Motion control system for reel to reel web transport apparatus

• US 4,801,853 A
• Filed: 11/16/1987
• Issued: 01/31/1989
• Est. Priority Date: 11/16/1987
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Anderson, Richard, Lewis, Martyn
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): MARTIN, DAVID S
• Application Number:
  US07/121,200
• Time in Patent Office: 442 Days
• Field of Search: 318/3-7, 318/54-56, 318/59-60, 318/65, 318/87, 242/75, 242/75.2, 242/75.4, 242/75.43, 242/75.44, 242/75.5, 242/75.51, 242/75.47, 242/201-205
• US Class Current: 318/7
• CPC Class Codes: G11B 15/43 Control or regulation of mechanical tension of record carrier, e.g. tape tension
• CPC Class Codes: G11B 15/50 by mechanical linkage, e.g. clutch

Abstract

A motion control system for a reel to reel web transport apparatus which maintains a controlled tension on a web as it is transported between reels. The motion control system includes brushless direct current motors directly coupled each reel. A magnetic hysteresis brake is coupled to each reel by means of respective one-way clutches. During transport of the web from reel to reel, a magnetic hysteresis brake applies a controlled torque only to the reel supplying web. Thus, a controlled tension is maintained on the web at all times, even during loss of power to the DC motors.

Claims

1. In web transport apparatus for transporting a web between first and second reels, a motion control system comprising:

first and second brushless direct current (DC) motors respectively coupled to said first and second reels;

a first rotatably mounted magnetic hysteresis brake;

a second rotatably mounted magnetic hysteresis brake;

first clutch means for coupling said first magnetic hysteresis brake to said first reel when said first reel is rotated in a first direction, said coupled brake applying a controlled torque to said first reel thereby effecting a controlled tension on said web as it is transported from said first reel to said second reel, and for uncoupling said first magnetic hysteresis brake from said first reel when said first motor rotates said first reel in a direction opposite to said first direction so that said first brake applies no torque to said first reel as web is transported onto said first reel;

second clutch means for coupling said second magnetic hysteresis brake to said second reel when said second reel is rotated in a first direction, said coupled brake applying a controlled torque to said second reel, thereby effecting a controlled tension on said web as it is transported from said second reel to said first reel, and for uncoupling said second magnetic hysteresis brake from said second reel when said second motor rotates said second reel in a direction opposite said first direction, so that said second brake applies no torque to said second reel as web is transported onto said second reel; and

including a first Hall device assembly mounted on said first brushless direct current motor and a second Hall device assembly mounted on said second brushless direct current motor, wherein said first and second Hall device assemblies produce respective motor control signals which are used to control both the commutation and servo voltage control of said respective first and second brushless direct current motors.

2. In magnetic tape transport apparatus for transporting magnetic tape between first and second reels past a magnetic head assembly, a magnetic tape motion control system comprising:

a first brushless direct current motor connected to said first reel;

a second brushless direct current motor connected to said second reel;

a first magnetic hysteresis brake;

a second magnetic hysteresis brake;

a first one way clutch coupled between said first magnetic hysteresis brake and said first reel;

a second one way clutch coupled between said second magnetic hysteresis brake and said second reel;

control means for actuating said second motor to rotate said second reel in a direction to transport magnetic tape onto said second reel from said first reel such that said first one way clutch couples said first hysteresis brake to said first reel to apply a controlled torque to said first reel to effect a controlled tension on said magnetic tape as it is transported from said first reel onto said second reel and for actuating said first motor to rotate said first reel in a direction to transport magnetic tape onto said first reel from said second reel, such that said second one way clutch couples said second hysteresis brake to said second reel to apply a controlled torque to said second reel to effect a controlled tension on said second reel to effect a controlled tension on said tape as it is transported from said second reel onto said first reel; and

wherein said first motor includes a first Hall device assembly for producing first Hall signals and wherein said second motor includes a second Hall device assembly for producing second Hall signals and wherein said control means receives said first and second Hall signals from said Hall device assemblies and as a function of said Hall signals, produces both commutation control signals and servo voltage signals to control said first and second motors.

3. The system of claim 2 wherein said first motor is directly connected to said first reel by a first shaft assembly and wherein said first one way clutch directly couples said first hysteresis brake to said first reel by means of said first shaft assembly and wherein said second motor is directly connected to said second reel by a second shaft assembly and wherein said second one way clutch directly couples said second hysteresis brake to said second reel by means of said second shaft assembly.

4. In web transport apparatus for transporting a web between first and second reels, a motion control system comprising:

a first brushless direct current (DC) motor including a stator having a plurality of motor windings and a permanent magnet rotor coupled to said first reel;

first Hall device means, mounted on said stator of said first motor for producing, in response to rotation of said permanent magnet rotor of said first motor, first Hall signals which are representative of the rotational position and rotational speed of said rotor;

a second brushless DC motor including a stator having a plurality of motor windings and a permanent magnet rotor coupled to said second reel;

second Hall device means mounted on said stator of said second motor for producing, in response to rotation of said permanent magnet rotor of said second motor, second Hall signals which are representative of the rotational position and rotational speed of said rotor;

control means for producing, in response to said first and second Hall signals, servo voltage signals and commutation signals which are selectively applied to said motor windings of said first and second motors to control the rotation of said respective rotors of said motors and thereby the transport of said web between said first and second reels;

a first magnetic hysteresis brake;

first one-way clutch means for coupling said first magnetic hysteresis brake to said first reel only when said first reel is rotated in a direction to transport web from said first reel to said second reel;

a second magnetic hysteresis brake; and

second one-way clutch means for coupling said second magnetic hysteresis brake to said second reel only when said second reel is rotated in a direction to transport web from said second reel to said first reel.