Untitled record

Requested December 22, 1949, at 4 p.m.^h 10^m, in Strasbourg.

Issued February 6, 1952. - Published May 5, 1952.

(3 patent applications filed in the United States of America on December 23, 1948, May 26, 1949 and August 9, 1949. - Declaration by the applicant.)

The subject of the present invention is a sealing device constituted by packings, seals or the like to be placed between fixed or rotating members relative to each other.

Such rotary seals used in installations subjected to pressure, one member of which is supposed to rotate with respect to the other, gives rise to a difficult problem, namely that of the hermeticity of the seal, all the more so since in many fields such as that the installation of radars, the rotary joints must be tight in the presence of relatively high fluid pressures and must have a relatively very low friction torque.

It has already been proposed previously to establish sealing devices for rotary joints using in particular braids or rubber seals and lap seals.

The rubber packings were not satisfactory, as it was impossible to find an organic substance capable of withstanding extreme changes in temperature. It was found that there was then a collapse of the sealing device itself.

As for the overlapping seals, they have also been shown to be unusable in a practical manner because the presence of two overlapping surfaces, engaged with an oil film serving as lubricant and made hermetic by a device acting under the action of the tension of a spring at each end of two tubes to be joined, causes play at the free end and floating after a relatively short operating time. For the same reasons, lateral leakage occurs, which results in operating conditions which are not to be sought for any type of rotation. The operating conditions due to lateral leaks will cause metal-to-metal support between the elements overlapping largely under pressure, which will cause necking, non-lubrication2 - 41034

Booklet price: 100 francs.

fication, floating, vibration and extreme wear producing high points on the bearing surface. By using such devices, it is difficult to balance the load to be carried and as a result, there is a predominance of necking and floating effects under the effect of axial and radial loads. If however a high spring pressure is used, a leak-free device requires a high torque.

It is therefore seen that the rotation of a pressurized part with respect to the other is relatively difficult if it is necessary to maintain at the same time a satisfactory seal between the members.

The current problem of the sealing of rotary joints becomes particularly important when rigid coaxial lines are used in an airborne installation, when the dielectric power of the air is likely to decrease under the effect of the reduction of atmospheric pressure at high altitudes, so that it can strike an arc in the line. In addition, the changes in temperature and pressure to which an airborne installation is subjected often produce a condensation of humidity in the line, which increases both the electrical losses and the possibility of piercing the insulation. (To avoid these drawbacks, the radio frequency lines of the airborne installation are hermetically closed and filled with dry air, nitrogen or other suitable fluid at a pressure above atmospheric pressure and the antenna and pressure modulator at the same time as the coaxial lines The possibility of a leak is considered dangerous due to the possible piercing of the insulation in the waveguides. But even intermittent leaks in the joint cause high frequency current modulations due to variations in conductivity due to the change in fluid pressure. Thus rotary joints often appear as the most critical parts of a transmission line and antenna assemblies in particular.

The sealing devices previously proposed for this purpose include springs or other elastic devices which, at least in certain cases and in combination with highly polished contact surfaces, seal between the two members; this works satisfactorily for a relatively short time and in the case of a relative movement between two members at low speed, because the wear is all the higher as the pressure applied in the assembly to be sealed is higher. To reduce wear, it has been proposed to use hard carbon compounds applied against metal surfaces. Such hard carbonaceous compounds have been used for example in linings, seals, vacuum lines, pistons, pivot joints, etc.

However, this palliative only makes it possible to obtain a wear-absorbing device and it is also more advantageous to replace the hard carbonaceous compound than to allow the essential elements of the assembly to be sealed to wear out, but without doing so. annoying wear itself.

The problem encountered is that even a highly polished surface of any metal still has a large number of raised and depressed areas, as can easily be seen under a microscope; moreover, under the effect of wear, there may be a leakage of fluid or liquid after a relatively short period. To take this fact into account, it has been proposed to increase the mechanical pressure between the sliding or contacting surfaces, from which it follows that the seal was improved but at the same time the wear of the material and the required torque increased even more.

Those skilled in the art will know that the effectiveness of known sealing devices decreases with increasing mechanical pressure between the contacting surfaces due to increased wear and increased torque, account given the higher friction to be overcome.

Consequently, the main object of the invention is a device comprising a tight rotary joint between two elements subjected to pressure.

Another subject of the invention is the establishment of a chamber between) the two elements to be joined, this chamber having to be filled with a liquid or gelled composition, comprising iron particles subjected to an open magnetic field, and stabilized by the fluid pressure.

According to other characteristics of the invention:

A seal obtained by a magnetic fluid is provided between the two elements to be joined together for a relative rotary movement;

The value of the static friction of this magnetic sealing fluid for rotary joints does not differ appreciably from the value of the kinetic friction.

There is no discontinuity in the torque in such a magnetic fluid sealing device for rotary joints when sliding begins;

The rotary joint between elements subjected to pressure allows the use of small servo motors;

A sealing device is provided according to the principle for mechanical drive and in particular for high speed mechanical drives for both static and dynamic operating conditions relating to a series of members applying the sealing principle in accordance with l invention; ''

Means are provided for limiting the centrifugal, acceleration or gravitational forces exerted on the fluid placed in the rotary tight seal;

The effects of the rotating seal are increased by giving a specific shape to the active surface of the magnet;

The rotary tight seal comprises means for placing the fluid in the magnetic field in a manner well determined in advance;

The rotating sealing device has a magnetic air gap of capillary dimensions so as to combine the magnetic and capillary effects;

The fluid that the seal comprises is capable of being mixed with magnetizable particles and preferably has a jelly consistency of well defined chemical composition.

Another object of the invention is to solve the problem on which the present invention is based, namely: obtaining a semi-liquid or solid material with which magnetizable particles are mixed or associated, this material being subjected with these particles to a magnetic field by means of electromagnets or permanent magnets and being placed in front of a polished or unpolished surface, the magnetic force repelling this material in the immediate vicinity of the projections and recesses of this metal surface so as to ensure excellent contact between the semiliquid or solid material and the metal surface.

Another object of the invention is to provide in the sealing device between the two surfaces in contact a semi-liquid or solid material mixed or associated with magnetizable particles, requiring minimum pressure and resulting in minimum wear and a minimum possibility of leak between the two surfaces in contact to be joined in a sealed manner.

In another aspect, the invention presents a sealing device making it possible to increase the efficiency of a reduced mechanical pressure, which it is necessary to exert between the surfaces in contact, and this due to wear. reduced metal surface entering the sealing device.

The sealing device also makes it possible to use a narrower interval between the surfaces in contact to be sealed.

It can also be considered that the sealing device comprises a semi-liquid, plastic, elastic or solid material mixed or associated with magnetic particles, all of this material and of these particles being placed in front of the metal surface of a device. sealing.

Finally, this sealing device comprises a semi-liquid, plastic, elastic or solid material, mixed or associated with metallic particles and which can be further added with a lubricating material to reduce friction and increase the sealing effect.

The invention covering the above arrangements as well as others which will appear in the following detailed description has been shown in the accompanying drawings for a better understanding of the said invention. In these drawings:

Fig. 1 is a sectional elevation view of a first embodiment of a rotary joint;

Fig. 2 is a section along line 2-2 of FIG. 1;

Fig. 3 is a sectional elevation of a variant of a rotary joint comprising two magnet systems offset in the radial direction;

Fig. 4 is a sectional elevation of another variant comprising a device of external magnets;

Fig. 5 is a sectional elevation of another external magnet seal device;

Fig. 6 is a sectional elevation of an embodiment of the rotary joint, the magnetic field of which has an adjustable length;

Fig. 7 is a sectional elevation of an embodiment where the rotary joint comprises a radial magnet device;

Fig. 8 is an elevational view partially in section of another embodiment of the rotary joint;

Fig. 9 is a section along line 9-9 of FIG. 8;

Fig. 10 is an elevational view, partially in section, of an embodiment similar to that of FIG. 8;

Fig. 11 is an axial section of an embodiment comprising a lubrication chamber for a rotating shaft bearing;

Fig. 12 is an axial section through a piston and a cylinder comprising a magnetic sealing device;

Fig. 13 is a partial section of an embodiment representing a floating ring arranged in the magnetic field;

Fig. 14 is a horizontal section of an embodiment - [1,007,372] of execution comprising a floating ring as in the case of FIG. 13;

Fig. 15 is a partial section of an embodiment representing a perforated floating ring arranged in the magnetic field;

Fig. 16 is a partial section of an embodiment representing a magnet of particular shape associated with a floating ring of complementary shape arranged in the magnetic field;

Fig. 17 is a partial section of an embodiment according to which the ring is arranged in the magnetic field and is held in place by a ball bearing;

Figs. 18 and 19 are axial sections of an embodiment representing different means for moving the fluid in the magnetic field;

Fig. 20 is a partial section of an embodiment representing a magnetic field with an air gap of capillary dimensions;

Fig. 21 represents a particle that can be moved on an enlarged scale showing its coarse outer surface;

Fig. 22 is a schematic representation of two surfaces in contact as they appear in the prior sealing devices;

Fig. 23 schematically represents two contact surfaces appearing in the execution of the sealing devices according to the invention;

Fig. 24 is an axial section of a connection between tubes;

Fig. 25 is a section along line 25-25 of FIG. 4;

Fig. 26 is an axial section of the sealing device applied to a rotating shaft and subjected to axial pressure;

Fig. 27 is a section along line 27-27 of FIG. 26;

Fig. 28 is an axial section of the sealing device being subjected to radial pressure;

Fig. 29 is a section along line 29-29 of FIG. 28;

Fig. 30 is an axial section of a device comprising a shaft and an element subjected to an additional reciprocating movement;

Fig. 31 is an axial section of the sealing device for a piston subjected to a reciprocating movement;

Fig. 32 is a section along line 32-32 of FIG. 31;

Fig. 33 is an axial section of a sealing device comprising a rotating shaft;

Fig. 34 is a section along line 34-34 of FIG. 33;

Fig. 35 is an axial section of the sealing device for a ball bearing associated with a rotating shaft;

Fig. 36 is a section along line 36-36 of FIG. 35;

1.

[1.007.372] —

Fig. 37 is an axial section of another embodiment of the sealing device for a rotating shaft;

Fig. 38 is a section along line 38-38 of FIG. 37;

Fig. 39 is an axial section of another embodiment using solids;

Fig. 40 is an axial section of a last embodiment where the sealing device comprises solid materials.

If we now refer to the drawings and in the first place to FIGS. 1 and 2, the present device comprises, as can be seen, two tubular bodies I and 2 which may be coaxial cables or waveguides or else a combination of coaxial cables and waveguides, the upper body 1 and the lower body 2 being carried by an appropriate frame 3 in such a way that one of the bodies can rotate relative to the other under the action of an appropriate control such as a servomotor not shown. The body 1 comprises an annular plate 4 having two projections 5 and 6 arranged annularly according to different radii and directed parallel to the axis downwards, these projections forming on either side of the hollow 7 of the plate 4 a housing for the ring magnet

8. B''en that we have represented a permanent magnet. it should be understood that one could use an electromagnet as well.

The body 2 comprises a similar annular plate 9 also comprising two annular projections 10 and 11 arranged at different distances from the axis and directed da^r's the direction of this axis but upwards, in the immediate vicinity of the projections 5 and 6 of the plate 4. these projections 10 and 11 also carry on either side of the hollow 12 of the plate 9 a housing for a corresponding magnet 13 in a position such that a magnetic field is established between the magnets 8 and 13.

The tubular bodies 1 and 2 have suitable movers, not shown, to provide a determined pressure above atmospheric pressure in the form of a suitable compressed fluid such as air or nitrogen.

The housings provided for the magnets 8 and 13 together form a single chamber containing iron particles suspended in a liquid or gelled composition, preferably oil, an icon or other suitable liquid. Iiqu'des silicones provide excellent results allowing the sealing device to operate both at very low temperatures and at very high temperatures.

The tension exerted or the force produced by the particles suspended in the magnetic field do not allow the extension of a discontinuity in the fluid. The composition used absorbs pressure changes and makes it possible to establish a permanent type sealing device without any risk of metal-to-metal contact or of a continuity solution in the fluid, thus causing the seal to break.

An unexpected but very advantageous characteristic, which is obtained in at least some embodiments of the new magnetic fluid sealing device, consists in that the value of the static friction does not differ appreciably from the value of the kinetic friction . As a result, there is no torque discontinuity when the slip begins to occur. According to a very important characteristic of the present invention, the pressure between the tubular members is much lower than in ordinary rotating joints, which allows the elimination of conditions allowing mechanical relaxation with the use of low-power servomotors.

It is known that, for the low speeds required in rotary radar devices, the existence of mechanical relaxation oscillations is extremely troublesome. Such mechanical relaxation oscillations can occur in a system where the frictional force depends on the speed. If the shaft speed is relatively low, the speed-torque characteristic curve decreases and in this case represents a “negative resistance”. At this point, there is a discontinuity for a constant potential energy. The whole jumps and returns to its starting point. At this time again, the characteristic is negative so that mechanical relaxation oscillations can occur if the operation is limited to an unstable part of the characteristic. There may be particular relaxation oscillations at low speeds. To obtain a uniform movement, an extremely large number of small jumps must be used. Larger jumps appear with a constant low speed and, under certain conditions, these jumps will modulate the beam of the radar and will appear on the cathode ray tube associated with the installation of this radar.

When the space separating two parallel magnetic surfaces is filled with magnetic particles in the state of fine subdivision and that a magnetic field is established, the magnetic particles can form a pressure resistance bridge in the form of a cable between the lovers. If the surface is small, the relative friction is low, but the mechanical power perpendicular to the movement is important. If there is a pressure perpendicular to the movement of the plates, as in the case of an installation subjected to pressure, the resulting movement will be a perbolic line for the mixture. The oil which prevents the compaction of the particles causes a more uniform operation. When the magnetic field acts on b

Part of the mixture, the iron particles attract each other and attach to each other inside the field, which is expressed by saying that the mixture takes or solidifies.

Since slip occurs between extremely fine iron particles and between them and the smooth surfaces of the seal and surfaces that are lubricated, the wear coefficient is extremely low. In addition, the used iron particles remain in the mixture and thus suffer no loss.

The embodiment of fig. 3 operates on the same principle as that described with reference to FIG. 1; it comprises an upper body 1 'and a lower body 2' each of which also comprises an annular plate 4 'or 9'. The upper plate 4 'has annular projections 5' and 6 'penetrating into corresponding recesses 14' and 15 'of the lower plate 9'. Instead of interposing a magnet in each of the plates, two pairs of magnets 8'-13 'are provided on the one hand and 16'-17' on the other, at different distances from the axis, to form two separate magnetic fields in the chamber containing the mixture of fluid and iron particles.

The embodiment shown in fig. 4 also has a tubular upper body l² and a tubular lower body 2². these bodies respectively having plates 4² and 9² while the chamber containing the mixture of a fluid and iron particles is constituted by the projections 5²and 6² of the upper plate penetrating into corresponding recesses 14² and 15² of the lower plate. Magnet 8²-13² is arranged outside the two plates 4² and 9² and produces its magnetic field through said plates. Although this mode of operation works very satisfactorily in some applications, the magnetic field seems weak in others,

Fig. 5 shows a device similar to that of FIG. 4, comprising an upper tubular body l³ and a lower tubular body 2³. Plateau 4³ upper body l³ ends with a cylindrical rim 18³ directed downwards and surrounding the plate 9³ lower body 2³. One thus obtains a chamber having a greater height between the plates and into which penetrate the rings with chamfered sections 19³ and 20³ made of soft iron or other material capable of being magnetized, these rings being fixed to the magnets 8^S and 13³ arranged outside and in contact with the plates.

Fig. 6 shows a variant which makes it possible to adjust the distance between the magnets and consequently to adjust the magnetic field. An upper tubular body l⁴ and a lower tubular body 2⁴each have a tray 4⁴ or 9⁴; the upper plate 4⁴ has a projection 5⁴ entering a recess 14⁴ of the lower plate 9⁴ which, in turn - has a projection 6⁴ entering a recess 15⁴ of the upper plate 4⁴. A chamber is thus obtained receiving the mixture of fluid and iron particles while a seat is provided for the magnets 8⁴-13⁴. The upper magnet 8⁴ is attached to a series of bolts ^ 21⁴ each of which can rotate in the bottom of the cylindrical part 22⁴ tapped for this purpose to allow the upper magnet to be raised and lowered 8⁴. The latter is integral with a cylindrical bellows 23⁴connected by welding or otherwise to the inner surface of the cylindrical part 22⁴.

The embodiment of fig. 7 comprises an upper tubular body l³ and a lower tubular body 2^B. The upper body l⁵ has at its lower end a cylindrical extension 24 · 'of slightly larger diameter, the lower end of this extension being folded inwards in the radial direction towards the external surface of the lower body 2³. A chamber is thus obtained for the mixture of fluid and iron particles which surrounds the lower body 2⁵. The upper and lower ends of the chamber form ball bearings 25⁵ and 26⁵ used to absorb radial and axial thrusts. Magnets 8 · 'and 13^s are fixed to the inner face of the cylindrical extension 24⁵ and on the outer surface of the lower body 2³ and their shape can be such that one or more magnetic fields are formed in the radial field. It is also possible to use more than one pair of magnets.

As has been said, the sealing principle according to the invention comprises a magnetic system arranged between the members which must be connected in a sealed manner, the magnetic air gap containing a fluid, preferably a gel, carrying magnetizable particles suitably distributed so as to form a continuous element from the mechanical and electrical points of view and capable of simultaneously resisting the differential pressures applied to its two well defined surfaces without there being any interaction between the sources providing the pressures differentials.

If we now refer to the device according to FIGS. 8 to 10, there is an inner tubular body 27 disposed inside an outer tubular body 28 capable of rotating relative to the inner body 27. A magnet, preferably a permanent magnet 29 of annular shape is fixed to the surface internal of the external body 28. It is provided in fig. 8 at 10 of the drawing, a thread 30 on the internal surface of the body 28 to receive the thread 30 'of the magnet 29 which thus screws into the external body 28. It should be understood, however, that any other suitable means can be provided for fix the magnet 29, for example by welding. The two bodies 27 and 28 have extensions in the form of flanges 31 and 32 intended [1,007,372] - to carry ball bearings 33 and 34 respectively to absorb vertical thrusts and radial thrusts. The outer face of the inner body 27 is shown with a thread 35 on which another magnet is screwed, the polarization of which differs from that of the magnet 29 or preferably an armature is screwed onto this thread. It should be understood, however, that the reinforcement can likewise be fixed by any other appropriate means, for example by welding on the external periphery of the internal body 27. Rings 36 ′ of non-magnetic material such as aluminum, plastics, etc., can be arranged between the magnet 29 and the armature 36 both preferably having a U-shaped cross section and these rings extend above and below the magnet 29 in order to minimize the friction between the magnet 29 and the magnetic fluid. There is thus obtained an air gap between the magnet 29 and the armature 36 as well as between the corresponding facing rings 36 ′, this air gap being filled with a fluid, preferably gelled, to be described below and mixed with magnetizable particles. The connection between the magnetizable particles arranged between the magnet 29 and the armature 36 and the fluid or the gel produces a mechanically continuous medium which does not depend on the relative movement between the magnet and its armature.

The embodiment according to fig. 10 is substantially identical to that shown in FIG. 8 and 9. The only difference that can be seen is the presence of a ball bearing 34 'receiving the radial thrust above the sealing device while the bearing 33' receiving the axial thrust is disposed at below this sealing device.

The embodiment shown in fig. 11 relates to a shaft bearing arranged in a pressure or vacuum chamber while a sealing device mounted on either side of this bearing seals the chamber in question. A shaft 37 can rotate in the bearing 38 disposed in the chamber 39. The latter is mounted on a part 40. The chamber 39 also receives a sealing device on either side of the bearing 38, each device preferably comprising a permanent magnet 41 on the interior surface of the chamber 39 and an annular frame 42 opposite each magnet 41 and at inside of it. It is advantageous to provide rings 41 ′ of non-magnetic material disposed respectively in an annular recess of the corresponding magnet 41 as well as discs 41² on one side of each magnet 41. ~

The gap between the magnets and the armature is here again filled with a gelled fluid 43 mixed with magnetizable particles. Although this is not essential, it is preferable to provide a disc 44 made of felt or other suitable material between the bearing 38 and the sealing devices in order to protect said bearing against any action of materials liable to damage it. The connection between the magnetizable particles under the action of the magnetic field and the fluid or the gel ensures mechanical continuity between the corresponding members 41 and 42. The chamber can be subjected to a differential pressure exerted between its internal volume and its surface exterior and its interior volume can also act to mechanically retain the material by preventing it from creeping or moving outward. The movement of materials in the opposite direction is also prevented. Examples of such materials include various gases, fluids, oil, grease, liquid silicones.

In the embodiment of fig. 12, there is shown the application of a sealing device to a piston 45 moving back and forth in the cylinder 46. There may be a relative displacement between said piston 45 and the cylinder 46 It is possible to replace the usual piston rings or to associate a sealing device fixed to the top of the piston 45 thereof by means of a bolt 47 or the like projecting beyond the piston 45. The sealing device comprises a permanent magnet 48 having an annular peripheral groove into which is introduced a ring 48 'of non-magnetic material, the air gap between the magnet 48 and the ring 48' on the one hand and the internal surface. of the cylinder 46 on the other hand being filled with a fluid 49 containing magnetizable particles. A magnetic flux will thus occur between the magnet 48 and the cylinder. 46 so as to ensure mechanical continuity under conditions both static and of reciprocating movements between; the different organs.

Although not essential, it may be advantageous to provide segments 50 above and below the seal to prevent loss of fluid.

Since centrifugal forces of acceleration and damping can interfere with the desired distribution of the fluid and in particular of the magnetizable particles, and moreover due to the shearing action which can be caused by the displacements of the fluid between the fixed part and the rotating part, a floating ring 51 can be introduced as shown in fig. 13 in the air gap between the magnet 52 and the armature 53. The magnet 52 is fixed to the rotating member 54 while the armature 53 is fixed to the fixed part 55 or vice versa. Preferably, the magnet 52 and its armature 53 receive the corresponding rings 56 and 57 made of non-magnetic material. The floating ring will rotate due to the displacement of the fluid and will separate the fluid cylinder into two separate parts.

In this way, the shearing effect will be at least reduced. While the floating ring 51 may be full (fig. 13), it may as well have transverse perforations 58, as shown in fig. 15.

To increase the surface of the magnet and that of the armature, it is possible according to the device of FIG. 18, give the magnet 52 'as well as the armature 53' a profile ensuring a more advantageous distribution of the magnetic flux from the point of view of its density. The floating ring 51² preferably follows the profile of the magnet 52 ′ and of the frame 53 ′ by reducing the air gap receiving the fluid.

A similar embodiment of the invention is shown in FIG. 17, where however there is provided a ring 51 of cylindrical shape. Instead of letting the ring 51 float freely, there are provided spans 59 defining the movement of Panel 51.

It is important to provide a homogeneous fluid due to the existence of acceleration or damping forces. This is achieved by means of a bias ring forming a thread 60, mounted on the rotating member 61, as shown in FIG. 18. Following the rotation of the member 61, an oblique force will occur under the effect of the ring 60. While the magnet 52 'of fig. 18 has a larger work surface, as in the case of FIG. 16, the device of FIG. 19 represents a magnet with a straight profile 52² and although it may be sufficient with a single bias ring, it may be necessary in some cases to use two bias rings 60 'as shown or even more. It should be understood, however, that one or more members of FIG. 18 can move relative to each other.

The magnetic force associated with a suitable fluid comprising magnetic particles is entirely sufficient in many cases to ensure a suitable seal. It is however possible to improve this sealing by associating the magnetic forces produced with capillary effects. Such a device is shown in fig. 20 where a magnet 52® and a corresponding armature 53® are formed in such a way that a long and narrow air gap is formed for the magnetic fluid. The length of the air gap can of course be defined in accordance with the specific requirements of the intended application. The length of the air gap will be a function of the differential pressures prevailing in the system as well as of the friction. A retaining device, not shown, may be provided to prevent the material from spreading.

Although a number of devices have been described by way of example for different applications, the possible modifications are by no means exhausted by this and other devices can be imagined for the application of the fundamental principle of the invention.

— [1.007.372]

If we refer again to the drawings and first to FIGS. 22 and 23, it will be noted that the two solid surfaces facing each other and for which it is desired to obtain sealing never come into intimate contact with one another when a relatively high mechanical pressure is applied to them. Even highly polished surfaces still have projections and recesses and if part 62 is applied to part 63 under high pressure (fig. 22) real contact will only be obtained between the projections opposite on the two parts, so that the pressure exerted only interests a small number of points. The higher the mechanical pressure, the more wear will appear, causing the obligation to replace the worn elements of the sealing device after a relatively short time.

If, however, a semi-liquid, elastic or solid material 64 · is used (fig. 23), this material being mixed or associated with magnetizable or magnetic particles and arranged in front of the metal surface which must be sealed, and if this material is subjected at the same time to a magnetic field, this material will be repelled in all the crevices of the metal surface so that the interval between the metal surface and this material will be reduced to a minimum, the fact that the material 64j will follow the shape of the projections and recesses on the surface of the metal body 65 (fig. 23). The interval between the material 64 and the surface of the metal body 65 will depend on the magnetic force to which the material particles are subjected.

The principle of the use of semiliquid, plastic, elastic or solid materials as a sealing device, as has been said, will now be described with regard to its application to different assemblies given solely by way of examples, given that it should be understood that this principle is applicable to all constructions in which sealing is sought between two fixed members or between two members moving in relation to one another. The application of the new sealing device to a tube connection is shown in Figs. 24 and 25. A pipe 66 having a flange 67 is connected to a tube 68 having a flange 69 by means of a series of bolts 70. A washer 71 is disposed between the flanges 67 and 69, the latter have recesses for receiving a magnet, preferably permanent, the flange 67 receiving in its recess. the magnet 72 and the recess of the flange 69 receiving the permanent magnet 73. A sleeve 74 protects the two magnets 72 and 73 and separates them from the opening of the tubes and the space separating the magnets 72 and 73, the washer 71 and the sleeve 74 is filled with a semi-liquid, elastic, plastic material 75 or solid, mixed or associated with magnetic or magnetizable particles. Thus [1,007,372] _ css particles of material are subjected to the magnetic field produced by the two magnets 72 and 73 and ensure a perfect seal between the two flanges 67 and 69 of the corresponding pipes 66 and 68.

Another application of the new sealing device between a rotating shaft and a fixed shaft is shown in Figs. 26 and 27. A shaft 76 carries a sleeve 77 fixed on it and on which is fixed an approximately cylindrical chamber 78, the fixing being ensured by suitable means not shown so that this chamber rotates integrally with the shaft 76. A annular magnet, preferably permanent, 79 is arranged at the bottom of the chamber 78. A fixed member 80 which can form a wall of the chamber and through which the shaft 76 defines an annular recess receiving a second magnet 81 also annular and being at a determined spacing from the first magnet 79. The annular space separating the magnets 79 and 81 and filled with a semi-liquid, elastic, plastic or solid material 75 ′, mixed or associated with magnetic or magnetizable particles which are thus subjected to the magnetic field established between the magnets 79 and 81. This material will exert pressure in the axial direction by constituting a pressure ring ensuring the tightness of the shaft 76 while it rotates relative to the fixed part 80.

The mode of execution of fig. 28 and 29 is roughly similar to that of FIGS. 26 and 27 with the difference however that the pressure exerted on the material is directed in the radial direction due to the modification of construction which is represented there. In this embodiment, the shaft 76 'carries a sleeve 77' on which is fixed an annular magnet 79 'rotating with the shaft 76'. A fixed member 80 ′ carries another annular magnet 81 ′, the internal surface of which is disposed at a determined distance from the external face of the magnet 79 ′. The same material 75 ′ semi-liquid, plastic, elastic or solid is disposed between the magnets 79 ′ and 81 ′, this material thus being subjected to the magnetic field formed by said magnets. Trays 82 'laterally cover the magnets 79' and 81 'and hold the material 75' in the annular space separating the magnets.

In the case of fig. 30. which is similar to the case of FIGS. 28 and 29. there appears to be a difference in that one of the magnets 79² is longer in the axial direction than the other magnet 81² to allow relative back and forth movement between the shaft 76² and the fixed part 80². When one of the magnets moves in the axial direction thanks to the greater length of the other magnet, the magnetic field will likewise perform a back-and-forth movement in the axial direction, so as to maintain a permanent seal .

There is shown in fig. 31 and 32 the application of such a variant of the sealing device. A piston rod 83 ends in a bolt 84 receiving two clamping plates 85 and 86. A piston ring 86 is mounted between the two clamping plates 85 and 86 which are held in place by the nut 88 in engagement with the bolt 84. The piston 89 thus formed undergoes a back-and-forth movement in the cylinder 90 which comprises, in line with the path of the piston 89, a frame 91 in the form of an inner jacket while a permanent magnet or an electromagnet 92 of annular shape is placed inside and in contact with segment 87. The latter consists of the material defined above mixed or associated with magnetizable particles. Due to the length of the armature 91, the magnetic field thus produced will perform a reciprocating movement in solidarity with the piston 89. This arrangement will ensure satisfactory sealing with maximum efficiency and minimum wear.

The mode of execution of fig. 33 and 34 is similar to that described with reference to FIGS. 28 and 29 where a magnetic force is applied approximately radially to ensure the tightness of a shaft. The only difference between this last mode of execution and the previous modes of execution consists, as one sees it immediately, in the presence of a magnet SI³ of particular shape, this magnet being annular with, however, an inner surface increased by the existence of circular grooves while the annular armature 79³ is at a defined distance from this magnet 81³. The free interval between the magnet 8I³ and frame 79³ is filled with the material already described 75³, which seals the shaft 76³.

According to another application of the principle which is at the base of the new sealing device, it can be used for a ball bearing carrying a shaft as shown in fig. 35 and 36. This application of the invention consists in providing a double seal, in other words the mounting of two sealing devices of the type shown in FIG. 28 and 29. A tree 76⁴ is disposed in a chamber 93 carrying the outer cage 94 of a bearing carried by the shaft and comprising a series of balls 95. On either side of the cage 94 is an annular magnet 79⁴ attached to tree 76⁴while at an appropriate distance beyond each magnet 79⁴ and surrounding the latter is a second annular magnet 81⁴ fixed to the interior wall of the chamber 93 »The free space separating the two magnets is filled with the material described above 75⁴ which is subjected to the magnetic field of the magnets. The two magnets and the material which separates them are retained laterally by the two discs 96 and 97 which seal the housing of the ball bearing mounted on the shaft 76⁴.

While in the above applications of the new sealing device the interlayer material is mixed or associated with magnet particles which are in the magnetic field of the magnets, it should be understood that the material can be mixed with small magnetic particles arranged between magnetizable rings as shown in fig. 37 and 38. This is how a tree 76^r> has a sleeve 79^r> keyed to it or attached to it in any suitable manner while an outer ring 81⁵ in magnetizable material is fixed to a fixed part 80⁵ at a determined distance from the first magnetic ring 79⁵. The material containing the magnetic particles is placed between the rings 79³ and 81⁵ however with mixing or association with magnetic particles which thus produce a magnetic field between the two rings 79³ and 81⁵ in magnetizable material. A sealing device of maximum efficiency and minimum wear is thus established between the rotating shaft 76^s and the piece fixed 80 ”. In all the applications described above, it is also possible to add or associate magnetic and no longer magnetizable particles to the material forming their support.

Figs. 39 and 40 describe two possible applications in which a solid material is associated with magnetizable or magnetic particles. In both cases. the application refers to a tree 76^fi or 76⁷ on which a sleeve 79 is keyed^e or 78⁷. A ring magnet 81^e or 81⁷surrounds the sleeve corresponding to a small distance from the latter. The free space is preferably filled with a series of laminated rings 75^e(fig. 39) or by a thin sleeve 75⁷(fig. 401, the material of these rings and sleeves being associated with magnetizable particles. It is also possible in this case also to use magnetic particles and to replace the annular magnet by an armature to produce the magnetic field between shaft and fixed part 80^G or 80¹.

In describing the different applications of the magnetic sealing device above, it has been said that the fluid is maintained in the space separating the magnet from its armature. We will now describe in more detail the nature of this fluid.

This fluid has an almost oily, oily or gelled consistency and must contain or be associated with magnetizable particles. Thus an organic or inorganic oil, including mineral, vegetable and animal oils, is well suited for use in this sense. By way of example, mention may be made of castor oil, peanut oil, shale oil, all lubricating oils, synthetic oils, as well as the lubricants known as oildag or castordag. which are mixtures of graphite and tannin in oil or colloidal graphite in castor oil, and [1,007,372] lubricating oils and compounds of mineral oil and soap. In addition, any plastic material of similar consistency can be used to achieve the same result. Among such plastics, it is possible to mention tetrafluoroethvlene known in the trade under the name of teflon or chemlon, which has a high resistance to heat and to chemicals while its waxy state gives it self-lubricating properties. Mention may also be made of the product known under the name of aquadag, that is to say a dispersion of graphite in water, the silicones obtained from silicon which is quadrivalent like carbon and, consequently, capable of forming long molecular chains like those found in carbon compounds, these silicones being combined with graphite or metallic soaps to form lubricants. Thus silicones are particularly suitable for use as heat transmitting agents and as hydraulic fluids. Another example is constituted by silicone rubber formed by a polymer which remains elastic between -57 ° and -d- 260 °, other examples being constituted by semi-plastic or plastic rubbers. These products are also resistant to oils and many chemicals and have good adhesive properties against many secondary materials. Other examples are also constituted by polymers based on methylsilicone, called silicone oils. They have a stable viscosity at both low and high temperatures. A wide variety of molecular combinations can be attained for silicon polymers forming resins of widely varying characters. Metals in the liquid state within a given range of temperatures, such as mercury, gallium, etc., can also be used.

As already indicated, magnetizable particles are mixed with the fluid and iron can be used from this point of view. nickel, cobalt, ferro-silicon and also the so-called Heusler alloys or the metal Muntz which are alloys of aluminum, copper and manganese and aluminum, iron and manganese respectively and finally we can use all alloys with high magnetic permeability.

It is preferable to use the magnetic particles in the finely pulverized state, although slightly larger particles can also be used. A mixture of fine and coarse particles can also be used in an advantageous manner; the particles should preferably have a rough surface to restrict any relative movement of the particles in the fluid. This can also be done by using particles [1,007,372] - cells intended to react with the fluid, which is made possible by subjecting the particles to a preliminary treatment. It is advantageous for certain applications to mix the oil with a plastic material which does not react chemically with the oil, the latter serving as a cooling and heat transfer agent.

The density of the particles in the fluid is essentially a function of the desired magnetic flux density, of the adhesion and cohesion forces between the magnetic particles and the fluid, of the differential or external pressure and of the viscosity of the fluid.

The sealing device according to the invention lends itself to multiple uses in a large number of technical fields; as examples of application and without this list being in any way exhaustive, mention may be made of the seals for radars, the grease or oil chambers, the tuning pistons for magnetrons, the expansion tubes, the sealing for turbines or pumps, pump pistons, ball joints, etc.

The materials to be used for sealing in accordance with the present invention may also be semi-liquid for a range of temperatures determined in advance, elastic, plastic or solid; they must lend themselves to rapid mixing or association with magnetic or magnetic particles solidifying semiliquid materials under the action of the magnetic field. Such materials can consist of latex, natural rubber having different consistencies such as semi-liquid or solid rubber, synthetic rubbers of all kinds, silicone rubbers, neoprene, tetrachlorethylene, known commercially under the name of teflon, a group of synthetic plastics consisting of long-chain polymer amides and known as nylon, trifluorochlorethylene polymers known as Kel-F, or compositions containing graphite, carbon or both, known as graphitar, morganite or purebon, asbestos, felt, etc.

The magnetizable particles can consist, for example, of powdered iron which can be mixed or combined with the basic material in the preliminary stages of production. A mechanical or chemical bond is thus obtained between the base materials and the magnetizable or magnetic particles so as to prevent any removal of the particles from the base material.

The plasticity of the basic materials will be determined by the pressure conditions prevailing in the application considered. As mentioned above, semi-liquid matter gets caught or solidified in some way by the action of the magnetic field. Consequently a change in the density of the field will modify the contact pressure and thus the manufacturer will be able to establish an interval between the contact surfaces in a way corresponding to the pressure produced by the density of the field itself chosen.

To reduce the friction between the magnetic material and the surface of the member to be sealed, it is preferable to add to the basic material defined above an appropriate lubricating substance which is mixed with the basic material in the state semi-liquid or that it is penetrated into the latter in the solid state to form a thin layer there. Any suitable lubricating material such as an oil or other material known to specialists can be used for this purpose.

The present invention relates to a simplified and more economical construction starting from a standard device which can be adjusted suitably by simply changing the field density of the magnets.

While in previous systems of seals or seals or other sealing devices the efficiency decreased with higher mechanical pressures at the same time as wear increased, the efficiency of the devices according to the present invention will increase thanks to the reduction of the point differential pressure, reduced wear and less torque required to move the members relative to each other.