ROTARY LOBE PUMP AND ROTARY LOBES

Abstract

The invention relates to a rotary lobe pump (10) for conveying fluids, in particular liquids laden with solid matter, comprising a casing (45) and at least one pair of intermeshing rotary lobes (1) arranged inside the casing (45), each rotary lobe (1) having at least one recess (13, 43) formed on the circumferential surface (5) thereof and/or at least one recess (41) formed on an end surface (7, 9) thereof. The invention relates to in particular a rotary lobe pump, in which at least one trap member (15, 17, 39, 51) is arranged in at least one recess (13, 41, 43) and is adapted to capture solid matter. The invention also relates to a rotary lobe (1) for a rotary lobe pump (10) for conveying fluids, in particular liquids laden with solid matter, said rotary lobe having at least one recess (13, 43) formed on the circumferential surface (5) thereof and/or at least one recess (41) formed on an end surface (7, 9) thereof.

Description

The present invention relates to a rotary lobe pump for conveying fluids, in particular liquids laden with solid matter, comprising a casing and at least one pair of intermeshing rotary lobes arranged inside the casing, each rotary lobe having at least one recess formed on the circumferential surface thereof and/or at least one recess formed on an end surface thereof.

The invention also relates to a rotary lobe for a rotary lobe pump for conveying fluids, in particular liquids laden with solid matter.

Rotary lobe pumps of the kind specified above are used not only to convey all kinds of fluid, but also and in particular to convey sludge, wastewater, black water, process water, thick matter, bilge water, faecal matter, liquid manure, chemicals and feedstuffs.

Prior art rotary lobe pumps are self-priming and resistant to dry running. The functional principle is based on the rotary lobe pump, operating as a displacement pump, transporting the fluid by means of the at least two rotary lobes along a wall of the casing from the pump inlet to the pump outlet, while the at least two intermeshed rotary lobes in the middle of the casing contact each other fluid-tightly and rotate in opposite directions.

In order to transport the fluid, cavities between two adjacent lobe tips and the casing wall are formed, in which the fluid is conducted along the casing wall from the pump inlet to the pump outlet. To ensure that conveying functions reliably, the gap between a lobe tip and the casing wall is designed to be as small as possible. However, in the case of solids-laden liquids, in particular, this results in greater stresses and strains being imposed on the surface of the lobe tip and the casing wall. During operation, solid matter becomes wedged between the lobe tip and the casing wall. Depending on the kind of solid matter involved, this can cause damage to the surfaces concerned. As a result, the seal tightness of the pump decreases, backflow occurs to a greater extent and the efficiency of the pump decreases. The pump then needs to be serviced, which may involve replacing the casing wall or the rotary lobes.

In order to extend the service life of rotary lobe pumps and concomitantly to extend the maintenance intervals, the approach pursued hitherto was to provide recesses on the circumferential surface of the rotary lobes. This was done with the aim of forcing the solid matter in the fluid into the recesses, thus mitigating wear of the rotary lobe surface and of the surface of the inner casing wall. Such a rotary lobe pump with appropriate rotary lobes is shown, for example, by WO 2007/026109. A rotary lobe pump in which the rotary lobes have a plurality of grooves is also proposed in DE 42 18 855 A1.

However, it has been found that the positive effect of these prior art devices on wear behaviour is dissatisfying.

The object of the present invention was therefore to specify a rotary lobe pump and a rotary lobe which have an enhanced resistance to wear.

The invention achieves its object with a rotary lobe pump of the kind initially specified, in which at least one trap member is arranged in at least one recess and is adapted to capture solid matter. It has been found that accumulation of solid matter in the recesses of the rotary lobe is significantly improved when a trap member is inserted into the recess. Although the volume available in the recesses of the rotary lobe decreases as a result, the trap member helps to capture larger amounts of solid matter and to divert it into the recess. The solid matter is pressed into the recess in any case, to some extent by subsequent solid matter.

Due to solid matter being continuously captured by means of the trap member, an ever-greater amount of solid material accumulates in the recess. The solid material is compacted, with the consequence that, in the medium term, the space between the circumferential surface of the rotary lobe and the casing wall becomes sealed by the compacted solid material. The drive means for the rotary lobes is exposed to stronger torque resistance as a result, but the backflow rate decreases.

The trap member preferably consists of a wear-resistant material so that the trap member also has a certain resistance against penetration of foreign matter that, for its part, exhibits a high level of strength or resistance. A particularly preferred embodiment is one in which the trap member is made of hardened steel. Any damage caused to the trap member due to such solid matter involves substantially less maintenance effort than damage to the rotary lobe or the casing wall. The trap member according to the invention is preferably arranged replaceably in the recess.

In one preferred embodiment of the invention, a gap is formed between an edge of the at least one recess and the at least one trap member. The gap is thus defined by the kind of edging and by the shape of the trap member. The smaller the trap member in comparison with the size of the recess, the greater the distance will usually be between the trap member and the edge, at least in one partial section of the edge. The gap is advantageously designed to receive solid matter captured by the trap member. From the point at which the solid matter captured by the trap member enters the gap, it is preferably pressed into the depths of the recess by subsequent solid matter.

In another preferred embodiment of the invention, the gap has widened wedge-shaped sections. It has been found to be particularly advantageous if the gap is not uniform in shape along its entire length. Sections in which the gap is widened in a wedge shape increase the amount of solid matter captured by the trap member. The widened wedge-shaped section is preferably arranged between the trap member and the edge of the recess in such a way that, in the circumferential direction of the rotary lobe of the rotary lobe pump, solid matter initially enters a wide portion of the wedge-shaped section, in order to then be driven between the increasingly narrowing sides of the wedge-shaped section.

The at least one recess is preferably in the form of a groove and has a cross-section which is substantially embodied as rectangular and/or at least partially conically tapered towards the bottom of the recess, or conically widened at least partially towards the bottom of the recess. From the production engineering perspective, a rectangular shape for the cross-section of the recess can be achieved quickly and cost-efficiently. When the lateral surfaces of the recess are designed to taper towards the bottom of the recess, this facilitates penetration of solid matter into the depths of the recess, whereas a conically extended profile for the lateral surfaces of the recess towards the bottom of the recess makes it more difficult for solid matter to escape from the recess. However, a conically widening profile towards the bottom of the recess also makes cleaning more difficult. An optimal recess design is obtained from the combination of the recess with the trap member inserted into the recess and may vary from case to case. Different geometries may also be provided, depending on the medium that is predominantly being conveyed.

According to a first preferred alternative, the at least one trap member is in the form of a flat body, the height of the flat body being less than or equal to the depth of the recess accommodating the at least one trap member. Making the flat body less high than the recess which accommodates it prevents the flat body itself from coming into frictional contact with the casing wall and damaging the latter as a result. At the same time, this measure ensures that solid matter also collects in compacted form above the trap member itself. This protects the trap member itself against further wear. If a rotary lobe in the rotary lobe pump reaches such a state, however, the disadvantage that the trap member can no longer perform its actual function, namely to channel solid matter into the recess, must be tolerated.

The first preferred alternative is advantageously developed in that one or more wedge-shaped recesses are provided on at least one lateral surface of the at least one trap member, which faces the edge of the recess. The wedge-shaped recesses define at least partially a widened wedge-shaped portion between the edge of the recess and the trap member. The trap member preferably has a distribution, arrangement and shape of wedge-shaped recesses that is optimised for the main application of the specific rotary lobe pump. The wedge-shaped recesses preferably extend in both the radial and the tangential direction (in the case of a trap member inserted into the rotary lobes). This configuration supports the displacement of solid matter into the depths of the recess by subsequent solid matter.

According to another preferred embodiment, the at least one trap member has a plurality of adjacently arranged projections, between each of which a gap is formed. The trap member, preferably embodied as a flat body and having the plurality of projections, preferably functions like a comb. The projections, which may be cylindrical or polygonal in shape, preferably extend from the bottom of the recess in the direction of the surface of the rotary lobe and define widened wedge-shaped sections that each extend between the edge of a recess and two adjacent projections.

According to a second preferred alternative of the present invention, the at least one trap member is embodied in the form of a dowel pin, threaded pin or head screw. A plurality of trap members are preferably fixed adjacently and reversibly detachably in the at least one recess. It is particularly preferred that a gap is formed between each of the adjacent trap members. It is also particularly preferred that the trap members are embodied in the form of dowel pins, threaded pins or head screws define, between themselves and the edge of the recess, widened, wedge-shaped sections of the gap between the edge of the recess and the trap member. Alternatively to the aforesaid elements, the trap members are embodied as elements having a cylindrical, elliptical or polygonal cross-section and which can be separately arranged and fixed in the recess. These elements are preferably arranged in such a way that solid matter is captured and collected between adjacent elements.

Designing the invention with a plurality of trap members per recess, for example in the form of dowel pins, threaded pins or head screws, or other elements are described above, is particularly preferred for use on the circumferential surface of slantingly profiled rotary lobes, also known as Wendelkolben. The possibility of arranging the individual trap members in the recess with exact positions and a precise fit provides significant advantages for production, compared to flat bodies that must be individually produced, particularly since the latter must be shaped precisely to match the profile of the twisted circumferential surface of the rotary lobe,

The one or more trap members in the form of head screws, and which are fixed inside the one or more recesses, preferably have no anti-fatigue portion, and/or are each screwed into a threaded hole whose thread extends in the screwed-in state as far as a contact surface on the head of screw, thus minimising the grip length of the screw connection. The applied tension is derived to as minimal an extent as possible from the longitudinal extension of the screw. This means, conversely, that the screws can be released by turning them a few degrees only. The screws can also be released, advantageously, by knocking them off, for example if the screw heads can no longer be gripped by a spanner due to damage or dirt.

According to a third preferred alternative, the at least one trap member is embodied in the form of a coil spring which is arranged at least predominantly inside the recess, wherein the longitudinal axis of the coil spring is arranged parallel to the bottom of the recess. Much solid matter is advantageously captured in this manner between the individual coils of the coil spring. Due to the coil spring being arranged in a lying position inside the recess, the coils of the coil spring are oriented in such a way that solid matter is guided along the coils into the interior of the recess. In addition to its elasticity in the longitudinal direction of the coil spring, the coil spring is preferably elastically deformable in the radial direction also. The coil spring may thus extend partly beyond the recess. Due to the coil spring being predominantly disposed inside the recess and only a small part of it extending outside the recess, the coil spring is elastically deformed when it comes into tangential contact with the casing wall, and in pressed into the interior of the recess as a result.

According to another preferred alternative embodiment of the invention, the rotary lobes have a sealing line on each vane, along which the rotary lobes are at a minimal distance from an inner wall of the casing of the rotary lobe pump. A plurality of recesses are arranged in the circumferential surface adjacently and preferably parallel to the sealing line, wherein elastically deformable seal members are provided as trap members, which extend partially outside the recess in the direction of the inner wall of the casing. Analogously to the coil springs described in the foregoing, the trap members in the form of elastically deformable seal members are also at a minimal distance from the inner wall of the case, or touch the latter. As a result, additional sealing lines are respectively formed by means of the elastically deformable seal members.

The elastically deformable seal members are preferably designed to be driven into the interior of the recess when they come into contact with the other, oppositely arranged rotary lobes, and to return to their original position after such displacement. In addition thereto, the elastically deformable seal members are also preferably designed to yield to any solid matter acting on them, such that the solid matter passes the displaced seal members into the depths of the recess by being pressed into the latter by subsequent solid matter. The embodiment with trap members in the form of elastic seal members also provides the advantage that, in one arrangement of the recesses accommodating the seal members, additional sealing lines are created immediately adjacent to the sealing line, if the distance between the surface of the rotary lobe from the inner wall of the casing at the location of the recess containing the elastic seal members is not greater than the amount by which the seal members extend beyond the recess that accommodates them.

The invention achieves its object with a rotary lobe of the kind initially specified, said rotary lobe having at least one recess formed on the circumferential surface thereof and/or at least one recess formed on an end surface thereof, at least one trap member being arranged in at least one recess and adapted to capture solid matter. For other advantageous embodiments of the rotary lobe according to the invention, reference is made to the above observations regarding the rotary lobe pump.

The invention further relates to a method for sealing a rotary lobe against an inner wall of the casing of a rotary lobe pump, said method comprising the steps of JOIN**: conveying a fluid, in particular a liquid laden with solid matter, by means of the rotary pump, and capturing the solid matter from the conveyed fluid by one or more trap members which are arranged in one or more recesses of the rotary lobe. With regard to the advantages of the method according to the invention and with regard to advantageous developments thereof, reference is made to the above descriptions of the rotary lobe pump and the rotary lobe.

In the following, the present invention shall be described with reference to preferred embodiments and to the attached drawings, in which

FIG. 1 shows a three-dimensional view of the inventive rotary lobe for the rotary lobe pump according to the invention;

FIG. 2 shows a cross-sectional view through a trap member for the rotary lobe according to the invention;

FIG. 3a shows a three-dimensional view of an alternative trap member for the rotary lobe according to the invention;

FIG. 3b shows a three-dimensional view of another alternative trap member for the rotary lobe according to the invention;

FIG. 4 shows a three-dimensional view of another alternative of a trap member for the rotary lobe according to the invention;

FIG. 5 shows a cross-sectional view of a detail of the rotary lobe according to the invention, in a preferred embodiment;

FIG. 6 shows a cross-sectional view of an alternative embodiment of the rotary lobe according to the invention;

FIG. 7 shows a cross-sectional view of a detail of another alternative embodiment of the rotary lobe according to the invention;

FIG. 8 shows a cross-sectional view of a detail of another alternative embodiment of the rotary lobe according to the invention;

FIG. 9 shows a three-dimensional view of a rotary lobe according to another preferred embodiment of the present invention;

FIG. 10 shows a three-dimensional view of another preferred embodiment of the rotary lobe according to the invention;

FIG. 11 shows yet another embodiment of a rotary lobe according to the invention;

FIG. 12 a partial view of a rotary lobe pump according to the invention;

FIG. 13 shows a cross-sectional view through the rotary lobe pump in FIG. 12; and

FIG. 14 shows a detailed perspective of the view shown in FIG. 12.

FIG. 1 shows an inventive rotary lobe according to a first preferred embodiment. Rotary lobe 1 has three slanting vanes each having a tip portion 3. Rotary lobe 1 has a circumferential surface 5, an upper end surface 7 and a lower end surface 9. A recess 11 extends from the upper end surface 7 to the lower end surface 9 and is adapted to receive a drive shaft. Recesses 13 are provided along the circumferential surface of rotary lobe 1 in each tip portion 3 of the lobes.

FIG. 1 shows examples of two alternative embodiments of the rotary lobe according to the invention. In recess 13, shown in the left in FIG. 1, a trap member in the form of flat body 15 is arranged. A substantially uniform gap 19 is formed between flat body 15 and one edge of recess 13.

A recess 13, in which a plurality of trap members in the form of screws 17 are inserted, is shown on the right in FIG. 1. Screws 17 are screwed with a minimal grip length into a respective thread in the bottom of recess 13. Due to their minimal grip length, screws 17 can still be removed even if they are damaged, or if the recess for the driver is severely deformed. On the right in FIG. 1, between the trap member embodied as screws 17 and the edge of recess 13, a gap is formed which is not uniform along its extension, however. Widened wedge-shaped sections are formed between respectively adjacent screws 17 and the edge of recess 13. The widened wedge-shaped sections 21 are adapted to hold solid matter which has been captured by the trap member, and to receive the solid matter in the recess.

FIGS. 2 to 4 show various embodiments of trap members for the rotary lobe 1 according to the invention. FIG. 2 shows a cross-section of a trap member in the form of a flat body 15.

When the trap members are inserted, the viewing direction substantially corresponds to a radial direction relative to the rotational axis of the rotary lobe. Flat body 15 has a base member 23. A plurality of wedge-shaped recesses 25 are provided in the opposite lateral surfaces of base member 23. Wedge-shaped recesses 25 are designed for catching solid matter.

FIG. 3a shows a three-dimensional view of a trap member in the form of a flat body 15, according to an alternative embodiment. Like the trap member shown in FIG. 2, the trap member shown in FIG. 3a likewise has a base member 23. Base member 23 in FIG. 3a has a substantially trapezoidal cross-section. Two opposite lateral surfaces 26 are oriented such that they taper towards each other. An upper side 27 which faces the casing wall when the trap member is inserted is wider than a underside 29 of the trap member, which when inserted faces the bottom of the recess accommodating it. A plurality of wedge-shaped recesses 25 are provided in the lateral surfaces of base member 23 of flat body 15. The wedge-shaped recesses are offset from each other in order to maximise the size of the wedge-shaped recess. According to FIG. 3a, flat body 15 is designed just like the flat body according to FIG. 4 to be secured in the recess along an axis 30 by means of fastening means (not shown).

The trap member shown in FIG. 3b differs from the one shown in FIG. 3a in that the lateral surfaces 26 of base member 23, into which wedge-shaped recesses 25 are introduced in an offset manner from each other, are aligned parallel to each other, which can be achieved, alternatively, by the base member having a rectangular cross-section or a cross-section in the form of a parallelogram. Also shown in FIG. 3b are two countersunk holes 28 arranged on the upper side 27 for receiving a matching screw head. The base member shown in FIG. 3b is optimised for use in the circumferential surface of a rotary lobe such as the one shown in FIG. 1 or FIG. 9. It is twisted along its longitudinal extension in order to ensure an optimal fit in the recess, likewise twisted, in the circumferential surface of such a rotary lobe.

FIG. 4 shows another embodiment of a trap member in the form of a flat body 15. The flat body 15 in FIG. 4 has a base member 23, from which a plurality of projections 31 project upwards from the upper side 27 of the base member. Projections 31 are arranged substantially parallel to each other and extend in the direction of the casing wall of the rotary lobe pump, when the rotary lobe is inserted. Projections 31 may be optionally arranged at an angle to each other, in order to form V-shaped or A-shaped gaps 33 between adjacent projections 31, which is advantageous for capturing solid matter. In order to secure the trap member in FIG. 4, which is embodied in the form of a flat body 15, a projection 31 is advantageously formed a part of a screw which is screwed along axis 30, through base member 23, into the bottom of the recess for the trap member.

FIGS. 5 to 8 show various advantageous designs for the recesses that accommodate the trap members. FIG. 5 shows a recess 13 of substantially rectangular cross-section. Recess 13 is optionally provided in circumferential surface 5, or in one of the end surfaces 7, 9, and has two substantially parallel lateral surfaces 35. The depth of recess 13 in rotary lobe 1 is slightly greater than the height of trap member 15 or 17 to be accommodated in the recess. When trap member 15, 17 is arranged at a maximum depth in recess 13, trap member 15, 17 preferably rests with its underside on the bottom 37 of recess 13. Each of FIGS. 5 to 8 shows a gap 19 which is formed between the edge of recess 13 and trap member 15, 17.

In contrast to FIG. 5, FIG. 6 shows a recess 13 which does not have an entirely rectangular cross-section. Instead, the cross-section of recess 13 in FIG. 6 is only partly rectangular. Commencing from surface 5, 7, 9, the cross-section of recess 13 tapers initially towards the bottom 37 of the recess and then adopts a rectangular shape.

Viewed from surface 5, 7, 9, the cross-section of recess 13 shown in FIG. 7 widens initially in a conical manner and only after that does it become rectangular in the direction of the bottom 37 of the recess. By comparison, the cross-section of recess 13 in FIG. 8 widens conically substantially entirely towards the bottom of recess 37.

The cross-sections shown in FIGS. 7 and 8 are particularly preferred for trap members having substantially cylindrical cross-sectional profiles, such as elastically deformable seal members 39, or coil springs 51 arranged in a lying position (see FIG. 14). However, it should be realised that trap members in the form of flat bodies 15 or screws 17 can also be disposed in recesses 13 in FIG. 7 or FIG. 8, or in other, appropriate geometries.

The rotary lobes shown in FIG. 1 have trap member receiving recesses disposed solely on the circumferential surface. FIGS. 9 to 11 show other preferred embodiments of the rotary lobe 1 according to the invention, with other, preferred arrangements of the recess.

For example, FIG. 9 shows a three-vaned rotary lobe 1 having three tip portions 3, one on each vane, and otherwise a similar layout to the rotary lobe shown in FIG. 1. Unlike the rotary lobe in FIG. 1, however, the rotary lobe 1 shown in FIG. 9 also has recesses 41 arranged on each vane on end surface 7 (and optionally also on the lower end surface 9), in addition to the recesses 13 arranged on the circumferential surface and having trap members 17 disposed therein. Analogously to the recesses 13 in circumferential surface 5, trap members in the form of screws 17 or as flat bodies 15 or as other forms of trap member according to the invention are formed in recesses 41. The recesses 41 shown in FIG. 9 are arranged substantially radially along the of axis of recess 11. In an optional configuration, recesses 41 must preferably be arranged outside the radial line, and/or at an angle to the radial line.

FIG. 10 shows a two-vaned rotary lobe 1 with a tip portion 3 on each of the two vanes. The two-vaned rotary lobe 1 shown in FIG. 10 has straight vanes. A recess 13 is disposed in each of tip portions 3, in the region of the sealing lip, said recesses extending in circumferential surface 5 from below the upper end surface 7 to just above the lower end surface 9. Recesses 41 are arranged on each vane on end surface 7 of rotary lobe 1 in FIG. 10. Like recesses 13, recesses 41 likewise have a longitudinal axis (not shown). According to the embodiment shown in FIG. 10, the axes of recesses 13 and 41—from the perspective of each vane—do not intersect. It is possible in this manner to continue the length of recesses 13, 41 as far as the edge of the respective surface, without recesses 13, 41 colliding with each other. With regard to receiving trap members in recesses 13, 41, reference is made to the description provided above with reference to FIGS. 1 to 9.

FIG. 11 shows another embodiment of the inventive rotary lobe 1. Rotary lobe 1 as shown in FIG. 11 is likewise a two-vaned rotary lobe with straight vanes. Rotary lobe 1 in FIG. 11 has a tip portion 3 on each vane, a circumferential surface 5, and an upper and a lower end surface 7, 9. Unlike the rotary lobe in FIG. 10, however, two recesses 41 are arranged substantially radially in end surface 7 on each vane of rotary lobe 1. The recesses 41 on end surface 7 are each embodied as a single row, whereas a recess 43 having multiple rows is provided on each vane, in the region of the sealing lip, on the circumferential surface 5 of rotary lobe 1 according to FIG. 11. In FIG. 11, two rows of trap members in the form of screws 17 are arranged in recess 43. Screws 17 are arranged adjacent to and laterally offset from each other inside multiple-rowed recess 43, thus improving the number of gaps formed between screws 17, and in particular their suitability for capturing and wedging solid matter.

FIG. 12 shows a part of a rotary lobe pump 10 according to the invention. Rotary lobe pump 10 has a rotary lobe 1 according to the invention, which is rotatably mounted inside a casing. The casing has a semi-cylindrical section 45. Inside section 45, an inner wall 47 concentric with rotary lobe 1 is formed. When rotary lobe 1 rotates, cavities are formed between rotary lobe 1 and the inner wall of casing 47, within which fluid is transported from a pump inlet to a pump outlet. A cavity is defined by the surface of the inner wall 47 and by the circumferential surface 5 of rotary lobe 1. In order to prevent loss of fluid from one cavity to the other, the distance of rotary lobe 1 from housing section 45 must be kept as small as possible. A sealing function is preferably provided in a sealing portion 49.

Since loss of fluid between the cavities can also occur via end surface 7 of rotary lobe 1, a seal is preferably provided on end surface 7 also. In one particularly preferred embodiment, the seal on the end surface is ensured by trap member 39, 51. This is shown in FIG. 13, which shows a cross-sectional view through the rotary lobe shown in FIG. 12. A recess 41 is provided in end surface 7 and in end surface 9, respectively. One trap member is inserted into the lower recess 41 shown in FIG. 13. The trap member has a substantially cylindrical cross-section. The trap member is embodied either as an elastically deformable seal member 39, or as a coil spring 51. The elastically deformable seal member 39 permits a better seal, whereas the trap member embodied as a coil spring 51 has a greater capacity to capture solid matter.

FIG. 14 shows an enlarged detail of FIG. 12. Sealing portion 49 of rotary lobe 1 has a first sealing lip 53. The clearance between circumferential surface 5 of rotary lobe 1 and inner surface 47 of casing section 45 is minimal along sealing line 53, ideally almost zero. To the right and left of sealing line 53, there are two trap members each arranged inside a respective recess 13, likewise connected along a line 55 to inner wall 47 of casing section 45, or at a minimal distance from inner wall 47. Lines 55 are thus embodied likewise as sealing lines. The sealing lines are oriented substantially parallel to the first sealing lip 53. The tightness of seal and hence the efficiency of rotary lobe 1 of rotary lobe pump 10 is improved by means of the additional sealing lines 55.

Claims

1. A rotary lobe pump for conveying fluids, in particular liquids laden with solid matter, comprising

a casing and at least one pair of intermeshing rotary lobes arranged inside the casing, each rotary lobe having at least one recess formed on the circumferential surface thereof and/or at least one recess formed on an end surface thereof,

characterised in that at least one trap member is arranged in at least one recess and is adapted to capture solid matter.

2. The rotary lobe pump according to claim 1,

characterised in that a gap is formed between an edge of the at least one recess and the at least one trap member.

3. The rotary lobe pump according to claim 1,

characterised in that the gap has widened wedge-shaped sections.

4. The rotary lobe pump according to claim 1,

characterised in that the at least one recess is in the form of a groove and has a cross-section which is

substantially rectangular, and/or

at least partially conically tapered towards the bottom of the recess, or

conically widened at least partially towards the bottom of the recess.

5. The rotary lobe pump according to claim 1,

characterised in that the at least one trap member is in the form of a flat body, wherein the height of the flat body is less than or equal to the depth of the recess accommodating the at least one trap member.

6. The rotary lobe pump according to claim 5,

characterised in that one or more wedge-shaped recesses are provided on at least one lateral surface of the at least one trap member, which faces the edge of the recess.

7. The rotary lobe pump according to claim 5,

characterised in that the at least one trap member has a plurality of adjacently arranged projections, between each of which a gap is formed.

8. The rotary lobe pump according to claim 1,

characterised in that the at least one trap member is embodied in the form of a dowel pin, threaded pin or head screw, wherein a plurality of trap members are preferably fixed adjacently and reversibly detachable in the at least one recess, and wherein a gap is formed between each pair of adjacent trap members.

9. The rotary lobe pump according to claim 1,

characterised in that the at least one trap member is embodied in the form of a coil spring which is arranged at least predominantly inside the recess, wherein the longitudinal axis of the coil spring is arranged parallel to the bottom of the recess.

10. The rotary lobe pump according to claim 1,

wherein the rotary lobes have a sealing line on each vane, along which the rotary lobes are at a minimal distance from an inner wall of the casing, and a plurality of recesses are arranged in the circumferential surface adjacently and preferably parallel to the sealing line,

characterised in that elastically deformable seal members are provided as trap members, which extend partially outside the recess in the direction of the inner wall of the casing.

11. The rotary lobe pump according to claim 8,

characterised in that one or more trap members embodied as head screws are fixed in the at least one recess, wherein the head screws preferably have no anti-fatigue portion, and/or

are screwed into a threaded hole, the thread of which extends in the fastened state to a contact surface of the head screw.

12. Rotary lobes for a rotary lobe pump for conveying fluids, in particular liquids laden with solid matter, said rotary lobe having at least one recess formed on the circumferential surface thereof and/or at least one recess formed on an end surface thereof,

characterised in that at least one trap member is arranged in at least one recess and is adapted to capture solid matter.

13. A method for sealing a rotary lobe against an inner wall of the casing of a rotary lobe pump, comprising the steps of:

conveying a fluid, in particular a liquid laden with solid matter, by means of the rotary lobe pump,

capturing solid matter from the conveyed fluid by means of at least one trap member which is arranged in at least one recess of the rotary lobe.