RAPID RESPONSE SOLENOID

Technical Field

The present invention generally relates to electromagnetic transducers , and more particular¬ ly to a rapid response solenoid of the type having short magnetic circuits and a large working face relative to the armature mass.

Background Art Recent advances in control system technology have generated a need for transducers having adequate power and response time for quickly converting control signals into movement of a mechanical control. Response time of previous transducers employed for this purpose, more commonly known as solenoids, decreased with the size and force developed by these devices. The n.eed for a rapid response, powerful solenoid has been satisfied by the device described in ϋ.S. Patent No. 4,003,013 issued to Seilly on January 11, 1977. The solenoid disclosed in the patent mentioned above comprises a long, thin E-core solenoid formed in a helical configuration which consists of two coaxial cylinders respectively defining an inner core and an outer armature; external threads on the inner core loosely mate with internal threads on the

outer armature. Both of the thread forms are of the twin start variety and a series of helical coil windings on the core are interconnected such that each conducting loop of wire initially passes along the first thread root of the core and returns along the second thread root thereof. Current flows in opposite directions in adjacent spiral channels thereby magnetizing only the very short local paths linking individual threads with additive flux lines extending between the working faces defined by the mating threads. This construction minimizes the amount of magnetizable material needed for a given thrust rating, and the reduced armature mass for a given working stroke is constant independent of the force required for a particular application.

Helical solenoids of the type described above possess two disadvantages. Because of the continuous helical coil windings, the resultant magnetic field applied to the armature possesses a torque component which causes the armature to rotate during the working stroke. This problem has been dealt with in the past by providing a slide mechanism between the armature and core so as to confine the armature movement to an axial direction; these slide mechanisms not only add to the complexity of the solenoid, but naturally add frictional resistance to the assembly which re¬ duces operating efficiency.

Another disadvantage associated with the above describee helical solenoids relates to the fact that the core and armature are each of unitary construction sized for a given application, i.e., each solenoid possesses a fixed force rating which is only suitable for a narrow ranσe of

applications. Accordingly, the costs of manufacturing an entire range of solenoid sizes having differing force ratings is relatively high.

Disclosure of the Invention The present invention overcomes the dis¬ advantages of the prior art helical solenoid through the provision of a unique coil winding arrangement and modular core construction which not only permit rapid, economical assembly of various sizes of solenoids producing differing force ratings, but eliminate"the tendency of the armature to rotate relative to the core.

According to one aspect of the invention, a first magnetizable member includes portions having a plurality of individual, circularly-shaped slots therein disposed about a longitudinally extending displacement ^' axis , each of the slots lying substan¬ tially within a corresponding reference plane ex¬ tending essentially perpendicular to the displace- ment axis. A second magnetizable member having por¬ tions defining a plurality of projections respec¬ tively extend into the slots of the first member and having a width less in magnitude than the respectively associated slots to define a plurality of gaps between the first and second members. An electrical winding through which electrical current may flow for producing a magnetic field to effect relative axial movement between the first and second members includes a plurality of winding portions respectively disposed within the slots and extending around the displacement axis. Means are provided for electrically interconnecting the winding portions to produce electrical current flow

in opposite circular directions in adjacent winding portions.

According to another aspect of the inven¬ tion, the first member includes a plurality of dis- crete, modular core sections disposed in side-by- side relationship to each other; the core sections each include a body upon which a corresponding wind¬ ing portion is wrapped, as well as a pair of elec¬ trical sockets and plugs which may be rotated during assembly of the core to alternately connect the windings of adjacent core sections to produce oppo¬ sitely directed current flows in adjacent winding portions.

Brief Description of the Drawings In the drawings:

FIGURE 1 is an elevational view of a rapid response solenoid forming the preferred embodiment of the present invention;

FIGURE 2 is a fragmentary view of the solenoid shown in FIGURE 1, with one half of the armature removed, and showing the armature in a retracted, starting position;

FIGURE 3 is a view similar to FIGURE 2, but showing the armature shifted to its extended position;

FIGURE 4 is a cross-sectional view taken along the line 4-4 in FIGURE 1;

FIGURE 5 is a fragmentary view of one end of the solenoid shown in FIGURE 1, parts being broken away in section for clarity;

FIGURE 6 is a exploded, perspective view of two adjacent core sections of the solenoid shown in FIGURE 1;

FIGURE 7 is a side view of the solenoid of the present invention, coupled between a station¬ ary support and a load;

FIGURE 8 is a sectional view of the sole- noid of the present invention adapted to be mounted within a housing; and,

FIGURE 9 is a fragmentary, cross-sectional view of the solenoid of the present invention, de¬ picting an alternate construction of the core sections,

Best Mode For Carrying Out the Invention

Referring first to FIGURES 1-6, the pre¬ sent invention is broadly concerned with an electro¬ magnetic transducer in the nature of a solenoid 10 which is adapted to convert electrical energy to mechanical movement suitable for operating various kinds of controls. Solenoid 10 includes a first magnetizable member 12 disposed within a second, generally cylindrical, hollow, magnetizable member 14. The first and second members 12 and 14, respectively, are mounted for relative axial move¬ ment along an axis of displacement designated by the numeral 36.

The first member 12 consists of an elon¬ gate, cylindrical core comprising a plurality of discrete, modular core sections 16 disposed in side-by-side relationship to each other. The core sections 16 are symmetrically disposed about the displacement axis 36 and collectively define a plurality of individual, circularly-shaped slots 18, each of which lie substantially within a reference plane extending perpendicular to axis 36.

The second member 14 functions as an armature and is formed by two longitudinal halves 14a and 14b which are held in assembled, mating relationship along seams 13 by longitudinally spaced, circumferential bands 68 secured by screws 86. Por¬ tions of the interior wall of the second member 14 define a plurality of annular projections 20 respec¬ tively associated with slots 18 and extending into the slots 18. The projections 20 have a width less in magnitude than the width of the respectively associated slots 18 to define a plurality of ring- shaped gaps 22 between opposing faces of the pro¬ jections 20 and core sections 16.

Each of the core sections 1'6 includes a magnetizable body portion 58 having a bore 82 longitudinally therethrough within which there is received an electrically insulative portion 60. Body portion 58 comprises a cylindrically-shaped surface 56 and an upstanding, annular sidewall 54 contiguous with one end of surface 56. Each body portion 58 is provided with a pair of diametri¬ cally opposed, radial apertures 96 and 98 in the cylindrical surface 56 thereof. Insulative por¬ tion 60 may comprise any suitable electrical insu- lative material and is provided with a pair of co-planar, longitudinally extending holes 62 and 64 therein, disposed on opposite sides of a longi¬ tudinally extending passageway 67 within which there is received an elongate member in the nature of a hollow rod 24.

As best seen in FIGURES 6 and 7, the core sections 16 are sleeved over rod 24 and held in abutting relationship to each ether by means of a shoulder 102 secured on one end of rod 24,

and a nut and washer combination 26 carried by a threaded portion of the opposite end of rod 24. Thus, it may be appreciated that rod 24, nut and washer combination 26 and shoulder 102 provide means for holding the core sections 16 in aligned, side-by-side relationship to each other.

Electrical winding means 34 for producing a magnetic field effecting relative axial movement between the first and second members 12 and 14 along axis 36 consists of a plurality of discrete, iden¬ tical winding portions 38 respectively associated with the core sections 16 and disposed within a cor¬ responding slot 18. The winding portions 38 may consist of one or more coil turns of a suitable conducting wire and have the ends 92 and 94 thereof respectively trained through apertures 96 and 98 of body portion 58 associated with the correspond¬ ing core section 16.

Means for electrically interconnecting the winding portions 38 of adjacent core sections 16 include a pair of electrical connectors 40 respectively received within the holes 62 and 64 of insulative portions 60. Each of the connectors 40 includes a male plug portion 42 extending longi- tudinally beyond the corresponding core section 16 and a female socket portion 44 for frictionally receiving the male plug portion 42 of an adjacent core section 16. Connectors 40 collectively de¬ fine a pair of electrical buses 66 which are coupled with a source of electrical power (not shown) by lead wires 90 trained through the rod 24 and coupled with the socket portions 44 of an end-most core section 16 by means of electrical plugs 104.

Each of the core sections 16 is prεassem- bled in an identical manner with the winding por¬ tions 38 and connectors 40. The ends 92 and 94 of each winding portion 38 are suitably connected to the corresponding connectors 40, as by brazing, etc. Although the individual core assemblies consisting of core portions 16, winding portions 38 and connec¬ tors 40 are identical in construction, the ends 92 and 94 of adjacent winding portions 38 are alter- nately connected to the two electrical buses 66 so as to produce oppositely directed current flow in adjacent ones of the winding portions 38.

This alternate connection arrangement of the winding portions 38 is achieved by rotating alternate ones of the core assemblies 180° rela¬ tive to the adjacent core assemblies during assem¬ bly of the first member 12. The alternate connec¬ tion arrangement may be better understood by reference to FIGURE 6, wherein two adjacent core assemblies 16a and 16b are depicted during the assembly process. The ends 92 and 94 of each winding portion 38 of assemblies 16a and 16b are respectively connected to connectors 40a and 40b. However, core assembly 16b has beer, rotated 180° relative to core assembly 16a, consequently the positions of connectors 40a and 40b of assembly 16a are diametrically opposite those of assembly 16b. The effect of this alternate connection ar¬ rangement is shown in FIGURE 2 wherein the positive symbol (÷) indicates current flow into the plane of the drawing and the dot symbol ( • ) designates cur¬ rent flow emanating upwardly from the plane of the drawing. In accordance with the so-called right- hand rule, current flowing in opposite directions

in adjacent winding portions 38 produces magnetic fields in opposite circular paths as indicated by the arrows 106 in FIGURE 2, which combine with each other at the interface between the projec- tions 20 and sidewalls 54 defining gaps 22. This additive magnetic attraction between the projections 20 and sidewalls 54 results in axial shifting of the projections 20 toward the sidewalls 54, thereby im¬ parting axial movement to the second member 14 along axis 36.

Attention is now directed to FIGURE 9 wherein alternate means for holding the core sec¬ tions 16 in aligned relationship is depicted. This alternate holding means consists of a nesting arrange- ment, generally indicated at 28, wherein each of the body portions 58 is provided with an annular projec¬ tion 32 which is received in tight frictional engage¬ ment within a mating, annular recess 30 in an adja¬ cent body portion 58. A suitable adhesive compound may be applied to the interfacing surfaces of the body portions 58 to assure that the core sections 16 are held in fixed relationsihp to each other. The insulative portions 60 may be comprised of rigid material to provide the first member 12 with addi- tional longitudinal rigidity. Additionally, con¬ nector assemblies 46, which are broadly similar to connectors 40 previously described, may consist of a plug 50 and socket 48 coupled by an electrical interconnect wire 52 integrally formed in each insulative portion 60.

Referring now also to FIGURE 7, the solenoid 10 may be mounted between a stationary support 84 and a load to be controlled, designated by the rod 76, by providing threaded means 72 for

connecting one end of the first member 12 to the stationary support 84. The second member 14 nay be formed with endwalls defining guide portions 78a and 78b circumscribing the rod 24. Annularly-shaped bearing means 80a and 80b interposed between the rod 24 and the guide portions 78a and 78b may be com¬ prised of plastic, Teflon, bronze or the like and slidably support each end of the second member 14 on the rod 24. One end of the second member 14 ad- jacent rod 76 is provided with a threaded neck 75 adapted to be threadably received within a threaded yoke 100 on rod 76. The guide portions 78a and 78b are provided with annular extensions 81a and 81b around which there is secured collars 69 for hold- ing the halves 14a and 14b in assembled relationship.

It may be readily appreciated from the foregoing description that the mounting arrangement depicted in FIGURE 7 causes the first member 12 to remain stationary while the second member 13 axi— ally reciprocates to move the load.

In some cases, it may be desired to mount the solenoid 10 within a housing. This may be ac¬ complished, as shown in FIGURE 8, by providing housing means 70 which substantially encloses the solenoid 10. Housing means 70 is provided with an opening 108 in one end thereof to accommodate means for coupling the second member 14 with the load, i.e., rod 76. Means for securing the first member 12 on the housing may include a threaded element 72 connected with one end of member 12. The outer cylindrical surface of the second member 14 is closely received in sliding engagement with the interior sidewalls of housing means 70. A bearing material 110, such as Teflon or the like, may be

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WIPO

applied to either the interior sidewalls of the housing means 70 or the exterior of the second member 14 in order to facilitate sliding engagement therebetween. Means including a collar 74 may be provided for coupling T-shaped extensions 77 and 79 of the second member with the rod 76.

Note that in connection with the embodi¬ ment depicted in FIGURE 8, the two halves 14a and 14b of the second member 14 are held in assembled relationship by longitudinally spaced, circular bands 112 disposed within recesses in the outer surface of the second member 14.

Industrial Applicability

The solenoid of the present invention is well adapted for quickly converting electrical control signals into mechanical movements, parti¬ cularly where relatively high magnitudes of force are required along with the need to minimize the volume of space displaced by the solenoid. Typi- cal applications of the invention include the opera¬ tion of fuel pumps and valve mechanisms.

As previously discussed, the solenoid of the present invention effects relative axial move¬ ment between the core and armature by additive magnetic fields generated by oppositely directed current flow in adjacent coil winding portions 38. In contrast to prior solenoids , the coil winding associated with the present invention produces the desired additive magnetic fields in spite of the fact that the winding portions 38 are wholly dis¬ posed within individual, circular slots. Conse¬ quently, whereas the prior art solenoid having a continuous helical coil winding produced magnetic

fields having a rotational or "torque" component tending to impart rotational movement to the arma¬ ture, no such torque component is created in the solenoid of the present invention. Accordingly, the present invention eliminates the need for anti- rotational slide mechanisms between the core and armature.

Moreover, the solenoid of the present invention is well adapted for use in various appli- cations presenting differing force requirements.

Since the core defined by the second member 12 c _* om- prises a plurality of discrete, modular core assem¬ blies, any selected number of the core assemblies may be assembled in order to meet the force reσuire- ents of a particular application. This feature eliminates the need for the various tooling, fix- turing, etc. necessary for producing unitary cores of differing dimensions.

While the present invention has been described in connection with a particular example thereof, various modifications will be apparent to those skilled in the art. Other aspects, ob¬ jects and advantages of the invention may be ob¬ tained from a study of the drawings, the disclosure and the appended claims.