HK1011237B - Electric circuit breaker with means for adjusting the contacts - Google Patents

Description

Automatic circuit breaker with contact adjusting device

The invention relates to an automatic circuit breaker with a contact adjustment device, comprising movable arms for the phases of the current and arcing contacts arranged on a terminal block, wherein the movable arms have main contacts and arcing contacts cooperating with the main contacts.

Known from the prior art are: industrial low-voltage circuit breakers fulfill essentially two tasks, namely allowing a nominal current to flow, blocking higher loads or short-circuit currents. These two tasks are contradictory from the point of view of the electrical contacts.

Thus, in order to ensure low losses and low operating temperatures when rated currents are passed, the electrical contacts have a low resistivity. On the other hand, in order to block an overcurrent, the electrical contact is required to have a high resistance and thus a high resistivity against an arc generated when an overcurrent or a short circuit is blocked.

It is not possible to satisfy both low and high resistivity requirements with the same material, so that two contacts made of different materials are used to achieve the purpose of transmitting rated current and blocking overcurrent.

The function of transmitting rated current is achieved by a first or main contact made of a softer material, and the function of blocking overload or short-circuit current is achieved by a second or arc-breaking contact made of a tougher material.

The metal inserts constituting the main contacts and the movable arc-breaking contacts are embedded at different heights on a movable arm supported by a crank that can pivot on the circuit breaker box. The corresponding metal insert constituting the main contact and the arc breaking fixed contact is embedded at the end of the upper wiring row of the circuit breaker.

In the open phase, the contact-carrying arm is rotated by a known linkage, so that the main contact is switched over to the arc-breaking contact. For the circuit automatic breaker to operate correctly, it is necessary to switch from the main contacts to the arc breaking contacts in a precise time sequence. The required timing accuracy can only be obtained by adjusting the distance of the respective fixed and movable contacts.

The adjustment is currently performed by rotating the moving contact-carrying arm by means of a known adjustment device acting on each contact-carrying arm.

Due to the internal conditions of three-phase or four-phase circuit breakers, each consisting of a plurality of contact-carrying arms, for example eight arms, each with a main contact and an arc-breaking contact, the adjustment of the position of the individual contacts of the entire circuit breaker becomes laborious and time-consuming.

These operations are usually performed by a professional, using for example feelers, interposed between the respective fixed and movable contacts of the arc circuit breaker, when the circuit breaker closes the main contacts. The adjustment operation is carried out by rotating each contact-carrying arm until the feeler is clamped between the arc-breaking contacts with the desired clamping force.

As can be easily understood, this adjustment operation requires a certain precision, and the considerable number of contacts in the automatic circuit breaker makes the production cycle of the automatic circuit breaker very long.

The object of the present invention is to overcome the drawbacks of the prior art and to allow all the contacts of the circuit automatic breaker to be adjusted simultaneously with a few simple operations.

The object of the invention is achieved with an automatic circuit breaker with a contact adjustment device, which comprises movable arms for the phases of the current and arc breaking contacts arranged on a line bank, wherein the movable arms have main contacts and arc breaking contacts cooperating with the main contacts. The circuit breaker is characterized in that: a pin for receiving a pivoting crank; the movable arms of the contacts, which are loaded by the springs, can pivot about the crank; the crank is operatively connected to a connecting rod, which is hinged to an operating shaft; and each end of the operating shaft is supported by a movable adjustment bracket.

A simple constructive solution for realising the present invention consists in that the supports are made as sliders movable in notches formed in the support of the case of the circuit breaker; and they have means for adjusting the position of the slides.

Preferably, the slider is, along its lateral direction, a seat for the head of a screw screwed into a threaded hole provided in a projection formed along the lateral direction of the notch, the screw being locked by a nut.

In order to obtain a precise and therefore play-free adjustment, the seat formed on the slider has its inner surface in contact with the upper and lower faces of the head of the adjusting screw. To facilitate the closing and opening action of the circuit breaker, the sliders have support members for the pins of the operating shaft, which are made of self-lubricating material.

The advantages of the invention can be summarized mainly in that the contacts of the circuit breaker can be adjusted simultaneously simply and conveniently.

The invention also has the advantage of reducing the number of additional parts required for adjusting the contacts, thus simplifying the work of assembling the circuit breaker and reducing the time taken.

The subject matter of the invention will be described in detail and illustrated by way of an exemplary embodiment only, as shown in the accompanying drawings, in which:

fig. 1 is a partially cut-away perspective view showing a current phase contact operating mechanism of the automatic circuit breaker.

Fig. 2 is a partially cut-away perspective view showing the operation shaft adjusting bracket.

Fig. 3 shows the operating shaft support viewed in the direction of arrow "X" in fig. 2;

fig. 4 is a partially cut-away side view of the mechanism of fig. 1.

The structure and operation of automatic circuit breakers are substantially understood and, accordingly, only the novel and important parts of this invention are set forth in detail below.

From the figures it can be seen some of the components that make up one of the phases of the circuit automatic circuit breaker, which is in the closed state.

An operating shaft 1 is connected by means of an insulating connecting rod 2 to a crank 3 which constitutes the supports of the movable arms which have contacts, indicated as a whole with the reference numeral "4".

The crank 3 is pivotable about a pin 12 integral with a support 21 of the automatic circuit breaker.

The movable contact 4 consists, for example, of eight movable arms or finger keys 5, each with a main contact 6 and an arc-breaking contact 7. The fixed contacts, generally designated by the reference numeral "8", face the movable contacts 6, 7. The fixed main contacts 9 and the fixed contacts 10 of the arc breaker are supported by an upper terminal block 11, which terminal block 11 serves as an electrical connection of the circuit breaker to electrical equipment.

The springs 13 press the movable arms 5 with the movable main contacts 6 against the fixed main contacts 9 with a force which is such as to form a contact surface whose area must be large enough to ensure low resistance and to create an additional preload for the linkage consisting of the crank 3, the connecting rod 2 and the operating shaft 1.

The operating shaft 1 transmits a rotation applied by a not-shown controller to three or four phases of the circuit automatic breaker at the same time. Only one phase is shown in the figure. The end of the operating shaft 1 is connected to a tank support 21 of the automatic circuit breaker by means of a bracket, generally designated by the reference numeral 20.

The main components that make up the adjustable support 20 can be seen in fig. 2 and 3.

The operating shaft 1 has a pin, in this case a terminal pin 22, which is inserted into an annular seat of a slide 23.

The annular seat is most preferably made of a self-lubricating material, so that the friction between the end pin 22 and the annular seat is reduced when the operating shaft 1 rotates.

The slider 23 has laterally a cylindrical extension 24 constituting an annular seat extension of the end pin 22. The cylindrical extension 24 is inserted in a notch 25 formed in the box support 21, which acts as a guide in which the cylindrical extension 24 of the slider 23 can move.

At the front of the slide 23 there is a seat 26 for the head 27 of a screw 28. The seat 26 formed in the slider 23 houses the head 27 of the screw, not allowing any axial movement of the screw with respect to the slider. In particular, the seat 26 is in contact with the upper and lower surfaces of the head 27 of the screw 28.

In front of the notch 25, a projection 30 is fixed to the side of the support 21, forming a stop for the slider 23.

The shank of the screw 28 is threaded into a threaded hole in the boss 30 and extends from the opposite portion of the boss 30. A nut 31 is screwed onto the shank of the screw 28, projecting from the projection 30.

The operation of the device which is the subject of the invention can be seen from fig. 4.

The operation of the shaft 1 through the insulating link 2 controls the rotation of the movable contact-carrying crank about the pin 12 (in the directions indicated by arrows a and B).

The operating shaft 1 is mounted on a slider 23, and the slider 23 translates inside a notch 25 formed in the seat 31 or in a central rib of the case of the automatic circuit breaker. Loosening the nut 31 allows to turn the screw 28, moving the slider 23 supporting the operating shaft 1 inside the notch 25 towards the front of the circuit breaker (direction F) or towards the rear of the circuit breaker (direction R), and thus causing the rotation of the movable contact-carrying crank 3 around the crank 12, clockwise (in the direction of arrow B) or anticlockwise (in the direction of arrow a), respectively.

By pivoting action at the relative point between the fixed main contact 9 and the movable main contact 6, the finger key 5 is rotated due to the displacement of the slider 23 towards the front (F) or the rear (R) of the automatic circuit breaker, thereby increasing or decreasing, respectively, the distance (D) between the fixed arcing breaking contact 10 and the movable arcing breaking contact 7 of the automatic circuit breaker.

This design data for the distance between the arc-breaking contacts 10 and 7 defines the timing required for switching the current from the main contacts 9, 6 to the arc-breaking contacts 10, 7, so that the main contacts 9, 6 made of soft material can be protected against burning due to the extinguishing of the arc during the opening operation of the circuit breaker.

The nut 31 is tightened to ensure that the adjustment made is not broken during the entire operation of the circuit automatic breaker.

The simultaneous adjustment of the distance between all the arc-breaking contacts 10, 7 by means of the displacement of the holder 20 of the operating shaft 1 presupposes that the finger keys 5 with the movable contacts 6, 7 are precisely aligned with one another in advance, which must be ensured with good constructional tolerances in the design and assembly phase.

Claims (5)

1. An automatic circuit breaker with contact (4) adjustment, the breaker comprising: -moving arms (5) for the phases of the current and-arcing contacts (7) arranged on a terminal block (11), wherein the moving arm (5) has main contacts (6) and arcing contacts (7) cooperating with the main contacts (6), characterized by a pin (12) for receiving a pivoting crank (3); the movable arms (5) loaded by the springs (13) can pivot around the crank (3); the crank (3) is operatively connected to a connecting rod (2), the connecting rod (2) being hinged to an operating shaft (1); and each end of the operating shaft (1) is supported by a movable adjusting bracket.

2. Circuit breaker according to claim 1, characterized in that the supports (20) are formed as sliders (23) movable in notches (25), the notches (25) being formed in a seat (21) of the case of the circuit breaker; and they have means for adjusting the position of the slides (23).

3. Circuit breaker according to claim 2, characterized in that the slide (23) is, along its lateral direction, a seat (26) for the head (27) of a screw (28), the screw (28) being screwed into a threaded hole provided in a projection (30) formed along the lateral direction of the notch (25), the screw (28) being locked by a nut (31).

4. The circuit breaker according to claim 3, wherein the seat (26) formed on the slider (23) has an inner surface contacting upper and lower surfaces of the head (27) of the adjustment screw (28).

5. Circuit breaker according to claim 2, characterized in that the sliders (23) have supports for the pins (22) of the operating shaft (1), the pins (22) being made of a self-lubricating material.