US3732561A

US3732561A - Electromagnetic controlled wheel indicator

Info

Publication number: US3732561A
Application number: US00076494A
Authority: US
Inventors: P Mcginnis
Original assignee: Litton Precision Products Inc
Current assignee: Northrop Grumman Guidance and Electronics Co Inc
Priority date: 1970-09-29
Filing date: 1970-09-29
Publication date: 1973-05-08
Anticipated expiration: 1990-05-08

Abstract

An electromagnetic wheel indicator having an alphanumeric indicating wheel disposed about a rotor that is rotatably mounted within a stator. The stator is provided with inwardly directed radial stator poles wound with individual coils, each encompassing more than one stator pole. A permanent magnet forming part of the rotor is provided with two, opposite pole faces, the first of which is as wide as the width between the more than one stator pole about which each coil is wrapped, while the second is at least one stator pole width narrower than the first.

Description

United States Patent 191 McGinnis 51 May8, 1973 [541 ELECTROMAGNETIC CONTROLLED WHEEL INDICATOR [75] Inventor: Peter J. McGinnis, Chester Township, Delaware County, Pa.

[73] Assignee: Litton Precision Products, Inc.,

Beverly Hills, Calif.

[22] Filed: Sept. 29, 1970 [21] Appl. No.1 76,494

[52] US. Cl. ..340/378 R, 340/373 R [51] Int. Cl. ..G08b 5/24 [58] Field of Search ..340/378 MW, 378

[56] References Cited UNITED STATES PATENTS 3,166,744 4/1965 Leonchick ..340/378 R 3,350,709 10/1967 Pursiano ....340/378 R 3,392,382 7/1968 Pursian0.. ....340/378 R 3,411,155 11/1968 Watkins ..340/378 R 3,113,301 12/1963 Templin ..340/378 MW 3,353,174 11/1967 Lang ..340/378 MW 3,530,461 9/1970 Steinberg ..340/378 MW Primary Examiner-Harold I. Pitts Attorney-M. Michael Carpenter, Alan C. Rose and Alfred B. Levine [57] ABSTRACT An electromagnetic wheel indicator having an alphanumeric indicating wheel disposed about a rotor that is rotatably mounted within a stator. The stator is provided with inwardly. directed radial stator poles wound with individual coils, each encompassing more than one stator pole. A permanent magnet forming part of the rotor is provided with two, opposite pole faces, the first of which is as wide as the width between the more than one stator pole about which each coil is wrapped, while the second is at least one stator pole width narrower than the first.

9 Claims, 5 Drawing Figures PATENT 5' WY 975 SHEET 1 OF 2 INVENTOR PETER J. M GINNIS ATTORNEY PATENHB W 75 SHEET 2 BF 2 Fl G.5

INVENTOR PETER J. M GINNIS ATTORNEY ELECTROMAGNETIC CONTROLLED WHEEL INDICATOR The present invention relates to electromagnetic wheel indicators; and, more particularly, to a magnetic indicating device having a stator which forms discrete magnetic field patterns to position a rotor supported drum upon which alphanumeric symbols are inscribed in a plurality of indicating positions.

Prior art electromagnetic wheel indicators, or magwheels as they are commonly known, translate electrical input signals into visual output information in the form of alphanumeric characters, for example. The electromagnetic indicator utilizes a stator having a plurality of inwardly directed radial poles. A discrete electrical input signal energizes a winding about one radial pole to create an electromagnetic field which position orients a rotatively mounted rotor therein. A drum attached to the rotor and bearing alphanumeric characters thereon is displaced before a viewing area to display the character which represents the input signal received.

When an even number of alphanumeric characters are to be indicated, such as when ten symbols are desired, it is necessary to provide ten discrete magnetic fields. As each coil is energized, the magnetic rotor responds to the magnetic field thus established and orients the drum to display a particular character thereon. A problem is created when the next succeeding character to be displayed is located 180 degrees from the character last displayed. In this situation, the new magnetic field established by the stator is parallel to the last established field and oriented in an opposite direction. Thus, there is no torque created within the rotor to cause a rotation displacement thereof; and the rotor will hang up or at least respond slowly. One prior art solution of this problem is to provide a rotor and stator pole configuration which aligns the rotor in one direction, when a coil is electromagnetically energized, and aligns the rotor in another slightly offset direction when the electromagnetic energy is removed from the coil. Such an arrangement is shown in U.S. Pat. No. 3,1 18,138 by Milas, et al. A second approach which reports to solve this same problem is shown in U.S. Pat. No. 3,260,871 by Lang. The second patent suggests placing the center of rotation of the permanent magnet forming the rotor at-a distance closer to one pole than the other. This second reference also teaches the idea of offsetting the magnetic poles from a line through the center of the rotational axis.

The Milas reference creates a small drum offset after the electromagnetic energy is removed from the coil. This causes the indicating drum to blink" after the indication is made and the electromagnetic energy is removed therefrom. The Lang reference does not blink, but the offset magnetic rotor creates a poor magnetic field pattern in the absence of the electromagnetic energy generated in the coils. This creates a poor holding force between the permanent magnet rotor and the stator with the result that the alphanumeric character indicated by the indicating drum may become erroneous as the magnetic wheel undergoes shock and vibration.

The prior art electromagnetic wheel indicators have also displayed poor damping characteristics. That is, the input signal which generates the field within the stator and causes the rotor to become aligned therewith often allows the rotor to rotate beyond the desired position and back thereto. This overshoot and the hunting that results aggravates the blinking problem mentioned above.

Today, the electromagnetic wheel indicator is being used in newer and more sophisticated equipment. Due to this, it has become desirable to provide a feedback signal which will indicate whether or not the wheel has responded correctly to the input information received. Since the indicators are designed to be relatively small and inexpensive, the prior art feedback arrangements proposed thus far have proven to be inadequate.

Accordingly, it is an object of the present invention to provide an improved electromagnetic indicating device.

Another object of the invention presented here is to provide an electromagnetic indicating device which is capable of displaying an even number of symbols without hanging up when the magnetic field established by the stator is reversed degrees.

A further object of this invention is to provide an electromagnetic wheel indicator which is capable of immediately displaying the desired alphanumeric character without overshooting the display position required or causing the character to assume more than one desired position.

A still further object of the present invention provides an electromagnetic wheel indicator with a means of determining whether the alphanumeric character indicated is the character originally required by the electrical input signal.

Yet another object of this invention is to provide an improved magnetic wheel which indicates an alphanumeric character without blinking or hunting, which will rotate 180 without hang-ups, and which provides a feedback signal to indicate the true position thereof.

In accomplishing these and other objects, there has been provided an electromagnetic wheel indicator having a stator capable of generating an electromagnetic field in a plurality of discrete positions by energizing certain coils wound about inwardly directed radial poles associated with the stator. An alphanumeric character bearing drum is rotatably mounted upon a rotor disposed within the stator. Energization of one of the coils displaces the rotor to the desired indicating position. Each coil is wound about more than one stator poles, while the permanent magnet formed within the rotor has a first pole face equal in width to the number of stator poles included within each coil winding. The opposite rotor pole face has a width that is less than the face width of the first mentioned pole.

Other objects and many of the attendant advantages of the present invention will become readily apparent to those skilled in the art, as a better understanding thereof is obtained by reference to the following description, when considered in connection with accompanying drawings, wherein:

FIG. 1 is a side elevational view showing the electromagnetic wheel indicator of the present invention with the cover removed therefrom;

FOG. 2 is a cross-sectional view taken along line 2- 2 of FIG. 1;

FIG. 3 is a perspective view showing the rotor and indicating drum of the present invention;

FIG. 4 is a schematic view showing the stator and rotor of an electromagnetic indicator embodying the present invention; and

FIG. 5 is a second schematic view, similar to FIG. 4, showing a second embodiment of the present invention.

Referring now to the drawings, and more particularly to FIGS. 1 and 2, the electromagnetic wheel indicator is shown generally at having a base plate 12 with a housing frame 14 mounted thereto, as by brazing. The outer dimensions of the housing 14 conform to the dimensions of the base plate 12 with the inner portions thereof relieved to form a cavity 16. The housing is pro vided with suitable threaded mounting holes 17 which receive screws, not shown, for mounting a cover, also not shown. An aperture 18 passing through the base plate 12 and centered within the cavity 16 receives a mounting shaft 20 having a collar 22 abutting the inner edge face of the mounting plate 12.The mounting shaft 20 is attached to the base plate 12 by spinning a lower, enlarged portion 24 of the shaft 20 over against the plate 12. A first toroidially shaped jewel bearing 26 is spaced from the collar 22 on shaft 20 by a shim 28. The bearing 26 is received within the axial bore 29 of a cylindrical housing 30, while a second toroidially shaped bearing 34 is mounted within the bore 29 to rotatively support the cylindrical housing 30 upon the shaft 20. The cylindrical housing 30 is retained upon the shaft 20 and spaced from the second jewel bearing 34 by a second shim 40.

The left-hand end, FIG. 2, of the cylindrical housing 30 is provided with an extended portion 42 which forms a shoulder against which a flux concentrating ring 44 is positioned and retained, as by a press fit. The flux concentrating ring is provided with oppositely extending

tab portions

46 and 48 whose function will be described hereinbelow. A rotor 50 is next pressed upon the cylindrical housing 30. The rotor may be constructed from one of several well known magnetic materials, such as alnico; and is provided with north and

south poles

52 and 54 respectively. Completion of the flux concentrating ring 44 is established by north and

south extending portions

56 and 58 forming north and

south air gaps

60 and 62, respectively. An indicating drum 64 is pressed upon the cylindrical housing 30 to complete the rotating assembly of the electromagnetic wheel indicator. The drum is formed by first and

second spacers

66 and 68 each on opposite sides of a disc 70. The disc is provided with a flange 72 perpendicular thereto having alphanumeric characters thereon, see FIG. 3. The disc 70 and flange 72 extend beyond the base plate 12 and out of the cavity 16 formed within the housing 14 for providing a display area where alphanumeric characters spaced about the outer surface thereof may be viewed.

An annular releaf 74 within base plate 12 receives an annular mounting ring 76 which may be secured by a press fit. The mounting ring is relieved to receive a toroidially stator 78 having inwardly directed radial stator poles 80. The stator poles are equally spaced about the 360 arc formed by the toroidially shaped stator, and equal the number of alphanumeric characters to be displayed upon the indicating drum 64. While the present embodiment has illustrated the alphanumeric characters as the numbers 0 through 9, it will be obvious that there could be other alphanumeric characters inscribed upon the drum 64 and that the number of characters inscribed can also be varied.

Referring now to FIG. 4, a preferred embodiment of the present invention will be described wherein the stator 78 is provided with a plurality of inwardly directed stator poles 80. In the present embodiment l0 poles numbered 80-A through 80.] are shown. A coil 82 is wrapped about three adjacent stator poles, 80-J, 80-A, and 80-B. The preferred embodiment illustrated here shows only one coil winding. However, it is to be understood that nine other coil windings are positioned upon the stator poles. Each coil winding 82 is connected to a source of electromagnetic energy through suitable terminals 84. In FIG. 4, the north pole 52 of rotor 50 is pictured with its pole face width equal to the width of the are formed by the three pole elements encompassed by coil winding 82, i.e., poles 80-J, 80-A and 80-B. The width of the south pole face is narrower than the north pole face by the width of one stator pole element and the air gap between adjacent stator poles. That is, the north pole 52 is arranged with a pole face width equal to the arc between the outer, opposite edges of the stator poles 80-J and 80-B; while the south pole is arranged with a face width as wide as the arc between the outer, opposite edges of the stator poles 80-E and 80-F.

In operation, the coil winding 82 is energized to align the rotor 50 in the position shown, i.e., with the north pole pointing upwardly. As the coil winding 82 is ener gized, an electromagnetic field is generated through the poles -J -A, and B such that the-inner ends of these stator poles become south pole electromagnets. The generated field displaces the rotor 50 about its rotational axis 30 for aligning the north pole 52 thereof with the three electromagnets formed in poles 80-J, 80-A and 80B. Should the next succeeding signal energize the coil, not shown, which is wound about the stator poles 80-E, 80-F and 230-6, it will be seen that a symmetrically arranged rotor would have difficulty in responding to this new signal from the previous signal. However, through the unique arrangement of the present invention, the nonsymmetrical south pole 54, which is narrower than the north pole 52, will create an unbalanced response to the electromagnetic field generated. Thus, when the coil about the poles 80-E, 80-F and 80-G is energized, the resulting flux pattern creates an unequal force upon the rotor 50 for rapidly displacing it 180 degrees. The north pole 52 thus aligns itself with the center thereof oriented with stator pole 80-F. Should the next succeeding signal be applied to the windings 82, a quick rotational response will again be generated for rotating the rotor 50 180 without hang-up.

Referring to FIG. 5, a second embodiment,'similar to the one illustrated in FIG. 4, is shown. Here the north pole 52 has a pole face width equal to the width between the outer, opposite edges of the stator pole elements 80-A and 80-B. The south pole 54 is arranged opposite one portion of the north pole 52 with a pole face width equalling the width of the stator pole 80-F. As in the embodiment discussed in Flg. 4, the rotor in FIg. 5 will not hang-up when the electromagnetic field is rotated 180 degrees during successive indicating signals.

Prior art electromagnetic wheel indicators utilize a rotor and permanent magnet with narrow pole faces. These devices are formed with the coil wound about individual stator elements for directing and controlling the positioning of the rotor. Once the electromagnetic energy is removed from the coil, a typical indicating drum is retained in its desired position by the magnetic field generated by the permanent magnet within the rotor. It will be understood that the force of this field is a function of the strength of the permanent magnet and, in turn, the pole face width thereof. Thus, the present invention is capable of generating a greater holding force than prior art devices due to the pole size and number of stator poles involved. That is, the embodiment illustrated in Flg. 5 generates a holding force 50 percent greater than the prior devices that used a symmetrically arranged permanent magnet within the rotor having narrow pole faces. The device illustrated in Fig. 4 generates a holding force 150 percent greater than the symmetrical prior art magnets. This arrangement allows the rotor to lock into the desired position and resist motion due to external shock and vibration.

As successive input signals are applied to the coils 82 wound on the poles 80 of the stator 78 the rotor 50 responds by aligning itself with each successive electromagnetic field generated thereby. The rotor 50 has a tendency to overshoot the position desired due to the inertial of the rotor 50 and indicating drum 64. Prior art devices which utilize a narrow rotor magnet having pole face widths equal or less than the width of a single stator pole generate very little damping resistance to this motion. The present invention provides increased resistance to the motion induced by the electromagnetic field through the increased number of stator poles which interact with the wider permanent magnet of the rotor 50. Once a rotor is aligned with the generated electromagnetic field, the increased damping force of the present invention tends to lock the rotor into this position without overshooting.

It will be noted that the present invention does not rely on offsetting schemes to eliminate the problem of 180 degree rotation, as in the prior art. Here, the opposite north and south poles are always aligned with the stator poles. This eliminates rotor blinking when the input signal is removed from the coil windings 82.

Referring once again to FIG. 2, it will be seen that the base plate 12 has been relieved at 86 to form a wire rough therein. This trough may be used to connect the wires which form a typical coil winding 82 to the terminals 84. Alternatively, the terminals may be connected via copper-plated strips upon the base plate 12 to terminals inside the housing 14 thus eliminating the wire trough 86.

As mentioned above, it is desirable to provide feedback information to indicate when the rotor 50 has been properly positioned. In FIG. 2, a magnetic field sensor mounting ring 88 is shown disposed about the cylindrical housing 30 and spaced therefrom by suitable stand-offs 90. The ring 88 provides a mounting support for magnetic sensing elements 92-A through 92-E. These sensing elements are arranged upon the mounting ring 88 in five equally spaced positions located within an annular are formed by the rotational movement of

air gaps

60 and 62. The magnet forming the rotor 50 generates a flux which is concentrated by 5 as they are sensitive to the presence or absence of a magnetic field and to the field direction thereof. This device is more fully disclosed in U. S. Pat. No. 3,389,230 by Hudson. Due to the dual sensitivity, it is necessary to utilize only five magnistor type magnetic sensors. If a Hall effect device were utilized, five sensors could be used; but it would be necessary to utilize operational amplifiers with each sensor.

In FIG. 1, when the rotor 50 is positioned as shown, the magnetic sensor 92-A is positioned within the air gap 60, for generating an output signal which is utilized as a feedback signal to indicate that the rotor is properly positioned. Should the rotor next turn the flux sensor 92-A will then be positioned within the air gap 62. The resulting reversal of the flux within the air gap thus causes the output signal generated by the magnistor 92-A to assume a polarity opposite the previously generated signal. Through this arrangement, therefore, it will be seen that five magnistors 92 and 25 capable of detecting the 10 positions of the rotor 50 within the electromagnetic wheel indicator 10.

There has been described an electromagnetic wheel indicator which is capable of indicating a plurality of alphanumeric characters without blinking." The indicator is capable of successive 180 rotational motion, has improved locking power and improved damping. Further, the indicator is capable of providing feedback information to check that the proper alphanumeric character is displayed. The preferred embodiments 35 have been described in some detail. The description of the north pole being larger than the south pole, of the ten indicating or rotor positions, of the coil winding being wrapped about two or three stator poles, or of the alphanumeric characters 0 9 inscribed upon the indicating drum is not intended to limit this unique invention. It will be obvious to those skilled in the art that various modifications of the specific embodiment described may be practiced without departing from the present invention.

The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:

1. An electromagnetic indicating device for indicating a plurality of discrete positions, comprising:

a stator having an annular ferromagnetic core including an even plurality of inwardly directed radial stator poles;

an even plurality of coil windings each wound about more than one stator pole and arranged to be separately energized by electromagnetic energy for establishing a plurality of discrete electromagnetic fields;

a rotor rotatively mounted upon a rotational axis within said annular core including a bipole permanent magnet having a first pole face width equal to the width of said plurality of stator poles about which each of said coil windings is wound and a second pole face width at least one stator pole width less than said first pole face width;

said first pole width arranged symmetrically about a rotor center line passing through said rotational axis of said rotor and said second pole face width offset from said center line; and

said plurality of stator poles and said first and second pole faces spaced in alignment with each other before and after said coil windings are energized by electromagnetic energy. 2. An electromagnetic indicating device as claimed in claim 1, wherein:

said plurality of coil windings are each wound about three stator poles; said first pole face width is three stator poles wide,

and said second pole face width is two stator poles wide offset from said rotor center line by the width of one stator pole. 3. An electromagnetic indicating device as claimed in claim 1, wherein: i

said plurality of coil windings are each wound about two stator poles: I said first pole face width is two stator poles wide, and said second pole face width is one stator pole wide offset from said rotor center line by the width of one stator polev 4. An electromagnetic indicating device as claimed in claim 1, additionally comprising:

an indicating wheel mounted upon said rotor; an said indicating wheel having alphanumeric characters thereon for providing a visual indication of the position of said rotor. 5. -,An electromagnetic indicating device as claimed in claim 1, additionally comprising:

flux concentrating means mounted upon said rotor;

and flux sensitive means mounted in the vicinity of said flux concentrating means for generating an output signal representing the position of said rotor. 6. An electromagnetic indicating device as claimed in claim wherein:

said flux concentrating means are mounted on the side of said rotor and have at least one air gap therein which forms a symmetrical annular path during the rotation of said rotor; and

said flux sensing means are mounted at the side of said rotor in a plane parallel to the rotational motion thereof and in juxtaposition to the annular path formed by said air gap.

7. An electromagnetic indicating device as claimed in claim 6, wherein:

said flux sensing means are magnistors mounted within the air gap formed by said flux concentrating means upon said rotor.

8. An electromagnetic indicating device as claimed in claim 1, wherein:

said stator poles include ten inwardly directed poles; said coil windings include ten windings each encompassing three of said stator poles; said first pole face is as wide as the are formed between three of said stator poles; and said second pole face is as wide as the are formed between two of said stator poles and is offset from said. rotor center line by the width of one stator pole. 9. An electromagnetic wheel indicator for indicating a plurality of alphanumeric characters positioned upon said wheel, comprising:

stator means having an annular core including a plurality of inwardly directed'stator poles; rotor means including said wheel rotatively mounted within said annular core; winding means wrapped about said stator poles for generating an electromagnetic field; permanent magnet means mounted upon said rotor means having two poles oppositely disposed thereon responsive to said electromagnetic field; said first pole arranged with flux concentrating .means located on the side thereof; said secondpole arranged with flux concentrating means located on the side thereof; and flux sensitive means mounted in the vicinity of said flux concentrating means for generating an output signal representing the position of said rotor.

Claims

1. An electromagnetic indicating device for indicating a plurality of discrete positions, comprising: a stator having an annular ferromagnetic core including an even plurality of inwardly directed radial stator poles; an even plurality of coil windings each wound about more than one stator pole and arranged to be separately energized by electromagnetic energy for establishing a plurality of discrete electromagnetic fields; a rotor rotatively mounted upon a rotational axis within said annular core including a bipole permanent magnet having a first pole face width equal to the width of said plurality of stator poles about which each of said coil windings is wound and a second pole face width at least one stator pole width less than said first pole face width; said first pole width arranged symmetrically about a rotor center line passing through said rotational axis of said rotor and said second pole face width offset from said center line; and said plurality of stator poles and said first and second pole faces spaced in alignment with each other before and after said coil windings are energized by electromagnetic energy.

2. An electromagnetic indicating device as claimed in claim 1, wherein: said plurality of coil windings are each wound about three stator poles; said first pole face width is three stator poles wide, and said second pole face width is two stator poles wide offset from said rotor center line by the width of one stator pole.

3. An electromagnetic indicating device as claimed in claim 1, wherein: said plurality of coil windings are each wound about two stator poles: said first pole face width is two stator poles wide, and said second pole face width is one stator pole wide offset from said rotor center line by the width of one stator pole.

4. An electromagnetic indicating device as claimed in claim 1, additionally comprising: an indicating wheel mounted upon said rotor; and said indicating wheel having alphanumeric characters thereon for providing a visual indication of the position of said rotor.

5. An electromagnetic indicating device as claimed in claim 1, additionally comprising: flux concentrating means mounted upon said rotor; and flux sensitive means mounted in the vicinity of said flux concentrating means for generating an output signal representing the position of said rotor.

6. An electromagnetic indicating device as claimed in claim 5 wherein: said flux concentrating means are mounted on the side of said rotor and have at least one air gap therein which forms a symmetrical annular path during the rotation of said rotor; and said flux sensing means are mounted at the side of said rotor in a plane parallel to the rotational motion thereof and in juxtaposition to the annular path formed by said air gap.

7. An electromagnetic indicating device as claimed in claim 6, wherein: said flux sensing means are magnistors mounted within the air gap formed by said flux concentrating means upon said rotor.

8. An electromagnetic indicating device as claimed in claim 1, wherein: said stator poles include ten inwardly directed poles; said coil windings include ten windings each encompassing three of said statoR poles; said first pole face is as wide as the arc formed between three of said stator poles; and said second pole face is as wide as the arc formed between two of said stator poles and is offset from said rotor center line by the width of one stator pole.

9. An electromagnetic wheel indicator for indicating a plurality of alphanumeric characters positioned upon said wheel, comprising: stator means having an annular core including a plurality of inwardly directed stator poles; rotor means including said wheel rotatively mounted within said annular core; winding means wrapped about said stator poles for generating an electromagnetic field; permanent magnet means mounted upon said rotor means having two poles oppositely disposed thereon responsive to said electromagnetic field; said first pole arranged with flux concentrating means located on the side thereof; said second pole arranged with flux concentrating means located on the side thereof; and flux sensitive means mounted in the vicinity of said flux concentrating means for generating an output signal representing the position of said rotor.