US3621422A

US3621422A - Magnetic actuator

Info

Publication number: US3621422A
Application number: US886451A
Authority: US
Inventors: James C Macy
Original assignee: THRUST Inc
Current assignee: THRUST Inc
Priority date: 1969-12-19
Filing date: 1969-12-19
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16

Abstract

A magnetic actuating device wherein the existing magnetic gap is broken up into a plurality of increments. Elastic material is affixed between adjacent segments or core pieces within the gap to limit the maximum and minimum separations between adjacent segments or core pieces, to provide a restorative force, and to maintain the segments or core pieces in alignment. The size of the gap may be positively limited by affixing either the elastic segments or the magnetic segments to a chain have relatively movable links or beads.

Description

' United States Patent Inventor James C. Macy North Lavallette, NJ. Appl. No. 886,451 Filed Dec. 19, 1969 Patented Nov. 16, 1971 Assignce Thrust Incorporated New York, N.Y. Continuation-impart of application Ser. No. 663,792, Aug. 28, 1967, which is a continuation-in-part of application Ser. No.

486,454, Sept. 10, 1965, now Patent No. 3,376,528, continuation-impart Ser. No.

715,387, Mar. 22, 1968, Pat. No. 3,467,927, continuation-in-part of Ser. No. 486,454, Sept. 10, 1965, Pat. No. 3,376,528, continuation-in-part of Ser. No. 663,792, Aug. 28, 1967.

MAGNETIC ACTUATOR 9 Claims, 8 Drawing Figs.

U.S.Cl

[51] Int. Cl H0lf7/08 [50] Field of Search 335/257, 264, 279, 296, 267, 28l

[56] References Cited UNITED STATES PATENTS 254,743 3/1882 Waterhouse 335/264 843,919 2/1907 Washburn 335/281 Primary Examiner-G. Harris AnorneyMorgan, Finnegan, Durham 81. Pine ABSTRACT: A magnetic actuating device wherein the existing magnetic gap is broken up into a plurality of increments. Elastic material is affixed between adjacent segments or core pieces within the gap to limit the maximum and minimum separations between adjacent segments or core pieces, to provide a restorative force, and to maintain the segments or core pieces in alignment. The size of the gap may be positively limited by affixing either the elastic segments or the magnetic segments to a chain have relatively movable links or beads.

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INVIL'NTOR. JAMES C, MAC) BY flw zzifi MAGNETIC ACTUATOR RELATED APPLICATIONS This application is a continuation in-part of Application Ser. No. 663,792 filed Aug. 28, 1967, which was a continuation-in-part of Application Ser. No. 486,454 filed Sept. 10, 1965 (now U.S. Pat. No. 3,376,528, issued Apr. 2, 1968). Application Ser. No. 715,387 filed Mar. 22, 1968 (now U.S. Pat. No. 3,467,927, issued Sept. 16, 1969) was a continuation-inpart of Application Ser. No. 486,454 filed Sept. 10, 1965 (now U.S. Pat. No. 3,376,528, issued Apr. 2, 1968) and Application Ser. No. 663,792 filed Aug. 28, 1967.

BACKGROUND AND BRIEF SUMMARY OF THE INVENTION This invention relates to electromagnetic actuating devices, and more particularly, to a novel type of electromagnetic actuating device capable of providing a powerful mechanical force over a relatively long traverse.

The conventional electromagnetic relay includes an electrical coil, a movable magnetic armature, and a magnetic structure for completing the flux path around the coil. Devices of this general structure can provide a relatively powerful mechanical force as the armature is attracted in response to energization of the coil. However, the magnitude of the force is inversely proportional to the square of the working-gap length associated with the armature. Thus, any attempt at increasing the length of the stroke brings about a decrease in the force at the beginning of the stroke which is approximately proportional to the square of the distance to be traversed. Electrical devices of this general structure are, therefore, inherently short stroke devices.

By comparison, the conventional plunger-type solenoid is a long-stroke device and usually includes an iron plunger adapted to pass through the center of an electromagnetic coil. The mechanical force is created by the interaction between the magnetic flux of the plunger and the current passing through the energizing coil. The force created by the solenoid is relatively weak and suffers from the further disadvantage of being strongest at the middle of the stroke and weakest at the ends where maximum force is often required.

In the above-mentioned patent applications a unique magnetic actuating device is disclosed wherein the magnetic structure includes a plurality of magnetic segments breaking up the working gap into similar increments.

In order for this actuating device to be effective, however, it is necessary to control the separation between adjacent segments as otherwise the magnetic segments would tend to gather in a manner forming a single gap. If the actuator provides'separation forces, a minimum spacing between adjacent segments must be maintained. Moreover, the structure limiting the spacing between magnetic segments should be nonmagnetic, thus normally leading to relatively complex and expensive rigid brass-coupling and alignment structures between magnetic segments.

In addition to disclosing an effective long, powerful stroke magnetic actuator and discrete positioning device, the application discloses a unique means for controlling the separation and alignment of the structure. This is achieved by locating an elastic nonmagnetic spacer in the working gap between magnetic segments and affixing the spacer to the segments such as by an adhesive. The elastic property of the spacer limits the maximum separation and tends to maintain an approximately equal spacing between magnetic segments. The elastic spacer can be located surrounding the working gap so that there is no minimum separation, or can be located within the working gap to provide a minimum separation, as is desirable in expanding magnetic actuators. Also, the elastic spacers provide a restoring force tending to return the magnetic segments to their initial positions and further securing one magnetic segment to the next to thereby maintain the entire multisegmcnt structure aligned.

The electromagnetic device constructed in accordance with this invention converts electrical energy directly into mechanical force and is capable of providing a powerful mechanical force without limitation on the length of the stroke or traverse. The force is created by the magnetic attraction or repulsion exerted upon a plurality of interconnected magnetic members which break up working gap into smaller increments. An elastic material such as sponge rubber is inserted between the magnetic segments and affixed to them. This elastic material, when compressed, functions to establish the minimum working gap between segments and when stretched functions to limit the maximum separation. The resiliency of the elastic medium also provides a restorative force for the actuator.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in greater detail with reference to the following specification which sets forth several illustrative embodiments. The drawings are part of the specification wherein:

FIG. 1 is a view in section illustrating an embodiment of the invention utilizing a single electromagnetic coil;

FIGS. 2A, 2B and 2C are views in section illustrating an embodiment of the invention utilizing a plurality of electromagnetic coils;

FIGS. 3A and 3B are schematic diagrams illustrating two arrangements for interconnection of the electromagnetic coils for the unit of FIG. 2A;

FIG. 4 is a perspective drawing of the elements comprising the core structure of a third embodiment of the invention; and

FIG. 5 is a view in section of the assembled core structure of FIG. 4.

DETAILED DESCRIPTION The mechanical force created by an electromechanical device can be expressed by the following formula:

where P is the pull or force, k is a constant, F is the magnetomotive force, u is the permeability of the working gap, A is the area of the pole face, and x is the length of the working gap. It should be noted that the created force is inversely proportional to the length of the working gap and therefore the force falls off rapidly as the working-gap length increases.

In the illustrated embodiments structures are described which provide a powerful force over a relatively long traverse which would normally require a corresponding long working gap. With the structure in accordance with the invention, the working gap is broken into relatively small increments to eliminate the problems associated with a long working gap.

The actuating device in accordance with one embodiment of the invention is illustrated in FIG. 1 wherein a plurality of magnetic segments 2 are located within a single electric coil 3. This structure includes a cylindrical outer housing 4 of magnetic material located between a pair of similar end plates 5 and 6 which are held together by bolts 11. The electric coil 3 is located just inside the housing 4 between the end plates surrounding magnetic segments 2. The electrical leads 7 for the coil 3 are brought out through a suitably located aperture in end plate 6. Coil 3 is protected from direct contact with either housing 4 or magnetic segments 2 by insulating material 8. End plate 5 is provided with a centrally located opening which accommodates a movable coupling 9 with a relatively closesliding fit. The movement of end coupling 9 is such that a portion of it is always within the opening in end plate 5 so that a magnetic path through end plate 5 and end coupling 9 is maintained.

Magnetic segments 2 are located in the working gap between end coupling 9 and end plate 6. Associated with each magnetic segment 2 is an elastic segment 10. The elastic segments are affixed, for example by an adhesive, to the magnetic segments 2, to end coupling 9 and to end plate 6. The insulating material 8 forms a smooth inner-cylindrical surface which permits free movement of the magnetic segments 2 and further assists in maintaining the segments in alignment. There is some space between the inner-cylindrical surface and the elastic segments to permit expansion of the elastic material when the elastic segments 10 are compressed.

When electrical coil 3 is energized, a magnetic flux is created which passes through end plate 6, housing 4, end plate 5, and coupling member 9 and through the working gap which includes the approximately equally spaced magnetic segments 2. As a result of the magnetic flux, the movable end member 9 is pulled toward end plate 6 and the elastic segments 10 are compressed. When the magnetic flux ceases, elastic segments 10 provide the restorative force necessary to return end member 9 to its original position. The elastic segments 10 limit the spacing between the magnetic segments 2 to maintain many small airgaps without the need for complex mechanical restraints. It is desirable to limit the spacing between the magnetic segments so that large working gaps are not formed since, as mentioned above, the force falls off rapidly with increasing size of the working gap. Finally, the elastic segments 10 provide structural alignment for the core assembly without the need for a guide rod.

If desired, the permeability of the elastic segments could be increased by impregnating them with a magnetic material such as iron particles.

A second actuating device in accordance with the invention is illustrated in FIGS. 2A, 2B and 2C, and includes a plurality of disc-shaped members 20, for convenience referred to as coil discs, each including an inner magnetic ring 26 and an outer magnetic ring 28. A concentrically wound electrical coil 21 is located between the inner and outer rings of the disc which form magnetic core pieces for the coil.

Elastic segments 27 are located between adjacent coil discs and are affixed thereto, for example by an adhesive. The elastic segments may be formed from a material such as sponge rubber. The embodiment of FIG. 2A discloses a means for positively limiting the maximum spacing between adjacent coil discs 20, consisting of hollow spheres 22 imbedded in the elastic segments 27 and connected together in chainlike fashion by links 23. The spheres and links are preferably of a nonmagnetic material such as brass.

At each end of the actuating device of FIG. 2A is an end cap 24 which is affixed to an elastic segment 27 and to one end of a link 23, the other end of which is attached to a sphere 22 embedded in the adjacent elastic segment. End cap 24 is preferably machined from a single piece of iron and includes an annular recess dimensioned to accommodate a circumferentially wound coil 25. The electrical leads from the

coils

21 and 25 can be brought out through suitable holes in the coil discs 20 and caps 24.

If the coils are interconnected so that current flows through each coil in the same direction, for example the clockwise direction as shown in FIG. 3A, the coil discs will be attracted to one another and an overall contracting force is provided as indicated by arrows. On the other hand, if the coils are interconnected in an alternate fashion as shown in FIG. 38 where current passes through one coil in a clockwise direction and through adjacent coils in a counterclockwise direction, the coil discs tend to repel one another and an overall expanding force is provided as indicated by the arrows. With suitable external switching, the same unit can be used to provide either a contracting or expanding force. The electrical coils can be energized simultaneously or sequentially depending on the type of motion desired.

The maximum linear traverse of the actuating unit, that is, the maximum distance that end caps 24 move relative to each other when the coil discs are energized is a function of the sum of the incremental working gaps existing in the fully extended condition. If it is desired to increase the travel distance, this is easily accomplished by adding additional coil discs 20 and elastic segments 27 intermediate and caps 24. Therefore, the

travel distance can be increased without decreasing the created force since the force is a function of the magnetic working gap associated with the individual coils. This working gap in turn is limited by the elastic segments so that a magnetic working contact is maintained between the core pieces of adjacent coil discs.

If the coil discs 20 are energized in accordance with FIG. 3A, then a magnetic flux is created which passes through outer rings 28, end cap 24, inner rings 26 and the second end cap 24. As a result of the magnetic flux, movable end caps 24 are pulled together and the elastic segments 27 are compressed. When the magnetic flux ceases, elastic segments 27 provide the restorative force necessary to return end caps 24 to their original position. The elastic segments, because they are affixed to the coil discs, limit the maximum separation between adjacent coil discs and prevent the incremental working gaps from accumulating to form a single large airgap, which would reduce the force generated by the actuating device. The spheres and links, attached together in chainlike fashion, function to impose a positive limitation on the size of the working gaps even though the elastic segments might be capable of further stretching. This is accomplished without the use of elaborate mechanical restraints.

If the coil discs 20 are energized in accordance with FIG. 38 a magnetic flux is created which passes through outer rings 28, end cap 24, inner rings 26 and the second end cap 24. As a result of the magnetic flux, movable end caps 24 are forced apart and the elastic segments stretched. When the magnetic flux ceases, elastic segments 27 provide the restorative force necessary to return end caps 24 to their original position. The elastic segments, in their relaxed state, provide a minimum spacing between the coil discs. This is significant, for if the coil discs were allowed to come into physical contact before being energized in accordance with FIG. 3B, no repulsive force would be generated between adjacent coil discs upon being so energized.

An alternative core structure including

magnetic segments

30 and 31 is illustrated in FIGS. 4 and 5. This core structure is specifically designed to provide efficient operation when a surrounding coil (such as shown in FIG. 1) is energized by an alternating current.

FIG. 4 discloses flat rectangular magnetic segments 30 wherein a portion of material is removed to form a slot 33 which begins in the middle of one of the longer sides of the rectangular segment 30, runs perpendicular to that side and continues until it intersects the center of a second slot 34 which runs parallel to the length of segment 30 along the centerline of the plate and extends for about one-half of the length of the plate. Holes 35 having a diameter slightly larger than the width of slot 34 are provided at the ends of the slot. The overall result is that a T-shaped portion of material is removed.

Magnetic segments 31 are similar to magnetic segments 30, having a T-shaped opening formed by

slots

36 and 37. Slot 37 and holes 35 at the ends thereof is identical to slot 34, while slot 36 is shorter than slot 33 due to the smaller peripheral dimensions. Magnetic segments 31 are located between adjacent magnetic segments 30 and are approximately one-half of the thickness of magnetic segments 30.

Elastic segments 32, also located between adjacent mag- I netic segments 30, have approximately the same outer dimensions as magnetic segments 30, including thickness. Each elastic segment is provided with a rectangular opening approximately the Same length and width as magnetic segments 31 so that magnetic segments 31 can be accommodated within the opening between adjacent magnetic segments 30.

FIG. 5 shows in cross section the completed core structure. Elastic segments are affixed to magnetic segments 30, for example by an adhesive, while magnetic segments 31 remain free to move in the space defined within opening 38 between adjacent magnetic segments 30.

When the coil surrounding the core is energized by an alternating current a magnetic flux path is established passing up and down through the core structure located in the working gap. As a result of the magnetic flux, the magnetic segments are pulled together and the elastic segments are compressed. Elastic segment 32 may be impregnated with a magnetic material such as iron particles to increase its permeability.

The

slots

33, 34, 36 and 37 in

magnetic segments

30 and 31 serve to reduce eddy-currents which would otherwise substantially reduce efficiency. When the magnetic flux ceases, elastic segments 32 provide a force for restoring the core structure to its original position. Thus, elastic segments 32 assist in keeping the core structure aligned and also in limiting the size of the incremental working gaps so that a large gap is not formed. Additional separation restraint can easily be added by passing a beaded chain through holes 35, attaching the beads to the magnetic segments 30 and having the chain run the length of the core structure.

The structure of FIG. 4 has the added advantage of permitting the working gap to be completely filled with magnetic material when the core structure is compressed, and yet still utilizes the elastic segments to provide structural alignment and a restoring force. Physical contact between adjacent

magnetic segments

30 and 31 results in optimizing the force developed by the actuating device of this configuration.

The invention is more particularly set forth in the following claims.

1. In a magnetic actuating device the combination of:

a magnetic structure including a plurality of relatively movable magnetic segments disposed to provide a working gap between each adjacent pair of magnetic segments;

a plurality of elastic segments positioned between said magnetic segments and affixed thereto for controlling the separation between said magnetic segments, said elastic segments being impregnated with a magnetic material to increase the permeability in said working gaps; and

electromagnetic-coil means operatively associated with said magnetic segments for creating a magnetic flux when energized, which magnetic flux passes through said magnetic segments and said gaps therebetween to cause relative movement of said magnetic segments.

2. In a magnetic actuating device the combination of:

a plurality of relatively movable electromagnetic coils having a common axis and disposed to provide a working gap between each adjacent pair of said coils;

a magnetic core structure magnetically coupled to said coils and including a plurality of magnetic segments;

a plurality of elastic segments, at least one elastic segment positioned between adjacent magnetic segments and affixed thereto for controlling the separation between said magnetic elements; and

said electromagnetic coils when energized being operative to create a magnetic flux which passes through said magnetic segments and said elastic segments in the working gap therebetween to cause relative movement of said magnetic segments.

3. A magnetic actuating device in accordance with claim 2 wherein said magnetic segments comprise a pair of core pieces associated with each of said electrical coils, one of said associated core pieces being disposed inside said coil and the other being disposed outside said coil.

4. A magnetic actuating device in accordance with claim 2 wherein said elastic segments include mechanical means for controlling the separation between said magnetic segments.

5. A magnetic actuating device in accordance with claim 4 wherein said mechanical means includes a chain.

6. In a magnetic actuating device, the combination of:

a magnetic structure including a plurality of relatively movable first magnetic segments having a common axis and disposed to provide a working gap between each adjacent pair of said first magnetic segments;

a plurality of relatively movable second magnetic segments positioned in said working gaps; the thickness of said second segments being substantially less than the maximum extent of said working ga the area of one said second segment being less than the area of one said first segment, a plurality of elastic segments positioned between said first segments and affixed thereto for controlling the separation between said first segments, said elastic segments having outer dimensions approximately the same as those of said first segments,

said elastic segments having a hollow inner section having an area approximately the same as that of said second segments and electromagnetic-coil means operatively associated with said magnetic segments for creating a magnetic flux when energized, which flux passes through said magnetic segments and said working gaps therebetween to cause relative movement of said magnetic segments.

7. An actuating device according to claim 6 wherein:

said electromagnetic-coil means comprises a single cylindrical coil surrounding said common axis, and

said magnetic segments are slotted and arranged perpendicular to said common axis.

8. An actuating device according to claim 6 wherein said elastic segments are impregnated with a magnetic material to increase the permeability in said working gaps.

9. An actuating device according to claim 6 wherein said magnetic segments contain cutout means adapted for attachment to mechanical means for controlling the separation between said magnetic segments.

Claims

1. In a magnetic actuating device the combination of: a magnetic structure including a plurality of relatively movable magnetic segments disposed to provide a working gap between each adjacent pair of magnetic segments; a plurality of elastic segments positioned between said magnetic segments and affixed thereto for controlling the separation between said magnetic segments, said elastic segments being impregnated with a magnetic material to increase the permeability in said working gaps; and electromagnetic-coil means operatively associated with said magnetic segments for creating a magnetic flux when energized, which magnetic flux passes through said magnetic segments and said gaps therebetween to cause relative movement of said magnetic segments.

2. In a magnetic actuating device the combination of: a plurality of relatively movable electromagnetic coils having a common axis and disposed to provide a working gap between each adjacent pair of said coils; a magnetic core structure magnetically coupled to said coils and including a plurality of magnetic segments; a plurality of elastic segments, at least one elastic segment positioned between adjacent magnetic segments and affixed thereto foR controlling the separation between said magnetic elements; and said electromagnetic coils when energized being operative to create a magnetic flux which passes through said magnetic segments and said elastic segments in the working gap therebetween to cause relative movement of said magnetic segments.

6. In a magnetic actuating device, the combination of: a magnetic structure including a plurality of relatively movable first magnetic segments having a common axis and disposed to provide a working gap between each adjacent pair of said first magnetic segments; a plurality of relatively movable second magnetic segments positioned in said working gaps; the thickness of said second segments being substantially less than the maximum extent of said working gap, the area of one said second segment being less than the area of one said first segment, a plurality of elastic segments positioned between said first segments and affixed thereto for controlling the separation between said first segments, said elastic segments having outer dimensions approximately the same as those of said first segments, said elastic segments having a hollow inner section having an area approximately the same as that of said second segments; and electromagnetic-coil means operatively associated with said magnetic segments for creating a magnetic flux when energized, which flux passes through said magnetic segments and said working gaps therebetween to cause relative movement of said magnetic segments.

7. An actuating device according to claim 6 wherein: said electromagnetic-coil means comprises a single cylindrical coil surrounding said common axis, and said magnetic segments are slotted and arranged perpendicular to said common axis.