Abstract:
The present invention provides low-power, sector-rotating, electro-magnetically and mechanically operable toggling actuator. The reluctance of the magnetic circuit of this invention is controlled to effect actuation with but little magneto-motive force and, little electrical power. The preferred embodiment of this invention provides a single-coil, sector-rotating, electromagnetically and mechanically operable toggling actuator. In this embodiment, a pivotally-mounted magnetically-permeable rotor is attracted to either of two stable rotary positions by permanent magnets affixed to a magnetically-permeable stator. A magnetic circuit between the stator and the rotor comprises an electromagnetic coil to provide magneto-motive force for toggling the rotor to a desired position responsive to the direction of electrical current through the coil. A switch may be provided for activating external circuits responsive to rotor position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. Provisional Application No. 61/460,465, filed on Jan. 3, 2010, which is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     The present invention was not developed with the use of any Federal Funds, but was independently developed by the inventor. 
     BACKGROUND OF THE INVENTION 
     This invention provides an actuator well-suited for use as a Stop Action Magnet, or SAM, which may be a component of a musical instrument, especially of an organ console. In addition to claviers for accessing notes of various musical pitches at the will of the organist, an organ also usually comprises so-called stops that control plural groups, called ranks, of pipes (or of sampled or synthesized sounds) whereby many musical timbres may be selected. Small organs may comprise but a few stops, but large organs may be equipped with several tens, or even hundreds of stops. For small organs, manual stop-controls often suffice. For large organs, however, it is necessary to provide means for the organist to preset chosen stop combinations prior to a performance, subsequently to be accessed during the performance using preset buttons, called pistons. For this purpose, large organs often include a memory with presetting and access means, called a combination action. When the organist pushes a piston, pre-selected stops are electrically (sometimes pneumatically) quickly activated or deactivated as if they had been simultaneously manually selected. The electro-mechanical device that activates or de-activates each stop responsive to the combination action, or responsive to manual operation, is called a SAM. 
     A primal prior-art “Reisner C3” SAM is offered as part no. 5566.19 by Organ Supply Industries of Erie, Pa. Subsequent improvements to early prior-art SAM designs are taught in U.S. Pat. No. 3,832,658, U.S. Pat. No. 4,726,277, FIGS. 7&amp;8, and U.S. Pat. No. 4,851,800, FIGS. 7, 8, and 10. These prior-art SAM&#39;s are sector-rotating designs comprising two solenoidal coils for rotor operation. 
     Prior-art sector-rotating SAM&#39;s comprise either a spring, or two or more permanent magnets, with at least one affixed to their rotors, to provide the toggling action required by organists. Some prior-art SAM&#39;s, for example those offered by Syndyne Corp. of Vancouver, Wash., are supplied with models having different toggle forces. 
     Most prior-art sector-rotating SAM&#39;s are supplied with plural rotor angle options to accommodate various organ console requirements. This plurality necessitates documentation, production, and stocking of rotors having various bend angles. 
     Because it is desirable for all the stop tabs (SAM handles) in a row of SAM&#39;s to rest at uniform positions, both when de-activated (up) and also when activated (down), most sector-rotating SAM&#39;s are fitted with leveling adjustments to unify their toggled positions. On the Reisner C3 SAM these adjustments are on the top and bottom of the SAM. On the SAM of U.S. Pat. No. 3,832,658 offered as part #SAM by Syndyne and in that of U.S. Pat. No. 4,726,277 offered by Peterson Electro-Musical Products, Inc., these adjustments are located on one side. Installed SAM&#39;s are often lie in closely spaced rows. The space below the lowest row of SAM&#39;S is often occupied by the tails of the upper clavier keys. Thus, once many prior-art SAM&#39;s are installed, the only adjustment likely to be accessible is the top adjustment of a top-row Reisner SAM. It is usually inconvenient to adjust an installed prior-art SAM. For this reason, organ technicians usually adjust SAM&#39;s sequentially as they are installed rather than iteratively to dismount, adjust, and remount each SAM to level it. 
     The Peterson PowerTab™ literature cites its “exclusive, patented Tip Polarization” as an efficiency improvement, illustrating the importance of efficient operation. Notwithstanding this citation, prior-art SAM&#39;s usually require about three watts of instantaneous power to toggle. This large instantaneous power demand often causes prior-art SAM&#39;s to fail to operate if the supply voltage becomes loaded down. This problem often occurs when a so-called “general cancel” piston is pushed, requiring simultaneous de-activation of many SAM&#39;s. Prior-art SAM&#39;s usually utilize needle-bearing pivots, through which and around which their magnetic circuits must close. The pivots of prior-art SAMS&#39;s usually offer substantial magnetic reluctance, causing inefficiency. The needle-bearing pivots of many prior-art SAM&#39;s are prone to bearing failure after a few hundred thousand operations, necessitating inconvenient replacement. 
     It is not unusual for prior-art SAM&#39;s to interfere with their own switches or those of adjacent SAM&#39;s, and sometimes the operation of other parts of the instrument, to the extent that at least one instance of disruption of an organ concert due to such interference has been recorded. 
     Whilst it is desirable that SAM&#39;s operate silently, the deceleration of the large rotor mass of two-coil SAM&#39;s militates against this desirable characteristic. 
     Also taught by Peterson in U.S. Pat. No. 4,726,277, FIG. 1, is a SAM of the “draw-knob” variety preferred for classical organs. It has a single-coil like the present invention, but is very different, providing rectilinear motion and being copiously endowed with linkages. Apparently such single-coil SAM&#39;s have proven problematic in the prior-art, as Peterson&#39;s present draw-knob offering is an adapted two-coil sector-rotating device. 
     OBJECTS OF THE PRESENT INVENTION 
     A first object of this invention to provide a sector-rotating toggling actuator that toggles with less power than prior-art actuators. Another object of the present invention is to provide such an actuator that operates with but a single coil. A further object of the present invention is to provide an adjustable SAM wherein a single model is compatible with, and may easily be co-installed and co-leveled with prior-art SAM&#39;s of various makes and angles. Another object of this invention is to provide such a SAM comprising but a single set of parts, with none devoted to a particularangle, to provide an adjustable arc of rotation that can easily be angularly positioned relative to a mounting surface. A further object of this invention is to is to provide such an actuator having its adjustments readily accessible from its rear direction. Yet another object of this invention is to provide a SAM that will survive one-million or more operations. A further object of this invention is to provide a SAM that operates more quietly than prior-art SAM&#39;s. Yet another object of this invention is to provide a SAM that is less subject to magnetic interference than prior-art SAM&#39;s. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention provides a low-power sector-rotating toggling actuator by reducing actuator magnetic circuit reluctance. The magnetic circuit of the present invention is made relatively stout of cross-section, enabling its operation with little magneto-motive force, thus requiring but little electric actuating power. The preferred embodiment of the inventive actuator comprises a magnetically-permeable rotor, a magnetically-permeable stator fitted with permanent-magnet poles, and a coil, all disposed in a magnetic circuit. The actuator of the preferred embodiment toggles between stable positions responsive both to mechanical operation of its rotor and to application of suitably poled electrical currents through its coil. The actuator of this invention may be fitted with magnetically-permeable bushings to minimize the reluctance of its magnetic circuit. The actuator of this invention may be fitted with one or more mechanical adjustments which may be made accessible from its rear direction. The actuator of this invention may be fitted with a mounting trunnion, whereby it may be angularly adjusted relative to a mounting surface. This actuator may comprise an electrical switch responsive its rotor position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side view of a prior-art SAM. 
         FIG. 2  shows a front view of a prior-art SAM. 
         FIG. 3A  shows a side view of a SAM with magnetic shunts. 
         FIG. 3B  shows a front view of a SAM with magnetic shunts. 
         FIG. 3C  shows a front view of a SAM with gap-narrowing. 
         FIG. 4  shows a side view of a single-coil actuator, the preferred embodiment of the present invention. 
         FIG. 5  shows details of the actuator of  FIG. 4 . 
         FIG. 6A  shows a side view of the rotor of the actuator of  FIG. 4 . 
         FIG. 6B  shows a top view of the rotor of the actuator of  FIG. 4 . 
         FIG. 7A  shows a front view of the stator of the actuator of  FIG. 4 . 
         FIG. 7B  shows a side view of the stator of the actuator of  FIG. 4 . 
         FIG. 8A  shows a side view of the coil of the actuator of  FIG. 4 . 
         FIG. 8B  shows a end view of the coil of the actuator of  FIG. 4 . 
         FIG. 9A  shows a rear view of the core of the actuator of  FIG. 4 . 
         FIG. 9B  shows a side view of the core of the actuator of  FIG. 4 . 
         FIG. 9C  shows a front view of the core of the actuator of  FIG. 4 . 
         FIG. 10A  shows a left-side view of the trunnion of the actuator of  FIG. 4 . 
         FIG. 10B  shows a front view of the trunnion of the actuator of  FIG. 4 . 
         FIG. 10C  shows a right-side view of the trunnion of the actuator of  FIG. 4 . 
         FIG. 11A  shows a right-side view of the mounting trunnion of the actuator of  FIG. 4 . 
         FIG. 11B  shows a rear view of the mounting trunnion of the actuator of  FIG. 4 . 
         FIG. 11C  shows a left-side view of the mounting trunnion of the actuator of  FIG. 4 . 
         FIG. 12  shows the circuit board of the actuator of  FIG. 4 . 
         FIG. 13A  shows a side view of the cap of the actuator of  FIG. 4 . 
         FIG. 13B  shows a rear view of the cap of the actuator of  FIG. 4 . 
         FIG. 14A  shows a rear view of the cam of the actuator of  FIG. 4 . 
         FIG. 14B  shows a side view of the cam of the actuator of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following terms are hereby defined for this application: 
     The term “sector-rotation” means rotation about an axis through an arc of less than 360 degrees. 
     The term “angular offset” means an angle between a fixed reference surface and one extreme of an arc of sector rotation. 
     The term “magnetically-permeable” means having a low magnetic reluctance, as exemplified by a ferrous material such as soft steel or iron. 
     The term “pole” means that surface of a magnet, of a coil, or of a coil core, disposed to coact with a magnetically related member. 
     The term “toggle” means to move between stable positions by overcoming force that resists rest in intermediate positions, as exemplified by the action of a well-known electrical toggle switch. 
     The term “coil” means a current dependent source of magneto-motive force, usually comprising a coil of wire, often wound on a bobbin, that produces magneto-motive force when conducting an electrical current. 
     The term “magnetic circuit” means a closed or near-closed magnetically-permeable path through which the magnetic flux of a magnet and/or of a coil passes. 
     The term “oppositely poled” refers to magnets or coils poled mutually to attract. Oppositely poled magnets attached to a permeable member share lines of magnetic flux through that member. Conversely, the flux of like poled magnets or coils may share a member, but like poled magnets or coils insignificantly share flux. 
     The term “permanently lubricated” refers to mechanical bearing material which has been saturated with a lubricant or otherwise endowed with a long-lasting low coefficient of friction. 
     The term “SAM” means a stop action magnet, a type of actuator commonly used in organ consoles, as described above. 
       FIG. 1  depicts a side view of a prior-art SAM  1000  comprising a magnetically-permeable rotor  2000  having a stop-tab end  2400  and a pole-piece end  2500 . Rotor  2000  sector-rotates on a needle-bearing pivot  2300 . The needle-tips of pivot  2300  rotate in seats in a magnetically-permeable stator frame  4000 , which supports two coils  5000 . Coils  5000  and  5100  surround magnetically-permeable stator pole rods  3000  and  3100 , to one or the other of which poles  2500  is magnetically attracted when one of the coils is electrically energized. Activating lower coil  5000  turns rotor  2000  clockwise; activating upper coil  5100  turns rotor  2000  counter-clockwise. A magnet  3300  is affixed to a magnetically-permeable vane  2600  affixed to rotor  2000 . A second magnet  3200  is affixed to a magnetically non-permeable circuit board  7000  which is fastened to stator frame  4000 . Magnets  3100  are poled to repel when armature  2000  is in the center of its rotation, enforcing stable toggle positions at the extremes of rotor  2000  travel and preventing rotor  2000  from resting in an intermediate position. Affixed to circuit board  7000  is a reed switch capsule  8000  which, through conductors connected to plated-through holes  5600 , reports information about the position of the rotor  2000  to the organ console. Wires powering coils  5000  and  5100  may be connected to similar holes. Switch capsule  8000  is turned on by the magnets  3300  and  3200  when stop-tab end  2400  is depressed and pole-piece end  2500  rises. Vane  2600  optimizes the magnetic fields affecting switch capsule  8000 . Pole-piece end  2500  is relatively massive, and moves at a relatively large radius relative to pivot  2300 . Adding to its moment of inertia are vane  2600  and a magnet  3300 . Not shown are bumpers at the travel extremes of pole-piece end  2500 . At the extremes of pole-piece end  2500  travel considerable shock is thereby transmitted through circuit board  7000 , to frame  4000 , thence to the woodwork of the organ console, producing audible noise. 
       FIG. 2  shows the prior-art SAM  1000  of  FIG. 1  in front view. In this typical prior-art SAM, both above and below rotor  2000  where it passes through frame  4000 , are gaps of about 0.11″ (0.28 cm.), and on its sides are gaps of about 0.05″ (0.127 cm.) Frame  4000  is about 0.125″ (0.33 cm.) thick. Rotor  2000  is about 0.375″ (0.95 cm.) wide. At toggle current, the flux densities in the gaps above and below its rotor  2000  were measured to be about 415 Gauss, using an Allegro A1302LH linear Hall-effect sensor. With upper and lower gaps providing a total area of about 0.6 square cm. we may deduce that their total flux of those gaps was about 250 Maxwells. The side gaps are too narrow to accommodate the sensor used, but based on their length, we may compute their flux densities to be about 910 Gauss. Their total area being about 0.2 square cm., we may deduce that they conducted about 183 Maxwells. Could pivot  2300  pin have conducted sufficient flux, there would have been little flux measured in the gaps, but it is evident that the pivot pin  2300  was saturated. Being a mere 0.063″ in diameter, they provide a tiny total cross section of about 0.04 square cm. of steel, which at saturation might conduct About 600 Maxwells of flux. The total flux was, therefore about 1033 Maxwells. 
     One CGS unit of reluctance is one Gilbert per Maxwell, being also the reluctance of a one centimeter cube of vacuum and, practically, of air. The gaps above and below the rotor  2000  have lengths of about 0.28 cm., which divided by an area about 0.6 square cm., yield about 0.467 CGS units of reluctance. The side gaps, with lengths of about 0.127 cm., divided by an area of about 0.2 square cm. yield about 0.635 CGS units of reluctance. Computing the reciprocal of the sum of the reciprocals of these two reluctances yields an incremental reluctance of about 0.27 CGS units for the gap between frame  4000  and rotor  2000  once the pivot  2300  pin has saturated. The pole gaps of this prior-art SAM, being about 0.02 cm in length, divided by 0.315 square cm. of area, yield a reluctance of only about 0.064 CGS units, one pole being active in each toggle position. The remainder of the magnetic circuit being stout and of steel offers but little reluctance. Since magneto-motive force drops across magnetic-circuit reluctances of a in proportion to those reluctances, one may see that in this prior-art SAM most of the magneto-motive force generated by the coils  5000  was wasted around pivots  2300  rather than doing useful work. Loss of magneto-motive force incurred by a high reluctance magnetic circuit usually wastes coil power. The measured instantaneous power needed to toggle this prior-art SAM was about three watts, much of which was wasted. 
       FIG. 3A  shows a partial side view of a two-coil stop action magnet  100  having a stator frame  400  which is analogous to both the prior-art stator frame  4000  of  FIGS. 1 and 2 , and to the stator  3  and trunnion  4  of  FIG. 4 . A rotor  200 , is analogous to both the prior-art stator frame  2000  of  FIGS. 1 and 2 , and to the rotor  2  of  FIG. 4 . In the gap between the rotor  200  and the frame  400  are fitted one or more magnetic shunts  290  surrounding pivot  230 , that pivot being analogous to pivot  2300  of  FIGS. 1 and 2  and to pivot  23  of  FIG. 4 . Shunts  290  are made of a magnetically-permeable material to provide a low reluctance path around pivot  230 , thus reducing magnetic circuit reluctance reduction in accordance with the present invention. 
       FIG. 3B  shows a front view of the stop action magnet  100  of  FIG. 3A . One or more shunts  290  may be applied in the form of washers running free in the gap between stator frame  400  and rotor  200 , or may be affixed to or manufactured as part of frame  400  and/or of rotor  200  to practice this invention. 
       FIG. 3C  shows yet another arrangement for magnetic circuit reluctance control according to this invention. Here the inner walls of frame  400  have been moved, from prior-art positions  480 , to new positions  490  according to this invention. These new positions are closer to rotor  200  to achieve a shorter gap in the magnetic circuit. A alternative method of embodying this invention may be practiced by making rotor  200  wider where it passes through frame  400 . 
       FIG. 4  shows a left-side view of a the preferred embodiment of a sector-rotating toggling actuator  1  according to the present invention. A magnetically-permeable rotor  2  has a stop-tab end  24  and a pole-tip  25 . Near its center, rotor  2  is fitted with a steel pivot  23 . Adjacent to pole-tip  25 , is a stator  3  bearing an upper magnet  30  and lower magnet  31 . Between the magnets is an inter-pole  34 . Stator  3  is penetrated by a hole through which pass an ordinary steel cap-screw  55 , and a threaded steel coil-core, to be described below. External threads on the core are engaged to secure stator  3  thereto by a nut  54  pressing on a washer  53 . A steel shim  52  is interposed between a shoulder on the core and stator  3 , for setting of the gap between magnets  30  and  31  and pole-tip  25 , and thereby the toggling torque, typically 1.5 inch-ounces, of this inventive SAM. Coil  5  surrounds the aforementioned steel core which closes the portion of the magnetic circuit between stator  3  and a trunnion  4 . Trunnion  4  has a rear wall which is penetrated by an orifice allowing passage of rotor  2 , and two sides walls both of which are penetrated by hole. Into this hole in each wall of trunnion  4  is pressed a ferrous bushing  41 . Rotating in the bores of bushings  41  is a pivot pin  23 , which also passes through an orifice in rotor  2 . Thus from rotor  2  though stator  3 , through coil  5 , through trunnion  4 , through bushing  41 , and through pivot  23  back to rotor  2  there exists a stout magnetic circuit of magnetically-permeable materials, according to this invention. Only the gap completing the magnetic circuit between to pole-tip  25  and stator  3  contributes significant reluctance to this magnetic circuit. 
     A crucial aspect of this invention is control of magnetic circuit reluctance, concentrating it in the gap between pole-tip  25  and the magnets  30  and  31  of stator  3 . The stray magnetic field density adjacent to the entire magnetic circuit of this invention was mapped using an Allegro A1302LH linear Hall-effect sensor, typically measuring less than 7 Gauss, save adjacent to bushings  41  where about 15 Gauss was measured and, as expected, immediately adjacent to the gap at the pole-tip  25  of rotor  2 , where the field strength exceeded sensor range. The reluctance of the magnetic circuit of actuator  1 , exclusive of the pole-tip gap, being approximately 0.020 CGS units, is far less than that of prior-art SAM&#39;s. The measured actuator  1  toggled reliably with an instantaneous toggling power of but one watt, a notable reduction relative to prior-art SAM&#39;s. High permeability steels might be used to practice this invention with dimensions different than those cited here, however such a selection may be problematic unless the material chosen offers higher saturation flux density than soft steel. It should be noted that magnetically-permeable shunts such as permeable washers surrounding their pivots, or equivalent magnetic closures, could be added in the region of the needle-bearing pivots of prior-art SAM&#39;s to practice magnetic circuit reluctance reduction according to this invention. 
     Pivot  23  rotates freely in bushings  41  through an angle of about 16 degrees, near the extremes of which it is attracted to either magnet  30  or  31 . Due to this attraction, rotor  2  will not rest save in its extreme positions, and requires torque, to be toggled between its extreme positions. Setting toggling high torques will require greater magneto-motive force for electromagnetic toggling than setting low torques. It should be noted that relative to those of prior-art SAM&#39;s, rotor  2  of this invention has less mass, which reduces audible noise. Actuator  1  is durable, a prototype having been subjected to over one-million operations without detectable degradation. 
     Actuator  1  toggles thusly: Let us assume that pole-tip  25  is resting near magnet  31 . When current flows through coil  5  in a first polarity, pole-tip  25 , as part of the aforementioned magnetic circuit, is repelled by magnet  31 . Its field is poled to attract it to magnet  30 , but the distance thereto is too great to toggle rotor  2  without an intermediate force. Mechanical force exerted by an attracting electromagnet seeks to minimize magnetic circuit reluctance. Therefore, when pole-tip  25  is repelled from lower magnet  31 , it is simultaneously attracted to the edges of electro-magnetic inter-pole  34 . Its rotation toward upper magnet  30  increases the intimacy between pole-tip  25  and inter-pole  34 , decreasing gap reluctance, until pole-tip  25  reaches a center position between magnets  30  and  31 . Upon reaching center position, pole-tip  25  is strongly attracted to and rotates toward magnet  30 , where it rests stably until rotor  2  is either manually toggled, or until current of opposite polarity is passed through coil  5 . Should coil  5  be thus reversed, rotor  3  toggles as described above, but oppositely, until pole-tip  25  then rests once again near magnet  31 . Electromagnetic inter-pole  34  is an important aspect of this invention, without which greater coil power would be needed to provide reliable toggling. 
     It is necessary not only to toggle actuator  1 , but also adjustably to restrict its sector-rotation, and to do so quietly. To this end, rotor  2  is fitted with adhesively attached elastomeric pads  71  and  72 . Adhesivly attached to the top of coil  5  is a similar-sized patch  70  of felt. Pad  71  and patch  70  quietly limit counter-clockwise rotation of rotor  2 . A stud  73 , permanently pressed into trunnion  4 , bears an off-center bored cylindrical cam  75 , which by friction is difficult to rotate on stud  73 , but may be rotated from the rear of this actuator  1  to adjust the distance from its surface to pad  72  on rotor  2 . By rotating cam  75 , the angle of sector rotation of rotor  2  may be adjusted. Pad  72  mitigates the noise and rebound of stopping clockwise rotation of rotor  2 . 
     Trunnion  4  is formed of a channel, inside which rests a similarly shaped and narrower mounting trunnion  6 , and through an aperture in the front wall of which rotor  2  passes, and the side walls of which are penetrated by a hole, in which freely rotates bushing  41 . Passing through a threaded hole in trunnion  4  is a set-screw  74 , preferably about 0.5″ long, 4-40 thread, nylon tipped, that bears on the inside rear surface of mounting trunnion  6 . Passing though coil  5  and engaging an internal thread in the core to be described below, is screw  55 , which further penetrates a hole in trunnion  4 . The tip of screw  55  is fitted with a cap  57  which transmits its force to the inside rear surface of mounting trunnion  6 . Since screws  55  and  74  are rotationally opposed on mounting trunnion  6 , tightening both locks them. By loosening one screw and tightening the other, trunnion  4  may be angularly adjusted relative to mounting trunnion  6 . Thus the entire actuator  1 , save mounting trunnion  6 , may be adjusted to a desired angular offset relative to the organ console. Using this adjustment and that of cam  75 , both the angular offset and the sector-rotation range of a stop-tab attached to rotor  2  may be adjusted relative to an organ console. Surface  65  is the usual surface for mounting to an organ console. The trunnion and rotor adjustments are made from the rear of this actuator  1  according to this invention. 
     Shown mounted on a circuit board  7  is a reed switch capsule  80  to be magnetically activated by rotation of rotor  2 . It should be noted that the axis of switch  80  is perpendicular to the axis of coil  5  to avoid interference. Such orthogonal arrangement is less practical in two-coil SAM&#39;s, in which considerable difficulty in positioning reed switches is customary. For compatibility, the reed switch is preferred for embodiments of this invention intended for replacement of installed SAM&#39;s, but this invention may be practiced with other switch types to report rotor  2  position. Other magnetic switches, opto-electronic switches, capacitive switches, ultrasonic switches, or even mechanical switches may be used. Circuit board  7  also receives leads  56  of coil  55  for connection to organ console circuitry. 
       FIG. 5  shows a right side view of actuator  1  with the circuit board  7  of  FIG. 4  removed to reveal details. In this figure rotor  2  has been toggled to its lower (activated) position. Also the entire actuator  1 , save mounting trunnion  6 , has been rotated counter-clockwise on bushing  41  with respect to mounting trunnion  6  to effect a new stop-tab angle. The nylon tip of set screw  74  is seen pressing against mounting trunnion  6 , and set screw  74  has been partially screwed out of trunnion  4 . Screw  55  has been screwed in to extend cap  57  to maintain pressure in opposition to screw  74 . Part of mounting trunnion  6  has been broken away to reveal cap  57 . The lower part of the actuator  1  has been sectioned to reveal details the aforementioned core,  58  that penetrates coil  5 . Nut  54  is seen to engage an external thread  87  on the rear of core  58 . Toward the front of core  58  may be seen an internal thread  59  which engages screw  55 . Core  58  is secured to trunnion  4  by a swage  60 . A magnet  86 , may be seen imbedded in the right side of rotor  2  which, in the rotor  2  position shown, activates the reed switch  80  of  FIG. 4 . Magnet  86  has little interaction with the magnetic circuit described above and plays no part in the toggling of the actuator  1 , its sole purpose being to operate switch  80  of  FIG. 4 . The right side of trunnion  4  is penetrated not only by the hole for bushing  41  but also by two small tapped holes  42  and  43  used for mounting circuit board  7  of  FIG. 4 . Tapped holes  35  and  36  in stator  3  are also provided for the same purpose. 
       FIG. 6A  shows a left-side view of rotor  2 . Two bars  26  and  27 , preferably of soft steel 0.375″ wide and 0.063″ thick, are compressed around a mandrel to create an aperture into which pivot pin  23  is tightly fitted and retained by a set-screw  28 , or by an adhesive. Bars  26  and  27  are preferably bonded tightly together by rivets, spot-welding, or other well-known means. One end of the joined bars  26  and  27  comprises pole-tip  25 , whilst the other end comprises a lever for stop-tab attachment. Pivot pin  23  is preferably an ordinary steel dowel pin 0.125″ in diameter by 0.625″ long, normally supplied hardened and ground properly to function as a journal. Many methods may be employed to make rotor  2 , for example the entire rotor with an integral pivot  23  can be machined, or the rotor can be molded and sintered by well-known powder metallurgy methods, all to practice this invention. Adhesively attached to rotor  2  are shown pads  71  and  72 , preferably about 0.5″ long, 0.375″ wide, and 0.063″ thick, of Gallagher Corp. GC965 material. 
       FIG. 6B  shows a top view of rotor  2 . The journals formed by protrusions of pivot pin  23  are visible. Near its stop-tab (handle) end  24 , rotor  2  is penetrated by a threaded hole  21  and an clear hole  22 , for stop-tab attachment. Magnet  86 , preferably of Neodymium-Iron-Boron, 0.125″ in diameter and 0.063″ thick, for activating switch  80  of  FIG. 4  is seen imbedded in the side of rotor  2 , where it is adhesively affixed. Pad  72  has been shown broken away to reveal magnet  86 . 
       FIG. 7A  shows a front view of stator  3  of  FIG. 4  which is preferably made of soft steel approximately 0.063″ thick. To stator  3  are adhesively attached upper magnet  30  and lower magnet  31 , preferably of grade 5 ceramic, 0.375″ in diameter and 0.125″ thick, so poled that opposite poles face pole-tip  25  of  FIG. 4 , for example magnet  30  might present a North pole whilst magnet  31  presents a South pole to pole-tip  25 , from which a face of one of the magnets is separated by a narrow gap in  FIGS. 4 and 5 . Between the magnets are inter-poles  34 , each about 0.188″ in height and protruding about 0.313″, preferably integral with stator  3  and bent up from same.  FIG. 7B  shows a right-side view of stator  3 . 
       FIG. 8A  shows coil  5  of  FIGS. 4 and 5 , which comprises a bobbin  51 , preferably nylon and about 1.175″ long, and having an outer diameter of about 0.625″ and an inner diameter of about 0.250″. Coil  5  also comprises a winding of, for 12 volt operation, about 3200 turns of #33 magnet wire, having a resistance of about 80 ohms, and having wire leads  56  through which its current is connected. Coil  5  may be protected, if desired, with tape or shrink-tubing applied to its cylindrical surface. Adhesivly attached to the top of coil  5  is patch  70 , preferably 0.063″ of thick dense wool felt about 0.5″ square.  FIG. 8B  shows an end view of coil  5 . 
       FIG. 9A  shows a rear view of the end of core  58  with shoulder  87 . Core  58  is hollow and clears screw  55  of  FIGS. 4 and 5 , save for the internal thread of its front portion, shown in  FIG. 5 , which engages the thread of screw  55  of  FIGS. 4 and 5 . 
       FIG. 9B  is a left-side view of core  58 , preferably made of soft steel about 1 0.250″ in outer diameter. On the rear of core  58  is shown a turned step  87  about 5 mm in diameter and externally threaded to engage nut  54  of  FIGS. 4 and 5 . At the front of core  58  is another step  60 , here shown prior to swaging into trunnion  4  of  FIGS. 4 and 5 . This same step  60  is shown swaged in  FIG. 5 , securing core  56  to trunnion  4 . 
       FIG. 9C  shows a front view of core  58  with its un-swaged step  60 . 
       FIG. 10A  is a left-side view of trunnion  4  of  FIG. 4 , which is preferably made of soft steel about 0.063″ thick. Into it is pressed a stud  73 , preferably of non-magnetic stainless steel, 0.75″ long and having a 6-32 thread. Also shown is a hole  44 , preferably 0.250″ in diameter, into which is to be pressed ferrous bushing  41  of  FIGS. 4 and 5 . 
       FIG. 10B  is a front view of trunnion  4 , showing an aperture  45  though which rotor  2  of  FIGS. 4 and 5  passes. The embedded head of stud  73  is shown, as is a threaded hole  47  that engages screw  74  of  FIGS. 4 and 5 . The edges of walls  48  and  49  of this trunnion are here visible. In addition to their mechanical function, these walls provide additional cross-section to the magnetic path through bushings  41  and pivot  23  of  FIGS. 4 and 5 . Also shown is a hole  46  into which is to be swaged the shoulder  60  of core  58  of  FIG. 10 , as shown in  FIG. 5 . Also shown pressed into holes in trunnion  4  are magnetically-permeable bushings  41 . It is to be understood that when these bushings are pressed into position their inner ends are to engage mating holes in mounting trunnion  6  of  FIG. 4 . Ferrous bushings  41 , are preferably composed of so-called “SAE  863  bronze”, having a 0.125″ bore, a 0.250″ nominal outer diameter, and 0.125″ length. There actual outer diameter is usually about 0.252″ making them a tight press fit in the holes of trunnion  4 . The so-called bronze of these bushings has been chosen for its high iron content, which adds but little reluctance to the magnetic circuit described above. This material is porous and “permanently lubricated” by saturation with a lubricant. Other bushing materials may be used to practice this invention, as ordinary soft steel makes a functional permeable bushing if one is diligent occasionally to lubricate it. 
       FIG. 10C  is right side view of trunnion  4 . 
       FIG. 11A  is a right-side view of mounting trunnion  6  of  FIGS. 4 and 5 , which is preferably made of soft steel about 0.063″ thick. A hole  62 , preferably about 0.252″ in diameter, which freely engages a bushing  41  of  FIG. 10B , is shown, as is a cutout  67  that provides room for the tip of screw  74  of  FIGS. 4 and 5 . 
       FIG. 11B  is a rear view of mounting trunnion  6 , showing an aperture  63  through which rotor  2  of  FIGS. 4 and 5  passes. The edges of walls  64  and  66  of this mounting trunnion are here visible. In addition to their mechanical function these walls provide additional cross-section to the magnetic path through bushings  41  and pivot  23  of  FIGS. 4 and 5 . Mounting holes  61  are provided for fastening this mounting trunnion to the organ console. 
       FIG. 11C  shows a left-side view of mounting trunnion  6 , the front surface  65  of which usually mounts to the organ console. 
       FIG. 12  shows a right-side view of the circuit board  7  of  FIG. 4 , which is preferably made of well-known glass-epoxy, 0.063″ thick. Shown in this figure are the mounting holes  77  through which to fasten it to the trunnion  4  and the stator  3  of  FIG. 4 . Cutout  79  insures that circuit board  7  does not interfere with the operation of actuator  1  of  FIG. 4 . 
       FIG. 13A  shows a side view of cap  57  of  FIGS. 4 and 5 , which is preferably made of nylon, and fits tightly on the tip of screw  55  of  FIGS. 4 and 5 . 
       FIG. 13B  shows a rear view of cap  57  and of a hole  79  into which screw  55  fits. 
       FIG. 14   a  shows a rear view of cam  75 , preferably made of nylon about 0.438″ in diameter, and having a threaded hole  78 , offset from center about 0.093″ and threaded with an undersized internal 6-32 thread that grasps stud  73  of  FIG. 10 . A slot  76  facilitates screwdriver adjustment from the rear of the actuator  1  of  FIG. 4 . 
       FIG. 14B  shows a side view of cam  75 .