Pump connection to drive shaft

Details Pump connection to drive shaft Pump connection to drive shaft

1998-12-23

2001-01-30

Walberg, Teresa (Department: 3742)

Pumps

Motor driven

Including means for facilitating assembly or disassembly of...

C417S302000

Reexamination Certificate

active

06179581

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a pump with a rotor, having a bore for receiving a drive shaft with positive locking and which is arranged inside a pump housing, wherein the pump housing comprises a cup-shaped housing part and a further housing part which is provided with a through bore. The invention additionally relates to a pump device with a pump which comprises a rotor having a bore, and relates to a drive device with a drive shaft for driving the pump.
Known pumps of this type are designed, for example, in the form of vane-type pumps or gear pumps and are used for conveying gaseous or liquid substances.
To drive the rotor, the pump is provided with a pump shaft which is coupled by a coupling to a drive shaft, for example, a motor shaft. The pump shaft is held rotatably inside the pump housing with the aid of bearings. The bearings require space in the pump housing, and this prevents a reduction in the size of the pump housing. Furthermore, additional assembly steps are necessary for fitting the bearings.
SUMMARY OF THE INVENTION
The object of the invention is to provide a pump device which is small in size and which is inexpensive to produce and assemble.
This object is attained by a pump including a pump housing, a pump rotor in the housing, a cup-shaped housing part over the rotor and a novel connection between the rotor and a drive shaft. The further housing part of the pump is provided with a centering aid which pre-centers the drive shaft with respect to the housing part during assembly to ensure simple and reliable assembly of the drive unit and the pump so as to form a pump device.
The centering aid is constructed like a sleeve and is in alignment with a through bore passing through the centering aid. The internal diameter of the centering aid exceeds the external diameter of the drive shaft defining a gap between the through bore and the drive shaft. This ensures that during pumping, i.e. while the drive shaft is rotating, unnecessary friction loss does not occur between an outer wall of the drive shaft and an inner wall of the sleeve shaped insertion aid.
In addition, the centering aid has a longitudinal sealing portion which is adjacent to the rotor and which is provided with at least one seal. The seal is attached concentrically immediately adjacent to the rotor to ensure that the conveyed medium cannot escape in the direction of the drive unit along the drive axis and also so that undesired particles or substances cannot penetrate into the interior of the pump in the opposite direction.
In a preferred embodiment, the centering aid has a longitudinal centering portion which is remote from the rotor and which has axial length which exceeds the axial length of the longitudinal end portion of the drive shaft that is used for the positively locking connection. This ensures that when the drive shaft is inserted in the centering aid, the longitudinal end portion of the drive shaft which is used for the positively locking connection, can engage, pre-centered by the through bore, in the bore in the rotor and thus cannot damage or destroy the seal. This makes it possible to insert the drive shaft into the rotor of the pump without jamming and thus to assemble the pump device without errors.
Further, a first housing part, which is over a second housing part, comprises a centering pin which is in alignment with the longitudinal axis of the rotor and which has a smaller external diameter than the internal diameter of the bore in the rotor. The centering pin is securely mounted on the first housing part, so that the first housing part cannot jointly rotate with the rotor. In the unassembled state, i.e. without the drive shaft or without the drive unit, the rotor is held by the centering pin substantially in the center of the first pump housing, so that the drive shaft can safely engage in the rotor when inserted into the pump. Since the rotor is situated precisely centrally in the rotor housing after the assembly of the rotor, and since the external diameter of the centering pin is smaller than the internal diameter of the rotor bore, there is no unnecessary friction between the rotor and the centering pin after the drive shaft has been completely inserted in the rotor.
As an additional feature, the bore in the rotor has an internal set of teeth which cooperates with an external set of teeth on the drive shaft. The external set of teeth on the drive shaft is provided on the positively locking longitudinal portion of the drive shaft, as explained above. The set of teeth is used for transmitting force from a drive to the pump rotor and should thus be dimensioned such that the driving moment can be transmitted without slippage.
In a further preferred embodiment, the pump is a single-stroke vane-type pump. In the rest position of this pump, its rotor is arranged eccentrically to components of a pump housing forming the pump chamber. This advantageously makes it possible for force acting radially upon one side of a drive shaft of the pump, because of the single-stroke design of the pump, to center the rotor. This ensures that the rotor runs centered even if the drive shaft is bent at the operating point of the single-stroke vane-type pump. In particular, this reduces noise and wear and improves efficiency.
In particular, it is preferred if a longitudinal axis of a drive shaft has an offset with respect to a longitudinal axis of the pump. That offset preferably corresponds in its size and direction to the bending of the drive shaft at the operating point of the single-stroke vane-type pump. This makes it possible to compensate for the bending of the drive shaft.
In the pump of the invention, a drive shaft engages in the bore in the rotor with positive locking, so that the pump itself is not provided with its own pump shaft. This pump device has the advantage that by reducing the number of components required, the weight of the pump is lower than that of a conventional pump, and more compact and smaller dimensions are achieved.
A further advantage of the invention is afforded by dispensing with the structural groups of the mounting and the coupling which are susceptible to wear. This increases the wear resistance of the pump device, in particular for pumps supplying diesel fuel, since on account of its low viscosity, diesel fuel is unsuitable as a lubricant.
Other objects and features of the invention are described in an embodiment described below with reference to the drawings.


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