Pressure cooker

Claim 2

In a steam autoclave including an inlet connected to a source of pressurized steam, a drain, pressure sensitive means communicating with the interior of said autoclave and responsive to pressure variations therein, a control circuit, timer means, and a timer switch for opening said control circuit a preselected interval after said timer is energized, the improvement comprising: a. a normally closed valve in said inlet, b. means for opening said normally closed inlet valve, c. a normally open valve in said drain, d. means for closing said normally open drain valve, e. pressure sensitive switch means operated by said pressure sensitive means, f. said pressure sensitive switch means including: i. a normally closed contact for energizing said inlet valve opening means when said timer switch is closed and said control circuit thereby completed, ii. a first normally open contact for energizing said drain valve closing means when pressure in said autoclave reaches a first value, and iii. a second normally open contact for deenergizing said inlet valve means when pressure in said autoclave reaches a second value in excess of said first value, to cause said inlet valve to close, and g. a manual switch including a first, open position and a second position for completing said control circuit through said second normally open contact when said pressure in said autoclave reaches said second value to retain said inlet valve open at pressures in excess of said second value.

Claim 3

The apparatus of claim 1 wherein: a. said pressure sensitive means is an expandable bellows communicating with said interior of said autoclave, and b. said switch means includes at least one switch arm caused to break with one of said contacts and make with another at a predetermined amount of expansion of said bellows.

Claim 4

The apparatus of claim 2 wherein: a. said manual switch is connected in series with one of said contacts.

Claim 5

A control unit for a steam autoclave comprising: a. pressure sensitive means in communication with the interior of said autoclave and responsive to changes in pressure therein, b. an inlet to said autoclave connected to a source of pressurized steam and including a normally closed, solenoid controlled inlet valve, c. a drain from said autoclave including a normally open, solenoid controlled drain valve, d. switch means including a first switch arm and first and second electrical contacts positioned for alternate engagement thereby, e. said pressure sensitive means causing said first switch arm to break with said first contact and make with said second contact at a first predetermined pressure in said autoclave, f. a manual switch including a manual switch arm and a third electrical contact engageable by said manual switch arm, g. one of said first and second electrical contacts being electrically connected with said third electrical contact and the other of said first and second electrical contacts being electrically connected to said manual switch arm, h. said first switch arm being adapted to be electrically connected to a source of potential, and i. a solenoid coil of said inlet valve being connected between said first electrical contact and being adapted to be connected to a source of potential at a different level whereby a circuit is established through said solenoid coil and said electrical contacts.

Claim 6

A control unit for a steam autoclave comprising: a. pressure sensitive means in communication with the interior of said autoclave and responsive to changes in pressure therein, b. an inlet to said autoclave connected to a source of pressurized steam and including a normally closed, solenoid controlled inlet valve, c. a drain from said autoclave including a normally open, solenoid controlled drain valve, d. switch means including a first switch arm and first and second electrical contacts positioned for alternate engagement thereby, e. said pressure sensitive means causing said first switch arm to break with said first contact and make with said second contact at a first predetermined pressure in said autoclave, f. a manual switch including a manual switch arm and a third electrical contact engageable by said manual switch arm, g. one of said first and second electrical contacts being electrically connected with said third electrical contact and the other of said first and second electrical contacts being electrically connected to said manual switch arm, h. said first switch arm being adapted to be electrically connected to a source of potential, and i. a solenoid coil of said inlet valve being connected between said first electrical contact and being adapted to be connected to a source of potential at a different level whereby a circuit is established through said solenoid coil and said electrical contacts.

Claim 7

The control unit of claim 4 further comprising: a. a timer including an electrical switch having a fourth electrical contact and a fifth electrical contact: b. one of said fourth and fifth electrical contacts being electrically connected to said first switch arm and the other of said electrical contacts being electrically connected to a source of potential; c. said fourth and fifth electrical contacts being opened and closed by said timer; d. a second timer having a different time scale than said first timer; e. said second timer having sixth and seventh electrical contacts; f. said sixth and seventh electrical contacts being opened and closed by said second timer; g. a timer selector switch having third and fourth switch arms; h. said timer selector switch having eighth, ninth, tenth and eleventh electrical contacts; i. said eighth electrical contact being electrically connected to one of said fourth and fifth electrical contacts and said ninth electrical contact being electrically connected to one of said sixth and seventh electrical contacts, the other two of said fourth and fifth, sixth and seventh electrical contacts being electrically connected together, to said switch arm, and to said fourth switch arm; j. said eighth electrical contact being electrically connected to one end of the armature of a motor within said first timer and said ninth electrical contact being electrically connected to an armature of the motor within said second timer; k. said fourth and fifth switch arms of said timer selector switch making contact at respectively with said eighth and tenth electrical contacts when in one position and with said ninth and eleventh electrical contacts when in another position.

Claim 8

The control unit of claim 5 wherein: a. said switch means includes a third switch arm and a sixth electrical contact; b. said pressure sensitive means causing said third switch arm to make with said sixth contact at a second predetermined pressure in said autoclave in excess of said first predetermined pressure; c. said third switch arm is electrically connected to said other of said fourth and fifth electrical contacts; and d. said normally-open, solenoid-controlled valve includes a solenoid coil electrically connected between a source of potential and said sixth electrical contact, whereby said normally-open, solenoid-controlled valve closes the drain outlet from said autoclave when pressure therein reaches said second predetermined pressure.

Claim 9

The control unit of claim 6 wherein: a. said first predetermined pressure is approximately 5 psi and said second predetermined pressure is approximately 3 psi.

Claim 10

The control unit of claim 6 wherein: a. said sixth electrical contact is electrically connected to said first timer, whereby said first timer is actuated at said second predetermined pressure.