Motor vehicles – Steered by walking attendant – Who steerably controls steerable wheel
Reexamination Certificate
2000-01-14
2001-09-18
Hurley, Kevin (Department: 3619)
Motor vehicles
Steered by walking attendant
Who steerably controls steerable wheel
C180S402000
Reexamination Certificate
active
06290010
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a pole-guided industrial truck with at least one steered wheel and a pole rotatable around an essentially vertical axis. The pole is effectively connected with the wheel such that a rotation of the pole around the vertical axis effects a steering movement of the wheel. The invention also relates to a damping element for use in a steering device of an industrial truck of the type described above.
2. Description of the Prior Art
Industrial trucks of this type are frequently operated as accompanied vehicles whereby an operator walks along beside the industrial truck and steers the industrial truck by rotating the pole around the vertical axis, for which purpose the pole is equipped with a handle. In the vicinity of the handle, there can also be control elements by means of which, for example, the traction drive system of the industrial truck can be controlled.
On industrial trucks of the prior art, the pole has a mechanical connection with a steerable wheel of the industrial truck, which is frequently also the drive wheel of the industrial truck. In the prior art, for example, the wheel is sometimes coupled to the pole by means of a chain gear.
On these devices of the prior art, the actuation force of the pole to steer the industrial truck depends to a very great extent on the current operating conditions, in particular on the load status and the speed of travel of the industrial truck, as well as on the characteristics of the road or floor over which the industrial truck is traveling. When the industrial truck is stopped, the actuation force required to rotate the pole is relatively large. To give the operator a feel for the most appropriate steering movements of the wheel and to prevent any unintentional steering actions of the industrial truck, it is desirable if the actuation force required to rotate the pole, even at higher speeds of travel, does not drop below a specified threshold.
The object of this invention is therefore to make available an industrial truck with a pole on which the force required to steer the industrial truck corresponds to ergonomic requirements.
An additional object of the invention is to make available a damping element for use in the steering device, which is capable of generating a corresponding actuation force.
SUMMARY OF THE INVENTION
With regard to the industrial truck, the invention teaches that the pole is connected with an electrical primary detector which detects or measures a rotational movement and/or a rotational position of the pole, and the primary detector is effectively connected with an electric steering motor of the wheel by means of an electrical signal line. Therefore, there is no mechanical connection by means of which a steering movement of the pole is transmitted to the wheel being steered. The signal is transmitted exclusively electrically. The actuation force of the pole is therefore independent of the forces necessary to overcome the friction of the wheel on the road or floor. An additional advantage that results from the electrical signal transmission is that the position of the pole can be selected practically independently of the position of the steered wheel. No high-maintenance mechanical transmission means are necessary for the transmission of the steering movement, which mechanical means would also occupy a considerable amount of space.
It is further advantageous if the pole is connected with a damping element that generates a counter-torque when the pole is rotated around the vertical axis. The torque generated with the damping element guarantees that the operator can feel some resistance during the steering of the industrial truck. As a result of this sensible steering resistance, incorrect maneuvers that may result from the unintentional or uncontrolled rotation of the pole can be avoided.
The damping element is advantageously connected on one hand with a component that is non-rotationally connected with the pole, and is directly or indirectly connected on the other hand with a frame of the industrial truck. The torque required to rotate the pole is thereby supported on the frame.
It is also appropriate if a component that is non-rotationally connected with the pole is mounted on a frame of the industrial truck by means of roller bearings.
The primary detector is advantageously a potentiometer which measures the relative movement between a component that is non-rotationally connected with the pole and a frame of the vehicle. With this arrangement, the potentiometer generates an unambiguous signal that reflects the rotational position of the pole.
In one appropriate configuration, the component that is non-rotationally connected with the pole is provided in the form of an essentially vertically oriented shaft. The roller bearings, the damping element and the potentiometer can be located along the shaft, at some axial distance from one another.
The damping element can be connected with the shaft in a particularly simple manner if the damping element has an essentially ring-shaped configuration, whereby the vertically oriented shaft is coaxial with the damping element. The inside of the ring-shaped damping element preferably has a cross section that is suitable for the transmission of torques.
With regard to the damping element, to achieve the object described above, the invention teaches that the damping element has at least two components that are located coaxially and can be rotated with respect to each other, each of which has at least one cylindrical or conical friction surface, whereby a friction surface of the first component is in contact against a friction surface of the second component. When the two components are rotated, a sliding friction force is generated between the two friction surfaces that rub against each other. In the application described above for the pole of an industrial truck, this sliding friction force represents a torque that counteracts a steering movement of the pole.
Preferably, each of the two components that rotates with respect to each other has a plurality of friction surfaces. The two rotational components are thereby engaged with each other in the manner of a comb.
It is particularly advantageous if the two components that can be rotated with respect to each other are made out of plastic. The components can be manufactured by injection molding, for example. As a result of the elasticity of the plastic material, it is possible to avoid problems of the fit between the two components.
A lubricant is located in the cavities between the rotational components. It thereby becomes possible to avoid sudden changes in the level of the friction force at the transition between static friction and sliding friction.
It is appropriate if a silicone lubricant is provided as the lubricant. Silicone grease is characterized by a particularly long useful life, which means that it is unnecessary to replace the lubricant for the entire useful life of the damping element.
REFERENCES:
patent: 5097917 (1992-03-01), Serizawa et al.
patent: 5375673 (1994-12-01), McCall et al.
Patent Abstracts of Japan, Publication No. 07206399 A, Aug. 8, 1995 entitled “Steering and Device for Ordered Picking Truck”.
Article entitled “Ergonomische Gestaltung von Flurför derzeugen für Lagerbereiche”, Dipl.-Ing. Friedrich Wilhelm Groll, Wagner Fördertechnik GmbH & Co KG Reutlingen (1995).
Briday Yves
Roudet Christopher
Hurley Kevin
Linde Aktiengesellschaft
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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