AU3133801A

AU3133801A - A latch

Info

Publication number: AU3133801A
Application number: AU31338/01A
Authority: AU
Inventors: Robert Atkins; Daryl Kennedy
Original assignee: Allegion Australia Pty Ltd
Current assignee: Allegion Australia Pty Ltd
Priority date: 2000-04-26
Filing date: 2001-03-27
Publication date: 2001-11-01
Anticipated expiration: 2021-03-27
Also published as: AU777688B2

Description

S&FRef: 551389

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Actual Inventor(s): Address for Service: Gainsborough Hardware Industries Limited 190 Whitehorse Road Blackburn Victoria 3130 Australia Daryl Kennedy and Robert Atkins Spruson Ferguson St Martins Tower,Level 31 Market Street Sydney NSW 2000 Invention Title: A Latch t ASSOCIATED PROVISIONAL APPLICATION DETAILS [33] Country [31] Applic. No(s) AU PQ7105 [32] Application Date 26 Apr 2000 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5815c A Latch Field of the Invention The present invention relates to a latch for doors.

Background of the Invention The use of latches to retain doors closed but not locked is widespread, particularly for internal doors of residences or offices where locking security is not required. Latches have a lock bolt that is spring-biased to a latching position, in which the lock bolt protrudes from an edge face of the door. Turning a knob or lever associated with the latch retracts the lock bolt to its unlatching position in which the lock bolt is retracted into the door, for opening the door. The knob or lever is also spring-biased to a o position corresponding to the latching position of the lock bolt. This is typically S•horizontal for a lever handle.

*15 When the door is closed without turning a knob or lever, the lock bolt initially engages a strike plate attached to a door jamb which urges the lock bolt to retract into the door, into the unlatching position. The lock bolt then travels across the strike plate and enters a recess in the strike plate. This allows the lock bolt to return to its latching position to retain the door closed.

20 A known simple latch uses a single spring to bias the lock bolt and the knob or 0000 lever to the latching position. A spring of sufficient stiffness to return the knob or lever to the latching position often makes it difficult to close the door without also turning the 000 0knob or lever, which is inconvenient. A spring of sufficient stiffness to allow easy door closure without turning of the knob or lever often does not return a lever to the latching position and allows it to sag away from horizontal, which is unsightly.

Another known latch uses a single spring for biasing the lock bolt and a separate return mechanism in the door furniture to return the knob or lever to the latching position.

This complicates the production and assembly of the latch.

Another known latch utilizes a relatively stronger spring to return the knob or lever to prevent sag and a relatively weaker spring to bias the lock bolt to provide easy door closure. Known latches of this type require the knob or lever to be rotated through at least 750 to sufficiently retract the bolt for door opening.

It is the object of the present invention to substantially overcome or at least ameliorate this last prior art disadvantage.

[R:\LIBLL]08884.doc:KXT:VJP:AVS Summary of the Invention Accordingly, the present invention provides a latch including; an outer casing adapted to be fixedly mounted in a door; a carriage mounted in the casing and biased to slide in a first direction relative to the casing by a first spring; a lock bolt assembly mounted to the carriage and biased to slide in said first direction relative to the carriage by a second spring; and a cam pivotably mounted in the casing and adapted, upon pivoting movement, to slide the carriage relative to the casing in a second direction opposite the first direction; wherein the cam is shaped such that pivoting the cam through at most 450 moves the carriage sufficiently to slide the bolt between a latching position where the lock bolt assembly at least partially protrudes from the door and an unlatching position where the lock bolt assembly is retracted into the door.

~The first spring preferably has a greater spring constant than the second spring.

15 The outer casing is preferably elongated and has a first end and a second end. A back plate is mounted at, and the lock bolt protrudes from, the first end. The cam is desirably mounted in the casing adjacent the second end. The cam is preferably pivotable •ooo• about an axis substantially perpendicular to the direction of travel of the lock bolt assembly.

S• 20 In a preferred form, the carriage is a substantially U-shaped member having two spaced apart side walls joined by a closed end, the closed end extending towards said casing first end. The U-shaped member walls preferably include apertures for engagement with the cam for sliding the carriage upon movement of the cam.

A stop is preferably disposed between the walls of the U-shaped member and fixed relative to the casing, the first spring being disposed between the U-shaped member closed end and the stop in order to bias the carriage to slide in the first direction.

The lock bolt assembly preferably includes a lock bolt and a stem. The stem extends to and is slidably received by an aperture in the U-shaped member closed end.

The stem has a flanged end for engaging with the U-shaped member closed end such that the lock bolt is retractable with the carriage. The second spring is desirably disposed between the U-shaped member closed end and the lock bolt, in order to bias the bolt to slide in the first direction.

[R:\LBLL]08884.doc:KXT:VJP:AVS 3 Brief Description of the Drawings Preferred forms of the present invention will now be described by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 shows cross-sectional, partly assembled and assembled views of a latch according to a preferred embodiment of the present invention with the lock bolt and the cam in a latching position; Fig. 2 shows cross-sectional, partly assembled and assembled views of the latch of Fig. 1 with the lock bolt in an unlatching position and the cam in a latching position; and Fig. 3 shows cross-sectional, partly assembled and assembled views of the latch of Fig. 1 with the lock bolt and the cam in an unlatching position.

Detailed Description of the Preferred Embodiments Figs. 1 to 3 show a preferred embodiment of a latch 10 according to the present 0: 15 invention. The latch 10 includes an elongated outer casing 12 having a first end 14 and a Ssecond end 16. A back plate 18 is mounted at the first end 14 to enable the latch 10 to be fixedly mounted in a door (not shown) by screws (not shown) that pass through holes 19.

ooooo A carriage 20 is slidably mounted in the casing 12. The carriage 20 is U-shaped and has walls 26 and a closed end 28. The closed end 28 extends towards the casing first end 14.

A stop 30 is disposed between the walls 26 of the carriage and fixed relative to the housing 12 via stop mounting slots 32. A first spring 34 is disposed between the carriage closed end 28 and the stop 30 in order to bias the carriage 20 to slide in a first direction 36 relative to the casing 12.

A lock bolt assembly 40 is mounted to the carriage 20 and is also biased to slide relative to the carriage 20 in the first direction 36 by a second spring 50. The second spring 50 has a lesser spring constant than the first spring 34. The lock bolt assembly includes a lock bolt 42 and a stem 44 within the second spring 50. The stem 44 extends to, and is slidably received by, an aperture 21 formed in the carriage closed end 28. The stem 44 has a flanged end 46 for engaging with the carriage closed end 28. The second spring 50 is disposed between the carriage closed end 28 and the lock bolt 42, and engages a recess 48 formed in the lock bolt 42.

A cam 60 is pivotably mounted in the casing 12 via cam mounting holes 62 adjacent the casing second end 16. The cam is pivotable about an axis 64 which is substantially perpendicular to the direction 36 of travel of the carriage 20 and lock bolt [R:\LIBLL]08884.doc:KXT:VJP:AVS 42. The cam 16 includes cam surfaces 66 which engage engagement surfaces 25 formed by apertures 23 in the carriage walls 26. The casing 12 also includes elongated apertures 13 to enable the cam surfaces 66 and engagement surface 25 to protrude from the casing 12.

Figs 1 shows the lock 42 bolt in a latching position in which the lock bolt 42 protrudes from the first end 14 of the casing 12. When the latch 10 is fixedly mounted in a door (not shown), the lock bolt 42 protrudes from an edge face of the door in the latching position.

Figure 2(a) show the lock bolt 42 in an unlatching position which corresponds to the closing of a door (not shown) without turning of the latch knob or lever (not shown). During the closing of the door, the lock bolt 42 engages a strike plate which is attached to a door jamb (not shown). The strike plate urges the lock bolt 42 to retract into the casing 12 into the unlatching position which compresses the second spring 50. When the lock bolt 42 is aligned with a recess 72 formed in the strike plate "i 15 (which corresponds to a recess (not shown) in the door jamb), the second spring 50 urges the lock bolt 42 to the latching position (see Figs l(a) to retain the door closed.

Figs 3(a) show the lock bolt 42 retracted to its unlatching position by turning of the cam 60 by turning of an associated knob or lever (not shown). The cam surfaces 66 of the cam 60 are dimensioned such that pivoting movement of the cam S 20 about the axis 64 slides the carriage 20 relative to the casing 12 in a second direction 37, which is opposite to the first direction 36. The engagement surfaces 25 of the carriage and the cam surfaces 66 are shaped such that pivoting the cam 60 through angle 70, of *°o*9o only at most 450, moves the carriage 20 sufficiently to slide the lock bolt 42 to the unlatching position to enable the door to be opened. The elongated apertures 13 allow the cam surfaces 66 to protrude from the casing 12 when the cam 66 is pivoted. In the absence of torque to the cam 60, the first spring 34 biases the carriage 20 to slide in the first direction 36, which urges the cam 60 via engagement surfaces 25 to return to the position shown in Figs. 1(a) and return the knob or lever (not shown) to a latched position.

In the preferred embodiment shown, the cam 60 is shaped such that pivoting the cam 60 through at most 450 moves the carriage 20 sufficiently to slide the lock bolt 42 from the latching position to the unlatching position. In another embodiment (not shown), the cam 60 is profiled shaped such that it only needs to be pivoted through 300 to move the lock bolt 42 to its unlatching position. In either case, the latch is more [R:\LIBLL]08884.doc:KXT:VJP:AVS convenient to operate and represents a commercially significant improvement over those of the prior art.

Although preferred forms of the present invention have been described, it will be apparent to persons skilled in the art that modifications can be made to the preferred embodiment described above or that the invention can be embodied in other forms.

*°oooo *o* [R:\LIBLL]08884.doc:KXT:VJP:AVS

Claims

1. A latch including; an outer casing adapted to be fixedly mounted in a door; a carriage mounted in the casing and biased to slide in a first direction relative to the casing by a first spring; a lock bolt assembly mounted to the carriage and biased to slide in said first direction relative to the carriage by a second spring; and a cam pivotably mounted in the casing and adapted, upon pivoting movement, to slide the carriage relative to the casing in a second direction opposite the first direction; wherein the cam is shaped such that pivoting the cam through at most 450 moves the carriage sufficiently to slide the bolt between a latching position where the lock bolt assembly at least partially protrudes from the door and an unlatching position where the .lock bolt assembly is retracted into the door. 15

2. A latch as claimed in claim 1, wherein the first spring has a greater spring constant than the second spring.

3. A latch as claimed in claims 1 and 2, wherein the outer casing is •oooo elongated and has a first end and a second end, a back plate is mounted at, and the lock bolt assembly protrudes from, the first end. 20

4. A latch as claimed in claim 3, wherein the cam is mounted in the casing *adjacent the second end.

5. A latch as claimed in claims 3 or 4, wherein the cam is pivotable about an axis substantially perpendicular to the direction of travel of the lock bolt assembly.

6. A latch as claimed in claims 3, 4 or 5, wherein the carriage is a substantially U-shaped member having two spaced apart side walls joined by a closed end, the closed end extending towards said casing first end.

7. A latch as claimed in claim 6, wherein the U-shaped member walls include apertures for engagement with the cam for sliding the carriage upon movement of the cam.

8. A latch as claimed in claim 7, wherein a stop is disposed between the walls of the U-shaped member and fixed relative to the casing, the first spring being disposed between the U-shaped member closed end and the stop in order to bias the carriage to slide in the first direction.

9. A latch as claimed in claims 6, 7 or 8, wherein the lock bolt assembly includes a lock bolt and a stem, the stem extending to, and slidably received by, an [R:\LIBLL08884.doc:KXT:VJP:AVS aperture in the U-shaped member closed end and having a flanged end for engaging with the U-shaped member closed end such that the lock bolt is retractable with the carriage.

A latch as claimed in claim 9, wherein the second spring is disposed between the U-shaped member closed end and the lock bolt, in order to bias the lock bolt to slide in the first direction.

11. A latch substantially as hereinbefore described with reference to the accompanying drawings. Dated 26 March, 2001 Gainsborough Hardware Industries Limited Patent Attorneys for the Applicant/Nominated Person V "0 SPRUSON FERGUSON 0 0 o 00.0 C0. [R:\LIBLL]08884.doc:oon