US 4,812,858 AGranted

Indexing mechanism

AssigneeEnter Computer, Inc.

InventorRichard A. Murray

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Abstract

The present invention comprises a mechanism for incrementally rotating a plotter carousel holding a plurality of pens around its perimeter. The rotational increments of the carousel are spaced to present any of the plurality of pens to a drawing arm on the plotter, or other graphics. A non-servo, non-stepper electric motor, such as a DC motor commonly used in slot cars, provides the rotational power to rotate the carousel. A control device switches the motor on or off with an output connected to the base of a driver connected between the power supply and the motor. The motor, when on, rotates an incremental indexing mechanism that in turn rotates the carousel in increments, each increment being a fraction of one full rotation. A switch is provided which detects that the carousel has been rotated one increment. This switch is connected to the control device, and, depending upon whether or not the desired pen is at the transfer point, the control device accordingly either switches off the motor or advances the carousel to the desired increment. Thus, the present invention uses event feedback to control the carousel. The event that the carousel has rotated one increment is this feedback.

Claims13

Dependent claims

An apparatus comprising:

a carousel in a plotter or other graphics mechanism, the carousel holding a plurality of pens, the carousel rotating about a carousel axle incrementally to present any of the plurality of pens to a drawing arm at a transfer position;
an electric power supply;
a control device;
a motor, responsive to the control device, said motor including a rotor shaft;
a geneva arm having a post end and a curved end;
a geneva axle connected to the geneva arm, so that the post end and the curved end rotate about the axis of rotation of the geneva axle, said geneva axle being connected to the rotor shaft so that the geneva arm rotates in response to rotation of the rotor shaft;
a geneva sprocket connected to the carousel, said geneva sprocket having a perimeter including a plurality of first surfaces for slidable contact with the post and a plurality of second surfaces for slidable contact with the curved surface of the geneva arm so that the carousel is maintains one of the plurality of pens at the transfer position when the geneva arm rotates while its curved surface contacts said second surface;
a switch for detecting the presence of the geneva arm at a predetermined angle of rotation of the geneva arm about the geneva axle, said switch producing an output signal which is applied to the control device, said predetermined angle being selected so that if the drive means is switched off after detection, the rotating geneva arm will coast to a stop without substantially affecting the position of the carousel.

5 more elements

An apparatus comprising:

a rotatable carousel in a plotter or other graphics mechanism, said carousel having a plurality of incremental angular positions;
a control device;
a motor responsive to the control device, the inertia of the rotor and rotor shaft of which causes said rotor to continue to spin after the removal of driving electric power from said motor;
an actuator connected to said motor, said actuator being rotatable in response to said motor;
one complete revolution defining a first angle wherein the carousel remains stationary and a second angle wherein the carousel if rotating;
means for maintaining the plotter carousel at one of a plurality of incremental positions while the actuator is rotating throughout the first angle;
means, connected to the motor, for rotating the carousel between the incremental positions while the actuator is rotating through the second angle;
a switch positioned within the arc of the first angle, thereby providing an output signal for detecting an event that said means for rotating the carousel has completed movement of the carousel by an incremental amount, the timing of said output signal being such that the control device has sufficient time to switch off power to the motor, subsequent to which the rotor and rotor shaft can coast to a stop while the actuator remains within the bounds of the first angle.

5 more elements

Dependencies are inferred from the claim text.