Method of blower control

• US 5,182,826 A
• Filed: 04/29/1991
• Issued: 02/02/1993
• Est. Priority Date: 03/09/1989
• Status: Expired due to Term

• Current Assignee: Hill-Rom Services Incorporated (Baxter International Inc.)
• Original Assignee: SSI Medical Services, Inc.
• Inventors: Stolpmann, James R., Sutton, William T., Romano, James J., Thomas, James M. C.
• Primary Examiner(s): Grosz, Alexander
• Application Number:
  US07/693,918
• Time in Patent Office: 645 Days
• Field of Search: 5/453, 5/455, 5/60, 5/469, 5/456, 5/914, 417/44, 417/12
• US Class Current: 5/713
• CPC Class Codes: A61G 2203/34 for pressure
• CPC Class Codes: A61G 7/001 with means for turning-over the patient
• CPC Class Codes: A61G 7/0527 Weighing devices
• CPC Class Codes: A61G 7/05776 with at least two groups of alternately inflated chambers

Abstract

A method for controlling the blower that supplies gas to the gas sacks of a patient support system uses a blower control circuit, a microprocessor, and a pressure sensor. The blower control circuit controls the power that is supplied to operate the blower. The microprocessor activates the blower control circuit with a control signal that causes the control circuit to supply power to the blower. A pressure sensor measures the pressure of the gas exiting the blower and supplies a signal indicative of this pressure, to the microprocessor. The microprocessor stores the measured pressure signal and calculates a reference pressure for the blower. The microprocessor compares the reference pressure to the measured pressure and determines any discrepancy resulting from this comparison. The microprocessor sends a signal to the blower control circuit, wherein the signal is indicative of the discrepancy from the compared pressure and the reference pressure of the blower. The second control signal is such as to enable the blower circuit to reduce the discrepancy calculated by the microprocessor between the reference pressure and the measured pressure. Only discrepencies of a certain magnitude will cause the microprocessor to send the second control signal to the blower control circuit. The time interval over which the microprocessor maintains storage of the measured pressure is chosen so as to reduce the possiblity of pressure instability in the gas sack.

Claims

1. A method for controlling the blower for supplying gas to at least one gas sack of a patient support, the method comprising:

(a) regulating the power supplied to operate the blower;

(b) at the expiration of a predetermined time interval, measuring the pressure of the gas exiting the blower;

(c) calculating an ideal blower reference pressure;

(d) determining the size of any discrepancy between the ideal blower reference pressure and the measured pressure; and

(e) when the discrepancy exceeds a predetermined magnitude, varying the power supplied to operate the blower so as to reduce the magnitude of the discrepancy.

2. A method for controlling the blower for supplying gas to at least one gas sack of a patient support, the method comprising:

(a) using a blower control circuit to regulate the power supplied to operate the blower;

(b) using a microprocessor to communicate a first control signal to said blower control circuit whereby said circuit controls the power supplied to the blower according to said first control signal;

(c) measuring the pressure of the gas exiting the blower;

(d) communicating the measured pressure to the microprocessor;

(e) storing the measured pressure in a memory of the microprocessor for a predetermined time interval;

(f) using the microprocessor to calculate a reference pressure for the blower;

(g) using the microprocessor to compare the reference pressure with the measured pressure and determine any discrepancy resulting from said comparison;

(h) using the microprocessor to determine a second control signal required by the blower control circuit to reduce said discrepancy; and

(i) communicating said second control signal to said blower control circuit.

3. A method as in claim 2, wherein:

said discrepancy must be greater than a predetermined magnitude before said microprocessor determines said second control signal.

4. A method as in claim 3, wherein:

said predetermined time interval for maintaining storage of said measured pressure is chosen so as to reduce the possibility of pressure instability in said gas sack.

5. A method as in claim 4, wherein:

said predetermined time interval is about 3 seconds.

6. A method as in claim 2, wherein:

said reference pressure equals the highest sack pressure plus the minimum pressure needed to maintain sufficient pressure in a sack to support the weight of a patient thereon.