Security door hinge system with locking elements

An improved security door hinging system, wherein the door hinge comprises locking elements in the shape of circular posts on each hinge leaf. Lock engaging means in the form of apertures are located on the door and the door frame to engage the locking elements of the hinge. The locking elements and the lock engaging means cooperate when the door is in the closed position to secure the door to the door frame in the event the conventional mounting screws become inoperable, as when excessive force is applied to the door hinge area.

BACKGROUND OF THE INVENTION 
The present invention relates to an improved system for hinging a door to a 
door frame, wherein the improved system comprises a plurality of locking 
elements extending between the mounting side of each hinge leaf and the 
door and the door frame. 
Conventional door hinges are fastened to the door and the door frame 
generally by means of a plurality of screws or bolts. The size and quality 
of the screws or bolts determine the ability of the conventional door 
hinge to withstand forces, in the vicinity of the hinge, directed to 
removal of the door in the closed position from the door frame. Typically 
a few heavy blows to the door in the vicinity of the conventional hinge is 
sufficient to cause the shearing of the fastening screws or bolts and the 
consequent removal of the door from the door frame. 
In security installations such as correctional institutions, mental 
institutions, hospitals, etc., it is desirable that the door hinge 
withstand abuse and intentional attempts to damage or remove the door. The 
conventional door fastening methods teach the use of larger and stronger 
fastening screws or bolts to enhance the ability of the hinge to withstand 
such forces. However, due to practical considerations of economy and 
physical space, the size and quality of these conventional fastening means 
is limited. 
SUMMARY OF THE INVENTION 
The present invention is directed to an improved system for hinging a door 
to a door frame. The improved system enhances the ability of the door 
hinge to maintain attachment of the door to the door frame under forces 
directed substantially transverse to the conventional attaching means. 
According to this invention, each leaf of a conventional style door hinge, 
preferably of the type with a hidden hinge pin, comprises at least one 
locking element. The locking element of one hinge leaf is designed to 
engage a respective lock engaging means located on the door and the 
locking element of the other hinge leaf is designed to engage a respective 
lock engaging means located on the door frame. 
In a preferred embodiment of the present invention the locking element 
comprises a circular post located in the mid-section of each hinge leaf. 
The locking element protrudes outwardly from the mounting face of each 
hinge leaf. The lock engaging means comprises apertures, one for each 
post, each aperture shaped and aligned to receive the locking elements. 
One aperture is located on the door and one is located on the door frame. 
One important advantage of the preferred embodiments described in detail 
below is that the hinge securing system can withstand substantially 
greater force directed in the vicinity of the hinge to the removal of the 
closed door from the door frame than a conventional door hinge. An 
additional advantage of these embodiments is that it provides a simple, 
effective and economical means of strengthening door hinging systems. A 
further advantage of these embodiments is that it complies with the 
National Association Of Architectural Metal Manufacturers (NAAMM) Standard 
HMDF-1-85 which requires that a security hinge withstand 50 impact blows 
of 200 ft. lbs. directed within 6 inches of the hinge. 
The invention itself, together with further objects and attendant 
advantages, will best be understood by reference to the following detailed 
description, taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
With reference to the drawings, FIG. 1 shows a presently preferred 
embodiment of the security door hinge of the present invention. The 
security hinge 5 shown in FIG. 1 is of the type comprising a hidden hinge 
pin to prevent the undesired removal of the pin. A detailed description of 
the hinge pin is not important to an understanding of the present 
invention and therefore the hinge pin is not shown or discussed in detail. 
Hidden hinge pins are commonly known and used in the industry. Although 
the hidden hinge pin is the type of hinge pin preferred in this 
embodiment, it should be understood that other types of hinge pin 
mechanisms can be used. 
The security hinge 5 comprises a left hinge leaf 10 and a right hinge leaf 
20 joined by a hinge pin (not shown). Each hinge leaf 10, 20 comprises 
four beveled apertures for the insertion of four flat head mounting screws 
30. The mounting screws 30 protrude through each hinge leaf 10, 20 and are 
screwed into a respective mounting surface. The mounting surface for one 
of the hinge leaves 10, 20 is located on the door and the mounting surface 
for the other of the hinge leaves 10, 20 is located on the door frame. The 
beveling of each mounting screw aperture substantially matches the 
beveling of the flat head screws 30 to ensure that the screws 30 mount 
substantially flush to the face of each hinge leaf 10, 20 and secure the 
hinge leaf 10, 20 to the mounting surface. 
The locking elements 40, 42 are in the form of circular posts. One post 40, 
42 protrudes from the mounting side of each hinge leaf 10, 20. The 
placement of the posts 40, 42 on each hinge leaf can be seen in FIG. 1 
where the posts 40, 42 are depicted as broken lines and in FIG. 2 where 
the security hinge 5 is shown from a top view with the mounting screws 30 
omitted for clarity. 
FIG. 3 shows the preferred embodiment of FIGS. 1 and 2 mounted to a steel 
door 60 and a steel door frame 50. As is common in security installations, 
the door 60 and the door frame 50 include steel reinforcement plates 62 
and 52, respectively. The installation of the preferred embodiment is 
conventional with respect to the mounting screws 30. Four threaded 
apertures 35 are formed in the door 60 and four threaded apertures 35 are 
formed in the door frame 50. Each aperture 35 is aligned with a respective 
mounting screw 30. The hinge may be mortised into the door 60 and door 
frame 50 as determined by the particular installation requirements. 
The lock engaging means of this preferred embodiment comprise apertures 45, 
47 of sufficient dimensions and alignment to engage the posts 40, 42. One 
aperture 45, 47 is aligned with each respective post 40, 42. As shown in 
FIG. 3 aperture 45 extends into the door 60 and through the reinforcement 
plate 62. Aperture 47 extends into the door frame 50 and through the 
reinforcement plate 52. 
The apertures 45, 47 for the lock engaging means do not require a precise 
fit with the posts 40, 42. The primary function of the posts 40, 42 and 
apertures 45, 47 is to maintain the attachment of the closed door to the 
door frame under forces substantially transverse to the mounting screws 30 
in the event the mounting screws 30 are no longer operable to do so. The 
apertures 45, 47 preferably define a radius up to 1/16 inches greater than 
the radius of the posts 40, 42. This degree of tolerance is an advantage 
in that manufacturing and installation costs of the security hinge system 
of this presently preferred embodiment are reduced. 
By way of illustration, and with no limitations intended, the following 
information is given to define this preferred embodiment in greater 
detail. In this preferred embodiment, the hinge leaves 10, 20 and posts 
40, 42 are investment cast, ASTM 300 series stainless steel, and the 
hidden hinge pin is formed of ASTM 303 stainless steel. The hidden hinge 
pin mechanism comprises hardened, AISI D3 tool-steel ball races and ASTM 
302 stainless steel ball bearings. Four flat tamper resistant steel 
TORX.RTM. 12-24 machine mounting screws are used to mount each hinge leaf 
10, 20. The hinge measures 41/2 inches by 41/2 inches in the fully spread 
position. Each hinge leaf 10, 20 is 3/16 inches in thickness. Each post 
40, 42 protrudes approximately 3/8 inches from the mounting face of the 
hinge leaves 40, 42 and is 15/32 inches in diameter. The posts 40, 42 are 
located 3/4 inches from the outside edges of each hinge leaf 10, 20 and 
21/4 inches from the upper edge of each hinge leaf 10, 20. 
The security hinge 5 was impact tested in accordance with the National 
Association Of Architectural Metal Manufacturers Standard HMDF-1-85. The 
security hinge 5 was subjected to 50 impact blows of 200 ft. lbs. directed 
within 6 inches of the improved hinge system 5 with the door 60 in the 
closed position. The 1/16 inch radial clearance between the post 40, 42 
and the aperture 45, 47 permitted the mounting screws 30 to be sheared 
after approximately 6 blows. However, the posts 40, 42 and apertures 45, 
47 held the security hinge 5 secure to the door 60 and door frame 50 for 
the remaining 44 blows to easily pass the NAAMM standard. 
A second preferred embodiment of this invention is shown in FIG. 4. In this 
embodiment, a lock engaging means is located on each leaf 10, 20 of the 
security hinge 5 in the form of apertures 40', 42'. A lock engaging means 
in the form of an aperture 44 is also located in the door 60 and through 
the reinforcement plate 62. A locking element, in the form of a post 46 of 
circular cross-section, extends from the door frame reinforcement plate 52 
and the door frame 50. The mounting of the security hinge 5 with the 
mounting screws 30 is similar to the mounting of the first preferred 
embodiment and therefore will not be discussed in detail. 
The apertures 40', 42', 44 and the post 46 are aligned and shaped such that 
when the door 60 is in the substantially closed position the post 46 
engages each of the apertures 40', 42', 44. The apertures 40', 42', 44 and 
the post 46 are further shaped and aligned such that substantial 
impairment of the pivotal operation of the door 60 about the security 
hinge 5 does not occur. As with the first preferred embodiment, the second 
preferred embodiment enhances the ability of the security hinge 5 to 
secure the door 60 to the door frame 50 in the substantially closed 
position against destructive forces. 
It should be understood that materials or components different from those 
used in the preferred embodiments may be selected to reduce the cost or to 
increase the holding characteristics of the security hinge system. For 
example, in the first preferred embodiment, the posts 40, 42 may be 
attached to the hinge leaves 10, 20 by means other than casting. 
Similarly, the posts 40, 42 may be of a form other than a circular post, 
such as a square or elliptical cross-section. Furthermore, the locking 
elements 40, 42 may be apertures and the corresponding lock engaging means 
45, 47 located on the door 60 and the door frame 50 may be in the form of 
circular posts. It should also be understood that the posts may comprise 
hollow cylinders or may be solid. Further, the post receptacles may 
comprise hollow cylinders for concentric engagement with the posts. 
Similarly, in the second preferred embodiment the post 46 may extend from 
the door reinforcement plate 62 rather than from the door frame 
reinforcement plate 52. Also, one of the hinge leaves such as leaf 20 may 
be attached to the door frame by welding means and the post 46 extended 
from the outer face of the leaf 20. 
The foregoing detailed description has been given for illustration purposes 
only. A wide range of changes and modifications can be made to the 
preferred embodiment described above. It should therefore be understood 
that it is the following claims, including all equivalents, which are 
intended to define the scope of this invention.