You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
   Motorized operators are widely used for controlling the movement of swing doors by remote or automatic control. Typically, swing door operators include an electric motor driving an output shaft through a reduction gear drive for controlling movement of the door between a closed position and an open position, the operator also including a return spring or the like for at least assisting the motor to move the door to the closed position. Several types of swing door operator mechanisms have been developed but prior art operators tend to be mechanically complicated, particularly if adapted for so called universal applications, that is, applications where the operator may be reversed in its working position for swinging doors of opposite “hands” or for controlling doors to swing inwardly or outwardly with respect to the operator, and/or the door frame. 
   It is desirable to provide a swing door operator with low maintenance requirements, and which may be easily adapted for controlling doors in inswing and outswing applications and where the swing movement of the door is of one hand or the other without modification to the operator and while the operator remains reliable for a long life. It is to these ends that the present invention has been developed. 
   SUMMARY OF THE INVENTION 
   The present invention provides an improved swing door operator including a mechanism operable for returning the door from an open position to a closed position regardless of the hand or swing direction of the door. 
   In accordance with one aspect of the present invention a motorized swing door operator is provided which includes a frame which may be mounted on a support member for controlling doors of one hand or the other without major modifications to the operator. The operator is characterized by a frame which supports an electric drive motor driving an output shaft through a reduction gear drive wherein the output shaft of the operator is drivingly connected to a return spring by way of a mechanism including a flexible member, such as a chain trained over a sprocket, connected to the output shaft. The mechanism is mechanically uncomplicated and provides for use of the operator for controlling doors of opposite hand or swing direction when moving from a closed position to an open position and back to a closed position. 
   In accordance with another aspect of the present invention a motorized swing door operator is provided which comprises a frame for supporting a speed reduction gear drive mechanism, a drive motor, a single return spring and a mechanism for storing energy in the spring and returning the spring energy to the operator for moving the door in one direction or the other. The frame may be conveniently mounted on a support plate in two opposed positions, depending on the so-called “hand” of the door to be operated. 
   The present invention also provides a swing door operator which is mechanically uncomplicated, compact, reliable in operation and easily modified as to its working position for controlling an inswing door, an outswing door, and for controlling a door regardless of the direction of swing movement or so-called hand of the door. 
   Those skilled in the art will further appreciate the advantages and superior features of the invention as well as other important aspects thereof upon reading the detailed description which follows in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a swing door operator in accordance with the present invention; 
       FIG. 2  is a front elevation view of the swing door operator shown in  FIG. 1 ; and 
       FIG. 3  is view taken generally along the line  3 — 3  of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In the description which follows like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawing figures may not necessarily be to scale and certain elements may be shown in generalized or schematic form in the interest of clarity and conciseness. 
   Referring to  FIGS. 1 and 2 , there is illustrated a swing door operator in accordance with the invention and generally designated by the numeral  10 . The operator  10  includes an elongated, generally rectangular support plate member  12  which is adapted to mount on a door frame, not shown, generally above a swing door in a conventional manner known to those skilled in the art. The support plate  12  is provided with plural spaced apart fastener receiving holes  14 , several shown in  FIGS. 1 and 2 , for receiving fasteners, not shown, for securing the support plate to a door frame or door jamb. Support plate  12  is adapted to support an operator frame, generally designated by the numeral  16 , which is reversely mountable on the support plate  12  as will be described in further detail herein. Support plate  12  includes spaced apart flanges  12   a  and  12   b  configured for receiving a snap-on removable cover, not shown, for the operator  10 . 
   The operator frame  16  is characterized by spaced apart, generally horizontally extending frame plate members  18  and  20  which are spaced apart by opposed end plates  22  and  24 . The frame plates  18  and  20  are suitably secured to the frame plates  22  and  24  by conventional mechanical fastener  23 , several shown in  FIG. 1 . Frame  16  may be reversely mounted on support plate  12  at opposed faces  16   a  and  16   b ,  FIGS. 1 and 3 , by fasteners  16   c ,  FIG. 3 , one shown, which may be threadedly engaged in opposed bores  18   a  and  20   a  formed in plates  18  and  20 ,  FIG. 1 . 
   The operator frame  16  supports an electric drive motor  26  having a rotatable output shaft  27  drivably connected to a pinion  28 . Drive pinion  28  is meshed with a face gear  30  which is mounted on and drivingly connected to a shaft  32 ,  FIG. 2 . Shaft  32  is adapted for rotation about an axis perpendicular to the axis of rotation of pinion  28  and motor output shaft  27 . Shaft  32  is mounted in suitable bearings  33  and  35  which, in turn, are supported in the frame plates  20  and  18 , respectively. As shown in  FIG. 2 , shaft  32  also drivingly supports a second stage pinion  36  which is meshed with a gear  38 . Gear  38  is mounted on an intermediate shaft  40  supported for rotation parallel to shaft  32  in spaced apart bearings  41  and  43  supported on the respective frame plates  20  and  18 . 
   Referring further to  FIG. 2 , intermediate shaft  40  is also adapted to drivingly support a third stage pinion  44  and third stage pinion  44  is meshed with a gear  46  which is supported on a rotatable operator output shaft  48  mounted parallel to shaft  40  in suitable bearings  49  and  51  mounted on frame plates  20  and  18 , respectively. Output shaft  48  is provided with a suitable drive part  52 , such as a tapered polygonal cross section distal end of shaft  48 , and adapted to be connected to a swing door power arm, not shown, for the operator  10 . Output shaft  48  also supports spaced apart rotary cams  54  and  56  at its opposite end for rotation with shaft  48  and engagable with respective door position limit switches  58  and  60 , see  FIGS. 1 and 2 . 
   Referring also to  FIG. 3 , output shaft  48  is adapted to drivingly support a sprocket  62  suitably keyed for rotation with output shaft  48 . In  FIG. 3 , frame plate  20  has been removed to provide for viewing certain components described herein. Sprocket  62  is engaged with an elongated flexible member comprising a conventional roller chain  64  which is trained around sprocket  62  and is characterized by opposed chain runs  66  and  68 ,  FIG. 3 . Respective chain runs  66  and  68  extend through an opening  69  in end plate  24  and terminate at a pivot link member  70 ,  FIG. 3 . Chain links  66   a  and  68   a  are suitably connected to the member  70  at spaced apart points on opposite sides of an axis  71  by respective pin members  66   b  and  68   b ,  FIG. 3 . 
   Referring further to  FIGS. 2 and 3 , link member  70  is mounted for limited pivotal movement on one end of a return spring transfer shaft  72  by a suitable pivot pin  74 ,  FIG. 3 . Link member  70  is disposed in a suitable slot  75 ,  FIG. 2  which opens to the distal end of the shaft  72 . As further shown in  FIGS. 2 and 3 , return spring transfer shaft  72  extends through a suitable bore formed in a spring cup member  76  and is secured in engagement with cup member  76  by a hex nut  77  and a locknut  78 , both disposed on a threaded portion  72   a  of shaft  72  formed generally on the end of shaft  72  opposite the slot  75 . Cup member  76  is provided with a transverse flange  76   a  engageable with one end of an energy storage member comprising a coil compression spring  80 . The opposite end of spring  80  is forcibly engaged with frame plate  24 . Frame plate  24  is preferably provided with a circumferential groove  24   c  for locating and retaining the return spring  80  in its working position. 
   As will be appreciated by those skilled in the art, the position of the nuts  77  and  78  on shaft  72  may be adjusted for adjusting the position of cup member  76  to provide a predetermined preload force on spring  80  which is reacted through the cup member  76  and shaft  72  to the chain  64  to properly tension the chain runs  66  and  68 . Alternatively, or additionally, the spring  80  may be replaced by springs of different lengths and spring rates to provide the requisite door closing force, which force is transferred as a torque by way of chain  64 , sprocket  62  and shaft  48 . 
   In operation, the operator  10  is suitably controlled by a control unit, generally designated by the numeral  11  in  FIG. 1 , to energize the motor  26  upon receiving a command from a remote controlled switch or an automatic sensor, for example, both not shown. Energization of motor  26  rotates pinion  28  which rotates gears  30 ,  36 ,  38 ,  44  and  46  to provide a high torque low speed rotation effort exerted on shaft  48 . Shaft  48  will rotate in one direction or the other, clockwise, for example in  FIG. 3 , whereby chain run  66  becomes slack while chain run  68  becomes taut and pulls the shaft  72  and spring retainer or cup member  76  toward frame plate  24  thus compressing spring  80  and storing energy therein. Specifically, the operation typically results in a door controlled by the operator  10  to be moved from a closed position to an open position as shaft  48  rotates approximately ninety degrees to one hundred twenty degrees about its axis  52   a ,  FIG. 2 . 
   When the door, not shown, reaches its open position one of switches  58  or  60  is actuated by its associated cam  54  or  56  which may result in control unit  11  energizing the motor  26  to apply braking power to hold the door in an open position, preferably for a predetermined period of time. Once the motor  26  is de-energized or energized at low power in the opposite direction of rotation of pinion  28 , energy stored in spring  80  will cause shaft  72  to translate to the right, viewing  FIG. 3 . Since chain run  68  is taut while chain run  66  is relaxed, the sprocket  62  will rotate in a counterclockwise direction driving the shaft  48  and associated power arm, not shown, attached thereto also in the counterclockwise direction to return the door to its closed position. 
   Those skilled in the art will appreciate that the operation just described may be reversed in its entirety. For example, upon driving the pinion  28  in the opposite direction from that just described during the operation to rotate the shaft  48  in the opposite direction, the chain run  68  will become slack while chain run  66  becomes taut and pulls shaft  72  and cup member  76  toward frame plate  24  also compressing spring  80 . Energy stored in spring  80  is thus returned to shaft  48  to rotate it in the opposite direction when the control unit  11  indicates that the aforementioned door is to be closed. In this way doors of opposite hand or direction of swing may be controlled by the operator  10  as needed, without any significant modification to the operator or adjustment thereof. Moreover, those skilled in the art will also appreciate the mechanical simplicity and dependability of the mechanism for providing storing of energy in spring  80  and returning energy from spring  80  during door opening and closing operations. 
   The fabrication and operation of the operator  10  is believed to be within the purview of one skilled in the art based on the foregoing description. Conventional engineering materials may be used to fabricate the components described herein as well as conventional mechanical assembly and disassembly procedures. Those skilled in the art will also recognize that the roller chain  64  and sprocket  62  may be replaced by various members, including but not limited to a cog belt and drive pulley, for example, or other types of chains and sprockets. 
   Although a preferred embodiment of the invention has been described in detail, those skilled in the art will also recognize that various substitutions and modifications may be made without departing from the scope and spirit of the appended claims.

Summary:
A motorized universal swing door operator includes a motor driving a gear reduction drive mechanism having an output shaft adapted to be connected to a swing door operating arm. The output shaft supports a sprocket around which is trained a chain having opposite ends connected to a link supported on a shaft which is connected to a return spring. The return spring stores and returns energy regardless of the direction of rotation of the output shaft so as to provide the universal operating capability of the operator.