Rotary positive displacement pump

Abstract

A rotary positive displacement pump 1 for pumping a fluid product includes a transmission housing 2 having front and rear sides and gears 6, 7, providing rotational support for drive shafts 4, 5, with first and second drive shafts 4, 5 rotating in opposite directions. The pump 1 further includes a rotor casing 15 connected to the front side 13 of the transmission housing and having an axial rear wall 20, an axial front wall 22 and a circumferential side wall 21. The rotor casing 15 houses a first rotor 23 and a second rotor 24. The fluid product enters the internal pumping cavity via a rotor casing inlet 30. The rotor casing 15 includes first and second sealing arrangements to prevent the fluid product from leaking out, and the pump 1 includes heating devices 51, 52 to heat the fluid product within the rotor casing, the first and second sealing arrangements / rotor casing 15.

Description

[Technical field]

[0001] The present disclosure relates to a rotary positive displacement pump. The present disclosure further relates to a set of rotary positive displacement pumps and a method for heating a rotor casing of a rotary positive displacement pump and / or a fluid product therein.

[0002] Although the rotary positive displacement pumps of the present disclosure will be described primarily in terms of circumferential piston pumps, pumps of the present disclosure are not limited to this particular type of pump, but may alternatively be implemented in terms of rotary lobe pumps, gear pumps, etc. [Background technology]

[0003] Rotary positive displacement pumps are typically used to transport relatively high viscosity fluid products for food, beverage, and hygiene applications, among others. Some of these high viscosity fluid products may be in a solid phase at temperatures of about 20 degrees Celsius and therefore may require heating to be transportable by the pump at room temperature. The pump itself may be equipped with a product heating arrangement to maintain the fluid product viscosity below a certain level and to reduce the risk of fluid product crystallization or solidification, or to shift solidified fluid products in the pump fluid from a solid phase to a fluid phase to enable operation of the pump.

[0004] However, despite activity in this field, there remains a demand for further improved pump designs in terms of, for example, compactness, cost-effectiveness, and flexibility. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present disclosure to provide a rotary positive displacement pump and a method for heating a rotor casing of a rotary positive displacement pump and / or a fluid product therein, with improved performance in terms of compactness, cost-effectiveness and flexibility. This object is at least partly achieved by the features of the independent claims. The dependent claims contain further developments of said pump and method. [Means for solving the problem]

[0006] According to a first aspect of the disclosure, a rotary positive displacement pump for pumping a fluid product is provided, the pump having a forward side and a rear side. The pump includes a transmission housing providing rotational support for first and second parallel, axially extending drive shafts having gears in constant mesh such that the first and second drive shafts are arranged to rotate in opposite directions. The pump further includes a rotor casing connected to the forward side of the transmission housing and having an axial rear wall, an axial forward wall, and a circumferential side wall that collectively define a stationary internal pumping cavity. The rotor casing houses a first rotor drivingly connected to the first drive shaft and a second rotor drivingly connected to the second drive shaft. The first and second rotors are configured to rotate in opposite directions and to interact to provide a positive pumping effect on a fluid product, the fluid product entering the pumping cavity through the rotor casing inlet and exiting the pumping cavity through the rotor casing outlet. The rotor casing further includes first and second sealing arrangements configured to prevent leakage of the fluid product from the stationary pumping cavity toward the rear side of the rotor casing along the first and second drive shafts, respectively. The pump further includes a heating device removably fastened to the axial rear wall of the rotor casing and configured to heat the rotor casing, the first and second sealing arrangements, and / or any fluid product within the rotor casing.

[0007] According to a second aspect of the disclosure, a method is provided for heating a rotor casing and / or a fluid product within a rotor casing of a rotary positive displacement pump having a forward side and a rear side. The rotary positive displacement pump includes a transmission housing and a rotor casing, the transmission housing providing rotational support for first and second parallel, axially extending drive shafts having gears in constant mesh such that the first and second drive shafts are arranged to rotate in opposite directions, the rotor casing is connected to the forward side of the transmission housing and has an axial rear wall, an axial forward wall, and circumferential side walls that collectively define a stationary internal pumping cavity, the rotor casing including a first rotor drivingly connected to the first drive shaft and a second drive shaft. and a second rotor drivingly connected to the rotor casing, the first and second rotors configured to rotate in opposite directions and to interact to provide a positive pumping effect on a fluid product, the fluid product entering the pumping cavity through the rotor casing inlet and exiting the pumping cavity through the rotor casing outlet, the rotor casing further including first and second sealing arrangements configured to prevent leakage of the fluid product from the stationary pumping cavity along the first and second shafts, respectively, towards a rear side of the rotor casing. The method includes removably fastening a heating device to an axial rear wall of the rotor casing and activating the heating device to heat the rotor casing, the first and second sealing arrangements, and / or any fluid product within the rotor casing.

[0008] Alternatively, according to a second aspect of the present disclosure, a method is provided for heating a rotor casing and / or a fluid product within a rotor casing of a rotary positive displacement pump having a forward side and a rearward side, the method including the steps of providing a rotary positive displacement pump having a transmission housing and a rotor casing, the transmission housing providing rotational support for first and second parallel, axially extending drive shafts having gears in constant mesh such that the first and second drive shafts are arranged to rotate in opposite directions, the rotor casing connected to the forward side of the transmission housing and having an axial rear wall, an axial forward wall, and circumferential side walls that collectively define a stationary internal pumping cavity, the rotor casing including a first rotor drivingly connected to the first drive shaft and a second rotor casing arranged to rotate in opposite directions ... and a second rotor drivingly connected to the drive shaft of the rotor casing, the first and second rotors configured to rotate in opposite directions and to interact to provide a positive pumping effect on a fluid product, the fluid product entering the pumping cavity through the rotor casing inlet and exiting the pumping cavity through the rotor casing outlet, the rotor casing further including first and second sealing arrangements configured to prevent leakage of the fluid product from the stationary pumping cavity along the first and second drive shafts, respectively, towards the rear side of the rotor casing. The method further includes the steps of removably fastening a heating device to an axial rear wall of the rotor casing and activating the heating device to heat the rotor casing, the first and second sealing arrangements, and / or any fluid product within the rotor casing.

[0009] Prior art solutions for heating the rotor casing and / or the fluid product therein included, for example, the attachment of a heating jacket to the front and / or circumferential surfaces of the rotary casing, or the use of a dedicated front cover and / or rotary casing with internal heating fluid channels. However, these prior art solutions resulted in an increase in the total external size of the pump installation or an increase in costs due to the requirement of developing a dedicated front cover or rotary casing. Moreover, locating the heating source on the front cover or circumferential wall of the rotary casing (i.e. relatively far from the first and second sealing arrangements of the rotary casing) meant that the rotor casing in the areas near the first and second sealing arrangements was heated relatively slowly, increasing the risk of damage to the first and second sealing arrangements due to still solidified product in the vicinity of said seals when starting the rotation of the rotor for the operation of the pump.

[0010] These problems and disadvantages of prior art solutions are largely overcome or at least reduced by mounting the heating device on the axial rear wall of the rotor casing. Among other things, by having the heating device manufactured as a separate part that can (or can not) be mounted on the rear wall of the rotor casing means that fewer individual variations of the rotor casing have to be developed and maintained, thereby providing improved product cost efficiency.

[0011] Because the heating device is removably fastened to the axial rear wall of the rotor casing, the heating device can be provided as an option. Because the heating device is removably fastened, the heating device can be mounted on an existing pump. If the application and media require heating, the heating device can be delivered with a new pump. If the application and media are changed to require heating, the heating device can be supplied and mounted on an existing pump as a retrofit. A special rotor casing is not required to provide a pump with a heating device. It is also not necessary to provide all pumps with a heating device, whether heating is required or not. Only one type of rotor casing is required, whether the pump is to be provided with a heating device or not.

[0012] Moreover, in mounting the heating device on the axial rear wall of the rotor casing (i.e., in the space between the rotor casing and the transmission casing), the outer dimensions of the pump may not be significantly affected by the heating device. In other words, the outer dimensions of the pump in the horizontal and vertical directions may remain almost or completely the same whether the heating device is installed or not. Thereby, existing installations can be easily and cost-effectively supplemented with the heating device without requiring additional modifications of the pumping equipment, thereby allowing for easy changes of fluid products or fluid product operating conditions, for example, when shifting to a fluid product requiring heating.

[0013] In addition, due to the installation of the heating device at the rear wall of the rotary casing, the heating device is located relatively close to the first and second sealing arrangements of the rotary casing. As a result, the rotor casing (especially the areas close to the first and second sealing arrangements) and the first and second sealing arrangements can be heated relatively quickly to increase the likelihood that the product in the vicinity of the seals is actually in a fluid form when the rotor starts to rotate for the operation of the pump. In other words, the proximity of the heating device at the rear wall of the rotary casing means that the risk of damage to the first and second sealing arrangements due to the still solidified product in the vicinity of the seals can be reduced when the rotor starts to rotate for the operation of the pump.

[0014] Consequently, removably mounting a heating device to the axial rear wall of the rotor casing for heating the rotor casing in an area close to the first and second sealing structures and / or any fluid product within the rotor casing provides improved performance in terms of compactness, cost efficiency and flexibility.

[0015] Further advantages are realised by implementing one or several of the features of the dependent claims.

[0016] The heating device can be removably fastened, such that the heating device is attachable, removable and reattachable. More precisely, the heating device can be attachable to the axial rear wall of the rotor casing, removable from the axial rear wall of the rotor casing and reattachable to the axial rear wall of the rotor casing. The heating device can be removably fastened to the axial rear wall of the rotor casing. The heating device can be reattachably fastened to the axial rear wall of the rotor casing. Thus, the heating device can be removably and reattachably fastened to the axial rear wall of the rotor casing.

[0017] The heating device can be releasably fastened such that the heating device is releasable, more precisely, the heating device can be releasable from the axial rear wall of the rotor casing.

[0018] The heating device can be removably fastened by a fastener. The heating device can be removably fastened by a releasable fastener (i.e. a fastener that releases the heating device or, more precisely, a fastener that can release the heating device). The fastener can be removable. The fastener can be a threaded fastener. Alternatively, the fastener can be a clamping member (e.g., a bracket, etc.).

[0019] The heating device can be a separate part. The heating device can be a separate part that is removably fastened to the axial rear wall of the rotor casing. The heating device can be separate from the rotor casing. The heating device can be a separate part that is separate from the rotor casing. The heating device can be a separate part relative to the rotor casing. The heating device can be separable from the rotor casing. The heating device can be a separate part that is separable from the rotor casing.

[0020] In some exemplary embodiments, the heating device is a heating casing having an internal fluid heating chamber, a fluid inlet, and a fluid outlet, the internal fluid heating chamber being fluidly connected to the fluid inlet and fluid outlet, whereby a heat transfer fluid can be used to heat and / or cool the rotor casing.

[0021] In some exemplary embodiments, the interior fluid heating chamber is defined in part by the heater casing and in part by the aft wall of the rotor casing, which allows for direct contact of the heat transfer fluid with the rotor casing for improved heating and / or cooling efficiency.

[0022] In some exemplary embodiments, the heating casing has an elongated channel formed in a surface of the heating casing, the elongated channel facing toward the axial aft wall of the rotor casing, and the elongated interior surface of the elongated channel and the surface of the aft wall collectively defining an interior fluid heating chamber, which allows for direct contact of the heat transfer fluid with the rotor casing for improved heating and / or cooling efficiency, and the elongated channel ensures a relatively large contact area for the heat transfer fluid.

[0023] In some exemplary embodiments, the elongated channel is formed in a flat exterior surface of the heater casing, the flat exterior surface surrounding the channel being in contact with and pressing against a corresponding flat surface of the rear wall of the rotor casing, whereby sealing of the elongated channel is simplified due to the planar contact surfaces.

[0024] In some exemplary embodiments, the elongated channels are machined into a flat exterior surface of the heating casing, or the elongated channels are formed into a flat exterior surface of the heating casing in conjunction with casting the heating casing, which allows for cost-efficient manufacturing of the heating casing.

[0025] In some exemplary embodiments, the elongated channels extend across at least 50% (specifically at least 75%) of the total length of the heating casing in a direction perpendicular to the pump axis, such that a relatively large surface area of ​​the heating casing can be used to provide direct contact between the heat transfer fluid and the rotor casing.

[0026] In some exemplary embodiments, the elongated channel has a length of about 5-30 cm, and the main part of the elongated channel has a depth of about 5-30 mm and a width of about 5-30 mm. This ensures that the heating channel is not too small, since this would reduce the heat transfer efficiency.

[0027] In some exemplary embodiments, the elongated channel follows a curved path from the fluid inlet to the fluid outlet, the curved path curving around the cylindrical outer surface of the first and / or second drive shaft, which allows the heating device to be positioned relatively close to a larger area of ​​the rotor casing that supports the sealing arrangement.

[0028] In some exemplary embodiments, the heating casing has a seal disposed on a flat surface of the heating casing and extending around the elongated channel to prevent leakage of the heating fluid at the contact area between the heating casing and the rotor casing. The provision of a seal on the flat surface allows for improved leak resistance, the use of less complex seals, and more cost-efficient manufacture of any associated sealing grooves.

[0029] In some exemplary embodiments, the seal is an O-ring seal, which is disposed in a circumferential sealing groove provided in a flat surface of the heated casing, thereby providing a cost-effective design, both in terms of cost for the seal and manufacturing of the sealing groove.

[0030] In some exemplary embodiments, the heating device has a flat surface that presses against a corresponding flat surface of the rear wall of the rotor casing, allowing for cost-efficient manufacturing and a relatively large contact surface for efficient heat transfer.

[0031] In some exemplary embodiments, the heating device is pressed against the rear wall of the rotor casing by a threaded fastener that engages into a threaded hole located in the rear wall of the rotor casing. This design provides a cost-effective solution that allows for easy installation and removal of the heating device from the rotor casing.

[0032] In some exemplary embodiments, the heating device has a curved surface that curves around and follows at least a portion of the cylindrical outer surface of the first and / or second drive shaft, allowing the heating device to be positioned relatively close to a larger area of ​​the rotor casing that supports the sealing arrangement.

[0033] In some exemplary embodiments, the contact surface between the heating device and the axial rear wall of the rotor casing, as viewed axially of the pump, extends over at least ⅓ of the circumference of the first or second drive shaft, which allows the heating device to be positioned relatively close to a larger area of ​​the rotor casing that supports the sealing arrangement.

[0034] In some exemplary embodiments, the pump has an axial direction parallel to the first and second drive shafts and a first lateral direction, the first lateral direction extending perpendicular to the axial direction through the center of rotation of the first and second drive shafts, the pump includes a first heating device disposed outboard of the first drive shaft in the first lateral direction, and the pump includes a second heating device disposed outboard of the second drive shaft in the first lateral direction. The area outboard of the first and second drive shafts is often less used for bearing support and / or rotor casing fluid product inlet / outlet, thereby providing more space for the heating device.

[0035] In some exemplary embodiments, the first heating device substantially or completely surrounds the first drive shaft and the second heating device substantially or completely surrounds the second drive shaft, which allows the first and second heating devices to be positioned relatively close to a larger area of ​​the rotor casing that supports the sealing arrangement.

[0036] In some exemplary embodiments, the pump includes a single heating device removably fastened to the axial rear wall of the rotor casing, the single heating device surrounding both the first and second drive shafts. A single heating device generally allows for a more cost-efficient design since only a single component is required to be manufactured, handled, and installed.

[0037] In some exemplary embodiments, the heating device does not affect the external pump dimensions, which is advantageous in terms of a more flexible use of the pump, since heating and / or cooling features can be added to the pump at a later stage without requiring additional modifications of the pump installation.

[0038] In some exemplary embodiments, the transmission housing includes first and second axially protruding mounting portions facing the rotor casing and positioned on either side of the drive shaft, the rotor casing being connected to a front side of the transmission housing via the first and second axially protruding mounting portions, such that an intermediate space is provided between the transmission housing and the rotor casing, and the heating device is disposed in said intermediate space, which allows good access to the intermediate space for visual inspection of the heating device and / or for connection of heat transfer fluid supply and return piping to the heating device.

[0039] In some exemplary embodiments, the rear wall of the rotor casing has a recess defined by a flat surface and a radial surface, the flat surface being perpendicular to the axial direction of the pump and facing towards the rear side of the pump, the radial surface facing in a direction perpendicular to said axial direction, and the heating device having a flat surface pressing against the flat surface of the recess and a radial surface facing the radial surface of the recess. The recess not only allows for a less protruding heating device, but also allows for improved heating efficiency due to heating of the rotary casing in both the axial and radial directions.

[0040] The axial direction of the pump in this specification refers to a direction parallel to the first and second drive shafts.

[0041] The direction perpendicular to the axial direction may include, for example, a first lateral direction or a second lateral direction, or any other direction perpendicular to the axial direction, where the first lateral direction extends perpendicular to the axial direction through the centers of rotation of the first and second drive shafts, and the second lateral direction is perpendicular to both the axial direction and the first lateral direction.

[0042] In certain exemplary embodiments, the rotor casing has a first cylindrical rotor case hub and a second cylindrical rotor case hub, each extending from an axial rear wall of the rotor casing, a stationary internal pumping cavity defined by the axial rear wall, the circumferential side walls, the forward wall, and the first and second cylindrical rotor case hubs, the first cylindrical rotor case hub receiving a first drive shaft therein and the second cylindrical rotor case hub receiving a second drive shaft therein, the first sealing arrangement being at least partially positioned within an annular space defined by an outer surface of the first drive shaft and an inner surface of the first hub, and the second sealing arrangement being at least partially positioned within an annular space defined by an outer surface of the second drive shaft and an inner surface of the second hub. The first and second hubs can act as good thermal conductors for heating the areas of the first and second sealing structures, and by positioning a heating device relatively close to the first and second hubs at the rear wall of the rotor casing, efficient heating of the areas of the sealing structures can be achieved.

[0043] The present disclosure also relates to a set of rotary positive displacement pumps, the set including a first rotary positive displacement pump as described above having a first displacement volume per revolution and a second rotary positive displacement pump as described above having a second displacement volume per revolution greater than the first displacement volume per revolution. Both the first and second rotary positive displacement pumps are configured with identical heating devices fastened to the axial rear wall of the rotor casing. This provides a more cost-efficient solution since fewer individual components have to be designed, handled and maintained.

[0044] In certain exemplary embodiments, the method includes deactivating the heating device to terminate heating and removing the heating device from the axial aft wall of the rotor casing.

[0045] In some exemplary embodiments, releasably fastening the heating device to the axially aft wall of the rotor casing includes attaching the heating device to the axially aft wall of the rotor casing. Thus, in some exemplary embodiments, the method includes attaching the heating device to the axially aft wall of the rotor casing prior to activating the heating device. In some exemplary embodiments, the method includes deactivating the heating device to terminate heating and removing the heating device from the axially aft wall of the rotor casing. In some exemplary embodiments, the method includes reattaching the heating device to the axially aft wall of the rotor casing and reactivating heating.

[0046] In certain exemplary embodiments of the method, the heating device is releasably fastened to the axially aft wall of the rotor casing by a fastener (eg, a release fastener, etc.).

[0047] Further features and advantages of the present invention will become apparent upon review of the appended claims and the following description. Those skilled in the art will recognize that different features of the present disclosure can be combined to produce embodiments other than those explicitly described above and below without departing from the scope of the present disclosure.

[0048] A pump according to the present disclosure will be described in detail below with reference to the accompanying drawings. [Brief description of the drawings]

[0049] [Figure 1] FIG. 2 illustrates a schematic side view of an exemplary embodiment of a pump. [Diagram 2] FIG. 2 illustrates a schematic front view of an exemplary embodiment of a pump. [Diagram 3] FIG. 2 illustrates a schematic perspective view of a rotor casing aft portion according to an exemplary embodiment of a pump; [Figure 4] FIG. 2 shows a schematic perspective view of an exemplary embodiment of a rotor of a pump; [Diagram 5] 2A-2D illustrate diagrammatically the principle of pumping action according to an exemplary embodiment of a pump; [Figure 6] FIG. 2 illustrates a schematic side view of an exemplary embodiment of a pump. [Figure 7] FIG. 2 shows a schematic cross-section of a side view of an exemplary embodiment of a pump. [Figure 8] FIG. 2 illustrates a perspective view of a rotor casing according to an exemplary embodiment of a pump; [Figure 9] FIG. 2 illustrates a schematic side view of a rotor casing according to an exemplary embodiment of a pump; [Figure 10] FIG. 2 shows a schematic perspective view of a transmission housing according to an exemplary embodiment of the pump; [Figure 11] FIG. 2 shows a schematic side view of a heating device according to an exemplary embodiment of a pump; [Figure 12A]FIG. 2 shows a schematic cross-section of the heating device along the section line AA. [Figure 12B] FIG. 2 is a schematic cross-sectional view of the heating device taken along the section line BB. [Figure 13] 1A-1D show schematic diagrams of some alternative designs of the heating device of the pump; [Figure 14] 1A-1D show schematic diagrams of some alternative designs of the heating device of the pump; [Figure 15] 1A-1D show schematic diagrams of some alternative designs of the heating device of the pump; [Figure 16] 1A-1D are schematic diagrams illustrating some alternative designs for the rotor casing of the pump. [Figure 17] 1A-1D are schematic diagrams illustrating some alternative designs for the rotor casing of the pump. [Figure 18] 1A-1D are schematic diagrams illustrating some alternative designs for the rotor casing of the pump. [Figure 19] FIG. 2 shows a schematic diagram of two alternative designs for the rotor of the pump. [Figure 20] FIG. 2 shows a schematic diagram of two alternative designs for the rotor of the pump. [Figure 21] FIG. 4 is a schematic cross-sectional view of a rotor casing according to another embodiment. [Figure 22] FIG. 1 shows a schematic diagram of the basic steps of a method for heating a rotor casing of a rotary positive displacement pump and / or a fluid product therein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Various aspects of the present disclosure will be described below in conjunction with the accompanying drawings, in order to illustrate, and not limit, the disclosure, where like designations refer to like elements, and variations of the described aspects are not limited to the specifically shown embodiments, but may be applicable to other variations of the disclosure.

[0051] 1 shows a schematic side view of a first exemplary embodiment of a rotary positive displacement pump 1 for pumping a fluid product according to the present disclosure. The pump 1 has a transmission housing 2 which includes a rotary support 3 for first and second parallel drive shafts 4, 5 which extend in an axial direction 10 of the pump 1. The rotary support 3 can be provided, for example, in the form of a set of annular rolling bearings, each of which surrounds one of the first and second drive shafts 4, 5 and is fastened to the transmission housing 2.

[0052] The first axially extending drive shaft 4 carries a first gear 6, and the second axially extending drive shaft 5 carries a second gear 7. The first and second gears 6, 7 (i.e. gear wheels) are arranged in constant meshing condition, meaning that they are in constant gear engagement with each other. Moreover, since the first and second gears 6, 7 are in direct engagement with each other, they rotate in opposite directions.

[0053] The transmission housing 2 has a first length in an axial direction 10, a second length in a first lateral direction 11 perpendicular to the axial direction 10, and a third length in a second lateral direction 12 perpendicular to both the axial direction 10 and the first lateral direction 11. The transmission housing further has a front side 13 and a rear side 14, as viewed in the axial direction 10.

[0054] An end portion 9 of one of the first and second drive shafts 4, 5 (e.g., the first drive shaft 4) may extend out through a wall of the transmission housing 2 at a rear side thereof for rotational connection with a source of rotational torque (e.g., a motor) to power the pump 1.

[0055] The transmission housing 2 may be made from a metal (such as, for example, stainless steel, cast iron, steel, or an aluminum alloy) and the first and second drive shafts 4, 5 may be made from steel.

[0056] The transmission housing 2 may additionally include a support structure 8 to allow attachment of the transmission housing 2 to an external support surface, for example by threaded bolts or other types of fasteners. The transmission housing may be made in one piece or may be composed of multiple sub-parts.

[0057] In the exemplary embodiment of the pump illustrated in Figure 1, the pump 1 further includes a rotor casing 15 that is connected to the transmission housing 2 at a front side 13 thereof. The rotor casing 15, which is made, for example, from stainless steel, can be removably fastened to the front side 13 of the transmission housing 2 via a suitable fastening arrangement. For example, the rotor casing 15 can be clamped against the front side 13 of the transmission housing 2 by a number of threaded bolts or nuts 16 or similar threaded members.

[0058] The assembled pump 1, including the transmission housing 2 and rotor casing 15, has a front side 17 and a rear side 18, and a front view of the pump 1 of FIG. 1 is shown diagrammatically in FIG. 2, with first and second rotors 23, 24 positioned within the rotor casing 15 shown in dotted lines.

[0059] As can be seen in FIG. 2, a number of threaded bolts or nuts 16 used to clamp the rotor casing 15 may extend entirely through the rotor casing 15 and may be visible from the front side 17 of the pump 1.

[0060] In the exemplary embodiment of Figures 1 and 2, rotor casing 15 includes an axial rear wall 20, a circumferential side wall 21, and an axial forward wall 22, which collectively define a closed, stationary internal pumping cavity.

[0061] The rotor casing 15 houses the first and second rotors 23, 24 positioned within the internal pumping cavity, so that the rotor casing 15 is openable to allow access to the internal pumping cavity. In the exemplary embodiment of Figures 1 and 2, this access is made possible by making the rotor casing 15 in two parts: a rotor casing aft portion 25 including the axial rear wall 20 and the circumferential side wall 21 of the rotor casing 15, and a separate forward cover 26 acting as the axial forward wall 22 of the rotor casing 15, the removable forward cover 26 being removably fastened to the rotor casing aft portion 25 by a suitable mounting arrangement.

[0062] A schematic 3D view of an exemplary embodiment of rotor casing aft section 25 according to the present disclosure is provided in FIG. 3 as viewed partially from the forward side of rotor casing aft section 25.

[0063] The removable front cover 26 may be clamped to the rotor casing aft portion 25 by the same threaded bolts or nuts 16 used to clamp the rotor casing 15 to the front side 13 of the transmission housing 2. Alternatively, a separate mounting arrangement may be provided to attach the front cover 26 to the rotor casing aft portion 25.

[0064] In the exemplary embodiment of Figures 1-3, the rotor casing 15 further includes a product fluid inlet opening 30 for allowing a product fluid to enter the internal pumping cavity (e.g., be sucked into the internal pumping cavity) and a product fluid outlet opening 31 for allowing a product fluid to exit the internal pumping cavity (e.g., be pumped out of the internal pumping cavity).

[0065] As mentioned above, the rotor casing 15 further houses the first and second rotors configured to generate the pumping functionality of the pump. The first rotor 23 is rotatably fastened to a forward end of the first drive shaft 4, and the second rotor 24 is rotatably fastened to a forward end of the second drive shaft 5. As a result, the first and second rotors 23, 24 are configured to rotate in opposite directions to one another, as illustrated by the arrows in FIG. 5.

[0066] Exemplary embodiments of the first and second rotors 23, 24 (which may have substantially identical designs) are illustrated diagrammatically in Figures 1 and 2, and a 3D view of an exemplary embodiment of one of the first and second rotors 23, 24, as partially seen from the rear side, is provided in Figure 4.

[0067] Each of the first and second rotors 23, 24 has at least one (and preferably a plurality of) rotor wings 32 and a rotor drive element 33 configured to be torque proof mounted on a rotor seat of the associated drive shaft 4, 5.

[0068] The rotor drive element 33 of each rotor 23, 24 may be substantially disk- or sleeve-shaped and includes a central hole or recess 44 for mounting onto the associated drive shaft 4, 5. The hole or recess 44 may be defined by a cylindrical mounting surface 48 having splines 45, or may be defined by a non-circular mounting surface to allow non-rotatable mounting of the rotor onto the rotor seat of the associated drive shaft 4, 5.

[0069] 5, in this exemplary embodiment of the pump 1, the first and second rotors 23, 24 are configured to rotate in opposite directions at the same rotational speed during operation of the pump 2. The first and second rotors 23, 24 are configured to define a pumping volume in a space 35 restricted by adjacent rotor wings of the same rotor and the walls 20, 21, 22 of the internal pumping cavity. Moreover, during rotation of the first and second rotors 23, 24, the product fluid is configured to be transported from the product fluid inlet opening 30 along the outside of the respective rotors 23, 24 to the product fluid outlet opening 31 (illustrated by the arrows in FIG. 5).

[0070] In particular, as the rotor wings (pistons) 32 rotate around the periphery of the pumping cavity, they continuously create a partial vacuum at the product inlet opening 30 as the first and second rotors 23, 24 disengage, causing the fluid product to enter the pump 1. The fluid product is then transported around the pumping cavity by the rotor wings 32. The direction of flow generated by the pump 1 can be reversed by simply shifting the direction of rotation of the first and second rotors 23, 24.

[0071] The specific configuration and number of rotor wings 32 can vary considerably, and the specific rotor twin wing design illustrated in Figures 2, 4, and 5 is merely one exemplary embodiment of the rotor wings, and thus the pump can have rotors 23, 24 having other types of rotor wing designs in accordance with the present disclosure.

[0072] 3, the rotor casing 15 may include a first cylindrical rotor case hub 36 extending from the rear wall 20 and a second cylindrical rotor case hub 37 extending from the rear wall 20. The first and second hubs 36, 37 are essentially hollow cylindrical sleeves that are open on both axial sides thereof. Moreover, the axis of each cylindrical hub 36, 37 is aligned with the axis 10 of the pump 1.

[0073] The first rotor case hub 36 is configured to receive the first drive shaft 4, and the second rotor case hub 37 is configured to receive the second drive shaft 5. In other words, in the assembled state, the first rotor case hub 36 is aligned with the first drive shaft 4, and the second rotor case hub 37 is aligned with the second drive shaft 5. Thus, the first and second hubs 36, 37 are displaced from one another in the first lateral direction 11.

[0074] Prior to assembly of the transmission housing 2 with the rotor casing 15, the forward ends of the first and second drive shafts 4, 5 project forwardly beyond the transmission housing front surface 13. When the transmission housing 2 and the rotor casing 15 are then assembled, said forward ends of the first and second drive shafts 4, 5 are inserted into the first and second hubs, respectively, from their rear sides, such that the rear sides of the rotor casing 15 contact the front surface 13 of the transmission housing 2. In this condition, the forward ends of the first and second drive shafts 4, 5 extend through the complete axial length of the first and second hubs 36, 37.

[0075] FIG. 6 shows a more detailed side view of an exemplary embodiment of pump 1, and FIG. 7 shows a cross-sectional side view of the same pump 1 in an assembled state.

[0076] As illustrated diagrammatically in Figures 1, 6 and 7, the transmission housing 2 may include first and second axially protruding mounting portions 60, 61, which face the rotor casing 15 and are positioned on either side of the drive shafts 4, 5. The rotor casing 15 may then be connected to the front side 13 of the transmission housing 2 via said first and second axially protruding mounting portions 60, 61, such that an intermediate space 42 is achieved between the transmission housing 2 and the rotor casing 15.

[0077] 6 and 7, the rotor casing 15 includes a rotor casing rear portion 25, a front cover 26, and a threaded fastener 16 for clamping the rotor casing 15 against the front surface 13 of the transmission housing 2. The first and second rotors 23, 24 are non-rotatably mounted on the first and second drive shafts 4, 5, respectively. In particular, each of the first and second rotors 23, 24 is fixed to a rotor seat of the associated drive shaft 4, 5 by a threaded fastener 38, which is engaged with a mating threaded section at an end region of the associated drive shaft 4, 5.

[0078] Moreover, the first rotor case hub 36 is provided with a first sealing arrangement 40a, 40b and the second rotor case hub 37 is provided with a second sealing arrangement 41a, 41b. Both the first and second sealing arrangements 40a, 40b, 41a, 41b are arranged to prevent a fluid product located in the stationary pumping cavity from leaking along the first and second shafts 4, 5 towards the rear side of the rotor casing.

[0079] Each of the first and second sealing structures 40a, 40b, 41a, 41b may, for example, include a single one of the dual annular sealing assemblies.

[0080] 7, each of the first and second sealing arrangements 40a, 40b, 41a, 41b includes a dual annular sealing assembly, including a forward annular sealing assembly 40a, 41a and an aft annular sealing assembly 40b, 41b, the aft sealing assembly 40b, 41b being spaced apart in the axial direction 10 from the forward sealing assembly 40a, 41a.

[0081] Each of the first and second annular sealing assemblies 40a, 40b, 41a, 41b may be implemented, for example, in the form of a mechanical face seal assembly having two main sealing parts (a first annular sealing part associated with the rotor case hub and a second annular sealing part associated with the rotor) that are held in axial sealing contact with one another while allowing relative rotation. Alternatively, other types of seals may be used.

[0082] As shown above, the pump 1 can be used to pump fluid products that may begin to solidify and / or crystallize when the temperature of the fluid product drops below a certain threshold. This may occur, for example, while the pump is stopped and then cause damage to the pump when the pump is subsequently started again. In particular, the first and second annular sealing arrangements 40a, 40b, 41a, 41b are at risk of being damaged due to their relatively delicate design and narrow tolerance range, but other parts (such as, for example, the first and second cylindrical rotor case hubs 36, 37 or the first and second rotors 23, 24) may also be damaged.

[0083] Consequently, it may be desirable to heat any solidified and / or crystallized fluid products in the pump 1 before commencing pumping action so that any solidified and / or crystallized fluid products are able to shift to a fluid state before the rotors 23, 24 begin to rotate.

[0084] 1, 6 and 7, the pump includes first and second heating devices 51, 52 removably fastened to the axial rear wall 20 of the rotor casing 15. The first and second heating devices 51, 52 are arranged in the intermediate space 42 between the transmission housing 2 and the rotor casing 15 and are configured to heat the rotor casing 15 in an area proximate the first and second sealing arrangements 40a, 40b, 41a, 41b and / or any fluid product in the rotor casing.

[0085] In other words, a rotary positive displacement pump 1 according to the present disclosure includes a transmission housing 2 that provides rotational support for first and second parallel and axially extending drive shafts 4, 5 having gears 6, 7 in constant mesh such that the first and second drive shafts 4, 5 are arranged to rotate in opposite directions. The pump further includes a rotor casing 15 that is connected to the forward side 13 of the transmission housing 2 and has an axial rear wall 20, an axial forward wall 22, and a circumferential side wall 21 that together define a stationary internal pumping cavity. The rotor casing 15 houses a first rotor 23 drivingly connected to a first drive shaft 4 and a second rotor 24 drivingly connected to a second drive shaft 5, the first and second rotors 23, 24 configured to rotate in opposite directions and to interact to provide a positive pumping effect on the fluid product, the fluid product entering the pumping cavity via the rotor casing inlet section 30 and exiting the pumping cavity via the rotor casing outlet section 31. The rotor casing 15 further includes first and second sealing arrangements 40a, 40b, 41a, 41b configured to prevent leakage of the fluid product from the stationary pumping cavity towards the rear side of the rotor casing along the first and second shafts, respectively. The pump further includes heating devices 51, 52 which are removably fastened to the axial rear wall 20 of the rotor casing 15 and configured to heat the rotor casing 15 in areas proximate the first and second sealing arrangements 40a, 40b, 41a, 41b and / or any fluid product within the rotor casing 15.

[0086] The term "close" in the above means that the positioning and mounting of the heating devices 51, 52 in the axial rear wall 20 of the rotor casing 15 is significantly closer to the areas of the rotor casing 15 holding the first and second sealing structures 40a, 40b, 41a, 41b, when taking into account the thermal conductive path length in the metallic material of the rotor casing, than, for example, positioning of the heating devices in the forward cover 26 or in the circumferential side wall 21.

[0087] In other words, even if a heating device, possibly positioned on the forward cover 26, could be positioned physically closer to the area of ​​the rotor casing 15 carrying the first and second sealing arrangements 40a, 40b, 41a, 41b than a heating device positioned on the rotor casing aft wall 20, the thermally conductive length in the metallic material of the rotor casing 15 will generally be significantly shorter if the heating device is located on the aft wall 20. This is because the area of ​​the rotor casing 15 carrying the first and second sealing arrangements 40a, 40b, 41a, 41b is generally integrally formed with the rotor casing aft wall 20 and not with the forward wall 22 or circumferential side wall 21.

[0088] For these reasons, the location of the heating device on the axial rear wall 20 of the rotor casing 15 can be considered particularly suitable for heating the rotor casing 15 in the area close to the first and second sealing structures 40a, 40b, 41a, 41b.

[0089] The heating devices 51, 52 transfer heat to the axial rear wall 20 of the rotor casing 15. The heating devices 51, 52 can be implemented, for example, in the form of heat exchangers for a circulating or non-circulating heat transfer fluid, condensers of a heat pump or electric heating devices.

[0090] For example, the heating devices 51, 52 can be electric heating devices that convert electrical power into heat. The electric heating devices can include electrical wires and coils that generate heat when conducting electrical current. Alternatively, the electric heating devices can be positive temperature coefficient (PTC) heaters with conductive ink printed on a thin, flexible, polymer-based substrate. The electric heating devices are typically implemented in the form of a bolt-on external heater that is fastened to the axial rear wall 20 of the rotor casing 15 and functions by heating the rotor casing block by direct contact. Still alternatively, the electric heating devices can be implemented in the form of an electric infrared heating device that is attached to the axial rear wall 20 of the rotor casing 15 and heats the rear wall 20 by infrared radiation generated by an electric element (e.g., a coiled electrical resistance wire, etc.).

[0091] When the heating device is implemented in the form of a heat pump condenser, heat from the heat pump condenser is transported to the axial rear wall 20 of the rotor casing 15. This heat can be transferred from the condenser to the rotor casing block by direct contact.

[0092] When the heating device is implemented in the form of a heat exchanger for a circulating or non-circulating heat transfer fluid, the heating device is configured to have an internal flow of the heat transfer fluid, the heating device enabling the transfer of heat from the heat transfer fluid to the rear wall 20 of the rotor casing 15. Moreover, the heating device, when implemented as a fluid heat exchanger, can also be used for cooling of the fluid product of the pump 1.

[0093] The heating device may be part of a heating system including a closed flow path with a pump for circulating a heat transfer fluid in the flow path, a heat source for heating the heat transfer fluid, and a heating device for transferring heat from the heat transfer fluid to the rear wall 20 of the rotor casing 15.

[0094] Each of the first and second heating devices 51, 52 illustrated in the exemplary embodiment of Figures 1, 6, and 7 includes an internal fluid heating chamber 55 that opens toward the axial rear wall 20 of the rotor casing 15. Thus, the heat transfer fluid flowing through each of the first and second heating devices 51, 52 is in direct contact with both the inner surface of the internal fluid heating chamber 55 and the rear wall 20 of the rotor casing 15.

[0095] The pump 1, the rotor casing 15 and the first and second heating devices 51, 52 according to the exemplary embodiments of Figures 1, 6 and 7 are further described below with reference to Figures 8 to 12B.

[0096] 8 shows a perspective rear view of the rotor casing 15 with first and second heating devices 51, 52 fastened to the rear wall 20 of the rotor casing 15 by threaded fasteners 50. In particular, each heating device 51, 52 is pressed against the rear wall 20 of the rotor casing 15 by the threaded fasteners 50, which engage into threaded holes located in the rear wall 20 of the rotor casing 15.

[0097] The threaded fasteners 50 may extend through dedicated mounting holes 73 provided in the heating devices 51, 52, for example, as shown in Figure 11. Alternatively, the heating devices 51, 52 may be clamped to the rear wall 20 of the rotor casing by a clamping member (e.g., a bracket, etc.).

[0098] In Figures 6, 8 to 11 and 13 to 15, the heating device is shown in a fluidly isolated state (i.e., the fluid inlet and fluid outlet of the heating device are not connected to a piping arrangement configured for the supply and return of heat transfer fluid).

[0099] 9 shows a rear view of the cross section of the pump 1 in the region of the intermediate space 42. The layout, size and extension of the first and second heating devices 51, 52 relative to the axial rear wall 20 of the rotor casing 15 as well as the relative locations of the first and second heating devices 51, 52 relative to the first and second drive shafts 4, 5 according to one exemplary embodiment of the pump are clearly shown.

[0100] In particular, FIG. 9 shows that the contact surface between the heating device 51, 52 and the axial rear wall 20 of the rotor casing 15, as viewed in the axial direction 10 of the pump 1, extends over at least 1 / 3 of the circumference of the first or second drive shaft 4, 5 (i.e. over at least about 120°). More specifically, an angle 49 is illustrated in FIG. 9, which indicates the level of the contact surface between the heating device 51, 52 and the axial rear wall 20 of the rotor casing 15, as viewed in the axial direction 10 of the pump 1. In FIG. 9, the angle is about 160°, but it can vary between about 120° and 360°. 360° means that the contact surface between the heating device 51, 52 and the axial rear wall 20 of the rotor casing 15, as viewed in the axial direction 10 of the pump 1, completely surrounds the first or second drive shaft 4, 5. A larger contact surface generally results in an increased heating capacity of the heating devices 51,52.

[0101] 8 and 9 further show that the pump 1 has an axial direction 10 parallel to the first and second drive shafts 4, 5 and a first transverse direction 11, the first transverse direction 11 extending perpendicularly to the axial direction 10 through the centers of rotation of the first and second drive shafts 4, 5, the pump 1 includes a first heating device 51 arranged on the outside of the first drive shaft 4 in the first transverse direction 11, and the pump 1 further includes a second heating device 52 arranged on the outside of the second drive shaft 5 in the first transverse direction 11. In other words, the first and second heating devices 51, 52 are arranged on opposite outsides of the first and second drive shafts 4, 5. As a result, the first and second drive shafts 4, 5 are surrounded by the first and second heating devices 51, 52 along the first transverse direction 11. This location for the first and second heating devices 51, 52 is beneficial because it is positioned close to the first and second sealing arrangements while still having sufficient free space to receive the first and second heating devices 51, 52.

[0102] Figure 10 shows a perspective front view of the pump 1 in a partially disassembled state, including the transmission housing 2 and the first and second heating devices 51, 52. Consequently, the internal fluid heating chamber 55, which opens towards the axial rear wall 20 of the rotor casing 15, is visible in Figure 10, as are the first and second drive shafts 4, 5, which project forwardly from the transmission housing 2.

[0103] Moreover, the first and second axially protruding mounting parts 60, 61 of the transmission housing 2 are also clearly shown in Fig. 10. The first and second axially protruding mounting parts 60, 61 protrude in the axial direction 10 towards the front side of the pump 1. When the rotor casing is mounted on the axially protruding mounting parts 60, 61 an intermediate space 42 is formed between the rear wall 20 of the rotor casing 15 and the front wall 19 of the transmission housing 2. The heating devices 51, 52 are arranged in said intermediate space 42.

[0104] For example, with reference to Figures 6-10, a further advantageous aspect of the pump according to the present disclosure is that the heating devices 51, 52 do not affect the external pump dimensions. In other words, the external pump dimensions remain the same with or without the heating devices 51, 52 fastened to the rotor casing 15. This results from the fact that in a direction perpendicular to the axial direction 10 of the pump 1, the total length 70 of the heating casings 51, 52 is smaller than the total length of the transmission housing 2 and / or the rotor casing 15 when compared in the same direction and in the fastened state of the heating casings 51, 52.

[0105] This allows for a more flexible use of the pump 1, since the heating and / or cooling of the rotary casing 25 can be a feature added to an already installed pump in a subsequent state, if desired, without the risk of interfering with neighboring equipment (e.g. pipes, etc.). Moreover, the location of the heating devices 51, 52 in the intermediate space 42 provides a more protected location for the heating devices 51, 52, thereby reducing the risk of damage to the heating devices 51, 52 and / or leakage of the heat transfer fluid.

[0106] Indeed, a further advantageous aspect of the pump according to the present disclosure is that one heating device 51, 52 (or one set of heating devices 51, 52) can be made suitable for installation on a variety of different pumps 1. In other words, thanks to the positioning of the first and second heating devices 51, 52 in the intermediate space 42 between the transmission housing 2 and the rotor casing 15, a particular size, shape and configuration of the heating devices 51, 52 can be relatively easily made to fit a number of different types of rotor casings 15, since the interface between the heating devices 51, 52 and the rotor casing 15 is typically just a flat contact surface.

[0107] Consequently, according to one aspect of the present disclosure, a set of rotary positive displacement pumps is provided, including a first rotary positive displacement pump as described herein having a first displacement volume per revolution and a second rotary positive displacement pump as described herein having a second displacement volume per revolution greater than the first displacement volume per revolution, both the first and second rotary positive displacement pumps being configured to have identical heating devices 51, 52 fastened to the axial rear wall 20 of the rotor casing 15.

[0108] In particular, both the first and second rotary positive displacement pumps are configured to have identical heating devices 51, 52 fastened to the axial rear wall 20 of the rotor casing 15, e.g., in terms of identical sizes, dimensions, mounting holes, sealing arrangements, etc. of the heating devices 51, 52. Thereby, fewer individual parts are required while still allowing the option to supply the pumps with heating / cooling.

[0109] FIG. 11 shows a schematic front view of a heating device 51 including an internal fluid heating chamber 55 and a continuous sealing groove 63 surrounding the opening of the internal fluid heating chamber 55 .

[0110] Figure 12A shows a cross-section of heating device 51 taken along section line AA in Figure 11, including a portion of rear wall 20 of rotor casing 15. Figure 12A shows an interior fluid heating chamber 55 defined by bottom wall 58 and first and second side walls 53, 54. Figure 12A also shows sealing groove 63 and a sealing ring or bead 64 disposed within sealing groove 63.

[0111] Figure 12B shows a cross section along section line BB in Figure 11 including a portion of rear wall 20 of rotor casing 15. Figure 12B shows fluid inlet 56 in fluid communication with interior fluid heating chamber 55 and arranged to connect with a heat transfer fluid supply pipe.

[0112] 12A and 12B also show the flat contact surfaces 65 of the heating devices 51, 52 abutting against the corresponding flat contact surface 27 of the axial rear wall 20 of the rotor casing 15, and the rear surfaces 66 of the heating devices facing the transmission housing 2. Specifically, the heating devices 51, 52 have flat surfaces 65 that press against the corresponding flat surface 27 of the rear wall 20 of the rotor casing 15.

[0113] 6-12B in particular, the heating devices 51, 52 may correspond to a heating casing having an internal fluid heating chamber 55, a fluid inlet port 56, and a fluid outlet port 57, as shown above, and the internal fluid heating chamber 55 may be fluidly connected to the fluid inlet port 56 and the fluid outlet port 57. The heating casing is typically hollow or includes open or closed channels 67 to provide the internal fluid heating chamber 55. The heating casing may be made, for example, from stainless steel, steel, aluminum, or other types of metallic materials, or even polymeric materials.

[0114] Moreover, as described with reference to Figures 7, 10-11, and 12A, the internal fluid heating chamber 55 can be partially defined by the heating casings 51, 52 and partially defined by the rear wall 20 of the rotor casing 15.

[0115] This scenario occurs, for example, when the heating casing has an open channel 67 (i.e., a channel that is open at a particular location and accessible in a direction perpendicular to the flow direction of the heat transfer fluid at said location), which is closed by the rear wall 20 of the rotor casing 15 upon installation of the heating casing to the rear wall 20 of the rotor casing 15.

[0116] In other words, the internal fluid heating chamber 55 may be considered to be limited, confined, or surrounded partially by the heating casings 51, 52 and partially by the aft wall 20 of the rotor casing 15. As a result, the internal fluid heating chamber 55 may be collectively defined by the internal bottom wall 58 of the channel 67, the first and second internal side walls 53, 54 of the channel 67, and the aft wall 20 of the rotor casing 15. Thereby, the heat transfer fluid may be in direct contact with the surface 27 of the aft wall 20 of the rotor casing for efficient heat transfer capacity.

[0117] Referring again to Figures 7, 10-11 and 12A, the heating casings 51, 52 may therefore have an elongated channel 67 formed in the contact surface 65 of the heating casings 51, 52, the elongated channel 67 facing toward the axial rear wall 20 of the rotor casing 15, and the elongated inner surfaces 53, 54, 58 of the elongated channel 67 and the surface 27 of the rear wall 20 collectively define an internal fluid heating chamber 55.

[0118] The term "elongated" in this specification means that the length of a portion of a channel 67 in the direction of flow of the heat transfer fluid in said portion is significantly greater than the internal width of the channel 67 in a direction perpendicular to the flow direction in said portion.

[0119] An elongated channel 67 can be formed in a flat outer surface 65 of the heating casings 51, 52, the flat outer surface 65 surrounding the channel 67 being in contact with and pressed against a corresponding flat surface 27 of the rear wall 20 of the rotor casing 15.

[0120] Moreover, the elongated channels 67 can be machined, for example, in the flat outer surface 65 of the heating casings 51, 52 that faces the rotor casing 15. Alternatively, the elongated channels 67 can be formed in the flat outer surface 65 of the heating casings 51, 52 in connection with the casting of the heating casings 51, 52.

[0121] The channel 67 may follow a curved path from the fluid inlet 56 to the fluid outlet 57, the curved path being curved around the cylindrical outer surface of the first and / or second drive shafts 4, 5. For example, the curved path of the elongated channel 67 may have a shape of a circular arc coaxial with a center of the first or second drive shafts 4, 5 over a particular length 68 of curvature. In particular, the elongated channel 67 may have a curvature having a shape of a circular arc over an arc angle 69 of at least 25° (specifically, at least 45°).

[0122] Moreover, the heating device 51, 52 may have a curved outer surface 74 that curves around and follows at least a portion of the cylindrical outer surface of the first and / or second drive shaft 4, 5. For example, the curved outer surface may have a shape of a circular arc coaxial with a center of the first or second drive shaft 4, 5 over a particular length 76 of curvature. In particular, the curved outer surface 74 may have a curvature having a shape of a circular arc over an arc angle 75 of at least 45° (specifically at least 75°).

[0123] The elongated channel 67 may have a length 69, in a direction perpendicular to the axial direction 10 of the pump 1, that is at least 50% (specifically, at least 75%) of the total length 70 of the heating casings 51, 52. This ensures that the heat transfer fluid is able to be in direct contact with the rear wall 20 of the rotor casing over a relatively large surface area, thereby providing good heating efficiency.

[0124] The elongated channel may have a length of about 5-30 cm, the main part of the elongated channel having a depth 71 of at least 5 mm (specifically in the range of 5-30 mm) and a width 72 of at least 5 mm (specifically in the range of about 5-30 mm). In particular, the elongated channel may have a length of about 5-30 cm in a direction perpendicular to the axial direction 10 of the pump 1, the main part of the elongated channel having a depth 71 of at least 5 mm (specifically in the range of 5-30 mm) in the axial direction 10 and a width 72 of at least 5 mm (specifically in the range of about 5-30 mm) in a direction perpendicular to the local flow direction.

[0125] Moreover, as mentioned above, the heating casings may have a seal 64 arranged on a flat surface 65 of the heating casings 51, 52 and extending around the channel 67 to prevent leakage of the heating fluid in the contact area between the heating casings 51, 52 and the rotor casing 15. The seal may be, for example, an O-ring seal arranged in a circumferential sealing groove provided in the flat surface 65 of the heating casings 51, 52.

[0126] A further exemplary embodiment of the pump 1 is described with reference to FIG. 13 in which a single heating device 51 completely surrounds both the first and second drive shafts 4, 5 and the area of ​​the rear wall 20 located between the first and second drive shafts 4, 5. The single heating device 51 has an internal fluid heating chamber 55 that is fluidly connected to a fluid inlet portion 56 and a fluid outlet portion 57 and is defined by first and second side walls 53, 54. The internal fluid heating chamber 55 can extend around both the first and second drive shafts 4, 5 and the area located between the first and second drive shafts 4, 5. In other words, the heat transfer fluid supplied to the fluid inlet 56 can follow a flow path either around the first drive shaft 4, around the second drive shaft, or through the central region between the first and second drive shafts 4, 5 on its way to the fluid outlet 57, as shown by flow arrows 77 in Figure 13. This exemplary embodiment of the heating casing can provide an even increased heating capacity due to the increased contact size.

[0127] A further exemplary embodiment of the pump 1 is described with reference to FIG. 14, in which a single heating device 51 completely surrounds the first and second drive shafts 4, 5. The single heating device 51 has an internal fluid heating chamber 55, which is fluidly connected to a fluid inlet section 56 and a fluid outlet section 57, and is defined by first and second side wall sections 53, 54. The internal fluid heating chamber 55 can extend around both the first and second drive shafts 4, 5, but does not cover the area located between the first and second drive shafts 4, 5. In other words, the heat transfer fluid supplied to the fluid inlet section 56 can follow a flow path either around the first drive shaft 4 or around the second drive shaft 5 on its way to the fluid outlet section 57, as indicated by the flow arrows 77 in FIG. 14. This exemplary embodiment of the heating casing can provide an even increased heating capacity due to the increased contact size.

[0128] Moreover, a further exemplary embodiment of the pump 1 is described with reference to FIG. 15, in which three heating devices 51, 52, 59 are provided. The first and second heating devices 51, 52 are arranged on the outside of the first and second drive shafts 4, 5, respectively, in a similar manner as described with reference to FIGS. 8-10, and are therefore provided with individual internal fluid heating chambers 55, fluid inlet ports 56 and fluid outlet ports 57. However, the exemplary embodiment of FIG. 15 differs in that a third heating device 59 is provided in the central area between the first and second drive shafts 4, 5. The third heating device 59 is also provided with individual internal fluid heating chambers 55, fluid inlet ports 56 and fluid outlet ports 57. Each of the first to third heating devices 51, 52, 59 can be completely individual parts with individual fastening devices, thereby allowing independent removal of the single heating devices 51, 52, 59. This exemplary embodiment of the heating casing can provide an improved modular design, since some pumps can have all heating devices 51, 52, 59 installed and some pumps can have only some of the heating devices 51, 52, 59 installed.

[0129] Figures 16-18 show, in schematic form, some further exemplary embodiments of the pump 1, with particular reference to the rotor casing design. The general design and functionality of the first and second drive shafts 4, 5, the first and second hubs 36, 37, the first and second rotors 23, 24, the first and second sealing arrangements 40a, 40b, 41a, 41b, the first and second heating devices 51, 52, as well as most aspects of the overall design of the rotor casing 15 are substantially the same as described above with reference to Figures 1-12B.

[0130] Figures 16 to 18, for example, clearly show the positioning of the first and second heating devices 51, 52 in the intermediate space 42 between the transmission housing 2 and the rotor casing 15, as well as the proximity of the first and second heating devices 51, 52 to the first and second sealing structures 40a, 40b, 41a, 41b.

[0131] 17 shows an exemplary embodiment of a pump 1, in which the axial rear wall 20 of the rotor casing 15 has a recess 80 defined by a flat surface 81 and a radial surface 82, the flat surface 81 being perpendicular to the axial direction 10 of the pump 1 and facing towards the rear side of the pump 1, the radial surface 82 facing a direction 11 perpendicular to said axial direction 10, and the heating devices 51, 52 have a flat surface 65 pressing against the flat surface 81 of the recess 80 and a radial surface 83 facing the radial surface 82 of the recess. The recess 80 can be provided, for example, by reducing the thickness of the rear wall 20 at the location of the first and second heating devices 51, 52, allowing the first and second heating devices 51, 52 to be positioned even closer to the first and second sealing arrangements 40a, 40b, 41a, 41b. Moreover, thanks to the radial surface 83 facing the radial surface 82 of the recess, the first and second heating devices 51, 52 are able to heat the rear wall 20 not only in the axial direction 10 but also in the radial direction 11, thereby contributing to further enhancing the heating efficiency.

[0132] FIG. 18 shows an exemplary embodiment, in which each of the first and second heating devices 51, 52 includes a closed internal fluid heating chamber 55. Thus, the heat transfer fluid does not have direct contact with the rear wall 20 of the rotor casing 15; instead, the heat must be conducted through the side walls 84 of the heating casings 51, 52 before reaching the rear wall 20 of the rotor casing 15. The side walls 84 of the heating casings 51, 52 can preferably have flat contact surfaces 65 that abut against corresponding flat contact surfaces 27 of the axial rear wall 20 of the rotor casing 15. The closed internal fluid heating chamber 55 eliminates the risk of leakage of the heat transfer fluid that may occur when the internal fluid heating chamber 55 is open towards the rear wall 20.

[0133] FIG. 18 also shows how the first and second heating devices 51, 52 can be fastened to the rear wall 20 of the rotor casing 15 by threaded fasteners 50 that extend through the first and second heating devices 51, 52 and engage into threaded holes positioned in the rear wall 20 of the rotor casing 15.

[0134] 7 and 16-18 also illustrate that rotor casing 15 can have a first cylindrical rotor case hub 36 and a second cylindrical rotor case hub 37, each extending from axial rear wall 20 toward forward wall 22 of rotor casing 15, with a stationary internal pumping cavity defined by axial rear wall 20, circumferential side wall 21, forward wall 22, and first and second cylindrical rotor case hubs 36, 37. First cylindrical rotor case hub 36 receives first drive shaft 4 therein, and second cylindrical rotor case hub 37 receives second drive shaft 5 therein. The first sealing arrangements 40a, 40b are positioned at least partially within the annular space defined by the outer surface of the first drive shaft 4 and the inner surface of the first hub 36, and the second sealing arrangements 41a, 41b are positioned at least partially within the annular space defined by the outer surface of the second drive shaft 5 and the inner surface of the second hub 37.

[0135] The rotary positive displacement pump according to the present disclosure has been described above in Figures 2, 4, 5, 7 and 16-18 primarily with reference to an implementation in the form of a circumferential piston pump. However, the rotary positive displacement pump according to the present disclosure may alternatively be implemented in the form of a rotary lobe pump having first and second counter-rotating rotors 23, 24 configured to interact to provide a positive pumping effect on the fluid product, as shown diagrammatically in Figure 19, or in the form of a gear pump having first and second counter-rotating rotors 23, 24 configured to interact to provide a positive pumping effect on the fluid product, as shown diagrammatically in Figure 20.

[0136] 21 shows a schematic cross-section of the rotary lobe pump 1 without the first and second cylindrical rotor case hubs 36, 37. In such a scenario, the first and second sealing arrangements 40a, 41a may be positioned between the rear wall 20 and the first and second drive shafts 4, 5, respectively, thereby providing even closer placement of the first and second heating devices 51, 52 to the areas of the rotor casing 15 that carry the first and second sealing arrangements 40a, 41a.

[0137] The present disclosure also relates to a method for heating a rotor casing 15 of a rotary positive displacement pump 1 having a front side and a rear side and / or a fluid product therein, the main steps of which will be described below with reference to Fig. 22. The method may include an optional first step S1 of providing a rotary positive displacement pump 1 having a transmission housing 2 and a rotor casing 15, the transmission housing 2 providing rotational support for first and second parallel, axially extending drive shafts 4, 5 having gears 6, 7 in constant meshing such that the first and second drive shafts 4, 5 are arranged to rotate in opposite directions, the rotor casing 15 being connected to the front side 13 of the transmission housing 2 and having an axial rear wall 20, an axial front wall 22 and a circumferential side wall 21 which together define a stationary internal pumping cavity, the rotor casing 15 comprising a first rotor 23 drivingly connected to the first drive shaft 4 and a second rotor 24 drivingly connected to the first drive shaft 4 and a second rotor 26 drivingly connected to the first drive shaft 4 and a second rotor 28 drivingly connected to the first drive shaft 4 and a second rotor 29 ... The rotor casing further includes a first and second sealing arrangement 40a, 40b, 41a, 41b configured to prevent leakage of the fluid product from the stationary pumping cavity towards the rear side of the rotor casing 15 along the first and second drive shafts 4, 5, respectively. The first and second rotors 23, 24 are configured to rotate in opposite directions and to interact to provide a positive pumping effect on the fluid product, the fluid product entering the pumping cavity via the rotor casing inlet section 30 and exiting the pumping cavity via the rotor casing outlet section 31, the rotor casing further including first and second sealing arrangements 40a, 40b, 41a, 41b configured to prevent leakage of the fluid product from the stationary pumping cavity towards the rear side of the rotor casing 15 along the first and second drive shafts 4, 5, respectively.In the absence of the first step S1, the rotary positive displacement pump (1) includes a transmission housing (2) and a rotor casing (15), the transmission housing (2) providing rotational support for first and second parallel, axially extending drive shafts (4, 5) having gears (6, 7) in constant mesh such that the first and second drive shafts (4, 5) rotate in opposite directions, the rotor casing (15) being connected to a forward side of the transmission housing (2) and having an axial rear wall (20), an axial forward wall (22) and a circumferential side wall (21) which together define a stationary internal pumping cavity, the rotor casing (15) including a first rotor (23) drivingly connected to the first drive shaft (4) and a second drive shaft (5) which are arranged to rotate in opposite directions. and a second rotor (24) drivingly connected to the rotor casing (15), the first and second rotors (23, 24) being configured to rotate in opposite directions and to interact to provide a positive pumping effect on the fluid product, the fluid product entering the pumping cavity via the rotor casing inlet section (30) and exiting the pumping cavity via the rotor casing outlet section (31), the rotor casing (15) further including first and second sealing arrangements (40a, 40b, 41a, 41b) configured to prevent leakage of the fluid product from the stationary pumping cavity along the first and second shafts (4, 5), respectively, towards the rear side of the rotor casing (15).

[0138] The method comprises a second step S2 of releasably fastening the heating devices 51, 52 to the axial rear wall 20 of the rotor casing 15.

[0139] Finally, the method includes a third step S3 of activating heating devices 51, 52 for heating the rotor casing 15 in the area near the first and second sealing structures 40a, 40b, 41a, 41b and / or any fluid product within the rotor casing 15.

[0140] The term "activate" in this specification means, for example, powering the electrical heating devices 51,52 or providing a flow of warm heating fluid through the heating devices 51,52.

[0141] It will be appreciated that the above description is merely exemplary in nature and is not intended to limit the disclosure, its application, or uses. Although specific examples have been described herein and illustrated in the drawings, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for the elements without departing from the scope of the disclosure as defined in the claims. Additionally, modifications can be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope of the disclosure.

[0142] Therefore, the present disclosure is not limited to the specific examples shown in the drawings and described herein as the best mode presently contemplated for carrying out the teachings of the present disclosure, but rather the scope of the present disclosure is intended to include any embodiment that falls within the foregoing description and the scope of the appended claims. The reference signs recited in the claims should not be understood as limiting the scope of the matter protected by the claims, but their only function is to make the claims more easily understandable. [Explanation of symbols]

[0143] 1 Rotary positive displacement pump 2 Transmission housing 3 Rotating Support 4. First parallel drive shaft, first axially extending drive shaft 5 second parallel drive shaft, second axially extending drive shaft 6 First Gear 7 Second Gear 8 Support structure 9 End section 10 Axial direction 11 First horizontal 12 Second Horizontal 13 Front side, front surface 14 Rear side 15 Rotor casing 16 Threaded bolt or nut 17 Front side 18 Rear side 19 Front wall 20 Axial rear wall 21 Circumferential side wall 22 Axial front wall 23 First Rotor 24 Second Rotor 25 Rotor casing rear part, rotary casing 26 Front cover 27 Flat Contact Surface 30 Fluid product inlet opening, rotor casing inlet 31 Fluid product outlet opening, rotor casing outlet 32 Rotor Wing 33 Rotor drive element 35 Space 36 First cylindrical rotor case hub 37 Second cylindrical rotor case hub 38 Threaded Fasteners 40a First sealing structure, annular sealing assembly 40b First sealing structure, annular sealing assembly 41a Second sealing structure, annular sealing assembly 41b Second sealing structure, annular sealing assembly 42 Intermediate Space 44 Central hole or recess 45 Spline 48 Mounting Surface 49 angle 50 Threaded Fasteners 51 First heating device, heating casing 52 Second heating device, heating casing 53 first side wall, first inner side wall, inner surface 54 second side wall, second inner side wall, inner surface 55 Internal Fluid Heating Chamber 56 Fluid inlet 57 Fluid outlet 58 Bottom wall, internal bottom wall, internal surface 59 Third Heating Device 60 first axially protruding mounting portion 61 second axially protruding mounting portion 63 Sealing groove 64 Sealing bead, seal 65 Flat contact surfaces of heating devices, flat external surfaces of heating casings 66 Rear surface of heating device 67 Channels, Open Channels 68 Specific Length of Curvature 69 Arc angle, length 70 Total length of heating casing 71 Depth 72 Width 73 Mounting hole 74 Curved exterior surfaces 76 Specific Length of Curvature 77 Flow Arrows 80 Recess 81 Flat Surface 82 Radial surface 83 Radial surface 84 Heating casing side wall

Claims

1. A rotary positive displacement pump (1) for pumping a fluid product, the pump having a front side and a rear side, a transmission housing (2) providing rotational support for first and second parallel, axially extending drive shafts (4, 5) having gears (6, 7) in constant meshing condition, said first and second drive shafts (4, 5) arranged to rotate in opposite directions; a rotor casing (15) connected to a forward side (13) of the transmission housing (2) and having an axial rear wall (20), an axial front wall (22), and a circumferential side wall (21) which together define a stationary internal pumping cavity; Including, the rotor casing (15) houses a first rotor (23) drivingly connected to the first drive shaft (4) and a second rotor (24) drivingly connected to the second drive shaft (5); the first and second rotors (23, 24) are configured to rotate in opposite directions and to interact to provide a positive pumping effect on a fluid product, the fluid product entering the internal pumping cavity through a rotor casing inlet (30) and exiting the internal pumping cavity through a rotor casing outlet (31); the rotor casing (15) further comprises first and second sealing arrangements (40a, 40b, 41a, 41b), the first and second sealing arrangements (40a, 40b, 41a, 41b) configured to prevent leakage of fluid product along the first and second drive shafts (4, 5), respectively, from the stationary internal pumping cavity towards the rear side of the rotor casing (15); the rotary positive displacement pump (1) further comprises a heating device (51, 52), the heating device (51, 52) being removably fastened to the axial rear wall (20) of the rotor casing (15) and configured to heat the rotor casing (15), the first and second sealing arrangements (40a, 40b, 41a, 41b) and / or a fluid product within the rotor casing (15); The heating device (51, 52) is a heating casing having an internal fluid heating chamber (55), a fluid inlet port (56), and a fluid outlet port (57), the internal fluid heating chamber (55) being fluidly connected to the fluid inlet port (56) and the fluid outlet port (57).

2. 2. The rotary positive displacement pump (1) according to claim 1, wherein the heating device (51, 52) is removable from the axial rear wall (20) of the rotor casing (15).

3. 3. The rotary positive displacement pump (1) according to claim 1 or 2, wherein the heating device is releasably fastened to the axial rear wall (20) of the rotor casing (15) by means of releasable fasteners (50).

4. 2. The rotary positive displacement pump (1) of claim 1, wherein the internal fluid heating chamber (55) is defined in part by the heating casing (51, 52) and in part by the axial rear wall (20) of the rotor casing (15).

5. 5. The rotary positive displacement pump (1) according to claim 1, wherein the heating casing (51, 52) has an elongated channel (67) formed in a surface (65) of the heating casing (51, 52), the elongated channel (67) facing towards the axial rear wall (20) of the rotor casing (15), and an elongated inner surface (53, 54, 58) of the elongated channel (67) and a surface (27) of the axial rear wall (20) jointly define the internal fluid heating chamber (55).

6. 6. The rotary positive displacement pump (1) of claim 5, wherein the elongated channel (67) follows a curved path from the fluid inlet (56) to the fluid outlet (57), the curved path being curved around a cylindrical outer surface of the first and / or second drive shafts (4, 5).

7. 7. The rotary positive displacement pump (1) according to claim 5 or 6, wherein the heating casing (51, 52) has a seal (64) arranged on a flat surface (65) of the heating casing (51, 52) and extending around the elongated channel (67) to prevent leakage of heating fluid in the contact area between the heating casing (51, 52) and the rotor casing (15).

8. 8. The rotary positive displacement pump (1) according to claim 1, wherein the heating device (51, 52) has a flat surface (65) which is pressed against a corresponding flat surface (27) of the axial rear wall (20) of the rotor casing (15).

9. 9. The rotary positive displacement pump (1) according to any one of claims 1 to 8, wherein the heating devices (51, 52) are pressed against the axial rear wall (20) of the rotor casing (15) by threaded fasteners (50) which engage in threaded holes located in the axial rear wall (20) of the rotor casing (15).

10. 10. The rotary positive displacement pump (1) according to any one of claims 1 to 9, wherein the heating device (51, 52) has a curved surface (74) that is curved around and follows at least a portion of the cylindrical outer surface of the first and / or second drive shafts (4, 5).

11. 11. The rotary positive displacement pump (1) according to claim 1, having an axial direction (10) parallel to the first and second drive shafts (4, 5) and a first transverse direction (11), the first transverse direction (11) extending perpendicularly to the axial direction (10) through a center of rotation of the first and second drive shafts (4, 5), the rotary positive displacement pump (1) comprising a first heating device (51) arranged on the outside of the first drive shaft (4) in the first transverse direction (11), and the rotary positive displacement pump (1) comprising a second heating device (52) arranged on the outside of the second drive shaft (5) in the first transverse direction (11).

12. The rotary positive displacement pump (1) according to any one of claims 1 to 11, wherein the heating device (51, 52) does not affect the external pump dimensions.

13. 13. The rotary positive displacement pump (1) according to any one of claims 1 to 12, wherein the axial rear wall (20) of the rotor casing (15) has a recess (80) defined by a flat surface (81) and a radial surface (82), the flat surface (81) being perpendicular to the axial direction (10) of the rotary positive displacement pump (1) and facing towards the rear side of the rotary positive displacement pump (1), the radial surface (82) facing in a direction (11, 12) perpendicular to the axial direction (10), and the heating device (51, 52) having a flat surface (65) pressing against the flat surface (81) of the recess (80) and a radial surface (83) facing the radial surface (82) of the recess (80).

14. The rotor casing (15) has a first cylindrical rotor case hub (36) and a second cylindrical rotor case hub (37), each extending from the axial rear wall (20) of the rotor casing (15), the stationary internal pumping cavity being defined by the axial rear wall (20), the circumferential side wall (21), the axial front wall (22), and the first and second cylindrical rotor case hubs (36, 37), the first cylindrical rotor case hub (36) receiving the first drive shaft (4) therein, and the second cylindrical rotor case hub (37) receiving the first drive shaft (4) therein.

14. The rotary positive displacement pump (1) according to claim 1, wherein an outer surface of the first drive shaft (4) is disposed on an inner surface of the first cylindrical rotor case hub (36), the first sealing arrangement (40a, 40b) being at least partially positioned in an annular space defined by an outer surface of the first drive shaft (4) and an inner surface of the first cylindrical rotor case hub (36), and the second sealing arrangement (41a, 41b) being at least partially positioned in an annular space defined by an outer surface of the second drive shaft (5) and an inner surface of the second cylindrical rotor case hub (37).

15. A first rotary positive displacement pump (1) according to any one of claims 1 to 14, having a first displacement volume per revolution; A second rotary positive displacement pump (1) according to any one of claims 1 to 14, having a second displacement volume per revolution that is greater than the first displacement volume per revolution; Including, A set of rotary positive displacement pumps, wherein both the first and second rotary positive displacement pumps (1) are configured to have identical heating devices (51, 52) fastened to the axial rear wall (20) of the rotor casing (15).

16. A method for heating a rotor casing (15) of a rotary positive displacement pump (1) having a front side and a rear side and / or a fluid product therein, the rotary positive displacement pump (1) comprising a transmission housing (2) and the rotor casing (15), the transmission housing (2) providing rotational support for first and second parallel, axially extending drive shafts (4, 5) having gears (6, 7) in constant mesh such that the first and second drive shafts (4, 5) rotate in opposite directions, the rotor casing (15) being connected to the front side of the transmission housing (2) and having an axial rear wall (20), an axial front wall (22) and a circumferential side wall (21) which together define a stationary internal pumping cavity, the rotor casing (15) providing a driving force to the first drive shaft (4). the rotor casing (15) contains a first rotor (23) drivingly connected to a second drive shaft (5), the first and second rotors (23, 24) configured to rotate in opposite directions and to interact to provide a positive pumping effect on a fluid product, the fluid product entering the internal pumping cavity via a rotor casing inlet (30) and exiting the internal pumping cavity via a rotor casing outlet (31); the rotor casing (15) further includes first and second sealing arrangements (40a, 40b, 41a, 41b) configured to prevent leakage of the fluid product from the stationary internal pumping cavity along the first and second shafts (4, 5), respectively, towards the rear side of the rotor casing (15); the method comprises: - releasably fastening a heating device (51, 52) to the axial rear wall (20) of the rotor casing (15); activating the rotor casing (15), the first and second sealing arrangements (40a, 40b, 41a, 41b) and / or the heating devices (51, 52) for heating the fluid product in the rotor casing (15); Including, The heating device (51, 52) is a heating casing having an internal fluid heating chamber (55), a fluid inlet port (56), and a fluid outlet port (57), the internal fluid heating chamber (55) being fluidly connected to the fluid inlet port (56) and the fluid outlet port (57).

17. A rotary positive displacement pump (1) as described in claim 1, wherein the heating devices (51, 52) are attachable to the axial rear wall (20) of the rotor casing (15), removable from the axial rear wall (20) of the rotor casing (15), and reattachable to the axial rear wall (20) of the rotor casing (15).

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