GB2199882A - Lock bolt retaining assembly - Google Patents

Abstract

A variable lock strike plate assembly for increasing the resistance to an impact force as applied to a door, the strike plate assembly allowing for various heights of the door lock above ground level in respect to the impact point. The lock bolt is also modified so that a long hinge pin, attached to the said assembly, can be inserted into a hole drilled in the lock bolt thus preventing the spring bolt from being slipped, or the door frame from being spread, to disengage the bolt from the strike plate assembly. The whole assembly is applied to spring bolt rim latches or other rim mounted locks.

Description

LOCK BOLT RETAINING SYSTEM BACKGROUND OF THE INVENTION.

Various systems are in use at the present time to provide a retaining means for the spring bolts of rim mounted locks. These retaining means, variously called strike plates or staple boxes, are attached to the door frame by means of wood screws such that when the lock bolt is extended in its locked condition it is housed within the staple box thus holding the door closed.

The first limitation of these standard staple boxes is that when an impact force, such as a kick or a shoulder charge, is applied to the door'a torque is developed vertically across the stale box which acts through the retaining screws. Because of the short distance between these retaining screws, and because these said screws are normally in line with each other, the developed torque exceeds the shear strength of the wooden frame and the staple box twists out of the frame.

In an attempt to obviate this limitation some standard staple boxes use longer wood screws or wood screws placed at 450 to the door plane. This does little or loathing to eliminate the effect of the torque on the staple box.

A second limitation of the standard staple boxes is that since the lock bolt is of the spring type, i.e., not dead locked, the bolt may be disengaged from the receptacle hole in the staple box by means of a thin metal shim, or, if the bolt is latched, the door glass may be broken, the latch unlatched and the thumbturn operated withdrawing the lock bolt.

Finally, the door frame may be spread by inserting a car jack across the width of the door between the uprights of the door frame such that when the jack is operated the frame uprights spread apart carrying the staple box away from the lock bolt and allowing the door to be pushed open.

A lock retaining means made in accordance with this invention overcomes the limitations of prior systems by obviating the leverage effect on the lock staple box and by winning the spring bolt in a dead locked condition which prevents the spreading of he door frame, slip?ing the lock or operating the dead locked spring bolt in any manner which is illegal. Thus the lock assembly is upgraded in security without changing the cylinder or lock mechanism in any way.

SUMMARY OF THE INVENTION A long strike plate of some 25 cms to 30 cms in length, but which may be longer or shorter, is mounted on top of a square bolt retaining strike plate in such a manner that the retaining wood screws extend through each of these plates2 where they coincide, when screwed to the door frame.

Since the height of the lock above ground level has already been established by the prior installation of the lock, and since the impact point on the door may wry depending upon the height of the assailant, the long strike plate has been designed such that the square strike plate may be placed in any one of three locations on this long strike plate. In this manner the variation in the geometry of the lock and the impact point may be compensated for.

Assuming the previously established height of the lock is 1.5 metres above ground level and that the impact point is between 1.4 metres and 1.25 metres which is the sariation due to the difference between a 1.83 metres tall man and a 1.62 metres tall man, the square strike plate will be placed in the top position of the tree possible positions on the long strike plate. In this way the bottom of the long strike plate will extend down towards the impact point, i.e. the bottom of the long strike plate will be at a height of 1.5 metres minus 30 cms 1.2 metres which is lower than the impact point. Thus any leverage effect due to the door bending under impact is removed since the fulcrum point is lower than the applied force point.

Alternatively1 if the previously established height of the lock is 1.22 metres above ground level and the impact point is the same as above, the square strike plate will be placed in the centre position of the three possible positions on the long strike plate when it is used to replace the old staple box. In this way the top of the long strike plate will be at a height of 1.22 metres plus 15 cms=l.37 metres and the bottom of the long strike plate will be at a height of 1.22 metres minus 15 cms= 1.07 metres.

Thus the impact point will be approximately between these two heights and any leverage will be drastically reduced.

A similar be used if the lock is at a height of 0.92 metres and the square strike plate is placed in the lowest of the three available positions on the long strike plate.

Thus the leverage effect on the long strike plate is considerably reduced with large variations of lock height and impact point.

Since the lock bolt is now exposed to view, because of the design of the square strike plate, and not enclosed as with a standard staple box, a hole can be drilled vertically through the lock sPring bolt such that a long hinged pin can be inserted through this hole. In this way the spring bolt of the rim lock may be dead locked in place such that it cannot be slipped or removed from the receptacle hole in the square strike plate.

This long hinged pin is an integral part of the assembly in that it is attached to the square strike plate by means of a rivet and flexible coupling. The long hinged pin also prevents the thumbturn being turned and the door frame being spread apart. The hinged section of the long hinged pin is turned at 900 to the plane of the pin and is hidden behind the square strike plate and below the lock bolt so that it cannot be removed from the outside of the door.

An object of this invention is the provision of a system of strike plates for affecting a greater resistance to an impact force applied to a door.

An object of this invention is the provision of a system of strike plates which can be varied in relationshi? to each other such that varying heights of lock locations above floor level can be compensated for with relationship to varying heights of impact force allied to a door.

An object of this invention is the provision of a system of strike plates which expose the lock bolt such that a hole can be drilled vertically through the lock bolt into which a long hinged pin can be inserted such that the bolt becomes dead locked.

An object of this invention is the provision of a system of strike plates and hinged pin assembly which can obviate the slipping of the lock bolt using some thin shiz or plate.

An object of this invention is the provision of a system of strike plates and hinged pin which helps prevent the spreading of the door frame to disengage the lock bolt fron the bolt receptacle plate.

An object of this invention is the provision of a system of strike plates and hinged pin which prevent the turning of the thumbturn fron the outside of the door even if the door glass is broken.

fiESCRIPTION OF THE DRAWINGS.

Inthe drawings wherein like reference numbers denote like parts in the several viewss- Figure 1 is a front view of both plates showing their various relationships with various heights of door locks above floor level.

Figure 2 shows the lever arm formed when an impact force is applied to a door, as viewed along the door plane.

Figure 3 is a top or plan view of the installation showing the location of the long hinged dead lock pin.

Figure 4 is a front view of the hinged dead lock pin inserted through the spring bolt of the rim mounted lock.

DESCRIPTION OF THE PREFERRED EMBODIMENT .

In Figure 1 the numeral (1) denotes the long strike plate and (10) the square plate. Holes (8) and (9) coincide with pairs of holes (2) and (3) in the section marked A, holes (4) and (5) in the section marked B and holes (6) and (7) in the section marked C, such that the square plate (10) can be mounted on the door frame under the long strike plate (1) in any of these three sections.

The rectangular hole (26) in the square strike plate (10) is the lock bolt retaining hole. The long hinged pin (15) is attached to the said square strike plate (103 by means of rivet (13) and the flexible coupling (14), The angled section (12) on the aquare strike plate (10) deflects the lock bolt into the retaining hole (26), In Figure 2 both strike plates (1) and (10) are shown attached to the door frame. The square strike plate (10) is identical in shape and size to the old staple box which it has replaced and so will respond to an impact force in a manner similar to that of the old staple box when viewed alone. Viewing this square strike late (10) alone, it can be seen that if an impact force is applied is applied at (19) the door will bend inwards, the degree of bending depending uon the mass and velocity of the assailant.Since the lock (24) is attached to the door (17) the lock bolt (16) will tend to turn within the receptacle hole (26) with the result that the top of the bolt (16) will bear upon the outside edge of the receptacle hole (26).

Thus, a torgue, developed within the lock bolt receptacle (26) will apply a force (29), perpendicular to the door plane and outwards from the door, which acts through the top wood screw (4).

Consequently a load force (28) will act through the lower wood screw (5) into the door frame. In this way R2, the distance between the impact point (19) and the fulcrum point, or pivot point (29), divided by R1, the distance between the fulcrum point (29) and the load point (28), nominally the velocity ratio, rvill provide a leverage of approximately 5.

This action invariably causes the frame (18) to split thus allowing the staple box to break away from the frame.

Referring now to the complete installation, i.e, the square plate (10) and the long plate (1) in Figure 2, it can be seen that a similar impact point (19), and the resulting twisting action of the lock bolt (16) within the receptacle hole (26) on on square plate (10) will establish a fulcrum point (30t at wood screw (2) since the wood screw (4) cannot move without wood screw (2) moving. Consequently the load (28) will move from wood screw (5) to wood screw (7) establishing a new load point at (27).

Hence the Rl/R2 ratio will change in that the newly established distance between the impact point (19) and the new fulcrum point (30), namely R2, divided by the new R1, that is the distance between the fulcrum point (30) and the load point (27) has decreased considerably, In fact, in the illustration in Figure 2, a measurement of these distances will show a leverage ratio of less than 1, i.e. no mechanical advantage.

Thus the door will be strengthened, in this case, by a ratio of 5s1.

A similar logic, employing the basic R2/R1 ratio of the lever arm, may be employed to show the change in leverage for each of the sections A, B and C, shown in Figure 1, when the square strike plate (leo) is moved into each of these said sections, with various heights of lock position above the ground level, and the impact point is held within a distance above ground level expected by the impact of assailants whose height varies from 1.83 meters down to 1.62 meters.

Figure 3 shows the plan view of the complete installation where the lock bolt (16) protrudes through the bolt receptacle hole in square strike plate (10) and where long hinged pin (15) is shown inserted through the hole drilled into the lock bolt.

The excess metal from the said bolt receptacle hole is bent ay 900 to the plane of the square strike plate (10) to form a mounting plate (11) through which wood screw (21) is inserted to provide additional strength for mounting. The rim lock (28) is shown with its thumbturn (23) and cylinder (22) in relationship to the strike plates (1) and (10).

Figure 4,a frontal view of the spring bolt (16), shows the sPring bolt protruding through the square strike plate receptacle hole (26) with the long hinged pin (15) inserted through the drilled hole (31) and showing the angled section turned at 900 to the plane of the hinged pin behind the angled section (12) of the square strike plate (10).

Having now described the invention, those skilled in this art will be able to make various changes and modifications without thereby de-zarting from the spirit and scope of the invention as recited in the following claims.

Claims (3)

(HAT IS CLAIMED ISs-

1. A door ?'ock bolt retaining system wherein a combination of two strike plates can be variously assembled to compansate for various heights of lock above floor level and various heights of impact forces which assembly obviates the effect of a lever arm developed during an impact force on the door and wherein a long hinged pin can be inserted through a hole drilled in the lock bolt thus preventing the lock bolt from moving.

2. A system for strengthening a door against impact forces and converting a rim lock sPring bolt into a dead lock bolt which system comprises.

(a) A long strike plate wherein a number of sets of holes a lows for various locations of a separate square strike plate.

(b) A square strike plate wherein mounting holes correspond to sets of mounting holes in a long strike plate and wherein a lock bolt locating and receptacle hole is located.

(c) A flexible means of retaining a long hinged pin to the said square strike plate such that when this said long hinged pin is inserted through a drilles hole in a lock bolt the lock bolt cannot be moved.

3. The invention as cited in claim 1 wherein a long hinged pin can be set such that its hinged section is at right angles to the plane of the long hinged pin and is hidden beneath the lock bolt and behind the angled section of the square strike plate thus preventing casual removal of the said long hinged pin,