Patent Application
20160324335
The present invention relates generally to refrigerated display cases and more particularly to a sliding door assembly for a refrigerated display case.
Refrigerated display cases (e.g., a refrigerators, freezers, refrigerated merchandisers, etc.) are used in a wide variety of commercial, institutional, and residential applications for storing and/or displaying refrigerated or frozen items. For example, self-service type refrigerated display cases or merchandisers are often used in grocery stores, supermarkets, convenience stores, florist shops, and other commercial settings to store and display temperature-sensitive consumer goods (e.g., food products and the like).
Many refrigerated display cases have a display case door (e.g., a door with an insulated glass panel) through which items within the refrigerated display case can be viewed. In some refrigerated display cases, the door is hingedly attached to a frame and swings open relative to the frame to facilitate consumer access to the refrigerated or frozen items. Other refrigerated display cases use sliding doors that move linearly relative to the frame.
Previous sliding door type refrigerated display cases suffer from a number of disadvantages. For example, the sliding doors are often designed to slide along a track at the bottom of the door frame. The bottom track can collect debris and must be regularly cleaned to ensure proper operation of the sliding doors. Sliding doors can be difficult to open and close due to the weight of the doors being supported by the bottom track, resulting in a friction force which must be overcome when sliding the doors along the bottom track. Additionally, sliding doors often fail to return to the closed position when not in use. It would be desirable to provide a sliding door assembly for a refrigerated display case that overcomes these and other disadvantages.
One implementation of the present disclosure is a sliding door assembly for a refrigerated display case. The sliding door assembly includes a door frame having a top frame segment that defines one or more substantially horizontal and parallel channels. The sliding door assembly includes a plurality of sliding bearings positioned within the one or more substantially parallel channels. The sliding bearings are configured to slide along the top frame segment within the one or more substantially parallel channels. The sliding door assembly includes a plurality of display case doors coupled to the plurality of sliding bearings and configured to slide, along with the plurality of sliding bearings, between an open position and a closed position. The sliding door assembly includes an automatic closure system coupled to the plurality of display case doors and configured to apply a closing force that automatically returns the plurality of display case doors to the closed position. The sliding door assembly includes one or more magnets coupled to the door frame and configured to apply a magnetic damping force as the plurality of display case doors approach the closed position. The magnetic damping force opposes the closing force applied by the automatic closure system and dampens a closure of the plurality of display case doors.
In some embodiments, the plurality of display case doors are suspended from the plurality of sliding bearings.
In some embodiments, the top frame segment defines a plurality of substantially parallel channels including a front channel and a rear channel. The plurality of sliding bearings may include a front set of sliding bearings that slide within the front channel and a rear set of sliding bearings that slide within the rear channel. The plurality of display case doors may include a front display case door suspended from the front set of sliding bearings and a rear display case door suspended from the rear set of sliding bearings.
In some embodiments, the top frame segment has an open bottom face. Each of the plurality of display case doors may include a suspension frame segment along a top of the display case door. Each suspension frame segment may extend through the open bottom face of the top frame segment and attach to one or more of the plurality of sliding bearings.
In some embodiments, each of the plurality of sliding bearings includes a body and a post extending substantially horizontally from the body. The body may include a ball bearing carriage and may be configured to slide substantially horizontally within the top frame segment. The plurality of display case doors may be suspended from the posts.
In some embodiments, the plurality of sliding bearings include a magnetic material. The one or more magnets may magnetically engage the plurality of sliding bearings as the plurality of display case doors approach the closed position.
In some embodiments, the one or more magnets are fixed to the top frame segment. In some embodiments, least one of the one or more magnets is fixed to an exterior of the top frame segment and configured to apply the magnetic damping force through the top frame segment.
In some embodiments, the one or more magnets are configured to apply a magnetic holding force when the plurality of display case doors are in the open position. The magnetic holding force may oppose the closing force applied by the automatic closure system and may hold the plurality of display case doors in the open position.
In some embodiments, at least one of the one or more magnets is configured to apply both the magnetic damping force to one of the plurality of display case doors and the magnetic holding force to another of the plurality of display case doors.
In some embodiments, the sliding door assembly includes one or more latches configured to engage the plurality of display case doors in the open position and to hold the plurality of display case doors in the open position.
In some embodiments, each of the plurality of sliding bearings has a height in a vertical direction and a depth in a horizontal direction substantially perpendicular to a direction that the sliding bearing slides. The height of each of each sliding bearing may exceed its depth.
Another implementation of the present disclosure is a sliding door assembly for a refrigerated display case. The sliding door assembly includes a door frame having a top frame segment that defines one or more substantially horizontal and parallel channels. The sliding door assembly includes a plurality of sliding bearings positioned within the one or more substantially parallel channels. The plurality of sliding bearings are configured to slide along the top frame segment within the one or more substantially parallel channels. The sliding door assembly includes a plurality of display case doors coupled to the plurality of sliding bearings. The plurality of display case doors are configured to slide, along with the plurality of sliding bearings, between an open position and a closed position. The sliding door assembly includes a weight system coupled to the plurality of display case doors. The weight system is configured to apply a closing force that automatically returns the plurality of display case doors to the closed position.
In some embodiments, the sliding door assembly includes one or more latches configured to engage the plurality of display case doors in the open position and to hold the plurality of display case doors in the open position.
In some embodiments, the sliding door assembly includes one or more magnets coupled to the door frame and configured to apply a magnetic damping force as the plurality of display case doors approach the closed position. The magnetic damping force may oppose the closing force applied by the weight system and may dampen a closure of the plurality of display case doors.
In some embodiments, the door frame further includes a first side frame segment and a second side frame segment opposite the first side frame segment. The top frame segment may extend substantially horizontally between the first side frame segment and the second side frame segment.
In some embodiments, the weight system includes a first weight suspended within the first side frame segment a second weight suspended within the second side frame segment. The first weight may be coupled to a first display case door of the plurality of display case doors. The second weight may be coupled to a second display case door of the plurality of display case doors.
In some embodiments, the weight system includes a first cable suspending the first weight within the first side frame segment and a second cable suspending the first weight within the first side frame segment. The first cable may extend upward from the first weight, bend around a first cable guide that redirects the first cable substantially horizontally, and apply a horizontal closing force to the first display case door. The second cable may extend upward from the second weight, bend around a second cable guide that redirects the second cable substantially horizontally, and apply a horizontal closing force to the second display case door.
Another implementation of the present disclosure is a sliding door assembly for a refrigerated display case. The sliding door assembly includes a door frame having a top frame segment that defines a front channel and a rear channel substantially parallel to the front channel. The sliding door assembly includes a plurality of sliding bearings including a front set of sliding bearings and a rear set of sliding bearings. The front set of sliding bearings is positioned within the front channel and configured to slide along the top frame segment within the front channel. The rear set of sliding bearings is positioned within the rear channel and configured to slide along the top frame segment within the rear channel. The sliding door assembly includes a plurality of display case doors including a front display case door and a rear display case door. The front display case door is coupled to the front set of sliding bearings and configured to slide with the front set of sliding bearings along the front channel. The rear display case door is coupled to the rear set of sliding bearings and configured to slide with the rear set of sliding bearings along the rear channel. The sliding door assembly includes an automatic closure system coupled to the plurality of display case doors. The automatic closure system is configured to apply a closing force that automatically returns the plurality of display case doors to a closed position.
In some embodiments, the automatic closure system includes one or more weights suspended within opposing side segments of the door frame. Each of the weights may be coupled to one of the plurality of display case doors via a cable.
In some embodiments, the automatic closure system includes one or more magnets coupled to the door frame. The one or magnets may be configured to apply a magnetic damping force as the plurality of display case doors approach the closed position. Thee magnetic damping force may oppose the closing force applied by the automatic closure system and may dampen a closure of the plurality of display case doors.
The foregoing is a summary and thus by necessity contains simplifications, generalizations, and omissions of detail. Consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices and/or processes described herein, as defined solely by the claims, will become apparent in the detailed description set forth herein and taken in conjunction with the accompanying drawings.
Referring generally to the FIGURES, a sliding door assembly for a refrigerated display case and components thereof are shown, according to various exemplary embodiments. The sliding door assembly described herein includes a perimeter frame and a plurality of display case doors that slide linearly (i.e., horizontally) along a top frame segment of the perimeter frame. Each of the display case doors is coupled to one or more sliding bearings that slide substantially horizontally within a channel defined by the top frame segment of the perimeter frame (e.g., a front channel, a rear channel, etc.). The display case doors may slide relative to the perimeter frame, along with the sliding bearings, between an open position and a closed position.
In some embodiments, the display case doors are suspended from the sliding bearings. For example, each sliding bearing may include a body (e.g., a ball bearing carriage) that slides within the top segment of the perimeter frame and a post that extends substantially horizontally from the body. The display case doors may include a suspension frame segment along a top of each door. The suspension frame segment may include one or more hooks or other coupling features that allow the display case doors to be suspended from the posts that extend from the sliding bearings. The top frame segment of the perimeter frame may have an open bottom face which allows the display case doors to attach to the sliding bearings.
In some embodiments, the perimeter frame has a bottom frame segment with a substantially flat upper surface. The flat upper surface of the bottom frame segment results in a bottom frame segment that is completely gutterless (i.e., without a track, channel, or gutter within the bottom frame segment). Advantageously, the gutterless design facilitates cleaning and prevents the bottom frame segment from collecting debris which could interfere with the sliding of the display case doors.
In some embodiments, the sliding door assembly includes an automatic closure system configured to automatically return the display case doors to the closed position. The automatic closure system may include one or more weights suspended within side segments of the perimeter frame. The weights may be suspended from cables that connect the weights to the display case doors. The automatic closure system may include an L-shaped housing or pulley at the top of each side frame segment to redirect the cables to apply a horizontal closing force to the display case doors.
In some embodiments, the sliding door assembly includes one or magnets coupled to the door frame. The magnets may be configured to apply a magnetic damping force as the plurality of display case doors approach the closed position. For example, the sliding bearings may be constructed from a magnetic material that is attracted to the magnets as the display case doors move past the magnets. The magnetic damping force opposes the closing force applied by the automatic closure system and dampens (i.e., slows) the movement of the display case doors as the doors approach the closed position. Advantageously, the magnetic damping force facilitates a soft closure of the display case doors.
In some embodiments, the magnets also function to hold the display case doors in the open position. For example, one or more of the magnets may apply a magnetic damping force to one display case door and a magnetic holding force to another display case door. The positions of the magnets may be selected such that each magnet is capable of providing both the magnetic damping force and the magnetic holding force (e.g., to different doors, to the same door, etc.). A mechanical latch may also be used to hold the display case doors in the open position. These and other features and advantages of the sliding door assembly are described in greater detail below.
Before discussing further details of the sliding door assembly and/or the components thereof, it should be noted that references to “front,” “back,” “rear,” “upward,” “downward,” “inner,” “outer,” “right,” and “left” in this description are merely used to identify the various elements as they are oriented in the FIGURES. These terms are not meant to limit the element which they describe, as the various elements may be oriented differently in various applications.
Referring now to
Sliding door assembly 10 is shown to include a plurality of display case doors 12-13 mounted in a perimeter frame 14. Each display case door includes a transparent unit 16. Transparent unit 16 acts as a physical and thermal barrier between the interior of the refrigerated display case and the environment external to the refrigerated display case to help to maintain the interior of the refrigerated display case at a desired temperature. In some embodiments, transparent unit 16 includes one or more panes of transparent or substantially transparent glass (e.g., insulated glass, tempered glass, non-tempered glass, etc.), plastics, or other transparent or substantially transparent materials through which the items stored within the refrigerated display case can be viewed.
Transparent unit 16 may include multiple layers of transparent panes (i.e., multiple panes per display case door). In some embodiments, the space between panes is filled with an insulating gas (e.g., a noble gas such as argon, krypton, etc.) which functions as a thermal insulator to reduce heat transfer through transparent unit 16. In other embodiments, the space between panes may be evacuated (e.g., by drawing a vacuum) to provide a layer of thermal insulation between the panes. Spacers may be inserted between adjacent panes of transparent unit 16 to maintain separation between the panes when the vacuum is drawn.
In some embodiments, a coating or laminate layer is applied to one or more panes of transparent unit 16. The coating or laminate layer can be used to keep transparent unit 16 intact if breakage occurs and may prevent the contamination of merchandise in the refrigerated display case in the event that transparent unit 16 is damaged (e.g., by containing glass shards). In some embodiments, the coating or laminate layer functions as an anti-condensate coating and/or an ultraviolet (UV) inhibitor. For example, one or more panes of transparent unit 16 may have an anti-condensate coating (e.g., a pyrolitic coating, a mylar coating, etc.) applied thereto. The anti-condensate coating may be used to prevent condensation from occurring. The anti-condensate coating can be applied by spraying, adhering, laminating, or otherwise depositing the coating (e.g., using chemical vapor deposition or any other suitable technique).
In some embodiments, the anti-condensate coating is an electrically-conductive coating. To provide electricity to the coating, transparent unit 16 may include parallel bus bars (e.g., top and bottom, left and right side, etc.). The bus bars may be spaced apart from one another and adhered to the electrically-conductive coating. Each bus bar may include a lead assembly or solder tab for adhering wires that are in communication with an electrical source. In this arrangement, electric current may pass through one of the lead assemblies, to a first of the bus bars, across the electrically-conductive coating to the second bus bar, and through the other lead assembly. The electric current may cause heat to be generated across transparent unit 16 (e.g., due to electrical resistance of the coating), which may assist in preventing condensation on transparent unit 16. An exemplary bus bar system which may be used in conjunction with transparent unit 16 is described in detail in U.S. Pat. Nos. 6,606,832, and 6,606,833, both of which are incorporated by reference herein in their entireties.
In some embodiments, display case doors 12-13 are configured to maximize visible light transmission from inside the case to the customer, thereby improving the ability of customers to view display items. However, it is also desirable to minimize the transmission of non-visible light (i.e., ultraviolet and infrared light) through transparent unit 16 from outside to inside the case in order to improve thermal performance (e.g., by reducing radiation heat transfer) and to protect items therein. In some embodiments, an anti-reflective coating is be applied to transparent unit 16. The anti-reflective coating may absorb or transmit infrared light, ultraviolet light, or any combination thereof. In some embodiments, the anti-reflective coating may absorb or transmit some frequencies of visible light in addition to infrared and/or ultraviolet light.
In some embodiments, display case doors 12-13 may be configured to use non-visible wavelengths of light to heat transparent unit 16, thereby reducing or preventing condensation. For example, one or more panes of transparent unit 16 may include a UV inhibitor. A UV inhibitor may increase the shelf life of products within the refrigerated display case by preventing ultraviolet light from passing through transparent unit 16. The ultraviolet light may be absorbed or reflected by the UV inhibitor and may be used as a source of energy to heat transparent unit 16. As another example, one or more panes of transparent unit 16 may be treated with a low-emissivity heat-reflective coating to improve overall thermal resistance (e.g., by reducing radiation heat transfer) and/or to prevent external condensation.
Still referring to
Referring now to
In some embodiments, one or more segments of perimeter frame 14 is an insulated frame segment. An insulated frame segment may be filled with an insulating material (e.g., insulating foam, an insulating gas, etc.) to reduce heat transfer through the frame segment. In some embodiments, perimeter frame 14 is a thermal frame as described in U.S. patent application Ser. No. 14/460,973, filed Aug. 15, 2014, the entirety of which is incorporated by reference herein. For example, one or more segments of perimeter frame 14 may include a vacuum panel configured to inhibit heat transfer through perimeter frame 14.
Referring now to
In some embodiments, display case doors 12-13 are suspended from top frame segment 18. For example, each of display case doors 12-13 may be attached to one or more bearings (e.g., linear bearings, shown in
Still referring to
Referring now to
Referring now to
In some embodiments, one or more of frame segments 26-32 include an edge guard (e.g., a seal, a wiper, a gasket, etc.) which provides a sealing feature for display case door 12. For example, frame segment 30 of display case door 12 is shown to include an edge guard 34 which contacts frame segment 22 of perimeter frame 14 when display case door 12 is closed. In some embodiments, edge guard 34 employs a flexible bellows and magnet arrangement. Bottom frame segment 28 of display case door 12 may include a seal which engages bottom frame segment 20 of perimeter frame 14 to provide a sealing feature along the bottom of display case door 12. In some embodiments, frame segment 32 of display case door 12 includes an edge guard (e.g., a wiper) which cooperates with a corresponding edge guard on display case door 13 to provide a sealing feature when display case doors 12-13 are closed. Although only display case door 12 is shown in
Referring now to
Sliding bearing 50 may be configured to attach to display case doors 12-13. For example, sliding bearing 50 is shown to include multiple posts 58 extending from body 52. When sliding bearing 50 is positioned within sub-channels 42-44, posts 58 may be oriented horizontally or substantially horizontally. Display case doors 12-13 may be hung from posts 58 via hooks 36. Sliding bearing 50 may support the weight of display case doors 12-13 (e.g., via posts 58 and hooks 36) such that display case doors 12-13 are suspended from top frame segment 18. In some embodiments, posts 58 include caps 60 at ends thereof. In various embodiments, caps 60 may be fasteners (e.g., threaded nuts) attached to ends of posts 58 or may be part of a unitary component that includes posts 58 and caps 60. Posts 58 may extend substantially horizontally between caps 60 and body 52. In some embodiments, posts 58 include a narrow end proximate to body 52 and a wide end proximate to caps 60. For example, posts 58 may increase in diameter or thickness as posts 58 extend outward from body 52.
Referring now to
Referring now to
Referring now to
Referring particularly to
Cable 66 may extend horizontally from housing 62 and attach to display case door 12. In some embodiments, cable 66 wraps around one of posts 58 via a cable loop 64. When display case door 12 is opened (i.e., moved to the right in
Referring particularly to
Cable 67 may extend horizontally from housing 63 and attach to display case door 13. In some embodiments, cable 67 wraps around one of posts 58 via a cable loop 65. When display case door 13 is opened, the movement of display case door 13 may cause the top end of cable 67 to be pulled horizontally along with display case door 13. As the top end of cable 67 is pulled by display case door 13, cable 67 may be pulled at least partially through housing 63, thereby lifting weight 69. When display case door 13 is released, the weight of weight 69 may cause cable 67 to pull display case door 13 toward the closed position.
Referring again to
Referring now to
Latch 74 is shown to include a mounting bracket 82, a body 84, and a swing bar 86. Mounting bracket 82 may be secured to an upper surface of top frame segment 18 (e.g., within channel 38 or 40) via a fastener 88. Body 84 is connected to mounting bracket 82 and is pivotally connected to swing bar 86. Swing bar 86 may pivot about an axis 90 that extends through body 84. In some embodiments, swing bar 86 rests upon supports 92 that extend outward from body 84. Supports 92 may maintain swing bar 86 in a substantially horizontal position when disengaged from hook 72. When hook 72 engages latch 74, swing bar 86 may rotate upward (e.g., clockwise in
Referring again to
In some instances, magnets 76-78 cause display case doors 12-13 to slow down. For example, magnet 76 may be configured to dampen the movement of display case door 12 as display case door 12 approaches the closed position. Advantageously, the damping provided by magnet 76 counteracts the closing force provided by weight 68 and causes display case door 12 to slow down shortly before reaching the closed position, thereby facilitating a soft closure of display case door 12. Magnet 78 may provide a similar damping effect for display case door 13.
In other instances, magnets 76-78 may hold display case doors 12-13 in the open position. For example, magnet 78 may be configured to align with one of sliding bearings 50 attached to display case door 12 when display case door 12 is in the open position. The magnetic force between magnet 78 and the sliding bearing 50 attached to display case door 12 may assist in holding display case door 12 in the open position. In various embodiments, the magnetic holding force may supplement or replace the physical holding force provided by hook 72 and latch 74. Magnet 76 may provide a similar holding force for display case door 13.
Advantageously, each of magnets 76-78 may be configured to magnetically engage (i.e., attract via magnetic force) multiple different sliding bearings 50. For example, magnet 78 may engage a sliding bearing 50 attached to display case door 12 to hold display case door 12 in the open position, and may engage a sliding bearing 50 attached to display case door 13 to dampen the closing of display case door 13. Similarly, magnet 76 may engage a sliding bearing 50 attached to display case door 13 to hold display case door 13 in the open position, and may engage a sliding bearing 50 attached to display case door 12 to dampen the closing of display case door 12. In this configuration, each of magnets 76-78 may provide a holding force to one of display case doors 12-13 and a damping force to the other of display case doors 12-13.
Referring now to
Referring now to
In the embodiment shown in
As shown in
Front display case door 13 may disengage magnets 76 and/or latch 75 to begin sliding toward the closed position (i.e., to the right in
Similarly, rear display case door 12 may slide within rear channel 40 between the closed position and the open position. Sliding rear display case door 12 into the open position may include moving display case door 12 horizontally (i.e., to the right in
Rear display case door 12 may disengage magnets 78 and/or latch 74 to begin sliding toward the closed position (i.e., to the left in
The construction and arrangement of the elements of the sliding door assembly as shown in the various exemplary embodiments are illustrative only. Although only a few implementations of the present disclosure have been described in detail, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited.
Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description. References to “some embodiments,” “one embodiment,” “an exemplary embodiment,” and/or “various embodiments” in the present disclosure can be, but not necessarily are, references to the same embodiment and such references mean at least one of the embodiments.
Alternative language and synonyms may be used for anyone or more of the terms discussed herein. No special significance should be placed upon whether or not a term is elaborated or discussed herein. Synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only, and is not intended to further limit the scope and meaning of the disclosure or of any exemplified term. Likewise, the disclosure is not limited to various embodiments given in this specification.
The elements and assemblies may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures, and combinations. Further, elements shown as integrally formed may be constructed of multiple parts or elements.
As used herein, the word “exemplary” is used to mean serving as an example, instance or illustration. Any implementation or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations or designs. Rather, use of the word exemplary is intended to present concepts in a concrete manner. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the preferred and other exemplary implementations without departing from the scope of the appended claims.
As used herein, the terms “approximately,” “about,” “substantially,” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.
As used herein, the term “coupled” means the joining of two members directly or indirectly to one another. Such joining may be stationary in nature or moveable in nature and/or such joining may allow for the flow of fluids, electricity, electrical signals, or other types of signals or communication between the two members. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature.
Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.
The background section is intended to provide a background or context to the invention recited in the claims. The description in the background may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in the background section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in the background section.
