Abstract:
A vehicle suspended from a trackway of an aerial trackway system is provided. The vehicle comprises a front traction unit having a supporting wheel and a rear traction unit having a supporting wheel. These traction units support a vehicle body of the vehicle and are rotatable relative to the vehicle body such that the supporting wheels may follow the trackway without slip. Apparatus is provided for linking the front and rear traction units such that a moment at the center of gravity of the front traction unit about its axis of rotation relative to the vehicle body and a moment at the center of gravity of the rear traction unit about its center of rotation relative to the vehicle body are balanced.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a vehicle, for use in an aerial trackway system, which comprises front and rear traction units to suspend a vehicle body from a trackway, each traction unit having a supporting wheel on the trackway, and means for improving running stability of the vehicle. 
     For use in an aerial trackway system, such as one using a rope or another using a rail, a vehicle is known which has front and rear traction units rotatably mounted on a vehicle body at forward and rearward parts of the vehicle body, respectively, so that supporting wheels of the traction units may follow a curve, with a small curvature, of the trackway. In the vehicle, owing to the fact that each of frames of the traction units is generally C-shaped so as to prevent the traction units from contact with the trackway, it is necessary to mount the traction units on the vehicle body with their centers of gravity disposed outside of a vertical plane including the center of the trackway and the center of gravity of the vehicle. This arrangement will cause the traction units to rotate, causing the wheels to wobble, thus degrading running stability of the vehicle. It is conceivable, to solve this shortcoming, to provide a counter weight to each traction unit to dispose its center of gravity adjacent a vertical plane including the center of the trackway and the center of gravity of the vehicle. However, this results in an increase of the weight of the vehicle and thus is disadvantageous. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a vehicle for use in an aerial trackway system which has eliminated the shortcoming as above. 
     According to the present invention, a front traction unit and a rear traction unit are linked such that a moment at the center of gravity of the front traction unit about its axis of rotation and a moment at the center of gravity of the rear traction unit are balanced, in order to prevent wobbling of supporting wheels upon acceleration or deceleration of the vehicle. 
    
    
     IN THE ACCOMPANYING DRAWINGS 
     The invention will be described further with reference to the accompanying drawings, in which:- 
     FIG. 1 is a side elevational view of a first embodiment of a vehicle constructed in accordance with the present invention; 
     FIG. 2 is a front elevational view of the vehicle shown in FIG. 1; 
     FIG. 3 is a top elevational view of the vehicle shown in FIG. 1; and 
     FIG. 4 is a similar view to FIG. 3 showing another embodiment of a vehicle. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 to 3, 1 designates a vehicle body, 2 and 3 front and rear traction units, respectively, 4 a trackway in the form of a rope, 5 two collector cables (see FIG. 2) suspended from the rope 5 in a conventional manner and 6 a current collector. 
     Each of the traction units 2 and 3 has a frame 7a or 7b, a traction motor 8a or 8b, a brake 9a or 9b, a supporting wheel 10a or 10b, an output shaft 11a or 11b of the corresponding motor 8a or 8b, a wheel shaft 12a or 12b of the supporting wheel 10a or 10b, timing belts 13a and 14a or 13b and 14b, and a plurality of gears 15a, 16a, 17a, and 18a or 15b, 16b, 17b and 18b. 
     For mounting the traction units 2 and 3 on the vehicle body 1, a bracket 19 rigidly secured to the vehicle body has a pin 20 by which a beam 21 is rotatably mounted on the bracket 19. The beam 21 has a forward section carrying a front swivel pin 22a and a rearward section carrying a rear swivel pin 22b with respect to a forward direction as by an arrow X in FIG. 1. The front traction unit 2 is rotatably mounted on the beam 21 for rotation about the front swivel pin 22a, whereas the rear traction unit 3 for rotation about the rear swivel pin 22b. 
     An axis k 1  of the front swivel pin 22a and an axis k 2  of the rear swivel pin 22b are disposed in a vertical plane including therein a vertical line passing through the center of the rope 4 and the center of gravity of the vehicle, as denoted by G 3  (see FIG. 2). 
     The axis k 1  is inclined forwardly, that is, the upper end of the swivel 22a is disposed forwardly, with respect to the vehicle body 1, of the lower end of the swivel 22a, and makes an angle α 1  with a vertical line l 1  passing through the wheel shaft 12a. The contact point P 1  of the supporting wheel 18a with the rope 4 is disposed on the axis k 1 . However, the point P 1  may be disposed at a location positioned upwardly of the axis k 1 . Denoted by G 1  is the center of gravity of the front traction unit 2 and the center of gravity G 1  is disposed at a location spaced from and on one side of the plane including therein the vertical line passing through the center of the rope 4 and the center of gravity of the vehicle G 3  (see FIG. 2), the location being spaced forwardly of the axis k 1  and nearer to a forward post portion 7a&#39; of the frame 7a. 
     The axis k 2  is inclined rearwardly, that is, the upper end of the swivel 22b is disposed rearwardly, with respect to the vehicle body 1, of the lower end of the swivel 22b, and makes the same angle α 2  as the angle the axis k 2  makes with a vertical line l 2  passing through the wheel shaft 12b. The contact point P 2  of the supporting wheel 12b with the rope 4 is disposed on the axis k 2 . However, in practice, the point P 2  may be disposed at a location spaced upwardly of the axis k 2 . Denoted by G 2  is the center of gravity of the rear traction unit 3 and the center of gravity G 2  is disposed at a location spaced from and on the same side of the plane including therein the vertical line passing through the center of the rope 4 and the center of gravity G 2  of the vehicle (see FIG. 2), the location being spaced rearwardly of the axis k 2  and nearer to a rearward post portion 76&#39; of the frame 7b. 
     Mounted within the vehicle body 1 are controllers 23 and 24 for the motors 8a and 8b respectively. The center of gravity of each of the controllers 23 and 24 is disposed at a location spaced from and on the opposite side the plane including the vertical line passing through the center of the rope 4 and the center of gravity G 3  of the vehicle by a length C(see FIG. 2) to dispose the center of gravity G 3  within this plane. By so arranging the vehicle can be suspended from the rope 4 adequently. 
     As best seen in FIG. 1, the connecting beam 21 has arm sections 25a and 25b projecting downwardly from the beam 21 toward the vehicle body 1 and the arm section 25a is linked to one end of a shock absorber 26 and another arm section 25b to one end of another shock absorber 27. Opposite ends of the shock absorbers 26 and 27 are linked to the vehicle body 1 at two locations spaced in a longitudinal direction of the vehicle body 1 to prevent an excessive swinging movement (denoted by a) in a longitudinal direction upon acceleration or deceleration of the vehicle. 
     The current collector unit 6, which supplies current to both motors 8a and 8b, is linked to the traction unit 3 to be pulled thereby along the rope 4. The current collector unit 6 has a current collector in sliding contact with the collector cables 5. 
     As best seen in FIG. 3, a ball joint 28 is rigidly attached to the frame 7a of the front traction unit 2 at a location spaced from the rope 4 to the right, viewing along a forward direction of the vehicle, by a distance b, whereas another ball joint 29 to the frame 7b of the rear traction unit 3 at a location spaced from the cable 4 to the left by a distance d. These ball joints 28 and 29 are linked by a rod 30. 
     A tension spring 31 has one end anchored to the frame 7a of the front traction unit 2 and an opposite end anchored to the rod 30. This tension spring arrangement prevents the traction units 2 and 3 from rotating about their swivel pins 22a and 22b, which otherwise would occur when the vehicle is not in motion owing to the fact that the centers of gravity of the front and rear traction units 2 and 3 are disposed outside of the plane including the center of the rope 4 and the center of gravity G 3  of the vehicle, and also prevents rattling of the supporting wheels 10a and 10b during operation of the vehicle. 
     A shock absorber 32 has one end linked to the frame 7b of the rear traction unit 3 and an opposite end to the rod 30 to prevent rattling of the supporting wheels 10a and 10b during operation of the vehicle. A shock absorber may have one end attached to the connecting beam 21 and an opposite end to the rod 30, if desired. 
     The vehicle constructed as described above operates as follows: 
     When, in operation, the vehicle accelerates, the front traction unit 2 and the rear traction unit 3 tend to rotate about their respective swivel pins 22a and 22b in a counter clockwise direction (viewing in FIG. 3). A moment at the center of gravity G 1  is denoted by M 1 , whereas a moment at the center of gravity G 2  by M 2 . The moment M 1  is substantially equal in its quantity to moment M 2 . These rotational movements occur because the center of gravity G 1  of the front traction unit 2 is spaced to the left from the rope 4 (as viewing along the rope 4 forwardly) by e (viewing FIG. 3) and forwardly from the axis k 1  by f, whereas the center of gravity G 2  of the rear traction unit 3 is spaced to the left from the rope 4 by e and rearwardly from the axis k 2  by f (viewing FIG. 1). These moments, however, are offset by the cross rod 30 thus preventing the tendency of the traction units 2 and 3 to rotate about their swivel pins k 1  and k 2 . 
     When the vehicle decelerates, the moments equal in quantity to each other but in a clockwise direction (viewing in FIG. 3) will occur. These moments are balanced by the cross rod 30. 
     In practice, the width of grooves of the supporting wheels 10a and 10b are great enough to allow the traction units 2 and 3 to rotate about their swivel pins 22a and 22b by a small angle of approximately 2 degrees. As a result the moment M 1  and the moment M 2  become different as the traction units 2 and 3 rotate, but this difference is negligible. 
     The shock absorber 32 mounted between the cross rod 30 and the traction unit 3 serves as a semi damper to prevent rattling of the traction units 2 and 3, thus improving running stability of the vehicle. For this purpose, a compression spring 31 may interconnect the rod 30 and the traction unit 2 instead of the shock absorber. 
     The locations on the frames at which both ends of the rod 30 are so determined as to offset the momenta on the traction units which would occur upon acceleration or deceleration of the vehicle. Thus, if the distance of the center of gravity G 1  of the traction unit 2 is different from the center of gravity G 2  of the traction unit 3, the moments can be offset by suitably selecting the location on the frames 7a and 7b at which the ends of the rod 30 are attached. 
     The tension spring 31 can be eliminated if the swivel pins are arranged vertically. 
     In order to prevent the excessive slip of a rear supporting wheel 10b when the vehicle runs from a straight portion of the cable to a curve thereof or from a curve to a straight due to rod connection between the forward and rearward traction units 2 and 3, curvature of a curve of the rope 4 and the width of the groove of each supporting wheel are adequately determined. 
     Referring to the embodiment shown in FIG. 4, in which like reference numerals or characters used in the embodiment shown in FIGS. 1 to 3 are used to designate like parts, the rod 30 and the shock absorber 32 used in the preceding embodiment are replaced by a shock absorber 33 interconnecting front and rear traction units 2 and 3. 
     With this arrangement, the shock absorber 33 acts as a rigid rod upon acceleration or deceleration of the vehicle, but will act as a damper upon normal cruising of the vehicle. 
     The effects accomplished by the present invention are: 
     (1) Rotational movements of the traction units which would otherwise occur upon acceleration or deceleration of the vehicle are prevented because the moments M 1  and M 2  are balanced by the rod or absorber, thus improving running stability of the vehicle. 
     (2) The shock absorber linked between the traction units serves both as a rod and a damper.