Device for detecting differential currents in electric systems

Abstract

 This device, eclosed in a box-like body (1) associable with conventional switches (2) of the movable-contact type, comprises at least one pin (5) protruding from the container body and subject to translatory motion upon the onset of differential current in the electric system, said pin (5) being accommodated, after the coupling of the device to a switch, within a port (11) provided in the coupling wall of said switch. In the coupled position the pin is arranged substantially in contact with the contact release lever (6) of the switch. The movable pin is guided, in its releasing and resetting strokes along first cam guides (13) provided in the walls of the container body, while second cam guides (16) are provided having such a path as to allow the pin (5) to pass below the release lever (6) and then assume its correct resetting position, thus allowing the coupling operation without errors in positioning the pin (5) with respect to the release lever (6).

Description

[0001] The present invention relates to a device for detecting differential currents in electric systems, enclosed within a compact box-like body which is electrically and mechanically preset so as to be associable to the side of ordinary switches, e.g. modular miniaturized switches.

[0002] As is known, in order to protect the safety of people and the integrity of electric systems, conventional movable- or oscillating-contact switches are associated to electric devices capable of detecting any differential currents which may arise for various reasons in the circuit in which said devices are inserted.

[0003] Normally, the differential device is enclosed in a box-­like body which is then coupled, side by side, to the body of the switch; said device is normally constituted, as well as by a known electric apparatus capable of detecting any differential currents, also by mechanical means protruding from the body of the device and entering the body of the switche, adapted to act on a release lever capable of performing the opening of the contacts. After each release action the differential device is reset, i.e. returned to its operative condition, so as to intervene in the case of a new occurrence of differential current.

[0004] Therefore, the function of a differential unit or device is to transmit to the switch with which it is coupled a release action capable of causing the opening of the contacts in the presence of a differential current.

[0005] In practice, the known types of differential devices associable to the side of a switch require specialized personnel for their correct assembly in order to avoid errors which can create severe damage and hazards both to the system and to people.

[0006] The aim of the present invention is to provide a device for detecting differential currents, enclosed in a box-like body or block, electrically and mechanically structured and preset so as to be correctly associable, side by side, to electric switches already available on the market even by unskilled personnel and with no possibility of unintentional assembly errors.

[0007] Another object of the invention is to provide a differential device with high reliability and durability, adapted for nominal currents of different intensities and also associable with miniaturized modular switches without requiring modifications and/or adaptations.

[0008] Not least object is to provide a device of the above described type which is structurally simple and has a low cost, i.e. a cost substantially corresponding to that of known differential devices.

[0009] This aim, as well as these and other objects which will become apparent hereinafter, are achieved by a device for detecting differential currents in electric systems, as defined in the appended claims.

[0010] The invention is described hereinafter in greater detail according to a preferred but not exclusive practical embodiment, with reference to the accompanying drawings, given only by way of non-limitative example, wherein:

figure 1 is a schematic front view of a conventional switch and of a differential current detector device, according to the invention, shown in the step of arrangement to the side of the switch before a stable coupling is achieved;

figure 2 is an also schematic view of the structure of a movable contact provided in a known switch, illustrating a port in the body of said switch, an oscillating contact release lever and a pin for the actuation of said lever;

figure 3 is a schematic view of two successive relative positions of the actuation pin with respect to the release lever, i.e. in ready or set position and in the position of maximum shift after the release of the contact;

figures 4 and 5 are again schematic views of a constructive detail of the differential device according to the invention, with the pin in two positions of maximum mutual distance before coupling to the switch.

[0011] As previously mentioned, a device for detecting the presence of differential currents in an electric system performs the function of transmitting to the outside of the box-like body which contains it a releasing action capable of causing the opening of the contacts of an electric switch to which said device is coupled upon every occurrence of differential currents produced by various causes.

[0012] The differential current detector device according to the present invention therefore uses a known detection apparatus capable of causing the movement of a pin which protrudes from the box-like body and in turn moves a release lever which is already provided in normal switches and has the purpose of being electrically and mechanically preset to be associable, side by side, with known switches (of the same series) with no possibility of unintentional errors in assembly by the installer.

[0013] In particular, with reference to the accompanying figures, the device according to the invention is constituted by a box-like body 1, which contains the conventional differential current detection means and is associable, side by side, with a switch 2 (figure 1) with a position defined by reference dowels 3 and with a stable electrical and mechanical coupling by means of locking elements 4.

[0014] A dowel or pin 5 protrudes from the box-like body 1 and has such dimensions as to be accommodated, when the device 1 is coupled, nearly in contact with an oscillating lever 6 (the free end whereof is visible in the drawing figures) which is already provided in the switch 2 and retains in closure position a movable contact 7 which is associated with a lever 8 pivoted at 9 (figure 2).

[0015] The free end of the release lever 6 and the pin 5 are movable according to the arrow 10 (figure 2) and their movement is allowed by a port or window 11 provided in the lateral coupling wall 11a of the switch 2; the port has such an extension or area as to allow a movement of the pin and of the release lever which is sufficient to allow the release of the lever 6 from the lever 8 upon any occurrence of differential currents in the system in which the device is inserted, as will become apparent hereinafter.

[0016] With this relative arrangement between the pin 5 and the release lever 6, in order to obtain the opening of the movable contact 7 (in the presence of differential currents which cause the movement of the pin) it is therefore necessary that the release lever 6 be moved by the pin (figure 3), e.g. from the ready or set position 6a to a stop position 6b, the pin accordingly passing from position 5a to position 5b; the extent of these movements must in any case be such as to remain within the port 11.

[0017] After every release, the device must be reset, i.e. returned to its initial conditions; this entails the backward movement of the pin 5 (by virtue of grip means external to the box-like body 1) from position 5b to position 5a, and the release lever 6, which is pivoted at 6c (figure 2), must be able to return to position 6a in order to allow a successive release.

[0018] These movements are possible without inconvenience when the differential device is correctly coupled to the switch.

[0019] A severe disadvantage which may cause damage to the systems and to people may instead occur if, before coupling the device to the switch, the pin 5 is still in position 5b (figure 3) e.g. because the device has not been reset; in this situation the pin would be on the opposite side of the release lever 6 which has instead returned to its ready position 6a and it would therefore be impossible for said pin to move the release lever upon the occurrence of a differential current.

[0020] In order to obviate this severe disadvantage, the differential device is preset so that when it is not coupled to the switch the position of the pin can be either position 5a (reset device) or a position 12 (figure 4) which is displaced with respect to the stop position 5b (device not reset) and is in any case such as to prevent the entry of the pin into the port 11 of the switch. The path for moving the pin from position 5a to the extreme position 12 is defined by cam guides 13 provided on the opposite walls of the box-like body which contains the differential device. As visible the cam guides 13 are longer than the longitudinal extension of the port 11 of the switch. Thus, by coupling, if the pin 5 is in position 5a the assembly is possible and correct as the pin can enter the port, thus allowing the coupling; if instead the pin is in position 12, the coupling is impossible since the pin cannot enter the port. Consequently, in order to perform the coupling, the operator is forced to reset the differential device by moving the pin to position 5a.

[0021] Still according to the invention, in order to prevent the operator from unintentionally attempting to arrange the device adjacent to the switch and simultaneously performing the resetting operation e.g. by moving the pin to an intermediate position 14 (figure 5) along a path indicated e.g. by the reference numeral 15, and therefore allowing it to enter the port but in incorrect position with respect to the release lever 6, the device has separate cam guides 16, also provided in the opposite walls of the body containing the differential device, which guides, by virtue of their particular arc-like path and by means of external grip elements associated with said cam guides 16, force the pin, in the resetting step before coupling, to pass below the free end of the release lever 6 before it reaches the ready position 5a, i.e. in correct position to cause the movement of the lever 6 and therefore the release of the movable contact 7.

[0022] In practice it has been observed that the differential device structured and present according to the invention fully achieves the intended aim and objects, ensuring complete freedom from unintentional assembly errors and therefore preserving the integrity of the system and the safety of the operators.

[0023] Naturally, in its practical embodiment the invention as described above according to a preferred embodiment may in practice be susceptible to structurally and functionally equivalent modifications and variations without abandoning the scope of the protection of the invention.

[0024] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims

1. A device for detecting differential currents in electric systems, comprising a box-like body (1), containing a known detection device associable, side by side, with an electric switch (2) or similar apparatus with movable contacts (7), comprising at least one pin (5) protruding from the container body and subject to translatory motion, with a preset stroke, upon the onset of differential current in the electric system, said pin (5) being accommodated, after the coupling of the device, within an opening (11) provided in the coupling wall of said switch (2) with such dimensions as to allow only the translatory stroke of said pin (5) arranged substantially in contact with the ordinary lever (6) for releasing the movable contact (7) of the switch upon the onset of differential current, characterized in that said movable pin (5) being guided, in its stroke for the release of the movable contact and in its resetting stroke after each release, along first cam guides (13) provided in the walls of the container body.

2. A device according to claim 1, characterized in that second cam guides (16) are provided for resetting the device before its coupling to the switch (2), in order to prevent errors in positioning the pin (5) with respect to the release lever (6), said second cam guides (16) having such a path as to allow the pin (5) to pass below the release lever (6) and then assume its correct resetting position, thus allowing the coupling operation.

3. A device according to claim 1, characterized in that said first cam guides (13) are longer than the longitudinal extension of the port (11) of the switch (2), so as to allow the pin to move, once the coupling is performed, from its ready position (5a) against said release lever (6) to its stop position, once the release has been performed, and to then return to its starting release position, always remaining within said port, and to allow, with the device (1) not coupled to the switch (2), said pin (5) to assume an end stop position (12) such as to not be insertable in said port (11) except after resetting said device.

4. A device according to claim 1, characterized in that said second guides (16), have an arc-like path different from the first guides (13).

Drawing