Abstract:
An asymmetrical drive motor and apparatus with the asymmetric drive motor driving a barrier. The asymmetric drive motor drives the barrier at different drive powers according to direction, time of travel, safety requirements or speed. The drive power is controlled by electrically changing the capacitance value for a permanent split capacitor motor.

Description:
The present application is a division, of prior application Ser. No. 10/102,122, filed Mar. 20, 2002, which is hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a movable barrier and more particularly, to a motor for driving a movable barrier such as a garage door. 
     2. Background Description 
     Movable barrier operators and, more particularly, garage door operators are well known and have become very sophisticated to provide users with increased convenience and security. The amount of drive power for such a barrier operator is usually selected based on a trade off between the need for power to start and continue the door&#39;s motion and the noise and vibration generated by the motor, as well as the availability of electrical power. Generally, it is desirable to have a higher power to open the door due to ice and snow freezing the door down. Also, during safety initiated operations larger amounts of power may be desired to reverse or stop the barrier. A problem is that a higher power motor usually create larger levels of noise and vibration and require more electrical power and thus, generate more heat to operate for the same level of mechanical power. 
     For example, in a situation where the door has become extremely heavy such as when the door&#39;s counter balance spring has broken and the door is required to reverse, a low power motor which is adequate to keep a door in motion may not have enough power to overcome both the inertia of motion and the extreme weight of the door. Typically, in selecting a drive motor for a barrier operator, safety takes precedence over noise and vibration or operational electrical efficiency and, the motor is selected to open the garage door in all situations. 
     By contrast selecting a high power motor allows the operator to have enough power to lift the door even when the door&#39;s spring has broken. In this situation the high power operator has the ability to open the door but is often more inefficient and has higher levels of, noise and vibration. 
     The typical motor used in such a garage door operators is a single phase motor. A single-phase motor may be classified as a split phase motor, a permanent split capacitor (PSC) motor, a capacitor start-induction run motor or a capacitor start-capacitor run motor. Further, most single-phase induction motors require a switching arrangement for starting the motor, e.g., switching start windings, a start capacitor, a run capacitor or a combination thereof, to assist the motor in reaching full speed. Capacitor start motors have a start capacitor that is only used to start the motor. 
     Thus, there is a need for a motor than can have higher power during intervals that require it, yet switch to a lower power, to reduce electrical power requirement and noise and vibration. 
     SUMMARY OF THE INVENTION 
     The present invention is an asymmetric drive motor and apparatus with the asymmetric drive motor for opening and closing a moveable barrier. The asymmetric drive motor may drive for example, a garage door open at a first drive power and closed at a second drive power. The first drive power is greater than the second drive power. A motor control circuit receives control commands and controls the motor to provide the first drive power if barrier is being opened and at the second drive power if the barrier is being closed. 
     Accordingly, the asymmetric motor of the present invention has improved power control for selecting higher power or lower power. Further, momentary application of higher power is available if needed at the start of travel for example to overcome inertia or ice that may have frozen the barrier shut. In emergency situations such as when the barrier has encountered an object on closing higher power is available to quickly open the barrier. Further, a power can be adjusted in the motor depending on the load driven by the motor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, aspects and advantages will be better understood from the following detailed preferred embodiment description with reference to the drawings, in which: 
     FIG. 1 shows an example of a movable barrier operator or garage door operator (GDO) according to the present invention; 
     FIG. 2 shows a first preferred embodiment of asymmetric drive motor according to the present invention, which acts as a hybrid permanent split capacitor/capacitor start single phase motor with more power in one direction than in an opposite direction; 
     FIG. 3 is a second preferred embodiment asymmetric drive garage door motor which is substantially similar to the embodiment of FIG. 2; 
     FIG. 4 is a third preferred embodiment asymmetric drive motor substantially similar to the first two embodiments of FIGS. 2 and 3 with like elements labeled identically; 
     FIG. 5 is an example of a controller controlling an asymmetric drive motor such as in FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and more particularly, FIG. 1 shows an example of a movable barrier operator or garage door operator (GDO) according to the present invention, generally referred to by numeral  100 . The preferred GDO  100  includes a preferred embodiment asymmetric drive motor  150  (FIG. 5) and a control circuit  208  (FIG. 5) controlling GDO operation in a head unit  102  that is mounted to the ceiling of a garage  104 . A rail  106  extends from the head unit  102 . A trolley  108  is releasably attached to the rail  106  and includes an arm  110  extending to a multiple paneled garage door  112  positioned for movement along a pair of door rails  114  and  116 . The GDO system  100  includes at least one hand-held remote control transmitter unit  118  adapted to send signals to an antenna  120  on the head unit  102 . Signals from the antenna  120  are provided to the control circuit in the head unit  102 . An external remote control pad  122  is positioned on the outside of the garage and includes multiple buttons thereon for communicating via radio frequency transmission with the control circuit in the head unit  102 . A wall switch module  124  is mounted on a wall of the garage. The wall switch module  124  is a wired remote control connected to the control circuit in the head unit  102  by a wire  126 . The wall switch module  124  may include a light switch  130 , a lock switch  132  and a command switch  134 . An optical emitter  138 , preferably emitting an infrared (IR) beam, is connected via a power and signal line  140  to the control circuit in the head unit  102 . An optical detector  142 , disposed opposite the optical emitter  138  and receiving the IR beam, also is connected by a wire  144  to the control circuit in the head unit  102 . The optical detectors  138  and  142  serve to sense if an obstruction is present in the barrier opening. 
     FIG. 2 shows a first preferred embodiment of asymmetric drive motor  150  according to the present invention, which acts a hybrid permanent split capacitor/capacitor start single phase motor with more or less drive power being selected by a controller of head unit  102 . The motor  150  includes two coils or windings  152 ,  154  in the stator. The common connection of the two windings  152  and  154  is connected to ground or a neutral reference voltage terminal. Capacitor  158  is permanently connected across terminals at the opposite ends of the two windings  152 ,  154 . A second capacitor  160  and parallel bleed resistor  162  are series connected with a relay  164  across first capacitor  158 . Line current is provided through a light relay  166  to a direction relay  168  which selectively passes line current directly to either side of capacitor  158  and one of windings  152 ,  154 . In this embodiment providing line current to winding  152  drives the garage door operator in the up direction. Down relay  170  passes line current to the motor at winding  154  only when the motor is driving the garage door down to close it. 
     When the garage door operator is activated to drive the door down, e.g., by pressing a button on a remote; the control circuit closes light relay  166 ; direction relay  168  remains in the position shown of FIG. 2; down relay  170  is closed; and, higher power relay  164  remains in its open position as shown in FIG.  2 . Alternating line current is provided to coil  154  at capacitor  158 . Capacitor  158  passes a current out of phase with the line current to coil  152 . As a result, the motor  150  drives the garage door down at a first drive power level, e.g., ½ horsepower (hp). When the garage door operator is activated, again, the control circuit closes light relay  166 . However, direction relay  168  switches to the up position, down relay  170  remains open as shown in FIG.  2  and high power relay  164  is closed. Since directional relay is in the up position, line current is provided to coil  152  at capacitor  158  and capacitor  158  provides a current out of phase with the line current to inductor  154 . With higher power relay  164  closed, effectively, capacitors  158  and  162  are in parallel to increase the drive power of the motor, e.g., from ½ hp to ¾ hp. Thus, the motor  150  drives the garage door open with 50% more power than is available for driving the garage door closed. 
     The control circuit may be programmed to keep the high power relay  164  closed for substantially the entire travel of the garage door, keep the high power relay  164  closed for a period of time or, as determined by the sensed speed of the motor  150 . Thus, the high power relay  164  may be closed for a period of time to initially open the garage door. When the high power relay  164  opens, bleed resistor  162  discharges any charge remaining on second capacitor  160 . Alternately, the control circuit  200  (FIG. 5) which includes a motor rotation sensor  226  may sense motor speed and keep the high power relay closed when the door is opening and until the motor reaches a pre-selected speed for a start capacitor-like operation. Also, in emergency situations, e.g., when an object is encountered by the closing garage door or an obstruction is sensed by optical detectors the controller may reverse the travel of the door. At such direction reversal the high power relay  164  is activated when the motor  150  reverses to drive the motor at high power for opening the garage door to recover from the emergency. In addition, the high power relay  164  may be closed to recover from a falling door situation, i.e., when the control circuit detects the door is falling, the motor is activated to keep it from hitting the floor. 
     FIG. 3 is a second preferred embodiment asymmetric drive garage door motor  180  which is substantially similar to the embodiment of FIG.  2 . Accordingly, in FIG. 3 like elements are labeled identically. In this embodiment the second capacitor  182  and parallel bleed resistor  184  are series connected with higher power relay  186  across the direction relay  168  and down relay  170 . Since the higher power relay  186  is energized when the motor  180  is raising the garage door, operation is substantially identical to the above description for operation of the motor  150  of FIG. 2, especially for lowering the garage door. When the door is closed and a button on a remote is pressed to cause the control circuit to activate the motor to open the door, the control circuit closes light relay  166  and switches direction relay  168  in its up position; down relay  170  remains open; and, high power relay  184  is closed. Again, with both the high power relay  186  closed and the direction relay  168  in its up position, the second capacitor  182  is essentially in parallel with the first capacitor  158 , boosting power of the motor substantially as in the embodiment of FIG.  2 . When higher power relay  186  is opened, any remaining charge across second capacitor  182  discharges through bleed resistor  184 . With this embodiment also, the higher power relay  186  may be closed then opened again at the beginning of the opening door travel or during an emergency situation. Alternately, higher power relay  186  may be held on until the motor  180  reaches a selected minimum speed. 
     FIG. 4 is a third preferred embodiment asymmetric drive motor  190  substantially similar to the first two embodiments of FIGS. 2 and 3 with like elements to FIG. 2 labeled identically. In this embodiment both the first capacitor  192  and the second capacitor  160  are switched in by power relays  196  and  164 , respectively. Each capacitor  192 ,  160  has a parallel respective bleed resistor  194 ,  162 . Thus, this embodiment has three selectable drive power levels determined by the first capacitor  192 , the second capacitor  160  and the sum of the two capacitors  160 ,  192 . The power level is selected by closing the appropriate one of power relay  164 ,  196  or the combination thereof. This embodiment may provide increased power on demand, e.g., selecting both capacitors  160 ,  192  when initially opening the garage door. Also, power can be controlled and provided as needed, e.g., when one capacitor  160  or  192  is switched in and the control circuit detects that the garage door is slowing down, the other capacitor  192 ,  160  may be switched in or substituted to boost motor drive. In response to the additional drive power, the drive motor  190  drives the door back to the minimum speed and then reduces power by opening one of switches  164  and  192 . 
     FIG. 5 is an example of a controller  200  controlling an asymmetric drive motor  150  such as in FIG.  2 . The controller  200  is powered by a power supply  202  that converts alternating current from an alternating current source, such as 110 volt AC, to required levels of DC voltage. The controller  200  is mounted in the head unit, e.g., head unit  102  of FIG. 1, with antenna  120  attached to receiver  204  which is coupled via a line  206  to supply demodulated digital signals to a microcontroller  208 . The microcontroller  208  is also coupled by a bus  210  to a non-volatile memory  212 , which stores user codes, and other digital data related to the operation of the control unit  200 . Emitter  138  and infrared detector  142  form an obstacle detector  214  and power and signal lines  140 ,  144  form an obstacle detector bus  218  connected to microcontroller  208 . The obstacle detector bus  218  includes lines  140  and  144 . The wall switch module  124  is connected via wire  126  to the microcontroller  208 . The microcontroller  208 , in response to switch closures and received codes, sends signals over a relay logic line  220  to a relay logic module  222  connected to asymmetric drive motor  150  which has a power take-off shaft (not shown) from the rotor coupled to the transmission of the garage door operator  100  of FIG. 1. A tachometer  226  is coupled to the asymmetric drive motor  150  and provides an RPM signal on a tachometer line  228  to the microcontroller  208 ; the tachometer signal provides an indication of the speed at which the door is being driven. The apparatus also includes up and down limit switches  230 , respectively sensing when the door  112  is fully open or fully closed. The limit switches  230  are connected to microcontroller  208  by leads  232 . A light  234  is controlled by microcontroller  208  through logic module  222 . 
     Accordingly, the asymmetric motor of the present invention has improved power control for selecting higher power or lower power depending on a direction of travel of the garage door. Further, momentary application of higher power is available if needed at the start of travel for example to overcome inertia or ice that may have frozen the garage door shut. Higher power is available in emergency situations such as when the door has encountered an object on closing, higher power is available to quickly open the door. Further, a power can be adjusted in the motor depending on the load driven by the motor and depending on the sensed speed of the motor. In the preceding embodiments the switches for controlling motor activation are shown as relays. Such relays may be replaced by other devices such as semiconductor triacs in other embodiments. 
     The embodiments described include a motor having a pair of windings with a neutral tap at a common winding terminal. The control principles discussed herein are not limited to such a winding configuration, but may apply to any motor configuration capable of producing two or more levels of power output. For example, but not by limitation, the motor could comprise multiple serially energized windings which can be individually removed from providing substantial motive force by switching arrangements such as by shorting across the terminals of individual windings. Further, the increase of power output as well as phase shifting could be performed by reactive components other than capacitors, such as inductors. 
     Having thus described preferred embodiments of the present invention, various modifications and changes will occur to a person skilled in the art without departing from the spirit and scope of the invention. It is intended that all such variations and modifications fall within the scope of the appended claims. Examples and drawings are, accordingly, to be regarded as illustrative rather than restrictive.