DOUBLE-PLATE ROTARY BARREL PUMP

Abstract

The present invention relates to a rotary barrel pump (6) comprising two plates: a mobile plate (2) also driven by drive shaft (5) and a variable-inclination plate (7), the two plates (2, 7) being linked to one another by a pivot connection.

Claims

1. A barrel pump comprising a casing and comprising, within the casing: a drive shaft, a cylinder block comprising at least two circumferentially distributed compression chambers, the cylinder block being driven by the drive shaft, a mobile plate, at least two pistons in translation respectively in the compression chambers of the cylinder block, the pistons being driven by the mobile plate by means of connecting rods, wherein in that the mobile plate is driven by the drive shaft and the barrel pump comprises a plate with variable inclination relative to the drive shaft, the mobile plate being in pivot connection relative to the variable-inclination plate about axis of the variable-inclination plate.

2. A pump as claimed in claim 1, wherein the pivot connection between the mobile plate and the variable-inclination plate consists of means for supporting the loads and means for holding up the assembly of the two plates.

3. A pump as claimed in claim 2, wherein the pivot connection between the mobile plate and the variable-inclination plate consists of a conical roller thrust and of a ball bearing.

4. A pump as claimed in claim 3, wherein the conical roller thrust is arranged between an outer shoulder of the mobile plate and an inner shoulder of the variable-inclination plate.

5. A pump as claimed in claim 3, wherein the ball bearing is arranged between an outer shoulder of the mobile plate and an inner shoulder of the variable-inclination plate.

6. A pump as claimed in claim 1, wherein the mobile plate is driven by the drive shaft through a pin spherical joint.

7. A pump as claimed in claim 6, wherein the pin spherical joint comprises a device for forming a pin spherical joint in form of a hollow revolution part comprising a substantially cylindrical inner surface and an outer surface having substantially the shape of a truncated sphere at both ends, the inner surface comprises at least one groove or one female spline, and the outer surface comprises at least one crowned spline.

8. A pump as claimed in claim 7, wherein device for forming a pin spherical joint is mounted on the drive shaft by means of a key or a splined shaft, and the mobile plate is mounted on the device by means of at least one groove cooperating with the at least one crowned spline.

9. A pump as claimed in claim 6, wherein the mobile plate comprises a partly spherical inner surface.

10. A pump as claimed in claim 1, wherein the barrel pump comprises a means for controlling the inclination of the variable-inclination plate.

11. A pump as claimed in claim 10, wherein the inclination control means comprises a worm drive system.

12. A pump as claimed in claim 1, wherein the are connected to the mobile plate without friction pads.

13. Use of the barrel pump as claimed in claim 1 for a drilling operation, in particular for injecting drilling mud into a wellbore.

14. A method for conducting a drilling operation, comprising injecting drilling mud into a wellbore using the barrel pump as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0032] 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:

[0033] FIG. 1, already described, illustrates a stationary barrel pump according to the prior art,

[0034] FIG. 2, already described, illustrates a rotary barrel pump according to the prior art,

[0035] FIG. 3 illustrates a barrel pump according to an embodiment of the invention,

[0036] FIG. 4 illustrates a device for forming a pin spherical joint link necessary for rotation and inclination of the mobile plate according to an embodiment of the invention, and

[0037] FIG. 5 illustrates the pivot connection between the mobile plate and the variable-inclination plate according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention relates to a rotary barrel pump. The purpose of the barrel pump is to pump a fluid (for example water, oil, gas, drilling mud, etc.) through 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, rotary barrel pumps are suited for high-pressure pumping.

[0039] The barrel pump according to the invention comprises a casing and it comprises within the casing: [0040] 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), [0041] a mobile (rotary) plate driven by the drive shaft: the mobile plate is driven in relation to the drive shaft, the plate is therefore rotary, furthermore the mobile plate is inclined relative to the drive shaft, [0042] 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), the cylinder block is rotary and driven by the drive shaft, [0043] at least two pistons in translation respectively in the compression chambers, the pistons are driven by the mobile plate by means of connecting rods (the rods connect, through the agency of spherical joints, the mobile plate and the pistons so as to convert the motion of the mobile plate to a translational motion of the pistons), and the translation of the pistons within the compression chambers generates pumping of the fluid, and [0044] a plate with variable inclination relative to the drive shaft, apart from the adjustment of the inclination thereof, this plate is stationary relative to the casing, and the mobile plate is in pivot connection relative to the variable-inclination plate about the axis of the variable-inclination plate (this axis corresponds to a normal direction to the plate and it can correspond to the axis of revolution of the variable-inclination plate when the plate has the shape of a disc), thus the inclination of the mobile plate is identical to the inclination of the variable-inclination plate.

[0045] The variable inclination of the variable-inclination plate allows to have a variable displacement of the pump, by modifying the stroke of the pistons.

[0046] Advantageously, the spherical joints between the connecting rods and the mobile plate are provided without friction pads (there is no friction connection between the rods and the mobile plate), which is made possible by the mobile plate. Indeed, one of the specific features of the invention is based on the double plate design and, more specifically, on the connection of the mobile plate with the variable-inclination plate and its drive via the power input shaft. Most plate pumps present on the market are intended for lower flow rate and pressure activities, and the mechanical stresses on the various pump components are therefore more limited. Within the context of a high flow rate and high pressure use of these pumps available on the market, the mechanical stresses involved are significant and friction pads are therefore essential for these pumps. Furthermore, the design of friction pads between the rods and the inclined plate becomes critical, in addition to reducing the final efficiency of the pump by a few points. The design of a double plate, one stationary and the other rotary, thus allows an increase in the final efficiency of the pump, without friction pads, and enables the pump to be used under high flow rate and high pressure conditions.

[0047] According to an embodiment of the invention, the pivot connection between the mobile plate and the variable-inclination plate can consist of means for supporting the loads and means for holding up the assembly of the two plates. For example, this pivot connection can be made up of a conical roller thrust and of a ball bearing. The conical roller thrust is capable of withstanding the axial and radial loads exerted on the plates, and the ball bearing allows to hold up the assembly of the two plates (mobile and variable-inclination plate).

[0048] According to an aspect of this embodiment, the mobile plate can comprise two outer shoulders for the arrangement of the conical roller thrust and the ball bearing. The shoulder with the smaller diameter can be intended to receive the conical roller thrust and it can be arranged on the side of the mobile plate remote from the connecting rods. Furthermore, the shoulder with the larger diameter can be intended to receive the ball bearing and it can be arranged near the side of the mobile plate close to the rods.

[0049] Besides, the variable-inclination plate can comprise two inner shoulders for the arrangement of the conical roller thrust and the ball bearing. The shoulder with the smaller diameter can be intended to receive the conical roller thrust and it can be arranged near the center of the variable-inclination plate. Furthermore, the shoulder with the larger diameter can be intended to receive the ball bearing and it can be arranged on the side of the variable-inclination plate close to the mobile plate.

[0050] This arrangement of the conical roller thrust and the ball bearing with the inner and outer shoulders provides a simple assembly of the two plates.

[0051] According to an implementation of the invention, the mobile plate can be driven by the drive shaft through a pin spherical joint. A pin spherical joint is a link between two mechanical elements with four degrees of connection and two degrees of relative movement; only two relative rotations are possible, the three translations and the last rotation being linked. It is generally a spherical joint provided with a pin hindering rotation. The operating principle of this type of link consists in providing torque transmission between two rotating assemblies whose axes are not colinear.

[0052] The pin spherical joint allows to synchronize the rotation of the mobile plate and of the cylinder block (barrel).

[0053] According to an aspect of this implementation of the invention, the pin spherical joint can consist of a specific device for forming a pin spherical joint. The device for forming the pin spherical joint can be a hollow revolution part. It is reminded that, in geometry, a revolution part is a part generated by a closed plane surface rotating about an axis located in the same plane and having no point in common therewith, or only boundary points.

[0054] For clarity of the description, the term “device” is used in the rest of the description below to designate the specific device for forming a pin spherical joint.

[0055] The device for forming the pin spherical joint comprises a substantially cylindrical inner surface. Thus, the hollow part of the device is substantially cylindrical. The device is therefore suited to be mounted on a cylindrical shaft. The inner surface comprises at least one groove for inserting a key or at least one female spline for inserting a splined shaft, so as to transmit the torque between a shaft and the device. Using a key or spline transmission enables high torque transmission.

[0056] The device according to the invention comprises an outer surface having substantially the shape of a truncated sphere at both ends. The sphere is truncated by two planes perpendicular to the axis of revolution of the device. This partly spherical shape of the outer surface provides a spherical joint. Furthermore, the outer surface comprises at least one crowned (or domed) spline. The crowned spline allows, on the one hand, to form the pin of the pin spherical joint and, on the other hand, to provide large torque transmission between the device and an element positioned on the outer surface of the device (a plate or a disc for example).

[0057] This design of the device for forming a pin spherical joint provides high compactness, large angular displacement and simplicity of use.

[0058] Advantageously, the groove(s) and the spline(s) are parallel to the axis of revolution of the device.

[0059] Preferably, the spline(s) of the outer surface have a crowned (or domed) shape parallel to the globally spherical shape of the outer surface of the device. Thus, the splines may be involute splines (splines which are developed along a circle) so as to have the greatest transmissible torque.

[0060] According to an aspect of this embodiment of the invention, the outer surface comprises a plurality of crowned splines evenly distributed over the circumference of the spherical surface. A higher torque can thus be transmitted between the device according to the invention and the element positioned on the outer surface of the device. The splines are preferably parallel to one another. For example, the outer surface of the device can comprise between five and nineteen crowned splines, preferably between seven and thirteen, in order to optimize the manufacture of the device and the torque transmissible thereby, and to optimize the distribution of forces in the splines.

[0061] Thus, for the pin spherical joint link between the drive shaft and the mobile plate, the device for forming a pin spherical joint is mounted on the drive shaft by means of at least one key or by means of a splined shaft. Furthermore, the mobile plate is mounted on the outer surface of the device so as to form a pin spherical joint link by means of at least one crowned groove (female spline) cooperating with the crowned spline(s).

[0062] With the invention, a pin spherical joint link is formed between the drive shaft and the mobile plate: the mobile plate can rotate by means of the spherical outer surface of the device, and the torque can be transmitted from the shaft to the plate by the key or the splines of the drive shaft or by the crowned spline(s).

[0063] This link is here a non-slip constant-velocity spherical joint, which means that the rotational speed at the joint input is identical to the rotational speed at the joint output, and this connection occurs without slip but through direct mechanical drive.

[0064] This design of the connection enables a pin spherical joint link providing high compactness, large angular displacement and simplicity of use.

[0065] To achieve the pin spherical joint link, the mobile plate can comprise a substantially spherical inner surface provided with female splines.

[0066] In order to facilitate assembly of the connection, the mobile plate can consist of two half-shells. Alternatively, the mobile plate can be made of a single piece.

[0067] According to an aspect of the invention, the mobile plate can comprise a means forming an angular stop. It can be a surface coming into contact with the shaft; for example, the plate can comprise a conical inner surface coming into contact with the shaft for the maximum angular displacement.

[0068] Alternatively to this embodiment of the pin spherical ball joint, the spherical joint link can be a ball joint bearing.

[0069] 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.

[0070] 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 provide a continuous flow upstream and downstream from the pump.

[0071] 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.

[0072] According to an embodiment of the invention, the angle of inclination of the variable-inclination plate relative to the axial direction of the drive shaft can range between 70° and 90°. In other words, the variable-inclination plate (and a fortiori the rotary plate) can be inclined at an angle ranging between 0° and 20° to a radial direction of the drive shaft.

[0073] According to an implementation of the invention, the barrel pump can comprise a means for controlling the inclination of the variable-inclination plate. For example, this control means can comprise a worm drive system.

[0074] According to an aspect of the invention, the barrel can be made of two parts, a first part being intended for guiding, and the second part being intended for sealing.

[0075] FIG. 3 schematically illustrates, by way of non-limitative example, a kinematic diagram of a rotary barrel pump according to an embodiment of the invention. Rotary barrel pump 1 comprises a drive shaft 5. 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 rotates with respect to casing 15. Furthermore, drive shaft 5 rotationally drives barrel 6 that comprises compression chambers 4.

[0076] Drive shaft 5 also drives a mobile plate 2 by means of a pin spherical joint 9.

[0077] Pump 1 further comprises a variable-inclination plate 7 which, except for the inclination adjustment thereof, is stationary relative to casing 15. The means for adjusting the inclination of variable-inclination plate 7 is not shown.

[0078] Mobile plate 2 is in pivot connection with respect to variable-inclination plate 7 about the axis of variable-inclination plate 7.

[0079] Pump 1 comprises a piston 3 driven by a translational motion (reciprocating motion) within a compression chamber 4.

[0080] The reciprocating motion of piston 3 is achieved by means of a rod 8 connecting mobile plate 2 and piston 3 by means of spherical joints. This reciprocating motion of piston 3 within compression chamber 4 allows the fluid to be pumped.

[0081] FIG. 4 schematically illustrates, by way of non-limitative example, a device for forming a pin spherical joint link according to an embodiment of the invention. Device 10 is a revolution part rotating about axis XX. Device 10 is hollow and it comprises a cylindrical inner surface 11. Inner surface 11 comprises a groove 14. The section of groove 14 is substantially rectangular. Device 10 comprises an outer surface 12 having substantially the shape of a truncated sphere at both ends, the truncation being achieved at two planes perpendicular to axis XX. Outer surface 12 comprises a plurality of crowned (or domed) splines 13, in the case illustrated here, nine crowned splines 13. Crowned splines 13 have an outer surface substantially parallel to outer surface 12 of the device. These splines 13 are involute splines.

[0082] FIG. 5 schematically illustrates, by way of non-limitative example, the pivot connection between the two plates (mobile and variable inclination). FIG. 5 is a sectional view along a plane comprising the axis of drive shaft 5. This figure shows variable-inclination plate 7, mobile plate 2 and connecting rods 8. Rods 8 are in spherical joint connection in mobile plate 2 without friction pads.

[0083] Axis YY is the axis of variable-inclination plate 7. Mobile plate 2 is in pivot connection on variable-inclination plate 7 about inclination axis YY of variable-inclination plate 7. Thus, the inclination of mobile plate 2 is identical to the inclination of variable-inclination plate 7. This pivot connection consists of a conical roller thrust 16 and of a ball bearing 18.

[0084] Mobile plate 2 comprises two outer shoulders 20 and 22 for arranging conical roller thrust 16 and ball bearing 18. Shoulder 20 with the smaller diameter is intended to receive conical roller thrust 16 and it is arranged on the side of mobile plate 2 remote from rods 8. Furthermore, shoulder 22 with the larger diameter is intended to receive ball bearing 18 and it is arranged near the side of mobile plate 2 close to rods 8.

[0085] Besides, variable-inclination plate 7 comprises two inner shoulders 19 and 21 for arranging conical roller thrust 16 and ball bearing 18. Shoulder 19 with the smaller diameter is intended to receive conical roller thrust 16 and it is arranged near the center of variable-inclination plate 7. Furthermore, shoulder 21 with the larger diameter is intended to receive ball bearing 18 and it is arranged on the side of variable-inclination plate 7 close to mobile plate 2.

[0086] FIG. 5 further illustrates the device for forming a pin spherical joint 10. This device 10 is in accordance with the device for forming a pin spherical joint illustrated in FIG. 4. Device 10 is mounted on drive shaft 5 by means of a key 17.

[0087] 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.

[0088] 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.