EP0138257B1

EP0138257B1 - Electric switch

Info

Publication number: EP0138257B1
Application number: EP84201353A
Authority: EP
Inventors: Willem Coppoolse
Original assignee: Holec Systemen en Componenten BV
Current assignee: Holec Holland NV
Priority date: 1983-09-21
Filing date: 1984-09-20
Publication date: 1988-01-20
Also published as: ATE32150T1; EP0138257A1; DE3468955D1; NL8303244A

Abstract

An electric switch comprising at least one movable contact and one stationary contact, a movable mass, which in the distant position of the movable contact, when the switch is open, rests against the stationary contact opposite to the side which will stop the movable contact upon closing the switch, upon which the impact energy will be transmitted as pressure waves through said stationary contact towards said mass, which waves, upon reaching said mass will be converted into energy of movement of said mass, which is moved thereby away from the stationary contact to be held at a distant position from said stationary contact. Said mass can be driven away again from said distant position towards said stationary contact, such that upon striking this contact the impact energy will be transmitted as pressure waves towards the movable contact now, to drive this away from the stationary contact thereby opening the switch. This switch will be free from contact vibrations, will be opened with high velocity and needs little supplied operating energy.

Description

The invention relates to an electric switch, comprising at least two cooperating contacts, at least one of which being movable to and from the other contact for switching on and off the switch respectively, driving means for the movable contact, driving this movable contact when the switch is open, from a position at a distance from the other contact to this other contact for switching on the switch, at least one movable mass, which in the given position of the movable contact, when the switch is open, is resting against the other contact on another side of this other contact than the side by which, upon switching on the movable contact is stopped, resilient means which press the movable contact against the other contact, such that the impact energy generated upon stopping is transmitted by the other contact to the mass where the impact energy is converted into movement energy of said mass.
A similar switch is known from DE-B-1,045,514.
When switching on such a switch, in the end the movable contact strikes against the other contact. As a result of this, it is possible that because of the impact energy which is released in the customary switches, contact vibrations can arise, resulting on contact interruptions of short duration with arc-forming and a chance of welding the contacts.
To prevent this in general the contact force is increased. However, higher contact forces demand extra energy in operating the switch, because in that case also said increased contact force must be produced, while the parts must be carried out heavier too in order to be able to take up the higher contact forces.
Such vibrations can also be avoided by strongly reducing the velocity of the movable contact just before touching the other contact, even by reducing it to zero. However, this demands rather constructive appliances.
Contact vibrations are avoided in the switch known from the above document by said movable mass, which is moved away from the contact by the collision energy, thereby absorbing all collision energy and preventing contact vibrations. Upon collision the kinetic energy of the movable contact is converted into pressure waves, which propagate through the other contact to the other side, where these pressure waves are converted into kinetic energy of the mass.
As both contacts also have a certain mass, one generally speaks of the so-called third mass in the case of the above-mentioned mass.
If the said conversion takes place with an efficiency of 100%, there will be no contact vibrations. It is true, the third mass must be stopped in the end, but this can be done more gradually.
When opening the electric switch, it is advantageous in removing the movable contact from the fixed contact with the highest velocity possible, in order to extinguish the generated arc as soon as possible. For practical reasons, the switch off velocity in the usual switches is limited to a maximum of 1 m per second.
The velocity of the movable contact, when switching off, can be increased considerably by the measures of the present invention, which are characterized by arresting means keeping in the said position of the movable contact, when the switch is closed, said mass at a distance from the other contact at another side of this other contact than the side against which the movable contact is resting in the switched on position, in which said resilient means, in which the movement energy of said mass upon switching on has been buffered into resilient energy, drive the movable mass to the other contact, after releasing the arresting means, such that the impact energy, when the movable mass strikes against the other contact is transmitted by said other contact to the movable contact, where the impact energy is converted into movement energy of the movable contact for switching off the switch.
Except the advantage, when applying the movable mass, that there is no contact vibration and that the switch is opened with a velocity as high as possible, the advantage arises that the switch can be operated with little extra energy both for opening and for closing.
In opening the switch with the help of the effects mentioned, the movement energy of the movable contact can be buffered in a spring, while also here means for maintaining the movable contact are applied, in order to lock it against the force of the drive means in the given position, when the switch is open. Also in this case said locking will occur at the moment that the movable contact has come to a standstill and all the movement energy has been buffered into the resilient means.
In the cases mentioned above, in addition to contact vibration being omitted, a switch is provided, which can be switched on and off with very little energy. In principle only the energy lost by friction needs to be replenished. Besides, high initial velocities are possible when opening the contacts.
The invention will now be explained further with the help of the drawings, in which two embodiments are shown.

Fig. 1 shows a switch according to the invention, having lock means and a spiral spring for buffering the movement energy of the third mass.
Fig. 2 shows a modified embodiment having resilient means for buffering the movement energy of the third mass.

In fig. 1, 1 shows a vacuum switch, provided with a fixed contact 2 and a movable contact 3. In the usual way, bellows provide the vacuum tight sealing of the vacuum interrupter. In this construction, the bellows 4 are also used for the driving of contact 3.
For switching on, in the first place, the movable contact 3 is moved away from the fixed contact 2, with the help of the electro-magnet 10. In doing so, the bellows 4 are stretched, so that both the bellows 4 and the atmospheric pressure will affect the movable contact 3. The movable contact 3 is held in this stretched position by a locking mechanism 9, only shown in principle, consisting of a tiltable lever, pressed against the movable contact 3 by a spring. With the help of an electro- magnet, the lever can be turned to the left, whereby the locking is removed.
This locking is removed when switching on and under the influence of the bellows 4 and the atmospheric pressure, the movable contact 3 will be moved then to the fixed contact 2.
When both contacts 3 and 2 touch, the impact energy will propagate in the form of a pressure wave through the fixed contact 2 and at the other side will be transmitted to the mass 5, due to' which said mass will move away from the fixed contact 2.
In order to capture the movement energy of mass 5, a buffer in the form of a spiral spring 6 or the like can be provided, in which then a conversion of kinetic or movement energy into potential energy will take place.
At the moment that the mass 5 is at a standstill, the locking mechanism 8 provides that no reversal of the movement of the mass 5 can occur. This locking mechanism 8 can be of similar construction as the locking mechanism 9.
Because the impact energy is transmitted fully to the mass 5 by the fixed contact 2, there will be neither contact vibrations, nor permanent contact deformation between the fixed and the movable contacts. All the forces stay within the elastic deformation region.
When switching off the switch, the mass 5 will be unlocked, after which this mass 5 is moved to the fixed contact 2, under the influence of the energy buffered in the spiral spring 6. The impact energy, which will arise then is converted again into a pressure wave in the fixed contact 2, which pressure wave propagates to the left through contact 2 and which in the left end is again converted in movement energy of the movable contact 3, by which the latter is driven to the left. In addition to the electromagnet 10, this impact energy of the mass 5 provides a very fast separation of the two contacts 2 and 3.
Both at switching on and switching off, the fixed contact remains practically motionless. Only a so-called 'thrust-through effect' will arise like e.g. with three billiard balls.
Fig. 2 shows another embodiment of the invention in which the locking mechanisms are not shown.
Instead of an electro-magnet, an extra energy buffer 13 is used here. With this energy buffer 13, the switching on energy can also be buffered. After unlocking, when switching on, this energy will, for example in the spring, which is shown, drive the movable contact 3 to the right, after which the same effects will arise as in the case of fig. 1, in which the mass 5 totally captures the impact energy. This mass 5 is again taken up by a buffer, here in the form of an electric mass 6, for example made of rubber, in which the energy is converted and stored as potential energy. In the position, in which the mass 5 comes to a standstill after moving to the right in the drawing, this mass 5 is locked again. When switching off, this buffered potential energy can be used again for accelerating the movable contact 3.
In applying a so-called third mass, there are a great number of advantages obtained. of which the most important are the following:

1. The switching on is totally free of vibrations.
2. The driving takes very little energy, which means that a switch can be manufactured having lighter components.
3. It is possible to work with higher movement velocities of the movable contact 3. When switching off initial velocities up to 4 m per second can certainly be reached. Also much higher switching on velocities can be applied. These velocities are now limited to a maximum of 1 m per second in connection with the vibrations.
4. A greater freedom of construction by which, for example, the driving rod with the associated isolation can be eliminated.

It stands to reason, that the invention is not restricted to the embodiment as shown in the drawings and the description above.
Thus the invention, in addition to the described vacuum switch, can be applied to other switches too.

Claims

1. Electric switch, comprising at least two cooperating contacts (3, 2), at least one (3) of which being movable to and from the other contact (2) for switching on and off the switch respectively, driving means for the movable contact (3), driving this movable contact (3) when the switch is open, from a position at a distance from the other contact (2) to this other contact (2) for switching on the switch, at least one movable mass (5), which in the given position of the movable contact (3), when the switch is open, is resting against the other contact (2) on another side of this other contact (2) than the side by which, upon switching on the movable contact (3) is stopped, resilient means (6), which press the movable mass (5) against the other contact (2), such that the impact energy generated upon stopping is transmitted by the other contact (2) to the mass (5) where the impact energy is converted into movement energy of said mass (5), characterized by arresting means (8) keeping in the said position of the movable contact (3), when the switch is closed, said mass (5) at a distance from the other contact (2) at another side of this other contact (2) than the side against which the movable contact (3) is resting in the switched on position, in which said resilient means (6), in which the movement energy of said mass (5) upon switching on has been buffered into resilient energy, drive the movable mass (5) to the other contact, after releasing the arresting means (8), such that the impact energy, when the movable mass (5) strikes against the other contact (2) is transmitted by said other contact (2) to the movable contact (3), where the impact energy is converted into movement energy of the movable contact (3) for switching off the switch.

2. Electric switch as claimed in claim 1, characterized in that the arresting means (8) for the mass (5) maintain this mass (5) in a position away from the other contact (2) in which driving energy for the movable mass has been mainly completely buffered into the resilient means.

3. Electric switch according to claim 1 or 2, characterized by arresting means (9) for the movable contact (3), locking this contact (3) in its position when the switch is open, against the force of the driving means for the movable contact (3), said movable contact (3) being moved to said position by the impact energy of the mass (5), when the moving mass strikes against the other contact (2).

4. Electric switch according to one of claims 1-3, characterized in that the resilient means consist of a spiral spring.

5. Electric switch according to claims 1-3, characterized in that the resilient means consist of an elastic mass.