Pneumatic thermostat

Claim 2

A thermostat for use in controlling an air conditioning system including a pneumatic actuator connected to a flow valve in an air duct, said thermostat comprising: a housing assembly including a base member; means on said base member having a bleed orifice at one end connected by a passage to an inlet at its other end adapted to be connected to an air pressure source that also supplies air to the actuator; an arm pivotally connected to said base member; and a temperature sensitive bimetal strip connected to said arm extending over said orifice; cam means mounted on said base member and having a sloping cam surface and including means forming a set point indicator and adjusting means accessible from outside said housing for moving said set point indicator to a preselected position; adjusting means for controlling the distance of said arm relative to said cam surface and thereby controlling the distance of said bimetal strip from said orifice and consequently the rate of air flow through it; a calibration indicator means; and means responsive to the positioning of said arm by said adjusting means for causing said indicator means to provide a visible indication that said arm is properly positioned commensurate with the air pressure being supplied to the thermostat.

Claim 3

The thermostat as described in claim 1 wherein said adjusting means comprises spring means for urging said arm toward said cam means on said base member and an adjustable set screw mounted in said arm at a distance from its pivoting end and engaging said cam surface.

Claim 4

The thermostat as described in claim 2 wherein said indicator meenas includes an axially movable pin mounted in said base means and a face member in said housing having an opening aligned with said pin, said pin having a length sufficient to cause one of its ends to extend through said opening in response to the restriction of air flowing through said orifice.

Claim 5

The thermostat as described in claim 3 wherein said indicator means further includes means forming a calibration chamber communicating with said passage to said bleed orifice, and diaphragm means within said chamber engaging one end of said pin.

Claim 6

The thermostat as described in claim 3 wherein said cam means has an exposed edge portion to facilitate its manipulation for moving said set point indicator, a first scale means on said face member adjacent said set point indicator and thermometer means having a second scale means attached to said face member.

Claim 7

The thermostat as described in cLaim 1 wherein said set point indicator comprises an integral upwardly extending portion of said cam means spaced from its central axis of rotation and having a bar shaped upper end portion to extend transversely in a window of said housing.

Claim 8

A thermostat for use in controlling an air conditioning system including a pneumatic actuator connected to a flow valve in an air duct, said thermostat comprising: a housing having a front cover portion with window means and a base member within said housing; means fixed to said base member having a bleed orifice at one end and connected by an internal passage to an inlet at its other end adapted to be connected to an air pressure source that also supplies air to the actuator; an arm pivotally connected to said base member; and a temperature sensitive bimetal strip connected to said arm extending over said orifice; a rotatable cam means mounted on said base member and having an arcuate sloping cam surface and including means forming a set point indicator and adjusting means accessible from outside said housing for moving said set point indicator to a preselected position; an adjusting means for controlling the distance of said arm relative to said cam surface and thereby controlling the distance of said bimetal strip from said orifice and consequently the rate of air flow through it; a movable calibration indicator means, and control means responsive to the positioning of said arm by said adjusting means and thus the rate of air flow through said bleed orifice for causing said indicator means to become visible through said window means to thereby indicate whether said arm is properly positioned commensurate with the air pressure being supplied to the thermostat.

Claim 9

A thermostat for use in controlling an air conditioning system including a pneumatic actuator connected to a flow valve in an air duct, said thermostat comprising: a housing having a front cover portion with window means and a base member within said housing; means fixed to said base member having a bleed orifice at one end and connected by an internal passage to an inlet at its other end adapted to be connected to an air pressure source that also supplies air to the actuator; an arm pivotally connected to said base member; and a temperature sensitive bimetal strip connected to said arm extending over said orifice; a rotatable cam means mounted on said base member and having an arcuate sloping cam surface and including means forming a set point indicator and adjusting means accessible from outside said housing for moving said set point indicator to a preselected position; an adjusting means for controlling the distance of said arm relative to said cam surface and thereby controlling the distance of said bimetal strip from said orifice and consequently the rate of air flow through it; a movable calibration indicator means, and control means responsive to the positioning of said arm by said adjusting means and thus the rate of air flow through said bleed orifice for causing said indicator means to become visible through said window means to thereby indicate whether said arm is properly positioned commensurate with the air pressure being supplied to the thermostat.

Claim 10

The thermostat as described in claim 7 wherein said calibration indicator means comprises a pin member supported in said base member, spring means for biasing said pin member toward a retracted position, a face member supported within said housing and spaced from said window means, said face member having an opening aligned with said indicator means and visible through said window means, said control means being operable to oppose said spring means and move said pin member to an extended position through said face member under certain flow conditions through said bleed orifice.

Claim 11

The thermostat as described in claim 8 wherein said control means comprises a disk-like member forming a sealed chamber under said base member which receives air from said internal passage of said means having a bleed orifice, diaphragm means forming one wall portion of said chamber and engaged with said pin member, whereby increased pressure within said chamber due to decreased flow through said bleed orifice causes said diaphragm to move said pin member.

Claim 12

The thermostat as described in claim 9 wherein said means having a bleed orifice is generally cylindrical and has a flange portion which bears against and retains said disk-like member on said base member.

Claim 13

The thermostat as described in claim 9 wherein said spring means has a force factor which will hold the outer end of said pin member generally flush with said face member when the thermostat is properly calibrated.

Claim 14

The thermostat as described in claim 9 wherein said window means comprises upper and lower glass windows, said upper window being adjacent a thermometer needle and a scale mounted on said face member and also said opening for said indicator pin member, said lower window being adjacent said set point indicator.

Claim 15

The thermostat as described in claim 9 wherein said lower window includes an opening to provide access for said adjusting means.

Claim 16

The thermostat as described in claim 13 wherein said adjusting means comprises means for urging said arm toward said cam means on said base member and an adjustable set screw mounted in said arm at a distance from its pivoting end and engaging said cam surface.