U.S. patent application number 11/007501 was filed with the patent office on 2006-06-08 for system and method for locating components on a tray.
Invention is credited to David M. Christensen.
Application Number | 20060118459 11/007501 |
Document ID | / |
Family ID | 36572999 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060118459 |
Kind Code |
A1 |
Christensen; David M. |
June 8, 2006 |
System and method for locating components on a tray
Abstract
A system and method for precisely locating the position of a
component in a tray. The tray is a unitary structure having a
plurality of protrusions on at least one side. A robot relies on
the protrusions to locate pockets adjacent to each protrusion. An
end effector reaches for a component in each pocket. The degree of
accuracy of locating a component in a tray is enhanced by employing
the plurality of protrusions and by following the method of the
present invention.
Inventors: |
Christensen; David M.;
(Fallbrook, CA) |
Correspondence
Address: |
Isabelle McAndrews;Peak International
Unit G
38507 Cherry Street
Newark
CA
94560-4743
US
|
Family ID: |
36572999 |
Appl. No.: |
11/007501 |
Filed: |
December 7, 2004 |
Current U.S.
Class: |
206/725 |
Current CPC
Class: |
B23P 19/10 20130101 |
Class at
Publication: |
206/725 |
International
Class: |
B65D 85/00 20060101
B65D085/00 |
Claims
1. A method for moving a component from a pocket of a tray, the
method comprising: (a) providing a plurality of datums on the tray;
(b) providing a pocket cluster around each datum; (c) moving an end
effector to a first datum on the tray; (d) manipulating the end
effector to reach for a component from one or more pockets in the
cluster surrounding the first datum; (e) manipulating the end
effector to locate a supplemental datum on the tray; (f) resetting
the end effector at the supplemental datum to zero; and (g)
manipulating the end effector to reach for a component from one or
more pockets in a cluster surrounding the supplemental datum.
2. The method of claim 1, further comprising repeating steps
(e)-(g) until the end effector has attempted to move a component
from each pocket in the tray.
3. The method of claim 1, wherein the location of a component is
determined within 0.0030-0.010 inches of accuracy.
4. The method of claim 1, wherein the step of reaching for a
component comprises retrieving the component and inserting it into
hardware.
5. The method of claim 1, wherein the datum is located by a touch
or vision sensor.
6. The method of claim 1, wherein the tray is advanced to a
stacking area after the robot has targeted all of the pocket
clusters in the tray.
7. A system for locating a component position on a tray in an
assembly line, the system comprising: a. a mechanical member that
is programmed to move a predetermined distance from a first datum
on a tray to a new datum on the same tray; b. a sensor on the
mechanical member that detects the new datum; c. a reset mechanism
within the mechanical member for establishing the new datum as a
zero point on the tray; d) a lever arm connected to the mechanical
member that reaches for a component in one or more pockets of a
cluster associated with the datum when a sensor detects a new
datum.
8. The system of claim 7, wherein the datums comprise a protrusion
having an x- and a y-axis.
9. The system of claim 8, wherein the datums comprise a protrusion
shaped in the form of an L, an X, or a +.
10. The system of claim 8, wherein each datum is surrounded by a
cluster of pockets.
11. A tray for storing components in an automation assembly line,
said tray comprising: a) a unitary structure having more than one
pocket for storing components; b) a first datum on the tray and
external to the pockets; and c) additional datums external to the
pockets, distributed throughout the tray, wherein each datum
enables a detector to precisely identify the location of components
stored within the tray.
12. The tray of claim 11, wherein the additional datums surround
the central datum,
13. The tray of claim 11, wherein each datum is a protrusion.
14. The tray of claim 13, wherein the protrusion comprises an L, an
X or a + shape that is molded together with the tray.
Description
FIELD OF INVENTION
[0001] This invention pertains to improving the accuracy of
locating a component during an automation process. More
specifically, the invention pertains to providing datums on an
automation tray for more precisely locating the presence of a
component within a specific pocket of the tray.
BACKGROUND OF THE INVENTION
[0002] In automated assembly lines, process trays with a single
datum are known. The single datum is located in the center of the
tray and acts as a point of reference for a robot that moves in
increments across the top surface of the tray. The robot preferably
contacts the center top surface of the component and lifts the
component out of its pocket to another location. The robot
determines where it is by computing the distance between its
current location and the datum. As the robot moves further away
from the central reference point its degree of accuracy in
identifying component locations decreases.
[0003] In reference to FIG. 1, the prior method of locating a
specific area will be described. In the prior art, use of a central
datum was adequate for components close to the center of the tray.
The degree of accuracy in locating a specific area on a tray is
affected by the molding compound and the mold used to mold the
tray. Each molding compound has a tolerance standard that ranges
between 0.001-0.005 inches/inch. The accuracy of the mold itself
also has an effect on the tolerance, or level of certainty, in
identifying a specific location on a tray decreases as the distance
from a reference point increases. The overall tolerance for a tray
that uses a single reference marker is illustrated in FIG. 1. The
tolerance is determined by considering the case of two pockets
separated from each other.
[0004] The degree of accuracy of pocket 20A is determined by the
distance from reference 25 to the center of pocket 20A multiplied
by the tolerance standard. Using a tolerance standard of 0.005, the
tolerance of pocket 25 is 4.0311 multiplied by 0.005 or 0.020
inches. Thus an end effector will locate a component to within
0.020 inches of accuracy.
[0005] Possible errors from relying on a single reference point
include inaccurate detection of a component location, failure to
pick up a component, and needless disposal of functional parts.
During automation, a robot is programmed to pick up components in
the center of their top surface and then transfer the component to
hardware. If a component is picked up off center it will be put
down in an off center position. The likelihood that the component
will be improperly installed into hardware is increased as a result
of the inaccurate pick up by the robot.
[0006] As electronic components shrink in size it becomes more
desirable to increase the precision of locating components on a
tray. In addition, the industry is approaching the technological
limits of the precision that can be maintained with the current
molding materials, tools, and molding processes. Therefore, the
need exists for a method and system that improves the accuracy of
locating components on a tray.
SUMMARY OF THE INVENTION
[0007] The invention is directed to a method for moving a component
from a pocket of a tray, by providing a plurality of datums on the
tray; and surrounding each datum with a pocket cluster. An end
effector of a robotic system locates a central datum on the tray;
and then reaches for a component from each pocket in the cluster
surrounding the central datum. Thereafter the end effector locates
a new datum and resets the zero point of the tray at the location
of the new datum. The end effector reaches for a component from
each pocket in the cluster associated with the new datum and then
the robot proceeds to sequentially target each pocket cluster,
until every pocket on the tray has had its component transferred to
hardware.
[0008] In another embodiment, the invention is directed to a system
for locating a component position on a tray wherein the system
comprises a mechanical member that is programmed to sequentially
move from one central datum to another on the same tray; a sensor
that detects datums; a reset mechanism for establishing the new
datum as a zero point on the tray; and an arm connected to the
mechanical member that reaches for a component in each pocket of a
cluster associated with the datum.
[0009] The tray of the invention comprises a unitary structure
having more than one pocket for storing components; a central datum
on the tray and external to the pockets; and additional datums
external to the pockets, distributed throughout the tray. Each
datum enables a detector to precisely identify the location of
components stored within the tray.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates a tray in accordance with the prior
art.
[0011] FIG. 2 illustrates a tray in accordance with the present
invention.
[0012] FIG. 3 is a flow chart that summarizes the various steps for
implementing the method of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The present invention enhances the accuracy of locating a
component on a tray by providing multiple datums, or reference
points, on a tray. In a preferred embodiment the datums are located
on only one side of the tray. However, datums can be placed on any
side which has pockets for carrying components.
[0014] This invention may be applied to automation trays of various
dimensions. FIG. 2 illustrates a tray 200 with a central datum 22
and supplemental datums 15. The precise position of each locating
datum molded on the tray is known. The supplemental datums 15 are
equally spaced on tray 200. A cluster of pockets 35 surround each
datum shown. An example of how the method of the invention is
implemented is discussed below.
[0015] A robot in an automated assembly works has a robotic arm
with an end effector attached to it. The end effector may be a
gripper or a vacuum suction device that reaches for a component
from each pocket in a cluster. The end effector relies on datums to
locate components in a pocket cluster.
[0016] A sensor detects the datums and relays the datum location to
the end effector. The robot is programmed to start at a specific
point on a tray, such as the central datum 22. The first datum 22
is then used by the end effector to find supplemental datums 15.
When the end effector reaches a supplemental datum 15, the robot
re-zeros itself at the location of datum 15. Then, the new zero
position is used to find supplemental datum such as 15B or 15C for
example.
[0017] The robot places its end effector over the central datum 22
on a 10-inch tray, and uses it as a 0,0 reference point to
sequentially find additional datums 15 on tray 200. The robot is
programmed to move from central datum 22 down 3.0 inches and then
left 3.0 inches to locate supplemental datum 15D. After the end
effector has targeted pocket cluster 45 it will move to datum 15E,
and re-zeroes at 15E and then begins targeting the pockets in
cluster 47. After the end effector has targeted cluster 47, it
proceeds to an adjacent cluster until all the pocket clusters have
been targeted and the tray is ready to be advanced to a stacking
area.
[0018] Suitable datums for this invention may include a protrusion
having the form of an L, an X or a +. For a touch sensor, an "L"
shaped datum is preferred. The sensor would move up until it hits
the bottom leg of the "L" and that position would be the zero for
the Y direction. Then it would move until it finds the vertical
portion of the "L" and set that as the X zero point. For a vision
system, an "X" is preferred to be used to mark the 0,0 location.
The protrusion is molded in the same mold as the tray. The trays of
this invention are preferably injection molded with a thermoplastic
polymer and have a unitary structure.
[0019] The component in pocket 30 is closer to datum 15D than it is
to central datum 22. Since the robot knows the precise location of
datum 15D, the degree of accuracy of locating a component in pocket
15D is enhanced. In other words, the proximity of pocket 30 to
datum 15B allows the robot to more precisely locate a component in
pocket 30 than if the robot relied on central datum 22 alone to
locate the component in pocket 30. Once a datum is located, the end
effector reaches for a component in each pocket of the cluster
closest to that datum. The robotic gripper moves the component to
hardware such as a circuit board, a disk drive, or any other type
of electronic hardware.
[0020] When an end effector approaches a new datum, the robot will
re-zero itself on the new datum and thereby reduce the overall
uncertainty in locating components within pockets that are
clustered around the new datum. It is not necessary to include any
inserts in the tray in order to benefit from the precision
characteristics of the method of this invention.
[0021] FIG. 2 illustrates the tolerance of a specific tray in
accordance with the present invention where multiple datums are
placed on tray 200. FIG. 2 shows that in each pocket cluster 35 the
distance from the center of one pocket to an adjacent pocket in the
cluster is 0.75 inches. Hence, the tolerance for any one pocket in
a cluster is 0.0038 inches [0.75.times.0.005 (tolerance standard)].
By adopting the method of the present invention, the degree of
accuracy improves more than five-fold from 0.020 inches to 0.0038
inches.
[0022] FIG. 3 is a flowchart that illustrates the various steps of
the invention. A handler positions a tray at an assembly station.
The robot moves to a central datum and targets components in the
pocket cluster associated with central datum 22. Components are
targeted when the robot's mechanical member reaches for a component
from each pocket and transfers the component to a desired hardware.
The mechanical member may make a transferring motion even if a
component has not picked up from a specific pocket. The robot
stores to memory each pocket that has been targeted. Consequently,
when the robotic memory bank indicates that all pocket clusters
have been targeted, the handler advances the tray to a stacking
area. At this point, the automation system is ready to receive a
new tray loaded with components.
[0023] The examples of the system and method described herein are
solely representative of the present invention for locating a
component. It is understood that various modifications may be made
to the foregoing examples and methods of operation without
departing from either the spirit or scope of the invention. It is
therefore the intent that the scope of the invention is to be
defined by the appended claims.
* * * * *