AU616068B2 - Latch tongue - Google Patents

Description

616068 COMMONWEALTH OF AUSTRALIA The Patents Act 1952-1969 Name of Applicant(s): WHITCO PTY LTD S Address of Applicant(s): 450 Sherwood Road Sherwood, Queensland, 4075 Actual Inventor(s): a b Address for Service: G.R. CULLEN COMPANY, Patent Trade Mark Attorneys.

Dalgety House, 79 Eagle Street, Brisbane, Qld. 4000, Australia.

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COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: LATCH TONGUE The following statement is a full description of the invention including the best method of performing it known to us: 2 THE INVENTION relates to a latch tongue for a lock.

The invention will be described by way of example with reference to a lock for a security screen door but it should be appreciated that this is by way of example only and that the latch tongue may be used for other locks also.

A typical security screen door lock is described and illustrated in co-pending Australian patent application 12029/88. That lock and other locks of this general type had *oo* a main tongue receivable within an aperture i9efined by a striker. Locks of that type may be forced by using a tool placed between the door and a door frame to deform the door So to cause the tongue to move out from the striker aperture.

This action usually causes a face of the tongue to come into contact with a peripheral edge of the striker aperture.

1 One attempt at making it more difficult to force a 9 door in this way was to provide a multi-point lock. Such locks had a main tongue and two spaced auxiliary tongues.

Forcing of the main tongue left the auxiliary tongues in engagement with respective auxiliary strikers. Such locks Q;0 were relatively more complex than single point locks, more S expensive and required more labour to install.

Another attempt at making it more difficult to I force a door was to have hooked tongues. Such tongues were generally only suitable for sliding and not swinging doors.

Such tongues, if used for swinging doors, were not readily adapted for right and left hand closing doors.

It is an object of the present invention to provide a latch tongue which at least minimises the disadvantages referred to above.

According to one aspect the invention provides a latch tongue for insertion through an aperture in a striker plate, said tongue having opposed side faces, at least one of said faces having serrations or teeth thereon extending at least part way along said one face, said serrations or teeth engaging with edges of said aperture to resist withdrawal of said tongue from said aperture upon forcing of the latch tongue.

The latch tongue may have a nose portion for engagement S: with a striker. The nose portion may have one tapered or contoured face to enable the striker to cause retraction of the tongue into a lock body upon closing in one direction of a door to which the lock including the tongue is fitted.

Preferably, the nose portion has two contoured or tapered faces such that the tongue may be equally employed for right and left hand closing doors without the need for making the tongue reversible. However, where the tongue has a nose portion with only one tapered or contoured face the tongue need not be reversible although this is preferred.

The serrations or teeth on the one face of the tongue may extend along that face for a substantial part of that face which is visible when the tongue is in its extended position.

Alternatively, the teeth may cover the whole face. Whilst the teeth may have any desired pitch or spacing either regular or irregular it is preferred that the pitch or spacing have a relationship to the thickness of the striker.

4 It is preferred that there be a minimum of two teeth for the thickness of the striker.

The shape of the teeth may be such that each tooth has an inclined leading face and an inclined trailing face.

The leading face may be that face of the tooth closer to the nose portion of the tongue. The faces may be inclined at the same or different angles. It is preferred that the leading face be inclined at an angle less than that of the trailing face.

It is preferred that both faces of the tongue be provided with serrations or teeth as described above.

The serrations or teeth need not extend the full width of the face of the tongue although it is preferred that they extend the full width.

If desired the tongue may be treated to harden the teeth or serrations. Case hardening or complete hardening of the tongue may be employed.

9 The invention will now be described by way of example with reference to the drawings in which: ooq: Figure 1 is a perspective view of a striker and lock inclllding a latch tongue according to an embodiment of the invention;A Figure 2 is a detailed perspective view of the latch tongue shown in figure 1; and, Figure 3 is a part sectional view showing the latch tongue received by the striker.

With reference to figure 1 a lock 10 is shown fixed to a frame member 11 of a security door. The lock 10 has two handles 12 (only one of which is visible). A main latch tongue 13 projects outwardly from a body of the lock. The lock 10 also has an auxiliary latch tongue 14. Lock 10 is generally of the type disclosed in co-pending Australian patent application 12029/88 and the disclosure of that specification is incorpoorated herein by way of cross reference.

Q' A latch plate 15 is mounted to the frame member 11.

So*. Plate 15 has two laterally extending projections 16 (only one *eg of which is visible the other is obscured by tongue 13).

Striker plate 17 is mounted to a door frame and has a contoured leading edge 18, a main aperture 19 for receiving tongue 13 and minor apertures 20 for receiving projections eo 0 16.

The tongue 13, as described in specification 12029/88 is movable between the fully extended position and a partially extended position. In figures 1, 2 and 3 the QI: tongue is shown in its fully extended position.

Greater detail of tongue 13 is shown in figure 2 and 3. The tongue 13 has tapered leading edges 21, 22 I defining a nose portion to enable it to function both for left or right hand closing doors. Side faces 23, 24 of the tongue are provided with a series of serrations 25. These serrations are of a general saw-tooth configuration and have 6 a pitch such that a minimum of two teeth are provided along a distance represented by the width W of the striker.

Typically the striker 17 has a width of about 1.6mm and the pitch of the teeth is about 0.75.m.

The teeth or serrations 25 function to engage the periphery of the edge of aperture 19 in the event that there is an attempt at forcing the door to which the lock is fitted. Forcing of the door to cause the tongue 13 to move out from aperture 19 will cause teeth 25 to engage either portion 26 or 27 of the periphery of aperture 19 in the striker. This engagement then resists the forcing action making it that much more difficult to force the door.

In addition, the location of projections 16 within apertures 20 also assists in resisting forcing.

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Claims (10)

1. 2. The latch tongue of claim 1 including a nose portion at one end.
2. 3. The latch tongue of claim 2 wherein the nose portion is provided by tapered faces on one or both said faces of the .tongue. o 4. The latch tongue of any one of claims 1 to 3 wherein the serrations or teeth extend at least part way along both said eoe side faces of the tongue.
3. 5. The latch tongue of any one of claims 1 to 4 wherein eooo 0 said teeth or serrations extend along a substantial part of the S or each said side face.
4. 6. The latch tongue of any one of claims 1 to 5 wherein S" the teeth or serrations each have an inclined leading face and an inclined trailing face.
5. 7. The latch tongue of claim 6 wherein the angle of inclination of the leading and trailing faces is the same.
6. 8. The latch tongue of any one of claims 1 to 7 wherein the teeth or serrations extend the full width of the or each said side face.
7. 9. The latch tongue of any one of claims 1 to 8 wherein the teeth or serrations are hardened. YI~ b~ The latch tongue of any one of claims 1 to 9 wherein said serrations or teeth have a pitch of about 0.75 mm.
8. 11. The latch tongue as claimed in any one of the preceding claims wherein the teeth or serrations extend across the face in a direction perpendicular to the movement of the tongue.
9. 12. A latch tongue substantially as herein described with reference to the drawings.
10. 13. A lock including a latch tongue according to any one of claims 1 to 12. DATED this Thirtyfirst day of July, 1991. .WHITCO PTY LTD by their Patent Attorneys CULLEN CO. a4eAT f