US3708769A

US3708769A - Electromagnetic contactor

Info

Publication number: US3708769A
Application number: US00160438A
Authority: US
Inventors: A Caltabiano
Original assignee: GHISALBA SpA
Current assignee: GHISALBA SpA
Priority date: 1970-10-22
Filing date: 1971-07-07
Publication date: 1973-01-02
Anticipated expiration: 1990-01-02
Also published as: CA952164A; DE2152506A1; FR2111754A3; ES173027U; ES173027Y; FR2111754B3

Abstract

An electromagnetic contactor with a magnetic core subdivided into two portions, wherein the first of said portions is mounted fixedly with respect to the operative closure stroke of the contactor, but with no positive connection to the contactor structure so as to move back under impact of the second core portion at the time of contactor closure. Said first core portion may be manually lifted for disengaging and removing the driving coil of the contactor.

Description

[451 Jan. 2, 1973 541 ELECTROMAGNETIC CONTACTOR 3,458,838 335/132 3,383,634 5/1968 Bauer et al. ..........................335/257 [75] Inventor: Alflo Caltabiano, Turin, ltaly [73] Assignee: Ghisalba S.p.A., Turin, Italy Primary Examiner-Harold Broome Attorney-Irvin S. Thompson and Robert J. Patch [22] Filed: July 7, 1971 [21] App]. No.: 160,438

ABSTRACT An electromagnetic contactor with a magnetic core 30 F0 n A cat- Prio D ta subdivided into two portions, wherein the first of said 1 relg W n y a portions is mounted fixedly with respect to the opera- Oct 22, 1970 Italy.........................................705l4 rive losure stroke of the contactor, but with no positive connection to the contactor structure so as to /2 move back under impact of the second core portion at [51] Int. ......H0111 50/18 the time of contactor closure. Said first core portion [58] Field of may be manually lifted for disengaging and removing the driving coil of the contactor.

8 Claims, 4 Drawing Figures References Cited UNITED STATES PATENTS 3,196,231 Meyer PAIENTEDJAN' 2191 3.708.769

SHEET 2 [IF 2 I INVENTOR 44 Ava CALTAB/fl/VO ATTORNEYS BACKGROUND OF'TI-IE INVENTION This invention refers to an electromagnetic contactor wherein improvements are made with the purpose of reducing core wear and tendency to bounce, of improving the closure power and of making easier mounting and dismounting the driving coil or coils.

In those electromagnetic contactors wherein the fixed portion of the magnetic core is stiffly connected" sequent contact damage.

In certain known contactors, said detrimental events have been somewhat reduced by connecting the fixed core portion to the contactor structure through yielding members capable of subduing up to a certain extent the impact of themovable core portion. Even in such contactors, however, the importance of .the above-mentioned detrimental events remains such as to produce fast wear and sometimes serious drawbacks.

Another disadvantage of a completely different kind,

which is found in most known electromagnetic contac tors, is the difficulty in mounting and dismounting the driving coil. Except for complicated and expensive arrangements, which sometimes produce disadvantages in operation, there is no means of replacing the coil without dismounting other members of the contactor too, as for example the unit of the movable contacts or the magnetic core. Therefore, contactors without coil, and coils of different characteristics to be mounted on demand according to the requirements of users, cannot be separately stored, as it would be of advantage for organization. Furthermore, when the contactor is in use, the"replacemer 1t of the coil, which is subjected to burnings, requires mostly disconnection of the feeding bars and thus a-ra'ther long operation during which all the appliance comprising the damaged contactor remains inactive.

BRIEF SUMMARY OF THE INVENTION This invention has the object of improving an elec tromagnetic" contactor by introducing therein a peculiarity suitable by itself for reducing in a substantial 'manner all the above stated disadvantages of different kinds of the known contactors, even by improving the closure power and without in any way increasing the manufacture costs.

-According to the invention, this object is attained by the fact that the socalled fixed portion of the magnetic core has no actual connection to the contactor structure, but it is simply supported in the rest position, when the contactoris .open, by a one-sided bond capable of preventing said fixed portionfrom approaching the movable core portion, but unable to oppose a noticeable resistance to a displacement of said socalled fixed portion of the core in a direction opposite said movable portion. Of course, the fixed portion of the core is so called only with reference to its operation stroke. In this manner, when the contactor closes and the movable core portion comes to contact with the fixed core portion, this latter yields due to the impact of the movable portion, without any resistance except its own inertia, and it moves back. Therefore the movable core'portion joined with the fixed portion continues to a-certain extent itsstroke beyond the normal closure position, up to exhaustion of its own kinetic energy and.

then, always joined with the fixed core portion, the movable portion returns'towards the normal closure position, without having caused any violent impact, noise or vibration. Both the core wear and the tendency to contact bounce are therefore substantially reduced. Furthermore, when the movable core portion effects the said additional stroke, it being connected as known to the driven unit of movable contacts, it loades beyond the normal value the springs of the movable contacts and thus it pushes said movable contacts against the fixed contacts, during a brief lapse of time after contactor closure, with an increased load. On one hand said increased load further reduces the bounce tendency, and on the other hand it gives rise to an unusual adherence between the contacts during the peak of maximum current absorption which immediately follows the contactor closure, thus increasing the closure power of the contactor, if all other features remain unchanged.

Finally, it becomes possible to allow manual retraction of the fixed core portion from its rest position to an extent sufficient for disengaging the magnetic core from the driving coil. By making the coil removable from the front portion of the contactor structure, between the movable contacts, it then becomes possible to mount and dismount the coil orcoils from the installed contactor by a simple and easy operation, without requiring dismounting of any other portion of the contactor.

BRIEF DESCRIPTION OF THE DRAWINGS This invention will be more clearly understood from the following description, drawn up with reference to a non limitative example of embodiment which is diagrammatically shown the annexed drawings. In the drawings:

- FIG. 1 shows a vertical section'of the contactor, I taken along the displacement direction of the movable contact unit and according to the broken line I-I of FIG. 2;

FIG. 2 is a rear'view of a section of th'econtactor, taken along the line II-II of FIG. Ii

FIG. 3 is a partial section similar to FIG. 1 but showing the fixed core portion in retracted position and the driving coil during its extraction operation;

FIG. 4 is a partial front view showing the respective positions of the coils and themovable contacts.

DETAILED DESCRIPTION members 4 are carried, under action of springs 5, by a movable unit 6 which passes through openings 7 of the intermediate wall 1 and which is pin connected, at the rear end thereof, to square levers 8. Said square levers 8 are hinged to pivots 9 fixed to the contactor structure 0, and at the opposite ends they are connected to the movable portion 10 of the magnetic core. Said movable portion 10 faces the socalled fixed portion 11 (which however, as already explained, may be considered fixed only with reference to the main operation stroke). The driving coils 12, which in the example are in number of two, are linked to the branches of the fixed and

movable portions

11 and 10 of the magnetic core. Near the fixed and movable contact members 3 and 4, on the cover 2 acting as a firescreen are mounted arc extinguishing plates 13. All the component parts described till now, as well as their arrangements and functions, are well known to those skilled in the art, and therefore they do not require a more detailed description.

In the known contactors, the fixed portion 11 of the magnetic core is fixed, stiffly or through shock-absorbing members of a somewhat yieldable material, to the contactor structure 0.

According to this invention, on the contrary, the socalled fixed portion 11 of the magnetic core has no fixed connection to the contactor structure, but it is guided with respect to said structure so that it may move in the same direction of displacement as the movable portion 10 of the magnetic core, along a sufficiently long stroke, but only in the direction of departing from said movable portion 10 and not in the direction of approaching it from the rest position. This has been practically obtained, in the shown example, by providing the fixed portion 11 of the magnetic core with extensions 14 inserted within guide members 15 fixed to the structure 0 and whose shape, which according to the shown example is like a -U-, allows the socalled fixed member 11 to displace only in the same direction of the operation closure stroke of the movable core portion 10. Moreover said guide members 15 limit the mobility of the socalled fixed portion 11 such as to establish a rest position thereof. Said fixed portion 11 is maintained in its rest position by its own weight or, if needed, by action or with the aid of light return springs, not shown. Preferably, the extensions 14 engage the guide members 15 by means of pads 16 of a shock-absorbing or somewhat yieldable material, such as rubber, nylon or the like.

The contactor operation takes place as follows. When the coils 12 are feeded in view of producing closure of the contactor, a magnetic flux is produced in the magnetic circuit comprising the movable and

fixed portions

10 and 11 of the magnetic core, and as a consequence an attraction force is applied onto the fixed core portion 11, in the direction downwards according to the drawing, as well as onto the movable core por tion 10, in the direction upwards according to the drawing. Since the extensions 14 rest through the pads 16 upon the transverse portion of the guide members 7 15, the fixed core portion 11 may not move under action of said attraction force which trends to approach said fixed portion 11 to the movable portion 10. As a consequence, during this phase of operation the fixed core portion 11 behaves in the same manner as in the known contactors, wherein it is fixedly connected to the contactor structure.

On the other side, the movable core portion 10 is displaced upwards (according to the drawing) by said attraction force and, in a well known manner, it causes the square levers 8 to rotate about the pivots 9 and the movable unit 6 to displace (towards the left hand side, according to the drawing) thus approaching the movable contact members 4 to the fixed contact members 3 up to contact thereof, and then compressing the springs S of the movable contact members 4.

When the movable core portion 10 takes contact with the fixed core portion 11, it has at this time a somewhat reduced speed due to the absorption of a portion of the kinetic energy by action of the compression springs 5, however the speed of said movable core portion still is noticeable. However the impact against the so-called fixed core portion 11 does not stop the movable core portion 10, thus dissipating its kinetic energy into vibrations, noise and heat produced by anelastic deformations of the materials, as in the known contactors the socalled fixed portion 11 of the core moves back, joined with the movable core portion 10, thus allowing the latter to travel along an additional stroke beyond its normal closure position. During said additional stroke, the contact springs 5 are further compressed, and so the return springs of, the movable unit 6, if they are provided as required in some contactor types, but not shown in the example. Compression of said springs exhausts the whole kinetic energy of the movable core portion 10. Thereafter, under return action of the compressed springs, the movable unit 6, the movable core portion 10 and the socalled fixed core portion 11 return towards the normal closure position and stop when the extensions 14 of the socalled fixed core portion 11 rest anew upon the transverse portion of the guide members 15. At this time the somewhat yieldable pads 16 absorbe the light shock which is produced.

Of course, the impact between both core portions when they take contact is substantially less severe than in the known contactors, since it is here supported only by the own inertia of the socalled fixed core portion 1 1. There is consequently a substantial reduction in the anelastic deformation which progressively damages the component parts of the contactor, with special reference to the magnetic core portions, and noise, vibrations and tendency to contact bounce are also considerably reduced. During the following additional stroke, the increased compression of the springs 5 further hampers the tendency to the contact bounce and moreover it produces an increased contact pressure between the movable and fixed contact members during the period of time, immediately following the contact closure, wherein there is generally a peak of maximum current absorption through the contactor, Therefore the closure power of the contactor is increased by unchanging other conditions.

Of course, the above stated advantages are obtained independently from the mounting manner of the coils 12 which therefore, as long as the reduction of the closure impact is concerned, may be of any kind and anyhow mounted. However, it is possible to take advantage of the stated feature of the so-called fixed magnetic core portion 11 being movably mounted instead of being fixed to the contactor structure 0, for further allowing easy mounting and dismounting of the driving coil or coils.

There is no absolute need for limiting the possible extension of movement of the socalled fixed core portion 11 in the direction of allowed displacement, however it is suitable to provide such a limitation, for example by means of a stop 17, for avoiding the fixed core portion leaving its place during transportation or as a consequence of a wrong manual operation. For operation purposes, the displacement stroke allowed to the fixed core portion may amount to only few millimeters, for example ten millimeters. On the contrary, the stop 17 is arranged as such a distance a from the fixed core portion, as to allow a displacement amounting at least to the difference between the height L of the coil 12 and the length T of the air gap provided in the magnetic core circuit, in open position. Moreover, the coil or coils l2 driving the contactor are arranged within suitable windows 71' of the intermediate wall 1; they are fixed in front of said wall, at 18, 19 and are arranged (as shown in FIG. 4) in the free spaces between the movable contact members 4 of the contactor. If said requirements are fulfilled, it is sufficient to release the

connections

18, 19 and to raise the fixed core portion 11 up to against the stop 17 for allowing removal of the coils 12 from the front side of the contactor, by passing them between the movable contact members 4 as diagrammatically shown in FIG. 3. Dismounting the coils, as it appears, requires the simple removal of the firescreen or cover 2 with the affixed arc-extinguishing plates 13, without requiring dismounting of any other component part of the contactor, even if it is installed. Since the operation is effected entirely from the front side, it founds no hindrance in other appliances which may be installed in the vicinity. As a consequence dismounting the coils is extremely easy, thus affording the already stated advantages.

According to the shown form of embodiment, the movable core portion is slightly engaged within'the coils 12-, and therefore said coils should be slightly raised for disengaging them from the magnetic core when they have to be removed. It is possible, however,

to arrange the'movable pore portion-as at 10' (FIG. 2), i.e. normallydisengaged from the coils 12, thusavoiding need for raising the coils before removal thereof.

, The electric connection of the coils 12 may take place, in a manner per se known, by means of their own mechanic connection, thus making'the operation still easier. Raising the fixed core portion may be effected by acting from the front side of the contactor by means of a'screw-driver or like suitable tool, and by operating onto a suitable extension 20 of the fixed core portion 11. I

Return of the fixed core portion 11 to its normal position may be effected by its own weight or by a return spring (not shown) which, however, should apply a sufficiently light effort such as not to hinder manual raising of the fixed core portion nor its going back at the time of impact against it of the movable core portion 10.

It is to be noted that the characteristic feature according to the invention is actually suitable for attaining the desired advantages yet without involving an increased cost or a complication in the manufacture of the concerned contactor, so that its application involves a considerable technical and industrial advantage.

The shape and the arrangement of the different component parts "of the contactor may, of course, .be modified in different ways with respect to the shown example of embodiment, without departing from the scope of the invention.

Having thus described my invention, what I claim is:

1. An electromagnetic.contactor comprising a structure, mounted in said structure at least one driving coil, a first magnetic core portion mounted in said structure for movement in a stroke direction and magnetically linked with said driving coil, a movable unit guided in said structure and operatively connected to said first core portion, movable contact members carried by said movable unit, fixed contact members mounted on said structure and cooperable with said movable contact members, a second magnetic core portion linked with said driving coil and cooperable with said first core portion, and guide members interposed between said structure and said second core portion and supporting said second core portion in a rest position, said guide members guiding said second core portion along a direction of movement corresponding to said stroke direction of said first core portion and allowing free displacement without noticeable resistance of said second core portion from said rest position thereof only in the direction of departing from said first core portion, whereby upon feeding of said coil the first core portion moves towards thesecond core portion by driving said movable unit and closing together said fixed and movable contact members, and upon impact of the first core portion the second core portion moves back thus allowing an additional stroke of the first core portion, and finally returns with said first core portion to the rest position.

2. An electromagnetic contactor as set forth in claim 1, wherein said guide members are U-shaped and have transverse portions, and wherein said second core portion has extensions engaged in said guide members,

said extensions resting upon said trasverse portions of the guide members in the open position of the contactor and during a first portion of the closure operation.

'3. An electromagnetic contactor as set forth in claim 1, wherein said guidemembers are U-shaped and have transverse portions, said second core portion has extensions engaged in said guide members, and pads of a somewhat yieldable material are inserted between each extension of the second core portion and each transverse portion of the guide members.

4. An electromagnetic contactor as set forth in claim 1, further comprising a stop cooperable with said second core portion in view of limiting the length of the displacement allowed thereto.

5. An electromagnetic contactor as set forth in claim 1, further comprising a stopcooperable with said second core portion, said stop being arranged at a distance from the rest position of the second core portion, at'least equal to the difference between the height of said driving coil and the distance between both said first and second core portions in the open position of the contactor, whereby upon displacing said second core portion up to against said stop, said driving coil can be disengaged form both the first and second core portions and removed.

6. An electromagnetic contactor as set forth in claim 1, wherein said structure comprises an intermediate wall, said intermediate wall has windows apertured therein in correspondence with free spaces between said fixed contact members, said driving coil or coils are inserted in said windows from the front part of the contactor through said free spaces between the fixed contact members, and connection members operable from the front part of the contactor are provided for between said structure and said driving coil or coils.

7. An electromagnetic contactor as set forth in claim l

Claims

1. An electromagnetic contactor comprising a structure, mounted in said structure at least one driving coil, a first magnetic core portion mounted in said structure for movement in a stroke direction and magnetically linked with said driving coil, a movable unit guided in said structure and operatively connected to said first core portion, movable contact members carried by said movable unit, fixed contact members mounted on said structure and cooperable with said movable contact members, a second magnetic core portion linked with said driving coil and cooperable with said first core portion, and guide members interposed between said structure and said second core portion and supporting said second core portion in a rest position, said guide members guiding said second core portion along a direction of movement corresponding to said stroke direction of said first core portion and allowing free displacement without noticeable resistance of said second core portion from said rest position thereof only in the direction of departing from said first core portion, whereby upon feeding of said coil the first core portion moves towards the second core portion by driving said movable unit and closing together said fixed and movable contact members, and upon impact of the first core portion the second core portion moves back thus allowing an additional stroke of the first core portion, and finally returns with said first core portion to the rest position.

2. An electromagnetic contactor as set forth in claim 1, wherein said guide members are U-shaped and have transverse portions, and wherein said second core portion has extensions engaged in said guide members, said extensions resting upon said trasverse portions of the guide members in the open position of the contactor and during a first portion of the closure operation.

3. An electromagnetic contactor as set forth in claim 1, wherein said guide members are U-shaped and have transverse portions, said second core portion has extensions engaged in said guide members, and pads of a somewhat yieldable material are inserted between each extension of the second core portion and each transverse portion of the guiDe members.

5. An electromagnetic contactor as set forth in claim 1, further comprising a stop cooperable with said second core portion, said stop being arranged at a distance from the rest position of the second core portion, at least equal to the difference between the height of said driving coil and the distance between both said first and second core portions in the open position of the contactor, whereby upon displacing said second core portion up to against said stop, said driving coil can be disengaged form both the first and second core portions and removed.

7. An electromagnetic contactor as set forth in claim 1, wherein in the open position of the contactor said first core portion is disengaged from said driving coil or coils.

8. An electromagnetic contactor as set forth in claim 1, wherein said second core portion has an extension operable with the aid of a suitable tool from the front part of the contactor for manually raising said second core portion.