GB2086481A

GB2086481A - Gearwheel pumps

Info

Publication number: GB2086481A
Application number: GB8132502A
Authority: GB
Original assignee: GLYCO IND AUTOMATION
Current assignee: GLYCO IND AUTOMATION
Priority date: 1980-10-29
Filing date: 1981-10-28
Publication date: 1982-05-12
Also published as: GB2086481B; DE3142328A1; JPS57102588A; FR2492905A1; FR2492905B1; CH649133A5

Abstract

A plurality of pairs of externally-meshing pumping gears 1a, 1c are driven by a central common gear-wheel, or "sun wheel", 9. The pressurized working-fluid is discharged by way of a chamber for the sun wheel within a body 3, Fig 2 (not shown), and a hollow driving-shaft 11. This arrangement permits a compact construction, a "step-up" drive of the pumping gears, a steadier noise-reducing output from the pumping gears, and (owing to transmission of torque to the pumping gears through the sun wheel) simplified axial sealing. <IMAGE>

Description

SPECIFICATION Gearwheel pump arrangement The invention relates to a gearwheel pump arrangement for a pressure medium and of the kind having a plurality of externally toothed planet wheels which are arranged in the same plane in a common casing and which are linked together by a central externally toothed sun wheel connected to a shaft.

Gearwheel pumps are tried components of hydraulic circuits with a pressure medium operating at intermediate pressure. However, large units are realisable to a limited extent only, because of the production and deformation occurring with them.

Admittedly it is possibleperse to interlink serially a plurality of gearwheel pumps of smaller construction. However, this mode of arrangement is limited in respect of output by the torque limitation of the input shaft. Moreover a mutual displacement of the teeth of the individual pumps for the purpose of reduction of pulsations which are inherent in every gearwheel pump, can be obtained only in a complicated and disadvantageous manner by means of an adjustment of clutches connecting the individual pumps.

It is known from French Patent Specifications 1 064 498 and 1 499827 to arrange a plurality, e.g. three or four, of externally toothed planet wheels around a central sun wheel which is externally toothed and driven by a shaft, and to construct the pump casing accommodating these wheels in such a manner that a suction chamber prevails on the one side of the engagement location of the planet wheel with the sun wheel, and a pressure chamber for the pressure medium prevails on the other side of the engagement location. In this way a plurality of gearwheel pumps linked together by the central sun wheel are to be produced in a single casing.However in practice such an arrangement cannot be realised, in particular because satisfactory sealing of the high pressure chambers is impossible in consequence ofthe naturally rigid mounting of the central sun wheel.

The present invention is directed towards the problem of providing a gearwheel pump arrangement of the kind referred to above, by means of which large volume streams may be produced by means of small individual pumps in a compact manner of construction in a symmetrical arrangement around an axis of rotation, while separating the torque transmission and the sealing function.

In accordance with the present invention a gearwheel pump arrangement ofthe kind referred to is characterised in that a plurality of pairs of mutually engaging planet wheels are arranged in the casing, each pair forming an individual gearwheel pump with a suction chamber and a pressure chamber, and that the central sun wheel meshes in a torque transmitting manner with one of the two planet wheels of each individual pump and is exposed to the pressure of the pressure medium prevailing in the pressure chambers of all individual pumps.

Thus in the arrangement according to the invention there is no need for extending a torquetransmitting shaft out of the sealing chamber of the volume-forming teeth of the planet wheels, so that in consequence of this separation of torque transmission and sealing function the pump conponents of the gearwheel pump arrangement can be constructed in a known and tried manner. Only the sun wheel must be sealed against the high pressure of the pressure medium, this is relatively free of problems. By appropriately selecting the number of teeth of the sun wheel in relation to that of the plant wheels a step-up, reducing the constructional volume, can be obtained without further additions between the rotary input speed of the pump arrangement and the actual rotary speed of the individual pumps.Furthermore, a displacement of the engagement between the individual pumps which reduces the pulsations and the generation of noise, respectively, can be obtained thereby without adjustment measures of any kind. Additionally, as will still be explained below, the gearwheel pump arrangement according to the invention provides the possibility of mounting the planet wheels of the individual pumps in a pump casing in a particularly simple manner. In consequence of its axiallysymmetrical construction the gearwheel pump arrangement according to the invention in suitable for use as a hydrostatic pump for a pressure medium as well as also for use as an adjustable hydrostatic clutch.

Constructional examples ofthe invention are explained hereinafter with reference to the accompanying drawings in which: Fig. 1 is a longitudinal section through an hydrostatic clutch, as an example of the use of the arrangement according to the invention; Fig. 2 is a section through the hydrostatic clutch on line ll-ll of Fig. 1, Fig. 1 being a section on the line I-I of Fig. 2, Fig. 3 is a plan view upon the one end face, and a side view of an individual bearing bush for the pinions of Figs. 1 and 2, on an enlarged scale; Fig. 4 is a longitudinal section through an hydrostatic pump as a further example of the use of the arrangement according to the invention.

According to Figs. 1 and 2, the illustrated hydrostatic clutch comprises a pump portion with altogether four externally toothed individual gearwheel pumps each of which contains in a substantially known manner per se a double-pinion la, 1b, 1c or 1d, respectively. Each double-pinion la, Ib, 1c, Idis mounted in an associated plain bearing bush 4 of a cylindrical pump body 3. The bores 2a, 2b, 2c, 2d are closed in a pressure-tight manner by a cover 6 which is securely connected to the pump body 3 by means of screws 7, an O-ring 8 being disposed between the pump casing 3 and the cover 6 for the purpose of freedom from external leakage.

The double-pinions la, 1b, 1c, 1d are kinematically and torque-transmittingly connected together by a centrally arranged sun wheel 9 which is securely connected to a transmission or take-off shaft 11 of the hydrostatic clutch by means of feather keys 10.

The take-off shaft 11 is radially and axially mounted in the cover 6 by means of a first antifriction bearing 12 and in the pump body 3 by means of a second anti-friction bearing 13. The take-off shaft 11 supports a stationary pressure medium guide block 14 in which there is a radial pressure connection 15 for the pressure medium, a distributor ring groove 16 which is in communication with the same and which is open towards the bore for the take-off shaft 11, a suction connection 18 for the pressure medium, and a suction chamber 17 which is formed as a recess. A leakage collecting ring groove 19 is in communication with the suction chamber 17 through a return bore 20 extending in the longitudinal direction.

Furthermore, the guide block on the take-off side and on the pump side has a lip seal 21 and 22, respectively.

A driving shaft 23 is appropriately screwed to the cover 6 by means of screws 24 and is thereby securely connected to the pump body 3. On the take-off side a suction funnel 25 is fastened to the pump body 3. O-rings 26 and 27 serve for the external sealing of the driving shaft 23 and the suction funnel 25.

The high pressure chambers 28 in the bores 2a, 2b, 2c, 2d of the gearwheel pumps formed by the double-pinions la, Ib, 1c, 1d extend into the shaft bore of the pump body 3 in which the sun wheel 9 is located (Fig. 2). Therefore the sun wheel 9 is located in a high pressure chamber. For the purpose of its sliding seal relatively to the suction chamber 29 limited by the suction funnel and the end facelocated suction chamber 29, elastic seals 30 press slide ring seals 31 against the end faces of the sun wheel 9.

The suction chamber 29 of the suction funnel 25 is in hydraulic connection through suction bores 32 with the suction side of the double-pinions la, 1b, 1c, ldand byway of the suction chamber 17 and the suction connection 18 of the guide block 14 with a pressure medium tank 33. The high pressure chamber of the double-pinions 1a, ib, 1c, ldis hyd- raulically connected through openings 34 in the sun wheel 9 and in the take-off shaft 11 to a longitudinal bore 35 and transverse bores 36 connected thereto.

The transverse bores 36 terminate in the distributor ring groove 16. The pressure connection 15 is likewise in communication with the tank 33 by way of a diagrammatically illustrated regulator valve 37.

If slip occurs between the driving shaft 23 and the take-off shaft 11 the double-pinions la, 1b, 1c, 1d rotate in consequence of the drive by the sun wheel 9. Accordingly the double-pinions suck pressure medium out of the tank 33 through the suction connection 18, the suction chambers 17,29 and the suction bores 32. The double-pinions la, 1b, 1c, ldforce the pressure medium into the high pressure chamber 28 from where the same travels back into the tank 33 by way of the openings 34, the bores 35 and 36, the pressure connection 15 and the regulator valve 37.Therefore, in the manner known for example from Swiss Patent Specification 479 the drive of the take-off shaft 11 may be infinitely adjusted dependently upon the degree ofthrottling effected by the regulator valve 37, of the return guidance on the pressure side of the pressure medium.

The units formed by the double-pinions la, 1b, 1c, 1d and the plain bearing bushes 4 are arranged in an axially floating manner in the bores 2a, 2b, 2c, 2d, since a large amount of play exists between the bottom faces of the bores 2a, 2b, 2c, 2d in the pump body 3, the said pinion bearing units and the cover 6.

This floating arrangement effects a favourable influence on the production accuracy and the residual torque at idling of the present hydrostatic clutch.

Consequently each pinion bearing unit la, 1b, 1c, 1d, 4, except for a small suction face at the suction bore 32, is completely surrounded by the pressure medium subjected to pressure. In order to compensate asymmetric pressure distributions occurring axially between pinion and bush which, in the case of large units, lead frequently to twisting or onesided wear, elastic seals cannot be disposed on the sides of the bush remote from the pinions for this reason. On the contrary, such compensation must be effected in the present arrangement in the gap between each pinion of the double-pinions la, 1b, 1c, 1d and the end face of the associated bearing bush 4.

Fig. 3 illustrates a constructional form of a bearing bush 4 by means of which the said compensation may be obtained in a simple manner. The side 38 facing the associated pinion has two kidney-like extending depressions 39, 39' which are thus located opposite a ring surface between the tooth bottom and the shaft of the respective pinion and into which there always terminates one bore 40,40' in the bearing bush 4. At their other ends the bores 40,40' terminate in surface regions 41,42 or 41 42', respectively, of which the one regions are located in the high pressure chamber 28 (Fig. 2) and the others on the opposite side are subjected to the suction pressure of the suction bore 32.According to Fig. 3, in this case the one depression 39 or 39', respectively, on the one side relative to the vertical longitudinal section plane of the bearing bush 4 is always connected to the surface regions 41,42 or 41 42', respectively, of the other side, that is to say crosswise. Thus the ring surface between the tooth bottom and the shaft of each pinion of the doublepinions la, 1b, 1c, 1d is always loaded to one half in a cross-wise manner by the high pressure orthe suc- tion pressure, respectively. In consequence of this symmetrical mode of construction the desscribed bearings are suitable for clockwise and anticlockwise running of the shafts 23 and 11, since a pressure change corresponding to the running direction is also accompanied by a change of the pressure loading of the depressions 39,39'.

The advantageous circumstances that in the arrangement according to the invention, no shaft has to extend out of the volume-forming sealing space in a torque-transmitting manner permits pressed bearing bushes to be completely omitted, since the otherwise leakage-forming axial spreading force can be absorbed directly at the bearing pin ends of the double-pinions of the individual pumps. Such an embodiment is explained below with reference to the example of use of the arrangement according to the invention in a hydrostatic pump illustrated in Fig.

4.

A pump shaft 51 mounted in a casing 50 is again securely connected by feather keys 52 to a sun wheel 53 which meshes with pinion pairs 54. The sun wheel 53 is sealed by slide ring seals 56 which are pressed by elastic seals 55, so that leakage from the high pressure chamber of the pinion pairs 54 is reduced to a minimum. The pinion pairs 54 run on stationay bearing pins 57 which are guided in a fitting manner in side flanges 58 and 59 of the casing 50. Cap nuts 60 urge the side flanges 58, 59 against a spacer member 61. The spacer member 61 is thicker by an operating play than the pinion pairs 54, whereby free movement of the pinion pairs is rendered possible. Suction and pressure ducts (not illustrated) of the suction chambers and pressure chambers, respectively, surrounding the pinion pairs terminate in collecting grooves 62 which are formed in peripheral collecting rings 63. O-rings 64 and 65 are arranged for sealing the collecting rings 63. Additionally the collecting rings 63 have connector screw threads 66 for a suction duct and a conveyor duct.

Claims

1. A gearwheel pump arrangement for a pressure medium, having a plurality of externally toothed planet wheels which are arranged in the same plane in a common casing and which are linked together by a central externally toothed sun wheel connected to a shaft, characterised in that a plurality of pairs of mutually engaging planet wheels are arranged in the casing, each pair forming an individual gearwheel pump with a suction chamber and a pressure chamber, and that the central sun wheel meshes in a torque transmitting manner with one of the two planet wheels of each individual pump and is exposed to the pressure of the pressure medium prevailing in the pressure chambers of all individual pumps.

2. An arrangement according to claim 1, characterised in that the number of teeth of the sun wheel is so selected in relation to the number of teeth of the planet wheels that a step-up of the rotary speed prevails between the shaft supporting the sun wheel and the actual rotary speed of the individual pumps containing the pairs of planet wheels.

3. An arrangement according to claim 2, characterised in that the numbers of the teeth of the sun wheel and the teeth of the planet wheels are so selected in relation to the numberof individual pumps containing the pairs of planet wheel that a displacement of the engagement of the teeth of the planet wheels arranged in pairs prevails between the individual pumps.

4. An arrangement according to any of claims 1 to 3, characterised in that the planet wheels are mounted in plain bearing bushes which are arranged in bores of a pump body in an axially floating manner.

5. An arrangement according to claim 4, characterised in that the bearing bushes in the bores of the pump body are arranged at least approximately completely in the pressure chamber of the bores.

6. An arrangement according to claim 5, characterised in that the faces abutting the end faces of the planet wheels constructed as pinions, of the bearing bushes have mutually oppositely disposed pressure pockets which are connected crosswise through bores in the bodies of the bearing bushes to the pressure prevailing at the opposite outside of the bearing bushes for the purpose of compensation of asymmetrical pressing forces.

7. An arrangement according to any of claims 1 to 3, characterised in that the planet wheels arranged in pairs are mounted on stationary bearing pins, and that the axial spreading force at the bearing pins is absorbed by means of nuts, the side faces of which press against a spacer member disposed therebetween.

8. A gearwheel pump arrangement according to claim 1 when associated with an hydrostatic clutch, characterised in that the sunwheel is mounted on a hollow shaft and the pressure medium is guided from the pressure chambers of the individual gearwheel pumps through the bore of the hollow shaft to a stationary guide body having connectors for the pressure medium.

9. A gearwheel pump arrangement according to claim 8, characterised in that a pump body having bores for the pairs of planet wheels and with suction bores for the pressure medium is flanged to a driving shaft and is mounted rotatably and in a sealed manner on the hollow shaft provided as a take-off shaft, the bores being open towards the hollow shaft for receiving the teeth of the sun wheel fixed on the hollow shaft.

10. A gearwheel pump arrangement substantially as hereinbefore described with reference to, and as shown in, any of the Figures of the accompanying drawings.