Material or article handling – Elevator or hoist and loading or unloading means therefor – Elevator wherein means comprises guide mounted for relative...
Patent
1982-03-08
1984-07-10
Sheridan, Robert G.
Material or article handling
Elevator or hoist and loading or unloading means therefor
Elevator wherein means comprises guide mounted for relative...
91 1, 91 27, 91 31, B66F 920
Patent
active
044590814
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates generally to vehicles which have a tiltable mast for supporting and carrying loads and more particularly to apparatus which informs the vehicle operator when the mast arrives at a predetermined inclination.
2. Background Art
The mast of a lift truck or the like is usually more or less upright as a load is being received or deposited and is tilted backward towards the body of the vehicle, to retain the load, during load carrying operations. Inadvertent forward tilting of the mast beyond a few degrees from vertical during load carrying operations can cause a loss of the load from the forks or other load engaging components. Stability of the vehicle may be adversely affected particularly if there is a substantial amount of forward tilt at a time when a load is being supported at an elevated location along the mast.
Accordingly, it has been a common practice to provide tilt motion limiting mechanisms of various kinds on lift trucks or the like to stop forward tilting of the mast at a position slightly past vertical such as at three degrees of forward tilt, for example. These may variously be mechanical stops or mechanisms which stop operation of the fluid motors that are typically used to tilt the mast.
There are circumstances under which a substantial degree of forward tilting of the mast may be desirable or even necessary. Forward tilting of the mast may be needed to enable travel of the vehicle under a low overhead obstacle. Lowering of the mast by forward tilting may also be desirable when the vehicle is being towed or transported on the bed of a truck or other conveyance. Forward tilt may also be necessary in order to deposit loads at elevated locations, such as openings in stacks of containers, under some conditions. Instances where forward tilting of the mast may be necessary have become more common with the advent of so called rough terrain lift trucks which typically have high masts and which may be designed to operate on uneven surfaces such as at construction sites or the like.
In many prior lift truck constructions, of which the mechanism described in U.S. Pat. No. 3,386,603 of H. D. Rueb, issued June 4, 1968; is an example, forward tilting of the mast beyond the predetermined limit cannot be accomplished unless the operator stops the vehicle, dismounts and disconnects or removes elements of the tilt motion limiting mechanism. Operators may then inadvertently or deliberately fail to reconnect the motion limiting mechanism before resuming work operations. Consequently, there is no positive alerting of the operator when the normal limit of forward tilt is about to be exceeded during subsequent operations.
Providing of an override system with which the operator could optionally inactivate the forward tilt motion limiting mechanism would add substantial structural complication and the override system could itself be left activated either by accident or purposely in order to avoid a need for repeated actuations during subsequent work operations. Audible or visual indicators such as buzzers or indicator lamps for alerting the operator when the mast is tilted forwardly past a predetermined inclination are not a preferred solution in view of the large number of other audible and visual indicator devices which are typically present on a lift truck. Indicators of this kind require considerable maintenance and are also readily susceptible to intentional disconnection. It would be advantageous to use some other system to signal the operator when the mast enters the forward tilt range of movement.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a load handling vehicle having a tiltable mast, means for supporting a load on the mast and motor means for tilting the mast between a first and a second position is further provided with speed reducing means for slowing tilting movement of the mast and inclination sensing means for detecting the inc
REFERENCES:
patent: 3386603 (1968-06-01), Rueb
patent: 3530766 (1970-09-01), Pilch
patent: 3591030 (1971-07-01), Pachter
patent: 4093091 (1978-06-01), Gregg et al.
Cameron Iron Works, Inc.
Sheridan Robert G.
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