Patent Publication Number: US-2021164456-A1

Title: Double-plate rotary barrel pump

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of pumps, in particular for high-pressure pumping, notably for drilling operations. 
     BACKGROUND OF THE INVENTION 
     Today, crankshaft drive pumps are the most widely used across all industry sectors: capital goods, oil, gas and food industries, automotive industry, building industry (heating, wells, air conditioning, water pumps, etc.), and more specifically for water and waste treatment (water network and wastewater system). However, they are still manufactured on the basis of designs dating from the  1930   s , and very few research and development surveys have been carried out to improve their performances, reduce their cost price, minimize their maintenance costs or decrease their environmental footprint. These pumps have limits in terms of power, pressure/flow rate torque (i.e. limits resulting in pressure surge type phenomena generated by the sinusoidal response of the pressure produced by the crankshaft), weight, efficiency and service life. Furthermore, they do not allow to have a variable displacement and they therefore lack flexibility in use. 
     Besides, in the field of hydrocarbon production, it is currently observed that wellbores need to reach increasingly great depths, which involves working at increasingly high injection pressures. Oil companies therefore need ultra-high pressure pumps to reach the required depths for drilling mud injection for example. These pumps must also be reliable, economical, flexible and compact, so as to meet the ever more demanding requirements of the energy sector. 
     Another positive-displacement pump technology is the barrel pump. It is mainly intended for pumping at lower pressure and flow rate (it is mainly used for pumping hydraulic oils) and it has many advantages:
         excellent weight/power ratio   very good price/performance ratio   interesting mechanical and volumetric efficiencies   variable displacement capacity through plate inclination adjustment.       

     Pumps designed with a barrel operate by means of a rotary plate system that actuates the various pistons one after another. When a piston is in an intake phase, the opposite piston is in delivery mode, which provides a constant flow upstream and downstream from the pump. The distribution of the piston positions guided by the barrel provides progressive distribution of the forces upon rotation of the shaft driven by the motor. 
     There are three main barrel pump architectures:
         stationary barrel pumps ( FIG. 1 ): in this configuration of pump  1 , where the barrel is stationary, it is inclined plate  2  that rotates (driven by shaft  5 ) so as to generate the motion of pistons  3  in their sleeves  4  (compression chamber). The link between pistons  3  and plate  2  is then provided by ball joint pads that rub on plate  2 . The advantage here is a very low inertia of the rotating parts. However, this configuration makes it difficult to have a variable displacement. Furthermore, in case of high pressures and flow rates, the friction forces between the plate and the pads are not negligible and make it difficult, or even impossible, to produce the pump;   swash-plate barrel pumps: the barrel is stationary in this architecture and there are two plates, a first inclined plate rotates and transmits to the second plate only the oscillating motion. Thus, the pistons can be linked to the second plate, the swash plate, without friction members being required, for example with a connecting rod linked to the piston and to the plate by spherical joints. This architecture is suited to high-pressure pumping due to the absence of friction elements (some can be found on the geothermal energy market). It also provides an excellent mechanical efficiency. This configuration makes it possible to produce a variable displacement, which however remains difficult to integrate and to design;   rotary barrel pumps ( FIG. 2 ): within pump  1 , it is plate  2  that is stationary and barrel  6  carrying pistons  3  rotates, which provides motion of pistons  3  in their sleeves  4  (compression chamber). The link between piston  3  and plate  2  is provided in the same manner as for the first configuration. The advantage of this architecture is that the plate can be readily adjusted in inclination, which makes it possible to have a variable displacement. On the other hand, the inertia of the rotating parts increases in a quite significant manner since the barrel and all of the pistons are rotated. Furthermore, for this configuration, significant friction occurs between the plate and the rods connected to the pistons, which generates efficiency loss.       

     In order to overcome these drawbacks, the present invention relates to a rotary barrel pump comprising two plates: a mobile plate also driven by the drive shaft and a variable-inclination plate, the two plates being linked to one another by a pivot connection. Thus, the drive of the mobile plate by the drive shaft allows contact between two rotating parts: the rods and the mobile plate, thereby limiting friction losses between these parts. The variable inclination enables variable displacement of the pump. 
     SUMMARY OF THE INVENTION 
     The invention relates to a barrel pump comprising a casing and comprising, within said casing:
         a drive shaft,   a cylinder block comprising at least two circumferentially distributed compression chambers, said cylinder block being driven by said drive shaft,   a mobile plate,   at least two pistons in translation respectively in said compression chambers of said cylinder block, said pistons being driven by said mobile plate by means of connecting rods.       

     Said mobile plate is driven by said drive shaft and said barrel pump comprises a plate with variable inclination relative to said drive shaft, said mobile plate being in pivot connection relative to said variable-inclination plate around the axis of said variable-inclination plate. 
     According to one embodiment of the invention, said pivot connection between said mobile plate and said variable-inclination plate consists of means for supporting the loads and means for holding up the assembly of the two plates. 
     Advantageously, said pivot connection between said mobile plate and said variable-inclination plate consists of a conical roller thrust and a ball bearing. 
     Preferably, said conical roller thrust is arranged between an outer shoulder of said mobile plate and an inner shoulder of said variable-inclination plate. 
     Advantageously, said ball bearing is arranged between an outer shoulder of said mobile plate and an inner shoulder of said variable-inclination plate. 
     According to an embodiment, said mobile plate is driven by said drive shaft through a pin spherical joint. 
     According to one aspect, said 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, said inner surface comprises at least one groove or one female spline, and said outer surface comprises at least one crowned spline. 
     Advantageously, the device for forming a pin spherical joint is mounted on said drive shaft by means of a key or a splined shaft, and said mobile plate is mounted on said device by means of at least one groove cooperating with said at least one crowned (or domed) spline. 
     Preferably, said mobile plate comprises a partly spherical inner surface. According to an implementation of the invention, said barrel pump comprises a means for controlling the inclination of said variable-inclination plate. 
     Advantageously, said inclination control means comprises a worm drive system. 
     Preferably, said rods are connected to said mobile plate without friction pads. 
     Furthermore, the invention relates to the use of said barrel pump according to one of the above features for a drilling operation, in particular for injecting drilling mud into a wellbore. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       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: 
         FIG. 1 , already described, illustrates a stationary barrel pump according to the prior art, 
         FIG. 2 , already described, illustrates a rotary barrel pump according to the prior art, 
         FIG. 3  illustrates a barrel pump according to an embodiment of the invention, 
         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 
         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 
     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. 
     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 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,   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,   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   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.       

     The variable inclination of the variable-inclination plate allows to have a variable displacement of the pump, by modifying the stroke of the pistons. 
     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. 
     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). 
     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. 
     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. 
     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. 
     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. 
     The pin spherical joint allows to synchronize the rotation of the mobile plate and of the cylinder block (barrel). 
     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. 
     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. 
     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. 
     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). 
     This design of the device for forming a pin spherical joint provides high compactness, large angular displacement and simplicity of use. 
     Advantageously, the groove(s) and the spline(s) are parallel to the axis of revolution of the device. 
     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. 
     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. 
     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). 
     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). 
     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. 
     This design of the connection enables a pin spherical joint link providing high compactness, large angular displacement and simplicity of use. 
     To achieve the pin spherical joint link, the mobile plate can comprise a substantially spherical inner surface provided with female splines. 
     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. 
     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. 
     Alternatively to this embodiment of the pin spherical ball joint, the spherical joint link can be a ball joint bearing. 
     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. 
     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. 
     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. 
     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. 
     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. 
     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. 
       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 . 
     Drive shaft  5  also drives a mobile plate  2  by means of a pin spherical joint  9 . 
     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. 
     Mobile plate  2  is in pivot connection with respect to variable-inclination plate  7  about the axis of variable-inclination plate  7 . 
     Pump  1  comprises a piston  3  driven by a translational motion (reciprocating motion) within a compression chamber  4 . 
     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. 
       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. 
       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. 
     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 . 
     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 . 
     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 . 
       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 . 
     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. 
     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 3 /h.