Patent GB-776466-A (GB)
Title: Improvements in latches for doors
IPC: E05B65/22
Filed: 1954-12-13
Abstract: 776,466. Door latches. THORNE, H. Aug. 25, 1955 [Dec. 13, 1954], No. 35987/54. Class 44. A door latch has a spring-loaded latch bolt retractable by handle at each side of the door (e.g. a vehicle door) wherein locking means are provided adapted to be actuated to the locking position by the operation of one handle in a reverse direction and to be released by operation of the other handle. In the construction shown in Fig. 1 (Complete Specification), the outer handle can be locked by its reverse rotation, release being effected by normal movement of the inner handle. A sliding latch bolt 1 is retracted by the inner handle through a lever 9 and the outer handle through a lever 5, both of the levers engaging projections (not shown) on the latch bolt. Pivotally mounted above the latch bolt is a locking detent 3 which is biased by a spring 4 which also acts on the lever 5. The detent 3 has an opening 7 through which a pin 8 on the lever 9 enters to engage a cam surface hump 10. As shown, the detent is in the locking position in which it is engaged behind the lever 5 and so prevents movement of the outer handle to withdraw the latch bolt. Movement of the inner handle to the left as shown causes the pin 8 to engage the cam hump 10 and to raise the detent so that the lever 5 is urged by the pressure of the spring 4 underneath the detent which is its normal position. The latch bolt can then be withdrawn by either handle. The lever 5 can also be moved so that the detent can drop behind it by a projection 11 on the inner handle lever 9 when the inner handle is moved in the reverse direction. In a modified construction shown in Fig. 2 (Complete Specification), the inner handle is locked by its reverse movement and its release is effected by normal movement of the outer handle. As shown, a sliding latch bolt 19 can be retracted either by the outer handle through a lever 23 or by an inner handle through a lever 15. Both levers engaging projections on the latch bolt. A locking detent 12 is pivotally mounted above the latch bolt and it is biased by a spring 17. The detent is provided with a cam surface 16 which is engaged by a pin 14 on the lever 15 so that when the inner handle is moved in the reverse direction to that which retracts the latch bolt against the pressure of a spring 22, the pin 14 engages the cam surface and rotates the detent clockwise until the pin is engaged by a hook 13 on the detent. The inner handle is then locked. The release of the inner handle by the outer handle takes place when the outer handle is rotated to retract the latch bolt. The latch bolt carries a projection 20 which underlies a cam surface 21 on the detent and which rotates the detent clockwise until the hook 13 becomes disengaged from the pin 14. The inner handle can also be locked by reverse rotation of the outer handle since a projection 24 is provided on the detent 12 and this is engaged by the lever 23 to rotate the detent clockwise when the outer handle is reversely rotated. The clockwise rotation of the detent causes the pin 14 to become engaged with the hook 13 as previously. Fig. 1 (Provisional Specification) shows a latch in which the outer handle is locked by reverse movement of either the inner or the outer handle, release being effected by normal movement of the inner handle. As shown, a sliding latch bolt d is retracted by the inner handle a by direct engagement of a lug w<SP>1</SP> on the lath of the bolt. The outer handle b retracts the bolt by means of a lever h which acts on a lug W<SP>2</SP> on the bolt lath. A locking detent c is pivotally mounted above the latch bolt and a cam surface c<SP>2</SP> on the detent is engaged by a pin y on the inner handle a so that when the handle is moved to retract the latch bolt the detent is lifted by engagement of the cam surface and pin. The end c<SP>1</SP> of the detent normally engages a notch in the end of the lever h and when the outer handle is turned to retract the latch bolt the detent is lifted from the notch since when the outer handle is so turned, the inner handle is also moved through a spur f which engages the lever h. When the inner handle is moved in the reverse direction (to the right as shown) the lever h is moved from beneath the detent by the spur f and the end c<SP>1</SP> drops behind the lever h and prevents retracting movement on the outer handle. The detent also drops behind the lever h when the outer handle is turned in the reverse direction. The detent is restored to its normal position with its end c<SP>1</SP> in the notch in the lever h by normal movement (to the left as shown) of the inner handle a. In the construction shown in Fig. 4 (Provisional Specification) the inner handle a can be locked by a reverse movement and released by a normal movement of the outer handle b and the outer handle b can be locked by a reverse movement and released by a normal movement of the inner handle a. The inner handle a is coupled through a spring-loaded positioning lever plate a<SP>1</SP> and a link o to a boltoperating slider f, the slider being slotted for engagement with a fixed guide stud g which also engages a slot d in the latch bolt. The bolt is provided with a stud w which engages in the slot f<SP>1</SP> in the slider so that there is a lost-motion connection between the latch bolt and the slider. The outer handle b retracts the latch bolt by means of a lever h which engages a pin w<SP>2</SP> on the bolt. A locking detent c is pivotally mounted underneath the latch bolt and when the inner handle a is moved in the reverse direction to that which retracts the latch bolt the slider f is moved independently of the bolt and a notched spur e on the slider becomes engaged with a hooked arm c<SP>1</SP> of the detent so that the inner handle becomes locked. Release of the handle a is effected by turning the handle b to retract the bolt, this causing a spur j on the bolt to engage an arm c<SP>2</SP> of the detent and to rotate the detent so that the arm c<SP>1</SP> becomes disengaged from the spur e. The outer handle becomes locked when it is moved in the reverse direction by the engagement of an arm c<SP>3</SP> on the detent with a projection h<SP>l</SP> on the lever h under the pressure of a spring s<SP>2</SP>. Release of the outer handle is effected by normal latch bolt retracting movement of the inner handle which causes the spur j to rotate the detent through the arm c<SP>2</SP>. In a modification of this construction the detent is provided with two arms only, the arm c<SP>2</SP> being omitted and to release the inner handle the detent is provided with a cam surface which is engaged by the projection on the lever h. When the outer handle is locked it is released by a slight reverse movement of the inner handle a. This slight reverse movement of the inner handle a causes a cam surface on the spur e to become engaged with a cam surface on the arm c<SP>1</SP> of the detent which rotates the detent so that the arm c<SP>1</SP> becomes disengaged from the projection h<SP>1</SP> on the lever h.