US3574383A

US3574383A - Fork lift

Info

Publication number: US3574383A
Application number: US854027A
Authority: US
Inventors: Adrian Robert Frater
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-08-26
Filing date: 1969-08-26
Publication date: 1971-04-13
Anticipated expiration: 1988-04-13

Abstract

A fork lift comprising a backing frame, for attachment to a lifting and lowering mechanism, a shock-absorbing suspension system mounted on the backing frame, and a fork suspended from the suspension system. By virtue of the provision of the suspension system the fork lift is capable of carrying a fragile or sensitive load over uneven ground. The fork lift may be attachable to a parallelogram four-point linkage lifting arrangement at the rear end of a tractor.

Description

United States Patent 1111 3,574,383

[72] Inventor Adrian Robert Frater [56] References Cited D Zoete lnval, Zuider Pearl, p UNITED STATES PATENTS l N gg a f 2,415,515 2/1947 McOscar 214/131 2 Q Y A 1969 2,530,375 11/1950 Cartwright 214/655 1 P e d 2,578,016 12/1951 Rike 214/655X [451 F E 2,989,201 6/1961 Hansen... 214/652 [32] Priority Apr. 19, 1966 [33] Republic of South Africa FOREIGN PATENTS 31] /2278 1,462,379 10/1965 France 214/652 Continuation of application Ser. No. Prima E C H b ry xammer arve orns 628,433 1967' now abandmed AttorneyWenderoth, Lini i & Ponack [54] FORK LIFT 6clalms4nrawmg ABSTRACT: A fork lift comprising a backing frame, for [52] U.S.Cl. 294/67, attachment to a lifting and lowering mechanism, a shock- 214/652 absorbing suspension system mounted on the backing frame, [51] Int. Cl B66c 1/24, and a fork suspended from the suspension system. By virtue of B66f 9/12 the provision of the suspension system the fork lift is capable [50] Field of Search 294/671, of carrying a fragile or sensitive load over uneven ground. The 671 (A&B),67, 82, 88, 87,214/652, 655,739, fork lift may be attachable to a parallelogram four-point 731, 750, 131 linkage lifting arrangement at the rear end of a tractor.

I as 12 1 FORK LIFT This application is a continuation of Ser. No. 628,433 filed Apr. 4, 1967, and now abandoned.

BACKGROUND OF THE INVENTION This invention concerns a fork lift of the type suitable for engaging with a pallet.

Fork lifts known to the applicant include various industrial types of fork lift in which the fork is guided vertically. Fork lifts mounted on the rear end of a tractor are shown in British Pat. specification Nos. 824,241, and 981,602. Where a known fork lift is, for instance, mounted on a tractor, particularly when mounted on the rear end of a tractor where the wheels are relatively far apart and apt to be lifted independently of one another over uneven ground, the fork is displaced to one or other side with the tractor. Furthermore, the fork will bump upwards and downwardly with the tractor. Thus, a load on the fork may receive sideward and upward and downward shock when uneven ground is traversed at any speed.

SUMMARY OF THE INVENTION The invention provides a fork lift comprising a backing frame for attachment to a lifting and lowering mechanism, a shock-absorbing suspension system mounted on the backing frame, and a fork freely suspended from the shock-absorbing suspension system forwardly over one side of the backing frame.

The suspension system may include a leaf spring mounted to afford resilience in a vertical plane, and the fork may be secured to the leaf spring inwardly of the ends of the leaf spring.

The fork may include two fork elements which may each be made up of an upright member and a load-receiving arm extending horizontally forwardly from the lower end of the upright member. The fork elements may be mounted at the upper ends of the upright members in laterally spaced relationship on a crossbar which is in turn secured to the leaf spring, such as by means of a central clamp on the crossbar to clamp onto the spring at a single central position thereof. The fork may thus be capable of swinging sidewardly about the clamp against the resilience of the spring element. The fork elements may be pivotally mounted on the crossbar to allow the fork elementsto pivot forwardly outwardly away from the backing frame. In this manner, for instance when the fork lift is mounted on the rear end of a tractor, the fork elements may swing outwardly away from the backing frame when the tractor climbs a hill and the load arms may thus maintain a substantially horizontal attitude.

The backing frame has a bracket converging to an apex rearwardly away from the backing frame, and the suspension system further includes location bars connected to the apex of the bracket and towards the outer ends of the crossbar. The location bars take up a certain amount of load on the fork, and also serve to locate the fork in position over the one side of the backing frame.

In the construction of the fork lift in which the fork elements are pivotally mounted on the crossbar, the backing frame may provide a stop to limit pivotal displacement of the fork elements rearwardly inwardly towards the backing frame, and the backing frame may further provide a friction face to frictionally control displacement of the fork sidewardly across the one side of the backing frame. A sideward rocking effect of the fork which may take place may thus be frictionally dampened.

An object of the invention is to provide a fork lift capable of carrying fragile or sensitive loads over uneven ground. For instance, the fork lift may be suitable for carrying fruit in boxes from vines or orchards to a central point, such as a warehouse. In fork lifts known to applicant, fruit would be likely to be bruised or damaged when conveyed over uneven ground at any speed. The fork lift may be particularly adapted for mounting on the rear end of a tractor, and the entire fork lift, not only the fork, may be lifted by means of two hydraulically operable power arms at the rear end of a tractor. The fork lift may be guided in a substantially vertical plane by guide arms each defining a parallelogram linkage arrangement with one of the power arms. An object of the invention is the provision of a fork lift for conveying a load rather than for lifting a load.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show, by way of example only, a particular embodiment of the invention in which:

FIG. 1 shows a side elevation of a fork lift;

FIG. 2 shows a rear elevation of the fork lift;

FIG. 3 shows a fragmentary front elevation of the fork lift; and

FIG. 4 shows a plan elevation of the fork lift.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the fork lift has an upright rectangular backing frame 10, and a bracket 12 converging to an apex rearwardly and upwardly away from the backing frame. A shock-absorbing suspension system, generally referred to by reference numeral 14, is provided over the backing frame 10, and a fork 16 is freely suspended from the suspension system forwardly over one side of the backing frame.

The rectangular backing frame 10 is made up of channel members which, apart from the bottom channel member 18, all face inwardly (see FIG. 2). The bottom channel member faces rearwardly outwardly, and has gusset lugs 22 welded into the channel for connection to two lower hydraulically operable power arms 24 (see FIG. 1) at the rear end of a tractor (not shown). The top channel member 26 has lugs 28 welded to its rearward side for connection to two upper guide arms 30 each defining a parallel linkage arrangement with one of the power arms, so that the fork lift will be guided vertically (see FIG. 1). The bracket 12 is also made up of channel members which converge to an apex where they are welded to an angle section 32.

The shock-absorbing suspension system 14 includes a leaf spring 34 mounted across the top channel member 26 by means of links 36 pivotally displaceably mounted in sleeves 38 secured to the top channel member 26. The leaf spring is mounted to afford resilience in a vertical plane.

The fork has the usual two-spaced fork elements, but these each comprise an upright member 40 and a load-receiving arm 42 extending horizontally forwardly from the upright member. The fork elements are mounted on an axle 44 at the upper ends of the upright members 40, and the axle is in turn pivotally mounted to a crossbar 46 of angle section. End mountings 48 and intermediate mountings 50 are spaced along the length of the crossbar for receiving the axle 44 pivotally through aligned holes in the mountings. Stop collars 52 are secured to the axle 44 to maintain the fork elements in their laterally spaced relationship towards the outer ends of the axle (see FIG. 3).

The crossbar 46 has a central clamp 54 secured to it for clamping the crossbar onto the leaf spring 34 at a single central position. The crossbar further has upwardly projecting lugs 56, towards its outer ends and the suspension system further includes location bars 58 connected to the lugs and to the angle section 32 at the apex of the bracket 12. Still further, the crossbar has spacer elements 60 projecting rearwardly from the crossbar to abut against the forward edge of the leaf spring 34 and thereby assist in maintaining the fork in position parallel to the backing frame 10.

In the construction of the fork lift shown in the drawings, it will be clear that the fork will be capable of being displaced vertically against the resilience of the leaf spring 34, although such displacement will be limited by the location bars 58. Similarly, the fork will be capable of displacement sidewardly across the one side of the backing frame, but such displacement will again be limited by the location bars. The

rearward sides ofthe upright members has spacer blocks 62 fixed to them to abut against the bottom channel member 20, and the backing frame accordingly provides a friction face which will frictionally control or dampen displacement of the fork sidewardly across the backing frame.

The embodiment described provides a fork lift such as may be attached to a tractor for conveying sensitive or fragile loads over uneven ground. The shock-absorbing suspension system operative between the fork and the backing frame serves to reduce shock which may otherwise be received by a load on the fork.

Iclaim:

1. In a fork lift vehicle having a lifting mechanism, the improvement comprising a lift fork having a backing frame for being raised and lowered by said lifting mechanism, a support member, a shock-absorbing suspension system on the backing frame resiliently supporting said support member and including means to support said support member in a manner to permit lateral sway, said fork having at least one suspension member depending from said support member and having a transverse tine member projecting therefrom, said fork being resiliently suspended for vertical and lateral resiliency by means of said shock-absorbing suspension system which, when the lift fork is coupled to the lifting mechanism, is interposed between said suspension member 'of the fork and said lifting mechanism to provide continuous resilient support to a full load on the fork, and said suspension member depending pivotally from said support member about pivot means having a transverse axis for movement relative to said backing frame, thereby permitting the tine of the fork to remain substantially level, even when the backing frame tilts.

2. A lift fork as defined in claim 1, wherein the backing frame includes a bracket converging to an apex rearwardly, and wherein the shock-absorbing suspension system comprises a crossbar, a leaf spring secured to said crossbar, and location bars connected to said apex of the bracket and diverging towards the outer ends of the crossbar to take up a certain amount of load on said fork and to locate the fork in a position over one side of said backing frame.

3. A fork lift which comprises a backing frame adapted for being raised and lowered, a support member resiliently supported by a leaf spring mounted on the backing frame in a manner to permit lateral sway, and a fork comprising at least one suspension member and a tine projecting transversely thereto, the suspension member being hung pivotally from the support member, about a transverse axis for movement relative to said backing frame, thereby permitting the tine of the fork to remain substantially level even when the backing frame tilts.

4. A fork lift which comprises a backing frame for being raised and lowered; a support member resiliently supported by the backing frame in a manner to permit lateral sway; a fork comprising at least one suspension member and a tine projecting transversely thereto; the suspension member being hung pivotally from the support member about a transverse axis for movement relative to said backing frame, thereby permitting the tine of the fork to remain substantially level, even when the backing frame tilts; and wherein the backing frame has attaching means for attachment to a hydraulic three-point lift of a tractor vehicle with which it is associable.

5. A fork lift which comprises a backing frame for being raised and lowered; a support member resiliently supported by the backing frame in a manner to pemiit lateral sway; and a fork comprising two suspension members and a tine projecting transversely from each; each suspension member being hung pivotally from the support member about a transverse axis for movement relative to said backing frame, thereby pemtitting the tines of the fork to remain substantially level, even when the backing frame tilts; and wherein said suspension members are laterally spaced and suspended independently of each other.

6. A fork lift which comprises a backing frame for being raised and lowered; a support member resiliently supported by to permit lateral sway; a for the backing frame in a manner comprising at least one suspension member and a tine projecting transversely thereto; the suspension member being hung pivotally from the support member about a transverse axis, thereby permitting the tine of the fork to remain substantially level, even when the backing frame tilts; said backing frame provides a stop to limit pivotal displacement of the fork inwardly towards the backing frame; and a friction face is provided on the backing frame to provide frictional damping to sideward rocking of the fork.

Claims

1. In a fork lift vehicle having a lifting mechanism, the improvement comprising a lift fork having a backing frame for being raised and lowered by said lifting mechanism, a support member, a shock-absorbing suspension system on the backing frame resiliently supporting said support member and including means to support said support member in a manner to permit lateral sway, said fork having at least one suspension member depending from said support member and having a transverse tine member projecting therefrom, said fork being resiliently suspended for vertical and lateral resiliency by means of said shock-absorbing suspension system which, when the lift fork is coupled to the lifting mechanism, is interposed between said suspension member of the fork and said lifting mechanism to provide continuous resilient support to a full load on the fork, and said suspension member depending pivotally from said support member about pivot means having a transverse axis for movement relative to said backing frame, thereby permitting the tine of the fork to remain substantially level, even when the backing frame tilts.

5. A fork lift which comprises a backing frame for being raised and lowered; a support member resiliently supported by the backing frame in a manner to permit lateral sway; and a fork comprising two suspension members and a tine projecting transversely from each; each suspension member being hung pivotally from the support member about a transverse axis for movement relative to said backing frame, thereby permitting the tines of the fork to remain substantially level, even when the backing frame tilts; and wherein said suspension members are laterally spaced and suspended independently of each other.

6. A fork lift which comprises a backing frame for being raised and lowered; a support member resiliently supported by the backing frame in a manner to permit lateral sway; a fork comprising at least one suspension member and a tine projecting transversely thereto; the suspension member being hung pivotally from the support member about a transverse axis, thereby permitting the tine of the fork to remain substantially level, even when the backing frame tilts; said backing frame provides a stop to limit pivotal displacement of the fork inwardly towards the backing frame; and a friction face is provided on the backing frame to provide frictional damping to sideward rocking of the fork.