Abstract:
A door operator with an electrical back check feature is disclosed. Embodiments of the present invention are realized by a motorized door operator that electrically creates a back check force for an opening door. The door operator simulates the back check normally created by hydraulic means in convention door closers, but without the use of pistons, springs or hydraulic fluid. The door operator includes a motor disposed to operatively connect to a door so that the door will open when the motor moves, and a position sensor to determine a position of the door. A processor is programmed to exert a closing force on the door in the back check region. In some embodiments, the closing force is exerted by injecting a voltage into the electric motor of the door operator.

Description:
BACKGROUND 
       [0001]    Automatic door operators are used on public buildings and residences to allow for access by the physically disabled or where manual operation of the door may be inconvenient to users. The purpose of a door operator is to open and possibly close a door. A variety of electro-mechanical automatic door operators are known. A typical door operator includes an electric motor and a linkage assembly for operatively coupling the drive shaft of the motor to a door so that the door will be opened and closed when the drive shaft rotates. Activation of the door operator is initiated by means of an electric signal generated in a variety of ways such as, for example, a pressure switch, an ultrasonic or photoelectric presence sensor, motion sensors, radio transmitters, wall switches, and the like. The door may then be closed by the operator motor or with a door closer. Many door closers are mechanically actuated and have a plurality of valves and springs for controlling the varying amounts of force applied to close the door as a function of door angle. 
         [0002]    Some door operator systems are provided with clutch mechanisms between the motor and the linkage assembly that enable the door to be moved freely under manual power. Door operators with clutch mechanisms may provide some level of safety when objects are in the door&#39;s pathway of movement. Various clutch mechanisms decouple powered opening systems during the closing cycle, which is particularly necessary in the event of an interruption of power supply or when an obstacle is encountered. 
         [0003]    When a door operator with a clutch mechanism is used with a mechanical door closer, the features of both a door operator and a full-featured door closer can be available to users of the door. As an example, the automatic opening available with a door operator is available, but in addition, varying amounts of force can be applied to the door by the door closer. Many door closers are designed to apply varying forces to a door as a function of the door angle (i.e., the angle at which the door is open). In this regard, when the door is first opened under manual operation, the door closer is designed to generate a relatively small force, which tends to push the door closed, so that the door closer does not generate significant resistance to the user&#39;s efforts to open the door. Many door closers are designed to provide a significant resistive force when the door is pushed open beyond a specific angle, for example, 60 to 70 degrees. This high-force region of operation of the door is often referred to as the “back check” region, and the high force is intended to prevent the back of the door from hitting a wall or stop, possibly causing damage. 
       SUMMARY 
       [0004]    Embodiments of the present invention are realized by a motorized door operator that electrically creates a back check for an opening door. The door operator according to embodiments of the present invention simulates the back check normally created by hydraulic means in a conventional door closer, but without the use of pistons, springs or hydraulic fluid. The back check force in embodiments of the invention is created by electrical control of the motor. 
         [0005]    A door operator according to example embodiments of the invention includes a motor disposed to operatively connect to a door so that the door will open when the motor moves, and a position sensor to determine a position of the door. A memory and a processor are also included, wherein the processor is operatively connected to the motor, the position sensor and the memory. The processor is programmed, for example, by information stored in the memory, to carry out a method of operating the door operator including determining that the door to which the door operator is attached is opening through a back check region, and electronically controlling the electric motor to exert a closing force on the door. In some embodiments, the closing force is maintained until the door comes to a stop. This “back check” force is created by electrical signals sent to the motor. 
         [0006]    In some embodiments, the processor can also determine if a door is being pushed open and prevent the electric motor from opening the door, either before, or concurrently with exerting the closing force on the door in the back check region. In some embodiments, the closing force is exerted by injecting a voltage into the electric motor of the door operator. In some embodiments, this voltage is of the same polarity as the voltage used to close the door where the door operator is also operative to close the door. In some embodiments, the level of the voltage is controlled by a potentiometer operatively connected to the controller. Such a potentiometer, as well as other components such as switches, can provide the means to adjust various operating parameters of the door operator. 
         [0007]    In some embodiments, the processor determines the position of a door by sensing the proximity of a magnet. In some embodiments, this position sensing is accomplished by a position sensor such as a Hall effect device or Hall effect sensor. In some embodiments, the door operator includes a wall switch by which a user can selectively operate the door operator. The position sensor and switch are connected to a control unit which includes the processor. The control unit together with any sensors, input devices and the like form a control system for the door operator and provide the means to control the motor, and the door operator in general. 
         [0008]    In some embodiments, the drive shaft of the motor is operatively connected to an output shaft. A clutch assembly can be mounted to the output shaft and conditionally, operatively engage a rotatable operator arm that can be operatively connected to the door. The clutch assembly in part enables the motor to be disengaged if a user manually opens the door, and if the user manually closes the door in an embodiment where the door operator motor is enabled to both open and close the door. The motor and any components necessary to operatively couple the motor to the door can form the means of opening the door. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of an installed, automatic, motorized door operator according to one embodiment of the present invention. In the illustration in  FIG. 1 , the door is in the fully-closed position. 
           [0010]      FIG. 2  is an enlarged perspective view of the door operator of  FIG. 1  where the door is in a fully-opened position. 
           [0011]      FIG. 3  is a perspective view of an installed, automatic, motorized door operator according to another embodiment of the present invention. In the illustration in  FIG. 3 , the door is in the fully-closed position. 
           [0012]      FIG. 4  is an enlarged perspective view of the door operator of  FIG. 3  where the door is in a fully-opened position. 
           [0013]      FIG. 5  is a schematic, block diagram of the electronic control system of a door operator according to example embodiments of the present invention. 
           [0014]      FIG. 6  is a flowchart that illustrates a portion of the method of operation of a door operator according to example embodiment of the invention, the method being carried out by the electronic control system of  FIG. 5 . 
           [0015]      FIG. 7  is a flowchart illustrating the electrical back check portion of the flowchart of  FIG. 6  in greater detail. The electrical back check in example embodiments of the invention is again carried out by the control system of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The following detailed description of embodiments refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operation do not depart from the scope of the present invention. 
         [0017]    Certain terminology is used herein for convenience only and is not to be taken as a limitation on the embodiments described. For example, words such as “top”, “bottom”, “upper,” “lower,” “left,” “right,” “horizontal,” “vertical,” “upward,” and “downward” merely describe the configuration shown in the figures. Indeed, the referenced components may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations unless specified otherwise. 
         [0018]    As used herein, the term “open position” for a door means a door position other than a fully closed position, including any position between the fully closed position and a fully open position as limited only by structure around the door frame, which can be up to 180° from the closed position. 
         [0019]    Referring now to the drawings, wherein like reference numerals designate corresponding or similar elements throughout the several views, an embodiment of a door operator is shown in  FIG. 1 , and is generally designated at  20 . The door operator  20  is mounted adjacent to a door  22  in a door frame  24  for movement of the door  22  relative to the frame  24  between a closed position and an open position. For the purpose of this description, only the upper portion of the door  22  and the door frame  24  are shown. The door  22  is of a conventional type and is pivotally mounted to the frame  24  for movement from the closed position, as shown in  FIG. 1 , to an open position for opening and closing an opening through a building wall  28  to allow a user to travel from one side of the wall  28  to the other side of the wall  28 . 
         [0020]    Continuing with  FIG. 1 , the door operator  20  includes a back plate  30 , a motor assembly  32 , a control unit  34 , and an operator arm assembly  36  for operably coupling the door operator  20  to a door  22  and including a clutch assembly  38 . The orientation of the door  22  and door operator  20  is a pull side configuration, in which the operator arm assembly  36  pulls the door  22  open towards the same side on which the door operator  20  and hinges  26  are disposed. Alternatively, the orientation could be a push side configuration, in which the operator arm assembly may include a linkage of, for example, two arm links to permit the door operator  20  to push the door  22  open in the direction away from the side of the door  22  on which the door operator  20  is located, as is known in the art. 
         [0021]    The back plate  30  in  FIG. 1  is securely mounted to the upper edge of the door frame  24  using mounting screws  50 , or other fasteners. The back plate  30  extends generally horizontally with respect to the door frame  24 . The motor assembly  32 , operator arm assembly  36 , and control unit  34  are mounted to the back plate  30 . A bubble level  40  is also mounted to the back plate  30 , and may therefore be integral to the back plate  30 , to assist an installer in mounting the back plate  30  to the door frame  24  or surrounding structure horizontally. The level  40  may be attached to the back plate  30  with fasteners or adhesive, and a recess  42  may be machined into the back plate  30  to receive the level  40 . An installer may use the integral level  40  to adjust the back plate  30  such that the level  40  is “level” before mounting the back plate  40  to the door frame  24 . The level  40  may be considered “level,” for example, when the bubble indicates that the level  40  is substantially or completely horizontal (as shown in  FIG. 1 ) or vertical, if the level  40  is vertically oriented on the back plate  30 . 
         [0022]    Still referring to  FIG. 1 , a cover (not shown) may be attached to the back plate  30  to surround and enclose the components of the door operator  20  that are within the limits of the back plate  30  to reduce dirt and dust contamination, and to provide a more aesthetically pleasing appearance. It is understood that although the back plate  30  is shown mounted directly to the door frame  24 , the back plate  30  could be mounted to the wall  28  adjacent the door frame  24 , concealed within the wall  28  or door frame  24 , or mounted to the door  22  with the operator arm assembly  36  mounted to the door frame. 
         [0023]    Referring now to  FIG. 1  and  FIG. 2 , the motor assembly  32  includes an electric motor and a gear train  54 , which may include a planetary gear, mounted to the back plate  30  with a mounting bracket  56 . The motor is a three-phase AC electric reversible motor with a motor drive shaft (not shown). A portion of the drive shaft extends from the housing of the motor. The motor is reversible such that the rotation of the motor in one direction will cause the drive shaft to rotate in one direction and rotation of the motor in the opposite direction will cause the drive shaft to rotate in the opposite direction. A suitable motor for use in the door operator  20  is available from Brother of Somerset, N.J., as model no. BHLM15L-240TC2N, which is a 240 volt motor providing 1/50 HP and a gear ratio of 240:1. 
         [0024]    It will be understood by those skilled in the art that the electric motor may be selected and sized according to the dimensions and weight of the hinged door  22 , and may include a gear train  54  disposed within a casing and include a gear train input shaft (not shown) coupled to the drive shaft of the motor. An intermediate shaft that is the output of the gear train  54  is coupled to the gear train input shaft. The gear train  54  may provide a proper reduction in output drive of the motor necessary to move the hinged door  22  at an appropriate speed. The control unit  34  regulates the operation of the motor and thus regulates the opening and closing of the door  22 . The control unit  34  is in communication with the motor, which is adapted to receive signals from the control unit  34 . The control unit  34  will be further described below with reference to  FIG. 5 . In addition to the electrical back check feature discussed herein, the control unit  34  may also function to maintain the door  22  in an open position for a selected period of time for enabling a person to pass through the door opening. The amount of time that the door  22  is held open may be varied and can be programmed into the control unit  34  at the time of installation, or altered at any time thereafter by reprogramming the control unit. The control unit  34  may also be adjusted to generate signals that control the speed of the motor for controlling the speed of opening the door  22 . It is understood that although the control unit  34  is shown mounted to the back plate  30 , the controller  34  could also be housed internally within the wall  28 , a ceiling, or remotely, such as in a mechanical room, for example. 
         [0025]    The control unit  34  is part of an overall control system which may include an input device in electrical communication with the control unit  34  for allowing a user to selectively control the delivery of electrical energy to the motor. The input device is operable to generate a door movement signal to the control unit  34  which, in turn, is responsive to receiving the door movement signal to control operation of the motor so as to selectively cause the motor to rotate the drive shaft and thereby affect powered opening of the door  22 . The input device may be of any known or desired type. For example, the input device may consist of a manual push pad wall switch for being mounted on the wall, or a post, adjacent to the door  22 . This arrangement is such that a user, such as, for example, a handicapped person wanting to pass through the door opening need only to press the push pad for sending a signal to the control unit  34  to open the door  22 . Various other input devices are also suitable for use, including any type of switch, sensors and actuators, such as pressure pads as in a switch type floor mat and other mechanical switching devices, infrared motion sensors, radio frequency sensors, photoelectric cells, ultrasonic presence sensor switches, and the like. As a result of implementing some of these input devices, an automatically operable door may be caused to open by mere proximity of a person to the door. Such proximity may cause the door to operate by virtue of the interruption of a light beam, distortion of an electrical field, or by actual physical closing of the switch by contact with the person or in response to the weight of the person approaching the door. Consequently, the particular manner for generating a door movement signal to the control unit  34  for energizing the motor can be accomplished through any of various means. 
         [0026]    It should be noted that when the term “input device” is used herein, the term is generally intended to refer to the device used to operate the door by a user on a day-to-day basis. The control unit of embodiments of the invention may receive other “input” from switches, potentiometers, and the like, where this input is designed to enable an installer, maintenance person, or the like to adjust the door operator. This input may include the setting of such parameters as hold-open torque, hold-open time, delay, etc. 
         [0027]    Still referring to  FIG. 1  and  FIG. 2 , an operator arm assembly is provided for applying opening and closing force to the door. The operator arm assembly includes an output shaft  80 , an operator arm  82 , a track  84 , a roller  86  and the clutch assembly  38 . The output shaft  80  is constrained to a vertical orientation by passing through bearings, such as bearing  92 , that are disposed in openings in a bottom brace  96  and a similar top brace that are mounted to the back plate  30  with bolts. The output shaft  80  is coupled to an intermediate shaft with an intermediate shaft bevel gear  98 , fixed to the end of the intermediate shaft, that engages an output shaft bevel gear  100  to translate the direction of rotation 90 degrees. A set screw secures the output shaft bevel gear  100  to the output shaft  80 . However, it is anticipated that other forms of gearing and linkages may be used, such as worm gears, helical gears, rack and pinion arrangements and the like to translate the rotation 90 degrees. Alternative arrangements are feasible; for example, the orientation of the drive shaft and the output shaft  80  axes may be parallel or coaxial. The operator arm  82  is an elongated member that has one end that may be considered an arm hub  108 , defining an opening in which a bearing is disposed, through which the output shaft  80  extends. An annular channel  114  surrounds the output shaft  80  at the arm hub  108 . At the opposite end of the operator arm  82 , the roller  86  is secured at an opening  116 . The track  84  is mounted to the door  22 , and the roller  86  rolls in the track  84  and may apply opening or closing force to the track  84  as the as the door  22  pivots. 
         [0028]    In the embodiment shown, the bottom brace  96  also holds a door position sensor  120 . As best seen in  FIG. 2 , the sensor  120 , preferably an electro-magnetic detection device such as a reed switch, as shown, or a Hall effect sensor device, extends through an opening in the bottom brace  96  to be in close proximity to the annular channel  114  of the operator arm hub. Magnets  124 ,  125  are disposed in the annular channel  114 . One magnet  124  is positioned to be under the sensor  120  when the door  22  is closed, while the other magnet  125  is positioned to be under the sensor  120  when the door  22  is fully open; the position of the magnets  124 ,  125  may be altered around the annular channel  114  to adjust these door positions. By sensing when a magnet  124  is in proximity, the sensor  120  indicates to the control unit  34  the status of the door position as closed, not closed, or fully open. The sensor  120  is in electrical communication with the control unit  34  by means of wires  128 . The sensor  120  may indicate the door position status by either sending signals or not sending signals to the control unit  34  depending on the position of the door and magnets. The switch associated with the sensor  120  may be designed as either normally open or normally closed, operating by sending a signal to the control unit  34  when there is a change in the magnetic field from the normal position, i.e., when the sensor  120  is actuated by a magnet, either ( 1 ) sending a signal when in the presence of a magnetic field and not sending a signal when not in the presence of a magnetic field, or (2) sending a signal when in the presence of a magnetic field and sending a signal when not in the presence of a magnetic field. It will be understood by one of ordinary skill in the art that other sensor and switch technologies may be used to indicate door position; other switches that could be used include microswitches, limit switches, proximity switches, optical sensors, and the like. 
         [0029]    When the control unit senses the “open” magnet approaching, the control unit creates a back check condition by quickly ramping the speed of the door down using voltage injection to the motor. For example, in some embodiments the control unit ramps the speed of the door down within about 50 milliseconds. The control unit then switches to the “hold-open” condition for the door operator. If the “hold-open torque” were adjusted to be very low, the door would feel like it is coasting beyond the open magnet. If the “hold-open torque” were adjusted to be very high it would be very hard to move the door at this point. 
         [0030]      FIGS. 3 and 4  show another embodiment of a door operator  200 . The door operator  200  includes a back plate  30 , a motor  202 , a controller  34 , and an operator arm assembly  204 . In this particular drawing for this embodiment of the door operator wires  72  can be seen interconnecting the controller and the motor. The motor may be selected by one of ordinary skill in the art, and in one embodiment may provide 1/75 HP and have a 200:1 gear ratio. The vertical orientation of the motor  202  eliminates the need that exists in the embodiment of  FIGS. 1 and 2  to translate the direction of rotation of the motor shaft to the output shaft, and makes it possible to shorten the back plate  30  if desired. The motor shaft extends directly to the operator arm assembly  204 . 
         [0031]    The operator arm assembly  204  includes an operator arm  208 , a track  82 , a roller  86 , a magnet holder  210 , a washer  212 , and a nut  214 . The operator arm  208  has an arm hub  216  defining an opening through which the motor shaft and magnet holder  210  extend, and is similar to the operator arm  82  of  FIGS. 1 and 2  but lacks an annular channel  114 . Instead, magnets  220  and  222  may be disposed on the magnet holder  210 , which includes an annular shelf  230  at one end, a tapered neck  232  beneath the annular shelf  230 , and an externally threaded stem  234  extending from the neck  232 . An axial cylindrical bore passes through the magnet holder  210 , and an internal longitudinal channel, not shown, may be provided to mate with a key, also not shown, on the motor shaft, which consequently requires the magnet holder  210  to turn with the motor shaft without slipping. A set screw in a radial opening in the magnet holder  210  also secures the magnet holder  210  to the motor shaft. The magnet holder stem passes through the operator arm opening and the washer  212 , and the nut  214  is threaded onto the stem  234  to secure the arm  208  to the magnet holder  210 . 
         [0032]    A door position sensor  240  is mounted to the back plate  30  with a bracket  242 . The sensor  240  design and operation is similar to the sensor  120  of the door operator  20  of  FIGS. 1 and 2 , but the sensor  240  is mounted horizontally to detect the presence of the magnets  220  and  222  on the shelf  230  of the magnet holder  210 . One magnet  220  is positioned to be in close proximity to the sensor  240  when the door  22  is closed, while the magnet  222  is positioned to be proximate to the sensor when the door  22  is fully open. The position of the magnets  220  and  222  may be altered around the shelf  230  to adjust these door positions. With the operator arm  208  in the closed position as in  FIG. 3 , the magnet  220  is proximate to the sensor  230 ; with the operator arm  208  in the fully open position as in  FIG. 4 , the magnet  222  is proximate to the sensor  230 . In the illustrated embodiment of  FIG. 4 , back check begins as soon as the controller begins to sense the proximity of the “open” magnet as previously described. It should be noted that in an alternate embodiment, additional magnets could be placed on the shelf to indicate other door positions such as the start of the back check region of the swing. 
         [0033]      FIG. 5  shows a control system,  500 , that can be used with a door operator according to embodiments of the present invention. Control system  500  includes controller  502 , programming interface  504 , power module  506 , and optionally, radio receiver/processor  508 . In example embodiments, these components are part of control unit  34  illustrated in the previous figures. Hall effect sensor  510  and push pad switch  512  are connected to the control unit via wires and functionally interface with controller  502 . If provision is made for remote control capability and an RF remote control is used, RF receiver/processor  508  might also be connected to antenna  520  via a wire or wires. The control system  500  serves to control the operation of three-phase motor  550 , which is the electric motor in a door operator according to example embodiments of the invention. 
         [0034]    In the example embodiments described herein, the control system includes components  580  to provide setup parameters to the controller. These components include potentiometers and dip switches. In one example, potentiometers are provided for hold-open torque, hold open time, closing force, obstruction sensitivity, motor delay, and the force by which the door is held closed against a doorframe. A dipswitch is provided to set the door operator for either left hand or right hand operation. Another dipswitch is provided in this example to activate or deactivate push-to-open mode. The hold-open torque is the amount of force by which the door resists movement in the open position. The hold-open time is the amount of time the door will stay open, and the obstruction sensitivity determines how hard the door will push on an obstruction when opening before stopping. In some embodiments, these input components are monitored continuously to determine the operating parameters of the door operator. However, it is possible to design an embodiment where these settings are stored in memory  554 . In such an embodiment, the input components are read at start-up. It is also possible to design an embodiment where these parameters are put in memory  554  through programming interface  504  rather than input via connected components such as potentiometers or switches. 
         [0035]    The power module of  FIG. 5  provides an interface between the controller or processor and the three-phase motor. Such a power module typically provides circuit protection and includes an inverter-based power supply for the motor. A power module to drive the motor may also include under-voltage lock-out and short circuit protection. As an example, a power module that could be used with some embodiments of the invention is the FSBB15CH60C Smart Power Module manufactured by Fairchild Semiconductor Corporation of South Portland, Me., United States. 
         [0036]    Controller  502  in this example embodiment includes a central processing unit (CPU)  552  and memory  554 . Many different types of processing devices could be used to implement an embodiment of the invention, including a processor, digital signal processor, or so-called, “embedded controller.” Any of these devices could include memory along with a processing core such as a CPU, or could use external memory or a combination of internal and external memory. In the illustrated embodiment the memory stores firmware or computer program code for executing a process or method on the CPU or other processor to carry out an embodiment of the invention. Such firmware or computer program code can be loaded into the control unit from an external computer system via programming interface  504 . The process or method of an embodiment of the invention could also be carried out by logic circuitry, a custom semiconductor device, or a combination of such a device or circuitry with firmware or software. As previously mentioned, in some embodiments the memory could also be used to store operating parameters. 
         [0037]    An embodiment of the invention take the form of an entirely hardware embodiment, or an embodiment that uses software (including firmware, resident software, micro-code, etc.). Furthermore, an embodiment of the invention may take the form of a computer program product on a tangible computer-usable storage medium having computer-usable program code embodied in the medium. A memory device or memory portion of a processor as shown in  FIG. 5  can form the medium. Computer program code or firmware to carry out an embodiment of the invention could also reside on optical or magnetic storage media, especially while being transported or stored prior to or incident to the loading of the computer program code or firmware into a door operator. This computer program code or firmware can be loaded, as an example, through programming interface  504  of  FIG. 5  by connecting a computer system or external controller to the programming interface. 
         [0038]      FIG. 6  is a flowchart that illustrates a portion of the operation of a door operator according to an embodiment of the invention. In this particular illustration, the electrical back check is used when a door operator opens the door automatically and a user also pushes on the door part way through the swing of the door. Like most flowchart illustrations,  FIG. 6 . illustrates process  600  as a series of process or sub-process blocks. At block  602  the door is closed. At block  604 , a signal is received by the control unit to open the door. This signal may come from an RF remote control, from a push panel switch, a proximity sensor, or any other input device that allows a user to selectively activate the door operator. At block  606  the control unit activates the motor of the door operator to open the door. 
         [0039]    Still referring to  FIG. 6 , at block  608  the controller in the control unit monitors the current being drawn by the motor of the door operator and at block  610  a determination is made as to whether the current being drawn by the motor is within the normal operating range of the motor. The normal operating range for the current drawn by the motor will be known in advance and programmed into the control unit as part of either the firmware that operates the controller or the operating parameters of the door operator. If the current within the normal range, monitoring continues at block  608 . Otherwise, a determination is made at block  612  as to whether the current is above or below the normal operating range. 
         [0040]    If the current drawn by the motor is greater than the normal operating current at block  612  of  FIG. 6 , it can be assumed that the door is meeting resistance or being pushed closed. The electric motor is stopped at block  614  and the door is closed or allowed to close at block  616 . Processing then returns to block  602  where the control unit waits for another open signal. It should be noted that at bock  616 , the door may be closed by activating the motor of the door operator in the other direction. The door may also be closed manually, or by causing the clutch assembly to allow a spring or other mechanical device to close the door. If the motor begins to draw less than the normal amount of current at block  612 , electrical back check routine  620  is executed prior to the processing returning to block  602 . 
         [0041]      FIG. 7  is a flowchart illustration of the electrical back check process  620  from  FIG. 6  as executed by the controller of a door operator according to example embodiments of the invention. It should be noted that the electrical back check process of embodiments of the invention can be initiated and carried out on its own, without necessarily being triggered by the process of  FIG. 6  or any other process. The back check would occur on its own, for example, in the case where a person pushes the door open without availing themselves of the door operator to open the door automatically. 
         [0042]    Process  620  of  FIG. 7  begins at block  702 . At block  704 , the door is being monitored to determine if it has moved into the back check region and the control unit determines when or whether the door is in the back check region at block  706 . If the door is not moving through or entering the back check region of the swing at block  706 , monitoring continues at block  704 . Otherwise, the electrical back check is initiated at block  708  wherein the control unit causes a voltage to be injected into the electric motor. This voltage is typically of a polarity that is the reverse of the polarity that is used to open the door, or of the same as the polarity of voltage that is used to close the door if the door is operable to be closed under the power of the door operator. If the door reaches a hold open position at block  710 , processing continues to block  712  where the door is held open for a specified time. The door then closes at block  714  and the process ends at block  716 . If the door does not reach the hold open position but remains in the back check region at block  710 , voltage injection continues at block  708 . 
         [0043]    The voltage injection in the embodiment pictured is accomplished by applying a continuous DC voltage to the motor. The level of this voltage is adjusted using the hold-open torque potentiometer. The voltage level is fixed relative to the position of the door in the pictured embodiment; however, an embodiment could be developed in which the voltage changed depending on the exact position of the door if a position sensor were included. A design could also be developed in which a pulsed voltage is used to create the electrical back check. 
         [0044]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. Additionally, comparative, quantitative terms such as “less” OR “greater” are intended to encompass the concept of equality, thus, “less” can mean not only “less” in the strictest mathematical sense, but also, “less than or equal to.” 
         [0045]    Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the invention has other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.