Patent Publication Number: US-2021172203-A1

Title: Smart door lock

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims benefit of U.S. Provisional Application Ser. No. 62/944,108, filed Dec. 5, 2019, entitled “Smart Door Lock,” which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to electromechanical door locks. 
     BACKGROUND 
     Locks can be configured to fasten doors to inhibit unauthorized entry into buildings. Conventional deadbolts are moved to an open position by rotating a lock cylinder with a key. Conventional spring bolt locks use a spring to hold a bolt in place, allowing retraction by applying force to the bolt itself. A deadbolt is often used to complement a spring-bolt lock on an entry door to a building. 
     In many cases, bolt locks may include electronically-powered mechanisms that facilitate automatic movement of a bolt between an unlocked position and a locked position. However, to accommodate components to facilitate automatic movement of the bolt, current electronic bolt locks require cumbersome hardware that extend exterior of a door. For example, some conventional electronic deadbolts include a large cylinder that protrudes out of a door. A side of the cylinder can include a paddle, or a twist knob. The rotation of the cylinder using the key (inserted into the key slot and rotated) or the paddle (moved or rotated to another position) can result in the deadbolt of the lock to retract (e.g., to unlock the door) or extend (e.g., to lock the door). However, some homeowners find it cumbersome to be limited to locking or unlocking the door lock of a door using the key or the paddle. In addition, current electronic bolt locks are difficult to install because of such cumbersome hardware and the wiring used for their electronic components. 
     Mechanical movement of a bolt may be configured to initiate upon reception of a communication signal. However, to consistently obtain wireless signals from a remote device, an antenna of the deadbolt mechanism may protrude exterior of the door. Locking mechanisms with a footprint that protrudes from a door may limit aesthetic appeal of the locking mechanism. Such a locking mechanism may have a greater vulnerability to unauthorized manipulation, such as breaking the locking mechanism to allow unauthorized entry. 
     SUMMARY 
     The disclosed embodiments include at least one door lock. The door lock can include a main housing, a bolt housing, an outer housing, and an inner housing. The main housing can be configured to be disposed interior of a door and to cause a deadbolt within the bolt housing to extend into a locked position or retract into an unlocked position. The main housing can include mechanical components to move the deadbolt and electronic components to operate the mechanical components. 
     The outer housing can be disposed exterior of the door. The outer housing can include conductive prongs. The conductive prongs can extend through openings of the main housing and engage with the inner housing to secure the components of the door lock. The conductive prongs can connect to conductive openings of the main housing and allow for electrical transmission between the outer housing and the main housing. 
     The outer housing can include leakage areas configured to facilitate wireless signal transmission between an antenna within the main housing of the door lock and an exterior of the door. The leakage areas can be configured to be disposed adjacent to the door. 
     The bolt housing can be configured to surround a power supply, such as a battery, disposed within the bolt housing. The power supply can be within the deadbolt. The bolt housing can be expandable to accommodate different size bolt caps that satisfy various bore hole sizes of a door. The bolt caps can be configured to allow for electrical transmission from the power supply to the main housing. While a battery can be disposed within the bolt housing, other components that allow for mechanical movement of the deadbolt between a locked position and an unlocked position can be disposed within the main housing. 
     The inner housing can be disposed exterior of the door and can face a secure environment, such as the interior of a house. The inner housing can include a first magnet. The inner housing can include a rotation member that facilitates manual transition of the deadbolt between the unlocked position and the locked position. The rotation member can include a second magnet with a second polarity. The magnets can allow for smooth rotation of the rotation member about the inner housing. The magnets can be configured to allow for magnetically favored orientations of the rotation member relative to the inner housing. 
     The disclosed embodiments include at least one method. The method can include installing a door lock in a door by disposing a bolt housing including a deadbolt within a door, disposing a main housing within a bore hole of the door, and extending a conductive prong of an outer housing to the main housing, wherein the outer housing includes a capacitive touch sensor. The method can further include associating the door lock with a user device, detecting the user device is within a wireless communication range of the door lock, and detecting a touch on the capacitive touch sensor. In response to detecting the touch, detecting the user device within the wireless communication range, or both, the deadbolt transitions between a locked position and an unlocked position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of an example door lock. 
         FIG. 2  shows an example door lock disposed within a door in various positions. 
         FIG. 3A  shows an example outer housing of the door lock. 
         FIG. 3B  shows a rear view of an example outer housing of the door lock. 
         FIG. 4A  shows an example inner housing of the door lock. 
         FIG. 4B  shows an example inner housing and rotating member of the door lock. 
         FIG. 5  shows an example main housing of the door lock. 
         FIG. 6A  shows an example bolt housing of the door lock in a default position. 
         FIG. 6B  shows an example bolt housing of the door lock in an extended position. 
         FIG. 7  shows an exploded view of an example bolt housing of the door lock. 
         FIG. 8  shows an example method for moving a deadbolt of a door lock between a locked position and an unlocked position. 
         FIG. 9  shows an example method for moving a deadbolt of a door lock between a locked position and an unlocked position. 
         FIG. 10  is a block diagram illustrating an example of a processing system in which at least some operations described herein can be implemented. 
     
    
    
     Like reference numerals refer to corresponding parts throughout the figures and specification. 
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth such as examples of specific components, circuits, and processes to provide a thorough understanding of the present disclosure. Also, in the following description and for purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present embodiments. However, it will be apparent to one skilled in the art that these specific details may not be required to practice the present embodiments. In other instances, well-known circuits and devices are shown in block diagram form to avoid obscuring the present disclosure. 
     Any of the signals provided over various buses described herein may be time-multiplexed with other signals and provided over one or more common buses. Additionally, the interconnection between circuit elements or software blocks may be shown as buses or as single signal lines. Each of the buses may alternatively be a single signal line, and each of the single signal lines may alternatively be buses, and a single line or bus might represent any one or more of a myriad of physical or logical mechanisms for communication (e.g., a network) between components. The present embodiments are not to be construed as limited to specific examples described herein but rather to include within their scope all embodiments defined by the appended claims. 
     System Overview 
       FIG. 1  is a perspective view of an example door lock  100 . The door lock  100  can include a main housing  110 , bolt housing  120 , outer housing  130 , and inner housing  140 . 
     The main housing  110  can include components to mechanically move a deadbolt between a locked position and an unlocked position. For example, the main housing  110  can include an actuator, gear drive, or any other components that can assist in mechanically moving a deadbolt between a locked position and an unlocked position. For example, the main housing  110  can include a motor that can be activated (e.g., turned on) to retract or extend the deadbolt  124  without having the homeowner manually use a key or paddle. 
     The main housing  110  can also include electronic components disposed within the main housing  110 , such as a circuit board, a processor, or an antenna. The door lock  100  can be a “smart” lock having a variety of functionality including computing devices having wireless communications capabilities that allow it to communicate with other computing devices. For example, a homeowner can have a user device, such as a smartphone, that can wirelessly communicate with electronic components in the main housing  110  via one of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards, Bluetooth®, Zigbee, Z-Wave, or other wireless communication techniques. In some implementations, electronic components in the main housing  110  can access a network such as the Internet via the user device. In other implementations, a network may be accessed without the user device as an intermediary. Thus, door lock  100  and the homeowner&#39;s smartphone can exchange data amongst themselves. For example, the door lock  100  can provide data regarding the state of the door lock  100  to the smartphone so that the homeowner knows whether the deadbolt  124  is in a locked position or an unlocked position. The main housing  110  can also receive data from a smartphone via wireless communications, for example providing an instruction to transition the deadbolt  124  from a locked position to an unlocked position. The electronic components in main housing  110  can be powered by a power supply disposed within the deadbolt  124  in the bolt housing  120 . 
     The main housing can have a substantially circular footprint and be configured to be disposed within a standard bore hole disposed within a door. For example, the main housing  110  can be configured to be disposed within an American National Standards Institute® (ANSI) deadbolt bore hole, which has a diameter of 2⅛ inches. In another example, a depth of the main housing  110  can be configured to fit within an ANSI standard door thickness, which is 1¾ inch. The main housing  110  can include openings  114  and  116 . These openings can include a conductive portion and/or be configured to facilitate mechanical movement of a deadbolt. For example, as shown in  FIG. 1 , openings  114  are conductive openings. As shown in  FIG. 1 , opening  116  is configured to rotate to facilitate extension or retraction of a deadbolt  124 . 
     The main housing  110  can be configured to engage with a bolt housing  120 . The main housing  110  and bolt housing  120  can be engaged at a bolt carriage  118  of the main housing  110 . For example, the bolt carriage  118  can include a female connector groove that connects to a male connector  122  of the bolt housing  120 , as shown in  FIG. 1 . Connections between the main housing  110  and the bolt housing  120  may take any number of forms, including mechanical or electromagnetic connections. The main housing  110  can engage with the bolt housing  120  to cause a deadbolt  124  within the bolt housing  120  to move between a locked position and an unlocked position. For example, the locked position can include extending the deadbolt  124  into a wall, and the unlocked position can include retracting the deadbolt  124  into the bolt housing  120 . As shown in  FIG. 1 , the deadbolt  124  is retracted in the bolt housing  120  in an unlocked position. The bolt housing  120  can further include a plate  126 . The plate  126  can be attached to a door, for example using screws. The plate  126  can be multiple sizes or shapes to accommodate different doors. For example, the plate  126  can have different height, width, or depth to match a cutout in a door. In another example, the plate  126  can be rectangular and have either rounded or sharp corners. 
     The deadbolt  124  can be configured to receive a power supply. The power supply can include, for example, an electrochemical cell (e.g., a flow battery, ultrabattery, and/or rechargeable battery), a capacitor (e.g., a supercapacitor), an energy storage coil (e.g., a superconducting magnetic energy storage device), a compressed air energy storage device, a flywheel, a hydraulic accumulator, a chemical energy storage device (e.g., hydrogen storage), or any combination of energy storage devices. For example, the power supply can be a small battery, such as a lithium CR2 battery. The bolt housing  120  can be configured to receive power from the power supply. The main housing  110  can be electrically connected to the bolt housing  120 . For example, the bolt carriage  118  of the main housing  110  and the male connector  122  of the bolt housing  120  can both include pins. Engaging the respective pins can then allow current to flow to the main housing  110  from the power supply within the bolt housing  120 . 
     The bolt housing  120  can be extendable to accommodate bolt caps on the bolt of varying size. In particular, the bolt housing  120  may extend to accommodate a bolt cap with a length matching a standard bore hole, such as an ANSI standard bore hole with 2⅛ inch diameter and 2¾ inch backset. 
     The outer housing  130  can be disposed exterior of a door and face outside of a secure environment. For example, the outer housing can be disposed outside of a house or apartment. The outer housing can include a keyhole  132  configured to receive a key that can lock or unlock the deadbolt  124 . 
     The outer housing  130  can include a set of prongs  134  and  136  to engage with the main housing  110 . In the example shown in  FIG. 1 , the center prong  136  can engage with the opening  116  of the main housing  110 . Rotation of the keyhole  132  can be coupled with rotation of the center prong  136 , which causes rotation of the opening  116  of the main housing  110  and thereby facilitating movement of the deadbolt  124  between a locked position and an unlocked position. 
     The prongs  134  and  136  can be conductive to allow for electrical transmission between the outer housing  130  and the main housing  110 . For example, as shown in  FIG. 1 , the prongs  134  are conductive prongs, while prong  136  is not conductive in this example. The conductive prongs  134  can engage with the conductive openings  114  of the main housing  110 , allowing for electrical transmission between the main housing  110  and outer housing  130 . As noted above, the main housing  110  can be electrically connected to the bolt housing  120 , which can include a power supply within the deadbolt  124 . Thus, current can flow from the power supply within the deadbolt  124  to the outer housing  130 , powering any electrical components included in the outer housing  130 . For example, a portion of the outer housing  130  can include a capacitive touch sensor  139  configured to detect a touch by a user. In another example, the outer housing can include a near-field communication (NFC) sensor configured to receive a signal from a card or mobile device. 
     The outer housing  130  can include a leakage region  138  that facilitates signal transmission through the outer housing. The leakage region  138  can allow for increased wireless transmission from an exterior of the outer housing  130  to a wireless communication component in the main housing  110 . For example, a main housing  110  disposed within a metal door can receive a weaker wireless signal compared to a main housing  110  disposed within a wood door. In that case, an outer housing  130  including a leakage region  138  disposed on an exterior of the metal door can have higher transmission of the wireless signal received by the main housing  110  relative to an outer housing  130  without a leakage region. In some embodiments, the leakage region  138  can be composed of any material that allows wireless transmission though the material. For example, a leakage region  138  designed to allow transmission of a Bluetooth signal can be composed of plastic, glass, or silicone. In other embodiments, the leakage region  138  can include components that amplify a wireless signal, such as an antenna or a signal booster. As shown in the example in  FIG. 1 , the leakage region  138  is located on a perimeter of the outer housing  130 . Also as shown in  FIG. 1 , the leakage region  138  is positioned to contact an exterior of a door, which can provide for increased security and aesthetics. 
     The inner housing  140  can be configured to protrude exterior of a door and face interior to a secure environment, such as inside a house. The inner housing  140  can engage with the main housing  110  and outer housing  130 . As shown in the example in  FIG. 1 , the inner housing  140  can engage with the main housing  110  and outer housing  130  via the prongs  134  and  136 . The inner housing  140  can include openings  144 , which can be secured to the prongs  134  of the outer housing, for example, by a set of screws. 
     The inner housing can be attached to a rotating member  142  that causes the deadbolt  124  to transition between a locked position and an unlocked position. For example, rotation of the rotating member  142  clockwise can initiate mechanical movement of the deadbolt  124  from the unlocked position to the locked position. As shown in the example in  FIG. 1 , the rotating member  142  can include a paddle to assist a user in manual rotation of the rotating member  142 . The rotating member  142  is not limited to a paddle, but can include any suitable hardware, such as a knob, lever, handle, button, etc. As shown in  FIG. 1 , the center prong  136  of the outer housing can extend through opening  116  of the main housing  110  into a notch  146  of the inner housing. Rotation of the rotating member  142  can cause the notch  146  to rotate, causing the opening  116  of the main housing  110  to rotate via the center prong  136 , thereby causing the deadbolt  124  to transition between a locked position and an unlocked position. As discussed in more detail below, the rotating member can include a magnet with opposing polarity to another magnet on the inner housing, which allows for smooth rotation and an enhanced tactile experience for a user. 
       FIG. 2  shows an example door lock  200  disposed within a door  205 . The door lock  200  can include a main housing  210  disposed within a bore hole of the door  205 . As shown in  FIG. 2 , the door  205  is adjacent to a wall  250 . A bore hole can be a cylindrical opening through a depth of the door  205 . The diameter and depth of the bore hole can be a standard size, such as an ANSI standard bore hole with diameter 2⅛ inches and depth 1¾ inches. In addition, the bore hole can be in various positions on the door. For example, the bore hole can have a backset distance of 2¾ inches between the center of the bore hole and an edge of the door  205 . In another example, the bore hole can have a backset distance of 2⅜ inches from the center of the bore hole and an edge of the door  205 . 
     The door lock  200  can also include a deadbolt  214  within a bolt housing. The deadbolt  214  can extend or retract through a cross bore of the door. The cross bore can have varying shapes and/or sizes and be orthogonal to the bore hole. For example, the cross bore can be cylindrical with a diameter of 1 inch. 
     The door lock  200  can include a paddle  212 . A homeowner can rotate the paddle  212  to cause the deadbolt  214  to retract into a bolt housing of door lock  200  or to cause the deadbolt  214  to extend into a slot  252  of the wall  250 . For example, a homeowner inside a house can rotate the paddle  212  clockwise to extend the deadbolt  214  into the slot  252  of the wall and lock the door  205 . The homeowner can rotate the paddle  212  counterclockwise to retract the deadbolt  214  into a bolt housing and lock the door  205 . Conversely, a homeowner can cause the deadbolt  214  to transition between a locked position and an unlocked position by other means, such as with a key or by a wireless communication to actuate the main housing  210 , in order to cause the paddle to rotate. Although  FIG. 2  displays a paddle  212 , other suitable hardware such as a lever, handle, or knob can be used. 
       FIG. 2  shows three example positions for a door lock. In an unlocked position  220 , the deadbolt  214  is retracted to allow the door to open and close freely. In a transitional position  225 , the deadbolt  214  is partially extended but does not reach the slot  252  of the wall  250 . In a locked position  230 , the deadbolt  214  is extended into the slot  252  of the wall  250 , preventing the door  205  from being opened. In each of the positions  220 ,  225 , and  230 , the paddle  212  can rotate, indicating to a homeowner the position of the deadbolt. 
     Outer Housing 
       FIG. 3A  shows an example outer housing  300  of the door lock. The outer housing may protrude exterior of a door facing exterior of a secure environment, such as outside of a house. The outer housing  300  can be mechanically and electrically connected to the main housing and the inner housing via prongs  330  and  335 . The prongs can extend through openings in the main housing to engage with an inner housing interior of the secure environment. The prongs  330  can be conductive prongs to allow for electrical transmission between the outer housing  300  and the main housing. In the example as shown in  FIG. 3A , the center prong  335  can be coupled with the keyhole  340  to rotate as a user rotates a key within the keyhole  340 . This rotation can be coupled with the main housing to facilitate a transition of the deadbolt between a locked and an unlocked position. 
     Outer housing  300  can include circuitry and other hardware to provide capacitive touch sensing and nearfield communication (NFC) to allow techniques to provide an instruction to lock or unlock. The circuitry of outer housing  300  can be powered by tapping into a power supply disposed within a deadbolt. The battery can be tapped via conducting prongs  330  such that the battery can power the circuitry and components housed within the outer housing  300 . In some implementations, outer housing  300  can also include another battery and conducting prongs  330  can be used to provide charge from that battery to components housed within the main housing. 
     In some implementations, outer housing  300  can include capacitive touch capabilities to lock or unlock the door. For example, a capacitive touch sense circuit can be installed on a flex or printed circuit board (PCB) within outer housing  300  to determine that a human finger has touched outer housing  300 . If a human finger is detected, then the door can be unlocked (e.g., the deadbolt can be retracted) or locked (e.g, the deadbolt can be extended). In some implementations, the fingerprint of the finger can be detected and imaged, and if that imaged fingerprint is determined to be an authorized fingerprint (e.g., of the homeowner who previously registered his or her fingerprints) then the door can be unlocked. As shown in  FIG. 3A , the outer housing  300  includes a capacitive touch portion  310 . 
     In one example of detecting touch to lock or unlock a door, a homeowner can swipe, or move a finger, along the capacitive touch portion  310  to lock or unlock the door by adjusting the position of the deadbolt along a linear path in response to the movement of the finger. For example, a user can swipe their finger in a clockwise direction along the capacitive touch portion  310  to extend the deadbolt and lock the door, and swipe their finger in a counterclockwise direction along the capacitive touch portion  310  to unlock the door. In another example, the deadbolt can fully retract or extend in response to a tap of a finger. 
     The door may also unlock or lock in response to the door lock detecting a wireless communication signal. For example, the door may only unlock upon activation of the capacitive touch portion  310  if the door lock also receives a wireless communication signal from an authorized user device. The wireless communication signal can be any electromagnetic transfer of information, such as radio, GPS, Bluetooth, Wi-Fi, near-field communication (NFC), 4G, 5G, etc. The wireless communication signal may be detected by a wireless communication component in the main housing or in the outer housing  300 . For example, the outer housing  300  can include an NFC sensor so that a user can transmit a signal to the door lock from a smartphone or NFC card. In another example, the main housing can include an antenna configured to receive a Bluetooth signal transmitted from a user&#39;s smartphone. 
     The deadbolt may also transition between a locked position and an unlocked position in response to both detecting a wireless communication signal and detecting a touch on the capacitive touch portion  310 . That is, rather than locking or unlocking the door in response to either detection individually, the door may lock or unlock in response to the door lock detecting both the wireless communication signal and the touch within a short time frame. For example, a homeowner can bring their paired smartphone into a Bluetooth communication range of the door lock and proceed to touch the capacitive touch portion  310 , causing the deadbolt to transition to an unlocked position. In that case, the door unlocks after the door lock detects the wireless communication signal and the touch on the capacitive touch portion  310 . In another example, a trespasser can touch the capacitive touch portion  310  but not have a smartphone paired with the door lock via Bluetooth. In that case, the door lock would not detect the wireless communication signal, and the door would not unlock, even if the door lock detects a touch on the capacitive touch portion  310 . 
     The outer housing  300  can include a leakage region  320  to facilitate wireless signal transmission through the outer housing into the main housing. For example, a main housing disposed within a metal door can have difficulty receiving certain wireless signal frequencies compared to a main housing disposed within a wood door. The leakage region  320  can provide a path that allows for improved signal transmission into the door lock. The leakage region  320  can be composed of any material that allows for transmission of a desired wireless signal frequency. For example, a leakage region  320  designed to allow transmission of a Bluetooth signal can be composed of plastic, glass, or silicone. In other embodiments, the leakage region can include components that amplify a wireless signal, such as an antenna or a signal booster. 
     The leakage region  320  can be positioned anywhere on the outer housing  300  to allow for a path to facilitate wireless signal transmission. In the example as shown in  FIG. 3A , the leakage region can be positioned along a perimeter of the outer housing  300 . Also shown in  FIG. 3A , the leakage region can also be positioned against the door, underneath exterior portion of the outer housing  300 . This positioning of leakage region  320  allows for improved aesthetics and security, as it allows the outer housing  300  to be more substantially made of metal. In other embodiments, the leakage region  320  could be positioned surrounding the keyhole  340 . 
       FIG. 3B  shows a rear view of an example outer housing  300 . Outer housing  300  includes a center prong  335 , which can extend through an opening of the main housing configured to rotate and facilitate a transition of a deadbolt between a locked position and an unlocked position. As shown in  FIG. 3B , center prong  335  is configured to rotate. The rotation of the center prong  335  can be coupled with the rotation of the opening of the main housing to cause the deadbolt to transition between a locked position and an unlocked position. Furthermore, the center prong  335  can engage with a rotating member of the inner housing so that rotation of the rotating member of the inner housing will also cause the deadbolt to extend or retract. 
     Conductive prongs  330  can extend through conductive openings in the main housing to engage with the inner housing. The electrical connection to the main housing can be established by the conductive pins  332  on the conductive prongs  330  when the conductive pins contact a conductive opening of the main housing. Electrically connecting the main housing to the outer housing  300  using conductive prongs  330  makes it easier for a homeowner to install the door lock on the door by reducing the need for wiring, which can easily become disconnected or pinched against the door during installation. 
     The conductive prongs  330  can be extended through the main housing to engage with the inner housing. For example, as shown in  FIG. 3B , the conductive prongs  330  include screw holes  334 . The inner housing can be screwed directly onto the screw holes  334  using a set of screws. This further simplifies installation by using the conducting prongs  330  to electrically and mechanically connect the outer housing  300 , the inner housing, and the main housing. Besides screws, the outer housing  300  can engage with the inner housing by any suitable attachment mechanism, such as nails, rivets, adhesive, magnets, etc. 
     As shown in  FIG. 3B , the leakage region  320  can be positioned on a perimeter of the outer housing  300 . The leakage region  320  can contact the door to provide improved aesthetics and security. For example, positioning the leakage region against the door allows for the portions of the outer housing facing the exterior of a secure environment, such as a house, to be metal, which is a more secure material against physical tampering but can inhibit transmission of wireless signals through the outer housing  300 . Furthermore, positioning the leakage region against a door can reduce scratches or other physical damage to the door during installation of the door lock. 
     Inner Housing 
       FIG. 4A  shows an example inner housing  400  and rotating member  410 . The inner housing  400  can protrude from the door facing interior of a secure environment, such as a home or business. The rotating member  410  can be engaged to the inner housing and facilitate transitioning of the deadbolt between a locked position and an unlocked position. The rotating member  410  can include a paddle  414  to allow a user to manually rotate the rotating member  410 . 
     In many cases, springs may be used to indicate specific rotation points of a rotating member. However, using springs may result in varying friction between the rotating member and inner housing in rotating the rotating member. For example, springs may increase friction such that mechanical components of the locking mechanism may be unable to overcome the friction in extending the deadbolt. This may result in the deadbolt being unable to extend or retract due to the friction provided by the springs. 
     Accordingly,  FIG. 4B  shows a view of the example inner housing  400  separate from the rotating member  410 . The inner housing can include a first magnet  402  with a first polarity, and the rotating member  410  can include a second magnet  412  with a second polarity. As shown in  FIG. 4B , the magnets  402  and  412  can be ring magnets. The magnets can be disposed adjacent to each other when the inner housing  400  and rotating member  410  are engaged as shown in  FIG. 4A . Adjusting the relative strength of the magnets  402  and  412  can adjust the force needed to rotate the rotating member  410 . 
     In addition, adjacent magnets will experience a torque to align their magnetic fields. Since the magnets  402  and  412  can be configured to have multiple poles, the magnets  402  and  412  can be configured such that the inner housing  400  and the rotating member  410  will tend to magnetically align at desired orientations. This effect can thus be used to “index” the relative orientations of the inner housing  400  and rotating member  410 . For example, if the magnets  402  and  412  have  8  poles each, then the rotating member will experience a magnetic force toward an orientation every  45  degrees of rotation. These orientations at 0 degrees, 45 degrees, 90 degrees, etc. can be considered “indexed.” Further, by using magnets instead of springs or other mechanical means, friction between the rotating member and the inner housing is reduced, increasing efficiency in mechanically moving the deadbolt between the locked and unlocked position. 
     As shown in  FIG. 4B , the inner housing  400  includes openings  404  and a fitting  405 . The fitting  405  can be configured to rotate. The openings  404  can engage with the conductive prongs  330  of the outer housing  300 . The inner housing  400  can then be secured to the conductive prongs  330 , for example with screws, nails, rivets, adhesive, or any other suitable attachment mechanism. The rotating member  410  can include a notch  415  to receive fitting  405  of the inner housing  400  and assist in rotation of the fitting  405 . For example, the rotating member can be rotated by the paddle  414 , causing the fitting  405  to rotate. The fitting  405  can be configured to receive center prong  335 , which can extend through a rotating opening of the main housing. Thus, the rotation of rotating member  410 , the fitting  405  of the inner housing  400 , the center prong  335  of the outer housing  300 , and the opening of the main housing can be coupled to each other, so that the rotation of the rotating member  410  can be coupled to the position of the deadbolt. 
     Main Housing 
       FIG. 5  shows an example main housing  500 . The main housing  500  can be configured to be disposed within a bore hole of a door. For example, the main housing  500  can be configured to be disposed within an American National Standards Institute® (ANSI) deadbolt bore hole, which has a diameter of 2⅛ inches. In another example, a depth of the main housing  500  can be configured to fit within an ANSI standard door thickness, which is 1¾ inch. 
     The main housing  500  can include conductive openings  502  and a bolt carriage  508 . The bolt carriage  508  can engage the bolt housing and draw electricity from a power supply disposed within a deadbolt carried in the bolt housing. The conductive prongs  330  of outer housing  300  can extend through the conductive opening  502  to establish an electrical connection between the outer housing  300  and the main housing  500 . Thus, the electricity from the power supply disposed within the deadbolt can power electronic components within the main housing  500  as well as other electronic components disposed within the outer housing  300 . As shown in  FIG. 5 , the bolt carriage  508  can include a female connector groove that engages with a male connector of the bolt housing. The bolt carriage  508  can include pins to allow for the transmission of electricity between the bolt housing and the main housing  500 . 
     The main housing  500  can include an opening  505  configured to rotate and cause a deadbolt to transition between a locked position and an unlocked position. The main housing can include actuating components such as an actuator, gear drive, lock gearbox, latch mechanisms, motor, etc. The actuating components can include any components that can assist in mechanically moving the deadbolt. The bolt carriage  508  can be mechanically connected to the deadbolt by the female connector groove, in addition to the electrical connection as described above. Rotation of the opening  505  can cause some of these actuating components to move the bolt carriage  508 , which then results in movement of the deadbolt. For example, a homeowner could turn a paddle coupled to the opening  505  to move the deadbolt. Some of these actuating components can be powered by a power supply, for example a battery disposed within the deadbolt. Transmitting electrical energy to the actuating components can cause the actuating components to move the deadbolt. This can allow for the main housing  500  to move the deadbolt without mechanical force from a user, such as by turning a key or paddle. 
     The main housing  500  can include electronic components, such as circuit boards, processors, and antennas, for example Bluetooth, Wi-Fi, or 5G antennas. These electronic components can be powered by any suitable power supply, for example, by a battery disposed within the deadbolt. 
     In some embodiments, a controller circuit (e.g., a processor) within the main housing  500  can receive an instruction via wireless communication from a mobile device (e.g., mobile phone, smart watch, electronic ring, tablet, etc.) indicative of a lock or unlock request. An antenna within the main housing  500  can relay the instruction to the controller circuit. In addition, the processor can receive a signal from the outer housing  300 , such as a signal from a capacitive touch sensor in the outer housing  300 , or an NFC signal. The signal from the outer housing  300  can be transmitted to the controller circuit through conductor prongs  330  of the outer housing  300 . The controller circuit can cause the actuator to extend or retract. 
     In some embodiments, the controller circuit can receive a gravity vector determined by an accelerometer as it rotates along the non-linear path. The controller circuit can determine a position of the deadbolt along the linear path based on the gravity vector. The controller circuit can determine that the position of the deadbolt along the linear path corresponds to an endpoint of the non-linear path of the accelerometer. The controller circuit can cause the actuator to stop extending the deadbolt based on the determination that the position of the deadbolt along the linear path corresponds to the endpoint of the non-linear path of the accelerometer. The controller circuit can transmit a message indicating a lock state (e.g., locked, unlocked, partially locked, 30% extended, 90% extended, etc.) via the antenna. The message can be transmitted to another device (e.g., a mobile device) directly (e.g., via a personal area network) or indirectly (e.g., via a router configured to relay the message). 
     Extendable Bolt Housing 
     Doors can have bore holes of various sizes and placements on the door. For example, an ANSI standard bore hole size can be 2⅛ inches. An ANSI standard backset distance between the center of the bore hole and the edge of the door can be 2⅜ inches or 2¾ inches. In addition, doors can have bore holes of non-standard sizes and backsets. This variation can result in a door lock having unsuitable dimensions for installation on a specific door. 
       FIG. 6A  shows an example bolt housing  600  in a default position  600   a.  The length of the bolt housing  600  in default position  600   a  can be configured to accommodate a desired backset distance. For example, the default position  600   a  can accommodate a backset distance of 2⅜ inches. The bolt housing  600  can include a male connector  602 , a plate  610 , and a first bolt cap  620   a.  The bolt housing  600  can be configured to surround a deadbolt. The male connector  602  can engage with a female groove connector on the main housing  500  to electrically and mechanically connect the bolt housing  600  to the main housing  500 . The plate  610  can include a front plate  612  and a back plate  614 . The plate  610  can be affixed to an edge of a door, for example by a set of screws or nails. 
     The first bolt cap  620   a  can be configured to engage a deadbolt to a battery within the deadbolt and allow for electrical transmission from the battery to the bolt housing  600  and other parts of the door lock, including the main housing  500 , outer housing  300 , and inner housing  400 . The length of the first bolt cap  620   a  can be configured to accommodate a desired backset distance. For example, the length of the first bolt cap  620   a  can accommodate a backset distance of 2⅜ inches without protruding past the edge of the plate  610  or being recessed into the bolt housing  600 . 
       FIG. 6B  shows an example bolt housing  600  in an extended position  600   b.  The bolt housing  600  includes a bolt sleeve  630  that allows the bolt housing  600  to vary in length. This allows the bolt housing  600  to accommodate different length backset distances. For example, the bolt housing  600  in extended position  600   b  can accommodate a backset distance of 2¾ inches. The bolt housing  600  can transition between the default position  600   a  and the extended position  600   b  and thus accommodate multiple bore hole sizes and/or backsets. 
     As shown in  FIG. 6B , a second bolt cap  620   b  can be used when the bolt housing  600  is in extended position  600   b.  The length of the second bolt cap  620   b  can be different than that of the first bolt cap  620   a  to accommodate a change in length when the bolt housing  600  changes position. For example, the default position  600   a  can accommodate a backset of 2⅜ inches, while the extended position  600   b  can accommodate a backset of 2¾ inches. In this example, the second bolt cap  620   b  can be ⅜ inches longer than the first bolt cap  620   a.  The bolt caps  620   a  and  620   b  can be replaced with each other as needed to accommodate different bore hole sizes and backsets. Note that the bolt housing  600  and bolt caps  620   a  and  620   b  can be configured to accommodate any bore hole sizes and backset distances and should not be limited to the lengths described in the examples. Similarly, the bolt housing can be configured to have any number of positions, not just the default position  600   a  and extended position  600   b  as shown. 
       FIG. 7  shows an exploded view of an example bolt housing  700  and deadbolt  720 . The bolt housing  700  can be configured to receive a deadbolt. For example, the deadbolt  720  can rest within a bolt sleeve  718  within the bolt housing  700 . The deadbolt  720  can extend out of the bolt sleeve  718  and the bolt housing  700  upon being positioned to a locked position. The deadbolt  720  can be retracted into the bolt sleeve  718  and the bolt housing  700  upon being positioned to an unlock state. 
     The deadbolt  720  can be approximately cylindrically shaped. The deadbolt  720  can include a hollow inner region configured to receive a power supply  754 . The energy storage device can include, for example, an electrochemical cell (e.g., a flow battery, ultrabattery, and/or rechargeable battery), a capacitor (e.g., a supercapacitor), an energy storage coil (e.g., a superconducting magnetic energy storage device), a compressed air energy storage device, a flywheel, a hydraulic accumulator, a chemical energy storage device (e.g., hydrogen storage), or any combination of energy storage devices. The power supply  754  can be approximately cylindrically shaped. For example, the power supply  754  can be a lithium CR2 battery. 
     The deadbolt  720  can be composed of a hardened material such as, for example, a nitride metal, a precipitation hardened alloy, or a combination thereof. The hardened material (e.g., steel or stainless) can be case-hardened or through hardened to increase the surface hardness of the deadbolt  720  and/or the strength of the deadbolt  720 . This can be accomplished via nitriding, carburization, precipitation hardening, other tempering applications, a combination of tempering applications. Despite the use of less material for the deadbolt  720  (e.g., due to the hollow inner region), the hardened material can enable the deadbolt  720  to have an approximately equal fracture strength as a conventional deadbolt. Thus, the deadbolt  720  can provide space for an energy storage device while maintaining structural integrity. 
     A back plate  714  can be attached to a front plate by an attachment mechanism (e.g., plate screws  752 ). A plate hinge  750  between the back plate  714  and the front plate  712  can allow the back and front plates  714 ,  712  to tilt independently of the bolt housing  700  over a range of angles while being attached to the bolt housing  700 . Enabling the back and front plates  714 ,  712  via the plate hinge  750  can allow the back plate  714  to rest against a door having an uneven surface. 
     The bolt cap  710  can be attachable to the deadbolt  720 . For example, the bolt cap  710  can be screwed into the deadbolt  720  via threading on the interior of the deadbolt  720 . As described above and shown in  FIGS. 6A and 6B , the bolt cap  710  can be of varying sizes to accommodate different bore hole dimensions and backsets. The bolt cap  710  can secure a power supply  754  within the deadbolt  720 . In some embodiments, the bolt cap  710  can be electrically connected to the power supply  754  to allow electrical transmission from the power supply  754  to other parts of the door lock. For example, the bolt cap can contact a negative terminal of a cylindrical battery within the bolt housing  700  while the positive terminal of the battery contacts another portion of the bolt housing  700 . The bolt cap  710  can be electrically connected to the bolt housing  700 , thus allowing current to flow from the battery. 
     Methods to Lock and Unlock a Door 
       FIG. 8  shows an example method  800  for transitioning a deadbolt of a door lock between a locked position and an unlocked position. At least some of the present embodiments can relate to disposing components of a locking mechanism in a door. The method can include disposing a bolt housing within a cross bore of a door ( 802 ). For example, the cross bore can be an ANSI standard bore with 1 inch diameter. The method can include disposing a main housing into a bore hole disposed within a door ( 804 ). For example, the bore hole can be an ANSI standard bore hole with diameter 2⅛ inches, and the door can have an ANSI standard depth of 1¾ inches. The bore hole can be positioned at different backset distances, for example 2⅜ inches or 2¾ inches. The method can include extending prongs of an outer housing through openings of a main housing to an inner housing ( 806 ). The prongs of the outer housing can be conducting prongs and/or be configured to rotate. For example, the outer housing can include a keyhole configured to rotate a prong upon rotation of the keyhole. The openings of the main housing can be conductive openings and/or be configured to rotate and facilitate a transition of a deadbolt from a locked position or an unlocked position. 
     At least some of the present embodiments can relate to extending a bolt housing and accommodating caps for the bolt that include varying sizes. The method can include disposing a power supply within a bolt housing ( 808 ). The power supply can be, for example, a battery, such as a lithium CR2 battery. The method can include engaging a first bolt cap to the bolt housing ( 810 ). The first bolt cap can be configured to secure the power supply within the bolt housing. The first bolt cap can also be configured to allow for electrical transmission from the power supply to other parts of the door lock. The method can include extending the bolt housing into an extended position ( 812 ). Extending the bolt housing into an extended position can be used to accommodate a bore hole size or a backset. The method can include replacing the first bolt cap with a second bolt cap configured to engage with the bolt housing in an extended position ( 814 ). The second bolt cap can also be configured to secure the power supply within the bolt housing and/or allow for electrical transmission from the power supply to other parts of the door lock. The second bolt cap can have different dimensions from the first bolt cap. For example, the second bolt cap can be ⅜ inches longer than the first bolt cap. 
     At least some of the present embodiments can relate to transitioning a deadbolt between a locked and unlocked position based on receipt of an input. The method can include associating a door lock with a user device ( 816 ). The user device can be a smartphone, computer, tablet, NFC card, smart watch, or any other suitable device. The method can include detecting a user device is within a wireless communication range ( 818 ). For example, a wireless communication component in the main housing or in the outer housing can detect whether a user device is within a wireless communication range when an appropriate signal is received. The wireless communication range can span any suitable distance. For example, an NFC signal has a range on the order of centimeters. In another example, a Bluetooth signal has a range on the order of hundreds of meters. Other communications signals can have longer ranges, such as kilometers. 
     The method can include detecting whether a user touches a capacitive touch sensor of the outer housing ( 820 ). For example, the mutual coupling between row and column electrodes can be determined to have been changed which can signify a presence of touch, or the parasitic capacitance can be changed. In some implementations, the change in the capacitance can be determined to be within a threshold capacitance range that can be correlated with a human finger (e.g., human skin). 
     The method can include transitioning a deadbolt between a locked position and an unlocked position ( 822 ). This can occur in response to detecting a touch on the capacitive touch sensor ( 820 ), in response to detecting a user device within a wireless communication range ( 818 ), or in response to both  818  and  820 . Alternatively, the step can be performed without detecting a touch ( 820 ) or detecting a user device within a wireless communication range ( 818 ). 
     In addition to detecting a touch, characteristics of a finger touching the capacitive touch sensor can be determined. For example, the movement of the finger upon the capacitive touch sensor along a circular path can be determined. Based on the characteristics, the deadbolt can be transitioned between a locked position and an unlocked position ( 822 ), for instance by extending and retracting the deadbolt. For example, the deadbolt can be extended or retracted to adjust the position of deadbolt along a linear path as a touch is detected to move in a clockwise or counterclockwise direction, respectively. Thus, touch sensor circuitry of the door lock can be configured to determine presence of a finger upon the capacitive touch sensor, and determine characteristics of the finger upon the determination of the presence of the finger upon the capacitive touch sensor. A controller circuit can then operate the motor of the door lock to retract or extend the deadbolt based on the characteristics of the finger. 
     In addition, other characteristics can be used. For example, merely the touch of a finger can be determined. In another example, a fingerprint reader can be implemented within the door lock and a person can place a finger upon the capacitive touch sensor to lock or unlock the door based on the fingerprint of the finger being recognized as an authorized fingerprint. In some implementations, a door can be locked by any fingerprint, but unlocked upon an authorized fingerprint. This can allow for a guest in the home to lock the door, but prevents the door from being unknowingly unlocked for the homeowner. 
     In another implementation, force or pressure sensitive sensors can be used to determine an amount of force or pressure applied to the outer housing. The characteristics of the finger can further be based on the amount of force or pressure applied. For example, a certain amount of pressure can be applied and the increase in amount of pressure can result in the deadbolt extending to lock the door. 
       FIG. 9  shows an example method  900  for transitioning a deadbolt between a locked position and an unlocked position. The method can include disposing a bolt housing within a cross bore of a door ( 902 ). For example, the cross bore can be an ANSI standard bore with 1 inch diameter. The method can include disposing a main housing into a bore hole disposed within a door ( 904 ). For example, the bore hole can be an ANSI standard bore hole with diameter 2⅛ inches, and the door can have an ANSI standard depth of 1¾ inches. The bore hole can be positioned at different backset distances, for example 2⅜ inches or 2¾ inches. The method can include extending prongs of an outer housing through openings of a main housing to an inner housing ( 906 ). The prongs of the outer housing can be conducting prongs and/or be configured to rotate. For example, the outer housing can include a keyhole configured to rotate a prong upon rotation of the keyhole. The openings of the main housing can be conductive openings and/or be configured to rotate and facilitate a transition of a deadbolt from a locked position or an unlocked position. 
     The method can include attaching an inner housing to the outer housing ( 908 ). For instance, the inner housing can be attached to the prongs of the outer housing by screws. This allows for the inner housing and the outer housing to be secured against both sides of a door. The method can include magnetically engaging a rotating member to the inner housing ( 910 ). The rotating member can be configured to rotate and facilitate transition of a deadbolt from a locked position and an unlocked position as it rotates. The rotating member can include a paddle, knob, lever, or other mechanism to assist a user in rotating the rotating member. The inner housing and the rotating member can each include a magnet, such as a ring magnet. The two magnets can be disposed adjacent to each other, magnetically engaging the rotating member to the inner housing. The magnets can be multipole magnets. The polarity of the magnets on the inner housing and the rotating member can be configured such that the two magnets magnetically align at desired orientations. For example, the magnets can have eight poles to create eight “index” orientations such that the rotating member and the inner housing will be attracted to these orientations as the rotating member rotates, e.g., at 45 degree intervals. In addition, the strength of the magnets can be configured to adjust the force necessary to rotate the rotating member. The polarity and strength of the magnets can both be configured to provide a smooth transition of the deadbolt and desired number or positions of index orientations. 
     The method can include transitioning a deadbolt between a locked position and an unlocked position ( 912 ). For example, the deadbolt can transition as a user rotates a paddle of the rotating member, as described above. In another example, the deadbolt can transition by other means, such as a key or by an actuator within the main housing in response to receiving a wireless signal. In some embodiments, transitioning the deadbolt between a locked position and unlocked position ( 912 ) can cause the rotating member to rotate. For example, the rotating member can be engaged with a fitting in the inner housing, the fitting in the inner housing engaged with a prong of the outer housing. If the prong of the outer housing rotates as the deadbolt transitions between a locked position and an unlocked position, then the rotating member can also rotate accordingly. 
     Processing System 
       FIG. 10  is a block diagram illustrating an example of a processing system in which at least some operations described herein can be implemented. For example, some components of the processing system  1000  can be hosted on an electronic device as described in the present embodiments. 
     The processing system  1000  can include one or more central processing units (“processors”)  1002 , main memory  1006 , non-volatile memory  1010 , network adapter  1012  (e.g., network interface), video display  1018 , input/output devices  1020 , control device  1022  (e.g., keyboard and pointing devices), drive unit  1024  including a storage medium  1026 , and signal generation device  1030  that are communicatively connected to a bus  1016 . The bus  1016  is illustrated as an abstraction that represents one or more physical buses and/or point-to-point connections that are connected by appropriate bridges, adapters, or controllers. The bus  1016 , therefore, can include a system bus, a Peripheral Component Interconnect (PCI) bus or PCI-Express bus, a HyperTransport or industry standard architecture (ISA) bus, a small computer system interface (SCSI) bus, a universal serial bus (USB), IIC (I2C) bus, or an Institute of Electrical and Electronics Engineers (IEEE) standard 1394 bus (i.e., “Firewire”). 
     The processing system  1000  can share a similar computer processor architecture as that of a desktop computer, tablet computer, personal digital assistant (PDA), smartphone, game console, music player, wearable electronic device (e.g., a watch or fitness tracker), network-connected (“smart”) device (e.g., a television or home assistant device), virtual/augmented reality systems (e.g., a head-mounted display), or another electronic device capable of executing a set of instructions (sequential or otherwise) that specify action(s) to be taken by the processing system  1000 . 
     While the main memory  1006 , non-volatile memory  1010 , and storage medium  1026  (also called a “machine-readable medium”) are shown to be a single medium, the term “machine-readable medium” and “storage medium” should be taken to include a single medium or multiple media (e.g., a centralized/distributed database and/or associated caches and servers) that store one or more sets of instructions  1028 . The term “machine-readable medium” and “storage medium” shall also be taken to include any medium that is capable of storing, encoding, or carrying a set of instructions for execution by the processing system  1000 . 
     In general, the routines executed to implement the embodiments of the disclosure can be implemented as part of an operating system or a specific application, component, program, object, module, or sequence of instructions (collectively referred to as “computer programs”). The computer programs typically comprise one or more instructions (e.g., instructions  1004 ,  1008 ,  1028 ) set at various times in various memory and storage devices in a computing device. When read and executed by the one or more processors  1002 , the instruction(s) cause the processing system  1000  to perform operations to execute elements involving the various aspects of the disclosure. 
     Moreover, while embodiments have been described in the context of fully functioning computing devices, those skilled in the art will appreciate that the various embodiments are capable of being distributed as a program product in a variety of forms. The disclosure applies regardless of the particular type of machine or computer-readable media used to actually effect the distribution. 
     Further examples of machine-readable storage media, machine-readable media, or computer-readable media include recordable-type media such as volatile and non-volatile memory devices  1010 , floppy and other removable disks, hard disk drives, optical disks (e.g., Compact Disk Read-Only Memory (CD-ROMS), Digital Versatile Disks (DVDs)), and transmission-type media such as digital and analog communication links. 
     The network adapter  1012  enables the processing system  1000  to mediate data in a network  1014  with an entity that is external to the processing system  1000  through any communication protocol supported by the processing system  1000  and the external entity. The network adapter  1012  can include a network adaptor card, a wireless network interface card, a router, an access point, a wireless router, a switch, a multilayer switch, a protocol converter, a gateway, a bridge, bridge router, a hub, a digital media receiver, and/or a repeater. 
     The network adapter  1012  can include a firewall that governs and/or manages permission to access/proxy data in a computer network and tracks varying levels of trust between different machines and/or applications. The firewall can be any number of modules having any combination of hardware and/or software components able to enforce a predetermined set of access rights between a particular set of machines and applications, machines and machines, and/or applications and applications (e.g., to regulate the flow of traffic and resource sharing between these entities). The firewall can additionally manage and/or have access to an access control list that details permissions including the access and operation rights of an object by an individual, a machine, and/or an application, and the circumstances under which the permission rights stand. 
     The techniques introduced here can be implemented by programmable circuitry (e.g., one or more microprocessors), software and/or firmware, special-purpose hardwired (i.e., non-programmable) circuitry, or a combination of such forms. Special-purpose circuitry can be in the form of one or more application-specific integrated circuits (ASICs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), etc. 
     CONCLUSION 
     Unless contrary to physical possibility, it is envisioned that (i) the methods/steps described above may be performed in any sequence and/or in any combination, and that (ii) the components of respective embodiments may be combined in any manner. 
     The techniques introduced above can be implemented by programmable circuitry programmed/configured by software and/or firmware, or entirely by special-purpose circuitry, or by a combination of such forms. Such special-purpose circuitry (if any) can be in the form of, for example, one or more application-specific integrated circuits (ASICs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), etc. 
     Software or firmware to implement the techniques introduced here may be stored on a machine-readable storage medium and may be executed by one or more general-purpose or special-purpose programmable microprocessors. A “machine-readable medium”, as the term is used herein, includes any mechanism that can store information in a form accessible by a machine (a machine may be, for example, a computer, network device, cellular phone, personal digital assistant (PDA), manufacturing tool, any device with one or more processors, etc.). For example, a machine-accessible medium can include recordable/non-recordable media (e.g., read-only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, etc.). 
     Any of the steps as described in any methods or flow processes herein can be performed in any order to the extent the steps in the methods or flow processes remain logical. 
     Note that any and all of the embodiments described above can be combined with each other, except to the extent that it may be stated otherwise above or to the extent that any such embodiments might be mutually exclusive in function and/or structure. 
     Although the present invention has been described with reference to specific exemplary embodiments, it will be recognized that the invention is not limited to the embodiments described but can be practiced with modification and alteration within the spirit and scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense.