Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1990-07-11
1992-01-07
Ng, Jin F.
Communications: electrical
Condition responsive indicating system
Specific condition
191 1R, 250202, G08B 2100
Patent
active
050795430
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a monitoring device for at least one current pickup of a conveyor truck in a conveyor system running on tracks.
BACKGROUND OF THE INVENTION
A monitoring device for at least one current pickup of a conveyor truck in a conveyor system is known from DE-GM 82 11 804. Underneath several parallel sliding contacts a transversely running shaft is arranged with entrainment means for each sliding contact, which in the case of a worn-out current pickup is actuated by a thereto assigned trigger. On the shaft, a cam disk is mounted which actuates a fixed switch. A prestressed spring restores the shaft with its entrainment means and the cam disk to their initial monitoring position. The drawback is that, on the one hand this mechanical monitoring device is of a relatively complicated construction, and, on the other hand, it does not work with precision, particularly in the case of sliding contacts, where the differences in height between new and used ones are relatively small. Besides, it has to be taken into account that due to the tolerances of the conveyor truck in operation, particularly under load, such a contact is actuated sometimes too early and other times too late and this way a safe monitoring of the state of the current collectors is not possible.
It is the object of the present invention to improve the monitoring device of the above-described type.
SUMMARY OF THE INVENTION
A monitoring system is herein provided for at least one current pickup of a conveyor truck in a conveyor system running on tracks, whereby in the direction of travel the worn-down current pickup presents a characteristic wear feature which differs from the unworn state. On one side of a live rail of the system, a fixed receiver is mounted which responds to the wear signs of the worn-down current pickup. Upon a particular state of wear, an alarm system is triggered. This signal is generated from a transmitter located on an opposite side of the live rail. A test signal is sent from the transmitter to the receiver. The test signal responds to a modified configuration arranged in a direction of travel serving as a wear indicator of the current pickup.
The test signal relay which responds to a wear-produced shaped change of the current pickup simplifies the monitoring device and improves considerably the precision of the response. Besides, the error sources which in mechanical systems result from wear and the like are here eliminated.
For instance, a projection or a recess of the current pickup or pickups arranged in travel direction can serve as wear indicators, and in case of unacceptable wear can change the signal duration of the test signal so that it triggers an alarm signal.
The current pickup may be designed as a double-point current pickup, wherein an evaluation unit does not respond to signals coming in pair (S.sub.1, S.sub.2), but responds instead to single signals (S.sub.3), preferably of the combined length of both signals coming in pairs (S.sub.1 +S.sub.2), triggering the alarm system. The use of two signals for a troublefree current pickup, as opposed to one signal for an objectionable current pickup, insures a secure monitoring operation, even with variable speeds of the conveyor trucks.
The test signal can be of a variety of types, particularly simple being an embodiment where the transmitter and the receiver are designed as a light barrier. Thereby it is particularly advantageous when such a light barrier is designed in the form of a light transmitter and light receiver each associated with the live rails via a photoconductor. This design makes possible an especially small construction, which can be fitted into already existing installation.
The monitoring device can be used for a single live rail with pertaining current pickup. However more advantageous is an embodiment wherein between the receiver and the transmitter at least two live rails are provided.
BRIEF DESCRIPTION OF THE DRAWING
Embodiment examples of the monitoring device of the invention are with the aid of
REFERENCES:
patent: 4184145 (1980-01-01), Fina
patent: 4723084 (1988-02-01), Reynolds
Buropatent AG
Dubno Herbert
Hofsass Jeffery A.
Ng Jin F.
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