Land vehicles – Wheeled – Attachment
Reexamination Certificate
1999-05-13
2001-05-08
English, Peter C. (Department: 3619)
Land vehicles
Wheeled
Attachment
C212S304000
Reexamination Certificate
active
06227569
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to forklift machines, and more particularly to systems for supporting or stabilizing forklift machines.
Forklift machines or “forklifts” used to lift, transport and deposit loads are generally well known. A typical forklift machine generally comprises a chassis or frame, two pair of wheels mounted to axles attached to the frame and a lifting mechanism including a pair of movable arms or “forks”. In use, an operator located in an operator cab maneuvers the vehicle to approach a load and engages the forks of the lift mechanism with the load, such as a pallet or crate of manufactured goods, a load of lumber or steel, etc. The lift mechanism raises the load and the forklift transports the load to a desired destination, where the load is then lowered and deposited.
One problem with forklift vehicles, particularly when lifting and/or transporting heavy loads on uneven terrain, is that the weight of the load may give rise to a moment about either the front pair of wheels and/or the right or left side pairs of wheels (e.g., the right side front and rear wheels) of the forklift. Such a moment, if not properly counteracted by moments arising from other forces, for example the weight of the forklift frame, may cause the forklift to “topple” over and lose the load. Therefore, support or stabilizing systems have been developed to counteract load-generated moments to prevent toppling of the forklift.
To prevent such toppling, systems have been developed whereby at least one and generally two stabilizing arms having an end contactable with the base surface at a location forward of the front pair of wheels. Generally, these systems are formed by a pair of arms, each arm having one end connected to the forklift machine and the other end being contactable with the base surface, and a pair of hydraulic cylinders each moving a separate connected arm. With such systems, the tendency of the load to tilt the vehicle forwardly about the front wheels causes the ends of the arms to press against the base surface, generating normal forces that, acting through the stabilizing arms, exert a moment directed oppositely the load moment. The moment exerted through the stabilizer arms (in combination with the moment generated by the weight of the forklift) is sufficient to prevent the forklift from toppling forwardly.
However, known stabilizing systems, such as those discusse above, have certain problems. With systems having stabilizer arms mounted to one of the vehicle axles, the axle must be reinforced to support stabilizer mechanism and the loads transmitted to the axle through the stabilizer arms. Further, as the stabilizer mechanisms are located beneath the forklift frame, the stabilizer system is both difficult to access for service purposes and have a limited range of vertical travel. Other systems having the arms connected to frame, the arms must generally be mounted proximal to the lateral sides of the frame so that the arms do not interfere with operator's field of vision when located in an upward storage position. Being mounted near the sides of the frame, the arms must be pivoted a relatively greater distance to cause a corresponding vertical displacement of the frame, thus requiring greater cylinder extension distances compared with axle-mounted cylinders.
It would therefore be desirable to have a system for supporting or stabilizing a forklift vehicle that overcomes the above-described drawbacks or limitations of the previously known support systems.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a linkage for supporting a vehicle frame on a base surface. The linkage comprises a base link having a first end attached to the frame and a second end. A contact link is rotatably attached to the second end of the base link and has a contact surface engageable with the base surface. A drive link has a first end connected with the frame and a second end connected with the contact link. The drive link is configured to move the contact link in a first direction such that the contact surface is moveable into engagement with the base surface and alternatively in a second direction such that the contact surface moves generally away from the base surface.
In another aspect, the present invention is a system for supporting a vehicle frame on a base surface, the system comprising a pair of support linkages each connected with the frame. Each linkage includes a base link having a first end attached to the frame and a second end. A contact link is rotatably attached to the second end of the base link and has a contact surface engageable with the base surface. Each linkage is configured to move the contact link of the linkage in a first direction such that the contact surface is moveable into engagement with the base surface to support the frame above the base surface and alternatively in a second direction such that the contact surface moves generally away from the base surface.
In yet another aspect, the present invention is a linkage for positioning a body with respect to a base surface. The linkage comprises a base link having a first end attached to the body and a second end. A contact link is rotatably attached to the second end of the base link and has a contact surface engageable with the base surface. A drive link has a first end connected with the body and a second end connected with the contact link. The drive link is configured to rotate the contact link about the base link in a first direction such that the contact surface is moveable into engagement with the base surface and alternatively in a second direction such that the contact surface moves generally away from the base surface.
REFERENCES:
patent: 3144138 (1964-08-01), Brown et al.
patent: 4026428 (1977-05-01), Shumaker
patent: 4082197 (1978-04-01), Stedman
patent: 4244599 (1981-01-01), Gauchet
patent: 36 26 989 (1988-02-01), None
patent: 1465607 (1967-01-01), None
patent: 308164 (1971-07-01), None
Dingeldein William R.
Golan John W.
English Peter C.
Ingersoll-Rand Company
Michael & Best & Friedrich LLP
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