Patent Publication Number: US-10760329-B1

Title: Fenestration frames with integral mull posts and methods of making same

Description:
RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. Section 119 of U.S. Provisional Patent Application Ser. No. 62/621,994 entitled “FENESTRATION FRAMES WITH INTEGRAL MULL POSTS AND METHODS OF MAKING SAME” and filed on Jan. 25, 2018, which is incorporated herein by reference in its entirety. 
    
    
     Fenestration unit frames with integral mull posts and methods of making the same are described herein. 
     Fenestration unit frames used in a variety of fenestration units may include an integral mull such that two or more windows, doors, etc. may be provided in a single unitary frame having one or more mull joints located therein. In one or more embodiments, the corners of the fenestration unit frames may include weldable frame components that are connected by welding the ends of the frame components together at each corner. 
     Weldable frame components along with methods of welding corner joints formed by those frame components to form fenestration unit frames are described in, e.g., U.S. Pat. No. 5,603,585 (Bruchu et al.). Although U.S. Pat. No. 5,603,585 does teach the joining of fenestration units together using a mulling strip, the mulling strip is not integrally located within a fenestration unit frame, but is, rather, used to connect two fenestration unit frames together. 
     SUMMARY 
     Fenestration unit frames with integral mull posts and methods of making the same are described herein. 
     In one or more embodiments, the integral mull posts (in the form of intermediate jambs) are supported and aligned with the jambs located at their opposing ends (e.g., sill and head jambs) using keys (e.g., sill and head keys) before complete assembly and connection of the corner joints of the fenestration unit frames. 
     In one or more embodiments of the fenestration unit frames described herein, the keys used at the ends of the integral mull posts may allow for an interlocking connection between the ends of the integral mull posts and the jambs located at the ends of the integral mull posts as described herein. 
     In a first aspect, one or more embodiments of a fenestration unit frame as described herein may include: a sill jamb extending along a sill axis between a first end and a second end; a head jamb extending along a head axis between a first end and a second end; a first side jamb extending between the first end of the sill jamb and the first end of the head jamb, wherein a first sill corner joint connects the first side jamb to the first end of the sill jamb and a first head corner joint connects the first side jamb to the first end of the head jamb; a second side jamb extending between the second end of the sill jamb and the second end of the head jamb, wherein a second sill corner joint connects the second side jamb to the second end of the sill jamb and a second head corner joint connects the second side jamb to the second end of the head jamb; an intermediate jamb extending along an intermediate jamb axis between the sill jamb and the head jamb at a location between the first side jamb and the second side jamb, wherein a sill end of the intermediate jamb and the sill jamb form an interlocking sill connection that prevents movement of the sill end relative to the sill jamb in a direction transverse to both the sill axis and the intermediate jamb axis, and wherein a head end of the intermediate jamb and the head jamb form an interlocking head connection that prevents movement of the head end relative to the head jamb in a direction transverse to both the head axis and the intermediate jamb axis; a sill key attached to the sill jamb, wherein the sill key comprises a sill key base proximate the sill and a sill key post extending away from the sill key base along the intermediate jamb axis, wherein the sill key post extends into a sill end cavity in the sill end of the intermediate jamb; and a head key attached to the head jamb, wherein the head key comprises a head key base proximate the head and a head key post extending away from the head key base along the intermediate jamb axis, wherein the head key post extends into a head end cavity in the head end of the intermediate jamb. 
     In one or more embodiments of a fenestration unit frame as described herein, the interlocking sill connection defines an interlocking sill connection distance measured along the intermediate jamb axis and wherein the sill key post extends into the sill end cavity over a post-cavity distance that is greater than the interlocking sill connection distance. In one or more embodiments, the interlocking head connection defines an interlocking head connection distance measured along the intermediate jamb axis and wherein the head key post extends into the head end cavity over a post-cavity distance that is greater than the interlocking head connection distance. 
     In one or more embodiments of a fenestration unit frame as described herein, the sill key post comprises a sill post end distal from the sill along the intermediate jamb axis, and wherein the interlocking sill connection comprises a terminal junction distal from the sill jamb along the intermediate jamb axis, and further wherein the terminal junction of the interlocking sill connection is located between the sill key base and the sill post end. 
     In one or more embodiments of a fenestration unit frame as described herein, the head key post comprises a head post end distal from the head along the intermediate jamb axis, and wherein the interlocking head connection comprises a terminal junction distal from the head jamb along the intermediate jamb axis, and further wherein the terminal junction of the interlocking head connection is located between the head key base and the head post end. 
     In one or more embodiments of a fenestration unit frame as described herein, the sill key post comprises a first sill key post, and wherein the sill key comprises a second sill key post extending away from the sill key base along the intermediate jamb axis, wherein the second sill key post extends into a second sill end cavity in the sill end of the intermediate jamb. 
     In one or more embodiments of a fenestration unit frame as described herein, the head key post comprises a first head key post, and wherein the head key comprises a second head key post extending away from the head key base along the intermediate jamb axis, wherein the second head key post extends into a second head end cavity in the head end of the intermediate jamb. 
     In one or more embodiments of a fenestration unit frame as described herein, the interlocking sill connection comprises a sill rail, and wherein the sill end of the intermediate jamb comprises a channel configured to receive the sill rail to form the interlocking connection. In one or more embodiments, the sill rail extends along the entire length of the sill jamb from the first end to the second end of the sill jamb. In one or more embodiments, the sill rail comprises a sill rail top and wherein the sill key post comprises a sill post end distal from the sill along the intermediate jamb axis, and wherein the sill rail top is located between the sill key base and the sill post end. 
     In one or more embodiments of a fenestration unit frame as described herein, the interlocking head connection comprises a head rail, and wherein the head end of the intermediate jamb comprises a channel configured to receive the head rail to form the interlocking connection. In one or more embodiments, the head rail extends along the entire length of the head jamb from the first end to the second end of the head jamb. In one or more embodiments, the head rail comprises a head rail top and wherein the head key post comprises a head post end distal from the head along the intermediate jamb axis, and wherein the head rail top is located between the head key base and the head post end. 
     In one or more embodiments of a fenestration unit frame as described herein, the first sill corner joint and the first head corner joint comprise welded corner joints. 
     In a second aspect, one or more embodiments of a method of manufacturing a fenestration unit frame as described herein may include: attaching a sill key to the sill jamb at an intermediate location between a first end and a second end of the sill jamb, wherein the sill key comprises a sill key base proximate the sill and a sill key post extending away from the sill key base along the intermediate jamb axis; attaching a head key to the head jamb at an intermediate location between a first end and a second end of the head jamb, wherein the head key comprises a head key base proximate the head and a head key post extending away from the head key base along the intermediate jamb axis; positioning the first side jamb between the first end of the sill jamb and the first end of the head jamb; positioning the second side jamb between the second end of the sill jamb and the second end of the head jamb; positioning the intermediate jamb between the sill jamb and the head jamb at a location between the first side jamb and the second side jamb, wherein an intermediate jamb axis extends along the intermediate jamb between a sill end proximate the sill jamb and a head end proximate the head jamb; inserting a portion of the sill key post into a sill end cavity in the sill end of the intermediate jamb after attaching the sill key to the sill jamb and after positioning the intermediate jamb between the sill jamb and the head jamb; inserting a portion of the head key post into a head end cavity in the head end of the intermediate jamb after attaching the head key to the head jamb and after positioning the intermediate jamb between the sill jamb and the head jamb; connecting the first end of the sill jamb and the first end of the head jamb to opposite ends of the first side jamb to form corner joints at the opposite ends of the first side jamb after inserting the portion of the sill key post into the sill end cavity in the sill end of the intermediate jamb and after inserting the portion of the head key post into the head end cavity in the head end of the intermediate jamb; connecting the second end of the sill jamb and the second end of the head jamb to opposite ends of the second side jamb to form corner joints at the opposite ends of the second side jamb after inserting the portion of the sill key post into the sill end cavity in the sill end of the intermediate jamb and after inserting the portion of the head key post into the head end cavity in the head end of the intermediate jamb; forming an interlocking sill connection between the sill end of the intermediate jamb and the sill jamb by moving the sill jamb and the sill end of the intermediate jamb closer to each other such that the sill key post advances to a fully seated position in the sill end cavity of the intermediate jamb before forming the corner joints at the first and second ends of the sill jamb, wherein the interlocking connection between the sill end of the intermediate jamb and the sill jamb prevents movement of the sill end relative to the sill jamb in a direction transverse to both a sill axis extending between the first and second ends of the sill jamb and an intermediate jamb axis extending along the intermediate jamb between the sill jamb and the head jamb; and forming an interlocking head connection between the head end of the intermediate jamb and the head jamb by moving the head jamb and the head end of the intermediate jamb closer to each other such that the head key post advances to a fully seated position in the head end cavity of the intermediate jamb before forming the corner joints at the first and second ends of the head jamb, wherein the interlocking connection between the head end of the intermediate jamb and the head jamb prevents movement of the head end relative to the head jamb in a direction transverse to both a head axis extending between the first and second ends of the head jamb and an intermediate jamb axis extending along the intermediate jamb between the sill jamb and the head jamb. 
     In one or more embodiments of a method of manufacturing a fenestration unit frame as described herein, the interlocking sill connection defines an interlocking sill connection distance measured along the intermediate jamb axis and wherein the sill key post extends into the sill end cavity over a post-cavity distance that is greater than the interlocking sill connection distance. In one or more embodiments, the interlocking head connection defines an interlocking head connection distance measured along the intermediate jamb axis and wherein the head key post extends into the head end cavity over a post-cavity distance that is greater than the interlocking head connection distance. 
     In one or more embodiments of a method of manufacturing a fenestration unit frame as described herein, the sill key post comprises a sill post end distal from the sill along the intermediate jamb axis, and wherein the interlocking sill connection comprises a terminal junction distal from the sill jamb along the intermediate jamb axis, and further wherein the terminal junction of the interlocking sill connection is located between the sill key base and the sill post end. 
     In one or more embodiments of a method of manufacturing a fenestration unit frame as described herein, the head key post comprises a head post end distal from the head along the intermediate jamb axis, and wherein the interlocking head connection comprises a terminal junction distal from the head jamb along the intermediate jamb axis, and further wherein the terminal junction of the interlocking head connection is located between the head key base and the head post end. 
     In one or more embodiments of a method of manufacturing a fenestration unit frame as described herein, the sill key post comprises a first sill key post, and wherein the sill key comprises a second sill key post extending away from the sill key base along the intermediate jamb axis, wherein the second sill key post extends into a second sill end cavity in the sill end of the intermediate jamb. 
     In one or more embodiments of a method of manufacturing a fenestration unit frame as described herein, the head key post comprises a first head key post, and wherein the head key comprises a second head key post extending away from the head key base along the intermediate jamb axis, wherein the second head key post extends into a second head end cavity in the head end of the intermediate jamb. 
     In one or more embodiments of a method of manufacturing a fenestration unit frame as described herein, the interlocking sill connection comprises a sill rail, and wherein the sill end of the intermediate jamb comprises a channel configured to receive the sill rail to form the interlocking connection. In one or more embodiments, the sill rail extends along the entire length of the sill jamb from the first end to the second end of the sill jamb. 
     In one or more embodiments of a method of manufacturing a fenestration unit frame as described herein, the sill rail comprises a sill rail top and wherein the sill key post comprises a sill post end distal from the sill along the intermediate jamb axis, and wherein the sill rail top is located between the sill key base and the sill post end. 
     In one or more embodiments of a method of manufacturing a fenestration unit frame as described herein, the interlocking head connection comprises a head rail, and wherein the head end of the intermediate jamb comprises a channel configured to receive the head rail to form the interlocking connection. In one or more embodiments, the head rail extends along the entire length of the head jamb from the first end to the second end of the head jamb. In one or more embodiments, the head rail comprises a head rail top and wherein the head key post comprises a head post end distal from the head along the intermediate jamb axis, and wherein the head rail top is located between the head key base and the head post end. 
     In one or more embodiments of a method of manufacturing a fenestration unit frame as described herein, connecting the first end of the sill jamb and the first end of the head jamb to opposite ends of the first side jamb to form corner joints comprises welding the first end of the sill jamb and the first end of the head jamb to opposite ends of the first side jamb. 
     As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a” or “the” component may include one or more of the components and equivalents thereof known to those skilled in the art. Further, the term “and/or” means one or all of the listed elements or a combination of any two or more of the listed elements. 
     It is noted that the term “comprises” and variations thereof do not have a limiting meaning where these terms appear in the accompanying description. Moreover, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably herein. 
     Where used herein, the terms “top” and “bottom” are used for reference relative to each other when fenestration units are properly installed in a building opening. 
     Where used herein, the terms “exterior” and “interior” are used in a relative sense, e.g., an exterior edge and an interior edge of a sill or any other component describe edges located on opposite sides of the fenestration unit. In other words, an exterior edge could be found within the interior of a building or other structure that would conventionally define an interior and an exterior, while an interior edge could be found outside of a building or other structure that would conventionally define an interior and an exterior. 
     The above summary is not intended to describe each embodiment or every implementation of the fenestration unit frames with integral mull posts and methods of making the same described herein. Rather, a more complete understanding of the invention will become apparent and appreciated by reference to the following Description of Illustrative Embodiments and claims in view of the accompanying figures of the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWING 
         FIG. 1  depicts one illustrative embodiment of a fenestration unit in the form of a twin casement window having a fenestration unit frame including an integral mull post. 
         FIG. 2  is an exploded assembly diagram of the fenestration unit frame of the fenestration unit depicted in  FIG. 1 . 
         FIG. 3  is an enlarged exploded view of a portion of the fenestration unit frame depicted in  FIG. 2 . 
         FIG. 4  is a side view of the enlarged exploded view of  FIG. 3 . 
         FIG. 5  is an enlarged end view of the assembly depicted in  FIGS. 3-4  after assembly of the components. 
         FIG. 6  is a perspective view of the mull post and sill jamb of  FIG. 5  as assembled. 
         FIG. 7  depicts one illustrative embodiment of a fenestration unit in the form of a twin single hung window having a fenestration unit frame including an integral mull post. 
         FIG. 8  is an exploded assembly diagram of the fenestration unit frame of the fenestration unit depicted in  FIG. 7 . 
         FIG. 9  is an enlarged exploded view of a portion of the fenestration unit frame depicted in  FIG. 8 . 
         FIG. 10  is a side view of the enlarged exploded view of  FIG. 9 . 
         FIG. 11  is an enlarged end view of the assembly depicted in  FIGS. 9-10  after assembly of the components. 
         FIG. 12  is a perspective view of the mull post and sill jamb of  FIG. 11  as assembled. 
         FIG. 13  is a perspective view of another illustrative embodiment of a fenestration unit frame including an integral mull post during assembly of the components as described herein. 
     
    
    
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     In the following description of illustrative embodiments, reference is made to the accompanying figures of the drawing which form a part hereof, and in which are shown, by way of illustration, specific embodiments. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     Each of the corner joints of the fenestration unit frames described herein includes a pair of frame members that meet at a corner where a corner joint is formed to connect the frame members. The frame members may, in one or more embodiments, be attached to each other at the corner joints by welding portions of each frame member to the opposing frame member in the corner joint. Potentially suitable examples of welding corner joints are described in, e.g., U.S. Pat. No. 5,603,585 (Bruchu et al.) although other welding techniques could potentially be used to form the corner joints of fenestration unit frames as described herein. Although welding may be used to form corner joints in one or more embodiments of fenestration unit frames and methods as described herein, any other suitable technique or combination of techniques may be used to form corner joints, e.g., one or more of welding, adhesives, mechanical fasteners, etc. may be used to form corner joints in fenestration frames that include an integral mull post (intermediate jamb) as described herein. 
     In one or more embodiments of the fenestration unit frames and methods described herein, the corner joints in the fenestration unit frames may or may not include a corner key that fits within either end of the frame members to assist with aligning and/or fastening the frame members together at the corner joints (see, e.g., U.S. Pat. No. 8,851,787 (Kelley et al.) which describes frames and methods in which corner keys are used in fenestration unit frames). Although corner keys may be used in one or more embodiments of fenestration unit frames and methods described herein, in one or more alternative embodiments, the connection between the frame members and their alignment relative to each other at the corner joints to form the desired fenestration unit frame may be achieved in the absence of corner keys. 
     The frame members used in the fenestration unit frames described herein may be manufactured by a variety of processes. It may, however, be preferred that the frame members be manufactured of an extruded material which may, in one or more embodiments, include fibers and a polymer, pultruded materials, etc. Examples of some potentially suitable constructions for frame members that include fibers and a polymer may include those described in, e.g., U.S. Pat. No. 5,585,155 (Heikkila et al.); U.S. Pat. No. 6,106,944 (Heikkila et al.); U.S. Pat. No. 6,210,792 Seethamraju et al.); U.S. Pat. No. 6,260,251 (Guhl); U.S. Pat. No. 6,280,667 (Koenig et al.); U.S. Pat. No. 6,342,172 (Finley); etc. Alternatively, the frame members could be made primarily of polymeric materials such as, e.g., vinyls, etc. 
       FIG. 1  depicts one illustrative embodiment of a fenestration unit  10  in the form of a twin casement window. The fenestration unit  10  includes a fenestration unit frame including an integral mull post in the form of an intermediate jamb  60 . Other components of the fenestration unit frame include a sill jamb  20 , head jamb  30 , left side jamb  40  and right side jamb  50 . The intermediate jamb  60  extends between the sill jamb  20  and head jamb  30  and is located between left side jamb  40  and right side jamb  50 . Casement windows  12  and  14  are located within the fenestration unit frame and separated from each other by intermediate jamb  60 . 
     Sill jamb  20  as seen in  FIG. 1  extends along a sill axis  21  between a first end  22  and a second end  24 . Similarly, head jamb  30  extends along a head axis  31  between a first end  32  and a second end  34 . 
     Left side jamb  40  extends between the first end  22  of sill jamb  20  and the first end  32  of head jamb  30 . In the depicted illustrative embodiment, a sill corner joint connects the first end  42  of left side jamb  40  to the first end  22  of sill jamb  20  and a head corner joint connects the first end  32  of head jamb  30  to the second end  44  of left side jamb  40 . In one or more embodiments, the sill corner joint and the head corner joint that may or may not include a corner key to assist in positioning and/or provide additional rigidity to the corner joints formed between the sill jamb  20 , head jamb  30 , and left side jamb  40 . 
     Right side jamb  50  extends between the second end  24  of sill jamb  20  and the second end  34  of head jamb  30 . In the depicted illustrative embodiment, a sill corner joint connects the first end  52  of the right side jamb  50  to the second end  24  of the sill jamb  20  and a head corner joint connects the second end  34  of head jamb  30  to the second end  54  of the right side jamb  50 . As above, in one or more embodiments, the sill corner joint and the head corner joint formed on the right side of the fenestration unit frame may or may not include a corner key to assist in positioning and/or provide additional rigidity to the corner joints formed between the sill jamb  20 , head jamb  30 , and right side jamb  50 . 
       FIG. 2  is an exploded assembly diagram of the fenestration unit frame used in fenestration unit  10  as depicted in  FIG. 1 . In addition to the components and features described in  FIG. 1 , the exploded assembly diagram of  FIG. 2  depicts, more clearly, various features regarding the intermediate jamb  60  provided as a part of the fenestration unit frame. 
     In one or more embodiments of fenestration unit frames as described herein, the intermediate jamb  60  extends along an intermediate jamb axis  61  between the sill jamb  20  and the head jamb  30  at a location between the left side jamb  40  and the right side jamb  50 . A sill end  62  of the intermediate jamb  60  and the sill jamb  20  form an optional interlocking sill connection that prevents movement of the sill end  62  of the intermediate jamb  60  relative to the sill jamb  20  in a direction transverse to both the sill axis  21  and the intermediate jamb axis  61 . A head end  64  of the intermediate jamb  60  and the head jamb  30  form an optional interlocking head connection that prevents movement of the head end  64  of the intermediate jamb  60  relative to the head jamb  30  in a direction transverse to both the head axis  31  and the intermediate jamb axis  61 . That same interlocking connection also prevents placement of the intermediate jamb  60  between the sill jamb  20  and the head jamb  30  after the corner joints have been formed at the opposite ends of the left and right side jambs  40  and  50 . 
     Attachment and fixation of the intermediate jamb  60  at selected locations along both the sill jamb  20  and the head jamb  30  are, in the depicted embodiment, accomplished using keys attached to the sill jamb  20  and the head jamb  30 . In particular, a sill key  70  is attached to the sill jamb  20  and a sill key  80  is attached to the head jamb  30 . In the depicted illustrative embodiment, the sill key  70  is attached to the sill jamb  20  and the head key  80  is attached to the head jamb  30  using threaded fasteners, although any suitable fastening technique or combination of techniques could be used in place of and/or in addition to threaded fasteners (e.g., adhesives, welding, rivets, etc.). 
     In the depicted illustrative embodiment, the fenestration unit frame members, i.e., sill jamb  20 , head jamb  30 , side jambs  40  and  50 , each include mitered ends configured to mate with each other at the corner joints to facilitate strong welds at the corners of the fenestration unit frame. As discussed herein, the corner joints may or may not include corner keys. 
       FIGS. 3-4  depict front and side views of the components found at the sill end  62  of the intermediate jamb  60  where the sill end  62  of the intermediate jamb  60  connects or is attached to the sill jamb  20 . In particular,  FIG. 4  may be described as an end view taken along the direction of sill axis  21  in  FIG. 3 . 
     In particular, features of the illustrative embodiment of sill key  70  are seen in  FIGS. 3-4 . Sill key  70 , in the depicted illustrative embodiment, includes a base  72  configured to be attached to the sill jamb  20 . As seen in, e.g.,  FIG. 4 , the base  72  of sill key  70  may include a profile or shape that is complementary to the shape of the sill jamb  20  to facilitate a strong and weatherproof connection between the base  72  of sill key  70  and sill jamb  20 . In one or more embodiments, adhesives and/or sealants may be used to further provide a strong and/or weatherproof connection between the base  72  of sill key  70  and sill jamb  20 . In the depicted illustrative embodiment, threaded fasteners  71  may also be used to attach sill key  70  to sill jamb  20 . 
     The depicted illustrative embodiment of sill key  70  includes a pair of sill key posts  74  that extend away from the sill key base  72  in the direction of the intermediate jamb axis  61 . The sill key posts  74  extend away from the sill key base  72  and terminate at sill post ends  76 . Although the depicted illustrative embodiment of sill key  70  includes two sill key posts  74 , alternative embodiments of sill keys used in fenestration unit frames as described herein may include as few as one sill key post or may include three or more sill key posts. Furthermore, although the sill key posts  74  depicted in the illustrative embodiment of sill key  70  are similar in shape (although mirror images of each other), sill keys including multiple sill key posts as described herein may include sill key posts that have different shapes and configurations. 
     As will be described further herein, the sill key posts  74  may preferably extend into sill end cavities in the sill end  62  of the intermediate jamb  60 . That interaction between sill key posts  74  and sill end cavities in the intermediate jamb  60  assist in retaining the intermediate jamb  60  in position between the sill jamb  20  and the head jamb  30 , as well as guiding the sill end  62  of intermediate jamb  60  into its proper position with respect to sill jamb  20  and, in one or more embodiments, may also provide additional structural rigidity to the connection between intermediate jamb  60  and sill jamb  20  when fully assembled into a fenestration unit frame. 
     Also depicted in  FIG. 4  are features that form one illustrative embodiment of an interlocking sill connection that prevents movement of the sill end  62  of the intermediate jamb  60  relative to the sill jamb  20  in a direction transverse to both the sill axis  21  and the intermediate jamb axis  61  (which, in  FIG. 3 , would involve movement of the sill end  62  of intermediate jamb  60  into or out of the page containing  FIG. 3 ). In the depicted illustrative embodiment those features include a sill rail  26  having a sill rail top  28  formed in sill jamb  20  and a channel  66  formed in the sill end  62  of intermediate jamb  60  that is configured to receive the sill rail  26  to form the interlocking connection as described herein. 
       FIG. 5  depicts the components of  FIGS. 3-4  after assembly such that the sill key  70  is attached to sill jamb  20  and sill end  62  of intermediate jamb  60  is seated against the sill key  70  and sill jamb  20 . An additional feature depicted in broken lines because it is not visible in the view seen in  FIG. 5  is a sill end cavity  68  formed in intermediate jamb  60  into which sill key post  74  (also depicted in broken lines) is inserted as a part of the assembly process. In one or more embodiments in which the intermediate jamb is formed as an extruded member, sill end cavity  68  may extend along the entire length of intermediate jamb  60  between the sill end  62  and the head end  64 . This feature is not, however, required, and the sill end cavity  68  may be separate and distinct from a head end cavity at the head end of the intermediate jamb  60 . 
     When assembled, the optional interlocking connection formed between sill end  62  of intermediate jamb  60  and sill jamb  20  involves positioning of sill rail  26  in channel  66  in the sill end  62  of intermediate jamb  60 . Because of this interlocking connection, sill end  62  of intermediate jamb  60  must be moved into position on sill jamb  20  along intermediate jamb axis  61  during assembly of the fenestration unit frame before the ends of the jambs are assembled and connected at the corner joints. Sill key post  74  and sill end cavity  68  assist in both retention and proper alignment of the sill end  62  of intermediate jamb  60  during that assembly process because sill key post  74  is positioned in sill end cavity  68  before sill rail  26  is positioned in channel  66  to form the interlocking connection between the sill end  62  of intermediate jamb  60  and sill jamb  20 . Further, sill key post  74  extends along the direction of intermediate jamb axis  61 . 
     In one or more embodiments, the interlocking sill connection formed between sill jamb  20  and intermediate jamb  60  may define an interlocking sill connection distance S measured along the intermediate jamb axis  61  between the sill end  62  and the sill rail top  28  on sill rail  26  as seen in  FIG. 5 . The sill key post  74  may be described as extending into the sill end cavity  68  over a post-cavity distance P measured along the intermediate jamb axis  61  between the sill end  62  and the sill post end  76 . In one or more embodiments, the post-cavity distance P is greater than the interlocking sill connection distance S. 
     Another manner in which the junction between sill end  62  of intermediate jamb  60 , sill key  70 , and sill jamb  20  may be characterized is in the position of various features of those components. In particular, in one or more embodiments, the interlocking sill connection may be described as having a terminal junction defined by the sill rail top  28  of sill rail  26  and the terminal end  67  of channel  66  in sill end  62  of intermediate jamb  60 . That terminal junction between sill rail top  28  and terminal end  67  of channel  66  may be described as being distal from the sill jamb  20  along the intermediate jamb axis  61 . Further, the terminal junction between sill rail top  28  and terminal end  67  of channel  66  may be described as being located between the sill key base  72  and the sill post end  76  along the intermediate jamb axis  61 . One embodiment of this arrangement of features is seen in, e.g.,  FIG. 5 . 
     In one or more embodiments of fenestration unit frames as described herein, the sill rail  26  of sill jamb  20  may extend along the entire length of the sill jamb  20  from its first end  22  to its second end  24 . Providing a sill rail  26  that extends along the sill jamb  20  provides flexibility in location of the intermediate jamb  60  at any position along sill jamb  20  as needed. Furthermore, in embodiments in which sill jamb  20  is an extruded member, providing a sill rail  26  that extends along the entire length of the sill jamb  20  simplifies the process of manufacturing sill jamb  20 . 
       FIG. 6  depicts the joint formed by the sill end  62  of intermediate jamb  60  with sill jamb  20 . In the depicted illustrative embodiment, a portion of the base  72  of sill key  70  may be visible in the finished joint, although that is not necessarily true in all embodiments. Also seen in  FIG. 6  is sill rail  26  that extends along the length of sill jamb  20 . Further seen in  FIG. 6  are threaded fasteners  27  that may optionally be used to secure the sill end  62  of intermediate jamb  60  to sill jamb  20  after assembly of the fenestration unit frame. 
     Although the discussion regarding the connection of intermediate jamb  60  within the fenestration unit frame and  FIGS. 3-6  has focused on the connection between the sill end  62  of intermediate jamb  60  with sill jamb  20 , it should be understood that, in one or more embodiments, the connection between the head end  64  of intermediate jamb with head jamb  30  using head key  80  (as seen in, e.g.,  FIG. 2 ) includes the same features and relationships. For example, head jamb  30  includes head rail having a head rail top similar to that depicted in connection with sill jamb  20  while the head key  80  includes head key posts extending from a head key base along the intermediate jamb axis  61  as described in connection with the sill key  70 . Further, the relationships between various features forming the optional interlocking sill connection are also, in one or more embodiments, replicated in an optional interlocking head connection at the junction between the head end  64  of intermediate jamb  60  and head jamb  30 . The similarities between the connection at the head and of the intermediate jamb and the head jamb to the sill end of the intermediate jamb and the sill jamb are illustrated below in connection with  FIGS. 7-12 , where the focus of  FIGS. 9-12  is on that head end connection. 
       FIG. 7  depicts an illustrative embodiment of a fenestration unit  110  in the form of a twin single hung window. The fenestration unit  110  includes a fenestration unit frame with an integral mull post in the form of an intermediate jamb  160 . Other components of the fenestration unit frame include a sill jamb  120 , head jamb  130 , left side jamb  140 , and right side jamb  150 . The intermediate jamb  160  extends between the sill jamb  120  and head jamb  130  and is located between the left side jamb  140  and right side jamb  150 . Single hung windows are provided on opposite sides of the intermediate jamb  160 . In particular, the left side single hung window includes a lower sash  112  and an upper sash  113 , while the right side single hung window includes a lower sash  114  and upper sash  115 . 
     Sill jamb  120  as seen in  FIG. 7  extends along a sill axis  121  between a first end  122  and a second end  124 . Similarly, head jamb  130  extends along a head axis  131  between a first end  132  and a second end  134 . 
     Left side jamb  140  extends between the first end  122  of sill jamb  120  and the first end  132  of head jamb  130 . In the depicted illustrative embodiment, a sill corner joint connects the first end  142  of left side jamb  140  to the first end  122  of sill jamb  120  and a head corner joint connects the first end  132  of head jamb  132  the second end  144  of left side jamb  140 . In one or more embodiments, the sill corner joint and the head corner joint may be welded joints that may or may not include a corner key to assist in positioning and/or provide additional rigidity to the corner joints formed between the sill jamb  120 , head jamb  130 , and left side jamb  140 . 
     Right side jamb  150  extends between the second end  124  of sill jamb  120  and the second end  134  of head jamb  130 . In the depicted illustrative embodiment, a sill corner joint connects the first end  152  of the right side jamb  150  to the second end  124  of the sill jamb  120  and a head corner joint connects the second end  134  of head jamb  132  the second end  154  of the right side jamb  150 . As discussed above, the sill corner joint and the head corner joint formed on the right side of the fenestration unit frame may, in one or more embodiments, may or may not include a corner key to assist in positioning and/or to provide additional rigidity to the corner joints formed between the sill jamb  120 , head jamb  130 , and right side jamb  150 . 
       FIG. 8  is an exploded assembly diagram of the fenestration unit frame used in fenestration unit  110  as depicted in  FIG. 7 . In addition to the components and features described in  FIG. 7 , the exploded assembly diagram of  FIG. 8  depicts, more clearly, various features regarding the intermediate jamb  160  provided as a part of the fenestration unit frame. 
     In the depicted illustrative embodiment, the intermediate jamb  160  extends along an intermediate jamb axis  161  between the sill jamb  120  and the head jamb  130  at a location between the left side jamb  140  and the right side jamb  150 . A sill end  162  of the intermediate jamb  160  and the sill jamb  120  form an interlocking sill connection that prevents movement of the sill end  162  of the intermediate jamb  160  relative to the sill jamb  120  in a direction transverse to both the sill axis  121  and the intermediate jamb axis  161 . A head end  164  of the intermediate jamb  160  and the head jamb  130  form an optional interlocking head connection that prevents movement of the head end  164  of the intermediate jamb  160  relative to the head jamb  130  in a direction transverse to both the head axis  131  and the intermediate jamb axis  161 . 
     Attachment and fixation of the intermediate jamb  160  at selected locations along both the sill jamb  120  and the head jamb  130  are, in the depicted embodiment, accomplished using keys attached to the sill jamb  120  and the head jamb  130 . In particular, a sill key  170  is attached to the sill jamb  120  and a sill key  180  is attached to the head jamb  130 . In the depicted illustrative embodiment, the sill key  170  is attached to the sill jamb  120  and the head key  180  is attached to the head jamb  130  using threaded fasteners, although any suitable fastening technique or combination of techniques could be used in place of and/or in addition to threaded fasteners (e.g., adhesives, welding, rivets, etc.). 
     In the depicted illustrative embodiment, the fenestration unit frame members, i.e., sill jamb  120 , head jamb  130 , side jambs  140  and  150 , each include mitered ends configured to mate with each other at the corner joints of the fenestration unit frame. As discussed herein, the corner joints may or may not include corner keys. 
       FIGS. 9-10  depicted front and side views of the components found at the head end  164  of the intermediate jamb  160  where the head end  164  of the intermediate jamb  160  connects or is attached to the head jamb  130 . In particular,  FIG. 10  may be described as an end view taken along the direction of head axis  131  in  FIG. 9 . 
     In particular, features of the illustrative embodiment of head key  180  are seen in  FIGS. 9-10 . Head key  180 , in the depicted illustrative embodiment, includes a base  182  configured to be attached to the head jamb  130 . As seen in, e.g.,  FIG. 10 , the base  182  of sill key  180  may include a profile or shape that is complementary to the shape of the head jamb  132  facilitate a strong and weatherproof connection between the base  182  of head key  180  and the head jamb  130 . In one or more embodiments, adhesives and/or sealants may be used to further provide a strong and/or weatherproof connection between the base  182  of the head key  180  and the head jamb  130 . Threaded fasteners may also be used to attach head key  182  head jamb  130 . 
     The depicted illustrative embodiment of head key  180  includes a pair of head key posts  184  that extend away from the head key base  182  in the direction of the intermediate jamb axis  161 . The head key posts  184  extend away from the head key base  182  and terminate at sill Post ends  186 . Although the depicted illustrative embodiment of head key  180  includes two head key posts  184 , alternative embodiments of head keys used in fenestration unit frames as described herein may include as few as one head key post or may include three or more head key posts. Furthermore, although the head key posts  184  depicted in the illustrative embodiment of head key  180  are similar in shape (although mirror images of each other), head keys including multiple head key posts as described herein may include head key posts that have different shapes and configurations. 
     As will be described further herein, the head key posts  184  may preferably extend into head end cavities in the head end  164  of the intermediate jamb  160 . That interaction between head key posts  184  and head end cavities in the intermediate jamb  160  assist in retaining the intermediate jamb  160  in position between the sill jamb  120  and the head jamb  130 , as well as guiding the head end  164  of intermediate jamb  160  into its proper position with respect to head jamb  130  and, in one or more embodiments, may also provide additional structural rigidity to the connection between intermediate jamb  160  and head jamb  131  fully assembled into a fenestration unit frame. 
     Also depicted in  FIG. 10  are features that form one illustrative embodiment of an interlocking head connection that prevents movement of the head end  164  of the intermediate jamb  160  relative to the head jamb  130  in a direction transverse to both the head axis  131  and the intermediate jamb axis  161  (which, in  FIG. 9 , would involve movement of the head end  164  of intermediate jamb  160  into or out of the page containing  FIG. 9 ). In the depicted illustrative embodiment, those features include a head rail  136  having a head rail top  138  formed in head jamb  130  and a channel  166  formed in the head end  164  of intermediate jamb  160  that is configured to receive the head rail  136  to form the interlocking connection as described herein. 
       FIG. 11  depicts the components of  FIGS. 9-10  after assembly such that the head key  180  is attached to the head jamb  130  and head end  164  of intermediate jamb  160  is seated against the head key  180  and head jamb  130 . An additional feature depicted in broken lines because it is not visible in the view seen in  FIG. 11  is a head end cavity  168  formed in intermediate jamb  160  into which head key post  184  (also depicted in broken lines in  FIG. 11 ) is inserted as a part of the assembly process. In one or more embodiments in which the intermediate jamb  160  is formed as an extruded member, head end cavity  168  may extend along the entire length of intermediate jamb  160  between the sill end  162  and the head end  164 . This feature is not, however, required and the head end cavity  168  may be separate and distinct from a sill end cavity at the sill end  162  of the intermediate jamb  160 . 
     When assembled, the optional interlocking connection formed between head end  164  of intermediate jamb  160  and head jamb  130  involves positioning of head rail  136  and channel  166  in the head end  164  of intermediate jamb  160 . Because of this interlocking connection, the head end  164  of intermediate jamb  160  must be moved into position on head jamb  130  along intermediate jamb axis  161  during assembly of the fenestration unit frame before the ends of the jambs are assembled and connected at the corner joints. Head key post  184  and head end cavity  168  assist in both retention and proper alignment of the head end  164  of intermediate jamb  160  during that assembly process because head key post  184  is positioned in head end cavity  168  before had rail  136  is positioned in channel  166  to form the interlocking connection between the head end  164  of intermediate jamb  160  and head jamb  130 . Further, head key post  184  extends along the direction of intermediate jamb axis  161  within head end cavity  168 . 
     In one or more embodiments, the interlocking head connection formed between head jamb  130  and intermediate jamb  160  may define an interlocking head connection distance H measured along the intermediate jamb axis  161  between the head end  164  and the head rail top  138  on head rail  136  as seen in  FIG. 11 . The head key post  184  may be described as extending into the head end cavity  168  over a post-cavity distance P measured along the intermediate jamb axis  161  between the head end  164  and the head post end  186  of head key post  184 . In one or more embodiments, the post-cavity distance P is greater than the interlocking head connection distance H. 
     Another manner in which the junction between the head end  164  of intermediate jamb  160 , head key  180 , and head jamb  130  may be characterized is in the position of various features of those components. In particular, in one or more embodiments, the interlocking head connection may be described as having a terminal junction defined by the head rail top  138  of head rail  136  and the terminal end  167  of channel  166  in head end  164  of intermediate jamb  160 . That terminal junction between head rail top  138  and terminal end  167  of channel  166  may be described as being distal from the head jamb  130  along the intermediate jamb axis  161 . Further, the terminal junction between head rail top  138  and terminal end  167  of channel  166  may be described as being located between the head key base  182  and the head post end  186  along the intermediate jamb axis  161  one embodiment of this arrangement of features is seen in, e.g.,  FIG. 11 . 
     In one or more embodiments of fenestration unit frames as described herein, the head rail  136  of head jamb  130  may extend along the entire length of the head jamb  130  from its first end  132  to its second end  134 . Providing a head rail  136  that extends along the head jamb provides flexibility and location of the intermediate jamb  160  at any position along head jamb  130  as needed. Furthermore, in embodiments in which head jamb  130  is an extruded member, providing a head rail  136  that extends along the entire length of the head jamb  130  may simplify the process of manufacturing head jamb  130 . 
       FIG. 12  depicts the joint formed by the head end  164  of intermediate jamb  160  with head jamb  130 . Threaded fasteners  137  are depicted in  FIG. 12  and may optionally be used to secure the head end  164  of intermediate jamb  160  to head jamb  130  during assembly of the fenestration unit frame. 
       FIG. 13  is a perspective view of another illustrative embodiment of a fenestration unit frame including an integral mull post during assembly of the components as described herein. In particular, the fenestration unit frame includes a sill jamb  220 , head jamb  230 , left side jamb  240 , and right side jamb  250 . At the corners of the fenestration unit frame, a series of connection tools  290 ,  292 ,  294 ,  296  are positioned between the mitered ends of the jamb components to connect the ends of the jambs with each other at the corners of the fenestration unit frame. 
     In one or more embodiments, the tools  290 ,  292 ,  294 ,  296  may be in the form of heated members used to supply thermal energy to weld the ends of the jambs at the corner joints, adhesive applicators to supply adhesive to connect the ends of the jambs at the corner joints, etc. In other embodiments, tools  290 ,  292 ,  294 ,  296  may be measuring plates used in the manufacturing of custom-sized fenestration unit frames, with the measuring plates  290 ,  292 ,  294 ,  296  being replaced by tools configured to connect the ends of the jambs together at the corner joints using, e.g., thermal energy, adhesives, mechanical connectors, etc. 
     An intermediate jamb  260  is depicted as being connected within the frame between sill jamb  220  and head jamb  230 , with retention and alignment of the intermediate jamb  260  being assisted before the corner joints are fully assembled and completed by sill key  270  and head key  280 . That alignment is possible because the posts of the sill key  270  and head key  280  are partially inserted into cavities in the opposing ends of the intermediate jamb  260 . 
     In one or more embodiments, the methods of manufacturing a fenestration unit frame such as that depicted in, e.g.,  FIG. 13  may include attaching the sill key  270  to the sill jamb  230  at an intermediate location between the ends of the sill jamb  220 . The method may further include attaching the head key  280  to the head jamb  230  at an intermediate location between the ends of the head jamb  230 . The method may further include positioning the side jambs between the ends of the sill jamb and the head jamb as seen in, e.g.,  FIG. 13 . The intermediate jamb  260  may be positioned between the sill jamb  220  and the head jamb  230  and may further involve inserting a portion of a sill key post of sill key  270  into a sill end cavity in the sill end of the intermediate jamb  260  after the sill key  270  has been attached to the sill jamb  220 . Similarly, the method may further involve inserting a portion of a head key post of head key  280  into a head end cavity in the head end of the intermediate jamb  260  after the head key has been attached to the head jamb  220 . 
     With the components thus situated, the ends of the sill jamb and head jamb as well as the ends of the side jambs may be welded or otherwise connected to each other after the sill key post and head key post have been at least partially inserted into their respective end cavities in intermediate jamb  260 . 
     The assembly process may further involve optionally forming an interlocking sill connection between the sill end of the intermediate jamb  260  and the sill jamb  220  by moving the sill jamb  220  and intermediate jamb  260  toward each other along the intermediate jamb axis  261 . In addition, the assembly process may further involve forming an interlocking head connection between the head end of the intermediate jamb  260  and the head jamb  230  by moving the head jamb  230  and intermediate jamb  260  toward each other along the intermediate jamb axis  261 . 
     The complete disclosure of the patents, patent documents, and publications identified herein are incorporated by reference in their entirety as if each were individually incorporated. To the extent there is a conflict or discrepancy between this document and the disclosure in any such incorporated document, this document will control. 
     Illustrative embodiments of the fenestration unit frames with integral mull posts and methods of making the same are discussed herein some possible variations have been described. These and other variations and modifications in the invention will be apparent to those skilled in the art without departing from the scope of the invention, and it should be understood that this invention is not limited to the illustrative embodiments set forth herein. Accordingly, the invention is to be limited only by the claims provided below and equivalents thereof. It should also be understood that this invention also may be suitably practiced in the absence of any element not specifically disclosed as necessary herein.