U.S. patent application number 09/965424 was filed with the patent office on 2002-04-11 for method of driving ejector pins to eject formed parts.
Invention is credited to Arends, Albert W..
Application Number | 20020040911 09/965424 |
Document ID | / |
Family ID | 26930578 |
Filed Date | 2002-04-11 |
United States Patent
Application |
20020040911 |
Kind Code |
A1 |
Arends, Albert W. |
April 11, 2002 |
METHOD OF DRIVING EJECTOR PINS TO EJECT FORMED PARTS
Abstract
A method of driving part ejector pins at a high cycle rate by a
reversible servo motor rotating a crank unidirectionally to advance
a pin mounting structure from a retracted position to an advanced
eject position, and back to the retracted position, and reversing
the motor to repeat the cycle with only a single motor
reversal.
Inventors: |
Arends, Albert W.; (Gladwin,
MI) |
Correspondence
Address: |
John R. Benefiel
Suite 100 B
280 Daines Street
Birmingham
MI
48009
US
|
Family ID: |
26930578 |
Appl. No.: |
09/965424 |
Filed: |
September 27, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60237338 |
Sep 29, 2000 |
|
|
|
Current U.S.
Class: |
221/1 |
Current CPC
Class: |
B29C 51/44 20130101;
Y10T 74/2173 20150115; Y10T 83/8699 20150401 |
Class at
Publication: |
221/1 |
International
Class: |
B65H 001/00 |
Claims
1. A method of driving ejector pins to eject parts from tooling of
a part forming apparatus, including the steps of: mounting ejector
pins to a slidably mounted pin mounting structure located with
respect to said tooling so as to engage and eject said parts with
said pins when said structure is moved to an advanced position from
a retracted position; reciprocating said structure by oscillating a
crank having a crank arm pinned to one end of a connecting link,
said connecting link pinned at the other end to said pin mounting
structure; said step of oscillating said crank comprising the steps
of rotating said crank unidirectionally with a motor from a first
angular position corresponding to said retracted position of said
pin mounting structure through a crank dead center position
corresponding to said advanced position of said pin mounting
structure, to a second angular position 180.degree. past said first
angular position, also corresponding to said retracted position of
said pin mounting structure; and reversing rotation of said motor
to rotate said crank and crank arm back through said crank dead
center position to said first angular position, whereby only a
single reversal of said motor produces an advance and retraction of
said ejector pins.
2. The method according to claim 1 wherein said crank is rotated by
a reversible servo motor.
Description
RELATED CROSS-REFERENCE APPLICATION
[0001] This application claims benefit of U.S. provisional ser. no.
60/237,338, filed Sep. 29, 2001.
BACKGROUND OF THE INVENTION
[0002] This invention concerns ejector mechanisms which are used to
eject formed parts from tooling used in their manufacture. In
thermoforming parts, a well known process is to vacuum form an
array of cups into a single sheet of plastic. The formed sheet is
then transferred into a trim die where the cups are cut free from
the rest of the sheet and ejected into a stacking mechanism and
transferred as a stack for further processing.
[0003] The ejector comprises an array of pins held on a member, the
pins advanced into the parts after die cutting is complete the same
from the sheet to push the cup free of the trim die. Such ejection
in the past has been typically accomplished by air cylinders
cycling the pin motion. Production speeds have greatly increased in
recent years, and reversing servo motors driving slider crank
mechanical movements have been used to increase the ejector cycle
rate. In this arrangement, the servo motor drives a crank which has
an arm pinned to one end of a link, the link pinned at the other
end to a slider mounting the ejector pins.
[0004] The servo motor rotates the crank to advance the slider to a
maximum advance or eject position, reverses, and then retracts and
reverses again to begin the next cycle. Thus, each cycle requires
two reversals of the servo motor.
[0005] This arrangement has worked satisfactorily despite the need
for two servo motor reversals, and offered each changes in the
retract and advanced positions to adapt to tooling changes.
However, because the demand for even higher cycle rates has grown,
this arrangement has been found to be deficient as being not
capable of executing even more rapid cycle rates now desired,
primarily due to the need to reverse the motor twice for each
ejection cycle.
[0006] It is an object of the present invention to provide a part
ejector of the type operated by a reversible servo motor which is
capable of higher cycle rates than the prior reversible servo motor
driven part ejectors.
SUMMARY OF THE INVENTION
[0007] The above recited objects as well as other objects which
will become apparent upon a reading of the following specification
and claims are achieved by a method for driving part ejectors in
which only a single reversal of the servo motor is required per
ejector cycle. This is achieved by continuing to advance the servo
motor unidirectionally past the point at which the ejector reaches
its maximum travel at the crank dead center position, retracting
the ejector pins by continued rotational advance of the servo motor
in the same direction, the crank-slider causing retraction of the
slider to a retracted position, where the servo motor is reversed
preparatory to the next cycle. Thus, only a single reversal of the
servo motor is required per ejector cycle.
DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a diagram of a prior art ejector mechanism.
[0009] FIG. 2 is a diagram of the ejector mechanism according to
the present invention.
[0010] FIG. 3 is a perspective view of a servo motor-slider crank
mechanism utilized in the present invention.
[0011] FIG. 4 is a side view of the servo motor-slider crank
mechanism shown in FIG. 3.
DETAILED DESCRIPTION
[0012] In the following detailed description, certain specific
terminology will be employed for the sake of clarity and a
particular embodiment described in accordance with the requirements
of 35 USC 112, but it is to be understood that the same is not
intended to be limiting and should not be so construed inasmuch as
the invention is capable of taking many forms and variations within
the scope of the appended claims.
[0013] Referring to FIG. 1, a prior art ejector mechanism includes
a slider 10 mounted for reciprocation in a bearing guide 12. An
ejector pin support beam structure 14 fixed to the slider 10 has a
plurality of ejector pins 16 projecting therefrom (only one shown
completely). In the advance position shown, the ejector pins 16 has
caused molded parts 18, here depicted as a disposable cup, to be
ejected away as shown from tooling 20 and the remaining part of a
sheet 22 from which the parts are formed.
[0014] A crank 24 has a crank arm 26 pinned to one end of a
connecting link 28, pinned at the other end to the slider 10, thus
forming a slider-crank mechanism.
[0015] The crank 24 is oscillated by a reversible servo motor (not
shown) between a retracted position R.sub.1 and advanced position
A.sub.1 whereat ejection occurs. Thus, the crank 24 is reversed at
the retracted position R.sub.1 and advanced position A.sub.1 for
each ejection cycle.
[0016] The end points R.sub.1, A.sub.1 can be readily adjusted, by
controlling the servo motor to position the crank arm at another
retracted position R.sub.2 and advanced position A.sub.2 as
required for a given tooling-part set up.
[0017] According to the method of the present invention, the servo
motor is controlled to drive the crank 26 unidirectionally from a
first angular position R-1A corresponding to the retracted position
of the pin mounting structure 14 through an advanced position A-1
at the dead center position of the crank 24 to a second retracted
position R-1B, 180.degree. from the first retracted position
R-1A.
[0018] The crank 24 is then reversed and driven unidirectionally
back to R-1A, passing through the second advanced or ejection
position A-2 which is the same as ejection position A-1. The
ejector pin support piece 14 is reciprocated between corresponding
retracted and advanced positions, whereat the pins 16 push the
parts 18 into a stacking mechanism (not shown), as indicated.
[0019] Thus, each eject cycle requires only a single reversal of
the servo motor, allowing 15 higher ejection cycle rates to be
achieved. It is noted that by merely changing the servo motor MS
controls other retracted positions R-2A, R-2B can be set. However,
the advanced positions A-1, 2 (and the stroke) cannot be so
changed, necessitating relocating of the tooling with respect to
the ejector.
[0020] FIGS. 3 and 4 illustrate an ejector mechanism enabling the
practice of the invention.
[0021] A servo motor-gear unit 30 oscillates a belt pulley wheel
32, driving a belt 34 passing around a larger belt pulley wheel
36.
[0022] A crank shaft 38 is thereby oscillated to oscillate a pair
of crank arms 40.
[0023] The outer end of the crank arms 40 are pinned to respective
connecting links 42 each pinned at their opposite end to an ejector
pin mounting structure including piece 48.
[0024] Slider bars 50 are included in the pin mounting structure to
the ejector pin mounting piece 48, guided in linear bearings 44, to
constrain the piece 48 to linear motion.
[0025] Mounting structures 52, 54 are also provided.
* * * * *