Fluid reaction surfaces (i.e. – impellers) – With control means responsive to non-cyclic condition...
Reexamination Certificate
1999-09-07
2001-02-20
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
With control means responsive to non-cyclic condition...
C416S15700A, C416S205000
Reexamination Certificate
active
06190126
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German application 198 40 843.9, filed in Germany on Sep. 7, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a fan impeller assembly, in particular a fan impeller which can be used in the cooling system of internal combustion engines. Preferred embodiments of the present invention relate to a fan impeller assembly for cooling systems of internal combustion engines, comprising: a cup shaped hub, adjustable fan blades which are guided rotatably in a peripheral wall of the hub, and an actuating drive operable to adjust the fan blades and situated in the cup-shaped hub, said actuating drive including: an actuating element spring-loaded toward an initial position and acted upon in an opposite direction by a pressure medium, and adjusting eccentrics which are situated at a transition between said actuating element and the fan blades and can be acted upon by the actuating element, the actuating element being formed by a concentrically arranged actuating piston which adjoins the cup wall in a sealing manner and is guided by the latter.
In the case of a known fan impeller of the abovementioned type (DE-A 28 07 899) with a cup-shaped hub, the fan blades are mounted in the cup wall and, at an axial offset therefrom, the hub forms the holder and sealing guide for an actuating piston which can be loaded by means of pressure medium, is supported resiliently in the opposite direction and acts as an actuating element for the fan blades. The adjusting eccentrics assigned to the fan blades are formed by pivoting levers which extend in the circumferential direction, are connected to the fan blades in a rotationally rigid manner within the hub and are acted upon by means of axially extending actuating rods which are supported against the piston. Although a configuration of this kind allows relatively large piston diameters, the axial offset of the piston relative to the fan blades leads to a relatively large overall depth of the hub, even in the case of relatively small pivoting angles for the fan blades, and also involves relatively high outlay on construction.
Other known publications relating to the technical background are DE 88 15 383 U1, DE 84 06 829 U1, DE 25 52 529 A1 and DE 44 38 995 A1.
The invention relates to the configuration of a fan impeller of the type stated at the outset and has the object of arriving at a basic design of fan impeller which is of simple, small and flat construction and allows such a fan, the direction of delivery of which can be reversed while the direction of rotation remains the same, to be used in existing designs instead of conventional blower impellers. This object is achieved according to preferred embodiments of the invention by providing a fan impeller assembly of the type referred to above, wherein a piston wall of the actuating piston lies in radial overlap with the fan blades as an actuating ring for receiving actuating stubs of the adjusting eccentrics, and wherein, by a pressure medium acting on the actuating piston, the fan blades can be changed over into a direction of delivery opposite to a direction of delivery in an initial position and, in both of the opposite directions of delivery, are loaded in the directions of the blade position corresponding to the respective direction of delivery.
By virtue of the fact that an axially displaceable actuating piston is used, the operation of the actuating piston is independent of the respective speed and its surface area can be dimensioned in such a way, based in particular on the respective size of the hub, that sufficiently high actuating forces are obtained even at low actuating pressures. This configuration furthermore provides the possibility of creating sufficient space for an elastically flexible return device of simple configuration, with the result that, overall, an actuating device is created in which active adjustment takes place in each case in only one direction of actuation and in which the return is accomplished by means of the passive elastically flexible return device, which operates against the actuating force of the pressure-loaded actuating piston. This makes it possible to obtain an actuating device in which pressure loading is necessary in only one direction and the change-over can be accomplished by switching the pressure loading on and off. If a pump, a compressor, an accumulator or the like is provided for the purpose of pressure loading, there is thus no need for any further control devices but only for the pressure source to be switched on and off. With a view to as compact as possible an axial overall length, an axially overlapping arrangement of the actuating piston and the fan blades is of particular and independent significance.
Particularly in the case of pneumatic actuation, this leads to a very simple solution, making possible a basic concept such that the end position which is adopted by means of the elastically flexible return device corresponds to a normal working position of the fan impeller as the forward-blowing direction. There is therefore no need for any pressure supply in the normal working position, maximum reliability of operation is thus ensured and, moreover, a very energy-saving operation is made possible if, upon pressure loading, only a brief working position is adopted as the reverse blowing direction. This can be accomplished simply by switching on a pump or a compressor, especially as the large-area dimensioning allows operation at very low pressures.
Particularly in connection with pneumatic actuation of the actuating device, it is possible, if the source of compressed air is switched on only briefly to build up the required actuating pressure and then switched off, for the change-over from the reverse blowing position as the brief working position to the normal working position as the forward-blowing position to be achieved simply by carrying out the pressure reduction in a delayed or time-controlled manner.
This can be achieved in a particularly simple manner if the volume closed off by the actuating piston is connected, for example, to atmosphere by a restrictor opening, if required in a controlled manner.
By virtue of the fact that, in the case of the solution according to the invention, the fan blades are loaded in their respective end position by a holding force which is independent of the actuating device and acts in the direction of the end position, in particular by the force of the air resistance acting on the fan blades, it is possible, in conjunction with a time-controlled pressure reduction as explained above, to design the actuating device in such a way that a virtually immediate change-over between the two end positions is obtained, not only when changing over from the normal working position into the brief working position but also when changing over in the opposite direction. This is because, with such a configuration, the actuating force supplied by the elastically flexible return device can be dimensioned in such a way in relation to the self-holding force that it is only slightly greater than the self-holding force, allowing a virtually complete pressure reduction to be formed before the change-over takes place, the change-over then taking place abruptly since there is no significant opposing force being exerted by the actuating piston once the self-holding force has been overcome, due to the pressure reduction which has taken place. The use of the force of the air resistance acting on the fan blades as a holding force represents a particularly advantageous solution.
As regards the switching time, switching from the normal working position to the brief working position is essentially dependent only on the delivery capacity of the pressure source or a corresponding reservoir volume acting as a source of supply.
The configuration of a fan impeller with adjustable fan blades and with a holding force, as the self-holding force, in their respective end position which is independent of the actuating devic
Haegele Karl
Munz Gebhard
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Haegele GmbH
Look Edward K.
Rodriguez Hermes
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