US 3890066 A
An axially and radially pressure compensated internally-geared high pressure gear pump in which the filler member is comma-shaped and abutted against a large supporting pin under operating pressure, the abutment position being maintained under dry run conditions by an elastically deformed pin biasing the filler member against the supporting pin, while allowing for radial adjustments of the filler member position.
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Description (OCR text may contain errors)
United States Patent Eckerle June 17, 1975  AXIALLY AND RADIALLY COMPENSATED 3,525,580 8/l970 Eckerle 4l8/7l "1G" PRESSURE GEAR PUMP R27,90I I974 Eckerle 4|8/7l  Inventor: Otto Eckerle, Benzstrasse 6, 7502 FOREIGN PATENTS OR APPLICATIONS Malsch' Germany 1.403923 11 /I969 Germany 1. 418/169  Filed: Mar. 18, 1974  Appl. No.: 452,282 Primary Examiner-John J. Vrablik Attorney, Agent, or Firm-Joseph A. Geiger  Foreign Application Priority Data Mar. 16, 1973 Germany 2313085  ABSTRACT  U S Cl 4l8/7l 8/131, 418/126 An axially and radially pressure compensated internal- 4ls/69 ly-geared high pressure gear pump in which the filler  Int. CLHM F02: 21/00 Folc 1/10, Folc 19/02 member is comma-shaped and abutted against a large  Field 0 Search iiiii U MS/H 72 31 132 supportmg pin under operating pressure, the abutment i position being maintained under dry run conditions by an elastically deformed pin biasing the filler member  References Cited against the supporting pin, while allowing for radial adjustments of the filler member position. UNITED STATES PATENTS 3,289,599 l2/l966 Eckerle et al 418/126 10 Claims, 4 Drawing Figures a 7 i l PATENTEDJUN17 I975 890,065 SHEET 2 Fig.4
AXIALLY AND RADIALLY COMPENSATED HIGH PRESSURE GEAR PUMP BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to gear pumps, and in particular to high pressure gear pumps of the internally-geared type having both radial and axial pressure compensation means.
2. Description of the Prior Art High pressure gear pumps of the internally-geared type normally consists of a housing, a central main bore, a pinion axially journalled inside the housing, and an internally toothed gear ring engaging the pinion, with a filler member positioned between the teeth of the pinion and gear ring. It is known, for example, from my US. Pat. No. 3,525,581, reissued under N0. Re 27,904, to provide radial pressure compensation means in this type of high pressure gear pump, by arranging a so-called control piston between the radially displaceable gear ring and the housing, in opposition to the hydraulic thrust which is generated by converging teeth of the rotating gears. This control piston is subjected to one or several compensation pressure fields urging the piston against the gear ring, which in turn bears against the filler member and against the pinion, or in some cases against a stop which limits the depth of tooth engagement.
It is further known from my aforementioned patent to provide axial pressure compensation means, using axially displaceable discs on each side of the pinion and gear ring, which discs are pressed against the flanks of the pinion and ring under the influence of axial compensation pressure fields arranged between these axial discs and the housing. The incorporation of radial and axial pressure compensation means in the internallygeared pump makes it possible to use as a filler member a simple wedge-shaped member, rather than the previously common sickle-shaped filler member. Due to the radial pressure compensation action, which assures clearance-free interaction between the pinion, filler member and gear ring, the area of the filler member which is exposed to the hydraulic pressure is relatively small. However, in spite of this small effective area, the filler member is nevertheless subjected to a force pushing it back, i.e. against the direction of gear rotation. Under very high pressures, these forces can become considerable, requiring appropriately resistant and stiff supporting means for the filler member on the housing walls. In the earlier-mentioned prior art pump of this type, the filler member includes a pin which extends axially through it and into both sides of the housing, thereby fixing the position of the filler member in both rotational directions. This arrangement has the disadvantage of necessitating a limitation of the diameter of the tiller member supporting pin, while weakening the ramaining cross section of the filler member.
Although the arrangement with the supporting pin extending through the filler wedge is satisfactory under normal operating conditions, showing only a very small deformation under high pressure operation, it was found to present a shortcoming under dry run conditions, when the normal hydrostatic biasing force on the filler member is not present, and when increased friction between the gear teeth and the filler member surfaces takes place. In this situation, the supporting pin cannot prevent this frictional engagement, and the filler member is drawn between the pinion and gear ring in a wedging action.
In the known gear pump disclosed in my US. Pat. No. Re 27,904, this forward rotation is prevented with the help of a second axial pin extending through the filler wedge into the axial discs of the axial pressure compensation means. However, when the pump design calls for the control piston to be radially supported not only on the filler member, but primarily on the axial discs, extremely tight manufacturing tolerances are necessary, unless the filler member is initially provided with a small excess thickness to be worn off in a run-in operation. Such a run-in operation in turn increases the testing and quality control costs of pump production.
SUMMARY OF THE INVENTION It is an objective of the present invention to suggest an improvement over the prior art devices of this type, by eliminating some of the earlier-mentioned shortcomings and by consequently realizing savings in manufacturing and testing expense.
The invention proposes to attain the objective by suggesting a high pressure gear pump of the above type in which the filler member is shortened to a commashaped filler member, the back side of which is supported against an axially extending supporting pin of maximum diameter in a known manner, and in which a second, elastic pin extends through the filler member and serves as a spring, urging the filler member rearwardly against the supporting pin. The bias exerted on the filler member by the elastic pin prevents the filler member from being drawn in the direction of rotation and wedged between the teeth of the pinion and gear ring under dry run conditions.
An additional advantage offered by this novel arrangement is realizable in connection with axial discs which are rotationally fixed in relation to the housing, where, through selection of a supporting pin of appropriate thickness on its abutment face, the manufacturing tolerances of the filler member, of the two gears, and of the two axial discs can be conveniently balanced so that the control piston compensation pressure is distributed between, and born by the axial disc and the filler member. Since it is much less expensive to grind the abutment faces on these pins to different dimensions than to use a run-in operation to achieve this same balance, a saving in manufacturing costs is realized.
BRIEF DESCRIPTION OF THE DRAWINGS Further special features and advantages of the invention will become apparent from the description following below, when taken together with the accompanying drawings which illustrate, by way of example, an embodiment of the invention, represented in the various figures as follows:
FIG. I shows a gear pump embodying the invention, as seen in a radial cross section taken along line I-l of FIG. 2;
FIG. 2 shows an axial cross section of the gear pump of FIG. 1 taken along line IIII thereof;
FIG. 3 shows a detail of the pump of FIGS. 1 and 2 in a partial axial cross section taken along line III-Ill of FIG. I; and
FIG. 4 shows in a partial cross section similar to that of FIG. 3 a modification of the embodiment of FIGS. 1-3.
DESCRIPTION OF THE PREFERRED EMBODIMENT The high pressure gear pump of PK]. 1 shows an externally geared pinion 1 engaging an internally geared gear ring 2 for clockwise rotation, the gear ring 2 being arranged in a floating mode so as to engage the pinion without tooth flank clearance. This ring is held in position by means of a control piston 3 which is biased radially inwardly by means of three circular compensation pressure fields 4. These compensation pressure fields 4 are constituted by short pistons 4' located in matching recesses inside the control piston 3 and sealed thereagainst by means of gaskets 5. On their back side, the pistons 4' are supported on the bore surface of the pump housing 6. The radially inwardly directed compensation pressure on the control piston 3 created by the compensation pressure fields 4 is somewhat in excess of the radially outwardly directed thrust exerted on the gear ring 2, causing the latter to be biased against the pinion l and against a filler member 7 which is located between the converging teeth of the pinion 1 and gear ring 2. The filler member 7 in turn is rotationally abutted against a supporting pin 8 which prevents the filler member 7 from moving against the direction of rotation under the hydrostatic forces impinging on its tip portion. The tooth crown surfaces of the pinion 1 and gear ring 2 are thus maintained in sealing and gliding contact with the inner and outer surfaces of the filler member 7. The orientation of the abutment face 8' in relation to the outline of the filler member 7 is preferably perpendicular to the direction of control piston bias against the gear ring 2 and the filler member 7.
In FIG. 2, the axially cross-sectioned pump shows, in addition to the pinion 1, the gear ring 2, and the control piston 3, two axial discs 9 and 10, arranged to axially adjoin the pinion l and gear ring 2. These axial discs 9 and 10 cooperate with axial pressure compensation means in the form of pressure fields l2 and 13 milled into the corresponding faces of the housing 6 and of the housing cover 11. O-rings l4 and 15 positioned inside these compensation pressure fields l2 and 13 provide a seal along the outline of each field. The axial compensation pressure exerted by these fields against the axial discs 9 and 10 force them against the flanks of the pinion 1 and gear ring 2 for clearancefree sealing contact. The control piston 3 not only bears against the filler member 7, through the gear ring 2, but is also supported against the axial discs 9 and 10, and through the latter against the shaft of pinion l, by axial shoulders on the control piston reaching axially over the width of the gear ring into engagement with appropriate abutment surfaces on the axial discs 9 and 10.
The arrangement of the supporting pin 8 for the filler member 7 is illustrated in more detail in FIG. 3 where the housing 6 and the housing cover 11 are shown to include appropriate seating bores 16 and 17, positioning the pin 8. The latter is flattened on one side to present an abutment face 8' against the filler member 7. This supporting pin 8 is as large in diameter as the space between the pinion l and gear ring 2 permits, in order to minimize its lateral deflection under the hydrostatic forces acting on the filler member 7, which forces have to e transmitted to the housing parts by pin 8.
The axial discs 9 and 10 are rotationally positioned relative to the housing parts 6 and 11 by means of two positioning pins 18 and 19. These positioning pins, pressed into the respective housing parts, are hollow for the accommodation of a thin, elastic pin 20 which extends axially through a bore 21 in the filler member 7. The corresponding bores inside the positioning pins 18 and 19 are ofi'set in the rotational direction in relation to the bore 21 in the filler member 7, so that the elastic pin 20 needs to be bent for assembly, thereby creating a spring bias on the filler member 7 against the supporting pin 8. The diameter of the filler member bore 21 is preferably larger than would be necessary, and correspondingly further offset in the circumferencial direction, so as to render it less sensitive to manufacturing tolerances and to allow for radial repositioning of the filler member 7 in relation to the pinion l. The bores inside the positioning pins 18 and 19 and inside the filler member 7 are appropriately tapered or otherwise widened, in order to accommodate the deflection of the elastic pin 20. The latter is conveniently made of spring steel (piano wire) so as to permit even excessive deflection, as during assembly operations, for example. Instead of positioning the pin extremities in side the hollow pins 18 and 19, it is of course also possible to locate the disc positioning pins elsewhere and to provide separate positioning bores in the housing parts 6 and 11, or preferably, to provide oblong positioning recesses which permit the aforementioned radial repositioning.
The axial discs 9 and 10 have on their outer periphery a semi-circular recess, the abuting shoulder portions of the control piston 3 having similar semicircular recesses which match the recesses in the axial discs 9 and 10 for the accommodation therein of short pins 22 and 23 fixing the control piston 3 rotationally in relation to the axial discs, and through their positioning pins 18 and 19 in relation to the housing parts 6 and 11.
In Fig. 4 is illustrated a modified embodiment of the invention in which the short pins 22 and 23 of P16. 3 are replaced by longer positioning pins 24 and 25 which are pressed into the housing parts 6 and 11 so as to directly position the axial discs 9 and 10 and the control piston 3 in the rotational direction. In this case, it is possible to use a shortened elastic pin 26 whose extremities, instead of being supported inside hollow pins pressed into the housing parts, are directly supported inside bores in the axial discs 9 and 10.
It should be understood, of course, that the foregoing disclosure describes only preferred embodiments of the invention and that it is intended to cover all changes and modifications of these examples of the invention which fall within the scope of the appended claims.
1. In a high pressure gear pump of the internallygeared type having a pinion, a cooperating gear ring, and a radially displaceable filler member arranged in the main bore of the pump housing, with a radially pressure-compensated control piston biasing the gear ring radially toward the pinion and the filler member, and with axially pressure-compensated discs bearing against the axial flanks of the pinion and gear ring in at least the area of pressure generation, the combination of:
means for abutting the filler member relative to the pump housing against back movement in the rotational direction opposed to the direction of gear rotation, while permitting a small radial displacement of the filler member; and
mechanical spring-biasing means engaging the filler member for biasing the latter toward said abutting means in said abutment direction, while permitting said radial displacement of the filler member.
2. A combination as defined in claim 1, wherein:
the filler member biasing means is a bendable, relatively thin elastic pin extending axially through the filler member and into the axial discs;
the axial discs include means for positioning the extremities of said pin; and
the pump housing includes means for rotationally positioning the axial discs.
3. A combination as defined in claim 1, wherein:
the filler member is comma-shaped in its general cross-sectional outline, having a substantially flat end face at its wider extremity oriented in said abutment direction;
the filler member abutting means is a rigid abutment pin mounted in the pump housing and extending axially across its bore in the space between the toothed peripheries of the pinion and internal gear ring.
4. A combination as defined in claim 3, wherein:
said abutment pin is cylindrical and has a peripheral portion of its cross section removed to form an abutment face for engagement with said filler member end face.
5. A combination as defined in claim 4, wherein:
the abutment face on the abutment pin and the cooperating end face of the filler member form a plane of abutment which is substantially perpendicular to the direction of control piston bias against the gear ring and filler member.
6. A combination as defined in claim 4, wherein:
the pinion has a bearing portion adjacent its axial flanks;
the axial discs have a shape which includes an inner radius portion engaging said pinion bearing portion and an outer radius portion which is engaged by the control piston for radially inwardly abutting the latter;
the control piston has two axially extending shoulder portions for said abutting engagement with the axial discs; and
the radial height of the abutment face on the abutment pin in relation to the mounting location of the pin in the housing is such that the control piston compensation pressure is distributed between, and born by said pinion bearing portion, via the axial discs, and the pinion teeth, via the gear ring and the comma-shaped filler member.
7. A combination as defined in claim I, wherein:
the tiller member biasing means is a bendable, rela tively thin elastic pin extending axially through the filler member and through the axial discs into the pump housing on both sides of the gears;
the pump housing includes means for positioning the extremities of said pin; and
the tiller member includes an axial bore for said elastic pin, said bore being offset in relation to said pin positioning means in such a way as to require biasing deflection of the pin away from said abutment direction, said bore further being enlarged to accommodate said deflection and to allow a small displacement of the tiller wedge in the radial direction, without affecting the operation of the biasing means.
8. A combination as defined in claim 7, wherein:
said pin positioning means in the pump housing is in the form of two elongated recesses permitting radial shifting of the elastic pin in conformance with radial displacements of the filler member.
9. A combination as defined in claim 7, wherein:
said pin positioning means in the pump housing is in the form of hollow positioning pins which also serve to rotationally position the axial discs, the positioning pins having an enlarged outer bore portion to accommodate the biasing deflection of the elastic pin.
10. A combination as defined in claim 7, wherein:
said elastic pin is a length of spring steel rod.