WO2000053869A1

WO2000053869A1 - Improvements in electric strikes

Info

Publication number: WO2000053869A1
Application number: PCT/AU2000/000169
Authority: WO
Inventors: Graham James Luker
Original assignee: Trimec Technology Pty. Ltd.
Priority date: 1999-03-09
Filing date: 2000-03-09
Publication date: 2000-09-14
Also published as: AUPP907899A0

Abstract

There is a strike plate (4) which receives a latch tongue (9) and a striker (5) pivotal therein. There is a roller (10) on the striker to reduce friction.

Description

IMPROVEMETS IN ELECTRIC STRIKES

This invention relates to strike plates. More particularly although not exclusively it discloses an improved form of electric strike plate for use with emergency exit doors.

Emergency exit doors in public buildings are required to be fitted with a transverse bar which extends across at about waist height. To enable a speedy and safe exit from a building under conditions of duress the bar when pressed against the door is adapted to withdraw a latch tongue from a locking position where it engages a fixed striker in the door jamb. The lock is thereby released and the door is able to immediately swing outward under the aforementioned pressure. Such mechanism however in its basic form provides no entry- means from the outside. Therefore, it is known to modify the lock by fitting an electronic access system to allow restricted entry through the use of a key pad. card reader or the like. One example of a striker plate used with this form of lock is shown in figure 1. There is a housing 1 which is fitted to the door jamb. The striker 2 is set within the housing and is pivotal from the locking position shown where the door latch sits in niche 3 to a release position where said striker is retracted into the housing so that the latch is free and the door can be opened. As mentioned earlier this arrangement allows restricted entry through emergency exit doors by the use of a security key .pad or the like to electrically retract the striker. In all other situations the striker 2 remains in its iocking position and the door has to be opened from the inside through pressure on the bar and

Substitute Sheet withdrawal of the latch tongue as described earlier. However as these electrically operated strikers remain in their locking position during emergency exits they have been found to provide a high resistance to withdrawal of the latch tongue. This resistance is caused by friction between the stationary surface 2A of the striker and the abutting surface of the latch tongue which must slide over it to disengage. Such mechanisms also commonly experience galling and excessive wear on these surfaces which further increases sliding friction. The problem is also exacerbated by the considerable outward pressure exterted on the door and latch in panic situations. Such pressure is carried by these abutting surfaces and can lead to jamming of the lock.

It is therefore an object of this invention to ameliorate the aforementioned disadvantage and accordingly a strike plate for an emergency exit door lock is disclosed, said strike plate including a recessed plate means which in use can be fitted into the door jamb to receive a latch tongue and striker pivotal in said plate means between a first position at which said latch tongue is held within the recess and a second position at which said latch tongue is released and said striker being lockable in said first position, wherein a portion of said striker which engages the latch tongue to hold said latch tongue within the recess comprises a roller means orientated so as to substantially e-iminate sliding friction between said latch tongue and striker during an emergency exit when said striker remains locked at said first

Substitute Sheet position and the latch tongue is withdrawn from said recess by operation of an exit mechanism associated with said door.

One currently preferred example of the invention will now be described with reference to the attached drawings in which:

Figure 2 shows a perspective view of a striker plate according to this concept when in the locked position.

Figure 3 shows the striker of figure 2 in the open position, and

Figure 4 is a partial cross-sectional view along the lines A-A of figure 2 showing the locked striker engaging a door latch tongue.

Referring first to figure 2 there is an electric strike plate 4 which is adapted for attachment to the door jamb of an emergency exit. The striker 5 together with fixed backing plate 6 forms a recess or cavity 7 for the door latch tongue when in the closed or locked position shown. The striker is pivotal to the open or unlocked position shown in figure 3 by activation of electromechanical means (not shown) within the plate 4. Therefore, when the striker plate is fitted to an emergency or fire exit the door may also be used as a security entry whereby the striker can be released by use of an exterior key pad or card reader.

Typical locking positions for the striker 5 and door latch

Substitute Sheet tongue 8 are shown in figure 4. With the striker 5 in its closed or locked position the latch tongue 8 is trapped within recess 7 and the door is held closed. When emergency exit is required pressure on the inside bar serves to rotate the latch tongue about pivot 9 in the direction of arrow B so as to withdraw it from the recess 7 and release the door. In accordance with this invention a roller 10 is fitted along the outer edge of the striker 5. This roller is positioned to contact the latch tongue and prevent any sliding friction arising between said latch tongue and striker. This insures that the tongue remains free to withdraw from the recess even when the door is under considerable pressure from the inside as is often the case in panic situations. As this sliding friction is eliminated galling and wear on the engaging surfaces is also greatly reduced which extends the life of the lock and reduces maintenance. Although the primary benefit of the roller would be during emergency exits it is considered that operation of the lock during entry from the outside and subsequent closing of the door would also be facilitated by elimination of sliding friction.

It will thus be appreciated that this invention at least in the form of the embodiment disclosed provides a novel and useful improvement in locks for emergency exit doors. Clearly however the example described is only the currently preferred form of the invention and a wide variety of modifications may be made which would be apparent to a person skilled in the art. For example, the shape and configuration of the striker

Substitute Sheet as well as the placement and design of the roller may all be changed according to application.

Substitute Sheet

Claims

The claims defining the invention are as follows:

1. A strike plate for an exit door, said strike plate including a plate means which in use can be fitted into a door jamb to receive a door latch tongue and a striker pivotal in said plate means between a first position at which said latch tongue is held within the recess and a second position at which said latch tongue is released and said striker being lockable in said first position wherein a portion of said striker which engages the latch tongue to hold said latch tongue within the recess includes a roller means adapted to substantially reduce sliding friction between said latch tongue and striker during use of said exit door when said striker remains locked at said first position and the latch tongue is withdrawn from said recess by operation of an exit mechanism associated with said door.

2. The strike plate as claimed in claim 1 wherein said roller means is fitted along an outer edge of the striker.

3. The strike plate as claimed in claim 2 where said roller forms at least part of the outer edge of the striker.

4. The strike plate as claimed in claim 3 wherein the surface of said roller means is positioned so as to provide the sole contact between said striker and latch tongue.

5. The strike plate as claimed in claim 4 wherein the striker

Substitute Sheet is pivotal from said first position to the second position by an electromechanical means within said strike plate.

6. The strike plate as claimed in claim 5 wherein in use of the strike plate said electromechanical means is operable from a remote key pad or card reader.

7. The strike plate as claimed in claim 5 wherein said recess is formed by said striker and a fixed backing plate in said plate means.

8. A strike plate for an exit door, said strike plate being substantially as described herein with reference to figures 2 to 4.

9. An exit door installation having a door jamb fitted with a strike plate as claimed in claim 1.

10. The exit door installation as claimed in claim 9 wherein said installation is operable as an emergency exit and the door is fitted with said latch tongue which is pivotal between a locked position where it is located in said recess and an unlocked position at which it is withdrawn from said recess by means of pressure exerted on an inside bar of said door wherein said latch tongue engages said roller during withdrawal from said recess.

Substitute Sheet