WO2003041226A1

WO2003041226A1 - Terminal for low voltage modular device

Info

Publication number: WO2003041226A1
Application number: PCT/EP2002/012168
Authority: WO
Inventors: Alberto Antoniazzi
Original assignee: Abb Service S.R.L.
Priority date: 2001-11-06
Filing date: 2002-10-30
Publication date: 2003-05-15
Also published as: EP1442502B1; DE60211009D1; EP1442502A1; DE60211009T2; ITMI20012324A1; ATE324682T1

Abstract

A terminal for low-voltage terminal device, whose particularity consists of the fact that it comprises: a cage, which is shaped substantially like a parallelepiped that has a cavity suitable to receive at least one first electrical conductor and one second electrical conductor, which are meant to be mutually connected electrically, the cage having an upper wall provided with a threaded through hole, a lower wall, two side walls, and two walls, respectively a front wall and a rear wall, that are open so as to allow access to the cavity; a lockdown screw, which is functionally coupled to the threaded hole and is arranged so as to pass through the upper wall so as to move within the cavity and facilitate the locking of the first and second electrical conductors; a first plate, which is coupled to the cage at the common edge between the front and lower walls and protrudes transversely from the lower wall outside the cavity; and a second plate, which is functionally connected to the screw so that it can move with respect to the screw and to the cage and is arranged so that a portion thereof is partially inserted in the cavity so as to cooperate with the screw for the locking of the first and second electrical conductors.

Description

TERMINAL FOR A LOW-VOLTAGE MODULAR DEVICE

DESCRIPTION The present invention relates to a terminal for a low-voltage modular device, i.e., for applications with operating voltages below 1000 volts, which has improved characteristics and functions.

It is known in the art that low-voltage electrical systems for both civil and industrial applications normally use devices that are termed modular because they are characterized in that they have a case whose two mutually parallel side walls are mutually spaced by a preset base multiple unit, which is common to all modular devices of the same type, as established by appropriate standards. These devices are conceived so as to provide a range of features required to ensure the correct operation of the electric circuit in which they are inserted and to protect the various user devices connected to said circuit against faults or malfunctions that might occur during the normal operating cycle.

A typical example of modular devices is constituted by circuit breakers of the magnetothermal or residual current-operated type, whose main function is to protect the system and the users connected thereto against any short-circuits or ground leakage currents, respectively. Moreover, circuit breakers are generally complemented by additional modular devices that allow to perform additional functions that are auxiliary with respect to the basic ones provided by circuit breakers: for example, it is possible to use minimum- voltage coils that allow to detect whether the voltage of the system in which they are inserted drops below a threshold limit, or signaling devices that allow to indicate remotely that the circuit breaker with which they are associated has tripped, or other devices.

In practical applications, depending on the circuit architecture to be provided, these modular devices can be used both individually and in groups that are functionally mutually associated, by mounting them for example on appropriate supporting guides and connecting them by virtue of connecting conductors in input and in output to a main power supply circuit and/or to the various user devices or branch circuits.

For this purpose, these devices are provided with suitable connection terminals, generally of the cage type, which are arranged in appropriate seats formed in the case of said devices and in which the connecting conductors are inserted from the outside of the case; said connecting conductors are then connected electrically to the active parts of the devices by locking down said terminals. Said terminals are conceived so as to ensure that the mechanical locking and electrical coupling of the connecting conductors to the device are provided as correctly, effectively, simply and quickly as possible during wiring work; they must also allow equally simple and quick interventions when one wishes to remove the cables in order to interrupt the connections.

Currently, known terminal types, despite achieving satisfactorily the functions for which they are intended, have some critical aspects, hi particular, the main drawback of known temiinal types is the fact that currently, once the connecting conductor has been locked down, a space remains exposed inside the terminal and can be accessed from the outside of the case, and that if there is a system requirement to connect the device with an additional connecting conductor, a careless intervention of an operator can lead to incorrect wiring in said space. For example, a practical case that can occur easily is that the additional conductor is inserted by forcing and in an incorrect position within the space of the terminal in which the previously inserted conductor is inserted; in such situations, even if the conductor is inserted in the terminal and is connected electrically to the device, one has wirings that are not optimum in terms of safety and can lead to dangerous overheating and possibly also to untimely and undesirable trippings of the modular devices.

The aim of the present invention is to obviate the drawbacks noted above and in particular to provide a terminal for a low-voltage modular device that allows to provide connections that are precise and adequate in terms of both safety and functionality of said connections, even when the device must be connected simultaneously to two different connecting conductors, while preventing, if a single connecting conductor is used at least initially, the possibility of subsequent careless interventions leading to incorrect and ineffective wiring.

This aim and these and other objects that will become better apparent hereinafter are achieved by a terminal for a low-voltage modular device, characterized in that it comprises: - a cage, which is shaped substantially like a parallelepiped that has a cavity suitable to receive at least one first electrical conductor and one second electrical conductor, which are meant to be mutually connected electrically, said cage having an upper wall provided with a threaded through hole, a lower wall, two side walls, and two walls, respectively a front wall and a rear wall, that are open so as to allow access to said cavity; - a lockdown screw, which is functionally coupled to said threaded hole and is arranged so as to pass through said upper wall so as to move within said cavity and facilitate the locking of said first and second electrical conductors;

- a first plate, which is coupled to the cage at the common edge between said front and lower walls and protrudes transversely from the lower wall outside the cavity; and

- a second plate, which is functionally connected to the screw so that it can move with respect to said screw and to said cage and is arranged so that a portion thereof is partially inserted in said cavity so as to cooperate with the screw for the locking of said first and second electrical conductors.

Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive embodiment of the terminal according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: - Figure 1 is a perspective view of a cage used in the terminal according to the invention;

- Figure 2 is a perspective view of a plate used in the terminal according to the invention;

- Figures 3 and 4 are general perspective views of the components of the terminal according to the invention during assembly;

- Figure 5 is a view of the terminal according to the invention inserted in a seat for accommodating a low-modular voltage electrical device;

- Figure 6 is a perspective view, taken from the outside, of the device of Figure 5 with the case closed;

- Figure 7 is a perspective view of the device of Figure 6, connected to a power supply cable inserted in the terminal according to the invention; - Figure 8 is a perspective view of the device of Figure 6, connected to a power supply bar inserted in the terminal according to the invention.

With reference to the cited figures, a terminal for a low-voltage modular device according to the invention, generally designated by the reference numeral 1 in Figure 5, comprises a cage 2, which is substantially shaped like a parallelepiped, is preferably provided by means of a single folded part, for example a metallic part, having a T-shaped end 30 inserted and locked in a contoured seat formed in the remaining portion of the body of said part, hi particular, the cage 2 has an upper wall 3 that is provided with a threaded through hole 4, a lower wall 5, two side walls 6, and a pair of walls, respectively a front wall 7 and a rear wall 8, that are open so as to allow access to a cavity 9; said cavity is suitable to receive at least one first electrical conductor and one second electrical conductor, which are meant to be connected electrically to each other, for the purposes and in the manners that will become better apparent hereinafter. Furthermore, as shown in Figure 1, the cage 2 has advantageously, at the common edge between the front wall 7 and the lower wall 5, a protruding tooth 10 that protrudes transversely to said front wall 7, preferably substantially at right angles thereto.

As shown in Figures 3 to 5, the terminal 1 according to the invention furthermore comprises a common lockdown screw, schematically designated by the reference numeral 11, and a first plate 12 and a second plate 13, which are functionally coupled to the cage 2, as described in detail hereinafter. hi particular, the first plate 12, shown schematically in Figure 2, preferably comprises a substantially rectangular flat body, which is made for example of electrically conducting material and on which there is a notch 14 that is suitable to be coupled geometrically to the protruding tooth 10 provided on the cage 2; in this manner, by virtue of the coupling between the tooth 10 and the notch 14, the plate 12 is coupled to the cage 2 at the common edge between the front wall 7 and the lower wall 5, so that its body protrudes transversely, preferably at right angles, from said lower wall 5, externally to the cavity 9. Furthermore, as shown in Figures 3 to 5, a covering element 15 is associated with the plate 12; said covering element is made of electrically insulating material and is coupled by forcing to said plate 12, so as to cover the face of said plate that is opposite with respect to the face on which the notch 14 is formed.

As an alternative, the plate 12 can be formed monolithically, for example by using electrically insulating material. In turn, the second plate 13, shown in detail in Figures 3 and 4, is functionally connected to the screw 11 so that it can move with respect to said screw and to the cage 2 in the manner described hereinafter, and comprises a substantially L-shaped body made of electrically conducting material; advantageously, in the illustrated embodiment, two portions 16 and 17 that constitute the body of the plate 13 are substantially mutually identical, and each portion is provided with at least one corresponding hole, designated by the reference numerals 18 and 19 respectively, h particular, the second plate 13 is arranged so that one of the two wings of the L-shape, for example as shown in Figures 3 and 4 the wing 16, is inserted at least partially in the cavity 9 of the cage 2, and the second wing 17 protrudes outside the cavity 9, transversely to the upper wall 3 and in the opposite direction with respect to the direction in which the body of the first plate 12 is arranged. A covering element 20, made of insulating material, is furthermore associated with the plate 13 and is suitable to be coupled with a snap action to the wing of the L-shaped body 17 that protrudes outside the cavity 9, so as to cover its opposite face with respect to said cavity. Clearly, since the two wings are substantially identical, the plate 13 can be arranged with the two wings swapped, so that the covering element 20 to still covers the wing that lies outside the cavity 9, according to a solution that is extremely simple in terms of practical use. hi turn, the lockdown screw 11 is arranged so as to pass through the upper wall 3 of the cage 2, so as to screw into the hole 4 and have a portion that moves inside the cavity 9; in particular, the end portion of the screw 11 that is inserted in the cavity 9 passes through the hole 18 of the plate 13 and is upset onto the surface of the corresponding wing 16. Advantageously, in the terminal 1 according to the invention the end of the screw 11 is upset loosely on the surface 16 of the plate 13 so that the coupling between these two components allows their movement with respect to each other and also with respect to the cage 2.

The practical use of the terminal 1 according to the invention in a modular device for low-voltage electrical applications is now described with particular reference to Figures 6 to 8.

During the assembly of the device, the terminal 1 is inserted in a suitable seat 21 provided in the case 22 of said device; in particular, the cage 2 is arranged so that it can move in the seat 21 with a first conductor 23, which belongs to the device and is connected to its electrically active parts, inserted in the cavity 9; in practice, said cage forms, together with the surrounding walls 3, 5, 6 and 7 of the cavity 9, two compartments 24 and 25. As shown in Figure 6, once the case 22 of the device is closed, the compartments 24 and 25 can be accessed from outside of said case and can receive respectively a second conductor and/or a third conductor for connection to the circuit in which the device is meant to be inserted functionally.

During wiring, if the device is wired with just one conducting cable 26, as shown for example in Figure 7, one end of said cable 26 is inserted in the compartment 25; then the lockdown screw 11 is screwed in and, by screwing into the hole 4, performs a rotary translational motion inside the cavity 9, drawing with it the plate 13, which in turn performs a substantially translational motion. The terminal according to the invention is conceived so that the tightening of the screw 11 simultaneously causes the movement of the cage 2 in the seat 21 in the opposite direction with respect to the advancement direction of said screw 11. In this manner, while the wing 16 of the plate 13 abuts against the cable 26, clamping it mechanically against the conductor 23 and ensuring an adequate electrical coupling between them, the movement of the cage 2 draws with it the plate 12, which at the end of the operation at least partially closes the corresponding compartment 24, preventing access thereto from the outside of the enclosure; at the same time, the wing 17 of the plate 13 blocks any space left in the compartment 25.

If instead the modular device is wired with a conducting bar 27, as shown for example in Figure 8, the end of said bar 27 is inserted in the compartment 24 and lockdown is performed by acting on the screw 11 in a manner that is fully similar to the one described earlier. In this case, the movement of the screw 11 places the wing 16 of the plate 13 against the conductor 23, while the movement of the cage 2 is limited by the presence of the bar 2, which in this case is clamped in a sandwich-like fashion between said conductor 23 and the lower wall 5 of the cage 2; in this situation, it is the second wing 17 of the plate 13 that closes at least partially the corresponding compartment 25, preventing access to it from outside of the case 22.

If the modular device has to be wired simultaneously with two different conductors, for example the cable 26 and the bar 27, the end of each one of said conductors is inserted in the corresponding compartment 24 and 25; by tightening the screw 11, the conductors are mutually locked and are adequately connected electrically by virtue of the combined action of the plate 13 on one side and of the lower wall 5 of the cage 2 on the other side, said plate and said wall moving in mutually opposite directions until there are no more free spaces in their respective compartments. h practice it has been found that the terminal according to the invention fully achieves the intended aim, providing improvements and advantages with respect to the terminals of the known art. hi the terminal according to the invention there are in fact clearly defined spaces, in each of which it is possible to insert only one conductor for connection to the electric circuit; as described earlier, the locking of the parts not only allows adequate mechanical and electrical coupling of the conducting parts but also allows to prevent the occurrence of accessible free spaces available for any incorrect interventions, both when using a single com ecting conductor and when using two conductors. Furthermore, the connections that are provided are optimum in terms of both safety and functionality, and allow to provide flexible circuit architectures. Finally, it should be noted that the terminal according to the invention, as a whole and in terms of its individual components, has a structure that is extremely simple from the point of view of manufacture and of practical use, which makes it applicable to the most disparate types of low- voltage modular device, be they interruption or protection devices, such as circuit breakers or undervoltage coils or shunt trip coils, or accessory devices, for example signaling devices, or other kinds of device. Therefore, another aspect of the present invention is a modular device for low-voltage electrical applications, characterized in that it comprises a terminal 1 of the type described above.

The terminal thus conceived is susceptible of modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with technically equivalent elements, hi practice, the materials used, so long as they are compatible with the specific use, as well as the dimensions, may be any according to the requirements and the state of the art.

Claims

1. A terminal for a low- voltage modular device, characterized in that it comprises:

- a cage, which is shaped substantially like a parallelepiped that has a cavity suitable to receive at least one first electrical conductor and one second electrical conductor, which are meant to be mutually connected electrically, said cage having an upper wall provided with a threaded through hole, a lower wall, two side walls, and two walls, respectively a front wall and a rear wall, that are open so as to allow access to said cavity;

- a lockdown screw, which is functionally coupled to said threaded hole and is arranged so as to pass through said upper wall so as to move within said cavity and facilitate the locking of said first and second electrical conductors;

2. The terminal according to claim 1, characterized in that said second plate comprises a substantially L-shaped body, a first wing of the L-shape being inserted at least partially in said cavity of the cage and being functionally coupled to the screw, a second wing protruding externally to the cavity transversely to said upper wall.

3. The terminal according to claim 2, characterized in that said second plate comprises a first through hole and a second through hole, which are arranged respectively on said first and second portions of the L-shaped body.

4. The terminal according to one or more of the preceding claims, characterized in that said lockdown screw has an end that is inserted in said first through hole and is upset on the surface of said first L-shaped wing, so as to functionally couple the movement of the screw and of the second plate, allowing at the same time a mutual movement thereof.

5. The terminal according to one or more of the preceding claims, characterized in that it comprises at least one first insulating covering element that is suitable to be coupled with a snap action to said second side of the L-shaped body of the second plate.

6. The terminal according to one or more of the preceding claims, characterized in that said cage comprises a monolithic part that has a T-shaped end that is bent so as to interlock said T-shaped end in a contoured seat formed in the body of said part.

7. The terminal according to one or more of the preceding claims, characterized in that said cage has, at the common edge between said front and lower walls, a protruding tooth that protrudes transversely to said front wall.

8. The terminal according to one or more of the preceding claims, characterized in that said first plate comprises a substantially rectangular flat body on which there is a notch that is suitable to be coupled geometrically to said protruding tooth formed on the cage.

9. The terminal according to claim 8, characterized in that it comprises a second insulating covering element that is suitable to be coupled by forcing to said second plate.

10. A modular device for low- voltage electrical applications, characterized in that it comprises at least one terminal according to one or more of the preceding claims.