Dead bolt guard

A guard mount structure for a dead bolt installation on a door has a preassembled condition wherein a dead bolt subassembly consisting of a housing and a dead bolt shaft is attached to a sheet metal guard. The sheet metal guard has opposite plates for attachment to opposite faces of the door and an end plate overlying the end face of the door, the housing of the dead bolt subassembly being attached to the inside face of the end plate.

The trend of improvements currently in door locks is to improve the locks 
from the point of view of security. In doing this the industry has 
recognized that in all probability as a commercial item, no lock is 
absolute assurance against forcible entry of some kind. Building 
structures and modern tools are such that an unauthorized person, given an 
adequate amount of time and opportunity, can forcibly open a door, even 
though the door is provided with a dead bolt lock or door lock of 
comparable kind, which, as a commercial item, has been made as secure as 
consumer demand warrants. 
The mode of operation of unauthorized persons to a large extent is one of 
forcing the door as quickly as possible by whatever means may be necessary 
to enable the unauthorized person to make the entry and then leave the 
premises as quickly as possible before the entry has been detected. 
Because of this anticipated mode of operation, it becomes quite worthwhile 
for the owner of the premises to provide a deterrent which, even though it 
may not be absolute assurance against forcible entry, makes the entry 
sufficiently time-consuming to discourage most unauthorized persons. 
It is further true that there are a great many installations of such things 
as dead bolts already in place, insufficiently guarded according to 
current demands. It is, therefore, in the interest of the building owner 
to renovate such existing door locks wherever it can be done in order to 
make unauthorized entry more difficult and time-consuming. 
It is, therefore, among the objects of the invention to provide a new and 
improved dead bolt guard which is applicable over a substantially 
conventional dead bolt assembly which covers a sufficient amount of the 
door surface adjacent the dead bolt to provide a deterrent for forcing 
entry by dislodgement of the dead bolt mechanism. 
Another object of the invention is to provide a new and improved dead bolt 
guard which is simple in its construction and sufficiently versatile so 
that it can be applied with equal effectiveness to doors already equipped 
with such a dead bolt as well as on new construction, and for either right 
or left hand mountings. 
Still another object of the invention is to provide a new and improved dead 
bolt guard which is capable of being preassembled with the dead bolt 
mechanism itself so that the entire unit can be easily and effectively 
installed as such on a door. 
Still further among the objects of the invention is to provide a new and 
improved dead bolt guard which is capable of encompassing and protecting 
virtually all portions of the dead bolt mechanism and the surrounding 
portions of the door, thereby to serve as an improved deterrent for 
unauthorized entry.

In an embodiment of the invention chosen for the purpose of illustration a 
door 10 is shown in end section providing an outside face 11, an inside 
face 12, and an end face 13. The door is provided with a conventional 
cross bore 14 extending between the inside and outside faces 11 and 12, 
and an edge bore 15 extending inwardly from the edge face 13 into the 
cross bore 14. 
A typical installation for a dead bolt mechanism is one which, by way of 
example, consists of an inside trim 16 on which is mounted a thumb turn 17 
provided with a conventional shaft 18. The shaft is in non-rotating 
slidable engagement with a tail piece 19 manipulated by an appropriate key 
actuated mechanism 20 through an outside trim 21 in which is an 
appropriate key way (not shown). The trim is incorporated in a guard ring 
having a beveled wall 27 to discourage the unauthorized application of a 
pipe wrench to dislodge the key actuated mechanism. 
The tail piece 19 is adapted to cooperate with a dead bolt subassembly 
indicated generally by the reference character 22. 
A typical installation is suggested by showing the door in cooperation with 
a frame 23 and stop 24, there being a dead bolt recess 25 in the frame 
behind a latch plate 26, each of the last mentioned parts being shown in 
phantom view in FIG. 2. 
The mechanism of the dead bolt subassembly 22 is substantially 
conventional, but for purpose of illustration may be referred to as 
comprising a housing 30 from which extends a bolt head 31. At the opposite 
end of the housing is a housing extension 32 provided with an appropriate 
conventional roll back assembly at the location 33 with which the tail 
piece 19 is engaged. 
To adequately guard the dead bolt subassembly and its operating mechanism, 
there is provided a cage 35 which consists of an inside plate 36, an 
outside plate 37 and an end plate 38. The end plate joins the inside plate 
at a corner 39 where adjacent edges join, there being also a corner 40 
where the outside edge of the end plate 38 joins the corresponding edge of 
the outside plate 37. One of the plates may be tilted 3.degree. to match 
the conventional bevel of the door. 
In the inside plate is an opening 41 which is in axial alignment with a 
corresponding opening 42 in the outside plate 37. The opening 41 provides 
for communication between the thumb turn 17 and the interior, the opening 
42 providing a space for mounting the key actuated mechanism 20. As shown 
in the drawing, only the end face of the door is recessed for reception of 
the end plate 38. The inside and outside plates 36 and 37 actually overlie 
the respective faces of the door. 
In the end plate is a hole 45 in which is located a circular central 
portion 46 of a ferrule 47, there being a perimetrical flange 48 for the 
ferrule lying behind the end plate 38. In the middle of the central 
portion 46 is a hole 49 for accommodation of the bolt head 31. The hole 45 
is expressly made circular to accommodate the circular central portion 46 
so that the ferrule together with the operating mechanism of the latch 
bolt can be rotated 180.degree. about the longitudinal axis, in order to 
properly accommodate the dead bolt to either a right-hand or left-hand 
installation. 
Additionally, in the end plate is a pair of mounting holes 50 and 51, the 
mounting holes being in alignment with each other on respective upper and 
lower sides of the bolt head 31. On a back plate 53 and on respective 
upper and lower sides of the housing 31 are wings 52 and 52', the upper 
wing being located behind the mounting hole 50 and the lower wing being 
located behind the mounting hole 51. Additionally, in the wing 52 is a 
countersunk hole 54, there being a corresponding countersunk hole 55 in 
the wing 52'. The material of the end plate is deformed to provide, in 
effect, a sleeve 56 rivetted with respect to the countersunk holes 54 and 
55 so that the sleeves are flared and ironed into engagement with the 
countersunk walls of the holes, thereby to fasten the corresponding wing 
52 to the end plate 38. A similar sleeve 57 serves the same purpose with 
respect to the wing 52' and the end plate. 
Attached as shown and described, the dead bolt subassembly 22 is secured to 
the cage 35 so that they together are handled as an assembly. 
It is of some further interest that the material of the respective wings 52 
and 52', where they have been deformed to provide their respective 
countersunk holes 54 and 55, are displaced in a direction toward the 
adjacent inside face of the end plate 38, the deformed portions actually 
spacing the wings a short distance from the end plate. As a consequence of 
this arrangement, the end face 13 of the door 10 will need to be chiselled 
out more deeply in the area of the wings as shown in FIG. 3, thereby to 
form a deeper recess 58 to accommodate the wings. 
When the installation is to be made, the customary cross bore 14 and edge 
bore 15 are made in the door. The cage may then be preliminarily applied 
in order to locate edges of the necessary recess, thereafter to be 
chiselled for reception of the end plate. This having been prepared as 
noted, the cage is then reapplied and at the same time the dead bolt 
subassembly 22 is projected into the edge bore 15. Appropriate screws (now 
shown) are then driven in conventional fashion through the mounting holes 
50 and 51 to fasten the cage in place. After the outside trim and guard 
ring 21 have been applied and secured in position by appropriate bolts and 
sleeves (not shown) from the inside trim 16, inwardly disposed faces of 
the trims are drawn into snug engagement with the respective faces of the 
inside and outside plates. The dead bolt subassembly is guarded from 
tampering by the interposition of the material of the cage, which covers 
the wood material of the door throughout the area surrounding the 
installation. 
By having the metal plates anchored by the trims in a position covering the 
relatively thin wood section between the edge bore 15 and the adjacent 
face of the door 10, the wood cannot be readily splintered to dislodge the 
dead bolt, which would othersied be possible, absent the protection of the 
plate.