US3103173A

US3103173A - Variable volume pumping apparatus

Info

Publication number: US3103173A
Application number: US205370A
Authority: US
Inventors: Nelson D Griswold
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1962-06-26
Filing date: 1962-06-26
Publication date: 1963-09-10
Anticipated expiration: 1980-09-10

Description

P 10, 1963 N. D. GRISWOLD 3,103,173

VARIABLE VOLUME PUMPING APPARATUS Filed June 26, 1962 INVENTOR. Nelson 0 Griswold gglwa w Unite This invention relates to pumps and particularly to reciprocating piston pumps which are capable of delivering varying volumes of fiuid 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 there-by deliver the maximum volume of pumped fluid against whatever pressure may develop without exceeding the strength limits of the equipment.

Such requirements necessitate 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 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 resuit in the cement setting up in the Well casing before displacement can be effected between the casing and well bore wall.

In conventional well treating pumping units, a power source or prime mover, usually an internal 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 permit the construction of a lighter treating unit or would permit the construction of a treating unit having an increased pumping capacity (either in volume or pressure, or both) without exceeding the normal weight limits.

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.

Another object of this invention is to provide an improved 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 im proved 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 .opcrate through connecting rods to an equal-legged walking beam pinned at its centerline to a plunger crosshead. Similar planetary gears, with the planet carriers 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 inverselywith the discharge pressure to provide a hydraulic horsepower output desirice ably 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 taken along the line 2-2 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, 80a showing chain drive coupling between the

drive shafts

36, 38.

Referring to the drawing, there is shown variable volume pumping apparatus, indicated generally by the nu meral 10, 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 15a, and to the center of an equallegge-d 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

19, 21, 27 and 19a, 21a, 27a, for example.

Each of the

crankshafts

22, 24 has an end (25 in FIG. 2) which is rigidly mechanically coupled to the sun gear (see 34 in FIG. 2) of a

planetary gear assembly

30, 32, respectively. The planetary gear assembly 32, shown in section in FIG. 2, is the same as the assembly 36 which is shown in plan in FIG. 1.

The

ring gear

26, 28 of each of the planetary gear assemblies 3!}, 32 is rigidly mechanically coupled to a shaft '36, 38. The shafts '36, 38 are disposed parallel to each other and are supported by

suitable bearings

40, 44 and 40a, 44a. The sun gears of each of the

assemblies

30, 32 are coupled to their

respective ring gears

26, 28 by pairs of planetary gears, the

planetary gears

46, 48 being shown in FIG. 2.

The planetary gears of each planetary gear assembly 39, 32 are journaled on two shafts 5t '52 (and 54, 56 in FIG. 1) which are parallel to the ring

gear driving shafts

36, 38 and which are fixedly connected by means of

brackets

59, 61, respectively, to a

hollow shaft

58 or 60, each of which is parallel to and surrounds one of the

respective shafts

24, 22 as shown. Each of the

hollow shafts

58, 60 is supported in position by two

bearings

62 p and 64 and 62a and 64a respectively. A worm wheel 66,

68 is disposed on and rigidly coupled to each of the hollow shafts 58, 617, respectively, the wheels 66, 63 being equal in size and in the number of teeth they contain.

A rotatable shaft 70, having worms 72, '74 in spaced apart relationship along its length, is disposed transversely with respect to the shafts 58, 66. The

worms

72, 74 engage the teeth of the worm wheels 66, 68, respectively, the pitch of the worms in each being equal and in the same direction of rotation so that each of the worm wheels 66 and 68 can be turned the same amount in the same direction at the same time. A turning or control wheel 76 is rigidly mechanically coupled to one end of the shaft 79 whereby the shaft 70 is rotated when the wheel 76 is rotated.

Spur gear wheels 78, St? are rigidly coupled in a fixed rotational relationship to the

shafts

36, 38, respectively,

the teeth of one wheel engaging those of the other.

Means, such as the

gears

82, 84 are coupled to the end of the shaft 36 whereby power from a prime mover may be coupled to the shaft 36 and thence through the spur wheels 78, 80 t 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 the shaft 87, to the gear 84.

Each of the

bearings

19, 19a, 21, 21a, 27, 27a, 40, 40a, 62, 62a, 64, 64a, 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 by means of the gear 82-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, 28 of each

planetary gear assembly

30, 32, respectively. The ring gear of each assembly is coupled to the sun gear of its

assembly

30, 32 through the planetary gears (46, 48 in FIG. 2) of the

respective assembly

30 or 32. The planetary gears of the assembly are free to rotate on their

shafts

50, 52 and 54, 56, but these pairs of shafts are held in a predetermined position with respect to each other by the

worm gear segments

72, 74 on the shaft 70 which do not rotate unless the wheel 76 is turned. The spur wheels 66, 68, as mentioned previously, each engage with one of the

segments

72, 74 and 'are each coupled in a fixed relationship with one of the

shafts

58, 60. Because the

shafts

50,52 and 54, 56 are mounted in fixed position except when the wheel 76 is rotated, the rotating of the planetary gears (46, 48 in FIG. 2) by the power driven ring gears (26, 28) results in the rotation of the sun gears (34 in FIG. 2) which are rigidly and fixedly coupled to the

crankshafts

24, 22. a

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. As the shaft 70 rotates the

worms

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

50, 52 and 54, 56 on which the planetary gears (46, 48 in FIG. 2) are rotatably mounted, are rotated as the

spur Wheels

78 and 80 rotate (and as the

hollow shafts

58, 60 rotate if these be then rotating). The

worm gear 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 crankshafts'22, 24 is changed as the

shafts

58, 60 are rotated. By in phase is meant that the crank throws viewed on the ends of the crankshazfts 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 pistonstroke length from a maximum 'intoa 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) diifer from each other. When the length of the piston stroke is at a minimum one of the connecting rod-s 18, 20 will be at its most forward position with respect to the piston 14 and the other conmeeting 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, 2t) and is practically zero as to the walking beam pivot-s 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

58, 60 are rotated in the same direction, the phase relationship of the crankshaft throws is changed.

The same phase relationship of the crankshaft 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

hollow shafts

58, 60 in opposite radial direction to one another.

'The apparatus described above provides means where by 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 two crankshafts 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 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

crankshafts

22, 24 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, for example, may be coupled to suitable crankshafts which are substituted for the

crankshafts

22, 24 and which are driven by the sun gears of the

planetary gear assembly

30, 32.

The apparatus of the invention permits the power source to. operate at a substantially constant r.p.m. rate eventhough the pumping rate varies widely. Thus, this apparatus is well adapted to be driven by turbines or by an internalcombustion piston-type engine operating at an optimum rpm. rate. 1 2

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 pressures or smaller volume at high pres sures. In fixed stroke reciprocating piston type pumps a so-called high volume pump has a relatively low maxi-- necting rod bearings may not be overloaded and the home power capabilities of the prime mover are not exceeded. Pumping apparatus in accordance with this invention is more versatile than conventional apparatus in 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 during 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:

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 said other crankshaft, a pair of planetary gear assemblies each comprising a sun gear, at least one planetary gear and a ring gear, one of said crankshafts being :operatively coupled to the sun gear of one of said planetary gear assemblies, the other of said pair of crankshaits being operatively coupled to the sun gear of the other of the planetary assemblies, a pair of drive shafts, means for coupling said prime mover to said drive shafts and for rotating each of said drive shafts at the same rate, one of said drive shafts being operatively coupled to one of said ring gears, the other of said drive shafts being operatively coupled to the other of said ring gears, a pair of rotatable members, one of said rotatable members being disposed around and coaxially aligned with one of said crankshafts, the other of said rotatable members being disposed around and coaxially aligned with the other of said crankshafts, said rotatable members each having at least one short shaft supported thereon in axial alignment with the crankshaft the rotatable member is disposed around, one of said planetary gears being rotatably mounted on each said short shaft, a pair of worm wheels, one of said worm wheels being operatively coupled to .one of the rotatable members and the other being operatively coupled to the other of the rotatable members, and at least one drive worm coupled to said worm wheels for varying the radial position of the planetary gear in tone planetary assembly with respect to its sun gear and for varying the radial position of the planetary gear in the other planetary assembly with respect to its sun 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 crank'shafts 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.

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 reciprocating piston-type internal combustion engine.

10. A pumping unit in accordance with claim 1, wherein said rotatable members comprise hollow shafts each of which surrounds one of said crankshafits.

11. A pumping unit in accordance with claim 1, wherein the sun gear, planetary 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 offset 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.

No references cited.

Claims

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 SAID OTHER CRANKSHAFT, A PAIR OF PLANETARY GEAR ASSEMBLIES EACH COMPRISING A SUN GEAR, AT LEAST ONE PLANETARY GEAR AND A RING GEAR, ONE OF SAID CRANKSHAFTS BEING OPERATIVELY COUPLED TO THE SUN GEAR OF ONE OF SAID PLANETARY GEAR ASSEMBLIES, THE OTHER OF SAID PAIR OF CRANKSHAFTS BEING OPERATIVELY COUPLED TO THE SUN GEAR OF THE OTHER OF THE PLANETARY ASSEMBLIES, A PAIR OF DRIVE SHAFTS, MEANS FOR COUPLING SAID PRIME MOVER TO SAID DRIVE SHAFTS AND FOR ROTATING EACH OF SAID DRIVE SHAFTS AT THE SAME RATE, ONE OF SAID DRIVE SHAFTS BEING OPERATIVELY COUPLED TO ONE OF SAID RING GEARS, THE OTHER OF SAID DRIVE SHAFTS BEING OPERATIVELY COUPLED TO THE OTHER OF SAID RING GEARS, A PAIR OF ROTATABLE MEMBERS, ONE OF SAID ROTATABLE MEMBERS BEING DISPOSED AROUND AND COAXIALLY ALIGNED WITH ONE OF SAID CRANKSHAFTS, THE OTHER OF SAID ROTATABLE MEMBERS BEING DISPOSED AROUND AND COAXIALLY ALIGNED WITH THE OTHER OF SAID CRANKSHAFTS, SAID ROTATABLE MEMBERS EACH HAVING AT LEAST ONE SHORT SHAFT SUPPORTED THEREON IN AXIAL ALIGNMENT WITH THE CRANKSHAFT THE ROTATABLE MEMBER IS DISPOSED AROUND, ONE OF SAID PLANETARY GEARS BEING ROTATABLY MOUNTED ON EACH SAID SHORT SHAFT, A PAIR OF WORM WHEELS, ONE OF SAID WORM WHEELS BEING OPERATIVELY COUPLED TO ONE OF THE ROTATABLE MEMBERS AND THE OTHER BEING OPERATIVELY COUPLED TO THE OTHER OF THE ROTATABLE MEMBERS, AND AT LEAST ONE DRIVE WORM COUPLED TO SAID WORM WHEELS FOR VARYING THE RADIAL POSITION OF THE PLANETARY GEAR IN ONE PLANETARY ASSEMBLY WITH RESPECT TO ITS SUN GEAR AND FOR VARYING THE RADIAL POSITION OF THE PLANETARY GEAR IN THE OTHER PLANETARY ASSEMBLY WITH RESPECT TO ITS SUN 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.