Abstract:
A multi-position actuator with three electromagnetic poles where the airgap of selected pole(s) is made different from the remaining pole(s). The multi-position actuator comprises a housing, an armature rotatably mounted in the housing, and three poles journaled around the armature. There is also a stop arm attached to the armature which stops the rotation of the armature when the stop arm hits an adjacent stop. These stops are positioned within the housing to limit the rotation of the armature. This multi-position actuator is designed to form either a fail safe actuator or a latching actuator by adjusting the spacing of the air gap between the poles and the armature. When used with continuous rotation without the stop mechanism, the air gap(s) of the pole(s) can be adjusted in a repetitive manner to produce a useful magnetic torque.

Description:
BACKGROUND OF THE INVENTION 
     FIELD OF THE INVENTION 
     The present invention relates to actuators, which may be used over a limited range or in a continuous direction where the desired result is obtained by varying a gap between a fixed stator pole and the permanent magnet rotatable armature. The proposed actuator can be used as a sector motor for devices that require two or three different positions in either a failsafe or a latching configuration or as in a continuous rotating device, which provides additional rotational energy to that device. 
     SUMMARY OF THE INVENTION 
     The invention relates to a multi-position or continuously rotating actuator, which includes stationary multi-pole (poles) journaled around a rotatable permanent magnet. Essentially, the design of this actuator includes at least two substantially similar poles positioned around an armature and a third pole. The third pole can either be preset at a specific gap distance for a limited range actuator or set to vary at set armature angles for a continuous rotating device. There is an air gap between each of the poles and the rotatable magnet wherein each air gap is set at a distance to produce the desired drive characteristics. Where this device relies on the principle that any freely rotatable magnet will seek or try to seek a position of maximum flux. Thus, with this design, the rotation characteristics of the armature within the housing are dependent upon the differential size of the air gaps between the poles and the armature. 
     With the design of the limited range multi-position actuator, there are a series of suitable mechanical stops that will limit the operating range to less than 180 degrees. The third pole can be adjusted to create either a failsafe mechanism or a latching mechanism. For the failsafe application, when the third pole is set closer to the armature, the rotatable magnet armature will always seek this mid position when electrical power is removed. Thus, when applying power to either of the first two poles, the armature will rotate to match the poles on the armature to these first two poles. When this power is removed, the magnet rotates back to its mid range fail safe position. 
     For the latching mechanism, the mid-pole gap is pre-set further away from the armature when compared to the adjacent poles resulting in the armature being stable or latched to either of the two stops since maximum flux occurs at this angle limited by the stops. When powered, this device becomes a simple two position actuator where the latching force is controlled by the gap setting. For a three-position actuator, the mid position will be obtained by using an auxiliary device such as a helper magnet or a spring detent. 
     For a continuous rotating actuator, the gap distance of the third pole can be varied by using an auxiliary means. Essentially, this gap distance can be made to vary from way out to close in once or twice for each armature cycle for a three-pole device. When timed properly, with the third pole effectively out, forming a large gap, the rotating armature will contribute energy to an attached rotating device by trying to seek a position of maximum flux. When the pole is totally in, forming a tight gap, the armature is effectively balanced and will be in a free wheeling mode. An obvious application for this invention is for a bicycle. If the sprocket hub contains the three-pole device and the rotating sprocket shaft contains the permanent magnet, then a hand linkage could be used to move this third pole in rhythm with the action of the feet pressing on the pedals creating an added energy pulse. 
     Letting go of this linkage will automatically result in the pole being driven to its tight gap stop. The use of a similar design is shown in U.S. Pat. No. 4,662,644 to Nelson, which is incorporated herein by reference. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings, which disclose several embodiments of the present invention. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention. 
     In the drawings, wherein similar reference characters denote similar elements throughout the several views: 
     FIG. 1A shows a simplified view of the adjustable pole continuous rotation armature wherein the poles are all spaced an equal distance apart from the armature; 
     FIG. 1B shows the actuator of FIG. 1A, wherein the armature rotate in a counterclockwise direction; 
     FIG. 1C shows the actuator of FIG. 1A wherein the armature rotates in a clockwise direction; 
     FIG. 2A shows a latching actuator in its middle position; 
     FIG. 2B shows the latching actuator of FIG. 2A in a first latched position; 
     FIG. 2C shows the latching actuator of FIG. 2A in a second latched position; 
     FIG. 3A shows a fail-safe actuator in a fail-safe position; 
     FIG. 3B shows a fail-safe actuator in a second position; 
     FIG. 3C shows a fail-safe actuator in a third position; 
     FIG. 4 shows a plot of a graph showing the rotational torque plotted against the operating angle of the actuator for a failsafe arrangement; 
     FIG. 5 shows a top view of the multi position device; 
     FIG. 6 shows a side view of the multi-position device; and 
     FIG. 7A shows the third pole connected to a hand linkage; and 
     FIG. 7B shows the arrangement of FIG. 7A with the third pole pulled out. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring in detail to the drawings, FIGS. 1A,  1 B and  1 C show a simplified schematic diagram of actuator  10  wherein there are shown poles  20 ,  30  and  40  positioned around an armature  50 . Surrounding poles  20 ,  30 ,  40  and armature  50  is a soft iron shell  60  (SEE FIGS.  2 A- 3 C). Poles  20 ,  30  and  40  are made from a magnetic material such as iron, and their distance from armature  50  is preset or can be adjusted by using a series of adjustment shims (not shown) positioned at the rear portion of the poles, or by providing a hand linkage that adjusts the distance of these pole gaps. 
     As shown in FIGS. 1A,  1 B, and  1 C, the spacing of air gap  70  between pole  40  and armature  50  equals the spacing of air gaps  72  between poles  20  and  30  and armature  50 . With this design, armature  50  is essentially free-wheeling, with no attraction to any pole. Thus, all flux paths are balanced in this situation. 
     FIGS. 2A,  2 B and  2 C show a first embodiment for the limited range actuator, which is a latching version of the actuator  10 . Each of these poles  20 ,  30  and  40  have a series of windings  22 ,  32  and  42  respectively. When power is applied to windings  22 ,  32 , and  42 , each of these windings along with poles  20 ,  30 , and  40  create a magnetic flux that acts upon armature  50 . Armature  50  is essentially a two-pole rotatable magnet in the form of a shaft that is supported by ball-bearings, and connected to a drive (see FIG.  5 ). Armature  50  may be rotated based on a magnetic flux applied to armature  50  by poles  20 ,  30  and  40  surrounding armature  50 . 
     These preset poles or stators are journaled around rotatable armature  50 . Rotatable armature  50  is a permanent magnet that has a north pole  52  and a south pole  54 . Essentially, this multi position actuator is rotatable about an axis when poles  20 ,  30  and  40  are charged. The magnetic torque acting on armature  50  is developed from the differential size of the air gaps between poles  20 ,  30  and  40  and armature  50 . 
     With this design, poles  20  and  30  are positioned closer to armature  50  than pole  40 . Thus, the spacing of air gaps  70  are less than the spacing of air gap  72 . With this embodiment, the typical size of air gap  70  between poles  20  and  30  and armature  50  is 0.015 inches, while the typical size of air gap  72  between pole  40  and armature  50  is 0.05 inches. In the latched design, shown in FIGS. 2A,  2 B, and  2 C, there is no required holding D.C. current for armature  50  to remain in a latched position. As shown in FIGS. 2B and 2C, the rotation of armature  50  is limited by a stop arm  80  which rotates into a series of stops  82  and  84 . With this design, armature  50  can only rotate across a limited range as shown in FIG. 4 when poles  20 ,  30 , and  40  are charged and uncharged. With this latching embodiment, once stop arm  80  contacts either stop pole  82  or  84 , armature  50  remains in that position via because of the magnetic torque developed by the different pole gaps causing the armature to try to seek a position of maximum flux. The middle position  2 B becomes a latching position because of the auxiliary magnet or detent arrangement. 
     FIGS. 3A,  3 B, and  3 C show the fail-safe embodiment of the invention. Here, there is shown a series of poles  20 ,  30 , and  40 , each having windings  22 ,  32 , and  42 . Pole  40  is positioned closer to armature  50  than poles  20  and  30 . Thus, the spacing of air gap  72  is less than the spacing of air gaps  70 . With this design, a D.C. current is required to hold armature  50  in the positions shown in FIGS. 3B and 3C. These positions are shown whereby in FIG. 3B, stop arm  80  is positioned adjacent to stop  82 , while in FIG. 3C, stop arm  80  is positioned adjacent to stop  84 . However, when power is removed from poles  20 ,  30 , and  40 , armature  50  returns to its original position shown in FIG. 3A, wherein stop arm  80  is positioned between stops  82  and  84 , due to the armature seeking a position of maximum flux. 
     Thus for the three position failsafe device, the angular positions may be 45 degree increments where the end positions are spaced at 90 degrees and defined by two hard stops, shown in FIGS. 2A-3C and the middle position by the inherent magnetic restoring torque to the close gap pole. 
     The failsafe type described may also be converted into a latching type by adding a suitable auxiliary device to secure the rotating actuator to the end stops. The auxiliary device may be simply a magnet at the end stops attracting a magnet located on the movable load of sufficient attractive force to overcome the restoring force inherent in the actuator and therefore securing the rotating load against the stop. 
     FIGS. 5 and 6 show a cross-sectional view of a complete latching, three-position assembly including the actuator and a typical load arrangement. Armature  50 , connected to shaft  55 , drives load  97  to any one of three positions. Essentially there are two end positions and a middle position with the end positions defined by stops  82  and  84  and the middle position by means of an auxiliary latching device  105 . The actuator consists of two end poles  20  and  30  with close gaps that provide the latching torque at the stops and a third pole  40 . The third pole  40  provides an electrical means  42  to drive the load to the middle position where the load is indexed and latched by the auxiliary device  105  and the ball detent  100 . 
     The middle position auxiliary switching device consists of a stationary magnet  105  which will be attracted to a magnet  110  located on the rotating load  97 . The rotating load magnet when driven under the stationary magnet  110  will result in an attractive force between the two magnets producing a suitable latching capability for the middle position. 
     With the latching version, there is also included a detent  100  included with the rotating load  97  designed to reduce the inherent overshooting or quivering of the load when driven to the middle position. Detent  100  includes a spring loaded or magnetically attractive ball  102 , which reacts to a stationary detent-magnet  100  to index and secure the load until electrically commanded to switch to another position. 
     All magnets described herein can be neodymium, alnico, samarium cobalt or any other high energy permanent magnets. 
     In a continuous rotating device, the armature magnet will rotate to seek a position of maximum flux. Once reaching this position of maximum flux, the armature will resist moving away because of its inherent restoring torque. 
     FIGS. 7A and 7B presents a view of a device that eliminates or reduces this inherent restoring force to instead provide a device that produces positive energy pulses over two 90 degree intervals during each revolution which results in a total rotation of 180 degrees. In addition, this device presents a suitable linkage in the form of a hand linkage  150  to eliminate the negative energy required to overcome the restoring torque for the other two 90-degree intervals for each revolution. To achieve this result there is provided a three pole device having poles  20 ,  30  and  40 , and an armature  50  housed in a soft iron shell  60 . These poles have equal pole gaps during the 90 degree intervals which are consistent with the restoring force or negative energy which results in free wheeling or zero restoring force. There is also provided a sufficient gap for the third pole during the 90-degree intervals allowing the armature to rotate to a position of maximum flux, thereby contributing to positive energy. With this design, hand linkage  150  controls the axial movement of pole  40  along axis  45  from an inner position show in FIG. 7A, to an outer position shown in FIG.  7 B. 
     This type invention can be used with a bicycle, wherein a bicycle sprocket which has a hand linkage can produce the gap as required and upon releasing the linkage, therefore, all gaps would become equal, having no effect on the bicycle rotation. 
     This principle of gap programming can apply to more than three poles. In addition, the armature magnet can be multi-poled, consisting of more than one north pole, and one south pole. Also, one can invert the arrangement where the armature can be soft iron poles and be stationary and the housing consist of arc magnets and rotate about the stationary armature where the gaps can be varied to produce the desired results. 
     Accordingly, while a few embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.