Description:
In the effort to provide an improved barrier against unauthorized entry, it is not practical merely to add bulk or substitute materials of known greater strength, particularly where a residential type of door, for example, rather than a commercial type, is involved. A balance between cost and effectiveness must be made, bearing in mind that resistance to standard expected threats, not extraordinary ones, is the objective.
It is therefore an object of the present invention to provide a security door which uses relatively inexpensive materials, yet which is put together in such a way as to afford an effective deterrent to several of the more frequent kinds of criminal threats, such as a prybar inserted between a door and the adjacent lock jamb and used to free the latch bolt.
It is another object of the invention to provide a security door which is effective to frustrate most onslaughts directed toward the door, both laterally, in the plane of the door, and perpendicular thereto, such as foot or shoulder impact, battering ram, heavy hammer, or the like.
It is still another object of the invention to provide a security door which is not only effective to accomplish its practical purpose but it also esthetically acceptable in that it presents the traditional appeal of a solid or flush door.
It is a further object of the invention to provide a security door which is well-balanced, relatively compact in size, light in weight, and compatible with all kinds of door hardware.
It is yet another object of the invention to provide a generally improved security door.
Other objects, together with the foregoing, are attained in the embodiment described in the following description and illustrated in the accompanying drawing in which:
FIG. 1 is an isometric view, to a reduced scale of a preferred embodiment with portions broken away to reveal interior details;
FIG. 2 is a fragmentary view of the lower, left-hand corner of the door as shown in the broken ellipse;
FIG. 3 is an exploded fragmentary view of the upper left-hand corner of the door;
FIG. 4 is similar to FIG. 3 but illustrating the upper, right-hand corner; and
FIG. 5 is similar to FIG. 3, but showing the structure in the vicinity of the lock end of the middle rail as indicated by the broken ellipse.
While the security door of the invention is capable of being built and used in numerous ways, the particular embodiment shown and described herein has proven to be eminently effective in accomplishing its intended purposes.
The security door of the invention, generally designated by the reference numeral 12, comprises a top rail 13, a middle rail 14 and a bottom rail 15, the rails being connected at their hinge ends to a divided, but co-linear, hinge stile 17 and at the lock end to a divided, but co-linear, lock stile 19.
An upper middle stile 21 and a co-linear, lower middle stile 22, respectively, span the top and middle rails and the middle and bottom rails.
As appears most clearly in FIGS. 2 - 5, the joints between the stiles and rails are mortised for added strength. For additional rigidity, triangular gussets 26 can be installed.
Since the middle rail 14 is the member ordinarily subjected to the greatest threat, the middle rail is of primary concern. Exhaustive tests have shown that 2 inches × 8 inches Select Structural Douglas Fir satisfactorily meets the requirements of cost effectiveness for the middle rail 14 in most security door installations.
In like manner, it has been determined that 2 inches × 6 inches Select Structural Douglas Fir serves adequately for the top rail 13 and the bottom rail 15. Gussets 26 can be made from 2 inches × 4 inches Douglas Fir (Dense No. 1).
Conventional hinges 28 and a lock mechanism 29 are installed as shown. FIG. 5 discloses the appropriate openings 31 in the middle rail 14 for a common lock mechanism.
In many instances, the threat to a door will consist of a prybar effort brought to bear against the lock end 33 of the middle rail 14. Powerful leverage can be directed against the middle rail by inserting the end of a crowbar between the lock end 33 and the adjacent lock jamb 34 of the door frame 35 shown in broken line in FIG. 1. The concentrated force is sometimes sufficient to compress and deform the wood adjacent the front plate of the lock, enabling the attacker to spring or destroy the latch structure.
In order to circumvent this approach, an opposing pair of stiffener plates 36, at least one of which is gained into the door, as at 37, is mounted adjacent the lock end 33 of the middle rail. If desired, the stiffener plate 36 on the outer side of the door is blank, i.e. it has no exposed openings. The connecting bolts in such case could be welded to the inner side of the blank stiffener plate with the threaded ends of the bolts inserted through respective openings in the door and the matching stiffener plate, for appropriate fastening. The stiffener plates, preferably, are 1/16 inch thick and of ASTM 1020 or 1025 steel; and instead of being installed separately, as shown and described, the plates 36 could be incorporated in the lock design.
The steel stiffener plates 36 located adjacent the latch mechanism 29 resist high concentrated loads at the latch. The two plates, acting as a bolt-spacer combination, distribute the load over a larger area of the door, thereby changing the concentrated latch load to a pressure distribution compatible with the wood's resistance to compression and destructive deformation.
A further effective measure to defeat crowbar attack on the edges of the door is the peripheral falsework structure, generally designated by the reference numeral 41.
Most prybar attacks are made on the lock end of the door in the vicinity of the lock mechanism, in an effort to displace the door in the direction of the hinges far enough so that the latch is withdrawn from the strike plate, thereby allowing the door to be opened.
In order to achieve this result, however, the crowbar must find a door edge which affords sufficient reaction for the force to be transferred from the point of engagement to the entire door.
The falsework 41 is therefore so constructed that it collapses under the very considerable concentrated force which must be brought to bear on the edge in order to displace the door in its own plane by an amount necessary to disengage the latch from the strike plate.
As appears most clearly in FIGS. 1, 4 and 5, the falsework 41 includes an upper lock edge closure 42 and a lower lock edge closure 43. Both closures are preferably strips of 1 inch × 2 inches clear soft pine. The upper closure 42 extends from the top 44 of the door 12 to the lock end of the middle rail 14 and the lower closure 43 reaches between the middle rail 14 and the bottom 46 of the door. Both strips are parallel to and spaced outwardly from the adjacent edge of the lock stile 19.
The soft pine edge closures, in other words, defeat crowbar attack by yielding to a force less than that required to displace the door. The falsework does not provide the necessary reaction for a crowbar owing to the relatively soft, non-resisting, low compressive strength of the respective closure strips 42 and 43.
In comparable fashion, a second portion of the falsework 41 is located on the hinge end of the door. However, since the hinges must be attached to the ends of at least two of the rails 13, 14 and 15, the falsework 41 must necessarily be interrupted. Thus, as shown most clearly in FIGS. 1, 2 and 3, the falsework comprises a top slat 51, or strip, a bottom slat 52 and a pair of intermediate slats 53 and 54. As before, the slats 51 - 54 are of clear soft pine having a cross-sectional size of 1 inch × 2 inches.
Along the top 44 of the door the falsework 41 includes a horizontal top strip 56 of 1 inch × 2 inches clear pine extending horizontally along the top of the door and being fastened at the hinge end to the top slat 51. At the lock end, the top strip 56 is secured both to the upper lock edge closure 42 and to the top of an upper horn 57 provided by an upward extension of the lock stile 19.
A comparable structure is provided at the bottom of the door, the falsework 41 there including a strip 61, of 2 inches × 2 inches clear pine extending horizontally between the bottom slat 52 and the lower lock edge closure 43, the bottom strip also being anchored to the bottom of a lower horn 63 formed by extending the lock stile 19 downwardly. The bottom strip 61 is thicker than the other strips in order to accomodate for weatherstripping and trimming, if necessary.
The falsework 41, in other words, provides a peripheral structure extending substantially around the entire margin of the door except for discontinuities required by the door hardware; and in the case of the particularly vulnerable area in the vicinity of the lock, the exposed end of the middle rail is "hardened" by the stiffener plates 36.
As previously indicated, high impact loads are also sometimes directed against a door perpendicular to the plane of the door, such as by the attacker's shoulder or foot, or by a heavy hammer or battering ram. Against threats of this nature, it has been found that a significant increase in the dynamic load resistance, with but a small increase in weight over the customary flush wooden door, is attained by the use of a steel reinforcing mesh 66 covering a substantial portion of one side of the door, as shown. In order that the exposed surface of the mesh 66 is flush, the mesh is inset into a corresponding shallow recess 67 formed in the door (see FIG. 4).
The beneficial effect of the mesh 66 which is preferably of expanded metal screen, 1/16 inch thick, ASTM 1010 steel, and which is secured to the door by staples and epoxy resin glue, is attributed to the increase in the elastic limit in bending achieved by the mesh.
Thus, instead of going plastic under dynamic loads, the door remains relatively elastic and returns more energy to the person attempting to gain entry by force than is the case with either conventional hollow or solid core doors.
Covering both sides of the door is a pair of planar panels 71 and 72, of 1/4 inch exterior grade plywood, glued to the underlying facing portions of the structure heretofore described. The plywood panels and particularly the interposed expanded metal screen 66 also serve effectively to resist cutting through the door.
In tests conducted with the security door herein, In comparison with hollow and solid core doors, the results showed that the security door is capable of withstanding substantially higher dynamic input loads. Yet, at the same time, in a comparative weight test, the security door of the invention weighed only 67 pounds as contrasted with about 28 pounds for a far weaker hollow core door and about 90 pounds for a weaker, yet much heavier solid core door.
It can therefore be seen that the security door disclosed herein corrects many of the weaknesses heretofore found in the customary solid and hollow core doors used in homes, apartments, and the like, and accomplishes this in an attractive, cost effective manner.