Lock catch for doors

A lock catch for doors having holding elements thereon includes a catch housing formed with at least one door-mounted holding element-receiving slot therein. At least one locking lever is pivotably mounted within the catch housing. A spring is positioned within the catch housing to normally bias the locking lever to project into the slot. A first bevelled surface is formed on the locking lever and is engageable by the holding element on the door when the door is closed, such engagement resulting in pivotal movement of the locking lever in a first direction to permit entrance of the holding element into an inner end region of the slot inwardly of the locking lever. A second bevelled surface is formed on the locking lever is engageable by the holding element of the door upon withdrawal of such element from the inner end region of the slot in which it has been locked releasably. Such engagement effects pivotal movement of the locking lever in a second and different direction to permit withdrawal of the holding element from the slot. The spring is so positioned relative to the pivot axis of the locking lever and the bevelled surfaces thereof that the effective lever arm of the locking lever when the first bevelled surface is engaged by the holding element entering the slot is greater than the effective lever arm of the spring acting on the locking lever. Further, the effective lever arm of the spring acting on the locking lever is greater than the effective lever arm of the locking lever when the second bevelled surface is engaged by the holding element during withdrawal of the holding element from the inner end region of the slot.

BACKGROUND OF THE INVENTION 
The invention relates to a lock catch for double doors in which 
door-mounted holding elements are cooperable with lock catch locking 
elements and wherein a spring within the catch housing biases the locking 
elements into their closing position, the holding element of one door 
being blocked in its closing position when the holding element of the 
other door is also brought into its closing position. With a lock catch as 
described, both doors can be closed only in a certain sequence and can be 
opened again only in the reverse sequence. 
Britsh Pat. No. 1,254,392 discloses a lock catch of the above mentioned 
kind which ensures the closing function. In this known lock catch the two 
locking elements are formed as slides which maintain within the catch 
housing in the closing positions by means of a compression spring. The 
catch housing is fastened to the frame of the doors so that the 
displacement direction of the slides is parallel to the open front of the 
door frame. The slides protrude from the catch housing by a triangular 
ratchet tip. On the doors, holding elements are fastened which have a 
triangular detent. When one door is closed, its holding element displaces 
the corresponding slide counter to the force of the spring, until the 
slide engages with the detent of the holding element in the closed 
position of the door. To block the door which is closed first, another 
slide is displaceably guided in the catch housing, this slide being 
displaced by the holding element of the second door. When the second door 
is brought into the closing position, the displaced second slide prevents 
a displacement of the slide associated with the first door, which slide 
thus blocks the holding element of the first door. Therefore, the first 
door can be opened only after the last-closed door has been opened and 
when the holding element on the first door releases its associated slide. 
This known lock catch, however, has the disadvantage that the closed doors 
do not closely abut the front edges of the door frame. As the slide and 
holding elements have a ratchet position defined in the closing direction, 
tolerances of the door, of the frame and in the attachment of the catch 
housing and of the holding elements cannot be compensated. 
To overcome the shortcomings noted above, attempts have been made to design 
the holding elements as inclined ratchet elements engageable over the 
triangular ratchet tips from behind. In this way, a part of the spring 
force acting on the slides is transformed into an attractive force 
component which pulls the closed door against the frame for the door. 
Since the ratchet flaps can only be very short, the holding elements and 
the catch housing must be mounted on the doors and on the door frame very 
precisely. Since the slides are pushed against the ratchet flaps with 
great force and acts on a large area, the preponderant part of the 
attractive force component is thereby cancelled out. 
It is an object of the invention to provide a lock catch of the above 
mentioned kind which is of relatively simple construction, can easily be 
fastened to the door frame and the doors, and yet chieves positive locking 
action, compensation of the parts and attachment tolerances and maintains 
blocking of the door which is closed first. 
SUMMARY OF THE INVENTION 
According to the invention, the holding elements are formed as holding 
bolts which can be introduced into receiving slots in the catch housing; 
the locking elements are formed as locking levers pivotably mounted in the 
catch housing and extendable into a receiving slot for each; the locking 
levers, as the holding bolts are introduced into the associated receiving 
slots, are deflected therefrom; the introducted holding bolts are then 
held in the end regions of the receiving slots by the spring action of the 
locking levers which are pivoted back; and one locking lever so protrudes 
by a blocking shoulder into the end region of the receiving slot 
associated with the other locking lever that such one locking lever is 
nonpivotably retained by the holding bolt introduced into this receiving 
slot. With this design of the locking elements no separate locking slide 
need be provided, and the spring force acting on the locking levers is 
fully transmitted, after the deflection and return pivoting of the locking 
levers upon introduction of the holding bolts, to the latter and hence to 
the closed door, which thus is pulled up snugly against the door frame. 
The pivoting of the locking levers which normally protrude into the 
receiving slots of the catch housing is achieved in a simple manner by the 
holding bolts being oriented with their edian axes perpendicular to the 
longitudinal axes of the receiving slots, the receiving slots being 
oriented horizontally and the holding bolts vertically. Further, the 
locking levers are rotatably mounted between the receiving slots on a 
common journal of the catch housing which is directed away from the 
introduction side of the receiving slots, the pivot axis being oriented 
perpendicular to the longitudinal axes of the receiving slots. Thereby 
enough space is created on the introduction side between the receiving 
slots to permit the required pivotal movement of the locking levers. 
To create predetermined starting positions for the locking levers when the 
holding bolts are initially introduced into the receiving slots, it is 
further provided that the locking levers are held by means of the spring 
at stops of the catch housing which is arranged outside the path of the 
receiving slots. 
A continuous deflection process for the locking levers during introduction 
and withdrawal of the holding bolts into and out of the receiving slots is 
achieved by providing the locking levers, toward the introduction side of 
the receiving slots, with deflection bevelled surfaces over which the 
holding bolt rides as it is being introduced, the locking lever being 
caused to pivot in the direction toward the other locking lever. The 
locking levers are provided, toward the inner end regions of the receiving 
slots, with pull-up (tightening) bevelled surfaces which form with the 
inner end regions of the receiving slots locking seats for the holding 
bolts which are retained in these locking seats under spring action. The 
pull-up bevelled surfaces are inclined so that also when the holding bolt 
is withdrawn, the associated locking lever is pivotable in the direction 
of the other locking lever. 
In order that the locking levers can be used for a lock catch disposed at 
the bottom or top edges of the doors, the locking levers are laid out 
symmetrically with respect to a median plane perpendicular to the pivot 
axis so that they can, therefore, be rotatably mounted on the journal of 
the catch housing in two positions 180 degrees apart. Merely by the 
mounting of the locking levers as described above, therefore, the blocking 
can be shifted to one or the other receiving slot, as is necessary for 
double doors which are locked in the region of the lower edges and upper 
edges of the doors by means of separate lock catches. 
The pivotable mounting of the locking levers is effected according to one 
embodiment in that one locking lever is mounted pivotably on the journal 
by means of two spaced bearing straps, while the other plate-shaped 
locking lever is rotatably mounted on the journal of the catch housing 
between these two straps. 
The support of the spring for the two locking levers according to one 
embodiment includes a blind bore which is open toward the other locking 
lever and receives a helical spring. 
In order that relatively large tolerances in the attachment of the doors or 
in applying the holding elements on the doors can be compensated for, it 
is further provided that the width of the receiving slots be greater than 
the diameter of the holding bolts. 
The catch housing is preferably designed so that the housing consists of a 
box type bottom portion having a side wall provided on one side thereof 
with recesses, and a box type top portion having a side wall provided with 
the receiving slots on one side and on a cover plate, the receiving slots 
in the top portion being in general alignment with the recesses in the 
bottom portion. 
For the simple attachment of the lock catch on the door frame, there is 
integrally formed on the bottom portion of the catch housing extending 
away from the introduction side of the housing, a fastening strap which in 
its opposed parallel edges is provided with open recesses or slots laid 
out to correspond with a given hole spacing on the door frame. 
In order that minimum force is needed for locking of the doors with the 
holding bolts, while maintaining a strong closing force for the locked 
door, the deflection bevelled surfaces of the locking levers subtend an 
acute angle in the closing direction to the longitudinal medium axis of 
the receiving slots, whereas the pull-up bevelled surfaces subtend an 
obtuse angle in the opening direction. 
The acute angle of the deflection bevelled surfaces provide when a holding 
bolt is being introduced, a greater lever arm relative to the fulcrum of 
the locking lever than that exerted by the compression spring which 
maintains the locking lever in its starting position. For this reason, the 
locking lever, when introducing the holding bolt, can be pivoted with 
little force. To this end the force of the return springs in the hinges of 
the hung door may be sufficient so that the door is brought into the 
locking position practically by itself. 
The obtuse angle of the pull-up bevelled surfaces serves primarily for the 
purpose that the full force of the compression spring pulls the locked 
door against the door frame. The lever arm acting on the holding bolt in 
this instance is smaller than the lever arm of the compression spring, so 
that a biasing force is developed. To open the locked door, therefore, 
this biasing force must be overcome. In addition, the closing forces of 
the return springs in the hinges must be overcome. 
It can thus be seen that by this design of the deflection and pull-up 
bevelled surfaces of the locking levers a closing-opening characteristic 
greatly different from the known lock catches is achieved. Closing of the 
doors occurs easily, i.e. practically automatically once brought by means 
of the holding bolts into the region of the lock catch particularly if the 
hinges are provided with return springs, while greater tractive forces are 
required to open the doors.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The lock catch according to the invention is contained in a catch housing 
which is composed of a bottom portion 10 shown in FIGS. 1 and 2 and a top 
portion 30 shown in FIGS. 3 and 4. 
The bottom portion 10 is a box type design, one end of the side wall 16 
having recesses 22 and 23 which are in alignment with receiving slots 35 
and 36 in the cover plate and side wall 31 of the box type top portion 30 
when the two portions are joined together. The joining of bottom portion 
10 and top portion 30 can be effected via connecting sleeves 19 integrally 
formed on the bottom portion 10 and connecting pins 33 integrally formed 
on the top portion 30. The connecting pins are dimensional and configured 
to be wedged or otherwise held in the connecting sleeves 19. The bottom 
portion 10 and top portion 30 are preferably made as metal die-cast parts. 
The edges of the side walls 16 and 31 of bottom portion 10 and top portion 
30 are provided with staggered connecting bridges 21 and 32, so that the 
overlapping connection between bottom portion 10 and top portion 30 of the 
catch housing effects a tight closing of the top and bottom portions. 
In the assembled state, the bottom portion 10 and top portion 30 form two 
interior and parallel seats for the door holding elements which are 
designed as holding pins. These seats are formed by the recesses 22 and 23 
in the bottom portion 10 and the receiving slots 35 and 36 in the top 
portion 30 and which open toward one end of the catch housing as can be 
seen from FIG. 6. This end is termed the introduction end. The end of the 
side wall 16 opposite the introduction end has a central recess formed 
therein in which the bottom plate of the bottom portion 10 is stepped 
upwardly and carries a journal 17. A raised shoulder 18 of the bottom 
plate serves as a bearing for the locking levers to be mounted to the 
catch housing, as will be shown later. The raised shoulder 18 extends 
outside the side wall 16 to form an attachment strap or plate 11. The 
rectangularly bent edges 14 and the integrally formed stiffening ribs or 
bridges 15 provide the fastening flange 11 with increased strength. In the 
parallel edges of the attachment plate 11, there are formed fastening 
slots 12 and 13 which are open to the outside and are matched to a given 
hole spacing. The catch housing can therefore be secured on the door frame 
by means of the bottom plate of the bottom portion 10 utilizing selected 
holes of a series of holes formed in the door frame. 
On the end opposite to the introduction end, the upper portion 30 also is 
given a recess 37 in the side wall 31. The cover plate of the top portion 
30 is extended outwardly in semicircular form, as reference numeral 34 
shows. This semicircular portion of the cover plate completes the abutment 
for the locking levers. 
Projecting inwardly from the mutually opposite inner sides of the side wall 
16, stops 20 are integrally formed which limit the outward pivotal 
movement of the locking levers 40 which are mounted pivotably about the 
journal 17 and which, thereby, fix starting positions thereof, as FIGS. 5 
and 6 show. 
On journal 17 a plate type locking lever 40 is rotatably mounted. This 
lever 40 extends into the seat or chamber formed by the receiving slot 35 
and recess 23. The locking lever 50, likewise rotatably mounted on journal 
17, extends into the seat or chamber formed by the receiving slot 36 and 
recess 22. Lever 50 is mounted rotatably on journal 17 by means of two 
bearing straps 51 and 52, as the enlarged illustrations of FIGS. 7 and 8 
show. The bearing straps 51 and 52 are reinforced in the region of the 
bearing bores 52 by ring elements 54, 55, 56 and 57. The locking lever 50 
therefore is supported by the reinforcement ring 54 on the bearing 
shoulder 18 of the bottom portion 10 and by the reinforcement ring 57 on 
the semicircular portion 34 of top portion 30. The locking lever 40 is 
supported in the region of its bearing bore 52 on the reinforcement rings 
55 and 56 of the locking lever 50 and therefore is pivotable between the 
two bearing straps 51 and 52. 
Within locking lever 50, in the region thereof connecting the two bearing 
straps 51 and 52, locking lever 50 has a blind bore 58 having its opening 
facing the locking lever 40. The open end of bore 58 is provided with an 
entrance chamfer 63. Within blind bore 58 there is positioned a spring 60 
formed as a helical spring, which is biased against a support surface 45 
of the locking lever 40. 
In the open position of the doors, therefore, spring 60 pushes the locking 
levers 40 and 50 against the stops 20 of the catch housing, so that they 
occupy the starting positions seen in FIG. 6. 
The doors are provided with holding elements in the form of bolts. The 
bolts are oriented vertically and are introduced in such manner into the 
seats or chambers of the catch housing when the doors are closed. 
Assuming that the lock catch is fastened to the door frame in the position 
shown in FIG. 6 in the region of the lower edges of the doors with 
upwardly open seats, the the left door must be closed first. As the door 
is being closed, the associated holding bolt is introduced into the seat 
or chamber formed by recess 22 and receiving slot 36. In so doing, the 
holding bolt strikes against the bevelled surface 59 of locking lever 50, 
which, on further introduction of the hold bolt, is pivoted 
counterclockwise. After the holding bolt has advanced into the inner end 
region of the receiving slot 36, the locking lever 50 can reset itself by 
pivoting clockwise under the influence of spring 60. The locking lever 50 
will then engage, by means of its bevelled surface 61, against the holding 
bolt, pulling the latter and the door against the door frame. If the 
receiving slot 36 is deep enough, it can be assured that the door will be 
urged against the front of the door frame snugly and under tension. 
If then the right door is closed, the associated holding bolt pivots the 
locking lever 40 clockwise via the bevelled surface 43 against the locking 
lever 50, which is again firmly in its initial starting position but not 
yet against stop 20. After the hold bolt has reached the inner end region 
of the receiving slot 35, the locking lever 40 pivots back 
counter-clockwise under the influence of spring 60 and retains the holding 
bolt under spring action or bias, through its bevelled surface 44, so that 
the second door also is urged against the front of the door frame snugly 
and under tension. 
Once in its closed position, the locking lever 50 protrudes by means of 
blocking shoulders 62 of both bearing straps 51 and 52 into the inner end 
region of the receiving slot 35. Once in this receiving slot 35 the 
holding bolt is held by the locking lever 40 and locking lever 50 can no 
longer be pivoted since blocking shoulders 62 then are urged against the 
holding bolt. The result is that the left door cannot be opened unless the 
last closed right door is opened first. Only then can the holding bolt be 
extracted form the receiving slot 36 by pivoting of locking lever 50. The 
bevelled surfaces 44 and 61 of the locking levers 40 and 50 are inclined 
at the same angle so that the locking levers 40 and 50 are mutually 
pivoted as the holding bolts are extracted. 
As the locking levers 40 and 50 are formed symmetrically with the edian 
plane perpendicular to the pivot axis, they may be mounted on the journal 
17 for 180 degrees rotation. The lock catch then fixed on the door frame 
when rotated 180 degrees in the region of the upper edges of the doors is 
then matched to the closing and blocking function of the just described 
lock catch on the lower edges of the doors, so that the left door is 
locked and blocked at the bottom and top. The two lock catches can be made 
with standard components merely by different installation. 
The receiving slots 35 and 36 as well as the seats 22 and 23 may be wider 
than the diameter of the holding bolts, so that also relatively great 
tolerances in the hanging of the doors and in the application of the 
holding bolts on these doors can be compensated. Also the play in the 
locking direction can be compensated to a large extent by appropriate 
design of the receiving slots 35 and 36, a tractive force being always 
additionally exerted on the doors in the end position to hold them in 
abutment on the front of the door frame. 
The rotatable mounting of the locking levers 40 and 50 on the end opposite 
the introduction end and the special design of the bevelled surfaces 43 
and 59, as well as the bevelled surfaces 44 and 61, offer a new 
closing-opening characteristic which differs essentially from that of 
known lock catches. The bevelled surfaces 43 and 59 of locking levers 40 
and 50 are oriented in the closing direction in an acute angle to the 
longitudinal median axes of the receiving slots 35 and 36 of about 
30.degree., so that when introducing the holding bolts fastened to the 
doors, a large lever arm is initially present in the action on the locking 
levers 40 and 50. The locking levers 40 and 50 can therefore be deflected 
with a small force. For this the force of the return springs in the hinges 
of the hung door is often sufficient, so that the door brought into the 
closing position practically locks by itself. Since the approach path of 
the holding bolt into the receiving bolt is relatively long, a continuous 
closing and locking process is achieved. The bevelled surfaces 44 and 61 
of the locking levers 40 and 50 are oriented in the opening direction in 
an obtuse angle to the longitudinal median axes of the receiving slots 35 
and 36 of about 110.degree., so that when extracting or withdrawing the 
holding bolts fastened to the doors a small lever arm is present in the 
action on the locking levers 40 and 50. This lever arm is smaller than the 
lever arm with which the compression spring acts in the contrary direction 
on the locking levers 40 and 50. Therefore a force differential exists so 
that the doors can be opened only with a greater tractive force. In 
opening the doors the additional closing forces of the return springs in 
the hinges must be overcome. 
Naturally, it is possible also to use the lock catch according to the 
invention as a simple/single catch for holding shut a single door. To this 
end the locking catch and holding bolt need only to be fastened on the 
door frame and on the door in the correct correlation. Preferably the 
holding bolt is provided with an attachment strap which offers two 
correspondingly offset attachment possibilities. 
For this application, however, the lock catch itself can be simplified when 
the catch housing is provided with only one receiving slot. 
In the catch housing only one locking lever is rotatably mounted, and the 
compression spring is supported therebetween this lever and the housing. 
Here the locking lever with the blind bore and the two bearing straps is 
used. The other locking lever is unnecessary. The housing parts remain the 
same except for the number of recesses in the end walls and the number of 
receiving slots. This can be achieved by simple inserts so that the single 
catch requires no new components.