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Патент USA US3064332

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Nov. 20, 1962
A. LODGE
3,064,322
VACUUM SWITCH
Filed Feb. 2'7, 1961
INVEN TOR.
4411:. ‘464%
3,064,322
United States Patent 0 "ice
1
3,064,322
VACUUM SWlTCH
Alvin Lodge, Erie, Pa., assignor to American Sterilizer
Company, Erie, Pa., a corporation oi? Pennsylvania
Filed Feb. 27, 1961, Ser.
91,714
3 Claims. (Ql. 21-94)
In sterilizers it is desirable that the sterilizing chamber
be evacuated before introducing the sterilizing agent to
insure prompt and uniform penetration of the load. At
the high vacuums required (e.g. 15-20 mm. of mercury
absolute pressure), ordinary vacuum switches require
barometric compensation and are so sensitive that they
are both expensive and unreliable. In a preferred form
this invention overcomes this problem by substituting for
the ordinary vacuum switch a thermostat responsive to
the boiling point of water. As the pressure within the
?atented Nov. 20, 1962
2
that the well will be kept ?lled with water. During each
steam sterilizing cycle, the steam ?ows through the line
11 and is condensed by the cooling eifect of the ambient
air. If the vacuum switch were used in other applica
tions, other arrangements could be used to ?ll the well
with water.
When the chamber 1 is evacuated at the start of the
sterilizing cycle, the vacuum above the surface of the
water in the well 9 is the same as the vacuum in the
sterilizing chamber because the well and chamber are
always connected by the line 11. As the vacuum be
comes higher, the boiling point of the water in the well
drops and ?nally reaches the temperature for which the
thermostat 13 is set. At this point, the switch 14 is
closed, starting the sterilizing control.
The desired
vacuum Within the chamber 1 is in the range of from 15
to 20 mm. which corresponds to a thermostat setting in
the range of from 64 to 71.9 degrees F. Thermostats in
sterilizing chamber is reduced, the boiling point of water
is correspondingly reduced and upon reaching the point
this range are accurate, cheap and reliable.
In use, the load to be sterilized is loaded into the cham
corresponding to the desired vacuum, the switch operates. 20
ber 1 and the door 2 closed. Valve 5 is then opened to
This provides a vacuum switch with a high degree of ac
connect the vacuum.- line to the chamber. When the de
curacy and which does not require any barometric com
sired vacuum is reached, the vacuum switch closes, start
pensation. The boiling point of water at 15 mm. to 20
ing the control 7 to perform the operations incident to
mm. of mercury absolute ranges from 63.5 to 71.9 de
grees F. Thermostats operating in this range of tem 25 the sterilizing cycle.
What is claimed as new is:
perature are very common and reliable.
1. In a sterilizer having a sterilizing chamber with
In the drawing, FIG. 1 is a diagrammatic view of a
means for evacuating the chamber and a switch to be op
sterilizer equipped with the vacuum switch and FIG. 2 is
erated when the vacuum in the chamber reaches a pre
an enlarged view of the vacuum switch construction.
The invention is shown applied to a sterilizer having 30 determined value, a well ?lled with water, a line con
nected from above the liquid level in the well to the
a chamber 1 with a door 2 at one end and vacuum and
chamber, and a thermostat immersed in the Water for
steam lines 3 and 4 respectively controlled by valves 5
operating the switch as the boiling point of the water in
and 6. After the material to be sterilized is loaded into
the well reaches the temperature corresponding to said
the chamber, the door 2 is closed and the valve 5 is
opened to connect the vacuum line 3 to the chamber. 35 predetermined value of vacuum.
2. A vacuum switch comprising a well ?lled with
When the desired degree of vacuum is reached, the valve
liquid which boils at temperatures within the ranges of
5 is closed and the valve 6 is opened to discharge steam
vacuum at which operation of the switch is desired, a.
to the chamber. These and other operations incident to
line connecting the well to the source of vacuum, and a
the operation of the sterilizer are performed in the de
thermostatic switch responsive to the temperature of the
sired sequence by a suitable control 7 connected in power
line 8. The parts so far described are or may be of com
mon construction.
liquid in the well.
the range of 15 mm. to 20 mm. of mercury and at these
low pressures, the available vacuum switches are ex
the chamber, a line from the well to a part of the cham
ber above the well so that steam from the chamber is
3. In a sterilizer having a sterilizing chamber with
means for supplying steam to the chamber, means for
In order to secure uniformity in the sterilizing cycle,
evacuating the chamber prior to the admission of steam,
it is desirable that the admission of steam be delayed
and a switch to be operated when the vacuum in the
45
until the desired vacuum in the chamber is reached. This
chamber reaches a predetermined value, a well outside
requires a vacuum switch which will operate reliably in
pensive and unreliable. In order to provide a reliable
vacuum switch, there is provided a well 9 outside the
sterilizer connected through the lower end of a T 10
to a line 11 leading to the upper part of the sterilizer
chamber. The upper end of the T is closed by a plug
12. The line 11 has a slight pitch draining to the well
9. When steam is admitted to the sterilizing chamber, 55
a small amount bleeds through the line 11 and is con
densed by the cooling e?ect of the ambient air. The
condensate drains into the well 9, keeping it ?lled with
water. In the well 9 is a thermostat bulb 13 controlling
a switch (diagrammatically indicated at 14) within the
casing 15 on which the thermostat is mounted. Having
the well 9 connected to the sterilizing chamber insures
60
condensed by the cooling effect of the ambient air and
maintains the well ?lled with water, and a thermostat
immersed in the water for operating the switch as the
boiling point of the water in the well reaches the tem
perature corresponding to said predetermined value of
vacuum.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,208,552
2,715,251
Walter ______________ __ July ‘16, 1940
Vischer _____________ .._ Aug. 16, 1955
608,614
Canada _____________ __ Nov. 15, 1960
FOREIGN PATENTS
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