U.S. patent number 3,876,385 [Application Number 05/276,803] was granted by the patent office on 1975-04-08 for fail-safe system for operating an autoclave door.
This patent grant is currently assigned to Johns-Manville Corporation. Invention is credited to Arthur Russell Markus, John Ostapovich.
United States Patent |
3,876,385 |
Markus , et al. |
April 8, 1975 |
Fail-safe system for operating an autoclave door
Abstract
A fail-safe key interlock system prevents an autoclave door from
being opened when steam pressure within the autoclave is above a
predetermined level, and prevents a steam supply valve of the
autoclave from being opened unless the autoclave door is closed,
latched and locked. The system is fail-safe in that if there is a
loss of electrical power or control air pressure, the door cannot
be opened and the steam supply valve is closed or remains
closed.
Inventors: |
Markus; Arthur Russell
(Englewood, CO), Ostapovich; John (Denver, CO) |
Assignee: |
Johns-Manville Corporation (New
York, NY)
|
Family
ID: |
23058132 |
Appl.
No.: |
05/276,803 |
Filed: |
July 31, 1972 |
Current U.S.
Class: |
422/118; 49/31;
220/316; 49/35; 422/242 |
Current CPC
Class: |
B01J
3/03 (20130101); F16J 13/24 (20130101) |
Current International
Class: |
F16J
13/24 (20060101); B01J 3/03 (20060101); F16J
13/00 (20060101); B01j 003/00 (); B65d 045/00 ();
E05d 065/00 () |
Field of
Search: |
;23/290 ;21/94-98
;49/31,35,68 ;220/55.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Wolk; Morris O.
Assistant Examiner: Phillips; Roger F.
Attorney, Agent or Firm: Krone; Robert M. Lister; John
D.
Claims
What we claim is:
1. A system for safely operating a door of an autoclave which is
normally pressurized when in operation comprising:
a. means for sensing pressure within the autoclave and for
preventing the door from being opened when the pressure within the
autoclave is above a predetermined level, the means for sensing
pressure within the autoclave and for preventing the door from
being opened including a first key interlock unit, said first unit
having a first lock and a key for said lock, and said first unit
having a means for preventing removal of the key from said lock
until the pressure within the autoclave is below the predetermined
level;
b. locking means for locking the door in a closed position, said
locking means including a second key interlock unit, said second
unit having a second lock which is fit by said key so that the door
can be unlocked only after said key has been removed from said
first unit; and
c. means for closing a steam supply valve of the autoclave and for
maintaining the steam supply valve closed when the door is being
opened, is open or is being closed.
2. The system of claim 1 wherein:
a. the means for maintaining the steam supply valve closed includes
means for preventing the steam supply valve from being opened in
said first key interlock unit which is actuated by moving the key
in the first lock to a position where the key can be removed from
the first lock.
3. The system of claim 2 wherein:
a. the means for maintaining the steam supply valve closed includes
means for preventing the steam supply valve from being opened which
is actuated when the door is unlocked.
4. The system of claim 1 wherein:
a. the means for maintaining the steam supply valve closed includes
means for preventing the steam supply valve from being opened which
is actuated when the door is unlocked.
5. The system of claim 1 wherein:
a. vent means is provided for venting the autoclave; and
b. the locking means includes means for opening the vent means as
the door is being unlocked.
6. A system for safely operating a door of an autoclave oven which
is pressurized when in operation comprising:
a. a door having lugs spaced about the perimeter of the door;
b. a retaining ring on the autoclave, the retaining ring having
lugs spaced about the ring for cooperating with the door lugs to
retain the door in a closed position;
c. rotating means for rotating the door and the ring relative to
each other to latch or unlatch the door by engaging or disengaging
the lugs;
d. means for opening and closing the door;
e. a steam supply valve for supplying the autoclaves with
pressurized steam;
f. means for sensing pressure within the autoclave and for
preventing the door from being opened when the pressure within the
autoclave is above a predetermined level, the means for sensing
pressure within the autoclave and for preventing the door from
being opened including a first key interlock unit, said first unit
having a first lock and a key for said lock, and said first unit
having a means for preventing removal of the key from said lock
until the pressure within the autoclave is below the predetermined
level;
g. locking means for locking the door in a closed position, said
locking means including a second key interlock unit, said second
unit having a second lock which is fit by said key so that the door
can be unlocked only after said key has been removed from said
first unit; and
h. means for closing a steam supply valve of the autoclave and for
maintaining the steam supply valve closed when the door is being
opened, is open or is being closed.
7. The system of claim 6 wherein:
a. vent means is provided for venting the autoclave; and
b. the locking means includes means for opening the vent means as
the door is being unlocked.
8. The system of claim 7 wherein:
a. the locking means includes means for preventing actuation of the
rotating means when the door is locked.
9. The system of claim 8 wherein:
a. means is provided to prevent actuation of the means for opening
and closing the door unless the door is unlatched.
10. The system of claim 9 wherein:
a. the retaining ring is stationary;
b. the door is rotatably mounted on the autoclave; and
c. the rotating means rotates the door to effect the latching or
unlatching of the door.
11. The system of claim 9 wherein:
a. the retaining ring is rotatably mounted on the autoclave;
and
b. the rotating means rotates the retaining ring to effect the
latching or unlatching of the door.
12. The system of claim 9 wherein:
the means for sensing pressure within the autoclave and for
preventing the door from being opened and the means for closing the
steam supply valve and for maintaining the steam supply valve
closed are electrically and pneumatically operated in such a manner
that an electrical or pneumatic failure prevents the door from
being opened and closes the steam supply valve.
Description
BACKGROUND OF THE INVENTION
The present invention is directed to a system for safely operating
an autoclave door and, in particular, to a fail-safe system which
assures that the autoclave door cannot be opened unless the
pressure within the autoclave is below a predetermined level and a
steam supply valve is shut off.
Autoclaves are usually thick-walled steel vessels utilized to carry
out chemical reactions and the like under relatively high pressure
and temperatures. These vessels, which typically employ steam under
pressures of 100-150 psi, have massive steel doors which range from
5-9 feet in diameter and can have up to about 1,700,000 pounds of
force exerted on them when the autoclave is pressurized. When one
of these doors is accidentally opened while an autoclave is still
pressurized, the results are disastrous. The hugh door is blown off
its hinges and sometimes through walls while the main portion of
the oven is generally moved several feet off its foundation in the
opposite direction. Obviously, anyone standing in front of one of
these massive doors is generally killed and even those who are not
hit by the door can be severely burned by the steam released from
the autoclave. Not only have these accidents resulted in the loss
of human life but, in addition, the damages caused are sometimes
extensive, amounting to hundreds of thousands of dollars.
Consequently, there is a need to provide a fail-safe system to
prevent the occurrence of such accidents.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a
fail-safe system for preventing an autoclave door from being opened
when steam pressure within the autoclave is above a certain level
and for assuring the steam supply valve is closed when the
autoclave door is being opened, is open or is being closed.
The present invention provides a fail-safe key interlock system for
an autoclave door. The system includes a control means for opening
and closing the steam supply valve for the autoclave; a means,
including a key interlock means, for preventing the door from being
unlocked or opened when the pressure within the autoclave is above
a predetermined level and for preventing the steam supply valve
from being accidentally turned on when the door is not closed,
latched and locked; a door-locking means; and hydraulic mechanisms
for latching or unlatching and opening and closing the door.
The system is fail-safe in that if there is a power failure or a
loss of control air pressure, the steam supply valve is closed or
remains closed and the door can not be unlatched.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of the fail-safe autoclave door-opening
system of the present invention as applied to a rotating door which
is shown closed, latched and locked;
FIG. 2 is a front elevational view of a typical rotating door
utilizing the control system of FIG. 1;
FIG. 3 is a side elevational view of the rotating door of FIG. 2
with portions broken away for clarity and to illustrate a latching
mechanism of the door;
FIG. 4 is a diagrammatic representation of a solenoid key-release
unit of the key interlock of the system;
FIG. 5 is an elevational view with portions broken away of a
locking mechanism for the door of FIGS. 2 and 3 with a second
component of the key interlock illustrated;
FIG. 6 is a plan view of FIG. 5;
FIG. 7 is a side elevational view of FIG. 5 taken generally along
lines 7--7; and
FIG. 8 is a schematic representation of a second embodiment of the
invention, modified somewhat for use with an autoclave door which
is latched by a rotating ring with the door shown closed, unlocked
and unlatched.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The fail-safe door-opening system of the present invention is
primarily intended for use with autoclaves. While the detailed
description will primarily deal with an autoclave having a rotating
door, as illustrated in FIGS. 1-7 of the specification, the system
with slight modifications can be used equally as well with a
rotating ring autoclave door assembly such as that illustrated in
FIG. 8 plus other types of autoclave doors.
As best shown in FIGS. 1, 2 and 3, an autoclave 20 comprises a
thick-walled steel vessel 22 with a door 24 mounted thereon. The
door 24 is rotatably mounted on a hub 26 for rotation about its
central axis. The hub 26 is located at the outer end of a support
arm 28 which is pivotally secured to the vessel 22 by a hinge
assembly 30. The periphery of the door 24 is provided with
circumferentially spaced-apart lugs 32. These lugs cooperate with
lugs 34 on a retaining ring 36, which is welded or otherwise
affixed to the vessel 22 to retain the door in a closed position
when the autoclave is pressurized. The length of each of the lugs
32 corresponds to the spacing between the lugs 34 and vice versa.
Consequently, when the lugs 32 on the door 24 are properly aligned
with the spaces between the lugs 34 on the retaining ring 36, the
lugs on the door can pass between the lugs 34 on the retaining ring
and the door can be opened or closed.
The autoclave door 24 is rotated about its central axis by a pair
of double acting hydraulic cylinders 38 and 40. These cylinders are
each pivotally secured at one end to the door 24 and at the other
end to support arm 28. Since the hydraulic cylinders 38 and 40 are
both double acting piston-type cylinders, they can be used in
unison to rotate the door 24 both clockwise and counterclockwise
about its central axis to latch or unlatch the door.
In addition to the hydraulic cylinders 38 and 40, the autoclave
door 24 is provided with a double acting piston-type hydraulic
cylinder 42 for swinging the door about the hinge assembly 30 to
open and close the door. The cylinder 42 is pivotally secured at
one end to the support arm 28 and at its other end to the vessel
22.
The door 24 is also provided with a locking mechanism 44 which is
illustrated in detail in FIGS. 5, 6 and 7. The locking mechanism 44
is provided with a locking bar 46 that is pivotally mounted on a
steam vent valve 48 which is secured to the vessel 22. The locking
bar 46 cooperates with and is received within a slot of a yoke 50
mounted on the door 24 to prevent rotation of the door about its
central axis. The locking bar 46 also cooperates with and is
received within a slot of a yoke 51 which is affixed to the
retaining ring 36. The yoke 51 holds the locking lever bar in
position when the door is locked and the locking bar 46 cooperates
with yoke 50 on the door to keep the door from rotating.
The door 24 can also be provided with a second locking mechanism to
prevent rotation of the door about its central axis. This second
locking mechanism comprises a lever 52 that is pivotally secured to
the door and provided with notches 54. The notches 54 cooperate
with a protrusion 55 on an extension of the support arm 28 to
secure the door in the correct angular position for opening and
closing the door and the correct angular position for maintaining
the door in a latched position.
The overall fail-safe door-opening system of the present invention
is best illustrated in FIG. 1. To facilitate the understanding of
the Figure, electrical connections between components are indicated
by lines having crossbars thereon; air control lines are indicated
by dashed lines, and hydraulic lines and all other lines are
indicated by solid lines. The sources of electrical power, control
air and hydraulic fluid are not shown.
As shown in FIG. 1, the autoclave is provided with a steam inlet
valve 56 which connects the autoclave with a source of pressurized
steam (e.g., pressurized to 100-150 psi). The valve 56 is a two-way
pneumatically actuated spring return valve. Consequently, the valve
is closed when the actuating mechanism 58 of the valve is vented or
not pressurized and the valve is open when the actuating mechanism
58 is pressurized. The actuating mechanism 58 is connected to a
supply of pressurized air through an air control line which is
provided with a three-way solenoid air valve 60, a three-way
pneumatically actuated spring return air valve 62, and a
conventional controller 64.
When the solenoid valve 60 is energized, the three-way solenoid air
valve 60 permits the passage of pressurized air through the air
control line to the actuating mechanism 58 of the steam valve 56.
When the solenoid valve 60 is de-energized the valve 60 is shifted
to interrupt the passage of air from the controller 64 through the
valve and to vent that portion of air control line leading from the
valve 60 to the actuating mechanism 58. Thus, when the solenoid
valve 60 is de-energized, the valve 60 functions to depressurize
mechanism 58 and thereby shut off the steam supply valve 56 for the
autoclave.
The three-way pressure actuated spring return air valve 62 permits
the passage of pressurized air through the air control line leading
to the actuating mechanism 58 when the valve 62 is pressurized. If
the valve 62 is depressurized, the spring shifts the valve to a
position where the flow of pressurized air through the valve to the
actuating mechanism 58 is cut off and that portion of the air
control line leading from the valve 62 to the actuating mechanism
58 is vented. Thus, when the valve 62 is depressurized, the
actuating mechanism 58 of steam supply valve 56 is depressurized to
shut off the steam supply valve 56.
The controller 64 is connected to a supply of pressurized air and
functions to regulate the degree of pressurization of the actuating
mechanism 58. When the pressure within the autoclave 20 is low, the
controller 64 pressurizes the actuating mechanism 58 to fully open
the valve 56. As the pressure within the autoclave increases, the
controller 64 gradually reduces the pressurization of the actuating
mechanism 58 to gradually close the steam supply valve 56. When the
correct operating pressure is reached within the autoclave, the
controller 64 reduces the pressure in the actuating mechanism 58
until the steam supply valve 56 is shut off.
A control panel of the system is provided with an "on-off" switch
having an "on" button 66 and an "off" button 68. This switch
energizes and de-energizes the solenoid valve 60 to turn the steam
supply valve 56 on or off.
The system also includes a pressure gauge 70 and a pressure switch
72. The pressure gauge 70 is provided to give a visual confirmation
of the actual pressure within the autoclave. When the pressure
within the autoclave drops to eight inches of water, the pressure
switch 72 is actuated to turn on green signal lights 74 and 76
which are located on the control panel and a solenoid key release
unit 78 respectively. At the same time, the switch turns off amber
signal lights 80 and 82 of the control panel and the solenoid key
release unit. Thus, the signal lights give visual indication as to
whether the pressure within the autoclave is above or below eight
inches of water. In addition to the above, pressure switch 72
energizes a solenoid 84 of the solenoid key release unit 78 when
the pressure in the autoclave drops below eight inches of
water.
As shown in FIG. 4, the solenoid key release unit 78 includes the
solenoid 84, a limit switch 86, an actuating bar 88, a lock 90 and
a key 92. The lock 90 has two positions. In a first position, a
slot in the actuating bar 88 is engaged by a rod of the solenoid 84
and the key 92 cannot be removed from the lock. In a second
position, where the limit switch is opened by the actuating bar 88,
the key can be removed from the lock. When the solenoid 84 is
energized by the pressure switch 72, it retracts the rod to free
the actuating bar 88 for movement. The key 92 can now be turned in
lock 90 from its first position to its second position to move the
actuating bar 88. When the actuating bar 88 has been moved, a
protruding portion on the upper side of the actuating bar 88
depresses the limit switch 86 to open that switch and shut off all
power to the "on-off" switch of the control panel. Thus, the
solenoid valve 60 cannot be energized to open the steam supply
valve 56. With the key 92 in its new position, the key can now be
removed from the lock 90 and utilized in the other component of the
interlock system to complete the unlocking of the door.
The door-unlocking mechanism 44 which comprises the other component
of the interlock unit, is provided with a lock 94 which is also
compatible with the key 92. By inserting the key 92 in the lock 94
and turning the key, a bolt 96 is retracted from an aperture within
the locking lever bar 46. With the bolt 96 removed, the locking
lever bar 46 can now be pivoted about the end which is secured to
valve 48 to open that valve and unlock the door 24. The locking
lever bar 46 is provided with a plate 98 which remains beneath the
bolt 96 when the lever 46 is swung open. Thus, the bolt 96 cannot
be re-extended unless it is aligned with the aperture in the
locking lever bar 46. Since the aperture in the locking lever bar
46 is only aligned with the bolt 96 when the bar is engaged with
yoke 50 and since the key cannot be removed unless the bolt 96 is
extended, the key 92 cannot be removed from the lock 94 unless the
locking lever bar is in the locked position.
Since the locking lever bar 46 is secured to a shaft 100 of the
steam vent valve 48 which is connected to the interior of the
autoclave. When the lever 46 is swung from its locked position,
where it engages yokes 50 and 51, to its opened position, the lever
46 turns the shaft 100 of the steam vent valve 48 to open this
valve. Consequently, the turning of the lever 46 vents any steam
which may still be left in the autoclave.
Locking lever bar 46 also carries a four-way cam operated spring
return air valve 102 which is connected directly to a supply of
pressurized air. The valve 102 is provided with a cam follower 104
which cooperates with a cam 106 secured to the door of the
autoclave. When the cam follower 104 is depressed by the cam 106,
the valve 102 connects the air actuated valve 62, a conventional
pressure actuated indicator light 108, and a pressure switch 110
with an air control pressure line. The pneumatic indicator light
108 is on when the air control pressure is normal. However, when
the air control pressure drops below its normal level, the
indicator light is automatically turned off to give a visual
indication of the pressure loss. The pressure switch 110 is
connected in series with the limit switch 86 and the "on-off"
switch of the control panel. Thus, the valve 102 normally maintains
the valve 62 open, the light 108 on, and the pressure switch 110
closed so that switch 110 does not interrupt the circuit for the
control panel. At the same time, the valve 102 vents a two-way air
actuated spring return valve 112 which is in a hydraulic line
connecting a control valve 114 with the hydraulic cylinders 38 and
40. With the valve 112 vented, the spring return of the valve 112
holds the valve in a closed position thereby preventing the
actuation of the cylinders 38 and 40 by means of the control valve
114.
When the lever 46 is swung to the unlocked position, the cam
follower 104 is no longer depressed by the cam 106 and the valve
102 is shifted to vent the valve 62, to vent the pneumatic
indicator light 108, to vent the pressure switch 110, and to
pressurize the valve 112. With the valve 62 vented, the valve 62
interrupts the air control line leading to the actuating mechanism
58 of the steam supply valve 56 and vents the actuating mechanism
58 to assure that the steam supply valve 56 cannot be opened while
the door is unlocked. With the pressure switch 110 vented, the
switch is opened to interrupt the control panel circuit for the
"on-off" switch. With the valve 112 activated, the hydraulic
circuit between the control valve 114 and the hydraulic cylinders
38 and 40 is complete and thus the actual unlatching and opening of
the door can now be commenced.
The valve 114 is a four-way lever operated valve. The valve is a
three-position valve and is spring centered so that when an
actuating lever 116 is in its neutral position, the ports leading
to the piston-type double-acting hydraulic cylinders 38 and 40 are
blocked and the pressure line for the hydraulic fluid is open back
to the reservoir. When the lever 116 is shifted to the left, as
viewed in FIG. 1, the hydraulic cylinders 38 and 40 are pressurized
to rotate the door in a clockwise direction. When the lever 116 is
shifted to the right from its neutral position, as viewed in FIG.
1, the hydraulic cylinders 38 and 40 are pressurized to rotate the
door in a counterclockwise direction.
The hydraulic circuit for the cylinders 38 and 40 which unlatch and
latch the door by rotating the door about its central axis is
provided with a two-way valve 118. When the door is in its closed
position, the valve 118 is open. When the door is not closed, the
valve 118 is closed and interrupts the hydraulic circuit for the
cylinders 38 and 40. The valve 118 is mounted on the retaining ring
36 and cooperates with a plate on the door hinge 30 which depresses
the valve roller when the door 24 is in the closed position. As
soon as the door 24 starts to open, the valve 118 is spring biased
to a closed position to thereby prevent any rotation of the door 24
by means of the hydraulic cylinders 38 and 40 when the door is
open.
The final component of the system is the hydraulic circuit for
actually swinging the door opened and closed. This circuit
comprises a control valve 120 having an actuating lever 122. This
valve is identical in construction to valve 114 and is connected to
the source of pressurized hydraulic fluid and the reservoir in
exactly the same manner as the valve 114. The hydraulic circuit
connecting the piston-type double-acting hydraulic cylinder 42 with
control valve 120 is also provided with a two-way valve 124. This
valve is mounted on the support arm 28 and is spring biased to a
closed position. However, the valve is provided with a cam follower
126 which cooperates with a cam 128 on the door 24 to open the
valve and complete the hydraulic circuit for the cylinder 42. The
cam on the door and the cam follower on valve 124 are so oriented
that when the door 24 is in its unlatched position, the hydraulic
circuit from control valve 120 to cylinder 42 is complete. However,
when the door is latched or only partially unlatched, the circuit
is interrupted. In this manner, the door cannot be swung open or
closed unless the lugs 32 on the door are properly oriented with
the lugs 34 on the retaining ring.
With this circuit, when the actuating lever 122 is swung to the
left from a neutral position, the hydraulic cylinder 42 is
pressurized and vented to the reservoir to swing the door open.
When the lever is swung to the right from a neutral position,
cylinder 42 is pressurized and vented to the reservoir to swing the
door closed. The hydraulic circuit for the cylinder 42 is provided
with a pair of valves 130 which can be adjusted to control the rate
of flow of the hydraulic fluid to and from the cylinder 42 to
regulate the rate at which the door is opened or closed.
The sequence of operation for opening and closing the door with the
system disclosed in FIG. 1 will now be set forth. To open the door,
the operator first presses "off" button 68. This de-energizes the
solenoid valve 60 thereby cutting off control air to the actuating
mechanism 58 of the steam supply valve 56 and venting the actuating
mechanism 58 of the steam supply valve 56 to the atmosphere. Thus,
the steam supply valve 56 is closed so that no more pressurized
steam is admitted to the autoclave. The operator then opens the
blow-down valve (not shown) for the autoclave to depressurize the
autoclave and exhaust the steam from the autoclave. When the tank
pressure drops to 8 inches of water, the pressure switch 72 turns
off the amber lights 80 and 82 and turns on the green lights 74 and
76. In addition, the pressure switch energizes the solenoid 84 of
the key release unit 78 of the interlock system to permit the key
92 to be turned in the lock 90 to open the limit switch 86. With
the limit switch 86 open, all power to the "on-off" switch of the
control panel is cut off. Consequently, if the "on" button 66 is
accidentally pushed, the valve 60 will remain closed and so will
the steam supply valve 56.
With the key 92 turned to its new position, the key can now be
removed from the lock 90 and inserted into the lock 94 of the
door-unlocking mechanism 44 which is the second component of the
interlock system. The key 92 is turned in the lock 94 to retract
the bolt 96 from the locking lever bar 46. With this bolt
retracted, the locking lever bar 46 can now be swung from its
normal position within the yoke 50 to its open position. The
rotation of the bar 46 from its normal operating position to the
open position opens the steam vent valve 48 to the atmosphere to
thereby assure that the autoclave is free of any pressurized steam.
At the same time the valve 48 is being opened, the valve 102 vents
and closes the valve 62 to further assure that the steam supply
valve 56 cannot be turned on; vents and opens pressure switch 110
to open the circuit for the "on-off" switch of the control panel
and pressurizes and opens valve 112 to permit the unlatching of the
door. It should be noted that since the cam follower 104 of valve
102 cooperates with the cam 106 of the door, once the door 24 is
rotated to the unlatched position or opened, the steam supply valve
cannot be turned on. Even if the lever 46 is swung back to its
original position, the key removed from the lock 94 and inserted
into interlock unit 78 in an attempt to energize the control panel,
the steam supply valve still cannot be turned on for two reasons.
The line from the air supply to the actuating mechanism 58 of the
steam supply valve 56 is still cut off by means of the valve 62.
The pressure switch 110 is open and interrupts the circuit for the
control panel so that even if limit switch 86 is closed, the
circuit will still be interrupted.
Once valve 112 is open, the door 24 can be rotated from its latched
position clockwise to its unlatched position by moving lever 116 to
the left from its neutral position. Since the door is closed at
this time, the valve 118 is open and permits the flow of fluid
through the hydraulic circuit to rotate the door by means of the
cylinders 38 and 40. Once the door has been rotated to its
unlatched position, the valve 124 is opened and the hydraulic
circuit for the cylinder 42 is complete. The lever 122 of the valve
120 can now be moved to the left and the door will be swung open.
With the door swung open, the valve 118 is now closed and the door
cannot be rotated by means of hydraulic cylinders 38 and 40.
To close the door, the lever 122 is moved to the right and as long
as the door is in the proper position, the valve 124 is open and
the door can be closed by means of the hydraulic cylinder 42. Once
the door is closed, the valve 118 is opened and the hydraulic
circuit for cylinders 38 and 40 is complete whereby the door can be
rotated back to its latched position by the hydraulic cylinders 38
and 40. Once the door is rotated back to its latched position, the
lever 46 can be swung back to its normal position to close the
valve 48 to prevent steam from escaping through the valve once the
autoclave is repressurized; to close the valve 112 so that the
hydraulic circuit for the cylinders 38 and 40 is interrupted; to
open the valve 62 so that it no longer interrupts the control air
line leading to the actuating mechanism of the steam supply valve;
and to close the pressure switch 110 so that it no longer
interrupts the circuit for the "on-off" switch of the control
panel.
With the lever 46 in its closed position, the key 92 can now be
turned in lock 94 to reengage the locking bolt 96 within the lever
46. With this done, the key 92 can be removed from the lock 94 and
inserted in the lock 90 of the solenoid key release unit 78. The
key is then turned in the lock 90 to move the bar 88 to the right
to close the limit switch 86. With the switch 86 closed, it no
longer interrupts the circuit for the "on-off" switch and the
solenoid valve 60 can now be opened to pressurize the actuating
mechanism of steam supply valve 56 by pushing "on" button 66. Once
the valve 56 has been opened, pressure begins to build within the
autoclave and as the pressure reaches and exceeds 8 inches of
water, pressure switch 72 is actuated to de-energize the solenoid
84 to thereby lock the bar 88 and, consequently, key 92 within the
lock 90 so that the door can no longer be opened. In addition, the
green lights go out and the amber lights go on indicating that the
autoclave is now under pressure.
The system is fail-safe. in the event of an electrical failure, the
solenoid valve 60 will be deenergized and steam valve 56 will be
closed. Furthermore, since the solenoid 84 will remain
de-energized, the key 92 cannot be removed from this interlock
component to permit the unlocking of the lever 46. In addition, if
there is a failure in the control air, the steam supply valve 56
will be closed by valve 62; the pressure switch 110 will be opened
to interrupt the circuit for the control buttons 62, 64 and the
valve 112 will remain closed to prevent the unlatching of the
door.
The embodiment of FIG. 8 is identical in many respects to the
embodiment of FIGS. 1-7. Consequently, to avoid unnecessary
repetition, like components of the embodiment of FIG. 8 will not be
discussed in detail.
The autoclave 200 comprises a thick-walled steel vessel 202 with a
door 204 mounted thereon. The door 204 is mounted on a support arm
206 which is pivotally secured to the vessel 202 by a hinge
assembly 208. A retaining ring 210 is rotatably mounted on the
vessel 202 to retain the door in a closed position when the
autoclave is pressurized. As with the first embodiment, the door
204 and the ring 210 are provided with lugs which cooperate to
maintain the door in a closed position when they are aligned, and
which permit the door to be opened or closed when the lugs on the
door and the ring are aligned with the spaces between the lugs of
the other member.
The retaining ring 210 is rotated about its central axis by a pair
of double-acting piston-type hydraulic cylinders 212 and 214. These
cylinders are each pivotally secured at one end to the ring 210 and
at the other end to the vessel 202. Since hydraulic cylinders 212
and 214 are both double-acting piston-type cylinders, they can be
used in unison to rotate the ring both clockwise and
counterclockwise about its central axis to latch or unlatch the
door 204.
The door 204 is provided with a double-acting piston-type cylinder
216 for swinging the door about the hinge assembly 208 to open and
close the door. The cylinder 216 is pivotally secured at one end to
support arm 206 and at its other end to the vessel 202.
The ring 210 is provided with a ring-locking mechanism 218 which is
substantially identical in construction to the door-locking
mechanism 44 of the first embodiment. The locking mechanism 218 is
provided with a locking bar 220 which is pivotally mounted on a
steam vent valve 252 of the vessel 202. The locking bar 220
cooperates with a plate 222 mounted on the ring 210 to prevent the
rotation of the ring 210 about its central axis when the door is
locked.
The autoclave is provided with a pneumatically actuated spring
return steam inlet valve 224 which is identical in construction to
the valve 56 of the first embodiment. An actuating mechanism 226 of
the valve is connected to a supply of pressurized air through an
air control line which is provided with a three-way solenoid air
valve 228, a three-way air valve 230 and a conventional controller
232.
The three-way solenoid air valve 228 is identical in construction
and function to the three-way solenoid air valve 60 of the first
embodiment. Thus, when the solenoid valve 228 is energized, it
opens the steam supply valve 224 and when the valve is
de-energized, the valve functions to close the steam supply valve
224 for the autoclave.
The three-way cam-actuated spring return air valve 230 permits the
passage of pressurized air through the control air line leading to
the actuating mechanism 226 when a cam follower 232 of the valve is
depressed by a cam 234 mounted on the retaining ring 210. When the
cam follower is no longer engaged by the cam 234, a spring in the
valve shifts the valve to a position where the flow of pressurized
air through the valve to the actuating mechanism 226 is cut off and
that portion of the air control line leading from the valve to the
actuating mechanism 226 is vented to shut off the steam supply
valve 224.
The controller 235 is identical in construction and function to the
controller 64 of the first embodiment and is connected to a supply
of pressurized air.
A control panel of the system is provided with an "on-off" switch
having an "on" button 236 and an "off" button 238. These buttons
energize and deenergize the solenoid valve 228 to turn the steam
supply valve 224 on or off.
The system also includes a pressure gauge 240 and a pressure switch
242. The pressure gauge 240 is provided to give a visual
confirmation of the actual pressure within the autoclave. When the
pressure within the autoclave drops to 8 inches of water, the
pressure switch 242 is actuated to turn on a pair of green signal
lights located on the control panel and a solenoid key release unit
244. At the same time, the switch turns off a pair of amber signal
lights on the control panel in the solenoid key release unit. 244.
Thus, the signal lights give a visual indication that the pressure
in the autoclave is above or below 8 inches of water.
The solenoid key release unit 244 is identical in construction to
the solenoid key release unit 78. Consequently, when a solenoid of
the unit is energized by the pressure switch 242, a key 246 can be
turned in a lock 248 of the unit 244 to open a limit switch of the
unit and thereby cut off all power to the "on-off" switch. As with
the other solenoid key release unit, the key 246 can only be
removed from this unit when the limit switch of the unit has been
opened.
The locking mechanism 218, which comprises the other component of
the interlock unit, is substantially identical in construction to
the locking mechanism 44 and is provided with a lock 250 which is
compatible with the key 246. As in the first embodiment, the
locking lever bar 220 is provided with a plate to prevent the
removal of the key 246 when the lever is not in its locking
position. The bar 22 is secured to a valve stem of the steam vent
valve 252 of the autoclave. Thus, when the lever 220 is swung from
its locking position where it engages plate 222 to an unlocked
position, the lever turns the valve stem of the steam vent valve
252 to open this valve and vent any remaining steam within the
autoclave.
As in the previous embodiment, the locking lever bar 220 also
carries a four-way cam operated spring return air valve 254 which
is connected directly to a supply of pressurized air. The valve is
provided with a cam follower 256 which cooperates with a cam 258 on
the retaining ring of the autoclave. When the cam follower 256 is
depressed by the cam 258, the valve 254 connects a pressure switch
260 and a pneumatic visual indicator 262 with an air control line.
The pneumatic visual indicator 262 is identical in construction and
function to indicator 108. The pressure switch 260 is connected in
series with the limit switch of the solenoid key release unit 244
and the "on-off" switch of the control panel. Thus, the valve 254
keeps the pressure switch 260 closed when the door is locked so
that the switch 260 does not interrupt the circuit for the control
panel. At the same time, the valve 254 vents a two-way air-actuated
spring return valve 264 which is in a hydraulic circuit connecting
a control valve 266 with the hydraulic cylinders 212 and 214. With
the valve 264 vented, the spring return of the valve 264 holds that
valve in a closed position thereby preventing the actuation of
cylinders 212 and 214 by means of the control valve 266.
When the lever 220 is swung to the unlocked position, the valve 254
is shifted to vent the pressure switch 260, to vent the pneumatic
visual indicator 262 and to pressurize valve 264. With the pressure
switch 260 vented, the switch is opened to interrupt the control
panel circuit for the "on-off" switch. With the valve 264
activated, the hydraulic circuit from the control valve 266 to
hydraulic cylinders 212 and 214 is complete and thus the actual
unlatching and opening of the door can be commenced.
The valve 266 is a four-way lever-operated valve. The valve is a
three-position valve and is spring centered so that when an
actuating lever 268 of the valve is in its neutral position, the
ports leading to the piston-type double-acting hydraulic cylinders
212 and 214 are blocked and the pressure line is open back to the
reservoir. When the lever 268 is shifted to the left, the hydraulic
cylinders 212 and 214 are pressurized to rotate the ring in a
counterclockwise direction. When the lever 268 is shifted in the
opposite direction, the hydraulic cylinders 212 and 214 are
pressurized to rotate the ring in a clockwise direction.
The final component of the system is the hydraulic circuit for
swinging the door opened and closed. This circuit comprises a
control valve 270 having an actuating lever 272. This valve is
identical in construction to valve 266 and is connected to the
source of pressurized hydraulic fluid in the reservoir in exactly
the same manner as 266. The hydraulic circuit connecting the
piston-type double-acting hydraulic cylinder 216 with control valve
270 is also provided with a two-way valve 274. This valve is
mounted on the autoclave and is spring biased to a closed position.
However, the valve is provided with a cam follower 276 which
cooperates with a cam 278 on the rotating ring to open the valve
and complete the hydraulic circuit for cylinder 216. The cam on the
ring and the cam follower on the valve 274 are so oriented that
when the ring is in the unlatched position, the hydraulic circuit
from the control valve 270 to the cylinder 216 is complete.
However, when the ring is rotated to latch the door or when the
door is only partially unlatched, the circuit is interrupted. In
this manner, the door cannot be swung open or closed unless the
retaining ring is properly oriented with the lugs on the door.
With this circuit, when the actuating lever 272 is swung to the
left, the hydraulic cylinder 216 is pressurized and vented to the
reservoir to swing the door open. When the lever is swung to the
right from a neutral position, the cylinder 216 is pressurized and
vented to the reservoir to swing the door closed. The hydraulic
circuit for the cylinder 216 is provided with a pair of valves 280
which can be adjusted to control the rate of flow of hydraulic
fluid to and from the cylinder 216 to regulate the rate at which
the door is opened or closed.
The sequence of operation for opening and closing the door is
essentially the same as the sequence for the embodiment of FIG. 1.
The only major distinctions are valve 230 of the second embodiment
which corresponds with valve 60 of the first embodiment and valve
274 of the second embodiment which corresponds with valve 124 of
the first embodiment. Valve 230, instead of being pressure-actuated
as is valve 60, is actuated by means of cam 234 on the retaining
ring. Thus, this valve acts to cut off the supply of pressurized
air to the actuating mechanism of steam valve 224 when the ring 210
is rotated to the unlatched position, rather than cutting off the
supply when the lever is swung out as in the first embodiment.
Valve 274 which completes or interrupts the circuit for the
hydraulic cylinder 216 used to open the door takes the place of
valves 124 of the first embodiment. When the retaining ring is in
the proper position for swinging the door open and closed, the
circuit for hydraulic cylinder 216 is complete. If hydraulic
cylinders 212 and 214 are actuated at any time while the door is
opened to change the position of the retaining ring, the circuit is
interrupted, thereby preventing the closing of the door.
Consequently, while the ring can be rotated when the door is open,
the valve 274 assures that the door is properly oriented before it
is swung either open or closed.
The system is fail-safe. In the event of an electrical failure, the
solenoid valve 288 will be de-energized and the steam valve 224
will be closed. Furthermore, since the solenoid of the solenoid key
release unit 244 will remain de-energized, the key 246 cannot be
removed from this interlock component to permit the unlocking of
lever 220. A loss in the air control pressure will cause the steam
supply valve 224 to close, the pressure switch 260 to open to
interrupt the circuit for the "on-off" switch of the control panel
and the valve 264 to remain closed to prevent the unlatching of the
door.
* * * * *