US3869047A

US3869047A - Load extending mechanism for material handling vehicle

Info

Publication number: US3869047A
Application number: US438815A
Authority: US
Inventors: Derek K Keene; Louis C Roll
Original assignee: Eaton Corp
Current assignee: Yale Materials Handling Corp
Priority date: 1974-02-01
Filing date: 1974-02-01
Publication date: 1975-03-04
Anticipated expiration: 1992-03-04
Also published as: FR2301476A1; CA1012495A; SE387617B; FR2301476B1; DE2504051A1; SE7500758L; GB1496795A

Abstract

A material handling vehicle including a platform, a carriage projectable and retractable with respect to the platform, at least one load support member or fork mounted on the carriage, and an elongated, telescopable extension or sheath on the load support member. An arrangement of pulley wheels and a flexible connecting member is provided to project and retract the extension with respect to the load support member, in response to the projection and retraction of the carriage. A ''''lost motion'''' mechanism is provided which permits a desired ''''pretravel'''' of the carriage before movement of the extension occurs, and this period of lost motion is repeated when the carriage is being retracted to its normal position.

Description

United States Patent [191 Keene et al. I

[451 Mar. 4, 1975 LOAD EXTENDING MECHANISM FOR MATERIAL HANDLING VEHICLE [75] Inventors: Derek K. Keene; Louis C. Roll, both of Philadelphia, Pa.

[73] Assignee: Eaton Corporation, Cleveland, Ohio 6/l9 72 Hansen Primary E.\'aminerRobert J. Spar Assistant Examiner-Lawrence .l. Oresky Attorney, Agent, or FirmTeagno & Toddy [57] ABSTRACT A material handling vehicle including a platform, a carriage projectable and retractable with respect to the platform, at least one load support member or fork mounted on the carriage, and an elongated, telescopable extension or sheath on the load support member. An arrangement of pulley wheels and a flexible connecting member is provided to project and retract the extension with respect to the load support member, in response to the projection and retraction of the carriage. A lost motion mechanism is provided which permits a desired pretravel of the carriage before movement of the extension occurs, and this period of lost motion is repeated when the carriage is being retracted to its normal position,

8 Claims, 9 Drawing Figures PAIENTED SHEET 1 0F 9 mmm 191s SHEET 3 0F 9 Q KN. Q 5 I an \\\I, :5 L

gin. j 2m M MJ QQ .m mw 1 mm K- I wx 'snm u m 9 PATENTEU 41975 PATENTEU W 41975 SHKEI E OF 9 PATENTED MR 415175 SHEET 7 BF 9 N. QI

LOAD EXTENDING MECHANISM FOR MATERIAL HANDLING VEHICLE BACKGROUND OF THE DISCLOSURE The present invention relates to a material handling vehicle, and more particularly, to a mechanism which projects and retracts a sheath or extension member with respect to a shuttle. While the present invention is equally applicable to any material handling or load lifting vehicle having a dual extension feature, i.e., a sheath extensible with respect to a shuttle, while the shuttle is extensible with respect to the carriage, the invention is especially advantageous for use with a vehicle having a rotatable platform and in which the extensible portion of the shuttle includes spaced, load engaging forks, and will be described in connection therewith.

In the construction and layout of modern warehouses, the trend has been toward the use of narrower aisles in an effort to get maximum utilization out of the available floor space. Such arrangements necessarily limit the space available for maneuvering material handling vehicles which must operate in the narrow aisles. This lack of space, in turn, limits the feasible size of material handling vehicles. Therefore, it has been attempted by those familiar with the art to provide a material handling vehicle of the type described which has a minimum possible swing radius, consistent with the ability to handle the particular loads.

In order to accomplish this, it may be necessary to establish two different positions of the carriage at which the sheaths are fully retracted with respect to the forks. These positions include 1. the carriage fully retracted so that the load on the sheaths is centered over the axis of rotation of the platform, and

2. the carriage slightly extended so that the sheath and carriage combination is centered over the axis of rotation to permit rotation of the shuttle within the smallest possible radius. For most efficient operation of this type of material handling vehicle, it is desirable that, as the carriage moves from position (I) to position (2), the sheaths not move relative to the forks and carriage, because any such movement would increase the swing radius, thus necessitating an increase in the overall size of the vehicle. The distance between these positions is referred to as the pretravel.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a material handling vehicle which is very compact, and able to maneuver in narrow aisles, even though the platform must be able to rotate with respect to the vehicle.

It is another object of the present invention to provide an improved material handling vehicle having a shuttle including extensible and retractable load supporting forks and load supporting sheaths mounted extensibly and retractably on the forks.

It is a more specific object of the present invention to provide a material handling vehicle of the type described wherein the sheath extends generally in response to the projection or retraction of the carriage, but which has a selected amount of lost motion between the sheath and the forks at the beginning of the carriage projection and at the end of the carriage retraction.

It is also an object of the present invention to provide such a material handling vehicle in which the lost motion device acts positively and utilizes, for its operation, the mechanism which extends the sheath relative to the forks.

These and other objects of the present invention, which will become apparent upon a reading of the following detailed description, are accomplished by the provision of an improved material handling apparatus having a load supporting shuttle mounted for extension and retraction with respect to a platform. A first drive means extends and retracts the shuttle. A secondary load supporting member is mounted for extension and retraction relative to the shuttle by operation of a second drive means which is interconnected to the first drive means. The second drive means includes a lost motion connection with the secondary load support member. As a result, initial movement of the secondary load support member with respect to the shuttle lags extension of the shuttle by a predetermined travel distance.

In accordance with another aspect of the present invention there is provided an improvement in a material handling vehicle including a platform, a carriage projectable and retractable with respect to the platform, at least one load support member mounted on the carriage, and an elongated, telescopable extension on the load support member, and means for projecting and retracting the carriage including a drive shaft. The improvement comprises:

a. a first pulley wheel mounted on the drive shaft;

b. a second pulley wheel mounted adjacent the load support member and oppositely disposed from the carriage;

c. a flexible connecting member passing around said first and second pulley wheels, at least a portion of said member extending longitudinally of the extension;

d. a first drive member fixedly attached to said flexible connecting member intermediate said first and second pulleys; and

e. driven means fixedly attached to the extension, said means defining a first slot adapted to receive said first drive member and maintain engagement therewith, during subsequent travel of said flexible connecting member. Said first drive member and said slot are spaced apart sufficiently, when the carriage is retracted, to permit a selected amount oflinear movement of said connecting member and projection of the carriage before said first drive member engages said driven means.

In accordance with still another aspect of the present invention, the pulley wheels are sprocket wheels, the flexible connecting member is a sprocket chain, and said driven means comprises a. a drive plate attached to the extension and defining said first slot, and

b. a third pulley wheel positioned adjacent said drive plate to support said flexible connecting member and as said first drive member passes around said third pulley wheel, to permit said first drive member to enter said first slot.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a crosssectional plan view of a typical material handling vehicle which may utilize the present invention.

FIG. 2 is a partly schematic side elevation shown partly in cross section illustrating a portion of a shuttle incorporating the present invention.

FIG. 3 is a partly schematic cross-sectional view illustrating the fork extension mechanism of the invention.

FIG. 4 is a partly schematic cross-sectional view similar to FIG. 2, but on a smaller scale illustrating the carriage fully extended.

FIGS. 5 through 7 are side elevations, all on the same scale, illustrating the lost motion device of the present invention at various stages of extension.

FIG. 8 is a rear elevation of the drive plate used herein, taken on line 88 of FIG. 7, but on a scale which is twice that of FIG. 7.

FIG. 9 is a view similar to FIG. 8, and on the same scale, showing an alternative embodiment of the drive plate.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, which are for the purpose of illustrating a preferredembodiment of the present invention and not for limiting the same, FIG. 1 is a plan view of a material handling vehicle taken on a section through the masts M. The shuttle, generally designated by the numeral 10, is in its fully retracted position which is preferred for transporting a load such as the pallet, shown by dotted line P, because with the shuttle in the position shown, the pallet P is centered with respect to the vehicle and the axis of rotation of the platform 12. When the load has been removed, and it is necessary to rotate the shuttle 10, it is apparent that to do so with the shuttle in the position shown in FIG. 1 would require a larger swing diameter than the desired swing diameter shown by dotted circle D, thereby requiring an increase in the overall size of the vehicle. Instead, the carriage 14 is projected or extended a certain pretravel distance with respect to the platform 12 to bring the entire shuttle within swing diameter D. In the subject embodiment, for example, the forks 34 are about 48 inches long and the sheaths 36 are about 40 inches long; therefore, a pretravel of about 4 inches enables the shuttle to rotate entirely within diameter D, thus minimizing the vehicle size. In order for the pretravel to accomplish the stated object, however, it is necessary that the sheaths 36 not begin to extend relative to the forks 34 and carriage 14 during the pretravel as such an extension would increase the swing diameter undesirably. Therefore, the present invention is a solution to the above and other problems by providing a lost motion connection between the drive means operating the carriage on fork assembly and the drive means operating the sheaths, as will be discussed below in greater detail.

The shuttle 10, as shown in FIG. 2 is still in its fully retracted position, and shows the rotatable platform 12, and carriage 14 which is projectable (to the right in FIG. 2) and retractable (to the left) with respect to platform 12. A cross member 16 is fixed with respect to platform 12 and a support bracket 18, preferably welded to cross member 16, anchors one end 20 of a sprocket chain 22. The chain 22 is fixed at its other end 24 to a mounting member 26 which is rigidly attached to platform 12. As the drive shaft 28 rotates in a counterclockwise direction, likewise turning the drive sprocket 30 counterclockwise, the sprocket chain 22 is wound about drive sprocket 30, then around idler sprocket 32, thus moving the carriage-14 to the right in FIG. 2. Mounted on the top of carriage 14 is fork 34, and positioned in sliding engagement therewith is the sheath or extension 36. Frequently, within one sheath there may be two spaced-apart forks instead of one fork per sheath.

FIGS. 3 and 4 illustrate semi-schematically the mechanism by which the sheath 36 is extended and retracted with respect to the fork 34, in response to the projection and retraction of the carriage 14. The main drive shaft 28 rotates a sprocket 38 which, in turn, drives sprocket chain 40. The chain 40 passes around a second sprocket 42 which, preferably is fixedly mounted with respect to the fork 34, and located at the opposite end of the fork 34 from the carriage l4.

Idler sprockets

44 and 46 are positioned as shown in FIGS. 3 and 4 to maintain the sprocket chain 40, passing around sprocket 42, in an orientation wherein the portions of the sprocket chain 40 between

sprockets

42 and 44 and between

sprockets

42 and 46 extend longitudinally of fork 34 within the sheath 36. It should be noted that in FIG. 3 the carriage 14 is shown in its fully retracted position with respect to platform 12, whereas in FIG. 4, the carriage is fully projected, and in response thereto, the sheath 36 is fully extended with respect to the fork 34. Extension of the sheaths 36 relative to the forks 34 is effected by engagement of drive blocks 48,50 with the sheath, as will be described in detail below.

FIGS. 5, 6, and 7 illustrate a portion of the apparatus shown in FIGS. 3 and 4, and in addition, the sheath drive means, generally designated by the numeral 52. The drive means 52 generally comprises a drive plate 54 attached to the rear face 56 of the sheath 36. The drive plate 54 defines a central slot or passageway 55, best seen in FIG. 8 extending perpendicular to the plane of the paper, and permitting the drive plate 54 to pass over the sprocket 44 and chain 40. In addition the above-mentioned central passageway, the drive plate defines a curvilinear slot 58 extending through the drive plate in a direction perpendicular to the plane of FIG. 5, and terminating in a terminal portion or slot 60. Offset from, but in open communication with the curvilinear slot 58 is another slot 62. Flrst drive block or drive member 48 and second drive member 50 are generally dumbbell-shaped assemblies.

Members

48 and 50 comprise, respectively, round,-

flat retaining members

64 and 64 connected to each other by means of

pins

66 and 66 passing through the chain 40, thus making the

members

48,50 immovable with respect to the chain 40.

FIG. 9 illustrates an alternative embodiment of the drive plate of the present invention, in which like elements are designated by the same numbers, but with added to each. This embodiment eliminates the central passageway perpendicular to the plane of FIG. 7, thus making the drive plate 154 a simplified flat plate with the drive members 148,150 being driven in the same manner by pins 166,166 which pass through the chain 140.

OPERATION Referring again to'FIGS. 5, 6, and 7, it should be noted that FIG. 5 corresponds to FIG. 3 and FIG. 7 corresponds generally to FIG. 4, except that in FIG. 7 the sheath 36 is not yet fully telescoped or extended with respect to fork 34. In FIG. 5, with the carriage 14 fully retracted the

drive members

48,50 are located along the chain 40 with respect to

slots

60,62, respectively, by a distance which is approximately equal to the desired pretravel of the carriage, i.e., the distance the carriage will travel before sheath extension begins. This is strictly true, however, only if drive sprocket 30 and sprocket 38 are the same size, thus making the ratio between them lzl. Therefore, as the drive shaft 28 begins to rotate, it turns drive sprocket 30 which begins projecting the carriage 14 as explained previously, and sprocket 38 is also rotated, driving the chain 40 in a direction which moves the

drive members

48,50 upward into the curvilinear slot 58, the position shown in FIG. 5. Additional travel of the chain 40 causes drive

members

48 and 50 to pass partly around idler sprocket 44 to the position shown in FIG. 6, wherein the pin 66 of first drive member 48 has reached the end of slot 60.

At this point, the driving force imparted to the chain 40 is conveyed through pin 66, acting on the bottom of slot 66, to the drive plate 54 which in turn begins to move sheath 36 with respect to the fork 34. As the second drive member 50 passes over the 12:00 position of the sprocket 44- the pin 66' of drive member 50 enters slot 62, and maintains engagement therewith during subsequent travel of the chain 40, such as is shown in FIG. '7. The configuration of slot 62 is such that after the sheath 36 has been extended fully, as shown in FIG. 4, and it is desired to retract the sheath, the pin 66 presses against the rear surface of slot 62, and is maintained therein, during subsequent retraction of the sheath. When the sheath has been retracted approximately to the position shown in FIG. 6, the pin 66' disengages from the slot 62 as it passes over idler sprocket 44 and begins to move downward. When this occurs, there is no longer a driving force being transmitted from the chain 40 to the sheath 36, and the retraction of the sheath is complete, even though the carriage l4 continues to retract through a distance which might be referred to as the post-travel which covers the same distance as the original pretravel.

Although the present invention is illustrated utilizing sprockets and a sprocket chain, it should be clearly understood that the invention is in no way dependent upon the use thereof, and any type of pulley wheel utilizing a flexible connecting member may be utilized advantageously herein.

It will be apparent to one skilled in the art that the present invention embodies apparatus for providing a selected amount of delayed or lost motion between a first member, which is projectable and retractable in response to the rotation of a drive shaft and a second member, generally projectable and retractable in response to the projection and retraction of the first member. Furthermore, it is a feature of the subject embodiment that the selected lost motion may occur at any desired point during the projection and retraction of the first and second members.

The invention has been described in great detail sufficient to enable one of ordinary skill in the art to make and use the same. Obviously, modifications and alterations of the preferred embodiments will occur to others upon a reading and understanding of the specification and it is our intention to include all such modifications and alterations as part of our invention insofar as they come within the scope of the appended claims.

We claim:

I. Material handling apparatus for handling a load including a platform rotatable about a vertical axis, a

load supporting shuttle mounted on said platform for extension and retraction relative thereto, first drive means operable to extend and retract said shuttle, a secondary load supporting member mounted on said shuttle for extention and retraction relative to said shuttle, and second drive means operable to extend and retract said secondary load supporting member, said first and second drive means being interconnected for simultaneous operation and said second drive means including a lost motion connection with said secondary load supporting member, whereby initial extension of said secondary load supporting member relative to said shuttle lags extension of said shuttle by a predetermined travel distance and full retraction of said shuttle lags full retraction of said secondary load supporting member by a predetermined travel distance whereby said load, shuttle and secondary member are shiftable from a fully retracted position to a position which al lows them to rotate within a minimum swing radius.

2. Apparatus as claimed in claim 1 in which said shuttle comprises at least one extensible and retractable fork and said secondary load supporting member comprises a sheath member partly surrounding said fork.

3. In a material handling vehicle for handling a load including a platform rotatable about a vertical axis, a carriage projectable and retractable with respect to the platform, at least one load support member mounted on the carriage, an elongated, telescopable extension on the load support member, and means for projecting and retracting the carriage including a drive shaft, the improvement comprising:

a. a first pulley wheel mounted on the drive shaft;

e. driven means fixedly attached to the extension, said means defining a first slot adapted to receive said first drive member and maintain engagement therewith during subsequent travel of said flexible connecting member, said first drive member and said slot spaced apart sufficiently, when the carriage is retracted, to permit a selected amount of linear movement of said connecting member and projection of the carriage before said first drive member engages said driven means whereby said load, carriage, load support member and extension are shiftable from a fully retracted position to a position which allows them to rotate within a minimum swing radius.

4. The improvement of claim 3 wherein said driven means comprises:

a. a drive plate attached to the extension, said plate defining said first slot; and

b. a third pulley wheel positioned adjacent said drive plate to support said flexible connecting member and, as said first drive member passes around said third pulley wheel, to permit said first drive member to enter said first slot.

cent said first drive member to be received in said third slot when said first drive member is received in said first slot and said second drive member passes around said third pulley wheel.

8. The improvement ofclaim 7 wherein said third slot has a configuration which permits it to maintain engagement with said second drive member, while the carriage is being retracted, until said second drive member passes over said third pulley wheel, disengaging from said third slot and reentering said second slot.

Claims

1. Material handling apparatus for handling a load including a platform rotatable about a vertical axis, a load supporting shuttle mounted on said platform for extension and retraction relative thereto, first drive means operable to extend and retract said shuttle, a secondary load supporting member mounted on said shuttle for extention and retraction relative to said shuttle, and second drive means operable to extend and retract said secondary load supporting member, said first and second drive means being interconnected for simultaneous operation and said second drive means including a lost motion connection with said secondary load supporting member, whereby initial extension of said secondary load supporting member relative to said shuttle lags extension of said shuttle by a predetermined travel distance and full retraction of said shuttle lags full retraction of said secondary load supporting member by a predetermined travel distance whereby said load, shuttle and secondary member are shiftable from a fully retracted position to a position which allows them to rotate within a minimum swing radius.

3. In a material handling vehicle for handling a load including a platform rotatable about a vertical axis, a carriage projectable and retractable with respect to the platform, at least one load support member mounted on the carriage, an elongated, telescopable extension on the load support member, and means for projecting and retracting the carriage including a drive shaft, the improvement comprising: a. a first pulley wheel mounted on the drive shaft; b. a second pulley wheel mounted adjacent the load support member and oppositely disposed from the carriage; c. a flexible connecting member passing around said first and second pulley wheels, at least a portion of said member extending longitudinally of the extension; d. a first drive member fixedly attached to said flexible connecting member intermediate said first and second pulleys; and e. driven means fixedly attached to the extension, said means defining a first slot adapted to receive said first drive member and maintain engagement therewith during subsequent travel of said flexible connecting member, said first drive member and said slot spaced apart sufficiently, when the carriage is retracted, to permit a selected amount of linear movement of said connecting member and projection of the carriage before said first drive member engages said driven means whereby said load, carriage, load support member and extension are shiftable from a fully retracted position to a position which allows them to rotate within a minimum swing radius.

4. The improvement of claim 3 wherein said driven means comprises: a. a drive plate attached to the extension, said plate defining said first slot; and b. a third pulley wheel positioned adjacent said drive plate to support said flexible connecting member and, as said first drive member passes around said third pulley wheel, to permit said first drive member to enter said first slot.

5. The improvement of claim 4 wherein said first, second and third pulley wheels are sprocket wheels and said flexible connecting member is a sprocket chain.

6. The improvement of claim 4 wherein said drive plate defines a curvilinear second slot, for passage therein of said drive member, said second slot being in open communication with said first slot.

7. The improvement of claim 6 including a third slot offset from, but in open communication with, said second slot and a second drive member fixedly attached to said flexible connecting member and positioned adjacent said first drive member to be received in said third slot when said first drive member is received in said first slot and said second drive member passes around said third pulley wheel.

8. The improvement of claim 7 wherein said third slot has a configuration which permits it to maintain engagement with said second drive member, while the carriage is being retracted, until said second drive member passes over said third pulley wheel, disengaging from said third slot and reentering said second slot.