US3039636A - Pusher attachment for lift trucks - Google Patents

Description

June 19, 1962 D. R. HOYT ETAL 3,039,636

PUSHER ATTACHMENT FOR LIFT TRUCKS Filed Dec. 12, 1958 3 Sheets-Sheet 1 I. o 6 m 0 LI. N g Q m P8 0 9 R5 W l H v 0 T a;

INVENTORS.

DERYL. R. HOYT DARYL W. STEVENS ATTY.

June 19, 1962 D. R. HOYT ETAL 3,039,636

PUSHER ATTACHMENT FOR LIFT TRUCKS Filed Dec. 12, 1958 s Sheets-Sheet 2 FICB. 2

INVENTORS. 'DERYL R. HOYT DARYL W. STEVENS ATTY.

June 19, 1962 D. R. HOYT ETAL 3,039,636

PUSHER ATTACHMENT FOR LIFT TRUCKS Filed Dec. 12, 1958 3 Sheets-Sheet 3 INVENTORS. DERYL R. HOYT DARYL W. STEVENS ATTY.

United States The present invention relates generally to attachments for industrial lift trucks, and specifically to improved pusher means which may be employed for selectively discharging a load from such a truck.

Industrial lift trucks are extensively used in the handling of goods such as logs. The load supporting carriage of the conventional truck is provided with forks having horizontal forwardly extending load supporting portions upon which the logs are stacked for transportation; the load supporting carriage ordinarily is arranged for vertical movement on a mast structure which is tiltable forwardly through a small angle. After the logs have been transported to the place of deposit, the logs heretofore have usually been rolled off the forks by tilting the mast forwardly, or by placing the logs on dunnage and withdrawing the forks. In the case of logs having a flat side, or in unloading logs where dunnage is not available, or in placing logs on top of othen logs, the forward tilt available may not be adequate to insuredischarge of the logs, and attempts to withdraw the forks from under a log may pull over the whole pile or otherwise be dangerous to workmen engaged in unloading and piling the logs;

US. Patent No. 2,742,167 to R. A. Brudi, dated April 17, 1956, discloses a remotely operable pusher device for use with industrial lift trucks which is employed for discharging a load such as logs from the forks of a lift truck, and constitutes an important step forward in the log handling art. The device of the patent utilizes pusher arms of telescopic construction in conjunction with actuating links which serve to urge the lower sections of the pusher arms downwardly relative to the upper section as the pusher arms are swung away from the load supporting carriage, whereby to enable the lower ends of the lower sections to follow a path which is approximately parallel to the load supporting means, such as forks, during outward swinging actuation thereof by hydraulic motor means.

By use of such construction logs can be pushed from the ends of the forks while utilizing a pusher structure which is retractable, when not in use, to a non-interfering position relative to the carriage and forks so that the latter may be used for handling loads other than logs without any loss in load-carrying capacity.

Despite the significance of the advance over the prior art of Brudis invention, however, certain disadvantages have been encountered in practice which it is the primary purpose of the present invention to overcome. A source of difficulty has developed in the use of the aforementioned telescopic pusher arms in that, under heavy loads, the arms tend to bend one relative to the other thereby causing a binding of the arms which either places undue strain on the mating parts as extension forces continue to be applied, or even causes the mechanism to fail to operate at certain times. In addition, the patented device depends upon hydraulic motor applied torque to effect operation of the arms. Utilization of a torque transmitted force within the space envelope available requires, at times, the application of extremely high forces in order to operate the mechanism.

It is a primary object of the present invention to provide an improved industrial truck attachment of the type contemplated which eliminates the disadvantages of prior devices while retaining the advantages thereof.

It is another object of the present invention to provide improved pusher means wherein the lower end thereof atent is confined to a path of travel which is approximately parallel to the load supporting means during outward swinging movement thereof so that certain kinds of loads may be discharged from the load supporting means.

It is a further object of the present invention to provide an improved pusher attachment which is simple in construction, extremely efficient in operation, and economical to manufacture.

The structure, which enables the foregoing objects to be attained comprises generally a scissors-like linkage including a main pusher arm and a link or radius rod which is connected to the arm intermediate its ends and to support means for the device, and a second link or radius rod connected to the top portion of the arm and to said support means at locations above the first link. Motor means is provided which directs a pushing force on the scissors-like linkage such that the pusher arm moves outwardly of the load supporting means in a path of travel which is approximately parallel thereto. The geometry of the interconnected parts which comprise the attachment device is, of course, of significance in enabling the pusher arm to follow the aforesaid path of travel.

Now, in order to acquaint those skilled in the art with the manner of constructing and using pusher means in accordance with the principles of our present invention, we shall describe in connection with the accompanying drawings a preferred embodiment of our present invention.

In the drawings:

FIGURE 1 is a side elevational view of an industrial truck with the improved pusher means of the present invention arranged at the forward end thereof in extended position;

FIGURE 2 is a detailed side elevational view of the pusher attachment wherein various attitudes of extension thereof are illustrated in phantom lines, the retracted position thereof being shown in full lines;

FIGURE 3 is a front elevational view of the attachmerit as shown in retracted position in FIG. 2, but with the fork tines removed; and

FIGURE 4 is a partial view of the machine as shown in FIG. 1, but with the pusher attachment in retracted position.

Referring now to the drawings, there is indicated generally by the reference numeral 10 an industrial truck which has a main frame and body portion 12 supported on pairs of wheels 14 and 16 (one of each pair being shown). The main frame, at its forward end, supports a vertically disposed mast structure 18. The mast in turn carries a load supporting carriage defined by a pair of vertically spaced, transversely extending beam members 20 and 22 which are connected together by a pair of transversely spaced, vertically extending channel members 32 and to the mast structure by transversely spaced bracket means which is shown partially at numeral 24 (FIGS. 2 and 3). Carriage member 22 carries a pair of transversely spaced and forwardly extending fork tines 26 (only one of which is shown) which are pivotally connected at pivot means 28 to a generally channel shaped transverse connecting beam 30 (FIG. 2) which is supported from the beam 22. The upstanding leg of each fork is formed to rest against the forward surface of beam 20 which reacts against the load supported by the fork (FIG. 2). It will be understood that the carriage and forks thereon are movable vertically up and down mast 18 in a conventional manner by hydraulic or other suitable means to raise and lower a load on the forks.

In the bottom portion of each channel beam 32 is secured a downwardly depending member 34 having an opening therethrough in which is mounted a pivot shaft 36. An upwardly and rearwardly extending bifurcated bracket member 38 is secured to the upper end of each member 32 and supports a transverse pivot shaft 40 therein to which is pivotally connected an upstanding link member or radius rod 42 which is also pivotally connected at its opposite end to a transversely extending shaft member 44. The shaft member 44 extends transversely outward of each link 42 and at each of its opposite ends supports for pivotal movement a mounting block 46 from which depends an elongated downwardly extending main pusher arm 48. A second main link member or radius rod 50 is pivotally secured at its one end to each pusher arm 48 intermediate the ends thereof, and at its opposite end to pivot shaft 36. Link members 50 are mounted inwardly of pusher arms 48 and outwardly of link members 42, the upper ends thereof being pivotally mounted upon a connecting transverse shaft member 52 which extends through the pusher arms. Inwardly of each link member 42 is mounted a hydraulic cylinder and piston assembly 53, which is secured for pivotal movement upon a trunnion 54 located at the upper end of a bracket means 56 which is secured at its lower end to beam 22. The piston rod of the hydraulic assembly is pivotally connected to a bracket means 58 which is secured to transverse shaft 52.

When the hydraulic motors 53 are pressurized to cause extension thereof by remote control means, not shown, located in the drivers compartment, the various parts of the pusher device will be actuated from a position of full retraction, as shown in FIGS. 3 and 4 and in the full lines of FIG. 2, to an extended position as shown in FIG. 1 and in phantom view in FIG. 2. When the pusher device is in a fully retracted position it will be observed that the entire assemblage of parts lies rearwardly of the plane of the forward face of the forks 26 Where it will not interfere with the engagement of loads other than logs, such as rectangular loads which may be stacked in abutment with the vertical legs of the forks rather than in a less stable position forwardly thereof. Thus, although the attachment is particularly adapted for handling cylindrical objects such as logs, it neither limits the truck solely to such use nor decreases its caapcity in handling other types of loads.

It will be further observed that as the attachment is caused to extend from the retracted position thereof the paths followed by the lower ends of the pusher arms 48 are moved outwardly of the forks with the lower ends thereof maintained closely adjacent to the forks irrespective of the pivotal position of the pusher arms, as best seen in FIG. 2. The paths followed by the lower ends of the members 48 are actually slightly serpentine; however, for all practical purposes these paths are approximately parallel to the horizontal portions of the forks. This result is eifected by the manner in which link members 42 and 50 are each pivotally interconnected with the pusher arms and the carriage portion of the attachment. It will be observed that a scissorslike action is effected between links 50 and pusher arms 48 as the hydraulic motors exert a direct pushing force upon the pivot shaft 52 which interconnects said links and arms. Shaft 52 moves in a circular are about the axis of pivot shafts 36, the curvature being fixed by the length of links 50 between the axes of shafts 36 and 52. At the same time pusher arms 48 are caused to be pivoted in a counterclockwise direction by link members 42 as the latter define circular arcs during movement thereof having radius equal to the distance between the axes of pivot shafts 40 and 44. The relationship between the length of pairs of link members 42 and 50, and the distances between the axes of pivot shafts 36 and 40 on the one hand and between pivot shafts 52 and 44 on the other is such that a forwardly or rearwardly directed force applied to shaft '52 effects movement of hte lower ends of the pusher arms in paths which are approximately parallel to the horizontal portions of the forks. The geometry of the attachment 4 device is fully illustrated in FIG. 2. Thus, the pusher arms 48 are enabled to push off of the tips of the forks loads such as small diameter logs.

It will be observed that considerable advantage is to be derived in the utilization of a direct pushing force applied to shaft 52 by the hydraulic motors 53 rather than utilization of an arrangement which necessitates the application of torque forces as applied, for example, to the crank arms of the attachment device of the aforementioned patent. A substantially greater effective force is derived in the use of the present invention, given hydraulic motor means of certain capacity, than in prior constructions. Also, the present structure tends to minimize the stress to which certain of the various parts are subjected.

Now, while we have shown and described what we believe to be a preferred embodiment of our present invention, it will be understood that various rearrange ments and modifications may be made therein without departing from the spirit and scope of our invention.

We claim:

1. For use with an industrial truck having a load supporting carriage, mechanism comprising first and second normally upright link means pivotably supported by the carriage in vertically spaced relation to each other, said second link means being longer than said first link means, a pusher means pivotably supported from the upper ends of said first and second link means, the pivotal connection of the first link means to the pusher means being spaced longitudinally of and above the connection of the second link means to be pusher means, the pivotal connection of each link means to the pusher means being located above its respective connection to the carriage means, and motor means operatively connected to the pusher means for actuating same in swinging movement outwardly of the carriage.

2. For use with an industrial truck having a load supporting carriage, mechanism comprising first link means, first pivot means connecting said link means to the carriage, second link means, second pivot means connecting the latter link means to the carriage at a location above said first pivot means, pusher means, third pivot means connecting said first link means to said pusher means intermediate the ends thereof, fourth pivot means conmeeting said second link means to said pusher means above said third pivot means, said first link means being longer than said second link means, and motor means operatively connected to the pusher means for swinging same outwardly of the carriage with outward swinging movement of the first and second link means in the same rotational direction.

3. A mechanism as claimed in claim 2 wherein the motor means is operatively connected to the pusher means at a location which is adjacent the third pivot means, said motor means being adapted thereby to effect outward swinging movement of the pusher means by direct application of a pushing force thereon.

4. For use with an industrial truck having a load supporting carriage and horizontal load supporting means extending forwardly therefrom, mechanism comprising pusher means operatively connected to the carriage and actuatable outwardly therefrom such that the lower end thereof can push a load from the load supporting means, said operative connection including first and second swingable link means pivotably connected in vertically spaced relation to the carriage and to the pusher means, said first link means comprising the lower link which is of greater length than the second upper link means, said first and second link means being cooperable to swing dilferent portions of the pusher arm along arcs of diflferent radii during outward swinging movement thereof, and motor means for actuating the pusher arm outwardly of the load supporting means, the lower end of the pusher arm being constrained by said first and second link means to move in a path which is approximately parallel to the load supporting means.

5. For use with an industrial truck having a load supporting carriage and horizontal load supporting means extending forwardly therefrom, mechanism comprising a short link pivotally secured adjacent its one end to an upper portion of the carriage, a long link pivotally secured adjacent its one end to a lower portion of the carriage, pusher means pivotally secured to the opposite ends of both said short and long links, said latter pivotal connections being displaced longitudinally of each other on said pusher means, and motor means connected to the pusher means for actuating same outwardly of said carriage with said short and long links, the lower end of said pusher means following a path which is approximately parallel to the load supporting means.

6. A mechanism as claimed in claim 5 wherein said motor means comprises a hydraulic cylinder and piston assembly supported by the carriage and connected at its operating end adjacent said third pivot means for applying a pushing force thereto which actuates the pusher arm outwardly of the load supporting means.

7. For use with an industrial truck having a load supporting carriage, mechanism comprising first and second means pivotally connected to the carriage in vertically displaced relation one to the other, pusher means pivotally connected to both the first and second means at the ends thereof opposite the pivotal connections to the carriage, and actuating means operatively connected to the pusher means for actuating same in swinging movement outwardly of the carriage, said first means tending to actuate the lower end of said pusher means downwardly during outward swinging movement thereof, said second means tending to actuate the lower end of said pusher means upwardly during outward swinging movement thereof, and said first and second means being combined with the pusher means in such a manner that said downward and upward movement tendencies of the lower end of the pusher means is essentially neutralized so that said pusher means moves in a path which is approximately parallel to the ground during outward swinging movement thereof.

8. For use with an industrial truck having a load supporting carriage and horizontal load supporting means extending forwardly therefrom, load push-01f attachment means comprising a pair of normally upright upper and lower radius rods pivotally supported by the carriage in vertically spaced relation, the upper radius rod being pivotally mounted adjacent its lower end to an upper portion of the carriage, the lower radius rod being pivotally mounted adjacent its lower end to a lower portion of the carriage transversely outwardly of and in partial overlapping relation to the upper radius rod, pusher means depending downwardly from and pivotally mounted upon the upper ends of both the upper and lower radius rods, and hydraulic motor means pivotably connected to the upper end of the lower radius rod, extension of said motor means effecting outward swinging movement of the pusher means with radial movement of said upper and lower radius rods such that the lower end of the pusher means moves in a path which is approximately parallel to the load supporting means.

9. An attachment as claimed in claim 8 wherein the upper radius rod means is of shorter length than the lower radius rod means and the pivotal connection of the upper radius rod means with said pusher means is displaced above the pivotal connection of the lower radius rod means with said pusher means.

'10. An attachment as claimed in claim 8 wherein said pusher means is displaced transversely outwardly of said lower radius rod means and in overlapping relation thereto.

11. An attachment as claimed in claim 10 wherein said upper radius rod means comprises a pair of transversely spaced link members, said lower radius rod means comprises a pair of transversely spaced link members, and said pusher means comprises a pair of transversely spaced bar members.

References Cited in the file of this patent UNITED STATES PATENTS 2,601,931 Dunham et al July 1, 1952 2,742,167 Brudi Apr. 17, 1956

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