US2709243A

US2709243A - Drive system for mechanical filter

Info

Publication number: US2709243A
Application number: US288349A
Authority: US
Inventors: Dean F Babcock
Original assignee: Collins Radio Co
Current assignee: Collins Radio Co
Priority date: 1952-05-16
Filing date: 1952-05-16
Publication date: 1955-05-24
Anticipated expiration: 1972-05-24

Description

May 24, 1955 D- F. BABcocK 2,799,243

DRIVE SYSTEM FOR MECHANICAL FILTER Filed May 16, 1952 2 Sheets-Sheet l IN VEN TOR.

BA /m if. 19/09 0001:

\ATTOYJE'IVIY May 24, 1.955 D. F. BABCOCK DRIVE SYSTEM FOR MECHANICAL FILTER 2 Sheets-Sheet 2 Filed May 16, 1952 5'22 af/TY Arron/wry United States Patent DRIVE SYSTEM FOR MECHANICAL FILTER Dean F. Babcock, Burbank, Califi, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Application May 16, 1952, Serial No. 288,349

4 Claims. (Cl. 33371) This invention relates in general to electromagnetic filters and in particular to an improved magnetostrictive driving means.

The co-pending application of Melvin L. Doelz entitled Mechanical Filters, filed September 24, 1951, Serial Number 248,011, discloses an electromechanical filter wherein a plurality of discs are attached together by longitudinal connecting wires and energy is coupled to and removed from opposite end discs by input and output driving wires. The driving wires are coupled to input and output coils. Applicant has discovered that the coupling between a magnetostrictive wire and a magnetic driving means may be increased appreciably by using a plurality of driving coils strategically spaced relative to the wire.

It is an object of this invention, therefore, to provide an improved, more efficient driving system for a magnetostrictive coupling.

Another object of this invention is to provide an improved magnetostrictive coupling means which utilizes a plurality of coils coupled to a magnetostrictive wire with adjoining coils wound in bucking fashion.

A feature of this invention is found in the provision for mounting a plurality of driving coils relative to a magnetostrictive wire at positions which increase the efiiciency of the coupling between the coils and the wire.

Further features, objects and advantages of this invention will become apparent from the following description and claims when read in view of the drawings, in which;

Figure 1 is a side view of an electromechanical filter showing the cover plate in section so as to illustrate the internal construction;

Figure 2a is a sectional view of the coupling means of the electromechanical filter shown in Figure 1;

Figure 2b is a plot of velocity versus position along the driving wire shown in Figure 2a;

Figure 3 is a sectional view of a modification of the coupling means shown in Figure 1; and,

Figure 4 is an end view of the coupling means of Figure 1.

Figure 1 illustrates an electromechanical filter wherein a base plate has a pair of stand-offs 11 and 12 mounted thereon. A pair of

hollow cylinders

13 and 14 pass through the stand-offs 11 and 12 and are supported thereby. End discs 16 and 17, respectively, are attached to the

cylinders

13 and 14 by welding.

A plurality of active discs 18 are supported between the end discs 16 and 17 by longitudinal supporting wires 19. The active discs adjacent the end discs 16 and 17 have output and

input driving wires

21 and 22, respectively, attached thereto. The

driving wires

21 and 22 extend within the confines of the

cylinders

13 and 14 and pass through magnetic driving and output means mounted in these coils.

A pair of input leads 23 and 24, respectively, extend from the cylinder 13 and are attached to terminals 26 which extend through the base plate 10. Similarly, a pair of output leads 27 and 28 extend from the cylinder 14 and are attached to terminals 29 which extend through the base plate 10. It is to be realized that there are two each of

contacts

26 and 29.

Mounting pins

31 and 32 are attached to the base plate 10 and may be used for attaching the filter to a chassis. A cover member 33 is generally rectangular in shape and is welded or crimped to the base plate 10 so as to form a cover for the filter.

Polarizing magnets 34 and 35, respectively, are mounted to the stand-offs 11 and 12 adjacent the

cylinders

13 and 14. The

cylinders

13 and 14 may be made of brass or any other suitable non-magnetic material.

This invention relates to an improvement in the magnetostrictive coupling means which are contained in the

cylinders

13 and 14. Previously, the cylinder 13 has contained a single driving coil which is mounted concentric about the magnetostrictive wire 21 to excite it with a driving signal.

Figure 2a is a sectional view taken through the cylinder 13 and illustrates the magnetostrictive wire 21 extending therethrough. It is to be noted that the disc 16 has a portion removed adjacent its lower edge so that the wire 21 does not touch it. Within the confines of cylinder 13 are mounted a pair of driving coils 36 and 37, respectively, which are held in place by

suitable rings

38, 39, 41 and 42, respectively.

The start wire 23 is connected to the coil 36 and the finish Wire 43 of the coil 36 is attached to coil 37. The output wire 24 is connected to the opposite end of the coil 37. It is to be noted that coils 36 and 37 are wound in opposite directions so that the flux produced by the coils will buck each other.

Figure 2b illustrates the spacing of the coils 36 and 37 relative to the wire 21. The axis of ordinates shows the velocity of a point on the wire 21 when being driven and the axis of abscissas corresponds to distance along the wire 21. It is to be realized that the curve of Figure 2b is a dynamic curve. It is to be noted that the length of the wire 21 from its free end to the disc 18 is wave lengths and that velocity nodes are located at and 7,, wave lengths from the free end.

It is to be realized, of course, that velocity nodes correspond to points of maximum stress in the wire 21. The coils 36 and 37 are mounted immediately below points A and B, respectively, which correspond to the velocity nodes of the wire 21. Thus, the coil 36 is spaced wave length from the free end of the wire 21 and the coil 37 is placed wave length from the free end of the wire. The wave length corresponds to the resonant frequency of the filter which is determined by the length of the wire and the physical characteristics of the discs 18.

The advantages obtained by using a pair of coils 36 and 37 connected in series opposition over a single driving coil is due primarily to the internal friction of the magnetostrictive wire which causes vibrations set up at one point of the wire to decrease exponentially as the distance increases from the driving point. By driving in opposite fashion at two points, such as shown in Figure 2a, a more efficient or closeness of coupling is obtained.

It is analogous to pushing a child in a swing, wherein a man standing on one side and giving the swing a push each time it returns will expend more energy than the total of two men standing on opposite sides of the swing and giving it a push each time it returns. This is assuming that the swing maintains a fixed maximum amplitude. Thus, the same amount of energy applied to two points along the wire 21 will cause greater vi- V bration of the disc 18 than when the energy is applied at one point.

A modification of this invention is shown in Figure 3 where the coils 36 and 37 have been surrounded by magnetic material 44, as for example, pressed. powdered iron. The magnetic material 44 may be divided into two parts to form half-cylinders, 46 and 47, as best shown in Figure 4, so that they may be assem bled with the coils 35 and 37 and mounted in cylinders 13.

The magnetic material 44 is formed with three

projections

48, 49 and 51 that extend down toward the wire 21 between and. at either side of coils 36 and 37. The coils 36 and 37 are connected in bucking fashion. The action of the structure shown in Figure 3 is in all ways the same as that shown in Figure 2a except that the higher permeability of the media achieved by the magnetic material shown in Figure 3 increases still further the closeness of coupling between the electrical and mechanical elements by increasing the amount of flux in the driving wires for a given current flowing through the coupling coils.

It is seen that this invention provides means for driving a magnetostrictive wire at a plurality of points so as to obtain an increased etficiency.

Although this invention has been described with respect to particular embodiments thereof, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention, as defined by the appended claims.

I claim:

1. An exciter system for an electromechanical resonator comprising, a coupling wire with a free end and an attached end connected to said resonator, a pair of coils mounted concentric about said coupling wire, the first coil mounted one quarter wave length at the resonant frequency of the resonator from, the free end of the coupling wire, the other coil mounted three quarter wave lengths at the resonant frequency of the resonator from the free end of the wire, and said first and second coils connected together in bucking fashion.

2. An electromechanical coupling means for coupling energy between a magnetostrictive coupling wire with a free end and an attached end and a plurality of coils comprising, supporting means, a mechanical resonating system, supporting wires extending from Said supporting means and connected to said resonating system, the attached end of said magnetostrictive coupling wire connected to said mechanical resonating system, a pair of electromagnetic coils mounted concentric about said coupling wire, the first coil mounted one quarter wave length of the resonant frequency of the mechanical system from the free end, and the second coil mounted three quarter wave lengths of the resonant frequency of the mechanical system from the free end.

3. Means for erficiently coupling energy between magnetic means and a magnetostrictive coupling wire which is connected to a mechanical vibrating system comprising, a pair of coils connected together in bucking fashion and mounted concentric about said coupling wire, a generally cylindrical shaped flux conducting means mounted about said coupling wire and said first and second coils, and portions of said flux conducting means extending inwardly closely adjacent said coupling wire intermediate said coils and at either side thereof.

4. Means for eificiently coupling energy to and from a magnetostrictive wire comprising, a pair of coupling coils mounted concentrically about said wire, magnetic material mounted concentric about said Wire and between the coupling coils, portions of said magnetic material extending closely adjacent said coupling wire, and said coils mounted at velocity nodal points along said wire.

References Cited in the file of this patent UNITED STATES PATENTS 2,167,078 Lakatos July 25, 1939 2,490,273 Kean Dec. 6,, 1949 2,526,229 Hazeltine Oct 17, 1950 FOREIGN PATENTS 633,429 Great Britain Dec. 19, 1949