Active control system

Details Active control system Active control system

1998-09-10

2001-04-24

Lopez, F. Daniel (Department: 3745)

Power plants

Pressure fluid source and motor

Apparatus having means responsive to or ameliorating the...

C060S481000, C091S452000, C091S453000

Reexamination Certificate

active

06220026

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active control system of the type including a fluid-operated piston-cylinder unit for moving a movable member, wherein provision is made for opening a fluid connection to the unit in emergency conditions to permit axial displacement of the piston rod relative to the cylinder.
2. The Prior Art
FIG. 7
of DE 42 24 132 discloses an active door-locking system that has a piston-cylinder unit which is connected by connecting lines to a pump unit. An on-off valve permits regulation of the flow of pressure medium into a working chamber of the piston-cylinder unit. Such a system allows a door or tailgate motion in a motor vehicle, for example, to be performed very conveniently by operation of the piston-cylinder unit.
In the case of such active control systems, it should be considered that fingers or objects may possibly be pinched when, for example, a vehicle is being loaded. Physical harm to humans or damage to the goods loaded would be the unfortunate consequence.
In addition, the supply of energy may be interrupted, so that the control system is no longer capable of performing the control motion automatically. In such circumstances, the possibility that the door or tailgate cannot be opened must be avoided, because otherwise one could be trapped in the vehicle.
SUMMARY OF THE INVENTION
The object of the present invention is to provide measures by which the above-described problems in the prior art can be eliminated.
According to the invention, this object is accomplished in that the control system is provided with a pressure-limiting valve which, in emergency operation, opens to permit a displacement motion of the piston rod. The piston rod can be initially displaced by manual force, so as to release the pressure-limiting valve and permit free displacement of the piston rod. A condition in which the door cannot be opened or closed is thereby avoided.
An additional part of the object is accomplished in that the pressure-limiting valve is connected controlwise with the on-off valve, and the on-off valve, in the event of unduly increased pressure in the piston-cylinder unit resulting from a displacement motion of the piston rod, switches to the on position, at which the piston rod, preloaded by a spring force, carries out an opposite displacement motion. Thus, even without additional manual force or pump operation, the piston-cylinder unit is moved in the opposite direction, thereby providing protection not only against pinching, but also advantageously a release motion. Controlwise, this means that a limit switch for example recognizes the switch position of the pressure-limiting valve, and transmits this information to the on-off valve electrically, pneumatically or hydraulically as a control signal.
In order to reduce the manual force required in emergency operation to a minimum and at the same time ensure reliable normal operation, the pressure-limiting valve has two pressure threshold values at which it will be moved to and held in the open position. The two pressure threshold values result from the provision of two pressurized surfaces of unlike size on the pressure-limiting valve piston.
In order to obtain as simple as possible a control system, the piston-cylinder unit is preferably designed as a single-acting hydraulic cylinder.
In order to prevent a vacuum from occurring in the piston-cylinder unit under unfavorable operating conditions, the working chamber of the piston-cylinder unit is preferably connected via a check valve with a reservoir which releases a flow of fluid medium from the reservoir to the working chamber.
To obtain as low as possible an input of energy, a passive energy accumulator is connected in parallel with the active control system. Especially in emergency operation, the advantageous use of the energy accumulator results in distinctly reduced manual force being required.
It has been shown to be particularly advantageous if the passive energy accumulator is a pneumatic spring.


REFERENCES:
patent: 3113490 (1963-12-01), Weaver
patent: 4250794 (1981-02-01), Haak et al.
patent: 4523513 (1985-06-01), Gudat et al.
patent: 5417011 (1995-05-01), Keszthelyi
patent: 5921604 (1999-07-01), Yu et al.
patent: 91 10 208 U (1993-02-01), None
patent: 2 203 486 (1988-10-01), None
patent: 5065782 (1993-03-01), None

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