Motor vehicles – Steered by walking attendant – Who steerably controls steerable wheel
Reexamination Certificate
1998-08-21
2001-05-08
Boehler, Anne Marie (Department: 3618)
Motor vehicles
Steered by walking attendant
Who steerably controls steerable wheel
C180S019300, C180S065510, C180S332000
Reexamination Certificate
active
06227320
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a follower industrial truck driven by a motor, with a handle lever.
From DE 12 39 573 there is known a follower industrial truck with a steering handle lever which is linked about a horizontal axis to a steering base which for its part is pivotally mounted about a vertical axis. From DE 27 51 333 there is known a follower industrial truck with which the steering handle lever is mounted to the upper end of a steering shaft which extends vertically downwards through the housing of the drive part. With both industrial trucks on the handle lever head there is provided a driving switch whose operation determines the direction of travel as well as the travel speed.
From DE 37 16 375 a handle lever guided motor-driven industrial truck is known with which the handle lever in the region of the handle, for controlling the drive motor, comprises a switch actuation organ which can be operated at random. For this purpose the handle is displaceably guided, wherein the movement is acquired by a suitable switch which instructs the direction of travel of the vehicle. With this provision it is to be prevented that on picking up the handle lever from the lowered down position or by lowering down from a folded up position the actuating organs for the travel drive are not inadvertently actuated on grasping the handle and the travel drive is switched on.
From DE 24 43 375 there is known an industrial truck with which the upper part of a handle lever is telescopically arranged with respect to the other handle lever part. A spring arrangement is provided so that the upper handle lever part is held in a neutral position. With the adjustment of the upper rod part this also carries out a rotational movement in order to make the adjustment noticeable to the operating person. Switches are provided which are actuated with an adjustment of the upper handle lever part in order to change the drive speed of the industrial truck when the adjustment has reached a predetermined value. The control of the travelling speed via the upper handle lever part on the one hand has a safety aspect. If the upper handle lever part is let go, it automatically goes into the neutral position so that the drive is switched off. With an approach somewhat onto the operating person there is effected an automatic switch-over so that a special approach switch is not required. On the other hand a special travel switch is not required.
BRIEF SUMMARY OF THE INVENTION
It is the object of the invention to provided a follower industrial truck driven by a motor, with a handle lever with which the operator is given a “direct” feeling for the industrial truck without the annoying operation of a travel switch.
The invention takes into account the substantive fact that the rotational path of an otherwise commonly used travel switch changes in dependency on the tilting path of the handle lever. With the operation of the industrial truck the driver must continuously convert the desired power into a rotational movement of the hand. This is particularly disadvantageous in critical travel situations, when the driver attempts to brake the rolling vehicle by “holding steady” or “displacing away” instead of actuating the travel switch and reversing the drive direction.
With the invention the handle lever head or a section connected to the handle of the handle lever head is movable with respect to a section of the handle lever head, which is connected to the handle lever rod, in the pull or push direction of the handle lever. The movability may be provided in a tilting plane or —preferably— linearly in a plane which extends through the axis of the handle lever. The relative movement must by nature be limited. Its extent is acquired by a suitable path sensor. The path sensor may either indirectly or directly measure the covered path. The path may be somewhat measured indirectly in that a spring is impinged and the spring force measured. The force is dependent on the extent of the spring deflection. A direct path measurement may be effected with the help of usual path sensors, for which there are numerous examples.
With the control according to the invention a controller, control or control signal for the drive motor is produced in accordance with a nominal value. According to one formation of the invention a control signal may be formed from the comparison of an actual value and a nominal value. Such a nominal or actual value may e.g. be a current value. With the invention a controller is provided which compares the signal of the path sensor with the nominal value zero and whose control signal forms the nominal value for the motor controlling or control. Thus there is created a control which is designed such that at an ergonomically “comfortable level” a load-dependent, force-dependent and speed-dependent pull and push force control is possible.
The controller with the invention is a so-called position controller which attempts to make the determined deflection zero. Of course however the deflection is not to be zero since otherwise no control signal would be produced for the controller. Therefore the controller comprises a stationary error which has the effect that it is not controlled.
Tremors and unevenness of the ground may, on the vehicle, lead to a relative movement between the handle lever head and the handle lever and thus to an effect on the drive speed. It is therefore useful to provide a damping means between the handle lever and the handle lever head. It may according to a further formation of the invention be made ready by a mechanical friction which must be overcome before a relative movement of the handle lever and head takes place. The path signal dependent on the force on the handle lever head thus describes a hysteresis; all force fluctuations within the hysteresis region do not lead to a change of the control signal.
With one formation of the invention the parts movable relative to one another are also relatively movable transversely to the pull or push plane, and the sensor or a second sensor produces a second signal dependent on the extent of the second relative movement. This signal is given to a steering aid device for producing a steering moment in accordance with the second signal. With follower industrial trucks a steering aid may be of an advantage, in particular with large loads to be transported. An additional steering motor pivots the steering base or the steering shaft in accordance with a control signal which is formed by the first sensor arrangement or a second sensor in dependency on the steering forces produced on the handle lever. It is to be understood that also with the second relative movement pretensioning springs may be provided which according to the exertion of force are deflected to a greater or lesser degree. The deflection of the springs may in turn be directly or indirectly evaluated with the help of suitable sensors, such as force and/or path/angular recorders, e.g. potentiometers, Hall sensors, inductive sensors etc.
The above describe control is load-dependent. It may also be desirable to obtain a load independent control. For this purpose a third controller may be provided which forms a control signal from the comparison of the nominal value from the second controller and of a rotational speed actual value which serves as the nominal value for the first controller.
The handle lever head with the invention may be linearly movably mounted at the upper end of the handle lever rod and be pretensioned in both directions into a neutral position. The pretensioning is effected with the help of springs. If desired the pretensioning in the pull direction may deviate from the push direction. In particular a compensation of the weight of the handle lever head may be carried out. With a more or less upright position of the handle lever the handle lever head produces a force between the movable parts. The pretensioning is selected such that this force does not lead to a deflection and thus does not produce a control signal.
In order to permit a linear movement, accor
Baginski Ralf
Eggert Nikolaus
Kube Matthias
Mänken Frank
Nissen Nis-Georg
Boehler Anne Marie
Jungheinrich Aktiengesellschaft
Vidas Arrett & Steinkraus P.A.
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