SLIDING VANE PUMP WTTH PLASTIC HOUSING BACKGROTTND OF THE INVENTION
The present invention relates to sliding vane pumps. More particularly, the invention relates to a moderately high pressure sliding vane pump having a non-metallic housing.
For the reliable delivery of moderately high pressure fluids at modest cost, the sliding vane pump is the standard of industry. Having relatively few moving parts, the machine will continuously deliver a spectrum of fluids from water to oil up to 250 psi for long operational periods.
Traditionally, many sliding vane pump housings are finish machined from forged or cast brass or stainless steel. The brass alloy for these blanks includes 1% to 2% lead to reduce machine tool fouling and improve forgability. However, when these leaded brass pump housings are used to move potable water, over time lead will leach from the brass alloy into the water. Although the leaching rate is not great, it is nevertheless measurable and by some, considered intolerable for potable fluid use. In a relative sense, sliding vane pump housings are simple and may be formed from numerous soft castable materials such as high density polymers. U. S. Patent No. 4,543,228 to D. J. Bingler is representative of a molded plastic housing for a sliding vane pump. The Bingler plastic housing design is also typical in that the Bingler design translates the prior art brass housing configuration directly into the plastic housing configuration. Unfortunately, the plastic modulus of elasticity, G, approximately 1.5 to 2.0 x 10 6 lb./iri is considerably less than the leaded brass modulus of about 15.0 x 10 6 lb./in 2 . As a consequence, the plastic housing perimeter tends to expand more under the same pressure as compared to brass thereby inducing considerably more leakage and flow loss .
The resulting plastic housed pump must be pressure derated considerably and the efficiency suffers from the flow loss.
It is an object of the present invention, therefore, to provide an efficient sliding vane pump having a non-metallic housing.
Another object of the invention is a relatively high pressure pump having a plastic housing.
Yet another object of the invention is a sliding vane pump that will not leach heavy metals into potable fluids. A still further object of the invention is a connector system for conduits to a polymer pump boss having no threads.
Still another object of the invention is a non-metallic connector system for securing fluid carrier conduits to a non etallic pump boss having no threads.
SUMMARY OF THE INVENTION These and other objects of the invention will be apparent from the following description of the preferred invention embodiment which comprises a sliding vane pump having a vane rotor cartridge seated in a relatively low/modulus, non-metallic material housing cavity such as glass fiber reinforced polyphenylene sulfide or polyphthalamide resin. Assembled with the cartridge as a unit are the pump rotor and vanes having an attached drive shaft. The drive shaft is axially unitized with the rotor which is supported by axially flanking bearing plates. In a first embodiment of the invention, the pump rotor assembly is closed within the cavity by an end-plug secured by a C-ring. The end-plug edge perimeter is sealed to the housing internal bore wall by a
first O-ring and against the outer face of the base side bearing plate by a second O-ring. Radially surrounding the rotor is a pump cam ring. The cam ring and bearing plates fit tightly within a non-metallic injection molded housing cavity to dispose the drive shaft through a radial support bearing. A spring loaded rotor face seal is disposed in a high pressure seal cavity between the shaft bearing and the pump rotor assembly. In this first invention embodiment, high pressure discharge fluid from the high pressure pump chamber is channeled into this shaft bearing seal cavity and away from the cam ring perimeter. The high pressure fluid is ported from the shaft bearing seal cavity. Seals between the rotor cartridge and the non-metallic housing walls isolate that portion of the housing surrounding the rotor from high pressure expansive stress.
Another embodiment of the invention, provides for high pressure discharge fluid to be channeled from the high pressure pump chamber into a small, high pressure cavity on the side of the rotor assembly opposite from the drive shaft connection. The housing end-plug is structurally reinforced with a fitting support boss to provide a high pressure fluid discharge port from the high pressure cavity between the end-plug and the rotor assembly.
The external conduit connectors are threadless plug and socket fittings sealed by an O-ring. The plugs are held in the sockets against fluid expulsion pressure by a saddle bracket pinned to the pump housing. C-clips in the saddle bight section engage an external ring groove in the plug connector body.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects of the invention will become apparent by reference to the following detailed description taken in connection with the accompanying drawings, in which: FIG. 1 is a top plan view of the invention;
FIG. 2 is a side elevational view of the invention;
FIG. 3 is an end elevational view of the invention;
FIG. 4 is a sectioned elevation of the invention viewed along cutting plane 4-4 of FIG. 1; FIG. 5 is a sectioned elevation of the invention viewed along cutting plane 5-5 of FIG. 2;
FIG. 6 is a side elevational view of the invention with port fittings;
FIG. 7 is a sectioned plan view of the invention viewed along cutting plane 7-7 of FIG. 6;
FIG. 8 is an end elevational view of the invention with port fittings;
FIG. 9 is a sectioned detail of a port fitting viewed along cutting plane 9-9 of FIG. 7; and, FIG. 10 is a sectioned elevation of an alternate embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Relative to the drawing wherein like reference characters designate like or similar elements throughout the several figures of the drawing, the present invention is illustrated by the three orthographic views of FIG. l, FIG. 2 and FIG. 3. Generally, the pump housing 10 materially comprises an injection- molded form of glass fiber reinforced polymer resin such as polyphenylene sulfide or polyphthalamide.
Representative is the proprietary material Ryton ® supplied by the Phillips 66 Company of Bartlesville, Oklahoma. Ryton ® is a composite having about 40% glass fiber in a polyphenylene sulfide binder. Among its material properties are a modulus of elasticity of 1.9 x 10 6 lb./in 2 .
Another suitable material, supplied by Amoco Polymers of Alpharetta, Georgia, is AMODEL ® , a composite of polyphthalamide and glass fiber. A 33% glass fiber composition of AMODEL is reported to have a 1.6 x 10 6 lb./in 2 modulus of elasticity whereas a 45% glass fiber composition has a 2.0 x 10 6 lb./in. modulus.
Due to the presence of glass fiber in these polymer compositions, components designed for direct contact with a potable fluid are finish formed by injection molding. Post-molding machine processes are undesirable.
With respect to our housing 10 design using Ryton ® or AMODEL ® , a pump cartridge ring 30 is positioned axially between a bearing ring 22 and a base ring 24. Between the bearing ring 22 and the pump cartridge ring 30 is a conically shaped bearing seal chamber 32. Each of the housing ring sections have cylindrical internal chambers of diminishing radius from base ring 24 to bearing ring 22 to facilitate assembly of the pump rotating elements. A cartridge rotor drive shaft 20 protrudes axially from the bearing ring 22 end of the housing. The base ring 24 external opening is sealed by an end-plug 26 secured by a C-ring 28.
Internally molded with the ring and seal chamber elements of the housing 10 are intake and discharge port bosses 12 and 14, respectively, connected by webs 16. Two axially
aligned pin apertures 18 pass through the webs 16 having a purpose in the overall invention to be explained hereafter.
Referring next to the sectional views of FIG. 4 and 5, the pump cartridge assembly includes a rotor element 40 directly driven by an integral drive shaft 20. Journal walls 42 and 44 include journal bearings 46 and 48 to relatively confine the rotor element 40 radially about the journal pin surfaces 50 and 52. The outer perimeters 54 and 56 of the journal walls are match fits to the internal cartridge chamber wall 58. The interior journal wall 42 includes an O-ring face seal 46 for a fluid pressure barrier against the step face 34 between the cartridge chamber wall 58 and the internal wall surface 36 of the bearing seal chamber 32.
In compressed assembly between the journal walls 42 and 44 around the rotor 40 is a cam ring 60 with an eccentrically aligned pumping crescent 62. The internal surface of the cam ring 60 radially confines the outwardly biased fluid drive vanes 48 as fluid is swept in front of the vanes from the low pressure, inlet portion 64 of the pumping crescent to the high pressure, discharge portion 66. The fluid drive vanes make a sliding, pressure sealed interface with the cam ring 60 that is resiliently biased by the summation of high pressure fluid loads and centrifugal loads.
O-rings 70 and 72, set in the outer rim and interior face of the base plug 26, provide a fluid pressure seal against the internal bore wall 74 of the housing base ring 24 and the outer face of base side journal wall 44.
The drive end of the drive shaft 20 is radially supported within the housing by a shaft roller or ball bearing assembly 80. A rotating fluid seal assembly around the shaft
comprises a stator 82 having a pressurized fluid seal fit within the static structure of the bearing seal chamber 32 and a smooth, low friction seal face 83. Cooperating with the seal face 83 is a sealing rotor 84 that translates axially along a small increment of the shaft 20 but is pressure sealed to the shaft 20 surface by an elastomer boot 85. A seal loading spring 86 seats between seal rotor 84 and a shaft shoulder 87 to preload the sealing interface between the rotor 84 and the seal face 83. On the exterior side of the seal stator 82 and secured to the shaft 20 for rotation therewith is a slinger ring 90. Vent or drain aperture 92 through the bearing ring 20 provides internal drainage to channel the pumped fluid that may escape past the rotor seal 84 away from the bearing assembly 80.
Dynamically, fluid enters the intake port 100 to flood the suction plenum 102. By channels 104 and 106 in the journal walls 42 and 44, respectively, the fluid floods the inlet portion 64 of the pumping crescent 62 in front of a rotatively advancing vane 48. Continued rotation of the vane 48 drives an increment of fluid around the crescent 62 into the discharge portion 66.
From the crescent discharge section 66, the fluid is forced by the advancing vane face into channels 108 and 110 respective to the drive side journal wall 42 and the base side journal wall 44. Hollows 112 and 114 respective to the end plug 26 and the rotor 40 transmit the high pressure fluid of discharge section 66 to the underside of vanes 48 as a source of a radial biasing force. The high pressure force also bears
against the outer face of base side journal wall 44 within the seals 72 to bias that element inwardly.
In the preferred embodiment of FIG.s 1-5, channel 108 transmits the majority flow of fluid across the drive side journal wall 42 into the interior of bearing seal chamber 32 and, ultimately, out the discharge port 120. Fluid pressure within the chamber 32 exerts force against the drive side journal wall 42 and the seal rotor 84.
An alternate embodiment of the invention shown by FIG. 10 provides for a majority of the high pressure fluid flow from the pumping crescent discharge section 66 to flow across the base side wall journal 44 through channel 148 into the chamber 112 between an end-plug 115 and the base side journal wall 44. The end-plug 115 of this embodiment is structurally reinforced with a conduit connector fitting support boss 117. High pressure fluid discharge follows an axial flow channel 119 from end chamber 112, through the boss 117, into a conduit connector fitting 146.
It is to be noted that the location of O-ring face seals 46 and 72 bearing against the outer faces of journal walls 42 and 44 near the respective outer rims isolate the radial perimeter of the cartridge ring 30 from high fluid pressure generated by the pump. Only the low, inlet fluid pressure in plenum 102 directly contacts the internal cartridge wall 58. Journal walls 42 and 44 partition the suction plenum 102 from the high discharge pressure standing at both axial ends of the cartridge assembly. Accordingly, the dominant high pressure stress on the housing is exerted axially except for that within the bearing seal chamber 32 which is of reduced axial section area. Consequently the total tensile hoop stress
distributed around the walls of the bearing chamber 36 and bearing ring 22 may be reduced due to the smaller diameter apertures in this area. Such reduced stress values are compatible with the polymer housing material . As a further consequence of the small diameter apertures of the present invention, the walls of bearing chamber 36 are also the stiffest in the pump. Although there is more radial deflection of the chamber walls with polymer γ_£ brass, such deflection is of little consequence because: the deflection values are low and within elastic limits; there is no performance leakage or flow loss potential in the bearing chamber section; and, there are no end leakage concerns since the polymer cooperates with the shaft stator to provide a resilient seal. Hence, the invention positions the highest internal pressures of the pump in chambers having the lowest hoop stress and greatest radial stiffness.
To overcome excessive shear stress on conduit connector threads in the plastic port bosses, a threadless connector system as described with respect to the invention embodiment of FIGs. 7-9 is applied with the present invention. The internal bores of intake and discharge ports 100 and 120, respectively, are smooth to receive male connector plugs 130 and 140, respectively. O-rings 132 seal the circular interface between the plug sealing cylinder wall 131 and the internal socket wall of boss 12.
In the axial mid-section of the plug 130 (and the identical mate 140) are a pair of circumferential shoulders 133 and 135 separated by a circumferential ring groove 134.
On the axial end of the plug opposite from the sealing cylinder 131 is a conduit connection structure shown by
FIGs. 6-9 as a hose nib 136 with circumferential ratchet barbs 138. An alternative conduit connection structure may be threads, whether pipe or machine.
To secure the connector plugs 130 and 140 against expulsion from the sockets of ports 100 and 120 due to fluid pressure forces, oppositely facing yokes 122 and 142 in the bight plate of a saddle bracket 125 mesh with the circumferential grooves 134 in the plugs 130 and 140. The saddle bracket legs 127 straddle the port boss webs 16. A transverse linchpin 129 passes through aligned apertures in both, the webs 16 and bracket legs 127.
Recommended assembly of the connector elements would normally begin with a clamp secured connection of the nibs 136 into respective hose bores. With the hoses secured, the circumferential ring grooves 134 respective to the two connectors are meshed with the bight yokes 122 and 142 and manually held together while the connector plugs are inserted into respective port sockets 100 and 120. With all elements aligned and in place, the linchpin 125 is aligned with all central apertures and inserted to interlock the several elements together.
Having fully disclosed our invention, those of ordinary skill in the art will note other approaches to the same objective and devise equivalent structures to accomplish such objectives. As our invention, therefore,
