Patent Publication Number: US-11377895-B2

Title: Door operator having an automated roller

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 62/876,230 filed on Jul. 19, 2019, the contents of which are incorporated in their entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
     Not Applicable 
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISC AND INCORPORATION-BY-REFERENCE OF THE MATERIAL 
     Not Applicable. 
     Copyright Notice 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a door opening and closing device that may be integrated into a smart home. More particularly, the invention relates to an automatic roller attachable to the bottom of a door that may be activated to open or close the door upon command. 
     Description of the Related Art 
     Door opening and closing devices are frequently found in airports, malls, supermarkets and other locations where manual operation of the door may be inconvenient to users. Many door operators are pneumatically, hydraulically, or electro-mechanically driven, and typically require substantial operating current and/or voltage. Installation of such a device can include substantial modification to the door, the doorframe, and indeed the structure wherein the door and doorframe are mounted. Installation of such an operator is also expensive and generally requires a skilled professional technician installer. In addition, conventional door operators often are expensive to maintain. 
     Most door operators are also large, bulky units that employ high torque, low rpm electric motors that require at least a minimal amount of gear reduction. Motors of this type are typically large when compared to high rpm motors of equivalent horsepower due to the large size of the magnets necessary to generate such a high torque at a low rpm. Often, these bulky door operators are too large to mount directly to the door and must be mounted on or above the door lintel. This may decrease the overall aesthetic appeal and, without substantial structural modification, may preclude installation and operation of the unit altogether. For example, in a retrofit installation where the upper portion or edge of the door is at or very near the ceiling, the amount of space provided between the door lintel and the ceiling may be insufficient to mount the unit. 
     With the advent of in-home voice activated computer personal assistants such as Amazon Echo® and Google Home®, a multitude of devices for automating various home functions have been developed. Collectively these devices are referred to as “Smart Home Devices.” Thermostats, electrical outlets, doorbells, security cameras, window blinds and home appliances such as refrigerators as well as door locks and garage doors may all now be integrated into a smart home and controlled via a smart phone app, a computer, wireless Internet connections and personal home assistants. One area that has been overlooked are internal doors in a home or office space. While doors may be automatically locked and unlocked, there is a dearth of mechanisms for reliably opening and closing a typical door using only a voice command. 
     The above-described deficiencies of today&#39;s systems are merely intended to provide an overview of some of the problems of conventional systems, and are not intended to be exhaustive. Other problems with the state of the art and corresponding benefits of some of the various non-limiting embodiments may become further apparent upon review of the following detailed description. 
     In view of the foregoing, it is desirable to provide a device for reliably opening and closing a typical door that may be integrated into a smart home and easily installed on any door. 
     BRIEF SUMMARY OF THE INVENTION 
     Disclosed is an automated door closing apparatus. 
     In one embodiment, the apparatus includes an automated roller case affixed to the bottom of a door. The roller is housed within the automated roller case aligned perpendicularly to the width of the door. The case also houses a motor for actuating the roller, a power supply for the motor, and a microcontroller including a wireless interface module connectable to a smart home system. 
     The automated door closing device may also include an inductive charger on the outside of the automated roller case and a complementary inductive charging source plate aligned with an flush against the inductive charger on the outside of the automated roller case when the door is in the closed position. A door stop extends from the automated roller case opposite to the door to which the roller case is affixed. A plurality of cleats for engaging carpeting may also be included on the roller. The microcontroller may include a limit switch that monitors the efficiency of the motor and turns off the motor when the roller has ceased to rotate. 
     In another embodiment, the door operator is incorporated into the bottom of a door, and a kickplate serves as the protective case. The roller is spherical and is rotatable from a retracted position inside the door to an extended position engaged with the floor beneath the door. A pneumatic cylinder or other mechanism rotates or translates the roller between the retracted and extended positions. 
     In another embodiment, the door operator having an automatic roller comprises a roller engaged with a floor underneath a door. The door rotates about a door hinge attached to a doorjamb of a doorway, and the roller has an axis of rotation substantially parallel to a width of the door and coplanar with an axis of rotation of the door hinge. A protective roller case at least partially encloses the roller and is attached to the door. A motor regulated by a microcontroller rotates the roller about the roller&#39;s axis of rotation. The door rotates to a closed position when the roller rotates in a first direction, and translates to an open position when the roller rotates in a second, opposite direction. The roller translates between an extended position engaged with the floor and a retracted position disengaged from the floor. 
     In another embodiment, a door attachment plate removably attaches the protective roller case to an exterior wall of the door. The automated door closing device includes a door stop extending from the automated wheel case opposite to the door to which the wheel case is affixed. The wheel further has a plurality of cleats for engaging carpeting. The microcontroller includes a limit switch that monitors the efficiency of the motor and turns off the motor when the wheel has ceased to rotate. 
     It is therefore an object of the present invention to provide an automated door closing apparatus such as a door operator having an automatic roller integrated into a smart home and retrofitted onto existing doors. 
     These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims. There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a cutaway side view of a door operator having an automated roller in accordance with the principles of the invention; 
         FIG. 2  is an environmental top plan view of a door operator having an automated roller in accordance with the principles of the invention; 
         FIG. 3  is a cutaway side view of an alternative embodiment of a door operator having an automated roller in accordance with the principles of the invention; 
         FIG. 4  is a front plan view of a mounting plate for a door operator having an automated roller in accordance with principles of the invention; 
         FIG. 5  is a perspective view of a roller for a door operator having an automated roller in accordance with principles of the invention; 
         FIG. 6  is a front plan view of a door latching mechanism of the prior arts in accordance with principles of the invention; 
         FIG. 7  is a front plan view of a solid plate for a door operator having an automated roller in accordance with principles of the invention; 
         FIG. 8  is a front plan view of a door modified for use with a door operator having an automated roller in accordance with principles of the invention; 
         FIG. 9  is a front plan view of a doorframe modified for use with a door operator having an automated roller in accordance with principles of the invention; 
         FIG. 10  is a cross-sectional view of an alternative embodiment of a door operator having an automatic roller in a retracted position in accordance with principles of the invention; 
         FIG. 11  is a cross-sectional view of an alternative embodiment of a door opener having an automatic roller in an extended position in accordance with principles of the invention; 
         FIG. 12  is an enlarged view of a roller and motor of a door opener having an automatic roller in accordance with principles of the invention; 
         FIG. 13  is a perspective view of another alternative embodiment of a door opener having an automatic roller in accordance with principles of the invention; 
         FIG. 14  is a side elevation view of another alternative embodiment of a door opener having automatic roller in a retracted position in accordance with principles of the invention; 
         FIG. 15  is a side elevation view of another alternative embodiment of a door opener having an automatic roller in an extended position in accordance with principles of the invention; 
         FIG. 16  is a cross-sectional view of another alternative embodiment of a door opener having an automatic roller in accordance with principles of the invention; 
         FIG. 17  is a top perspective view of another alternative embodiment of a door opener having an automatic roller in accordance with principles of the invention; 
         FIG. 18  is a side perspective view of another alternative embodiment of a door opener having an automatic roller in accordance with principles of the invention; 
         FIG. 19  is a bottom perspective view of another alternative embodiment of a door opener having an automatic roller in accordance with principles of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed subject matter is described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the various embodiments of the subject disclosure. It may be evident, however, that the disclosed subject matter may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the various embodiments herein. 
     The invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. The term “roller” is used throughout to refer to mechanisms utilized to converts rotational motion to linear motion, for example a wheel. However, it should be understood that the “rollers” of the present invention may have any of a variety of shapes, for example cylindrical, spherical, frustoconical, and toroidal rollers are generally all suitable for use in the invention. “Rollers” should be interpreted broadly to refer to any device for converting angular momentum into linear momentum and may therefore include more complicated rollers such as sprocket driven belts similar to tank treads or other devices, unless it is clear from the context that a more specific meaning is intended. 
     In addition, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances. Moreover, articles “a” and “an” as used in the subject specification and annexed drawings should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. 
     Various embodiments of the disclosure could also include permutations of the various elements recited in the claims as if each dependent claim was a multiple dependent claim incorporating the limitations of each of the preceding dependent claims as well as the independent claims. Unless explicitly stated otherwise, such permutations are expressly within the scope of this disclosure. Similarly, the embodiments shown and described herein include elements that perform the same or similar functions but are distinct and one or more ways from each other. Unless explicitly stated otherwise, elements of one embodiment be replaced with one or more similar elements from a different embodiments. For example, some embodiments disclose a spherical roller while other embodiments disclose a cylindrical roller. Unless expressly stated otherwise, it should be understood that these different types of rollers are interchangeable between embodiments and that all such permutations are within the scope of this invention. As an additional example, inductive charging plates disclosed in one embodiment should be understood as components that could be added to other embodiments that do not expressly include inductive charging plates. These are only two examples, and those skilled in the art will appreciate that these various features may be mixed and matched among the various embodiments shown herein. 
     Disclosed is door operator having an automated roller for automatically closing and opening a door, which may be programmed and/or operated remotely for example as a components of a smart home or office. The device includes a motorized roller affixed to the bottom of the door and integrated into a smart home environment. 
       FIG. 1  shows a door operator  10  having an automated roller  20  in accordance with principles of the invention. The door operator is contained within a protective roller case  12  which houses the entire apparatus. The roller case  12  is formed by an outer wall  14  which attaches to a door attachment plate  16  and is at least partially open at the bottom  18 . The roller  20  is powered by a motor  22  housed within the roller case  12 . A power supply, in this embodiment a rechargeable battery  24 , is also housed within the protective roller case  12 . A microcontroller  26 , also inside the protective roller case  12 , has a wireless interface module providing a wireless and/or Bluetooth® connection. A door bumper  28  extends outward from the case  12  in a direction opposite to the door  30 . 
     The roller case  12 , along with the components it houses, is removably affixed to the door attachment plate  16 , which is affixed to the door  30  by screws  32 . This embodiment of a door operator  10  is thus easily retrofitted onto existing doors. The doorstop  28  may be a typical doorstop formed from a metal spring with a rubber end or may optionally have another design such as a telescoping bumper. The roller  20  may include a rubberized exterior wall  34  to improve traction on solid surfaces such as wood or tile. Optionally, the exterior wall  34  of the roller  20  may include cleats, nodules, tread or other similar surface features to better engage carpeting or other surfaces. 
     As best seen in  FIG. 2 , the protective roller case  12  may have a substantially rectangular shape when viewed from above or below, having two sidewalls  36 . One of the sidewalls may include an inductive charger  38  complementary to an inductive charging source plate  40  affixed to a wall  42  adjacent to the door&#39;s frame by a bracket  41 . The door  32  to which the door operator  10  is attached is itself attached to a doorjamb  43  of wall  42  by a hinge  48 . The hinge  48  defines an axis of rotation about which the door  30  rotates. When the door  30  rotates in direction  44  to a position flush with and coplanar with the wall  42 , the door  30  is in the closed position. When the door  30  rotates in direction  46  out of the plane defined by the wall  42  to a predetermined maximum angle of rotation it is in the open position. The angle of rotation is defined such that the closed position represents 0° rotation of the door  30 . The open position can be as much as about 170° or about 90°, roughly perpendicular to the wall  42 . Regardless of the angle of rotation of the door  30 , the angle of rotation  33  of the roller  20  remain substantially parallel to the width  45  of the door  30  and substantially coplanar with the axis of rotation defined by a hinge  48 . When the angle of rotation  33  of the roller  20  is fixed, it is actually slightly skew to planes parallel to the axis of rotation of the hinge  48 . Door operator  230 , shown in  FIGS. 13-15  and explained below, actually allows the axis of rotation of the roller to be adjusted such that it is precisely coplanar with a playing through a door hinges axis of rotation. 
     When the door  30  is in the closed position, the inductive charger  38  and the inductive charging source plate  40  align and lie flush against each other, thereby allowing the rechargeable battery  24  to receive a charge. When the door operator  10  is actuated, it rotates the door  30  in either a closed direction  44  or an open direction  46 . It may be desirable to synchronize the door operator  10  with a door latch opening and closing apparatus in order to allow the apparatus  10  to open a door  30  from a fully closed and latched configuration. The invention may optionally include a transmission or clutch mechanism to disengage the motor  22  from the roller  20  when not in use to allow manual opening and closing of the door  30  without resistance. The device may optionally disengage the motor  22  from the roller  20  whenever the device  10  is inactive. Those skilled in the art will appreciate that the inductive charger  38  in the inductive charging plate  40  may optionally be positioned in the door jam between the door  30  and the wall  42 . Optionally, the motor  22  may operate as a servo motor, preventing rotation of the roller  20  when the motor  22  is not actuated. This allows the door operator  10  to also serve as a doorstop, securing the door  30  at a desired position, preventing rotation about the hinge  48 . 
     When the door operator  10  is integrated into a smart home, a user may simply utter a voice command which is then received and interpreted by a home assistance system which then actuates the door operator  10 . For example, the door operator  10  may be attached to a door to a home office. When the user of the home office desires privacy or to block noise from other regions of the home, he or she may simply say “Alexa, close my office door.” An Amazon Echo® device will receive the user&#39;s command and close his or her office door without requiring the user to get up and walk over and manually close a door. 
     The door closing and opening apparatus of the present invention is shown in the Figures as being affixed to the side of a door that swings outward and is hidden when a door is fully opened, not the side of the door facing the door frame when in the open position. This may generally be preferred because it is the side of the door hidden when the door is open and is therefore less likely to be accidentally impinged upon by people or objects moving through the doorway. Optionally, the door operator may be positioned on the other side of the door. The door operator  10  is also shown affixed to a distal end of a door opposite to hinges  48 . This generally reduces the amount of force required to move the door. Optionally, the door operator may be positioned at any point along the door. 
       FIG. 3  shows an alternative embodiment of a door operator  50  in accordance with the principles of the invention. The door operator  50  is attached to a door  52  and has an automated roller case  54  housing a roller  55  attached to a motor  58  and powered by a rechargeable battery  60 . A microcontroller  62  controls the door operator  50 . The various components are all housed within the protective automatic roller case  54  defined by an outer wall  56  and an attachment plate  68 . The outer wall  56  optionally includes a doorstop  64 . The attachment plate  68  is configured to lie flush against and coextensive with a door mounting plate  70 . The door mounting plate  70  includes screws  72  for securely holding the mounting plate  70  to the door  52  to which it is attached. The door mounting plate  70  includes two hooks  74 . Attachment points  76  on the attachment plate  68  align with and are complementary to the hooks  74  such that the attachment points  76  and the hooks  74  form a secure fastener that holds the roller case  54  securely to the door  52 , but also provides relatively easy and quick detachment from the door  52 . 
       FIG. 4  shows an alternative embodiment of a mounting plate  84  affixed to the side of a door to facilitate attachment of a roller case. The mounting plate  84  has two mounting screws  86  and two hooks  88  for attaching a roller case.  FIG. 5  shows an exemplary roller  90  for use with the invention. Roller  90  is a typical rubberized roller-skate roller. The rubberized outer surface  92  of the roller  90  provides sufficient static friction to allow the door closing apparatus to function properly. 
     The door closing apparatus in accordance with principles of the invention may be employed with additional devices to provide a door that both opens and closes on its own. These additional devices are shown in  FIGS. 7-9 .  FIG. 6  shows a typical door latch mechanism  100 . Each of two knobs  102  may be used to extend or retract a bolt  104  that extends through a bolt plate  106  secured to the door  108  by two screws  110 . To modify such a typical door, the bolt plate  106  is replaced with the solid plate  112  shown in  FIG. 7 . The bolt  104  and/or the entire latch mechanism may be removed from a door. Optionally, the solid plate  112  is affixed over the bolt  104  and the entire latch mechanism, thereby holding the bolt  104  in the retracted position permanently. By preventing the bolt from securing a door in a closed position, the automated door closing device in accordance with the principles of the invention may easily both open and close doors to which they are attached. 
     Because the bolt is removed or permanently retracted, the door is not restrained when in the closed position. To overcome this, the present invention utilizes a pair of magnetic plates  120  and  122  to hold a door in a closed position.  FIG. 8  shows a door  124  having two hinges  126  and a handle  128 . At the top of the door, a magnetic plate  120  is affixed.  FIG. 9  shows a door frame  130  having hinges  132  to which a second magnetic plate  122  has been affixed. When the door  124  closes in the door frame  130 , the magnetic plates  120  and  122  align and hold the door in place due to magnetic force. The automated door closing device in accordance with the principles of the invention applies sufficient force to overcome the magnetic attraction between the plates  120  and  122  so that it may be open and closed freely using only the device. 
       FIGS. 10-12  show an alternative embodiment of a door operator  150  having an automated roller  152  that is retractable.  FIG. 10  shows the door operator  150  in the retracted position  206 , and  FIG. 11  shows the door operator  150  in the extended position  208 . In both  FIGS. 10 and 11 , the door  158  is in the closed position, lying flush and coplanar with a wall  160 . A hinge  162  connects the door  158  to a doorjamb  164  of the doorway  168  in the wall  160 . In this embodiment, the door  158  rotates about the hinge  162  as much as 180° relative to the wall  160 , from a closed position at 0° to an open position of about 90° or more, relative to the wall. Optionally, the hinge  162  may allow the door to rotate in either direction from the closed position, thus translating between about 170° to about −170°, such as for example swinging doors commonly used for entryways into kitchens. The bottom  170  of the door  158  is suspended above the floor  172  which it does not come into contact with. The distance between the bottom  170  of the door  158  and the floor  172  may vary from door to door. One of the advantages of the door operator  150  shown in  FIGS. 10-12  is that it may be installed on any door and begin operation immediately without need for calibrating the door operator  150  according to the distance between the bottom  170  of the door  158  and the floor  172 . 
     In this embodiment, the door operator  150  is mounted on the interior side  174  of a kickplate  176 , which is attached to the door  158  having a bottom region that is at least partially hollow to accommodate the components of the door operator  150 . The kickplate  176  serves as the protective roller case and is attached to and incorporated into the bottom of a door  158 . As a result, the door operator  150  of this embodiment is more discreet and less likely to be damaged. The roller  152  is actuated by a motor  178 . A gearbox  180  connects the axle  182  of the roller  152  to the motor  178 . The roller  152  is substantially spherical which allows it to engage a floor beneath the door without requiring precise measurement of the distance between the floor and the retracted position of the roller  152 . So long as the door operator  150  is capable of extending the roller the distance from the bottom  170  of the door and the floor  172 , the spherical roller  152  when not only engage the floor  172  but will also rotate the door  158  about the hinge  162 . Those skilled in the art will appreciate that this simplifies installation and use of the door operator  150 . 
     The both the roller  152  and the motor  178  which actuates the roller are mounted on a plate  182  which rotates about a pivot pin  184  of a hinge  186 . The pivot pin  184  of the hinge  186  is perpendicular to the kickplate  176 , allowing the mounting plate  162  to rotate upward and downward relative to the hinge  186 . A pneumatic cylinder  190  extends from an anchor point  192 . The actuating rod  194  extends out of the pneumatic cylinder  190  and is attached at its distal end  196  to the plate  182 . A compressor  198  regulates air pressure inside the pneumatic cylinder  190  to extend or retract the actuating rod  194 . An air filter  200  is attached to the air inlet  202  of the compressor  198 . A microcontroller  204  regulates both the motor  178  and the compressor  198 . Either or both of the motor  178  in the compressor  198  may operate as a servo mechanism, that is, positive feedback may be utilized to regulate their actuation. 
     To rotate the roller  152  from the retracted position  206  to the extended position  208  shown in  FIG. 11 , the compressor  198  forces air into the pneumatic cylinder  190 , causing the actuating rod  194  to extend, which in turn rotates the plate  182  downward. When the microcontroller  204  determines that the roller  152  has been extended sufficiently to properly engage the floor  172 , it shuts the compressor  198  off. To achieve this, the microcontroller  204  may be programmed to shut off the compressor  198  when it receives a signal from a sensor indicating that a predetermined maximum air pressure has been attained within the pneumatic cylinder  190 . Optionally, the microcontroller  204  may determine that the roller  152  has been sufficiently extended when the voltage required by the compressor to continue increasing air pressure within the cylinder  190  reaches a predetermined value. Optionally, the microcontroller  204  may use a variety of other sensors to determine when the roller  152  has been sufficiently extended to engage the floor  172 . 
     A buffer tank  209  may also be placed in fluid communication with the pneumatic cylinder  190  to accommodate modulations in internal air pressure of the cylinder  190  as the door  158  rotates about the hinge  162 . For example, there may be dips, bumps, other imperfections or minor obstacles on the floor  172 . The use of a buffer air tank  209  also allows the door operator  152  function in the presence of a doorjamb on the floor  172  or across a slanted or otherwise uneven floor. By incorporating the buffer tank  209 , the roller  152  may traverse an uneven surface more easily. The microcontroller  204  may continuously monitor the air pressure within the cylinder  190  and reactivate the compressor  198  as necessary to maintain a minimum air pressure. By maintaining constant air pressure within the cylinder  190 , the microcontroller  204  ensures that the roller  152  engages the floor  172  sufficient force to efficiently rotate the door  158  about the hinge  162 . Sensors may also be used to detect when the door  158  has been rotated to a predetermined position and provide this information to the microcontroller  204  which may then retract the roller  152  back into the retracted position  206  by reversing airflow through the compressor  198  until the actuating rod  194  is sufficiently retracted into the cylinder  190 . 
     The pneumatic cylinder  190  may optionally be replaced with a hydraulic cylinder or other mechanisms, such as for example a servo motor, for raising and lowering the roller  152 . However a pneumatic cylinder  190  is generally preferred to a hydraulic cylinder because it may use the ambient air, as opposed to a hydraulic cylinder which would require additional components to manage the fluid. In this embodiment, the pneumatic cylinder  190  is oriented approximately 45° relative to the floor  182  when in the roller  152  retracted position  206 . Those skilled in the art will appreciate that the pneumatic cylinder  170  may be oriented in a variety of different configurations so long as it is capable of rotating the plate  182  two rotate the roller  152  between the retracted an extended positions  206  and  208 , respectively. 
     As mentioned above, the motor  178  may also act as a servo, such that it automatically shuts off when the voltage attains a predetermined value, indicating that the door  158  has reached a maximum degree of rotation in a particular direction. The present invention may also optionally include a sensor  210  attached to the hinge  162  which detects the angle between the door  158  and the wall  160 . The microcontroller  204  may be configured to automatically stop at various predetermined angles. For example, the microcontroller  204  may be programmed to cease rotating the door when it has reached a closed position, defined as the door  158  being flush with the wall  160 , or when it has reached a maximal open position, for example defined as the door  158  being perpendicular to the wall  160 . 
     Optionally, the door operator  150  may be used to secure the door  158  in a particular orientation by extending the roller  152  into the extended position  208  engaging the floor  172 , and using the motor  178  to prevent rotation of the roller  152 . The door operator  150  thus acts as a doorstop, holding the door  158  in a fixed position. The microcontroller  204  of the door operator  150  may be preprogrammed or controlled in real time by connecting it to a wireless or directly wired network. In this embodiment, an external power supply provides power to the door operator  150 . 
       FIG. 12  shows the roller  152  in greater detail. A linchpin  210  secures the axle  182  to the roller  152 . A setscrew  212  secures the shaft  214  extending from the gearbox  180 . The distal end  196  of the actuating rod  194  is pivotally attached to connector  220  on the rotating plate  182 . The spherical roller  152  may optionally be replaced with a disc shaped or ovoid roller. However, the spherical roller typically maximizes efficiency over a range of distances between the retracted an extended positions. In addition, the roller  152  and motor  178  may optionally be attached to a sliding rail instead of a rotating hinge. If the roller  152  and motor  178  are extended and retracted by translation in a purely vertical direction, a disc shaped or cylindrical roller may be almost as or equally efficient as using a spherical roller. 
       FIGS. 13-15  show another alternative embodiment of a door operator  230  having a retractable roller  232 . In this embodiment, the roller  232  is cylindrical and is attached to a motor  234  by a gearbox  236 . The bracket  238  for the roller  232  is attached to a mounting plate  240  on which both the motor  234  and the gearbox  236  are mounted. A worm shaft  242  connects the bracket  238  for the roller  232  to a worm drive  244  which raises and lowers the roller  232 . The worm drive  244  is in turn connected to the protective roller case  246  by a rotatable shaft  248 .  FIG. 14  shows the roller  232  in the retracted position  250  and  FIG. 15  shows the roller  232  in the extended position  252 . A microcontroller  254  raises and lowers the roller  232  by actuating the worm drive  244 . The microcontroller  254  also uses a servo motor  258  to rotate the worm drive  244 , roller  232  and motor  234 . The protective roller case  246  of this embodiment attaches to the exterior of the door in a manner similar to that shown for door operator  10  in  FIGS. 1-3 . Because the roller  232  is rotatable, the orientation of the rollers axis of rotation may be altered relative to the door to which it is attached. This allows the axis of rotation of roller  32  to be precisely aligned so that it is precisely coplanar with axis of rotation of a door hinge. Those skilled in the art will appreciate that this will improve the efficiency door operator, minimizing force required to rotate the door. 
       FIG. 16  shows another alternative embodiment of a door operator  270 . Door operator  270  is located inside a door  272 , which serves as the protective roller casing. A motor  274  is controlled by a microcontroller  275  and is powered by a battery  276  which is connected to an inductive charger plate  278  which can be used to recharge the battery  276 . The motor  274  is attached to a differential joint  280  which is connected to and rotates two rollers  282  via two axles  283 , which partially extend downward through the bottom  284  of the door  272 . In this embodiment, the rollers  282  do not retract and must be adjusted during installation to ensure that they adequately engage a floor beneath the door  272 . The differential joint  280  allows each of the rollers  282  to spin at different rates. This is important when the door rotates out word or inward because each of the rollers  282  will travel different distances. 
       FIGS. 17-19  show another alternative embodiment of a door operator  300 . The door operator  300  may be located either entirely or partially within the bottom of a door. The various components are mounted on a protective roller case  302  which is open at the top. Either rechargeable or disposable batteries may be inserted into the battery holder  304  and provide power to the door operator  300 . A microcontroller  306  controls the motors  308 . Each of the motors  308  rotates a separate roller  310 . Each of the rollers  310  partially extend downward out of the slots  312  and engage a floor underneath a door. This embodiment provides more power to the rollers because it uses two motors. 
     The microcontrollers of the various embodiments are all capable of being preprogrammed or receiving instructions in real time, such as for example voice commands using a “smartphone” network system. They are also capable of utilizing motors and pneumatic cylinders as servos so that a door may be secured in a desired position such as an open position, a closed position or another desired orientation of the door. The rollers of the invention may be cylindrical, disc shaped, spherical conical, frustoconical or have another configuration so long as it is efficient in achieving traction with a floor underneath a door, enabling it to rotate a door about a door hinge. If multiple rollers are used, it is beneficial to allow different rollers to have different angular velocities. 
     Whereas, the present invention has been described in relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention. Descriptions of the embodiments shown in the drawings should not be construed as limiting or defining the ordinary and plain meanings of the terms of the claims unless such is explicitly indicated. 
     As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.