WO2004014775A1

WO2004014775A1 - Method and apparatus for forklift fork extension

Info

Publication number: WO2004014775A1
Application number: PCT/US2002/025599
Authority: WO
Inventors: Chad Stone
Original assignee: Navy Island Plywood
Priority date: 2002-08-13
Filing date: 2002-08-13
Publication date: 2004-02-19
Also published as: AU2002327443A1

Abstract

A novel forklift extension apparatus and method is capable of being installed, locked, unlocked and uninstalled without manual intervention. The automatic locking and unlocking capability arises from the use of a cradle (10) which causes a pivoting stirrup to pivot downward when the extension device is placed in the cradle into an unlocked and open position. The forklift driver engages the extension sleeve and lifts the extension sleeve vertically out of the cradle. This causes the pivoting stirrup (8) to rotate upward to the locked and closed position. The pivoting stirrup rotation to the locked, closed position is a gravitationally assisted operation. The extension sleeve is unlocked automatically by lowering the forks back onto the cradle. Also disclosed is a sideway pivoting stirrup (61) and a fixed stirrup (60), wich operates with an incline cradle (54).

Description

METHOD AND APPARATUS FOR FORKLIFT FORK EXTENSION

FIELD OF THE INVENTION

This invention relates generally to extending the length of standard forks attached to forklifts.

BACKGROUND OF THE PRESENT INVENTION

Forklifts are equipped with standard length forks. In certain industries, it is conventional to use adaptors to extend the length of the forks to allow for safe handling of large size palletized or other loads. The increased fork length adds stability and minimizes the risk of damage to the material as well as injury to the forklift operator as well as those working in the general area.

Currently, fork extension devices required manual intervention to secure the extension device to the fork. This is accomplished by a fork extension sleeve that is manually slipped over the fork and then bolted on, usually behind the heel of the fork. The process is then manually reversed when the sleeve is removed from the fork. Though the intended purpose of added stability and risk minimization is accomplished, the process requires manual intervention.

SUMMARY OF THE INVENTION A principal object and advantage of the present invention is to provide a novel apparatus and method for extending standard forklift forks. Another object is to provide a forklift fork extension sleeve that is attached to the forks without the need for manual assistance. A final objective is to provide a forklift extension sleeve that automatically locks in place without the need for the forklift driver or other individual to manually perform the locking function, thus reducing assembly time and operator fatigue. The present invention discloses a forklift extension apparatus that isrcapable of ^lb"eirιg locked and unlocked without the need for manual intervention. In the preferred embodiment, this automatic locking and unlocking capability arises from the use of a cradle which causes a pivoting stirrup to pivot downward when the extension device is placed in the cradle. This is the unlocked, open position. The forklift driver then engages the extension sleeve with the forklift forks by driving the forks into the extension sleeve and begins to lift the extension sleeve vertically out of the cradle. This causes the pivoting stirrup to automatically rotate upward to the locked, closed position. The pivoting stirrup rotation to the locked, closed position is a gravitationally assisted operation and occurs automatically once the extension sleeve is lifted from the cradle. The extension sleeve is unlocked automatically by lowering the forks back onto the cradle. The cradle operates to cause the pivoting stirrup to rotate downward as the stirrup engages the sides of the cradle, unlocking the forklift forks and allowing the forklift driver to disengage the forks from the extension sleeves.

The foregoing objects of the invention will become apparent to those skilled in the art when the following detailed description of the invention is read in conjunction with the accompanying drawings and claims. Throughout the drawings, like numerals refer to similar or identical parts.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the extension sleeve installed on a forklift with the standard fork in phantom outline.

Figure 2 shows the extension sleeve on the cradle, with the pivoting stirrup biased in the open and unlocked position.

Figure 3 is a side view of the extension sleeve with the standard fork and fork heel in phantom outline and the pivoting stirrup in the locked and closed position around the fork heel. Figure 4 is a top view of the extension sleeve in the locked and closed position with the standard fork in phantom outline.

Figure 5 is a side view of the pivoting stirrup in the locked and closed position around the forklift heel, shown in phantom outline. Figure 6 is a side view of the extension sleeve resting in the cradle, the pivoting stirrup biased in the open and unlocked position and the forklift fork, shown in phantom outline, being disengaged from the extension sleeve.

Figure 7 is a side cross sectional view of the fork engaged in the extension sleeve with the pivoting stirrup in the closed and locked position around the fork heel. Figure 8 is a rear cross sectional view of the fork engaged in the extension sleeve with the pivoting stirrup in the closed and locked position around the fork heel and an end view of the cradle.

Figure 9 is an alternate embodiment showing the extension sleeve resting on an inclined plane and the rigid stirrup on the ground with the forks engaging the rigid stirrup. Figure 10 is a view of the bottom of the alternate embodiment shown in Figure 9.

Figure 11A shows an alternate embodiment for automatically locking and unlocking the device in the closed and locked position.

Figure 1 IB shows the alternate embodiment in the open and unlocked position. DETAILED DESCRIPTION OF THE INVENTION With reference to the accompanying figures, there is provided an extension sleeve (2) for forklifts (generally designated as 1) that is slipped over the forks (4), locked and unlocked without the need for manual assistance. Figure 1 depicts a side view of the extension sleeve (2) installed on the forklift (1). The standard forks (4) are shown in phantom outline and are received inside the extension sleeve (2). There is also shown a mechanism for locking the exxension sleeve (2) to the forks (4) by securing the sleeve (2) to the heel (6) of the forks (4). In the preferred embodiment, the locking mechanism is a pivoting stirrup (8).

Figure 2 shows the preferred sleeve (2) embodiment resting in a cradle (10). The sleeve (2) has a top surface (12), side surfaces (14) and an optional bottom surface (16) and is essentially hollow so that the forklift forks (4) can slip inside the sleeve (2). The cradle (10) is shown in Figure 2 may be comprised of two separate components, a front brace (18) and a rear brace (20). However, it is understood that an equivalent structure could be manufactured as a single unit. The front brace (18) is designed to receive and support the distal end (38) of the extension sleeve (2). The front brace (18) is comprised of two side members (22) and a front member (24). The side members are depicted as wedge-shaped because it provides for ease of entry into the cradle (10). However, it is understood that virtually any shape will suffice to support and receive the distal end (38) of the extension sleeve (2).

The rear brace (20) is shown in Figure 2 and comprises two wedge-shaped side members (22) and a base member (28) rigidly attached to the two side members (22). The rear brace (20) performs two functions. First, it receives and supports the proximal end (36) of the extension sleeve (2). Second, it engages the lower surface (34) of the U-shaped pivoting stirrup (8). The side members (30) of the pivoting stirrup (8) are rotatably attached to the side surfaces (14) of the extension sleeve (2) and a middle member (32) is connected to the two side members (30). As the proximal end (36) of the extension sleeve (2) is lowered onto the cradle (10), the wedge-shaped side members (26) engage the lower surface (34) of the pivoting stirrup's side members (30). As the extension sleeve (2) continues to be lowered onto the cradle (10), the pivoting stirrup (8) is caused to rotate in a downward fashion and, when the sleeve (2) rests on the cradle (10), the stirrup (8) is in the open and unlocked position. Figure 2 also shows an open lock stop (40) and a closed lock stop (42) disposed on the side surface (14) of the sleeve (2). The open lock stop (40) is located beneath the bottom surface (34) of the pivoting stirrup's side member (30). As shown in closer detail in Figure 3, the top surface (44) of the open lock stop (40) engages the bottom surface (34) of the pivoting stirrup to prevent the stirrup (8) from opening too far. The closed lock stop (42) is disposed above the pivoting stirrup (8). The bottom surface (46) of the closed lock stop (42) engages the top surface (48) of the pivoting stirrup (8) to prevent the pivoting stirrup (8) from unnecessary and unwanted movement during operation. The purpose of the open and closed lock stop devices is to provide for limited action rotation of the pivoting stirrup (8). It is understood by those skilled in the art that a variety of similar devices may accomplish the hinging function in the same or similar way as the open and closed lock stop devices.

Figures 3 and 5 are side views showing the forklift fork (4) engaged within the extension sleeve (2) and the pivoting stirrup (8) in the closed and locked position. The preferred embodiment provides for a notch (50) in at least one of the top surfaces of the side members pivoting stirrup (52) which, when closed and locked, engages the bottom (46) surface of the closed lock stop (42). Figure 4 depicts the same configuration in a top view with the forklift fork (4) shown in phantom outline. Figure 7 is a cross-sectional side view showing the fork (4) engaged in the extension sleeve (2) and the pivoting stirrup (8) in the closed and locked position. Figure 6 is a side view of the sleeve (2) at rest in the cradle (10), with the pivoting stirrup (8) being held biased open and unlocked position by the side members (26) of the rear brace (20). The forklift fork (4), shown in phantom outline is depicted as partially engaged within the sleeve (2). Figure 8 is a rear view of the cradle (10) with the fork (4) engaged and locked within the sleeve (2) shown in cross section and demonstrates the relationship between the extension sleeve (2), the side members (26) of the rear brace (26) and the iloting stirrup (18). The extension sleeve (2) rests between the side members (26) while the top surface (52) of the side members (30) engages the bottom surface (34) of the side member (30) of the pivoting stirrup, causing the stirrup (8) to rotate downward and into the open and unlocked position. Operation of the preferred embodiment may now be described. The extension sleeve

(2) is placed on the cradle (10), causing the bottom surface (34) of the side members (30) of the pivoting stirrup (8) to engage the side members (26) on the rear brace (20). This results in the pivoting stirrup (8) being held biased in the open and unlocked position. The front brace (18) of the cradle (10) receives and supports the distal end (38) of the extension sleeve (2). The forklift driver next fully inserts the forks (4) inside the extension sleeves (2) and begins to raise the forks (4) and the extension sleeves (2). The vertical movement of the extension sleeves (2) is accompanied by a concomitant rotation of the pivoting stirrup (8). The pivoting stirrup (8) is designed so that the resting bias is in the closed and locked position. Removing the apparatus from the cradle (10) results in a gravitionally assisted rotation of the pivoting stirrup (8) to the closed and locked position with the pivoting stirrup (8) securing the extension sleeve (2) to the fork heel (6). The notch (50) disposed on at least one of the top surfaces of the side members pivoting stirrup (8) engages the closed lock stop (42) to prevent unwanted and unnecessary movement by the stirrup (8) during operation.

When it is desired to remove the extension sleeves (2), the forklift operator lowers the extension sleeves (2) back onto the cradle (10). The bottom surfaces of the side members (34) of the pivoting stirrup (8) engage the rear brace side members (26) as the extension sleeve (2) settles into the cradle (10). The pivoting stirrup (8) is then held biased in the open and unlocked position. The bottom surface of the side members of the pivoting stirrup (34) also engage the top surface of the open lock stop (44) to prevent the stirrup (8) from rotating ιυυ far in the open direction. The driver then places the forklift (1) in reverse and disengages the forks (4) from the extension sleeve (2).

Figure 9 depicts an alternate embodiment for the apparatus. The extension member (53) is shown resting on an inclined plane or ramp (54) with the stirrup (8) resting on the ground. Figure 10 indicates that in this embodiment, there is no bottom surface on the extension member, only side surfaces (56) and a top surface (58). Another difference in this embodiment as compared with the preferred device is that here the stirrup (60) is rigidly attached to the side surfaces (56) of the extension member (53).

To engage the alternate extension member (53), the forklift operator moves forward, slipping the forks (4) through the stirrup (60) until the fork heel (6) engages the stirrup (60). The operator then moves in reverse and tilts the forks (4) vertically to allow the forks (4) to engage the hollow portion of the extension member (55). The stirrup (60) remains engaged around the fork heel (6), securing the extension member (53) to the fork (4). When it is desired to disengage this alternate sleeve member (53), the operator engages the extension member (53) with the lower portion of the ramp (54) allowing the extension member (53) to slide up the ramp (54). When the extension member (53) rests on the ramp (54), the operator reverses the forklift (1) and disengages the forks (4) from the stirrup (60).

Figures 11A and 1 IB depict an alternate automatic locking and unlocking mechanism. Referring to Fig. 11 A, this embodiment, as in the preferred embodiment, the extension sleeve (2) has side surfaces (14) and top (12) and bottom (16) surfaces. The sleeve (2) is essentially hollow as in the preferred embodiment. The pivoting stirrup, generally designated as (61) in this embodiment, comprises a horizontally rotating locking and unlocking mechanism. The rigid side member (62) is shown fixed to the side surface (14) of the extension sleeve (2). The rigid side member (62) has an aperture (66) disposed on its front portion (64). A pivoting side member (68) is shown hingedly attached (70) to the sleeve side surface (14) opposite that to which the rigid side member (62) is attached. A tab (71) is fixedly attached to the pivoting side member (68). The pivoting side member (68) and the tab (71) hingedly rotate as one unit with respect to the extension sleeve (2). One end (76) of a spring (74) is attached to the side surface of the sleeve (14) to which the pivoting side member (68) is attached. The other end (78) of the spring (74) is attached to the interior side surface of the pivoting side member (72). The spring (74) is biased so that it pulls the pivoting side member (68) toward the extension sleeve (2). A transverse bar (80) is rigidly attached to the front portion (64) of the interior side surface (72) of the pivoting side member (68). Finally, one side member (26) of the cradle's rear brace (20) is shown in Figure 10 and is the same as in the preferred embodiment. The side member (26) is wedge-shaped in this embodiment, as in the preferred embodiment, to allow engagement of the tab (71) as the extension sleeve (2) is lowered into the cradle (10). Engagement of the tab (71) by the side member (26) causes the pivoting side member (68) to rotate out away from the side surface (14) of the extension sleeve (2). The transverse bar (80) is then disengaged from the rigid member aperture (66) as the pivoting side member (68) rotates outward. This allows the locking mechanism to be in the open and unlocked position when the sleeve (2) is cradled.

Following insertion of the forklift forks (4) into the cradled extension sleeve (2) in the manner previously described with regard to the preferred embodiment, the operator lifts the sleeve (2) from the cradle (10). Removing the sleeve (2) from the cradle (10) causes the tab (71) to disengage from the side member (26) of the cradle (10) resulting in the spring (74) rotating the pivoting side member (68) toward the extension sleeve (2) and reengaging the transverse bar (80) in the rigid side member aperture (66). This is the closed and locked position.

The above specification describes certain preferred embodiments of this invention. This specification is in no way intended to limit the scope of the claims. Other modifications, nterations, or substitutions may now suggest themselves to those skilled in the art, all ot which are within the spirit and scope of the present invention. It is therefore intended that the present invention be limited only by the scope of the attached claims below:

Claims

WHAT IS CLAIMED IS:

CLAIMS 1. An apparatus for extending standard forklift forks, the apparatus comprising: an extension sleeve with a distal and a proximal end, top, bottom and side surfaces, said extension sleeve being essentially hollow and said proximal end being capable of slidably receiving a standard forklift fork without manual intervention; and a means for automatically locking and unlocking said extension sleeve in place.

2. The apparatus of Claim 1, wherein said means for automatically locking and unlocking said extension sleeve is comprised of a pivoting stirrup, said stirrup pivoting in the vertical plane.

3. The apparatus of Claim 1, wherein said means for automatically locking and unlocking said extension sleeve is comprised of a pivoting stirrup, said stirrup pivoting in the horizontal plane.

4. The apparatus of Claim 1, wherein said means for automatically locking and unlocking said extension sleeve is comprised of: a pivoting stirrup, said stirrup having a U-shaped profile comprised of two side members and a middle member, said side members being rotatably connected to said side surfaces of said extension sleeve, said side members further having a top surface and a bottom surface; and

wherein said extension sleeve further comprises an open lock stop and a closed lock stop, said open lock stop having a top and bottom surface and said closed lock stop having a top and bottom surface, wherein said pivoting stirrup is in the open and unlocked position when said bottom surface of said pivoting stirrup engages said top surface of said open lock stop and said pivoting stirrup is closed and locked when said top surface of said pivoting stirrup engages said bottom surface of said closed lock stop.

5. The apparatus of Claim 4 wherein at least one of said side members includes a notch in said top surface of said side member, said notch engaging said the bottom surface of said closed lock stop when said pivoting stirrup is in the closed and locked position.

6. The apparatus of Claim 4 further comprising a cradle for biasing said pivoting stirrup in the open and unlocked position when said extension sleeve is resting in said cradle and for receivably supporting said apparatus.

7. The apparatus of Claim 6 wherein said cradle is comprised of forward and rear braces; said rear brace having a base member and two side members, said base member being fixedly attached to said side members, said side members receivably supporting said proximal end of said extension sleeve, said side members further engaging said bottom surfaces of said side members of said pivoting stirrup as extension sleeve is lowered into said cradle, causing said pivoting stirrup to rotate downward into the open and unlocked position; and said forward brace having a base member, two side members and a front member, said forward brace receivably supporting said distal end of said extension sleeve.

8. An apparatus for extending standard forklift forks, the apparatus comprising: an extension member with a distal and a proximal end, a top surface and side surfaces, said extension sleeve being capable of receiving the forklift forks without manual intervention; and a stirrup, said stirrup being fixedly attached to said proximal end of said extension sleeve, said stirrup automatically locking said extension member into place when said extension member engages the forks.

9. The apparatus of Claim 8 further comprising

an inclined plane, said plane capable of supporting said extension sleeve such that said stirrup rests on the ground, said plane further configured to allow the engagement and disengagement of the forklift forks with the stirrup without manual intervention.

10. The apparatus of Claim 2, the apparatus comprising:

an extension sleeve with a distal and a proximal end and side surfaces, said extension sleeve being essentially hollow and said proximal end being capable of receiving a standard forklift fork; and

said pivoting stirrup further comprising:

a side member fixedly attached to one said side surface of said proximal end of said extension sleeve, said side member further having a front portion and an aperture disposed on said front portion;

a pivoting side member, said pivoting side member having a front portion and an interior side surface, said rear portion of pivoting side member being hingedly attached to the second said side surface of said proximal end of said extension sleeve, said pivoting side member having a transverse locking bar fixedly attached to said front portion of said pivoting side member; and

a biasing spring, said spring having two attachment ends, one said end being fixedly attached to said pivoting side member and the second said end of said spring being fixedly attached to said side surface of said extension sleeve.

11. The apparatus of Claim 10, further comprising a cradle for receivably supporting said apparatus, said cradle comprising a rear brace and a forward brace;

said rear brace having a base member and two side members, said base member being fixedly attached to said side members, at least one of said side members being wedge-shaped, said wedge capable of insertion between said pivoting side member and said side surface of said extension sleeve so that said pivoting side member hingedly rotates away from said extension sleeve and transverse bar is disengaged from said aperture as said extension member is lowered onto said cradle; and said forward brace receivably supporting said distal end of said extension member.

12. The apparatus of Claim 10 wherein said side member and said transverse locking bar are engaged and secured by a pin when in the closed and locked position.

13. A method for extending standard forklift forks with extension members without manual intervention, the method comprising: placing said extension sleeves on a cradling system, said cradling system biasing a pivoting stirrup in the open and unlocked position, said pivoting stirrup being rotatably attached to said extension sleeves; engaging said extension members with the standard forklift forks; lifting said extension sleeves with the standard forklift forks, causing the pivoting stirrups to disengage from said cradling system; locking said extension sleeves in place by the gravitationally assisted rotational closing and locking of said pivoting stirrups; removing said extension sleeves from the forklift forks by engaging said extension sleeves with said cradling system; reengaging said pivoting stirrups with said cradling system, causing the pivoting stirrups to open and unlock; disengaging said extension sleeves from the forklift forks by driving the forklift forks out of said extension sleeves.

14. A method for extending standard forklift forks with extension members without manual intervention, the method comprising:

resting said extension members on an inclined plane, so that the rigid stirrup attached to said extension members are resting on the ground;

engaging said stirrup with the forklift fork;

tilting the tips of said forklift forks vertically upward to engage the forks with the interior of said extension members and disengage said extension members from said inclined plane; reengaging said extension members with inclined plane, allowing said stirrups to rest on the ground;

decreasing the vertical tilt of the tips of said forklift forks to disengage the forks from the interior of said extension members; and

disengaging the forks from said stirrups.

15. A method for extending standard forklift forks with extension sleeves without manual intervention, the method comprising:

placing said extension sleeves on a cradling system, said cradling system biasing a spring attached to a pivoting side member and a transverse bar fixedly attached to said pivoting side member to be held in the open and unlocked position, engaging said extension sleeves with the standard forklift forks; lifting said extension sleeves with the standard forklift forks, causing the pivoting side member to disengage from said cradling system and to rotate toward said extension sleeve, resulting in said transverse bar engaging a rigid side member fixedly attached to the opposite side surface of said extension sleeve; unlocking said extension sleeves from the forklift forks by lowering said extension sleeves onto cradling system and reengaging said pivoting side member with said cradling system, forcing said spring open and said pivoting side member to rotate away from said extension sleeve, resulting in said transverse bar to disengage from said rigid side member into the open and unlocked position; disengaging said extension sleeves from the forklift forks by driving the forklift forks out of said extension sleeves.