Positive displacement rotary pump with bearings in countersunk portions of the rotors

A positive displacement rotary pump is provided for use in circulating a viscous product at high pressures. The pump includes a housing having a product inlet and a product outlet communicating with an interior cavity. One wall of the cavity is defined by a removable cover. A pair of spaced substantially parallel shafts extends through a wall of the cavity opposite the cover wall. One end of each shaft is supported by the cover. A pair of meshing rotors is locked on the shafts and disposed uniformly within the cavity. The endface of each rotor adjacent the removable cover has a substantial countersunk portion. Bearing means, substantially isolated from the product, is disposed within each rotor endface countersunk portion and supportingly engages a segment of the rotor shaft one end. At least a portion of each bearing means is located between planes defined by the surfaces of the cover and the wall opposite thereto which coacts to form the cavity. Means for supporting the bearing means is removably mounted on the cover.

BACKGROUND OF THE INVENTION 
Various positive displacement rotary pumps have heretofore been provided 
for circulating various viscosity products; however, such pumps have been 
ineffective in handling such products at pressures within the range of 
200-350 psi. When operating within such a pressure range, such pumps have 
been beset with one or more of the following shortcomings: (a) serious 
shaft deflection occurs; (b) an inordinate amount of bearing wear results; 
(c) serious galling between the rotors and the cavity surfaces; (d) the 
rotors are higly susceptible to product corrosion and product 
abrasiveness; (e) the shafts are not effectively isolated from the product 
thereby causing the potential for serious contamination problems; and (f) 
makes disassembly of the pump for cleaning and maintenance a difficult and 
time-consuming operation. 
SUMMARY OF THE INVENTION 
Thus, it is an object of the invention to provide a positive displacement 
rotary pump which is capable of operating within a pressure range of 0-350 
psi while circulating products of various viscosities without encountering 
the aforenoted problems. 
It is a further object of the invention to provide a positive displacement 
rotary pump wherein the shaft-supported rotors are interchangeable and, 
thus, facilitate assembly and disassembly of the pump. 
It is a further object of the invention to provide a positive displacement 
rotary pump having means for locating and adjusting the shafts thereof so 
as to maintain uniform rotor clearances within the pump cavity. 
It is a further object of the invention to provide a positive displacement 
rotary pump wherein the relative location of one bearing of each rotor 
shaft with respect to the axial centerline of the rotor is such that a 
substantial mechanical advantage is obtained thereby significantly 
reducing shaft deflection when the rotor is subjected to substantial 
downstream pressure of the circulating product. 
It is a still further object of the invention to provide a pump of the type 
described which is of compact construction; is efficient in operation; and 
the rotor shafts are effectively isolated from the circulating product by 
seals vented to the atmosphere thereby permitting the flushing of the 
atmosphere side of the seal with a productcompatible fluid or a sterile 
fluid when the pump is being in aseptic application. 
It is a still further object of the invention to provide a positive 
displacement rotary pump which is capable of handling a wide variety of 
highly viscous, corrosive and abrasive products. 
Further and additional objects will appear from the description, 
accompanying drawings and appended claims. 
In accordance with one embodiment of the invention, a positive displacement 
rotary pump is provided for use in circulating a viscous product at high 
pressures (e.g., 200-350 psi). The pump includes a housing having a 
product inlet and a product outlet, both of which communicate with an 
interior cavity. One wall of the cavity is defined by a removable cover. A 
pair of spaced, substantially parallel shafts extend into the cavity from 
the cavity wall opposite the cover wall and have end portions thereof 
supported by the cover. Each shaft is driven by a first means which is 
isolated from the cavity. Meshing rotors are locked on the shafts and are 
diposed within the cavity. The endface of each rotor, which is disposed 
adjacent the cover wall, is provided with a substantial countersunk 
portion. Disposed within each countersunk portion and supportingly 
engaging segments of the shaft is a bearing means which is isolated from 
the product. Each bearing means has at least a portion thereof located 
between planes defined by the surfaces of the cover and the wall opposite 
thereto which form the cavity. A second means is carried by the cover and 
supports the bearing means. The engagements between the shafts and rotors 
are isolated from the product during operation of the pump.

Referring now to the drawings and more particularly to FIG. 1, one form of 
an improved positive displacement rotary pump 10 is shown which is 
particularly suitable for handling a variety of heavy viscous products at 
high pumping pressures (e.g., 200-350 psi). Examples of products which are 
capable of being handled by pump 10 are as follows: meat emulsions, 
chopped meats, bread dough, pizza dough, dough slurry, high flour content 
doughs, processed cheese, icings, gravy base and batter. 
Various pumps have been provided in the past which were capable of handling 
these products when operating at pressures below 200 psi. When attempts 
were made, however, to operate such pumps at and above 200 psi, serious 
problems arose due to the substantial stress and strain imposed on the 
bearings, rotor shafts and rotors, and because of the demand for close 
tolerances to exist between various moving components. Furthermore, the 
number and configuration of the lobes formed on the pump rotors and the 
materials utilized in making the rotors also became important factors to 
be considered in an effort to reduce galling between the rotors and the 
walls defining the pump cavity. Such past efforts, however, were not 
successful because of the cost and difficulty in manufacturing the various 
components, the inordinate amount of maintenance and servicing required, 
and the time and labor required in assembling and disassembling the pump 
components for cleaning and/or servicing. 
The pump 10 as seen in FIGS. 1 and 2 includes a housing 11 having an 
interior cavity 12 in which is uniformly positioned a pair of meshing 
rotors 13, 14. One side of the housing is provided with a cover 15 which 
is removably mounted on the remainder of the housing by a plurality of 
symmetrically arranged stud bolts 16 and nuts 17. The threaded ends of the 
bolts extend through suitable openings 18 formed in the cover 15. The 
number and location of the stud bolts and the openings in the cover may 
readily vary from that shown, if desired. 
The bolts 16 are anchored to and project from an end wall 20 which is 
disposed in spaced substantially parallel relation to cover 15 when the 
latter is assembled on the studs. The end wall 20 forms a part of a 
conventional drive gear casing 21 which will be described more fully 
hereinafter. As seen more clearly in FIGS. 2 and 3, the end wall 20 is 
provided with outwardly extending cylindrical bosses 22 from which the 
studs 16 protrude. The bosses 22 serve as spacers between the drive gear 
casing 21 and the back wall 23 of the housing 11, see FIG. 1. The back 
wall of the housing is provided with a continuous peripheral flangelike 
wrapper 23a which extends transversely from the back wall towards the 
cover and abuts the interior surface of the cover when the latter is in 
assembled relation therewith. The surface of the cover which abuts wrapper 
23a is provided with a continuous groove 24 in which is disposed a 
suitable seal 25 (e.g., an "O" ring). As seen in FIG. 1, the seal 
surrounds the outside of cavity 12 of the housing. 
Extending from drive gear casing 21, through openings 23b formed in the 
housing back wall 23, and into cavity 12 is a pair of shafts 26, 27. The 
corresponding ends 26a, 27a of the shafts are supported by the housing 
cover 15 as will be described in detail hereinafter. A portion 26b, 27b of 
each shaft, which is disposed within the cavity 12, is provided with 
suitable splines. Mounted on the splined portion of each shaft is the 
rotor 13, 14. In the illustrated embodiment, each rotor is of like 
construction and is provided with internal splines which mesh with the 
shaft splines and with five radially extending symmetrically arranged 
lobes L. When the pump is assembled the lobes of the rotors mesh with one 
another so as to effect circulation of the product through the housing 
cavity when the rotors are rotating. The product will enter the cavity 
through an inlet, not shown, formed in wrapper 23a and disposed to one 
side of the rotors and will be discharged therefrom through an outlet, not 
shown, formed in said wrapper and disposed on the opposite side of the 
rotors. The inlet and outlet are normally horizontally aligned with one 
another and disposed substantially equidistant from the axes of shafts. 
Each shaft 26, 27 has a portion thereof disposed within the drive gear 
casing 21 and has secured thereto a drive gear 28. The gears are in 
meshing relation. Disposed axially on opposite sides of the drive gear are 
preloaded tapered roller bearings 30 of conventional design. 
As aforementioned, the rotors 13, 14 are of like design and therefore only 
one will be described in detail. The rotor 13, as seen in FIG. 6, has an 
opening 31 formed therein to accommodate a substantial portion of the 
shaft 26, 27 protruding from the wall 20 of the drive gear casing 21. The 
end of opening 31 which terminates at the endface of the rotor disposed 
adjacent the cover 15, when the pump is assembled, is countersunk 32 a 
substantial amount. The end portion of opening 31 adjacent the opposite 
endface of the rotor is defined by internal splines 33 which are adapted 
to closely mesh with the splined portion 26b, 27b of the shaft 26, 27. As 
seen in FIG. 1, the countersinking 32 of opening 31, which extends to 
approximately the transverse center line of the rotor, is partially 
stepped so as to form shoulders 32a and 32b and an internal groove 32c 
located between the shoulders. 
The opposite endface of the rotor is provided with a groove 33 which is 
spaced from and concentric with the splined end of opening 31. Groove 33 
is adapted to accommodate a suitable spring 34, the latter being used to 
maintain pressure on the face seal sections while awaiting product 
pressure during start-up. 
As previously noted, the protruding end 26a, 27a of the shaft 26, 27 is 
supported by cover 15 through a roller bearing 35 carried by a retainer 
36. The retainer 36 includes a sleevelike section 36a which encompasses 
and is in shrunk-fit relation with the raceway of bearing 35. The section 
36a projects into the countersunk portion 32 of opening 31 and thus 
locates the bearing 35 between the planes defined by the cavity-forming 
surfaces of cover 15 and housing back wall 23, see FIG. 1. 
Surrounding the shaft end portion 26a, 27a and disposed within the retainer 
sleeve section 36a is a cylindrical liner 37. The inner end of the liner 
is provided with a flange 37a which abuts shoulder 32b formed in the 
countersunk portion 32 of opening 31. Liner 37 is provided with a 
plurality of circumferentially spaced openings 37b. The openings 37b are 
substantially aligned with the roller bearing 35 and thus enable the 
bearing to be lubricated. 
As seen more clearly in FIG. 3, lubrication for the bearing 35 is attained 
through a conventional grease fitting 38 which is affixed to and extends 
axially from the end of the shaft 26, 27. The fitting 38 communicates with 
one end of an axial bore 40 formed in the end of the shaft. The inner end 
of bore 40 terminates in a radially extending passage 41. The outer end of 
the passage terminates at an annular groove 42 formed on the interior 
surface of the liner 37. Groove 42 is aligned with the liner openings 37b 
which in turn are aligned with bearing 35. To prevent leakage of grease, 
or similar lubricant, into the housing cavity 12, a first seal 45 is 
positioned in groove 32c formed in the countersunk portion 32 of opening 
31, and a spring 46 is positioned against shoulder 32a. Spring 46 
resiliently engages an inner section 47 of a face seal which in turn 
engages an outer section 48 of the seal, see FIGS. 1 and 6. The spring 46 
and inner section 47 of the face seal rotate with the shaft while the 
outer section 48 of the face seal remains in a stationary position. The 
face seal section 48 is held in place by a flange section 36b, the latter 
being integral with the outer end of sleeve section 36a and forming a part 
of retainer 36. A substantial part of flange section 36b is disposed on 
the exterior of cover 15 and is removably secured to the latter by a 
plurality of bolts 50. 
As seen in FIG. 1, a protective cap C is removably mounted on flange 
section 36b and serves to protect grease fitting 38 when the latter is not 
to be used. 
The liner 37, which encompasses the portion of the shaft disposed within 
the countersunk portion 32, is held in place against endwise movement by a 
caplike washer 51, the latter encompassing a shank of a bolt 52 which is 
threaded into the end of the axial bore 40 formed in the shaft. As seen in 
FIG. 1, the washer 51 is provided with a lug 51a which fits into a keyway 
53 formed in the end of liner 37 and the end of the shaft 26, 27. Thus, by 
reason of this arrangement, the liner 37, washer 51, bolt 52 and grease 
fitting 38 will rotate as a unit with the shaft 26, 27. 
The pressure from the tightened bolt 52 holds the liner 37 firmly against 
the shoulder 32b of the rotor 13 which in turn is held against a shaft 
shoulder 26c and thus prevents lateral movement of the rotor within the 
cavity 12. By reason of this arrangement galling between the rotor and 
cavity walls is avoided. 
Pump 10 is provided with means for circulating a flushing media between the 
exterior of the retainer sleeve section 36a and a substantial part of the 
countersunk portion 32 of the rotor opening 31, without requiring even 
partial disassembly of the pump components. A radially extending passage 
54, see FIG. 1, is formed within the flange section 36b of the retainer 
and then the inner end of the passage terminates at a second passage 55, 
which is also formed within the flange section. Passage 55 terminates 
adjacent the face seal section 48, thereby enabling a flushing fluid to 
circulate about face seal sections 47, 48, groove 32c and seal 45. 
It will be noted in FIG. 1 that by reason of the depth of the 
countersinking of the opening 31, the center line of bearing 35 is located 
between the interior faces of cover 15 and back wall 23. Such a 
relationship is important because there is a close proximity (e.g., 1") of 
the center line of bearing 35 relative to the transverse center line L of 
the rotors 13, 14, and thus the mechanical advantage is greatly improved. 
By mechanical advantage is meant the ratio of a resistance to an applied 
force. In determining the mechanical advantage the distance from the 
center line of the nearest bearing to the center line L of the rotors 13, 
14 is normally squared. Thus, if in the pump illustrated in FIG. 1, the 
bearing 35 for each shaft was eliminated and only the bearings 30 embodied 
in the drive gear casing 21 were utilized, the distance between the center 
line of the left bearing 30 (FIG. 1) and the rotor center line would be 
approximately 4.75". It is apparent therefore with the same applied load 
that pump 10 with bearing 35 in place would have a mechanical advantage in 
the magnitude of 22.6 to 1 as compared to the pump without bearing 35. 
As aforementioned, the inboard faces of the rotors are each provided with a 
groove 33 in each of which is disposed a spring 34. Spring 34 resiliently 
engages a face seal section 57 which extends into groove 33. Section 57 in 
turn resiliently engages a second section 58 of the face seal. The 
outwardly disposed side of section 58 is engaged by a back member 60 which 
loosely encompasses the shaft 26, 27. The back member 60 is removably 
secured to the back wall 23 of the housing by a plurality of symmetrically 
arranged bolts 61. Thus, spring 34 and back member 60 coact to maintain 
the face seal sections 57, 58 in a static sealing contact. The bosses 22, 
from which the stud bolts 16 extend, provide adequate spacing between 
housing 11 and casing 21 to accommodate the members 60. Various other 
conventional seals 62 (including face seals) are provided which encompass 
each shaft and are disposed between the back member 60 and the front wall 
of casing 21, see FIG. 1. 
Each back member 60 is provided with internal passages, not shown but 
similar to passages 54, 55 formed in flange section 36b of retainer 36, 
through which a suitable flushing media may be circulated. The circulating 
media would contact the rotor groove 33, spring 34, face seal sections 57, 
58, and back member 60 due to clearance between such components and the 
portion of the shaft encompassed thereby. The circulating media, however, 
is blocked from the atmosphere by the conventional seals 62. 
Where the product being circulated by the pump 10 is a food product, the 
matter of contamination by the lubricant and/or flushing media must be 
avoided. In addition to the numerous seals heretofore described as being 
utilized, various provisions are made that migration of such lubricant 
and/or flushing media is to the atmosphere rather than to the housing 
cavity 12. To facilitate such migration a passage 63 is provided adjacent 
the outwardly facing end of bearing 35. 
As seen in FIG. 1, the tapered roller bearings 30 located within the gear 
casing 21 are pre-loaded by adjustable nuts 64 which are threaded into 
opposite sides of the casing. Each nut 64 engages one end of the bearing 
raceway 30a and the opposite end of bearing engages a shoulder formed on 
the shaft. 
While the illustrated pump embodies 5-lobe rotors, it is to be understood 
that the invention is not intended to be limited thereto. 
Thus, an improved positive displacement rotary pump has been provided which 
is readily capable of operating at high pressures and to circulate various 
viscous products. the improved pump is of sturdy compact construction and 
may be readily serviced when required, and provides an effective means of 
avoiding contamination of the product by lubricants and/or flushing media.