Abstract:
A method for controlling a door, comprising the steps of storing energy during a manual opening of a door, sensing an object within a doorway, selectively applying a force derived from the stored energy, to close the door, based on the sensing of an object in the doorway. The closure is preferably controlled by an electronic control. A door closing device comprising an energy storage device for storing energy during door opening and releasing the stored energy to subsequently close the door, a damping system for damping a closure of the door, a sensor for detecting an object within a doorway, having an output, a controllable device for selectively restraining the energy storage device from closing the door, and a control system for controlling the controllable device based on the output.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation of U.S. patent application Ser. No. 11/290,168, filed Nov. 30, 2005, now U.S. Pat. No. 8,225,458, issued Jul. 24, 2012, which is a Continuation of U.S. patent application Ser. No. 10/196,684, filed Jul. 15, 2002, which claims benefit of priority from Provisional U.S. Patent Application No. 60/305,130, the entirety of which are each expressly incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of automatic door closing devices, and in particular devices that hold a door open to allow people to pass through. 
     BACKGROUND OF THE INVENTION 
     Door closing devices are well known, and have existed for centuries. A simple string, pulley and counterweigh is sufficient to close a door after opening. Modern designs incorporate hydraulic or pneumatic devices to moderate the closure rate. 
     Modern designs also include fully automatic door controls, which are expensive, and typically require continuous availability of power. These systems are almost universally electrically powered, and employ line power with limited or lacking facilities for closely coupled backup. 
     A typical door closing device provides sufficient closure force to overcome a strong wind, friction, or to push small objects. Due to the damper in the door, a typical symmetric damping function, and a requirement to arm the device while opening the door, opening a door having an automatic door closing device involves application of a significant force. Perhaps more importantly, if a stream of people seek to pass through the door, it is necessary, or polite, for the first person through to hold the door for later people. This often results in significant delays and bottlenecks, since the person holding the door open often must stand in the door passage, applying a force, or stand in a contorted position to avoid being in the doorway.); Hydraulic and pneumatic door closures for controlling closing characteristics of swing doors are well known and have been widely used. See, for example, U.S. Pat. Nos. 4,793,023, 4,414,703 and 4,378,612. Primarily hydraulically, pneumatically operated openers, or opening assist mechanisms are also known. U.S. Pat. Nos. 3,948,000, 3,936,977, 4,955,194 and 4,429,490 teach such mechanisms. Additionally, a variety of electromechanical automatic door operators are known. See, for example, U.S. Pat. Nos. 2,910,290, 3,127,160, 4,045,914 and 4,220,051. Each type of door opener, hydraulic, pneumatic and electromechanical, has its own advantages and disadvantages. It has also been known to combine these mechanisms in order to obtain some of the advantages of each. See, for example, U.S. Pat. Nos. 3,874,117, 3,129,936, 1,684,704, 2,256,613, and 4,438,835. See also, U.S. Pat. No. 5,956,249, expressly incorporated herein by reference. 
     Thus, there is a need for an improved device for closing doors which is power efficient and avoids the requirement for manual override for a second person passing though the door. 
     See, for example, U.S. Pat. Nos. 6,138,412; 6,002,217; 5,992,444; 4,580,365; 5,488,896; expressly incorporated herein by reference. 
     See also, patents now in US Class 16/62, each patent therein being expressly incorporated herein by reference, including but not limited to U.S. Pat. No. 6,154,924 (Door closer unit); U.S. Pat. No. 6,151,753 (Door closer to generate a sudden change in the transmission ratio during the closing phase); U.S. Pat. No. 6,047,440 (Non-rotating pinion cap); U.S. Pat. No. 5,943,736 (Door closer); U.S. Pat. No. 5,802,670 (Door closer); U.S. Pat. No. 5,553,353 (Door damping system); U.S. Pat. No. 5,535,514 (Method for making a hydraulic door closer having a one-piece molded housing body); U.S. Pat. No. 5,502,874 (Speed regulating valve for fluid filled door closers); U.S. Pat. No. 5,343,593 (Door closer); U.S. Pat. No. 5,272,787 (Overhead concealed door closer, mechanically, hydraulically operated); U.S. Pat. No. 5,265,306 (Automatic door closing device); U.S. Pat. No. 5,259,090 (Fluid door closer with means to permit entrapped gases to move); U.S. Pat. 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No. 4,267,619 (Controlled release door holder); U.S. Pat. No. 4,254,308 (Vandal resistant public telephone); U.S. Pat. No. 4,237,578 (Releasable retaining means and fire door control system); U.S. Pat. No. 4,232,798 (Automatic vending machine for delivering containers having edible product therein); U.S. Pat. No. 4,185,356 (Door closer); U.S. Pat. No. 4,179,092 (Mounting device for door closer); U.S. Pat. No. 4,161,804 (Heat-actuated door latch); U.S. Pat. No. 4,161,183 (Vibration sensitive valve operating apparatus); U.S. Pat. No. 4,155,199 (Lockable gate mechanism with automatic reindexing feature); U.S. Pat. No. 4,155,144 (Damper device); U.S. Pat. No. 4,151,380 (Post mounted public telephone); U.S. Pat. No. 4,148,111 (Temperature compensating hydraulic door closer); U.S. Pat. No. 4,146,405 (Unitary dishwasher); U.S. Pat. No. 4,139,182 (Spring device); U.S. Pat. No. 4,130,913 (Door closer); U.S. Pat. No. 4,121,319 (Releasable retaining means); U.S. Pat. No. 4,112,127 (Method for processing and filling a dough product); U.S. Pat. No. 4,103,392 (Door closing apparatus); U.S. Pat. No. 4,102,006 (Door closer); U.S. Pat. No. 4,102,005 (Door closer arm); U.S. Pat. No. 4,083,080 (Door closer); U.S. Pat. No. 4,079,479 (Sliding door closure and locking mechanism); U.S. Pat. No. 4,075,734 (Door closer); U.S. Pat. No. 4,069,546 (Soffit plate and limit stop for use with hydraulic door closer); U.S. Pat. No. 4,069,544 (Electrically actuated door holder and release); U.S. Pat. No. 4,067,084 (Automatic door closer); U.S. Pat. No. 4,064,589 (Door closer); U.S. Pat. No. 4,050,114 (Door closer assembly); U.S. Pat. No. 4,048,694 (Hydraulic door closer with adjustable time delay dampener); U.S. Pat. No. 4,040,144 (Door assister); U.S. Pat. No. 4,034,437 (Pressure-free fail-safe emergency door closer); U.S. Pat. No. 4,016,381 (Switch arrangement for door closers); U.S. Pat. No. 3,989,286 (Device for arresting a door); U.S. Pat. No. 3,966,289 (Electric power coupler); U.S. Pat. No. 3,935,614 (Electromechanical door holder-closer); U.S. Pat. No. 3,934,306 (Door closure device). 
     See also the following patents relating to door closers, which are expressly incorporated herein by reference: IN175305 (A Spring Actuated Door Closer); EP1219770 (Swing Door With Sliding Arm Door Closer); US2002070564 (Door Closer); US2002066228 (Movable Partition With A Plurality Of Laterally Movable Wall Elements); US2002066157 (Door Closer); U.S. Pat. No. 6,397,431 (Spring Assembly Normally Inactive That Opts For Causing Towards Any Position With Reciprocative Door Closer Devices); U.S. Pat. No. 6,397,430 (Adjustable Hydraulic Backcheck Door Closer); US2002063430 (Door Lock Drive Unit); TW459890Y (Improved Structure Of Door Closer); TW459889Y (Improved Structure Of Door Closer); TW430014Y (Sliding Seat For Hydraulic Press Door Closer); TW430013Y (Oiling Control Device For Hydraulic Press Door Closer); IE890371L (DOOR CLOSER); IE800525L (DOOR CLOSER); NZ503115 (Door Closer); NZ502364 (Arrangement For Controlling An Angularly Movable Member); NZ502403 (Device For Controlling An Angularly Movable Member, Such As Overhead Door Closers And Floor Springs); U.S. Pat. No. 6,375,018 (Jewelry Support Rack); U.S. Pat. No. 6,374,505 (Installation Template For A Door Closer; PL346265 (DOOR CLOSER); JP2002038805 (CRIME PREVENTION DEVICE TO FIX DOOR CLOSER); JP2002038791 (DOOR CLOSER APPARATUS FOR VEHICLE); CN2483483U (Closer For Door); U.S. Pat. No. 6,354,343 (Automatic Fueling System And Components Therefor); CA2321871 (DOOR CLOSER); CA2320809 (DOOR CLOSER); CA2311054 (BALANCED DOOR CLOSING APPARATUS); CA2305994 (DOOR CLOSER); JP2002061453 (STOP-ANGLE ADJUSTING MECHANISM FOR DOOR CLOSER); CA2305214 (DOOR CLOSER); AU743753 (Door Closer); JP2002013343 (JOINT DEVICE FOR LINK MECHANISM FOR DOOR CLOSER); TW450308Y (Door Closer); U.S. Pat. No. 6,345,412 (Arrangement For Controlling An Angularly Movable Member); AU3918401 (Door Hinge With Integrated Door Closer); US2002007564 (Installation Template For A Door Closer); US2002007563 (INSTALLATION TEMPLATE FOR A DOOR CLOSER); ZA200000390 (Door Closer.); DE10031786 (Door Closer With Slide Rail And Shaft Comprises Basic And Positively Connected Reinforcing Modules Whose Shafts Protrude From Housing From); DE10030332 (Track For Fixing To Door Frames Or Door Leaves Comprises A Slider, Guide Surfaces Running At An Angle To The Vertical Central Plane Of The); DE10030325 (Slider For Door Frames/Leaves Is Arranged In A Guide Rail So That Moves In The Longitudinal Direction And Is Connected To A Tilting Arm Of); WO0198615 (CONFIGURATION FOR OPENING AND CLOSING A DOOR OR A GATE); US2001054260 (Patio Screen Door Closer); US2001052728 (Motor Vehicle Door Locking System Arrangement); CN2467721U (Closer And Opener With Friction Brake For Sliding Door); JP2001323720 (DOOR CLOSER); JP2001329743 (DOOR CLOSER); CN2463523U (Pneumatic Spring Door Closer); GB2362923 (Installation Template For A Door Closer); EP1159503 (DOOR CLOSER); U.S. Pat. No. 6,317,996 (Installation Template For A Door Closer); U.S. Pat. No. 6,317,922 (Door Closer); DE10023763 (Door With Door Closer Has Drive Housing Mounted To Engage In Or Through Recess Provided In Upper Edge Of At Least The Outer Pane); JP2001303847 (STOP DEVICE OF DOOR CLOSER); JP2001295544 (DOOR STOP ANGLE ADJUSTING MECHANISM FOR DOOR CLOSER); JP2001288956 (DOOR CLOSER); U.S. Pat. No. 6,314,683 (Seal); TW439851Y (Improved Door Closer); U.S. Pat. No. 6,312,803 (Process Of Manufacturing From Natural Fiber A Door Closer And Stopper Which Also Serves As A Scrapper, Wiper Or Mat; U.S. Pat. No. 6,308,749 (Process And Device For Transfer Of Sterile Products Between A Container And An Isolator); GB2361737 (Cavity Closer And Base Frame); CN2455886U (Sliding Door Closer); WO0165041 (DOOR HINGE WITH INTEGRATED DOOR CLOSER); U.S. Pat. No. 6,298,520 (Door Closer And Mounting Bracket); U.S. Pat. No. 6,296,230 (Door Lifting Device); PL342839 (DOOR CLOSER); EP1141508 (DOOR CLOSER MOUNTING BRACKET WITH SCREW HOLDERS); CN2451673U (Hinge Hidden Buffer Door Closer With Braking Device); JP2001234663 (STOPPER FOR DOOR CLOSER); JP2001214661 (JOINT DEVICE BETWEEN ARMS IN DOOR CLOSER); JP2001207723 (HINGED DOOR PROVIDED WITH DOOR CLOSER); JP2001200675 (STOP DEVICE FOR DOOR CLOSER); JP2001193345 (AUTOMATIC DOOR CLOSER); EP1134350 (Blocking Device For A Door Provided With A Door Closer); EP1134349 (Overhead Door Closer With Improved Means Of Rotation); U.S. Pat. No. 6,282,750 (Power Adjustment Size Indicator For A Door Closer); US2001013762 (Automated Garage Door Closer); SK4452000 (DOOR CLOSER); JP2001173306 (DOOR AUTOMATIC CLOSER; TW428658Y (Improvement On Door Closer); HU0101011 (DOOR CLOSER); EP1126119 (Door Closing Arrangement For Double Doors); EP1126118 (Door Closing Arrangement For Double Doors); EP1126117 (Adjustable Power Closure); WO0155541 (DRIVE ROD FITTING); U.S. Pat. No. 6,266,847 (Door Operator And Process For Operation Of A Door Operator); EP1120523 (Turning Device For Sectional Overhead Door); JP2001065233 (DOOR CLOSER); US2001007163 (Damper Assembly That Opts To Open Doors For Usage With Reciprocating Door Closer Devices); HU0100767 (DOOR CLOSER); CN2438809U (Closer For Sliding Door); U.S. Pat. No. 6,260,236 (Door Closer With Hydraulic Back Checking); KR202611Y (LOCKING DEVICE OF A HINGE SHAFT FOR A DOOR CLOSER); GB2358222 (Power Adjustment Size Indicator For A Door Closer); KR202010Y (PISTON OF DOOR CLOSER); KR202006Y (CLOSE CONTROL OF DOOR CLOSER); KR198717Y (DOOR CLOSER); TW417716Y (Modified Hydraulic Door Closer); TW416465Y (Improved Positioning Structure Of Hydraulic Door Closer; KR265254 (DOOR CLOSER); GB897848 (Improvements In Or Relating To A Door Closer); GB754913 (Concealed Door Closer); CN2435488U (Door Closer With Folding Arm); CN1299433T (Hinge Type Automatic Door Closer); WO0142604 (SLIDING PANEL COMPRISING SEVERAL WALL ELEMENTS THAT CAN BE DISPLACED LATERALLY); U.S. Pat. No. 6,240,598 (Arrangement For Controlling An Angularly Movable Member); HU0003821 (DOOR CLOSER); CN2431369U (Automatic Door Closer); U.S. Pat. No. 6,234,520 (Method And Apparatus For Disabling An Airbag System In A Vehicle); KR190952Y (A AUTO STOPPER FOR DOOR CLOSER); KR190951Y (A AUTO STOPPER FIXED DEVICE FOR DOOR CLOSER); KR190950Y (A AUTO STOPPER FOR DOOR CLOSER); KR190914Y (DOOR CLOSER LEVER); CN1293733T (Door Closer); EP1101893 (Blocking Device For Door Closer, Electromagnet And Slider); DE10015769 (Door-Closer Comprises Three Self-Contained Stages Arranged So That Open-Hold-Close Functions Are Performable Through Interaction Of Elements . . . ); EP1096094 (Jack Apparatus For The Opening/Closing Of A Door Wing); DE19951610 (Closure Sequence Control For Two-Paneled Door Involves Door Having Stand Panel And Passage Panel Automatically Closed By Door Closer, Stop); GB750067 (Production And Treatment Of Filamentary Materials; GB217146 (Improved Door Closer And Check); GB413459 (Improvements In Or Relating To Door Closer); GB324872 (Door Closer); GB268623 (Adjustable Door-Closer For Motor-Car Doors); U.S. Pat. No. 6,205,615 (Door Closer); GB581425 (An Improved Automatic Door Closer And Check Device); GB542467 (Improvement In And Relating To Door Closer); GB495687 (Door Closer); DE19946516; WO0123202 (VEHICLE DOOR); U.S. Pat. No. 6,199,222 (Portable Combined Toilet And Waste Holding Tank); GB918777 (Door Closer); GB914660 (Automatic Door Closer); GB908001 (Automatic Door Closer); GB903664 (Door Closer Assembly); U.S. Pat. No. 6,185,868 (Automatic Closer Of Pop-Up Door Of Vehicle); U.S. Pat. No. 6,167,589 (Control Mechanism Including A Permanent Magnet System); GB937926 (Hydraulically Operated Door Closer); GB936320 (Concealed Overhead Door Closer); GB839419 (Door Closer With Expansion Chamber); GB775719 (Door Closer); GB774241 (Door Closer); U.S. Pat. No. 6,179,187 (Ergonomically Enhanced Backpack); U.S. Pat. No. 6,178,698 (Balanced Door Closing Apparatus); GB978966 (Hydraulically Retarded Door Closer); GB978693 (Automatic Door Closer In Combination With Mechanism For Connecting It To A Door); GB879278 (Door Closer); FR2798693 (Automobile Door Lock For Increasing Travel Of Rod Comprises Lock Striker And Return Striker Articulated On Pivots Connected To Lock, Lock R); JP2001049946 (DOOR CLOSER HAVING STOPPER); JP2001049924 (DOOR CLOSER DEVICE); JP2001049923 (DOOR CLOSER DEVICE); GB991149 (A Process And Apparatus For Steel Manufacture); GB982139 (Improvements In Or Relating To A Door Closer); DE19940728 (Profiled Pin For Door Closer Has Plastics Pin Set In Longitudinal Slit Of End Part Of Closer To Be Axially Pretensioned By Screw With Tip); JP2001032618 (DOOR CLOSER TYPE HYDRAULIC HINGE); GB1014354 (Means For Connecting A Door To A Door Closer); GB1000864 (Door Closer); EP1081317 (Door Lock Device With Automatic Door Closing Mechanism); DE10032418 (Cylindrical Door Closer Has Damper And Gas Compression Spring In Cylinder With Sealing Packets For Time Constants); GB1120102 (Door-Closer); GB1114973 (Spring Operated Door Closer With A Hydraulic Check Device); GB1103966 (Automatic Door Closer); GB1103857 (Door Closer); GB1039690 (Door Closer); JP2001012138 (DOOR CLOSER); KR261344 (DOOR CLOSER BODY AND MANUFACTURING METHOD THEREOF); KR187638Y (DOOR CLOSER OF SHIELD ROOM); KR187613Y (DOOR CLOSER OF A HINGE TYPE); KR187428Y (FIREPROOF DOOR CLOSER); KR187352Y (DOOR CLOSER BODY INSERT MOLDED ALUMINUM PIPE); GB1142819 (Hydraulic Door-Closer); TW392032 (Hinge Type Automatic Door Closer); EP1076141 (Door Lock Device For Motor Vehicles); DE19938282 (Fire Safety Door Has Automatic Door Closer With Release Element Activated In Response To Fire For Operation Of Door Closure Element); JP2001003621 (DRIVING CONTROLLER FOR DOOR CLOSER DEVICE); EP1073821 (HINGE TYPE AUTOMATIC DOOR CLOSER); WO0105612 (IMPROVEMENTS TO TELESCOPIC GUIDES USED FOR FIXING NESTABLE DOORS OF RAILWAY WAGONS); IE911745 (Door Closer); IE911447 (Door Closer); DE19953570 (Hydraulic Door Closer Joint Has Axle Fitting Through Lower Rotary Cylinder, Fixing Cylinder And Upper Rotary Cylinder And Has Guide Element); U.S. Pat. No. 6,164,685 (Deployment Door For Air Bag Module); GB2351766 (Cavity Closer/Window Or Door Frame Fixing Clip); EP1066443 (DEVICE IN CONNECTION WITH MOUNTING OF A DOOR CLOSER); EP1064446 (DOOR CLOSER); EP1062401 (DOOR CLOSER); U.S. Pat. No. 6,154,924 (Door Closer Unit); DE10018725 (Closing Sequence Control Device For Two-Leaf Door With Door Closer Transmits Modulated And Encoded Signals Between Resting Leaf And Outer); JP2000291326 (DOOR CLOSER FOR OPENED DOOR); U.S. Pat. No. 6,151,753 (Door Closer To Generate A Sudden Change In The Transmission Ratio During The Closing Phase); KR179181Y (JIG FOR BODY OF DOOR CLOSER); CN1273620T (Door Closer); AU2313300 (Installation Template For A Door Closer); SG73357 (Floor-Mounted Door Closer Device); GR3033849T (AUTOMATIC DOOR CLOSER AND PROCESS FOR MOUNTING THE SAME); U.S. Pat. No. 6,145,942 (Hold-Open Door Closure Assembly And Method For Using Same); KR173511Y (SPEED CONTROL VALVE FOR FLOW PATH OF DOOR CLOSER); JP2000240349 (DOOR CLOSER); JP2000240350 (SLIDING DOOR CLOSER); U.S. Pat. No. 6,138,412 (Door Opener And Closer); EP1051558 (BLOCKING DEVICE FOR A DOOR PROVIDED WITH A DOOR CLOSER); AU2106400 (Door Closer); AU1792300 (Door Closer Mounting Bracket With Screw Holders); U.S. Pat. No. 6,131,967 (Door Lock Assembly For Automotive Vehicles); KR172493Y (DOOR-CLOSER); GB2349173 (Door Closer); WO0061903 (VERTICAL TYPE DOOR CLOSER); U.S. Pat. No. 6,125,505 (Door Closer And Mounting Bracket); KR165486Y (VERTICAL TYPE DOOR CLOSER); EP1042576 (DOOR CLOSER); CN2397236U (Improved Closer For Door); CN1266938 (Lamp Tube Type Noiseless Door Closer); WO0052291 (DOOR CLOSERS); DE19857295 (Automatic Door Closer Has Spring Loaded Sliding Piston Provided With Compression Fitted Minimum Play Linear Sliding Bearing); JP2000204841 (DOOR CLOSER); FR2790275 (Door Closer Has Lock Assembly Masked By Strip With Pivot Rib And Pull Handle); WO0047854 (INSTALLATION TEMPLATE FOR A DOOR CLOSER); EP1030140 (Tray Of Adjustable Capacity For Refrigerator Doors); CN87207062U (AUTOMATIC DOOR CLOSER); U.S. Pat. No. 6,092,334 (Door Locking Device For A Door Closer Having A Fire Actuated Mechanism For Unlocking The Door Locking Device); CN85200341U (AN AUTOMATIC DOOR CLOSER); JP2000192726 (DOOR CLOSER); JP2000186460 (DOOR CLOSER); CN1219214 (DOOR CLOSER UNIT); WO0042283 (DOOR CLOSER); WO0042282 (DRIVE); WO0042281 (DOOR CLOSER MOUNTING BRACKET WITH SCREW HOLDERS); WO0037755 (ARRANGEMENT AT A DOOR LOCKING SYSTEM FOR A MOTOR VEHICLE); WO0036255 (DOOR CLOSER); WO0032897 (DOUBLE-WING DOOR, ESPECIALLY A FIRE PROTECTION DOOR); WO0011297 (DOOR CLOSER); WO0008285 (DOOR CLOSER); CN2377322U (Two-Position Door Closer); JP2000160925 (SAG REMOVING DEVICE FOR WIRE IN CLOSER OF SLIDING DOOR); DE19932291 (Car Door Lock Of Pre-Alerted Swivel Catches Has Catch Axes Eccentric To Their Bearer Axes Using Counterpart Locking Component Opposing End); DE19922916 (Door Closer With Drive For Closing Door Casement Has Spring Piston And Damping Piston Mounted Rotationally Secured Relative To Stroke Cam); DE19901769 (Sequential Door Closer For Double Doors Has Control Device For Controlling Blocking Device Of Overlapping Door Panel Only On Each N—Th One); DE19901517 (Door Closer For Automatically Closing Doors Has Hollow Compensating Body Mounted In Pressure Compensating Chamber Of Piston Cylinder Unit); JP2000130005 (DOOR CLOSER); JP2000104431 (DRIVE CONTROL DEVICE FOR DOOR CLOSER DEVICE); KR205613 (AUTOMATIC STOPPER DEVICE AND DOOR CLOSER FOR FIRE PREVENTION); DE19857297 (Door Closer.); RU2133861(THRUST REVERSER FOR TURBOJET ENGINE WITH DOORS CONNECTED TO FRONT PANEL FORMING INTAKE); KR149513Y (A SIDE CLOSER FOR EMERGENCY DOOR OF FIRE-PROOF SHUTTER); KR149512Y (A SIDE CLOSER FOR EMERGENCY DOOR OF FIRE-PROOF SHUTTER); KR8603003Y (DOOR CLOSER); KR199991 (DOOR CLOSER); DE19855425 (Swing Fire Doors Have Door Closers With Sliding Blocks At The Closer Arms On A Horizontal Guide At The Door Frame And A Lock For The . . . ); CN1248660 (Multi-Purpose Door Closer Installed Behind Door); U.S. Pat. No. 6,061,964 (Portable Remote Controlled Door Closer); AU5623899 (Door Closer); AU4139599 (Door Closer); DE19856285 (Building Break E.G. Window Or Door Closer Hinge Has Axis In Tubular Sleeve Containing Coaxial Hinge Roller Axis Plus Hinge Axis End Cover); DE19855402 (Twin Leaf Fire Door For Building Has Flap, Servo And Locking Strips Mounted Under Common Cover); U.S. Pat. No. 6,049,444 (Rotatable Door And Door Opening Mechanism For A Cartridge); U.S. Pat. No. 6,047,440 (Non-Rotating Pinion Cap); GB2343713 (Door Closer: Mounting Bracket); GB2343712 (Door Closer: Mounting); GB2343711 (Door Closer: External Cover For Pinion Shaft); CN2363031U (Door Bottom Gap Automatic Closer); CN2363011U (Wind-Proof Door Closer); AU1679488 (DOOR CLOSER); EP0993535 (DEVICE FOR TRANSMITTING MECHANICAL CONTROL MOVEMENTS AND/OR ELECTRIC SIGNALS BETWEEN A DOOR ACTUATING DEVICE AND A DOOR CLOSER DEVICE OF A); DE19848071 (Locating Structure Of Oil Pressure Door Closer Is Composed Of A Locating Plate, A Main Body And A Number Of Fastening Pins); AU3443599 (Hinge Type Automatic Door Closer); CN2361797U (Full-Automatic Door Closer For Fire-Proof Door); JP2000054723 (METHOD AND DEVICE FOR REDUCING OPENING OF DOOR CLOSER); JP2000045624 (DOOR CLOSER); CN2357089U (Improved Positioning Structure For Oil Hydraulic Door Closer); U.S. Pat. No. 6,032,330 (Locating Structure Of Oil Pressure Door Closer); U.S. Pat. No. 6,029,403 (Method For The Sealed Mounting Of A Window-Lifter Mechanism In A Vehicle Door And Door For The Application Of This Method); DE19901234 (Door Closer For Building Has Adjustable Spacing Between Drive Shaft And Follower Roller); DE19842568 (Drive Mechanism For Door Closer Preferably Consists Of Piston Cylinder Unit In Housing, Energy Accumulator, And Driven Shaft); JP2000017944 (ADJUSTMENT MECHANISM FOR STOPPING ANGLE OF DOOR CLOSER); JP2000017943 (ADJUSTMENT MECHANISM FOR STOPPING ANGLE OF DOOR CLOSER); JP2000008696 (STOP ANGLE ADJUSTING MECHANISM FOR DOOR CLOSER); U.S. Pat. No. 6,024,137 (Automatic Fueling System And Components Therefor); KR166651 (DOOR CLOSER); ZA9002428 (SLIDING DOOR CLOSER); DE19834889 (Door Closer Has Structured Body Surfaces In A Lightweight Casting To Give A Compact And Visually Attractive Unit); U.S. Pat. No. 6,011,468 (Garage Door Alarm); CN2343292U (Door Closer); CN2342081U (Hinge Type Closer For Door Bottom Seam); AU3350399 (Device In Connection With Mounting Of A Door Closer); AU713769 (A Motorised Door Opener And Closer And A Shuttle Therefor); JP11336424 (SLIDING DOOR CLOSER); JP11324474 (DOOR CLOSER); JP11336416 (CLOSER FOR AUTOMATIC CLOSING USED ESPECIALLY IN VEHICLE DOOR); CN1230624 (Hydraulic Damping Door Closer); U.S. Pat. No. 6,003,568 (Automatic Fueling System And Components Therefor); KR9304980Y (PISTON ASSEMBLY IN DOOR CLOSER); KR9304468Y (DOOR CLOSER); KR9301037Y (ARM IN DOOR CLOSER); KR9301036Y (ATTACHMENT DEVICE IN DOOR CLOSER); KR9301035Y (DOOR CLOSER); KR9203850Y (DOOR CLOSER); KR9108391Y (DOOR CLOSER); KR9107346Y (DOOR CLOSER); KR9104710Y (DOOR CLOSER); KR9101528Y (DOOR CLOSER (KR9010938Y (DOOR CLOSER); KR9009664Y (DOOR CLOSER); KR9009663Y (DOOR CLOSER); KR9000691Y (SPRING PRESS CONTROL DEVICE FOR DOOR CLOSER); KR8800141Y (BRAKING DEVICE OF DOOR-CLOSER); KR8703627Y (O-SHAPE RING OF DOOR CLOSER FOR PREVENTING OF A OIL FLOW); EP0972902 (Door Closer With Reduced Dimensions); DE19831783 (Door Closer With Automatic Closing Action For Swing Doors Has Two Force-Transferring Rods Mounted In Swivel Bearing On One Side And . . . ); JP11324484 (CLOSER FOR TOP-RAILED SLIDING DOOR); JP11315662 (CLOSER FOR SLIDING DOOR); JP11324487 (LINEAR MOTOR TYPE DOOR CLOSER); JP11324450 (DOOR CLOSER DEVICE FOR VEHICLE); JP11324489 (AUTOMATIC DOOR CLOSER); JP11324482 (DOOR CLOSER); KR9301633 (POWERED SLIDING DOOR OPENER/CLOSER FOR VEHICLES); KR9301488 (DOOR CLOSER); KR9301487 (DOOR CLOSER); KR8503284Y (DOOR CLOSER); KR8200088U (DOOR CLOSER); KR8001195U (DOOR CLOSER); KR8000602U (DOOR CLOSER OF A SIGNAL APPARATUS BOX FOR RAILROAD); U.S. Pat. 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No. 5,706,551 (Door Closers And Dampers Primarily For Door Closers); JP9296652 (DOOR CLOSER DEVICE); JP9291737 (DOOR CLOSER DEVICE); JP9291736 (DOOR CLOSER DEVICE); JP9291735 (DOOR CLOSER DEVICE); JP9273353 (DOOR CLOSER JP9287336 (DOOR CLOSER DEVICE FOR CAR); JP9264092 (DOOR CLOSER WITH DOOR OPENING ANGLE LIMITER); GB2314049 (Vehicle Interior Trim Member); U.S. Pat. No. 5,687,451 (Revolving Door Device); JP9228736 (CONTROL DEVICE FOR SLIDE DOOR CLOSER DEVICE); EP0808983 (Door Closer); EP0807741 (Cabinet Door Prop Unit); U.S. Pat. No. 5,680,674 (Device For Controlling The Movement Of A Wing); JP9184355 (DOOR CLOSER STOPPER); U.S. Pat. No. 5,676,459 (Vibration-Tolerant Lamp Mounting Assembly); WO9737099 (WINDOW REGULATOR WITH IMPROVED GLIDER ASSEMBLY); ZA8001593 (DOOR CLOSER); ZA7904400 (SLIDING DOOR STARTER AND CLOSER); U.S. Pat. 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No. 5,630,248 (Door Closer With Semi-Automatic Latching); DE19606204 (Electromechanical Restraint For Door With Automatic Door Closer); DE19540506 (Automatic Door Closer With Shafted Rod Off Spring); DE19540505 (Automatic Door Closer With Damped Rod Movement); U.S. Pat. No. 5,529,148 (Automatic Brake And Hold Mechanism For Sliding Rods); U.S. Pat. No. 5,519,988 (Narrow Row Cotton Picker And A Row Unit Therefor); U.S. Pat. No. 5,515,649 (Automatic Door Operator); U.S. Pat. No. 5,510,686 (Automated Garage Door Closer); U.S. Pat. No. 5,379,033 (Remote Control Device); U.S. Pat. No. 5,131,188 (Automatic Return Mechanism For Sliding Door Or Window); U.S. Pat. No. 5,016,317 (Lightly-Operating Automatic Door Closer With Double Cylinders); U.S. Pat. No. 5,004,148 (Automatic Flag For Rural Mailbox); U.S. Pat. No. 4,953,260 (Automatic Door Closer Having An Adjustable Torsion Spring And Configured End Fittings); U.S. Pat. No. 4,894,883 (Door Closers); U.S. Pat. No. 4,845,811 (Automatic Door Closer Having An Adjustable Torsion Spring And Configured End Fittings); U.S. Pat. No. 4,756,051 (Door-Closer Hinge With Rotary-Movement Shock Absorber); U.S. Pat. No. 4,660,250 (Door Closer); U.S. Pat. No. 4,658,545 (Automatic Door Opener And Closer); U.S. Pat. No. 4,639,969 (Door Closer Mechanism); U.S. Pat. No. 4,501,090 (Automatic Door Operator For Swing Doors); U.S. Pat. No. 4,483,043 (Automatic Door Closer); U.S. Pat. No. 4,460,030 (Collapsible Garage Door); U.S. Pat. No. 4,376,323 (Automatic Door Closer); U.S. Pat. No. 4,366,595 (Door Closer); U.S. Pat. No. 4,357,732 (Automatic Door Closer Kit); U.S. Pat. No. 4,349,939 (Automatic Door Closer); U.S. Pat. No. 4,289,995 (Electric Door Operator With Slip Clutch And Dynamic Braking); U.S. Pat. No. 4,234,996 (Automatic Door Closer Constructed For Releasably Holding A Door In A Predetermined Partly Open Position); U.S. Pat. No. 4,067,084 (Automatic Door Closer); U.S. Pat. No. 4,054,008 (Automatic Door Opening Arrangement); U.S. Pat. No. 3,874,117 (ELECTRIC DOOR OPENER); U.S. Pat. No. 3,787,924 (AUTOMATIC DOOR CLOSER WITH SUBSTANTIALLY PRISM-SHAPED HOUSING); U.S. Pat. No. 3,776,611 (AUTOMATIC DOOR CLOSER); U.S. Pat. No. 3,724,023 (AUTOMATIC DOOR CLOSER); U.S. Pat. No. 3,699,608 (AUTOMATIC DOOR CLOSER); U.S. Pat. No. 3,668,737 (AUTOMATIC DOOR CLOSER); U.S. Pat. No. 3,518,715 (AUTOMATIC HINGE-MOUNTED DOOR CLOSER); U.S. Pat. No. 3,474,485 (AUTOMATIC UNIVERSAL DOOR CLOSER); U.S. Pat. No. 3,409,341 (Automatic Door Closer); U.S. Pat. No. 3,147,034 (Automatic Vehicle Door Window Closer); U.S. Pat. No. 3,108,315 (Automatic Door Closer, Especially Loft Door Closer); U.S. Pat. No. 3,098,259 (Automatic Door Closer); U.S. Pat. No. 3,078,500 (Automatic Door Closer And Check Mechanism); U.S. Pat. No. 2,945,255 (Adjustable Hold-Open Guide Rail For Automatic Door Closer); U.S. Pat. No. 2,177,059 (Thermally Controlled Automatic Door Closer); U.S. Pat. No. 2,059,833 (Automatic Safety Overhead Door Closer); U.S. Pat. No. 1,908,706 (Automatic Door Closer); U.S. Pat. No. 1,868,149 (Automatic Door Opener And Closer); U.S. Pat. No. 1,786,782 (Automatic Door Closer); U.S. Pat. No. 1,714,887 (Automatic Door Closer); U.S. Pat. No. 1,705,334 (Automatic Door Closer); U.S. Pat. No. 1,599,729 (Automatic Electric Door-Closer Structure); U.S. Pat. No. 1,590,690 (Automatic Door Closer And Lock); U.S. Pat. No. 1,455,691 (Automatic Door Closer); U.S. Pat. No. 1,346,366 (Automatic Door-Closer); GB2293198 (A Door Latch Having A Serrated Striker Element); GB2257590 (MICROWAVE OPERATED AUTOMATIC DOOR); GB2214566 (Door Actuator); GB2204093 (Automatic Door Closer); GB2192426 (AUTOMATIC DOOR CLOSER); GB2190954 (Automatic Door Closer); GB2082248 (AUTOMATIC DOOR CLOSER); GB1400661 (AUTOMATIC DOOR CLOSER); FR2738865 (Door Closer To Facilitate The Automatic Closing Of A Door); WO9626344 (AUTOMATIC DOOR CLOSER AND PROCESS FOR MOUNTING THE SAME); WO9532145 (AN ANTI-CRUSH SAFETY DEVICE FOR AUTOMATIC DOORS, IN PARTICULAR FOR LIFTS AND ELEVATORS HAVING TRANSPARENT DOORS); WO9502107 (REVOLVING DOOR DRIVE); WO8809860 (AUTOMATIC DOOR-CLOSER); EP0757742 (AUTOMATIC DOOR CLOSER AND PROCESS FOR MOUNTING THE SAME); EP0635613 (A Sliding Door Stopper Device.); EP0390178 (Sliding Door Closer.); EP0368871 (AUTOMATIC DOOR-CLOSER.); EP0252554 (Automatic Door Closer.); EP0170940 (Operating Process Of A Door Closer, And Door Closer.); EP0166285 (Automatic Door Closer.); EP0137861 (Automatic Door Closer.); EP0120489 (Time-Controlled Window Closer.); EP0068963 (Automatic Door Closer Incorporating Braking Means.); DE19506355; DE19501565 (Mechanical Assembly System For Producing Door Or Window Drive); DE19500844 (Door Drive Esp. Door Closer For Automatic Door Closing And Manual Opening Of Door); DE4323152 (Swing-Door Drive); DE4323151 (Swing-Door Drive); DE4101640 (Automatic Door Closing Device With Hydraulic Damper—Has Pressure Compensating Chamber For Damping Fluid); DE4002889 (Body For Automatic Door Closer—Is Formed From Aluminum Or Plastics Extrusion); DE3906356 (Door Closer); DE3839188 (Lock For One-Handed Operation); DE3527287 (Automatic Closing System For Fire-Proof Cabinets); DE3411189 (Automatic Door Closer); DE3320609 (Automatic Door Closer With Electrohydraulic Stop Device); DE3315913 (Automatic Door Closer Having A Hydraulic Stop Device); DE3234319 (Automatic Door Closer); DE3225559 (Automatic Door Closer With A Hydraulic Stop Device); DE3117193 (Time-Controlled Window Closer); DE3116881 (Dynamic Door Closer); CZ278798 (AUTOMATIC DOOR CLOSER); CN2242312U (Automatic Door Closer); CN2213217U (Automatic Closer For Door); CN2193910U (Crankshaft Automatic Door Closer); CN2193909U (Automatic Door Closer); CN2143660U (Multifunction General Automatic Door Closer); AU4481096 (Automatic Door Closer And Process For Mounting The Same); AU1808888 (AUTOMATIC DOOR-CLOSER); CN1083161 (Automatic Door Closer); JP8126714 (DOOR CLOSER WITH AUTOMATIC CLOSING DEVICE); JP52081940 (AUTOMATIC DOOR CLOSER); JP57054684 (AUTOMATIC DOOR CLOSER); JP55022570 (FLAP DOOR AUTOMATIC CLOSER); JP56003777 (AUTOMATIC DOOR CLOSER); JP52121940 (AUTOMATIC DOOR CLOSER); JP57137581 (AUTOMATIC DOOR CLOSER); JP1187278 (AUTOMATIC CLOSER FOR AUTOMOBILE DOOR); JP52087845 (AUTOMATIC DOOR CLOSER). 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention provides a power efficient door closing device whose design permits operation without a permanent line power connection, for example, a device whose primary door closing functions are principally powered from the initial opening of the door. 
     Another aspect of the present invention provides a door closing device which stores door closure energy, and comprises a lock which prevents closure based on a doorway sensor, e.g., a sensor for detecting a subsequent person passing though the door. 
     A further aspect of the invention provides an automatic or semiautomatic door control which is energy and space efficient, low cost, and which is readily installed without requiring permanent line wiring, while providing the benefits of an electronic control. The control therefore derives operational energy from manually initiated door movement, which is extracted and later employed to operate the control, close the door, or both. 
     According to a preferred aspect of the invention, a door closer presents a counter force to door opening, and thus tends to maintain the door in a closed position, unless restrained. This serves two purposes; first, the force counters wind, other air pressure differences, and incidental jarring to change the position of the door. Second, the energy exerted by moving the door against the counter force is preferably captured and efficiently reutilized in a controlled manner. In contrast to simple hydraulic door closers, an intelligent control is provided which restrains door closure based on a sensor, rather than a simple immediate or time delayed closure. 
     Known sensors for detecting persons in doorways, such as pad sensors in the walkway, passive infrared sensors, ultrasonic sensors, microwave sensors, optical sensors (imaging or non-imaging), or the like may be used, alone or in combination. Preferably, however, the sensor is part of or operates in close proximity to a door closer mechanism, and does not require separate wiring to a distant location. 
     The sensor and control system typically requires a power source, which may be a battery, solar power, wired power, an energy draw from the door opening, or the like. In many instances, the control will be capable of operation at low power draw, and therefore battery power for the control will be possible. The use of a battery for powering the electronic control allows a reliable power source independent of door operation. On the other hand, powering large or power intensive actuators with a battery will likely result in short operating life and frequent service to replace the battery. Therefore, it is preferred that any power intensive actuators draw energy from the door operation. In low duty operation environments, such as homes or some offices and closets, battery power is a feasible option for actuator power, especially lithium batteries. 
     Since the device is operative principally to delay closure of the door, the sensor need only be operative while the door is open, and thus the duty cycle of operation will typically be small. Further, since the control system need only block closure, a single valve or solenoid, magnetic clutch, or other device, may be used, requiring only a small amount of power. 
     The device preferably mounts in the place of a known type of door closing device, to the door and door frame, and thus does not require a specialized installation. Other mounting options include in a space within the door, within the door frame, or as a part of one or more hinges. 
     In a preferred design, a door closing mechanism includes a hydraulic cylinder damper coupled with a spring, acting together to slowly close the door. According to the present invention, a controllable valve is provided to selectively block flow of hydraulic fluid, halting the closure of the door. This valve is, for example, a latching solenoid actuator (i.e., drawing power only when switching states) acting on a piston having a cross-drilled hole. In one position, fluid flows through the hole. In the other position, the hole is not aligned with corresponding flow passages, and no flow occurs. As can be seen, the power required by the system is typically the power to operate the electronic control, the power required to operate the sensor, and the power require to operate the actuator. Assuming the door is operated 4 times per day over the course of a year, there are less than 1,600 cycles of operation. If the system has a quiescent draw of 100 μA, and an operating draw of 1 A for 2 seconds per closure, then the total power for operation over a year will be less than about 2 AH (0.875 AH quiescent plus 0.811 AH active). Therefore, under such use, a primary lithium battery could be employed to power the entire system, with an annual replacement cycle. On the other hand, as the duty cycle increases, the ability to reasonably provide a low maintenance reliable system running off battery power decreases, and power extraction systems become more cost efficient. 
     A sensor mounted on the door closing device detects whether there is traffic within the doorway. If there is traffic, the door is restrained. Since people are conditioned for dumb (i.e., non-intelligent) door closing devices, and will be tempted to manually hold the door, a visual indicator, such as a blinking light emitting diode (LED) is provided to alert users that the device is operational. When the door is opened, a magneto generator may be operated, which charges a supercapacitor or rechargeable battery. A set of primary back-up batteries may also be provided. Since the magneto operation will damp the opening of the door, the hydraulic cylinder is provided with an asymmetric flow pattern, such that there is little hydraulic damping during door opening, since this would be redundant and would consume power which could be efficiently used by the magneto. 
     The sensor is preferably a passive infrared sensor system, with sensitivity in both directions (i.e., ingress and egress), as well as a micropower microwave sensor, to detect existence and movement of objects (e.g., by radar techniques including phase shifts, Doppler shift and echo). A control is activated when the door is open, and begins reading sensor data. In a typical case, at least one person will pass through the door after it is opened. Thus, the control awaits this passage. In the rare case that no person passes through, or the sensors fail to read the person, the control allows the door to close after a preset period. If the control is inoperative, the door defaults to a standard mode that emulates a traditional door closing device. Thus, the control is preferably fail-safe. In addition, it is also possible for the control to provide additional functions, such as door locking, fire alarm mode, RFID and theft prevention using RF, magnetic, optical or other known techniques, room occupancy sensing (e.g., for public rest rooms), and wireless communications. 
     After the first person passes through the door, the control analyzes sensor data to determine whether a second person is passing through the doorway. If so, then the door remains restrained from closing until the doorway is clear. A visual indicator is provided to indicate that the door is restrained, and preferably also indicates when the door is about to begin closing with a different signal, for example a different visual signal and possibly an additional audio signal. A voice or sound sensor system may also be provided to allow the door to be instructed. For example, a speaker independent voice recognition could be programmed to detect a number of variants of “hold door!”, including foreign languages. Likewise, an instructed override could also be programmed for “close door!”, which would override operation in extenuating circumstances, for example where a dog is meant to be left outside, but follows its master. Likewise, the sensor or control may be adapted or programmed to distinguish between types of operating conditions. 
     As stated above, in a preferred high duty cycle design, the door opening operates a mechanical to electrical energy transducer, e.g., a magneto. In a typical design, as the door is opened, a gear train rotates an armature within a magnetic field, generating an electrical current. This electrical current is either directly, or through a power converter, used to store charge in a large-valued capacitor or rechargeable battery (or hybrid type device), for subsequent operation of the system. The opening of the door also activates the control, which begins monitoring the sensors. As the door opens, there will typically be a person on one side of the doorway. (If there is no person detected, the system may be programmed to interpret this as a wind gust, and the door opening may be restrained. In this way, the normal closing force may be limited to a level less than the wind gust force). The sensors detect this person, and monitors as he or she passes through the door, and out of the doorway. During this period, the closure is prevented. After the initial person passes through the doorway, the sensors determine whether there is another person entering the doorway. If so, the closing device remains locked open. If not, the valve is released, and the hydraulic closing device allowed to close the door. 
     In an alternate embodiment, the hydraulic damper is dispensed with, and the magneto serves to damp the opening and closing. The load on the magnetic may be controlled to provide various damping factors. The control, in this case, is preferably a magnetic clutch to stop the armature from rotating, or a solenoid brake operating on a displaceable rod that moves with the door. In this case, in order to extract sufficient energy from a door opening event to complete a subsequent door closing event, the force applied for door opening will generally exceed the door closing force. Otherwise, a supplemental source of power may be provided. For example, in an office ceiling, there are often ballasts for fluorescent lighting. These ballasts emit a substantial amount of magnetic waves, which may be captured by a coil antenna and stored. Likewise, exterior doors may receive sunlight, which may be converted with a solar cell into electric power. 
     In order to provide resilience against externally applied forces, a bypass or friction plate is provided to prevent damage to the closing device. 
     A battery backup, for example having alkaline or lithium batteries, is provided in case the charge on the capacitor is insufficient for operation. The audible or visual indicator may provide a low battery indication. These batteries also allow some operation of the device while the door is closed, for example to periodically self-calibrate sensors for a non-operating condition. 
     It is understood that the present invention therefore provides, according to a first embodiment, an improvement for a standard door closer in the manner of an intelligent control, which, for example, may be retrofitted to existing door closers or form the basis for an improved design. In a second embodiment, an electrical system replaces the traditional hydraulic system to provide improved performance, enhanced control capability, and potentially more cost effective manufacture. 
     The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention as will be described. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the following Detailed Description of the preferred embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention and the advantages thereof, reference should be made to the following Detailed Description taken in connection with the accompanying drawings in which:); 
         FIG. 1  shows a door-closing device according to a first embodiment of the present invention mounted to a door in a door frame; 
         FIG. 2  shows a sensor configuration detail according to the embodiment of  FIG. 1 ; 
         FIG. 3  shows a side view of a second embodiment of the present invention, having a hinged sensor module; 
         FIG. 4  shows a schematic diagram of a generic control system according to the present invention; 
         FIG. 5  shows a mechanical configuration of a third embodiment of the present invention; 
         FIG. 6  shows a mechanical configuration of a fourth embodiment of the present invention; 
         FIG. 7  shows a mechanical configuration of a fifth embodiment of the present invention; 
         FIG. 8  shows a mechanical configuration of a sixth embodiment of the present invention; 
         FIG. 9  shows a flow chart of the control system operation according to the present invention; 
         FIGS. 10A and 10B  show a detail of a valve in a magnetically controlled damper, in the On and OFF states respectively; 
         FIG. 11  shows a schematic view of an electronically controlled, hydraulically damped door closer according to the present invention; and 
         FIG. 12  shows a schematic view of a hydraulically damped door closer with an intelligent hold-open device according to the present invention. 
     
    
    
     Similar reference characters refer to similar parts or steps throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following detailed description sets forth numerous specific details to provide a thorough understanding of the invention. However, those of ordinary skill in the art will appreciate that the invention may be practiced without these specific details. In other instances, well-known methods, procedures, protocols, components, and circuits have not been described in detail so as not to obscure the invention. 
     The invention provides a control system for a passive door closing system to alleviate the problem of the requirement for manual efforts, sometimes significant, in order to overcome the tendency of an automatic door closing mechanism to close the door immediately (or after a preset delay) after being opened. Such door closers are provided to prevent insects and debris from entering a doorway, and to maintain controlled climates separate from uncontrolled climates. The force on the door is typically sufficient to keep the door closed under windy conditions and against possible air pressure differences seeking to open it. Since the door is typically 2.5 feet by 7 feet, even a low 0.05 psi pressure differential is sufficient to create a 126 pound force. Likewise, the door must be damped, since the spring would tend to slam the door closed, and an undamped door when pushed open abruptly might hurt an unseen person on the other side. 
     A sensor is provided to sense a person in or approaching the doorway, and preferably distinguishes a person leaving the doorway or congregating in the vestibule. These may be distinguished by a motion analysis. 
     The system is powered by a door opening, which typically provides a significant force exerted over a short period of time. Part of this force is to provide potential energy for the door closing mechanism to later close the door, and part is normally lost in a damping mechanism. According to the present invention, the damping forces may be captured and stored as electrical energy to power the control system. 
     The control system may be relatively simple: it receives sensor data, and makes a decision as to whether to delay door closure, and then controls an actuator to either close the door or to permit door closure. Other ancillary functions are optional. Since electronic devices have become quite sophisticated, and doors are located in strategic locations, the door closer may be suitable for integration with various electronic systems, including theft prevention, RFID, person recognition, portal inventory, fire alarm condition, alarm or security system sensing and/or control, occupancy sensing, pet control, or the like. 
     The control system controls an actuator, for example a solenoid valve, clutch/friction plate, electro-rheological phenomenon, catch, or other type of mechanism. Typically, an electronic control system will control an electrical transducer, which is typically an electromagnetic or piezoelectric system. Other possibilities include electrochemical (e.g., hydrolyzing a liquid to produce a gas, which exerts a pressure. To reverse, the gas may be explosively or catalytically recombined), and electrothermal (e.g., heating a shape memory alloy above its transitional temperature to cause a shape reconfiguration). 
     A backup battery is provided to provide power in case the capacitor discharges or fails to fully charge. For example, if the door is opened very slowly, the voltage generated by the magneto will be insufficient to charge the capacitor. Likewise, a long delay between opening and closing may allow the capacitor to self-discharge. 
     As shown in  FIG. 1 , a door  1  is provided in a door frame  3 , having a doorknob  2 . A door closing mechanism  8  is provided at the top of the door  1 , and connected to the door frame  3 , by a linkage including arms  5 ,  7  and hinge  6 , held to the door frame by a mount  4 . The door closing mechanism  8  includes a system for returning the door to a closed position, a selective control for delaying door closure while a person or object is in the doorway, a sensor housing  11 , having a sensor  12  for detecting the presence of a person or object in or near the doorway. The door closing mechanism also include a feedback device, e.g., a set of light emitting diodes (LEDs)  9 , which provide an indication that the device is operative to hold the door open, and therefore that it need not be manually held for a next person. These LEDs  9  may also provide indication of a failure condition, such as low battery, watchdog timer timeout, or mechanical or electronic failure. 
       FIG. 2  shows in greater detail an embodiment of the sensor housing  11 , which in this case is separated from the door closing mechanism  8  by a coiled wire  10 . In this embodiment, two sensors are provided; a passive infrared (PIR) sensor  13 , and a microwave sensor having a microwave antenna  15 . The sensor housing  11  may also include a set of LEDs  14 , to indicate that the sensor has sensed an object or person, or to otherwise indicate the status of the system. In this case, since the sensor housing is mounted to the door frame  3 , it may optionally be wired to receive line power, which may be provided to the door closing mechanism  8  through the coiled wire  10 . 
     It is thus clear that a separation from line power is not a negative limitation on all embodiments of the invention, and in fact, where accessible, line power is a quite efficient power source. However, one of the advantages of the present design is that the operational principles are compatible with non-line powered operation. 
     In this embodiment, the sensor housing is mounted in predetermined position on the side opposite where the door opens. The sensors  13 ,  15 , are this in fixed position, and may be aligned with the normal path of travel through the doorway. The PIR sensor  13  is sensitive to a change in heat patterns, i.e., infrared wave emissions, through a lens portion, and, for example, includes a sheet of pyroelectric material, such as polyvinylidene fluoride (PVDF). Alternately, the sensor system could include an optical sensor, for example an imaging complementary metal-oxide-silicon (CMOS) or charge coupled device (CCD) sensor. In that case, the LEDs  14  could advantageously provide illumination. Likewise, the LEDs (as laser diodes) could form part of a LIDAR sensor system to detect object range and motion. 
     The microwave sensor emits a signal through microwave antenna  15 . This sensor can detect object presence, range, and/or motion, depending on the control system and implementation. Preferably, it is used to detect object presence and as a Doppler sensor to detect velocity with respect to the antenna sensitivity pattern. 
     The sensor system is preferably inactive while the door is closed, conserving power. As the door is opened, which may be detected in any suitable manner, the sensor become active, and remain active until the door is closed or is beginning to close. In some cases, the control and infrared sensor may be continually active, since these are relatively low power components. This permits control over operation prior to door opening. For example, the control may lock the door when no sensed person is nearby, but when a person is in the doorway, allow the person to open the door. The control may authenticate the person to implement controlled access, through optical feature recognition, RFID, security token, fingerprint, iris or other biometric recognition technique, voice recognition, password, PIN, or other control technique. 
     The door opener may receive an optical, magnetic or RF signal to receive control instructions from another system, and may provide a platform for the mounting of antennas for wireless networks and the like. 
       FIG. 3  shows an alternate embodiment of the invention, in which the sensor housing  24  is mounted on an arm  23  hinged by hinge  18  to lift up with respect to mounting  17  as the door is closed and down as the door is opened. This embodiment extends the faces  25 ,  26  of the sensor below the top of the door frame  3  to sensor objects and people in the doorway. The arm  23  is connected though arms  20 ,  22  and hinge  21  to the arm  5  of the door closing mechanism.  FIG. 3  also shows that the mount  4  may be replaced with an “L” shaped member  16  to fit around a corner of the door frame  3 . 
       FIG. 4  shows a generic embodiment of a control system, i.e., one which includes a number of optional features, not all of which are provided or necessary in all cases. 
     A control  40  provides implements the logic necessary for intelligent operation, and is, for example, a microcontroller of known type. Preferably, the microcontroller includes power driver capabilities, minimizing the requirement for external driver circuitry, but is otherwise of a low power design. It is understood, however, that any sort of logic, including discrete devices, various levels of semiconductor integration, or powerful microprocessors, may be used in the control. Further, while it is preferred that the control be included within and integral to the door closing mechanism, it may be provided separately, for example in a sensor housing or as a part of a centralized control system. The control  40  may therefore optionally have a communications interface  58 . 
     The control  40  generally communicates with a sensor network  41 , which, as shown in  FIG. 4  may include one or more sensors, for example, a PIR sensor  42 , a microwave/Doppler sensor  43 , optical sensor  44  (imaging or non-imaging), a pressure switch  45  (for example, a door mat or surface on the door  1 ), a microphone  46 , or a remote control/key  47  interface. In the later case, the door closing mechanism may also serve as a lock for the door, or be manually operated or overridden through, for example, an infrared or radio frequency interface. It is noted that this interface may be consolidated with the communications interface  58 . 
     As the door  1  is opened, generally energy is stored for later closing the door  1 . The energy storage mechanism also supplies a force which prevents the door from opening rapidly. In a prior art design, this energy storage is typically in a spring or pneumatic chamber. While these are used in various embodiments of the invention, one embodiment of the present invention captures some of the energy supplied during door  1  opening to supply power for control  40  system operation. For example, magneto  52  is rotated during door opening, to supply an electrical charge to super capacitor  50  and/or battery  51 . The control  40  may intermediate, for example controlling an electrical impedance of the magneto to damp door  1  motion. The magneto  52  may also be operated as a motor to return the door  1  to the closed position, for example replacing the traditional spring and damper of prior designs. 
     It is noted that, in order to provide a fail-safe design, the system preferably does not rely on active devices for door  1  closure. Thus, a mechanical or pneumatic spring (not shown in  FIG. 4 ) cooperates with a damper to ensure that the door closes in a predictable and controlled fashion. 
     A door open switch  48  and door closed switch  49  sensor may be provided. The door closed switch, for example, may be used to turn on and off the system, while the door open switch  49  may be used to control a damping factor of the door  1  through the damping control  53 . 
     When a person or object is detected in the doorway by the sensor network  41 , a damper control  53  or door stop  54  (or both) are activated to block or impede door  1  closure. The door remains open until the obstruction is clear, as determined by the sensor network  41 , or another condition causes the door to close, for example, a watchdog timer inherent in the control  40  expires (a timeout condition), or a signal is received through the communications interface  58  or remote control/key sensor  47 . A feedback system  55  may be provided with audible  57  and/or visible  56  indicators, to indicate the status of the system. For example, low battery, failure (mechanical or electronic), object sensed, timeout, and/or door restraint active. 
       FIG. 5  shows an embodiment of the invention having a so-called coil-over design damper  66  and spring  67  (the spring  67  may also be housed within the damper  66 ). In this case, a piston rod  65  has rack gearing on an end portion, and is withdrawn from the damper  66  as the arm  7  is rotated, thus rotating mating gear  63 , through connecting shaft  64 . Connecting shaft  64  also connects with magneto  61  through a gearhead  62  reducer, such that the magneto  61  produces a usable current for charging a rechargeable battery pack  51 ′ and/or capacitor (not shown). The terminal movement of the piston rod  65  is detected by a set of microswitches  48 ′,  49 ′. The control  40  receives input from a sensor module including PIR  42  and microwave  43  sensors, which, in this case, are provided on the bottom of the door closing mechanism  8  housing. 
       FIG. 6  differs from  FIG. 5  in that this embodiment provides electrically controlled damping of the door  1 , with mechanical retraction through spring  67 ′, acting through cable  70  and winch  71 . Arm  7  acts through shaft  64 , mounted on bearings  74 ,  75 , to turn gear  72 . Gear  72 , in turn, acts on gear  73  to rotate the armature of magneto  52 . The electrical energy produced by the magneto  52  is stored in storage capacitor  50 ′ to power the control  40 . A backup battery  51 ′ is provided if the power available from the storage capacitor  50 ′ is insufficient. In this case, the sensor housing  11 , including the sensor network  41  having PIR sensor  42  and microwave  43  sensor, is shown separated from the door closing mechanism  8  housing. 
       FIG. 7  shows a still different embodiment, wherein arm  7  is rotationally connected to shaft  83 , which acts through planetary gearhead  81  with motor  80 . A brake  82 , and shaft sensor  84  are provided. In this case, a fully active design is provided. The motor  80 , during door  1  opening, may act as a generator to charge super capacitor  50 ′, or act as a power assist to open the door. Once the door is open, the brake  82  is engaged, to hold the door in position. When the doorway is clear, the brake  82  is released, and the motor  80  driven to close the door. In this case, the power supply  51 ″ may be a battery or line power. The sensor  84  is used to determine whether the door is being pushed or held open, this providing feedback to prevent the motor  80  from fighting a person manually operating the door. Likewise, the sensor may be used as part of a servo or brushless motor design. 
       FIG. 8  shows a still further embodiment of the invention. In this case, a servo motor  90 , with optical encoder  91 , drives shaft  92  with worm gear  94 , meshing with gear  93  attached to shaft  64 , linked to the arm  7 . A torque sensor  95  senses a manual force on the door  1 , which is then used by control  40  to drive the servo motor  90 . After the force ceases, the control  40  maintains the door  1  in the open position until the doorway is cleared, and then closes the door by rotating the servo motor  90  in the opposite direction. If an obstruction is sensed by the torque sensor, the control stops the door  1  closure. In this case, a battery  51 ′ system or other power supply is necessary, since no energy is stored from door opening. Alternately, an asymmetric drive may be provided, using the servo motor  90  only for door closure, and using a magneto to store energy from door  1  opening. 
       FIG. 9  shows a flow chart of control  40  system operation. Initial, at start  100 , the device is typically powered down. An opening of the door is detected  101 , and the sensor(s) and control turned on  102 . As the door is opened, energy is stored  103 . After the door is opened, it is held open  104 . The control then uses the sensor network to determine whether the doorway is clear  105 . If it is clear, the door is allowed to close  107 , the system shuts down  108 , and the process stops  109 . If the sensor network does not indicate that the doorway is clear, a watchdog timer is referenced  106 , to determine whether a maximum door retention time is exceeded. If it is exceeded, the door is allowed to close  107 , preferably with an audible or visual advance warning. If the maximum door retention time is not exceeded, the door is held open  104 , and the sensing process is repeated to determine whether the doorway is clear  105 . The sensor network  41  may be operative, for example, once per second, to save energy. The maximum door retention time is, for example, 20 seconds. 
       FIGS. 10A and 10B  show a valve detail of a magnetically controlled damper according to the present invention. A magnetorheological fluid, for example a magnetic powder suspended in a viscous oil, is provided. During device operation with a low damping coefficient, the fluid  200  flows viscously through a relatively large port  201 , within a conduit  202 . See, Jolly, Mark (Lord Corporation), “Pneumatic Motion Control Using Magnetorheological Technology”, SPIE ( 2001 ), expressly incorporated herein by reference. In this case, a displaceable permanent magnet  203  is retained in an ON (flowing) position by a fixed permanent magnet  204  in a guide  205 . A coil  206  is activated to produce a magnetic field in the guide, to selectively control displacement of the displaceable permanent magnet  203  away from the fixed permanent magnet  203 , toward the conduit  202 , which causes an apparent sharp increase in the viscosity of the fluid  200 , thereby reducing flow rate in the OFF (non-flowing) state. Thus, fluid flow rate can be simply controlled, with a relatively simple electrically controllable and sealed device. This damper may be used as a primary effector for the control, for example to maintain the door in an open position as the door stop  54 , by effectively blocking fluid  200  flow, or as a secondary control over the rate of fluid flow through as the damper control  53 , or as both. For example, a spring inserted between the displaceable permanent magnet  203  and the conduit  202  might permit proportional operation. 
       FIG. 11  shows a schematic view of a hydraulically damped door closer according to the present invention. Typical commercial door closers for sale in the U.S Domestic market are of two types: those for fire doors, which are generally rated by Underwriters Laboratories (UL), and which have no means for locking the door in an open position, and unrated door closers for applications in which fire codes and the risk of fire hazard in the event that the door is held open is not a substantial issue. See, for example, Ryobi 8800 Series, D1550 Series, D2100 Series, D3550 Series, Sargent Bradford Series. In order to provide an efficient design, the two type of door closers generally share common parts, and for example, have a different arm (called a hold-open arm) for the unrated application. On the other hand, some door closers have an internal hold-open, as an option for the main body of the closer. The hold open feature not only poses a fire hazard under various circumstances, but also defeats a number of advantages of the presence of a door closer. 
     Many hydraulically damped door closers for commercial application have three (or more) adjustments; a first setting  201  for adjusting the initial door closure rate, a second adjustment  202  for setting a mid-swing door closure rate, and a backcheck adjustment. The door closure rate settings are established by a set of screw adjustable bleed valves. The initial door closure rate is typically higher than the mid-swing rate, so in order to maintain the door in an open condition, all bleed valves would have to be blocked. (In order to provide a fail-safe mode, the minimum door closure rate may be set at a very slow rate, such as 1-5 minutes, instead of locked.) Therefore, the present invention provides a hydraulically damped door closer which provides one or more electronically controlled bleed valves (which may be mechanically adjusted to control respective closure rates). These valves may be linear solenoids (latching or non-latching)  201 ,  202 , or rotary valves. In a held-open condition, a solenoid is activated to maintain the door in an open position by blocking flow of hydraulic fluid through the orifice. In a closure condition, the hydraulic fluid flows according to the normal arrangement of passages. Generally, door opening bypasses the damping mechanism and transfers energy to a spring  203 . 
     According to the present invention, the electronic control therefore bypasses or supplements the relatively simple “hydraulic logic” to provide a higher intelligence. 
     Examples of this intelligence include object sensing in a doorway, fire or smoke detection (and therefore door closure and/or alarm), remote activation, room occupancy sensing, and the like. In a first embodiment, a spring biased solenoid actuator is linked to a needle which controls flow through a restricting orifice  201 ,  202 . The control  210  holds the actuator  201 ,  202  in the active and therefore hold-open state for so long as an object is in the doorway, or other condition exists for which the door should be held open. This method is fail safe, since a battery failure would result in default hydraulic door closure. A control  210  failure which activates the solenoid actuator  201 ,  202  would likely drain the battery  211  over a few hours. Thus, a fire safety rating or special exemption may likely be obtained. Since power is required to maintain the solenoid actuator  201 ,  202  in an activated state, a magneto generator  204  driven by the door opening through gear  205  is preferred. 
     In a second embodiment, the actuator employs a latching armature. In this case, it is possible for the battery to fail with the unit held in the open position; therefore this embodiment generally includes a base bleed which causes the door to close within 1-5 minutes, and so provide a graceful and fail safe mode. This type of system may have lower battery drain than a system in which continuous power is required to restrain door closure. 
     In a third embodiment, shown in  FIG. 12 , a collapsible mechanical toggle linkage  220  is reset each time the door is opened by extension of a moveable member  221  within the door closer. See, U.S. Pat. No. 6,031,438, expressly incorporated herein by reference. The control  222  then generates a signal which activates a solenoid  223  which pulls an armature  224 , which displaces a seer pin (not shown in  FIG. 12 ) and collapses the toggle linkage  220  when the door closure is to be activated, which allows the normal hydraulic door closure mechanism  225  to operate. In this case, only a single actuator pulse is required to close the door. On the other hand, this acts as an automatic hold-open, and thus would likely be applicable especially for non-fire safety rated operation. 
     As can be seen, the control  222  may receive, for example, an external signal to trigger door closure, such as a fire alarm or a timer. A manual reset may also be provided to trigger the door closure in case of control  222  failure. The door closer may also include a variety of sensors and/or sensor inputs, of particular importance being a fire and/or smoke detector, or remote indication of such conditions. A remote communication may take place by means of wires, radio frequency, audio signals, infrared, optical signals or the like. Thus, the door closer may watch or listen for activation of proximate fire alarms, and thus need not be permanently wired. Typically, this design will also incorporate an object or person sensor in accordance with the above examples, but need not. 
     It is noted that while hydraulic damping is preferred, other damping means may be provided, especially if electronically controlled. In particular, a magneto which spins during door closure (and possibly opening), having a controllable (or fixed) load, would damp closure. Likewise, a magnetically activated clutch (linear or rotary) could be controlled to regulate closure speed, and effect damping. 
     From the above description and drawings, it will be understood by those of ordinary skill in the art that the particular embodiments shown and described are for purposes of illustration only and are not intended to limit the scope of the invention. Those of ordinary skill in the art will recognize that the invention may be embodied in other specific forms without departing from its spirit or essential characteristics. References to details of particular embodiments are not intended to limit the scope of the claims.