Pneumatic detector integrated alarm and fault switch

An integrated switch to indicate pressure changes in an environment includes a housing with a cavity between a first retainer portion and a second retainer portion, a first diaphragm held in the cavity of the housing to indicate fault conditions, and a second diaphragm held in the cavity of the housing to indicate alarm conditions.

BACKGROUND

The present invention relates to a pneumatic detector, and in particular, to a pneumatic detector with an integrated alarm and fault switch.

A pneumatic detector is typically comprised of both an alarm switch and a fault switch. Pneumatic detectors typically utilize a pressure tube that contains a gas that will expand as it is heated, thus increasing the pressure in the tube. An alarm switch is used to indicate overheat or fire situations. An alarm switch will include a deformable diaphragm that is at a normal state when the system is at a normal pressure. As the pressure rises, the diaphragm will deform and close an electrical circuit, indicating that there is an alarm condition in the system. A fault switch is used to indicate whether there are leaks, disconnects, or other problems in a pneumatic detector system. A fault switch will include a deformable diaphragm that is deformed when the system is at a normal pressure. If the pressure drops below normal, the diaphragm will resume its normal state and open an electrical circuit, indicating that there is a fault condition in the system.

Pneumatic detectors that utilize both alarm switches and fault switches are used on aircrafts to detect alarm and fault conditions. The pressure tubes for the alarm and fault switches can typically run anywhere from one foot long to fifty feet long, and can be placed in systems that are prone to overheating or fires.

SUMMARY

According to the present invention, an integrated switch to indicate pressure changes in an environment includes a housing with a cavity between a first retainer portion and a second retainer portion, a first diaphragm held in the cavity of the housing to indicate fault conditions, and a second diaphragm held in the cavity of the housing to indicate alarm conditions.

DETAILED DESCRIPTION

In general, the present invention relates to pneumatic detectors with integrated alarm and fault switches. An integrated alarm and fault switch will have one housing that contains two diaphragms. A first diaphragm will indicate fault conditions and a second diaphragm will indicate alarm conditions. Fault conditions typically occur when there is a disconnection, leak, or other problem in a system. Alarm conditions typically occur when there is overheat or a fire in a system.

FIG. 1is a side cross-sectional view of integrated switch10, including both an alarm switch and a fault switch, when there is atmospheric pressure in integrated switch10. Integrated switch10includes housing11(including first retainer portion12and second retainer portion14), pressure tube16, contact pin18, fault diaphragm20, alarm diaphragm22, insulator24, insulator26, and cavity28. In the embodiment seen, there is no pressure in integrated switch10.

Integrated switch10includes housing11that is constructed of first retainer portion12and second retainer portion14. First retainer portion12and second retainer portion14are connected to one another with insulator24running between them. Housing11includes cavity28that is bound by first retainer portion12and second retainer portion14. First retainer portion12contains contact pin18with insulator26running between first retainer portion12and contact pin18. Second retainer portion14contains pressure tube16. Pressure tube16extends into cavity28. Fault diaphragm20and alarm diaphragm22are held between first retainer portion12and second retainer portion14in cavity28. Fault diaphragm20is held in integrated switch10between insulator24and second retainer portion14. Alarm diaphragm22is held in integrated switch10between first retainer portion12and insulator24.

First retainer portion12and second retainer portion14are constructed out of a refractory metallic material that is capable of conducting an electrical signal. Refractory materials are used so that the components can maintain their strength when they are subject to high temperatures. Fault diaphragm20and alarm diaphragm22are also constructed out of refractory metallic materials that are capable of conducting an electronic signal. Fault diaphragm20and alarm diaphragm22can have any thickness that allows fault diaphragm20and alarm diaphragm22to deform. Fault diaphragm20has a smaller thickness in the embodiment shown so that it deforms at lower pressures than alarm diaphragm22. This allows integrated switch10to be used to indicate different pressure levels in integrated switch10.

Insulator24runs between first retainer portion12and second retainer portion14to insulate the two portions and to prevent electronic signals from being passed between them. Insulator26runs between first retainer portion12and contact pin18to insulate them and to prevent electronic signals from being passed between them. Insulator24and insulator26can be made of any material that is capable of acting as an electrical insulator.

Pressure tube16runs through second retainer portion14and connects to cavity28. Pressure tube16contains a gas that expands as it is heated, therefore as pressure tube16is heated the pressure in pressure tube16will increase. As the pressure in pressure tube16increases, the pressure in cavity28will also increase. The pressure in cavity28can cause fault diaphragm20and alarm diaphragm22to deform. In the embodiment shown inFIG. 1, there is no pressure in integrated switch10and fault diaphragm20and alarm diaphragm22are in their normal configuration. Pressure tube16can have a typical length between 0.305 meters (1 foot) and 15.24 meters (50 feet) depending on where integrated switch10will be used. Pressure tube16will be placed next to components that are capable of overheating or components where a fire could occur, such as an engine or auxiliary power unit.

Contact pin18is held in first retainer portion12with insulator26running between contact pin18and first retainer portion12. If the pressure in integrated switch10gets high enough, fault diaphragm20and alarm diaphragm22can both deform and come into contact with contact pin18. A signal can then be sent through contact pin18. Insulator26acts as a barrier and only allows the signal to travel through contact pin18and not through first retainer portion12.

Integrated switch10is advantageous over the prior art models, as it is reduced in size and weight. Integrated switch10can be used in pneumatic detector systems, making these systems smaller, lighter, and more compact. The reduction in size means integrated switch10can be used more efficiently in pneumatic detector systems. A reduction in size and weight also makes integrated switch10advantageous for use in applications where space is limited and weight needs to be kept to a minimum. If integrated switch10is housed in a housing, having a smaller and lighter system is also advantageous, as the size of the housing needed can be reduced.

Integrated switch10also requires less parts than prior art models, which reduces the cost of the system and simplifies the manufacturing process. A lower cost and simpler manufacturing process are advantageous over the prior art systems. An integrated switch is also advantageous over prior art systems that utilized separate fault switches and alarm switches, as it reduces the possibility of having a disconnection, leak, or other problem in the system.

Integrated switch10is included in system40in the embodiment shown. System40includes power source42that is connected to fault diaphragm20along path A. Power source42can include any power source that is capable of supplying electric power to integrated switch10. System40also includes electronic controller44. Electronic controller44is connected to integrated switch10to read the signals being sent from integrated switch10. Electronic controller44is connected to alarm diaphragm22along path B and to contact pin18along path C. System40also includes path D exiting electronic controller44to send a signal to an electronic component that will indicate what type of pressure conditions are present in integrated switch10. These electronic components can include electrical equipment in the cockpit of an aircraft.

FIG. 2depicts integrated switch10at normal pressure conditions. In the embodiment shown, normal pressure conditions exist under normal operating temperatures. Normal operating temperatures exist between a pre-set fault temperature and a pre-set alarm temperature. The pre-set fault temperature defines a lower limit of the normal operating temperatures and is the point at which pressure conditions will drop below normal. Fault diaphragm20will deform when the temperature rises above the pre-set fault temperature. The pre-set alarm temperature defines an upper limit of the normal operating temperatures and is the point at which pressure conditions will rise above normal. Alarm diaphragm22will deform when the temperature rises above the pre-set alarm temperature. Normal pressure conditions thus exist between the pre-set fault temperature and the pre-set alarm temperature. At normal pressure conditions, fault diaphragm20deforms and comes into contact with alarm diaphragm22.

Under normal pressure conditions, an electronic signal is being sent through fault diaphragm20from power source42. When fault diaphragm20comes into contact with alarm diaphragm22under normal pressure conditions, an electrical circuit between the two is closed and the electric signal from power source42will travel through fault diaphragm20to alarm diaphragm22. This electric signal can then travel through alarm diaphragm22and along path B to electronic controller44. Electronic controller44will register this electric signal and will send out a signal along path D indicating that there are normal pressure conditions in integrated switch10.

Utilizing integrated switch10in pneumatic detectors is advantageous, as integrated switch10can send a signal that indicates a system is at a steady state. This allows a user to verify that the pneumatic detector is operable and that the system is functioning normally.

FIG. 3is a side cross-sectional view of the integrated switch ofFIG. 2at a higher than normal pressure. Integrated switch10includes housing11(including first retainer portion12and second retainer portion14), pressure tube16, contact pin18, fault diaphragm20, alarm diaphragm22, insulator24, insulator26, and cavity28. System40includes power source42and electronic controller44. Integrated switch10and system40are connected to one another with path A, path B, path C, and path D.

FIG. 3depicts integrated switch10at above normal pressure conditions. Above normal pressure conditions exist at temperatures above the pre-set alarm temperature. In the embodiment shown, the pre-set alarm temperature of the sensor is 316 degrees Celsius (600.00 degrees Fahrenheit). Temperatures above the pre-set alarm temperature of the sensor will cause above normal pressure conditions. In alternate embodiments, the pre-set alarm temperature of the sensor can vary based on the thickness of alarm diaphragm22in integrated switch10and the quantity of gas contained in pressure tube16. At above normal pressure conditions, both fault diaphragm20and alarm diaphragm22will deform. This will cause fault diaphragm20to come into contact with alarm diaphragm22and it will cause alarm diaphragm22to come into contact with contact pin18.

In operation, an electronic signal is being sent through fault diaphragm20from power source42. When fault diaphragm20comes into contact with alarm diaphragm22under normal pressure conditions, an electrical circuit between the two is closed and the electric signal from power source42will travel through fault diaphragm20to alarm diaphragm22. When alarm diaphragm22comes into contact with contact pin18, an electrical circuit between them is closed and the electric signal will travel through alarm diaphragm22to contact pin18. This electric signal can then travel through contact pin18and along path C to electronic controller44. Electronic controller44will register this electric signal and will send out a signal along path D indicating that there are above normal pressure conditions in integrated switch10.

Above normal pressure conditions can occur when there is a fire or overheat condition in a component, such as an engine or auxiliary power unit. Pressure tube16can run along these components. As the heat rises in or around the components, the pressure in pressure tube16will increase, which will increase the pressure in cavity28of integrated switch10. If the temperatures get above the pre-set alarm temperature, the pressure will get high enough to cause alarm diaphragm22to deform and come into contact with contact pin18. This closes the circuit between alarm diaphragm22and contact pin18and causes an electric signal to travel between the two. This signal will be sent to electronic controller44. Electronic controller44can then send a signal indicating that there is an alarm condition in integrated switch10.

FIG. 4is a side cross-sectional view of the integrated switch ofFIG. 2at a lower than normal pressure. Integrated switch10includes housing11(including first retainer portion12and second retainer portion14), pressure tube16, contact pin18, fault diaphragm20, alarm diaphragm22, insulator24, insulator26, and cavity28. System40includes power source42and electronic controller44. Integrated switch10and system40are connected to one another with path A, path B, path C, and path D.

FIG. 4depicts integrated switch10at below normal pressure conditions. Below normal pressure conditions exist at temperatures below the pre-set fault temperature of the sensor. In the embodiment shown, the pre-set fault temperature of the sensor is −54 degrees Celsius (−65 degrees Fahrenheit), which is the temperature at a lower limit of the normal operating temperatures. Temperatures below the pre-set fault temperature of the sensor will cause below normal pressure conditions. In alternate embodiments, the pre-set fault temperature of the sensor can vary based on the thickness of fault diaphragm20in integrated switch10. At below normal pressure conditions, both fault diaphragm20and alarm diaphragm22will be in their normal configuration and they will not be touching.

In operation, an electronic signal is being sent through fault diaphragm20from power source42. Because fault diaphragm20is not in contact with alarm diaphragm22when there are below normal pressure conditions, an electrical circuit between the two is open. The electric signal from power source42will not travel through fault diaphragm20and alarm diaphragm22to electronic controller44. Electronic controller44will register that there is no electric signal coming in and will send out a signal along path D indicating that there are below normal pressure conditions in integrated switch10.

Below normal pressure conditions can occur when there is a leak, disconnect, or other problem in pressure tube16or integrated switch10. If there is a leak or disconnect, the pressure in pressure tube16and cavity28of integrated switch10will decrease. As the pressure decreases, both alarm diaphragm22and fault diaphragm20will retain their normal configurations and will not be touching. This will open the circuit between alarm diaphragm22and fault diaphragm20and will prevent a signal from traveling along path B to electronic controller44. The lack of a signal entering electronic controller44will indicate that there is a fault condition in the system. Electronic controller44can then send a signal along path D indicating that there is a fault condition in integrated switch10.