US3904230A

US3904230A - Two stage lock

Info

Publication number: US3904230A
Application number: US477403A
Authority: US
Inventors: William Fane; Dennis Potter; Joseph Potschka
Original assignee: Norris Industries Pty Ltd
Current assignee: Norris Industries Pty Ltd; Norris Industries Inc
Priority date: 1974-06-07
Filing date: 1974-06-07
Publication date: 1975-09-09
Anticipated expiration: 1992-09-09
Also published as: GB1484301A; AU7214374A

Abstract

A two stage door lock for mobile units and similar habitable structures makes use of a relatively thin lock structure secured to the inside face of the door cooperating with a strike pin mounted on a bracket on the exterior of the door frame. Oppositely pivoted latching elements have complementary recessed jaws spring urged toward closed position and adapted to be latched around one or the other of two annular recesses in the strike pin in either a partially closed position or full closed position. A transversely extending rectangular hole slidably accommodates a locking latch bolt, fingers of which slide into recesses at the jaw end of the latching elements to lock them in engagement with the strike pin when the door is in full closed position. When the latch bolt is slid away to unlocked position, a rectangular spindle is rotated by action of a handle to spread the jaws away from engagement with the strike pin. When the jaws do not engage the latch bolt in closed position they cannot be locked by the latch bolt because a shoulder in a rectangular hole prevents the latch bolt from sliding to locked position.

Description

United States Patent Fane et al.

TWO STAGE LOCK Inventors: William Fane, North Vancouver;

Dennis Potter, Delta; Joseph Potschka, Vancouver, all of Canada Primary ExaminerRichard E. Moore [57] ABSTRACT A two stage door lock for mobile units and similar habitable structures makes use of a relatively thin lock structure secured to the inside face of the door cooperating with a strike pin mounted on a bracket on the exterior of the door frame. Oppositely pivoted latching elements have complementary recessed jaws spring urged toward closed position and adapted to be latched around one or the other of two annular recesses in the strike pin in either a partially closed position or full closed position. A transversely extending rectangular hole slidably accommodates a locking latch bolt, fingers of which slide into recesses at the jaw end of the latching elements to lock them in engagement with the strike pin when the door is in full closed position. When the latch bolt is slid away to unlocked position, a rectangular spindle is rotated by action of a handle to spread the jaws away from engagement with the strike pin. When the jaws do not engage the latch bolt in closed position they cannot be locked by the latch bolt because a shoulder in a rectangular hole prevents the latch bolt from sliding to locked position.

20 Claims, 12 Drawing Figures 44, 47 @is g '5 as \g 20 47 PATENTED SE? 975 SHKET 1 BF 5 PATENTED SEP 91975 SHEET 5 [IF 5 IIII I-l TWO STAGE LOCK In campers, self propelled motor homes, and similar types of vehicles door openings exist, provided with hinged doors which should be capable of being opened, and subsequently closed and securely locked at virtually anytime. One of the contingencies which impairs the security of locks under such circumstances is the fact that the structure of such vehicles tends to yield. Another more important contingency occurs in the event of a collision which could force the door open from a normally closed position and possibly eject someone inside the vehicle. One or another of such or a similar contingency tends to push the wall structure slightly out of initial alignment. When such movement occurs in a doorway and more particularly in a door frame the door, if closed or even locked, tends to spring open. Hence, no matter what the keying may be for locks on such vehicles, conventional locks suitable for residential and other building structures can not be depended on for uses of the kind herein made reference It is therefore among the objects of the invention to provide a new and improved door lock which remains secure under exceptional conditions.

Another object of the invention is to provide a new and improved door lock for self propelled motor homes and the like which is small and compact and which can be mounted on an exterior face of the door.

Still another object of the invention is to provide a new and improved door lock which interlocks with a strike pin in latched position in such a way that a springing of the door frame or door out of initial alignment or spacing with respect to each other will still not permit the door to inadvertently open.

Further among the objects of the invention is to provide a new and improved door lock for mobile vehicles which has a two stage latching engagement, both stages of which are secure under all circumstances.

Further still among the objects of the invention is to provide a new and improved door lock for mobile vehicles of such construction that it cannot be locked in open position but only in closed position.

With these and other objects in view, the invention consists of the construction, arrangement, and combination of the various parts of the device, whereby the objects contemplated are attained, as hereinafter set forth, pointed out in the appended claims and illustrated in the accompanying drawings.

FIG. I is a side perspective view of the door lock in place on a door.

FIG. 2 is a side perspective view of the door frame with a strike pin mounted in the appropriate position.

FIG. 3 is a transverse sectional view of the door lock on the line 3 3 of FIG. I but showing the parts in full latched position as though the door were closed.

FIG. 4 is a vertical sectional view on the line 4 4 of FIG. 3 showing the parts in locked position.

FIG. 5 is a vertical sectional view similar to FIG. 4 showing the parts in unlocked and unlatched position.

FIG. 6 is a vertical sectional view similar to FIGS. 4 and 5 but showing the parts in unlocked position from which the door can be latched by closing it on the strike pin.

FIG. 7 is a transverse sectional view similar to FIG. 3 but showing the parts in partially latched position.

FIG. 8 is an exploded view of all the parts in perspective in the general relationships they have with respect to each other, and viewed from the inside of the door.

FIG. 9 is a fragmentary sectional view taken on the line 9 9 of FIG. 3.

FIG. 10 is a fragmentary cross sectional view showing addition of a screen door structure.

FIG. 1 l is a fragmentary cross sectional view of parts of FIG. 10 not visible in FIG. 10.

FIG. 12 is a perspective view of the friction bushing of FIG. 10.

In an embodiment of the invention chosen for the purpose of illustration there is shown in FIG. 1 a fragment of panel or door 10 having an outside face 1 1, an inside face 12 and an edge face 13. A lock indicated generally by the reference character 14 is mounted on the inside face 12 and its outer trim escutcheon I5 is visible on the outside face 11.

A section of door frame 16 is shown in FIG. 2 on which a bracket 17 is attached to its face 18 which normally faces the edge face 13 of the door 10. Fasteners 19 extend through a leg 20 of the bracket, the frame 16 and an anchor plate 21 on the face 18'.

On another leg 22 of the bracket is a strike pin indicated generally by the reference character 23. The strike pin 23 has a threaded shank 24 anchored by a nut 25 to the leg 22 which draws against an annular flange 27 on the opposite side of the leg.

Adjacent a truncated strike 30 (see FIGS. 3 and 7) is a first outer partially closed peripheral reduced section 31 which is annular in shape and provides a shoulder 32. Inwardly therefrom is a second inner full close reduced section 33 which forms on one side a shoulder 34 and on the other side a shoulder 35. An integral stop 37 on which is a cushion 37' may be provided to stop against an outside face 38 of the frame.

The diameter of the reduced section 31 may be the same as that of the reduced section 33, when there is need to be able to lock the door lock in either partially or full close position. When the door lock is not to be locked in partially closed position the diameter of the reduced section 31 is made so small that when the latching elements engage it they are in the same relative positions as they have when the door is open.

Spacers 39 (see FIG. 8) are inserted into larger ends of respective elongated slots 39' in the base plate 42 and are then slid laterally to the smaller ends of the slots to lock them in place. Once in position they hold the base plate 42 and the structural plate 43 apart to form a chamber 44.

A significant portion of the lock construction resides in the pair of latching

elements

40 and 41, shown in side elevation in FIGS. 4, 5, and 6. These are housed in what may be described as a frame consisting of a base plate 42 for engagement with the inside face 12 of the door and a structural plate 43 parallel to and spaced from the base plate 42 forming the chamber 44. On the inside there is an inner trim escutcheon 45 overlying the structural plate 43 and anchor bolts 46 extending through the escutcheon, the structural plate 43, base plate 42, and a hole 51 in the door engage sleeves 47 in the outer trim escutcheon 15 to hold the parts in position on the door.

For pivotally mounting the latching

elements

40 and 41 there are provided half pivots 48 in the structural plate 43 which project into recesses 48' in the respective latching element 40 as shown in FIG. 3. A similar half pivot 49 in the latching

element

40 or 41 as the case may be extends into a hole 49' in the base plate 42.

The latching

elements

40 and 41 are mounted individually in a similar fashion. By this

construction operating edges

52 and 53 of the

respective latching elements

40 and 41 respectively are opposite to and generally spaced from each other.

A substantially U shaped spring 54 has one leg 55 bearing against the latching element 40 and another leg 56 against the latching element 41 normally urging them towards each other, namely to the positions of FIGS. 4 and 6.

The ends of the latching

elements

40 and 41 opposite from the pivots 48 may aptly be described as

jaws

57 and 58. In the jaws extending inwardly from the operating edges are compelmentary latching

recesses

59 and 60 which roughly circumscribe either the partially closed peripheral reduced portion 31 or the full close peripheral reduced protion 33 (as in FIG. 3).

An opening 69 in the outer trim escutcheon and an aligned opening 69' in the structural plate 43 serve as a guide for directing the lock into engagement with the strike pin 23.

For locking the door there is provided a latch bolt 61 of a generally rectangular outline as shown in FIGS. 4, 5, and 6. The latch bolt is slidably amounted in an appropriate hole formed by complementary latch bolt recesses 62 and 63 respectively in the operating edges 52 and 53 intermediate jaw ends 57 and 58, and the half pivots. The hole thus formed is substantially rectangular and longer than the latch bolt 61.

There are two latch bolt recesses in the chosen embodiment, one recess 64 in the jaw 57 and the other recess 65 in the jaw 58. The recess 64 receives the locking extension 66 and the recess 65 receives the extension 67 in locked condition of the lock. This is the position of FIGS. 4 and 7 when the door and the lock are in full close position.

To move the latch bolt to locked position there is provided a lock bar 70 on which is a connecting arm 71 integral with the lock bar and having a connection to the latch bolt 61 in a pocket 72. A spring 73 assists in holding the parts of the connection snug. The end 71' of the arm extends for convenience through a clearance slot 68 in the base plate 42.

There are two ways for moving the lock bar and hence the latch bolt. One way makes use of a button 74 extending through an elongated slot 75 in the structural plate 43 and a corresponding slot 76 in the trim escutcheon 45. The button 74 engages a shoulder 77 on the lock bar 70.

A second way for moving the lock bar between locked and unlocked positions is by use of a tail piece 78 on a conventional plug 79. A pin or wafer tumbler cylinder 80, as the case may be, manipulated by a key 81, has a sliding extension 82 adapted to engage in the plug 79 to rotate the plug 79 and rotate the tail piece 78. The tail piece in turn moves against a shoulder 83 of the lock bar to shift the lock bar and latching bolt left to right as in FIG. 4 to locked position.

Conversely the tail piece when rotated in the opposite direction is moved against a shoulder 84 to shift the lock bar 70 and cooperating latch bolt 61 in a direction right to left as in FIG. 5 to unlatched position.

Stops

86 and 87 on the base plate 42 extend to positions blocking excessive movement of the latch plate,

the stop 86 preventing movement too far in a locking direction and the stop 87 movement too far in an unlocking direction.

An interesting expedient of the door lock is one which prevents the lock from being locked when the door is open. This is accomplished by providing a stop shoulder 90 in one of the latch bolt recesses 63. As shown in FIG. 6 when the

jaws

57 and 58 are free to be moved to full shut position, as when not prevented by the presence of the latch pin 23, the stop shoulder 90 is in line with the adjacent corner 91 of the extension 67 and blocks it from being moved into the corresponding recess 65. Hence the lock cannot be locked.

When, for example, the jaws are spread slightly by engagement with the reduced section 33, as shown in FIG. 4, the stop shoulder is moved clear of the comer 91 and the extension 67 together with the extension 66 is free to move into the corresponding recess so that the door can be locked.

Moving the latch bolt 61 to the unlocked position does not automatically unlatch the latching elements from engagement with the strike pin. For this handles and 101 interconnected by a spindle 102 are used. The handle 100 on the inside is rotatably mounted on the structural plate 43 in a substantially conventional fashion and has the spindle non-rotatably engaged with it. Similarly the handle 101 on the outside is rotatably mounted and retained by substantially conventional expedients on a boss 104 in a cavity 105 in the outer trim escutcheon 15. The handle 101 is also non-rotatably engaged with the spindle 102. Pairs of notches 106, I06, 106" are provided at edges of the spindle to accommodate doors of different thickness. The spindle 102 is inserted through the configurated opening 107 in the base plate 42 in vertical alignment with the recesses for a distance determined by the door thickness. and a corresponding pair of

notches

106, 106', 106" as the case may be engage the base plate when the spindle is rotated 90. After the spindle has been located between the

jaws

41 and 42 it can no longer be rotated 90 and therefore is locked in position. The

handles

100 and 101 non-rotatably engage opposite ends of the spindle.

By having the spindle 102 extend between the operating edges 52 and 53 of the

respective latch elements

40 and 41 clearly by rotating the spindle in response to rotation by one or another of the handles the latching

elements

40 and 41 can be moved apart to the positions of FIG. 5, provided the lock is unlocked. In this position the

jaws

57 and 58 are free of engagement with corresponding shoulders of the strike pin and the door can be swung open. When the spindle is released the spring 54 moves the latching

elements

40 and 41 back together to the position of FIG. 6, if the door is open. or to the positions of FIG. 4, if the door is closed.

To provide uniform travel of the jaws to unlatch the latching elements, sloping complementary spindle recesses 108 and 109 are formed in the respective operat ing edges 52 and 53 of the latching

elements

40 and 41. It is of significance that the bottoms of these

recesses

108 and 109 which are engaged by the edges of the spindle 103 have a progressively diminishing slope from the end nearest the pivot pins 48 and 51 toward the opposite end. If the recesses I08 and 109 were parallel the difference in effective leverage ratio from one edge to the other would cause one latchingjaw to travel farther than the other as the spindle is rotated. Sloping as shown, this effect is corrected so that both jaws reach the limit of their travel at the same time. The effect of this construction is to permit the device to be made smaller by eliminating the need to allow room for overtravel of one jaw.

A gasket 110 fits beneath the outer trim escutcheon and the corresponding face of the door to provide a weathertight seal. A clearance opening 111 in the gasket is large enough to accommodate all necessary obstructions which may protrude into it. In the structural plate 43 a relatively long wide opening 112 is large enought to receive the connecting arm 71 and to permit it the necessary lateral movement.

A further significance of Applicants two stage lock resides in the fact that in both stages of engagement of the lock with the strike pin, i.e. ether in partial close position or in full close position the lock and hence the door, is interlocked with the strike pin and hence the door frame. Consequently, should the structure be seriously sprung by a violent impact the door will remain latched shut, the problem being entirely difi'erent from that present in the conventional house structure on a foundation wherein the door will always remain shut, whether locked or not.

Additionally. the parts are made flat and operate close to each other in a compact functioning sandwich and therefore protrude for no more than a minimum distance from the face of what could be a relatively thin door. A minimum amount of space is therefore all that is needed for the installation.

By reason of the special construction of Applicant's two stage lock a screen door may be mounted in the same door frame 16 and be made to cooperate with the door 10. A strike pin 23' is slightly longer than the strike pin 23, as shown in FIGS. and 11. A screen door indicated generally by the reference character 115 consists of a rectangular frame adapted to swing on conventional cabinet type hinges (not shown) attached to the frame on the vertical side opposite the side on which the strike pin 23' is mounted. A vertical member 116 of the frame is a hollow section in which a synthetic plastic sleeve bushing 117 is installed, a central opening 1 18 of which is adapted to surround the strike pin 23' adjacent the base when in engagement with the leg 22 of the bracket 17.

Spring fingers 129 of the bushing lock with the vertical member 116 and alternate spring fingers I30 provide a friction grip for the strike pin.

To accommodate the thickness of the screen door frame the strike pin 23 is made longer for a distance outwardly from the leg 22 so that when the screen door is in closed position, the other portions of the strike pin extend far enough outwardly so as to be engaged by the latching

elements

40 and 41 in both full closed and partially closed position.

In order to provide access to the handle 100 on the inside of the door where the screen is located, an opening 119 is provided through the screen 120.

When the need arises to manipulate the handle 100 to open the door from the inside a cover 121 is slid in a direction from right to left as shown in FIG. 10 to expose the handle 100. Appropriate horizontal spaced parallel slots are provided to accommodate opposite edges of the cover 121, one slot 122 being shown in FIG. 10. The slots are located in corresponding spaced horizontal slide frames, one frame 123 of which is shown in FIG. 10.

When the door 10 is unlatched and swung open the screen door will normally follow it, being releasably attached to the door by means of appropriate magnetic catches 124, one part 125 of which is attached to the door by a bolt 126 and the other part, 127 of which is anchored to the vertical member 116 of the screen door frame. Additional magnetic catches may be located at spaced positions sufficient to hold the screen door to the door 10.

On those occasions where the screen door is to be closed while the door 10 is open the screen door is released by forceably releasing the magnetic catches and the screen door then swung to the position of FIG. 10 where frictional engagement of the sleeve bushing 117 on the strike pin 23' is sufficient to hold it in closed position. A flange 128 extending into the doorway from the door frame 16 provides a stop against which the vertical member 1 16 of the screen door is engaged with the screen door in closed position.

To completely close the screen door the cover 121 is slid from left to right as shown in FIG. 10 until it completely covers the opening 119.

Having described the invention what is claimed as new in support of Letters Patent is as follows:

1. A lock adapted to be mounted on a hinged panel for engagement with a strike pin wherein the strike pin has a first peripheral reduced section forming a stop shoulder for a partially closed position of the panel and a second peripheral reduced section forming a stop shoulder for a full closed position of the panel longitudinally spaced from the first peripheral reduced section and wherein said pin has a mounting on the face of a surrounding structure,

said lock comprising a frame including a base plate for engagement with the panel and a structural plate parallel to and spaced from the base plate forming a chamber therebetween,

complementary latching elements in the chamber each having a pivotal mounting at one end on the frame and an operating edge in face to face relationship with the opposite edge,

a jaw at the other end of each latching element including means forming a latching recess in at least one of said edges and adapted to receive the reduced sections of the strike pin,

means forming a latch bolt recess in at least one of said edges and a latch bolt slidably mounted in said latch bolt recess.

means forming a lock pocket at one end of the latch bolt recess adapted to receive an adjacent end of the latch bolt in locked position.

a latch bolt operator adjacent the exterior of said frame extending into operating engagement with the latch bolt,

and unlatching means comprising a handle rotatably mounted on said frame and a spindle extending between said latching elements adapted upon rotation to move said latching elements away from each other.

2. A lock as in claim 1 wherein there is a spring means normally urging the latching elements toward each other in latching position.

3. A lock as in claim 2 wherein the spring means is a spring member extending around the exterior of both latching elements.

4. A lock as in claim 1 wherein there is a shoulder in the latch bolt recess in the path of movement of said latch-bolt when the latching elements are out of engagement with the strike pin whereby to inhibit a locking of the lock when the panel is in other than one of the latched positions.

5. A lock as in claim 1 wherein the means forming the latch bolt recess fonns a recess in each of said edges complementary to each other, and wherein the latch bolt slides in both said latch bolt recesses and has two locking projections thereon, there being two lock pockets adapted respectively to receive said locking projections.

6. A lock as in claim 1 wherein there is a separate pivot mounting for each latching element mounting said latching elements on the frame at laterally spaced locations.

7. A lock as in claim 1 wherein the spindle has opposite parallel faces and wherein there are complementary spindle recesses in the respective operating edges, the bottoms of said spindle recesses being sloped pregressively inwardly in a direction away from said pivotal mounting whereby both jaws reach the limit of their travel at the same time.

8. A lock as in claim 1 wherein the latch bolt operator is a locking bar parallel to and in substantially the same plane as said latch bolt and movably mounted on the frame for movement in a direction parallel to the direction of movement of said latch bolt, and wherein there is a connecting arm from the locking bar to engage the latch bolt. r

9. A lock as in claim 8 wherein there is on the locking bar, a locking shoulder, a lock pin on the one side of the panel in engagement with said locking shoulder and slidably mounted for movement in a direction parallel to the direction of movement of the locking bar for locking and unlocking said lock.

10. A lock as in claim 8 wherein there is a fixed shoulder on the locking bar, a tail piece rotatably mounted on the frame and a lock member on one side of the panel in operative association with the tail piece whereby the locking bar is shifted between locked and unlocked positions.

11. A lock as in claim 8 wherein there are two locking shoulders on the locking bar, a lock pin on one side of the panel in engagement with one of locking said shoulders and slidably mounted for movement in a direction parallel to the direction of movement of the locking bar, a tail piece rotatably mounted on the frame and a lock member on the other side of the panel in operative association with the tail piece, whereby the locking bar is shifted between locked and unlocked positions from either side of the panel.

12. A lock as in claim 1 wherein there is an opening in the frame in axial alignment with the means forming the latching recess in the latching element whereby to admit the latch pin into engagement with the latching elements.

13. A lock as in claim 12 wherein the end of the frame adjacent the strike pin is substantially flush with the panel at the edge adjacent said strike pin.

14. A door assembly including a door frame,

a main door having a hinged mounting on one side of the frame,

a strike pin on the opposite side of the frame,

said strike pin being perpendicular to the plane of the door when the door is in closed position and being spaced from the frame,

said strike pin having shoulder means thereon,

a lock mounted on the door for cooperation with said strike pin,

said lock comprising complementary latching elements having a pivotal mounting means and an operating edge in face to face engagement with the opposite edge,

at least one of said latching elements having a jaw element adapted to engage said shoulder means on the strike pin,

and means forming a strike pin opening in said lock in alignment with said jaw element, and an auxiliary door having a hinged mounting on the same side of said frame as said main door,

means forming an opening through said auxiliary door at a location in alignment with the strike pin and the strike pin opening of the main door when both doors are closed,

said strike pin having a shank portion of length not less than the thickness of said auxiliary door at the location of the opening therein whereby to engage said strike pin when the main door is closed and when the main door is open.

15. A door assembly as in claim 14 wherein there is a handle on the side of said lock facing said auxiliary door, said auxiliary door having a hole therein in alignment with said handle when the doors are in closed position whereby to enable opening of said main door without opening said auxiliary door.

16. A door assembly as in claim 15 wherein there is a cover for said hole having a slidable mounting on said auxiliary door for movement between positions respectively covering and uncovering said hole.

17. A door assembly as in claim 14 wherein there is a sleeve in the opening in said auxiliary door having resilient means in engagement with the auxiliary door and resilient means in releasable engagement with said strike pin when the auxiliary door is in closed position.

18. A door assembly as in claim 14 wherein there is a yieldable detent means respectively on said main door and said auxiliary door in positions of mutual engagement for holding said doors in engagement.

19. A lock as in claim 1 wherein there is a spindle opening in the base plate providing shoulder means and complementary shoulder means on the spindle in sliding engagement with the first identified shoulder means in all operative positions of the spindle for interlocking the spindle in place.

20. A lock as in claim 19 wherein the spindle has multiple sets of shoulder means at axially spaced locations.

Claims

1. A lock adapted to be mounted on a hinged panel for engagement with a strike pin wherein the strike pin has a first peripheral reduced section forming a stop shoulder for a partially closed position of the panel and a second peripheral reduced section forming a stop shoulder for a full closed position of the panel longitudinally spaced from the first peripheral reduced section and wherein said pin has a mounting on the face of a surrounding structure, said lock comprising a frame including a base plate for engagement with the panel and a structural plate parallel to and spaced from the base plate forming a chamber therebetween, complementary latching elements in the chamber each having a pivotal mounting at one end on the frame and an operating edge in face to face relationship with the opposite edge, a jaw at the other end of each latching element including means forming a latching recess in at least one of said edges and adapted to receive the reduced sections of the strike pin, means forming a latch bolt recess in at least one of said edges and a latch bolt slidably mounted in said latch bolt recess, means forming a lock pocket at one end of the latch bolt recess adapted to receive an adjacent end of the latch bolt in locked position, a latch bolt operator adjacent the exterior of said frame extending into operating engagement with the latch bolt, and unlatching means comprising a handle rotatably mounted on said frame and a spindle extending between said latching elements adapted upon rotation to move said latching elements away from each other.

5. A lock as in claim 1 wherein the means forming the latch bolt recess forms a recess in each of said edges complementary to each other, and wherein the latch bolt slides in both said latch bolt recesses and has two locking projections thereon, there being two lock pockets adapted respectively to receive said locking projections.

8. A lock as in claim 1 wherein the latch bolt operator is a locking bar parallel to and in substantially the same plane as said latch bolt and movably mounted on the frame for movement in a direction parallel to the direction of movement of said latch bolt, and wherein there is a connecting arm from the locking bar to engage the latch bolt.

14. A door assembly including a door frame, a main door having a hinged mounting on one side of the frame, a strike pin on the opposite side of the frame, said strike pin being perpendicular to the plane of the door when the door is in closed position and being spaced from the frame, said strike pin having shoulder means thereon, a lock mounted on the door for cooperation with said strike pin, said lock comprising complementary latching elements having a pivotal mounting means and an operating edge in face to face engagement with the opposite edge, at least one of said latching elements having a jaw element adapted to engage said shoulder means on the strike pin, and means forming a strike pin opening in said lock in alignment with said jaw element, and an auxiliary door having a hinged mounting on the same side of said frame as said main door, means forming an opening through said auxiliary door at a location in alignment with the strike pin and the strike pin opening of the main door when both doors are closed, said strike pin having a shank portion of length not less than the thickness of said auxiliary door at the location of the opening therein whereby to engage said strike pin when the main door is closed and when the main door is open.