Patent Publication Number: US-7215250-B2

Title: Proximity detaching for electronic article surveillance tags

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This application relates to electronic article surveillance (EAS) tags, and more particularly to a reusable EAS tag that is proximity detached by electromagnetic energy. 
     2. Description of the Related Art 
     Electronic article surveillance systems are well known in the art and are used in many applications including inventory control and to prevent theft and unauthorized removal of articles from a controlled area. Typically, in such systems a system transmitter and a system receiver are used to establish a surveillance zone, which must be traversed by any articles being removed from the controlled area. 
     An EAS tag is affixed to each article and includes a marker or sensor adapted to interact with a signal being transmitted by the system transmitter into the surveillance zone. This interaction causes a further signal to be established in the surveillance zone which further signal is received by the system receiver. Accordingly, upon movement of a tagged article through the surveillance zone, a signal will be received by the system receiver identifying the unauthorized presence of the tagged article in the zone. 
     Certain types of EAS tags have been designed to be reusable and, thus, include releasable attachment devices for affixing the tags to the articles. Such attachment devices are further designed to be releasable by authorized personnel only so that unauthorized removal of a tag from its article is avoided. To this end, many attachment devices are made releasable only through the use of an associated special tool or detaching mechanism. 
     An EAS tag employing an attachment device and an associated detacher is described in U.S. Pat. No. 3,942,829, entitled Reusable Security Tag, issued to Humble, et al. on Mar. 9, 1976. The EAS tag of the &#39;829 patent includes a tag body and an attachment device in the form of a tack assembly. The tack assembly includes an enlarged head and a tack body having a pointed end, which serves to pierce through an article and to be receivable in and clamped to the tag body. This secures the article and tag together. 
     In the tag of the &#39;829 patent, the tack is clamped to the tag body using a spring clamp formed as a clutch lock with spreadable jaws. Once the article is pierced, the pointed tack end is received in the tag body and is secured between the jaws of the clutch lock. This locks the tack and the tag body forming the EAS tag to the article so that the tag and article cannot be readily separated from each other. 
     In order for authorized personnel to be able to release the tack from the clutch lock and, therefore, the tag from the article, the &#39;829 patent utilizes a detacher mechanism which is adapted to grip the tag body and apply a bending force thereto. This force is sufficient to deform the clutch lock so that the jaws of the clutch lock are spread apart, thereby releasing the tack. The tack can then be removed from the tag body so that the article and tag become separated from one another. 
     To permit the bending of the tag body sufficiently to deform the clutch lock, the tag body of the &#39;829 patent must be made of a flexible material. Typically, flexible plastic materials such as, for example, polypropylene, have been used. Such materials, however, are susceptible to being cut and damaged. This tends to be a disadvantage, since it increases the likelihood that the locking feature of the tag can be separated from the EAS sensor part of the tag or can be exposed and defeated. 
     Another type of EAS security device is known in which a variation of the spring clamp of the &#39;829 patent has been incorporated into a so-called keeper for a compact disc. This type of device is disclosed in U.S. Pat. No. 5,031,756, entitled Keeper For Compact Disc Package Or The Like, issued to Buzzard, et al. on Jul. 16, 1991. 
     The keeper of the &#39;756 patent comprises a rigid plastic frame. One side of the frame is provided with an enlarged section which houses a tack-like button assembly and a spring clamp as in the &#39;829 patent. In this case, the spring clamp is used to lock the button assembly in a first position. In this position, the pointed end of the button assembly protrudes into the frame to pierce and hold to the frame a cardboard container containing a compact disc. As a result, unauthorized removal of the compact disc with the frame causes an EAS sensor also incorporated into the frame, to generate a detectable signal for alarming an EAS system. 
     In the keeper of the &#39;756 patent, the enlarged section of the frame is provided with opposing linear slots, which lead to the region between the jaws of the spring clamp. By inserting ramped linear fingers into these slots, the fingers are guided into this region, causing the jaws to flex outward. This releases the button enabling it to be withdrawn from the cardboard container. The container and its housed compact disc can then be separated from the frame. 
     While the keeper of the &#39;756 patent utilizes a spring clamp of the &#39;829 patent type in a rigid frame, it also has certain drawbacks. One drawback is that the linear slots leading to the spring clamp permit in-line viewing and access to the clamp. This increases the susceptibility of the clamp to defeat, since linear objects can be inserted into the slots in an attempt to open the jaws. Another drawback is that the fingers of the detacher are required to be of high precision, since they must be received in the region between the spring clamp jaws. This increases the cost and complexity of the detacher. 
     U.S. Pat. No. 5,426,419, entitled Security Tag Having Arcuate Channel And Detacher Apparatus For Same, issued to Nguyen, et al. on Jun. 20, 1995, discloses an EAS tag that has a hard tag body, which is adapted to be releasable from an article in an easy and simple manner by insertion of an arcuate probe of an associated detacher device into an arcuate channel of the tag to release a spring clamp mechanism. The spring clamp mechanism is a releasable locking mechanism that prevents removal of the tack assembly that is adapted for insertion through an article, which is captured when inserted into an opening in a portion of the tag body. The EAS tag of the &#39;419 patent is more difficult to defeat than the above tags and is in worldwide use. 
     The EAS tag of the &#39;419 patent can be defeated by insertion of a segment of relatively rigid metal bent in an arcuate manner to simulate the arcuate probe of the associated detacher device. U.S. Pat. No. 6,373,390, entitled Electronic Article Surveillance Tag Having Arcuate Channel, issued to Hogan, et al. on Apr. 16, 2002, discloses a device usable in the EAS tag of the &#39;419 patent to reduce the potential for defeats by insertion of simulated arcuate probes. As each improvement in defeat resistance is implemented, new techniques for unauthorized tag removal are developed. An improved EAS tag detachment mechanism is needed to reduce the incidence of unauthorized EAS tag detachments. 
     An alternate to a reusable EAS tag is a disposable EAS tag or EAS label. Instead of detachment from an article that is authorized for removal, EAS labels are typically deactivated so they do not interact with the EAS surveillance zone and are not detected by the associated EAS receiver when the article is removed. Deactivation is normally accomplished by exposing the label to an electromagnetic field or pulse of preselected waveform, frequency, amplitude, and/or duration. Deactivation normally occurs near the cash register in a retail environment, and may be linked to a barcode scanner or to radio frequency identification (RFID) equipment. In some cases, the deactivator equipment may be triggered as the article is scanned for checkout. 
     U.S. Pat. No. 5,867,101, entitled Multi-Phase Mode Multiple Coil Distance Deactivator for Magnetomechanical Marker, issued to Copeland, et al. on Feb. 2, 1999, and U.S. Pat. No. 6,060,988, entitled EAS Marker Deactivation Device Having Core-Wound Energized Coils, issued to Copeland, et al. on May 9, 2000, disclose deactivators suitable for deactivating magnetomechanical or acoustomagentic EAS labels and are available from Sensormatic Electronics Corporation, Boca Raton, Fla. Deactivators for radio frequency (RF), and other technology EAS labels are also commercially available. In some instances, retail merchants may use reusable EAS tags and disposable EAS labels in one store, which requires separate detaching and deactivation mechanisms for different purchases. If a deactivator could be used to detach EAS tags, the burden of the retailer to have multiple mechanisms would be eliminated, and the mechanical techniques for unauthorized detaching of EAS tags could also be reduced. 
     In addition, detaching of EAS tags requires the presentation of the tag to the detaching device and/or the application of mechanical force by the operator. Detaching by simply placing the EAS tag in proximity to a detaching mechanism would speed up the detaching process, thereby reducing the time required for each transaction, decreasing costs, and increasing customer satisfaction. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is an electronic article surveillance (EAS) tag that is detachable from an article by placing the EAS tag in proximity to a detaching device. The detaching device transmits a signal to detach the tag from an article to which the tag is attached. The tag includes an energy coupler, a micro-actuator, and a clamping mechanism. 
     In one aspect, the EAS tag is detachable from an article by an electromagnetic signal, and includes an energy coupler for receiving energy from the electromagnetic signal. The energy coupler provides electrical energy in response to the electromagnetic signal. An actuator, connected to the energy coupler, converts the electrical energy to mechanical energy. A clamping mechanism, connected to the actuator, prevents release of the tag from an article to which the tag can be attached. The clamping mechanism is responsive to the mechanical energy to enable release of the tag from the article to which the tag can be attached. 
     The energy coupler can be an inductively coupled coil or may include a battery and trigger mechanism for switching the battery on to apply power to the actuator. 
     The actuator can include a plurality of shape memory alloy members disposed in cooperative arrangement to provide movement, such as linear motion, upon conversion of the electrical energy to mechanical energy, the mechanical energy can be defined as the linear motion. The actuator could alternately be a piezoelectric member. The piezoelectric member deforms and provides movement in response to the electrical energy, and where the mechanical energy can be defined as the linear motion. The actuator could also be an electrostrictive polymer member. The electrostrictive polymer member compresses in thickness and elongates in length to provide movement in response to the electrical energy and where the mechanical energy can be defined as the linear motion. 
     The clamping mechanism can include a pin assembly having a pin body, and jaw assembly having at least one jaw moveable from a first position to a second position in response to the mechanical energy, the first position retaining the pin body in a locked position where the pin body can be inserted through an article and retains the tag to the article. The second position releases the pin body to move out of the article releasing the tag from the article. The clamping mechanism may include a release member responsive to the mechanical energy. Where the jaw assembly includes a leg member adapted for moving the jaw between the first position and the second position, the release member is disposed between the actuator and the leg member and where the mechanical energy includes linear motion to move the release member to engage and disengage the leg member to move the jaw from the first position to the second position, respectively. 
     Alternately, the actuator may include a plurality of shape memory alloy members. The plurality of shape memory alloy members are disposed in cooperative arrangement and adapted to provide rotational motion upon conversion of the electrical energy to mechanical energy, the mechanical energy defined as rotational motion. 
     The energy coupler further may include a decoder to recognize the transmitted signal where the transmitted signal includes a code or preselected waveform that is recognizable by the decoder. 
     The electronic article surveillance tag may be a container where the article to be protected is placed inside. 
     The invention includes methods for electronic article surveillance tag removal corresponding to the above apparatus. 
     Objectives, advantages, and applications of the present invention will be made apparent by the following detailed description of embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a block diagram of the present invention. 
         FIG. 2  is an exploded perspective view of one embodiment of the present invention. 
         FIG. 3  is a side elevational view of that of one embodiment of the present invention. 
         FIG. 4  is a cross-sectional view of that of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of that of  FIG. 3  with the pin assembly inserted. 
         FIG. 6  is a side elevational view of that of  FIG. 3  in the released state. 
         FIG. 7  is a cross-sectional view of that of  FIG. 6 . 
         FIG. 8  is a schematic diagram of one embodiment of a linear motion micro-actuator used in the present invention. 
         FIG. 9  is a schematic diagram of an embodiment of a rotational motion microactuator used in the present invention. 
         FIG. 10  is a schematic diagram of a rotational motion micro-actuator incorporating a clamping mechanism. 
         FIG. 11  is an alternate block diagram of the present invention. 
         FIG. 12  is an alternate block diagram of the present invention. 
         FIG. 13  is a perspective view of an alternate embodiment where the article is placed inside a carrier. 
         FIG. 14  is a latch mechanism of the embodiment of  FIG. 13 . 
         FIG. 15  is a plan view of portions of one embodiment of the present invention associated with the embodiment of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , the invention includes an energy coupling device or energy coupler  2 , a small or micro-actuator  4 , and a mechanical locking or clamping mechanism  6 , which are each fully described hereinbelow. Energy coupler  2  may be any device that receives transmitted energy, and coverts that energy into electrical energy. Energy coupler  2  may be an antenna or coil, such as an inductively coupled coil, with or without a magnetic core, that receives electromagnetic energy and transfers that collected energy to micro-actuator  4 . Energy coupler  2  may alternately be a transducer that receives acoustic energy. Energy coupler  2  may alternately be a trigger mechanism and a battery. In that embodiment, the trigger mechanism would receive an electromagnetic signal, and switch the battery power to the micro-actuator  4 . The transmitted signal, which may be an electromagnetic field or signal that notifies the tag of an authorized detaching of the tag, may be generated from existing EAS deactivators presently in commercial use, or new equipment specifically adapted for detaching can be implemented as needed. The electromagnetic release signal can be any selected waveform, frequency, amplitude, and duration, and either pulsed or continuous. Alternately, the detaching signal can be acoustic, or any other transmitted signal adapted for the release of the tag. 
     Micro-actuator  4  converts the electrical energy received from energy coupler  2 , into mechanical energy to actuate clamping mechanism  6 . Micro-actuator  4  can be any actuator that, preferably, can receive sufficient energy from a conventional EAS tag deactivator and trigger the release of a clamping mechanism, and which is small enough to fit into an EAS tag. The selection of the micro-actuator  4  is dependent on the design of the clamping mechanism, and may include shape memory alloy, piezoelectric cantilever, and electroactive polymer actuator materials. 
     An example of shape memory alloy is a crystalline alloy of NiTi (Nickel and Titanium). When the NiTi alloy is heated, its crystalline structure rearranges resulting in a mechanical contraction. The material can be formed into a thin wire. When electrical current produced from energy coupler  2  is passed through the wire it is heated and contracts. When power is removed, the wire relaxes, but remains in its contracted position. Application of a tensile force is required to return the wire to its extended position. Many wires together can form an actuator having linear motion or actuation. The above described shape memory alloy exhibits what is called one-way response. In an alternate configuration called two-way response, the shape memory alloy wires can be trained to return to their extended position state when in the relaxed state. Further information about two-way shape memory effect can be found in: Perkins, J., et al., “The Two-Way Shape Memory Effect”, Engineering Aspects of Shape Memory Alloys, (Butterworth-Heinemann, 1990), at 195–206. Applications using shape memory alloy as described herein are commercially available from NanoMuscle, Inc., Antioch, Calif. 
     Piezoelectric material expands and contracts in relation to an applied voltage. The piezoelectric material can be bonded or connected to another material in a sandwich configuration to cause a bend in the material when the piezoelectric material expands or contracts. The bend can be used for linear actuation. Examples of piezoelectric material applications can be found in U.S. Pat. Nos. 6,071,087; 5,632,841; and 5,471,721. 
     Electroactive or electrostrictive polymer actuators can be formed by placing a dielectric film of elastomeric polymer material between two compliant electrodes. When a voltage difference is applied between the electrodes, the polymer is compressed in thickness and expanded in length and width as a result of the electrostatic forces generated by the free charges on the electrodes. Examples of elastomeric polymer material include, but are not limited to, polyurethane, silicone, fluorosilicone, ethylene propylene, polybutadiene, and isoprene. Compliant electrodes can be, but are not limited to, graphite powder, carbon powder, carbon fibers, and ionically conductive water-based polymers. The compliant electrodes can be formed directly onto the polymer film, or made as separate layers and then attached. The actuator may be constructed in different shapes such as planar, tubular, and the like, depending on the application. Further information on electrostrictive polymers can be found in: Pelrine, R., et al., “Electrostriction of Polymer Dielectrics with Compliant Electrodes as a Means of Actuation”, Sensors and Actuators A: Physical 64, 1998, at 77–85. 
     Clamping mechanism  6  can be any mechanical locking mechanism that prevents unauthorized removal of the EAS tag from the article to which it is attached. Examples of various clamping mechanisms have been previously described herein. A further example of clamping mechanism  6  is presented herein in the following description of one embodiment of the present invention. 
     Referring to  FIGS. 2 and 3 , one embodiment of the present invention  7  is illustrated, and includes coil  8 , shape memory actuator  10 , and clamping mechanism  12 . Coil  8  receives energy from an electromagnetic pulse emitted from a conventional deactivator, which are commercially available from Sensormatic Electronics Corporation, Boca Raton, Fla., and couples or transfers the received energy to actuator  10 . Actuator  10  is made of a plurality of shaped memory alloy wires  11 , as described herein. Wires  11  are better illustrated in  FIG. 8  hereinbelow. Clamping mechanism  12  is a spring clamp that includes jaws  14  that are adapted to grip pin body  15 , which extends from pin assembly  16 . Retaining ring  19  retains pin assembly  16  within tag housing  18 . Jaws  14  are biased in a first position and are moved into a second position by release member  20 , as fully described hereinbelow, to release or grip pin body  15 , respectively. A portion of an article to which tag  7  is to be attached is placed in opening or slot  22 , and when pin assembly  16  is depressed into housing  18 , pin body  15  is inserted through the article and into jaws  14 . Jaws  14  will firmly grip pin body  15  until spread apart by force as described below. Pin assembly  16 , with pin body  15  through an article in slot  22 , prevents removal of tag  7  from the article unless pin body  15  is released from jaws  14 . 
     Referring to  FIG. 4 , a cross-sectional view of  FIG. 3  shows how release member  20  retains jaws  14  in a clamped position by pressing against legs  13  of clamping mechanism  12  when actuator  10  is in an extended position. Legs  13  are biased to spring towards each other, which rotates jaws  14  apart, and will do so unless legs  13  are forced apart by release member  20 . Cavity  24  will include a spring  25 , shown in  FIG. 2 , to bias pin assembly  16  in the extended position as illustrated. Coil  8  is not shown in  FIG. 4  and subsequent figures for simplicity. 
     Referring to  FIG. 5  the position of pin assembly  16  when depressed into tag body  18 , which pushes pin body  15  through an article (not shown) disposed in slot  22  and through jaws  14 , which are clamped to prevent withdrawal of pin body  15 , is illustrated. Jaws  14  are sufficiently bendable to allow insertion of pin body  15  therethrough, but are rigid enough to prevent withdrawal of pin body  15  without spreading apart the jaws  14 . 
     Referring to  FIGS. 6 and 7 , upon receiving a preselected electromagnetic signal or pulse, coil  8  delivers current through wires  11  of actuator  10  causing each wire  11  to contract resulting in actuator  10  contracting. Wires  11  are better illustrated in  FIG. 8  hereinbelow. Actuator  10  is connected to release member  20  by linkage  21 . When actuator  10  contracts, release member  20  is pulled linearly into a retracted position as shown. When actuator  10  retracts release member  20 , legs  13  spring toward each other, thus separating jaws  14  and placing clamping mechanism  12  in the released state thereby unclamping pin body  15 . The bias spring  25  in cavity  24 , shown in  FIG. 2 , pulls pin assembly  16  away from clamping mechanism  12 . In this embodiment, shaped memory alloy wires  11  exhibit a two-way response. However, bias spring (not shown) located in cavity  26  can be used to help force actuator  10  back to the extended position after the release electromagnetic signal or pulse is removed. 
     Referring to  FIG. 8 , one embodiment of actuator  10  is illustrated having a plurality of shape memory alloy wires  11  connected to plates  30 , which are relatively rigid. When current is applied from energy coupler  2 , wires  11  contract resulting in linear motion  32 . Energy coupler  2  is represented in this embodiment as including a battery and trigger switch, but can be any of the embodiments described herein or suitable equivalents. 
     Referring to  FIG. 9 , and alternate embodiment is illustrated using shape memory alloy wires  11  to cause rotation motion  34  instead of linear motion as in the above-described embodiment. In this embodiment, when current is applied to wires  11 , they contract causing circular plates  36 , which are relatively rigid, to rotate about fixed center  38 . In this embodiment, an external force  39  exerted in the axial or radial direction will not cause rotation of plates  36 , and will not result in an unwanted release. 
     Referring to  FIG. 10 , an example of an implementation of a rotation motion micro-actuator that incorporates one embodiment of clamping mechanism  6  is illustrated. Each circular plate  36  includes a keyway  40  in an opening  39  near the center of rotation  38 . A pin shaft  42 , which is part of an attachment pin assembly (not shown), has a key  44  along shaft  42 . When wires  11  are in the relaxed state, bias spring  46  orients the plates so that keyways  40  will be slightly misaligned with each other. Key  44  is angled so that when pin shaft  42  is inserted into opening  39 , key  44  will rotate each plate  36  in turn, which are biased by spring  46  to return plates  36  to their starting position where keyways  40  are misaligned. When pin shaft  42  is inserted through opening  39 , the misalignment of keyways  40  will prevent withdrawal of pin shaft  42  due to key  44 . When current is applied to wires  11  they contract causing plates  36  to rotate, aligning keyways  40 . When keyways  40  are aligned, key  44  and pin shaft  42  can be removed from opening  39 . 
     Referring to  FIG. 11 , the transmitted signal received by energy coupler  2 , can be a coded signal or a specific waveform that must be decoded or recognized by decoder  50  before power is delivered to micro-actuator  4 . Decoder  50  can help prevent an unauthorized signal from being used to release clamping mechanism  6 , to detach the EAS tag. 
     Referring to  FIG. 12 , in an analogous manner to that shown in  FIG. 1 , a decoder  52  can be used to decode or recognize a coded signal or specific waveform, respectively, which is received by trigger input transducer  5 . Trigger input transducer  5  can be any receiver for the transmitted signal used for detaching. Once decoder  52  identifies the transmitted signal as being a valid release signal, the power from battery  56  is connected to micro-actuator  4 . 
     As described hereinabove, alternate actuators and energy couplers can be implemented along with alternate clamping mechanisms. Actuation by linear motion and rotation motion is described herein, but other actuations can be implemented to correspond to alternate clamping mechanism designs. The main feature of the invention is detaching using a transmitted signal or an electromechanical field instead of using conventional mechanical detaching of the EAS tag. 
     Referring to  FIG. 13 , in an alternate embodiment of the invention, a carrier case containing an EAS label is used to hold retail items. If the items are taken through the interrogation zone near a store exit, the EAS label within the carrier case sets off an alarm. Upon a sale of the article, the carrier case is removed at the cash register, and the customer can remove the purchased item from the store without setting off an alarm. An example, of a typical application is a compact disc (CD) carrier  60 . The disc carrier  60  is removed at the cash register upon the purchase of the CD. The carrier  60  usually contains an EAS label, but may be used merely as a deterrent device because the physical size of the carrier is bigger than the CD, and more difficult to conceal. In any event, removal of the CD carrier  60  is analogous to the EAS tag in that, prior to the present invention, removal required a mechanical mechanism to open the CD carrier  60  to remove the CD. 
     Referring also to  FIG. 14 , in one embodiment, slide switch  62  is used to move latch member  64  to engage latch teeth  65  into and out of corresponding openings  66  in carrier  60 , to latch lid  61  closed on carrier  60 . Lid  61  is hinged at hinge  67 . Slide switch  62  includes peg members  68 , which protrude into slots  69  and which facilitate conversion of the direction of motion of slide switch  62  to move latch member in a perpendicular direction for latching. Slide switch  62  is constrained to lateral movement with respect to lid  61  by a suitable mechanism, such as constraining ribs on lid  61 , or an additional member having a slot to guide peg members  68 , not shown. The details are simplified, as it is believed that the specific mechanical mechanism is merely a design choice for one skilled in the art. The present conventional release mechanism uses a locking pin that prevents the sliding of slide switch  62  unless slide switch  62  is inserted into a detacher mechanism that releases the locking pin (not shown). The present invention can be implemented for application of a transmitted signal to release a similar locking pin to open the CD carrier. 
     Referring to  FIG. 15 , slide switch  62  is biased by compression spring  70 , which is secured by a fixed block  71 . Spring  70  tries to force slide switch  62  into an unlocked position that results in latch member  64  being in a corresponding retracted or unlocked position. Support member  72  is fixed to carrier  60  and is used to retain the following. Locking pin  74  is biased in the extended, or locked position by spring  75 . Locking pin  74  prevents bias spring  70  from pushing slide switch  62 , and latch member  64 , from the locked position to the unlocked position. Micro-actuator  76 , which contracts upon activation, pulls locking pin  74  from the extended and locked position. Once locking pin  74  is retracted, spring  70  forces slide switch  62  into the unlocked position, and allows lid  61  of carrier  60  to fall open. The energy coupler for actuator  72 , which is not specifically illustrated, can be any as described hereinabove. 
     It is to be understood that variations and modifications of the present invention can be made without departing from the scope of the invention. It is also to be understood that the scope of the invention is not to be interpreted as limited to the specific embodiments disclosed herein, but only in accordance with the appended claims when read in light of the forgoing disclosure.