US 3193315 A
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Description (OCR text may contain errors)
July 6, 1965 M. J. JAMES 3,193,315
DOOR LATCHES Filed May ll, 1962 2 Sheets-Sheet l 106,0 10a l /2 I3 4 /4 [5 J7 July 6, 1965 Y M. J. JAMES 3,193,315
DOOR LATCHES Filed Mayll, 1962 2 Sheets-Sheet 2 United States Patent Oliice lglS Patented July 6, 1965 3,193,315 DOR LTCHES Michael Joseph lames, Charlton Kings, Cheltenham, England, assignor to Micro and Precision Mouldings (Cheltenham) Limited, Cheltenham, England Filed May 11, 1962, Ser. No. 194,112 Claims priority, application Great Britain, May 16, 1961, 17 ,713/ 61 11 Claims. (Cl. 292-169) This invention relates to door latches .of the type having an operating shaft which is :turned by the door handles to release the latch for door opening.
Door latches of this type normally have a squared 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. Locking means for this purpose commonly act to lock the door handles against rotation, and the object of the invention is to provide an improved form of door latch which can be locked from one side of the door in a particularly simple and efficient manner.
According t the invention a door latch has an operating shaft which is adapted to be rotationally coupled to door handles respectively mounted on opposite sides of the door, the arrangement being such that the shaft in use can be axially displaced 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.
Preferably the shaft is permanently coupled in the rotational sense to an internal release element or elements which it controls, displacement of the shaft serving to uncouple it from the opposite side door handle. The shaft may have a portion of square section normally engaging a corresponding aperture in the opposite side door handle for rotation therewith, and a circular or otherwise reduced section 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 other or locking side door handle.
The shaft may project through and from that handle to form, in effect, a pushhuttcn which is depressed to lock the latch. Alternatively the shaft may have a lateral projection of trigger-like form which can be pulled to the locking position by the index finger of a hand by which the associated door handle is grasped.
A return spring preferably urges the shaft to the normal position and against which it is displaced to the locking position, and detent or index means may be provided which automatically come into operation when the shaft is displaced to the locking position and act to retain it in that position. The arrangement may be such that release of the latch by means of the locking side handle automatically frees the detent and allows the shaft .to return to its normal position under the influence of the return spring.
A self-cmcelling arrangement may be provided which acts to release the shaft and allows it to return to the normal position if the door is closed when the shaft is in the locking position. To this end .the latch memher, which is conveniently a slam bolt, may he arranged to engage the detent means during door closure to free the detent if the latter is operative at the commencement of door closure.
The invention will now be further described with reference to ythe accompanying drawings which illustrate, by way of example, two forms of mortice door latch of the slambolt type in accordance with the invention, and in which:
FIGURE 1 is a view of a portion of the corresponding edge `of a door with one of the mortice latches in position therein,
FIGURE 2 is a sectional view on the line II-Il in FIGURE 1 showing the associated door handles and the adjacent frame structure,
FIGURE 3 is a sectional View on the line III- III in FIGURE 2,
FIGURE 4 is a sectional view on the line IV-IV in FIGURE 3,
FIGURE 5 is a sectional view on the line V-V in FIGURE 3, and
FIGURE 6 is a view corresponding to that of FIG- URE 2 but of ythe other mortice latch.
In each case the latch has a generally tubular hous ing 1 morticed into the door 2, the housing 1 having the usual end fixing flange 3. A sliding bolt 4 is mounted in the housing 1 and urged by a latch return spring 5 to a position in which it projects from the housing 1 for latching engagement in the normal manner with a keeper plate 6 which is mounted ,on the associated door frame 7. In the drawings the bolt 5 is shown in the latched position relatively to the keeper 6.
An internal release element S of generally tubular form is mounted in bearings in the housing 1 for rotation about an aYis perpendicular to the plane :of the door 2. The holt 4 has an elongated cut-out aperture 9 through which the element 8 passes, and the latter has two relatively divergent projecting ears lil which respectively engage the inner edges of upper and lower apertures 12 in the bolt 4 when the element 8 is turned. The apertures 12 are formed in upper and lower limbs 13 of a stem portion of the bolt 4 above and below the cut-out aperture 9. Engagement of one of the ears lll by its outer surface 10a with the inner end of the corresponding aperture 12, on rotation of the element S, acts to displace the bolt 4 and release the latch.
The element 8 has a central through aperture 414 of square cross-section, and rotation of the element 8 is mainly limited by engagement of the rear end of the bolt 4 with a stop face 11 in the housing l. At the same time the rinner surface 10b of the other ear 16 engages either the upper or lower surface of the cut-out aperture 9. An operating shaft 15 which passes through the releasing element F has a mid portion 16 of square cross-section which engages both the aperture 14 and a similarly shaped aperture 17 in a drive plate 18 of an inner door handle 19.
In each case the shaft 15 is axially displaceable from a normal or unlocked position (as shown in FIGURE 6), in which both door handles are operative to release the latch, to a locking position (as shown in FIGURES 2 and 3) in which the outer door handle 20 is inoperative to krelease the latch and turns freely on the shaft 15. Movement of the shaft 15 to the locking position takes place against the action of a return spring 22 which `constantly urges the shaft 15 back to the normal or unlocked position.
In the latch of FIGURES 1 to 5 the shaft 15 is moved inwardly to the locking position (shown in full lines in FIGURE 2) by means of a lateral projection 23 of trigger-like form which is pulled to the locking position by the index linger of the hand by which the door handle 19 is grasped; in this case the return spring 22 is housed in the handle 19, and the projection 23 projects from the boss of the housing 19 through an axially directed slot 24. The shaft 1S has an outer end portion 25 of circular cross-section equivalent to the square portion 16 with the corners thereof rounded off.
The shaft 1S also passes through an aperture 26 inV a drive plate 27 of the outer handle 20 which is of similar shape to the aperture 14, and as shown in FIGURE 2 in the locking position the shaft portion is engaged within the aperture'Z. Thus the drive plate 27 and hence the handle 2) can turn freely without turning the `shaft 15. In the unlocked position of theV shaft 15, as shown in broken lines in FIGURE 2, the square .portion 16 of the shaft 15 engages all three apertures 14, 17 and 26 so that both handles 19 and 20 are operative to turn the shaft 15 and hence to release the latch.
Referring now to the latch of FIGURE 6, at the inner end the shaft 15 thereof is of plain cylindrical form and projects at 28 through and from the inner door handle 19 in the manner of a pushbutton. The inner end 28 can be depressed manually to move the shaft from the normal position shown in FIGURE 6 to the locking position against the spring 22. Again the length of the mid portion 16 of the shaft 15 is such that in both positions of the latter it permanently couples the inner door handle 19 to the internal Areleasing element 8 in the rotational sense.
At the outer end the shaft 15 of FIGURE 6 has a square end portion 29 which inthe normal position er1- gages the squared aperture 26 in the drive plate 27 of the outer door handle 20, so that as shown the handle 26 is again normally operative to release the latch. In
this 'case the return spring 2-2 is housed in the handle V20 so that the shaft 15 is urged inwardly to the normal posiy tion, and when the shaft 15 is moved tothe locked posi- Ation a rounded portion of the shaft intermediate the square portions 16 and 29 engages the aperture 26 in the outer drive plate 27 and is freely rotatable therein in the same manner as the shaft portion 25 of the arrangement of FIGURES 1 to 5. Thus, on any attempt to open the door from outside the door handle 20 in both cases turnsrfreely without releasing the latch and can be said to freewheeL A detent bolt 32 aligned with the latch bolt 4 is mounted in the housing 1 on the side of the shaft 15 remote from the edge of the door 2, and the bolt 32 is urged by a detent spring 33 into engagement with the yshaft 15. When the shaft 15 is moved to the locking position (as shown in FIGURE 2) the detent boltV 32 is aligned with a lateral notch 34-V in the mid portion'16 of the shaft and engages the notch 34 to retain the Vshaft 15 in the locking position when the latter is moved thereto, either by pulling on the projection 23 of FIGURE 2 or depressing the end 28 of FIGURE 6.
The notch 34 has an arcuate base which terminates at eachend at the normal periphery ofthe shaft 15. Thus release -of the latch by the inner door handle 19, when the door is locked and the bolt 32 engaged in the notch '34, has an initial smooth cammin-g action on the bolt 32 which yis displaced inwardly by the base of the notch 34 towardsaposition in which the shaft 15 is free to return 4to the normal position under the action of the return spring r22. Final displacement of the detent bolt 32 to this position results from engagement of a shoulder 35 on the plunger 34 by the rear face 36 of the bolt 4 as the latter is moved inwardlyto the unlatched position. At the inner 4end the bolt 4 has an aperture 37 from the face 36 intov the cut-out aperture 9 and through which the bolt 32 projects'.
A self-cancelling arrangement is providedwhich prevents the -door from being closed and latched with the shaft 15 retained in the locking position. To this end the Ylatch bolt 4, during latching, engages and displaces the detent bolt `34pm the manner just described if the bolt 32 Vis in the shaft retaining position when the door is closed. As described, such displacement of the detent jbolt 32 is suiiicient to free the detent and allow the `shaft 15 t0 return to the normal position.
In addition to the normal leading edgebevel 38 which is of curved form and engages the keeper plate 6 during door closure to move the bolt 4 inwardly in the usual manner, the outer end of the bolt 4 has a trailing bevel 39 which normally engages the keeper 6 to hold the door closed. The bevel 39 is, as shown in FIGURES 2 and 6, relatively steep and acts so that for all normal purposes the door is firmly latched but can, in the event of an emergency, be'opened from outside by the application of a sufficient door opening force.
The necessary door opening force depends upon the frictional Vcharacteristics of the material from which the bolt 4 and the keeper `6 are manufactured and the angle of the bevel 39, and these are normally so related that an opening force of the order of 100 lbs. is necessary to force the door; this is chosen as a force which would not normally be applied accidentally-but which can easily be applied by a single person if necessary. Latches of the type described are commonly'used with bathrooms and the like so that they can be locked from inside, and it is with suchrooms that it is at -times necessary to gain access in an emergency when the door is locked. The illustrated bolt formation provides a novel arrangement in which entrance Vcan be gained in an emergency without damaging the door or latch structure and without the use of tools. With previous forms of latches'a locked door can only be opened in an emergency either by applying a damaging and excessive opening force and/or by the use of tools.
I claim: Y
1. A door latch comprising `a housing, a latch bolt slidablyV mounted in said housing, a 4latch spring urging the bolt to the latching position in which it projects from the louter end :of said housing, anV operating shaft adapted to be rotationally coupled to door handles respectively mounted on opposite sides of the door, .said bolt being apertured to allow passage of said shaft laterally therethrough and the shaft being axially disp'laceable fromV one side yof the door from a position -in which rotation of the handles withdraws the bolt from the latching position to release ythe latch to a locking position in which the shaft is inoperative lon turning the handle on the other side of the door to release the latch, and detent means which are mounted in the bolt on the inner side of the shaft and automatically come into operation when the shaft is disp-laced to Vthe locking position and act to retain the shaft in that position, the detent means being automatically disengaged from the shaft on inward movement with the latch bolt from the latching position.
2. A door latch according to claim 1, wherein the shaft is'permanently coupled in the rotational sense to an internal release element or elementswihich it controls, displacement of the Ashaft t-o the locking posit-ion serving to uncouple the shaft from the opposite side door handle.
3. A door latch laccording to claim 2, wherein the shaft has a portion lof square cross-section normally engaging la corresponding aperture in the oppositeside door handle for rotation therewith Iand a reduced section which engages and can `turn freely 'within said aperture when the shaft is in the locking position. Y
4. A'door latch according to claim 3, wherein the shaft remains permanently coupled to the locking side door handle.
`5. A door latch according to claim 4, wherein the shaft has a lateral projection by which i-t can be moved to the locking position.
16. A door latch .according to claim'S, wherein the Ilateral projection is of trigger-like for-m and when fitted projects between' the lock-ing side door handle and the door. Y
l7. A Ido-or latch assembly comprising a housing, -a ilatch ybol-t slidably mounted in said housing, a latch `spring urging the bolt to the latching position in which it projects from ,the router end of said housing, an operating shaft, iirst and seconddo-or handles respectively mounted on opposite sides of the door and from and through the first of which said `shaft projectsy in the manner of a pushbutton, a return spring urging said shaft to the projecting position, and 4.a release element mounted on the shaft and rotatable therewith to engage and displace said bolt from the latching posit-ion, said bolt being -arpert-ured to Iallow passage of said shaft laterally therethrough and the shaft eing axially displaceable against said return spring from n position in which the shaft is rot-ationally coupled to both Ihandles to .a locking position in which the shaft is not rotationally coupled to the second handle and hence lis inoperative to release the latch on turning of said second handle, and 'detent means which are mounted in the bolt on the inner side of the shaft `and automatically come into operation when the shaft is displaced .to the Alocking position and act to retain the shaft in that position, and are automatically released on inward movement of the bolt from said latching position.
8. A door latch accor-ding to claim 7, wherein the detent means comprise a detent bolt which is aligned with and engages a notch in the shaft when the latter is in the locking position.
9. A door latch according to claim 7, wherein the latch member is a slam bolt which is formed on the trailing side with 'a steep ibevel which, when latched, enables a door with which the latch is used lto :be opened in an emergency by the application of a non-damaging opening force to the door.
16. A ldoor latch comprising a housing, a latch bol-t slida'bly mounted in said housing, a latch spring urging the bolt to the latehing position in which it projects from said housing, an operating shaft rotationally coupled to door handles respectively mounted on the inner and outer sides of ,the door, said bolt being cut away to allow passage of said shaft laterally therethrough 'and ythe :shaft being accessible from said inner side of the door, and being axially -displaceable from a normal position in which rotation of either lhandle withdraws lthe bol-t from the latching position to release the latch .to la looking position iin which the shaft .is inoperative -to release the latch from said outer `side of `the door, a return spring urging the shaft `to said normal position, .a release element mounted on lsaid shalt with-in the cutaway section of said bolt and adapted to engage the bolt on rotation of said shaft -to withdraw the bolt against said latch spring, and a detent -bolt mounted in the Ilatch bolt on lthe inner side of 'the shaft and which on displacement of the .shaft to the locking position is aligned Awith .and engages .a notch in the shaft :and acts to retain the shat in that position, whereby withdrawal .of the bolt, either by rotation of said inner side handle or on door closure, should the latter be fopen, will cause movement lof the detent bolt with the latch boit to free the shaft which then returns to the normal position under the return spring force.
11. A door llatch according to cla-im 1d, wherein said shaft has a multi-sided cross-section for engagement With said door handles and said release element `and a reduced moss-section which engages and allows the outer side door handle to turn freely When the shaft is in the locking position; the housing latch bolt, latch spring, release element and idetent bolt forming -a single assembly which can be fitted complete yas such from the adjacent edge of the door.
References Cited by the Examiner UNITED STATES PATENTS 2,497,328 =2/50 Snr-ith et al 292-169 `2,602,318 7/ 52 Belausteguigoitia 70-2'17 2,645,516 7/ 5 3 Robertson 292-2 X 3,026,136 A3/62 -Russell et al 292-169 X FOREIGN PATENTS 7,045 1893 Great Britain. 8,086 1908 Great Britain.
M. HENSO'N WOOD, IR., Prmm'y Examiner.