GB2235492A - Door latch - Google Patents

Abstract

A door latch comprising a housing (4) adapted to be secured in a recess in a door in conventional manner, having a latch member (10) guided for rectilinear movement, and being urged to an advanced or latched position by a spring. Slidable mounted in the housing, in a direction generally at right angles to the line of movement of the latch member is a locking member (40). With the latch member in a latched position, the locking member may be moved from a retractive position (fig 2) to an advanced position (fig 3) in which advanced position it prevents movement of the latch member to its retracted position. In a first embodiment the latch comprises a first operating member (14) operative from one side of the latch by the use of a latch handle to retract the locking member and to withdraw the latch member, and a second (16) operating member operative from the other side of the latch to withdraw the latch member, the locking member being retracted from said other side by the use of a key. In a second embodiment the latch comprises a first operating member which is operative to retract the bolt and to withdraw the latch member, said operating member being operative from one side of the latch by the use of a latch handle and from the other side of the latch by the use of a key. <IMAGE>

Description

Title: Door Latches Descriptlon of Invention Thls invention Is concerned with Improvements relating to door latches, particularly of the kind (herelnafter referred to as belng of the kind pecifled) where it is desired lo secure the latch against opening movement from ono aide, but not the other slde.

For example, In railway carriages, it may be desired to prevent members of the public grining access to the driver cab, but to allow free movement of the driver from the cab. It is in addition desirable that on the outside there be only one key hole for both locking and unlocking, whllst from the inside (the driver's side), It is desirable that freedom of movement of the driver from the cab should not be impaired.

Conventlonally, a door latch of the kind specified comprises a latch membermounted in a housing and which Is spring-urged to a forward (latchlng) position. Operable from each side of the housing, by means of a latch handle, is a mechanism to withdraw the latch member to allow the door to be opened Such e latch comprlses a key-operated lock which is operable from one side of the door to prevent the latch member being withdrawn from that side of the door, but not the other.

Conventionally, In the use of such a key-opersted lock, Insertion of tho key into the lock and rotation of the key in a locking mode forces a lever to be lifted against the ection of a spring which allows a slide to be moved forwardly against the action of a sprlng behind the latch member to prevent retractive movement of Lhe bolt.

In an unlocking mode the key lifts the lever, allowing the slide to retract under the action of the spring, the lever dropping down behind the slide.

It is one of the varlous objects of this invention to provide a door latch of the kind specified which Is simple in Its construction and reliable in its operation, Accordlng to this invention, therc is provided a door latch comprlslng: (a) a housing: (b) e latch member mounted In thc housing for movement between a forward position and 8 retracted position:: (c) a locking membor movable between an advanced position In which It prevent retroactive movement of the latch member and a withdrawn position; whereln retroactive movement ot the locking member le effected from one tide of the latch by a handle end from the other side of the latch by the use of a koy.

Thus the door latch may comprlse e fixed gate having a formation which co-operates wlth the key to ensure that only a correct key may be inserted Into the keyhole to move the slide member.

Preferably the gate Is provided wlth a fixed formation complementary to the key profile and which co-operates wlth the key during rotation thereof, conveniontly the fixed formation being such as to prevent rotational movement of the key, If the key has other than a correct operating formation.

Advantageously the formation is a circumferential formation, extending around the longitudinal axis about which the key, In use, is turned, ongaging with e suitably-shaped outer edge of the key.

In this manner, it may be ensured that only 8 correct key may operate the door latch, without the utilisation of undesirable moving parts, liable to failure or breakage.

Alternatively a conventional splndle key, having a cross-section of rectangular shape, may be utilised.

Preferably the locking member is movable equally between its advanced and retracted positions, I.e. Is not urged Into one or other position by sprlng means. However preferably means is provided to restrain movement of the locking member in said first and second position, such as by the use of an element (such as a ball) sprlng-urged and cngagable wlthin one of spaced recesses on the locking member. In this manner whilst the locking member may bo moved freely between said positions, some stability in said positions Is provided.

Advantageously movement of the locking member between oaid positions ls sliding movement generally In a direction at right angles to the direction of movement of the lolct member4 Preferably tiie leich comprises a first operating member which Is operative to withdraw the bolt end to withdrew the latch. Preferably the first operating member Is operative from said one slde of the latch by means of a handle, and may be operated from the other side of the latch by means of a key.

Where sald first porting member Is not operative from the other slde of The latch, preferably the latch comprlses 8 second operatIng member operative from said other side to withdraw the latch member.

Conveniently said second oeprating member is operated from sald other side by the use of s handlc.

Preferably the locking member is advanced from both sides of the latch by the use of a key.

According to this invention there Is also provided a door latch comprising a housing, a latch member mounted between 8 forward position and a retracted position, and a locking member movable between en advanced position In which It prevents retracted movement of the latch bolt and a withdrawn position, the latch comprlsing a first operating member operative from one slide of the latch by a handle lo retract the bolt end to wlthdraw the latch member, and a second operating member operative from the other side of the latch to withdraw the latch member, the bolt being retracted from said other slde by the use of o kcy.

Preferably the bolt is advanced from both sides of the latch by the use of a key According to this Invention there is also provlded a door latch comprising e housing, a latch member mounted for movement between a forward position and a retracted position, and a locking member movable between an advanced position In which it prevents retroactive movement of the latch member end a wlthdrawn position, the latch comprlslng a first operating member operative to retract the bolt and to withdraw ll.e latch mcmbor, said operating member being operative from one side of the latch by the use of n handle and from the other side of the latch by the use of a key.

The key may be In the form of a spindle key having a rectangular cross- section.

Preferebly separate key apertures are utlllsed to advance the locking member from the two sides of the latch.

There will now be given a detailed description, to be read wlth reference to the accompanying drawings, of two door latches which are the preferred embodiments of this Invention, which have been selected for the purposes of Illustrating bile Invention by way of example. In title accompanying drawings: FIGURE 1 Is an elevatlonal vlew of the door latch which 13 tiie first embodiment of the invention In its latched and unbolted conditIon: FIGURE 2 is a view of the door latch In unlatched and unbolted conditlonst FIGURE 3 is a vlew of tile door latch In Its latched and bolted condition:: FIGURE 4 Is a cross-sectional vlew, taken on the line 4-4 showing a key and a gate therefor: and FIGURE 5 Is a vlew, similar to Figure 1, showIng the door latch which Is the second embodiment of this invention.

The door latch which Is the preferred embodiment of tkls invention comprises a housing 4 adapted to be secured In e recess In a door In a conventional manner, having a front plate 6 adapted to be located flush wlth a forward edge of the door, sald front plate 6 belng provided wlth an aperture 8.

Slidably mounted In the housing wlth n forward portion at least extending Into the aperture 8, Is a latch member 10, sald latch member belng gulded for rectilinear movement, and being urged from B retracted position (shown In Figure 2) to a forward or latched condltlon (shown In Figures 1 and 3) by e spring 12.

The door latch comprises first and second operating members 14, 16 mounted for soparate rotatlon on a spindle 18, end each of which may be rotated ebout the axis of the splndle le by movement a respective latch handle secured on each side of the door. The operating member 14 is urged In on anti-clockwise direction agalnst a sLop 51 by a sprlng 50, whilst the operating member 16 is urged anti-clockwise against a stop 53 by a spring 52.

For the purpose of illustration, the operating member 14 is inlended to be that on the inner side, or area protected by the door latch, whilst the operating member 16 Is provided on the outcr side, or unprotected area.

With tho latch member free to move against the ectlon of the sprlng 12, the door rnay be unletched by rotary movement of zither of the latch handles, causing the operating members 14 or 16 to engage, by means of respective formations 14a, 16a, with a shoulder 13 on the latch member.

the housing is provided with a keyhole 20 defined by a keeper plate or gate 22 (see Figure 4), sald keeper plate tiavlng an Internal circumferential surface 24 which is of a particular shape, allowing an appropriate key 30 to be Inserted Into tho keyhole and rotated about the keyhole axis.

Sildably mounted in tiie housing, in a direction generally at right angles to the line of movement of the latch member, is a locking member in the form of 8 sllde member 40. Whon the latch member Is In a forward or latched position figure 3.) the Locking member 40 may be moved from 8 retracted position (shown in Figure 1) to an advanced position (shown in Figure 3) In which advanced position it prevents movement of the latch member to Its retracted position.Movement of the locking member 40 between sald posltions Is effected by the insertion of a key 30 Into the keyhole 22, and rotation of the key about the longitudinal axis, the key engaging wlth a detent 42 on the slide member 40.

The locking member 40 Is provlded wlth two spaced depresslons 44, Into elther of which a ball 46 may be located by a sprlng 48, provlding means to restraln movement of the locking member from said two positions.

Alien ttie locking member Is In its advanced position, shown In Flgure 3, retractive movement of the latch member Is prevenled. Rotation of the latch handle On the outer side of the door (that is, tile latch handle associated wlth the operating member 16) is ineffective therefore to wlthdraw the latch member, by virtue of the fact that It Is acting only on the latch member Itself, such movement belng prevented by the interposition of the locking member 40.

However, by virtue of an additional formation 14b provided on the operating member 14, which formation on rotation of sald operating member acts against a shoulder 41 of the locking member, to wittidraw the locking member 41 to its retracted position, the latch member may be retracted from the Inner side of the door by rotation of the operating member 14.

Thus, from the inner or protected slde of the door, an operative may secure himself against unauthorised intrusion by closing the latch and advancing the locking member 40 by the use of a key Inserted Into the key aperture 20. The operative may however open the door simply by rotation of the inside handle, to rotate the operating member 14.

Conversely from the outside the door may only be open when the locking member 40 Is In Its retracLed position, I.e. by the use of a key if It is In Its advanced position, together wlth rotation of the outside handle and rotation of the operating member 1G.

The door latch which is the second embodiment of the invention is illustrated In Figure 5, in which Ilke numerals, Increased by 100, have been used to Indicate like parts. Thugs the door latch which is the second embodiment of the inventloil comprises a housing 104 adapted to be secured in e recess in a door In a conventional manner, having a front plate 106 adapted to be located flush with a forward edge of the door, said front plate 106 being provided wlth an aperture 108.

As wlth the first embodiment, slldably mounted In the housing a latch member 110 Is provlded, urged to a forward position by a spring 112, and which may be prevented from retracting by a locking member 140 In the form of a slide.

Mounted on a splndle 118 Is a three-lobed operatIng member 114, urged by a spring 150 In en enti-clockwlse directlon (as vlewed in the drawing) Into engagement wlth the stop 151.

Located on the lower portion of Lhe housing 104 is a rectangularapertured splndle 120, into which a key may be inserted to rotate a second operating member 160 to cause Llie locking member 140 lo move from its withdrawn to Its advanced position, behind the latch member 110. However in the second embodiment, the operating member 160 is operable only from sald one side of the door latch (I.e. wlthln the protected area).

For unlocklng from the second side (unprotected area), the splndle 118 carries a third operating member 116, urged anti-clockwlse agalnst a stop 153 by a spring 152, and which on anti-clockwise rotation of the splndle 118 engages beneath a seating 141 of the locking member 140 lo move the locking member Into Its advanced position.

From the Inside (protected area), the operating member 14 can be rotated by the door handle Lo withdraw the locking member 140 and to retract the latch member 110, and the latch can be deadlocked from the inner side by the use of a key inserted Into the aperture 120 to rotate to the operating member 160 to advance the locking member 140.

Conversely on the outertide, the door may be opened by the use of e key Inserted Into the aperturo 118 to withdraw the looking member )a0 and lo retract tlie latch member 110, and deadlocked by rotatlon In the opposite directlon, the operating member 116 advancing the locking member 140.

Thus where the door latch is used In the door of 8 rallway cab, the driver'6 side belng the first slde, the driver may withdraw the latch member 110 by use of the handle, whether the locking member 140 is In Its advanced (lockIng) position or not. Should the driver wlsh to secure hlmself within the cab, he may move the locking member 140 to Its advanced position by rotatlon of the spindle 120 by the use of 8 key, nonetheless belng permItted to opon tho door simply by operation of the handle.

From the other side of the door, a guard (for example) may galn access to Ll)e cab by rotation of the splndle 118 In an anti-clockwise direction, or may lock the door against unauthorised openIng by rotation of the spindle llB In 8 clockwise direction, the operating member 316 moving the locking member 140 to Its advanced position.

The features disclosed in the foregoing descrlptlon, or the following claims, or the accompanying drawings, expressed In their specific forms or In terms of a means for performing the disclosed function, or 8 method or process for attaining the disclosed result, or a class or group of substances or composltlons, as appropriate3 may, separately or In any combination of such features, be uLlllsed for realising the Invention In diverse forms thereof.

Claims (1)

1. CLAIMS:

   1. A donor latch comprising! (a) a housing: (b) a latch member mounted In the housing for movement between a forward position and a retracted position: end (c) a locking member movable between an advanced position In which It prevents retractive movement of tho latch member end a wlthdrawn position; whoreln retractive movement of the locking member Is effected from one side of the latch by a handle and frond the other slde of the latch by the use of G key.

   2. A latch according to Claim 1 wherein the locking member is movable equally between Its advanced end retracted positions.

   3. A latch according to one of Claims 1 and 2 comprising means to restreln movement of the locking member In sald first and second positions.

   4. A latch according to Claim 3 whereln said means comprlses an element which Is spring-urged and engagable within one of spaced recesses on the locking member.

   5. A latch according to any one of the preceding claims wherein said locking member Is slideable between sald positions in a direction generally at rlght angles to the direction of movement of the latch member.

   6. A latch according to any one of the preceding claims comprlslng B first operating member operative to withdraw the bolt and to wIthdraw the latch.

   7. A latch according to Clalm 6 whereln said first operating member is operative from one side of the latch by means of a handle.

   8. A latch according to one of Claims 6 and 7 whereln the first operating member is operative from the other side of the latch by means of a key.

   9, A latch eccordlng to one of Claims 6 end 7 whereIn Bald fIrst opereting member is not operative from the other slde of the latch, the latch comprising a second operating member operative from acid other elde to withdraw the latch member.

   10. A latch according to Claim 9 whereln said second operating member is operated from weald other side by a handle.

   11. A latch according to any one of Claims 6 to )0 wherein the locking member Is advanced from both sides of the latch by a key.

   12. A door latch comprising a housing, a latch member mounted In the housing between s forward position end a retrected position, end a locking member movable between an advanced position In which it prevents retractive movement of the latch member and a withdrawn position3 the door latch comprising a first operating member which may be operated from one side of the latch by a handle to retract tiie bolt and to withdraw the latch member, and a second operating member operative from the other side of the latch to wlthdraw the latch member, the locking member belng retracted from said other side by the use of X key.

   13. A latch member according to Claim 12 wherein the locking member is advanced from both sldes of the latch by the use of a key.

   14. A door latch coniprtslng a housing, a latch member mounted In the houslng for movement between a forward position and retracted position. and a locking member movable between an advanced position In which It provento retractive movement of the latch member and a withdrawn position, comprlslng a first operating member operative to retract the locking momber and to withdraw the latch member, said first operating member belng operative from one side of tho latch L,y the use of a handle and from the other slde of the latch by the use of a key.

   13. A latch according to Claim 14 whereln the key is In the form of a spindi@ koy of rectangular cross-6ectlon, 16. A latch accordIng to one of Claims 14 ond 15 comprlalng soperato key apertures to advance the locking member from thc two sidon of tho latch.

   17. A door latch constructed and arranged substantially as hereinbefore descrIbed with reference (a) lo Figures 1 to 4, or (b) to Figure 5 of the accompanying drawings.

   18. Any novel feature of novel combination of features as hereinbefore described end/or as shown In the accompanying drawings.