US3233552A

US3233552A - Pump

Info

Publication number: US3233552A
Application number: US315315A
Authority: US
Inventors: Roger J Kinnavy
Original assignee: Crane Co
Current assignee: Crane Co
Priority date: 1963-10-10
Filing date: 1963-10-10
Publication date: 1966-02-08
Anticipated expiration: 1983-02-08

Description

R. J. KINNAVY Feb. 8, 1966 PUMP 2 Sheets-Sheet 1 Filed Oct. 10, 1963 INVENTOR Y ROGER J. KINNAVY Feb. 8, 1966 R. J. KINNAVY 3,233,552?

PUMP

Filed Oct. 10, 1963 2 Sheets-Sheet 2 ENTOR VY B ROG J KINNA T FQQ ATTORNE S United States Patent 3,233,552 PUMP Roger J. Kinnavy, Salem, Ohio, assignor to Crane (30., New York, N.Y., a corporation of Illinois Filed Get. Ill, 1963, Ser. No. 315,315 6 Claims. (Q1. 103--126) This application is a continuation-in-part or" my copending application, Serial No. 263,207, filed March 6, 1963, now abandoned.

This invention pertains to the art of pumps and particularly to an improved gear type of pump having an external driven rotor and an internal idler.

The present invention is more particularly applicable to a rotary pump of the type comprising a driven external rotor having a disc-shaped support plate with axially extending teeth spaced around the outer periphery thereof, and an eccentrically mounted internal idler gear having peripheral teeth coacting with the rotor teeth to create a pumping action and the invention will be discussed with particular reference thereto; however, it is to be appreciated that the invention may have somewhat broader applications and may be used in other analogous pump constructions.

A pump of the type to which the present invention is directed is described in my United States Letters Patent No. 3,038,413 wherein there is disclosed a means for balancing the axial forces on the rotor by setting up liquid pressures in a series of increments on the back face of the rotor with each increment increasing and decreasing in pressure in accordance with the pumping pressure in the Zones of the rotor on the opposite side thereof in the pumping zone.

However, pumps of this type known in the prior art are still subject to stresses created by imbalance of radial forces arising from a variation of internal pressures during the pumping operation. If these internal radial pressures are not also balanced, the maximum eiliciency and life for the parts of the pump and the pump itself cannot be obtained.

In such pumps the subject of this invention, the pressure applied at the inlet of the pump is substantially low, and the pressure gradually increases by increments until it reaches a maximum value at the outlet of the pump. in particular, the pressure adjacent the outlet, being substantially greater than the pressure adiacent the inlet, tends to bend or cant the rotor on its drive shaft thus producing increased wear on the rotor shaft bearing and uneven wear at various points Where the rotor makes contact with other pump parts during its rotation. quently, the present invention is directed toward improving the design of this type of pump to secure an effective pressure balance of the so-cailed differential radial pres sures within the pump so that, while the pressure incrc' merits may vary about the rotor, such pressures will be balanced around the drive shaft of the rotor to reduce large wear producing forces between the shaft and its support bearing.

In acordance with the present invention there is provided a housing with a pumping chamber having a cylindrical wall, an external rotor gear having a disc-shaped teeth support plate with an outer surface concentric with and facing the wall and an internal gear rotatably mounted in the housing with teeth meshing the teeth of the rotor for creating a pumping action as the gears are rotated. The improvement in such a pump comprises a means for hydraulically balancing the radial forces exerted on the bearing of the rotor shaft wherein the baiancing means include a low resistance fluid connection between a portion of the pump subjected to the pump discharge pressure and a portion of the outer surface of the r Conse- Patented Feb. 8, 1966 rotor support plate opposite the pump outlet and the area of the portion of the outer surface being dimensioned to substantially balance the radial forces on said hearing.

In accordance with a more specific aspect of the present invention the hydraulic balancing means as defined above includes a circumferentially exten.ding,- circular groove between the cylindrical walls of the housing and the outer surface of the rotor support plate.

Further in accordance with the present invention, the balancing means as defined above is included, in combination, with the balancing means for axial forces as defined in my previously-mentioned Letters Patent.

The primary object of the present invention is the provision of a pump of the type described wherein the forces on the rotor drive shaft are balanced to minimize the wear of the drive shaft bearing and to increase the life and improve the operation of the pump.

Another object of the present invention is the provision of a pump of the type described above which includes a low resistance fluid connection or conduit between a portion of the pump subject to the pump discharge pressure and a portion of the outer surface opposite the pump outlet.

Still another object of the present invention is the provision of a pump of the type described above wherein the low resistance fluid connection is acomplished by provision of a circumferentially extending, circular groove between the radially outwardly facing surface of the rotor support plate and the cylindrical wall of the pumping chamber.

These and other objects and advantages will become apparent from the following description used to illustrate the preferred embodiment of the present invention as read in connection with the accompanying drawings in which:

FIGURE 1 is a vertical axial cross-sectional view through a pump embodying the present invention;

FIGURE 2 is a cross-sectional view taken along line 2-2; of FIGURE 1;

FIGURE 3 is a cross-sectional view taken along line 3-3 of FIGURE 1; and

FIGURE 4 is a partial-cross-sectional view illustrating a modification of the embodiment shown in FIGURES 1-3.

Referring now to the drawings, wherein the showings are for the purpose of illustrating preferred embodiments of the present invention only and not for the purpose of limiting same, FIGURES 1-3 show my improved pump which comprises a housing 10 made of a casting of suitable shape with a generally cylindrical wall or surface Illa defining an inner pumping chamber rotatably receiving a rotor 11.. The rotor 11 has the general form shown in FIGURE 2 and includes a rearwardly positioned disc-shaped support plate 13 having an outwardly facing, circumferentially extending surface 13a adapted to support thereon a series of teeth 12 of the general shape shown. The rotor ll rotates concentrically with cylindrical wall or surface lilo, and the surface 13a is spaced slightly therefrom to prevent any substantial drag of the rotor on the cylindrical wall.

Meshing with the teeth 12 of the rotor 11 are teeth 14 of an idler 15 mounted as shown. The shapes of the

teeth

12 and 14 resepctively are so arranged as to mesh properly together and provide a pumping action as hereafter described. The idler is mounted on an axis 17 that is parallel to but eccentric with respect to the rotor axis, as shown in FIGURE 2. Due to this eccentricity, there is provided between the outer periphery of the idler and the inner periphery of the rotor teeth a space that is substantially filled by a partition 2t? shaped as a crescent or a portion thereof.

An inlet port is provided at 22, and an outlet port 24 is also provided in the housing with the inlet and outlet ports being so arranged that the latter is spaced cir-cumferentially from the .ilet in the direction of rotation of the rotor. In the preferred form of invention shown in the drawings this spacing is approximately 270, although it will be understood that modifications in arrangement may be made without departing from my invention to include any such spacing between approximately 180 and 360. It will be further understood that the inlet port 22 and the outlet port 24 may occupy similar locations in the cover 45 (hereafter described) or partially in the cover and housing, as desired. Fluid is admitted at the inlet 22, and, as shown in FIGURE 2, fills the spaces between the teeth of the rotor and idler and by such teeth is carried to the forward end 25 of the crescent 20. At this point, the teeth 12 and id begin to mesh together and reduce the volume available for liquid thereby forcing it under pressure out of the outlet 24. To facilitate ingress and egress of the liquid, the housing is relieved at 27 and 23, respectively, as shown in FIGURE 2.

The rotor 11 is driven through a shaft 36 as shown in FIGURE 1, which shaft is connected to a suitable prime mover. Packing 32, packing seat 33, and

thrust washers

34 and 35 are provided as is usual in this type of pump. The primary object of the invention defined in my above-mentioned Letters Patent is to relieve the end thrust from right to left (FIGURE 1) on the thrust washers due to pumping pressures in the pump. A housing bearing 37 is disposed between the packing and the thrust washers, and this bearing permits lubrication through a fitting 39.

The idler 15 is mounted on an idler pin 40 that is carried in a cover plate adapted to be removably secured by bolts 47 to the housing ill. The idler 15 is carried. on a suitable idler bushing 43 with a grease retainer 5:) held in place by a retaining ring 52. The idler pin 4i) is held in the cover 45 by a shoulder 54 and an idler pin nut 55. Lubrication for the idler is provided at the grease fitting 58.

It will be seen from the description thus far that the housing w and the cover plate 45 define between them a chamber in which the rotor and the idler rotate with the latter being driven through teethlZ and 14- by the former.

The cover 45 is provided with an internal plane face 60, generally unbroken except for the protruding crescent 2%, which face is adapted to make sliding contact with complementary faces on the rotating idler and rotor.

0n the rear side of the rotor 11, the housing in is formed with a face 76 that is normal to the axis of rotation of the rotor and is shown in FIGURE 3 as a plane.

The rear face of the rotor ill that cooperates with the face '70 is provided with a series of scaling vanes 72 that extend radially outward from a hub 73 of the rotor. These vanes extend outwardly (to the left in FIGURE 1) and terminate in a common plane that is normal to the rotor axis of rotation and parallel to the plane in the housing. The vanes are widely separated to provide between them a series of pressure equalizing cavities as indicated at 75. The construction is such that the projected area of the cavities toward the plane 78 is as nearly as possible equal to the area of said plane 70, being reduced in amount only by the width of the adjacent sealing vanes.

in order to equalize the pressure on opposite sides of the rotor, namely, between the back side adjacent the plane 70 and the front side at which the pumping is taking place in accordance with my previously-mentioned Letters Patent, there are provided in the outer periphery of the rotor 11 a series of passages or channels 77, as shown. If desired, these passages may take the form of holes cored or drilled inside the periphery of the ro- :2. tor. Each channel extends axially of a respective tooth 12 across the rotor to provide communication between the front and back sides thereof as shown. Thus, it will be seen that as many cavities 75 are provided as there are teeth 12. Hence, the differential pressure set up by a particular tooth 12 is immediately neutralized as far as end thrust is concerned by transmission of pressure through adjacent channel '77 to adjacent cavity 75.

A study of the construction of the pump as described thus far will disclose that two important objects have been obtained. First, the cavities 75 supplied with liquid by the channels 77 provide a general over-all equalization of pressure between the front and back of the rotor. Thus, any end thrust, particularly against the

thrust washers

34 and 35, is eliminated, and the rotor floats axially in its bearing. In addition to this achievement, there is provided a balancing of the diiferential pressures that arise due to the pumping action of the parts. At the inlet the pressure is relatively low and at the outlet it is relatively high with various gradations of pressure at all points inbetween. By providing the series of cavities described, each fed by a channel 77, as shown, that bleeds from the front to the rear side of the rotor, it is possible to have liquid under one pressure in the cavity 75a, and under another pressure in the cavity 75b, and under still a different pressure in the cavity 75c, etc. Thus, while the overall front to back pressure of the rotor is balanced, it will be apparent that the different local increments of pressure due to the pumping action also are balanced, thus eliminating any tendency of the rotor to "bend or cant with respect to the housing.

The pump as so far described is substantially identical to the pump disclosed in my above mentioned Letters Patent and by the provision of the cavities '75 and channels 77 there is an equalization of the axial forces on the rotor support plate 13. The present invention is directed particularly toward a means for balancing the radial forces on shaft 39 which forces are transmitted to the shaft by the rotor 11 secured thereto. Referring now to FIGURE 2, the reaction force R exerted on the rotor 11 by the idler 15 during the pumping operation is in a generally upward direction and faces generally toward the high pressure or discharge portion of the pump. The pressure of the fluid in outlet 24 creates a radial force P directly downward on the rotor as is indicated. The pressurized fluid in outlet 2 .4 flows into the clearance between wall iila and outer surface 13a so that the magnitude of force P is determined primarily by the width of surface 13a. Although the radial forces R, P extend generally in opposite directions, a balance of these forces has not been heretofore achieved because of the width of surface 13a necessary to provide the pump with required operational characteristics. Consequently, the magnitude of force P has in the past been substantially greater than the resultant balancing force created by radial force R.

The present invention is directed toward a means for offsetting a portion of force I? so that it can be substantially balanced by force R without reducing the actual width of surface 13a. In effect, the present invention decreases the effective width of surface 13a, by subjecting an accurately dimensioned portion of that surface generally opposite outlet 24 to a fluid pressure substantially at the discharge pressure of the pump. The force it" is created by the differential in pressure between the pump inlet pressure and the pump outlet pressure; and its magnitude is dependent on the area against which this dinerential pressure acts. Consequently, by subjecting an accurately dimensioned area of surface 13a opposite outlet 24 to a pressure equal to the pump discharge pressure, the area subjected to a differential in pressure is decreased, thereby decreasing force P proportionately. To assure that a fluid under a pressure substantially at the discharge pressure of the pump reaches the accurately dimensioned portion of surface 13a, the conduit or passage connecting this area with a portion of the pump subjected to discharge pressure of the pump must have relatively low hydraulic resistance and should have a relatively high response to a change in discharge pressure.

Although a variety of structural embodiments could be utilized to accomplish the present invention as broadly explained above, in accordance with the preferred embodiment as shown in FIGURES 1-3, a circumferentially extending, circular groove 80 is provided in housing directly opposite surface 13a. Groove 80 has a sufficiently large cross-sectional area so that the pressure within the groove is substantially equal at all circumferential positions, i.e. the groove has low hydraulic resistance and high response or sensitivity to changes in discharge pressure, and the width of the groove is accurately dimensioned so that the width of surface 13a subject to a pressure differential is reduced to a level at which force R substantially balances force F. By this arrangement, the radial forces on shaft 30 are minimized which substantially increases the life of bearing 37 and improves the operation of the pump.

Referring now to FIGURE 4, a modification of the preferred embodiment as illustrated in FIGURES 1-3 is shown wherein the circular groove 80 in housing 10 is replaced by a similar circumferentially extending, circular groove 90 in rotor support plate 13. The operation of groove 90 is similar to the operation of groove 30 and a detailed discussion is not necessary.

It is appreciated from the above disclosure of two preferred embodiments of the present invention that the invention is directed toward a means for balancing the radial forces on the shaft 30 which means include a low resistance fluid connection between a portion of the pump subjected to the pump discharged pressure and an accurately dimensioned portion of the outer surface 13a adjacent the pump inlet 22 or, at least, opposite pump outlet 24. It is appreciated that certain structural modifications may be made in the preferred embodiment disclosed herein without departing from the intended spirit and scope of the present invention as defined in the appended claims.

Having thus described my invention, I claim:

1. In a pump of the type described, including a housing with a pumping chamber having a cylindrical Wall, an external rotor gear having a disc-shaped support plate with an outer surface concentric with and facing said wall, an internal idler gear rotatably mounted in said housing and eccentrically mounted with respect to said rotor gear, the teeth of said gears meshing with each other during one portion of their rotati-ve movement and separated from each other by a partition during another portion of their rotative movement, mean-s to drive said gears including a bearing in said housing, a shaft extending through said bearing and means for drivingly connecting said shaft to said rotor, an inlet port in said pump housing to receive liquid under low pressure and an outlet port in said pump housing to transmit liquid under substantially higher pressure from said gears, a face formed in said housing and a cooperating opposite face formed on said rotor rearward of the teeth thereon, one of said faces having a sealing surface and the other of said faces having a plurality of radially extending vanes extending axially and terminating in a common second sealing surface such that said vanes make sealing contact with said first face when said rotor gear is rotated in said housing, said vanes being relatively narrow with respect to the space between them to provide a series of pressure balancing cavities of such size that the total area of said cavities is substantially equal to the area of the face having a sealing surface, and a series of passages affording communication between said respective cavities and the pumping chamber to equalize the pressure between respective cavities and at portion of the pumping chamber immediately adjacent thereto, the improvement comprising: means for reducing the radial force on said bearing caused by a differential in pressure between fluid at discharge pressure and fluid at intake pressure acting on said outer rotor surface and between the rotor surface and housing wall, said force lowering means including a low resistance fluid connection between a portion of the pump subjected to fluid at the discharge pressure and a portion of said outer surface adjacent said inlet port whereby said portion adjacent said inlet port is also subjected to discharge pressure so that the area of said surface subjected to a pressure differential is reduced.

2. The improvement as defined in claim 1 wherein said fluid connection is a circumferentially extending groove in said wall.

3. The improvement as defined in claim 1 wherein said fluid connection is a circumferenti-ally extending groove in said outer surface.

4. A fluid pump comprising a housing with a pumping chamber having a cylindrical wall, and an external rotor having a disc-shaped teeth support plate with an outer surface concentric with and facing said wall, said surface being slightly spaced from said wall to allow rotation of said rotor within said chamber, said pump having a discharge passage and an intake passage with fluid under discharge pressure being introduced between the surface and wall adjacent said discharge passage and fluid under intake pressure being introduced between the surface and Wall adjacent said intake passage whereby the difference in discharge and intake pressure acting between said surface and wall causes a resultant force depending on the total area of said rotor surface being subjected to said pressure differential, said rotor being supported on a shaft extending through said housing, and a bearing in said housing for supporting said shaft, said bearing being loaded by said resultant force, the improvement comprising: a means for lowering said resultant force, said force lowering means including a low resistance fluid connection between a portion of the pump subjected to fluid at the pump discharge pressure and a portion of said outer surface adjacent said intake passage whereby said portion adjacent said intake passage is also subjected to discharge pressure so that the area of said surface subjected to a pressure differential is reduced.

5. The improvement as defined in claim 4 wherein said fluid connection is a circumferentially extending groove in said wall.

6. The improvement as defined in claim 4 wherein said fluid connection is a circumferentially extending groove in said surface.

References Cited by the Examiner UNITED STATES PATENTS 1,719,640 7/1929 Wilsey 103-126 1,970,146 8/1934 Hill 230-141 2,076,664 4/1937 Nichols 103-126 2,124,140 7/1938 Poster of al 10.3-126 2,132,813 10/1938 Wahlmark 103-126 2,940,399 6/1960 Zieg et a1. 103-126 2,998,783 9/1961 Lee 103-126 3,034,446 5/ 1962 Brundage 103-126 3,034,447 5/1962 Brundage 103-126 3,034,448 5/1962 Brundage 103-126 3,038,413 6/1962 Emeny et a1 103-126 DONLEY I. STOCKING, Primary Examiner, WILBUR J. GOODLIN, Examiner,

Claims

1. IN A PUMP OF THE TYPE DESCRIBED, INCLUDING A HOUSING WITH A PUMPING CHAMBER HAVING A CYLINDRICAL WALL, AN EXTERNAL ROTOR GEAR HAVING A DISC-SHAPED SUPPORT PLATE WITH AN OUTER SURFACE CONCENTRIC WITH AND FACING SAID WALL, AN INTERNAL IDLER GEAR ROTATABLY MOUNTED IN SAID HOUSING AND ELECTRICALLY MOUNTED WITH RESPECT TO SAID ROTOR GEAR, THE TEETH OF SAID GEARS MESHING WITH EACH OTHER DURING ONE PORTION OF THEIR ROTATIVE MOVEMENT AND SEPARATED FROM EACH OTHER BY A PARTITION DURING ANOTHER PORTION OF THEIR ROTATIVE MOVEMENT, MEANS TO DRIVE SAID GEARS INCLUDING A BEARING IN SAID HOUSING, A SHAFT EXTENDING THROUGH SAID BEARING AND MEANS FOR DRIVINGLY CONNECTING SAID SHAFT TO SAID ROTOR, AN INLET PORT IN SAID PUMP HOUSING TO RECEIVE LIQUID UNDER LOW PRESSURE AND AN OUTLET PORT IN SAID PUMP HOUSING TO TRANSMIT LIQUID UNDER SUBSTANTIALLY HIGHER PRESSURE FROM SAID GEARS, A FACE FORMED IN SAID HOUSING AND A COOPERATING OPPOSITE FACE FORMED ON SAID ROTOR REARWARD OF THE TEETH THEREON, ONE OF SAID FACES HAVING A SEALING SURFACE AND THE OTHER OF SAID FACES HAVING A PLURALITY OF RADIALLY EXTENDING VANES EXTENDING AXIALLY AND TERMINATING IN A COMMON SECOND SEALING SURFACE SUCH THAT SAID VANES MAKE SEALING CONTACT WITH SAID FIRST FACE WHEN SAID ROTOR GEAR IS ROTATED IN SAID HOUSING, SAID VANES BEING RELATIVELY NARROW WITH RESPECT TO THE SPACE BETWEEN THEM TO PROVIDE A SERIES OF PRESSURE BALANCING CAVITIES OF SUCH SIZE THAT THE TOTAL AREA OF SAID CAVITIES IS SUBSTANTIALLY EQUAL TO THE AREA OF THE FACE HAVING A SEALING SURFACE, AND A SERIES OF PASSAGES AFFORDING COMMUNICATION BETWEEN SAID RESPECTIVE CAVITIES AND THE PUMPING CHAMBER TO EQUALIZE THE PRESSURE BETWEEN RESPECTIVE CAVITIES AND AT PORTION OF THE PUMPING CHAMBER IMMEDIATELY ADJACENT THERETO, THE IMPROVEMENT COMPRISING: MEANS FOR REDUCING THE RADIAL FORCE ON SAID BEARING CAUSED BY A DIFFERENTIAL IN PRESSURE BETWEEN FLUID AT DISCHARGE PRESSURE AND FLUID AT INTAKE PRESSURE ACTING ON SAID OUTER ROTOR SURFACE AND BETWEEN THE ROTOR SURFACE AND HOUSING WALL, SAID FORCE LOWERING MEANS INCLUDING A LOW RESISTANCE FLUID CONNECTION BETWEEN A PORTION OF THE PUMP SUBJECTED TO FLUID AT THE DISCHARGE PRESSURE AND A PORTION OF SAID OUTER SURFACE ADJACENT SAID INLET PORT WHEREBY SAID PORTION ADJACENT SAID INLET PORT IS ALOS SUBJECTED TO DISCHARGE PRESSURE SO THAT THE AREA OF SAID SURFACE SUBJECTED TO A PRESSURE DIFFERENTIAL IS REDUCED.