US3500753A - Injection pump apparatus - Google Patents

Description

March 17, 1970 G. J. GREENE, JR v 3, 0,7

INJECTION PUMP APPARATUS Filed April 16. 1968 2 Sheets-Sheet 1 GEORGE J. GREENE, Jr

/N l/E N TOR ATTORNEY G. J. GREENE, JR

INJECTION PUMP APPARATUS 2 Sheets-Sheet 2 GEORGE J. GREENE, Jr.

/NVENTOR.

BV Alum, poglhnce,

WUunhe ATTORNEYS March 17, 1970 Filed April 16, 1968 United States Patent 3,500,753 INJECTION PUMP APPARATUS George J. Greene, Jr., Shreveport, La., assignor to Greene Research & Engineering Company, Houston, Tex., a joint venture of Texas Filed Apr. 16, 1968, Ser. No. 721,662 Int. Cl. F04b 17/00; F011 /02 US. Cl. 103--50 17 Claims ABSTRACT OF THE DISCLOSURE This application discloses an injection pump operated by a fluid motor, with a valve assembly for the fluid motor which includes a vent tube functioning to control pressure buildup and venting on one side of the piston. The vent tube is axially moveable and is engaged by the piston of the fluid motor using a resilient cup which contacts the head of the vent tube and covers the vent hole.

Injection pumps are commonly used for metering a controlled amount of a liquid into a line on a continuous basis. The location of the line may be such that a convenient power source is not available, and the site may be inspected very infrequently. So, the motive power mechanism used for the injection pump must use a power supply readily transportable or available at the site, and the mechanism itself must be able to operate for long periods of time without maintenance or adjustment.

Pressurized gas has been found to be a preferred motive power source for injection pumps of this type, since a supply of gas is often available at the location for other purposes, or may be easily provided by a tank of pressurized air. The gas is used to operate the piston in a fluid motor, the piston of course being mechanically coupled to the plunger of the injection pump. A valve arrangement is needed to control the operating cycle of the fluid motor and the arrangement must provide for variable pumping rates or cycle times.

Valve mechanisms for fluid motors of this type, for operation of injection pumps, have been quite widely used; however, such pumps have had the disadvantage of including a relatively complex valve mechanism for controlling the cycle of the motor. Primarily, the disadvantages of such devices have been the lack of reliability for operation over long periods of time, and a likelihood of being fouled by debris, etc.

It is the primary feature of this invention to provide a motive power mechanism for an injection pump, pri marily a fluid motor having a valve assembly which is reliable for operation in remote locations over long periods of time, and which permits variation of the pumping rate with rather close control.

In accordance with one embodiment of this invention, a fluid motor for operating the plunger of an injection pump is provided with a valve assembly which includes a vent tube operable to cause pressure buildup on, and venting, one side of a piston in the fluid motor, in alternate half cycles. Movement of the vent tube is controlled by a resilient cup which engages a flat plate-like head of the vent tube. A vent passage extends through the vent tube from the head to a vent aperture which is open to atmosphere when the tube is in the outward position, then is open to the interior of the cylinder when the piston pulls the tube inward. The cup thus holds the vent head, then releases, as the piston moves back and forth. Either the cup or the plate may be slightly resilient to facilitate sealing.

Novel features which are believed to be characteristic of the invention are set forth in the appended claims.

3,500,753 Patented Mar. 17, 1970 The invention itself, however, as well as further features and advantages thereof, may best be understood by reference to the following detailed description of particular embodiments, when read in conjunction with the accompanying drawing, wherein:

FIGURE 1 is an elevation view in section of an injection pump and fluid motor according to one embodiment of the invention;

FIGURE 2 is a sectional view of the apparatus of FIGURE 1, taken along the line 22 in FIGURE 1;

FIGURE 3 is a top view of the valve plate in the apparatus of FIGURE 1;

FIGURE 4 is a sectional view of a portion of the valve assembly in the apparatus of FIGURE 1, taken along the line 44 in FIGURE 1;

FIGURES 5a and 5b are simplified sectional views of the apparatus of FIGURE 1 to show the steps in the operation;

FIGURE 6 is a detail view in section of the cup and plate assembly in another embodiment of the apparatus of FIGURE 1; and

FIGURE 7 is a detail view of another embodiment of the cup and plate arrangement.

It will be noted that like parts appearing in several views of the drawings will bear like reference numerals. The drawings are considered a part of this specification and are incorporated herein.

With reference now to FIGURE 1, an injection pump along with a fluid motor for driving the pump is illustrated. The pump itself comprises a cylindrical pump housing 10 having an inlet port 11 and outlet port 12. One- way check valves 13 and 14 are connected to the inlet and outlet ports to permit fluid flow only in the direction indicated. The inlet is connected through the check valve to a source of liquid supply which may be under pressure or may be static. The outlet is connected through the check valve 14 to the line or chamber into which the liquid is to be injected at a controlled rate. A rod 15 extends into a central cylindrical bore or chamber 16, and reciprocating movement of the rod 16 produces the pumping function. When the rod 15 moves downward, a reduced pressure exists in the chamber 16 so that fluid will be drawn in the port 11 through the check valve 13. The check valve 14 will prevent return of liquid through the outlet port 12. In this manner, the bore 16 will be filled with liquid from the supply during the downward stroke of the piston 15. Then, when the piston 15 is moved upward, an increased pressure existing in the bore 16 will cause the check valve 13 to close, while the check valve 14 will permit the liquid to flow through the outlet port into the chamber or line where it is utilized. The diameter of the rod 15 is somewhat smaller than the inside diameter of the bore 16 so that liquid may be still drawn in through the inlet port 11 even though the top of the rod 15 is higher than the port 11. Sealing is provided by an O-ring 17. Thus, during the pressure stroke, or upward stroke of the rod 15, liquid will not be forced down along the sides of the rod 15 past the O-ring seal.

For a given diameter of the piston 15, and a given length of stroke, it is thus seen that a fixed amount of liquid will be pumped for each stroke. Injection pumps of this type are used for metering the amount of a chemical in liquid form injected into a pipeline which carries a petroleum product, or for similar operations. In any event, the device is capable of operating at quite high pressures, 6,000 psi. or more in a typical embodiment, and is able to inject controlled amounts of from a few pints or less per day up to many hundreds of gallons per day, depending upon the stroke rate and diameter of the piston 15. The fluid motor which provides the primary feature of the invention as described below, provides a nechanism for producing a controlled reciprocating movenent of the rod 15.

The fluid motor comprises a large cylindrical chamber 20 which has a floating piston 21 positioned therein. The piston 21 is free to move in an up-and-down reciprocating notion within the cylinder 20, and the rod 15 which Functions as the piston of the injection pump is connected this piston and moves therewith. The piston 21 divides :he cylinder 20 into an upper chamber 22 and a lower :hamber 23, and so, of course, movement of the piston will be dependent upon the pressure differential between : hese chambers 22 and 23. In one embodiment, a fixed pressure of a fairly low value of about 4 p.s.i. is maintained in the upper chamber 22 by a gas supply 23 con- Jected through a regulator valve 25 to an inlet port 26. The pressure at the gas supply 24 may be, for example, 25 p.s.i., although this value is not critical. The regulator valve 25 is of conventional design and merely functions to maintain a constant low pressure in the upper chamber 22.

The piston 21 is a circular disc having a peripheral groove 27 into which fits an O-ring 28 functioning to seal the upper and lower chambers 22 and 23 from passage of gas from one to the other. This sealing be- :omes necessary when the cycle time is very lengthy, sometimes approaching an hour, wherein a slight amount of gas leakage would be quite objectionable.

Pressurized gas is admitted to the lower chamber 23 through an inlet port 29 which is connected to the gas supply 24 through a valve 30. The setting of the valve 30 determines the cycle time of the fluid motor by determining the pressure admitted to the lower chamber. Depending upon the setting of the valve 30, pressurized gas Will be continually admitted to the lower chamber; however, in the condition illustrated in FIGURE 1 the lower chamber 23 will be vented to atmosphere through the valving assembly.

The valve arrangement includes an elongated rod or tube 31 having a flat circular plate or head 32 fixed to the top, the rod 31 extending through a valve fitting 33. A vent passage 34 extends from the top of the plate 32 through the rod 31 a substantial length to terminate at a hole 35 located a distance along the rod about equal to the stroke of the piston 21. In the position shown the lower chamber 23 is vented to atmosphere through the passage 34 and the hole 35. The remainder of the valve assembly may include a nut or other fastening means 36 holding the fitting 33 in place, along with a cylindrical shield 37 which merely functions to prevent mechanical damage to the rod 31. A flange 38 is positioned at the lower end of the rod 31 to engage a spring 39 which is in compression between the flange 38 and the lower end of the fitting 33.

A pair of O-ring seals 40 surround the rod 31 within the fitting 33 to prevent escape of pressurized gas along the rod. These sealing O-rings prove an important feature of the invention as will be explained in relation to the operation of the unit.

The control mechanism for the fluid motor includes the valve stem or rod 31 along with the plate 32, which is engaged by a resilient cup 41 fixed to the lower side of the piston 21.

In operation, the fluid motor mechanism may be first observed when in the condition of FIGURE 1, that is, with the valve member 31 in the lower position as shown, the vent passageway 34 being open to prevent any buildup of pressure in the lower chamber 23. Thus the pressurized gas in the upper chamber 22 admitted through the regulator valve 25 will force the piston 21 in a downward direction at a fairly low rate. During this downward stroke, the withdrawal of rod from the chamber 16 will cause the chamber 16 to fill with the fluid being pumped, through the check valve 13. Gas will continue to be admitted through the inlet 29 to the lower chamber 23, but there will be no pressure buildup due to the vent 34 through the rod 31 and the hole 35.

In the next step, the piston 21 will reach its lowermost position as seen in FIGURE 5a, wherein the cup member 41 will come into engagement with the top of the plate 32. This will close the vent passageway 34 and prevent any more of the gas in the lower chamber 23 from escaping. A slight buildup of pressure in the chamber 23 will now cause a pressure differential across the cup member 41 so that it will compress slightly against the plate 32 and will be held firmly in engagement therewith.

Now, as the vent to atmosphere remains closed as it is covered by the cup member 41, pressure will continue to build up in the lower chamber 23, soon exceeding that in the upper chamber 22. At this point, the piston 21 will begin to move in the upward direction. Movement of the rod 15 upward applies pressure to the fluid in chamber 16, closing the the check valve and opening the outlet valve 14. Due to the large difference in diameters of the piston 21 and the rod 15, a relatively small pressure differential in the lower chamber 23 over the upper chamber 22 can cause a very large pumping pressure in the chamber 16.

As the piston 21 continues to move upward, it will pull the valve rod 31 and plate 32 along with it since the cup 41 will continue to engage the plate 32. The spring 39 will be compressed as the rod 31 moves upward, but the large pressure differential across the cup 41 and the plate 32 will prevent the rod 31 from being pulled downward, this pressure differential increasing as the pressure in the lower chamber 23 increases.

As the piston 21 approaches the top of its upward stroke, the rod 31 will be raised to an extent such that the hole 35 will pass upward through the fitting 33 to a position so that the hole 35 is exposed above the top of the bore 34. This is the position illustrated in FIG- URE 5b. At this point, the pressure differential across the cup 41 will be destroyed by pressurized gas entering the hole 35 and passing upward through the bore 34 into the lower side of the cup 41. Then, the cup 41 will no longer hold the plate 32, so the compressed spring 39 will force the rod 31 downward to resume the position shown in FIGURE 1. This will cause the lower chamber to be vented to atmosphere through the passageway 34 since the hole 35 will now be below the valve fitting and so the piston 21 will begin its downward stroke.

Referring now to FIGURE 6, a slightly modified version of the invention is illustrated wherein the cup 41' is composed of metal or other rigid material, and the plate 32 includes a slightly resilient covering 32' which functions to provide the seal to permit the cup 41 to engage the plate and pull the rod 31 upward. The covering 32' may be composed of neoprene or Teflon, for example.

Rather than use a gas at a low pressure in the chamber 23 to force the piston 21 downward on the return stroke, a spring surrounding the rod 15 and extending from the top of the cylinder 20 to the top of the piston 21, may be employed. The spring would be designed to exert a rather light pressure, equivalent to that produced by about 4 p.s.i. gas pressure in the chamber 22.

Depending of course upon the pressure at the supply 24, and the setting of the regulator 25, as well as the liquid pressure against which the pump 10 is acting, the mechanism of FIGURE 1 may be adjusted by varying the setting of the valve 30 to provide a wide variety of pumping rates or volume of liquid output from the injection pump 10. For example, for a pump piston diameter, i.e., diameter of the rod 15, of Ms inch the volume output per day might be varied from about 1 pint to 2 or 3 gallons. By increasing the pump piston size, larger volumes may be provided. For example, with a diameter of the rod 15 of 2 inches, the liquid output volume per day may be varied up to 600 gallons, this also requiring a higher gas supply pressure at the line 24. The variation in pumping rate for a pump of a given size, is controlled by the speed of the upward stroke, the downward stroke remaining about the same. For example, the upward stroke might be varied from a few seconds up to perhaps one or two minutes by means of the valve 30 in a small unit, or almost an hour in a large unit.

In FIGURE 7, an embodiment of the invention is shown wherein the resilient cup 41" is mounted in the head of the vent tube 31, rather than on the piston 21. Here the flat lower surface of the piston functions as the plate.

While the invention has been described with reference to particular embodiments, it is understood that this description is not meant to be construed in a limiting sense. various modifications of the disclosed embodiments, as well as other embodiments of the invention, may be apparent to persons skilled in the art upon reference to this description.

What is claimed is: 1. A pneumatic motor for operating an injection pump comprising:

cylinder means with piston means moveable therein with means mechanically coupling the piston means to the pumping element of the injection pump,

means for biasing the piston means toward one end of the cylinder means,

means for supplying fluid under pressure to said one end of the cylinder means,

valving means at said one end of the cylinder means operative to vent the cylinder means during part of the cycle of the piston means and to seal the cylinder means during the other part, the valving means including an elongated vent tube having a head to releasably engage one side of the piston means, the vent tube being axially moveable and extending through said one end of the cylinder means, the cylinder means being sealed when the head of the vent tube engages the side of the piston means and being vented when the head of the vent tube is released from the side of the piston means.

2. Apparatus according to claim 1 wherein the vent tube is a plate-like member, and a cup-like member is positioned on said one side of the piston means for engagement with the plate-like member.

3. Apparatus according to claim 2 wherein a vent passage extends along a substantial length of the vent tube, the vent passage communicating with the space between the cup-like member and the plate-like member and extending to a vent position spaced substantially along the tube.

4. Apparatus according to claim 3 wherein at least one of the cup-like member and the plate-like member includes at least a resilient surface.

5. Apparatus according to claim 4 wherein the cuplike and plate-like members are held in engagement during part of the cycle of the piston means by fluid pressure differential.

6. Apparatus according to claim 5 wherein the cuplike and plate-like members are held in engagement when the vent position of the vent tube is external of the cylinder means and are released when the vent position is drawn interior of the cylinder means.

7. .Apparatus according to claim 6 wherein the vent tube is biased toward an outward position.

8. Apparatus according to claim 7 wherein the means for biasing the piston means toward one end of the cylinder means includes a supply of gas under pressure, while gas at a higher pressure is supplied to said one end of the cylinder means.

9. Apparatus according to claim 8 wherein the injection pump includes a chamber with a plunger moveable therein, along with an inlet port connected to a liquid supply through a check valve and an outlet port connected to a utilization chamber through another check valve, and wherein the plunger is a rod integrally connected to the piston means of the pneumatic motor.

10. Valve means for a fluid-operated piston within a chamber, comprising:

an elongated vent rod extending into one end of the chamber, the rod having an internal vent passage extending from adjacent its internal end to a vent aperture spaced substantially therefrom,

releasable engagement means associated with the internal end of the vent rod and with the side of the piston adjacent said one end of the chamber, the engagement means including mating surfaces, the vent passage of the vent tube communicating with the space between the mating surfaces, the engagement means being held while in engagement by fluid pressure differential when the vent aperture of the rod is external of the chamber and being released when the vent aperture is drawn interior of the chamber.

11. Apparatus according to claim 10 wherein the vent tube is biased toward a position external of the chamber.

12. Apparatus according to claim 11 wherein the vent tube is biased by a spring generally coaxially with the tube.

13. Apparatus according to claim 10 wherein at least one of the mating surfaces is provided by a resilient member.

14. Apparatus according to claim 10 wherein the pair of mating surfaces is provided by a cup-like member and a plate-like member.

15. Apparatus according to claim 14 wherein the cuplike member is mounted at said one side of the piston, and the plate-like member provides the head of the vent tube.

16. Apparatus according to claim 10 wherein the vent tube extends through the end of the chamber through sealing means.

17. Valve means for gas-operated piston means within a chamber, comprising:

an elongated vent rod extending into one end of the chamber, the rod having a vent passage extending from adjacent its internal end to a vent aperture spaced substantially therefrom.

releasable engagement means associated with the internal end of the vent rod and with the side of the piston means adjacent said one end of the chamber, the engagement means including mating surfaces, the vent passage of the vent tube communicating with the space between the mating surfaces, the engagement means being held while in engagement by gas pressure differential when the vent aperture of the rod is external of the chamber and being released when the vent aperture is drawn interior of the chamber.

References Cited UNITED STATES PATENTS 2,239,298 4/1941 Kraut 91-50 2,319,608 5/1943 Kraut 91-50 2,652,973 9/1953 Dibble et al 103-6 X 2,813,516 11/1957 Dulaney 9l-50 2,940,720 6/1960 Birr 248-363 2,987,047 6/1961 Young 9150 3,167,326 6/1965 Hessels 248363 3,385,218 5/1968 West 10326 FOREIGN PATENTS 323,303 1/ 1930 Great Britain.

WILLIAM L. FREEH, Primary Examiner US. Cl. X.R. 9150 22 g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,5 ,753 Dated March 17, 1970 Inveutofls) George J. Greene, Jr.

It; is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column l,1ine 599, delete -"on".

Column 1, line 60, before one insert on Column 2, line #0, change "16" (second occurrence) to l5 swam-:0 AND swan

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