US3381181A - Electromagnetic device - Google Patents

Description

April 30, 1963 L. c. WEATHERS 3,381,181

ELECTROMAGNETIC DEVICE Filed June 27, 1966 515, FIG. I. J2

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/ 'llm 0 Pic. 3- 29 2 United States Patent 3,381,181 ELECTROMAGNETIC DEVICE Leland Clay Weathers, Plymouth, Mich., assignor to Sperry Rand Corporation, New York, N.Y., a corporation of Delaware Filed June 27, 1966, Ser. No. 560,627 7 Claims. (Cl. 317-155.5)

ABSTRACT OF THE DISCLOSURE A solenoid has an elongated tube to confine and guide the armature thereof, has a permanent magnet of annular configuration mounted on and integral with the tube so there are substantially no air gaps between that permanent magnet and that tube, has a winding mounted on one end of the tube adjacent one side of the permanent magnet, and has a second winding mounted on the other end of the tube adjacent the other side of the permanent magnet, and the magnetic flux lines provided by the magnet constitute the predominant flux lines used to operate the solenoid.

This invention relates to improvements in electromagnetic devices. More particularly, this invention relates to improvement in solenoids.

It is, therefore, an object of the provide an improved solenoid.

The solenoid provided by the present invention includes a tube which confines and guides the armature of that solenoid. A permanent magnet is mounted at the exterior of that tube, and that permanent magnet is made integral with that tube; and hence there are substantially no air gaps between that permanent magnet and that tube. As a result, the solenoid provided by the present invention can have a low reluctance path for the flux lines developed by the permanent magnet thereof. It is, therefore, an object of the present invention to provide a solenoid armature thereof, and a permanent magnet mounted at the exterior of and made integral with that tube to substantially eliminate air gaps between itself and that tube.

A winding is mounted on one end of the tube adjacent one side of the permanent magnet, and a second winding is mounted on the other end of the tube adjacent the other side of that permanent magnet. That permanent magnet always develops flux lines in the armature of the solenoid, and either of the windings can be selectively energized to selectively develop magnetic flux lines in that armature. The permanent magnet develops the major portion of the magnetic flux lines in the annature of the solenoid; and this is important because it enables that solenoid to use windings which supply less than one-fourth of the ampere turns supplied by the windings of a conventional solenoid and yet enables that solenoid to provide the same force which that conventional solenoid provides. It is, therefore, an object of the present invention to provide a permanent magnet intermediate two windings for a solenoid, and to have that permanent magnet develop the major portion of the magnetic flux lines for that solenoid.

The tube on which the permanent magnet is mounted is made of magnetic material and is made long enough to project beyond both sides of the magnet and into the present invention to windings of the solenoid. As a result, that tube has low reluctance and provides a large area, in confronting relation with the armature therein, through which magnetic flux lines can flow. This means that ample clearance can be provided between that armature and the interior of the tube to prevent sticking and binding of that armature without an undue reduction in the force supplied by that solenoid.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description a preferred embodiment of the present invention is shown and described, but it is to be understood that the drawing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawing, FIG. 1 is a side elevational view of one preferred embodiment of solenoid that is made in accordance with the principles and teachings of the present invention and of a device actuated by that solenoid,

FIG. 2 is a sectional view through the solenoid of FIG. 1, and it is taken along the plane indicated by the line 2-2 in FIG. 1, a

FIG. 3 is a partially broken-away sectional view, on a larger scale, through the solenoid of FIG. 1, and it is taken along the plane indicated by the line 33 in FIG. 2, and

FIG. 4 is a schematic diagram of the electrical circuit for the solenoid of FIG. 1.

Referring to the drawing in detail, the numeral 20 generally denotes one preferred embodiment of solenoid that is made in accordance with the principles and teachings of the present invention. That solenoid can be used to actuate many different types of devices; but, for convenience of showing, that solenoid is shown as actuating a valve 22. The solenoid 20 has a housing which includes a cylindrical portion 24, and that cylindrical portion has openings 26 and 28 therein. A permanent magnet 30, which is annular in configuration, is disposed within the cylindrical portion 24; and the outer periphery of that permanent magnet is disposed intermediate the openings 26 and 28 in that cylindrical portion. As shown particularly by FIG. 3, the outer periphery of the permanent magnet 30 is narrower than the inner periphery of that permanent magnet. A tube 32 is formed integrally with the permanent magnet, as by casting that permanent magnet onto that tube; and this is important because it substantially eliminates air gaps between that permanent magnet and that tube. An annular recess 34 is formed in the left-hand end of the tube 32, as that tube is viewed in FIG. 3; and an annular recess 36 is formed in the right hand end of that tube. A sleeve 38 of nonmagnetic material extends into the annular recess 34 in the tube 32 to form a rabbet joint; and the outer end of that sleeve projects axially beyond the left-hand end of that tube. A sleeve 40 of non-magnetic material extends into the a11- nular recess 36 in the tube 32 to form a rabbet joint; and the outer end of that sleeve extends axially beyond the right-hand end of that tube.

A coil form 42 is telescoped over the sleeve 38 and over the left-hand end of the tube 32; and that coil form abuts the left-hand face of the permanent magnet 30. A winding 44 is Wound onto the coil form 42; and leads 45 from that winding extend outwardly through the opening 26 in the cylindrical portion 24 of the housing. A coil form 46 is telescoped over the sleeve 40 and over the right-hand end of the tube 32, and that coil form abuts the right-hand face of the permanent magnet 30. A winding 48 is wound onto the coil form 46; and leads 49 from that winding extend outwardly through the opening 28 in the cylindrical portion 24 of the housing. An end wall 50 that is square in end elevation is provided with an annular recess; and that annular recess coa-cts with the left-hand end of the cylindrical portion 24 of the housing to constitute a rabbet joint. An end wall 52 that is square in end elevation is provided with an annular recess; and that annular recess coacts with the right-hand end of the cylindrical portion 24 of the housing to constitute a rabbet joint.

The valve 22 has an end wall 56 that abuts the end wall 52; and the end wall 56 has threaded sockets therein. Elongated machine screws 54 extend through aligned openings in the corners of the end walls 50 and 52 and are seated in the threaded sockets in the end wall 56 of the valve 22. Those machine screws hold the end walls 50 and 52 in intimate engagement with the cylindrical portion 24, and also hold the end Walls 56 and 52 in intimate engagement with each other. The sleeves 38 and 40 will have press fits with the central openings in the end Walls 50 and 52, but the ends of the tube 32 will be spaced away from those end walls. The cylindrical portion 24 of the housing, the tube 32, the sleeves 38 and 40, and the end walls 50 and 52 coact to completely enclose the windings 44 and 48. The cylindrical portion 24, the tube 32, the armature 64, and the end walls 50 and 52 are made of magnetic material; and they substantially completely confine the permanent magnet 30 and the windings 44 and 48 within an enclosure of magnetic material. As a result, all of the outer surfaces of the solenoid are at one magnetic potential. This is desirable because it eliminates stray external magnetic fields, and hence renders the solenoid 20 insensitive to the presence of nearby magnetic material. If the permanent magnet and the windings 44 and 48 were not substantially completely confined within an enclosure of magnetic material, the mounting of the solenoid 20 adjacent a valve or other device which had a housing of magnetic material could shift the operating point of that permanent magnet 30 downwardly along the demagnetization curve of that permanent magnet.

The end wall 56 of the valve 22 has an annular recess therein to accommodate the right-hand end of the sleeve 40. In addition, that end wall hasa further, larger-diameter, annular recess 58 therein which accommodates an O-ring 60 of resilient material. That O-ring will be under compression whenever it is disposed within the recess 58 and bears against the outer periphery of the sleeve and that O-ring will coact with the walls of that recess and with the sleeve 40 to provide a liquid-tight seal.

The numeral 62 denotes a stop ring which is disposed within the sleeve 48 and which abuts the end wall 56 of the valve 22. That stop ring will be in register with an annulus at the right-hand end of the armature 64. The stop ring 62 will preferably have a press fit with the inner periphery of the sleeve 40. The armature 64 is disposed within the tube 32; and it will be guided and confined by that tube, but it will be able to move axially relative to that tube. Movement of that armature to the right will be limited by a closure 70. That closure has a cylindrical portion which extends into the left-hand end of thesleeve 38; and a cylindrical recess 71 is provided in the inner face of that cylindrical portion. The resulting annulus at that inner face of that cylindrical portion is in register with an annulus at the left-hand end of the armature 64. An annular recess 72 in the cylindrical portion of that closure accommodates an O-ring 74; and that O-ring will be under compression whenever it is disposed within the recess 72 and the cylindrical portion of the closure 70 is disposed within the left-hand end of the sleeve 38. That O-ring will coact with the walls of the recess 72 and with the left-hand end of the sleeve 38 to provide a liquid-tight seal.

A push-pull rod 66 extends through the geometric center of the armature 64; and it has a snap-ring seated in a groove adjacent the left-hand end thereof to limit movement of that push-pull rod to the right relative to that armature. A spacer tube 68 encircles the right-hand end of the push-pull rod 66, and it will bear intimately against the right-hand end of that armature. Movement of the armature 64 will thus enforce simultaneous concomitant of the push-pull rod 66.

The numeral 76 in FIG. 4 denotes a diode which has the cathode thereof connected to one terminal of the winding 44 by one of the leads 45. A diode 78 has the cathode thereof connected to one terminal of the winding 48 by one of the leads 4 9; and the anodes of those diodes are connected together and to the live terminal of a source of alternating current by a junction 80 and a conductor 90. The other terminal of the winding 44 is connected to a stationary contact 84 of a switch 82 by the other lead 45; and the other terminal of the winding 48 is connected to the stationary contact 88 of that switch by the other lead 49 The movable contact 86 of the switch 82 is connected to the grounded terminal of the source of alternating current.

The permanent magnet 30 is preferably made from oriented Alnico VI material; and the tube 32 is preferably cast so it is integral with that permanent magnet. The outer periphery of the permanent magnet 30 can be furnished in a centerless grinder; and the inner periphery of the tube 32 will then be made concentric with that outer periphery. The sleeves 38 and 40 will be preferably silver soldered to the ends of the tube 32. The cylindrical portion 24 of the housing will be heated, telescoped over the ground outer periphery of the permanent magnet 30, and then cooled to shrink it into intimate, gap-free engagement with that outer periphery.

The permanent magnet 30 will be radially magnetized after the solenoid has been assembled; and it will cause some magnetic flux lines to fiow axially to the left through the tube 32 and the armature 64, radially outwardly through the end wall 50, and then axially through the cylindrical portion 24, and it will cause further magnetic flux lines to flow axially to the right through the tube 32 and the armature 64, radially outwardly through the end wall 52, and then axially through the cylindrical portion 24. The radial orientation and the radial magnetization of the permanent magnet 30 will make it possible to use a permanent magnet which is from twenty to twenty-five percent shorter than a permanent magnet which was not radially oriented and was not radially magnetized.

If it is desirable for the armature 64 to move to the central position shown by FIG. 3 whenever both of the windings 44 and 48 are deenergized, the stop ring 62 and the closure should be made of nonmagnetic material. Also, if the movable portion of the device to be actuated by the solenoid 20' is resistant to movement, a centering spring should be associated with that movable portion to center the armature 64 whenever the windings 44 and 48 are denergized. Whenever the winding 44 is energized, as by rotation of the movable contact 86 in the counterclockwise direction in FIG. 4, the flux density at the air gap adjacent the sleeve 38 will increase; and hence the armature 64 will move to the left. Conversely, whenever the winding 48 is energized, as by rotation of the movable contact 86 in the clockwise direction in FIG. 4, the flux density at the air gap adjacent the sleeve 40 will increase; and hence the armature 64 will move to the right.

The permanent magnet 30 provides more than one-half of the magnetomotive force applied to the armature 64; and each of the windings 44 and 48 provides less than onehalf of that magnetomotive force. This is important; because it enables the solenoid 20 to use windings which supply less than one-fourth of the amper turns supplied by the windings of a conventional solenoid and yet enables that solenoid to provide the same force which that conventional solenoid provides. As a result, the windings 44 and 48 can be made so they will not burn out, even if they are kept energized indefinitely.

The alternating current supplied to the conductors 90 and 92 will be rectified by the diode 76 or the diode 78; and hence a half-wave rectified voltage will be applied to the winding 44 or the winding 48. That voltage will consist of a DC. term, a fundamental frequency sine term, and and infinite series of even cosine terms. The peak value of the AC. voltage will be about three times the value of the DC. component of the half-wave rectified voltage; and this is desirable because such a peak value Will sharply reduce the response time of the solenoid.

The alternating current components in the half-wave rectified current supplied to the windings 44 and 48 will tend to develop eddy currents; and those eddy currents will flow in the tube 32. Those eddy currents will tend to increase the apparent resistance and to decrease the apparent reactance of the solenoid; and this is desirable because it"will increase the values of the energy dissipated by, relative to the values of the energy stored within, the solenoidwith a consequent decrease in the time constant of that solenoid. If the time constant of the solenoid were to tend to become so short that the armature 64 would tend to chatter, the sleeves 38 and 40 could be made from materials having high resistivities.

Whenever the armature 64 is in the intermediate position shown by FIG. 3, the inductance of the winding 44 will be less than the inductance of that winding when that armature is abutting the closure 70. Similarly, whenever the armature 64 is in the intermediate position shown by FIG. 3, the inductance of the winding 48 will be less than the inductance of that winding when that armature is abutting the stop ring 62. This is desirable because it permits a rapid build-up of current, and hence a fast response, whenever the winding 44 or the winding 48 is initially energized. The increased inductance of the winding 44 or the winding 48, whenever the armature 64 is abutting the closure 70 or the stop ring 62, is desirable; because it will reduce the ripple in the half-wave rectified current. That reduction in ripple is desirable because it minimizes the tendency of the armature 64 to chatter.

The inductance of the winding 44 can be calculated by use of the following formula:

wherein N is the number of turns in that winding P+ is the permeance of the magnetic gap adjacent the sleeve 38 P- is the permeance of the magnetic gap adjacent the sleeve 40 P is the leakage permeance of the permanent magnet 30 P is the permeance of the permanent magnet 30 P is the intermediate position gap permeance P N+ P 11+ P M The inductance of the winding 48 can be calculated by use of the same formula; but P+ will be the permeance of the magnetic gap adjacent the sleeve 40, and P will be the permeance of the magnetic gap adjacent the sleeve 38. In one preferred embodiment of the present invention, the inductance of the winding 44 of the widing 48 will be about nine henrys when the armature 64 is in its intermediate position and will be about twelve henrys when that armature is in its fully moved position.

If desired, a small inverse magnetic gap could be provided adjacent the sleeve 38, and a further small inverse magnetic gap could be provided adjacent the sleeve 40. Those small inverse magnetic gaps could, if desired, be

made so they merely compensated for the ampere turns absorbed by the armature 64 and by the cylindrical portion 24, the end walls 50 and 52, and the tube 32. Where that was done, the force-displacement curve of the solenoid of FIG. 1 would be substantially linear.

If large inverse magnetic gaps were provided adjacent the sleeves 38 and 40, as by making the stop ring 62 and the closure of magnetic material, and if no centering spring was used, the solenoid could be used to operate a one-way on-oif valve or a two-way bistable valve. The use of such large inverse magnetic gaps would make it possible for just a pulse of current to shift the solenoid armature, and thus shift the movable element of the valve.

The tube 32 is important because it materially increases the inductance of the solenoid 20'; and that materially increased inductance will reduce the tendency of the armature 64 to chatter. That tube also is important because it has a low reluctance and it provides a large area, in confronting relation with the armature 64, through which the magnetic flux lines can flow. As a result, a clearance of two-thousandths of an inch can be provided all around the exterior of the armature 64 without an undue reduction in the force supplied by the solenoid 20; and such a clearance will prevent sticking or binding of the arrnature 64.

Whereas the drawing and accompanying description have shown and described a preferred embodiment of the present invention, it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

1. An electromagnetic device that comprises:

(a) a tube,

(b) a permanent magnet mounted at the exterior of said tube,

(c) said permanent magnet and said tube being integral to substantially eliminate any air gaps therebetween,

(d) said tube being substantially longer than the axial dimension of said permanent magnet and being made of magnetic material,

(c) said tube having one end thereof projecting axially outwardly a substantial distance beyond one side of said permanent magnet and having the other end thereof projecting axially outwardly a substantial distance beyond the other side of said magnet,

(f) a winding encircling said one end of said tube,

(g) a second winding encircling said other end of said tube,

(h) a housing that intimately engages the outer periphery of said permanent magnet,

(i) said housing being made of magnetic material,

(j) said housing projecting axially outwardly beyond both sides of said permanent magnet and axially beyond said windings,

(k) an end wall that is secured to one end of said housing .and that extends inwardly toward said one end of said tube,

(1) a second end wall that is secured to the other end of said housing and that extends inwardly toward said other end of said tube,

(In) a nonmagnetic member, that is substantially shorter than said tube, extending between said one end wall and said one end of said tube to help completely enclose the first said winding while providing a nonmagnetic gap between the first said end wall and said tube,

(11) a further nonmagnetic member, that is substantially shorter than said tube, extending between said second end wall .and said other end of said tube to help completely enclose said second winding while providing a nonmagnetic gap between said second end wall and said tube,

(0) an armature disposed within said tube for movement axially of said tube,

(p) said armature being of magnetic material and having a length greater than the distance between the first said and said further nonmagnetic members and having the ends thereof adjacent the outer ends of said windings,

(q) said housing, said end walls, said tube, and said armature substantially completely enclosing said permanent magnet by magnetic material and thereby substantially eliminating stray external magnetic fields,

(r) said permanent magnet acting, whenever said windings are dc-energized, to establish predetermined flux densities at the nonmagnetic gaps defined by the first said and said further nonmagnetic members,

(s) the first said winding being energizable to increase the flux density adjacent the first said nonmagnetic member and thereby urge said armature to move toward said one end of said tube,

( said second winding being energizable to increase the flux density at the nonmagnetic gap defined by said further nonmagnetic member and thereby urge said armature toward said other end of said tube,

(u) said permanent magnet providing the major portion of the magnetic flux lines for said electroma netic device,

(v) said windings being wound so said electromagnetic device can operate safely even if one of said coils is kept energized indefinitely,

(w) a diode connected in series with the first said winding to enable said winding to be connected to a source of alternating current and thereby receive a peak voltage having a value several times higher than the average D.C. voltage applied to that winding while also providing substantially unidirectional flow of current through said winding,

(x) a second diode connected in series with said second winding to enable said winding to be connected to a source of alternating current and thereby receive a peak voltage having a value several times higher than the average D.C. voltage applied to that Winding while also providing substantially unidirectional flow of current through said second winding, and

(y) a common conductor connectable to both of said windings,

(z) the nonmagnetic gap defined by the first said nonmagnetic member being a continuous annulus,

(aa) the nonmagnetic gap defined by said second nonmagnetic member being a continuous annulus,

(ab) said magnet being a continuous annulus and establishing substantially uniform flux densities in said annular nonmagnetic gaps,

(ac) said diodes and said windings being connected so current can not flow through both of said windings at the same time,

(ad) said tube and said armature being coextensive throughout the major portion of the length of said armature to enable said tube to reduce the density of the magnetic flux flowing through said major portion of said length of said armature.

2. An electromagnetic device that comprises:

(-a) an elongated tube of magnetic material,

(b) an armature that is disposed within said tube, that is elongated, and that is reciprocable along the long axis thereof within said tube,

(c) a permanent magnet that is mounted on and made integral with said elongated tube, that is disposed adjacent said armature, and that encircles said armature to cause magnet flux lines to flow through said armature along said long axis thereof,

((1) a winding that is disposed adjacent one side of said permanent magnet and that surrounds said elongated tube and said armature and is adapted to cause magnetic flux lines to flow through said armature along said long axis thereof,

(e) a second winding that is disposed adjacent the other side of said permanent magnet and that surrounds said elongated tube and said armature and is adapted to cause magnetic flux lines to flow through said armature along said long axis thereof,

(f) said armature being disposable in an intermediate position within said elongated tube,

(g) the first said winding being energizable to cause said armature to move out of said intermediate position and along said long axis thereof into a position closer to the first said winding,

(h) said second winding being energizable to cause said armature to move out of said intermediate position and along said long axis thereof into a position closer to said second winding,

(i) said permanent magnet providing the major portion of the magnetic flux for said electromagnetic device,

(i) said elongated tube and said armature being coextensive throughout the major portion of the length of said armature to enable said elongated tube to reduce the density of the magnetic flux flowing through said major portion of said length of said armature.

3. An electromagnetic device as claimed in claim 2 wherein said magnet is a solid mass, is free of laminations, and wherein said magnet is annular in configuration, said magnet having the axis thereof coaxial with the axes of said windings, said armature being disposed at the axis of said magnet and at the axes of said windings, and wherein rectifiers are connected to said windings to enable said windings to be connected to a source of alternating current, said source of alternating current enabling each of said windings to receive a peak voltage value several times higher than the average D.C. voltage applied to that winding, said source of alternating current causing eddy currents to flow in said tube and thereby tend to increase the apparent resistance and decrease the apparent reactance of said electromagnetic device.

4. An electromagnetic device as claimed in claim 2 wherein said elongated tube and said permanent magnet are integral to substantially eliminate air gaps there-between, wherein a housing of magnetic material engages the outer periphery of said permanent magnet, wherein end walls extend inwardly from said housing toward said elongated tube, wherein said elongated tube and said end walls are made of magnetic material, and wherein nonmagnetic gaps which are substantially shorter than said elongated tube are located between the ends of said elongated tube and said end walls.

5. An electromagnetic device as claimed in claim 2 wherein said permanent magnet is annular in configuration and has sides that are frusto-conical in configuration, said frusto-conical sides making the outer periphery of said magnet narrower than the inner periphery of said magnet and wherein a housing of magnetic material engages the outer periphery of said permanent magnet.

6. An electromagnetic device that comprises:

(a) a tube,

(b) a permanent magnet mounted at the exterior of said tube and integral with said tube to substantially eliminate air gaps therebetween (c) a housing that intimately engages the outer periphcry of said permanent magnet,

(d) a winding that is disposed between said housing and said tube and that is adjacent one side of said magnet,

(e) a second winding that is disposed between said housing and said tube and that is adjacent the opposite side of said magnet,

(f) end walls extending inwardly from said housing toward said tube, and

(g) nonmagnetic gaps, each of which is substantially 0 shorter than said tube, between said tube and said end walls,

(h) said tube, said housing, and said end walls being made of magnetic material and substantially completely enclosing said magnet and said windings to make said solenoid substantially insensitive to nearby magnetc material.

7. An electromagnetic device as claimed inclaim 6 wherein rectifiers are connected to said windings to enable said windings to be connected to a source of alternating current and yet have unidirectional current flowing through them, and wherein said tube provides a path 10 for eddy currents which will increase the apparent resistance of said solenoid.

References Cited 5 UNITED STATES PATENTS 3,022,450 2/1962 Chase 335229 X 3,178,151 4/1965 Caldwell 335229 X 3,200,591 8/1965 Ray 317-155.5 X

10 BERNARD A. GILHEANY, Primary Examiner.

G. HARRIS, Assistant Examiners.

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