US3489335A - Oscillating free piston pump - Google Patents

Description

Jan. 13, 1970 M. SCHUMAN\ 3,489,335

OSCILLATING FREE PISTON PUMP Filed July 31, 1968 2 Sheets-Sheet l E 3 L J K (0 W4 Q14 rm m W E 2/ 19 FIGS INVENTOR MARK SCH UMAN wa /Ei- BY q /gw fiwmf/ g M ATTORNEYS Jan. 13, 1970 M. SCHUMAN 3,489,335

OSOILLATING FREE PISTON PUMP Filed July 31, 1968 2 Sheets-Sheet 2 57 FIG. IO

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ii I INVENTOR MARK SCHUMAN BY gwfl M ATTORNEYS United States Patent O 3,489,335 OSCILLATING FREE PISTON PUMP Mark Schuman, Ann Arbor, Mich. (101 G St. SW., A516, Washington, D.C. 20024) Filed July 31, 1968, Ser. No. 749,130 Int. Cl. F04b 35/00 U.S. Cl. 230-51 6 Claims ABSTRACT OF THE DISCLOSURE A thermal powered pump formed of a cylinder, containing a free, oscillating piston, and having a heating chamber for providing above the piston, heated, expanding gases to be pumped for moving the piston downwardly to compress the gas located beneath it which, in turn raises piston so that the piston oscillates up and down, and with the pump outlet located above the piston for expelling the gas. A shunt interconnects the cylinder portions above and below the piston for carrying gas to the portion below the piston for maintaining the center of oscillation of the piston with respect to the cylinder.

BACKGROUND OF INVENTION Conventional piston type pumps used for pumping gases, such as air or the like, generally include a cylinder containing a movable piston which is connected to a motor or engine as a power operating means for the pump. In addition, such types of pumps are generally bulky, noisy, and relatively expensive in construction, and cannot operate on continuously applied thermal power.

Thus, this invention is concerned with providing a simply construction, thermally powered pump mechanism, in the form of a free floating piston oscillating within a cylinder. Power is supplied by a suitable heating means, such as a continuously operated electrical heating coil or carbon-type fuel heater, which is relatively eflicient and inexpensive. The relative size of the pump, as compared to prior pumps, is reduced and its noise of operation, both electrical and audible, is considerably reduced. The improved pump may serve a number of pumping functions, as for example, to provide high pressure gases to a turbine or turbo-generator, etc.

SUMMARY OF INVENTION Summarizing, the invention herein contemplates oscillating a free piston by means of initially placing it between equal volumes of gas which act like a pair of compression springs to push the piston back and forth between them, but with one spring having an added push on its expansion to prevent the oscillation from dying out. Thus, one of the gas volumes is heated and expands to push the piston to compress the other gas volume which rebounds like a spring to return the piston to expel, and

thereby pump the heated gas. The repeated oscillation steps generally comprise supplying heated expanding gas, movement of piston to compress the opposite gas volume, and rebound and expulsion of the heated gas. The supply of heated gas provides the pressure to maintain the oscillation and prevent it from slowing down and stopping. Additional gas is intermittently supplied to the opposite gas volume to maintain the center of oscillation of the piston. The oscillation is initially started by use of an auxiliary starting pump which use is discontinued once the piston oscillation stabilizes.

An object of this invention is to drive an oscillating, free piston within a cylinder by means of heated expanding gas applied to one face of the piston and non-heated compressed gas, which is compressed by the piston itself, at the opposite face of the piston, and to expel or pump the heated gas.

Patented Jan. 13, 1970 f ce Another object is to provide a simple, quiet operating pump construction utilizing a constantly operated heater which continually, rather than intermittently, heats he gas, but wherein the gas intermittently applies pressure to the piston to cause continued oscillation thereof.

Another object of this invention is to utilize, as the ther mal power means for such pump, a temperature differ ential provided by means of heating and cooling reservoirs, or by means of natural temperature difierentials such as the heat of sunlight as compared to ambient temperature or available water temperature or the like.

A further object of this invention is to provide a pump as described above but utilizing a double action operation, which includes a pair of opposed pistons operating oppositely and synchronously to thereby balance out low frequency piston vibrations.

These and other objects and advantages of this inven tion will become apparent, upon reading the following description, of which the attached drawings form a part.

DESCRIPTION OF DRAWINGS FIG. 1 is a schematic, elevational, cross-sectional view of the oscillating free piston pump herein.

FIG. 2 is an enlarged, cross-sectional schematic view of the upper, heating chamber portion of the cylinder.

FIG. 3 is an enlarged, fragmentary, elevational view of the piston and a portion of the cylinder.

FIGS. 4 through 8 show successive steps in the operation of the pump.

FIG. 9 schematically illustrates the use of the pump in powering a turbo-generator, and also illustrates a modified heater.

FIG. 10 illustrates a modification wherein a heat diiferential is utilized to provide the thermal power.

FIG. 11 illustrates a further modification showing a double acting pump utilizing a pair of opposed free pistons.

FIG. 12 illustrates another modification similar to that of FIG. 10.

DETAILED DESCRIPTION FIG. 1 illustrates a pump 10 formed of a vertically arranged, closed cylinder 11, containing a loosely fitted, free piston 12 adapted to oscillate vertically up and down within the cylinder. The cylinder includes an inlet pipe 13 through which the gas to be pumped enters the cylinder.

Between the inlet pipe and the body of the cylinder is arranged a heating chamber 14 containing a suitable heating element 15 such as an electrical heating coil powered by an outside electrical source, such as a conventional house circuit.

The inlet to the heating chamber is closed by a valve 16 and the outlet is closed by a valve 17, these being one- Way type of valves, passing the gas only in the direction from the inlet towards the main body of the cylinder and closing when necessary to prevent the gas from returning back to the inlet.

A pump outlet pipe 18 is arranged at the upper portion of the cylinder and contains a suitable one-way outlet valve, as for example, a conventional ball check valve 19, which leads into a surge or storage tank 20' for smoothing out the pulsating pumped gas.

A shunt pipe 21 is arranged around the cylinder, with its upper end 22 connected to the inlet pipe 13 and its lower end 23 connected to the interior of the bottom of the cylinder through a one-way inlet valve 24, such as a suitable ball check valve or the like which permits the flow of gas into the bottom of the cylinder through the shunt pipe but not in the reverse direction.

The piston 12, being loosely fitted within the cylinder, is gas lubricated for substantially frictionless movement. Preferably, the piston is formed of a cylindrically shaped,

porous, sintered metal, side wall 25 which is gas pervious (see FIG. 3). The piston is closed by a top cover 26 having a central opening 27 and closed by a suitable oneway valve 28 (shown schematically) so that it will fill with gas on its up stroke while permitting the pressurized gas to continuously leak through the wall 25. This serves to gas lubricate the piston relative to the cylinder wall and to maintain the piston co-axially with the cylinder.

While a variety of one-way valves may be found for the inlet and outlet of the heating chamber, FIG. 2 illustrates one suitable form which comprises wafers 16 and 17 having an inlet stop or limit 29 and an outlet stop or limit 31. The outlet stop provides a greater distance of movement for the wafer 17 than is provided for the wafer 16 so that the wafer 17, in efiect, is a delayed acting valve because of its greater required movement and lower restriction of reverse gas flow. The wafers close the inlet opening 30 and the outlet opening 32 of the heating chamber 14. The object here is to provide an outlet valve for the heating chamber which closes at a short time interval after the inlet valve closes for reasons to be explained below. Thus, other forms of valves such as solenoid operated valves or other suitable timed valves may be utilized for this purpose.

Referring to FIG. 1, the pump also includes an auxiliary starter pump 35 for start-up purposes. This comprises an inlet pipe 36 leading from the bottom of the cylinder and opening into a bellows 37 which is connected to a piston rod 38 having a piston 39 arranged within a cylinder 40 containing a compression spring 41. In addition, the rod is surrounded by a conventional solenoid coil 42. The solenoid is arranged to periodically move the piston rod 38 to the left, as referring to FIG. 1, whereas the spring -41 returns the piston rod to the right to thereby pump the bellows. The bellows sucks gas out of the cylinder to lower the piston 12, and pumps gas into the cylinder to raise the piston 12. It is used for a short time to start the normal pump operation.

OPERATION During normal operation, the piston oscillates upwardly and downwardly, with heated gas entering the cylinder, above the piston, from the heating chamber and with this gas being pumped out of the cylinder through the outlet 18 during the top portion upstroke of the piston stroke. FIGS. 4 through 8 schematically show certain of the steps in the operation of the pump.

FIG. 4 illustrates the piston travelling upwardly near the top of its upstroke. Here the heating chamber valves 16 and 17 are closed, gas is being expelled through the outlet 18 whose check valve 19 is open. The arrows beneath the piston, within the cylinder, represent the expansion or rebound of gas, located below the piston, which has been previously compressed by the downward movement of the piston.

During this time, the heating element 15, which is continuously operated, heats the gas contained within the heating chamber 14, causing the gas pressure to increase, as shown by the arrows in FIG. 4. Next, as seen in FIG. 5, gas compressed by the upward movement of the piston, slows such upward movement, stops it, and starts to drive it downwardly. Simultaneously, gas exhausts through outlet 18, until outlet check valve 19 closes due to the higher pressure of the gas contained within the surge tank 20. In FIG. 5, the valve 16 is shown in its open position.

In addition, a small amount of gas, as needed, may enter into the bottom of the cylinder through the shunt pipe 21, whose check valve 24 is open so that pressure below the piston does not drop below the inlet pressure. Where the gas being pumped is atmospheric air, the shunt pipe may be omitted and the check valve simply opened to atmosphere, so that, in efiect, there is still a shunt.

In FIG. 6, the exhaust check valve 19 is closed, and the pressure of the gas in the heating chamber 14 causes inlet valve 17 to open to release heated gas into the cylinder, which gas expands and drives the piston down.

As the piston moves further down, reducing the pressure within the heating chamber to below inlet 13 pressure, the heating chamber inlet valve 16 also opens to admit more gas through the inlet 13 (see FIG. 7). The downward movement of the piston not only permits the cylinder portion above the piston to become filled with the incoming gas, but also compresses the gas located Within the cylinder below the piston. Hence, at the lowermost part of the stroke downwardly, the compressed gas beneath the piston reaches its point of maximum compression where it and the piston tend to rebound as a result of this pressure exceeding the pressure above the piston. At that point, as shown in FIG. 8, the piston again starts upwardly, compressing the gas above it, and expelling a portion of the gas into the heating chamber 14 through the valve 17 which remains open slightly longer than does the upper valve 16 to insure closing of the valve 1 6 and to accumulate additional gas within the heating chamber for higher efficiency. As the piston rises towards the top of the stroke, the pressure above it exceeds the surge tank pressure and gas is expelled out the outlet 18. The cycle is then repeated as shown beginning with FIG. 4.

In this manner, the piston rapidly oscillates upwardly and downwardly, pumping out a pulsating discharge into the surge tank 20 and relying upon the continuously applied heat energy to provide it with the expanding gases necessary for operation.

Before the piston stabilizes and oscillates as described above, at the outset of its operation, it is necessary to start at the regular oscillation by means of starter 35. In essence, its bellows 37 alternately pumps and draws an amount of gas into and from the cylinder, beneath the piston, at approximately the natural frequency of the oscillation of the piston. Thus, the solenoid is properly timed to move the rod 38 with the bellows at such frequency. The starter is used until such time as the piston oscillation stabilizes, at which time the starter is turned off. This may amount to a few minutes of operation.

MODIFICATION FIG. 9

FIG. 9 illustrates a modification wherein the heating coil is in the form of a pipe 45 opening into a suitable fossil type heater 46, such as a natural gas burner type heater, connected in turn to a tank 47 of fuel gas. Other types of suitable heaters may be used, such as a petroleum heater, coal burner or the like. The heated gas from the heater 46 passes through the coil 45 and then out through the end 48 into a discharge stack.

FIG. 9 also illustrates the pump as being used to power a conventional turbo-generator 49 which generates electricity. The gas pumped through the generator 49 is cooled in a cooling tank 50 or by other cooling means such as fins surrounding the return pipe 51 which returns the gas back to the inlet 13. This illustrates a closed circuit gas movement wherein the gas is recirculated.

In the embodiment illustrated in FIG. 1, the gas may be air, in which case no recirculation is contemplated, or it may be a gas of more value which required recirculation and hence, interconnection between the inlet and outlet pipes ultimately.

The operation of the pump shown in FIG. 9 is otherwise the same as that described above.

FIG. 10

FIG. 10 illustrates a further modification which contemplates utilizing a temperature differential in providing the heat to the pump. As an example, above the heating chamber 14 is located a cooling chamber 55 having a cooling coil 56 for first cooling the inlet gases, which are then heated by the heating coil located within the heating chamber. Once the gas is heated and enters the cylinder, the operation is the same as described above, with the gas powering a turbo-generator 49 and then being recirculated back to the cylinder through the return pipe 51.

The coil 56 may be cooled by the use of a cold water reservoir 57, with the heated coil 58 warmed by a warm reservoir. The cooled reservoir may be an available water supply, such as a natural well, pond, etc.

It is contemplated that this arrangement may utilize ambient temperatures and sun heat to operate around the clock. To this end, a heat exchanger coil 60 is provided and mounted upon a panel 61 which could be arranged upon a rooftop or out of doors where it is exposed to the sun. The coil is connected through valve 62 to a cool reservoir inlet pipe 64 and a warm reservoir inlet pipe 65 and through a valve 63 to a cool reservoir outlet pipe 66 and a warm reservoir outlet pipe 67. In this case, the reservoirs may be large water tanks. Thus, during the day, when the sun is available to provide heat, by adjusting the valves 62 and 63, the liquid in the warm reservoir may be heated and the liquid in the cool reservoir simply left at ambient temperature, preferably in a cool, shaded place. In the evening, when the sun is no longer available, the valve 62 and 63 may be reversed to utilize radiant cooling and the cold ambient temperature to cool the cool reservoir further below the liquid in the warm reservoir.

In this manner, the net result is that the gas entering through inlet 13 is first cooled by the coil 56 and is then heated by the coil 58 to provide for greater pressure buildup and subsequent expansion. Thus, the differential of temperature, provided as described above or in other equivalent ways, serves as a means for operating the pump.

FIG. 11

FIG. 11 illustrates a modification in the form of a double ended or double acting pump 70 comprising a cylinder 71 containing a pair of free pistons 72 and 73. The inlet 74 delivers the gas to the heating chamber 75 which contains the heating coil 76 and has an inlet valve 77 and an outlet valve 78 located between the two pistons. Also, the pump outlet pipe 79 is located between the two pistons and discharges through a one-way valve 80 into the surge tank 81.

The opposite ends of the cylinder are connected to the inlet 74 by means of a shunt pipe 82 containing one-way valves 83 at each end of the cylinder.

For purposes of starting the pump, a pair of starters 35 are provided at each end of the cylinder, although one starter might be used with pipes leading to each of the opposite ends.

The operation of this pump is the same as described before except here, the two pistons move oppositely and synchronously.

FIG. 12

FIG. 12 illustrates a modification similar to that of FIG. 10, with the exception that no separate heating chamber is provided below cooling chamber 55 which contains the cooling coil 56 and is closed at its bottom by a one-way valve 85. Here the heating coil is exposed above the piston. While heating the gas in the up-stroke is relatively inefi'icient, this construction is simpler and may have certain low efficiency applications.

Having fully described an operative embodiment of this invention, I now claim:

1. An oscillating free piston pump, for pumping gas, comprising a closed vertical cylinder containing a free piston loosely fitted therein for vertical oscillation;

a gas inlet and a gas outlet located above the piston, the

inlet being also connected by a shunt pipe through a shunt one-way valve to the opposite end of the cylinder for permitting gas to flow into the cylinder below the piston;

a heating chamber connected between said inlet and the cylinder above the piston for heating incoming gas before entry into the cylinder and having a oneway chamber inlet and chamber outlet valves for controlling gas flow only towards the cylinder and for closing upon upward movement of the piston, with the chamber outlet valve being formed to close shortly after the chamber inlet valve closes;

said gas outlet having a one-way outlet valve for passing the pumped gas only out of the cylinder;

whereby downward movement of the piston is efiected by expansion of the heated gases entering the cylinder from the heating chamber and by gas compressed above the piston applying a force to the top of the piston, and upwards movement of the piston is effected solely by compression and rebound of the compressed gas below the piston applying an upwards force upon the bottom of the piston.

2. A construction as defined in claim 1, and including a starter pump connected to the cylinder below the piston, said starter pump having means for regularly and periodically pumping gas into and out of the cylinder below the piston at the natural frequency of oscillation of the piston for a period of time sufficient to stabilize the normal oscillation of the piston within the cylinder.

3. A construction as defined in claim 1, and including a heater element contained within said heater chamber and constantly operated to maintain a continuous heat input into said chamber by an outside source of heat energy.

4. A construction as defined in claim 1, and including a cooling chamber, containing means for cooling gases passed therethrough, connected between the gas inlet and heating chamber for reducing the temperature of and contracting the specific volume of the gas prior to entry of the inlet gas into said heating chamber.

5. A construction as defined in claim 1, and including a second free piston located in the cylinder spaced above the first piston and the gas inlet and outlet, with the upper end of the cylinder also connected to the gas inlet by a shunt pipe containing a one-way shunt valve for controlling gas flow only into the upper end of the piston above the second piston;

whereby the two pistons move respectively oppositely and synchronously upon entry of heated gas into the cylinder between them and upon rebound of the compressed gas when the pistons reach near their respective opposite cylinder ends.

6. An oscillating free piston pump for pumping a gas, comprising a closed cylinder containing a free piston loosely fitted therein for oscillation along the axis of the cylinder;

said piston dividing the cylinder into a pumping chamber closed by an end of the piston and compression chamber closed by the opposite end of the piston;

a gas inlet and a gas outlet located in said pumping chamber with a continuously operating heater located between said inlet and outlet, and including a one-way inlet valve at said inlet and a one-way exit valve at said outlet;

means for initially starting the piston to oscillate within said chamber at a predetermined frequency;

and means for connecting the compression chamber to inlet gas pressure at about the time that the piston reaches the end of its stroke towards the inlet;

wherein movement by the piston away from the inlet compresses gas contained in the compression chamber until maximum compression is reached and the compressed gas rebounds and acts as the sole means for driving the piston towards the inlet for expelling gas out through the outlet and simultaneoutly compressing gas in the pumping chamber, and movement away from the inlet is efiected by a combination of expanding heated gas entering the pumping chamber and compressed gas resulting from piston movement towards the inlet.

(References on following page) 7 8' References Cited 3,170,406 2/1965 Robertson. UNITED STATES PATENTS 3,285,001 11/ 1966 Turnblade.

2,910,119 10/1959 wennelbergi WILLIAM L. FREEH, Pnmary Exammer 2,040,433 5/ 193 6 Dufiaud.

5 US. Cl. X.R. 3,087,438 4/1963 Ciesielski. 23056

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