Drive system

A mechanical power conversion device for receiving rotary power from a rotary power supply and delivering two independent power outputs, the conversion device having: a drive screw connectable to the rotary power supply, a drive nut engaging the drive screw to receive a drive nut axial force and drive nut torsion therefrom, the drive nut axial force being parallel to the drive screw and the drive nut torsion being about an axis of the drive screw. One of the two independent power outputs is connected to the drive nut to receive the drive nut axial force and the second is connected to the drive nut to receive the drive nut torsion so that power from the rotary power supply flows to either or both of the first independent power output and the second independent power output.

BRIEF DESCRIPTION OF THE PRESENTLY PREFERRED AND VARIOUS ALTERNATIVE EMBODIMENTS OF THE INVENTION Attention is now directed to FIG. 1 , with reference to FIGS. 2 and 3 . A door operator 10 for a transit vehicle door drive, which is the presently preferred embodiment of the invention is illustrated in these figures. Door operator 10 has a carriage 20 mounted for movement on frame 12 by carriage rollers 21 . A curved track member 14 having a curved track 15 is connected to frame 12 . Frame 12 and curved track member 14 are stationary with respect to the transit vehicle. Carriage 20 , which carries the other components shown, moves in and out of an opening (not shown) in a sidewall (not shown) in a transit vehicle (not shown). Additional general features include drive gear assembly 30 , left drive nut assembly 40 L and right drivenut assembly 40 R. A motor 16 is mounted on a motor base 17 , which is mounted on carriage 20 . (This connection is not shown). Motor 20 drives motor pinion 18 , which engages drive gear 32 . Drive gear 32 is captured between left drive screw 52 L, which has a right hand thread and right drive screw 52 R, which has a left hand thread. Drive gear 32 is mounted on a deep groove ball bearing (not shown) around independently rotating center 34 . Drive nut assembly 40 L engages left drive screw 52 L to receive axial force and torsion therefrom. Drive nut assembly 40 R engages right drive screw 52 R to receive axial force and torsion therefrom. A right door panel (not shown) is supported on right hanger bracket 23 R. A left door panel (not shown) is supported on left hanger bracket 23 L. In FIG. 3 , it can be seen that 23 R is situated above 23 L. Left hanger bracket 23 L is supported by linear bearing 24 L on the lower support rod, 25 L. The right hanger bracket 23 R is supported by linear bearing 25 R on the upper support rod, 25 R. Linear bearing 24 L has a flat surface 26 L to which a drive nut fork (not shown) is attached. This drive nut fork engages right drive nut housing 42 R to communicate axial forces to linear bearing 24 L to move the left door panel (not shown). A similar flat surface (not shown) on linear bearing 24 R carries a drive nut fork (not shown) engaging left drive nut housing 42 L to communicate axial forces to linear bearing 24 R to move the right door panel (not shown). The Left partial length semicircular tube 44 L and left full length semicircular tube 45 L pass through semicircular cuts in left drive nut housing 42 L to receive torsion from the left drive nut (not seen, inside left drive nut assembly 40 L). Likewise, the right partial length semicircular tube 44 R and right full length semicircular tube 45 R pass through semicircular cuts in right drive nut housing 42 R to receive torsion from the right drive nut (not seen, inside right drive nut assembly 40 R). Semicircular tubes 44 L and 44 R communication torsion to left pinion 46 L, which engages left unplug gear 47 L. A left overcenter link 40 L connected to left unplug gear 47 L to move carriage 20 in and out of the transit vehicle wall (not shown). Since 48 L is an overcenter link, it provides for locking the doors in closed positions. Similarly, semicircular tubes 44 R and 45 R exert torsion on a pinion 46 R (not shown) which engages unplug gear 47 R. Torsion is communicated between semicircular tubes 44 L and 45 L by rollers 49 L on left drive nut assembly 40 L. A similar arrangement for the right drive nut assembly 40 R is now shown. FIGS. 1, 2 and 3 show the system with the doors in a closed position. When motor 16 is first energized to open the doors, rollers for the linear bearings 24 L and 24 R are in the curved end portions of track 15 . This prevents the doors from opening, but allows the carriage 20 to move out of the wall of the transit vehicle. This movement is energized by torsion communicated by the drive nuts to the semicircular tubes, thence to the pinions 46 L and a similar pinion on the right to the unplug gears 47 L and 47 R, which pull on the overcenter link 48 L and a similar link on the right. When the carriage 20 is displaced out of the transit vehicle wall, the rollers in curved track 15 are in the straight portions, the doors move apart. This movement is energized by axial forces communicated from drive nut assemblies 40 L and 40 R to the forks (not shown) attached to surface 26 L on linear bearing 24 L and a similar surface on linear bearing 24 R. An alternative embodiment which, presently, is not preferred is shown in FIGS. 4 and 5 . An alternative mechanism for applying plug/unplug forces to carriage 20 is denoted 50 . Right drive nut assembly 40 R has an eccentric member 54 having a connection 56 . Torsion communicated to the drive nut causes eccentric member 54 to rotate to the position shown in FIG. 5 . This rotation causes connection 56 to move from the right side in FIG. 4 to the left side shown in FIG. 5 . For this embodiment, drive screws 52 L and 52 R do not move with carriage 20 . They are fixed relative to the transit vehicle. Curved link 58 is attached to connection 56 and to second connection 62 which is attached in such a way as to move carriage 20 . That movement is a plug or unplug movement. 
 DESCRIPTION OF PLUG DOOR OPERATOR DRIVE The door operator functions as follows: The drive gear, motor pinion, and motor are all mounted on the motor mount.( FIG. 1 ) The motor pinion drives the main gear, which is captured between the right hand and left hand drive screws. This arrangement evenly distributes the load on each half of the drive screw. Mounted on the gear is a deep groove ball bearing, which takes the radial and thrust loads generated by the drive screw and gear. The drive screw itself is a multi-start, long lead, rolled thread stainless steel screw. The drive screw engages replaceable nut halves, which are located in the nut housing. The nut halves and screw do not require any lubrication. There are two nut housings, each driving its own hanger bracket. In the fully closed and locked position, the nut housings are located at the far ends of the drive screw. The nut housing has a removable end cap ( FIG. 2 ), allowing replacement of the drive nut halves. The end cap captures the drive fork (not shown). The drive fork is the interface between the nut housing and the hanger bracket. It is mounted directly to the hanger bracket and has radial clearance between itself and the nut housing. This eliminates the need for a two-piece pivoting fork. Mounted on the drive nut housing are two housing rollers ( FIG. 2 ), which contact the semicircular tube (full length), providing antirotation for the nut housing. The hanger bracket ( FIG. 2 ) is guided by a roller (not shown) which engages the curved track. When the curved track roller comes into the curved portion of the track, it allows the drive nut housing to rotate. By this time, the housing rollers have engaged the semicircular tube (partial length). The two semicircular tubes are rigidly attached to the hub on which resides a pinion. The drive nut housing rotates the semicircular tube also rotating the pinion. The pinion ( FIG. 1 ) in turn rotates the unplug gear at a ration of 1:6, providing the torque necessary to unplug the system. The unplug gear rotates 1500 while the pinion goes through 2.5 revolutions. Mounted on the unplug gear is an overcenter link. The other side of the link is mounted to the frame (which is stationary with respect to the car structure). The link creates an overcenter lock between the frame and the carriage. When the unplug gear rotates, it effectively pulls itself forward along with the rest of the system. The drive screw and hanger brackets move inboard and outboard together because they are both mounted to the carriage ( FIG. 2 ). The carriage is supported by the carriage rollers ( FIG. 2 ), which roll in the frame. While a presently preferred embodiment for carrying out the instant invention has been set forth in detail in accordance with the Patent Act, those persons skilled in the drive system art to which this invention pertains will recognize various alternative ways of practicing the invention without departing from the spirit and scope of the claims appended hereto.