US3707924A

US3707924A - Electromagnetic motion imparting means and transportor system embodying the same

Info

Publication number: US3707924A
Application number: US00032774A
Authority: US
Inventors: M Barthalon; A Moiroux; P Watson
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-01-25
Filing date: 1970-04-28
Publication date: 1973-01-02
Anticipated expiration: 1990-01-02
Also published as: ES349697A1; CA918742A; CH493140A; GB1208201A; DE1613758A1; FR1592065A

Abstract

An electromagnetic device producing a mechanical action, as in a transporter system comprising a suspended car, or in an electric motor, includes a magnetizing assembly and a magnetized assembly adapted to move one with respect to the other. The magnetizing assembly comprises at least one magnetic circuit defining an air gap and provided with at least one inductor winding, the magnetized assembly, subjected to the action of the magnetizing assembly comprising at least one magnetic portion associated with at least one non-magnetic portion and being in part housed in the air gap of said magnetizing assembly. This latter comprises at least two electromagnetic units each comprising an air gap and disposed in line whereas said magnetized assembly comprises a number of separate magnetic sections at least equal to two, the pitch of which is different from that of the electromagnetic units of said magnetizing assembly, said magnetic sections being coupled together mechanically, separated by non-magnetic sections and constituting a series in line. The windings of said electromagnetic units are connected to a switch adapted to ensure their energization following a predetermined sequence, guiding means being provided so as to permit the displacement of the magnetic sections of said magnetized assembly in the air gaps of said electromagnetic units in a transverse direction relative to the lines of force in said air gap.

Description

tutu-1g SR P198502 XR United States Patent [1 1 Barthalon et al.

I 54] ELECTROMAGNETIC MOTION IMPARTING MEANS AND TRANSPORTOR SYSTEM EMBODYING THE SAME Filed: April 28, 1970 Appl. No.2 32,774

Related US. Application Data Division 58 Ser. No. 697,089, Jan. 11, 1968, abandoned.

[30] Foreign Application Priority Data Jan. 25, 1967 France ..67924ll US. Cl ..104/148 LM, 310/12 Int. Cl. ..B60l 13/00, H02k 41/02 Field of Search ..3l0/12, 13; 318/119-138; 68/23; 103/53; 160/331; 104/148 LM; 246/182 R, 182 B, 182 C [5 6] References Cited UNITED STATES PATENTS 12/1965 Roshala ..l04;3l0/l48 LM;12 2/1966 Smith et al ..l04/l48 LM 2/1905 Zchden 2/1952 Holmquist 5/1968 Kwangho Chung ..l04/l48 LM 8/1969 Reeks et a1 ..l04/l48 LM 2/1966 Smith et al "104/148 LM 51 Jan. 2, 1973 Primary Examiner-Drayton E. Hoffman Attorney-Young & Thompson ABSTRACT An electromagnetic device producing a mechanical action, as in a transporter system comprising a suspended car, or in an electric motor, includes a magnetizing assembly and a magnetized assembly adapted to move one with respect to the other. The magnetizing assembly comprises at least one magnetic circuit defining an air gap and provided with at least one inductor winding, the magnetized assembly, subjected to the action of the magnetizing assembly comprising at least one magnetic portion associated with at least one non-magnetic portion and being in part housed in the air gap of said magnetizing assembly. This latter comprises at least two electromagnetic units each comprising an air gap and disposed in line whereas said magnetized assembly comprises a number of separate magnetic sections at least equal to two, the pitch of which is different from that of the lelectromagnetic units of said magnetizing assembly, said magnetic sections being coupled together mech ni all se ara ted b non-m n etic secti ns nd constiluting a sei ies 1n ling. The wi dmgs of said e ectromagnetic units are connected to a switch adapted to ensure their energization following a predetermined sequence, guiding means being provided so as to permit the displacement of the magnetic sections of said magnetized assembly in the air gaps of said electromagnetic units in a transverse direction relative to the lines of force in said air gap.

.4". 9. 2m 40 Bre Figures PATENTEU JAN 2 I973 sum 01 0F 11 will.

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ELECTROMAGNETIC MOTION IMPARTING MEANS AND TRANSPORTOR SYSTEM EMBODYING THE SAME This application is a division of copending applica- 5 tion Ser. No. 697,089, filed Jan. ll, 1968, now abandoned.

The present invention relates to an electromagnetic device capable of producing a mechanical action, as in transporter systems comprising suspended cars, or in electric motors, or the like.

This device is of the kind comprising a magnetizing unit and a magnetized unit which are movable one with respect to the other, the magnetizing unit comprising at least one magnetic circuit defining an air gap and provided with at least one field winding, while the magnetized unit which is subjected to the action of the magnetizing unit comprises at least one magnetic section associated with at least one non-magnetic section, and it is housed in part in the air gap of the magnetizing unit In particular, one of the units may be fixed, in which case the other may be associated with any device for receiving mechanical power.

Linear or rotary electric motors are already known which utilize polyphase electric current and work by conversion of electro-magnetic energy to mechanical energy, and more precisely by the effect of magnetic induction generated by the field assembly in the armature assembly.

The practical construction of linear motors of this type has serious inadequacies: the controls of speed, acceleration and braking are not satisfactory, the armature has a considerable mass and its conductivity must be high, which necessitates the use, whenever the armature is long, of large quantities of copper or aluminum which are particularly expensive metals. Finally, the existence of a relative slip between the field and the armature aggravates the problem presented by the control of movement, and prevents the development of a large force at low translation speeds.

Certain forms of linear electric induction motors permit the armature to besupportedwith respect to the field or vice-versa andconstitute an electromagnetic suspension, but this necessitates a power per unit of weight which is too high to be utilizable in practice.

Another type of linear electric motor already described comprises a succession of cylindrical windings surrounding a magnetized assembly sliding along the axis of the unit: however, the movement generated can then only be transmitted by the extremity, which limits the possibilities of application. The power/weight ratio is low and the unit power is limited. The control of the movement and speed necessitates complicated and expensive switching and relay arrangements, since the air-gap is not precisely defined; the force varies considerably with the position of the magnetic cores and the impulses received by themoving system are not well defined in time and in space.

Finally, amongst the rotary induction motors, the polyphase asynchronous machines can only operate in a narrow range of speeds of rotation, and only have a moderate starting torque, contrary to the requirements of numerous applications. Rotary direct-current motors do actually comply with the requirements, but these are of expensive construction since the field and the armature must both be wound. Furthermore, the rotor cannot be fixed in a pre-determined position.

The foregoing machines employ two well-known physical laws:

The so-called electrodynamic machines utilize the action of a field on a current;

in the others, the displacement of the moving system is parallel to the field lines, and following the law of magnetic attraction, the force variation is inversely proportional to the square of the displacement.

The devices which form the object of the present invention make use of a different physical law, namely the fact that if there is established in a first element an electromagnetic circuit supplied at constant current and closed by an air-gap in which is arranged a second element comprising a magnetic tooth, the edges of which are arranged transversely with respect to the flux, the attraction is very low when the tooth is out of the air-gap, but increases abruptly at the moment when the edge of the tooth passes into the air-gap, and then remains substantially constant, in spite of the displacement, until the converse phenomenon takes place. Under these conditions, the attraction is in fact substantially proportional tothe variation of magnetic permeance per unit displacement.

The present invention thus employs this particular law of force in order to overcome the abovementioned difficulties and disadvantages, for the purpose of con-' structing machines in which the force, the displacement, the speed and the acceleration of the magnetized unit with respect to the magnetizing unit can be controlled in an accurate manner, whether the speed is in- 5 creasing or decreasing. Another object of the invention is to obtain a particularly low mass for one of the two units, which is particularly advantageous in the case of linear electric traction motors, in which the fixed portion is long, and of rotary motors with high speeds of rotation, in which the rotor must be capable of withstanding large centrifugal forces.

, Another object of the invention is to obtain rotary motors with high starting torques and variable speed of rotation over a wide range, these motors having furthermore a low production cost.

According to the invention, the electromagnetic device of the kind defined above is characterized in that the magnetizing assembly comprises at least two electromagnetic units, each comprising an air-gap and arranged in line, in that the magnetized assembly comprises a number of separate magnetic sections at least equal to two, the pitch of which is different from that of the electromagnetic units of themagnetizing assembly, these sections being mechanically coupled together, separated by non-magnetic sections and forming a line; in that the windings of the electromagnetic units are connected to a commutator ensuring their excitation following a predetermined sequence; and in that guiding means are provided to permit the displacement of the magnetic sections of the magnetized assembly in the air-gaps of the electromagnetic units in a transverse direction relative to the lines of force in the said air- S P A particular, one of the two parts, the magnetized assembly, has a low weight and a high power/weight ratio A device of this kind has appreciable advantages. In

and its cost is small since it is not bulky and is made of cheap magnetic material. The starting force is very high. The controls of the position of the moving system, of its speed and acceleration, positive or negative, are easily effected by acting on the electric impulse switch.

The pitch of the electromagnetic units of the magnetizing assembly, measured along the axis of relative displacement of the two assemblies is preferably constant, but is different from the also constant pitch of the magnetic sections of the magnetized assembly. In particular, the axial length corresponding to N pitches of one of the assemblies, and especially of the magnetizing assembly, may be equal to the length of (N l pitches of the other assembly, where N is a whole number.

This arrangement produces a uniform driving effort.

Depending on the applications, the magnetizing assembly and the magnetized assembly may extend in parallel rectilinear or coaxial circular directions, or finally along any curvilinear directions, the moving system being then constituted by an in-line series of articulated elements.

According to an advantageous feature of the invention, the device comprises means for regulating the starting and end instants of the electric impulse supplying an electromagnetic unit, these means being operated as a function of at least one of the following parameters: position, speed, acceleration of the moving system with respect to the fixed system.

In particular, the device may advantageously comprise a detector of the relative position of a magnetic section and an electromagnetic unit which cooperates therewith, this detector being itself preferably adjustable in position with respect to the assembly on which it is carried enabling the electric impulse to be initiated or interrupted at an adjustable pre-determined position. This detector may be advantageously combined with a device introducing, with a variable phase according to the desired conditions of operation, this detection signal in a device which modulates the electric impulses. This combination of regulating means having very great flexibility, makes it possible to ensure precise control of the movement, the force, the speeds and the accelerations, and furthermore ensures optimal efficiency.

According to another outstanding aspect of the invention, provision is made to utilize the device in question as an effective system of electromagnetic suspension of one of the assemblies with respect to the other. A suspension of this kind represents a considerable economy of means per unit of lifting force, with respect to other known suspensions. In fact, when an electromagnetic circuit is excited by an electric impulse, a slight relative displacement of the magnetizing and magnetized assemblies in a direction which is simultaneously normal to the direction of movement and to that of the lines of force in the air-gap (namely a vertical downward direction) creates a large restoring force on the magnetic section in the air-gap (namely an upward force), and this does not involve a considerable consumption of additional energy.

The industrial constructions which will now be described show that, depending on the application, the force applied by the magnetizing assembly may only cause a small displacement of the moving assembly, such as is the case in machines producing a vibratory movement. The device may also produce a resultant movement of medium amplitude (as is the case for pumps and compressors) or a movement of large amplitude (the case especially of conveyors of any kind: industrial conveyors, trains, etc.

In applications for which a large travel is required, it may be advantageous to provide a fixed magnetized assembly and a moving magnetizing assembly, and conversely for applications requiring a small travel. The various forms of construction of the invention vary between two extreme cases: a machine in which the magnetized assembly comprises two magnetic sections successively attracted into the air-gaps of a large number of electromagnetic circuits, and conversely a machine in which a large number of magnetic sections forming the magnetized assembly are attracted successively into the air-gaps of two consecutive electromagnetic units. In the long-travel machines, if a small number of electromagnetic units is employed, a large number of magnetic sections is necessary for the magnetized assembly and vice-versa.

A remarkable special case of the long-travel construction is that in which the movement is rotating and there is thus obtained a rotary motor having the advantageous characteristics specified above, and in particular a great aptitude for operation at high torque, at variable speed and at high speed of rotation.

The electromagnetic device in accordance with the invention constitutes a driving machine which can be used over a large field of applications and especially in the case of the following apparatus:

Devices for lifting, or braking during lowering, with a linear movement, for lifts, lifting trucks, extraction of boring rods, pile-driving equipment;

Sliding control devices, especially for doors, shuttles,

machine carriages;

Propulsion and braking devices for transport or handling means for passengers, goods or equipment, comprising guided vehicles such as: trains, trolleys, launching catapults for aircraft or rockets, toys;

Actuating motors giving considerable power, for example for driving tools for cold-forging metals by percussion or broaching tools;

Driving motors for alternating machines at relatively low speed and large travel, such as pumps and compressors;

Driving motors for devices of the chain type for caterpillar tractors, conveyors, bucket dredgers, etc.;

Driving motors for rotating machines such as cranedriving tables or drilling platforms, vehicle wheels and more generally rotary machines requiring a high torque at low speeds, accurate control, a very wide range of speeds and a rotor having a low weight and low inertia;

Torque or force limiting or transmitting devices;

clutches;

Transmission to a distance of angles of rotation or linear displacements, remote recording, remote synchronization, servo-controls.

Further particular characteristics of the invention will be brought out in the description which follows below.

In the accompanying drawings, given by way of nonlimitative examples, there have been shown various industrial constructions according to the invention.

FIG. 1 is a general perspective diagram of the device according to the invention.

FIG. 2 is a view in cross-section taken along the line Illl of FIG. 3, of a first industrial construction relating to an actuating device.

FIG. 3 shows a cross-section taken along the line IIIIII of FIG. 2.

FIG. 4 is a cross-section taken along the line IVIV of FIG. 2.

FIG. 5 shows to a larger scale a detail of the crosssection along the line VV of FIG. 2.

FIG. 6 shows diagrammatically an immobilizing device for the moving element of the first construction.

FIG. 7 is a transverse section of an alternative form of the first construction, constituting an electromagnetic suspension.

FIG. 8 is a plan view from above of a magnetizing as sembly forming a conveyor.

FIG. 9 is a view to a larger scale of the above conveyor in cross-section along the line IXIX of FIG. 8.

FIG. 10 is a side view of the magnetized assembly assumed to be isolated.

FIG. 11 is a transverse section of a lifting device for a vehicle.

FIG. '12 is a diagram of an electronic switching system of impulses utilizable for the previous constructions.

FIG. 13 is a view in side elevation taken along the section XIIIXIII of FIG. 14, showing an industrial construction intended for vehicle traction.

FIG. 14 is a cross-section taken along the line XIV XIV of FIG. 13.

FIG.15 is a section taken along the line XVXV of FIG. 13.

FIG. 16 shows the diagram of the electrical supply for the device of FIGS. 13 to 15. i

FIG. 17 is a transverse section along the line XVII XVII of FIG. 18, showing an alternative form of the previous construction applied to wall-effect vehicles.

FIG. 18 is a cross-section taken along the line SVIIIXVIII of FIG. 17.

FIG. 19 shows a detail of the cross-section XIX- XIX of FIG. 18.

FIG. 20 is a view in longitudinal section taken along the line XXXX of FIG. 21, of a motor with a reciprocating movement.

FIGS. 21 and 22 are views in cross-section along the line XXL-XXI and XXII-XXII of FIG. 20.

FIG. 23 is a view in elevation of the cross-section XXIII-XXIII of FIG. 24, showing another industrial construction intended for driving a member in rotation.

FIG. 24 is a cross-section taken along the line XXIV-XXIV of FIG. 23.

FIG. 25 shows diagrammatically the method of supplying the windings of the device of FIGS. 23 and 24.

FIG. 26 is a cross-section along the line XXVI- XXVI of FIG. 27, showing the application of the invention to the construction of a micro-motor.

FIG. 27 is an axial cross-section along the line XXVII-XXVII of FIG. 26.

FIGS. 28 and 29 are detail explanatory diagrams concerning the starting system.

FIGS. 30 and 31 are diagrams of electrical supply devices.

FIG. 32 is a partial view of an alternative form of construction of the magnetized assembly of the above micro-motor, following the section XXXIIXXXII of FIG. 33.

FIG. 33 is a partial view in transverse section of an alternative form of construction of the magnetizing circuit.

FIG. 34 is a diagrammatic view in cross-section along the line XXXIV-XXXIV of FIG. 35 of a motor with mechanical self-commutation.

FIG. 35 is a cross-section along the line XXXV- XXXV of FIG. 34.

FIG. 36 shows an alternative form with electrical self-commutation, taken along the line XXXVI XXXVI of FIG. 37.

FIG. 37 is a cross-section along the line XXXVIl- XXXVII of FIG. 36.

FIG. 38 is a diagram showing the electric switching device of the construction of FIGS. 36 and 37.

FIG. 39 is an explanatory diagram.

FIG. 40 is a diagram of a supply circuit.

There will first be described, with reference to FIG. 1 of the accompanying drawings, a simplified construction of the device according to the invention.

This device is intended to produce a mechanical action (development of a driving or static force) and comprises essentially a magnetizing assembly 1 including at least two electromagnetic units 2 forming a series. Each unit 2 comprises a magnetic circuit 3 having an air-gap 4 and carrying a magnetizing winding 5 which creates a magnetic flux in the said air-gap.

The device further comprises a magnetized assembly 6 including at least two sections 7 of magnetic material (that is to say having a magnetic permeability greater than 1). The sections 7, the number of which is furthermore different from that of the electromagnetic units 2, are coupled mechanically to each other, arranged in line and separated by non-magnetic sections 8 (for example of air).

The relative mechanical couplings of the assemblies 1 and 6 are such that a relative displacement may take place between them, this displacement being effected in the air-gaps 4, in a substantially transverse direction with respect to the lines of force of the magnetic flux created in these air-gaps.

The windings 5 of the electromagnetic units 2 are supplied from a source 13 of electrical impulses through a commutator 14 which distributes these impulses cyclically between the various windings 5.

The device may also comprise a system 15 for modulating the impulses, acting on the commutator l4 and controlled in turn simultaneously by the orders and operating data inscribed in a recording system 12, and by a unit 9 connected to a detector 10 of the position of the magnetized assembly 6.

Means may further be provided for determining a preferential direction of displacement of the magnetized assembly 6.

In operation, the windings 5 of the magnetizing assembly 1 receive successive electric impulses through the commutator 14 in such manner that the magnetic flux is established in at least one of the air-gaps 4 at the moment when one of the magnetic sections 7 of the magnetized assembly 6 has reached the entrance of this air-gap. The section 7 is thus attracted and tends to take up the position of minimum reluctance in the airgap 4. When this condition is reached, or during the course of the previous movement, a new circuit 3 is excited and attracts another section 7 at the moment or time when this latter also reaches the entrance of its air-gap, and so on.

Apart from special geometric relations which may be established between the pitches of the air-gap 4 and those of the sections 7 in order that one of these sections may be at the entry of an air-gap 4 when the other section is located in this air-gap, for the purpose of permitting the systematic and sequential development of a driving attraction, the invention provides means for acting on the amplitude, the duration and the phase of the impulses from the commutator 14 in order to provide a regulation, especially of the acceleration or the speed of the magnetized assembly 6.

The general features which have been specified above will now be detailed and illustrated with reference to the description of the particular applications of the invention.

The first particular construction of the invention illustrated in FIGS. 2 to relates to a linear actuating device constituting a semi-static driving machine with controlled displacement. This device comprises a frame 21, on which is mounted the magnetizing assembly formed by a succession of electromagnetic units 22, five in number in the case selected. Each unit 22 comprises a magnetic circuit 23 formed by an assembly of magnetic laminated sheets, stamped out to the shape of a C. The interrupted arm thus forms a parallelepiped air-gap 24, between the two poles 25.

The circuits 23 are retained by a transverse bar 32 arranged in their central portion and fixed to the frame 21 by screws 33. The bar 32, of non-magnetic metal has a U-shaped section as shown in FIG. 5, and it is bor-.

dered by lugs 26 slotted with a bevel at the level of the poles 25 similar to a rack, which ensures an absolutely firm fixing of the units 22.

On each of the lateral branches of the circuits 23 are mounted the magnetizing windings 28 which, for the same unit, are supplied in phase from a source of direct-current 36, through a switch 39, a potentiometer 39a. and a rotary switch 37, the rotating contact 38 of which is driven by a motor 301 with two directions of rotation and variable speed regulated by the operator. This device could furthermore be replaced by a manually-operated crank-handle.

Each winding 28 of the electromagnetic unit 22 is connected to one of the

terminals

37a, 37b, 37c, 37d and 37e of the rotary switch 37. The rotating contact 38 simultaneously establishes contact with several of the said terminals, as will be described later. The potentiometer 39a provides a regulation for the power of the impulses and therefore of the force applied on the moving element.

The magnetized assembly 27 is composed of a flat strip of magnetic material having a substantially parallelepiped shape, adapted to the air-gaps 24 and to the free space provided between the lugs 26 of the bar 32. The assembly 27 has a succession of magnetic sections formed by teeth 30 produced by cutting-out and forming a toothed rack. The non-magnetic sections arranged between the teeth 30 are constituted by blocks 31, of plastic material for example, which restore the parallelepiped shape of the strip and ensure the continuity of the guiding surface.

The assembly 27 thus constituted is slidably mounted axially on the bar 32 between the poles 25 of the electromagnetic units 22.

The clearance between the magnetized assembly and the poles remains practically constant over the greater part of the travel, due to the fact that the magnetic fields in the air-gaps 24 are transverse with respect to the movement. The magnetized assembly 27 is guided in its displacement by the lugs 26 of the bar 32, the play in this guiding action being substantially twice as small as that existing between the elements 27 and the poles 25. The element 27 is coupled to the utilization device by a crank-arm 34 by means of an articulation shaft 35. The friction of the element 27 with the bar'32 and the lugs 26 can be reduced by employing self-lubricating materials 303 for the parts in contact (plastic material, non-magnetic alloy, for example) (see FIG. 5).

In order to ensure the effective operation of the actuating device, the following particular relations are preferably provided for the assemblies 22 and 27:

The parallelepiped shape of the air-gap 24 is such that its section perpendicular to the flux approximates to that of a square, the side of which is larger than the thickness of the air-gap in the direction of the flux. I

Theaxial length of the non-magnetic sections 31 is slightly greater than the length of the poles 25 relative to the direction of the movement L or M, and their height is slightly greater than that of the poles 25.

The axial length of the magnetizing assembly corresponding to N pitches (the pitch being the axial length of a pole plus the distance separating two poles) is equal to that of (N 1) pitches of the magnetized assembly. 1

The number of electromagnetic units is odd. Thus, in

the present embodiment, 5 pitches of the electromagnetic units 22 occupy the same axial length as 6 pitches of the magnetic sections 30.

This value of the pitch makes it possible to obtain a high proportion of electromagnetic units 22 which are active at any particular moment, while at the same time having an attraction in the opposite direction with respect to the desired direction of movement having a value as small as possible on the magnetized assembly 27. To the same end, it is provided that the axial length of the non-magnetic sections 31 of the magnetized assembly 27 is greater than that of the magnetic sections 30 in the proportion of 5 to percent. The spacing between the electromagnetic units is thus fixed by all the foregoing points.

To the magnetized element 27 there may advantageously be added a solenoid-brake 40 (FIG. 6) intended to prevent any relative movement between the magnetizing assembly 22 and the magnetized assembly 27 when none of the windings 28 is excited. When stationary, the magnetized assembly 27 is gripped by two mechanical jaws 41 by the action of springs 42 applying a force in opposition to that of release electromagnets 43, the sliding cores 302 of which are fixed to the jaws 41. When theswitch 39 is closed, the jaws 41 move away from the element 27 due to he attraction effect of the electromagnets 43 on the cores 302.

The differential spacing of the electromagnetic units 22 and the magnetic sections 30 of the magnetized assembly 27 provides the following operation: when one of the magnetic sections 30a is exactly between the poles of one of the electromagnetic units 22a, another magnetic section b of the magnetized as sembly is partially between the poles of the following electromagnetic unit 22b, while the magnetic section 30c is ready to pass into the electromagnetic unit 22c and the magnetic section 30d is half-way between the

units

220 and 22d.

The rotary switch 37 is arranged with respect to the fixed

contacts

37a, 37b, 372, in such manner that for this position of the element 27, the electromagnetic unit 22b is excited, so that the magnetic section 30b is attracted in the direction L between the poles of this section. At the end of this movement, the section 30c is partially engaged in the electromagnetic unit 22c, and the electromagnet unit 220 is then excited instead of the electromagnetic unit 22b, so that the movement of the magnetized assembly 27 in the direction L may continue.

Thus, the excitation in sequence of the electromagnetic units 22 produces a movement of the magnetized assembly in the same direction as the order in which these units are excited. Under these conditions however, it will be observed that only one of the electromagnetic units is excited at a given instant, so that the power/weight ratio of the system does not have its maximum value. In order to remedy this, the invention provides for the simultaneous excitation of a second electromagnetic unit 22 as follows:

The rotating contact 38 of the switch 37 is arranged in such manner as to connect continuously two of the terminals such as 37a and 37b to the source 36, and to establish contact with a fresh terminal 370 at the exact moment when it breaks the contact with the terminal 37a which it leaves behind.

Under these conditions, the magnetized element 27 being in the position shown in FIG. 3, the unit 22a which supplies no driving force is not excited, whereas the units 22b and 22c are excited simultaneously. When the section 30b has come into the air-gap 24 of the unit 22b, the corresponding winding 28 is de-excited in turn to the benefit of the winding of the following unit, and so on. A reverse order of switching is utilized in order to obtain a movement of the magnetized assembly 27 in the opposite direction.

Rotation of the contact 38 thus controls the position, the direction, the movement and the acceleration of the moving magnetized element 27. The potentiometer 39a permits the regulation of the force applied in the axial direction by this magnetized assembly 27 which, by means of the crank-arm 34 communicates the movement and the force of the actuating device to the member which is to be driven. This latter may equally well be a sliding door, a control device for a machinetool, or an aircraft control device. The device considered can also be employed in place of rotary electric motors with reduction gearing and worm-screws or toothed racks.

In certain applications of this embodiment, it is essential that the movement under load of the mag- This can be effected by various means, such as: magnetic sections having a sinusoidal profile, magnetic sections having a slightly variable thickness and a permeability less than that of the circuit, lamination of this latter perpendicular to the movement, air-gap with a lightly variable thickness, switching de-phased with respect to the passage into and out of the air-gap, and more generally by any means controlling the increase of flux at the beginning of the introduction of a magnetic section 30 into the air-gap. There is thus obtained simultaneously an optimum efficiency and an easier control of the movement.

By way of an alternative form, the present invention provides an actuating device of the foregoing type to ensure at the same time the propulsion and also the lifting of a driven element. This embodiment is illustrated in FIG. 7, in which there is seen at 45 the driven element which is to be simultaneously displaced and held in suspension. To this end, the element 45 is attached by slings 46 to the magnetized assembly 27 similar to that described above, but which is in this case located below the units 22 of the magnetizing assembly, itself fixed to the lower part of a fixed support 47 such as a ceiling or framework. The weight of the element 45 tends to pull the magnetized assembly 27 downwards and to pull the magnetic sections 30 out of the air-gaps 24, which creates restoring forces increasing rapidly with the vertical displacement. These forces finally counterbalance the weight of the element 45. An additional lifting force may be obtained by joining together the magnetic sections 30 by a transverse magnetic piece 48.

In order that the lift forces may be well distributed over the length of the magnetized assembly 27 it is provided to employ at least two magnetizing assemblies, adequately spaced apart. The lift force is proportional to the axial length of the magnetic sections or teeth 30, while the propulsion force is proportional to the height of these teeth. Flanges or angle-iron sections 4, continuous over the whole length of the device and located below the element 27 prevent the latter from falling in the event of a failure of current supply.

In the foregoing devices, the switch 37 and the potentiometer 39a provide a precise control of the actuating device and especially of its position, of the direction of movement, of the speed and the acceleration of the driven element. The driving force for starting-up is large. The moving system may be held stopped in any position, even on load. The direct transmission of electromagnetic energy to the magnetized assembly 27 serving as an actuating slide results in a very simple unit having no intermediate transmission element. The bulk of the magnetized assembly 27 is small and its construction of magnetic metal results in a very low cost. By virtue of a magnetic play, substantially greater than the mechanical play and practically constant, and due to the rules for dimensioning and switching indicated above, the force on the moving magnetized element can be made practically constant for a given current. The displacement is thus effected without appreciable shocks and there is no sticking effect on the poles.

A prototype machine in accordance with FIGS. 2 to 5 has been built and tested. Its characteristics are as follows:

Axial length of poles 19 mm.

Distance between poles 30 mm. Height of poles mm. Axial length of magnetized sections 19 mm. Axial length of non-magnetic sections 22 mm. Axial length of magnetic assembly 600 mm. Number of electromagnetic units 5 Total weight of magnetizing assembly 2.5 kg. Supply voltage 12 volts Power absorbed 100 watts Resistance of each winding l.40 ohms Number of turns 2 X 2l0 Average force 2.5 kg.

Mechanical commutator.

The following operational results were obtained during the tests:

Maximum linear speed 2 m./sec. Pulsation speed obtained with alternating current for a travel of 100 mm 2 cmJsec. Maximum slope climbed by the magnetizing assembly forming a trolley 80% Maximum force of magnetic lift: 3,700 g.: 100 37g.lwatt.

An alternative form of construction of the conveyor device of FIG. 7, intended to permit of movement over a curve, is shown in FIGS. 8 to 10. In this embodiment two magnetized assemblies 27a, 27b are provided, each constituted by an articulated assembly of magnetic sections 260 forming successive castellations in which are interleaved non-magnetic sections 261, also in the form of castellations which have an arrangement reversed with respect to the preceding. The

sections

260 and 261 form in pairs substantially rectangular plates joined to each other by hinges through which pass the pivotal shafts 262. On each of these plates are provided guiding shoes 263. The assemblies 27a, 27b each carry a supporting rod 46a, 46b, and these two suspension rods are coupled together by a swing-bar 264 which carries a lifting hook 265.

The magnetizing assembly constitutes a continuous supporting track with a curvilinear outline (FIG. 8) formed by a succession of electromagnetic units 22 each comprising a C-shaped circuit 23, as in the case of FIG. 7, fixed to the support 47, and in theair-gap 24 of which can circulate the magnetized assemblies 27a, 27b. In this case it is provided however to mount the magnetizing windings 28 on the horizontal limbs of the circuits 23 and in the vicinity of the air-gaps 24. Above the pole-pieces 25 are arranged continuous friction bands 266 with which the shoes 263 are in contact. At the lower part of these pole-pieces are arranged guiding and safety angle-irons 49, by which the lower shoes 263 are supported. The articulation axes 262 permit the assemblies 27a, 27b to follow the curves.

The units 22 are supplied with current in pairs, the corresponding windings of the same pair being separated by a distance which corresponds to that separating the homologous sections 260 of the assemblies 27a, 27b.

The actuating device provided thus constitutes a particularly simple electromagnetic suspension .having a high power/weight ratio and low friction, the trajectory of which may have any desired form in space.

In the constructions which have just been described, the magnetized assembly is moving and the magnetizing assembly is fixed, but this arrangement may be reversed without departing from the scope of the invention, especially in the cases where, for reasons of practical construction, it is preferable to keep the magnetized assembly stationary and to cause the magnetizing assembly to move by attaching the driven element 45 to this latter.

A version of this kind is shown diagrammatically in FIG. 11. The conveyor comprises a magnetized assembly 250 fixed to the lower part of the support 47 and which comprises, as previously, a succession of magnetic and non-magnetic sections, such as 251. The magnetizing assembly 252 comprises a series of electromagnetic units 253 in line, fixed to the upper part of a vehicle 254 and playing simultaneously the parts of lifting and propulsion motors. Each unit 253 comprises in particular two windings 267 located in the vicinity of the poles 268. As previously, supporting angle-irons 269 prevent the fall of the vehicle 254 in case of interruption of the current by coming to rest on a widened portion of the magnetized assembly 250.

The rotary switch 37 of FIG. 3, intended to ensure the sequential switching of the current supply to the electromagnetic units 22 may, according to a preferred embodiment of the invention shown in FIG. 12, be replaced by a static electronic device, in particular with thyristors.

More precisely, this device comprises a thyristor 51 assigned to each winding 28. The thyristor 51 is connected between the conductor 50a coupled to the negative pole of the source 36 and one of the terminals of the winding 28 concerned, the other terminal of which is connected to the positive pole of the source 36 by the conductor 50b.

The trigger of each thyristor 51 is controlled by an electronic gate 52 of the AND type, of which one of the inputs is connected to an impulse generator 53 and the other input to a routeing contact 54. The fixed studs of the contact 54 terminate respectively at the output circuit of the preceding thyristor 51 and of the following thyristor 51.

It can thus be seen that the control gate 52b of the thyristor 51b is connected to the contact 54b, the fixed studs of which terminate respectively at the outputs of the thyristor 51a and of the thyristor 51c.

Condensers 55 are connected between the corresponding conductors of the windings 28, two by two, following a circular permutation, and diodes 56 are connected in parallel with each winding 28, their cathode being coupled to the positive pole of the source 36 in order to prevent voltage surges in the windings 28 when these latter are de-energized.

The operation is as follows: if the displacement takes place in the direction L, the contacts 54 are connected as shown in FIG. 12. Assuming that the

windings

28a and 28b are excited, the excitation of the following winding 280 is determined by the striking of the thyristor 510 which is triggered by the gate 52c. This release occurs when the generator 53 delivers an impulse and the preceding winding 28b is excited simultaneously. The striking of the thyristor 51c short-circuits the condenser 55a and thus creates a reverse potential at the terminals of the thyristor 51a which becomes blocked. The winding 28a of the unit 220 is no longer excited, while the winding 28c is put into circuit. At the following impulse, the thyristor 51d strikes and the thyristor 51b becomes blocked and so on, the successive excitation of the electromagnetic units 22 being effected in the direction L. In order to reverse the direction of movement, that is to say to effect it in the direction M, it is only necessary to modify the position of the switch 54 which changes the sequence of excitation of the second input of the gates 52. The diodes 56 protect the thyristors 51 against voltage surges which may occur during the break of the corresponding circuit.

This electronic switch enables high powers to be controlled with accuracy and avoids the problems presented by mechanical switches, especially the arcs due to voltage surges on interruption of inductive circuits.

The checking of the control impulses can readily be made automatic in order to ensure that the moving system has a movement at constant speed or at progressive acceleration, depending on the applications. For this purpose, it is only necessary to control the impulse generator 53 in dependence on an appropriate parameter.

The electromagnetic device contemplated by the invention may, following another industrial application, be employed for the propulsion of vehicles guided by a track for handling, transport of goods or passengers. In particular, this device may equip railway vehicles, monorails or ground-effect vehicles.

In these applications, the magnetized assembly is preferably stationary and follows the outline of the track. The electromagnetic units which form the magnetizing assembly are mounted on the vehicle and are supplied with electric current derived from any known means.

While in certain cases, especially of conveyors, it is necessary to provide control means external to the vehicle, as in the machines which have been described in the preceding embodiments, in the present case the control and in consequence the switching of the electromagnetic units is effected directly from the interior of the vehicle.

In the construction shown in FIGS. 13 to 16, there is indicated diagrammatically at 60 the frame of a vehicle fitted with wheels 61 and moving along a normal railway track 62. The fixed magnetized assembly 63 which constitutes a rail and follows the outline of the track is arranged at equal distances from the two rails 62. The upper part of the magnetized assembly 63 comprises a succession of teeth 64, separated by non-magnetic sections 65, produced very economically by simple cutting-out. A suitable magnetized assembly may be made from a normal carbon steel of good quality.

The driving section is preferably constituted by several magnetizing assemblies distributed amongst the vehicles of a train. There is thus obtained a moving assembly having a small mass, which more readily follows the irregularities of profile of the magnetized assembly 63. Furthermore, this multiplication of the driving units results in a better utilization of the magnetized assembly, pennits of manufacture on a larger scale and at low cost of small light driving units which are readily housable in and removable from all the vehicles of a train, and provides an installed power proportional to the size of the train.

In the particular construction described, the magnetizing assembly provided for a vehicle 60 comprises four electromagnetic units 67 fixed on a frame 66 mounted elastically in the lower part of the vehicle 60. Each unit 67 comprises a circuit 68 made from magnetic sheet, and two windings 69 mounted on poles 71 defining an air-gap and arranged in such manner that the teeth 64 of the magnetized assembly 63 may pass in line through the abovementioned air-gap, perpendicular to the lines of force between the poles 71, when the windings 69 are excited. The magnetic circuits 68 which are of C-shape are laminated in the plane of this latter and are arranged at right angles to the direction 0 or N of the movement.

The non-magnetic frame 66 comprises enclosing flanges 70 and re-entrant flanges 72, which provide a housing for the circuits 68. This mounting reinforces the transverse rigidity of the assembly and offers remarkable resistance to the forces of attraction of the poles between each other. In particular, the flanges 70 which surround the base of the poles 71 of each magnetic circuit 68, preventing the bending of the sheets of this latter due to the effect of the attraction force acting on the magnetic teeth 64.

The frame 66 is fixed to the lower part of the vehicle 60 by means of crank-arms 73, mounted between elastic articulations 311, 312 (see FIG. 15). The thrust or traction efforts of the magnetizing assembly are transmitted to the vehicle 60 by at least one elastic coupling 74 which damps out the variations and the shocks of these efforts.

The guiding of the frame 66 with respect to the rail 63 is ensured by two pairs of rollers 75 mounted in opposition on each side of the magnetized rail 63, at the front and at the rear of the frame. The rollers 75 run just beneath notched portions 65 of the rail 63, and the mechanical play is regulated in such manner that the distance between the poles 71 and the magnetic teeth 64 is greater than at least twice the value of the mechanical play. Thus, the attraction forces of the poles are balanced and the residual lateral force is negligible. A sticking effect of the poles on the magnetized assembly is a fortio i made impossible. These mechanical and magnetic clearances and the wheel base of the rollers 75 are determined in such manner that in curves of short radius, the pole surfaces 71 remain sufficiently distant from the magnetized assembly 63.

According to an improvement, the magnetized rail 63 also serves as a third rail for supplying current. For this purpose, it is insulated from the track by a nonconductive sole-plate 77. The current is taken-off by one or more collector shoes (not shown) supported on the lateral surface of the rail.

According to a further special feature of the invention, it is provided that the four electromagnetic units of the driving assembly are associated in pairs, 67a, 670 on the one hand and 67b, 67d on the other, in such manner that in each pair (FIG. 39) when one of the electromagnetic units 67a comes opposite a magnetic section 64 of the magnetized assembly 63, the other unit 67c is facing a non-magnetic section 65. In addition, the distance between the pairs of associated

units

67a, 67c is such that when the poles of one pair are located respectively opposite a magnetic section 64 and a non-magnetic section 65, the poles of the other pair are situated opposite the half of a magnetic section 64 and the half of a non-magnetic space 65.

The supply of current to the windings 69a 69d associated in pairs is effected as shown in FIG. 16 by means of a two-phase current source 79 of variable frequency, such as a Diesel electric generating set carried by the train. The conductors 3130 of the same phase supply two associated windings 69a, 690, by means of two power diodes 78 connected in opposition so that one of the associated windings is supplied at each half-wave. The same arrangement is adopted for the second phase (conductors 311%). The source 79, associated if necessary with a phase-shifting system, is furthermore arranged in such manner that the phaseshift between the phase conductors 313a, 3l3b is 90.

Thus, the four electromagnetic units 67 of the magnetizing assembly begin to be excited respectively at 90, 180, 270 and 360 of the cycle, and each one of them ceases its operation 180 later.

In addition, if the electromagnetic units 67 are excited following the sequence a, b, c, d, the vehicle 60 will be propelled in the direction 0. If the excitation sequence is a, d, c, b, the movement will take place in the opposite direction N.

No other means for controlling the direction of displacement is necessary, since if the first electromagnetic unit excited tends to cause the movement to start in the wrong direction (the case, for example, of the unit d, whereas the movement is desired in the direction the subsequent windings (b, c, d, a, etc. will correct this tendency and the movement will continue in the desired direction. The control of speed can be effected by varying the frequency of the source 79, and especially by increasing it as the train gathers speed.

According to another alternative form shown in FIG. 40, the determination of the direction of the speed is effected by means of a feeler 76 such as a magnetic or capacitive detector which controls the triggers of the thyratrons 401 or of the thyristors forming part of the electronic switching device 402 of the electromagnetic units 67, whenthe latter are supplied, for example, in accordance with FIG. 12.

The control is regulated in such manner that the release impulse is produced at a suitable moment with respect to the relative forward movement of the tooth 64 nearest the magnetized assembly 63. When an acceleration is necessary, the release of the thyratrons or thyristors referred to above can be effected in phase advance. This variation of phase can be obtained by any means known per se and forming part of the electronic triggering system (and especially by a phase-shift stage 403), or by mechanically displacing the feeler 76 with respect to the chassis 66. The deceleration of the vehicle is effected in a similar manner by a phase delay. This deceleration is independent of the adhesion of the wheels. For this reason, the braking of the vehicle can be made very effective, flexible and silent, and gives a greater degree of safety.

Due to the high inductive impedance of the circuits, the increase and decrease of the current in the magnetizing windings 69 is delayed with respect to the beginning and the end of the electric impulse delivered by the generator 79.

In order to compensate for the effects of this 'delay at high speeds, the invention provides for increasing with the speed the advance of the setting of the instants of the beginning and end of the driving electric impulse with respect to the relative positions of the poles 71 and the teeth 64 of the magnetized assembly.

This advance makes it possible to prevent the subsistence of a magnetizing field in the air-gap at the moment when the poles 71 are about to pass beyond the tooth 64 considered of the magnetized assembly 63. in an arrangement of this kind, the feeler 76 may operate as a speed-detection device and may permit the frequency modulation of a signal which is employed for the regulation of the phase between the impulse periods and the instants when the magnetizing and magnetized assemblies occupy pre-determined relative positions.

The reluctance of the magnetic circuit of the units 67 varies according to the displacement of the magnetizing assembly. According to a further particular feature of the invention, it is then provided to adapt this law of variation to the most probable speed of the vehicle in the section of track considered. The modifications of this law of variation may be obtained by acting on the longitudinal profile of the magnetic sections 64, on their thickness and on their magnetic characteristics.

In particular, provision is preferably made on the portions of track intended for high speeds, for the formation of teeth such as 64a (FlG. 13) of which at least the leading edge forms an acute angle with the direction of movement, and the mean length of which is greater than for low speeds, while the permeability and thickness are reduced.

These arrangements considerably reduce shocks and vibrations, and increase the effort developed.

The method of propulsion of guided vehicles thus provided by the invention may be advantageously applied to wall-effect vehicles and especially to those of the air-cushion type. An application of this type, shown in FIGS. 17 to 19, is advantageous since vehicles of the kind considered have no physical contact with the wall, so that it is difficult for them to utilize the adhesion effect with the wall for acceleration or braking.

in this embodiment, the vehicle 80 is supported above an area 81 serving as a track by the ground effect resulting from air cushions 82 supplied by distribution channels 83. The vehicle is guided by a vertical rib 84 which forms the magnetized assembly with the magnetic sections 85 and the non-magnetic sections 86 uniformly spaced apart. The magnetic sections 85 are in this case constituted by parallelepiped blocks of magnetic material embedded in the guiding rib 84 of a non-magnetic material such as concrete. There is thus formed a low-cost magnetized assembly which furthermore plays an essential part in guiding the vehicle along the track.

The magnetizing assembly 87 comprises, in this example, four electromagnetic units each comprising a magnetic circuit 88 in the form of a C, which has an airgap defined by the poles 91.

The windings 89 are mounted in pairs on each magnetic circuit 88 close to he poles 91, in order to concentrate the magnetizing field in the air-gap, to reduce the leakage flux and to have the maximum driving force on each magnetic section for a given magneto-motive force.

The guiding of the magnetizing assembly 87 is effected by the wall effect resulting from air cushions 94 created between the rib 84 and the said assembly. The cushions 94 are supplied through channels 93, depending on the size of the vehicle.

Claims

1. A transporter system comprising at least one beam serving as a track, at least one car suspended from and movable along said track and provided with drive means for imparting motion thereto, said drive means comprising a magnetizing assembly and and a magnetized assembly adapted to move one with respect to the other and mounted one on said beam and the other on said car, the magnetizing assembly comprising a plurality of electromagnetic units disposed in line and each said unit comprising one magnetic circuit having two oppositely facing pole faces defining an air gap therebetween and having at least one inductor winding, the magnetized assembly projecting into said air gap in the magnetic field of the magnetizing assembly and comprising a plurality of magnetic sections disposed in line in alternate relation with non-magnetic sections, each said magnetic section comprising at least a pair of oppositely facing surfaces, at least a pair of said section surfaces facing respectively two of the said pole faces of a said magnetic circuit so that the magnetic flux generated by said inductor winding and acting upon said magnetic section enters one of said section surfaces and leaves the opposite surface of said magnetic section, the pitch of said magnetic sections being different from that of the electromagnetic units of said magnetizing assembly, switching means for supplying current pulses to the windings of said electromagnetIc units according to a predetermined sequence, each pulse of the sequence being supplied at about the time when one of the magnetic sections reaches the entrance of the corresponding air gap, means for guiding the relative displacement of the said magnetized assembly through the air gaps of said electromagnetic units in a direction crossing the lines of force within said air gaps, the direction of said lines of force being substantially the same in said air gaps and in said magnetic sections of said magnetized assembly, sensing means for detecting a parameter of that assembly which is moving with respect to the other assembly, and means controlled by said sensing means for controlling the current pulses supplied to said windings.

2. A system as claimed in claim 1, said sensing means detecting the position of said moving assembly.

3. A system as claimed in claim 1, said sensing means detecting the speed of said moving assembly.

4. A system as claimed in claim 1, said sensing means detecting the direction of movement of said moving assembly.

5. A system as claimed in claim 1, said controlling means controlling the beginning of the current pulses.

6. A system as claimed in claim 1, said controlling means controlling the end of said current pulses.

7. A system as claimed in claim 6, said means controlling the end of the current pulses effecting the interruption of a current pulse fed to an electromagnetic unit before the corresponding magnetic section reaches a central position in the corresponding air gap.

8. A system as claimed in claim 1, said controlling means controlling the order in which said current pulses are supplied to said windings.

9. A system as claimed in claim 1, the line in which said electromagnetic units are disposed being a straight line.

10. A system as claimed in claim 1, the line in which said electromagnetic units are disposed being a curved line.

11. A system as claimed in claim 1, the amount by which the pitch of said magnetic sections is different from that of the electromagnetic units of said magnetizing assembly being such that the axial length of N pitches of one said assembly is equal to the length of (N+1) pitches of the other assembly, N being a whole number.

12. A system as claimed in claim 1, said guiding means being so arranged that the mechanical play of said magnetized assembly in a direction parallel to the lines of force within the air gaps of said electromagnetic units is substantially less than the value of the residual air gap between the pole faces of said units and the oppositely facing surfaces of the magnetic sections of said magnetized assembly when the latter are in the position of minimum reluctance.

13. A transporter system comprising at least one member serving as a track, at least one member movable along said track and provided with driving means for imparting motion thereto, said driving means comprising a magnetizing assembly and a magnetized assembly, one of said assemblies being carried by one of said members and the other of said assemblies being carried by the other of said members, the magnetizing assembly comprising a plurality of electromagnetic units disposed in line and each said unit comprising one magnetic circuit having two oppositely facing pole faces defining an air gap therebetween and having at least one inductor winding, the magnetized assembly projecting into said air gap in the magnetic field of the magnetizing assembly and comprising a plurality of magnetic sections disposed in line in alternate relation with non-magnetic sections, each said magnetic section comprising at least a pair of oppositely facing surfaces, at least a pair of said section surfaces facing respectively two of the said pole faces of a said magnetic circuit so that the magnetic flux generated by said inductor winding and acting upon said magnetic section enters one of said section surfaces and leaves the opposite surface of said magnetic section, the pitch of said magnetic seCtions being different from that of the electromagnetic units of said magnetizing assembly, switching means for supplying current pulses to the windings of said electromagnetic units according to a predetermined sequence, each pulse of the sequence being supplied at about the time when one of the magnetic sections reaches the entrance of the corresponding air gap, means for guiding the relative displacement of the said magnetized assembly through the air gaps of said electromagnetic units in a direction crossing the lines of force within said air gaps, the direction of said lines of force being substantially the same in said air gaps and in said magnetic sections of said magnetized assembly, sensing means for detecting a parameter of that assembly which is moving with respect to the other assembly, and means controlled by said sensing means for controlling the current pulses supplied to said windings.

14. A system as claimed in claim 13, said sensing means detecting the position of said moving assembly.

15. A system as claimed in claim 13, said sensing means detecting the speed of said moving assembly.

16. A system as claimed in claim 13, said sensing means detecting the direction of movement of said moving assembly.

17. A system as claimed in claim 13, said controlling means controlling the beginning of the current pulses.

18. A system as claimed in claim 13, said controlling means controlling the end of said current pulses.

19. A system as claimed in claim 18, said means controlling the end of the current pulses effecting the interruption of a current pulse fed to an electromagnetic unit before the corresponding magnetic section reaches a central position in the corresponding air gap.

20. A system as claimed in claim 13, said controlling means controlling the order in which said current pulses are supplied to said windings.

21. A system as claimed in claim 13, the line in which said electromagnetic units are disposed being a straight line.

22. A system as claimed in claim 13, the line in which said electromagnetic units are disposed being a curved line.

23. A system as claimed in claim 13, the amount by which the pitch of said magnetic sections is different from that of the electromagnetic units of said magnetizing assembly being such that the axial length of N pitches of one said assembly is equal to the length of (N+1) pitches of the other assembly, N being a whole number.

24. A system as claimed in claim 13, said guiding means being so arranged that the mechanical play of said magnetized assembly in a direction parallel to the lines of force within the air gaps of said electromagnetic units is substantially less than the value of the residual air gap between the pole faces of said units and the oppositely facing surfaces of the magnetic sections of said magnetized assembly when the latter are in the position of minimum reluctance.

25. A system comprising guide means, means movable on said guide means, drive means for imparting motion to said movable means on said guide means, said motion-imparting means comprising an electromagnetic device producing a mechanical action and comprising a magnetizing assembly and a magnetized assembly adapted to move one with respect to the other, one of said assemblies being carried by said guide means and the other of said assemblies being carried by said movable means, the magnetizing assembly comprising a plurality of electromagnetic units disposed in line and each said unit comprising one magnetic circuit having two oppositely facing pole faces defining an air gap therebetween and having at least one inductor winding, the magnetized assembly projecting into said air gap in the magnetic field of the magnetizing assembly and comprising a plurality of magnetic sections disposed in line in alternate relation with non-magnetic sections, each said magnetic section comprising at least a pair of oppositely facing surfaces, at least a pair of said section surfaces facing respectively tWo of the said pole faces of a said magnetic circuit so that the magnetic flux generated by said inductor winding and acting upon said magnetic section enters one of said section surfaces and leaves the opposite surface of said magnetic section, the pitch of said magnetic sections being different from that of the electromagnetic units of said magnetizing assembly, switching means for supplying current pulses to the windings of said electromagnetic units according to a predetermined sequence, each pulse of the sequence being supplied at about the time when one of the magnetic sections reaches the entrance of the corresponding air gap, said guide means guiding the relative displacement of the said magnetized assembly through the air gaps of said electromagnetic units in a direction crossing the lines of force within said air gaps, the direction of said lines of force being substantially the same in said air gaps and in said magnetic sections of said magnetized assembly, sensing means for detecting a parameter of that assembly which is moving with respect to the other assembly, and means controlled by said sensing means for controlling the current pulses supplied to said windings.

26. A system as claimed in claim 25, said sensing means detecting the position of said moving assembly.

27. A system as claimed in claim 25, said sensing means detecting the speed of said moving assembly.

28. A system as claimed in claim 25, said sensing means detecting the direction of movement of said moving assembly.

29. A system as claimed in claim 25, said controlling means controlling the beginning of the current pulses.

30. A system as claimed in claim 25, said controlling means controlling the end of said current pulses.

31. A system as claimed in claim 30, said means controlling the end of the current pulses effecting the interruption of a current pulse fed to an electromagnetic unit before the corresponding magnetic section reaches a central position in the corresponding air gap.

32. A system as claimed in claim 25, said controlling means controlling the order in which said current pulses are supplied to said windings.

33. A system as claimed in claim 23, in which the residual air gap between the pole faces of said electromagnetic units and the oppositely facing surfaces of the magnetic sections of said magnetized assembly is at least equal to twice the maximum mechanical play of said magnetized assembly in a direction parallel to the lines of force within the air gaps of said electromagnetic units.

34. A system as claimed in claim 25, in which the section of passage of the magnetic flux in the magnetic circuits of said electromagnetic units and in the magnetic sections of said magnetized assembly is determined in such a way that said magnetic sections are saturated before said magnetic circuits reach saturation.

35. A system as claimed in claim 25, in which the moving assembly is mounted below the fixed assembly and is suspended by magnetic attraction, retention means being further provided for preventing said moving assembly from falling in case of interruption of current supply to said magnetized assembly.

36. A system as claimed in claim 25, in which said electromagnetic units of the magnetizing assembly are connected in parallel to a single source of electrical energy through means for differential regulation of the voltage across the terminals of the windings of said electromagnetic units, said means comprising synchronized sliders and means for controlling the displacement of said sliders in dependence of the desired position of the moving assembly.

37. A system as claimed in claim 25, the line in which said electromagnetic units are disposed being a straight line.

38. A system as claimed in claim 25, the line in which said electromagnetic units are disposed being a curved line.

39. A system as claimed in claim 25, the amount by which the pitch of said magnetic sections is different from that of the electromagnetic units of said magnetiZing assembly being such that the axial length of N pitches of one said assembly is equal to the length of (N+1) pitches of the other assembly, N being a whole number.

40. A system as claimed in claim 25, said guiding means being so arranged that the mechanical play of said magnetized assembly in a direction parallel to the lines of force within the air gaps of said electromagnetic units is substantially less than the value of the residual air gap between the pole faces of said units and the oppositely facing surfaces of the magnetic sections of said magnetized assembly when the latter are in the position of minimum reluctance.