Electricity: circuit makers and breakers – Special application – Feeler moves into detecting contact with object
Reexamination Certificate
1999-03-10
2002-04-16
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Special application
Feeler moves into detecting contact with object
C200S061430, C049S028000
Reexamination Certificate
active
06373005
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a device for detection of a trapping condition in a power-operated closing element. Devices of this type are used to switch off the drive unit of the closing element and if necessary reverse its movement in the event of a trapping condition arising, e.g. the trapping of a part of the body between two opposite closing edges. These anti-trapping devices are used, for example, on electrically operated window lifters and sliding roofs, automatic vehicle doors, e.g. in buses and trains, as well as in lift doors or the like.
BACKGROUND OF THE INVENTION
The well-known devices for detection of trapping are based essentially on two different methods of operation.
In a first type of anti-trapping device the information on possible trapping is taken from the power data of the drive unit for the closing element. In the case of electrical drives, for example, this is done by monitoring the motor current or torque output, both of which increase in the event of trapping. If a specific threshold value of the respective parameter is exceeded, the drive motor is switched off and, if necessary, the direction of movement is reversed. Problems are caused in these systems in particular by friction losses of the closing element on guide devices and sealing elements for the closing element. These friction losses are heavily dependent on external factors such as outside temperature or lubrication condition, which leads to wide variation of the monitored drive characteristic values and frequent faulty tripping.
In a second type of anti-trapping device pressure-operated switching elements are used, which are arranged on a closing edge and switch off or reverse the drive unit of the closing element when pressure is applied. LU-A-87 942 describes, for example, an anti-trapping device in which a film pressure sensor is mounted on the closing edge of the closing element. If an obstacle is in the path of movement of the closing element, the film pressure sensor is tripped by direct application of pressure when the obstacle is struck and the drive control of the closing element reverses the direction of movement of the latter. An arrangement of this type is characterised by an extremely high probability of response, but problems are caused in this arrangement by the direct transmission of the trapping force to the active area of the actual switching element. In fact, moving obstacles in particular may exert heavy impacts on the switching element and destroy the latter.
DE-PS-33 47 945 describes a moulding on the closing edge of a moving closing element, in which a closing force is transmitted via several segments, some of which are arranged in a V-shape, to a switching rib. The switching rib is forced in the direction of the closing force on to the switching element and trips the latter by direct application of pressure. Although the closing force is transmitted via segments and a switching rib to the switching element with this moulding, with the result that the actual switching force exerted on the switching element is easily reduced, impacts nevertheless cause significant displacement of the switching rib towards the switching element. However, this in turn produces inadmissibly high direct loading of the active area of the switching element, which leads to its destruction.
SUMMARY OF THE INVENITON
Consequently, the task of the present invention is to propose a device for detection of a trapping condition in which direct application of a trapping force to the switching element is prevented.
According to the invention this problem is solved by a device for detection of trapping in a power-operated closing element with a switching element which is arranged along a first closing edge within an elastic hollow section. The hollow section comprises a central area extending longitudinally, in which an active area of the switching element is arranged, and at least one side area extending longitudinally, in which a non-active edge area of the switching element is arranged, the side area on the side of the hollow section facing the first closing edge being more deformable than the central area. The device also has a longitudinally extending force transmitter, which transmits a trapping force essentially at right angles to the side area of the hollow section. It should be noted that the first closing edge may belong to a moving closing element and also to a fixed element which interacts with the closing element when it is closed to close an opening.
Consequently the device according to the invention is characterised by transmission of the trapping force to the side area of the hollow section instead of directly to the active area of the switching element. This ensures that the side area of the hollow section in the area of the point of attachment of the force transmitter is deformed towards the trapping force, the central area largely retaining its shape because of the relatively smaller deformability. The switching element is thus deflected in its edge area towards the trapping force, so that the dimensionally stable central area of the hollow section exerts a switching force on the active area of the switching element, which acts in the opposite direction to the trapping force. If the closing element is withdrawn from the trapping position, which is effected by reversal of the drive device, the trapping force diminishes and the hollow section resumes its original shape because of its elasticity. Consequently the pressure exerted by the central area of the hollow section on the active area of the switching element diminishes, and the switching element opens.
The important advantage of the indirect tripping of the switching element is that the maximum deflection of the edge area of the switching element and thus also the switching force exerted by the central area of the hollow section on the active area of the switching element can easily be limited without impairment of the response of the device. This is done by limiting the maximum deformation of the side area of the hollow section by suitable design of the side area.
The higher deformability of the side area in relation to the central area may be achieved, for example, by making the side area from a softer material than the central area. Suitable material selection and appropriate dimensioning of the thickness of the side area ensure that the side area can initially be deformed very easily, which ensures high response probability but with increasing deformation exerts a greater counter-force and thus limits further deformation.
In an alternative design of the hollow section the central area and side area are made from the same material. In this case the side area has a longitudinal hollow chamber, which absorbs the deformation of the side area, in its wall facing the closing edge. After this hollow chamber has been fully compressed by a trapping force, a side area designed in this way cannot absorb any further deformation.
To allow particularly accurate transmission of the switching force to the active area of the switching element, the central area has a longitudinal elevation, which projects into the hollow space of the hollow section, preferably on the side of the hollow section facing the first closing edge. The switching force exerted by the central area is then transmitted locally by this elevation to the switching element, so that tripping of the switching element already takes place reliably with very small deflection of its edge area. Consequently this measure significantly improves the response of the device.
The hollow space in the central area is preferably curved concavely outwards on its side facing away from the first closing edge. If the side area is deformed by a trapping force, the wall of the hollow space in the side area facing away from the first closing edge may be displaced towards the switching element. Undesirable direct tripping of the switching element can be prevented by the curved design of the hollow space on this wall.
The force transmitter is advantageously connected on the side of
Gamerdinger Hans
Griesbach Peter
Lorig Roland
Mickeler Reinhold
Petri Volker
Friedhofer Michael
I.E.E. International Electronics & Engineering S.A.R.L.
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