Note: Descriptions are shown in the official language in which they were submitted.
:lZSlZ~
-- 1 --
Door latch arran~ement
The invention relates to a door latch arrangement.
The invention is particularly useful as an
emergency release mechanism for actuator driven doors
which are positively latched in the closed position.
Doors of this type may be found on vehicles,
particularly railway vehicles, and most recently as
safety doors along the edge of a platform in an
underground railway or mass rapid transit railway
system.
According to the invention there is provided a
latch arrangement for at least one door having an
opening and closing mechanism comprising co-operating
latch members arranged to mutually engage to latch a
door in the closed position and, for unlatching the
door manually, a handle in the door connected to a
first unlatching member carried in the door which is
arranged upon movement of the handle to unlatch the
co-operating members, and in a door-frame a member
disposed to abut the member in the door, in the closed
postion, for movement therewith to effect
de-energisation of a prime mover in the opening and
closing mechanism.
In the case where the door is driven by a
pneumatic actuator, the door-frame member is arranged
to release pneumatic pressure from an actuator
cylinder to permit movement of the door. Preferrably
when the actuator is electrically controlled the
headframe member may be arranged to effect electrical
isolation of the actuator.
The invention, and how it may be carried into
practice, will now be described by way of example of
L~40
only, with reference to the accompanying drawings, in
which:
Fig 1 shows a general view of a door latch
arrangement,
Fig 2 shows a detail view of part of the emergency
release mechanism, and
Fig 3 shows a detail view of the door latching
mechanism.
The embodiment of the invention which will now be
particularly described concerns platform edge doors,
which according to latest safety thinking, are
installed along a platform edge in an underground
railway or mass transit station to provide an
effective safety screen between waiting passengers on
the platform and the railway track area and
20 particularly a moving vehicle. In a typical
installation there is provided a continuous
half-glazed screen along the platform edge with
sliding doors spaced apart at intervals co-incident
with the door spacing of the railway vehicles.
The screen doors are operated by actuators and
normally latched in the closed position except when a
train has come to rest in the correct position
whereupon the screen doors are opened, together with
the vehicle doors, to permit passengers to enter and
exit the vehicle. The screen doors maybe
automatically or, at least, remotely operated and are
not intentionally provided with any means of opening
accessible to waiting passengers.
However, in order to allow vehicle passengers to
leave the vehicle in an emergency, it is intended to
~'~5~1 'Z~
provide an emergency door unlatching mechanism which
can be operated by passengers only from the track side
of the screen doors, although facility is provided for
operation from the platform side by authorised
personnel by means of a special key. Each door, or
each set of doors, is provided with a handle on the
track side which may be operated by a passenger
standing in the open doorway of a vehicle, and which
unlatches the doors. Preferrably this also releases
pneumatic pressure from the door actuator which maybe
retained normally to positively hold the screen doors
in the closed position. Thus in an emergency the
screen doors can be opened manually.
Referring now to Fig 1 there is shown a side view
of part of a screen door carriage and latching
mechanism for a pair of bi-parting doors. The two
doors are of the sliding type and are carried by
roller carriages, two of which are shown at 3 and 4
respectively which run in roller tracks 5 and 6
extending longitudinally with respect to the screen
(not shown) and positioned above the door opening and
to either side thereof. The inner edges of the doors
are provided with lip seals la and 2a which abut each
other when the doors are closed, as shown in the
drawings.
The doors 1 and 2 are suspended from carriages 3
and 4 by brackets 7 and 8 which extend downwardly
through elongate slots in the underside of a headframe
cover. The tracks 5 and 6 carriage, brackets and
other parts of the mechanism are all concealed by the
headframe cover, not shown in the drawing.
The actuator which powers the door closing/opening
mechanism is generally indicated at 9 and comprises a
long stroke, double-acting linear actuator in which a
12S~
moving piston (not shown) located within the cylinder
10 of the actuator is connected to an actuator rod 11.
The motive power of the actuator 9 is provided by
pneumatic pressure which maybe admitted through valve
means to either end of the actuator cylinder 10.
Thus, by moving the piston the rod 11 can be extended
leftwards in the drawing to open the doors, or
retracted to close the doors. The actuator rod 11 is
connected to the drive bracket 13 of the left hand
door 1 and the actuator force is transmitted to the
right hand door 2 by an endless belt 30 connected to
both brackets. In the drawing the door on the ]eft is
driven and that on the right is a slave door.
The mechanism for latching the doors in the closed
position comprises a pivoted latch member 12 mounted
on the bracket 13 of the driver door and which a
hooked part 12a engages with a peg or block 14a fixed
to ~he bracket 14 of the slave door. The latch member
12 may be pivoted anti-clockwise to disengage the
latch release the doors from the locked position.
The latch member 12 is operated by abutment with a
flanged latch striker 15 carried towards the outer end
of the actuator rod 11. This remote end of rod 11 is
provided with a resilient overtravel mechanism 16, by
means of which the drive bracket 13 is connected to
the actuator rod 11 for limited relative movement.
When the driven door and therefore drive bracket 13,
has reached the closed position the rod 11 is
permitted a limited amount of overtravel during which
the latch striker 15 abuts a heal 17 on part of the
latch member 12, and rotates the member 12 into
locking engagement with latch block 14a on the
brackets 14, providing that the slave door has not
been obstructed and has also completely closed. This
position of the rod 11 and associated parts, reached
lZ5~Z~O
-- 5 --
through the overtravel movement, is held while the
doors are locked, by residual pressure in the actuator
9.
In a normal opening sequence as soon as pressure
is vented from the "closing" end of the actuator
cylinder 10 the resilience of the overtravel mechanism
15 takes up the overtravel distance thereby moving the
latch member 12 to the unlatched position which allows
the doors to be moved by subsequent further movement
of the actuator rod 11 under the influence of
pneumatic pressure in the "opening" end of the
cylinder. The emergency unlatching mechanism provided
by the invention is intended inter alia to permit
15 manual release of the trapped pressure in the actuator
thereby unlatching the doors so that they may be
pushed open.
As previously mentioned, the screen doors have an
emergency release handle (not shown) for manual
operation located on the track side of one of the
doors. The emergency release handle is connected to a
push rod 18 mounted within the door 2 for vertical
axial movement. Co-axial with the rod 18, but mounted
for vertical axial movement within the headframe space
is a further rod or member comprising two parts 19
(Fig. 2) and l9a (Fig. 3) which carry several fixed
abutments or flanges, a first of these is a member 20
fixed to the rod 19 adjacent latch member 12 and in a
position to abut a pin 20a secured in the latch member
12. A second such member provides a shoulder 21 on
the rod 19 adjacent an isolating valve 22 connected in
the pneumatic system of actuator 9. Isolating valve
22 comprises a pressure release valve having a valve
operating member 23 which is depressed to open the
valve 22 and release actuator press~re.
~ ~ 5~
Normally, that is when the door emergency release
handle is not operated, the upper end of rod 18 is
substantially flush with the upper surface of door 2,
when the handle is operated the rod 18 is extended
into the headframe space abuting the lower end of rod
19 thereby moving it axially and vertically upwards.
The corresponding upward movement of rod 19 brings
member 20 into abutment with the pin 20a of latch
member 12 (see Fig 3), and the shoulder 21 into
contact with the operating member 23 of the isolating
valve 22 (see Fig 2). Deployment of the emergency
release handle causes the shoulder 21 to depress the
operating member 23 releasing pressure from the
actuator cylinder, to rotate the latch member 12 in an
anti-clockwise direction to unlatch the doors.
Thereafter, it is possible for the doors 1 and 2 to be
manually pushed back from the closed position since
there will now be no opposing force other than the
inertia and friction of the mechanism.
The emergency release arrangement of the described
embodiment only isolates the pneumatic parts of the
door actuator system and leaves the electrical control
system uninterrupted. In an alternative arrangement
it may be preferred to break the electrical control
circuits also, for example by means of a switch, such
as a microswitch 24, connected in series with the
control circuits and operated by the shoulder 21. The
switch 24, in the embodiment, is a rocker type switch
and the rocker operating member is disposed to be
engaged by the shoulder 21 formed on rod 19 and
preferably subsequent to said shoulder having deployed
the valve operating member 23.
Upon the doors being manually opened, the lower
part of the rod 19a resets to allow the doors to be
manually closed and latched, but retaining pneumatic
i~ 51'~ ~
or pneumatic and electrical isolation. The member
comprising shoulder 21 on rod ].9 also provides two
stepped shoulders 25 and 26, seen in Fig 2, which
co-operate with a spring loaded plunger or detent
mechanism to engage and hold the rod 19 in either of
two deployed positions. This mechanism comprises a
plunger 27, sprung against the member 21a by a coil
spring 28 in compression. The plunger may be
withdrawn against the bias of spring 28 by means of a
latch type arrangement operated by a square drive
keyway 29, a co-operating key being normally issued to
authorised personnel for the purpose of resetting the
emergency door release mechanism.
In emergency operation use of the passenger handle
raises the member 21a sufficiently for the plunger 27
to extend by a first step and positively engage the
first step 25, in which position the pneumatic
isolation valve 22 is operated enabling the doors to
be opened manually. Engagement of the plunger 27 with
the shoulder 25 ensures that pneumatic pressure cannot
be readmitted to the actuator until the mechanism is
reset.
The rod l9 may be raised further to obtain
operation of the electrical isolation switch 24, in
which position plunger 21 extends to a second step
engaging with the second stepped shoulder 26. Again
the electrical circuits can only be remade by
resetting the mechanism by withdrawal of plunger 27.
This second position cannot normally be achieved by
operation of the passenger accessible door mounted
emergency handle only, because the rod located in the
door does not impart sufficient lift to the rod in the
door-frame housing.
The additional lift required is provided in one
~251,'~
-- 8
embodiment by means of a straight forward lifting
handle 34 attached to the member 21a, see Fig 2.
In an alternative arrangement, which is depicted
in Fig 1 the door actuator may be isolated e.g. for
maintenance by means of a lever 33 pivoted about a
horizontal a~is 31 and having at one end a handle 32
which may be pulled down on the platform side of the
platform doors. The other end of lever 33 is linked
to the upper end of rod 19, so that by pulling down on
the handle 32 the rod 19 is lifted and the actuator
isolating valve 22 is operated.
