Rotary piston pump having converging inlet and outlet openings for conveying a fluid medium containing solids

Abstract

Embodiments provide a rotary lobe pump for conveying a fluid medium containing solids. Two rotary lobes have rotational axes that are spaced apart from each other a minimum length distance. A housing enclosing the two rotary lobes has an inlet opening and an outlet opening, each with a continuously decreasing convergence and defined lengths.

Claims

1. A rotary lobe pump for conveying a fluid medium containing solids, comprising: two rotary lobes, each rotary lobe of the two rotary lobes having rotary lobe vanes engaging with other and each rotary lobe having a rotational axis and an outer periphery, wherein the rotational axes of the two rotary lobes lie in a first plane and are spaced a first minimum length apart from each other in the first plane, wherein the outer peripheries of the two rotary lobes partially intersect each other, and a housing including a wall having a predetermined thickness, the wall defining an inner chamber, an inlet opening, and an outlet opening, the wall having an inner surface and an outer surface spaced apart from and opposing the inner surface, wherein the outlet opening is positioned on the wall of the housing opposite from the inlet opening across the inner chamber, the inner surface of the wall enclosing the two rotary lobes and wherein the rotary lobe pump is adapted to convey the medium in a feeding direction through the inner chamber from the inlet opening to the outlet opening in a direction transverse to the first plane, wherein the inlet opening extends through the wall between the outer surface to the inner surface and has a converging cross-section shape that decreases in the feeding direction from the outer surface to the inner surface, the inlet opening having a first flow length that spans from the outer surface to the inner surface in the feeding direction, the inlet opening further including a second length defined at the outer surface between opposing surface portions of the outer surface and a third length defined at the inner surface between opposing surface portions of the inner surface, the second length and the third length each having a respective parallel, spaced relationship with the first plane and are respectively disposed transverse to the feeding direction, wherein the inlet opening guides the fluid medium in between the two rotary lobes in the feeding direction, wherein the outlet opening extends through the wall between the inner surface and the outer surface and has a converging cross-section shape that decreases in the feeding direction from the inner surface to the outer surface, the outlet opening having a second flow length that spans from the inner surface to the outer surface in the feeding direction, the outlet opening further including a fourth length defined at the inner surface between opposing surface portions of the inner surface and a fifth length defined at the outer surface between opposing surface portions of the outer surface, the fourth length and the fifth length each having a respective parallel, spaced relationship with the first plane and are respectively disposed transverse to the feeding direction, wherein the converging cross-section of the inlet opening through the wall that decreases in the feeding direction is a continuous decreasing convergence that occurs along the entire first flow length of the inlet opening, and continuously decreasingly converges in a direction from the outer surface to the inner surface, wherein the converging cross-section of the outlet opening through the wall that decreases in the feeding direction is a continuous decreasing convergence that occurs along the entire second flow length of the outlet opening, and continuously decreasingly converges in a direction from the inner surface to the outer surface, wherein the third length of the inlet opening at the inner surface is less than each of the first minimum length between the axes of the two rotary lobes and the fourth length at the inner surface of the outlet opening, respectively, and wherein the fourth length at the inner surface of the outlet opening is greater than the first minimum length between the axes of the two rotary lobes.

2. The rotary lobe pump according to claim 1, wherein the third length of the inlet opening at the inner surface is less than the fifth length at the outer surface of the outlet opening.

3. The rotary lobe pump according to claim 1, wherein the fourth length at the inner surface of the outlet opening is greater than and the second length at the outer surface of the inlet opening.

4. A rotary lobe pump for conveying a fluid medium containing solids, comprising: two rotary lobes, each rotary lobe of the two rotary lobes having rotary lobe vanes, wherein outer peripheries of the vanes of the two rotary lobes partially intersect each other, and a housing defining a chamber that receives the two rotary lobes therein, the housing including an inner wall and an outer wall spaced opposingly outbound from the inner wall, the inner wall being disposed so as to be adjacent the chamber and surrounding the two rotary lobes and the outer wall having an adjacent, facing relationship to an environment external to the rotary lobe pump that surrounds the outer wall, the housing further defining an inlet opening and an outlet opening, the inlet opening having a first flow length that spans from the outer wall to the inner wall, and the outlet opening having a second flow length that spans from the inner wall to the outer wall, wherein the rotary lobe pump is adapted to convey the fluid medium in a feeding direction of flow flowing through the inlet opening to the chamber containing the two rotary lobes and subsequently flowing through the outlet opening, wherein the inlet opening guides the fluid medium in between the two rotary lobes in the feeding direction of flow, and wherein both the inlet opening and the outlet opening each have a converging cross-section that decreases in the feeding direction of flow such that: (i) the decreasing converging cross-section of the inlet opening is a continuous decreasing convergence that occurs along the entire first flow length of the inlet opening, the continuous decreasing convergence of the inlet opening converging in a direction from the outer wall to the inner wall of the housing, and (ii) the decreasing converging cross-section of the outlet opening is a continuous decreasing convergence that occurs along the entire second flow length of the outlet opening, the continuous decreasing convergence of the outlet opening converging in a direction from the inner wall to the outer wall of the housing.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) A preferred embodiment of the invention shall now be described with reference to the Figures, in which:

(2) FIG. 1: shows a cross-section through a rotary lobe pump according to the prior art,

(3) FIG. 2: shows a cross-section through a first embodiment of a rotary lobe pump according to the invention and

(4) FIG. 3: shows a cross-section through a second embodiment of a rotary lobe pump according to the invention.

DETAILED DESCRIPTION

(5) FIG. 1 shows the prior art, comprising a rotary lobe pump 100 with two rotary lobes 110, 120 and a housing 130. The two rotary lobes 110, 120 each have a rotational axis 111, 121 and four rotary lobe vanes 112, 122. Housing 130 has an inner wall 131 enclosing sections of the outer peripheries of rotary lobes 110, 120, an outer wall 132 defining the outer periphery of the rotary lobe pump and feet 133, 134. Housing 130 has one inlet opening 150 and one outlet opening 140. Outlet opening 140 is surrounded by a pipe connector flange 143 to which a pipeline 160 with an upper wall 161, a lower wall 162 and a middle axis 163 is connected. The middle axis 163 of pipeline 160 is the same as the middle axis of pipe connector flange 143. Inlet opening 150 is also surrounded by another pipe connector flange 153, to which another pipeline 170 with an upper wall 171, a lower wall 172 and a middle axis 173 is connected.

(6) To convey a medium in the direction from inlet opening 150 to outlet opening 140, rotary lobes 110, 120 turn in the direction of rotation shown by arrows 113, 123. Inlet opening 150 and outlet opening 140 each taper towards inner wall 131 of the housing and are embodied with mirror symmetry in relation to mirror plane SF. Between inner wall 131 and outer wall 132, the inlet and outlet openings form side faces 141, 142, 151, 152.

(7) The enclosed angle of the housing, in both the region of the inlet opening and the region of the outlet opening, is α+Δα, i.e., the inner wall of the housing encloses a respective section of the outer periphery of a rotary lobe of (2×α)+(2×αΔ). Such a mirror-symmetrical configuration of the inlet opening and the outlet opening is advantageous with regard to a possible switching of the feeding direction of the rotary lobe pump. However, this solution according to the prior art needs to be improved with regard to sensitivity to foreign matter, frequency of shut-downs, pressure loss, wear and tear, service life and costs of repair and maintenance.

(8) FIGS. 2 and 3 show two embodiments of rotary lobe pumps according to certain embodiments the invention. Components with the same or similar functions are marked with the same reference signs plus 100 (FIG. 2) and plus 200 (FIG. 3) compared to FIG. 1. In the following, the main focus is on the differences between the rotary lobe pump according to the invention, as shown in FIGS. 2 and 3, and the rotary lobe pump known from the prior art, as shown in FIG. 1, and on the differences between the two variants of the invention as shown in FIGS. 2 and 3. FIGS. 2A and 2B illustrate dimensions identifying a first flow length at the housing inlet and a second flow length at the housing outlet, as well as a first minimum length between rotational axes of the two rotary lobes. The figures also illustrate a second length at the outer surface of the inlet opening, a third length at the inner surface of the inlet opening, a fourth length at the inner surface of the outlet opening, and a fifth length at the outer surface of the outlet opening. FIG. 2 illustrates that the third length is less than the first minimum length between axes of the two rotary lobes and a fourth length at the inner surface of the outlet opening. FIG. 2 also illustrates that each of the inlet and the outlet have a continuous decreasing convergence that occurs along the entire first flow length and the second flow length.

(9) FIGS. 2 and 3 differ from the prior art solution shown in FIG. 1 by the configuration of outlet openings 240, 340. In both the variants shown in FIGS. 2 and 3, outlet openings 240, 340 have the same design. FIGS. 2 and 3 differ in that inlet opening 250 in FIG. 2 is the same as inlet opening 150 according to the prior art in FIG. 1, whereas FIG. 3 shows an inlet opening 350 that differs not only from the prior art in FIG. 1 but also from the variant of the invention shown in FIG. 2.

(10) The different configurations of inlet openings 250, 350 in FIGS. 2-4 is made clear, in particular, by the different inflow characteristics of the medium, as schematically represented by the arrows in the region of inlet openings 250, 350. Due to the inlet opening 250 tapering in the direction of inner wall 231 of housing 230 in FIG. 2, the medium is guided in the middle between the two rotary lobes 210, 220. In the non-tapering inlet opening 350 in FIG. 3 and FIG. 4, in contrast, the medium flows across the entire cross-section of inlet opening 350 towards a wider region of the two rotary lobes 310, 320.

(11) In accordance with the invention, outlet openings 240, 340 in FIGS. 2-4 taper in the feeding direction, i.e. in the direction from the inner wall 231, 331 to the outer wall 232, 332 of housing 230, 330. The circular paths on which the tips of rotary lobe vanes 212, 222, 312, 322 turn define the outer peripheries 214, 224, 314, 324 of the rotary lobes, which partially intersect. The enclosed angle of inner wall 231, 331 of the housing is β−Δβ above and below the outlet side of the rotary lobe pump. The enlargement of outlet opening 240, 340 on discharge is therefore greater in a direction running parallel to the plane of rotational axes 211, 221, 311, 321 and perpendicularly to rotational axis 211, 221, 311, 321 than the distance between rotational axes 211, 221, 311, 321.

(12) The lower side face or discharge ramp 242, 342 slopes more strongly than the upper side face 241, 241. This is realized, in the variant of the invention shown in FIGS. 2 and 3, by the upper discharge ramp 241, 341 of outlet opening 240, 340 ending at the outer wall 232, 332 of housing 230, 330 at the height of the rotational axis 211, 311 of the upper rotary lobe 210, 310, and by the lower discharge ramp 242, 342 of outlet opening 240, 340 not ending at the outer wall 232, 332 of housing 230, 330 until an angle of β+Δρ is reached. A vertical offset V thus ensues between outlet opening 240, 340 and the lower wall 262, 362 of the connected pipeline 260, 360, said offset serving as a barrier for the solids a, b. The dot-dash arrows show the tangential direction in which the solids are flushed out of the cavities between the rotary lobe vanes. These tangential directions point away from the rotary lobe vanes of the respective opposite rotary lobe. As can be seen from the dotted arrows, the paths of motion of the solids a conveyed by the lower rotary lobe 220, 320 extend in a curve from outlet opening 240, 340 into the interior of the connected pipeline 260, 360. The paths of motion of the solids b conveyed by the upper rotary lobes 210, 310 likewise extend in a curve from outlet opening 240, 340 into the interior of connected pipeline 260, 360. These paths of motion of the solids, achieved by the outlet openings being configured in accordance with the invention, substantially reduce clogging with the solids in the rotary lobe pump and thus lead to improvements with regard to sensitivity to foreign matter, frequency of shut-downs, pressure loss, wear and tear, service life and costs of repair and maintenance of the rotary lobe pump according to the invention, in comparison with the prior art.