Electricity: motive power systems – Braking
Reexamination Certificate
2000-04-14
2001-09-25
Fletcher, Marlon T. (Department: 2837)
Electricity: motive power systems
Braking
C318S371000, C318S372000
Reexamination Certificate
active
06294887
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a motor brake device for controlling the drive of a motor.
As shown in
FIG. 6
, a conventional motor brake device for controlling the drive of a motor uses a brake release power supply to an electromagnetic brake which locks a motor shaft. The brake release power supply is formed by full-wave rectifying an AC power souse received through an insulating transformer.
Also in a power supply to a motor-drive indicator section, a voltage received from the insulating transformer is full-wave rectified, and the rectified one is formed into a constant voltage source by use of a capacitor, and the constant voltage source is supplied to the indicator section.
Contacts to synchronously turn on and off those two circuits must be provided for those circuits, respectively, since voltages supplied thereto are different from each other.
An AC power source
1
of a single phase is connected to an input side of an insulating transformer
2
. AC powers of different voltages are supplied from the insulating transformer
2
to a motor-brake power supple circuit
3
and an indicator power supply circuit
6
.
In the a motor-brake power supply circuit
3
, a motor-brake release switch contact
3
a
is closed as needed, and a single-phase AC power is full-wave rectified by a bridge diode circuit
3
b
, and the rectified voltage is supplied to brake coils
4
1
to
4
n
(n: number of existing coils) of an electromagnetic brake for locking the motor shaft, whereby the motor shaft is released from its locking state.
An indicator section
5
is provided for visually presenting a release of the motor brake to the operator.
The indicator power supply circuit
6
includes a switch contact
6
a
, which is operated synchronously with the motor-brake release switch contact
3
a
. When the switch contact
6
a
is closed, the single-phase AC power is full-wave rectified by a bridge diode circuit
6
b
, and the full-wave rectified power is further smoothed into a constant voltage by a capacitor
6
c
. The resultant constant voltage is applied to the indicator section
5
, to thereby turn on the indicator section
5
.
After seeing the lighting-on of the indicator section
5
, the operator knows that the motor brake is released and the motor is in a driving state.
As described above, in the conventional motor brake device, the electric power is supplied, at different voltages, to the a motor-brake power supply circuit
3
and the indicator power supply circuit
6
. For this reason, those power supply circuits are separately provided. Those circuits, respectively, include switch contacts for turning on and off the insulating transformer
2
(mainly used for voltage decreasing) and the bridge diode circuits
3
b
and
6
b
for full-wave rectifying. For this reason, the weight and size reduction is impossible.
In a trouble of poor contact in the switch contacts for synchronously turning on and off the power supply circuits, if one of the switch contacts is inoperative, an indication of the indicator section mismatches a driving state of the motor. As a result, the operator will be placed in a dangerous state.
SUMMARY OF THE INVENTION
Accordingly, the present invention has an object to provide a motor brake device which succeeds in achieving the weight and size reduction, and eliminating the mismatching between the indication of the indicator section and the driving state of the motor.
The first aspect of the invention provides a motor brake device for a robot which includes a motor brake power supply section. The input of the motor brake power supply section is connected to a power source, and the output thereof is connected to the coils of an electromagnetic brake. In the motor brake power supply, a rectifying element is inserted between a first end of the input and a first end of the output, and an opening/closing element is inserted between a second end of the input and a second end of the output.
According to the first aspect of the invention, a rectified AC power source by a rectifying element is used as a power supply of an electromagnetic brake, and it is turned on and off by a motor brake release switch contact. Therefore, the motor brake device is superior to the conventional one in space saving and is more economical than the latter.
The second aspect of the invention provides a motor brake device for a robot includes a motor brake power supply section, an indicator section, a first resistor, a second rectifying element, a second resistor, and a capacitor. The input of the motor brake power supply section is connected to a power source, and an output thereof is connected to coils of an electromagnetic brake. In the motor brake power supply section, a first rectifying element is inserted between a first end of the input and a first end of the output, and an opening/closing element is inserted between a second end of the input and a second end of the output. A first end of the first resistor is connected to a first end of the output of the motor brake power supply section, a second end of the first resistor is connected to a first end of a second rectifying element, a second end of the second rectifying element is connected a first end of a second resistor, a second end of the second resistor is connected to a second end of the output of the motor brake power supply section, a capacitor is connected in parallel with the second resistor, and both ends of the capacitor are connected to the input of an indicator section.
With such an arrangement, a divided voltage may be applied to the indicator section. Accordingly, a power supply of the motor brake power supply section may be used for the indicator section. In other words, power of both the driving of the electromagnetic brake and the indicator section is provided from a single power supply. Therefore, there is no need of the insulating transformer and the bridge diode circuit, which are essential to the conventional device. Space saving is secured, and the device is economical.
Further, the electromagnetic brake and the indicator section are synchronously turned on and off by use of a switch contact. Accordingly, the present invention eliminates the mismatching between the indication of the indicator section and the driving state of the motor in a trouble of poor contact in the switch contacts in the motor brake power supply section or the indicator power supply section. Thus, a motor-brake releasing state always matches an indication by the indicator section, to thereby securing a safety of the operator.
A third aspect of the invention define the second motor brake device such that a third rectifying element is inserted between the second end of the second resistor and the second end of the output of the motor brake power supply section.
According to the third aspect of the invention, the indicator power supply section and the indicator section can be protected against spike noise that is caused by a counter electromotive force generated in the electromagnetic brake.
The rectifying element inserted does not function as a flywheel diode (damper diode) for the line of the coil of the electromagnetic brake. It is independent of a time taken for the electromagnetic brake to operate, thereby ensuring a safe operation.
A fourth aspect of the invention defines a constant voltage element is connected in parallel with the capacitor, and a voltage output value of the constant voltage element is lower than the withstanding voltage value of the capacitor but higher than a drive voltage of the indicator section.
According to the forth aspect of the invention, when the indicator section is exchanged with another in maintenance work, current is fed to the motor brake device in a state that the connector is opened, or when a harness connecting to the connector is disconnected, the output voltage is equal to the output voltage value of the constant voltage element, and hence can be set at a voltage value below the withstanding voltage of the capacitor. As a result, the capacitor is not broken and the indicator power
Muto Yasumichi
Shimogama Shigeru
Fletcher Marlon T.
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
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