Patent Description:
Most medium voltage (MV) circuit breakers (CB) are driven by a mechanical drive that contains a main spring to store and release the energy for an operation. The main spring can either be charged manually or by use of an electric drive, usually an electric motor. This also applies to low and high voltage circuit breakers and other switching systems.

<CIT> discloses a switching system according to the preamble of claim <NUM> and relates to an operation mechanism using a helical spring used as a switch for a breaker or the like as an operation source, and particularly to miniaturize an operation mechanism when a large output is required. it is described that in the operating mechanism of the switchgear, a coil spring, a disc spring in advance by a drive source such as a motor or the like, and that alternatively, energy may be accumulated in the operation source of the spiral spring temple, and when the switch operation or release operation of the switch is released, it is discharged to the energy store of the prestressing energy source.

<CIT> relates to operating mehanism for electric circuit-breakers, of the type in which a spring is set under tension by hand or bv means of a motor and when released closes the circuitbreaker. It is described that the spring is permanently connected with mechanism for setting it under tension the said mechanism comprising among other members a non self-locking helical gearing, and this gearing is actuated by the spring during the closing operation so as to exert a damping action and mitigate the shock which otherwise would occur.

The electric motor requires some mechanism or means to switch it on when it is needed to charge the spring and to switch it off when the spring is charged. This control of the switching on and off of the motor to turn the motor on to charge the spring when required and to turn the motor off when the spring is charged, is via a mechanism that checks the mechanical position of the spring. This is control of the motor is therefore via an additional mechanism that increases the complexity of the CB drive system, and that could potentially fail.

There is a need to address these problems.

Therefore, it would be advantageous to have an improved technique to charge the main spring of a switch such as a circuit breaker.

The invention and its scope of protection is defined by the appended independent claims. Claim <NUM> defines a switching system. Claim <NUM> defines a low, medium or high voltage switchgear.

The following aspects and examples of the disclosure provide the skilled person with examples of how technical subject matters can be combined.

In a first aspect, there is provided a switching system comprising a low, medium or high voltage switch and a charging device, comprising:.

A first end of the main spring is connected to the spring support. A second end of the main spring is connected to the main shaft. The spring support is configured to rotate about an axis of the main shaft. At least part of a circumference of the spring support comprises a thread. The motor comprises a worm thread configured to engage with the thread of the spring support. The motor is configured to rotate the worm thread. Rotation of the worm thread is configured to rotate the spring support to store energy in the main spring. The motor is configured not to rotate the worm thread when the energy stored in the main spring has reached a threshold level. Energy release from the main spring is configured to rotate the main shaft.

In other words, a completely new and surprising mechanism has been developed for charging the mainspring of a switch system where the power is turned off to the motor that charges the spring based on the energy stored in the mainspring itself. This provides a self-contained charging system, with no further external complex monitoring systems or devices required.

In an example, the spring support comprises a cup.

In an example, at least part of an outer circumference of the spring support comprises the thread.

According to the invention a mounting of the motor is configured to enable the motor to move.

When the energy stored in the main spring has reached the threshold level the motor is configured not to rotate the worm thread when the motor has moved a threshold distance.

Thus, simple mechanism is provided based on a lateral movement of the motor resulting from energy stored in the mainspring reaching a threshold level. This movement of the motor can then be utilised to switch the power off to the motor.

In an example, the mounting of the motor comprises a spring configured to resist the movement of motor to the threshold distance.

By using a spring in this manner, simple mechanism is provided to adjust the resisting power of the spring, either by changing the spring, or put in for example spaces between the mounting of the spring and the spring itself to put it under tension.

In an example, movement of the motor to the threshold distance is configured to trigger a switch to stop the motor from rotating the worm thread.

Thus, a simple microswitch or switch can be triggered based on a lateral movement of the motor then turns the motor off.

In an example, the motor comprises at least one power connection. The at least one power connection of the motor is configured to be in electrical connection with at least one fixed connection to provide power to the motor to rotate the worm thread. When the motor has moved a threshold distance the at least one power connection of the motor is configured to be electrically disconnected from the at least one fixed connection.

In this manner, simple in effect mechanical system is provided where movement of the motor itself laterally leads to a disconnection of power to the motor in a completely self-contained manner.

In an example, the motor is configured not to rotate the worm thread in response to a threshold torque being applied from the spring support to the worm thread when the energy stored in the main spring has reached the threshold level.

Thus, as the mainspring is charged an increasing torque is developed in the spring support or cup and this in effect pushes against the worm thread. An internal sensor within the motor can for example sense this increasing pushing force and when a threshold torque has developed, the motor can be switched off. Alternatively, the motor is fixed and only the worm thread moves itself laterally with respect to the body of the motor, and this movement can be utilised to turn off the motor when for example a threshold movement distance has occurred. The switch or sensor that detects the lateral movement of the worm thread can be outside of the housing of the motor, or it can also be integrated in the motor.

In an example, application of the threshold torque from the spring support to the worm thread is configured to move the motor the threshold distance.

In an example, the motor is configured to continuously rotate the worm thread when a power source is connected to the motor.

In this manner, a very simple charging mechanism is provided, where when the mainspring is not fully charged the charging system continuously challenges the mainspring until the mainspring is fully charged at which point charging of the mainspring automatically stops. When the mainspring has been discharged, the motor will automatically turn back on and charging continue again.

In an example, the motor is configured not to rotate the worm thread when the power source is dis-connected from the motor.

In an example, the worm thread is configured to engage with the thread of the spring support to stop the spring support from rotating when the energy stored in the main spring has reached the threshold level.

In an example, the motor is configured to rotate the worm thread upon energy release from the main spring that has reached the threshold energy level.

In an example, a circuit breaker comprises the low, medium or high voltage switch.

In a second aspect, there is provided a low, medium or high voltage switchgear comprising a switching system according to the first aspect.

<FIG> relate to a switching system <NUM> that has a low, medium or high voltage switch, or at least part of such a switch, and a charging device, and to a switchgear that has such a switching system.

An example of a switching system <NUM> comprises a low, medium or high voltage switch and a charging device. In more detail, the switching system comprises a main spring <NUM> of the low, medium or high voltage switch, a spring support <NUM> of the low, medium or high voltage switch, a main shaft <NUM> of the low, medium or high voltage switch and a motor <NUM> of the charging device. A first end <NUM> of the main spring is connected to the spring support. A second end <NUM> of the main spring is connected to the main shaft. The spring support is configured to rotate about an axis of the main shaft. At least part of a circumference of the spring support comprises a thread <NUM>. The whole circumference can have the thread in certain examples. The motor comprises a worm thread configured to engage with the thread of the spring support. The motor is configured to rotate the worm thread, and rotation of the worm thread is configured to rotate the spring support to store energy in the main spring. The motor is configured not to rotate the worm thread when the energy stored in the main spring has reached a threshold level. Energy release from the main spring is configured to rotate the main shaft.

In an example, a mounting of the motor is configured to enable the motor to move. When the energy stored in the main spring has reached the threshold level the motor is configured not to rotate the worm thread when the motor has moved a threshold distance.

In an example, the mounting of the motor comprises a spring <NUM> configured to resist the movement of motor to the threshold distance.

In an example, the motor comprises at least one power connection <NUM>, <NUM>. The at least one power connection of the motor is configured to be in electrical connection with at least one fixed connection <NUM>, <NUM> to provide power to the motor to rotate the worm thread. When the motor has moved a threshold distance the at least one power connection of the motor is configured to be electrically disconnected from the at least one fixed connection <NUM>, <NUM>.

A circuit breaker can be or comprise the low, medium or high voltage switch as described above.

In this manner, a simple and effective system is provided to charge the main spring of a drive for a circuit breaker for example, that continuously charges the mainspring until it reaches a threshold charge level, where charging stops, and upon discharge of the main spring the charging of the mainspring again begins.

A low, medium or high voltage switchgear can have a switching system as described above.

The switching system is now described in specific detail with respect to a circuit breaker (CB), where again reference is made to <FIG>.

<FIG> shows the switching system <NUM> that CB main spring charging device with a discharged main spring <NUM> of a CB. The main spring <NUM> is installed in a cup <NUM>. The main spring <NUM> has an outer end <NUM> that is connected to the pin <NUM> in the cup <NUM> and an inner end <NUM> that is connected to the groove <NUM> in the main shaft <NUM> of the CB. Unless the CB is operating, the main shaft <NUM> is not rotating, so that the main spring <NUM> can be charged when its outer end <NUM> is rotated counter clockwise. For that purpose, a charging motor <NUM> is provided. The charging motor <NUM> is movable from the left to right. Its worm thread <NUM> engages with the thread <NUM> of the cup <NUM>, which provides a self-locking function based on the worm thread principle. In this way no back movement will take place after the charging is done. The auxiliary spring <NUM> pushes the motor <NUM> to the leftmost position shown in <FIG>. When the motor <NUM> operates the worm thread <NUM>, the cup <NUM> is rotated counter clockwise to charge the main spring <NUM>. The torque that is building up in the main spring <NUM> pushes the motor <NUM> with a corresponding force to the right. During charging, this force is lower than the force of the auxiliary spring <NUM>, so that the charging motor <NUM> stays in the leftmost position shown in <FIG>. The leftmost position of the motor <NUM> can be defined with a mechanical stop (not shown). In this leftmost position, the motor <NUM> is connected to its electrical supply via the electrical contacts <NUM>, <NUM> and <NUM>, <NUM>, where <NUM> and <NUM> are fixed to the motor <NUM> while <NUM> and <NUM> are fixed to the environment.

In <FIG>, the switching system is shown where charging of the main spring <NUM> is complete. The torque that was built up in the main spring <NUM> is now strong enough to push the motor <NUM> to the right, against the force of the auxiliary spring <NUM>, to the rightmost position of the motor <NUM>. This rightmost position can be defined with a mechanical stop (not shown). In this rightmost position, the electrical contacts <NUM> and <NUM> are away from their fixed counterparts <NUM> and <NUM>, so that the electrical feeding circuit of the motor <NUM> is interrupted and the charging process is terminated.

When the CB is operating, the main shaft <NUM> is released for rotation and it will therefore reduce the torque of the main spring <NUM>. Then, <NUM> will be pushed to the left, the electrical contacts will close and the main spring <NUM> will be recharged. This also applies in case the CB should operate during the charging process.

As an alternative to the electrical contacts <NUM>, <NUM> and <NUM>, <NUM> an off-the-shelf switch or microswitch can be used that is operated by the change of the position of the motor <NUM>. As an alternative to two electrical contacts <NUM>, <NUM> and <NUM>, <NUM>, that realise a bipolar connection / disconnection of the electrical feeding circuit of the motor <NUM>, one of the two electrical contacts <NUM>, <NUM> or <NUM>, <NUM> may be replaced by a solid electrical connection, e.g. a cable. This would save one electrical contact while the switching function of the motor is still provided.

For the adjustment of the charging torque, the pre-load of the auxiliary spring <NUM> may be adapted for example by changing the position of the fixed plate <NUM> towards or away from the auxiliary spring <NUM>, or by inserting distance plates of a certain thickness between the auxiliary spring <NUM> and the fixed <NUM> or between the auxiliary <NUM> and the motor <NUM>.

<FIG> shows an example of a planetary drive system for a circuit breaker, that utilizes a main spring <NUM> charged as described above with respects to <FIG>, and where rotation of the main shaft is utilized.

<FIG> shows three instants of the closing operation, from left to right: OFF position, intermediate position, ON position. The energy for the operation is stored in the closing or main spring <NUM>.

In the OFF position, both the planetary cogwheel carrier <NUM> and the hollow cogwheel ring <NUM> are locked against rotation by their relevant locking features shown as <NUM>, <NUM> and locking devices shown as <NUM>, <NUM>.

The closing spring <NUM> is charged to drive the closing operation while the opening spring <NUM> is discharged.

For closing, the locking device <NUM> is unlocked, so that the closing spring <NUM> can drive the carrier <NUM> counter-clockwise. The outer end <NUM> of the closing spring <NUM> is currently locked in the shown position. The counter-clockwise rotation of <NUM>, while the hollow cogwheel ring <NUM> is locked, results in a counter clockwise rotation of the sun cogwheel <NUM>.

The sun cogwheel <NUM> is connected or coupled to the pushrod <NUM> by for example a high helix thread <NUM> (or another thread type) so that a counter-clockwise rotation of the sun cogwheel <NUM> shifts the pushrod <NUM> away from the OFF-position towards the ON-position. This motion of the pushrod <NUM> charges the opening spring <NUM>, as its upper end <NUM> is permanently locked in the shown position while the lower end of <NUM> is connected to the pushrod <NUM>.

The sun cogwheel <NUM> can have a male thread and the pushrod <NUM> have a female thread, or the sun cogwheel <NUM> can have a female thread and the pushrod <NUM> have a male thread.

In the intermediate position shown in the centre of <FIG>, the closing spring <NUM> has rotated the carrier <NUM> by <NUM>° counter-clockwise. According to the chosen number of teeth, this corresponds to a counter-clockwise rotation of <NUM>° of the sun cogwheel <NUM>. Due to the high helix thread <NUM>, the pushrod was moved half of its way upwards from OFF to ON. The opening spring was charged by the movement of the pushrod. In the ON-position shown at the right side of <FIG>, the closing spring <NUM> has rotated the planetary carrier <NUM> by <NUM>° counter-clockwise. According to the chosen number of teeth, this corresponds to a rotation of <NUM>° counter-clockwise of the sun cogwheel <NUM>. Due to the high helix thread <NUM> (or another thread type), the pushrod was moved its complete way upwards from OFF to ON. The opening spring was fully charged. Now the next locking feature <NUM> is in a position where the locking device <NUM> can push a pin, e.g. driven by a spring, into the locking feature <NUM> and so stop and latch the closing operation. Alternatively, the closing operation can also be stopped and latched by separate devices.

In <FIG>, where the closing operation is shown, locking features <NUM> are not only provided at the OFF and the ON positions of the cogwheel planetary carrier <NUM>, but also in the intermediate position.

It is to be noted that in a different embodiment, not shown, the pushrod <NUM> is again threaded but is not connected or coupled to the sun cogwheel <NUM>. Rather, the hollow cogwheel ring <NUM> has a top cover that can be for example a disk, and a centre of this disk is threaded. Thus looking at <FIG>, the sun cogwheel <NUM> and planetary cogwheels <NUM> in this example are underneath the top cover of the cogwheel ring <NUM>.

Then, the closing spring <NUM> can again drive the carrier <NUM> and the planetary cogwheels <NUM> around the axis of the sun cogwheel <NUM>. However, the sun cogwheel <NUM> can then be locked in position and not rotate and the hollow cogwheel ring <NUM> then rotates in a clockwise direction. The pushrod <NUM> can then be threaded in the opposite direction to that described above, and again the pushrod moves away from the off position towards the on position. Rather than having pushrod <NUM> threaded in the opposite direction, the closing spring <NUM> can be in effect rotated <NUM>° and the energy release can rotate the carrier in the opposite direction to that described above and again rotation of the cogwheel ring <NUM> now again in the counter clockwise direction leads to movement of the pushrod from the opposition to the on position.

The cogwheel ring <NUM> can have a male thread and the pushrod <NUM> have a female thread, or the cogwheel ring <NUM> can have a female thread and the pushrod <NUM> have a male thread.

Also, in a different embodiment, the pushrod <NUM> is again threaded and connected or coupled to the sun cogwheel <NUM>. However now, the closing spring <NUM> is coupled to the cogwheel ring <NUM> and now drives rotation of the cogwheel ring <NUM> rather than driving rotation of the carrier <NUM> of the planetary cogwheels <NUM>. The carrier <NUM> of the planetary cogwheels <NUM> is then held in a fixed position, and does not rotate, but the individual planetary cogwheels <NUM> then rotate about their axes with rotation of the cogwheel ring <NUM> then rotating the sun cogwheel <NUM>, which then drives the pushrod <NUM>.

Claim 1:
A switching system (<NUM>) comprising a low, medium or high voltage switch and a charging device, comprising:
- a main spring (<NUM>) of the switch;
- a spring support (<NUM>) of the switch;
- a main shaft (<NUM>) of the switch; and
- a motor (<NUM>) of the charging device;
wherein, a first end (<NUM>) of the main spring is connected to the spring support;
wherein, a second end (<NUM>) of the main spring is connected to the main shaft;
wherein, the spring support is configured to rotate about an axis of the main shaft;
wherein, at least part of a circumference of the spring support comprises a thread (<NUM>);
wherein, the motor comprises a worm thread configured to engage with the thread of the spring support;
wherein, the motor is configured to rotate the worm thread, and wherein rotation of the worm thread is configured to rotate the spring support to store energy in the main spring;
wherein, the motor is configured not to rotate the worm thread when the energy stored in the main spring has reached a threshold level;
wherein, energy release from the main spring is configured to rotate the main shaft; characterized in that
a mounting of the motor is configured to enable the motor to move, and wherein when the energy stored in the main spring has reached the threshold level the motor is configured not to rotate the worm thread when the motor has moved a threshold distance.