Patent Publication Number: US-2019178025-A1

Title: Corner key for extruded windows and doors

Description:
INTRODUCTION 
     Window and door frames may be held together at a corner joint by an “L”-shaped piece of hardware known as a corner key. Corner keys enable two side members of the frame to be secured together without the hardware being visible. These corner keys are press fit into the frame members to induce a retention force therein and restrict the corner key from being pulled out, which can cause the frame members to separate. However, some known corner keys do not provide a consistent retention force to restrain movement of the frame members. Additionally, some known corner keys create a gap between two frame members because the corner keys become skewed within the frame members. 
     SUMMARY 
     In one aspect, the technology relates to a corner key including: a heel; and at least one leg extending along an axis from the heel, the at least one leg including a retention element and a lifting cam, wherein upon insertion into a frame member the lifting cam induces a bending stress in the retention element. 
     In an example, the at least one leg further includes a first surface and a second surface, and wherein the retention element is disposed on the first surface and the lifting cam is disposed on the second surface. In another example, the first surface is opposite the second surface. In yet another example, the retention element includes a cantilevered arm defined in the at least one leg and extending towards the heel along the axis. In still another example, the cantilevered arm includes a free end, and wherein the cantilevered arm tapers towards the free end. In an example, the cantilevered arm includes a free end and a barb disposed on the free end. 
     In another example, the bending stress is configured to apply a retention force from the barb to the frame member. In yet another example, the retention element and the lifting cam are offset along the axis. In still another example, the at least one leg further includes a tip, the tip including a tapered nose. In an example, the tapered nose is substantially conically-shaped. In another example, the at least one leg is a first leg and the corner key further includes a second leg extending along a second axis from the heel, the second leg including a second retention element and a second lifting cam, wherein upon insertion into a second frame member the second lifting cam induces a second bending stress in the second retention element. 
     In yet another example, the first leg and the second leg are spaced approximately 90° apart. In still another example, the corner key further includes an inner surface and an opposite outer surface, and wherein an undercut corner is defined in the inner surface at the intersection of the first leg and the second leg. In an example, the heel includes a corner extension opposite the undercut corner. In another example, the first leg is axially longer than the second leg. In yet another example, the bending stresses are configured to apply at least 35 pounds of retention force from the corner key to the first and second frame members. In still another example, the bending stresses are configured to apply at least 50 pounds of retention force from the corner key to the first and second frame members. 
     In another example, the technology relates to a corner key including: a heel; a first leg extending along a first axis from the heel, wherein the first leg includes a first inner surface defining a first tapered cantilevered arm and an opposite first outer surface defining a first lifting cam; and a second leg extending along a second axis from the heel, wherein the second leg includes a second inner surface defining a second tapered cantilevered arm and an opposite second outer surface defining a second lifting cam. 
     In another example, the technology relates to a method of installing a corner key into a frame member, the method including: aligning a leg of the corner key with a channel of the frame member via a tapered nose of the leg; sliding the leg into the channel such that a retention element defined in the leg is fully received within the channel; and after receipt of the retention element within the channel, actuating the retention element via a lifting cam such that a bending stress is induced in the retention element to secure the leg to the frame member. In an example, the frame member is a first frame member and the leg is a first leg, and the method further includes: over-inserting the first leg into the first channel such that a portion of the first frame member is received in an undercut corner; and sliding a second frame member onto a second leg of the corner key, wherein the second frame member engages a corner extension of the corner key to induce a tension load on the retention element and align the corner key within the first and second frame members. 
    
    
     
       DRAWINGS 
       There are shown in the drawings, embodiments which are presently preferred, it being understood, however, that the technology is not limited to the precise arrangements and instrumentalities shown. 
         FIG. 1  is a perspective view of a prior art corner key. 
         FIGS. 2A and 2B  are perspective views of an example of a corner key. 
         FIGS. 3A-3C  is a series of cross-sectional perspective views of the corner key shown in  FIGS. 2A and 2B  being inserted into a frame member. 
         FIG. 3D  is an enlarged cross-sectional side view of the corner key shown in  FIGS. 2A and 2B  inserted into the frame member. 
         FIG. 4A  is a perspective view of another example of a corner key. 
         FIG. 4B  is a side view of the corner key shown in  FIG. 4A . 
         FIG. 4C  is a stress distribution diagram of the corner key shown in  FIG. 4A . 
         FIG. 4D  is a deformation diagram of a frame member. 
         FIG. 5  is a side view of another example of a corner key. 
         FIG. 6  is a perspective view of another example of a corner key. 
         FIG. 7  is a perspective view of another example of a corner key. 
         FIG. 8  is a perspective view of another example of a corner key. 
         FIG. 9  is a perspective view of another example of a corner key. 
         FIG. 10  is a flowchart illustrating a method of installing a corner key into a frame member. 
         FIG. 11A  is a perspective view of another example of a corner key. 
         FIG. 11B  is a side view of the corner key shown in  FIG. 11A . 
         FIGS. 11C and 11D  are stress distribution diagrams of the corner key shown in  FIGS. 11A and 11B . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a perspective view of a prior art corner key  10 . The corner key  10  is a die cast “L”-shape with a short leg  12  and a long leg  14  connected at a heel  16 . Each leg  12 ,  14  defines a slot  18 ,  20 , respectively, that receives a steel tab  22  which is inserted therein. The steel tabs  22  are angled so as to act as retention devices when installed at a corner joint of a window or door frame. As the slots  18 ,  20  are relatively thin, the die cast molds used for manufacturing the corner key  10  are fragile and are known to break. The manufacturing process for the corner key  10  requires the separate steel tabs  22  to be inserted either manually, which is a laborious and time consuming process, or automatically, requiring a machine that must be frequently maintained. Additionally, the steel tabs  22  may undesirably shift out of position or fall out prior to use of the corner key. As such, the corner key  10  provides inconsistent retention forces at the corner assembly with push-in forces (e.g., the force required for corner assembly) ranging from  17  pounds to  70  pounds and pull-out forces (e.g., the force required to pull the corner assembly apart) ranging from 27 pounds to 75 pounds. 
     Broadly speaking, this disclosure describes configurations that improve the performance of a corner key. Specifically, examples, configurations, and arrangements of a corner key are shown and described in more detail below with reference to the following figures. The corner keys for extruded windows and doors described herein increases efficiency of installing the corner key as well as manufacturing the corner key. The corner key includes a retention element that is automatically actuated after insertion into the frame member, thereby reducing wear to the edge of the frame member. Additionally, the retention element uniformly distributes the bending stress along the length of an arm, inducing consistent retention forces on the frame member to provide a more secure connection. A heel of the corner key facilitates pre-loading tension into the corner key and aligning the corner key within the frame members thereby forming a more snug connection and reducing undesirable pull-out. Furthermore, the corner keys may be manufactured by a die-cast method that is automated thereby reducing manufacturing costs. 
       FIGS. 2A and 2B  are perspective views of an example of a corner key  100  and are described concurrently. In the example, the corner key  100  includes an “L”-shaped body  102  that may be formed from a one-piece zinc die casting method, such that the body  102  is unitary. The body  102  includes a first leg  104  spaced approximately 90° from a second leg  106  and intersecting at a heel  107 . The body  102  also includes an inner surface  108  and an opposite outer surface  110 . As described herein, inner and outer refer to the orientation of the corner key  100  when being assembled in a frame of a window or door. 
     The first leg  104  extends along a longitudinal axis Li and includes a tip  112  defining a tapered nose  114 . The tapered nose  114  increases ease of assembly and enables the leg  104  to be received more easily within the frame member. The leg  104  includes a retention element formed from an arm  116  extending along the longitudinal axis Li opposite the nose  114 . The arm  116  is cantilevered from the tip  112  and extends over a recess  118  defined in the body  102 . The arm  116  is resilient and flexible with a tapered profile such that bending stresses are uniformly distrusted along the length of the cantilever as described further below. Because the arm  116  is tapered, a free end  120  may deflect more than other sections of arm  116 . At the free end  120  of the arm  116 , a barb  122  extends outward from the inner surface  108 . In the example, the barb  122  has a steep inclined surface  124  adjacent the free end  120  and an opposite shallow inclined surface  126 . The shallow inclined surface  126  enables the arm  116  to be slidably received within the frame member, while the steep inclined surface  124  provides for an engagement surface when the barb  122  engages with the frame member to secure the corner key  100  within the frame member. The leg  104  also includes a lifting cam  128  defined on the outer surface  110 . The lifting cam  128  is offset along the longitudinal axis L 1  from the arm  116  and includes an oblique surface  130  such that a depth  132  of the leg  104  at the oblique surface  130  is less than a depth  134  of the tip  112  of the leg  104 . The lifting cam  128  is discussed further below. 
     The second leg  106  extends along a longitudinal axis L 2  and includes a tip  136  defining a tapered nose  138 . The tapered nose  138  increases ease of assembly and enables the leg  106  to be received more easily within the frame member. The leg  106  includes a retention element formed from an arm  140  extending along the longitudinal axis L 2  opposite the nose  138 . The arm  140  is cantilevered from the tip  136  and extends over a recess  142  defined in the body  102 . The arm  140  is resilient and flexible with a tapered profile such that bending stresses are uniformly distrusted along the length of the cantilever as described further below. Because the arm  140  is tapered, a free end  144  may deflect more than other sections of arm  140 . At the free end  144  of the arm  140 , a barb  146  extends outward from the inner surface  108  with two inclined surfaces as described above. The leg  106  also includes a lifting cam  148  defined on the outer surface  110 . The lifting cam  148  is offset along the longitudinal axis L 2  from the arm  140  and includes an oblique surface  150  such that a depth  152  of the leg  106  at the oblique surface  150  is less than a depth  154  of the tip  136  of the leg  106 . 
     In the example, the first leg  104  is longer than the second leg  106  such that additional window or door hardware may be located within the frame member. In alternative examples, the first leg  104  length may be approximately equal to the second leg  106  length. 
     At the intersection of the first leg  104  and the second leg  106 , the heel  107  is defined and includes an undercut corner  156  defined in the inner surface  108 . The undercut corner  156  reduces the depth of the heel  107  to enable an over-insertion of the corner key  100  within the frame member. At the outer surface  110  of the heel  107 , a corner extension  158  is defined. The corner extension  158  increases the depth of the heel  107  along both the first and second legs  104 ,  106  to align the corner key  100  within the frame member to correct the over-insertion provided by the undercut corner  156  and to induce a tension force within the corner key  100  as described further below. 
       FIGS. 3A-3C  is a series of cross-sectional perspective views of the corner key  100  being inserted into a frame member  200 . Starting with  FIG. 3A , the first leg  104  of the corner key  100  is partially inserted into a channel  202  of a frame member  200 . The channel  202  includes an inner surface  204  and an outer surface  206 . The tapered nose  114  facilitates aligning the first leg  104  within the channel  202  so that it may be slidably received therein. The inner surface  108  of the corner key  100  slides against the inner surface  204  of the channel  202  and the outer surface  110  of the corner key  100  slides against the outer surface  206  of the channel  202 . In the example, the frame member  200  is illustrated in cross-section and can be either part of a window frame or a door frame with a 45° edge  208 . The corner key  100  is configured to couple the frame member  200  to another frame member (not shown) so as to secure the two frame members together without the corner key  100  being visible. 
     Referring now to  FIG. 3B , the leg  104  of the corner key  100  is further inserted into the channel  202  such that the outer surface  206  of the channel  202  begins to engage the lifting cam  128 . The barb  122  and the oblique surface  130  are spaced such that the barb  122  clears the edge  208  of the frame member  200  before the outer surface  206  engages with the lifting cam  128 . Before the lifting cam  128  is engaged, the arm  116  and the barb  122  are slidably inserted into the channel  202  and there are no bending stresses induced on the arm  116  because the depth of the leg  104  progressively decreases from the tip  112  to the oblique surface  130  as described above. This reduces wear on the edge  208 , reduces excessive abrasion to the barb  122 , and also reduces the amount of insertion force necessary to initially slide the leg  104  within the channel  202 . Once the barb  122  clears the edge  208  and the outer surface  206  of the channel  202  engages the oblique surface  130 , bending stresses are induced on the arm  116  by the lifting of the leg  104  relative to the inner surface  204  of the channel  202 . More specifically, the arm  116  is depressed into the recess  118  as the outer surface  206  of the channel  202  passes along the oblique surface  130  and lifts the leg  104  within the channel  202 . The bending stress causes the barb  122  to engage with the inner surface  204  with a retention force to secure the corner key  100  within the channel  202 . 
     Turning now to  FIG. 3C , the leg  104  of the corner key  100  is fully inserted into the channel  202 . Once the leg  104  is within the channel  202 , the barb  122  is engaged with the inner surface of the channel  202  with the retention force to secure the corner key  100  to the frame member  200 . The undercut corner  156  enables the leg  104  to be over-inserted into the channel  202  and apply a preloaded tension force on the corner key  100  as described further below. 
       FIG. 3D  is an enlarged cross-sectional side view of the corner key  100  inserted into the frame member  200 . The corner key  100  is over-inserted into the channel  202  of the frame member  200  such that the edge  208  extends into the undercut corner  156  and to the second leg  106 . Additionally, the corner extension  158  of the heel  107  is at least partially received within the channel  202 . When a second frame member (not shown) is inserted on to the second leg  106 , the oblique surface  150  lifts the leg  106  relative to the channel of the second frame member to engage the barb  146 . This lifting of the second leg  106  also generates a pullback force  210  on the first leg  104  so as to place the barb engagement in tension. This pullback force  210  also reduces the over insertion of the leg  104  such that the edge  208  retracts from the undercut corner  156 . Additionally, the pullback force  210  moves the corner extension  158  out of the over-insertion within the channel  202  and aligns the heel  107  within each frame member channel and match the edges of the frame members together for a sung clean fit without any gaps therebetween. 
       FIG. 4A  is a perspective view of another example of a corner key  300 .  FIG. 4B  is a side view of the corner key  300 . Referring concurrently to  FIGS. 4A and 4B , the corner key  300  includes a first leg  302  having a tapered nose  304 , a barb  306  extending from a resilient flexible arm  308 , and a lifting cam  310 , and a second leg  312  having a tapered nose  314 , a barb  316  extending from a resilient flexible arm  318 , and a lifting cam  320  as described in the example above. Additionally, the corner key  300  includes an undercut corner  322  and a corner extension  324  positioned at a heel  326  as describe in the example above. However, in this example, the length L of the first leg  302  is approximately equal to the second leg  312 . 
       FIG. 4C  is a stress distribution diagram of the corner key  300 . When a load  328  is applied to the barb  316 , for example, when the leg  302  is inserted into the frame member (not shown) and the arm  308  is depressed into a recess  331 , the bending stresses  330  induced on the arm  308  are uniformly distributed along the length  332  of the arm  308 . The tapered shape of the arm  308  facilitates that the bending stresses  330  occur along the inner surface  334  of the arm  308  and be approximately consistent along the length  332 , even through the free end of the arm  308  deflects more than a middle or end section of the arm  308 . This stress distribution on the arm  308  reduces fatigue of the corner key  300  and generates a uniform resultant force (e.g., the retaining force) so as to maintain engagement of the barb  316  within the frame member. Additionally, the bending stresses  330  induced on the arm  308  are not transferred to the rest of the corner key  300 . In this example, the corner key  300  provides approximately 35 pounds of retaining force (the force required to pull the corner assembly apart). 
       FIG. 4D  is a deformation diagram of a frame member  336 . As described above, the bending stresses induced in the arm  308  results in the barb  316  engaging with the frame member  336  with a retaining force  338 . The size and shape of the barb  316 , and the force  338  upon which it acts, results in the deformation of the frame member  336  about an engagement area  340 . In the example, the engagement area  340  has a deformation that is relatively constant throughout the area thereby providing for a more secure engagement of the corner key  300 . 
       FIG. 5  is a side view of another example of a corner key  400 . The corner key  400  includes a first leg  402  having a tapered nose  404 , a barb  406  extending from a resilient flexible arm  408 , and a lifting cam  410 , and a second leg  412  having a tapered nose  414 , a barb  416  extending from a resilient flexible arm  418 , and a lifting cam  420  as described in the examples above. Additionally, the corner key  400  includes an undercut corner  422  and a corner extension  424  positioned at a heel  426  as described in the examples above. However, in this example, the length L of the cantilevered arms  408 ,  418  are shorter than the previous examples to increase the retaining force of the corner key  400  with respect to the frame member. By shortening the arms  408 ,  418  the same amount of deflection that occurs from inserting the corner key  400  into the window frame induces a greater amount of bending stresses therein and an increased retaining force that engage the barbs  406 ,  416  with the window frame. For example, the corner key  400  provides approximately 50 pounds of retaining force. In alternative examples, each cantilevered arm  408 ,  418  may have different lengths so as to vary the retaining force for each leg as required or desired. 
       FIG. 6  is a perspective view of another example of a corner key  500 . The corner key  500  includes a first leg  502  having a tapered nose  504 , a barb  506  extending from a resilient flexible arm  508 , and a lifting cam  510 , and a second leg  512  having a tapered nose  514 , a barb  516  extending from a resilient flexible arm  518 , and a lifting cam  520  as described in the examples above. Additionally, the corner key  500  includes an undercut corner  522  and a corner extension  524  positioned at a heel  526  as described in the examples above. However, in this example, the tapered nose  504 ,  514  is more elongated and having a substantially conically-shaped nose than the previous examples. As such, any misalignment of either leg  502 ,  512  when inserting into the frame member is easier to correct and enables easier window and door frame assembly. 
       FIG. 7  is a perspective view of another example of a corner key  600 . The corner key  600  includes a first leg  602  having a tapered nose  604 , a resilient flexible arm  606 , and a lifting cam  608 , and a second leg  610  having a tapered nose  612 , a resilient flexible arm  614 , and a lifting cam  616  as described in the examples above. Additionally, the corner key  600  includes a corner extension  618  positioned at a heel  620  as describe in the examples above. However, in this example, the arms  606 ,  614  include a raised corner  622 ,  624  instead of a barb as in the previous examples. The raised corners  622 ,  624  facilitate engaging the frame member as described above. By using the raised corners  622 ,  624  instead of the barbs, the corner key  600  may be manufactured by a stamping process. 
       FIG. 8  is a perspective view of another example of a corner key  700 . The corner key  700  includes a first leg  702  having a tapered nose  704 , and a second leg  706  having a tapered nose  708  as discussed above. Additionally, the corner key  700  includes an undercut corner  710  positioned at a heel  712  as described in the examples above. However, in this example, each leg  704 ,  706  defines an opening  714  that is configured to receive an omega-shaped spring clips  716 . Each end of the clip  716  extends partially from the legs  704 ,  706  so as to engage the sides of the frame member channel and secure the corner key  700  therein. In the example, the legs  704 ,  706  are zinc die cast and the clips  716  are carbon steel. 
       FIG. 9  is a perspective view of another example of a corner key  800 . The corner key  800  includes a first leg  802  having a tapered nose  804 , an opening  806 , and an omega-shaped spring clip  808 , and a second leg  810  having a tapered nose  812 , an opening  814 , and an omega-shaped spring clip  816  as described above in  FIG. 8 . Additionally, the corner key  800  includes an undercut corner  818  positioned at a heel  820  as describe in the examples above. However, in this example, the length L of the first leg  802  is shorter than the previous example in  FIG. 8  to accommodate hardware within the frame member. 
       FIG. 10  is a flowchart illustrating a method  900  of installing a corner key into a frame member. The method  900  includes aligning a leg of the corner key with a channel of the frame member via a tapered nose of the leg (operation  902 ), sliding the leg into the channel such that a retention element defined in the leg is fully received within the channel (operation  904 ), and after receipt of the retention element within the channel, actuating the retention element via a lifting cam such that a bending stress is induced in the retention element to secure the leg to the frame member (operation  906 ). In some examples, the frame member is a first frame member and the leg is a first leg and the method  900  further includes over-inserting the first leg into the first channel such that a portion of the first frame member is received in an undercut corner (operation  908 ), and sliding a second frame member onto a second leg of the corner key, wherein the second frame member engages a corner extension of the corner key to include a tension load on the retention element and align the corner key within the first and second frame members (operation  910 ). 
       FIG. 11A  is a perspective view of another example of a corner key  1000 .  FIG. 11B  is a side view of the corner key  1000 . Referring concurrently to  FIGS. 11A and 11B , the corner key  1000  includes a first leg  1002  having a substantially conically-shaped nose  1004 , a barb  1006  extending from a resilient flexible arm  1008 , and a lifting cam  1010 , and a second leg  1012  having a substantially conically-shaped nose  1014 , a barb  1016  extending from a resilient flexible arm  1018 , and a lifting cam  1020  as described in the examples above. Additionally, the corner key  1000  includes an undercut corner  1022  and a corner extension  1024  positioned at a heel  1026  as described in the examples above. However, in this example, each recess  1028 ,  1030  defined within each leg  1002 ,  1012  is larger than the previous examples and has a curved surface  1032 ,  1034 . In this example, a depth D of the recess  1028 ,  1030  extends further within each leg  1002 ,  1012  such that a thickness T of the legs  1002 ,  1012  are reduced. 
       FIGS. 11C and 11D  are stress distribution diagrams of the corner key  1000 . As described above, when a load  1036  is applied to the barb  1006 , the bending stresses  1038  induced on the arm  1008  are distributed along the length of the arm  1008 . Additionally, the reduced thickness of the leg  1002  enables the bending stresses  1038  induced on the arm  1008  to be transferred  1040  to an outer surface  1042  of the arm  1008  so as to deflect the nose  1004  and to increase the overall deflection of the barb  1006 . By increasing overall deflection of the barb  1006  the retaining force of the corner key  1000  may also be increased. The bending stresses  1040  are positioned adjacent the nose  1004  and opposite the arm  1008 . This configuration enables the corner key  1000  to be used for a wide range of frame member sizes and thicknesses without having to extend the length of the leg  1002 . 
     The materials utilized in the corner keys described herein may be those typically utilized for window, window component manufacture, door, and door component manufacture. 
     Material selection for the components may be based on the proposed use of the window or door. For example, the corner keys may be die-cast zinc. Aluminum, steel, stainless steel, plastic or composite materials can also be utilized. The window and door frame members may be extruded plastic, vinyl, or aluminum and contain other hardware therein. 
     While there have been described herein what are to be considered exemplary and preferred embodiments of the present technology, other modifications of the technology will become apparent to those skilled in the art from the teachings herein. The particular methods of manufacture and geometries disclosed herein are exemplary in nature and are not to be considered limiting. It is therefore desired to be secured in the appended claims all such modifications as fall within the spirit and scope of the technology. Accordingly, what is desired to be secured by Letters Patent is the technology as defined and differentiated in the following claims, and all equivalents.