Rotary expansible chamber devices – Moving cylinder – Rotating
Reexamination Certificate
1999-10-12
2001-05-08
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
Moving cylinder
Rotating
C418S171000, C418S179000, C418S206100, C029S888023
Reexamination Certificate
active
06227833
ABSTRACT:
The invention relates to a fluid machine having a first displacement element that is rotatable about an axis of rotation, connected to a shaft so as to rotate therewith, which shaft is mounted rotatably in a housing, and co-operates with a second displacement element, the axis of rotation being arranged at a predetermined distance from the centre axis of the second displacement element.
Such machines are used both as pumps, in which the shaft is driven by a motor, for example an electric motor, and as motors, in which fluid is supplied under pressure to the displacement elements so that at least the displacement element that is connected to the shaft rotates and can deliver a mechanical output. As fluid there may be used a liquid or a gas. In the former case, the machines are hydraulic machines and, in the latter case, they are pneumatic machines. The following explanation is based on the example of hydraulic machines.
Such hydraulic machines have been known for a long time. In order for them to operate well, that is to say with acceptable efficiency, the parts must be matched with one another with small tolerances. If the gaps between moving parts are too great, the volumetric efficiency deteriorates as a result of internal leakages. If, on the other hand, the fits are too tight, increased losses due to friction occur, which likewise reduce efficiency. Adherence to close tolerances renders production difficult, which results in a corresponding increase in the costs of such machines.
The problem underlying the invention is to simplify the construction of such machines.
The problem is solved in a hydraulic machine of the type mentioned at the outset in that the housing has a pocket in which the displacement elements are so arranged that the housing covers the displacement elements axially on both sides at least in a working region and in the circumferential direction over a maximum of 180°.
That construction starts from the conventional design in which it is assumed that the displacement elements have to be arranged in a chamber that is sealed on all sides. Instead, one side is left open. The displacement elements can be inserted through that opening of the pocket in which the chamber is formed. Since the pocket is arranged in the housing, it can be manufactured with predetermined precision which is no longer altered, or is altered only to a small degree, by subsequent assembly steps. The displacement elements can also be manufactured with predetermined precision in such a manner that they fit axially exactly into the pocket. Further assembly steps to close off the pocket, which might again be troubled by tolerances, are not necessary. This becomes possible as a result of the recognition that a pressure needs to be enclosed only in the so-called working region. Accordingly, it is sufficient for the housing to cover the working region. The working region is the region between the displacement elements in which, in a pump, the hydraulic fluid is placed under pressure, generally by reducing the volume of chambers formed between the displacement elements or, in the case of a motor, the region into which the hydraulic fluid is fed to effect an expansion of work chambers. If it is no longer necessary for work chambers to be closed off in such a manner, then a pressure-tight covering by the housing, and the complication that that involves, is also unnecessary. The opening that is necessary for assembly can therefore be left open without it being necessary to accept a deterioration in the running properties of the machine. As a result, production is simplified dramatically and the production costs may also be reduced.
Preferably, an axial end wall of the pocket has a slit. The slit is provided mainly for manufacturing reasons. In most cases, the pocket must be of arcuate cross-section in the region in which it surrounds the displacement elements in the circumferential direction. Such a cross-section is obtained advantageously by using a milling cutter, the axis of rotation of which runs parallel to the future axis of rotation of the first displacement element. If it is desired to introduce the displacement elements further into the pocket, that is to say, for example, so that they are completely inside the housing, then the milling cutter must be introduced correspondingly deeply. The slit serves that purpose, enabling, for the manufacture of the pocket, an appropriately deep insertion of the milling cutter and its drive shaft into the housing. The slit can be made at the same time as the pocket. Alternatively, it can be produced in an earlier work operation.
Advantageously, the slit is arranged offset to the side of the shaft. That ensures that the working region between the displacement elements is covered by the end face even when the end face comprises the said slit.
Advantageously, the shaft projects through the first displacement element and into an opening at the end of the slit. The shaft is thus guided not only in the housing on one side of the displacement element but, by the projecting end, also in the opposite end wall of the pocket. Although that guidance is weaker because the slit effects an interruption in the guidance, it is still sufficient to provide high stability of the shaft mounting.
During assembly, advantageously, the shaft is movable only axially relative to the housing and the displacement elements are movable only radially relative to the housing. The displacement elements are inserted radially into the pocket. The shaft can be inserted into the housing at the same time or thereafter. When the shaft is moved in the axial direction, it passes through the displacement elements and thereby holds the displacement elements captive in the pocket. The displacement elements can thus no longer be moved outwards through the opening of the pocket. A self-securing mechanism is thus produced for at least one direction of movement.
This is further improved by fastening the shaft axially to the first displacement element. As soon as the fastening has been effected, the machine is fully assembled at least in respect of its main function. The shaft cannot be removed axially from the housing because the fastening to the displacement element prevents such a movement, nor can the displacement elements be removed sideways from the pocket because the shaft stops such a movement. Since only two work steps are required to achieve that “final assembled state”, which steps are, moreover, relatively simple to effect and can be carried out, for example, by a production robot, manufacture involves very little complication, with accordingly low costs.
Preferably, the axial extent of the pocket is substantially as great as that of the displacement elements. The two end faces of the pocket thus seal the displacement elements, that is to say together with the displacement elements they define work chambers that can increase and decrease in size during operation. Additional elements, such as seals, are not required. The corresponding work chambers are created by the insertion of the displacement elements into the pocket.
The displacement elements and the housing preferably have similar thermal expansion coefficients. As a result, operation with equal efficiency is possible even with varying temperatures.
Advantageously, there is provided in the housing a high-pressure channel arrangement which is connected to the working region. When the machine is used as a pump, the high-pressure channel arrangement takes up the hydraulic pressures that are produced and passes them on to a high-pressure connection from which hydraulic fluid can then be taken off at the desired higher pressure. When the machine is used as a motor, hydraulic fluid is supplied under relatively high pressure to the work chambers by way of the high-pressure channel arrangement in order to cause the work chambers to expand. Only the high-pressure channel arrangement needs to be produced so as to have the necessary strength, for which purpose the housing is advantageously provided. That specification is not necessary in a low-pre
Frøslev Peter
Klausen Jørn Holger
Madsen Ingvard Mosby
Thomsen Franz
Danfoss A/S
Lee Mann Smith McWilliams Sweeney & Ohlson
Vrablik John J.
LandOfFree
Fluid machine having cooperating displacement elements and a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fluid machine having cooperating displacement elements and a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluid machine having cooperating displacement elements and a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2459483