US3915593A

US3915593A - Controlled displacement sewage air lift station

Info

Publication number: US3915593A
Application number: US107294A
Authority: US
Inventors: Jess L Chamberlain
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-01-18
Filing date: 1971-01-18
Publication date: 1975-10-28
Anticipated expiration: 1992-10-28

Abstract

An air lift station for lifting sewage from a sewage receiver tank in discrete ejection cycles by forced air, is provided with means for maintaining constant the quantity of air injected into a sewage receiving tank from an accumulator tank. The station provides improved reliability of the air compressor motor circuit and improved overall lift station efficiency. Specifically, during each timed ejection cycle, the air is injected at the same constant pressure.

Description

United States Patent Chamberlain Oct. 28, 1975 1 CONTROLLED DISPLACEMENT SEWAGE 3,322,306 5/1967 Munderich 222/373 x I LIFT STATION 3,393,644 7/1968 Boswell 137/209 X 3,537,472 11/1970 Yulio 417/138 X [76] Inventor: Jess L. Chamberlain, 1482 Antomette, Clncmnati, Ohio 45230 Primary Examiner Robert Reeves [22] Filed: Jan. 18, 1971 Assistant Examiner-Hadd Lane [2]] App O 107 294 Attorney, Agent, 07" Firm-Wood, Herron & Evans [57] ABSTRACT [52] US. Cl 417/138; 222/373 51 Im. C1. F04F 1/06 1 ftmg sewage from a Sewage 58 Field of Search 137/13, 209, 386, 395; tank 3 discr-ete by forced is 222/373; 302/14; 417/138, 145, 146,141 1 f l 9 mamammg l i the quant1ty of an m ected into a sewage rece1v1ng tank [56] References Cited from an accumulator tank. The station provides imd bTt UNITED STATES PATENTS 51371152765 58111121211135ZiELEJJZfEiZZET 1,253,558 1/1918 Aikman 417/145 X cally, during each timed ejection cycle, the air is in St gg 22 /373 X jected at the same constant pressure. a or 3,203,637 9/1965 Heick 222/1373 X 5 Claims, 1 Drawing Figure A3 01/2 07 A i ZfVfL 7K5 may/m E/Yrs /0 57 7522 4 2 2 t t /a ZZZ 17a 22] a 24 u AM 6fl\ e 4/ I 1 CONTROLLEDDISPLACEMENT SEWAGE AIR LIFT STATION The present invention relates to sewage handling apparatus,j and,- more particularly, to low maintenance, high efficiency sewage lift stations of the air lift type.

BACKGROUND OF THE INVENTION I Sewage systems, particularly in metropolitan areas, usually employ one or more centrally located sewage treatment facilities. These facilities are located at a relatively low elevation, and sewer lines from the surrounding community conduct the sewage on a gravity flow basis to these facilities. The normal flow of sewage in these sewers requires that a certain grade or incline be maintained so that the sewage can flow with sufficient velocity so that the sewers can accommodate the requirements of the community. Frequently, however,

the outlying areas around a community are of such distances andelevations that an adequate incline cannot be maintained to the central facility, and in such cases it is necessary to employ sewage lift stations to lift the sewage from a low elevation to a higher elevation so that it can continue to flow under the influence of gravity to the central treatment facility.

Normally, it is not possible to employ conventional pumps for the purpose of the sewage lift station. This is primarily due to the consistency of the sewage and the volume flow rate of the sewage which is normally encountered. For example, the sewage which is received must be expected to contain suspended solid material which many mechanical pumps cannot handle. Furthermore, the particles of solid material may be several inches in diameter requiring sewer line diameters of at least 4 inches and usually greater at the ports of the pumps. With lines of such size, the pumps used will have an inherently large displacement, and with most mechanical pumps of such size, it would be rare if the flow rate of the sewage into a given lift station were sufficiently high to allow the continuous operation of such pumps to lift the sewage. Therefore, it is essential for most situations to use pumps that are operable on an intermittent basis. Such intermittently operable pumps are provided with sewage receiving tanks which can accumulate a sufficient amount of sewage to allow for the efficient operation of the pump in discrete ejection cycles in transferring the sewage to a higher elevation.

Mechanical pumps which are suitable in handling line diameters of this magnitude are inordinately expensive and inefficient for intermittent operation. Thus, the general approach taken in the art has been to employ, pneumatic lift stations which accumulate sewvage in a receiver tank until the receiver tank is filled used, to directly supply this air. In many systems two compressors are used to increase reliability in case one should fail. For more efficient operation, however,

manyisystems'employ an air accumulator. These systems operate the compressor intermittently to charge the accumulator toa high pressure. Air then intermittently emitted from the accumulator into the receiver tank to eject the sewage from the receiver tank during ejection cycles, which may occur either between or during the compressor cycles.

While such systems of the prior art have been usually adequate when considered from a dynamic and fluid handling point of view, such systems have been inefficient in their use of electrical power to operate the compressors, and, most importantly, these systems of the prior art have placed an extremely heavy demand upon the durability of the compressor motors and the starter switches which energize them. Such heavy demand has resulted in frequent breakdowns and malfunctions in the electrical equipment, high maintenance costs, and added capital expense for emergency backup equipment to reduce the downtime of the sewage lift stations.

It has been found that the maintenance required to service the compressor motors and the motor starters is directly proportional to the number of times that the motor is required to start and stop. This maintenance is manifested in a wearing of the contacts of the starter switches and in an accelerated deterioration of the motor windings.

This problem is particularly acute when one-phase motors are used, but it is also significant when threephase motors are employed. This effect on three-phase motors, however, is not as pronounced as in the case of one-phase motors due to the inherent suitability of three-phase motors to frequent start and stop operations. Therefore three-phase motors are normally used whenever three-phase power has been available. In many locations, however, three-phase power is not available and one-phase power must be employed.

SUMMARY OF THE INVENTION Accordingly, it is a primary objective of the present invention to provide an improved sewage lift station in which the electrical power system requires less maintenance and has greater reliability that has been provided by lift stations of the prior art, and which has a good overall operational efficiency.

It is another object of the present invention to provide a sewage air lift station of the type having an air accumulator to supply motive fluid wherein the motive air is conserved to the greater extent than in the prior art systems, thereby reducing the requirement to frequently'charge the air accumulator through frequent intermittent operation of a compressor motor, in relation to the ejection cycle frequency.

The present invention is predicated in part upon the concept of reducing the frequency of compressor motor cycles in relation to the: ejection cycle frequency by metering the air used in each ejection cycle so as to supply a constant quantity of air in each ejection cycle. Since said lift stations are usually moving sewage against a constant hydro-static back pressure, a constant quantity of air provides :a constant fluid displacement in each sewage ejection cycle. One specific way contemplated by the present invention of metering the quantity of air is to regulate the air from the air accumulator on a time basis, and more particularly by controlling the pressure-time relationship of the injected air in a sewage ejection cycle so as to provide a constant sewage displacement, from cycle to cycle.

More particularly, the specific embodiment of the present invention provides the injection of air under constant pressure from cycle to cycle for ejection cycles of constant time duration.

A primary advantage of the present invention is in the significant reduction in the maintenance required of the lift station, particularly of the compressor motors and the motor starter circuits. Furthermore, the present invention allows the use of electrical components of reduced cost and durability. The present invention has particularly increased the ratio of ejection cycles per compressor motor starts. For example, by operating conventional lift stations in accordance with the present invention, this ratio has been increased by up to factors of 30, in some cases.

When higher pressures were used, prior to the present invention, it was found that much more air was used in the first ejection cycle after a compressor cycle, than in the last ejection cycle before a compressor cycle. This has been primarily due to the fact that with fixed time duration ejection cycles, more air was used at high pressure than at low pressure. Thus, a given ejection cycle which is adequate for low pressures has resulted in a considerable use of excessive air at the higher pres sures. This factor has placed a practical upper limit on the overpressurization of the air accumulator.

Another advantage of the present invention. is that the electrical power required to operate the lift station is reduced, increasing materially the power efficiency of the station.

Another and important advantage of the present in vention is that, in addition to the advantages manifested to the electrical system as set forth above, the overall operating efficiency of the system is increased in an increased pumping capacity of the lift station.

DETAILED DESCRIPTION OF THE DRAWING AND OPERATION These and other objects and advantages of the present invention will be more readily apparent from the following detailed description of the drawing, in which the sole FIGURE is a diagrammatic representation of a sewage lift station having a pneumatic motive fluid system and an electrical motor and control system, and embodying principles of the present invention.

Referring to the FIGURE, a sewage lift station is provided with an inlet 11 and an outlet 12. The inlet 11 connects with a sewer at an inlet level 13 and the outlet 12 connects at an outlet level 14 to a sewage delivery line (not shown) which conducts sewage to a sewage treatment plant. The outlet level 14 is at some elevation represented by the dimension line 15 above the inlet level 13. The essential function of the lift station 10 is to receive sewage at the inlet port 1 l where it enters by gravity flow, and to discharge it at the outlet 12 at level 14, where it can further proceed by gravity flow toward the treatment station.

The lift station 10 includes a sewage handling unit 20, a pneumatic motive fluid system 40 which supplies pressurized air to the unit 20, and an electrical control system 60 which controls and times the operation of the pneumatic system 40 and thus the sewage handling unit of the lift station 10.

The lift station 10 further includes a wet well 16. The wet well 16 has an inlet 17 which forms the inlet 11 of the lift station 10, and an outlet 18 which connects with an inlet 21 of the unit 20. The wet well 16 serves as an accumulator tank in which sewage is continuously received through the inlet 17, into which it flows under its own weight, and from which it flows, also by gravity, to the unit 20 via the wet well outlet port 18. When the outlet 18 is closed, as it will be, for example, during a unit ejection cycle as will be explained below, the wet Well 16 accumulates the sewage from the inlet port 11 until such time as the outlet port 18 is again opened.

The lift station 10 also includes an outlet sewage line 19 which communicates between an outlet 22 of the unit 20 and the station outlet port 12. The outlet line 19 is not physically a part of the lift station 10. It is designed to withstand the pressurized output of the sewage handling unit 20.

Generally, the diameter of the outlet duct 19, as well as the inlet and

outlet ports

11 and 12, the wet well inlet and

outlet port

17 and 18, and the unit inlet and

outlet ports

21 and 22, must be of a diameter of usually four inches or more, in order to accommodate sewage which may contain solid particles of several inches in diameter. Accordingly, the internal sewage transmitting passages of the unit 20 must be of a similarly large diameter.

The sewage handling unit 20 is the sewage displacing portion of the lift station 10. It includes a conduit 23 which is connected through a check valve 24 to the unit inlet 21, and through a check valve 25 to the unit outlet 22. Connected between the

check valves

24 and 25 in the duct 23 is a T 26. The T 26 has a side port connecting to a vertical duct 27, which connects through the mouth 28 in the top of a sewage receiver tank 30 to the tank interior. Of the components of the lift station 10, the tank 30 is physically located at the lowest level in most cases. The pneumatic and

electrical control systems

40 and 60 are usually housed just above or below ground level at the lift station location. The extension of the vertical duct 27 inside the tank 30 com municates with a region 32 near the bottom of the tank 30. Connected near the top of the tank 30 on the inside thereof, is a liquid level sensing switch 34 which is at a vertical level 35 below the level of the output port 18 of the wet well 16. The mouth 33 of the vertical duct 27 is located at a level 36 at some distance 37 below the level 35, and at some distance 38 below the output level 12. At the top of the tank 30 is provided an air port 39. The tank 30 is essentially airtight except for the

ports

28 and 39. Sewage accumulates and is ejected from the tank 30 through the port 28. Air is vented from the tank 30, while sewage is accumulating in the tank, and is injected into the tank 30 under pressure to force sewage from the tank 30 through the port 39.

The pneumatic system 40 is provided with a port 41 which connects through a line 42 to the air port 39 of the tank 30, and with a vent port 54 which communicates with the atmosphere. A three-way solenoid controlled valve 43 is provided to selectively connect the port 41 alternatively to the exhaust port 54 and a pressurized air supply line 44. When the solenoid 43' of the solenoid valve 43 is de-energized, the port 41 is normally connected to the exhaust port 54 while the supply line 44 is blocked. When the valve solenoid 43' is energized, the port 41 communicates with the air supply line 44 and the exhaust port 54 is blocked. Preferably, the exhaust port 54 is vented through the wet well to reduce noise and confine odors.

A compressor 45 is provided having an inlet port 46 connecting to atmosphere and an outlet port 47 connecting through a pressure release safety valve 48 to an air delivery line 49. The air delivery line 49 connects to the mouth 50 of an accumulator tank 51, .and through a pressure regulator valve 52 to the air supply line 44. The valve 52 maintains the air to the supply line 44 from the accumulator tank 51 or the compressor 45 at a constant pressure.

The electrical control circuit 60 includes a timer 61 having an input 62 connected to the level sensor switch 34 of the tank 30, and an output 63 connected to the winding 43 of the solenoid valve 43. The timer 61 is energized by a signal from the level sensor 34 whenever the level in the tank 30 has reached the level 35, to activate the solenoid 43' for a fixed period of time. The control 60 also includes an electric motor 66 having an output shaft connected to the drive shaft 67 of the compressor 45 so as to drive the compressor. The motor 66 is illustrated as a one-phase AC electric motor provided with leads 68 which are connected through the contacts 69 of a starter assembly 70 to a one phase AC power source 71. The starter assembly 70 includes the sets of normally opened switch contacts 69 connected in series with the leads 68 of the motor 66. The starter further includes an actuator 74 which operates to close the contacts 69 when energized. The actuator 74 is provided with an input 75 which is connected to a pressure switch 76 in the accumulator tank 51 which energizes the winding 74 to close the contacts 69 when the pressure' switch is activated. The pressure switch 76 activates when the pressure in the tank 51 falls below a minimum pre-set pressure to thereby energize the winding 74 to turn on the compressor motor 66. When the pressure has reached a prescribed maximum value, another pressure switch 78 is provided at the accumulator tank 51 which is connected to another input 79 of the winding 74 so as to de-energize the winding 74 to turn off the motor 66 and the compressor 45. Thus, the starter switch 70 acts as a conventional double-acting relay. The starter assembly 70 also includes overload protection (not illustrated) to de-energize the relay 74 if the motor is overloading the power lines 68.

In some systems, a second back-up compressor is provided to operate if the first compressor were to fail. In such a case, a third sensor would be provided to start the second compressor rather than the sensor 76. This sensor would be set to a pressure below that of the sensor 76, to start the second compressor if the first compressor fails to keep the accumulator pressure at an adequate level.

In operation, sewage enters the inlet port 11 at the inlet level 13 and flows under the force of gravity through the wet well 16, through the outlet of the wet well 18 to the inlet port 21 of the unit 20. The sewage proceeds under the force of gravity through the check valve 24 to the line 23 and into the sewage port 28 of the receiver tank 30. The sewage will continue to accumulate in the tank 30 in this manner until the level in the tank 30 has reached the level 35 of the sensor switch 34. When the sewage has reached this level 35 to trip the level sensor switch 34, a sewage ejection cycle is initiated in which air under pressure is injected into the receiver tank 30 through the air port 39 to force the sewage out of the tank 30 through the duct 27. This pressure in the line 23 causes a check valve 24 to close and the check valve 25 to open as the sewage is ejected from the tank through the output port 22 of the pump 20, and into the outlet line 19 toward the outlet port 12 at the level 14.

At the end of the ejection cycle, the air pressure is relieved through the air port 39 and the sewage from the ou'tp'ut line 19 will tend to flow backward toward the tankunderthe influence of gravity, causing the check valve 25to close, trapping the ejected sewage in the outletline 19. At the end of this ejection cycle, the sewage level at the receivertank 30 is at the level 36 adjacent the'mouth 33 of the duct 27. During the ejection cycle, while the check valve 24 is closed, the sewage has accumulated in-the wet well 16. When the pressure is relieved from the tank 30 at the end of the ejection cycle, this sewage in the wet well forces open the check valve 24 and proceeds to accumulate in the receiver tank 30 and the next cycle proceeds in the manner set forth above.

During the ejection cycle, the air pressure injected into the receiver tank 30 through the port 39 acts directly on the sewage liquid within the tank 30 to force it up through the duct 27 toward the outlet port 12 at the level 14. To force the sewage out of the tank 30, air pressure equal to or greater than the hydrostatic pressure caused by sewage standing in the duct 27 and output line 19 equal to a height 38 between the levels 36 and 14 is required. Normally, a slightly greater pressure 'is' desired to accelerate the ejection cycle; however, ex-

cessive ejection pressures are preferably avoided in order to prevent an excessive loss of power due to the dynamic losses of the sewage moving through the sewage lines at high velocities.

The ejection cycle is controlled by the timer 61 and the valve 43. When sewage is accumulating in the tank 30, the valve 43 is de-energized connecting the air port 39 with atmosphere through the line 42 and the exhaust port 54 of the valve 43. At the start of an ejection cycle, the sewage at the level 35 trips the level sensing switch 34 to energize the timer 61. 'Once the timer is energized, an electrical signal is produced on line 63. This signal has a fixed duration which energizes the solenoid 43' of the valve 43 for a fixed period of time. This feeds air from the accumulator tank 51 through the pressure regulator valve 52 through the valve 43 and the line 42 into the tank 30 at a constant pressure through the air port 39. Ideally, the valve 43 remains open for a period of time long enough to obtain a pump displacement which causes a reducing of the sewage level in the tank 30 from the level 35 to the level 36, during an ejection cycle. Typically, this'displacement is determined by the volume to which the injected air has attained when it is fully expanded in the sewage receiver tank. The setting of the timer 61 which is required to most effectively achieve this is best determined by experimentation. Generally, the time required will vary with the different systems and plumbing configurations employed. Important considerations are the dynamic losses and the hydrostatic pressure at the mouth 33 of the duct 27.

The setting of the timer 61 and the pressure regulator valve 52 are mutually dependent. A higher pressure setting on the valve 52 requires a shorter time setting on the timer 61. Thisrelationship is not necessarily a linear relationship in order to maintain a given displacement of the pump 20. Instead, the relationship might vary with pressure for some systems due primarily to the effects of dynamic forces involved in accelerating the fluid out of the tank 30 and due to the dynamic losses caused by the moving fluid through the sewage lines.

The combination of the regulator 52 and the timer 61 provides a means for regulating the quantity "of injected air and thus the displacement of the pump during each ejection cycle and maintaining it constantfromcycle to cycle. In this manner, the displacement of each injection cycle is optimized, thereby eliminating the waste of air by using air in excess of receiving tank capacity, and also preventing a loss in the overall lift station capacity by using less air than the receiver tank capacity.

The air pressure supplied through the regulator 52 is supplied from the air accumulator 51 where air is stored at a pressure which is maintained above the pressure setting of the regulator 52. This pressure is so maintained above a prescribed minimum level by the setting of the pressure sensing switch 76. When the air pressure falls below this pre-set level of the switch 76, an electrical signal is generated on the line 75 to energize the starter actuator 74. This closes the set of switch contacts 69, turning on the compressor motor 66 which drives the compressor 45 to pump air from the atmosphere port 46 into the accumulator 51. At some maximum pressure as set by the sensing switch 78, an electrical signal is generated on the line 79 to de-energize the starter actuator 74, breaking the contacts of the switch 69, turning. off the motor 66 and the compressor 45. The number of stops and starts of the motor 66 determines the service life of the starter 70 and the motor 66. This number of stops and starts is primarily determined by the amount of air used in each ejection cycle, and the amount of air stored in the accumulator 51. In this respect, it is desirable to use a minimum amount of air in each ejection cycle, while storing a maximum amount of air in the accumulator 51. The amount of air stored in the accumulator 51 is determined by the size of the accumulator 51 and the pressure difference between the maximum and minimum pressures as determined by the pressure sensor switches 76 and 78.

Also, the overall power efficiency of the system is greater when the motor 66 is run at a continuous speed than it is when it is being stopped and started frequently. In this respect, it is desirable to select a wide range between the minimum and maximum pressures in the accumulator 51. The pressure regulator 52 permits usage of greater pressure differential between the maximum and minimum pressures of the accumulator 51 while maintaining constant pump displacement from cycle to cycle. For example, the minimum pressure as set by the sensing switch 76 is maintained at, say, 3 psi above the setting of the regulator 52, while the maximum pressure set by the sensing switch 78 is maintained as high as possible but within the pressure ratings of all of the components which are subject to high pressure. The regulator 52, on the other hand, is set for the best efficiency considering the dynamic head and other factors of the system.

Furthermore, the motor operates more efficiently if his being operated at a relatively high optimum speed under an optimum load. The optimum speed and load are different for different compressor-motor combinations. Because the motor starts less and runs longer, more work is done when the motor is running under opti'mum load.

advantage of providing a pressure regulator is that the pressure sensor 76 can be set enough above the setting of the pressure regulator 52 so that, in a given ejection cycle, the pressure of the accumulator 51 will not drop below the setting of the pressure regulator 52.

If this occurs, the pump displacement and lift station capacity will be reduced. In such a case, the compressor motor 45 cannot supply enough air to maintain the regulator pressure, and the pump displacement will drop below the receiver tank capacity, decreasing the effective capacity of the lift station. Furthermore, be cause the tank would not be completely evacuated, it would fill faster, and when the sewage flow rate is high, this may occur before the compressor can charge the accumulator to adequate pressure to empty the receiver in the next ejection cycle.

Therefore, the present invention provides for increased lift station capacity particularly when this capacity is most needed, in cases of high sewage flow.

What is claimed is: 1. An air lift station for receiving sewage from an inlet at a first level and for delivering said received sewage to an outlet at a second level at a higher elevation than said first level, by intermittently ejecting said received sewage toward said outlet in discrete ejection cycles with controlled blasts of pressurized air, said station comprising:

a sewage receiver having means for communicating sewage to said receiver from said inlet, and means for communicating sewage from said receiver to said outlet; means for supplying pressurized air to said receiver at each ejection cycle, said air supplying means including: an air accumulator for storing air under pressure, a fluid path connecting said accumulator with said receiver,

valve means in said fluid path for selectively opening said path during said ejection cycles and closing said path between said ejection cycles;

an air compressor for supplying pressurized air to said accumulator, said compressor having an outlet connecting with said air accumulator;

means for intermittently driving said compressor in discrete compression cycles, said driving means including an electric motor and selectively operable circuit means for connecting said motor to a source of electrical power; and

means for controlling the injection of air to said receiver in a plurality of ejection cycles between each of said compression cycles so as to maximize the number of ejection cycles per each compression cycle, said control means including means for maintaining the quantity of air injected into said receiver approximately constant from cycle to cycle comprising:

a. regulator means connected in said fluid line between said accumulator and said receiver, and

b. timing means operable to open said valve means for an interval that is approximately constant from cycle to cycle.

2. An air lift station according to claim 1 wherein:

said regulator means in a pressure is effective to control the pressure of the air injected into said receiver in the same manner during each of said ejection cycles.

3. An air lift station according to claim 2 wherein:

said pressure regulator means is effective to maintain a constant pressure of the injected air throughout each ejection cycle.

4. An air lift station according to claim 1 wherein:

said regulator is a flow regulator effective to control the flow rate of the air into said receiver in the same manner during each of said ejection cycles. 5. An air lift station for receiving sewage from an inlet at a first level and for delivering said received sewage to an outlet at a second level at a higher elevation than said first level, by intermittently ejecting said received sewage toward said outlet in discrete ejection cycles with controlled blasts of pressurized air, said station comprising:

means for intermittently driving said compressor,

said driving means including an electric motor and selectively operable circuit means for connecting said motor to a source of electric power;

means for controlling the injection of air to said receiver during each of said ejection cycles to maintain the quantity of the air injected into said receiver tank constant from cycle to cycle;

a first pressure sensor in said accumulator for generating a first signal when the pressure in said accumulator falls below a predetermined minimum value;

a second pressure sensor in said accumulator for gen erating a second signal when the pressure in said accumulator rises above a predetermined maximum value;

said circuit means being operative to connect said motor in response to said first signal and to disconnect said motor in response to said second signal; and

said control means including a pressure regulator for maintaining the air injected into said receiver at a pressure which is less than said predetermined minimum pressure of said accumulator but greater than the hydrostatic pressure at said receiver of sewage moving toward said outlet.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN PATENT NO. 2 3 915 593 DATED October 28, 1975 |NVENTOR(S) Jess L. Chamberlain It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 40, "that" should be than-.

Column 2, line 46, delete the word "the" (second occurrence) Column 8, line 59, Claim 2, delete "in a pressure is" and insert -is a pressure regulator.

Signed and Scale this Tenth Day of August 1976 (SEAL! Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Parents and Trademarks

Claims

1. An air lift station for receiving sewage from an inlet at a first level and for delivering said received sewage to an outlet at a second level at a higher elevation than said first level, by intermittently ejecting said received sewage toward said outlet in discrete ejection cycles with controlled blasts of pressurized air, said station comprising: a sewage receiver having means for communicating sewage to said receiver from said inlet, and means for communicating sewage from said receiver to said outlet; means for supplying pressurized air to said receiver at each ejection cycle, said air supplying means including: an air accumulator for storing air under pressure, a fluid path connecting said accumulator with said receiver, valve means in said fluid path for selectively opening said path during said ejection cycles and closing said path between said ejection cycles; an air compressor for supplying pressurized air to said accumulator, said compressor having an outlet connecting with said air accumulator; means for intermittently driving said compressor in discrete compression cycles, said driving means including an electric motor and selectively operable circuit means for connecting said motor to a source of electrical power; and means for controlling the injection of air to said receiver in a plurality of ejection cycles between each of said compression cycles so as to maximize the number of ejection cycles per each compression cycle, said control means including means for maintaining the quantity of air injected into said receiver approximately constant from cycle to cycle comprising: a. regulator means connected in said fluid line between said accumulator and said receiver, and b. timing means operable tO open said valve means for an interval that is approximately constant from cycle to cycle.

2. An air lift station according to claim 1 wherein: said regulator means is a pressure regulator effective to control the pressure of the air injected into said receiver in the same manner during each of said ejection cycles.

3. An air lift station according to claim 2 wherein: said pressure regulator means is effective to maintain a constant pressure of the injected air throughout each ejection cycle.

4. An air lift station according to claim 1 wherein: said regulator is a flow regulator effective to control the flow rate of the air into said receiver in the same manner during each of said ejection cycles.

5. An air lift station for receiving sewage from an inlet at a first level and for delivering said received sewage to an outlet at a second level at a higher elevation than said first level, by intermittently ejecting said received sewage toward said outlet in discrete ejection cycles with controlled blasts of pressurized air, said station comprising: a sewage receiver having means for communicating sewage to said receiver from said inlet, and means for communicating sewage from said receiver to said outlet; means for supplying pressurized air to said receiver at each ejection cycle, said air supplying means including: an air accumulator for storing air under pressure, a fluid path connecting said accumulator with said receiver, valve means in said fluid path for selectively opening said path during said ejection cycles and closing said path between said ejection cycles; an air compressor for supplying pressurized air to said accumulator, said compressor having an outlet connecting with said air accumulator; means for intermittently driving said compressor, said driving means including an electric motor and selectively operable circuit means for connecting said motor to a source of electrical power; means for controlling the injection of air to said receiver during each of said ejection cycles to maintain the quantity of the air injected into said receiver tank constant from cycle to cycle; a first pressure sensor in said accumulator for generating a first signal when the pressure in said accumulator falls below a predetermined minimum value; a second pressure sensor in said accumulator for generating a second signal when the pressure in said accumulator rises above a predetermined maximum value; said circuit means being operative to connect said motor in response to said first signal and to disconnect said motor in response to said second signal; and said control means including a pressure regulator for maintaining the air injected into said receiver at a pressure which is less than said predetermined minimum pressure of said accumulator but greater than the hydrostatic pressure at said receiver of sewage moving toward said outlet.