Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a safety device for
~ locking a door, cover or the like openable or removable
guard which is normally kept locked to guard machinery
or an area which is potentially hazardous.
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British Patent No. 1 260 322 discloses a safety ,
device comprising a lock unit for connection to a fixed
structure of machinery, and a captive key unit for
connection to a door, cover or guard of the machinery,
~the two units being adapted so that they can be engaged
and locked together by rotation of the captive key when
the door is closed. The lock unit also incorporates
electrical switching means which is controlled by ~'
rotation of the captive key and which in turn controls ' , ','
the power supply to the machinery so that power is ~- '`''
connected only when the two units are locked together '~
and is disconnected when the captive key is turned to
an OPEN position in which the two units can be freely
disengaged and engaged to open and close the door. ~ ,,
This known safety device is adequate for machinery ~' '
which is rendered safe as soon as the power supply is i~ ','-
disconnected. ~Iowever, it is not ade~uate for machinery -'
which remains potentially dangerous for some time after ~ :-
power is disconnected, because the door can then be ~'
opened ,while the machinery is still in a dangerous state. ,`~''~1 '
For example, the machinery may have rotating parts which 1 '';
do not come to rest immediately power is disconnected,
either because of the inertia of these parts or because ~1',' ;
they are stopped gradually, such as in a textile mill , ';
to prevent the breaking of fibres. An object of the , ~,;,,
present invention is to provide a safety device which ' ' ,
overcomes this shortcoming of the known safety device.
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The present invention consists in a safety device
comprising a first unit which is adapted for connection '. .'
to a fixed structure of machinery and which includes ' , '" ,
electrical switching means for controlling power to the
machinery; a second unit which is adapted for connection
to a door, cover or guard and which includes manuaIly ¦'
operable keying means wh~ich is movable between successive '"'
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OPEN, OFF and ON positions and is engagable with and
disen~ageable from said first unit when in the OPEN -.
position and co-operates with the first unit to prevent
separation of the two units when engaged with the first
unit and moved to the OFF and ON positions, the keying .
means further controlling operation of the switching
means when both units are engaged so that power is :
connected to the machinery on:Ly when the keying means is : .
in the ON position; and delay means which is operative on ~ .
movement of said keying means from the ON to the OFF
position and which then acts for a limited time to
positively prevent movement of the keying means from
the OFF to the OPEN position. Said limited time
is such as to allow dangerous conditions in the
machinery to abate following disconnection of power,
the time being either a predetermined time or a time
determined by sensor means which senses said dangerous
conditions.
. The delay means preferably comprises mechanical
stop means which arrests the keying means in the OFF
position and timer means which is triggered when the
keying means reaches said OFF position and which, a
predetermined time thereafter, operates the stop means ~: :
to allow continued movement of the keying means to
the OPEN position. ~
The keying means may comprise a rotatable key ~::.~-
captive in the second unit and having laterally extending .~
lugs which are insertable through corresponding slots ~-
in the first unit when the key is in ~he OPEN position
and which co-operate with abutment surfaces in the .~
first unit to prevent withdrawal of the key when the ~ -
latter is inserted into the first unit and turned:to ~ :
the ON position. . .:
Further, said key may be provided with bittings :.,
which engage a cylinder lock mechanism in the first -
unit to effect release of a lock spindle, the lugs of
the key engaging corresponding grooves in the lock
spindle so that the key and lock spindle rotate together, ~ ..
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rotation of the lock spindle in turn controlling
operation of the electrical switching means. By these
means operation of the-switching means by any~hing other
than the captive key o~ the second unit is prevented so
that the guard must be closed and the two units locked
together before the switchinc~ means can be operated to
connect power to the guarded machinery.
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The invention will now be described by way of
example with reference to the accompanying drawings in
which:-
Figure 1 is a side elevation of an embodiment
of the invention,
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Figure 2 is a plan view of the embodiment of
Figure 1, ;
Figure 3 is a view along the line 3-3 in
Figure 2, and
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Fi~ure 4 is a perspective of the captive key
unit and lock unit of Figures 1 and 2.
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Figures 1 to 4 o~ the drawings show a safety device
comprising two-separate units, one of which units 1 - ~ -
f comprises a casing 2 which houses a lock body 3 and is ~-
adapted for connection to the frame 4 of machinery to
be guarded~ and the other of which units 5 comprises a ~-
captive key body 6 which is adapted for connection to ,
i a door, cover or guard 7 provided on the frame ~ and
which slidably and -rotatably supports a control knob 8
and a key 9 which is adapted to co-operate with the lock
body 3 as hereinafter described to lock both units 1 ~
and 5 together with the guard 7 closed. ~;
The control knob 8 is a hollow cylindrical
member which fits telescopically over the key body 6
and which has the key 9 pro~ecting axially from it
inside. The key 9 is a slidable and rotatable fit in a
bore in the key body 6 and is hollowed out at its free -
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end to form a key bit 10 with a cylindrical socket to
engage a locating peg 11 in the lock body 3. Two laterally
extending diametrically opposed key lugs 12 are formed
at the extremity of the key bit 10 and these are received
in a corresponding pair of guide recesses 13 in the key
body 6 when the door 7 is open and the control knob 8
is released, as shown in Figure 1, a coil spring 14
then acting between the head of the control knob and the
key body to retract the key into the key body.
l~ The lock body 3 houses a cylinder lock mechanism
of the axial pin tumbler type comprising a barrel or
pin tumbler holder 15 fixed in the body 3 and a co-operating
rotatable barrel or pin tumbler holder 16 which is
integral with a lock spindle 17 rotatable in the body 3.
The lock body 3 has a coned face bezel 18 `
to engage a corresponding coned seating l9 on the key
body. In the front wall of the bezel a keyhole 20 is formed -
comprising a central hole to receive the key bit 10 and a ,
pair of diametrically opposed slots 21 to receive the key
~o lugs 12 on the key bit. Further, the lock spindle 17 is ' -~
formed with a pair of diametrically opposed grooves 22
in its barrel 16 to receive the key lugs 12.
When-the door 7 is-closed the seating 19 on
the key body 6 engages-the bezel 18 on the lock body 3.
The control knob 8 can then be depressed against the
action of the spring 14 to insert the key bit 10 through
the keyhole 20, it being guided by the locating peg 11
and the key lugs 12 passing through the slots 21 in the
bezel 18 on the lock body and enyaging the grooves 22
in the barrel 16 on the lock spindle 17. Key bittings 23
are provided circumferentially between the key lugs 12
in the end of the key bit 10 (see Figure 4), and these
co-operate with the pin tumblers 24 of the cylinder lock
mechanism in the lock body 3 (as shown in Figure 1) to
release the barrel 16 for rotation of the lock spindle
by the key 9 acting through the key lugs 12 in the
grooves 22. In turning the key 9 and lock spindle 17,
the key lugs 12 move behind the portions of the front
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wall of the bezel 18 which lie between the keyhole slots
20 and which form abutment surfaces against which the
key lugs engage to lock the two units 1 and 5 together.
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The lock spindle 17 is connected by a sleeve 25to a further spindle 26 which carries the cams 27,28
of each of two electrical switches 29j30, respectively.
Both switches are o~ the type in which the cam controls ~`
the position of a bridge member which serves to form a
bridging connection between input and output terminals
\a of the switch. The one switch 29 is connected so as
to control the supply of power to the machinery being
guarded and serves to connect power only when the two
units 1 and 5 are locked together with the control knob 8 ~
in an ON position. From this O~ position the control -
knob can be turned towards an OPEN position in which the
two units 1 and 5 are unlocked, the key 3 then being
disengageable from the lock body 3. Between these two
positions the control knob assumes an OFF position in
which the switch 29 disconnects power from the machinery ~;
being guarded but in which the two units 1 and 5 are
still locked together.
The safety device therefore protects personnel
against injury by preventing the connection of power
to the machinery unless the door 7 is closed and locked : -
- by depression and rotation of the control knob 8 to
the ON position. Subse~uent unlocking of the door
automatically disconnects the power. The provision of
the coded bittings 23 on the key to operate the lock -
tumbler mechanism makes it impossible to connect power
to the unguarded machinery by insertion of a simple
object through the keyhole in the lo~k body. ~:
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The safety device described so far is as disclosed ;
in our Patent No. 1 260 322. However, the present device ~ ,
is further modified according to the present in~ention
by providing delay means which, when units 1 and 5 are
Iocked together, responds to turning of the control knob
from the ON to the OFF position by introducing a tlme
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delay before the control knob can be turner further to
the OPEN position.
The delay means includes a solenoid-operated
plunger 31 which is mounted within the casing 2 so as
to extend parallel to the lock spindle 17 and to
co-operate with a cam plate 32 which is connected to
the sleeve 25. When the solenoid is de-energised and
the control knob 8 is in the ON and OFF positions,
; the plunger 31 is spring urged outwardly of the solenoid
V so that its outer end engages in a peripheral notch 33
in the- cam plate 32 (see Figure 3). In the ON position,
the plunger 31 engages one end of the notch 33 and
in the OFF position the plunger 31 engages the other
end of the notch, as shown in Figure 3. The plunger 31
then prevents the control knob from being turned further i
to the OPEN position. The delay means further comprises ~`
the electrical switch 30 and a timer circuit 34 which is
controlled by the switch 30 and which in turn controls;~
energisation of the solenoid oE plunger 31. The switch 30
~Dis operated when the control knob reaches thè OFF position
and then triggers the timer circuit 34 which in turn
energises the solenoid after a predetermined time delay.
The plunger 31 is thereby withdrawn from the notch 33
in cam plate 32, whereupon the control knob can be -
turned to the OPEN position and the door 7 opened.
The predetermined time delay o the timer circuit is
selected so as to allow dangerous conditions in the
machinery to abate before the door can be opened. i
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- In an alternative embodiment of the invention,
~V the timer circuit 34 of the illustrated embodiment may
be replaced by sensor means which senses the existence ~
of a potentially dangerous condition in the guarded -
machinery and energises the solenoid of plunger 31 only
when this condition has abated. The sensor means may
be triggered by a switch, such as the switch 30, so
as to operate only after the control knob 8 is turned
from the ON to the OFF position. Alternatively, the
sensor means may operate continuously to sense said
potentially dangerous condition and to allow energisation
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of the solenoid only when said condition abates
~ irrespective of whether the control knob is in the
I ON or OFF position.
! It will be appreciated that failure of the solenoid
`. circuitry will prevent energisation of the solenoid,
whereupon the control knob will be locked in the Oi~
or OFF position and the two units 1 and 5 will be
locked together. The illustrated safety device is
therefore "fail-safe" in design.
o- It will be further appreciated that the position
of the cam plate 32 is not important and that it may be
preferable to mount it on the shaft 26 on the other
side of the switches 29,30 from the lock body 3~ The
solenoid-operated plunger 31 would then be suitably
relocated.
Further, although the illustrated embodiment is
provided with a tumbler lock mechanism so as to prevent
rotation of the lock spindle by insèrtion of a simple
object into the keyhole, it will be appreciated that ~ -
~0 this tumbler lock mechanism can be omitted either from
the illustrated embodiment or any of the other
embodiments described above. This does allow the
possibility of rotation of the lock spindle by means
other than the captive key in the key body, but this may
be acceptable in some non-industrial applications,
- for example in domestic appliances such as spin driers.; <~
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