A latch assembly for a door lock comprising, in combination:
- a base (3) including first and second sidewalls (32) and a main section (31) extending between the first and second sidewalls (32), with each of the first and second sidewalls (32) of the base (3) including a first sliding slot (321), a first guiding slot (323), and a second guiding slot (324), with the first guiding slot (323) of each of the first and second sidewalls (32) of the base (3) including a vertical section (327) and an inclined section (328), with the main section (31) adapted to be mounted to a door (1);
- a latch (41) movably received between the first and second sidewalls (32) of the base (3), with the latch (41) having a first pivotal portion (411) pivotably connected to the first and second sidewalls (32) of the base (3) and a second pivotal portion (412), with the latch (41) movable between a latching position outside the base (3) and an unlatching position inside the base (3);
- a link (42) including a first end (421) pivotably connected to the second pivotal portion (412) of the latch (41) and a second end (422), with the second end (422) of the link (42) slideably engaged with the first and second sidewalls (32) of the base (3), with movement of the link (42) along a first axis (X) causing movement of the latch (41) between the latching position and the unlatching position;
- a follower plate (5A) movable along the first axis (X), with the follower plate (5) including first and second sidewalls (52) spaced along a second axis (Y) perpendicular to the first axis (X) and an intermediate portion (51) extending between the first and second sidewalls (52) of the follower plate (5A), with each of the first and second sidewalls (52) of the follower plate (5A) including first and second ends (53, 54), with the first and second sidewalls (52) of the follower plate (5A) movably received between the first and second sidewalls (32) of the base (3), with a restraining slot (523A) formed in each of the first and second sidewalls (52) of the follower plate (5A) and located between the first and second ends (53, 54) of the first and second sidewalls (52) of the follower plate (5A), with the restraining slot (523A) of each of the first and second sidewalls (52) of the follower plate (5A) including upper and lower edges (523C, 523D) spaced along the first axis (X) and parallel, spaced, first and second lateral edges (523E, 523F) extending between the upper and lower edges (5234C, 523D), with the upper edge (523C) having an upper end connected to an upper end of the first lateral edge (523E), with the upper edge (523C) having a lower end connected to an upper end of the second lateral edge (523F), with the first and second lateral edges (523E, 523F) substantially parallel to the vertical sections (327) of the first guiding slots (323) of the base (3), with a first corner (523G) formed between a lower end of the second lateral edge (523F) and an end of the lower edge (523D), with a second corner (523H) formed between the upper end of the upper edge (523C) and the upper end of the first lateral edge (523E), with a third corner (5231) formed between a lower end of the first lateral edge (523E) and another end of the lower edge (523D), with each of the first and second sidewalls (52) of the follower plate (5A) further including an engaging notch (524A) and a slot (522), with the restraining slot (523A) located between the engaging notch (524A) and the intermediate portion (51) of the follower plate (5A) along a third axis (Z) perpendicular to the first and second axes (X, Y), with the slot (522) extending in a direction parallel to the first and second lateral edges (523E, 523F), with the first ends (53) of the first and second sidewalls (52) of the follower plate (5A) pivotably connected to the second end (422) of the link (42), with the first corners (523G) of the restraining slots (523A) of the follower plate (5A) aligned with the inclined sections (328) of the first guiding slots (323) of the base (3) when the latch (41) is in the latching position, with the second corners (523H) of the restraining slots (523A) of the follower plate (5A) aligned with distal ends of the vertical sections (327) of the first guiding slots (323) of the base (3) and with the engaging notches (524A) of the follower plate (5A) aligned with the second guiding slots (324) of the base (3) when the latch (41) is in the unlatching position;
- a linking rod (6) including a first end (61) slideably coupled with the slots (522) of the follower plate (5), with the linking rod (6) further including a second end (62) adapted to be connected to a door lock (2) mounted to the door (1) to move therewith;
- a safety plate (71A) mounted between the first and second sidewalls (52) of the follower plate (5A), with the safety plate (71A) including two sidewalls (712) spaced along the second axis (Y), with each of the two sidewalls (712) of the safety plate (71A) including first and second ends (713, 714), with the second end (714) of the two sidewalls (712) of the safety plate (71A) pivotably connected to the first end (61) of the linking rod (6), with each of the two sidewalls (712) of the safety plate (71A) further including an engaging notch (715) and a first hole (716),
- a pin (73) extending through the first guiding slots (523) of the base (3), the restraining slots (523A) of the follower plate (5A), and the first holes (716) of the safety plate (71A), with the safety plate (71A) pivotable relative to the follower plate (5A) about a pivot axis defined by the pin (73),
- a positioning pin (72) extending through the second guiding slots (324) of the base (3);
- a spring (74) attached between the positioning pin (72) and the pin (73) to bias the positioning pin (72) and the pin (73) towards each other,
- wherein with the latch (41) in the latching position, the engaging notches (715) of the safety plate (71A) are engaged with the positioning pin (72), the pin (73) is located in distal ends of the inclined sections (328) of the first guiding slots (323) of the base (3) and in the first corners (523G) of the restraining slots (523A) of the follower plate (5A), with the safety plate (71A) being stopped by the positioning pin (72) when the latch (41) is picked, preventing the latch (41) from moving from the latching position to the unlatching position by avoiding the follower plate (5A) from moving along the first axis (X),
- wherein with the latch (41) in the latching position and with the linking rod (6) moving along the first axis (X) away from the latch (41) through a travel substantially equal to a length of each of the slots (522) of the follower plate (5A), the engaging notches (715) of the safety plate (71A) disengage from the positioning pin (72), the pin (73) moves to an intersection of the vertical section (327) and the inclined slot (328) of each of the first guiding slots (323) of the base (3) and abuts the first lateral edge (523E) of each of the restraining slots (523A) of the follower plate (5A),
- wherein with the latch (41) in the latching position and with the linking rod (6) moving along the first axis (X) away from the latch (41) through a travel larger than the length of each of the slots (522) of the follower plate (5A), the latch (41) moves from the latching position to the unlatching position, the positioning pin (72) moves along the second guiding slots (324) of the base (3) under action of the spring (74) and engages with the engaging notches (524A) of the follower plate (5A) to retain the latch (41) in the unlatching position, the pin (73) is located in the distal ends of the vertical sections (327) of the first guiding slots (323) of the base (3) and in the second corners (523H) of the restraining slots (523A) of the follower plate (5A),
- wherein with the latch (41) in the unlatching position and with the lining rod (6) moving along the first axis (X) towards the latch (41) through a travel slightly smaller than the length of each of the slots (522) of the follower plate (5A), the first ends (713) of the two sidewalls (712) of the safety plate (71A) press against the positioning pin (72) to move the positioning pin (72) along the second guiding slots (324) of the base (3), disengaging the positioning pin (72) from the engaging notches (524A) of the follower plate (5A) and releasing the follower plate (5A), and the latch (41) moves from the unlatching position to the latching position.