1. Field of the Invention
The present invention generally relates to a vane pump and, more particularly, to a vacuum vane pump for use on aircraft to generate a vacuum condition necessary for the operation of aircraft instrumentation.
2. Description of the Related Art
Sensitive analog guidance instrumentation and indicator displays such as gauges used on small aircraft and principally relied upon by aircraft pilots in the operation of such aircraft require a suitable operating environment to properly function. Such instrumentation are highly susceptible to variations in their operating environment and, in particular, to changes in barometric or cabin pressure which will affect, among other things, altimeter measurements and, hence, the gauge displays of such measurements. For these reasons, it is imperative that such guidance equipment and indicators operate in as close to a vacuum condition as practicable so that they provide a true indication of aircraft operating parameters.
Vane pumps are commonly used to generate the necessary vacuum for small aircraft instrumentation. With reference to
In order to extend the resulting vacuum to the appropriate instruments in, for example, an aircraft cockpit, porting of vacuum chamber 34 is effected, as is known in the art, for example in the manner shown in U.S. Pat. No. 5,100,308 which also describes multiple stages and arrangements for changing the eccentricity of the rotor in the housing to enable regulation of the amount of vacuum or positive pressure generated by the vane pump. The slots and vanes need not be oriented in a strictly radial manner but may, instead, be skewed as for example disclosed in FIGS. 6 and 7 of U.S. Pat. No. 6,086,332.
The vanes 20 in a conventional vane pump of the type heretofore described and depicted in
The long-accepted solution, according to the prior art, is regular scheduled maintenance of vane pumps through periodic disassembly to detect the extent of vane wear, a time consuming and costly procedure that, without early replacement of pumps typically capable of safely operating for additional extended periods of time, is an unreliable predictor of imminent pump failure.
It is therefore an object of the invention to provide an improved vane pump in which the likelihood of unexpected broken vanes and the resulting catastrophic loss of a vacuum condition caused by the vane pump is reduced.
In accordance with the invention, a vane pump is provided for creating a vacuum condition in a pump chamber formed between a housing wall and a rotor. The rotor has a plurality of slots, each containing a vane slidably engageable within the respective slot. The vanes are radially outwardly displaced by centrifugal force as the rotor is operatively rotated in that the leading edges of the vanes are outwardly advanced from the respective slot mouths or openings into pressed contact with the housing wall. The vanes and slots are configured to capture within the slots a stop or obstruction carried on the radially inner end of each vane and thereby limit the radial displacement of the vanes beyond the slot openings or mouths. This construction thereby prevents or notably reduces the possibility of vane breakage within the chamber and, hence, prevents an abrupt catastrophic loss of vacuum.
In a preferred embodiment, the stop is created by forming a unitary flange on an engagement region of each vane, such as at or proximate an inner end of each vane, for engagement with a protrusion, shoulder or other obstruction positioned at a predetermined location relative to the slot opening. As the vanes erode or decrease in length through continued frictional contact with the housing wall, a gradual, rather than an abrupt, decrease or loss of vacuum pressure can be detected, indicating that immediate maintenance or servicing of the vane pump is required.
In another embodiment, a switch is activated to trigger an alarm or service indicator when a predetermined amount of wear has occurred on one or more of the pump vanes to signal that immediate pump maintenance is required.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.
In the drawings, wherein like reference numerals indicate similar elements throughout the several views:
A vacuum vane pump 50 constructed in accordance with the present invention is shown in FIG. 2. Like the prior art vane pump 5 of
Unlike the prior art pump of
In accordance with a preferred embodiment of the invention, the safety feature includes a reconfigured vane having a narrow elongated shaft portion 48 and an engagement region such as a head portion 46, which may, for example, be disposed at or proximate the radially innermost end of the vane 20 as shown in
Other slot and vane configurations and modification can be employed and will be apparent to those having ordinary skill in the art for capturing the vanes and preventing them from completely exiting from their corresponding slots. Thus, the vanes 20 depicted in
Another vane construction is shown by way of example in FIG. 5. There, a vane head 146 having a tapered sidewall 142 may be mounted within a rotor slot 116 having an opposingly defined wall 144 for mating engagement with the vane sidewall 142 as the vane erodes at its leading tip to captively prevent dislodgement of the vane from within the slot.
In still another embodiment of the invention shown in
Under ideal conditions, all of the vanes should experience through normal vane pump operation, substantially the same amount of erosion over time. Thus, a single switch 52 positioned for engagement with a selected one of the vanes may suffice to provide an appropriate vane pump erosion indicator. In reality, of course, variations in material characteristics and numerous other factors cause the vanes to wear, as their tips frictionally slide along the opposed housing inner wall surface, at rates that are at least slightly or marginally different. Indeed, such variations from vane to vane in the rate of wear are both expected and desired to result in only a relatively small and gradual decrease in the vacuum generated by the vane pump as the captive vanes variously wear down to predetermined points at which their individual tips at first no longer sealingly press against, and then define a gap with, the housing inner wall surface. It is accordingly preferred that an indicator switch or the like is provided for activation by each of the vanes as its outward tip wears down to the predetermined extent, or alternatively that an other detection arrangement is employed to detect the predetermined threshold wear of each vane of the inventive vane pump.
While there have shown and described and pointed out fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described and the systems and components and devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
This application is a continuation of U.S. patent application Ser. No. 10/269,117 which was filed with the U.S. Patent and Trademark Office on Oct. 11, 2002, now abandoned.
Number | Name | Date | Kind |
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3301194 | Brunson | Jan 1967 | A |
3627456 | Gerlach | Dec 1971 | A |
3744939 | Grennan et al. | Jul 1973 | A |
Number | Date | Country |
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2311168 | Sep 1974 | DE |
1078008 | May 1954 | FR |
100177 | Jul 1962 | NO |
Number | Date | Country | |
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20040136852 A1 | Jul 2004 | US |
Number | Date | Country | |
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Parent | 10269117 | Oct 2002 | US |
Child | 10725975 | US |