Abstract:
A latch assembly for securing a furnace door to a furnace casing includes a latch for placement on an inside of the furnace door; a knob for placement on a front surface of the furnace door; a latch plate for placement between the latch and the knob; and a threaded screw for threadably coupling the knob to the latch. The latch plate supports the weight of the furnace door in a closed position and reduces a pinch force used for rotating the knob.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional patent application Ser. No. 61/613,615 filed Mar. 21, 2012, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     This invention relates generally to furnaces and, more particularly, to a furnace door latch assembly that is ergonomically designed. 
     DESCRIPTION OF RELATED ART 
     Furnaces often include doors to provide access to internal components. Door latches are used to secure the door to the furnace cabinet, and allow for the door to be opened. Typically, a door latch includes a two piece door knob and latch to secure the door. However, this latch requires a greater amount of turning or pinch force to rotate the knob and unlock the door. Improvements in a door latch assembly for a furnace door would be well received in the art. 
     BRIEF SUMMARY 
     According to an aspect of the invention, a latch assembly that secures a furnace door to a furnace casing includes a latch for placement on an inside of the furnace door; a knob operable for placement on a front surface of the furnace door; a latch plate for placement between the latch and the knob; and a threaded screw for threadably coupling the knob to the latch. The knob includes a knob body having a cylindrical portion and an arcuate portion that is directly opposed. Also, the latch plate supports the weight of the furnace door in a closed position and reduces a pinch force used for rotating the knob. 
     Other aspects, features, and techniques of the invention will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Referring now to the drawings wherein like elements are numbered alike in the FIGURES: 
         FIG. 1  depicts a perspective cross-sectional view of latch assemblies mounted on furnace doors according to an exemplary embodiment of the invention; 
         FIG. 2  depicts an exploded perspective view of a latch assembly according to an exemplary embodiment of the invention; 
         FIG. 3A  depicts a perspective view of a knob according to an exemplary embodiment of the invention; 
         FIG. 3B  depicts a bottom elevation view of the knob shown in  FIG. 3A  according to an exemplary embodiment of the invention; 
         FIG. 4A  depicts a perspective view of a latch plate according to an exemplary embodiment of the invention; 
         FIG. 4B  depicts a bottom elevation view of the latch plate shown in  FIG. 4A  according to an exemplary embodiment of the invention; 
         FIG. 5A  depicts a perspective view of a latch according to an exemplary embodiment of the invention; 
         FIG. 5B  depicts a front elevation view of the latch shown in  FIG. 5A  according to an exemplary embodiment of the invention; and 
         FIG. 6  depicts a perspective cross-sectional view of a latch assembly according to an exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of a latch assembly for a door of a furnace includes a latch plate coupled to a latch, a knob and a threaded screw. The latch plate is coupled to the door and is located inside the furnace. In an embodiment, the latch plate includes tabs that support the weight of the door when the latch assembly is in a latched position. Also, the latch includes a plurality of tabs that are coupled to corresponding grooves in the knob. A screw threadably couples the knob to the latch and creates a seal between the latch plate and the furnace door as it securely holds the assembled latch, latch plate and knob together. 
     Referring now to the drawings,  FIG. 1  depicts a partial perspective view of a furnace  100  including latch assemblies  102  and  104  according to an exemplary embodiment of the invention. Particularly, furnace  100  is shown with latch assemblies  102 ,  104  that may be selectively coupled to respective furnace doors  106 ,  108  for securing the furnace doors  106 ,  108 . The furnace doors  106 ,  108  provide access to compartments in furnace  100 . In one non-limiting embodiment, furnace  100  is shown with two latch assemblies  102 ,  104 , but additional latch assemblies that are substantially similar may be used without departing from the scope of the invention. In an exemplary embodiment, two furnace doors  106 ,  108  may be used, one to access the upper compartment (or burner compartment) and one to access a lower compartment (or blower compartment). The upper compartment houses a heat exchanger (not shown) while the lower compartment houses a controller and a blower (not shown). Also, latch assemblies  102 ,  104  may be selectively rotated clockwise or counter-clockwise in order to secure doors  106 ,  108  to respective furnace casings  110 ,  112 . Specifically, each latch assembly  102 ,  104  may be continuously rotated every 90 degrees (i.e., perform a complete rotation in either the clockwise or counter-clockwise direction) in order to latch or unlatch doors  106 ,  108 . In another example, the latch assemblies  102 ,  104  may be rotated by 90 degrees in either direction in order to latch or unlatch the doors  106 ,  108 . Each latch assembly  102 ,  104  includes a pair of equally spaced fingers ( FIG. 5 ) that allows the latch assemblies  102 ,  104  to stay in its rotated position after every 90 degrees of rotation until the next rotation of latch assembly  102 ,  104 . Also, latch assemblies  102 ,  104  include a latch plate (shown in  FIG. 2 ) that allows the latch assemblies  102 ,  104  to be used in multiple orientations (e.g., top of door and bottom of door) so that only one latch design is needed and doors can be moved from a top location to a bottom location by reorienting the latch assemblies  102 ,  104 . It is to be appreciated that the latch assemblies  102 ,  104  are substantially similar, and a description of latch assembly  102  described herein provides an adequate description of latch assembly  104 . 
       FIG. 2  depicts an exploded perspective view of latch assembly  102  according to an exemplary embodiment of the invention. Particularly, latch assembly  102  includes a knob  202 , latch plate  204 , latch  206  and screw  208  that may be selectively coupled to each other. In one embodiment, the knob  202 , latch plate  204 , and latch  206  may be made from a polycarbonate material, but other similar types of materials may be used in other embodiments. The knob  202  has a generally circular or “disc-shaped” body portion  210  with a generally cylindrical portion  212  at a first end and an “hour-glass” shaped arcuate portion  220  at a directly opposed second end. The cylindrical portion  212  may be slidably coupled to latch plate  204  in latch assembly  102 . Also, the arcuate portion  220  serves as a finger grip for a user to rotate knob  202  in order to latch or unlatch the latch assembly  102 , as is shown and described herein. Further, the latch plate  204  is generally rectangular in shape and includes a plurality of protrusions  216  that are diametrically opposed along a horizontal axis around the circumference of aperture  214 . The plurality of protrusions  216  may engage corresponding grooves or slots in furnace door  106  ( FIG. 1 ) to position the latch plate  204  on door  106  ( FIG. 1 ) in a vertical direction. Also, the protrusions  216  cooperate with corresponding grooves or slots in furnace door  106  and prevent the latch plate  204  from rotating when knob  202  is rotated during latching or unlatching of latch assembly  102 . Further, latch  206  has a plurality of substantially similar arcuate tabs  218  that frictionally snap or engage grooves  310  ( FIG. 3A-3B ). The arcuate tabs  218  facilitate rotation of the latch  206  when the knob  202  is rotated, as is shown and described herein. Further, a threaded screw  208  is provided to threadably couple the latch  206  to knob  202  and hold the latch assembly  102  together. The orientation of arcuate portion  220  provides a visual cue into whether the latch assembly  102  is in latched or unlatched. In a latched position, the arcuate portion  220  is rotated and oriented vertically (as is shown in  FIG. 2 ), which causes the latch  206  to be vertically oriented (i.e., the longitudinal axis of latch  206  is oriented vertically). In an unlatched position, the arcuate portion  220  is oriented horizontally, which causes the latch  206  to be similarly horizontally oriented (i.e., the longitudinal axis of latch  206  is oriented horizontally). 
       FIGS. 3A-3B  depict a view of knob  202  including the cylindrical portion  212  according to an exemplary embodiment of the invention. As shown in  FIG. 3A , knob  202  has a generally cylindrical “disc-shaped” body portion  210  with a generally arcuate portion  302  at a first end and a generally cylindrical portion  212  at a diametrically opposed second end. The cylindrical portion  212  is located transversely to the body portion  210  and includes partitions  304 , which are recessed within an interior cavity  306  of cylindrical portion  212 . The interior cavity  306  is substantially coextensive with a longitudinal length of cylindrical portion  212 . In an embodiment, as shown in  FIG. 3B , partitions  304  separate the interior cavity  306  ( FIG. 3A ) into a plurality of spaced grooves  310  that are substantially similar. As particularly shown in  FIG. 3B , four grooves  310  are provided in interior cavity  306  ( FIG. 3A ) for receiving the tabs  218  ( FIG. 2 ). The tabs  218  ( FIG. 2 ) frictionally engage the grooves  310  when knob  202  is coupled to latch  206  ( FIG. 2 ). But, in another embodiment, additional grooves that are substantially similar to groove  310  may be provided to receive additional tabs that are substantially similar to tabs  218  in latch  206  ( FIG. 2 ). Referring back to  FIG. 3A , interior cavity  306  includes a threaded portion  308  that is substantially coextensive with the cavity  306 . Also, threaded portion  308 , which includes a cavity  312 , which is threaded on an internal surface for receiving complementary threads of screw  208  ( FIG. 2 ). In an embodiment, portion  308  may be initially provided with a smooth blind cavity  312  of a sufficient diameter for receiving screw  208 . The screw  208  forms threads on an interior surface of the cavity  312  as the screw  208  is threadably inserted into the cavity  312  during initial assembly of the latch assembly  102  ( FIG. 2 ). In another embodiment, the cavity  312  may be threaded during manufacture without having the screw  308  form the threads on the interior surface of the cavity  312 . 
       FIGS. 4A-4B  depict a view of latch plate  204  according to an embodiment of the invention. As shown in  FIG. 4A , latch plate  204  has a generally rectangular shaped body  402  from first end  410  to second end  412 . Body  402  has a generally cylindrical portion  404  that extends orthogonally from a longitudinal axis of body  402 . Also, cylindrical portion  404  has a bore or opening  214  therethrough for receiving cylindrical portion  212  ( FIGS. 2-3 ) of knob  202  ( FIG. 2 ). The cylindrical portion  212  of knob  202  ( FIG. 3A ) rotates within the bore  214  when the assembled latch assembly  102  ( FIG. 1 ) is rotated during latching or unlatching. This rotation within bore  214  prevents the cylindrical portion  212  from direct contact with an edge of either furnace door  106 ,  108  and possible wear when knob  202  ( FIG. 3A ) is rotated. A plurality of spaced ribs  406  and  408  are provided at first end  410  and second end  412 , respectively. In one non-limiting example, the latch plate  204  may be installed in door  106  ( FIG. 1 ) with end  410  positioned above end  412  with the door  106  ( FIG. 1 ) in a closed position. In this configuration, the ribs  408  rest on an edge of casing  110  or  112  ( FIG. 1 ) and support the weight of the furnace door  106  ( FIG. 1 ). This reduces the turning or pinching force needed to rotate knob  202  clockwise or counter-clockwise during latching or unlatching latch assembly  102 . In another embodiment, the latch plate  204  may be installed with end  412  positioned above end  410  without departing from the scope of the invention. 
     In an embodiment, as shown in  FIG. 4B , latch plate  204  has a plurality of semi-spherical protrusions  422 ,  424  that are equally spaced around the circumference of cylindrical portion  404 . In the example shown, the protrusions  422  are vertically oriented around the circumference of aperture  214  while protrusions  424  are horizontally oriented around the circumference of bore or aperture  214 . The protrusions  422 ,  424  engage or abut tabs  510  ( FIG. 5A ) for every 90 degrees of rotation of latch  206  ( FIG. 2 ) as is shown and described in reference to  FIG. 5A . Also, aperture  214  is offset from first end  410  and second end  412  in order to accommodate varying tolerances during manufacturing (i.e., aperture  214  is offset from a center point of the body  402 ). Particularly, the center of aperture  214  is at a height  414  from end  410  and at a height  416  from end  412 . Height  414  varies from height  416  and may be adjusted accordingly to accommodate varying manufacturing tolerances. 
       FIGS. 5A-5B  depict a view of latch  206  including a pair of spaced tabs  218  according to an exemplary embodiment of the invention. As shown in  FIG. 5A , latch  206  has a generally oval shaped body  502  and includes a first latch portion  504  and a diametrically opposed second latch portion  506 . In one non-limiting example with reference to door  106 , when the latch  206  is in a first orientation (i.e., latch portions  504 ,  506  aligned horizontally), door  106  ( FIG. 1 ) can be mounted against casing  110  ( FIG. 1 ) as latch body  502  and latch portions  504 ,  506  clear the opening in casing  110  ( FIG. 1 ) and allow door  106  to be opened in this orientation (i.e., latch assembly  102  is unlatched). In another example, when the latch  206  is in a second orientation (i.e., latch portions  504 ,  506  are aligned vertically), door  106  can be mounted against casing  110  ( FIG. 1 ) and latch portions  504 ,  506  engage the inside surface of casing  100  ( FIG. 1 ), and prevents the latch  206  from clearing an edge of the casing, thereby latching the door  106  to the casing  110  ( FIG. 1 ). 
     Also, body  502  has a generally cylindrical portion  508  that is orthogonal to the longitudinal axis of the body  502 . The cylindrical portion  508  has a pair of spaced tabs  510  that are diametrically opposed to each other around a circumference of portion  508 . Additionally, cylindrical portion  508  includes a plurality of arcuate tabs  218 , which are substantially similar, within an interior of the portion  508 . The tabs  218  are received in grooves  310  ( FIG. 3B ) and cause a rotation in latch  206  as knob  202  ( FIG. 2 ) is rotated. Also, as shown in  FIG. 5B , latch  206  includes an aperture  512  that traverses body  502 . The aperture  508  has a diameter that is slightly larger than a width of the body of screw  208  but smaller than the head of screw  208 . 
     In operation and with reference to  FIG. 6 , latch plate  204  may be coupled to an inside surface of door  106  by aligning aperture  214  ( FIG. 2 ) with a complementary sized opening in door  106  so that protrusions  216  ( FIG. 2 ) of latch plate  204  are received within complementary shaped grooves in door  106 . Cylindrical portion  212  is mounted to door  106  and is coupled to latch plate  206  by passing cylindrical portion  212  from the outside of door  106  through the aperture  214  ( FIG. 2 ). Also, knob  202  is coupled to latch  206  and receives the arcuate tabs  218  that engage grooves  310  within portion  212 . The screw  208  holds the assembly together and creates an airtight seal between the latch plate  204  and the inside surface of furnace door  106 . Also, ribs  408  ( FIG. 4A ) ride (or rest) on an edge of casing  112  to support the weight of furnace door  106  and position the door  106  ( FIG. 1 ) in a vertical direction, thereby reducing the turning or pinching force needed to rotate knob  202  clockwise or counter-clockwise during latching or unlatching latch assembly  102 . As shown, when the latch  206  is in a first orientation (i.e., latch portions  504 ,  506  are aligned vertically), door  106  can be mounted against casing  112  (and latch portions  504 ,  506  engage the inside surface of casing  112  to latch the door  106  to the casing  112  and prevent the door  106  from being opened in this orientation. In another non-limiting example, the knob  202  may be rotated 90 degrees clockwise or counter-clockwise until tabs  510  ( FIG. 5A ) engages protrusions  424  ( FIG. 4B ) causing the latch portions  504 ,  506  to correspondingly rotate 90 degrees. In this orientation, latch portions  504 ,  506  clear the opening in casing  112  allowing door  106  to be opened (i.e., latch assembly  102  is unlatched). 
     The technical effects and benefits of embodiments relate to a latch assembly for a door of a furnace. The latch assembly includes a latch plate coupled to a latch, a knob and a threaded screw. The latch plate is coupled to the door and is located inside the furnace. The latch plate includes tabs that support the weight of the door when the latch assembly is in a latched position. Also, the latch includes a plurality of tabs that are coupled to corresponding grooves in the knob. A screw threadably couples the knob to the latch and creates a seal between the latch plate and the furnace door as it securely holds the assembled latch, latch plate and knob together. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. While the description of the present invention has been presented for purposes of illustration and description, it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications, variations, alterations, substitutions, or equivalent arrangement not hereto described will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. Additionally, while the various embodiments of the invention have been described, it is to be understood that the aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.