US 5,681,151 AGranted

Motor driven air compressor having a combined vent valve and check valve assembly

AssigneeDeVilbiss Air Power Company

InventorMark W. Wood

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Abstract

An air compressor driven by a permanent split capacitor electric motor of the type having substantially the same value capacitance for starting as for operating and which has insufficient starting torque for starting when the air compressor is loaded with pressurized air. The pressurized air output from the air compressor is delivered through an air line to a compressed air storage tank. A check valve between the air line and the tank permits air flow from the air line to the tank while preventing a reverse air flow. A vent valve is connected to vent air pressure from the air line when the motor is stopped to unload the air compressor. When the motor is restarted, closure of the vent valve is delayed until the output torque from the motor exceeds the torque requirements of the compressor when loaded. Vent valve closure may be delayed for a predetermined me or until the motor reaches a predetermined high operating speed or until the air flow from the unloaded air compressor reaches a predetermined level.

Claims8

Dependent claims

An electric motor operated compressor comprising:

an air compressor having a pressurized air output;
a compressed air storage tank;
an air line connected to deliver pressurized air from said compressor output to said tank;
a motor connected to drive said air compressor, said motor having insufficient torque to start when said air compressor is loaded by pressurized air in said air line;
a valve body located between said air line and said tank, said valve body having:
a check valve in a first bore for preventing the flow of pressurized air from said tank to said air line while permitting the flow of pressurized air from said air line to said tank;
and
a vent valve for venting pressure from said air line, said vent valve being positioned in a second bore communicating with said first bore, said second bore having an open vent end, and said vent valve including:
an unloader valve;
and
spring means urging said unloader valve away from said open vent end;
where said unloader valve is adapted to be moved against the force of said spring means to interrupt venting of said air line in response to a predetermined air flow from said second bore through said open vent end;
means for opening said vent valve when said motor is stopped to vent air from said air line to unload said air compressor and for closing said vent valve when said motor is operating;
and
means for preventing closure of said vent valve when said motor is initially started until after the torque developed by said motor exceeds the torque required to drive said air compressor when loaded by pressurized air in said air line.

12 more elements

An electric motor operated compressor comprising:

an air compressor having a pressurized air output;
a compressed air storage tank;
an air line connected to deliver pressurized air from said compressor output to said tank;
a permanent split capacitor motor connected to drive said air compressor, said motor having substantially the same capacitance for starting as for operating and having insufficient torque to start when said air compressor is loaded by pressurized air in said air line;
a valve body located between said air line and said tank, said valve body having:
a check valve for preventing the flow of pressurized air from said tank to said air line while permitting the flow of pressurized air from said air line to said tank, said check valve being positioned in a stepped first bore having a step defining a conical valve seat facing one end of said first bore, and said check valve including:
an annular ledge extending radially inwardly at said one bore end;
a check valve ball positioned in said first bore and adapted for seating against said seat;
and
a compression spring compressed between said annular ledge and said check valve ball to urge said check valve ball towards said seat;
and
a vent valve for venting pressure from said air line, said vent valve being positioned in a second bore communicating with said first bore, said second bore having an open vent end, and said vent valve including:
an unloader valve;
a conical seat for said unloader valve adjacent said open vent end;
spring means urging said unloader valve away from said open vent end;
where said unloader valve is adapted to be moved against the force of said spring means to engage said conical seat for said unloader valve in response to a predetermined air flow from said second bore through said open vent end;
means for opening said vent valve when said motor is stopped to vent air from said air line to unload said air compressor and for closing said vent valve when said motor is operating;
and
means for preventing closure of said vent valve when said motor is initially started until after the torque developed by said motor exceeds the torque required to drive said air compressor when loaded by pressurized air in said air line.

16 more elements

A valve assembly for an air compressor having an air line delivering pressurized air to an air tank, said valve assembly comprising a valve body having:

a check valve in a first bore for preventing the flow of pressurized air from said tank to said air line while permitting the flow of pressurized air from said air line to said tank;
and
a vent valve for venting pressure from said air line, said vent valve being positioned in a second bore communicating with said first bore, said second bore having an open vent end, and said vent valve including:
an unloader valve;
and
spring means urging said unloader valve away from said open vent end;
where said unloader valve is adapted to be moved against the force of said spring means to interrupt venting of said air line in response to a predetermined air flow from said second bore through said open vent end.

4 more elements

Dependencies are inferred from the claim text.