US2888650A - Two end wire mechanical filter - Google Patents

Description

May 26, 1959 M. L. DOELZ TWO END WIRE MECHANICAL FILTER Filed Dec. 14, 1955 FIE '1- 'lnvsm-olz MELVIN L. DOELZ A'rrg RNEY,

United States Patent TWO'END WIRE MECHANICAL FILTER -Melvin L. Doelz, Glendale, Califi, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of. Iowa This invention relates in general to electromechanical filters, and in particular to an electromechanical filter with a single input means and a plurality of output means.

My Patent No. 2,717,361, which issued September 6, 1955, entitled, Mechanical Filters, discloses a mechanical filter wherein the discs of the filter are joined by a number of wires attached to their peripheries and which have input magnetostrictive means connected to the periphery of a first disc and output magnetostrictive coupling means attached to a last disc.

My Patent No. 2,693,579, issued November 2, 1954, entitled, Longitudinal Support of Mechanical Filter, discloses a mounting means for the above-referenced filters wherein the filter is mounted and held firmly without damping and detuning of the vibrating discs.

In co-pending application filed concurrently with the present application entitled, Mechanical Filter Frequency Discriminator (assigned by' Dean F. Babcock to the assignees of the present invention) is disclosed a multifrequency discriminator for stabilization of a plurality of related frequencies in .but a single discriminator circuit, wherein electromechanical filterphase shifting means are employed. Two such filters are then employed in conjunction with a phase detector to form a multi-frequency discriminator.

A further embodiment in the Babcock application discloses the use of but one filter with a single input means and two output means, to provide the phase shifting action of two filters having a different number of resonant sections.

It is an object of this invention, therefore, to provide a single filter with plural output means, each said output means'driven' from a'difierent resonant section. This invention is featured in the provision for such a two end wire filter which incorporates construction principles and mounting'means such-that'the' vibrating disc assembly is firmly mounted without damping or detuning.

Further features, objects and advantages of this invention will become apparent'from the. following description 'when-read-in-viewofthe'drawings, in which Figure 1 is a side elevation view of the invention with one end shown in cross section from line A.A;

Figure 2 is an oblique side view taken on line AA of Figure 1.

Figure 1 illustrates a side view of the filter and shows a base plate supporting standoffs generally designated as 11 and 12. Standofl 11 is composed of a top section 13 and a bottom section 14. The bottom section 14 is attached to the base plate 11] by screws 15. The top section 13 is secured to the bottom section 14 by screws 16. As best seen in Figure 2, standoff 12 is composed of a bottom section 17 secured to base member 16 by screws 18, a midsection 19 and a top section 21) secured to bottom section 17 by screws 21 which pass through midsection 19.

At the junction of the upper and lower parts of standoff 11 is formed a circular opening lined with a suitable gasketing material through which a cylinder 22 extends.

2,888,650 Patented May 26, 1959 Cylinder 22 is clamped'bystandoif '11. Similarly, at the junction of the upper and lower sections 17 and 20 of standofi 12 with the midsection 19 of standoff 12 are formed circular openings lined with asuitable gasketing material through which extend cylinders 23 and 24,respectively. Cylinders 23 and '24 are clamped by stand-' off 12. i

As seen in Figure 1, all three cylinders are hollow, and each contains a magnetic driving coil of which coils 25 and 26 are shown within cylinders 23 and 24 respectively. which extend through base plate 10. Driving coil 25 in cylinder 23 has output leads 30 and 31 which attach respectively to a pair of contacts 32 which pass through base plate 10. Similarly, driving coil 26 in cylinder'24 has output leads 33 and 34 which attach respectively to a pair of contacts 35 which pass through base plate 10.

A polarizing magnet 36 is supported by standoff 11 immediately above cylinder 22 and a polarizing magnet 37 is supported bymidsection 19 ofstandolf 12 midway The driving coil for cylinder 22 is identical, but not shown in Figure 1. The driving coil in cylinder 22 has output leads 27 and 28 which attachto a pair of contacts 29 between cylinders 23and 24. The cylinders 22, 23, and 24 may be made of a non-magnetic material as, forexample, brass.

Mounted between cylinder 22 and cylinders 23 and 24 is the vibratingfilter assembly comprising a plurality of active discs 45, 38, 49, and 47, and a pair of inactive end discs 39 and 40. End disc 40 is best shown in Figure 2, All discs are axially aligned and connected together by longitudinal coupling wires 41 which are attached te-the periphery of the discs by welding. All discs are spaced equidistant tap art. 7

Disc 39 (Figure l) is formed with an opening and cylinder 22 is received therein. The cylinder is firmly attached to the disc by welding. Cylinder 22 is recessed in disc 39 such that the axis of the cylinder substantially aligns with the periphery of the disc assembly.

Disc 40 is formed with diametrically opposed openings to receive cylinders 23 and 24. The openingsare generally shown as 42 and 43 in Figure 2. Disc 40lis firmly attached to cylinders 23.and 24 by welding. Thus, the end disc, 39. is firmly supported by cylinder 22 and end disc 40 is firmly supported by cylinders 23 and 24. Said cylinders are firmly held to the base'plate by standofis lland, 12. i The spacing between inactive end'discs 39 and 4b and adjacent active discs 45 and 47 is the same as that between active discs45, 38, and 49. The short lengths of coupling wire 41 joining the active filter discs to the inactive end discs act .as springs spaced between the vibrating filter structure and the fixed mounting structure.

A driving rod 44 extends through cylinder. 22, passing through the driving coil mounted therein, and is rigidly attached by welding to the periphery of active disc 45. A driving rod 46 extends through cylinder 24, passing through driving coil 26 and is attached by welding to the periphery of active disc 47. A third driving rod 48 extends through driving coil 25 within cylinder 23 and is attached to the periphery of a second active disc such as for example disc 49. Cylinder 23 might be so mounted within standoff 12 that its axis lies slightly above the periphery of the vibrating disc assembly, so that driving rod 48, which is located axially within cylinder 23, does not touch the periphery of the discs. At the point of desired attachment of driving rod 48 to the disc assembly the rods axis may be displaced by bending such that the tip of the rod touches the periphery of the disc as shown in Figure 1. It is to beunderstood, however, that alternatively the two cylinders 23 and 24 may be symmetrically spaced about the axis of the vibrating disc assembly and driving rod 48 may be formed with a .displaced axis such 3 that it does not contact the periphery of those discs between the point of its attachment and the end of the vibrating section.

It is to be further understood that the choice of connections illustrated in Figure 1 for driving rod 48 is by way of example only, and should not be construed in a limiting sense.

It is seen that this invention provides a mechanical filter with a dual output means, said output means connected individually to different vibrating discs such that the filter assembly between the input means and one output means includes all active resonant discs while a second output means includes a lesser number of active resonant discs.

It is further seen that a supporting means for said mechanical filter is provided wherein the active discs are firmly supported without interference with the mechanical vibrations of the system.

Because of the phase characteristic of such mechanical filters, which is a direct function of the number of active resonant sections contained therein, such a device is particularly useful as a two-channel phase shifting circuit such as might be incorporated in the circuitry disclosed in the co-pending application of Babcock. As described in the reference application, a plurality of received signals, each of which might be a subcarrier frequency modulated on a carrier, are mixed with a variable frequency oscillator. The subcarrier frequencies are so chosen that corresponding L-F. frequencies developed therefrom lie at predetermined points within the pass band of electromechanical filters to which the I.-F. frequencies are applied. Two mechanical filters having discretely different numbers of resonant discs are employed, wherein the input L-F. signals are phase shifted by different degrees in each filter such that the difference in phase between the filter outputs follows a periodic circular variation through in-phase, quadrature phase, and out-of-phase relationships as the input L-F. frequencies traverse the filter pass band. The output from the two phase shifting channels is then applied to a phase detector. The phase detector produces a plurality of zero outputs corresponding to the input I.-F. frequencies within the filter pass band which are chosen to so lie in the filter pass band spectrum that the phase shift experienced in the two filter sections is in quadrature relationship. Should any one of the subcarriers vary in frequency, or should the carrier frequency drift or the variable frequency oscillator drift, an error voltage is developed in the detector which changes the oscillator frequency to correct for any frequency error in the I.-F. frequencies. The difference in the number of discs in the two filters determines the number of such sary parallel phase shifting means of the multi-frequency discriminator circuit disclosed by Babcock. With reference to Figure 1, the I.-F. frequencies might be applied to input terminals 28 and the discretely phase shifted outputs from terminals 32 and terminals 35 might be applied to the phase detector. The present invention thus serves as the functional equivalent of separate mechanical filters having a difierent number of resonant sections. By this invention the separate filters employ a number of common discs. For example, in the particular filter illustrated in Figure 2, input terminals 28 and output terminals 32 function as a first filter with five active discs (45, 38, and 49), while input terminals 28 and output terminals 35 function as a second filter with six active discs (45, 38, 49, and 47) Although this invention has been described with respect to a particular embodiment 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 claim.

I claim:

An electromechanical filter with predetermined pass band comprising a base member, a magnetostrictive driving means mounted on said base member, a plurality of magnetostrictive output means mounted on said base member, a plurality of discs having thickness substantially less than the diameter thereof including a first end disc and a second end disc, a. plurality of longitudinal coupling wires connected to the peripheries of said discs to hold them in assembled paralleled relationship, said discs being space separated such that the lengths of said coupling wires extending between adjacent discs are non-resonant at frequencies within said pass band, the first end disc mechanically connected to said magnetostrictive driving means, the second end disc mechanically connected to a plurality of magnetostrictive output means, the remaining of said discs mechanically resonant at the center frequency of said filter pass band, a driving rod of said magnetostrictive driving means connected to the periphery of the disc adjacent said first end disc, and driving rods of said plurality of magnetostrictive output means connected individually to the periphery of each of selected ones of said plurality of discs between said first and second end discs, whereby said discs between said first and second end discs form a cascaded resonating assembly with said selected outputs having discretely diifcrent phase shift characteristics, each being a function of the number of reasoning discs between said first end disc and each said selected disc.

References Cited the file of this vpatent UNITED STATES PATENTS 1,678,116 Harrison July 24, 1928 2,709,243 Babcock May 24, 1955 2,711,515 Mason June 21, 1955 2,716,887 Smith Sept. 6, 1955 2,754,481 Hirsch July 10, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,888,650

May 26, 1959 Melvin L. Doelz s in the -printed specification It is hereby certified that error appear tion and that the said Letters of the above numbered patent requiring correc Patent should read as corrected below.

Column 4, line 47, for "reasoning" read resonating Signed and sealed 6th day of October 1959,

Attest: KARL H, AXLlz NE ROBERT C. WATSON Commissioner of Patents Attesting Officer

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