US3913961A

US3913961A - Safety latch

Info

Publication number: US3913961A
Application number: US436099A
Authority: US
Inventors: Branko Markovitch
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-01-24
Filing date: 1974-05-10
Publication date: 1975-10-21
Anticipated expiration: 1992-10-21
Also published as: GB1486665A; US3924885A

Abstract

Safety latch has a base securable to a door and a latchplate securable to a doorframe, or vice versa. An intermediate link is pivoted to the base and a latch link is slidably mounted on the intermediate link so the intermediate link can interengage its nose with the latchplate to permit the door to swing open only a limited extent.

Description

Oct. 21, 1975 [54 LATCH IMPROVEMENTS [76] Inventor: Thomas J. Dugan, 2501 El Camino Real, #206, San Clemente, Calif. 92672 Filed: May 10, 1974 Appl. No.: 469,025

Primary Examiner-Richard E. Moore Attorney, Agent. or Firm-Boniard I Brown [5 7 ABSTRACT A pick-proof latch for a closure, such as a door, having a keeper plate for attachment to the closure frame or jamb and a striker plate hinged to the keeper plate for movement to a locked closure-engaging position wherein the striker plate is located in the path of opening movement of the closure to lock the latter in closed position. The latch is released to open the closure by first raising the striker plate and then swinging the latter plate to a closure-releasing position. The keeper plate projects beyond the lower end of the striker plate in the locked closure-engaging position of the latter plate and has a tab to provide an abutment, extending between the keeper plate and the closure to prevent raising of the striker plate to release the latch by insertion of a card between the closure and its jamb or frame.

4 Claims, 6 Drawing Figures 1 LATCH IMPROVEMENTS RELATED APPLICATIONS The present invention represents improvements Field of the Invention This invention relates generally to closure latches of the kind commonly referred to as night latches. The invention relates more particularly to a pickproof latch of the kind having a hinged striker plate which is movable to locked position in the opening movement of the closure and is released to open the closure by raising the plate to release the latter for swinging to a closure-releasing position. Discussion of the Prior Art Pat. No. 2,794,665 discloses a door night latch which is in common use in homes, hotels, motels and the like. This night latch has a striker plate hinged to a keeper plate which is secured to the door jamb. The striker plate is swingable between a door-engaging position and a door-releasing position relative to the keeper plate. When in its door-engaging position, the striker plate is located in the path of opening movement of the door and is movable downwardly along the hinge axis to a locked position wherein the striker plate is locked against swinging to its door-releasing position by interengagement of locking lugs on the striker and keeper plates to lock the door against,

opening. The latch is released to open the door by first raising the striker plate to disengage the locking lugs and then swinging the plate to its door-releasing position.

The existing latches of this kind suffer from one disadvantage which this invention overcomes. The disadvantage referred to resides in the fact that the latch can be opened from the outside by inserting a thin card or blade between the door and jamb below the striker plate and raising the plate to its unlocked position by sliding the card upwardly. The latch can be picked or unlocked in this way for the reason that in the locked position of the striker plate, its lower end extends below the lower end of the keeper plate such that the striker plate may be engaged and raised to unlocked position by inserting a card below the plate, as described.

SUMMARY OF THE INVENTION The present invention provides improvements on the invention of my Pat. No. 3,810,667, which relates to a pick-proof latch whose striker plate cannot be raised to unlocked position by insertion of a card between the door and jamb. To this end, the latch plates are so sized and pivotally connected that in the locking position of the striker plate, its lower end does not project below the keeper plate, the keeper plate projecting below the striker plate in the locking position of the striker plate. Accordingly, when a card is inserted between the door and jamb and moved upwardly, the card will engage the lower end of the keeper plate rather than the striker plate and thus will be prevented from raising the striker plate to unlocked position. According to another feature of the invention, the lower end of the keeper plate has a tab to provide an abutment or stop to extend between the outer side of the keeper plate and the door in the event the gap between the keeper plate and door is wider than the keeper plate thickness. This tab is bendable, as by means of a tool, to be adjustable in its extension distance from the keeper plate to extend sufficiently across the gap between the keeper plate and the door to prevent sliding a card or similar thin element upwardly between the door and keeper plate into contact with the striker plate and thereby raising the latter to unlocked position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a present latch in unlatched or closure-releasing position;

FIG. 2 is a view looking in the direction of the arrows 2-2 in FIG. 1;

FIG. 3 illustrates the latch in latched position;

FIG. 4 is a view looking in the direction of the arrows 4-4 in FIG. 3;

FIG. 5 is a section taken on line 5-5 in FIG. 4; and

FIG. 6 is a fragmentary view, illustrating the adjustment by bending of the tab according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The closure or night latch 10 illustrated in the drawings has a keeper plate 12 and a striker plate 14 arranged edge to edge. The latch plates are joined along their adjacent edges by hinge means 16 for swinging of the striker plate relative to the keeper plate on the hinge axis 18 and endwise movement of the striker plate relative to the keeper plate along the axis. The keeper plate 12 is secured by screws 20 to the jamb 22 of an opening containing a hinged closure 24, such as a door. The side of the keeper plate seating against the jamb is referred to as its rear side. The opposite side of the keeper plate is referred to as its front or outer side.

Hinge means 16 comprise a number, in this instance three, of generally cylindrical bearings 26 spaced along the inner edge of the keeper plate 12 and rotatably receiving pivot shafts 28along the inner edge of the striker plate 14. Pivot shafts 28 are formed by pinching openings 30 through the striker plate adjacent its edge so as to leave narrow shaft-like sections of the plate along the inner edges of the openings.

' The bearings 26 are formed by slotting the inner edge of the keeper plate to form tongues along the edge and then curling these tongues through the striker plate openings 30 and about the pivot shafts 28 into cylindrical bearing shapes which surround the shafts. The axial dimension of the bearings 26 is less than the corresponding dimension of the striker plate openings 30 to provide the striker plate 14 with limited freedom of endwise movement relative to the keeper plate 12.

Hinge means 16 support the striker plate 14 for swinging relative to the keeper plate 12 between a closure-releasing position (FIGS. 1 and 2) and a closure-engaging position (FIGS. 3-5). When in closure-releasing position, the striker plate is located either generally coplanar with or rearwardly of the keeper plate such that the striker plate has no projection beyond the outer side of the keeper plate which would obstruct swinging of the closure 24 between open and closed position. The striker plate of the illustrated latch when in closure-releasing position is located at the rear side of the keeper plate, against the inner edge of the jamb 22. When in closure-engaging position, the striker plate is located at the front or outer side of the keeper plate and generally normal to the keeper plate. In this position, the striker plate overlaps the adjacent edge of the closure 24 when the latter is closed and is thus situated in the path of opening movement of the closure.

Keeper plate 12 and striker plate 14 have coacting latch means 32 for releasably locking the striker plate against swinging from its closure-engaging position to its closure-releasing position and thereby locking the closure 24 in closed position. Latch means 32 comprise slots 34 in the ends of the hinge bearings 26 for receiving the upper edges of the striker plate openings 30 when the striker plate occupies its closure engaging position. Latch means 32 comprise addi' tional slots 36 in the bearing ends for receiving the upper edges of the striker plate openings when the striker plate occupies its closure-releasing position to lock the striker plate from swinging from this position to its closure-engaging position. Latch means 32 are disengaged to permit swinging of the striker plate 14 between the closure engaging and releasing positions by raising the plate endwise to retract the upper edges of the plate openings 30 from the

hinge bearing slots

34 or 36, as the case may be.

It is now evident that the striker plate 14 has a locked closure-engaging position and an unlocked or released closure-engaging position. In its locked closure-engaging position, the striker plate is located in its closure-engaging position with the latch means 32 engaged to lock the plate against swinging to its closure-releasing position. In its unlocked or released closure-engaging position, the striker plate is located in its closure-engaging position with the latch means disengaged to permit swinging of the plate to its closure-engaging position. The striker plate is movable endwise between these locked and released positions.

It is significant to note here that the illustrated latch is reversible end for end and the hinge bearings 26 are slotted at each end to permit installation of the latch on either right or left-hand opening closure or door structures. The striker plate 14, when in its unlocked or released closure-engaging position, is centered endwise relative to the keeper plate 12. The striker plate is movable in each endwise direction from this centered unlocked position to a locked closure-engaging position. In both the right and lefthand closure installations, the striker plate 14 is raised to disengage the latch means 32 and lowered to engage the latch means so that gravity acts to retain the latch means in engagement. At each end of the striker plate is a hole 38 for receiving a plastic button 40 having head and shank portions, as shown. This button is force-fitted in the lower hole 38 in both the right and left-hand installations and its head portion is dimensioned to engage the lower hinge bearing 26 in such a way as to prevent raising of the striker plate to its upper locked position.

The present invention is concerned with latch improvements which assist in rendering the latch immume to being picked or unlocked by means of a card or the like inserted between the closure 24 and jamb 22. With the striker plate 14 in its lower locked closure engaging position, its lower edge does not project below the lower edge of the keeper plate 12. In the latch described, the striker plate is made sufficiently shorter than the keeper plate that in each locking position of the striker plate, its lower edge is located a distance above the lower edge of the keeper plate. Under these conditions, assuming the keeper plate to be of sufficient thickness to virtually fill or bridge the gap between the jamb 22 and closure 24, a card 42 inserted into the gap below the latch, in the manner shown in FIG. 5, and slid upwardly through the gap will encounter the lower edge of the keeper plate rather than the striker plate. The keeper plate will thus prevent the striker plate from being raised to its unlocked position by the card to open the closure.

The present invention provides an improved solution to the problem arising in those cases when the gap between the jamb 22 and closure 24 is substantially wider than the thickness of the keeper plate 12, and where it would be possible to slide the card 42 upwardly between the door and keeper plate into contact with the striker plate 14 and raise the latter to unlocked position to open the closure. According to the invention, this possibility is prevented by providing tabs 44 at the ends of the keeper plate. Tab 44 is bendable to the desired degree, as illustrated, as by bending by pliers or other appropriate tool as illustrated in FIG. 6 to bridge the gap between the keeper plate and door, at a position below the lower edge of the striker plate, at least in the unlocking position of the plate and, preferably, in the locking position of the plate, as shown. When thus adjusted, the tab provides an abutment which will prevent raising of the striker plate 14 with a card 42, despite a gap between the keeper plate and door.

What is claimed is:

1. A latch for a swinging closure such as a door, having a vertical edge which faces an upright jamb in closed position comprising:

a keeper plate and a striker plate arranged edge to edge,

said keeper plate having a rear side for seating against said jamb and an opposite outer side,

hinge means pivotally connecting said plates along their adjacent edges for swinging of said striker plate relative to said keeper plate on the hinge axis and endwise movement of said striker plate relative to said keeper plate along the hinge axis,

means for securing said keeper plate to the door jamb with said rear side seating against the jamb and said hinge axis vertical, whereby said plates have edges which are lower edges and opposite edges which are upper edges when the latch is secured to the jamb,

said striker plate being swingable beyond said outer side of said keeper plate to a closure-engaging position relative to said keeper plate and toward said rear side of said keeper plate to a closure-releasing position relative to said keeper plate, and said striker plate when in said closureengaging position being vertically movable along position and upper striker plate unlocking said latch is reversible for attachment to a jamb in Said X S between a IOWCI Striker Plate locking an inverted position wherein said opposite plate positions, coacting means on said plates which edges are lowermost,

engage in Said locking Position to lock Said said striker plate when in said unlocking position Striker Plate against Swinging to said C1051" is movable along said hinge axis from said striker releasing Position and disengage in Said unlocking plate unlocking position toward said opposite position to Permit Swinging of said Striker plate keeper plate edge to a second striker plate lockto said closure-releasing position, and i position,

Said keeper Plate having a manually bendable tab additional coacting means on said plates which Portion defined y 510i means Opening through 10 engage in said second locking position to lock an edge of the keeper Plate and adapted to be said striker plate against swinging to said closurebent so as to project beyond said outer side of releasing iti d Said keeper Plate at a Position which is below a manually bendable tab portion defined by slot the lower edge of said striker plate at least when means opening through an d f th keeper the latter plate is in said locking position to preplate d d t d t b b t so as to project Vent raising of Said Striker plate to unlocking beyond said outer side of the keeper plate at a position and rotation of the striker plate to closure iti b l w aid opposite striker plate edge releasing position y insertion of an implement when the striker plate is in said locking position between said j and closure edgewith the latch in said inverted position.

A latch aeeofding to Claim 1 Whereini 2O 4. A latch according to claim 3 wherein:

Said keeper Plate tab portion is located below the said second keeper plate tab portion is located lower edge of the striker plate when the latter is b l id opposite trik lat d e wh n said in its locking position. striker plate is in said second locking position 3. A latch according to claim 1 wherein: ith id l t h i invert d position.

Claims

1. A safety latch for limiting the opening of a door with respect to a doorframe, comprising: a latchplate for securement to the doorframe, said latchplate having a T-shaped engagement opening therein; a structure for mounting upon the door, said structure comprising a base with a stop formed therein; a guide pivotally mounted to said base, said guide having guide flanges; an engagement link slidably mounted with respect to said guide flanges to slide from a retracted to an extended position, a stop on said engagement link to limit the amount said engagement link can slide out of said guide, said engagement link engaging with respect to said stop to retain said engagement link with respect to said base when said engagement link is in its retracted position, said engagement link also having a manually operable handle thereon, and a T-shaped engagement nose on said engagement link, said engagement nose extending into said engagement opening on said latchplate when the door is closed and said engagement link is extended with respect to said guide, said nose and said opening being configured so that said nose can engage said opening only when said engagement link is lying in said base.

2. The safety latch of claim 1 further including an intermediate link, said intermediate link being slidably mounted in said pivoted guide and said engagement link being slidably mounted with respect to said intermediate link so that said engagement link can extend beyond said guide.

3. The safety latch of claim 2 wherein a stop is formed on said base, said engagement link engaging with respect to said stop to retain said engagement link with respect to said base when said engagement link is in its retracted position.

4. The safety latch of claim 3 wherein said guide has flanges which guide said engagement link with respect to said guide.

5. The safety latch of claim 4 wherein said engagement link has a manually operable handle thereon, said handle operating through a slot to limit motion of said engagement link.

6. The safety latch of claim 5 wherein said engagement nose is T-shaped and said engagement opening is T-shaped, said nose and said opening being configured so that said nose can engage said opening only when said engagement link is lying in said base.