Patent Publication Number: US-2020300481-A1

Title: Hvac door and linkage assembly for doors rotating along non-parallel axes

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/822,316, filed on Mar. 22, 2019. The entire disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to an HVAC door assembly, and, more specifically, to a linkage mechanism for a rotating HVAC doors along non-parallel axes in the HVAC door assembly. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Conventional heating, ventilation, and air conditioning (HVAC) designs use actuator(s) to drive one or multiple doors to control airflow through designated air pass. Existing designs require actuators mounted parallel to a door rotating axis. Therefore, for an HVAC system having doors rotating along nonparallel axes, multiple actuators are required to actuate the movement (one actuator for one set of doors moving along the same axis). Existing kinematic designs involve low cost competitiveness and high packaging space occupancy due to the increasing amount of actuators. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     At least one example embodiment of a heating, ventilation, and air conditioning (HVAC) door assembly according to the present disclosure includes a first HVAC door rotating about a first axis, a second HVAC door rotating about a second axis that is nonparallel with the first axis, an actuator, and a mode cam. The mode cam is engaged with the actuator and controls movement of the first HVAC door and the second HVAC door. 
     In at least one example embodiment, a first linkage assembly may connect the mode cam with the first HVAC door. A second linkage assembly may connect the mode cam with the second HVAC door. 
     In at least one example embodiment, the first linkage assembly may include a mid-link and a link. The mid-link may include a protrusion that engages with at least one groove on a surface of the mode cam to transfer movement from the mode cam. The link may engage with the mid-link to transfer movement from the mid-link to the first door. 
     In at least one example embodiment, the second linkage assembly may include a mid-link, a rack link, and a link. The mid-link may include a protrusion that engages with at least one groove on a surface of the mode cam to transfer movement from the mode cam. The rack link may engage with the mode cam to translate rotational movement into linear movement. The link may engage with the rack link to translate linear movement into rotational movement for the second door. 
     In at least one example embodiment, the mid-link may include a gear having a plurality of teeth that mesh with a plurality of teeth on the rack link. 
     In at least one example embodiment, the gear may be a spur gear. 
     In at least one example embodiment, the mid-link may move linearly along a first end of the rack link. The gear may turn to move the plurality of teeth along the plurality of teeth on the rack link. 
     In at least one example embodiment, the rack link may include a pin on an end of the rack link that is received within a slot defined by the link. The pin may slide within the slot to transfer movement of the rack link to the link. 
     In at least one example embodiment, the first linkage assembly may transfer rotational movement about the first axis from the mode cam to the first door. 
     In at least one example embodiment, the second linkage assembly may translate rotational movement about the first axis from the mode cam to rotational movement about the second axis to the second door. 
     In at least one example embodiment, the second linkage assembly may translate rotational movement about the first axis into linear movement along a third axis and may translate linear movement along the third axis into rotational movement about the second axis. 
     At least one example embodiment of a heating, ventilation, and air conditioning (HVAC) door actuation assembly according to the present disclosure may control movement of a first HVAC door rotating about a first axis and a second HVAC door rotating about a second axis that is nonparallel with the first axis. The door actuation assembly includes an actuator and a mode cam. The mode cam may be engaged with the actuator and may control movement of the first HVAC door and the second HVAC door. 
     In at least one example embodiment, a first linkage assembly may be configured to connect the mode cam with the first HVAC door. A second linkage assembly may be configured to connect the mode cam with the second HVAC door. 
     In at least one example embodiment, the first linkage assembly may include a mid-link and a link. The mid-link may include a protrusion that engages with at least one groove on a surface of the mode cam to transfer movement from the mode cam. The link may engage with the mid-link to transfer movement from the mid-link to the first door. 
     In at least one example embodiment, the second linkage assembly may include a mid-link, a rack link, and a link. The mid-link may include a protrusion that engages with at least one groove on a surface of the mode cam to transfer movement from the mode cam. The rack link may engage with the mode cam to translate rotational movement into linear movement. The link may engage with the rack link to translate linear movement into rotational movement for the second door. 
     In at least one example embodiment, the mid-link may include a gear having a plurality of teeth that mesh with a plurality of teeth on the rack link. 
     In at least one example embodiment, the mid-link may move linearly along a first end of the rack link. The gear may turn to move the plurality of teeth along the plurality of teeth on the rack link. 
     In at least one example embodiment, the rack link may include a pin on an end of the rack link that is received within a slot defined by the link. The pin may slide within the slot to transfer movement of the rack link to the link. 
     In at least one example embodiment, the first linkage assembly may transfer rotational movement about the first axis from the mode cam to the first door. 
     In at least one example embodiment, the second linkage assembly may translate rotational movement about the first axis into linear movement along a third axis and may translate linear movement along the third axis into rotational movement about the second axis. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a perspective view of an example embodiment of a heating, ventilation, and air conditioning (HVAC) assembly including a linkage assembly according to the present disclosure. 
         FIG. 2  is an exploded view of the HVAC assembly of  FIG. 1 . 
         FIG. 3A  is a front view of a single linkage assembly, actuator, and mode cam of the HVAC assembly of  FIG. 1  in a first mode. 
         FIG. 3B  is a top view of the single linkage assembly, actuator, and mode cam of the HVAC assembly of  FIG. 3A  in the first mode. 
         FIG. 4A  is a front view of a single linkage assembly, actuator, and mode cam of the HVAC assembly of  FIG. 1  in a second mode. 
         FIG. 4B  is a top view of the single linkage assembly, actuator, and mode cam of the HVAC assembly of  FIG. 4A  in the second mode. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     A linkage mechanism to drive doors rotating along non-parallel axes according to the present disclosure includes a linkage mechanism which enables one actuator to drive multiple doors rotating along nonparallel axes. The design of the present disclosure results in cost savings and packaging space savings by reducing an amount of actuator usage. 
     For example, the linkage mechanism may include a single actuator that drives two doors. The first door may rotate along a first axis, such as the Y-axis, and a second door may rotate along a second axis, such as the Z-axis. A set of linkages and a mode cam may cooperate to transfer torques and movements from the single actuator to the first door and second door. An output shaft out of the actuator may directly drive the mode cam, which has multiple grooves determining a mode pattern for one of the first door and the second door. 
     For the first door moving along the first axis, different door angles for different modes may be achieved through a motion transfer path such as: actuator, mode cam groove A, mid-link A, link A, door A. For the second door moving along the second axis, different door angles for different modes may be achieved through a motion transfer path such as: actuator, mode cam groove B, mid-link B, rack link, link B, door B. In the examples with door A and door B, the rotation axis of door A and the rotation axis of the actuator may be in parallel while the rotation axis of the actuator and the rotation axis of the door B may be an axis that is non-parallel (for example, an axis intersecting or perpendicular) to the rotation axis of door A. The motion direction change for door B may occur through the rack link. A gear-rack meshing mechanism and a pin-groove driving mechanism enables the change in motion direction. The gear-rack meshing includes a rack link that meshes with a spur gear of the mid-link B. The pin-groove driving involves a pin portion of the rack link engaging with the groove on link B. The link B then drives the door to be rotated along the second axis. 
     Now referring to  FIG. 1 , a door linkage assembly  10  according to the present disclosure is illustrated. The door linkage assembly  10  may transfer movement from an actuator  14  to a first door  18  and a second door  22 . A first case  26  may house the first door  18  which moves along a first axis, and a second case  30  may house the second door  22  which moves along a second axis. 
     In at least one example embodiment, the first door  18  may pivot about the first axis from an open position to a closed position and various angles therebetween. For example only, the closed position may be an angle of 0° and the open position may be an angle of 90°. Different door angles may be achieved for different movement modes controlled by the actuator  14  and door linkage assembly  10 . 
     In at least one example embodiment, the second door  22  may pivot about the second axis from an open position to a closed position and various angles therebetween. For example only, the closed position may be an angle of 0° and the open position may be an angle of 90°. Different door angles may be achieved for different movement modes controlled by the actuator  14  and door linkage assembly  10 . 
     In at least one example embodiment, the first axis and the second axis may be non-parallel axes. More specifically, the first axis and the second axis may be perpendicular axes. For example only, the first axis may be a y-axis and the second axis may be a z-axis. Further, it is understood that the first axis and the second axis may be any axes, including parallel axes, perpendicular axes, or axes separated by any angle. 
     Referring additionally to  FIG. 2 , the door linkage assembly  10  may include a mode cam  34 , a first linkage assembly  38  that cooperates with the mode cam  34  and actuator  14  for controlling movement of the first door  18 , and a second linkage assembly  42  that cooperates with the mode cam  34  and actuator  14  for controlling movement of the second door  22 . 
     In at least one example embodiment, the mode cam  34  may be a substantially planar cam having a first surface, or front surface,  46  and a second surface, or rear surface,  50  opposite the front surface  46 . At least one groove  54  may be cut on one or both of the front surface  46  and the rear surface  50 . In at least one example embodiment, a first groove  54 A may be cut on the front surface  46  of the mode cam  34  for controlling a movement mode of the first door  18  and a second groove  54 B may be cut on the front surface  46  of the mode cam  34  for controlling a movement mode of the second door  22 . In at least one alternative example embodiment, a first groove  54 A may be cut on the front surface  46  of the mode cam  34  for controlling a movement mode of the first door  18  and a second groove  54 B may be cut on the rear surface  50  of the mode cam  34  for controlling a movement mode of the second door  22 . 
     The shape of the groove  54  may determine a path of the door (for example, an angle of the door). In at least one example embodiment, the groove  54  may have spiraling segments and circular segments. For example, the groove  54 A includes one end  58 A nearer to a center  62  of the mode cam  34  and a second end  58 B further from the center  62 . The groove  54 B includes one end  66 A nearer to the center  62  of the mode cam  34  and a second end  66 B further from the center  62 . 
     In at least one example embodiment, circular segments and spiraling segments may be arranged in alternating order for groove  54 A (i.e., one spiraling segment may connect to two circular segments at opposing ends of the spiraling segment). The ending segments of groove  54 A may be circular segments. 
     In at least one example embodiment, circular segments and spiraling segments may be arranged in alternating order for groove  54 B (i.e., one spiraling segment may connect to two circular segments at opposing ends of the spiraling segment). The ending segments of groove  54 B may be circular segments. In at least one example embodiment, groove  54 B may be located outside of groove  54 A (i.e., the circular segment of  54 B with the smallest radius may be larger than the circular segment of  54 A with the largest radius). 
     In at least one example embodiment, the spiraling segment may be a transition between two adjacent modes (i.e., move the door from one mode position to another mode position with a certain angle). In at least one example embodiment, the circular segment may be an idle zone for a designated mode (i.e., may maintain the door at a designated mode position for a period of time regardless of the rotation of the mode cam  34 ). 
     The mode cam  34  may be driveably engaged with the actuator  14 . For example, an output shaft  74  out of the actuator  14  may be fixed or locked within one or more central apertures (for example only, a t-cut male end)  78  for selectively rotating the mode cam  34 . In at least one example embodiment, the output shaft  74  may include one or more prongs  82  (for example only, a t-cut female end  82 ) that engage with the central apertures  78  to fix the mode cam  34  for rotation with the output shaft  74 . 
     In at least one example embodiment, the first linkage assembly  38  may include at least one mid-link  86  and at least one link  90 . The mid-link  86  may be engaged with the groove  54  (for example only, groove  54 C) on the mode cam  34  (for example, the rear surface  50  of the mode cam  34 ) for directing the movement of the first door  18 . In at least one example embodiment, the movement from the mode cam  34  may be movement about a first axis (for example, the Y-axis)  92 . The link  90  may be engaged with the mid-link  86  and the door  18  for transferring the movement from the mid-link  86  to the first door  18 . In at least one example embodiment, the movement of the first door  18  may be movement about the first axis (for example, the Y-axis). 
     In at least one example embodiment, the mid-link  86  may include at least one projection  94  and at least one groove  98 . The at least one projection  94  may be configured to engage the groove  54  (for example only, the groove  54 C) in the mode cam  34 . For example, the projection  94  may be a cylindrical projection configured to ride in, and follow, the path of the groove  54  in the mode cam  34 . In at least one example embodiment, the at least one projection  94  may be a pin or other cylindrical projection or rod on the mid-link  86  that may engage with the groove  54  (for example, groove  54 C) on the rear surface  50  of the mode cam  34 . 
     In at least one example embodiment, the groove  98  may be configured to receive one projection  102  of the link  90  (for example, attaching or fixing the link thereto). For example, the portion of the link  90  protrudes through the groove  98  and is slideable therein, such that the link  90  may pivot relative to the mid-link  86 . In at least one example embodiment, the link  90  may be positioned on a same side of the mid-link  86  as the mode cam  34 . 
     The link  90  may include at least one projection  102  and at least one aperture  106 . The at least one projection  102  may be engaged with the groove  98  in the mid-link  86 . For example only, the at least one projection  102  may be a pin or other cylindrical projection or rod that engages the groove in the mid-link  86 . 
     The at least one aperture  106  may configured to receive a portion of the first door  18 , fixing the door  18  thereto. For example, the portion of the first door  18  may be immovably fixed within the aperture  106  such that the door  18  moves with, and is fixed relative to, the link  90 . In at least one example embodiment, the first door  18  may be fixed to an opposing side of the link  90  and rotates along with link  90 . 
     In at least one example embodiment, the first door  18  may include a projection  110  extending along the pivoting axis of the first door  18  and from an end  114  of a body  118  of the first door  18 . The projection  110  may be integral with the body  118  of the first door  18 . In at least one example embodiment, the projection  110  may have a T-shaped cross-sectional male end that mates with a T-shaped aperture  106  (or female end) in the link  90 , such that the projection  110  cannot pivot or rotate within the aperture  106  and relative to the link  90 . As such, when the link  90  rotates or turns, the first door  18 , through the projection  110 , also pivots, rotates, or turns with the link  90 . 
     In at least one example embodiment, the projection  110  of the first door  18  may extend through an aperture  120  in the first case  26  before engaging with the aperture  106  in the link  90 . The projection  110  may be pivotably engaged with the aperture  120  in the first case  26  such that the projection  110 , the first door  18 , and the link  90  may pivot or rotate relative to the first case  26 . 
     In other words, in at least one example embodiment, movement of the first door  18  may be achieved through a torque and motion transfer path from the actuator to the first door  18  as follows: (1) actuator  14 ; (2) mode cam  34 ; (3) mid-link  86 ; (4) link  90 ; (5) door  18 . 
     In at least one example embodiment, the second linkage assembly  42  may include at least one mid-link  122 , at least one rack link  126 , and at least one link  130 . The mid-link  122  may be engaged with the groove  54  (for example, groove  54 A) on the mode cam  34  for directing the movement of the second door  22 . In at least one example embodiment, the movement from the mode cam  34  may be about a first axis (for example, the Y-axis). The rack link  126  may be engaged with the mid-link  122  to translate the rotational movement along the first axis (for example, the Y-axis) to linear movement along any axes in XZ-plane (for example, the X-axis)  166 . The link  130  may be engaged with the rack link  126  and the second door  22  for transferring the linear movement along any axes on XZ-plane from the rack link  126  to a rotational movement along any axes in the YZ-plane (for example, the Z-axis) of a second door  22 . In at least one example embodiment, the movement of the second door  22  may be rotational movement about the second axis (for example, the Z-axis) that is non-parallel to the first axis (for example, the Y-axis). 
     In at least one example embodiment, the mid-link  122  may include at least one projection  134  and at least one spur gear, or toothed wheel,  138 . The at least one projection  134  may be configured to engage the groove  54  (for example only, the groove  54 A) in the mode cam  34 . For example, the projection  134  may be a cylindrical projection configured to ride in, and follow, the path of the groove  54  in the mode cam  34 . While only one projection  134  is illustrated, it is understood that multiple projections  134  may be included on the mid-link  122  for engaging with the mode cam  34 . In at least one example embodiment, the at least one projection  134  on the mid-link  122  may engage with the groove  54  (for example, the groove  54 A) on the front surface  46  of the mode cam  34 . 
     In at least one example embodiment, the spur gear  138  may be a toothed wheel having a plurality of teeth  142  configured to engage with mating teeth  146  on the rack link  126 . For example, the spur gear  138  may rotate to “roll” along the rack link  126 , with the teeth  142  of the spur gear  138  intertwining or meshing with the teeth  146  on the rack link  126 . 
     In at least one example embodiment, the rack link  126  may be an elongated plate having a rectangular shape with rounded corners. The plurality of teeth  146  may be disposed on a top planar surface  150  of the rack link  126  on a first end  154  of the rack link  126 . The rack link  126  may include a pin  158  or cylindrical rod protruding therefrom. For example, the pin  158  may be disposed on an end  162  of the rack link  126  opposite the end  154  of the rack link  126  having the plurality of teeth  146 . The pin  158  may project to any perpendicular directions to the linear movement of the plurality of teeth  146  on rack link  126 . In at least one example embodiment, the pin  158  may project to Z-axis while to the movement of the plurality of teeth  146  on rack link  126  may be a linear movement along X-axis. 
     In at least one example embodiment, the rack link  126  may translate the motion of the mid-link  122  from rotational movement about the first axis  92  to movement about the second axis  132 . The movement of the spur gear  138  along the rack link  126  transfers the first axis rotation of mid-link  122  into a third axis (for example, the X-axis)  166  linear movement of rack link  126 . The pin  158  may engage with the link  130  to transfer the third axis  166  linear movement of the rack link  126  into rotational movement about the second axis  132  at link  130 . 
     In at least one example embodiment, the rack link  126  may be fixed to an opposing side of the mid-link  122  from the mode cam  34 . 
     In at least one example embodiment, the link  130  may include at least one slot or channel  170  and at least one aperture  174 . The slot  170  may be configured as a groove to receive the pin  158  of the rack link  126 . For example, the pin  158  of the rack link  126  may protrude through the slot  170  and be slideable therein to translate the third axis  166  linear movement of the rack link  126  into rotational movement about the second axis  132  at link  130 . 
     In at least one example embodiment, the link  130  may be engaged with any side of the rack link  126  depending on the projecting direction of pin  158  at an end  162  of rack link  126 . For example, the link  130  may be engaged with the same side of the rack link  126  as mid link  122 . 
     The at least one aperture  174  may configured as T-shape female end to receive a projection  178  of the second door  22 , fixing the second door  22  thereto. For example, the portion of the second door  22  may be immovably fixed within the aperture  174  such that the second door  22  moves with, and is fixed relative to, the link  130 . In at least one example embodiment, the second door  22  may be fixed to a same side of the link  130  as the rack link  126 . 
     In at least one example embodiment, the second door  22  may include a projection  178  extending along the pivoting axis  132  (i.e., the second axis  132 ) of the second door  22  and from an end  182  of a body  186  of the second door  22 . The projection  178  may be integral with the body  186  of the second door  22 . In at least one example embodiment, the projection  178  may have T-shaped cross-sectional male end that mates with an T-shaped aperture  174  (or female end) in the link  130 , such that the projection  178  cannot pivot or rotate within the aperture  174  and relative to the link  130 . As such, when the link  130  rotates or turns, the second door  22 , through the projection  178 , also pivots, rotates, or turns with the link  130 . 
     In other words, in at least one example embodiment, movement of the second door  22  may be achieved through a torque and motion transfer path from the actuator to the second door  22  as follows: (1) actuator  14 ; (2) mode cam  34 ; (3) mid-link  122 ; (4) rack link  126 ; (5) link  130 ; (6) door  22 . 
     Now referring to  FIGS. 3A and 3B , a first example mode pattern for an HVAC door of the present disclosure is illustrated. For example only, the first example mode pattern is illustrated for the second door  22 , although the first example mode pattern is applicable for either the first door  18  or the second door  22 . 
     As shown in  FIG. 3A , the projection  134  of the mid-link  122  may travel within the groove  54 A on the surface  46 ,  50  of the mode cam  34 . As the mode cam  34  is rotated by the actuator  14 , the travel of the projection  134  in the groove  54 A forces the gear  138  of the mid-link  122  to rotate along an axis parallel to the rotating axis of mode cam  34 . The teeth  142  of gear  138  on the mid-link  122  mesh with the teeth  146  on the rack link  126  to pull and push the rack link along an axis through the rack link and to transfer the rotational movement of mid link  122  to a linear movement of rack link  126 . 
     Linear movement of the rack link  126  caused by the meshing of teeth  142  on gear  138  with teeth  146  on rack link  126  drives movement of the pin  158  on rack link  126  within slot  170 . Movement of the pin  158  in slot  170  on link  130  forces rotational movement of the link  130  and thus the projection  178  fixed to the second door  22 , causing the second door  22  to rotate or pivot. 
     As shown in  FIGS. 3A and 3B , when mode cam  34  is at a position  190 , pin  134  of mid link  122  is located at a first circular segment of groove  54 A starting from end  58 B to move mid link  122  to a position  194  for a first mode. Gear teeth  142  of mid link  122  mesh with rack teeth  146  of rack link  126  to enable pin  158  of rack link  126  to move to a position  198  for the first mode. Pin  158  of rack link  126  is engaged with groove  170  of link  130  to move aperture  174  to a position  202  for the first mode. Aperture  174  of link  130  may be engaged with door mating projection  178  of door  22  to move door  22  to the first mode position. 
     As shown in  FIG. 3B , in at least one example embodiment, the mid-link  122  may be positioned on the front surface  46  of the mode cam  34  while the actuator  14  may be positioned on the rear surface  50  of the mode cam  34 . The mid-link  122  may be positioned on a first end  154  of the rack link  126  while the link  130  may be engaged with the pin  158  on a second end  162  spaced from the end  154 . The pin  158  on the rack link  126  may be engaged with the slot  170  on an end of the link  130  spaced from the aperture  174  receiving the projection  178  on the second door  22 . 
     Now referring to  FIGS. 4A and 4B , a second example mode pattern for an HVAC door of the present disclosure is illustrated. For example only, the second example mode pattern is illustrated for the second door  22 , although the second example mode pattern is applicable for either the first door  18  or the second door  22 . 
     As shown in  FIG. 4A , the projection  134  of the mid-link  122  may travel within the groove  54 A on the surface  46 ,  50  of the mode cam  34 . As the mode cam  34  is rotated by the actuator  14 , the travel of the projection  134  in the groove  54 A forces the gear  139  of the mid-link  122  to rotate along an axis parallel to the rotating axis of mode cam  34 . The teeth  142  of gear  138  on the mid-link  122  mesh with the teeth  146  on the rack link  126  to pull and push the rack link along an axis through the rack link and to transfer the rotational movement of mid link  122  to a linear movement of rack link  126 . 
     Linear movement of the rack link  126  caused by the teeth  142  on gear  138  meshing with teeth  146  on rack link  126  drives movement of the pin  158  on rack link  126  within slot  170 . Movement of the pin  158  in slot  170  on link  130  forces rotation movement of the link  130  and thus the projection  178  fixed to the second door  22 , causing the second door  22  to rotate or pivot. 
     As shown in  FIGS. 4A and 4B , when mode cam  34  is at position  206 , pin  134  of mid link  122  may be located at the third circular segment of groove  54 A starting from end  58 B to move mid link  122  to a position  210  for the second mode. Gear teeth  142  of mid link  122  mesh with rack teeth  146  of rack link  126  to move pin  158  of rack link  126  to a position  214  for the second mode. Pin  158  of rack link  126  is engaged with groove  170  of link  130  to move aperture  174  to a position  218  for the second mode. Aperture  174  of link  130  may be engaged with door mating projection  178  of door  22  to move the door  22  to the second mode position. 
     As shown in  FIG. 4B , in at least one example embodiment, the mid-link  122  may be positioned on the front surface  46  of the mode cam  34  while the actuator  14  may be positioned on the rear surface  50  of the mode cam  34 . The mid-link  122  may be positioned on one end  154  of the rack link  126  while the link  130  may be engaged with the pin  158  on the opposite end  162  from the end  154 . The mid-link  122  may be positioned on a first end  154  of the rack link  126  while the link  130  may be engaged with the pin  158  on a second end  162  spaced from the first end  154 . The pin  158  on the rack link  126  may be engaged with the slot  170  on one end of the link  130  spaced from the aperture  174  receiving the projection  178  on the second door  22 . 
     While the above two movement modes are illustrated, it is understood that different configurations of the grooves on the surface  46 ,  50  of the mode cam  34  will generate different movement modes of the doors  18 ,  22 . It is further understood that while movement control of two doors  18 ,  22  is discussed herein, additional linkage assemblies could be added to the mode cam  34  and actuator  14  to control additional doors. 
     The ability to add multiple linkage assemblies to a common mode cam  34  and actuator  14  provides a reduction in parts for HVAC door assemblies. The reduction in parts reduces cost of the assemblies, both in part cost and assembly cost. The reduction in parts also reduces the space occupied for the HVAC door assemblies, allowing the HVAC units and assemblies to fit in smaller places. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.