Pumps – Motor driven – Including means for facilitating assembly or disassembly of...
Reexamination Certificate
1999-11-26
2001-03-06
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
Including means for facilitating assembly or disassembly of...
C417S415000, C384S536000
Reexamination Certificate
active
06196812
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is based on a pump unit.
A pump unit, which is comprised of a piston pump and a drive motor that drives the piston pump, has already been disclosed by DE 44 30 909 A1 and U.S. Pat. No. 5,564,909. The pump pistons of the piston pump are disposed in a pump block to which the motor housing of the drive motor is flange mounted. A shaft, which is driven by the drive motor and protrudes from the motor housing into the pump block, is used to drive the pump pistons of the piston pump. The motor housing has a projection which protrudes into a recess provided in the pump block. This projection of the motor housing contains a bearing which is supported on the shaft.
In the pump unit disclosed by DE 44 30 909 A1 and U.S. Pat. No. 5,564,909, it is disadvantageous that the bearing forces which arise at the center bearing cannot be optimally absorbed by the motor housing. DE 195 36 794 A1 has disclosed an embodiment which attempts to solve this problem by virtue of the fact that the bearing is built directly into the pump block between the drive motor and the pump pistons. However, this produces considerable technical manufacturing difficulties because with this embodiment, it is not possible to carry out a separate assembly and a possible separate testing of the drive motor before mounting the motor onto the pump block.
It has turned out that the connection, which is not optimally play-free, between the drive motor and the pump block contributes to the generation of noise.
In DE 44 30 909 A1 and U.S. Pat. No. 5,564,909, a radial clearance fit is disposed between the end of the shaft protruding into the pump block and the inner bearing ring of the bearing, there so that it is possible to assemble the components. With this bearing there is also the problem that this clearance fit also contributes to the generation of noise.
Because tolerances and clearance fits cannot be entirely avoided despite extremely high manufacturing precision, unpleasant noise produced by them must be expected.
DE 44 30 909 A1 and U.S. Pat. No. 5,564,909 disclosed pump units in which, the shaft is supported by means of an additional bearing in the motor housing, on the end remote from the pump block. However, the cost of manufacturing this bearing and the considerable space requirement for this bearing have up to now been significant disadvantages.
ADVANTAGES OF THE INVENTION
The pump unit according to the invention has an advantage over the prior art that a considerable reduction of the noise produced by the pump unit and frequently also an improvement in the service life of the pump unit can be achieved at a low manufacturing cost.
The clearance fit can advantageously be generous enough so that the drive motor, together with the shaft, can be very simply connected to the pump block.
Because the motor housing, the shaft, and the at least one bearing contained by the motor housing constitute a preassembled unit, the advantage of a low manufacturing cost and the advantage that when needed, the drive motor, together with the shaft, can be separately tested before being mounted onto the pump block are retained; and the advantage is also attained that the bearing forces of the at least one bearing can be optimally absorbed by the relatively rigid pump block, which results in a considerable degree of noise reduction. Because of the increase in rigidity, it is advantageously possible without risk to reduce the material thicknesses used, in particular the wall thickness of the motor housing or the thickness of the pump block.
Advantageous improvements and updates of the pump unit are possible by means of the measures set forth herein.
Injecting plastic into the clearance fit, which can be made fluid for example by means of heating or which hardens for example by means of a chemical reaction only after the passage of time, attains the advantage that the manufacturing cost as a whole is not significantly increased because it is possible to introduce the plastic with ease.
The first bearing, which is held by the motor housing between the at least one pump piston and the drive motor, absorbs a considerable part of the forces acting on the shaft. Eliminating the radial play at the projection of the motor housing, which protrudes into the recess of the pump block, by means of the introduced plastic, attains the advantage that the significant part of the bearing forces can be absorbed by the pump block, which is of significant importance for the service life of the pump unit and for an effective noise reduction.
Eliminating the clearance fit between the second bearing and the pump block, attains the advantage that the production of unpleasant noise in the vicinity of the second bearing is eliminated or at least sharply reduced.
Since the second bearing can be built into the pump block with a radial clearance fit, the second bearing can be connected to the shaft that protrudes from the motor housing before the drive motor is mounted onto the pump block, which significantly decreases the manufacturing cost in an advantageous manner and significantly increases the testability.
In the vicinity of the first bearing and in the vicinity of the second bearing, if the radial play between these two bearings and the pump block is eliminated by means of the introduced plastic, then the advantage is attained that the noise generation is eliminated or sharply reduced at both bearings.
If the shaft in the motor housing is supported by means of a bearing pin provided on the motor housing, which engages in a bush protruding axially beyond the shaft, then the advantage is attained that the drive motor is made significantly more rigid for a low manufacturing cost and without a noticeable increase in the required installation space. Another advantage is that the shaft does not have to be machined especially for the additional bearing, in particular the end of the shaft oriented toward the additional bearing also does not have to be bored on the end face, which would entail a considerable cost.
The engagement of the bearing pin in the bush attains the additional advantage that the diameter of the additional bearing can be selected as relatively large without this resulting in additional cost for manufacturing or material.
REFERENCES:
patent: 3813826 (1974-06-01), Bando
patent: 4412707 (1983-11-01), Buffet
patent: 4925408 (1990-05-01), Webb et al.
patent: 5620311 (1997-04-01), Wetzel
patent: 5839349 (1998-11-01), Volz
patent: 5895207 (1999-04-01), Burgdorf et al.
Evora Robert Z.
Freay Charles G.
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
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