Metal door with continuous frame and method

A metal door has a unitary rectangular frame of generally uniform cross section providing stiles and rails, and a pair of substantially rectangular panels which are secured to the frame. The panels have opposed flanges overlying and engaged with the adjacent side margins of the stiles of the frame to secure the panels thereto. The door is fabricated by forming an elongate metal strip into a frame element of generally uniform cross section with channels between a generally planar central portion and inwardly offset marginal portions. A predetermined length of the strip is bent to form a substantially rectangular frame, the ends of which are fastened together. The panels have lips on their flanges and are assembled to the frame with the flanges inserted into the channels and the lips frictionally engaging the side walls thereof.

BACKGROUND OF THE INVENTION 
The present invention pertains to doors and, more particularly, to doors 
comprising a pair of opposed metal panels affixed to a peripheral frame, 
and to a method for making such doors. 
Metal entry and fire doors with insulating cores have enjoyed substantial 
popularity due to their strength and to their temperature and sound 
insulating qualities and, when utilized with metal wall frames, due to 
their fire resistance. One drawback to such doors, however, is that the 
process of producing them is generally comparatively labor intensive and 
involves multiple steps. In addition to the direct costs of the labor 
involved, the manufacturing process can result in variability in the 
dimensions of the product and in poor joints. This results in waste, scrap 
and rejected units, all of which further increase the cost of the 
marketable units. 
It is a primary object of the present invention to provide novel metal 
entry and fire doors which are strong, durable and economical to produce. 
A further object is to provide such doors which may be accurately produced 
to minimize rejects and to provide ease of installation. 
Another object of the invention is to provide a novel method for making 
such entry and fire doors with increased efficiency and economy in a 
manner suitable for commercial mass production. 
SUMMARY OF THE INVENTION 
It has now been found that the foregoing and related objects may be readily 
attained in a metal door comprising a substantially rectangular frame with 
stiles and rails, and a pair of substantially rectangular panels engaged 
with the frame. The frame is provided by a continuous, unitary metallic 
member of generally uniform cross section, and the panels have opposed 
flanges extending along the sides thereof which overlie and engage with 
the adjacent side margins of the stiles of the frame to secure the panels 
thereto. 
Generally, the door includes an insulating core of cellular synthetic resin 
substantially filling the space between the panels and the frame. 
The cross section of the metallic frame member has a generally planar 
central portion and marginal portions extending along the sides thereof. 
The marginal portions are inwardly offset from the plane of the central 
portion, and the flanges of the panels extending thereover. Desirably, 
channels are provided between the marginal portions and the central 
portion, and the flanges of the panels have inturned lips extending 
thereinto. Preferably, the width of the channels is greater than twice the 
thickness of the panels, and the lips have reversely extending angularly 
oriented segments along their free edges which functionally engage the 
side walls of the channels. 
In the preferred embodiment, the cross section of the frame member includes 
inwardly directed tail portions which extend from the outer sides of the 
marginal portions and extend in spaced relationship along the inner 
surface of the panels. The tail portions include distal segments inclined 
at an angle to the plane of the panels of not more than about 30.degree.. 
The cellular synthetic resin of the core extends between the body of the 
tail portions and their distal segments and the metal panels to secure the 
panels to the frame and provide insulation therebetween. 
The frame member has overlapping end portions which are engaged, and these 
are conveniently disposed along the bottom rail. The top and bottom of the 
panels also have opposed flanges overlying the rails of the frame. 
In the method of fabricating the metal door, an elongate metal strip is 
provided with a contoured and generally uniform cross section and the 
strip is bent to form a substantially rectangular frame with stiles and 
rails with overlapping ends being fastened. A pair of substantially 
rectangular panels have flanges extending along the side edges thereof and 
are assembled onto the frame with the flanges overlying and engaged with 
the adjacent side margins of the stiles to secure the panels to the frame. 
Preferably, the frame is squared with the panels snapped thereon and edge 
portions of the panels are bent over the frame to lock the assembled door 
in the squared condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning first to FIG. 1, a door embodying the present invention has a 
unitary rectangular frame 2 with a pair of substantially rectangular 
panels 5 secured thereto and a core 3 of cellular synthetic resin filling 
the cavity. 
As best seen in FIG. 8, the frame 2 is a continuous unitary metallic member 
of generally uniform cross section which includes a pair of parallel 
stiles 4 and upper and lower rails 6. Preferably, the ends of the frame 2 
are joined in the middle of lower rail 6 as seen in FIGS. 15-17. 
As best seen in FIGS. 4-7, the frame cross section includes a planar 
central portion 31, a pair of flanking marginal portions 33 which are 
inwardly offset from the plane of central portion 31, and a pair of 
channels 35 between the marginal portions 33 and central portion 31. The 
marginal portions 33 have inwardly directed flanges or tail portions 37 
along their outer edges and distal segments 34 on the ends of the tail 
portions 37 extend inwardly at an angle of about 17.5.degree. to the body 
of the tail portion. It is to be noted that the frame member cross section 
is generally symmetrical along its length. As illustrated in the drawings, 
various recesses and openings are provided at appropriate locations on the 
stiles 4 for the attachment of hinges (not shown) and a lockset and/or 
dead bolt (not shown). As seen in FIGS. 5, 10, 11, 16 and 17, the metal of 
the strip may be punched to provide dimples which will seat the fasteners 
(not shown) for securing the hinges and locksets. FIGS. 12-14 show the 
lockset area with an embossed recess 20. An opening may also be formed in 
a rail 6 for the insertion of a foamable resin to provide the core 3 
hereinafter described. All of these recesses and openings are in central 
portion 31 of the frame element. 
As best seen in FIG. 19, the metallic panel 5 is generally planar and 
rectangular, and it may have an embossed face 8 as seen therein. As seen 
in FIGS. 4 and 5, the edges of the longer sides of the panel 5, i.e., the 
sides which will be vertical when the door is installed, have flanges 10 
extending at a right angle to the plane of the face 8 of the panel 5 and 
these seat in the channels 35 of the stiles 4. As also seen, the ends of 
the flanges 10 have reversely and inwardly bent segments 12 which deflect 
when the flanges 10 are inserted into the channels 35. This produces a 
snap fit and frictional engagement with the sidewalls of the channels 35 
to secure the panels 5 on the frame 2. The edges of the shorter side of 
panels 5, i.e., the sides which will be horizontal when the door is 
installed also have flanges 16 which extend at a right angle to the face 
and these seat on the surface of the marginal portions 33 of the upper and 
lower rails 6 of the frame 2 and serve both to prevent the panels 5 from 
sliding vertically on the frame 2 and to prevent deformation of the door 
from its desired rectangular configuration. 
Backing blocks 7 of wood or plastic may be placed within the door frame 2 
to support a lockset (not shown) and to provide backing for the attachment 
of hinges or other items such as emergency closures and handles (not 
shown) in a conventional manner. The remainder of the space bounded by the 
frame 2 and panels 5 is filled with a cellular synthetic resin core 3. If 
the core 3 is provided by introducing beads or pellets which are expanded 
or in place by heat, the expanding material of the core 3 extends between 
and engages the tail portions 27 and the inwardly projecting distal 
segments 12 of the frame 2, further serving to strengthen and rigidify 
door 1 as well as to provide insulation therebetween. The 17.5.degree. 
inward inclination of the distal segments 37 has been found to maximize 
this engagement. 
As diagrammatically illustrated in FIG. 22, the frame 3 of the door may be 
formed in a single piece from a coil of metal strip of suitable thickness 
and width. The strip is first prenotched and prepunched and then roll 
formed into the desired cross section. The roll formed strip is next 
embossed with the desired recesses and notched, and finally cut into 
desired lengths. These lengths are bent at the notches which are located 
at the corners to form the desired rectangular shape. 
The ends of the frame element are then fastened together to complete the 
frame 2. As seen in FIGS. 15-17, the ends 18 of the length of strip 
providing the frame 2 may overlap and be secured by clenching or staking 
(not shown) or by any other suitable means such as the insertion of a 
tongue into a slot, welding, rivets, etc. 
To assure optimum engagement between the frame 2 and the panels 5, the 
width of channels 35 is greater than twice the thickness of the panels 5 
so that the angularly oriented segments 12 snap fit therein and be 
retained therein. 
This assembly of the panels 5 to the frame 2 begins with the positioning of 
a first panel 5 on an assembly table with the flanges 10, and top flange 
16 extending upwardly. The frame 2 is placed atop the prepositioned panel 
5 and pressed downwardly, causing the channel flanges 10 to enter into the 
channels 35 and deflect the segments 12 which the snap fit and 
frictionally engage the channel walls. The top and bottom edges have 
perpendicular flanges 33 which snugly fit over the rails 6. 
A second panel 5 is now placed on the frame 2 and pressed downwardly into 
engagement therewith in the same fashion. In one embodiment, the bottom 
portions of both panels 5 may be bent to provide the bottom flanges 16 
which extend over the surface of the bottom rail 6 to lock the assembly in 
a squared condition. 
Lastly, the cellular synthetic resin core 3 may be provided in a 
conventional manner by introducing, through an opening in the frame, a 
foamable fluid synthetic resin into the cavity and foaming it in place or 
by inserting prefoamed plastic beads into the door interior through an 
opening previously formed in the frame 3 and applying heat to cause the 
beads to expand. Alternatively, the core 3 may be produced by an open pour 
process in which the resin is introduced before the top panel is placed 
thereon and the top panel placed thereon, after which the resin cures 
fully. 
Thus, it can be seen from the foregoing detailed specification and attached 
drawings that the metal door of the present invention is readily and 
easily fabricated with a minimum of assembly labor and steps. The 
continuous frame eliminates many of the problems encountered by assembling 
separate stiles and rails.