Abstract:
An elevator door interlock incorporates cast parts thereby drastically reducing the number of parts required for assembly. Other elements are also incorporated to further reduce complexity in manufacturing, servicing, and configuration.

Description:
TECHNICAL FIELD  
       [0001]     Embodiments relates to elevator door interlocks. Embodiments also relate to simplifying the manufacture, repair, and configuration of elevator door interlocks.  
       BACKGROUND OF THE INVENTION  
       [0002]     Elevators are complex machines. Interlocks help insure proper elevator operation. One of the interlocks ensures that the elevator door is opened only when the elevator is present or during maintenance operations. At a minimum, an elevator door interlock includes a sensor, that senses whether the door is open or closed, and a locking mechanism, that locks the door in the closed position.  
         [0003]     Elevator door interlocks should have a housing that protects the parts from outside interference. Current housings are made from stamped pieces of sheet metal. The components of the interlock must be mounted to the housing. The current solutions are to attach mountings to the housing via welding, soldering, screws, bolts, or similar devices or means. It takes considerable time and skill to assemble a housing in this manner. Furthermore, the assembly is prone to breakage because of the large number of parts that are used.  
         [0004]     Elevator door interlock housings are typically sheet metal formed into 5 sides of a box type enclosure and a cover, making up the sixth side, completes the enclosure. The covers currently used are simple squares or rectangles of sheet metal. Components of the interlock can be attached to the cover as they are to the housing, bringing along similar problems. The inconvenience of attaching parts to the sheet metal cover usually leads to the cover being merely a cover and otherwise not a part of the elevator door interlock structure.  
         [0005]     The sheet metal solutions used for housings and covers also require that any text that should be on the housing or cover to be added as part of a separate operation. That separate operation is usually painting, printing, or affixing an adhesive backed label. These are poor solutions because, over the life of the unit, they wear off.  
         [0006]     Elevator doors typically open to the left or to the right. The elevator door interlocks currently used are designed only for left opening or right opening doors. As such, elevator maintenance organizations must stock both the left and right opening varieties. Furthermore, repairmen must go into the field with the correct unit and have the risk of arriving at the job site with the wrong one.  
         [0007]     Elevator door interlocks must have a mechanism for locking the door closed and releasing the door when it is proper to do so. The solution is usually to mount a locking fixture to the door that mates with a locking fixture in the elevator door interlock. The elevator door interlock is then mounted to the doorframe. When the door is shut, the two locking fixtures engage. Another part in the interlock housing controls merely engaging the locking fixtures or locking them together. In modern elevators, the controlling part is usually a solenoid. A solenoid, a mechanism wherein an actuator remains in a default position until electrical current is applied causing the actuator to move to an energized position, is well known in the art of electromechanical devices and particularly in the art of elevator door interlocks. Solenoids require a specified electrical current or voltage for proper operation. For example, a 24-volt DC solenoid requires a steady voltage of approximately 24 volts. Alternating current or too low a voltage would not work. Too high a voltage could destroy the solenoid. Furthermore, keeping a solenoid energized for long periods of time can cause the device to overheat and fail. Once again, repairmen must arrive at the job site with elevator door interlocks that match the electrical power used at that job site.  
         [0008]     Elevator door interlocks often keep the solenoid energized when the door is unlocked. This shortens solenoid life.  
       BRIEF SUMMARY  
       [0009]     It is therefore one aspect of the embodiments to provide a cast housing for an elevator interlock housing.  
         [0010]     It is another aspect of the embodiments to provide for the use of a cast cover instead of a stamped sheet metal cover to close the housing.  
         [0011]     It is a further aspect of the embodiments to form text or pictograms into the cast housing or into the cast cover for conveying information.  
         [0012]     It is also another aspect of the embodiments to use an electrical circuit that utilizes either AC or DC electricity as a power source.  
         [0013]     It is an additional aspect of the embodiments to use symmetrical parts to reduce manufacturing costs and enable easy reconfiguration of the elevator door interlock.  
         [0014]     It is yet a further aspect of the embodiments to utilize a snap over center arrangement of a locking cam to hold and release the door.  
         [0015]     The aforementioned aspects and other objectives and advantages can now be achieved as described herein. As indicated above, one aspect of the embodiments is the use of a cast housing for an elevator interlock housing. Casting is a process by which a mold is used to produce a shaped part as a single piece. The shape of the housing can include the mountings and fasteners for the parts that must go into the housing. For example, solenoids are often fastened with a bolt and a nut. A cast housing allows other mounting methods to be used. One fastening method that can be used is to form a thickened threaded portion of the housing to mate with a bolt instead of using a nut to mate with the bolt. A mounting method that can be used is forming a mounting, as part of the housing, into which the solenoid snaps or slips into place. This example illustrates the reduction in parts count that is possible for the solenoid. There are many more components that must be similarly mounted in the housing. The mountings for many of those components can be formed into the cast housing.  
         [0016]     Another aspect of the embodiments is to use a cast cover instead of a stamped sheet metal cover to close the housing. The mounting for a component can be formed in two parts. One part of the mounting is formed as part of the housing and the other part is formed as part of the cover. When the cover is attached to the housing, the two parts of the mounting are also joined to form a complete mounting that holds a component securely.  
         [0017]     Another aspect of the embodiments is to form text or pictograms into the cast housing or into the cast cover for conveying information. Cast in text or pictograms are unlikely to wear off during the useful life of the housing or cover.  
         [0018]     Another aspect of the embodiments is use an electrical circuit that uses either AC or DC electricity as a power source. Elevator door interlocks are usually part of an elevator control circuit. Different circuits are constructed with different electrical power supplies. Some installations use direct current, or DC. Others use alternating current, or AC. Elevator door interlocks that operate with either AC or DC electricity allow the same interlock to be used in more installations. This results in stocking fewer parts and a lower likelihood that repairmen reach the job site with the wrong part.  
         [0019]     Another aspect of the embodiments is the use of symmetrical parts to reduce manufacturing costs and enable easy reconfiguration of the elevator door interlock. Doors can open to the left or to the right. The correct elevator door interlock must be used for each installation. Designing the unit with symmetrical components allows the exact same components to be used in either left or right opening units. If a repairman needs to install a left opening unit, but only has a right opening one, it is a simple operation to open up the unit, move the components, and thereby convert the left opening unit into a right opening one. The result is that fewer components are required for the manufacture of left and right opening units because both types use the same components. Another advantage is that a repairman at the job site with the wrong unit can easily convert it instead of returning for the correct unit.  
         [0020]     Another aspect of the embodiments is using a snap over center arrangement of a locking cam to hold and release the door. In certain elevator door interlocks, a cam is a part of the locking fixture that resides in the housing. Snap over center is a type of action where a mechanism has two resting positions and, when not at rest, exerts force in an attempt to reach one of the resting positions. The cam rests in either the locked or the unlocked position. Snap over center action can be obtained by pressing a ball bearing against the side of the cam if the cam profile is properly designed.  
         [0021]     One advantage of the snap over center action is that, unless there is outside force applied, the cam is always in a rest position. This enables more accurate alignment between the locking fixtures. It also enables use of cam position sensors that detect when the cam is in a rest position. When the locking cam is in the locked position, a solenoid can be used to lock the cam in place, thereby locking the door. A cam position sensor can be used to sense that the cam is in the locked position and turn off electrical power to the solenoid, which will keep the door locked without causing the solenoid to heat up. A similar sensor can cut solenoid power when the cam is in the unlocked position. As such, the solenoid is only energized when it needs to be, increasing the lifespan of the solenoid.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  illustrates a cast housing in accordance with a preferred embodiment;  
         [0023]      FIG. 2  illustrates a cast cover in accordance with an embodiment  
         [0024]      FIG. 3  illustrates a cast inner cover in accordance with a preferred embodiment;  
         [0025]      FIG. 4  illustrates a cast inner cover in accordance with a preferred embodiment;  
         [0026]      FIG. 5  illustrates a cast cover in accordance with a preferred embodiment;  
         [0027]      FIG. 6  illustrates a circuit diagram in accordance with a preferred embodiment;  
         [0028]      FIG. 7  illustrates a cam in accordance with a preferred embodiment;  
         [0029]      FIG. 8  illustrates a cam actuator in accordance with a preferred embodiment;  
         [0030]      FIG. 9  illustrates snap over center operation accordance with a preferred embodiment;  
         [0031]      FIG. 10  illustrates a cam in accordance with a feature of the embodiment; and  
         [0032]      FIG. 11  illustrates a circuit diagram in accordance with a feature of the embodiment.  
     
    
     DETAILED DESCRIPTION  
       [0033]     In accordance with a preferred embodiment,  FIG. 1  illustrates a cast housing  101  that can be formed as a single piece that incorporates mounting points and other elements. One of the advantages of the cast housing  101  is that it can possess thickened areas such as thickened areas for bolts  102  or thickened areas for other mountings  109 . The thickened area for bolts  102  can be simply a place where a bolt hole  103  is placed and threaded so that a bolt can be screwed into that location.  
         [0034]     Bolts are used to fasten things together. Single bolt holes and bolt hole patterns are examples of mount points. In general, a mount point is a place where two or more components of an assembly are joined together. The cast housing  101  can also have a locking fixture window  104  that is an opening where a locking fixture, such as the cam actuator illustrated later, can enter. The cast housing  101  can have a cam axle mount  105 , which is a thickened area with a hole meant to hold an axle on which a cam rotates. The cast housing  101  can have a door sensor window  106 , which is a place to mount a sensor that detects the presence of the elevator door.  
         [0035]     The cast housing  101  can have a portion of a mounting, such as a solenoid mount portion  107 . The portion that is part of the cast housing  101  can be designed such that a solenoid drops into it and then another portion of the mount is added to form a complete mount that holds the solenoid completely. The cast housing  101  also has a wire window  108 . The elevator door interlock has some electrical parts and they must be electrically connected to elevator control circuitry. The wires from the control circuitry enter the cast housing  101  via the wire window  108 . Usually the outside wires from the control circuitry connect to the circuitry inside the cast housing  101  via multi element electrical connectors.  
         [0036]      FIG. 2  illustrates the top side of a cast cover  200 . The cast cover  200  is also formed as a single piece that incorporates other elements. The cast cover  200  can have countersunk holes  201 . The countersunk holes  201  shown are ideal for bolting the cast cover  200  to the cast housing  101 . The cast cover  200  can have lettering  202  or other patterns formed into its surface. The cast housing  101  can also have patterns other than lettering formed into its surface. The cast cover  200  can also have windows such as the manual release window  203 . A manual release window  203  is designed to enable manual operation of the locking mechanism inside the elevator door interlock.  
         [0037]      FIG. 3  and  FIG. 4  show a cast inner cover  300 . The specific cast inner cover  300  shown is meant to mate with the solenoid mount portion  107 . When the two parts mate, a complete solenoid mount is formed. A cast housing  101  can have other mount portions for components other than solenoids. As such, there can be other cast inner covers that mate with those portions to form complete mounts.  
         [0038]      FIG. 5  illustrates the bottom side of a cast cover  200 . The cast cover  200  can have a cam axle mount  105  that, in concert with the cam axle mount  105  in the cast housing  101 , completely contains the cam axle. Two cam axle mounts are not necessary for all types of cam mountings. The arrangement shown here conveys the wide range of elements that can be incorporated into a single cast part. The arrangement described herein is not intended to limit the types of cam mountings that can be utilized, because there are many types of cam mountings well known to those skilled in designing elevator door interlocks. The cast cover  200  can also have a solenoid mount portion  501 . The solenoid mount portion  501  shown is analogous to that shown in  FIG. 3  and  FIG. 4 , except that it is incorporated into the cast cover.  
         [0039]      FIG. 6  illustrates a circuit diagram of one way to operate a solenoid  601  with either AC or DC electrical power. A solenoid  601  is an electromechanical device wherein the actuator  602  moves when electrical power is applied to the coil  603 . Electric current is commonly direct current (DC), such as a battery produces, or alternating current (AC), such as a generator produces. A rectifier is an electrical device that causes electrical current to flow in only one direction. A full wave bridge rectifier  604  is a type of rectifier.  
         [0040]     When an electric current, either AC or DC is applied to the full wave bridge rectifier input  605 , rectified current flows out of the rectifier positive output  607  into the coil  603 , and then into the rectifier negative output  608 . A flyback diode  606  is connected in parallel with the coil  603  to protect against flyback, a condition that occurs when the coil  603  is de-energized. Rectifiers, solenoids, flyback diodes, and full wave bridge rectifiers as individual components or subassemblies are known to those skilled in the art of electric circuitry.  
         [0041]      FIG. 7  illustrates a cam  700 . The cam  700  rotates around an axle that goes through the axle hole  703 . At least one cam axle mount  105  holds a cam axle that goes through the axle hole, thus confining the cam within the cast housing  101  wherein it rotates about a single axis. The cam  700  is one part of the locking fixture.  FIG. 8  illustrates another part of the locking fixture, the cam actuator  800 . The cam actuator  800  is attached to the elevator door. The cast housing  101  is attached to the doorframe. As the elevator closes, the lock bar  801  portion of the cam actuator  800  enters into the cast housing via the locking fixture window  104 .  
         [0042]     Inside the cast housing  101 , the lock bar  801  engages the lock bar notch  701  and causes the cam  700  to rotate. When the elevator door reaches its closed position, the cam  700  reaches the lock position at which time the solenoid actuator  602  can enter into the solenoid notch  702  thereby locking the cam  700 , cam actuator  800 , and elevator door in place. To unlock the elevator door, the solenoid actuator  602  must be retracted from the solenoid notch  702 . This is accomplished by applying electrical power to the solenoid  601  or by physically pushing the solenoid actuator  602 .  
         [0043]      FIG. 9  illustrates an example of a type of snap over center action. A hill  900  resides between two valleys  903 . A ball  903  rests in a valley  901 . To move the ball  903  from one valley  901  to the other, it must be pushed up the hill  900 . When it passes the cusp  902 , the ball  903  rolls to the other valley  901 . It takes force to move the ball  903  toward the cusp  902 . The force of gravity moves the ball  903  toward a valley  901 . This is an example of snap over center action. The ball  903  has two resting positions and a cusp  902  between them. It takes force to move the ball  903  from a resting position and a force always pushes the ball  903  toward a resting position.  
         [0044]      FIG. 10  illustrates a cam  700  with snap over center action. A spring  1003  presses a ball bearing  1002  against the side of the cam  700 . This is analogous to the example of  FIG. 9 . The ball bearing  1002  is like the ball  903 . The force of the spring  1003  is like the force of gravity. The cam profile is like the hill  900  in that it has a cusp  1007  and two resting positions  1006 . The cam  700  also has a protrusion  1004 . When the ball bearing  1002  is in a rest position  1006 , the protrusion  1004  engages one protrusion sensor  1005  or the other. The protrusions sensors  1005  detect when the cam  700  is in the lock position, unlock position, or neither position because rest positions  1006  correspond to the lock and unlock positions.  
         [0045]     The protrusion sensors  1005  can be used to cut electrical power to the solenoid  601  when the cam  700  is in either the lock or unlock position. When the elevator door is fully closed, the cam  700  is in the lock position. When someone tries to open the elevator door, the cam actuator  800  pulls the cam  700  slightly out of the locked position thereby allowing the solenoid  601  to be energized. This is possible because the solenoid notch  702  is wide enough to allow it. If it is proper to open the elevator door the solenoid  601  can be energized which withdraws the solenoid actuator  602  from the solenoid notch  702 , and allows the door to be fully opened. If the door can&#39;t be properly opened, the solenoid  601  is not energized and the door remains locked shut. Whoever is attempting to open the door then lets go and the snap over center action rotates the cam  700  to the locked position. In this manner, the solenoid  601  is not continuously energized whenever it is proper to open the door, only when it is proper and someone is attempting to open the door. Similarly, if the door is open and the cam  700  is resting in the unlock position then the solenoid  601  should not be energized. When the solenoid  601  is not energized, the solenoid actuator  602  pushes against the side of the cam  700 , but does not enter a notch because none is present. As the door closes, the cam actuator  800  engages the cam  700  and rotates it to the locked position whereupon the solenoid actuator  602  snaps into the solenoid notch  702 .  
         [0046]     The protrusion sensors  1005  are presented as examples of a way to sense cam  700  position. One skilled in the art of elevator door interlocks should appreciate many different and equivalent ways to sense cam  700  position after reading this disclosure. In accordance with this aspect, any sensor that can sense cam position can be used to sense when the cam  700  is in any particular position such as the lock position or the unlock position.  
         [0047]      FIG. 11  is a circuit diagram showing one of the many possible circuits that can cut electrical power to the solenoid  601  when the cam  700  is in either the lock or unlock position. The lock position sensor  1101  is a switch that opens when the cam  700  is in the lock position. In any position other than lock, this switch is closed. The unlock position sensor  1102  is a switch that opens when the cam  700  is in the unlock position. In any position other than unlock, this switch is also closed. When either switch is open, the solenoid  601  receives no electric power.  
         [0048]     Another aspect of the embodiment that is shown in all the figures is symmetry. The only figures in which symmetry is not apparent is  FIG. 7  and  FIG. 8 . The symmetry of the cam  700  is exploited by flipping it over. The direction indicator  704  is an “R” indicating that the cam  700  is in the right side opening position. Flipping the cam  700  over means placing it such that the “R” is facing down instead of up as it is in  FIG. 7 . The cam actuator  800  does not need to be configured. It needs to be mounted to the elevator door such that it enters into the cast housing  101  via a locking fixture window  104 . The cast housing  101  has locking fixture windows  104  on both the left and right sides.  
         [0049]     Another aspect of the embodiment is an electrical door sensor. The door sensor senses when the elevator door is in the shut or nearly shut position.  
         [0050]     It will be appreciated that variations of the above-disclosed and other features, aspects and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.