Machine element or mechanism – Flexible sealing diaphragm attached to moving rod and to casing – Pivoting or nutating rod
Patent
1997-11-18
1999-11-16
Graysay, Tamara L.
Machine element or mechanism
Flexible sealing diaphragm attached to moving rod and to casing
Pivoting or nutating rod
418 49, 92 34, F16J 1550, F01C 102, F01B 1900
Patent
active
059837381
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an airtight rotating driving device with eccentricity, especially for volumetric pump, i.e. a driving device enabling the conversion of a rotary movement into a circular orbital movement, while isolating with an absolute and lasting airtightness, the parts carrying out the orbital movement with respect to those carrying out the rotary movement.
Such a driving device is already used in off-centered or eccentric rotating piston volumetric pumps, and it will be described hereafter with reference to such a pump, being understood that this device may be used also for instance in eccentric screw volumetric pumps, or even may be mounted in order to make up a driving assembly for transmitting a rotating movement in a completely airtight way.
For the application of the device according to the invention, to the driving of an eccentric piston volumetric pump, it is known that in this type of pump, a circular piston carries out an orbital movement inside a cylinder bounded by two circular walls of different diameters. The diameter of the piston ranges obviously between these two diameters. The cylinder is provided with a wall enabling the isolation of the exhaustion and discharge chambers. The piston skirt is interrupted in the alignment of this wall, designated also as partition.
The center of the piston has a circular rotating movement whereas the piston does not revolve around itself, i.e. that the abscissa and ordinate axes remain permanently parallel to their initial orientation.
It is particularly interesting to have available an airtight and non-rotatable sleeve, designated hereafter as <<sleeve >>, around the shaft and all along the whole length of the shaft. The main advantage of such a rotating piston pump with a non-rotatable airtight sleeve, is its absolute airtightness as opposed to other rotating pumps which always require a rotating airtight means (for instance, packing, lipped joint or mechanical gasket).
Another solution to this rotatable airtightness problem consists in a magnetic driving, but this latter has the drawback of not being applicable to all the products which have to be pumped and especially of being expensive.
The solution used heretofore consists in associating to the eccentric piston an elastomer airtight sleeve provided internally with an intricate device, which enables ensuring the conversion of a rotating movement into an orbital movement.
However, apart from the complexity of the internal device of the sleeve, this solution which uses an elastomer sleeve presents a certain number of limitations related to:
Thus attempt has been made for achieving a stainless steel sleeve. However, it is known that stainless steel bellows and diaphragms can absorb axial distortions and angular distortions but that they present a close limitation to radial distortions. Yet, the principle of operations of the volumetric pump with rotating piston requires inherently a strictly radial distortion at a frequency or angular velocity ranging from 50 to 1000 rpm.
Heretofore, the only possible solution would have led to a considerable lengthening of the bellows, this being incompatible with the overall dimensions required, with the hydrodynamic effects and with the distortion due to the weight of the bellows itself.
The researches which have led to the present invention enable to cope with the above mentioned drawbacks, and to solve the problems considered by providing an airtight rotatable driving device with improved eccentricity which can be used in a volumetric pump with a rotating piston.
Generally, according to the invention, the airtight rotatable driving device with eccentricity, especially for volumetric pump is of the type comprising a shaft having an input section, rotatably supported by a fix bearing and rigidly linked to a rotating driving means, and an output section the axis of which is parallel and off-centered by a distance d, with respect to the input section, in such a way as to describe an orbital circular movement around the said input axis dur
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Graysay Tamara L.
Mouvex
Stallman Brandon C.
LandOfFree
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