Abstract:
An electromechanical push to close latch has a pawl positioned for linear movement in a housing, with the pawl being biased to the outward extended position. An electric motor operates a cam to change the position of the pawl thereby retracting it into the housing. An electronic circuit board controls the operation of the electric motor under the direction of an outside control signal. The circuit board also senses the position of the pawl to stop the operation of the motor when the pawl is fully retracted. The pawl mounting can be reconfigured for the pawl to extend and thereby operate in a plurality of selectable directions.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority of U.S. provisional application 60/686,036, filed May 29, 2005, for electromechanical push to close latch, and incorporates by reference the disclosure of that application. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention is directed to push to close latches, and specifically a release mechanism for opening the push to close latch.  
         [0003]     Push to close latches typically, have a tapered, ramp-ended, blade-shaped pawls or bar-shaped pawls. These pawls are spring-biased to the latched/closed position, wherein the pawl extends outwardly from the latch housing. As the pawl of a push to close latch encounters the striker, the ramping force pushes the pawl inward against the spring force until the pawl clears the striker, wherein after the spring then forces the pawl to its extended position and the latch becomes latched.  
         [0004]     A lock plug with a pivoting blade striker can be incorporated to provide both the striker and a key lock function, wherein the push to close latch is in a separate housing. When a passive striker is used, a retraction knob may be incorporated into the pawl housing to retract the pawl against its outwardly biasing spring. A lock plug can be used instead of the retraction knob, wherein as the key turns the plug a linkage retracts the pawl into the housing.  
         [0005]     Alternately, paddles have been used instead of knobs or lock plugs to activate the pawl to retract it against the force of its biasing spring and into the housing.  
         [0006]     With the advent of more security systems, it has become desirable to utilize push to close latches, which are thereby locked when latched. With such security push to close latches it has also become desirable to active, i.e., to operate the latch remotely. Such remotely operated, push to close latches are electrically operated, and therefore are electromechanical devices. The remote activation can be by the operation of an electric signal button operated by a guard or a security officer, or by an electric signal button operated by a resident of an apartment in an apartment building, or by a signal generated by a code entry pad or swipe card reader. The electric signal causes the pawl to be retracted so that the door may be opened.  
         [0007]     Typically, the activation device at the latch is an electromagnet or a solenoid. When the electric current flows, the pawl is retracted into the housing and the door can open. When the electric current stops the biasing spring forces the pawl to the extended position.  
         [0008]     These electrically operated, prior electromechanical push to close latches have developed problems because of wear and erratic operation, and because of the timing and length of the electric activation signal when the button operator is out of sight of the door and the latch being operated. As an example, if the door is pulled prior to the pawl being retracted, the pawl can bind and the solenoid activator is unable to retract the pawl. Various installations limit the size of the latch housing and therefore the capacity and strength of electromagnetic activator or the solenoid.  
         [0009]     What is desired is a latch which is smoothly operating and which has a controlled operation for pawl movement.  
         [0010]     What is further desired is a latch which is easily reconfigured for a plurality of different installations.  
       SUMMARY OF THE INVENTION  
       [0011]     An object of the present invention is to provide an electromechanical push to close latch which is remotely operated under the direction of an input control signal. The latch has a spring loaded (biased) linear retracting pawl. When not being commanded to retract, the pawl is spring biased to its normally extended position. From the extended position, the pawl is free to retract, into a housing, when sufficient force is applied to overcome the spring biasing. The pawl, which is blade or bar shaped, has a tapered or ramped end, which acts against a striker to move the pawl against the spring force. Thus the latch is used as a push to close latch.  
         [0012]     An electric DC motor is coupled through a gearbox to rotate a cam which is connected to retract the pawl into the pawl housing when a control signal is sent to the motor. The pawl can be maintained in the retracted position without power being further applied to the motor, when the motor is stopped as the pawl is sensed to be in the appropriate position.  
         [0013]     This push to close latch may be operated against various keepers to provide for different latching functionality. When operated against a fixed keeper or enclosure undercut, a simple mechanical push to close and thereby “latch” function is implemented. When operated against a rotateable flange on a lock plug, the mechanical override function of the key lock is provided.  
         [0014]     The latch has a multi-sectional housing which contains the motor, a circuit board connected to control the motor operation and to sense the pawl position, a gear box which couples the motor to a cam, and a cam which is mounted to move the pawl in a linear motion. The pawl and its biasing spring are mounted in a separable housing section. The pawl housing can be mounted with the pawl extending and operating in any of three directions with respect to the motor and gearbox portion of the housing. These three positions have the pawl extending longitudinally from an end of the housing, or transversely to the right or to the left.  
         [0015]     The output gear of the gearbox has associated with it a ribbed or toothed hub. The cam snaps onto that hub and is driven, i.e., rotated. The cam engages an opening or pocket in the pawl. When the output gear rotates, the hub rotates the cam to drive the pawl in a reciprocating linear motion. When the pawl housing orientation is changed from longitudinal to transversely to the right or to the left, the cam is removed from the hub and reoriented consistent with the reorientation of the pawl.  
         [0016]     A small electric DC motor provides the power to operate the latch. The gearbox provides a gear reduction system to reduce the rotational speed of the motor from about 8000 rpm to about 60 rpm and multiplies the torque available from the motor to operate the latch. An electronic circuit board monitors the position of the output gear and thereby the position of the cam, and ultimately the position of the pawl. This circuit board provides power to the motor which controls the pawl position, i.e., the status of the latch.  
         [0017]     The circuit board also includes a dual position sensor to provide a feedback signal to a controller circuit to confirm one or two positions of the latch. The latch has two operating positions, these being the pawl fully extended position and the pawl fully retracted position. The two positions are defined and sensed by two different size holes in the output gear. Two sensors on the circuit boar monitor for the presence of a hole and determine if it is the larger hole or the smaller hole. One of the sensors is used as an endpoint sensor to stop the motor in either position. The other sensor is used as a position sensor to detect if the gear and thereby the pawl is in position “1” or “2”. The position sensor will only detect the larger of the two holes and thus can distinguish between position 1 and 2. With the output gear in position 1, the pawl is and/or can be fully extended under the force of its biasing spring, and only the endpoint sensor is detecting a hole (the small hole). With the output gear in position 2, the pawl is in the retracted position and both the endpoint sensor and the position sensor are detecting a hole (the larger hole).  
         [0018]     When a signal is received for the latch to change positions, the electrical circuits are delayed to initially ignore a start hole and after the short delay period begin to sense for the new end point and position.  
         [0019]     The sensing circuit may be altered to provide the same functions. As an example, there need be only one hole in the output spur gear and the sensors can be positioned 180 degrees apart. The present design uses infrared light and infrared sensors. Alternatively, Hall-effect sensors can be used, or other types of sensors suitable to the size and power application. If position feedback is not required, only one position sensor need be used.  
         [0020]     The gearbox output spur gear and the cam are two separate parts that are configured in different keyed positions to one another as a function of the pawl housing orientation. When for size considerations, it is desirable to have the output gear and cam as one molded integrated part, three different output gears would be needed for the change over between different pawl housing orientations.  
         [0021]     The concept of this invention of a gear driven, cam operated, push to close pawl latch is equally applicable to smaller sized latches which require less power and larger sized latches which require more power.  
         [0022]     The layout of the gearbox relative to the cam/pawl can be altered to accommodate different mounting and space constraints. The number of gears in the gearbox will depend upon the motor selected, the motor speed, and the torque increase needed to successfully control the pawl position under actual operating conditions and wear  
         [0023]     In some instances, it could be desirable to have a non-reconfigureable pawl housing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The features, advantage and operation of the present invention will become readily apparent and further understood from a reading of the following detailed description with the accompanying drawings, in which like numerals refer to like elements, and in which:  
         [0025]      FIG. 1  is a perspective view of the electromechanical push to close latch;  
         [0026]      FIG. 2  is a partial cut-away, perspective view of the latch of the invention in a cabinet having a lock plug rotatable blade keeper rotated to the open/unlocked position;  
         [0027]      FIG. 3  is a partial cut-away, perspective view of the latch and the cabinet of  FIG. 2 , where the pawl of the latch is engaged with the keeper to lock the cabinet;  
         [0028]      FIG. 4  is a partial cut-away, perspective view of the latch and the cabinet of  FIG. 2 , with the pawl retracted so that the cabinet door is free to open;  
         [0029]      FIG. 5  is a partial cut-away, perspective view of the latch and the cabinet of  FIG. 2 , with the latch pawl remaining in the retracted position and the cabinet door open;  
         [0030]      FIG. 6  is a partial cut-away, perspective view of the latch and the cabinet of  FIG. 2 , with the pawl released and extended under its spring biased force and the cabinet door ready to close the keeper against the latch pawl;  
         [0031]      FIG. 7  is an exploded perspective view of the electromechanical latch of the present invention;  
         [0032]      FIG. 8  is a perspective view of the latch of  FIG. 1  with the pawl housing repositioned for left-hand operation;  
         [0033]      FIG. 9  is a perspective view of the latch of  FIG. 1  with the pawl housing repositioned for right-hand operation;  
         [0034]      FIGS. 10   a - 10   f  are top, bottom, right side, left side, pawl end, and opposite end views, respectively, of the latch of  FIG. 1 ;  
         [0035]      FIG. 11  is a top view of the left-hand pawl orientation for the latch of  FIG. 8 ;  
         [0036]      FIG. 12  is a top view of the right-hand pawl orientation for the latch of  FIG. 9 ;  
         [0037]      FIG. 13  is an exploded view of the pawl housing portion of the latch for a straight on longitudinal pawl operation;  
         [0038]      FIG. 14  is an exploded view of the pawl housing portion of the latch for a left-hand operation/orientation;  
         [0039]      FIG. 15  is an exploded view of the pawl housing portion of the latch for a right-hand operation/orientation;  
         [0040]      FIG. 16  is a right side view of the motor, gear and cam drive of  FIG. 7 ;  
         [0041]      FIG. 17  is a left side view of the motor, gear and cam drive of  FIG. 16 ;  
         [0042]      FIG. 18  is a top orientation sectional view of the latch, with the pawl released to extend under spring pressure, taken as shown in  FIG. 18   a;    
         [0043]      FIG. 18   a  is a right orientation sectional view taken as shown in  FIG. 18 ;  
         [0044]      FIG. 19  is a top orientation sectional view of the latch, with the pawl retracted under striker pressure, taken as shown in  FIG. 19   a;    
         [0045]      FIG. 19   a  is a right orientation sectional view taken as shown in  FIG. 19 ;  
         [0046]      FIG. 20  is a top orientation sectional view of the latch, with the pawl retracted by the motor, gear and cam drive, taken as shown in  FIG. 20   a;    
         [0047]      FIG. 20   a  is a right orientation sectional view taken as shown in  FIG. 20 ;  
         [0048]      FIG. 21  is a bottom orientation sectional view of the latch taken as shown in  FIG. 21   a , wherein the latch is in the same position as seen in  FIG. 18   a;    
         [0049]      FIG. 21   a  is a right side orientation sectional view taken as shown in  FIG. 21 ;  
         [0050]      FIG. 22  is a top orientation sectional view of the latch taken as shown in  FIG. 22   a , wherein the latch is in the same position as seen in  FIG. 20   a;    
         [0051]      FIG. 22   a  is a right side orientation sectional view taken as shown in  FIG. 22 ;  
         [0052]      FIGS. 23   a - 23   c  are perspective, bottom, and side views, respectively, of the first gear;  
         [0053]      FIGS. 24   a - 24   c  are perspective, bottom, and top views, respectively, of the second gear;  
         [0054]      FIGS. 25   a - 25   c  are perspective, bottom, and top views, respectively, of the third gear;  
         [0055]      FIGS. 26   a - 26   c  are perspective, bottom, and top views, respectively, of the fourth gear;  
         [0056]      FIGS. 27   a - 27   c  are perspective, bottom, and top views, respectively, of the fifth gear;  
         [0057]      FIGS. 28   a - 28   c  are perspective, bottom, and tope views, respectively, of the cam of  FIG. 7 ;  
         [0058]      FIGS. 29   a - 29   g  are perspective, top, bottom, right side, left side, ramp end, and opposite end views, respectively, of the pawl of  FIG. 7 ;  
         [0059]      FIGS. 30   a - 30   c  are perspective, top and bottom views, respectively, of the circuit board of  FIG. 7 ;  
         [0060]      FIG. 31  is a perspective view of the motor of  FIG. 7 ;  
         [0061]      FIGS. 32   a - 32   c  are perspective, outside end, and inside end views, respectively, of the motor pinion gear;  
         [0062]      FIG. 33  is a perspective view of the inside of the housing bottom section;  
         [0063]      FIG. 34  is a perspective view of the outside of the housing top section which encases the motor and reduction first through fourth gears;  
         [0064]      FIG. 35  is a perspective view of the outside of the pawl housing which encases the spring, output/fifth gear, cam, and pawl; and  
         [0065]      FIGS. 36   a - 36   c  are top, bottom and pawl opening side views, respectively, of the pawl housing. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0066]     The present invention is an electromechanical, gear driven, cam operated, push to close pawl latch, having a pawl housing portion which is reconfigurable with respect to the main portion of the housing for selectively changing pawl orientation. A DC electric motor drives the gears under the control of a circuit board which includes pawl/cam position sensors and provides a feedback signal to a motor controller circuit on the board. The motor controller circuit is implemented with a microprocessor circuit which is capable of controlling the motor for selectively positioning a pawl drive cam in either of two positions, which thereby selectively permits the pawl to be retracted or released to extend under a spring biasing force. The spring force is insufficient to overcome the inertial of the motor and gears, so that the pawl may remain retracted with no power to the motor. The microprocessor receives input signals through a circuit board connector.  
         [0067]     The push to close latch  41 ,  FIG. 1 , has a three part housing, with a base  43 , a motor and gearbox encasement  45 , and a pawl housing  47 . A pawl  49  operates linearly in the pawl housing  47 .  
         [0068]     The latch  41  can be installed on cabinets, entrance doors or cases. In  FIG. 2 , it is installed on a cabinet  51  wall and functions in combination with a lock plug  53  having a blade-type striker plate  55 .  
         [0069]     With the pawl is freed,  FIG. 3 , it is free to operate as the pawl in a traditional push to close latch with the pawl  49  engaging the striker blade  55  under the force of its biasing spring. When the input signal to the microprocessor causes a control signal to operate the motor, the pawl  49  is retracted from the lock plug striker blade  55 ,  FIG. 4 , even when the key of the lock plug  53  is not operated.  
         [0070]     With the pawl electromechanically retracted, the door of the cabinet is free to open,  FIG. 5 . When the door of the cabinet  51  is closed, with the striker blade interrupting the ramp end of the pawl  49 , the latch locks as a push to close latch,  FIG. 6 .  
         [0071]     The latch  41  is shown in an exploded view in  FIG. 7 . The housing base  43  is a molded structure, with a series of journals, pass-through openings and stand off structures. The motor and gearbox encasement  45  is held to the housing base  43  with a plurality of at least four screws  57 . The circuit board  59  is shaped to seat down into the housing base  43 . Carried on the circuit board is a connector  61 , a microprocessor chip  63 , and a pair of infrared sensors  65 ,  67 .  
         [0072]     A small DC electric motor  69  mounts above the circuit board  59 . This motor  69  is controlled to rotate in one direction by control signals from the microprocessor  63 .  
         [0073]     The output shaft of the motor  69  has a pinion gear  71  which engages a gearbox of 5 reduction gears,  73 ,  75 ,  77 ,  79 ,  81 . The first four of these gears ( 73 ,  75 , 77 ,  79 ) are mounted on three gear spindles  83  which mount into individual bosses  85  in the housing base  45  and extend upwardly to the motor and gearbox encasement  45  which encases the motor  69 , circuit board  59  and the first four gears  73 ,  75 ,  77 ,  79 . The fourth gear  79  and the fifth gear  81  are mounted in the housing base  43  below the circuit board.  
         [0074]     The fifth gear  81 , being the output gear rides on a bushing  87  which mounts on a boss  89  in the housing base  43 . The output gear  81  has a central upward projecting hub  91  with four quadrant vertically extending ribs  93 . These ribs  93  extend radially outward from the center of the hub  91 . This hub  91  can alternately carry a plurality of splines.  
         [0075]     A cam  95  mounts on the hub  91  of the output gear  81  to engage a pocket in the pawl  49 . The pawl operates linearly in the interior  97  of the housing  47  and is biased to the extended outward position by a compression spring  99 . The pawl housing is held to the housing base  43  with four screws (not shown). The motor gearbox encasement has four closed walls as the output gear  81  and the fourth gear  79  operate below the circuit board  59  and within the confines of the side walls of the housing base  43 .  
         [0076]     The pawl housing  47  and thereby the pawl  49 , may be mounted on the housing base  43  for left hand operation,  FIG. 8 , or for right hand operation,  FIG. 9 . What is required to effect these conversions, is to remove and rotate (reposition) the pawl housing  47  and to remove and reorient (reposition) the cam  95  on the output gear  81 .  
         [0077]     The external features of the latch  41  are readily seen from  FIGS. 10   a - 10   f . The reconfigured left hand operation pawl  45 , and right hand operation pawl  45  are shown in  FIGS. 11 and 12  respectively.  
         [0078]     As seen in  FIG. 7 , and in  FIGS. 13-15 , respectively, the cam  95  has a base flange  101 , and upstanding hub  103  and a projecting cam finger or plug  105 .  FIGS. 13-15  each show an exploded view of the pawl housing  47 , cam  95  and output gear  81 . The cam  95  is mounted onto the output gear hub  91  with the cam plug  105  facing in the direction of the outward extension of the pawl  49 .  
         [0079]      FIGS. 16 and 17  show right side views and left side views of the motor and gearbox, respectively. The pinion gear  71  on the motor  69  shaft drives a crown gear  73  (the first gear), which carries a downward projecting pinion  107 ,  FIG. 23   a . This second pinion gear  107  being a part crown gear  73  engages the teeth of a spur gear  75  (the second gear) which also carries a downward facing pinion  109 ,  FIG. 24   a . The third pinion  109  being a part of the spur gear  75  engages the spur gear teeth of the spur gear  77  (the third gear). This third gear  77  also has a downward facing pinion  111 ,  FIG. 25   a . The fourth pinion  111  on the third gear  77  engages the spur gear teeth of a spur gear  79  (the fourth gear). The fourth gear  79  drives the output spur gear  81  (the fifth gear) carrying the cam  95 .  
         [0080]     Various views of the first gear  73  are seen in  FIGS. 23   a - 23   c , while various views of the second gear  75  are seen in  FIGS. 24   a - 24   c . Several views of the third gear  77  are seen in  FIGS. 26   a - 26   c , while several views of the fourth gear  79  are seen in  FIGS. 26   a - 26   c.    
         [0081]     As seen in  FIGS. 27   a - 27   c , the perspective, bottom and top views of the output gear  81 , the output gear  81  carries a larger, arc-like hole  113  and a smaller, arc-like hole  115 , which is diametrically across from the larger hole  113 .  
         [0082]     The flange  101  on the cam extends outwardly from the cam hub,  FIGS. 28   a - 28   c . This flange covers inner portion of the output gear  81  so that the infrared signals from the sensors  65  and  67  mounted on the circuit board  59  reflect off of the flange material and back to the sensors  65 ,  67 . The interior of the cam hub  103  carries four quadrant slots  117  which fit the ribs  93  on the output gear hub  91  to lock the cam  95  onto the output gear  81 .  
         [0083]     The circuit board  59  is shaped to seat down within the side walls of the housing base  43  and carries various holes for the gear spindles  83 , for the mounting bushing  87  for the output gear  81 , and for the pinion  111  extending downward from the third gear  77 .  
         [0084]     The motor  69  is shown in a perspective view in  FIG. 31 , and the housing base  43  is shown in a perspective view in  FIG. 33 . In  FIGS. 32   a - 32   c  various views of the motor pinion gear  71  can be seen. The relationship between the motor gearbox encasement  43  and the pawl  47  is understood by from  FIGS. 34 and 35 . While the pawl housing is seen from the top, bottom and the pawl cavity  97  side in  FIGS. 36   a ,  36   b , and  36   c , respectively. The pawl housing bottom,  FIG. 36   b  has two step-out circular cavities  119 ,  121  (i.e., circular sockets to receive the cam thereinto), to accommodate the cam base flange  101  and upstanding hub  103 , respectively. A concentric opening  122  permits an access for the cam plug  105  to extend into the pawl cavity  97  and engage the pawl  49 .  
         [0085]     The pawl  49  is seen in various views in  FIGS. 29   a - 29   g . The end of the pawl  49  has a ramped camming surface  123  which engages the striker  55 . The top of the pawl has an open channel  125  partially extending the length of the pawl  49 , in which the compression spring  99  operates to bias the pawl  49  outwardly from the pawl housing  47 . The bottom face of the pawl  49  has a cam cavity  127  having a curved wall  129  at the ramp  123  end of the pawl  49 , and a straight wall  131  at the opposite end of the pawl  49 .  
         [0086]      FIGS. 18-22   a  show the position of the pawl and cam for various operating situations. In  FIGS. 18 and 18   a , the motor is off, the cam plug is in the outward facing position, and the pawl is free to move under the force of the biasing spring or a force against its ramp surface, as defined by the depth of the pawl cavity. These figures show the pawl in the extended position.  FIGS. 19 and 19   a  have the latch components in the same position, but with the pawl in the fully retracted position.  FIGS. 20 and 20   a  shown the pawl and came when the motor has rotated the cam to retract the pawl to the retracted position.  
         [0087]     When the cam  95  is rotated, the cam plug  105  operates against the straight wall  131  of the cam cavity  127  to retract the pawl  49  into thee housing  47  against the spring force. The curved wall  129  provide a clearance for the cam plug  105  to rotate without operating against the pawl.  
         [0088]      FIG. 21  shows the bottom of the gearbox when the pawl is in the free position and both of the two sensors  65 ,  67  sense the big hole  113 . This is the situation where the cam plug is in the outward position to allow free movement of the pawl against its biasing spring and the ramp force against a striker.  
         [0089]      FIG. 22  shows the bottom of the gear box when motor and gearbox dictated retracted position, whereby the cam plug is in the inward position. In this state, only one of the sensor  65 ,  67  is able to obtain a reading. The sensors sense the presence of the small hole  115  in this state.  
         [0090]     When in operation, the microprocessor  63  receives an open command from the desperate signal device, such as the code entry pad, swipe card reader, a lock key plug. This signal enters the circuit board  59  at the connector  61 . The microprocessor then controls the operation of the motor  69  to cause the cam to rotate 180 degrees to fully retract the pawl  49  into the housing  47 . When the cam  95  reaches the 180 degree position, the sensors  65 ,  67  sense that position and feed a signal to the microprocessor which stops the rotation of the cam  95 . After a predetermined period of time, e.g., a time sufficient for the cabinet  51  door to be opened, the microprocessor again causes the motor to operate to cause the cam to rotate 180 degrees to its initial position.  
         [0091]     This is the cam inoperative position. When the cam is in this position, the latch can remain locked, if the door of the cabinet was not timely opened, or the latch is returned to a mechanically-operated push (slam) to close operation, under the influence of its biasing spring  99 .  
         [0092]     Many changes can be made in the above-described invention without departing from the intent and scope thereof. It is therefore intended that the above description be read in the illustrative sense and not in the limiting sense. Substitutions and changes can be made while still being within the scope and intent of the invention and of the appended claims.