Claims
- 1. In a changeable sign, apparatus for positioning a plurality of display devices in individually selectable rotative positions, a common drive shaft for all of said devices, a reversible motor connected with the drive shaft, a separate clutch means for each device adapted to be engaged for coupling the respective device to the drive shaft, selector means for producing a desired position signal for each device, shaft position encoding means connected with said drive shaft and adapted to produce a shaft position signal, motor control means connected with the shaft position encoding means for energizing the motor in a reverse direction to drive each device to a home position and energize it in a forward direction when the home position is reached, said encoded means being connected with said selector means to cause the selector means to produce a command signal when the shaft position signal bears a predetermined relation to the desired position signal for each device, clutch control means connected with the clutches and the selector means and being responsive to the command signals for selectively engaging each of the clutch means to couple the respective devices to the shaft during shaft displacement corresponding to the rotational distance between the home position and the desired position for the respective device.
- 2. The invention as defined in claim 1 wherein said clutch means includes an input member connected with said shaft and an output member connected with said device, clutch operating means for coupling the input member with the output member when the operating member is actuated, said operating member including means for braking said output member when the operating member is deactuated, said clutch operating means being connected with said clutch control means for actuation in response to a command signal.
- 3. The invention as defined in claim 2 wherein said clutch means includes an auxiliary clutch operating means for coupling the input member to the output member while said motor is energized in a reverse direction.
- 4. The invention as defined in claim 3 wherein said auxiliary clutch operating means includes memory means connected with said drive shaft while said operating member is deactuated for counting the shaft revolutions when the output member is being braked and including means for coupling said input member to said output member when the shaft is rotated in a reverse direction by a number of revolutions in excess of the number stored in said memory means.
- 5. The invention as defined in claim 1 wherein said clutch means comprises a differential gear set having an input gear connected with said drive shaft, an output gear connected with said device and a control gear, said operating member including means for braking the control gear when actuated and thereby coupling the input member to the output member, said operating member including means for braking said output gear when deactuated.
- 6. The invention as defined in claim 5 wherein said differential gear set is a planetary gear set with a sun gear being said input gear, a planetary gear being said output gear and a ring gear being said control gear.
- 7. The invention as defined in claim 6 including a fixed member, and a rotary lost motion connection between said ring gear and said fixed member whereby the lost motion connection is extended while the planetary gear is braked with the motor energized in the forward direction and the lost motion connection is retracted when the planetary gear is braked with the motor running in the reverse direction so that the lost motion connection brakes the ring gear and connects the sun gear with the planet gear, after the lost motion is taken up, to drive the respective device to its home position.
- 8. The invention as defined in claim 7 wherein said operating member comprises a latch member having a first latch element engageable with said planetary gear carrier at discrete angular positions thereof, a second latch element engageable with the ring gear at discrete angular positions thereof, and actuating means for causing one of the latch elements to be engaged and the other latch element to be disengaged and for alternately causing said other latch element to be engaged and said one latch element to be disengaged.
- 9. The invention as defined in claim 8 wherein said latch member comprises a body pivotally mounted on said fixed member and said first and second latch elements comprise first and second rollers rotatably mounted on said body on opposite sides of the pivot axis thereof, said planetary gear carrier having plural detent notches equally spaced around the circumference thereof, each being adapted to receive said first roller, said ring gear carrier having a plurality of detent notches equally spaced around the circumference thereof, each adapted to receive said second roller.
- 10. The invention as defined in claim 9 wherein said lost motion connection comprises a stack of dog washers.
- 11. The invention as defined in claim 2 wherein said encoding means comprises a plurality of conductive elements corresponding to discrete rotative positions of said shaft and means for applying a voltage to the element which corresponds to the existing position of the shaft, said motor control means being connected with selected ones of said conductive elements.
- 12. The invention as defined in claim 11 wherein said selector means comprises a set of switches corresponding to each of said clutch means, there being a number of switches in each set equal to the number of said conductive elements with each switch of a set being connected with a different one of said conductive elements, all of said switches in a set being connected with said clutch control means for the respective clutch, and means for selectively actuating said switches according to the desired position for the respective device to actuate the respective clutch when the shaft reaches a predetermined rotative position.
- 13. The invention as defined in claim 12 including disabling means connected with said motor control means and said clutch control means for disabling the clutch control means when said motor is energized in a reverse direction.
- 14. The invention as defined in claim 2 wherein said encoding means is a commutator having a plurality of commutator segments and a slip ring, a voltage source connected with said slip ring, an armature driven by said drive shaft with a first brush engaging said slip ring and a second brush engaging said commutator segments.
- 15. The invention as defined in claim 14 wherein said selector means comprises a punch card reader.
- 16. The invention as defined in claim 12 wherein said motor control means is a logic circuit having one input connected with the conductive element of the encoding means which corresponds with the rest position of said shaft and another input connected with the conductive element which corresponds with the home position of said shaft.
- 17. The invention as defined in claim 15 wherein the motor control means is a logic circuit having one input connected with the commutator segment corresponding to the rest position of the shaft and another input connected with the commutator segment corresponding to the home position of said shaft and a start switch in said card reader for energizing the motor control circuit when a punch card is inserted.
- 18. The invention as defined in claim 2 wherein said clutch control means comprises a solenoid connected with said clutch operating member and switching means connected between the selector means and the solenoid.
- 19. The invention as defined in claim 18 wherein said switching means is a silicon controlled rectifier.
- 20. The invention as defined in claim 11 wherein said means for applying the voltage comprises a pulse generator operated synchronously with rotation of said shaft.
- 21. The invention as defined in claim 20 wherein said pulse generator comprises a magnet operated switch and a magnet mounted on said shaft for rotation therewith to operate the magnet operated switch.
BACKGROUND OF THE INVENTION
This is a continuation-in-part of patent application Ser. No. 547,081 filed Feb. 4, 1975, now abandoned.
Automatically changeable printed signs of the roller curtain type are used notably for destination signs on buses and trains. In this application a printed opaque display is preferred because of its readability under widely varying conditions of ambient light. Destination signs must be changeable according to the particular route of the vehicle and each sign must be capable of displaying a large number of different destination names. A typical destination name may require forty or more alphanumeric characters and the sign must be changeable quickly from one name to another.
In the past, destination signs have taken the form of a roller curtain wide enough to accommodate the requisite number of characters and long enough to hold a full set of destination names required for a given transit vehicle. One difficulty with this type of destination sign is that the roller curtains must be printed with a special set of destination names, according to the route of the vehicle on which it is to be used. This requires printing of a large number of different destination signs for each metropolitan area.
A universal destination sign has been developed in which any alphanumeric destination name may be displayed by forming any desired alphanumeric character in any one of plural window areas. Identical sets of printed roller tapes are used for each window area with each set being capable of displaying any desired character by properly positioning the tapes of the set. The individual tapes of a set carry plural segments of different characters and the tapes of the set must be positioned relative to each other such that all segments of a given character may be displayed together. This sign is truly universal in that it utilizes a broken-character, broken-word arrangement and has the advantage of being able to form any combination of characters with the use of relatively short display tapes. Such a destination sign is disclosed and claimed in copending patent application Ser. No. 546,696 filed Feb. 3, 1975 by William H. Saylor and James O. Narey and entitled Changeable Information Display.
Such a broken-character, broken-word destination sign requires individual positioning of each set of tapes to form the character to be displayed in the respective window area. In order to change the sign quickly, all sets of tapes must be reset concurrently as opposed to the time consuming procedure of resetting them one after the other. Because of the broken character arrangement, precise positioning of each set of tapes is required to faithfully reproduce each character.
The prior art includes automatic positioning systems for alphanumeric, changeable printed signs, such as that shown in the Dozer U.S. Pat. No. 3,582,937. In the system of the Dozer patent, a single tape is provided in each window area and carries a full set of alphanumeric characters each shown in its entirety. All of the tapes are selectively movable independently of each other to display one of the characters on the respective tapes. This sytem uses a separate drive motor for each of the tapes and the positioning is achieved by a closed loop system.
According to this invention, a changeable, alphanumeric printed display is provided with automatic individual positioning of plural character displays in a concurrent manner by means of a common motor and shaft. In general, this is accomplished by means of an open-loop positioning system with each character display positioned through a separate clutch means controlled by individual command signals.
The positioning apparatus comprises a common drive shaft and a reversible motor for all of said devices with separate clutch means adapted to couple the respective devices to the shaft. A selector means produces a desired position signal for each display device and a shaft position encoding means connected with the drive shaft produces a shaft position signal. Motor control means, respective to the encoding means, energizes the motor in a reverse direction to drive each display device to a home position and energizes it in a forward direction when the home position is reached. The encoding means is connected with the selector means to produce a command signal when the shaft position signal bears a predetermined relation to the desired position signal for each device. Clutch control means is responsive to the command signals for selectively engaging each of the clutch means to couple the display devices to the shaft during shaft displacement corresponding to the rotational distance between the home position and the desired position for the respective device.
Further, according to this invention, the clutch means is operative to drive its respective display device from its home position to its selected position and to hold it there; it is also operative to drive the display device for resetting it from its previously selected position to its home position. This is accomplished by a clutch means in the form of a differential device having an input member connected with the shaft, an output member connected with the display device and a control member which is operative to effect coupling or decoupling of the input and output members. The control member is actuated by a primary operating member for use in setting the display device to its selected position and by a secondary operating member for use in resetting the display device. Preferably, the clutch means takes the form of a planetary gear set; the primary operating member is a solenoid actuated latch and the secondary operating member is a variable limit stop.
US Referenced Citations (5)
Continuation in Parts (1)
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547081 |
Feb 1975 |
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Patent Grant
4064502
