Elevator cab door drive system

The door or doors on an elevator cab are driven during their opening and closing cycles by a linear induction motor drive system. The primary of the linear motor is fixed to the cab assembly, and the secondary is mounted on the door hanger panel and moves with the door. In order for the secondary to maintain a proper spacing relative to the primary, a flexible connection is provided between the secondary and the remainder of the door. In this way, shifting of the door during its opening and closing movements will not cause misalignment of the secondary with respect to the primary.

TECHNICAL FIELD 
This invention relates to an improved elevator door operating system which 
utilizes a linear induction motor to open and close the doors. The primary 
component of the linear motor is secured to the cab, and the secondary 
component is formed by an upper marginal portion of the door which is 
flexibly connected to the remainder of the door. 
BACKGROUND ART 
Elevator cab doors are typically mounted on a track via guide rollers, the 
track being secured to the cab. Door opening and closing motion of the 
door or doors is caused by an electric drive motor which is mounted on the 
cab. The drive motor is a reversible motor which drives one or two sets of 
articulated arms that are pivotally attached to the door or doors. These 
drives are relatively complex assemblages, and require a large number of 
components. These drives also create high levels of stress on the cab due 
to the long levers used to open and close the doors. The reaction forces 
created by flexing the levers tend to cause the drive motor to twist on 
the cab. This reactive twist occurs in both directions, and requires 
reinforced cab structure to stabilize the cab. 
DISCLOSURE OF THE INVENTION 
This invention is directed to a linear induction motor elevator cab door 
drive assembly which includes a primary winding component which is fixed 
to the cab (there being one primary component to each door panel in an 
opposite opening and closing door system). The secondary component of the 
linear motor is disposed on the upper marginal portion of the doors being 
driven by the respective primaries. The secondary component is attached to 
the remainder of the door panel by means of a flexible joint, preferably a 
piano-type hinge joint. The motor secondary component is disposed above 
the door hanger panels on which the door guide rollers are mounted. The 
hanger panel and the remainder of the door are rigidly connected to each 
other. The flexible connection between the secondary panel and the 
remainder of the door ensures that the proper positioning of the secondary 
relative to the primary will be maintained during opening and closing 
movement of the doors. Without the flexible connection between the 
secondary panel and the remainder of the door, forward and backward motion 
of the door which may be caused by deviations in the position of the 
roller guide track, or by deviation in the position of the door sill guide 
channel can disrupt the delicate primary/secondary positioning needed to 
ensure proper operation of the linear motor drive assembly. 
It is therefore an object of this invention to provide an elevator cab door 
drive which employs a linear induction motor for supplying motive drive to 
the doors during the opening and closing motion on the elevator cab. 
It is a further object of this invention to provide a door drive of the 
character described which significantly reduces door drive-induced cab 
stress so as to allow cab structures which do not need to be unduly 
reinforced. 
It is another object of this invention to provide a door drive of the 
character described which ensures proper primary-secondary spacing during 
opening and closing of the door, irregardless of door oscillations which 
may occur as the doors move between their closed and open positions.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to the drawings, there is shown in FIG. 1 an embodiment of 
the linear motor door drive and door mounting system of this invention. 
The cab door 2 includes a hanger panel 4 on which the door guide rollers 6 
are mounted. The rollers 6 move back and forth over the upper surface 8 of 
a guide track 10 which is secured to a header beam 12 which is mounted on 
the cab 14 above the cab entrance 16 (shown in phantom). 
The linear motor door drive assembly is denoted generally by the numeral 
18. The door drive assembly 18 includes a primary assembly denoted 
generally by the numeral 20 which is fixedly mounted on the cab header 
beam 12, and a movable secondary 22 which is a sheet of a conductive 
metal, preferably copper. The secondary 22 is flexibly connected to the 
door hanger panel 4 by means of a hinge mount 24. The hinge mount 24 is 
preferably a piano type hinge but may also be a continuous flexible 
plastic or metallic strip. 
As shown in FIG. 2, the primary assembly 20 includes a clamshell housing 26 
which has opposed end walls 28 with openings 30 through which the 
secondary 22 passes. The openings 30 have arched upper surfaces 32 which 
aid in resisting the normal forces exerted on the housing 26 by the 
primary assembly 18. The primary assembly 18 includes a primary winding 
component 34 which is disposed inside of the housing 26, and a fixed 
magnetic backiron component 36 which completes the electromagnetic flux 
path through the copper secondary 22. The secondary 22 will be thrust in 
either direction (door-closing, or door-opening) depending on the 
direction of current flow through the primary assembly 18. 
In the event that the path of the guide track 10 or the door sill guide 
(not shown) deviates from a straight opening/closing line, the door 
assembly, i.e., the hanger panel 4, and door 2 can pivot about the hinge 
24 to the positions 2' 2" and 4', 4" (which are illustrated in exaggerated 
fashion in FIG. 2) without causing a significant deflection of the copper 
secondary panel 22 relative to the primary winding 34 and magnetic 
backiron 36. 
The flexible connection between the door and the linear motor secondary 
allows the drive system to operate efficiently even when door guidance 
components are misaligned and deviate from a straight door opening and 
closing line of motion. 
Since many changes and variations of the disclosed embodiment of the 
invention may be made without departing from the inventive concept, it is 
not intended to limit the invention otherwise than as required by the 
appended claims.