US3003426A

US3003426A - Gear pump

Info

Publication number: US3003426A
Application number: US801052A
Authority: US
Inventors: John A Lauck
Original assignee: Clark Equipment Co
Current assignee: Doosan Bobcat North America Inc
Priority date: 1959-03-23
Filing date: 1959-03-23
Publication date: 1961-10-10
Anticipated expiration: 1978-10-10

Description

J. A. LAUCK Oct. 10, 1961 GEAR PUMP 2 Sheets-Sheet 1 Filed March 25, 1959 FIG. l

INVENTOR.

JOHN A. LAUCK I ATTORNEY Oct. 10, 1961 J. A. LAUCK 6 GEAR PUMP Filed March 25, 1959 2 Sheets-Sheet 2 FIG. 3 lo 2 2 QA M Y INVENTOR.

JOHN A. LAUCK ATTORNEY pressure side. journals and would create high pressure at the drive shaft States Patent Filed Mar. 23, 1959, Ser. No. 801,052 Claims. (Cl. 103-126) This invention relates to gear type positive displacement pumps, and more particularly to means for directing fluid to the inlet section of the pump adjacent the intermeshing gear elements thereof.

Since the advent of the gear pump there has always been the problem of relieving the Vacuum created in the pocket between the teeth as the volume of the pocket increases prior to complete opening thereof following disengagement of the teeth. It is highly desirable that this vacuum be relieved during operation of the pump, particularly under adverse inlet conditions as, for example, at high altitudes with relatively low inlet fluid pressure. The problem of adequately filling the geartooth pockets tends to become somewhat aggravated in the well known pressure loaded type of gear pump wherein discharge pressure actuated thrust plates are arranged to be urged into sealing relationship with the side faces of gears associated therewith. Due to the relatively high elficiency of such gear pumps, and consequently low leakage from discharge to inlet, adverse inlet conditions tend to be further aggravated. The problem is not so serious in a gear pump of relatively low efficiency wherein the leakage back to the inlet side of the pump from the discharge side is sufficiently great to tend to compensate for inadequate filling of the gear tooth pockets. Inadequate filling of gear tooth pockets causes the pump to become noisy in operation, and also, causes erosion of the gear teeth, and where the condition is serious, increases the rate of wear of other pump parts. flonversely, by providing adequate filling of. the gear tooth pockets the foregoing undesirable results are avoided, thereby contributing to smoother and quieter operation of the pump, as well as to a longer life thereof.

Various means have been heretofore proposed to solve the problem, including provision for communicating the gear tooth pockets with a high pressure portion of the pump. However, in providing a source of relatively high pump pressure for the purpose, it will be apparent that some pumping efficiency will be necessarily sacrificed; i.e. the work done by the pump in pressurizing such fluid is lost insofar as utilization of such fluid at the discharge side of the pump is concorned.

It is well known that in any gear pump there is a certain amount of fluid which bleeds past the faces of the gears from the high pressure side of the pump toward the low This fluid then leaks through the pump seal and in the journal chambers were there no provision for conducting the fluid back to the inlet side of the pump. Heretofore, such leakage fluid has been directed into the passageway leading to the inlet of the pump in such a manner that no useful work has been accomplished thereby.

l have found that by providing a properly located passageway in one or both of the thrust plates which communicates with the source of such leakage fluid, that such fluid may be utilized to fill the gear tooth pockets, thereby performing a useful function. This is accomplished by locating such a passageway so that it introduces leakage fluid at a location where the gear teeth begin to open from meshing relation. By thus conducting leakage fluid from the journal chambers, the problem of gear tooth pocket suction is solved, and the leakage fluid, heretofore 10st for any useful purpose, does useful work.

It is therefore a principal object of the present invention to provide improved means for filling gear tooth pockets on the inlet side of gear pumps.

It is another object of the invention to provide a gear pump wherein means are adapted to communicate leakage fluid in the pump with the inlet gear pockets of the pump.

It is a feature of the invention to provide valve means in pumps of the type specified which inhibits the passage of pump leakage fluid to gear tooth pockets under a predetermined fluid leakage pressure.

In the drawings:

FIGURE 1 is an axial cross-sectional view showing an intermeshing gear type pump incorporating a preferred embodiment of the present invention;

FIGURE 2 is an elevational view of the pump taken from the right end of FIGURE 1;

FIGURE 3 is an enlarged sectional view of the pump taken on line 33 of FIGURE 1; and

FIGURE 4 is a view in perspective illustrating one of the thrust plates of the invention.

Referring now in detail to the drawings, the numeral 10 denotes a suitably chambered gear pump housing in which are rotatably mounted a driven gear 12 and an intermeshing driving gear 14. Driven gear 12 is supported on a shaft 16 journalled on its right side in a roller bearing 18 and on its left side in a roller bearing 20. Roller bearing 16 is located in a chamber 22 formed in the pump housing. A fixed thrust plate 24 is located inter-mediate bearing 18 and gear 12 and provides an annular recess 26 in registry with the left end portion of the hearing. The bearing member 20 is located in a housing chamber 28 in registry with an annular recessed portion 3!? of an axially movable thrust plate 32 intermediate said bearing and the one side face of gear 12.

Driving gear 14 is mounted for rotation upon a drive shaft 34 journalled on its right side in a roller bearing '36 and intermediate its ends in a roller bearing 33, said roller bearings being mounted in

chambers

40 and 42 in a manner similar to the mounting of

bearings

18 and 20 in

chambers

22 and 28. A fixed thrust plate 44 is mounted intermediate gear 14 and bearing 36 in a manner similar to the mounting of thrust plate 24, said

plates

24 and 44 mating in sealing relationship along complementary flat surfaces thereof indicated at numeral 46. An axially movable thrust plate 48 is mounted intermediate gear 14 and bearing 38 in a manner similar to the mounting of thrust plate 32, said thrust plates abutting in sealing relationship along complementary fiat surfaces thereof as indicated at numeral St}.

A cover body 54 is secured to the pump body 10 by a plurality of bolts, one of which is shown at numeral 56. A shaft seal 58 is located in an enlarged chamber 60 of cover body 54 between a seal retainer member 62 and a portion of the cover body 54. A snap ring 64 locates seal retainer 62 in chamber 60. A plurality of O-rings are mounted in annular grooves formed in various of the parts of the pump construction, as shown, to provide sealing means.

As shown in FIGURE 3, the pump body 10 has an inlet conduit 68 formed in its left side and an outlet conduit 70 formed in its right side. Pressure generated, by the. gears is communicated from the outlet or discharge side of the pump to the pressure

responsive surfaces

72 and 74 of the axially

movable thrust plates

48 and 32 through passageways 76 and 78 in said thrust plates respectively. The pressure fluid is directed through the latter passages into a chamber 80 formed between the inner surface of the cover body 54 and the pressure

responsive surfaces

72 and 74. Thus the inner facing surfaces of

opposed thrust plates

48 and 44 are maintained during operation of the pump in sealing relation to the abutting side surfaces of gear 14, and, likewise, the correspending surfaces of

thrust plates

24 and 32. are maintained in sealing relationship with adjacent faces of gear 12, in a well-known manner. To provide an initial seal between the thrust plates and the gears, a plurality of compression springs, one of which is illustrated at numeral 82, are disposed in recesses formed in the peripheral port-ion of each of the movable plates 32. and 48 to urge the sealing faces of these thrust plates into engagement with the respective gear side faces.

As explained hereinbefore, it is known that as the gears rotate and the gear teeth rotate away from meshing relation at the inlet side of the pump, an undesirable high suction is oftentimes created in the gear tooth pockets until the tooth contacts have opened sufficiently to permit fluid to enter the cavity. I have found that by providing passageways 84 and S6 in

thrust plates

44 and 24, respectively, adjacent the gear tooth pockets on the inlet side, and by providing means permitting communication between

passages

84, 86 and leakage fluid passing through the various bearings, the inlet gear tooth pocket suction condition is substantially eliminated. Preferably, a pair of inlet ports 88 and 949 are formed in the inlet side of

plates

44 and 24, respectively, for aiding in the filling of the gear cavities. If desired, a single enlarged passageway through the thrust plate 24 can be provided to efiect a similar result as if efiected by the pair of

passages

84 and 86.

The location of the passage or passages is critical only within rather wide limits. If the passage or passages are formed in the general area of gear pocket expansion, such as illustrated in FIGURE 3, the desired result will be achieved, the only important limitation being that the passage or passages communicate with the adjacent gear pocket during enlargement thereof and prior to free and open communication of the pocket with the inlet to the pump following breaking of mesh of the teeth.

An annular seal chamber 94 is formed between drive shaft 34, cover body 54 and seal 58, as shown in FIG- URE 1. It communicates with the inlet gear teeth pockets by way of a passageway 96 in the cover body, bearing chamber 28, a conduit 98 formed in driven shaft 16, bearing chamber 22, a vertically extending passageway 100 formed in the body of pump 10 and in communication with chamber 22, a passageway 102 which preferably houses a spring loaded check valve 104, and the

thrust plate passageways

84 and 86. A plug 108 is located in the pump body 10 for closing the end of passageway 100. Preferably, the passageway 10% is also connected with bearing chamber 40, as shown, whereby leakage fluid which tends to collect in each of the

bearing chambers

22, 28 and 40, as well as in the seal chamber 94, communicates with

thrust plate passages

84 and 86 by way of passageway 102 and check valve 104.

The fluid which leaks past the faces of the gears then leaks through the various roller hearings in the pump and into the bearing chambers. In FIGURE 1 arrowed lines are shown extending in opposite directions along drive shaft 34 and driven shaft 16 which illustrate the manner in which leakage into the various bearing chambers occurs. It is recognized that the practice of venting such chambers to the inlet conduit 68 upstream of the gears is known. However, the venting of such chambers in the above described manner whereby a useful function is performed has not, to my knowledge, been heretofore considered.

The check valve 104 is utilized for the purpose of inhibiting a How of fluid from passage 1% through

passageways

84 and 86 below a perdetermined fluid leakage pressure in passage 100. The check valve functions to prohibit the generation of a partial vacuum in the seal and bearing chambers which would tend to cause an undesirable increase in the volume of leakage fluid. If valve 104 were not provided, it will be appreciated that the partially evacuated inlet gear pockets would, on occasion,

tend to produce a vacuum in the bearing and seal chambers. Such a condition would most likely occur upon starting the pump, during which period the discharge pressure is relatively low, resulting in a normally relatively small amount of leakage into said chambers. It should be pointed out that the check valve spring is preferably of low rate so'that the valve will open under the influence of a few pounds of pressure. It should also be pointed out that in some gear pump designs the aforementioned problem is not serious, in which instance the check valve can be eliminated from the leakage circuit.

It will now be apparent that during operation of the pump the leakage fluid which inherently collects in the bearing chambers and in the drive shaft seal chamber is directed through a hydraulic circuit which communicates with the

thrust plate passageways

84 and 86 in order to fill the inlet gear tooth pockets, whereby to alleviate conditions of noisy pump operation, gear tooth erosion, and the like, as discussed above. It will also be understood that the

inlet port sections

88 and 90 in

thrust plates

44 and 24 provide a means which not only aids in filling the inlet gear tooth pockets, but prevents a tendency of the pressure of the fluid flowing through

passageways

84 and 36 to pulsate as the gear teeth rotate in and out of overlapping relation with said passageways. This feature also, of course, tends to smooth out pump operation.

It will be understood that certain changes in detail may be resorted to without departing from the field and scope of my invention, and I intend to include all such variations, as fall within the scope of the appended claims, in this application in which the preferred form only of my invention has been disclosed.

I claim:

1. In a pressure generating pump of the type including a housing containing intermeshing gears and having an inlet leading to and. an outlet loading from said housing, axially movable thrust plate means responsive to pumping pressure to maintain sealing engagement with the gear side faces during operation of the pump, a fixed thrust plate located adjacent each opposite side face of said gears and maintaining sealing engagement with said opposite side faces, and a passage through at least one of said fixed thrust piates at the inlet side of the pump, the opening of said passage at the sealing face of the fixed thrust plate being located such that the expanding gear pocket of intermeshing gear teeth during operation is placed directly in communication with the passage prior to breaking of intermeshing of such gear teeth, and conduit means conducting gear support bearing leakage fluid from the discharge side of said pump to said passage.

2. In a pressure generating pump of the type including a housing containing intermeshing gears and having an inlet leading to and an outlet leading from said housing, axially movable thrust plate means responsive to pumping pressure to maintain sealing engagement with the gear side faces during operation of the pump, a fixed thrust plate located adjacent each opposite side face of said gears and maintaining scaling engagement with said opposite side faces, a passage in each fixed thrust plate which opens into the inlet side of the pump on the scaling sides of said thrust plates, at least one of which passages is located relative to said intermeshing gears such that communication is established directly between each ad jacent expanding gear pocket and said passage as said gears rotate prior to breaking of mesh of the respective intermeshing teeth, and conduit means conducting gear support bearing leakage fiuid from the discharge side of said pump to both said passages in said fixed thrust plates.

3. In a pump as claimed in claim 1, a recessed portion in the sealing side of said one thrust plate, said passage in said one thrust plate opening into said recess, whereby to avoid pulsations in fluid conducted through said passage as said intermeshing gears rotate.

4. A pump as claimed in claim 2 wherein complementary recesses are formed in the sealing sides of said fixed thrust plates on the inlet side of the pump, said thrust plate passages terminating in ditferent ones of said recesses and radially outwardly of the root diameters of the respective gears.

5. In a pressure generating pump of the type including a housing containing intermeshing gears and having an inlet leading to and an outlet leading from said housing, an end plate on one side of each of said gears having a forward surface engageable with the side face of said gears to maintain sealing engagement with the gear side faces during operaiton of the pump, a passage extending in an axial direction through at least one of the end plates and opening radially outwardly of the root diameter of the associated gear and on the inlet side of the pump, said passage opening on the sealing side of the thrust plate in direct communication with an adjacent gear pocket formed between intermeshing gear teeth as said pocket expands in volume during breaking of mesh of said teeth and prior to opening of said pockets to said pump inlet, and conduit means formed in said pump collecting bearing leakage fluid from the discharge side of said pump and conducting such leakage fluid into said gear pockets through said passage in said end plate.

6. A pump as claimed in claim 5 wherein one of the gears is mounted for rotation upon a driving shaft, the intermeshing gear is mounted for rotation upon a driven shaft, bearing means are provided for rotatably supporting said driving and driven shafts and said discharge leakage fluid flows through said bearing means and is thence collected in a common conduit for direct communication with said gear pockets through said end plate passage.

7. A pump as claimed in claim 6 wherein one-way check valve means is located in said common conduit to inhibit the flow of said leakage fluid to the end plate passage helow a predetermined pressure of said fluid.

8. In an intermeshing gear pump, a housing having an inlet port and a discharge port formed therein, a pair of intermeshing pumping gears in said housing arranged to force liquid from said inlet out of said housing through said outlet, bearing means supporting said gears for rotation, a pair of end plates associated with said gears and having faces adapted to engage the adjacent gear side faces in substantially sealing relationship, passage means in said housing collecting pump pressure leakage fluid flowing through said bearing means, and port means extending axially through at least one of said end plates and connected to said passage means for communicating at least a portion of said leakage fluid to directly to the gear tooth pockets for filling same during expansion thereof prior to breaking open of the intermeshing gear teeth.

9. A pump as claimed in claim 8 wherein check valve means in said passage means inhibits flow of leakage fluid to said gear pockets under a predetermined leakage fluid pressure.

10. A pump as claimed in claim 8 w herien a second port means extends axially through the other end plate and also communicates with said passage means, said second port means conducting a portion of said leakage fluid into said gear pockets following the breaking of mesh of the respective gear teeth.

References Cited in the file of this patent UNITED STATES PATENTS 2,540,235 Berkley Feb. 6, 1951 2,714,856 Kane Aug. 9, 1955 2,772,638 Nagely Dec. 4, 1956 2,781,730 Newmier Feb. 19, 1957 2,842,066 Hilton July 8, 1958 2,884,864 Bobnar May 5, 1959 2,885,965 Haberland May 12, 1959 2,891,483 Murray et a1. June 23, 1959 FOREIGN PATENTS 738,782 Great Britain Oct. 19, 1955