US2407603A - Electromagnet - Google Patents

Description

Sept. 10, 1946.7 E. A. DERUNGS ELECTROMAGNET Filed Dec. 23, 1945 2 Sheets-Sheet 2 Mal/Z07:

ERNEST LPHONSE DERUNGS flmrney Patented Sept. 10, 1946 UNITED STATES BPATENT ()FFICE ELECTROMAGNET Ernest Alphonse Derungs, Le Locle, Switzerland Application December 23, 1943, Serial No. 515,404 In France April 23, 1940 trcmagnet and the object controlled by the same,

for instance, cams for compensating the great differences in the force of attraction between the moment when the ai is a maximum and the moment when it is a minimum. In this case, the loss of energy caused by the dispersion of the lines of force occurring at the beginning of the attraction is not recoverable. Besides this the mechanical device for obtaining a uniform force of attraction to be transmitted represents a com plication diminishing the efiiciency of the appa ratus.

Object of the present invention is to obtain elcctrom-agnet permitting the force of attract on to be rendered uniform without providing additional means, while constantly disposing of the required energy at a maximal efliciency.

electromagnet according to the invention comprises two mutually movable core and armature members approaching each other when the exciting circuit. is closed, the end portion of at least one of these members comprising a number of arranged in steps with surfaces gradually d nishing towards the end of the member, in order, during the mutual approaching of the members, to obtain a canalisation of the lines of force and, in consequence, an adjustment of the force of attraction.

In a preferred embodiment means are provided for avoiding a violent shock at the end of the armature stroke. These means are: amplifying the attraction at the beginning of the stroke of the movable armature and reducing it towards the end of the stroke.

The first of these means consists in the form given to the end portions of the members appreaching each other. By preference, one of these members a staggered end portion which corresponds to a hole of slightly greater lateral dimensions in the other member.- The steps of substantially regular form can be interconnected by parts whose inclination is preferably in the order of 45 degrees. The said corresponding hole in the other member need not necessarily lit the steps exactly. The ratio between the cross sections of the end portion and of the cross section of the main body of the armature, as well as the ratio between the lengths of the difierent steps can be chosen so that maximal recovery of the leakage lines of the magnetic field is obtained, this, however, within limits in which the force of attraction, owing to the deflection of the lines of force in the interior of the hole, does not show 9 a diminution which is injurious to a reliable working during the closing of the electromagnet.

The second means consists in the manner of excitation. By preference, the intensity of the exciting current is greatest at the beginning of the attraction of the movable armature and gets smaller towards the end of the stroke where the gap is smallest. This variation in the current intensity can be obtained by well-known means, g. by the use of one or several change-over switches operated by the movable armature during its stroke and by separate circuits which are successively connected in parallel and in series by these change-over switches, or by the use of any resistances which are connected to the exciting circuit by means of these change-over switches.

It is understood that these two means can be used separately and that the first one alone can s ecially form a sufficient adjusting means for many applications.

The accompanying drawings illustrate, by way of examples, two embodiments of the electromagnet according to the invention.

Fig. l is axial section of the first embodiment;

Fig. 2 is a partial plan view of the same,

Fig. 3 illustrates a detail of a switch.

Fig. 4 is an axial section of the second embodiment.

Fig. 5 shows the movable armature and the fixed core in another mutual operating position, than that in Fig. 4.

Fig. 6 is an elevation, partly in section, of a switching device controlling the excitation of the windings in the second example, and

Fig. 7 is a plan View thereof.

In Figs. 1 to 3 an electromagnet with a movable, central dipping armature is represented, which is greatly saturated and receives the exciting current from a source of current with practically constant voltage, for instance, from a storage battery.

As may be seen in Figs. 1 and 2 of the drawings, a tubular, subdivided steel body ll] of the electromagnet ends on the one side in a steel disc H comprising a fixed core l2 provided with a hole i3 ending in a bore M. This hole l3 has a truncated cone portion l5 followed by a cylindric part l8 and another truncated cone portion IT. The cone angle of the portions l5 and I1, that is the angle between the generating line of these portions and the central axis of the electromagnet, is about 45. On the other end the tubular body H! has a steel disc l8 having a flange IQ for centering the movable armature 2| and at 29 a diameter slightly greater than that of the flange H3. The movable steel armature 2| of cylindrical form carries on its outer end a shoulder 22 and on its inner end a truncated cone surface 23 followed by two cylindrical portions 24 and 26 interconnected by another truncated cone 25, further followed by a third truncated cone 21 and a cylindrical guide rod 28 slidably arranged in the bore M of the disc Hence, the section of the inner end portion of the armature 2| diminishes by steps. A spool made of a non-magnetic tube 29 fixed to the core l2 and of two steel plates 36 and 3| is centered in the disc |8 by the shoulder 32 of the plate 3| and held in place by the screw 33. In the annular space 34 are mounted two windings one of which, made of fine wire, receives the exciting current directly by the conductor 35, while the second one, formed by a thicker wire, receives the current by the intermediary of the conductor 31 from the contact 38, the conducting blade 38, the contact 40 and from the conductor 4| in order to be earthed by the conductor 42. A limit switch is formed by the support 43 fixed to the disc II. This support 43 carries an axle 44 on which the support 45 can freely rotate. The latter is connected by two insulating. bars 46. 46', on the one side, to the conducting blade 39, on the other side, to the adjustable holder 41 for a draw spring 48. Two columns 49 and 49' fixed to the disc carry the insulating plate 5i! held by the screws 5|. To this insulating plate 50 the two contacts 36 and 40 are fixed, to which the conductors 31 and 4| are connected by the screws 52 and 52. The proportion of the diameter of the cylindrical part 2| to the diameter of the portion 24 determines the degree of uniformity of attraction, and owing to the arrangement of the conical surfaces on the armature and on the fixed core most of the leakage lines lost in ordinary magnets are absorbed by the surfaces I5, 25 and 21; however, when the cylindrical part 26 is on the level of the cylindricalart IS, the closing of the lines of force between these two cylindrical parts 26 and I6 remains small enough as not to cause too great a diminution of the attraction force of the armature; this is also the case when the cylindrical surface 24 is on the level of the cylindrical surface I 6. Besides, in order to augment the effects of canalisation of the lines of force, the passage section for the magnetic field in the interior of the tube l0 and in the pieces I8, 30 and 3| is much greater than that in the cylindrical portion of the armature 2|.

Operation:Before the beginning of attraction, the electromagnet is in the position shown in Fig. 1, that is, the armature 2| has the greater distance from the core l2. When excitation takes place, the two windings are connected in parallel. The current passes through the conductor 31, the contact 38, the conducting blade 39, the contact 40 and the conductor 4| through the winding with the thicker wire and the earthed conductor 42, and for the winding with the thin-. ner wire through the conductor 35 and the earthed conductor 36. As above-mentioned, the current density in the thicker wire is comparatively very great and the magnetisation of the armature 2| quickly reaches the limit of saturation. By the special form of the inner end portion of the movable armature 2| constituted by the cylindrical and conical parts 23, 24, 25, 26, 21 and 28 the path of the lines of force is shortened with regard to that which should have been effected by the lines of force in the air; this diminishes by so much the leakage flux which might occur between the cylindrical surfaces of the armature 2| and the tube |6. In proportion as the movable armature 2| app-roaches the fixed core |2, the penetration of the cylindrical parts 26 and 24 into the hole 3 tends to reduce the force of attraction owing to the deflection of some of the lines of force in a direction perpendicular to the stroke of the movable armature 2|. In this way the attraction force is augmented at the beginning of the movement of the armature and diminished from the moment when it attains a value exceeding the prescribed effort to be exerted by the movable armature. As soon as the armature 2| is at the end of its stroke and the stop 22 is only at a small distance from the disc l8, the rod 28 lifts the support 45 which pivots around the axle 44 and, by means of the bars 46 and 46 takes along the conducting blade 39 which is thereby disconnected from the contacts 38 and 40 on which it was supported by the spring 48. Therefore, the exciting current of the winding with the thick wire passing through conductor 37, the contact 38, the conducting blade 39, the contact 40, the conductor 4| etc. is interrupted at this moment and the armature is now held in attracted position by the Winding with the thin wire only, fed by the conductor 35; the winding with the thick wire being thus traversed by a current for a short time only.

Although the thin wire fed through the conductor 35 produces a relatively small excitation, the excellent utilisation of this excitation owing to the armature 2| and the core l2 being brought together, allows the armature to be sufficiently held by the thin wire winding only.

Fig. 4 illustrates an electromagnet which comprises a. movable armature forming a dipping core 60 cooperating with a portion of the fixed core 6|. The inner end portion of the core 6|] presents several parts diminishing by steps towards the end in the following manner: a first truncated cone 62 is followed by a cylindrical portion 63, a second truncated cone 64, a cylindrical part 65, a third truncated cone 66, a cylindrical part 61, a fourth truncated cone 68, a cylindrical portion 69 and by a fifth truncated cone 10. To the end of this armature 60 a centering rod H is fixed, guided in a bore 12 of the fixed core 6|. The rod might even be attached to the fixed core 6| and enter a bore of the movable armature 60. The fixed core 6| has a hole 13 with inner steps which, on the movable armature 60 being at the end of its attraction stroke, fit the outer steps of the armature 60. The hole 13 of the fixed core 6| has thus a truncated cone 14, four cylindrical parts 15, 16, l! and 18 interconnected by truncated cones T9, and 8|, while the part 18 is followed by a truncated cone 82. The surfaces of the truncated cones of the movable armature 6D and of the fixed core 6| have preferably an inclination of about 45 with regard to the axis of the electromagnet.

The length of the cylindrical parts 63, 65, 6'! and 09 in axial direction gradually diminishes towards the inner end of the armature 60, and in an analogous manner, the length of the cylindrical parts of the hole 13 of the fixed core 6| diminishes from'the exterior to the interior of the hole. Moreover, thedifierence between the cross sections of the cylindrical parts 63 and 65 of the armature 60 is smaller than the difference between the cross sections of the cylindrical parts 65 and 61 and this difierence-is smaller than that between the cross sections of the parts 61 and 69, so that the surfaces of the connecting truncated cones become higher towards the inner end of the armature 65, for compensating the diminution of the diameter of these surfaces.

Around the fixed core 6| and the movable armature 68 an exciting coil is-arranged which is subdivided into five different windings 83, 84, 85, 8 6 and 81. The coil is carried by a tube 88 of non-magnetic material and two steel discs 89 and 98 and the closing of the magnetic circuit is obtained by atubular steel-member 9|, an annular steel disc 92 and the fixed core 6|. The disc 92 has a flange 93 which, on the excitation of the coil, is saturated by the magnetic fiux and prevents a lateral adherence of the movable armature 60.

The excitation of the coil is controlled by means of a switching device which can be operated by hand or automatically in dependence on the driving moment or on the speed of a machine, or on the time, or on a combination of these means. This switching device preferably operates in such a way that one can excite at will either the first winding 83 solely, or the two windings 83 and 84, or thethree windings 83, 84 and 85, the four windings 83 to 86, or all the five windings together. The switching device might also be operated by the guide rod 7|. An example of a switching device is given in Figs, 6 and 7, allowing the excitation of the windings to be progressively controlled. A frame I08 carries yieldably mounted contact members I81, Hi2, I83, I04, and I85 connected to the outgoing lines 83a to 81a of the windings 83, 85, 84, 86 and 81. Said contact members l] to I cooperate with additional contact members in the form of pivoted arms HI I01, I08, I08 and H8 kept open by springs I28. Each of these arms is operated by rods H6 and H7 acted upon by a single cam disc possessing a helicoidal part HI and a fiat part H2. The shaft H3 of this cam disc is mounted in a bearing of the frame Hit and carries a driving means in the form of a pulley H4. When the cam disc is rotated in the anticlockwise direction, it causes progressively the closing of all contacts beginning at the winding 83and ending at the winding 81. When the edge I l2a of the cam disc releases the arms 155 to H8, these latter abut with their ends H5 on the frame I00 while the rods H6 and Ill take the position shown in dotted lines in Fig. 6. The arrangement shown in Figs. 6 and '7 insures both an abrupt interruption of the Contact members when the cam disc releases the rods H5, H7 and a contact pressure which suffices for adequate switching. All winding lines Fig. 4 are connected at one end to the positive pole I of a current source and the excitation of each winding is established as soon as the other end is connected to the negative pole by the switching device.

The rest position of the movable armature 68 is approximately that shown in Fig; 4. If, in this position, an electric current traverses the inner winding 83, a small excitation is produced and the lines of force are formed in the air gap between the inclined surfaces 14 and 64 of the core GI and the armature 60. Since these surfaces lie relatively close together, the small excitation produced by the winding 83 sufiices to attract the armature 68 until the cylindrical surfaces 63 and I5 begin to overlap each other (Fig. 5). In this case the lines of force produced by the winding '83 are deflected perpendicularly to the axis of the armature 88 and, in consequence, can no longer advance the latter. If the two windings 83 and 84 are new fed with current, the saturation of the lines of force in the portion 15 of thefixed core BI is such that further lines of force pass through the air gap between the inclinedsurfaces 66 and F9 and the movable armature is again attracted until the cylindrical surfaces 65 and I6 overlap each other and the lines of force are deflected anew perpendicularly to the axis. When the winding is excited together with the windings 84 and 83, a similar process is repeated and so forth until the entire coil is excited and the movable armature 60 is at the end of its stroke.

From the foregoing it may be seen that by the variation of the excitation during the displacement of the armature it is possible to obtain a canalisation of the lines of force and an adjusting of the attraction force.

The movable armature can, for instance, carry out the whole stroke in an intermittent movement of any duration whatever. On exciting the five windings simultaneously the stroke is carried out in a rapid continuous movement. On exciting only the inner winding 83, or the two windings 83 and 84, or the windings 83, 84 and 85 etc., the armature 68 is displaced up to an intermediary position corresponding to the degree of excitation of the coil.

It is evident that in lieu of utilising a certain number of different windings, the variation of the excitation can be reached by a single, nonsubdivided coil which is combined with a variable outer resistance progressively connected in by an independent control or by the movement of the rod H.

The described electromagnet might be combined with a device transmitting movement by means of cams, operating as moment and speed varier, or with an absorbing device (dash-pot).

In order to fi-x the stops between two partial excitations exactly, the single steps of the end portions of the armature and the fixed core might have a saturation flange analogous to the guide flange 93.

The outer end of the armature 5i! has a shoulder 22 destined to come into contact with the fixed disc 92 so that between the cooperating surfaces of the core 6! and the armature 68 a small air gap is possible for acting against the remanence in the fixed core and the armature. This shoulder 22 might be adjustable in order to adjust the period of remanence when the period of' excitation is controlled.

What I claim is:

1. In an electromagnet, an exciting circuit, a core member, and an armature member arranged to approach each other when. said exciting circuit is closed, at least one of said members having a number of relatively fixed parts arranged in steps and comprising surfaces gradually diminishing towards the end of member, said member being disposedv with regard to the other member in such a cooperating position that during the mutual approaching of said members a canalisation of the lines of force is obtained.

2. In an electromagnet, an excitin circuit, a core member, and an armature member arranged to approach each other when said exciting circuit is closed, at least one of said members having, parts of rectangular axial section, arranged in steps, gradually diminishing towards the end of said member, and portions comprising surfaces inclined with regard to the axis of said armature member and interconnecting said parts.

3. In an electromagnet, an exciting circuit, a core member, and an armature member arranged to approach each other when said exciting circuit is closed, at least one of said members having, parts of rectangular axial section arranged in steps, gradually diminishing towards the end of said member, and portions comprising surfaces inclined by 45 with regard to the axis of said armature member and interconnecting said parts.

4. In an electromagnet, an exciting circuit, a core member, and an armature member arranged to approach each other when said exciting circuit is closed, one of said members having outer staggered surfaces gradually diminishing towards the end of said member, the other of said members comprising a hole staggered correspondingly to said staggered surfaces, said staggered surfaces and said staggered hole being disposed in such mutual cooperating position that during the mutual approaching of said members a canalisation of the lines of forces is obtained.

'5. In an electromagnet, an exciting coil comprising different concentrical windings, a core member, and an armature member arranged to approach each other when one of said windings is closed, at least one of said members having a number of relatively fixed parts arranged in steps and comprising surfaces gradually diminishing towards the end of said member, said member being disposed with regard to the other member in such a cooperating position that during the mutual approaching of said members a canalisation of the lines of force is obtained.

6. In an electromagnet, an exciting circuit, a core member, and an armature member arranged to approach each other when said exciting circuit is closed, one of said members having outer staggered surfaces gradually diminishing towards the end of said member, the other of said members comprising a hole staggered correspondingly to said staggered surfaces, said staggered surfaces and said staggered hole being disposed in such mutual cooperating position that during the mutual approaching of said members, a canalisation of the lines of force is obtained, a guide on one of said members, and a rod slidably entering said guide to guarantee mutual concentricity of said members.

7. In an electromagnet, an exciting circuit, a core member, and an armature member arranged to approach each other when said exciting circuit is closed, one of said members having outer staggered surfaces gradually diminishing towards the end of said member, the other of said members comprising a hole staggered correspondingly to said staggered surfaces, said staggered surfaces and said staggered hole being disposed in such mutual cooperating position that during the mutual approaching of said members a canalisation of the lines of force is obtained, and a saturation flange on at least one of said members destined to the passage of the magnetic flux between said members.

8. In an electromagnet, an exciting circuit, a core member, an armature member arranged to approach each other when said exciting circuit is closed, one of said members having outer relatively fixed staggered surfaces gradually diminishing towards the end of said member, the other of said members comprising a hole staggered correspondingly to said staggered surfaces, said staggered surfaces and said staggered hole being disposed in such mutual cooperating position that during the mutual approaching of said members a canalisation of the lines of force is obtained, a guide on one of said members, a rod slidably entering said guide to guarantee mutual concentricity of said members, and a switch arranged to vary the exciting current and to be controlled by said rod.

9. In an electromagnet, an exciting circuit, a fixed core member, a movable armature member arranged to approach said core member when said exciting circuit is closed, at least one of said members having a number of parts arranged in relatively fixed steps and comprising surfaces gradually diminishing towards the end of said member, said armature member being disposed with regard to said core member in such a cooperating position that during the approaching of said armature member a canalisation of the lines of force is obtained, and a shoulder on said armature member destined to come into contact with said fixed core member outside of the concentration of the lines of force, for establishing an air gap acting against the remanence in said members.

10. In an electromagnet, an exciting coil comprising a number of concentrical windings, a core member, and an armature member arranged to approach each other when one of said windings is closed, at least one of said members having a number of parts corresponding to the number of said concentrical windings and arranged in steps and comprising surfaces gradually diminishing towards the end of said member, said member being disposed with regard to the other member in such a cooperating position that during the mutual approaching of said members a canalisa tion of the lines of force is obtained.

11. In an electromagnet, an exciting coil comprising a number of concentrical windings, a core member, an armature member arranged to approach each other when one of said windings is closed, at least one of said members having a number of parts corresponding to the number of said concentrical windings and arranged in steps and comprising surfaces gradually diminishing towards the end of said member, said member being disposed with regard to the other member in such a cooperating position that during the mutual approaching of said members a canalisation of the lines of force is obtained, and a switching device arranged to allow the inner of said concentrical windings of being at first excited and then one after the other of said concentrical windings following one another towards the outside until the entire coil is excited.

12. In an electromagnet according to claim 1, an adjustable resistance in series with said'exciting circuit.

13. In an electromagnet according to claim 1, a resistance in series with said exciting circuit and adjustable by the movement of said armature member.

ERNEST ALPHONSE DERUNGS.

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