Printer system ribbon drive having constant ribbon speed and tension

A system for driving an elongated web member comprising the combination of:

• a pair of rotatable reel members;
• an elongated web member extending between and having the opposite ends thereof wound on opposite ones of the pair of rotatable reel members;
• a pair of DC motors, each coupled to a different one of the pair of rotatable reel members;
• and
• circuit means coupled to the pair of DC motors to energize the DC motors and including common junction means, a pair of constant voltage sources, a pair of servo circuits, each of which includes a different one of the pair of DC motors and is coupled between the common junction means and a different one of the pair of constant voltage sources and is operative when actuated to produce a current through the included DC motor which maintains the voltage at the common junction means substantially constant, and means for alternately actuating the pair of servo circuits, and wherein each of the pair of DC motors has a pair of terminals and each servo circuit includes a differential amplifier having an output coupled to one of the pair of terminals of the included DC motor and a pair of inputs, one input of which is coupled to one of the pair of constant voltage sources, means coupling the other one of the pair of terminals of the included DC motor to the common junction means, first resistor means coupled between the common junction means and the other one of the pair of inputs of the differential amplifier, and second resistor means coupled between the output and the other one of the pair of inputs of the differential amplifier.

A system for driving an elongated web member comprising the combination of;

• a pair of rotatable reel members;
• an elongated web member extending between and having the opposite ends thereof wound on opposite ones of the pair of rotatable reel members;
• a pair of DC motors, each coupled to different one of the pair of rotatable reel members;
• and
• circuit means coupled to the pair of DC motors to energize the DC motors and including common junction means, a pair of constant voltage sources, a pair of servo circuits, each of which includes a different one of the pair of DC motors and is coupled between the common junction means and a different one of the pair of constant voltage sources and is operative when actuated to produce a current through the included DC motor which maintains the voltage at the common junction means substantially constant, and means for alternately actuating the pair of servo circuits, and wherein the circuit means includes means responsive to an increase in voltage at the common junction means for signaling a run-away condition for the elongated web member.

A system for driving an elongated web member comprising the combination of;

• a pair of rotatable reel members;
• an elongated web member extending between and having the opposite ends thereof wound on opposite ones of the pair of rotatable reel members;
• a pair of DC motors, each coupled to a different one of the pair of rotatable reel members;
• and
• circuit means coupled to the pair of DC motors to energize the DC motors and including common junction means, a pair of constant voltage sources, a pair of servo circuits, each of which includes a different one of the pair of DC motors and is coupled between the common junction means and a different one of the pair of constant voltage sources and is operative when actuated to produce a current through the included DC motor which maintains the voltage at the common junction means substantially constant, and means for alternately actuating the pair of servo circuits, and wherein the circuit means includes means responsive to a decrease in voltage at the common junction means for signaling a loose hub condition for the elongated web member.

A system for driving an elongated web member comprising the combination of:

• a pair of rotatable reel members;
• an elongated web member extending between and having the opposite ends thereof wound on opposite ones of the pair of rotatable reel members;
• a pair of DC motors, each coupled to a different one of the pair of rotatable reel members;
• and
• circuit means coupled to the pair of DC motors to energize the DC motors and including common junction means, a pair of constant voltage sources, a pair of servo circuits, each of which includes a different one of the pair of DC motors and is coupled between the common junction means and a different one of the pair of constant voltage sources and is operative when actuated to produce a current through the included DC motor which maintains the voltage at the common junction means substantially constant, and means for alternately actuating the pair of servo circuits, and wherein the circuit means includes means responsive to a decrease in the voltage in either one of the pair of servo circuits at the side of the included DC motor opposite the common junction means for signaling a jam condition for the elongated web member.

In an impact printer system, the combination of:

• a platen;
• means for disposing a printable medium against the surface of the platen;
• an elongated ink ribbon having a portion thereof disposed adjacent and on the opposite side of the printable medium from the platen;
• a hammer bank mechanism mounted adjacent said portion of the ribbon on the opposite side of the ribbon from the printable medium and the platen, the hammer bank mechanism being capable of undergoing reciprocating motion relative to the printable medium and the platen and including a plurality of hammers for impacting the ribbon and the printable medium against the platen;
• a pair of rotatable reels receiving the opposite ends of the ribbon, the amounts of the ribbon wound around the reels defining ribbon packs which vary in complementary fashion;
• a pair of motors, each being coupled to a different one of the pair of reels;
• and
• means coupled to the pair of motors for energizing the motors to drive the ribbon between the pair of reels at substantially constant speed and substantially constant tension independent of varying ribbon packs on the pair of reels, said means including constant voltage source means coupled to each of the pair of motors, common junction means coupled to each of the pair of motors opposite the constant voltage source means and a pair of servo circuits, each of which is coupled to a different one of the pair of motors and to the common junction means and is operative to be activated only when the motor to which the servo circuit is coupled is acting as a supply reel motor and to cause a current to flow through the motor to which the servo circuit is coupled and into the common junction means to maintain the voltage at the common junction means substantially constant, and wherein the motors comprise DC permanent magnet motors and the means for energizing includes means for maintaining the sum of currents through the pair of motors substantially constant.

An arrangement for driving a pair of ribbon holding reels in an impact printer, the reels having a determinable torque-speed characteristic which will produce substantially constant ribbon speed and tension, the arrangement comprising:

• a pair of motors, each being operative to drive a different one of a pair of reels in the impact printer and having a torque-speed characteristic substantially like a torque-speed characteristic which will produce substantially constant ribbon speed and tension in the impact printer;
• and
• means coupled to the pair of motors to energize the motors and including common junction means coupled to each of the pair of motors, means for providing a first current through a first one of the pair of motors chosen to operate as a takeup motor, the first current flowing through the first motor and the common junction means from a first constant voltage source and providing a given voltage drop across the first motor, and means for providing a second current through a second one of the pair of motors chosen to operate as a supply motor, the second current being determined by the voltage at the common junction means, the second current flowing through the second motor and the common junction means and maintaining the voltage at the common junction means substantially constant and thereby the given voltage drop across the first motor constant, the means for providing a first current comprising the first source of constant voltage coupled to the first motor opposite the common junction means and the means for providing a second current comprising a second source of constant voltage and a servo circuit coupled between the second source of constant voltage and the second motor and operative to vary current through the second motor in accordance with the voltage at the common junction means to maintain the voltage at the common junction means substantially constant.

An arrangement for driving a pair of ribbon holding reels in an impact printer, the reels having a determinable torque-speed characteristic which will produce substantially constant ribbon speed and tension, the arrangement comprising:

• a pair of motors, each being operative to drive a different one of a pair of reels in the impact printer and having a torque-speed characteristic substantially like a torque-speed characteristic which will produce substantially constant ribbon speed and tension in the impact printer;
• and
• means coupled to the pair of motors to energize the motors and including common junction means coupled to each of the pair of motors, means for providing a first current through a first one of the pair of motors chosen to operate as a takeup motor, the first current flowing through the first motor and the common junction means from a first constant voltage source and providing a given voltage drop across the first motor, and means for providing a second current through a second one of the pair of motors chosen to operate as a supply motor, the second current being determined by the voltage at the common junction means, the second current flowing through the second motor and the common junction means and maintaining the voltage at the common junction means substantially constant and thereby the given voltage drop across the first motor constant, the motors comprising DC motors and the means coupled to energize the pair of DC motors comprising the first constant voltage source and a second constant voltage source, a common current path coupled to the common junction means, means coupling one of the pair of DC motors between the common current path and the first constant voltage source and servo means coupling the other one of the pair of DC motors between the common current path and the second constant voltage source, the servo means being operative to produce sufficient current in the other one of the pair of DC motors so as to maintain the voltage at the common current path substantially constant.

An arrangement for driving a pair of ribbon holding reels in an impact printer so as to maintain substantially constant ribbon speed and tension comprising:

• first and second DC motors, each having first and second terminals and operative to drive a different one of a pair of reels in an impact printer;
• a common terminal coupled to the first terminal of each of the first and second DC motors;
• a common voltage reference;
• a common resistor coupled between the common terminal and the common voltage reference;
• first and second sources of constant voltage;
• first and second differential amplifiers, each having an output terminal and a pair of differential input terminals, one of the differential input terminals of the first differential amplifier being coupled to the first source of constant voltage, one of the differential input terminals of the second differential amplifier being coupled to the second source of constant voltage, and the output terminals of the first and second differential amplifiers being coupled to the second terminal of the first and second DC motors respectively;
• first and second feedback resistances coupled between the output terminal and the other one of the pair of differential input terminals of the first and second differential amplifiers respectively;
• first and second input resistances coupled to the other one of the pair of differential input terminals of the first and second differential amplifiers respectively;
• and
• first and second switches coupled between the common terminal and the first and second input resistances respectively.