LOBULAR TYPE ROTARY PUMP

Abstract: A self-cleaning, lobular-type rotary pump which includes means for detecting seal failure between the gear box (11) and pump housing (12). Passages (55, 56) extend from the low pressure side of the seals to the exterior of the pump, so that any liquid or lubricant bleeding past the seals will be observable from outside the pump. The rotors are cut with lobes, the tips of which are provided with scraping means (59, 60, 61) for cleaning the clearance surfaces of the housing and the adjacent rotor to prevent excess build-up of deposits on such surfaces.

Description: LOBULAR TYPE ROTARY PUMP Background 1. Field of the Invention The present invention relates to an improved positive displacement pump and more particularly to a lobular type rotary pump which is self-cleaning and highly efficient. In general, pumps for moving liquids and/or fluids have been classified or typed according to structure and mode of operation in three main categories, i.e. , centri- fugal, rotary and reciprocating. Particular uses have developed for each type of pump depending upon the capa¬ bilities, cost, efficiency, etc. of each type. The char¬ acteristics of the fluid to be pumped or the task to be accomplished often dictate the type of pump to be used. in this respect, the viscosity of the fluid, the presence or absence of entrained air or solid materials in the fluid, constant or intermittent flow requirements, quantity and rate of flow required, suction and lift requirements, etc., all enter into the determination of the type of pump which is best suited for a particular application. Rotary pumps are generally positive displacement pumps consisting of a housing containing gears, lobes, cams, screws, vanes, plungers or similar elements actuated by rotation of a drive shaft (see U.S. Patent No. 4,057,375). These pumps are characterized by their close running clear¬ ances and the absence of suction and discharge valves. Neglecting leakage, such pumps deliver almost constant capacity, against variable discharge pressures. Rotary s.£ G .T pumps, by virtue of their positive displacement action, are particularly suited for applications where suction lift (pressure below atmospheric) exists at the pump inlet. Typically, such pumps are used in the transfer of liquids of all viscosities and find application in chemical pro¬ cesses, food handling, marine cargo loading and unloading, ire protection and various industrial services. O ten thought of as viscous liquid pumps, these pumps are actu¬ ally not confined to such service alone. In fact, they will handle almost any liquid that is free of hard and abrasive solids. Lobular type rotary pumps are characterized by rotors cut with 2—4, or more, lobes on each rotor. The rotors are synchronized for positive rotation in proper angular relationship by external timing gears which transmit power between the rotor shafts but do not displace liquid or fluid. Because of the close running clearances, such pumps are self-priming and will, if necessary, handle liquids with entrained gas or air. This type of pump de- pends upon the close running clearances between the rotors and between the rotors and the housing to transport the liquid from the inlet to the outlet and to then force it into the outlet. The close clearances allow such pumps to operate efficiently with very little slip, since the surface tension of the liquid tends to decrease the clear- - ances and innibit leakage past the lobes of the rotors. This characteristic has been beneficial with fluids which tend to lubricate the surfaces of the housing and rotors, O but nas created problems in connection with liquids which tend to precipitate solids that build up on the mating surfaces of the rotors and housing. As materials, such as salts or minerals, are deposited through alternate use and subsequent drying, the running clearances are reduced to the point that uneven pressures can be created on the shaft bearings, causing uneven wear and consequent mis¬ alignment, or the freedom of the rotor to revolve within the housing can be impaired or even prevented. The pump then becomes clogged and is unuseable. The pump must then be removed from service, dismantled and cleaned to remove the deposits and restore the running clearances. In addition, lobular type rotary pumps in which both rotors are driven require external timing gears to maintain the rotors in synchronized relationship with each other. These timing gears are mounted in a gear box in close prox¬ imity to the pump housing and are well-lubricated to resist wear. Seals are provided between, the gear box and the pump housing to prevent seepage of lubricant or liquid from one to the other. However, failure of one of the seals may allow passage of lubricant or liquid along a shaft to contaminate either the lubricant in the gear DOX or the liquid in the pump housing. Such seal failure has been difficult to detect and has usually gone un- detected, resulting in destruction of, or damage to, the pump and/or contamination and spoilage of the liquid being pumped. OMPI SUMMARY OF THE INVENTION The present invention provides a lobular type rotary pump in which the initial running clearances are on the order of .003 inch and which therea ter decrease during operation of the pump. The pump also includes means for detecting seal failure between the gear box and the pump housing before either the pump or the liquid being pumped is damaged or contaminated. This includes a pas¬ sage between the low pressure side of the seals and the exterior of the pump, so that any liquid or lubricant oleeding past the seals will be observable from the ex¬ terior of the pump. The rotors of the pump are each pro¬ vided with a plurality of radially-extending lobes which are configured to mesh with the lobes of the adjacent rotor. Tne tips of the lobes are shaped to closely fol¬ low the contours of the roots of the adjacent lobes and the spaces therebetween, as well as the surfaces of the pump housing. Means are provided on the tips for cleaning the clearance surfaces of the housing and the adjacent rotor to prevent excess build-up of deposits on such sur¬ aces. BRIEF DESCRIPTION OF THE DRAWINGS The best mode presently contemplated of carrying out the ' invention will be understood from the detailed descrip- tion of the embodiments illustrated in the accompanying drawings, in which: Fig. 1 is a perspective view of a pump according to the present invention; Fig . 2 is an elevation view partly in section of the pump of Fig . 1 ; Fig. 3 is a plan view of the center plate of Fig. 2; Fig. 4 is a plan view of a rotor illustrating the shape of the lobes; and Fig. 5a is a plan view and 5b an elevation view of the tip of a lobe of Fig. 4 at an enlarged scale. DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS As shown in Fig. 1 of the drawing, a lobular type ro¬ tary pump according to the present invention includes a gear box 11 and a pump housing 12 separated by a center plate 13. A base 14 is secured to the lower surface of the pump housing 12 for attachment of the pump to a sup- porting surface. Two drive shafts 15 and 16 protrude from the upper surface, of the gear box, shaft 15 being intended for manual rotation by means of a suitable crank, while shaft 16 is intended for connection to an electric motor which may be mounted on the gear box. Referring to Fig. 2, the gear box 11 is a hollow casting shaped like an inverted bowl with a horizontal peripheral flange 17. The top of the casting constitutes the upper surface of the pump and is provided with two vertically protruding bosses 18 and 19 through which the shafts 15 and 16 extend. The center plate 13 has a geometric shape with 180 arcuate ends and parallel tangent,,, sides. The lower surface is flat, while the upper surface is provided with a circumferential flange 20 which bears against flange 17. A pair of vertically extending bosses 21 and 22 protrude from the upper surface of the center plate, along with a pair of transverse ridges 23 and 24 which extend across the plate, joining each boss to the opposite sides of the flange 20. Bosses 21 and 22 are pro¬ vided with vertical bores 25 and 26 which are aligned with similar bores 27 and 28 in bosses 18 and 19. The pump housing 12 is a hollow casting having a thick bottom 29 and straight sides 30 extending normal thereto with a cir¬ cumferential flange 31 protruding horizontally from the upper edge of the sides. The gear box 11, center plate 13 and pump housing 12 are joined together by bolts passed through aligned openings in flanges 17, 20 and 31. The bottom 29 of the pump housing is provided with two blind bores 32 and 33 which are aligned with bores 25 and 26. The motor drive shaft 16 is received within bores 26, 28 and 33 and is journalled in bearings 34, 35 and 36 in the respective bores. A gear 37 is hobbed into shaft 16 near its upper end and a timing gear 38 is positioned on the shaft just above boss 22. The manual drive shaft 15 is relatively short and is maintained in place in bearings 39 and 40 within bore 27 by means of a collar 41 and a roll pin 42 passed through the shaft above the gear box and a pinion gear 43, the hub of which is pinned to the opposite end of the shaft by a roll pin 44. Pinion gear 43 is dimensioned so as to mesh with gear 37 of shaft 16. A rotor drive shaft 45 is received in bores 25 and CMPI 32 and is journalled in bearings 46 and 47 positioned in the respective bores. A timing gear 48, which is identical to timing gear 38, is positioned on the upper end of shaft 45. The two timing gears mesh and are pinned to the shafts 16 and 45 by means of roll pins 49 and 50 passed through the hubs of the respective gears. A ball bearing 51 is spring-loaded within a recess in the lower extremity of shaft 15 and bears against the upper extremity of shaft 45. The gears 43, 37, 38 and 45 form a gear train through which rotation of either shaft 15 or 16 causes shafts 16 and 45 to rotate in opposite directions and with a constant angular relationship. Since pinion gear 43 is considerably larger than gear 37, manual rotation of shaft 15 causes shaft 16 to rotate several times for each revolution of shaft 15, and in the opposite direction. Rotation of shaft 16 is transmitted through timing gears 38 and 48 on a 1 x 1 relationship to shaft 45, but in the opposite direction. The gear train is covered by the gear box 11 which is filled with a suitable liquid lubricant to in¬ hibit wear between the gear teeth and to keep the gears turning freely. Oil seals 51 and 52 are positioned on shafts 45 and 16 below the bearings 46 and 34 to seal the gear box and prevent the lubricant from seeping down along the shaf s. Pressure seals 53 and 54 are positioned on the shafts 45 and 16 on the bottom surface of the center plate to prevent the liquid being pumped through the pump nousing from being forced up along the shafts. Weep holes 55 and 56 are drilled laterally through the flange 20, ridges 23 and 24, and bosses 21 and 22 to provide passages rom bores 25 and 26 to the exterior of the pump. In case of failure of an oil seal 51 or 52 or a pressure seal 53 or 54, lubricant or liquid will seep past the failed seal, along the shaft to the remaining seal and will flow through the weep hole 55 or 56 until it runs out on the exterior of the pump. Thus, periodic inspection of the weep holes will provide visual indication of a seal failure before damage occurs to the pump or the lubricant, or be¬ fore the liquid being pumped is contaminated. Rotors 57 and 58, as shown in Fig. 4, are each cut with four lobes spaced about a central hub which is drilled to receive one of the shaf s 16 or 45. The two' lateral surfaces of each lobe are mirror images of each other and are cut on adjacent arcs with reverse curvature. The portion of each lobe nearest the hub, i.e. , the root, is defined by two oppositely-directed, radially-divergent arcs and is relatively narrow. At the approximate mid- length, the lobe is at its maximum width and from that point to tne tip is defined by two oppositely-directed, con¬ vergent arcs. The tip 59 of each lobe is cut on a radius of the rotor and, as shown in Fig. 5a and 5b, protrudes slightly, about .03 inch, beyond the arcuate body of the lobe. The lateral surfaces 60 and 61 of the tip lie on radii of the rotor and define sharp right angled corners with the arcuate end surface of the tip. The portions of the hub between lobes are recessed on arcs which are ' OM tangent to the divergent arcs of the adjacent lobes. When the rotors are assembled on the shafts 16 and 45 and pinned in place by pins 62 and 63, the lobes of the adjacent ro¬ tors mesh as the shafts rotate. The proper angular rela- tionship between the lobes of the adjacent rotors is maintained by the timing gears 38 and 48. The clearance between the tips of the lobes and the internal surfaces of the sides 30 of the pump housing, as well as that between the tips of the lobes and the lobe roots and hub of the adjacent rotor, are approximately .003 inch and form the' unning clearances of the pump. As the rotors revolve within the pump ' housing, liquid from the inlet 64 is captured between the lobes and the inner surfaces of the sides of the pump housing and transported around the housing to the outlet 65. The lobes mesh and close off the return passage between the rotors, so the liquid is forced into the outlet. As liquid circulates through the housing, a residue of solids builds up on the housing and the rotors. When the pump is turned off, this residue congeals and forms a hard layer which reduces the running clearances of the pump. As the residue continues to build up, the clearances would ordinarily be reduced to zero, at which point, the pump would be clogged and the rotors frozen in a stationary position. However, in the present pump, the sharp corners of the lateral surfaces 60 and 61 scrape the residue from the sides of the housing, the lateral surfaces of the lobes, and from the hubs between the lobes. The residue is thus allowed to build up enough OMP to reduce the running clearances, but not enough to clog the pump. The pump is thus self-cleaning and does not need to be dismantled and cleaned periodically to remain operable. The base 14 includes a casting with legs 66 and 67 depending therefrom at the opposite extremities. The base is secured to the outside of the bottom of the pump housing by means of bolts received within internally-threaded open- ings tapped into the housing. The present pump operates freely in either direc¬ tion, either manually or by motor drive. The gear ratio between the pinion gear 43 and the gear 37 is selected - at 8.6 x 1, but this can be changed if desired by replacing the pinion gear with one of the desired size. The pump is designed for ease of assembly and is constructed without expensive thrust bearings. The pump is light and easy to handle and may be constructed in a wide range of sizes, up to approximately five feet in diameter. While the invention has been described with reference to specifically illustrated preferred embodiments, it should be realized that various changes may be made without depart¬ ing from the disclosed inventive subject matter particularly pointed out and claimed herebelow. O

Claims: I claim : 1. A positive displacement rotary pump including: a pair of rotors (57 and 58) mounted for rota¬ tion about parallel axes, drive- means (16, 38, 45, 48) for rotating the rotors and maintaining a pre¬ determined angular relationship therebetween; each rotor having a plurality of similar lobes formed thereon, the lobes on each rotor intermeshing with the lobes on the other rotor, characterized by means (59, 60, 61) on at least one lobe of each rotor for cleaning the clearance surface between the lobes of the adjacent rotor as the rotors turn. 2. A pump as defined in Claim 1 which .includes: a pump housing (12) surrounding said rotors, said housing having a side wall (30) parallel to the axes of rotation of the rotors, said housing being spaced from said rotors such that said means will clean said side wall as the rotors turn. 3. A pump as defined in Claim 2 which includes: means on the periphery of each lobe of each rotor for cleaning the side wall of the housing and the surface between the lobes of the adjacent rotor. OMP 4. A pump as defined in Claim 3 in which: said means includes an arcuate surface (59) with an approximate right angle step (60) protruding at the periphery of each lobe. 5. A pump as defined in Claim 4 in which: said means includes an arcuate surface (59) with an approximate right angle step (60, 61) at the leading and at the trailing edges. 6. A pump as defined in Claim 1 including: a center plate (13) pierced by two shafts (16, 45); a gear box (11) above the center plate and surrounding the drive means; a pump housing (12) below the center plate and surrounding the rotors; seals (51, 52, 53, 54) on each shaft; and means (55, 56) on the center plate for prevent¬ ing migration of fluid along the shafts between the upper and lower surfaces of the center plate when a seal leaks. 7. A pump as defined in Claim 6 in which: two seals are positioned on each shaft, one (53, 54) adjacent the pump housing and the other (51, 52) adjacent the gear box. OMP 8. A pump as defined in Claim 7 wherein: said last-named means includes an opening com¬ municating from each shaft between the seals to the periphery of the center plate to drain any fluid leaking through one of the seals. 9. A center plate for use in a rotary pump which includes a gear box (11) and a pump housing (12) joined by parallel shafts (16, 45), the improvement characterized by a center plate (13) adapted to be positioned between the gear box and the housing, said plate having a pair of bosses (21, 22) protruding from the upper surface thereof, each boss having a bore (25, 26) therein to receive one of the shafts, and transverse ridges (23, 24) on the upper surface extending from the bosses to the periphery of the " plate. 10. -A center plate for use in a rotary pump as defined in Claim 9 which includes sealing means (51, 52, 53, 54) in the bores to seal the gear box and the pump housing. 11. A center plate for use in a rotary pump as defined in Claim 10 which includes means (55, 56) for preventing migration of fluid or lubricant along the shafts between the upper and lower surfaces when said sealing means leaks. 12. A center plate for use in a rotary pump as defined in Claim 11 in which said means includes openings extending from the periphery of the plate through said ridges to the bores within the bosses. 13. A center plate for use in a rotary pump as defined in Claim 12 in which the sealing means includes oil seals in the upper portion of the bores to seal the gear box and pressure seals in the lower portions of the bores to seal the pump housing, and the openings communi- cate with the bores between the oil seals and the pressure seals. OMP

Inventors: PATTERSON JIMMIE WESLEY, PATTERSON, JIMMIE, WESLEY
Applicants: PATTERSON JIMMIE WESLEY, PATTERSON, JIMMIE, WESLEY
Application year: 1983
Main classification: F01C1
IPC codes: F04C2, F04C15