Electricity: electrical systems and devices – Control circuits for electromagnetic devices – For relays or solenoids
Reexamination Certificate
2001-08-31
2004-04-13
Berhane, Adolf D. (Department: 2838)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
For relays or solenoids
C361S103000
Reexamination Certificate
active
06721159
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power feeding apparatus that prevents circuit elements from being destroyed due to an applied over load, and to a transporter and a transport system equipped with the power feeding apparatus.
2. Description of the Related Art
Conventionally, many transport systems have been realized in order to transport goods by means of transporters moving along a guide rail, and the efficiency of the transportation of goods within a plant or a warehouse has been increased. Generally, a motor is used to drive such a transporter, and the electric power is supplied to the motor via a feeder line attached along the guide rail.
As for the power feeding apparatus, there are two types, i.e., a trolley type and a non-contacting type. Because less dust is generated and less maintenance service is required, the non-contacting type power feeding apparatus system is frequently used. In the non-contacting type power feeding system, a pickup equipped to the transporter is disposed adjacent to the feeder line, and an induced electromotive force is generated on the coil by means of the electromagnetic coupling between the pickup and the feeder line to supply the electric power.
FIG. 1
is a block diagram showing a conventional non-contacting type power feeding apparatus. In the figure, reference numeral
1
denotes a pickup, which is comprised of a pickup coil L wound around a pickup core (not shown). The pickup
1
is equipped on a transporter or the like and is disposed adjacent to the feeder line
9
connected to an electric power source
11
. The feeder line
9
is laid along a guide rail (not shown) or the like disposed within a plant. The transporter is movable along the guide rail. Connected in parallel to the pickup coil L are a resonance capacitor C and a rectifier circuit
4
. The resonance circuit
2
is comprised of the coil L and the resonance capacitor C. The output terminals of the rectifier circuit
4
are connected to the input terminals of a constant voltage circuit
40
, and the output terminals of the constant voltage circuit
40
become the output terminals U and V of the non-contacting type power feeding apparatus, and at the output terminals U and V, the driving unit of the transporter is connected thereto.
In the non-contacting type power feeding apparatus structured as described above, when AC electric power is supplied to the feeder line
9
connected to the electric power source
11
, induced electromotive force is generated on the pickup coil L. The induced electromotive force is resonated in the resonance circuit
2
to obtain maximum electric power, and further, rectified in the rectifier circuit
4
, converted into electric power having constant voltage characteristic by the constant voltage circuit
40
and outputted from the output terminals U and V. The electric power outputted from the output terminals U and V is supplied to the driving unit of a transporter or the like (not shown) and the transporter is driven thereby.
In the non-contacting type power feeding apparatus described above, when the rectifier circuit
4
or the constant voltage circuit
40
is opened, or in case the load
10
has an inverter and when the circuit is short circuited, an overcurrent flows through the pickup coil L and resonates resulting in generation of an overvoltage on the resonance capacitor C. Accordingly, there is a danger that circuit elements may be destroyed or burnt out due to overheat. Accordingly, in order that a service person carries out an inspection and repair service on a point in which the abnormality has occurred, it is necessary to shut down the electric power source
11
even when the other non-contacting type power feeding apparatuses are normal.
As described above, in the conventional non-contacting type power feeding apparatus, when an overcurrent flows through the pickup coil L and resonates, there is a danger that circuit elements may be destroyed or burnt out due to an overvoltage generated on the resonance capacitor C. In order to solve this problem, a non-contacting type power feeding apparatus is disclosed in Japanese Patent Application Laid-Open No. 11-164497 (1999). In the above-mentioned non-contacting type power feeding apparatus, a thermo-responsive mechanical latch relay having a heat-sensing device installed adjacent to the pickup coil L and a contact provided between the both ends of the pickup coil L or between the output terminals of the rectifier circuit
4
, which maintains the contacting state even when the electric power supply is discontinued, is provided. When the temperature of the pickup coil L exceeds a predetermined temperature, the contact of the mechanical latch relay is closed to establish a short circuit between the both ends of the pickup coil L or between the output terminals of the rectifier circuit
4
so that the circuit elements are prevented from being destroyed or burnt out.
According to the non-contacting type power feeding apparatus disclosed in Japanese Patent Application Laid-Open No. 11-164498 (1999), when an abnormality has occurred, even when a service person has not completed the inspection and repair service yet, but when the temperature of the pickup coil L decreases lower than the predetermined value, since the contact of the thermostat opens automatically to return to the original position, there is a danger that the service person may get an electric shock, and also, abnormalities due to the identical cause may be repeated.
In order to solve the troublesomeness and danger residing in the latch-releasing service of the above-mentioned mechanical latch relay, a non-contacting type power feeding apparatus is disclosed in Japanese Patent Application Laid-Open No. 11-164498 (1999). In the above-mentioned non-contacting type power feeding apparatus, a thermostat having a contact between the both ends of the pickup coil L or between the output terminals of the rectifier circuit
4
, and a heat-sensing device adjacent to the pickup coil L is provided. When the temperature of the pickup coil L exceeds a predetermined value, the contact is closed to prevent the circuit elements from being destroyed, and when the temperature decreases lower than the predetermined value, the contact opens automatically to restart supplying the electric power.
According to the non-contacting type power feeding apparatus disclosed in Japanese Patent Application Laid-Open No. 11-164498 (1999), when am abnormality has occurred, even when a service person has not completed the inspection and repair service yet, but when the temperature of the pickup coil L decreases lower than the predetermined value, since the contact of the thermostat opens automatically to return to the original position, there is a danger that the service person may get an electric shock, and also, abnormalities due to the identical cause may be repeated.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made to solve the above-described problems. Accordingly, it is an object of the invention to provide a power feeding apparatus equipped with a switching element connected between the output side terminals of a rectifier circuit and the output terminals of the power feeding apparatus, which becomes into a discontinuous state when an overvoltage exceeding a predetermined value has occurred at the both ends of the pickup coils due to a short circuit of a load or the like. Accordingly, the power feeding apparatus according to the invention enables to prevent an overcurrent from flowing through the load, and enables to prevent the circuit elements from being destroyed or burnt out due to an overcurrent generated in the pickup coils or an overvoltage generated in the resonance capacitor. Further, the power feeding apparatus according to the invention enables to make the switching element to become into a discontinuous state without any delay at an occurrence of instantaneous overvoltage.
Further, since the above-mentioned switching circuit is structured so that the electric power is fed fro
Koyama Shingo
Takashige Satoshi
Uehira Makoto
Berhane Adolf D.
Birch & Stewart Kolasch & Birch, LLP
Luk Lawrence
Tsubakimoto Chain Co.
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