ROTARY ELECTROMAGNETIC ACTUATOR OF FLAT FORM
United States Patent 3766548
A rotary electromagnetic actuator for actuating visual signal or other device comprises an electromagnet having a winding and a core, elongated pole pieces projecting laterally of the electromagnet parallel to one another and perpendicular to the core, parallel end plates connecting the free ends of the pole pieces, a shaft rotatably supported by the end plates midway between the pole pieces and a rotor on the shaft. Stop pins on one of the end plates limit rotation of the rotor to define an actuated position in which the rotor together with the pole pieces and the core forms a substantially closed flux path for the electromagnet and a rest position in which the flux path is interrupted. A hair spring biases the rotor to rest position. An arm fixed on the shaft carries an indicating flag at one end and a counterweight at the other.
US Patent References:
Annunciator system
Davis - November 1956 - 2772408
Electrical indicating means
Edwards - August 1965 - 3199100
Magnetic device having a permanently magnetized rotor
Bieger - March 1967 - 3311859
MAGNETICALLY OPERATED TWO POSITION ELECTRICAL INDICATOR
Knecht - April 1971 - 3573811
ELECTROMAGNETIC INDICATOR
Pihl - April 1971 - 3573812
Annunciator system
Davis - November 1956 - 2772408
Electrical indicating means
Edwards - August 1965 - 3199100
Magnetic device having a permanently magnetized rotor
Bieger - March 1967 - 3311859
MAGNETICALLY OPERATED TWO POSITION ELECTRICAL INDICATOR
Knecht - April 1971 - 3573811
ELECTROMAGNETIC INDICATOR
Pihl - April 1971 - 3573812
Application Number:
05/223925
Publication Date:
10/16/1973
Filing Date:
02/07/1972
View Patent Images:
Export Citation:
Assignee:
Sensonics, Inc. (Hicksville, NY)
Primary Class:
Other Classes:
340/815.870
International Classes:
G08B5/24; G08B5/22; G08B5/14
Field of Search:
340/373R
Primary Examiner:
Pitts, Harold I.
Claims:
What I claim and desire to secure by letters patent is
1. A rotary electromagnetic actuator comprising an electromagnet having a core of ferromagnetic material and a single winding around said core, two elongated pole pieces of ferromagnetic material fixed to opposite ends of said core and extending laterally of said electromagnet parallel to one another and perpendicular to the longitudinal axis of said core, parallel plates of non-magnetic material extending between free end portions of said pole pieces and secured respectively on opposite sides of said pole pieces, a shaft rotatably supported by said plates midway between said pole pieces and with its axis of rotation perpendicular to a plane defined by the longitudinal axis of said core and longitudinal center lines of said pole pieces, said pole pieces having forward end portions with arcuate inner surfaces concentric with said shaft, a rotor fixed on said shaft for rotation therewith, said rotor comprising a bar of ferromagnetic material extending transversely of said shaft and being of a length to extend substantially to but clear said arcuate surfaces of the end portions of said pole pieces, said rotor being rotatable with said shaft between said pole pieces between an actuated position in which said rotor together with said pole pieces and core forms a substantially closed magnetic circuit for said electromagnet and a rest position in which said circuit is open, means on one said plate for engaging said rotor to limit rotation of said rotor to define said rest and actuated positions, and means applying a torque to said shaft to rotate said rotor to rest position, said rotor being rotatable to actuated position by magnetic forces applied to it when said electromagnet is energized.
2. A rotary electromagnetic actuator according to claim 1, in which visual indicating means is carried by and rotates with said shaft.
3. A rotary electromagnetic actuator according to claim 2, in which said indicating means comprises an arm projecting radially from said shaft and a flag carried by said arm.
4. A rotary electromagnetic actuator according to claim 3, in which said arm extends in opposite directions from said shaft with said flag at one end and a counterweight at the other end.
5. A rotary electromagnetic actuator according to claim 1, in which said means for limiting rotation of said rotor comprises at least one stop pin projecting inwardly from one of said plates and engageable by said rotor.
6. A rotary electromagnetic actuator according to claim 1, in which opposite end portions of said core project beyond said winding of said electromagnet and said pole pieces have holes tightly receiving said projecting end portions.
7. A rotary electromagnetic actuator according to claim 2, comprising removable a cover enclosing the assembly of said electromagnet, pole pieces, plates, shaft and rotor, said cover having a window to accommodate said visual indicating means.
8. A rotary electromagnetic actuator according to claim 1, in which said pole pieces have rear end portions embracing opposite ends of said winding and of approximately the same cross-sectional width as said winding and forward portions which are narrower than said rear end portions but thicker so as to have approximately the same cross-sectional areas as said rear end portions.
9. A rotary electromagnetic actuator according to claim 8, in which a first side edge of each of said pole pieces is straight and a second side edge has a forward portion offset inwardly, and in which said plate secured to forward portions of said second side edges of said pole pieces has terminal arcuate flange portions engaging said second side edges to space an intermediate portion of said plate outwardly of a plane defined by said second side edges of said pole pieces.
10. A rotary electromagnetic actuator according to claim 9, in which said rotor is disposed adjacent said plate secured to said first side edges of said pole pieces and said means for limiting rotation of said rotor comprises at least one stop pin projecting inwardly from said adjacent plate and engageable by said rotor, and in which said torque applying means comprises a spiral spring disposed between said rotor and said plate secured to said second side edges of the pole pieces, said spring having one end secured to said shaft and another end anchored to one of said pole pieces.
11. A rotary electromagnetic actuator according to claim 10, in which actuating means secured to said shaft between said spring and said plate secured to said second side edges of the pole pieces comprises a counter-balanced arm and a flag carried on one end of said arm.
1. A rotary electromagnetic actuator comprising an electromagnet having a core of ferromagnetic material and a single winding around said core, two elongated pole pieces of ferromagnetic material fixed to opposite ends of said core and extending laterally of said electromagnet parallel to one another and perpendicular to the longitudinal axis of said core, parallel plates of non-magnetic material extending between free end portions of said pole pieces and secured respectively on opposite sides of said pole pieces, a shaft rotatably supported by said plates midway between said pole pieces and with its axis of rotation perpendicular to a plane defined by the longitudinal axis of said core and longitudinal center lines of said pole pieces, said pole pieces having forward end portions with arcuate inner surfaces concentric with said shaft, a rotor fixed on said shaft for rotation therewith, said rotor comprising a bar of ferromagnetic material extending transversely of said shaft and being of a length to extend substantially to but clear said arcuate surfaces of the end portions of said pole pieces, said rotor being rotatable with said shaft between said pole pieces between an actuated position in which said rotor together with said pole pieces and core forms a substantially closed magnetic circuit for said electromagnet and a rest position in which said circuit is open, means on one said plate for engaging said rotor to limit rotation of said rotor to define said rest and actuated positions, and means applying a torque to said shaft to rotate said rotor to rest position, said rotor being rotatable to actuated position by magnetic forces applied to it when said electromagnet is energized.
2. A rotary electromagnetic actuator according to claim 1, in which visual indicating means is carried by and rotates with said shaft.
3. A rotary electromagnetic actuator according to claim 2, in which said indicating means comprises an arm projecting radially from said shaft and a flag carried by said arm.
4. A rotary electromagnetic actuator according to claim 3, in which said arm extends in opposite directions from said shaft with said flag at one end and a counterweight at the other end.
5. A rotary electromagnetic actuator according to claim 1, in which said means for limiting rotation of said rotor comprises at least one stop pin projecting inwardly from one of said plates and engageable by said rotor.
6. A rotary electromagnetic actuator according to claim 1, in which opposite end portions of said core project beyond said winding of said electromagnet and said pole pieces have holes tightly receiving said projecting end portions.
7. A rotary electromagnetic actuator according to claim 2, comprising removable a cover enclosing the assembly of said electromagnet, pole pieces, plates, shaft and rotor, said cover having a window to accommodate said visual indicating means.
8. A rotary electromagnetic actuator according to claim 1, in which said pole pieces have rear end portions embracing opposite ends of said winding and of approximately the same cross-sectional width as said winding and forward portions which are narrower than said rear end portions but thicker so as to have approximately the same cross-sectional areas as said rear end portions.
9. A rotary electromagnetic actuator according to claim 8, in which a first side edge of each of said pole pieces is straight and a second side edge has a forward portion offset inwardly, and in which said plate secured to forward portions of said second side edges of said pole pieces has terminal arcuate flange portions engaging said second side edges to space an intermediate portion of said plate outwardly of a plane defined by said second side edges of said pole pieces.
10. A rotary electromagnetic actuator according to claim 9, in which said rotor is disposed adjacent said plate secured to said first side edges of said pole pieces and said means for limiting rotation of said rotor comprises at least one stop pin projecting inwardly from said adjacent plate and engageable by said rotor, and in which said torque applying means comprises a spiral spring disposed between said rotor and said plate secured to said second side edges of the pole pieces, said spring having one end secured to said shaft and another end anchored to one of said pole pieces.
11. A rotary electromagnetic actuator according to claim 10, in which actuating means secured to said shaft between said spring and said plate secured to said second side edges of the pole pieces comprises a counter-balanced arm and a flag carried on one end of said arm.
Description:
The present invention relates to a rotary electromagnetic actuator of the kind used for operating a signal or performing other useful work. For example, an actuator in accordance with the invention may operate a visual indicator on an instrument or control panel or may provide torque for rotating any desired device.
It is an object of the invention to provide a rotary electromagnetic actuator in which the parts are so arranged and asembled that the actuator can be made very small and compact and yet have sufficient power to actuate the indicator or other device for which it is employed. In particular the actuator in accordance with the invention has a relatively thin, flat configuration so that a plurality of actuators can be placed side by side or the actuator can be placed close to or between other instruments or equipment. By way of example an actuator in accordance with the present invention may have a length of the order of 2 cm, a width of the order of 1.36 cm and a thickness of the order of 0.6 cm.
A further object of the invention is to provide a small compact rotary electromagnetic actuator that can be economically manufactured and is efficient, reliable and durable in its operation.
The nature, objects and advantages of the invention will be more fully understood from the following description of a preferred embodiment shown by way of example in the drawings in which
FIG. 1 is an enlarged side view of an electromagnetic actuator in accordance with the invention with a portion of the cover removed and parts broken away to show internal construction,
FIG. 2 is a cross section taken approximately on a line 2--2 of FIG. 1,
FIG. 3 is a longitudinal section on a smaller scale taken approximately on a line 3--3 in FIG. 1, and
FIG. 4 is a partial side view illustrating the location of means for limiting the angle of rotation of the rotary actuator.
The rotary electromagnetic actuator shown by way of example in the drawings comprises an electromagnet 5 having a winding 6 around an insulated cylindrical core 7. The core is formed of soft iron or other suitable magnetic material and is longer than the winding so that end portions of the core project beyond the winding. The winding is wound of insulated self-bonding wire contiguous convolutions of which adhere to one another so that the winding is self-supporting and no coil form is required. After the coil is wound, it is preferably wrapped with tape or coated with insulating material to provide mechanical and electrical protection for the coil. Suitable leads are provided for connecting the coil to a circuit for supplying current to it.
A pair of pole pieces 10 extend laterally from opposite ends of the core 7. The two pole pieces are parallel to one another and are perpendicular to the longitudinal axis of the core 7. Each of the pole pieces 10 has an approximately square inner end portion 10a provided with a central hole which receives the projecting end portion of the core. The core fits into the holes provided in the pole pieces with a press fit or is otherwise assembled with the pole pieces so that the core, winding and pole pieces constitute a unitary rigid structure. Intermediate portions 10b of the pole pieces are straight and are of rectangular cross section with a width which is less than that of the end portions 10a but a thickness that is greater so that the cross sectional area is approximately the same. Outer end portions 10c of the pole pieces have arcuate inner faces which are concentric with an axis located midway between the pole pieces and perpendicular to a plane defined by the longitudinal axis of the core 7 and the longitudinal center lines of the two pole pieces. The end portion 10c of each of the pole pieces is provided with a hole 11 which extends through the pole piece in a direction perpendicular to the aforementioned plane. The pole pieces are formed of soft iron or other suitable magnetic material.
A left end plate 12 and a right end plate 13 are secured on opposite sides of the outer end portions 10c of the pole pieces by means of pins 14 which pass through the holes 11 in the pole pieces and aligned holes in the end plates 12, 13. The pins 14 are a press-fit in the holes of the end plates so as to hold them in assembled relation on the two pole pieces. They may, if desired, be further secured, for example, by adhesive. Suitable screws can be used in place of the pins 14 but are less convenient for assembly. As viewed in side elevation, the end plates are approximately rectangular but with rounded ends. The right end plate 13 is flat while the left end plate 12 is provided at its ends with inwardly projecting, arcuate flange portions 12a so as to space the intermediate portion of the end plate farther from the plane of the pole pieces 10. The end plates 12 and 13 are formed of non-magnetic material, for example, aluminum or brass.
A back plate 16 of non-magnetic material is shown extending between the inner ends of the pole pieces 10 parallel to the core 7. The back plate is a flat, rectangular piece of material that is suitably secured to the ends of the pole pieces, for example, by adhesive. The back plate 16 is preferably provided with a grommeted hole to accommodate the lead wires of the winding 6. The back plate serves merely to close the end of the electromagnetic-pole piece assembly and may, if desired, be omitted.
A shaft 18 extends between the end plates 12 and 13 and is rotatably supported by bearings 19 set in central recesses in the end plate. The bearings 19 are shown as being jewel bearings but roller bearings, ball bearings or friction bearings may be used if desired. The shaft 18 is coaxial with the inner faces of the outer end portions 10c of the pole pieces. It is thus perpendicular to a plane defined by the axis of the core 7 and the longitudinal center lines of the pole pieces 10.
A rotor 20 is mounted on the shaft 18 so as to rotate therewith. The rotor 20 is approximately rectangular with rounded ends and is formed of soft iron or other suitable magnetic material. The shaft 18 passes through a central hole in the rotor 20 and is preferably a press-fit therein. The ends of the rotor 20 are arcuate and are concentric with the rotor axis. The radius of the rotor as measured from the axis to the arcuate end faces is slightly less than the radius of the arcuate faces of the pole pieces so that the rotor does not frictionally engage the pole pieces but when in a position extending across between the pole pieces, it provides a substantially closed flux path for the electromagnet. On the other hand, when the rotor is parallel to the pole pieces, the flux path is open.
Means is provided for limiting the rotary movement of the rotor 20 with its shaft 18 to define an "actuated" position and a "rest" position of the rotor. Such means is shown as comprising stop pins 21, set in appropriate holes in the right end plate 13 in position to be engaged by the rotor. As illustrated in FIG. 4, a plurality of holes may be provided for at least one of the stop pins so as to permit selection of the position in which the rotor is stopped. Moreover the stop pins may, if desired, be tapered to provide fine adjustment. The stop pin defining the "actuated" position of the rotor is located so as to stop the rotor before it reaches a position in which it extends diametrically between the opposite pole pieces 10. In this position the pull of the electromagnet holds the rotor firmly against the stop pin as long as the electromagnet is energized.
Means is provided for biasing the rotor to its rest position when the electromagnet is not energized. Such means is shown as comprising a spiral hair spring 23, the inner end of which is secured to a hub 24 fixed on the rotor shaft 18 while the outer end is anchored to a stationary portion, for example, one of the pole pieces 10. For this purpose the outer end of the spring is preferably provided with a hook which is received in a hole or recess formed in the pole pices and cemented in place. The spring is wound in the proper direction and is tensioned to tend to move the rotor from its actuated position to its rest position.
The shaft 18 is the "power output" shaft of the actuator and is accordingly used to actuate an indicator or other device that is to be operated by the actuator. In the embodiment illustrated in the drawings, the rotary electromagnetic actuator in accordance with the invention is used to operate a visual indicator comprising an indicator element mounted on the shaft 18 so as to rotate therewith. The indicator element is shown as comprising an arcuate flag 25 carried on one end of an elongated arm 26 at the opposite end of which there is provided a counter weight 27. At approximately its midpoint the arm 26 is provided with a hole receiving the shaft 18 to which the arm is fixed, for example, by a hub 28, so as to rotate with the shaft. The flag 25 is curved to conform to the surface of a cylinder coaxial with the shaft 18. The flag projects laterally from the arm 26 and is integral therewith or is suitably secured thereto, for example, by being spot welded to a portion of the arm bent at right angles to the length of the arm. The outer surface of the flag 25 may be colored, for example, red or yellow, to provide an indication as desired or may be provided with a number, letter, word or other indicia. The counter-weight 27 is shown as being a small cylindrical weight having a reduced hub portion which is pressed into a hole in the arm 26. The arm can be conveniently an elongated strip or bar of sheet metal. The mass of the counterweight is selected so as to provide at least approximately static and kinetic balance for the rotating assembly.
The actuator is enclosed by a cover 30. The cover is shown as being made of two similar parts which are generally rectangular in shape but with two rounded corners at one end of the cover. At opposite sides and at the end having the rounded corners the cover sections are provided with inwardly extending flanges 30a which abut one another when the cover is assembled and are secured together, for example, with adhesive. As seen in the drawings, the cover 30 fits over the assembly comprising the electromagnet pole pieces and end plates. The end of the cover with the rounded corners is at the end of the assembly where the rotor is located and the flange at this end of one cover section is provided with a cut-out or notch 30b to accommodate the arm 26 of the flag 25. As will be seen in FIG. 3, the counter-weight is accommodated in a space between the cover and the intermediate portions 10b of the pole pieces, the width of which is reduced, as pointed out above, so as to accommodate the counter weight. The rear end of the cover is closed by the back plate 16. A very compact assembly is thereby provided.
Suitable means is provided for mounting the actuator. As illustrated in the drawings, the mounting means comprises brackets 31 provided on the cover 30. It will be understood that one or more brackets of suitable form may be provided according to where and how the actuator is to be mounted.
The operation of the rotary electromagnetic actuator illustrated in the drawings will be readily understood from the foregoing description. When the electromagnet 5 is not energized, the rotor 20 is held in "rest" position by the spring 23 and the flag 25 is thereby held in corresponding position as shown in solid lines in FIG. 1. When the electromagnet 5 is energized, the resulting magnetic force acting on the rotor 20 causes the rotor to turn to the "actuated" position as defined by the respective stop pin 21 as shown in dot-dash lines in FIG. 1. The flag 25 is thereby moved to actuated position and is held in such position as long as the electromagnet is energized. When it is de-energized, the rotor 20 and hence the flag 25 are returned to rest position by the spring 23.
While a preferred embodiment in accordance with the invention has been illustrated in the drawings and is herein particularly described, it will be understood that the invention is in no way limited to the details of construction of this embodiment.
It is an object of the invention to provide a rotary electromagnetic actuator in which the parts are so arranged and asembled that the actuator can be made very small and compact and yet have sufficient power to actuate the indicator or other device for which it is employed. In particular the actuator in accordance with the invention has a relatively thin, flat configuration so that a plurality of actuators can be placed side by side or the actuator can be placed close to or between other instruments or equipment. By way of example an actuator in accordance with the present invention may have a length of the order of 2 cm, a width of the order of 1.36 cm and a thickness of the order of 0.6 cm.
A further object of the invention is to provide a small compact rotary electromagnetic actuator that can be economically manufactured and is efficient, reliable and durable in its operation.
The nature, objects and advantages of the invention will be more fully understood from the following description of a preferred embodiment shown by way of example in the drawings in which
FIG. 1 is an enlarged side view of an electromagnetic actuator in accordance with the invention with a portion of the cover removed and parts broken away to show internal construction,
FIG. 2 is a cross section taken approximately on a line 2--2 of FIG. 1,
FIG. 3 is a longitudinal section on a smaller scale taken approximately on a line 3--3 in FIG. 1, and
FIG. 4 is a partial side view illustrating the location of means for limiting the angle of rotation of the rotary actuator.
The rotary electromagnetic actuator shown by way of example in the drawings comprises an electromagnet 5 having a winding 6 around an insulated cylindrical core 7. The core is formed of soft iron or other suitable magnetic material and is longer than the winding so that end portions of the core project beyond the winding. The winding is wound of insulated self-bonding wire contiguous convolutions of which adhere to one another so that the winding is self-supporting and no coil form is required. After the coil is wound, it is preferably wrapped with tape or coated with insulating material to provide mechanical and electrical protection for the coil. Suitable leads are provided for connecting the coil to a circuit for supplying current to it.
A pair of pole pieces 10 extend laterally from opposite ends of the core 7. The two pole pieces are parallel to one another and are perpendicular to the longitudinal axis of the core 7. Each of the pole pieces 10 has an approximately square inner end portion 10a provided with a central hole which receives the projecting end portion of the core. The core fits into the holes provided in the pole pieces with a press fit or is otherwise assembled with the pole pieces so that the core, winding and pole pieces constitute a unitary rigid structure. Intermediate portions 10b of the pole pieces are straight and are of rectangular cross section with a width which is less than that of the end portions 10a but a thickness that is greater so that the cross sectional area is approximately the same. Outer end portions 10c of the pole pieces have arcuate inner faces which are concentric with an axis located midway between the pole pieces and perpendicular to a plane defined by the longitudinal axis of the core 7 and the longitudinal center lines of the two pole pieces. The end portion 10c of each of the pole pieces is provided with a hole 11 which extends through the pole piece in a direction perpendicular to the aforementioned plane. The pole pieces are formed of soft iron or other suitable magnetic material.
A left end plate 12 and a right end plate 13 are secured on opposite sides of the outer end portions 10c of the pole pieces by means of pins 14 which pass through the holes 11 in the pole pieces and aligned holes in the end plates 12, 13. The pins 14 are a press-fit in the holes of the end plates so as to hold them in assembled relation on the two pole pieces. They may, if desired, be further secured, for example, by adhesive. Suitable screws can be used in place of the pins 14 but are less convenient for assembly. As viewed in side elevation, the end plates are approximately rectangular but with rounded ends. The right end plate 13 is flat while the left end plate 12 is provided at its ends with inwardly projecting, arcuate flange portions 12a so as to space the intermediate portion of the end plate farther from the plane of the pole pieces 10. The end plates 12 and 13 are formed of non-magnetic material, for example, aluminum or brass.
A back plate 16 of non-magnetic material is shown extending between the inner ends of the pole pieces 10 parallel to the core 7. The back plate is a flat, rectangular piece of material that is suitably secured to the ends of the pole pieces, for example, by adhesive. The back plate 16 is preferably provided with a grommeted hole to accommodate the lead wires of the winding 6. The back plate serves merely to close the end of the electromagnetic-pole piece assembly and may, if desired, be omitted.
A shaft 18 extends between the end plates 12 and 13 and is rotatably supported by bearings 19 set in central recesses in the end plate. The bearings 19 are shown as being jewel bearings but roller bearings, ball bearings or friction bearings may be used if desired. The shaft 18 is coaxial with the inner faces of the outer end portions 10c of the pole pieces. It is thus perpendicular to a plane defined by the axis of the core 7 and the longitudinal center lines of the pole pieces 10.
A rotor 20 is mounted on the shaft 18 so as to rotate therewith. The rotor 20 is approximately rectangular with rounded ends and is formed of soft iron or other suitable magnetic material. The shaft 18 passes through a central hole in the rotor 20 and is preferably a press-fit therein. The ends of the rotor 20 are arcuate and are concentric with the rotor axis. The radius of the rotor as measured from the axis to the arcuate end faces is slightly less than the radius of the arcuate faces of the pole pieces so that the rotor does not frictionally engage the pole pieces but when in a position extending across between the pole pieces, it provides a substantially closed flux path for the electromagnet. On the other hand, when the rotor is parallel to the pole pieces, the flux path is open.
Means is provided for limiting the rotary movement of the rotor 20 with its shaft 18 to define an "actuated" position and a "rest" position of the rotor. Such means is shown as comprising stop pins 21, set in appropriate holes in the right end plate 13 in position to be engaged by the rotor. As illustrated in FIG. 4, a plurality of holes may be provided for at least one of the stop pins so as to permit selection of the position in which the rotor is stopped. Moreover the stop pins may, if desired, be tapered to provide fine adjustment. The stop pin defining the "actuated" position of the rotor is located so as to stop the rotor before it reaches a position in which it extends diametrically between the opposite pole pieces 10. In this position the pull of the electromagnet holds the rotor firmly against the stop pin as long as the electromagnet is energized.
Means is provided for biasing the rotor to its rest position when the electromagnet is not energized. Such means is shown as comprising a spiral hair spring 23, the inner end of which is secured to a hub 24 fixed on the rotor shaft 18 while the outer end is anchored to a stationary portion, for example, one of the pole pieces 10. For this purpose the outer end of the spring is preferably provided with a hook which is received in a hole or recess formed in the pole pices and cemented in place. The spring is wound in the proper direction and is tensioned to tend to move the rotor from its actuated position to its rest position.
The shaft 18 is the "power output" shaft of the actuator and is accordingly used to actuate an indicator or other device that is to be operated by the actuator. In the embodiment illustrated in the drawings, the rotary electromagnetic actuator in accordance with the invention is used to operate a visual indicator comprising an indicator element mounted on the shaft 18 so as to rotate therewith. The indicator element is shown as comprising an arcuate flag 25 carried on one end of an elongated arm 26 at the opposite end of which there is provided a counter weight 27. At approximately its midpoint the arm 26 is provided with a hole receiving the shaft 18 to which the arm is fixed, for example, by a hub 28, so as to rotate with the shaft. The flag 25 is curved to conform to the surface of a cylinder coaxial with the shaft 18. The flag projects laterally from the arm 26 and is integral therewith or is suitably secured thereto, for example, by being spot welded to a portion of the arm bent at right angles to the length of the arm. The outer surface of the flag 25 may be colored, for example, red or yellow, to provide an indication as desired or may be provided with a number, letter, word or other indicia. The counter-weight 27 is shown as being a small cylindrical weight having a reduced hub portion which is pressed into a hole in the arm 26. The arm can be conveniently an elongated strip or bar of sheet metal. The mass of the counterweight is selected so as to provide at least approximately static and kinetic balance for the rotating assembly.
The actuator is enclosed by a cover 30. The cover is shown as being made of two similar parts which are generally rectangular in shape but with two rounded corners at one end of the cover. At opposite sides and at the end having the rounded corners the cover sections are provided with inwardly extending flanges 30a which abut one another when the cover is assembled and are secured together, for example, with adhesive. As seen in the drawings, the cover 30 fits over the assembly comprising the electromagnet pole pieces and end plates. The end of the cover with the rounded corners is at the end of the assembly where the rotor is located and the flange at this end of one cover section is provided with a cut-out or notch 30b to accommodate the arm 26 of the flag 25. As will be seen in FIG. 3, the counter-weight is accommodated in a space between the cover and the intermediate portions 10b of the pole pieces, the width of which is reduced, as pointed out above, so as to accommodate the counter weight. The rear end of the cover is closed by the back plate 16. A very compact assembly is thereby provided.
Suitable means is provided for mounting the actuator. As illustrated in the drawings, the mounting means comprises brackets 31 provided on the cover 30. It will be understood that one or more brackets of suitable form may be provided according to where and how the actuator is to be mounted.
The operation of the rotary electromagnetic actuator illustrated in the drawings will be readily understood from the foregoing description. When the electromagnet 5 is not energized, the rotor 20 is held in "rest" position by the spring 23 and the flag 25 is thereby held in corresponding position as shown in solid lines in FIG. 1. When the electromagnet 5 is energized, the resulting magnetic force acting on the rotor 20 causes the rotor to turn to the "actuated" position as defined by the respective stop pin 21 as shown in dot-dash lines in FIG. 1. The flag 25 is thereby moved to actuated position and is held in such position as long as the electromagnet is energized. When it is de-energized, the rotor 20 and hence the flag 25 are returned to rest position by the spring 23.
While a preferred embodiment in accordance with the invention has been illustrated in the drawings and is herein particularly described, it will be understood that the invention is in no way limited to the details of construction of this embodiment.