Patent Application
20090110565
Progressing cavity pumps may be used in various industries to pump materials such as solids, semi-solids, fluids with solids in suspension, highly viscous fluids and shear sensitive fluids, including chemicals, oil, sewage, or the like. A typical progressing cavity pump (also known as a helical gear pump) includes a rotor having one or more externally threaded helical lobes which cooperate with a stator having an internal bore extending axially therethrough. The bore includes a plurality of helical grooves that forms a plurality of cavities with the stator. As the rotor turns within the stator, the cavities progress from the suction end of the pump to the discharge end of the pump. A feeder assembly, such as a twin-screw feeder, may feed the material to the pump.
In one embodiment the present invention is a progressing cavity pump for use in sanitary applications. A twin-screw feeder may be utilized to feed the product to the progressing cavity pump.
More particularly, in one embodiment the present invention is a progressing cavity pump system including a feeder assembly including a hopper for receiving material to be pumped therein. The feeder assembly includes an auger housing receiving an auger therein. The auger housing has an underlying portion positioned generally below the hopper and having a radial opening open to the hopper, and an extension portion which is generally radially closed. The extension portion and the underlying portion are of a one-piece, seamless construction. The pump system further includes a progressing cavity pump including a rotor, a stator, an inlet and an outlet. The rotor is rotationally disposed inside the stator such that rotation of the rotor causes material in the pump to be pumped from the inlet toward the outlet, and the inlet is fluidly coupled to the extension portion.
As shown in
The feeder assembly 12 includes an elongated hopper 16 which is open at its top 18 and bottom ends 20. The hopper 16 maybe relatively wide at its top end 18 to increase its capacity and tapers down to a narrower width at its bottom end 20. The open bottom end 20 is fluidly connected to an auger housing 22 which houses a pair of augers 24 therein (see
The auger housing 22 includes an upper opening 30 (
The augers 24 are counter-rotatably driven by a drive motor 32. In the illustrated embodiment, the motor 32 driving the augers 24 is different from the motor 28 driving the ribbon auger 26. However, if desired, the same motor may be utilized to drive both the augers 24 and the ribbon auger 26, although in this case gearing may need to be implement to drive the augers 24 and ribbon auger 26 at differing rotational speeds.
The auger housing 22 includes an underlying portion 22a positioned below the hopper 16, and an extension portion 22b that is not positioned below the hopper 16 and extends beyond the upper opening 20 of the auger housing 22. The extension portion 22b lacks any radially-positioned openings (i.e. such as the radial opening 20 of the underlying portion 22a), and therefore is generally closed and allows pressure to be generated therein.
The extension portion 22b may be integrally coupled to underlying portion 22a of the auger housing 22. For example, the extension portion 22b may be permanently coupled to the underlying portion 22a (i.e. by welding or the like), or the underlying 22a and extension 22b portions may be formed as a unitary, one-piece (i.e. molded) seamless item. By permanently or integrally or non-removably forming the extension portion 22b with the underlying portion 22a, seams and other points of connection in the internal surface of the auger housing 22 are reduced. This reduces the chances of leakage, eliminates seals and part count, reduces the size of the assembly 12. This connection also creates a smooth inner surface which reduces/eliminates areas in which the pumped materials may be trapped to provide a sanitary transition between the underlying portion 22a and the extension portion 22b. The unitary/one-piece extension portion 22b also makes the feeder assembly specially designed for use with the pump 14.
As shown in
The extension portion 22b may include a removable cover or hatch 36 positioned on an upper side thereof. The hatch 36 (or its inner surface 36a) is contoured to match the profile of the extension portion 22b and/or the profile of the augers 24 received therein. Thus the hatch 36 (or its inner surface 36a) in end view may take the shape of two arcs or circle segments arranged end-to-end to allow the hatch 36 to conform to the augers 24 and provide the benefits described above. As shown in
The downstream end of the extension portion 22b terminates in a flange 40. The flange 40 is attached to a corresponding flange 42 of an input section 44 of a suction housing 46 of the pump 14. The input section 44 may be generally rectangular in cross section, and may take the shape of a rectangle closely drawn around or through the “intersecting circle” cross section of the extension portion 22b of the auger housing 22. In particular, the cross section of one input section 44 is shown in hidden lines in
In this manner, since the input section 44 is at least as large as the extension portion 22b, a “bottleneck” area between the feeder assembly 12 and the pump 14, which would create pressure loss, is avoided. Moreover, since the input section 44 has a generally rectangular cross section (as opposed to, for example, circular), the cross sectional size and shape of the input section 44 closely matches (i.e. within about 10% by cross sectional area, in one case) the cross sectional size and shape of the extension portion 22b to provide for a smooth transition of the pumped materials into the pump 14/suction housing 46.
Thus, the pump 14 and feeder assembly 12 are specifically designed and formed to be utilized together, and the use of a transition piece or pieces to fluidly couple the pump 14 and the feeder assembly 12 are eliminated. The pump 14 and feeder assembly 12 may each be positioned on a wheeled pallet 45 to allow those components, and the system 10, to be maneuvered as desired. Moreover, by eliminating a transition piece, seams and other points of connection in the internal surface of the pump 14 are reduced.
It should also be noted that the input section 44 is integrally coupled to the suction housing 46. For example, the input section 44 may be permanently coupled to the suction housing 46 (i.e. by welding or the like) or may be formed as a unitary, one-piece molded item. Thus, the use of a unitary input section 44 and the elimination of a transition piece reduces the chances of leakage, eliminates seals and part count, and also creates a smooth inner surface which reduces/eliminates areas in which the pumped materials may be trapped to provide a sanitary transition between the feeder assembly 12 and the pump 14.
The suction housing 46 may house an auger 48 therein (see
The rotor 56 fits within the stator 50 to provide a series of helical seal lines where the rotor 56 and stator 50 contact each other or come in close proximity to each other. In particular, the external helical lobe of the rotor 56 and the internal helical grooves of the stator 50 define the plurality of cavities 58 therebetween.
The rotor 56 is rotationally coupled to a motor 59 which drives the rotor 56 to rotate about its central axis and eccentrically rotate within the stator 50. As the rotor 56 turns within the stator 50, the cavities 58 progress from an inlet or suction end of the rotor/stator pair to an outlet or discharge end of the rotor/stator pair. During a single 360° revolution of the rotor 56, one set of cavities 58 is opened or created at the inlet end at exactly the same rate that a second set of cavities 58 is closing or terminating at the outlet end which results in a predictable, pulsationless flow of pumped fluid.
The pitch length of the stator 50 may be twice that of the rotor 56, and the present embodiment illustrates a rotor/stator assembly combination known as 1:2 profile elements, which means the rotor 56 has a single lead and the stator 50 has two leads. However, the present invention can also be used with any of a variety of rotor/stator configurations, including more complex progressing cavity pumps such as 9:10 designs where the rotor 56 has nine leads and the stator 50 has ten leads. In general, nearly any combination of leads may be used so long as the stator 50 has one more lead than the rotor 56. The operation, assembly and components of progressing cavity pumps are discussed in greater detail in U.S. Pat. Nos. 2,512,764, 2,612,845, 5,722,820, 6,120,267 and 6,491,501, the entire contents of which are incorporated herein by reference.
The hopper 16, ribbon auger 26, auger housing 22, augers 24, suction housing 46, auger 48, rotor 56 and stator 50, along with all of the surfaces to which the pumped materials are exposed (i.e. the wetted surfaces of the system 10) may be made of material appropriate for sanitary applications. For example, these surfaces may be made of a relatively hard, non-absorbent and easy to clean material, such as polished stainless steel or nearly any stainless, carbon or alloy steels.
Each auger 24 may each have a shaft 60 that is journaled to the auger housing 22 using a seal assembly 62, as shown in
The bushings 64 can be made of a variety of materials, but may be made of a relatively compliant, high lubricity material. For example, in one embodiment the bushings 64 are made of DELRIN® synthetic resinous plastic material. The bushings 64 may be made of a sanitary material that is approved/appropriate for use in sanitary applications (i.e. FDA-approved materials). Each bushing 64 may have a flange 74 that abuts up against a mounting plate 76 that is part of or coupled to the auger housing 22. The bushings 64 may be split bushings 64 (i.e. each has a radially extending cut 65 entirely through its thickness).
Each o-ring 66 can be made of a variety of materials, such as material suitable for sanitary applications, including fluoroelastomers, VITON® synthetic rubber, or the like. Each o-ring 66 may be mounted on the flange 74 of the bushing 64.
The seals 68 are mounted adjacent to the end of the bushing 64. As shown in
The axially outer-most seal 69 may be made of the same materials as the seals 68, and also have a split. However, the seal 69 may be slightly concave on its axial inner surface 84 and generally flat on its axial outer surface 86 to correspond in shape to the adjacent seal 68 and clamp plate 88, respectively. Each seal 68, 69 may be rated to seal up to a certain pressure (i.e. 25 psi in one embodiment) so the number of seals 68, 69 can be adjusted as necessary to provide the desired sealing characteristics.
The cap or packing gland 70 fits over, and covers, the bushing 64, o-ring 66 and seals 68, 69 to provide mechanical protection to the seal assembly 62. A clamp plate 88 is positioned adjacent to the cap 70 and includes a pair of recesses 90 therein (i.e. circular recesses in the illustrated embodiment) to receive the distal end of the caps 70 therein and retain the caps 70 in place.
The clamp plate 88 receives a set of three knobbed threaded fasteners 94 therethrough, which are in turn threadably received in corresponding threaded holes 96 in the mounting plate 76 to secure the clamp plate 88 to the mounting plate 76. As the clamp plate 88 is secured in place by tightening the threaded fasteners 94, the clamp plate 88 and cap 70 compresses the bushing 64 and o-ring 66, along with the seals 68, 69. The cap 70 is sized to limit the compressive force that can be applied to the seals 68, 69 by the clamp plate 88 to place the seal assembly 62 in the desired state of compression. When properly compressed the ends 82 of the seals 68 can flare outwardly to form the desired seal, as described above.
Because the bushing 64 bears the weight of the auger shaft 60, the bushing 64 is a wear component that may need to be replaced over time. Accordingly, in order to access the bushing 64, the threaded fasteners 94 are unfastened, and the clamp plate 88 is moved along the auger shaft 66, away from the auger housing 22. The cap 70 is then moved along the auger shaft 60, away from the auger housing 22, exposing the bushing 64, o-ring 66 and seals 68, 69. Because the bushing 64 is a split bushing, the bushing 64 can then be removed off of the auger shaft 60 in a radial direction and replaced. If desired, the o-ring 66 and seals 68, 69 can also be removed or cleaned, and replaced. Once the bushing 64, o-ring 66 and seals 68, 69 are reassembled on the auger shaft 60 to form the seal assembly 62, the cap 70 is then slid along the auger shaft 60 to cover the seal assembly 62. The clamp plate 88 is threaded to the mounting plate 76 to place the seal assembly 62 back into the desired state of compression.
Because the bushing 64 and seals 68, 69 are all split components, those components can all be removed from and mounted onto the auger shaft 60 in a radial direction without being slid off of the end of the auger shaft 60. Moreover, although the o-ring 66 may not necessarily be split, if desired the o-ring 66 may be of a type which can be split (i.e. pulled apart) and reassembled by glue, other adhesives, or the like. Alternately, however, the o-ring 66 may not be split or reattachable, which may be acceptable since the o-ring 66 may not often need repair. Thus this arrangement provides significant advantages in that the entire seal assembly 62, or the replaceable/wear components of the seal assembly 62, can be removed and replaced, without having to disassemble the auger shaft 60. Instead, the seal assembly 62 can be accessed, removed and replaced while the auger shaft 60 remains in place.
Moreover, as best shown in
The drawings described above show the use of a seal assembly 62 for journaling the shaft 60 of the augers 24 in the auger housing 22. However, if desired, the same seal assembly 62 described and shown herein may be used to journal the ribbon auger 26 to the hopper 16 in the same manner as described above, to provide the same advantages.
In the embodiment shown in
As shown in
The split portions 50a, 50b can be aligned and coupled together by various structures and mechanisms such that the portions 50a, 50b abut against each other along generally axially-extending seams. In the embodiment of
Moreover, in the illustrated embodiment each stator portion 50a, 50b includes a pair of opposed, axially-extending grooves 108. A sealing component 110 can be positioned in each groove 108 to help seal and align the stator portion 50a, 50b along the axial direction. The sealing component 110 can be made of a variety of materials, such as o-ring material (i.e. a hollow tube). If desired, each groove 108 may be slightly smaller in diameter than the sealing component 110 to ensure the sealing components 110 form an appropriate seal. An o-ring 112 may also be positioned at each axial end of the stator 50. The o-ring 112 and sealing components 110 may be made of the same material as the o-rings 66 discussed above in the context of the seal assembly 62.
Various clamps, rings, and the like can be positioned about the periphery of the stator 50 to keep the stator portions 50a, 50b in place. For example, as shown in
The nature of the split stator 50 can be exploited to address jamming or clogs in the pump 14. In particular, in the event of a jam or clog, the clamps, rings and the like compressing the stator portions 50a, 50b together may be loosened, thereby allowing the split portions 50a, 50b to move radially outwardly which can allow unusually large masses to pass through the stator 50. Once the large mass has passed through, the clamps, rings and the like may be tightened back down. This procedure can be utilized to enable quick servicing of the pump 14 without disassembly. Alternately, the state of compression of the stator portions 50a, 50b can be adjusted (i.e. loosened) and left in that state to correspondingly adjust the pump characteristics.
In the illustrated embodiment the stator 50 is split by a plane extending through its central axis to provide two equally-sized (i.e. 180°) stator portions 50a, 50b. However, if desired the stator 50 can be split in other configurations such that the stator portions 50a, 50b are not equally sized (i.e. a 150° portion and a 210° portion). Moreover, if desired, multiple splits may be provided such that the stator 50 is split into three, four, or more stator portions. These variations may be useful if there are structures surrounding or immediately adjacent to the pump 14 that may hinder access. In this case the stator portions can be configured such that the stator portions can be lifted radially away from the pump 14 in a manner that avoids the surrounding structures.
As noted above, the stator 50 can be made of metals or relative rigid materials, which may be useful for sanitary applications. In this case, the entire stator 50 is made of single type of material throughout its thickness (i.e. there may not be a distinct stator tube 52 and stator liner 54). However, if desired, a stator tube 52, which can be made of metal or the like, may be provided, and a softer inner stator material or stator liner 54 (which defines the helical inner surface) is received in the stator tube 52. In this case the stator tube 52 and stator liner 54 are both split through their entire thickness, as shown in
The stator liner 54 can be any of a variety of materials, silicone, plastic, durameter rubber, nylon, elastomers, nitrile rubber, natural rubber, synthetic rubber, fluoroelastomer rubber, urethane, ethylene-propylene-diene monomer (“EPDM”) rubber, polyolefin resins, perfluoroelastomer, hydrogenated nitriles and hydrogenated nitrile rubbers, polyurethane, epichlorohydrin polymers, thermoplastic polymers, polytetrafluoroethylene (“PTFE”), polychloroprene (such as Neoprene), synthetic elastomers such as HYPALON® polyolefin resins and synthetic elastomers sold by E. I. du Pont de Nemours and Company located in Wilmington Del., synthetic rubber such as KALREZ® synthetic rubber sold by E. I. du Pont de Nemours and Company, tetrafluoroethylene/propylene copolymer such as AFLAS® tetrafluoroethylene/propylene copolymer sold by Asahi Glass Co., Ltd. of Tokyo, Japan, acid-olefin interpolymers such as CHEMROZ® acid-olefin interpolymers sold by Chemfax, Incorporated of Gulfport Miss., and various other materials.
As shown in
Although the stator casing 52 shown in
Having described the invention in detail and by reference to the preferred embodiments, it will be apparent that modifications and variations thereof are possible without departing from the scope of the invention.
