GB2085081A - Submersible Gear Pump for Viscous Liquids - Google Patents

Abstract

The pump 10 comprises a pair of gears 20, 21 rotatable mounted in a casing, or "body", with a substantial proportion of the teeth 30 of each of the gears exposed so as to admit working fluid to the spaces between the teeth, the body being immersed in said fluid. Bearings for shafts supporting the gears may be encircled by chambers (35, 36), Fig. 4 (not shown), which can be charged with a lubricant or a sealing fluid. Leakage of working fluid along said shafts may be prevented by annular seals (40), the pressure thereon being relieved through a pair of openings 44 in a cover plate 26. <IMAGE>

Description

SPECIFICATION Submersible Gear Pump Background of the Invention This invention is directed generally to gear type pumps and more particularly to a submersible gear pump which is particularly adapted for the pumping and handling of highly viscous liquid materials, which can range from hot melts through water based or solvent type materials, and filled liquid and semi-liquid adhesive type materials. Conventional gear-type pumps for handling such materials have prooven to be generally inadequate in view of the difficulty in providing sufficient time or dwell for the material to flow through an inlet opening or port into the pumping cavity and/or the difficulty of providing a sufficiently high-pressure output with uniform or surgeless flow characteristics. ShLs, gear-type pumps have generally not been successfully used for such materials.The materials which are particularly difficult to pump include the RTV type (room temperature vulcanizing) solvent-based materials, plastisol materials, and pseudo-plastic materials up to and in excess of 1,000,000 centipoise in viscosity. However, viscosity alone, in such materials, is not indicative of the difficulty in handling or pumping the same in view of their non-linear or non-uniform characteristics when subject to shear, elevated temperature or the like.

In addition, certain materials, such as moisture curing RTV rubber, and the water sensitive cataiysts associated with two-part urethanes, acrylics and the like, tend to set up or crystallize or tend to cure in the presence of water or moisture. It is thus important to pump or move these materials in an isolated environment, effectively preventing contact with atmosphere or with other moisture or water-carrying media.

Summary of the Invention The invention is particularly directed a gear pump which is adapted to be received within a container of material for pumping the same, such as by lowering the gear pump into the material within the container or by suitably positioning the same within the container. For example, the gear pump of the present invention may be used as a cartridge pump in conjunction with a follower plate of the kind disclosed in Gardner et al, U.S.

Patent No. 4,073,409 issued February 14, 1978, or it may be lowered or positioned within a container or barrel or drum of the material without regard to a follower plate.

The gear pump of the present invention includes a body which rotatably supports a pair of intermeshing pumping gears and in which a substantial portion of the peripheral extent of each of the gears is exposed at an inlet region to receive material directly from the container into the spaces between the gear teeth for delivery to an outlet port formed in the body. In other words, a substantial portion of each of the gears is exposed along an inlet region of the pump peripherally about each of the gears, in the order of one-third of the peripheral extent of each of the gears, to provide a generally open space or a plurality of open spaces and a corresponding dwell time so that the material may flow into the spaces between the gears and be carried by the rotation of the gears to the pump outlet.

In one embodiment, the pump is further provided with lip seals at the gear shafts which are vented for flow of material back into the container, to relieve any undue or excess pressure or build-up of material at the seals. Means are provided within the pump for isolating the seals, by the provision of means for the application of an isolation fluid, to prevent the possibility of water or other contaminants becoming mixed with material being pumped through the seals.

It is accordingly an important object of the invention to provide a submersible gear pump which may be lowered irito a container of highly viscous material, such as by being incorporated into a follower plate, by being lowered directly into the material or forming a permanent part of a pumping system, in which substantial peripheral portions of intermeshing rotating pumping gears are directly exposed to receive material from the container at an inlet region of the pump.

Another important object of the invention is to provide a submersible gear-type pump which is particularly adapted for handling highly viscous materials which are otherwise difficult to pump on a positive volumetric basis.

A further object of the invention is to provide a gear pump as outlined above which is easy to clean and maintain.

The invention will become more readily apparent from the following description and the accompanying drawings.

Brief Description of the Drawings Fig. 1 is a bottom plan view of a pump made in accordance with one embodiment of this invention; Fig. 2 is a side elevational view of the pump looking generally along the line 2-2 of Fig. 1; Fig. 3 is a bottom view similar to Fig. 1, with the bottom cover plate removed, looking generally along the line 3-3 of Fig. 2; and Fig. 4 is a vertical section through the pump, showing certain parts thereof in elevation, taken generally along the line 4 4 of Fig. 3.

Description of Preferred Embodiment Referring to the figures of the drawings, a preferred embodiment of a gear pump is illustrated generally at 10. The pump 10 is provided with a generally cylindrical body 12 which is adapted to be inserted, for example, into a cartridge pump opening formed in a follower plate of the type described and claimed in the above-identified patent of Gardner et al.

Alternatively, the pump 10 may be positioned, suspended or lowered into a pail, barrel, or container of the highly viscous material to be pumped for delivery under pressure to a remote location.

Thus the body 12 is of generally right cylindrical shape and rotatably supports a vertical drive shaft 14 and a vertical driven shaft 15, respectively mounted on upper and lower needle bearings 18 and 19. The drive shaft 14 carries at its remote end a pumping gear 20, which is in constant intermesh with a cooperating pumping gear 21 mounted on the shaft 15. The gears 20 and 21 are preferably of identical diameter and rotate in intermeshed relation in close relation to an adjacent and exposed surface of the pump as defined by a pump plate 25, as shown in section in Fig. 4. The pump plate 25 is mounted flush to the flat bottom surface of the body 12, and is provided with apertures to receive the respective shafts 14 and 15.

The body or housing 12 is further provided with a gear closure plate 26 of controlled thickness supported on the plate 25 and is formed with opposed arcuate portions 28 which partially encircle the respective gears 20 and 21 and defines a close running fit with the outer surfaces of the teeth 30 of the respective gears 20 and 21.

The plate 26 also provides a clearance cut out 31 for an outlet opening 32 formed in the pump body 12 leading to a discharge port or discharge conduit, not shown, and for a pressure relief valve 33 (Fig. 3).

Annular spaces 35 and 36 surround each of the shafts 14 and 1 5 connected by a central conduit 38, as shown in section in Fig. 4, by means of which the bearings 18 and 19 may be lubricated, or by means of which a suitable isolation fluid may be introduced into the interior of the pump. The isolation fluid, which is nonreactive in the event that it comes into contact with the material being pumped, effectively forms a barrier between this material and the atmosphere or any moisture or other contaminants at the rotary seals. Further, it is understood that the shaft 14 is provided with a suitable drive connection at its upper end, not shown, by means of which the intermeshed gears 20 and 21 are rotated.

The pump plate 25 is further provided with means to support a pair of lip seals 40, which may be formed of a filled polytetrafluoroethylene, as shown in section in Fig. 4. The lip seals 40 are received within the shaft openings formed in the plate 25 in surrounding relation to the respective shafts 14 and 15 to provide a seal for the adjacent needle bearings 1 9 to prevent the intrusion of the material being pumped. The pump includes special means for venting each of the lip seals 40, so as to prevent an undue build-up of pressure at the seals by reason of leakage of the pumped material past the inner faces of the gears.

For this purpose, each of the gears 20 and 21 is provided with a narrow key-way like axial relief passageway or slot 42. A transverse communicating slot 43 formed in the lower end or face end of the shaft which opens into a relief opening 44 formed in a gear cover plate 50. The axial slot 42 extends the depth of the gears and opens into the seal regions for pressure relief. As each of the shafts and gears rotate, the axial passageways 42 rotate in communication with the seals 40 and serves to bleed off any excess pressure by communication with the radial passage 43 so that the bleed-off occurs as indicated by the arrows 52 on Fig. 4.

To complete the structure, the gear cover plate 50 is retained by recessed cap screws 53 which extend through the clearance openings formed in the gear plate 26 and the pump plate 25 and are threaded into the body. The cover plate 50 holds and retains the gears in place on their respective shafts. The plate 26 is of controlled thickness so that the gears from a close running fit with the adjacent flat surfaces of the plates 25 and 50.

Substantial portions of each of the gears 20 and 21 are exposed to receive material directly into the inlet of the pump 10. The inlet is defined by the regions illustrated generally at 55 in Fig. 1, and it can be seen that the cover plate 26 only partially covers the gears 20 and 21 leaving arcuate segments of these gears exposed to receive material. The cover plate 50 cooperates with the gear closure plate 26 so that approximately one-third of the circumference of each of the gears is exposed to the interior of the container in which the pump may be placed and mounted, to receive material between the teeth 30 of the gears as the gears rotate in the direction of the arrows 56 of Fig. 1.In this manner, a substantial dwell time is afforded as the gears rotate through the material, permitting time for the material to flow or move into the sapces between the teeth and be captured between the teeth and the opposed arcuate surfaces 28 formed on the pumpplate 26.

If desired, more or less of the teeth may be exposed at the inlet region 55 by suitably conforming the gear closure plate 26 and cover plate to increase or decrease the arcuate extent of the exposed teeth. Increasing the angle of acceptance may provide even further time for material to flow into the spaces between the individual teeth 30, but also has the effect of shortening the land areas which forms a seal at the ends and sides of the teeth, and thus tends to increase leakage of the pump. Increasing the land areas and thus decreasing the angle of acceptance has the advantage of providing a pump with somewhat greater efficiency or less by-pass leakage, but a pump which is somewhat less capable of pumping and handling highly viscous or highly difficult materials.

The arcuate portions 28 of the plate 26 are preferably extended as shown at 55' to have terminal ends which tend to form throats or tapered regions at the inlet 55 with respect to the gear circle, to provide a tapered or funnel-like entrance into the teeth. It is expected that at least a portion of the material which is being pumped will be set into rotation by reason of the rotation of the gears 20 and 21, and the extension portions 55 have inner surfaces which provide a wedge-like action, to intercept the rotating material and to cause the rotation of to be stopped at that point, and the tapered region at the inlet regions 55 tends to increase the packing effect of the material into roots of the teeth.

While the invention has been described in terms of a conventional pumping gear of teeth having an involute form, it is understood that other tooth forms of the intermeshing pumping gears may be used, and for example, an intermeshing tooth form in which the teeth have concave, convex surfaces in contact conforming to each other of the cloidal form may also be used.

Where filled-type adhesive products or the like are to be pumped reliably at high pressure, such as at 1,500 psi or greater, the teeth 30 of the gears or the gears themselves may be hardened or carbide coated or nickel coated for the purpose of reducing wear. The use of the gear pumps embodying the present invention makes possible the metering of adhesives from a drum or container of such adhesives directly onto a finished product without the employment of an intermediate storage arrangement or accumulator which has heretofore been required where reciprocating pumps have been employed. The pump embodying the invention is of simple construction which may be readily maintained and cleaned by removing the screws 53 and the cover plate 50, thereby exposing the gears 20 and 21.These gears are quite simply keyed on to their respective shafts by keys 70, so that they may be readily removed, if desired, the axial passageway 52 formed in the gears, is formed diametrically opposite the keyways receiving the key 70, and communicate with the high pressure side of the side of the seals 40, for bleeding off and removing any excess pressure which would otherwise tend to accumluate at these seals.

Any suitable isolation fluid may be applied to the interior cavities 36 and the same is preferably a lubricant which can also serve to prevent contamination or exposure of the material being pumped to atmosphere, or to moisture which may otherwise tend to seep or find its way through the seals.

While the form of apparatus herein described constitutes a preferred embodiment of this invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention.

Claims (7)

Claims

1. A submersible gear pump for pumping highly viscous liquid materials from a container of such materials in which said pump is adapted to be lowered or otherwise received or positioned within such container, comprising: a pump body, a pair of pumping gears, means mounting said gears for rotation on said body in intermeshing relation, means on said body defining a pump outlet port positioned on one side of said gears, and cover plate means enclosing said port and partially covering and enclosing said gears to expose a substantial peripheral portion of the teeth of each of said gears to direct contact with material in said container for flow into the spaces between said teeth.

2. The gear pump of claim 1 in which said cover plate means exposes approximately onethird of the teeth of said gears to material within said container.

3. The gear pump of claim 1 in which said cover plate means comprises a partial gear closure on said body in close peripheral contact with a portion of the outer surface of each of said gears and opening at said outlet, and a cover plate secured to said gear closure and formed generally co-terminous with said gear closure plate, thereby exposing a substantial arcuate extent of each of said gears to receive material from said container.

4. A submersible gear pump or the like for pumping highly viscous fluid from a container of such fluid comprising: a body, a pair of shafts, means rotatably mounting said shafts in said body in generally parallel relation, a pair of intermeshing pumping gears mounted on said shafts adjacent a flat terminal end of said body, means in said body defining an outlet port positioned at one side of said gears, means on said body defining a gear closure plate proportioned to form a close running fit with opposed peripheral portions of each of said gears leaving a substantial peripheral portion of each of said gears an inlet side thereof opposite said outlet port uncovered, a cover plate mounted on said gear closure plate substantially co-terminous with said closure plate forming a close running fit with the side of said gears opposite from said body, said cover plate also exposing a substantial peripheral portion of each of said gears, to receive material from said container directly into the spaces between the gear teeth for transfer to said outlet port, and means for rotatably driving one of said shafts.

5. The gear pump of claim 4 in which approximately one-third of the teeth on each of said gears are exposed at any one time to material within such container.

6. The gear pump of claim 4 further including rotating seal means associated with each of said shafts at the associated said gears, and means in said body defining a cavity for the application of an isolation fluid to said seals on the sides thereof remote from said gears to prevent moisture contamination through said seals of the materials being pumped.

7. Submersible gear pumps substantially as hereinbefore described with reference to the accompanying drawings.