Locking device for a sliding door

A sliding door of the type employed in public transport vehicles and driven by an electric motor comprises at least one door-leaf coupled with a nut mounted on an endless screw which is driven in rotation in order to open and/or close the door. The nut is displaced in translational motion within a guide which prevents rotational motion. The locking device comprises means for interrupting the translational displacement of the guided nut at the end of travel and for permitting angular rotation of the nut with the endless screw, means for limiting the angular displacement of the nut and finally means for limiting the translational motion of the nut if it is displaced along the endless screw and no longer engaged in the guide.

This invention relates to a door-locking control device, the opening and/or 
closing of the door being carried out by means of a screw and nut system 
driven by a motor. 
This device is particularly suitable for locking a sliding door or a pair 
of associated sliding doors such as doors of the automatic opening and/or 
closure type for public transport vehicles and especially railway 
vehicles. 
It is known that doors of this type usually have locking means which are 
actuated by the driver and utilize the electrical, hydraulic or 
compressed-air supplies provided on board the vehicles. 
Thus it is a known practice to lock the doors by means of a push-rod which 
is actuated by an electromagnetic, hydraulic or pneumatic control system 
and effects the displacement of a locking bolt when it is supplied by this 
system. When the push-rod is no longer supplied, the locking bolt returns 
to the inactive position under the action of a restoring spring. 
In other versions, remote control of the locking bolt is ensured by 
transmission of a variation in hydraulic or compressed-air pressure. 
Remote control of the locking operation has already been carried out by 
means of direct mechanical linkages. 
All these known designs thus make it necessary to employ locking control 
devices as well as separate devices for controlling the opening and 
closing of doors, thereby entailing a duplication of control means. 
In consequence, these designs are often cumbersome, complex, costly and 
sometimes unreliable. 
In order to overcome this disadvantage, it has been attempted to combine 
the means for operating the doors with the means for controlling the 
locking operation. 
By way of example, one known system for controlling a sliding door 
comprises a crank driven in rotation about an axis at right angles to the 
plane of the door by means of a motor. The end of said crank is guided in 
translational motion by means of a guide arranged along the vertical edge 
of the door so that rotation of the crank results in translational 
displacement of the door. 
The crank can be constituted by two elements which slide with respect to 
each other and are maintained by means of an elastic restoring member in 
the position of maximum extension. 
When the crank is horizontal, the door is locked in the closed position 
with a slight opening play corresponding to the possibility of compression 
of the elastic member. In point of fact, doors equipped in this manner are 
usually suspended and control of their lower portions proves 
unsatisfactory from a mechanical standpoint since the crank has a tendency 
to lift the door. 
Moreover, the reduction-gear motor which drives the crank is of substantial 
overall size and reduces the space available for passengers since it has 
to be housed in the bottom portion of the vehicle. 
The aim of the present invention is to overcome these disadvantages by 
making it possible to control the locking of one or two doors by means of 
a mechanism which is both compact, efficient and inexpensive to produce. 
In accordance with the invention, the device for locking a door and 
especially a sliding door driven by a motor in which said door comprises 
at least one leaf coupled to a nut mounted on an endless screw driven in 
rotation in order to effect opening and/or closing of the door, said nut 
being displaced in translational motion within a guide which prevents 
rotational motion. The locking device essentially comprises means for 
interrupting the translational displacement of the guided nut at the end 
of travel and for permitting angular rotation of said nut with said screw, 
means for limiting the extent of angular displacement of said nut and 
finally means for limiting the translational motion of the nut if it is 
displaced along the screw and no longer engaged in the guide. 
Thus, when guiding of the nut in translational motion in one direction is 
interrupted, said nut rotates about the screw in a predetermined angular 
displacement, is then locked translationally either in the same direction 
if it continues to be driven by the screw or in the opposite direction if 
the action on the door-leaf tends to move said nut away from its 
end-of-travel position. 
By virtue of this combination of means, locking of the nut takes place 
automatically at the end of travel under the action of the system for 
controlling its displacement without entailing the need for a specific 
locking device. 
Moreover, any action produced on the door-leaf which tends to move the nut 
away from its end-of-travel position also tends to lock said leaf. 
In a first embodiment of the invention, said nut carries a projecting 
member which serves to locate its angular position and is provided with 
means for facilitating the guiding of said nut. 
Moreover, the means for interrupting translational guiding of the nut 
consist of a limitation of the guide before the position of end of travel 
of said nut on the endless screw. 
After said limitation of the guide, provision is advantageously made for a 
recessed portion which permits rotational motion of the nut, said recessed 
portion being provided with a stop for preventing further rotation of the 
nut when this latter has reached a predetermined angular position which 
corresponds to locking. 
Preferably, the means for limiting the translational displacement of the 
nut when this latter is freed from the guide comprise two stops for 
arresting said nut, said stops being intended to limit the length of the 
recessed portion and to extend transversely with respect to the axis of 
the endless screw. 
The recessed portion can thus be provided at the end of the guide in the 
vicinity of the end-of-travel position of the nut and receives the 
projecting member carried by the nut when the movement of said member is 
no longer controlled by the guide. The nut is thus locked within the 
recessed portion by means of its projecting member and stops which limit 
said recessed portion. 
The arrangement described above has small space requirements since the 
projecting member is of small size. Moreover, the control device is of 
very simple and inexpensive design. 
In accordance with one alternative form of this first embodiment of the 
invention, the locking device comprises remote-controlled means for 
returning the nut from its locking position to the predetermined angular 
position with respect to the guide, which corresponds to unlocking. 
Thus, in the event of an electrical failure of the control system, the 
unlocking means which are provided make it possible to release the nut and 
open the door simply by producing action on the door-leaf, the endless 
screw being driven in rotation by the nut since the direction of rotation 
of said screw is reversible. 
The locking device in accordance with the invention can be disposed at the 
end of travel on the side corresponding to either closing or opening of 
the sliding door or alternatively to both opening and closing of said 
door. 
In an advantageous embodiment of the invention, the locking device applies 
to a door having two associated leaves operated in opposition by means of 
a common endless screw having two threaded portions of opposite hand, each 
threaded portion aforesaid being fitted with a nut coupled with one of the 
door-leaves in translational motion. An essential and distinctive feature 
of the locking device lies in the fact that, in the locking position, each 
nut is capable of angular displacement when driven by the enldess screw 
and thus escapes from the translational-motion guide which is associated 
with said endless screw. 
The invention also applies to a door which has two associated leaves, each 
door-leaf being coupled with one nut in translational motion by means of a 
fork which embraces said nut. The two nuts are mounted on a common endless 
screw having two threaded portions of opposite hand and are guided in 
translational motion over their entire range of travel by means of a 
guide. 
In a preferred embodiment of the invention, the locking device for a door 
of the type aforesaid is characterized in that it is applied to a second 
endless screw which is driven in rotation in both directions and carries a 
driving nut mounted within a fork and that connecting means provide a 
mechanical linkage between said fork and the forks carried by the 
door-leaves in order to couple them in translational motion over at least 
part of their range of travel. Thus a single locking device can be 
employed for two associated door-leaves. 
Moreover, the fork associated with the door-leaf can be subjected to a 
relative movement of translation with respect to the driving fork, this 
movement being limited in the direction of opening and performed by means 
of a slide arranged between the two forks and an elastic restoring member 
which tends to maintain said slide in the position of maximum extension. 
The driving nut can thus be locked on the second endless screw despite the 
presence of any obstacle which prevents complete closure of the two 
door-leaves. 
This form of construction is therefore particularly suitable for the 
equipment of public transport vehicles.

In the first embodiment of the invention which is described with reference 
to FIG. 1, the system for controlling a sliding door having a single leaf 
is equipped with the locking device 1 to which the invention is more 
especially directed. 
Said control system comprises an electric motor 2 for driving an endless 
screw 3 in rotation, said screw being rotatably mounted in two stationary 
bearings 4 fixed on a rail 5 from which the sliding door-leaf 6 is 
suspended. The means for suspending the door-leaf 6 from the rail 5 
comprise two suspension plates 7 fixed on the top edge of the door-leaf 6 
and pivotally attached respectively to two carriages 8 which are capable 
of moving along the rail 5. 
The nut 9 mounted on the endless screw 3 is coupled with the fork 10 in 
translational motion, said fork being in turn rigidly fixed to the 
door-leaf 6. 
The guide 13 which is parallel to the endless screw 3 constitutes a means 
for guiding a roller 11 in translational motion, said roller being 
rotatably mounted on a shaft 12 which is rigidly fixed to the nut 9. Said 
shaft 12 defines the angular position of the nut 9 as will be explained 
hereinafter. 
One of the end portions of the guide 13 comprises the locking device 1 
which is illustrated in greater detail in FIGS. 6 and 7. 
The guide 13 has two opposite and parallel bearing walls 13a and 13b spaced 
at a distance from each other which is slightly greater than the diameter 
of the roller 11. 
The bearing walls 13a and 13b are interrupted at one end of the guide 13 so 
as to constitute a recessed portion A which is intended to receive the 
roller 11 at the end of travel. 
Said recessed portion A comprises a wall 13c which is joined to the wall 
13a and makes an angle of approximately 90.degree. with this latter, a 
wall 13d which is joined to the wall 13c and is substantially at right 
angles thereto, an angle of approximately 45.degree. being made between 
said wall 13d and said wall 13a. 
In the particular example under consideration, the recessed portion A is 
also limited by an oblique wall 13e which makes an angle of approximately 
30.degree. with the wall 13b and is extended by a wall 13f which is 
substantially parallel to the wall 13b. 
A stationary stop 14 is placed in the proximity of the endless screw 3 in 
order to constitute a means for limiting the displacement of the nut 9 in 
translational motion. Said stop is placed in such a manner as to ensure 
that a clearance d (FIG. 3) is provided between the roller 11 and the wall 
13c when the nut is applied against said stop 14 and the roller 11 is 
applied against the wall 13d, said clearance being exaggerated in FIG. 3 
for the sake of enhanced clarity. 
The operation of the device as thus constituted is as follows: 
When the nut 9 is moving towards the end-of-travel position and the endless 
screw 3 is rotating in the direction S as can be seen in FIGS. 2 to 7, the 
roller 11 which is applied against the face 13a of the guide 13 
accordingly travels in the direction of the arrow U. When guiding of the 
roller 11 in translational motion is discontinued as a result of 
interruption of the bearing face 13a, the nut 9 which is driven by the 
endless screw 3 rotates and in turn drives the roller 11 in rotation along 
the wall 13c until it comes into contact with the wall 13d which thus 
constitutes a means for limiting the range of angular displacement of the 
nut 9. If the endless screw 3 continues to rotate, the nut 9 continues to 
travel in the direction of the arrow U whilst the roller 11 is guided in 
translational motion by the wall 13d while rolling in contact with this 
latter until the nut 9 encounters the stop 14 which limits its 
translational motion. The endless screw 3 is no longer permitted to rotate 
in the direction of the arrow S. 
The door-leaf 6 which is rigidly fixed to the fork 10 (said fork being in 
turn coupled to the nut 9 in translational motion) has reached the 
end-of-travel position of the door-closing movement and is thus locked. 
The supply of current to the electric motor 2 which drives the endless 
screw 3 is cut-off by the control means of said motor. 
In order to unlock the door-leaf 6 automatically, the electric motor 2 is 
controlled so as to drive the endless screw 3 in rotation in the direction 
T. The nut 9 which is driven by the screw 3 first rotates in the direction 
T, whereupon the roller 11 moves from the bearing position on the wall 13d 
to the bearing position on the wall 13f, which constitutes a means for 
limiting its range of angular displacement. From this moment onwards, said 
roller 11 is guided in translational motion as it rolls in contact with 
the wall 13f, then with the wall 13e and finally with the wall 13b of the 
guide 13, thereby preventing rotational displacement of the nut 9 and 
causing translational displacement of this latter along the endless screw 
3 in the direction V. 
Thus the door-leaf 6 is unlocked automatically and slides in the direction 
V. 
Locking and unlocking of the door-leaf in the end-of-travel position are 
thus performed automatically by means of a very simple kinematic system in 
which the means for controlling the displacement of the nut 9 along the 
endless screw 3 cooperate so as to produce this effect in conjunction with 
the means which guide the roller 11 and limit the translational and 
rotational displacements of this latter without any need to have recourse 
to specific means for controlling the locking or unlocking operation. 
Moreover, when the door-leaf 6 is in the locked position and the endless 
screw 3 is stationary, any action produced on said door-leaf tends to move 
it away from its end-of-travel position in the direction V and increases 
the thrust of the roller 11 on the wall 13d, thus increasing the locking 
force. 
In the embodiment shown in FIGS. 8 to 17, a remote-controlled unlocking 
device 15 is associated with the locking device 1. 
The nut 17 being mounted on the endless screw 3, a roller 16 is associated 
with said nut 17 by means of a support 18 which is rigidly fixed to said 
nut by means of two screws 19 (as shown in FIG. 9). Said support 18 for 
the roller 16 is provided with a finger 18a which is parallel to the 
endless screw 3 and directed towards the end-of-travel position. 
An unlocking lever 20 which is rotatably mounted on a stationary pin 21 is 
so arranged that one end 20a of said lever is located at a distance e from 
the finger 18a in the non-unlocking position. 
A pawl 22 is pivotally mounted on a pin 23 which is rigidly fixed to the 
unlocking lever 20. The pawl 22 carries a roller 24 at one end. 
A tension spring 26 attached between the other end 22a of said pawl 22 and 
a fixed point 27 maintains the lever 20 in the unlocking position whilst 
the roller 24 is applied against a fixed stop 28. The unlocking lever 20 
also carries an index 20b which is capable of bearing on the movable tip 
29a of a position detector 29. 
The end portion 20c of the unlocking lever 20 is connected to a 
remote-control member (shown diagrammatically at 30) of the unlocking 
device 15, such as a link-rod system. 
The fork 33 which is coupled with the nut 17 is translational motion 
carries a rod 31 which is fixed by means of screws 32 and extends parallel 
to the endless screw 3. The free end of the rod 31 which is directed 
towards the locking position carries a yoke 31a in which a lug 34 is 
pivoted about a pin 35. The lug 34 is provided in the direction V with a 
heel-shaped projection 34a which, in the rest position, is maintained 
applied against the rod 31 by means of a restoring spring 36. The lug 34 
is located in the plane of the roller 24 carried by the pawl 22 and is 
located on the other side of the roller 24 in the locking position (FIG. 
8). When the pawl 22 is in the position shown in full lines in FIG. 9 
(namely the inactive position), the path of travel of the bottom portion 
34d of the lug 34 passes at a distance x from the top portion of the 
roller 24. 
FIG. 10 shows the respective positions of the finger 18a and of the end 20a 
of the lever 20. In this embodiment, the locked position of the roller 16 
is detected by means of a position detector 37, the movable end portion 
37a of which is applied against the roller 16 by means of the push-rod 
unit 38 which is slidably mounted in the wall 13d of the guide 13. 
As shown in FIG. 11, the endless screw 3 is adapted to carry at the end of 
travel a stop-ring 39 which is secured to said endless screw by means of a 
locking-pin 40. 
The stop-ring 39 is intended to limit the translational displacement of the 
fork 33 and therefore of the nut 17 along said endless screw 3 whilst 
sliding motion of the fork 33 along the screw is carried out by means of 
two bearings 41 and 42. 
A helical spring 43 mounted on the bearing 42 which forms a drum connects 
the support 18 of the roller 16 to the fork 33. The spring 43 thus 
prevents unlocking of the nut 17 under the action of vibrations when said 
nut is in the locked position. 
The operation of the device as thus constituted will now be described with 
reference to FIGS. 12 to 17. 
When the endless screw 3 is driven in rotation by the electric motor 2 in 
the direction V, the roller 16 travels in contact with the wall 13b of the 
guide 13 (FIG. 12). If the movement of translation takes place in the 
direction U, the roller 16 travels in contact with the wall 13a of said 
guide. 
At the end of travel (for example in the position of closure of the 
door-leaf 6), the nut 17 reaches the recessed portion A (FIG. 13) in which 
it is no longer guided in translational motion and then rotates with the 
endless screw 3 in the direction of the arrow S, assuming that the nut 17 
moves in the direction of the arrow U. 
The roller 16 also rotates in the direction of the arrow S along the wall 
13c and is applied against the pushrod 38 of the wall 13d. The position 
detector 37 then stops the electric motor 2. The nut 17 and the fork 33 
are then maintained stationary without being applied against the stop-ring 
39 (as shown in FIG. 14). 
In order to effect the unlocking of the nut 17 and of the roller 16, the 
unlocking lever 20 is rotated in the direction W by means of the 
remote-control member 30. The lever 20 which rotates about its pivot-pin 
21 takes up the position shown in chain-dotted lines in FIG. 9 and in full 
lines in FIG. 15. The end 20a of the lever 20 thrusts back the finger 18a 
during this movement of rotation. 
The pawl which is coupled to the unlocking lever 20 by means of its 
pivot-pin 23 is displaced at the same time as a result of rotation of said 
lever. 
Also at the same time, the roller 24 of the pawl 22 passes upwards onto the 
stationary stop 28 against which it had been applied and remains engaged 
with said stop under the action of the restoring spring 26 when the 
remote-control member 30 no longer exerts any effort in the direction of 
the arrow W. The lever 20 thus remains in the unlocking position (FIG. 
15). 
FIG. 20 serves to show the functions performed by the stop-ring 39 and by 
the different walls of the guide 13 with respect to the roller 16. 
When the roller 16 is locked in the position M.sub.1, the action of the 
unlocking lever 20 first tends to cause the nut 17 to rotate about the 
stationary endless screw 3, thus initiating the displacement of the roller 
16 towards the stop-ring 39 in the position M.sub.2. The action of the 
unlocking lever 20 then necessarily causes the endless screw 3 to rotate 
in the direction T whilst the nut 17 is secured against translational 
motion by means of the stop-ring 39. 
The roller 16 is thus brought into the position M.sub.3 corresponding to 
the end of angular displacement of the unlocking lever 20 opposite to the 
guide 13. 
If said roller 16 is locked in an intermediate position N.sub.1, for 
example, and applied against the wall 13d, the unlocking lever 20 will 
first bring said roller to position N.sub.2 against the stop-ring 39, then 
to position M.sub.3. 
The unlocking operation is thus completed. 
In order to engage the nut 17 within the guide 13, it is only necessary to 
exert an effort on the nut in the direction of the arrow V by means of the 
door-leaf which is associated with the fork 33. The nut 17 then undergoes 
translational motion and drives the endless screw 3 in the direction of 
the arrow S. During this movement, the roller 16 is guided in 
translational motion by the finger 18a which is maintained applied against 
the end 20a of the unlocking lever 20 by means of the helical spring 43. 
Then, when the finger 18a moves away from this position of application at 
M.sub.4 for example, the roller 16 comes into contact with the wall 13a of 
the guide 13 and moves away in the direction V as it runs along said wall. 
The relative positions on the one hand of the walls 13a and 13c and on the 
other hand of the walls 13b and 13e make it possible to ensure correct 
engagement of the roller 16 within the guide 13 in respect of different 
settings of angular displacement of the unlocking lever 20, namely in 
respect of different positions of the rectilinear path of travel M.sub.3 
-M.sub.4 of the roller 16. 
Resetting of the unlocking device is carried out as follows: 
As it moves away from the end-of-travel position, the fork 33 is 
accompanied by the rod 31, the lug 34 of which withdraws at the time of 
passage of the roller 24 which thus remains engaged with the stationary 
stop 28 (FIG. 16). In order to restore the unlocking lever 20 to its 
initial position, it is only necessary to return the door-leaf 6 to the 
end-of-travel position, either by means of the motor 2 or by hand. During 
this displacement in the direction of the arrow U, the lug 34 which is 
retained by the heel-shaped projection 34a thrusts the roller 24 away from 
the stationary stop 28. Since it is no longer retained by the pawl 22, the 
lever 20 is accordingly reset (FIG. 17). 
The position detector 29 delivers a signal which indicates the position of 
the unlocking lever 20 and the movable tip 29a of said detector still 
remains applied against the index 20b of said lever. 
In order to release the nut 17 without having recourse to the unlocking 
device 15, it is only necessary to cause said nut to rotate in the 
direction T as indicated in FIG. 13. When the roller 16 comes into contact 
with the wall 13f, said roller is guided in translational motion by the 
walls 13f, 13e and 13b and subsequently moves in the direction of the 
arrow V. 
It is shown in FIG. 20 that, starting from a bearing position P.sub.1 on 
the wall 13d, the roller 16 comes directly to the position P.sub.2 in 
which it is applied against the wall 13f solely as a result of rotational 
motion, whereupon the roller follows the wall 13e, then the wall 13b. 
The embodiment under consideration makes it possible to remedy a failure of 
the system for controlling the endless screw 3, for example in the event 
of occurrence of an electric fault condition. A simple action produced by 
the remote-control member 30 in the direction of the arrow W makes it 
possible to release the door-leaf and actuate this latter by hand. 
Moreover, the position detectors 29 and 37 serve respectively to detect the 
position of the unlocking lever 20 and the locked or non-locked position 
of the roller 16, thus making it possible to achieve automatic operation 
of the control systems. 
Finally, the helical spring 43 serves to maintain the nut 17 in the locked 
position in spite of any vibrations. 
In the embodiment which is shown diagrammatically in FIG. 24, the manual 
unlocking device comprises two bevel drive pinions 101, 102. The pinion 
101 is carried by the endless screw 3. The pinion 102 is capable of axial 
sliding motion in the direction of the arrow R at right angles to the 
endless screw 3 but is normally maintained at a distance from the pinion 
101 by means of an opposing spring 103 which is mounted coaxially on the 
sliding shaft 104, a hand-wheel and operating crank 105 being also mounted 
on said shaft. It is apparent that, by displacing the crank-handle 105 in 
the direction of the arrow R, the pinion 102 is disposed in meshing 
engagement with the pinion 101 (position 102a). By turning the 
crank-handle 105 and thus causing the endless screw 3 to rotate, the 
roller 11 of the nut 9 can be brought opposite to the guide 13. An 
end-of-travel contact 106 serves to cut-off the supply of the motor 2 when 
the pinion 102 is in the position 102a. 
Other alternative modifications can be made in this first embodiment with a 
view to preventing the nut 9 or 17 in locked position from being released 
under the action of vibrations. 
In the embodiment shown in FIG. 21, provision is made for a retractable 
ball 64 fitted with a restoring spring 65. 
The spring 65 is applied against the bottom of a housing 66 secured to the 
wall 13c of the guide 13 and urges the ball 64 against an orifice of the 
wall 13c. The ball 64 projects to a slight extent into the recessed 
portion A, thus maintaining the roller 16 abuttingly applied in the locked 
position. 
In the embodiment shown in FIGS. 8 and 9, the locking device 1 is disposed 
at the end of travel in the direction of closure so as to constitute a 
means for locking the door in the closed position. As can readily be 
understood, this device can also be disposed at the end of travel in the 
direction of opening. 
Two locking devices can also be disposed in one case at the end of travel 
in the direction of closure and in the other case at the end of travel in 
the direction of opening in order to lock the sliding door in its two end 
positions. 
The two recessed portions formed at the ends of the guide are located in 
one case in such a manner as to interrupt the wall 13a as described 
earlier at one end of said guide and in the other case in such a manner as 
to interrupt the wall 13b at the other end. 
As shown in FIG. 18, the invention can be applied to a sliding door having 
two leaves 50, 51, each door-leaf being fitted with a locking device 44, 
45 respectively as described in the foregoing. 
The control system aforesaid comprises an electric motor 46 for driving an 
endless screw 47 in rotation, said screw being provided with two portions 
47a and 47b having screw-threads of opposite hand and being rotatably 
mounted in two stationary bearings 48 fixed on a rail 49 from which the 
two leaves 50 and 51 of the sliding door are suspended. 
The means for suspending each door-leaf from the rail 49 comprise two 
suspension plates 52 pivotally attached respectively to two carriages 53. 
The nuts 54 and 55 having screw-threads of opposite hand are mounted 
respectively on each portion 47a and 47b of the endless screw 47. Said 
nuts are coupled with the forks 56 and 57 in translational motion, the 
forks themselves being rigidly fixed respectively to the door-leaves 50 
and 51. The guides 62 and 63 which are located in the line of extension of 
each other and parallel to the endless screw 47 constitute respectively 
means for guiding the rollers 58 and 59 in translational motion, said 
rollers being rotatably mounted on the nuts 54 and 55. 
The locking devices 44 and 45 of the aforementioned type are illustrated by 
way of example in FIG. 18. Said devices are placed symmetrically with 
respect to each other at the end of travel of the door-leaves 50 and 51 in 
the direction of closure. 
The displacements of the door-leaves are combined by means of the rotation 
of the endless screw 47 having threads of opposite hand and the locking 
devices 44, 45 come into action conjointly in the manner explained above. 
In the closed position, the junction of the two door-leaves may not take 
place exactly in the plane P; in this case, the rollers 58 and 59 are each 
in the locked position at unequal distances from the walls 62c and 63c, 
for example p and g as shown in FIG. 22. In this configuration, the two 
door-leaves can be displaced either simultaneously or separately in both 
directions by the distance p+q which constitutes an operating clearance at 
the time of closure. 
This form of construction is advantageous since it makes it possible to 
control a sliding door having two leaves and to ensure locking of this 
latter in the closed position by means of a single operating member. 
It will further be noted from the embodiment of FIG. 18 that, as soon as 
one of the two nuts is caused to rotate, the second nut is necessarily 
driven in rotation. Since the difference in position between the two nuts 
is very small, the fact of unlocking one of the two nuts necessarily 
initiates unlocking of the second nut. 
In a third embodiment which is illustrated in FIG. 11, the nut 17 is 
coupled in translational motion with a fork 71 which is slidably mounted 
on the endless screw 3 by means of two bearings 41 and 42. The fork 71 
carries a roller 72 mounted on a shaft 73. The roller 72 cooperates with 
the guide 13 so as to guide the fork 71 in translational motion. 
The fork 71 carries a sliding rod 75 provided with a stop 75a at one end 
and connected at the other end to the door-leaf (not shown) by means of a 
support member 76. The rod 75 passes through an orifice 74 having a double 
flare and formed in a projecting portion 71a of the fork 71, thus 
permitting an angular displacement of the rod 75 through approximately 
10.degree. with respect to the fork 71. 
There is placed around the rod 75 a helical spring 77 which is applied 
against the support member 76 and a travel-limiting sleeve 79, the length 
of which is shorter than the distance y between the projecting portion 71a 
and the support member 76. 
The operation of the device is as follows: 
When the door-leaf which is attached to the connecting support member 76 
moves in the direction of the arrow U towards its end-of-travel position 
without meeting any obstacle, limitation of translational motion of the 
nut 17 is ensured by means of the stop-ring 39 which is placed at the end 
of the endless screw 3 and secured to said screw by means of the 
locking-pin 40. 
Locking of the nut 17 is performed in the normal manner as described in the 
foregoing. The same applies to the unlocking operation which is performed 
by means of the endless screw 3 which disengages the nut 17 or by means of 
the unlocking device which produces action on the finger 18a attached to 
the nut 17. 
The angular displacement of the fork 71 about the axis of the endless screw 
3 which corresponds to the operating clearance permitted between the walls 
of the guide 13 and the roller 72 is made possible despite the presence of 
the rod 75 by virtue of the flared orifice 74. 
On the other hand, if the door-leaf encounters an obstacle 80 which forms a 
stop at a distance m from the plane Q, the nut 17 can continue its travel 
as well as the fork 71 by virtue of the sliding motion of the rod 75 
within the orifice 74 with correlative compression of the spring 77. The 
clearance m which is thus permitted is equal at a maximum to the distance 
z between the sleeve 79 and an end-piece 76a of the support member 76 in 
the fully closed position. 
The effort exerted by the spring 77 maintains the roller 16 applied against 
the wall 13c (FIG. 20) and the helical spring 43 maintains said roller 16 
applied against the wall 13d. When the unlocking operation is carried out 
by means of the endless screw 3, the roller 16 moves away from the wall 
13c at M.sub.10 towards a position in which it is applied against the wall 
13b and continues to move in the direction of the arrow V. 
If the unlocking operation takes place by means of the unlocking device 15, 
the roller 16 is moved from M.sub.1 to M.sub.10 and then to M.sub.12 as a 
result of action produced on the finger 18a. 
When the door-leaf is displaced by hand in the direction V, the roller 
moves from M.sub.12 to M.sub.4, at which point the finger 18a moves away 
from the end portion 20a of the unlocking lever; the combined effects of 
the reaction of the endless screw 3 which is driven by the nut 17 and of 
the action of the helical spring 43 result in displacement of the finger 
which is applied against the wall 13a at M.sub.5. 
If m is higher than the initial and predetermined value z which corresponds 
to the maximum permissible clearance in the closed position, locking of 
the nut 17 is not possible. 
This embodiment is advantageous since it endows the door-leaf with a degree 
of freedom in translational motion with respect to its control system. 
Thus, even if an obstacle having a dimension smaller than the 
predetermined value z is placed between the fixed jamb post of a doorway 
and the movable edge of the door-leaf, locking and unlocking take place in 
the normal manner. 
The locking device which provides a predetermined opening clearance z in 
accordance with FIG. 11 can be applied to a door having two associated 
leaves as shown in FIG. 19. To this end, the support member 76 of FIG. 11 
is not only attached to one of the door-leaves 50 but also carries a fork 
76a for a nut 81 mounted on an endless screw having two threaded portions 
83a, 83b of opposite hand. The portion 83b is intended to receive a nut 82 
which is coupled to the doorleaf 51 in translational motion by means of a 
fork 57 attached to this latter. 
By virtue of these connections, locking is possible as long as the 
controlled door-leaf 50 is located at a distance m from its end-of-travel 
position Q, said distance being shorter than the initial predetermined 
length of z. It is accordingly possible to interpose between the two 
door-leaves 50 and 51 an obstacle 84 which forms a stop and maintains said 
door-leaves at a distance equal to 2 z at a maximum. 
If the interposed obstacle 84 is greater than double the predetermined 
initial value of z, locking of the nut 17 will not be possible. 
This alternative embodiment combines all the advantages provided by a 
single and independent control system applied to the control of a sliding 
door having two leaves while at the same time ensuring that the safety 
conditions laid down in public transport vehicles are satisfied, namely 
that an obstacle of a certain size can be interposed between the two 
door-leaves without interfering with their locking action. 
The invention is clearly not limited to the embodiments described in the 
foregoing and alternative forms of construction can in any case be 
contemplated. 
Thus the forks can be located in a plane which is different from that of 
the door-leaf and different from the plane which passes through the axes 
of the endless screws and corresponding guides. The arrangements thus 
obtained are readily adaptable to the curvature of transportation vehicle 
bodies equipped with doors of this type. 
Moreover, the nut 9 which serves to carry out the locking operation need 
not be mounted on an endless screw but, as shown in FIG. 23, could be 
placed on the threaded end 91 of a sliding rod 92 which can be displaced 
in translational motion in the directions U and V by means of a linear 
motor 93. 
As in the embodiments described earlier, the nut 9 carries a roller 11 
which is capable of displacement within a guide 13; said guide opens into 
the recessed portion A which is limited by a stop 94. 
When the roller 11 is applied against the stop 94 and the rod 92 continues 
to advance at least over a predetermined distance, the nut 9 cannot 
advance with rod 92 and so is caused to rotate about the rod 92 by the cam 
action of the screw threads at 91 and comes into the locking position. Of 
course, the fact that the nut 9 rotates about the rod 92 means that the 
rod 92 does not rotate relative to motor 93. 
It will further be noted that, in the design of the recessed portion A 
shown in FIG. 20, for example, the setback portion 13e, 13f of the wall 
13b corresponds to a particular case related to a particular arrangement 
of the manual unlocking device (not shown). As a general rule, it is 
possible to replace the walls 13e, 13f by a single rectilinear wall 13q 
located in the line of extension of the wall 13b. The result thereby 
achieved is to facilitate the operation of the device.