US3103890A

US3103890A - Variable output pumping means

Info

Publication number: US3103890A
Application number: US205363A
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: 1963-09-17
Anticipated expiration: 1980-09-17

Description

p 17, 1963 I N. D. GRISWOLD 3,103,890

VARIABLE OUTPUT PUMPING MEANS Filed June 26. 1962 EI El 64 50 l 50 62 58 2 INVENTOR. A/e/son 0. Gnswo/o United States Patent Ofitice 3,103,890 Patented Sept. 17, 1963 3,103,890 VARIABLE OUTPUT PUMPING MEANS Nelson D. Griswold, Lake Jackson, Tex., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed June 26, 1962, Ser. No. 205,363 14 Claims. (Cl. 103-38) This invention rel-ates to pumps and particularly to reciprocating piston pumps which are capable of delivering 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 or other earth 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 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 hevcause 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 can be effected between the casing and wellbore wall.

In conventional we-ll 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, trailer, or barge.

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 in volume or pressure, or both) within allowable gross weight limitations.

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

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 crankshafits operate through connecting rods to an equal-legged walking beam pinned at its centerline to a plunger crosshead. Similar planetary gears, with the ring gears interconnected by means of a phase control gear, are used to drive the crankshafts and also to establish and maintain the desired phase relationship between the crankshafts during operation. By actuating the phase control gear and thus changing the phase of the ring gears which are coupled to each crankshaft through the planet gears, the

phase relationship between crankshafits and hence the piston stroke may be changed inversely with the discharge pressure to provide a hydraulic horsepower output desirably matched to the available horsepower of the prime mover.

The invention, as well as additional objects and a vantages 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 33 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 variaible volume pumping apparatus, indicated generally by the numeral 10 mounted on a common frame (not shown). The apparatus includes a single action reciprocating pistontype 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 equallegged 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, 17a, 19, 21 and 19a, 21a, for example.

Each of the

crankshafts

22, 24 has a

spur gear

23 or 25 coupled coaxially thereto near the end of the crankshaft which is adjacent to a

planetary gear assembly

30, 32, respectively. The planetary gear assembly 30, shown in section in FIG. 3, is the same as the assembly 32 which is shown in plan in FIG. 1.

The sun gear (see FIG. 3, sun gear 34) of each of the

planetary gear assemblies

30, 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, 42, 44, 45 and 40a, 42a, 44a, respectively. The sun gears of each of the

assemblies

30, 32 are coupled to their

respective ring gears

26, 28 by pairs of planet gears, the planet gears 46, 48 being shown in FIG 3.

The planet gears of each

planetary gear assembly

30, 32 are j ournaled on to shafts 50, 52 (and 54, 56 in FIG. 1) which are parallel to the sun

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

36, 38 as shown. Each of the hollow shafts 58, 60 is supported in position by two

bearings

62 and 64 and 62a and 6401, respectively. A

spur wheel

66, 68 is disposed on and rigidly coupled to each of the hollow shafts 58, 60, the

wheels

66, 68 being equal in size and in the number of teeth they contain, their gear teeth being coupled to the teeth of the

spur wheels

23, 25, respectively.

Sprocket wheels

78, 80 are rigidly coupled in a fixed rotational relationship to the

shafts

36, 38, respectively, near the end of the

shaft

36 or 38 which is remote from the

planetary gear assemblies

30, 32. The

sprocket wheels

78, 80 are of equal diameter and have an equal number of teeth, and are coupled together by drive chain 79. Means, such as the spur gear 82, coupled to the end of the shaft 36"and the gear 84 coupled to a prime mover 86, couple power to the shaft 36 and thence through the

sprocket 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 the shaft 87, to the gear 84.

A rotatable shaft 70, having

worms

72, 74 in spaced apart relationship along its length, is disposed transversely with respect to the

shafts

36, 38 and 58, 60. The

worms

72, 74 engage

teeth

76, 77 on the outer peripheral surface of the

ring gears

26, 28, respectively, the pitch of the worms in each being equal but in the opposite direction of rotation so that each of the

ring gears

26, 28 can be turned the same amount but in opposite direction at the same time. A turning or control means, such as the spur wheel 88 is rigidly mechanically coupled to the shaft 70 whereby the shaft 70 is rotated when the wheel 88 is rotated by means of a control motor 90 which drives the gear 92 coupled to the gear 88. Each of the ring gears is coupled coaxially by means of

brackets

97, 97a to a

short shaft

94 or 96 which is journaled in

bearings

98, 100 and 98a, 100a, respectively.

Each of the

bearings

17, 17a, 19, 19a, 21, 21a, 62, 62a, 64, 64a, 98, 100, 98a 100a, 102, 104, 106, 108, the pump 12, guide a 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, (see FIG. 2 particularly) has the

ring gears

26, 28 arbitrarily so positioned that the crank throws cause one connecting rod (18) to advance towards the piston 14 while the other connecting (rod) 29 is moving away from the piston 14. With such orientation of the crank throws the walking beam rocks but the pump piston stroke is practically Zero as power from the gear 84 is coupled by means of the gear 82 to the shaft 36 and, by means of the

sprocket wheels

78, 80 and chain79, to the shaft 38.

The

shafts

36, 38 drive the sun gear (34 in FIG. 3) of each

planetary gear assembly

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

assembly

30, 32 through the planet gears (46, 48 in FIG. 3) of the

respective assembly

30 or 32. The

ring gears

26, 28 are held in a fixed position by the teeth of the

worm segments

72, 74 of shaft 70 engaging the

teeth

76, 77 on the outer peripheral surface of the ring gears except when the shaft 70 is rotated. Thus, the planet gears of the assembly are rotated on their

shafts

50, 52 and 54, 56, and, because the ring gears are in fixed position, the rotation of the planet gears causes the shafts 58, 60 to be rotated (because the brackets 59, 61 rotate with the planet gears).

Spur wheels

66, 68, rotated bythe shafts 58, 6t) drive the

spur gears

23, 25, thus rotating the

crankshafts

22, 24.

When the stroke length of the piston 14 is to be changed, the shaft 70 is turned (as by driving the spur wheel 88 by the gear 90 coupled to the motor 92, 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, engaging the

teeth

76, 77, cause the

ring gears

26, 28 to rotate. Such rotating of the ring gears is usually at a slow rate as compared with rate of rotation of the shafts 58, 60. Because the shafts 36, 38 (the drive shafts for the sun gears) rotation in the same direction, the

worms

72, 74 and

teeth

76, 77 are disposed so that, on rotation of the shaft 70, the ring gears are rotated in opposite radial directions, e.g. one is rotated clockwise and the other is rotated counterclockwise, for example. Thus, even through the

crankshafts

22, 24 rotate in the same direction, the relative phasing between the

crankshafts

22, 24 is changed as the

shafts ring gears

26, 28 are rotated. The

crankshafts

22, 24 are considered to be in phase when their throws are sooriented that maximum length of piston stroke is achieved as the crankshafts rotate. The crankshafts are considered to be in their most out of phase condition when their throws are so-oriented that minimum stroke length of the piston 14 is achieved. When the length of the piston stroke is at a minimum, the movement of the two connecting rods 18, is such that the walking beam pivots around its point of attachment to the crosshead with little reciprocating motion applied to the piston 14.

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.

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 two crankshafts operating on an in-phase relationship results in maximum volume being displaced through the pump 12. As the pressure head increases the gear 88 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 rotating planet gears (46, 48 in FIG. 3).

The apparatus. of the invention permits the power source to operate at a substantially constant r.p.m. rate even though 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 r.p.m. 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 pressures or smaller volume at high pressures. In fixed stroke reciprocating piston-type pumps a so-called high volume pump has a relatively low maximum 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 r.p.m. 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 in that it is good both as a high pressure-low volume pumpand 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 smaller 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 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 planet gear and a ring gear, each of said ring gears having teeth on both the inner and outer peripheral surfaces, one :of said crankshafts being operatively coupled to the planet gear of one of said planetary gear assemblies, the other of said pair of crankshafts being operatively coupled to the planet 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 sun gears, the other of said drive shafts being operatively coupled to the other of said sun gears, and at least one phase control gear, said control gear being coupled to the teeth on the outer peripheral surface of said ring gears for varying the radial position of the ring gear in one planetary assembly with respect to its sun gear and for varying the radial position of the ring 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, and means for actuating said phase control gear.

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, Where in said phase control gear includes means for rotating the ring gears in opposite radial direction to one another.

5. A pumping unit in accordance With claim 1, wherein said phase control gear is disposed along a rod-like member. I

6. A pumping unit in accordance with claim 5, said coupling between each crankshaft and its planet gear comprises a hollow shaft surrounding one of said drive shafts along part of its length, said hollow shaft having said planet gear jcurnaled thereon and being gear couglad to the crankshaft.

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 phase control gear is a Worm gear member having separated worm sections whose pitch is in opposite direction to one another.

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 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.

14. A pumping unit in accordance with claim 1, Where in said means for actuating said phase control gear is a small prime mover.

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 PLANET GEAR AND A RING GEAR, EACH OF SAID RING GEARS HAVING TEETH ON BOTH THE INNER AND OUTER PERIPHERAL SURFACES, ONE OF SAID CRANKSHAFTS BEING OPERATIVELY COUPLED TO THE PLANET GEAR OF ONE OF SAID PLANETARY GEAR ASSEMBLIES, THE OTHER OF SAID PAIR OF CRANKSHAFTS BEING OPERATIVELY COUPLED TO THE PLANET 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 SUN GEARS, THE OTHER OF SAID DRIVE SHAFTS BEING OPERATIVELY COUPLED TO THE OTHER OF SAID SUN GEARS, AND AT LEAST ONE PHASE CONTROL GEAR, SAID CONTROL GEAR BEING COUPLED TO THE TEETH ON THE OUTER PERIPHERAL SURFACE OF SAID RING GEARS FOR VARYING THE RADIAL POSITION OF THE RING GEAR IN ONE PLANETARY ASSEMBLY WITH RESPECT TO ITS SUN GEAR AND FOR VARYING THE RADIAL POSITION OF THE RING 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, AND MEANS FOR ACTUATING SAID PHASE CONTROL GEAR.