US3102485A - Variable output pumping apparatus - Google Patents

Description

Sept. 3, 1963 N. D. GRISWOLD VARIABLE OUTPUT PUMPING APPARATUS Filed June 26, 1962 INVENTOR 0. Gris wold Ive/son 221 4). Q 0W HGENT United States Patent 3,102,485 VARIABLE OUTPUT PUMPING APPARATUS Nelson 1). Griswold, Lake Jackson, Tex., assignor to The Dow Chemical Company, Midland, MiClL, a corporation of Delaware Filed June 26, 1962, Ser. No. 205,360

13 Claims. (Cl. 103-38) This invention relates to pumps and particularly to reciprocating piston pumps which are capable of deliverin-g varying volumes of fluid While the piston or pistons of the pump reciprocate at a substantially constant rate.

Other so-called variable volume pumps have been known for many years for specific uses, but for one reason or another these pumps are not well adapted for use in mobile service, such as oil and gas Well treating service, for example. Such service requires maximum utilization of available horsepower to thereby deliver the maximum volume of pumped fluid against whatever pressure may develop without exceeding the strength limits of the equipment. Such requirements necessitates minimum weight and bulk consistent with the achieving of other requirements, and ease and reliability in controlling the variable volume feature of the pump while under load. Exceptional reliability is necessary because the pump will be used, at least occasionally, in remote areas where facilities are not available for making major repairs and because in well treating service equipment breakdown can result in great damage to the well under treatment. For example, a pump breakdown during a well cementing job could result in the cement setting up in the well casing before displacement could be effected between the casing and well bore wall.

In conventional well treating pumping units, a power source or prime mover, usually an interal combustion engine, transmission (which may include a torque converter) and the pump are disposed on a truck.

Any reduction in weight which can be achieved in the coupling :of power to the pump of the treating unit would, obviously, permit the construction of a lighter treating unit or would permit the construction of a treating unit having an increased pumping capacity (either involume or pressure, or both) without exceeding gross weight requirements.

Accordingly, a principal object of this invention is to provide an improved variable volume pumping apparatus which is suitable for use in treating earth wells or the like.

Another object of this invention is to provide an improved variable volume pumping apparatus which is compact in size with respect to its pumping capacity and power utilization over a wide range of pumping pressures.

A further object of this invention is to provide an improved mobile fluid pumping system for well treating service or the like.

In accordance with this invention a piston type positive displacement pump achieves an infinitely variable stroke between maximum and minimum limits through a controlled variable phase relationship between two mechanically interlocked crankshafts. These crankshafts operate through connecting rods to an equal-legged walking beam pinned at its centerline 'to a plunger crosshead. Similar planetary gear assemblies with the sun gears of the assemblies, interconnected by means of a worm and worm wheel, are used to drive the'crankshafts and also to establish and maintain the desired phase relationship between the crankshafts during operation. By rotating the worm and thus changing the phase of the planetary gears coupled to each crankshaft, the phase relationship between crankshafts and hence the piston stroke may be changed inversely with the discharge pressure to provide a hydraulic horseice power output desirably matched to the available horsepower of the prime mover.

The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawing, in which FIG. 1 is a simplified plan view, partly broken away and in section, of apparatus in accordance with this invention;

FIG. 2 is a sectional view of one of the planetary gear assemblies of FIG. 1;

FIG. 3 is "a sectional View taken along the line 3-3 of FIG. 1; and

FIG. 4- is a fragmentary end view of drive gears 78a, a showing chain drive coupling between the drive shafts 36, 38.

Referring to the drawing, there is shown variable volume pumping apparatus mounted on a common frame (not shown). The apparatus includes a single action reciprocating piston-type pump 12 (see FIG. 3 especially) whose piston 14 is coupled to a crosshead plunger 15, adapted to reciprocate in the guide 1511, and to the center of an equal-legged walking beam .16 which in turn is coupled at its ends by connecting rods 18, 20 to crankshafts 22, 24, respectively, which are journaled in bearings 17, 19, 21 and 17a, 19a, 21a, for example.

Each of the crankshafts 22, 24 has an end rigidly coupled to a spur gear 23, 25 which is rigidly mechanically coupled to another spur gear 29, 31, respectively, on a hollow shaft 58, 61), respectively, to which are coupled the planet gears (46, 48 in FIG. 2) of each of the planetary gear assemblies 30, 32, respectively. The planetary gear assembly 30, shown in section in FIG. 2, is the same as the assembly 32 which is shown in plan in FIG. 1.

The planet gears of each planetary gear assembly 30, 32 are journaled on to shafts 50, 52 (and 54, 56 in FIG. 1) which are fixedly connected by means of brackets 59, 61, respectively, to the previously mentioned hollow shafts 58 or 60. Each of the hollow shafts 58, 60 is supported in position by two bearings 62 and 64 and 62a and 64a, respectively.

Spur gear wheels 78, 80 are rigidly coupled in a fixed rotational relationship onto shafts 36, 38, respectively. Each of the shafts is journaled in bearings 40, 42 and 40a, 42a, respectively, and has one end mechanically coupled to one of the ring gears 26, 28. The gears 78, 80 are of equal diameter, have an equal number of teeth, the teeth of one wheel engaging those of the other. Means, such as the spur gear 82 is coupled to the end of the shaft 36 whereby power from a prime mover 86 may be coupled to the shaft 36 through a spur gear 84 and thence through the spur wheels 78, 80 to the shaft 38. The power source 86, which may be an internal combustion engine or a gas turbine, for example, is diagrammatically indicated by the block 86 and is coupled, as indicated by a shaft, to the gear 84.

The sun gear (34 in FIG. 2) of each of the planetary gear assemblies 30, 32 is rigidly and coaxially coupled to a shaft 65, 67, respectively, which extends through and is coaxial with the hollow shafts 58, 60, previously mentioned. The shafts 65, 67 are journaled in bearings 43, 44 and 43a, 44a, respectively.

A worm Wheel 66, 68 is disposed coaxially on and rigidly secured to each of the shafts 65, 67, respectively, near the end of the shaft which is remote from the sun gear (34 in FIG. 2).

A rotatable shaft 70, Which has worm sections 72, 74 disposed along its length, is disposed transversely to the shafts 65, 67, the worm sections 72, 74 engaging the worm wheels 66, 68, respectively. The shaft 70 is journaled in bearings such as the bearing 98, for example.

The worm sections 72, 74 have the same pitch and their flights turn in the same direction of rotation. The worm wheels 66, 68 are of the same diameter.

A hand wheel 76, attached to one end of the shaft 70, is provided for turning the shaft 70 to cause rotation of the worm sections and the worm wheels which are coupled to the sun gears through the shafts 65, 67

Each of the bearings 17, 17a, 19, 19a, 21, 21a, 40, 40a, 62, 62a, 64, 90 the pump 12, guide 15a and shaft 70 are mounted on common framework for the apparatus, which framework also carries the power source '86, the framework being attached to or supported by the mobile unit, e.g., a truck, which carries the apparatus.

In operation the apparatus, as shown, has the hand wheel 76 arbitrarily positioned so that the angle A is equal to the angle A, for example, in FIG. 3. In this position, the throws of the crankshafts 22, 24 are connected in an in-phase rotational relationship, and move the piston 14 of the pump 12 backwards and forward in the pump cylinder 88 at maximum stroke length as power from the gear 84 is coupled to the shaft 36 and, by means of the spur gears 78, 80, to the shaft 38.

The shafts 36, 38 drive the ring gear (26 in FIG. 2) of each planetary gear assembly 30, 32, respectively. The ring gear of each assembly is coupled to the sun gear (34 in FIG. 2) of its assembly 30, 32 through the planet gears (46, 48 in FIG. 2) of the respective assembly 30 or 32. The planet gears of the assembly are free to rotate on their short shafts 50, 52 and 54, 56 as the ring gear(s) rotate, but the rotation of these pairs of planet gears causes the shafts 58, 60 to rotate, thus rotating crankshafts 22, 24. The sun gears are held in a predetermined position with respect to each other by the worm segments 72, 74 on the shaft 70 which do not rotate unless the Wheel 76 is turned. The worm wheels 66, 68, as mentioned previously, each engage with one of the worm segments 72, 74 and are each coupled in a fixed relationship with one of the shafts 65, 67. Because the shafts 65, 67 are mounted in fixed position except when the wheel 76 is rotated, thus holding the sun gears in a predetermined position, the rotating of the planet gears (46, 48 in FIG. 2) by the power driven ring gears (26 in FIG. 2) results in the rotation of the shafts 58, 60 which are mechanically coupled by gears 29, 31 to gears 23, 25, respectively, to the crankshafts 22, 24.

When the stroke length of the piston 14 is to be changed, the shaft 70 is turned (as by turning the wheel 76, for example), the amount of turning depending upon the degree of phase change desired between the crankshafts 22, 24. As the shaft 70 rotates the worm segments 72, 74 rotate and cause the worm Wheels 66, 68 to turn. Such turning is usually at a slow rate as compared with the rate of rotation of the crankshafts 22, 24. The shafts 65, 67 on which the sun gears (34 in FIG. 2) are rotatably mounted, are rotated as the worm wheels 66 and 68 rotate supplementing the motion of the sun gears to that of the ring gears to produce the rotation of the planet gears. The worm segments 72, 74 each have the same pitch and their flights turn in the same direction so, with the crankshafts 22, 24 rotating in opposite directions (one clockwise, one counterclockwise), the relative phasing between the erankshafts 22, 24 is changed as the shafts 65, 67 are rotated. By in phase is meant that the crank throws viewed from the ends of the crankshafts occupy mirror image positions as in FIG. 3 'where angles A and A are the same; when angles A and A differ the crankshafts are out of phase. The angular difference between the angles A and A can be varied by suitably turning wheel 76 and therefore shaft 70, thereby providing for a variation in the piston stroke length from a maximum to a minimum. The length of the piston stroke is at a maximum when the crankshafts 22, 24 are in phase as shown. Piston stroke length decreases as the crankshafts become out of phase 'with respect to each other, that is, when angles A and A (FIG. 3) differ from each other. When the length of the piston stroke is at a minimum one of the connecting rods 18, 20 will be at its most forward position with respect to the piston 14 and the other connecting rod will be at its most rearward position with respect to the piston. Since both connecting rods 18, 20 are connected to the walking beam 16 which is coupled at its center to the crosshead 15, the movement of the piston 14 is a resultant of the movement of the two connecting rods 18, 20 and is practically zero as the walking beam pivots around its point of attachment to the crosshead.

When the phase relationship of the crankshafts is at an intermediate point between the in-phase relationship and the maximum out-of-phase relationship there will be some rocking of the Walking beam about its point of attachment to the crosshead, and also some forward and backward motion of the piston 14.

It should be noted that in the apparatus thus far described, the rotation of the drive shafts 36, 38 has been in opposite radial direction because of the coupling together of the spur gears 78, 80. Thus, even though the rotatable shafts 65, 67 which drive the sun gears are rotated in the same direction, the phase relationship of the crankshaft throws is changed.

The same phase relationship of thecrankshaft throws may be achieved if the drive shafts 36, 38 are coupled, as by the spur gears 78a, 80a and chain drive 92 shown in FIG. 4, for example, to rotate in the same radial direction and the worm wheels 66, 68 and worms 72, 74 are adapted to, on turning the shaft 70, rotate the sun gear drive shafts 65, 67 in opposite radial direction to one another.

The apparatus described above provides means whereby constant horsepower may be applied to the pump 12 even though the pressure head against which the pump works may vary over a wide range. When the pressure head is low enough to permit such operation, keeping the twocrankshafts operating on an in-phase relationship results in maximum volume being displaced through the pump 12. As the pressure head increases the wheel 76 is rotated to cause the crankshafts to be moved in an increasingly out-of-phase relationship with respect to each other so that the available driving horsepower may be used to drive the piston 14 in increasingly shorter strokes and thus deliver less volume at a higher pressure.

Also, since the pump output can be continuously varied between practically no output and maximum output, there is no need for a torque converter or an additional speed varying transmission to be interposed between the power source and the pump apparatus providing the coupling between the power source 86 and the gear 82 does not cause the shafts 36, 38 to be rotated at excessive speeds.

While the apparatus has been illustrated as driving a single barrel single action reciprocating piston pump, a triplex pump, either single or double acting, or other multiple cylinder pump may be coupled to suitable crankshafts which are substituted for the crankshafts 22, 24 and which are driven by the planet gear driven shafts 58, 60.

The apparatus of the invention permits the power source to operate at a substantially constant rpm. rate even through the pumping rate varies widely. Thus, this apparatus is well adapted to be driven by turbines or by an internal combustion piston-type engine operating at an optimum rpm. rate.

Because the pump is driven by two crankshafts, the bearing loading on the individual connecting rods is reduced. A single pump may deliver either a large volume at moderate pressure or smaller volume at high pressures. In fixed stroke reciprocating piston-type pumps a socalled high volume pump has a relatively low maxmium pumping pressure in order to prevent overloading of the connecting rod bearings or to prevent the stalling of the prime mover. Conversely, a so-called high pressure fixed stroke piston pump is limited in the volume it can pump at lower pressures because of the maximum safe rpm. rate of the crankshaft even though the connecting rod bearings may not be overloaded and the horsepower capabilities of the prime mover are not exceeded.

Pumping apparatus in accordance with this invention is more versatile than conventional apparatus is that it is good both as a high pressure-low volume pump and as a low pressure-high volume pump and it admits of continuous variation of the relationship between pressure or volume driving operation. Also, because no intermediate torque converter or speed varying transmission is used, the apparatus is more compact and lighter than a conventional unit of similar work capabilities.

What is claimed is:

l. A mobile pumping unit comprising in combination a prime mover and a variable displacement pump, said pump comprising a cylinder and piston reciprocal therein, a crosshead, means for mechanically coupling the piston to the crosshead to reciprocate the piston with reciprocation of the crosshead, a walking beam having a central part and two end parts, said walking beam being pivotally coupled at its central part to the crosshead, a pair of crankshafts, each of said cranlcshafts having at least one throw, a pair of connecting rods, one of said connecting rods being pivotally coupled to one end part of said walking beam and to a throw on one of said pair of crankshafts, the other connecting rod being pivotally coupled to the other end of the walking beam and to a throw on other crankshaft, a pair of planetary gear assemblies each comprising a sun gear, at least one planet gear and a ring gear, means for coupling one of said crankshafts to said planet gear of one of said planetary gear assemblies, means for coupling the other of said pair of crank-shafts to said planet gear of the other of the planetary gear assemblies, a pair of drive shafts, means for coupling said prime mover to said drive shafts and for.

rotating each of said drive shafts, means for operative ly coupling one of said drive shafts to one of said ring gears, means for operatively coupling the other of said drive shafts to the other of said ring gears, ,a pair of phase control shafts, one of said phase control shafts being mechanically coupled to the sun gear of one of said planetary gear assemblies, the other of said phase control shafts being mechanically coupled to the sun gear of the other planetary gear assembly, a pair of worm wheels, one of 'said Worm wheels being operatively coupled to one of the phase control shafts and the other being operatively coupled to the other of the phase control shafts, and at least one drive worm coupled to said worm wheels for varying the radial position of the sun gear in one planetary assembly with respect to its planet gear and for varying the radial position of the sun gear in the other planetary assembly with respect to its planet gear whereby the throw of one crankshaft has its radial position changed with respect to the radial position of the corresponding throw of the other crankshaft.

2. A pumping unit in accordance with claim 1, wherein said crankshafts are disposed parallel to one another.

3. A pumping unit in accordance with claim 1, wherein said drive shafts are disposed parallel with one another.

4. A pumping unit in accordance with claim 1, wherein the means for coupling the prime mover to the drive shafts includes means for rotating the drive shafts in opposite radial direction to one another and at the same rate of rotation.

5. A pumping unit in accordance with claim 1, wherein said drive Worm is disposed along a rod-like shaft.

6. A pumping unit in accordance with claim 5, wherein said means to rotate the worm wheels comprises a control wheel which is coupled to said rod-like shaft.

'7. A pumping unit in accordance with claim 1, wherein said prime mover is coupled to said drive shaft through fixed-ratio gear means.

8. A pumping unit in accordance with claim 1, wherein said prime mover is a gas turbine.

9. A pumping unit in accordance with claim 1, wherein said prime mover is a reciprocating piston-type internal combustion engine.

, 10. A pumping unit in accordance with claim 1, wherein said at least a part of said means for coupling said crankshafts to said planet gears is a pair of hollow shafts, one of which surrounds each of said phase control shafts.

11. A pumping unit in accordance with claim 1, wherein the sun gear, planet gear and ring gear in one planetary gear assembly are the same as the corresponding part in the other planetary gear assembly.

12. A pumping unit in accordance with claim 1, wherein the longitudinal axis of the crank throw of each crankshaft is ofiset from the longitudinal axis of its crankshaft by an equal amount.

13. A pumping unit in accordance with claim 1, wherein the point of coupling of the crosshead to the walking beam is along a line perpendicular to and bisecting a line drawn between the points of coupling of the connecting rods to the walking beam.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A MOBILE PUMPING UNIT COMPRISING IN COMBINATION A PRIME MOVER AND A VARIABLE DISPLACEMENT PUMP, SAID PUMP COMPRISING A CYLINDER AND PISTON RECIPROCAL THEREIN, A CROSSHEAD, MEANS FOR MECHANICALLY COUPLING THE PISTON TO THE CROSSHEAD TO RECIPROCATE THE PISTON WITH RECIPROCATION OF THE CROSSHEAD, A WALKING BEAM HAVING A CENTRAL PART AND TWO END PARTS, SAID WALKING BEAM BEING PIVOTALLY COUPLED AT ITS CENTRAL PART TO THE CROSSHEAD, A PAIR OF CRANKSHAFTS, EACH OF SAID CRANKSHAFTS HAVING AT LEAST ONE THROW, A PAIR OF CONNECTING RODS, ONE OF SAID CONNECTING RODS BEING PIVOTALLY COUPLED TO ONE END PART OF SAID WALKING BEAM AND TO A THROW ON ONE OF SAID PAIR OF CRANKSHAFTS, THE OTHER CONNECTING ROD BEING PIVOTALLY COUPLED TO THE OTHER END OF THE WALKING BEAM AND TO A THROW ON OTHER CRANKSHAFT, A PAIR OF PLANETARY GEAR ASSEMBLIES EACH COMPRISING A SUN GEAR, AT LEAST ONE PLANET GEAR AND A RING GEAR, MEANS FOR COUPLING ONE OF SAID CRANKSHAFTS TO SAID PLANET GEAR OF ONE OF SAID PLANETARY GEAR ASSEMBLIES, MEANS FOR COUPLING THE OTHER OF SAID PAIR OF CRANKSHAFTS TO SAID PLANET GEAR OF THE OTHER OF THE PLANETARY GEAR ASSEMBLIES, A PAIR OF DRIVE SHAFTS, MEANS FOR COUPLING SAID PRIME MOVER TO SAID DRIVE SHAFTS AND FOR ROTATING EACH OF SAID DRIVE SHAFTS, MEANS FOR OPERATIVELY

Images