Rotary positive displacement pump with shroud

Abstract

A rotary positive displacement pump (1) for pumping fluid products, wherein the pump (1) has a front side and a rear side. The pump includes a drive housing (2) having an axial front wall (38) and an axial rear wall, and providing rotational support for a first drive shaft (4) and a second drive shaft (5) having gears (6, 7) in a constant meshing state, such that the first drive shaft (4) and the second drive shaft (5) are arranged to rotate in opposite directions. The pump further includes a rotor housing (15) connected to the front side (13) of the drive housing (2), and having an axial rear wall (20), an axial front wall (22), and a circumferential side wall (21) that together define a fixed internal pumping chamber. The rotor housing (15) houses a first rotor (23) driven to the first drive shaft (4) and a second rotor (24) driven to the second drive shaft (5). The first rotor (23) and the second rotor (24) are configured to rotate in opposite directions and interact to provide a positive pumping effect for the fluid product entering the pumping chamber via the rotor housing inlet (30) and exiting the pumping chamber via the rotor housing outlet (31). Furthermore, the axial front wall (38) of the drive housing (2) and the axial rear wall (20) of the rotor housing together define an intermediate space (42) through which the first drive shaft (4) and the second drive shaft (5) extend. The rotary positive displacement pump (1) further includes a first shield (51) located in the intermediate space (42) and surrounding the first drive shaft (4) and the second drive shaft (5) to prevent human contact with the first drive shaft (4) and the second drive shaft (5); or a first shield (51) located in the intermediate space (42) and surrounding the first drive shaft (4) to prevent human contact with the first drive shaft (4), and a second shield (52) located in the intermediate space (42) and surrounding the second drive shaft (5) to prevent human contact with the second drive shaft (5).

Description

Technical Field

[0001] This disclosure relates to a rotary positive displacement pump. The rotary positive displacement pump according to this disclosure will be described primarily in the context of a circumferential piston pump, but the pump according to this disclosure is not limited to this particular type of pump, but may alternatively be implemented in the form of a rotary cam pump, a gear pump, etc. Background Technology

[0002] In the field of rotary positive displacement pumps, health and safety regulations require adequate protection of the exposed area of ​​the drive shaft between the rotor housing and the drive housing to prevent injury to people (e.g., workers, technicians, cleaners, etc.). Conversely, to comply with industry hygiene regulations, a portion of the drive shaft must be exposed or visible to allow for rapid identification of seal leaks at the drive shaft.

[0003] One known solution involves mounting a shroud on the outer surface of the pump to cover the entire area between the rotor housing and the drive housing. However, this approach sometimes requires the complete temporary removal of the shroud for detecting small drive shaft seal leaks. Another drawback of this method is that fluid leaking from the drive shaft seals may solidify and accumulate in the enclosed area, posing a hygiene risk and potentially damaging the drive housing oil seal.

[0004] Existing covers are easily removed, lost, and damaged, and it is not uncommon for end users to completely remove the covers to give permanent visibility of the sealed area, thus rendering the entire purpose of the cover assembly ineffective.

[0005] The shroud, fitted to the outer surface of the pump and covering the intermediate space between the rotor housing and the drive housing, presents other challenges. For example, pumps equipped with flushable drive shaft seals require suitable flushing media connections, but pre-cutting the shroud to allow for the installation of flushing connections when assembling unflushed drive shaft seals may violate health and safety requirements. Similarly, pumps equipped with rotor housing heating / cooling also require suitable heating / cooling media connections, but pre-cutting the shroud to allow for the installation of heating media connections when assembling unflushed drive shaft seals may violate health and safety requirements.

[0006] This means that different shroud designs may be required depending on the type of seals assembled to the pump and whether rotor housing heating / cooling is implemented, thus significantly increasing the cost and complexity associated with the design, manufacture, distribution, and spare parts handling of shrouds for pumps.

[0007] Therefore, there is a need for a rotary positive displacement pump that is improved in terms of cost-effectiveness and user-friendliness. Summary of the Invention

[0008] One object of this disclosure is to provide a rotary positive displacement pump that avoids the problems mentioned above. This object is achieved at least in part by the features of the independent claim. The dependent claims cover other developments of the rotary positive displacement pump.

[0009] According to a first aspect of this disclosure, a rotary positive displacement pump for pumping fluid products is provided. The pump has a front side and a rear side, and includes: a drive housing having an axial front wall and an axial rear wall, and providing rotational support for parallel, axially extending first and second drive shafts having gears in a constant meshing state, such that the first and second drive shafts are arranged to rotate in opposite directions; and a rotor housing connected to the front side of the drive housing, having an axial rear wall, an axial front wall, and a circumferential side wall that together define a fixed internal pumping chamber. The rotor housing houses a first rotor driven to the first drive shaft and a second rotor driven to the second drive shaft, the first and second rotors being configured to rotate in opposite directions and interacting to provide a positive pumping effect for a fluid product entering the pumping chamber via a rotor housing inlet and exiting the pumping chamber via a rotor housing outlet. The axial front wall of the transmission housing and the axial rear wall of the rotor housing together define an intermediate space through which the first drive shaft and the second drive shaft extend, and the rotary positive displacement pump further includes a first guard located in the intermediate space and surrounding the first drive shaft to prevent human contact with the first drive shaft, and a second guard located in the intermediate space and surrounding the second drive shaft to prevent human contact with the second drive shaft.

[0010] A rotary positive displacement pump for pumping fluid products is also provided. The pump has a front side and a rear side, and includes: a drive housing having an axial front wall and an axial rear wall, and providing rotational support for parallel, axially extending first and second drive shafts having gears in a constant meshing state, such that the first and second drive shafts are arranged to rotate in opposite directions; and a rotor housing connected to the front side of the drive housing, having an axial rear wall, an axial front wall, and a circumferential side wall that together define a fixed internal pumping chamber. The rotor housing houses a first rotor driven to the first drive shaft and a second rotor driven to the second drive shaft, the first and second rotors being configured to rotate in opposite directions and interacting to provide a positive pumping effect for a fluid product entering the pumping chamber via a rotor housing inlet and exiting the pumping chamber via a rotor housing outlet. The axial front wall of the drive housing and the axial rear wall of the rotor housing together define an intermediate space through which the first and second drive shafts extend. The rotary positive displacement pump further includes a first shroud located within the intermediate space and surrounding the first drive shaft, and a second shroud located within the intermediate space and surrounding the second drive shaft. This prevents human contact with the first and second drive shafts.

[0011] According to a second aspect of this disclosure, a rotary positive displacement pump for pumping fluid products as described above is provided, but wherein the rotary positive displacement pump includes, instead of a first and second shield, a single first shield located in the intermediate space and surrounding a first drive shaft and a second drive shaft to prevent human contact with the first and second drive shafts.

[0012] A rotary positive displacement pump for pumping fluid products, as described above, is also provided, but wherein the rotary positive displacement pump includes a single first shield located in the intermediate space and surrounding the first and second drive shafts, instead of a first shield and a second shield. This prevents human contact with the first and second drive shafts.

[0013] In this way, a pump with a new type of shroud is provided, which allows the shroud to be positioned closer to the shaft, allowing access to the seals, flushing connections, and other optional pump features, while maintaining the same shroud design, thus providing a cost-effective pump. Because the shroud does not need to be disassembled and reinstalled during maintenance, the new pump is more user-friendly. Consequently, the risk of operating the pump without the shroud is reduced.

[0014] Other advantages are achieved by implementing one or more of the features of the dependent claims.

[0015] In some exemplary embodiments, the first shield, or each of the first and second shields, is made of a curved metal plate, particularly stainless steel, and preferably includes an integral attachment piece. This achieves a robust shield.

[0016] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the first shield, or each of the first and second shields, is fastened to the front wall of the transmission housing. This provides a concealed and compact shield, and makes shield removal more difficult for increased safety.

[0017] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the first shield, or each of the first and second shields, is fastened to the front wall of the transmission housing by a plurality of fastening members having a longitudinal direction arranged parallel to the axial direction of the first and second drive shafts. This also allows for a more concealed and compact shield installation, and makes shield removal more difficult for increased safety.

[0018] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, as seen along the radial direction of the pump and in areas without shroud attachments, the cross-section of the first shroud, or each of the first and second shrouds, may have a length in the axial direction and a thickness in the radial direction, wherein the length is at least three times, particularly five times, and more particularly at least ten times, the thickness. As a result, an aesthetically pleasing shroud that does not occupy a large amount of space is provided.

[0019] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the radial distance between the outer surface of the first drive shaft or the second drive shaft and the radial outer surface of the first shield, or any of the protective bodies in the first shield or the second shield, over at least 50%, particularly at least 75%, of the circumference of the first shield or the first shield and the second shield does not exceed 50%, particularly 30%, of the diameter of the first drive shaft in the axial region where the first shield and the first drive shaft overlap. Therefore, the shield is installed relatively deep and concealed in an intermediate space, thus conforming to the construction of various types of pumps.

[0020] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the radial distance between the outer surface of the transmission housing and the first shield, or any of the protective elements in the first and second shields, is greater than 50% of the diameter of the first drive shaft in the axial region where the first shield overlaps with the first drive shaft. Therefore, the shield is installed relatively deep and concealed in the intermediate space, thus conforming to the construction of various types of pumps.

[0021] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the first shield surrounding the first drive shaft and / or the second drive shaft, or the protective body of each of the first shield and the second shield, is made as a single piece. This achieves a robust and cost-effective design.

[0022] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the protective body surrounding the first drive shaft and / or the second drive shaft, or each of the first and second drives shafts, is made of multiple parts, particularly two parts, assembled adjacent to each other. This design simplifies installation and disassembly when needed.

[0023] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the rotary positive displacement pump further includes a first outer end plate for securing a roller bearing of a first drive shaft to a drive housing, and a second outer end plate for securing a roller bearing of a second drive shaft to a drive housing, wherein the first and second outer end plates are attached to the drive housing by means of the same fastening means used for attaching a first shroud, or a first and second shroud, to the drive housing. As a result, fewer parts are required to manufacture the pump.

[0024] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the protective body of the first shield, or each of the first and second shields, is axially displaced from the adjacent surface of the shield attachment device such that a first axial clearance is provided between the protective body and the front surface associated with the front wall of the drive housing, and / or axially displaced from the rear surface of the rear wall of the rotor housing such that a second axial clearance is provided between the protective body and the rear wall of the rotor housing, to allow improved visibility of the first and second drive shafts, and to allow improved detection of leaks of fluid products and / or drive oil at the seals of any of the drive shafts associated with the first shield, or any of the first and second shields. These exemplary embodiments may be described as follows: the protective body of the first shield, or each of the first and second shields, is axially displaced from the adjacent surface of the shield attachment device and / or the rear surface of the rear wall of the rotor housing, such that a first axial clearance is provided between the protective body and the front surface associated with the front wall of the transmission housing, and a second axial clearance is provided between the protective body and the rear wall of the rotor housing, to allow improved visibility of the first and second drive shafts, and to allow improved detection of leaks of fluid products and / or transmission oil at the seals of any of the drive shafts associated with the first shield, or either the first or second shield.

[0025] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the protective body of the first shield, or each of the first and second shields, is axially displaced from the adjacent surface of the shield attachment device such that a first axial clearance is provided between the protective body and the front surface associated with the front wall of the drive housing, and / or axially displaced from the rear surface of the rear wall of the rotor housing such that a second axial clearance is provided between the protective body and the rear wall of the rotor housing. This allows for improved visibility of the first and second drive shafts. This also allows for improved detection of leaks of fluid products and / or drive oil at the seals of any of the drive shafts associated with the first shield, or any of the first and second shields. These exemplary embodiments can be described as the protective body of the first shield, or each of the first and second shields, being axially displaced from the adjacent surface of the shield attachment device and / or the rear surface of the rear wall of the rotor housing such that a first axial clearance is provided between the protective body and the front surface associated with the front wall of the drive housing, and a second axial clearance is provided between the protective body and the rear wall of the rotor housing. This allows for improved visibility of the first and second drive shafts. This also allows for improved detection of leaks of fluid products and / or transmission oil at drive shaft seals associated with the first shield, or any of the first and second shields.

[0026] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, each of the first axial clearance and the second axial clearance is at least 5 mm, particularly in the range of 5-10 mm. This allows for leak detection while preventing accidental contact between a person and the drive shaft.

[0027] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the protective body of the first shield, or each of the first shield and the second shield, includes recesses and / or through holes to allow improved visibility of the first drive shaft or the first drive shaft and the second drive shaft, and to allow improved detection of leaks of fluid products and / or transmission oil at any of the drive shaft seals associated with the first shield, or the first shield and the second shield.

[0028] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the protective body of the first shield, or each of the first and second shields, includes a recess and / or a through-hole. This allows for improved visibility of the first drive shaft or the first and second drive shafts. This also allows for improved detection of leaks of fluid products and / or transmission oil at any associated drive shaft seals in the first shield, or the first and second shields.

[0029] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the first and second shields have the same design. This allows for improved overall cost-effectiveness of the pump.

[0030] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the first shield, or each of the first and second shields, has a protective body. This allows for a combination of compact shield design with robust construction and a simple, cost-effective design. The protective body may surround the first drive shaft and / or the second drive shaft.

[0031] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, the first shield, or each of the first and second shields, has a plurality of shield attachment devices. This allows for a combination of compact shield design with robust construction and a simple, cost-effective design. The shield attachment devices may extend from the protective body. The shield attachment devices may clamp to the front wall or intermediate component of the drive housing.

[0032] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, each of the first and second shields has an annular protective body. This allows for a combination of compact shield design with robust construction and a simple, cost-effective design. The annular protective body may have a sleeve-like shape.

[0033] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, each of the first and second shields has a plurality of shield attachment devices. This allows for a combination of compact shield design with robust construction and a simple, cost-effective design. The shield attachment devices may extend from the annular protective body. The shield attachment devices may clamp to the front wall of the drive housing.

[0034] In some exemplary embodiments that can be combined with any one or more of the embodiments described above, each of the first and second shields has an annular protective body with a sleeve-like shape, and a plurality of shield attachment devices extending from the annular protective body and clamping to the front wall of the transmission housing. This allows for a combination of compact shield design with robust construction and a simple and cost-effective design.

[0035] Other features and advantages of the invention will become apparent when examined in conjunction with the appended claims and the description below. Those skilled in the art will recognize that different features of this disclosure can be combined to produce embodiments other than those explicitly described above and below, without departing from the scope of this disclosure. Attached Figure Description

[0036] The rotary positive displacement pump according to this disclosure will now be described in detail with reference to the accompanying drawings, in which...

[0037] Figure 1 A side view of an exemplary embodiment of the pump is schematically shown.

[0038] Figure 2 A front view of an exemplary embodiment of the pump is shown schematically.

[0039] Figure 3 A perspective view of the rear portion of the rotor housing according to an exemplary embodiment of the pump is schematically shown.

[0040] Figure 4 A perspective view schematically illustrating an exemplary embodiment of the pump rotor is shown.

[0041] Figure 5 The principle of pumping operation according to an exemplary embodiment of the pump is schematically illustrated.

[0042] Figure 6 Another side view of an exemplary embodiment of the pump is schematically shown.

[0043] Figure 7 A perspective view of the drive housing according to an exemplary embodiment of the pump is schematically shown.

[0044] Figure 8 The cross-section of the area of ​​the first shield is schematically shown.

[0045] Figure 9-10 An exemplary embodiment of the first shield is schematically shown.

[0046] Figure 11A -C schematically illustrates three views of an exemplary embodiment of the shield.

[0047] Figure 12A -C schematically illustrates three views of another exemplary embodiment of the shield.

[0048] Figure 13A -C schematically illustrates three views of yet another exemplary embodiment of the shield.

[0049] Figure 14 A side view of the transmission housing with a drive shaft and a first and second shield is shown, as well as

[0050] Figure 15 A side view of the transmission housing with a single first shield surrounding the two drive shafts is shown. Detailed Implementation

[0051] The various aspects of this disclosure will be described below in conjunction with the accompanying drawings to illustrate, but not limit, the disclosure, wherein similar names denote similar elements, and variations of the described aspects are not limited to the specifically illustrated embodiments but may be applied to other variations of this disclosure.

[0052] Figure 1A side view schematically illustrates a first exemplary embodiment of a rotary positive displacement pump 1 for pumping fluid products according to the present disclosure. The pump 1 has a drive housing 2 including swivel supports 3a and 3b for a first drive shaft 4 and a second drive shaft 5 extending parallel to each other in an axial direction 10 of the pump 1. For example, for each of the first drive shaft 4 and the second drive shaft 5, the swivel supports 3a and 3b may be provided in the form of a front annular roller bearing 3a and a rear annular roller bearing 3b, both fastened to the drive housing 2 and rotatably holding the first drive shaft 4 and the second drive shaft 5, respectively.

[0053] The first axially extending drive shaft 4 carries the first gear 6, and the second axially extending drive shaft 5 carries the second gear 7. The first gear 6 and the second gear 7, i.e., the gear bodies, are arranged in a constant meshing state, meaning that they are constantly geared into each other. Furthermore, since the first gear 6 and the second gear 7 are directly engaged with each other, they rotate in opposite directions.

[0054] like Figure 2 As shown, the transmission housing 2 has a first length along the axial direction 10, a second length along a first lateral direction 11 perpendicular to the axial direction 10, and a third length along a second lateral direction 12 perpendicular to both the axial direction 10 and the first lateral direction 11. The pump is also defined in a radial direction 19, which herein refers to any direction perpendicular to the axial direction 10. Therefore, both the first lateral direction 11 and the second lateral direction 12 are also radial directions.

[0055] As seen along the axial direction 10, the transmission housing further has a front side 13 and a rear side 14.

[0056] The end portion 9 of one of the first drive shaft 4 and the second drive shaft 5 (e.g., such as the first drive shaft 4) may extend through the wall of the transmission housing 2 at the rear side of the transmission housing 2 for rotational connection with a rotational torque source (e.g., such as a motor) to power the pump 1.

[0057] The transmission housing 2 may be made of metal (e.g., such as stainless steel, cast iron, steel or aluminum alloy), and the first drive shaft 4 and the second drive shaft 5 may be made of steel.

[0058] The transmission housing 2 may also include a support structure 8 for allowing the transmission housing 2 to be attached to an external support surface, for example by means of threaded bolts or other types of fasteners. The transmission housing may be made as a single piece or composed of multiple sub-parts.

[0059] exist Figure 1In an exemplary embodiment of the pump shown, the pump 1 further includes a rotor housing 15 connected to the front side 13 of the transmission housing 2. For example, the rotor housing 15, made of 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 housing 15 can be clamped against the front side 13 of the transmission housing 2 by means of a plurality of threaded bolts or nuts 16 or similar threaded components.

[0060] The pump 1, comprising the transmission housing 2 and the rotor housing 15, has a front side 17 and a rear side 18, and Figure 1 Front view of pump 1 Figure 2 The diagram schematically shows the first rotor 23 and the second rotor 24 located within the rotor housing 15, indicated by dashed lines.

[0061] like Figure 2 As can be seen, multiple bolts or nuts 16 for clamping the rotor housing 15 extend through the entire rotor housing 15 and are visible from the front side 17 of the pump 1.

[0062] exist Figure 1 and Figure 2 In an exemplary embodiment, the rotor housing 15 includes an axial rear wall 20, a circumferential side wall 21, and an axial front wall 22 that together define a closed, fixed internal pumping chamber.

[0063] Because the rotor housing 15 accommodates the first rotor 23 and the second rotor 24 located within the internal pumping chamber, the rotor housing 15 is openable to allow access to the internal pumping chamber. Figure 1 and Figure 2 In an exemplary embodiment, the proximity is made possible by making the rotor housing 15 into two parts: a rear portion 25 of the rotor housing including an axial rear wall 20 and a circumferential side wall 21, and a separate front cover 26 that serves as an axial front wall 22 of the rotor housing 15, wherein the removable front cover 26 is removably fastened to the rear portion 5 of the rotor housing by a suitable attachment arrangement.

[0064] A schematic 3D view of an exemplary embodiment of the rotor housing rear portion 25 according to the present disclosure, as seen partially from the front side of the rotor housing rear portion 25, is shown in... Figure 3 Provided by China.

[0065] The removable front cover 26 can be clamped against the rear portion 25 of the rotor housing by means of the same plurality of threaded bolts or nuts 16 for clamping the rotor housing 15 against the front side 13 of the drive housing 2. Alternatively, a separate attachment arrangement may be provided for attaching the front cover 26 to the rear portion 25 of the rotor housing.

[0066] exist Figure 2-3In an exemplary embodiment, the rotor housing 15 further includes a fluid product inlet opening 30 for allowing a fluid product to enter (e.g., be drawn into) the internal pumping chamber, and a fluid product outlet opening 31 for allowing a fluid product to leave (e.g., be pumped out) the internal pumping chamber.

[0067] As mentioned above, the rotor housing 15 also houses a first rotor and a second rotor configured to generate the pumping function of the pump. The first rotor 23 is rotatably secured to the front end of the first drive shaft 4, and the second rotor 24 is rotatably secured to the front end of the second drive shaft 5. Therefore, as by Figure 5 As indicated by the arrows, the first rotor 23 and the second rotor 24 are configured to rotate in opposite directions.

[0068] An exemplary embodiment of a first rotor 23 and a second rotor 24 that may have substantially the same design is shown in Figure 1 and Figure 2 A 3D view schematically showing, and partially seen from the rear, of an exemplary embodiment of one of the first rotor 23 and the second rotor 24. Figure 4 Provided by China.

[0069] Each of the first rotor 23 and the second rotor 24 has at least one, and preferably multiple, rotor blades 32 and rotor drive element 33, which is configured to be mounted torque-resistantly on a rotor seat of the associated drive shafts 4, 5.

[0070] The rotor drive element 33 of each rotor 23, 24 may be substantially disc-shaped or sleeve-shaped, and includes a central bore or recess 44 for mounting on the associated drive shaft 4, 5. The bore or recess 44 may be defined by a cylindrical mounting surface 48 having a spline 45, or by a non-circular mounting surface, to allow the rotor to be mounted torque-resistantly on the rotor seat of the associated drive shaft 4, 5.

[0071] refer to Figure 5 In this exemplary embodiment of pump 1, during operation of pump 2, the first rotor 23 and the second rotor 24 are configured to rotate in opposite directions at the same rotational speed. The first rotor 23 and the second rotor 24 are configured to define a pumping volume within a space 35, which is limited by adjacent rotor blades of the same rotor and the walls 20, 21, 22 of the internal pumping chamber. Furthermore, as by Figure 5 As indicated by the arrows, during the rotation of the first rotor 23 and the second rotor 24, the fluid product is configured to be conveyed from the fluid product inlet opening 30 along the outside of each rotor 23, 24, and to the fluid product outlet opening 31.

[0072] Specifically, as the rotor blades (pistons) 32 rotate around the circumference of the pumping chamber, as the first rotor 23 and the second rotor 24 disengage, they continuously generate a partial vacuum at the product inlet opening 30, causing fluid product to enter the pump 1. The fluid product is then transported around the pumping chamber by the rotor blades 32. The flow direction generated by the pump 1 can be reversed by simply changing the rotational direction of the first rotor 23 and the second rotor 24.

[0073] The specific form and number of rotor blades 32 can vary considerably, and Figure 2 , Figure 4 and Figure 5 The specific rotor wing design shown is merely an exemplary embodiment of the rotor wing, and therefore the pump may have rotors 23, 24 with other types of rotor wing designs according to this disclosure.

[0074] refer to Figure 3 The rotor housing 15 may include a first cylindrical rotor housing hub 36 extending from the rear wall 20 and a second cylindrical rotor housing hub 37 extending from the rear wall 20. The first hub 36 and the second hub 37 are substantially hollow cylindrical sleeves that open toward their two axial sides. Furthermore, the axial direction of each cylindrical hub 36, 37 is aligned with the axial direction 10 of the pump 1.

[0075] The first rotor hub 36 is configured to receive the first drive shaft 4, and the second rotor hub 37 is configured to receive the second drive shaft 5. In other words, in the assembled state, the first rotor hub 36 is aligned with the first drive shaft 4, and the second rotor hub 37 is aligned with the second drive shaft 5. Therefore, the first hub 36 and the second hub 37 are displaced from each other along the first lateral direction 11.

[0076] Before the transmission housing 2 is assembled with the rotor housing 15, the front ends of the first drive shaft 4 and the second drive shaft 5 protrude forward beyond the front surface 13 of the transmission housing. Subsequently, during the assembly of the transmission housing 2 and the rotor housing 15, the front ends of the first drive shaft 4 and the second drive shaft 5 are inserted into the first hub and the second hub from the rear, respectively, and the rear side of the rotor housing 15 contacts the front surface 13 of the transmission housing 2. In this state, the front ends of the first drive shaft 4 and the second drive shaft 5 extend through the entire axial length of the first hub 36 and the second hub 37.

[0077] refer to Figure 1 According to some exemplary embodiments, the pump includes a rotor housing seal 57 configured to prevent fluid product from leaking from the pumping chamber into the intermediate space 42 along the first drive shaft 4 or the second drive shaft 5. Similarly, according to some exemplary embodiments, the pump includes a drive housing seal 58 configured to prevent drive oil from leaking from the drive housing into the intermediate space 42 along the first drive shaft 4 or the second drive shaft 5.

[0078] Figure 6 A side view of an exemplary embodiment of pump 1 is shown, and Figure 7 A side view of the same pump 1 is shown, with the rotor housing 15 removed.

[0079] refer to Figure 1 , Figure 6 and Figure 7 The transmission housing 2 may include a first axially protruding attachment portion 60 and a second axially protruding attachment portion 61 facing the rotor housing 15 and located on opposite sides of the drive shafts 4 and 5. The rotor housing 15 may then be connected to the front side 13 of the transmission housing 2 via the first axially protruding attachment portion 61 and the second axially protruding attachment portion 62, thereby creating an intermediate space 42 between the front wall 38 of the transmission housing 2 and the rear wall 20 of the rotor housing 25.

[0080] like Figure 1 and Figure 6 As shown, the first axially protruding attachment portion 60 and the second axially protruding attachment portion 61 are provided only on two opposite sides of the transmission housing 2, making it possible to approach the intermediate space 42 from the second side to the side 12.

[0081] exist Figure 1 In an exemplary embodiment, the pump does not have a rotating housing heating and no seal flushing connection, thus providing a relatively empty intermediate space 42. To ensure that people such as workers, technicians, or cleaners do not accidentally come into contact with the rotating first drive shaft 4 or second drive shaft 5 during operation of the pump 1, a separate and independent first shield 51 is provided in the intermediate space 42 and surrounds the first drive shaft 4 to prevent people from contacting the first drive shaft 4, and a separate and independent second shield 52 is provided in the intermediate space 42 and surrounds the second drive shaft 5 to prevent people from contacting the second drive shaft 5.

[0082] Each of the first guard 51 and the second guard 52 is fastened to the front wall 38 of the drive housing 2 by a plurality of fastening members 53, the fastening members 53 having a longitudinal direction arranged parallel to the axial direction 10 of the first drive shaft 4 and the second drive shaft 5. Thus, removing the first guard 51 and the second guard 52 by the user without first separating the rotor housing 15 from the pump 1 is typically complex or even impossible. Therefore, the risk of the pump 1 operating with the guards not properly installed is reduced, thereby improving user-friendliness.

[0083] For example, the fastening member 53 may be a threaded member, such as a screw, nut, or bolt. Alternatively, the fastening member 53 may be inserted into a hole or recess formed in a cover attachment device 56 (such as an integral attachment piece 56) passing through each of the first cover 51 and the second cover 52.

[0084] Each of the first shield 51 and the second shield 52 is designed and installed to provide a first axial clearance 54 of at least 5 mm between the protective body of each of the first shield 51 and the rear wall of the rotor housing, particularly an axial clearance in the range of 5-10 mm.

[0085] Similarly, each of the first shield 51 and the second shield 52 is designed and installed to provide a second axial clearance 55 of at least 5 mm between the protective body of each of the first shield 51 and the front wall 38 of the transmission housing 2, particularly an axial clearance in the range of 5-10 mm.

[0086] exist Figure 6 In an exemplary embodiment, the pump is provided with a seal flushing arrangement. For example, a seal flushing arrangement may be provided to the pump to cool or clean, for example, the sealing area of ​​rotor housing seal 57. A compatible flushing fluid must then be used and supplied at the correct pressure and flow rate. The flushing may be opened, for example, simultaneously with or before starting the pump, and closed simultaneously with or after stopping the pump.

[0087] To provide flushing fluid to the seal, a dedicated rotor housing 15 is provided with integrally formed tubing and a first flushing connector 63 and a second flushing connector 64. This seal flushing arrangement and flushing connectors 63, 64 are partially located in the intermediate space 42, but primarily in the region near the outer surface of the pump to allow easy access to the connectors 63, 64. However, since the first shield 51 and the second shield 52 are located relatively close to the first drive shaft 4 and the second drive shaft 5, i.e., not in the region near the outer surface of the pump, they can be used in accordance with... Figure 1 The pump's shields are the same as shields 51 and 52, thereby reducing the number of different versions of the first and second shields.

[0088] Therefore, refer to Figure 1-7This disclosure relates to a rotary positive displacement pump 1 for pumping fluid products, wherein the rotary positive displacement pump 1 according to some exemplary embodiments has a front side 17 and a rear side 18, and includes a drive housing 2 having an axial front wall 38 and an axial rear wall, and providing rotational support for a parallel and axially extending first drive shaft 4 and a second drive shaft 5 having gears 6, 7 in a constant meshing state, such that the first drive shaft 4 and the second drive shaft 5 are arranged to rotate in opposite directions. The rotary positive displacement pump 1 further includes a rotor housing 15 connected to the front side 13 of the drive housing 2 and having an axial rear wall 20, an axial front wall 22, and a circumferential side wall 21 that jointly define a fixed internal pumping chamber. The rotor housing 15 houses a first rotor 23 drivenly connected to the first drive shaft 4 and a second rotor 24 drivenly connected to the second drive shaft 5, wherein the first rotor 23 and the second rotor 24 are configured to rotate in opposite directions and interact to provide a positive pumping effect for a fluid product entering the pumping chamber via a rotor housing inlet 30 and exiting the pumping chamber via a rotor housing outlet 31. The axial front wall 38 of the transmission housing 2 and the axial rear wall 20 of the rotor housing 15 together define an intermediate space 42 through which the first drive shaft 4 and the second drive shaft 5 extend. The rotary positive displacement pump 1 further includes a first shield 51 located in the intermediate space 42 and surrounding the first drive shaft 4 to prevent human contact with the first drive shaft 4, and a second shield 52 located in the intermediate space 42 and surrounding the second drive shaft 5 to prevent human contact with the second drive shaft 5.

[0089] Thus, the first shroud 51, or the first shroud 51 and the second shroud 52, can be positioned significantly closer to the first drive shaft 4 and the second drive shaft 5, allowing for increased access to the seal flushing connection and / or heating / cooling arrangements as an optional additional feature in some embodiments, while largely maintaining the same shroud and eliminating the need for shroud removal. In other words, by reducing the radial distance between the shroud and the first and second drive shafts, and by securing the shroud to the gearbox in the intermediate space 42 between the drive housing 2 and the rotor housing 15, the need for shroud removal during operation or minor maintenance procedures is eliminated. The net result is a more compact, robust, and cost-effective design that requires fewer shroud modifications and reduces the risk of operating the pump without properly installed shrouds.

[0090] The term "enclose" as used above means that the first shield 51 substantially or completely encloses the first drive shaft 4, and the second shield 51 substantially or completely encloses the second drive shaft 4. A shield is considered to substantially enclose the drive shaft when it encloses at least 75%, particularly at least 90%, of the total circumference of the drive shaft. In other words, a shield is considered to enclose the shaft even if, for any reason, it has a relatively small and short gap along its circumference.

[0091] like Figure 1 , Figure 6 and Figure 7 As illustrated in the schematic, according to some exemplary embodiments, depending on the characteristics and design of the transmission housing 2, each of the first shield 51 and the second shield 52 is fastened to the front wall 38 of the transmission housing 2, with or without any intermediate components, such as exemplary outer end plates 73, 74 as will be described below.

[0092] In addition, such as Figure 1 , Figure 6 and Figure 7 As illustrated schematically, according to some exemplary embodiments, the first shield 51 and the second shield 52 may have the same design. In other words, the first shield 51 and the second shield 52 may be identical to simplify manufacturing and reduce costs associated with spare parts handling.

[0093] Figure 8 A cross-sectional view of an exemplary embodiment of the attachment area from the first shield 51 to the transmission housing 2 is shown schematically.

[0094] refer to Figure 1 , Figure 7 and Figure 8 According to some exemplary embodiments, each of the first shield 51 and the second shield 52 has an annular protective body 70 with a sleeve-like shape, and a plurality of attachment devices 56 in the form of attachment pieces 56 extending from the annular protective body 70 and clamping to the front wall 38 of the transmission housing 2.

[0095] By making the shield and attachment device 56 a single piece, i.e. having an integrally formed or integrally formed attachment piece 56, a particularly robust shield is provided. However, the attachment device 56 may alternatively be a separate part for holding and securing the shield to the transmission housing 2.

[0096] In some exemplary embodiments, the first shield 51, or each of the first shield 51 and the second shield 52, is made of a bent sheet of metal, particularly stainless steel, and includes an integral attachment piece. Thus, the shield can be manufactured, for example, by stamping the sheet metal to provide a flat working portion, which is then rolled or bent into a more annular shape. Edges can be welded to form a closed annular protective body, and the integral attachment piece 56 can be folded outwards to be oriented substantially perpendicular to the axial direction of the annular protective body.

[0097] Therefore, the protective body 70 surrounding the first shield 51 or the first shield 51 and the second shield 52 of the first drive shaft 4 and / or the second drive shaft 5 can be made as a single piece.

[0098] refer to Figure 1 , Figure 7 and Figure 8 In some exemplary embodiments, the rotary positive displacement pump 1 may further include a first outer end plate 73 for securing the roller bearing 3a of the first drive shaft 4 to the transmission housing 2, and a second outer end plate 74 for securing the roller bearing 3a of the second drive shaft 5 to the transmission housing 2, wherein the first outer end plate 73 and the second outer end plate 74 are attached to the transmission housing 2 by means of the same fastening member 53 used to attach the first shield 51 and the second shield 52 to the transmission housing 2. This reduces the number of components required, further improving cost-effectiveness.

[0099] Figure 9 A cross-section of an exemplary embodiment in which the first protective cover 51 is in the assembled position relative to the front wall 38 of the transmission housing 2 and the rear wall 20 of the rotor housing 15 is schematically shown. Figure 10 The same view is shown, but only the first shield 51 is included.

[0100] According to some exemplary embodiments, each of the first shield 51 and the second shield 52 may have an annular body region 70 surrounding the associated drive shafts 4, 5, and an attachment means 56 for securing the annular shield 70 to the drive housing, such as an integral attachment piece 56. Complete closure of the first drive shaft 4 and the second drive shaft 5 may be undesirable in order to comply with regulations regarding leak detection from the rotor housing seal 57 or the drive housing seal 58.

[0101] Therefore, according to some exemplary embodiments, the annular guard may be positioned slightly axially displaced from adjacent wall surfaces (e.g., the front wall 38 of the drive housing 2 and the rear wall 20 of the rotor housing 15), as this allows for visible detection of any leaks in this area of ​​the pump 1. This axially displaced installation of the guard 70 is achieved, for example, by causing the attachment device 56 to protrude axially from the guard by a certain distance, thereby creating a first axial gap 76 between the guard 70 and the front surface 78 of the wall to which the guard is attached.

[0102] Figure 9 and Figure 10 The shield in Figure 11A-11C Further shown in various views, and as Figure 11B As shown, the first axial clearance 76 extends over certain sections 80 of the entire circumference of the shield 51. Figure 11B In an exemplary embodiment of the shield, the first axial gap extends substantially continuously between adjacent attachment devices 56, thereby extending over at least about 75% of the total circumference of the shield.

[0103] Refer again Figure 9 The first shield further defines a second axial gap between the shield and the rear wall 20 of the rotor housing 15 by simply not extending all the way to the rear wall 20.

[0104] Therefore, particularly in at least about 50% of the total circumference of the associated shields, the protective body 70 of each of the first shield 51 and the second shield 52 is axially displaced from the adjacent surface 75 of the shield attachment device 56 and / or the rear surface 85 of the rear wall 20 of the rotor housing, such that a first axial clearance 76 is provided between the protective body 70 and the front surface 78 associated with the front wall 38 of the transmission housing 2, and a second axial clearance 77 is provided between the protective body 70 and the rear wall 20 of the rotor housing. This allows for improved visibility of the first drive shaft 4 and the second drive shaft 5, as well as improved detection of leaks, such as from fluid products and / or transmission oil from any of the drive shaft seals associated with the first shield 51 and the second shield 52.

[0105] The first axial clearance 76 and the second axial clearance 77 may have a length 81 of at least 5 mm, particularly in the range of 5-10 mm, in the axial direction 10 of the pump. The size of the clearance may extend, for example, at least 25%, particularly at least 50%, of the total circumference of each of the first shroud 51 and the second shroud 52.

[0106] refer to Figure 10 As seen along the radial direction of the pump and in the area without the shroud attachment device 56, each of the first shroud 51 and the second shroud 52 has a cross-section having a length 59 in the axial direction 10 and a thickness 65 in the radial direction, wherein the length 59 is at least three times, particularly five times, and more particularly at least ten times the thickness 65.

[0107] The cross section of the first shield 51, defined by its length 59 along the axial direction 10 and its thickness 65 along the radial direction, corresponds to the annular protective body of the first shield 51.

[0108] Here, the total axial length 82 of the first shield 51 basically corresponds to the axial length 59 of the body of the first shield 51 and the axial length 82 of the first axial gap 76.

[0109] In this exemplary embodiment, the integrally formed attachment piece has a material thickness of about 0.5-3 mm 83 and a protruding length of about 10-40 mm 84.

[0110] Depending on size and specific operating conditions, the first shield 51 and the second shield 52 can have various designs. Three different exemplary designs of the first shield 51 and the second shield 52 are shown in... Figure 11A -C, 12A-C and 13A-C are schematically shown.

[0111] exist Figure 12AIn an exemplary embodiment of -C, the protective body 70 of each of the first shield 51 and the second shield 52 includes a recess 79 to allow for further improved visibility of the first and second drive shafts, and to allow for improved detection of leaks of fluid products and / or transmission oil at the drive shaft seals associated with the first shield, or any of the first and second shields. Figure 12A As shown in -C, such a recess 79 can be combined with the first axial clearance 76 described above. Alternatively, the first axial clearance 76 can be omitted, and only any recess 79 can be used.

[0112] exist Figure 13A In an exemplary embodiment of -C, the protective body 70 of each of the first shield 51 and the second shield 52 includes a through hole 86 for allowing improved visibility of the first drive shaft 4 and the second drive shaft 5, and for allowing improved detection of leaks of fluid products and / or transmission oil at any associated drive shaft seals in the first shield 51 and the second shield 52. Figure 13A As shown in -C, such a hole 86 can be combined with the first axial clearance 76 described above. Alternatively, the first axial clearance 76 can be omitted, and any hole 86 can be used alone, or the hole 86 can be combined with the recess 79.

[0113] Figure 14 A side view of the transmission housing 2 in the axial direction 10 according to an exemplary embodiment of the pump 1 is shown, wherein the radial distance 66 between the outer surface of the first drive shaft 4 or the second drive shaft 5 and the radial outer surface of any of the protective bodies 70 in the first and second housings 51 and 52 does not exceed 50% of the diameter 71 of the first drive shaft 4 in the axial region 72 where the first housing 51 overlaps with the first drive shaft 4. This is measured in the radial direction orthogonal to the surfaces of the drive shafts 4 and 5.

[0114] In other words, the radial distance between the shroud and the associated drive shaft is relatively small, thus providing a compact design in which a particular shroud is compatible with a wide range of pump variations.

[0115] In addition, refer to again Figure 14 In some exemplary embodiments of the pump, the radial distance 67 between the outer surface 68 of the drive housing 2 and any of the protective bodies 20 in the first shroud 51 and the second shroud 52 is greater than 50% of the diameter of the first drive shaft in the axial region 72 where the first shroud 51 overlaps with the first drive shaft 4. This is measured in the radial direction orthogonal to the surface of the protective body 70 in each of the first shroud 51 and the second shroud 52. Furthermore, this can be applied to at least 50%, particularly at least 75%, of the circumference of the first shroud 51 and the second shroud 52.

[0116] In other words, the shroud is spaced apart from the outer surface 68 of the transmission housing 2, thus providing a compact design in which the particular shroud is compatible with a wide range of pump variations.

[0117] In addition, such as Figure 15 As schematically shown, according to some exemplary embodiments, the rotary positive displacement pump 1 may include a single first shield 51 located in the intermediate space and surrounding both the first drive shaft 4 and the second drive shaft 5, for preventing human contact with the first drive shaft 4 and the second drive shaft 5. In some pump designs, this design may be advantageous in terms of manufacture, assembly, and compactness.

[0118] like Figure 15 As shown, a single shield may have a generally elliptical shape with or without a narrow central waist. Figure 15 In the example, the shield can be viewed as an elliptical shape with a central region that narrows sharply, similar to an hourglass shape, but the narrowing can alternatively be less pronounced.

[0119] Furthermore, although not explicitly shown, the protective body 70 surrounding the first shield 51 or each of the first shield 51 and the second shield 52 may alternatively be made of multiple parts, particularly two parts, assembled adjacent to each other. This design would likely allow for the removal of the shields without removing the rotor housing 15.

[0120] It will be appreciated that the above description is merely exemplary in nature and is not intended to limit this disclosure, its application, or use. Although specific examples have been described in the specification and shown in the accompanying drawings, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from the scope of this disclosure as defined in the claims. Furthermore, modifications may be made to adapt particular situations or materials to the teachings of this disclosure without departing from the essential scope of this disclosure.

[0121] Therefore, it is intended that this disclosure is not limited to specific examples of the best mode currently contemplated for carrying out the teachings of this disclosure, as shown in the accompanying drawings and described in the specification, but rather that the scope of this disclosure shall include any embodiments falling within the foregoing description and the appended claims. Reference numerals mentioned in the claims should not be construed as limiting the scope of the subject matter protected by the claims, and their sole function is to facilitate the understanding of the claims.

Claims

1. A rotary positive displacement pump (1) for pumping fluid products, the pump (1) having a front side and a rear side and comprising: A transmission housing (2) having an axial front wall (38) and an axial rear wall and providing rotational support for a first drive shaft (4) and a second drive shaft (5) having gears (6, 7) in a constant meshing state, extending parallel and axially, such that the first drive shaft (4) and the second drive shaft (5) are arranged to rotate in opposite directions. The rotor housing (15) is connected to the front side (13) of the transmission housing (2) and has an axial rear wall (20), an axial front wall (22) and a circumferential side wall (21) that together define and fix the internal pumping chamber. The rotor housing (15) houses a first rotor (23) driven to the first drive shaft (4) and a second rotor (24) driven to the second drive shaft (5). The first rotor (23) and the second rotor (24) are configured to rotate in opposite directions and interact to provide a positive pumping effect for the fluid product entering the pumping chamber via the rotor housing inlet (30) and exiting the pumping chamber via the rotor housing outlet (31). The axial front wall (38) of the transmission housing (2) and the axial rear wall (20) of the rotor housing together define an intermediate space (42), through which the first drive shaft (4) and the second drive shaft (5) extend. The rotary positive displacement pump (1) further includes: - A first shield (51) located in the intermediate space (42) and surrounding the first drive shaft (4) and the second drive shaft (5) to prevent human contact with the first drive shaft (4) and the second drive shaft (5), or - A first shield (51) located in the intermediate space (42) and surrounding the first drive shaft (4) to prevent human contact with the first drive shaft (4), and a second shield (52) located in the intermediate space (42) and surrounding the second drive shaft (5) to prevent human contact with the second drive shaft (5). The protective body (70) of each of the first shield (51) or the first shield (51) and the second shield (52) is axially displaced from the adjacent surface (75) of the shield attachment device (56) such that a first axial clearance (76) is provided between the protective body (70) and the front surface (78) associated with the axial front wall (38) of the drive housing (2), and / or axially displaced from the rear surface (85) of the axial rear wall (20) of the rotor housing such that a second axial clearance (77) is provided between the protective body (70) and the axial rear wall (20) of the rotor housing, to allow improved visibility of the first drive shaft and the second drive shaft, and to allow improved detection of leakage of fluid products and / or drive oil at the seals of any of the drive shafts associated with the first shield (51) or the first shield (51) and the second shield (52).

2. The rotary positive displacement pump according to claim 1, wherein, The first shield (51), or each of the first shield (51) and the second shield (52), is made of a bent metal plate.

3. The rotary positive displacement pump according to claim 2, wherein, The first shield (51), or each of the first shield (51) and the second shield (52), is made of stainless steel sheet.

4. The rotary positive displacement pump according to claim 2, wherein, The first shield (51), or each of the first shield (51) and the second shield (52), includes an integral attachment piece.

5. The rotary positive displacement pump according to any one of claims 1-4, wherein, The first shield (51), or each of the first shield (51) and the second shield (52), is fastened to the axial front wall (38) of the transmission housing.

6. The rotary positive displacement pump according to any one of claims 1-4, wherein, Each of the first shield (51), or the first shield (51) and the second shield (52), is fastened to the axial front wall (38) of the transmission housing (2) by a plurality of fastening members (53), the fastening members having a longitudinal direction arranged parallel to the axial direction (10) of the first drive shaft (4) and the second drive shaft (5).

7. The rotary positive displacement pump according to claim 6, wherein, The fastening component is a screw, nut, or bolt.

8. The rotary positive displacement pump according to any one of claims 1-4, wherein, As seen along the radial direction (19) of the pump and in the area without the shroud attachment device (56), the cross section of the first shroud (51), or each of the first shroud (51) and the second shroud (52) has a length (59) along the axial direction (10) and a thickness (65) along the radial direction, wherein the length (59) is at least three times the thickness (65).

9. The rotary positive displacement pump according to claim 8, wherein, The length (59) is at least five times the thickness (65).

10. The rotary positive displacement pump according to claim 9, wherein, The length (59) is at least ten times the thickness (65).

11. The rotary positive displacement pump according to any one of claims 1-4, wherein, At least 50% of the circumference of the first shield (51) or the first shield (51) and the second shield (52), the radial distance (66) between the outer surface of the first drive shaft (4) or the second drive shaft (5) and the radial outer surface of the first shield (51) or any of the protectors (70) in the first shield (51) and the second shield (52) does not exceed 50% of the diameter (71) of the first drive shaft (4) in the axial region (72) where the first shield (51) overlaps with the first drive shaft (4).

12. The rotary positive displacement pump according to claim 11, wherein, At least 50% of the circumference of the first shield (51) or the first shield (51) and the second shield (52), the radial distance (66) between the outer surface of the first drive shaft (4) or the second drive shaft (5) and the radial outer surface of the first shield (51) or any of the protective bodies (70) in the first shield (51) and the second shield (52) does not exceed 30% of the diameter (71) of the first drive shaft (4) in the axial region (72) where the first shield (51) overlaps with the first drive shaft (4).

13. The rotary positive displacement pump according to claim 11, wherein, At least 75% of the circumference of the first shield (51) or the first shield (51) and the second shield (52), the radial distance (66) between the outer surface of the first drive shaft (4) or the second drive shaft (5) and the radial outer surface of the first shield (51) or any of the protectors (70) in the first shield (51) and the second shield (52) does not exceed 50% of the diameter (71) of the first drive shaft (4) in the axial region (72) where the first shield (51) overlaps with the first drive shaft (4).

14. The rotary positive displacement pump according to claim 13, wherein, At least 75% of the circumference of the first shield (51) or the first shield (51) and the second shield (52), the radial distance (66) between the outer surface of the first drive shaft (4) or the second drive shaft (5) and the radial outer surface of the first shield (51) or any of the protectors (70) in the first shield (51) and the second shield (52) does not exceed 30% of the diameter (71) of the first drive shaft (4) in the axial region (72) where the first shield (51) overlaps with the first drive shaft (4).

15. The rotary positive displacement pump according to any one of claims 1-4, wherein, The radial distance (67) between the outer surface (68) of the transmission housing (2) and the first shield (51), or any of the protective bodies (70) in the first shield (51) and the second shield (52) is greater than 50% of the diameter (71) of the first drive shaft in the axial region (72) where the first shield (51) overlaps with the first drive shaft (4).

16. The rotary positive displacement pump according to any one of claims 1-4, in, The protective body (70) of the first shield (51) surrounding the first drive shaft (4) and / or the second drive shaft (5), or each of the first shield (51) and the second shield (52), is made of a single piece.

17. The rotary positive displacement pump according to any one of claims 1-4, wherein, The protective body (70) surrounding the first shield (51) and / or the second drive shaft (5) is made of a plurality of parts assembled adjacent to each other to form an annular shield.

18. The rotary positive displacement pump according to claim 17, wherein, The protective body (70) of the first shield (51) surrounding the first drive shaft (4) and / or the second drive shaft (5), or each of the first shield (51) and the second shield (52), is made of two parts assembled adjacent to each other to form an annular shield.

19. The rotary positive displacement pump according to any one of claims 1-4, wherein, The rotary positive displacement pump (1) further includes a first outer end plate (73) for securing the roller bearing (3a) of the first drive shaft (4) to the transmission housing (2), and a second outer end plate (74) for securing the roller bearing (3a) of the second drive shaft (5) to the transmission housing (2), wherein the first outer end plate (73) and the second outer end plate (74) are attached to the transmission housing (2) by means of the same fastening member (53) as the fastening member for attaching the first shield (51), or the first shield (51) and the second shield (52) to the transmission housing (2).

20. The rotary positive displacement pump according to any one of claims 1-4, wherein, Each of the first axial clearance (76) and the second axial clearance (77) is at least 5 mm.

21. The rotary positive displacement pump according to claim 20, wherein, Each of the first axial clearance (76) and the second axial clearance (77) is in the range of 5-10 mm.

22. The rotary positive displacement pump according to any one of claims 1-4, wherein, The protective body (70) of each of the first shield (51) or the first shield (51) and the second shield (52) includes a recess (79) and / or a through hole (86) to allow improved visibility of the first drive shaft (4) or the first drive shaft (4) and the second drive shaft (5) and to allow improved detection of leakage of fluid products and / or transmission oil at any drive shaft seal associated with the first shield (51) or the first shield (51) and the second shield (52).

23. The rotary positive displacement pump according to any one of claims 1-4, wherein, The first shield (51) and the second shield (52) have the same design.

24. The rotary positive displacement pump according to any one of claims 1-4, wherein, Each of the first shield (51), or the first shield (51) and the second shield (52), has a protective body (70) and a plurality of shield attachment devices (56) extending from the protective body (70).

25. The rotary positive displacement pump according to any one of claims 1-4, wherein, Each of the first shield (51) and the second shield (52) has an annular protective body (70) with a sleeve-like shape, and a plurality of shield attachment devices (56) extending from the annular protective body (70) and clamping to the axial front wall (38) or intermediate part of the transmission housing (2).

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