-stage upright in negative lift.

Another object of the invention is to provide in a triple-stage lift truck upright a lifting cylinder for elevating a portion of the upright above ground level and a lowering cylinder for lowering a portion of the upright below ground level.

A further object of the invention is to provide generally improved lift truck upright structure for functioning both in positive and negative lift, which maximizes the utilization of vertical space for storage in warehouses and the like.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a lift truck having mounted thereon an upright which embodies our invention and which is shown engaging a boat in a position of maximum elevation or positive lift;

FIG. 2 is a perspective view of the truck and upright shown in FIG. 1 wherein the upright is shown engaging a boat at dockside in a position of negative lift;

FIG. 3 is a rear elevational view of the upright in a position of zero lift;

FIG. 4 is a side view in elevation of the upright as shown; and

FIG. 5 is an enlarged plan view of the upright shown partially in section.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the drawing, a conventional outdoor-type industrial lift truck is shown at numeral 10. The upright assembly of the present invention is illustrated generally at numeral 12, the assembly being mounted on the truck by means of a pair of rearwardly extending bearing brackets 14 secured to opposite fixed side portions of the upright assembly and adapted to be pivotally mounted in a conventional manner by means ofopenings 16 upon bearing portions of the front drive axle of the lift truck. The upright assembly, which includes an outer fixed mast section 18 and intermediate and

inner mast sections

20 and 22, is further connected to the lift truck for fore and aft tilting movement about the front axle by means of a pair of tilt cylinders 24, one of which is shown, which are connected to opposite sides of mast section 18.

The pairs of I-beam rails of

mast sections

18, 20 and 22 are nested together in interlocking and overlapping telescopic relationship in essentially known manner, such as is disclosed in US. Pat. No. 3,298,463. Outer fixed mast section 18 comprises a pair of parallel transversely spaced I-beam rails 24 secured together by a plurality of vertically spaced U-shaped ties 26 and upper and lower cross bars 28. The inner opposed channels of rails 24 are arranged to receive the intermediate mast section 20 formed of two laterally spaced I-beams 30, the intermediate mast section being mounted inwardly of, roller supported on, and arranged for longitudinal movement relative to the outer stationary mast section, as described below. The intermediate mast section is cross braced for rigidity by means of a plurality of vertically spaced transverse tiebars 32 which connect together the rear flanges of I- beam rails 30. The inner extensible mast section 22 is formed of two laterally spaced I-beams 34 which are mounted inwardly of, are roller supported on, and are arranged for longitudinal movement relative to the rails of the intermediate mast section in a manner similar but in a reverse direction to the mounting of the intermediate section in the outer section, as will be described. A plurality of vertically spaced transverse brace members 36 connect together the rear flanges of I-beam rails 34. The cross-braces and tie-

bars

26, 32 and 36 of the respective mast sections are arranged so that they pass inside of each other as required during positive and negative lift of the various mast sections as will be described, i.e., there is no interference between the braces of the different mast sections during telescopic movement in either direction thereof. A load or fork carriage 40 is roller mounted for elevation in wellknown manner in inner mast section 22, as will be described further below.

Inner mast section 22 is nested within intermediate mast section 20 in such a manner that the forward flanges of I-beams 34 are disposed outside of the forward flanges of I-beams 30, and the rearward flanges of I-beams 34 are disposed within the adjacent channel portions and forwardly of the rearward flanges of beams 30, sets of rollers being suitably mounted between said adjacent pairs of nested I-beams for supporting each of the I-beams 34 longitudinally and later ally for extensible movement in elevation relative to the adjacent I-beams 30. One of the upper rollers of each said set is illustrated at 42 and one of the lower rollers thereof at 44 (FIG. the upper rollers being stub shaft mounted from the upper ends of the webs of lbeams 30 and the lower rollers being stub shaft mounted from the lower ends of the webs of I-beams 34. Upper rollers 42 normally ride in abutment with the outer rear flange portions of I-beams 34 and lower rollers 44 normally ride in abutment with the inner rear flange portions of I-beams 30, suitable cut-outs 43 and 45 being provided in the areas of forward and rearward flanges of the l-beams which are adjacent said roller sets for the passage therethrough of the relatively large diameter rollers, all as is conventional in the art.

Similarly, I-beam rails 30 of the intermediate mast section are nested in forwardly offset and overlapping relation to the respective flange portions of outer fixed l-beam rails 24 of mast section 18, mast section 20, however, being mounted for downward telescopic movement relative to section 18 upon similar sets of guide and support rollers which support I-beams 30 longitudinally and laterally relative to l-beams 24. One of the upper rollers is illustrated at 46 and one of the lower rollers at 48. In this instance in order to accommodate negative lift operation as between

mast sections

18 and 20, the upper rollers 46 are stub shaft mounted from the webs at the upper ends of I-beams 30 and the lower rollers are similarly mounted from the websat the lower ends of l-beams 24. For negative lift support of section in section 18 the upper rollers 46 normally ride in abutment with the forward inner flange portions of I-beams 24 and the lower rollers 48 normally ride in abutment with the forward outer flange portions of I-beams 30, suitable cut-

outs

50 and 52 being provided in the respective flanges adjacent the roller sets as previously described in respect of

roller sets

42 and 44.

The load carriage 40 is mounted in known manner forwardly of the upright assembly. having a pair of transversely spaced lift bracket members 54 secured to the fork bar members 55 of load carriage and having mounted thereon upper and lower pairs of

rollers

56 and 58 which support the load carriage for extensible movement within the inner channel portions of l-beams 34, the upper and lower rollers normally riding along the forward and rearward flanges of I-beams 34, respectively.

A pair of tandem mounted hydraulic lift cylinder assemblies are shown generally at and 72, cylinder 70 being operatively connected between

mast sections

20 and 22 and cylinder 72 being operatively connected between

mast sections

18 and 20 in a manner to be described. Lift cylinder 70 is fully retracted when the upright assembly is in the fully nested ground level position shown in FIGS. 3 and 4, or when

mast sections

20 and 22 have been lowered together to a negative lift position as shown in FIG. 2, and cylinder 70 is operable to extend to elevate the load carriage 40 in mast section 22 and the latter mast section in mast section 20 to the full extension position shown in FIG. 1. Lift cylinder 72 is in a fully extended position when the upright assembly is nested as in FIGS. 3 and 4 and retracts to lower the

mast sections

20 and 22 with the load carriage, as in FIG. 2.

Cylinder and piston assembly 72, as illustrated, is shorter in its extended length than is the collapsed height of cylinder and piston assembly 70, which as disclosed extends substantially the length of collapsed

mast sections

20 and 22. The cylinder assembly 72 is suitably supported from the cylinder base end thereof in a pair of transversely spaced brackets 74 which are in turn mounted centrally of the transverse plate 28. At the cylinder rod end a cross head 76 is mounted which has a rearwardly located transversely extending projection 78 at the opposite ends of which are mounted a pair of rollers 80 engaging a pair of transversely spaced vertical tracks 82 which extend through and are supported in a plurality of vertically aligned C-shaped cutouts 84 in tie-bars 26. Laterally spaced sprockets 86 are mounted on stub shafts which extend outwardly of cross head 76 in the usual manner. A pair of chains 88 are reeved on said sprockets, being anchored at fixed ends to a pair of ears 92 of a collar which is secured to the cylinder, and being secured at the opposite ends to anchor and bolt members 94 which are mounted on the one tie-bar 32.

The front cylinder assembly 70 is supported longitudinally forwardly of cylinder assembly 72 from a lowermost transverse plate and bracket means and 102 located at the bottom of the intermediate mast section 20 and similar to the bottom support means 28 and 74 of cylinder 72. The piston rod end is connected to a contoured transverse plate 104 (FIG. 5) which is secured to the upper ends of the rear flanges of I-beam rails 34 and from which depends a box-shaped plate assembly 106, outwardly of the side plates of which are mounted a pair of sprockets on stub shafts 112. A bottom plate 114 of the box assembly 106 is secured to the side plates thereof and to the upper end of the piston rod, a pair of lifting chains 118 being reeved on the sprockets and secured at the one end to anchor members 120 on fork carriage 40 and at the opposite end to a collar which is secured to the cylinder. Thus, the cylinder assembly 70 is mounted in the upright as a no free-lift" cylinder in that it is at all times secured to the bottom of intermediate mast section 20 and to the top of inner mast section 22. As cylinder 70 is extended from a retracted position it effects simultaneously an elevating movement at a 2:1 lifting speed ratio of carriage assembly 40 in mast section 22 and an elevating movement at a 1:1 lifting speed ratio of mast section- 22 in section 20.

The hydraulic system, not shown, may be conventional and is controlled to supply pressure fluid successively to

cylinders

72 and 70 in that order from the fully retracted position of both said cylinders as shown in FIG. 2 to the full extension of both as shown in FIG. 1, cylinder 72 first extending fully to elevate the entire assembly of mast sections and 22 and cylinder 70 to the FIG. 3 position, and then cylinder 70 being extended to elevate the fork carriage and mast section 22 to any selected height up to the full elevation shown in FIG. 1. It will be understood that both cylinder assemblies are single-acting, that the inner mast section 22 and carriage 40 are lowered from the FIG. 1 position to ground level by gravity upon communicating cylinder 70 through a control valve to the reservoir, and that the cylinder 72 when lowered by gravity through a second control valve to the reservoir lowers the intermediate and inner mast sections with the fork carriage from the FIG. 3 to the FIG. 2 position. A pair of fork tines 130 are mounted as shown in a track 132 and areadjustable laterally as shown in FIGS. 1 and 2 for engaging boats and other loads having varying widths.

Following engagement ofa boat, as shown in FIG. 2, the mast sections are elevated by

cylinders

72 and 70 to a position a short distance above the zero lift position of FIG. 3; i.e., to a transporting position. The lift truck then transports the boat to a marina warehouse for stacking it and other boats in successive vertical tiers by merely adjusting cylinder 70 in extension. It should be noted that ordinarily in an upright of the overall configuration and design as disclosed herein, the maximum negative lift of the fork tines will equal approximately one-half the maximum positive lift since the carriage 40 is elevated from zero lift to the top of mast section 22 while mast section 22 is being elevated to the FIG. I position, whereas in negative lift downward movement of the fork carriage is the same as the negative lift available between the mast sections.

It will now be appreciated that our invention provides a highly efficient and compact upright assembly for marina operations, or for any other application in which a substantial negative lift is required in combination with positive lift. It is particularly useful in warehousing type marina operations in which it is important to maximize utilization of vertical space.

Although we have described and illustrated a preferred embodiment of our invention, it will be understood by those skilled in the art that modifications may be made in the structure, form and relative arrangement of parts without necessarily departing from the spirit and scope of the invention. Accordingly, it should be understood that we intend to cover by the appended claims all such modifications which fall within the scope of our invention.

We claim:

1. An upright structure for lift trucks comprising outer, intermediate and inner mast sections in telescoping relation to each other, a load carriage mounted on and movable along said inner mast section, a first lift cylinder assembly supported from the intermediate mast section and operatively connected to the inner mast section and the load carriage for elevating the load carriage on the inner mast section and the latter section on the intermediate mast section from a zero lift position to a positive lift position, and a second lift cylinder assembly supported from the truck and operatively connected to the intermediate mast section for lowering the intermediate mast section, the inner mast section and the load carriage and first lift cylinder assembly all as a unit with the intermediate mast section lowered by the second lift cylinder assembly from a zero lift position to a negative lift position.

2. An upright stiucture as claimed in claim 1 wherein the first lift cylinder is a no free-lift cylinder assembly wherein the rod end is connected continuously to the upper end portion of the inner mast section, and the rod end of the second lift cylinder is supported in tracks of the outer mast section for supporting laterally the second lift cylinder.

3. An upright structure as claimed in claim 1 wherein the intermediate and inner mast sections comprise pairs of laterally spaced inter-connected telescopic I- beam rails, roller mounted in nested and overlapping relation to each other, and the intermediate mast section being similarly mounted in relation to the outer mast section.

4. An upright structure as claimed in claim 1 wherein lift chain means is operated by the first cylinder assembly, being anchored at one end to the load carriage, reeved at the rod end of the first cylinder assembly and secured at its opposite end to the intermediate mast section, and lift chain means operated by the second cylinder assembly is secured to the intermediate mast section, is reeved at the rod end of the second cylinder assembly and is operatively secured at its opposite end to the outer mast section.

5. An upright assembly for lift trucks comprising outer, intermediate and inner mast sections in telescoping relation to each other, a load carriage mounted on and movable along the inner mast section, and motor means operatively connected to the mast sections and the load carriage such that the load carriage and inner mast section are elevatable in relation to each other and in relation to said outer and intermediate mast sections from a zero lift position to a maximum positive lift position wherein the load carriage is located adjacent the top of the inner mast section and the inner mast section is telescoped upwardly of the intermediate mast section, the outer and intermediate mast sections remaining in non-elevated positions in relation to each other, said motor means being also operative to lower the inner and intermediate mast sections and the load carriage as a complete unit from said zero lift position to a negative lift position wherein said latter unit is actuated downwardly out of said outer mast section to said negative lift position.

6. An upright assembly as claimed in claim 5 wherein said motor means comprises a pair of lift cylinder assemblies mounted in tandem and each being operatively connected to different pairs of said three mast sections, one of said lift cylinder assemblies being also operatively connected to the load carriage.

7. An upright assembly as claimed in claim 6 wherein both of said lift cylinder assemblies are operatively connected to the intermediate mast section.

8. An upright assembly as claimed in claim 6 wherein the said one cylinder assembly is retracted at zero lift position and the other cylinder assembly is extended at zero lift position.

9. An upright assembly as claimed in claim 8 wherein the said one cylinder assembly extends to elevate the load carriage in the inner mast section and to elevate the inner mast section in the intermediate mast section, 10. An upright assembly as claimed in claim 9 and the said other cylinder assembly retracts to lower wherein maximum positive lift is substantially greater the load carriage and inner and intermediate mast secthan maximum negative lift in relation to zero lift. tions to said negative lift position.

Claims

2. An upright structure as claimed in claim 1 wherein the first lift cylinder is a no free-lift cylinder assembly wherein the rod end is connected continuously to the upper end portion of the inner mast section, and the rod end of the second lift cylinder is supported in tracks of the outer mast section for supporting laterally the second lift cylinder.

3. An upright structure as claimed in claim 1 wherein the intermediate and inner mast sections comprise pairs of laterally spaced inter-connected telescopic I-beam rails, roller mounted in nested and overlapping relation to each other, and the intermediate mast section being similarly mounted in relation to the outer mast section.

9. An upright assembly as claimed in claim 8 wherein the said one cylinder assembly extends to elevate the load carriage in the inner mast section and to elevate the inner mast section in the intermediate mast section, and the said other cylinder assembly retracts to lower the load carriage and inner and intermediate mast sections to said negative lift position.

10. An upright assembly as claimed in claim 9 wherein maximum positive lift is substantially greater than maximum negative lift in relation to zero lift.