Patent Publication Number: US-2022213727-A1

Title: Door opening system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 63/199,551, filed Jan. 7, 2021, and entitled “Foot-Powered Door Opener with Force Assist from Bodyweight,” which is incorporated by reference herein in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not applicable. 
     TECHNICAL FIELD 
     This disclosure is related to a system and method for opening doors. More specifically, the system and method allows a user to use their own body weight to assist in opening a door. 
     BACKGROUND 
     Generally, doors can be opened by a user pulling on a handle of a door. However, in some cases, in particular, public places such as restrooms, users may be reluctant to, or prefer not to, contact these high-touch surfaces with their bare hands. Accordingly, doors can be provided with structures and other mechanical devices that allow for hands-free or touchless opening of doors. 
     For example, some known devices allow a user to open a door using only their foot. Such devices typically include a bracket that is attached to a lower portion of a door (e.g., below a handle of the door). The bracket is configured to allow a user to use their foot to apply a force to the bracket to open the door. More specifically, a bracket can include a platform wherein a user can place their foot on the bracket, and the user can simultaneously apply downward and lateral forces to the bracket to cause the door to open. However, such brackets require that a user have a minimum level of coordination, balance, and strength in order to safely open the door using the bracket. Consequently, some individuals may find it difficult or impossible to use these types of hands-free opening systems. Additionally, when such devices are used, the downward force applied by the user must be counteracted by the hinges of the door, leading to damage of the hinges over time. 
     Some other known systems can help to alleviate some of these issues. In particular, another hands-free door opening device uses a platform that is mounted to the floor and or the wall adjacent to the doors, which engages a ramped bracket attached to a door. A user can apply a downward force to the platform to move the platform downward towards the floor. As the platform moves downward, the contact with the ramped bracket causes the door to be opened. While such a system eliminates the need for a user to physically apply a lateral force at the same time that they are pressing downward, these systems can only open a door to a limited extend, as the ramped brackets must become larger to provide a greater degree of opening. Accordingly, a user must typically touch the door with their hand or another portion of their body to open the door a sufficient amount to pass through. Moreover, these systems can only be used where there is sufficient space around the door to mount the platform. 
     In view of the above, a need exists for an improved hands-free door opening system. In particular, it is desirable to provide a system that can be supported only by a door, reduce excessive and unfavorable loading on the door, which can reduce longevity, and that can allow a user to use their own weight to assist in opening the door. The discussion above is merely provided for general background information and is not intended to unduly limit the scope of the claimed subject matter. 
     SUMMARY 
     Aspects of the present disclosure can provide for a door opening system that can allow for hands-free opening of doors and that can allow a user to advantageously use their own weight to open the door. 
     According to one aspect of the present disclosure, a door opener for opening a door is provided. The door opener can include a frame that is coupled to the door and a wheel that is rotatably supported by the frame. The wheel can be configured to convert a downward force applied to the frame by a user into a lateral force to open the door. 
     In some aspects, a wheel can be configured to move between an unloaded configuration, in which the wheel is elevated above the ground, and a loaded configuration, in which the wheel is in contact with the ground. The downward force can cause the wheel to move between the unloaded configuration and the loaded configuration, and to rotate in the loaded configuration to open the door. Relatedly, the frame can include a base plate configured to couple to the door and a support arm movably coupled to the base plate. The support arm can be configured to rotatably support the wheel so that the wheel moves with the support arm between the unloaded configuration and the loaded configuration. More specifically, the support arm can be pivotally coupled to the base plate. Further, the frame can also include a foot pedal coupled to the support arm. The foot pedal can be configured to support a foot of a user to allow the user to apply the downward force. 
     In some aspects, a frame can further include a first resilient member extending between the support arm and at least one of the door and the base plate. The first resilient member can be configured to move the wheel from the loaded configuration to the unloaded configuration when the downward force is removed. The first resilient member can be configured as a tension spring. 
     In some aspects, the support arm can include an axle that is received by the wheel and the wheel can rotate about the axle. A second resilient member can extend between the support arm and the wheel. The second resilient member can be configured to rotate and retain the wheel in an initial rotational position when the wheel is in the unloaded configuration. The second resilient member can be configured as a torsion spring. 
     In some aspects, at least a portion of the wheel can be configured as a kinetic shape having a radius that varies as a function of an angular position of the wheel. In particular, at least a first portion of a wheel can be configured as an Archimedes spiral. 
     According to another aspect of the present disclosure, a door opening assistance device for opening a door is provided. The door opening assistance device can include a base plate, a support arm, and wheel. The base plate can be configured to couple to a door. The support arm can be pivotally coupled to the base plate. The wheel can be rotatably supported by the support arm. The wheel can be configured to pivot with the support arm relative to the base plate between an unloaded configuration, in which the wheel is elevated above the ground, and a loaded configuration, in which the wheel is in contact with the ground. The wheel can be shaped to rotate in the loaded configuration in response to a downward force applied by a user to open the door. In some aspects, the downward force applied by the user can cause the support arm to pivot from the unloaded configuration to the loaded configuration. 
     According to yet another aspect, a method of opening a door using a door opening assistance device is provided. The method can include the step of applying a downward force to a frame of the door opening assistance device. The door opening assistance device can be coupled to the door and can be configured to move a wheel from an unloaded configuration, in which the wheel is elevated above a support surface, to a loaded configuration, in which the wheel is in contact with the support surface in an initial rotational position. The method can further include the step of continuing to apply the downward force to cause the wheel to rotate away from the initial rotational position, along a curved surface of the wheel. The rotation of the wheel can result in a lateral force that opens the door. 
     In some aspects the method can further include the step of applying a secondary lateral force to the frame to continue opening the door once the wheel has rotated to a final rotational position. The wheel may stop rotating after reaching the final rotational position. 
     In some aspects, the method can further include the step of removing the downward force to allow the wheel to move back to the unloaded configuration and to rotate back to the initial rotational position. 
     This Summary and the Abstract are provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the disclosure. Given the benefit of this disclosure, skilled artisans will recognize the examples provided herein have many useful alternatives that fall within the scope of the disclosure. 
         FIG. 1  is an isometric view of an exemplary door opener according to aspects of the disclosure, with the door opener mounted to a door; 
         FIG. 2  is a side elevational view of the door opener of  FIG. 1 ; 
         FIG. 3  is a front elevational view the door opener of  FIG. 1 ; 
         FIG. 4  is an exploded view of the door opener of  FIG. 1 ; 
         FIG. 5  is a schematic view of the door opener of  FIG. 1  illustrating forces that are applied to the wheel during operation of the door opener; 
         FIG. 6  is a side elevational view of the door opener of  FIG. 1 , with the door opener in a first, unloaded configuration and the wheel in an initial rotational position; 
         FIG. 7  is a side elevational view of the door opener of  FIG. 1 , with the door opener in a second, loaded configuration and the wheel in an initial rotational position; 
         FIG. 8  is a side elevational view of the door opener of  FIG. 1 , with the door opener in the loaded configuration and the wheel rotated away from the initial rotational position; 
         FIG. 9  is a side elevational view of the door opener of  FIG. 1 , with the door opener in the loaded configuration and the wheel in a final rotational position; and 
         FIG. 10  is a schematic illustration of a method of opening a door using a door opener according to aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” and variations thereof, herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled,” and variations thereof, are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Likewise, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings unless identified as such. Furthermore, throughout the description, terms such as front, back, side, top, bottom, up, down, upper, lower, inner, outer, above, below, and the like are used to describe the relative arrangement and/or operation of various components of the example embodiment; none of these relative terms are to be construed as limiting the construction or alternative arrangements that are within the scope of the claims. 
     The following discussion is presented to enable a person skilled in the art to make and use embodiments of the disclosure. Given the benefit of this disclosure, various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the disclosure. Thus, embodiments of the disclosure are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the disclosure. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the disclosure. 
     As noted above, a need exists for an improved door opener (i.e., a door opening assistance device) that can allow for hands-free opening of a door, while also improving usability. In particular, it is appreciated that a door opener can allow a user to apply a downward force to the door opener, which is then converted into a lateral force by the door opener to open the door. Accordingly, a user can use their own bodyweight to cause and/or assist the door to open. Such door openers can be used on both swinging and sliding doors. Relatedly, such door openers can be configured to provide a force to either push or pull a door open. 
       FIGS. 1-3  illustrate an example door opening assistance device for opening a door, configured as a door opener  100 . As will be described in greater detail below, the door opener  100  is generally configured to be coupled to a door and to allow a user to advantageously use their own body weight to open the door without having to contact high touch surfaces (e.g., a handle or edge of the door) with their bare hands. In that regard, the door opener  100  is configured as a hands-free door opener, and more specifically, a foot-operated door opener that allows a user to use and take advantage of their own body weight to assist in opening a door. More specifically, the door opener  100  is a mechanical assistance device that does not rely on electricity or another external power source to operate. Accordingly, the door opener  100  can be easily fitted to any door, which can be useful for retrofit applications and can reduce installation costs. 
     The door opener  100  generally includes a frame  104  that is configured to support a wheel  108 . That is, the frame  104  acts as an intermediate body that is coupled between a door  112  and the wheel  108  to support the wheel  108  on the door  112 . Put another way, the door  112  is the sole means of support for the door opener  100 , directly supporting the frame  104  and indirectly supporting the wheel  108  via the frame  104 . The frame  104  can be configured to movably support the wheel  108  so that the wheel  108  can move between a first, unloaded configuration (see  FIG. 6 ) and a second, loaded configuration (see  FIGS. 7-9 ). In the unloaded configuration the frame  104  is configured to support the wheel  108  in an elevated state, wherein the wheel is not in contact with a support surface  116  (e.g., the ground or floor). In the loaded configuration, the wheel  108  is moved downward and into contact with the support surface  116  in response to a downward force  120  (e.g., a force that is directed towards the support surface  116 , see  FIG. 5 ) acting on the frame  104 . In particular, the downward force  120  can be applied by a foot of a user pressing or stepping onto the frame  104 . As will be described in further detail below, continued application of the downward force  120  to the frame  104  in the loaded configuration, in combination with the shape of the wheel  108 , causes the wheel  108  to automatically begin rotating, thereby generating a lateral force  122  (see  FIG. 5 ) to open the door  112 . Correspondingly, a frame can be made of one or more materials having sufficient strength to withstand any loading, including adverse loading, that may occur, for example, aluminum, steel, and polymers, in particular, fiber-reinforced polymers. 
     Continuing, the frame  104  generally includes a mounting bracket or base plate  124  that is configured to couple to the door  112 . In particular, the base plate  124  can include a plurality of mounting holes  128  that are configured to receive a corresponding plurality of fasteners  132  (e.g. wood screws, metal screws, and self-tapping screws). Each of the plurality of fasteners  132  can be inserted through a corresponding mounting hole  128  to extend through the base plate  124  and into the door  112 . Correspondingly, the base plate  124  can be fixedly coupled to the door  112  so that the door opener  100  moves with the door  112  and vice versa. In other embodiments, a base plate can be coupled to a door by other means as known in the art, for example, by an adhesive. Relatedly, a base plate can be mounted at a height above the floor so that a wheel is not in contact with the ground or other support surface when the wheel is in the unloaded configuration. Additionally, a base plate can be arranged on a door so as to obtain an increased mechanical advantage that reduces the lateral force required to open the door. In particular, on a swinging type door, a base plate can be secured along an outer edge of a door that is radially furthest from the door hinges (i.e. an edge opposite the door hinges). More specifically, a base plate can be mounted substantially below a handle of the door (e.g., between the handle and the ground). 
     Additionally, a frame can further include a support bracket or arm that is configured to rotatably support a wheel. The support bracket or arm can be moveably coupled to a base plate that is secured to a door to allow the wheel to move relative to the base plate and the door between a first, unloaded configuration and a second, loaded configuration. For example, as illustrated, the frame  104  includes a support arm  136  configured as a pivot arm that is pivotally coupled to and extends from the base plate  124 . The support arm  136  includes two pivot arms  138  (e.g., a first pivot arm and a second pivot arm) that are pivotally coupled to the base plate  124  along opposing edges of the base plate  124 . Each pivot arm  138  is pivotally coupled to a corresponding pivot bracket  140  extending substantially perpendicularly from the base plate  124  (e.g., away from the door  112  and toward the wheel  108 ). More specifically, each pivot arm  138 , is disposed along an interior side of the respective pivot bracket  140  so that a distance between the pivot arms  138  is smaller than a corresponding distance between the pivot brackets  140 . As illustrated, the pivot arms  138  are identically shaped, but this may not always be the case and the pivot arms can also be configured differently from one another. Likewise, in other embodiments the support arm may be coupled to and arranged differently on a base plate. 
     To allow the support arm  136  to pivot relative to the door  112  and the base plate  124 , each pivot bracket  140  defines a corresponding pivot hole  144 . The pivot holes  144  can be in coaxial alignment with one another to define a pivot axis  148 , about which the support arm  136  and the wheel  108  can pivot. In particular, each pivot hole  144  can be configured to rotatably receive a corresponding stub axle  150  (e.g. a pivot axle) extending from the respective pivot arm  138  and through the pivot bracket  140 . Each stub axle  150  can be secured at each of its respective ends to prevent the stub axle  150  from dislodging (e.g., by a press-fit, threaded connection, fastener, or a cotter pin). For example, as illustrated, each stub axle  150  is secured in a hole  154  formed in the respective pivot arm  138  (e.g., via a threaded or press-fit connection). Additionally, each stub axle  150  includes a threaded distal end  156  that extends through the pivot hole  144  in the pivot bracket  140 , where it is secured with a nut  160  (e.g., an acorn or cap nut). Furthermore, spacers  164  (e.g., washers or bushings) may be provided at each side of the pivot brackets  140 . In particular, spacers  164  can be disposed between the nut  160  and the pivot bracket  140  and between the pivot arm  138  and the pivot bracket  140 . The spacers  164  can be used to align the pivot arms  138  and help the support arm  136  to pivot freely. 
     In other embodiments, a support arm may include only a single pivot arm or more than two pivot arms. Additionally, in other embodiments, only a single pivot axle configured as a through axle that extends between one or more pivot brackets. Relatedly, a frame can also be configured differently to permit a wheel to move between an unloaded configuration and a loaded configuration. For example, a frame can be configured to allow linear translation of the wheel between a first, unloaded configuration and a second, loaded configuration. More specifically, a wheel can be supported on a support plate or arm that is coupled to a base plate via one or more linear rails. 
     To move a wheel from an unloaded configuration to a loaded configuration, a user can apply a force to a frame, and more specifically, a support arm of a door opener. In particular, the force can be a downward force (e.g., a force wherein at least a portion of the force is directed downward, towards the ground or other support surface), which can be applied by a foot of a user. In this way, the user can use their own bodyweight to apply the downward force. Accordingly, a support arm of a frame can sometimes be provided with a foot plate or pedal that is configured to receive a foot of a user. The foot pedal can be coupled to and supported by a support arm so that the downward force supplied by the user is transmitted to the support arm, causing the support arm to move the wheel from the unloaded configuration to the loaded configuration. In that regard, the foot pedal can be supported anywhere on the support arm, for example, a side of the support arm or above the support arm. It may be preferrable to mount the foot pedal so that it does not interfere with the rotation of the wheel in the loaded configuration. Additionally, a foot pedal can be rigidly coupled to the support arm, or in some cases, movably coupled to the support arm. 
     For example, as illustrated in the figures, the support arm  136  is configured to support a foot pedal  168  above the wheel  108 . In that regard, each pivot arm  138  is provided with an extension  172  that extends (e.g., obliquely extends) from the respective pivot arm  138 . More specifically, the extensions  172  extend upwardly (e.g., away from the support surface  116 ) and outwardly (e.g., away from the base plate  124 ) to provide a user with a large lever arm, giving the user a greater mechanical advantage, which reduces the amount of downward force  120  required to operate the door opener  100 . The extensions  172  are provided with a plurality of foot pedal mounting holes  176  (e.g., clearance holes) that are configured to receive a corresponding plurality of fasteners  180 . The fasteners  180  pass through the extensions  172  to engage with a corresponding plurality of threaded holes  184  provided in the foot pedal  168 . More specifically, the threaded holes  184  can be provided in a mounting tab  188  that extends from a foot-receiving portion  192  of the foot pedal  168 . The mounting tab  188  may have a width (e.g., a dimension taken between the pivot arms  138 ) that is less than a corresponding width of the foot-receiving portion  192 . Accordingly, the mounting tab  188  can be received between the pivot arms  138  and the foot-receiving portion  192  can provide a user with a larger surface area on which to engage the foot pedal  168  with their foot. This larger surface area can improve ease of use and make the door opener  100  more comfortable to operate by reducing pressure that is exerted onto a user&#39;s foot when they engage the foot pedal  168  to apply the downward force  120 . 
     In some embodiments, a foot-receiving portion of a pedal can be configured to improve and optimize force transfer from the user to the foot pedal. In particular, a foot-receiving portion may have flat portions and/or curved portions, in particular with a pivoting support arm, so that the user is provided with a horizontal surface on which to apply a downward force, no matter the position of the support arm. Similarly, a user can also be provided with a surface that is angled to allow a user to apply a force in a tangential direction relative to a swing path of the support arm, minimizing the force that needs to be applied by the user to move the wheel. For example, as illustrated, the foot-receiving portion  192  of the foot pedal  168  includes a curved portion  196 , which extends from a planar portion  200  that includes the mounting tab  188 . Accordingly, even as the support arm  136  is pivoted downward, the user is always provided with an optimal surface for applying force to the foot pedal  168 . Relatedly, in some embodiments, a foot pedal can be provided with tractive features that can increase grip between a user&#39;s foot and the foot pedal. For example, a foot pedal can include knurling or a treaded pattern, or it can include a rubber pad or other similar material with a high coefficient of friction. 
     In some cases, a support arm or bracket can be configured to return and retain a wheel in a first, unloaded configuration so that the wheel is not in contact with the ground and the door can thereby be opened conventionally (e.g., by a user grabbing a handle). That is, the support arm can be configured to reset the wheel to the unloaded configuration between uses so that the door can be opened again. Accordingly, a frame can include one or more resilient members that are configured to return and retain a wheel in an unloaded configuration. Correspondingly, it is appreciated that a user may have to overcome an opposing force provided by the one or more resilient members to move the wheel from the unloaded configuration to the loaded configuration. For example, as illustrated, the frame  104  can further include first resilient members configured as a pair of tension springs  202 . Each tension spring  202  is coupled to and extends between a respective one of the pivot arms  138  and the base plate  124 . In other embodiments, the tension springs  202  can be coupled to structures other than the base plate  124 , for example, the door  112 . 
     It is appreciated, that each tension spring  202  may be pre-loaded so as to be under a predetermined amount of tension in the unloaded configuration. Correspondingly, a base plate or support arm may include one or more rotation stops (not shown) configured to prevent the support arm  136  and the wheel  108 , and any other attached structures, from pivoting upward (i.e., toward the base plate  124  and the door  112 ) beyond the unloaded configuration. In other embodiments, only one resilient member may be provided, or more than two resilient members may be provided. Relatedly, other types of resilient members can also be provided, for example, gas spring, compression spring, torsion springs, spiral springs, and counterweights. 
     Additionally, with continued reference to  FIGS. 1-4 , a support arm can be configured to rotatably couple to and support a wheel of a door opener. In particular, a support arm can include an axle that can be configured to extend between pivot arms or to be cantilevered from a support arm. In the illustrated example, support arm  136  includes an axle  204  that extends between each of the pivot arms  138 , so that the axle  204  is supported on each end. More specifically, each pivot arm  138  is provided with a hole  208  configured to allow a threaded end  212  of the axle  204  to pass through the pivot arm  138 , where it is secured with a nut  214  (e.g. an acorn or cap nut). In other embodiments, the axle  204  can be secured between the arms differently, for example a press-fit connection or threaded connection provided in the pivot arm  138 . In that regard, an axle can be configured as a partially threaded fastener (e.g., a bolt) with a smooth central shaft portion disposed between a threaded end and a head. The fastener can be passed through a clearance or through hole in one of the pivot arms and subsequently threaded into a threaded hole formed in the other pivot arm. 
     Correspondingly, the wheel  108  includes an axle hole  216  that is configured to rotatably receive the axle  204 . The axle hole  216  can define a wheel axis  220 . In this way, the wheel  108  is rotatably supported by the axle  204  and can freely rotate about the axle  204  and the wheel axis  220 , while also pivoting with the support arm  136  about the pivot axis  148 . Relatedly, as illustrated, the wheel  108  is disposed between the pivot arms  138 ; however, this may not always be the case. Additionally, in some embodiments, a door opener may include a bearing (e.g., a roller bearing or a needle bearing) or a bushing (not shown) between the axle  204  and the wheel  108  to reduce friction therebetween and to increase longevity of the door opener. Similarly, spacers  222  can be supported on the axle  204  on the sides of each of the pivot arms  138 . The spacers  222  can ensure proper alignment of the wheel  108  and can allow the wheel  108  to rotate freely. In that regard, in the illustrated embodiment, spacers  222  are provided between the nuts  214  and the pivot arms  138 , and between the wheel  108  and the pivot arms  138 . 
     Relatedly, in some cases, a wheel can be configured as a multi-part wheel. For example, as illustrated, the wheel  108  includes two wheel halves  224  that are configured to be coupled together by a plurality of fasteners  228 . Additionally, as will be discussed in greater detail below, each wheel half  224  further defines open-sided recesses  232  that, together, form open cavities  236  that open along an outer perimeter of the wheel  108 . Each open cavity  236  is configured to retain a secondary wheel  240  (e.g., a bearing) and corresponding secondary wheel axle  244 , which can allow the wheel  108  to move in the loaded configuration, with the wheel  108  in a final rotational position (see  FIG. 9 ), without further rotation. In other embodiments, a wheel can be configured differently. For example, a multi-part wheel may include more or fewer additional recesses, or no recesses at all, or a wheel can be configured as single piece wheel. Likewise, a wheel may include more or less secondary wheels, or no secondary wheels. In that regard, a wheel may include other wear parts, which can be configured to contact a support surface to reduce and/or prevent damage to the wheel. For example, a wheel can include polymer slide pads, to allow the wheel to slide in the loaded configuration with the wheel in a final rotational position. Moreover, a wheel can also be made of one or more materials, for example, polymers, metals, and rubber. 
     Still referring to  FIGS. 1-4 , a door opener can be configured to return and retain a wheel in an initial rotational position (e.g., an un-rotated or starting position) when the wheel is in a first, unloaded configuration. That is, the wheel can be configured to be reset to its initial rotational position between uses so that the door can be opened again. Accordingly, a door opener can include one or more resilient members that are configured to return the wheel to the initial rotational position. For example, in the illustrated embodiment, the door opener  100  includes a pair of second resilient members configured as torsion springs  248 . Each torsion spring  248  is disposed between the wheel  108  and one of the respective pivot arms  138  to provide a return force or torque that biases the wheel  108  to the initial rotational position. In particular, each torsion spring  248  is retained on one end within a corresponding first channel or recess  252  (only one shown) formed in the pivot arm  138  and at the other end within a corresponding second channel or recess  254  (only one shown) formed in the wheel  108 . In other embodiments, other types of resilient members can also be used, for example, a spiral spring. 
     As mentioned above, the wheel can be configured to automatically rotate when the wheel is in contact with a support surface in a loaded configuration. More specifically, a wheel can define an outer surface extending along a perimeter of the wheel, which is configured to contact the ground as the wheel rotates to open the door. In that regard, at least a portion of the outer surface of the wheel can be a curved surface to allow the wheel to automatically rotate when a downward force is applied to the wheel (e.g., a force that is applied to a foot pedal and transmitted to the wheel via an axle extending through the wheel). That is, the curvature of the curved surface can provide the wheel with a kinetic shape that converts the downward force that rotates the wheel to produce a lateral force that opens the door. Accordingly, the larger the perimeter of the wheel, the greater the opening angle of the door will be. Thus, the size of the wheel can be selected by a manufacturer or installer to allow the door opener to provide assistance over a desired opening angle of a door. 
     For example, with additional reference to  FIG. 5 , the wheel  108  defines an outer perimeter having a curved portion  256  (e.g., a curved outer surface), which contacts the support surface  116  at a contact point  260  in the loaded configuration. In general, a radius  264  of the curved outer portion  256  becomes smaller moving away (e.g., clockwise or counter-clockwise) from the contact point  260 . In the illustrated example, the radius  264  of the curved portion  256  becomes smaller moving counter-clockwise so as to pull the door  112  open. Conversely, if the radius  264  of the curved portion  256  became smaller moving clockwise, the door  112  would be pushed open. In the illustrated embodiment, the radius  264  can vary as a function of an angular position of the wheel  108 . In particular, the radius  264  (R) can be defined by the following equation, where θ is the angular position of the radius  264  along the wheel  108  and S is a scaling factor: 
         R (θ) 0   2π   =S*e   0.125(θ−cos(θ))+ln(1.5)  
 
     In one embodiment, the scaling factor can range between approximately 1.2 and approximately 0.7, and more specifically, can be approximately 0.9. In other embodiments, a largest value of the radius  264  may be approximately 5 inches and a smallest value of the radius  264  may be approximately 1 inch. The scaling factor will increase or decrease the size of the shape, but will not affect the generated force. The distance travelled will increase with a larger size and decrease with a smaller size. In other embodiments, a curved portion of a wheel can be shaped differently, for example, as an Archimedean spiral or according to a different equation. In either case, the shape of the curved portion  256  results in the contact point  260  being laterally offset by an offset distance  268  from the wheel axis  220 , so that the wheel axis  220  is not directly below the wheel axis  220 , as shown in  FIG. 5 . The offset distance  268  may range between 0.1 inches and 0.5 inches with door opener  100  in the loaded configuration and the wheel  108  in the initial rotational position, and preferably between 0.1 inches and 0.3 inches, or 0.15 inches and 0.25 inches, or approximately 0.2 inches. 
     As a result of the offset distance  268  and the reduction in the radius  264 , the curved portion  256  effectively acts as a sloped surface, which causes the wheel  108  to automatically rotate to roll away from the door  112  when the downward force  120  is applied. That is, with the wheel  108  in the loaded configuration and in an initial rotational position (see  FIG. 7 ), the continued application of downward force  120  causes the wheel  108  to rotate away from the initial rotational position (see  FIG. 8 ), effectively moving the contact point  260  along the curved portion  256 . The rotation of the wheel  108  thereby generates the lateral force  122  that opens the door  112 . It is appreciated that the lateral force  122  must be sufficiently high to overcome the inertia of the door  112  and any friction or other resistive forces associated with the movement of the door  112 . In that regard, the resultant lateral force  122  (F x ) is a function of the downward force  120  (F y ), as defined by the following equation: 
         F   x   =F   y  sin(θ)+ F   y  
 
     In some embodiments, an outer surface of a wheel, in particular, a curved portion of a wheel, can include a coating or outer layer of a high-friction material (e.g., a rubber or polymeric compound) to increase traction between the wheel and a support surface. Accordingly, the high-friction material can improve force transfer between the wheel and the ground so that the wheel does not slip against the support surface. Relatedly, the downward force can also help to improve traction between the wheel and the support surface. 
     Additionally, a door opener can include a damper (not shown) to control the rotation of a wheel. That is, a damper can be configured to provide a resistive force to limit or reduce the rotational speed of the wheel. Such dampers can be unidirectional dampers that control the rotation of the wheel in one direction, while allowing free or uninhibited rotation in the opposite direction. Accordingly, the rotational speed of the wheel can be limited when a downward force is applied to rotate the wheel away from the initial rotational position (i.e., when opening the door), while allowing the wheel to quickly reattain the initial rotational position when a downward force is removed. 
     In some cases, a perimeter of a wheel can also be provided with a flattened portion which is configured to contact a support surface once the wheel has rotated beyond a curved portion. The flattened portion can ensure that the wheel does not over rotate, such that a radius of the wheel begins to increase as the wheel rotates. In this way, the flattened portion can act as a physical rotation stop for the wheel. Additionally, the flattened portion can be configured to allow the wheel to move (e.g., slide or otherwise translate) with the door, without further rotation of the wheel. In this way, if necessary, a user may continue to open the door by applying a lateral force to the foot pedal to increase an opening angle of a door even further. For example, in the illustrated non-limiting example, the wheel  108  defines a flattened portion  276  (e.g. a generally flattened portion) that is configured to face the support surface  116  once the wheel  108  has rotated beyond the curved portion  256  to a final rotational position (see  FIG. 9 ). Accordingly, as discussed above, when the flattened portion  276  faces the support surface  116 , the secondary wheels  240  can contact the support surface  116  instead of the wheel  108  itself. Thus, if a user were to continue opening the door  112  with the wheel  108  in the final rotational position, the secondary wheels  240  can freely rotate to allow the wheel  108  to translate with the door  112  without further rotation. Relatedly, in some cases, a wheel  108  may include an indent  278  disposed between the curved portion  256  and the flattened portion  276 . The indent  278  can provide a physical indication to a user that the wheel  108  is transitioning from the curved portion  188  to the flattened portion  276 . 
     Referring now to  FIGS. 6-10 , a method  300  of opening a door using a door opener, in particular the door opener  100 , is illustrated. The method  300  includes the step  304 , wherein a downward force  120  is applied to the door opener  100  in the unloaded configuration (see  FIG. 6 ) to move the door opener  100  into the loaded configuration (see  FIG. 7 ) so that the wheel  108  contacts the support surface  116 . More specifically, a user can apply the downward force  120  to the foot pedal  168  that is supported on the support arm  136 . Since the support arm  136  is moveably (e.g. pivotally) coupled to the base plate  124 , the support arm  136  moves downward (e.g., by pivoting about the pivot axis  148 ) toward the support surface  116 . Correspondingly, because the support arm  136  rotatably supports the wheel  108 , the wheel  108  moves with the support arm  136 . The contact of the wheel  108  with the support surface  116  stops the support arm  136  from moving further downward. At step  304 , the wheel  108  is in an initial rotational position, wherein the contact point  260  between the wheel  108  at the support surface  116  is along the curved portion  256  of the wheel  108 . More specifically, in the initial rotational position, the contact point  260  is proximate a portion of the curved portion  256  where the radius  264  of the curved portion  256  is largest. 
     At step  308 , the downward force  120  is continuously applied to the door opener  100  (e.g., the foot pedal  168 ) to rotate the wheel  108  away from the initial rotational position in the loaded configuration (see  FIG. 8 ). That is, since the wheel  108  is configured as a kinetic shape, wherein the radius  264  becomes smaller moving along the curved portion  256  and the contact point is laterally offset and not directly below the wheel axis  220 , the curved portion  256  effectively acts as a sloped surface that causes the wheel  108  to automatically rotate. This resulting motion is similar to a circular wheel rolling down a hill except that the slope is attached to the wheel. Accordingly, the wheel  108  converts or translates the downward force  120  supplied by the user into the lateral force  122 , which causes the door  112  to open (e.g., to swing or slide away from a door frame). The wheel  108  will continuously apply the lateral force  122  to the door  112  as the wheel  108  rotates along the curved portion  256 , thereby assisting the user in opening the door  112 . In this way, the user can use their own weight to assist in opening the door  112 . In some cases, the downward force  120  may be increased during step  308 . 
     In some cases, the method  300  may optionally include the step  312  of applying a secondary lateral force to the door opener  100 . In particular, the secondary lateral force can be applied once the wheel  108  has rotated to a final rotational position. In this way, the user can continue to open the door  112  by contacting only the door opener  100  and not the door  112  itself. 
     Additionally, the method  300  can further include the step  316  of releasing or removing the downward force  120 , for example, by a user removing their foot from being in contact with the foot pedal  168 . With the downward force  120  removed, the door opener  100  can move to reattain the unloaded configuration of  FIG. 6 , and the wheel  108  can also reattain the initial rotation position of  FIGS. 6 and 7 . In particular, the tension springs  202  pull on and move (e.g., pivot) the support arm  136  to move the door opener  100  from the loaded configuration to the unloaded configuration. At the same time, if the wheel  108  is rotated away from the initial rotational position, the torsion springs  248  will apply a torque to the wheel  108  to rotate the wheel  108  back to the initial rotational position.