Abstract:
An aspirator assembly for enabling rapid inflation of evacuation slides and life rafts is configured for direct attachment to the inflatable article. The aspirator assembly comprises an open-ended body housing, a nozzle arrangement for introducing a pressurized fluid into the aspirator and toward a pair of counter-rotating impeller arrangements. The counter-rotating impeller arrangements allow for minimizing the internal forces to enable the stable mounting of the aspirator to the inflatable article without causing damage to the article material during operation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to devices used for rapid inflation and deployment of inflatable structures such as evacuation slides, rafts and the like, and more particularly it relates to aspirators utilized for this purpose. 
     2. Description of the Prior Art 
     Rapid inflation systems are currently used in various applications, but have achieved significant commercial recognition in the aviation industry in connection with the rapid inflation of evacuation slides and life rafts deployed during emergency situations. Typical rapid inflation systems incorporate an aspirator functioning in accordance with the Venturi principle. Specifically, such aspirators utilize pressurized primary gas to induce, or aspirate, a secondary gas or ambient air to combine with the pressurized gas to effect rapid inflation of the inflatable structure. The pressurized primary gas is rapidly introduced into the aspirator assembly through a nozzle arrangement. The rapid introduction of pressurized primary gas creates a partial vacuum within the aspirator assembly, thereby entraining the secondary gas or ambient air to enter the aspirator assembly. Once inside the aspirator assembly, the ambient air generates a combined air-gas flow mixture. This combined air-gas flow exits the aspirator through a discharge region of the aspirator capable of being disposed within an inflatable structure. Thus, the aspirator assembly uses a relatively small volume of pressurized primary gas to entrain a relatively large volume of a secondary gas or ambient air to inflate an inflatable structure. The efficiency of the aspirator assembly is often measured by its “mass-flow ratio”, or “augmentation ratio,” which is a ratio of the volume of primary gas used by the aspirator assembly to the volume of secondary gas or ambient air entrained by the aspirator assembly. 
     In the prior art, turbo or fan-type impeller driven aspirators used for inflating relatively large inflatable articles, such as airplane escape slides and rafts, are typically provided hard mounted to a fixed structure physically independent of the inflatable article. Generally, permanent attachment to the greater mass is required to compensate for external movement or gyration of the aspirator resulting from internal forces generated during operation of the aspirator. For example, external mounting is necessary to support the rotation of an unbalanced single impeller, such as a fan, and to withstand corresponding reactive inertial forces. For instance, aspirators for aircraft escape slides are generally provided within the body of the aircraft secured to a fuselage wall or other aircraft framework. It is necessary to bolt or otherwise permanently secure the aspirator to a frame or other external structure having mass substantially greater than the mass of the aspirator itself. The movement or gyration of an aspirator directly attached to an inflatable article introduces an often substantial risk of damage to the aspirator and/or inflatable article. 
     It is well recognized in the art that it should be advantageous to be able to attach an aspirator directly to an inflatable article. In the case of an aircraft, there are numerous internal systems that can negatively affect operation of an internally mounted aspirator and, thus, reliability of the evacuation procedure. Consequently, the ability to reposition an aspirator from the interior of an aircraft to the evacuation slide or life raft itself would make the entire evacuation system more independent and reliable. Furthermore, directly attaching the aspirator to the inflatable article would enable greater utilization of surrounding environmental atmospheric air, thereby enhancing inflation speed and efficiency. 
     Accordingly, there is an established need for an aspirator overcoming the aforementioned drawbacks and limitations of the prior art. In particular, it would be desirable to provide an aspirator assembly capable of being directly mounted to an inflatable structure, such as an escape slide or life raft, while maintaining stability of the aspirator with respect to the inflatable structure and, thereby, avoiding damage to the inflatable structure from external forces generated during operation of the aspirator. Furthermore, it would be desirable to provide such an aspirator having an improved mass-flow ratio, while maintaining a ace, simplified design lending itself to cost-effective manufacture. 
     SUMMARY OF THE INVENTION 
     The invention is directed to an aspirator assembly particularly adapted for the rapid inflation of relatively large inflatable structures such as emergency escape slides and life rafts found on aircraft. 
     One aspect of the present invention provides an aspirator assembly capable of providing faster and more efficient inflation of inflatable articles. 
     A further aspect of the present, invention provides an aspirator assembly having internal components designed and configured in a manner encouraging neutralization of generated internal forces during operation. 
     Still a further aspect of the present invention provides an aspirator assembly having a force balancing construction wherein gyrations and other external aspirator body forces are substantially neutralized during operation to enable direct attachment of the aspirator to an inflatable article without imparting undue loads thereto, thereby preventing ripping/tearing of the article material and entanglement between the aspirator and article material. 
     Yet a further aspect of the present invention provides an aspirator assembly having a relatively lightweight, simple, and low cost construction. 
     The invention provides an aspirator assembly adapted for direct attachment to inflatable articles, including: a generally cylindrical open-ended body having opposite upstream and downstream ends; a main conduit member disposed within and attached to the housing and disposed transverse to the longitudinal central axis thereof, the main conduit having an inlet for introducing a first pressurized gas therein and at least a pair of exit nozzles for directing a balanced flow of pressurized gas downstream therefrom; a central shaft extending downstream from the main conduit along the central axis of the aspirator body; and at least one pair of adjacent counter-rotating impeller members rotationally mounted on the central shaft, wherein the impellers include central vane portions and outer blade portions having mirror image surface geometries. 
     During operation of the aspirator, the first pressurized gas is directed through the exit nozzles to impinge upon the central internal vanes of a primary impeller in a radial symmetric fashion, causing substantially planar rotation of the primary impeller. This creates a pressure gradient for entraining a secondary gas or ambient air into the main body and directed downstream toward the secondary impeller. Internal flow swirl velocities generated by primary impeller rotation effect corresponding counter-rotation of the secondary impeller. The counter-rotating secondary impeller recovers the kinetic energy from the induced swirl velocities and counteracts the generated inertial forces to substantially neutralize internal forces within the aspirator body. 
    
    
     These and other aspects, features, and advantages of the present invention will become more readily apparent from the attached drawings and the detailed description of the preferred embodiments, which follow. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, where like designations denote like elements, and in which: 
     FIG. 1 is a perspective view of the aspirator assembly of the present invention, viewed from the upstream end of aspirator housing; 
     FIG. 2 is a longitudinal full-sectional view of the aspirator assembly of the present invention with one pair of impeller units; 
     FIGS. 3 and 4 are respective side views of the primary and secondary fan members, in their assembled orientation, with the left side being upstream and the right side downstream; 
     FIG. 5 is a perspective view of secondary fan member, viewed from upstream, illustrating the preferred internal fan vane and external fan blade surface geometries; and 
     FIG. 6 is a partial-sectional view of the aspirator assembly with multiple pairs of impeller units. 
    
    
     It is noted that the drawings of the invention are not necessarily to scale. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. The drawings are intended to depict only typical embodiments of the invention, and therefore should not be considered as limiting the scope of the invention. The invention will now be described with additional specificity and detail through the accompanying drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Shown throughout the figures, the present invention is generally directed to a turbo aspirator for rapid inflation of large inflatable articles, such as aircraft emergency slides and life rafts, wherein the aspirator has an improved structure for minimizing internal forces generated during operation and thereby enabling the aspirator to be stably mounted directly to the inflatable article. 
     Referring now primarily to FIGS. 1 and 2, the aspirator assembly of the present invention, shown generally by reference numeral  10 , is primarily contained within an open-ended main substantially cylindrical body  12 , or housing, having flared opposing upstream and downstream ends,  14  and  16 , respectively. The main components of the aspirator assembly include: a duct work, or duct arrangement, shown generally as reference numeral  20 ; a main central shaft  30 ; a primary fan-type impeller member  50 ; and a secondary fan-type impeller member  70 . 
     The duct work  20  includes a main center tube  28  fixedly attached to the inner surface  18  of body  12 . Inlets  21  and  22  are provided for introducing a pressurized primary gas into the main center tube  28  from a pressurized gas reservoir or other pressure source (not shown). Two or more exit nozzles  24 ,  26  extend transversely from tube  28  for directing the introduced pressurized primary gas downstream. In the embodiment of FIG. 2, inlet  22  can be substantially axially aligned with the longitudinal axis, or central axis, of cylindrical body  12 . Nevertheless, as will be apparent to those skilled in the art, one or more inlets can be provided at alternative positions along main center tube  28  without departing from the scope of the invention. Similarly, although only two exit nozzles are illustrated in the accompanying drawings, more than two exit nozzles are possible. For reasons further described below, it is important that the exit nozzles are provided in a radial symmetric relation about the common central axis of main shaft  30  and aspirator body  12 . 
     The main shaft, shown generally as reference numeral  30 , is provided for rotatably supporting primary and secondary impeller members,  50  and  70 , respectively. Preferably, fan-type impellers are used with the present invention. However, it will be apparent to those skilled in the art that the term “impeller” broadly defines any rotating member of a turbine, blower, fan and the like, and alternate impeller arrangement can be employed with the present invention. Accordingly, specific references herein to a “fan”, “fan member”, “fan unit” or similar designation, are not intended to be limiting. Preferably, the main shaft  30  is comprised of individual mating shaft segments each supporting a single fan unit. Specifically, the first shaft segment  32  supporting primary fan unit  50  extends from leftmost shaft portion  31  to rightmost shaft portion  33 ; and the second shaft segment  37  supporting secondary fan unit  70  extends from leftmost shaft portion  35  to rightmost shaft portion  38 . 
     Although the aspirator apparatus of the present invention is described as having a single pair of impeller units, it should be understood that a system having multiple pairs of impeller units or fans is within the scope of the invention. As will be apparent to those skilled in the art, such multiple pairs of impeller units should generate a greater pressure differential between the aspirator body upstream end  14  and downstream end  16 , thereby creating greater efficiency of the suction resulting therefrom. In this respect, FIG. 6 illustrates the aspirator with two pairs of impeller units  50 ,  70  and  50 ′,  70 ′. 
     Returning back to FIG. 2, primary fan unit  50  includes a plurality of evenly spaced inner vanes  56  interposed between inner cylindrical hub wall  52  and outer cylindrical hub wall  54 ; and a plurality of symmetrically designed and balanced outer blades  58  extending from the outer surface of outer hub wall  54 . In like fashion, secondary fan unit  70  includes a plurality of evenly spaced inner vanes  76  interposed between inner cylindrical hub wall  72  and outer cylindrical hub wall  74 , and a plurality of symmetrically designed and balanced outer blades  78  extending from the outer surface of outer hub wall  74 . The symmetric design and balance of the outer blades  58 ,  78  minimize the creation of any inertial imbalance during rotation. For example, such imbalance might occur if an odd number of impeller blades or non-symmetric positioning of impeller blades are provided. 
     Inner substantially cylindrical hub wall  52  of fan unit  50  is rotationally mounted upon thickened shaft portion  32  such that the fan unit  50  is freely rotatable about shaft portion  32  with minimal friction. Furthermore, inner substantially cylindrical hub portion  52  includes a reduced diameter end portion  53  captivated between end  34  of shaft segment  32  and end  36  of shaft segment  35 . In this manner, axial travel of fan  50  is substantially restricted. Likewise, inner cylindrical hub portion  72  of fan unit  70  is rotationally mounted upon thickened shaft portion  37 , enabling free rotation of fan unit  70  thereabout. Inner cylindrical hub portion  72  includes a reduced diameter end portion  73  captivated between end  39  of shaft portion  37  and stop member  40 , thereby substantially restricting axial movement of fan unit  70 . Additionally, fan units  50  and  70  rotate about main shaft  30  independently of one another. 
     The particular design and construction of the fan units  50 ,  70 , as well as the orientation of the fan units with respect to each other in the assembled aspirator unit  10 , are important aspects of the present invention. In fact, the construction and orientation of the fan units are primarily responsible for enabling the improved stability of the aspirator during operation. 
     A significant aspect of the individual fan unit design is the relationship of the surface contour, or curvature, of the inner vanes vis-à-vis that of the outer blades. This relationship of the corresponding inner vane and outer blade designs is best illustrated with particular reference to FIG.  5 . 
     In FIG. 5, secondary fan unit  70  is viewed from the front, or upstream, side. In this orientation, the inner vanes  76  have a concave front surface contour which acts to capture the energy of a fluid stream impinging thereon. Furthermore, the vanes extend in a rearward direction at an angle such that the impinging flow causes rotation, and in this case clockwise rotation, of the fan unit  70  about the central shaft  30 . The outer fan blades  78  have a convex front surface contour, and they extend in a rearward direction at a similar angular orientation to the corresponding vanes  76 . Consequently, during clockwise rotation of the fan unit  70 , the outer fan blades  78  tend to cause a corresponding downstream-directed clockwise fluid swirl. 
     As stated above, another significant aspect of the present invention is the orientation of the individual fan units of each fan pair to one another, and particularly the orientation of the cooperating inner vanes and outer blades of each fan unit comprising a pair. Specifically, the individual fan units must cooperate to cause counter-rotation with respect to each other. In the present invention, optimal counter-rotation is achieved using cooperating fan units having mirror-image inner vane and outer blade surface contours. As used herein, the term “mirror-image” is intended to generally describe the relationship of the surface contours and orientations of the corresponding vane portions  56 ,  76  and blade portions  58 ,  78  of the fan units  50 ,  76  with the aspirator assembly in a fully constructed operational state. 
     Accordingly, primary fan unit  50 , viewed from the front, or upstream side, includes inner vanes  56  having a concave surface contour and extending in a rearward direction at an angular orientation diametrically opposing that or secondary fan inner vanes  76 . Consequently, an impinging fluid stream causes rotation, and in this case counter-clockwise rotation, of the fan unit  50  about the central shaft  30  opposite that of secondary fan unit  70 . Similarly, the outer fan blades  58  have a convex front surface contour and extend in a rearward direction at an angular orientation diametrically opposing that of secondary fan outer blades  78 . Consequently, during counter-clockwise rotation of the fan unit  50 , the outer fan blades  58  tend to cause a corresponding downstream-directed counter-clockwise fluid swirl opposing the clockwise fluid swirl effected by rotating secondary fan unit  70 . 
     As will be apparent to those skilled in the art, the particular orientations of the inner vane portions  56 ,  76  and outer blade portions  58 ,  78  in the accompanying drawing figures are merely exemplary. That is, the particular order of the primary and secondary fan units  50 ,  70  along the central supporting shaft  30  could be reversed without effecting overall operation of the aspirator assembly. 
     The fan units  50 ,  70  can be constructed from a lightweight polymer resin in order to further minimize tangential centrifugal accelerations which could deleteriously affect the stability of the assembly. 
     Referring now to FIGS. 1-5, the operation of the aspirator assembly  10  will be described in more detail. The initial energy for the system is derived from a conventional source of a pressurized fluid which can be a reservoir, a compressor arrangement, etc. This source is not considered part of the invention. It is well known in the art and further description is not provided. The primary pressurized fluid is introduced into the aspirator assembly  10  through center tube  28 . The pressurized fluid escapes the high-pressure duct arrangement  20  via a balanced set of exit nozzles  24 ,  26 . As used herein, the term “balanced” refers to the radial symmetry of the positioning of the exit nozzles about the central axis of main shaft  30 . The significance of the balancing of the exit nozzles  24 ,  26  is to enact a uniform pressure distribution upon the main central vanes  56  of the primary fan unit  50  in order to minimize or prevent any dynamic imbalance in the fan unit  50  during rotation. In other words, the main internal vanes  56  are symmetrically loaded in order to maintain a single uniform plane of rotation which is substantially perpendicular to the shared central axis of main shaft  30  and aspirator body  12 . 
     The primary pressurized gas is thrusted into the central vanes  56  of the primary impeller  50  to cause rotation of outer fan blades  58 . The surface geometry of the central vanes  56  is particularly designed to capture the thrusting pressure from the exit nozzles  24 ,  26  and to provide a medium for releasing the resulting energy while causing minimal airflow disturbance and avoiding the creation of any turbulence flow. The outer fan blades  58  are utilized to capture, or entrain, ambient air, i.e., taking air from upstream of the primary fan unit  50  and forcing it downstream toward the end  16  and the secondary fan unit  70 . Specifically, the outer blades  58  of primary fan  50  rotate in a manner such that a partial vacuum is created upstream of fan unit  50 , entraining ambient air into the aspirator body  12  through upstream end  14 . Correspondingly, the region of the aspirator body  12  downstream of fan unit  50  is pressurized. This secondary downstream pressure induces rotation of the secondary fan unit  70 . Thus, the operation of the secondary fan unit  70  is a function of, or subordinate to, the operation of the primary fan unit  50 . 
     After the working fluid and ambient drawn fluid have traversed the primary fan  50 , the generated pressurized ambient air and slightly degraded pressurized working fluid continue to expand into the secondary fan unit  70 . Furthermore, as a byproduct of the applied angular energy of the rotating primary fan unit  50 , an aerodynamic vortex is induced in the drawn ambient fluid and vectored downstream of the primary fan blades  58  in conjunction with the primary working fluid. 
     The arrow of vortex acts on any surface or any wall that it comes into contact with. The kinetic energy generated by these forces will act on the walls and the shaft of the aspirator. Thus, as: the fan spins clockwise, the nature of these forces is to counteract the rotational force and move the aspirator body  12  counterclockwise. Similarly, as the air is given kinetic energy through the swirl or through a vortex, as it comes into contact with the walls  18  of the aspirator body  12 , or the walls of the inflatable structure, the tendency for those walls is to counteract the swirl through motion in the opposite direction. 
     The primary function of the secondary fan vanes  76  and blades  78  is to capture any of the high-pressure air not utilized by the primary fan vanes  56 , with the objective of minimizing, and preferably nullifying, any unwanted energy generated by the primary fan unit  50 . As previously mentioned, the surface geometry of the vanes  76  and blades  78  of the secondary fan unit  70  mirror-image the corresponding surface geometry of the vanes  56  and blades  58  of the primary fan unit  50 , effecting rotation of the secondary fan unit in the direction counter to that of the primary fan unit. This counter-rotational relationship is an important aspect of the present invention, in that it minimizes or nullifies internal aspirator forces generated during operation. 
     Specifically, the inertial load caused by the rotating mass of the primary fan unit  50  is substantially neutralized by the corresponding rotating mass of the secondary fan unit  70 , while the angular velocity of the vortex generated by the primary fan unit  50  is counteracted by a mirror image angular velocity of flow generated by the counter-rotating fan blades  78  of the secondary fan unit  70 . The counter-rotating outer blades  78  of the secondary fan unit  70  induce an airflow having an angle of velocity that is the mirror image of the primary fan unit generated vortex. Thus, the induced angular momentum or arrow of vortex is substantially neutralized. 
     The arrangement of the present invention results in improved stability and reduced movement of the entire aspirator assembly  10 . This is especially advantageous since the aspirator of the invention does not require fixed mounting to the structural elements of the aircraft. Consequently, the aspirator assembly of the invention can be conveniently separated from the aircraft and positioned within the inflatable evacuation slide or life raft. 
     Since many modifications, variations, and changes in detail can be made to the described preferred embodiments of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the, appended claims and their legal equivalence.