Piston pump

Details Piston pump Piston pump

1997-08-21

1999-02-02

Thorpe, Timothy

Expansible chamber devices

Abutment connection between working member and power...

92 72, 417415, F16J 110

Patent

active

058650903

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a piston pump with a pump piston which is supported on an eccentric formed on a shaft, including a pump bearing with a bearing ring and bearing needles which is provided between the eccentric and the pump piston, and including at least one further bearing, in which the shaft rotates.
A pump of this type is disclosed in European patent No. 436 564, for example. A bearing including a brearing ring and single bearing needles is provided between the eccentric and the pump piston. To prevent displacement of the bearing needles and the bearing ring in an axial direction, two collars are provided laterally of the eccentric against which the end surfaces of the needles and the ring will bear.


SUMMARY OF THE INVENTION

Therefore, the present invention discloses designing the bearing assembly so that at least one end surface of the bearing ring can be supported on the inner ring of a bearing for the shaft.
It is, further, important that the axial movability of the bearing needles is not provided by collars on the bearing ring but rather by inwardly offsetting the peripheral surface of the eccentric with respect to the peripheral surface of the shaft. The so produced stepped transitions between the shaft and the eccentric are used as axial abutment surface for the bearing needles.
Preferably, the shaft on which the eccentric is provided is supported by bearings on either side of the eccentric. The shaft itself, which is an extension of an armature shaft of an electric motor, may be the freely floating type, that means that the armature-side end of the shaft is not supported by a bearing.
However, the disadvantage of this assembly is that a function check of the electric motor driving the piston pump cannot be made irrespective of the pump, that means prior to the assembly with the pump.
Therefore, the present invention discloses the provision of an auxiliary bearing in the housing of the electric motor driving the piston pump. The auxiliary bearing is provided on the end of the shaft close to the armature. The most simple design of an auxiliary bearing of this type includes a sliding bearing ring made of a material that yields to a great degree of wear. Thus, the shaft is supported by the auxiliary bearing and a main bearing prior to the installation of the electric motor on the pump. This type of bearing is appropriate to check the electric motor for its operability. After the assembly of the electric motor and the pump, the main bearing is accommodated in the pump housing where it can take up the considerably increased forces, which occur during operation of the pump, to direct them into the pump housing. In the initial period of operation, the auxiliary bearing is destroyed by the bearing forces because the material is subject to major wear, as has been explained hereinabove. Ultimately, the effect of the auxiliary bearing is removed, with the result of a freely floating shaft.


BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is shown in two Figures, wherein
FIG. 1 is a cross-section taken through a motor-and-pump assembly.
FIG. 2 is an alternative design for supporting the motor shaft in the motor housing.


DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 does not show the entire pump but only the area where the eccentric is placed. The pump is accommodated in a housing 1 having a flange surface 2. An electric motor 3 is screwed to surface 2, and pump housing 1 is used as a bearing plate.
Pump housing 1 has a blind-end bore 4 which is stepped several times and opens into the flange surface 2. A first area 5 of the blind-end bore which directly succeeds the flange surface 2 is used to accommodate a main bearing 6.
Following the first area 5 is a second area 7 into which bores 8 open vertically. Pump pistons 9 are guided in bores 8. A third area 10 of stepped bore 4 is used to accommodate an auxiliary bearing 11.
The main bearing 6 and the auxiliary bearing 11 carry a shaft 12 which is configured as an extended armature shaft of the electric mot

REFERENCES:
Patent Abstracts of Japan, vol. 018, No. 360 (M-1634), Jul. 7, 1994.
German Patent Application No. G 9307692.4 dated May 5, 1994.

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