Live tape position sensor

Abstract

A real-time tape position sensor to accurately determine the location of several consecutive carrier tape pockets in order to pick or place electronic semiconductor devices into or out of a tape pocket. The invention generates an on-going map of the pocket locations by coupling data from a photosensor inspecting between the tape pockets with data from an encoder that records the position of the carrier tape as it moves.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric illustration of a piece of carrier tape with some electronic devices in some pockets.

FIG. 2 is a side view illustration of prior art.

FIG. 3 is a side view of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3 illustrates a preferred embodiment of the present invention. The invention generally comprises a photosensor 6, tape drive wheel 7, tape drive roller 8, tape drive motor 9, tape tension wheel 10, tape tension roller 11, a high-resolution encoder 12, and an electronic processor.

The photosensor 6 is a common thru-beam photosensor that consists of an emitter and a detector. This is an LED based product such as Keyence #FU59. The photosensor has an LED which is constantly on. The LED light travels thru a fiber optic cable to an emit location. A receiving fiber optic cable is positioned opposite the emitter on the opposite side of the tape. This fiber optic cable attaches to an amplifier and circuit which acts as an indicator switch when activated. The photosensor may be retro-reflective. The photosensor may eliminate the fiber optics. Other types of sensors such as a proximity sensor would also work.

The tape drive wheel 7 is a cylindrically shaped wheel made of hard rubber or a similar material. The material could vary. Alternatively a sprocket wheel could be used to drive the tape.

The tape drive roller 8 consists of two coaxial cylindrically shaped rollers made of hard rubber or a similar material. It is used to create an opposing force for the Tape Drive Wheel 7. The material could vary. The rollers straddle the tape pockets and contact the flange of the tape. The distance between the tape drive rollers can be adjusted to accommodate various width tape pockets.

The tape drive motor 9 is an electric motor. This motor could be a stepper motor, a servomotor, a direct current motor or an alternating current motor. Other actuators could also work. The tape drive motor is attached to the tape drive wheel.

The tape tension wheel 10 consists of two coaxial cylindrically shaped wheels made of metal or a similar material. The material could vary. The wheels straddle the tape pockets and contact the flange of the tape. The distance between the tape tension wheels can be adjusted to accommodate various width tape pockets. Alternatively a sprocket wheel could provide tension.

The tape tension roller 11 is a cylindrically shaped roller made of hard rubber or similar material. It is used to create an opposing force for the tape tension wheel. The material could vary.

The tape tension wheel and tape tension roller provide tension on the tape to keep it taught between said components and the tape drive roller and motor.

The high-resolution encoder 12 is a device that attaches to the end of a rotary shaft and electrically outputs data about the rotational location of the shaft. In the preferred embodiment it attaches to the shaft of the tape tension roller 11, but it could attach to any of the aforementioned wheels or rollers.

The electronic processor is a microprocessor that is electronically connected to the high-resolution encoder and the photosensor. It reads the data from the encoder and the photosensor to create a map of tape pocket locations versus encoder data.

The tape is loaded by feeding it around the tape tension wheel 10 and between the tape tension roller 11. The tape tension roller puts pressure against the flange of the tape so that the tape is pinched between the tape tension roller and the tape tension wheel. The tape is further loaded by feeding it between the tape drive wheel 7 and the tape drive roller 8. The tape drive wheel and the tape drive roller are under tension to pinch the tape flange such that when the tape drive wheel rotates under the activation of the electric motor 9, the tape is consequently moved as desired. The section of tape between the tape drive wheel 7 and the tape tension roller 11 remains taut during the operation of the invention.

The high-resolution encoder 12 is attached to the shaft of the tape tension roller so as to measure the rotation of the tape tension roller and thus the movement of the tape. The photosensor 6 is positioned to sense in between pockets after the tape has passed around the tape tension wheel. The high-resolution encoder could be attached to a sprocket wheel that engages the sprocket holes in the tape. The high-resolution encoder could attach to a roller located on the underside of the tape or to one of the other rotational devices that rotates along with the tape movement. The photosenser could be a retroreflective sensor, or a laser sensor, or another type of sensor.

The tape is advanced thru the system by activating the tape drive motor 9. The tape advances in the direction indicated by arrow 16. As the tape moves, photosensor 6 senses the leading and trailing edge of each pocket. When each pocket edge is detected, the high-resolution encoder value is noted via an electronic processor. As tape advances, an accurate map of tape pocket locations relative to encoder values is made. By sensing the leading and trailing edge of each pocket, the exact middle of the pocket can be known by bisecting the edges. This works regardless of the sensitivity setting of the photosensor. Even variations in pocket locations in the tape can be compensated for (i.e. pocket pitch variations). By querying a current value from the encoder at any time, an electronic processor can determine the current middle location of pockets accessible to the pick-n-place that recently passed by the photosensor. For example, when the leading edge of the first tape pocket triggers the photosensor to switch on, the encoder value is X₁. When the trailing edge of the pocket triggers the photosensor to switch off, the encoder value is X₂. The tape continues to move and then is stopped. The encoder value is queried and found to read X₃. The location of the leading edge of the tape pocket can be calculated as X₃−X₁, where this value represents the distance from the photosensor to the leading edge of the tape pocket. The trailing edge of the tape pocket can be calculated as X₃−X₂. Thus the center of the tape pocket can be calculated as the average of these 2 distances as ((X₃−X₂)+(X₃−X₁₎)/2. These distances can be calculated for any of the tape pockets between tape drive wheel 7 and photosensor 6.

In this invention, any inaccuracy of stopping the tape at a specific location can be compensated for because the pick-n-place can adjust its pick or placement location according to live information regarding the exact tape pocket location.

Claims

1. A real-time carrier tape pocket position sensor to accurately determine the location of at least one tape pocket in order to pick or place electronic semiconductor devices into or out of said tape pocket, said position sensor comprising: a) a photosensor positioned to sense the leading and trailing edges of tape pockets,b) a rotational device that turns in accordance with the movement of said tape,c) a rotary encoder that is mechanically coupled to said rotational device so as to turn proportionally with said rotational device,d) an electronic processor that stores and correlates data from said rotary encoder with data from said photosensor so that the current location of at least one tape pocket that has passed said photosensor can be determined.

2. A tape pocket position sensor as in claim 1 where the center location a pocket is determined by bisecting the leading and trailing edge data from said photosensor and said rotary encoder.

3. A real-time carrier tape pocket position sensor to accurately determine the location of several consecutive tape pockets in order to pick or place electronic semiconductor devices into or out of said tape pockets, said position sensor comprising: a) a photosensor positioned to sense the leading and trailing edges of tape pockets,b) a rotational device that turns in accordance with the movement of said tape,c) a rotary encoder that is mechanically coupled to said rotational device so as to turn proportionally with said rotational device,d) an electronic processor that stores the encoder value when the leading edge of a tape pocket is sensed and that stores the encoder value when the trailing edge of a tape pocket is sensed and further can determine the present location of said tape pocket relative to said photosensor by referencing the current encoder value with the previously stored values.

4. A method to accurately determine the location a tape pocket in order to pick or place electronic semiconductor devices into or out of said tape pockets, said method comprising: a) positioning a photosensor to sense the leading or trailing or both edges of tape pockets,b) positioning a rotational device to turn in accordance with the movement of said tape,c) positioning a rotary encoder that is mechanically coupled to said rotational device so as to turn proportionally with said rotational device,d) utilizing an electronic processor to store the values read from said encoder when the leading edge and trailing edge of a tape pocket is sensed,e) utilizing an said electronic processor to determine the present location of a tape pocket by performing a mathematical calculation on the current encoder value and a previously stored value.

5. A method as in claim 4 whereby the locations of multiple tape pockets are determined.