US2505136A - Internal helical gear pump - Google Patents

Description

April 25, 1950 R. J. L. MOINEAU INTERNAL HELICAL GEAR PUMP Filed June 18, 1946 .rum

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Patented Apr. 2.5 119,50

INTERNAL GEAR PUMP Ren Joseph Louis Moineau, Paris, France; Adele Moineau, administratrix of said Ren Joseph Louis Moineau, deceased, assigner to Robbins & Myers, Inc., Springfield, hio,a corporation of Ohio Application June 18 1946, 'Serial No. 677,609

9 Claims. (Cl. 10S-117) It is an object of my present invention to pro I vide for improvements in pumps of the above described character which will result in certain advantages not found in other pumps.

Another object of my invention lies in the provision of a pump having rotationally balanced inner and outer pumping elements. This object isancillary to my object in providing a pump of the character described, in which the inner` and outer pumping elements rotate about fixed axes which are parallel to each other but displaced from each other.

A further object of my invention` includes the provision of a pump in which the coaction between the pumping elements is such that the fluid being pumped passes directly through Vthe pump from inlet to outlet without moving in a helical path. In this way there is no radial component of velocity of the fluid being pumped. The relatively low fluid velocity characteristics of the pumping elements permit of high rotational speeds, so that large capacity pumps can be built in relatively small size casings.

A still further object of my invention is the provision of a pump which, because of its characteristics, is especially well adapted for use in deep well installations. In one aspect it is an object of my invention to'provide a pump inwhich v' the internal and external helical gear members are housed and in which the external member is subjected on all sides to the discharge pressure of the pump. By this means end thrust on the external element can be completely eliminated. Other objects include the provision of a pump which will be relatively simple in construction, eiilcient in operation, and which will have a low maintenance expense. These and other objects of my invention which will be pointed out hereinafter or which will be apparent to one skilled in the art upon reading these specifications I accomplish by that certain construction and arrangement of parts of which I shall now describe some exemplary embodiments.

Reference is made to the drawings forming a part hereof and in which Figure 1 is a cross-l sectional view through a pump according to my invention.

Figure 2 is a cross-sectional view of the saine taken on the line 2, 2 of Figure l.

Figure 3 is a vertical cross-sectional view of a modification of my invention, incorporated in a deep well casing.

Briefly in the practice of my invention I provide a casing generally indicated at Ill and having an intake port I I and an exhaust port I2. Within the casing at I3, I provide a spider having perforations I4 and having a bearing member I5. Adjacent the intake port II I provide a disclike element I6 provided with a bearing I'I. The member I6 is imperforate except for a bleeder orifice I8. The external helical gear element indicated generally at I9 is provided with the annular portions 20 and 2I which are journaled respectively in the bearings I5 and II so that the member I9 is free to rotate in those bearings. It should be noted that the bearing I 5 is provided with the lubricating grooves 22 whereas the bearing I1 is provided with a packing gland 23.

The internal helical gear element is indicated generally at 24 and is mounted on a shaft 25 which is a drive shaft for the pump. The shaft 25 is journaled in the casing as indicated generally at 26 and 21. It will be noted that the bearing 26 has the lubricating grooves 28 while the bearing at 21 which must be tight is provided with a seal member or packing gland indicated generally at 29.

AIt should` be noted that the axis of rotation of the internal element 24 and the axis of rotation of the external element I9 are not co-axial. but these axes must be parallel. As the shaft 25 is rotated about its own axis, the member 24 which is fixed upon the shaft 25 drives the member I9 which is free to rotate in its bearings at I5 and I'I. With this arrangement the pumping pockets 3D are moved along through the pump from right to left in Figure 1 in a straight line rather than helically around the internal element.

This means that high rotational speeds may be used without danger of cavitation; and with the relatively low fluid velocity characteristics of the elements, large capacity pumps can be provided in relatively small size casings. .j

From a consideration of Figure 1 it will be observed that the fluid being pumped is free to asoman space 3| around the external element I9 and into the space indicated generally at 32 so that the external element is on all sides exposed to the discharge pressure of the pump. The only axial.

thrust on the member I9 therefore is that produced by friction within the member I9. I have found that by determining the aperture 2 Ia in the member 2l I can eliminate even this end thrust on the member I9. I, therefore, prefer to make the area of the aperture 2Ia slightly larger than the area of the pumping space between the members I9 and 24, in any cross section through the pump. In other words, if the cross-sectional area of the space 30 in any vertical cross-section through the pump is X then I make the net crosssectional area at 2Ia, i. e., the area at 2Ia minus the cross sectional area of the shaft, slightly greater than X. This amount can be determined empirically to balance the member I9 for any desired operating pressure. Also with any standardized line of pumps it would be possible to have empirically designed orifice bushings for the member 2I so that the orifice opening 2Ia could be sized to balance various known operating pressures.

It will be noted that there is provided the bleeder orifice I8 in the disc element I6. This orifice, although not essential to the basic design, does serve to make the pump self priming and prevents the pump from running dry. For example, if the' pump has not been running for sometime and it is then started up, fluid remaining in the casing I can bleed back through the orifice I8 so as to recirculate through the pump; and although the volume of recirculation is only a small fraction of the pump's displacement it is suillcient to keep the pump from running dry until such time as the newly pumped fluid is again flowing through the intake port II.

In Fig. 3 I have shown a modification in which the pump is incorporated in the casing of a. deep well. The deep well casing is indicated at 40, and forms the casing for the pump itself. At 42, I provide a 'bearing for the upper end of the external pumping element 44 and 43 a bearing for the lower end thereof and having the bleed port 43a, similar to the port I8 of Figure 1. The internal pumping element is shown at 45 andis provided with a drive shaft 46. The drive shaft is journaled in the bearings 41 and 49 in the spiders 48 and 58 respectively. It should be noted that the drive shaft 46 is disposed centrally of the casing 4I). With the modification of Fig. 3 it is of course possible to provide more than one pumping stage in a deep well pump, with devices as shown in Fig. 3 disposed at more than one elevation within the casing.

It will also be noted that the members 44 and 45 have helical threads of considerably elongated pitch. The purpose of this feature is to enable th pump to approach the theoretical maximum velocity of flow without cavitation.

The maximum velocity of fluid through the pump is governed by that which atmospheric pressure will support. For water this is determined from the formula V=\/2gh where V=velocity in feet per second, g=acceleration due to gravity (normally 32.2 feet per second per second) and h=head in feet of water representing atmospheric pressure (about 33.9 feet at sea level). Thus in the absencewof flooded head, the maximum sea level velocity above which cavitation takes place is 46.8 feet per second.

In accordance with this invention, it is possible to build pumps which closely approach the limit- 4 ing condition where the pitch of the internal element (in feet) multiplied by the revolutions per second thereof, equals 46.8 feet per second.

Since the internal and external elements are mounted for rotation about their own axes, each may be perfectly balanced. The combination of rotating inner and outer pumping elements, together with the elongated pitch of the elements, tending toward the maximum theoretical now rate, results in being able to build large capacity pumps in small diameter casings. This is highly important from the economy stand point in deep well pump practice.

In the claims, the term Moineau pair means an external and an internal helical pumping element, the external element having one more thread than the internal element.

It will be understod that numerous modifications may be made without departing from the spirit of my invention. I do not, therefore, intend to be limited otherwise than as pointed out in the claims which follow.

Having now fully described my invention what I claim as new and desire to secure by Letters Patent is:

1. A pump comprising a casing, inlet and exhaust ports in said casing, an external and an internal helical pumping element in said casing, the external element having one more thread than the internal element, the internal element being mounted for rotation about a fixed axis, the external element being mounted for rotation about another fixed axis parallel to said first axis but offset therefrom, and means for driving said internal element, whereby said internal element drives said external element, whereby the material being pumped is moved axially in a straight line through said pump, the outside of said external element inside said casing being subjected to the discharge pressure of said pump, thereby controlling end thrust on said external element,

2. A pump according to claim 1 in which there is 'a bleeder orifice communicating between said casing under discharge pressure and the inlet side of said pump.

3. A pump comprising a casing, inlet and exhaust ports in said casing, a spider in said casing adjacent said exhaust port, said spider being perforate, a disc in said casing adjacent said intake port, said disc having a bleeder aperture. bearings in said spider and said disc, an external and internal helical pumping element in said casing, the external element having one more thread than the internal element, the external element having its bearings in said spider and disc, the internal element being within said external element and having a driving shaft passing through a wall of said casing, and bearings 'for said drive shaft in said casing non-coaxial with said first mentioned bearings.

4. A device according to claim 3, in which said external element is exposed on all sides to the discharge pressure of the pump whereby end thrust on said external element is controlled.

5. A device according to claim 3 in which there is an orifice between said intake port and said pumping elements, through which said driving shaft passes, the area of said orifice minus the area of said shaft being at least equal to the crosssectional area of the space between the elements of said engaged pumping elements in any crosssection thereof. A

6. In a deep well having a casing, a. pump in said casing, said casing constituting also the casing for said pump, an external and an internal;

helical pumping element in saidA casing. the external element having one more thread than the internal element, bearings for the external ciement of said pair eccentric to said casing and bearings for the internal element oi said pair concentric to said casing, 'said internal element having a drive shaft mounted in said concentric bearings.

7. A deep well pump comprising a casing, a pair of perforated spider members mounted in said casing in spaced relationship, a second pair of spider members mounted in said casing in spacedA relationship between said first mentioned spider members, an external and an internal helical pumping element in said casing, the external element having one more thread than the internal element, the inner element 'of said pair having a drive shaft, bearings in said irst mentioned pair of spider members concentric with said casing. and constituting bearings for said drive shaft,

bearings in said second mentioned pair of spiders eccentric with said casing, and constituting bearings for the external element of said pair.

8. A device according to claim 'I in which the speed of rotation of said drive shaft in revolutions per second and the pitch of said inner element in feet are such that their product is substantially equal to 46.8 feet per second.

9. In a deep well having a casing. at lcasttwo 6 pumps in said casing disposed at diilercnt depths and constituting at least two pumping stages. said casing constituting also a casing for said pumps. each of said pumps comprisingA an external and an internal helical pumping element, the external element having one more thread than 'the' internal element, bearings for said external elements eccentric to said casing, and bearings for said internal elements concentric to said casing. said internal elements having a drive shaft mounted in said concentric bearings.

REN JOSEPH mms MOINEAU.

REFERENCES The following references are of record in the ille of this patent:

UNITED STATES PATENTS

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