Patent Description:
Mud motor stators and pumps are in some cases constructed of hard materials such as metal and sometimes softer materials faced on the metal for sealing purposes. The overall structure is a helical one with lobes extending toward an axis of the stator which makes them difficult to machine and impossible to adjust properties. Since adjustment can improve efficiency of mud motors, the art is always receptive to enhancements in manufacturing processes and functional characteristics of the resulting product. <CIT> discloses a stator for a progressive cavity pump or motor. <CIT>, discloses a stator for a helical gear device which is formed of a plurality of duplicate disks. <CIT> discloses a stator for an eccentric spiral pump. <CIT> discloses a segment for use in a mud motor or progressive cavity pump.

Disclosed herein is a mud motor stator or a pump. The mud motor stator or pump includes a tubular outer portion and a number of lobes extending radially inwardly from the tubular outer portion, at least one of which comprises a skeletal structure.

In one aspect, there is disclosed a method for producing a mud motor stator as claimed in claim <NUM>.

Also disclosed is a downhole system including a mud motor stator or a pump, the stator or pump being as defined in any prior embodiment including a tubular outer portion and a number of lobes extending radially inwardly from the tubular outer portion, at least one of which comprises a skeletal structure.

Referring to <FIG> and <FIG> simultaneously, stator <NUM> which may be used in a mud motor or pumps and made part of a downhole system includes a tubular outer portion <NUM> and a number of lobes <NUM>, which may be asymmetric, extending toward an axis of the stator <NUM>. Also visible is a sealing material <NUM> disposed radially inwardly of the stator body <NUM> and which may or may not be disposed symmetrically with the lobes <NUM>. In one embodiment, the sealing material on the seal side is thicker than it is on the load side. The exact positioning and construction of the lobes <NUM> and material <NUM> can dramatically affect the function and operation of the stator <NUM> in terms of sealing capability, vibration reduction, power output, mass, and longevity, among other things.

Weight, material cost, and properties such as resilience, compliance, sealing, load bearing, vibration resonant frequencies, etc. are all important characteristics of the function of a stator but heretofore have not been recognized as such and have not been addressed.

As can be seen in <FIG> and <FIG>, the lobes <NUM> are not configured as are those of the prior art (solid and sinuous) but rather are configured to provide a greater rigidity on the load side <NUM> of each stator lobe <NUM> versus the seal side <NUM> of each stator lobe <NUM>. Specifically, a skeletal structure <NUM> is constructed having, in one embodiment just a hollow <NUM> (<FIG>) of the lobe <NUM> and in another embodiment having a number of ribs <NUM> (<FIG>). Skeletal structure is defined herein as any configuration of solid portions and open spaces defined between the solid portions to exhibit a framework. The hollow <NUM> is bounded by an operating portion <NUM> of the lobe <NUM>. In the <FIG> embodiment, the ribs <NUM> extend from one point to another point inside the otherwise hollow space bounded by the operating portion <NUM> of the lobe <NUM>. As illustrated in <FIG>, the ribs <NUM> extend from the tubular portion <NUM> radially inwardly until they connect to the operating portion of the lobe <NUM>. Other reinforcing structure patterns are also contemplated. In some embodiments, the load side of the lobe <NUM> follows a contour that is close to the load surface of the lobe <NUM>. This makes the sealing material <NUM> thin at this side of the lobe but well supported for high load carrying capability while still providing a sealing function. Conversely, the contour at the sealing side of the lobes <NUM> is left largely unsupported by the skeletal structure <NUM>. In other embodiments, the lobes are more asymmetric and the sealing material <NUM> may have the same thickness throughout. See <FIG> for a schematic view of an asymmetric lobe pattern. The sealing material <NUM> often is constructed of rubber though other compounds including metal with adjusted material properties such as density, resilience, etc. is also contemplated herein. In addition, the configuration of the lobes <NUM> whether symmetric or asymmetric may be optimized to avoid the generation of resonant frequencies during use.

In the <FIG> iteration, the ribs <NUM>, (three shown but more or fewer contemplated) are oriented to be substantially normal to the surface of the load side <NUM> of the lobes <NUM>. This structurally provides great rigidity to the load side of lobe <NUM> while reducing weight over prior art configurations. As noted, it is contemplated to provide ribs or other structure or shapes in other configurations as well and one purpose of such is to adjust the compliance of the load side of the lobe <NUM> for applications that may benefit from such.

In <FIG>, there are no ribs at all but rather merely a hollow <NUM> within the lobe <NUM>. The sealing material <NUM> is however the same in the embodiment for purposes of comparison to the embodiment of <FIG> and therefore understanding of the concept.

In addition to the structural and weight characteristics of the structures disclosed and shown, it is also to be appreciated that the volume between the ribs <NUM> or the hollow <NUM> may be employed as a fluid conduit (conveyance and/or cooling)or a conductor conduit (for electric, hydraulic or optical line).

In addition to the overall shape and structure of the lobes <NUM> as noted above, it is also contemplated herein to change the surface condition on the lobes <NUM> and the internal surface <NUM> of the stator body <NUM>. Referring to <FIG> and <FIG>, the surface in some embodiments is randomly roughened, a diamond shaped pattern (<FIG>), wavy (<FIG>), having grooves <NUM> and/or bumps <NUM> (<FIG>), etc. for the purpose of increasing adhesion of the material <NUM> that will be disposed thereon as well as improving the function of the rubber injection process by increasing adhesion and reducing injection pressure and temperature.

The stator or pump <NUM> may be created by conventional manufacturing methods but would be laborious to achieve. Therefore the inventors hereof also note that additive manufacturing or 3D printing is highly suited to producing all of the features noted above with respect to the various alternate embodiments of a stator or pump disclosed herein. Each of the stator or pump embodiments may be created using one or more of selective laser melting, direct metal laser sintering, direct metal laser melting, selective laser sintering, electron beam manufacturing, direct laser deposition, cold gas processing, laser cladding, direct material deposition, ceramic additive manufacturing, ultrasonic welding, or binder jetting and subsequent sintering, for example in powder bed or nozzle feed or wire feed configurations. The material deposited is bonded together by welding, binding and sintering, etc. Additive manufacturing processes are known to the art and require no specific discussion in connection with this disclosure.

In each of the additive manufacturing processes noted above (or others functioning similarly) the complex shapes represented in the figures are easily created in the layer by layer or particle by particle approach of additive manufacturing processes. In addition to the overall shape as shown, AM also supports the other adjustments discussed above with respect to density, resilience, compliance, etc. (see above) of the material used to make the stator <NUM>, to wit: one of the operating parameters of the process may be modified to produce a material property in a location within the stator <NUM> that is different than that material property elsewhere in stator <NUM>. For example, the process of melting may be halted where an opening is to be located. Alternatively or additionally, the process may be altered to change the density of the base material in certain areas to cause a feature to be resilient or compliant.

In order to change properties as noted above, changes in one or more parameters of the additive manufacturing process used to create the material may be made. These changes include but are not limited to: varying the energy applied to the feed material by the energy source e.g. laser or electron beam (varying the energy source power including zero power, varying the energy source focus, varying the energy source scanning speed, varying the energy source line spacing) or varying the feed material itself may be employed. More specifically, with respect to energy applied, the energy source being employed, whether e.g. <NUM>, <NUM>, <NUM> W or any other energy source power, may be reduced in power at the selected location to reduce the melting of the powdered (or other type) feed material. Reduction in the amount of melt will change the density of the manufactured part in locations where melting was reduced or eliminated in the case of zero power (which will simply leave feed material unaltered, e.g. still powdered). Alternatively, one may change the energy source focus, which also changes the energy applied to the feed material. Further, another alternative is to change the laser energy source scanning speed to alter the energy imparted to the feed material in certain locations. Varying the line spacing of the scanning energy source results in altered porosity or density of the stator <NUM> in locations where line spacing diverges from otherwise normal line spacing for the part. Causing line spacing to become larger will result in a lower density and greater porosity of the stator <NUM> in those areas in which line spacing is increased. Each of these will change the degree of fusing of the feed material at that location with the surrounding particles of feed material and hence change the density or porosity of the final manufactured product at that location. It is to be understood that other material properties such as thermal conductivity, electrical conductivity, magnetism, etc. may also be altered using processes that change feed materials.

While reducing energy applied is discussed above it is also important to note that energy increase can also be useful in achieving specific material properties desired in the Stator <NUM>. Increasing energy source power will tend to vaporize the powdered metal thereby leaving porosity.

Referring back to the other identified method for altering the material properties in a stator that does not rely upon energy supplied, the feed material itself may be altered. This may be accomplished by changing the material supplied at a feed head for powdered feed material or by changing the wire composition in a wire feed process. Processes capable of additive manufacturing with different materials include cold gas processes, energy source cladding or direct laser deposition, for example.

Materials contemplated for construction of the stator or pump include fine particles of or a wire including metal and/or metal alloy material and may optionally further include plastic, ceramic, and/or organic material. More specifically, material may include, for example, cobalt, nickel, copper, chromium, aluminum, iron, steel, stainless steel, titanium, tungsten, or alloys and mixtures thereof, magnetically responsive materials, polyetheretherketone (PEEKTM), carbon-based materials (e.g., graphite, graphene, diamond, etc.), and/or glass. Specific, nonlimiting examples, of materials that may be employed include PA12-MD(Al), PA12-CF, PA11, 18Mar <NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM> (<NUM>), Alloy <NUM>, Alloy <NUM>, CoCrMo,UNS R31538, Ti6AI4V andAlSi10Mg, Alloy 945x, <NUM>-<NUM>/<NUM>, Alloy <NUM>, CrMnMoN-steel, CoCrAlloys (STELLITE®), CoNiAlloy, MP35 or equivalent, <NUM>, <NUM>, WC-Ni, WC-Co, and/or W. Another example of material employed is fine particles of metal or metal alloy material intermixed with fine particles of ceramic material, the material being configured to form a metallic-ceramic composite material (e.g., a cermet), in which ceramic particles are embedded within a metal or metal alloy matrix, upon melting and coalescence of the particles of metal and/or metal alloy material. More specifically, these materials may be fine particles of cobalt, nickel, iron, steel, stainless steel, or alloys and mixtures thereof intermixed with fine particles of tungsten carbide, titanium carbide, tantalum carbide, molybdenum carbide, and other metal-carbide ceramic materials.

Referring to <FIG>, a downhole system is schematically illustrated having a stator or pump as disclosed herein disposed therein. The system comprises a string <NUM> disposed in a borehole <NUM>, the string including a stator or pump <NUM>.

Set forth below is an embodiment of the foregoing disclosure:.

A method for producing a mud motor stator or a pump comprising: creating a computer model of a stator or pump; loading the model into an additive manufacturing apparatus; and operating the additive manufacturing apparatus to produce a physical replica of the model.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should further be noted that the terms "first," "second," and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier "about" used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity).

Claim 1:
A method for producing a mud motor stator (<NUM>) comprising:
creating a computer model of the stator, the stator having a design shape comprising a number of lobes (<NUM>), at least one of which comprises a skeletal structure (<NUM>), wherein the skeletal structure (<NUM>) is asymmetric and has a load side (<NUM>) and a seal side (<NUM>), the skeletal structure configured so as to provide a greater rigidity on the load side (<NUM>) versus the seal side (<NUM>);
loading the computer model into an additive manufacturing apparatus; and
operating the additive manufacturing apparatus to use the model to produce a physical replica of the model by, as part of an additive manufacturing process, placing material and bonding the material together in a pattern dictated by the design shape of the stator.