Patent Description:
<FIG> illustrates a partial, cross-sectional view of a progressive cavity pump according to the prior art, also commonly referred to as an eccentric screw pump (collectively referred to herein as a progressive cavity pump without the intent to limit) <NUM>. Progressive cavity pumps <NUM> may include a helical rotor <NUM> (<FIG>) and a stator <NUM>.

The stator <NUM> may have a shell portion <NUM> within which is disposed an elastomeric material having internally molded cavities <NUM>. The rotor <NUM> may be rotatably located within the stator <NUM>. Generally speaking, the rotor <NUM> may be manufactured from a metal such as, for example, hardened steel, stainless steel, etc. The internal molded cavities <NUM> of the stator <NUM> may be formed by a synthetic or natural rubber such as, vulcanized elastomer. The elastomer may be formed by filling the space between the inner surface <NUM> of the shell portion <NUM> of the stator <NUM> and a jacket or form placed within the stator <NUM>.

In use, the rotor <NUM> seals tightly against the elastomeric stator <NUM> as it rotates, forming a set of tightly seal, fixed-size cavities. Rotation of the rotor <NUM> causes the cavities to move towards a discharge port resulting in movement of any material (e.g., liquid) inside of the cavities.

One problem generally associated with progressive cavity pumps is referred to as dry-running. During a dry-running event, friction between the rotor <NUM> and stator <NUM> causes the temperature at the internal surface of the stator <NUM> to quickly rise. When the operating temperature at the internal surface of the stator <NUM> exceeds its maximum permissible operating temperature, the elastomer can burn or otherwise degrade, causing a malfunction of the progressive cavity pump. That is, as the heat energy generated in the conveying elements (e.g., rotor <NUM> and stator <NUM>) of the progressive cavity pump is no longer being adequately dissipated, the elastomeric stator <NUM> can be thermally damaged within a short period resulting in failure of the progressive cavity pump, and causing unscheduled operating failures, downtimes and costly repairs to, for example, replace the stator <NUM>.

In view of this, progressive cavity pumps often incorporate a dry-running protection device. <FIG> shows one form of dry-running protection that is often used. A temperature monitoring system <NUM> can be employed to monitor the operating temperature in the elastomeric stator <NUM>. The temperature monitoring system <NUM> may protect against dry-running by monitoring the temperature of the elastomeric stator <NUM>, and when the system detects that the temperature of the elastomeric stator <NUM> has exceeded a predetermined threshold temperature, the temperature monitoring system <NUM> may transmit a signal to a control unit <NUM> to shut-off or otherwise control operation of the progressive cavity pump <NUM> in a manner that minimizes or eliminates the risk of thermal damage to the stator. The control unit <NUM> may be a digital, electronic control unit located in a switch cabinet. The control unit <NUM> may include a microprocessor, memory and one or more user interfaces so that an operator can set the predetermined threshold temperature for switching off the progressive cavity pump <NUM>. In addition, the control unit <NUM> may include a display for displaying the predetermined threshold temperature. The control unit <NUM> may be communicatively coupled to the temperature monitoring system <NUM> via a wire <NUM>. Alternatively, the control unit <NUM> may be wirelessly coupled to the temperature monitoring system <NUM>. Alternatively, the control unit may be internally located within the connection head of the temperature monitoring system <NUM>.

In use, the control unit <NUM> is arranged and configured to receive signals from the temperature monitoring system <NUM> and to determine when the operating temperature of the elastomeric stator portion has exceeded the predetermined threshold temperature. When the control unit <NUM> determines that the current operating temperature of the elastomeric stator portion is greater than or exceeds the predetermined threshold temperature, the control unit <NUM> may shut off operation of the progressive cavity pump <NUM>.

Referring to <FIG>, known temperature monitoring systems <NUM> may include a sleeve <NUM> and a temperature sensor <NUM>. The temperature monitoring system <NUM> may also include a ferrule <NUM>, a locking screw <NUM> and a connection head <NUM>. The connection head <NUM> may include electronic connections and devices for communicating with the external control unit <NUM>. Alternatively, the connection head <NUM> may include an internal control unit (not shown). The locking screw <NUM> may be used to secure the position of the sleeve <NUM>. The ferrule <NUM> may be coupled to the connection head <NUM> before rotatably coupling the connection head <NUM> in place.

Generally speaking, known temperature monitoring systems <NUM> may be coupled to progressive cavity pumps <NUM>, by forming a precisely positioned borehole <NUM> into the finished elastomeric stator <NUM>. The borehole <NUM> may extend completely through the elastomeric stator <NUM> into the delivery space of the stator <NUM> occupied by the rotor <NUM> or the borehole <NUM> may cease somewhere within the elastomeric stator <NUM>. The sleeve (e.g., metallic sleeve) <NUM> may then be inserted into the borehole <NUM>. A temperature sensor <NUM> may then be inserted into the sleeve <NUM>.

A screw pump with a built in temperature sensor is disclosed in <CIT>.

Some of the challenges faced by known temperature monitoring systems <NUM>, which rely on introducing the temperature sensor <NUM> into the sleeve <NUM>, include:.

In view of the foregoing, it would be desirable to provide a new and improved temperature monitoring system for use in a progressive cavity pump to protect against dry-running.

Disclosed herein is a progressive cavity pump having improved stator dry-running protection. More specifically, the present disclosure describes an improved monitoring system, for example, an improved temperature monitoring system, for use in a progressive cavity pump.

In one embodiment, the present disclosure is directed to a method for coupling a monitoring system (e.g., temperature monitoring system) to a progressive cavity pump. The method includes forming a borehole in a shell portion of a stator; inserting a sleeve into the borehole; forming an elastomeric portion of the stator such that the sleeve is vulcanized to the elastomeric portion of the stator; and inserting a sensor (e.g., temperature sensor) into the sleeve. Forming the elastomeric portion of the stator may include pouring an elastomer into the shell portion of the stator and vulcanizing the poured elastomer.

The borehole and sleeve may include corresponding threads so that inserting the sleeve into the borehole includes threading the sleeve into the borehole. The externally threaded surface may be pre-treated with a binder or primer.

In an alternate embodiment, the present disclosure is directed to a progressive cavity pump. The pump includes a stator including a shell portion and a molded elastomeric portion having internally molded cavities; a helical rotor rotatably located within the stator; and a monitoring system (e.g., temperature monitoring system) for measuring an operating parameter (e.g., operating temperature) of the elastomeric portion of the stator, the monitoring system including a sensor (e.g., temperature sensor). The monitoring system further includes a sleeve, the sleeve being vulcanized to the elastomeric portion of the stator, the sensor being slidably received within the sleeve.

The shell portion may include a borehole for receiving the sleeve. The sleeve may be inserted into the shell portion before vulcanizing the elastomeric material for forming the molded elastomeric portion of the stator.

The inner surface of the borehole and the external surface of the sleeve may include corresponding threads so that the sleeve may be threadably coupled to the borehole formed in the shell portion of the stator.

The borehole formed in the shell portion of the stator may be positioned at a predetermined location with respect to the elastomeric portion so that no portion of the sleeve is exposed to pumped media.

The vulcanized connection between the sleeve and the elastomeric portion may result in the sleeve forming an integral part of the stator.

The sensor (e.g., temperature sensor) may be configured to monitor an operating temperature of the elastomeric portion of the stator. The temperature sensor may be communicatively coupled to a control unit. The control unit being configured to receive signals from the temperature monitoring system and to determine when the operating temperature of the elastomeric portion of the stator has exceeded a predetermined threshold temperature. The control unit further being configured to control operation of the progressive cavity pump when the operating temperature of the elastomeric portion of the stator is determined to have exceeded the predetermined threshold temperature.

The temperature sensor or sleeve may include a pointed or spherical shaped tip.

The inner surface of the shell portion and an outer surface of the sleeve may be coated with a chemical binder system for enhancing a connection between the elastomeric portion, the shell portion and the sleeve.

By way of example, specific embodiments of the disclosed device will now be described, with reference to the accompanying drawings, in which:.

A device and method in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the device and method are shown. The disclosed device and method, however, may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the device and method to those skilled in the art. In the drawings, like numbers refer to like elements throughout.

The present disclosure describes an improved system and method for coupling a temperature monitoring system within a progressive cavity pump. More specifically, the present disclosure describes a temperature monitoring system and method wherein the sleeve element may be vulcanized to the elastomeric stator. Referring to <FIG>, an exemplary embodiment of a temperature monitoring system <NUM> according to the present disclosure is illustrated. As shown, the temperature monitoring system <NUM> may include a sleeve <NUM>, and a temperature sensor <NUM> disposed therein. The temperature monitoring system <NUM> may also include a clamp hose <NUM>, a clamping screw <NUM>, and a connection head <NUM>. The connection head <NUM> may include electronic connections and devices for communicating with the external control unit <NUM>. Alternatively, the connection head <NUM> may include an internal control unit (not shown). The clamp hose <NUM> and clamping screw <NUM> may be incorporated to assist with properly positioning of the temperature sensor <NUM> within the sleeve <NUM>. The temperature sensor <NUM> may be any temperature sensor now known or hereafter developed such as, for example, a Pt100 sensor, a thermocouple, a bimetal switch, etc..

Alternatively, the connection head <NUM>, the sleeve <NUM> and the temperature sensor <NUM> can be replaced with a temperature switch (not shown), which can monitor the temperature in the stator, and may control operation of the pump <NUM> when it determines that the temperature of the stator <NUM> exceeds a predetermined threshold. Such an arrangement can be entirely mechanical, and may eliminate associated electronic components. In use, as will be described in greater detail, the temperature switch is positioned inside of the sleeve <NUM> (e.g., similar to the temperature sensor).

The present disclosure achieves the desired results by inserting the sleeve <NUM> into the shell portion <NUM> of the stator <NUM> before vulcanizing the elastomeric stator. Generally speaking, the stator can be formed by incorporating a stator jacket within the shell portion <NUM> of the stator <NUM> and then filling the space between the stator jacket and the inner surface <NUM> of the shell portion <NUM> of the stator <NUM> with elastomeric material. The elastomeric material may then be vulcanized.

The shell portion <NUM> of the stator <NUM> may have any shape appropriate for such purposes. For example, the shell portion <NUM> of the stator <NUM> may be in the form of a tube. Alternatively, the shell portion <NUM> of the stator <NUM> may have, for example, a shape substantially matching the inner contour of the stator so that the shell portion may have a uniform wall thickness.

By inserting the sleeve <NUM> into the shell portion <NUM> of the stator <NUM> prior to forming and/or vulcanizing the elastomeric stator <NUM>, a number of advantages are achieved. For example, the sleeve <NUM> may now be an integral part of the stator <NUM>. That is, with the sleeve <NUM> positioned in the shell portion <NUM> of the stator <NUM>, when the elastomer is vulcanized, the sleeve <NUM> may be enclosed and bonded by the vulcanized elastomer, and preferably completely enclosed by the vulcanized elastomer. As a result, the sleeve <NUM> becomes a fixed and unchanging part of the stator <NUM>. As such, subsequent unscrewing of the sleeve <NUM> is no longer possible. Thus, subsequent undesirable movement of the sleeve <NUM> due to vibrations or incorrect operation is minimized or eliminated. The elastomeric stator <NUM> may be made from any appropriate elastomer including, for example, Butyl, EPDM, Perbunan, hydrogenated Perbunan, Alldur, Neoprene, Polyurthan, Silicon, Viton, Butadien, Hypalon, etc..

In addition, the disclosed arrangement and technique allows the sleeve <NUM> to be precisely and correctly located. Because the borehole <NUM> may be formed in the shell portion <NUM> of the stator at the manufacturing facility during initial construction of the progressive cavity pump <NUM>, the location of the sleeve <NUM> may be precisely and accurately controlled. In addition, the insertion depth of the sleeve <NUM>, which is optimally determined by the design of the progressive cavity pump <NUM>, may also be precisely determined and located. As a result, the risk that the sleeve <NUM> will extend completely through the elastomeric stator <NUM> and into contact with the rotor <NUM> or medium, as can occur with prior arrangements, is minimized or completely eliminated.

Moreover, by vulcanizing the sleeve <NUM> within the elastomeric material of the stator <NUM>, a tight elastomer-metal connection between the elastomeric stator <NUM> and the sleeve <NUM> can be provided, which, as will be appreciated, can maximize heat transfer between the elastomer and the sleeve (and hence the temperature sensor <NUM>). In addition, because the sleeve <NUM> will no longer be exposed directly to the pumped media, the sleeve <NUM> needn't be manufactured from a corrosion resistant material (e.g., stainless steel). For example, the sleeve <NUM> may be manufactured from a structural steel (e.g., S185, S235, S275, S355, E295, E235, E360, etc.), a quenching or tempering steel (e.g., C22, C45, C60, 42CrMo4, etc.), a stainless steel (e.g., <NUM>, <NUM>, <NUM>, SS316, etc.), etc..

In addition, the disclosed arrangement can minimize or eliminate leakage problems between the sleeve <NUM> and stator <NUM> because gaps between the sleeve <NUM> and the elastomer are minimized or eliminated. Moreover, the disclosed arrangement eliminates the need to drill the borehole through the elastomeric stator <NUM>, thus the interior contour of the stator <NUM> is not interrupted, which minimizes or eliminates any danger of the elastomer being damaged. Dynamic resilience of the elastomer is maintained throughout, even in the area between the end of the temperature sensor <NUM> and the inner contour of the stator <NUM>.

Referring to <FIG>, in an example not according to the invention, the temperature monitoring system <NUM>' may include a temperature sensor <NUM> that is adapted and configured to be inserted into the borehole <NUM> and thus into the stator <NUM> directly, without an intervening sleeve. In this manner, the temperature sensor <NUM>' can be vulcanized V directly into the elastomeric stator without the intervening sleeve.

Referring to <FIG>, according to one aspect of the present disclosure, an improved method <NUM> for coupling a temperature monitoring system to a progressive cavity pump is disclosed.

At <NUM>, the stator may be manufactured per known, standard processes except as disclosed herein. At <NUM>, a borehole is formed in the shell portion of the stator. The borehole may be threaded, which in one non-limiting exemplary embodiment is an M10 screw thread. Using standard manufacturing processes, the stator may be rotated so that the threaded borehole (e.g., M10 screw thread) may be easily and consistently positioned in the same position with respect to the mold. Thus, the sleeve may be consistently positioned in the region where the wall thickness of the elastomer is the greatest, after elastomer filling.

At <NUM>, a sleeve may be inserted into the borehole. The sleeve may include a corresponding outer thread (e.g., M10) for threadably engaging the threads of the borehole. According to the invention, the sleeve is inserted (e.g., threaded) into the shell portion of the stator until a protruding shoulder of the sleeve presses firmly against an outer surface of the shell portion. By positioning the protruding shoulder a predetermined distance from the tip of the sleeve, this may automatically ensure a consistent and accurate sleeve depth within the stator. In one embodiment, the external threads and the outer surface of the sleeve may be pre-treated with a binder or primer to enhance the connection between the sleeve and the elastomer upon vulcanization. The binder or primer may be any primer or binder appropriate for the application. For example, a <NUM>-layer system consisting of binder and primer, a <NUM>-layer system with a binder, a <NUM>-layer adhesion promoter, etc. In use, the binder or primer may be coated by spraying. In one embodiment, the metal surfaces of the shell portion of the stator and/or the sleeve should be degreased and sand blasted with a blasting agent. The layer of the binder or primer may include a defined thickness (e.g., min. ) to have a maximum bond.

At <NUM>, elastomer may be poured into the pump thus forming the molded elastomeric portion of the stator. For example, unvulcanized elastomer may be poured into the shell portion of the stator in-between the jacket of the stator and the inner surface of the shell portion. During this process, the sleeve (or the temperature sensor if no intervening sleeve is used) may be enclosed by the elastomer, and preferably completely enclosed by the elastomer. At this point, the sleeve along with the inner surface of the shell portion, are not yet vulcanized to the elastomeric stator.

Alternatively, it is envisioned that a plug screw may be used in the place of an externally threaded sleeve. In this embodiment, a suitable device such as, for example, a press, extruder, etc. can be used to press the unvulcanized elastomer. Thereafter, after the pouring of elastomer, the plug screw may be removed and replaced by a corresponding sleeve. This prevents the elastomer from mechanically deforming the sleeve during the filling process.

At <NUM>, the unvulcanized elastomer may be vulcanized. Generally speaking, vulcanization of an elastomer is a well-known chemical process for converting natural rubber or related polymers into more durable materials via the addition of sulfur or other equivalent curatives or accelerators. These additives modify the polymer by forming cross-links (bridges) between individual polymer chains. Vulcanization can be accomplished by any process now known or hereafter developed, including for example, via an oil bath vulcanization, a hot air vulcanization process, or via an automatic machine for stator manufacturing.

At <NUM>, the temperature sensor is inserted into the sleeve. Further assembly of the individual components of the temperature monitoring system may be carried out according to existing operating instructions.

In one embodiment, depending on the diameter of the stator, a corresponding sleeve size may be selected. In addition, as the sleeves are preferably sized so as not to contact the medium, the sleeve can be made from carbon steel or other non-corrosion resistant material.

In an alternate embodiment, while the present disclosure has been illustrated and described as vulcanizing, via a sleeve, a temperature sensor, the present disclosure should not be so limited. Rather, the present system and method may work to vulcanize, either directly or indirectly, other types of sensors as well including, for example, a pressure sensor, a vibration sensor, etc..

In one embodiment, the inner surface of the shell portion may be provided with or coated with a chemical binder system prior to filling with elastomer. As a result, an insoluble rubber-metal compound may be produced during the vulcanization process. Similarly, the sleeve may be provided or coated with a chemical binder system. As a result, an insoluble rubber-metal compound may be produced during the vulcanization process.

In one embodiment, the vulcanization process preferably takes place under pressure and temperature (e.g., oil bath, heating furnace, autoclave, etc.). In this case, due to the pretreatment, an inseparable connection is established between the vulcanized elastomer of the stator and the inner surface of the shell portion of the stator as well as with the outer surface (e.g., threaded surface) of the sleeve. Thus, the sleeve may now be completely vulcanized within the elastomer.

In one embodiment, the temperature sensor or sleeve may have a pointed or spherical shape. By providing a pointed or spherical shaped end, the wall thickness of the elastomer does not remain constant but rather may increasing towards the sides. This ensures that the elastomer has a sufficient flexibility in this region.

Claim 1:
A progressive cavity pump (<NUM>) comprising:
a stator (<NUM>) including a shell portion (<NUM>) and a molded elastomeric portion having internally molded cavities;
a helical rotor (<NUM>) rotatably located within the stator (<NUM>); and
a monitoring system (<NUM>) for measuring an operating parameter of the elastomeric portion of the stator (<NUM>), the monitoring system (<NUM>) including a sensor (<NUM>) and a sleeve (<NUM>), the sleeve (<NUM>) being vulcanized to the elastomeric portion of the stator (<NUM>), the sensor (<NUM>) being slidably received within the sleeve (<NUM>),
characterised by the fact that the sleeve (<NUM>) comprises a protruding shoulder at a predetermined distance of a tip of the sleeve (<NUM>).