Wobble pump comprising a wobble plate

Abstract

The present invention relates to a barrel-type piston pump (1) with a swash plate (7) where the angle of inclination of rotary plate (2) relative to drive shaft (5) is adjustable by means of a finger joint (8).

Claims

1. A barrel-type piston pump comprising a casing and comprising within the casing: a drive shaft, a rotary plate driven by the drive shaft, a swash plate caused to oscillate by the rotary plate, and the swash plate being pivotably connected about the axis of the rotary plate relative to the rotary plate, a cylinder block comprising at least two circumferentially distributed compression chambers, and at least two pistons in translation respectively in the compression chambers of the cylinder block, the pistons being driven by the swash plate by connecting rods, wherein the rotary plate is driven by the drive shaft by a finger joint, the position of the finger joint determining the inclination of the rotary plate and of the swash plate relative to the drive shaft, and the rotary plate comprises a groove in which a finger of the finger joint moves, the groove being substantially parallel to the axis of the drive shaft.

2. The pump as claimed in claim 1, wherein the pump further comprises a return rod, the return rod being in ball jointed connection with the casing and the swash plate.

3. The pump as claimed in claim 1, wherein the angle of inclination of the rotary plate and of the swash plate relative to the axis of the drive shaft ranges between 70 and 90.

4. The pump as claimed in claim 1, wherein the pump comprises means for controlling the inclination of the rotary plate relative to the drive shaft.

5. The pump as claimed in claim 4, wherein the energy of the control means comes from a source external to the pump.

6. The pump as claimed in claim 5, wherein the source external to the pump comprises a fluid under pressure.

7. The pump as claimed in claim 4, wherein the energy of the control means is taken from the drive shaft.

8. The pump as claimed in claim 1, wherein the cylinder block is stationary relative to the casing.

9. A method for carrying out a drilling operation, comprising injecting drilling mud into a wellbore using the barrel-type piston pump as claimed in claim 1.

10. A barrel-type piston pump comprising: a drive shaft, a rotary plate, a swash plate pivotably connected about the axis of the rotary plate, a finger joint connecting the drive shaft to the rotary plate, the position of the finger joint determining the inclination of the rotary plate and the swash plate relative to the drive shaft, the rotary plate comprising a groove in which a finger of the finger joint moves, the groove being substantially parallel to the axis of the drive shaft, a cylinder block comprising two compression chambers, pistons in the compression chambers, and connecting rods between the swash plate and the pistons.

11. The pump as claimed in claim 10, wherein the pump comprises a casing and a return rod, and the return rod is in ball jointed connection with the casing and the swash plate.

12. The pump as claimed in claim 10, wherein the angle of inclination of the rotary plate and of the swash plate relative to the axis of the drive shaft ranges between 70 and 90.

13. A method for carrying out a drilling operation, comprising injecting drilling mud into a wellbore using the barrel-type piston pump as claimed in claim 10.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Other features and advantages of the device according to the invention will be clear from reading the description hereafter of embodiments given by way of non-limitative example, with reference to the accompanying drawings wherein:

(2) FIG. 1, already described, illustrates a stationary barrel pump according to the prior art,

(3) FIG. 2, already described, illustrates a rotating barrel pump according to the prior art,

(4) FIG. 3 illustrates a pump according to an embodiment of the invention,

(5) FIG. 4 schematically illustrates a pump according to an embodiment of the invention,

(6) FIG. 5 illustrates a finger joint according to an embodiment of the invention in three positions,

(7) FIG. 6 shows pressure curves as a function of the flow rate for a pump according to the invention for various gear ratios with a plate inclined at 87 to the axis of the drive shaft, and

(8) FIG. 7 shows pressure curves as a function of the flow rate for a pump according to the invention for various gear ratios with a plate inclined at 70 to the axis of the drive shaft.

DETAILED DESCRIPTION OF THE INVENTION

(9) The present invention relates to a barrel-type pump in a swash plate design. The purpose of the barrel pump is to pump a fluid (for example water, oil, gas, drilling mud, etc.) through a linear displacement of several pistons. This type of pump affords the advantage of being compact, of having interesting mechanical and volumetric efficiencies, as well as an excellent weight/power ratio. Furthermore, barrel pumps in a swash plate design are suited for high-pressure pumping.

(10) The barrel pump according to the invention comprises a casing and it comprises within the casing: a drive shaft driven in rotation relative to the casing by an external energy source, notably a prime mover (thermal or electric for example), in particular by means of a transmission (a gearbox for example), a rotary plate driven by the drive shaft: the rotary plate is inclined relative to the drive shaft; the inclination of the rotary plate generates an oscillating motion of the rotary plate; the rotary plate has a rotational motion and an oscillating motion relative to the casing, a swash plate caused to oscillate by the rotary plate: the swash plate is pivotably connected about the axis of the rotary plate relative to the rotary plate; the rotary plate only transmits the oscillating motion to the swash plate and it does not transmit the rotational motion, a cylinder block (referred to as barrel) comprising at least two circumferentially distributed (in other words, arranged in a circle) compression chambers (also referred to as sleeves), and at least two pistons in translation respectively in the compression chambers, the pistons are driven by the swash plate by means of connecting rods (the rods connect, through the agency of ball joint links, the swash plate and the pistons so as to convert the oscillating motion to a translational motion of the pistons), and the translation of the pistons within the compression chambers generates pumping of the fluid.

(11) According to the invention, the rotary plate is driven by the drive shaft by means of a finger joint, the position of the finger joint determining the inclination of the two plates (rotary and swash plate) relative to the drive shaft. It is reminded that a finger ball joint link is a link between two elements (here the drive shaft and the rotary plate) having four degrees of linkage and two degrees of relative motion; only two relative rotations are possible, the three translations and the last rotation being linked. In general, it is a ball joint provided with a finger that prevents rotation. For the invention, the finger of the ball joint allows the inclination of the plates to be adjusted relative to the drive shaft. Indeed, the pump comprises means for controlling the finger joint, and therefore the inclination of the plates relative to the drive shaft.

(12) Thus, the inclination of the rotary and swash plates is continuously adjustable, which enables a variable displacement. Indeed, the inclination of the plates influences the stroke of the pistons. Furthermore, the pump according to the invention enables good flexibility thanks to the continuous variation of the unit cylinder displacement. Moreover, the pump according to the invention enables good reliability thanks to the possibility of progressive start-up of the pump: for example, upon start-up, the angle of inclination may be small and, subsequently, it can be increased depending on the desired conditions (fluid flow rate and pressure). This reliability cannot be obtained with a pump whose plate inclination is fixed, or whose plate inclination cannot be continuously varied.

(13) The plates can have substantially the shape of a disc. However, the plates may have any shape. Only the compression chambers (and the pistons) are arranged in a circle.

(14) Advantageously, the pump according to the invention can comprise a number of pistons ranging between three and fifteen, preferably between five and eleven. Thus, a large number of pistons provides a continuous flow upstream and downstream from the pump.

(15) Thus, by means of this system, the rotational motion at the inlet (drive shaft) is first converted to an oscillating motion (swash plate), then to a translational motion, i.e. a reciprocating motion (pistons). The reciprocating motion of the pistons in the compression chambers provides pumping of the fluid.

(16) Conventionally, the pump further comprises an inlet and an outlet for the fluid to be pumped. The fluid passes through the pump inlet, flows into a compression chamber, where it is compressed, then it is discharged from the pump through the outlet by means of the piston.

(17) In addition, conventionally, the pivot links consist of bearings or rollers, promoting the relative motion of the elements.

(18) According to an embodiment of the invention, adjustment of the inclination can be achieved by moving the finger of the ball joint in a groove provided in the rotary plate, and the axis of the groove can be parallel to the axis of rotation of the drive shaft.

(19) According to an implementation of the invention, continuous adjustment of the inclination (for example the movement of the finger in the groove) can be provided in different ways, for example by means of a fluid under pressure supplied to the finger joint through a specific circuit.

(20) According to a design of the invention, the energy required for adjusting the inclination (for example for the movement of the finger in the groove) can be taken from the energy used for the input shaft. Alternatively, the energy required for adjusting the inclination can come from an external source (an electric motor for example).

(21) Preferably, the cylinder block (or barrel) is stationary relative to the casing. Thus, the energy supply for pumping is provided at the drive shaft only, through the rotation thereof; the number of rotating parts is thus limited.

(22) According to an embodiment option of the invention, the pump further comprises a return rod. The return rod is arranged between the swash plate and the casing. The return rod is in ball jointed connection with the casing and the swash plate. The return rod makes it possible to prevent a rotating motion of the swash plate about the axis thereof. Thus, the swash plate is only driven by an oscillating motion.

(23) Since the swash plate has no rotational motion, no friction element can be interposed between the swash plate and the rods transmitting the motion to the pistons.

(24) According to an embodiment of the invention, the angle of inclination of the rotary plate relative to the axial direction of the drive shaft ranges between 70 and 90. In other words, the rotary plate (and a fortiori the swash plate) is inclined at an angle ranging between 0 and 20 to a radial direction of the drive shaft.

(25) FIGS. 3 and 4 schematically illustrate, by way of non-limitative example, a barrel pump according to an embodiment of the invention. FIG. 3 is a three-dimensional view where the casing and the compression chambers are not shown. FIG. 4 is a kinematic diagram of the pump. In these figures, only one piston 3 is represented. However, the pump according to the invention comprises at least two pistons that are circumferentially distributed within a cylinder block.

(26) For pump 1 according to the illustrated embodiment, drive shaft 5 is rotatingly mounted in a casing 11. The rotation of drive shaft 5 is performed by an external source, not shown, an electric machine and a gearbox for example. Drive shaft 5 drives rotary plate 2 by means of a finger ball joint link 8. The position of the finger joint allows to adjust the inclination of rotary plate 2 relative to drive shaft 5. Rotary plate 2 is linked to a swash plate 7 by a pivot link about the axis of the rotary plate. Pump 1 further comprises a return rod 9 arranged between swash plate 7 and casing 11 by means of ball joint links. Return rod 9 prevents rotation of swash plate 7 about the axis thereof. Pump 1 comprises a piston 3 driven by a translational motion (reciprocating motion) within a compression chamber 4. Compression chamber 4 belongs to the cylinder block (barrel) that is stationary relative to casing 11. The reciprocating motion of piston 3 is achieved by means of a rod 10 connecting swash plate 7 and piston 3 by means of ball joint links. This reciprocating motion of piston 3 within compression chamber 4 allows the fluid to be pumped.

(27) FIG. 5 schematically shows, by way of non-limitative example, a finger joint in three positions according to an embodiment of the invention, in order to illustrate the relative motions between the rotary plate and the drive shaft. In this figure, rotary plate 2 is partly represented: only the central part of rotary plate 2 is illustrated. Finger joint 8 between drive shaft 5 and rotary plate 2 consists of a ball joint link between two spherical parts and of a finger 12 that moves in a groove 13 provided in rotary plate 2. Groove 13 is parallel to the axis of drive shaft 5. Thus, only two rotations between rotary plate 2 and the drive shaft are allowed. It is noted that the adjustment of the position of finger 12 in groove 13 allows to adjust the angle of inclination of rotary plate 2 relative to drive shaft 5.

(28) The invention also relates to the use of the pump according to the invention for a drilling operation, in particular for injecting drilling mud into a wellbore. Indeed, the pump according to the invention is well suited for this use due to its flexibility, compactness and high pressure strength.

(29) For example, the pump according to the invention can be sized to operate up to pressures of the order of 1500 bar, i.e. 150 MPa. Besides, the pump according to the invention can be sized to operate at flow rates ranging from 30 to 600 m.sup.3/h.

Example

(30) The features and advantages of the system according to the invention will be clear from reading the application example hereafter.

(31) This example relates to a barrel-type pump according to the invention where the drive shaft is connected to a prime mover by means of an eight-speed gearbox. It is a 2500 HP (approximately 1900 kW) barrel pump comprising five pistons. Table 1 shows the rotational speed of the drive shaft as a function of the gearbox ratio.

(32) TABLE-US-00001 TABLE 1 Ratio 1 2 3 4 5 6 7 8 Speed 198 269 300 365 407 485 555 660 (rpm)

(33) This example notably shows the impact of the angle of inclination of the plates on the pressure and the flow rate for a barrel pump according to the invention.

(34) FIG. 6 shows curves of the pressure P (in bar) as a function of the flow rate D (in m.sup.3/h) for a pump according to the invention, for various gearbox ratios (denoted by 1st, 2nd, 3rd, . . . , 8th) with a plate inclined at 87 relative to the drive shaft axis (i.e. with an angle of 3 to a radial direction of the drive shaft).

(35) FIG. 7 shows curves of the pressure as a function of the flow rate for a pump according to the invention (the same pump as the one used for FIG. 6), for various gearbox ratios (denoted by 1st, 2nd, 3rd, . . . , 8th) with a plate inclined at 70 relative to the drive shaft axis (i.e. with an angle of 20 to a radial direction of the drive shaft).

(36) It is noted that an angle of inclination of the (rotary and swash) plates close to 90 allows higher pressures than an angle of inclination close to 70. Furthermore, an angle of inclination of the plates close to 70 allows higher flow rates than an angle of inclination close to 90 (thanks to the variable displacement). It is thus possible to adjust the inclination of the plates depending on the desired pumping conditions (pressures, flow rates). It is also noted that, by means of the various gearbox ratios, the rotational speed of the drive shaft influences the pressure and the flow rate of the fluid: the pressure is higher at low speed and the flow rate is higher at high speed.