US3544147A

US3544147A - Door latches

Info

Publication number: US3544147A
Authority: US
Inventors: Michael Joseph James
Original assignee: Micro and Precision Mouldings Cheltenham Ltd
Current assignee: Micro and Precision Mouldings Cheltenham Ltd
Priority date: 1968-05-03
Filing date: 1968-05-03
Publication date: 1970-12-01
Anticipated expiration: 1987-12-01

Description

Dec. 1,-1970 M. J. JAMES I 3,

I DOOR LATCHES I I Filed May a, 1968 3 sheet -sheet 1 INVENTOR ATTORNEYS Dec. 1, 1970 M. J. JAMES 4 3,544,147

DOOR LATCHES Filed May 3, 1968 k (5 Sheets-f-Sheet 2 I v. 4 32 3 35 l g 43 42 7 Hal INVENTOR Mama JOSEPH/194155- ATTORNEYS Dec. 1, 1970 M. J. JAMES 3, 7

' DOOR LATGHES Filed May 3, 1968 v 3 Sheets-Sheet 3 [T10 N] O III/I 2 Fla. 8.

H6 9 29 I 29 He l0.

INVENTOR Max/ 54 Joaaw (/fl/MSS' BY f ATTORNEYS U nited States Patent US. Cl. 292-169 9 Claims ABSTRACT OF THE DISCLOSURE A door latch having a latch bolt and an operating shaft adapted to be rotationally coupled to door handles respec tively mounted on opposite sides of the door and rotation of which produces inward movement of the bolt. When the latch is fitted the shaft is axially displaceable from one side of the door to a locking position in which rotation of the handle on the opposite side of the door is not prevented but is ineffective to release the latch, and retaining means are provided which comprise a resilient locking arm projecting from the inner end of the bolt for engagement with the shaft to retain the latter in the locking position.

This invention relates to door latches of the type having a slidable latch bolt which can be released by door handles respectively mounted on opposite sides of the door and interconnected by an operating shaft.

Door latches of this type normally have a square section shaft which engages both door handles, and the arrangement is commonly such that the door can be locked from one side so that it cannot be released by the handle on the opposite side which is thereby rendered ineffective. It has been proposed to effect locking by axial displacement of the operating shaft to a locking position in which rotation of said opposite side door handle is not prevented but is ineffective to release the latch. Such an arrangement is described in my US. Pat. No. 3,193,315, and the object of the present invention is to provide improved retaining means which engage and retain the shaft in the locking position.

According to the invention a door latch has a latch bolt, an operating shaft rotation of which produces inward movement of the bolt and which is adapted to be rotationally coupled to door handles respectively mounted on opposite sides of the door, when the latch is fitted the shaft being axially displaceable from one side of the door to a locking position in which rotation of the handle on the opposite side of the door is not prevented but is ineffective to release the latch, and retaining means comprising a resilient locking arm which projects from the inner end of the bolt for engagement with the shaft to retain the latter in the locking position.

The locking arm is moulded integrally with the main body of the bolt from a synthetic plastic material, for example from a material commonly known by the trade mark Delrin. The locking arm is conveniently one of two such arms which respectievly engage opposite sides of the shaft.

A return spring preferably urges the shaft to the unlocked position, the shaft being displaceable against that spring to the locking position in which it is retained by engagement of the, or each locking arm when two such arms are provided, locking arm with a suitable lateral notch or recess in the shaft. Thus release of the latch, by turning the operative door handle, frees the retaining means as the locking arms move with the latch bolt free of the shaft which is automatically spring returned to the unlocked position. A very satisfactory self-cancelling arrangement is also obtained, i.e. if the latch is locked with the door open then on subsequent door closure the retaining means will be freed and the locking cancelled.

Preferably the shaft is permanently coupled in the rotational sense to an internal release element or elements which it controls, axial displacement of the shaft serving to uncouple it from the opposite side door handle. In a preferred construction a single release element is employed with upper and lower apertures through which end portions of two locking arms project for engagement with the shaft when the bolt is in the latching position.

The shaft may have a position of square section to engage in the unlocked position a corresponding aperture in the opposite side door handle for rotation therewith, and a circular or otherwise reduced portion which engages and can turn freely within said aperture when the shaft is in the locking position. The shaft conveniently remains permanently coupled to the locked side door handle through and from which it may project to form, in effect, a pushbutton which is depressed to lock the latch. Alternatively the shaft may have a lateral projection of trigger-like form which projects from a boss of the inner door handle and can be pulled to the locking position by the index finger of a hand by which that door handle is grasped.

The invention will now be further described with reference to the accompanying drawings which illustrate, by way of example, a mortice door latch in accordance with the invention. In the drawings:

FIG. 1 is a view of the latch from the edge of a door in which it is fitted,

FIG. 2 is a sectional view on the line IIII in FIG. 1,

FIG. 3 is a sectional view on the line III-III in FIG. 2,

FIG. 4 is a view similar to FIG. 3 showing the various internal elements in the latch-released positions,

FIGS. 5 and 6 are respectively sectional views on the lines VV and VIVI in FIG. 3,

FIG. 7 is a sectional view on the line VII-VII in FIG. 2,

FIG. 8 is a sectional view again on the line III-III of a housing of the latch,

FIG. 9 is a similar view of an internal element of the latch, and

. FIG. 10 is an inner end view of the element shown in FIG. 9.

A moulded nylon tubular housing 1 is morticed into the door 2, the housing 1 having the usual outer end fixing flange 3. The outer end of the housing 1 is therein referred to as being the end adjacent the door edge into which it is morticed. The housing is closed at the inner end and at the flanged end has an opening 4 through which a slidably mounted slam bolt 5 projects when the latter is in the latching position as shown in FIGS. 1 to 3.

All the internal elements of the latch are included in a sub-assembly comprising a moulding 6 (shown in FIGS. 9 and 10) with an outer end abutment wall 7 disposed laterally of the housing and two side limbs 8 each formed with two locating projections 9 which on assembly snap into bores 10 in the wall of the housing 1 (see particularly FIG. 8) to locate all the internal elements in position. Towards the outer end the side limbs 8 of the yoke moulding 6 are moulded with aligned longitudinal slots 12 which are engaged by two projecting stub shafts 13 of a follower member 14 so that these slots define longitudinal sliding movement of the pivot axis of the member 14 within the housing. Towards the inner ends of the side limbs 8 they are formed with journal bores 15 for a moulded nylon release element 16 which has a squaresection through aperture 17 for reception of an operating shaft 18.

The release element 16 is of generally H section, with vertical side webs 19 which are joined by a central web 20 and lie close against the slide limbs 8 of the yoke moulding 6. Projected journal pegs 22 on the side webs 19 are of the same depth as the shaft aperture 17 but considerably wider, having only a partial bearing with said journal bores 15, which are of truncated circular section, to provide" only horizontal location of the release element 16. The side webs 19 of the element 16 have arcuate upper and

lower edge surfaces

23 and 24 respectively which bear on the upper and lower walls of the housing 1 to provide vertical location.

The bolt is moulded from Delrin with a solid outer end portion 25 providing the usual bevelled and radiused nose of the bolt, and an adjoining short hollow box section 26-beyond which the bolt is split to provide upper and lower inwardly projecting

limbs

27 and 28 respectively. The corners of the abutment wall 7 are cut away at 29 and the

limbs

27 and 28 of the 'bolt 5 are longitudinally slotted over an intermediate portion 30 and 32 respectively so that the limbs can fit over and around the abutment wall 7 with the cut-away corners 29 thereof providing clearance for inward withdrawal of the bolt 5 to the release position of FIG. 4. The

bolt limbs

27 and 28 are sufiiciently resilient to allow fitting of the bolt 5 over the abutment wall 7 of the yoke moulding 6 to complete the sub-assembly, with the outer end of a latch spring 33 housed within the box section 26 of the bolt and the inner end of the spring 33 engaging an annular spring 7 location groove 34 on the outer side of the abutment .wall 7.

At the outer end the follower member 14 is moulded with a flat face 35 which engages the inner surface of the abutment wall 7 to define the resting and latching position of the follower member which, also at the outenend, has upper and lower projecting ears 36 and 37 which respectively engage the slots in the intermediate portions 30 and 32 in the

bolt limbs

27 and 28. Engagement of the inner ends of these slots with the ears 36 and 37 also defines the resting and latching position of the bolt 5, the parts being urged to the resting position by the spring 33. The follower member 14 projects inwardly of the pivot axis thereof between the

boltlimbs

27 and 28 and has an elongated slot 38 which is disposed axially of the housing 1 in the resting position, as shown in FIG. 3. The release element 16 has two spaced outwardly projecting arms .39 joined across at the outer ends by an integral peg 40 of the circular section. The peg engages the slot 38 in the follower member 14, which fits with clearance between the have radially inwardly directed bulbous formations 43 and are disposed between the side webs 19 of the release element 16. In the latching position the bulbous formations 43 project through apertures provided by slots in the central web 20 above and below the shaft aperture 17 for engagement with the shaft '18. In FIG. 3 the shaft 18 is omitted to show the full projection of the bulbous formations 43 which, as later described, is utilised for locking purposes. With the shaft in latching position the locking arms engage a square section of the shaft and exert a centralising force thereof.

The operating shaft 18 is axially displaceable to a locking position for locking purposes, in which position it is retained by-engagement of the locking

arms

27 and 28 with notches 44 in the shaft. On withdrawal of the bolts 5 into the housing 1 by turning the inside door handle with the latch locked the ends of the

arms

27 and 28 move inwardly of the shaft 18 and in fact ride out of the slots in the release element, thus allowing the shaft 18 to be moved by a return spring 45 back to the unlocked position shown in the drawings.

The operating shaft 18 has a mid portion 46 of square cross-section which engages the shaft aperture 17 inthe release element 16 and a similarly shaped aperture in a drive plate 47 of an inner door handle 48. At the inner end 49 the shaft is of plain cylindrical form and projects through and from the door handle 48in the manner of a pushbutton, and this end canbe depressed manually to move the shaft 18 to the locking position, in which the notches 44 are engaged by the

bolt limbs

27 and 28 to retain the shaft. The length of the shaft portion 46 is such that in both positions of the latter it couples the innerdoor handle 48 to the release element 16 in the rotational sense.

At its outer end the shaft has a square section and portion 50 whichin the unlocked position engages a square aperture in the drive plate 51 of the outside door handle 52, so that the latter is also normally operative to release the latch. The return spring 45 is housed within the handle 52, and 'when the shaft 18 is moved to the locking position a portion 53 of the shaft of reduced crosssection intermediate the two square section portions engages within the aperture in the outer drive plate 51 and is freely rotatable therein. Thus on any attempt to open projecting arms 39, to provide a peg and slot connection between the release element 16 and the follower member 14.

When the release element 16 is turned by means of the operating shaft 18 it turns the follower member 14. The projecting ears 36 and 37 of the follower member 14 are reduced so that as the member 14 turns one of the ears 36, 37 slides along and engages the inner surface of the abutment wall 7 in a cam-like manner with attendant sliding movement of the pivot axis of the follower member 14 inwardlyof the housing 1, this sliding movement being accommodated by the peg and slot connection 40, 38. At the same time the other ear 36 or 37 of the follower member 14 engages the inner end of the slot in the corresponding bolt limb portion 30 or 32 to produce inward withdrawal movement of the bolt 5 to release the latch, with the elements as shown in FIG. 4.

The side webs 19 of the release element 16 extend inwardly of the operating shaft 18 with a tapering tail-like formation, the edges 42 of these webs engaging in a face to face mariner withthe housing 1 to limit the operative handle movement, as shown in FIG. 4. This arrangement is of sufficient strength for separate handle stops to be dispensed with, thus enabling the use of door furniture of an extremely simple and cheap nature which in particular is not handed.

The inner ends of the

bolt limbs

27 and 28 are considerably narrowed and extend centrally of the housing 1 in vertical view to provide locking arms moulded integrally withthe bolt. At the free inner ends these arms the door 2 from outside the handle 52 turns freely without releasing the latch and can be said to freewheel.

I claim:

1. A door latch having a latch bolt, an operating shaft axially displaceable between an unlocked and a locking position and rotation of which produces inward movement of the bolt, the shaft being adapted to be rotationally coupled to door handles respectively mounted on opposite sides-of the door so that axial displacement of the shaft from one side of the door to said locking position renders rotation of the handle on the opposite side of the door inefiective to release the latch, and retaining means comprising a resilient locking arm which projects from the inner end of the bolt for engagement with the shaft to retain the latter in the locking position, said locking arm and bolt comprising an integral moulding of a synthetic plastic material.

2. A door latch according to claim 1, wherein a return spring urges the shaft to the unlocked position, the shaft being displaceable against that spring to the locking position in which it is retained by engagement of the locking arm with a lateral notch or recess in the shaft.

3. A door latch according to claim 1, wherein the shaft is permanently coupeld in the rotational sense to an internal release element, rotation of the release element with the shaft producing inward movement of the bolt, and wherein said axial displacement of the shaft serves to uncouple it from said opposite side door handle.

4. A door latch according to claim 3, wherein said locking arm is one of two such arms of the integral release element with upper and lower apertures through which end portions of the two locking arms project, for engagement respectively with opposite sides of the shaft, when the bolt is in the latching position.

5. A door latch according to claim 1 wherein the locking arm is one of two such arms which respectively engage opposite sides of the shaft.

6. A door latch according to claim 4, wherein the locking arms when the bolt is in the latching position engage a square-section portion of the shaft and exert a centralising force thereon.

7. A door latch according to claim 1 wherein the shaft has a portion of square section to engage when in the unlocked position a corresponding aperture in the opposite side door handle for rotation therewith, and a circular or otherwise reduced portion which engages and can turn freely within said aperture when the shaft is in the locking position.

-8. A door latch according to claim 7, wherein the shaft remains permanently coupled to said one side door handle References Cited UNITED STATES PATENTS 2,185,863 1/1940 Miller 702l8 X 2,736,597 2/1956 Russell 292169.l9 X 3,125,366 3/1964- Cetrone 292169 3,193,315 7/1965 James 292169.2l X

MARVIN A. CHAMPION, Primary Examiner E. J. MCCARTHY, Assistant Examiner US. Cl. X.R. 29235 8