Patent Publication Number: US-6213026-B1

Title: Propulsion plate connector system for a pneumatically propelled vehicle

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to pneumatic transportation systems wherein vehicles are pneumatically propelled along a vehicle guideway by one or more vehicle propulsion plate extending into an air duct of the guideway. The invention more particularly relates to the manner of connecting a propulsion plate to a pneumatically propelled vehicle, and has particular application in respect to vehicles having horizontal stabilizing beams on the underside of the vehicle for counter-balancing torsional forces transmitted to the vehicle from the propulsion plate. 
     U.S. Pat. No. 4,658,732 issued to Oskar H. W. Coester (the Coester &#39;732 patent) discloses a pneumatic transportation system wherein vehicles capable of transporting freight or passengers are propelled along an elevated vehicle guideway having an enclosed air duct beneath a trackway support platform. The vehicle is propelled by pneumatic propulsion forces acting against a propulsion plate in the guideway air duct, which in turn is connected to one of the vehicle&#39;s wheel trucks by a mast or pylon that passes through a longitudinal sealed guide slot in the guideway support platform. Also disclosed is the use of a horizontal stabilizing or traction beam connected between the pylon and the underside of the vehicle body to counteract the bending moment produced at the top of the vertical pylon by the horizontal propulsion forces on the propulsion plate attached to the bottom of the pylon. This beam reduces the tendency of the pneumatic propulsion forces to lift the vehicle truck wheels from the track, thereby increasing traction or contact between the track and the vehicle. This is especially important in transportation systems of this type, since the vehicles are relatively light as compared to vehicles having onboard motors or other onboard power sources. 
     While the pneumatically propelled vehicle shown in the Coester &#39;732 patent would perform suitably along straight sections of guideway, its disclosed use of a stabilizing beam is not practical for pneumatic transportation systems having a guideway configuration employing horizontal curves. Specifically, the disclosed rigid connection between the stabilizing beam and propulsion plate of the vehicle would prevent the pylon from rotating with the wheel truck as the wheel truck enters a curve thereby preventing rotation of the wheel truck. The rigid connection between the pylon and stabilizing beam and the vehicle&#39;s wheel trucks would also cause the wheels of the wheel trucks to lose contact with the tracks of the guideway when the wheel trucks enter and exit vertical curves due to the inability of the wheel trucks to freely follow changes in gradients in the trackway. 
     Another difficulty with the wheel truck design shown in the Coester &#39;732 patent relates to its conventional placement of the propulsion plate in a centered position relative to the wheel truck, that is, midway between truck wheels. This centered position results in small misalignments between the propulsion plate and air duct in horizontal curves of the guideway as well as misalignments between the vertical pylon and the support platform guide slot. These temporal misalignments require compensations in the sizing of the propulsion plate and guide slot which increase air leakage and reduce system efficiency. Furthermore, failure to keep the propulsion plate and pylon centered relative to the air duct and guide slot as the vehicle negotiates a horizontal curve increases wear on the seals of the propulsion plate and guide slot. 
     The present invention provides an improved propulsion plate connector system which overcomes the above-mentioned problems of propulsion plate and pylon alignment as a vehicle negotiates curved sections of the vehicle guideway of a pneumatic transportation system. The invention provides a mechanism for connecting the propulsion plate to the wheel truck of a pneumatically propelled vehicle in a manner that permits the vehicle to freely negotiate horizontal and vertical curves while maintaining contact between the truck wheels and the trackway, and while keeping the propulsion plate and its connecting pylon in a true centered position relative to the air duct and guide slot. Using the pylon connector system of the invention, a propulsion plate can be designed closer to the dimensions of the air duct (that is, with very small gaps between the edges of the propulsion plate and the walls of the guideway) resulting in reduced air flow across the propulsion plate. Maintaining a centered pylon as it passes through the guide slot will also reduce air leakage through the slot seal and slot seal wear. 
     SUMMARY OF THE INVENTION 
     Briefly, the invention involves an improved propulsion plate connector system having a vertical pylon which connects a propulsion plate in the air duct of a vehicle guideway to a wheel carriage structure of a vehicle pneumatically propelled on the guideway. One aspect of the invention also involves the use of a horizontal stabilizing beam connected between the pylon and the vehicle to counteract torque about the top of the pylon produced by propulsion forces on the propulsion plate. 
     In accordance with the invention, the top end of the pylon is connected to the wheel carriage of the vehicle at a pylon joint that fixes the rotational position of the pylon and the propulsion plate relative to the wheel carriage such that the propulsion plate follows the travel of the wheel carriage as the wheel rotates in a horizontal curve. Typically the wheel carriage will be in the form of a convention wheel truck having two wheel sets defining two wheel axes, however, a wheel carriage structure for a single wheel set could also be used, such as with relatively short vehicles which are also relatively light. 
     In one aspect of the invention, a horizontal hinge joint connects the base end of the stabilizing beam to the top end of the pylon proximate the pylon joint to permit horizontal articulation of the stabilizing beam relative to the wheel carriage so as to permit the propulsion plate connected to the pylon to follow horizontal curves in the air duct of the vehicle guideway. In another aspect of the invention, the pylon joint provides a vertical pivot joint which permits the pylon to pivot in the longitudinal vertical plane so as to permit the wheel carriage to maintain contact in vertical curves in the vehicle guideway. The pylon joint and the hinge joint for the horizontal beam preferably provide for both vertical and horizontal articulation to permit the vehicle to readily negotiate both vertical and horizontal curves. 
     In a further aspect of the invention, the pylon joint is located proximate the wheel axis of one of the wheel sets of the wheel carriage so as to position the propulsion plate connected to the bottom end of the pylon in approximate vertical alignment with the wheel axis. In yet another aspect of the invention both the pylon and the propulsion plate are positioned in approximate vertical alignment with the wheel axis. As hereinafter described in greater detail, such approximate alignment of the propulsion plate and the pylon with the axis of one of the wheel sets of a wheel carriage such as a two axle wheel truck, instead of centering the pylon and propulsion plate between the wheel sets, will minimize deviations from the optimum centered position of the propulsion plate and connecting pylon as the propulsion plate and pylon pass through a horizontal curve in the vehicle guideway. 
     In still a further aspect of the invention, the pylon joint joins the top of the pylon to a static wheel axle on a wheel carriage at a location that is proximate to and in front of the wheel axle such that the pylon joint and wheel axle are in the same approximate horizontal plane. Such positioning of the pylon joint will facilitate disassembly of the pylon and propulsion plate from the wheel axle for maintenance purposes and will reduce the longitudinal forces transmitted to the axle by propelling forces on the propulsion plate. In accordance with another aspect of the invention, the top end of the pylon is joined to a static axle of the wheel carriage by cushioning means for providing a degree of isolation between the propulsion plate assembly and the pneumatically propelled vehicle. Bracing means connected across the wheel carriage are also provided for reducing loads on the wheel truck&#39;s static axle. 
     The present invention also includes a method of propelling a vehicle of a pneumatic transportation system through curves in the guideway of the transportation system including fixing the propulsion plate in the guideway air duct so that it is in approximate vertical alignment of a wheel axis of a wheel carriage of the vehicle as the wheel carriage travels through a horizontal curve of the guideway. 
     Therefore, it will be seen that it is a primary object of the present invention to provide an improved propulsion plate connector system for a pneumatically propelled vehicle of a pneumatic transportation system which permits efficient operation of the pneumatically propelled vehicles in curved sections of the guideway. It is another object of the invention to provide an improved propulsion plate connector system which allows the propulsion plate of the pneumatically propelled vehicle to remain centered in the air duct of the vehicle guideway when negotiating horizontal curves. It is a further object of the invention to reduce wear on the seals used around the perimeter of a propulsion plate of a pneumatically propelled vehicle, as well as minimizing wear on the seals used in the guide slots of the guideway&#39;s support platform. It is yet a further object of the invention to provide an improved propulsion plate connector system that permits the vehicle&#39;s propulsion plate to easily disconnect from a wheel truck or other wheel carriage of the vehicle for maintenance and inspection purposes. Other objects of the invention will be apparent from the following specification and claims, as well as from the accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a vehicle on an elevated guideway of a pneumatic transportation system as seen from lines  1 — 1  in FIG. 2, and generally illustrates a propulsion plate in the air duct of the guideway connected to a wheel truck of the vehicle. 
     FIG. 2 is a pictorial view of the vehicle and vehicle guideway of FIG. 1, further showing a slight vertical curve at the left end of the guideway. 
     FIG. 3 is a pictorial top plan view of the wheel trucks of the pneumatically propelled vehicles shown in FIGS. 1 and 2, travelling on a straight section of the vehicle guideway. 
     FIG. 4 is a pictorial top plan view of the wheel trucks of the vehicle shown in FIG. 3, traveling on a section of vehicle guideway having a horizontal curve, and showing the horizontal articulation of the stabilizing beams connected between the vehicle&#39;s propulsion plate pylons and the undercarriage of the vehicle as it negotiates the horizontal curve. 
     FIG. 5 is an enlarged pictorial view of one of the wheel trucks of the vehicle shown in FIG. 4 negotiating the horizontal curve of guideway, and illustrating in greater detail the alignment of the propulsion plate in the air duct of the guideway. 
     FIG. 6 is a pictorial top plan view of a wheel truck of a pneumatically propelled vehicle negotiating a curved section of guideway, and illustrating the interference between the propulsion plate and sidewalls of the guideway air duct that would occur if the propulsion plate were allowed to rotate with vehicle&#39;s horizontal stabilizing beams. 
     FIG. 7 is a pictorial view of a prior art configuration of a wheel truck and pylon wherein the pylon is connected centrally of the wheel truck, and illustrating the deviation of the propulsion plate and pylon from a true centered position relative to the guideway and guideway slot. 
     FIG. 8 is a top perspective view of a vehicle wheel truck having an improved propulsion plate connection system accordance with the invention. 
     FIG. 9 is a bottom perspective view of the wheel truck shown in FIG. 8, and also showing the full extension of the stabilizing beam connected to the undercarriage of the vehicle. 
     FIG. 10 is a top perspective view of a portion of the improved propulsion plate connector system of the invention, including collar assemblies for holding the pylon and propulsion plate to a static axle and crossbeam of the wheel truck. 
     FIG. 10A is a cross-sectional view of the collar assembly shown in FIG. 10 for the crossbeam of the wheel truck. 
     FIG. 11 is an exploded top perspective view of the improved propulsion plate connector system of the invention showing the pylon, propulsion plate, pylon joint and stabilizing beam joint. 
     FIG. 11A is an exploded view of the horizontal pin assembly and axle connector plates which form the pylon joint of the propulsion plate connector system shown in FIG.  11 . 
     FIG. 12 is a side elevational view of the propulsion plate pylon, connector plates and collar assembly for holding the pylon to the static axle of the wheel truck. 
     FIG. 12A is an enlarged cross-sectional view of the top of the pylon showing the axle connector plates and the axle collar assembly in cross-section taken along lines  12 — 12  of FIG.  13 . 
     FIG. 13 is a side elevational view, in partial cross-section, of a static axle of a wheel truck and the axle collar assembly and axle connector plates holding the pylon thereto. 
     FIG. 14 is an exploded top perspective view of one of the horizontal stabilizing beams of the pneumatically propelled vehicle, showing the horizontal stabilizing beam joint for permitting horizontal articulation of the stabilizing beam relative to the pylon, and showing a swivel joint for attaching the pylon to the undercarriage of the vehicle. 
     FIG. 15 is a side elevational view of the swivel joint for the horizontal stabilizing beam shown in FIG.  14 . 
     FIG. 16 is a cross-sectional view of the swivel joint shown in FIG. 15 taken along lines  16 — 16 . 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
     Referring now to the drawings, the improved propulsion plate connector system of the invention is used to connect a propulsion plate to the wheel carriage of a vehicle of a pneumatic transportation system such as pictorially illustrated in FIGS. 1 and 2. Referring to FIGS. 1 and 2, a vehicle guideway  11 , suitably fabricated in pre-cast concrete sections and elevated above the ground on suitable tower structures  12 , includes an upper support platform  13 , a track  15  on the upper support platform, and an enclosed air duct  17  beneath the support platform. A vehicle  19  having a body  20 , undercarriage  33 , and wheel carriage structures in the form of wheel trucks  21  is propelled along the track of the guideway by means of a propulsion plate  23  positioned crosswise and moveable within the air duct. The propulsion plate is connected to the vehicle&#39;s wheel trucks on the underside of the vehicle by means of a flat vertical pylon  25  aligned with and passing through a guide slot  27  in the guideway&#39;s support platform  13 . Propulsion forces are generated against propulsion plate  23  by controlling air flow states in the guideway&#39;s air duct by a system of distributed air flow generators such as described in prior U.S. Pat. No. 4,587,906. To prevent air leakage through the pylon guide slot  27 , the guide slot is provided with suitable sealing flaps  29  which are deflected as the pylon passes through the guide slot. 
     As shown in FIG. 2, it is contemplated that, for a long vehicle, a propulsion plate  23  will be provided at each end of the vehicle, one for each wheel truck  21  located at the extremities of the vehicle. A horizontal stabilizing beam  31  is connected to and extends inwardly from each of the wheel trucks, with the distal ends  32  of the stabilizing beams being connected to the bottom of the vehicle undercarriage  33  by means of swivel joints  35 . The stabilizing beams  31  function to counteract the bending moments produced on the propulsion plate pylons  25  by the propulsion forces exerted against the propulsion plate. Such bending moments are transmitted directly to the vehicle undercarriage through the horizontal beams, rather than being exerted on the connecting structure between pylons  25  and wheel trucks  21 . It will be understood that, while a separate stabilizing beam is shown for each wheel truck, it would be possible to provide a common stabilizing beam for both wheel trucks in the case of shorter vehicles. In this case each end of the beam would be connected to a wheel truck without a direct connection to the vehicle&#39;s undercarriage. 
     The positioning of the propulsion plate  23  in reference to the vehicle&#39;s wheel trucks  21  and the manner of connecting the propulsion plate and stabilizing beam to the wheel trucks is vitally important to the ability of the vehicle to operate in a transportation system having sections of guideway with horizontal and vertical curves, as well as straight sections of guideway. To understand this importance, the performance of the vehicle in both straight and curved sections of guideway will now be described in reference to FIGS. 3-7. 
     FIG. 3 shows wheel trucks  21  of vehicle  19  traveling in a straight section  11   a  of the guideway, whereas FIGS. 4 and 5 show the vehicle traveling through a guideway section  11   b  having a horizontal curve. In the straight guideway section  1  la, wheel trucks  21  of vehicle  19 , along with the horizontal stabilizing beams  31 , are aligned with the vehicle undercarriage  33  and the vehicle body  20  which is shown in phantom lines. However, as the vehicle enters a horizontal curve as shown in FIGS. 4 and 5, horizontal beams  31  articulate in the horizontal plane at beam joints  37 , thereby allowing the wheel trucks to rotate about bolster pins  39  relative to the vehicle body  20 . (As described below, the distal ends  32  of the horizontal beams do not move in a horizontal plane.) Without such horizontal articulation, the vehicle  19  would be unable to enter the curved section of guideway since the horizontal beams would prevent the wheel trucks from rotating in the turn. 
     FIG. 5 pictorially shows a portion of one of the vehicle&#39;s rotated wheel trucks  21  and reveals the position of the propulsion plate  23  in a curved portion of the guideway&#39;s air duct  17 . It can be seen that the propulsion plate has a rotationally fixed position relative to the wheel trucks such that it remains in a perpendicular orientation relative to the air duct  17  as the wheel truck passes through the curve. By maintaining this squared position relative to the air duct, the propulsion plate structure remains relatively centered in the air duct such that the gap between the edges  41  of the propulsion plate and the air duct sidewalls  43   a ,  43   b  remain constant. 
     FIG. 6 illustrates the consequences of allowing the propulsion plate to rotate relative to wheel truck  21  as the wheel truck enters a horizontal curve of the guideway. In FIG. 6, wheel truck  21  has a propulsion plate  23   a  that rotates with the horizontal beam  31 . As illustrated, such rotation of the propulsion plate would cause the propulsion plate to interfere with the air duct sidewall  43   a  on the outside of the curve, and to produce a gap between the propulsion plate and the sidewall  43   b  on the inside of the curve. To accommodate anticipated rotations of the propulsion plate in systems having guideway curves, the rotating propulsion plate shown in FIG. 6 would have to be undersized in relation to the width of the air duct. As mentioned above, such reduced sizing of the propulsion plate would increase air leakage across the propulsion plate resulting in lower system efficiency. Such a configuration would also cause uneven wear on the seals used around the edges of the propulsion plate. 
     FIG. 7 pictorially illustrates the disadvantage of conventional approaches to attaching propulsion plates to the wheel trucks of a pneumatically propelled vehicle. In FIG. 7, a propulsion plate  47  is connected to the underside of wheel truck  49  midway between static axles  51 ,  53  for wheel sets  55 ,  57 . The propulsion plate is connected to the wheel truck by means of vertical pylon  59  which is centered between the two lateral edges  65 ,  67  of the propulsion plate in order to align the pylon with the longitudinal guide slot of the guideway&#39;s support platform as generally illustrated in FIG.  1 . In a straight section of guideway, such as illustrated in FIG. 3, propulsion plate  47  and pylon  59  are centered relative to the air duct sidewalls (represented in FIG. 7 by dashed lines  61   a  and  61   b ), and the pylon is centered relative to the guide slot represented by dashed line  63 . However, in a curved section of guideway (such as shown in FIG. 4) having curved sidewalls represented by phantom lines  62   a ,  62   b , the propulsion plate, though perpendicular to the air duct, will experience a lateral deviation from its normally centered position in the air duct as represented by arrows “d c ”. A similar deviation will occur between the pylon and curved guide slot  64 . This deviation from a true centered position will cause problems similar to those described in connection with the propulsion plate configuration shown in FIG. 6, that is, the propulsion plate must be sized to accommodate this deviation, thereby increasing the gaps between the air duct and the propulsion plate and air flow across the propulsion plate. Similarly, the deviation of the pylon  59  from a true centered position will require a wider guide slot with increased air leakage and increased wear on the guide slot seals. As hereinafter described, the present invention provides for relocating the propulsion plate and pylon to a position close to the inboard static axle  53  of wheel truck  49 . With such relocation, the positional deviations experienced in horizontal curves between the actual position of the propulsion plate and pylon and a true centered position in the air duct is essentially zero as indicated by arrows “d a ”. With such placement of the propulsion plate and pylon, leakage across the propulsion plate is again minimized with a resulting improvement in system efficiency. This will also have the benefit of reducing vibration and noise cause by such air flows. Further, by keeping the propulsion plate&#39;s nominal width as large as possible, more surface area is available for the generation of a propulsion thrust against the propulsion plate by pressurized air flow in the air duct. 
     FIGS. 8-13 illustrate structure of the invention for connecting the propulsion plate and propulsion plate pylon to the inboard wheel axle of the vehicle&#39;s wheel truck as pictorially illustrated in FIGS. 1-5, and for also connecting the horizontal stabilizing beam to this structure. In accordance with the various aspects of the invention, the connecting structure allows for the horizontal articulation of the stabilizing beam  31  in relation to the wheel truck to which it is connected, as well as the vertical articulation of the set formed by the horizontal beam and pylon in a longitudinal vertical plane as the wheel truck enters vertical curves of a guideway, such as the vertical curved portion  18  of guideway  11  shown in FIG.  2 . When the vehicle enters vertical curves, the differences in gradient encountered by the vehicle and each of the vehicle&#39;s wheel trucks cause the wheel trucks to turn in the vertical longitudinal plane in relation to the connection to the vehicle body. Vertical articulation between the propulsion plate and horizontal beam in relation to the vehicle&#39;s wheel truck, as herein described, allows for this freedom of movement. Without vertical articulation, the rigid connection between the pylon, wheel truck and horizontal beam would inhibit the ability of the wheel truck to follow vertical curves, thereby reducing traction or contact between the wheel sets in the guideway track, and would place severe strain on the system components. 
     It will be appreciated that the required degree of vertical articulation between the propulsion plate pylon and wheel truck will be relatively small as compared to the required horizontal articulation of the horizontal stabilizing beam, due to the relatively large radii experienced in vertical curves as compared to horizontal curves. It is anticipated the articulation range in the vertical plane will typically be limited to approximately 8 degrees (4 degrees either side of vertical), whereas horizontal articulation of the horizontal beam will typically be in the range of 26 degrees (13 degrees to each side of the center axis of the vehicle). 
     Referring to FIG. 8, each of the vehicle&#39;s wheel trucks includes a transverse inboard static axle  69  for inboard wheel set  71  and a transverse outboard static axle  73  for outboard wheel set  75 . The static axles  69 ,  73 , along with a crossbeam  77 , extend between longitudinal side beams  79  to form a rigid frame for supporting a transverse suspension beam  81 . The suspension beam, which has slide plates  83  for engaging and supporting the undercarriage of the vehicle, is in turn supported and held in place by air springs  85  mounted to bracket structures  87  extending laterally from each of the truck&#39;s side beams. A connecting rod assembly  89  mounted to the side beams holds the suspension beam in place while allowing the beam a degree of vertical motion on the air springs. A connection between the wheel truck and the undercarriage of the vehicle is made by bolster pin  39  which allows the truck to rotate relative to the vehicle body. 
     The vertical pylon  25  has a top end  24  for connecting the propulsion plate to the static axle  69  as hereinafter described. It also has an extended bottom end  26  for connecting to the propulsion plate  23  in the air duct, and beveled edges  28  intermediate its top and bottom ends to facilitate passage of the pylon through the guideway slot seal (see FIG.  1 ). It is noted that the propulsion plate  23  is attached in offset relation to pylon  25  such that the pylon leads the propulsion plate on the inboard side of the vehicle. This offset construction has the advantage of allowing the pylon to pass through the slot seal on the side of the propulsion plate opposite the side of the pneumatic propulsion force as more particularly described in U.S. Pat. No. 4,658,732. With such a construction, air leakage through the slot seal is minimized due to the lower pressure differentials between atmosphere and the inboard side of the propulsion plate as compared to its propulsive force side. 
     Also, the rigid structure formed by pylon  25  and propulsion plate  23  is preferably centered below the wheel axis formed by static axle  69  so that the pylon and propulsion plate is each in approximate vertical alignment with the wheel axis. By centering this structure in relation to the wheel axis, lateral deviations of the propulsion plate and pylon in the guideway air duct and guide slot in horizontal curves can be minimized as illustrated in FIG.  7 . 
     The top end of pylon  25  is connected to inboard static axle  69  by means of a pylon connector assembly  93  which permits a small degree of articulation of the pylon in the longitudinal vertical plane relative to the wheel truck  21 . This connector assembly also provides for a cushioned connection between the wheel truck and the pylon that acts to dampen noise and vibrations generated at the propulsion plate. The connector assembly is seen to include a pair of longitudinal connector plates  95  having ring-shaped axle ends  97  for capturing the centrally located collar assembly  99  surrounding the static axle. Suitably, the ends  97  of connector plates  95  are secured to the tubular outer metal jacket  101  of collar assembly  99  by welding the plates to the collar. This securement produces a unitary structure which holds the connector plates in their longitudinally extended position when the collar assembly is installed as hereinafter described. 
     As shown in FIGS. 9,  10 ,  10 A, and  11 , the pylon connector assembly  93  further includes a second, longitudinally displaced collar assembly  103  having outer split metal jacket  105  formed by upper and lower halves  107 ,  109  joined together at mating flanges  111 ,  113 . Longitudinal bracing beams  115  rigidly join the outer jacket  101  of collar assembly  99  to the lower jacket half  109  of collar assembly  103 , such that the collar assembly is spaced from collar assembly  99  a suitable distance to engage and clamp over the crossbeam  77  of the wheel truck. The bracing beams and second collar assembly provide bracing means connected to the wheel truck for reducing loads on the static axle by allowing a transfer of propulsion forces acting on the static axle  69  to the crossbeam of the truck, and provide vertical stabilization for the connection of the top end  24  of pylon  25  at the pivot pin assembly  119 , which is in offset position in relation to the static axle  69 . It will be appreciated that other designs for the bracing means are possible. For example, the bracing beams  115  could extend between the two static axles  69 ,  73  of the wheel truck, instead of between a separate crossbeam structure and the inboard static axle, or a different number of bracing beams could be used, including diagonal beams. 
     It can be seen that the top end of pylon  25  fits between the projecting ends  96  of connector plates  95  to form a pylon joint  117  which prevents any rotation of the pylon and propulsion plate about a vertical axis “A”, but which permits a degree of vertical articulation of the pylon and propulsion plate about a horizontal axis. The vertical articulation of the pylon between the connector plates occurs about a pivot pin assembly  119  which is illustrated in greater detail in FIGS. 11 and 11A. The pivot pin assembly, which connects through pivot openings  121  at the projecting ends  96  of the connector plates and opening  120  at the top end of the pylon, includes a pivot pin  123  having a pivot shaft  125  and threaded end  127 , suitable inner and outer bushings  129 ,  131 , and a spacer  133  having conical surface  135  for receiving the conical end  126  of pivot pin shaft  125 . Fastening nut  137  with backing washer  139  fastens to the threaded end  127  of the pivot shaft for fastening the pivot pin assembly together. An additional spacer  141  is provided between the connector plates to maintain a separation of parts. 
     Proper maintenance of the pylon connector assembly will require lubrication of the pivot pin assembly  119  and the contacting surfaces of connecting plates  95  and pylon  25 . Lubrication can be supplied by a suitable grease applied to these components. 
     FIGS. 12,  12 A and  13  show in greater detail the connection of the collar assembly  99  to the wheel truck&#39;s static axle  69 . This collar assembly includes axially opposed, cylindrical cushion elements  143 , suitably fabricated of neoprene rubber, inserted between the static axle and the collar assembly&#39;s metal jacket  101 . End clamps  145  releasably clamp to the static axle for holding the collar assembly in its desired centered position on the axle. A radially extending shoulder portion  147  at the outer end of the cushion elements  143  provides a cushioning interface between clamps  145  and flanged ends  149  of the collar jacket  101 . The cushion element thus provides a degree of mechanical isolation between the static axle and the outer metal jacket of the collar assembly to which the pylon  25  is held for absorbing vibrations generated by air flowing across the propulsion plate. It is noted that a recess  151  is provided in the top end of the pylon along the pylon&#39;s interior edge  153  to accommodate the outer cylindrical jacket of the collar assembly. This recess is provided with a sufficient radius to provide a gap between the collar jacket and the pylon (as illustrated by phantom lines in FIG. 11A) to permit rotational motion of the pylon in relation to the collar assembly. 
     The collar assembly  103  for wheel truck crossbeam  77  is similar in construction to the collar assembly for the static axle, except for its split jacket  105  as described above. This second collar assembly, which is shown in greater detail in FIGS. 10A and 11, also includes clamps  104  for holding the collar assembly in position on the crossbeam (see FIG.  10 ), and a cushion for providing isolation between the crossbeam and the collar assembly jacket  105 , in this case in the form of axially split cushion elements  106 . Using the cushioned collar assemblies  99 ,  103  to join the connector assembly  93  to wheel truck  21 , suitable mechanical isolation between the propulsion plate and wheel truck can be achieved. 
     Installation of the collar assemblies requires removal of one of the wheels of wheel set  71  on the inboard static axle  69  so that the clamps  145 , cushion elements  143 , and jacket  101  of the first collar assembly  99  can be slipped over the axle. With the jacket  101  centered on the axle, the cushion elements can be inserted through the ends of the jacket and the clamps secured. However, before securing the clamps, the bracing beams  115  secured to jacket  101  are rotated until the lower half  109  of the jacket  105  of the second collar assembly  103 , which is secured to the opposite ends of the bracing beams, engages crossbeam  77  so that the second collar assembly can be assembled around this beam. 
     The structure for attaching the horizontal stabilizing beam  31  between the wheel truck  21  and the vehicle undercarriage will now be described in reference to FIGS. 13-16. Referring to FIGS. 13 and 14, the base end  34  of the stabilizing beam is joined to the top end of pylon end  25  by means of an upper and lower hinge bracket  157 ,  159 , and a vertical hinge pin  161  which inserts through the hinge pin ends  163 ,  165  of the hinge brackets and pin sleeve  167  in the stabilizing beam base end  34 . Thus connected, this hinge structure provides a stabilizing beam joint  169  proximate the pylon joint  117  which provides a horizontal pivot connection between the stabilizing beam and the pylon so as to permit horizontal articulation of the stabilizing beam relative to the vertical axis of the pylon. Suitable fastener holes  171 ,  173  are provided in the hinge brackets and pylon for fastening the hinge brackets to the pylon, such as by rivets or screw fasteners. Also, it is noted that the brackets are positioned above and below the connector plates  95  so as to produce a gap between the connector plates and brackets. Such a gap is necessary to allow for rotation of the pylon between the connector plates, albeit a small degree of rotation, whenever the wheel truck enters and exits vertical curves. 
     It can be readily appreciated that the base end  34  of the horizontal stabilizing beam can be readily detached from the pylon by simply removing hinge pin  161 . 
     The stabilizing beam&#39;s distal end  32  is attached to the vehicle&#39;s undercarriage  33  by means of swivel joint  35 , which allows for play of the stabilizing beam in the longitudinal direction as the stabilizing beam articulates about hinge joint  169 . Also, the swivel joint permits small longitudinal displacements of the stabilizing beam that may otherwise occur when the wheel truck  21  rotates relative to the vehicle undercarriage. Since the stabilizing beam remains parallel to the vehicle body in a horizontal curve (see FIGS.  4  and  5 ), the only movement of the distal end  32  of the stabilizing beam is longitudinal; no movement is experienced about the vertical axis of the swivel joint and thus the swivel joint can be secured in a fixed position to the undercarriage of the vehicle. 
     Referring to FIGS. 14 and 15, swivel joint  35  includes upper and lower swivel block assemblies  177 ,  179 , each of which includes a pivot pin  181 ,  183  extending through and supported in a pair of coaxial pivot pin blocks  185 ,  187  and pivot collars  189 ,  191 . The abutting pin blocks of each swivel block assembly form an interior cavity  193 ,  195  for holding a suitable lubricant, and are surrounded by a pair of abutting rubber bushings  197 ,  199 , suitably fabricated of a soft neoprene rubber, surrounded by outer cylindrical metal jackets  201 ,  203  and held by circular side plates  202 ,  204  which are welded to and radially extend from pivot pin blocks  177 ,  179 . The upper pivot block assembly  177  is mounted to the undercarriage  33  of the vehicle by a mounting bracket structure consisting of mounting plate  205  and connecting brackets  207  welded together with the upper block assembly jacket  201 . The lower swivel block assembly  179  is interconnected in swivel relation to the upper block assembly  177  by means of swivel plates  209  which connect to and are free to rotate about pivot collars  189 ,  191 . Connecting plates  211  welded to the distal end  32  of the stabilizing beam are secured to the outer jacket  203  of the lower swivel block assembly of the swivel joint to provide the desired swivel connection between the beam and swivel joint. 
     Referring to FIGS. 8,  10  and  11 , it can seen the pivot pin assembly forming the pylon joint  117  permits the pylon and propulsion plate to be readily detached from wheel truck  21  for maintenance and inspection. To detach the pylon, the base end of stabilizing beam  31  is first uncoupled from the pylon by removing hinge pin  161 . The pivot pin of pivot pin assembly  119  is then removed and the vehicle moved forward on the track of the guideway to permit the top end of the pylon to slide out of connector plates  95 . Because the pylon joint is positioned in front of the static axle  69  outside the wheel truck, the pivot pin will be relatively accessible from maintenance ports provided in the vehicle floor. Removal of the propulsion plate from the bottom of the pylon can similarly be accomplished through maintenance ports in the bottom of the vehicle guideway  11 . The propulsion plate is detached from and reattached to the propulsion plate pylon brackets  213 ,  215 ,  217  as shown in FIG.  11 . 
     The swivel joint is readily assembled and disassembled for maintenance and inspection by simply removing pivot pins  181 ,  183  and separating the parts of the swivel block assemblies, including the pivot pin blocks  185 ,  187  and the rubber bushings  197 ,  199 . 
     Therefore, it can that the present invention provides an improved propulsion plate connector system for a vehicle of a pneumatic transportation system which permits the vehicle to readily negotiate horizontal and vertical curves in a vehicle guideway without sacrificing system efficiency, which reduces the transmission of noise and vibrations generated at the propulsion plate, and which facilitates inspection and maintenance of the component parts of the propulsion plate, pylon and connector assemblies. While the connector system has been described in considerable detail in the foregoing specification and accompanying drawings, it is understood that it is not intended that the invention be limited to such detail, except as necessitated by the following claims. For example, the desired positioning of the propulsion plate and pylon in approximate vertical alignment with the inboard static axle  69  of wheel truck  21  as herein described might alternatively be achieved by connecting the top end  24  of the pylon  25  directly to the inboard axle such that the pylon and stabilizing beam pivot in the longitudinal vertical plane about the axle itself, instead of a separate pivot point. Such a construction would reduce components—it would eliminate pivot pin assembly  119 —and would reduce or eliminate the bending moment about the axle produced by having an offset between the pylon joint and axle, thereby eliminating the need of the longitudinal bracing beams  115  and second collar assembly. It will also be appreciated that the wheel trucks  21  can be constructed without static axles, but with wheel sets attached directly to the wheel truck frame. In this case, the placement of the propulsion plate and pylon in accordance with the invention would be in approximate vertical alignment with the axis of one of the wheel sets. Nor is it intended that the invention be limited to the use of a wheel truck having two wheel sets. The use of a truck with one or more than two wheel sets is possible. 
     Finally, it will be appreciated that the invention can be used with a vehicles having wheel sets mounted to single axle wheel carriage structures instead of to conventional two axle wheel trucks. Such an application might be used in transportation systems having relatively short vehicles where the vehicles can be adequately supported on two wheel sets involving just two single wheel axles and a suspension beam and bolster pin for each axle. In such vehicle designs the pylon connection would be made to the single axle of the wheel carriage structure in the same manner as described herein for vehicles having two axle wheel trucks. The connection could also be made as herein described to position propulsion plate and pylon in approximate vertical alignment with the single wheel axis of the wheel carriage to which the pylon is attached, to provide vertical articulation of the propulsion plate and horizontal stabilizing beam, if any, in the longitudinal vertical plane, and to also provide horizontal articulation of the horizontal beam relative to the wheel carriage structure.